GB620962A - Improvements in multipole electric switches - Google Patents

Abstract

620,962. Snap-action switches. CRABTREE & CO., Ltd., J, A., and HILL, W. E. Feb. 5, 1947. No. 3380. [Class 38(v)] A multipole switch comprises a number of similar switch units each operated by a cam, the cams being mounted on a hand actuated spindle which has a snap-action arrangement. Each switch unit consists of an insulating 'box c having two fixed strip contacts h, h' the under-surfaces of which are engaged by contacts o on a contact strip p, which is pressed upwardly by helical springs r, r' of unequal strength. The contact boxes c are spigoted in and secured to a bracket a having upturned ends a<SP>1</SP>, a<SP>2</SP>, which support a spindle b on which is a moulded insulating sleeve u having cam formations u<SP>1</SP>. When the spindle is turned each cam u<SP>1</SP> presses on a strip p displacing one end of it against the weaker spring r'. If the contacts at this end have become welded, the other end of the strip p is displaced against the stronger spring r to open the contacts at that end. The snap action is provided by a two-lobed cam v, Fig. 5, on which a spring urged roller y<SP>1</SP> bears ; the contacts being closed rapidly due to the impetus obtained as the roller runs down the steeper side of one lobe. A stop x<SP>1</SP> co-operating with this cam v limits the rotation of the spindle. When this switch is used as an isolating switch in conjunction with a motor starting contactor, one of the cams u' may be forwardly disposed so as to open the contactor coil circuit before the other isolating switch contacts open.