Patent GB-712482-A (GB)
Title: Improvements in and relating to automatic electric circuit breakers
IPC: H01H71/68
Filed: 1950-12-05
Abstract: 712,482. Automatic circuit-breakers; electromagnetic switches; snap-action switches. BRITISH THOMSON-HOUSTON CO., Ltd. Dec. 5, 1950 [Dec. 21, 1949], No. 29754/50. Class 38(5) A trip-free circuit-breaker has the circuit of its closing solenoid 5 controlled by a switch having contacts 15, 16 actuated by the core 25 of a coil 24 which may be energized by closure of a pushbutton 28, or by operation of an automatic switch .arranged to give rapid reclosure. Contact 15 is mounted on a switch arm 17 which is pivoted at 19 and is normally held in the open position shown by a permanent. magnet 20. Movement of the core 25 to the right when attracted causes a pin 37 thereon to move a crank 33, also pivoted at 19, clockwise by means of a pawl 38 pivoted thereon. The crank has a lug 34 and the arm 17 a lug 29, arranged between the ends 30, 31 of a torsion spring 32, so that when the crank 33 is so moved, the spring 32 is stressed until the lug 34 engages and pushes the lug 29 to overcome the force of magnet 20, the arm 17 then being moved rapidly to the " on " position by the spring 32. In order that continued depression of button 28 shall not hold the contacts 15, 16 closed, the core 25 moves further to the right so that the pin 37 rides over the pawl 38, the contacts 15, 16 being held closed by a further permanent magnet 22. When coil 24 is de-energized, the core is pulled to the left by its spring 26 and the pin 37 tilts the pawl 38 against its spring 40 without affecting the crank 33 and arm 17. Closure of contacts 15, 16 energizes the solenoid 5, so that its plunger 6 rises to set the toggle 46, 47. The left-hand end of link 46 is guided by a spring-pressed link 48 and is prevented from upward movement by a spring-urged latch 8, so that the right-hand end of link 47 is moved upwards to cause clockwise movement of a crank 2 to pull down the contact rod 1 against the action of a spring 3, the parts being held in this position, Fig. 3, by a spring-pressed latch 55 which engages beneath the knee 45 of toggle 46, 47. At or near the end of the closing stroke, the knee tilts a lever 58 clockwise about its pivot 59 so as to push a rod 60 downwards, the lower end of the latter having a slot 62 engaging a pin 63 on the crank 33, so that the latter is moved counter-clockwise to open contacts 15, 16 and de-energize solenoid 5. In order to permit earlier opening of the contacts 15, 16 in response to a tripping impulse given during closure of the circuit breaker, the lever 58 has an arm 65 extending down beside the knee 45 so as normally to be unaffected thereby but lying in the path of tripping movement of the knee, i.e. upwards to the left. A tripping impulse applied to a coil 13 causes its armature 12 to move the latch 8 clockwise, thereby permitting upward movement of the roller 50 joining the links 46, 48 to permit counterclockwise movement of the crank 2 under the action of spring 3. The knee 45 thus returns to the Fig. 1 position thereby allowing the arm 65 of lever 58 to move clockwise under the action of a spring 66 so as to lift the rod 60 and free the crank 33 ready for the next reclosure.