Patent ID: 6851363

Claim:
A short inking unit for a rotary printing machine, said short inking unit comprising a plurality of inking unit rolls comprising at least one ink applicator roll which rotates in an ink fountain filled with printing ink and picks up printing ink from said fountain, and a plate cylinder having a printing plate onto which ink can be transferred from said ink applicator roll, each of said inking unit rolls having a circumferential surface which carries an ink layer, a coating having microdipoles provided on one of said circumferential surfaces, and electric means for producing a sporadic DC voltage excitation for producing an electric field which polarizes said microdipoles to a desired extent so that a desired surface roughness of said ink layer on said one of said circumferential surfaces is obtained, and for producing an AC voltage for producing an electric field which depolarizes said microdipoles, whereby said polarized and depolarized microdipoles produce a charge image which permits a desired amount of ink to be transferred from said one of said circumferential surfaces to another one of said circumferential surfaces.