Hollow profile decking system comprising plank and anchor using anchor flange construction
Kind Code:

A decking system, decking components and an installed deck for use on a support structure. The decking system comprises hollow profile planking units having anchor flanges on opposite edges that cooperate with an anchor structure to form a deck or platform. The flanges and the anchor units are shaped and configured to closely interact and form an installed platform structure. The planks comprise an extruded thermoplastic wood fiber composite having an internal structure sufficient to withstand installation, engineering forces placed on the installed platform, weathering and use. The anchor structures have a shape that conforms to the anchor flanges on the decking profiles to hold the deck in place.

Bruchu, Todd (Lake Elmo, MN, US)
Dalquist, Kurt (North Branch, MN, US)
Puppin, Giuseppe (Bayport, MN, US)
Worm, Thomas B. (Brooklyn Park, MN, US)
Garofalo, Robert F. (Stillwater, MN, US)
Evans, Harold H. (Hudson, WI, US)
Heikkila, Kurt E. (Marine on St. Croix, MN, US)
Galowitz, Dennis A. (Stillwater, MN, US)
Application Number:
Publication Date:
Filing Date:
Andersen Corporation (Bayport, MN)
Primary Class:
International Classes:
E04F15/10; E04F19/06; (IPC1-7): E04B1/32
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Primary Examiner:
Attorney, Agent or Firm:

We claim:

1. A system for the installation of a decking structure on a support, the system comprising: (a) one or more hollow profile deck members, the members free from an installation slot, each member comprising a tread surface, a parallel opposite support surface and an anchor flange on opposite edges of the member; and (b) one or more anchors that can cooperate with the profile flange in the installation of the profile on the support, the anchor comprising means to attach the anchor to the support using an anchor base portion, the anchor further comprising a vertical member extending from the base portion ending in a transverse portion, the transverse portion extending from the vertical portion forming an anchor flange that can interact with the profile flange in installing the member on the support.

2. The system of claim 1 wherein the profile deck member comprises a hollow profile comprising a thermoplastic polymer-biofiber composite material.

3. The system of claim 2 wherein the hollow profile comprises vertical support webs extending between the support surface and the tread surface, the webs horizontally spaced at a distance of about 2 centimeters or more between vertical support web structures.

4. The system of claim 3 wherein adjacent support webs form an arch support structure within the hollow profile positioned such that the arch is compressed by a force normal to the tread surface of the plank.

5. The system of claim 4 wherein the hollow profile contains two or more arch like supports within the profile.

6. The system of claim 1 wherein the arch like support structure within the profile also forms a void space defined by the tread surface and the upper surface of the arch surface.

7. The system of claim 6 wherein the profile also comprises a void space defined by the support surface and the bottom surface of the arch structure.

8. The system of claim 1 wherein the anchor comprises a base, a vertical member extending from the base and a transverse member extending from the vertical member, the vertical member having an aperture for an attachment hardware, the aperture extending through the vertical member.

9. The system of claim 8 wherein the anchor member comprises an extruded metallic unit having a length of greater than 2 centimeters with the base portion extending along the length of the extruded anchor and the anchor flange extending along the length of the extrusion.

10. The system of claim 8 wherein the anchor member comprises an extruded thermoplastic unit having a length of greater than 2 centimeters with the base portion extending along the length of the extruded anchor and the anchor flange extending along the length of the extrusion.

11. The system of claim 8 wherein the anchor has at least one integral screw fastener.

12. The system of claim 8 wherein the anchor flange extends from the vertical portion of the anchor but departs from the horizontal by an angle of greater than about 5° to form an area that contacts a complementary area in the anchor flange of the deck member.

13. A plank, for deck or platform installation, comprising an extruded thermoplastic-biofiber hollow profile, the plank comprising a linear member having a tread surface and a parallel opposite support surface and parallel opposite edges, each edge comprising an anchor flange, said member comprising at least one internal arch support structure, wherein the plank has a compressive strength of at least 1500 pounds per square inch (10 megapascals) and a coefficient of thermal expansion of less than about 1.5×10−5 inch per inch ° F.

14. The plank of claim 13 wherein the anchor flanges are proximate the support surfaces.

15. The plank of claim 13 wherein the thermoplastic comprises a polyolefin.

16. The plank of claim 13 wherein the thermoplastic comprises a polyvinyl chloride.

17. The plank of claim 13 wherein the biofiber comprises wood fiber.

18. The plank of claim 13 wherein the plank comprises three or more arch support structures formed within said linear member.

19. The plank of claim 13 wherein the anchor flange extends from the plank at an angle that departs from the horizontal by at least 5°.

20. The plank of claim 13 wherein the plank has a width of at least 3 inches.

21. The plank of claim 13 wherein the width of the plank is about 3 to about 18 inches.

22. The plank of claim 13 further comprising a capstock layer.

23. The plank of claim 22 wherein said capstock comprises an abrasion resistant coating.

24. The plank of claim 23 wherein said abrasion resistant coating comprises acrylic polymer.

25. The plank of claim 24 wherein said acrylic polymer is chemically cross-linked.

26. The plank of claim 22 wherein said capstock comprises an anti-slip coating.

27. The plank of claim 26 wherein said anti-slip coating is chemically crosslinked.

28. The plank of claim 26 wherein said anti-slip coating comprises grit.

29. The plank of claim 13 wherein said tread surface is cambered.

30. The plank of claim 23, wherein said camber has a slope of about 1 degree of arc, said slope being measured from plank center to plank edge.

31. An anchor structure that can be used to install a plank having a flange in a deck or platform, the anchor comprising a base and extending from the base a vertical member having an installation hardware aperture, and extending substantially horizontally from the vertical member, a transverse member, the transverse member positioned at an angle that departs from the horizontal by at least 5°.

32. The anchor of claim 31 wherein said base member comprises an extended base member.

33. The anchor of claim 31 wherein the aperture is configured to accept a screw fastener.

34. The anchor of claim 33 wherein the aperture is further configured to retain a screw fastener.

35. A decking structure comprising: (a) a support, (b) one or more hollow profile deck members, the members free from an installation slot, each member comprising a tread surface, a parallel opposite support surface and an anchor flange on opposite edges of the member; and (c) one or more anchors that can cooperate with the profile flange in the installation of the profile on the support, the anchor comprising means to attach the anchor to the support using an anchor base portion, the anchor further comprising a vertical member extending from the base portion ending in a transverse portion, the transverse portion extending from the vertical portion forming an anchor flange that can interact with the profile flange in installing the member on the support; wherein said deck members are attached to said support by engaging said anchor flanges within the region partially enclosed by said anchor base, vertical, and transverse members and then attaching said anchor base members to said support via said attaching means and upon attachment to said support, longitudinal expansion and contraction of said deck members is not constrained by said anchors.

36. The structure of claim 35 wherein said deck members are hollow planks further comprising an extruded thermoplastic-biofiber composite material, said plank including at least one internal arch support structure, wherein said plank has a compressive strength of at least 1500 pounds per square inch (10 megapascals) and a coefficient of thermal expansion of less than about 1.5×10−5 inch per inch ° F.

37. The structure of claim 36, wherein said attachment means comprises screws.

38. The structure of claim 36, wherein said anchors substantially engage said anchor flanges the entire length of said planks.

39. The structure of claim 36, wherein said plank tread surface is cambered.

40. The structure of claim 39, wherein said camber has a slope greater than about 1 degree of arc, said slope being measured from plank center to plank edge.

41. The structure of claim 36 wherein said anchor base and transverse members include two or more distinct widths whereby the spacing between planks can be varied to produce a variety of predetermined patterns.

42. The structure of claim 36, further comprising distinct end capping and edge capping trim members attached to the periphery of said structure.

