Title

Method and Apparatus for Providing Products with a Desired Surface Finish

Field of the Invention This invention relates to a method and apparatus for providing products with a desired surface finish. In one form, the invention concerns a method and apparatus for providing a product with a surface coat of sealer. In a preferred form, the invention concerns a method and apparatus for providing a product with a surface coat of sealer incorporating particulate matter such as sand, so as to provide a textured surface finish. The method and apparatus have been developed chiefly to provide surface finishes to building products and will therefore be described in this context. It is to be appreciated, however, that the method and apparatus may be used to provide a surface finish for virtually any type of product, be it made of wood, paperboard, plastics material, foam, ceramics material, cementitious material, fibreglass, glass or metal. Background of the Invention

Hand operated spray guns and brushes are normally used to apply surface coats of polyurethane and adhesives to products, such as foam building products. Those products requiring a textured (rough and grainy) surface finish require the subsequent application of particulate matter (usually sand) to the coat of polyurethane or adhesive. This again is usually done by hand.

There are disadvantages in applying coats of polyurethane and adhesives by hand. One disadvantage is that it may be difficult to apply a coat uniformly over an entire surface of a product. Another disadvantage is that it may be difficult to maintain surface finish consistency from one product to the next. This is particularly the case if each surface has been textured using incorporated particulate matter. Another disadvantage is that applying coats by hand may be extremely time consuming, hi addition, depending on the setting time of the sealer, the coat may have already set at the time the particulate matter is applied. Yet another disadvantage is that the hand of an experienced operator may be needed to apply the coats.

Summary of the Invention

It is an object of the present invention to minimize or ameliorate at least one of the disadvantages referred to above.

According to a first aspect of the present invention, there is provided an apparatus for providing a product with a desired surface finish, said apparatus comprising: a spray booth assembly comprising a booth having an inlet and an outlet for a product and containing at least one spray nozzle for spraying a coat of sealer onto a surface of the product; and a conveyor for conveying the product through the inlet and outlet. The spray booth assembly may comprise at least one tank of sealer, a pump and a supply manifold for communicating sealer from the tank to the spray nozzle. The tank, pump and supply manifold may be of any suitable size, shape and construction. Colourants may be added to the sealer prior to application.

The spray booth assembly may comprise more than one spray nozzle. Preferably, the spray booth assembly comprises three spray nozzles that are located within the booth. The spray nozzles may be at any suitable locations within the booth. The spray nozzles may be located directly above the product and/or at one or more sides of the product so that one or more surfaces may be coated at the one time. Preferably, the spray nozzles are positioned directly above the product and are located within a common plane that extends transversely with regard to the direction of travel of the product through the booth.

The spray nozzle may spray the sealer continuously, the nozzle may only spray sealer at timed intervals, or the nozzle may spray sealer only when the product is within range of the nozzle. With regard to the latter, the spray booth assembly may have a sensor for detecting the location of the product and for controlling the nozzle accordingly. Preferably, the spray nozzle sprays the sealer uniformly onto the surface as the product is being conveyed from the inlet to the outlet.

The booth may be of any suitable size, shape and construction. The booth may have end walls, side walls, base walls and a roof. The inlet and outlet may be horizontally extending slits in the end walls of the booth. The roof may be pitched and the spray nozzle(s) may be located

at an apex of the roof, preferably about 750 mm above the surface of the product.

The spray booth assembly may comprise one or more extractor fans for maintaining an interior of the booth at a low pressure, so that sealer fumes cannot readily escape the booth via the inlet and outlet. Preferably, the extractor fans extend upwardly from the roof of the booth. The spray booth assembly may have a removable waste collection bin located beneath the spray nozzle, for collecting sprayed sealer that has not been applied to the product. Preferably, a said side wall of the booth has an opening for the waste collection bin and the bin may be moved between a collecting position beneath the spray nozzle whereby the side wall opening is substantially sealed, and an emptying position external of the booth whereby the bin may be emptied of waste sealer.

The waste collection bin may be of any suitable size, shape and construction. Preferably, the waste collection bin has a body and ground-contacting wheels mounted to the body.

