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Starter Motor

Descripción: Starter Motor     Motor starters are usually fitted with a trip device which deals with overcurrents from just above normal running current of the motor to the stall current. The aim should be for the device to match the characteristics of the motor so that full advantage may be taken of any overload capacity. Equally, the trip device must open the starter contactor before there is any danger of permanent damage to the motor.     Contactors are not normally designed to cope with the clearance of short-circuit conditions, and it is therefore usual for the contactor to be backed up by HRC fuses or by circuit-breaker.     The arrival on the scene of very compact motor starters and the need to provide proper back-up protection to them has posed a problem. BS EN 60947-4-1 (1992) (previously BS 4941) ‘Motor starters’, describes three types of co-ordination, the most onerous condition (type C) requiring that under fault conditions there shall be no damage to the starter or to the overload relay. The usual back-up device will be the HRC fuse. It is important that the user check with the manufacturer's catalogue to ensure that the correct fuse is used to secure this co-ordination.     The starter motor in your automobile is a DC motor. If you were to accidentally reverse the battery polarity, the DC motor would still rotate in the same direction. Reversing polarity of the battery will not cause the motor to rotate in the opposite direction.     To reverse the direction of rotation of this type of motor, either the current through the stator winding or the current through the armature must be reversed. Reversing both of them will result in the same magnetic polarities between the armature and the stator poles. This results in the same direction of rotation.     The industry's standard for reversing the direction of rotation of a DC motor is to reverse the direction of the current through the armature. When a DC motor has more than one set of windings, shunt and series, as well as interpoles, the currents through all the stator windings would need to be reversed in order to change direction of rotation. This is far more complicated than merely reversing armature current.     All engines require a toyota starter motor to turn them over before firing. In conventional vehicles, this is a straightforward, but powerful, direct-current electric motor. When the starter switch is activated by the driver, current flows to a solenoid attached to the starter motor. This current moves a lever into the solenoid that then causes a cogwheel of the motor to mesh with the teeth on the circumference of the flywheel. At the same time, an electrical contact is closed to allow a large current to flow and rotate the starter motor as well as the engaged flywheel. Typically, currents of hundreds of amperes are required to start the engine and are provided by the battery, which is generally a 12-V lead–acid module. The battery is recharged by the alternator–rectifier combination when the engine is running. Automotive batteries have improved enormously over the years and have far longer lives than formerly, even though they may be called upon to power many more functions. Although guarantees may be for two or three years, in practice batteries often operate for eight years or longer before failing. Moreover, modern car batteries no longer require periodic ‘topping-up’ with de-ionized water. Further information on the evolution of the lead–acid battery is given in Section 7.4, Chapter 7.     A starter motor is required to run the internal combustion engine up to a speed sufficient to produce satisfactory carburation.     The starter motor is mounted on the engine casing and a pinion on the end of the BMW starter motor shaft engages with the flywheel teeth. The gear ratio between pinion and flywheel is about 10:1. A machine capable of developing its maximum torque at zero speed is required. The series wound motor has speed and torque characteristics ideal for this purpose.     The engagement of the pinion with the flywheel is effected in different ways. Perhaps the two most commonly used are the inertia engaged pinion and the pre-engaged pinion methods.     In inertia engagement the drive pinion is mounted freely on a helically threaded sleeve on the armature motor shaft. When the starter switch is operated, the armature shaft revolves, causing the pinion, owing to its inertia, to revolve more slowly than the shaft. Consequently, the pinion is propelled along the shaft by the thread into mesh with the flywheel ring gear. Torque is then transmitted from the shaft to the sleeve and pinion through a heavy torsion spring, which takes up the initial shock of engagement. As soon as the engine fires, the load on the pinion teeth is reversed and the pinion tends to be thrown out of engagement. Inertia drives are usually inboard, i.e. the pinion moves inward towards the starter motor to engage with the ring gear; an inboard is lighter and cheaper than an outboard starter.     To obtain maximum lock torque (i.e. turning effort at zero speed), the flux and armature current must be at a maximum, so resistance in the starter circuit (windings, cables, switch and all connections) must be a minimum; any additional resistance will reduce the starting torque. Generally, the inertia engaged mercedes starter motor is energised via a solenoid switch, permitting the use of a shorter starter cable and assuring firm closing of the main starter-switch contacts, with consequent reduction in voltage drop. The use of graphite brushes with a high metallic content also assists in minimising loss of voltage.     While inertia drive has been the most popular method of pinion engagement for British petrol-engined vehicles, the use of outboard pre-engaged drive is increasing. The pre- engaged starter is essential on all vehicles exported to cold climates and for compression ignition engines which need a prolonged starting period.     The simplest pre-engaged type of drive is the overrunning clutch type. In this drive, the pinion is pushed into mesh by a forked lever when the starter switch is operated, the lever often being operated by the plunger of a solenoid switch mounted on the motor casing. Motor current is automatically switched on after a set distance of lever movement. The pinion is retained in mesh until the starter switch is released, when a spring returns it. To overcome edge-to-edge tooth contact and ensure meshing, spring pressure or a rotating motion is applied to the pinion. An overrunning clutch carried by the pinion prevents the motor armature from being driven by the flywheel after the engine has fired. Various refinements may be incorporated, especially in heavy-duty starters. Among these are: a slip device in the overrunning clutch to protect the motor against overload; a solenoid switch carrying a series closing coil and a shunt hold-on coil; an armature braking or other device to reduce the possibility of re-engagement while the armature and drive are still rotating; a two-stage solenoid switch to ensure full engagement of the starter pinion into the flywheel teeth before maximum torque is developed (Figure 44.15).     The engine may be started either by an electric honda starter motor or by compressed air.      An increasing used form of motor starter is known as “soft start”. Soft starters utilise sold state technology, typically thyristors, to supply the motor.     In a “soft starter” voltage and frequency of supply to the motor is varied in a controlled way in order to provide the required torque as the speed increases up to full load.     Soft starts can be arranged to provide up to 200% full load torque at starting, whilst limiting the current drawn from the supply to perhaps 350% rather than the 600% typically experienced from direct on line. Other parameters and facilities including kick start ability, ramp time to full speed and low load energy saving are available depending upon supplier.     Soft starters are available for the largest 400/600 volt motors. By specifying soft starters the specification of the associated supply system can be relaxed since large starting currents and resultant voltage drops will not occur.     Some users are specifying speed control inverters for motor starting even when full speed control facilities are not needed. So used inverters provide a soft starter capability, have good motor control, protection and diagnostic facilities as well as providing an energy saving function, if needed.     The engine starting quality is strongly influenced by the Jeep starter motor and the injection strategy. Indeed, an insufficient amount of kinetic energy initially provided to the system will not compensate for the energy loss caused by the DMF resonance. An adequate starter motor must be carefully chosen to fulfil this requirement, even under critical conditions with low battery voltage or corroded components of the starter system. Moreover, the engine should not be fired too soon during the starting phase before the starter motor reaches a stationary speed.

