GB1199074A - Improvements in Interlock Devices - Google Patents

Abstract

1,199,074. Interlocking switches. WATFORD ELECTRIC CO. Ltd., and W. A. J. SAUNDERS. 22 July, 1968 [31 July, 1967], No. 35126/67. Heading H1N An interlock mechanism to prevent closure of an isolating switch while a contactor is closed comprises a plate 4 pivoted at 7 to a support 10 and carrying a latch arm 1 also pivoted at 7. Plate 4 is urged anticlockwise by a spring 8 while arm 1 is urged clockwise, against a stop 11 on plate 4, by a spring 5. The end of arm 1 extends into an L-shaped slot 12 in a plate 2 which is coupled to the isolating switch to slide on pillars 6 secured to support 10. A rod 3, having a chamfered nose, is moved perpendicularly to the plane of the drawing by operation of the contactor. As shown, the plate 2 is at its right-hand limit corresponding to the closed condition of the isolating switch, and the portion 12a of slot 12 is holding arm 1, and hence plate 4, against the action of spring 8. When the contactor is closed the rod 3 moves freely to project below plate 4 (Figs. 1 and 2, not shown). If the isolating switch is then opened plate 2 moves to the left but rod 3 prevents plate 4 from rotating; hence arm 1 rides up the sloping portion 12a of slot 12 against the action of spring 5 which latches it into the vertical portion of slot 12 (Fig. 1, not shown). The isolating switch cannot then be moved to the closed position until the contactor is opened, withdrawing rod 3 to allow plate 4 to rotate under action of its spring 8 and thus lift arm 1 to unlatch plate 2. If the isolating switch is open (plate 2 to the left) when the contactor closes the nose of rod 3 lifts plate 4 against its spring 8 and moves arm 1 into the latching position so that the isolating switch again cannot be closed until the contactor is first opened. A spring 9 assists movement of plate 2 to the left (switch-open) position. Reference has been directed by the Comptroller to Specifications 1,061,890, 1,069,551 and 1,138,963.