DE20016311U1 - Printing plate mounting system - Google Patents

Description

AKL Flexo Technik Gpfcö*..* *.« ·· ·· **
33,122 MR

Printing plate mounting system

19.09.2000

The invention relates to a printing plate mounting system for mounting a printing form on a printing press, in particular for flexographic printing.

In the printing industry, printing forms (printing clichés) are mounted on the steel printing cylinders of printing machines. In the context of this application, "printing cliché" is understood to mean any printing surface regardless of the material and application technique. This is usually a fusible photopolymer, rubber or other plastics that can be applied to printing cylinders either as plates or films.

The printing surfaces of the printing plates are raised, particularly in so-called flexographic printing. There are generally truncated cone-shaped printing dots that widen elastically due to the forces that occur during the printing process (so-called "dot gain"). To avoid this undesirable effect, the printing plates are not attached directly to the printing cylinders, but an elastic or compressible intermediate layer is provided that elastically deforms during the printing process and thus reduces the dot gain, which would lead to a loss of print quality.

Traditionally, the production or assembly of a printing form, which is produced using a printing plate, is carried out as follows. A double-sided adhesive, compressible foam tape is applied to a rigid support sleeve made of plastic or metal, to which the printing plate is fixed. The printing form produced in this way is mounted on the printing cylinder either directly or via an adapter sleeve using an air cushion built up using compressed air from inside the printing cylinder.

When using a photopolymer plate, a layer of glue is applied to a rigid support sleeve, onto which a compressible foam tape is wound in a spiral shape.

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Finally, the foam tape is sanded to the correct external dimensions and provided with an adhesive layer. The photopolymer layer is then applied and fused by heat both at the joint and on the substrate, creating a seamless printing form. The printing form thus formed is fixed to the printing cylinder in the same way as described above.

The previously known methods have the following disadvantages.

The conventional production of printing forms using thick-walled sleeves requires a high level of material and a considerable amount of work during production. This in turn leads to a large amount of logistics involved in transporting and storing the printing forms. In the event of damage or errors, the high production costs lead to considerable replacement times and thus to an increased risk for frequently occurring print jobs with tight deadlines.

Conventional printing forms are extremely sensitive to shock due to their high weight.

The use of thin support sleeves cannot eliminate the above problems, since a compressible intermediate layer below the printing plate is necessary to ensure good print quality and therefore a foam layer has to be installed between the support sleeve and the printing plate at great expense.

Based on the state of the art, the invention is based on the object of reducing the production, storage and re-procurement costs in printing form production.

According to the invention, this object is achieved by the features recited in the claims.

The main advantages of the invention are that the printing form produced according to the invention requires less material due to the very small wall thickness,

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which reduces manufacturing costs. Due to the flexibility of the film-like support sleeve, it is possible to dispense with the compressible foam layer that is traditionally provided between the support sleeve and the printing plate, which means that the very considerable amount of work involved in producing this foam layer can be dispensed with. The compressibility of the entire system is achieved according to the invention by the compressible layer being firmly present on the adapter sleeve provided beneath the film sleeve and acting through it due to the flexibility of the film sleeve.

The invention makes it possible for a number of foam adapter sleeves with different parameters (diameter, elasticity and thickness of the compressible layer) to be kept in stock on the printer side and only the printing form manufactured without a compressible layer needs to be mounted.

In addition, the lower weight of the printing plates according to the invention means that the transport and storage of the printing plates is less complex.

The invention is explained in more detail below with reference to the accompanying drawings, in which:

Fig. 1: a printing form according to the invention consisting of a film sleeve with applied printing cliché in side view;

Fig. 2: a side view of an adapter sleeve with foam coating.

