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Title:
LIGHTWEIGHT STRUCTURAL MEMBER
Document Type and Number:
WIPO Patent Application WO/2001/049483
Kind Code:
A1
Abstract:
A lightweight structural member (10, 24) suitable for load-bearing uses. The member has opposing ends (22), and a core (12) with a first surface extending between the opposing ends. The core comprises alternating veneer layers (18) and polymer layers (20), and the veneer layers each include at least one sheet of veneer. Additionally, a first laminated veneer lumber face (14 and 16) is bonded to at least a substantial portion of the first surface of the core. The member may include a second surface extending between the opposing ends, with a second laminated veneer lumber face bonded to at least a substantial portion of the second surface of the core.

Inventors:
BRIGHTWELL LIONEL
Application Number:
PCT/US2001/000502
Publication Date:
July 12, 2001
Filing Date:
January 03, 2001
Export Citation:
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Assignee:
TRUS JOIST MACMILAN A LTD PART (US)
International Classes:
B32B21/04; (IPC1-7): B32B5/14; B32B3/00; B32B7/12
Foreign References:
US5640812A1997-06-24
US5365705A1994-11-22
US4005239A1977-01-25
US3976526A1976-08-24
US3637459A1972-01-25
Attorney, Agent or Firm:
Heuser, Peter E. (Hartwell Dickinso, McCormack & Heuser Suite 200 520 S.W. Yamhill Street Portland OR, US)
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Claims:
I CLAIM:
1. A lightweight structural member, having opposing ends, comprising: a core with a top surface extending between the opposing ends, wherein the core comprises alternating veneer layers and polymer layers, and wherein each veneer layer comprises at least one sheet of a veneer; and a first laminated veneer lumber face bonded to at least a substantial portion of the top surface of the core.
2. The structural member of claim 1, wherein the polymer is a closedcell foam.
3. The structural member of claim 1, wherein the polymer is a polystyrene foam.
4. The structural member of claim 1, further comprising an adhesive disposed between the alternating veneer layers and polymer layers.
5. The structural member of claim 1, wherein the first laminated veneer lumber face is bonded to the core with an adhesive.
6. The structural member of claim 5, wherein the adhesive is a phenolic resin.
7. The structural member of claim 1, wherein the core includes a bottom surface, and further comprising a second laminated veneer lumber face bonded to the bottom surface of the core.
8. The structural member of claim 1, wherein the first laminated veneer lumber face has a longitudinal axis, and wherein each layer of the alternating veneer layers and polymer layers has a longitudinal axis, and wherein the longitudinal axes of the veneer layers and polymer layers are parallel to the longitudinal axis of the first laminated veneer lumber face.
9. The structural member of claim 1, wherein the core includes sides, and further comprising a first side piece and a second side piece extending the length of the structural member, so that the first side piece and second side piece are positioned perpendicular to the first laminated veneer lumber face and parallel to each other, and the first side piece and second side piece substantially cover the sides of the core.
10. The structural member of claim 9, wherein the first side piece and the second side piece are laminated veneer lumber.
11. The structural member of claim 9, wherein the first side piece and the second side piece are bonded to the core with an adhesive.
12. The structural member of claim 11, wherein each of the side pieces is comprised of at least three laminates, with one of the laminates disposed between the other two laminates and having at least a portion with its grain extending in a direction perpendicular to the grain in the two other laminates.
13. The structural member of claim 12, wherein the one laminate disposed between the other two laminates includes a central portion and two end portions, the central portion having its grain extending in a direction parallel to the other two laminates, the end portions having grains extending in a direction perpendicular to the grain in the two other laminates.
14. The structural member of claim 9,12 or 13, further comprising a protective end cap mounted to each end of the member.
15. The structural member of claim 9,12 or 13, further comprising a plastic protective end cap mounted to each end of the member.
