Elastic Fabrics And Methods And Apparatus For Making The Same

Abstract

The invention relates to methods and apparatus for making a length of woven fabric comprising an elastomeric weft yarn.

Description

The present invention relates to elastic fabrics and methods of making the same. The fabrics are particularly suitable for incorporating into textile goods, particularly clothing garments, and especially brassieres and other garments which include a shoulder strap. The fabric of the invention can also be incorporated into other goods with straps, such as bags, carrying cases, etc.

It is known to make elastic shoulder straps having variable width along their length. Because of their elasticity, the shoulder straps can follow the movements of the body or the body parts of the wearer, so that the article of clothing supported by the shoulder strap exerts no tensile or compressive stresses or only slight tensile or compressive stresses onto the body of the wearer of the article of clothing. A shoulder strap of this type is placed over the shoulder of the wearer, wherein the longitudinal middle portion of the shoulder strap rests on the shoulder and the two shoulder strap portions connected to the middle portion extend downwardly along the chest and back, respectively, of the wearer and are connected at their ends to the article of clothing

U.S. Pat. No. 5,507,682 describes a shoulder strap that includes elastic warp threads and weft threads extending transversely of and woven into the elastic warp threads.

The strap has a longitudinal middle portion whose width is enlarged as compared to the width of the shoulder strap portions extending longitudinally from the middle portion. The spacing between the elastic warp threads in the middle portion is greater than the spacing of the elastic warp threads in the shoulder strap portions connected to the middle portion. The number of weft threads per unit of length in the longitudinal middle portion is greater than in the shoulder strap portions connected to the middle portion. The number of weft threads per unit of length in the middle portion may be approximately 50% greater than the number of weft threads per unit of length in the shoulder strap portions connected to the middle portion.

The present invention aims to provide a simple, quick and economical method and apparatus for making an elastic fabric of variable width.

According to the invention there is provided a method of making a length of woven fabric having a variable width, the method comprising weaving warp yarn with weft yarn; characterised in that the weft yarn is are elastomeric and the elastomeric weft yarn is arranged across the warp yarn to vary the width of the woven fabric along its length.

Conveniently, the method involves varying the tension under which the elastomeric weft yarn is laid across the warp yarn by varying the weft yarn feeding speed. Increasing the weft yarn feeding speed lowers the tension on the weft yarn and the width of the woven fabric increases. Lowering the weft yarn feeding speed increases the tension and the width of the woven fabric decreases.

Hence, simply by controlling the elastomeric weft yarn feeding speed one can control the width of the resulting woven fabric according to the method of the invention.

Alternatively, or additionally, the tension under which the weft yarn is laid across the warp yarn can be varied by varying the weaving pattern. For example, weaving a weft thread under every other warp thread will produce a tighter weave than weaving the weft thread under two or more warp threads at a time.

Normally, a non-elastomeric yarn is used for the weft yarn in known methods of making shoulder straps. However, in a preferred embodiment of the present invention both the warp yarn and weft yarn are elastomeric. This produces a woven fabric that can be stretched along its length (i.e. warp-ways) and across its width (i.e. weft-ways). Stretchiness in both directions leads to greater comfort for a user when the length of a fabric is used as a shoulder strap as it makes the strap move with the shoulder muscles rather than causing abrasion by rubbing against the skin.

A particularly unexpected and advantageous property of fabric woven according to the present invention is that when the fabric is stretched close to its maximum extent, its width increases compared to its width in a relaxed state. This is particularly beneficial when the fabric is used as a shoulder strap because increasing the width spreads the load over a bigger area. This reduces the pressure that a wearer will feel on their shoulder, making it much more comfortable than conventional shoulder straps.

In a further aspect the invention provides a method of making a length of woven fabric, the method comprising weaving warp yarn with elastomeric weft yarn; characterised in that the elastomeric weft yarn is laid across the warp yarn under tension whereby the width of the woven fabric increases compared to its width in a relaxed state upon applying a longitudinal load to the fabric.

The invention also relates to a woven length of fabric characterised in that the fabric comprises warp yarns and elastomeric weft yarns arranged whereby the width of the fabric can be increased compared to its width in a relaxed state by applying a longitudinal load to the fabric.

Preferably, both the weft and warp yarns consist of or comprise elastomeric yarn.

