GB1296196A - - Google Patents

Abstract

1296196 Variable resistors ALLEN BRADLEY CO 21 Jan 1970 [5 Feb 1969] 2956/70 Heading HIS Two potentiometers within a common housing 26 comprise outer resistive tracks 14, 15 and inner, annular collector tracks 16, 17 moulded in opposed surfaces 11, 12 of insulating elements 10, 13 respectively. The resistive tracks 14, 15 are in the form of incomplete annuli, rotationally offset by 180 degrees with respect to each other, and are connected to the collector tracks 16, 17 by bridging contacts 42, 43 respectively. The contacts 42, 43 lie in respective recesses 40, 41 on opposite sides of a central insulating rotor 35 which is carried on a knurled end 34 of a shaft 32 and which extends in the form of an axial sleeve 39 to insulate the track 17. Metallic inserts 22, 23 are embedded in the elements 10, 13 for removing heat from the adjacent tracks 14, 15 respectively and for anchoring the metallic housing 26. Each potentiometer has three terminals 20, 21 likewise moulded in the elements 10, 13 respectively and the terminals 20 may be attached to a printed circuit plate providing downwardly projecting terminals as terminals 21. The contacts 42, 43 and the recesses 40, 41 are of triangular cross-section and the contacts are pressed axially outwardly by multiple transverse springs 44, 45, so that projecting feet 47, 48, 49 of each of the contacts 42 and 43 bear on the tracks 14, 16 and 15, 17 respectively. The springs 44, 45 press against angled rear surfaces 51 of the contacts 42, 43 so that the latter are also pressed slightly radially outwardly which is stated to facilitate assembly. The recesses 40, 41 may have their outer apices, which engage the feet 47, formed by planar surfaces (52, 53, Fig. 4, not shown) to prevent jamming of the brushes.