US2363871A - Method of making electrical conductors - Google Patents

Description

Nov. 28, 1944. A. w. KEEN ET AL METHOD OF MAKING ELECTRICAL CONDUCTORS Filed Aug. 5, 1942 2 Sheets-Sheet 1 ABELSTO CELLOPHANE ATTR [Y Nov. 28, 19,44. A. w. Kl-:EN ET AL METHOD OF MAKING ELECTRICAL CONDUCTORS Filed Aug. 5, 1942 2 Sheets-Sheet 2 TORNEY Patented Nov. 28, 1944 METHOD OF MAKING ELECTRICAL CONDUCTORS Alexis W. Keen, Paekanack Lake, and Raymond B. Frost, Rutherford, N. J., assignors to United States Rubber Company, New York, N. Y., a corporation of New Jersey Application August 5, 1942, Serial No. 453,676

7 Claims.

This invention relates to improvements in methods of making electrical conductors of the type having a serving formed by helically wrapping yarn or thread about the conductor, and more particularly to a construction whereby a serving of a single thickness may be provided which will afford the conductor good protection.

Heretofore when electrical conductors have been provided with a cover, other than a woven construction, formed of yarns or threads, such yarns or threads have usually been braided about the conductor to prevent the cover from opening lup when the conductor is bent sharply, or such conductor has been provided with two or more servings wound helically thereupon in opposite directions so that the helically wound coils forming one layer will help to prevent the helically wound coils of the other layer from opening up when the conductor is bent.

When either of these prior constructions is employed the textile cover or covers thus formed will have at least twice the thickness of a single yarn or thread forming such cover, due to the crossing of the yarns in the braided construction or in the oppositely wound serving construction.

Prior to the present invention no practical way was known of providing an electrical conductor with a single-layer serving that would give satisfactory protection, because of the tendency of the helical coils forming the serving to separate when the conductor is bent sharply. The present invention contemplates a simple and practical method of bonding the coils of a serving together so that the tendency of these coils to separate when the conductor is bent is greatly reduced.

The present invention, as will be hereinafter more fully pointed out, requires the use of yarns or threads formed of short fibers and preferably of fibers that are considerably less than one inch in length. The invention is therefore particularly well adapted for use in the construction of fireproof or fire-resisting conductors having a serving of asbestos yarn, as asbestos bers usually are nearer a half-inch than an inch in length. It is desired to point out, however, that yarns formed of other short fibers such as cotton, wool or glass may be used in carrying out the present invention.

Through the present construction a reproof electrical conductor of a given current carrying vcapacity and capable of withstanding the various exacting tests required of such a commerical electrical conductor can be provided which has a smaller overall diameter than the constructions available heretofore. As a result a greater number of these covered conductors can be placed in a conduit of a given diameter than heretofore.

Due to the diiculty of spinning asbestos yarns in small sizes, and to the fact that covers formed heretofore of asbestos yarn had the yarns disposed in crossing relation to each other, it was not practical to provide conductors with an asbestos cover of the thinness made possible by the present invention. Wires insulated with asbestos applied in the form of asbestos rovings or of felted fibers are especially bulky.

Having in mind the foregoing, an important feature of the present invention resides in an insulated electrical conductor provided with a serving of short-staple yarn wound helically about the conductor, and having some of the fibers of each coil displaced laterally so that they extend across one or more of the adjacent coils, and are adhered thereto, to hold the coils together.

Another important feature of the present invention resides in the method whereby the bers at the outer surface of the serving are raised, without appreciably decreasing the strength of the yarn, and are then displaced laterally from one coil onto the next and are adhesively secured in this condition to anchor the adjacent coils together.

Still another feature of the invention resides in the method whereby the serving is acted upon by air jets to thereby raise the fibers.

The above and other features of the present invention will be more fully understood from the following description when read in connection with the accompanying drawings showing an insulated electrical conductor such as contemplated by the present invention and apparatus for carrying out the present method.

In the drawings:

Fig. 1 is an enlarged elevation of an insulated electrical conductor constructed in accordance with the present invention and showing the different steps involved in making such a conductor.

Fig. 2 is an enlarged plan view showing a small area of the outer surface of the finished insulated conductor of Fig. l.

Fig. 3 is a more or less diagrammatic side elevation with parts in section of portion of apparatus for carrying out the method of the present invention.

Fig-4 is a continuation of the apparatus of Fig. 3 wherein the conductor drying means is shown in side elevation.

Fig. 5 on an enlarged scale is a vertical sectional view through air jet means for directing air Jets against the covered conductor to raise the fibers.

Fig. 6 is a sectional view taken on the line 8-6 of Fig. 5.

