US2058525A - Rheostat - Google Patents

Description

Oct. 27, 1936. I TAKANASH] Q 2,058,525

RHEOSTAT Filed April l0,'l935 Patented a. 27, 1936 UNITED STATES PATENT OFFICE BHEOSTAT Masami Takanashi, Tokyo, Japan, assignmof one-half to Shungo Furui, Yokohama, Japan Application April 10, 1935, Serial No. 15,642 In Japan June 12, 1934 4 Claims. (c1. 201-40) varies linearly with its length. For this reason, 7

Such means, moreover, do not give very satisfactory results from practical point of view.

It is accordingly an object of the present invention to obviate the aforesaid disadvantages 20 of the rheostats known heretofore and to provide a rheostat by means of which the volume of reproduced sounds can be controlled in a manner proportionate with the movement of controlling means.

It is a further object of the'invention to provide a rheostat of the sort just mentioned in a cheap and economical manner.

According to my invention, any desired resistance characteristics, in which the effective re- I 30 sistance, instead of linearly with its length, varies accordingto any desired curve, can be obtained by coating a portion or whole of each turn of the coil making up a rheostat with material of a higher electric conductivity. In other words,

by making the boundary line formed by the edges of coated portions of the turns of coil to extend along a straight line or in accordance with a suitable curve, the effective resistance, or the resist- 40 ance from one terminal to a contactor brush, can be made to vary parabolically, exponentially or in any predetermined manner with respect to the position of the brush. By this means, it is made possible to control the volume of reproduced 1 sound in such a manner that it is substantially proportional to the displacement of the contactor brush.

In the accompanying drawing:

Fig. 1 shows an end view, as cover removed, of

50 a rheostat assembly according to my invention.

Fig. 2 shows a central cross sectional view thereof taken at the line IIII of Fig. 1, with the cover on.

Fig. 3 shows a plan view of a part of the rheo- 55 stat proper, as it is developed in a plane.

' Fig. 4 is a plan view of a modified form of the invention, corresponding to Fig. 3.

Referring to Figs. 1 to 3, and more particularly to Figs. 1 and 2, I is a casing in which are housed a rheostat proper and accessories thereof. The

casing -I has rigidly mounted thereon a sleeve 2,

through the inner bore of which extends a controlling shaft 3. The sleeve 2 has screw-threads 4 and is adapted with the cooperation of nut 5, to serve as a support for mounting the rheostat on a suitable panel. At the inner surface of the cylindrical peripheral portion of the casing I is provided a lining 6 of a suitable insulating material for protecting the rheostat proper from coming into contact with the wall of the casing I. The rheostat proper which is designated by numeral l is composed of an insulating inner core 8, resistance wire 9 wound on the core and terminals IIl connected to the ends of the resistance wire. The rheostat proper is so disposed within the casing I that it is prevented from coming into contact with the wall of the casing by means of the lining 6 and the terminals III are caused to project outwardly from the apertures provided at the peripheral wall of the casing and fixed to the casing in known manner. At the upper edge portion of the rheostat proper a sliding contactor I I is provided to contact resiliently with it. The contactor I I is formed as an extension of a metallic disc I2 having an arcuate aperture I3 to render the disc resilient. The metallic disc I2 is mechanically fixed to the controlling shaft 3, but insulated electrically therefrom in known manner. Another terminal I4 is provided on the casing I, as insulated therefrom. This terminal I4 is connected to a metallic member I5, which is adapted to be in sliding contact with the disc I2, the terminal I4 being in this manner in electrical connection with the contactor II. The hub portion of the member I5 is electrically insulated from the shaft 3 by means of the central insulating member I6. The shaft 3 is formed with an annular groove I] for receiving therein a wedge member I8 for preventing the longitudinal'displacement along the shaft of the assembly including the sleeve 2 and the casing I. The casing I is covered by a cover member I9. The casing I, in cooperation with the cover I9, serves also as electrostatic shield.

The above mentioned construction is known in itself. The main feature of invention will now be described in detail.

Referring to Fig. 3 in particular, which illustrates one realization of my invention, the resistance wire 9, such as Manganin, Nichrome and Advance, is wound on the core of insulator l in such a manner that adjacent turns do not come into contact with each other. 20 indicates portions of turns of wire which are coated, electrolytically for example, with material of a higher electric conductivity, such as copper or silver. In this connection, I have found that the electro lytical coating can be advantageously carried out by first coating the wire preliminarily with nickel and then with copper or silver. Adjacent turns of the coated portions too are so arranged that they do not come into contact with each other.

The coating of the turns of the wire is carried out in such a manner that the contour line 2| of the edges of coated portions form substantially a straight line, when developed, extending diagonally from one side to the other side of the coil. The coating portions 20, however, can be so prepared as to make the contour line 2| to extend from one side to the other side of the coil according to any desired curve, for example according to an exponential curve, as shown in Fig. 4.

The core of insulator 8 need not necessarily be in plate form, but it may be made cylindrical or oval in cross-section, or any other suitable form.

In case a rheostat according to the invention is intended to be utilized for the purpose of controlling the volume of reproduced sounds in an electrical phonograph or a radio broadcasting receiver, it can be treated under suitable heat and pressure in a mold with molding powder, such as bakelite or ebonite, so as to form around it an external protective covering.

The invention is particularly useful, in its application, as rheostats for controlling the volume of sound in electrical phonographs or radio broadcasting receivers, as has been indicated hereinbefore, although it is also useful in general current regulating purposes, inasmuch as its characteristic curve can be varied at will by suitably forming the conductive coating on the rheostatic coiled wiring. Moreover, its manufacture is very easy and inexpensive owing to the fact that it can be produced by a mere coating of ordinary rheostat by a material of good electrical conductivity.

What I claim is:

l. A rheostat for controlling the volume of reproduced sound, comprising a coil of resistance wire, the turns of which are spaced apart out of contact with each other, and a coating on a portion or the turns 01' said coil of metal having higher electrical conductivity than said wire, said coating consisting of an electrolytic deposit of nickel on the wire and an electrolytic deposit of copper on the nickel.

2. A rheostat for controlling the volume of reproduced sound, comprising a coil of resistance wire, the turns of which are spaced apart out of contact with each other, and a coating on a portion of the turns of said coil of metal having higher electrical conductivity than said wire, said coating consisting of an electrolytic deposit of nickel on the wire and an electrolytic deposit of silver on the nickel.

3. A rheostat for controlling the volume of reproduced sound, comprising a coil of resistance wire, the turns of which are spaced apart out of contact with each other, and a coating of metal of higher conductivity than said wire on said coil, said coating consisting of a deposit .of nickel on said wire and a deposit ofmetal of higher conductivity than nickel on said nickel deposit, the contour line connecting the boundary of said coated portion of each turn of wire extending from one end of the coil to the other substantially 3 according to an exponential curve.

4. A rheostat for controlling the volume of reproduced sound, comprising a coil of resistance wire, the turns of which are spaced apart out of contact with each other, and a coating of metal of higher conductivity than said wire on said coil, said coating consisting of a deposit of nickel on said-wire and a deposit of metal of higher conductlvity than nickel on said nickel deposit, the contour line connecting the boundary of said coated portion of each turn of wire extending from one end of the coil to the other substantially according to a parabolic curve.

MASAMI TAKANASHI.

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