| 摘要 |
PURPOSE:To prevent the floating of an armature at a fulcrum by making torque in the periphery of the fulcrum by a hold-down spring fitted inside the fulcrum smaller than that in the periphery of the fulcrum by a return spring mounted inside the fulcrum and increasing torque in the periphery of a stopper by the hold-down spring. CONSTITUTION:The point of application of the force P1 of a return spring 23 is determined to the inside of a fulcrum 18 and the point of application of the force P2 of a hold-down spring 24 to the outside of the fulcrum 18. Torque P1l1 by the return spring 23 in the periphery of the fulcrum 18 is set to a value larger then torque P2l2 by the hold-down spring 24. When a coil 16 is excited, an armature 17 is turned around the fulcrum 18 and attracted to a core 14, and a needle 19 is brought into contact with a platen, thus resulting in printing. The armature 17 is returned by a difference between said torque and a stopper 15 is brought into contact immediately after conduction to the coil 16 is interrupted, and a gap between the armature and the core 14 is determined. Moment through which the armature 17 is floated from a yoke centering around a contact section 25 works at the moment of the return, but the armature 17 does not float from the yoke and is stabilized rapidly by opposite moment of P1l1'+P2l2'. Accordingly, the fulcrum 18 is not abraded by collisions, and the density of printing can be kept constant.
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