GB2332393A

GB2332393A - Rotary short inker

Info

Publication number: GB2332393A
Application number: GB9813512A
Authority: GB
Inventors: Philip Miles Hardy; Peter Greenway
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-12-05
Filing date: 1998-06-24
Publication date: 1999-06-23
Anticipated expiration: 2018-06-24
Also published as: GB2332393B; GB2344071B; AU1344599A; WO1999029510A1; GB9813512D0; GB2344071A; GB2332393A9; GB0007462D0

Abstract

In an inker for a printing press capable of producing high coating weights as well as low ones, an ink train of at least two roll cylinders 7, 8 transports ink from a reservoir 1 to a printing plate 4, the final roll cylinder 8 is provided with a doctor blade 9 and (preferably with the other rollers of the train) has a surface of rubber or synthetic polymeric or resin material. In use the doctor blade is spaced from the cylinder 8, preferably using a control system for maintaining a predetermined coating weight as measured on the product. The rollers 7, 8 may be vertically or generally horizontally aligned, but the vertical alignment shown can also be used with a hard anilox roll for producing high coating weights. The roll cylinders may be mounted in individual cassettes for ease of removal or replacement, and guards may be provided for preventing egress of the printing medium into the environment.

Description

2332393 Rotary Short Inker The advent of electronically controlled

printing systems and computerised setting systems which are capable of quick and easy adaptation to a number of printing tasks in succession, and which are economic to use insofar as they are less labour intensive than more traditional printing methods, has made progressive inroads into the traditional methods in many applications.

Nevertheless, there remain tasks which are more suited to a traditional method, by virtue of the type of printing to be done, e.g. the properties of the material to be applied or the nature of the material being printed upon, or by virtue of the relative smallness or specialism of the task, since many of the more modern systems are particularly adapted for mass production, often at high speeds.

Among such tasks are to be found those requiring application of high coat weights, as in products with high visual impact, for example printed packaging, and the application of scratch-off inks or metallic colours. The application of silicone, adhesive, thermally sensitive or fluorescent coatings can also fall within this definition, as can the provision of patterned and protective coatings. At present, the only viable solution in some instances appears to be the deposition of a plurality of thin coatings rather than a single thick coating, since attempts to apply a thick coating tend to produce a product which is unacceptable, for example as regards uniformity of thickness or appearance.

All materials intended to be coated on a substrate by printing/ screening (i.e. the laying down ofa layer of the material from a roll cylinder irrespective of whether the layer is patterned), including those referred to in 1 the preceding paragraph, will henceforth be referred to generically as printing media, irrespective as to whether they are intended to form a visible image.

It is possible to adopt known screen or gravure methods for high coating weights, at least to a certain extent, but such methods require a large capital outlay, and are relatively difficult to adapt for different tasks. if the press in use was not originally adapted to such methods, retrofitting can be slow and expensive, and even where the press is so adapted, alteration to accommodate different sizes of the printed articles, etc., dictated by a specific task, can be very expensive.

as slow and There therefore exists a need for a relatively simple printing system which is capable of providing high coating weights, which can be readily changed to produce different products, and which is economical to maintain and adjust for coating weight. There is also a need for a printing system in which fly and splash of the printing medium to the external environment can be reduced or avoided, and for a printing system comprising a train of roll cylinders in which at least one or more of the roll cylinders may be simply and cleanly removed for replacement or cleaning. For example, it would be advantageous to be able to substitute a final anilox cylinder by another of differing Shore hardness, e.g. one being a conventional "hard" cylinder, and the other having a surface of rubber or synthetic polymeric or resin material.

The invention will now be more particularly described with reference to the accompanying drawings, in which:- Figure 1 shows a rotary short inker in sideways crosssection; 2 1 Figure 2 shows a cross section of the inker of Figure 1 taken along lines A-A; Figure 3 is a first perspective view of the inker of Figure 1; and Figure 4 is a second perspective view of the same inker.

