ES279992A1 - Re-settable switch device - Google Patents

Abstract

A limit switch operated by a monitor arm 11 has to be reset manually by a push-button 27 but resetting is prevented until the arm 11 is restored to its non-operated position. The arm 11 is secured to a shaft 9 carrying a seal ring 13 and a cam disc 10 which has a recess 10a normally accommodating one end of a rod 25. Rod 25 is slidable in fixed cross-members 20 and 23 but is stable only in its two end positions due to two leaf springs 26 arranged as an overcentre toggle mechanism as shown. The other end of rod 25 engages a push button 27 moulded in rubber-like material with a flexible skirt sealingly fitted into an aperture in the switch casing. When arm 11 is operated by the movable member to be monitored recess 10a cams the rod 25 sufficiently to make it snap to its other stable position wherein it forces the button 27 to stand proud of the casing (Fig. 3b, not shown). The disc 10 then prevents the rod 25 being moved back over dead-centre until lever 11 is returned to bring recess 10a in line with the rod, whereupon manual pressure on button 27 will make the rod snap back again. Switch units 30, such as those described in Specification 872,030, are provided and have movable contact strips 33 carried by spring-loaded insulator rods 32 which are engaged by cross-members 28 and 29 on the rod 25 such that the movement thereof causes contacts 33 to be snapped into and out of engagement with fixed contacts (not shown). Arc blow-out means are preferably provided as described in Specification 853,162. Instead of cross-members 28 and 29 the rod 25 may be provided with fingers engaging with lost motion in elongated slots in the insulator rods 32.