Printing – Printing members – Rolling contact
Reexamination Certificate
2000-03-16
2004-06-15
Colilla, Daniel J. (Department: 2854)
Printing
Printing members
Rolling contact
C101S376000
Reexamination Certificate
active
06748861
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to a printing form permeable to moistening agent and to a printing form cylinder with a printing form permeable to moistening agent for wet offset printing. Furthermore, it pertains to a process for preparing a printing form permeable to moistening agent for wet offset printing. The present invention is used especially in newspaper offset printing and preferably in web-fed newspaper offset printing.
BACKGROUND OF THE INVENTION
In newspaper offset printing, the preliminary printing stage has changed greatly as a consequence of the progressive development of computer technology. Operations that were previously carried out manually have been replaced by so-called computer-to technologies. The current stage of development has been reached with computer-to-plate in newspaper printing. The further development is toward computer-to-press, i.e., toward direct illustration in the press.
A printing form cylinder that can be illustrated directly has been known from U.S. Pat. No. 5,293,817. The printing form cylinder has a porous outer jacket. The moistening is performed through the interior of the cylinder through the porous outer jacket. The porosity of the cylinder jacket is between 20% and 45%. The diameter of the pores of the cylinder jacket decreases toward the outside of the cylinder jacket and is between 3 &mgr;m and 100 &mgr;m. The pores of the cylinder jacket communicate with one another. The illustration is performed according to a thermo transfer or ink jet process by means of an image information transfer means. As an alternative, the use of a heated electrode in the form of a pin in order to apply oleophilic material to the cylinder jacket is mentioned.
SUMMARY AND OBJECTS OF THE INVENTION
The primary object of the present invention is to provide a printing form for wet offset printing that makes possible the simple and accurate moistening and illustration of its ink-transferring surface.
According to the invention, a printing form is provided for a printing form cylinder for wet offset printing. The printing form has an ink-transferring surface that can be illustrated or is illustrated and has passage channels opening on the ink-transferring surface for a moistening agent. The said printing form has a multilayer structure.
According to another aspect of the invention, a process is provided for preparing a printing form for wet offset printing. The printing form is provided with a porous printing layer with an ink-transferring surface and passage channels opening on the ink-transferring surface for a moistening agent. A sublayer, which is permeable to moistening agent and consists of a first material is applied to a printing form carrier. The porous printing layer comprises a second. Other material is applied to the sublayer by plasma spraying.
The present invention pertains to a printing form that is permeable to moistening agent and to a process for preparing such a printing form. The printing form is a printing form for wet offset printing, especially a wet offset rotary printing press. The printing form has a surface that can be or is illustrated for transferring printing ink. The surface will hereinafter be called the ink-transferring surface in both the illustrated and non-illustrated state because of its ink transfer function.
The non-illustrated printing form is moistening agent-friendly or it absorbs moistening agent and is preferably hydrophilic at least on its ink-transferring surface. Like prior-art printing forms as well, the printing form may be, e.g., a printing form plate or preferably a printing form shell, which is fastened to a carrier cylinder, e.g., by means of a prior-art clamping device. Such inherently stable printing forms, which can be or are illustrated, are as such also the subject of the present invention. The carrier cylinder forms the printing form cylinder together with the fastened printing form in this case. The printing form may, in principle, also be a cylinder sleeve. However, the drawback of such a printing form sleeve would be that the carrier cylinder would be able to be mounted rotatably on one side only to make it possible to replace the printing form sleeve in a simple manner. Printing form cylinders that have a printing form that can be or already is illustrated on a cylinder jacket surface, in which case the printing form cannot be removed, are also the subject of the present invention; at any rate, the printing form cannot be removed without destruction in this embodiment.
The printing form is permeable to a moistening agent in a radial direction. In the case of a printing plate that is fastened to a carrier cylinder, the direction is indicated relative to the mounted state. The printing form cylinder including the printing form has a means by means of which the moistening agent can be fed to the printing form. The carrier cylinder is defined according to the present invention as the cylinder body of the printing form cylinder on which the printing form is arranged, either as an independent printing plate or, as was described above, as a fixed part. The moistening agent, especially moistening water, is brought from the rear side of the printing form to the ink-transferring surface of the printing form in both embodiments. Since passage channels for the moistening agent open onto the ink-transferring surface because of the radial permeability of the printing form, the moistening of the printing form, i.e., of the ink-transferring surface, and consequently the ink absorption or repulsion can be brought about by specifically closing passage channels on the ink-transferring surface. No moistening agent can reach the ink-transferring surface in the area of closed passage channels, so that ink is absorbed in the area enclosing the passage channel.
Even though the ink-transferring surface can be prepared, in principle, by perforating an initially closed surface, the printing form preferably has an outer material layer that is porous as the printing layer.
The printing form is built up layer by layer according to the present invention and has an outer printing layer with the surface that can be or is illustrated and an adjacent, subjacent sublayer. The flowability through the printing form preferably decreases abruptly several fold according to the present invention at a boundary layer from the sublayer into the printing layer. The resistance to flow increases correspondingly. These two layers may advantageously consist of different materials and they can also be optimally adapted to different functions as a result according to the present invention as well.
Flowability is defined according to the present invention as the volume of the moistening agent used that flows through a layer of a given thickness relative to a pressure difference acting over this layer per unit of time and area, where the area is defined as the outer surface of the layer. The flowability as a material characteristic will hereinafter be related to the non-illustrated state of the ink-transferring surface.
An abrupt reduction according to the present invention is defined not only as a sudden change in flowability, which change can be considered to be discontinuous for practical purposes, but also as a continuous change. In the latter case, the flowability has a steep gradient at the transition from the sublayer into the printing layer. A transition zone from the sublayer into the printing layer, which can never be avoided altogether in practice, and in which the change in flowability according to the present invention takes place, is always thinner than the printing layer. The steepest possible reduction in flowability from the sublayer into the printing layer is desirable according to the present invention.
According to a process for preparing such a cylinder, the sublayer is first formed, preferably by a mat made of rustproof metal fibers. Such a mat advantageously has high tensile strength and compressive strength compared with materials of equal porosity. Sintered mats of rustproof metal fibers, rolled to a
Jiang Yufan
Riepenhoff Matthias
Colilla Daniel J.
Maschinenfabrik Wifag
McGlew and Tuttle , P.C.
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