Patent GB-690812-A (GB)
Title: Improvements in electrical switches for heavy currents
IPC: H01H33/00
Filed: 1949-11-29
Abstract: 690,812. Heavy-current switches; switch contacts; actuation of switches; locking switches. BRITISH THOMSON-HOUSTON CO., Ltd., COX, H. E., and DIXON, C. J. E. Feb. 12, 1951 [Nov. 29, 1949], No. 30601/49. Class 38 (v) An isolating switch comprises bridging contactmembers co-operating with the aligned edges of a pair or pairs of stationary contact blades or strips, the bridging members co-operating with the opposite edges of the blades being movable together in opposite directions. The arrangement is primarily for use in heavy-current circuits where the current is carried by multiple blades or strips of copper mounted in spaced relationship, in which case a pair of bridging contact-members is arranged to bridge the isolating gap between each pair of aligned blades, the bridging contacts being moved by common toggle linkage. Switch contacts.-The strips of the or each pair of stationary contact strips 13, 13<SP>1</SP>, Fig. 2 have rounded edges 17 for co-operation with rounded contact faces 18 of the associated bridging contact-member 16, so that point or line contact is obtained between the blades or strips 13, 13<SP>1</SP> and the contacts 16. In a multiple blade arrangement there are two rows of contacts 16 co-operating with opposite edges of the blades, each row being supported in a channel-shaped member 20 secured to pivoted mounting arms 21. Each contact 16 is secured to a carrier plate 22 having forked ends engaging plungers 23, which are surrounded by biasing springs 24, outward movement of the contacts 16 being limited by stops 25. Actuation.-The mounting arms 21 are pivoted at 28 on side members 11 of a supporting structure and the free end of the right-hand arm is to a link 31 pivoted at 32 on a bell-crank lever 29 pivoted at 30 on the free end of the left-hand arm, the link 31 and lever 29 forming a slightly-underset bent toggle which when partially straightened opens the contacts (the arms moving to the chain-line position). The lever 29 is connected through a link 33 with one end of a lever 34 pivoted at 28, the lever 34 being connected by a coupling lever 40 to a crank arm 39 secured to an operating shaft 38. The lever 40 and arm 39 form an overset bent toggle when the switch is closed and when the shaft 38 is turned in an anticlockwise direction, the straightening of the toggle causes the lever 34 to pivot in a clockwise direction to move the link 33 upwards to open the contacts. A telescopic spring member 35 is connected between the lever 34 and a fixed side member 11, the member 35 serving to provide a closing force and to absorb the energy released by the contact biasing springs 24 when the switch is opened. Locking switches.-The shaft 38 is operated by a removable handle 37, which may be removed from the shaft only when the switch is locked in its closed or open position. When the switch is unlocked, as shown, a slidable locking plate 44 engages with a groove in the hub of the hand wheel 37 to retain the handle. When the plate 44 is slid to the left, a pin 45 enters one of two slots 48 in an indicating disc 42 secured to the shaft and prevents operation of the switch. The pin 45 may be padlocked to a locking ear 47. The arrangement shown enables an isolating break to be introduced into a straight run of current conducting plates or strips, the bridging contacts moving in the planes of the major extensions of the strips. The bridging members may engage the blades transversely of their major extension but such an arrangement involves cranking of the stationary strips, Fig. 4 (not shown).