16. A lightweight structural member, comprising: a first laminated veneer lumber piece; a plurality of layers of a polymer material, including a first layer and a last layer, wherein each layer of the polymer material is spaced apart from other layers of the polymer material, and wherein the first layer of the polymer material is bonded to the first laminated veneer lumber piece; a plurality of veneer layers, each veneer layer comprising at least one sheet of veneer, disposed between the layers of the polymer material, wherein each veneer layer has opposing faces, and wherein each face of each veneer layer is in contact with and bonded to the adjacent layers of the polymer material; a second laminated veneer lumber piece bonded to the last layer of the polymer material, with the resulting member including a top and a bottom surface extending between and perpendicular to the laminated veneer lumber pieces; a top side piece in the form of a plurality of veneers mounted to the top surface; and a bottom side piece in the form of a plurality of veneers mounted to the bottom surface.
17. The structural member of claim 16 wherein the side pieces are each formed of at least three veneers, with an inner, an outer and a central veneer, and wherein at least a portion of the central veneer includes a grain extending in a direction perpendicular to the grain of the inner and outer veneers.
18. The structural member of claim 16 wherein the side pieces are each formed of at least three veneers, with an inner, an outer and a central veneer, and wherein the central veneer includes a central portion and two end portions, with the end portions having a grain extending in a direction perpendicular to that of the central portion and that of the inner and outer veneers.
19. The structural member of claim 16, wherein the polymer material is a closedcell foam.
20. The structural member of claim 16, wherein the polymer material is a polystyrene foam.
21. The structural member of claim 16, wherein each veneer layer is bonded to the adjacent layers of polymer material with an adhesive.
22. A process for fabricating a woodbased structural member, comprising : gluing a plurality of veneers to one another to form a first wall; gluing a first layer of foam to the first wall; gluing at least one veneer to the foam; repeating the gluing of foam and at least one veneer a plurality of times; leaving a last glued veneer at the outer position thereof ; gluing at least one veneer to the lastglued veneer to complete the formation of a core blank; ripsawing the core blank through the plurality of veneers and foam layers in a direction perpendicular to the veneers and foam layers to form a plurality of foam/veneer cores; gluing a plurality of veneers to each side of at least one of the foam/veneer cores to form at least one structural member having sides defined by pluralities of veneers, with a foam/veneer core.
23. The process of claim 22, wherein the step of gluing a plurality of veneers to at least one foam/veneer core comprises simultaneously pressing the veneers to each other and to the foam/veneer core.
24. The process of claim 23, wherein the step of gluing a plurality of veneers to at least one foam/veneer core comprises selecting a first veneer, selecting a centrallydisposed veneer having a grain extending in a first direction parallel to the grain of the first veneer, selecting two end veneers, each having a grain extending in a second direction perpendicular to the first direction, selecting a third veneer having a grain extending in the first direction, and then mounting the veneers to each other and to the foam/veneer core, with the first veneer disposed against the foam/veneer core, the centrallydisposed veneer being disposed against a central portion of the first veneer, the two end veneers being disposed against end portions of the first veneer, and the third veneer being disposed against the centrallydisposed and end veneers.
25. The process of claim 22, further comprising the step of positioning a plurality of foam/veneer cores side by side prior to the step of gluing a plurality of veneers to at least one of the foam/veneer cores, and the step of gluing a plurality of veneers to at least one foam/veneer core comprises simultaneously gluing the plurality of veneers to the plurality of foam/veneer cores.
26. The process of claim 22, wherein the step of gluing a plurality of veneers to each side comprises laying a first veneer down, sequentially laying down a plurality of veneers over the first veneer, laying down at least one core blank on the veneers, sequentially laying down a plurality of veneers over the core blank to form an assembly, and then directing the formed assembly to a press for curing.
27. The process of claim 26, further comprising applying glue to the veneers or the core blank between each laying down step.
28. The process of claim 26 wherein a plurality of core blanks are laid down on the veneers, and subsequently the laid down veneers are laid down over the plurality of core blanks.
29. The process of claim 28, further comprising cutting between the core blanks to form individual structural members.
Description:
LIGHTWEIGHT STRUCTURAL MEMBER Background of the Invention The present invention relates to a lightweight, wood-based structural member with strength, weight and cost properties superior to solid sawn lumber.

