GB2026387A

GB2026387A - Method and apparatus for reducing the wear of a doctor and/or associated surface of a printing-image carrier for printing

Info

Publication number: GB2026387A
Application number: GB7914147A
Authority: GB
Original assignee: Max Daetwyler and Co
Current assignee: Daetwyler Global Tec Holding AG
Priority date: 1978-04-24
Filing date: 1979-04-24
Publication date: 1980-02-06
Also published as: FR2424132A1; FR2424132B1; DE2817964B1; IT7922147A0; DE2817964C2; SE7903353L; IT1112730B; CH638723A5; SE421513B; ES479838A1; GB2026387B; CA1135114A; NL7903224A; JPS54143309A

Abstract

A lubricant is applied to an intaglio printing cylinder 6 or other printing-image carrier and serves to reduce wear of the carrier and associated doctor 4. The lubricant can be formed of a suitable solid lubricant, for instance molybdenum disulfide, or of a carrier in which there is embedded the solid lubricant. The lubricant is then usually rubbed on to the cylinder surface. However, the lubricant need not be solid and can also be applied in a different manner, for instance, by rolling or spraying. The lubricant can be applied to the printing-image carrier at any site before or after inking <IMAGE>

Description

SPECIFICATION Method and apparatus for reducing the wear of a doctor and/or associated surface of a printing-image carrier for printing The present invention relates to a new and improved method of, and apparatus for, reducing the wear of a doctor and of the corresponding surface of a printing-image carrier, especially a printing cylinder during gravure, rotogravure or other intaglio printing.

With intaglio printing processes the surface of the printing-image carrier is freed of excess printing ink by means of a doctor blade or doctor. For this purpose, the doctor bears with pressure against the surface of the printingimage carrier. However, and as is known, this in turn causes wear of the doctor and wear of the surface of the printing-image carrier.

Many different attempts have been made to overcome this drawback. However, up to the present these attempts were predominantly directed to improving the doctor and its mounting. The solutions which have been strived for and found in this respect are either complicated from the stand-point of fabrication or contruction aspects, or, during operation do not fully afford the desired success.

Furthermore, there has already been proposed to add additives to the printing ink which are intended to reduce the doctor wear and the damage to the surface of a gravure printing-image carrier. These attempts however were unsuccessful because, through the addition of such additives, there was automatically a negative effect on the chemical and physical properties of the printing ink. Among other things, this manifested itself by the poor drying properties of the ink, which in turn resulted in a poor quality of the printed products.

Hence, with the foregoing in mind, it is a primary object of the present invention to provide a new and improved method of, and apparatus for, reducing doctor wear and wear of the surface of a printing-image carrier for intaglio printing processes, in a manner not associated with the aforementioned limitations and drawbacks of the prior art proposals.

In order to implement this and other objects of the invention, the method of the present invention involves applying, independently of the printing ink, a lubricant to the surface of the printing-image carrier.

Apparatus particularly suitable for the performance of the method of the invention is characterized by a device for applying lubricant to the surface of the printing-image carrier, especially a printing cylinder used in intaglio printing.

In contrast to heretofore proposed solutions, the present invention does not seek to improve the construction of the doctor itself or its mounting or support arrangement. Rather, through the application of a lubricant, the friction is reduced between the doctor and the printing-image carrier. This affords a corre sponding reduction in the wear of the doctor and the printing-image carrier. The printing process is not disadvantageously affected, so that there is no impairment in the quality of the printed products.

The lubricant or lubricating agent can be rubbed or rolled onto the surface of the print ing-image carrier. Different devices can be suitably employed for the application of the lubricant to the surface of the printing-image carrier, and various types of applicators will be mentioned more fully below. It is also possible to use as the applicator a doctor which contains the lubricant or which con ducts the lubricant to the surface of the print ing-image carrier.

Particularly suitable as the lubricant is mo lybdenum disulfide in powder or solid form or embedded in an appropriate carrier, for in stance plastics material.

Embodiments of the present invention will be described by way of example in the follow ing detailed description. Such description makes reference to the accompanying draw ings wherein: Figure 1 is a perspective, schematic frag mentary view showing part of a printing image carrier and a doctor blade or doctor; Figures 2 to 5 respectively schematically show different devices for applying lubricant to the surface of a printing cylinder used during gravure or intaglio printing; and Figure 6 is a schematic and simplified illustration of a gravure printing machine or printing press.

Referring now to the drawings, Fig. 1 serves to explain the problems of wear or the like occurring during gravure or intaglio print ing and shows part of a printing-image carrier 1 which may be constituted by a plate, a rotating cylinder or a plate which is clamped or otherwise affixed to a rotating cylinder.

