GB2102344A

GB2102344A - Cooler for printing machine

Info

Publication number: GB2102344A
Application number: GB08220719A
Authority: GB
Inventors: Hermann Fischer
Original assignee: MAN Roland Druckmaschinen AG
Current assignee: Manroland AG
Priority date: 1981-07-18
Filing date: 1982-07-16
Publication date: 1983-02-02
Also published as: FR2509665B1; CH657092A5; DE3128430A1; GB2102344B; IT8248785A0; IT1148198B; DE3128430C2; FR2509665A1

Abstract

The cooler (7) which is located downstream of the drier (6), itself located downstream of printing units (3, 4, 5), comprises cooling rollers (9, 10, 11), at least two (9, 10) being positionable apart or against one another and are constructed as calendering rollers so that the web (2) running between them can be both cooled and calendered. The difference in the web path-length caused by the displacement of the roller (9) between its two positions, is compensated by two rollers (12, 13) arranged to operate simultaneously to change the path length so that the overall path- length remains the same. Alternatively, the displaceable roller may be arranged for movement that does not alter the web path-length. Two pairs of cooling/calendering rollers may be located one above the other like the four cylinders of an offset two-sided printing unit enabling similar side walls to be used for the cooler as for the printing unit. <IMAGE>

Description

SPECIFICATION Rotary printing machine with a cooler This invention relates to a rotary printing machine with at least one printing unit for printing a web, a drier located downstream of the, or the last, printing unit and a cooler located downstream of the drier and having a number of cooling rollers around which the web is guided.

Certain printing machines apply ink in a more or less surface-covering fashion in the individual printing units. However, since, because of its hydroscopicity, the web takes on a certain dampness of its own and, during the printing process, additionally absorbs water, this moisture can no longer escape from the extensively inkcoated surfaces. This leads to a waviness of the printed product during heat addition in the drier and the quality suffers. It also frquently happens that with certain papers printed and dried in this way there is no compact smooth surface since through the effect of the drier connected at the outlet side the paper fibres rise up and give a relatively rough appearance to the printed product.

An object of the invention is to provide a printing machine in which the above-mentioned disadvantages can be eliminated by an additional treatment in the cooler without additional expense on construction.

According to the present invention, there is provided a rotary printing machine including at least one printing unit for printing a web, a drier located downstream of the, or the last, printing unit and a cooler located downstream of the drier and having a number of cooling rollers around which, in use, the web is guided, wherein at least two of the cooling rollers are selectively positionable apart or against each other so as to be capable of acting as a pair of calendering rollers simultaneously to calender the web as it is cooled, means being provided whereby the overall web path-length is, or can be arranged to be, substantially the same with the two cooling rollers apart and against each other.

Conventional cooling rollers, in particular with so-called jobbing web-fed offset rotary printing machines, are merely aimed at chilling the ink heated in the drying installation and also the web, so that the ink is hardened and is therefore resistant. The cooler of a printing machine according to the invention has a two-fold function.

Through the pressing together of the cooling rollers, they are additionally used as calender rollers, by means of which the web passing between them is pressed, so that its surface has a smooth appearance. The waviness mentioned is therefore almost ironed out to give a flat web and the originally rough surface is smoothed, without the necessity of additional costly construction.

In one form of the invention, positioning means for altering the relative position of the two cooling rollers is such that the web path-length from a point immediately upstream of the two rollers to a point immediately downstream of the two rollers is the same when the rollers are apart and when they are against each other.

In anotherform of the invention, positioning means for altering the relative position of the two cooling rollers is such that the web pathlength from a point immediately upstream of the two rollers to a point immediately downstream of the two rollers is different when the rollers are apart and when they are against each other, and the said means whereby the overall path-iength is substantially the same is constituted by pathlength adjustment means which is adapted to change the path-length by an amount equal and opposite to the difference.

A particular advantage can be obtained by using cooling rollers, e.g. four arranged one on top of the other, with their relative bearing positions in the side wall corresponding to the bearing positions of the printing cylinders, e.g. of the plate and blanket cylinders, in the preceding printing unit(s). Thus an economy can be achieved in the production of the cooler side walls by utilising standardised printing unit side walls both for the printing units and also for the cooler. Furthermore, silicon inking devices, numbering units and web catching devices can be used in simple fashion, preferably in pre-arranged mounting positions provided on those side walls.

