GB809867A - Improvements in or relating to time controlled electric switches - Google Patents

Abstract

809,867. Time switches; cam-operated switches. SMITH & SONS (ENGLAND), Ltd., S. June 20, 1957 [July 11, 1956], No. 21501/56. Class 38 (5). A time switch, which is operated by a periodically acting time-control mechanism, incorporates an overriding hand-control member which is movable from an inoperative position in either of two directions so as to open or close the switch and which is returned to the inoperative position by the time control mechanism. As shown, a disc 10, which is rotated once every 24 hours by a synchronous motor, carries a pair of tappets 11 which engage a star wheel 12 fixed to one end of a rotatable sleeve 13 carrying at its other end a cam 14 having pairs of lobes 15. Contact springs 16, 17 carrying contacts 18, 19 bear on the cam lobes so that the first anticlockwise movement of the star wheel 12 causes the spring 16 to drop off its corresponding lobe 15 and thus open the contacts and the second anticlockwise movement of the star wheel causes the spring 17 to drop off its lobe and reclose the contacts. The overriding hand control mechanism comprises a rod 20 which is rotatable in the sleeve 13 and to which is fixed a locking plate 26 at one end and a cam 21 having two lobes 22, 23 at the other end. In the inoperative position shown, a projection 36 on a spring-biased latch 32, pivoted at 33, abuts the curved periphery of the locking plate 26 and a pin 35 carried by the latch is consequently held clear of the teeth of the star wheel 12. To open the contacts 18, 19 when they are in the closed position at shown, the locking plate 26 is moved clockwise by a knob (not shown) on a setting plate 40, through a lost-motion connection 31, 41, until the projection 36 on the latch engages in a notch 28 in the locking plate so that the pin 35 on the latch moves into the path of the teeth of the star wheel 12. Movement of the locking plate 26 also rotates the cam 21 so that the lobe 22 engages the tail-piece 24 on the contact spring 17 and opens the contacts. Subsequent anti-clockwise movement of the star wheel 12 by a tappet 11 causes a tooth of the star wheel to move the pin 35 outwards thus unlatching the locking plate 26 and allowing the hand control mechanism to be returned to the inoperative position by a spring 38 engaging a flat 39 on the rod 20. To close the contacts if they are open, the locking plate 26 is moved anti-clockwise by the knob until the projection 36 drops into the notch 29. Movement of the locking plate rotates the cam 21 until the lobe 23 engages the tail-piece 25 on the spring 16, thus closing the contacts. The hand control mechanism is returned to the inoperative position by the subsequent movement of the star wheel as described above. The hand control mechanism can also be returned to its inoperative position by manual rotation of the knob which causes a projection 42 on the setting plate 40 to move the pin 35 outwards.