Engineered lumber products have been used for many years to avoid the problems and limitations of solid sawn lumber. For instance, the dimensions in which sawn lumber can be produced are limited by the size of the trees available for production. Old growth timber has become increasingly unavailable due to forest depletions and decreased harvests, and as a result, younger and thinner trees are being used for lumber production. Additionally, sawn lumber is often dimensionally unstable, and may shrink or warp after production. Furthermore, defects such as knots and splits are often found in sawn lumber. To compensate for these defects, structural pieces such as planks and beams produced from sawn lumber must be cut to greater widths thicknesses than would be necessary with defect-free lumber. As a result, the pieces weigh more, and the manufacturing process uses more raw timber.

Many of the problems encountered with ordinary lumber have been overcome with engineered lumber products such as laminated veneer lumber, or LVL. LVL is similar to plywood in that it is made by laminating a sandwich of thin wood veneers together with glue. However, where the grain of each layer of veneer is oriented perpendicular to the grain of adjacent layers in plywood,

the grain of each veneer is oriented parallel to the long axis of the stock in LVL. This construction maximizes the strength of the material for beam edge or plank face loading. The moisture content of the veneers is set to the desired level before lamination, minimizing any post-lamination shrinkage caused by the drying of the veneer sheets. Furthermore, every second veneer sheet is laminated tight side up or down to minimize warping in the final product.

One of the major benefits of LVL over solid sawn lumber is the highly predictable nature of LVL. The laminating process disperses naturally occurring defects throughout the LVL material, rendering LVL pieces more structurally uniform than sawn lumber pieces. As a result, a member constructed of LVL is significantly stronger than an similarly-dimensioned member constructed from sawn lumber, and thinner and narrower pieces may be used for load-bearing purposes. A second benefit is that there is no size limitation imposed upon LVL members by the size of the raw trees, as the veneers may be joined together to make LVL stock of any length. Yet another benefit is that the LVL production processes waste far less raw timber than solid sawn lumber production processes. This makes the production and use of LVL products a more efficient use of raw materials than the production and use of solid sawn lumber. Because of these benefits, LVL has proven to be a popular material for many applications, including headers, beams, 1-joist flanges, and industrial products such as concrete forms and scaffold planks.

There are, however, certain drawbacks with LVL. For example, LVL cannot easily be fabricated in larger dimensions without warping or twisting during the manufacturing process. Even for those dimensions which do not actually warp during fabrication, a buildup of uneven pressures can result in subsequent cracking. Also, for certain applications such as scaffold planking, the weight of LVL can be a problem. This can become even more of a problem when a plank is exposed to rain and thus absorbs water.

There have been some prior attempts to develop hollow wood- based members, but these have been primarily for non load-bearing applications such as panels and doors where crushing will not be a problem. Even the addition of grids to provide internal structural support has not really resulted in a product which has sufficient structural integrity to be of use in rugged applications, such as scaffold planking.

Some hollow members have been constructed with a foam core.

While these members are relatively lightweight due to the low density of the foam, the foam offers little, if any, structural support, and the panels may crush if the panel face is exposed to a load. They are therefore typically used for thermal and acoustic insulation, rather than for load-bearing applications.

Thus, there remains a need for a lightweight structural member that is suitable for load-bearing purposes, and is lower in cost and absorbs less water than solid sawn lumber or solid engineered lumber members.

Summary of the Invention One aspect of the present invention provides a lightweight structural member. The member has opposing ends, and a core with a first surface extending between the opposing ends. The core comprises alternating veneer layers and polymer layers, and the veneer layers each include at least one sheet of veneer. Additionally, a first laminated veneer lumber face is bonded to at least a substantial portion of the first surface of the core.