43. The structure of claim 36, wherein said support comprises joists.

44. The structure of claim 36, wherein said planks include mortise-tenon joints.

45. The structure of claim 36, further comprising an underlayment of insect screen between said support and plank installation surfaces.

46. The structure of claim 36, further comprising one or more fasteners installed to fixedly attach said planks to said support structure whereby: (a) longitudinal movement of said planks is constrained at the points of fixed attachment, and (b) length changes induced by environmental fluctuations in temperature and humidity are partitioned into zones adjacent said points of fixed attachment.



[0001] The invention relates to a system for forming a surface suitable for human occupation or use such as a deck or platform. The invention includes an installed deck or platform. The invention also includes a construction system including an extruded plank for a deck or platform formed from system components including a plank and an anchor. The invention also includes a construction system including an extruded plank for a deck or platform. The plank having an internal structure and exterior installation components, that can be combined with an anchor structure during installation. These components can interact in the decking structure to result in a deck or platform that can resist the undesirable effects of sun, weathering and hard use. The installation, construction and use of platforms or decks have come increasingly important in commercial, institutional, residential and other construction locations. Such platforms or decks are commonly installed during original construction or can be retro-installed in improvement projects. Decks provide use for commercial activities, recreational activities, farm activities, manufacturing activities and other use modes. A variety of installation systems for such decking structures have become common.


[0002] Wood, vinyl and metal components in the form of planking or decking components have been a primary focus of deck and platform manufacture over the last few years. Such systems are extruded from resin or aluminum or are milled from stock. Both sized lumber, plywood or chipboard materials have been used in decking systems. Such systems are typically installed by nailing or screwing individual planks or sheets of material to a support or foundation structure. Such wood products and even plywood and chipboard materials have become increasingly expensive due to cost and scarcity of components. Hollow profile vinyl components have also been suggested, but suffer from substantial structural and thermal drawbacks. Metal components of aluminum and steel are common but are not generally considered to be of more than utility grade materials.

[0003] Composite thermoplastic fiber materials have been suggested for use as a replacement for vinyl wood products. Such materials have enjoyed increasing utility in the prior art. A family of patents related to thermoplastic fiber composites are shown in U.S. Pat. Nos. 5,441,801, 5,497,594, 5,539,027, 5,827,607, 5,932,334, 5,948,524, 6,004,668 and 6,015,612 and others relating to thermoplastic composites using a biofiber such as a wood fiber in a high strength profile or structural member. When using such materials as a replacement for wood, the materials must be used in a decking system in a form that can be assembled with relative ease, can support the weight and dynamic load from its occupants and can have an extended useful life. The material should be capable of economic manufacture, ease of storage and transport and can be readily installed with simple hand tools in the field.

[0004] Apart from the planking systems, installation systems that can be used to secure a plank to a support structure are also known in the art. An array of wooden, metallic and vinyl installation components are known. Decking and installation hardware are shown, for example, in Svensson, U.S. Pat. No. 5,033,147, showing a bridge deck slab having a tongue and groove attachment for adjacent bridge deck slabs and an anchor bolt system that interacts with a single installation flange of one bridge deck slab. The Svensson bridge decks are typically aluminum structures that can endure vehicular traffic on bridge construction. Pollack, U.S. Pat. No. 5,613,339, shows an extruded two part deck plank structure. A first part comprises an elongate bottom “pan-shaped” deck plank member adapted for installation on a support. The second portion comprises a cover for the shaped deck plank. The deck plank is installed using conventional screws or other attachment means and adjacent deck planks are not connected during installation. Johnson, U.S. Pat. No. 5,953,878, shows hollow profile decking systems that use an anchor that engages a slot formed in the edges of adjacent deck planks that cooperate to hold the deck planks in place and maintain the appropriate spacings between planks. The slots are either formed along the entirely of the edge or are formed at specific locations in the plank edge. These systems use no anchor systems that cooperatively interact with a flange.

[0005] Erwin et al., U.S. Pat. No. 5,660,016, describes a decking system constructed of foam-filled, extruded plastic decking planks attached to support structure by means of clamps or hold-down blocks that engage a flange along the side of each plank.

[0006] A substantial need exists in establishing a structurally strong, low cost, easily installed decking structure.


[0007] The invention comprises a variety of aspects including a platform or decking system, an installed platform or deck, an extruded hollow profile deck plank and an anchor system in a cooperative kit. The deck plank of the invention comprises an extruded hollow profile in the form of a uniformly sized unit with integrally formed anchor flanges and planar surfaces. The plank comprises a composite of a thermoplastic and a biofiber. The planking unit of typical planking dimensions can have coplanar surfaces comprising a tread surface and an opposite installation or support surface that is installed in contact with a base support or foundation. Along the edges of the plank, anchor flange components are formed for installation purposes that can cooperate with an anchor unit. The tread surface is a surface configured for and exposed to traffic by a user. The plank is extruded in a form that has substantial strength arising from the formation and shape or configuration of internal support webs positioned between the tread surface and the installation or support surface to provide compression strength suitable to survive hard use by users of the installed platform or deck.

[0008] The anchor units comprise a structure adapted to be attached to a support structure or foundation with conventional attachment hardware. The anchor structure uses an anchor flange that interacts with a complementary flange on the plank or deck member without using a slot based installation. The anchor structure additionally contains a generally T-shaped structure having a base that contacts the support or foundation, a vertical member extending from the base ending in a “T-shaped” transverse member. The T-shaped transverse member is shaped and configured to cooperate with the anchor flanges of the plank edge to hold the plank or planks of decking system in place during installation and use. The base can also comprise a transverse base portion. One anchor unit interacts with adjacent typically parallel, appropriately spaced apart planks to form a deck or platform portion. In a preferred mode, the anchor flange extends from the plank at the installation surface of the plank, proximate the installation surface and is placed at an angle that departs from the horizontal upwardly from the installation surface by at least 5°. The T-shaped anchor structure is angled to conform to the flange position and departs from the horizontal by a similar angle. The angle of the transverse portion of the T-shaped member matches, (i.e.) is substantially parallel to, the anchor flange at a surface or zone of interaction between the flange and anchor member. The T-shaped anchor member can also contain an extended or transverse base portion that extends from the base, provides reliable support and stability and cooperates with other anchor parts and encloses the anchor flange of the plank. The anchor can be in the form of an H-shaped or an I-shaped member. See FIG. 1, showing a modified T-shape or an I-shaped member. The form can take a number of shapes depending on overall dimensions and sizing of the individual portions of the member.

[0009] The deck planking units of the invention comprise a deck plank having an internal support structure sufficient to maintain the dimensions of the plank under structural load conditions. The internal profile structure comprises vertical support webs in a hollow structure that provide mechanical integrity by extending from the tread surface to the installation surface and are of sufficient size and extent to maintain the mechanical integrity of the plank. Preferably the internal support webs comprise arched web members co-extruded into the interior of the plank. The aches are formed in the plank with the arches positioned in a support configuration.


[0010] FIGS. 1 through 3, 10 and 13 are isometric, top and end views of the anchor structure of the invention used to hold the deck plank extruded profile of the invention in place on a support surface.

[0011] FIGS. 4 and 5 are end views of two embodiments of the deck plank hollow profile extruded unit with varying anchor flanges. In FIG. 5, two of the deck plank extruded profiles are shown installed using an anchor flange and an anchor of the invention held in place with a fastener.

[0012] FIG. 6 is a substantially isometric view of the plank of the invention showing the installation surface, the internal support structure and the anchor flanges.

[0013] FIGS. 7 and 12 show an alternate decking member and a trim piece. The member with legs forms a space that cooperates with a trim piece and its constituent parts to form an attractive and pleasing installation.

[0014] FIGS. 8 and 9 show alternate embodiments of the decking member of the invention using mortise and tenon joinery to assemble the decking system that can provide means to drain water from the deck assembly. The mortise and tenon are milled into the profile of the member and accept the shape in the milled portions made available by the conformation of the member.

