Spring loaded, bistable connect/disconnect for MCC unit

A motor control center unit, comprising:

• a housing configured to be inserted into a motor control center, the housing including an outer structure comprising side walls, a bottom plate, a back wall, and a front door hinged to one of the side walls and configured to open a front side of the housing to provide access to an interior space, an exterior face of the back wall of the housing being configured to be located adjacent to an electrical power bus when the housing has been inserted into the motor control center;
• stabs configured to project through an opening in the back wall of the housing, to mechanically and electrically engage the power bus for electrical connection therewith, when pushed in a backward direction toward the power bus, the stabs being electrically connected to a circuit breaker electrical switch actuated by a circuit breaker switch handle of a circuit breaker located within the housing;
• a connect/disconnect handle located on the front side of the housing, connected to a spring loaded, bistable connect/disconnect mechanism configured to push the stabs to connect the stabs to the power bus or pull the stabs to disconnect the stabs from the power bus;
• the spring loaded, bistable connect/disconnect mechanism, comprising:
• a stab holder slideably mounted on the motor control center unit, configured to slide in a longitudinal direction to connect the stabs to the power bus, when pushed toward the power bus, and to disconnect the stabs from the power bus when pulled away from the power bus;
• a balance arm pivotally mounted on the motor control center unit on a first transverse side of the stab holder, pivotally connected to a link connected to the stab holder, configured to follow motion of the stab holder as the stab holder moves through an intermediate longitudinal center point, as the stab holder is pushed or pulled in the longitudinal direction;
• a spring mounted on the motor control center unit on a second transverse side of the stab holder opposite to the balance arm, having an end connected to the balance arm, configured to apply a compression force in the transverse direction, on the balance arm as the balance arm follows the motion of the stab holder as the stab holder moves through the intermediate longitudinal center point;
• whereby when the stab holder is pushed toward the power bus and moves through the intermediate longitudinal center point, the spring forces the balance arm to further urge the stab holder toward the power bus, to assume a first bistable position, and when the stab holder is pulled away from the power bus and moves through the intermediate longitudinal center point, the spring forces the balance arm to further urge the stab holder away from the power bus, to assume a second bistable position.

A connect/disconnect assembly for a motor control center unit, comprising:

• stabs moveably mounted in a motor control center unit, the stabs configured to project through an opening in a back wall of the motor control center unit, to mechanically and electrically engage a power bus adjacent to the motor control center unit, when pushed in a backward direction toward the power bus, the stabs being electrically connected to a circuit breaker;
• a stab holder connected to the stabs and slideably mounted on the motor control center unit, configured to slide in a longitudinal direction to connect the stabs to the power bus, when pushed toward the power bus, and to disconnect the stab from the power bus when pulled away from the power bus;
• a balance arm pivotally mounted on the motor control center unit on a first transverse side of the stab holder, pivotally connected to a link connected to the stab holder, configured to follow motion of the stab holder as the stab holder moves through an intermediate longitudinal center point of an over-center spring mechanism, as the stab holder is pushed or pulled in the longitudinal direction;
• a spring mounted on the motor control center unit on a second transverse side of the stab holder opposite to the balance arm, having an end connected to the balance arm, configured to apply a compression force in the transverse direction, on the balance arm as the balance arm follows the motion of the stab holder as the stab holder moves through the intermediate longitudinal center point;
• whereby when the stab holder is pushed toward the power bus and moves through the intermediate longitudinal center point, the spring forces the balance arm to further urge the stab holder toward the power bus, to assume a first bistable position, and when the stab holder is pulled away from the power bus and moves through the intermediate longitudinal center point, the spring forces the balance arm to further urge the stab holder away from the power bus, to assume a second bistable position.