The rotary short inker shown in Figure 1 comprises an ink feeder portion 1 above which is mounted a printing portion 2. The printing portion comprises an impression or plate cylinder 3 carrying a printing plate 4, which in use is contacted a web of a printable substrate, for example of paper, transported round a paper transport cylinder 5. Commonly the web will be continuous, but alternatively, for example, some form of sheet feeder will be provided.

As herein particularly described, plate 4 is a relief plate, constituting a known, economically produced and readily changeable f orm of image bearing means, but it should be understood that the alternative forms of plate, for example a lithographic plate, could be used.

Furthermore, although a direct printing arrangement i. in which ink from the plate s shown is transferred directly to the paper web, an offset arrangement in which a blanket roll cylinder is placed between the printing plate and the printable substrate, could alternatively be provided. Thus it should be understood that the invention is not to be construed as being limited to direct printing processes, nor to the use of relief printing plates, nor to the use of any particular form of printable substrate.

The ink feeder portion 1 comprises a base portion 6 which in use acts as a reservoir for the ink or other printing 3 medium. A meter roll cylinder 7 is arranged so that its lower surface dips into the reservoir and picks up and becomes coated by printing medium therefrom. Although a simple reservoir is shown, it should be understood that any known form of printing medium source could be used, and commonly the medium is pumped to the reservoir by a recirculating pump to maintain the reservoir at a predetermined level. An alternative arrangement would be, for example, one in which the printing medium is pumped over the meter roll, excess medium from the meter roll being collected in a tray for recirculation.

An upper roll cylinder 8 is arranged to contact the meter roll cylinder or at least the printing medium coated thereon, whereby the printing medium is transferred to roll cylinder 8, and is located vertically above the meter cylinder. The roll cylinder 8 is commonly known as an anilox roll, and this term will henceforth be used for the final roll of any train of inking roll cylinders, immediately preceding the printing plate bearing an image to be printed.

The anilox roll cylinder 8 is arranged to contact the surface of the relief plate 4 so that ink is transferred to the image portions thereof, and from the plate 4 to the paper web around the roll cylinder 5. It will be understood that successive roll cylinders in the train from meter roll cylinder 7 to paper transport roll cylinder 5 are arranged in a counterrotating sequence.

A doctor blade 9 is mounted adjacent the roll cylinder 8, and is rotatably mounted so that the distance of the edge of the blade 9 can be adjusted with respect to the roll cylinder 8, to control the amount of ink on the roll cylinder, and thus the amount of ink which is transferred to the relief plate and the paper web. In part, it also serves to ensure that the coating weight of the printing 4 1 1 medium on the paper web is uniform over the whole area of the printed image.

In a conventional letterpress, the ink is passed to a 5 soft or hard plain roller via a series of alternatively soft and hard rollers, arranged so that the ink film, which when initially picked up from a reservoir is thick, is progressively thinned. No doctor blade is provided on the final roller in this arrangement.

In other conventional printing arrangements, the anilox roll cylinder is formed of a hard material, such as steel or a ceramic, and its surface is screened or has a cell structure, to receive the printing medium. As is well known in the art, the provision of a screen lowers the apparent Shore hardness, and in general the lower the viscosity of the printing medium the lower the Shore hardness which is required for a given coating weight. Part of the printer's skill in enabling efficient and effective printing lies in the selection of an anilox roll cylinder with a suitable cell structure, together with a printing medium of suitable properties, including flow properties such as viscosity (and variation of the latter with temperature), and an appropriate printing speed, all bearing in mind the nature of the substrate to be printed upon. Other variables include the relative spacing or contact pressure between the roll cylinders 7 and 8, and adjustment of the doctor blade.

In this conventional type of set-up, the edge of the doctor blade is relatively sharp, and in direct or extremely close contact with the surface so that when the latter contacts the relief plate 4 the only ink thereon for transfer is essentially that within the cell structure. The blade can be arranged to point in or against the direction of rotation of the anilox roll cylinder 8 as determined by the printer. Contact between the doctor blade and the anilox roll cylinder wears both components, which eventually need to be replaced.

