WO2008025081A1

WO2008025081A1 - Method and apparatus for forming a wpc coated elongate member

Info

Publication number: WO2008025081A1
Application number: PCT/AU2007/001258
Authority: WO
Inventors: Ian Scott; Reginald Charles Bourne
Original assignee: Ian Scott; Reginald Charles Bourne
Priority date: 2006-09-01
Filing date: 2007-08-30
Publication date: 2008-03-06
Also published as: AU2007202376B1

Abstract

A building material which comprises a core containing timber or metal and a shell comprising wood plastic composite material (WPC material), is manufactured by a particular type of apparatus.

Description

Method and Apparatus for Forming a WPC Coated Elongate Member

Field of the Invention.

This invention is directed to encased products and typically a core comprising an elongate length of solid or hollow timber or metal (but possibly other core products as well) which is covered by a particular shell material to provide beneficial properties. The material which surrounds the core may comprise a WPC (wood plastic composite material). The encased products have a large range of uses including scaffolding planks and building products.

Background Art.

WPC materials (wood plastic composite materials) are quite well known in the marketplace and have some advantages over ordinary timber products.

The WPC material typically consists of crushed wood material (sometimes known as wood flour), or alternatively crushed rice husks, wheat straw, waste wood material etc which is mixed with a plastic resin such as polyvinyl chloride (PVC) or polyethylene (PE). The material is mixed and heated and can be extruded into various shapes such as planks, boards, slats and the like.

Most of the WPC material manufactured today is used in the housing industry and the landscape industry for use in walkways, decking, hand rails, stairways and the like.

The WPC material resembles wood and combines the advantages of wood with those of plastic. One advantage of WPC material is that it can be extruded to make continuous profiles of any desired cross-section with great dimensional consistency and accuracy with very little waste. Another advantage is that the WPC material is virtually maintenance free. That is, painting is generally not necessary (but can be applied if desired) and outdoor durability is much better than many types of softwood, and a lifespan of between 25-30 years is expected of WPC materials.

Typically, the WPC material comprises about 60% resin and 40% wood flour. The material is added to a screw extruder via a hopper and fed into a heated chamber and reduced to a thick consistency. The screw forces the hot resinous material into a mould of a shape desired to form a constant length of the desired profile. The material subsequently cooled to permanently form the profile desired. The profile can be cut to any desired length.

There are some disadvantages with WPC material. One disadvantage is that the material is not particularly suited for higher weight loading. Thus, the material is not particularly suited for use with bearers or joists or similar load bearing members. Alternatively, if the WPC material is used and formed into a bearer or joist, these need to be supported more closely than otherwise necessary. This can increase cost and assembly time. Another disadvantage is that the WPC material can be quite heavy especially if larger load bearing members are desired to be formed. An attempt has been made to reduce the weight of the WPC material by forming hollows or recesses in the WPC material, but it is found that this further reduces the unsupported span length of the WPC material. Therefore, conventional thinking has been that WPC materials are not considered strong enough or safe enough to span greater distances (typically over 1 m).

Another known product which uses wood but which does not use WPC is laminated lumber/timber. This product comprises lengths of wood which are glued and processed together to form a laminated material which is sometimes known as Laminated Veneer Lumber or LVL. This material is extremely strong and can be used to support floors, trusses, and the like. While LVL is a desired product, there are some disadvantages with it. The main disadvantage is that any deterioration of the LVL can substantially affect the strength of the material and therefore great care has to be taken to make sure that the LVL is not subjected to weathering, solvents, knocks and bumps, ultraviolet light deterioration, and the like. This can make the LVL unsuitable for use in many applications where otherwise the properties of the LVL would be excellent. For instance, some uses of LVL that would be beneficial but where the LVL is not used would be, external doors, outdoor flooring timbers, external stairways, outdoor furniture and the like.

Similarly, while timber beams, bearers, joists and the like are widely used in the construction industry, it is found that the timber products do not have a lifespan which is as long as a WPC product but do have the benefits of load bearing and weight per length which the WPC product may not necessarily have. For instance, these timber materials may be subjected to termite damage, water damage, weathering and the like. Also, many timber products are difficult to handle and can present sharp splinters. Some timber products (typically used as concrete edging) can only be used once or twice due to the build up of cement on the wood which is difficult to remove.

Throughout the specification, the term "timber" and "lumber" can be used interchangeably, hi the USA and Canada, the term "lumber" is usually meant to include logs which have been cut into boards, hi Australia and many other countries, the term "timber" is used.

Another known product comprises lengths of metal which are rolled off a mill, forming various shapes such as RHS rectangle hollow section, SHS square hollow section which is not limited to size or dimensions.

The sections of metal are not limited to hollow sections and solid section are used for additional strength. Also known as steel this material is extremely strong and can be used to support floors, trusses, and the like.

While metal is a desired product, there are some disadvantages with it. The main disadvantage is that any deterioration of the metal can substantially affect the strength of the material and therefore great care has to be taken to make sure that the metal is not subjected to weathering, solvents, and corrosive substances such as salts, ammonia, water and the like.

