GB2316063A - Feeding webs through printing presses - Google Patents

Abstract

A web 46 makes a single pass through a printing press, during which pass it is fed through successive print stations 1 to 4 and then, via rollers 54 to 70, through the same print stations a second time. The first and second feedings through the print stations are positioned at first and second locations, axially spaced along the print rollers, and result in four-colour printing on first and second sides of the web. The printing stations may be replaced by any other surface treatment station.

Description

METHOD AND APPARATUS FOR COLOUR PRINTING This invention relates to a method and apparatus for colour printing and is particularly applicable to the printing of labels, flexible packaging, and like materials in the field of product and service presentation and wrapping, and the broad aspects of the invention are applicable in the printing field generally, particularly in relation to articles which are printed in continuous web form, in the sense that the web is of length of the order of several hundreds of metres, and is thus printed continuously and wound continuously onto a paper core.

The invention may be applicable to more general processes of surface treatment and techniques there for for webs and the like. Although the process disclosed herein has been developed and is intended primarily for achieving a spectacular increase in the colour treatment of web materials, the techniques disclosed herein are of more general application and, for example, may lead to significant technical advantages in the enhanced utilisation of apparatus related to printing apparatus employing web treatment stations other than printing stations.

An example of an article which is printed in the continuous web form mentioned above is a web of labels, in which the main body of the web takes the form of a continuous sheet of release material or carrier agent and comprises a sheet of paper or plastics material coated with a release agent such as silicone, together with a face material (on which the labels are to be printed), comprising a film or paper substrate coated with adhesive for application to a product.

In the case of the colour printing of such a web of labels, the Ko-Pack All-In-One-Pass press has established the technique of colour printing such a web, for example in 6 colours, these being applied at 6 corresponding colour printing stations at circumferentially spaced positions around the periphery of one or more impression drums.

Where, for example, it is desired to print different colours, then a further drum and 6 further printing stations need to be provided, but this inevitably increases both the capital cost of the press and its operational costs.

We have identified a marketplace requirement for a facility to print additional colours in one press, without the attendant increase in cost and complexity inherent in the above-mentioned approach of simply duplicating the printing facilities.

There is disclosed in US 5,483,887 (Koenig & Bauer) a web-fed rotary printing press which prints multiple colours on both sides of a paper web. As disclosed in columns 3 and 4 of the text, the printing machine comprises a right side printing group 3 which prints a first side of the web 14. The printing machine further comprises a printing group 10 on the left or second side of the printing machine 1 which prints the web in additional colours. These facilities amount merely to additive printing steps achieved by additive provision of printing stations with appropriates paths between them to permit air drying. This proposal does not provide for enhanced utilisation of printing stations.

An object of the present invention is to provide a method and apparatus applicable to the "all-in-one-pass" technique of printing utilising a single printing press having corresponding printing stations for printing colours onto a web, which is colour-printed in one pass through the press, wherein the number of colours obtainable from the printing press in a single pass exceeds the number of printing stations in the press and through which the web passes. A further alternative objective of the present invention is to provide a method and apparatus adapted to increase the output of a single printing or surface treatment station in a printing press or surface treatment apparatus, or to provide improvements generally in such methods and apparatus.

According to the invention there is provided a method and apparatus for colour or other printing or surface treating a web in a press or apparatus on an "all-in-one-pass" basis, as defined in the accompanying claims.

In an embodiment described below, the method and apparatus provides the step of passing the web to be printed successively through a number of printing stations, for example six, in each of which a single colour is printed onto the web. Then, after that preliminary colour printing stage and suitable drying of the ink, the web is caused to re-enter the assembly of printing drum and printing stations so as to be subjected to a second sequence of colour printing stages, during which for example, six further colours are applied to the web so that it has then been printed with twelve colours during the course of one pass through the press.

Moreover, this has been achieved by use of only six printing stations, each of which, in the embodiment, prints the web with two colours, one during each pass of the web through that station.

It will be understood that web synchronisation means which effects accurate registration between the web and the rotary elements of the printing station is provided in order that the successive printing steps at each subsequent station are effected with accurate registration of the web and associated printing elements.

For this purpose a synchronising mechanism may be provided, for example comprising dancer rollers providing the facility for positional manipulation of the web with respect to the printing assembly between successive passes of the web through the printing stations. As part of the synchronisation means, there may be provided suitably placed registration marks on the web to enable proper synchronisation between the printing stages to be achieved. Methods and apparatus for achieving web synchronisation in printing apparatus are known and as such may be utilised for the purposes of the present invention.