Such an arrangement serves well with conventional printing inks and coating weights of up to 1 to 3 gM/M2. However, attempts to increase coating weight, for example by adjusting the cell structure of the anilox roll cylinder, altering the viscosity of the printing medium, or spacing the doctor blade away from the anilox roll cylinder, tend to be unsuccessful. In particular, attempts to provide a thicker layer of printing medium on the anilox roll cylinder by adjustment of the doctor blade away from the roll cylinder tend to produce a layer of non-uniform thickness, with consequential effects in the printed image, such as vertical lines, or streaking of intensity of the printed portions of the image.

It has now been found that if the surface of the anilox cylinder is soft relative to steel or ceramics materials, higher coating weights can readily be achieved without impairing image quality, particularly when a doctor blade spaced from the anilox roller is employed. The spacing of the doctor blade not only enables higher coating weights, but avoids or reduces wear of both blade and anilox roller. It is also possible to employ a train of rollers in which the material forming the surface of each of the roll cylinders in the train from the reservoir to the anilox cylinder is soft relative to steel or ceramics materials, to obtain higher coating weights without impairing image quality.

Coating weights of up to around 30 gm/m2 have been achieved, and there is no reason to suppose that somewhat higher weights could not be obtained under certain circumstances.

6 1 Thus, in a first aspect the present invention provides an inker for a printing press, said inker comprising an ink train of at least two roll cylinders extending between an ink reservoir and a final roll cylinder which in use comes into contact with a printing plate, wherein the final roll cylinder of the train is provided with a doctor blade and has a surface of rubber or synthetic polymeric or resin material.

Also according to the first aspect, the invention provides a method of printing, in which the material to be coated on a substrate is transferred from a reservoir to a printing plate via a train of at least two roll cylinders, the final roll cylinder of the train having a surface of rubber or synthetic polymeric or resin material, wherein the thickness of the material on the final roll cylinder of the train is controlled by a doctor blade. Preferably the doctor blade is spaced from the final roll cylinder.

In a second aspect the present invention provides an inker for a printing press, said inker comprising an ink train of at least two roll cylinders extending between an ink reservoir and a final roll cylinder which in use comes into contact with a printing plate, wherein the surface of each roll cylinder of the train is of rubber or synthetic polymeric or resin material.

Also according to the second aspect, the invention provides a method of printing, in which the material to be coated on a substrate is transferred from a reservoir to a printing plate via a train of at least two roll cylinders, the surface of each roll of the train being of rubber or synthetic polymeric or resin material.

The first and second aspects of the invention may be combined.

7 In practising the invention according to the first and/or second aspects, the printer will exercise skill in the choice of printing medium, in particular the flow characteristics thereof, printing speed, etc. as before.

However, there is now a further variable which can be controlled to produce desired results, viz. the Shore hardness of the surfaces of the soft roll cylinders of the train, particularly that of the anilox roll cylinder. It is believed a soft cylinder surface yields to a certain extent in the vicinity of the nip formed with an adjacent doctor blade and/or the surface of an adjacent cylinder, depending on the viscosity of the printing medium, so permitting a fixed amount of printing material to pass through the nip. Excess printing medium is retained at the f ront of the nip, providing a reservoir for distribution along the length of the nip if necessary, as determined by the image to be printed.

Preferably the Shore hardness (as measured by a conventional Shore hardness meter) of at least the anilox cylinder (and more preferably of all the cylinders in the train) is 150 or more, and preferably 200 or more. It is preferably 600 or less, and more preferably 400 or less.

Preferably the coating weight produced by the use of the invention is greater than 4 gm/m2, and more preferably at least 8 gm/m2. As mentioned above, it has proved possible to produce imagewise uniform coating weights of up to at least 30 gM/M2 without the undesirable features found using conventional anilox roll cylinders, such as streaking of the image, or stringing of adhesive. Thus, a commonly desired range of coating weight of 8 to 15 qm/m', more commonly 8 to 10 gm/rd can easily and routinely be achieved with the present invention.

