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Eddy Current Print Actuator

IP.com Disclosure Number: IPCOM000043244D
Original Publication Date: 1984-Aug-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Wallace, JE: AUTHOR

Abstract

A nonmagnetic cup is used in place of the well-known armature in a print actuator for a wire matrix printer. Induced eddy current in the cup causes an acceleration force which goes to zero as the magnet saturates, permitting free flight of the print wire. As the magnetic flux in the print actuator coil collapses, a reverse accelerating force is imparted to the eddy current cup to retract the cup and wire back onto the magnetic pole piece. As shown in Fig. 1, base 11, poles 13, and coils 15 are analogous to their counterparts in an electromagnetically actuated wire printer. Wire guide 17 is formed so as to permit direct actuation of the print wires by the nonmagnetic metal cups 19. When it is desired to actuate a wire, the coil is energized which causes an increasing magnetic flux in the pole piece 13.

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Eddy Current Print Actuator

A nonmagnetic cup is used in place of the well-known armature in a print actuator for a wire matrix printer. Induced eddy current in the cup causes an acceleration force which goes to zero as the magnet saturates, permitting free flight of the print wire. As the magnetic flux in the print actuator coil collapses, a reverse accelerating force is imparted to the eddy current cup to retract the cup and wire back onto the magnetic pole piece. As shown in Fig. 1, base 11, poles 13, and coils 15 are analogous to their counterparts in an electromagnetically actuated wire printer. Wire guide 17 is formed so as to permit direct actuation of the print wires by the nonmagnetic metal cups 19. When it is desired to actuate a wire, the coil is energized which causes an increasing magnetic flux in the pole piece 13. While the magnetic flux is building up, eddy currents are being generated in the low resistivity, low density material of eddy current cup 19. Aluminum is an appropriate material for cup 19. The eddy currents being generated in the print actuator are the result of the induced EMF divided by the resistance of the eddy current path. The induced EMF is equal to the rate of change of flux times 10 to the minus eight. The generated eddy current reacts with the leakage flux density from the magnetic pole pieces 13, as shown in Fig. 2, resulting in a force equal to the cross product of the current times the leakage of flux. When maximum steady-s...