[0015] FIG. 11 shows an alternative installation of the decking member of the invention.

[0016] FIG. 14 shows a trim piece adapted for insertion into the open end of the deck member of the invention.


[0017] FIGS. 1, 10, and 13 show isometric views of the anchor structure of the invention. Referring now to FIG. 1, the anchor structure 10 is installed by placing the anchor structure on a support surface. The anchor structure is placed on the base 11 interacting with the installation surface (not shown). The anchor structure is then installed or fixed in place by inserting fastener hardware through aperture 12. Anchor structure 10 comprises a base portion having base 11 and an extended transverse base flange 15 forming a support area with a large surface area to ensure stable installation. The anchor structure 10 has a vertical member or portion 13 supporting a transverse portion comprising an anchor flange 14 and a second anchor flange 14a. These anchor flanges 14 and 14a interact with the plank anchor flange (not shown, see FIGS. 4, 5, and 6) of a plank or of a second, adjacent deck plank.

[0018] FIG. 2 is a top view of the anchor structure 10 of FIG. 1. In the center of the anchor structure is aperture 12 for the insertion of a fastener. The aperture extends from the top of the anchor structure through the base 11. At the edges of the top of the anchor structure 10 of FIG. 2 are installation anchor flanges 14 and 14a. FIGS. 1 and 2 can be of any arbitrary length. In one embodiment the anchor can be 0.25 to 10 inches in length. In another embodiment, the anchor can be of a length to match the installed length of one plank of the installation, i.e. 1 to 10 feet in length or more. In another embodiment the anchor can be made in arbitrary long portion that can be cut to size to fit the installed length of two or more planks, i.e., 5 to 50 feet, 6 to 25 feet or other selected installed length.

[0019] FIG. 3 is an end view of the anchor structure 10 of FIG. 1. The installation aperture 12 is shown in phantom. The installation base 11 and base flange 15 are shown. The vertical member 13 is shown in conjunction with transverse portions or anchor flanges of 14 and 14a. A departure angle alpha is shown in FIG. 3 that represents the departure from horizontal of flange 14a. This departure angle alpha creates an interface area, zone or surface 59 at which the anchor flange 14a contacts the anchor flange of the profile (not shown, see FIGS. 4 and 5) to form a stable installation of the deck.

[0020] FIG. 4 shows one installed hollow profile deck member or plank 40 of the invention. The deck member or plank 40 is installed in place using an anchor 10 and an anchor/trim piece 49. The anchor 10 is held in place with a fastener (an appropriately sized screw) 58. The anchor/trim piece 49 hides the edge portion of the deck plank and holds the anchor flange 45 in place for a mechanically stable installation (compare the anchor flange 45 of FIG. 4 to the flange 55 of FIG. 5). The anchor flange 40 is parallel to the support surface 48 (in phantom). Hollow profile extruded deck plank 40 comprises a tread surface 41 and an installation surface 42 in contact with the installation support surface or base 48 (in phantom). The deck plank 40 has anchor flanges 45 that cooperate with the anchor structure to provide a structurally sound installation while permitting longitudinal expansion and contract of the plank in its end use environment. The structural integrity and mechanical compressive strength of the deck plank is maintained using support webs 43 and arc support portion 44 of the deck member or plank in the form of a hollow profile 40. The formation of the support webs 43 and arc support portions 44 results in the formation of various hollow profile apertures or openings 46 and 47 formed in the structure during extrusion.

[0021] FIG. 5 shows the installation of two parallel, spaced apart hollow profile deck plank structures 50 of the invention. Plank structures 50 use an anchor flange 55 with a unique configuration (compared to the plank 40 and flange 45 of FIG. 4) on a base or support surface 60 (in phantom) using the anchor structure 10 and a fastener 58. The deck profiles 50 are installed on a base or support surface 60. The hollow profile planks 50 interact with the base or support surface 60 using plank installation surface 52 of the deck plank 50. The deck plank comprises a tread surface 51 to support user traffic, internal support webs 53 and arc like support structures 54. The deck plank 50 comprises an anchor flange 55 having a cooperating shape that matches the shape of the transverse portion or anchor flange 14 or 14a of the anchor 10. The transverse portion or anchor flange 14 or 14a of the anchor 10 has a cooperative interface that contacts a similarly shaped surface on the anchor flange 55. The transverse portion or anchor flange 14 or 14a interacts with the anchor flange 55 at an interface area, surface or zone 59. The formation of the arc like support structure 54 and vertical support webs 53 results in the formation of aperture or openings 56 and 57 that are formed within the plank structure to provide controlled weight while preserving high strength. The planks 50 can be extruded with a surface 51 adapted to promote drainage. The center of the surface 51 can be elevated above the edges to promote water flow toward the edges. Preferably the top surface 51 of the plank 50 has a triangular shape. The equilateral triangle shape has an apex along the centerline of the plank with sides that slope toward the plank edge thus promoting drainage. The angle at the apex is greater than about 170 degrees of arc. The equal angles of the sides of the triangle to the horizontal are about 0.5 to 5 degrees of arc, preferably about 0.75 to 2 degrees of arc. This relatively small angle promotes drainage but does not interfere with use of the deck surface.

[0022] FIG. 6 is an isometric view of the plank 50 of the invention. The plank installation surface 52 is shown. The plank 50 comprises the tread surface 51, the anchor flange 55, and the vertical support webs 53 including the arc support structure 54. The internal structure of the deck plank 50 includes openings 56 and 57 which remain after the extrusion of the deck structure 50 resulting from the extrusion die configuration.

[0023] FIG. 7 is an end view of an alternate embodiment of the deck member 40a of the invention. Deck member 40a is similar to deck member 40 with the addition to 40a of legs 77 that are formed in the installation surface 42a of deck member 40a. The leg 77 holds the deck member 40a above the rough surface 48 and creates a space 76 between the installation surface 42a and the rough surface 48. The installation surface can provide ventilation, water drainage and permits insertion of a tab or insert portion 78 of the trim materials into the open space at each end of the deck member 40a. FIG. 7 further displays a trim piece 79 and 79a. The trim piece can be installed on the exposed sides of the deck member 40a or the exposed (not in contact with any structure an obscured) opposite ends or an end of the deck member 40a. Such a trim piece participates in anchoring the deck member to the support surface 48 and cooperates with the anchor 10 to hold the deck members in place. The trim piece 79 comprises a top piece 75 and a tab 78. The top piece 75 forms a neat cover for the trim on the edge of the deck while the tab contacts the support surface and can be inserted into the trim tab space 76.

[0024] FIG. 8 is an end view of a deck member having a mortise and tenon joint structure 84. The deck member is similar to that shown in FIG. 6. The deck member additionally comprises a capstock, coating, anti-skid surface, or an UV or wear protective surface 80 covering the exposed tread surface with a protective or colored coating or layer. The mortise and tenon deck member has a mortise 81 formed in the end of the deck member 84. The mortise has a top surface 82 and a bottom surface 82a. The base or wall 85 of the mortise is also shown. The mortise is sized and configured to accept the tenon 90 shown in FIG. 9.

