EP0711665A1 - Sleeve arrangement and intermediate sleeve for carrying a thin sleeve, in particular for a flexographic printing machine - Google Patents

Abstract

The roller consists of a hollow supporting cylinder (10) of a given diameter, designed to be rotated and equipped with an inner compressed air feed (20) and transverse jets (22) at given intervals. The roller has at least one intermediate sleeve (12) with an inner diameter which is compatible with the outer diameter of the supporting cylinder (10) and an outer diameter which is compatible with a thin outer sleeve carrying the image to be printed. The intermediate sleeve has jets (38) in a ring at the same angular intervals as those in the cylinder, and shutters (29) for use when the sleeve is being fitted to the supporting cylinder. The shutters are in the form of a ring which can be rotated between open and closed positions and is equipped with seals.

Description

The subject of the present invention is an intermediate sleeve-sleeve holder for a flexographic machine in particular and the arrangement of a complete printing cylinder.

Flexographic printing machines include several successive groups of prints depending on the number of colors, each group having the role of printing, in the given color which has been assigned to it, an image so as to obtain the graphic representation in colors as desired.

Such machines have very large printing capacities so that they produce images of high graphic quality at high rates. Also, the operators are brought very regularly to change the cylinders carrying the stereotypes.

In order to save time and money, the images are carried by cliché sleeves or rubber-lined sleeves which are directly lasered in the thickness of the lining.

Thus, it is possible to save precious time to make production changes; the plates are prepared, that is to say mounted and wedged and then fixed on the sleeve, then the plate or engraved sleeves are mounted on additional cylinders while a first set is in place and operating on the machine.

When changing, the cylinders and their sleeves are removed from the machine while the set of waiting cylinders and sleeves are then placed on the machine.

It then remains to wedge the machine, that is to say to wedge the displacement of the strip to be printed from one group to another so that there is a superposition of the prints in each of the colors. We understand, if it is a different image but with the same development, that it takes two sets of metal support cylinders.

Thus, the fleet must be doubled, otherwise, the machine must be stopped, the clichés used must be removed, the new ones must be positioned on the sleeves, which is impossible from the point of view of profitability.

Such an operation is thus a clear progress.

Thus, it can be seen that investing in sets of duplicate cylinders is already an attractive solution, but one which is still very expensive.

However, the cliché or trim sleeves have a small thickness and a very large number of support cylinders is required to cover the range of developments required. Rectified metal cylinders are expensive and the investment of the cylinder fleet of a flexographic machine is very high, especially since there are colors.

A first solution to reduce the fleet has been proposed by the Applicants in French patent application No. 94 06417 which consists in making sleeves of very thick material suitable for having sufficient hardness, qualities of resistance over time perfect and be suitable for rectification when they have to support glued plates or be suitable for attaching a rubber lining for later laser engraving.

This very attractive solution makes it possible to reduce the investment in metal support cylinders because the thick sleeves made of composite material are less expensive. In addition, they are much easier to handle thanks to a much lower weight than that of metal cylinders.

For standard widths, a sleeve made of composite material can be worn by one person, without break labor laws, regardless of diameter, in the current range. This avoids all handling with the hoist with all the drawbacks attached to it. As a result, it not only becomes unnecessary to have a set of metal support cylinders covering each development and the immediately higher developments, but the second set of cylinders in the same development is also eliminated.

It therefore suffices to constitute a reduced fleet of metal support cylinders with deviations of one or more tens of developments and to invest in sleeves with the same internal diameter, but covering intermediate developments, with a number doubled if the we want to prepare the shots beforehand when the replacement development is identical to the development in progress.

Of course, if the developments are different but the inside diameter of the sleeve is identical, that is to say that the development is located in the development interval between two sets of consecutive metal support cylinders, we understand everything the advantage of these thick sleeves; it is indeed possible to leave the metal support cylinders in place, remove the sleeves used and mount the new sleeves previously prepared. The machine downtime is reduced to a minimum.

