Patent GB-406754-A (GB)
Title: Improvements in or relating to flame-proof electric switches and switchgear
IPC: H01H9/04
Filed: 1932-09-09
Abstract: 406,754. Snap-action switches; electric motor controllers. FAWCETT, H., 12, Woodlands Avenue, Stretford, Manchester, WATKINS, G. S., Kinver, Whitethorn Avenue, Burnage, near Manchester, and ASSOCIATED ELECTRICAL INDUSTRIES, Ltd., Crown House, Aldwych, London. Sept. 9, 1932, No. 25209. [Classes 38 (iii) and 38 (v).] Interlocked switches ; cases ; handles.- Flame-proof switchgear for starting and reversing conveyer motors in mines, comprises a flame-proof box 1 with a removable lid 2, a pair of stub shafts 8, 9, disposed one at each end of the box, a drop-in switch assembly comprising a shaft 3 having means at each end for coupling it to the stub shafts, and two independent drums 20, 21 carrying contacts 5, 7, for forward or reverse movement of the motor, the drums being mounted on a shaft 4 parallel to the shaft 3 and actuated with a snap-action by rotation of either of the stub shafts, one drum being moved to the closed position while the other is simultaneously locked in the open position by rotation of the stub shaft in one direction, while the first-drum is locked in the open position and the second drum moved to the closed position by rotation of the stub shaft in the opposite direction. In the arrangement shown, the coupling members between the shaft 3 and the stub shafts 8, 9 comprise cranks 15, 16, secured to the shaft 3, carrying pins 13, 14 which engage slotted cranks 10, 11 secured to the stub shafts. The handle 38, Fig. 5, which can be secured to either of the stub shafts, is provided with an interlocking device in the form of a catch 41 mounted on a pin 42 carrying a locking plate 43 with three holes, either of which can be engaged by a spring pressed pin 48 slidably mounted in a boss 50 on the handle. The catch 41 co-operates with stops 51, 52 on each end of the box 1, and either prevents rotation of the handle from the off position, or allows it to be rotated in either the forward or reverse direction, according to which of the holes in the plate 43 is engaged by the pin 48. The snap-action mechanism comprises cams 17, 18, respectively secured to the drums 20, 21, and having biassed against their surface rollers 22, 23 carried by rockers 24, 25 pivotally mounted in rocking members 26, 27, which for one direction of movement of the stub shafts are held positively, and in the other direction of movement are caused to rotate about their pivots 28, 29 by means of rollers 30, 31 which engage slots 34, 35 in cam plates 36, 37 integral with the cranks 15, 16 respectively. A plug box 53 for the incoming plug connector 54 and motor cables 55 can be mounted in a flame-proof manner in any one of four positions on the top of the box 1. An interlock pin 57, with a groove 58 near its end, is secured to the plug member 54, and, in any of the four positions of the plug box, is located at the centre thereof when the plug is inserted. A plunger 59 is biassed by a spring 60 on to a cam 61 with a central depression 62. This cam is secured to the shaft 3, in such a manner that when either of the drums 20, 21 is in its "on" position, the plunger 59 is moved upwardly to engage the groove 58, if the plug connector 54 is in its socket, or to obstruct the insertion of the plug connector if it is not in its socket. One of the stub shafts 8, 9 may be dispensed with.