AU2006235768A1 - Encased Product Comprising a Core of Wood or Metal and a Shell of WPC - Google Patents

Description

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SEncased Product Comprising a Core of Wood or Metal and a Shell of WPC o Field of the Invention.

This invention is directed to encased products and typically a core comprising an elongate 00 1,1 length of timber or metal (but possibly other core products as well) which is encased in a t'particular shell material to provide beneficial properties. The material which surrounds the ¢€3 C core may comprise a WPC (wood plastic composite material).

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c LO Background Art.

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

L 5 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 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 extruded via a hopper and fed into a heated chamber and reduced to a N 2 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 O 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 oO ,O not particularly suited for higher weight loading. Thus, the material is not particularly suited t 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 C LO 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 L 5 (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 scaffolding planks, 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 I3 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 O concrete edging) can only be used once or twice due to the build up of cement on the wood M which is difficult to remove.

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

NI LO 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 L 5 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 scaffolding planks, 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 O 4 Sindustry, it is found that the metal products do not have a lifespan which is as long as a WPC U product but do have the benefits of load bearing and weight per materials may be subjected to 0 corrosion from water damage, weathering and the like.

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

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

C LO 0 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.

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 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).

If the core 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 contains a wood substitute material such as materials that are sometimes known as "custom wood or materials that are IND made from pieces of wood which are glued together.

.)a O The building 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.

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

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N 1 o made.

The timber core 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, that is, the core will comprise the timber. This will provide good strength to the material. However, there may be circumstances where the core 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 containing empty areas.

It is also envisaged that the material may comprise a core which is made substantially of IND 6 0 timber, but which contains other materials as well. For instance, the core may comprise S timber together with areas or zones containing foam material or plastic material and the like.

For instance, there may be circumstances where the core contains a length of timber together with a further passageway which may be empty or filled with foam material or something 00 Ielse.

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

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N LO section).

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

The size and shape of the metal core may vary. For instance, the metal core 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 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 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.

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S The metal may comprise mild steel, high tensile steel, aluminium, stainless steel, brass,

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copper, lead, nickel, chromium and which would include treated steel like galvanized steel or M painted steel and the like.

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

O It is envisaged that the material will contain a relatively hollow core, that is, the core will

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N' L 0 comprise the metal. This will provide good strength to the material. However, there may be circumstances where the core 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.

L 5 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 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 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 is substantially covered or encased with the WPC material.

However, there may be some circumstances where certain parts of the core are not covered (for instance longitudinal ends) and these may need to be separately capped or covered. It is 3 0 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.

O8 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 0 WPC material although the non-resin material may also comprise materials such as crushed Srice 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.

00 11The non-resin material may comprise a combination of various materials that are used in the Smanufacture of WPC material.

The amount of resin material and non-resin material can vary. Typically, the amount of resin C1 LO0 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%.

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.

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 I9

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then be placed within the channel member or box section and a lid or cover can then be fitted a to encase the core into the shell. The lid or cover will typically be formed of WPC material.

0 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 00 -1 encase the core within the shell.

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

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rK1LO e 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 L 5 have an open end with the core being pressed through the open end and into the shell.

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

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 IO 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 Cc the shell of WPC material.

oO 00 t Brief Description of the Drawings.

An embodiment of the invention will be described with reference to the following drawings C' 0O in which:.

Figure 1. Illustrates a rectangular product containing an LVL core and a WPC shell or casing.

Figure 2. Illustrates a round product.

L 5 Figure 3. Illustrates a square product.

Figure 4. Illustrates in greater detail a snap locking arrangement to snap lock the cover of the WPC shell.

Figure 5. Illustrates a product having a steel core and a WPC shell.

Best Mode.

The embodiment of figures 1-4 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 embodiment of figure 5 is similar except that the core is metal.

The ultimate shape and size of the member 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.

\O 11 ,l The WPC material can be premixed to suit the requirements of the outer casing specification.

C That is, a stronger and longer lasting casing can be formed by increasing the percentage of cC the resin. In the embodiment, three specifications are used being to 75% plastic and wood flour, 65% plastic and 55% plastic. The plastic (resin) will be polyvinyl chloride, 00oO 11polypropylene or poly-ethylene and the plastic may comprise recycled plastic. The chosen t"t plastic is melted and mixed with the ratios chosen with the wood flour (this being crushed I 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.

r O 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 L 5 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 182-190C, 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 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 1- ID12 3. In figure 1 and figure 3, 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 0 suitably configured core of LVL or metal 15 is formed. The internal walls of the WPC shell c 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 00 IND 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 N L 0 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 2 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 1).

Figure 4 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 crosssection 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.

Figure 5 illustrates a building product comprising a core 20 which comprises a metal rectangle hollow section 220 mm X 48 mm and having a thickness of 2 mm. The core is S13 O 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 O for ordinary steel boards (such as scaffolding planks).

The uses for the WPC encased product are many and include (but are not limited to) oO 00 scaffolding planks, external doors, plywood, outdoor flooring timbers, concrete forming, Sexternal stairways, pergolas, outdoor furniture, support beams, facia boards for housing, fence N. 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, rural areas, window frames, marine structures such as jetties, harbours and berthing facilities, C L0 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 WPC encased product has a variety of benefits including the following: Protection against industrial environmental damage.

L 5 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.

S0 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 in crease in weight, and provides ease of visual inspection to lead to quick identification of damaged articles which will need replacement.

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 INO 14 O exclusion of any other integer or group of integers.

t,, 0 Throughout the specification and claims (if present), unless the context requires otherwise, CC the term "substantially" or "about" will be understood to not be limited to the value for the range qualified by the terms.

00oO t 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 N LO and scope of the invention.

For instance, it is envisaged that the WPC encased product may be formed by another suitable process including a co-extrusion process.

Claims (17)

1. A building product which comprises a core comprising timber or metal and a shell comprising wood plastic composite material (WPC material).

2. The product of claim 1, wherein the core comprises timber.

3. The product of claim 2, wherein the core comprises LVL.

4. The product as claimed in claim 1, wherein the core comprises metal.

The product as claimed in any one of the preceding claims wherein the core is substantially solid.

6. recesses. The product as claimed in any one of claims 1-4, wherein the core contains

7. The product as claimed in any one of the preceding claims, wherein the core is substantially rectangular in cross-section.

8. The product as claimed in any one of claims 1-6, wherein the core is substantially circular in cross-section.

9. The product as claimed in any one of the preceding claims, which has a length ofbetween 1-10 m.

The product as claimed in any one of the preceding claims, wherein the WPC material comprises resin in an amount of between 50-80% and non resin material which comprises a wood flour.

11. The product as claimed in any one of the preceding claims, wherein the WPC material comprises resin, the resin comprising polyvinyl chloride. ID16

12. The product as claimed in any one of the preceding claims wherein the shell is formed separately and the core is fitted into the shell. O c

13. The product as claimed in claim 12, wherein the shell comprises a main body and a lid, the lid adapted to be fitted to the main body after the core is fitted into the shell. 00 r"- S

14. The product as claimed in any one of the preceding claims, comprising an adhesive between the core and the shell. ,I t0

15. The product as claimed in claim 14, wherein the adhesive comprises a phenolic adhesive.

16. The product as claimed in any one of the preceding claims 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.

17. A product substantially as hereinbefore described with reference to the accompanying drawings.