The spray nozzle may be removable from the booth for maintenance (cleaning and repair) or replacing. This may be achieved in any suitable way. Preferably, the spray booth assembly comprises a lifting cylinder assembly having a lifting cylinder, a lifting cylinder support and a spray nozzle carrier. The lifting cylinder may have a cylinder housing supported above the booth by the cylinder support and a piston extending from the cylinder housing to the nozzle carrier. The cylinder housing may be supported in any suitable way, for example, using stays. The piston may extend through an opening in the roof of the booth. The lifting cylinder may be hydraulically or pneumatically driven. Preferably, the piston of the lifting cylinder can be retracted to lift the nozzle carrier out of the booth and the piston of the lifting cylinder can be extended to position the nozzle carrier within the booth.

Any suitable type and quantity of sealer may be used. The sealer may be an adhesive or paint. The sealer may comprise a binder and a solvent, and the solvent may be either water or oil based. The binder may be, for instance, a low or high molecular weight resin or polymer selected from the following table: .

In one embodiment, the sealer is a resin comprising a base component and a cure component that upon curing provides a hard, durable and essentially impervious flexible coat.

Preferably, the sealer is a rapidly drying resin. Two-part polyurethane is an example of a particularly preferred rapidly drying sealer and the two parts may be supplied to the spray nozzle from two separate tanks.

The product may be of any suitable size and shape. The product may be, for instance, in the shape of a cylinder, cuboid, panel or strip. Preferably, the product is in the shape of a panel and has a thickness ranging from about 50 mm to 200 mm. Preferably, the panel is up to about 2500 mm in length and up to about 1800 mm in width.

Any suitable type of product may be coated. For instance, the product may be made of metal, wood, paperboard, fibreglass, concrete, glass, ceramics material, foam material, cementitious material, or plastics material. Preferably, the product is foam manufactured from one or more of the following synthetic polymers: polyvinyl chloride (PVC), polystyrene (PS), polyurethane (PU), polymethyl methacrylamide (acrylic), polyetherimide (PEI) and styreneacrylonitrile (SAN). The foam may be of any suitable density, but will typically be in the range of 30 kg/m ³ to 300 kg/m ³ .

The apparatus may have a particulate matter applicator for applying particulate matter to the sealer coat such that the particulate matter is incorporated into the coat. Preferably, the conveyor extends beneath the applicator and the applicator applies the particulate matter uniformly onto the coat as the product is being conveyed by the conveyor.

The particulate matter applicator may be of any suitable size, shape and construction. The applicator may comprise a hopper having a body extending above the product, wherein

particulate matter may be introduced at a top of the body and discharged from a bottom of the body. Preferably, the hopper body extends transversely with regard to the direction of travel of the product so that particulate matter may be discharged across the entire width of the product.

The hopper may have a door movable between an open position in which particulate matter may be discharged from the hopper body and a closed position in which particulate matter may not be discharged from the hopper body. The door may be mounted to the hopper body in any suitable way and may be movable in any suitable way. Preferably, this is achieved by way of at least one hydraulic or pneumatic cylinder having a cylinder housing mounted to the hopper body and a piston mounted to the door, for sliding the door between open and closed positions relative to the hopper body.

The apparatus may include a particulate matter collection bin located beneath the hopper, for collecting waste particulate matter that has not been incorporated into the coating of the product. The particulate matter collection bin may be of any suitable size, shape and construction. Preferably, the particulate matter collection bin has convergent side walls and at least one outlet located at a bottom of the bin.

Any suitable type and size of particulate matter may be applied to the coat. The particulate matter may be, for instance, sand, quartz, marble, dolomite, kaolin, glass, gravel, stone or plastics material. The particulate matter may be a mixture of any two or more of these.

The apparatus may comprise a particulate matter retrieval system for returning particulate matter from the particulate matter waste collection bin to the hopper. The particulate matter retrieval system may be of any suitable size, shape and construction. Preferably, this retrieval system comprises a vacuum pump having a body having a suction inlet and a particulate matter outlet, and a return line extending from the particulate matter collection bin outlet to the suction inlet. The vacuum pump outlet may feed fluidised particulate matter to the top of the hopper.

The vacuum pump may have a door movable between an open position in which particulate matter may be discharged through the particulate matter outlet and a closed position in which particulate matter may not be discharged via the outlet. The door may be mounted to the vacuum pump body in any suitable way and may be movable in any suitable way. Preferably, this is done by way of a hydraulic or pneumatic cylinder having a cylinder housing

mounted to the vacuum pump body and a piston mounted to the door, for sliding the door between open and closed positions relative to the vacuum pump body.

