| 摘要 |
An impact print head for a matrix printer employs the usual set of wires slidably mounted in the head which are selectively extended from the working end of the head toward a platen by energizing solenoid actuators. However, in lieu of the usual solenoid strikers, return springs therefor and print wire return springs, a single set of unitary ferromagnetic spring arms connected directly to the print wires and positioned opposite the solenoids mounted in a unitary solenoid frame assembly. Also a shunt plate is mounted in the head and positioned on the opposite sides of the spring arms from the solenoids. The shunt disk and frame assembly shape the magnetic flux pattern from each energized solenoid so that a maximum number of flux lines from each solenoid intercept the associated spring arm to attain maximum dynamic print range and efficiency. Higher print speed may be attained by preloading each spring arm toward its associated solenoid and substituting for the shunt disk, a set of permanent magnets positioned on the opposite sides of the spring arms from their solenoids. Their magnetic field strengths are such as to overcome the self-biases of the associated spring arms so that each spring arm, when quiescent, is spaced from its solenoid and contains appreciable potential energy. When energized, each solenoid produces a field which is opposite to and at least equal in strength to that produced by the corresponding permanent magnet so that the potential energy stored in the associated spring arm is released as kinetic energy which helps to rapidly move the spring arm to promptly extend the associated print wire.
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