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. For such tasks an inker serves to transfer a printing medium from a source or reservoir to a final roll which in use contacts a printing plate on a plate cylinder.

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 of a layer of the material from a roll cylinder irrespective of whether the layer is patterned), including those referred to in the preceding paragraph, are herein referred to generically as printing media, irrespective as to whether they are intended to form a visible image.

In a conventional letterpress, the ink is passed to a 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. The rotation axes of successive roll cylinders are normally at a small angle above the horizontal to each other. Coat weights are low.

In other conventional printing arrangements, the final or anilox roll cylinder is formed of a hard material, such as steel or a ceramic. It is provided with a doctor blade, and its surface is screened or has a cell structure, to receive the printing medium. Again, the

rotation axes of successive roll cylinders are normally at a small angle above the horizontal to each other.

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

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 roll cylinders, particularly the pressures between the anilox roll cylinder and its adjacent preceding cylinder (which may be the meter roll cylinder for picking up printing medium from a reservoir) and between the anilox cylinder and the plate cylinder, and adjustment of the doctor blade.

Such conventional arrangements serve 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 is also 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., as dictated by a specific task, can be very slow and expensive.

There therefore exists a need for a relatively simple printing system which is capable of providing high coating weights, and which is economical to maintain and adjust for coating weight.

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.

Although both embodiments described herein show arrangements in which the anilox roller is vertically above the preceding roll cylinder, it should be noted that the invention is not limited thereto. It is equally possible to use a"soft"anilox cylinder in a conventional arrangement in which the rotation axes of successive roll cylinders are normally at a small angle above the horizontal to each other.

In a first aspect the present invention provides 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. The surface of the cylinder may or may not have a cell structure, and the Shore hardness of its surface is preferably in the range of 25 to 70°. In practice the Shore hardness of the said surface may be selected conjointly with the flow properties of a printing medium to be used.

The first aspect extends to a method of printing using such a roll cylinder with doctor blade (an anilox cylinder), to an inker comprising such an anilox cylinder, and to a method of printing using an inker comprising such an anilox cylinder.

The inker will comprise an ink train of at least two roll cylinders which extends from an ink reservoir and includes a final anilox roll cylinder which in use comes into contact with a printing plate, the anilox roll cylinder being constituted by the"soft"anilox cylinder.

In such an inker the surface of each roll cylinder may be of rubber or synthetic polymeric or resin material.

In use, the printer will exercise skill in the choice of printing medium, in particular the flow characteristics thereof, printing speed, etc. as with conventional arrangements. However, there is now a further variable which can be controlled to produce desired results, viz. the Shore hardness of the surface (s) of the soft roll cylinder (s) of the train, particularly that of the anilox roll cylinder.

Where the"soft"surface includes a screen structure, this lowers the apparent Shore hardness. In general the lower the viscosity of the printing medium the lower the Shore hardness which is required for a given coating weight.

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 at least 15°, preferably at least 20°, and more preferably at least 25°. It is preferably 70° or less, and more preferably 40° or less.

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 front of the nip, providing a reservoir for distribution along the length of the nip if necessary, as determined by the image to be printed.

As described with respect to the second embodiment, the "soft"roll cylinder is demountable, preferably as an integral unit including its associated doctor blade (as with the cassette frame construction outlined below), thus facilitating changing of cylinders, for example to another"soft"cylinder, or to a hard cylinder. Thus the invention extends to the combination of an inker according to the first aspect with at least one further

final roll cylinder, the final cylinders having different Shore hardnesses. 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. However, as noted below, once the inker is set up, the wide range of coating weights available by varying other parameters such as print speed and doctor blade spacing, mean that it is likely that further substitution of the anilox roll cylinder may only be necessary for very particular requirements.

Advantageously, the other cylinders of the train are also be replaceable in a similar manner, as appropriate.

The use of a"soft"anilox cylinder means that the doctor blade can be, and preferably is, spaced from the surface, so that no contact wear occurs between the blade and the cylinder surface. In the embodiments the doctor blade is reversed and blunt.

The spacing is believed to permit a printing medium to have a finite thickness beyond the periphery of the final cylinder, and adjustable control of the amount of spacing enables the coating weight to be adjustably controlled, at least within the limits indicated above. 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 gm/m2, more commonly 8 to 10 gm/m2 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 weights, for example 2.8 gm/m2, 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 adjusting the doctor blade.

