GB452752A - Improvements in and relating to electric circuit breakers - Google Patents

Abstract

452,752. Automatic circuit-breakers. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London. Jan. 3, 1936, No. 308. Convention date, Jan. 3, 1935. [Class 38 (v)] The movable contacts 3 of a circuit-breaker are moved into engagement with the fixed contacts 2 against the action of a spring 23 by means of a lever 16 which is pivotally mounted near one end and movable in an endwise direction by force applied through its fulcrum, the resulting movement of the other end of the lever being caused to urge the movable contacts into the engaged position by a non-articulated engagement of said end with a member connected to the movable contacts, means being provided for maintaining the lever in the engaged position and for moving it about its fulcrum when the contacts are to be disengaged. In the two-pole switch shown, a pair of contacts 2, 3 are provided for each pole, and in the closed position, the current of each pole flows through a pair of bimetallic strips 4, 5 and through a coil 6. The lever 16 is pivoted at 15 on one arm of a bell-crank lever 13 pivoted at 14, the other arm of the lever having a shoulder 12 which is engaged by a fork 11 on a pushbutton 10. When the button is pressed to the left to close the circuits, a pivoted catch 25 engages the shoulder 12 to maintain the lever 16 in the circuit-closing position. The other end 17 of the lever 16 engages a roller 18 carried by a double fork 19, 19<1>, which also carries an element 20 carrying the movable contacts 3. The fork is carried by a guide rod 22 sliding in a member 24 against the action of the spring 23. Automatic release is effected by a member 37 pivoted at 38 and having an arm 39 adapted to engage an arm 40 carried by the lever 16. On heavy overloads, the core 36 of the winding 6 rises and strikes the member 37, the arm 39 of which then engages the arm 40 and pushes the lever 16 to the right to release the roller 18. At the same time a link 29 connected to a pin 30 on the lever 16 moves the catch 25 out of engagement with the shoulder 12. On prolonged overloads of less intensity, the bimetallic strips 4, 5 move in the direction of the arrow f, Fig. 5, and release a member 42 pivoted at 44. The member 42 then moves under the action of a spring 46, and a member 45 carried by the member 42 strikes the release member 37 to open the circuit. When the circuit opens, a head 47 on the contact carrier 20 resets the member 42. The member 42 may incorporate a second bimetallic strip to compensate for variations in ambient temperature. The setting of the bimetallic blades 4, 5 may be regulated by a screw. A separate push-button 31 is provided for use when manual opening of the circuit is desired.