Patent Abstract:
A paddle blade for use in watersports is provided. The paddle blade includes: a shaft interface portion; a stiffening spine; and a blade portion including a fan-shaped tapered portion, a tip region and blade edges; wherein a hollow region is defined in the blade portion extending through the fan-shaped tapered portion toward the tip region but short of the blade edges.

Full Description:
[0001]     This application claims the benefit of U.S. provisional patent application No. 60/600,828 filed Aug. 10, 2004 entitled Injection Molded Paddle Blade, which is hereby incorporated by reference in its entirety for all purposes. 
     
    
     TECHNICAL FIELD  
       [0002]     The present disclosure relates to a paddle blade for a self-propelled watercraft molded by a gas-assisted injection molding process.  
       SUMMARY  
       [0003]     A paddle blade for use in watersports is provided. The paddle blade includes: a shaft interface portion; a stiffening spine; and a blade portion including a fan-shaped tapered portion, a tip region and blade edges; wherein a hollow region is defined in the blade portion extending through the fan-shaped tapered portion toward the tip region but short of the blade edges. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]      FIG. 1  is a view of the underside of a first embodiment of a gas assisted injection molded blade for a paddle, showing the hollow region.  
         [0005]      FIG. 2  is a side elevation view of the embodiment of  FIG. 1 .  
         [0006]      FIG. 3  is a plan view of the upper side of the embodiment of  FIG. 1 .  
         [0007]      FIG. 4  is a view of the underside of a second embodiment of a gas assisted injection molded blade for a paddle.  
         [0008]      FIG. 5  is a side elevation view of the embodiment of  FIG. 4 .  
         [0009]      FIG. 6  is a plan view of the upper side of the embodiment of  FIG. 4 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0010]     The present disclosure relates to a novel blade for a paddle for a self-propelled personal watercraft such as a kayak, and a novel paddle having at least one blade. Generally, gas assisted injection molding is used to form a paddle blade (shown at  10  in  FIGS. 1-3 ) having improved buoyancy, stiffness, anti-cavitation characteristics, and other performance features compared to prior paddle blades. In particular, in some embodiments, gas assisted injection molding is used to form a paddle blade with a unique combination of a stiffening spine formed along a first portion of the blade, shown at  12  in  FIGS. 1-3 , and a fan-shaped extension/taper of the stiffening spine, shown generally at  14 , along the remainder of paddle blade  10 . Fan-shaped extension/taper  14  allows an area of paddle  10  to include a hollow region  16  with improved buoyancy. Furthermore, fan-shaped extension/taper  14  of stiffening spine  12  acts as a double airfoil, providing lift to aid in the removal of paddle blade  10  from the water and during a paddle stroke.  
         [0011]     Careful control of the temperature zones of the injection mold during the injection molding process allows the hollow region to be formed. The outer area of the mold, near a tip region  18  of blade  10 , is maintained at a higher temperature than a shaft interface  20  (i.e. where the paddle shaft meets the blade) of the mold so that resin at the tip region of the mold remains at a low enough viscosity for the gas injected into the mold to form a gas bubble near the tip region of the mold. The nominal wall thickness of the paddle (i.e. the thickness between the hollow interior and the exterior) in some embodiments is approximately ⅛ inch, but may be either greater or lesser than this. Furthermore, the walls may be thinner in the tip region  18  of paddle  10  than in other regions.  
         [0012]     Paddle blade  10  also is lighter weight than known gas assisted injection molded paddles due to the hollow tip and spine structure. For example, paddle blade  10  has a mass of approximately 300 grams, whereas another gas assisted injection molded paddle blade of a substantially similar size having a solid tip and different stiffening structure than stiffening spine  12  was found to have a mass of approximately 370 grams. Furthermore, paddle blade  10  was found to have a buoyancy of 49 grams, centered about tip region  18 , whereas the other blade was found to have a buoyancy of only 11 grams, centered about its shaft interface. Therefore, paddle blade  10  offers superior buoyancy at its tip, thereby offering superior assistance in removing the paddle blade from the water at the end of a stroke.  
         [0013]     As shown in  FIG. 1 , stiffening spine  12  is appears on the back face of the paddle, and in the depicted embodiment extends approximately ⅔ the full length of paddle  10 . Hollow spine  12  provides a channel for material and gas flow from shaft interface  20  to tip region  18 , and is the primary structure for paddle rigidity, and retention of form. Tip region  18 , representing approximately ⅓ of the full length in the depicted embodiment, fans out to meet the blade edges. This results in the unique visual form, provides stiffness to the tip region of paddle  10  and additional structural support to the blade edges. It also results in a hollow region that extends symmetrically through the blade.  