The invention may be put into practice in a number of ways but certain specific embodiments will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic representation of a three-colour web-fed offset rotary printing machine for first and second forme printing Figure 2 is a detailed representation of the cooler of the printing machine of Figure 1; Figure 3 shows a second embodiment of the cooler: and Figure 4 shows a third embodiment variant of a cooler in accordance with the invention.

The three-colour web-fed offset rotary printing machine shown in Figure 1 includes a web indentation unit 1, from which a web 2 passes through three printing units 3, 4, 5 arranged one behind the other. In the printing units 3 to 5 the web 2 can be printed on both sides in conventional manner. In the drier 6 the web is dried after passing through the printing units 3 to 5. Finally the cooling is carried out in a cooler 7, after which the web is cut in conventional manner in a cutting and folding apparatus 8 the copies that are cut to size being then folded.

As can be seen in detail in Figure 2, the cooler 7 disposed between the drier 6 and the cutting and folding apparatus 8 includes three cooling rollers 9, 10 and 11 around which is guided the web 2 that is to be cooled.

In accordance with the invention at least two of the cooling rollers present in the cooler, i.e. the cooling rollers 9 and 10 in the cooling unit 7 in the embodiment according to Figure 1, can be positioned next to one another in order to submit the web 2 passing between them to a pressing or calendering operation. Thus the cooling rollers normally required in the cooling units carry out a double function. In order to fulfill the second, i.e.

the calendering function, the cooling rollers must be constructed as calender rollers so that they can be positioned against one another with a corresponding press force and hence the necessary pressure can be transmitted onto the top and underside of the web 2.

It is sufficient if, of two cooling and calendering rollers that can be positioned against each other, e.g. 9 and 10, only one of those rollers e.g. 9, can be positioned with the necessary force by adjustment means against the second fixedposition axis cooling and calendering roller, e.g.

1 0. For this reason the cooling and calendering roller 9 is eccentrically mounted. The separated position of the roller 9 is shown in Figure 2 by dashed lines and is referenced 9', whilst in the connected position the cooling and calendering roller 9 is shown in full lines.

Figure 2 shows that by swivelling of the cooling and calendering roller 9 from one of its two positions into the other, there is a difference in the length of the path of the web 2 in the cooling unit 7 from a point upstream of the roller 10 to a point downstream of the roller 9. In order to avoid a path-length difference of this kind leading to a tear in a web 2 due to the swivelling of the cooling and calendering roller 9, advantageously a so-called path compensating device acting as an overall path-length adjusting means is used which, in the embodiment according to Figure 2, consists of two paper carrier rollers 12 and 13. The paper carrier roller 12 can be mounted with a fixedposition axis, whilst the paper carrying roller 1 3 must be displaceable e.g. by being swivellable.

Through the swivelling of the paper carrier roller 1 3 into position 13', in accordance with the swivelling of the cooling and calendering roller 9 into the position 9', the web 2 can occupy the position referenced 2', and thus there is a path compensation equal and opposite to the difference brought about by a change in the position of the roller 9 such that the entire path length of the web 2 remains contant in both positions of the rollers 9 and 13.

It is advantageous to link the swivelling movement of the paper carrier roller 1 3 positively to the swivelling movement of the cooling and calendering roller 9. Therefore the paper carrier roller 13 mounted on a swivellable lever 1 3A, is positively connected via a bell-crank lever 14 to the eccentric lever 1 5 for the swivelling of the cooling and calendering roller 9, whereby both the bell-crank lever 14 and the eccentric lever 1 5 are together swivellable by a servo piston, e.g. a hydraulic adjustment piston 1 6 or an electromagnetic device. Thus it is ensured that at the same time as the swivelling of the cooling and calendering roller 9, a corresponding swivelling of the paper carrier roller 1 3 is effected for the path length compensation.

Figure 3 shows a second advantageous embodiment of a cooler 1 7. In contrast to the already described embodiment, at least two pairs of cooling rollers are placed next to each other.

The four cooling rollers 1 8, 19, 20 and 21 shown in Figure 3 are again, in accordance with the invention, used both for cooling and for calendering. For calendering, the two cooling and calendering rollers of each pair must be positioned against one another, i.e. the rollers 18 and 1 9 on the one hand and the rollers 20 and 21 on the other. Again it is sufficient, for each pair, to mount only one of the rollers swivellably or otherwise displaceably. The cooling and calendering rollers 1 8 and 20 are for this purpose mounted eccentrically.The cooling and calendering roller 1 8 can be swivelled by an eccentric lever 22 with the aid of a hydraulic adjustment piston 23 and the cooling and calendering roller 20 by an eccentric lever 24 by means of a hydraulic adjustment piston 25, i.e. can be pressed respectively against the fixed-position axis mounted cooling and calendering rollers 1 9 and 21.

