(57) A matrix printer comprises a printing head which includes a plurality of printing
needles (11) each having a respective electromagnetic maneuvering device (10) by means
of which the needle, carried by a spring-biassed, movable armature (12), can be caused
to carry out a working cycle, which includes a working stroke and a subsequent return
stroke. The maneuvering device (10) is activated by temporarily lowering the magnetomotive
force in the magnetic circuit (12,14) of the device from a previous, constant value.
The previously attracted armature (12) will herewith commence to move in a direction
away from the stationary part (14) of the magnetic circuit as a result of the spring
force acting on the armature. The magnetomotive force is then caused to return to
its previous value. For the purpose of reducing the noise and wear generated by the
armature (12) and to reduce the tendency of the armature to rebound, the armature
is slowed down during the final stage of its return stroke, by again lowering the
magnetomotive force temporarily for a limited part of the time taken to effect the
return stroke.
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