Dot matrix printing head for high-definition or high-speed printing

A dot matrix printing head comprising a printing body, a plurality of needles slidable axially in the printing body, first and second matrix elements, respective tips of the needles being guided in two parallel rows by the first and second matrix elements (7, 8) which are disposed side by side, said first matrix element being carried by a first fixed support (11) fixed to the printing body and said second matrix element being carried by a second movable support (12) carried by the printing body and arranged to move the second matrix element parallel to the first matrix element to locate it selectively in a first position, in which the tips of the needles in the two rows are at the same heights for effecting high-speed printing, and in a second position, in which the tips of the needles in one row are disposed at the heights of the spaces between the tips of the needles in the other row in order to effect high-definintion printing, a parallelogram structure, a resilient means (200), a first abutment and a second abutment each provided on and fixed to the printing body, the second movable support (12) being connected to the printing body (2) by said parallelogram structure in which two parallel sides are constituted by the second movable support and by the printing body and other two sides are constituted by respective articulation members which are acted upon respectively by the resilient means (200) which is pre-loaded so as to hold the second movable support normally against the first abutment (22) of the printing body, and an electromagnetic actuator (23) provided separately from said parallelogram structure and being adapted to displace the second movable support selectively against the action of the resilient means into contact with the second abutment (24) of the printing body, said second abutment being opposed to and facing said first abutment.