This is particularly so if the metal product comprises an elongate substantially hollow or void containing member having a relatively thin wall construction to give a good length to weight ratio. Any deterioration of the metal skin can cause quite considerably reduction in strength, and this deterioration is not always observable.

This can make the metal unsuitable for use in many applications where otherwise the properties of the metal would be excellent. For instance, some uses of metal that would be beneficial but where the metal is not used would be external doors, outdoor flooring, external stairways, outdoor furniture and the like. Similarly, while metal beams, bearers, joists and the like are widely used in the construction industry, it is found that the metal products do not have a lifespan which is as long as a WPC product but do have the benefits of load bearing and weight per materials may be subjected to corrosion from water damage, weathering and the like.

In addition, many metal products are difficult to handle and can present sharp metal edges.

Some metal products (typically used as concrete edging) can only be used once or twice due to the build up of cement on the metal, which is difficult to remove.

The metal typically comprises steel.

In the USA and Canada, the term "metal" is usually meant to include raw molten iron which have been rolled into various profiles. In Australia and many other countries, the term "steel" is used.

The metal may also comprise aluminium.

It is known to protect a timber "core" [ typically a plank] with a cover or layer of thick plastic. US 2006/0179733 is directed to improving the strength of timber flooring in vehicle trailers.

To do so, strips of durable plastic are glued on to the top face (and sometimes also the sides) of the timber flooring. The strip of durable plastic can comprise a plastic composite material.

The plastic composite material is formed separately and is then cut to size. The upper face of the timber flooring is covered with a glue and the strips are clamped onto the timber flooring to be bonded thereto by the glue. One disadvantage with this arrangement is the time and complexity required in gluing strips of durable plastic over the top of the, or each timber floor plank. Another disadvantage is the possibility of "de lamentation" which can occur if the glue is not applied properly or if the strips are not applied at the correct time and at the correct pressure and for the correct length of time to ensure consistent bonding of the strips to the plank. Therefore, it is not considered that the adhesive bonding of plastic strips to a timber

"core" is a desirable option to provide a good reliable encased product. Also, to provide total encasement, it will be necessary to provide join lines which are not considered to be desirable. US patent 6662515 describes a post which is cladded with plastic strips which are formed separately and attached to the outer sides of the post. A specially designed top cap is then attached over the top of the post.

Another way in which reinforcing members can be attached to a substrate is illustrated in US patent application 2004/0219357. In this application, a preformed "core" of material is initially formed and is kept in a hot soft plastic state. The "plastic" soft material is pushed into a die and at the same time reinforcing strips (cables) are pushed into the soft mixture. After exiting the die, the shaped material is cooled and hardened and contains the strengthening reinforcing strips. Clearly, this type of process cannot be used if the core is wood or metal.

Various other techniques are known to coat core materials such as planks and metal members. These include painting, applying a thick gel coat which hardens, dipping into a liquid or resinous paint or coating which then cures, applying a "two pack" resin which hardens, trowelling a thick curable material onto the core material and the like. However these suffer from various disadvantages including difficulty in ensuring comprehensive coverage and uniform thickness, adhesion problems, the need to apply multiple layers to form a good thick coat, restrictions on the application materials, the danger of solvent fumes, flammability issues with some paints/coatings, toxicity issues, application time, and the like.

There would be an advantage to provide an apparatus and method which would enable a WPC material to be applied to a core material such as wood (including laminated veneer lumber) or metal in a single pass (thereby reducing the time in the manufacture of the products) and enabling a relatively uniform thickness of WPC material to be applied to the core material and without any requirement to separately form WPC strips and then to glue or otherwise attach to strips to the core material.

It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country. Object of the Invention.

It is an object of the invention to provide a material which may overcome at least some of the above-mentioned disadvantage or provide a useful or commercial choice.

In one form the invention comprises an apparatus to manufacture a product comprising a core material having side wall(s) which is/are covered with a WPC material, the apparatus comprising: a hopper to hold granulated WPC material, a conveyor to convey the material from the hopper, a die having:

1. an inlet communicating with the conveyor such that the conveyor can convey the WPC material into the die,

2. a heater to heat the die and to melt the WPC material, 3. a core material inlet,

4. a core material outlet,

5. at least one WPC outlet to allow molten WPC material to coat the or all the side wall(s) of the core material with the WPC, a guide to guide the product in the die, a vacuum former downstream from the die, and a cooler to cool the encased product, the WPC material being applied to the core material in a single pass, and wherein the die, in use, is heated to between 120-300°C .

The core material may have a single side wall (if the core material is cylindrical) or a number of sidewalls (for instance four sidewalls if the core material is rectangular).

hi another form, the invention resides in a material, such as a building product, which comprises a core comprising timber and/or metal or something else, and a shell comprising wood plastic composite material (WPC material).

hi another form the invention resides in an apparatus for forming an encased product such as a metal or wood core encased with a WPC. In another form the invention resides in a method for forming an encased product such as a metal or wood core encased with a WPC.

If the core material is timber, the timber may comprise a single length of timber or a plurality of lengths of timber. It is preferred that the timber comprises a LVL (laminated veneer lumber).

It is envisaged that there may be circumstances where the core material contains a wood substitute material such as materials that are sometimes known as "custom wood ", or materials that are made from pieces of wood which are glued together.

