Plate lockup apparatus for printing press

A plate lockup apparatus for a printing press, comprising:

• a lockup table supported on a bottom surface of a gap in a circumferential surface of a cylinder, the lockup table being movable forward and backward in a direction perpendicular to an axial direction of said cylinder, the lockup table extending in the axial direction of said cylinder;
• a gripper plate swingably and pivotally supported on said lockup table such that a gripper surface thereof opposes said lockup table, said gripper plate having a substantially L-shaped section constituted by a horizontal member extending in a circumferential direction of said cylinder and a vertical member extending in a radial direction of said cylinder;
• a cam shaft, disposed between said lockup table and a side wall surface of the gap corresponding to said lockup table, the cam shaft extending in the axial direction of said cylinder, the cam shaft being rotatable for closing the gripper surface of said gripper plate;
• a transmission pin, supported in a pin hole with a step portion formed in said lockup table, the transmission pin having a head portion contacting a cam surface of said cam shaft and a distal end portion contacting said vertical member of said gripper plate, the transmission pin moving forward and backward in accordance with rotation of said cam shaft;
• a first spring member for biasing said transmission pin toward said cam shaft;
• and
• a second spring member for biasing said lockup table toward said cam shaft,
• wherein:
• a first partial rotation of the cam shaft causes the transmission pin to move forward in said pin hole, the distal end portion of the transmission pin acting on the vertical member of the gripper plate causing the gripper surface of the gripper plate to close, the first partial rotation of the cam shaft lasting from a time when the gripper surface of the gripper plate is at least partially open until the transmission pin is moved forward by a predetermined distance and the head portion of the transmission pin abuts the step portion of the pin hole;
• a second partial rotation of the cam shaft causes the transmission pin to initially move the lockup plate forward and subsequently to allow the lockup plate to be moved backward, the lockup table being biased by the second spring member, the second partial rotation of the cam shaft lasting from the time of the end of the first partial rotation and as long as the head portion of the transmission pin abuts the step portion of the pin hole;
• and
• a third partial rotation of the cam shaft allows the transmission pin to move backward in said pin hole, the transmission pin being biased by the first spring member, the distal end portion of the transmission pin allowing the gripper plate to open at least partially.