APPARATUS AND METHOD FOR REDUCING TORQUE IN GARMENTS

A method of reducing torque in garments includes calculating a needle wale skew measurement for the fabric. A knitting machine can orient fabric along its negligible torque line. The knitting machine includes a cylinder having a plurality of needles for knitting the fabric, a take-down component for pulling the fabric from the cylinder, and the knitting machine is adapted for rotating the take-down component at a predetermined rotation ratio relative to rotation of the cylinder. The predetermined rotation ratio can be calculated using the needle wale skew measurement. Torque can be accurately measured at all textile/apparel processes.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION AND BEST MODE

Torque or skew in fabric can be tested and predicted based on the yarn, stitch and knitting machine used, according to a preferred embodiment of the invention.FIGS. 1 and 1Ashow stitches12in a relaxed state, and illustrate how they angle around throughout the fabric10. In comparison,FIGS. 2 and 2Ashow stitches22in the traditional knitted state in fabric20, and illustrates precise vertical orientation of the stitches22.

Garments have needle wale lines11that angle off from the vertical position when torque is controlled. Fabric made with the same yarn, stitch and machine consistently that is processed the same way will have the same skew.

According to a preferred embodiment of the invention, fabric torque/skew can be determined by performing a skew/torque measurement on tubular knit fabric that has been laundered to simulate the relaxed state of the fabric. The number of needle wales11that angle off the longitudinal edge14in a one inch segment30of length of the fabric10is counted and is referred herein as needle wale skew per inch. The fabric10shown inFIG. 3has six needle wales11that angle off the vertical edge14in one inch of length30of fabric10, thus yielding a needle wale skew per inch of six. Alternatively, the number of needle wales that angle off the vertical edge14in a six inch length of fabric10can be counted, and then divided by six to attain the needle wale skew per inch. A stitch glass or other magnifying device can be used to aid in the counting of the needle wales11on the fabric10.

The fabric10should be completely relaxed by laundering and tumble drying prior to measuring the needle wale angle to the vertical. The needle skew per course is calculated to determine the correlation of skew per course in greige or finished fabric. This provides the relationship between the traditional knitted state and the relaxed state after laundering and tumble drying, as illustrated byFIGS. 1 and 2.

As shown inFIG. 4, the angle40of the needle wales11in relation to a vertical line42indicates the amount of natural skew/torque in the fabric10. This measurement can be documented as part of the product specifications as needle wale skew per inch. This skew specification can be used to correctly orient the fabric10to eliminate torque and bow in garments.

Since this is a non-destructive test it can be performed randomly throughout the batch for ensuring process control. Various devices that can be developed based on the above described method to accurately and quickly determine accuracy of wale orientation. Templates with angles or measures can be used to quickly check fabric in many locations. The torque/skew specification angle40can be measured with a common protractor. Once the specifications (skew to balance torque) are known, calculations can be worked out to approximate the value for new fabrics given the yarn, stitch and knitting machine.

A measuring device for checking the fabric10for correct skew according to a preferred embodiment of the invention is illustrated inFIG. 5, and shown at reference numeral50. The measuring device50can be comprised of plexi-glass other similar transparent material, and has a diagonal line54extending at the desired torque/skew specification angle40. As such, the device50can placed upon the fabric10, as shown inFIG. 5, and the number of that angle off the vertical edge14within the area defined by the diagonal line54can be counted to determine whether the fabric10has the desired torque/skew.

The replication of knitted stitches22inFIG. 2Ashows the vertical stitch alignment of wales and horizontal alignment of courses in the traditional knitted state. The relaxed stitches12inFIG. 1Ashow the replication of stitches in fabric10that has been washed and tumbled dry. The known relationship between the knitted state20and relaxed state10is used to orient the fabric accurately on a knitting machine60.

The end result is a greige fabric10that can be made into garments with negligible torque and minimal bow. The greige fabric garments can be garment washed, bleached, or dyed to complete the finishing process. Thus, all garments can be acceptable after wash by the consumer for skew and bow, and products that have side seams or garment wash can be successfully produced.

A knitting machine according to a preferred embodiment of the invention is illustrated inFIG. 6, and shown generally at reference numeral60. The knitting machine60comprises a needle cylinder62, and a take-up unit70, as shown inFIG. 6. The cylinder62preferably has a diameter of thirty inches and 2088 needles. The take-up unit70comprises a take-down section72for pulling fabric off the cylinder62, a roll-up section74that rolls up the finished fabric into rolls for transport, and a center driven take-up shaft76under constant spring tension positioned between the take-down72and roll-up74.

