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Magnetic Shielding of Print Wire Actuator

IP.com Disclosure Number: IPCOM000051295D
Original Publication Date: 1981-Jan-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Siegl, LR: AUTHOR

Abstract

In the print actuator of the type shown in the IBM Technical Disclosure Bulletin 21, 15 (June 1978), a severe interaction exists when two or more closely packed actuators are fired simultaneously. This interaction between actuators is caused by stray magnetic fields of the energizing coils. These stray fields cause a significant reduction of the useful magnetic flux in the actuator and a degradation of actuator performance.

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Magnetic Shielding of Print Wire Actuator

In the print actuator of the type shown in the IBM Technical Disclosure Bulletin 21, 15 (June 1978), a severe interaction exists when two or more closely packed actuators are fired simultaneously. This interaction between actuators is caused by stray magnetic fields of the energizing coils. These stray fields cause a significant reduction of the useful magnetic flux in the actuator and a degradation of actuator performance.

One way to overcome this degradation of actuator performance is to increase the coil power of each actuator. However, this causes a higher coil operating temperature, making it difficult to remove the generated heat. In addition, the higher coil power requires more power from the supply and more expensive, higher power drive transistors.

A better way to overcome the magnetic interaction problem is to fully enclose each coil in a closed magnetic shield, such as an iron can. In this manner, each actuator becomes magnetically independent of the firing of the neighboring actuators.

Fig. 1 illustrates the side elevation of an actuator, and Fig. 2 shows the details of the individual components of Fig. 1. The actuator consists of a number of elements arranged in a generally concentric manner on bracket 10. The actuator includes a barrel 12 for supporting print wire 14 in proper relationship for printing when mounted in an actuator block and guide. Attached at the leftmost end of print wire 14 is an armature 20 which is arranged against a stop portion 22 of an adjustment screw 24 by forces exerted from a permanent magnet 26. A lock nut 28 retains the adjustment screw 24...