GB742995A - Improvements relating to automatic defrost control mechanism for refrigerators - Google Patents

Abstract

742.995. Thermal switches. GENERAL ELECTRIC CO. Dec. 19, 1952 [Dec. 19, 1951], No. 32251/52. Class 38(5) [Also in Group XXIX] A refrigerator control having a cycling refrigerating action and automatic defrosting action comprises a pivoted arm 8 for operating a switch or valve 4 for starting or stopping refrigeration and actuated by a thermal element 20 against a spring 22, a pivoted interfering member, e.g. the toggle 36, 37, movable between a position where it acts as a stop for the arm to a position where it frees the arm. means biasing the toggle against a cam 28 which allows the toggle to move between its two positions, and means actuated at a pre-determined abnormally high maximum temperature when the toggle is in its stop position for shifting the toggle in the opposite direction to free the arm. 'The arm has a first part 9 pivoted at 14 and connected by a toggle spring 11 to a second part 10 flexibly supported at 9 by the bracket 16 and carrying a magnetic yoke 7 whereby a magnet 6 carrying the valve moves with snao action. Each time the arm moves upwards under the cycling action of the valve and thermal bellows 20 responsive to evaporator temperature, a pawl 29 on the part 9 engages a gear wheel 31, and progressively rotates the cam 28. A tongue 41 on the toggle rides on the cam which thus keeps a stop 39 out of the path of a member 40 on the part 10. When a cam slot 51 comes opposite the tongue a spring 48 pulls the toggle over its dead centre so that the stop 39 prevents downward movement of the part 10 due to a temperature rise, and thus prevents the opening of the valve and the start of the refrigeration cycle. The temperature thus increases and since the part 9 is held against a stop 58, continued expansion of the bellows pivots an arm 26 about a knifeedge 53 against a spring 55 until the arm 26 contacts an arm 52 of the toggle and snaps the stop out of the way of the part 40, so that after defrosting the normal refrigeration cycle re-commences. The spring-adjusting screw 57 determines the defrosting temperature independently of the spring-adjusting screw 24 determining the refrigerator temperature setting. The toggle may be replaced by a lever or a lever carrying a roller stop. Specification 695,850 is referred to.