Patent ID: 6490972
Filing Date: 2002-12-10
Classification: B41F,B41M

Abstract:
An offset printer comprising:a frame; a plate cylinder rotatably supported by the frame and having a peripheral surface sectioned into at least two plate segments extending between ends of the plate cylinder; a plurality of ink supply units each supplying a different colored ink, the ink supply units being provided in one-to-one correspondence with the plate segments, and each ink supply unit including an ink roller contactable with its corresponding plate segment so that the at least two plate segments receive inks of different colors; and a moving mechanism provided for each ink supply unit and supported on the frame and connected to the ink roller of each ink supply unit for moving the ink roller into contact with the corresponding plate segment and for moving the ink roller out of contact from each non corresponding plate segment, wherein the at least two plate segments include a first plate segment having a semicircular cross-section and a second plate segment having a remaining semi-circular cross-section, and wherein the moving mechanism comprises: a support arm pivotally movably supported on the frame and rotatably supporting the ink roller, a pivotal movement of the support arm moving the ink roller into contact with and out of contact from the plate cylinder; a cam member pivotally movably supported on the frame and having one end contactable with the support arm and another end provided with a cam follower, a pivotal movement of the cam member pivotally moving the support arm; and a generally circular center cam disposed coaxially with the plate cylinder and positioned therebeside, the circular center cam comprising a first radius cam face provided at a rotation phase equal to the first plate segment, and a second radius cam face having a radius different from the first radius and provided at a rotation phase equal to the second plate segment, the cam follower being in contact with the first radius cam face for contacting the ink roller with the first plate segment, and the cam follower being in contact with the second radius cam face for moving the ink roller out of contact from the second plate segment.