US2314168A - Strand handling apparatus - Google Patents

Description

March 16, 1943. c. c. SMITH 2,

STRAND HANDLING APPARATUS Filed July 31:1941

a/ a2 F! a. I T T FIG. 6

INVENTOP C. 6. SMITH Patented Mar. 16, 1943 2,314,168 STRAND HANDLING APPARATUS Charles C. Smith, Cranford, N. L, assignor to Western Electric Company, Incorporated, New

York, N. Y.,

a corporation of New York Application July 31, 1941, Serial No. 404,892 4 Claims. (Cl. 91-53) This invention relates to strand handling apparatus, and more particularly to apparatus for coating strands.

Insulating sheathings on electrical conductors are made, at the present time, in a multitude of ways, some of which include the application to a bare or previously variously sheathed strand of hardenable materials applied in liquid, semiliquid, or pasty form and subsequently hardened. Thus materials in the nature of paint, enamel, varnish, or waxes, asphalts, parafiins and the like dissolved in volatile vehicles, artificial resins hardenable by polymerization induced by heat, and other analogous materials are used for one or another specific purpose. In many such instances a solvent or vehicle is used which is volatilized to be subsequently recovered; and a considerable part of the cost of the coating operation may arise out of the volume of such solvent or vehicle to be recovered for subsequent reuse. Hence it is desirable and may be vitally important to apply the raw sheathing or sheath treating materials in a condition approaching dryness as nearly as may be practicable, i. e. as a smoothly plastic highly viscous paste, in order that the volume of vehicle or solvent circulated in the process, or perhaps wasted, may be kept low.

An object of the present invention is to provide simple, reliable and easily interchangeable means for applying to strands of a considerable range of diameters, material whose physical state is that of a smoothly plastic but highly viscous and thick paste to form a uniform coating on the strands.

With the above and other objects in view, the invention may be embodied by providing in an apparatus having means to apply coating material to a strand and including a chambered body to contain the material and formed with entrance and exit apertures to pass a strand to be coated through the material, means to wipe the strand comprising a plug of elastic material having a bore therethrough of approximately the diameter of the strand, and means to support the plug in the exit aperture of the body, the plug being further formed to have a free surface running in the same general direction as the bore to provide room for dilation of the bore upon the passing therelthrough of a swollen portion of the strand.

Other features and objects of the invention will appear from the following detailed description of one embodiment of the invention taken in connection with the accompanying drawing'in which the same reference numerals are applied to identical parts in the several figures and in which Fig. 1 is a view in vertical transverse central section of an apparatus for coating strands and constructed in accordance with the invention;

Fig. 2 is a central section on an enlarged scale of the wiper plugs of Fig. 1;

Fig. 3 is a plan view of the plug of Fig. 2;

Fig. 4 is a view similar to Fig. 2 of a modified form of plug;

Fig. 5 is a plan view of the plug of Fig. 4;

Fig. 6 is a view similar to Fig. 4 of another form of plug; and

Fig. 7 is a plan view thereof.

As herein shown the invention is illustrated as embodied in a device for applying a smooth, even, continuous coating of smoothly plastic, highly viscous, thick, pasty material on a strand passed through the device. The device comprises a metal body IE] of generally parallelopipedal outer form having a cylindrical chamber ll axially therein and enclosed laterally and at one end by the body but opening at l2 through the other end and through a conical nipple l3 integral with the body. Four radial bores in diametral pairs M, I5 and l6, l1 respectively communicate from the chamber ll out through opposite sidewalls of the body.

A metal supporting cup [8, flanged to be supported on the outer surface of the body I0, fits tightly in the bore l4 and contains and supports a short cylindrical sealing plug IQ of soft vulcanized rubber having an axial bore 20. The plug I9 fits tightly into the cup and is supported on its inner face by the bottom of the cup which has a central, tapered, radially inwardly widening aperture 2| coaxial with the bore 20 of the plug. On the outward face of the plug l9 rests the broad flange of a coaxial tubular lead in guide 22, which in turn is held in place by a centrally bored nut 23 screwed into (the outer end of the cup I8.

