Printing needle moving armature drive damping system - has aluminium alloy cap over armature, containing plastics buffer pad

摘要

The moving armature drive unit for the needle of a needle printer includes a damping system to ensure a constant pressure on the needle at high operating frequencies. The housing for the coil with the armature in its middle is fitted with a cap (13) inside which is a pad (11) made of a special rubber, located under the closed top. This pad has a hole in the centre, into which fits the stem of a headed piece (12) which acts as a buffer for the headed end of the armature. This buffer is made of a plastics material with a good impact resistance and the cap is made of an aluminium alloy with a good heat conductivity. The cap has cooling ribs (15) with longitudinal slots (9) and has internal screw threads (19) at the bottom.