However, it is also possible with the invention of the first and/or second aspects to provide lower coating 8 1 weights, for example 2.8 gm/m, so that the same apparatus can be used for weights within the printing range provided by conventional presses. This could be achieved, for example, by employing lower printing speeds, and when a screened final cylinder is employed it is believed that this is due to there being less printing medium being squeezed out of the cells at higher speeds, and vice versa. Control of coating weight to a desired high or low level may also be effected by the invention according to the fifth and sixth aspects as described below.

Normally, the anilox roll cylinder is replaceable, and this feature is preferably retained. This enables the inker to be used with different "soft" anilox cylinders as in the present invention, but with different degrees of Shore hardness, and/or with a conventional hard steel or ceramic roll cylinder.

Thus, preferably, an inker according to the first and/or second aspects comprises a plurality of anilox roll cylinders of differing Shore hardness, and during set-up the printer will select the appropriate anilox roll cylinder having regard to other parameters such as printing speed and flow properties of the printing medium. In particular, the Shore hardness and viscosity of the printing medium may be selected conjointly to produce a desired coating weight. Advantageously, the other cylinders of the train may also be replaced in a similar manner, as appropriate.

Particularly in view of the relative softness of the anilox roll cylinder, the operative edge of the doctor blade is preferably blunt and adjusted in use to be spaced somewhat away from the anilox roll cylinder. This also facilitates any requirement for a high coating weight, by enabling a thicker coating to be formed on the 9 anilox roll cylinder. Still more preferably, in such an arrangement, the doctor blade is reversed, with its operative edge facing in the direction of rotation of the anilox roll cylinder. It is believed that this is the best arrangement, for ensuring that the streaking referred to above is avoided, the blade merely acting to shear away surplus printing medium over a predetermined thickness, rather than exerting any cutting action. Furthermore, the lack of mutual contact markedly reduces wear of both the blade and the anilox roll cylinder.

While it is preferred that the anilox roll cylinder has a screened or cell structure, an untextured surf ace could be employed. Where there is a cell structure, and contrary to conventional practice with a steel or ceramic anilox roll cylinder, the doctor blade can be adjusted away from the cylinder surface so that the printing medium thereon as it comes into contact with the printing plate lies not only within the cell structure, but above such structure, i.e. above the cylinder surface.

A further advantage of having the doctor blade spaced from the surface of the anilox cylinder is that it provides a further variable for control of the printing process, and of the coating weight. Whereas coating weight in a system using a hard anilox roller is dependent on factors such as viscosity of the printing medium and the cell structure of the anilox cylinder, some or all of which can be difficult to alter readily, doctor blade spacing can be altered relatively easily. This feature therefore permits a printing press to be set up with final control of coating weight being left to adjustment of the position of the doctor blade.

In fact, it is possible to measure coating weight of the printed product, and to use the result to assess how or in which direction the doctor blade should be adjusted.

1 Since it is possible automatically to measure coating weight as a printed product leaves the press (or the anilox cylinder), the process can be automated by using the measurement to control the doctor blade spacing so as 5 to ensure a predetermined coating weight is attained.

This enables a single run to have a consistent coating weight despite the influence of other variables which may change during the run, for example a change in viscosity of the printing medium as the temperature changes, or for a coating weight to be changed either during a run or from one run to another, the latter option perhaps involving a different printed product, while the former option could be useful if products which are identical apart from coating weight are required from a single run.

Thus, in a third aspect, the invention provides an inker for a printing press comprising a final roll cylinder provided with a doctor blade, means for measuring the coating weight or coating thickness of a printed product leaving, or which has left, the final roll cylinder, and means for controlling the position of the doctor blade relative to the surface of the final roll cylinder in accordance with the measured coating weight or coating thickness.

Also according to the third aspect, the invention provides a method of printing using an inker for a printing press comprising a final roll cylinder provided with a doctor blade, wherein the coating weight or coating thickness of a printed product leaving, or which has left, the final roll cylinder is measured, and the position of the doctor blade relative to the surface of the final roll cylinder is controlled in accordance with the measured coating weight or coating thickness.

