Warp crimp fabric

Abstract

A method for weaving extremely low warp crimp fabrics is introduced. The weft yarns are allowed to take up the crimp in the fabric by weaving with pre-crimped weft yarn.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Application Ser. No. 60/640,188 and incorporating that provisional application by reference.

FIELD OF THE INVENTION

The present invention relates generally to weaving fabric on a loom.

BACKGROUND OF THE INVENTION

Textile fabrics woven on any type of loom are comprised of warp and weft yarns which cross over and under each other. The warp constitutes the yarns which run lengthwise in the fabric, and the weft constitutes the yarns which run in the direction of the fabric's width. The over and under interlacing involves crimping of the yarns as the weaving takes place. Crimp in a fabric is measured by first marking gage marks on the fabric with crayon or ink, for example exactly 1 meter apart on one of the yarns in the fabric. The marked yarn is then unraveled out of the fabric. The unraveled yarn is straightened out and its length is then measured. The excess length of the yarn over 1 meter is a measure of the crimp of the yarn in the fabric. If for example the warp yarn removed from the sample measures 1.15 meters long after being straightened out, the “crimp” of the warp yarn is defined as being 15%.

Because the warp and the weft yarns are interlaced under and over each other the crimp can in principle be all in the warp or all in the warp or the crimp can be shared by both warp and weft. A fabric with all of the crimp in the weft is illustrated in FIG. 1. A fabric with all of the crimp in the weft is illustrated in FIG. 2.

The distribution of crimp between the warp and the weft yarns is an important factor having an influence on a number of properties of the cloth especially the stretch resistance or modulus of elasticity in the warp and weft directions of the cloth. Heretofore this distribution of crimp has been very difficult to control. Tightly woven fabrics commonly called “high beat up fabrics” have more crimp than loosely woven fabrics because the yarns have to make large excursions in short spaces. Furthermore the crimp in high beat up fabrics tends to go almost entirely into the warp yarns during the weaving process. The reason for this is the crimping requires extra yarn length. When weft yarn is inserted into the weaving shed on the loom the length of weft yarn available is basically equal to the width of the fabric in the loom. There is very little excess weft yarn available to do the crimping. For example see FIG. 3. If the width of the fabric in the loom w is 100 centimeters and we wanted 20 percent crimp in the fill yarn we would need 120 cm of yarn. The weft yarn xy in the figure in the figure is also only 100 centimeters long. As it is being pushed into the fabric by the reed it tries to pull in excess yarn from its end in order to crimp itself. It can do so only near the selvages (the edges of the fabric), in from the edge one or two yarn crossings before the friction becomes so great that it becomes hopeless to pull that much yarn into the center of the fabric. The warp yarns on the other hand pull excess yarn in through zero yarn crossings with no friction directly from the warp beam. Furthermore there are thousands of warp yarns each of which only needs a small fraction of a centimeter to achieve 20% crimp because at the moment the weft yarn is beat into the fabric each warp yarn is creating only one yarn crossing while the weft yarn is creating thousands of yarn crossings along its length.

A very small amount of weft yarn crimping can come from a narrowing of the fabric as it comes off of the loom. The amount of weft crimp which can come from this fabric narrowing is very limited because the loom will not weave if the fabric is substantially narrower than the reed width. When the fabric narrows substantially the reed has trouble pushing the picks in and the warp yarns near the selvage are subject to severe abrasion where they go through the reed. From a practical standpoint weavers find that the fabric must be held out to the width of the reed where the weaving is taking place.

SUMMARY OF THE INVENTION

The essence of the invention is to weave with pre-crimped weft yarn which already contains the extra length needed to permit the weft to take up the crimp during weaving.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 Shows woven fabric with straight (uncrimped) weft threads and warp threads that are crimped.

FIG. 2. Shows a woven fabric with straight (uncrimped) warp threads and weft threads that are crimped.

FIG. 3. Shows a typical loom having elongated warp yarns arranged side-by-side and a pre-crimped warp yarn in the weaving shed which when interlaced with these warp yarns creates the situation shown in FIG. 2.

FIG. 4. Shows a schematic view of an apparatus for pre-crimping yarn.

DETAILED DESCRIPTION

Pre-crimped (or elastic) synthetic elastic yarn is used in the weft of the fabric when weaving. Non crimped yarn is used in the warp direction. The pre-crimped or elastic weft yarn contains extra length. This allows the weft yarns to take up the crimp during weaving allowing the warp yarns to remain predominately straight with very little crimp. During the weaving action the warp and weft yarns push against each other. Whichever can crimp more easily takes up the most crimp. With the elastic pre-crimped yarn the weft can and does take up most of the crimp. The warp yarns which do not contain the pre-crimping therefore tend to remain straighter and nearly crimp-free.

There are many ways to pre-crimp the yarn.

The crimp can be set in the yarn by passing the yarn over hot gears as in FIG. 4.

The yarn can be twisted then heat set to lock in the twist. The yarn is then untwisted The natural tendency for the yarn is to revert to its heat set twisted configuration resulting in crimps and curls. These crimps and curls contain the extra length we need.

The yarn can be crimped by random compression in a heated stuffing box.

The yarn can be crimped by transverse jets of air as the yarn passes through a heated oven.

All of these crimped yarns have in common the incorporation of extra geometric length of the fibers within the yarn which can be straightened with a modest amount of tension without significantly stretching the fibers themselves within the yarn.

Many of these methods for crimping yarn are not new. What is new is the use of the pre-crimped yarn to weave high beat up tightly woven fabrics with very low warp crimp.

Conventional looms have warp threads much longer than those used in the weft direction (n×w) where w is the length of the weft threads and n is a number greater than 10, and depending upon the capacity of the loom, n may be much greater than 10.

Claims

1. A woven fabric with extremely low warp crimp produced by using pre-crimped yarn in the weft of the fabric.

2. A method of weaving fabric pre-crimping the weft yarns allowing the weft yarns to take up the normal crimp induced by the interlacing of the warp and weft yarns, leaving the warp yarns relatively straight and the weft yarns highly crimped.

3. A method of making fabric web of width w and length at least n times the width w (n×w) said method comprising:

a) pre-crimping a supply of weft thread to increase the overall length by a percent in the range of 10 to 20 percent,

b) weaving lengths of pre-crimped weft threads into the array of warp threads, whereby the usual crimping in the weft direction can be more readily accommodated in the resulting fabric.

4. A method of making fabric with a higher beat up (weft yarns per inch) as a result of using pre-crimped weft threads to reduce the tensions and abrasion which normally occurs during the interlacing of the threads during weaving.

5. A method of making closely woven fabric on a loom and comprising;

pre-crimping yarns to create a non-linear set to these yarns, at least when these pre-crimped yarns are not under tension,

weaving these pre-crimped yarns into a fabric on the loom, with warp yarns of length and tension significantly greater than that of the weft yarns,

using the pre-crimped yarns for at least some weft yarns in the loom weaving process, whereby the tendency for unequal crimping in the warp and weft directions during the loom weaving process can be alleviated.

6. A fabric woven from pre-crimped weft yarn according to the method of claim 5.