A dot-matrix print head (1) wherein a casing (2) houses a number of sliding print needles (3) arranged radially about a central axis (7), respective rocking members (4) associated with the needles (3), and respective electromagnets (5) for controlling the rocking members and for attracting the respective rocking members in opposition to elastic contrasting means (6) to move the respective rocking members selectively into a rest position and a print position; the elastic contrasting means (6) are defined by a substantially U-shaped monolithic annular element (6) made of elastomeric material and having two continuous circumferential projections (21, 22) spaced radially to rest, with respective predetermined loads, on respective first and second contact portions of the rocking members (4); and the annular element (6) is so shaped and sized that the ratio between the respective predetermined loads exerted by the projections (21, 22) on the respective first and second contact portions (23, 24) of the rocking members (4) ranges between roughly 7:1 and roughly 3:1 when the rocking members are in the rest position, and between roughly 3:1 and roughly 1:1 when the rocking members are in the print position.

The line-wise printing of a image composed of an as. sembly of image elements (pixels) by means of a printing nead which embodies a row of N (N 2) printing elements which are arranged along a image line at a mutual distance from each other. The printing stroke is greater than the distance between two neighbonng ponting elements, as a result of which there is created at least one strip in the image in which there are pixel positions which are covered by m (2 ≦ m ≦ N) printing heads. For this stno (or stnos) severai options are then presented for printing the pixels situated within them. A pixel in such a strip can now be pnnted by one or by several of these m pnnung elements, the allocation of one or more of these m printing elements to a position being capable of being chosen as fixed or vanable. Furthermore, it is possible, if a pixel can be printed by several printing elements, to distribute the pixel printing values of the relevant pixel point over these several printing elements according to a fixed or variable distribution code.

A needle printing head comprising a support (11) able to axially guide a plurality of printing needles (15), each of which has one end attached to a mobile armature (16) of a corresponding actuation electromagnet (17) having a ferromagnetic core (18) provided with polar extensions. A separation element (30) is interposed between the mobile armatures (16) and the corresponding polar extensions. The separation element (30) is made of a metal material and comprises elements (33, 34) able to reduce the effects of the eddy currents which are generated by the energizing of every electromagnet (17).

The printing head is of the type in which the tips of the needles are guided in two parallel rows by a pair of matrices (7, 8) disposed side by side and carried, a first by a support fixed to the printing body and a second by a support movable on the printing body so as to move the second matrix parallel to the first from a position in which the tips of the needles in the two rows are at the same heights (high-speed printing) to one in which the tips of the needles in one row are located at the heights of the spaces between the tips of the needles in the other row (high-definition printing); the movable support is fixed to the printing body by a parallelogram structure in which two parallel sides are constituted by the support (12) and the body (2) and the other two sides by resiliently-deformable members (20, 21); pre-loaded, resilient biasing means (200) keep the movable support against a first abutment (22) and an electromagnetic actuator (23), when operated, moves the movable support into contact with a second abutment (24).

A printer head consists of a yoke (11), magnet members (12) mounted to the yoke, a base plate (14) attached to the front of the yoke (11), and a plurality of head pins (17) provided between the yoke (11) and the base plate (14). In this printer head, the head pins (17) are arranged in straight rows, which are inclined at a specified angle to the direction of stroke of the printer head. The base plate (14) is formed with a plurality of through- holes (18) at positions corresponding to the head pins so that the head pins can be advanced and retracted through the through-holes (18) by the action of the magnet circuit.

In a wire dot print head in which each of armatures (2) are attracted toward a core (9) to resiliently deform a plate spring (3) when an associated coil is not energized, and is released and moved forward by the action of the plate spring when the coil is energized, with the rear surface of the armatures (2) being kept in contact with the front end of the fulcrum members; a partition sheet is disposed between the rear surfaces of the armatures and the front ends of the cores and the front ends of the fulcrum members to interrupt transfer of fluid, and to prevent direct contact between the cores and the fulcrum members, and the armatures. The partition sheet comprises a front plastic film (14), a metallic residual sheet (13), a rear plastic film (15) which are stacked in the stated order from the front side to the rear side; and the front film (14) is bonded to the metallic residual sheet (13) over the entire surface of the metallic residual sheet. By bonding the front film and the metallic residual sheet, migration of grease (20) from the rear side to the front side of the partition sheet is prevented, and adhesion of the grease component to the plate spring is also prevented. Moreover, because of the bonding, the metallic residual sheet (13) is prevented from contacting the air and hence from rusting.