| 摘要 |
PURPOSE:To obtain an impact dot head consuming less power and considerably not affected by the magnetic interference by providing a cylindrical member made of magnetic substance in an inner periphery of an electromagnet, a cross section of said cylindrical member in a radial direction being formed in the shape of C. CONSTITUTION:A core part 3a of a base core 3 is provided confronting to the lower part of an armature 2 of an impact dot head. A coil 10 is wound around the core part 3a. A ring-shaped inner bypass 13 which is made of a magnetic substance having a cross section in the shape of C is fixedly pressed into a projection 12a of a rear lid 12 in the inner periphery of the coil 10. When a current runs in the coil 10 during printing, a part of the generated magnetic flux forms a loop A passing the inner bypass 13 which is adjacent to the magnetic flux. However, since the inner bypass 13 is formed in C-shaped cross section, an eddy current cannot be produced in a circumferential direction. Therefore, even when a plurality of coils are simultaneously excited, the loop A can be favorably formed, while less affecting the adjacent cores. Adverse affection by the magnetic interference can be accordingly reduced. Thus, an impact head that can reduce the electric power to be supplied to the coils is obtained. |
