CA1185413A - Elongate structural members comprised of composite wood material - Google Patents
Elongate structural members comprised of composite wood materialInfo
- Publication number
- CA1185413A CA1185413A CA000403136A CA403136A CA1185413A CA 1185413 A CA1185413 A CA 1185413A CA 000403136 A CA000403136 A CA 000403136A CA 403136 A CA403136 A CA 403136A CA 1185413 A CA1185413 A CA 1185413A
- Authority
- CA
- Canada
- Prior art keywords
- elongated
- panels
- flakes
- wood flakes
- longitudinal axis
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C3/00—Structural elongated elements designed for load-supporting
- E04C3/02—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces
- E04C3/12—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces of wood, e.g. with reinforcements, with tensioning members
- E04C3/127—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces of wood, e.g. with reinforcements, with tensioning members with hollow cross section
Landscapes
- Engineering & Computer Science (AREA)
- Architecture (AREA)
- Life Sciences & Earth Sciences (AREA)
- Wood Science & Technology (AREA)
- Civil Engineering (AREA)
- Structural Engineering (AREA)
- Dry Formation Of Fiberboard And The Like (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An elongated structural member has a longitudinal axis and is comprised of a plurality of elongated panels having lateral edges, the panels being arranged to form an elongated central cavity with lateral edges of adjacent panels being fixedly joined together. The elongated panels are each comprised of a plurality of wood particles intermixed with a suitable binder and compressed to form a densified product. A
rigid foam material is provided filling at least a portion of the elongated central cavity thereby for reinforcing the elongated structure, the rigid foam material also being bonded to the inwardly facing surfaces to further reinforce the elongated structure.
An elongated structural member has a longitudinal axis and is comprised of a plurality of elongated panels having lateral edges, the panels being arranged to form an elongated central cavity with lateral edges of adjacent panels being fixedly joined together. The elongated panels are each comprised of a plurality of wood particles intermixed with a suitable binder and compressed to form a densified product. A
rigid foam material is provided filling at least a portion of the elongated central cavity thereby for reinforcing the elongated structure, the rigid foam material also being bonded to the inwardly facing surfaces to further reinforce the elongated structure.
Description
S L?~ 13 FIELD OF THE INVENTION
The present invention relates to the construction of elongated structural members such as utility poles, pilings, cross-ties and cross-arms from composite wood material, such structural members having strength properties as good as or better than similar structures comprised of high grade solid wood and such structural members being manufactured at a cost making them competitive with such solid wood structures.
RELATED APPLICATION_ Attention is directed to the related Canadian Patent Application Serial No. 402,715~ filed May 11, 1932 and titled "Elongated Structural Members Comprised of Composite Wood Material"; and the U.S. Lund et al. Patent No. 4,241,133, issued December 23, 19~0, and titled "Structural Members of Composite Wood Material and Process for Making Same", both the patent application and patent referred to above being assigned to the assignee of the present invention.
BACKGROUND PRIOR ART
Various types of structural members, such as utility poles, construction pilings and structural sd~
beams are commonly made from solid wood. Continuing demand for solid wood poles and beams, increasing production cost, limited supplies of suitable species in all sizes required, and competition for the wood for other products has caused a growing need for substitute materials from which th~ abo~e described structural members can be made. These substitute materials should be adequate in supply and have a low stable cost.
While comminuted wood materials have been found to be useful in other applications such as in the construction of panels or other planar structural wood products, the prior art does not suggest a suitable or commercially viable means for producing a high strength elongated structural member from such wood material.
Attention is directed to the U.S. Elmendorf Patent No. 3,164,511, issued January 5, 1365; the U.S.
Holman Patent No. 4,122,236, issued October 24, 1978;
the U.S. Shoemaker et al. Patent No. 3,930,110, issued December 30, lg75; the U.S. Millerbernd Patent No.
3,365,778, issued January 30, 1968; and the U~S.
Sahlberg Patent No. 2,230,628, issued February 4, 1941.
Attention is also directed to the U.S.
Wendworth Patent No. 902,631, issued November 3, 1908;
the UOS. Hoyle Patent No. 2,834,073, issued May 13, 1958; the U.S. Hoyle Patent No. 2,824,342, issued February 25, 1958; and the U.S. De Walt Patent No.
6~8,603.
Attention is further directed to German Patent 904,693, issued June 1954; the U.S. Overton Patent 3,570,376, issued March 16, 1971, and the U.S. Turnbull Patent 3,446,692, issued May 27, 1969.