In the diametrally opposite bore i5 is a metal sleeve 24 flanged to be supported on the outer face of the body l0 and having a radially inwardly narrowing, tapered bore in which is seated a correspondingly dimensioned, conically tapering wiping die or plug 40 of soft vulcanized rubber. A cap 25 of metal is seated in a counterbore in the outer end of the sleeve and supports the plug 40 against outward movement. The cap 25 is further formed with a central aperture 26 coaxial with an axial bore 4| in the plug, A

sleeve 21 and cap 28, duplicates of the sleeve 24 and cap 25, are positioned in the bore I I and hold in place a rubber plug 50 identical in form with the plug 45. A cup 29 analogous to the cup I 8 but having a conical recess instead of a cylindrical one is mounted in the bore l5 and has a cap 30 identically like the caps 25 and 28. The caps 25 and 28, and thereby the sleeves 24 and 21, are held in place by a suitable yoke 3| held in place on the body by a screw 32. The cap 30 and thereby the cup 29 are held in place by a yoke 33 which also holds the cup |8 in place and is held by a screw 34. A soft rubber plug 60, identically like the plugs 40 and 50, is seated in the cup 29.

Turning now to Figs. 2 and 3, the plug 40 is a frusto-conical body of soft vulcanized rubber with parallel end faces. It is formed with the axial, cylindrical bore 4|. As oriented in Fig. 2, there is also a recess 42, 43 opening upwardly from the bottom (smaller) end face 45. This recess or groove has an inner cylindrical wall 43 coaxial with the bore 4|, and an outer slightly conical wall 42 also coaxial with the bore 4| and therefore with the wall 43. At something more than half the height of the plug above the bottom the walls 42 and 43 are joined and the recess closed by a short cross wall 44.

It is found that, for optimum operation as hereinafter described, the diameter of the inner wall 43 should be about of the diameter of the bottom face 45; the recess should be about as deep as the plug is h gh and the width of the recess at its opening should be about of the diameter of the face 45. The relative width of the top face 45 and the slope of the conical outer face 41 are not materially important. The diameter of the top face 40 as shown is about of the diameter of the bottom face 45. The height of the plug between the faces 45 and 45 should be about the same as the diameter of the wall 43, i. e. about of the diameter of the face 45. Furthermore, the diameter of the hole 25 in the cap 25 which supports the plug 40, should be about of the diameter of the face 45 or about A of the diameter of thewall 43. These optimum values have been determined in connection with the specific case of operation described below in which a strand of 22 gauge (A. W. G.) tinned and enamelled wire with three served layers of textile threads on it and having an average overall diameter of 0.047 inch, is to be coated with two consecutive layers of a thick, highly viscous, smoothly plastic paste comprising cellulose acetate softened with acetone. The dimensional ratios given above are not acutely critical and in other cases may well be somewhat modified without harm to the results desired; but, generally speaking they appear to be optimum values.

The coating of strands with such materials as are here in question presents difficulties as well as advantages not known in the earlier art. A typical materialv heretofore in use contains about 20% of solids, largely cellulose acetate, in about 80% of solvent, largely acetone. Such a preparation is a sirupy but definitely fluid liquid, can be poured, and will flow through apipe under gravity alone. Its viscosity willbe around 2000 poises or less at 105 F.

As already pointed out it is the particular purpose of the present invention to create a strand having a coating of thick. pastily almost solid, viscous material ordinarily five or six times as thick as that which can be created on a strand in the case of the relatively thin Sirupy,

raw coating materials heretofore used. This is highly advantageous, because the number of coating passes of the strand and therefore of the ensuing hardening passes is cut to one-fifth or one-sixth in number of those heretofore required to produce coats of like final thickness; also because the volume of solvent required to be evaporated off and either wasted or expensively recovered is very materially diminished, so much so that it may well be cheaper to waste the evaporated solvent than to maintain and operate the expensive recovery plant previously necessary.

In one instance a coating material was used. typical in physical characteristics of materials adapted for the present invention, which contained' 58% by weight of solids (largely cellulose acetate) and 42% by weight of a liquid vehicle containing, in 42 parts, 40 parts of acetone and 2 parts of other liquids. The viscosity of this was about 25,000 poises at 75 F. and at the extrusion temperature of about F. it was about 18,000 poises. It could not be poured or transferred in the manner of ordinary liquids except under pressure. In one instance in practise, it required a ressure of lbs. per square inch to transfer the above mixture through a pipe.

In using the device hereinabove described for coating a strand such as the 0.047 inch diameter, textile thread served, No. 22 wire above mentioned with the pasty preparation of cellulose acetate described above, a wire 35 such as described, drawn from some suitable supply below (Fig. 1), is threaded through the tubular guide 22 and the rubber seal IS, the bore 20 of which is of about the same diameter as the wire or minutely larger, say in the particular instance under consideration from 0.047 to 0.050 inch. The wire is led across the chamber H and out through the bore 4| of the plug 40 and the aperture 26 of the cap 25. Thence the wire passes through suitable means to partially or wholly harden the coating, which means are not shown as they form no part of the present invention. Thence the once coated wire returns to pass upwardly again through the plug 60, the chamber H and the plug 50 to enter the hardenmg means again.

