stem 80 is pivoted at 79 to an intermediate point of the arms 76 said stem 80 belongs to a respective pneumatic cylinder and piston assembly 81 arranged to press the auxiliary pressure roller 75 against the upper pressure roller 14 so that it forms together with the pressure roller 14 a composite traction assembly which assists in ensuring constant tension of the ribbon or tape material to be printed the lower pressure roller 13 and the upper pressure roller 14 are operated independently from one another by a respective electric motor thereby making it also possible to rotate the two rollers in opposite directions this is particularly advantageous for the application of primers with a 34 kiss coating 34 effect in order to remove the primer ink excess with a contactless process thus it is possible to apply a thicker or thinner layer of primer depending upon the rotation speed in opposite directions of the rollers 13 and 14 the automatic back movement of the rollers every time the machine stops is about 2 mm whereas it is approximately 100 mm for a color changing a positive doctor blade 36 is provided on the engraved cylinder 12 and arranged to eliminate the ink in excess the doctor blade can be actuated by two pneumatic cylinder and piston units 37 which are controlled by the.