Abstract:
A towable water sports device having a hydrofoil assembly including a strut, fuselage and front and rear blades carried by the fuselage wherein said parts are extruded aluminum.

Description:
[0001]     This patent application claims the benefit of Provisional Patent Application Ser. No. 60/524,657, filed Nov. 25, 2003. 
     
    
     BACKGROUND OF INVENTION  
       [0002]     Towable hydrofoil water sports devices for supporting a human rider are described in U.S. Pat. No. 5,100,354, granted March  31 ,  1992 , U.S. Pat. No. 5,249,998, granted Oct. 5, 1993, U.S. Pat. No. 6,179,676, Jan. 30, 2001, and U.S. Pat. No. 6,551,158, granted Apr. 22, 2003  
         [0003]     These towable water sports devices have a strut, fuselage and front and rear wings or blades which are made by casting a molten aluminum alloy. This process requires pouring molten aluminum into a sand or steel mold. The alloy used in this process is a 356A aluminum which is then heat-treated to T-6 hardness. The casting is then ground or sanded down to eliminate all entry gates, all venting gates and the receiving canals. This requires a lot of grinding, sanding and machining of the cast part after it has been taken out of the mold. Cutting and grounding a part from a rolled or pressed aluminum billet wastes material and requires a lot of machine time. Another disadvantage in manufacturing using the cast process is that the metal as it cures releases or gives off gases, resulting in the production of many small voids. This porosity in the part results in a poor finish. In addition as the casting comes out of the mold, there is shrinkage and the extent of the shrinkage is variable due to the nature of the alloy and weather conditions during the curing process. The primary disadvantage of a part cast from 356A aluminum is that it does not have the ability to flex which can result in a catastrophic failure or breakage of the part. There is a large rejection rate when casting an aluminum part due to the temperature of the mold, the outside temperature, and the amount of the metal as it is poured into the mold. The temperature of the mold has to be compatible with the heat of the material poured into the mold and this changes on a daily basis. There is a lack of overall consistency in the parts. The porosity of the cast part is present on the surface of the part. The surface porosity of the cast part adds drag to the foil assembly, which hinders the performance of the hydrofoil assembly. The porosity of the cast part also is not compatible with and does not accept the anodizing process. The anodizing is, however, desirable in that it offers a protective, maintenance free and corrosion-resistant finish.  
       SUMMARY OF INVENTION  
       [0004]     In a water sports device for supporting a seated human rider while said rider and device are towed behind a powered watercraft, comprising: an elongate board having a front end and a back end; a seat secured to said board for supporting the buttocks of a seated rider at a position spaced above said board; a holder spaced toward the front end of said board from said seat for securing at least one foot of said rider over the top of said board; an elongate strut perpendicular to and extending downward from said board; a fuselage having a forward end and a rearward end fixed at a point between its forward end and rearward end to said strut at a position spaced below said board; a forward planing wing or blade secured proximate the forward end of said support, generally parallel to said board, wherein said forward planing wing or blade has a generally flat upper face and a generally flat lower face; and a rear planing wing or blade secured proximate the rearward end of said support, generally parallel to said board, wherein said rearward planing wing or blade has a generally flat upper face and a generally flat lower face; 
        the improvement wherein at least said strut and fuselage are made of extruded aluminum alloy.        
 
       DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0006]     The invention uses an extruded aluminum out of a AA6061 alloy heat-treated to T-6 in advance of the extrusion. The 6061 heat-treated aluminum is one of the alloys to be used, but it is not the only one suitable for use in this manufacturing process. For example, suitable aluminum alloys include the M 6000 series which are disclosed in Park U.S. Pat. No. 4,589,932, and Wade et al U.S. Patent No. 5,503,690, the disclosures of which are expressly incorporated herein by reference. This eliminates the need to take the casting from the foundry to a separate location for the heat-treating process. Extrusion does not involve the pouring of metal. The metal is billet or rolled aluminum is pushed or pulled through a pre-cut die. This gives the material a grain as opposed to a porosity as in a part made by the cast process. This grain allows the running of the grain in the long dimension of the part for added strength. This process eliminates the porosity (that offers no strength) and gives the part more strength with completely different characteristics. The extruded part can bend or flex with a memory that allows it to retain its original shape. The extruded part is less brittle which avoids breakage while under stress in use and danger to the rider. Eliminating the porosity on the exterior surface of the part gives it: a)more visibly aesthetics; 2) polishes up nicely; 3) less drag due to little or no porosity; and 4) it is compatible with the anodizing protective coating. The surface anodizing of aluminum extrusions described, for example, in Fukagawa et al U.S. Pat. No. 5,911,845.  
         [0007]     The advantages of extruded aluminum are applicable to the strut, fuselage, front and rear blade or wing comprising the foil assembly used in a towable hydrofoil. 
     