The apparatus may comprise a particulate matter remover for removing particulate matter that has not been incorporated into the coat. The particulate matter remover may be of any suitable size, shape and construction. Preferably, the particulate matter remover comprises a suction head extending above the product whereby unincorporated particulate matter is sucked from the product. Preferably, the conveyor extends beneath the suction head, the suction head extends across the entire width of the product, and the suction head removes loose particulate matter as the product is being conveyed by the conveyor. The particulate matter remover may include a return line extending between the suction head and the suction inlet of the vacuum pump, for returning loose particulate matter to the hopper. Alternatively, another source of vacuum may be used.

Any suitable type of conveyor may be used. The conveyor may comprise, for example, dynamic rollers, belts and/or static rollers. The conveyor could comprise one or more robotic arms. Preferably, the conveyor comprises dynamic rollers located within the booth that are spaced from the spray nozzle as far as possible (eg. 800-900 mm between adjacent rollers) yet allow for conveyance of the product. Preferably, the discharge end of the hopper body is situated directly above a gap in the conveyor such that particulate matter may collect within the waste collection bin. If only a coat of rapidly drying sealer (eg. polyurethane) is to be applied to the product, then the product may be conveyed through the booth at a speed of about 10-30 (preferably 20) metres per minute whilst the sealer is being applied.

If both a coat of rapidly drying sealer (eg. polyurethane) and particulate matter (eg. river sand) are to be applied to the product, then the product may be conveyed through the booth and under the hopper at a speed of about 24-44 (preferably 34) metres per minute - such that the coat does not set before the particulate matter is applied.

The apparatus may comprise a stand, platform, stairs etc. for supporting different parts of the apparatus and for providing operator access to same.

The apparatus may include one or more computerised control stations operatively

connected to parts of the apparatus, for partially or fully automating the surface finishing process. Preferably, the apparatus allows for high product throughput.

According to a second aspect of the present invention, there is provided a method for providing a product with a desired surface finish, said method comprising the steps of: conveying a product through a booth of a spray booth assembly, wherein the booth has an inlet and an outlet for the product, and contains at least one spray nozzle; and spraying a coat of sealer onto a surface of the product using the spray nozzle as the product is conveyed to the outlet.

Preferably, the method further comprises the step of conveying the product to a particulate matter applicator for applying particulate matter to the coat such that the particulate matter is incorporated into the coat.

Preferably, the method further comprises the step of conveying the product to a particulate matter remover for removing particulate matter that has not been incorporated into the coat. Preferably, the method allows for high product throughput.

The above-mentioned steps of the method, as well as additional steps of the method, may be carried out using the apparatus according to the first aspect of the invention.

According to a third aspect of the present invention, there is provided a surface finished product when produced by the apparatus according to the first aspect or by the method according to the second aspect.

A preferred embodiment of the invention will now be described by way of example with reference to the accompanying figures.

Brief Description of the Figures

Figure 1 is a detailed plan view of part of an apparatus for providing a product with a desired surface finish, according to an embodiment of the present invention;

Figure 2 is a detailed side elevation view of part of the apparatus shown in Figure 1; and

Figure 3 is a detailed side elevation view of part of the apparatus shown in Figure 1.

Description of the Preferred Embodiment

In the figures, like reference numerals refer to like features.

The figures show an apparatus 1 for providing a surface 3 of a product 2 with either a smooth finish or a textured (ie. rough and grainy) finish. The apparatus 1 includes a spray booth assembly 4, a particulate matter applicator 5, a particulate matter remover 6, a conveyor system

13-20, a particulate matter collection bin 7, a particulate matter retrieval system 8, a platform 9, a set of stairs 10, handrails 11, and a computerized control station 12.

The conveyor system 13-20 comprises belt conveyor 13, dynamic roller conveyor 14, belt conveyor 15, dynamic roller conveyor 16, transfer conveyor 17, dynamic roller conveyor 18, belt conveyor 19 and dynamic roller conveyor 20. Frames and motors for driving the rollers and belts are shown but have not been labelled. Such conveyors 13-20 are well known in the art.

