GB755927A - Control apparatus for fuel burning appliances - Google Patents

Abstract

755,927. Thermal switches. ROBERTSHAW-FULTON CONTROLS CO. July 15, 1952, No. 17870/52. Class 38(5) [Also in Group XI] A thermal switch actuated by an expansible element 98 connected by capillary tubing to a bulb containing liquid and located to respond to temperature conditions caused by a burner comprises an overcentre snap-action mechanism comprising a main lever 106 having a knife edge 108 seated in bearings in a fixed bracket 112, an H-shaped control lever 118' having knife edges seated in bearings in an adjustable support 122 and a tension spring 114 extending between the free end of the main lever 106 and the cross bar of the H-shaped lever. One of the legs of the H-shaped lever carries a contact bridge 130 co-operating with a pair of contacts 134 in the circuit of a fan; the other leg carries an arm which abuts a fixed member 131 to limit the movement of the snap-action mechanism. As the temperature increases the expansible element tilts the main lever 106 clockwise and when the lower end of the main lever passes the line joining the cross bar of the H-lever and the bearing of the H-lever the spring moves the H- lever anticlockwise with snap action. When the expansible element contracts the main lever is tilted anti-clockwise by the spring and when its lower end crosses the line previously defined the H-lever moves clockwise with snap action. Specifications 650,601 and 755,921 are referred to.