Another advantage of the method of the invention is that the spacing between threads of the weft yarn is substantially the same throughout the length of the fabric. Hence the stretch and modulus properties will not vary significantly between portions of the fabric having different widths.

In a preferred embodiment the method involves arranging the elastomeric weft yarn across the warp yarn so as to produce a tapered fabric. By “tapered” we mean that the width of the fabric decreases incrementally.

Conveniently, such an arrangement is achieved by varying (i.e. increasing or decreasing) incrementally the tension under which the elastomeric weft yarn is fed across the warp yarn.

According to this embodiment the method can be used to produce tapered elastic fabric panels which are useful as components of a bra, especially wing (side) panels. Normally, a wing panel fora bra is made from several separate components, the elastic fabric being stitched to the edges of the panel. However, such a multi-component construction has the disadvantage that it is complicated to assemble, bulky and sometimes uncomfortable for the wearer, especially on bras with larger cup sizes.

Bra wing panels made according to the method of the invention offer better levels of elastic support than known multicomponent panels, but they are far easier to make and more comfortable to wear because they can be made as a monocomponent seam-free fabric.

Improved support over conventional bra wing panels can result from the use of elastomeric warp and weft yarns. The resulting woven fabric can stretch across its width in addition to the normal stretch along its length.

In a still further aspect the invention provides a method for making a length of woven elastic fabric comprising weaving warp yarn and elastomeric weft yarn; wherein the pick density and/or weave pattern is varied during weaving to produce two or more portions along the length and/or width of the woven fabric having different elastic modulus/stretch properties.

The warp density can be used to vary the elastic modulus/stretch properties across the width of the woven fabric, for instance, as described in the following examples.

Preferably the warp yarns comprise or consist of elastomeric yarn.

Preferably, the pick density is varied by varying the speed of the take-off roller of a weaving machine.

Conventional weaving machines are arranged to feed weft yarns at a constant speed.

Thus, according to a further aspect the invention provides a weaving machine wherein the machine is equipped with a controller for feeding weft yarn at two or more different speeds.

Preferably, the weaving machine is equipped with a sensor for detecting a predetermined length of fabric. Once a predetermined length has been detected the sensor can signal the controller to vary the speed at which the weft yarn is fed and thereby vary the width of the resulting woven fabric. Conveniently the controller is arranged to operate a motor, the motor being connected to the weft feed wheel of the weaving machine.

It will be appreciated that the preferred weaving machine of the invention can be programmed or otherwise set to produce a length of woven fabric with a desired variable width pattern.

The invention also provides a weaving machine having a take-off roller and having means to vary the speed of the take-off roller to vary the pick density during a weaving operation.

Alternatively or additionally, warp yarns of a higher/heavier count than those used in another portion of the fabric can be used to achieve two or more portions having different elastic modulus properties.

In the illustrative example below, more warp ends per dent are used on the outer edge portions than in the centre body panel. This is seen most clearly from the drawing-in plan where the underband and underarm portions have 10 ends, whereas the centre body panel only has 2 ends per dent (see FIGS. 9A and 9B).

In an embodiment, the invention provides a tubular fabric formed from a length of woven fabric of the invention, such as a flat or open form of the fabric of the invention. Methods for manufacturing a tubular fabric from a flat or open form of a fabric are known in the art. For example, the OB1 AT116 system produced by Sew Systems Ltd., 53 Iliffe Avenue, Odeby, Leicester, LE5 5LH, England, provides a convenient automated method whereby flat fabric is passed through a folder system which takes the single flat strip and forms it into a tubular form which can be sewn into a garment.

Tubular fabrics are known to be of use in housing underwires (such as brassiere wires) in underwired garments such as brassieres or swimming costumes. Thus, the tubular fabric of the invention may conveniently be used to house an underwire in an underwired garment (such as brassiere or swimming costume), for example where a tubular fabric having the advantageous properties of the fabric of the invention are desired.

In a preferred embodiment, an anti-slip material is applied to wide sections of the length of fabric after weaving. For example, a silicone monolayer or two layers of silicone where the first layer is silicone (against the fabric surface) and has a higher viscosity than a second silicone layer on top of the first layer. The low viscosity silicone has a much tackier (anti-slip) surface. Silicone with low viscosity has a very tacky nature but it bonds very weakly with textiles. Hence, by putting it over a higher viscosity silicone that bonds well with textiles, the lower viscosity silicone layer bonds well with the higher viscosity silicone which in turn bonds well with the surface of the fabric to create a durable layer of tacky silicone on the surface of the fabric.

