GB915301A - Improvements in lever operated electric switches - Google Patents

Abstract

915,301. Snap-action switches; unlatching switches. DOWTY ELECTRICS Ltd. June 1, 1959 [June 5, 1958], No. 17960/58. Class 38 (5). A lever-operated switch has an electromagnetically-releasable latch for locking it in one position but may be released in emergency by twisting the lever about its longitudinal axis. An insulating base 2 carrying four sets of three acts 45, 46, 47, located in four grooves 48, is attached to a cover member 12 by four metal bars 4 having a pair of upper cross-bars 5 and a pair of intermediate cross-bars 6. A metallic bush 7 pivoted on trunnions 11 in bars 5 is operable by a rod 8 extending therethrough and having a flattened knob 17 at its upper end. Spring-loaded balls 15 at the sides of slot 14 in cover 12 give the bush 7 a snap-action. Pins 66 extending from bush 7 engage slots in two levers 63 pivoted at 64 in cross-bars 6 to move a transverse pin 62 coupling the four insulating carriers 51 so that metal contact-strips 49 thereon bridge contacts 45, 47 or 46, 47. The carriers 51 are pressed downwards by spring steel wires 53 engaging small projections 54. A platform 32 is supported from two bars 4 by members 33 and carries an electromagnet 35 having an armature 38 pivoted in platform 32, counterbalanced by weight 41 and urged by spring 42 to the position shown in Fig. 1 wherein it engages a groove 44 around the lower end of rod 8 to lock the lever against pivotal movement until electromagnet 35 is energized. In an emergency, however, the knob 17 may be rotated to turn rod 8 and cause a pin 27 to depress the armature 38 clear of groove 44 and allow the switch to be operated. Spring-loaded balls 29 urge the pin 27 to the desired one of its extreme positions. A spring- loaded plunger inside the part 25 of rod 8 enters a hole in bush 7 (Fig. 4, not shown) when the knob 17 is turned to the emergency position and prevents it being restored. A cylindrical member 19 sliding on rod 8 is spring-loaded to engage in a double-ended keyhole slot 22 in an upper cover 13 and prevent accidental operation of the switch. An interior rubber cover 74 fits around bush 7 to prevent dust and the like entering the switch which is enclosed by a metallic shell 3, and has a lower rubber cover 68 enclosing the connections to the switch contacts.