GB1247757A - Miniaturised trimmer potentiometer - Google Patents

Abstract

1,247,757. Variable resistors. ELECTRA/ MIDLAND CORP. 1 July, 1969 [1 July, 1968], No. 33239/69. Heading H1S. A small trimmer potentiometer comprises a housing 14 (e.g. of glass-filled nylon or other thermoplastic) having an open side and an internal shoulder 26; a worm-wheel 30 (e.g. of same material as housing) mounted on a boss 28 in the housing and engaged by a worm gear 15; a wiper 60 maintained on a stub shaft 32 on the worm-wheel by two curled arms 61, 62 and with resilient arms 64, 63 for contacting a resistance and a central contact, and a substrate 40 which fits on the shoulder 26 and carries an interrupted annular cermet resistance element 50, a central contact 55 conductive strips 51, 52, 53, and terminals 11, 12, 13. A tab 66 on the wiper co-operates with a stop 13b on the hooked end 13a of the centre terminal 13. The terminal leads 11, 12, 13 are hooked over the corners of the substrate, and run along the edges and down holes (71, 72 or 72, 73, Fig. 5, not shown), in the corners of the housing and may be bent through grooves 81, 82, 83 or 101, 102, 103. They may lead out at right angles (Fig. 1, not shown) or parallel to the adjusting worm gear 15. The worm gear has ridges 96 of sawtooth cross-section and is inserted in the housing by sonar vibration which softens the material of the housing (Fig. 5a, not shown). The housing may have embosses 85 to secure the substrate, and there are recesses 26a in the shoulders 26 for the terminal ends 11a &c. Potting material (105, Fig. 3, not shown) is applied over the substrate 40 and in the holes 71, 72 and grooves 81, 82, 83.