Another aspect of the present invention provides a lightweight structural member, including a first piece of laminated veneer lumber with an upper face, a lower face and a longitudinal axis parallel to the upper and lower faces. A plurality of veneer layers, each with a longitudinal axis and opposing faces, are bonded to the first piece of laminated veneer lumber. Each veneer layer includes at least one sheet of veneer. The longitudinal axes of the veneer layers bonded to the first piece of laminated veneer lumber are parallel to the longitudinal axis of the first piece of laminated veneer lumber, and the opposing faces of the veneer layers are perpendicular to the upper face and lower face of the first piece of laminated veneer lumber. A plurality of polymer layers are dispersed between the veneer layers, completely filling the space between the veneer layers.

Yet another aspect of the present invention provides a lightweight core suitable for use as an interior of a structural member. The core includes a first laminated veneer lumber piece and a plurality of layers of a polymer

material, including a first layer and a last layer, wherein each layer of the polymer material is spaced apart from other layers, and wherein the first layer of the polymer material is bonded to the first laminated veneer lumber piece. A plurality of veneer layers, each veneer layer including at least one sheet of veneer, is disposed between the layers of the polymer material. Each veneer layer has opposing faces, and each face of each veneer layer is in contact with and bonded to the adjacent layers of the polymer material. Additionally, a second laminated veneer lumber member is bonded to the last layer of polymer material.

The advantages of the present invention will be understood more readily after a consideration of the drawings and the Detailed Description of the Preferred Embodiment.

Brief Description of the Drawings Fig. 1 is an isometric view of a lightweight structural member according to a first embodiment of the present invention.

Fig. 2 is an isometric view of a core blank from which core pieces may be cut for use in the lightweight structural member according to the first embodiment of the present invention.

Fig. 3 is an isometric view of a core blank with two core pieces cut from the blank.

Fig. 4 is a sectional view of a core piece taken along line 4-4 of Fig. 3, depicting a core piece before the first and second laminated veneer lumber face pieces have been bonded to the core piece.

Fig. 5 is a sectional view taken along line 5-5 of Fig. 1, depicting a lightweight structural member after the laminated veneer lumber face pieces have been bonded to the core piece.

Fig. 6 is a top plan view of one end of a second embodiment, after it has been prepared to receive a molded plastic end cap.

Fig. 7 is a side sectional view taken along line 7-7 of Fig. 6; Fig. 8 is a top plan view of one end of the second embodiment, with the plastic end cap in place.

Fig. 9 is a side sectional view taken along line 9-9 of Fig. 8; Fig. 10 is an isometric view of the first embodiment, with the second or center veneer of the first face piece glued in place.

Fig. 11 is an isometric view of the first embodiment corresponding to Fig. 10, except that the third or outer veneer of the first face piece has been glued in place.

Fig. 12 is a schematic representation of the laying-up process for fabricating the preferred embodiment.

Detailed Description of the Preferred Embodiments The present invention provides a novel lightweight structural member constructed with laminated veneer lumber, or LVL, that avoids the

problems of many known structural members. A first embodiment of the present invention is depicted in Fig. 1 and is indicated generally at 10. This structural member 10 has a core piece 12, a first face piece 14 and a second face piece 16. The length L of member 10 is typically greater than the width W. The thickness T of member 10 can be chosen to suit the strength and weight properties desired for a particular application.

In a typical application, the first and second face pieces 14 and 16 are formed of 3/8-inch thick LVL, while the distance between the first and second face pieces is one inch. This defines a one-inch space for core piece 12.

The core piece 12 is constructed of alternating layers of a veneer 18 and an expanded polymer 20. The side pieces 22 of the core piece 12 are made of LVL. The veneer layers 18 provide support for the center portions of the member. If ordinary hollow or foam-filled structural members are subjected to a load on the center portion of the face of the member, the face may deflect or even fail due to the lack of support. The addition of the thin, vertically aligned veneer layers 18 between the face pieces provides the support necessary to prevent the faces from deflecting, and in effect form a series of evenly-spaced I-beams extending the entire length of the member 10. Veneer layers 18 also combine with first and second face pieces 14 and 16 to increase torsional stiffness, reducing the tendency of member 10 to twist about its long axis when exposed to an unbalanced force. If a stronger member 10 is desired,

two or more veneer sheets (not shown) may be used for each veneer layer 18 instead of a single sheet.

