Patent Application
20070020438
The present invention relates to foam sports boards for recreational use and, more particularly, to a contour-molded laminated foam sports board having a polyurethane foam core.
Body boards for riding waves, ski boards and gliding boards made for use on snow, and other recreational sports boards made of foam, are known in the prior art. Such boards typically include a core with laminated layers surrounding the core. The outer base layer of the laminate is adapted to used on a particular sports surface (water or snow) and the top laminated layer often includes some type of imprinted graphics.
For example, it is known that ski or snow boards may be constructed with a polyethylene base layer having longitudinally extending steel edges laminated to a thermoset composite such as uncured preimpregnated fiberglass. This base laminate is then applied to a preformed polyurethane foam core. Upper layers, generally consisting of a plastic top sheet, a non-woven fabric intermediate layer, and a fiberglass reinforcement layer, are applied to the top surface of the core. The conventional manufacturing process for this type of board is by compression molding. The process calls for hand laying each layer and applying resin, typically epoxy or polyester based, to impregnate the different layers. Heat and pressure are then applied, with the bonding between layers provided by the resin after it has cured for a period of time at a raised temperature. However, this type of board and manufacturing process has a number of drawbacks. For example, the preformed polyurethane foam core, the polyethylene layer and the thermoset fiberglass composite layer are generally required to be subjected to a special sanding process in order to roughen the bonding surfaces and get the bond strength required. In addition, the thermoset fiberglass composite layers are difficult to work with and require substantial curing periods during the production process.
Another type of sports board known in the prior art is a wakeboard. These boards generally have a preformed and preshaped polyurethane foam core with layers of reinforcement, such as fiberglass, carbon fiber or the like, applied to the bottom and top surfaces of the foam core. A plastic sheet having an intermediate layer of non-woven fabric forms the base of the board. The top of these boards are formed of one or more layers of reinforcement, typically fiberglass, with a graphic imprinted fabric top sheet laid above the fiberglass reinforcement layer. These boards are also manufactured using the above described compression molding and have the same drawbacks as described with the prior art snow boards.
A second manufacturing process known in the prior art is to use thermosetting resins, such as a polyurethane foam resin, to laminate the boards. For example, with the snow board, a thermoset fiberglass composite layer is laid onto a polyethylene base sheet. However, here too the bonding surfaces have to roughened and a special primer is applied to obtain the required bonding strength when bonding the two layers together. This two layer laminate is then placed on the bottom of a mold. A top laminate of a graphically imprinted plastic sheet, a non-woven fabric intermediate layer, and a thermoset fiberglass composite is then formed. Again, however, the surface of the thermoset composite must be sanded to provide a rough surface for bonding and a special primer is normally used to bond the thermoset composite layer to the non-woven fabric surface of the plastic top sheet. This three layer laminate is then placed on the top of the mold. After the top and bottom mold portions are mated, a polyurethane foam resin is then injected between the base laminate and the top laminate to join the two together by bonding to the roughened thermoset fiberglass composite surfaces.
As mentioned above, these conventional processes generally require the surfaces of the fiberglass that comes into contact with the foam core to be roughened so that the mechanical bond between these parts is strong enough to avoid premature delamination. In addition, the steps of laying up each layer and applying by hand the thermoset resin for the complete wetting of each layer, as well as waiting for it to cure, and preparing the surfaces to bond well with the foam are labor intensive, time consuming and require experienced technical workers. Thus the cost of manufacturing such boards is high.
In addition, conventional boards of this type generally include a graphic image which is normally printed on either a rigid plastic top sheet or a fabric sheet. These conventional rigid plastic sheets may include PBT, PA, ABS or TPE and have a typical thickness of 0.5 mm. However, due to the high rigidity of the plastic sheet, they can only be molded into relatively flat surface profiles and cannot be used to provide a more highly contoured surface. The alternative fabric sheets may include natural or synthetic fabrics such as cotton or non-woven fabric and they commonly have a thickness of about 0.3 mm. With fabric sheets, while they can be molded into more contoured shapes, they have other limitations such as inferior image resolution and susceptibility to wrinkle defects in areas of high contouring.
