EP0683040A1 - Process for the manufacture of a sleeve for a printing machine, and sleeve obtained thereby - Google Patents

Abstract

Prodn. of an expandable print roller sleeve consists of preparing a rotary support cylinder with release agent; winding on a layer (24) of material (26) having regularly distributed holes (34) over its surface. The material is a complex composed of a layer (28) of non woven material over which is placed a layer of expanded natural (30) having a high space ratio and scream printed with a given pattern (32); This layer is coated with a resin (22), e.g. of vinyl ester or epoxy base, having the ability to retract a given amount on curing. After gelification of the resin an air tight material (37) e.g. of polyester is wound (36) over it. The system is cured at temp. coated (44) with a finishing resin (46), cured and the sleeve removed by dilation under gas press. Finally a layer of elastomer is joined to the sleeve. <IMAGE>

Description

The present invention relates to a method of manufacturing a printing sleeve, in particular for flexography, of composite material, as well as the corresponding sleeve.

Numerous methods are known for mounting flexographic printing sleeves on support cylinders and in particular the European patent application EP-A-0 196 443.

Such methods use hollow support cylinders inside which air under pressure is introduced.

The outer wall of each of these hollow cylinders is provided with holes which allow the pressurized fluid to escape radially.

Thus, the sleeve, which is perfectly adjusted, is expanded during assembly by the pressurized air which escapes from the cylinder through the holes, forming a layer of pressurized air.

This expansion is of very small amplitude but nevertheless sufficient.

The sleeve can thus be moved in translation easily, on an air cushion.

The sleeve must have a certain capacity for radial deformation but, conversely, it is known that it must be very rigid on the outside in order to receive either a finishing layer capable of being rectified or a layer of elastomer according to the different applications.

In all cases, the sleeve with this finishing layer or this elastomer layer must have a low deformation capacity and it must have perfect concentricity.

These two constraints of radial expansion capacity and rigidity are mutually exclusive and the current solutions are unsatisfactory compromises.

We also know that users of printing sleeves have support cylinders and sets of sleeves of different thicknesses for the same support cylinder diameter so as to obtain, for a given support cylinder, different external diameters so that the linear developments obtained cover as wide a range as possible.

It is therefore understandable that the more the sleeves can vary in thickness from a small thickness to large thicknesses and the less support cylinders are required since for the same support cylinder it is possible to cover with the sleeves a greater development range.

• les manchons sont moins chers que les cylindres support,
• il ne faut pas nécessairement démonter le cylindre support pour mettre le manchon et dans ce cas le gain de temps est intéressant,
• en cas de démontage, les manchons peuvent être préparés à l'avance sur d'autres cylindres support, et
• dans tous les cas, il y a un gain de poids qui facilite de façon très importante la manutention, car les utilisateurs sont obligés de stocker, manutentionner et gérer des dizaines et même des centaines de manchons.

Of course, additional sleeves are needed, but we know that:

• the sleeves are less expensive than the support cylinders,
• it is not necessary to dismantle the support cylinder to put the sleeve and in this case the time saving is interesting,
• in the event of disassembly, the sleeves can be prepared in advance on other support cylinders, and
• in all cases, there is a weight gain which greatly facilitates handling, because users are forced to store, handle and manage dozens and even hundreds of sleeves.

Unfortunately, the sleeves known from the prior art do not make it possible to achieve performances capable of generating the advantages listed above.

Attempts have so far been made to make sleeves which are lighter, less expensive and whose mechanical characteristics are improved.

Thus, sleeves have been made of composite material comprising glass fiber mats embedded in resin matrices, but the results are not entirely satisfactory since the weight and the cost increase very rapidly with the thickness. Also, it is impossible to achieve very wide ranges of developments because the variations in thickness for the same internal diameter, corresponding to a given support cylinder, are of small amplitude.

In addition, in large thicknesses, the amount of resin is also very large, which gives such sleeves a rigidity incompatible with mounting under pressure by radial expansion, especially if one wishes to remain within current industrial pressure ranges. on the order of a few bars.

