Electromechanical actuator used in wire-dot printing head

An electromechanical actuator, comprising:

• a stack of electromechanical elements, the stack being disposed in and having a variable length in a first direction, comprising a first length in a rest condition and a second, increased length in an electrically energized condition of the electromechanical elements;
• a support member extending in the first direction, the stack having first and second end portions and the support member having first and second mounting portions, the first end portion of the stack being mounted on the support member at the first mounting portion thereof, the stack extending adjacent to and along the support member, so as to position the second end portion of the stack adjacent to the second mounting portion of the support member;
• first and second parallel leaf spring elements respectively having first and second ends, the first end of the first leaf spring being mounted to the second mounting portion of the support member and the first end of the second leaf spring being mounted to the second end portion of the stack;
• a lever arm having a first end portion commonly connected to the second ends of the leaf spring elements and extending generally transversely thereof to a second end portion of the lever arm, electrical energization of the stack increasing the stack variable length from the first length to the second length and moving the lever arm in an advancing rotation direction about the second end of the first leaf spring from an initial, rest position and toward an actuated, operative position, the stack returning to the first length when electrically deenergized and the lever arm moving in a return rotation direction from the actuated, operative position to the initial position;
• and
• a resilient regulator, connected between the lever arm and a selected one of the stack and the support member, which resiliently regulates the return rotation of the lever arm relatively to the initial position thereof and comprises a wire link extending substantially parallel to the first and second parallel leaf spring elements and a leaf spring link connected at a first end thereof to a first end of the wire link and extending substantially perpendicularly to the first and second parallel leaf spring elements, the resilient regulator have a first resilient span of movement when the lever arm moves in the advancing rotation direction and a second resilient span of movement when the lever arm moves in the return rotation direction, the first resilient span of movement being greater than the second resilient span of movement.

An electromechanical actuator, comprising:

• an electromechanical element comprising a support member and an electromechanical actuator member disposed in parallel, spaced relationship and extending in a first direction, the actuator member having a first length in a rest condition and a second, increased length in an electrically energized condition;
• first and second driver elements respectively connected to and extending from the support and electromechanical actuator elements in spaced parallel relationship in the first direction and having corresponding first and second end portions disposed selectively at first and second different relative positions in the first direction corresponding to the rest and electrically energized conditions, respectively, of the actuator member;
• a lever arm having a driven end and an actuator end, the driven end engaged pivotally with the first and second end portions of the first and second drive elements, respectively, and the lever arm being supported thereby at a rest position in the rest condition of the actuator member and moved thereby in an advancing rotation direction to an actuated position in response to electrical energization of the actuator member, the rest and actuated positions of the lever arm forming different angular relationships of the lever arm relative to the first direction and corresponding movement of the actuator and thereof between rest and actuated positions;
• and
• a resilient regulator comprising a wire link having first and second ends and a leaf spring having a first end connected to the first end thereof and of the wire link, the leaf spring extending from the first end substantially transversely of the wire link to a remote, second end thereof, the resilient regulator interconnecting the lever arm with a selected one of the support and electromechanical actuator elements so as to have a first resilient span of movement when the lever arm moves in the advancing rotation direction to the actuated position thereof and a second resilient span of movement when the lever arm moves in a return rotation direction to the rest position thereof, the first resilient span of movement being greater than the second resilient span of movement.

A printing head for a wire-dot printer comprising:

• a plurality of printing elements;
• a plurality of electromechanical actuators mounted on a common support member and respectively associated with the plurality of printing wire elements, each electromechanical actuator being selectively operable in response to electrical energization to be driven from a rest position and to an actuated position and correspondingly driving said respectively associated printing wire element from an initial position to a printing position and returning from the printing position to the initial position upon deenergization of the electromechanical actuator;
• a common stopper associated with said electromechanical actuators and mounted on said support member and positioned relatively to said plurality of electromechanical actuators for stopping said mechanical actuators at the respective, initial positions thereof when returning from the printing positions thereof toward the initial positions thereof, upon deenergizing said electromechanical actuator;
• and
• a flexible sheet disposed on the stopper so as to be engaged by each electromechanical actuator where returning from the printing position and toward the initial position thereof, and protecting a stopper face of the stopper from being struck and worn by the returning electromechanical actuator, the common stopper having a toothed stopper face and arranged with the flexible sheet and subject to a rotational force when being struck by each electromechanical actuator in returning to the initial position thereof.