CA1221269A

CA1221269A - Process and arrangement for sealing the gap between the ends of a gravure printing plate mounted on a printing cylinder

Info

Publication number: CA1221269A
Application number: CA000449283A
Authority: CA
Inventors: Gerhard Bleckmann; John Lynch; Heinz Mohr
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1983-03-12
Filing date: 1984-03-09
Publication date: 1987-05-05
Also published as: US4515375A; DE3475285D1; ATE38802T1; DK159251B; DK136084D0; EP0118866A3; JPS59169863A; EP0118866A2; EP0118866B1; DK136084A; ES8501311A1; DK159251C; ES530516A0; JPH0324898B2

Abstract

ABSTRACT OF THE DISCLOSURE:

The gap formed between the end portions of a gravure printing plate which is anchored in a groove of a printing cylinder on which the plate is mounted is covered with a sheet which overlaps the end portions. The gap cavity thus formed is then filled with a thermoplastic and/or hardenable material and when this has hardened the cover is removed.

Description

- 1 - 12;~26~

The present invention relates to a process for sealing the gap between the ends of a gravure printing plate mounted on a printing cylinder of a sheet-fed or reel-fed rotary gravure printing machine, and to an arrangement for carrying out the process.
It is known that gravure printing plates consisting of a dimensionally stable and flexible carrier and a printing layer, for example consisting of a plastic, applied to the said carrier, may be mounted on a printing ` 10 cylinder of a sheet-fed or reel-fed rotary gravure printing machine. For this purpose, the printing cylinder is provided with a groove, running parallel to or obliquely to the printing cylinder axis; the prlnting plate has one or both edges folded-over and hooked at an acute angle into the groove, thus holding the plate. The gap thus formed between the two ends of the gravure printing plate is preferably sealed with a plastic composition. Hitherto, the procedure followed as a rule has been to introduce a flowable and hardenable composition into the gap from the ~; 20 cylinder surface and, when the composition has hardened, to subject the gap zone between the plate ends to a surface-finishing operation, for example by grinding, so that a continuous uniform surface resulted in the zone of the plate ends. The work involved in this is relatively much and requires craft skill. Moreover, the printing cylinder has ;; to be removed from the printing machine.
Further, it is known that in the case of wrap-round plate magnetically mounted on a gravure printing cylinder, the groove into which the plate is hooked may be covered, at the cylinder surface, by a shaped member, a ; rapidly hardening two-component mixture, for example an epoxy, polyester or acrylic resin mixture, being injected into the groove cavity thus formed. In this case, the shaped member must be very accurately machined to the :

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curvature of the cylindrical surface of the gravure printing cylinder, and this is difficult and very expensive.
Separate shaped members are required for different cylinders, i.e. changing the cylinder size is not immediately possible. Moreover, it is very difficult to compensate for varying tolerances of the wrap-round plates, and yet this is necessary~ if the gap is to be sealed accurately. It has been found, therefore, that the sealed groove often needs a mechanical finishing operation.
It is an object of the present invention to provide a method of sealing the gap between the ends of a gravure printing plate mounted on a printing cylinder of a rotary gravure printing machine, especially of a plate provided with a plastic printing layer, and to do so at little expense and more simply than in the prior art, while ensuring that good surface quality results.
We have found that this object is achieved by a process, and an arrangement for carrying out this process, as described in the claims.
According to the present invention there is provided a process for sealing the gap between the ends of a gravure printing plate mounted on a printing cylinder of a ; sheet-fed or reel-fed rotary gravure printing machine, one or both ends of the gravure printing plate being folded over 2S and hooked into a groove running parallel to or obliquely to the printing cylinder axis, the process comprising:
- placing a sheet over the gap and the adjoining two end portions of the surface of the gravure printing plate, - pressing the sheet against the surface of the gravure printing plate so that the gap is covered in a flush manner by the sheet, - filling the resulting gap cavity with a thermoplastic and/or hardenable material, - solidifying the filling material, and , ~, ~ 1 :' .