11 The third aspect may be combined with the f irst and/or second aspects.

In a conventional inker, the axes of successive roll cylinders lie in a plane which is at most only somewhat inclined above horizontal in the ink feeding direction. It has now been additionally found that relatively high coating weights can be attained even with a final hard anilox roll cylinder when the rotation axis of the anilox roll cylinder lies generally vertically, say within 201, preferably within 10", more preferably within 50, and ideally substantially vertically, above the axis of the immediately preceding roll cylinder.

In such a case the anilox cylinder is provided with a doctor blade which in use will be in contact with it, in reverse or forward orientation, but, even so, coating weights are increased over the equivalent arrangement where the final two rollers are not substantially vertically arranged with respect to each other.

Without wishing to be bound by any theory, it is thought that the vertical arrangement of the final two rollers will result in excess ink collecting at the nip, where it is forced into the cells of the anilox roller, so filling the cells more effectively, whereas in a "horizontal,, arrangement excess ink would tend to collect away from the nip.

Thus in a fourth aspect the invention provides a rotary inker comprising an ink train consisting of at least two roll cylinders extending between an ink reservoir and a final roll cylinder which in use comes into contact with a printing plate, wherein the final roll cylinder of the train is provided with a doctor blade, and has a rotation axis which is generally vertically above that of the immediately preceding roll cylinder.

12 Also according to the fourth aspect the invention provides a method of printing in which the material to be coated on a substrate is transferred from a reservoir to a printing plate via a train of at least two roll cylinders, wherein the final roll cylinder of the train is provided with a doctor blade, and has a rotation axis which is generally vertically above that of the immediately preceding roll cylinder.

The f ourth aspect may be combined with any one, or any pair, or all, of the first to third aspects. However, while, as particularly described, the invention according to the first and/or second aspects can be used in conjunction with the "vertical" arrangement of the third aspect, so that the final roll cylinder is relatively soft and is used in conjunction with a preceding train of soft roll cylinders and/or a doctor blade, it should be noted that the first and second aspects of the invention can also be practised, and high coating weights obtained, with other cylinder alignments, including the more conventional "near horizontal" alignment referred to above.

It is common for sequential cylinders to drive each other through frictional contact. However, it is preferred to provide at least one of the cylinders of the train of the invention in any of the preceding aspects, and preferably each cylinder, with gearing, which may be individually driven or coact with the gearing of adjacent cylinder(s).

This feature is particularly advantageous in embodiments using soft rollers, in view of reduced frictional contact between the rollers, but is applicable to any embodiment.

The versatility provided by being able to use roll cylinders of different hardnesses and/or "vertically', arranged roll cylinders means that printing media having widely different flow characteristics can be employed.

13 One problem that arises with any inker employing a roll cylinder train is that the printing medium tends to become widely distributed both in and outside the by splash and fly as the inker is operated, particularly since the framework around the roll cylinders is often rather open, for example for ease of access and adjustment, even if precautions are taken to provide some form of sealing at the ends of the cylinders themselves. Although reversal of the doctor blade means that much of the printing medium trimmed from the anilox roll cylinder tends to f low back to the reservoir in the inker, this does not wholly solve the problem.

1 C% In addition to a basic skeleton (not shown), the framework for the basic roll cylinder arrangement shown in the Figures is provided with removable webbed side guards 10 which enclose the ends of the roll cylinders in both the ink feeder and the printing portions. Fixed vertical panels 11, 12 lie to front and back of the ink feeder portion 1, and a cranked lid panel 13 is hinged to the rear panel 12 so as to overlie the plate cylinder and paper transport cylinder for access thereto. Guards 10 and panels 11 to 13 provide essentially continuous sealing of the interior of the inker save for a relatively narrow opening for feeding the substrate to the transport cylinder. External adjustment of the position of the doctor blade is provided by a mechanism 14 of known structure.