The knitting machine60includes a variable take-up70to cylinder62rotation feature comprising two independent variable speed motor drives68,78. One motor drive68is operatively connected to the cylinder60, and the other motor drive78is operatively connected to the take-up unit70. The motor drives68,78are electronically synchronized such that the take-down72turns at a predetermined speed ratio to the cylinder62. The take-up70is driven with a coordinated but different ratio drive system78, than the cylinder62. This provides a means for inputting the appropriate ratio so that the fabric strand10is oriented with negligible torque. The take-up70includes an electronic encoder79that detects the speed of the cylinder62, and regulates the speed of the take-up70to account for any changes in the speed of the cylinder62to maintain the desired take-up70to cylinder62speed ratio.

The known negligible skew/torque specification (by yarn, stitch and machine) can be used to determine the ratio of the take-up70to the cylinder62, such that the resulting fabric oriented to negligible torque. Open width fabric can be slit along the negligible torque line in the greige state. The center driven take-up shaft76ensures that stitches and wales per inch remain consistent through the roll so that garments cut from this greige fabric will have the same garment dimensions before and after wash.

Fabric coming off the knitting machine60is oriented to negligible torque state prior to processing so all of the fabric knitted has negligible torque. Because the fabric is not linear finished fabric bow can be measured and controlled at knitting.

Because the fabric is rolled up with the edge along the negligible torque line, the edge for slitting on open width fabrics can be easily marked. This works especially well on feed stripes since the stripes can be straightened (and stripe matched) to this vertical line throughout the strand of fabric. With this method, feed stripe garments have acceptable stripe straightness and side seam location after wash. Feed stripes can be constructed so that the feed stripes are perpendicular to the negligible torque line that is aligned with the edge of the knit roll. Fabrics can be checked coming off the knitting machine60for course straightness (bow) by using a course maker (dyed yarn or marked yarn).

The following examples illustrate a method of calculating the desired cylinder to take-up ratio according to a preferred embodiment of the invention.

The appropriate take-up to cylinder ratio can be calculated by performing the following steps. The number of needles on the cylinder (2088) is divided by the needles skew per inch (eight) to yield a quotient (261). The number of yarn feeds going into the cylinder (120) is divided by the number of courses per inch (52) to yield a second quotient (2.307). The first quotient (261) is divided by the second quotient (2.307) to yield a third quotient (113). The third quotient (113) represents the number of cylinder revolutions. For Z-twist yarn on a knitting machine turning right to left when facing the machine (clockwise when looking down on the machine), one revolution is added to the number of cylinder revolutions (113) to yield a sum (114), which represents the number of revolutions for the take-up, thereby yielding a desired cylinder to take-up rotation ratio of113cylinder revolutions for every114take-up revolutions. Accordingly, the motor drives68,78and electronic encoder79of the knitting machine60are programmed to drive the take-up at114revolutions per every113revolutions of the cylinder62. For S-twist yarn, one revolution is subtracted from the number of cylinder revolutions (113) to yield a difference (112), which represents the number of revolutions for the take-up, thereby yielding a desired cylinder to take-up rotation ratio of113cylinder revolutions for every112take-up revolutions. As such, the motor drives68,78and electronic encoder79of the knitting machine60would be programmed to drive the take-up at112revolutions per every113revolutions of the cylinder62. The examples herein are based on knitting machines that turn right to left when facing the machine (clockwise when looking down on the machine). In knitting machines rotating counter-clockwise, for Z-twist yarns, one rotation is subtracted from the number of cylinder rotations (third quotient) to yield the number of take-up revolutions, and for S-twist yarns one rotation is added to the number of cylinder rotations (third quotient) to calculate the number of take-up revolutions.

A Z twist 22/1 weight ring spun yarn knit on a four feed per diameter inch single jersey knitting machine results in fabric skew of 5.8 needles per inch. To relieve the torque in this fabric, the fabric tube is allowed to de-twist approximately twelve revolutions for each 100 yards. The ratio of cylinder to take-up turns would be 132.25:133.25 to achieve negligible torque. As such, the take-up70would make an extra revolution every 132.25 turns of the cylinder (or the take-up would turn 133.25 revolutions to each 132.25 revolutions of the cylinder).

A Z twist 18/1 weight open end spun yarn knit on a four feeds per diameter inch single jersey knitting machine results in fabric skew of 2.8 needles per inch. The ratio of cylinder to take-up turns would be 164.77:165.77 to achieve negligible torque. The take-up would turn an extra revolution about every 164.77 turns of the cylinder.

Each fabric processed can have a specification for skew or negligible torque (angle of needles wales versus a vertical line). Fabric can be checked at any process or in garments for correct skew by using the stitch glass aligned to the vertical (folded edge on tubular). By counting the number of needle wales that angle out of the stitch glass on the fabric edge per inch you can establish a value for wale skew. Since this is a non-destructive test it can be performed randomly throughout the batch for ensuring process control. Once the specifications (skew to balance torque) are known tables can be worked out to approximate the value for new fabrics given the yarn, stitch and knitting machine.