Fecha de Publicación: 29-10-21

5 of the best yoga pants: Health benefits and risks

Descripción:   5 of the best yoga pants: Health benefits and risks     Wearing yoga suit while exercising may make a workout more comfortable and therefore more enjoyable. It may also prevent overheating. That said, it also carries some health risks.     This article discusses the health benefits and risks of wearing yoga pants, what to look for, some of the best options available to buy online, and alternative gym clothing to consider.     Yoga pants describe a variety of different styles of pants, from formfitting leggings to looser trousers. However, nearly all yoga pants have some stretch to them due to the materials that they contain.     Many yoga pants contain materials that wick moisture from the body and promote airflow. The moisture-wicking technology prevents overheating by keeping body temperature stable during exercise, while ventilating fabrics increase airflow.     A 2014 studyTrusted Source found that synthetic polyester was more beneficial than a 100% cotton T-shirt in terms of both breathability and moisture-wicking.     This may suggest that yoga suit-summer made of synthetic material, such as polyester and elastane, may prevent overheating and promote airflow. This in turn may make workouts more comfortable, especially in warm or hot environments.     Health risks of wearing yoga pants     The stretchy material in yoga pants should not feel too tight or limit movement, as restrictive clothes can contribute toward musculoskeletal disorders.     For example, a 2016 studyTrusted Source found that males wearing tight pants are at a greater risk of musculoskeletal disorders, because they cause abnormal movement and posture in the lumbar spine and pelvis.     While this study focused on males and restrictive clothing, especially around the waist, it suggests that wearing flexible and comfortable clothing may decrease the risk of abnormal movement and posture.     Wearing tight or formfitting yoga pants may also lead to other conditions:     Yeast infection     Some people may develop a vaginal yeast infection. Certain clothes, such asTrusted Source those that are too tight or use synthetic materials, are factors in people developing this infection.     Tight clothes and sweating allow the yeast that naturally occurs in the vagina to thrive, which leads to inflammation.     Learn more about yeast infections here.     Tinea cruris     Another condition that people may develop while wearing yoga suit-autumn is tinea cruris, or jock itch. Excessive sweating, restrictive clothing, and not showering properly after exercise are risk factorsTrusted Source for developing this condition.     People wearing tight yoga pants that do not have moisture-wicking or breathable fabrics may be at risk of jock itch.     Learn more about jock itch risk factors and prevention here.     Intertrigo     People wearing yoga pants may also develop intertrigo. This condition is an inflammation that appears in skin folds. Risk factors for intertrigo includeTrusted Source warm temperatures, sweating, friction, and poor ventilation.     Wearing yoga pants that do not have breathable and moisture-wicking materials may contribute to this condition.     Learn more about intertrigo here.     List of top yoga pants     There are many yoga pants available to buy. However, people should look for yoga suit-pattern that are:     nonrestrictive     breathable     moisture wicking     Below, we present a selection of the top yoga pants available on the market.     Please note that the writer of this article has not tried these products. All information presented is purely research-based.     These leggings contain moderate compression fabric that flattens the stomach and shapes the waist and legs. Shaper clothing does not offer fitness benefits.     The leggings also feature mesh cutouts around the knees that promote extra airflow and breathability. The fabric in the leggings wicks moisture, preventing overheating.     The company recommend these leggings for people doing high impact exercise, such as agility, strength, and resistance training.     These leggings are available in small, medium, large, and extra-large sizes.     These pants are lightweight, moisture wicking, and quick drying. They do not contain spandex, but they prevent sagging or bagging with FREEFLEX fabric.     They also feature a wide pull-on waistband, four pockets, and a gusseted crotch for freedom of movement. Additionally, they have a water-repellent finish.     The company recommend these pants for people who work out in the gym and outdoors.     These pants are available in small, medium, large, extra-large, and double extra-large sizes, with a variety of inseam options.     These polyester and lycra pants have a capri length and an over-the-belly waistband that a person can wear up or fold down, depending on their needs. These leggings feature a four-way stretch and UV protection. They also absorb moisture.     The company recommend these for both a workout and general use. Additionally, the leggings are suitable throughout pregnancy.     They come in the following sizes: extra-small, small, medium, large, and extra-large.     Whether you’re working out or just working from home, yoga pants are probably somewhere in your day-to-day wardrobe rotation. To help you find the right pair for your preferences — whether you like high-waisted or fold-over or capris or boot cut — we’ve scoured thousands of Amazon reviews for the best of the best. And if you’re looking for more activewear, be sure to check out our roundups of the best sports bras, leggings, and plus-size workout clothes.     More than 31,000 reviewers give these high-waisted yoga tops-vest five stars, and over 300 describe them as “buttery soft.” One such reviewer writes, “I cannot express how much I LOVE these leggings! They make the booty look good, and I honestly like them better than my Lululemon Aligns. And at this price, they’re hard to beat.” Another self-proclaimed “avid gymgoer ” also prefers these over Lululemon’s leggings because they “don’t cost $100/pair, have good pockets, give enough compression for belly support, are super-stretchy and comfortable, and they stay put.” Plenty of reviewers appreciate the 7/8 length of these slightly shorter leggings, including one reviewer who’s under five feet tall. “The fit is perfect for my small, hard-to-shop-for body!” they write. “It can be hard to find leggings with little to no slack on the legs, but these fit just right, no bunched-up fabric at my ankles!”     Over 3,000 reviewers give these even less expensive yoga pants five stars, with many describing them as lightweight enough to workout in. “I was looking for cool, light material because I use these pants for running on an indoor track. They are perfect,” one writes, while another says, “I have hiked in them a couple times now and found them to feel comfortable, and yet very supportive on my legs.” And while they are breathable, one assures, “They’re not see-through like a lot of leggings can be; so wearing them at the gym is totally fine.” As far as the length goes, some reviewers say they are a little long, but one five-foot-one-inch reviewer says, “Once I put on a sneaker they are just above the ground.” Reviewers also appreciate that they’re affordable — and that that doesn’t impact their quality. “I had them for 2.5 years and they still look like new,” one owner says. “I wear them weekly. Amazing quality. No stretch, no holes, no sign of wear. Just amazing.”     According to the majority of positive reviewers here, Baleaf High Waist yoga pants don ’t press, squeeze, pinch, or leave indents on your stomach, and they stay put. “The high waist stays up through all kinds of movement,” said one reviewer. Another satisfied customer who wears them for work and yoga said, “I love that they don’t slide down, flatten out my waist without leaving indents in my stomach or putting too much pressure like most high-waisted pairs do.” A woman who said she wears them running called them “perfect workout pants” saying “they fit wonderfully, and they’re so comfortable I don ’t even feel like I’m wearing pants (wore them for my run tonight). The waistband comes up high enough to cover what I want covered without squeezing the hell out of my belly. Super breathable, moisture-wicking, not see-through!” And a reviewer who bought another pair “immediately” after receiving the first ones said “the fit on these pants are amazing! They hold everything in yet still manage to feel breathable and so comfortable! They’ll make your booty look great also!”     “I’ve been searching for a LONG time on Amazon for the perfect leggings,” writes one customer who wanted Lululemon quality “without spending a lot of money.” She tested many different Amazon leggings before these, and says “these by far are the most comfortable to work out in. They def pass the squat test, are not see-through at ALL, and have convenient pockets that I didn’t think I needed but love.” And plenty of five-star reviewers mention the pockets on these IUGA leggings. One calls them “great, deep pockets.” She says that women should “DEMAND more and better pockets” because after all “pockets are not just for men.” Another customer says these leggings “are everything.” She appreciates the pockets because they’re large enough for her utility knife and keys, but like nearly 200 other five-star reviewers, she loves the high waist. “The high waist allows me to look slimmer and feel better about myself which ironically makes me work harder and faster,” she explains, adding, “I can bend and squat and kneel and lift easily with no restrictions or material pulling in certain places and not in others.”     “So take it from me and get one of these pants, if not multiple, because they will change your life,” writes one reviewer who thinks these leggings are top-quality. Many are especially impressed with the mesh panel on the calves; one notes that it “is very flattering” and “slimming,” while another adds that “the mesh panels gives better cooling effect.” But the mesh isn’t the only draw: As one reviewer notes, “The bottom of the legs is cut on a slight angle (which doesn’t show in the image), but it adds to the styling along with some the diagonal seaming, which is the inverse of the mesh insert. There’s also mesh trim on the pocket, a nice detail.” The fit is another selling point. Reviewers describe the leggings as stretchy and comfortable, but thick enough to be supportive. “They keep my ‘jiggles’ controlled for yoga, barre, and boxing workouts (told you … GOALS!),” one says. “The high waisted ‘tummy tuck’ also stays put during all my activities, no rolling down! And finally, the material is dense, no awkward ‘see- through’ spots on the bum.”