S~ARY OF THE INVENTION
The present invention may be considered as an elongated structural member having a longitudinal a~is and comprising a plurality of elongated panels having lateral edges, the panels being arranged to form an elongated structure, and the panels each having an inwardly facing surface, the inwardly facing surfaces of the panels defining an elongated central cavity, the lateral edges of adjacent panels being fixedly joined together, and the elongated panels each being comprised of elongated wood flakes intermixed with a suitable binder and compressed to form a densified product, the elongated wood flakes each having a longitudinal axis, and the wood flakes having a length of about 0.5 inches to about 3.5 inches, a width of about 0.1 to 0.5 inches, and a thickness o~ about 0.Ql to 0.05 inches, the grain direction of the wood flakes being aligned substantially parallel with the longitudinal axes of the wood flakes, and the wood flakes forming each of the panels being generally planar and lying in parallel planes parallel to the inwardly facing surfaces, the wood flakes being aligned with their longitudinal axes parallel to the longitudinal axis of the elongated member and such that the grain direction of the flakes in panels is parallel to the longitudinal a~is of the elongated member~
Furthermore, the present invention relates to a method for forming an elongated structural member comprising the steps of forming a plurality of elongated planar panels, each of the panels being comprised of elongated wood flakes mixed with a binder and compressed to form a densified product, the wood flakes being a length of about 0.5 inches to about 3~5 sd/~
~s~ l~
inches, a width of about 0.1 to 0.5 inches, and a thi.ckness of ~out 0.01 to 0.05 inches, each of the panels having a major plane and a longitudinal axis and the wood flakes comprising each such panel being planar and lying in planes parallel to the major plane of that panel, and the wood flakes having a longitudinal axis, the grain direction of the wood flakes being parallel to the longitudinal axis of the flakes~ and the longitud.inal a~es of the flakes being parallel to the longitudinal axis of the panel, fixedly joining the panels together to form an elongated composite member having an elongated central cavity, the panels being joined together with the lateral edges of each of the panels being bonded to a lateral edge of an adjacent panel, and filling at least a portion of the central cavity with a rigid foam material.
Various other features and advantages of the invention will become apparent by reference to the following description and claims and by reference to the drawings.
sd/~
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. l is an elevation view of an elongated structural member embodying the present invention.
Fig. 2 is a cross section view taken along line ~-2 in Fig. 1.
Fig. 3 is a cross section elevation view of the elongated structural member shown in Fig. l.
Fig. 4 is an enlarged partial cross-section perspective view o the composite wood material comprising the elongated structural member of Fig. l.
Fig. 5 is a perspective view showing an alternative embodiment of an elongated structural member embodying the invention.
Before describing the preferred embodiments of the invention in detail, it is to be understood that the invention is not limited in its application to the details of cons-truction or arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminoloyy employed herein is for the purpose of description and should not be regarded as limiting.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Illustrated in Fig. l is an elongated structural member 10 comprised of composite wood material and defining an elongated hollow tapered pole of the type used as a utility pole, piling, or in another similar application.
The elongated structural member 10 is constructed of a plurality of elongated composite panels or boards 14, the panels 14 being comprised of composite wood material. In the construction shown in Figs. 1-3, the panels 14 are illustrated as each being comprised of a plurality of planar layers 18 of composite wood material laminated together, the layers 18 being secured together by an interface adhesive 19.
The panels 14 so formed are miter cut or otherwise cut to shape and combined to form a composite wood pole.
In the illustrated construction, the respective elongated lateral edges 20 of the panels 14 are joined together by an interface adhesive to thereby join the panels 14 in an octagonal shape as illustrated in Fig.
The present invention relates to the construction of elongated structural members such as utility poles, pilings, cross-ties and cross-arms from composite wood material, such structural members having strength properties as good as or better than similar structures comprised of high grade solid wood and such structural members being manufactured at a cost making them competitive with such solid wood structures.
RELATED APPLICATION_ Attention is directed to the related Canadian Patent Application Serial No. 402,715~ filed May 11, 1932 and titled "Elongated Structural Members Comprised of Composite Wood Material"; and the U.S. Lund et al. Patent No. 4,241,133, issued December 23, 19~0, and titled "Structural Members of Composite Wood Material and Process for Making Same", both the patent application and patent referred to above being assigned to the assignee of the present invention.
BACKGROUND PRIOR ART
Various types of structural members, such as utility poles, construction pilings and structural sd~
beams are commonly made from solid wood. Continuing demand for solid wood poles and beams, increasing production cost, limited supplies of suitable species in all sizes required, and competition for the wood for other products has caused a growing need for substitute materials from which th~ abo~e described structural members can be made. These substitute materials should be adequate in supply and have a low stable cost.
While comminuted wood materials have been found to be useful in other applications such as in the construction of panels or other planar structural wood products, the prior art does not suggest a suitable or commercially viable means for producing a high strength elongated structural member from such wood material.
