US2156332A - Elastic yarn - Google Patents

Description

May 2, 1939. A E 2,156,332

ELASTIC. YARN Filed July 14, 1957 BYMIQW ATTORNEYS Patented May 2, 1939 UNITED STATES PATENT OFFICE ELASTIC YARN Company, New York, N. Y.,

New Jersey a corporation of Application July 14, 1937, Serial No. 153,494 In Canada February 15, 1937 3 Claims.

This invention relates to elastic yarns of the character employed in fabrics adapted for use in the manufacture of corsets, foundation garments, surgical appliances and other types of elastic wearing apparel and for certain industrial uses.

One of the most important uses of the present elastic yarn is as a laid-in elastic yarn extending along the courses in knitted fabrics.

Heretofore elastic yarn employed in the manufacture of elastic fabrics for the above uses has been commonly provided with a solid rubber core having a round, square, rectangular, oval or other shape in cross section. When pieces of these elastic fabrics are stitched together, or. are stitched to non-elastic fabrics, it frequently happens that the needle used in the sewing operation penetrates many of the rubber threads so that they are weakened or entirely severed. Subsequent flexing and stretching of the elastic fabric tends to break the threads that have been nicked or pierced by the needle and causes these broken ends to pull back in the fabric and gradually protrude from a face thereof in an unsightly manner.

This difficulty which is known as needle-cutting detracts materially from the appearance of the fabrics and also impairs the strength of the fabric, itself, and is the cause of serious losses and other difiiculties in the manufacture and sale of elastic garments.

An important feature of the present invention resides in an elastic yarn which will largely overcome these difliculties caused by needle cutting. This is accomplished by employing as the rubber core of the elastic yarn not a solid core as heretofore, but an extremely thin flat rubber tape which is many times as wide as it is thick.

After this very thin but wide rubber tape is produced it is provided with a textile cover which may take the form of a tubular braid, or a cover wound helically about the rubber core in one direction, or more frequently it is provided with an inner cover wound about the core in one direction and an outer cover wound about the core in the opposite direction. Whatever form of textile cover is used it is preferably so applied about the thin wide rubber tape that it will hold this tape tightly rolled or folded into substantially a circular condition.

As a result of the construction in which a tightly compact thin rubber tape is employed as the core in elastic yarn, in place of the solid rubber core commonly employed heretofore, several important advantages are secured. In the first place when the elastic yarn of the present invention is pierced with a sewing needle it will do less damage than when a solid rubber core is similarly pierced, for even if the needle pierces several folds of the fiat strip the total width of the unpunctured surface across which the tear must spread before the thread will break is much greater than in the solid rubber core.

In the second place the type of core of the present invention when severed will pull back in its textile covers to a much less degree than when a solid core is employed. This is due to the fact that the lateral spreading force of the tightly coiled or folded strip tends to take up any slackness that occurs in the out cover.

It is also found that this coiled or folded fiat tape'is better adapted to resist the destructive action of sunlight than a solid core. It also will withstand friction or chafing better than a solid core. Furthermore when this fiat tape is held stretched during the operation of applying a cover thereupon it will not turn or rotate about its longitudinal axis as freely as will a solid core under the twisting force exerted thereupon by the cover applying mechanism, and as a result the present core will have fewer longitudinal twists and will be straighter and better balanced in the finished elastic yarn than the solid rubber core. The above and other features of the invention will be more clearly understood from the following description when read in connection with the accompanying drawing.

In the drawing:

Figure 1 is a plan view of a piece of knitted fabric provided with laid-in strands of elastic yarn constructed in accordance with the present invention, a second piece of fabric being shown as sewed to the knitted fabric.

Figure 2 is a vertical sectional view through the sewed portions of the fabrics of Figure 1.

Figure 3 on a larger scale is a side elevation of a piece of elastic yarn constructed in accordance with the present invention, the inner and outer covers being partly removed.

Figure 4 is an end view of the tightly folded rubber tape, the cover being omitted; and

Figure 5 is a transverse sectional view through the elastic yam of. Figure 3.

