GB521599A - Thermally responsive temperature regulating device - Google Patents

Abstract

521,599. Thermal switches. WILCOLATOR CO. Nov. 18, 1938, No. 33630. [Class 38 (v)] [Also in Group XXIX] A thermally operated electric switch or valve has setting means comprising a pointer and dial, behind one of which a lamp is placed to be visible therethrough, which lamp is operated upon operation of the switch or valve. In the two pole switch for controlling an oven as shown in Figs. 2 and 8, a rise in the temperature of a bulb 10 causes fluid pressure to compress a bellows 18 against a spring 26 and thereby to move to the right a stem 24 inside which is screwed one end of a rod 25 which has freedom of longitudinal but not of rotary movement relative to a rod 65 upon which a handle 83 is rigidly fixed. A spring 34 is in compression between the lower end of a lever 28 pivoted at its upper end, and the upper end of a spring 36 rigidly fixed at its lower end. Also carried at the upper end of spring 36 is an H-shaped member 44 of insulating material on which two contacts 47 are mounted pivotally for self alignment, which bridge pairs of contacts such as 52, 53. When a pointer 88 on the handle 83 points to the off position, a cam 93 on the handle pushes a rod 94 against a spring 97 which holds the member 44 in the open circuit position. Upon rotation of the handle 83 in a clockwise direction so that the pointer indicates the required temperature, the contacts are released and the rod 25 is screwed to the left against the spring 34 and whose lower end is moved across the line joining the two ends of the spring 36 and the switch closes with a snap action. As shown .in Fig. 9, this closes the circuit to a lamp 100, preferably a neon tube, in series with a high resistance 103, and a heating element 106. The temperature rises, the bellows 18 is compressed and the rod 25 and the lever 28 move back until the required temperature is reached when the switch opens with a snap action, and the heating circuit and the lamp are switched off. The lamp 100 which shines through a transparent or translucent dial 73 or a hole 75 therein thus indicates whether the switch is on or off. In a modification described, a fixed pointer co-operates with a dial which rotates with the handle. Specification 521,556 is referred to.