GB2409890A

GB2409890A - Roller with thickening strips and elastic sleeve

Info

Publication number: GB2409890A
Application number: GB0427620A
Authority: GB
Inventors: Klaus Theilacker
Original assignee: MAN Roland Druckmaschinen AG
Current assignee: Manroland AG
Priority date: 2003-12-19
Filing date: 2004-12-16
Publication date: 2005-07-13
Anticipated expiration: 2024-12-16
Also published as: GB0427620D0; CH697344B1; DE10360013A1; GB2409890B

Abstract

A paper-guiding roller 1 consists of a roller body 5 with axle journals 3, 4. In order to increase the web tension in the edge regions of the print-carrier web 7 that is to be conveyed, adhesive strips, sleeve pieces or similar materials 6 that enlarge the roller diameter at these points are positioned at these edge regions. An elastic tube 2 is positioned over the paper-guiding roller thus prepared. The elastic tube preferably consists of PTFE, and the paper-guiding roller 1 can be chrome-coated. This arrangement makes the roller easy to clean. Additional thickening portions may also be arranged on the roller if it is to be used for narrower webs, for example quarter webs (figures 2-5).

Description

Roller, in particular a paper-guiding roller for rotary printing machines

The invention relates to a roller, in particular to a paper-guiding roller for guiding at least one print-carrier web in a rotary printing machine, consisting of a roller body and axle journals and at least one thickening strip that radially surrounds the roller.

It is known that when printing or transporting, or conveying, printcarrier webs in rotary printing machines, in particular in web-fed offset rotary printing machines, the use of rollers and cylinders with a cylindrical casing or a cylindrical outer contour entails various disadvantages. For example, disadvantages arise in consequence of the deflection of the rollers, in particular as a result of impression throwon in the case of pull rollers, but also during the transportation of a web, in particular a print-carrier web. It is known, for example, from Patent Specification DE 21 51 650 that the rollers used in offset rotary printing machines can be given a shape that deviates from the cylindrical form. For example, such rollers can be provided with a lateral surface that is concave or convex in longitudinal section.

These measures give rise to advantages during the printing process; in particular the action of transportation of a web can be improved thereby. In principle, such varying profiles can be applied, for example in the case of driven pull rollers and non-driven paper-guiding rollers, as are described in detail in Patent Specification DE 44 36 973 C2.

Roller profiles that deviate from the cylindrical contour are also used in the case of rollers, in particular in the case of paper-guiding rollers, for conveying print- carriers or ribbons consisting in each case of a plurality of printed webs. In this connection, in practice the printer often uses so-called frogs. These are multi-layer adhesive strips that are stuck onto the paper-guiding rollers in order to enlarge the diameters of the rollers at these points. These adhesive strips are usually set in such a way that they come to lie exactly at the edge of the webs that are to be printed or exhibit their effectiveness at that point. As a result, a considerably smoother web run is produced.

The reason for the more favourable or smoother run of the web lies in the fact that in the course of the width of the web the web tension is not uniform, but usually has the highest web-tension value in the centre of the web, sometimes dropping to a very great extent towards the edge.

As a result of enlarging the effective roller diameter at the edge of the web there is more or less a lengthening of the web path at these points in relation to the centre of the web at which the roller diameter is smaller, as a result of which the web tension is also increased at the edge of the web. Thus the drop in web tension at the web edge in relation to the centre of the web can be reduced at least in part. As a result of this known measure an improved, that is, smoother, web run can already be achieved.

The change in the cylinder or roller profile mentioned earlier, where in the centre of the roller a smaller diameter is provided than at the edge, this change also often being applied in the field of illustrations since in that case the web has a higher tension when travelling, brings about an increase in costs, since such rollers are more expensive to produce than rollers that have a cylindrical outer profile. The outlined use of adhesive strips as practiced by the printer could be found in particular in the case of newspaper-printing machines, because there a plurality of paper-guiding rollers are required and thus the production of these paperguiding rollers would be particularly expensive in the way that has been outlined above. Even if in the field of newspapers for cost reasons rollers are already produced from thin- walled unmachined tubes, conical machining of these tubes would also be very expensive. On the other hand, the manual application of the so- called frogs, that is, sticking on multi-layer strips, is time-consuming and thus ultimately again very burdensome in terms of costs and, moreover, added to this there are cleaning problems, since rollers with adhesive strips stuck on them cannot be cleaned as easily as rollers that have a smooth roller surface.

With this background, the object of the present

invention is to set forth a cost-effective roller, in particular a paperroller for web-fed offset rotary printing, for which a cylindrical roller casing can be used and with which roller-surface contours that deviate from the cylindrical form can be produced, and which is nevertheless easy to clean.

In the invention an elastic tube is arranged over the radially thickened portions of the roller body that enlarge the effective outside diameter of the roller.

The present invention is particularly suitable for use in web-fed offset rotary printing machines, since very many rollers are required for the transportation of the printed webs or web ribbons. If the elastic tube, preferably a shrink-on tube, that is used in accordance with the invention covers the cylindrical roller that has the thickened portions provided at certain points, the result is that easy cleaning is possible, in particular if PTFE (e.g. Teflon@) is used, which, as is known, is inkrepellent (oleophobic). Thus a cylindrical roller casing, for example a cylindrical tube, can be used, which after corresponding treatment, for example chrome-plating at the desired points, is provided with thickened portions, over which the elastic Teflon tube is pulled. In comparison with the known practice of sticking on so-called frogs, in addition to the greater ease of cleaning, a longer service life of the adhesive strips that are applied can be achieved and, as pointed out, there is also greater ease of cleaning. As a result of using ink-repellent materials on the roller surface or on the surface of the shrink-on tube, instead of daily cleaning just more weekly cleaning becomes necessary. As a result, the odious use of solvents may possibly even become superfluous.