The elastic yarn of the present invention may be used in the construction of woven, knitted or other types of elastic fabric, and this elastic yarn may be small enough for use as either warp or weft in a fine woven fabric, or it may be fine enough to be knitted on a fine gauge knitting machine. It is particularly well adapted however, as above pointed out, for use as laid-in elastic yarn to be placed in the courses of a knitted fabric.

In Figure 1 of the drawing the elastic yarn I of the present invention is shown in connection with an ordinary 1 and 1 ribbed knit fabric having the front wales II and rear wales l2, the elastic yarn l0 being shown as extending along every course of the rib knit fabric.

This elastic fabric is shown as sewed to an underlying fabric I3. These two fabrics are secured together by a row of stitches such as is formed on the ordinary lock-stitch sewing machine, and the seam is shown as formed of the interlocked threads l4 and I5.

It will be noted upon examining Figure 2, that the sewing machine needle for the thread M has pierced through a substantial portion of one of the elastic yarns ID. This frequently happens when an elastic fabric is sewed, and when an elastic yarn having a solid rubber core is used many elastic threads are either badly injured or entirely severed by the sewing machine needle.

In accordance with the present invention the core of the elastic yarn I0 is formed of a very thin wide rubber tape [6, and it is found in practice that the wider the tape the better within practical limits. A rubber tape l6 may be cut from a thinsheet of rubber, or it may be formed by depositing a thin strip or layer of latex upon a travelling surface so that the latex may be dried thereupon. This rubber tape, however, is preferably formed by extruding latex through an extruding nozzle having a very wide but thin slot.

The extruded latex material should be a compound containing rubber latex properly compounded to give satisfactory vulcanization, aging characteristics and physical properties. The extruded latex compound is subsequently coagulated then dried and vulcanized.

The wide, thin rubber tape however formed is provided with a. textile cover, which as it is applied to the tape serves to roll or fold the tape tightly upon itself into substantially a circular condition. This textile cover may be braided, wrapped or otherwise formed about the rubber tape, and in the construction shown the elastic yarn I0 is provided with an inner cover formed of a single strand of yarn I'I helically wound about the compressed rubber tape in one direction, and an outer cover formed of the two strands of yarn 18 which are helically wound about the rubber core in the opposite direction over the inner cover.

The operation of placing the covering strands tightly about the rubber core l6 may serve to cause the thin rubber sheet to fold back and forth upon itself a number of times as clearly shown in Figures 4 and 5, or the operation of applying the cover to this rubber tape l6 may serve to roll this rubber tape into a spiral coil in which the outer edge of the coil lies parallel to the longitudinal axis of the coiled rubber thread.

The covered elastic yarn as shown in Figure 3 may be formed on the ordinary core covering machine which is now in extensive use in covering solid rubber cores.

The rubber tape I6 is preferably held in a stretched condition while the cover is being applied thereto as is customary in covering elastic yarn. It is found in practice in covering the ordinary solid rubber core that as the first cover is wound upon such core its centrifugal force during the covering operation exerts a tangential pull upon the core which twists the core about its longitudinal axis. This twisting or rotation of the core during the operation of applying the cover thereto sets up counter forces in the opposite direction in the rubber thread and these stresses tend to cause the finished yarn to kink and snarl. The usual way of offsetting this tendency of the yarn to kink is to balance the force in the opposite direction by properly applying the second cover thereto.

It is found that when the thin tape rubber core of the present invention is covered, the pull exerted by the covering thread during the covering operation serves to fold the tape or to roll it upon itself into the, desired compact circular shape, and that most of the pull exerted by the covering yarn at this time is spent in converting the tape into a round core without rotating the tape about its longitudinal axis to the extent that is experienced in covering ordinary solid rubber core. tion of an elastic yarn in which the core is freer from longitudinal twist than the ordinary solid core.

