Patent ID: 7578235

Claim:
A unit for printing a web of paper comprising: a frame; at least a first and a second printing group, the first printing group including a first blanket cylinder and a first plate cylinder, the second printing group including a second blanket cylinder and a second plate cylinder; and a throw-off mechanism supporting and moving the first and second printing groups into a first position and a second position, the first position being a throw-on configuration, wherein the first blanket cylinder is pressed against the second blanket cylinder, the first plate cylinder is pressed against the first blanket cylinder and the second plate cylinder is pressed against the second blanket cylinder, the second position being a throw-off configuration wherein the first blanket cylinder is spaced apart from the second blanket cylinder, the first plate cylinder is spaced apart from the first blanket cylinder and the second plate cylinder is spaced apart from the second blanket cylinder, the throw-off mechanism returning a mass of at least one of the first plate cylinder and the first blanket cylinder towards at least one of the second plate cylinder and the second blanket cylinder and vice-versa so that the masses form mutual counterweights between the first and second positions.