Plate cylinder and plate mounting device

1. A plate cylinder comprising:

a cylindrical plate-mounting surface on which a cylindrical printing plate is capable of being fitted from a front end side and mounted,

a plate fixing member mounting surface having a flat surface arranged on an outer circumferential surface of the plate cylinder and bordered by the cylindrical plate-mounting surface, and

a front stopper provided at an end portion of the front end side, wherein the front stopper includes a stopper main body and an operation permissible hole,

wherein the front stopper is configured using the operation permissible hole to regulate a rotation of the stopper main body to switch the front stopper between a protruding orientation in which at least a portion of the stopper is positioned so as to protrude to an outside of the plate fixing member mounting surface in a radial direction and to come into contact with a circular plane surface end portion of the fitted cylindrical printing plate, and

a retracted orientation in which an entire stopper is positioned to an inside of the plate fixing member mounting surface in the radial direction.

2. The plate cylinder as recited in claim 1 , further comprising:

a plate fixing member provided in the plate fixing member mounting surface on the outer circumferential surface of the plate cylinder so as to move radially inward and outward and configured to contact with an inner surface of the printing plate and to bring the printing plate in close contact with the plate-mounting surface to fix the printing plate to the plate-mounting surface,

wherein the front stopper switches the orientations in conjunction with a radially outward movement of the plate fixing member.

3. The plate cylinder as recited in claim 2 ,

wherein the front stopper switches the orientations in conjunction with a rotational movement of a rotation shaft configured to movably operate the plate fixing member.

4. The plate cylinder as recited in claim 2 , wherein the front stopper and the plate fixing member are separated from each other.

5. The plate cylinder as recited in claim 1 ,

wherein the front stopper includes a fixing mechanism configured to fix the protruding orientation.

6. The plate cylinder as recited in claim 1 , further comprising:

an end stopper provided on a base end side opposite to the front stopper.

7. A plate-mounting device equipped with the plate cylinder as recited in claim 1 .

8. The plate cylinder as recited in claim 1 ,

wherein the operation permissible hole is formed to fit a regulating member.

9. The plate cylinder as recited in claim 8 , wherein the regulating member is in contact with a first end portion of the operation permissible hole in the protruding orientation and in contact with a second end portion of the operation permissible hole in the retracted orientation.

10. The plate cylinder as recited in claim 7 ,

wherein the stopper main body includes a circular hole formed in a central part thereof.

11. The plate cylinder as recited in claim 7 ,

wherein the stopper main body includes a notch part.

12. The plate cylinder as recited in claim 11 ,

wherein the notch part is located opposite the operation permissible hole.

13. The plate cylinder as recited in claim 1 , wherein the operation permissible hole regulates the rotation of the main stopper in a range of 180 degrees.

14. The plate cylinder as recited in claim 1 , wherein the operation permissible hole penetrates the front stopper in a thickness direction.