Fecha de Publicación: 29-10-21

Yoga Equipment Guide for Beginners

Descripción: Yoga Equipment Guide for Beginners     When you first start doing yoga, it's hard to know what you really need to buy. The yoga mat continues to develop so much clothing and equipment that you might feel you need to spend hundreds of dollars before ever stepping foot in a studio.     The good news is, you actually need very little to get started. That said, if you're starting a home practice, or you'd feel better purchasing yoga-specific apparel and equipment prior to your first class, here's what you need to know.     It should go without saying that most aerial yoga accessories want you to wear something to class, but you don't need scores of printed yoga pants or designer gear to be accepted by your peers. Start with the comfortable, breathable athletic apparel you already have on hand, and purchase mid-level basics for anything you're missing.      Pants or Shorts: You can't go wrong with a few pairs of solid-color yoga pants in black, dark grey, navy, or brown. You can mix-and-match these tights with a wide variety of tops, and if you purchase high-quality options, they can last a long time.     If tight pants aren't your thing, look for jogger-style pants or the popular harem-style pants that have elastic around the ankles. These pants are stretchy and offer a little extra room, but due to the ankle elastic, they'll stay in place throughout your practice.     Shorts are a popular option for guys, and they're also appropriate for women, especially if you plan to try hot yoga. Just keep in mind, you may want to wear form- fitting spandex shorts or looser shorts with connected tights underneath because some poses require you to position your legs in a way that could leave you uncomfortably uncovered with looser, running-style shorts.      Tops: It's important to wear tops that are fairly form-fitting so your shirt doesn't fly over your head during forward bends. Wicking material is helpful, especially if you tend to sweat a lot or if you plan on attending a hot yoga class.     Because yoga rooms are sometimes kept cool, you may want to bring a light cover up or sweater with you to class. You can wear it until class starts, and if you keep it by your mat, you can put it on before the final savasana.     Sports Bras: If you're a woman, make sure you wear a sports bra. While TPE yoga mat tends to be a low-impact activity, a decent sports bra can help keep your "girls" in place as you transition between poses, making your practice more comfortable.     Hair Ties or Headbands: Whether you're a man or woman, if you have long hair, you need to secure it in place before you start class to prevent stray locks from falling in your eyes and face. A basic hair tie or headband should do the trick.     Yoga Socks: To be clear, yoga socks are not a requirement to attend a class. In fact, it's preferable to do yoga barefoot. That said if you can't fathom the thought of taking your socks and shoes off in front of strangers, invest in a pair of yoga socks with grips on the bottom so you can keep your feet covered while maintaining good traction. Standard socks absolutely won't do, as you'll end up slipping and sliding all over your mat.     These days, you can buy yoga apparel practically anywhere, and it's not unusual to see yoga pants priced at over $100. Don't feel you need to lay out that much cash for a single pair of pants! Target, Amazon, and YogaOutlet offer quality options for well under $50. Buy a couple pairs of pants and a few tops, and you'll be set for months.     As you commit yourself to your practice, you may decide to add trendy prints or styles to your wardrobe.     In gyms and yoga studios, it’s commonplace to use a yoga mat, also called a sticky mat. The mat helps define your personal space, and, more importantly, it creates traction for your hands and feet so you don’t slip, especially as you get a little sweaty. The mat also provides a bit of cushioning on a hard floor.     Most gyms provide mats and studios have them for rent, usually for a dollar or two per class. This is fine for your first few classes, but the disadvantage to these mats is that lots of people use them and you can't be sure how often they're being cleaned, so you may consider buying your own.     Premium yoga mats can be expensive, often around $80 to $120, but it's possible to find a starter mat for as little as $20 from retailers like Target and Amazon. Just keep in mind, if you decide to buy a cheaper mat, you'll probably find yourself replacing it in short order if you use it often. If you're really ready to commit to a yoga practice, your mat is one place it's worth it to lay out some cash.     Decide which mat features are important to you—for instance, length, thickness, material, durability, comfort, traction, or how to keep it clean—then buy a mat with good reviews based on your needs. Manduka and Lululemon are known for the quality of their Pro Mat and The Reversible Mat, respectively, but other brands, including Jade and Yellow Willow, also offer high-quality, durable mats with good traction and support.     Yoga props are a boon to a fledgling suede yoga mat practice. Props allow students to maintain the healthiest alignment in a range of poses as the body bends, twists, and opens up. They also help you get the most out of each pose while avoiding injury.1     You should familiarize yourself with the props described below, but you don't need to buy your own (unless you're starting a home practice) because they are almost always provided by studios and gyms.      Mat Bags or Slings     If you own your own yoga mat, and you're going to be lugging it back and forth to the studio on a regular basis, there's a legitimate case to be made for purchasing a mat bag or sling. These accessories do exactly what they suggest—they make it easy for you to sling your rolled mat over your shoulder without it coming unrolled.     Slings usually use velcro straps to bind your mat in its rolled configuration with a connecting strap you can throw over your shoulder. Slings sometimes offer additional pockets for storage, but not always. Bags, on the other hand, typically come in one of two styles. One version uses velcro straps to keep your rolled mat secure against a larger gym bag. The other version is essentially a snap- or zipper-closure bag specifically designed to hold your rolled mat. Both styles provide extra storage for clothing, wallets, cell phones, and the like.     The style and brand you choose really comes down to personal preference and budget, as slings can cost as little as $10, and heavy-duty bags can cost well over $100. For variety, check out YogaOutlet, where you can find an array of brands at reasonable prices.     Blankets     Yoga studios usually have stacks of blankets available for students to use during class. Grab one or two blankets at the beginning of class.     Folded blankets can be used to lift the hips during seated poses, or to offer support during lying poses. For instance, when you sit cross-legged, you can place a blanket under your sit bones to elevate the hips above your knees. Blankets come in handy for all sorts of things during class, and if it’s chilly, you can use them to cover up during the final relaxation.     For a home practice, there's truly no reason to purchase new blankets. Simply use what you already have on hand around the house. If, however, you don't own any extra blankets, YogaOutlet offers them for as little as $13.     Blocks     Like blankets, yoga blocks are used to make you more comfortable and improve your alignment. Blocks are particularly useful for standing poses in which your hands are supposed to be on the floor.     Placing a block under your hand has the effect of "raising the floor" to meet your hand rather than forcing the hand to come to the floor while effectively compromising some other part of the pose. This can be seen in half moon pose. Many people don't have the hamstring flexibility or core strength to hold the position with proper form.     By placing a block under the hand that's reaching toward the floor, it's easier to keep the chest open and torso strong. Without the block, the chest might be inclined to turn toward the floor, the supporting knee might be inclined to bend, and the torso might be inclined to "collapse." The simple use of the block helps maintain proper alignment.     Yoga blocks are made of foam, wood, or cork. They can be turned to stand at three different heights, making them very adaptable. If you plan to do a lot of swivel at home it's worth it to get a set of blocks (helpful for poses where both hands are reaching toward the ground). If you're going to attend classes, blocks will be provided for you.     The good news is, almost any block is sufficient, so this is an area you don't have to worry too much about scrimping on. But slightly wider blocks—those that are at least four-inches wide—provide better stability. YogaOutlet and Amazon offer several sizes and styles for under $10 each. If you're willing to pay a little more, Yoga Hustle offers some fun options for $24 a pop.     Straps     Yoga straps, also called belts, are particularly useful for poses where you need to hold onto your feet but cannot reach them. The strap basically acts as an arm extender. For instance, in pascimottanasana, if you can't reach your feet with your hands in the seated forward fold, you can wrap the strap around the bottom of your feet and hold onto the strap to maintain a flat back instead of slumping forward.     Straps are also great for poses where you bind your hands behind the back (marichyasana, for example). If your shoulders don't allow enough flexibility for the bind, you can use a strap to "connect" both hands without excess strain. And with the strap's help, you can move your hands toward each other over time to make progress toward the full bind.     You probably have something around your house that would work as a strap (like a belt or even a towel) and yoga studios supply them for use during class. That said, if you really want to buy an official version, it's hard to beat the price of YogaOutlet, where you can find straps for under $10.     Bolsters     Bolsters have many uses for yoga students. You can use them in place of a stack of blankets to make seated and forward bending poses more comfortable. You can place them under your knees or your back when reclining for support and passive stretching. They are particularly handy in restorative and prenatal yoga classes. If you take this type of class, the bolsters will be provided. If you want to do restorative yoga at home, it may be worth it to invest in your own bolster.     The are two basic bolster shapes: round and flat (more of a rectangular shape). Flat bolsters tend to be more ergonomic; however, round bolsters can be useful when you want more support or a deeper stretch. It comes down to personal preference.     If you have the option, use both styles in class before you decide which one best suits your home practice. Amazon is the best place to shop for sheer variety and price, but if you want a pretty bolster, check out Hugger Mugger, Inner Space, or Chattra. The prices are in line with the marketplace ($40 to $80), and the designs are bright and beautiful.     Wheels     Yoga wheels are a relatively new prop starting to gain a foothold in the yoga studio. These wheels are roughly 12-inches in diameter and are about four-inches wide. When set upright, you can lie back on the wheel or place a foot or hand on top of the wheel to deepen your stretches and enhance flexibility, slowly rolling the wheel farther as you relax into each stretch. Wheels can also be used in more advanced practices as a way to challenge stability or to offer support during challenging poses.     While it's unlikely that you'll need a yoga wheel as a beginner, you may want to consider a purchase down the line. Most wheels range in price from $40 to $60. Yoga Design Lab, for instance, offers one for $48.

