Patent Publication Number: US-8534609-B2

Title: Traction kite with high projected leading edge

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of provisional U.S. Patent Application Ser. No. 61/362,463, filed on Jul. 8, 2010. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     N/A 
     COPYRIGHT NOTICE 
     A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or patent disclosure as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyrights rights whatsoever. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to propulsive wings and traction kites, used for applying a traction force and/or pulling a load. More particularly the present invention relates to a sport traction kite having a generally tubular inflatable leading edge that is concave when viewed from the side in flight mode. 
     2. Description of Related Art 
     The use of kites as a means of propulsion has existed for over a century. Kites were first used as a means of propulsion in pulling boats. The use of sport kites in water and land based activities, such as kiteboarding and snowboarding, has grown tremendously in recent years. These sports adapt the principals of surfing and snowboarding to include kites as a method for generating propulsion, speed, and elevation. A number of advances in kite design have led to improvements in safety, attainable speeds, and overall performance. 
     Most sport traction kites currently used in board sports are constructed with flexible canopy having an inflatable leading edge armature which distributes loads via ropes attached along the leading edge and at the lateral ends. As used therein the terms “sport kite,” “traction kite,” or “kite” shall mean a propulsive wing that harnesses wind power to pull a rider over or through, land, water, or snow on a riding platform (e.g. a board). A traction kite of this type is described in U.S. Pat. No. 4,708,078 to Legaignoux et al., wherein a basic design for a leading edge inflatable (“LEI”) kite is disclosed. Legaignoux discloses a traction kite having a leading edge with an inflatable leading edge armature covered by a flexible envelope. 
     As kite sports have evolved, demand for kites with improved performance characteristics has grown. Specifically, kite users desire kites with improved handling and control, faster turning speeds, and more responsive control achieved with minimal user input force. As a result, several different types of leading edge inflatable kites have been developed. The C-kite is the most common kite design that has been available for the longest period of time. It is named for the arc-like shape it forms while in flight which resembles the letter “C”. The attachment of four lines at the four corners of the kite cause the kite to arc sharply while in flight. When viewed from overhead, the C-kite characteristically forms a convexly shaped trailing edge.  FIG. 1  depicts a side view of a prior art C-kite, generally referenced as  1 , having an inflatable leading edge  2 , a trailing edge  3 , and a canopy  4 , supported by inflatable struts or ribs  5 . A slight variation of the C-kite is the 5 th  line C-kite which includes an extra line attached at the middle of the leading edge of the kite. The sole purpose of the 5 th  line is to assist the rider in de-powering and re-launching the kite. De-powering is essentially a safety mechanism for the rider which reduces the propulsive surface area thereby reducing the force of the wind on the kite and the lines. 
     A recent innovation in kite design was the introduction of the Bow kite. The Bow kite has two defining characteristics which differentiate it from the C-kite: 1) the trailing edge of the bow kite is concave; and 2) the Bow kite is controlled by a series of control lines, commonly referred to as a bridle. The bridle is affixed to the kite in a web-like fashion and causes the kite to possess a flatter shape when in flight. The concave trailing edge and the addition of the bridle to the leading edge of the kite allow the kite to be de-powered with ease thus eliminating the need for a 5 th  line. Furthermore, these features allow the bow kite to be adaptable to varying wind speeds, whereas the C-kite&#39;s design relegates it to specific wind speeds. U.S. Pat. No. 7,374,133, issued to Legaignoux et al., provides an example of a conventional Bow kite. 
     Even more recently hybrid kites have been produced which combine elements of both the C-kite and the Bow kite. Although there are various forms of hybrid kites, all of the known versions are characterized as having convex trailing edge and a leading edge bridle. The convex trailing edge is adapted from the C-kite and the leading edge bridle and bow configuration is adapted from the Bow kite. The hybrid kite achieves a middle ground between the C-kite and the Bow kite. It possesses a greater ability to de-power than the C-kite, but also allows for a greater performance and turning capability than the Bow kite. 
     In general there has been an increased demand for fraction kites having improved performance characteristics for use in kite sports, such as kiteboarding and snowkiting (a/k/a snow kiteboarding). The curvature of the vertical leading edge of the kite in flight affects the performance of the kite. The angle and radii of curvature from the bridle tie-lines to the top of the kite dictate the size of the surface area of the central propulsive region. The greater the surface area, the greater the performance of the kite. 