Indeed, the operation of changing sleeves is made very easy thanks to the use of support cylinders inside which air is introduced under pressure which is evacuated by nozzles distributed over the periphery of the cylinder along d 'a circle in an area located in the immediate vicinity of the end of the support cylinder by which said sleeve is inserted or removed.

The air, under a pressure of a few bars, forms an air mattress between the external surface of the metal support cylinder and the sleeve, expanding the latter very slightly but sufficiently so that it slides easily in translation on said cylinder support. As soon as the introduction of pressurized air inside the cylinder is interrupted, the sleeve is pressed under the effect of its own elasticity on the support cylinder. We could see that the radial clamping force over the entire surface ensures perfect immobilization of the sleeve on the support cylinder, in any case, quite sufficient for the application concerned.

If such a solution of thick sleeves is a considerable improvement over the solutions of the prior art by reducing the number of metal support cylinders, by great ease of handling, by very substantial time savings during assembly, by ease of removal and rests on the support cylinders, the fact remains that it is necessary in the case of the same development, two sets of sleeves. The additional cost is also proportional to the thickness even if this proportionality is not linear.

The object of the present invention is therefore to propose intermediate sleeves which solve this problem of the double series in the same development and which, more generally, make it possible to use sleeves for cliché or trimmed and laser engraved of small thickness, this for all developments, while requiring a reduced fleet of metal support cylinders. The thin sleeves are renewed for each plate because they cannot be refilled with rubber, or they may be damaged when the plate is removed.

To this end, the subject of the present invention is an arrangement of a complete cylinder for flexographic printing, comprising a hollow support cylinder of a given diameter, intended to be driven in rotation and equipped with an internal supply of compressed air. with through nozzles, arranged according to a given angular distribution, at the periphery substantially along a circle in the immediate vicinity of the insertion end, and which is characterized in that it comprises at least one intermediate sleeve of a internal diameter compatible with the external diameter of the support cylinder for a radially tight mounting, and an external diameter compatible with the diameter of a thin sleeve bearing the image for a radially tight mounting whose external diameter is equal to that of the desired development, said intermediate sleeve comprising nozzles substantially along a circle, having the same angular distribution as that of the support cylinder and means for closing off these nozzles so as to allow the mounting of this intermediate sleeve on the support cylinder.

According to a preferred embodiment, the sealing means comprise a ring mounted fixed in translation, in particular by means of a fixed ring, along the longitudinal axis of the intermediate sleeve and movable in rotation between two positions, open and closed, in a projection formed in line with the nozzles of the intermediate sleeve, said ring itself being provided with nozzles having the same angular distribution as that of the nozzles of the support cylinder and of the intermediate sleeve with the open position corresponding to the coincidence of the nozzles of the intermediate sleeve with the ring nozzles and a closed position in which the ring nozzles are offset from those of the sleeve.

According to this embodiment, the ring comprises seals, so as to avoid the leakage of compressed air between the ring and the sleeve and the ring is mounted in a projection formed from the inner periphery.

According to an alternative embodiment, the closure means comprise hollow fixed inserts passing through the thickness of the intermediate sleeve, said inserts having an angular distribution identical to that of the nozzles of the support cylinder, said inserts being tapped to receive removable threaded plugs.

In the case of several coaxial intermediate sleeves, these sleeves include indexes so as to allow the alignment of the different nozzles in radial directions.

The invention also relates to the intermediate sleeve for the implementation of the arrangement indicated above.

The advantages linked to the intermediate sleeves are practical because, on the one hand, the storage is reduced and, on the other hand, the "journeys" of sleeves of great thickness to be relined and engraved are eliminated. This influences investment costs and production costs both by reducing storage and management costs, but also handling and above all by further reducing machine downtime.

