Printing system for rotary screen printing including a screen printing cylinder with a flexible surface member - Patent 7336633

Abstract

To provide a screen-printing cylinder compatible with impression cylinders having an elevated gripper system.SOLUTION: A printing system for rotary screen printing includes a screen-printing cylinder 1 having flexible surface elements 6. The flexible surface elements 6 warp upon contact with sheet grippers 4 projecting from an impression cylinder 2, so that it is not necessary to remove the screen-printing cylinder 1 to avoid contact with the sheet grippers 4.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a printing system for rotary screen printing comprising a screen printing cylinder with a flexible surface member, a printing machine for rotary screen printing comprising such a printing system, a screen printing cylinder with a flexible surface member, a method for manufacturing such a screen printing cylinder and the use of such a screen printing cylinder in a rotary screen printing process.

[0002] In the printing industry, the printing method of rotary screen printing has been widely used. In rotary screen printing, a screen printing cylinder generally cooperates with an impression cylinder to form a printing nip. A doctor blade applies the printing medium, for example printing ink, to the substrate via the screen printing cylinder. With rotary screen printing, many different substrates can be printed, for example textiles, wallpaper, paper, cardboard and films. On the one hand, rotary screen printing is used for continuous printing, in which the substrate is transported from roll to roll. One important application of continuous rotary screen printing is the printing of labels. On the other hand, rotary screen printing is also used in sheet-fed presses, in which the substrate is not continuously fed to the press from roll to roll, but in the form of individual printed sheets.

[0003] In the case of rotary screen printing in sheet-fed printing presses, the impression cylinder generally has a gripper system with one or more sheet grippers, which transports and guides the individual sheets past the screen printing cylinder. In order to prevent the gripper system of the impression cylinder, which usually protrudes from the cylinder periphery of the impression cylinder, from hitting the screen printing cylinder, various solutions have been proposed in the prior art. On the one hand, it is known to periodically disengage the screen printing cylinder with a doctor blade, i.e. to increase its distance to the impression cylinder, in order to create space for the raised gripper system. On the other hand, it has been proposed to embed the gripper system in the impression cylinder.

[0004] EP 0 723 864 A describes a rotary screen printing machine for sheet-fed printing, which comprises an impression cylinder having a cylinder groove in which a sheet gripper is embedded.

[0005] In the rotary screen printing method for printing sheets described in WO 9948690, the sheet is guided by a gripper through a coating section.

[0006] WO 0154907 describes a sheet-fed printing press with two screen printing cylinders for double-sided printing of a printing material, in which at least one of the screen printing cylinders has a holding device for the sheet-like printing material and at least one of the screen printing cylinders has a recess on its circumferential surface that corresponds to the holding device.

[0007] The prior art solutions are associated with several drawbacks. The periodic disengagement and application of the screen cylinder and the doctor blade must be precisely aligned with respect to the screen cylinder, the doctor blade and the impression cylinder. The simultaneous disengagement and application of the screen cylinder and the doctor blade is demanding in terms of control technology and mechanics, which can limit the printing speed and can lead to high maintenance frequency for the components involved. The embedding of the gripper system in the impression cylinder places high demands on the gripper mechanism, so that the relatively robust and inexpensive grippers used for raised gripper systems are often not usable. One undesirable effect of an embedded gripper system is an increased fold in the guided sheet, which can lead to problems when transferring the sheet to the next transport roller and when stacking the completely printed sheets.

[0008] The object of the present invention is to provide a printing system which includes a screen printing cylinder for rotary screen printing of sheet-like printing material and an impression cylinder with a raised gripper system, which avoids the disadvantages of the prior art, preferably by fitting a conventional impression cylinder with a raised gripper system and without requiring frequent application and removal of the screen printing cylinder, and preferably by avoiding an increase in the fold of the guided sheet.

[0009] Surprisingly, it has been found that in a printing system including a screen printing cylinder and an impression cylinder with a raised sheet gripper system, if an elastic and / or spring-resilient surface member is provided at the contact point between the screen printing cylinder and the sheet gripper system of the impression cylinder, it is not necessary to disengage the screen printing cylinder before contact with the raised sheet gripper system of the impression cylinder.

[0010] The printing system according to the invention makes it possible to use a conventional impression cylinder with a raised gripper system and places relatively low demands on the control and mechanics of the cylinder. Frequent application and disassembly of the screen printing cylinder is avoided. Wear and maintenance of the components involved is reduced. The guided sheets are not unduly folded during transport due to the printing nip. A visually high quality printed product is obtained.

[0011] Accordingly, the present invention relates to a printing system for rotary screen printing, comprising a screen printing cylinder and an impression cylinder cooperating with the screen printing cylinder, the impression cylinder having one or more surface members protruding from a peripheral wall of the screen printing cylinder, the screen printing cylinder having one or more flexible surface members on its peripheral wall, which surface members cooperate with one or more surface members protruding from the peripheral wall of the impression cylinder.

