Apparatus and method for electromechanically retracting a door latch

An apparatus use in an exit device for holding a latch mechanism including a latch bolt in a retracted position on a door pivotally mounted along one edge for movement about an axis, the exit device including a housing adapted to be secured to the surface of a door, the latch bolt disposed at one end of the housing adjacent an edge of the door and movable relative to the housing between a projected position extending outwardly of the housing for latching the door in a closed position and the retracted position where the latch bolt is inside the housing for allowing the door to be opened, an actuator member mounted on the housing for movement relative to the housing from a first position to a second position, and an electrically energizable retracting mechanism mounted to the housing operative to hold the latch in the retracted position when energized, the apparatus for holding the latch bolt in the retracted position comprising:

• a retractor element disposed in the housing, the retractor element including
• a rigid slide connected between the latch bolt and the solenoid plunger for movement along the longitudinal axis of the housing between a first position and a second position, the slide including a pin extending transversely of the direction of movement of the slide and operably connected to plunger,
• a pivoting link defining a slot having an inner end portion extending transversely to the longitudinal axis of the housing, the slot configured for receiving the pin for pivoting the link when the slide moves between the first position and the second position of the slide, and
• a spring for biasing the pivoting link away from the plunger;
• and
• a controller adapted to control the operation of the retracting mechanism,
• wherein when the retracting mechanism is energized the plunger moves to the second position of the plunger causing movement of the slide to the second position of slide and the pin to enter the transverse end of the slot in the pivoting link against the bias of the spring where a bearing surface defining at least a portion of the end of the slot intersects the path of movement of the pin such that significantly less current is required for retaining the plunger armature in the retracted position than to retract the plunger for blocking the return of the latch bolt to the projected position, and
• wherein upon de-energizing the retracting mechanism allows the pivoting link to move to the first position under force of the spring and the plunger to move to the extended position such that the latch moves to the projected position.

In combination,

• a door frame;
• a door hinged along one edge to the door frame;
• an exit device, comprising
• a housing having a longitudinal axis, the housing adapted to be secured to a surface of the door;
• a latch mechanism including a latch bolt disposed at one end of the housing adapted to be adjacent an edge of the door, the latch bolt movable relative to the housing between a projected position extending outwardly of the housing for latching the door in a closed position and a retracted position where the latch bolt is inside the housing for allowing the door to be opened;
• an actuator movably mounted on the housing for movement relative to the housing between a first position and a second position, the actuator operably connected to the latch mechanism for moving the latch bolt to the retracted position when the actuator is moved to the second position in response to application of manual force on the actuator;
• an electrically energizable retracting mechanism mounted to the housing, the retracting mechanism including a reciprocating plunger and selectively connected to a source of electrical power for moving the plunger from an extended position to a retracted position when the retracting mechanism is energized and for releasing the plunger from the retracted position when the retracting mechanism is de-energized;
• a retractor element disposed in the housing, the retractor element including
• a rigid slide connected between the latch bolt and the solenoid plunger for movement along the longitudinal axis of the housing between a first position and a second position, the slide including a pin extending transversely of the direction of movement of the slide and operably connected to plunger,
• a pivoting link defining a slot having an inner end portion extending transversely to the longitudinal axis of the housing, the slot configured for receiving the pin for pivoting the link when the slide moves between the first position and the second position of the slide, and
• a spring for biasing the pivoting link away from the plunger;
• and
• a controller adapted to control the operation of the retracting mechanism,
• wherein when the retracting mechanism is energized the plunger moves to the second position of the plunger causing movement of the slide to the second position of slide and the pin to enter the transverse end of the slot in the pivoting link against the bias of the spring where a bearing surface defining at least a portion of the end of the slot intersects the path of movement of the pin such that significantly less current is required for retaining the plunger armature in the retracted position than to retract the plunger for blocking the return of the latch bolt to the projected position, and
• wherein upon de-energizing the retracting mechanism allows the pivoting link to move to the first position under force of the spring and the plunger to move to the extended position such that the latch moves to the projected position.