Patent GB-1309530-A (GB)
Title: Electric switch
IPC: H01H3/30
Filed: 1971-11-18
Abstract: 1309530 Switches held set and freed mechanically; time switches PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 18 Nov 1971 [21 Nov 1970] 53605/71 Heading H1N A switch which may be snapped on and off by the aid of a switch-on spring 17 and switchoff spring 35 respectively, both springs being stressed and locked in the stressed state by a single mechanical operation, has a carriage 5 adapted to reciprocate in a housing 1 with fixed contacts 3, a slide 7 having movable contacts 9 being arranged to reciprocate in said carriage 5, the spring 17 acting between the housing 1 and carriage 5 while spring 35 acts between carriage 5 and slide 7, said springs being unlockable by a trigger mechanism 23 journalled in the housing 1 and movable in at least two consecutive stages in the same direction to unlock the switch-on spring 17 during the first stage so that the carriage 5 and slide 7 together shift relative to the housing 1 to close the contacts and to unlock the switch-off spring 35 during the second stage so that the slide shifts relative to the carriage to open the contacts. As shown, a pawl 33 urged by spring 45 normally locks the slide 7 to the carriage 5, maintaining spring 35 compressed, while a pawl 21 pivoted on carriage 5 engages the arm 29 of trigger 23 under action of a leaf spring 28 to lock the carriage 5 in the housing 1, maintaining spring 17 compressed. Slight anti-clockwise movement of arm 25 of trigger 23 releases pawl 21 and the carriage 5 and slide 7 move to the left under action of spring 17 to engage contacts 9 with fixed contacts 3 (Fig. 2, not shown). Further anti-clockwise movement of arm 25  causes arm 47 of trigger 23 to tilt pawl 33 allow-  ing spring 35 to urge slide 7 to the right, opening contacts 3, 9 (Fig. 3, not shown). Both springs 17 and 35 are cocked by manual pressure on button 19 on an extension 13 of carriage 5, the slide 7 being restrained by abutment of contacts 9 against uprights 49 in housing 1. A light spring 61 allows small movement of button 19 relative to carriage 5 and this enables the pawl 33 to be manually released (by means of pin 59 acting on leg 57) to open the contacts 3, 9 when the switch is in the " on " condition. Interlock of knob 19 and a valve for safeguard of high-vacuum installations is disclosed but not described in detail. To allow cocking of the switch before the trigger 23 has returned to its starting position an additional pawl (51, Figs. 2, 3 and 4, not shown), on the same pivot 20 as pawl 21, is provided and this then engages a recess 55 in the housing 1 until the trigger returns to latch pawl 21. Timing-mechanism.-A member 63 for mov-  ing the trigger 23 may comprise an axially movable gear (Fig. 6) coupled by a gear 81 to a clock accommodated, together with the switch,  in a casing 99 and having hour and minute  hands 101, 105. A nose 73 on gear 63 co-operates with recesses 75, 77 in switch-on and switch-off  discs 69, 71 which are coaxial with gear 63 and may be set by rotation of a knob 91 which is axially movable to engage a pinion 87 with an idler gear 83 or 85 coupled respectively to discs 69, 71. Discs 107, 109 secured to discs 69, 71 provide an indication of the set time interval via window 111 in dial 113. The switch may be arranged such that the additional pawl (51) may be engaged with the extreme end of trigger arm 29 and first movement of the trigger then merely releases pawl (51) to engage recess 55 and the switch is therefore not operated until the trigger has returned to start and is actuated a second time; this arrangement may be used when the timing mechanism operates on a twelve-hour cycle and a switch-on is required at between twelve and twenty-four hours.