In accordance with the invention, the adhesive strips or sleeves can be arranged at any points on the cylindrical roller casing so that any desired profiling of the roller surface can be achieved, since any local change in diameter can be realized. The shrunk Teflon tube ensures, moreover, that there is a closed and, as pointed out, readily cleanable surface with gentle transitions.

It is particularly advantageous if the profiling is fixed as a function of the web width, that is, for the use of full webs, or half or threequarter webs, the thickened portions are arranged on the roller in such a way that the effective cylinder diameters are greater or smaller at the desired points. As a rule, the roller is smaller or has a smaller diameter in the centre in comparison with the diameter at the web edge. However, other profiles are also possible, for example an undulating increase and decrease of the diameter to give the web or the ribbon a stiffening corrugated-sheet form in cross section.

For a better understanding of the invention embodiments of it will now be described, by way of example, with reference to the accompanying drawings, in which: Figure l shows in a diagrammatic sectional representation a paper-guiding roller in accordance with the invention; and Figures 2 - 5 show in a diagrammatic representation the arrangement of adhesive strips or sleeves at the edge regions of the webs or partial webs that are to be conveyed.

In accordance with Figure l, the paper-guiding roller 1 comprises axle journals 3, 4 on a roller body 5. The axle journals are of differing outside diameter. Arranged on the roller body 5 there are adhesive strips or ring or sleeve pieces 6 radially embracing the roller body 5.

If the paper-guiding roller l is to be used to convey a so-called fullwidth print-carrier web that extends substantially over the full width of the paper-guiding roller l when viewed in the axial direction, it is advantageous to arrange the adhesive strips or sleeve pieces 6 mentioned on the roller body 5 at the edge regions of the print-carrier web 7, that is, also substantially at the edge regions of the paper-guiding roller 1. The roller body 5 can be solid-cylindrical or consist of a tube.

In a novel way, an elastic tube 2, in particular an elastic Teflon PTFE tube, is pulled up onto the thus prepared paper-guiding roller l from the side, that is, axially. Teflon reduces the deposit of ink to a very great extent, which has a favourable effect on the cleaning cycle, as pointed out at the beginning.

Figures 2 - 5 diagrammatically show the arrangement of adhesive strips, sleeve pieces or similar materials that enlarge the roller-diameter at points that are determined as a function of the width of the webs or partial webs to be conveyed.

Thus Figure 2, in the case of the conveyance of a quarter-width web, shows the arrangement of adhesive strips or sleeve pieces 13 each at the ends (sides) of the quarter webs, though it is of course possible to arrange just one adhesive strip or sleeve piece wide enough to span the distance between the two ends of adjacent quarter webs.

The structure of the paper-guiding rollers lO, 20, 30, 40 shown in Figures 2 - 5 is otherwise basically identical with that of the paper- guiding roller l shown in Figure 1.

In Figures 3, 4 and 5, the adhesive strips or sleeve pieces 23, 33, 43 are in each case arranged in the manner described above so that the thickened portions of the roller bodies of the rollers lO, 20, 30, 40 become effective at the edge regions of the print-carrier webs or partial print-carrier webs that are to be conveyed.

The invention is not limited to the embodiments that have been described and are shown, but can in principle be applied anywhere on rollers and cylinders whose diameters should vary in the axial direction, yet no machining deviating from the cylindrical form at the cylinder or roller body needs to be carried out. In this connection, convex and concave profiled sections can be produced and so too can alternating profiled sections in order to produce a more or less undulating increase and decrease of the effective roller diameters.

Claims

Claims 1. A roller for guiding a print-carrier web in a rotary printing

machine, having a roller body 5 and at least one thickening strip that radially surrounds the roller over part of its length, characterized in that an elastic tube (2) is arranged over the radially thickened portions (6, 13, 23, 33, 43) of the roller body (5) that enlarge the effective outside diameter of the roller (1).
2. A roller according to claim 1, in which the roller is a paper-guiding roller (1) for the transportation of a full width print-carrier web (7), and the radially thickened portions (6, 33) are arranged at the two ends of the roller body (5).
3. A roller according to claim 1, in which the roller is a paper-guiding roller (10) for the transportation of quarter-width print-carrier webs and the thickened portions (13) are arranged on the roller body (5) at the respective edge regions of the quarter-width webs.
4. A roller according to claim 1, in which in order to produce undulating increases and decreases in the diameter of the paper-guiding roller (40) the thickened portions (43) are provided at predetermined points so that the web or web ribbon that is to be conveyed obtains a stiffening corrugated form in cross-section.
5. A roller according to any preceding claim, in which the elastic tube (2) is a PTFE shrink-on tube.
6. A roller according to any preceding claim, in which the thickened portions (6, 13, 23, 33, 43) consist of adhesive strips or sleeve sections that are stuck or pushed onto the roller body (5).
7. A roller according to any preceding claim, in which the roller (1, 10, 20, 30, 40) is used as a paper-guiding roller in a web-fed offset rotary printing machine.
8. A roller substantially as described with reference to any of the attached Figures 1 - 5.
9. A method of assembling a web guide roller, in which annular strips are applied at selected points along the axis of the other, and the entire roller is then surrounded by a tight-fitting elastic sleeve.