Breathable elastic fabric and method of making same

A method of making a breathable elastic web fabric comprises the steps of forming rows of chain stitches using a set of chain threads to define a plurality of lengthwise wales and widthwise courses, moving the front and back weft threads from side to side on each course in a pre-determined pattern as each course is formed to tie the wales and chain stitches together and to provide a plurality of staggered ventilation holes, and laying-in one elastomeric thread in each of the wales. The elastomeric thread is sandwiched between the front weft threads and the back weft threads, and enclosed in the underlap of each chain stitch. Preferably, the holes are formed in sets, the holes in each set being separated by at least one locking stitch to provide widthwise stability. In a pattern repeat of twelve courses and twenty four wales, the pattern for each weft bar is 1, 9, 1, 10, 1, 9, 5, 13, 4, 13, 5, 13. The holes comprise approximately 12 to 25 per cent of the extended surface area of the fabric.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to breathable elastic web fabric with 
ventilation holes and a method for making same. More specifically, the 
invention relates to a breathable elastic web fabric with ventilation 
holes suitable for use as in an orthopedic belt and lumbar support. 
2. Related Art 
In order to produce elastic webbing of varying widths, for example from 2 
inches to 24 inches, for use as orthopedic belts and lumbar supports, it 
has been customary to traverse the weft threads completely across the web 
width, thereby giving a solid structure to the webbing and providing 
stability from widthwise stretch. This method produces a dense fabric 
which allows very little "breathing" or interchange of air through the 
web. The resulting fabric also inhibits moisture transport which is 
essential for body comfort when the belts are worn for extended periods of 
time. Frequently, body rash can develop from such moisture imperviousness. 
In an effort to overcome these problems, various efforts were made in the 
prior art to design elastic webs which would have openings, meshes, or 
holes which would facilitate the necessary breathing and moisture 
transport and still maintain the strength and stability necessary to the 
ultimate use of the web in lumbar support belts and devices. Early efforts 
to create the necessary holes in general caused a deterioration of 
widthwise stability of the web, making it less suitable for lumbar 
support. When widthwise stress was applied to the fabric with holes, it 
was strained around the holes and did not fully recover its original 
configuration. It is the solution of these and other problems to which the 
present invention is directed. 
SUMMARY OF THE INVENTION 
It is therefore a primary object of the present invention to provide an 
elastic web fabric with a pattern of holes which are in sufficient 
quantity and size to allow ventilation and the escape of moisture. 
It is another object of the present invention to provide an elastic web 
fabric which in addition to the pattern of holes, has resistance from 
distorting strain in a crosswise direction when stress is applied. Any 
small strain resulting from the stress recovers once the stress is 
removed. 
To accomplish these and other objects, a series of weft threads is used 
instead of threads which traverse the entire width of the fabric. The weft 
threads are divided into two sets, the front weft threads and the back 
weft threads. The threads are spaced eight needles apart in each set. The 
set of threads carried by a bar is traversed back and forth across the 
needle bed using the same pattern sequence for each bar.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In describing preferred embodiments of the present invention illustrated in 
the drawings, specific terminology is employed for the sake of clarity. 
However, the invention is not intended to be limited to the specific 
terminology so selected, and it is to be understood that each specific 
element includes all technical equivalents which operate in a similar 
manner to accomplish a similar purpose. 
Referring now to FIG. 1, there is shown a segment of the web fabric 100 in 
accordance with the present invention. The segment comprise twelve courses 
and twelve wales, designated respectively as A-L and one repeat comprising 
twelve courses and twenty four wales. The wales are parallel to each other 
and to the longitudinal axis which extends the length of the fabric 100. 
The successive courses are parallel to the transverse axis which is 
perpendicular to the longitudinal axis and spans the fabric 100. 
The fabric 100 comprise four sets of threads, the chain threads 110, the 
elastomeric threads 120, the front weft threads 130, and the back weft 
threads 140. Once the fabric 100 is released from the machine knitting 
elements it coalesces into a very compact configuration, because the 
elastomeric yarn used in each wale is under considerable tension while 
being knit and compacts the fabric once the tension is released. 
As shown in FIG. 1, the fabric 100 is in a fully extended condition both 
crosswise and lengthwise. The extended view allows the complex interlacing 
of the four sets of threads 110, 120, 130, and 140 to be viewed. 
