US2093087A - Insulated conductor - Google Patents

Description

Sept. 14, 1937. A, M, L 2,093,087

INSULATED CONDUCTOR Original Filed Nov. 21, 1928 lA/VE/VTOR CHM/06E ACETATE ATTORNEY Patented Sept. 14, 1937 PATENT OFFICE mam-ran commc'roa Alger M. Lynn, OakParkJlL, muwm v Electric Company, Incorporated, New York, N. Y., a corporation of New York Original application November 21, 1928, Serial Divided and this appllcation March 13, 1934, Serial No. 715385 8 Claims- (Cl. INF-264) This invention relates to insulated conductors and this application is a division of my copending application Serial No. 320,794, filed November 21, 1928 issued as Patent No. 1,966,509, dated July 17, 1934. a

Objects of the invention are to provide inexpensive insulating materials having high insulating properties, and which may be readily applied to electrical conductors and to provide electrical l0 conductors having thin, smooth, uniform and adherent coverings of eifective insulating materials thereon.

In accomplishing the objects of the invention,

' one specific method embodying the invention 13 comprises serving a fiat band of artificial silk filaments around a conductor to 'produce a smooth, uniform layer of the silk upon the conductor, and heating the covered conductor to reduce the elasticity of the silk, so that it will have little tendency to unravel.

The above enumerated and other objects and features of the invention will be apparent from the following detailed description of specific embodiments of the invention taken in connection with the accompanying drawing,'in which Fig. 1 is a fragmentary, longitudinal view of a conductor embodying the invention showing how the insulating material is applied and having a part of the insulating material broken away to 80 more clearly show the structure thereof;

Fig. 2 is a transverse sectional view thereof taken on line 2-2 of Fig. 1; and

Fig. 3 is a sectional view of the insulating ma terial taken on line 3-3 of Fig. 1.

Natural silk has been used heretofore as an insulating material for electrical conductors, particularly for fine gauge wire such as magnet wire. In employing natural silk for this purpose it has been the practice in some cases to use a fiat band 40 comprising four to twenty-five parallel ends of substantially untwisted twenty denier threads composed of extremely fine individual filaments of one to three denier. This band is frequently applied to the wire in a thin spiral layer. Although natural silk is an excellent insulator, it

is quite expensive, especially when used for insulating fine gauge wires because very fine, continuous filament silk yarns are required for such purposes. The present invention contemplates the substitution of a specially prepared artificial silk insulating material for natural silk and the application thereof to an electrical conductor in such manner that the conductor will be as effectively insulated as when natural silk is' employed and at a much lower cost,

In the manufacture of artificial silk the material from which the silk is made is extruded in the form of a liquid through dies, commonly called spinnerets, having a large number of minute holes therein through which the 'material passes and from which the material emerges in 1 the form of extremely fine filaments, after which the filaments are passed through a suitable treating process, wherein the silk is solidified and converted into its final form.. However, since artificial silk yarn of the usual type is of cylindrical cross-section and is composed of a plurality of individual filaments of the silk, it is difiicult to produce a smooth, uniform insulating layer of such silk upon a conductor to form an insulator cover therefor. In practicing the present invention a special type of artificial silk yarn is employed consisting of a single band of individual filaments, wherein the filaments lie substantially parallel to one another, and are so positioned that the finished yarn will consist of a fiat, thin, comparatively wide band which may be readily applied to a conductor to produce an exceptionally smooth and uniform insulating covering for the conductor. Also artificial silk as usually produced in an economical manner at present is considerably larger than the twenty denier yarn now employed in the natural silk insulating bands. In the present invention a sufficientnumber of individual fine filaments of artificial silk are extruded through a spinneret so as to produce a single fiat band of eighty to five hundred deniers and comparable with the natural silk bands heretofore used for this purpose.