Fig. '7 is an enlarged plan view of the conductor ironer shown in Fig. 3.

Fig. 8 is an enlarged plan view with part in section of the ber laying eccentric horn shown in Fig. 3. Fig. 9 is a longitudinal sectional view through revolving roll-carrying mechanism for ironing the conductor; and

Fig. 10 is a sectional view taken on the line III-I0 of Fig. 9.

'I'he present invention, as above pointed out, is concerned primarily with the construction of a serving formed of yarn of short iibers wound helically around an electrical conductor. Therefore the construction of the conductor itself and the inner covers over which the serving is applied are not important so far as the present invention is concerned and may be varied eX- tensively. However, since the main object of the present invention is to produce a satisfactory electrical conductor of minimum overall diameter, every part of the insulated conductor has been designed with this purpose in mind.

In Fig. 1 of the drawings there is shown an electrical conductor I 0, which may be either a solid or a stranded wire, surrounded by the rubber cover II. 'I'his cover is preferably what is known as a latex dip cover since it may be made thinner than the usual tubed stock cover of equal insulating value, due to the superior properties of a latex cover over a tubed stock cover. The usual way of applying a latex cover to a wire is by successive dipping or coating operations. This places the wire accurately in the center of the cover and forms walls of uniform thickness about the conductor, which are free of blowholes. On the other hand when masticated rubber stock is tubed about a conductor the wire is not always accurately centered, and blowholes may be formed.

In the construction shown the latex cover II has wound thereupon a thin Cellophane ribbon I2 which protects the rubber from the outer serving I3, and also prevents the outer coating material, to be described, from reaching the latex cover. The outer serving is formed by wrapping helically about the conductor one or more ends I4 of yarn or thread; sixteen of these ends are shown as disposed in parallel relation to each other to form a ribbonlike construction which is wound as a unit over the Cellophane cover I2,

with successive turns touching but not overlapping.

The construction so far described by reference characters isvnot new in itself and may be varied extensively. The construction of the present invention whereby the adjacent coils of the strands I4 are firmly secured together so that the covered conductor may be bent at a sharp angle without causing 'an opening to occur between the coils will now be described.

Such a construction is secured by raising the fibers disposed near the outer surface of the serving I3, and an extremely satisfactory way of raising these fibers without appreciably injuring the yarn I4 is to act upon the serving I3 with a plurality of strong jets of air impinging upon the conductor radially. 'I'he appearance of the covered conductor immediately after the fibers are raised is or may be substantially as indicated by a in Fig. l of the drawings.

After the iibers have been thus raised they may then have applied thereto an adhesive or binding material as indicated by b in Fig. 1, whereupon the adhesive covered ilbers are subjected to a wiping or ironing operation around the covered conductor in such direction as to cause them to extend across one or more strands so that when these ilbers are iirmly bonded thereto bythe adhesive they will secure the adjacent coils firmly together in the iinished cover, which is indicated by C.

It will be understood that various i'orms of mechanism could be employed for carryin' out the method of the present invention. One good practical construction to this end is shown in the drawings more or less diagrammatically and will now be described.

The covered electrical conductor C having a construction such as shown in Fig. l oi' the drawings at the lpoint where the numeral I 3 is applied, may be unwound from theI let-oi! spool I4 of Fig. 3. From this spool the conductor is pulled forward in the direction indicated by the arrow, against the resistance of the friction brake I5 which cooperates with the spool Il. 'I'he conductor C is shown as passing from the spool Il under an idler roll I8 and then about the grooved pulley I I which is driven at a predetermined constant rate of speed by a chain I8. The conductor C is looped around a suiiicient portion of the pulley I1 to prevent slippage from occurring between the pulley and conductor, whereupon the conductor passes from the 4lower surface of this pulley to the idler roll Il disposed some distance therefrom, and in position to rotate within the adhesive contained'within the tank to lbe described. As the conductor C travels from the pulley I'I to the idler roll I9 it passes through the air jet ring 20, the construction of which is best shown in Figs. 5 and 6. This ring is provided with the annular air chamber 2| to which air is supplied under pressure by the ilexible tube 22 that forms the connection between this ring and the air supply pipe Z3. This ring is provided with the central opening 2l, through which the electrical conductor C passes,'and is formed with the small radially disposed holes 25, three being shown, adapted to direct `iets of air against the conductor.

