GB1151063A - Thermal Cut-Outs for Electrically Heated Appliances. - Google Patents

Abstract

1,151,063. Thermal switches. BULPITT & SONS Ltd. 6 July, 1966 [6 July, 1965; 23 Nov., 1965], Nos. 28490/65 and 49798/65. Heading H1N. A thermally operative cut-out of the kind comprising a spring-loaded plunger normally anchored to a fixed part by the engagement of a pawl on the plunger with a ratchet secured and prevented from rotation by fusible metal which melts on overheating has a ratchet assembly including two or more ratchets 53 arranged in axial alignment each secured by fusible metal to a fixed part and each engaged by an associated pawl 70 on or coupled to a common plunger 64. In a preferred embodiment two ratchets 53 are joined by and integral with a common shaft 54 which rests in a U-shaped block 55 being retained by a guide pin of plunger 64 about which pin is the compression spring 71 loading the plunger which is made from bent sheet metal with two pawls 70, the end face 67 projecting from socket 75 on heater head housing 13 in which the cutout is mounted so that when the fusible metal is melted, plunger 64 ejects a plug plugged into socket 75, having contact pins 27, 30, breaking the circuit. Fusible metal 59 is run in around shaft 54 in block 55, a slug 63 of fusible metal is melted in an axial hole 61 through the ratchet assembly and a slug of fusible metal 62 is melted in a hole 60 in block 55 radial to shaft 54 to secure the ratchet assembly to block 55 and to the inside of sheet metal part 14 in which the cut-out is mounted and which is secured to part 16 of the heater head housing 13. Part 16 is made from sheet metal with its rim spun over an annular plate to which is secured an insulating block 26 by screws, one screw also securing earthing terminal 30 to the plate, block 26 having an external screw thread 32 on to which a protective sleeve is threaded. Leads from the heater element pass into the bores of contact pins 27. In a modification, Fig. 10 (not shown) the heater head is a hot brass stamping. An alternative ratchet assembly comprises a small rectangular metal block with a ratchet mounted on a trunnion in the opposite largest faces of the block.