GB1193053A - Electromagnetic Devices. - Google Patents

Abstract

1,193,053. Selective printing. INTERNATIONAL BUSINESS MACHINES CORP. 28 Jan., 1969 [27 Feb., 1968], No. 4666/69. Heading B6F. [Also in Division H1] An electromagnetic print hammer device comprises a leaf spring, incorporating at least a portion of magnetizable material, anchored at one end so that it can be attracted into contact with the shaped pole faces of a plurality of electromagnets arranged side by side transversely to the longitudinal axis of the spring, the shaped pole faces being curved nearest the anchored end of the spring and then changing to a tangent to the curve. As shown, the print hammer comprises a spring 1 which is clamped at its lower end to a non-magnetic member 3a, and at its upper end carries three wafers 6a, b, c of magnetic material applied by plating. A pair of polepieces 7a, b are arranged adjacent to the upper end of the spring and the pole faces are shaped to an arc of a circle over region 8 and to a tangent to the circle over region 9. The lower end of the spring also rests against a further non-magnetic member 3b which is shaped to an arc of a circle over region 10, and has a transverse groove 12 to receive dust. The polepieces 7a, b are linked by a yoke (7, Fig. 2) and a plurality of such structures are mounted side by side and their yokes threaded by a common holding coil (16). The holding coil retains the spring against the shaped faces of the pole pieces which are provided with windings 15a, b which when energized release the spring, the end 4 of which is formed as a print hammer head. The member 3a to which the spring is secured may be moved relative to member 3b to adjust the flight time of the hammer. The magnetic circuit may be modified so that each device is provided with its own holding winding, and the shaped portion of the upper non-magnetic base member (3b) may be provided with transverse grooves to receive dust and to reduce the air suction effect, Fig. 3 (not shown).