Plate cylinder

1. A plate cylinder to be attached to a rotationally driven plate driving shaft and configured to mount a cylindrical printing plate thereon from a tip end side of the plate cylinder, the plate cylinder comprising:

a plate cylinder main body having a plate mounting surface on which the printing plate is to be mounted;

a flat portion formed into a flat surface positioned radially inner than the plate mounting surface on an outer peripheral surface of the plate cylinder main body along an axial direction;

the outer peripheral surface of the plate cylinder main body includes the plate mounting surface and the flat portion formed as a single surface;

a plurality of hole portions formed in the flat portion side by side in the axial direction in a separated state, wherein the plurality of hole portions are through-holes; and

a plurality of plate contacting members configured to closely contact the printing plate to the plate mounting surface, wherein the plurality of plate contacting members are positioned in the flat portion and move along with a plurality of eccentric cams provided on a rotating shaft,

wherein a plate contacting member of the plate contacting members is fitted in a hole portion of the plurality of hole portions from an inner side of the plate cylinder so as to be movable radially inward and outward of the plate cylinder, and

wherein when the plate contacting member is moved radially outward of the plate cylinder, the plate contacting member having a plate contact surface that is arranged to come into contact with an inner peripheral surface of the printing plate, and when the plate contacting member is moved radially inward of the plate cylinder, the plate contacting member becomes approximately parallel to the surface of the flat portion.

2. The plate cylinder as recited in claim 1 , wherein the plate contacting member is configured such that an outer peripheral surface of the plate contacting member is movable within a range inner than an inner surface of the printing plate mounted on the plate mounting surface.

3. The plate cylinder as recited in claim 1 , wherein the plate contacting member is configured to be fixable at an arbitrary position within a range inner than an inner surface of the printing plate mounted on the plate mounting surface.

4. The plate cylinder as recited in claim 1 , wherein an inner portion of the plate cylinder is formed in a hollow shape.

5. The plate cylinder as recited in claim 1 , wherein the plate cylinder main body is provided with an air ejection hole at a position away from a tip end side by 20 mm to 50 mm, and a surface roughness Ra of the plate cylinder main body is set to 0.025 μm to 0.5 μm.

6. The plate cylinder as recited in claim 5 , wherein a plurality of the air ejection holes is arranged in a circumferential direction on the tip end portion side.

7. A method of attaching and detaching a printing plate with respect to the plate cylinder as recited in claim 5 , wherein attaching and detaching the printing plate with respect to the plate cylinder is performed while ejecting air through the air ejection hole.