US1719241A - Coil construction - Google Patents

Description

July 2, 1929. BRQSCOTT 1.719.241

COIL cousmucnon f Fil ed Feb. 19, 1926 INVENTOR Patented July 2, 1929.

UNITED STATES PATENT o -FICE.

I BEVERLEY RANDOLPH SCOTT, OF WOODLYNNE, NEW JERSEY, ASSIGFTOR 'I'O THE HAM- MARLUND MANUFACTURING COMPANY, INCORPORATED, A CORPORATION'OF NEW YORK.

COIL CONS Application filed February My invention relates particularly to-wire Y coils used for various purposes such as electric inductances.

One object is to provide a coil -of high inductance value and low dielectric loss. relatively low resistance and small distributed capacity. I 1

Another object is to provide a coil which can be readily handled and mounted. 7

Another object is to provide a coil having permanent and uniform characteristics.

I have solved the problem by the simple expedient of winding a coil upon a very thin layer of dielectric material to Which it is permanently anchored. The method of manufacture which will be hereinafter de scribed makes it possible to maintain any desired spacing of the various turns.

Fig. 1 is a side view of the coil made according to my invention.

Fig. 2 is an end view of the same.

Fig. 3 is a perspective view of a mandrel showing one method of applying the dielectric.

Figs. at and 5 are diagrammatic end views of two other arrangements of the supporting dielectric.

Fig. 6 is a diagrammatic end view of a coil of angular cross-section supported on two strips of dielectric.

Fig. 7 is an enlarged longitudinal sectional view showing a fragment of a coil in process of manufacture.

Fig. 8 is a similar sectional view showing the same after the wire hasbeen permanently secured in place. 7

The foundation 10 of the coil is made up of one or more strips of a material such as a nitrocellulose composition, for instance, celluloid or pyroxylin.

The conductor 11 is covered with insulating material 12 such as silk or cotton fibre.

In making the coil I preferably employ a mandrel 18 made up of a series of sections such as shown in Fig. 3 and provided with a tapered shaft 14 capable of expanding and su imorting the mandrel. According to the preferred method of manufacture, a very thin sheet of celluloid, say five-thousandths of an inch thick, is wrapped around the mandrel and the edges of the sheet overlapped, as indicated in Fig. 3, and stuck together by the simple expedient of applying a suitable solvent, such as ethyl-acetate TBUCTION.

19, 1926. Serial No. 89,292.

to the material. along the line of overlap,

the edges of the sheet to be drawn together smoothly and pressed together immediately after the solvent is applied. I have found that this operation of cementing the edges together on the mandrel can be most conven ently affected by the use of asphincter spring 15. Thisspring normally rests in a groove 16 in one endof the mandrel and,

is run alongthe surface of the celluloid as soon as the overlapping edges have been moistened with the solvent. Springs 16' hold the mandrel parts together. When the edges of the strip have been united on the mandrel, the mandrel is expanded in the usual mannerby simply driving thev shaft longitudinally. This places the celluloid tube under tension. The mandrel is then placed in a winding machine and thewire;

wound on it under tension. "This tension should remain substantially constant throughout the winding operation and the feeding of the wire should of course be at the proper rate to lay the wire with the desired spacing between adjacent turns. When the coil has been wound, a suitable solvent, such as ethyl-acetate is applied to the foundation between the adjacent turns of the wire, for instance, by means of a brush. This solvent penetrates the insulation of the wire and immediately softens the surface of the foundation. The coil being under tension, as before described, of course tends to contract in diameter and thus sinks ver slightly into the softened surface of the co luloid or the like. The change in condition before and after the application of the solvent is shown bythe difference between the relative positions of the coil and foundation as shown in Figs. 7 and 8. The mandrel may be contracted and withdrawn as soon as the material has hardened, which requires only a few minutes. The finished coil will, however, continue to dry out for some time, the length of time varying with the composition of the material, the nature of the solvent, and the amount applied, as well as the atmospheric conditions. In drying out the coil shrinks lengthwise, sometimes as much as 10% and becomes corrugated in the longitudinal section as shown in Fig. 8. These corrugations remain permanent and tend to hold the coils in position even if they become loosened from the celluloid.

It is obvious that the coil may be wound at any length desired for special purposes. The method of manufacture lends itself particularly to the production of long tubes which can be readily cut up into such lengths as may be desired.

In the manufacture of these tubes, particularly in small sizes, there is sometimes a tendency for the tube to warp when made as above described, due-to the overlapped joint along one edge. This can be readily avoided, however, by using two strips, such as 20 and 21, as shown in Fig. 4, so that there will be oppositely disposed joints which will offset each other in the shrinking process.

It should also be understood that any number of foundation strips may be used and that these strips may be spaced apart as shown for instance in Fig. 5. Here I have shown four strips 23 with spaces 24 between them. A coil wound in this manner has an added advantage of reducing the dielectric material to a minimum.

The forms shown in Figs. 5 and 6 are specifically claimed in my application #209,277, filed J'uly'29, 1927. I

' Although the coil is preferably circular in cross-section, it should be understood that certain features of the invention'are applicable to coils of other cross-sections, for instance, in Fig. 6, I have shown a square coil wound on two strips 25 on opposite sides. This would, of course, leave the wires 26 on the other sides spaced apart without supports except at the edges of the strips 25.

Coils wound according to my invention may be used for various purposes, such, for instance, as radio frequency variable couplers, antenna couplers, interstage couplers, neutrodyne coils, short wave coils, etc.

The method of forming coils according to my invention is claimed in my Patent- #1,643,998, dated Oct. 4, 1927.

I claim:

tubular foundation of thin material such as sheetcelluloid of substantlally uniform thickness, and a helix 01 wire cement-ed in the outer surface of the'foundation, the founda- I, t1on being corrugated and the turns of the wire helix being cemented in the grooves of the corrugations.

2. A coil comprising a foundation sheet of thin celluloid-like material having its 4.

BEVERLEY RANDOLPH SCOTT.

I I 1. A self supporting coil comprising a'

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