Attention is directed to the U.S. Elmendorf Patent No. 3,164,511, issued January 5, 1365; the U.S.
Holman Patent No. 4,122,236, issued October 24, 1978;
the U.S. Shoemaker et al. Patent No. 3,930,110, issued December 30, lg75; the U.S. Millerbernd Patent No.
3,365,778, issued January 30, 1968; and the U~S.
Sahlberg Patent No. 2,230,628, issued February 4, 1941.
Attention is also directed to the U.S.
Wendworth Patent No. 902,631, issued November 3, 1908;
the UOS. Hoyle Patent No. 2,834,073, issued May 13, 1958; the U.S. Hoyle Patent No. 2,824,342, issued February 25, 1958; and the U.S. De Walt Patent No.
6~8,603.
Attention is further directed to German Patent 904,693, issued June 1954; the U.S. Overton Patent 3,570,376, issued March 16, 1971, and the U.S. Turnbull Patent 3,446,692, issued May 27, 1969.
S~ARY OF THE INVENTION
The present invention may be considered as an elongated structural member having a longitudinal a~is and comprising a plurality of elongated panels having lateral edges, the panels being arranged to form an elongated structure, and the panels each having an inwardly facing surface, the inwardly facing surfaces of the panels defining an elongated central cavity, the lateral edges of adjacent panels being fixedly joined together, and the elongated panels each being comprised of elongated wood flakes intermixed with a suitable binder and compressed to form a densified product, the elongated wood flakes each having a longitudinal axis, and the wood flakes having a length of about 0.5 inches to about 3.5 inches, a width of about 0.1 to 0.5 inches, and a thickness o~ about 0.Ql to 0.05 inches, the grain direction of the wood flakes being aligned substantially parallel with the longitudinal axes of the wood flakes, and the wood flakes forming each of the panels being generally planar and lying in parallel planes parallel to the inwardly facing surfaces, the wood flakes being aligned with their longitudinal axes parallel to the longitudinal axis of the elongated member and such that the grain direction of the flakes in panels is parallel to the longitudinal a~is of the elongated member~
Furthermore, the present invention relates to a method for forming an elongated structural member comprising the steps of forming a plurality of elongated planar panels, each of the panels being comprised of elongated wood flakes mixed with a binder and compressed to form a densified product, the wood flakes being a length of about 0.5 inches to about 3~5 sd/~
~s~ l~
inches, a width of about 0.1 to 0.5 inches, and a thi.ckness of ~out 0.01 to 0.05 inches, each of the panels having a major plane and a longitudinal axis and the wood flakes comprising each such panel being planar and lying in planes parallel to the major plane of that panel, and the wood flakes having a longitudinal axis, the grain direction of the wood flakes being parallel to the longitudinal axis of the flakes~ and the longitud.inal a~es of the flakes being parallel to the longitudinal axis of the panel, fixedly joining the panels together to form an elongated composite member having an elongated central cavity, the panels being joined together with the lateral edges of each of the panels being bonded to a lateral edge of an adjacent panel, and filling at least a portion of the central cavity with a rigid foam material.
Various other features and advantages of the invention will become apparent by reference to the following description and claims and by reference to the drawings.
sd/~
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. l is an elevation view of an elongated structural member embodying the present invention.
Fig. 2 is a cross section view taken along line ~-2 in Fig. 1.
Fig. 3 is a cross section elevation view of the elongated structural member shown in Fig. l.
Fig. 4 is an enlarged partial cross-section perspective view o the composite wood material comprising the elongated structural member of Fig. l.
Fig. 5 is a perspective view showing an alternative embodiment of an elongated structural member embodying the invention.
Before describing the preferred embodiments of the invention in detail, it is to be understood that the invention is not limited in its application to the details of cons-truction or arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminoloyy employed herein is for the purpose of description and should not be regarded as limiting.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Illustrated in Fig. l is an elongated structural member 10 comprised of composite wood material and defining an elongated hollow tapered pole of the type used as a utility pole, piling, or in another similar application.
The elongated structural member 10 is constructed of a plurality of elongated composite panels or boards 14, the panels 14 being comprised of composite wood material. In the construction shown in Figs. 1-3, the panels 14 are illustrated as each being comprised of a plurality of planar layers 18 of composite wood material laminated together, the layers 18 being secured together by an interface adhesive 19.
The panels 14 so formed are miter cut or otherwise cut to shape and combined to form a composite wood pole.
In the illustrated construction, the respective elongated lateral edges 20 of the panels 14 are joined together by an interface adhesive to thereby join the panels 14 in an octagonal shape as illustrated in Fig.
2.
