AU773193B2 - Improvements in or relating to a method and apparatus for applying a coating to a mesh material - Google Patents

Description

1

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Name of Applicant: Actual Inventor: Address for Service: RODNEY GEORGE WADE RODNEY GEORGE WADE CULLEN CO., Patent Trade Mark Attorneys, 239 George Street, Brisbane, Qld. 4000, Australia.

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Invention Title: IMPROVEMENTS IN OR RELATING TO A METHOD AND APPARATUS FOR APPLYING A COATING TO A MESH

MATERIAL

Details of Associated Provisional Application: No. PQ2796 filed 13 September 1999 The following statement is a full description of this invention, including the best method of performing it known to me: 2 IMPROVEMENTS IN OR RELATING TO A METHOD AND APPARATUS FOR APPLYING A COATING TO A MESH MATERIAL BACKGROUND OF THE INVENTION This invention relates to a method and apparatus for applying a coating to a mesh material. The invention is particularly applicable to the application of paint to wire mesh to enhance the life and appearance of the mesh and to enable colour matching.

Wire mesh is commonly used to eliminate the build-up of flammable materials in roof guttering and other water catchment systems and the present invention can be used to colour match the mesh with guttering, roofing tiles and other architectural features of a structure.

:"At present, wire mesh is generally supplied in an uncoated form. A form with a paint coating is known but this is produced by a process which is not suitable for short product runs with time restrictions as would be the case where coated mesh is required straightaway for a small job.

Although there is a possibility of applying S 25 paints to wire mesh using paint spray systems, this is cote extremely wasteful and not a practical proposition.

Powder coating is perhaps another option however this process does not readily lend itself to continuous production of elongate product.

OBJECTS OF THE INVENTION A broad object of the present invention is to provide a method and apparatus for coating a mesh material which can be effected in a short time with the option for quick change of coating colours without too much down time.

A further but subsidiary object of the invention is to control the thickness of the coating on the mesh to ensure adequate cover without being wasteful of the coating solution used.

A yet further but also subsidiary object of the invention is to overcome the problem of microbubbles formed at the intersection of the cross-wires of the mesh. Such microbubbles prevent proper coating in these regions and can lead to a shortening of the product life due to accelerated corrosion at the intersections.

An overall object of the invention is to provide the public with a usefully alternative mesh coating process and apparatus.

FIRST SUMMARY OF THE INVENTION According to one aspect of the present invention there is provided a continuous process for producing a coated metal mesh, comprising the steps of: passing the mesh through an applicator bath which coats the mesh with a liquid coating, (ii) passing the wet coated mesh to coating 25 modification equipment which regulates the application of the coating onto the mesh, and (iii) passing the coated mesh through a dryer which dries the coating.

Preferably, the process includes an initial step of unwinding the mesh from as reel, and a final step of rewinding the coated mesh onto a new reel at the end Sof the process.

The process step of regulating the coating to a required parameter can comprise passing the mesh in contact with a brush which spreads the coating solution into the corners of the mesh and dispels microbubbles formed in the liquid coating. A preferred brush is a vacuum brush.

Another process regulating step comprises passing the mesh between two spring loaded rollers, one at least of which has an absorbent sheath, said spring loading being regulated so as to control the thickness of coating on the mesh.

Yet another process regulating step comprises passing the mesh past either a blower or a vacuum arrangement. The blower is designed to blow a curtain of air over the mesh to even out the wet coating and remove excess coating solution from the mesh. The vacuum arrangement draws air over the mesh and likewise evens out the coating and removes excess solution.

In some instances, it is also preferable to control the humidity of the drying step within predetermined parameters in order to maximise the through-put capacity.

SECOND SUMMARY OF THE INVENTION 25 According to another aspect of the present •invention there is provided apparatus for producing a continuous coated metal mesh, comprising: a liquid coating applicator in the form of a bath, (ii) liquid coating modification equipment which regulates the coating of the liquid onto the mesh for the final product, (iii) a dryer positioned downstream of the liquid coating modification equipment, and (iv) means for continuously conveying the mesh through the apparatus.

Further since the mesh is typically in a rolled form, means are provided for unwinding the mesh from a suitable support reel upstream of the coating applicator.