The advantages of the present tape core over the solid'rubber core heretofore used lies primarily in the fact that when a sewing machine needle pierces even several folds of the present tape, a much greater total width of unpunctured surface across which the tear must spread before the threads will sever, remains than in the solid rubber core. This will be better understood upon considering the following example: If a thin rubber tape is substituted for a size 30's round or square rubber thread (.033 inch in diameter or width) the tape would be made .290 inch wide with a thickness of .003 inch. The needles used for stitching fabrics vary in diameter from .027 inch to .032 inch. When a solid thread is punctured by this needle the diameter of the needle is from 82% to 97% of the total width of the round or square thread. When the tape of the present invention is pierced the diameter of the needle is only from 9.3% to 11.0% of the total width of the tape. The tape, because of its folded or rolled condition beneath the cover, will be pierced possibly as many as four times if it has the above mentioned width of .290 inch, but even with four pierces in the tape, the total pierced area would be only from 37.3% to 44.1% of the total width as compared with the 82% to 97% pierced area of the solid rubber core. Not only does a needle upon striking the present rubber core pierce a less percent of its total width than in a correspondent solid rubber core, but a nick formed in this thin rubber tape will not cause it to tear transversely as readily as will a similar nick in a solid rubber core.

In carrying out the present invention it is found that the wider the tape is for a given crosssectional area, the better it is adapted to prevent serious injury from a needle, within certain practical limits; that is, the wider the tape, the more folds or coils will be formed, and the more folds or rolls produced in the tape, the lower will be the percentage of the total surface area thereof which is injured by the piercing of a needle. It will therefore be seen that the tape should be This results in the producmade as thin as possible within practical limits.

' forming size S rubber core might be made .00785 inch thick and 1 inch wide. This would give a ratio of width to thickness of 127.4 to 1.'

plated is believed to provide new advantages not heretofore contemplated.

An elastic yarn constructed in accordance with the present invention may be produced with a high degree of uniformity in size, and this tape core when entirely severed in an elastic fabric will not pull back appreciably in its cover or protrude from a face of the fabric. This is due largely to the fact that the cut end of the tape core will spread as soon asit is released in its cover and this spreading of the end will prevent it from pulling back in its cover and from protruding from a face of the fabric.

An elastic yarn having a tape rubber core such as herein contemplated has a further advantage over an elastic yarn having a solid rubber core, in that it is found that the pressure or binding action which a helically wound cover exerts on a solid rubber core over a period of time tends to weaken the core by forming a helical groove thereabout. When the thin tape rubber core of the present invention is used it is found that it will be cut or injured less by the covering yarn than will a solid rubber core.

The present tape rubber core is also better adapted to resist the destructive or aging action of sunlight than a solid rubber core. This is due to the fact that when this type of deterioration once starts it migrates from the surface to the center of the solid rubber thread, where as in the present tape core the rolling or folding of the tape upon itself forms a discontinuous ,mass in which the migration just mentioned must work around from the outside spiral or fold to the inner folds instead of travelling radially to the center of the thread.

Having thus described my invention, what I claim and desire to protect by Letters Patent is: 1. An elastic yarn that will not readily needle cut in a fabric when sewed with a sewing machine needle not over .032 inch in diameter, comprising a rubber core formed of a. thin fiat strip of rubber that is at least ten times as wide as said needle diameter, and a textile cover that holds said fiat strip compressed and folded back and forth upon itself many times into an approximately round core not more than .035 inch in diameter.

2. An elastic yarn that will not readily needle cut in a fabric when sewed with a sewing machine needle not over .03 inch in diameter, comprising a rubber core formed of a flat strip of rubber'that is at least twenty times as wide as it is thick and at least ten times as wide as said needle diameter, and a textile cover that holds said flat strip compressed and folded back and forth upon itself many times into an approximately round core not much largerthan said needle so that when the needle hits this core it will pierce not much over half of the total area of the width of the strip.

3. An elastic yarn that will not readily needle cut in a fabric when sewed with a sewing machine needle not over .03 inch in diameter, comprising a rubber core formed of a flat strip of rubber that is at least fifty times as wide as it is thick and at least ten times as wide as said neeof the area of the total width of the strip.

ARTHUR cont.

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