Abstract:
A marine deck member with enhanced surface traction and the process for forming the same. The marine deck member comprises a sandwich-type composite panel made by a compression molding process. In such a process, the panel is made by subjecting a heated stack of layers of material to cold-pressing in a mold. The cellular core has a 2-D array of cells, each of the cells having an axis substantially perpendicular to the outer surfaces, and extending in the space between the layers or skins, with end faces open to the respective layers or skins. The surface traction of this type of composite panel can be enhanced for marine deck applications by controlled debossing, or embossing, of the first skin while it cools in the compression mold. The debossing effect can be effected by applying pressurized gas, e.g., pressurized air, onto the outer surface of the first skin while in the compression mold. The embossing can be effected by applying vacuum pressure on the outer surface of the first skin while in the compression mold.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of U.S. applications Ser. No. 13/479,974, filed May 24, 2012, and U.S. Ser. No. 13/762,879, filed Feb. 8, 2013 the disclosures of which are hereby incorporated in their entirety by reference herein. This application is also related to U.S. Ser. No. 14/603,418, filed Jan. 23, 2015 (now U.S. Pat. No. 9,567,037, issued Feb. 14, 2017); and Ser. No. 13/517,877, filed Jan. 14, 2012 (Abandoned). 
     
    
     TECHNICAL FIELD 
       [0002]    This invention relates to marine decking for use with pontoon boats, docks, rafts, swim platforms, watercraft docking stations and the like, and methods for making the same. 
       BACKGROUND 
       [0003]    The surfaces of boat decks, swim platforms, docks and similar marine structures are commonly made of fiberglass, aluminum, treated plywood, vinyl or perforated rubber. These surfaces are subjected to sun light/heat, rain, humidity, etc. in harsh marine service environments. These materials can deteriorate and require repair or replacement over extended periods of use. 
         [0004]    Another factor is these materials can be slippery. Prior efforts to provide non-slip marine surfaces are found in U.S. Pat. No. 4,737,390, for Non-Slip Coating for Molded Articles, and Pub. No. US 2013/0233228, for Porous Anti-Slip Floor Covering. In U.S. Pat. No. 4,737,390 a layer of latex or latex-impregnated sheet material is adhered to molded thermoset plastic article while curing in the mold.  FIG. 4  illustrates the application of this sheet material in a boat deck. In Pub. No. US 2013/0233228 a porous anti-slip floor covering uses a layer of curled strands placed on an underlayment. 
         [0005]    Factors affecting the suitability of a material for marine deck applications, in addition to the ability to withstand the environmental factors above, include cost, weight, strength, traction and buoyancy. 
       SUMMARY 
       [0006]    The marine deck materials of the present invention utilize sandwich-type, compression-molded, composite components. Sandwich-type composite panels including cores have very important characteristics because of their light weight and high strength. Such panels are constructed by sandwiching a cellular core having low strength characteristics between two outer plastic layers or skins, each of which is much thinner than the core but has excellent mechanical characteristics. The core is made of a 2-D array of cells, each of the cells having an axis substantially perpendicular to the outer surfaces, and extending in the space between the layers or skins, with end faces open to the respective layers or skins. 
         [0007]    Sandwich-type composite panels are conventionally made by a compression molding process. In such a process, the panel is made by subjecting a heated stack of layers of material to cold-pressing in a mold. The stack is made up of, at least: a first skin of plastic material, a cellular core, and a second skin also of plastic material. The stack may be pre-heated outside the mold or heated inside the mold to a softening temperature. Once the stack is placed in the mold, the closing of the mold halves causes the inner surfaces of the softened skins to bond to the mating faces of the core. 
         [0008]    In one embodiment, the sandwich-type composite panel has a first skin of thermoplastic material, a second skin of thermoplastic material, and a cellular core of thermoplastic material positioned between the skins. The skins are bonded to the core by press molding. The cellular core has a 2-D array of cells, each of the cells having an axis substantially perpendicular to the outer surfaces, and extending in the space between the layers or skins, with end faces open to the respective layers or skins. 
         [0009]    In another embodiment, the sandwich-type composite panel has a first skin of a fiber-reinforced thermoplastic material, a first sheet of thermoplastic adhesive, a second skin of fiber-reinforced thermoplastic material, a second sheet of thermoplastic adhesive and a cellular core of a cellulose-based material positioned between the skins. The skins are bonded to the core by the first and second adhesive sheets and by press molding. The cellular core has a 2-D array of cells, each of the cells having an axis substantially perpendicular to the outer surfaces, and extending in the space between the layers or skins, with end faces open to the respective layers or skins. 
