GB614717A - Improvements in or relating to thermostatic electric switches and to snap-action mechanism therefor - Google Patents

Abstract

614,717. Thermal switches. THOMPSON & CO. (SUNBURY), Ltd., R. E., and ANDREWS, J. B. July 22, 1946; No. 21795. [Class 38 (v)] A thermal switch of the type that is actuated by the differential expansion of a rod and tube has a snap-action mechanism in which a resilient blade 4 has one end clamped to the rod 3 and its other end riveted to one end of a slotted switch arm 11. The other end of the switch arm carries an armature 19 which cooperates with a magnet 16, and a contact 13 which co-operates with a fixed contact 14 on an adjusting screw 18 threaded through a clamping plate 15, 15a for the magnet 16. The resilient blade has a bush 26 through which a stud 27 is screwed so that its end bears on an insulating stop 28 and causes the bending of the resilient blade when subject to the pull of the rod 3. When the required temperature is reached the tendency of the blade, in bending, to tilt the switch arm is sufficient to overcome the force exerted by the magnet 16 on the armature 19 and the contacts are opened with a snap action, the movement of the switch arm being limited by a stop 20 screwed into an arm 7 attached to the rod 3. The insulating stop 28 is mounted on a frame 30 which may be moved up or down within an outer frame 31, by means of a screw 35 to permit adjustment of the switch over a range of operating temperatures. Other methods of adjustment, in which spring loaded stops are used to avoid any over-stressing of the switch mechanism, are described in the Specification.