Flooring Panels for Flat Platform Trailers

The invention will further be described by way of example only, with reference to the accompanying drawings wherein:

FIG. 1 is a somewhat schematic perspective view of a flat platform trailer having a decking comprised of composite panels in accordance with this invention;

FIG. 2A is a plan view of part of the trailer deck illustrating the frame work thereof;

FIG. 2B is a sectional view taken on the line IIb--IIb in FIG. 2A;

FIG. 3 is a fragmentary perspective view illustrating the means of attachment of the composite panels to the trailer framework;

FIG. 4 is a longitudinal sectional view to an enlarged scale of a portion of the trailer deck;

FIG. 5 is a perspective view of a composite panel in accordance with the invention;

FIGS. 6A and 6B are fragmentary sectional views illustrating eleven ply panels;

FIG. 7 is a fragmentary sectional view illustrating a thirteen ply panel;

FIG. 8 is a diagram illustrating a loading condition of the trailer platform;

FIG. 9 is a loading diagram; and

FIGS. 9A, 9B and 9C illustrate loading deformations of portions of the platform.

As shown in FIG. 1, a truck/trailer 11 has a horizontal deck 12 formed by a series of composite panels 13 arranged in abutting end-to-end configuration. As shown in FIGS. 2A and 2B, the trailer 11 has a pair of longitudinally extending parallel main frame beams 14 of I section, and is bounded by longitudinal edge beams 15 of channel section, the overall width of the trailer typically being about eight feet. These beams are interconnected by a series of closely spaced joists 16 extending transversely between the edge beams 15. These joists extend through apertures in the webs 14a of the main beams 14 and are positioned with their top surfaces beneath the underside of the top flanges 14b of the main beams and the top flanges 15b of the edge beams. The joists 16 are connected to the beams 14 and 15 by any suitable means, e.g. by welding, all the beams and joists preferably being of steel. Thus, the upper flanges 16a of the joists form a planar support grid for the panels 13, this surface being at a spacing below the top surface of the beams 14 and 15 that corresponds to the thickness of the panel, so that when installed, the panels are flush with those top surfaces, as indicated in FIG. 2B.

The panels 13 are of rectangular outline and are arranged with their major dimension extending in the longitudinal direction of the deck 12. The relative dimensions of the panels and the trailer frame members are such that the width of the panels of the central row exactly matches the spacing between the flanges 14b of the main frame beams. The outer rows of panels have a width that exactly matches the spacing between the main beam flange 14b and the edge beam flange 15b. The panels are of a length that is a multiple of the spacing between adjacent joists 16 so that, as shown in FIGS. 2A and 3, each end of every panel is located on and supported by one of the joist upper flanges 16A.

As indicated in FIGS. 3 and 4, the ends of the panels 13 are secured to the joist flanges 16A by a fastening arrangement in the form of a transverse metal plate 20 which is received into rebates 21 formed along each end of each of the panels so that the upper surface of the plate 20 is flush with the top surface of the panels. The metal plates 20 are secured to the underlying flange 16b by countersunk screws 22 passing through the panel and in threaded engagement with the flange 16A. Thus the ends of each panel 13 are securely clamped against the underlying flange 16A.

The fabrication and structure of the composite panel 13 will now be described with reference to FIGS. 5 through 7. As shown in FIG. 6A, a laminated wood substrate is provided comprising a total of eleven plies 24 of wood veneer. There are three central plies 24a the wood grain of which extends in the longitudinal direction of the panel; two intermediate plies 24b arranged with the wood grain extending in the transverse direction of the panel and arranged one on each side of the central plies, and on each outer side three outer plies 24c all arranged with the wood grain extending in the longitudinal direction. The plies are bonded together using a suitable adhesive such as phenolic resin, using the same techniques of heat and pressure as used in the manufacture of plywood panels. These techniques are well known and need not be described here.

The thickness of the panel will of course depend upon the thickness of the plies 24 and the number of plies used. A panel of 13/8 inch thickness is preferably constructed using eleven 1/8 inch thick plies as illustrated in FIG. 6A. A panel of 11/8 inch thickness as shown in FIG. 6B is produced using eleven plies of 1/10 inch thickness. FIG. 7 illustrates a variant in which the panel 13 includes five central plies 24a, two intermediate plies 24b and six outer plies 24c, the plies being of various thicknesses as indicated to provide an overall panel thickness of 13/8 inches.