Such an arrangement is effective in preventing the printing medium widely contaminating the workplace around the inker. Furthermore, it avoids the need to have seals directly on the roll cylinders, the printing medium being free to move around the interior of the inker, and particularly the ink feeder portion itself, and eventually to return to the reservoir in the ink f eeder portion 1.

14 1 According to a fifth aspect of the invention, there is provided an inker comprising a train of roll cylinders extending between a meter roll cylinder adjacent a reservoir for printing medium and a plate cylinder, wherein the train of roll cylinders is substantially enclosed by guards other than for an opening for a web substrate to be printed upon, so as to materially prevent egress of the printing medium to the environment. The fifth aspect may be combined with any one, any two, any three, or all four, of the first to fourth aspects.

However, it is considered that such an arrangement is more conveniently replaced by one (not shown) in which at least one, and preferably each, of the plate or impression cylinder, the meter roll cylinder and the anilox roll cylinder is rotatably mounted in a respective cassette, the or each cassette being easily removable from a basic skeleton framework of the inker, for example by sliding or lifting. Other cylinders (if any) or may be similarly mounted. In certain cases combinations of cylinders may be mounted in a single cassette.

Each cassette provides means for rotatably mounting a respective cylinder and immediately associated parts, and has apertures necessary for operation, e.g. for contact with adjacent cylinders, or for any necessary adjustment, but is otherwise essentially sealed. The rotatable mounting preferably comprises a seal or seals to prevent egress of printing medium or other material.

Thus in a preferred embodiment, the cassette for the meter cylinder provides the ink reservoir in addition to rotatably mounting the meter cylinder. The cassette for the anilox cylinder will also contain the doctor blade and associated adjusting means. Insofar as the doctor blade and anilox cylinder remain associated, it would be possible to arrange the adjustment means so that it is impossible for the doctor blade to contact the surface of the anilox cylinder when the latter is of Ilsoftly material.

The cassette for the print cylinder will require access for changing the printing plate, and this can be effected either by providing an openable lid to the cassette, or by providing a cassette with an open top which is effectively closed by a hinged lid 13 mounted to the skeleton framework such as shown in the drawings.

Any or (preferably) all of the cylinders may be provided with gearing for drive purposes, and this may be provided externally of the respective cassette on the cylinder shaft, either exposed, or shielded as far as possible, i.e. merely allowing operative contact with adjacent gearing or other drive means.

Conveniently, the skeleton framework may be adapted for horizontally slidably receiving the cassettes so that the roll cylinders are in correct register- Alternatively or additionally, a lid panel 13 such as is shown in the illustrated arrangement, may be raised to enable lifting of the cassette containing the print cylinder.

Because the cassettes are largely closed to the external environment, the need for the guards illustrated in the drawings is obviated.

This arrangement also facilitates replacement of worn roll cylinders when necessary, or the replacement of roll cylinders upon changing jobs, for example to alter the hardness of an anilox roll cylinder. Alternatively, in the latter case, where the same type of roll cylinder is required, withdrawn roll cylinders could be cleaned and 16 1 re-inserted. it is also particularly useful in conjunction with the "vertical,, arrangement of the fourth aspect, insofar as it enables both soft and hard final roll cylinders of the train to be used interchangeably for high coating weights, according to requirements. Therefore, according to a sixth aspect of the invention, there is provided

an inker comprising a reservoir for a printing medium, and a train of roll cylinders including a meter roll cylinder for picking up the printing medium from the reservoir, a plate cylinder, and at least one roll cylinder between the meter roll cylinder and the plate cylinder, said at least on roll cylinder including an anilox roll cylinder contacting the plate cylinder for transferring thereto printing medium picked up by the meter roll cylinder, wherein at least one of said anilox roll cylinder, plate cylinder and meter roll cylinder is mounted in a cassette, said cassette being removable with the roll cylinder from said inker. The sixth aspect may be combined with any one, or any combination of two, three or four, or all five, of the first to fifth aspects.