In the manufacture of artificial silks there are four commonly used processes; namely,

1. Cellulose-acetate 2. Viscose 3. Cupra-ammonium 4. Nitro-cellulose By employing the cellulose-acetate process an artificial silk is produced which consists essentially of cellulose-acetate, which possesses insulating properties comparable to those of natural silk, whereas by practicing the other three processes enumerated above an artificial silk is produced which consists substantially of pure cellulose, which possesses insulating properties somewhat inferior to those of the cellulose acetate and natural silks. The differences in the insulating properties of these artificial silks necessitate the use of slightly different procedures in the processes of insulating electrical conductors therewith, and various processes embodying the invention will now be described.

' indicated by the numeral III in the accompanying drawing, and the thus formed band is served spirally around an electrical conductor l I, so as to form.therearound a thin, smooth, and substantially uniform covering which comprises an efiective insulator for the conductor.

Since artificial silk is generally smooth and comparatively free from interlocking fibres, and because it possesses comparatively high elasticity, it has a tendency to unravel from the cut end of a wire insulated therewith, and this tendency is overcome in the case of cellulose-acetatesilk by either one of two methods. The conductor, after having been covered with the silk insulation, may be heated at a moderate controlled temperature to remove the natural strains in the silk and possibly to slightly soften the celluloseacetate of which the silk is composed, whereupon the elasticity of the silk is reduced and the tendency of the silk insulation to unravel is there- 28 fore substantially eliminated.

Electrical conductors, may also be insulated with satisfactory results by means of artificial silks made in accordance with the viscose, cupraammonium, nitro-cellulose or other processes in which the finished silk consists substantially of a regenerated cellulose only. when these silks are employed, they are served upon electrical conductors in the form of fiat, thin, comparatively wide bands in the same manner as has been described hereinbefore in connection with the cellulose-acetate silk, to form smooth, substantially uniform, helical coverings upon the conductors. The' insulated conductors are then treated with a lacquer composed of cellulose- 40 acetatedissolved in acetone. which lacquer serves the double function of increasing the insulating properties of the silk insulation to a valuesubstantially equal to that of natural silk, and at the same timeactcsing as an adhesive to retain the insulation in intimate contact with the conductor, so that the insulation will not readily unravel.

It will thus be seen that the invention provides inexpensive insulating materials having high in- 60 sulating properties, that insulated conductors embodying the invention may be made therewith which'have very desirable characteristics, and that such insulating materials may be easily, cheaply and eifectively employed in practicing the as methods embodying the invention to produce such conducto v a suitable solvent, such as Whatisclaimed is:

1. An insulated conductor, comprising a conductive'wire and a substantially uniform covering therefor composed of a band of untwisted artificial filaments of a cellulose derivative helicallywrapped around said wire, said filaments being ununited and heat treated to remove internal strains.

2. An insulated conductor, comprising a conductive wire and a substantially uniform covering therefor composed of a band of untwisted and ununited artificial filaments of a cellulose ester helically wrapped around said wire, said filaments being heat treated to remove internal strains. v

3.- An insulated conductor comprising a conductive wire and a substantially uniform covering therefor composed of artificial filaments of a cellulose derivative wrapped around said wire, said filaments being ununited and heat treated to remove internal strains.

'4.A method of making insulated wire which comprises helically wrapping a band of u'ntwisted filaments .of a cellulose derivative around a conductive wire and heating the filaments below the coalescing temperature of said cellulose derivative but sufiiciently to removeinternai strains.

5. A method of making insulated wire which comprises wrapping a uniform covering of artificial filaments of a cellulose derivative around a conductive wire, and heating said filaments below the coalescing temperature of said cellulose derivative but sufficiently to remove internal strains.

6. A method of making insulated wire which comprises helically wrapping a band of untwisted filaments of a cellulose ester around a conductive wire, and heating the filaments below the coalescing temperature of said cellulose ester but sufiiciently to remove internal strains.

7. An insulated conductor, comprising a con- Amaa M. LYNN.

ductive wire and a substantially uniform cover-

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