• la figure 1, une vue schématique en perspective d'un ensemble cylindre support en métal, manchon intercalaire et manchon mince,
• la figure 2, une vue en coupe longitudinale d'un mode de réalisation préférentiel de l'invention,
• les figures 2A, 2B, 2C montrent des vues éclatées du montage de la bague du manchon de la figure 2,
• la figure 3A une vue en section transversale, suivant la ligne 3-3, de l'ensemble de la figure 2, dans la position pose ou dépose du manchon mince sur le manchon intercalaire,
• la figure 3B, une vue en section transversale dans la position pose ou dépose du manchon intercalaire, et
• la figure 4, une vue en coupe longitudinale d'une variante de réalisation du manchon intercalaire.

The present invention is described below according to a particular embodiment with variants, this with regard to the appended drawings which show on:

• FIG. 1, a schematic perspective view of a metal support cylinder, intermediate sleeve and thin sleeve assembly,
• FIG. 2, a view in longitudinal section of a preferred embodiment of the invention,
• FIGS. 2A, 2B, 2C show exploded views of the mounting of the ring of the sleeve of FIG. 2,
• FIG. 3A is a cross-sectional view, along line 3-3, of the assembly of FIG. 2, in the position of placing or removing the thin sleeve on the intermediate sleeve,
• FIG. 3B, a cross-sectional view in the position of placing or removing the intermediate sleeve, and
• Figure 4, a longitudinal sectional view of an alternative embodiment of the intermediate sleeve.

In Figure 1, there is shown the coaxial mounting of the metal support cylinder 10, the intermediate sleeve 12, the thin sleeve 14 on which we have shown under the reference 16, either a rubber lining engraved with the image 18, or an actual photograph with the same image, according to the choice of the user and the needs dictated by the type of image.

The central nozzle 20 for introducing compressed air is generally formed coaxially with one of the axes of the metal support cylinder.

Identical references are given in FIG. 2. The support cylinder is made of metal and the intermediate sleeve as well as the thin sleeve are made of polymer material.

Advantageously, the intermediate sleeve is produced according to the teaching of French patent application No. 94 06417.

The metal support cylinder 10 comprises nozzles 22 distributed regularly, along a through circle, at the periphery of said cylinder in order to put the interior of this cylinder into communication with the outside, the air path 24 being symbolized by arrows 26.

The intermediate sleeve 12 comprises a ring 28 fixed in rotation relative to the body of the intermediate sleeve and a movable ring 29, free to rotate on the fixed ring 28. The fixed ring has an outside diameter equal to that of the outside diameter of the sleeve, and an internal diameter equal to the diameter of a projection 30 formed at the end of the intermediate body.

This fixed ring has a reduced diameter over a part of its length, equal, apart from play, to the inside diameter of the movable ring.

The movable ring 29 has an outside diameter equal to the outside diameter of the body of the intermediate sleeve and to the outside diameter of the fixed ring in its non-reduced diameter portion.

Nozzles 34, 36 are machined respectively through the thickness of the reduced diameter portion of the fixed ring 28 and through the thickness of the movable ring 29.

The sleeve body also carries nozzles 38 in the part located to the right of the projection.

The mounting of this intermediate sleeve is carried out according to steps 2A to 2C. The movable ring 29 is threaded onto the reduced diameter part of the fixed ring 28 and then the fixed ring is mounted with its movable ring coaxially with the projection 30 of the corsp of the intermediate cylinder by interposing a fixing means such as a cyanoacrylate type adhesive sold under the name "loctite" taking the precaution of making the nozzles 34 of the fixed ring coincide with the nozzles 38 of the projection 30 of the intermediate sleeve.

Thus, the movable ring 29 can rotate relative to the reduced diameter portion of the fixed ring while this same fixed ring is immobilized in translation, thus retaining the mobile ring.

In FIG. 3A, it can be seen that the nozzles 22, 34, 36 and 38 are distributed along identical angular sectors so that in a given position, they can be aligned.

The assembly of such an assembly is carried out by introducing pressurized air through the nozzle 20 which passes through the nozzles 22 of the support cylinder 10.