As shown in Fig. 3 the panels 14 may be comprised of a plurality of planar composite wood material layers 18 of successively increasing lengths such that the thickness of each of the panels 14 tapers from the base portion of the pole 14 toward the upper end of the pole, the portions of the elongated panels 14 at the base portion of the illustra~ed pole 10 having a thickness of three layers 18 of composite material and the upper portions of the panels 14 being comprised of a sin~le layer 18 of composite wood material. In other embodiments of the invention the panels 14 can comprise a single layer 18 of composite wood material, those panels being tapered in thickness such that when assembled they can form a pole as illustrated in Fig. 1.
Referring more specifically to the material composition of the panels 14, in the preferred embodiment of the invention, they are comprised of composite wood material formed from wood flakes 22 (Fig. 4) intermixed with a suitable binder material and compressed in a suitable press. Generally, the compressed product is formed by constructing a loosely felted mat of wood flakes 22, the wood flakes having been mixed with a binder material. More particularly, the mat is formed by disbursing generally planar wood flakes 22 such that the planes of the flakes 22 are generally parallel to the major plane of the mat and with substantially all of the flakes being aligned as illustrated in Fig. 4 such that the longitudinal axes of the flakes 22 are mutually parallel and parallel to the longitudinal axis of the elongated structural component to be formed. The mat is then compressed to form the dense elongated planar layers 18, the mat being compressed in generally the same manner and using the same operating conditions as are used in the manufacture of conventional particleboard.
In the pre~erred form of the invention, at least 90% of the wood flakes 22 are to be aligned in the planar layers 18 so as to be parallel to the longitudinal axis of the elongated panel 14 or the layer 18 being formed. The planar flakes 22 also lie in planes which are parallel to the major plane of the layer comprised of those flakes. `The flakes 22 each have a grain direction extending generally parallel to the longitudinal axis of the flakes. Alignmen~ of the flakes 22 also results in alignment of the wood grain of the flakes with the longitudinal axis of the structural member or pole 10 in a manner similar to a solid wood pole. In fact, the pole 10 of the invention may have a more uniform grain direction than that of a solid wood pole since conventional poles will normally have innate grain inconsistencies and knots.
Wood flakes 22 of the type forming the layers 18 are conveniently formed using a conventional ring flaker or a round wood flaker to commutate small logs, branches, or rough pulp wood and form suitably shaped flakes 22. In the production of the elongated panels 14, it is preferred that the wood flakes 22 have a length of from 0O5 to 3.5 inches, a width of 0.1 to 0.5 inches, and a thickness of .01 to .05 inches.
Additionally, it is preferred that the ratio of the average length of the flakes to the average width of the flakes be from about 4:1 to about 10:1~ An example of a convenient flake geometry is the use of flakes having a length of approximately 1.6 inches, a thickness oE approximately .02 inches, and a wid~h of 0.2 to 0.5 inches.
A convenient binder for use in the manufacture of the panels 14 can comprise phenol-formaldehyde or an isocyanate adhesive. In one preferred form of the invention the binder may comprise an organic polyisocyanate having at least two active isocyanate groups per molecule. It has been found that an 8%
resin solids composition of such binder, based on oven-dry flake weight gives satisfactory strength properties to the resulting elongated structureO To maximize coverage of the flakes, the binder may be applied by spraying droplets of the binder in liquid form onto the flakes.
To preserve the elongated structuraL members from decay due to decay fungi and insects it is also desirable to further include a suitable fungicide in the composite wood mat. The wood flakes may also be treated or mixed with a suitable biocide such as pentachlorophenol, creosote, chromated copper arsenate and ammoniacal copper arsenate.
While the elongated pole 10 is shown as having an octagonal cross-sectional configuration, it should be understood that the ~ole could alternatively have other cross-sectional configurations such as a circular or a hexagonal cross-sectional configuration.
While the respective panels 14 of the elongated pole 10 are conveniently fixedly joined together at their elongated lateral edges 20 by any high strength adhesive such as resorcinol-formaldehyde, an isocyanate adhesive, or other adhesive suitable for bonding wood products, it is contemplated that the panels 14 could also be joined together by splines or by a combination of splines and an adhesive.
The pole 10 also includes means for providing structural reinEorcement for the panels 14 forming the pole and for further bonding the panels 14 together.