In the embodiments, it has been found that substantially effective web synchronisation can be achieved by means of controlling web tension with the web drive and guide rollers, in combination with automatic means for web tension control. In this way, the registration between the web and the rollers maintains synchronisation at the web/roller contact regions. The tension maintenance system operates to maintain an operating environment in which web control forces applied to the web material are maintained generally constant so that web de-synchronisation factors can be largely eliminated.

In the embodiment, the web passes through each half of the printing station during its progressive pass, at laterally displaced portions of the station, whereby those portions of the station can each simultaneously print with their respective one of the two colours printed by that station, ie double the number of colours can be printed relative to the number of printing stations fitted or used.

In this manner there is achieved the advantage that a printing press having N printing stations is able to print up to 2N different colours on a single web in one pass. The web width handled by the printing station in each successive pass of the web through it is less than the total working width of the station. Usually, the working width of the printing station will be approximately twice the actual width of the web.

It will be understood that the economies of construction and use in relation to the printing stations include the fact that each such printing station has its own individual drive input facility, and indeed requires only single provision of other facilities such as socalled washing-up facilities (utilised at the time of changing one or more printing colours at a printing station).

It is, of course, a matter of common practice that a web will be printed with any number of colours in two or more successive passes through colour printing apparatus with appropriate synchronisation for colour alignment (registration) purposes. The method and apparatus of the present invention offers the ability to print up to double the number of colours by enabling a web to pass a second time through the same printing station in the course of a single pass through the printing press, so that a second colour is printed on the web in appropriate registration with a second and different colour image printed thereon by the same station during the same pass of the web through the press.

In this specification, references to "the same station" should be interpreted as follows. Broadly, the expression refers to a single printing station with respect to the location of that station in relation to the central impression (or printing) drum(s) in the press, and around which the two or more stations are grouped. Usually, a given printing station will have a single drive facility, and single other facilities as described above. It is not to be understood that references to "the same printing station" necessarily indicates that successive passes of a web through that printing station will cause the web to be printed at the same portion of that station. Thus, for example, usually the web will be printed by two different halves of the same station in its one pass through the press.

Further in accordance with the described embodiment, the method and apparatus provides for the web during its single pass through the press to be turned and offset laterally with respect to its longitudinal direction prior to its second pass through a given printing station, whereby the web is reintroduced to the printing station from which it has relatively recently emerged, and is then printed again, on its back side or its front face, with additional colours. Usually, the number of additional colours will be the same number as were originally printed on the web in the course of its first pass through the said station.

In the embodiments, the printing stations are not described in detail as these are, in their general construction, substantially of known technology, apart from the measures described below and provided for the purpose of minimising ink migration. The printing stations are accordingly chosen with regard to the web printing requirements and the principles of the present invention are applicable to printing stations of any required kind, for example letterpress or rotary screen printing stations, the latter being particularly applicable to the printing of acetate web materials for "invisible" labelling applications.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which : Fig 1 shows a side elevation view of a printing press in accordance with the invention; Figs 2, 3, 4 and 5 show modifications of the embodiment of Fig 1 to provide for, respectively, four and six and eight and ten colour printing; Fig 6 shows a general view of web pass-turning arrangements for transferring a continuous web, laterally with respect to several printing stations, between its successive passes around the impression drum and through the printing stations; Fig 7 shows a modification of the apparatus of Fig 1 incorporating, interalia, modified and additional registration means for the web; and Fig 8 shows a perspective view, somewhat similar to that of Fig 6 showing apparatus for lateral transfer of a web between opposite side portions of a set of printing rollers between successive passes of the web through the printing stations of those rollers in accordance with the invention; and Figs 8A and 8B show enlarged portions of Fig 8 in which the sequence of web paths is, in each case, indicated by a corresponding alphabetical sequence.

As shown in Fig 1, a printing press 10 comprises first and second unwind stations 12, 14, a printing assembly 16, comprising six printing stations 18, 20, 22, 24, 26 and 28, two rotary die cutting stations 30, two waste matrix rewinders 32, and a rewind station 34, for the finished and printed product.

Press 10 comprises numerous additional processing stations, some of which will be described below, and notably among these is the web cross-over unit 36 whereby the web is reintroduced to the printing stations so that it passes a second time through these and is printed with a second set of colours.

The general mode of operation of press 10 is as described in our prior patent EP 0 324 764 B1, and will therefore be described more briefly and generally here, in the following terms.