Likewise means will be provided for rewinding the coated mesh downstream from the dryer. Control means can be provided for regulating the rewind speed in accordance with the progress of the rewinding, and constraining means can be provided for regulating the unwinding speed of the uncoated mesh. Such means can include a tension brake.

The dryer suitably comprises a chamber with an inlet for the uncoated mesh at one end and an outlet for the coated mesh at the other. The drying chamber can comprise side, top and bottom walls, and height adjustable infra-red heating means can be positioned in the upper region of the chamber. Support means can be provided for supporting the mesh as it is transported within the chamber and internal reflection means can be provided to cover at least the lower wall of chamber. As an alternative, the heat source can be provided by radiation, microwave, convection heating or by a gas burner. Suitably, sensors are provided within the drying chamber to enable monitoring of the temperature so that 25 suitable adjustments can be made to control the S"temperature to within desired limits.

:Preferably, internal heat reflecting means are located in the lower region of the chamber. They can comprise one or more sheets of aluminium such as aluminium foil. The heat reflecting means can be adjustable with respect to the position of the mesh as it moves through the dryer.

35 The liquid coating modification equipment can include a brush which spreads the liquid coating solution into the corners of the mesh and dispels microbubbles formed in the coating solution. Preferably, the brush is arranged transversely of the mesh with respect to the direction of movement of the mesh. The brush can be suitably located in a stationary position beneath the mesh and comprise multiple rows of bristles which gently move over the mesh as the mesh moves along its path to the dryer. A preferred form of brush is a vacuum brush.

In a further aspect, the liquid coating modification equipment includes two spring loaded rollers between which the mesh is passed. One of the rollers, at least, has an absorbent sheath and the spring loading is regulated so as to control the thickness of the liquid coating on the mesh. The absorbent sheath on the at least one tension roller will preferably be a fabric and be of a thickness which will be determined by the nature of the coating being applied and the intended thickness.

Thus, for coatings formed from a water-based paint, the absorbent sheath can be a synthetic or natural fibre which is either woven or in the form of a wadding. A particularly suitable material is a wool wadding.

In a still further aspect, the liquid coating e modification equipment includes a blower which blows a curtain of air over the mesh to even out the liquid coating and remove excess liquid coating from the mesh.

The blower is suitably located above the mesh and is designed to eject air onto the mesh in a controlled manner whereby coating splatter is minimised. The blower can include a triangular-shaped, in transverse crosssection, plenum chamber arranged transversely if the direction of travel of the mesh, with a lower apex of the triangle defining an outlet for the air. Preferably the outlet for the air comprises a leading edge which projects slightly below a trailing edge to control coating splatter.

As an alternative to the blower, a vacuum arrangement can be used. This is designed to draw air over the mesh so that a similar result can be achieved as with the blower.

The humidity within the chamber can be regulated if need be by means of a combination of controls, including a dehumidifier on the air inlet to the dryer, a damper control unit adjacent the air inlet, a damper control adjacent the air outlet from the dryer and a damper control on the exhaust pipe, in addition to a flue at the end of the exhaust pipe which restricts the maximum amount of air to be removed from the system.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional diagrammatic *go• illustration of a first portion of a coating apparatus according to one preferred embodiment of the invention, and Figure 2 is a cross-sectional diagrammatic illustration of a second portion of the coating apparatus of Figure 1.

DESCRIPTION OF PREFERRED EMBODIMENT A preferred embodiment of the invention will 25 now be described with reference to these drawings.

The equipment illustrated in Figure 1 is intended to be in line with the equipment illustrated in Figure 2 and is merely shown in two separate drawings to facilitate an easier understanding of the invention.

Firstly, referring to Figure 1, the apparatus comprises a wire mesh support, unwind, and feed means a liquid coating applicator 11 and liquid coating modification equipment 12.

The support, unwind and feed means 10, consists of a reel 13 on which a coil of sheet mesh 14 is wound.

8 A tension brake 15 is provided to constrain the unwinding of the mesh which is driven by a motorised reel 16 on the other end of the apparatus (see Figure 2) Rollers 17 also assist in constraining the sheet metal mesh 20 as it is unwound and also act to straighten and direct the mesh in an orderly fashion into the liquid coating applicator. An optional roller 9 can also be provided to further regulate the feeding of the mesh into the applicator.

The liquid coating applicator comprises a bath 21 in which a reservoir of paint 22 is contained. A S•free-wheeling roller 23 is located within the bath 21 to retain the mesh 20 in the paint 22 as it passes through the bath.

