GB1466555A - Electromagnetic stylus actuator for a stylus printer - Google Patents

Abstract

1466555 Electromagnets ITT CREED Ltd 27 Aug 1975 35364/75 Heading H1P An electromagnetic actuator for a stylus of a matrix printer comprises opposed polepieces 11a 11b carried by a magnetic yoke 12 with inwardly facing polepieces; the gaps therebetween being surrounded by a radially polarized permanent ring magnet 12 and containing an armature 14 carried by stylus 15 slidable in axial bores of the polepieces. Energizing windings 16a, 16b are located in the spaces bounded by the polepieces and a threaded extension enables the device to be fixed to a printhead carrier (not shown). With the armature in its median rest position flux from the magnet traverses the armature equally in opposed directions (Fig. 2, not shown) and an energization of the windings in series (Fig. 3, not shown) a flux traversing the armature in a single direction is produced to respectively weaken or strengthen the corresponding fluxes of the permanent magnet. Thus the armature moves in a sense dependent on the sense of the excitation of the coil, and remains in situ and in energization until translated by reverse excitation to the opposite polepiece where it remains. In a modification (Fig. 4) a polepiece 41a carries the winding and is opposed by vestigial unwound polepiece 41b; the polepieces being connected by a magnetic yoke 42 and the gap surrounded by a radially magnetized annular rare earth permanent magnet carried by the yoke. An armature positioned in the gap carries a stylus extending through an axial bore of polepiece 41a which is threaded to engage a printhead carrier (not shown). An energizing winding 46 surrounds polepiece 41a.