The spray booth assembly 4 comprises a spray booth 20, three spray nozzles 21, two extractor fans 22, a removable waste collection bin 23, a lifting cylinder assembly 24, one or more tanks 25 of sealer, a pump (not shown) and a sealer supply manifold (not shown).

The booth 20 has a pair of sloping end walls 30, 31, a pair of side walls 32, 33, a pair of base walls 34, 35 and a pitched roof 36. End wall 31 has an inlet 37 in the form of a horizontally extending slit. End wall 30 has an outlet 38 in the form of a horizontally extending slit. The spray nozzles 21 are located at an apex of the roof 36. The spray nozzles 21 spray liquid sealer uniformly onto a surface 3 of a product 2 as the product 2 is being conveyed by the conveyor 14 from the inlet 37 to the outlet 38. The spray nozzles 21 are at a distance of about 750 mm from the top surface 3 of the product 2.

Sealer is pumped from the tanks 25 to the nozzles 21 by way of the supply manifold.

The extractor fans 22 extend upwardly from the roof 36 and maintain an interior of the booth 20 at a low pressure, so that sealer fumes cannot readily escape the booth 20 via the inlet 37 and outlet 38.

The waste collection bin 23 collects sprayed sealer that has not been applied to a product. The waste collection bin 23 has a body and castor wheels mounted to the body (not

labelled). Side wall 32 of the booth 20 has an opening (not labelled) for the waste collection bin 23 and the bin 23 may be moved between a collecting position directly beneath the spray nozzles 21 whereby the side wall 32 opening is substantially sealed, and an emptying position external of the booth 20 whereby the bin 23 may be emptied of waste sealer. The side wall 32 opening is of similar shape to the bin body.

The lifting cylinder assembly 24 comprises a pneumatic lifting cylinder 42, stays 46, and a carrier frame (not labelled) to which are mounted the spray nozzles 21. The lifting cylinder 42 has a cylinder housing 43 supported above the booth 20 by the stays 46. A piston 44 of the lifting cylinder 42 extends from the cylinder housing 43 through an opening in the roof 36 to the carrier frame. The piston 44 can be retracted to lift the spray nozzles 21 out of the booth 20 for maintenance (cleaning and repair) or replacing.

Conveyor 14 has six rollers 14 located within the booth 20 and these are mounted for rotation between the side walls 32, 33. The carrier frame extends above and parallel with the rollers 14. Two of the rollers 14 nearest the carrier frame are not positioned directly beneath the spray nozzles 21 and are spaced about 800-900 mm from one another, so that waste sprayed sealer will preferentially collect within the collection bin 23 and so that there will be little contamination of the rollers 14 with sprayed sealer.

The particulate matter applicator 5 applies particulate matter to the coat of sealer such that the particulate matter is incorporated into the coat. The particulate matter applicator 5 comprises a hopper 50 having a body 51, a door 52 and a pneumatic cylinder 53. Particulate matter may be introduced at a top of the body 51 and discharged from a bottom of the body 51 when the door 52 is open. Bags 65 of particulate matter (eg. sand) are used to fill the hopper 50. The pneumatic cylinder 53 has a cylinder housing (not labelled) mounted to the body 51 and a piston (not labelled) mounted to the door 52, and slides the door 52 between open and closed positions relative to the body 51.

The hopper body 51 extends transversely of the belt conveyor 15 so that particulate matter may be discharged across the entire width of the product 2. Particulate matter is dropped fairly uniformly onto the product 2 as it is being conveyed.

The particulate matter collection bin 7 is located directly beneath the hopper 50 and collects waste particulate matter that has not been incorporated into the sealer coating of the

product 2. The collection bin 7 has convergent side walls (not labelled) and an outlet 58 located at a bottom of the bin 7. The positioning of the collection bin 7 coincides with a space between the belt conveyor 15 and the last of the rollers of conveyor 14.

The particulate matter retrieval system 8 returns, inter alia, particulate matter from the waste collection bin 7 to the hopper 50. This retrieval system 8 comprises a vacuum pump 80 (ie. a sand cyclone), a stand 87, conduits 83-85 and a branched connector 86 containing a vacuum valve.

The pump 80 has a body 81 having a suction inlet 82, a particulate matter outlet 79 and a door (not labelled) for opening and closing the outlet 79. The pump 80 is supported by the stand 87. A pneumatic cylinder (not shown) moves the door between open and closed positions. The pump door closes when the hopper door 52 opens, and vice-versa.

