US2840882A

US2840882A - Fibrous covering for elastic thread

Info

Publication number: US2840882A
Application number: US513773A
Authority: US
Inventors: Charles C Smith
Original assignee: Darlington Fabrics Corp
Current assignee: Darlington Fabrics Corp
Priority date: 1951-12-12
Filing date: 1955-06-07
Publication date: 1958-07-01
Anticipated expiration: 1975-07-01

Description

July l, 1958 c. c. sMrrH 2,840,882

FIBROUS COVERING FOR ELASTIC THREAD Original Filed Deo. '12. `19511 46g i INVENToR.

144.2 y ww le@ f5 475 26M \\f) u 465 l l /V nited States Patent O FIBRoUs CoVERlNG Fon ELASTIC THREAD Charles C. Smith, Providence R. I., assigner to Darlington Fabrics Corporation, New York, N. Y., a corporation of Delaware Original application December 12, 1951, Serial No. 261,231, now Patent No. 2,733,179, dated January 31, 1956. Divided and this application June 7, 1955, Serial No. 513,773

15 Claims. (Cl. 28-81) This invention relates to covered rubber elastic thread. As contrasted with customary prior practice wherein a rubber elastic core thread is encased in a helical wrapping or wrappings of textile yarn, the present invention provides a covered elastic thread wherein the covering or jacket consists of a multitude of independent bers or laments arranged substantially parallel to each other without twist and extending lengthwise of the core to which each ber or filament is attached at two or more spaced points in its length so as to provide, between adjacent points of attachment, a free length of the ber which forms a bight or loop, the projecting bights or loops collectively forming a soft jacket or covering which is longitudinally stretchable with the core.

Objects of the invention are to provide a covered elastic thread which is soft to the hand, so that it may be worn next to the human body without harsh chang of the delicate body tissues; to provide a series of softly enclosed air cells adapted to absorb body exudation, and to provide for heat or cold insulation; to provide a core with soft parallelized covering bers, free at certain intervals, and to permit the garment made from the thread to accommodate itself to minute body movements, without excessive sliding; and other objects which will become clear and evident as the specication of the selected embodiment proceeds.

In contradistinction to customary prior practice, the present invention provides for covering the elastic core with parallel bers such, for example, as are obtained by carding, combing or drawing staple length bers such as cotton, wool, rayon, nylon or the like, or by cutting synthetic laments into staple lengths, or with independent, continuous synthetic laments which have not been twisted together and which are, in this form, known in the trade as toW.

Any length of ber, or a blend of various ber lengths or continuous laments may be employed in the covering operation, as may be desired or convenient.

According to a preferred embodiment of the invention a continuous or unbroken layer of substanti-ally parallel bers, either staple or continuous, is anchored at intervals to the elastic core. i

However, the bers employed should be longer than flock bers and, in fact, lthe majority of the bers should be long enough to be attached to the core at two points, at least, separated from one another by a predetermined distance so as to permit the fibers, when the thread is relaxed after covering, to form bends or bights projecting from the core, such bends or bights being shaped, for example, more or less like the Greek letter omega. These projecting bights or bends collectively form a soft, continuous covering or jacket for the core.

By staple fibers is meant natural bers, for example, like cotton, in which there is considerable variation in ber length. For example, in what is known as 1%; inch American cotton, the ber length will vary from 2,840,882 Patented July l, i958 ICC 2 about 1/16 of an inch up to about 2 inches, with only about 35% of the bers having a length of lli/16 inches.

Short fibers, say about 1A inch or shorter, are sometimes known as ilock, particularly when they have been separated, as by combing for example, from the longer bers.

Synthetic staple bers may also have considerable length variation in the ber length array. However, as a general rule, the manufactured staple bers are more uniform in length than the natural staple bers.

For some products, a substantially uniform length staple is desired, while in some other cases a substantial variation in ber length will result in the optimum product. The ratio of length to diameter of the bers should be very substantial. In staple bers, it is preferable to use lengths of about from say 65 to 25,000 times the diameter of the ber. When continuous laments are used, the length to diameter ratio is almost innite.

A single relatively short staple ber will form but a few omega-like loops, for instance only one, while a longer staple ber or a continuous lament may form a larger number of loops, depending on the length of the fiber and the size of the loop.