[0025] FIG. 9 shows the tenon, a projection portion of the mortise and tenon containing member 84 and shows FIG. 8 (in phantom). The tenon comprises a tenon top 91, a tenon bottom 92 formed in the composite material of the deck member 84. As can be readily appreciated from the Figure, the tenon is not a continuous tenon across the width of the deck member, but is formed in the material remaining after the deck member is extruded with the interior structure shown in FIGS. 4, 5, and 6. However, the tenons are shaped and configured to fit into the mortise shown in FIGS. 8 and 9. Further, the length of the tenon and the depth of the mortise are shaped and configured to leave a aperture or gap 93 between the ends of the joined deck members 84. The gap 93 preferably acts as a water drain permitting water to drain from the tread surface 41 or capstock layer or coating 80 through the decking member 40 or 84. The drainage water can be directed to further drains in the support surface or base 48 or to the environment below the deck structure. The tenon 90 can be inserted into the mortise 81 (shown in phantom) and can provide structural support simply by its insertion. Alternatively, the mortise and tenon can be joined using an adhesive material to bond the mortise and tenon structure securely to cooperate with the anchor 10 and trim piece 79 to form a secure structure. In an alternative embodiment of the invention, applicants envision planks having the mortise and tenon formed in opposite plank ends so that planks of various lengths can be readily formed from standard length stock by simply cutting a pre-determined length of material from the plank center, reversing the plank halves, and assembling the joint interior to the foreshortened plank.

[0026] FIG. 10 additionally displays a sloped support 17 between base 11 and transverse portions/anchor flange 14. FIG. 10 shows a base portion 11 and a two-part base flange 15 and 15a. In FIG. 10, vertical member 13a comprises a cylindrical portion formed into the one piece anchor 100 of FIG. 10.

[0027] FIG. 11 shows the installation of a deck member 40 ripped lengthwise leaving a ripped surface 111 installed on an installation surface 42 using hardware 112 and the anchor 100 of FIG. 10.

[0028] FIG. 12 shows an alternate embodiment of the installation similar to that in FIG. 7. The deck member 40a is shown ripped lengthwise leaving a ripped surface 111 and installed using the anchor 100 of FIG. 10 and the trim piece 79 of FIG. 7 installed with a screw fastener 49a.

[0029] FIG. 14 is an end trim piece 140 adapted to cover the end of a deck member 50. The trim piece 140 has an end cover portion 141 and one or more insert portions 142. The inset insert portions 142 are adapted for a snug friction fit to the hollow profile 56 section of the deck member 50. When used, the trim piece 140 is brought into contact with deck member 50 and the inserts 142 are inserted into the hollow profile 56. The end cover 141 covers the entire exposed end portion of the deck member 50. The insert 142 comprises a base portion 143, a curved top portion 144 and a vertical connecting portion 145. When the insert 142 is inserted into the hollow profile 56, the curved portion 144 contacts the arched support section 54 of the hollow profile 56 while the base portion 143 contacts the base portion of the hollow profile. The vertical member 145 provides mechanical integrity to the insert 142 that maintains the trim piece 140 in place.

[0030] Plank Structure

[0031] The plank structure of the invention preferably comprises a composite comprising a thermoplastic resin and a biofiber; however, hollow plastic and metal planks are envisioned as falling with the scope of the invention. The thermoplastics that can be used include polyolefins such as polyethylene or polypropylene or other thermoplastic polymers such as polyvinyl chloride, polystyrene, polyacrylic materials, polyester materials and other common thermoplastics. In manufacturing the preferred composite of the invention, the thermoplastic and fiber are blended, often in dry form, and then introduced into an extruder in which the materials are intimately blended, melted and formed into a composite material as described in greater detail hereinbelow. Often, the structural components of the invention are directly extruded from the initial blending of these materials or can be first extruded in the form of a pellet which then can be introduced, in turn, into a plank forming extruder device at a later time or different location.

[0032] The composite materials of the invention, formed into a plank can be manufactured using a surface layer, protective coating, capstock layer on any surface, portion thereof on the exterior or interior of the decking member or plank. The coating, layer, or capstock can provide environmental stability, wear resistance, resistance to environmental moisture, stability to ultraviolet light or any other physical or chemical property that can tend to improve the wear ability or lifetime of any aspect of the deck plank structure. Extruded capstock materials are known for use in the formation of extruded hollow profile materials. Coextruding a layer of an acrylic, a chloropolymer, a fluoropolymer, or other blended polymeric material that can maintain the surface quality of the profile typically makes an effective protective layer. A representative abrasion resistant coating is LUCITE® TufCoat 4600, available from ICI Acrylics, Memphis, Tenn. Capstocks can have a clear, colored or patterned appearance. The colors can be formed by the addition of dyes and/or pigments to the capstock layer to form a green, Terratone, white, or other colored appearance. Further, the capstock can take the appearance of a wood grain, a stone-like appearance or other natural surface quality. Such capstock layers are typically manufactured by coating, painting or coextruding the thermoplastic material in a thin layer onto the plank during the extrusion of the plank material. During extrusion, the capstock layer is typically carefully gauged in thickness to conserve material but to provide an excellent surface and acceptable appearance (less than two millimeters, typically less than 1 millimeter).

[0033] The deck plank can also be manufactured with a roughened or substantially non-skid surface. Preferably, the tread surface of the plank can be supplied with an anti-skid surface. Such anti-skid surfaces can be manufactured in a number of ways. First, a capstock layer can be manufactured with a substantial wood grain relief or substantial rough surface. Such a surface can be substantially non-skid and can prevent accidental slipping accidents. Alternatively, the tread surface of the deck can be supplied with a grit or particulate material to enhance slip resistance. The grit or particulate can be bonded to the tread surface using conventional bonding agents. In the manufacture of such particulate non-skid surfaces, the particulate and the bonding agent are typically applied to the surface, the bonding agent is cured (using catalysts, UV or electron beam radiation, heat or other curing means) to form a solid phase from the originally applied liquid phase, binding the particulate to the surface. The order of addition of the materials is optional depending on the nature of the add-on materials. Either the binder or the particulate can be added to the surface or the binder and the particulate can be blended into a uniform dispersion of the particulate and the liquid. This uniform dispersion can be applied to the surface and cured in place to form a hard, non-skid, durable surface.

[0034] The inclusion of means to drain the surface of the accumulation of water is an important aspect and can be used with an appropriately shaped plank profile. Water can accumulate as a result of rain fall, washing and/or rinsing of the deck surface or from accidental spray from lawn sprinkling, house cleaning, car washing or other accidental water sprays. The substantially flat surface of the deck can accumulate substantial quantities of water. Obtaining drainage of accumulated water is important. Drainage can be promoted by forming a camber in the tread surface of the plank such that the plank is the highest at its center. Any water falling on such a cambered surface will be forced by gravity to run off the plank from the center to the edge. A center-to-edge camber having a slope equal to, or greater than, one degree slope (1°) is sufficient to promote the required drainage. Furthermore, the spacing between planks affects drainage efficiency. The spacing between planks should be sufficient to overcome the plugging effects of surface tension and small amounts of accumulated dirt and debris arising in the use environment. Applicants envision installations where it may be advantageous to introduce apertures into the planks per se to pass water from the top surface, or through the plank sides, into the hollow arched regions, enroute to a second set of exit apertures in the plank installation surface. Such apertures can be in the form of holes or by forming gaps at the site of assembly of one plank with another at a joint or plank end.

[0035] In installations where the anchor extends contiguously the entire length of the plank (to provide extra support in demanding applications), drain apertures in the form of holes can be formed in the anchor. The diameter and spacing of such drains should not compromise the structural integrity of the anchor. The diameter of the drains should be large enough to prevent capillary bridging due to surface tension effects and permit drainage of small particle debris as described above. Conceivably, the spacing between planks could be great enough to accommodate passage of small quantities of pine needles, acorns, leaves, twigs, and the like providing a limited “self-cleaning” flushing of the deck surface. On the other hand, the apertures in the anchors would pass only water-soluble debris and small insoluble dirt particles. Spacing of the drains should be related to the volume of water to be drained per unit area of deck surface during a heavy rainfall. While not wishing to limit the scope of the invention by the following disclosure, applicants believe useful “rules of thumb” for determining proper drainage are: a flow rate of about 5 gallons per hour per square foot of deck surface, and aperture areas of about ⅜ square inch, which provide sufficient drainage if the apertures are not elongated to the point where water is retained by capillary action.

