EP1735157A2

EP1735157A2 - Printing cylinder with a plastic sleeve containing carbon fibers

Info

Publication number: EP1735157A2
Application number: EP05706893A
Authority: EP
Inventors: Jan Thorsten Weber; Jürgen VUTZ; Heinfried Hinrichsmeyer; Dietmar Pötter
Original assignee: Windmoeller and Hoelscher KG
Current assignee: Windmoeller and Hoelscher KG
Priority date: 2004-01-15
Filing date: 2005-01-14
Publication date: 2006-12-27
Also published as: WO2005067364A3; WO2005067364A2; CN1960872A; US20070119319A1

Abstract

The invention relates to a cylinder (1, 15, 16) for receiving a printing form, which can rotate about its main axis of symmetry during printing and which has at least one first sleeve (7, 20) that contains carbon fiber-reinforced plastic. The invention is characterized in that the majority of the carbon fibers in the plastic are oriented essentially parallel to the main axis of symmetry of the cylinder (1, 15, 16). The invention also relates to production methods for producing the inventive cylinder.

Description

Cylinder for holding a printing form

The invention relates to a cylinder for receiving a printing form according to the preamble of claim 1. Such printing cylinders, which have a sleeve made of carbon fiber reinforced plastic (CFRP), have long been known. All of these sleeves are produced by winding carbon fiber threads around a winding mandrel in a winding machine and embedding them in a plastic matrix. US 4359356 shows such a device. Recently, a patent was granted for a printing cylinder shown in EP 1025996 B1, which also contains a sleeve with such a wound framework. The advantages of these cylinders have been obvious to the specialist for some time. The low weight and high bending stiffness of the CFRP result in good handling of the cylinders when changing jobs as well as good print quality. A preferred place of use for these printing cylinders is flexographic printing. An exclusive use of these cylinders, however, stands in the way of the high costs of the CFRP sleeves. The costs of a CFRP printing cylinder are often 10 times higher than those of an aluminum cylinder of the same size. These costs come about both because of the high prices for the carbon fibers and because of the long stress on the expensive winding machine.

The object of the present invention is therefore to propose a cylinder for receiving a printing form which contains a less expensive sleeve of the same or better bending stiffness. The task is solved by the characterizing part of claim 1. In all sleeves according to the prior art, the carbon fibers are arranged at a considerable angle to the main axis of symmetry of the sleeve and thus generally the pressure cylinder. The improvement in the bending stiffness of the sleeve through the tensile carbon fibers is optimal if the carbon fibers are aligned parallel to the main axis of symmetry of the sleeve. It is therefore possible to achieve the same bending stiffness with fewer carbon fibers that are wound in less time. The manufacture of such sleeves, which contain axially parallel or approximately axially parallel fibers, can be carried out, for example, using devices such as those shown in US 5213275 or US 5468329. However, it is preferable to produce the sleeves in a so-called pultrusion process which is similar to strand extrusion. With this method, it is possible to align the carbon fibers in a still viscous plastic matrix in a predominantly axially parallel alignment already during the pultrusion process. The extrusion of the plastic-carbon fiber mixture is usually carried out by an extrusion tool and is often further drawn off by a trigger. The plastic matrix hardens into a sleeve or a tube, which can be separated into sleeves. Other extrusion processes are also possible, since long carbon fibers will usually align themselves in a suitable manner in the plastic melt. If the output is sufficient, further cost advantages can be achieved with this process.

