GB1331212A - Electromagnetic actuator - Google Patents

Abstract

1331212 Selective printing INTERNATIONAL BUSINESS MACHINES CORP 28 March 1972 [15 April 1971] 14419/72 Heading B6F [Also in Division H1] Hammer impression.-A magnetically operated actuator 10, e.g. for a print hammer comprises a tripartite magnetic core 12 with upper, middle, and lower legs 13, 14, 15 of which 14 has a cylindrical surface profile 16 engaging cylindrical surface profile of armature 18 pivoted about shaft 20. This has upwardly extending arm 22 defining an air gap 2 with upper leg 13 and having a hammer face impacting a ribbon and a document 26 against a movable type member 38. A hook shaped lower end of the armature forms a polepiece 32 abutting and co-operating with lower leg 15, and a permanent magnet 11 forming upper leg 13 (replaceable by an electromagnet winding, not shown) retains armature 18 in a normal rest position, while an operating winding 34 on lower leg 15 also surrounds the polepiece of armature 18 and air gap G1. A flat radial pole face of middle leg 14 co-operates and abuts with a similar face on armature 18. Pulsing winding 34 overcomes the effect of magnet 11 to rotate armature 18 closing gap G1 and operating print hammer 24, until on pulse cessation magnet 11 restores the armature to normal. In a modification (Fig. 2, not shown) the restoring magnet has pole face defining air gap G2, and also having a curved face formed with plural spaced teeth co-operating with a similar curved and toothed portion of the armature; such that the teeth are respectively displaced into overlap in the operated position and are aligned in the normal position. A mathematical analysis of the equivalent magnetic circuit is given (Figs. 3, 4, not shown). Specification 1,331,211 is referred to.