An actuator for a wire matrix printer including a plunger which is mounted in a frame for reciprocal movement between first and second positions therein, and the plunger has a print wire fixed thereto by a special swaging technique. The plunger is moved to and held in the first position against the bias of a special spring by a permanent magnet. When the actuator is to be fired, a neutralizing coil is energized to nullify the holding effect of the magnet, enabling the spring to accelerate the plunger towards the second position (towards a platen). The spring is disconnected from the plunger after it is accelerated, enabling the plunger and print wire attached thereto to travel ballistically at least part of the way to the second position from the first position.

A wire matrix printer includes a print head having one or more banks of a plurality of generally horizontal, vertically spaced print wires arranged parallel to each other for linear reciprocation toward and away from a recording surface by associated actuators. The print wires in each bank are of progressively varying length so that the wire associated with the actuator furthest from the recording surface is the longest and each adjacent wire is a predetermined amount shorter than the preceding wire. Outer or actuator ends of the wires define a vertically spaced and stepped array. The actuators in each bank are also in an array vertically spaced and stepped and are respectively coupled to the outer print wire ends by armatures. The inner or printing ends of the wires define a vertically spaced, nearly planar array near the recording surface, and a spaced, planar array at such surface. If there is more than one bank of print wires, the banks are angularly spaced from a line extending perpendicularly from the recording surface, and the inner ends of the wires in each bank are alternately interleaved near the recording surface. The actuators in each bank include the armatures, as well as torsion springs, a pair of pole pieces, a permanent magnet and an electrical coil. The armatures are mounted to the pole pieces by both the torsion member and the magnetic attraction of the permanent magnet for generally horizontal, pivoting movement. The pole pieces are magnetized by the permanent magnet to normally attract and hold each armature adjacent thereto against the action of its associated torsion spring thereby storing potential energy therein. The flux of the permanent magnet is selectively counteracted, or neutralized or cancelled for a selected armature by energization of its associated coil to rotate the armature on and about one of its pole pieces for impacting the inner end of the print wire coupled thereto against the recording surface due to conversion of the potential energy stored in the torsion spring to kinetic energy of the armature. Further details relate to the positioning and geometry of the print wires, the armatures, the pole pieces, the permanent magnets, and the coils in certain environments, such as in print heads of a wire matrix printers.

A dot matrix impact print head uses a combination of cooperating forces produced by a deflected spring and dual electromagnetic fields to increase the striking force of a printing wire or needle element without adversely affecting operating frequency capabilities.

Device for marking or writing a parallel bar code onto a document such as a postal article, comprising a number of parallel separately electromagnetically selected printing-styli and cooperating spring, crank, lever, and stop means for moving the end of each selected stylus toward and across or along the surface of the document to write or mark a bar thereon.