The operator threads the intermediate sleeve 12 through the end of the cylinder provided with these nozzles 22. The air film allows easy insertion of this intermediate sleeve.

The ring 29 is in the position shown in FIG. 3B, that is to say a position in which the nozzles 36 and 38 are in coincidence by manufacture but in which the nozzles 34 are not in coincidence with the nozzles 36 and 38.

The intermediate sleeve, once inserted as far as possible and correctly positioned on the metal support cylinder, is locked on this support cylinder by rotation of the movable ring 29 in order to bring the nozzles 36 and 38 in coincidence with the nozzles 34, c ' that is to say in the position of FIG. 3A.

The thin sleeve 14 is then threaded in turn on the intermediate sleeve 12, because the air which escapes through the four series of nozzles forms an air film which allows a very easy assembly.

Once this thin sleeve is correctly positioned, the operator cuts off the supply of compressed air, which has the immediate effect of blocking the thin sleeve on the intermediate sleeve, itself secured to the metal support cylinder.

For removal, simply carry out the above operations in reverse order.

If the development is identical, we note that it suffices to supply the assembly with compressed air, to remove the thin sleeve without touching the ring, so that the intermediate sleeve remains in place.

The operator can then mount a new thin sleeve.

In the case where it is necessary to change development, the intermediate sleeve is removed by rotation of the ring and the operator mounts, after removal of the sleeve used, the new sleeve.

If the development is very different from the diameter of the metal support cylinder, and cannot be covered by an intermediate sleeve, the metal support cylinder should also be changed.

In Figure 4, there is shown a variant of the intermediate sleeve in which the ring has been removed and replaced by threaded cylindrical inserts 40 in which threaded plugs 42 can be screwed.

Threaded plugs play the same role as the ring and if they are a little less flexible to use, their cost is lower.

One can imagine, with the knowledge of those skilled in the art alone, other solutions for letting the air pass or closing the passage provided for this purpose, without departing from the scope of the invention.

We can also give a numerical example which, even if it does not necessarily give exact amounts in absolute value, nevertheless represents the scale and the relationships.

• PREMIERE SOLUTION :
  • Achat de 4 cylindres supports en métal de 820 mm.
  • Pour une laize donnée, le prix est de : $$\text{7.000 F x 4 = 28.000 F.}$$
    
• INCONVENIENT :
  • L'imprimeur doit arrêter sa machine après chaque tirage, retirer les cylindres, retirer les clichés de ces cylindres, repositionner les nouveaux clichés du tirage suivant. Arrêt de 5 heures à 6 heures suivant la dextérité des opérateurs.
  • Au coût horaire d'une machine 4 couleurs, la perte est de : $$\text{800 F x 55 = 44.000 F}$$
    
  • Il vaut donc mieux, ainsi que cela a été mentionné dans le préambule, prévoir l'investissement de deux jeux de cylindres, soit 56.000 F.
• DEUXIEME SOLUTION :
  • Achat de deux jeux de manchons composites de forte épaisseur (22 mm) au prix de 3.200 F. $$\text{3.200 x 8 = 25.600 F.}$$
    
  • Il y a alors un gain sur l'investissement par rapport à la solution métal car la manutention est aisée. De plus, les cylindres supports en métal restent sur la machine, il suffit de déposer et reposer les manchons sur les cylindres, ce qui procure un gain de temps à nouveau important.
  • Un problème se pose lorsque les manchons épais sont directement garnis en caoutchouc car la présente opération de 10 tirages successifs différents oblige à avoir tous les manchons épais prêts et ceci pour chaque tirage.
  • Cette solution présente tout son intérêt mais essentiellement pour les manchons porte-cliché.
• TROISIEME SOLUTION :
  • Achat de 4 manchons intercalaires de 21 mm d'épaisseur et de 20 manchons minces porte-clichés ou garnis, soit : $$\text{(3.800 x 4) + (850 x 20) = 32.200 F.}$$
    
