US2393530A - Flexible sleeving - Google Patents

Description

Jan.22,1946. J. M. HARRIS 2,393,530

FLEXIBLE SLEEVING Filed sept. 23, 1943 lll/l1 Patented Jan. 22, 1946 FLEXIBLE sLEEvlNG l Joseph M. Harris, Gladwyne, Pa., assigner to Bentley, Harris Mfg. Co., Conshohocken, Pa., a corporation of Pennsylvania Application September 28, 1943, Serial No. 504,189

2 claims. (cl. 117-9) 'This invention relates to ilexible dielectric tubing adapted for use as insulating sleeving on wires of electrical apparatus, or wherever the use of such insulation may be desired.

The invention relates particularly to dielectric sleeving of the braided type, wherein the structure is made of yarn composed of what is commercially known as Fiberglas, i. e. a yarn composed of a multiplicity of extremely fine continuous flexible glass filaments. This type of tubing is well known in the art and has been in general use for the purposes noted for a number of years.

Fiberglas filaments are inherently resilient, and when bent to a small radius are, such as takes place when yarns composed ofA these filaments are interwoven or interbraided in a fabric, tend to straighten out when released. This condition causes excessive fraying or ravelingof the fabric when the braided sleeving is out' to length for use.

The excessive fraying of the sleeving has been a constant source of annoyance in assembling and repairing electrical devices where this sleeving is extensively used, as on the-pigtail wires connected to the brushes of certain popular types of electric motors.

In order to reduce the excessive fraying of the sleeving, to a minimum, it has been the customary practice to coat the sleeving with a varnish, lacquer or dye, which, when it dries has a tendency to harden. This hardening of the lacquer reduces the flexibility of the tubing, proportionately to the thickness of the coating, and the reduction in fraying is more or less proportionate to the thickness of the coating, i. e. the thicker the coating the less tendency there is to fraying. and vice versa. f

Consequently, in order to obtain a workable condition, the coating is reduced in thickness, which is only` partially effective in reducing the tendency of the cut sleeving to fray. 5,

The primary object 0f the invention is .t'o eliminate the inherent tendency of the braided sleeving to fray, without reducing the exlbility of the sleeving.

In fact, tubing or sleeving produced in accordance with the present invention has a higher degree of exibility than the sleeving normally had before coating, i. e., as .the sleeving comes oil' the braiding machine, as will be clearly understood from the following description taken in connection with the accompanying drawing, of which:

Fig. 1 is a side view of one end of a :piece of Fiberglas tubing, drawn to a somewhat enlarged scale, and showing the tubing as it comes from the braiding machine on which it has been fabricated, with the end of the tubing frayed as it occurs simultaneously with the cutting or the tubing;

Fig.2isaviewsimilartoFig.1illustratmg how the fraying of the primary tubing increases with handling thereof;

Fig.3isasideviewofoneendofapiec eof tubing made in accordance with the principles of the present invention;

Fig.4isaviewsimi1artoFig.3i11ustrating the tubing as having been forcibly raveled by picking the yarns apart, at the cut end of the tubing, with a sharp instrument; and

Fig. 5 diagrammatically illustrates a piece of apparatus employed in treating the tubing in accordance with the present invention As shown in the drawing, the tubing A is composed of a multiplicity of yarns a, a which are interbraided in the usual manner, with each of the yarns a composed of a Vmultiplicity of individual continuous exible glass filaments extending substantially parallel to each other and loosely twisted together to produce the individual As previously noted, the individual filaments have an inherent tendency to straighten out when bent sharplyJ and then released. This tendency carries through and is somewhat increased in each of the yarns a, as a result of the multiplicity ofnlamentsofwhichtheyarniscomposedbeing loosely twisted together. When the tubing iscuttransverselyasindicated attherighthand endofFig.1,thisinherenttendencyoftbeiila ments and yarns to straighten out causes the yarnstospring apartatandadiacentthecut, whichcausesthetubingtoravelorfrayexcessively, simultaneously with the cutting of the tube.

