Instantaneous trip means

Claim 1

A circuit breaker including cooperating contact means, an operating mechanism for opening and closing said contact means, trip means including an electromagnet comprising a relatively stationary section and an armature mounted for movement toward said relatively stationary section to a trip position from a normal position remote from said stationary section, said armature moving to said trip position upon the occurrence of fault current above a predetermined level, thereby automatically actuating said operating mechanism to open said contact means, a trip member interposed between said armature and said operating mechanism, a spring means acting through said trip member to bias said armature toward said normal position, a pivot about which said trip member pivots as said armature moves from the normal position to the trip position, a relatively fixed anchor for one end of said spring means and another anchor connecting the other end of the spring means to the trip member at a point very close to said pivot to minimize increased loading of said spring as the armature moves toward the trip position; adjustable means to adjust biasing forces exerted by said spring means on said armature by repositioning the relatively fixed anchor without altering the normal position of the armature; said adjustable means including a cam means selectively operable to reposition the relative fixed anchor; a pivotally mounted element which carries the relatively fixed anchor, said spring means biasing a follower portion of said element into operative engagement with said cam means.