     As stated in the aforementioned background, the curvature of the various edges of the kite affects the performance characteristics that the kite will possess. The Bow kite handles a myriad of wind velocities and can be easily depowered due to a concave trailing edge. Likewise, the C-kite&#39;s convex trailing edge gives the rider a more direct feel when riding and provides greater responsiveness to rider maneuvers. Furthermore, it is well known that a convex leading edge is the most effective design for all supported leading edge kites. 
     One known prior art kite, sold by Globe Kites, under the designation V-SONIC, wherein a small projecting V-shape was formed at the mid-point of the leading edge. While providing a marginal increase in surface area, the V-SONIC kite failed to achieve significant performance enhancement since the wingtips were swept back as was customary on Bow and hybrid kites. As a result, the V-SONIC kite failed to realize gains and advantages in performance characteristics relating to fast and responsive turning as the V-SONIC kite leading edge, when viewed from the side, extends from the propulsive region to the tip in a liner shape and thus fails to maximize the surface area transition between the propulsive center region. 
     The prior art fails to disclose or suggest a propulsive wing in which the curvature of the vertical portion of the leading edge of the kite is concave when viewed from the side in flight mode. This curvature also lends itself greatly to the performance of the kite. There is therefore a need for a propulsive wing with an inflatable support structure that is designed to maximize the surface area of the central propulsive region, while still providing a responsive and easily-controllable kite. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention overcomes the disadvantages and limitations of the prior art by providing a leading edge inflatable traction kite that defines a projected leading edge, namely a lead edge that, when viewed from the side while in flight, is concavely shaped. The present invention thus provides a traction kite wherein the surface area is maximized in a propulsive region formed along the central region of the leading edge (or top part of the kite) and minimized in control regions disposed on either side of the propulsive region and terminating at the kite/wing tips. 
     Accordingly, it is an object of the present invention to provide a leading edge inflatable traction kite having a larger central propulsive region for towing a load. 
     Another object of the present invention is to provide a leading edge inflatable traction kite that overcomes the less responsive turning characteristics and lower efficiency of the prior art. 
     Still another object of the present invention to provide a leading edge traction kite that provides optimum performance characteristics, in particular maximizing propulsive forces while maintaining the ability to perform quick turns and maneuvers. 
     It is furthermore another object of the present invention to provide a leading edge inflatable traction kite that is inexpensive to manufacture, therefore allowing for widespread distribution. 
     These and other objects are met by the present invention which will become more apparent from the accompanying drawing and the following detailed description of the drawings and preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a side elevation view of an traction kite with an inflated leading edge in accordance with the prior art; 
         FIG. 2  is a front perspective view of an inflated leading edge fraction kite in accordance with the present invention fitted with control lines; 
         FIG. 3  is side view of the inflated leading edge traction kite fitted in accordance with the present invention illustrating the concave leading edge; 
         FIG. 4  is a plan view of the inflated leading edge traction kite in accordance with the present invention spread out on a flat surface. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference now to the drawings,  FIGS. 2-4  depict a traction kite in accordance with the present invention. Traction kite  10  includes an inflatable, elastically deformable leading edge spar  12  extending across the entire longitudinal front side of kite  10 . Leading edge spar  12  comprises an inflatable tubular structure. A series of inflatable struts or ribs  14  extend generally perpendicularly from the inflatable leading edge  12  towards the trailing edge  13  of the kite  10 . Inflatable ribs  14  are preferably in fluid communication with leading edge  12  such that inflation of leading edge  12  causes inflation of ribs  14 . Leading edge  12  and ribs  14  form the support structure for the canopy  16  of kite  10 . Canopy  16  is connected to and extends between parallel ribs  14  and the leading edge strut  12  as is generally known in the art. Leading edge  12  and canopy  16  serve as the main surfaces over which air flows, leading to the creation of an area of low pressure over the top of the canopy  16  and an area of high pressure beneath the canopy  16  such that kite  10  aerodynamically functions as a wing. Kite  10  further includes lateral ends or tips  18 . 
