Patent GB-222631-A (GB)
Title: Improvements in and relating to electric switches
IPC: H01H3/30
Filed: 1923-08-23
Abstract: 222,631. British Thomson-Houston Co., Ltd., (General Electric Co.). Aug. 23, 1923. Electrically-tripped switches; electric-motor actuation; interlocking; latching and unlatching; indicators; sparking, preventing. - To reduce burning of the contacts under conditions such as when the switch is opened immediately after being closed or vice versa, there are provided two separate sets of contacts connected in series, one for opening and one for closing the circuit, together with mechanism for so operating them that, when both switches are locked in closed position, the opening of the closing switch is effected only by the opening movement of the spring switch, the mechanism being also arranged to prevent improper operating sequence when closing. As shown in Fig. 1, the main circuit L is controlled by an opening switch A and a closing switch B in series, their functions being to effect respectively the initial opening and the final closing movement. Switch A comprises a bar 1 supported on a rod 4 from a lever 5, which is pivoted to an abutment 6, and is opened by gravity when the toggle 7 is tripped. Switch B comprises a bar 18 and a rod 21 having a rectangular lower end and a cylindrical upper end on which slides a block 23 and which carries a spring 24 and a head 22. The block 23 is connected by a toggle 25 to an abutment 26 and the head 22 is connected to the same abutment by a toggle 27, 28, while the head 22 and rod 21 are held in lowered position by a toggle 33 and abutment 34. Fig. 2 shows a development of the switch-closing contact-drum 50 which carries contacts 57 - - 59 adapted to bridge springs 51 - - 56 in pairs. The normal position of the drum is shown in dot-anddash lines and then the contacts 57, 58 bridge respectively the springs 51, 52 and 53, 54, while the springs 55, 56 are not bridged until after a slight movement of the drum, when they are bridged by contact 59 during almost an entire revolution of the drum. In operation, and assuming the parts to be as shown in Fig. 1, to open the switches the hand switch 49 is thrown down to energize the solenoid 12, or, in the event of an overload in the circuit L, the current transformer 69 will energize solenoid 68 to close the circuit of the solenoid 12; the solenoid 12 attracts its core 11 and rotates a shaft 10 clockwise to break the toggle 7 and open the switch A. Owing to lost, motion between a lever 31 and link 32, the toggle 27, 28 is not at first affected, but after the lost motion is taken up the toggle is broken and the bar 18 begins its opening movement, the pin 30 afterwards acting on the link 29 to break the toggle 25 and complete the movement. The toggle 33 straightens out, and the descent of the block 23 rotates a, lever 37 about its pivot on abutment 38 to move the switch arm 63 away from contacts 64 to engage those 65, thereby putting out an indicating lamp 61 and lighting another 60 to show that switches A, B are open. To close the switches the hand switch 48 is thrown up to close a circuit from the operating bus-bars through contacts 53, 58, 54 to the motor 44 and solenoid 46, which latter attracts a lever and throws in the clutch 43 so that the motor 44 drives the shaft 16. Just before the circuit afore-described through contact 58 is broken by rotation of drum 50, the springs 55, 56 become bridged so that the switch 48 may be opened without disconnecting the motor 44 and solenoid 46, this disconnection only being made after a complete rotation of the drum. Clockwise rotation of shaft 16 causes cams 15, 40 to engage pins 14, 39 and raise the levers 5, 37 so that the switch A is closed and held by toggle 7 and the block 23 is raised and held by toggle 25. This constitutes a setting action as the spring 24 is compressed, and the toggle 33 still holds the bar 18 in its lowest position until, at the proper time, the operator throws the switch 49 upward to close a circuit through contacts 51, 52, 57 and solenoid 36. Thus the toggle 33 is tripped, the spring 24 lifts the bar 18 to close the switch B, which is held by the toggle 27, 28, and the circuit of lamp 61 is closed by the return movement of lever 63 thus indicating that the main circuit is closed. A third indicating lamp 62 burns while the contacts 53, 54 are bridged and shows whether the drum is in normal position. In the modification shown in Fig. 3 the switches are shown in the open position and are closed electromagnetically and held by toggles acting on abutments 76, 97. To close the switches A, B from the open position shown the hand switch 107 is moved on to contact 108 to energize the solenoid 79 from the generator G through contacts 101. The solenoid lifts the rod 75 and bar 1 which is held by toggle 85. The switch 107 is then moved to contact 109 to energize the solenoid 94 from generator G through contacts 84, which were closed by the closing movement of the bar 1. The, solenoid 94 lifts the rod 91 and bar 18, which is held by the toggle 96 and simultaneously the contact 100 disconnects contacts 101. The switches A, B may be opened either by means of a handswitch 109' bridging contacts 110 or by an overload coil 113 in the main circuit lifting a contact 111 to bridge contacts 114. In either case the solenoid 88 is energized by generator G and trips the toggle 85 opening the switch A, and by thus bridging contacts 90 closes the circuit of the solenoid 104 through contacts 106, which were bridged by the closing movement of the bar 18. The toggle 96 is thus tripped and the switch B opens.