The quantity of resin also has a major influence on the weight and the price of the sleeve thus produced, which quickly makes it uncompetitive.

The present invention aims to overcome these drawbacks and it proposes a method of manufacturing sleeves which is simple to implement, which makes it possible to produce sleeves of desired thickness in a very wide range, of suitable mechanical strength and of a certain elasticity, sufficient to allow mounting by radial expansion using a pressurized gas, on a chamber cylinder, drilled radially, which is of reduced weight which facilitates its handling, and which can be used either directly after rectification, either after coating with an elastomer layer and subsequent machining, or again by heliography, after the deposition of a conductive metallic coating and its etching.

• mise en rotation et préparation de la surface extérieure du cylindre avec un agent démoulant,
• enroulement sur ce cylindre support d'une couche d'un matériau comportant des trous traversants, régulièrement répartis sur sa surface, ce matériau étant un complexe composé d'une couche de matériau non tissé sur laquelle est déposée une couche d'un matériau ayant un fort taux de vide, du type expansé et sérigraphié avec un motif donné,
• enduction de cette couche avec une résine ayant un pouvoir de retrait déterminé à la polymérisation,
• attente de la gélification,
• enroulement d'une couche d'un matériau d'étanchéité sur la couche enduite de résine,
• polymérisation en température,
• enduction d'une couche de résine de finition,
• attente de la gélification,
• polymérisation en température,
• extraction du manchon fabriqué par dilatation radiale de ce manchon à l'aide de gaz sous pression introduit dans la chambre du cylindre, et
• reprise du manchon pour un traitement final par rectification mécanique ou par adhérisation d'une couche d'élastomère.

To this end, the method of manufacturing an expandable printing sleeve according to the invention, in particular for flexography, intended to be mounted on a non-deformable support cylinder provided with an internal chamber equipped with radial holes opening out at the outer surface of the cylinder, this cylinder having a diameter equal to that of the diameter of the cylinder on which the sleeve will be mounted as well manufactured, is characterized in that it comprises the following stages:

• rotation and preparation of the external surface of the cylinder with a release agent,
• winding on this support cylinder of a layer of a material comprising through holes, regularly distributed over its surface, this material being a complex composed of a layer of nonwoven material on which is deposited a layer of a material having a high vacuum rate, of the expanded type and screen printed with a given pattern,
• coating of this layer with a resin having a withdrawal power determined during polymerization,
• waiting for gelation,
• winding a layer of sealing material on the resin-coated layer,
• temperature polymerization,
• coating of a finishing resin layer,
• waiting for gelation,
• temperature polymerization,
• extraction of the sleeve produced by radial expansion of this sleeve using pressurized gas introduced into the chamber of the cylinder, and
• resumption of the sleeve for a final treatment by mechanical rectification or by adhesion of a layer of elastomer.

According to another characteristic, a priming layer is wound on the release agent from the support cylinder, this priming layer comprising a layer of a woven or nonwoven coated with a layer of resin.

In the case of thick sleeves, the winding of layers of complex with resin coating is repeated several times until the desired thickness of sleeve is obtained.

According to another feature of the invention, the thicknesses of the complex, the patterns and their density are variable as well as the diameters of the holes.

Preferably, the resins used are based on vinyl ester or epoxy.

In a particular embodiment, a shrinkable film is placed on the last layer of complex before the temperature polymerization and this film is removed after the polymerization so as to give a surface condition suitable for the final operation.

The subject of the invention is also the sleeve obtained by the method, a sleeve which comprises a concentric succession from the center outwards, of at least one layer of a material comprising through holes, regularly distributed over its surface, this material being a complex composed of a layer of nonwoven material on which is deposited a layer of a material having a high void content, of the expanded type and screen printed with a given pattern, of a layer of resin having a shrinking power determined at the polymerization, of at least one winding of an intermediate sealing fabric on the layer of resin coated on the complex, and of at least one layer of finishing resin.