         [0014]     The fanned profile of tip region  18  has a section profile described as two opposing airfoils. These airfoils provide lift to the paddle during the paddle stroke, increasing paddle efficiency and reducing user strain. It also provides lift to the paddle as it exits the water, reducing the energy required for the user raise the blade at the end of paddle stroke. This airfoil and lift minimizes splash during entry and exit of paddle into water, reducing incidental wetness of the user. It also provides low resistance of the paddle during entry and exit modes of the paddle stroke, thereby reducing user strain.  
         [0015]     The fact that the hollow region  16  extends through stiffening spine  12  and toward tip region  18  results in a paddle blade that is positively buoyant. Buoyancy is centered about tip region  18 , which is where buoyancy has the greatest effect on paddle performance. Buoyancy provides upward momentum to the paddle as it exits the water, reducing the energy required for the user to raise the blade at the end of the paddle stroke. Buoyancy counteracts the overall weight of the paddle in use, reducing user strain.  
         [0016]     Paddle blade  10  represents an ideal relationship of size and length of the hollow spine, and fan shaped tip, providing a continuous structure for the full length of the paddle blade for retention of form, rigidity in use, and durability. It also results in minimal material usage and overall paddle weight, matching or less than existing designs, while providing the additional maximization of positive buoyancy. Moreover, this design provides minimum cavitation of water throughout the entire stroke. Cavitation severely reduces efficiency during the paddle stroke. Cavitation may be induced in normal use by the articulation of the spine, which in this design is most severe at the shaft and blending into the relatively flat, fan shaped tip profile that has no relative articulation.  
         [0017]     In the embodiment of  FIGS. 1-3 , stiffening spine  12  and fan shaped extension/taper  14  are generously blended into the blade faces and ultimately to tip region  18 , resulting in a form devoid of severe articulations. This minimizes cavitation of water throughout the entire stroke, and minimizes cavitation of water during slicing modes of paddle use; i.e., during entry and exit of the paddle into the water, and during bracing and draw strokes.  
         [0018]     The embodiment of  FIGS. 1-3  further represents an ideal relationship of tip location, power face dihedral, and back face geometry including blade edges, hollow spine, and hollow fan tip. From the end view of the paddle, the relationship of blade edge height, maximum dihedral on the power face, and maximum spine height on the back face minimizes water cavitation during slicing modes of paddle use by allowing positive flow along all surfaces. During modes of paddle use where water pressure is normal to the power face, the dihedral curvature on the power face equally directs water flow from the center line to the edges of the paddle. This effectively stabilizes the paddle as it travels through the water reducing the tendency flutter from side to side which reduces user strain. Cavitation of water is minimized as the flow wraps around the blade edges and meets along the spine on the back face of the blade. During the entire paddle stroke, the tip position and its relation to the paddle blade curvature directs water flow toward the tip of the blade, which results in superior paddle efficiency. It also results in positive water flow toward the tip along all blade surfaces, minimizing the occurrence of water cavitation, and maximizing paddle efficiency. Moreover, the tip position, its relation to the paddle blade curvature, and the power face dihedral results in a rapid shedding of water during the exit mode of the paddle stroke. This minimizes user strain and reduces incidental wetness of user during the paddle stroke.  
       Embodiment of FIGS.  4 - 6   
       [0019]     Another embodiment of a gas assisted injection molded blade, is shown at  100  in  FIGS. 4-6 . Therefore, as showing in  FIG. 4 , a hollow region  116  is shown to extend through stiffening spine  112 , fan-shaped extension/taper  114 , tip region  118 , all the way out to adjacent blade edges  122 . In the depicted embodiment, hollow region  116  extends to within one half inch of the blade edges  122 , although in the same embodiment it might extend only to within three-quarters of an inch. Corresponding numbers have been used for this embodiment, except that they are in the 100 series. In this second embodiment  100 , the entire blade is hollowed by a gas assisted injection molded process. Blade  20  may include stiffening ridges or depressions (not shown) formed along the length or width of the blade to impart greater rigidity to the blade. This paddle blade  100  would increase buoyancy, reduce the occurrence of water cavitation, reduce water splashing and user wetness, on entry and exit. It will also improve paddle stroke efficiency by providing the maximum amount of airfoil lift for the exit portion of the stroke.  
         [0020]     Each of the depicted embodiments are designed to be used with a paddle shaft  24  or  124  and paddle handle  26  or  126 , although these have only been schematically depicted in the figures.  
         [0021]     Variations may be made that will be obvious to those skilled in the art. Such variations are intended to be covered by the claims that follow.

Technology Classification (CPC): 1