FR2757795A1 - COMPOSITE SLEEVE WITH CERAMIC COATING, PARTICULARLY ADAPTED FOR INK TRANSFER SLEEVES - Google Patents

Abstract

The present invention relates to a composite sleeve adapted in particular to be mounted on a metal carrier cylinder and used for ink transfer, comprising a radially deformable base sleeve (10), a layer (12) with limited deformability, a layer (14 ) intermediate for absorbing radial deformations, and a layer (16) of material with a high heat dissipation capacity, ceramized. The ceramic coating (18) is etched, usually laser, to provide the outer surface of the sleeve with ink-holding capabilities to enable its use as an anilox in a printing machine.

Description

COMPOSITE SLEEVE WITH CERAMIC COATING, ADAPTED

  IN PARTICULAR FOR THE INK TRANSFER SLEEVES

  The present invention relates to a composite sleeve with a ceramic coating, intended to be etched on the surface, in particular with a laser and

  used in flexographic printing machines for ink transfer.

  Composite sleeves are already commonly used as clutch sleeves in flexographic printing machines. Such sleeves allow easy handling, rapid changes and above all allow to cover a very wide range of

  developments from the same carrier cylinder.

  Thus, the applicants have developed a composite high-tech sleeve described in the European patent application N 95 450009. This sleeve is mounted on a carrier cylinder perforated on one side with nozzles that allows air to pass. compressed introduced inside the carrier cylinder. This pressurized air makes it possible to dilate the sleeve very weakly but sufficiently to ensure radial expansion and mounting on the carrier cylinder. When the pressure stops, the perfectly adjusted sleeve returns to its nominal diameter and the radial clamping ensures a rotational locking

  and in translation of said sleeve on the cylinder.

  This composite sleeve comprises at least one layer of material of the type comprising a complex composed of a layer of nonwoven material and a layer of material having a high void content of the expanded type in a determined geometry, the assembly being coated with a resin layer having a high shrinkage power determined upon polymerization. Bridges of

resin provide the bonds.

  In a flexographic printing machine, it is also necessary to anchor the images carried by the composite sleeves. This system of inking is excessively solicited, since it is not changed like the clutch sleeves. Its role is, after adjustment of the key, ie the pressure to be exerted on the plate, to deposit on this plate, a thin layer of ink, of extreme regularity in order to deliver a very precise dose

  of ink, which is the guarantee of a quality impression.

  This type of cylinder is commonly called in the "anilox" trade. It is currently made of steel and then undergoes a ceramic deposit by spraying molten ceramic powder, generally in a plasma, which explains the realization of the steel support cylinder and the deposit directly on the metal cylinder. The retained material, the ceramic is

  dictation, for reasons well understandable, by its resistance to wear.

  In order to give this coating its printing qualities, the coating is ground to give it a perfect round and then engraved, usually by laser, to give it its capacity to retain a volume.

  given ink per unit area.

  This product is sophisticated and the cost price of such a cylinder is high. When for reasons dictated by the impression to be made the cylinder must be changed or broken because the ceramic is resistant to wear but remains very fragile, the only way is to change the complete cylinder, which

  requires very long machine shutdown times.

  To give an idea, mechanics, that is to say the machining of rockets with rectified spans, the bearings, intervenes for 25% of the price

total of the finished cylinder.

  We must therefore invest in mechanics significant costs for each

  cylinder only to change engraving.

  It is known that a flexographic machine can comprise three basic types of screen, which leads to 18 anilox cylinders for a six-color machine. The aim is therefore to propose anilox cylinders with a single support cylinder on which is mounted a sleeve ceramised on the surface and etched, although the ceramic is very fragile and does not support any radial expansion and although the ceramic deposit generates temperature rises. very important. The economy will then be almost 25% of the total investment plus a very valuable time saving in machine stop since the time of change of the anilox will be of the same order of magnitude as the

clutch sleeves.

  For this purpose, the composite sleeve adapted in particular to be mounted on a metal carrier cylinder and used for the transfer of ink, comprises a radially deformable base sleeve, a layer with limited deformability, an intermediate layer for absorbing radial deformations, and a layer of material with a high capacity for dissipating heat,

veneered.

  The base sleeve more particularly comprises at least one

  layer of complex type material composed of a layer of non-material

  woven material and a layer of material having a high void content of the expanded type in a determined geometry, the assembly being coated with a layer of

  resin having a high shrinkage power determined upon polymerization.

  According to the preferred embodiment, the layer with limited deformability is made of fiberglass embedded in a hard resin that can be ground,

forming a reinforcing belt.

  The intermediate layer for absorbing radial deformations comprises a triplex composed of an elastomer sandwiched between an inner layer of hard resin and the binder with the layer with limited deformability, and an outer layer of resin hardens the binder with the layer of strong heat dissipation ability. Preferably, the elastomer has a hardness of substantially 60 shore and the resin has a hardness of 85 shore, the thickness of

  the intermediate layer being a few millimeters.

  According to another characteristic, the material of the layer with high heat dissipation capacity is carbon or a conductive polymer embedded in a high glass transition point resin or a metal alloy. In addition, the material of the layer with high heat dissipation capacity is coated directly with a ceramic coating,

  which is rectified to the given diameter and engraved.

  The invention is described below according to a particular embodiment, not limiting, with reference to the accompanying drawings in which the different figures represent: FIG. 1, a view of a preferred embodiment of an anilox cylinder according to FIG. 1, a longitudinal sectional view of the anilox cylinder of FIG. 1, and FIGS. 3A and 3B, a comparative view of the effects of a radial force on the invention. a sleeve of the prior art and on a sleeve according to the invention,

respectively.

