US2203622A - Rubber thread and method of making same - Google Patents

Description

June 1940. G. s. VAN VOORHIS' RUBBER THREAD AND METHOD OF MAKING SAME Filed March 23, 1938 Patented June 4, 1940 RUBBER THREAD AND METHOD OF MAKING SAME Georges S. Van Voorhis, Northampton, Mass., assignor to United Elastic Corporation, Easthampton, Mass., a corporation of Massachusetts Application March 23, 1938, Serial No. 197,655

4 Claims.

This invention relates to rubber threads and methods of making the same. It is more especially concerned with covered rubber thread and with the manufacture of this material.

Such thread is used extensively in the manufacture of a great variety of elastic products, particularly articles of wearing apparel and parts of such articles. When the processes of making products of this nature require sewing or stitching operations, it .is a common experience to find that the needle of the sewing machine has cut one or more of the rubber threads. While such a cut may not completely sever the thread, it-is the usual experience that when a thread has been nicked by a needle, or in any other manner, it will thereafter tear relatively easily at the nicked point and will break if subjected'to any great amount of strain. When this happens the ends of the rubber core of the thread draw back into the covering, and the difference in elasticity between this part of the fabric and adjacent areas produces a flaw in the goods which either makes them unsaleable, or greatly reduces their saleability.

With a view to overcomingrthis difiiculty, it has been customary heretofore to make the rubher core of a covered rubber thread of several independent strands. However, unless great care is taken in the manufacture of such a thread,

and sometimes in spite of such care, it is found that the thread has a tendency to twist or will not lie straight. Sometimes this is due to a twisted core and often, also to differences in the initial tension applied to the threads during the covering operation. These are serious objections in the manufacture of most elastic webbings since an important requirement is that they must lie flat and smooth. 7

The present invention is especially concerned with the foregoing conditions and the problems presented by them. It aims to produce a rubber thread which will be relatively immune to the effects of needle cuts, which will lie smooth and J fiat, and which can be manufactured economiwith which the method of this'invention may conveniently be performed; and

Fig. 2 is a side view showing a covered rubber thread made in accordance with this invention, the parts being separated at one end in order better to show the construction.

Figure 1 of the drawing shows a typical arrangement for covering the rubber core C to produce a covered rubber thread. It comprises upper and lower covering heads, indicated in general at 2 and 3, the two being arranged in vertical alinement with each other. The lower head comprises a rotary support 4 on which a spool, cop, or other thread body 5 is mounted, and includes a pulley 6 by means of which the head may be revolved about a vertical axis from any convenient source of power. This entire structure is provided with a central bore or tube, the lower end of which is shown at I, through which the rubber core C to be covered is fed upwardly. The thread T unwound from the spool or cop 5 is led through a thread guiding eye in the outer end of a flyer 8, and from there to the core C where it is wound around this core as the latter is fed upwardly through the head.

The upper head 2 is of the same construction, and corresponding parts are indicated by. the same, by primed, numerals. From the upper head the covered thread travels over a takeup roll I and goes thence to a spool l2 on which it is wound.

This arrangement is like that commonly used in this industry so that no detailed construction of it is necessary.

According to the present invention, the rubber core, instead of being supplied to the covering mechanism in the form of a thread, is brought to it in the form of a fiat tape I3. It is fed to. the head between, upper and lower feed rolls l4 and I which are positively connected with the takeoff roll l0 so that the speed of the latter bears a definite and fixed ratio to the delivery speed of the rolls l4 and i5. This ratio is made such that the, rubber core is held in a stretched and elongated condition continuously while it passes simply a single fold or curve in the middle, and

the free edges will be bent somewhat toward each other. It is preferable, however, to use a tape of such dimensions that it will be folded or curved longitudinally into a true tubular form with the free edges in abutting relationship to each other. If the tape is wide enough the edges obviously will be overlapped more or less, one upon the other. Since the particular form which it will take depends upon the width of the tape at the time the thread is wrapped around it and this width, in turn, will depend to some degree upon the extent to which it is stretched at that time. these various curved forms will be hereinafter referred to as approximately tubular forms. The covering thread or threads thereafter hold the tape in this form or condition. Subsequently, as the rubber core is fed through the upper head 2, one or more other threads are wound around it in a reverse direction to that in which 131."; first thread or threads are wound. It may here be noted that while a single thread is shown at T and T in Figs. 1 and 2, a more common arrangement is to wind two or three strands of thread simultaneously around the core at each covering point.

