GB2100672A

GB2100672A - Printing machines

Info

Publication number: GB2100672A
Application number: GB08219199A
Authority: GB
Inventors: Hermann Fischer
Original assignee: MAN Roland Druckmaschinen AG
Current assignee: Manroland AG
Priority date: 1981-07-04
Filing date: 1982-07-02
Publication date: 1983-01-06
Also published as: IT8248716A0; FR2508846A1; DE3211454A1; DE3211454C2

Abstract

For printing, with one printing unit (1), a web (2) with uninterrupted printing along the printed surface, it is partially printed between a blanket cylinder (4) - or a forme cylinder - and an impression cylinder (5) and is then turned back via a path-length adjustment device (6) and is pressed again onto the blanket cylinder (4) by means of a proof or secondary impression roller (7). The web loop between the blanket cylinder (4) and the impression cylinder (5) and the blanket cylinder (4) and the proof roller (7) is so dimensioned that on the second pressing of the web (2) onto the blanket cylinder (4), the gaps remaining after the first printing process are completely printed if the length of the image (B) corresponds to half the circumference of the plate cylinder (3) or the blanket cylinder (4); with a greater image length, there is a partial double print. In alternative arrangements, the proof roller and path-length adjustment device may be upstream of the impression cylinder; and for printing a web on both sides by passing it between two blanket cylinders one or both sides of the web may be printed additionally by means of one or more proof rollers arranged adjacent the respective blanket cylinder upstream or downstream of the nip between the blanket cylinders. <IMAGE>

Description

SPECIFICATION Web-fed rotary printing machine and method for continuous printing This invention relates to a web-fed rotary printing machine with at least one printing unit, having a printing cylinder carrying the image and an impression cylinder by means of which the web can be pressed against the printing cylinder, and to a method of printing a web, in which the web can be printed without interruption in the printing along the printed surface.

For the continuous printing of paper or material webs, it has previously been proposed to use two printing cylinders arranged at a specific distance from one another adjacent a common impression cylinder, taking into account the image length obtaining on the circumference. The disadvantage with this is that in practice two printing units are necessary, namely two blanket cylinders and two plate cylinders with respectively a damping and inking device.

An object of the invention is to be able te print, in one single printing unit, the full-Wvdth web without interruption, i.e. without a gap.

According to the present invention there is provided a web-fed rotary printing machine having at least one printing unit, comprising at least one printing cylinder which in use carries the image to be printed and an impression cylinder by means of which the web can be pressed against the printing cylinder, there being further provided a proof, or secondary impression, roller or cylinder arranged for an additional pressing of the web onto the printing cylinder and a web path-length adjustment means arranged between the impression cylinder and the proof roller or cylinder.

The path-length adjustment means and the proof roller or cylinder may be arranged in that order relative to the web travel direction downstreamof the nip between the printing cylinder and the impression cylinder whereby the proof roller or cylinder causes a second printing on the web from the printing cylinder after a first printing at the said nip.

Alternatively, the proof roller or cylinder and the path-length adjustment means may be arranged in that order relative to the web travel direction upstream of the nip between the printing cylinder and the impression cylinder whereby the proof roller or cylinder causes a printing on the web from the printing cylinder before the printing at the said nip.

According to a further aspect of the invention, there is provided a method of printing a continuous web in a web-fed printing machine, wherein after an image is printed onto the web by a printing cylinder, the web is brought into contact with the same printing cylinder a second time thereby to have the same image printed again.

The web may be first printed by passing it between the printing cylinder and an impression cylinder and a second time by passing it between the printing cylinder and a secondary impression cylinder, or the web may be first printed by passing it between the printing cylinder and a secondary impression cylinder and a second time be passing it between the printing cylinder and a main impression cylinder.

In a further aspect, there is provided a method of printing a continuous web on both sides in a web-fed printing machine, wherein the web is passed between two printing cylinders rolling adjacent one another and wherein one or both sides of the web are printed additionally by contact with the respective printing cylinder upstream or downstream of the nip between the printing cylinders.