The grain orientation of individual plies is important owing to the end-use condition and the high mechanical strength requirements. For the 11-ply construction and for both thicknesses (i.e. 11/8 in. and 13/8 in.), the three outer plies 24c on both the face and the back of the panel have a grain running in a direction parallel to the longitudinal direction of the panel. It is intended that this direction be perpendicular to the direction of the longitudinal axis of the trailer supporting cross member joists 16, as illustrated in FIG. 2A. This grain orientation provides the required panel flexural capacity. The intermediate fourth and eighth plies 24b (FIG. 6A, 6B) have a grain in a direction perpendicular to the longitudinal direction of the panel. With this grain orientation, dimensional stability is provided to the panel, and some degree of flexural capacity in a direction parallel to the supporting joists is developed. Finally, the three innermost plies 24a have a grain in a direction parallel to the longitudinal direction of the panel to permit the optimization of the planar shear capacity of the panel.

The preferred species of wood for the individual plies 24 is Douglas Fir. Any other species may however be used, providing the several requirements for the particular end-use as previously discussed can be met. The grade of individual plies and the species, may affect the dimensional stability of the panel, at the same time as they may impact on the manufacturing process inasmuch as bonds can be affected by species and grade characteristics.

An important aspect of the panel of the present invention lies in the laminate overlays that are provided on each side of the panel. The overlays are not shown in FIGS. 6A, 6B or 7, but are illustrated in FIGS. 4 and 5. Both the upper and lower overlay, 30, 31 respectively in FIG. 4, comprise a plurality of resin impregnated cellulose sheets that are adhered to the outer faces of the panel. Specifically, as shown in FIG. 5 there is an inner sheet 32 of cured cellulose material impregnated with medium density resin (hereinafter referred to as a Medium Density Overlay or MDO), an intermediate cellulose sheet 33 and an outer cellulose sheet 34a (top overlay) and 34b (bottom overlay). The sheets 33, 34a and 34b are uncured cellulose impregnated with high density resin (hereinafter referred to as High Density Overlay or HDO). An adhesive is employed to glue the MDO to the wood substrate, as the resin of the MDO is fully cured prior to the manufacture of the composite planar panel. In contrast, HDO sheets 33, 34a, 34b are not fully cured during their manufacture, and their resin component will be re-activated during manufacture of the composite planar panel as heat and pressure are applied, thus acting as an adhesive between the MDO sheet and the first HDO sheet, and between the two HDO sheets.

The MDO sheet 32 provides an intermediate layer that will receive the pattern necessary for developing a slip-resistant surface in the upper overlay 30. The two HDO sheets essentially fulfill two functions as 1) a moisture barrier, and 2) an improved abrasion resistant surface. In addition, although this is not the primary intent of the invention, the three layer overlay provides a mechanism for masking any defect that may be present on the outer surface of the wood substrate, thus enhancing the visual appearance of the resulting product.

FIGS. 8 and 9 specifically illustrate a structural requirement that is particular to the intended end-use of the composite panel in the illustrated application as in a truck or trailer deck. As indicated schematically in FIG. 8, a critical loading configuration arising from the front wheel 40 of a loaded fork lift truck is illustrated as providing a moving point load. As the forklift travels on the trailer deck, the wheel 40 applies a point load which is represented in different positions by the arrows P1 and P2 in FIG. 9. The structural capacity of the panel 13 to resist loading at the central position of arrow P2 is referred to as the baseline capacity. The baseline capacity is not affected by boundary conditions arising from the connection of the panel ends to the joists 16. The panel capacity to resist loading at position P1 however will vary depending upon the type of connection between the panel and the trailer frame at the end of the panel. Where the panel ends are simply screwed to the joists, the resultant deflection is indicated at FIG. 9B. In this configuration a substantial decrease in the structural capacity of the panel (of the order of 25 percent of the baseline capacity) may be expected due to the repeated panel deformations around the screws, as a result of the moving loads. In contrast, a sandwich type of construction as illustrated in FIGS. 3 and 4 herein utilizing metal plates 20 screwed to the joists flanges 16A through the panel ends will minimize panel deformation around the screws 22, this condition being represented in FIG. 9A.

The plate 20 has a thickness of approximately 1/4 inch and a width of 3 inches, the spacing between the adjacent screws 22 being not more than 4 inches at the ends of the panel. Screws 22 are also used to secure the panel to joist flanges 16A at intermediate locations in the lengths of the panels, and in this case the screw spacing should not exceed 8 inches. Preferably 5/16 inch diameter screws are used.