| 摘要 |
The head includes a number of electromagnetic structures each one coupled to actuate a respective printing needle. Each structure has a supporting disc to which electromagnets are secured. The magnet forms its magnetic core having sheets on which a locating appendix is provided to fit in a respective aperture in the disc. A coil is wound on each core. A movable armature closes the magnetic circuit, an extension arm acting as a lever arm for the actuation of the needle. The arm is inserted between two posts disposed internally of an armature retainer. The rest position of the lever arm is provided by internal bumps of a resilient ring. Each bump is adjusted in position by an adjusting screw housed in a threaded seat in a rubber ring supported by a cap, on one side of which the ring is vulcanised. Any tendency of the screws to come unscrewed due to vibrations of the head is resisted by the frictional engagement with the rubber ring. |
