GB669642A - Improvements in or relating to electric current switches with magnetically controlled contacts - Google Patents

Abstract

669,642. Thermal switches. HOLLISTER, F. L. Nov. 21, 1949. [Nov. 20, 1948] No. 30211/48. Class 38 (v). In thermal or other switches with magnetically controlled contacts, one of which is resiliently mounted so as to be movable towards or away from the other, the one contact carries a permanent bar magnet of highly magnetic alloy arranged with its axis parallel to the direction of relative movement and adapted to co-operate with an armature carried by the other contact. In the form shown, the magnet 20 is carried by a fixed member 19 on which is mounted a spring 22 carrying a square iron frame 25 surrounding the magnet and carrying the movable contact 26 which engages the fixed contact 27. The upper and lower sides of the square 25 constitute armatures for the two poles of the magnet and in all positions the lower gap between armature and magnet is less than the upper gap so that the resultant magnetic force on the contact 26 is always upwards. The switch is opened by rise of temperature causing the tube 37 to expand relatively to the rod 35 so that a screw 34 carried. by the rod presses down a lever 31 bearing on the spring 22 which flexes till the contacts suddenly separate. The tube and rod may be replaced by a Bourdon tube or diaphragm and the magnet and armatures may take other forms, Figs. 4-7' (not shown). Reference has been directed by the Comptroller to Specification 625,492.