Patent GB-444109-A (GB)
Title: Improvements in or relating to electric circuit-breakers
IPC: H01H3/32
Filed: 1934-09-13
Abstract: 444,109. Automatic circuitbreakers. REYROLLE & CO., Ltd., A., Hebburn-on-Tyne, and CHRISTIE, J., 4, Sidecliff Road, Sunderland. Sept. 13, 1934, No. 26277. [Class 38 (v)] In order to ensure rapid tripping of a breaker in the event of any hesitation in the closing movement, such as would be caused by electromagnetic forces on the moving contacts when they first close on to a short-circuit, a trip-free device is mechanically released to interrupt the transmission of the closing force by means operated by relative movement between a driving arm, which is rotated about its pivot by part of the closing mechanism, and a weighted arm, which is so mounted that it will normally move with the driving arm in closing, but will move relatively thereto under its own inertia if the driving arm lags behind its normal closing movement. In Fig. 1, the arm A is free on the shaft B and connected by a toggle D D<1>, having a trip extension D<2>, to the closing lever C, shown as a handle keyed to the shaft B which is moved clockwise to close the breaker. Also keyed to B is a driving arm E having projections El, E<2> co-operating with a weighted arm F loose on the shaft B. Pivoted to F is a lever G having a surface G<1> normally urged by a light spring H<1> against a surface E<3> on the arm E. The spring H<1> is also anchored to an arm H pivoted to E and co-operating with a stop H<2> in the closed position of the parts. In closing from the position shown, the projection E<1> engages and carries with it the arm F, but if at any part of the movement the arm E hesitates, the arm F will by inertia move forward relatively to it, thereby causing the lever G to swing about its pivot to break the toggle by engagement of the roller G<3> with extension D<2>. This relative movement is prevented at the closed position by the engagement of H with the stop H<2>. In Figs. 4, 5, the toggle is tripped by a lever K having a curved surface K<1> which is concentric with shaft B and co-operates with a roller J<2> on a trip lever J pivoted at J<1>. The driving arm L is pivoted at M and is slotted at L<1> for engagement with a pin C<2> on the lever C. Pivoted to L at L<2> is a weighted arm N having an aperture N<1>, which contains the shaft M, a cam surface N<2> engaging the roller J<3>, and a roller N<3> engaging in the open position a cam M<1> on the shaft M. In moving to the closed position, Fig. 5, the arm L, driven by C<2>, takes the arm N with it. At an early stage, the roller N<3> leaves the raised cam surface and is free to fall within the limits allowed by N<1> and M, but with a steady movement of C, no relative movement occurs between L, N and the cam surface N<2> on the arm N remains concentric with M. When the arm N drops at the end of the movement, the corner N<4> of the cam surface N<2> has left the roller J<3> and tripping cannot occur, but such an effect could alternatively be obtained by making N<3> again engage the raised part of M<1>. The cam is shown as being shaped to ensure proper resetting, and by making it adjustable, the moment at which the inertia device comes into action can be adjusted.