Circuit breaker having a thermally responsive latching member

Claim 1

A circuit breaker including in combination a housing of insulating material; a fixed contact mounted in said housing; a movable handle mounted in said housing; a contact carrier with a movable contact thereon and pivotally engaging said handle at a pivot point; a trip arm pivotally mounted in said housing; an overcenter spring connected between said contact carrier and said trip arm urging said contact carrier against said handle; said handle, contact carrier, and overcenter spring forming an overcenter arrangement for closing said contacts when the spring is on one side of said pivot point and for opening said contacts when the spring is on the other side of said pivot point; a load terminal mounted in said housing; a thermally responsive latching member connected in circuit between said load terminal and said movable contact, said latching member having a locating hole therewithin; an armature; an armature spring affixed to said armature and having a free end provided with an annular boss adapted to fit within said locating hole; a mounting member holding the thermally responsive latching member at a portion thereof adjacent to one end; said mounting member being pivotally mounted in said housing at a pivotal connection; a U-shaped field piece affixed to said mounting member with legs of said piece extending at both sides and toward said thermally responsive latching member and facing said armature; a support member mounted in said housing and bearing against said field piece; and a mounting spring bearing against the housing and urging said field piece against said support member whereby said pivotal connection, said support member, said field piece, and said mounting member in combination hold the portion of the thermally responsive latching member adjacent said one end fixed with respect to the housing, said thermally responsive latching mechanism being rotatable about the pivotal connection against the urging of said mounting spring; said thermally responsive latching member having a latching surface adjacent the opposite end thereof engaging said trip arm and maintaining said trip arm in a set position when said contacts are closed, with said overcenter spring urging said trip arm toward a tripped position; said thermally responsive latching member bending in response to a predetermined current condition to move said opposite end of the thermally responsive latching member and disengage said latching surface from said trip arm releasing said trip arm for movement to the tripped position; said U-shaped field piece being adapted to intercept lines of flux of a magnetic field created by a predetermined amount of current flowing through said thermally responsive latching member to attract said armature against said latching member to rotate said latching member thereby disengaging said latching surface from said trip arm, releasing said trip arm for movement to said tripped position; and movement of the trip arm to the tripped position moving the overcenter spring to the other side of said pivot point causing said contacts to open.