Sin-ce the ber lengths are not always, and in fact, se1- dom are exact multiples of the lengths necessary to form a single bight or loop, free ends of many of the bers will project, being interspersed among the loops, and will impart -something of a velvet or flocked effect to the covering.

In the process of manufacture the core (round, square or of any other convenient cross-sectional shape) is rst flattened and simultaneously tensioned to elongate it to the desired degree. Then while the core is tensioned, a series of properly spaced, transverse or diagonal lines are printed on diametrically opposite sides of the elongated core while the latter is flattened to form a thin ribbon. The printing fluid is of an elastic and adhesive nature and the parallel bers are pressed into the printed lines so that on curing, the bers become permanently fastened to the core at the printed lines while being free from the core between adjacent printed lines. When the covered core is relaxed the free portions of the covering bers project out from the core to form the bights or loops above mentioned, successive bights of a given ber longitudinally of the thread normally substantially contacting.

In accordance with the present invention, the possible elongation of the covered yarn is entirely independent of the presence or absence of the pre-stresses in the core. In the prior art product the elongation of the covered yarn is directly related to and is a function of the prestresses in the core. l

In prior practice, wherein the core is covered with a helical wrapping, the core is always pre-stressed to elongate it to a predetermined percentage of its maximum safe elongation (elongation to the elastic limit) while the wrapping is being applied. From its normal relaxed condition, the covered yarn is only capable of elongation in response to a load greater than that necessary to stretch the core to said predetermined percentage elongation and furthermore, since the core, in the relaxed yarn, is held under radial compression, the relaxed yarn is sti and has aharsh feel.

For example, in the prior art, a spirally wound core, for example, the base core, may be elongated to about its maximum, consistent with safety, and a number of `spirally wound covering coils Vwound tight on the eloni prior art, the elastic core has a maximum safe elongation of 600%, and a 150% elongation is desired in the covered product, then such a number of covering convolutions is wound on the elongated core as to permit it to recover only 150% out of the 600% elongation. In such case the elastic core is longitudinally pre-stressed at 450% and prevented from further contraction by the convolutions wound thereon.

According to the present invention the core of the relaxed covered yarn may have any desired elongation from zero to the maximum safe elongation. The covered yarn may be made to begin to respond in stretching to any load which would stretch the uncovered core or to begin to stretch in response to the application of any predetermined greater load up to that which would produce maximum elongation, and correlatively, to contract, after extension, to any predetermined percentage of its maximum elongation. Moreover, since in the relaxed cover yarn the core is not under radial compression, the yarn is very pliable and has a soft, pleasant feel.

In the practice of the present invention, the core is widened by compression while being stretched longitudinally. For specific example, if a resilient core has a safe total cubieal displacement factor equal to the cubical displacement resultant from a 600% longitudinal elongation alone, and it is desired that the covered yarn have a lengthwise elongation of 150% and at the same time have a soft feel and goed pliability, the core may be widened, by transverse compression to provide 450% of the permissive cubical displacement and simultaneously stretched longitudinally to provide the remaining 150% of the permissive cubieal displacement. The filaments or fibers are then anchored to the stretched and flattened core by transverse bands of adhesive with such spacing between adjacent bands as will permit the core to contract transversely to the equivalent of 450% of the permissive cubical displacement and simultaneously to contract in length the equivalent of 150% of the permissive cubical displacement. In such a case, the core of the covered yarn will have transverse and 0% longitudinal pre-stress. In other words, it is fully relaxed. For further example, with proper spacing of the fiber anchoring bands during application of the fibers, the relaxed covered yarn may begin to stretch upon application of a very small load, but stretch may be limited, by the straightening of the fiber bights, at a point where the core has been stretched only 150% as compared with a possible 600% stretch of the uncovered core.

Again, with proper spacing of the fiber anchoring bands, the action of the bands may be such that in the relaxed thread the core will have a predetermined elongation, for example, 150% of its maximum elongation and thus a substantial load must be applied before the covered yarn begins to stretch. The stretch is limited, as in the preceding case, by vthe straightening of the fibers, for example, at a point where the core has extended to 400% of its maximum elongation.

