GB894891A - Improvements in or relating to temperature responsive devices - Google Patents

Abstract

894,891. Thermal switches. GENERAL ELECTRIC CO. Ltd. Jan. 15, 1960 [Jan. 16, 1959], No. 1689/59. Class 38 (5). [Also in Group XIII] In a room thermostat switch, a bimetal strip 24, tapered at one end, Fig. 1 (not shown), is riveted at the other end to one end of a channelshaped carriage member 23 the other end of which has projections 22 extending from the outside of the carriage side walls to engage in notches 21 in the side walls of the channelshaped main body 1 of the device. A tapered spring 28 is secured between a cap 18 on the main body and the riveted end of the carriage 23 so that that end tends to be raised against the rounded end 37 of an adjusting screw 36 which carries a dial 38 and determines the operating temperature. The carriage is thus capable of limited movement by the rotation of the projections 22 in the notches 21 against the action of the spring 28. Riveted to the end of the bimetal 24 remote from the carriage 23 are both a knife edge 30 and an insulating plate 31 bearing a movable contact 12. The contact 12 may be carried directly by the bimetal. A U- shaped spring 32 stretches from the knife-edge 30 to an adjustable knife edge 19 to compress the bimetal 24. The head of an adjusting-screw 20 is held on to the cap 18 and the screw is threaded into an extension of the knife edge member 19. When the temperature rises, the bending moment on the bimetal 24 decreases and a snapaction break occurs so that the contact 12 drops from a fixed contact 4 to a back-stop 17 which may also include a contact. The position of the bimetal may be reversed so that the contacts close with a rise in temperature. There is a heating resistor 41 over the bimetal so that the switch may operate with light currents. The temperature range is pre-set by altering the tension in the U-spring 32 by means of the screw 20. There may be a device for locking the U-spring 32 up or down to lock the switch. The fixed contact 4 is screwed into a parttubular member 5 held by a screw on moulded insulation 2 screwed to the main body 1. A screw 8 holds supply wires in the tubular part. A terminal block, Figs. 1, 3 (not shown), is held on the insulation 2 by a screw which attaches a jumper strap, from the moving contact 12, to the block. A lead 44 from the heating resistor 41 is attached to the member 5 so that the resistor may be connected in parallel with the load by an extra wire from the neutral side of the circuit to a terminal block 42 to which the other side of the resistor is connected. The Provisional Specification describes a modified switch in which the moving contact is connected to a terminal by copper foil passing through an aperture in the main body 1 and insulation. The back stop for the contact end of the bimetal is a bridge formed on a bent-up portion of the switch body.