[0036] Finally in installations where the decking structure forms the floor of a larger enclosed structure, inter-plank spacing can be eliminated to prevent intrusion of insects since water drainage is not a problem an interior decking structure. Alternatively, an underlayment of insect screening can be installed between support and plank installation in installations where ventilation through the inter-plank gaps is desired.

[0037] Thermoplastic Polymer-Biofiber Composite Materials

[0038] Polymer Resin

[0039] A polyolefin composite combines about 5 to 50 parts of a polyolefin such as a polyethylene or polypropylene homopolymer or copolymer with greater than about 50 to 90 parts of a fiber having an aspect ratio greater than about 2. The useful polyolefin material is a polyethylene or polypropylene polymer having a melting point of about 140 to 160° C., preferably about 145 to 158° C. The preferred polyethylene material is a polyethylene homopolymer or copolymer with 0.01 to 10 wt % of a C2-16 olefin monomer. The preferred polypropylene material is a polypropylene homopolymer or copolymer with 0.01 to 10 wt % of ethylene or a C4-16 olefin monomer or mixtures thereof. Having a melt index greater than 0.5 g-10 min−1 preferably about 2 to 20 g-10 min−1 by ASTM 1238. The composite is also compatibilized using a compatibilizing agent that promotes the desired intimate contact between polymer and fiber whereby fiber particles are completely encapsulated by a continuous polymer phase. The biofiber is dried to a content of less than about 5000 parts, preferably less than 3500 parts of water per each million parts of fiber (PPM) to promote the desired encapsulated morphology which applicants believe results from opening fiber cellular structure to wetting and penetration by fluidized thermoplastic polymer. The combination of these factors results in a composite having surprisingly improved structural and thermal properties. A representative polypropylene random copolymer is Montell SV-258. Representative compatibilizers are Eastman Epolene™ Series—E43, G3003, G0315, etc.

[0040] The composite can also comprise a polyvinyl chloride and biofiber composite. Polyvinylchloride (PVC) is a common commodity thermoplastic polymer that can be used in the composite. PVC homopolymers in a variety of molecular weights (K values) are readily available from a number of sources, GEON and Shin-Tech, for example. Polyvinylchloride can also be combined with other vinyl monomers in the manufacture of polyvinyl chloride copolymers. Such copolymers can be linear copolymers, branched copolymers, graft copolymers, random copolymers, regular repeating copolymers, block copolymers, etc. Monomers that can be combined with vinyl chloride to form vinyl chloride copolymers include a acrylonitrile; alpha-olefins such as ethylene, propylene, etc.; chlorinated monomers such as vinylidene dichloride, acrylate monomers such as acrylic acid, methylacrylate, methylmethacrylate, acrylamide, hydroxyethyl acrylate, and others; styrenic monomers such as styrene, alphamethyl styrene, vinyl toluene, etc.; vinyl acetate; and other commonly available ethylenically unsaturated monomer compositions.

[0041] Such monomers can be used in an amount of up to about 50 mol-%, the balance being vinyl chloride. Polymer blends or polymer alloys can be useful in manufacturing the pellet or linear extrudate of the invention. Such alloys typically comprise two miscible polymers blended to form a uniform composition. Scientific and commercial progress in the area of polymer blends has lead to the realization that important physical property improvements can be made not by developing new polymer material but by forming miscible polymer blends or alloys. A polymer alloy at equilibrium comprises a mixture of two amorphous polymers existing as a single phase of intimately mixed segments of the two macro molecular components. Miscible amorphous polymers form glasses upon sufficient cooling and a homogeneous or miscible polymer blend exhibits a single, composition dependent glass transition temperature (Tg). Immiscible or non-alloyed blend of polymers typically displays two or more glass transition temperatures associated with immiscible polymer phases. In the simplest cases, the properties of polymer alloys reflect a composition weighted average of properties possessed by the components. In general, however, the property dependence on composition varies in a complex way with a particular property, the nature of the components (glassy, rubbery or semicrystalline), the thermodynamic state of the blend, and its mechanical state whether molecules and phases are oriented. Polyvinyl chloride forms a number of known polymer alloys including, for example, polyvinyl chloride/nitrile rubber; polyvinyl chloride and related chlorinated copolymers and terpolymers of polyvinyl chloride or vinylidene dichloride polyvinyl chloride/alphamethyl styrene-acrylonitrile copolymer blends; polyvinyl chloride/polyethylene; polyvinyl chloride/chlorinated polyethylene and others. The primary requirement for the substantially thermoplastic polymeric material is that it retain sufficient thermoplastic properties to permit melt blending with wood fiber, permit formation of linear extrudate pellets, and to permit the composition material or pellet to be extruded or injection molded. Useful PVC resin blends (including foaming agent and stabilizers) and extrusion conditions therefore are described by Suzuki et al. in U.S. Pat. No. 5,712,319 the disclosure of which is hereby incorporated by reference.

[0042] Biofiber

[0043] A variety of biofiber materials can be used in the composites of the invention. Such fibers are fibers of naturally occurring sources that have significant aspect ratio to provide structural properties of the composite. Such fibers include wood fiber, flax, cotton, bagasse, wood flour, straw, recycled fiber, pulp, or other cellulosic material, etc. Wood fiber, in terms of abundance and suitability can be derived from either soft woods or evergreens or from hard woods commonly known as broad leaf deciduous trees. Soft woods are generally preferred for fiber manufacture because the resulting fibers are longer, contain high percentages of lignin and lower percentages of hemicellulose than hard woods. While soft wood is a primary source of fiber for the invention, additional fiber make-up can be derived from a number of secondary or fiber reclaim sources including bamboo, rice, sugar cane, and recycled fibers from newspapers, boxes, computer printouts, etc.

[0044] However, the primary source for wood fiber of this invention comprises the wood fiber by-product of sawing or milling soft woods commonly known as sawdust or milling tailings. Such wood fiber has a regular reproducible shape and aspect ratio. The fibers based on a random selection of about 100 fibers are commonly at about 0.1 to 3 mm in length, 0.05 to 1 mm in thickness and commonly have an aspect ratio of at least 1.8, preferably 2.5 to 7.0. The preferred fiber for use in this invention is fiber derived from processes common in the manufacture of windows and doors. Wooden members are commonly ripped or sawed to size in a cross grain direction to form appropriate lengths and widths of wood materials. The by-product of such sawing operations is a substantial quantity of sawdust. In shaping a regular shaped piece of wood into a useful milled shape, wood is commonly passed through machines which selectively removes wood from the piece leaving the useful shape. Such milling operations produce substantial quantities of sawdust or mill tailing by-products. Furthermore, substantial waste trim is produced when shaped materials are cut to size and subsequently have mitered joints, butt joints, overlapping joints, mortise and tenon joints formed therein. Such process produce large trim pieces which can comminuted by well-known methods to form wood fiber having dimensions approximating sawdust or mill tailings. Blending of wood fibers with other biofibers (all of which may have different particle sizes and particle size distributions) is envisioned as falling within the scope of the present invention. Alternatively, the fiber stream can be pre-sized, or can be sized after blending, to yield input fiber have a preferred size and size distribution. Finally, the fiber can be pre-pelletized before use in composite manufacture.

[0045] Frequently the waste trim pieces and sawdust material contains substantial proportions of other materials used to make wood sashes and frames for windows and doors including, but not limited to, for example, polyvinyl chloride or other polymer materials that have been used as coating, cladding or envelope on wooden members (about 10 wt %); recycled structural members made from thermoplastic materials; polymeric materials from coatings; adhesive components in the form of hot melt adhesives, solvent based adhesives, powdered adhesives, etc.; paints including water based paints, alkyd paints, epoxy paints, etc.; preservatives, anti-fungal agents, anti-bacterial agents, insecticides, etc., and other non-wood materials (ONWM) used in the manufacture of wooden doors and windows. The ONWM content is commonly less than 25 wt-% of the total biofiber input into a preferred polyvinyl chloride wood fiber product. Commonly, the intentional recycle ranges from about 1 to about 25 wt-%, preferably about 2 to about 20 wt-%, most commonly from about 3 to about 15 wt-% recyclable ONWM based on the weight of input biofiber.