It has been found that the operation of these jets to raise the iibers of the yarn serving I3 is greatly improved by reciprocating the air jet ring 20 rapidly for a short stroke lengthwise of the conductor C as the latter travels therethrough, and to this end in the construction shown the ring 20 is mounted upon a slide 28 which is supported by a bar 21 for limited reciprocating movement. This bar is carried by the frame 28. The desired reciprocatory movement is imparted to the slide 26 in the construction shown by a connecting rod 29 one end of which is pivotally secured to the slide 26 and the other end of which is secured to one side of the center of the rotating disc 30 as shown.

The air supplied to the ring 20 is preferably under considerable pressure, say 70 pounds per square inch or more, and the length of stroke, of the slide 26 is preferably about two inches, assuming that the covered conductor C is being advanced at the rate of approximately 7.5 feet per minute. Under this condition it is preferable to cyclesper minute.

The air jets 25 act upon the serving I3 to raise the fibers substantially as indicated by a in Fig. 1, whereupon a coating material or bonding material may be applied thereto that is capable of forming a good protecting outer coating for the conductor and of bonding the fibers firmly to the adjacent textile strand. This adhesive may be conveniently applied t6 the conductor by passing the conductor C into the relatively long narrow tank "containing the adhesive material 32, and underthe idler roll I9 so that the conductor will dip below the surface of and become thoroughly coated with the adhesive. The idler roll I9 is disposed somewhere near the middle of the tank and is partially immersed inthe adhesive. The liquid used may be so viscous that the body of liquid tends to be carried|to one end of the tank by the conductor. In such case it is desirable to provide the circulatingpump 33 and the pipe connections 34' and 35 through which the liquid may be forced from the `rightI-hand end of the tank in the construction shown to the left-hand end thereof.

As soon as the raisedfibers indicated by a in Pig. 1 have been thoroughly coated with the adhesive or bonding material 32, as indicated by b in Pig. 1, the conductor may be subjected to a wipving' operationthat will lay these fibers around the covered conductor in such direction that they will extend diagonally from one strand I4 to another as indicated by F in Fig. 2; that is, the surface fibers are laid about the conductor in the direction opposite to that in which the yarn was.

:tank an. The slight bend in the horn is such that the lip of the horn. presses lightly on the coated serving and lays the fibers around `the covl ered conductor, substantially as shown in Fig. 2. The fibers are indicated by F as disposed in a left-hand direction about the conductor, and at a slight angle to a plane normal to the axis of the conductor. This angle will depend on the relative speed of the wiper and the conductor. A whipping action is induced in the reach of wire between the roller I9 and the horn 36, by the rotation of the horn, and this results in better penetration of the coating material into the fibrous mass.

As soon as the fibers are laid about the conductor it is preferable that the conductor be subjected to a drying operation. and this is accomplished in the construction shown by causing the conductor to pass over the idler roll 39 and then through a small opening in a collar 40 leading into the heated drying tube 4I of substantial length, say 10 feet or more. As the conductor approaches the right-hand end of the tube 4I, it is preferably led upwardly around the grooved wheel 42, confined within the boxlike air chamber 43 through which hot air passes upwardly from the lower tube 4I to the upper tube 44. The conductor C then travels inthe opposite direction within the upper tube 44. Hot air is preferably supplied to the tube 4I by a fan 45 which receives heated air from the heater 4E. This air travels lengthwise of the tubes 4I and 44 in the same ss'csgsn 3 reciprocate the slidey 29 at approximately 720 direction in which the conductor travels therein.

The conductor upon reaching the end of the upper tube 44 passes outwardly through a small opening in the collar 41. It may then pass immediately through the ironer shown in Figs. 3 and 7, which consists of a hollow shaft 43 that is rotatably supported by the bracket 49 and is rotated by the pulley 50 and belt 5I. The construction is such that, as the conductor C passes through this rapidly rotating shaft 48, the spring blades or ironers 52 fastened to this shaft have a Iwiping action upon the hot coating on the conductor. the directionvof rotation being the same, relative to the conductor, as that of horn 35. The conductor may then pass around the grooved pulley 53 driven by a slip belt 54 which permits the rotation of this pulley 53 to accommodate itself to the speed of the positively driven pulley II. This completes the treatment of the insulated conductor upon the apparatus shown in Figs. 3 and 4 and the covered conductor can then he wound upon the take-up'reel 55.

In some cases it may be desirable to subject the covered conductor C to a further ironing operation after it has cooled. in which case it may be passed through the ironer shown in Figs. 9 and 10, which consists of a frame or squirrelcage 56 rotatably supported by the bracket 51 and driven by the pulley 59. This squirrel-cage has rotatably mounted therein the three ironing rolls 59 adapted to exert an ironing pressure upon the cover of the conductor as the squirrelcage is rotated and the conductor is passed therethrough.