Expanded polymer layers 20 provide lateral support for veneer layers 18. The application of a load to the face of member 10 may impose forces on veneer layers 18 that are out of the plane of the layers. In the absence of any lateral support, these forces may cause veneer layers 18 to buckle or fail.

The addition of expanded polymer layers 20 to the sides of veneer layers 18 provides the lateral support needed to prevent the veneer layers 18 from buckling. For maximum support, the expanded polymer layers 20 should extend fully between each veneer layer 18. Solid polymers may also be used instead of expanded polymers for layers 20, but they are heavier than the expanded polymers and thus would reduce the advantages of the lightweight core design. Either a closed or an open cell expanded polymer may be used for polymer layers 20. However, if the member is to be used in an application where it may be exposed to rain, a closed cell material is preferable to an open cell material. The preferred closed cell expanded polymer is foamed polystyrene, such as STYRAFOAM@.

The sides 22 of core piece 12 are normally made of pieces of LVL comprising multiple layers of veneers. The use of a thicker layer of material for sides 22 is advantageous because these layers greatly reinforce the light core against the effects of field rough handling and abuse.

Though a structural member according to this first embodiment of the present invention may be fabricated in any number of ways, an example manufacturing process will now be described. Member 10 is constructed by first manufacturing core piece 12, and then adding face pieces 14 and 16 to core piece 12. The core manufacturing process is illustrated in Figures 2 and 3.

Figure 2 shows a core blank at 24, from which individual core pieces may be cut. Core blank 24 is manufactured to be essentially the same length as the completed member. Though a small portion of the length of the core may be trimmed off in the final manufacturing steps, this portion is negligible. Thus, the same indicator L is used for the length of core blank 24 in Figure 2 and the length of member 10 in Figure 1. Similarly, core blank 24 is constructed to a thickness equal to the combined thickness of all of the cores 12 that are cut from it (see Fig. 3); thus, the thickness of core blank 24 is indicated as T', which is the combined thickness of all of the cores 12. It should, of course, be appreciated that the thickness T of member 10 in Fig. 1 includes the thickness of the added face pieces 14 and 16, which are normally 3/8-inch each, so thickness T is normally 1% inches. Core blank 24 has a width that corresponds to the desired width of member 10, so like member 10, its width is indicated with the letter W.

The first step in the manufacture of the core piece 12 is the assembly of core blank 24. The dimensional figures given in this example correspond to the construction of a core for a 1 3/4"x 9 1/4"x 16'structural

member suitable for use as a scaffold plank, but the same process may be used to construct a member with any dimensions. Before assembling the core blank from the individual layers, it may sometimes be necessary to assemble the veneer to be used in the core blank assembly process from two or more shorter pieces of veneer. To join two shorter pieces of veneer, scarfs with a 1 in 12 slope are cut into opposite ends of two 1/8"x 27"x 101"veneers. A resorcinol adhesive is applied, and the scarfed ends are matched and cured in a hot clamp at a temperature of about 350-400° F, with a cure time of around five seconds.

After curing, the resulting longer veneer piece is trimmed to a length of 16'1" and a width of 24 l/2." Once the veneer pieces for core blank 24 have been scarf jointed and cut to the correct size, core blank 24 may be constructed. Corresponding reference numbers are used to refer to like elements in Figs. 1 and 2. For example, veneer layer 118 in the core blank 24 corresponds to veneer layer 18 in member 10. Core blank 24 is made of alternating layers of 1/8"thick veneer 118 and 0.55" thick expanded polymer 120. Bottom layer 122 and top layer 122a of core blank 24 are 1"x 24l/2 x 16. 1' pieces of laminated veneer lumber.

