Means for the production of lithographic printing plates

Claim 1

Means for producing lithographic printing plates by image transfer from either a right way reading recording member or a wrong way reading recording member, as by first transferring an image from the recording member to a transfer receiving member and then subsequently transferring the image from the transfer receiving member to an offset member, which means comprise: (a) a conductive base having register means and ancillary register means thereon, the first said register means being arranged and positioned to engage and locate the image receiving member and the recording member on said base and the said ancillary register means being arranged and positioned to engage and locate the offset member on said base, the first said register means and said ancillary register means being spaced apart to allow access to the first said register means while said offset member is engaged on said ancillary register means, (b) a roller having at least a conductive core arranged to move over said base outwards from said register means and return in the opposite direction toward said register means, (c) means to apply an electrical field between said roller and said base, and (d) means to change the polarity of said electrical field whereby the said field has one polarity in relation to the said roller on its outward movement and an opposite polarity on its return movement, said polarities being selected to prevent electrostatic image transfer while said members are pressed into intimate contact during the outward movement of the said roller and to cause electrostatic image transfer during the return movement of the said roller.