Fecha de Publicación: 29-10-21

Everyone Is Buying Mirrors Right Now

Descripción: Everyone Is Buying Mirrors Right Now     2020 was the year our appearances mattered the least. There were no parties to go to, no fancy dinners, no 500-person weddings. Yet, ironically, wall mirror interest skyrocketed. CB2 reported that mirrors were their most-searched home product, with over 4 million inquiries. 1stDibs saw a double digit increase in mirror searches overall, and a triple digit increase for one in particular: the “Ultrafragola” designed by Ettore Sottsass for Poltronova. (Celebrity owners include Lena Dunham and Bella Hadid.) Meanwhile, New York Design Center says they, too, have “seen an uptick in mirror sales” at their brick-and-mortar outpost, The Gallery at 200 Lex.     The question is, why? Are we masochists who like to gaze upon our unkempt, sweatpant- clad reflection? Are we so vain that we needed “selfie mirrors” to keep our Instagram content flowing? Turns out, we were buying mirrors not because we wanted to look at something—we bought them because we wanted to look away.     For so many of us, life was once spent in several other locations besides our residences: the office, the car, a neighborhood restaurant, a family or friend’s place. But the pandemic shut everything down, rendering us homebound. Suddenly, we were, quite literally and constantly, staring at our walls for months on end. And their blankness began to bug us.     So how to fill them? Art, sure—but art can be intimidating to pick out, and expensive. Mirrors, however, are a simple yet effective way to fill the void. “Mirrors are an accessible and foolproof way to fill in wall space without having to put too much creative energy behind it,” CB2’s product development lead, Andrea Erman, tells Vogue.     Accordingly, it’s not the plain-framed, rectangular wall mirrors that are trending. Rather, it’s more decorative ones that double as aesthetic accents. “They’re statement pieces,” Erman explains. Emily B. Collins, the director of New York Design Center’s The Gallery at 200 Lex, agrees: “Most people that shop The Gallery at 200 Lex aren’t necessarily looking for round mirror to check their reflection or do their makeup in, but to instead act as an alternative to art.”     It’s an interesting return to the mirror’s historical purpose—to reflect the sun, rather than human faces. “Many of the mirrors we sell, from carved 18th century rococo examples to Francois Lembo’s mid-century modern mirrors with rich enamel and hammer decoration, were designed primarily to reflect light,” says Collins. “So as consumers and designers alike have focused more on the appearance of home in the past year, we’ve seen an uptick in mirror sales that reflect the trend antique mirrors were originally designed for—to brighten a space.”     But how do you pick a mirror that meets your room’s needs? Justina Blakeney, lifestyle expert and founder of Jungalow, says that first, you need to figure out its intended functionality. Room feeling too boxy or square? “A floor-length mirror with an arched top can add architectural interest to your space, as it may feel like you’ve added an arched doorway to the room.”     For the cramped apartment dwellers, here’s what she recommends: “If you’re using a mirror to make a space brighter, hang it opposite a window. If you’re using a mirror to make a room feel larger, think about a large-scale mirror that echoes the shape of the room, hang it at eye-level and watch as your room seems to double in size.”     And then there’s the problem that plagues so many of us—the too-blank wall: “If your room is lacking in personality and needs a little somethin’ something’, an ornate or highly decorative mirror can add a lot of flair without making your space feel busy,” she says.     Below, shop a curated selection of our 15 rectangle mirror.     Designed Specifically for Women     The Daily Mirror stands alone as the only major national daily newspaper in Britain ever to be designed specifically for women. Launched in that format, in November 1903, it was a resounding failure, and dissuaded others from similar experiments. Even if its experiment as a ‘high class’ journal for ‘ladies’ only lasted a few weeks from its launch,  it retained a distinctly ‘feminine’ identity for many years, and it continued to attract a much higher percentage of female readers than any other paper until well into the 1930s. It finally shook off this reputation with its tabloid relaunch in the mid-1930s, but high-profile female columnists, such as Dorothy Dix, Marje Proops, Felicity Green, Anne Robinson and Miriam Stoppard have remained a key part of the paper’s appeal to its audience right up to the present day.     Targeting a New Audience     The serious morning newspapers of the Victorian era, such as The Times, had tended to assume that their readership was male, and focused almost entirely on a public sphere dominated by men. The new popular daily papers launched at the turn of the twentieth century, on the other hand, actively sought to maximise their audience, and this meant reaching out in an obvious way to women as well as men. Female readers did not just boost the overall circulation statistics, they also had a special economic importance to the newspaper business. Women were – or were perceived to be – the major spenders of the domestic budget, and hence they became the prime targets for advertisers looking to sell their products. As newspapers came to rely ever more heavily on the revenue from branded advertising, attracting female readers became a financial necessity. In a society in which men and women were still heavily segregated in both work and leisure, editors and journalists were confident that appealing to women meant providing a different sort of content from that aimed at men – the sort of content, in fact, that had fuelled the success of the burgeoning women’s magazine sector throughout the nineteenth century. From the first issue of the Mail, in May 1896, the paper’s owner, newspaper magnate Alfred Harmsworth, asked Mary Howarth, previously a weekly magazine editor, to oversee regular women’s columns providing material on fashion, housewifery and motherhood. Comparisons between the sexes also became a staple of the feature pages, and women – at that time campaigning for the vote and other rights – became more visible in the news columns too. Much, though by no means all, of this content, was ultimately based on conservative gender stereotypes.     The Daily Mail’s success in reaching out to this relatively untapped female market encouraged Harmsworth to think that there was room for a whole newspaper dedicated to women. Accordingly, he launched the Daily Mirror in November 1903 with an all-female staff under the editorship of Mary Howarth. The Mirror’s first issue declared that the paper would not be ‘a mere bulletin of fashion, but a reflection of women’s interests, women’s thought, women’s work’, covering ‘the daily news of the world’ and ‘literature and art ’ as well as the ‘sane and healthy occupations of domestic life’.1 Gendering sections within a newspaper was one thing: gendering the whole paper was another. The mainstream market was not yet ready for a women’s daily newspaper, at least not in this form. The Mirror struggled to find a consistent tone and identity, and seemed caught between being a magazine and a newspaper. As its circulation plummeted, the oval mirror was rescued only when Harmsworth removed the female staff, handed over the editorship to the experienced journalist Hamilton Fyfe, and turned it into an illustrated paper – as which it was a major success, becoming the first daily to rival the readership levels of the Mail. The illustrated Mirror was keen to display the female body: the front page of the first relaunched issue was dominated by a sketch of the Parisian actress Madeleine Carlier, who, tantalisingly, had just won a court case after breaching her contract by refusing to wear an ‘immodest dress’.2 In 1908, the paper claimed that 15,000 women had submitted pictures for its competition to find ‘the most beautiful woman in the world’; each received a certificate of merit.3       The Mirror experiment encapsulated the different aspects of Harmsworth’s attitudes to women. His faith in the potential of the women’s market led him to take extraordinary risks: he lost around ￡100,000 supporting the failing Mirror in its early months. At a time when women had barely gained a foothold in the world of journalism, he demonstrated his willingness to place a great deal of responsibility onto an inexperienced female editorial team, while simply by launching a ‘women’s newspaper’ he continued to challenge assumptions about gender and popular publishing. Nor did the failure of the Mirror seem to alter his perceptions about the female audience. ‘While we learnt there was no room in London for a women’s daily paper,’ recalled Kennedy Jones, Harmsworth’s right-hand-man, ‘we also discovered there was room in a daily paper for more letter press that directly appealed to women.’4 Tom Clarke, another experienced colleague, noted that the setback to the Mirror did not undermine Harmsworth’s ‘faith that the future for popular newspapers and magazines depended on a big woman readership’.5       Gender Stereotypes     On the other hand, Harmsworth shared many of the conventional gender prejudices and stereotypes of his time. He continued to view women as being largely defined by their roles as wives and mothers, and the ‘women’s material’ for his papers was produced on these terms. When he told staff to find ‘feminine matter’, he assumed that his meaning was self-evident: he wanted domestic articles, fashion tips, and recipes. His forward-thinking with regard to the female market was tempered by what the new Mirror editor Hamilton Fyfe described as ‘an old-fashioned doubt’ as to whether women were ‘really the equals of men ’.6 Until the First World War, Harmsworth was sceptical about the need for female suffrage. ‘Sorry to see the outburst of Suffragette pictures again’ he complained to Alexander Kenealy, the editor of the Mirror, in 1912. ‘I thought you had finished with them. Except in an extreme case, print no more of them.’7 It was only when women demonstrated their ability to serve the nation during the war that he changed his mind and became a proponent of women’s suffrage.  Women were also thought to be particularly interested in gossip and celebrity news, and Harmsworth was convinced that most were fundamentally aspirational: ‘Nine women out of ten would rather read about an evening dress costing a great deal of money – the sort of dress they will never in their lives have a chance of wearing – than about a simple frock such as they could afford’.8 Editors and journalists firmly believed that women were particularly keen on the vicarious enjoyment that could be obtained by reading about wealthy lifestyles and luxurious goods, and the steady rise of celebrity culture across the century was partly driven by the desire to cater for the female audience.     These traditional gender stereotypes were even more evident under the proprietorship of Alfred Harmsworth’s brother Harold, Lord Rothermere, between 1914 and 1936. Although the Mirror enthusiastically accepted the enfranchisement of (most) women over 30 in 1918, ten years later Rothermere became preoccupied that the proposed equalisation of the franchise at age 21 would lead to lots of young women voting for the Labour Party, considerably weakening the forces of conservatism. ‘Stop The Flapper Votes Folly - This is Not The Time For Rash Constitutional Innovations’ declared the paper in April 1927, and, like Rothermere’s other paper, the Mail, resisted the proposal until it sailed through the House of Commons the following year.9  Rothermere also became sympathetic to the hyper-masculine fascist dictators, Mussolini and Hitler, and in 1934 swung the arched mirror (and the Mail) behind Oswald Mosley’s British Union of Fascists. For all the press attention on the achievements and freedoms of the ‘modern young women’ of the 1920s and 1930s, underlying attitudes to gender remained resilient.

