GB1070086A - Improvements in or relating to resistive devices - Google Patents

Abstract

1,070,086. Variable resistors. PAINTON & CO. Ltd. Jan. 21, 1966 [March 30, 1965], No. 13490/65. Heading H1S. Precise control of the position of wiper contact 47, on wire-wound resistance element 48 is obtained by driving it from thumb-wheel 8 through reduction gears (17) (Fig. 3, not shown), 24 and 26 (Fig. 6, not shown) and the toothed periphery of hub 21 of follower wheel 10, which carries a conductive disc 43 with integral wiper contact 47 and pick-up contacts (45), (46) (Fig. 3, not shown) and which may have calibration marks on its rim 12. Cover 3 carries collector ring 54 in seating 39 and resistance element 48 in channel 50, and has connections of these to external terminals (52), (53) (Fig. 3, not shown) moulded into it. A spring (36), (38), (38<SP>1</SP>) (Fit. 3, not shown) prevents rotation of the follower wheel beyond the ends of resistance element 48 by engaging a tab (40) (Fig. 3, not shown) on one of its arms with projection 23 and yielding resiliently, so as to engage the toothed periphery of hub 21. The untoothed segment 22 of hub 21 comes opposite gear-wheel. 24 with further rotation and drive is then no longer transmitted. When the turning force is removed the spring returns wheel 10 and the toothed part of periphery 21 re-engages gear-wheel 24. Thumbwheel 8, gear-wheel 24 and follower wheel 10 are of nylon, and are self-lubricating. In a variable resistor with a vernier scale on the thumb-wheel and its adjacent cover stops, the spring clutch (36), (38), (38<SP>1</SP>), one of the terminals (52) and the untoothed part of hub 21 may be omitted and the wheel 10 be allowed to revolve freely.