[0046] Pellet

[0047] The thermoplastic resin and biofiber can be combined and formed into a pellet using thermoplastic extrusion processes. Fiber can be introduced into pellet making process in a number of sizes. We believe that the biofiber (when wood fiber) should have a minimum length of at least 0.1 mm because wood flour tends to be explosive at certain wood to air ratios. Further, wood fiber of appropriate size of an aspect ratio greater than 1, preferably greater than 2, tends to increase the physical properties of the extruded structural member. However, useful structural members can be made with a fiber of very large size. Fibers that are of reinforcing length up to 3 cm in length and 0.5 cm in thickness can be used as input to the pellet or linear extrudate manufacturing process. However, particles of this size do not produce highest quality structural members or maximized structural strength. The best appearing product with maximized structural properties are manufactured within a range of particle size as set forth below. Further, large particle wood fiber an be reduced in size by grinding or other similar processes that produce a fiber similar to sawdust having the stated dimensions and aspect ratio. One further advantage-of manufacturing sawdust of the desired size is that the material can be pre-dried before introduction into the pellet or linear extrudate manufacturing process. Further, the wood fiber can be pre-pelletized into pellets of wood fiber with small amounts of binder if necessary.

[0048] During the pelletizing process for the composite pellet, the thermoplastic resin and fiber are intimately contacted at high temperatures and pressures to insure that the fiber and polymeric material are wetted, mixed and extruded in a form such that the polymer material, on a microscopic basis, coats and flows into the pores, cavity, etc., of the fibers. During the extrusion process, the fibers are substantially longitudinally oriented into the extrusion direction by the extrudate flow profile. Such substantial orientation causes overlapping of adjacent parallel fibers and polymeric coating of the oriented fibers resulting a reinforced material that has substantially improved mechanical properties such as tensile strength, coefficient of thermal expansion, and a modulus of elasticity.

[0049] Moisture control is an important element of manufacturing a useful linear extrudate or pellet. Depending on the equipment used and processing conditions, control of the water content of the linear extrudate or pellet can be important in forming a successful structural member substantially free of internal voids or surface blemishes. The concentration of water present in the biofiber during the formation of pellet or linear extrudate when heated can flash from the surface of the newly extruded structural member and can come as a result of a rapid volatilization, form a steam bubble deep in the interior of the extruded member which can pass from the interior through the hot thermoplastic extrudate leaving a substantial flaw. In a similar fashion, surface water can bubble and leave cracks, bubbles or other surface flaws in the extruded member. Fiber sources when harvested, depending on relative humidity and season, can contain from 30 to 300 wt-% water based on fiber content. After cutting and drying the fiber can have a water content of from 20 to 30 wt-%. Because of the variation in water content of fiber source and the sensitivity of extrudate to water content, the control of water to a level of less than 8 wt-% in the pellet, based on pellet weight, is important. When a structural members, such as the decking plank of the present invention, is extruded in non-vented extrusion process, pellets should be as dry as possible and have a water content between 0.01 and 5 wt-%, preferably less than 3.5 wt-%. When using vented equipment in manufacturing the extruded linear member, a water content of less than 8 wt-% can be tolerated.

[0050] The pellets or linear extrudate of the invention are made by extrusion of the resin and fiber composite through an extrusion die resulting in a linear extrudate that can be cut into a pellet shape. The pellet cross-section can be any arbitrary shape depending on the extrusion die geometry. However, we have found that a regular geometric cross-sectional shape can be useful. Such regular cross-sectional shapes include a triangle, a square, a rectangle, a hexagonal, an oval, a circle, etc. The preferred shape of the pellet is a regular cylinder having a roughly circular or somewhat oval cross-section. The pellet volume is preferably greater than about 12 mm3. The preferred pellet is a right circular cylinder, the preferred radius of the cylinder is at least 1.5 mm with a length of at least 1 mm. Preferably, the pellet has a radius of 1 to 5 mm and a length of 1 to 10 mm. Most preferably, the cylinder has a radius of 2.3 to 2.6 mm, a length of 2.4 to 4.7 mm, a volume of 40 to 100 mm3, a weight of 40 to 130 mg and a bulk density of about 0.2 to 0.8 gm/mm3.

[0051] We have found that the interaction, on a microscopic level, between the resin, polymer mass and the fiber is an important element of the invention. We have found that the physical properties of an extruded member are improved when the polymer melt, during extrusion of the pellet or linear member, thoroughly wets and penetrates the wood fiber particles. The thermoplastic material comprises an exterior continuous organic polymer phase with the biofiber particle dispersed as a discontinuous phase in the continuous polymer phase. The material during mixing and extrusion obtains an aspect ratio of at least 1.1 and preferably between 2 and 10, optimizes orientation such as at least 20 wt-%, preferably 30% of the fibers are oriented in an extruder direction, and are thoroughly mixed and wetted by the polymer such that the exterior surfaces of the wood fiber are in contact with the polymer material. This means, that pores, crevices, cracks, passageways, indentations, etc., are filled by thermoplastic material. Such penetration is attained by ensuring that the viscosity of the polymer melt is reduced by operating at elevated temperature and using sufficient pressure to force the polymer into accessible internal pores, cracks and crevices within the biofiber in addition to filling like features on the biofiber surface.

[0052] During the pellet or linear extrudate manufacture, substantial work is done in providing a uniform dispersion of the fiber into the fluidized polymer. Such work produces a substantial number of orientable, acicular fiber particles. Such particles are easily oriented into the extrusion direction by the flow field of the extrusion process resulting in extrusion of parts having improved structural properties.

[0053] The pellet dimensions are selected for both convenience in manufacturing and in optimizing the final properties the extruded materials. A pellet is with dimensions substantially less than the dimensions set forth above difficult to extrude, pelletize and handle in storage. Pellets larger than the range recited are difficult to introduce into extrusion or injection molding equipment, and are difficult to melt and form into a finished structural member, such as a decking plank.

[0054] Composite and Pellet Manufacture-I

[0055] Thermoplastic polymer-biofiber composite material used to produce the decking plank of the invention is made under high shear conditions that are conducive to achieving intimate contact between polymer and fiber that result in the unique physical and mechanical properties exhibited in structural parts made from the composite. Appropriate high shear conditions can be produced in a variety of powder blenders and mixers. For example Nishibori uses a blade mixer (U.S. Pat. No. 5,725,939) in tandem with an extruder to produce biofiber composite sheet materials. Screw mixers, especially extruders, are preferred processors ideally suited for cascading continuous chemical process unit operations such as heating, mixing, and devolatizing for example. Because small, controlled volumes of material sequentially pass through isolated zones along the screw(s) process parameters can be continuously monitored and adjusted using microprocessors. Therefore, a preferred process is the Krupp Werner & Pfleiderer (W & P) KombiPlast process wherein a co-rotating, twin screw extruder is used to make composite that is delivered to a single screw extruder operating in tandem where composite is further heated and compressed prior to delivery to an extrusion die. The die can be either a profile die for direct extrusion of the inventive decking plank or a pellet die.

[0056] The process steps used to make thermoplastic-biofiber composite in a screw mixer generally begin with a fiber drying step wherein biofiber is conductively heated under mild shear conditions and the steam generated is vented from the mixer. Temperature, heat transfer, and shear are closely controlled to optimize moisture vaporization to avoid fiber scorching, breaking, and geysering at the vent (at high moisture levels the steam generated blows fiber out the vent in geyser like fashion). If it is necessary to cushion the fiber during drying part or the entire thermoplastic can be added with the fiber during the drying step. Fiber moisture is preferably reduced to between 3 and 5 wt % during drying. Thermoplastic and optional regrind material is added to dried fiber at pre-selected point down the screw.