The term "wood" in the specification and claims is meant to include custom wood, LVL and the like.

The product may have any suitable length. This will depend on the use of the building product. Thus, the length may be between 1-10 m. Alternatively, the material can be manufactured continuously and cut to length.

The size and shape of the timber core material may vary. For instance, the timber core material may be rectangular when viewed in cross-section, circular when viewed in cross- section, oval when viewed in cross-section, or have other shapes that can enable the "core/shell " material to be made.

The timber core material may have any suitable cross-section and size. For instance, if the material will be used as a bearer or something similar, the cross-section will typically have a length of between 5-20 cm and a "height" of something similar. If the material is used as a decking plank, the cross-section width will typically be between 5-20 cm and the thickness will typically be between 5-30 mm. If the material is used as a door, the cross-section will typically be the typical "width" of the door, and a thickness will be the typical thickness of the door as well. Therefore, will readily be understood that the cross-section shape and size will depend on the ultimate use of the material, and it is not considered that any unnecessary limitation should be placed on the shape and size of the timber core. The timber may comprise hardwood timber, softwood timber, laminated timber, timber composite materials and the like. It is considered an especially preferred feature of the invention that the timber core comprises a LVL material.

It is envisaged that the material will contain a relatively solid core material, that is, the core material will comprise the timber. This will provide good strength to the material. However, there may be circumstances where the core material may contain timber together with various recesses or voids and the like. For instance, this type arrangement may be more suitable if the material is used as a door. There may also be other instances where the material may comprise a core material containing empty areas.

It is also envisaged that the material may comprise a core material which is made substantially of timber, but which contains other materials as well. For instance, the core material may comprise timber together with areas or zones containing foam material or plastic material and the like.

For instance, there may be circumstances where the core material contains a length of timber together with a further passageway which may be empty or filled with foam material or something else.

If the core material comprises metal, the metal may comprise a single length of metal or a plurality of lengths of metal. It is preferred that the metal comprises a mild steel RHS (rectangle hollow section).

It is envisaged that there may be circumstances where the core material contains a metal substitute material such as alloys, or materials that are made from pieces of metal which are welded together.

The size and shape of the metal core material may vary. For instance, the metal core material may be rectangular when viewed in cross-section, circular when viewed in cross-section, oval when viewed in cross-section, or have other shapes that can enable the "core/shell " material to be made. The metal core material may have any suitable cross-section and size. For instance, if the material will be used as a bearer or something similar, the cross-section will typically have a length of between 5-20 cm and a "height" of something similar.

If the material is used as a decking plank, the cross-section width will typically be between 5- 20 cm and the thickness will typically be between 5-30 mm.

If the material is used as a door, the cross-section will typically be the typical "width" of the door, and a thickness will be the typical thickness of the door as well.

Therefore, will readily be understood that the cross-section shape and size will depend on the ultimate use of the material, and it is not considered that any unnecessary limitation should be placed on the shape and size of the metal core.

The metal may comprise mild steel, high tensile steel, aluminium, stainless steel, brass, copper, lead, nickel, chromium and which would include treated steel like galvanized steel or painted steel and the like.

It is considered an especially preferred feature of the invention that the metal core material comprises a mild steel material.

It is envisaged that the material will contain a relatively hollow core material, that is, the core material will comprise the metal. This will provide good strength to the material. However, there may be circumstances where the core material may contain metal together with various recesses or voids and the like.

For instance, this type arrangement may be more suitable if the material is used as a door. There may also be other instances where the material may comprise a core containing empty areas.

It is also envisaged that the material may comprise a core material which is made substantially of metal, but which contains other materials as well. For instance, the core may comprise metal together with areas or zones containing foam material or plastic material and the like.

For instance, there may be circumstances where the core material contains a length of metal together with a further passageway which may be empty or filled with foam material or something else.

The material further comprises a "shell" which is made of WPC material. The term "shell" is meant to include that the core material is covered or encased with the WPC material. However, there may be some circumstances where certain parts of the core material are not covered (for instance longitudinal ends) and these may need to be separately capped or covered. It is not envisaged that the term "shell" should limit the thickness of the WPC material, and the term is merely meant to include that the core is substantially protected or covered by the WPC material.

The WPC material may comprise a resin together with a non-resin material. The non-resin material will typically comprise a wood flour which is quite common in the manufacture of WPC material although the non-resin material may also comprise materials such as crushed rice husks, wheat straw and the like, and it is considered that the term WPC material should include any non-resin material that is known to be used in the manufacture of WPC material. The non-resin material may comprise a combination of various materials that are used in the manufacture of WPC material.

The amount of resin material and non-resin material can vary. Typically, the amount of resin material will be greater than 50% and typically between 50-80%. Therefore, the amount of non-resin material will typically be less than 50% and typically between 20-50% and can include a shrinking agent, flame retardant chemicals and ultra violet stabilizing chemicals.

The resin material may comprise polyvinyl chloride, polyethylene, polypropylene or other materials which are known in the manufacture of WPC material. A combination of resins may be provided if desired.