This means includes a foam material 24 poured or injected into the central elongated cavity 26 formed by the panels, the foam material 24 filling at least a portion of the elongated cavity 26. In a preferred form of the invention, the Eoam material 24 can conveniently comprise a foam-in-place rigid polyurethane foam which can be poured into the elongated central cavity 26 as a pourable liquid and which will then foam so as to form a rigid core filling the pole. The rigidity of the polyurethane foam core provides structural support for the elongate structure formed by the panels 14, and the polyurethane foam will also form an adhesive bond with the inner planar surfaces 28 of the panels 14 and will thus act as an additional means for bonding the panels 14 together and for preventing them from separating. An example of a suitable polyurethane foam is BAYT~ERM B51 produced by Mobay Chemical Corporation of Pittsburgh, Pennsylvania~
As is conventional, the polyurethane foam is made by mixing two liquid components~ whereupon the liquid material foams and cures at room temperature to form a rigid foam ~. While the density of the resultant rigid polyurethane foam can be varied in a conventional manner by varying the quantities of the two components combined, it has been found that a suitable density is 2 lbs/ft3. On the other hand, the rigidity of the foam and the reinforcing strength of the foam can be increased by increasing the density of the foam used.
For e~ample, a pole having increased strength may be produced by employing foam having a density of 5 lbs/ft3, but the expense of the pole increases due to the increase in the amount of foam material used.
One of the features of the employment of polyurethane foam material in the elongated cavity 26 is that it has a closed cell structure and thereby does not readily absorb moisture and provides an effective barrier to movement of moisture in the pole in~erior.
While the rigid foam material 24 has been described as comprising polyurethane, in other ~ ~S~l~
embodiments, the foam material could comprise other suitable foam-in-place materials. It is preferred, however, that the material have the properties of inhibiting the movement of moisture into the pole, and that it so form a bond with the panels to thereby provide structural rigidity or reinforcement to the pole. It is also preferred that the foam material be a rigid foam rather than a flexible foam so that the rigid foam provides structural support for the pole.
In a pre~erred form of the invention it is also desirable that the foam material selected have the property of curing at room temperature. Though other foam materials can be used, manufacturing costs can be reduced if heating of the foam material to effect curing can be avoided. In other alternative forms, ~iller materials such as wood chips, saw dust, wood strands or the like could also be mixed into the liquid material poured into the cavity 26 to form the rigid foam.
While in the illustrated embodiment the foam material could fill only the upper and lower ends of the elongated central cavity, in other arrangements the foam material could fill the entire central elongated cavity 26. In the illustrated construction, foam material 24 in the lower end of the pole lO will be particularly effective for inhibiting movement of moisture into the pole. The foam material 24 in the upper end o~ the pole lO provides reinforcement of that end of the pole which is intended to support utility pole cross~arms or the like.
Illustrated in Fig. 5 is an alternative embodiment of an elongated structural member embodying the invention. The elongated structural member 40 shown there comprises a hollow elongated cross-arm of the type commonly employed with utility poles and used to support telephone lines or power lines. ~ore particularly, the cross-arm 40 is comprised of four planar elongated panels 42 each comprised of composite wood material produced in the manner described above and having a construction as shown in Fig. 4. The elongated panels 42 are fixedly joined together at their interfaces 44 by a suitable adhesive of the type previously described. It should be understood that the panels 42 could also be secured together by other suitable joining means.
As in the case of the elongated hollow pole shown in Figs. 1 3, the elongated panels 42 of the cross-arms 40 are comprised of elongated wood flakes 22 aligned such that substantially all of the flakes are positioned with their longitudinal axes parallel to the longitudinall axis of the elongated panels 42 and with the generally planar flakes 22 oriented so as to define planes substantially parallel to the major plane of the elongated panel defined by the flakes.
As in the case of the elongated pole 10, means are also provided for filling at least a portion of the elongated central cavity 46 of the cross-arm, the means for filling also functioning to provide structural reinforcement or support for the elongated panels 42 forming the cross-arm and to provide means for further bonding the panels 42 together~ The means for filling includes a rigid foam material 48 which can be poured or injected into the central elongated cavity 46 defined by the elongated panels. It is preferred that the foam material 48 have the property of forming an adhesive bond with the internal surfaces 50 of the panels as previously described so that the internal foam material 48 will bond the panels together. As previously describedl one preerred foam material having this property and also providing structural rigidity is a rigid polyurethane foam.
The rigid foam material is placed in the cross-arm by positioning the cross-arm vertically, whereupon the polyurethane foam can be poured in its liquid state into the cross-arm. This material will then foam-in-place to fill the elongated central cavity of the cross-arm and will cure to form a rigid core for the cross-arm. The polyurethane could also be injected into the cavity 46 using a conventional foam injection nozzle arrangement.
Various features of the invention are set forth in the following claims.
As shown in Fig. 3 the panels 14 may be comprised of a plurality of planar composite wood material layers 18 of successively increasing lengths such that the thickness of each of the panels 14 tapers from the base portion of the pole 14 toward the upper end of the pole, the portions of the elongated panels 14 at the base portion of the illustra~ed pole 10 having a thickness of three layers 18 of composite material and the upper portions of the panels 14 being comprised of a sin~le layer 18 of composite wood material. In other embodiments of the invention the panels 14 can comprise a single layer 18 of composite wood material, those panels being tapered in thickness such that when assembled they can form a pole as illustrated in Fig. 1.
