GB817483A - Improvements in or relating to variable potentiometers - Google Patents

Abstract

817,483. Variable resistances. METALLUX S.r.L. Dec. 13, 1955 [Dec. 13, 1954], No. 35810/55. Class 37. [Also in Group XL (c)] A variable potentiometer comprises two or more electrically conductive tracks and a movable resilient conductive bridging member which is associated with contacts, one of each of which presses against each track so that on rotation of the movable member the contacts slide along the tracks. Figs. 1 and 2 show a variable resistance element comprising a circular base 1 of insulating material for example steatite, ceramic or vitrous material on which has been deposited by evaporation in vacuum two layers of metal or of a compound of oxides and metals forming tracks 2 and 3. To the outer ends of the tracks are welded terminals 5, 51, 6. A shaft 10 extends through a bush 7 in the support and at one end has an arm 14 of insulating material which is riveted to a resilient conductive bridge element which presses brushes 15, 15<SP>1</SP> against the tracks 2, 3 respectively. The assembly is enclosed by an hermetically sealed cover 4 through which the terminals pass. The outer track 2 is of resistive material and the inner track serves as a collector being of negligible resistance. Alternatively, the inner track 3 may be also of resistance material either or both of the tracks having linear or non-linear resistance characteristics. Thus the potentiometer may serve as a combined volume and tone control in a radio receiver or one or both tracks may be interrupted along the length so as to switch in additional resistance elements as the shaft 10 is rotated to form either a discontinuous resistance or to give a desired law. In a modification, Fig. 3 (not shown), the track 3 is in the form of a closed annulus and acts only as a collector. In a further modification, Fig. 4 (not shown), the inner track 3 has a terminal welded at each end and may act either as a collector or resistive track. There may be one or more main resistive tracks associated with one or more auxiliary or collector tracks.