At unwind stations 12 and 14 there are provided corresponding rolls of paper or other roll material such as plastics, film and foil materials and flexible material for packaging applications. These web materials are unwound from rolls 38, 40 and conveyed via webtensioning and drive and control roller systems indicated at 42, 44 and 46 to the region of printing assembly 16.

Roll 40 comprises web material to be printed at printing stations 18 to 28. Roll 38 comprises web base carrier material for coating with release materials such as silicone and for subsequently assembly with the printed and adhesively-coated web material from roll 40, for subsequent die-cutting at stations 30 and removal of waste matrix material at 32 and subsequent rewinding at 34 of the finished product.

The two webs of, respectively release material and printed and adhesively-coated label material 44, 46 are merged and joined at the region 48, after which diecutting and removal of the resultant matrix occurs prior to rewinding at 34.

Press 10 includes provision for numerous other operations which are incidental to the principal area of interest in the present application, namely the printing operation, and these will not be further described here.

Figs 2, 3, 4 and 5 show modifications of the press 10 of Fig 1 in which corresponding parts are identified by the same reference numerals as in Fig 1, notably the printing drums 50, 52 and their associated printing stations 20, 22, 24, 26 and 28. These embodiments differ in the numbers of printing stations which are provided, these being two in Fig 2, three in Fig 3, four in Fig 4 and five in Fig 5.

In accordance with the principles of the present invention, and the use of the web cross-over unit 36 whereby the web 40 of material to be printed is passed twice through the printing stations 20 to 28, the numbers of colours achieved from the press corresponds to twice the number of printing stations, and thus ten such colours are obtained from the five printing stations in the embodiment of Fig 5.

In these embodiments, the web return means 36 seen in Fig 1 is not shown as such, for simplicity of illustration, and will now be described in more detail with reference to Fig 6.

As shown in Fig 6, the web return means 36 comprises an assembly whereby the web 46 is able to pass twice through each of the four printing stations (identified in Fig 6 by numerals 1, 2, 3 and 4, this being achieved by the provision of appropriate turn rollers at 54, 56, 58, 60, 62, 64, 66, 68 and 70. As a result, the web is reintroduced to the printing stations 1, 2, 3 and 4 at an axially off-set position so that it is additionally printed with four further colours on the back or rear side of the web with respect to its first passage through those stations. After printing, the web passes onwards at 72.

In the embodiment of Fig 7, the press 74 is generally constructed in the same manner as the press 10 of Fig 1, but is provided additionally with flying splice twin unwind stations 76, 78 and an associated dancer-roll web tensioning station 80. As a result, the press 74 has a capability of producing more complex label assemblies in which (as, for example, in the case of booklet labels) there is a requirement for three separate webs to be assembled to produce the finished product. The twin unwind stations 76, 78 permit alternative use of rolls 82, 84 of web material according to requirements.

Press 74 also incorporates a second similar dancerroll tensioning station 86 for the web material from primary roll 40 of web material to be printed.

Turning to the embodiment of Fig 8, it is to be noted first that the general layout of the printing components shown in Fig 8, and the associated structures, correspond generally to the printing region of the press 10 of Fig 1. Accordingly, for convenience of reference, the same reference numerals have been inserted in Fig 8 as appear in Fig 1.

Fig 8 shows the assembly on a larger scale and in perspective so that the paths of the webs can be seen more clearly, and the details will be described in more detail than was adopted in the case of Fig 1.

Broadly, the functions performed in the apparatus of Fig 8 comprise the printing of two webs 100, 102 in printing assembly 16, namely at the printing stations 18, 20, 22, 24, 26 and 28. Each of the webs 100, 102 is passed twice through its group of printing stations, so as to be subjected to the dual printing process according to the invention. In each case, the two printing passes through the relevant print stations are identified at P1 and P2. In Fig 8, the opposite sides of the webs are identified, for both web 100 and web 102, by means of shading for one side and an unshaded showing for the other side. Hence, it can be seen that the web 100 is printed in its pass P1 on its unshaded side whereas in its pass P2 it is printed on its shaded side. In the case of web 102, the web is printed, on both passes P1 and P2 on its unshaded side. This illustrates the versatility of the process and is achieved by means of the dispositions of the web transfer rollers to be described below.

It will be noted in Fig 8 that web 100 is subjected to a folding operation commencing at roller 104 and continuing via roller 106 until the webs in a fully folded condition at roller 108. This folded configuration is adopted for the purpose of booklet label-making, which is not a matter of concern for the present invention and is therefore not further described.