Foam sleds that include a graphic-imprinted polyethylene film top layer and a polyethylene foam core, together with a polyethylene bottom slick skin are also well-known in the prior art. These can be manufactured using conventional heat lamination to processes because each of the layers has the same polyethylene structure. However, such polyethylene-core foam boards lack the desired rigidity and stiffness that other polymeric foam core boards may have. This lack of rigidity in a polyethylene foam core will cause the sled to flex with the weight of the rider, which can result in the foam sled submerging below the snow surface and thereby reduce the speed and directional stability of the board on a snow covered slope.
Accordingly, it would be desirable to provide a foam slide having a rigid foam core for faster sliding speed and better tracking stability, while also provide a board that has a top laminate that provides adequate mechanical strength, is soft, is flexible enough to be molded into highly contoured shapes, and can be provided with a wear resistant graphic top surface. It would also be advantageous to be able to manufacture such a board in a cost effective manufacturing process.
With parenthetical reference to the corresponding parts, portions or surfaces of the disclosed embodiment, merely for the purposes of illustration and not by way of limitation, the present invention provides a method of manufacturing a contoured sports board comprising the steps of providing a non-expanded film layer (16), providing a polymer foam layer (18/19), bonding the film layer to the foam layer to form a top laminated sheet (16/17/18/19), providing a bottom sheet (21/22/23, 30), providing a mold having a top portion (44) and a bottom portion (45), the top and bottom portions having inner surfaces (63, 64) and configured to be placed in opposition to each other with their inner surfaces defining a cavity (49) therebetween, the inner surface of the top portion of the mold having contouring defining at least one valley (61, 62), placing the film layer of the top sheet against the inner surface of the top mold portion, mixing an isocyanate and a polyol component to provide a urethane foam forming mixture (50), spraying the mixture on the foam layer of the top sheet, placing the bottom sheet on the top sheet with the mixture between the top sheet and the bottom sheet, placing the inner surface of the bottom portion of the mold on the bottom sheet, mating the bottom portion of the mold with the top portion of the mold, applying pressure to the mold, allowing the mixture time to expand between the top sheet and the bottom sheet, unmating the top and bottom portions of the mold, whereby heat from the expansion of the mixture to form a polyurethane foam core heat laminates the top sheet and the bottom sheet to the polyurethane core to form a board having an outer surface contour generally conforming to the contour of the inner surfaces of the mold.
The bottom sheet may be formed by extruding a polymer film layer (23) and heat laminating the polymer film to a polymer foam layer (21/22) to form a film/foam laminated sheet (21/22/23). The polymer film may have a thickness in the range of about 0.3 to about 1.5 mm. The bottom sheet may comprises a thermoplastic polyurethane film layer (30) and the thermoplastic polyurethane film may have a thickness in the range of about 0.3 to about 1.5 mm. The bottom sheet may have a bottom surface with longitudinally-extending alternating grooves and ridges. The method may further comprise the steps of providing a second non-opaque polymer film layer having an outer surface and an inner surface, applying a graphic image to the inner surface of the second film layer, and laminating the inner surface of the second film layer to the film layer. The film layer may be selected from a group consisting of polyethylene, polypropylene, and a copolymer of ethylene vinyl acetate and polyethylene. The polymer foam layer may be selected from a group consisting of polyethylene foam, polypropylene foam, a copolymer foam of polyethylene and ethylene vinyl acetate, a copolymer foam of polyethylene and polypropylene, and a copolymer foam of polystyrene and polyethylene. The polymer foam layer may be thermoplastic polymer foam.
The present invention also provides a molded sports board comprising a polyurethane foam core (20), a graphically imprinted film layer (16) having an outer surface, an intermediate polymer foam layer (18/19) between the film layer and the core, the film and intermediate layers having a molded profile such that the outer surface of the film layer has a contoured cross-section having multiple ridges (55, 56) and valleys (57, 58) therebetween. The valleys may have a depth (65) of at least 2 mm.
Accordingly, the general object of the present invention is to provide an improved manufacturing process for a polyurethane foam core sports board.
Another object is to provide a sports board that can be molded with deep or severe contouring on the top surface.
Another object is to provide a sports board having a soft top surface.
Another object is to provide a sports board having a semi-rigid to rigid polyurethane foam core.
Another object is to provide a sports board having a sharp and wear-resistant graphic surface.
Another object is to provide a sports board which can have a graphic-imprinted film surface on both the top and bottom outer surfaces of the board.
Another object is to provide a board that can be manufactured in a short production cycle time.
