US2300241A - Covered rubber thread - Google Patents

Description

Oct. 27, 1942. 5 VAN voo -us 2,300,241

COVERED RUBBER THREAD Filed Jar 1. 8, 1941 Patented Oct. 27, 1942 UNITED STATES PATENT OFFICE COVERED RUBBER THREAD George S. Van Voorhis, Easthampton, Mass, assignor to United Elastic Corporation, Easthampton, Mass.,- a corporation of Massachusetts Application January 8, 1941, Serial No. 373,591

4 Claims. (01. 57-140) mined degree. Usually two such layers of yarn are wound around the core, one outside the other, the second layer being wound reversely to the first so that the twist of one will be neutralized by the other.

The most common use of covered rubber thread is in the manufacture of braided, knit, or woven fabrics. It has long been recognized in the trade, however, that no two pieces of elastic webbing have exactly the same degree of stretch or elongation. This objectionable characteristic of fabrics of this type is well illustrated in corsets, girdles, or similar articles, where one side will stretch more easily than the other so that as the garment is worn it stretches more and more in localized areas, and finally becomes practically worthless.

With a view to remedying this condition it was proposed some years ago to lay a stretch-limiting or stay thread of cotton, or other textile fiber, be-

with relatively few turns per foot of length, around the core during the thread covering operation, so that this non-elastic thread would be included in the covering with the rubber thread.

break relatively easily, especially under a quick snap. It is a common experience, therefore, to find that elastic webbing made of covered rubber threads in which these stay threads are incorporated will, after a period of severe wear, and particularly if subjected to sudden strains in the nature of snap actions, begin to lose their smoothness and uniformity. Such a piece of webbing will exhibit pin-holes where the stay threads have broken and the advantages of such threads, of course, are lost at and adjacent to thepoints of rupture.

The present invention is especially concerned.

with these conditions and it aims to devise a covered rubber thread in which this difficulty will be largely eliminated. v

The nature of the invention will be readily understood from th followingdescription when read in connection with the accompanying drawing, and the novel features will be particularly pointed out in the appended claims.

In the drawing,

Figure 1 is a side view, on a large scale, showing a short section of covered rubber thread with the covering partly unwound therefrom;

Fig. 2 is a cross-sectional view, also on a large scale, of the thread shown in Fig. 1; and

Fig. 3 is a similar view showing a slight modification. side the rubber core, or to wind it loosely, and '30 Referring first to Figs. 1 and 2, the article there shown comprises a rubber core 2 which may be either of square, circular, or other suitable crosssectional form, and a fibrous thread or yarn 3 lying beside it. The inner and outer layers or By this means the extent to which the covered wrappings of covering yarn or thread are shown rubber thread could thereafter be stretched or elongated was permanently and definitely limited to the length of the stay thread.

This improvement in covered rubber thread has been of great value in enabling manufacturers 40 to predetermine and control the degree of stretch of elastic fabrics, and consequently, to produce fabrics which will retain their original smoothness for a longer period of wear and greatly reducing the liability of the goods becoming over-stretched in localized areas and thus causing them to lose their shape.

In making covered rubber thread of thecharacter just described, however, it has been necessary to use stay threads of small size, that is,

those of high count or dernier. As a practical matter, also, cotton or rayon threads have been found best suited to this purpose. Even these, however, fail often to perform the functions for which they are intended, largely because they that a stretch-limiting thread of nylon need not at 4 and 5, respectively.

I have found that if the stretch-limiting element 3 consists of a thread of suitable strength which is relatively non-elastic but still has a very limited degree of elasticity, the difficulty above described is successfully avoided. Such a thread is rarely broken by a sudden snap, apparently for the reason that it has a certain shock-absorbing action or quality which cushions or nullifies the breaking effect of a quick snap. Those threads made of polymerized polyamides, of which nylon is the best known commercial example, answer this purpose very satisfactorily. Nylon yarn is readily available commercially and while it is slightly more expensive than cotton thread, the quantity used for stay thread purposes is so limited that the difference in price is not an important commercial factor. A nylon thread is stronger than a cotton thread of the same size so be 'as large as one of cotton, and, in addition, it has the important advantage of beingrelatively immune from breakage under suddenly applied stresses which would certainly break a cotton thread. In other words, while the cotton thread has a sharp. and comparatively definite breaking point, the nylon thread does not, but has a limited degree of elasticity which serves to absorb shock and thus to prevent breakage under a sharp snap of the type above referred to. Such degree of elasticity is relatively low, permitting perhaps not over about 15% of elastic elongation, whereas a rubber thread may be stretched 50( l% or 800%.

If desired, the advantages of both the cotton and nylon threads can rea y be combined by including a stretch-11m thread of cotton,

together with the nylon thread 3, in a covered rubber assembly of the character above described. This is illustrated in Fig. 3. The cotton thread,

said core and enclosed in said cover with said core in a stretch-limiting relationship thereto. said nylon thread having a limited degree 01'- elasticity but being devoid of a sharp breaking point. whereby it serves to limit the extent of stretch of the rubber thread without breaking under a sharp snap.

2. A covered rubber thread, comprising a rubber core, a flexible cover of fibrous thread or yarn wound around said core, and a stretch-limiting thread of nylon extending along said rubber core and enclosed therewith in said cover, said nylon thread having a limited degree of elasticity but being of a fibrous nature, has the advantage of exhibiting less tendency to pull back into the cover when it is broken than would a nylon thread, since the latter has a smoother, more slippery surface.

The invention thusprovides a covered rubber thread much superior to those heretofore produced in :performing those functions for which in: the same. and a nylon thread extending alon 40 I being devoid of a sharp breaking point, whereby it serves to limit the extent of stretch of the rubber thread without breaking under a sharp snap.

3. A covered rubber thread, comprising a rubber core, a flexible cover comprising reversely wound layers of fibrous thread or yarn enclosing said rubber core, one of said layers being wound around the other, and a nylon thread extending along said core and enclosed in said cover, with said rubber core in a stretch-limiting relation ship thereto, said nylon thread having a limited degree of elasticity but being devoid of a sharp breaking point, whereby it serves to limit the extent of stretch of the rubber thread without breaking under a sharp snap. I

4. A covered rubber thread, comprising a rubber core, a flexible cover of fibrous thread or parn wound around said core, and two stretch-limiting threads, one of nylon and the other of fibrous material, extending along said rubber core and enclosed therewith in said cover, said nylon threadhaving a limited degree of elasticity but being devoid of a sharp breaking point, whereby it serves to limit the extent of stretch of the rubber thread without breaking under a sharp snap.

GEORGE s. VAN ,voomns.

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