Conventionally a coating is applied to a roll of sheet-like metallic substrate by passing the substrate around a driven roller. As the substrate passes around the driven roller, a coating is applied to the surface of the substrate by one or more coating application rollers mounted such that their respective circumferential surfaces contact the surface of the substrate as it passes around the driven roller. The application rollers are mounted such that their circumferential surfaces are in close proximity to the circumferential surfaces of respective take up rollers which take up coating from an open reservoir and transfer this to the application roller for application to the substrate.

A problem arises with this known apparatus insofar as it is necessary to continuously monitor and adjust, where necessary, the gap between the surface of the application roller and the take up roller to ensure that the correct thickness of coating material is applied and that the coating material is therefore applied in an accurate manner. A further problem arises with this known apparatus insofar as due to the manner of take up of coating from an open reservoir, it is possible for considerable coating material wastage to occur due to the inaccuracy of this take up. This wastage can be as much as 10 to 15% of the coating material used. A still further

problem arises due to the manner of take up of coating material insofar as it is not usually possible to ensure that the coating material is taken up evenly by the take up roller and therefore to ensure that an even coating is eventually applied to the substrate.

It is an object of the present invention to provide a coating apparatus in which these problems are overcome or at least minimised.

Thus and in accordance with a first aspect of the present invention there is provided a coating apparatus, particularly for coating a continuous roll of sheet-like metallic substrate, said apparatus comprising an enclosed reservoir containing coating material under pressure, an engraved roller disposed in close proximity to said enclosed reservoir to take up coating material therefrom and an application roller to take up coating material from said engraved roller and apply said material to a surface of a substrate.

With this arrangement, with the use of an engraved roller, it is possible to arrange for the take up of coating material to be (considerably more) accurate than with conventional apparatus. Furthermore the application of coating under pressure onto the engraved roller reduces coating wastage since only the amount of coating required to fill the engraved pattern is used. Furthermore use of an engraved roller means that once the engraved roller has been manufactured to particular predetermined parameters for a particular application, there is no necessity to arrange for continuous monitoring of a gap between the engraved roller and the application roller since no gap is necessary as the thickness of coating is

controlled by the depth of the engraved pattern.

Preferably one or more doctor blades are provided which wipe the surface of the engraved roller to remove coating from areas of the roller other than the engraved pattern and ensure that a uniform depth of coating is provided in the engraved pattern.

Preferably the reservoir is enclosed by rear, top and bottom walls of the reservoir and at least a part of the surface of the engraved roller. Most preferably, the reservoir is enclosed by rear, top and bottom walls of the reservoir, at least a part of the surface of the engraved roller and said one or more doctor blades.

Preferably a pair of doctor blades are provided, one depending from a top wall of the reservoir and the other extending upwardly from a bottom wall of the reservoir, both blades terminating adjacent the surface of the engraved roller.

In accordance with a second aspect of the present invention there is provided a method of applying a coating to a continuous roll of sheet-like metallic material comprising applying coating material to a surface of an engraved roller under pressure from an enclosed reservoir of coating material, transferring the coating material from the engraved roller to an application roller and applying the coating material from the application roller to the substrate.

With this method it is possible to ensure the even application of a coating to a continuous roll of substrate.

Preferably the substrate is provided in the form of a continuous roll and is fed to the application roller, is coated thereby and is then wound once again into a finished roll.

The second aspect of the invention can include any one or more of the features of the first aspect of the invention.

The invention will now be described further by way of example only and with reference to the accompanying drawings in which : - Fig. 1 shows a diagrammatic representation of one form of conventional coating apparatus ; and Fig. 2 shows a diagrammatic representation of one form of coating apparatus according to the present invention.

Referring now to the drawings, there is shown in Fig. 1 a conventional form of coating apparatus 10 for coating a continuous roll of substrate 11, for example steel or aluminum, in sheet-like form. The continuous roll ouf substrate 11 is referred to in the art as a coil. The substrate 11 is fed around the driven roller 12 from a storage roll (not shown) to a finished roll (not shown). As the substrate 11 passes around the driven roller 12 it passes at least one coating application device 13 which applies a coating material to one surface of the substrate 11. In the embodiment shown in Fig. 1, a pair of coating application devices 13 are provided, one to apply coating material to each respective side of the substrate 11. In practice, however, any number of coating application devices 13 can be used as desired or as appropriate.

Each coating application device 13 comprises a reservoir of coating material 14, a take up roller 16 to take coating up from the reservoir 14 and an application roller 17 to take coating from the take up roller 16 and apply to the surface of a substrate 11.

The reservoir 14 of coating material comprises an open topped receptacle containing coating material.

The take up roller 16 comprises a rubber, steet or ceramic router mounted such that upon rotation its surface takes up coating from the reservoir. Alternatively the take up roller 16 can be formed from any suitable material, as desired, or as appropriate.

The application roller 17 also comprises a rubber, steel or ceramic roller mounted in such a manner that its surface is in close proximity to both a surface of the take up roller 16 and the surface of the substrate to which the coating is to be applied.