As above suggested, the permissive elongation of the covered core is controlled by printing the anchoring lines of adhesive closer or farther apart or by elongating the flattened ribbon more or less preparatory to printing. Thus, for example, if a 150% elongation be desired in the finished product, the attened ribbon is elongated about 150% while being printed. desired, then the ribbon is elongated to 400%, while being printed. Alternatively, by printing the anchoring lines of adhesive on a core which has been stretched substantially to its elastic limit, with a spacing so dimensioned as to permit a 150% of a 400% recovery in the completed thread, there will be produced a pre-stressed core such that the thread will have a greater load-carrying capacity before elongation starts than in the former case, which results in a softer acting thread. Thus any desired elongation may be provided for the finished coY-. ered thread.` It may be noted that the knitting trade If a 400% elongation be' thereafter will retain that original shape during normal use. On such recovery the covering bers attached to the diametrically opposite faces of the core, while it was fiat, will be substantially uniformly distributed, peripherally, about the outer surface of lthe relaxed core, the projecting bights forming a low pitch helix coaxial with the core.

In the accompanying drawings Fig. l is a diagrammatic, vertical section illustrating one desirable form of apparatus for use in the practice of the invention;

Fig. 2 is a greatly enlarged, fragmentary elevation of a rubber elastic core thread showing various steps in the process of covering it;

Fig. 3 is a transverse section on the line 3*?) of Fig. 2, illustrating a core of circular normal section;

Fig. 4 is a transverse section through the core as it appears when flattened preparatory to the application of adhesive;

Fig. 5 is a transverse section illustrating the diagonal, sticky areas on one side of the flattened core resultant from the printing operation;

Fig. 6 is a transverse section, substantially on the line 6.-6 of Fig. 2, showing the parallel covering fibers partially embedded in the sticky area on one side of the flattened core, the fibers on the opposite side being free from the core;

Fig. 7 is a transverse section, to very large scale, substantially on the line 7 7 of Fig. 2, showing the core after the tension has been partly relaxed and indicating the uniform peripheral distribution of the covering fibers puffed out into radial bights or loops;

Fig. 8 is a fragmentary elevation partly in section and to very large scale, showing one of the rows of bights as they appear in the relaxed thread;

Fig. 9 is a greatly enlarged longitudinal, fragmentary section, showing one of the omega-like bights or loops and the way in which it is anchored to the core; and

Fig. 10 is a diagram illustrative of a principle made use of in the practice of the present invention.

In accordance with the present invention use is made of a phenomenon observed in the stretching of a rubber elastic thread which is illustrated in Fig. l0. In this view the character T represents a relaxed rubber elastic thread of circular transverse section which is passed between a pair of rigid rollers R, one of which is shown. For purposes of illustration it may be assumed that the rollers R do not turn but that they are spaced apart a distance such that the thread squeezed between them is widened and flattened so that at this portion its Width exceeds the diameter of the original thread T.

Assuming that initially a length of the thread has been passed between the rollers, for example by turning them, so as to provide a portion T2 to which tension may be applied in the direction of the arrow A by a force IT, and that this tension has been increased until the combined transverse and longitudinal displacement of the molecules of the rubber, due to the compression of the thread between the rolls and the application of longitudinal tension, substantially equals the cubic displacement which would result from the application of stress, longitudinally only, up to the elastic limit of the thread, the thread will begin to iiow from between the stationary rollers R. Assuming that the point K is the point in the thread which was being gripped by the rolls at the instant the tension F reached the above intensity, the thread willv emerge from the rolls as a ribbon T1, thepoint K advancing and all ofthe thread between the point K and the rollers R being liat, while all of the thread below the point K will remain of its initial circular transverse section. If the force F for advancing the thread be applied by passing the thread through a second pair of rolls R2, driven at the proper speed, the entire length of thread between the two sets of rolls, after the point K has passed the rolls R, will be fiat, but as the thread emerges from between the rolls R2 it will resume its initial circular section. By the use of this principle, it is possible to subject a portion of a normally circular thread to a treatment which ordinarily could be applied only to a flat ribbon, but the result of such treatment, as compared to its application to a normally flat ribbon, will bemodied when the thread resumes its normal circular section.

