Printing – Printing members – Rolling contact
Reexamination Certificate
2003-03-14
2004-04-13
Nolan, Jr., Charles H. (Department: 2854)
Printing
Printing members
Rolling contact
C101S377000, C101S378000, C101S477000, C101S212000, C101S216000, C101S415100, C101S404000, C101S382100
Reexamination Certificate
active
06718873
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a proof press for mounting flexographic printing plates.
As is known, an apparatus for the flexographic printing of corrugated cardboard is provided with one or more flexographic printing plates, which are fixed, by way of double adhesive tape, to corresponding mounting and supporting blankets. Generally, these printing plates are mounted on a curved surface, i.e., on a blanket cylinder of a suitable machine.
Printing plates with gradually increased dimensions were used, which gave rise to unwelcome phenomenon such as separation of the printing plate from the blanket, with infiltration of air and formation of pockets, particularly when the blanket with the corresponding printing plate is spread flat. This is due substantially to the generation of two opposite actions: a traction on the blanket and a compression on the thin polyester film provided on the lower face of the printing plate. These opposite actions can reach intensities that overcome the adhesive action of the tape, causing unacceptable bulges in one or more points.
However, it has been noted in this regard that the separation of the printing plate from the blanket is less evident if blanket cylinders are used, having a large diameter and in which therefore the ratio between the length of the printing plate and the length of the circumference of said cylinder is low.
In order to obviate the problem of the separation of the printing plate from the blanket, machines for mounting the printing plate on the blankets in a flat configuration have been devised: in this case, no significant separations are observed when the blanket and the printing plate are laid flat, but when they are wound in a curved configuration onto a cylinder to perform a proof print, one or more bulges of the blanket with respect to the printing plate are observed. A compression on the blanket and a traction on the printing plate are generated and can overcome the adhesion forces produced by the presence of the tape.
Although in this last mounting situation the phenomenon is in practice less conspicuous than observed in conventional mounting on a curved surface, it is known that machines for mounting printing plates in a flat configuration are unable to perform proof prints, which can be performed exclusively on proof presses provided with a blanket cylinder.
SUMMARY OF THE INVENTION
The aim of the present invention is to provide a proof press that is suitable for the mounting of a flexographic printing plate in a curved configuration without the drawbacks noted above, i.e., that is capable of performing proof prints without causing separations of the printing plate from the blanket.
Within this aim, an object of the present invention is to provide a structure that is simple, relatively easy to provide in practice, safe in use, effective in operation, and relatively low in cost.
This aim and this object are achieved by the present proof press for the mounting of flexographic printing plates, comprising a printing cylinder, which is covered by a blanket for mounting at least one of said printing plates by means of double adhesive tape and is movable at right angles to its own axis in order to be placed in contact, along a generatrix, with a respective impression roller for performing proof prints, and optical means for collimating points of said impression roller with respective points of said printing plate viewed directly, characterized in that it comprises a compression device that is adapted to produce the forced adhesion of said printing plate to said double-adhesive tape and to said blanket, so as to provide uniform fixing over the entire contact surface, avoiding the onset of separation or bulging.
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patent: 5488781 (1996-02-01), Van Der Horst
patent: 5666881 (1997-09-01), Zanoli
patent: 6308629 (2001-10-01), Smith
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Sambri Stefano
Zanoli Alberto
Bieffebi S.p.A.
Evans Andrea H.
Josif Albert
Modiano Guido
Nolan, Jr. Charles H.
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