0 Upon exiting the bath 21, the mesh 20 passes *over the bristles 24 of a vacuum brush 25. The bristles are sufficiently pliable to extend into the interstices between adjacent mesh strands and dislodge any microbubbles present. The bristles aid in spreading the coating solution evenly over the mesh. A vacuum applied to the bristles ensures that the bristles are kept free from clogging with paint.

The mesh 20 then passes between two freely counter-rotating rollers 26, 27; the upper one of which viz. 26, is maintained under tension by spring 29 so as to exert the desired pressure against the wet coated mesh and the lower roller 27. The upper roller 26 also includes an absorbent sheath 30 of wool wadding.

By regulating the tension in the spring 29, the thickness of the coating applied to the mesh 20 can be controlled within the predetermined limits.

Final precision control of the coating thickness is achieved when the mesh 20 passes beneath a blower arrangement 31. This arrangement consist of a plenum chamber 32 and an air compressor 33. The plenum chamber 32 is located at a small-predetermined height above the travelling mesh 20 and has a substantially triangular, in cross-section, configuration. An outlet 34 in the lower section of the plenum chamber directs a band of air over the mesh in such a manner as to minimise splatter and to control the coating thickness. The outlet 34 has a specially designed configuration having a long leading edge 35 and a shorter trailing edge 36 to enable this to be achieved.

S•The mesh then passes into a dryer 37.

Reference is now made to Figure 2 which illustrates one such suitable dryer 37. This comprises an elongate chamber defined by top and bottom walls 41, side walls, and end walls 42, 43. End wall 42 of the 20 chamber is adjacent the liquid coating modification 0 0 equipment 12, and end wall 43 is adjacent a rewind coil 44. The process of the present invention enables a mesh 20 to be continuously fed through the apparatus in the direction indicated by the arrows.

0 Within the chamber 40 wheels or knife edges support the mesh 20. In the upper region of the chamber a bank of infra-red heaters 46 are positioned. The infra-red heaters are arranged so as to be vertically movable over a range denoted by the double headed arrows The ambient temperature within the chamber is detected by sensors 48 so that the positioning of the infra-red heaters can be adjusted and their output regulated, to suit the requirements for the coated mesh.

In the lower region of the chamber, sheet aluminium foil 47 is provided. This is arranged to be movable up or down with respect to the base 41 of the chamber by an amount shown by the double headed arrow to ensure that the bottom of the mesh is also properly dried.

A dehumidifier 49 covers an air inlet to the chamber in end wall 43, and together with an associated damper 50, rotatable through 900, regulates the humidity of the air upon entry. Further dampers 51, 51A, also rotatable through 900, and respectively located at the air outlet 52 and within the chamber, also function as humidity controllers along with an outlet flue cover which restricts the maximum amount of air which can be.

removed.

A fan 53 is located in the outlet and functions to draw air through the chamber and then to exhaust it to the atmosphere by way of an appropriate ducting 54 and the aforementioned flue cover A temperature gauge 56 is provided for monitoring the temperature of the exhaust air.

The process thus described enables the coating ooo on the mesh to be accurately regulated and overcomes the 25 problem associated with microbubble formation at the ".interstices of the mesh.

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Claims (23)