The above principle, that is to say the retention of its liattened condition in response to the concomitant application of liattening pressure and tension, is applicable to rubber elastic threads of any initial transverse section and even to the covering of elastic sheet material, on one or both sides, but for most purposes its utility is directed to its application to threads of initially regular transverse section, that is to say threads of circular or regular polygonal section, and when hereinafter reference is made to a thread of regular transverse section such term is intended to apply to threads of any regular polygonal section and also to threads of circular transverse section.

Referring to Fig. 1, which illustrates a selected mechanical embodiment of means for use in the practice of the invention, a plurality of core-supporting spools (three such spools being shown by way of example) are indicated at 20, 20a and 20h, these spools being driven by a conventional uniform surface speed drive mechainism comprising the drive rolls 21, 21a and 2lb by means 4of which the relaxed elastic core yarns 22, 22a and 22b .are unwound from the spools or supply packages and are fed through guide eyes 23 (only one of which is shown) into the nip of a pair of feeding tensioning :means 24, 24. These rolls 24, 24 are positively driven :at a uniform, peripheral speed and are adjustably supported in a manner conventional in the art so that any desired space may be provided between them at the nip point. Since the means for driving and adjusting the

rolls

24, 24 may be conventional they have not been herein illustrated. The nip rolls 24, 24 are of a length such as to grip a substantial number of core threads simultaneously. The eyes 23 guide the longitudinally spaced elastic core yarns from the several supply packages 20, 20a, 2Gb, etc. so that they enter the nip rolls in spaced, side-by-side relation. Any number of core yarns may be covered simultaneously but to facilitate the operation it is preferable to space the core yarns so that there are from four to sixteen core yarns per inch of length of the nip of the

rolls

24, 24, depending on the size of the core yarns.

The core yarns are drawn through the mechanism by a second pair of nip rolls 25, 25 spaced a suitable distance from the

rolls

24, 24. The

rolls

25, 25 are driven at a higher peripheral speed than the

rolls

24, 24 thereby to elongate the core threads to the desired degree within the zone at which the actual covering operation is performed. The desired elongation may be produced (within the capacity of the elastic material) by adjusting the peripheral speed of the

rolls

25, 25 relatively to that of the

rolls

24, 24, any convenient means being provided for adjusting the speed of either one or both of the pairs of

rolls

24, 24 or 25, 25. The linear speed dilierence between the nip rolls 24, 24 and 25, 25 shall be such as to provide the necessary balancing tension, on that portion of the-transversely elongaged core which is located between theseV two sets of nip rolls, to prevent the premature recovery of the transverse displacement. No speed-adjusting mechanism is here illustrated since 6 such mechanism is well known in the art and may be conventional.

The printing, liber deposit and curing and setting of the adhesive anchoring material are all performed within the space between the two sets of

rolls

24, 24 and 25, 2S and simultaneously at diametrically opposite sides or faces of the flattened and tensioned elastic core.

Any desired design, including lines, dots, etc., may be printed on the faces of the core while the latter is flattened by the action of the engraved printing rolls 26, 26 (these rolls being at opposite sides of the core). The printing rolls are supplied with suitable printing compound 27 held in containers 2S, 28 from which it is carried up by the feed rolls 29, 29 and deposited on the undersides of the engraved printing rolls 26, 26. This printing compound a type which, when first applied, is sticky or tacky which sets when properly treated so as to be retentive of the libers which may be placed in contact with it while in its tacky condition. The adhesive material is also of a nature such that when it has set it is elastic so that it is capable of elongating with the elastic core without separating from the latter. The excess printing compound is removed by

doctor blades

30, 30 of conventional design. The printing rolls 26, 26 and the feed rolls 29, 29 are suitably driven in the direction indicated by the arrows in Fig. l, by any conventional type of drive mechanism, not shown.

The printing rolls 26, 26 are relatively adjustable thereby to permit contacting of the iiattened core at the printing point and any appropriate conventional means may be provided for driving and adjusting the printing rolls.

