GB575945A - Improvements in controls for electric heating appliances - Google Patents

Abstract

575,945. Control systems for consumption apparatus. WOOD, B. I. Feb. 16, 1944, No. 2921. [Class 38 (iv)] [Also in Group XXXVII] In a control system for an electric heater, a switch is provided which has sparking contacts 1 which open immediately before the other contacts 6, 7, as the knob 22 is moved from one position to the next to effect different circuit connections of the resistances R1, R2 ; the contacts 1 are also adapted to be continuously interrupted to provide a continuously adjustable " simmering " control. In the form shown, the knob has off, high, medium, low and simmer positions and the switches 6, 7 and 1 are operated respectively by cams 4, 5 and 3 on the same shaft 13. For the low, medium and high positions the operating plunger 2 of the switch rests in a notch of a wide portion of 'the cam 3 so that movement away from each of these positions causes the plunger to move to the right and open the switch 1. The " simmer " positions of the knob correspond to a considerable angle of the cam wherein its width varies gradually and in any of these positions the switch 1 is caused to " interrupt " periodically, the relative duration of " on " to " off " depending on the setting. This interruption may be effected by a bimetallic strip 9 and heating coil 10 which press the switch 1 bodily to the left about an axis 12 till the cam 3 is engaged by the plunger 2 and the switch 1 is opened, breaking the circuit both of the heaters R1, R2 and of the heating coil 10. Compensation for variation of ambient temperature is provided by a bimetal strip 8. Alternatively, interruption may be effected by an electromagnet or motor.