These layers become the side pieces 22 of core piece 12 once core piece 12 is cut from core blank 24. To assemble core blank 24, first an adhesive is added to one surface of bottom layer 122. This adhesive, used between all layers of core blank 24, is a pressure sensitive hot melt glue. It serves to hold together the individual layers of core blank 24, and core piece 12 once it is cut from the

blank, until first and second face pieces 14 and 16 can be added to core piece 12. Next, a layer 120 of 0.55" thick expanded polymer of the same length and width as bottom layer 122 is placed on the adhesive-coated surface of bottom layer 122. Then, the exposed surface of expanded polymer layer 120 is coated with the same adhesive, and veneer layer 118 is added to this surface. Next, the exposed surface of veneer layer 118 is coated with adhesive, and another expanded layer 120 is added. Alternating layers of veneer 118 and expanded polymer 120 are added until the width W of core blank 24 approaches the desired width W of member 10. The last layer added is the LVL top layer 122a.

After top layer 122a is added, the entire core blank 24 is pressed together, for example by"nip-rolling", to ensure that each layer is in intimate contact with adjacent layers and that no voids exist in the structure.

Once core blank 24 has been assembled, individual core pieces may be cut from core blank 24 by ripping vertical, lengthwise portions of the blank as shown in Figure 3. In this figure, two core pieces, indicated at 12 and 26, have been cut from core blank 24, and dashed lines such as the one indicated at 28 represent additional cuts that may be made to remove more core pieces.

Figure 4 shows a sectional view of the finished core piece 12 taken along line 4-4 of Figure 3. Each of the alternating layers of veneer 18 and expanded polymer 20 are in complete contact with adjacent layers.

Similarly, both side pieces 22 are in full contact with the adjacent expanded

polymer layers. Furthermore, both the top surface 30 and the bottom surface 32 of the core piece are relatively smooth and level. This ensures that the edges of each veneer layer 18 will be in good contact with face pieces 14 and 16 of the completed structural member, and all expanded polymer layers 20 will completely fill the voids between veneer layers 18.

Figure 5 is a sectional view of a completed structural member taken along line 5-5 of Figure 1. The lamination of the individual layers of veneer to form LVL face pieces 14 and 16 occurs simultaneously with the bonding of the face pieces to core piece 12. The way this is typically done is by first laying up the veneers with the core piece and then simultaneously pressing the entire structural member 10 together to cure the thermosetting glue. This lay up is schematically shown in Fig. 12. Thus, a first veneer 16a (the outer-most veneer of face piece 16) is first laid up and a coat of phenolic resin or other glue is applied to its upper face. Then the first three-piece veneer 16b is laid over veneer 16a and glue is applied to it. The inner-most veneer 16c is then positioned over veneer 16b, glue is applied to it, and core piece 12 is laid down.

After glue is applied to core piece 12, veneers 14a, 14b and 14c are sequentially laid up as with veneers 16a, b and c.

The assembly is then passed to a microwave press where approximately 150-200 psi of pressure is applied for about 2 minutes, at a temperature of between 160° and 170° F. The temperature cannot be much higher than 170° F. or the polystyrene foam 20 may begin to degrade.

Alternatively, but less desirably, a conventional press may be used without microwave assist. In that event curing is likely to take about 8 hours.

One real advantage of the preferred embodiment is that the structural integrity of core piece 12 is such that it can withstand these curing pressures. It is often difficult to fabricate 3/8 inch LVL without warping or other deformation, and the simultaneous assembly with the core piece facilitates the fabrication of such LVL.

To expedite the assembly process, five core pieces 12 are typically assembled side by side (with sides 22 positioned adjacent a side of an adjacently-positioned core piece), although in Fig. 12 only one such core piece has been depicted. Once the glue has been cured, structural members 10 are thus formed by sawing through side pieces 14 and 16 at the edges where the core pieces were positioned side by side. After curing, minor shaping steps are used to smooth the edges of member 10 to the desired configuration, such as that shown in Fig. 5, and to reduce its dimensions to those desired.

In the preferred embodiment, an end cap 40, shown in Figs. 8 and 9, is provided at each end of member 10 to prevent the ends from splitting or otherwise being damaged as a result of being dropped on their ends. End caps 40 are normally fabricated of a polyurethane composition formed by combining a polyol and an isocyanate in amounts effective to form a polyurethane.

