GB1267265A - - Google Patents

Abstract

1,267,265. Mechanical relay and follow-up devices; temperature-responsive actuating elements. LANDIS & GYR A.G. Jan.23, 1970 [Jan.31, 1969], No.3338/70. Headings G1D and G1J. A mechanical follow-up device or thermal actuator comprises closed vessels 1, 2 communicating by way of a tube 3, and a source of heat 9 ensuring that the vessel 2 contains only vapour and the vessel 1 only liquid, the arrangement being such that an input changes the mass of liquid in the first vessel whereby the pressure in the second vessel changes and causes movement of an output plunger 8. A small force can be applied by an electromagnet, a motor or a pressure senser to reduce the volume of a bellows 1, Fig. 1, and inject liquid through the narrow tube 3 of poor thermal conductance into bellows 2 where its evaporation raises the vapour pressure moves the plunger 8 against the force of a spring 7, the additional energy being derived from the heat supplied by an electrical resistor 9. The tube 3 acts as a damper preventing rapid injection and thermally insulating material is used for supports 5 and jacket 4 for the vessel 2. Overloading is prevented by a safety device comprising a sleeve 10 spring 11 and plunger 12 limiting the pressure in the bellows system and the force exerted by the plunger 8. In a modification, Fig. 2, the plunger 8 can be actuated by a change of temperature sensed by a senser 13, a rise of temperature injecting liquid into bellows 2 formed of plate springs welded together. The bellows 1 act as a setting control, if dispensed with an alternative safety device is desirable. The working fluid may be (Registered Trade Mark) "Freon".