GB631621A - Improvements in electrical snap-action switch devices - Google Patents

Abstract

631,621. Snap-action switches; thermal switches. KERCHER, A. J. July 8, 947, No. 18021. Convention date, July 29, 1940. [Class 38(v)] A snap-acting switch has a spring blade 11 cut intermediate its fixed and moving ends 11a, 11c, to form a spring tongue 12 which engages a fixed abutment 13 so as to place the spring 11 in tension. Adjacent the fixed end 11a the spring 11 has resinlient portion in the form of a loop 11b. The moving contacts 27 are fixed on an insulating strip 29, which has a stud 31 with a groove 32 engaged by a slot in the free end 11c of the spring blade 11 so as to form a lost motion connection. Each moving contact 27 cooperates with a fixed contact 26 and when the switch is thermally operated, the contacts 26, 27 are normally held closed by a magnet 36 which co-operates with an armature 37 carried by the strip 29. In the switch shown, the expansion of a tube 38 retracts a rod 39 to exert pressure on the spring blade 11, which at the required temperature snaps over the dead centre position to open contacts 26, 27. The operating temperature may be adjusted by turning a member 42 which engages a bushing 44 attached to the spring 11, and the initial tension of the spring is adjusted during the assembly of the switch by turning an eccentric bushing 16, engaging a hole in the end 11a of the spring, before this end is clamped by a stud 18. Each moving contact 27 is connected to a terminal 23 by a conductor 34 of woven or braided wire ribbon, one end of which is soldered between the contact 27 and a mounting rivet 48. Figs. 7, 8, (not shown), illustrate a thermal switching arrangement in which two snap-action switch units are mounted one above the other and operated by a single bellows. Sequential operation of the switches may be obtained by adjusting, as by a member 42, the top spring relative to the lower spring.