Typically castor oil is used as a polyol, and the isocyanate is polymeric methane diphenol diisocyanate. Calcium carbonate is used as a filler. A chain extender

such as ethylene glycol may also be added, as may a cross-linking agent such as glycerin. If a pigment is desired, titanium dioxide may be used. In some applications it may be desirable to use a dessicant to control foaming. A typical mixture could be comprised of the following materials in these percentages by weight: Slurry (about 78% of mixture by weight) About 61 parts by weight calcium carbonate About 2 parts by weight ethylene glycol About 33.5 parts by weight castor oil About 2 parts by weight glycerin About 1.3 parts by weight titanium dioxide About 0.1 parts by weight desiccant About 0.1 parts by weight organotin Isocyanate (about 22% of mixture by weight) polymeric methane diphenol diisocyanate To form end caps 40, the castor oil is first mixed with the calcium carbonate to form a slurry with the other components. The castor oil may be heated to reduce its viscosity prior to mixing. The slurry may then be heated to about 110° F and the isocyanate is added. This mixture is then poured into a mold (not shown) mounted on the end of a member 10, and it is cured, thus forming an end cap 40.

End caps 40 are applied to each of the members 10 by first cutting each of the ends to a configuration shown in Fig. 6, and then using a router to chamfer or bevel the end edges as shown at 42 in Fig. 7. Each of the ends is then clamped to form an open mold (not shown), and the plastic material is poured in to form in the depicted shape, identified with the numeral 44 in Fig.

8. Other forms of end caps may be used, or they may be deleted altogether. The depicted and described end cap 40 is, however, the preferred embodiment.

It has also been determined that there are certain advantages in providing a cross-wise laminate adjacent the ends of the LVL side pieces 14 and 16, as depicted in Figs. 10 and 11. Fig. 10 shows side piece 14', before the top or outer laminate or veneer of the three-laminate LVL has been applied.

The cross-laminate, shown at 46, is typically about 18 inches wide. Grain lines have been schematically shown at 48 so that it can be seen that the grain is running cross-wise in laminate 46. Fig. 11 shows the side piece 14'after the third or outer laminate or veneer has been applied over the top of the center laminate.

There are several advantages in providing cross-laminate adjacent the ends of the members. Any member which is formed of wood will have some tendency to swell when it absorbs moisture. While the absorption of the preferred embodiment is certainly less than that of solid sawn lumber or solid LVL, there still may be some absorption in certain wet environments. If the grain in the LVL extends the same lengthwise direction, swelling will tend to

take place across the width of the plank. This is because swelling tends to take place in a direction transverse to the grain. If the ends are covered with end caps 40, splitting may take place because the wood covered by the end caps is held in place and therefore will not be permitted to swell, while the wood immediately adjacent the end caps will swell. By using a cross-wise extending center laminate 46, swelling is kept to a minimum because that laminate 46 will not swell in the cross-wise direction. If there is any swelling of laminate 46, it will tend to take place in the lengthwise direction of the member 10, which will be held from swelling by the outer two laminates. While the term"laminated veneer lumber"normally includes laminates having grains extending the same direction, as used herein the term encompasses a design in which ends of one of the laminates has portions having a grain extending perpendicular to the grain of the other laminates.

For the foregoing reasons, the presently preferred embodiment includes cross wise laminate 46, as well as end caps 40. It may be that in some applications the crosswise laminate is provided for the entire length of member 10, but that is not the preferred version.

Although the invention has been disclosed in its preferred forms, the specific embodiments thereof as disclosed and illustrated herein are not to be considered in a limiting sense, because numerous variations are possible.

The subject matter of the invention includes all novel and non-obvious combinations and subcombinations of the various elements, features, functions,

and/or properties disclosed herein. No single feature, function, element or property of the disclosed embodiments is essential. The following claims define certain combinations and subcombinations of features, functions, elements, and/or properties that are regarded as novel and nonobvious. Other combinations and subcombinations may be claimed through amendment of the present claims or presentation of new claims in this or a related application.

Such claims, whether they are broader, narrower, equal, or different in scope to any earlier claims, also are regarded as included within the subject matter of the invention.