GB455288A - Improvements in and relating to thermostatic switches - Google Patents

Abstract

455,288. Thermal switches. TURNER, C. A., 33, Crespigny Road, Hendon, and DIAMOND H. SWITCHES, Ltd., Gunnersbury Avenue, Chiswick, both in London. April 16, 1935, No. 11708. [Class 38 (v)] In a thermostatic switch a thermal element such as a bimetallic coil 16 rotates a shaft carrying a cam 13 which engages a roller 12 on a contact arm 1 pivoted at 9 and biassed by a spring 6 causing a contact 2 to move away from a contact 3. The cam also has fixed to it a pointer 25 which moves over a dial 20 indicating the temperature. The dial may be adjusted relatively to a fixed pointer 24, indicating the temperature at which the circuit is to be broken, by rotating a knob 24<1> which turns a wheel 22 gearing with teeth 21 on the dial. The dial is also adjustably connected to a toothed plate 26 by means of a screw 28 which passes through one of a number of holes in the dial and engages between the teeth of the plate 26, and the plate 26 is connected by a sleeve 27 to a disc 19 which carries a pillar 18 connected to the one end of the bimetallic coil by means of a link 17. Rotation of the knob 24<1> therefore not only moves the dial 20 but also the bimetallic coil and the cam and pointer 25. In a modification, suitable for use with a water heater, Figs. 3 and 4 (not shown), the flat bimetallic coil is replaced by a helix. In other modifications, Figs. 5 and 6 (not shown), the adjusting knob 24<1> is mounted on the end of a flexible shaft coupled to the switch. In place of a single cam there may also be two ; one operating in advance of the other and cutting off part only of the heater and the other operating later and cutting off the remainder.