GB610485A - Improvements in and relating to electric control devices - Google Patents

Abstract

610,485. Interrupters. BRITISH THOMSONHOUSTON CO., Ltd. April 8, 1946, No. 10773. Convention date, April 12, 1945. [Class 38 (v)] An interrupter for controlling the relative " on " and " off " periods of a heating circuit comprises a fixed contact 16 engaged by a contact 19 on a pivoted arm 20, which is periodically depressed as a cam 29 actuates an arm 26, co-pivoted with the arm 20 on a shaft 23, and a wedge 37 transmits motion between the arms 20, 26, which are biassed in a clockwise direction by springs 25, 28. To vary the ratio of " on " and " off periods, the wedge 37 is mounted on the outer end of a bimetal spiral 38 and is movable between stops 46, 47 longitudinally with respect to the arms 20, 26 in response to ambient temperature changes or by manual adjustment of a knob 45 pivoted at 42 and driving the inner end of the spiral 38 through gearing 43, 44. An electric motor 31 drives the cam 29 at a constant speed of about 1 r.p.m. and the cam has a depression 36 which releases the wedge 37 once each cycle so that it may take up a new position. The device is mounted on a base-plate 5 within an insulating casing 6 which also houses a three-position push-button switch 51 with an " off " and two " on " positions, in one of which an indicator lamp 57 in the knob 45 is energized through a resistance during " on " periods of the contacts 16, 19, Fig. 6 (not shown). A grid 11 and apertures 50 ventilate the casing to ensure correct temperature of the spiral 38.