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V. S. MARTIN Filed March 24, 1955 INVENTOR. Ymm u s. MAR T//v A fro/wf y April 21, 1959 METHODS OF MAKING INSULATED CoNDUCToRs --Unid States Patent O METHODS OF MAKING INSULATED CONDUCTORS Victor S. Martin, Towson, Md., assignor to Western Electric Company, Incorporated, New York, N.Y., a corporation of New York Application March 24, 1955, Serial No. 496,418 7 Claims. (Cl. 154--2.24)
This invention relates to methods of making insulated conductors, and more particularly to methods of making flexible tinsel conductors.
In the manufacture of certain types of tinsel conductors for use in communication devices, a plurality of tinsel ribbons are wrapped in various ways around textile strands, a cover of non-conductive material is knitted therearound and an outer covering of plastic insulating material is formed over the conductors while the knitted covering holds them in place. It has been found desirable to eliminate the knitting o eration and to cover the twisted tinsel threads with longitudinally extending strands of material, such as cotton or the like. However, it would be diicult to maintain a plurality of longitudinal strands of this nature positioned around the conductors uniformly during the forming of the outer covering.
It is, therefore, an object of this invention to provide new and improved methods of making insulated conductors.
Another object of this invention is to provide new and improved methods of making iexible tinsel conductors.
A method of making insulated conductors illustrating certain features of the invention may include positioning a plurality of conductive strands along an axis, positioning strands held together by a binding material longitudinally of the axis and around the conductive strands, forming insulation around the material-held strands, and dissolving the binding material.
Other objects and advantages of the invention will appear from the following detailed description of a method of making insulated conductors forming a specic embodiment thereof, when read in conjunction with the appended drawings, in which: ,p
Fig. 1 Vis a fragmentary view of a exible conductor embodying the invention;
Fig. 2 is a schematic diagram of an apparatus with which methods embodying the invention may be practiced, and l vFig. 3 is an enlarged, fragmentary section taken along line 3 3 of Fig. 2. Y Y l Referring now to the drawings, a flexible tinsel conductor consists of a plurality of flexible tinsel threads 11-11 wrapped helically around a center ycord 12. Fig. l shows six of such threads 11-11, but any number could be wound around the cord 12. The individual tinsel threads 11-11 have stranded cores 15-15 composed of a multiplicity of textile strands, such as cotton or the like. Inner layers 16-16 of tinsel ribbons, preferably of material having high conductivity and flexibility, such as copper, bronze, or the like, are wound in a somewhat helical fashion tightly about the stranded cores 15-15. Outer layers 17-17 of similar tinsel ribbons are wound in identical fashion over the inner layers 16 16. It will be noted that the outer layers 17-17 are so positioned as to cover the interstices between adjacent convolutions of the inner layers 16-16. As far as the tinsel ribbons 16--16 and 17-17 are concerned, the stranded cores 15-15 are chiefly designed to provide tensile strength and to relieve the tinsel ribbons themselves of tensile stress, and at the same time afford minimum resistance to ilexure.
A tape 20 is formed into a tube tinsel conductor 10. The tape 20 consists of a plurality of strands 22-22 (Fig. 3), preferably of textile thread spun from cotton, or the like, placed in side-by-side position and secured together by a binding material 23. The binding material 23 may be a heat-dissolving adhesive, such as glue, a thermoplastic material, or the like. The material 23 forms the body of the tape 20 with the strands 22-22 spaced uniformly across the tape and embedded therein. The tape 20 is formed into a longitudinally extending tube 21, whereby the strands 22-22 are positioned uniformly around the ilexible tinsel conductor 10 so that the axes of the strands are parallel to the axis of the center cord 12, and the strands are so held initially by the binding material 23. A covering 25 of insulating material is formed by a suitable process, such as extrusion, around the tube 21. The insulating material 25 may be a vulcanizable material, such as a compound of rubber, neoprene or the like, or it may be a thermoplastic material, such as polyvinyl chloride, polyethylene, or the like.
ln Fig. 2, apparatus is disclosed which may be utilized in performing the objects of the invention. A supply 'reel is shown at 26 to provide a supply of the conductor 10 consisting of the twisted tinsel threads 11-11 wound helically around the center cord 12, as described above. A supply pad 27 of the tape 20 is provided, and the tape is passed therefrom over a guide roller 30 and through a suitable tube forming device 31, which forms the tape into the tube 21 around the flexible tinsel conductor 10. The flexible tinsel conductor 10 and the tube 21 formed therearound are then passed as a unit through an extruding machine 32, and the covering 25 is extruded around the tube 21. The completed conductor is wrapped around a capstan 35 which draws the conductor through the extruding machine 32, and iinally is Wound on a takeup reel 36.
The tape 20, which consists of the longitudinal threads 22-22 held together initially by the binding material 23, is relatively stiff at room temperature and may be formed 21 around the flexible at will. ductor.