Preferably at least two, and more preferably each, of saidanilox roll cylinder, plate cylinder and meter roll cylinder are mounted in respective cassettes, each said cassette being removable with the roll cylinder from said inker. Preferably, the inker comprises a skeleton framework on which the or each cassette is slidably mounted for removal or for replacement with the roll cylinders in a predetermined register.

Further details of the invention may be found on consideration of the appended claims.

17

Claims

An inker for a printing press, said inker comprising an ink train of at least two roll cylinders which extends from an ink reservoir and includes a f inal roll cylinder which in use comes into contact with a printing plate, wherein the final roll cylinder is provided with a doctor blade and has a surface of rubber or synthetic polymeric or resin material.

2. An inker according to claim 1 wherein the surface of each roll cylinder is of rubber or synthetic polymeric or resin material.

3. An inker for a printing press said inker comprising an ink train of at least two roll cylinders which extends from an ink reservoir and includes a final roll cylinder which in use comes into contact with a printing plate, wherein the surface of each roll cylinder of the train is of rubber or synthetic polymeric or resin material.

4. An inker according to any preceding claim wherein said surface has a screened or cell structure.

S. An inker according to any one of claims 1 to 3 wherein said surface has no screened or cell structure.

6. An inker according to any preceding claim, where said final roll cylinder is demountable.

7. An inker according to any preceding claim wherein the Shore hardness of the surface of at least said final roll cylinder is in the range of 25 to 700 18 1 1 8. The combination of an inker according to any preceding claim with at least one further final roll cylinder, the final cylinders having different Shore hardnesses.

9. A method of printing, in which the material to be coated on a substrate is transferred from a reservoir to a printing plate via a train of at least two roll cylinders, the final roll cylinder of the train having a surface of rubber or synthetic polymeric or resin material, wherein the thickness of the material on the final roll cylinder of the train is controlled by a doctor blade.

10 The method according to claim 9 wherein the operative edge of the doctor blade is spaced from said final cylinder to permit a printing medium to have a finite thickness beyond the periphery of the final cylinder.

11. The method according to claim 9 or claim 10 wherein the doctor blade is reversed.

12. A method according to any one of claims 9 to 11 wherein the surface of each roll of the train is of rubber or synthetic polymeric or resin material.

13. A method of printing, in which the material to be coated on a substrate is transferred from a source to a printing plate via a train of at least two roll cylinders, the surface of each roll of the train being of rubber or synthetic polymeric or resin material.

14. The method according to any one of claims 9 to 13 wherein the Shore hardness of the said surface is selected conjointly with the flow properties of a printing medium to be used.

19 15. The method according to any one of claims 9 to 14 wherein the said coating is applied at a weight greater then 4 gm/m.

16. The method according to claim 15 wherein the coating is applied at a weight greater then 8 gm/m.

17. The method according to any one of claims 9 to 16 wherein the printing plate is a relief plate.

18. A rotary inker for a printing press, said inker comprising a source of a printing medium, and a train of roll cylinders including a meter roll cylinder for picking up the printing medium from the source, a plate cylinder, and at least one roll cylinder between the meter roll cylinder and the plate cylinder, said at least one roll cylinder including an anilox roll cylinder contacting the plate cylinder for transferring thereto printing medium picked up by the meter roll cylinder, wherein at least one of said anilox roll cylinder, plate cylinder and meter roll cylinder is mounted in a cassette, said cassette being removable with the roll cylinder from said inker.

19. An inker according to claim 18 wherein at least two of said anilox roll cylinder, plate cylinder and meter roll cylinder are mounted in respective cassettes, each said cassette being removable with the roll cylinder from said inker.

20. An inker according to claim 18 wherein each of said anilox roll cylinder, plate cylinder and meter roll cylinder are mounted in respective cassettes, each said cassette being removable with the roll cylinder from said inker.

1 1 21. An inker according to any one of claims 18 to 20 and comprising a skeletal framework on which the or each cassette is slidably or liftably mounted for removal or for replacement with the roll cylinders in a predetermined register.

22. An inker according to any one of claims 18 to 21 wherein the or each said cassette is sealed save for apertures necessary for operation.