The relation between blade spacing and coating weight makes it possible to operate such an inker by providing 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 its associated roll cylinder in accordance with the measured coating weight or coating thickness, e. g. to produce a closely controlled constant coating weight, or to vary the coating weight in a controlled manner, even during a print run.

The invention therefore also encompasses 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, and a method of printing using such an inker.

The range of coating weights obtainable with a single "soft"anilox roll cylinder according to the invention, and the control thereof even during the printing process would normally be expected to require the substitution of several different conventional hard anilox roll cylinders, with consequent inconvenience, mess, and cost in stopping and/or adjusting the machinery.

Furthermore, since the amount of spacing between doctor blade and anilox roller affects the coating weight, it is possible to provide a doctor blade with an edge profile which is different from the profile of the anilox roll cylinder, and/or to orientate the doctor blade relative to the anilox cylinder, so that the spacing varies along the axial length of the roll cylinder.

In this manner variable printing weights can be obtained widthwise. For example, a continuous smooth gradation of tone of large range (even a range extending to white) across the print width could be obtained by angling a doctor blade (conformable to the anilox cylinder) relative to the anilox cylinder. If the blade is not conformable, a gradation other than linear/smooth could be obtained. The gradation on the printed product will also be modified by what is on the plate cylinder.

As mentioned above, both of the embodiments of inker to be described include an anilox roll cylinder vertically above the preceding cylinder.

It has been found that this configuration gives improved coating weights even in the case where the anilox roll cylinder is a conventional hard (screened) cylinder roll.

It is believed that at least some of the difficulties encountered when using a hard anilox roll cylinder in the more conventional near horizontal alignment are caused by the entrapment of air between the anilox and preceding cylinder at the nip, resulting in less than complete filling of the screened surface.

As shown schematically in Figure 8a, in the conventional set-up, although a printing medium brought to a downwardly pointing nip 16 by the preceding roll cylinder 7 tends to gather there, there is a counteracting gravitational force tending to empty the nip, thereby leading to possible entrainment of air and reduced filling of the surface of the anilox roll cylinder 8. By contrast, where the nip is more horizontal, as in Figure 8b, the counteracting gravitational force is reduced.

This is believed to have two consequences. The first is that the nip 16 tends to be more completely filled with ink, thereby avoiding any danger of air entrainment. The second consequence, which may in fact turn out to be the more important, is that ink tends to rise up the surface of the anilox roll cylinder 8 prior to the nip, presumably because of the"pumping"action of the

preceding cylinder 7 and the reduced gravitational pull downwards. This means that the anilox cylinder surface encounters fresh printing medium at an earlier stage, giving the medium more time to enter the screened surface and fill it completely.

Thus in a second aspect the invention provides a rotary inker comprising an ink train consisting of at least two roll cylinders extending between means for supplying a printing medium 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 the final roll cylinder and the preceding roll cylinder have rotation axes in a common plane at no more than 30°, and preferably no more than 15°, to the vertical. Most preferably the common plane is substantially vertical.

There is also a need for a system which can be readily changed to produce different products. Another need is 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. It would also be advantageous to have a printing system in which fly and splash of the printing

medium to the external environment can be reduced or avoided.

The employment of cylinders with rotation axes which are vertical one over the other as in the second aspect of the invention gives rise to a further advantage in that it is relatively easy to provide a cassette frame system for an inker in which at least one roll cylinder is mounted in a cassette frame. Preferably the cassette frame is mountable in a skeletal or basic framework which holds the cylinders in a predetermined register, preferably adjustable. The cassette frame (s) is demountable from the framework, for example by lifting, but preferably by sliding, for easy removal or replacement and storage of the associated cylinder.

Preferably when the or each cassette is in position in the skeletal framework it is sealed save for apertures necessary for operation, thereby reducing exposure of the cylinders to the environment, and also reducing external splashing or spray of the printing medium.

Furthermore, any adjuncts normally associated with a particular roll cylinder, such as the doctor blade of an anilox cylinder, or an ink reservoir or other feed arrangement for a meter cylinder can also be mounted in the associated cassette.