Fecha de Publicación: 29-10-21

Circular Knitting Machine

Descripción: Circular Knitting Machine     The term knitwear includes two main textile techniques, weft and warp knitting (Spencer, 2001; Weber and Weber, 2008) (Table 7.1). After weaving, it is the most common method of manufacturing textile fabrics. Because of the interlooped structure of the knitted fabric, the properties are completely different to woven fabrics. The difference in weft and warp knitting originates in the way the needles move during the production and in the way the yarn is supplied. Weft knitting is a one fibre technique, which means that only one fibre is needed to build the stitches. The needles are moved separately, whereas the warp knitting needles are moved simultaneously. Therefore, all needles need the fibre material at the same time. For this reason, the yarn is supplied with the help of warp beams. The most important knitwear fabrics are circular knitted, warp knitted, flat-knitted fabrics and fully-fashioned fabrics.     The specific features influencing yarn delivery on large-diameter single jersey circular knitting machine are high productivity, continuous knitting and a great number of simultaneously processed yarns. Some of these machines are equipped with a striper (yarn guide exchange), but only a few enable reciprocated knitting. Small diameter hosiery machines have up to four (or occasionally eight) knitting systems (feeders) and an important feature is the combination of rotary and reciprocal movement of the needle bed (beds). Between these extremes are the middle diameter machines for ‘body’ technologies.     Figure 4.15 shows the simplified yarn supply system on a large-diameter double jersey circular knitting machine. Yarns (1) are brought from the bobbins (2), passed through the side creel to the feeder (3) and finally to the yarn guide (4). Usually the feeder (3) is equipped with stop-motion sensors for yarn checking.     The knitted textile structure evolves from loops that are intermeshed row after row. The needle hook is responsible for the formation of a new loop with the supplied yarn. During the upward movement of the needle in order to catch the yarn to build a new loop, the old loop slides down the needle (Fig. 7.20). This causes the opening of the needle. The needle hook is now open to catch the yarn. The newly built loop is drawn through the old loop from the previous knitting circle. During this movement, the needle is closed. Now the old loop can be released as the new loop remains in the needle hook.     The creel of the knitting machine controls the placement of yarn packages (bobbins) on all machines. Modern large-diameter circular machines use separate side creels, which are able to hold a large number of packages in a vertical position. Floor projection of these creels may differ (oblong, circular, etc.). If there is a long distance between the bobbin and the yarn guide, the yarns may be threaded pneumatically into tubes. The modular design facilitates the changing of the number of bobbins where required. Small-diameter machines with a smaller number of cam systems use either side creels or creels designed as integral to the machine.     Modern creels make it possible to use double bobbins. Each pair of creel pins is centred on one thread eye (Fig. 4.16). The yarn of a new bobbin (3) may be linked to the end of the previous length of yarn (1) on bobbin (2) without stopping the machine. Some of the creels are equipped with systems for blowing off dust (fancreel), or with air circulation and filtration (filtercreel). The example in Fig. 4.17 shows the bobbins (2) in six rows, closed in a box with internal air circulation, provided by fans (4) and tubes (3). A filter (5) clears dust from the air. The creel can be air-conditioned. When the machine is not equipped with a striper, this can be supplied by yarn exchange on the creel; some systems enable the knots to be positioned in the optimal area of the fabric.     The sinker is also important for the production of knitwear (Fig. 7.21). It is a thin metal plate, which can have different shapes. Each sinker is positioned between two needles and its main purpose is to help build the loop. Furthermore, it holds the loops that were formed in the previous circle down when the needle moves upwards and downwards to build the new loops.     Both single set und double set machines also exist as Jacquard machines, which are needed for special designs. In these machines, the movement of each needle can be controlled from each cam. Common products that are produced with circular knitted fabric are T-shirts. For production, nearly every material can be used. The form varies from filament to staple fibre yarn. For special purposes, also monofilaments and wires are used.     Machines that possess just one set of needles are only able to produce plain- knitted structures (Fig. 7.22). In these structures, one side of the fabric shows right loops and the other side rib loops. The following picture shows the loop structure of a plain knitted fabric.     Yarn length control (positive feeding), when not used for patterned fabric knitting, must enable different yarn lengths to be fed into courses in different structures. As an example, in Milano-rib knit there is one double-faced course (1) and two single-faced (2), (3) courses in the repeated pattern (see Fig. 4.18). As a double-faced course contains twice as many stitches, the yarns must be fed at approximately twice the length per machine revolution. This is the reason why these feeders use several belts, individually adjusted for speed, whilst feeders using yarns of the same length are controlled by one belt. The feeders are usually mounted onto two or three rings around the machine. If a configuration with two belts on each ring is used (Fig. 4.5), yarns can be fed simultaneously at four or six speeds.     The interlock structure was derived from the rib structure (Fig. 7.23). For the production of this kind of fabric, two needle sets are necessary and the needles need to be arranged in a different way. The loops are formed in two different directions (Fig. 7.24). The result is a fabric with smooth surfaces on both sides. This is due to the right loop structure on each side. The rib structure shows rib loops on both sides of the fabric. These fabrics can be produced using loop- or needle transfer.     Normally, the machine for flat knitting has two stationary beds that are arranged in an inverted V formation. These beds possess tracks in which the needles can be moved. The fabrics produced by a flat-knitting machine are mainly coarse and intensely patterned. An advantage of flat-knitted products is that vertical and horizontal stationary threads can be integrated into the fabric. In this case, the fabric serves to fix these threads. Fabrics produced this way can be used for technical textiles. Common products produced on conventional flat knitting machines are outer-wear, such as jumpers that consist of staple fibre yarns.     In small diameter circular knitting machine spare parts as well as flat bed knitting machine, generally one yarn is fed at a time to the needle for loop formation through the desired feeding system or feeder. However, in medium to larger diameter circular knitting machines, more number of feeders are arranged/accommodated at regular intervals for supplying more number of yarns to the needles simultaneously for achieving higher production. Each feeder produces separate course in each revolution of the machine. Production can also be increased by increasing the machine speed. But there is a limitation in increasing the machine speed as vibration, jerk, noise, yarn breakage and ultimately power consumption increase to a great extent at higher speed. So instead of increasing the machine speed, attempts are being made to increase the number of feeders in the machine. Machines are available with up-to 152 feeders for 42 inch diameter . Number of feeders on a circular machine depends on machine diameter, type of machine (plain, rib etc.), patterning facility and machine gauge. Number of feeder is mostly even number.     Traditionally, loop cut circular knitting machine were used for producing pantyhose . In 2002 Karl Mayer introduced the RDPJ 6/2 warp knitting machines for making seamless, jacquard patterned tights and fish-net pantyhose. Karl Mayer’s MRPJ43/1 SU and MRPJ25/1 SU jacquardtronic raschel knitting machines can manufacture pantyhose with relief-like and lace patterns . Other developments in machinery were aimed to increase the efficiency, productivity and quality of pantyhose .     Matsumoto et al. have also carried out some studies on the control of sheerness in pantyhose fabrics . They produced an experimental hybrid knitting system composed of two experimental covering machines and a circular knitting machine. Each covering machine had two sections of single covered yarn. The pantyhose samples were knitted under a constant condition, while the single covered yarns were produced by controlling the covering levels of 1500 turns per metre (tpm) and 3000 tpm in nylon yarn with a draw ratio of 2 = 3000 tpm/1500 tpm for the core polyurethane yarn. The lower covering level produced a higher sheer in the pantyhose. Four different pantyhose samples were produced with different covering levels of tpm in different leg regions. The results showed that the aesthetics and sheerness of pantyhose fabric were greatly influenced by changing the covering level of the single covered yarn in the leg parts, and the mechanical hybrid system could improve the aesthetic properties of pantyhose fabric.     Weft knit fabrics are produced predominantly on cut pile circular knitting machine. The simplest of the two major weft knitting machines is a jersey machine. Generally, the terms circular knit and plain knit refer to jersey goods. The loops are formed by knitting needles and the jersey machine has one set of needles. Typical fabrics are hosiery, T-shirts, and sweaters.     Rib knitting machines have a second set of needles at approximately right angles to the set found in a jersey machine. They are used for the production of double-knit fabrics. In weft knits, design effects can be produced by altering needle movements to form tuck and miss stitches for texture and color patterns, respectively. Instead of a single yarn, several yarns can be used in the production of these structures. This increases the design possibilities.

Fecha de Publicación: 29-10-21

Towards understanding the improved stability of palladium supported on TS-1 for catalytic combustion

Descripción: Towards understanding the improved stability of palladium supported on TS-1 for catalytic combustion     A novel Pd supported on TS-1 combustion catalyst was synthesized and tested in methane combustion under very lean and under highly humid conditions (

Fecha de Publicación: 29-10-21

State of the art baby strollers

Descripción: State of the art baby strollers     The current work is an attempt to design and fabricate an ergonomic baby stroller with the latest state of the art features. A review on the design of baby strollers in the previous years was done ranging from the year 1980 to 2014. Based on the review it was found out that the idea of a foldable frame emerged since the early 1980s where people started to prioritize space saving. The use of electronics devices in strollers has not been properly implemented due to the bulkiness of the battery and the clutter mess of wires. Infant’s safety and comfort has always been the number one priority by designing a seat that is contoured to a baby’s spine, ultimately making baby’s growth much safer. In lieu of the current work, a harmonious prototype design was fabricated using Rapid Prototyping system. The idea was to fuse the usage of electronics with the stroller by inventing modular “plug and play” attachment devices that provide customizability to baby strollers which include headlights and cooling fan attachments. Besides that, the latest state of the art designs of the ergonomic baby stroller such as a ventilated back rest, on-board rocking baby chair, bidirectional push handle with ergonomic grip support, frame with integrated hooks for storing different types of “plug and play” attachments and hooks for attaching the foldable stroller to a typical standard shopping cart were implemented.     Baby strollers are increasingly popular among the generations of baby boomers. Despite the popularity, the state of innovations in the design of baby strollers has plateaued in recent years. This article illustrates the evolution of the design of baby strollers from the year 1980 to 2014. Based on the review, it was found out that the idea of a foldable frame emerged since the early 1980s where users started to prioritize space saving. The use of electronics devices in strollers has not been properly implemented due to the bulkiness of the battery and the clutter mess of wires. In lieu of the current work, the idea was to fuse the usage of electronics with the 3 in 1 stroller by inventing modular “plug and play” attachment devices that provide customizability to baby strollers that include headlights and cooling fan attachments. The possibilities of various types of attachments will be endless.     There is significant design knowledge of baby strollers since 1980 to 2014, in which, is reviewed to identify flaws and advantages of each design. There are many methods used to transport babies around and it varies among different cultures and countries. The idea of infant transportation emerges as multitasking and convenience becomes a necessity in parent ’s everyday lives. Having an infant transportation made it easier for parents as babies are no longer needed to be carried by the parents or sit on top of their parents’ back. Babies that are lacking the ability to support their head still and upright are usually carried with slings. Cradleboards are popular among Native Americans to keep babies secure and comfortable (Garrett, McElroy, & Staines, 2002).     The early stroller was developed by William Kent in 1733. William Kent designed the pockit stroller to be clam shaped and it was richly decorated and meant to be driven by a small animal such as a goat. Benjamin Potter Crandall saw the potential of this and was the first person in America to sell baby strollers commercially in 1830s. His son, Jesse Armour Crandall further improves the design by adding brake to carriages, designing a frame that is foldable, and a frame that receives devices such as an umbrella (Amato, 2004).     Baby strollers that were built in the old days were usually made of wood and wicker with brass joint as seen in Figure 1. Those strollers are sometimes heavily decorated with carvings making it as a canvas for the work of art. Baby strollers then are usually named after a royal family such as Balmoral. In 1889, William Richardson design the first reversible baby stroller where the pusher can choose to face the baby or to face away from the baby. In order for this to be possible, the seat of the stroller is reversible. Richardson designed each wheel to move separately so the stroller can be easily be maneuvered. In 1920, prams are very popular with the advantage of larger wheels and the implementations of braking system into prams. The prams are deeper so the baby will have difficulty to climb out. The frame is also sturdier, lighter, and safer thanks to the improvement of designs over the years (Amato, 2004; Wall-Scheffler, Geiger, & Steudel- Numbers, 2007). In 1965, Owen Maclaren designed a light stroller where light material such aluminium is used as the frame. His design was then mass produced and more light strollers are available for people worldwide (Wall-Scheffler et al., 2007). In 1970, a more basic baby strollers was preferred that has a detachable seat (Amato, 2004; Wall-Scheffler et al., 2007).     The design as seen in Figure 2(a) is invented by Kenzo Kassai. The baby stroller can be collapsed down but increases the size length forward. The stroller has a handle which can be pivoted to change the direction, either forward facing position or a back facing position with respect to the baby sitting in the stroller or carriage (Kassai, 1980). Forward facing push type is where the person pushes the carriage is facing the back of the baby in the stroller, and the back facing push type is where the person pushes the carriage views the face of the baby (Kassai, 1980).     Figure 2(b) shows a design by Shinroku Nakao, Kouchi Kobayashi, and Kazao Moriya. It is stated as an ornamental design which similar to any other stroller in terms of practicality, but visually appealing (University of Cambridge, 2015). The design consists of a fixed chair, with a canopy that folds outwards. The front wheels have no rotating mechanism, which makes maneuvering a little less convenient (Nakao, Kobayashi, & Moriya, 1980).     The invention presented in Figure 3(a), by Henry Fleischer shows a collapsible frame travel stroller. The collapsible frame uses slider slots and pin joint mechanism. The handle can be rotated to suit the user. The handle also pivots forward, which doubles as a mechanism to engage the folding action. The wheels are not rotatable and use simple axel to keep the wheels in place (Fleischer, 1981).     As seen in Figure 3(b), the stroller design made by John P. Ettridge has a lower seat position where the toddler facing forward. The handle, seat, frame and undercarriage are interconnected by a linkage so that the components fold down towards the wheels as the wheels move towards each other (Ettridge, 1981). The design also has a footrest for the toddler. The design has a locking mechanism which keeps the stroller erected. The locking mechanism is conveniently placed at reachable height when standing.     The stroller in Figure 4(a) has an adjustable backrest collapsible stroller that has a stroller frame formed in two matched side half-frames each whereof comprises three tubular elements, constituting respectively a rear leg, front leg and a stroller pushing arm. It was designed by Pietro Giordani. The construction of baby strollers of the collapsible or fold down type having an adjustable backrest (Giordani, 1982).     Figure 4(b) shows a mechanism for adjusting the height of the handles of a pocket stroller , consists of two telescopic tubes in which, one sliding in the other and the handle connected to one tube. The spring with two arms with a V-shape fixed on the inside the inner tube. It was designed and drawn by Giuseppe Perego. The handle can be secured in place with notches that has different levels of elevation (Perego, 1982a).     Another design also made by Giuseppe Perego which enables the stroller to be folded from side to side. It is made possible by placing linkages that holds the left and the right frames together as shown in Figure 4(c). The seat has to be made of soft material in order to be folded properly. This design features a rotatable front wheels and lockable back wheels (Perego, 1982b).     The stroller designed by Maurice-Claude Duvignacq has an inclinable support for the seat, connected to a frame which can be folded as shown in Figure 5(a). The seat is made of sling-like manner, permanently connected to the frame and it is reversible. The hind legs are able to articulate and be fold to form a flat folded position (Duvignacq, 1983).