These and other objects and advantages will become apparent from the foregoing and ongoing written specification and drawings.
a-e show the process by which the top and bottom sheets are laminated to the core to form the contoured board shown in
At the outset, it should be clearly understood that like reference numerals are intended to identify the same structural elements, portions or surfaces consistently throughout the several drawing figures, as such elements, portions or surfaces may be further described or explained by the entire written specification, of which this detailed description is an integral part. Unless otherwise indicated, the drawings are intended to be read (e.g., cross-hatching, arrangement of parts, proportion, degree, etc.) together with the specification, and are to be considered a portion of the entire written description of this invention. As used in the following description, the terms “horizontal”, “vertical”, “left”, “right”, “up” and “down”, as well as adjectival and adverbial derivatives thereof (e.g., “horizontally”, “rightwardly”, “upwardly”, etc.), simply refer to the orientation of the illustrated structure as the particular drawing figure faces the reader. Similarly, the terms “inwardly” and “outwardly” generally refer to the orientation of a surface relative to its axis of elongation, or axis of rotation, as appropriate.
Referring now to the drawings and, more particularly, to
As shown in
Layer 17 is an extruded adhesive resin between layers 16 and 18. In the preferred embodiment, layer 17 is an ethylene and methyl acrylic copolymer. Layer 17 has a thickness of between 0.02 and 0.15 mm, and preferably a thickness of 0.07 mm. Layer 17 has a density in the range of 0.90 to 0.98 g/cm3, and preferably a density of 0.95 g/cm3. The ethylene methyl acrylate copolymer EMAC provided by Eastman Chemical Company, of 100 North Eastman Road, Kingsport, Tenn. 37662, may be employed in the preferred embodiment. It is contemplated that alternative adhesive resins, such as anhydride-modified polyolefin, anhydride-modified ethylene vinyl acetate, anhydride-modified low-density polyethylene, and anhydride-modified linear low-density polyethylene, may be employed. The Bynel® adhesive resin, provided by Dupont Packaging, of 1007 Market Street, Wilmington, Del. 19898, may be employed in such an alternative embodiment.
Layer 18 is expanded polyethylene foam having a thickness of between about 1 and 6 mm, and preferably a thickness of about 4 mm. Layer 18 has a density of between about 4 to 10 lbs/ft3, and preferably a density of about 7 lbs/ft3. Layer 19 is also an expanded polyethylene foam. Layer 19 has a thickness of between about 1 and 20 mm, and preferably a thickness of about 2 mm. Layer 19 has a density in the range of about 1.6 to 4 lbs/ft3, and preferably a density of about 2.2 lbs/ft3. This dual polyethylene foam laminate sheet 18/19, with outer layers of differing densities, between graphic film layer 17 and polyurethane core 20 facilitates a strong bond to the film and core layers, respectively. A higher density foam 18 is used next to graphic film layer 16 because this higher density foam 18 will bond better to the film layer, in part because it has a smoother outer surface. Using a lower density polyethylene foam sheet 19 next to polyurethane foam core 20 is beneficial in that this low density foam 19 will melt faster to polyurethane core 20 and therefore provide a faster bond.
Layer 20 is polyurethane foam, and acts as the core of board 15. Layer 20 has a thickness of between about 5 and 45 mm, and preferably a thickness of about 18 mm. Layer 20 has a density in the range of about 6 to 30 lbs/ft3, and preferably a density of about 8 lbs/ft3. A polyurethane foam core provides improved rigidity and stiffness to the board.
Layer 21 is expanded polyethylene foam. Layer 21 has a thickness of between about 1 and 20 mm, and preferably a thickness of about 3 mm. Layer 21 has a density in the range of about 1.6 to 4 lbs/ft3, and preferably a density of about 2.2 lbs/ft3. Layer 22 is also expanded polyethylene foam. Layer 22 has a thickness of between about 1 and 6 mm, and preferably a thickness of about 4 mm. Layer 22 has a density in the range of about 5 to 11 lbs/ft3, and preferably a density of 9 lbs/ft3.
Bottom layer 23 is non-expanded polyethylene film. Layer 23 has a thickness of between about 0.3 and 1.5 mm, and preferably a thickness of about 0.5 mm. Layer 23 has a density in the range of about 0.91 to 0.96 g/cm3, and preferably a density of about 0.95 g/cm3.
Layer 29 is expanded polyurethane foam, and acts as the core of board 24. Layer 29 has a thickness of between about 10 and 50 mm, and preferably a thickness of about 22 mm. Layer 29 has a density in the range of about 6 to 30 lbs/ft3, and preferably a density of about 8 lbs/ft3.
