DE1949550A1 - Attachment for flexible thin pressure plates - Google Patents

Description

W.R. Grace & Co. (Prio J. October 1968 -

ü, S, 764,924 - 14568 - 6523)

New York, N.Y.A.St.A. 1949

Hamburg, September 29, 1969

Attachment for flexible thin printing plates

The present invention relates to fastening flexible thin pressure plates on support surfaces; it relates in particular to shims or so-called Saddle socket to support thin flexible pressure plates.

In printing technology, and especially in newspaper printing, it is common to use heavy printing plates, as they are also used for stereotype printing and which are releasably attached to the circumference of a fixed cylinder roller will. In a known embodiment, several circular arc-shaped pressure plates with internal screws or clamping bolts attached to the printing cylinder. in the in general, it is a question of two cylinder shells that enclose the pressure cylinder.

When printing it is necessary to replace these plates quickly, because large editions are produced in a short time with high-pressure machines that run high, after which the Plates need to be replaced quickly to avoid excessive avoid long downtimes.

A better and more practical suggested method of making printing surfaces is to have a relatively thin plate of, for example, 1.02 mm Applying starch to the surface of a cylinder.

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Such printing plates can be used as a plastic plate or by electrodeposition on a metal plate. However, it is difficult and costly make such printing plates thick enough so that they can be attached with the usual fasteners or can be held. It is still a problem to have such thin printing plates on one To attach the cylinder without large empty areas on the Cylindrical surface to be accepted.

Since the existing printing machines for stereotype printing. plates of metal verhältnismässlg "require thick dimensions, there are considerable difficulties in adapting such printing machines for receiving thin, flexible printing plates. For example, it is required that the new system for the thin plates is formed so that substantially they have the same wall thickness like the normal metallic stereotype plates, so that they can be used with the existing printing devices or printing cylinders.

If a printing cylinder, which is designed to accommodate stereotype plates, is to accept thin, flexible printing plates instead of the usually thicker plates of the stereotype printing, a pad or so-called saddle of sufficient thickness must be used together with the thin flexible printing plate so that the total thickness of Base and flexible printing plate essentially corresponds to the thickness of a conventional stereotype plate. In addition, this pad or saddle should be strong enough to be attached with the usual clamping devices and at the same time be able to withstand the forces that occur in high-performance printing machines.

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The plastic printing plates that are used in the plexographic process and in various gravure or letterpress printing processes generally consist of a surface which has a relatively low durometer hardness of, for example, a Schore hardness A of 25 to 60. Even with a slight pressure exerted, the relatively soft printing surface shifts, making the transferred image look blurry or smeared. On the other hand, materials with a high durometer hardness are unsuitable because they cause the paper to be embossed. One attempt to eliminate these disadvantages consists in using printing plates made of a layer structure made of rubber or plastic with different durometer hardnesses, for example the printing layer having a relatively high hardness and the base layer having a lower hardness. However, such laminates cannot adequately distribute the pressures. If you want to increase the pressure exerted during printing, to compensate for irregularities in the plate, the plate fastening or the printing device, some time is used to set up the press, for example by applying layers of paper in the relevant areas below the printing plate. This is extremely tent-stealing and difficult.

According to US Patent 3,377 9 ^ 9 a new printing plate has been proposed which does not have this' night hurry and which consists of a volume compressible upholstery material and a Layer of polymer »material as a print layer on the compressible material. Thus, a printing plate having a large durometer hardness can be used or any desired durometer hardness to achieve clear and accurate reproduction, but at the same time any irregularities in the plate in which

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Plate mounting, in the printing machine or on paper to compensate and prevent the paper from being embossed.

According to the invention is now a base plate for a Proposed pressure cylinder to which a volurealompressible, resilient element adheres to a surface is attached, which is made of a porous fibrous web consists «which is impregnated with an elastomeric material is »whereby this part has such strength,

that a pressure of at least 0.7 kg / cm must be exerted on the material in order to obtain an initial compression of 50.8 yes , and a residual porosity at 101.6 ax compression of at least about 57 %

In one embodiment, the fiber web can be implemented with a rubber-like layer, such as, for example, made of Buna N in a thickness of 76 to 127 / U and preferably 101 Ai .

The invention therefore proposes a fastening device which is simple and easy to use without the need for complicated printing plates. The invention has other advantages as well with it, which can be seen from the following description.

Although the particular saddle system according to the invention both is suitable for rotary printing cylinders as well as for sheet printing, the invention will be described below in connection with arched saddle pieces, which can be used with rotary printing cylinders.

The saddle piece itself can be designed as a single workpiece and glued to the laminate, which is made of

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a compressible material and a porous one Is a fibrous web that is impregnated with an elastomeric material. Any suitable means can be used to bond the compressible material to the saddle, including adhesives that are produced by heat and pressure to be activated. Chemically activatable adhesives are also suitable.

The cushioning material used in the present invention is a volume compressible compliant product. With volume compression valve a property is referred to, according to which the material is directly dependent on the exercised Pressure can be squeezed without going in other directions a deformation occurs. A non-woven web is preferably used as the cushioning material. The fibers This web can contain natural fibers, such as cellulose fiber or synthetic fibers such as nylon, rayon, and the like ”. Elastomeric foamed materials such as small-sized polyurethanes, silicones or other foams can also be used as cushioning material.

