Abstract: An impact printer (30) comprises a printhead (31) traversing along a guide for printing a line on a document (32) of thickness S, and is provided with contrast means for supporting the document (32) against the head (31) and for contrasting the impact force exerted by the latter against the document. The printhead (31) bears a spacing roller (34) which causes the contrast means to yield in order to compensate for thickness S, which varies according to the document (32), and thus maintain the distance D between the head (31) and the document (32) constant. The contrast means comprise a flexible platen (33) attached yieldingly at the ends, of length at least equal to or greater than that of the print line and having a variable section frame so that the pressure generated between the platen (33) and the roller (34) is substantially constant all along the print line.

Abstract: The device comprises an external inertia element which is fixed to a damping member which is coaxially fixed with respect to a shaft of a stepping motor, in such a way that it can rotate together therewith. The external inertia element comprises a metal mass in the form of an annulus of limited thickness. The damping member comprises a first circular flange to which the annulus is fixed, a second circular flange by means of which the device is fixed to the shaft and an annulus of elastomeric material connecting the two flanges. The materials and the dimensions of the device can be calculated, proportioned and pre-arranged in such a way that the device is compact but can stop oscillations of the stepping motor in a very short time. The device is particularly suited to damping the oscillations of a stepping motor which is used for example for positioning a printing member with respect to a print point or for positioning a recording head with respect to a magnetic disc.