Printing plate unloading apparatus and method

Apparatus according to any preceding claim, wherein the extraction member comprises a fixed bar extending across the width of the plate cylinder adjacent to its surface.

Apparatus according to any preceding claim, wherein the extraction bar includes a lip upstanding from an edge thereof to engage the partially extracted leading edge of printing plates and fully extract the leading edge from the plate cylinder to complete the removal of the printing plates from the plate cylinder.

Apparatus according to any preceding claim, wherein the plate loading/unloading head is also configured to insert the trailing edge of printing plates into a lock up slot of a plate cylinder subsequent to manual insertion of the leading edge, the plate loading/unloading head including a pusher element movable between retracted and extended positions to deflect the trailing edge of printing plates held by the suction cups toward the plate cylinder, when the plate loading head is in a raised position, so that the deflected edge slides into the trailing edge lock-up slot when the suction is deactivated or the plate loading head is lowered from its raised position back onto the plate cylinder.

A method of removing one or more printing plates each having leading and trailing edges located in a lock-up slot in a plate cylinder of a rotary printing press, from said plate cylinder, comprising the steps of:

• (d) extracting the trailing edge of the printing plates from a lock-up slot of a plate cylinder;
• (e) partially extracting the leading edge from a lock up slot of a plate cylinder and,
• (f) rotating the plate cylinder so that an extraction member engages a portion of the leading edge of the printing plate protruding from the lock up slot following its partial extraction, to remove of the printing plate from the plate cylinder and leave the removed plate, hanging by its leading edge, on the extraction member.

A rotary web-offset printing press including a plate cylinder defining a plurality of individual printing plate positions thereon and apparatus for removing printing plates from said individual printing plate positions or, for locating printing plates in said individual printing plate positions, the apparatus including a discrete vacuum circuit associated with each individual printing plate position so that a negative pressure is generated within a vacuum circuit associated with an individual printing plate position when that vacuum circuit is closed by the presence of a printing plate in that individual printing plate position, wherein the plate cylinder is configured so that closure of a vacuum circuit and generation of a negative pressure is prevented when no printing plate is present in an individual printing plate position on the plate cylinder, the press including means for detecting the generation of negative pressure in each vacuum circuit and for providing information relating to the outcome of that detection to an operator to enable the presence of a printing plate in each individual printing plate position to be determined.

A method of determining the presence of a printing plate in a plurality of individual printing plate positions on a plate cylinder of a rotary web-offset printing press comprising apparatus for removing printing plates from said individual printing plate positions or, for locating printing plates in said individual printing plate positions, the apparatus including a discrete vacuum circuit associated with each printing plate position so that a negative pressure is generated within a vacuum circuit associated with an individual printing plate position when that vacuum circuit is closed by the presence of a printing plate in an individual printing plate position, and the closure of a vacuum circuit and generation of a negative pressure is prevented when no printing plate is present in an individual printing plate position, the method including the step of detecting whether a negative pressure is generated within a discrete vacuum circuit associated with each individual printing plate position and for supplying information relating to the result of that detection to an operator.