It should further be noted that in the embodiment of Fig 8 there are provided, in the course of the passage of the webs along their paths as shown in Fig 8, numerous web treatment and processing facilities and stations which effect various operations such as application of glue/hot melt, web guidance, flatbed die-cutting, ultraviolet drying, folding etc. These processes are not further described here, being in most cases relatively conventional for the processing of label and other webs.

Considering now the arrangements provided in the Fig 8 embodiments for the so-called web cross-over unit for re-introduction of the web to the printing stations, the arrangements are as follows. Web 102 initially passes (P1) via printing stations 18 and 28 and guide rollers 110, 112 to a first lateral web turn roller 114 whence the web proceeds via a lateral run 116 to an end roller 118 and a lateral return run 120 to an offset second lateral turn roller 122. Then the web proceeds via an in-line run 124, and a roller 112. After passing round roller 112, the web returns in a run (not shown) to printing station 18, followed by printing station 28, with the shaded side of the web uppermost prior to entry into the nip of printing station 18, as in the case of its first pass through that printing station.

Effectively, the web has been laterally offset by virtue of the distance of offset between the lateral turn rollers 114 and 122, so that it then re-enters between the rollers of printing station 18 at a laterally offset position.

Fig 8A shows, on a larger scale than Fig 8, the portion of Fig 8 corresponding to the web movements described in the last preceeding paragraph. In Fig 8A, the portions of the travel of the web are indicated in sequence by the corresponding alphabetical sequence A to Q.

In the case of web 100, the general arrangement is somewhat similar to that described above for web 102, with differences of detail as follows.

In its initial pass (P1) web 100 passes a first time through printing stations 22, 20, 26 and 24, and thence via runs 126 and 128 to a first web lateral turn roller 130 and web lateral runs 132, 134 to a second web lateral turn roller 136 and web runs 138, 140, and hence into printing stations 22, 20, 26 and 24 in sequence.

In Fig 8B, in a manner similar to that of Fig 8A, the portion of the travel of the web described in the last preceding paragraph above is shown on a larger scale and with the sequence of web paths indicated by the corresponding alphabetical sequence from A to T.

It can now be seen that by virtue of the use of inclined web lateral turn rollers, convenient lateral offsetting of the web runs is achieved enabling re-entry of the web into the printing stations at the respective laterally offset positions.

In the above embodiments, the system for representation of the web to the printing stations enables double the number of colours to be printed in one pass of the web through the press, as compared with conventional press systems, and thus a press having, for example, four print stations is capable of printing eight colours in just one pass of the web through the press.

Each of the print stations is constructed so as to enable two different colours to be printed by that station simultaneously, while the web passes once through the press and twice through the print stations. This dual colour printing is achieved by using only the cylinders, plates and gears normally associated with single colour printing, while achieving the dual colour process as described, thereby significantly reducing the "make-ready" time and costs normally associated with extra printing colours. To minimise the effect of printing two colours with one roller at each printing station, there may be provided means to inhibit lateral movement of colours/ink lengthwise of the rollers. For example, the rollers may be relieved or grooved at their outer peripheries at a central location so that ink migration is thereby inhibited.

Each of the dual printing stations is individually driven and fitted with its own single wash-up unit and just one inking system. An ultra-violet drying unit is provided for each print station.

In the embodiments, for example, printing or impression drums of 400 millimetres width enable maximum web widths of 400 millimetres or two webs at 200 millimetres width each, or of course a single 200 millimetre web.

Also in the embodiments, the printing stations are disposed around printing drums, such as central impression drum 50. However, the invention is equally applicable to other printing arrangements including printing stations in which the relative disposition of the printing stations is that of a stacked configuration with the individual stations generally vertically disposed with respect to each other. The arrangements whereby the web makes a second pass through a given printing station are otherwise generally as described above.

As to the products which can be printed by the press, these include, in continuous web form, labels, smart cards, plastics articles, film and foil items and flexible packaging. Examples of labels suitable for this format are booklet labels and Piggyback labels and other promotional labels.

The web material itself may comprise a continuous carrier with silicone release material thereon and combined with a continuous face material laminated with adhesive. Alternatively, the web may be a continuous single web which is printed and converted ie a paper or board or film or plastic substrate.

The web may be printed on both of its sides, including on the side which is coated with adhesive, with the web being turned prior to passage through the same printing stations a second time.

Amongst other modifications which could be made in the above embodiments while remaining within the scope of the present invention are modifications to the details of the web lateral offset facility for transfer of the web between the laterally offset portions of the printing stations. Thus, for example, it may not in certain applications be necessary for the direction of lateral offset to be at 90 degrees with respect to the main direction of travel of the web. By appropriate adjustment of the inclination of the turn rollers, various attitudes of the generally laterally-directed runs could be adopted.