After the adhesive has been printed onto the core the fibers are delivered for contact with the printed areas. As here illustrated the fibers or filaments are applied to the core by means of a pair of endless belts -or blankets 3l. and 3l.2L suitably supported and driven by

rollers

32, 33

and 32a, 332l which may be supported on a frame (not These rolls are made of wool, felt, fine cotton duck, canvas or similar material to which the bers will ten-d to cling and so as to be carried thereby, and which have a comparatively smooth surface with which to press the fibers into the printed anchoring places. The fibers for use in making the covering are supplied as a pair of packages 34 and 343'. These packages may be rolls of carded -or combed staple fiber in sliver form or a continuous filament tow, the constituent fibers or lilaments being substantially parallel. Any other convenient arrangement may be used for supplying the fibers to the belts 3l and 31a. The fibers are delivered to the belts 31 and 31a by a set of feed rolls 35 and 36; 35a and 36EL (one pair for each belt), driven in any conventional manner. The belts 3i and 31a are provided with pressure plates 37, 37 each located between corresponding belt-supporting rollers and each being adapted yieldingly to bear aaginst the inside run of the corresponding belt so as to provide the necessary pressure to press the fibers against the sticky areas formed on the core by the printing rolls. These pressure plates 37 may be yieldingly urged toward each other in any suitable way, for example, by springs or weighted levers (not shown).

rEhe pressure plates 37, 37 may be mounted on electrically insulating standards (not shown) and electrically grounded (not shown) so as, in effect, to constitute a tribo-electric magnetic condenser plate, resiliently to hold the fibers onto the belt or blanket.

Such a tribo-electric magnetic condenser plate is fully arrows the sticky areas of the core will pick up all of the bers from the surfaces of the belts which can be embedded inthe adhesive material by the pressure plates 37, 37. Any excess fiber not thus picked up continues to follow the belts 31 and 31a. The speed `of the feed rollers 35, 36 when properly adjusted, is such as to deliver only enough fibers to the belts to replenish the supply on the latter. Combs 39 and 39a are arranged to even up the fibers on the belts or blankets 31 and 31a. The linear speed of the printing rolls 26, 26 and the linear speed of the belts or blankets 31 and 31a are so relatively adjusted as to coincide with the linear speed of the core thread at the particular elongation determined by the speed difference between the

rolls

24, 24 and 25, 25.

After the fibers have been deposited and adhesively attached to the sticky areas of the core thread, the covered thread is drawn through a drying, curing cr vulcanizing device 40 provided with inlet and outlet openings 41 and 42 respectively. If the adhesive employed is such as becomes set by exposure to a high temperature, the apparatus 40 may be provided with

heating elements

43, 43 of any desired type and adapted to dry, cure or vulcanize the printed compound. lf the adhesive material is such as becames set by exposure to a gaseous or other uid medium, then the device 40 may be provided with means for exposing the covered thread to such a uid medium on its way through the device 40. Obviously if the sticky material be of a self-curing nature, such that it sets quickly upon exposure to the air, or if it be a thermoplastic material which sets upon cooling, the device 40 may be dispensed with.

The covered and cured elastic thread passes between the

rolls

25, 25 and as soon as the tension is relaxed it resumes its original cross-section shape which it had before it entered the

rolls

24, 24. Thus if the normal section of the elastic thread was round before entering the

rolls

24, 24, it will resume its round shape after leaving the rolls 25, 2S. Likewise a square thread will become square, a triangular thread will become triangular and so on, it being noted that the flattening action which the core undergoes during the operation of attaching the fibers results in no permanent deformation, assuming, of course, that the elastic thread has such a normal elasticity as to cause it to resume its original cross-sectional shape. However, as has been stated, the discharge nip

rolls

25, 25 have a higher `peripheral speed than the feeding nip rolls 24, 24 so that the portion of the core body, located between these pairs of rollers, will be under the desired longitudinal stress which shall be of such magnitude as to balance the transverse stresses and thus hold the core body in a transversely attenuated condition.

The covered and relaxed threads 44, 44a and 441 are wound on

suitable cores

45, 45" and 45b driven by drums 46, 46a and 46h respectively, at a uniform surface speed in a conventional manner, the drums turning in the direction indicated by the arrows. Distributing lingers 47, 47a and 47 may be provided for distributing the completed elastic thread longitudinally of the cores, these distributing fingers being moved back and forth in a conventional way.

The various parts of the apparatus are supported on appropriate frame members (not shown) and the driving means for the various rotating parts may comprise conventional gears, belts, chains or the like which receive their motion from a suitable power source (not shown).