The thickness of the WPC material extending about the core can vary and will typically be between 2-40 mm. It is envisaged that the thickness of the WPC will be substantially uniform across the ultimately formed product. However, there may be advantages in providing a groove or recess in the outer wall of the WPC material, or providing some form of anti-slip profile or something similar or having some other type of non-uniform thickness of the WPC material extending about the core. Alternatively, the WPC material can be formed with the uniform thickness and a profile (such as an anti-slip profile or a decorative profile) can be formed separately .and subsequently attached to the shell.

If desired, end caps or end sealing means may be provided'to fully encase the core material.

In one form, there is provided an apparatus to manufacture a product comprising a core which is at least partially encased with a WPC, the apparatus comprising a hopper to hold WPC material, a conveyor to convey the material from the hopper, a die having an inlet communicating with the conveyor such that the conveyor can convey the WPC material into the die, a heater to heat the die, the die having a product inlet and a product outlet, the product comprising core material which is to be encased with the WPC, a guide to guide the product in the die such that the WPC material and coat all the surfaces of the product in the die, a vacuum former downstream from the die, and a cooler to cool the encased product.

Suitably a feeder is provided to feed product into the die,

The hopper may be of any suitable shape and size to contain any suitable volume or amount of WPC. The WPC in the hopper may comprise pellets, or any other type of loose form of WPC. If desired, more than one hopper may be provided. If desired, the apparatus, rather than having a large storage hopper, may have a small hopper in which the WPC can be added "upon demand", hi this alternative, the small hopper may comprise a flared opening or outlet at or adjacent one end of the conveyor. It is not considered that any unnecessary limitation should be placed on the term "hopper".

The conveyor may comprise a conventional conveyor and functions to convey the WPC material from the hopper/inlet and towards and into the die. It is preferred that the conveyor is a "push" conveyor which can push the WPC material with some force into the die. These types of conveyors are known and typically comprise a screw conveyor. In the particular embodiment, it is preferred to have a twin screw extruder which is relatively standard in configuration and having a suitable force to push the WPC material into the die. A typical force will be between the 100-300 Kgs/cubic centimetre, and in the particular embodiment, the force will be about 110 Kgs/cubic centimetre. The conveyor may have any suitable length and size and this can vary depending on the size and the throughput of the apparatus. It is also envisaged that there may be circumstances where more than one conveyor is provided and under the circumstances, the die may also have more than one inlet which communicates with the more than one conveyor. Other types of conveyors may also be used such as some form of pump or other type of drive means to drive the WPC material into the die. The conveyor may be provided with some form of heating means to heat the WPC material. The heating means may comprise an external heater. Alternatively, the conveyor may be designed to compress the WPC material and provide strong shear forces which may cause heating of the WPC material.

The die will typically comprise a body containing a through passageway along which the product (core material) can pass. Therefore, the die will contain a product inlet (typically at one end of the die) and a product outlet (typically at the other end of the die), and it is envisaged that the inlet, passageway and outlet will be axially aligned.

The through passageway will typically be rectangular in cross-section especially if the product (core material) is rectangular in cross-section and the through passage will typically be slightly larger than the cross-section of the core material to provide a space for the WPC material to be coated over the core material in the die. The tolerances of the die will vary depending on the size of the core material and the desired thickness of the WPC coating. It is envisaged that the thickness of the WPC coating will be between 1-10 mm and typically between 1-5 mm, and therefore the size of the passageway will be such that there is a gap of between 1-10 mm and typically between 1-5 mm between the surface of the core material and the inside wall of the passageway.

The die may be any suitable shape and size. It is envisaged that the passageway will typically have a length of between 40-200 cm although this may vary to suit. If the die is rectangular in cross-section, it is envisaged that the width of the passageway will be between 10-60 cm and the "height" of the passageway will be between 5-20 cm but this will depend on the size of the core material and the desired thickness of the WPC coating etc.

The die passageway need not be rectangular. For instance, if the core material is cylindrical in configuration, the die passageway may also be cylindrical. If the core material is oval or otherwise rounded, the die may have a corresponding shape.

The die has some form of inlet communicating with the conveyor such that the WPC material can enter the die. An inlet example is illustrated in figure 7 but it is not considered that the invention should be limited only to this particular illustration. As mentioned previously, more than one inlet maybe provided especially if the die passageway is rather long.

The body of the die as well as having the passageway, may also contain one or more flow pathways to facilitate molten WPC material coating all sides of the product passing through the die passageway. Thus, flow pathways may be provided along an upper wall of the die passageway and/or a lower wall of the die passageway and/or the or each side wall of the die passageway. It is envisaged that some form of "manifold" arrangement will be provided and each of the flow pathways can communicate with the die passageway and with the manifold and the manifold communicates with the inlet of the die which communicates with the conveyor.

A heater is provided to heat the die. The heater may comprise conventional heating means which are used to heat dies. Thus, the die may be provided with flow passageway through which a heated fluid may pass to heat the die. The heated fluid may comprise water, oil, or any other suitable liquids, or may comprise a hot gas such as air. Alternatively, the die may be electrically heated or heated by any other means. It is envisaged that the heater can control the temperature of the die to within certain desired parameters. As an example, it is envisaged that the die will be kept at a temperature of between 120-300⁰C and typically between 150-200°C. Any type of regulator can be used to keep the temperature of the die within desired parameters.