It is advantageous to so determine the swivel paths of each of the cooling and calendering rollers 1 8 and 20, that path-length differences for the web 2 in the cooler 7, do not occur through their swivelling into the separated positions, shown in dashed lines and referenced by the corresponding reference number with prime; that is, on swivelling of the cooling and calendering roller 18, no path-length change occurs for the web 2, and the same applied for the positioning of the cooling and calender roller 20.

In an alternative embodiment it would be possible to arrange that respective path-length differences would occur on displacement of the rollers 1 8 and 20 but for those differences to be equal and opposite so that there is no change in the overall path length.

The actuation of the calender rollers occurs through the pistons 23 and 25 (or electromagnetic devices possibly) which can be both individually actuated and also commonly controlled. Individual actuation allows, for example, the use of the first two calender rollers 1 8 and 1 9 as a conventional pair of cooling rollers, whilst the calender rollers 20, 21 are used for calendering and cooling. Such a setting is advantageous if the print is inclined to come off to a particular extent. The printed web then first of all undergoes the conventional cooling, which makes the ink more resistant, and only then does the calendering take place without the fear of ink deposition. It is also possible to carry out the calendering in stages, i.e. the first pair of rollers operates with only moderate pressure the pressure being adjustable to zero and only the second roller pair operates with full i.e.

greater pressure.

The surfaces of the calendering rollers should basically be extremely smooth and this is true particularly for the downstream calendering rollers. With the first group of calendering rollers, in certain circumstances a certain roughness may be desirable.

The surface or peripheral speed of the rollers can also with advantage be given a slight variation, increasing in the web travel direction.

This can be achieved by a different rotational speed or, for a given rotational speed, a 2% diameter increase from one roller pair to a subsequent roller pair. This compensates for the change in paper tension that might occur through calendering and moreover an additional smoothing can be obtained in this way.

Figure 4 shows a further advantageous embodiment of a cooler 26 in accordance with the invention, which is excellent in particular with regard to functional economic advantages. Here again four cooling and calendering rollers 27, 28, 29 and 30 are shown which, in contrast to the embodiment of Figure 3 are arranged one over the other. Through the positioning and path-length adjustment means which, for the sake of clarity are not shown further in Figure 4, the cooling and calendering rollers 27 and 28 and the cooling and calendering rollers 29 and 30 are positioned against each other or apart with no change in the overall path-length for the web 2.Preferably the cooling and calendering rollers 27 to 30 of the cooler 26 in the side walls, of which in Figure 4 only one sidewall 37 can be seen, are mounted in predetermined positions which coincide with the bearing positions of the printing unit cylinders in the, or at least one of the, printing units, which are connected in series with the cooler 26. Thus a standardisation of the side wails 37 and the side walls 38 of the cooling and printing units is possible.

At the same time there can be provided on the side walls 37 that are standardised in this way, mountings for silicon-inking devices 31 and 32 for the surface and underside coating of the printing carrier web 2. In addition, because of the space available, there is the possibility of the arrangement of numbering units 33 and 34 and a paper catching device 35. The latter can be located either (or both) in front of and behind the group of cooling rollers and is particularly advantageous when a web tear occurs in the folding apparatus connected to the cooler 26 at the outlet side or in a pre-arranged unit.

Alternatively, reference 36 indicates a further arrangement possibility of a paper web catching device.

The four cooling and calendering rollers 27 to 30 shown in Figure 4 are mounted in predetermined bores which are identical with the bores of the four cylinders of the printing unit 38.

These printing cylinders lying one on top of the other are plate cylinders 39 and 42 and blanket cylinders 40 and 41, with which the web can be printed on both sides as it passes through the printing unit 38.

Depending on the required contact pressure, the conventional coolers can be reinforced or their casings can be appropriately strengthened so that even in the middle zones a sufficient calendering effect can be achieved.

The invention also resides in providing a cooler per se for a printing machine, in which at least two of the cooling rollers can act as calendering rollers and in which the web path-length is arranged to be the same whether the two rollers are positioned against each other or apart.