However, disadvantages can also arise due to the relatively uniform alignment of the carbon fibers along the main axis of symmetry of the sleeve, which is caused by the quality of the manufacturing process. If the sleeve is subjected to a torsional load - for example when there are changes in speed - it can be seen that the fibers aligned axially parallel can contribute to intercepting the torsional load to a lesser extent than fibers whose alignment has a significant angle to the axis. It is therefore advantageous to equip the pressure cylinder with additional means for absorbing this torsional load. As a rule, these means for absorbing the torsional load will be in an intimate mechanical connection with the first sleeve. For example, a braid or fabric made of a tensile material could be applied - preferably glued - to the inner or outer peripheral surface of the sleeve. The tensile material could be CFRP, GFRP or wire. It is often advantageous if the printing cylinder contains an additional sleeve. It is particularly advantageous if this additional sleeve takes over the function of the means for absorbing the torsional load. In this case, this additional sleeve can be produced using a different production process than the first sleeve. Thus, a first sleeve produced in the pultrusion process can be usefully supplemented with a second sleeve that is wound diagonally to the first sleeve. Even if a further sleeve made of CFRP is wound on a first sleeve produced in the pultrusion process, cost advantages remain over an exclusively wound sleeve, since the torsional forces acting on the pressure cylinder are generally lower than those due to the weight of the cylinder and the tension of the web acting bending forces. This means that a small amount of additionally wound CFRPs is sufficient to compensate for the torsional forces. Due to the cost situation described at the outset, however, the use of GRP (glass fiber reinforced plastic) or a metal sleeve is recommended. The connection between the different sleeves will usually be an intimate, flat connection. Adhesives and, in particular, metal sleeve shrinking methods can be used for the connection. Even if a further sleeve is applied to the first sleeve in a winding process, this additional sleeve remains a further sleeve in the sense of this application, even if it consists of the same plastic and / or carbon fiber material as the first sleeve. The majority of the carbon fibers can be understood to mean more than 50, 80, 90 or 95%. In particular, however, this designation means that the fibers in the first sleeve are produced using a production process which enables such alignment of the fibers. This includes pulltrusion and extrusion processes. However, winding processes are also known which have such an approximately axially parallel alignment of the fibers allow. This alignment can be achieved, among other things, by providing a winding mandrel with winding mandrels at its ends at the end of the winding process, which hold the fibers on these ends. With regard to the means for absorbing the torsional load, it should be emphasized that in addition to the use of further sleeves, the use of rings is also an option. Such rings can comprise the first sleeve or be arranged within the same. Since the outer surface of the printing plate cylinder should be flat on the whole, it is preferable to arrange the ranks on the inner peripheral surface. The rings can consist of a metal such as steel or of a plastic or plastic composite material such as the materials mentioned. They can also be connected to the first sleeve in the same way as the other sleeve (glue, shrink, etc.). Such rings can be hollow to save weight. A metal ring can, for example, be "turned" from the inside, so that its cross-sectional area (in its axial and radial plane) is U-shaped.

Fig. 1 shows a longitudinal section through an impression cylinder according to the invention

Fig. 2 shows a longitudinal section through a second pressure cylinder according to a modified embodiment. Fig. 3 shows a longitudinal section through a third pressure cylinder according to a modified embodiment

Figure 1 shows a pressure cylinder 1, which is composed, among other things, of a mandrel 5 and an adapter 8. The mandrel 5 is an integral part of the printing press and is connected to its drive either directly or via a gear and is rotatably mounted in the machine frame. The storage is single-ended, especially with small printing widths, with larger printing presses one end of the dome is often fixed and the other is quickly detachable. In this way, the adapter 8, which in this exemplary embodiment is composed of the sleeve 7, the fiber 3 and the disks 6, can be reached via the free end the cathedral 5 are deducted. The adapters 8 are exchanged when the printing length that is to be achieved with the printing cylinder 1 is changed. There is a great need for such changes in the printing length, among other things, in flexographic and gravure printing. This is particularly the case when packaging materials such as film webs or beverage cartons are to be printed with these printing methods, since the most varied formats occur in packaging goods.