The apparatus may have some form of feeder to feed the product into the die. The feeder may comprise some form of conveying means on which the product (e.g. core material) can be placed. In an example, the conveying means may comprise a tractor feed bench. Other forms of feeders may be used including opposed rollers between which the product passes, push feeders which have some form of advancing piston or wall to push the material into and preferably through the die. It is also envisaged that the feeder, or an additional feeder may be provided downstream of the die to pull the material through the die. It is also envisaged that the die itself may comprise some sort of feeder or advancement means to convey the material into and through the die. hi a very simple system, the material may be manually fed and pushed through the die.

The apparatus will typically have some form of guide to guide the product (e.g. core material) in and through the die in such a manner that the WPC material provides a relatively even thickness around the product. Thus, the guide may comprise some means member to advance the core material through the die in such a manner that the core material is spaced equally from the internal wall of the die passageway, such that molten WPC material can pass about and around the core material with an even thickness. The guide may be provided in front of the die, downstream from the die, or both. A number of guide may be provided. The guides may comprise rollers or something similar to keep the product passing into the die in a desired position.

The apparatus may include a vacuum former provided downstream from the die. The vacuum former may comprise a body having a through passageway with the WPC encased material passing through the passageway. The passageway may be depressurised (e.g. under vacuum), and the function of the vacuum former is to provide the exact shape of the encased product. Typically, the vacuum will keep the sides of the product firmly against the passageway (forming mould) as it moves along the passageway and the product may be cooled as is moves through the vacuum former to harden the product and to make the product more dimensionally stable. It is envisaged that more than one vacuum former may be provided with the product passing from the outlet of one vacuum former into the inlet of an adjacent vacuum former. As an example, an embodiment of the present invention comprises four vacuum formers. An example of the vacuum formers is illustrated in figure 11 and figure 12, and each vacuum former may be provided with small cooling canals constructed within the forming mould and through which chilled water (or something else) can pass to cool the outer areas of the WPC material so that the product is totally formed. The passageway in the vacuum former may also comprise a pattern to form a pattern on the WPC material. The pattern may comprise a "wood grain" pattern, or a "grip enhancing" pattern etc.

The apparatus also comprises a cooler to cool the encased product. The cooler may comprise the vacuum former through which chilled water can pass. Alternatively, an additional cooler may be provided downstream from the vacuum former and this may comprise a chilled water bath or something similar.

The encased product can then be cut to length and some form of cutting means such as a cut off saw may be provided.

In another form there is provided a method to manufacture a product comprising a core which is at least partially encased with a WPC, the method comprising passing WPC material into a heated die which has a product inlet and a product outlet, a feeder to feed product into the die, the product comprising core material which is to be encased with the WPC, a guide to guide the product in the die such that the WPC material and coat all the surfaces of the product in the die, a vacuum former downstream from the die, and a cooler to cool the encased product.

In another invention, there may be provided a core material covered by WPC material and where the WPC material is formed separately and the core material is then placed into the WPC material. That is, rather than providing strips of WPC material that is glued to the outside walls of the core material, the WPC material is formed into a tube (for instance) or into an elongate box configuration (for a rectangular post) and the core material can then be forced or pushed into the tubular or boxlike WPC material.

In this form of the invention, the WPC material can be seen as a "shell".

The shape and size of the shell can vary and this will depend inter alia on the shape and size of the core material. It is envisaged that the shape of the shell will be substantially rectangular, circular or oval when viewed in cross-section or have some other type of shape which can enable the shell to be easily or readily fitted about the core.

It is envisaged that the shell made of WPC material will be formed separately and the core will then be fitted into the shell. Thus, the shell may comprise a substantially elongate channel member or box section or something similar with an open top. A shaped core can then be placed within the channel member or box section and a lid or cover can then be fitted to encase the core into the shell. The lid or cover will typically be formed of WPC material.

Alternatively, the shell may be substantially circular and may comprise two halves. A cylindrical core can then be placed in one half of the shell and the other half can be fitted to encase the core within the shell.

Other shapes and designs are also envisaged and it is not considered that the invention should be limited only to the shell being made in the shapes described above.

There may be circumstances where the box section of the shell may be made of thicker material and the lid part of the shell may be made of thinner material or vice versa.

Alternatively, the shell may be formed separately without any top lid and the like and may have an open end with the core being pressed through the open end and into the shell.

It is envisaged that the shell will be extruded in a manner which is known for the manufacture of WPC material. For this reason, there may be certain profiles that cannot be readily manufactured using an extrusion process. However, there may be circumstances where the shell can be moulded in much more complicated profiles to enable decorative timber shapes (for instance fence pickets) to be encased.

It is envisaged that the shell of WPC material will be made in two parts typically comprising a base part and a lid or something similar and that the lid can be fitted to the base part in such a manner to provide a weatherproof seal. Thus, the upper edge of the base part may be formed with a recess, and the lower edge of the lid may be provided with a projection that can fit into the recess to form a weatherproof seal.