     A plurality of control lines  20  may be connected to the tips  18  and/or leading edge  12  of kite  10 . Kite  10  may be fitted with any suitable configuration of control lines, including a four (4) line configuration, a 5 th  line configuration, or a bridle configuration wherein a plurality of control lines are attached along the leading edge. In the preferred embodiment illustrated in  FIG. 2 , kite  10  may be fitted with a four (4) line control system, with two (2) lines attached to each wing tip  18  (namely the four outermost corners when the kite  10  is laid flat), and no lines are attached to the leading edge. The four tie lines allow the rider to selectively apply control forces to portions of kite  10 . These applied control forces, cause the kite  10  to deform thus changing the angle of attack. The arrangement of lines may vary; in an alternative embodiment the inventor contemplates the existence of a series of control lines arranged in a web-like fashion, commonly referred to as a bridle. Changing the angle of attack changes the aerodynamic characteristics of kite  10  thereby causing it to turn, or depower, or increase power, depending on the resulting angle of attack. For example, lowering the angle attack on one side of the kite  10  lowers the pressure difference on that side of the kite  10  thereby reducing the propulsive force generated and causing the kite  10  to turn in a direction towards the side with the higher angle of attack. Through this mechanism, the direction in which the kite  10  is flying is controlled thereby allowing the kite to be maneuvered in kite propulsion based sports. As should be apparent, any suitable bridle and control line configuration is considered suitable for use with a kite  10  of the present invention. 
     A significant aspect of the present invention involves providing a traction kite  10  having improved performance and control characteristics, namely, the ability to quickly turn and change direction in response to the rider&#39;s control motions and selective application or reduction of force. This characteristic is directly related to how quickly and easily the angle of attack of the kite  10  is changed. The degree and speed by which the angle of attack is changed largely depends the curvature of the leading edge  12  of the kite  10 . 
     Kite  10  of the present invention defines a convex leading edge shape when the kite  10  is viewed from overhead, and further defines a concave leading edge shape when the kite  10  is viewed from the side while it is in flight. Accordingly, a significant aspect of the present invention involves providing a kite  10  that has a concave leading edge  12  when the structure is viewed from the side while in flight.  FIG. 3  best illustrates the leading edge geometry wherein the leading edge is depicted as significantly concave as seen with the aid of reference line A-A. More particularly, a variable geometry leading edge  12  provides kite  10  with a high projected central propulsive region of increased surface area along the top portion of the kite (e.g. the central or mid-portion) resulting in increased propulsive force thereby allowing the kite to have a greater efficiency with respect to harnessing the power of the wind. Further, the variable geometry leading edge  12  provides kite  10  with a concave leading edge  12  extending from the leading edge centerline to the tip  18  when the kite is viewed from the side when deployed in flight. The concave shaped defined by leading edge  12  preferably defines an arcuate or curved profile extending from the centerline of the kite to the tip or end of the leading edge. Providing kite  10  with a concavely curved leading edge profile is seen in  FIG. 3 , functions to maximize control and turning performance by minimizing the surface area of the control regions, namely those generally vertically disposed regions that begin at the tips and end at the propulsive region. 
     Accordingly, the present invention differs from the prior art,  FIG. 1 , with respect to the curvature of the leading edge  12 . The kite of the prior art ( FIG. 1 ) comprises a generally straight leading edge which offers little benefit from a performance standpoint. Kite  10  further differs significantly from the Globekites V-SONIC kite wherein the leading edge if viewed from the side extends from the propulsive region to the tip in a liner shape. The kite  10  of the present invention may be best characterized as a C-kite hybrid because it is sharply curved in-flight. In a preferred embodiment, the trailing edge  13  is relatively straight, but it may be contemplated that the trailing edge be convex similar to that of a C-kite. Through the curved design of the inflatable leading edge strut  12 , a traction kite  10  with maximized performance characteristics, and in particular turning ability, is achieved. 
       FIG. 4  further illustrates the kite geometry of traction kite  10  as if it is spread out on a flat surface in order to illustrate the existence of an enlarged propulsive region, referenced as  20 , as compared to the control regions referenced as  22 . The top section of the traction kite  10  is the part which achieves the highest efficiency with respect to harnessing the force of the wind. The design of the present invention provides a propulsive section with a maximized surface area. The vertical curvature of the leading edge  12  allows the rider to maintain a responsive turning character by providing a standard four-line arrangement while enlarging the propulsive region to maximize efficiency. 
     The instant invention has been shown and described herein in what is considered to be the most practical and preferred embodiment. It is recognized, however, that departures may be made therefrom within the scope of the invention and that obvious modifications will occur to a person skilled in the art.