Abstract: A circuit breaker includes an operation knob rotatably mounted on a frame, an actuator rotatably mounted on the frame, the actuator being rotatably moved with the operation knob so as to operate a handle of the circuit breaker, an engagement member rotatably movable between first and second positions in response to the reciprocal movement of the actuator. The engagement member engages with an interlocking arm for the locking of the compartment door while it is being moved to the second position. The engagement member allows the interlocking arm to pass by when occupying the first position. An engagement portion is formed in the operation knob so as to engage with the engagement member when it occupies the second position. The location of the engagement portion corresponds to an OFF position of the operation knob where the circuit breaker is opened. Engagement of the engagement member with the engagement portion prevents the circuit breaker from being closed when the compartment door is opened.

Abstract: An electrical contact assembly used for a circuit breaker comprises a pair of relatively movable U-shaped contact and bar conductor, and a holder provided with a recess for receiving the U-shaped contact. The U-shaped contact has contacting portions formed by slightly bending both sides thereof inwardly to form a narrow opening for clamping the bar conductor. The electrical contact assembly further comprises conductive members which are disposed on both sides of the U-shaped contact and electrically connected thereto, so that currents passing through the conductive members symmetrically flow in a direction opposite to a flow direction of currents passing through the both sides of the U-shaped contact when the U-shaped contact and the bar conductor are engaged.

Abstract: A handle operating mechanism adapted for use with an electric circuit breaker including a manually operable handle member, an operating axle having an elongated hole formed therein, a cylindrical member having a guide hole of predetermined formation provided therein, and a pin engaged with each of the above members. In a certain position, when the handle is moved in the axial direction of the operating axle, a hole is formed on the handle for cooperation with a locking member.

Abstract: A handle operating mechanism is provided to actuate an electric circuit breaker having a release lever and to interlock the electric circuit breaker and the door of a casing accommodating the circuit breaker. A manually operable handle is rotatably mounted on a case and is integrally coupled with a cam, disposed within the case, having a pin and a trapped portion. An actuating member which is engaged with the pin of the cam is linearly moved along a guide rod in response to rotation of the handle. One end of the guide rod contacts and slides along the circumference of the cam, the other end of the guide rod extending from the case to interlock with the door of the casing.

Abstract: In a motor control center of the present invention, a plurality of units are mounted on a frame. Each of these units has an appliance mounting plate with two walls which extend transversely from the floor plate in stepped form. A first group of electrical appliances which requires relatively frequent maintenance and inspection among the electrical appliances to be mounted in the unit is mounted at the front sides of said two walls and a second group of electrical appliances which requires less frequent maintenance and inspection is mounted on the back side of the wall nearest the front.