Fecha de Publicación: 29-10-21

Paper Bag Making Machine: The Ultimate Guide

Descripción: Paper Bag Making Machine: The Ultimate Guide     I know you’re looking for a paper bag making machine that’s why you are here.     Maybe, you want to be a paper bag wholesaler or make branded designs for your retail business.     The truth is, paper bags are dear packages for food vendors, retailers, and even manufacturers.     But, how can you venture in this business?     Or, what is the most cost effective way of making paper bags?     Today’s guide debunks the facts behind paper bag making process and machine such basic definition, working principle, classification, design, technical specification, etc.     So stay with me to be an expert in paper bag making industry.     Let’s begin with some facts.     Apart from the other devastating problems associated with plastic bags, did you know that synthetic bag manufacturers produce about one trillion of those bags in a year globally?     Did you also know that it takes one thousand years for a single bag of this kind to biodegrade?     Yes, that’s the scariest part of it.     Due to that, most governments are imposing bans on these carriers.     The alternative?     A mega-shift to more environmentally friendly paper bags.     So basically a plastic shopping bag making machine is a state of the art machine that gathers, folds, stamps, and processes papers to produce clean paper bags.     These paper bags are for use in the packaging of goods in various industries such as food, pharmaceutical products, grocery, and baking industries.     The plastic t shirt bag making machine come in various configurations depending on the type of bags for final production.     Therefore, the paper bag making system should be versatile enough to cater to the dynamics in the paper bag manufacturing.     Today different paper bag making stakeholders such as the machine manufacturers, raw material suppliers face a lot of shifting customer demands, government regulations, changing prices, etc.     It’s thus good only if the machine can afford the manufacturer some relief.     For that matter, it means that you need to know all the factors related to the paper bag making the machine.     Besides, all the accompanying dynamics before making a purchase.     Luckily, I have compiled all that you need to know in this article.     The history of development and use of eco friendly carry bags manufacturing machine dates back to the 19th century.     During these early stages, the systems were simple and mechanically operated.     With that, we move to the next step.     Take a moment to reflect on the occasions you use a paper bag.     Indeed paper bag forms a vital integral in our lives today.     From simple uses such as carrying random goods to more complex ones such as in pharmaceuticals to wrap up drugs.     One thing is for sure.     Without paper biodegradable bags manufacturing machines, we would be missing a significant aspect of our lives.     Surely, there are numerous uses of paper bag making the machine.     Subsequently, the produced paper bags can be classified under different distinct categories depending on their purposes.     Some of the major classifications are:     · Bread paper bags     Usually, if you go to the bakery store or supermarkets, you will find the bread wrapped up in brown paper bags and displayed.     There is a significant reason why grocery stores do this kind of wrapping.     Now, most of you might have had guesses about the reasons why the bakery stores bread in paper bags.     Is it for aesthetical values to make it look fancy so that you get wanting to buy some?     Or, is it to make you believe about the degree of freshness of the loaf?     Some firmly think it’s solely for being environmentally conscious.     Trust me;     The bread paper bag covers serve much more values than those reasons above for maintaining more prolonged periods of freshness.     That’s right;     The paper bag plays a significant role in helping to keep the bread stay fresh for an extended period — this how it works.     The paper bags especially the open ones provides a path for the continuous circulation of air in and out of the bread.     The constant air circulation would then make the bread to form a crust which is also vital for the maintenance of freshness.     The bread crust formed on the outer layer of the bread may seem dry but beneath that crust, lies a moist and sweet food.     For that matter, it remains fresh for an extra three to four days.     On the contrary, if you do the same packaging in a plastic bag, this what will undoubtedly happen.     The plastic bag will retain moisture in the bread thereby keeping the whole crust and bread soaked in moisture thus becoming mushy.     As a result, the dough will likely give you two or one day window for you to consume it a failure of which it loses taste.     For that matter, the best packaging for your bread would undoubtedly be the one.     It gives you freedom for consumption for at least within 3-4 days.     More extended consumption period is what paper bag presents you.     · Shopping paper bags     Paper bags are suitable products for easy carrying to various places.     One of these places should be the market or store.     Paper bags are very much ideal for packing and fitting your goods when shopping.     Hence, if you need a place to stack up and pack all your shopping, then paper bags would serve you dearly.     Another thumbs up for paper bags is because they are open to customization to meet the customer’s requirements.     Such kinds of specialization could be the production of different sizes, colors, and branding.     In fact in the present, most countries around the globe have banned the use of plastic bags for shopping purposes.     As a result, a paper bag would dearly serve your shopping needs.     · Clothing paper bags     Do you always feel bothered with packing your clothes in a heavy traveling bag?     Are you tired of carrying your clothing in heavy bags everywhere you go?     We have a solution for you.     Over recent years, the clothing bags have proved to be very simple to use, flexible, convenient and light in weight.     Indeed am very sure everyone will one time encounter these kinds of new bags.     Besides, they come in different sizes giving you options for selecting the one that satisfies your needs.     Above all, they comprise of different types of materials such as black cardboard paper, white cardboard, coated paper, kraft paper or special paper.     Again, the different kinds of material variety give you the freedom to select your favorite material.     Notably, this class of paper bags is also much appealing to the eye as it’s possible to print them using different customized models such as logos, pictures, etc.     These customizations can as well help you promote your brand or company.     · Leisure paper bags     If you’re not aware, some brands of paper bags are solely suited for leisure purposes.     Today, several ladies carry specially designed paper bags when going to special occasions such as a walk, date, shopping or parties.     A survey conducted in Tokyo revealed that most teenagers prefer carrying leisure paper bags whenever going for a leisure walk to standard backpacks or even briefcases.     These leisure bags have got beautiful printable designs with different portrays to look good。     The custom printing and designs would help you reach a more diversified market.     Do you visit the nearest gymnasium to your house     Then a leisure paper bag is suitable for you to carry along your fitness clothing, shoes, and even a water or energy drink bottle.     · Fruit paper bags     When it comes to the handling of fruits, a paper bag does so many functions.     Most common roles of a fruit paper bag are:     i. Packing fruits or carrying fruits from the market.     I trust whenever you go to the market to buy fruits of your choice, the attendant places them in a paper bag.     The packaging style is vital to help you carry the fruits along back home without worrying about wherever to put them.     Furthermore, the paper bags are very hygienic to shield them from getting contaminated with germs or harmful chemicals.     ii. Ripening fruits     Have you ever been in a stressful hurdle of trying to get fruits to ripen faster?     Continue reading…     It’s so much simpler to get fruits to ripen up. You only need to have a paper bag by your side.     Then do the following.     Place the fruits in a paper bag.     Leave the top of the paper bag slightly open.     Wait for a few days for the fruit to ripen. That’s it.     The technique behind this innovation is that most fruits release small quantities of ethylene gas.     Since you left the paper bag slightly open, the emitted ethylene gas doesn’t escape but in turn, gets reabsorbed by the fruits.     Continuous reabsorption of the ethylene gas initiates several physiological changes to the fruits.     The most notable one is accelerating the ripening process of the fruits.     Though it’s not easy to accurately estimate the rate of ripening of the fruits using this method.     What researchers have proven is that ripening via paper bags takes shorter time compared to natural maturation.     However, you need to ensure that the paper bag isn’t tightly closed because by doing that the fruits may instead rot.     How?     Tightly or thoroughly closed paper bag would leave no space for emission of other fruit emissions majorly moisture.     Apart from causing the rotting effect, the humidity also facilitates the growth of mold in the fruits. The same results will occur if you use plastic bags.     · Food paper bags     Unquestionably paper bags form the foundation of most food packaging needs because other than from being eco-friendly, they’re economical, variety and flexible.     On the economic perspective, if you’re dealing with a newly established business, then food paper bags is right for you to enable you to save on expenses.     Besides, you can custom print the bags to make you give your company the correct exposure you need to gain ‘muscle strength’ in the market.     Amongst a variety of diverse range of paper bags, the most popular ones include sulfite and kraft.     The food paper bags are always coated free and non-treated to reduce the initial costs     The bags are suitable for packing low – wet or moisture-containing food.     For that matter, you can use these bags for packing takeaway foods such as cookies, pastries, sandwiches, muffins, rolls, chips, etc.     They are specially designed to keep the food always fresh and crispy without it losing its taste.     Besides, the bags come in a variety of sizes.     Some of the typical categories of food paper bags are:     Coffee bags – they are available in different content carrying capacity such as 0.5 lb,2lb, 5 lb, etc. to make them even more effective, they are grease resistant.     Candy/bakery bags –perfect for a variety of foods.     Bread bags     Glassine bags     Cookie and sandwich bags – these are moisture and grease resistant.     Chicken carry bags     · Drug packaging bags     The pharmaceutical industry is a critical field that hugely relies on the use of paper bags.     The environmentally suitable and recyclable paper bags are often used to pack almost everything from prescriptions, dosing to the cards issued out.     These bags can be printed in many colors up to four and are available in different sizes depending on the application for use.     Other forms of customization are also familiar with these paper bags to assist you in branding and to advertise your business and the services you offer.     The bags are available in different raw materials including white or brown kraft, clay coated gloss.     Pharmacies, veterinary clinics, hospitals, and other health centers are just a few areas which utilize the need for paper bags.     Since packaging is an integral service in the pharmaceutical industry, it’s always thoroughly regulated depending on the country of origin of the bags.     Some of the standard measures put in place for the production of paper bags are:     Assurance of the patient wellbeing,     Confirmation of the efficacy of the drugs for the intended shelf life     Sufficient documentation of all the materials and processes of production     Regulation of any chances of contamination of the drugs by the packagings.     Avoidance of microbial contamination.     Control of quality degradation of the drugs by moisture, heat, etc.     The smaller packs of drugs are usually precisely measured and placed into smaller original paper bag packages.     Over the counter drugs are also the primary beneficiary of the paper bags     The packaging contains all the relevant usage information including the dosage.     These drug paper bags are usually resistant to tamper as well as having the child resistant properties.     Those are some of the main areas and applications where you may use the paper bag making machines.     With that, we should move to the next segment of our discussion. Shall we?     Chapter 3: Classification of Paper Bag Making Equipment     Due to the versatility nature of the paper bag making machines, they are available in different types.     Interestingly, each type of machine does a specific job of producing a single variety of bag since each can only work with a particular kind of raw material.     These machines belong to the following categories:     a) Fully Automatic Paper Bag Making Machine     A fully automatic paper bag making machine is a unique brand of device.     Indeed it’s the modern machine that manufacturers developed to solve problems earlier associated with the other systems.     For this one, almost all its operations are automated to work efficiently.     This kind of operational basis makes it suitable for accurately gathering the raw materials, folding them, stamping and finally processing the elements at high speed.     This machine is built using leading modern technology to optimize its performance.     Talking of fully automatic machine means that most of it’s provisions are computer driven.     Taking for example:     The machinery has got a touch screen and PC control system indicating that the machine shows the real time progress of the work.     Programmed counting system- the machine has got an automatic counting provision. So once the user inputs the number, the device ejects out the right quantity of paper bags set from the system.     Color mark tracking system – this function ensures that the paper bags cutting is precise in a form pattern after printing.     Dense designed mechanical transmission -this kind of design ensures that the material is stably passed, improves the mechanical properties and producing clean paper bags with superior appearance.     Furthermore, these kinds of machines are entirely automatic.     It only requires an operators involvement to refill the raw materials, collect the end products and key in the commands.     You need to know that even the fully automatic machines vary depending on the type of paper bag they process.     For example, we have got; medicine paper bag, grocery bag, butter paper bag, etc. as earlier mentioned.     Therefore, it implies that you don’t need to pick on any, but you select depending on the type of container you wish to produce.     To make this machine suitable and usable by all, they come in different sizes, ie.     Large, medium and small.     Therefore, you have got the freedom to purchase the best scope that you require.

