Circuit breaker fitted with a device for indicating a short circuit

In an air-type circuit breaker provided with a device for indicating the existence of a short-circuit and comprising, for each circut-breaking pole, separable contacts disposed inside a breaking chamber in which an electric arc develops upon separation of the contacts, the improvement wherein said short-circuit indicating device comprises means responsive to a gas pressure wave created by said electric arc developed in the breaking chamber at a current level constituting a short-circuit condition of the circuit-breaker as contrasted to an abnormally high over-current, said short-circuit indicating device comprising a movable member subject both to a stress developed by the gas pressure wave and to an opposing stress, and wherein said movable member comprises a member passable from a first "no pressure" position to a second "pressurized" position when the stress developed by the gas pressure wave is greater than the opposing stress, said air-type circuit breaker further comprising a casing, said short-circuit indicating device comprising a casing mounted to the short-circuit breaker casing and closing off said breaking chamber, said short-circuit indicating device casing including an opening communicating the interior of the indicating device casing to the breaking chamber, said movable member comprising a flap positioned within said indicating device casing and overlying the opening communicating the interior of the indicating device casing to the breaking chamber, and wherein a spring clip biases said flap against the indicating device casing wall to close off said opening, and wherein said indicating device further comprises shiftable means operatively coupled to said flap and shiftable in response to movement away from said opening from said first position to said second position when the current level creates a gas pressure wave by the electric arc developed in the breaking chamber reaches a short-circuit condition.

In an air-type circuit breaker provided with a device for indicating the existence of a short-circuit and comprising, for each circuit-breaking pole, separable contacts disposed inside a breaking chamber in which an electric arc develops upon separation of the contacts, the improvement wherein said short-circuit indicating device comprises means responsive to a gas pressure wave created by said electric arc developed in the breaking chamber at a current level constituting a short-circuit condition of the circuit-breaker as contrasted to an abnormally high over-current, said short-circuit indicating device comprising a movable member subjected both to a stress developed by the gas pressure wave and to an opposing stress, and wherein said movable member comprises a member passable from a first "no pressure" position to a second "pressurized" position when the stress developd by the gas pressure wave is greater than the opposing stress, means for maintaining said movable member in the "pressurized" position after disappearance of the gas pressure wave, and means for restoring it to the "no pressure" position by an interntional resetting action, and wherein said circuit breaker comprises a closed casing, the pressure wave generated in the breaking chamber being propagated through the entire casing, and wherein said short-circuit indicating device comprises a hole within said circuit breaker casing, a bistable capsule of spherical form being fixedly mounted in overlying position with respect to said hole so as to be bistably movable between a first position where it projects spherically away from the opening and interiorly of the circuit breaker casing, and a second position where it protrudes through said opening such that upon the occurrence of a short-circuit condition, the pressure wave displaces the bistable capsule from retracted to projected position, and wherein the presence of said hole within said casing permits manual shift of the bistable capsule from projected to retracted position to reset the short-circuit indicating device, said bistable capsule comprises said movable member.