It is also envisaged that the shell will be made in two parts which can be snapped fitted or press fitted together and preferably in such a manner to also provide a weatherproof seal. Thus, the upper edge of one part may be formed with a recess and the lower edge of the other part may be provided with a projection that can press-fit or snap lock into the recess.

If desired, and an adhesive, or sealant may also be provided to improve weather proofing of the shell of WPC material.

Brief Description of the Drawings.

Embodiments of the invention will be described with reference to the following drawings in which:.

Figure 1. Illustrate schematically the process method of encasement of core material with WPC to form a product. Figure 2. Illustrates an end of view of the apparatus.

Figure 3. Illustrates a partially cut away view of the heated die.

Figure 4. Illustrates further "downstream" components from the heated die.

Figure 5. Illustrates a close up view of the outlet of the die.

Figure 6. Illustrates a number of vacuum formers. Figure 7. Illustrates one vacuum former opened up to show the internal parts.

Figure 8. Illustrates a product having a steel core and a WPC shell.

Figure 9. Illustrates a rectangular product containing an LVL core and a WPC shell or casing which is formed separately and attached to the core. Figure 10. Illustrates a round product formed using a separately formed WPC casing.

Figure 11. Illustrates a square product formed using a separately formed WPC casing. Figure 12. Illustrates in greater detail a snap locking arrangement to snap lock the cover of the WPC shell.

Best Mode.

Figures 1-7 illustrate an apparatus and method to product the encased material. The core material 30 can be any metallic or wooden profile that can be covered during this process; the core material can be solid or hollow in nature.

The process line consists of the following equipment necessary for the successful extrusion process, core guide and tolerance gauge 31, heated die/mould 32, twin screw extrusion machine 33, vacuum former(s) 34 and water cooling jackets 35. The following is the explanation to each area of the process:

• Core guide and tolerance gauge 31 - This piece of equipment is necessary in the process so that the core being coated can be securely held in place for as long as possible during the coating of the core material, if the core material was allowed to move during the process then the coating would not be even. This apparatus is also used as a tolerance guide so that if the core material is "oversized" and not within the designated tolerance of 0.03mm in width and thickness then the process operators have the opportunity to remove the offending core at this point, if the oversized core material was to proceed past this point then it would be possible for severe damage to the internal workings of the extruder head.

• Heated Mould/Die 32- After the core material has passed through the tolerance gauge it enters into the heated mould area, this is the area of the process that provides the coverage of the core material with the plastic composite. The entrance 36 to the mould is the same size as that of the core guide and tolerance gauge. The mould is positioned at right angles to the exit region 37 (figure 2) of a twin screw plastic extruder 33. The mould is manufactured from solid stainless steel so as to withstand the pressure applied during the process of coating the core material, in our process the pressure required within the mould will be >110kgs/cubic centimetre. The molten plastic composite is forced into the mould head via the twin extruder and into the cavities ( flow passageways) 38 within the mould with vanes positioned and designed to distribute the molten composite evenly around all areas of the core material for complete coverage. The temperature of the molten composite (185 degrees centigrade) is kept high with the mould having heating probes strategically placed to stop cooling within the mould head. The vanes within the mould are also strategically placed to aid the movement of the core through the mould, therefore not requiring any external drive or force to move the core through the mould. The aperture for the exit 39 from the mould is sized to suit the measurements of the core material plus the thickness of the composite encasement.

• The twin screw extruder 33 may be standard in configuration and has a maximum possible force of greater thanl90kgs/cubic centimetre. For the purpose of manufacture the extruder would be set to operate at 1 lOkgs/cubic centimetre. The raw materials of the composite are pre-mixed and fed into the extruder via a large hopper

40 positioned above the machine.

• Having exited the mould head the WPC coated product continues on into the "forming area" ( one or more vacuum formers 34). This is an area where the final exact shape is finalised, this is assisted with the use of a vacuum keeping the sides of the product firmly against the forming mould as it moves forward and is slowly cooled, there is small cooling canals constructed within the forming mould, through which chilled water is passed, this cooling will not completely cool the finished product but cooling the outer areas so that the product is totally formed. This area of the process can also be used, if required for other surface treatments that may enhance the properties of the composite shell, such as providing wood graining, applying anti-slip treatments or aesthetic "grooving" and styling.

• After the forming or associated processing the finished item will then be subjected to a chilled water bath 35 that will totally cool the profile to normal room temperature and it is then ready for the trimming 42 to size and final QA inspection.

Referring to figures 6-7, there are four separate units 34 because this design allows for some cooling during the process of the vacuum forming, prior to it entering the cold water bath 35 used to chill the WPC to normal temps. A slower cooling process whilst being vacuum formed means a lot less shrinkage once the WPC meets the chilled water.

Figure 7 shows one vacuum unit open illustrating the small slits 43 inside that allows the

WPC to be sucked to the exact shape required, the vacuum exits the forming area via fittings on the outside of the units. The inside is highly polished s/s so as to allow the WPC to pass through with minimal force. The WPC encased product has a variety of benefits including the following:

Protection against industrial environmental damage.

Absorption percentage equal to water proofing. Absorption protection against industrial chemical spills and coverage.

The non-porous surface resists adherence of common building materials such as cement, water, plaster, sand, oils and the like.

