GB853494A - Improvements in electrothermally actuated relays - Google Patents

Abstract

853,494. Thermal switches. G-V CONTROLS Inc. July 12, 1957, No. 22196/57. Class 38 (5). [Also in Group XIII] A hot-wire relay has a tensioned thermal element 20 made by winding resistance wire 22 over an insulating frame 24 having a window 21 and retaining the ends of the wire in notches 25. Stainless steel staples 28, 30 pass through holes 26 in the frame 24 and clamp mica leaves 32, 34 on each side of the wire. A further staple 36 of nickel ribbon passes round the leaves 32 inside the window 21, Fig. 14. After assembling the element in the switch the sides of the window are removed by cutting the frame along the lines 38. The staple 30 is mounted on a leafspring 40 attached to a support 42 and the staple 28 is mounted on a leaf-spring 44 attached to a bracket 46 secured to the upper end of an arm 54 carrying a spring-biased contact 66 for co-operation with a fixed contact 68. A rigid ambient compensating member 48 is attached to the arm 54, as described in Specification 765,610 and is adjustable by means of a bracket 74 thereon engaging a glass bead 80 on a lever 78 pivoted in a sealed diaphragm 76. A V- spring 72 urges the members 48, 54 apart to apply tension to the element 20 that when the wire 22 is heated it is elongated to allow the arm 54 to pivot about P to open the contacts. Normally open contacts may be provided. Member 48 may compensate for the ambient temperature changes of the element 20 or to vary its characteristic with the ambient temperature.