GB905784A - Electric switch and enclosure therefor - Google Patents

Abstract

905,784. Snap-action switches; switch cases; locking switches; earthing parts of switches. FEDERAL PACIFIC ELECTRIC CO. Feb. 3, 1960 [Feb. 19, 1959], No. 3873/60. Class 38 (5). Electrical switching mechanism is contained within an enclosure having a door retained closed by an internal latch released by the switching mechanism through a yieldable connection so that the switch may be opened although the latch may be jammed. Switch cases.-A switch-box 10, containing two snap-action switches 12, 12<SP>1</SP>, is closed by two doors 16, each of which has an aperture 34 through which projects an operating handle 60 mounted on the switch cover 36. Each door 16 is retained closed by a spring-loaded catch 106 (Fig. 3) pivoted on a wall of the box 10 and co-operating with a fixed member 110 on the door 16. Opening the switch 12 rotates a contact-carrying shaft 50 and hence a camplate 160 to tilt a lever 140, which is held by a spring 152 against shoulders 138, 138<SP>1</SP> on the catch 106. The catch is thus tilted and releases the door 16. Should the catch 106 become fixed in the latched position, the switch may still be opened as the lever 140 will then rise against spring 152 and turn about its end 142 on shoulder 138<SP>1</SP> as a fulcrum. The door 16 may be opened with the switch in the closed position by inserting a screwdriver or like tool T in a slot 166 in the door to release the catch 106. Each door 16 is additionally latched by a spring-biased catch 170 pivoted on a side wall of the box 10 and which may be locked in the closed position by passing a padlock through the aperture 188 (Fig. 2, not shown). When both catches 106 and 170 have been released, a spring-loaded plunger 92 rises to lift the door 16 and interpose a member 94 in the path of a slider 72 provided in each switch handle 60, thus preventing operation of the switch when the door is open. For test purposes, the plunger 92 may be depressed manually to permit operation of the switch. In order that the switch handle 60 may not foul the door 16, in each limiting position a switch-operating member 61 is arranged to function as a stop member by striking the switch casing. In addition, the hub 68 of the handle rotates within a shaped slot in the cover-plate 82 which thus also acts to twist the movement of the handle. Locking switches.-The spring-loaded slider 72, in either the open or closed switch position, can be pushed inwards, a lug 72a then engaging a slot in the cover-plate 82 to lock the switch. The slider 72 is retained in the locking position by one or more padlocks through apertures 74 and slots 70. Earthing parts of switches.-Each handle 60, which is metallic, is well insulated from live parts of the switch, but for maximum safety a brush in the form of a helical spring connects the hub 68 of the handle 60 to the metallic cover-plate 82. A spring 206 (Fig. 1), lying in a groove in the cover-plate, makes connection with the plunger member 92 and hence with the earthed switch-box 10 when the box is closed.