GB786278A - An electric temperature control device - Google Patents

Abstract

786,278. Thermal switches. LICENTIA PATENT-VERWALTUNGS-GES. Dec. 15, 1954 [Dec. 15, 1953; April 6, 1954; Nov. 8, 1954], No. 36396/54. Class 38 (5). A switch comprises two heat-responsive twolayer strips, each of which is U-shaped with one strip arranged within the other which latter has one leg bent back to face one leg of the inner strip, the two facing ends being interconnected by a toggle member and being movable in opposite directions when heated or cooled so as to actuate contacts. As shown, the strips 1, 2 are clamped to a metal plate 20 which is in thermal contact with a nut 30 arranged to be placed in thermal contact with, e.g., the evaporator of a refrigerator. The free ends of the strips are interconnected by a U- shaped spring 8 and the inner strip 2 carries an insulating rod 25 acting on contact springs 26, although one of the strips may carry a contact co-operating with a spring-mounted contact. A cable 32 is received in a liquid-tight manner in grooves in a cover 21b and a base-plate 21a, which are secured together in a liquid-tight manner as by fusing together or by casting a material into a groove 33 between the rims of the cover and base-plate. A locking wire may be arranged in the groove, Fig. 2 (not shown). A heating coil controlled by a rheostat may surround one or both of the strips, or the strips may carry the heating current, as by a resistance material applied to the strips. Alternatively, a resistance 18 may be arranged in the casing adjacent the bends of the strips, either outside the bend as shown or inside, Fig. 4 (not shown). If a resistance 18 is used, the inner wall of the cover 21b may have a metal coating. The strips may be of bimetal or different insulating materials with different heat coefficients.