As the tubing or sleeving is subsequently handled, dln-ing application of the sleeving to electrical wires, for example, or during assembling ofthe sleeved wires in an electrical apparatus inwhichthesleevedwiresareemployeiagtrlvates the fraying condition to an extent substantially as illustrated in Fig. 2.

Asiswellknownintheartofbraidingand lweaving,attheplaceswhereanytwoyarnsare interlacedasaresultottheweavlngorbrnidingV operationtheyarnsarebentonaradiusccnsistent with the radii of the respective yarns aroundwhichtheyarebentandtheindivldual yarnsaremaintainedinthissharplybentccnditionintheilnishedfabrlc.

Il Inaccordancewiththopresentinventimit has been found that if and when the sharp bends in the yarns of braided tubing composed of Fiberglas filaments are set," the bends of the crossing yarns remain hooked around and substantially lock with each other and that as a result thereof all tendency of the Vsleeving or tubing to ravel, when cut transversely disappears. 'I'he set crimps or bends are diagrammatically illustrated at ai in Fig. 4 of the drawing.

It has also been noted in practicing the present invention that the setting of the sharp bends or crimps increases the iiexibility of the tubing or sleeving as a whole, as a result of the elimination of the tendency of the individual yarns and filaments to straighten out.

In accordance with the principles of the present invention, the "setting of the interlacing crimp in the individual yarns and laments is effected by subjecting the finished tubing, i. e., the tubing as it comes from the braiding machine, for example, to heat of a predetermined temperature sufilcient to produce a slight softenor annealing of the glass filaments. For the purpose of the present invention, it has been found that heating of the filaments to a temperature of about 1200* F. to 1500 F. produces the result desired.

In order to soften or anneal the glass filaments in accordance with the present invention, the tube A is preferably passed through a snug-fitting bore b or a cylindrical die B of desired length and which is heated to the annealing temperature, as by electrical heating coils C. The tube A passing through the bore of the heated die B, in the direction o! the arrow Fig. 5, emerges as the iinished tube AI of Figs. 3, 4 and 5 at a rate of substantially 500 feet per hour.

During the passage of the tube through the heated die the exterior surface oi' the tube A is preferably in contact with the bore b of the die B which causes the individual yarns and filaments of which the tubing is composed to become softened at points of interlacing thereof, and, as

the tube Al emerges from the die B and is permitted to cool, the individual yarns and iilaments become permanently set in the interlacing curvatures assumed during the braiding operation.

This "setting" of the curves o! the individual yarns and nlaments reduces the inherent tendencies of the yarns and filaments to straighten out, and, in so doing. eliminates the tendencies of the tube to ravel when cut.

The setting of the interlacing kinks in the individual yarns and iilaments subsequent to the interlacing of the yarns in the tubing, also reduces the collective eifort oi' the yarns and filaments to straighten out and produce a resilient stiiness in the tubing, thus the tube assumes a more iiaccid state than when it came from the braiding machine.

In some instances it may be desirable to eii'ect a slight or partial fusing oi the interlaced yarns and filaments together. in addition the aforesaid setting" of the lnterlacing kinks in the yarns, to eliminate the raveling or fraying oi.' the tubing. This may be accomplished by elevating the temperature of the setting" die to a point where ilowing of the glass begins. However, fusion is not particularly desirable as it tends to destroy rather than promote ilaccidity in the tubing.

It desired, the tubing of the present invention may be given a coating oi' varnish, lacquer or dye for the purpose of providing dlii'erently colored wires in an electrical circuit or apparatus and the density of the coating may be employed to control the state of fiaccidity of the sleeving il desired.

I claim:

1. The process of treating a braided textile tubing composed of yarns formed of flexible glass laments which consists in moving the tubing axially through a heating device heated to a temperature of approximately 1200 F. to 1500 F. at a linear speed of approximately 500 feet per hour for permanently crimping said filaments at points of interlacing of said yarns as effected by fabrication of said tubing subsequent to said fabrication, to eliminate fraying of the tubing when cut transversely and to increase the ilaccidity of the tubing.

2. A accid di-electric sleevlng comprising a braided textile tubing made in accordance with the process of claim 1.

JOSEPH M. HARRIS.

Images