The preferred cushioning material according to the invention is from an impregnated fiber web that connects a large number of very small, evenly distributed ones with one another Has voids or air spaces which are surrounded by solid reinforced fiber / rubber structures. The cavities form areas into which the surrounding material can penetrate when pressure is exerted, so that no Flow of the entire mass occurs and also does not Form pressure zones when reducing the wall thickness. That The material surrounding the cavities, on the other hand, acts like a multitude of small, almost microscopic feathers, which again exert their force in the direction of the track surface «

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An impregnated Paserbahn, especially for the present Invention suitable is in US patent J .147 698.

A particularly preferred cushioning or cushioning material is a porous felt fiber sheet, which is covered with an elastomer Material of the desired strength is impregnated.

Any foamed material that can be used can be made compressible by adding the foam layer encloses between non-stretchable dimensionally stable layers, for example the plastic printing material one side and the saddle surface on the other. others Page.

Since the new upholstery material no longer requires the effort Excessive printing required to remove unevenness in the printing plate surface is also not necessary Embossing of the paper occurs during printing itself and furthermore, there is a distortion of the surface or the image plane significantly reduced or turned off.

example 1

A compressible element was produced by impregnating cotton liner with a total weight of 55 kg with a mixture consisting of a medium aeryl nitrile copolymer latex and 10% by weight melara resin (Parez 6i>), based on the solids content of the aeryl nitrile copolymer. The impregnated paper had a total impregnation equal to the weight of the fiber. The impregnated sheet was dried, lightly calendered and then heated to 149 ° C for about 20 minutes. The compressible material was about -Qyf mm thick. ^m

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The! Compressible sheet was then adhered to a respective saddle and adhered on the surface with a thin flexible printing plate ¹ AU3 a photohardenable polymeric substance. A printing cylinder, which could accommodate two such plates as a cylinder jacket surface, was used to apply a printing plate directly to a saddle piece and to cover the other half of the jacket with a corresponding pressure plate, which had a compressible element according to the invention glued between the saddle and the pressure plate. Both cylinder shells or saddle pieces were attached at the same printing height. «In one pass, 10 layers of paper were wrapped around the printing cylinder. The printing blanket behind the saddle with the compressible element showed no damage. The saddle according to the invention with the compressible element thus results in a shock absorption layer which prevents damage to the printing blanket.

Example 2

The procedure was as in Example 1, but now the compressible element also contained a layer of Buna N with a wall thickness of 0.102 mm above it. One flexible thin printing plate made from a photohardenable polymer mixture was firmly attached to the surface of the Buna N-layer and the printing results were compared with those of Example 1.

An example of a suitable photohardenable mixture for the production of printing plates 1st described in the parallel patent application P 18 02 559 * 7, namely a light-curable polymeric composition consisting of a polyene.

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which has at least two unsaturated carbon / carbon. substance bonds per molecule, a polythiol and an activator such as benzophenone. ·

Of course, other fastening means can also be used other than glue can be used to attach the pressure plate to the saddle piece to which the compressible element is glued. Pressure tests with the flexible thin printing plate showed good ink transfer to the paper with minimal pressure. The plate requires no preparation to enable even color transfer.

The flexible thin printing plate used herein can be made from almost any flexible thin printing plate material. In particular, the flexible thin pressure plates are composed of thin metal sheets, aluminum, steel, copper, brass, magnesium alloys and the like, or are made of a polymeric or plastic material such as synthetic organic resin or polymers, rubber or other desired material.

The saddle or the base plate should be sufficiently thick so that it is sufficiently stiff and not excessive bends when a printing plate is applied or when it is attached to the printing cylinder. A Saddle or plate with a wall thickness of at least 4.77 mm and preferably between 4.77 mm and 9 # 54 mm is generally sufficient, while the flexible plates have a total thickness in the range of 0.25 to 2 mm. The thickness of the saddle is selected so that it corresponds to the total thickness of the pressure plate so that the Print surface is at the desired diametrical height

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located above the outer cylinder surface of the printing cylinder · The saddle can be made of metal or alloys of the type described above for printing plates, or made of hard, semi-solid plastics such as phenol formaldehyde, Acrylic resins, phenolic resins, nylon and the like such as also made of other light materials,

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Claims (1)

P a t e η t a η s ρ r Uc h e 1.) washer plate for printing cylinder «characterized in that a volume-compressible flexible part is adhesively attached to a surface of the base plate and that this part consists of a porous fiber web which is impregnated with an elastomeric material and that this part has such a Festig- ■ 2 It is possible that a pressure of at least 0.7 kg / cm must be exerted on the material in order to achieve an initial compression of 0.05 mm and that the material * has a residual porosity at 0.1 mm pressure of at least 37 % . . 2. Production board according to claim 1, characterized in that that a flexible thin pressure plate is attached to the flexible part. 3. Production board according to claim 2, characterized in that dad the flexible thin pressure plate made of a lioht- hai · tbartn polymeric material. ■ ", ■■ '..' .: '...' _: - ... J, 4. Production board according to claim 3, characterized in that that the photohardenable polymeric mixture consists essentially of a polyene which is at least two Has unsaturated carbon / carbon bonds per molecule, and also contains a polythol and a light activator. 5. Production board according to claim 4, characterized in that 'that the activator is benzophenone " 009817/0439 Base plate according to claims 1 to 5 #, characterized in that a rubber-like material ^{1 is applied} over the base plate in an essentially uniform layer and has a thickness in the range from 0.075 to 0.125 mm. 7 Production board according to Claim 6, characterized in that that the thickness of the layer of rubbery material is 0.1 mm. 8. Production board according to claim 6 or 7> characterized in that the rubbery material is Buna N. 9. production plate according to claims 1 to 8, characterized characterized in that the fibrous web is a nonwoven web is. ue: wy 0098 17/043 9 8AD ORIGINAL Empty ropes