A printer has a plurality of print hammers displaceable between a rest position and a print position, and respective deformable elastic bodies maintained in a deformed position by each print hammer in its rest position and biasing the print hammer toward its print position. Respective magnetic circuit control means are selectively operable to hold each print hammer in its rest position and to release the print hammer for displacement to the print position by the respective elastic body. Each magnetic circuit control means includes a permanent magnet, a first hammer-hold magnetic circuit including a portion of the respective hammer and a second release magnetic circuit including a release coil operable to release the print hammer from its rest position responsive to a print command signal thereto in a direction to increase the magneto-motive force in the second magnetic circuit with a corresponding decrease in the magneto-motive force in the first magnetic circuit to release the respective print hammer for movement to its print position by the associated elastic body. The second magnetic circuit has a magnetic reluctance greater than that of the first magnetic circuit. The first and second magnetic circuits are connected in parallel with the permanent magnet. In one embodiment of the invention, the greater magnetic reluctance is provided by an adjustable air gap in the second magnetic circuit. In another embodiment of the invention, the two magnetic circuits are connected in parallel with the permanent magnet through a common air gap having a reluctance greater than that of the print hammer portion in the first magnetic circuit.
A hammer mechanism which undergoes reciprocating motion across platen-supported paper webs in a dot matrix printer effects printing by momentarily energizing coils associated with selected resilient hammer elements mounted on a common magnetic structure to neutralize a magnetic field from the common magnetic structure and release the hammer elements from a retracted position. Each end of the common magnetic structure extends to define dummy hammer positions adjacent the first hammer element on each end, providing uniform magnetic field strength to the end hammer elements and to all hammer elements in between. The hammer elements are fabricated and mounted as individual elements of resilient magnetic material with mounting of the elements being accomplished in pairs using a common plate for each pair and screws which have a portion of reduced diameter directly behind the head thereof to provide easy access to the shaft of the screw in the event of breakage during installation. The hammer mechanism is surrounded by a housing having a front face adjacent the hammer elements which is of magnetic material to increase the flux density for hammer elements of given size and which has an opening therein equipped with a filter to permit the exit of cooling air introduced under pressure into the housing while preventing contaminants from getting inside the housing.
An impact printing mechanism is disclosed having an electrostatic clutch assembly, including a rotatively mounted semiconductive coated drum and a conductive band wrapped around the circumference thereof. The printing mechanism includes a printing hammer and a print spring for actuating the printing hammer. When a print command is issued, a voltage is applied to the band to create a field between the band and the drum coating. An electrostatic force is therefore generated when the drum is rotating slowly or synchronous with the drum step motion. That motion will pull the band and compress the print spring. The potential energy stored in the spring is then ready to fire the hammer. A hammer firing command turns off the voltage pulse and discharges the field, releasing the electrostatic holding force instantaneously and firing the hammer by the compressed spring.
A magnetic field is applied to a recording element by energization of an electromagnet or by a permanent magnet to a saturation point of the element material to cause the recording element to move in relation to the electromagnet or to the permanent magnet when the magnetic field is reversed. The polarity opposes or reverses the field to enable a controlled repulsion force and causes the recording element to move in an opposite direction. Magnetic hysteresis is thus utilized in the repulsion and attraction of such an element in both directions of movement.
This invention relates to a wire matrix printer system using a plurality of unique print wire actuator mechanisms operable to print dots on a printing medium. The novelty is in each print wire actuator mechanism using an electro-mechanical combination including (1) a print wire actuator; (2) a permanent magnet collector; (3) a solenoid collector; and (4) a connector assembly holding the aforementioned together as a unit. The print wire actuator includes a print wire assembly having a wire member moved through a printing stroke under the unique combined force of (1) a torsion rod, and (2) a solenoid member. Additionally, the wire member is returned to the rest or starting position under the force of the torsion rod and a permanent magnet collector member.
A variable impact printing mechanism includes a supporting magnetic structure having a plurality of circumferential coils mounted thereon and having a central bore in which a magnetic hammer element is positioned for linear movement to cooperate with a type member positioned adjacent to one end of the bore in order to effect printing on a record member positioned between the hammer and the type member. A controller is provided to energize drivers for the various coils in predetermined sequences to vary the velocity achieved by the hammer element at the end of its printing movement in accordance with varying printing requirements.