. Frequently a non-elastic stretch-limiting thread, such as an ordinary cotton thread, of suitable size, is included in the rubber core, and such a thread is shown at l6, Fig. 1, as it unwinds from the'supply spool I1 and is fed over the guide roll Hi, this thread meeting the rubber tape I3 as the latter is guided around the roll 20. The use of such a thread in this process is of advantage in affording a central form around which the tape is folded in the manner above described. Subsequently, when the tension on the finished thread is removed, it contracts longitudinally to a degree depending upon the tension maintained in the core during the covering operation, and depending, also, to some degree, upon the nature of the covering and, consequently, the degree to which it permits the thread to contract, and during such contraction the stretch-limiting thread.

or so-called gut thread, I6, is gathered or puckered more or 'less within its rubber covering. Also, as the core contracts longitudinally, it expands laterally and this fact modifies to some degree the shape which it takes inside the covering. In the absence of a gut thread the rubber substantially fills the space which would be occupied by such a thread if it were used.

While the tape l3 may consist of a single piece .of rubber, I prefer to use a tape made substanby the inherent adhesion of the rubber and vulcanized in this condition, but the degree of adhesion is reduced and controlled by the presence of a limited amount of talc, or some other dry separating substance, between the threads, so that while the threads ofier considerable. resistance to separation from each other, nevertheless they are not united into an integral. structure. v

When a needle is forced through a thread made in this manner, it is rarely that it cuts one of the strands. The usual effect seems to be that the needle separates the individual strands and breaks the bond uniting them sufficiently to allow the needle to pass through. Apparently the thread more or less dodges the needle or, in other words, the needle finds the weakest place in the tape, which is the line of binding between adjacent strands. However, if a strand should be cut, it adheres to the other uninjured threads with sufiicient strength to prevent them from drawing back into the covering and thus producing a flaw in the goods in the manner above described. it

Whether, however, the rubber core is made from an integral tape, or of one composed of a series of threads or strands adhesively united to each other, the method above described provides an economical process of making covered rubber thread. It requires no operations additional to those necessarily used in making such a thread by the usual processes, and it lends itself conveniently to the manufacture of threads having cores of different gages. For example, these thin tapes canbe made of extremely thin thicknesses, even down to a hundredth of an inch. Consequently, the gage of a core made of tape of this thickness will depend upon the width of the tape. Thus the desired flexibility in the manufacture of a product of this character is easily obtainable.

A further advantage of this method is that it is easy to feed the tape to the covering instrumentalities without twisting it. In fact, it would be more difficult to feed it otherwise. Consequently, the objectionable characteristics re sulting from a twisted core are readily avoided.

When the core consists of, or includes, a tape composed of a series of rubber strands adhesively united to each other, as above described, the difficulty heretofore experienced in making covered rubber thread with a ,core composed of a plurality of independent rubber threads is avoided because the tape, being a unitary structure. all the threads or strands are subjected to the same degree of tension. Also, in this construction the fact that the threads composing the tape are adhesively united to each other practically eliminates the difficulty heretofore experienced with the breakage of rubber threads, A contributing factor to this result is the fact that the tape tends constantly to spring into its original flat form, this tendency being additional to its inherent disposition to expand laterally.

Thus the invention materially reduces the difficulties previously described in using rubber threads of the orthodox types. Y

Having thus described my invention, what I desire to claim as new is:

1. A rubber thread comprising a strip rubber tape composed of a. series of parallel rubber threads adhesively bonded to each other in a side by side relationship but not integrally united. said tape being curved longitudinally into an ap proximately tubular form, and means holding it in said form;

2. A rubber thread comprising a strip of rubber tape composed of a series of parallel rubber threads bonded directly to each other by a controlled adhesion which holds them releasably in said relationship without integrally uniting them, but by a union offering substantial resistance to the separation of the threads, said tape being curved longitudinally into an approximately tubular form, and a covering of thread wound around said tape and holding it in said form.

3. A covered rubber thread comprising a strip of rubber tape composed of a series of parallel rubber threads united to each other in a parallel side by Side relationship by a controlled adhesion, a central stretch limiting thread, said tape being curved longitudinally around said stretch-limiting thread, and acovering of thread ams-p22 3 side and into contact with the flat race 0! said tape, and winding one or more covering threads around said tape while it is being so fed and thereby curving the tape around the first thread into an approximately tubular form and binding 5 it in said form by said covering thread or threads.

GEORGE S. V AN VOORHIS.

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