Patent GB-775861-A (GB)
Title: Improvements in electrical circuit breakers with automatic reclosing mechanism
Inventor: GIBSON ARTHUR CHARLES
IPC: F16H35/14
Filed: 1954-05-21
Abstract: 775,861. Automatic reclosing circuitbreakers; electromagnetic switches. BRITISH THOMSON-HOUSTON CO., Ltd: Aug. 19, 1955 [May 21, 1954], No. 15017/54.. Class 38(5) An automatic reclosing circuit-breaker in which the contacts are opened on overload by a solenoid a certain number of times and, if the overload still persists, are finally locked open, comprises a head casting 1 supporting an oil tank 2 and a pair of insulating bushings 3 (only one shown) extending through the head 1 having terminal clamps 5 for connection to the line conductors. The circuit between conductors within the bushings is completed through a vertically-moving contact rod 11 co-operating with a fixed contact 12a within an explosion pot 12, and a solenoid 34 operating the moving contact. The mechanism is supported within the tank by a frame comprising four rods- 7...10 (only two shown) depending from the head 1. The solenoid plunger 35 has a link 36 biased upwardly by the reclosing spring 43 and connected to a lever 37 pivoted at 38. A link 41 connected to the lever 37 at 40 is connected at 42 to a toggle link 30 pivoted at 31, the other toggle link 29 being connected to a link 28 connected at 24 to a link 22. A spring 33 stretched between pins 28a, 31 holds the toggle 29, 30 over-centre. The link 22 is connected at 25 to a link 26 mounted on a fixed pivot 27, and connected at 23 to an insulating link 17 connected to the contact 11. A link 18 mounted on a fixed pivot 19 is connected to the link 22 at 24 and ensures the pin 23 has a vertical straight line motion. In order to prevent the toggle 29, 30 collapsing on the other side of its over-centre position to raise the contact 11 until the plunger 35 has almost completed its downward movement, the left-hand end of the link 29 is engaged by the lower end of a latch lever 48 when the toggle is in its straight-line position, the lever 48 being pivoted at 49 and biased by a compression spring 50 against a stop (not shown). The final movement of the plunger moves the end of the link 29 to the right to disengage the latch 48, whereupon the stored energy in the spring 33 lifts the link 28 to raise the link 22 and thus open rapidly contact 11. The contactopening force is augmented by a compression spring 60 in which energy is initially stored and then released by the latch 48. 'The spring 60 is mounted on a rod 57 and its upper end engages the lower edge of a lever 58 pivoted at 59. The rod passes through the lever 58 and carries at its upper end an abutment (not shown) for limiting downward movement of the rod relatively to the lever. The lower end of the spring 60 engages an upwardly facing surface on a member 56 from which the rod 57 extends, a slot 55 in the member 56. co-operating with a pin 51 on the tail 32 of the toggle link 30. The lever 58 has a pin and slot connection 61 with a lever 62 mounted on a fixed pivot 63, a heel part 64 of the lever 62 engaging beneath the pivot 24. Thus upward movement of the tail 32 when the plunger 35 moves down stresses the spring 60 but the spring energy cannot be imparted to the pivot 24 by the heel part 64 until the link 28 is free to move by release of the link 29 from latch 48. In the open condition the left-hand end of the toggle link 29 is above the latch pivot 49 so that on return of the plunger 35 by the spring 43 the link is initially retamed against downward movement but is eventually released causing rapid closure of the contact 11 at the end of the plunger stroke. A dashpot 65 has a vertically-moving piston connected by a link 67 to the pivot 40 whereby the piston moves up and down with the plunger 35. The rate of the upward piston movement is constant but the downward rate is variable by a discharge valve having an operating member 68 pivoted at 69 and moved by a cam member 70 pivoted at 71. The member 70 is controlled by a rack member 72 moved upwardly step-by-step each time the circuit breaker re-closes, the arrangement being such that for the first closure the valve remains fully open and thus the contact 11 opens twice without delay. On the second reclosure the valve is closed and there is a time-delay