Patent GB-420042-A (GB)
Title: Improvements in and relating to arc extinguishing arrangements for electric circuit breakers
IPC: H01H73/18
Filed: 1934-04-25
Abstract: 420,042. Automatic circuit-breakers. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London. April 25, 1934, Nos. 12467 and 12468. Convention dates, April 25, 1933. [Class 38 (v)] Arc-rupturing devices ; springs, arrangement of.-A circuit-breaker comprises stationary and movable butt engagement contacts supported within a permanently-sealed arcing- chamber, operating mechanism for actuating the movable contact to a closed-circuit position with a snap action, and thermal-responsive means for controlling the movement of the movable contact to open position with a snap action in response to a given overload current. The chamber 15 comprises a steel cylinder 50 enclosed in insulation 60 and with a pair of kerosene-free, fibre bushings 51, 52 over which the cylinder ends are swaged, a leather sealing washer 65 with an extension 66 being provided around the movable contact 31. The Specification states that the rise in pressure within 15 depends on the current interrupted, so that the greater the current the sooner the pressure reaches a point at which the arc resistance is so great that the arc cannot exist, The fixed contact 43 is threaded to engage the conductor 44, whereas the reciprocable contact 31 is secured to floating links 26 to the ends 34 of which are anchored springs 37 also anchored to the frame 13. The breaker is closed by rotating the lever 18 clockwise about its pivot 17, so that projections 21 thereon engage the ends of notches 22 in the links 26 and impart a combined rotational and translational movement thereto, so that pins 48 thereon engage behind latches 49 on a series bimetal element 14. The lever 18 is released and springs 37 rotate links 26 counter-clockwise about 48 to move contact 31 into engagement with 43 in which position the links rotate about 30 to disengage 22 from 21. When the element 14 flexes the pins 48 are freed and springs 37 move the links bodily to separate 31 from 43. In Fig. 3, the chamber 15 is located in an integrally-moulded extension 82 of the base and closed by a member 86 which is held by the framework 89. The manual operating handle 101 is pivoted at 104, and between it at 100 and a pin 102 taking in a slot in the movable contact 31 are anchored a pair of dead-centre springs 98. Also pivoted at 104 are the limbs of a member 104<a> which are pivoted also to pin 102 and inter-connected by cross-member 104b. Thus operation of handle 101 up and down causes the rod 31 to reciprocate to the closed and open positions. For automatic tripping, a spring plunger 112, 115 acts on a trip member 110 also pivoted at 104, but normally prevented from moving by the bimetal element 108 engaging the end 109. When the element flexes, member 110 is rotated clockwise to engage the cross-member 104b and rotate 104<a> clockwise to separate the contact 31 from the contact 43. To reset, 101 is moved back to the position shown so that a part 125 thereon engages a surface of member 110 to latch it again, upward movement of 101 then reclosing the breaker. A stop 127 on the handle 101 engages the frame 89 in the upper position of the handle. Contacts.-The contacts 31, 43 are of silver molybdenum or other arc-resistant alloy and 31 is kept free of condensed metal vapour by washer 65. Indicators.-An opening 130 in handle 101 allows a suitably-coloured part on member 110 to be seen, so giving an indication that the breaker has been tripped open.