The use of such anti-slip material helps to prevent the increased width section from slipping off the shoulder of a wearer when the length of fabric is used as a shoulder strap.

Instead of, or as well as, applying an anti-slip coating after weaving the product a tacky material like natural rubber may be used in the warp yarn.

It is preferred that the above methods and apparatus are used in combination with one or more of the other aspects of the invention.

Details of exemplary preferred embodiments of the above methods and apparatus of the invention are provided in the following Examples and Figures.

BRIEF DESCRIPTION OF FIGURES

FIG. 1( i) is a schematic showing the arrangement of a weaving machine for use in the methods of the invention.

FIG. 1( ii) is a schematic representation of a woven fabric of the invention showing the warp and weft yarn arrangement and illustrating how the width of the fabric can be controlled by varying the feed speed of the weft yarn during the weaving process.

FIG. 1( iii): photograph of actual length of fabric having variable width.

FIG. 2A: shows exemplary lengths of fabric having different variable width Designs.

FIG. 2B: photograph of actual fabric having variable width designs shown in FIG. 2A.

FIG. 2C: corresponding weft yarn feed speeds used to achieve the width variations A to D shown in FIGS. 2(A) and 2(B).

FIG. 3( a)(a-1)(a-2): exemplary weaving plan and a preferred fabric construction according to the invention.

FIGS. 4A and 4B: schematic showing how the width of a preferred fabric of the invention increases (FIG. 4B) as compared to its width in a relaxed state (FIG. 4A) when a longitudinal load is applied to the fabric.

FIG. 4C: drawings in plan and construction of the fabric shown in FIGS. 4A and 4B.

FIG. 4D: photographs showing width extensions of actual fabric.

FIG. 5: schematic showing arrangement of warp and weft yarns to achieve portions along the length of the fabric having different elastic modulus/stretch properties.

FIG. 6: shows variation in speed of take-off roller used to achieve variations in stretch properties seen in FIG. 5.

FIG. 7: photograph of tapered fabric of the invention in the form of a bra wing. Outer edge portions (“power bands”) have a different stretch property than the inner body panel. However the entire bra wing is made as a single fabric using the weaving methods of the invention.

FIG. 8: photograph of a conventional bra wing construction. Elastic strips are stitched or bonded to a non-elastic fabric panel which is cut to achieve a tapered shape. The attachment of the elastic strips forms seams which adversely affects comfort for a wearer.

FIG. 9A: shows weave construction of the preferred fabric of the invention for use as a bra wing shown in FIG. 7. The underarm and under-band outer edge portions have a high warp density.

FIG. 9B: shows the drawing-in plan and weave construction of the inner body panel of the fabric shown in FIG. 7.

EXAMPLES

Example 1

Variable Width Fabric

The width of various types of narrow elastic and non elastic tapes can be altered along the length at predefined positions using a standard narrow fabric weaving or jacquard weaving loom. The resultant product can be used for many applications and few options are as follows.

• 1. Shoulder straps of ladies undergarments (bra's or camisoles) as the wide area can be positioned over the shoulder to reduce the pressure thus make the garment comfortable.
• 2. Waist bands of apparel as the wider area positioned to the front will help to control the stomach better. If the wider area is positioned to the side it will help to suite the natural curves of the body, especially on women.
• 3. Shoulder straps for cameras, Camcorders or any equipment that is required carry over the shoulder.
• 4. Straps of Bags.
• 5. Decorative straps
• 6. Bra wings
• 7. Tubular fabrics, such as fabrics for housing an underwire in an underwired garment (such as a brassiere or swimming costume).

Normally the width of a narrow tape is entirely dependent on the width of the front read and the feed/tension of the weft yarn. Both these parameters are constant once set, hence products woven using these machines end up having a consistent width through out its length.

In order to achieve various widths at different places along the length of the elastic fabric according to the invention it is preferred that the feed/speed of the weft yarn is varied at pre-defined places whilst the weaving machine is in continuous operation, without interrupting the rest of its functions.