Referring more specifically to the material composition of the panels 14, in the preferred embodiment of the invention, they are comprised of composite wood material formed from wood flakes 22 (Fig. 4) intermixed with a suitable binder material and compressed in a suitable press. Generally, the compressed product is formed by constructing a loosely felted mat of wood flakes 22, the wood flakes having been mixed with a binder material. More particularly, the mat is formed by disbursing generally planar wood flakes 22 such that the planes of the flakes 22 are generally parallel to the major plane of the mat and with substantially all of the flakes being aligned as illustrated in Fig. 4 such that the longitudinal axes of the flakes 22 are mutually parallel and parallel to the longitudinal axis of the elongated structural component to be formed. The mat is then compressed to form the dense elongated planar layers 18, the mat being compressed in generally the same manner and using the same operating conditions as are used in the manufacture of conventional particleboard.
In the pre~erred form of the invention, at least 90% of the wood flakes 22 are to be aligned in the planar layers 18 so as to be parallel to the longitudinal axis of the elongated panel 14 or the layer 18 being formed. The planar flakes 22 also lie in planes which are parallel to the major plane of the layer comprised of those flakes. `The flakes 22 each have a grain direction extending generally parallel to the longitudinal axis of the flakes. Alignmen~ of the flakes 22 also results in alignment of the wood grain of the flakes with the longitudinal axis of the structural member or pole 10 in a manner similar to a solid wood pole. In fact, the pole 10 of the invention may have a more uniform grain direction than that of a solid wood pole since conventional poles will normally have innate grain inconsistencies and knots.
Wood flakes 22 of the type forming the layers 18 are conveniently formed using a conventional ring flaker or a round wood flaker to commutate small logs, branches, or rough pulp wood and form suitably shaped flakes 22. In the production of the elongated panels 14, it is preferred that the wood flakes 22 have a length of from 0O5 to 3.5 inches, a width of 0.1 to 0.5 inches, and a thickness of .01 to .05 inches.
Additionally, it is preferred that the ratio of the average length of the flakes to the average width of the flakes be from about 4:1 to about 10:1~ An example of a convenient flake geometry is the use of flakes having a length of approximately 1.6 inches, a thickness oE approximately .02 inches, and a wid~h of 0.2 to 0.5 inches.
A convenient binder for use in the manufacture of the panels 14 can comprise phenol-formaldehyde or an isocyanate adhesive. In one preferred form of the invention the binder may comprise an organic polyisocyanate having at least two active isocyanate groups per molecule. It has been found that an 8%
resin solids composition of such binder, based on oven-dry flake weight gives satisfactory strength properties to the resulting elongated structureO To maximize coverage of the flakes, the binder may be applied by spraying droplets of the binder in liquid form onto the flakes.
To preserve the elongated structuraL members from decay due to decay fungi and insects it is also desirable to further include a suitable fungicide in the composite wood mat. The wood flakes may also be treated or mixed with a suitable biocide such as pentachlorophenol, creosote, chromated copper arsenate and ammoniacal copper arsenate.
While the elongated pole 10 is shown as having an octagonal cross-sectional configuration, it should be understood that the ~ole could alternatively have other cross-sectional configurations such as a circular or a hexagonal cross-sectional configuration.
While the respective panels 14 of the elongated pole 10 are conveniently fixedly joined together at their elongated lateral edges 20 by any high strength adhesive such as resorcinol-formaldehyde, an isocyanate adhesive, or other adhesive suitable for bonding wood products, it is contemplated that the panels 14 could also be joined together by splines or by a combination of splines and an adhesive.
The pole 10 also includes means for providing structural reinEorcement for the panels 14 forming the pole and for further bonding the panels 14 together.
This means includes a foam material 24 poured or injected into the central elongated cavity 26 formed by the panels, the foam material 24 filling at least a portion of the elongated cavity 26. In a preferred form of the invention, the Eoam material 24 can conveniently comprise a foam-in-place rigid polyurethane foam which can be poured into the elongated central cavity 26 as a pourable liquid and which will then foam so as to form a rigid core filling the pole. The rigidity of the polyurethane foam core provides structural support for the elongate structure formed by the panels 14, and the polyurethane foam will also form an adhesive bond with the inner planar surfaces 28 of the panels 14 and will thus act as an additional means for bonding the panels 14 together and for preventing them from separating. An example of a suitable polyurethane foam is BAYT~ERM B51 produced by Mobay Chemical Corporation of Pittsburgh, Pennsylvania~
As is conventional, the polyurethane foam is made by mixing two liquid components~ whereupon the liquid material foams and cures at room temperature to form a rigid foam ~. While the density of the resultant rigid polyurethane foam can be varied in a conventional manner by varying the quantities of the two components combined, it has been found that a suitable density is 2 lbs/ft3. On the other hand, the rigidity of the foam and the reinforcing strength of the foam can be increased by increasing the density of the foam used.
