GB1384586A - Isolating switch construction and mechanism therefor - Google Patents

Abstract

1384586 Isolating switch WESTINGHOUSE ELECTRIC CORP 17 April 1972 [28 April 1971] 17615/72 Heading H1N During closing movement of the operating handle 9 of an isolating switch a toggle, formed by a contact carrying structure 35 pivotally connected at 66 to a cross-bar structure 68, is rotated anticlockwise about a fixed pivot 69 until a pad 86 on the contact carrying structure 35 co-operates with a fixed cam surface 88 and causes the toggle to straighten against the bias of a tension spring 70 so that movable contacts 36 carried by the structure 35 move upwards to engage fixed contacts 50. In the closed position the toggle structures 35, 68 are overcentre. On opening movement of the handle 9, the toggle joint 66 will initially move overcentre prior to contact separation. A spring biased pawl roller 98 co-operates with a cam plate 74 bolted to cross-bar structure 68 so that in the closed position of the contacts 36, 50 it biases the contacts closed, in the open position it biases the contacts open and after collapse of the toggle during opening it assists and may complete the movement of the toggle to the fully open position. A door interlock mechanism (Figs. 26-31 and 33-36, not shown) is provided for preventing closing of the isolating switch when the door of the cabinet in which it is mounted is open and preventing opening of the door when the switch is closed. Connected in series with the isolating switch is an electromagnetic contactor (not shown). An interlock arm 102 movable between upper and lower positions co-operates with the cam plate 74. The cam plate 74 prevents movement of the interlock arm 102 from its lower position to its upper position, which corresponds to the contactor closed position, during movement of the toggle 35, 38 between the contact closed and contact open positions. The cam plate 74 is itself locked against movement from the contact closed position by the interlock arm 102 when the arm 102 is in its' raised position and the contactor is closed. Thus the interlock prevents opening and closing of the isolating switch under load. An interlock switch 60 in the control circuit of the contactor is closed during closing movement of the isolator to prepare the control circuit for energization. Closure of a manual switch completes the control circuit to energize the contactor. On opening of the isolating switch, the interlock switch 60 is opened prior to separation of the isolator contacts 36, 50 so that the contactor is opened before the isolator. Overload protective relays and fuses are provided in each line of the isolator.