~L22~ 9 - removing the sheet after the filling material has hardened.
According to the present invention there is also provided an arrangement for sealing the gap between the ends of a gravure printing plate mounted on a printing cylinder of a sheet~fed or reel-fed rotary gravure printing machine, the arrangement comprising:
- a printing cylinder with a groove running parallel to or obliquely to the printing cylinder axis, in which groove one or both ends of the gravure printing plate have, after being folded over, been hooked and anchored, - a sheet resting on the two end portions, adjoining the gap, of the surface of the gravure printing plate so as to cover the gap, 15- a pressure member which overlaps these end portions, supports the sheet and is connected to a holding-down device, and - one or more feed channels, opening into the gap cavity, for the filling material or for a pressure-generating medium and/or a heating or cooling medium.
Preferred embodiments will now be described, as ~; examples without limitative'manner, having reference the attached drawings, wherein:
~; . Figure 1 shows, in cross-section, a portion of a printing cylinder in the region of the groove for hooking-in the ends of the gravure printing plate, together with the sheet connecting the ends and with the pressure member placed thereon.
Figure 2 shows the printing cylinder as in Figure 1, but in lengthwise section.
Figure 3 shows the printing cylinder as in Figure 1, with a hollow body of circular cros-section arranged in the gap cavity.
Figure 4 shows the printing cylinder as in Figure }
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Figure 5 shows the printing cylinder as in Figure 1, with a source of radiation located in the pressure member.
As shown in Figure 1, the printing cylinder 1 of a sheet-fed or reel-fed rotary gravure printing machine is : provided with a groove 2 running parallel to the printing cylinder axis and widening from the cylinder surface in the direction of the center of the ~cylinder; the gravure printing plate 3 mounted on the printing cylinder is hooked at an acute angle into the groove by, in the /

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2~2S~3 - 4 - O.Z~ 0050/36419 example sho~n both, folded~over edges 4. To seal the gap 15 between the two ends, a ~heet 6 which overlaps the two end port;ons 5 of the gravure pr;nt;ng plate, for example a piece of foil or a f;rm res;lient plate, is placed over the gap, the sheet being supported, and pressed against the surface of the gravure print;ng plate, by a pressure member 7 ~h;ch can be brought into pos;tion by a holding-down dev;ce not shown in the draw;ng.
The sheet 6, ~h;ch in general ;s from 1 to 10 mm, espec;ally from 2 to 8 mm, th;ck ;s preferably transpar-ent, s;nce th;s perm;ts observat;on of the sequence of f;~l;ng the ~ap cav;ty 9 as well as of the absence of leaks between the sheet 6 and the surfaces on wh;ch ;t rests. The sheet 6 ;s ;n part;cular a plast;c fo;l or a res;liently bendable plast;c pLate9 for example consist-ing of a poly2ster, nylon, polystyrene, polyethylene, polypropylene or, preferably, polyacrylates or polymeth-acrylates, eg. polymethyl methacrylate~ If phstohardening react;ve res;ns are used to fill the gap, the sheet 6 transm;ts the actin;c l;ght used for harden;ng. If, as d;scussed ;n more deta;l below, the pressure member 7 comp-r;ses heat;ng or cool;ng elements, wh;ch can ;n par-t;cular be advantageous for thermosett;ng reactive res;ns or thermoplast;c f;l~;ng materials~ the sheet 6 can Z5 moreover cons;st of a material of good heat conduct;v;ty, for example a metal plate. In other respects, the mate-r;al const;tut;ng the sheet 6 ;s so chosen that ;t can eas;ly be pulled off or l;fted off the hardened gap f;ll~
;ng. If appropr;ate, the sheet 6 can be surface-coated w;th a release agent, for example can be s;l;con;zed, or a th;n release f;lm can be placed between the surface of the gravure pr;nt;ng plate and the sheet 6.
The pressure member 7 can, as shown in Figure 1, ; be a closed - substantially solid - shaped member, whose support;ng surface 8 advantageousLy has about the same curvature as the surface of the end port;ons 5 of the gravure print;ng plate 3, though ;t may dev;ate there-~ 5 - O.Z. 0050/36419 from, i~. it may ;n particular have a greater curva-ture. As may be seen from F;gure S the pressure member 7 can, ;n another and also very advantageous embodiment, be formed by, for example, a beam of U-shaped cross-section open toward the pr;nt;ng cyl;nder 1.
After apply;ng the sheet 6~ the gap 15 ;s sealed w;th a suitable filling mater;al which must of course be resistant to ~he pr;nting inks. In one embodiment of the ;nvent;on, the gap cavity 9 formed ;s, for this purpose, f;lled from the end face of the printing cyl;nder 1 ~F;gure 2), v;a one or more feed channels 11 located in ;ts bear;ng s;de-plates 1U, w;th a flowable and hardenable material, for example a thermoplastic or a hardenable reactive resin.
A meter;ng dev;ce 12, for example a me~ering plunger, for the thermoplast;c material or for the react;ve res;ns ;s prnv;ded for th;s purpose. After hardening has occurred, ~he pressure member 7 is retracted and the sheet 6 removed.
A surface ~h;ch prov;des a flush connect;on between the surfaces of the two end port;ons 5 of the gravure printing ~ ~ 20 plate 3 has thus been formed and no longer needs to be I ; subjected to any finishing operation.
Advantageous f;ll;ng materials wh;ch may be used~ ;n add;t;on to conventional thermoplastics, are hot-meLt adhesives based, for example, on polyvinyl acetate, Z5 nylon, polyesters or thermoplast;cs such as polyolefins, ~ styrene-butadiene block copolymers etcO Moreover, thermo-;~ setting and ;n particular photoharden;ng reactive resins, eg. epoxy resins~ acrylate res;ns~ ;socyanate res;ns, silicone resins, unsaturated polyester res;ns and the l;ke, are very su;table.
For better adhesion of the filling material, the ends of the gravure printing plate may be treated with an adhes;on promoter. More rapid hardening of the reactive resins used as the filling material may be ach;eved by treating the pr;nt;ng plate ends w;th an acti-; vator or catalyst~
~ The harden;ng of the fill;ng mater;al after ." ~