The chain threads 110 are fed from a warp with one thread fed to each 
needle on which a chain is desired, to form rows of chain stitches 
defining the wales a-l. The chain stitch is common to all knitted elastic 
and forms the base structure of the fabric. 
The elastomeric threads 120, which give the fabric its elastic qualities, 
are fed from a device common to all knit elastic machines, and provide the 
high tension necessary while knitting. One thread is placed in each needle 
wale and is sandwiched between the front weft threads 130 and the back 
weft threads 140. It is laid-in, and thus is never formed into stitches by 
the needles. The underlap of the chain stitch ties it to the fabric 100. 
The front and back sets of weft threads 130 and 140 provide the widthwise 
integrity of the fabric 100 by tying the wales and chain stitches 
together. Each set of weft threads 130 and 140 is carried in a separate 
bar on the machine and each bar is moved to the desired position from side 
to side on each course by a pattern wheel. While a pattern is needed for 
each bar, the pattern is the same for both front and back weft bars in the 
fabric 100. 
Beginning with course A at the bottom of FIG. 1 the pattern for each weft 
bar is as follows: 1, 9, 1, 10, 1, 9, 5, 13, 4, 13, 5, 13. The pattern is 
shown in relative position at the right of FIG. 1 as pattern repeat 
numbers. These numbers indicate the aisles, designated 1-12, between the 
chain stitch wales a-l to which the weft thread moves while the course is 
formed. Courses A-L are the horizontal rows of stitches. 
FIG. 1 shows exactly one half of a repeat of the pattern in both the 
lengthwise direction and the crosswise direction. The pattern repeats each 
twelve courses lengthwise of the fabric 100, and also repeats each 
twenty-four wales in width. A weft guide is used every eight needles in 
both weft bars. As many width repeats are used as in needed to produce a 
fabric of the desired width. Length of the fabric 100 is determined by 
continually repeating the twelve course pattern. 
This unique pattern gives the fabric 100 desired qualities for elastic web 
to be used for orthopedic and lumbar support belts. It provides about 18% 
open space in the fabric in the form of holes 210, 220, 230, 240, 310, 
320, 330, 340, 350, and 360, thus enabling the fabric 100 to pass air and 
water vapor more readily than would solid fabric. The holes are 
coincidentally in a pleasing pattern, allowing the garment to look better 
when worn. Earlier efforts, while giving sufficient hole size, lacked 
sufficient widthwise stability. 
An important feature of this structure is the dividing of large holes into 
two smaller holes, designated in FIG. 1 as 210, 220, 230, and 240. The 
traversing of both front and back weft yarns 130 and 140 across wales e 
and d and h and i divides what was one large hole in the prior art into 
the four small holes 210-240. The large holes tended to open up under 
lateral stress. 
A further stabilizing factor in the resistance to lateral stress results 
from traversing both bars the entire width of the twelve wale repeat once 
every twelve courses. This is represented by the long inlays of yarns 130 
and 140 from point 410 at the junction of the first wale a and the last 
course L to point 420 at the junction of the twelfth wale 1 and the last 
course L. Such long straight segments of yarn greatly reduce widthwise 
stretch. 
In addition to the four larger holes designated in FIG. 1 as 210-240, there 
are the six smaller holes designated as 310-360. All together each repeat 
of the pattern has ten holes which gives sufficient ventilation of 12 to 
25% of the surface area depending on extension. 
The fabric 100 in accordance with the present invention having the 
described stitch structure allows other advantages in the production of 
vented elastic webbing. For example, because the pattern repeats in a 
twenty four wale width it can be readily produced in any multiple of 
twenty four wales. However, if four needles are removed on each side of 
the desired web width, a selvage will be formed. This selvage would 
ordinarily be four wales wide on either side but can be reduced to three 
wales or two wales, if desired, by conventional means as will be 
understood by those of ordinary skill in the art. 
In other methods of producing solid elastic webs, only webs of the same 
width could be produced on a machine simultaneously. With the fabric in 
accordance with the present invention, varying widths can be produced on a 
machine at the same time thus allowing greater utilization of equipment 
and greater productivity. 
Modifications and variations of the above-described embodiments of the 
present invention are possible, as appreciated by those skilled in the art 
in light of the above teachings. 
It is therefore to be understood that, within the scope of the appended 
claims and their equivalents, the invention may be practiced otherwise 
than as specifically described.