In Fig. 1, a printing form 10 according to the invention is shown, which consists of a film sleeve 12, an adhesive layer 14 applied thereto and a printing plate 16. For better visibility, the axial extension of the adhesive layer 14 and the printing plate 16 is shown shorter, while it is generally just as long as the film sleeve 12. The film sleeve 12 has a wall thickness of at most 0.5 mm, preferably between 0.15 mm and 0.35 mm and particularly preferably between 0.25 mm and 0.30 mm. It preferably consists of

The sleeve 12 can be made of plastic, for example, but could also be made of metal or other materials, provided that it is sufficiently flexible, i.e. has sufficiently low rigidity. Polyester is particularly suitable as a sleeve material. The film sleeve 12 can be provided on the outside with micro-grooves 18 running in the axial direction for the drainage of air between the film sleeve and the printing plate when producing the printing form using photopolymer films. These micro-grooves 18 are only indicated in a small area in Fig. 1, but in reality they are provided on the entire outside of the film sleeve 12.

A method according to the invention for producing a printing form using the film sleeve described above comprises the following steps:

at least one nonwoven mat, preferably made of polyester nonwoven, is wrapped around a forming cylinder and impregnated with a resin, preferably vinyl ester resin;

Depending on the type of resin used, the resin is cured using heat or UV light;

a photopolymer film forming the printing plate 16 is placed around the film sleeve 12 and the system of film sleeve 12 and printing plate 16 is placed under negative pressure or vacuum in order to drain the air between the film sleeve 12 and the printing plate 16 via the microgrooves 18 formed;

the printing plate 16 and the film sleeve 12 are baked together under the influence of elevated temperature, whereby the joint of the photopolymer film is fused to form a seamless photopolymer sleeve.

This results in a printing form with very low wall thickness, low stiffness and low weight, which can be mounted on a foam adapter sleeve.

For this purpose, the pressure shown in Fig. 2 is applied to a pressure cylinder (not shown) with air outlet holes on the outer surface.

The foam adapter sleeve 20 is pushed axially, forming an air cushion between the pressure cylinder and the foam adapter sleeve 20. The foam adapter sleeve 20 comprises a supporting layer 22, on the outside of which a compressible layer 24 is applied. The supporting layer 22 is normally made of plastic and has a thickness of 3 to 70 mm. The elastic layer 24 firmly applied to the supporting layer 22 is preferably a foam layer, mainly consisting of PU foam and has a thickness of 0.5 mm to 3 mm.

The foam adapter sleeve 20 has through-holes 26 which lead from the inside of the supporting layer 22 through the elastic layer 24 and ensure that, when pushed onto the pressure cylinder (not shown), compressed air can reach the outside of the foam adapter sleeve 20 from the inside of the pressure cylinder.

The printing form 10 is then pushed axially using an air cushion that forms between the elastic layer 24 of the intermediate sleeve 20 and the film sleeve 12.

The printing form is then aligned and the air supply is turned off, thus completing the assembly of the printing form 10.

During the flexographic printing process, the printing plate can be elastically supported on the compressible layer of the foam adapter sleeve via the thin and flexible film sleeve, which ensures high printing quality. After the printing process has finished, the printing plate can be removed and stored without much effort.

Claims (7)

1. Printing cliché mounting system, consisting of a rigid sleeve which can be fixed on a printing cylinder and whose outer circumference is provided with a compressible layer (foam adapter sleeve) and of a printing form which can be pushed axially onto the foam adapter sleeve and consists of a flexible sleeve (foil sleeve) with a wall thickness of less than 0.5 mm, on which the printing cliché is attached. 2. Printing cliché mounting system according to claim 1, characterized in that the foam adapter sleeve has radial air passages distributed around the circumference for the passage of compressed air from an inner pressure cylinder to the outside of the foam adapter sleeve. 3. Printing cliché mounting system according to claim 1, characterized in that the wall thickness of the film sleeve is between 0.15 mm and 0.35 mm. 4. Printing cliché mounting system according to claim 1, characterized in that the film sleeve consists of natural fiber or plastic, preferably polyester. 5. Printing plate mounting system according to claim 1, characterized in that the film sleeve is provided on the outside with microgrooves running in the axial direction. 6. Printing cliché mounting system according to claim 1, characterized in that the compressible layer of the foam adapter sleeve is a foam layer, preferably made of PU foam. 7. Printing plate mounting system according to claim 6, characterized in that the compressible layer has a thickness of 0.5 mm to 3 mm.