Patent GB-1257191-A (GB)
IPC: H01H9/10
Filed: 1968-03-25
Abstract: 1,257,191. Snap-action switches. ENGLISH ELECTRIC CO. Ltd. 21 March, 1969 [25 March, 1968], No. 14251/68. Heading H1N. A switching mechanism for making and breaking contact blades 45, 46 mounted in a movable body 39 with co-operating contacts mounted in a fixed housing comprises an operating member 19, a toggle spring device 17 and an interlock latch 18, operating member 19 actuating toggle spring device 17 which moves movable body 39 to actuate the contacts, interlock latch 18 co-operating with a door 13 on the housing and with operating member 19 to hold the door closed when the contacts are made and to free the door when the contacts are opened and to prevent the contacts being closed when the door is open. As shown, operating member 19 is pivoted at 35 to side plate 1 of the housing, has a bifurcated end 36, a cam surface on offset portion 37 and carries a bracket 20 with which operating handle 21 is engaged. Toggle spring device 17 comprises a quadrant plate 22 pivoted at 23 to plate 1 of the housing, has an upstanding pillar 28 projecting between the bifurcated end 36 of operating member 19, carries a pin 29 which projects through an arcuate slot 16 in side plate 1 and has pivoted to it an arm 24 which is parallel with an arm 25 pivoted at 26 to side plate 1, arms 24, 25 being surrounded by a compression spring 27. Interlock latch 18 comprises a lobe 31 which co-operates with a catch 15 on door 13, is pivoted at 30 to plate 1, has a recess 34 into which projects pin 29 on quadrant 22 and carries a pin 32 against which bears a spring 33 to bias latch 18 clockwise. If, in the position shown in Fig. 3, with door 13 open, handle 21 is moved clockwise to attempt to close the contacts, operating member 19 is moved clockwise and bifurcated end 36 engages pillar 28 on quadrant 22 to move quadrant 22 anti-clockwise and pin 29 on quadrant 22 is moved along arcuate slot 16 but engages the end of recess 34 in latch 18 which prevents further movement of pin 29 and hence of quadrant 22, member 19 and handle 21. If now door 13 is closed, it engages lobe 31 and pivots latch 18 anti-clockwise so that recess 34 is removed from pin 29 so that if handle 21 is moved clockwise there is nothing to impede movement and member 19 and quadrant 22 move so that spring 27 snaps over centre. When door 13 is closed lobe 31 engages catch 15 so that if now an attempt is made to open door 13, pin 32 on latch 18 engages the cam surface on portion 37 of operating member 19 so that latch 18 cannot be moved and door 13 cannot be opened. To open door 13, handle 21 must be moved back to the position shown to open the contacts and move member 19 so that the cam surface on portion 37 of member 19 no longer impedes pin 32 so that latch 18 is free to move back to the position shown under the action of spring 33. Pin 29 on quadrant 22 projects through arcuate slot 16 in side plate 1 into the interior of the housing and engages projections on the side 58, Fig. 4, of moulded insulating contact carrier 39, which has three compartments 40, 41, 42 containing three fuses 44 (only one shown) connected to movable contacts 45, 46 separated by insulating barriers 48. When handle 21 is turned and pin 29 is moved forward, contact carrier 39 is moved forward to engage an insulating block 3, Figs. 1, 2 (not shown) in the housing and movable contacts 45, 46 pass through slots 6, Fig. 1, in block 3 to engage contacts which may be as in Specification 1,257,035, barriers 48 also passing through slots 4, Figs. 1, 2, in block 3. A handle 57 is provided on carrier 39. A manual catch (not shown) may be provided for the door, spring means (not shown) may be provided to urge the -handle into a rest position and provision may be made for locking the .handle in one position, e.g. open.