GB1149699A - Electromagnetic actuator - Google Patents

Abstract

1,149,699. Selective printing. INTERNATIONAL BUSINESS MACHINES CORP. 28 March, 1968 [12 April, 1967], No. 14869/68. Heading B6F. [Also in Division H1] An electromagnetically operated hammer drive for a printer comprises a hammer 4 attached to a copper ring 12 which completely surrounds one limb 10 of a magnetic core 11. A coil 16 fits over an extension 15 of the core and has a polepiece 17 attached thereto whose legs 17a and 17b lie close to the ring 12. In one embodiment (Fig. 5, not shown) the legs completely surround the ring. The thicknesses of the legs and the ring (d and b) are chosen such that during operation of the hammer, the ring never moves outside the legs. The coil 16 may be fed with D.C. current or may be periodically energized as required to establish a motive magnetic field in the core 11 and partially through legs 17 and ring 12. Upon excitation of coil 13 the hammer 4 is moved across support 22 to push paper 5 against ribbon 6 and type face 8, because of the eddy currents in the ring 12. When the current pulse in 13 is reversed the hammer is withdrawn and the force produced in the ring by the leakage current opposes the force generated by the constant motive flux thereby damping the return stroke. In an alternative embodiment a permanent magnet provides the constant magnetic flux.