Effect of knitting parameters on fabric quality Positive Yarn Feeders & Take-down Tension M.T.Warusamana F P.V.T. Weereasinghe131065M S.Y. Weerasinghe131066R D.K.J. Wijekoon131068B H.A.A. Wijesinghe131070A K.A.P. Wijesinghe131071D K.M.D.M.P. Kalpage131073K

Yarn Feeding Device  Main Purpose : Draw yarn from a package and deliver it to the needles to form stitches during a defined interval. Yarn Feeding System Negative system Positive system The needle draws yarn directly from the package An external device decide the length of yarn released to the needle.  Limitations of Negative Yarn Feeding :  Feed rate (amount of yarn) and Yarn tension variations from yarn to yarn  Yarn breakages

Positive Yarn Feeding  The positive feed units usually driven by external force (motor, gear driven) rather than by the needles, extract yarns from the packages and deliver them to the needles. 1.Rosen’s Tape Feed Mechanism 2.Yarn Storage Feeder 3.Positive storage yarn delivery device

Rosen’s Tape Feed Mechanism  A series of wheels are encompassed by an endless tape driven from a dimeter adjustable pulley called Quality Adjustable Pulley (QAP).  By altering the diameter of the QAP, speed of the tape and the yarn delivery speed can be changed.  Each yarn pass between its own wheel & the common feeding tape thus the yarn delivered to the needles at same linear speed as the tape. Tape nip positive yarn feeding Schematic Representation of tape nip positive yarn feeding Quality Adjustable pulley

Advantages  Uniform yarn delivery rate to all the knitting systems  Less slippage.  More simplified central adjustment facility.  Less space requirement.  Disengage the positive feeding during machine setting up.  Weight reduction of yarn feed wheel and less dust accumulations.  No guaranteed of uniform yarn feeding at higher run-in yarn tensions.  Yarn faults from defective winding of the packages are not eliminated.  Avoid yarn break stop motion being activated thus fabric press- off and needle breakages.  Quality wheel can’t be adjusted while machine is running. Limitations

Yarn storage feeder  Suitable in knitting multi-coloured jacquard structures. (As yarn consumption vary from knitting system to knitting system and from course to course within the pattern repeat.)  This unit consist of a motor driven serrated drum which winds yarn from the package when operating.  A sensor ring monitors the amount of yarn on the drum and as well as an empty drum. Limitation :  Does not feed the yarn to the needle as a fully positively feeding system. (only up to the temporary storage)

Positive storage yarn delivery device  Integration of positive yarn feed (Tape Feeder) with temporary yarn storage facility.  Each yarn delivery device consists of two wheels fixed to a shaft;  Driven wheel – Yarn delivery wheel  Drive wheel – light weight plastic gear wheel driven by a punched belt.  Number of contact points between feed wheel & yarn is increased by wrapping yarn several turns on the feed wheel.  Safety margin against a yarn breakage (before broken end reaches the knitting zone) by giving wraps & providing a yarn reserve over 2m. Advantages Detect yarn faults before entering to the knitting zone. Increase the efficiency Reduce needle breakages

Yarn Unwinding Option – Shima Seiki  Tool for supporting industrial textile applications in knitting.  When knitting with stiff materials such as metallic and monofilament yarns, the yarn has a tendency to kink or twist, making it practically impossible to feed smoothly into the knitting machine.  The yarn Unwinding Option is equipped with a motorized bobbin that actively unwinds yarn in the direction of the wind.  Bobbins are mounted on motorized bobbin mounts that turn in sync with yarn consumption, providing smooth yarn feed into the knitting machine. PET MonofilamentBobbin mount Types of bobbin Features  No twist is applied – No unbalanced monofilament yarn or fabric structure.  Any type of package can be fed (pirn type, with flanges)  Rewind the excessive yarn delivered to the needles.  Real-time adjustments in bobbin rotation speed according to the amount of yarn consumption.  Support variety of yarn (tape yarn (ribbon yarn), monofilament and metallic yarns). Source :

UNIFEEDER 2 – BTSR Yarn Feeding Solutions  A multi-patented system of a total combined yarn feeding and storage control, representing the first ‘ Positive Storage Feeder ’  Features:  Yarn taking from the bobbin and storage on feeding device  Knot catching, correct yarn feeding control and run out or broken yarn condition detection  Yarn feeding with constant tension from the storage device to the textile machine -Tension is kept constant even when the yarn package tension is subjected to change due to environment conditions such as humidity, temperature, etc., or when the yarn packages are gradually emptying during the normal working process. -Yarn tension variation, due to the progressive yarn bobbin emptying, decreases the quality level of the product, increases the actual yarn consumption (thus affecting the manufacturing costs), and reduces the efficiency of the textile machine (yarn breakage)  Yarn storing constant within the feeding device according to the amount taken from the textile machine  A real time display and accurate real time control of the exact yarn tension

1)Ceramic bush for yarn self-threading 2)Yarn-brake device with adjustable pressure 3)Knot catcher blade 4)Lower ceramic bush for yarn self-threading 5)Coil storage revolving drum with optical ring 6)Fixed electromagnetic braking device with yarn unwinding detection encoder 7)Floating Ring outlet removable electromagnetic yarn-brake device 8)Ceramic bush for yarn self-threading 9)Tension sensor loading cell 10) Ceramic bush for yarn self-threading

