Patent GB-290715-A (GB)
Title: Improvements relating to electric switch-gear
IPC: H02B11/24
Filed: 1927-02-16
Abstract: 290,715. British Thomson-Houston Co., Ltd., Heath, H. C., and Trencham, H. Feb. 16, 1927. Sliding switch-carriage arrangements. - Polyphase draw-out type switchgear is provided with a trigger which, during the movement of the movable part towards the fixed part, is automatically moved from one position to a second position, but only if none of the plugging members is missing from the selected set of sockets on the movable part. The bus-bar chambers 12, 13 and feeder chamber 14 (which may contain the current and/or potential transformer) are provided with sets of sockets 22 - - 24 of which 22, 23 are selectively adapted to engage by means of removable plugging members (not shown) sets of sockets 20, 21 connected in parallel with one set of poles of the circuit-breaker 18 on the movablepart 17. The sockets 22 - - 24 are closed by pivoted shutters 29 - - 31 interconnected by a link 35 and connected by a further link 36 with a lever 37 which is pivoted at 38 to the fixed part 11. When the movable part 17 is withdrawn, a roller on the lever 37 enters an incline 42 on the part 17 so that the shutters drop down in front of their respective sockets, by which time the plugging members are withdrawn therefrom. A layshaft 47 is journaled on each screen and carries a trigger 49 outwardly biassed by a spring. Associated with each screen is a cam 51 - - 53 rigidly mounted on the shaft 47, catches 54 on pivoted trip levers 57 - - 59 being urged by springs so as normally to engage the respective cams. With this arrangement, it is necessary for all the catches 54 of one set of sockets to be tripped before the shaft 47 can be rotated to move the trigger 49 to its set position, and this condition can only be fulfilled if all the plugging members have been correctly inserted by the operator when the movable part is in the withdrawn position. The tripping action takes place when the tips of the plugging members engage the trip levers 57 - - 59 as the latter are being raised with the shutters during the act of moving the part 17 into the engaged position A trigger 49 is provided for each set of sockets 22, 23 (Fig. 3), and, when set, is adapted to engage, as the shutter nears the end of its travel, the appropriate one of two relay devices 62, 62<1> which may operate a blocking mechanism or an indicating mechanism or both (Fig. 7). The blocking device comprises a bolt 70 which is moved by a solenoid 66 out of the way of a stop 71 on the part 17 when either relay 62, 62<1> closes its contacts. Thus if the plugging members are properly set, the device 62 or 62<1> will allow the( part 17 to be moved into complete engagement, and an indicator 82 may be arranged in circuit to indicate the number of the bus-bar engaged. An auxiliary switch 81 finally cuts out the blocking or indicating device. In a modification (Fig. 8, not shown) the device 62 or 62<1> may be arranged to close the circuit cf an " all clear " signal and open that of a " danger " signal, in the event of correct coupling, but in the event of incorrect coupling, the latter circuit will not be opened by the device 62 or 62<1> but wilt be finally closed bv a switch in series with that controlled by device 62 or 62<1>, that switch being closed by the movement of the part 17. A stop 78 engages a plate 80 to rock the trigger into position ready for the next operation when the shutter is next lowered. Specification 209,527 is referred to in the Provisional Specification.