In flexographic printing, it is customary to apply a flexible printing form to the outer circumference of the adapter. This can be a flat cliché, which is glued on, or a sleeve, which bears a flexible printed image and which in turn is pulled over the adapter 8. Neither sleeve nor cliché are shown here. A sleeve can be pulled over the - that is to say equipped adapter - applied to the mandrel by applying pressure to the openings 10 in the sleeve 7 from the inside of the printing cylinder 1, preferably in the form of compressed air. Then the essentially flexible sleeve can be pulled over the outer surface of the printing cylinder 1. After this process, the pressure is released so that the sleeve is stuck. The pressure medium can be fed into the interior of the printing cylinder 1 via the channel 12 and the openings 11 in the mandrel 5.

It is customary to fix the adapter 8 on the mandrel 5 without twisting. This can be done in a variety of ways. Clamping with wedges, shrinking by heating and subsequent cooling of the disks 6, clamping with hydraulic and pneumatic expansion sleeves etc. are known. The fastening elements 13, 14 are representative of these fastening options. The fastening elements 13 secure the disks 6 on the mandrel 5. In this way, the entire adapter consisting of the rings 6, the sleeve 7 and the fiber 3 can be attached and detached on the mandrel. In contrast, the fastening elements 14 are located in the “wrong place”, since they can only be used to detach the sleeve 7 from the rings 9. The fastening elements 14 are therefore only intended to indicate that in addition to the classic adapter solution, the rings 6 and sleeve 7 simultaneously can be solved, also other possibilities are conceivable. As a rule, it will not be possible to provide both fastening elements 13 and 14 in a pressure cylinder 1.

FIG. 2 shows another, very similar printing cylinder 14. The differences exist in the disks 6, which are indented with respect to the axial ends of the printing cylinder 15, and in the further sleeve 4, which comprises the sleeve 7. This printing cylinder 15 can be used in the same way as the printing cylinder 1.

FIG. 3 shows a further pressure cylinder 16 according to the invention, in which the mandrel 5 has been dispensed with. Accordingly, the printing cylinder 1 is often referred to as a roller. The first sleeve 20, which also stops carbon fibers aligned in the manner according to the invention, is mounted on stub axles 23, 25 with the aid of end disks 21 and 22. In addition to the cylinders shown in the other figures, this cylinder also contains a special type of introduction of compressed air for releasing the sleeves which are often used as carriers of the printed image in flexographic printing. The compressed air is passed through the channels 31 and 32 through the stub shaft 25 and the tubes and pipe sections 28, 26, 27 and 33 to the openings 24. The opening 34 receives its air via a channel 30 which runs around the circumference of the disk 22.

However, the type of air duct shown is not the subject of the present invention, has already been described in DE 19846677 A1 and need not be discussed in more detail here.

In contrast, the means for absorbing torsional loads 2, 3, 4, which are shown in the various figures, are of great importance. Cross sections 2 of fibers 3 can be seen in FIG. These fibers 3 have been applied to the inside of the first sleeve 20. They have been roughly depicted to scale. They are suitable for absorbing torsional loads. It can be CFRP or GFRP fibers but also metal wires. Coarse metal spirals or support rings can also play the role of fibers. The fibers 3 run along the inner wall of the first sleeve 20 and thus from the viewpoint of the viewer behind the mandrel 5. In FIG. 1, the fibers were helical or screw-like along the Wrapped inside diameter of the sleeve 7. In this context, however, it would be better to have several windings with different angles of attack to the axis of the cylinder 1. Of course, when using fibers, it is more common to provide the fibers with a plastic matrix. In this case, a further sleeve 4 is created. Braids of fibers such as carbon fibers can also be attached to the first sleeve 7 and used advantageously. If rings are used at this point, as mentioned, it is advantageous to provide these rings, for example, with a lathe with a U-shaped cross section. It appears most advantageous if the opening of the U-profile points in the direction of the main axis of symmetry of the pressure cylinder 1. Of course, turning the rings is particularly useful for metal rings.

In Figure 2, a further sleeve 4 has been applied to the first sleeve 20, which also serves as a means for receiving torque in this embodiment. Another sleeve could also be attached to the inside diameter of the first sleeve 20.