In use, as substrate 11 is fed around the driven roller 12, each application device 13 applies coating material to a respective surface of the substrate 11. To do this, the take up roller 16 is rotated such that its circumferential surface 18 takes up coating material 19 from the reservoir 14 and transfers it to the surface 21 of the application roller 17. The surface 21 of the application roller 17, when rotated, applies this coating material to the surface of the substrate 11.

In this conventional system, in order to control the thickness of coating material applied to the substrate 11, it is usual for there to be a gap

(not shown in the drawing for the sake of clarity) between the surface 18 of the take up roller 16 and the surface 21 of the application roller 17. It will be appreciated that the dimensions of this gap determines the thickness of the layer of coating material eventually applied to the substrate 11.

Therefore with this conventional system it is necessary for this gap to be correctly set up prior to the apparatus being operated and for the gap to be continuously monitored during operation to ensure that an accurate and even application of coating material to the substrate 11 is achieved.

Furthermore due to the manner in which the take up roller 16 takes up coating material from the open top reservoir 14 there is considerable scope for wastage of coating material and it is not uncommon in these arrangements for there to be a wastage of approximately 10 to 15% of the coating material used.

Referring now to Fig. 2 there is shown one form of coating apparatus 30 according to the invention in which more accurate application of a coating material to a substrate can be achieved with minimal or no wastage of coating material.

In the apparatus of Fig. 2, simitarty to the conventional apparatus, the substrate 31 is fed around a driven roller 32 from a storage roll to a finished roll. As the substrate 31 passes around the driven roller 32 it passes at least one application device 33 which applies a coating material to one surface of the substrate 31. As with the conventional system of Fig. 1, whilst in Fig. 2 a pair of application devices 33 are shown, each one of

which applies a coating material to a respective surface of the substrate 31, in practice any number of application devices 33 can be used as desired or as appropriate.

The application device 33 as used in the apparatus of the invention is considerably different from that used in the conventional apparatus. The application device 33 comprises an enclosed reservoir 34 of coating material, a take up roller 36 in close proximity to the reservoir 34 to take up coating material from the reservoir 34 and an application roller 37 to take up coating material from the take up roller 36 and transfer it to the substrate 31.

The enclosed reservoir 34 comprises a rear wall 36, top wall 37 and bottom wall 38. A doctor blade 39 depends downwardly from the top wall 37 and another doctor blade 41 projects upwardly from the bottom wall 38, both doctor blades 39,41 terminating at the surface of the take up roller 36 for a purpose to be described hereinafter.

The reservoir 34 has an open front part which in the apparatus of the invention is closed off, to give an enclosed reservoir, by positioning of the take up roller 36 such that at least a part of its surface 42 of the roller 36 extends into and closes off the open front part of the reservoir 34.

The take up roller 36 comprises an engraved roller having a preselected engraved pattern engraved onto the surface thereof. This pattern can be as few as 11"cells"per linear inch and as many as 250 "cells"per linear inch engraved with the surface of the roller 36. The

engraved pattern has a particular depth and size and is configured to give a desired thickness and extent of coating to the substrate. The engraved pattern can comprise a multiplicity of engraved"cells"of many different configurations such as for example quadrangular or pyramid and can of any desired density.

The application roller 37 is a rubber roller of the same type as used in the conventional apparatus. Alternatively, as with the conventional apparatus, the application roller can be formed with any suitable material, as desired, or as appropriate.

In use, the engraved roller 36 rotates with its surface 42 in close proximity to the open front of the reservoir 34. Coating material is applied under pressure to the surface 42 of the roller 36 and enters the engraved pattern. The doctor blades 39, 41 wipe the surface of the engraved roller 36 as it rotates and therefore coating material is removed from the surface of the roller 36 other than in the region of the engraved pattern. As the engraved roller 36 continues to rotate the material within the engraved pattern is transferred to the surface 43 of the application roller 37. Rotation of the application roller 37 causes application of the coating to the substrate.

It will be noted from Fig. 2 that there is a no gap between the surface 42 of the engraved roller 36 and the surface 43 of the application roller 37.

This arises due to the fact that all the coating material is confined within the engraved pattern on the engraved roller 36 and the thickness of the coating

eventually applied is dictated solely by the depth of the engraved pattern.

There is no coating on the surface 42 of the engraved roller 36 other than in the engraved pattern. Therefore there is no need for a gap between the engraved roller 36 and the application roller 37. The lack of a gap means that the transfer of coating material from the engraved raller 36 to the application roller 37 is accurate and reduces coating material wastage. It also leads to the removal of the requirement for initial set up and continuous monitoring of such a gap as is required in conventional apparatus.

Furthermore the application of coating material to the surface 42 of the engraved roller 36 under pressure leads to a uniform and even application of the material onto the engraved pattern of the roller 36. This means that the pattern is completely filled with coating material as required and results in a considerably more accurate application of material to the substrate. Furthermore this means of application of coating material to the engraved roller further reduces material wastage.

It is of course to be understood that the invention is not intended to be restricted to the details of the above embodiments which are described by way of example only.