Needle drive unit for needle printer - has dished ring on top of housing round armature coil, forming closed magnetic path

摘要

The moving armature forms the drive for the printing needle of a needle printer. The housing (1) forms a closed shape around the coil, with the armature (5) in the middle, and the needle (6) projecting from the end of the armature. Inside the adjusting cap (8) which fits over the end, is a spacer ring (2) on top of which rests a return spring (4). This supports the flanged top (7) of the armature which is held down by a damping layer under the closed top of the cap. The interior of the spacer ring is dished, so as to centre the return spring, and is in contact with the housing so as to form a return flow path for the magnet.