Apart from the simpler construction of the web-fed rotary printing machine of the invention compared with known machines for continuous printing, there is considerable advantage in the fact that the printing unit only requires the normal amount of water which is necessary in the offset printing process with a conventional printing unit. This therefore means a saving of 50% damping solution as against the gap-free printing by means of two printing units.

The value of this saving in damping solution is not financial but lies essentially in the higher quality that can be thus achieved. The reason for this is the fact that with continuous printing, such as continuous (remouline) perforated products, e.g. forms, what matters most is the dimensional stability, i.e. the tensional behaviour of the paper web. In comparison with the known printing units, the dimensional stability is great due to the reduced water supply, i.e. in particular the elongation of the web during the printing process is kept very slight indeed--especially as a result of the supply of damping solution.

Beliefs that the second print, i.e. the second removal of image, could lead to optically detectabe differences in inking or intensity with an image length laid out on half the circumference of the cylinder in gap-free adjacent printing, have not been confirmed in practice, since it was established that in offset machines, a large number of perfect prints can still be taken from the blanket cylinder after the ink supply has been stopped, the ink intensity of which has no variations that are detectable with the naked eye.

Web-fed printing machines in accordance with the invention are particularly suitable for electronic data processing papers with their unalterable registration stability with regard to the feed holes, also for printing wallpaper.

The invention may be put into practice in a number of ways but various embodiments will now be described by way of example, with reference to the accompanying drawings, which show schematically: Figure 1 a web-fed offset rotary printing machine for first forme (i.e. one-sided) printing. in accordance with the invention, Figure 2 a web-fed offset rotary printing machine for first and second forme (both sided) printing with four printing units.

Figure 3 a web-fed offset rotary printing machine according to Fig. 2 with another web guide, and Figure 4 a second embodiment variant of a web-fed offset rotary printing machine for first forme printing in accordance with the invention.

The printing unit shown in Fig. 1 is an offset printing unit in which a printing carrier web 2 can be provided with a first forme printing. The printing unit 1 comprises a plate cylinder 3, a blanket cylinder 4 and an impression cylinder 5. The web 2 is conveyed between the blanket cylinder 4 and the impression cylinder 5 during the printing process.

In known printing units, because of the region, indicated for the nip in Fig. 1 in dotdash line only. where there is no image transferred from the plate cylinder 3 to the blanket cylinder 4, an uninterrupted print, e.g. for the printing of forms or wallpaper, is not possible.

Therefore, as mentioned above, until now in practice two printing units have been required, either in integrated form with a common impression cylinder or arranged in series.

In accordance with the invention, the printing carrier web 2 is guided bac' < to the blanket cylinder 4 round a path-length adjustment device 6 after passing between the blanket cylinder 4 and the impression cylinder 5. With the aid of a proof roller 7 acting as a second impresion cylinder located at a circumferential position around the axis of the blanket cylinder 4 downstream of the nip between the blanket and impression cylinders 4 and 5, the web 2 that has already been partially printed between the blanket cylinder 4 and the impression cylinder 5 is printed again on the same side.

By means of a swivelling device 8, only schematically represented in Fig. 1, a path length adjustment in the web is possible in such a way that the places that are not printed during the first passage between the blanket cylinder 4 and the impression cylinder 5, i.e. the gaps remaining free, are printed on the return and repeated pressing of the paper web 2 by the proof roller 7 onto the blanket cylinder 4.