Fecha de Publicación: 29-10-21

How a laser printer works

Descripción: How a laser printer works     Have you ever tried writing with a beam of light? Sounds impossible, doesn't it, but it's exactly what a CO2 laser printer does when it makes a permanent copy of data (information) from your computer on a piece of paper. Thanks to sci-fi and spy movies, we tend to think of lasers as incredibly powerful light beams that can slice through chunks of metal or blast enemy spaceships into smithereens. But tiny lasers are useful too in a much more humdrum way: they read sounds and video clips off the discs in CD and DVD players and they're vital parts of most office computers printers. All set? Okay, let's take a closer look at how laser printers work!     Laser printers are a lot like photocopiers and use the same basic technology. Indeed, as we describe later in this article, the first laser printers were actually built from modified photocopiers. In a photocopier, a bright light is used to make an exact copy of a printed page. The light reflects off the page onto a light-sensitive drum; static electricity (the effect that makes a balloon stick to your clothes if you rub it a few times) makes ink particles stick to the drum; and the ink is then transferred to paper and "fused" to its surface by hot rollers. A laser printer works in almost exactly the same way, with one important difference: because there is no original page to copy, the laser has to write it out from scratch.     Imagine you're a computer packed full of data. The information you store is in electronic format: each piece of data is stored electronically by a microscopically small switching device called a transistor. The printer's job is to convert this electronic data back into words and pictures: in effect, to turn electricity into ink. With an inkjet printer, it's easy to see how that happens: ink guns, operated electrically, fire precise streams of ink at the page. With a 30W CO2 laser printer, things are slightly more complex. The electronic data from your computer is used to control a laser beam—and it's the laser that gets the ink on the page, using static electricity in a similar way to a photocopier.     When you print something, your computer sends a vast stream of electronic data (typically a few megabytes or million characters) to your laser printer. An electronic circuit in the printer figures out what all this data means and what it needs to look like on the page. It makes a laser beam scan back and forth across a drum inside the printer, building up a pattern of static electricity. The static electricity attracts onto the page a kind of powdered ink called toner. Finally, as in a photocopier, a fuser unit bonds the toner to the paper.     Millions of bytes (characters) of data stream into the printer from your computer.     An electronic circuit in the printer (effectively, a small computer in its own right) figures out how to print this data so it looks correct on the page.     The electronic circuit activates the corona wire. This is a high-voltage wire that gives a static electric charge to anything nearby.     The corona wire charges up the photoreceptor drum so the drum gains a positive charge spread uniformly across its surface.     At the same time, the circuit activates the laser to make it draw the image of the page onto the drum. The laser beam doesn't actually move: it bounces off a moving mirror that scans it over the drum. Where the laser beam hits the drum, it erases the positive charge that was there and creates an area of negative charge instead. Gradually, an image of the entire page builds up on the drum: where the page should be white, there are areas with a positive charge; where the page should be black, there are areas of negative charge.     An ink roller touching the photoreceptor drum coats it with tiny particles of powdered ink (toner). The toner has been given a positive electrical charge, so it sticks to the parts of the photoreceptor drum that have a negative charge (remember that opposite electrical charges attract in the same way that opposite poles of a magnet attract). No ink is attracted to the parts of the drum that have a positive charge. An inked image of the page builds up on the drum.     A sheet of paper from a hopper on the other side of the printer feeds up toward the drum. As it moves along, the paper is given a strong negative electrical charge by another corona wire.     When the paper moves near the drum, its negative charge attracts the positively charged toner particles away from the drum. The image is transferred from the drum onto the paper but, for the moment, the toner particles are just resting lightly on the paper's surface.     The inked paper passes through two hot rollers (the fuser unit). The heat and pressure from the rollers fuse the toner particles permanently into the fibers of the paper.     The printout emerges from the side of the copier. Thanks to the fuser unit, the paper is still warm. It's literally hot off the press!     Until the early 1980s, hardly anyone had a personal or office computer; the few people who did made "hardcopies" (printouts) with dot-matrix printers. These relatively slow machines made a characteristically horrible screeching noise because they used a grid of tiny metal needles, pressed against an inked ribbon, to form the shapes of letters, numbers, and symbols on the page. They printed each character individually, line by line, at a typical speed of about 80 characters (one line of text) per second, so a page would take about a minute to print. Although that sounds slow compared to modern 60W CO2 laser printers, it was a lot faster than most people could bash out letters and reports with an old-style typewriter (the mechanical or electric keyboard-operated printing machines that were used in offices for writing letters before affordable computers made them obsolete). You still occasionally see bills and address labels printed by dot-matrix; you can always tell because the print is relatively crude and made up of very visible dots. In the mid-1980s, as computers became more popular with small businesses, people wanted machines that could produce letters and reports as quickly as dot-matrix printers but with the same kind of print quality they could get from old-fashioned typewriters. The door was open for laser printers!     Fortunately, laser-printing technology was already on the way. The first fiber laser printers had been developed in the late 1960s by Gary Starkweather of Xerox, who based his work on the photocopiers that had made Xerox such a successful corporation. By the mid-1970s, Xerox was producing a commercial laser printer—a modified photocopier with images drawn by a laser— called the Dover, which could knock off about 60 pages a minute (one per second) and sold for the stupendous sum of $300,000. By the late 1970s, big computer companies, including IBM, Hewlett-Packard, and Canon, were competing to develop affordable laser printers, though the machines they came up with were roughly 2–3 times bigger than modern ones— about the same size as very large photocopiers.     Two machines were responsible for making laser printers into mass-market items. One was the LaserJet, released by Hewlett-Packard (HP) in 1984 at a relatively affordable $3495. The other, Apple's LaserWriter, originally cost almost twice as much ($6995) when it was launched the following year to accompany the Apple Macintosh computer. Even so, it had a huge impact: the Macintosh was very easy to use and, with relatively inexpensive desktop-publishing software and a laser printer, it meant almost anyone could turn out books, magazines, and anything and everything else you could print onto paper. Xerox might have developed the technology, but it was HP and Apple who sold it to the world!     Dipping into the archives of the US Patent and Trademark Office, I've found one of Gary Starkweather's original laser-printer designs, patented on June 7, 1977. To make it easier to follow, I've colored it in and annotated it more simply than the technical drawing in the original patent (if you wish, you can find the full details filed under US Patent 4027961: Copier/Raster Scan Apparatus).     What we have is essentially a laser scanning unit (colored blue) sitting on top of a fairly conventional, large office photocopier (colored red). In Starkweather's design, the laser scanner slides on and off the glass window of the photocopier (the place where you would normally put your documents, face down), so the same machine can be used as either a 30W fiber laser printer or a copier—anticipating all-in-one office machines by about 20 –25 years；     I used to share an office with someone who refused to share our office with a laser printer; we had to move our machine into a closet and keep the door shut tight. This kind of worry is far from rare, but is it simply superstition? As we saw up above, laser printers use a type of solid ink called toner, which can be a source of dusty, fine particulates (remember that sooty particulates, released by such things as car tailpipes, are one of the more worrying ingredients in urban air pollution). One recent study found some printers emit nearly 10 billion particles per printed page (although it's important to note that the type and quantity of particle emissions vary widely from model to model). They also produce volatile organic compounds (VOCs) and a gas called ozone (a very reactive type of oxygen with the chemical formula O3), which is toxic and, at high enough concentrations, produces a variety of health impacts. Thankfully, ozone is transformed into ordinary oxygen (O2) relatively quickly inside buildings.     Do printers and copiers present any risk to our health? A few scientific studies have been done; although the results are mixed, they do seem to suggest it's well worth taking precautions, such as placing your printer well away from your workstation, if you use it a great deal, and ensuring good ventilation. You should also take great care when changing toner cartridges or handling empty ones. You'll find a list of recent studies in the further reading below.

