US1342594A - Variable-resistance device - Google Patents

Description

PATENr-i orrics.'f

' Join; PARKIN,I .13.,- or SAN RAFAELLCALIFORNIA.

' VARIABLE-RESISTANCE DEVICE.

. and useful VariablerResista-nce' Device, of

" provide a durable'high resistance element.

which the following is a specification.

The invention relates to variable resistance devices for use as rheostats and potent ometers. An object of the invention is to provide a variable resistance device which is not sub jected to wearand which may be readily manipulated to vary resistance within the limits of its capacity. f g Another object of the invention is to pro.-' vide a simple and cheap variable resistance device, which is particularly adapted to handle small currents. A further object of the invention is The invention possesses other advantageous features, some of which, with the foregoing, will be set forth at length in the following description, where I shall outlinein full that form of the invention which I have selected for illustration in the drawings accompanying and forming part of the present specification, In said drawings I have shown two, forms of the device of my invention, but it is to be understood that'l do not limit myself to such forms, since the invention, as expressed in the claims, may be embodied in other forms. Referring to said drawings: Figure 1 is a rear elevation of one form of device of my invention, part thereof being shown in section to disclose the con- 'struction. r

Fig. 2 is a side elevation of the device shown in Fig. 1, mounted on a panel.

Fig. 3 is a rear elevation, partly in section of a modified form-of the device.

The device of my invention is primarily adapted for handling small currents, but it may be constructed tohandle larger currents. when desired. It is particularly adapted for use as a rheostat or a potentiometer, and finds utility in radio signaling apparatus, as a potentiometer for varying the plate potential in a vacuum tube or as a grid leak for a vacuum tube, or in other uses. lVhile its construction renders it particularly adaptable for use in radio signaling apparatus, its utility is not confined to such, but it ay be employed in all instances where it is desired to vary 1919. Serial No. 814,5 18.

electric circuit. 1 Y

r The device comprises a circular or curvedtube 2, preferably made of insulating ma-' terial, and which is preferably closed at the ends, asby the plugs 3, of insulating material. Arranged in the tube. and extending longitudinally thereof is a wire or con-- ducting element 4, of relatively low resistance, one end of which extends through the plug at the end of the tube. Disposed within the'tube and spaced from the conducting element 4, is a relatively high resistance element 5, which is substantially parallelto the wire 4. The high resistance element 5'is preferably connected at its endsand within the tube with wires 6 and 7 of low resistance, such as iron wires, and these wires extend through theplugs at the ends of the tube. Disposed in the tube and forming contact with the conductor 4 and the resistance element 5., is a rolling contact device, which maybe a steel ball, but which is preferably a drop of mercuryS.

mercury varies, thereby varying the amount of resistance in circuit, and this resistance can beadjusted very closely by a careful turning of the curved tube. 1

In the drawings I have shown the tube as,

being circular in form and have provided means so that the tube may be turned on the iron wire 6 extends into thetube so that the mercury can contact with the wire, thereby cutting out all resistance when desired.

The tube is preferably seated in an annular groove 13 formed in a knob 9 of bakelite or other comparable material, and the knob is provided with'an axially disposed stem 14: which projects through a panel 15 or other supporting element. By rotating the knob,

the position of the tube is shifted and the mercury flows to a different position, varying the resistance. The rotation is limited by a stop 16 on the back of the knob which engages a projection or stop 17 on the panel.-

the resistance of an By turning orrocking the curved tube, the position of the v I fsmmc'am of Letters Patent- P t ted J n 8, 1920,

have obtained excellent results employing a resistance element consisting of a piece of cotton or other fabric, cord or string, soaked in a mixture which when dry has a high re sistance. For this purpose I have employed a mixture of hot glue and lamp black, in which the string is soaked and then dried. This resistance element possesses many advantageous features. It is more or less flexible and will not break due to expansion or contraction or shocks, and is much more durable than rigid carbon resistance elements which have heretofore been largelyused.

I claim I 1. A variable resistance device,-c0mprising a curved tube, a conducting element in saidvtube, a resistance element in said tube insulated from and disposed in substantial parallelism with said element, and a rolling contact engaging said conducting element and resistance element.

2. A variable resistance device, comprissistance element.

4. A variable resistance device comprising a circularly bent tube of insulatlng material closed at the ends, a conducting element disposed within said tube and extending longitudinally thereof,'a resistance element in said tube in substantial parallelism with said conducting element, a rolling contact in said tube contacting with said conducting element and said resistance element, and a mount for said tube whereby said tube may be turned about its axis to cause said contact to roll.

5. A variable resistance device comprising a curved tube, a conducting element disposed longitudinally in said tube, a fabric string impregnated with resistance material disposed in said tube in substantial parallelism with said element and insulated there from, and adrop of mercury in the tube making contact with the element and the string.

6. A variable resistance device comprising a curved tube of insulating material closed at the ends, a conducting element disposed longitudinally in said tube, a resistance element in said tube spaced from and in substantial parallelism with said conducting element, a drop of mercury in said tube contacting with said elements, a mount in which said tube is arranged and a stem on said mount for supporting the mount and about the axis of which the mount is adapted to be rogated to cause the mercury to roll in the in e.

' In testimony whereof, I have hereunto set my hand at San Francisco, California, this 23rd day of July, 1919.

JOHN PARKIN, JR.

. n presence oflV. W. HEALEY, C. S. EVANS,

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