[0012] In one preferred embodiment, the one or more surface members protruding from the peripheral wall of the impression cylinder are one or more sheet grippers.

[0013] In one further preferred embodiment, one or more flexible surface members of a screen printing cylinder in a printing system according to the invention are configured to be elastically and / or spring-like.

[0014] Within the scope of the present invention, the term "flexible surface element" refers in particular to a surface element which, when subjected to a force by an element protruding from the cylinder wall of the impression cylinder, is brought from its original shape into an elongated shape and which returns from this elongated shape to its original shape again when the force is removed. The flexible surface element or elements are preferably configured elastically and / or spring-elastically. In one particularly preferred embodiment, the surface element or elements are configured elastically.

[0015] Insofar as the flexible surface element is designed to be elastic, it comprises at least one elastic material, preferably one or more plastics, particularly preferably one or more elastomers. Very particular preference is given to vulcanized natural and synthetic rubbers, in particular rubber. Insofar as the flexible surface element is designed to be spring-elastic, it preferably comprises one or more flat springs.

[0016] The invention also relates to a screen printing cylinder which can be advantageously used in the printing system according to the invention.

[0017] Accordingly, the invention also relates to a screen printing cylinder for rotary screen printing, which has one or more flexible surface elements on its peripheral wall.

[0018] In a preferred embodiment, the flexible surface member or members of the screen printing cylinder according to the invention are made elastically and / or spring-like. Suitable materials for the flexible surface members are the materials listed above as suitable.

[0019] In one further preferred embodiment, the flexible surface member or members of the screen printing cylinder according to the invention are formed as elliptical patches, particularly preferably as circular patches.

[0020] In another preferred embodiment, the screen printing cylinder according to the invention has a plurality of flexible surface elements arranged in a row parallel to the cylinder axis of the screen printing cylinder, preferably having two, three, four, five or six flexible surface elements, particularly preferably having three, four or five flexible surface elements.

[0021] The present invention provides a method for manufacturing a screen printing cylinder having one or more flexible surface members on a peripheral wall of the cylinder, the method comprising the steps of: a) providing a sheet of screen printing cylinder material; b) optionally forming one or more apertures in a sheet of screen printing cylinder material; c) attaching a flexible material to the sheet of screen printing cylinder material and / or within one or more openings in the sheet of screen printing cylinder material; d) fixing a sheet of screen printing cylinder material into a cylindrical shape to hold the screen printing cylinder; The present invention also relates to a method comprising the steps of:

[0022] The screen printing cylinder material provided in step a) is usually an already imaged screen printing cylinder material. In principle, however, the formation of the openings in step b) can also take place in a screen printing cylinder material that has not yet been imaged, in which case the image of the screen printing cylinder material usually takes place before or after step c), i.e. after step a) and optionally step b) and before step c), or after step c) and before step d). Image can be carried out by methods that are in principle known from the prior art and usually include exposure, rinsing and drying. Suitable screen printing cylinder materials are commercially available, for example, under the trade name Screeny, from Gallus Ferd. Rueesch AG, St. Gallen, Switzerland. The formation of the openings in step b) can take place by methods that are in principle known to the person skilled in the art, for example by punching, laser cutting or mechanical cutting. The attachment of the flexible material in step c) can take place by methods that are in principle known, for example by gluing. The fixing of the sheet-like screen printing cylinder material in cylindrical form in step d) can take place by methods known in principle to the person skilled in the art, for example by means of a welding device.

[0023] The invention also relates to a printing press for rotary screen printing, comprising one or more printing systems according to the invention.

[0024] The present invention also relates to the use of a screen printing cylinder having one or more flexible surface members disposed on a peripheral wall of the cylinder in a rotary screen printing process. [Brief description of the drawings]

[0025] [Figure 1] 1 illustrates a printing system according to the present invention; [Diagram 2] FIG. 2 illustrates the same printing system as shown in FIG. [Diagram 3] FIG. 1 shows a screen printing cylinder according to the present invention. [Figure 4] FIG. 1 shows a screen printing cylinder according to the present invention. [Diagram 5] 5a, 5b and 5c respectively show different possibilities for attaching a flexible material to a sheet of screen printing cylinder material or into an opening in the sheet of screen printing cylinder material.

[0026] In Fig. 1, a printing system according to the invention is shown. A screen printing cylinder (1) has four flexible surface elements (6) which are arranged in a row parallel to the cylinder axis of the screen printing cylinder (1) (side view). An impression cylinder (2) conveys a printing material, for example a paper sheet (10), which is gripped by a pair of sheet grippers (4). The doctor blade (9) has not yet been removed. The screen printing cylinder (1) and the impression cylinder (2) are aligned with each other in such a way that the flexible surface elements (6) of the screen printing cylinder (1) are positioned exactly above the two pairs of sheet grippers (4) of the impression cylinder (2) during successive rotations of both cylinders (1, 2).