Usefully, the finishing resins have a color code depending on the diameters and / or applications, flexography or rotogravure.

In the case of an application to flexography with an added plate, there are provided inserts fixed by machining, in particular for receiving sizes.

According to another practical characteristic of the sleeve, there is provided at least one identification label embedded in the mass during manufacture.

• Figure 1, une vue d'un manchon selon l'invention, en perspective avec un arrachement partiel faisant apparaître les différentes couches,
• Figure 2, une vue de détail en coupe transversale du manchon,
• Figure 3, une vue en perspective schématique agrandie d'un ensemble de cellules d'une couche obtenue lors de la fabrication d'un manchon par le procédé selon l'invention,
• Figures 4A, 4B, 4C respectivement, une demi-vue en perspective, une demi-vue en coupe longitudinale et une demi-vue en coupe transversale d'une réalisation flexographique avec un cliché,
• Figures 5A, 5B, 5C respectivement, une demi-vue en perspective, une demi-vue en coupe longitudinale et une demi-vue en coupe transversale d'une réalisation avec une couche d'élastomère gravé, et
• Figure 6A, 6B, 6C respectivement, une demi-vue en perspective, une demi-vue en coupe longitudinale et une demi-vue en coupe transversale d'une réalisation avec un revêtement métallique conducteur pour une application héliographique.

The invention is described below according to a preferred embodiment, with reference to the appended drawings which represent:

• FIG. 1, a view of a sleeve according to the invention, in perspective with a partial cutaway showing the different layers,
• FIG. 2, a detailed view in cross section of the sleeve,
• FIG. 3, an enlarged schematic perspective view of a set of cells with a layer obtained during the manufacture of a sleeve by the method according to the invention,
• FIGS. 4A, 4B, 4C respectively, a half-view in perspective, a half-view in longitudinal section and a half-view in cross section of a flexographic embodiment with a plate,
• FIGS. 5A, 5B, 5C respectively, a half-view in perspective, a half-view in longitudinal section and a half-view in transverse section of an embodiment with an etched layer of elastomer, and
• Figure 6A, 6B, 6C respectively, a half-perspective view, a half-view in longitudinal section and a half-view in cross section of an embodiment with a conductive metallic coating for a heliographic application.

In Figure 1, there is shown a sleeve 10, mounted on a support cylinder 12 of manufacture. The different dimensions are strongly exaggerated to show the different layers and to be able to distinguish them from each other.

The support cylinder 12 comprises, in known manner an internal chamber 14 and radial holes 16, coming from the chamber 14 and opening at the outer periphery of said cylinder.

For the production of a sleeve according to the method of the invention, either one of the support cylinders supplied by the user is used so that it is used as a mandrel for manufacturing the sleeve, which is the guarantee of certain precision. , or a sleeve machined and rectified template to the exact dimensions of the support cylinder on which the sleeves must be mounted.

The support cylinder is fixed on a mandrel holder in suitable jaws then it is prepared, in a known manner, by coating it over its entire outer surface with a release agent.

On this cylinder, first of all, at least one first layer 18 is wound under tension, for example by wrapping, a woven or nonwoven veil 20, which is coated with a resin 22, the characteristics and properties of which are will be described later in the text, so that the veil is impregnated and is pressed onto the release agent, thus perfectly matching the external periphery of the support cylinder 12.

On this so-called priming layer, there is wound a first layer 24 of a complex 26 comprising a layer of nonwoven material 28 on which is deposited a layer of expanded material 30. This expanded material 30, as shown in FIG. 3 , is screen printed with a given pattern, in this case a hexagonal pattern, with a physical separation between two adjacent patterns. That is to say that in the preferred embodiment of the method of the invention, the expanded material has a honeycomb structure, with isolated cells 32, of full hexagonal section, and a network of channels 35 separating said cells. The height of each of these cells is identical so that the complex has a given thickness which is sufficiently precise.

This first layer 24 of complex 26 is produced by winding a strip of complex, helically, edge to edge, over the entire length of the support cylinder, by placing the nonwoven 28 inside.