 Possibility of viewing and selecting directly from the navigation menu the desired application (socks, pantyhose, seamless, medical socks, raschel, etc.) without the need to manually set the relevant parameters  Real time total control from yarn inlet inside the device (with immediate knot detection, breaks, tears) to yarn storage (constant collection) up to yarn outlet (LFA and textile machine feeding with constant tension)  Prevent yarn twisting - revolving drum and the optical technology with closed loop integrated within the system (collection speed equal to the yarn feeding speed)  Possibility to work with any of the yarn types (including bare and covered elastomers, nylon, cotton and others) - perfect control of yarn tension values chosen by user  Real time constant tension self-adaptive technology with high production based on high magnetic frequency controlled by the floating ring and by integrated tension sensor UNIFEEDER 2 – BTSR Yarn Feeding Solutions Advantages:

IROSOX Positive Yarn Delivery Device

 Using for socks and stockings.  Positive yarn delivery,to manufacture the socks of consistent length.  Intermittent positive yarn delivery unit.  The unit is programmable to control yarn delivery.  Positive yarn delivery-Leg and the foot portion, negative-toe and heel area.  Yarn is trapped between feed tape and the yarn feed wheel,when solenoids are actuated and positively driven.  The IROSOX unit isn’t driven by the socks knitting machine.

 The tape and the positive feed pin wheels are driven by a DC motor.  To have constant tension and loop length there should be a synchronize between machine speed and delivery speed.  Sensors compare the speed of pin wheel,motor and speed of machine.  There is a numerical ratio between speed of machine and pin wheel can be changed by a hand held controller.

Electrical Positive Yarn Feeding Device

 Each delivery wheel is motor driven.  Stitch sizes are controlled by individual knitting systems is set by means of a precise apportioning of the yarn running into knitting stations.  To have smooth yarn running,system is controlled by electronic system rather than rigid mechanical coupling between machine and delivery devices.  The rotated position of the yarn delivery wheel detected with high precision by angle encoder and speed by a tachometer.  Angle encoder has high resolution which is greater than the circumference of the yarn delivery wheel.

 controls the speeds of devices.  By the close loop feed back system automatically compares detected speeds by signals and require speeds and according to predetermine ratio control the speed of the delivery devices.  Deviation between desired delivery and actual delivery effect to the quality of knitting goods.  To control the tension, yarn tension sensors give signals to the comparator.  Constant delivery rate and constant yarn amount is controlled by the system.

Take Down Mechanisms and Effects on Fabric Quality

Take-down Tension & Effects on Quality  Desired tension on the formed fabric may vary due to  Different constructions  Different types of yarn  Variations in stitch length  To much tension on fabric will make the fabric torn or the needles are stressed where the breakages may occur

1 - cylinder 2- needle dial 7 – 12 the adjustable spreader 7 to 12 hangs 4,5 - the frames 3 - the rotating needle dial shaft. 6 - lamp (The fabric tube is internally illuminated to detect fabric faults easily) 8,9 – clamps ( Initially the round fabric tube is brought into an elliptical form) and 10,11 – clamps (press the fabric in the elliptical form into a flat form by the spreader) 12 -rod Driven mechanically by main drive of the machine fabric tension is obtained either by spring or weight loading Fabric Spreader Winding and Tensioning

Active Indirect Take-down Mechanism(Fukuhara)  Works on the principle of spring loading  The roller follows the contour of the fixed curve on the machine frame by means of the traction spring  The torque, created by the traction spring on the lever over the pawl is acting on the notched wheel and can be braced on the middle take - down roll, which is firmly attached to the notched wheel  The middle take down roll is pressed by two outer rollers and fabric taken down  stop latches prevent a reverse motion of the take -down rolls during the pawl switching movements 1- Fixed curve 2- Roller 3- lever 4- traction spring 5- stop latches 6- adjustable pressure lever 7- lever 8- notched wheel 9- pawl 10- cam 11- traction spring

Developments in Take-down Mechanisms  The circular knitting machine includes a rotating knitting cylinder, a takedown assembly, and a fabric receiving tub.  The takedown assembly and the knitting cylinder rotate synchronously.  A vertical shaft associated with a motor cooperates with a cylinder ring gear of the knitting cylinder and a takedown ring gear of the takedown assembly.  A drive unit including a drive assembly and a clutch assembly is mounted to the takedown ring gear  The clutch assembly includes a drive gear which cooperates with the stationary ring gear of the fabric receiving tub to transmit toque to the rollers of the roller assembly.