This printing-image carrier 1 posseses, in known manner, wells 3 enclosed by screen webs 2, these wells 3 serving for reception of printing ink. To remove excess printing ink from the surface of the printing-image carrier and formed by the screen webs 2, there is provided a doctor blade or doctor 4 which bears by means of its contact surface 5 (chamfer or bevel) with a certain pressure on the screen webs 2. As is known and also previously already mentioned, there exists the problem of the wear or abrasion of the doctor 4 and the wear of the surface of the printingimage carrier 1. As will be explained more fully hereinafter, this problem is solved by application of a lubricant or lubricating agent between the doctor 4 and the printing-image carrier 1.Basically there can be used all suitable lubricants, especially solid, pasty, liquid and pulverulent lubricants. In selecting the lubricant it is important to bear in mind that the lubricating agent should neither negatively influence the printing process or the printing quality or the drying properties of the printing ink; the lubricant should not cause any impairment in the quality of the printed product.

The manner of applying the lubricant between the doctor and the printing-image carrier is dependent upon the lubricant employed.

Based upon the remaining figures of the drawings there will now be explained a number of possibilities for the application of the lubricant.

More specifically, in Figs. 2 to 5 there are shown different applicator devices or means for the application of a lubricant to the surface of a printing cylinder used in gravure printing.

In these figures a schematically illustrated printing cylinder 6 has a surface 7, which as already explained previously in conjunction with Fig. 1, is formed by the screen webs 2 or equivalent structure. The direction of rotation of the printing cylinder 6 is indicated by the arrow A.

Now in Fig. 2 the applicator device for the application of the lubricant to the surface 7 of the printing cylinder 6 comprises a bladeshaped body 8 of lubricant which is pressed at a constant pressure against the printing cylinder 6 by any suitable means, such as conventional springs or other resilient elements not shown. The lubricant or lubricating body 8 bears by means of its contact surface 9 against the cylinder surface 7. In order to maintain essentially constant the size of this contact surface 9, in the presence of progressive wear, both of the boundary surfaces 8a and 8b, in other words the upper and lower surfaces of the lubricant body 8, extend essentially parallel to one another. With the area of the contact surface 9 remaining constant and with essentially constant contact pressure, the application of the lubricant to the surface 7 is also usually essentially constant.The lubricant body 8 can comprise a suitable solid lubricant, or it can also consist of a carrier, formed for intance of plastic or sintered material, within which there is embedded solid lubricant or lubricating agent. Due to the movement of the surface 7 of the printing cylinder 6 past the lubricant body 8 the lubricant is rubbed onto the surface 7, so that a lubricant film is formed upon such surface.

The lubricant body 8 is clamped between two holder plates 10 and 11 or equivalent structure which fixedly retain the lubricant body 8.

In order to prevent irregular wear of the contact surface 9 of the lubricant body 8, the lubricant 8 and the holder plates 10 and 11 can be moved approximately transverse to the direction of rotation A of the printing cylinder 6, back-and4orth, in the direction of the double-headed arrow B by any suitable drive which had merely been schematically indicated by reference character 50. Particularly suitable as a solid lubricant is molybdenum disulfide.

The lubricant body 8 can also consist of a porous material in to which there is fed in suitable manner a liquid lubricant. Owing to capillary action the lubricant or lubricating agent will distribute within the porous lubricant body 8 and be applied to the surface 7 of the printing cylinder 6 which moves past such lubricant body 8. As explained in conjunction with Fig. 2, in this case also the lubricant body 8 can be moved to-and-fro and structured such that the contact surface 9, with progressive wear, remains essentially constant.

