Patent GB-287561-A (GB)
Title: Improvements in and relating to electric switch mechanisms
IPC: H02H7/22
Filed: 1928-03-16
Abstract: 287,561. British Thomson-Houston Co., Ltd., (Assignees of Rankin, W. K.). March 25, 1927, [Convention date]. High - potential switches; automatic circuit - breakers etc.; electromagnetic switches. -Relates to electric switch mechanism wherein a plurality of similar switches are adapted for simultaneous operation by individual operating mechanisms, for instance, the switches in each phase of a polyphase switchgear. To minimize or remove the dangers which might arise if all the switches failed to move or close together, means are provided in association with each operating mechanism for automatically rendering the mechanism inoperative. Three such switches are shown, each with its operating mechanism and parallel-motion linkage of conventional type for securing straight line movement of the rod 4. This linkage is operated by a crank 8 from a closing solenoid 10 which rotates the crank 8 and shaft 9 a half-turn, the shaft being moved in the reverse.direction by a spring 28. Each shaft 9 also carries a drum 30, Fig. 2, carrying a double set of contacts, whereof 31 is a long plate and is connected to each of the shorter plates 32 - - 34. The closing solenoids 10 are in series with a main contactor 37 having a closing solenoid 38 under control of a manual switch 41 and thermal cut-out 40. The moving contact of the switch 41 is adapted to connect first the pivoted contact 43 to energize the solenoid 38, and then the contacts 44 in the sealing-in circuit of the contactor 37. The contacts 43 have insulating parts which prevent remaking of the solenoid circuit on the backward movement of the switch. When it is desired to close the switches, the switch 41 is operated to energize the circuit of solenoid 38 through the time delay relay 39, contacts 32, 31 of the drums in series and through contacts 20, 22 of a latching-in device 16. The shafts 9 are thus rotated by the solenoids 10, but if one mechanism should fail to start, its contact 32 would still engage its fixed contact whereas the other drums would have advanced to the next contact 33. The circuit of solenoid 38 would thus be broken and contactor 37 would open and allow the switches to return. This would be indicated by the presence of the green light G and absence of a red light R. Similarly if the mechanisms fail to keep together in closing, the switches would be returned to their original position, and the drums could be provided with more than three contacts for this purpose. As each switch reaches the closed position it is latched-in by the arm 16 dropping over the shoulder of a cam 14, which movement disconnects the contacts 20, 22, and as these are in parallel in the circuit of solenoid 38, the latter will only open when all the switches are latched in. If one mechanism fails to operate its switch to the latched-in position, the contactor 37 will remain closed until switch 41 is released or the time delay relay 39 closes its contacts and energizes the trip coils 23 to trip all the latches 16. The switches can also be tripped open by means of a manual switch 47, or overload relay 48 in parallel with the contacts of the relay 39. The contacts 32 - - 34 may be arranged to overlap so as to allow slight difference in the relative position of the switches, but preferably the solenoid 38 is instead arranged to have a time lag so that the contactor 37 will only open when the permissible difference is exceeded.