Claims (26)

1 A method of colour printing in a printing press comprising at least one printing station for printing at least one colour on a continuous length of web comprising a) passing said web through said printing station to print said one or more colours successively on said web; characterised by b) passing said web through said printing station a second time and causing said station to print a second colour on said web; and c) said second passage of said web through said printing station being effected in the course of a single passage of said single length of web through said printing press and said first and second printing steps being effected simultaneously on said web.

2 A method of colour printing in a printing press characterised by passing a web through a printing station a second time and causing said station to print a second colour on said web in the course of a single passage of said web through said printing press.

3 A method according to claim 1 or claim 2 characterised by effecting said first and second printing steps at distinct portions of said printing station.

4 A method according to claim 3 characterised by effecting said first and second printing steps at opposite ends of said printing station.

5 A method according to claim 4 characterised by the step of moving said web laterally with respect to the directions of normal lengthwise web movement by passing the web around a turn roller and directing web travel in said lateral direction before turning the web back into one of the lengthwise directions.

6 A method according to claim 5 characterised by the step of passing said web around an end return roller between said two web turns.

7 A method according to claim 6 characterised by said step of moving said web laterally comprising moving said web initially in the opposite direction to the direction required for the offset between said opposite ends of said printing station, and then more than offsetting this in the travel of the web in the return run thereof.

8 A method according to claim 5 characterised by passing the web through a ultra-violet drying station therefor between the first and second passes of the web through said printing stations.

9 A method according to any one of the preceding claims characterised by the step of carrying out said printing steps on opposite faces of said web.

10 A method according to any one of the preceding claims characterised by the step of causing web drive or guide rollers to be held in positive registration with said web and causing automatic tension control means to maintain web tension between said rollers.

11 A method according to claim 10 characterised by employing as said web drive or guide rollers, rollers having mutually interfitting or nesting conical portions for holding said web in positive registration therewith.

12 A method of surface treating a web in a surface treatment apparatus characterised by passing said web through a surface treatment station a second time and causing said station to surface treat for a second time said web in the course of a single passage of said web through said surface treatment apparatus.

13 A method of colour printing in a printing press substantially as described herein with reference to the accompanying drawings.

14 Apparatus for colour printing comprising a printing press having at least one printing station for successively printing at least one colour on a continuous length of web, said printing press comprising : a) means for passing said web through said printing station to print said at least one colour on said web; characterised by b) means adapted to pass said web through said printing station a second time, and said printing station being adapted to print a second colour on said web; c) said means for passing said web through said printing stations being adapted to permit said printing steps to be effected in the course of a single passage of said single length of web through said printing press whereby said first and second printing steps are effected simultaneously on said web.

15 Apparatus for colour printing characterised by means adapted to pass a continuous length of web through a printing station a second time to print a second colour on said web in the course of a single passage of said web through said printing press.

16 Apparatus according to claim 14 or claim 15 characterised by said printing station comprising distinct portions for effecting said first and second printing steps.

17 Apparatus according to claim 16 characterised by said printing station having said distinct portions at opposite ends of said printing station.

18 Apparatus according to claim 17 characterised by means to move said web laterally with respect to the directions of normal lengthwise web movement through the press, said means comprising a turn roller adapted to direct the web travel in said lateral direction before it is turned back lengthwise of the press.

19 Apparatus according to claim 18 characterised by an end return roller adapted to have said web passed around it between said web turns.

20 Apparatus according to claim 19 characterised by said end return roller being positioned so that said web initially moves in the opposite direction with respect to the direction corresponding to the offset between said printing station portions so that the return run of the web can then more than offset this.

21 Apparatus according to claim 18 characterised by an ultra-violet drying station for said web located to operate on said web between the first and second passes of said web through said printing station.

22 Apparatus according to any one of claims 14 to 21 characterised by said apparatus being adapted to effect said printing said first and second printing steps on opposite sides of said web.

23 Apparatus according to any one of claims 14 to 22 characterised by said printing station being one of a plurality of stations grouped around a central impression drum.

24 Apparatus according to any one of claims 14 to 22 characterised by said printing station being one of a plurality of printing stations disposed in a generally vertically-stacked configuration.

25 Apparatus for surface treatment of a web in surface treatment apparatus characterised by means adapted to pass a continuous length of said web through a surface treatment station a second time to surface treat said web a second time in the course of a single passage of said web through said surface treatment apparatus.

26 Apparatus for colour printing in a printing press substantially as described herein with reference to the accompanying drawings.