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~, ~, 122~269 - 6 - O~Z. 0050/36419 the 93p has been filled is effected, ;n the case of ther-moplast;cs, by cooling the molten polymer, in the case of thermosetting reactive resins by sui~able application of heat (the heat sources being located within or above the gap cavity 9) and ;n the case of photohardening reactive resins by irradiation with actinic l;~ht, using the con-vent;onaL radiation sources for such light.
To prevent pene~ration of the f;ll;ng material into the inter;or of the printing cylinder, and especially into any clamping devices and components, the gap cavity 9 is sealed ;n the radially inward direction, ie. toward the center of the cylinder. Th;s sealing can be achieved and assured through purely constructional features of the printing cylinder 1. However, it is aLso possible, and advantageous, to provide in the gap cavity 9 a sealing element 13 extending over the entire length of the gap tFigure 3). This sealing element 13 can be compact or, as the dra~ing shows, can be a hollow body, preferably of circular cross-section, for example a silicone rubber tube. If such hollow bodies are used, they can be con-nected to a source of a pressure medium via a further feed channel (not shown in the drawing~ and can ~hereby be inflatable~ This makes it possible both to achieve a secure and reliable seal and to compensate for any shrink-~Z5 age of the filling material which may occur on harden-;ing. If not only a Teed channel but also an exit channel is provided for the hollow body 13, then the latter can be connected into a circuit of a heating medium or cool-ing medium which is under pressure, so that, depending on 3û the filling material used, the flow of the mater;al uhen filling the gap cav;ty 9 and/or the hardening of the material after filling the gap cavity 9 may addition-ally be controlled and influenced.
In a very advantageous embod;ment of the process~
the flowable, hardenable filling material can be intro~
duced ;nto the gap cavity 9 through the hollow body 13.
For th;s purpose, the hollow body 13 is provided, along ~ S 9 ~ 7 ~ -Z- 0050/36419 the gap, with one or more small or;f;ces opening into the gap cavity 9, through wh;ch or;fices the fillin9 mate-r;al can enter the cav;ty 9 from the hollow body 13. This ensures rap;d un;form d;stribution of the fill;ng mate- -r;aLf which is important ;n ach;eving a perfect seal ofthe gap. For exampleO it has proved advantageous to intro-duce the f;lling ~materia~-- ;nto the cavity 9 through an orifice ~hich is about half way along the length of the hollow body 13. In this embodiment of the proiress, the 1û hollow body 13 is connected to the metering device 12 (F;gure 2) for the flowable, hardenable f;ll;ng mate-rial via the feed channels 11 located ;n the bear;ng side-plates 10 of the print;ng cylinder 1. Any pressure in the hollow body 13 ~hich may be needed to seal the gap cavity 9 securely in the radially ;nward direction toward the cyLinder center can in that case be created by means of the f;ll;ng material in the hollo~ body 13.
In a further embod;ment according to the inveno tion, the gap 15 is sealed by introduc;ng into the gap cavity 9, in place of a flowable f;ll;ng material, a deformable hollow prof;le body 14 ~Figure 4) made of a thermoplastic and extend;ng over the ent;re length of the gap. The prof;le body ;s connected, v;a a feed channel ;n the bear;ng sideplate 10, ~ith a source of heat;ng medium ~hich is under pressure, so that the surface of the prof;le body is pressed into the gap 15 between the end port;ons 5 of the gravure pr;nting plate 3 to f;ll the gap and harden there;n. The pressure ;n the profile body can also be created by any desired pressure-generat-ing and pressure-transferring medium, for example by com-pressed air, in which case the swrface of the prof;le is heated via, for example, the pressure member 7.
For .h;s purpose the pressure member~ wh;ch in this case may for example be of steel or aluminum, is pro-vided with channels 16 which extend over the ent;re lengthof the gap cav;ty 9 and are connected to a heating medium c;rcu;t. Th;s construction of the pressure member can .

