Printing plate unit

A plate cylinder apparatus for a printer comprising:

• a printing plate unit;
• a plate drive shaft;
• and
• a printing plate mounting portion for mounting the printing plate unit to the plate drive shaft, wherein
• the printing plate unit comprising:
• a printing plate having a plate portion provided on part of a surface of a sheet formed of a resilient material and engaging projecting ridges projecting on a rear surface side or a front surface side at both end portions in a longitudinal direction and extending in a width direction;
• and
• a printing plate coupling member coupling both end portions of the printing plate formed cylindrically in the longitudinal direction by engaging the both engaging projecting ridges of the printing plate formed cylindrically, wherein
• a length of the printing plate coupling member is larger than a width of the printing plate so that the printing plate coupling member is provided with a projecting portion projecting from the printing plate formed cylindrically in an axial direction,
• the printing plate unit is fitted to the printing plate mounting portion from one end side, and is demounted from the same one end side by gripping the projecting portion of the printing plate coupling member in a state both end portions of the printing plate formed into a cylindrical shape are coupled to each other by the printing plate coupling member, and
• the printing plate mounting portion includes a cylindrical plate cylinder portion fixedly provided on the plate drive shaft and allows the printing plate unit to be mounted on an outer periphery thereof from a side of a distal end of the plate drive shaft, and the printing plate mounting portion further includes;
• a printing plate coupling member accommodating groove configured to accommodate the printing plate coupling member of the printing plate unit from the side of a distal end of the plate drive shaft, an axial direction positioning stopper portion to which a proximal end portion of the plate drive shaft of the printing plate coupling member is configured to abut, a printing plate coupling member guiding portion configured to guide the printing plate coupling member so as to be movable within a predetermined range in a radial direction of the plate cylinder portion, and a printing plate coupling member biasing apparatus configured to bias the printing plate coupling member radially outward of the plate cylinder portion, wherein
• a depression configured to avoid interference between a printing plate unit retaining apparatus configured to retain the printing plate unit and the plate cylinder portion at the time of mounting and demounting of the printing plate unit at a position radially opposing the printing plate coupling member accommodating groove at an end portion of the distal end of the plate drive shaft of the plate cylinder portion.