before the contact 11 is'opened. If the overload still persists on the third reclosure there is a similar time-delay and then the plunger 35 locks the breaker open through mechanism set by the rack 72 when in its uppermost position. The rack 72 is guided at its lower end by a pin 73 extending through a rack slot 74 and is connected at 78 to a link 77 having a pin and slot connection 79 with the cam 70. A clockwork timing device 88 coupled to the rack by a lever 87 ensures a relatively slow downward movement of the rack by gravity, after it has been raised. The rack is lifted by a pawl 80 pivoted at 81 on the lever 37 and having a catch 82 urged by a hairpin spring 84 towards the rack to engage rack teeth 83, a fixed stop 85 holding the catch away from the rack when the breaker is in the closed position shown. Thus each time the plunger 35 moves down the catch 82 engages successive rack teeth  83, the lost-motion in the connection 79 ensuring that the discharge valve is not closed until the rack has been raised by the second tooth. The upper end of the rack has a pivoted connection 75 with a toggle link 76 pivoted at 63, the other toggle link 90 being pivoted at 91 to a lever 92 mounted on a pin 54 carried by a bellcrank 93 pivoted at 94. The lower end of the lever 92 is normally clear of the tail 32 of the toggle link 30 but in the top position of the rack 72 the link 90 draws the lever 92 to the left and thus the lever 92 is lifted to rotate the bell-crank 93 clockwise in the locking-out operation. A link 53 pivoted at 54 has a slot 52 receiving the pin 51 on the toggle link tail 32. The bellcrank has a pin connection 96 with the link 97 of a re-entrant toggle 97, 98, the link 98 being pivoted on the pin 27. Tension springs 99 extend between a pin 100 connecting the links 97, 98 and fixed pins 101, the line of action of the springs being beneath the pin 27 so that the toggle is set with the link 97 retained by the pin 27. Since the line between pivots 96, 100 lies above pivot 27 clockwise rotation of the bell crank 93 by lever 92 causes raising of pin 100 and the line of action of springs 99 moves above pivot 27. whereby pins 96, 100 move rapidly clockwise to rotate further bell-crank 93 and lift link 53. The bottom of the link slot 52 engages pin 51 and transmits the force of springs 99 to the toggle link 30, this force acting downwardly on the link 41 to overcome the spring 43 and hold the breaker open. The breaker is manually reset by a lever 102 fixed to a shaft 103 fixedly carrying a lever 105 connected to the pin 96 by a toggle 106, 107. The pin 108 lies above the pins 96, 109, so that the toggle collapses when the breaker is locked open. The breaker is reset by clockwise rotation of the lever 102 to bring the links 106, 107 into line whereupon a spring (not shown) on the pin 108 moves the links just to over-centre. Return movement of the lever 102 then restores the bellcrank 93 and the link 53 releases the link 30 permitting the spring 43 to close the breaker. An abutment 110 engages the link 106 in its final movement to break the toggle 106, 107 and place it in its initial condition. The toggle 106, 107 renders the breaker trip-free. In a modified construction of the locking-out and re-setting linkage (Figs. 5, 6, not shown) intended for use with a number of breakers mounted side-by-side, each breaker controlling a separate phase, the breakers are connected together by a shaft such that locking-out of one breaker causes the other breakers to lock-out, resetting of one breaker also resetting the others. The link 22 is brought to rest in the contact-opening operation by striking an anvil 111 on a link 112 pivoted at 113, the anvil in turn being arrested by a buffer 115, this matter forming the subject of Specification 775,865. A buffer 116 arrests the final opening movement of the link 17. The buffers 115, 116 may be constructed in accordance with Specification 775,866 [Group XXXII]. The construction of dashpot 65 is' described with reference to Fig. 4 (not shown) and may be modified in accordance with Fig. 5 of Specification 775,864 (see Group XXXII), this modification comprising a further discharge valve opening automatically on severe overload to permit rapid movement of the piston. Specifications 775,862, 775,863 and 775,867 also are referred to.