Conduit 84 has an end connected to the suction inlet 82 and an end connected to the branched connector 86. Conduit 83 has an end connected to the collection bin outlet 58 and an end connected to the branched connector 86. The vacuum pump 80 draws particulate matter from the collection bin 7, fluidises the matter, and returns the matter to the top of the hopper 50.

The particulate matter remover 6 removes particulate matter that has not been incorporated into a sealer coat of the product 2. The particulate matter remover 6 comprises a suction head 90 extending above and across the entire width of the product 2, so that unincorporated particulate matter can be sucked from the product 2. The suction head 90 extends transversely of belt conveyor 19 and removes loose particulate matter as the product 2 is being conveyed.

The suction head 90 is connected to an end of conduit 85 such that pump 80 provides the vacuum. Figure 1 shows how products 2a-2e, such as 2500 mm x 1500 mm x 50 mm foam panels

2, may be processed by the apparatus 1. Panel 2a is about to be conveyed by conveyor 13 into the booth 20. Panel 2b is being conveyed from the particulate matter applicator 5 to conveyor 16. Panel 2c is being conveyed by conveyor 17 from conveyor 16 to conveyor 18. Panel 2d is being conveyed by conveyor 19 to the particulate matter remover 6. Panel 2e has been

conveyed to an accumulation area by way of conveyor 20.

The apparatus 1 has different modes of operation, in that (1) it may be used to only apply a coat of sealer to a product, or (2) it may be used to apply both a coat of sealer and particulate matter so as to provide a textured finish. For mode (1), a panel 2 is placed onto belt conveyor 13 and conveyed to booth 20. As the roller conveyor 14 conveys the panel 2 from the booth inlet 37 to the outlet 38, the spray nozzles 21 apply a substantially uniform coat of sealer to the surface 3 of the panel 2. The nozzles 21 may be about 750 mm above the surface 3. As one panel 2 enters the booth 20, another may be placed onto the conveyor 13. Conveyor 15 then conveys the sealed panel 2 to conveyors 16-20. The panel 2 can then be flipped over and fed through the booth 20 again, so that the other major surface of the panel 2 may be coated as well.

If the sealer is rapidly setting polyurethane, then the panel may be conveyed at a speed of about 20 metres per minute. A rapidly setting sealer would allow for the high throughput of panels 2. For mode (2), a panel 2 is placed onto conveyor 13 and conveyed to booth 20. As conveyor 14 conveys the panel 2 from the booth inlet 37 to the outlet 38, the spray nozzles 21 apply a substantially uniform coat of sealer to the surface 3 of the panel 2. As one panel 2 enters the booth 20, another may be placed onto the conveyor 13. The sealed panel 2 is then conveyed beneath the hopper 50 and particulate matter (such as river sand) is substantially uniformly deposited onto the coat, for incorporation into the coat. Conveyors 15-19 then, in turn, convey the panel 2 to suction head 90 whereby loose matter is removed from the panel 2. Conveyor 20 then conveys the panel 2 to the accumulation area. The surface finished panel 2 may then be flipped over and fed through the apparatus 1 again, so that the other major surface of the panel 2 may be given a textured finish as well. If the sealer is rapidly setting polyurethane, then the panel 2 may be conveyed at a speed of about 34 metres per minute, so that the sealer does not set before the sand is applied.

Foam panels coated with polyurethane using the apparatus 1 typically have a hard, durable and essentially impervious flexible coating. Foam panels further treated with sand have a textured finish that resembles sand stone. The finished panels are suitable for use, for example, in the construction offences, walls, houses, letter boxes and dog kennels.

Advantages of the present invention include that:

• substantially uniform coats can be readily applied to product surfaces without the need for a skilled spray gun operator;

• surface finish consistency is substantially maintained for all products; • surface finishes can be applied in a short period of time; and

• automatic high throughput of products is possible.

Whilst the above has been given by way of illustrative example of the invention, many modifications and variations may be made thereto by persons skilled in the art without departing from the broad scope and ambit of the invention as herein set forth. The term "comprise" and variants of the term such as "comprises" or "comprising" are used herein to denote the inclusion of a stated integer or stated integers but not to exclude any other integer or any other integers, unless in the context or usage an exclusive interpretation of the term is required.