Stock material or miscellaneous articles – Structurally defined web or sheet – Nonplanar uniform thickness material
Reexamination Certificate
2001-06-15
2004-02-17
Pyon, Harold (Department: 1772)
Stock material or miscellaneous articles
Structurally defined web or sheet
Nonplanar uniform thickness material
C428S182000, C428S184000, C428S186000, C428S176000, C428S114000, C428S105000, C428S076000, C428S068000, C428S541000, C428S537100
Reexamination Certificate
active
06692815
ABSTRACT:
BACKGROUND OF THE INVENTION
Structural composite lumber or so-called plastic wood products have been developed in recent years wherein the composite structures are characterized by reinforced polymer compositions. So-called plastic lumber, for example, has been developed wherein wood fibers or wood flour is mixed with polymer materials, such as polypropylene or polyethylene, to form a composition which can be extruded into structural shapes, including conventional sizes and shapes of lumber. The advantages of such types of plastic lumber include high strength, rot resistance and ease of fabrication.
However, one disadvantage of prior art composite shapes comprising so-called plastic wood or plastic lumber, is competitive costs resulting from the cost of raw material but primarily resulting from the speed with which the so-called plastic wood shapes can be fabricated as compared with conventional lumber. Wood flour or wood particle/polymer compositions must be heated to substantial temperatures to perform extrusion processes required to form the structural shapes of plastic lumber. The speed of plastic lumber manufacturing processes has not, in many instances, been sufficient to make plastic lumber competitive with conventional lumber due to the relatively slow extrusion speeds required to allow the temperature of plastic or similar composite articles to be reduced to a level which will permit final fabrication and storage in an economical manner.
For example, the cross-sectional thickness of most types of conventional plastic lumber shapes is such that heat transfer from the core portion of the article being manufactured is not sufficient to allow finish processing of the article at a speed which is cost competitive with conventional lumber. Polymer materials used in fabricating conventional plastic lumber or plastic wood shapes have a relatively low heat transfer rate and the core temperature of conventional plastic lumber shapes remains too high to permit processing of the material at a competitive rate. However, in accordance with the present invention an improved composite or plastic lumber article is provided which is fabricated by an improved process, also in accordance with the invention.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a composite or so-called plastic wood or plastic lumber article which may be fabricated in selected conventional cross-sectional shapes and dimensions. The present invention also provides an improved method for fabricating extruded composite structural articles, such as so-called plastic lumber.
In accordance with one aspect of the present invention, a composite, extruded lumber or extruded plastic wood article is provided which may be of a conventional cross-sectional shape, that is a rectangular cross-sectional shape of standard lumber dimensions, and which is characterized by a corrugated composite core part encapsulated in an outer layer of composite material to form a conventional cross-sectional shape of standard lumber dimensions, for example. The plastic lumber article may be fabricated using an extrudable polymer material which is reinforced by a wood particle or wood flour filler. The extruded plastic lumber articles may also be fabricated using other types of filler or reinforcement materials, such as glass fibers or other reinforcing fibers. Metal foil or sheet may also be encapsulated in or comprise part of the extruded plastic lumber article.
In accordance with another aspect of the invention, conventional lumber shaped articles are provided which include a corrugated core portion of composite material encapsulated within an outer layer of composite material and which are fabricated in a way which increases the speed of production of the articles. By way of example, a composite plastic board of a type used as a conventional fence picket may be fabricated by extruding a corrugated core part, cooling the core part and compressing the corrugations toward each other and then encapsulating the core part within an outer layer of material to form a so-called plastic lumber article having conventional cross-sectional dimensions of board width and thickness. Moreover, the composite lumber article may be cut to any specified length in a conventional manner and may be otherwise worked in the same manner as a conventional wood structural article.
The present invention further contemplates a method of fabricating composite or reinforced polymer structural articles, such as conventional lumber shapes, by extruding a reinforced plastic core part from a first extrusion die, cooling the core part and then encapsulating the core part by extruding an overlay of the same or similar composite material to form the final dimensions of the article. The time required to fully fabricate the article and to cool the article to a temperature where it may be worked further or placed in storage without any deleterious effects is minimized as compared with prior art methods.
In a preferred embodiment, a core part of the article is extruded from a first extrusion die as a corrugated, or zigzag cross-sectional shape, or is subsequently formed into such a shape to provide for rapid cooling of the extrudate, initially. The corrugated shape is compressed and guided by respective sets of guides to bring the folds or corrugations substantially contiguous with each other, after initial extrusion and cooling, and so as to maintain the desired flatness and size of the core shape prior to further working. The continuous extruded and compressed core part is then subjected to further cooling via a liquid spray, followed by submersion of the core part in cooling liquid, normally water, as it is being pulled from the extruder. The core part is guided through the cooling liquid spray by spaced apart sets of guide rollers to maintain flatness and sizing of the core part.
The continuous composite core part of the article is then passed through a dryer comprising a vacuum chamber and pressure air blowers to remove moisture from the core part. In a preferred arrangement of the processing apparatus, the core part is then passed through a conveyor type puller apparatus characterized by opposed endless belts which grip and traverse the core part along a fabrication path.
In accordance with a further aspect of the present invention, the composite extruded core part of the structural article is then passed through a second die wherein a coating of a second composition, preferably the same as the core part, is applied over the core part to completely encapsulate the core part. The article may then be passed through a set of rollers for final sizing of the article cross-sectional shape to provide sharp edges and flat surfaces, for example. The continuous article, after sizing, enters an elongated cooling trough filled with cooling liquid, preferably water, followed by exit from the cooling trough and passage through an air blast curtain to remove water from the surface of the cooled and finished article. Prior to cooling, the article may be passed through one or more sets of embossing rollers to emboss the outer surfaces of the article to provide a woodgrain appearance, for example. Still further, a continuous belt-type pulling apparatus may be disposed downstream, in the direction of movement of the continuous extrudate, from the cooling water trough. The continuous finished composite lumber article may then be cut to length by a conventional sawing apparatus.
The composition of the article of the present invention may be somewhat varied. Conventional polymers used for extruded shapes may be used in forming the article and such polymers may be reinforced by various reinforcement materials including wood fibers, wood flour and fibers of other compositions including glass, carbon and the like.
Those skilled in the art will further appreciate the above-mentioned advantages and superior features of the invention together with other important aspects thereof upon reading the detailed description which follows in conjunction with the drawing.
REFERENCES:
patent: 4119750
Gardere Wynne & Sewell LLP
Pyon Harold
Simone Catherine A.
Vinylex Corporation
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