Preferred elastomeric yarn for use in the methods of the invention includes “spandex” or “elastane” which is a block copolymer of polyurethane and polyethylene glycol. Trademarks associated with spandex products include Lycra™, Elaspam™, ROICA™, Darlaston™ and Linel™.

Spandex is produced as monofilament or fused multifilament yarns in a variety of deniers, as is well known in the art.

Upon application of a tensile load at room temperature, elastomeric yarn such as spandex can be stretched without breaking to more than twice its normal length in a relaxed state. When the tensile load is released the elastomeric yarn immediately returns to its original (relaxed) length.

Spandex (Elastane™) or another elastomeric yarn can be used in it's bare form or covered ones (single covered) or twice (double covered) or even air covered with another textile yarn (Nylon, Polyester, Rayon . . . etc). The advantage in using an elastomeric yarn is that even when the feed speed is reduced to a great extent, it only gets stretched out and does not break. Further, it also gets woven into the product under tension in its stretched out form and contracts the product once the woven fabric passes the front reed of the weaving machine. It is important to note that when an elastomeric yarn such as spandex is used as the weft yarn a width reduction of upto 50% can be achieved compared to 15% that can be achieved when using a non-elastomeric textile yarn.

Procedure

Control of the speed at which the weft yarn is fed is accomplished by means of a sensor, a micro controller and an electric motor that are all interconnected (see FIG. 1(i)).

Sensor: The prime function of the sensor is to identify each revolution of the Main Shaft while the machine is in operations. Each revolution of the Main shaft is equivalent to a pick. This information is fed in to the microcontroller so that it can keep a count on picks of the repeat while the machine is in operation.

Electric Motor: Drives the weft transport units and varies its speed based on the instruction that it receives from the Micro Controller. The weft transport unit is normally driven through a series of pulleys and belts connected to the main or the crank shaft. This drive is dismantled when fixing the electric motor because in this new set-up the motor is connected directly to the weft transport unit through a belt making it operate independently of the main motor of the weaving machine.

A Micro Controller: A programmable device which controls the speed of the motor that is fixed to the weft transport unit. The inputs to the Micro controller are signals from the sensor which help it to count the picks while the woven machine is in operation and the Data inputs. The data input is the instruction that we feed which advice the motor to change its speed from R1 to R2 from pick P1 to P2. Speed values (R1, R2, R3 . . . Rx) are set based on the desired width at different points and the shape in which the width should be varied is set by the number of picks (P1, P2, P3 . . . Px) over which the speed change is done. (See FIG. 2)

Width Increase when Fabric is Stretched

Another feature of the invention is that when the fabric is stretched to its maximum extent, it increases its width by about 10-15% compared to its width in a relaxed state. This is advantageous because the increased width spreads the load over a larger area. Hence the pressure that a wearer feels will be less on the shoulder and thus will be more comfortable.

As shown in FIGS. 4A and 4B, when the elastomeric weft yarn (e.g. Spandex/Elastane) is fed in under tension (at a low rate) it gets woven in stretched out and when the length of woven fabric comes out of the take off rollers it contracts across its width. This contraction causes the down points of the face warp yarns (which works on a 7 up 1 down weave and up points of the back yarns that works on a 7 down 1 up weave) to move underneath 7 up floats and 7 down floats respectively. Since the elastomeric warp yarns are stretched out on the loom lengthwise, when it retracts back (lengthwise) once it comes out of the take off rollers, all the non-elastic yarns specially the 7 down and 7 up floats jut out of the surface creating a space underneath it. This makes it easier for the single up and single down points of the warp to move underneath those floats.

When the elastic is stretched to its maximum extent, once the non-elastomeric warp yarns get stretched overcoming the crimp, the single up points and single down points move out from underneath the long warp floats and orient parallel to each other, resulting in an increase of width by about 10%-15%.

The given construction is only an example and similar products can be made using various different configurations using the above principle.