With the torque/skew specification, greige fabric can be accurately oriented to the correct needle skew at the batching process (also known as lotting), by positioning a turntable under the fabric roll as fabric is being pulled off the roll. The turntable rotates the correct number of turns per pound as the fabric is batched, because the yards per pound by fabric is known and typical batching uses a scale to accurately batch to the pound for dyeing.

Skew and shrinkage can be quickly checked by counting needle wales that angle off the edge, wales, and stitches per inch. There are devices to assist with this, so there is no reason to use the costly destructive wash testing method. Non destructive testing can be used, the test can be performed in seconds and multiple samples of in process and finished garments can be checked for statistically sound process control.

Fabric can be scanned with a hand held electronic device or manually count and measure needle wale skew, stitches, wales, and bow. Thus, pass/fail parameters can be easily determined and the data recorded by machine, batch or production order without the use of destructive testing. An electronic scanner can be used below the take down70on the knitting machine60to accurately check for quality parameters at the beginning of each roll.

Multi-weight fabrics can be made from commodity yarns having excellent quality characteristics (no torque, exceptionally low shrinkage, excellent drape, great hand, no linear finishing defects, consistent garment fit). Torque is negligible because the fabric is oriented to its torque specification on the knitting machine. Shrinkage is minimized by garment wash, bleach, or dye and tumble drying. Fabric drape and hand is enhanced by garment wash and tumble drying, and is also improved by being able to make lighter weight fabric and control quality parameters. Linear defects such as compactor sheen, phantom lines, finishing creases and processing holes are eliminated. Shape and fit of garments from this process can be excellent due to minimal torque, less bow, minimal shrinkage, and comfort of fabric.

Although the cost of dyeing garments instead of fabric may be slightly higher, there is a cost savings on fabric weight, lower off quality, dyeing less pounds of fabric, reduced waste, less destructive quality assurance testing, less lead time, lower obsolescence, and increased inventory turns. Also, garment dyeing has advanced and low liquor ratio garment dyeing is getting closer to the cost of fabric dyeing. Savings on fabric weight can be realized by knitting a lighter weight fabric and increasing the fabric weight by garment dye, bleach, or wash and then tumble drying. A traditional finished fabric that has thirteen percent (seven length by six width) additive total shrinkage can be knit ten percent lighter and bulked by this process to a shrinkage of less than three percent total. The resulting fabric weight savings would be about ten percent. The customer gets the same garment fit but does not get the bulkier fabric one would get after washing a traditional finished garment. Because of the above fabric weight savings, no dyed cutting or finishing waste and no dyeing of unbalanced components, there is a huge savings in material, dye, and chemical usage.

The textile apparel process is reduced to knit, cut, and sew. Dyeing and preparation for customer can be done to customer order or to finished garment inventory. Less lead time, lower inventory requirements (by storing some garment inventory as greige), less obsolescence (higher inventory requirements with dyed garments) reduced inventory investment can be realized. The cost of quality assurance is lower due to lower staffing requirements and less destructive testing is necessary.

There is an additional advantage of the knitting machine60orienting fabric to negligible torque state for traditional finishing. A problem with current textile finishing is that the fabric does not get oriented correctly resulting in variable torque and bow throughout the fabric lot. The knitting machine60orients the fabric to a negligible torque providing correct orientation and a pattern for how the needle wales should angle to achieve negligible torque. Therefore, new finishing devices can be adapted to properly orient fabric with traditional linear wet processing, drying, and compacting or calendaring.

Traditional linear finished fabric does not have the same torque/skew as cut to length, washed and tumble dried fabric without incorporating changes to existing equipment. If fabric is knitted on a knitting machine that orients the needle wales to a negligible torque position, traditional processing with length tension straightens the needle wale skew through the extraction/pad process. To accept enough needle wale skew at wet processing it is necessary to make changes to entry of the pad. An entry spreader for the pad that will permit more needle wale skew to stay in the fabric through wet processing is needed.

A pad spreader system according to a preferred embodiment of the invention is illustrated inFIG. 7, and shown generally at reference numeral100. The pad spreader system100comprises a pad102for extracting water, a prespreader104, a pair of idler turn bars105,106, ring guiders108, a de-twisting device110, and a wet box112on a turntable114. The turn bars105,106lower or raise to rotate the fabric tube10, and can be adjusted to turn fabric10more or less to agree with negligible torque. The turn bars105,106are positioned between the spreader104and the ring guiders108opening mechanisms. The turn bars105,106raise the fabric tube up on one side and lower the fabric tube on the other side so that it rotates the fabric clockwise or counter clockwise on the second set of spreaders as needed to orient the fabric to negligible torque.