Fecha de Publicación: 29-10-21

Design and Analysis of a Novel Tension Control Method for Winding Machine

Descripción: Design and Analysis of a Novel Tension Control Method for Winding Machine     The filament winding technique has evolved in recent decades moving from classical lathe-type towards winding with an increased number of degrees of freedom using more complex equipment. These advancements complicate the selection of an optimum toroid winding machine set-up for the realization of particular winding methods and correlating part designs. This is further complicated by the variety of approaches. In order to investigate existing equipment technologies regarding feasibility, operational and economic aspects, different filament winding equipment is established in an experimental environment. Thereby advantageous solutions can be assigned to particular winding methods and the selection of appropriate filament winding equipment is facilitated.     Filament winding has emerged as the main process for carbon fiber reinforced plastic (CFRP) fabrication, and tension control plays a key role in enhancing the quality of the winding products. With the continuous improvement of product quality and efficiency, the precision of the tension control system is constantly improving. In this paper, a novel tension control method is proposed, which can regulate the fiber tension and transport speed of the winding process by governing the outputs of three different driven rollers (the torque of the unwind roll, the torque of the magnetic powder brake roller, and the speed of the master speed roller) in three levels. The mechanical structures and dynamic models of the driven rollers and idle rollers are established by considering the time- varying features of the roller radius and inertia. Moreover, the influence of parameters and speed variation on fiber tension is investigated using the increment model. Subsequently, the control method is proposed by applying fiber tension in three levels according to the features of the three driven rollers. An adaptive fuzzy controller is designed for tuning the PID parameters online to control the speed of the master speed roller. Simulation is conducted for verifying the performance and stability of the proposed tension control method by comparing with those of the conventional PID control method. The result reveals that the proposed method outperforms the conventional method. Finally, an experimental platform is constructed, and the proposed system is applied to a gear toroidal winding machine. The performance and stability of the tension control system are demonstrated via a series of experiments using carbon fiber under different reference speeds and tensions. This paper proposes a novel tension control method to regulate the fiber tension and transport speed.     High modulus carbon fiber is an excellent industrial material, which is widely used in several fields such as satellite supporting cylinder, shells of rocket engine, and solar array. The composite manufacturing process is the key to the application of carbon fiber. Filament winding has emerged as the main process for fabricating composite structures. It is widely used in building rotational parts. In the filament winding process, the carbon fiber is delivered from the unwind roll and passed through the resin bath to mix with resin under different temperatures and finally wrap around the surface of the mandrel in the designed pattern. The major specifications that should be satisfied during the winding process are the winding line type and the fiber tension, which are considered to be the key factors related to the tensile strength of the fiber products. The winding line type is determined using the numerical control system, so this paper focuses on the tension control problem during the winding process. Researchers have shown that unstable tension may lead to loss in strength of fiber winding products . Therefore, fiber tension should be maintained at the reference value during the winding process for ensuring the product quality.     Several factors shape the tension control design to be challenging, which include significant parameter variations and disturbances. Small variations in the change of velocity of the transport rollers can cause significant variations in tension. On the other hand, we used different shapes of mandrels for maintaining the line speed in acceleration or deceleration states. Because of the coupling between the tension and the line speed, it is difficult to maintain the tension at a desired value. Researchers have investigated considerably for acquiring better control result. Lee et al. used a magneto rheological brake to provide back tension to prevent frequent part changes and fatal malfunction for a tension control system, and a PID controller was designed, and test results showed the feasibility with satisfying the time constant and the allowable error. Nishida et al. divided the transport system into several subsystems and a self-tuning PI controller with an estimator based on a novel adaptive particle swarm optimization method was constructed to solve the strong coupling between the velocity and tension of the web. A self-tuning PID controller to control the tension for tape winding of composites was designed and the constant extension ratio is guaranteed. To reduce the time required for the stabilization of the tension, a faststabilization method for web tension is proposed. The model of dancer system and stabilization of web tension in drying process are established, and the variation of tension is used as a reference value for the tension stabilization. The integration of load cells and active dancer system for printed electronics applications was used to improve the accuracy of web tension, and self-adapting neural network control was proposed to reduce tension spikes due to the change in roll diameter of winder and unwinder rolls. Wu et al. developed a tension detection and control mechanism and analyzed the main causes of wire tension variation, and then a PI algorithm was proposed to reduce tension variation. An accurate dynamic model for the unwind roll by considering the time variation of the roll inertia and radius was developed, and a decentralized controller for computing the equilibrium inputs for each driven roller was proposed . A sliding mode control with guaranteed cost technique was applied for reducing the system uncertainties. The simulation results showed that the proposed method had good robustness and quick response time. Compensation method by calculating the torque of a driven loop lifter was developed to control the tension and thickness of hot-rolled strip. For the control strategy, several control methods have been proposed including disturbance rejection control , neuro-fuzzy control , and H∞ control . Choi et al. conducted a survey on various types of control algorithms by investigating their strengths and weaknesses, and demonstrated some areas of potential future development.     Most of the above studies considered the dynamics of driven rollers in the models but the behavior of idle rollers was ignored. Consequently, the models were under some limited conditions, which ignored detailed complex tension dynamics. On the other hand, most research focused on dynamic modeling and control strategy design, but the mechanical structure and the influence of parameter variation on fiber tension were ignored. In this paper, a novel tension control method is presented, which can regulate the tension and speed of the filament winding process. The mechanical structure and dynamic model of the system are established, and the influences of the parameter and the speed variation on fiber tension are examined. Subsequently, according to the features of driven rollers and the influence of variation, the control method is proposed by regulating the outputs of the torque of unwind roll, the torque of magnetic powder brake roller, and the speed of the master speed roller in three levels. Simulations are conducted for verifying the effect by comparing the results with those of the conventional PID controller. Finally, the performance of the proposed control system is verified through experimental studies using a filament slider coil winding machine.     The structure of the paper is organized as follows. Section 2 presents the mechanical structure of system. In addition, the dynamic models are constructed, and the influence of parameter and speed variation on the rollers is examined. In Section 3, the control strategy is proposed. Simulations are conducted for verifying the effect of the proposed controller by comparing with that of the conventional PID controller in Section 4. In Section 5, the proposed mechanical structure and control strategy are applied to a belt head winding machine, and the experimental study is conducted for verifying the performance of the tension control system.     The process line is divided into three zones (Figure 1): the unwind section, the process section, and the rewind section. In each zone, one or two rollers are driven using motors for transporting the carbon fiber from the unwind roll to the rewind roll. The carbon fiber is delivered from the unwind section to the process section, which consists of the magnetic powder brake roll, the master speed roller, and some idle rollers. In the process section, the carbon fiber passes through the surface of the master speed roller. As the carbon fiber is comprised of thousands of threads, the resin is properly pasted on the surface of the carbon fiber. The master speed roller is driven using an AC servomotor, and the speed is controlled for acquiring the desired speed and tension. The rewind section consists of a four-axis CNC system for acquiring the winding pattern.     The control method of hook type winding machine is shown in Figure 2 in three levels. The control system can regulate the tension and speed of the filament winding process by governing the output of three different driven rolls—the torque of the unwind roll, the torque of the magnetic powder brake roller, and the speed of the master speed roller. In the first level, the unwind roll, which is driven using a torque motor generates a reverse force for applying a pretension to the carbon fiber. The pretension is set at a small value because large tension will cause the tension to deviate from the set point owing to the time-varying radius and the disturbance caused by the periodic swing. In the second level, the magnetic powder brake generates another pretension to the carbon fiber. The feature of the magnetic powder brake is to generate torque in a wide range without introducing considerable tension interference. However, its disadvantage is that the accuracy and response speed are inadequate than the speed control using the AC servomotor. Finally, in the third level, as the tension is close to the set value, the master speed roller is controlled for acquiring the desired tension. On one hand, the speed of the master speed roller traces the line speed of the carbon fiber as the reference speed. On the other hand, the speed is adjusted for maintaining tension at a desired value. The response speed is high when the AC servomotor operates in the speed control mode. Consequently, when the line speed of the carbon fiber changes rapidly or in the start-time period, the master speed roller maintains tension in a small range. The control system measures the speed and tension of the carbon fiber, and then controls the multivariable output of the torque of the unwind roll, the torque of the magnetic powder brake roller, and speed of the master speed roller. The mechanical structure and dynamic modeling of the system is presented as follows.

Fecha de Publicación: 29-10-21

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