Referring to Fig. 2, one of the elastic core threads is shown to greatly enlarged scale. In the upper part of the figure the core thread 22 is shown in its normal or relaxed form, this core being of round or circular section, as shown at Fig. 3. As the core thread passes between the

rolls

24, 24 and later through the

rolls

25, 25 it is flattened by the

rolls

24, 24 to form a thin ribbon and by virtue of the tensioning effect of the rolls 25, 2S this flattened core will 4retain its ribbon-like cross section throughout the portion intervening between the rolls 24, 24 'and '25, 25, as illustrated, for example, at the central part of Fig. 2, and in the transverse sections of Figs. 4, 5 and 6. It is preferred to flatten the thread sufficiently to produce a 10 to 50% transverse enlargement in the width of the flattened section, as compared with the normal relaxed diameter of the thread, while at the same time, by the tensioning action of the

rolls

24, 24 and 25, 25 the flattened portion is elongated to result in a reduction in thickness of 50 to 90% of the original diameter of the relaxed cylindrical thread. For example, if a round thread having a relaxed diameter of 0.020 incl-i is used, ir may be so attened and tensioned that the flattened portion of the thread will be about 0.022 inch wide and about 0.002 inch thick at the point at which the adhesive is printed on.

In printing this attened ribbon-like thread the socalled lake printing process may be used. According to this process the printing rolls have engraved cavities which become filled with the printing compound, the excess being removed by a doctor blade. As the printing rolls press against the flattened thread these small lakes of printing compound will adhere to the face of the attened thread and will be pulled out of the cavity in the rolls, thus depositing a predetermined measured quantity of compound on the thread. As suggested, the printing compound is such as to produce sticky areas on the core thread. Usually the printing compound will be adhesive when applied and capable of setting when subjected to appropriate treatment. In the particular illustration shown in Fig. 2, the flat surfaces of the core thread have been printed with diagonal bands 51 on one side and 52 on the opposite side. The printed section, as a whole, is designated by the numeral 53. The diagonal lines 51 may be so arranged as to form a substantially unbroken helix when the elastic thread is subsequently relaxed. Obviously any other design may be printed on the core, if preferred.

The covering fibers stick to the printed areas as the core passes between -the belts 31 and 31a. These bers indicated at 54 (Figs. 2 and 6) are straight and substantially parallel with each other and extend longitudinally of the elastic core thread. The initial spacing of adjacent

sticky bands

51 or 52 determines the height of the omega-like bights or loops which the covering bers form when the thread is relaxed; that is if the initial distance between

adjacent bands

51 or 52 is made long, the omegalike loops will be high, that is to say they will project a substantial distance from the core when the latter is relaxed. If the distance between adjacent bands 51 is short, the loops will be low; thus the thickness of the jacket or covering material may be controlled as dcsired. For purposes of illustration a relaxed thread having a diameter of 0.020 inch may be provided with

bands

51 or 52 spaced from 0.015 to 0.02 inch apart. Such spacing will produce a loop height of approximately 0.005 to 0.007 inch measured radially out from the periphery of the core. Such omega-like bights or loops are indicated at 56 on the relaxed core (Figs. 2, 7, 8 and 9).

Since the anchoring bands l51 and 52 are printed on the diametrically opposite, attened faces of the core, a small gap l57 (Fig. 6) will be left near each edge of the attened section. As a rule these gaps are of a lesser thickness than that of the flattened core. By reducing the viscosity of the printing compound so that it flows around the edges of the flattened core these gaps may be eliminated. However for ornamental purposes such gaps may be retained or even made purposely wider.

Referring to Fig. 9, one of the omega-like loops 56 and also parts of two adjacent yprinted bands 51 are shown in a part of the relaxed core 46. The space between adjacent bands 51 (as shown in Fig. 2) has shortened as the core contracted so that the bands S1 in Fig. 9 are much closer together than those in Fig. 2. Those portions 54X of vthe ber which have become embedded in the adjacent bands 51 remain substantially parallel to 9 the axis of the core while the intervening loose portion of the ber buckles out to form the loop 56 (Fig. 9). This projecting loop with the portions 54X which may be referred to as the legs of the loop, forms a gure suggestive of the Greek letter omega. However, it may be observed that if the spacing of the bands 51, as applied to the tensioned core, is substantially less than that illustrated in Fig. 2, the resultant loops or bights, when the core is relaxed, may be of a shape less closely resembling the Greek letter omega and, in fact, may more nearly approach the shape of the letter U.