Referring to Figure 2, it is understood that the cells 32 of the complex 26, when it is wound on the cylinder, edge to edge, leaves the network of channels 35. These channels, by the curvature to which the complex, open slightly on the convex side and close slightly on the concave side, thus forming channels with a V-section truncated at the base, funnel-shaped. This is not visible in Figure 2 to maintain the clarity of the drawing.

On the other hand, it is noted in this FIG. 2 the presence of holes 34, of a given diameter, formed through the complex, perpendicular to its surface so that the holes, once the complex is wound, are oriented radially or close to a radial orientation.

The complex thus wound is retained by the resin layer 24 of the initiation layer 18 since the nonwoven of the complex is wetted by this resin.

This first layer 24 of complex 26 is coated with a layer of resin 24, in suitable quantity, which is housed in the channels 35, because the expanded material does not absorb the resin and there is amalgamation of the resin from these two layers of resin, on either side of the material expanded by the channels as shown in the figure 2.

It is also noted that the holes 34 allow connections to be made between the interior and exterior faces of the complex, resin bridges, forming as many spacers as will be described later.

The winding is carried out with a certain tension so as to press the complex 26 well and to avoid the presence of air bubbles during manufacture.

When the resin 24 of the complex is gelled, there is then wound on the complex 20, at least one layer 36 of a material 37 known as "sealing", in the present case a polyester nonwoven. This material makes it possible to wet the entire outer surface of the complex by distributing the resin.

A second layer 38, of a complex 40, is then wound up, which is either identical to the complex 26, or different with cells of different dimensions, height and pattern. In the embodiment shown and for the sake of simplification, an identical complex has been shown.

The nonwoven is also placed on the concave face.

This second layer 38 of complex 40 is in turn coated with a layer of resin 24 and optionally with a layer 42 of sealing material 37 to homogenize and distribute the resin.

In the embodiment shown, provision is made for a layer 44 of a finishing resin 46. This resin is capable, after polymerization, of being rectified by mechanical machining. This resin can include mineral and / or organic fillers.

In the case of the production of sleeves, the surface of which is machined in order to receive plates directly, a slightly retractable veil is placed on the surface of the finishing resin in order to compress the various superimposed layers.

This fine mesh veil withstands baking temperature and is removed after the sleeve has been brought to the crosslinking temperature of the resin.

Thus the layers are well concentric, coaxial and the surface condition, with a very fine grain, allows machining and rectification of quality.

In the case of the manufacture of sleeves intended to support an elastomer layer, the finishing layer receives a tear-off fabric, also retractable, so as to maintain the layers concentrically and coaxially, this fabric also having to withstand temperature of crosslinking resins.

This coarse mesh tear-off fabric leaves, after removal, a relief on the top layer, which allows better adhesion of the elastomer layer which must be deposited and vulcanized there.

According to the process of the invention, the formulation of the resin is adapted to shrink and give the sleeve thus produced a radial shrinkage capacity which is of great interest. As a family of polymers used for the preparation of resins, vinyl esters or epoxies may be mentioned.

Indeed, as indicated in the preamble, the sleeve is produced on a cylinder with the exact dimensions of the support cylinder on which it will be subsequently mounted.

Therefore, the withdrawal leads to a reduction in the diameter of the sleeve which is smaller than the diameter of the cylinder.

It is this withdrawal which allows the sleeve to be pressed later against the working cylinder and which generates clamping forces such that the sleeve does not rotate relative to the cylinder on which it is mounted, despite the rotational torques generated by the rotation speed.

Note that the tightening force, therefore the corresponding shrinkage must be inversely proportional to the diameter of the cylinder.

In fact, the more the diameter decreases, the more the contact surface between the sleeve and the working cylinder decreases, the more the clamping force must be increased to obtain a identical locking for all sleeves, whatever the diameter.

