GB814813A - Variable resistor - Google Patents

Abstract

814,813. Variable resistors. CHICAGO TELEPHONE SUPPLY CORPORATION. Dec. 9, 1955, No. 35480/55. Glass 37. A variable resistor of the rotary type comprises a length of resistance wire wound toroidally around a strip of insulating material curled into a hoop with the opposite ends thereof abutting, a terminal tag for each end of the winding having a U-shaped portion formed therewith and embracing the respective end of the strip and riveted thereto so as to make contact with the end of the wire and a further short insulating strip overlying the abutting ends of the strip and retained in position by the terminal tags and supporting a further terminal tag connected electrically to a sliding member making electrical contact with the resistance wire. The resistance wire and terminal assembly is mounted within a metal casing having an inner layer of insulating varnish; by virtue of the close contact between the resistance element and the casing the resistor has good heat-dissipation properties. Fig. 5 shows the resistance element 20 with terminals 31 riveted to the ends of the resistance winding and also embracing an insulating strip 33 on which is mounted a terminal 40. Contact ring 18 having legs which rest on the front surface of the casing 4 when the resistance assembly is mounted therein, is attached to terminal 40. As shown in Fig. 1, a contact 16 attached to a disc 22 driven by the shaft 9 makes contact with the ring 18 while further contacts 19 also attached to the disc 22 and connected to the contact 16 make contact with the inner surface of the resistance element 20. Also attached to the disc 22 is a plate 23 having a forwardly bent portion 24 which limits the rotation of shaft 9 by engaging with a piece 25 bent in from the front surface of the casing 4. A rearwardly bent portion 26 engages with the operating member of a switch 8 attached to the rear wall of the casing to actuate the switch during the rotation of the shaft. The front wall of the casing is provided with forwardlybent portions 14, Fig. 5, which hold the resistor against rotation relative to the surface upon which it is mounted and an indentation 50 which engages a slot 51 in the insulating strip 33 to hold the resistance assembly against rotation within the casing.