[0057] A “stuffer” screw may be used to add the thermoplastic depending on the pressure in the barrel at the addition point, which is related to the material throughput rate and compression. The proto-composite is mixed and heated to distribute thermoplastic throughout the fiber stream. Further downstream kneading blocks shear mixes the composite. At this point, the thermoplastic melts (polyolefins) or fluxes (PVC) to form a fluid mass capable of forming a melt seal in the extruder. The temperature at this point is typically 195-215 C for PVC composites. The fluid composite then passes through a high free volume vacuum devolatization zone operating at a vacuum of sufficient strength to remove volatile products from the composite but of insufficient strength to pull the composite apart (typically a negative pressure of from 50 to 90 kilopascals). During devolatization the compressed composite abruptly expands and cools by as much as about 10° C. such that any thermal decomposition initiated during high shear mixing is quenched. Expanding volatile products vented through a vacuum port include, for example, steam, terpenes, lubricants, stabilizers, and small amounts of hydrogen chloride (when PVC comprises the thermoplastic). The expanded composite is recompressed to further intimate contact between fiber and thermoplastic before it is discharged into an evacuated transition box between the twin and single screw extruders. Upon entering the transition box, the composite now free of the confines of the extruder screw(s) is free to expand and cool in three dimensions. This expansion is sufficiently violent that some of the remaining, unruptured biofiber cells that have become steam filled during processing explode thus opening their interior volumes for subsequent introduction of fluxed polymer. Newly formed volatile products are evacuated at negative pressure in the range of from 50 to 95 kilopascals. Upon entering the single screw extruder, the composite is compressed and heated to a pressure and temperature dictated by operating requirements of the extrusion die. Optional materials can be added to the composite at pre-selected points along the single screw. For example, blowing agents can be added when a foamed extrudate is desired similar to the method shown in the flow chart (FIG. 1) and block diagram (FIG. 2) and more fully described by Kamoski, U.S. Pat. No. 5,997,784, which is hereby incorporated by reference.

[0058] When the composite is directly extruded through a profile die to form the inventive decking plank, the die may be optionally adapted to co-extrude capstock(s) on predetermined areas of the extruded profile external surface. Such capstocks include, but are not limited to, colored materials that enhance weatherability, abrasion resistant coatings, friction promoting anti-slip coatings, and the like.

[0059] Thermoplastic polymer-biofiber composite material is visco-elastic. Upon exiting the die, the hot extruded part is more a viscous fluid than an elastic solid. Important post extrusion cooling and shaping process are applied to the part as it transforms to become more an elastic solid than a viscous fluid as it cools to ambient temperature. Therefore, the temperature, draw down, and cooling rate of the extruded part are controlled to minimize the residual stress in the finished part. Such “frozen in” stresses gradually relax over time at different rates that depend on the temperature of the end use environment. This stress relaxation can cause a retinue of mechanical problems for structures constructed from the extrude parts (profiles). Post extrusion cooling and shaping (calibrating) processes and apparatus are described by Purstinger, U.S. Pat. No. 5,514,325; DeCoursey et al., U.S. Pat. No. 5,008,051; and Groeblacher, U.S. Pat. Nos. 5,578,328 & 5,484,577 the disclosures of which are hereby incorporated by reference.

[0060] When the composite is extruded through a stranding die to form pellets, the pressure, temperature, and cutter rotation speed are adjusted to optimize pellet uniformity and density. Pelletizing the composite permits decoupling of the composite making and extrusion processes. Pellets can be extruded as described above for the single screw portion of the W&P KombiPlast process, but pellets are preferably extruded using counter-rotating, twin screw extruders like the Cincinnati-Milicron CM-80, for example, that develop high die head pressures at low screw rotation speeds. Composite foaming, capstock co-extrusion, and down stream profile cooling and calibration processes are identical to those for direct profile extrusion described above.

[0061] In a variation of the process disclosed above, biofiber can be dried, thermoplastic can be melted or fluxed, and the fiber and plastic then mixed together separate extruders. Such multi-extruder processes permit more precise control of the heat transfer during heating and the shear during mixing. Such an approach reduces the stress and comminution of acicular fiber particles that degrades the particle size distribution of the fiber and mechanical properties of structures made from the composite.

[0062] The high throughput process used to make thermoplastic-biofiber composite operate at a rate of at mass flow rates in the range of from about 10 to 5000 kg-hr−1 and are capable of efficiently converts the maximum available mechanical energy supplied by blade and/or screw mixers into composite. However, the densification process further requires delivery of this energy at a rate sufficient to overcome the energy barriers opposing densification. Therefore the energy delivery of the process occurs at a shear rate and for a time sufficient to force thermoplastic into the biofiber cell interior without breaking acicular fibers (or otherwise commuting/degrading the biofiber size distribution). The desired composite morphology is one where the fibers are surrounded and filled with thermoplastic to form a dense void free material as opposed a porous, unfilled structure of collapsed fibers that is to be avoided.

[0063] During extrusion of fluid composite through a profile die, the torque exerted on acicular fibers by shear gradients tend to rotate them in the flow direction thus producing a more aligned morphology that generally improves the mechanical properties of the resulting profile, the torque can easily exceed that required to break the fiber. Therefore, when the input fiber is highly acicular the shear rate, and/or the time spent by the material, in high shear parts of the process are minimized to prevent excessive particle breakage.

[0064] The versatility of W & P co-rotating, fully intermeshing twin screw extruders used in the KombiPlast process is described in greater detail by Marten et al. in U.S. Pat. No. 5,051,222. The screw is designed in a segmented fashion so that a variety of different screw elements can be placed on keyed shafts to achieve the desired degree of mixing for a particular application. Screw elements can vary along the length of the screw, but the two screws must be matched to achieve fully intermeshing surfaces. Generally speaking there are two different types of elements, screw conveying elements and kneading or mixing disks. The screw elements can have either a forward or reverse pitch, while the kneading disks can have a neutral pitch in addition to the forward or reverse pitch. The kneading disks consist of staggered elliptical disks that are offset to achieve an overall conveying pitch. The disks can vary in width from one element to another but are typically of uniform width within an element. In addition to a varied pitch in the kneading blocks, different screw elements can have different conveying pitches. The worker skilled in the art would be able to assemble an appropriate screw to achieve the optimum shear history and conveying efficiency to result in the desired final product.

[0065] As can be expected, all of the elements impart different levels of shear history and conveying ability. These can be summarized in the following list of elements and their relative shear intensity:

[0066] Greatest Shear—Least Forward Conveying Efficiency

[0067] reverse pitch screw elements

[0068] reverse pitch kneading blocks

[0069] neutral kneading blocks

[0070] forward pitch kneading blocks

[0071] forward pitch screw elements

[0072] Least Shear—Most Forward Conveying Efficiency

[0073] In addition, wider kneading blocks imparts more shear to the melt. Also tighter pitch imparts more shear. A worker skilled in the art can combine all of these factors to design a screw that maximizes shear input without thermally degrading the product.