The disassembly of the sleeve from the manufacturing cylinder and its mounting on the working cylinder are only made possible by radial expansion under the effect of pressurized air which escapes from the holes 16 of these cylinders.

This radial expansion, of a few hundredths of a millimeter, therefore very small compared to the diameter of the sleeve, is made possible by the fact that the expanded material does not absorb resin and that the connections of the layers by the resin in the channels, on the one hand, and in the holes, on the other hand, give the assembly a possibility of deformation in the elastic domain.

This beach is very short but it exists.

If one continues the deformation, one arrives in a plastic range which requires forces of deformation much higher than those generated by the air under pressure coming from the holes of the cylinder, so that during the withdrawal or the assembly, one remains in the elastic zone, without the possibility of mechanical degradation of the sleeve.

This arrangement of layers with at least one waterproof layer is essential to obtain the desired effects.

It is also noted that the resin bridges obtained by the holes 34 make it possible to impart very high rigidity to the sleeve, in particular to compression.

A large number of thicknesses can be obtained with the same inner diameter of the sleeve corresponding to the diameter of the working cylinder by varying the number of layers, which leads to thicknesses of between a few millimeters and several centimeters.

We can also play on combinations of different complexes, with different thicknesses, various cell patterns, of greater or lesser density.

It is also considered as included in the method according to the invention the use of complexes obtained in any way as long as they have an expanded material or having a certain void content such as beads for example, associated with a veil woven or non-woven. Indeed, one can resort to a prepared complex industrially by screen printing by printing a pattern or a complex prepared by coating a nonwoven with a projection of beads, which material is then pierced with multiple holes.

As has been explained, the method consists in reducing the quantity of resin by a very light filling material while maintaining connections between the layers of resin.

In order to be able to classify the sleeves during their storage or simply to be able to check at a glance that it is the desired sleeve, it is planned to choose color resins for the top coat with a predetermined code in depending on applications or dimensions.

Similarly, one can introduce inside the sleeve, under the first layer of complex, a reference label for example, which remains visible after manufacture, inside and which is therefore inviolable by the manufacture of the sleeve itself.

Such sleeves are applied to flexography, FIG. 4A, 4B, 4C and 5A, 5B, 5C, but it is also possible to manufacture sleeves for heliography in the same way. There are sections of such sleeves in Figures 6A, 6B and 6C. In these figures, the finishing layer and the complementary elements are simply shown depending on the application, the other interior layers being identical and produced according to the method described above.

In FIG. 4A, a sleeve-bearing cylinder 60 is shown, used in flexographic printing. A sleeve 62 is mounted on this sleeve-carrying cylinder 60. This sleeve is produced according to the method of the invention and the finishing layer has been corrected to have a smooth surface condition and so that the developed diameter corresponds exactly to the length of printing sought. On this surface, it is mechanically produced generators 64 for placing and positioning the plates. The picture is in the form of an engraved plate 66, made of a photopolymer or rubber material, which allows the arrange in a winding around the sleeve. This plate is fixed by interposing a double-sided adhesive tape 68. In FIGS. 4B and 4C, the identical elements have the same references.

In FIG. 5A, a sleeve-carrying cylinder 70 is shown, designed to receive a sleeve 72 according to the invention. The outer surface has received a finishing layer 74 of rubber material fixed with an adhesive. This coating is vulcanized and rectified then it is engraved using a laser, generally. This type of engraving allows continuous printing, for example for wallpaper. In FIGS. 5B and 5C, the identical elements have the same references.

In FIG. 6A, for application to heliography, the mandrel cylinder 80 supports a specific sleeve 82 produced according to the invention but with a subsequent metal deposition treatment. For this purpose, the finishing layer of the sleeve 84 is made conductive by incorporating conductive particles or by depositing a layer of carbon, then a metal deposit of a given thickness is deposited by electrolysis on a thickness sufficient to allow recovery. and mechanical machining. Once the development sought, the metal deposit is engraved in hollow to reproduce an engraving of variable depth depending on the intensity of the color to be obtained. The metal deposit is generally made of copper and chrome after etching. In FIGS. 6B and 6C, the identical elements have the same references.