  • Cette solution permet de rentabiliser au mieux la machine en optimisant les changements qui ne prennent plus que quelques minutes, si bien que l'arrêt machine peut être quasiment négligé et cette fois-ci quelle que soit la technique retenue, manchon mince porte-cliché ou garni et gravé. De plus, la manutention est encore diminuée puisque les manchons minces sont d'un poids très faible et le positionnement est également très aisé.
  • On constate que pour un investissement du même ordre que pour la deuxième solution, seul le manchon intercalaire permet de gagner en coût d'immobilisation machine, en temps et qualité de pose et dépose, quel que soit le mode de cliché imprimant retenu.
  • On remarque également que la présence d'un manchon intercalaire permet de jouer sur le garnissage du manchon mince pour traiter les développements très voisins également. Il n'est mentionné que les développements très voisins car le caoutchouc est cher, lourd et, de plus, la qualité d'impression serait altérée par une épaisseur trop importante.

A printer wishes to fulfill an order for 10 different printing models in four colors, with the same printing development, for example 820 mm. This printer has only one set of metal support cylinders of 680 mm, that is fifteen developments less than that of the order. There are therefore 40 engraved pictures and 10 machine changes so he has the opportunity to make the following solutions.

• FIRST SOLUTION :
  • Purchase of 4 820 mm metal support cylinders.
  • For a given width, the price is: $$\text{7,000 F x 4 = 28,000 F.}$$
    
• DISADVANTAGE :
  • The printer must stop his machine after each print, remove the cylinders, remove the photos from these cylinders, reposition the new photos from the next print. Stop from 5 hours to 6 hours depending on the operators' dexterity.
  • At the hourly cost of a 4-color machine, the loss is: $$\text{800 F x 55 = 44,000 F}$$
    
  • It is therefore better, as mentioned in the preamble, to plan the investment of two sets of cylinders, that is 56,000 F.
• SECOND SOLUTION :
  • Purchase of two sets of thick composite sleeves (22 mm) at a price of 3,200 F. $$\text{3.200 x 8 = 25.600 F.}$$
    
  • There is then a gain on the investment compared to the metal solution because the handling is easy. In addition, the metal support cylinders remain on the machine, it suffices to deposit and rest the sleeves on the cylinders, which again saves time.
  • A problem arises when the thick sleeves are directly lined with rubber because the present operation of 10 different successive prints obliges to have all the thick sleeves ready and this for each draw.
  • This solution is of great interest, but mainly for plate-holding sleeves.
• THIRD SOLUTION :
  • Purchase of 4 intermediate sleeves, 21 mm thick and 20 thin sleeves for plate or trim, either: $$\text{(3.800 x 4) + (850 x 20) = 32,200 F.}$$
    
  • This solution makes it possible to make the machine profitable as much as possible by optimizing the changes which only take a few minutes, so that the machine stop can be almost neglected and this time whatever the technique chosen, thin sleeve cliché holder or trimmed and engraved. In addition, handling is further reduced since the thin sleeves are very light and positioning is also very easy.
  • It is noted that for an investment of the same order as for the second solution, only the intermediate sleeve makes it possible to save in machine immobilization cost, in time and quality of installation and removal, whatever the mode of printing cliché adopted.
  • It is also noted that the presence of an intermediate sleeve makes it possible to play on the lining of the thin sleeve to treat very similar developments as well. Only very similar developments are mentioned because the rubber is expensive, heavy and, moreover, the print quality would be impaired by an excessively large thickness.

On the other hand, it is possible to envisage, taking into account the notably mechanical qualities of the intermediate sleeves made of composite material, the price and the weight, to have several intermediate sleeves mounted coaxially. It is therefore understandable that with a set of metal support cylinders and a few sets of intermediate sleeves and by varying the thickness of the lining of the thin sleeves, a very large range of developments is covered.

This arrangement is of great interest for this field of activity that constitutes flexographic printing. According to an embodiment as shown, the ring is formed in a projection machined from the inner periphery of the intermediate sleeve, but such a projection can be formed from the outer periphery.