[0074] In co-rotating, twin screw extruders preferred for practicing the invention, the shear rate and residence time spent by extrudate in the high shear (generally the kneading) zones of the extruder is a complex interactive function of screw rotation speed (RPM) and extruder screw/barrel geometry. However, the following general observations are relevant:

[0075] For a given geometry the shear rate increases in direct proportion to screw speed and narrowing of the clearance between the tips of various screw elements and the extruder barrel (affected by the degree of wear);

[0076] The residence time spent by the extrudate in the high shear zone is determined by the degree of fill of the extruder screw and the following interactive geometrical factors: 1) the width of the narrow clearance zone (the number and width of kneading block elements used in the screw design), 2.) the number of lobes on the screw elements—(increasing number of lobes increases the volume of material in the narrow clearance zone while simultaneously reducing the free volume of lower shear zone between the tip and root of the screw element); and 3.) the number and type of reverse (left-handed) elements included in the screw design). Suitable extruders useful for making thermoplastic polymer-biofiber composite material are available from Krupp Werner Pfleiderer, Leistritz, Davis Standard, and Entek Manufacturing, Inc.

[0077] Thermoplastic Polymer—Biofiber Composite Decking Planks

[0078] The preferred composite hollow decking plank includes an exterior wall or shell substantially enclosing a hollow interior. The interior can contain at least one structural web providing support for the tread surface. The web is typically shaped by the extrusion die and can take a variety of shapes with surface contours adapted to support assembly. The interior webs support the plank by distributing the applied load. The webs typically comprise a wall, post, support member, or other formed structural element, which increases compressive strength, torsion strength, or other structural or mechanical properties. Such structural webs connect the adjacent or opposing surfaces of the interior of the plank. More than one structural web can be placed to carry stress from surface-to-surface at the high stress locations of the application to protect the plank from crushing, torsional failure or general breakage.

[0079] After the plank is extruded and cut to length, any number of additional shaping processes can be applied to the plank. For example, the plank can have drilled apertures for passage of fasteners such as screws, nails, etc. Such passageways can be countersunk, metal line, or otherwise adapted to plank geometry or the composition of the fastener materials. The planks can be milled to introduce mating surfaces at the ends or edges thereof to facilitate rapid assembly with other components of the decking system having similar or different compositions with similarly adapted mating surfaces. The plank exterior can have surfaces adapted to an exterior trim and interior mating with trim pieces and other surfaces formed into the exposed sides of the structural member adapted to the installation of metal runners, wood trim parts, door runner supports, or other metal, plastic, or wood members commonly used in conjunction with a platform or deck.

[0080] Mechanical Properties

[0081] The minimum compressive strength for a weight bearing plank member must be at least 1500 pounds per square inch (psi), preferably 2000 psi as measured by ASTM D695. The compressive strength is typically measured in the direction that load is normally placed on the plank. The Young's modulus of the plank in the extrusion direction should be about at least 500,000 psi, preferably 800,000 and most preferably about 1×106 psi as measured by ASTM D3039.

[0082] Thermal Properties

[0083] We have found that the Coefficient of Thermal Expansion of the thermoplastic polymer-biofiber composite materials useful in practicing the invention is about 1.5×10−5 to 3.0×10−5 depending upon the proportions and homogeneity of the materials as measured by ASTM D696. The Heat Deflection Temperature is the temperature at which a standard test bar deflects a specified amount under a stated load. The composite used in the invention has a Heat Deflection Temperature of about 78 degrees Celsius at 1.82 megapascals and a Heat Deflection Temperature of about 105 degrees Celsius at 0.46 megapascals as measured by ASTM D648. The flash ignition temperature is the minimum temperature at which sufficient flammable gas is emitted to ignite momentarily upon application of a small external pilot flame. The Flash Ignition Temperature of the composite is about 410 degrees Celsius as measured by ASTM D1929. The Self-Ignition Temperature is the minimum temperature at which the specimen spontaneously ignites in the absence of a flame ignition source. The Self-Ignition Temperature of the composite is about 425 degrees Celsius as measured by ASTM D1929. The Flame Spread Index is the a number or classification indicating a comparative measure of surface burning behavior derived from observations made during the progress of the boundary of a zone of flame under defined test conditions. The Flame Spread Index of the composite is about 10 as measured by ASTM E84. The Average Flame Spread Index is a number indicating a comparative measure of surface flammability of materials using a radiant heat source under defined test conditions. The Average Flame Spread Index of the composite is about 22.7 as measured by ASTM E162.

[0084] Installation of the Decking System

[0085] The decking system of the invention can be assembled with a variety of known mechanical fastener techniques. Such techniques include screws, nails, and other hardware. When screws are used in assembly, the diameter of the screw head versus the width of the inter-plank spacing gap becomes an issue in some installation and repair situations. Therefore, it is generally preferable that the screw head diameter be less than inter-plank spacing. In installations utilizing long length planks, longitudinal expansion and contraction can be partitioned by fixedly attaching the plank to the support surface by “toe-screwing”, “toe-nailing”, or otherwise fixedly fastening the plank to the support structure. The low coefficient of thermal (humidity) expansion and structural strength of the thermoplastic polymer-biofiber composites, when coupled with partitioning of potential bucking inducing length changes, permits use very long length planks. The inventive decking installations envision constraining longitudinal movement of the planks at the points of fixed attachment thereby effectively partitioning environmentally induced length changes into zones adjacent the points of fixed attachment.

[0086] Components of the system can also be joined by use of: glue, or a melt fusing technique wherein a fused weld forms a joint between two decking components, or planks can be joined by inserts adapted to fit with the interior web structure of the hollow plank. The planks can be cut or milled to form conventional mating surfaces including 90 degree(s) angle joints, rabbit joints, tongue and groove joints, butt joints, etc. Such joints can be bonded using an insert placed into the hollow profile that is hidden when joinery is complete. Such an insert can be glued, thermally welded, or heat staked into place. The insert can be injection molded or formed from similar thermoplastics and can have a service adapted for compression fitting and secure attachment to the structural member of the invention. Such an insert can project from approximately 1 to 5 inches into the hollow interior of the structural member. The insert can be shaped to form a 90 degree(s) angle, a 180 degree(s) extension, or other acute or obtuse angle required in a deck assembly.

[0087] Further, non-load bearing components of the decking system can be assembled by gluing components together with a solvent, structural or hot melt adhesive. Solvent borne adhesives that can act to dissolve or soften thermoplastic present in the components and to promote solvent based adhesion or welding of the materials. In the welding technique, once the joint surfaces are formed, the surfaces of the joint can be heated to a temperature above the melting point of the composite material and while hot, the mating surfaces can be contacted in a configuration required in the assembled structure. The contacted heated surfaces fuse through an intimate mixing of molten thermoplastic from each surface. Once mixed, the materials cool to form a structural joint having strength typically greater than joinery made with conventional techniques. Any excess thermoplastic melt that is forced from the joint area by pressure in assembling the surfaces can be removed using a heated surface, mechanical routing, or a precision knife cutter.

[0088] Using these general assembly techniques, the deck or platform of the invention is typically constructed by installing deck planks on a support surface. Such support surfaces can often comprise a concrete surface, a wood framing, I-beam joist framing, a plywood subfloor on a frame support or any other suitable contact surface. The decking is often cut to appropriate length and laid on the surface. The anchor structures are then applied to engage the anchor flanges of the planking and fastened to the underlying support. Alternatively, the anchor structures can be installed on the installation surface and the plank can be then inserted into the anchors for appropriate assembly. Once a starter course of anchor structure or plank is installed, further anchor structures and planking can be added to the assembly until the deck surfaces are fully assembled. Should a surface require a length of plank longer than is available, the planks can be butt joined without connection or can be assembled using glue inserts or other conventional assembly techniques. Alternatively, the planks can be mitered appropriately and fitted to avoid butt joinery.

[0089] Once the entire deck system is installed, the deck surface can be appropriately treated, coated, painted or otherwise finished.

[0090] The various embodiments described above are provided by way of illustration only and should not be construed to limit the invention. Those skilled in the art to which the invention most closely pertains will readily recognize various modifications and changes that may be made to the present invention without strictly following the exemplary embodiments and applications illustrated and described herein, and without departing from the true scope of the present invention that is set forth in the following claims.