         [0010]    The surface traction of this type of composite panel can be enhanced for marine deck applications by controlled (i) debossing, or (ii) embossing, of the first, outer skin while it cools in the compression mold. The air in the core cavities causes thermal gradients relative to the cell walls that result in uneven cooling over the surface area of the skin. The resultant uneven cooling is manifested as “debossing” (or, “sink marks”) on the surfaces of the skins. The phenomenon of debossing can be used advantageously to enhance surface traction of the outer surface of the first skin. 
         [0011]    The debossing effect can be accentuated by applying pressurized gas, e.g., pressurized nitrogen or air, onto the outer surface of the first skin as it cools in the compression mold. 
         [0012]    Alternatively, the uneven cooling phenomenon can be used to “emboss” the surface of the skin be application of vacuum pressure while the skin is cooling in the mold. The embossments are raised surfaces that also enhance surface traction on the outer surface of the first skin. 
         [0013]    The debossing/embossing pattern on the outer surface can be defined by the cross-sectional shape of the cells. Cells of circular cross-sectional will produce circular debossments/embossments; cells of honeycomb shape will produce hexagonal debossments/embossments; and cells of cleated shape will produce cleat-shaped debossments/embossments. 
         [0014]    The invention provides marine deck materials that have a relatively high strength-to-weight ratio, buoyancy, and enhanced surface traction. These properties make these deck materials suited for use in such applications as boat decks, swim platforms, docks and similar marine structures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a perspective view of a pontoon deck as a representative product application of the present invention; 
           [0016]      FIG. 2A  is an enlarged view of the pontoon deck surface, encircled as “ 2 A” in  FIG. 1 , showing debossments matching the cross-sectional shape of the circular cells in the core; 
           [0017]      FIG. 2B  is an enlarged view of a pontoon deck surface showing embossments matching the cross-sectional shape of the circular cells in the core; 
           [0018]      FIG. 3  is a perspective view of a swim platform or diving raft as another representative product application of the present invention; 
           [0019]      FIG. 4  is a perspective view of a dock as another representative product application of the present invention; 
           [0020]      FIGS. 5A-C  are top plan schematic views, partially broken away, of different configurations, e.g., honeycomb-like, of cellular cores; 
           [0021]      FIG. 6  is an exploded, side sectional view showing a sandwich-type composite panel with a first skin of a fiber-reinforced thermoplastic material, a first sheet of thermoplastic adhesive, a second skin of fiber-reinforced thermoplastic material, a second sheet of thermoplastic adhesive and a cellular core of a cellulose-based material positioned between the skins; 
           [0022]      FIG. 7  is an exploded, side sectional view showing a sandwich-type composite panel with first skin of thermoplastic material, a second skin of thermoplastic material, and a cellular core of thermoplastic material positioned between the skins; 
           [0023]      FIG. 8  is a schematic, side sectional view showing a fluid pressure-assisted compression mold useful in facilitating debossing of the of the upper surface of the molded composite component to enhance its surface traction; 
           [0024]      FIG. 9  is a top perspective view, in cross section, of the composite component of  FIG. 6 , with debossments, by application of fluid pressure; 
           [0025]      FIG. 10  is a schematic, side sectional view showing a vacuum pressure-assisted compression mold useful in facilitating embossing of the of the upper surface of the molded composite component to enhance its surface traction; 
           [0026]      FIG. 11  is a top perspective view, in cross section, of the composite component of  FIG. 6 , with embossments, by application of vacuum pressure; 
           [0027]      FIG. 12  is a cross-sectional view, partially broken away, of a marine deck member of the present invention having a fastener component mounted within. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. 
         [0029]      FIG. 1  shows a pontoon boat  10  as a representative application of the present invention. The deck  12  can be composed of modular panels or tiles fitted to the surface configuration of the pontoon boat. The deck  12  has mounted on it conventional surface cleats  14  to facilitate docking. In addition to pontoon boat decks, the present invention is also suited for other marine applications where enhanced surface traction is desired, for example, docks, diving boards, swim platforms, watercraft docking stations and the like. 
         [0030]      FIG. 2A  is a close-up view of the encircled portion of the pontoon deck  12  of  FIG. 1 . The deck surface has a pattern of debossments, formed with the assistance of pressurized gas in the process of compression molding the marine deck. The shape of the debossment  16  corresponds to the cross-sectional shape of the cell in the cellular core used in the composite molding. 
