GB759398A - Improvements in or relating to variable electric resistances or potentiometers - Google Patents

Abstract

759,398. Variable resistances. ELECTRIC & MUSICAL INDUSTRIES, Ltd. Feb. 28, 1955 [Feb. 26, 1954], No. 5665/54. Class 37. A variable electric resistance comprises a flat track of resistive material against which a sliding contact having a contact surface of annular form is pressed by means of a resilient arm. Figs. 1 and 2 show a variable resistance comprising a flat resistive track 12 of, for example, carbon, which may be deposited on a narrow strip of paper and is supported on an insulating former 11 the whole being mounted on a frame 1 which also carries an operating rod 5 having a helical thread 10. A sliding contact 20 having a contact surface of annular form is constituted preferably by a tubular metal eyelet spun over at one end to provide a smooth surface. The contact is coupled to a resilient arm 21 (see also Fig. 4) which is made of phosphor bronze spring, the contact 20 being mounted in a circular aperture in the arm so that it has a limited freedom of movement relative to the arm. The arm is bent and formed integrally with a movable carrier 22 and has spaced protuberances 24 which make contact with the wall of metal frame 1. The carrier 22 has metal ribs 23 which engage the helical groove 10 in rod 5 and thus move contact 20 along resistive track 12 when knob 8 is rotated. The resistive track may be arcuate in form the contact 20 moving along a curved path for example by angular movement of arm 21. Specification 722,284 is referred to.