Patent GB-250656-A (GB)
Title: Improvements in or relating to the control mechanism of electric switchgear
IPC: H01H71/52
Filed: 1925-01-14
Abstract: 250,656. Reyrolle & Co.; Ltd., A., Anderson, W., and Clothier, H. W. Jan. 14, 1925. Automatic circuit-breakers &c.-In the control mechanism of electric switchgear, of the kind in which an operating arm is connected to a handle by a toggle so arranged that after being broken to open the switch it is reset by the movement of the handle before that member can act to close the switch, the handle and operating arm are mounted to turn about the same axis and connected by a toggle adapted to be tripped by energy stored during the closing movement of the switch, the trip mechanism itself comprising a second toggle and catch arranged so that substantially the same power is required to operate the trip whether the switch is closing or closed, such power being practically unaffected by wear of the catch. The switch handle A is pivoted on a spindle B to which is secured a forked lever D attached to the switch by ropes E, the latter being attached to a bar E<2> in a slot in the lever D and being normally in tension due to the tendency of the switch to open. To a spindle F on the lever D is pivoted one end of a toggle G<1>, G<2>, the other end of which is pivoted at G<4> to a lever H pivoted at H<1> on the upper part A' of the handle A. A stop G<5> prevents relative movement between the toggle levers beyond a predetermined amount past the dead centre. The longer arm of lever H is connected by a link J to the arm K' of a lever pivoted on the spindle B, the other arm K<2> of the lever carrying a roller K<3> engaging a catch L pivoted on a member M on a spindle M<1>, on which is a tappet actuated by electrical, mechanical or other means to trip the switch. The member M and catch L form a toggle in which the catch L, after a short movement of the member M, rotates and falls clear of the arm K<2>, thus preventing wear of the catch surface affecting the trip mechanism. The handle A is pivoted at A<2> to the part A<1> and is rotatable about the pivot against the action of a spring A<3> to cause a projection A<5> to trip the switch by engaging the member M. The upper part A' is locked, when the switch is closed, by a catch A<4> which is released on opening the switch by a pin B<1> on the spindle B. In operation, on release of the catch L the tension in the rope E rotates the lever D and also the lever H about its pivot H', and the toggle G<1>, G<2> is carried with the lever D while the arm K<2> moves clockwise through about 90‹. A projection H<3> on the lever H engages and breaks the toggle G', G<2> and is then arrested by a stop A' on the part A<1> of the handle. Breaking the toggle upsets the rigid connection between the lever D and handle A so that the ropes E pull the lever clockwise through about 90‹, rotating the spindle B so that the catch A' is released by the pin B<1> and the handle freed. To reset, the handle is raised as a whole, causing the lever H to rotate and reset the toggle, the arm K<2> also re-engaging the catch L. Lowering the handle again closes the switch, but the trip mechanism is now ready for operation even during closure. By means of the toggle arrangement J, K<1> the load on the catch L is kept as constant as possible during closure.