Example 2

Variable Stretch/Modulus Elastic

The stretch of woven elastic fabric is primarily dependent on the stretch of the elastomeric yarn, rate at which the elastomeric yarn is fed, weave construction; warp density and the pick density (picks per centimetre). However for a given product all the parameters except the weave construction are uniform throughout the weaving process. Hence the resultant elastic fabric ends up with uniform stretch and modulus right along its length. By using a jacquard machine, one can change the weave construction to different areas to give different stretch and modulus properties. When the construction is with a tight weave the stretch becomes low and when the construction is loose the stretch becomes high and the modulus becomes low. For example at one part the non elastic warp yarns work on a 1 up 1 down weave working opposite to the elastomeric/rubber yarns which also work on a 1 up 1 down weave one will end up with a very low stretch and high modulus) compared to a 2 in 2 or 3 in 3 weave construction. However with this method it is not possible to achieve specific stretch values because not only the stretch gain or loss is limited the weave combinations that can be used are limited too.

Control of pick density at portions along the length of the fabric is achieved by controlling the speed of the take-off roller without interrupting the other operations of the machine during the weaving process. The pick density of a fabric product is primarily dependent on the surface speed of the take-off rollers.

$\mathrm{Machine}\mathrm{picks}\mathrm{per}\mathrm{centimetre}=\frac{\mathrm{Picks}\mathrm{per}\mathrm{minute}}{\mathrm{Surface}\mathrm{speed}\mathrm{of}\mathrm{the}\mathrm{take}\mathrm{off}\mathrm{roller}}$ $\mathrm{Picks}\mathrm{per}\mathrm{minute}=\mathrm{RPM}\mathrm{of}\mathrm{the}\mathrm{main}\mathrm{Shaft}\mathrm{Surface}\mathrm{speed}\mathrm{of}\mathrm{the}\mathrm{take}\mathrm{roller}=\mathrm{Circumference}\mathrm{of}\mathrm{the}\mathrm{take}\mathrm{off}\mathrm{roller}\times \mathrm{RPM}\mathrm{of}\mathrm{the}\mathrm{take}\mathrm{off}\mathrm{roller}.$

As mentioned above, with conventional narrow fabric woven or Jacquard weaving looms, the machine picks per centimetre is uniform throughout the weaving process because the take-off roller is worked by a series of gear wheels driven from the main shaft where the gear ratio is fixed once set. The speed of the main shaft is consistent throughout the process of weaving.

The machine for varying the stretch and modulus along the length of the fabric is like that used to make fabric of variable width according to Example 1. However, the machine is equipped with means (an additional electric motor) to vary the speed of the take-off roller while the weaving process is in operation without interrupting any other operations. In order to do the above modification the transmission from the main shaft to the take-off roller has to be dismantled. The additional electric motor is also connected to the microcontroller and it can instruct the two motors independently to work at different speeds over different pick intervals.

The nature of any elastic fabric is such that, if all the other variables are kept consistent and only the pick density is reduced the product will end up with a higher stretch compared to the original product, similarly if the pick density is increased the resultant elastic will end up with a lower stretch. Since the speed of the take-off roller is varied which in turn changes the pick density, an elastic fabric with portions along its length having different stretch properties can be produced according to the invention.

Example 3

Bra Wing

Using the variable width methods of the invention an elastic fabric can be made to the tapered shape of a bra wing (as shown in FIG. 7). Since an elastomeric yarn is used for the weft, the resultant fabric has a stretch both lengthwise as well as widthwise. By using very fine single covered elastomeric yarn, e.g. spandex, along the length, a quite thin fabric can be woven which is very similar to a conventional bra wing panel fabric in terms of the hand feel and the drape. Further, it is also possible to achieve the features (“power bands”) that a regular cut and sew or bonded bra wing has where an elastic is stitched or bonded to the edge of the tapered fabric panel, by either increasing the warp density at the edges or by using a thicker elastomeric yarn at the edge of the tapered elastic fabric. This eliminates the irritating stitching as well as the bulky seams of conventional bra wings and thereby increases the user comfort for a wearer.

However, since this method of making a fabric can create a very strong modulus along the length, even without having power bands like explained above, this product is suitable to use as a bra wing.

Further by incorporating the variable modulus aspects of the invention and/or by using different weave constructions it is possible to create different portions with different elastic modulus/stretch properties (“power zones”). Such features also help to create a better fitting bra.

Although example 3 relates to bras, it will be appreciated that the above features of the invention are beneficial in a range of other applications, especially garment manufacture.

