Adjustable electromagnetic tripping mechanism for a circuit-breaker

An adjustable electromagnetic tripping mechanism for a circuit-breaker having at least one pole, including in each pole:

• a fixed magnetic circuit element excited by the current passing through said pole;
• a movable magnetic member, a stop, and a return spring for holding said movable magnetic member by the force of said return spring, against said stop at a predetermined distance from the fixed magnetic circuit element;
• a movable adjusting element bearing said stop and including a point of attachment of said return spring, which enables the limiting operation current of the circuit-breaker to be varied, such that movement of said movable adjusting element modifies at the same time and in the same sense of variation, firstly the distance predetermined by said stop between the movable magnetic member and the fixed magnetic circuit element, and secondly the force exerted by said return spring upon the movable magnetic member, the improvement wherein said movable adjusting element consists of a small plate of generally plane form guided in translation in slides for movement in a direction parallel to the face of said plate.