GB922117A - Improvements in adustable electric resistance devices - Google Patents

Abstract

922,117. Variable resistors. HOWELL INSTRUMENTS Inc. Aug. 19, 1959 [Oct. 29, 1958], No. 28406/59. Class 37. A variable resistor comprises an elongated resistance element 10 carrying engageable indicia (such as the holes 62) previously positioned in accordance with progressive electrical measurements along the element, the element arranged to be wound between two reels having a common axis, a contact (such as 40) being provided, capable of relative movement along the element and indicia engaging means( such as the sprocket 58) for locating the position of the contact relative to particular indicia. As shown, a moulded insulating body 16 has a cylindrical portion 20 carrying two discs 42, 44 and a sprocket 58. A resistive tape 10 of the type described in Specifications 833,347 and 833,351 is previously perforated in accordance with progressive electrical measurement along its length. One end of the tape 10 is fixed to the cylinder 20 near the left-hand end and wound on the reel formed by the space between the disc 42 and the left-hand end of the casing 72. The tape 10 is then carried over guide arms 36, 38 of a cage-like member 32 attached to the shaft 26. The tape is retained on sprocket 58 by an arm 34 which also carries a sliding contact 40. The other end of the tape is secured to the right-hand end of cylinder 20 and wound on the reel formed at the right-hand side of disc 44. The contact 40 is connected to a yoke 40a which rotates against a slip ring 64 connected to a terminal 68. When shaft 26 is rotated, the guide arms 34, 36 wind the tape 10 from one reel to the other, the tape moving around the sprocket 58 so that the contact 40 travels from one end of the tape to the other. The shaft 26 may alternatively be fixed and the body 16 rotated. Figs. 11, 12 (not shown) relate to a slidable mounting of the arm 34 on the disc 32 to facilitate assembly. Specification 857,597 also is referred to.