For e~ample, a pole having increased strength may be produced by employing foam having a density of 5 lbs/ft3, but the expense of the pole increases due to the increase in the amount of foam material used.
One of the features of the employment of polyurethane foam material in the elongated cavity 26 is that it has a closed cell structure and thereby does not readily absorb moisture and provides an effective barrier to movement of moisture in the pole in~erior.
While the rigid foam material 24 has been described as comprising polyurethane, in other ~ ~S~l~
embodiments, the foam material could comprise other suitable foam-in-place materials. It is preferred, however, that the material have the properties of inhibiting the movement of moisture into the pole, and that it so form a bond with the panels to thereby provide structural rigidity or reinforcement to the pole. It is also preferred that the foam material be a rigid foam rather than a flexible foam so that the rigid foam provides structural support for the pole.
In a pre~erred form of the invention it is also desirable that the foam material selected have the property of curing at room temperature. Though other foam materials can be used, manufacturing costs can be reduced if heating of the foam material to effect curing can be avoided. In other alternative forms, ~iller materials such as wood chips, saw dust, wood strands or the like could also be mixed into the liquid material poured into the cavity 26 to form the rigid foam.
While in the illustrated embodiment the foam material could fill only the upper and lower ends of the elongated central cavity, in other arrangements the foam material could fill the entire central elongated cavity 26. In the illustrated construction, foam material 24 in the lower end of the pole lO will be particularly effective for inhibiting movement of moisture into the pole. The foam material 24 in the upper end o~ the pole lO provides reinforcement of that end of the pole which is intended to support utility pole cross~arms or the like.
Illustrated in Fig. 5 is an alternative embodiment of an elongated structural member embodying the invention. The elongated structural member 40 shown there comprises a hollow elongated cross-arm of the type commonly employed with utility poles and used to support telephone lines or power lines. ~ore particularly, the cross-arm 40 is comprised of four planar elongated panels 42 each comprised of composite wood material produced in the manner described above and having a construction as shown in Fig. 4. The elongated panels 42 are fixedly joined together at their interfaces 44 by a suitable adhesive of the type previously described. It should be understood that the panels 42 could also be secured together by other suitable joining means.
As in the case of the elongated hollow pole shown in Figs. 1 3, the elongated panels 42 of the cross-arms 40 are comprised of elongated wood flakes 22 aligned such that substantially all of the flakes are positioned with their longitudinal axes parallel to the longitudinall axis of the elongated panels 42 and with the generally planar flakes 22 oriented so as to define planes substantially parallel to the major plane of the elongated panel defined by the flakes.
As in the case of the elongated pole 10, means are also provided for filling at least a portion of the elongated central cavity 46 of the cross-arm, the means for filling also functioning to provide structural reinforcement or support for the elongated panels 42 forming the cross-arm and to provide means for further bonding the panels 42 together~ The means for filling includes a rigid foam material 48 which can be poured or injected into the central elongated cavity 46 defined by the elongated panels. It is preferred that the foam material 48 have the property of forming an adhesive bond with the internal surfaces 50 of the panels as previously described so that the internal foam material 48 will bond the panels together. As previously describedl one preerred foam material having this property and also providing structural rigidity is a rigid polyurethane foam.
The rigid foam material is placed in the cross-arm by positioning the cross-arm vertically, whereupon the polyurethane foam can be poured in its liquid state into the cross-arm. This material will then foam-in-place to fill the elongated central cavity of the cross-arm and will cure to form a rigid core for the cross-arm. The polyurethane could also be injected into the cavity 46 using a conventional foam injection nozzle arrangement.
Various features of the invention are set forth in the following claims.
Claims (13)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An elongated structural member having a longitudinal axis and comprising a plurality of elongated panels having lateral edges, said panels being arranged to form an elongated structure, and said panels each having an inwardly facing surface, said inwardly facing surfaces of said panels defining an elongated central cavity, said lateral edges of adjacent panels being fixedly joined together, and said elongated panels each being comprised of elongated wood flakes intermixed with a suitable binder and compressed to form a densified product, said elongated wood flakes each having a longitudinal axis, and said wood flakes having a length of about 0.5 inches to about 3.5 inches, a width of about 0.1 to 0.5 inches, and a thickness of about 0.001 to 0.05 inches, the grain direction of said wood flakes being aligned substantially parallel with said longitudinal axis of said wood flakes, and said wood flakes forming each of said panels being generally planar and lying in parallel planes parallel to said inwardly facing surfaces, said wood flakes being aligned with their longitudinal axes parallel to the longitudinal axis of the elongated member and such that the grain direction of the flakes in panels is parallel to the longitudinal axis of the elongated member.