3 also shows a sleeve 20 with fibers, not shown, running parallel to the axis. A further sleeve 4 or another means for absorbing the torsional load has been omitted here.

Claims

claims

1. cylinder (1) for receiving a printing form which (1) can be rotated about its main axis of symmetry during printing and which (1) comprises at least one first sleeve (20) which contains (20) plastic reinforced with carbon fibers, characterized in that the majority the carbon fibers in the plastic are aligned essentially parallel to the main axis of symmetry of the cylinder (1).

2. Cylinder according to claim 1, characterized in that the angular deviation between the main axis of symmetry of the cylinder (1) and the majority of the carbon fibers is less than 10 °.

3. Cylinder according to claim 2, characterized in that the angular deviation between the main axis of symmetry of the cylinder (1) and the majority of the carbon fibers is less than 5 °.

4. Cylinder according to claim 1, characterized in that ^• the angular deviation between the main axis of symmetry of the cylinder (1) and the majority of the carbon fibers is less than 2 °.

5. Cylinder according to one of the preceding claims, characterized in that the first sleeve (20) contains pultruded carbon fiber reinforced plastic.

6. Cylinder according to one of the preceding claims, characterized by means for absorbing torsional loads (2, 3, 4) which are arranged such that they at least partially absorb the torsional loads which act on the first sleeve in particular when the speed changes.

7. Cylinder according to one of the preceding claims, characterized by at least one further, by a different manufacturing method, and / or made of an alternative material sleeve (4).

8. Cylinder according to the preceding claim, characterized in that the further sleeve (4) consists of a plastic composite material.

9. Cylinder according to the preceding claim, characterized in that the plastic composite material of the further sleeve (4) is wound or spun CFRP or GRP.

10. Cylinder according to the preceding claim, characterized in that the further sleeve (4) consists of metal.

11. Cylinder according to one of the preceding claims, characterized in that at least the first sleeve (20) and the further sleeve (4) are connected to one another are, wherein there is a connection between the outer peripheral surface of one of the two sleeves (4, 20) and the inner peripheral surface of the other sleeve (4, 20).

12. Cylinder according to claim 10, characterized in that the connection consists of an adhesive substance.

13. Cylinder according to one of the preceding claims, characterized in that the length of the plurality of carbon fibers in the first sleeve (20) is in a range between 90 and 100% of the length of the first sleeve (20).

14. Cylinder according to one of the preceding claims, characterized in that the length of the plurality of carbon fibers in the first sleeve (20) sleeve (20) is in a range between 95 and 100% of the length of the first sleeve.

15. A method for producing a cylinder (1) according to one of the preceding claims, characterized in that the first sleeve (20) is produced by pultrusion.

16. The method according to the preceding claim, characterized in that the first sleeve (20) is obtained from a long tube produced by pultrusion, the length of the first sleeve (20) being defined by sawing or an alternative singling process.

17. The method according to any one of the two preceding claims, characterized in that a further sleeve is applied to the first sleeve (20) or the long tube by winding fibers on the outer peripheral surface of the first sleeve or spun, which are embedded in a plastic matrix.

18. Cylinder according to one of claims 6 to 17, characterized in that the means for absorbing torsional loads comprises at least one ring.

19. Cylinder according to the preceding claim, characterized in that at least one ring is arranged within the sleeve 7.

20. Cylinder according to one of the two preceding claims, characterized in that at least one of the rings contains carbon fibers which are aligned along the radial direction of the ring.

21. Cylinder according to one of the three preceding claims, characterized in that at least one of the rings contains metal.

22. Cylinder according to the preceding claim, characterized in that at least one of the rings is a metal ring, preferably a steel ring.

23. Cylinder according to one of the five preceding claims, characterized in that at least one of the rings has a cross-sectional area that deviates from the rectangular shape.

24. Cylinder according to the preceding claim, characterized in that at least one of the rings has a U-shaped profile.