A particular application is the field sports clothing, where garments having desirable elastic modulus/stretch properties have been shown to enhance comfort and athletic performance.

Example 4

Tubular Fabric Production from a Flat Fabric

A further embodiment of the invention relates to the production of a tubular fabric from a flat (or “open”) form of the fabric of the invention.

The flat fabric can be formed into a tubular fabric by a variety of methods. For example, the OB1 AT116 system produced by Sew Systems Ltd., 53 Iliffe Avenue, Odeby, Leicester, LE5 5LH, England, provides a convenient automated method whereby flat fabric is passed through a folder system which takes the single flat strip and forms it into a tubular form which can be sewn into a garment.

As the flat fabric is sewn into the garment, an underwire (such as a bra wire) can be inserted as the fabric is formed into a tubular form.

Claims

1. A method of making a length of woven fabric having a variable width, the method comprising weaving warp yarn with weft yarn; and characterised in that the weft yarn is elastomeric and is arranged across the warp yarn to vary the width of the woven fabric along its length.

2. A method as claimed in claim 1 wherein the elastomeric weft yarn is arranged by varying the weft yarn feeding speed.

3. A method as claimed in claim 1 wherein the warp yarn consists of or comprises an elastomeric yarn.

4. A method of making a fabric as claimed in claim 1 wherein the elastomeric weft yarn is arranged to produce a tapered fabric.

5. A method as claimed in claim 4 wherein the elastomeric weft yarn is arranged to produce a tapered fabric by increasing or decreasing the weft yarn feeding speed incrementally.

6. A method as claimed in claim 4 wherein the tapered fabric has outer edge portions flanking an inner body panel; and wherein the outer edge portions have different elastic modulus properties as compared to the elastic modulus properties of the inner body panel.

7. A method of making a length of woven fabric comprising weaving warp yarn and elastomeric weft yarn; wherein either the pick density, the warp density, or both the pick density and warp density is varied during weaving to produce two or more portions along either the length, the width, or both the length and width of the woven fabric having different elastic modulus properties.

8. A method of making a length of woven fabric comprising weaving elastomeric warp yarn with elastomeric weft yarn under tension, whereby the width of the woven fabric increases compared to its width in a relaxed state upon applying a longitudinal load to the fabric.

9. A method as claimed in claim 1 further comprising a step of incorporating the length of fabric into a textile article.

10. A method as claimed in claim 9 wherein the textile article is an article of clothing.

11. A method as claimed in claim 9 wherein the fabric is incorporated as all or part of a shoulder strap or waistband.

12. A method as claimed in claim 9 wherein the article of clothing is a bra.

13. A method as claimed in claim 1 wherein the length of fabric is incorporated into a non-textile article as all or part of a shoulder strap.

14. A length of woven elastic fabric obtainable by a method as claimed in claim 1 the fabric having along its length two or more portions of different width.

15. A length of woven fabric having two or more portions of different width along its length; wherein the fabric comprises elastomeric weft yarn arranged across warp yarn.

16. A length of woven fabric as claimed in claim 14 wherein the fabric is tapered.

17. A length of woven fabric as claimed in claim 14 wherein the warp yarn consists of or comprises an elastomeric yarn.

18. A length of woven fabric comprising warp yarn and elastomeric weft yarn; characterised in that the elastomeric weft yarn is arranged whereby the width of the fabric can be increased compared to its width in a relaxed state by applying a longitudinal load to the fabric.

19. A length of woven fabric comprising elastomeric weft yarn arranged across warp yarn; wherein either the pick density, the warp density, or both the pick density and the warp density varies along either the length, the width, or both the length and width of the woven fabric to produce two or more portions having different elastic modulus properties.

20. A tubular fabric formed from a length of woven fabric as defined in claim 14.

21. A textile article incorporating a length of fabric as claimed in claim 14.

22. A textile article as claimed in claim 21 wherein the article is an article of clothing.

23. An article as claimed in claim 22 selected from sportswear and undergarments.

24. An article as claimed in claim 21 wherein the length of fabric is incorporated as all or part of a shoulder strap.

25. An article as claimed in claim 22 wherein the length of fabric is incorporated as all or part of a waist band.

26. A non-textile article which incorporates a length of fabric as claimed in claim 14 as all or part of a shoulder strap.

27. (canceled)