GB439242A - Improvements in, or relating to, release mechanism for electrical switchgear - Google Patents

Abstract

439,242. Automatic circuit-breakers. SCHIELE & BRUCHSALER-INDUSTRIEWERKE AKT.-GES., Baden-Baden, Germany, and CRABTREE & CO., Ltd., J. A., Lincoln Works, Walsall, Staffordshire. May 28, 1934, No. 15776. Convention date, May 26, 1933. [Class 38 (v)] Springs, arrangements of ; cases.-A compensated release system for motor-protection and other automatic switches comprises a series of thermally-sensitive releases which are coupled to, and adapted to operate a trip member, and a further thermal element not influenced by current-generated heat, but adapted to compensate for ambient temperature, the releases and compensator being mounted in separate chambers in an insulating housing whereby they are thermally and electrically insulated from one another. The thermal releases of a three-phase switch are mounted in compartments C of a casing A which contains a compartment D for the compensator. Each release comprises a ring- shaped bimetal strip E surrounding, and connected at one end to, a heating coil F, each strip acting on a member 8 passing through apertures P in the partitions B and into chamber D. Terminals G, H are connected to the free ends of the coil and strip respectively. The compensating strip 1 is similar to strips E and is mounted freely on a pivot 2 and carries at one end a crank-lever 3, which is urged by a spring 4 against a stop 5. The other end of the strip 1 carries the pivot 7 of a lever 6 having a pin-and-slot connection 6<a>, 9<b> with a releasesetting lever 9, which is mounted fast on pivot 2 and projects through a slot in casing D. Clockwise movement of 9 moves the lower end of 6 nearer to the member 8 and so lowers the tripping point, and 9 is prevented from being moved on the engagement of 6, 8 by passing the pivot 2 through a terminal 11 and placing a flat spring between the latter and a pin passed through the pivot 2. The action of the compensator strip is to produce, due to ambient temperature variations, movements of 6 corresponding to those of member 8. When 6, 8 engage, they cause separation of contacts 13, 14 and, simultaneously, the movement of the nose of 3 clear of catch 17 which is thereby moved by spring 4 to separate contact 16 from a contact 15. The contacts 14, 15 are connected to terminals 19, 20, respectively, and if 19 is connected in circuit with terminal 11 a momentary break of circuit is produced, whereupon 13, 14 re-engage, whereas if 20 is connected in circuit with 11, a permanent break is effected and reclosure must be effected by means of a handle connected to the pivot 18. Alternatively, a toggle or other mechanical trip may be operated by rotation of pivot 18. The Specification as open to inspection under Sect. 91 stated also that resetting of contacts 15, 16 might be effected by automatically tensioning spring 4 by the movement of a switch member, also that the coils F might each attract an armature rotatable on a pivot to operate the member 8 in the tripping direction. This subject-matter does not appear in the Specification as accepted.