i - 8 - 0.Z. 0050/36419 also be used advantageously for the other process embodi-ments and arrangements described above, especially ;n the case of flowable thermoplastic or thermosetting filling material~, cool;ng media also being émployable where appropriate~ Of course, electr;cal heating, for exampLe resistance heating or ;nduct;ve heating, may be prov;ded ;n place of a heating med;um or cool;ng med;um c;rcu;t in the pressure member.
Instead of a heat;ng medium c;rcuit or of elec-trical heat;ng, a rad;at;on source 17 for act;n;c light, for example a fluorescent tube tF;gure 5), extend;ng over the ent;re length of the gap cav;ty 9~ may be located ;n the pressure member 7, th;s be;ng particularly advantage-ous when us;ng photoharden;ng fill;ng composlt;ons~ In that case the pressure member 7 cons;sts, for example, of a beam 18 of U-shaped cross-sect;on open toward the print-;ng cyl;nder 1, the rad;at;on source 17 be;ng held in the beam. On applying the beam 18 against the cyl;nder, the light-transm;tt;ng fo;l or, more espec;ally, f;rm res;-Z0 l;ent plate employed as the sheet 6 ;s bent ;n a curvedl;ne between the two arms of the beam 18 and f;rmly pressed aga;nst the cylindrical surface, the line of cur-vature correspond;ng exactly to the curvature of the sur-face of the end port;ons 5 of the gravure printing plate 3. Th;s creates a flush seal of the gap cav;ty 9 a~ the cylinder surfaceO The cav;ty 19 of the open beam 18 can also be filled w;th a material which in particular `~ transm;ts act;nic l;ght9 for example a casting res;n. If, on cover;ng the gap 15, the pressure member 7 used is a mold;ng member hav;ng a sol;d support;ng surface 8 (simi-larly to the arrangement shown in Figure 1), and a radi-at;on source 17 (F;gure 5) ;s located ;n this mold;ng mem-ber, then at least the supporting surface 8 must be made of a material ~h;ch transm;ts actinic light.
~n other respects, the pressure member 7 can in principle be made of~any material, namely not only metals but also, in part;cular, plast;~s.

Using the process according to the invention and the arrangement for carrying out this process, the gap in a gravure printing wrap-round plate mounted on a printing cylinder can be sealed in a simple manner, in such a way that during sheet-fed or reel-fed rotary gravure printing no problems are observed, especially in respect of doctor performance or of creation of an imprint of the gap.
Moreover, depending on the filling material used, image information in the form of ink-accepting cells can be introduced into the gap zone, for example by mechanical engraving or laser engraving. The process according to the invention is simple to carry out and the arrangement for doing so can be handled quickly and economically without having to remove the printing cylinder from the printing machine. All known and conventional gravure printing wrap-round plates which can be mounted on the printing cylinder of a sheet-fed or reel-fed rotary gravure printing machine may be employed in the process according to the invention, for example the conventional gravure printing plates made of ; 20 metal with a Ballard skin or, particularly advantageously, gravure printing plates having a plastic printing layer, in which plates a suitable printing layer carrier is provided with a plastic layer into which the ink-accepting recesses (cells) have been introduced by rnechanical engraving or laser engraving or photomechanically by imagewise exposure and development of a suitable photosensitive recording material. Similarly, the cells can of course be introduced into the gravure printing plate after the latter has been mounted on the printing cylinder and after the gap has been sealed. For the purposes of the present invention, gravure printing plates include both wrap-round plates with cells already formed and wrap-round plate blanks in which the cells have not yet been formed.
To remove the gravure printing plate from the :~

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printing cylinder after printing, the filling of the gap between the plate ends can be removed again by machining or by the use of a tear-wire which has been introduced ; beforehand.

