Suction apparatus for printing press

A paper suction apparatus for a printing press, comprising a plurality of suction ports, arranged in an axial direction and provided to a paper convey cylinder, for temporality sucking and holding a paper sheet transferred from an upstream cylinder, and air shutter devices provided to said suction ports on two end sides not used for a suction operation of a small-size paper sheet,

• wherein each of said air shutter devices is constituted by
• a passage block having an air passage through which air for sucking a paper sheet passes,
• a magnetic member arranged around an opening of said air passage, and
• a shutter member consisting of a magnetic material and movable between a closed position where said opening of said air passage is closed and an open position where said opening of said air passage is open, one of said magnetic member and said shutter member being magnetized, and
• said shutter member moves to the closed position to close said opening of said air passage of said passage block by an air suction force and a magnetic attraction force between said shutter member and said magnetic member when the suction operation of said small-size object is performed, thereby preventing air leakage from said suction ports on the two end portion sides which are not used.