| 摘要 |
A dot-matrix printing device for a printing office machine, comprising a series of striking bars in the proximity of the recording medium movable transversely of the medium for printing dots in different locations. The bars are adapted to be actuated by the armatures of corresponding electromagnets for impressing individual dots of characters. The striking bars are guided in the proximity of the recording medium by a movable guide which effects the transverse movement and each electromagnet has a fixed core and a movable armature in articulated engagement with the corresponding bar. Each armature is provided with an actuating spring which tends to move the armature away from the core of the electromagnet. A permanently magnetized rubber establishes a bias magnetic flux such as to keep the armatures at rest in opposition to the action of the actuating springs and a plurality of windings can be energized selectively to generate a flux opposed to the bias flux so as to allow the actuating springs to move the armatures away from the cores for impression of the dots. The device further includes a reloading member which acts on the armatures to bring them back into contact with the cores of the electromagnets. |
