GB680626A - Improvements in or relating to resistances - Google Patents

Abstract

680,626. Casing and enclosures for resistances; combinations and sets of two or more resistances; resistance coatings and deposits. LIEBMANN, D. M. June 23, 1950 [May 10, 1949], No. 12393/49. Class 37. In Fig. 1 a carbon or metal film resistor 1 is shown hermetically sealed in a casing comprising a metal tube 12 closed at both ends by metal discs 13. The axial leads 17 extending from the resistor 1 are silver soldered at 18 to the main outgoing leads 14 which are sealed into apertures 16 in the end discs 13 by means of fused glass beads 15. The end discs 13 are provided with flanges 7 radially resilient so as to ensure a tight fit into the tube 12 and soldered to the latter by induction heating. The casing may be evacuated or filled with an inert gas or packed with heat-conductive insulating material or with a de-humidifying agent such as silica gel or activated carbon. The casing may accommodate a dual or composite resistor, Fig. 2, comprising a negative resistance/temperature coefficient carbon film section 25 in series with a positive resistance/ temperature coefficient metal film section 26 to produce a resistance unit of zero resistance/ temperature coefficient. The two sections 25, 26 are secured together coaxially by means of an externally screw-threaded rod 27. The Provisional Specification discloses a resistance unit comprising a stack of mica discs or sheets, each of which carries on a face or periphery a resistance element in the form of a long and narrow, for example, zig-zag or spiral, metallic or carbon ribbon layer or deposit.