Conveyors for box making machines

Abstract

A vacuum belt conveyor sequentially delivers sheet articles to a digital printer. The sheets are held in position by vacuum on the underside of the sheets through apertures in the belts and covered by the sheets. A plurality of independent plenums on the underside of the belt have chambers respectively communicating with rows of apertures extending along the belt. Vacuum is selectively applied from a manifold only to the plenum chambers that supply apertures that are covered by the sheets so that the ink from the printer will not be directed from its intended position on the sheet by vacuum from adjacent uncovered belt apertures. The sheets are fed to the conveyor in synchronism with the conveyor speed by a timed feeder so that the sheets are carried by the conveyor with a predetermined gap between the sheets and no belt apertures in the gap. A sensor counts the apertures in the belt and activates the feeder at predetermined time intervals.

Description

FIELD OF THE PRESENT INVENTION[0001]The present invention generally relates to conveyors and methods of conveying articles such as sheets, and more particularly in a preferred form, to conveyors for box making machines where the articles are typically corrugated cardboard sheets called “boards” or “corrugated boards” or even “corrugated” alone.BACKGROUND OF THE INVENTION[0002]In the field of box-making, sheets, typically corrugated boards, are sequentially conveyed along a horizontal path to one or more stations along the path where operations like cleaning, printing, cutting, slotting or scoring are performed on the boards in a timed sequence. It is essential that the boards arrive at each of the aforementioned work stations in “registration”, that is, in a predetermined timed sequence. Various examples of corrugated board conveyors including timed feeders may be found in U.S. Pat. Nos. 4,045,015; 4,494,745; 4,632,378; 4,681,311; 4,889,331; 5,184,811 and, 7,635,124 B2.[0003]Several...

AI Technical Summary

Benefits of technology

The present invention provides a new vacuum transfer conveyor for digital printing of sheets that is designed to improve the quality of the printed image without affecting the conveyor belt. The invention also includes a new vacuum control system for controlling the distribution of vacuum to the conveyor belt for holding the sheets without interfering with the printing process. Overall, the invention aims to improve the overall efficiency and quality of the printing process.

Problems solved by technology

However when a digital printer is used instead of the above system, a problem may arise when the boards are conveyed to the printer by a vacuum belt conveyor.

If any of the belt apertures adjacent to the edges of the boards is not covered or closed by the board, ink emitted from these apertures is subject to deviation (“windage”) from its intended position on the image being printed on the board.

If the vacuum used to hold the boards on the conveyor belt is free to divert the flow of ink from the print head to the board to form the desired image, the resulting image will be adversely affected—smudged, distorted, off-color, etc.

Such a result is of course not acceptable in the printing industry.

The operator of the apparatus will open the vacuum (suction) to the apertures covered by the sheets to hold the sheets on the belt but will close the vacuum to the apertures that are not covered by the sheets and are close enough to the edges of the sheet and would otherwise communicate the vacuum with the ink discharged by the print head to possibly cause unwanted deviation of the ink on the sheet being printed.

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