48-Stationary ring gear 52-Drive gear 70,74- Transmission Shaft 72,73- Support and bearing 68- Slip Coupling 80,74- Pulleys 82-Belt 76-worm 78-wheel(driver) 96- driven roll

Advantage of the Development  Difficulty of crease mark removing is diminished  Effectively utilized for high pile forming fabric  Clutch has adjustable torque range and sensitive than spings and weight systems (hard pull on the thick/strong fabric and light pull on thin/weak fabric)  Even and constant fabric tension

The Cadratex unit The Cadratex unit now commercially fitted to machines, has been developed by “ITF Maille” of France. It replaces the conventional spreader with two complementary elements, one inside and the other outside the fabric tube, that cause the tube to adopt a square cross-section and then a gradually flatter configuration but of constant circumference, right into the nip of the take-down rollers. The distance from any needle to the take- down rollers is the same so that wale and course density remains constant around the fabric tube and throughout its length whilst enabling a lower uniform take-down tension to be employed. During adjustment, the outer guide frame is maintained in an exact relationship with the inner frame. Conventional spreader The cadratex unit

Benefits of the above mechanism In the conventional machines, the spreader bends the fabric (courses) and that increases the take down tension. Therefore this eliminates that drawback and hence keeps constant take down tension over the time. Uniform take-down tension leads to lower number of knitting faults (e.g. cuts and holes ) in the fabric and that increases the fabric quality. Uniform take-down tension would eliminate undesirable stretching in the length direction of fabric. It gives a fabric with desirable number of courses per unit length. Damage to knitting elements, issues when knitting weaker yarns, a greater length-wise deformation and undesirable consequent shrinkages after knitting also can be reduced due to this mechanism. Uniform stitch shape across the entire fabric width can be obtained. As fabric defects/knitting faults can be reduced, higher productivity, reduction of lead times and customer satisfaction would result.

Takedown Unit for Circular Knitting Machine Patent No : US 6,601,412 B1 (2003) Purpose of Takedown Mechanism  In a circular knitting machine the takedown unit is presented for drawing down tubular fabric that hangs downwardly in the knitting machine.  The knitted fabric is delivered from the needles in a hanging condition from the knitting cylinder and rotates with the cylinder.  A takedown unit is positioned under the knitting cylinder to draw the knitted fabric from the cylinder. Effect of Takedown Mechanism on Fabric Quality  Conventional takedown units can introduce defects and distortion in the knitted fabric Pinched points, Folds, and Slippage marks - Caused by the use of pinch rollers and the pressure between the pinch rollers as the fabric passes through them. Fail to provide accurate control (or to provide accurate control only by incorporating equipment that is unnecessarily cost prohibitive or complicated)

Special Features of the Invention  Easy assembling and replacing with the existing knitting machine (Takedown unit which is separately connecting to the knitting machine).  The Floating guide mechanism is preferably not rigidly connected to any structure of the circular knitting machine (tubular fabric hangs downward and floating guide mechanism encircled by the hanging tubular fabric and interacting with the takedown rollers). equalizes the forces applied to the fabric by the takedown unit to promote optimal operation  At least one actuator for driving at least one of the takedown rollers and the actuator is positioned for engaging the cams in response to the relative rotation between the takedown rollers and cams. With this rotation being for drawing down the fabric smoothly.

 The throws of the cams are adjustable for the purpose of adjusting the action of the actuators and thereby the rotation of the takedown rollers.  The takedown unit of the present invention may reduce the amount of tension imparted on the fabric for takedown, thus allowing the fabric to be drawn down from the knitting cylinder with a minimum force and pressure on the fabric.  The advantages of the present invention also include the possibility of using less power than a traditional takedown unit.  Less expensive than prior pinched-type takedown units by eliminating the magnetic takedown clutch and the big ring gear that drives the traditional pinch rolls.

A circular knitting machine having a takedown assembly for applying constant tension to the knitted fabric A 2-roller take-down motionTake-up and winding motion with fabric spreader

A takedown assembly is often positioned beneath the knitting assembly to pull the knitted fabric from the cylinder and to flatten the tubular fabric The takedown assembly thereby rotates synchronously with the cylinder to avoid twisting the fabric as it rotates with the cylinder. the desired tension on the formed fabric from the takedown assembly may vary due to different stitch construction, different types of yarn, variations in stitch lengths adjusting the torque of the rollers responsive to the tension of the fabric, include systems utilizing weights and counterweights. As a result, the fabric may be taken down unevenly and one side of the fabric may be subjected to stretch or will be torn.

MEASURES TAKEN TO MINIMIZE THE TAKE-UP PROBLEM  keep the rollers of the takedown assembly in a level position (rather than allowing it to rock back and forth) -- This has been attempted by controlling the speed of the rollers by means of two adjustable pulleys.  provide a motor, separate from the motor driving the cylinder and knitting assembly, for applying torque to the rollers of the takedown assembly  As such, the motor for driving the rollers is adjustable relative to the take- up speed of the take-up roller.

 A ring gear is associated with the cylinder. A drive motor is supported on the frame of the knitting machine and is associated with a vertical drive shaft  The vertical drive shaft includes an upper drive pinion gear which cooperates with the rotating cylinder ring gear.  the cylinder ring gear and the takedown ring gear rotate concurrently when the motor is actuated.  A drive unit and a roller assembly are mounted to the takedown ring gear. The drive unit includes a clutch assembly, such as a magnetic clutch.  The use of the magnetic clutch allows for an even and constant fabric tension, which will in turn provide superior quality and better control of the fabric.

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