23. An inker according to any one of claims 18 to 22 wherein each cassette contains or provides adjuncts normally associated with its cylinder.

24. A rotary inker for a printing press, said inker comprising a train of roll cylinders extending between a meter roll cylinder adjacent a source of a printing medium and a plate cylinder, wherein the volume encompassing the train of roll cylinders is substantially enclosed by guards other than for an opening f or a web substrate to be printed upon, so as to materially prevent egress of the printing medium to the environment.

25. An inker according to claim 21 wherein at least one of said guards is removable or removable to permit access to at least one of said roll cylinders.

26. An inker according to any one of claims 1 to 8, 18 to 25 wherein at least one said cylinder is provided with gearing on its shaft.

27. An inker according to claim 26 wherein each said cylinder is provided with gearing on its shaft.

28. An inker according to any one of claims 1 to 8, 18 to 27, wherein said source of printing medium is a reservoir.

21 30. An inker for a printing press comprising a final roll cylinder provided with a doctor blade, means for measuring the coating weight or coating thickness of a printed product leaving, or which has left, the final roll cylinder, and means for controlling the position of the doctor blade relative to the surface of the final roll cylinder in accordance with the measured coating weight or coating thickness.

31. An inker according to any one of claims 1 to 7, further comprising means for measuring the coating weight or coating thickness of a printed product leaving, or which has left, the final roll cylinder, and means for controlling the position of the doctor blade relative to the surface of the final roll cylinder in accordance with the measured coating weight or coating thickness.

32. A method of printing using an inker for a printing press comprising a final roll cylinder provided with a doctor blade, wherein the coating weight or coating thickness of a printed product leaving, or which has left, the final roll cylinder is measured, and the position of the doctor blade relative to the surface of the final roll cylinder is controlled in accordance with the measured coating weight or coating thickness.

33. A method of printing according to any one of claims 9 to 17 wherein the coating weight or coating thickness of a printed product leaving, or which has left, the final roll cylinder is measured, and the position of the doctor blade relative to the surface of the final roll cylinder is controlled in accordance with the measured coating weight or coating thickness.

22 1 34. A method according to claim 32 or claim 33 wherein the coating weight is controlled so as to remain substantially constant during a print run.

35. A rotary inker comprising an ink train consisting of at least two roll cylinders extending between an ink reservoir and a final roll cylinder which in use comes into contact with a printing plate, wherein the final roll cylinder of the train is provided with a doctor blade, and has a rotation axis which is generally vertically above that of the immediately preceding roll cylinder.

is 36. A rotary inker according to claim 35 wherein the final roll cylinder of the train is a hard anilox cylinder.

37. A rotary inker according to any one of claims 1 to 7 or claim 31 wherein the final roll cylinder of the train has a rotation axis which is generally vertically above that of the immediately preceding roll cylinder.

38. A rotary inker according to any one of claims 35 to 37 wherein the rotation axis of the final roll cylinder of the train is substantially vertically above the immediately preceding roll cylinder.

39. A method of printing in which the material to be coated on a substrate is transferred from a reservoir to a printing plate via a train of at least two roll cylinders, wherein the final roll cylinder of the train is provided with a doctor blade, and has a rotation axis which is generally vertically above that of the immediately preceding roll cylinder.

40. A method according to claim 39 wherein the final roll cylinder of the train is a hard anilox roller.

23 41. A method according to any one of claims 9 to 17, 33 and 34, wherein the final roll cylinder of the train has a rotation axis which is generally vertically above that of the immediately preceding roll cylinder.

42. A rotary inker according to any one of claims 39 to 41 wherein the rotation axis of the final roll cylinder of the train is substantially vertically above the immediately preceding roll cylinder.

43. A roll cylinder for an inker for a printing press, said roll cylinder having a surface of rubber or synthetic polymeric or resin material and being provided with a doctor blade.

44. A roll cylinder according to claim 43 wherein the surface of the cylinder has no cell structure.

45. A roll cylinder according to claim 43 wherein the surface of the cylinder has a screened or cell structure.

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