GRAVURE PRINTING METHOD WITH EXCHANGEABLE PRINTING PLATE
A gravure printing system has a roll body extending along and rotatable about a roll axis and formed with a radially outwardly open and axially extending recess. The roll body has an outer surface with a region outside the surface lying on a cylinder centered on the axis. A generally part-cylindrical printing plate fitted over the roll body has angularly adjacent ends extending radially into the recess. These ends of the plate are fastened to the roll body in the recess. The plate also has an outer surface with a part-cylindrical central part centered on the axis and a pair of end parts flanking the recess and angled inward from the central part so as to define with the axis radii that are increasingly shorter from the central part to the recess.
1 . In a gravure printing system, the improvement comprising:
a roll body extending along and rotatable about a roll axis and formed with a radially outwardly open and axially extending recess, the roll body having an outer surface with a region outside the surface lying on a cylinder centered on the axis;
a generally part-cylindrical printing plate fitted over the roll body and having angularly adjacent ends extending radially into the recess; and
means fastening the ends of the plate to the roll body in the recess, the plate having an outer surface with a part-cylindrical central part centered on the axis and a pair of end parts flanking the recess and angled inward from the central part so as to define with the axis radii that are increasingly shorter from the central part to the recess.
2 . The improvement defined in claim 1 wherein the plate is of substantially constant thickness and the roll-body outer surface has a pair of end regions flanking the recess and angled inward from the outer-surface region of the roll body.
3 . The improvement defined in claim 2 wherein the end regions of the roll-body outer surface are substantially planar.
4 . The improvement defined in claim 1 wherein the recess is an axially extending and radially outwardly open groove having generally radially extending flanks to which the ends of the plate are fastened.
5 . The improvement defined in claim 1 , further comprising:
an ink applicator comprising a pair of doctor blades extending parallel to the axis and radially engageable with the outer surface of the plate; and
means for rotating the plate about the axis for movement of the outer surface relative to the doctor blades such that the blades lose contact with the plate outer surface as the recess approaches the blades and then regain contact with the plate outer surface after the recess has passed them.
6 . The improvement defined in claim 5 , further comprising
means for applying a subatmospheric or superatmospheric pressure to the applicator dependent on angular position of the roll body.
7 . The improvement defined in claim 5 wherein the blades have outer edges one of which is movable toward the other to close the applicator.
8 . The improvement defined in claim 1 wherein the printing plate is a gravure plate and has a gravure surface into which gravure cells are embossed.