Such heliographic sleeves are of particular interest in combined flexography-heliography printing for the printing of certain solid areas or bar codes.

The method thus described allows the production of specific sleeves which also form part of the present invention.

One can also provide for attaching inserts added by machining in the last layers so as to be able to subsequently mount shoe sizes for fixing the plates.

In the case where the thicknesses reached are very large, it is possible to produce an intermediate belt, with a large thickness of resin of the order of 1 to 3 millimeters to fix an order of magnitude, so that this belt blocks the capacities radial expansion. This belt is formed at a distance from the inner periphery of the sleeve which is a function of the different characteristics of the sleeve, inside diameter, outside diameter, application in particular.

Claims (10)

Method of manufacturing an expandable printing sleeve, in particular for flexography, intended to be mounted on a non-deformable support cylinder (12) provided with an internal chamber (14) equipped with radial holes (16) opening out at the surface outside of the cylinder, this cylinder having a diameter equal to that of the diameter of the cylinder on which the sleeve thus manufactured will be mounted, characterized in that it comprises the following steps: - rotation and preparation of the external surface of the cylinder with a release agent, winding on this support cylinder a layer (24) of a material (26) comprising through holes (34), regularly distributed over its surface, this material being a complex composed of a layer of nonwoven material (28 ) on which is deposited a layer of a material (30) having a high void content, of the expanded type and screen printed with a given pattern (32), - coating this layer with a resin (22) having a shrinkage power determined during polymerization, - waiting for gelation, winding a layer (36) of a sealing material (37) on the resin-coated layer (22), - temperature polymerization, - coating a layer (44) of finishing resin (46), - waiting for gelation, - temperature polymerization, extraction of the sleeve produced by radial expansion of this sleeve using pressurized gas introduced into the cylinder chamber, and - recovery of the sleeve for a final treatment by mechanical rectification or by adhesion of a elastomer layer. Method of manufacturing an expandable printing sleeve according to claim 1, characterized in that a priming layer (18) is wound on the demoulding of the support cylinder, this priming layer comprising a layer (20) of a woven or nonwoven coated with a layer of resin (22). A method of manufacturing an expandable printing sleeve according to claim 1 or 2, characterized in that the winding of layers of complex with resin coating is repeated several times until the desired sleeve thickness is obtained. Method of manufacturing an expandable printing sleeve according to any one of the preceding claims, characterized in that the thicknesses of complex, the patterns of the cells (32) and their density are variable as well as the diameters of the holes (34) . A method of manufacturing an expandable printing sleeve according to any one of the preceding claims, characterized in that the resins (22) used are based on vinyl ester or epoxy. Method for manufacturing an expandable printing sleeve according to any one of the preceding claims, characterized in that a shrinkable film is placed on the last layer of complex before the temperature polymerization and that this film is removed after the polymerization so as to give a surface condition suitable for the final operation. Sleeve for cylinder of printing machine produced by the implementation of the method according to any one of the preceding claims, characterized in that it comprises a concentric succession of the center towards the outside, of at least one layer (24 , 38) of a material comprising through holes (34), regularly distributed over its surface, this material being a complex composed of a layer of nonwoven material (28) on which is deposited a layer of a material (30 ) having a high void content, of the expanded type and screen printed with a given pattern (32), of a resin layer (22) having a shrinkage power determined during polymerization, of at least one winding of a layer (36) a sealing material (37) on the layer of resin coated on the complex, and at least one layer (44) of finishing resin. Sleeve for printing machine cylinder according to claim 7, characterized in that it includes finishing resins with a color code depending on the diameters and / or applications, flexography or rotogravure. Sleeve for a printing machine cylinder according to claim 7 or 8, characterized in that it includes inserts added by machining, in particular for receiving sizes. Sleeve for a printing machine cylinder according to claim 7, 8 or 9, characterized in that it comprises at least one label embedded in the mass during manufacture.

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