The fabric10may come to de-twisting110oriented to negligible torque or the de-twister110can be programmed to add needle wale skew so that the fabric10is in agreement with negligible torque specifications.

Using the known fabric needle wale torque/skew the fabric10can be oriented at wet processing to a negligible torque state. The needed needle wale skew can be added at the pad to achieve negligible torque in garments that are washed and tumbled dried. To achieve this amount of wale skew through the pad102the turn bars105,106turn the fabric tube10clockwise or counter clockwise to orient fabric to negligible torque.

A basket spreader according to a preferred embodiment of the invention is illustrated inFIG. 8, and shown generally at reference numeral200. The basket spreader200comprises a pair of S-shaped members202,204. As shown inFIG. 9, the basket spreader200can be used in front of a spreader on the pad102, and has a rotation that encourages fabric10rotation prior to the fabric being spread to the width on the pad102.

By testing the fabric and setting up a torque/skew specification, fabric coming to wet processing from the traditional knitted and dyed state would have wale skew added at the pad to equal negligible torque by devices that rotate the fabric tube correctly from the entry orientation.

Fabric may come to wet finishing with negligible skew (by orientation at knitting) and the turn bars105,106can be used to rotate the fabric after opening to allow negligible skew through the pad102. Without the turn bars105,106, wet processing can straighten the needle wales such that fabric will be under skewed (after wet processing) for negligible torque.

In addition, the turntable114at the extractor and turning device105,106can add the needle skew needed based on stitches per inch, extractor speed and the current level of needle wale skew versus the known needle wale skew specification and force negligible skew through the pad102.

Alternatively, the extractor can control the needle skew by counting courses (camera, electronics and servo motor) and adjusting the needle wale skew to agree with known fabric skew specification. The turntable114and skew assist devices105,106can be adjusted as the fabric10comes through the pad102.

While wet finishing is a likely place to orient fabric to negligible torque in the finishing operation, it is also possible to orient at compacting. The torque/skew specification can be used and the courses scanned, and the wale skew can be introduced to compacting to determine the additional skew needed. Skew needed to agree with negligible torque can be induced by having the fabric lot on a turntable that would rotate clockwise or counter clockwise as needed.

The amount of needle skew in fabrics oriented to negligible torque can be reduced by appropriately changing the yarn twist direction or the direction that a knitting machine turns. Slitting and moving one edge appropriately forward or backward can also reduce needle skew. Reduction in needle skew may be advantageous to traditional manufacturing or making garments from greige.

Washed and tumbled dried fabric gives you the needle skew that is needed to manage torque through the processes. Washed and tumble dried (WTD) griege needle skew is higher (approximately 25-30% on ring spun) than in finished fabric because linear processes reduce the WTD skew in finished fabric. The needed needle skew (NS) can be used to produce negligible torque in finished fabric as a reference through the process. By associating needle skew with courses per inch (CPI) the needle skew value can be easily calculated for knitting, pre-extracting, post-extracting, post-drying, and after compacting.

The torque/skew specification (NS value) provides a process control tool that can be used at any process. It can be used in combination with courses per inch (CPI) so that torque/skew specification is stated as needle skew per inch with known courses, needle skew per course, or yards per complete wrap of a needle around the tube of fabric with known CPI. Once the torque/skew specification for WTD fabric of a given style is determined, it can be to measure control at any process.

Using needle skews to manage torque eliminates the need for destructive testing and wait time thus controlling torque within the process. This can be done using a stitch glass and other devices (angle measurement) to speed the quality assurance process so that multiple samples can be taken to ensure greater accuracy of results. Using needle skew to manage torque can be done with manual measurement and/or digital scanning of fabric for control.

For example, using the knitting machine60with a cylinder62having 2088 needles to make a fabric having a needle skew per inch of 7.5, a single needle will wrap all the way around the fabric tube in 7.73 yards. In 3.87 yards (139.32 inches) the needle will create a diagonal line300from one edge302to the other edge304. Using the diagonal line300length and the width302of the fabric, the needle skew angle can be calculated, as shown inFIG. 10. For example, if the finished fabric has a width302of twenty-eight inches and the diagonal length300is 3.87 yards (139.32 inches), the fabric has a needle skew angle306of 11.4 degree angle. It should be noted that this is not the torque that would be expected on WTD fabric but the angle of the needle wales needed for zero torque or seam deflection in finished garments.

An apparatus and method for reducing torque in garments are described above. Various changes can be made to the invention without departing from its scope. The above description of the preferred embodiments and best mode of the invention are provided for the purpose of illustration only and not limitation—the invention being defined by the claims and equivalents thereof.