GB878359A - Control system - Google Patents

Abstract

878,359. Thermal switches. CONTROLS CO. OF AMERICA. Jan. 21, 1960 [July 20, 1959], No. 2181/60. Class 38 (5). [Also in Groups XI and XIII] A thermal switch comprises a blade 50 having a barrel spring 64 located between the free end of a flexible tongue 62 on the blade and a contact bearing end of the blade. A pin 58 is attached to the flexible tongue 62 and is biased by a spring 60 into contact at its lower end with an actuating arm 44 attached to a stainless-steel thermal strip 40 attached at its other end to a shield extending from the side of a housing 46 containing the switch. The thermal strip 40 is heated by the flame of a gas burner and expands to move the actuating arm 44 downwards. The tongue 62 is thus moved over-centre, out of contact with a lower contact 54 and engages an upper contact 56. The lower and upper contacts 54, 56 are mounted on leaf springs and the blade momentarily engages both contacts in transferring from one to the other. In a modification, Figs. 9, 11, a switch blade 70 is secured at one end to a bracket 73 and flexed upward slightly by a contact post 77 forming therewith a normally closed switch 32. A bimetal arm 72 is pivoted on a bracket 82 and is held thereon by a spring 79. One end of the bimetal arm is biased by a spring 83 to engage an adjusting screw and the other end has a contact 75 adapted to engage a contact 76 on the switch blade 70. An electric heater 74 is wrapped on and insulated from the bi-metal arm and is energized through the normally closed switch 32. When the bi-metal arm warps it first closes the contacts 75, 76 and later opens the switch 32 to de-energize the heater 74. It then cools and again energizes the heater 74.