Printing – Rolling contact machines – Rotary
Reexamination Certificate
1998-09-24
2001-03-27
Asher, Kimberly (Department: 2854)
Printing
Rolling contact machines
Rotary
C101S177000, C101SDIG029, C428S909000
Reexamination Certificate
active
06205920
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an image transfer belt for use in a variable image size offset printing system, and more particularly to a continuous belt construction for transferring inked images from a variable size printing plate to a substrate.
In traditional offset printing processes, the printing press includes a plate cylinder or drum, a blanket cylinder, and an impression cylinder supported for rotation in the press. The plate cylinder carries a printing plate wrapped around the cylinder, which printing plate defines an image to be printed. The blanket cylinder carries a printing blanket having a flexible surface which contacts the printing plate in a nip between the plate cylinder and blanket cylinder. A web or substrate to be printed is passed through a nip between the blanket cylinder and impression cylinder. Ink is applied to the surface of the printing plate which transfers the inked image to the surface of the blanket at the nip between the plate and blanket cylinders. The inked image is then transferred (offset) to the web at the nip between blanket cylinder and impression cylinder.
Typically, the printing plate cylinder is of a fixed diameter, and the printing blanket cylinder is selected to match this diameter. This diameter fixes the maximum length of image which can be printed. Thus, typical offset presses provide printed matter having a fixed size. While smaller sized images may be transferred, this wastes space by leaving unprinted areas on the web, which unprinted areas must be discarded. Depending on the amount of space which is wasted, the economic costs may be substantial.
This waste factor has prevented offset printing press manufacturers from offering press designs that incorporate changeable plate cylinders having different diameters. Unless the blanket cylinder is also changed to match the plate diameter, the amount of wasted areas on the web will still be substantial. However, designing a press in which both the plate cylinder and blanket cylinder diameters are changeable significantly complicates the press design. Further, the labor and down time involved to change the press components adds further costs to the printer. Accordingly, these design limitations have to date restricted owners and users of offset press equipment from serving customers who have needs for various sizes of printed matter. Thus, there remains a need in this art for an offset press which can accommodate various sizes of printed matter without the waste associated with prior designs.
SUMMARY OF THE INVENTION
The present invention meets that need by providing a continuous image transfer belt which is useable in a variable image size offset press system and which is adapted to permit the press to print a variety of different sized printed matter. In accordance with one aspect of the present invention, an image transfer belt is provided and comprises at least one base ply, at least one layer of a compressible material over the base ply, and a surface ply over the layer of compressible material. Preferably, the belt is continuous. However, the belt may also be formed from a flat blanket which includes a seam.
The base ply of the belt forms a reinforcement layer which adds dimensional stability to the belt. The reinforcement material may be a woven fabric ply, a non-woven fabric ply, a polymeric material, a metal, or a spun filament or cord. The fabric, filament, and/or cord may be of either a synthetic polymer or natural material such as cotton. In one embodiment of the invention, the base ply comprises a woven fabric ply which is rigid in a direction across the width of the belt and flexible along the longitudinal axis of the belt. Preferably, the inner surface of the base ply is capable of providing precise registration of any image transferred to the working surface of the belt. The inner surface may be comprised of a high friction material or a material which has been treated or roughened to increase its frictional properties.
In another aspect of the invention, an offset printing system having the capability to print variable-sized images is provided and includes a source of ink; at least one plate cylinder and a replaceable sleeve for the plate cylinder, the replaceable sleeve adapted have mounted thereon a printing plate, the printing plate adapted to receive ink from the ink source; at least one blanket cylinder; an image transfer belt positioned to contact the printing plate in a nip formed between the plate and blanket cylinders; an image transfer belt tensioning system to register the image transfer belt to the blanket cylinder position in the area of desired image transfer; and an image belt cleaning station adapted to remove residual ink from the surface of the image transfer belt. In a preferred form, the belt tensioning system comprises a plurality of tensioning rolls about which the image transfer belt is driven. To control and enhance the dissipation of heat from the belt, at least one of the tensioning rolls may be temperature controlled. Further, to aid in proper image registration in the system, one or more sensing devices may be located to sense the position of the image transfer belt. Through proper feedback control techniques, the printed image may be maintained in proper registration.
Accordingly, it is a feature of the present invention to provide a continuous image transfer belt which is useable in a variable image size offset press system and which is adapted to permit the press to print a variety of different sized printed matter. This, and other features and advantages of the present invention, will become apparent from the following detailed description, the accompanying drawings, and the appended claims.
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Andrew Robert
Dzierzynski Edward P.
McLean Michael E.
Asher Kimberly
Day International Inc.
Killworth, Gottman Hagan & Schaeff LLP
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