2. An elongated structural member as set forth in claim 1 including means for reinforcing said elongated structure, said reinforcing means comprising a rigid foam material filling at least a portion of said elongated central cavity, said rigid foam material being bonded to said inwardly facing surfaces.
3. An elongated structural member as set forth in claim 2 wherein said rigid foam material comprises rigid polyurethane foam.
4. An elongated structural member as set forth in claim 1 wherein the lateral edges of the elongated panels are adhesively bonded together in abutting relationship.
5. An elongated structural member as set forth in claim 1 wherein said binder comprises an organic polyisocyanate having at least two active isocyanate groups per molecule.
6. An elongated structural member as set forth in claim 1 wherein each of said elongated panels is comprised of a plurality of planar layers of composite wood material laminated together, each planar layer being comprised of elongated wood flakes intermixed with a binder and compressed.
7. An elongated pole having a longitudinal axis and comprising a plurality of narrow elongated panels each having lateral edges, the lateral edges of said elongated panels being fixedly joined together in side-by-side abutting relation to form an elongated pole, said panels each having an inwardly facing surface, said inwardly facing surfaces defining an elongated central cavity therein, and each of said elongated panels being comprised of a plurality of elongated wood flakes intermixed with a binder and compressed to form a densified product, said elongated wood flakes each having a longitudinal axis, and said wood flakes having a length of about 0.5 inches to about 3.5 inches, a width of about 0.1 to 0.5 inches, and a thickness of about 0.01 -to 0.05 inches, the grain direction of said wood flakes being aligned substantially parallel with said longitudinal axes of said wood flakes, and said wood flakes forming each of said panels being generally planar and lying in parallel planes parallel to said inwardly facing surfaces, and said wood flakes being aligned with their longitudinal axes parallel to the longitudinal axis of the elongated pole and such that the grain direction of the flakes in the panels is parallel to the longitudinal axis of the elongated pole.
8. An elongated pole as set forth in claim 7 and including means for reinforcing said fixedly joined panels, said reinforcing means comprising a rigid foam material filling at least a portion of said elongated central cavity, said rigid foam material being bonded to said inwardly facing surface.
9. An elongated pole as set forth in claim 8 wherein said rigid foam material comprises rigid polyurethane foam.
10. An elongated pole as set forth in claim 7, 8 or 9 and wherein said elongated panels have a tapered thickness, the thickness of one end of each of said elongated panels being greater at one end of said elongated pole than the thickness of said panels at the opposite end of said elongated pole.
11. An elongated pole as set forth in claim 7, 8 or 9 wherein said binder comprises an organic polyisocyanate having at least two active isocyanate groups per molecule.
12. A method for forming an elongated structural member comprising the steps of forming a plurality of elongated planar panels, each of the panels being comprised of elongated wood flakes mixed with a binder and compressed to form a densified product, said wood flakes being a length of about 0.5 inches to about 3.5 inches, a width of about 0.1 to 0.5 inches, and a thickness of about 0.01 to 0.05 inches, each of the panels having a major plane and a longitudinal axis and the wood flakes comprising each such panel being planar and lying in planes parallel to the major plane of that panel, and the wood flakes having a longitudinal axis, the grain direction of the wood flakes being parallel to the longitudinal axis of the flakes, and the longitudinal axes of the flakes being parallel to the longitudinal axis of the panel, fixedly joining said panels together to form an elongated composite member having an elongated central cavity, said panels being joined together with the lateral edges of each of said panels being bonded to a lateral edge of an adjacent panel, and filling at least a portion of said central cavity with a rigid foam material.
13. The method as set forth in claim 12 wherein said step of filling said central elongated chamber with foam material comprises the step of introducing a foam-in-place polyurethane foam into said central elongated chamber and causing said foam to fill said chamber and to bond said panels.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000403136A CA1185413A (en) | 1982-05-17 | 1982-05-17 | Elongate structural members comprised of composite wood material |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000403136A CA1185413A (en) | 1982-05-17 | 1982-05-17 | Elongate structural members comprised of composite wood material |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1185413A true CA1185413A (en) | 1985-04-16 |
Family
ID=4122799
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000403136A Expired CA1185413A (en) | 1982-05-17 | 1982-05-17 | Elongate structural members comprised of composite wood material |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1185413A (en) |
-
1982
- 1982-05-17 CA CA000403136A patent/CA1185413A/en not_active Expired
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