| 摘要 |
A printer hammer bank for a dot matrix or other type printer is reciprocated at high speed along a printing position by a low mass, low inertia servo-controlled drive. Precise control is maintained even though a positive drive structure is not used. A reciprocable drive mechanism supporting the hammer bank is mounted to undergo free flight with low friction along a selected axis parallel to a printing line. At each limit of movement, the drive mechanism encounters resilient stop members which reverse the direction of motion of the drive mechanism and included hammer bank following a natural cosine function of the spring mass of the stop members and with low kinetic energy loss. Losses occurring during reversal are compensated by an energy impulse from a coupled linear electromagnetic drive and an associated velocity servo system which eliminates the need for close servo control during reversal, allowing the drive mechanism to rebound naturally. During reversal the servo system which is driven into saturation senses the occurrence of zero motion of the drive mechanism and reverses the direction of energization of the electromagnetic drive. Hammer bank velocity during movement through a print span is sensed, and further kinetic energy is supplied by the servo system as required to compensate for friction losses, braking effects during printing, and other causes of variation in hammer bank speed.
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