GB454083A - Improvements in and relating to electric circuit breakers - Google Patents

Abstract

454,083. Heavy - current switches. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London. May 4, 1936, No. 12581. Convention date, May 4, 1935. [Class 38 (v)] Magnetic blow - outs.-a circuit-breaker comprises a pair of relatively-movable contacts enclosed within walls of pressure-resistant material forming a sealed compression chamber having a volume such that high gas pressures' are generated therein by the arc formed between the contacts, and means including a permanent magnet for producing a magnetic field substantially at right-angles to the path of movement of the operated contact adjacent the point of separation of the contacts. The use of the magnetic field renders the breaker suitable for D.C. working. Fig. 1 shows the invention applied to a breaker as described in Specification 420,042, in which a brass or other non-magnetic compression chamber 12 is housed in an enclosure 11 integral with the moulded-insulation base 10, and has insulating bushings 13, 14, in the former of which the fixed contact 15 is secured, while the movable contact 17 is slidable in 14 and sealing means co-operate with 14, 17 to seal the chamber 12 in a gas-tight manner. The permanent magnet 19, Fig. 4, is U-shaped and its poles pass through apertures 20 in the enclosure 11 and are curved in conformity with the curvature of the chamber 12 on which they abut, so providing a blow-out field at right-angles to the direction of movement of contact 17. The magnet comprises material of high coercive force, alloys as described, for example, in Specifications 423,897 and 424,746, [both in Group II], being suitable. The switch " movement " comprises a pin 34 serving as a pivot for an operating handle 33, for a member 39 having a pin 35 taking in a slot in contact 17, and for a trip member 43 carrying a latch part 42 normally held in the position shown by a bimetallic latch 41. By means of a pair of springs 31 anchored between the pins 32, 35, contact 17 can be moved on and off with a snap action by means of the handle 33. When the latch 41 flexes on overload and releases the latch part 42, a part (not shown), on the member 43 engages the cross-arm 40 uniting the two limbs of member 39 and forces the switch to the off position. The driving force is provided by a rod 44 engaging a notch in member 43 and having a compression spring 45 engaging at one end an enlargement on the rod 44 and at the other a stop 46 co-operating with parts 27 on the frame 26. The stop 46 also clamps between itself and the enclosure 11 a part 24 of the bracket 22, the part 23 of which lies over the yoke of the magnet 19 and holds it in place against the enclosure 11. A member 25, Fig. 4, insulates the magnet from the bracket 22 and switch " movement." The breaker is adapted for D.C. working by inserting the magnet and bracket and clamping the whole by mounting the frame 26 on the base 10. For A.C. working the bracket and magnet are omitted.