Preferably the plate, which is stretched in conventional manner on the plate cylinder 3, has an image B, the length of which corresponds exactly to half the circumference of the plate cylinder 3 and hence half the circumference of the equally large blanket cylinder 4. If in this case, with the aid of the path adjustment device 6, care is taken that the web loop between the blanket cylinder 4 and the impression cylinder 5 on the one hand and the blanket cylinder 4 and proof roller 7 on the other hand, also correspond to half the circumference of the plate blanket cylin derr to an odd number multiple of it, perhaps plus an amount equal to the arcuate distance between the nips of the impression cylinder 5 and proof roller 7 with the blanket cylinder 4. then with the repeated pressing of the web 2 by the proof roller 7, there is a repeated print of the image B into the intermediate spaces which remain free during the first printing process between the blanket cylinder 4 and the impression cylinder 5. Hence an uninterrupted, i.e. gap-free, printing of the web is possible by means of a single conventionally constructed printing unit.

It will be understood that instead of the offset printing unit shown in Fig. 1, the Invention can also be used with printing machines operating according to other printing processes. e.g. letterpress rotary printing machines.

The image B that is indicated in Fig. 1, the length of which corresponds in the circumferential direction to half the circumference of the plate blanket cylinder, can also be longer. In this case, with the second removal, i.e. with the second pressing of the web 2 by the proof roller 7, there is at least a partial, and in extreme cases an almost complete, overlapping or a double print. However, to achieve uninterrupted printing a complete double print is not possible. On the other hand. a partial overlapping is frequently desirable, especially in the printing of wallpaper, if certain parts of the printing web are to be emphasised as regards colour intensity. Indeed, it would be quite possible with this or with any of the following embodiments to use the invention for achieving exactly overlapping additional printing if uninterrupted printing is not required.

Fig. 2 shows the use of the invention with a web-fed offset rotary printing machine for first and second forme printing, which consists of an indentation unit 9 and four printing units 1 0, 11, 1 2 and 1 3 arranged one behind the other in the web travel direction, and in which the web 2 can be printed respectively on both sides with a colour in each of the printing units 10 to 1 3 that have been mentioned.

Since the printing units 10 to 1 3 are identically constructed, the invention is described below merely with reference to the first printing unit 1 0. This incorporates an upper plate cylinder 1 4 and an upper blanket cylinder 1 5 as well as a lower plate cylinder 1 6 and a lower blanket cylinder 1 7. The blanket cylinders 1 5 and 1 7 are used for printing and advancing the web 2, each blanket cylinder, in addition to constituting a printing cylinder, also serving as an impression cylinder in cooperation with the other blanket cylinder.As has already been described in connection with Fig. 1, after the web has passed between the two blanket cylinders 1 5 and 17, there is a reversal or turning back of the web path by means of a path-length adjustment device 1 9 and a repeated pressing with the aid of a proof roller 1 8 onto one of the blanket cylinders, e.g. on the blanket cylinder 1 5.

In the guiding of the web 2 shown in Fig.

2, an uninterrupted, i.e. gap-free, printing of the upper surface of the web 2 is therefore possible in each of the printing units 10 to 1 3. Through the use of the four printing units 1 Q to 13, moreover, both the upper surface of the printing carrier web 2-uninterrupted -and the under side of the printing carrier web 2-with gaps---can be printed with four colours.

In the guiding of the web 2 throught the web-fed printing machine shown in Fig. 3, the construction of which is identical to the construction shown in Fig. 2, both the upper surface and the under side, i.e. both first and second forme printing, can be printed uninterrupted in accordance with the invention. For this, apart from the first reversal mentioned in connection with the description in Fig. 2 and the repeated pressing of the web 2 onto the upper blanket cylinder 15, there occurs a further reversal of the web 2 round a second path adjustment device 21 which can also be constructed as a displaceable or swivellable paper carrying roller mounted on the side parts of the machine.The path-length adjustment device 21 ensures that the intermediate space remaining on the underside of the web 2 after the first print between the blanket cylinder 1 5 and the blanket cylinder 1 6 can be exactly filled in after a further pressing of the underside of the web 2 onto the lower blanket cylinder 1 7 with the aid of another proof roller 20. Thus with the embodiment according to Fig. 3, the web 2 in the printing units 10 to 1 3 can be printed with four inks both on the upper surface and on the lower surface without gaps.

