GB688649A - Improvements in current-responsive automatic electric circuit-breakers - Google Patents

Abstract

688,649. Automatic circuit-breakers. MARCOZ, J. A. E. June 26, 1950 [July 6, 1949], No. 15901/50. Class 38(v) In a trip-free circuitbreaker, the movable contact is biased towards the "open" position by a spring and towards the "closed" position by a stronger spring, a connection between the two springs being released by a bimetallic strip to trip the switch and a resetting push-button indicating whether the circuit-breaker is open or closed. In Figs. 1 and 2, the moving contact 2 is biased towards the open position by the blade spring 3 on which it is mounted and is normally held in the closed position by the stronger blade spring 5. The two blade springs are connected by a latch 6 which is moved aside by the bimetallic strip (not shown) to trip the breaker. Alternatively the latch 6 itself may be a current-responsive bimetallic strip. The switch is reclosed by depressing the push-button 4, so moving the strip 5 downwards until its end engages under the latch 6. On release of the push-button 4, the spring 5 moves the spring 3 upwardly until the contacts 1, 2 reclose, the arrangement ensuring that the contacts cannot be held closed by the push-button if an overload exists. In Fig. 3, the bimetallic strip 10 is secured between the spring 3 and a C-shaped contact and latch member 2, 6. When the strip 10 is heated sufficiently by the current flowing through it, it withdraws the latch 6 allowing the spring strip 3 to open the contacts 1, 2. The - switch may be opened manually by depressing a push-button 12 which acts on a member 14 fixed to the blade 5 to disengage a catch 7 from the latch 6. The current-setting may be altered by a screw 15 which adjusts the relative position of the catch 7 with respect to the latch 6. Contacts 18 in an indicator circuit are closed when the main contacts are tripped open. In a modification Fig. 6 (not shown), the stronger spring is in the form of a helical spring acting on the push-button 4 to which the opening spring blade is latched. In Fig. 7 (not shown) the fixed contact-carrying member is adjustably mounted and carries the bimetallic strip which actuates a latch member pivotally mounted on the spring strip 3. Specification 498,376 is referred to.