1. 2. A process as claimed in claim 1 and including an initial step of unwinding the mesh from a reel, and a final step of rewinding the coated mesh onto a new reel at the end of the process.
2. 3. A process as claimed in claim 1 or claim 2, wherein the step of regulating the coating to the required parameters of the final coated mesh includes passing the wet coated mesh into contract with a brush which spreads the liquid coating into the corners of the mesh and dispels microbubbles formed in the liquid ooooo coating.
3. 4. A process as claimed in any one of the preceding o4. claims, wherein the step of regulating the coating to the required parameters of the final coated mesh includes passing the wet coated mesh between two spring rollers, one at least of which has an absorbent sheath, said spring loading being such as to control the thickness of the coating on the mesh. A process as claimed in any one of the preceding 35 claims, wherein the step of regulating the coating to :required parameters of the final coated mesh includes passing the wet coated mesh by a blower, or vacuum equipment, which blows, or sucks, a curtain of air over the mesh to even out the wet coating and/or to remove excess liquid coating from the mesh.
4. 6. A process as claimed in any one of the preceding claims and including controlling the humidity in the drying step to within a predetermined range.
5. 7. A process for producing a coated mesh substantially as herein described with reference to the accompanying drawings.
6. 8. An apparatus for producing a continuous coated metal mesh, comprising: a liquid coating applicator in the form of a bath, (ii) liquid coating modification equipment which regulates the coating of the liquid onto the mesh for the final product, (iii) a dryer positioned downstream of the liquid coating modification equipment, and (iv) means for continuously conveying the mesh through the apparatus. ooo e eo eoee e o a. a
7. 9. An 25 including: apparatus as claimed in claim 8, and means for unwinding uncoated mesh from a reel upstream of the liquid coating applicator, and (vi) means for rewinding the coated mesh downstream from the dryer.
8. 10. An apparatus as claimed in claim 9 and including a control means for regulating the rewind speed in accordance with the progress of the rewinding.
9. 11. An apparatus as claimed in claim 9 or claim and including a constraining means for regulating the unwinding speed of the uncoated mesh from the reel..-- 13
10. 12. An apparatus as claimed in any one of claims 8 to 11, wherein the dryer is a chamber having internal infra- red heating means.
11. 13. An apparatus as claimed in claim 12, wherein the infra-red heating means is located in the upper region of the chamber.
12. 14. An apparatus as claimed in claim 12 or claim 14, and including internal heat reflecting means. An apparatus as claimed in claim 14, wherein the internal heat reflecting means is located in the lower region of the chamber.
13. 16. An apparatus as claimed in claim 15, wherein the internal heat reflecting means comprises one or more sheets of aluminium.
14. 17. An apparatus as claimed in any one of claims 12 to 16 and including support means for the coated mesh as it is transported through the chamber. oooo 25 18. An apparatus as claimed in any one of claims 8 to o :17, wherein the liquid coating modification equipment o• includes a brush which spreads the liquid coating "solution into the corners of the mesh and dispels microbubbles formed in the coating solution.
15. 19. An apparatus as claimed in claim 18, wherein the brush is arranged transversely of the mesh with respect to the direction of movement of the mesh. 35 20. An apparatus as claimed in claim 18 or claim 19, ••go wherein the brush is located in a stationary position beneath the mesh and comprises multiple rows of bristles which gently move over the mesh as the mesh moves along its path to the dryer.
16. 21. An apparatus as claimed in any one of claims 8 to wherein the liquid coating modification equipment includes two spring loaded rollers through which the mesh is passed, one at least of the rollers having an absorbent sheath, said spring loading being regulated so as to control the thickness of the liquid coating on the mesh.
17. 22. An apparatus as claimed in claim 21, wherein the absorbent sheath on the at least one spring loaded roller is a fabric sheath of such a thickness which is predetermined by the nature of the coating being applied and the intended thickness.
18. 23. An apparatus as claimed in claim 22, wherein the fabric is a wool wadding.
19. 24. An apparatus as claimed in any one of claims 8 to 23, wherein the liquid coating modification equipment includes a blower, or vacuum device, which blows, or sucks, a curtain or air over the mesh to even out the "liquid coating and remove excess liquid coating from the 25 mesh.
20. 25. An apparatus as claimed in claim 24, wherein the .blower is located above the mesh and is designed to eject air onto the mesh in a controlled manner whereby coating splatter is minimised. 00 *26. An apparatus as claimed in claim 24 or claim wherein the blower includes a triangular-shaped, in transverse cross-section, plenum chamber arranged 35 transversely if the direction of travel of the mesh, with oo o a lower apex of the triangle defining an outlet for the Sair. air.
21. 27. An apparatus of claim 26, wherein the outlet for the air comprises a leading edge which projects slightly below a trailing edge to control coating splatter.
22. 28. An apparatus as claimed in any one of claims 12 to 27, wherein the chamber includes means to regulate the humidity of the air within the chamber.
23. 29. An apparatus as claimed in claim 28, wherein the means for regulating the humidity comprises a damper control on an air-intake to the chamber and/or a damper control on the air-outlet control from the chamber. An apparatus for producing a coated metal mesh substantially as herein described with reference to the accompanying drawings. Dated this 1 ith Day of February 2004 Rodney George Wade By his Patent Attorneys CULLEN CO. ooooo S.i o•* oo oo