It is advantageous to automate the swivel ing device 8 for the path-length adjustment device 6 indicated in Fig. 1, i.e. to make it remotely controllable. For this e.g. the swivelling mechanism can be actuated by means of an electromagnet or hydraulic piston 22 shown in dot-dash line by means of a control or regulation circuit (not shown). A so-called web displacement device is particularly suitable as a path-length adjustment device, as described in German patent application P 31 19 398.6.

The proof rollers 7 or 1 8 and 20 necessary for the second printing can, however, either be made also in the form of a normal printing cylinder or also as a roller with barrelling. The barrelling, i.e. the diameter thickening in the middle region, is so designed that a uniform and sufficiently high proof can be produced over the entire length of the cylinder. The rollers used as proof rollers and as path-length adjustment devices should have an ink-repellent coating or a coating carrying peaks to prevent, or at least reduce, the danger of smearing the still frest print.

The path adjustment devices 6 and 19, as well as 21 may comprise or preferably include air blast strips. When using conventional paper carrying rollers, on the other hand, it is advantageous to provide means for blasting anti-smearing powder between the freshly printed webs and the paper carrying rollers.

Fig. 4 shows a further variant in which the printing unit 100 comprises a plate cylinder 300, a blanket cylinder 400 and an impression cylinder 500. The web 2 is guided round a proof roller or cylinder 700 and is pressed by this a first time against the image, i.e.

printing, cylinder 400. By means of a displaceable or swivellable roller 600, which can be swivelled by a servo piston 220 and a swivel arm 800, the control adjustment is made and after that the second print is effected between the cylinders 400 and 500. The printing carrier web 2 conveyed out of the printing unit 100 is thus printed without a gap.

The principle, shown in Fig. 4, of arranging the proof roller and path adjustment device in that order upstream of the nip between the printing and impression cylinders may be utilised in variants of the arrangements shown in Figs. 2 or 3. Thus one or both sides of the web may be printed with the additional contact of the web with the respective printing cylinder being upstream or downstream of the nip between the printing cylinders, or (with both sides being printed twice) upstream for one side and downstream for the other.

Claims

1. A web-fed rotary printing machine having at least one printing unit, comprising at least one printing cylinder which in use carries the image to be printed and an impression cylinder by means of which the web can be pressed against the printing cylinder, there being further provided a proof, or secondary impression, roller or cylinder arranged for an additional pressing of the web onto the printing cylinder and a web path-length adjustment means arranged between the impression cylinder and the proof roller or cylinder.

2. A printing machine as claimed in claim 1, in which the path-length adjustment means and the proof roller or cylinder are arranged in that order relative to the web travel direction downstream of the nip between the printing cylinder and the impression cylinder whereby the proof roller or cylinder causes a second printing on the web from the printing cylinder after a first printing at the said nip.

3. A printing machine as claimed in claim 1, in which the proof roller or cylinder and the path-length adjustment means are arranged in that order relative to the web travel direction upstream of the nip between the printing cylinder and the impression cylinder whereby the proof roller or cylinder causes a printing on the web from the printing cylinder before the printing at the said nip.

4. A printing machine as claimed in any one of claims 1 to 3, in which the printing unit is an offset printing unit which comprises a plate cylinder which. in use, transfers the image to be printed to a blanket cylinder, the web path passing between the blanket cylinder (constituting the said printing cylinder) and the impression cylinder.

5. A printing machine as claimed in claim 4, which two plate cylinders and two respective blanket cylinders are provided, the two blanket cylinders being arranged adjacent one another so that the web can be printed on both sides between these, each blanket cylinder, in addition to constituting one printing cylinder, also serving as the impression cylinder in co-operation with the other blanket cylinder.