The product provides impact protection.

Less maintenance is required. Gives up to five times the life expectancy over not protected lumber.

Gives up to ten times the life expectancy over not protected metal.

Does not break away when cleaned with high-pressure water or air equipment.

Does not rot or attract mould making the surface less slippery when wet.

When wet, the surface has greater adhesion properties than unprotected core product. There is greater easy material handling as the product does not rust or corrode or splinter, is more ergonomic, does not absorb moisture and therefore increase in weight, and provides ease of visual inspection to lead to quick identification of damaged articles which will need replacement.

Figure 8 illustrates a building product comprising a core material 20 which comprises a metal rectangle hollow section 220 mm X 48 mm and having a thickness of 2 mm. The core is encased within a WPC casing 21 and the metal core is fully glued on the entire length with a gap tolerance to be less than 0.15 mm. This particular product can be used as a replacement for ordinary steel boards (such as scaffolding planks).

The uses for the WPC encased product are many and include (but are not limited to) scaffolding planks, external doors, plywood, outdoor flooring timbers, concrete forming, external stairways, pergolas, outdoor furniture, support beams, facia boards for housing, fence posts, posts which are resistant to termites, gables and roofing timbers in open front sheds in rural areas, window frames, marine structures such as jetties, harbours and berthing facilities, flooring in shipping containers, and any other wood or metal product used in areas where chemical or ultraviolet may cause damage to exposed woodwork or metal . The invention of figures 9-12 describes an elongate member which can be used as a bearer or beam in which contains a core of LVL encased within a shell of WPC material.

The ultimate shape and size of the product can vary quite substantially, and some preliminary work is required this being that the LVL or the natural timber, or metal which is to form the core needs to be sized according to specifications, the mould for the WPC casing or shell needs to be manufactured to suit the exact size of the core which is to be encased, and some decisions need to be made as to the method of encasing such as whether or not a two-piece WPC shell is to be made, or a one-piece shell is made.

The WPC material can be premixed to suit the requirements of the outer casing specification.

That is, a stronger and longer lasting casing can be formed by increasing the percentage of the resin. In the embodiment, three specifications are used being to 75% plastic and 25% wood flour, 65% plastic and 55% plastic. The plastic (resin) will be polyvinyl chloride, polypropylene or poly-ethylene and the plastic may comprise recycled plastic. The chosen plastic is melted and mixed with the ratios chosen with the wood flour (this being crushed and pulverised wood typically pine, spruce or recycled wood. Once the plastic and the wood flour are fully mixed, it is pelletised and bagged ready for use. This arrangement is known.

The machinery used to manufacture the WPC profiles is a single or twin screw extruder which is used to force molten WPC through the desired mould. The twin screw extruder can offer a higher density product which will be harder wearing. The pelletised mix is added to the extruder via a hopper which has a variable feed choke which is preset to allow just enough mix to satisfy the demand of the mould. The extruder in machine preheats the WPC gradually until meeting the screws at this point the temperature of the mix is approximately 182-19O⁰C, and subject to a pressure of approximately 22-50 kg per cubic centimetre. This pressure is variable depending on the specifications required for the end product.

On exiting the mould, the semi-molten WPC is kept in shape as it is passed through a series of cooling jackets. Firstly, the cooling jackets have a shape equal to that of the outside measurements of the item produced, the jackets are "cored" internally with water passages cut into the jacket to maximise the cooling, and there is a second cooling stage, where the profile 58

22 moved slowly through a cool bath of water which is recycled water pumped via a cooling tower. A "pultruder" is provided to pull the profile slowly through the cooling system. This uses two caterpillar type rubber tracks positioned one on top of the other and through which the WPC profile is fed and the tracks are positioned to hold and pull the profile. The profiles can then be cut to the desired lengths by an automatic measuring/cut-off apparatus.

The WPC profile has a wall thickness of between 4-5 mm and the process takes approximately 20 minutes.

The above system is used to manufacture a two-piece WPC profile as illustrated in figures 9- 11. In figure 9 and figure 11 , there is provided a substantially box shaped base profile 10 and a substantially flat lid 11. Once these two pieces have been extruded and cut to length, a suitably configured core of LVL or metal 15 is formed. The internal walls of the WPC shell and the external surface of the core are coated in adhesive which, in the particular embodiment comprises a waterproof phenolic type adhesive or a waterproof silicone-based adhesive/sealant. The core 15 is placed into the box shaped base profile 10 and the lid 11 is attached. Adhesive can be provided to form a barrier against moisture or chemicals. The formed product can then be stacked one on top of the other to form a weight to ensure that the two-piece profile is properly pressed together. If desired, a separate manual press may be provided. End caps (not illustrated) of thin strips of WPC or rubberised plastic are adhered to the ends of the length of material and end caps will be necessary if the ultimate product is subjected to the possible contamination of chemicals or water which may otherwise rot the internal core material over time.

Figure 10 illustrates a product which is round and which contains two halves of WPC material.

The lid can be fitted to the base portion by providing the base portion with a recess 12 and a lid with a corresponding projection 13 (see for instance figure 9).