         [0031]      FIG. 2B  is a close-up view of an alternative embodiment of a pontoon deck surface  12 ′ showing embossments  16 ′ matching the cross-sectional shape of the circular cells in the core. The embossments  16 ′ are formed with the assistance of vacuum pressure in the process of compression molding the marine deck. 
         [0032]      FIG. 3  shows the marine deck surfaces of the present invention applied with a swim platform (or diving raft)  20 . The deck  12  or  12 ′ can be formed with debossments or embossments, respectively, as discussed below. 
         [0033]      FIG. 4  shows the marine deck surfaces of the present invention applied with to the deck surface of a dock  22 . Again, the deck  12  or  12 ′ can be formed with debossments or embossments, respectively, as discussed below. 
         [0034]      FIGS. 5A-5C  show exemplary surface shapes for the debossments and embossments to be formed in the marine deck surface, whether a watercraft deck, swim platform, dock, or other application.  FIG. 5A  shows circular shapes for debossments  16 C, or circular embossments  16 C′.  FIG. 5B  shows honeycomb shapes for debossments  16 H, or honeycomb embossments  16 H′.  FIG. 5C  shows rectangular shapes for debossments  16 R, or rectangular embossments  16 R′. The surface shape of the debossments or embossments will correspond to the cross-sectional shape of the cells in the core of the sandwich-type structure. 
         [0035]      FIG. 6  is an exploded side view of the constituent parts of the composite panel  32  preparatory to compression molding. As shown in  FIG. 6 , a stack includes first and second reinforced thermoplastic skins or outer layers  24  and  26 , respectively, a plastic core  30  having a large number of cells disposed between and bonded to plies or films or sheets of hot-melt adhesive (i.e. thermoplastic adhesive)  28  which, in turn, are disposed between and bonded to the skins  24  and  26  by compression molding. The sheets  28  may be bonded to their respective skins  24  and  26  prior to the press molding or are preferably bonded during the press molding. The thermoplastic of the sheets  28  is typically compatible with the thermoplastic of the skins  24  and  26  so that a strong bond is formed therebetween. One or more other plastics may also be included within the adhesive of the sheets  28  to optimize the resulting adhesive  24  and  26  and their respective sheets or film layers  28  (with the core  30  layers  28 ) are heated typically outside of a mold (i.e. in an oven) to a softening temperature wherein the hot-melt adhesive becomes sticky or tacky. The mold is preferably a low-pressure, compression mold which performs a thermo-compression process on the stack of materials. 
         [0036]    The sticky or tacky hot-melt adhesive  28  extends a small amount into the open cells during the thermo-compression process. The skins  24  and  26  are bonded to the top and bottom surfaces of the core  30  by the sheets  28  to seal the cells of the core  30  to the facing surfaces of the skins  24  and  26 . 
         [0037]    The step of applying the pressure compacts and reduces the thickness of the cellular core  30  and top and bottom surface portions of the cellular core penetrate and extend into the film layers  28  without penetrating into and possibly encountering any fibers located at the outer surfaces of the skins  24  and  26  thereby weakening the resulting bond. 
         [0038]    Each of the skins  24  and  26  may be fiber reinforced. The thermoplastic of the sheets or film layers  28 , and the skins  24  and  26  may be polypropylene. Alternatively, the thermoplastic may be polycarbonate, polyimide, acrylonitrile-butadiene-styrene as well as polyethylene, polyethylene terphthalate, polybutylene terphthalate, thermoplastic polyurethanes, polyacetal, polyphenyl sulphide, cyclo-olefin copolymers, thermotropic polyesters and blends thereof. At least one of the skins  24  or  26  may be woven skin, such as polypropylene skin. Each of the skins  24  and  26  may be reinforced with fibers, e.g., glass fibers, carbon fibers, aramid and/or natural fibers. At least one of the skins  24  and  26  can advantageously be made up of woven glass fiber fabric and of a thermoplastics material. 
         [0039]    The cellular core  30  of the  FIG. 6  embodiment may be a cellulose-based honeycomb core. In this example, the cellular core has an open-celled structure of the type made up of a tubular honeycomb. The axes of the cells are oriented transversely to the skins  24  and  26 . 