Cassette frames with their cylinders which are not in use could be stored in a further framework, again preferably by sliding therein, e. g. one over another, to protect the

cylinders. This is important in protecting the surfaces of the cylinders, and avoids the contamination of or from the inked surfaces thereof, and is particularly important where the printing medium is sensitive to a factor, for example ultra-violet light, insofar as it can be arranged for the cylinder surface to be shielded from such a factor while being stored.

Thus the invention also encompasses a rotary inker for a printing press, said inker comprising means for supplying 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 any one, or any two, or each of said anilox roll cylinder, plate cylinder and meter roll cylinder is mounted in a respective cassette frame, said cassette frame being removable with its roll cylinder from said inker.

Other features and advantages of the invention may become clear on a consideration of the appended claims, to which the reader is directed, and to a consideration of the following more particular description of exemplary embodiments, made with reference to the accompanying drawings, in which:-

Figure 1 shows a first embodiment of rotary short inker in sideways cross-section; 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.

Figure 5 is a front view of a second embodiment of short inker; Figure 6 is a side cross-sectional view of the embodiment of Figure 5; Figure 7 is a cross-section view along the line 7-7 og Figure 6; and Figures 8a and 8b illustrate very schematically the nip for different cylinder arrangements.

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 by a web 15 of a printable substrate, for example of paper, transported round a paper transport cylinder 5. Commonly the web 15 will be continuous, as

shown, 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 form 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 is shown, in which ink from the plate 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 or printing or coating medium.

The ink feeder portion 1 comprises a base portion 6 which in use acts as a reservoir for the ink or other printing 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 is herein 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 counter-rotating 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 medium on the paper web is uniform over the whole area of the printed image.

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.

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 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 surface 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.

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 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.

In a conventional inker, the axes of successive pairs of roll cylinders lie in a common 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 and that of the immediately preceding roll cylinder lies in a generally vertical plane which is within 30°, preferably within 10 or 15°, more preferably within 5°, of the vertical, and which ideally is substantially vertical.

Where the anilox cylinder is a hard one, it will be 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. Where the anilox roll cylinder is a"soft" one, extremely good results are obtained in terms of high coating weight, uniformity of coating weight, etc.

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.

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 flow back to the reservoir in the inker, this does not always wholly solve the problem. Another problem is the time taken to exchange the roll cylinders, and the storage of cylinders not in use, which sometimes requires special conditions, for example protection from ambient light for ultra-violet curing media.

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 feeder portion 1.

However, it is considered that such an arrangement is more conveniently replaced by one 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 frame, the or each cassette being easily removable from a basic 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.

Figures 5 to 7 schematically illustrate an embodiment of such an arrangement. Parts in these Figure which generally correspond to parts in Figures 1 to 4 have been given the same reference numbers where appropriate.

The basic framework comprises two continuous side panels, and a rear panel 17 of lesser height, which are connected together so as to stand vertical. Other joining means, such as tie rods or plates can be provided to ensure rigidity. Towards the top rear of the framework a paper transport cylinder 5 is journalled to the panels 16, or otherwise rotatably mounted thereto.

There are three cassette frames 18 to 20 which are mountable in superposition within the basic framework in known manner, each provided with pull handles 26. For example they may cooperate with guides in the framework, so that they can be individually inserted or withdrawn by sliding independently of the other cassette frames. In this embodiment, the upper cassette frame 20 is so mounted, being top hung on a slide arrangement 24; and the bottom cassette frame 18 rests on a bar support 25, also having a pull handle 26 which itself is slidably mounted in the framework. The intermediate cassette frame 19, however, merely rests on the frame 18.

Thus, to withdraw either frame 18 or frame 19, the bar support is pulled forward from the framework until its motion is arrested by a suitably placed stop. Frame 19

can then be removed by lifting, followed by frame 18 if required.

The lowest cassette frame 18 consists of a rectangular base plate and two upstanding sides plus a back and a front, all of equal height, to form an open box. The box shape enables the storage or handling of printing media, and it may act as a simple reservoir, as shown, provided with means such as a chute 21 for adding the printing medium, the base plate being substantially continuous.

However, it should be understood that other printing medium supply arrangements known per se may be employed, for example, a pump inlet and outlet for continuous circulation of the medium.

