Patent GB-408983-A (GB)
Title: Improvements in or relating to electric switch mechanism with automatic tripping action
IPC: H01H83/12
Filed: 1932-10-18
Abstract: 408,983. Automatic circuit-breakers ; actuating controllers. WEST & CO., Ltd., A., and PAVITT, F. J., Lewes Road, Brighton. Oct. 18, 1932, No. 29119. [Classes 38 (iii) and 38 (v).] A three-position switch, particularly for use as a motor starter having 'off,' 'start,' and run positions, has a loose handle connection between the operating member and the contact mechanism so as to open an overload or no voltage independently of the position of the operating handle. The movable contact mechanism is biassed to a central off position and is movable in one direction to a starting position and in the opposite direction to the running position. Fig. 3 shows the mechanism connecting the operating handle to the contact mechanism in the neutral off position. A lug 12 on the operating handle and a lug 13 on the contact mechanism are situated in a slot formed between the ends of two levers 7, 8 pivoted at the common axis 1 of the contact spindle and actuating spindle. The levers 7, 8 are connected by toggle links 9, 10 to a radial link 15 pivoted to a trip lever 16 pivoted to a fixed frame at 17. When the lever 16 is held as in Fig. 3 so that the pivotal point of levers 15, 16 coincides with the common axis 1, the levers 7, 8 are constrained to rotate together and so the lug 12 on the operating member drives the lug 13 on the contact mechanism. The lever 16 is normally retained by a catch 20 on a lever 26 pivoted at 27. A gravity controlled sequence catch 22 is pivoted at 17 and has a projection 24 which in the off position is beneath a pin 23 carried by the actuating mechanism. Thus from the off position shown in Fig. 3 the switch must first be rotated clockwise onto the start position shown in Fig. 4, the sequence catch being displaced by the pin 23. The switch is not retained in this position and if released would return to the off position. To pass from the start position to the run position the switch is turned anticlockwise from the position of Fig. 4 very rapidly before the catch 22 has time to fall into the position shown in Fig. 7. The catch 22 then falls and engages above the pin 23 to hold the switch in the run position. On the occurrence of overload or no volt conditions the latch 20 is depressed thus freeing the lever 16 and collapsing the toggle 9, 10 allowing the levers 7, 8 to separate. In this case (Fig. 8) the lug 13 on the contact member returns to the off position although the lug 12 on the operating member is held in the run position. The latch can also be tripped by a handle 40 operating a pivoted U-shaped member 38 engaging a pin 41 on the catch 20. When the lever 16 is released it strikes a pin 25 on the sequence catch to release the pin 23 on the operating member. The no-volt release mechanism is shown in Fig. 6 and comprises an armature 32 connected to a rod 28 having a projection 29 engaging under a part 30 of the catch lever 26. When no-volt conditions occur the armature is released and lifts the rod to trip the catch 20 free of the lever 16. A lever 35 is connected by a spring 33 to the rod 28. In the off position a projection on the lever 35 lies in the low part 37 of a cam on the contact spindle and the rod 28 is lowered enabling the catch 20 to be set. When the switch is turned the lever 35 is raised by the cam but just before this the no-volt coil is energized and so the rod 28 is not raised when the spring 33 is tensioned. The overload release is in the form of a bimetallic strip which on overload releases a spring urged member to tilt the catch lever 26.