It is found desirable to provide a splash hood over the eccentric horn wiper 38. and to provide an air outlet pipe 6I at the discharge end of the upper tube 44.

As one construction embodying the present invention which has been found to work very well in practice, the following example is given of an electrical conductor having a No. 14 wire vand designed to carry volts:

v u Inches Diameter of copper wire .065 Diameter of latex cover T .105 Diameter of Cellophane cover .108 Diameter of finished conductor .132

This conductor was provided with an asbestos cover such as indicated by I3 in the drawings and formed of sixteen 50-cut 2-ply asbestos yarns wound about the conductor so that they formed an angle of approximately 54 with the longitudinal axis of the wire III. Mostl of the asbestos fibers were less than 3A of an inch in length. These fibers F were wiped across the threads I4 so as to form an angle of approximately 60 with the length of each thread. The eccentric horn 36 was rotated at 1,750 R. P. M. and the ironer 49 was rotated at 4,200 R. P. M. The covered conductor was advanced at '1.5 feet per minute. The temperature of the lower tube 4| where the conductor entered the same was 175 C., and the temperature of the upper tube 44 where the conductor left the same was C. The length of each run of the drier was 1l feet. 'I'he adhesive 32 used was a Vinylite solution, comprising 15 parts of Vinylite, 15 parts of plasticizer, and '70 parts of solvent (Vinylite" being a. commercial vinyl chloride-acetate copolymer) to which pigment may be added if desired-for example, a small percentage of carbon black.

It will be apparent from the foregoing that by imparting to the serving I3 the construction of the present invention, the coils of the yarns I4 willbe firmly anchored together by the fibers F, and that this will greatly reduce the tendency of the coils to separate when the conductor is bent upon a small radius. The arrangement of the fibers F diagonally of the yarns I4 instead of at right angles thereto reduces the tendency of these fibers to break when the conductor is bent.

It will of course be understood that the above example is merely illustrative of one embodiment of the invention and is not given with any intention of limiting the invention more than is required by the scope of the prior art.

Having thus described our invention, what we claim and desire to protect by Letters Patent is:

1. The method of making an insulated electrical conductor, which consists in winding yarn helically about an electrical conductor to form a serving having the strands thereof lying closely side by side, raising flbers of the serving by an air blast, pressing these raised fibers over the next adjacent strand at a definite angle thereto, and firmly securing the fibers in this relation by an adhesive to hold the strands together 2. The method of making an insulated electrical conductor, which consists in winding short staple yarn helically about an electrical conductor to form a serving having the strands thereof lying closely side by side, raising fibers of the serving by an air blast, laying these raised fibers over the next adjacent strand at a definite angle thereto, and firmly adhering the fibers in this relation to hold the strands together.

3. The method of making an insulated electrical conductor, which consists in winding yarn helically about an electrical conductor to form a serving in which the strands lie closely side by side, raising fibers of the cover by playing a plurality of air jets back and forth along the serving, pressing these raised fibers laterally onto the next strand, and firmly securing the fibers in this relation to hold the strands together. l

4. The method of making an insulated electrical conductor, which consists in advancing in the direction of its length an electrical conductor having a serving thereupon consisting ofn short staple yarn wound helically about the conductor so that the strands lie closely side by side, raising fibers of the serving by acting upon the advancing covered conductor with an air jet, applying an adhesive coating to the advancing covered conductor, and then wiping the adhesive covered fibers laterally from one strand over another to thereby hold the strands together.

5. The method of making an insulated electrical conductor, which consists in winding yarn helically about an electrical conductor to form a serving having the strands thereof lying closely side by side, raising fibers of the serving by air jets disposed in encircling relation about the conductor, laying the raised fibers over the next adjacent strand at a definite angle thereto, and firmly adhering the fibers in this relation to hold the strands together.

6. The method of making an insulated electrical conductor, which consists in winding yarn helically about an electrical conductor to form a serving having the strands thereof lying closely side by side, raising fibers of the serving entirely around the conductor by air jets, impregnating the serving with a saturant while the fibers are raised, and then laying the fibers over the next adjacent strand at a definite angle so that the fibers will be held in this condition by the saturant to bind the strands together.

7. The method of making an insulated electrical conductor, which consists in winding yarn helically about an electrical conductor to form a serving in which the strands lie closely side by4 side, raising fibers of the serving by an air blast, passing the conductor with the fibers tiereof raised through a bath of coating material, then acting upon the conductor with a rotating wiper to lay the fibers over and adhere them to the next strand, and utilizing the rotation of the wiper to whip the conductor in the bath and thereby secure better impregnation of the coating material.

ALEXIS W. KEEN. RAYMOND B. FROST.

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