         [0040]    The stack of material may be pressed in a low pressure, cold-forming mold  42  shown schematically in cross-section in  FIG. 8 . The mold has halves  44  and  46 , which when closed have an internal cavity for the stack. The stack is made up of the first skin  24 , the adhesive layers  28 , the cellulose-based cellular core  30 , and the second skin  26 , and is pressed at a pressure lying in the range of 10×105 Pa. to 30×105 Pa. The first and second skins  24  and  26 , and the first and second film layers  28  are preferably pre-heated to make them malleable and stretchable. Advantageously, in order to soften the first and second skins  24  and  26 , and their respective film layers  28 , heat is applied to a pre-assembly made up of at least the first skin  24 , the first and second film layers  28 , the cellular core  30 , and the second film layer  26  so that, while the composite panel  32  is being formed in the mold, the first and second skins  24  and  26  and the film layers  28  have a forming temperature lying approximately in the range of 160° C. to 200° C., and, in this example, about 180° C. 
         [0041]    Air in the sealed cavities urges softened portions of the sheets  24  and  26  and portions of the core  30  inwardly towards the cavities of the core  30 . 
         [0042]    The mold  42  is formed with a pattern of fluid passageways  50 , aligned with the cell openings, to permit the application of fluid pressure onto the surface of the first skin  24  from a fluid pressure source  48 . The applied fluid pressure augments the tendency of the sheets to deboss in the area above the cells. The pressure level and duration can be selected to determine the depth of the debossments  16  formed in the outer surface of the first skin  24 . The debossments  16  enhance the surface traction of the outer surface of the skin  24 . 
         [0043]      FIG. 9  shows a composite panel  52  with the debossments  16 R formed in rectangular shapes. The cells in the core  30  are similarly rectangular in cross-section. The outer surface of the first skin  24  has enhanced surface traction. The outer surface of the second skin  26  may be naturally debossed, but it will not be visible as part of a marine deck member. 
         [0044]      FIG. 8  is an exploded side view of the constituent parts of an alternative embodiment of a composite panel  40  preparatory to compression molding. In this embodiment, thermoplastic skins  34  and  36  are bonded to a thermoplastic core  38  in sealed relation by heating to the softening point of the plastic. The stack may be preheated, or heated in the mold. 
         [0045]    The core may be injection molded by the process disclosed in U.S. Pat. No. 7,919,031, titled “Method And System For Making Plastic Cellular Parts And Thermoplastic Composite Articles Utilizing Same,” commonly assigned to the assignee of the present invention. 
         [0046]    A stack whether in the embodiment of stack  32  in  FIG. 6 , or the stack  40  of  FIG. 7 , may be formed with either debossments, per the mold configuration of  FIG. 8 , or formed with embossments, per the mold configuration of  FIG. 10 . 
         [0047]    In  FIG. 10 , the mold  68  is equipped with a vacuum source  66  to apply vacuum pressure through channels  70  to the outer surface of the plastic skin  24  while the skin is heated and formable in the mold. 
         [0048]    The application of sufficient vacuum pressure causes the outer surface of the skin  24  to the raised with embossments  16  R on the composite panel. In this case the embossments  16 R are rectangular in shape to correspond with the cross-sectional shape of the cells in the core  30 . The outer surface of the skin  24  has enhanced surface traction due to the embossments. 
         [0049]      FIG. 12  shows the mounting of a fastener component  80  in the composite panel  32 . The fastener component can be used to secure cleats  14  to a marine deck formed of the inventive composite panel. 
         [0050]    After compression or press molding, at least one hole is formed in the composite panel  52  such as by cutting through the first skin  24 , through the core  30  right up to but not through the second skin  26 . A rivet-like fastener such as the fastener component  80  is positioned in the hole. Each fastener component  80  is generally of the type shown in U.S. patent publications 7,713,011 and 2007/0258786 wherein the preferred fastener component is called an M4 insert, installed by use of a hydro-pneumatic tool both of which are available from Sherex Fastening Solutions LLC of New York. During installation, an outer sleeve  44  of the fastener component  50  is deformed, as shown in  FIG. 7 . 
         [0051]    The fastener component  80  typically has a relatively large annular flange, generally included at  82 , with a plurality of integrally formed locking formations or wedges (not shown) circumferentially spaced about a central axis of the component  80  on the underside of the flange  82  to prevent rotary motion of the fastener component  80  relative to the first skin  24  after installation. The wedges grip into the outer surface of the first skin  24  after the fastener component  80  is attached to the first skin  24 . 
         [0052]    A fastener  80  of the type illustrated in  FIG. 12  can withstand (i) large pull-out forces, (ii) large push-in forces, and large rotational forces (torque). These performance criteria must be met while preserving the mechanical and aesthetic properties of the composite panel  52 . Additionally, in this use environment, the underside of the composite panel  32  must remain impervious to moisture absorption. Moisture absorption may result in increased weight and performance degradation over a prolonged period, especially on the underside of a marine deck. 
         [0053]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.