A meter roll cylinder 7 is journalled into the side of the cassette frame 18, its upper extremity lying substantially at the top of the frame. In addition, the meter roll cylinder 7 is provided with an adjustable doctor blade 30, shown reversed, for controlling the amount of ink in the nip between the cylinder 7 and an adjacent anilox roll cylinder 8. Blade 30 is also mounted to the frame 18. It would normally be spaced from the cylinder 7.

The intermediate cassette frame 19 comprises two sides a front and a back, all of equal height, arranged to form a rectangle or square, and the anilox roll cylinder 8 is journalled to the sides, with its upper and lower extremities substantially level with the top and bottom of the sides. In addition, a doctor blade 9 is mounted to

the sides and is adjustable for spacing relative to the anilox roll cylinder. Where the latter is a"soft" cylinder, it is preferred that the range of doctor blade adjustment is such that contact with the anilox cylinder is not possible, or only just possible.

The uppermost cassette frame 20 comprises two sides and a front, all of equal height, providing three sides of a rectangle. If necessary, further joining members may be provided to ensure rigidity, but this may be provided by the journalling to the sides of the plate cylinder 3 so that its lower extremity is substantially level with the bottom of the sides. The back of the cassette frame is left open to permit contact between the plate cylinder 3 and the paper transport cylinder 5 when the front of the cassette frame is flush with the front of the basic framework, Figure 6, and the horizontal position of journalling of the cylinder 3 is selected accordingly.

When all three cassette frames are in position as shown in the Figures, the construction'is such that the anilox cylinder 8 contacts both the meter cylinder 7 and the plate cylinder 3.

The basic framework may be provided with means for adjusting the relative height of at least one cassette frame, to adjust contact between the cylinders, and/or to facilitate insertion of removal of individual cassettes, for example. As shown, the vertical position of the bar support 25 is adjustable by a cam arrangement operated by rotatable levers 27, so to adjust frames 18 and 19

together, following they are locked in place by operation of levers 28 of a locking arrangement. Lowest cassette 18 fixed. There may also be some relative height adjustment between the frames 18 and 19, but the degree of contact between cylinders 7 and 8 is not often particularly critical, and in the embodiment there is no adjustment.

However, the contact pressure between the plate cylinder and both the anilox cylinder and the paper transport cylinder can be critical, and to this end the upper cassette can be adjusted relative to the framework both vertically and also horizontally, by any suitable means known per se. In the embodiment such adjustments are each performed by a respective cam arrangement comprising an eccentric acting against the framework (Figure 5 shows part of 29 of such an arrangement for the horizontal adjustment. The other cam arrangement may act vertically directly on the frame 20, but preferably and more conveniently on the slide 24).

Once all three frames 18 to 20 are in place, they are held there by fastening means 22 on the framework.

It will be understood that this arrangement provides an assembly which is sealed against egress of printing medium (or ingress of other material), apart from necessary apertures, where it matters, viz. in the vicinity of the cylinders 7 and 8. Necessary apertures include those for operation, and for making adjustments.

It may be found desirable to provide a top covering for cassette 20, which will require access for changing the

printing plate. 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 lid, preferably hinged, mounted to the skeleton framework, in a similar manner to the lid 13 of Figure 3.

Each rotatable mounting of the cylinders preferably comprises a seal or seals to prevent egress of printing medium or other material Because the cassettes are largely closed to the external environment when in position, the need for the guards illustrated in the drawings is obviated.

Any or (preferably) all of the cylinders may be provided with gearing 23 for drive purposes, and this may be provided externally of the respective cassette frame 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. As shown, the gearing remains within the basic framework adjacent a side 16.

As particularly described the skeleton framework is adapted for horizontally slidably receiving the cassettes so that the roll cylinders are in correct register.

Alternatively or additionally, a lid panel arranged much as the lid panel 13 is shown in Figure 3, may be raised to enable lifting of the cassette containing the print cylinder.

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 re-inserted.

For storage purposes, a second framework may be provided, preferably having two continuous side panels, continuous top and bottom plates, and a continuous back, and means for slidably receiving cassette frames inserted from the front. Means may be provided for sealing any of the front of such a framework for ensuring that the front is substantially closed if not wholly occupied by cassette frame front, for example dummy cassette frame fronts. In this manner, a cylinder which has already been used for a particular job may be safely stored without cleaning, for re-use on a similar job in the future.