Bottom layer 30 is non-expanded thermoplastic polyurethane (TPU) film. Layer 30 has a thickness of between about 0.3 and 2.0 mm, and preferably a thickness of about 0.7 mm. Layer 30 has a density in the range of about 0.96 to 1.16 g/cm3, and preferably a density of about 1.06 g/cm3. It is contemplated that other thermoplastic films may be used such as chlorinated polyethylene (CPE), chlorinated propylene (CPP), chlorosulfonated polyethylene (CSPE) and ethylene-propylene-diene copolymer (EPDM).
Layer 34 is expanded polyethylene foam. Layer 34 has a thickness of between about 4 and 10 mm, and preferably a thickness of about 7 mm. Layer 34 has a density in the range of about 1.6 to about 4 lb/ft3, and preferably a density of about 2.2 lb/ft3.
Layer 35 is expanded polyurethane foam, and acts as the core of board 31. Layer 35 has a thickness of between about 5 and 45 mm, and preferably a thickness of about 18 mm. Layer 35 has a density in the range of about 6 to 30 lbs/ft3, and preferably a density of about 8 lb/ft3.
Layers 36-38 are generally of the same structure and composition as layers 21-23, respectively, of second embodiment 24.
As shown in
Boards 15, 24 and 31 are formed in a series of steps. As shown in
Once mold 43 is created, the board is formed in a series of steps, some of which may vary somewhat depending on the embodiment. For each embodiment however, a top and bottom sheet are first formed.
For board 15, layer 16 is imprinted with the desired graphics using a conventional imprinting procedure. Foam layers 18 and 19 are then heat laminated to each other using a conventional heat lamination method to form a foam laminate 18/19. As shown in
For board 24, a laminated top sheet of layers 25, 26, 27 and 28 is formed using the same general procedure for forming the top sheet 16/17/18/19 with board 15. The bottom sheet for board 24 is a single layer 30, and is not necessarily a laminated sheet.
For board 31, the laminated top sheet of layers 32, 33 and 34 is formed using the same general procedure for forming the top sheet 16/17/18/19 with board 15. However, for this embodiment, a single foam layer 34 is fed from roller 47, rather than a two layered foam laminate 18/19 or 27/28 as with board 15 and 24, respectively. The laminated bottom sheet of layers 36, 37 and 38 is formed using the same general procedure for forming the bottom sheet 21/22/23 with board 15.
Once these top and bottom sheets are formed, the top portion 44 and bottom portion 45 of mold 43 are separated and rotated such that portion 44 is at the lowest level and inner surface 63 faces upward to act as a tray upon which the other elements will be stacked, as shown in
The proportioning FPL mixer produced by Canon, of Via C, Colombo, 49 20090 Trezzano S/N, Milan, Italy, may be used in the preferred embodiment.
Immediately after mixture 50 has been sprayed onto the inner surface of the top sheet, the bottom sheet is placed over the top sheet such that the mixture is between the inner surfaces of the top and bottom sheet, as shown in
As shown in
The sports board may further include one or more handles attached to the top surface of the board. The handles are generally attached to the board by snap-rivets and snap-posts passing through apertures in the board and coupled with the board through a flexible strap member.
The method employed provides a fast curing process, which enables finished boards to be pulled from the mold after cooling for about 2 to 15 minutes. This is substantially shorter than the curing time required on conventional fiberglass reinforced polyester molding.
The properties of the finished sports board may be varied from a more flexible board to a stiffer board by adjusting the density of the urethane foam. This production process results in greater efficiencies, with 20 or 30 foam boards being able to be produced per hour. Because chemical mixture 50 is completely encapsulated by the top and bottom sheets, the process does not require a mold releasing agent. The urethane mixture 50 inside the mold expands and fills up the mold cavity 49 very quickly, providing excellent wet-out to the mold surfaces and reproducing the detailed contours of the mold profile without substantial voids, pinholes or other surface defects that occur with conventional fiberglass reinforced products.
The present invention contemplates that other many changes and modifications may be made. Therefore, while the presently preferred form of the sports board have been shown and described, and several modifications discussed, persons skilled in this art will readily appreciate that various additional changes and modifications may be made without departing from the spirit of the invention, as defined and differentiated by the following claims.
