US 5,296,664 AGranted

Circuit breaker with positive off protection

AssigneeWestinghouse Electric Corp.

InventorsRonald W. Crookston, Douglas C. Marks, David C. Turner, Richard E. White, III, Steven Castelein

Life of this patent

Estimating the term…

Loading patent…

Abstract

A positive off mechanism for a circuit breaker includes a pair of positive off levers slideable in slots in the side plates and extendable into the path of the operating handle to prevent movement of the handle to the off position when the contacts are welded closed. The positive off levers are actuated by positive off links pivotally mounted to the side plates and coupled to the positive off levers by "dog bone" connections. The positive off links in turn are actuated by the toggle mechanism of the circuit breaker which collapses to open the contacts during normal circuit breaker operation, but which remains erect when the contacts are welded closed.

Claims13

Dependent claims

A circuit breaker comprising:

a housing;
one or more pairs of separable contacts mounted in said housing;
an operating mechanism operatively coupled to said one or more pairs of separable contacts;
a pair of side plates mounted in said housing and supporting said operating mechanism;
a handle assembly operatively coupled to said operating mechanism and selectively movable reciprocally along a path between an on position in which said separable contacts are closed by said operating mechanism and an off position in which said separable contacts are opened by said operating mechanism;
and
positive off means comprising:
least one positive off lever slidable in a slot in one of said side plates between an extended position in which said positive off lever extends into said path of said handle assembly and blocks movement of said handle assembly toward said off position, and a retracted position in which said handle assembly is free to move to said off position;
and
actuating means coupled to said operating mechanism actuating said positive off lever to said extended position to block movement of said handle assembly to said off position when said separable contacts are welded closed.

7 more elements

A circuit breaker comprising:

a housing;
one or more pairs of separable main contacts mounted in said housing each including a fixed contact and a movable contact mounted on a movable contact arm assembly;
an operating mechanism including a toggle mechanism having a pair of toggle links pivotally connected by a cross-bar and pivotally connected by one of said toggle links to said movable contact arm assembly, said toggle mechanism having an erect position in which said separable contacts are closed and a collapsed position in which said separable contacts are open;
a pair of side plates mounted in said housing and supporting said operating mechanism;
a handle assembly operatively coupled to said operating mechanism and selectively movable reciprocally along a path between an on position in which said separable main contacts are closed by said operating mechanism, and an off position in which said separable contacts are opened by said operating mechanism;
and
positive off means comprising:
at least one positive off lever slidable in a slot in one of said side plates between an extended position in which said positive off lever extends into said path of said handle assembly and blocks movement of said handle assembly towards said off position and a retracted position in which said handle assembly is free to move to said off position;
a positive off link, and a pivot pin supported in said side plate and laterally offset from said slot pivotally supporting said positive off link;
coupling means coupling said positive off lever to said positive off link for movement of said positive off lever between said extended and retracted positions by rotation of said positive off link about said pivot pin by said operating mechanism;
and
a projection on said movable contact arm assembly limiting pivoting of said one toggle links relative to said movable contact arm assembly with said separable contacts welded closed.

9 more elements

Dependencies are inferred from the claim text.