As hereinbefore stated, the binding material 23 of the tape 20 may be an adhesive, such as glue, a suitable thermoplastic material, or other material capable of bindingtthe strands together, but which decomposes, disintegrates or melts at a temperature no higher than that reached in the extruder. If the material is made of glue, the glue Will disintegrate in the extruder 32 when the covering 25 is formed therearound, be reduced to small particles of powder-like form, and be dispersed within the covering. If the binding material is made of a thermoplastic material, the material will melt during the extruding operation and may become integral with the covering 25. When a polymerized thermoplastic material is utilized to form the covering 25, it may be desirable to use the same material of lower polymerization, or another low melting point plastic, for the binding material 23, so that the binding material will melt at a temperature lower than that to which the covering material will be heated during the extrusion operation. By so doing, the material 23 will be assured of melting within the covering 25. When the term dissolving is used herein and in the annexed claims, it is intended to mean a decomposition, disentegration or melting of the binding material, as distinguished from the dissolving of a material in a solvent.
If the covering 25 is a vulcanizable material, such as rubber, neoprene, or the like, a vulcanizing chamber of conventional design wouldbe placed between the extruder 32 and the capstan 35 to cure the material. 1f the covering 25 is a thermoplastic material, a Water trough may be placed therebetween to cool the material.
'Ihe spacing between the strands 22-22 is greatly exaggerated in thedrawings, and in fact is quite small. These strands, while lending flexibility to the nished tinsel conductor 1), also contribute great tensile strength thereto, They act further as a` barrier between the metallic tinsel ribbons 16-16, 17-17 and the extruded covering 25. This barrier is necessary if, for example, the tinsel ribbons are made of copper or bronze and the covering of rubber has some sulfur therein. The sulfur would have a corrosive effect on the copper or bronze and this effect is prevented by interposing the strands 22-22 between the two. The strands also act as a mechanical barrier to protect the tinsel ribbons 16--16 and 17--17 against damage by crushing or other compressive forces to which the conductor may be subjected in use.
It is manifest that the invention is not limited to the preferred embodiments hertofore described and various modications may be made within the spirit and scope of the invention. Thus, the covering 25 may be applied in any manner as long as the requirement is satisfied that suicient heat be generated during such application to dissolve the binding material 23.
Also, it is evident that the tinsel conductor may comprise a single textile core around which a plurality of tinsel ribbons are helicallyY wound. For example, four tinsel ribbons may be wound around a textile core and the tape 20 and outer covering 25 applied therearound, as hereinbefore described.
What is claimed is:
1. The method of making insulated conductors, which comprises positioning a along an axis, positioning strands held together by a binding material disintegrable at a predetermined temperature parallel to said axis and around said conductive strands, and forming insulation around said material-held strands at a temperature at least as high as said predetermined temperature so that said binding material is disintegrated. f
2. The method of making insulated conductors, which comprises positioning a plurality of conductors along an axis, forming a tube `of together by a heat-disintegrable binding material disintegrable at a predetermined temperature around said conductors and parallel to said axis, and forming a plastic covering around said non-conductors at a temperature at least as high as said predetermined temperature such that the said material is disintegrated.
i 3. The method of making insulated conductors, which comprises positioning a plurality of conductors together, forming a tube of non-conductive strands secured together by a thermoplastic material disintegrable at a predetermined temperature around said conductors and longitudinally with respect thereto, forming a covering of inplurality of conductive strands sulating material around said tubeat at least said predetermined temperature, and disintegrating said thermo plastic material during the formation of said covering.
4l The method of making insulated conductors, which comprises positioning a plurality of conductive strands along an axis, positioning strands held together by glue disintegrable at a predetermined temperature longitudinally of said axis and around said conductive strands, form ing a covering of insulation around said glue-held strands at at least said predetermined temperature, and disintegrating said glue during the formation of said covering.
5. The method of making flexible conductors, which comprises winding a plurality of conductors helically around a center core, forming a tube of textile strands secured together by an adhesive disintegrable at a predetermined temperature around said conductors so that the axes of said strands are parallel to the axis of said center core, forming a covering of plastic material around said tube at at least said predetermined temperature, and causing said adhesive to disintegrate during the formation of said covering.
6. The method of making tinsel conductors, which cornprises winding a plurality of tinsel ribbons helically around textile strands to form tinsel strands, winding a plurality of said tinsel strands helically about a center textile'core, forming around said wound tinsel strands a tube made of a tape comprising thermoplastic material disintegrable at a predetermined temperature in which is embedded a plurality of textile strands having axes parallel to the axis of the core, and extruding an outer covering around said tube at a temperature at least as high as said predetermined temperature such that said thermoplastic material disintegrates.
7. The method of making flexible tinsel conductors, which comprises winding la plurality of ilat tinsel ribbons helically around a cotton thread to form a tinsel strand, winding a plurality of said tinsel strands helically around a center textile core, forming a tape made of ilexible, parallel cotton strands held together by glue disintegrable at a predetermined temperature longitudinally into a tube around said helically wound tinsel strands, passing said tube-covered tinsel strands through an extruding device to extrude a covering of insulation'material therearound at at least said predetermined temperature, and disintegratnon-conductive strands secured ing said glue during the extruding of said covering so that said glue is dispersed and said cotton strands are relatively free.
References Cited in the tile of this patent UNITED STATES PATENTS
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