| 摘要 |
PURPOSE:To eliminate the need to take into consideration fixing or release of fixing of a carriage at each operation, by a construction wherein a magnetic material is fixed to a part of a carriage, a permanent magnet is provided at an operating end of the carriage, and a magnetic shield shutter for shielding the magnetic field of the permanent magnet in an ON state of a power source in conjunction with a power source switch of the device is provided. CONSTITUTION:The magnetic shield shutter 17 is energized in the direction for opening an opening part 15 by springs 21, and when the power source is turned ON, a plunger 19a is protruded to close the opening part 15 by the shutter 17 against the elastic force of springs 21, the magnetic field of the permanent magnet 18 is shielded, and the attractive force exerted on an iron piece 14 by the magnet 18 is canceled, to set the carriage 2 free. When the power source is turned OFF, the shutter 17 is moved upward to open the open ing part 15, and the magnetic field of the magnet 18 attracts the iron piece 14 to lock the carriage 2 immovably. |
