Offset printing machine

Claim 1

An offset printing machine having a master cylinder (1) with gripping means (98) for releasably holding a master plate (90) thereon and comprising an actuation member (4) movable from a neutral position to a first position (4A) to activate a master plate feed unit (39) to feed said master plate (90) to the master cylinder (1), said master plate feed unit (39) comprising: a master plate feed tray (89) for supporting a stack of master plates (90); master plate feed means (87) operable, when actuated, to feed said master plate (90) from the stack of master plates (90) on the master plate feed tray (89) toward the master cylinder (1); master plate feed command means (58) having a neutral position in which it is out of driving connection with the master plate feed means (87) and a released position in which it is drivingly connected with the master plate feed means (87) to actuate the master plate feed means (87) only for a defined segment of the rotation of the master cylinder (1) to thereby cause the feeding of said master plate toward the master cylinder; master plate feed cam means (60, 63, 79) having a neutral position in which it is out of driving connection with the gripping means (98) and a released position in which it is drivingly connected with the gripping means (98) of the master cylinder (1) for temporarily opening the gripping means (98) only at a defined rotational position of the master cylinder (1) with respect to the feed tray (89) to cause the gripping means to receive the leading edge of said master plate fed thereto, and for thereafter closing the gripping means to hold said master plate; means (28, 47, 53) for drivingly connecting the actuation member (4) with the master plate feed command means (58) and with the master plate feed cam means (60, 63, 79) for moving the two last mentioned means from their neutral to their released positions when the actuation member (4) is moved from its neutral position (4) to its first position (4A) to thereby feed said master plate (90) from said stack of master plates (90) on the master plate feed tray (89) to the master cylinder (1); and means (18) for selectively disabling the driving connection between the actuation member (4) and the master plate command means (58) and the master plate feed cam means (60, 63, 79) to thereby selectively prevent the feeding of said master plate (90) from the master plate feed tray (89) to the master cylinder (1) when the actuation member (4) is moved from its neutral position to its first position (4A), said disabling means (18) comprising a switching actuation member (18) and means for mounting the switching actuation member (18) on the actuation member (4) for movement between a neutral position with respect to the switching member (4) in which it does not interfere with the driving connection of the switching member (4) with the master said command means (58) and the master plate feed cam means (60, 63, 79) to thereby allow the switching member (4) to cause the feeding of said mater plate (90) toward the master cylinder (1) when the switching member (4) is moved from its first to its second position, and a released position with respect to the switching member (4) in which the switching actuation member (18) disables the driving connection between the actuation member (4) and the master plate feed command means (58) and the master plate feed cam means (60, 63, 79) to thereby prevent the feeding of said master plate (90) from the master plate feed tray (89) in response to moving the switching member (4) to its first position, and to thereby allow for manual feeding of said master plate (90).