Vacuum transfer apparatus for rotary sheet-fed printing presses

A vacuum transfer apparatus for use in combination with a rotary sheet fed offset printing press having an impression cylinder for applying wet ink to one side of a sheet, and a transfer conveyor having means for gripping and pulling the freshly printed sheet from the impression cylinder and conveying the sheet along a transfer path to a further processing station of the press, said vacuum transfer apparatus comprising:

• a frame defining a vacuum chamber having first and second chamber sections;
• a plurality of support bars mounted on said frame overlying said chamber and arrayed to extend in spaced side-by-side parallel relation;
• means communicating with said vacuum chamber for inducing a negative pressure within said chamber, whereby negative pressure induced within said chamber causes air to flow into said chamber through the spaces between said support bars to draw the unprinted side of a sheet into engagement with said support bars;
• means for producing a differential airflow between the support bars overlying said first section of said vacuum chamber relative to the airflow between the support bars overlying said second section of said vacuum chamber, said differential airflow being greater per unit area into the first chamber section than into the second section of said vacuum chamber;
• and,
• wherein said means for producing said differential airflow comprises a greater airflow spacing between the support bars overlying the first section of said vacuum chamber than the airflow spacing between the support bars overlying the second section of said vacuum chamber.

A vacuum transfer apparatus for use in combination with a rotary sheet fed offset printing press having an impression cylinder for applying wet ink to one side of a sheet, and a transfer conveyor having means for gripping and pulling the freshly printed sheet from the impression cylinder and conveying the sheet along a transfer path to a further processing station of the press, said vacuum transfer apparatus comprising:

• a frame defining a vacuum chamber;
• a plurality of support bars mounted on said frame overlying said chamber and arrayed to extend in spaced side-by-side parallel relation;
• means communicating with said vacuum chamber for inducing a negative pressure within said chamber, whereby negative pressure induced within said chamber causes air to flow into said chamber through the spaces between said support bars to draw the unprinted side of a sheet into engagement with said support bars;
• and,
• wherein said support bars have a plurality of semicylindrical slots disposed at longitudinally spaced locations thereon, with adjacent semicylindrical slots being separated by support bar portions each having a sheet engagable surface, said semicylindrical slots of adjacent support bars being aligned with each other to permit rotary passage of said gripping means.

A vacuum transfer apparatus for use in combination with a rotary sheet fed offset printing press having an impression cylinder for applying wet ink to one side of a sheet, and a transfer conveyor having means for gripping and pulling the freshly printed sheet from the impression cylinder and conveying the sheet along a transfer path to a further processing station of the press, said vacuum transfer apparatus comprising:

• a frame defining a vacuum chamber;
• a plurality of support bars mounted on said frame overlying said chamber and arrayed to extend in spaced side-by-side parallel relation;
• means communicating with said vacuum chamber for inducing a negative pressure within said chamber, whereby negative pressure induced within said chamber causes air to flow into said chamber through the spaces between said support bars to draw the unprinted side of a sheet into engagement with said support bars;
• and,
• a curved back plate mounted on said frame and interposed between said support bars and said vacuum chamber, said back plate being intersected by a plurality of apertures providing airflow communication between the vacuum chamber and the spaces between adjacent support bars.

In combination with a sheet fed rotary offset printing press having an impression cylinder for applying wet ink to one side of a sheet, and a transfer conveyor having means for gripping and pulling the freshly printed sheet from the impression cylinder and conveying the sheet along a transfer path to a further processing station, vacuum sheet transfer apparatus comprising:

• a frame having top and bottom end panels and laterally spaced side panels interconnected with a rear panel to define an internal vacuum chamber, said frame being positioned adjacent the impression cylinder, wherein said vacuum chamber includes an initial chamber portion and a final chamber portion, said initial chamber portion being disposed closest to the impression cylinder, and means for providing a greater airflow per unit area into said initial chamber portion than that into said final chamber portion;
• a plurality of elongated support bars mounted on said frame side panels overlying said vacuum chamber and arrayed to extend in spaced side-by-side parallel relation;
• means communicating with said vacuum chamber for creating a negative pressure within said chamber, whereby said negative pressure within said chamber causes air to flow into said chamber through the spaces between said support bars to draw the unprinted side of a freshly printed sheet into engagement with said support bars;
• and,
• wherein said means for providing a greater airflow includes a greater effective spacing between said support bars overlying said initial chamber portion than the effective spacing between the remaining support bars overlying said final chamber portion.

A method of supporting a freshly printed sheet during transfer of the sheet from the impression cylinder of a sheet fed rotary printing press to a further processing station of the press comprising the steps of:

• gripping the leading edge of the freshly printed sheet as it emerges from the impression cylinder and pulling the sheet therefrom;
• pulling the freshly printed sheet along a transfer path such that the unprinted side of the sheet passes over a vacuum transfer apparatus having a plurality of support bars arrayed in spaced side-by-side parallel relation laterally across the transfer path;
• applying a pressure differential across the sheet as it is pulled over the vacuum transfer apparatus by drawing air through the spaces between the support bars, whereby the unprinted side of the sheet is drawn into engagement with the support bars as the sheet is pulled along the transfer;
• and,
• imposing a greater pressure differential across the sheet during movement of the sheet over an initial portion of the vacuum transfer apparatus than that imposed across the sheet during movement of the sheet over a remainder portion of the vacuum transfer apparatus.

Apparatus for guiding sheet material along a transfer path in a printing press comprising, in combination:

• a manifold housing having an airflow inlet opening formed therein and having an air discharge port for connection to an air suction pump;
• an array of support bars mounted on said manifold housing, said support bars extending across the airflow inlet opening in spaced apart relation thereby defining a plurality of elongated inlet apertures, said support bars each providing a smooth surface for supporting and guiding sheet material while simultaneously limiting the flow of inlet air through the elongated inlet apertures;
• wherein selected support bars of said array are characterized by alternating segments which are of unequal diameters, thereby defining a plurality of elongated inlet apertures of unequal flow areas extending across the airflow inlet opening between adjacent support bars;
• and,
• wherein said array of support bars includes a first support bar group and a second support bar group, the support bars of said first group having greater spacing separation than the spacing separation of the support bars in said second group.