In passing through the curing device 40 the leg or foot portions 54X of the loops are permanently anchored to the core by the setting of the adhesive. The projecting portions 56 of the loops collectively form the peripheral surface of the core cover or jacket in the completed thread, it being noted that the parallel bers are quite close together peripherally of the thread and that successive bights of any given ber may be very close together and substantially touch when the core is fully relaxed.

Since the bands 51 of rubber adhesive are applied to and cured (and thus in fully relaxed condition) while the core is tensioned, the relief of core-tensioning stress tends to compress each band axially of the core and thus, collectively, the resistance of the bands 51 to such compression may limit contraction of the core to a predetermined amount, dependent upon the initial spacing and width of the bands 51.

When the covered thread prepared as above described is elongated during use, each of the loops 56 will, at full extension of the thread, become a straight continuation of its leg orV foot portion 54X. If the thread is stretched to any substantial further degree the bers will rupture and the core will thereafter break. The extensibility of the complete thread may be so calculated that the bers 54 and the core 46 will rupture simultaneously or practically so. For most uses such a simultaneous break of the covering and core is desirable. However for certain specic purposes it may be desirable to provide a construction such that the fibers 54 will break while the core 46 is still capable of substantial further elongation before reaching its elastic limit. n the other hand, it may sometimes be desirable to construct the covered thread so that the core 46 will rupture rst and the ber covering will rupture only on further elongation. However, the `greatest tensile strength of a given covered thread is obtained when the rupture of the core and covering is substantially simultaneous.

The improved covered thread, according to the present invention, has a very soft, lofty covering or jacket providing a wholly diiferent feel from that -of a thread covered by the usual spiral windings of the prior art. Furthermore, the improved thread of the present invention is capable of elongation to a very substantial degree without exposing the ycore whereas threads covered with spiral coverings, according to usual prior practice, can only be elongated to a limited extent before the core thread is exposed. Moreover, by the present procedure the core is adequately covered by the use of a `substantially less amount of fibrous covering material than is necessary when other prior methods of covering are employed.

The term rubber elastic is herein employed as a convenient expression to denote a material having the elastic stretch characteristics similar to those ofl natural India rubber and is to be understood as inclusive of all such other materials, among them the synthetic rubbers, as have similar physical characteristics.

While as herein specically described the ber is attached to the elastic thread by the use of adhesive, usually a material different from that of the thread, it is contemplated as within the scope of the invention, particularly when the elastic thread is of a synthetic material, that the adhesion of the ber may be obtained by causing the stance, by the use of a volatile solvent or by the application of heat in any convenient way.

While a desirable embodiment of the invention has herein been illustrated and described by way of example it is to be understood that the invention is Ibroadly inclusive of any and all modifications falling within the scope of the appended claims.

This application is a division of my copending application for Fibrous Covering for Elastic Thread and Method of Producing It, Serial No. 261,231, led December 12, 1951, now Patent No. 2,733,179.

I claim:

l. A relaxed rubber elastic core thread and jacket encasing and substantially concealing the thread, the thread and jacket being stretchable when the thread is subjected to longitudinal tension, the jacket being attached at longitudinally spaced intervals to the thread, and having a plurality of projecting brous bights between each adjacent pair of points of attachment.

2. A relaxed rubber elastic core thread and jacket encasing the thread, the thread and jacket being stretchable to substantially the same degree, thejacket comprising a substantially uninterrupted row of brous loops which collectively form a soft cushion-like surface.

3. In c ombination with a single bare, radially uncompressed rubber elastic core thread, a multitude of elongate bers disposed about the peripheral surface of the core, side by side, and means adhesively attaching each ber to the core at spaced points in its length and with portions between adjacent points of attachment projecting as open bights.

4. In combination with a single bare rubber elastic core thread, said core being radially uncompressed so as to be free to relax completely in the absence of stress applied longitudinally thereto, a multitude of bers, each ber forming projecting bights and adhesive attaching each ber to the core at points intervening between adjacent bights.

