GB741103A - Snap acting thermostat - Google Patents

Abstract

741,103. Thermal switches; snap-action switches. STEVENS MANUFACTURING CO., Inc. April 23, 1953, No. 11241/53. Class 38(5) [Also in Group XXIX] A switch comprises a moving contact mounted on a flexible snap-acting member having tension and compression elements, the compression element being in engagement with two axially-aligned abutments, one of which is adjustable, the movable contact being actuated by a bimetal strip. In one form, Fig. 1, a contact 40 is carried by a trifurcated blade spring 24, the central, compression member 32 of which bears against an adjustable member 23 and a spring abutment 37. A bimetal strip 26 has an insulating button 46 which bears against a downwardly biased spring arm 25 carrying the co-operating contact 41 and having a bent-over end 42 with an insulating stop 45. When the bimetal bendsup on heating, the arm 25 moves the spring 24 upwards also, until the latter snaps over-centre to open the contacts. When the bimetal cools, it bends down again and arm 25 follows it, this movement causing the stop 45 to push the spring 24 over-centre again to reclose the contacts. Movement of member 23 varies the operating temperature. In a modification (Fig. 6, not shown), the abutment 37 is replaced by an insulating stud arranged between the arm 25 and spring 24. In a further modification (Fig. 9, not shown), a further contact-carrying arm is arranged above the spring 24 so that the switch acts as a changeover switch. In a further arrangement, Fig. 10, the adjustable member 23 is replaced by a screw 64 acting on a spring arm 62 and the part 42 of arm 25 is omitted, so that the switch has to be reclosed by depression of a push-button 68.