Abstract: A pressostat comprises an operating pressure chamber (4) which is limited by its housing (1) and by an operating membrane (5) or the like including a pressure surface for an output adjustment member (3), at least one spring counteracting the pressure (P) in the operating pressure chamber (4), a switch member (2) which responds when a limit pressure value is exceeded in said working pressure chamber (4), and an enclosed protective chamber (6) arranged concentrically to the working pressure chamber (4) limited by the housing (1), the operating membrane (5) and a protective membrane (7) or the like including pressure surface for the output adjustment member (3).

Abstract: A thermostatic switch unit for controlling a freezer or, for example, refrigeration apparatus in automotive air conditioning, includes a switch (1) which is acted upon by a thermostat mechanism responsive to the working temperature of the evaporator so as to maintain this temperature within a normal working range which is presettable by means of a control knob (18) in a conventional manner. By depressing manually a push button (26) mounted centrally in the control knob a spring loaded trip lever (29) is rotated to release a spring loaded lever (35) into engagement with a switch operating plunger (2, 3), closing the associated switch contacts (21) and causing the compressor motor of the apparatus to run until a low temperature, below the preset working range of the equipment, is reached, when the latch mechanism (29, 35) is reset automatically by the temperature sensing bellows (8) acting through the operating lever (4) of the thermostat mechanism.

Abstract: The accumulation of ice on a surface such as an evaporator fin in a refrigerator unit is detected by a mechanical probe which is moved by a bimetal bender element upon periodic timer-controlled energization of a bimetal heater so as to pass over the surfaces of an evaporator fin. If the movement of the probe is obstructed by ice on the evaporator fin surfaces a switch is operated by a bistable mechanism, causing energization of a defrosting heater and switching off the refrigerator compressor motor. If no ice is detected the probe returns to its original reset position without operating the defrost control switch.