As shown in Fig. 3, liquid or pasty lubricants can be applied to the surface 7 of the printing-image carrier 6, by means of an applicator device which can be constructed similarly to an inking mechanism or device employed for ink application. The applicator device comprises a supply container 1 2 within which there is located the lubricant or lubricating agent 1 3. A generally lip-shaped applicator element 14 is connected with the supply container 1 2. The applicator element 1 4 extends by means of its edge 1 5 at a slight spacing from and approximately parallel to the surface 7 of the printing cylinder 6.The lubricant is applied, by means of the applicator element 14, to the cylinder surface 7 and distributed over the width of the printing cylinder 6 such that a lubricant film 1 6 is formed upon the cylinder surface 7. Depending upon the viscosity and surface tension of the lubricant the edge 1 5 of the applicator element 14, as shown, can extend at a spacing with respect to the surface 7, or, however, can be in contact with such cylinder surface 7. In the last-mentioned case, at least this edge 15, if not the entire applicator element 14, can be formed of a wear resistant material, for intance a wear resistant plastic, and further, the inherent stress or bias of such edge 1 5 or the applicator element 14 can be beneficially employed for maintaining edge 1 5 in contact with the cylinder surface 7.The use of steel, especially doctor blade steel, is however also possible. In order to avoid irregular wear of the edge 1 5, such edge, or in fact the entire applicator element 14, can be moved back-and-forth in a direction transverse to the direction of rotation A of the printing cylinder 6, and there can be used for this purpose the drive 50 shown in Fig. 2. A constant flow of lubricant can either be brought about by capillary action, by a constant lubricant level in the supply container 12, or by ap'plication of an excess pressure effective upon the surface of the lubricant. In the last-mentioned case there must be used as the supply container 1 2 a closed supply container or vat 1 2 equipped with a cover or closure member 1 2a, as such has been shown in broken lines in Fig. 3.

Opening into this closed supply container 1 2 is a feed line or conduit 1 7 for a suitable pressurized fluid medium, for instance a gas which is at essentially constant pressure.

With the exemplary embodiments shown in Figs. 4 and 5, the lubricant is applied to the surface 7 of the printing cylinder 6 by means of a rotatably mounted applicator roll 1 8. This applicator roll 1 8 is in contact with the printing cylinder 6 and rotates in the direction of the arrow C opposite to the direction of rotation A of the printing cylinder 6.With the exemplary embodiment shown in Fig. 4 the applicator roll 1 8, during its rotation, immerses partially in the lubricant or lubricating agent 1 3 which is located in the supply container or vat 1 2. Excess lubricant is removed by a doctor or doctor blade 1 9 from the applicator roll 1 8 and returned back into the supply container 1 2. Due to the contact of the applicator roll 18, carrying the lubricant, with the cylinder surface 7 there is formed upon the latter a lubricant film 16.

In Fig. 5 the applicator roll 1 8 contacts an immersion or immersible roll 20 rotating in the directional sense D which is opposite to the direction of rotation C of the applicator roll 1 8. This immersion roll 20, during its rotation, immerses partially in the bath of lubricant 1 3 in the supply container 12, thereby entrains a certain amount of lubricant and transfers lubricant to the applicator roll 1 8 at the zone of contact therewith. The lubricant is then applied by the applicator roll 18, similar to the arrangement of Fig. 4, in the form of a lubricant or lubrication film 1 6 to the cylinder surface 7 of the printing cylinder 6.If necessary, there is provided a doctor or doctor blade 1 9 for the removal of excess lubricant from the immersion roll 20.

Of course, the lubricant can also be applied to the surface 7 of the printing cylinder 6 in a different manner. For instance, liquid lubricant can be sprayed on to the cylinder surface 7 by means of a suitable spraying device. In the case of pulverulent lubricant there can be used atomizer devices which dust or atomize the lubricant onto the cylinder surface 7. As a further variant there is proposed the utilization of a vapourizing device, by means of which the lubricant can be vapour-deposited on to the cylinder surface 7. This possibility particularly comes under consideration when working with liquid lubricants.

The site of application of the lubricant at the surface 7 of the printing cylinder 6 basically can be differently selected, and especially is dependent upon the nature of the employed lubricant, the nature of the employed application process and the construction of the printing machine. Based upon the showing of Fig. 6, illustrating purely schematically and in markedly simplified form a gravure or intaglio printing machine or press, there will now be explained the different possible ways of applying the lubricant. The gravure printing machine comprises a printing cylinder 6, whose surface 7 is freed or printing ink by means of a doctor blade or doctor 4. This doctor 4 is supported in known manner in a doctor holder or mounting arrangement 21.

During its rotation the printing cylinder 6, rotating in the direction of the arrow A, partially immerses in the inking vat 23 of an inking device 22 and which contains the printing ink. Web-shaped material 25 which is to be printed is moved between the printing cylinder 6 and an impression or pressure cylinder 24. Along the printing line 26 there occurs transfer of the printing ink from the printing cylinder 6 to the web material 25.