The Wire having been threaded in this fashion, the nipple i3 at the entrance I2 is connected to some suitable source (not shown) of the pasty cellulose acetate material under pressure which fills the chamber II, the contained air be ng forced out the bores of the several plugs. When the chamber is filled with paste under pressure (about 90 pounds per square inch in. the particular instance illustrated), the wire is advanced by any suitable means (not shown) in the direction indicated by the arrows. The bore 4| and the corresponding bore 5| in the plug 50 are of approximately the average diameter of the strand 9. The paste under pressure clings to the strand and is wiped off by the Wiping dies 40 and 55, leaving a coating of suitable thickness on the wire emerging from the dies, the thickness being controlled by the size of the bores 4| and 5|, bythe hardness of the rubber plugs 40 and 5|) and bythe pressure in the charm ber Plugs 40 and 50 having the dimension ratios indicated and a bore of about 0.048 inch anda 50-60 durometer hardness are satisfactory for the particular wire in question.

In practise there will inevitably be irregularities in diameter of the wire. Perhapsthe most frequent cause of such are splices in the wire where ends have been joined together by welding. Or there may be knots in textile threads served on the wire core. A plug 40 must necessarily be temporarily and locally distorted when a knot, weld or other swelling of the strand passes through it. Rubber is elastically and easily distortable, as is well known. However, it is not always realized that rubber is much like a liquid in that it is nearly incompressible volumetrically. If a mass of soft rubber is to be shortened by pressure in one direction, it must be free to expand in some other direction.

In the present instance, when a knot enters the bottom of the bore 4| and moves upwardly in it, the rubber of the stem-like part within the wall 43 is free to expand into the annular recess 42, 43. When the knot is at the level of the end 44 of the recess, the rubber in front of it (above) can swell out into the opening 26 of the cap 25, M

which opening is about two and one-half times the diameter of the bore 4|. Thus every part of the rubber stressed by the dilation of the bore by the passage of a swelling in the strand is free to yield in some direction with substantially con?- stant resistance, for every part of the bore 4| is at substantially the same distance from some free surface of the plug, except of course theentrancje and exit parts which are nearer. But no part is farther from a free surface than the middle p01 tion of the bore is from the surface 43. Hence a swelling on the strand may pass through the bore without undue resistance at any point. Were the recess 42, 43 not there, all the substance of the plug would be contained within rigidly confined faces except the small portion near the exit of the bore. That the rear face 45 is free is immaterial because all the stress occasioned by a knot passing in the direction indicated is toward the walls 46 and 41. Hence with an unrecessed plug, the resistance to passage of a knot rises abruptly and severely shortly after the knot enters the bore.

A less satisfactory but still sometimes practicable way of accomplishing the same result is shown in Figs. 4 and 5. Here a plug I40 is identically like the plug 40 in general dimensions, in mode of use and in the diameter of the bore 4|. There is, however, no annular recess. Instead a segment is cut away at one side along a vertical plane, leaving the flat surface I48. Thus the material around the bore 4| has the free surface I48 to move toward when a knot goes erally in which the devices herein described may be found, such may befound in copending application Serial No. 382,726 filed March 11, 1941,

5 by E. E. Newton et a1. and assigned to the same assignee as the present application.

The embodiments of the present invention herein disclosed are illustrative and may be variously modified and departed from without departing from the spirit and scope of the invention as pointed out in and limited only by the appended claims.

What is claimed is:

1. A strand wiping die of elastically deformable material having a boretherethrough and formed with a recess having a free surface running in the same general direction as the bore to provide room for dilation of the bore upon the passing therethrough of a swollen portion of the strand.

2. A strand wiping die of elastically deformable material having a bore therethrough and formed with a curved recess coaxial with the bore and having a free surface running in the same general direction as the bore to provide room for dilation of the bore upon the passing therethrough of a swollen portion of the strand.

3. A strand wiping die of elastically deformable material having a bore therethrough and formed with an annular recess coaxial with the bore and having a free surface running in the same general direction as the bore to provide room for dilation of the bore upon the passing therethrough of a swollen portion of the strand.

4. A strand wiping die of elastically deformable material having a bore therethrough and formed with arecess in a side wall thereof having a free surface running in the same general direction as the bore to provide room for dilation of the bore upon the passing therethrough of a swollen portion of the strand.

CHARLES C. SMITH.

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