Figure 12 illustrates a snap lock arrangement where the lid 11 is formed with a snap locking bead 14 which fits within a recess (which is in the shape of an inverted T) such that the lid 11 can be pressed on to the base part 10 and snap fitted into position. In an alternative, the shell can be made in a single piece of square, round or rectangular cross- section and cut to length. A core of a complimentary profile can then be pressed into the shell or the shell can be pushed over the core using a manual or hydraulic press. It is envisaged that adhesive will still be used but preferably an adhesive which also functions as a temporary lubricant to facilitate fitment of the core into the shell.

End caps can again be used if desired.

An advantage of the above arrangement is that while the WPC shell is formed separately, it can provide a substantially seamless shell about the core material. This is in contrast to previous designs which comprised flat strips of WPC material that needed to be glued to each side of the core material. Thus, the above arrangement provides:

A method for forming a product comprising a core material which is made of metal or wood and an outer layer of WPC material the method comprising melting the WPC material, applying the molten WPC material over the core material to provide a coated material and cooling the coated material to provide the product.

The above arrangement can also provide a product which has a cylindrical side wall and which comprises a core material which is made of metal or wood and an outer layer of WPC material the outer layer comprising a seamless layer about the side wall of the product.

The above arrangement can also provide a product which is rectangular in cross-section and which comprises a core material which is made of metal or wood and an outer layer of WPC material the outer layer comprising a seamless layer extending about three sides of the rectangular product.

Throughout the specification and the claims (if present), unless the context requires otherwise, the term "comprise", or variations such as "comprises" or "comprising", will be understood to apply the inclusion of the stated integer or group of integers but not the exclusion of any other integer or group of integers. Throughout the specification and claims (if present), unless the context requires otherwise, the term "substantially" or "about" will be understood to not be limited to the value for the range qualified by the terms.

Any embodiment of the invention is meant to be illustrative only and is not meant to be limiting to the invention. Therefore, it should be appreciated that various other changes and modifications can be made to any embodiment described without departing from the spirit and scope of the invention.

Claims

CLAIMS:

1. An apparatus to manufacture a product comprising a core material having side wall(s) which is/are covered with a WPC material, the apparatus comprising: a hopper to hold WPC material, a conveyor to convey the material from the hopper, a die having:

1. an inlet communicating with the conveyor such that the conveyor can convey the WPC material into the die, 2. a heater to heat the die and to melt the WPC material,

3. a core material inlet,

4. a core material outlet,

2. The apparatus of claim 1, including a feeder to feed core material into the die.

3. The apparatus as claimed in any one of the preceding claims, wherein the conveyor is a twin screw extruder.

4. The apparatus as claimed in any one of the preceding claims, wherein the die comprises a body containing a through passageway along which the core material can pass the inlet and the outlet being axially aligned, the through passageway being slightly larger than the cross-section of the core material to provide a space for the WPC material to be coated over the core material in the die.

5. The apparatus of claim 4, wherein the space is between 1-20 mm and preferably between 1-5 mm.

6. The apparatus of claim 4 or claim 5, wherein the die has one or more flow pathways, and a plurality of WPC outlets to facilitate molten WPC material coating all sides of the core material passing through the die through passageway.

7. The apparatus of claim 6, wherein flow pathways and WPC outlets are provided along an upper wall of the die passageway and a lower wall of the die passageway and the, or each, side wall of the die passageway.

8. The apparatus of any one of the preceding claims, including a tractor feed bench.

9. The apparatus of any one of the preceding claims including a core guide and tolerance gauge (31) to securely hold the core being coated in place for as long as possible during the coating of the core, the tolerance gauge functioning such that if the core is

"oversized" and not within a designated tolerance of 0.03mm in width and thickness then the offending core is removed at this point.

10. The apparatus of any one of the preceding claims, wherein at least one said vacuum former is provided downstream from the die, the vacuum former comprising a body having a through passageway through which the WPC encased material can pass, and to provide the exact shape of the encased product, the vacuum former being cooled a to harden the product and to make the product more dimensionally stable.

11 The apparatus of any one of the preceding claims comprising more than one vacuum former.

12. A WPC encased product formed by the apparatus of any one of the preceding claims .

13 The product of claim 12, wherein the core is selected from timber, metal and

LVL.

14 The product of claim 12 or 13, wherein the WPC material comprises resin in an amount of between 50-80% .

15. The product of any one of claims 12-14, selected from the group consisting of planks including scaffolding planks, doors including external doors, plywood, outdoor flooring timbers, concrete forming, external stairways, pergolas, furniture including outdoor furniture, support beams, facia boards, fence posts, posts, roofing timbers, window frames, jetties, berthing facilities, flooring products.

16. A method for forming a product comprising a core material which is made of metal or wood and an outer layer of WPC material the method comprising melting the WPC material, applying the molten WPC material over the core material to provide a coated material and cooling the coated material to provide the product.

17. A product which has a cylindrical side wall and which comprises a core material which is made of metal or wood and an outer layer of WPC material the outer layer comprising a seamless layer about the side wall of the product.

18. A product which is rectangular in cross-section and which comprises a core material which is made of metal or wood and an outer layer of WPC material the outer layer comprising a seamless layer extending about three sides of the rectangular product.