GB796111A - Improvements in or relating to mechanicallyoperated electrical switch devices - Google Patents

Abstract

796,111. Retractive switches; snap-action switches. SQUARE D CO. Feb. 7, 1956 [Feb. 10, 1955], No. 3725/56. Class 38 (5). A mechanically-operated switch has an operating member pivoted within its casing, a spring operatively interposed between the operating member and the movable contacts, a cam pivoted on the casing and movable in either direction to engage one or other of two lobes on the cam with the operating member, and a plate member having at least one pair of opposed recesses for engagement with fixed posts, the disposition of the plate member determining the initial position of the movable contacts. As shown applied to a limit switch, the movable contact member 24 comprises an insulating piece 28 carrying bridging contacts 34, 36 and a bracket 32 which is attached to a bush 41 mounted on a stud 26. A spring 42 surrounds the bush 41 and its ends 44 extend on opposite sides of the bracket 32 and of a roller 52 carried by an operating lever 46 pivoted at 48. The lever 46 also has a roller 50 engaged by the ends 69, 70 of a return spring 39. surrounding a part of a plate 57. The bracket 32 has lugs 47, 49 engageable by latches 60, 64 pivoted at 62, 66 so that tilting of lever 46 in either direction causes stressing of spring 42 by roller 52 until one or other latch is released by the end of the lever 46, the contacts thereupon moving with a snap action to engage fixed contacts 12 or 14. The latches are each formed with a one-step surface 63 or 67 and a two-step surface 61 or 65, so that the latches can be interchanged to vary the switch characteristics. The latches may also be omitted altogether so that the switch acts without quick-action; the return spring 39 may also be omitted. The plate 57 has notched edges so that it may be placed in any one of three positions with opposite notches engaging pivots 62, 66 so as to hold or bias the contacts in any one of three positions. The lever 46 in one form has two rollers 54, 56 engageable by a cam 25 operable by external arm 23 engageable by a part of a machine, so that the lever is movable in opposite directions by the cam. In a modification, Fig. 6, the roller 52 is omitted and a larger roller 72 engages a cam 25M so that the lever is tiltable in one direction only regardless of the direction of movement of the cam; in this modification also, the plate 57M has only one position. The cam 25 or 25M is carried by a spindle 27 surrounded by a return spring 29 having ends 31, 33 on either side of a part 73 of the cam and engageable with shoulders 35, 37 on the casing 2.