  The sleeve shown in FIG. 1 comprises a base sleeve 10 to which a radially limited deformability layer 12 is attached, a compressible intermediate layer 14 and a heat dissipating layer 16 capable of being coated with a

layer 18 of ceramic material.

  The base sleeve 10 is of the type comprising at least one layer of low density material as described in the European patent application N 95 450009 in the names of the present applicants with impregnation of resin to bind the layers together and build bridges in the radial direction, so as to leave a certain capacity of radial deformation by expansion under the effect of pressure to allow mounting on the carrier cylinder and a necking effect sufficient to prohibit any rotation of the

  sleeve once the flow of gas under pressure interrupted.

  This type of material comprises a layer of nonwoven material and a layer of material having a high void content of the expanded type in a determined geometry, the assembly being coated with a layer of resin having

  a high shrinkage power determined in the polymerization.

  All the constituents make it possible to reach very low densities. The layer 12 with limited deformability is made in the particular embodiment shown with fiberglass, arranged by filament winding or wrapping and impregnated with a very hard resin

once polymerized.

  This layer forms a reinforcing belt.

  In order to obtain a surface condition allowing the installation of other

  layers of material, it is provided a rectification to a given diameter.

  The intermediate layer 14 preferably comprises a triplex, ie a layer of a microcellular elastomer comprising open cell pores, sandwiched between two layers of very hard resin of 85 shore. The hardness of the elastomer is rather located in values

from 50 to 60 shore.

  This type of elastomer thus sandwiched leads to very interesting deformation capacities as shown in FIGS. 3A and 3B. Indeed, the open-cell foam compresses in perfectly radial directions without lateral deformation, that is to say parallel to the

  area. There is no lateral creep under load.

  The resin that permeates this triplex also ensures the connection between the layer to

  limited deformability and this triplex.

  This intermediate layer 14 is thin, of the order of a few millimeters, it is imperatively arranged immediately under the

  layer 16 with high heat dissipation.

  The layer 16 with high heat dissipation is for example carbon or a conductive polymer embedded in a high glass transition point resin. This layer may also comprise a metal alloy based

aluminum or copper.

  This layer 16 is then directly coated with a projection of

  molten ceramic powder, in a plasma for example.

  The localized heat of the deposit is thus diffused in the support layer

without degrading it.

  The composite sleeve is then rectified in a known manner to the diamond wheel to give it a regular outer diameter having a

  controlled particle size adapted to undergo etching by means of a laser.

  The structure of the sleeve according to the invention is such that the heat generated by the ceramic coating is dissipated without reaching the sleeve

  base, neither the intermediate layer nor the inner layer of Triplex.

  The manufacture of such a sleeve is possible.

  Then, it is still necessary to mount such a sleeve on the carrier cylinder knowing that the outer ceramic layer is provided with no

  elasticity and that it is fragile so that it breaks.

  When pressurized by the gas flow, it is the base sleeve that compresses to gain the few hundredths of a millimeter of radial expansion required for assembly. The layer 12 with deformability

  limited avoids the spread of radial expansion.

  If radial expansions persist and propagate, the intermediate layer is there to absorb this dilation, prohibiting any transfer of dilation to the layer with a high capacity of

  heat dissipation coated with ceramic.

  As soon as the sleeve is mounted, the air flow is interrupted and the base sleeve engages the carrier cylinder and immobilizes said

sleeve on said cylinder.

  It is noted that the deformable intermediate layer is carried outside the sleeve, which at the same time limits the shear effects between the different coaxial layers. Indeed, the microporous elastomers have low shear strengths and the more they are in the center and the less there is material to absorb the forces generated by the rotation of the cylinder

carrier and his sleeve.

Claims (8)

  1. Composite sleeve adapted in particular for being mounted on a metal carrying cylinder and used for ink transfer, comprising a radially deformable base sleeve (10), a layer (12) with limited deformability, an intermediate layer (14), absorption of the radial deformations, and a layer (16) of high-capacity material   heat dissipation, ceramized.   Composite sleeve according to Claim 1, characterized in that the base sleeve (10) comprises at least one layer of material of the type comprising a complex composed of a layer of nonwoven material and a layer of material having a high vacuum rate of the expanded type according to a determined geometry, the assembly being coated with a layer of resin   having a high shrinkage capacity determined on polymerization.   3. composite sleeve according to claim 1 or 2, characterized in that the layer (12) limited deformability is made of glass fiber embedded in a hard resin capable of being ground, forming a reinforcing belt. 4. Composite sleeve according to claim 1, 2 or 3, characterized in that the layer (14) intermediate radial deformation absorption comprises a triplex composed of an elastomer sandwiched between an inner layer of hard resin binder to the layer (12) with limited deformability and an outer layer of resin lasts the binder to the layer (16) made of strong material   heat dissipation capacity.   5. composite sleeve according to claim 4, characterized in that the elastomer has a hardness between 50 and 60 shore and the resin has a hardness of 85 shore.   Composite sleeve according to claim 4 or 5, characterized in that   that the thickness of the intermediate layer is a few millimeters.   7. Composite sleeve according to any one of the claims   previous, characterized in that the material (16) of the layer with high heat dissipation capacity is carbon or a conductive polymer embedded in a high glass transition point resin or a metal alloy. 8. composite sleeve according to claim 7, characterized in that the material (16) of the layer with high heat dissipation capacity is coated directly with a coating (18) of ceramic, which is ground to diameter given and engraved.