In an improved manner, positioning indexes can be displayed to facilitate assembly and prior adjustment operations.

The intermediate sleeves are produced according to the teaching of patent application FR-A-94 06417.

Each sleeve comprises a succession of layers of honeycomb material preferably embedded in a resin matrix. The manufacturing support is a metal cylinder rectified to the diameter of the subsequent support cylinder.

Thus, the peripheral inner surface has a polished appearance.

The outer surface is ground to the exact diameter allowing tight fitting of the thin sleeve.

The composition of the resin is adapted to give the sleeve a calculated shrinkage which ensures a tight fitting radially. In the case of mounting a ring, a known mechanical machining is provided and within the reach of those skilled in the art.

In the case of assembly with inserts, these are previously embedded in the layers during manufacture, to a depth sufficient to allow the final rectification of the intermediate sleeve.

Claims (9)

Arrangement of a complete flexographic printing cylinder, comprising a hollow support cylinder (10) of a given diameter, intended to be driven in rotation and equipped with an internal supply (20) of compressed air with through nozzles ( 22), arranged according to a given angular distribution, at the periphery substantially along a circle in the immediate vicinity of the insertion end, characterized in that it comprises at least one intermediate sleeve (12) with an internal diameter compatible with the outside diameter of the support cylinder (10) for a radially tight mounting, and an outside diameter compatible with the diameter of a thin sleeve (14) bearing the image for a radially tight mounting whose outside diameter is equal to that of the development sought, said intermediate sleeve comprising nozzles (38) substantially along a circle, having the same angular distribution as that of the support cylinder and m shutter means (29, 42) of these nozzles so as to allow the mounting of this intermediate sleeve on the support cylinder. Arrangement according to claim 1, characterized in that the closure means comprise a ring (29) mounted fixed in translation along the longitudinal axis of the intermediate sleeve and movable in rotation between two positions, open and closed, in a projection (30 ) provided with nozzles (38) having the same angular distribution as that of the nozzles (22) of the support cylinder (10) and the nozzles (34) of the intermediate sleeve (12) with the open position corresponding to the coincidence of the nozzles (38 ) of the sleeve inserted with the nozzles (34) of the ring and a closed position in which the nozzles (34) of the ring are offset with respect to those (38) of the sleeve. Arrangement according to claim 2, characterized in that it comprises a fixed ring (28) integral with the body of the intermediate sleeve and rotationally supporting the movable ring 29, said fixed ring also being provided with nozzles (36) whose angular distribution is identical to that of the nozzles (22, 34, 38). Arrangement according to claim 2 or 3, characterized in that the movable ring (29) comprises seals, so as to prevent leaks of compressed air between the ring and the sleeve. Arrangement according to claim 2, 3 or 4, characterized in that the fixed and movable rings are mounted in a projection formed at the corresponding end of the intermediate sleeve. Arrangement according to claim 1, characterized in that the closure means comprise hollow fixed inserts (40) passing through the thickness of the intermediate sleeve, said inserts having an angular distribution identical to that of the nozzles (22) of the support cylinder, said inserts being tapped to receive removable threaded plugs (42). Arrangement according to any one of claims 1 to 6, characterized in that, in the case of several coaxial intermediate sleeves, these sleeves include indexes so as to allow the alignment of the different nozzles in radial directions. Intermediate sleeve for implementing the arrangement of claims 1 to 7, characterized in that it comprises a very thick sleeve body, corresponding to the difference between the outside diameter of the support cylinder and the inside diameter of the thin sleeve carrying the image to be printed, provided with mounting nozzles and means for closing these nozzles. Intermediate sleeve according to claim 8, characterized in that it comprises a succession of layers of materials of the honeycomb type, embedded in a resin matrix, the external surface being rectified and the internal surface being of polished appearance, imparted by the surface condition of the manufacturing cylinder.

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