5. In combination with a relaxed rubber elastic core thread, a multitude of open bights of brous -material collectively substantially concealing the core thread, the legs of each bight being permanently attached to the surface of the thread.

6. In combination with a bare rubber elastic core thread, said core being radially uncompressed, substantially parallel bers extending longitudinally of the thread and disposed peripherally, side by side, on the bare surface of the core thread, and adhesive attaching each ber to the core thread at points spaced lengthwise of the core thread, the points of attachment deiining a helix about the periphery of the core thread, each ber being free from the core thread between adjacent turns of the helix.

7. In combination with a relaxed rubber elastic core thread, a multitude of omega-shaped bights of brous material, and adhesive attaching the legs of each bight to the thread.

8. In combination with a relaxed rubber elastic core thread, a multitude of omega-shaped bights of fibrous material, the legs of each bight extending parallel to the axis of the core -thread and being permanently attached to the thread, the bights collectively forming a helix of low pitch coaxial with the thread.

9. In combination with a relaxed rubber elastic core thread, a longitudinally extensible jacket of textile ber 'encasing and substantially concealing the thread, said jacket comprising a multitude of independent, substantially parallel bers of staple or greater length, and means 'attaching each ber at spaced points in its length to the thread, the bers forming loose bights intermediate their points of attachment whereby elongation of the thread, when subjected to tension, is permitted.

l0. In combination with a relaxed rubber elastic core thread, a multitude of laments of synthetic textile material extending lengthwise of the thread, each lament thread itself to become temporarily adhesive as, for informing a plurality of omega-shaped bights, means pereach bight being disposed in a substantially radial plane,`

the bights collectively forming a jacket which substany tially covers the thread but which does not substantially limit the elongation of the thread.

1l. In combination with a single rubber elastic core thread, substantially parallel bers extending longitudinally of the thread, means attaching each fiber to the thread at points spaced lengthwise of the thread, each fiber forming a radially projecting bight between adjacent points of attachment, the bights collectively forminga helix of low pitch extending around the thread and substantially concealing the thread when the latter is relaxed.

12. In combination with a single rubber elastic core thread, substantially parallel fibers extending longitudinally of the thread, means attaching each ber to the thread at points spaced lengthwise of the thread, each fiber projecting as a loose loop between adjacent points of attachment, the points of attachment being so close together when the thread is relaxed that adjacent loops of the same ber substantially contract.

13. In combination with a relaxed rubber elastic core thread, a jacket of textile ber encasing and substantially concealing the thread, said jacket comprising a multitude of independent bers of staple or greater length, each liber being attached at spaced points in its length to the thread and having a projecting bight intermediate its points of attachment, the lengths of said bights being such as to permit substantial elongation of the elastic thread but to limit such elongation to a predetermined fraction of its normal possible stretch.

14. In combination with a relaxed rubber elastic core thread, a jacket of textile ber encasing and substantially concealing the thread, said jacket comprising a multitude of independent fibers of staple or greater length, each ber being attached at spaced points in its length to the thread and having a projecting bight intermediate its points of attachment, the bights disappearing and thetibers becoming substantially straight when the core thread is stretched substantially to its elastic limit.

15. In combination with a single rubber elastic core thread, substantially parallel fibers extending longitudinally of the thread, means attaching each ber to the thread at points spaced lengthwise ofthe thread, each fiber projecting as a bight between adjacent points of attachment, the length of ber between adjacent points of attachment substantially equalling the possible separation of adjacent points of attachment by the elongation of the thread within its elastic limits whereby the maximum strength of the covered core substantially equals the sum of the tensile strength of the uncovered core and the collective strength of the fibers.

References Cited in the le of this patent UNITED STATES PATENTS 2,048,360 Spanel et al. n July 2l, 1936 2,072,775 Smith et al Mar. 2, 1937 2,213,290 Rowe Sept. 3, 1940 2,424,743 Davis July 29, 1947 2,705,687 Petterson et al. Apr. 5, 1955 2,733,179 Smith Jan. 31, 1956 FOREIGN PATENTS 475,399 Great Britain Nov. 18, 1937 661,530 Great Britain Nov. 21, 1951