This far, what has been described and illustrated corresponds to a conventional gravure printing machine. According to the invention, there is applied a lubricant to the surface 7 of the printing cylinder 6 preferably in one of the previously described manners. The application of the lubricant can be accomplished, for instance between the inking device 22 and the doctor 4 (Sector I), between the doctor 4 and the printing line or nip 26 (Sector II), or between the printing line 26 and the inking device 22 (Sector Ill). However, it is also possible to apply the lubricant by means of the doctor 4. For this purpose it is for instance conceivable to embed the lubricant in the doctor or doctor blade 4 so that it appears and is available at the base or free end of the doctor 4. It is also possible to conduct the lubricant through the doctor 4 to the contact zone between doctor 4 and the printing-image carrier or printing cylinder 6. In particular, liquid lubricant could be applied to the surface of the doctor 4, from which location the lubricant is fed, by means of such doctor 4, to the contact zone between the doctor 4 and the printing cylinder 6. This infeed of the lubricant, with the aid of the doctor or doctor blade 4, has been symbolized in Fig. 6 as the Position IV.

While there are shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto.

Claims

1. A method of reducing wear of a doctor and/or of the surface of an associated printing-image carrier during printing, wherein a lubricant is applied to the surface of the printing-image carrier separately from the printing ink.

2. A method as defined in claim 1, wherein the lubricant is applied by rubbing it on to the surface of the printing-image carrier.

3. A method as defined in claim 1, wherein the lubricant is applied by rolling it on to the surface of the printing image-carrier.

4. A method as defined in claim 1 or 2 wherein the lubricant is molybdenum disulfide.

5. A method as defined in claim 1, wherein the lubricant is applied by means of the doctor.

6. A method as defined in any preceding claim wherein the printing-image carrier is an intaglio printing cylinder.

7. An apparatus for reducing the wear of a doctor and/or of the surface of an associated printing-image carrier, the apparatus comprising applicator means for applying a lubricant to the surface of the printing-image carrier.

8. Printing apparatus equipped with an apparatus as defined in claim 7.

9. An apparatus as defined in claim 7 or 8, wherein the applicator means comprises a lubricant body intended to bear against the surface of the printing-image carrier.

10. An apparatus as defined in claim 9, wherein the lubricant body consists of a lubricant.

11. An apparatus as defined in claim 9, wherein the lubricant body contains the lubricant.

1 2. An apparatus as defined in any of claims 9 to 11, further including means for moving to-and-fro and lubricant body in directions extending transversely with respect to relative movement between the lubricant body and the printing-image carrier.

1 3. An apparatus as defined in any of claims 9 to 12, wherein the lubricant body is structed such that its contact surface area bearing on the printing-image carrier remains essentially constant during progressive wear thereof.

14. An apparatus as defined in any of claims 9 to 1 3, wherein the solid lubricant comprises molybdenum disulfide.

1 5. An apparatus as defined in claim 9, wherein the lubricant body comprises a porous material which is imbued with a liquid lubricant.

1 6. An apparatus as defined in claim 7 or 8, wherein the applicator means comprises a supply container for the lubricant with a generally lip-shaped applicator element which has an edge intended to be situated in close proximity and generally parallel to the surface of the printing-image carrier or to bear against the surface of the printing-image carrier.

1 7. An apparatus as defined in claim 1 6, wherein the edge of the applicator element contacting the surface of the printing-image carrier is formed of a wear-resistant material.

1 8. An apparatus as defined in claim 17, wherein the wear resistant material is of wear resistant plastics.

1 9. An apparatus as defined in claim 16, 1 7 or 18, further including means for moving to-and4ro at least the edge of the applicator element in directions extending transversely with respect to the direction of relative movement between the edge and printing-image carrier.

20. An apparatus as defined in claim 7 or 8, wherein the applicator means comprises a rotatable applicator roll for contact with the surface of the printing-image carrier and to which there is applied the lubricant.

21. An apparatus as defined in claim 20, further including a supply container for lubricant arranged so that the applicator roll, during its rotation, partially immerses in lubricant within the supply container.

22. An apparatus as defined in claim 20, further including a supply container for lubricant, a rotatable immersion roll arranged for at least partially immersion in the lubricant contained in the supply container and to contact the applicator roll to apply lubricant thereto.

23. An apparatus as defined in claim 21 or 22 further including a doctor for removing excess lubricant from the surface of the immersion or applicator roll.

24. An apparatus as defined in claim 7 or 8, wherein the applicator means comprises the doctor for the printing-image carrier, the doctor containing the lubricant.

25. An apparatus as defined in claim 7 or 8, wherein the applicator means comprises the doctor and conducts the lubricant to the surface of the printing-image carrier.

26. A method of intaglio printing using a printing-image carrier with associated doctor, in which wear of the doctor and/or carrier is reduced by employing a process as defined in any of claims 1 to 6 or by using apparatus as defined in any of claims 7 to 25.

27. Printed matter when printed by a method as defined in claim 26.