[0027] In Fig. 2 the same printing system as in Fig. 1 is shown, where in this case the pair of sheet grippers (4) which guide the sheet and the flexible surface element (6) are in contact with each other. The doctor blade (9) is removed. Due to the flexible properties of the surface element (6), the surface element (6) is curved inwards when it comes into contact with the pair of sheet grippers (4). After this contact ends, the surface element (6) is curved again to its starting position (not shown).

[0028] 3 shows a screen printing cylinder (1) according to the present invention. The screen printing cylinder (1) has three flexible surface members (6) on its cylinder wall (5). These surface members (6) are arranged in a row parallel to the cylinder axis (7) of the screen printing cylinder (1).

[0029] The screen printing cylinder (1) according to the invention shown in FIG. 4 has only one flexible surface member (6), which extends the entire length of the cylinder.

[0030] 5 shows various possibilities for attaching the flexible material to the sheet-like screen printing cylinder material or into the opening in the sheet-like screen printing cylinder material in step c) of the method according to the invention. In embodiment 5a), the flexible material of the surface element (6) is attached, for example by gluing, to the edge of the opening in the sheet-like screen printing cylinder material which will later form the cylinder casing (5). In embodiment 5b), the flexible material of the surface element (6) is additionally attached to the sheet-like screen printing cylinder material from the other side. In embodiment 5c), no opening is formed in the sheet-like screen printing cylinder material. In this embodiment, the flexible material of the surface element (6) is attached directly to the sheet-like screen printing cylinder material, for example by gluing. [Explanation of symbols]

[0031] 1 Screen printing cylinder 2 Impression cylinder 3. Pressure cylinder wall 4 Sheet Gripper 5. Screen printing cylinder wall 6 Flexible Surface Members 7. Cylinder axis of screen printing cylinder 9 Doctor Blade 10 Sheets

Claims

1. A printing system for rotary screen printing, comprising a screen printing cylinder (1) and an impression cylinder (2) cooperating with the screen printing cylinder (1), the impression cylinder (2) having one or more first surface members (4) protruding from a peripheral wall (3) thereof, the first surface members (4) being one or more sheet grippers, The screen printing cylinder (1) has one or more elastically and / or spring-elastically formed second surface members (6) on its cylinder peripheral wall (5), the second surface members (6) being curved inwards when they come into contact with the first surface members (4); A printing system for rotary screen printing, characterized in that the second surface member (6) is formed as an elliptical patch.

2. A screen printing cylinder (1) for rotary screen printing, cooperating with an impression cylinder (2), The impression cylinder (2) has one or more first surface members (4) protruding from its peripheral wall (3), the first surface members (4) being one or more sheet grippers; The screen printing cylinder (1) has one or more elastically and / or spring-elastically formed second surface members (6) on its cylinder peripheral wall (5), the second surface members (6) being curved inwards when they come into contact with the first surface members (4); A screen printing cylinder (1) for rotary screen printing, wherein the second surface member (6) is formed as an elliptical patch.

3. 3. The screen printing cylinder (1) according to claim 2, comprising a plurality of said second surface members (6) arranged in a row parallel to a cylinder axis (7).

4. A method for manufacturing a screen printing cylinder (1) for rotary screen printing, which cooperates with an impression cylinder (2), comprising the steps of: The impression cylinder (2) has one or more first surface members (4) protruding from its peripheral wall (3), the first surface members (4) being one or more sheet grippers; The screen printing cylinder (1) has one or more elastically and / or spring-elastically formed second surface members (6) on its cylinder peripheral wall (5), the second surface members (6) being curved inwards when they come into contact with the first surface members (4); a) providing a sheet of screen printing cylinder material; b) optionally forming one or more apertures in said sheet of screen printing cylinder material; c) attaching to said sheet of screen printing cylinder material one or more elastically and / or spring-elastically shaped second surface members (6) formed as elliptical patches; d) fixing the sheet-like screen printing cylinder material into a cylindrical shape to hold the screen printing cylinder (1); A method comprising:

5. A printing press for rotary screen printing comprising one or more printing systems according to claim 1.

6. Use of a screen printing cylinder (1) for rotary screen printing in cooperation with an impression cylinder (2), comprising: The impression cylinder (2) has one or more first surface members (4) protruding from its peripheral wall (3), and the first surface members (4) are one or more sheet grippers. The screen printing cylinder (1) has one or more elastically and / or spring-elastically formed second surface members (6) on its cylinder peripheral wall (5), the second surface members (6) being curved inwards when they come into contact with the first surface members (4); The use of a screen printing cylinder (1), wherein said second surface member (6) is formed as an elliptical patch.

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