6. A printing machine as claimed in claim 5, in which after passing between the blanket cylinders the web path is turned back towards the printing unit by the or a path-length adjustment means to the or a proof roller or cylinder adjacent one of the blanket cylinders whereby, in use, one side of the web is printed again.

7. A printing machine as claimed in claim 6, in which in the web travel direction there is disposed, downstream of the said proof roller or cylinder adjacent one of the blanket cylinders, a further path-length adjustment via which the web can be guided to a further proof roller or cylinder adjacent the other of the blanket cylinders whereby the opposite side of the web can be printed again by being pressed onto that other blanket cylinder.

8. A printing machine as claimed in claim 5, in which before passing between the blanket cylinders the web path first passes between the or a proof roller or cylinder and one of the blanket cylinders, whereby one side of the web is printed, and then to the path length adjustment means.

9. A printing machine as claimed in claim 8, in which in the web travel direction there is disposed downstream of the path length adjustment means, a further proof roller or cylinder adjacent the other of the blanket cylinders whereby the opposite side of the web can be printed by being pressed onto that other blanket cylinder, and downstream of this further proof roller or cylinder a further path length adjustment means which is arranged to turn the web back towards the nip between the blanket cylinders.

1 0. A printing machine as claimed in claim 8, in which the path length adjustment means is arranged to guide the web to pass between the blanket cylinders, and in which after passing between the blanket cylinders the web path is turned back towards the printing unit by a further path length adjustment means to a further proof roller or cylinder adjacent the other of the blanket cylinders whereby the opposite side of the web can be printed again by being pressed onto that other blanket cylinder.

11. A printing machine as claimed in any one of the preceding claims, in which several printing units are disposed one downstream of the other.

1 2. A printing machine as claimed in any one of the preceding claims, which is adapted so that the or each printing cylinder is to carry an image which extends over at least half the circumference of that cylinder whereby the web can be printed on one or both sides with printing which extends continuously along the printed surface without interruptions (gaps).

1 3. A printing machine as claimed in claim 12, which is adapted so that the or each printing cylinder is to carry an image which extends over exactly half the circumference of that cylinder.

1 4. A printing machine as claimed in any one of the preceding claims, in which the or each path length adjustment means comprising a displaceable paper-carrying roller.

1 5. A printing machine as claimed in claim 14, in which the or each paper-carrying roller constituting the path-length adjustment means is mounted for displacement in swivel mountings.

1 6. A printing machine as claimed in claim 14 or claim 15, in which the or each path-length adjustment roller is displaceable by a hydraulic or electromagnetic adjustment device.

1 7. A printing machine as claimed in any one of the preceding claims, in which the path-length adjustment means comprise or are provided with air blast strips.

1 8. A printing machine as claimed in one of claims 1 to 16, in which means is provided for blasting anti-smearing powder between the path-length adjustment means formed as paper carrying roller and the web.

1 9. A method of printing a continuous web in a web-fed printing machine, wherein after an image is printed onto the web by a printing cylinder, the web is brought into contact with the same printing cylinder a second time thereby to have the same image printed again.

20. A method as claimed in claim 19, in which the web is first printed by passing it between the printing cylinder and an impression cylinder and is printed a second time by passing it between the printing cylinder and a secondary impression cylinder.

21. A method as claimed in claim 19, in which the web is first printed by passing it between the printing cylinder and a secondary impression cylinder and is printed a second time by passing it between the printing cylinder and a main impression cylinder.

22. A method of printing a continuous web on both sides in a web-fed printing machine, wherein the web is passed between two printing cylinders rolling adjacent one another and wherein one or both sides of the web are printed additionally by contact with the respective printing cylinder upstream or downstream of the nip between the printing cylinders.

23. A web-fed rotary printing substantially as specifically described herein with reference to.any one of Figs. 1 to 4 of the accompanying drawings.

24. A method of printing a web in a webfed rotary printing machine, substantially as specifically described herein with reference to any one of Figs. 1 to 4 of the accompanying drawings.