GB935526A - Control apparatus - Google Patents

Abstract

935,526. Thermal switches; fluid actuation of switches. RANCO Inc. Feb. 20, 1962, No. 6517/62. Class 38 (5). A control apparatus comprises co-pivotal first and second flanged levers 24, 30, the flanges of lever 30 stradling those of lever 24, and a spring 27 biasing the levers apart, the first lever 24 being moved against a load 26 by a pressure responsive element 22 and the second 30 moving between upper and lower stops to operate a control device 21. In a refrigerator temperature control apparatus, the pressure element 22 is connected via a capillary tube 22c to either a thermally responsive bulb or directly to the pressure system. Expansion of bellows 22 due to rising temperature lifts lever 24 against the range spring 26; as spring 27 passes through .dead centre lever 30 snaps downwards to close switch contacts 33a, 34a. The temperature range is determined by the tension of spring 26; the differential is determined by the position of the two stops; all of these are adjustable. In a first embodiment (Fig. 1), range spring 26 and the upper stop 31 are preset and the lower stop comprises a cam 32 engaging a flat 30h on the lever 30 and rotatable by a knob attached to spindle 32a. In this case the upper operating temperature is preset while the lower operating temperature is adjustable. In a second embodiment (Fig. 5), both stops 131 and 65 are preset while range spring 126 is adjustable by a cam 132 operating on a third lever 60 to which is attached the lower end of the spring. The control apparatus may be modified to actuate normally open contacts (Fig. 8, not shown) instead of normally closed as shown.