Safety device for a sheet-fed rotary press

In a sheet-fed rotary printing press of the kind having an impression cylinder carrying the fed sheets and a second cylinder engaging said impression cylinder at a nip, said cylinders being rotated at a first speed by a press drive during printing and being selectively rotated by the press drive at a second reduced speed during maintenance, a safety device comprising a guard which is movable from a predefined safety position shielding said nip, a first mechanically operated electrical switch for preventing said press drive from rotating said cylinders at said first speed during maintenance, a second mechanically operated switch for preventing said press drive from rotating said cylinders at said reduced second speed during maintenance in response to said guard being contacted by a maintenance person and moved from said safety position, a mechanical linkage connecting said first mechanically operated electrical switch and said second mechanically operated electrical switch and said guard, said mechanical linkage being actuated at the end of maintenance to move said guard in a direction away from said impression cylinder and away from said safety position to a predefined second position operating said first electrical switch to enable said press drive for printing, and being actuated at the end of printing and the beginning of maintenance to return said guard to said safety position, thereby insuring both the smear-free printing of the fed sheets and the safety of the maintenance person.

In a five cylinder sheet-fed rotary printing press of a kind having an impression cylinder carrying the fed sheets and second and third cylinders each engaging said impression cylinder, said cylinders being journaled to a press frame, and a press drive for rotating said cylinders at a first speed during printing and selectively rotating said cylinders in a forward and reverse direction at a reduced second speed during maintenance, a safety device comprising first and second guard rails pivotally mounted at their ends to the press frame and disposed near respective ones of the two nips between the impression cylinder and the second and third cylinders, each guard rail being moveable from a respective predefined safety position shielding its respective nip, and means for stopping the press drive in response to either of the guard rails being moved from its respective safety position, wherein said printing press has an access cover which is closed during continuous printing to shield said impression cylinder and is open during maintenance to gain access to said impression cylinder, a first mechanically operated electrical switch operated by the opening and closing of said access cover to enable said press drive for rotating said cylinders at said first speed during printing and to disable said press drive from rotating said cylinders at said first speed during maintenance, said first mechanically operated electrical switch being mechanically operated by the opening and closing of said access cover, a second mechanically operated electrical switch for preventing said press drive from rotating said cylinders at said reduced second speed during maintenance in response to either of said guard rails being contacted by a maintenance person and moved from its respective safety position, and a linkage including a resilient element and abutments limiting the degree of extension and contraction of said resilient element for mechanically connecting said access cover and first mechanically operated electrical switch to said guard rails and said second mechanically operated electrical switch for moving said guard plates away from their respective safety positions in a direction away from said impression cylinder to respective second predefined positions when said access cover is closed, and to return said guard plates to their respective safety positions when said access cover is open, to thereby insure both the smear-free printing of the fed sheets and the safety of the maintenance person.