Claims

1. A rotary printing machine including at least one printing unit for printing a web, a drier located downstream of the, or the last printing unit and a cooler located downstream of the drier and having a number of cooling rollers around which, in use, the web is guided, wherein at least two of the cooling rollers are selectively positionable apart or against each other so as to be capable of acting as a pair of calendering rollers simultaneously to calender the web as it is cooled, means being provided whereby the overall web path-length is, or can be arranged to be, substantially the same with the two cooling rollers apart and against each other.

2. A printing machine as claimed in claim 1, in which positioning means for altering the relative position of the two cooling rollers is such that the web path-length from a point immediately upstream of the two rollers to a point immediately downstream of the two rollers is the same when the rollers are apart and when they are against each other.

3. A printing machine as claimed in claim 1 or claim 2, in which at least four cooling rollers are arranged so as to be capable of acting as calendering rollers in pairs, the rollers in each pair being positionable apart or next to one another in such a way that, independent of the position of the cooling rollers the web path-length in the cooler is always the same.

4. A printing machine as claimed in claim 3, in which of each pair of cooling rollers, respectively one cooling roller is mounted for rotation about a fixed-position axis and the other cooling roller is displaceable.

5. A printing machine as claimed in claim 1, in which positioning means for altering the relative position of the two cooling rollers is such that the web path-length from a point immediately upstream of the two rollers to a point immediately downstream of the two rollers is different when the rollers are apart and when they are against each other, and in which the said means whereby the overall path-length is substantially the same is constituted by path-length adjustment means which is adapted to change the path-length by an amount equal and opposite to the difference,

6.A printing machine as claimed in claim 5, in which the path-length adjustment means is provided upstream or downstream of the cooler and consists of a fixed-position axis web carrier roller and of a displaceable web carrier roller, and in which the displaceable carrier roller is linked to the positioning means for altering the relative position of the two cooling rollers so that adjustment of the displaceable web carrier roller is effected upon operation of the positioning means.

7. A printing machine as claimed in any one of the preceding claims, in which the positioning means for altering the relative position of the or each pair of cooling rollers comprises an eccentric mounting of one of the cooling rollers of the or each pair, which can be actuted by driving means.

8. A printing machine as claimed in any one of the preceding claims, in which the bearing positions of the cooling rollers in the side walls of the machine corresond to those of the printing unit cylinders of the or one of the printing units.

9. A printing machine as claimed in claim 8, in which the printing unit with cylinder bearing positions to which the bearing positions of the cooling rollers correspond, is a four cylinder offset, first and second forme printing unit.

10. A printing machine as claimed in claim 8 or 9, in which there is provided a silicon-inking device.

11. A printing machine as claimed in any one of claims 8 to 10, in which there is provided a paper catching device.

1 2. A printing machine as claimed in any one of claims 8 to 11, in which there is provided a numbering unit.

13. A printing machine as claimed in any one of the preceding claims, in which the force acting between the cooling rollers of the or each pair when they act as calendering rollers can be adjusted.

14. A printing machine as claimed in claim 13, having at least two pairs of cooling rollers which can act as calendering rollers, and in which the force between the first pair of cooling rollers can be adjusted to zero and that of the or a following pair of cooling rollers can be adjusted progressively greater.

15. A printing machine as claimed in any one of the preceding claims, having at least two pairs of cooling rollers which can act as calendering rollers, and in which the rollers are adapted or arranged so that the peripheral speed of the pairs of rollers increases in the web travel direction.

1 6. A printing machine as claimed in claim 15, in which the diameters of the rollers of the or a downstream pair of cooling rollers is larger than the diameters of the rollers of an upstream pair whereby a higher peripheral speed is obtained for the downstream pair for a given rotational speed.

1 7. A printing machine as claimed in any one of the preceding claims, having at least two pairs of cooling rollers which can act as calendering rollers, and in which the surface roughness of the first pair of cooling rollers is relatively greater than that of the or a following pair.

1 8. A cooler for a rotary printing machine, including at least two cooling rollers which are selectively positionable apart or against each other so as to be capable of acting as calendering rollers simultaneously to calender the web as it is cooled, means being provided whereby the overall web path-length through the cooler is, or can be arranged to be, substantially the same with the cooling rollers apart and against each other.

19. A cooler for a rotary printing machine, substantially as specifically described herein with reference to any one of Figures 2 to 4 of the accompanying drawings.

20. A rotary printing machine having a cooler as claimed in claim 18 or claim 19.

21. A rotary printing machine substantially as specifically described herein with reference to Figure 1 with any one of Figures 2 to 4 of the accompanying drawings.