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Claims

We claim:-

1. A process for sealing the gap between the ends of a gravure printing plate mounted on a printing cylinder of a sheet-fed or reel-fed rotary gravure printing mach-ine, one or both ends of the gravure printing plate being folded over and hooked into a groove running parallel to or obliquely to the printing cylinder axis, the process com-prising placing a sheet over the gap and the adjoining two end portions of the surface of the gravure printing plate, pressing the sheet against the surface of the gra-vure printing plate so that the gap is covered in a flush manner by the sheet, filling the resulting gap cavity with a thermo-plastic and/or hardenable material, solidifying the filling material and removing the sheet after the filling material has hardened.

2. A process as claimed in claim 1, wherein the sheet is a plastic film or plastic plate.

3. A process as claimed in claim 1, wherein the sheet has a thickness of from 1 to 10 mm.

4. A process as claimed in claim 1, wherein the sheet is transparent.

5. A process as claimed in claim 1, wherein the sheet is provided with a release agent on the surface facing the gravure printing plate.

6. A process as claimed in claim 1, wherein a thin release film is placed between the sheet and the surface of the gravure printing plate.

7. A process as claimed in claim 1, wherein the gap cavity is filled with flowable and hardenable material through one or more feed channels opening into the cavity.

8. A process as claimed in claim 7, wherein a ther-moplastic is employed as the filling material.

9. A process as claimed in claim 7, wherein a hot-melt adhesive is employed as the filling material.

10. A process as claimed in claim 7, wherein a ther-mosetting or photohardening reactive resin is employed as the filling material.

11. A process as claimed in claim 7, wherein the gap cavity is sealed in the radially inward direction toward the cylinder center by means of a sealing element extend-ing over the entire length of the gap cavity.

12. A process as claimed in claim 11, wherein the seal-ing element used is a hollow body which is deformable under pressure and which is internally subjected to a pressure medium.

13. A process as claimed in claim 12, wherein the hollow body has, along the gap, one or more small orifices opening into the gap cavity and the flowable hardenable filling material is introduced into the gap cavity through the hollow body.

14. A process as claimed in claim 1, wherein, to seal the gap, a profile body made of a thermoplastic and ex-tending over the entire length of the gap cavity is intro-duced into the cavity, and the said body is deformed and softened under the action of pressure and heat, thereby pressed fillingly into the gap between the end portions of the gravure printing plate, and thereafter hardened again by cooling.

15. Arrangement for sealing the gap between the ends of a gravure printing plate mounted on a printing cylin-der of a sheet-fed or reel-fed rotary gravure printing machine, the arrangement comprising a printing cylinder with a groove running paral-lel to or obliquely to the printing cylinder axis, in which groove one or both ends of the gravure printing plate have, after being folded over, been hooked and anchored, a sheet resting on the two end portions, adjoin-ing the gap, of the surface of the gravure printing plate so as to cover the gap, a pressure member which overlaps these end por-tions, supports the sheet and is connected to a holding-down device, and one or more feed channels, opening into the gap cavity, for the filling material or for a pressure-generating medium and/or a heating or cooling medium.

16. Arrangement as claimed in claim 15, wherein the feed channels are connected to a metering device for a flowable, hardenable filling material.

17. Arrangement as claimed in claim 16, wherein the gap cavity has a further feed channel, for a hollow body extending over the entire length of the cavity, the chan-nel being connected to a source of pressure medium or heating medium and/or cooling medium.

18. Arrangement as claimed in claim 16, wherein the feed channels inside the cylinder groove are connected to a hollow body extending over the entire length of the groove, the body having, along the gap, one or more small orifices opening into the gap cavity.

19. Arrangement as claimed in claim 15, wherein there is located, in the gap cavity, a deformable hollow pro-file body made of a thermoplastic and extending over the entire length of the cavity, the body being connected, via a feed channel, to a source of pressure or to a source of a heating and/or cooling medium which is under pres-sure.

20. Arrangement as claimed in claim 15, wherein the pressure member has channels, extending over the entire length of the gap cavity, for a heating medium or cooling medium circuit, or has heating elements.

21. Arrangement as claimed in claim 15, wherein the pressure member has one or more radiation sources for actinic light, the sources extending over the entire length of the gap cavity and acting in the direction of the latter.

22. Arrangement as claimed in claim 15 or 21, wherein the pressure member consists of a beam of U-shaped cross-section open toward the printing cylinder.

23. Arrangement as claimed in claim 15, wherein the sheet consists of a plastic foil or plastic plate of a thickness from 1 to 10 mm.

24. Arrangement as claimed in claim 15, wherein the sheet is transparent.