    
     THE DRAWINGS  
       [0008]     Turning to the drawings:  
         [0009]      FIG. 1  is a perspective view of the water sport device of this invention with the rider seated and being towed through the water by a power boat (not shown).  
         [0010]      FIG. 2  shows at the left a top plan view of the fuselage and front and rear planing blades, and at the right, a side view of the strut, the parts being unassembled.  
         [0011]      FIG. 3  shows the strut being inserted into the opening provided in the fuselage, the fuselage and planing blades being shown in longitudinal section.  
         [0012]      FIG. 4  shows the strut fully in place in the fuselage and welded to the fuselage.  
         [0013]      FIG. 5  depicts a die through which aluminum alloy is extruded to make the parts from which the strut, fuselage and planing blades are ultimately formed. 
     
    
       [0014]     Turning to the drawings in more detail, the water sports device of this invention has a seat  10  for the rider  11  which is affixed to the curved board  12 , the strut  14  projects downwardly from board  12  in a generally perpendicular fashion. The lower end of strut  14  is received in opening  16  of fuselage  18 . The fuselage  18  carries the front planing blade  20  and rear planing blade  22 .  
         [0015]     A further feature of this invention concerns the combination of parts. In the past the castings for the foil assembly were three different parts: 1) a t-bar consisting of strut and fuselage as a single component; 2) front wing; and 3) rear wing. The new means of manufacturing includes four parts: 1) the rear wing  22 ; 2) front wing  20 ; 3) the strut  14 ; and 4) the fuselage  18 . The strut  14  and the fuselage  18  are heliarced (a means of welding aluminum) together to form the t-bar as shown in  FIG. 4 . The extruded strut  14  fits into the fuselage slot  24  as shown in the drawings and heliarced  26  as depicted in the drawing. This process is completely new from the previous method of manufacturing in the past. The extrusion process also provides the capability of including the front wing  20  and rear wing  22  within the extruded fuselage  18  as a single unit, thus reducing the number of parts to two. For example, the fuselage  18  and front wing  20  and rear wing  22  can be cut to the desired shape from a single aluminum extrusion using a programmable milling machine which is available in the marketplace. This reduces assembly time since the wings do not have to be joined to the fuselage in separate operations.  
         [0016]     The extrusions are formed by drawing hot formable aluminum through a die such as die  28 . The extrusion is then quenched and heat treated. The strut can be extruded through a die of appropriate cross section, cut to length and used as such without further working. This process conforms generally to  FIG. 1  of Wakabayashi U.S. Pat. No. 5,321,967. The slot  24  is cut into the fuselage. The fuselage, wings and strut in the desired configuration are polished smooth. The resultant surface is quite slick and well adapted to anodizing which provides an esthetically pleasing appearance which is highly resistant to corrosion. The avoidance of corrosion is an important benefit of this invention in that the strut, fuselage and blades or wings remain smooth and do not acquire or build up added drag in the water over time due to oxidation and mineral build-up.  
         [0017]     The heliarc process is an oxygen gas mix and can be used for the welding of the extruded parts and it represents one option to be used for welding aluminum parts, but is not the only one available for this method of manufacturing. Other techniques for welding or joining pre-formed aluminum parts are known to those skilled in the art.  
         [0018]     The benefits of this invention include a less expensive part, stronger part, more consistent part and a part with less drag, increased performance, and fewer warranty problems. Extrusion has been used in other industries such as screen doors, window frames and others. The present invention is a completely new concept in the manufacturing of hydrofoils for water sport devices and it provides results which are not manifested in prior extruded parts.