GB817122A - Improvements in or relating to electrical thermally responsive relays - Google Patents

Abstract

817,122. Temperature-responsive actuating-elements. BRYANT ELECTRIC CO. Aug. 22, 1957 [Aug. 29, 1956], No. 26521/57. Class 64(2) [Also in Group XXXVII] A thermal relay has a U-shaped framework of insulating material comprising two side legs 2 and 4 and a base portion 6 carrying four plug pins 50. Resistance wire 116 is wound around the base portion and an insulating member 92 pivoted at 98 in recesses in a metallic contact actuator 82, itself pivoted at one end in the top of leg 2 and guided by a slot in the top of leg 4. The wire 116 may be secured in place by being partially embedded in an asbestos member 118 or by coating members 92 and 118 with varnish or adhesive. The wire 116 is tensioned by a spring blade 100 bowed between the actuator 82 and the free end of a metal plate 64 connected to one plug pin 50. The blade 100 carries a contact 102 co-operating with a fixed contact 78 mounted on an extension from a plug pin 50. The other two plug pins 50 act as terminals for the wire 116. Adjustment of the moving contact 102 is provided by a screw (Fig. 2, not shown) engaging an indentation 68 in the free end of the plate 64, to lift or lower the latter and thereby vary the initial amount of bow in the blade 100. Side cover plates 126 fit in grooves in the legs 2 and 4 and are retained by tabs 128 on a top cover 120. The side covers 126 may have perforations 130 or may be omitted so that the relay may respond to rate of flow or change in temperature of a stream of fluid. In a modification (Fig. 8, not shown) the spring blade 100 is mounted centrally on the plate 64 and the actuator 82, the latter being loosely guided at each end, and the contacts are arranged to break instead of make as the wire 116 expands. The casing may be sealed and evacuated.