Abstract:
A shaft structure with an adjustable stiffness is provided for golf clubs, fishing rods and like apparatuses. The shaft structure employs an inner and outer shaft structure. The golfer, in practice, configures the stiffness of a golf shaft, by adjusting the pressure of an inner shaft structure. The combination of outer and inner shaft structure stiffness results in an advantageous stiffness profile. The golfer can, at any time and very easily, change the stiffness profile of the golf shaft.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to shafts for golf clubs, fishing rods and like apparatuses and more particularly where the stiffness of these devices can be adjusted by the user in an advantageous manner to match their physical abilities. 
       BACKGROUND OF THE INVENTION 
       [0002]    Golf shafts are typically manufactured with a predetermined stiffness or flex. The stiffness of a golf shaft refers to its resistance to bend under load and is typically measured as the amount of deflection the shaft experiences when the shaft is positioned horizontally and subjected to a constant force. Presently, golf shafts are mass produced with a predefined stiffness or flex without regard for a golfer&#39;s individual swing mechanics. Typically, the flex is provide in discreet stiffness&#39;s such as A, R, S, X. These flex ranges are designed in an attempt to accommodate a vast multitude of golfers. 
         [0003]    The correct stiffness of a golf shaft plays a pivotal role in proper club performance. A golf shaft that is too flexible tends to promote a hook whereas a golf shaft that is too stiff tends to cause the golf ball to slice. As an alternative to off the shelf golf clubs golfers have often sought out experienced professional club makers in order to have their golf clubs fitted to the proper stiffness. Typically, the process is time consuming and involves numerous pieces of equipment, expertise and expense. Ultimately the attempt is to fine tune the stiffness of the golf shaft to match the golfer&#39;s swing dynamics and physical performance. However, a golfer&#39;s performance can dramatically change over time. 
         [0004]    Prevailing weather conditions can also dictate the stiffness required of a golf shaft. For example, on a windy day, a golfer might choose to readjust their shaft for a stiffness that promotes a lower, penetrating ball flight which reduces the affects of the wind. Conversely, on a day with little or no wind, a golfer may choose to readjust the stiffness to promote a higher launch angle. 
         [0005]    Course conditions will also dictate what type of shaft stiffness is required. For instance, on a golf course with narrow fairways accuracy is at a premium whereas a wide open fairway would be more forgiving. Longer courses require a greater distance off the tee. Accuracy in a golf shot calls for a stiffer shaft whereas achieving more distance is a benefit derived from a more flexible golf shaft. 
         [0006]    Various proposals to provide variable stiffness for a golf Club shaft (or even a fishing pole) have previously been made that involve using a hollow shaft charged with a gas or liquid fluid that can be pressurized and by mechanical devices such as rods, jackscrews and the like. Increasing the fluid pressure in the shaft increases the shaft stiffness. Increasing the length, of the rod increases the tension and, hence shaft stiffness. 
         [0007]    Such pressurizable shafts are illustrated, for example, by Menzies U.S. Pat. No. 1,831,255, Sears U.S. Pat. No. 2,432,450, Busch U.S. Pat. No. 3,037,775, Burrough U.S. Pat. No. 4,800,668 (a fishing rod), Simmons U.S. Pat. No. 5,316,300, Koch et al. U.S. Pat. No. 5,540,625, Painter U.S. Pat. No. 5,632,693, Qualizza U.S. Pat. No. 7,226,365. 
         [0008]    So far as is known, these variable stiffness, hollow shaft structures of attempt to change the stiffness of golf shaft by pressurizing a fluid which introduces an axial stress on the golf shaft. All suffer from several significant shortcomings. Hollow golf shafts that are filled with a liquid are dramatically heavier as compared to conventional golf shafts. For example, a, standard golf shaft filled with a liquid is two to three times heavier than a standard golf shaft. The heavier, liquid filled golf shaft will profoundly slow down a golfer&#39;s swing speed thereby resulting in an unacceptable loss of distance which would, of course, have a, detrimental effect. Golf shafts that are filled with a compressible gas such helium cannot possibly provide a force great, enough to affect a stiffness change without requiring extremely high pressures due to the high Young&#39;s modulus of the material used in modern golf shafts such as graphite composites. These high pressures are most assuredly unachievable and absolutely unacceptable from a safety standpoint. The anticipated high pressures would create a potentially serious situation if the golf shaft were to rupture such as would be the case when all irate golfer would strike the ground with their club or strike a tree. 
       SUMMARY OF THE INVENTION 
       [0009]    In order for a golf club to be effective and ultimately configured for a golfer by the golfer without requiring the golfer to have intimate knowledge or club-building skills, the present invention provides for a device that can be easily changed to accommodate the golfer&#39;s abilities for any given day any given weather condition and course conditions as well. The invention allows the golfer the unique ability to tune a golf club from observations of ball flight while they are using the golf club rather than having to seek out a club-maker and use misleading equipment which is time consuming and costly. 
         [0010]    The present invention overcomes the inability of prior art shafts in providing the ability to change the stiffness of a golf shaft. A shaft structure is provided which can be easily and safely tuned, to match the golfer&#39;s abilities so as to maximize both shot accuracy and distance while maintaining an acceptable weight. 
         [0011]    More particularly, this invention relates to a shaft structure for golf clubs, fishing poles and like apparatuses incorporating an innovative variable stiffness shaft-in-a-shaft structure without compromising other performance characteristics such as weight or structurally integrity and safety as well. Additionally, the present invention does not serve to change the stiffness of shaft structure by imposing an axial stress or compression force upon the shaft but rather provides for a device which allows for the changing of the stiffness of shaft structure by virtue of a shaft-in-a-shaft structure wherein the absolute overall stiffness is born from the compounded stiffness of both the inner and outer shaft structure stiffness acting in a total harmonious arrangement. As such, existing golf shafts can be easily retrofitted with the present invention. 
         [0012]    One object of the present invention is to provide a shaft structure which allows a golfer to change the stiffness of a shaft structure in order to match their athletic abilities while maintaining structural integrity and safety. 
         [0013]    One object of the present invention is to provide a shaft structure which allows a golfer to change the stiffness of a shaft structure in order to match the course conditions of the day. Course condition plays a huge part of being able to score well. For instance, on a course that has very tight fairways a golf shaft should be stiffer so as to improve accuracy. On courses that are more open and longer it is beneficial to have a golf shaft that is less stiff so as to gain more distance. 
         [0014]    Another object of the present invention is to provide a shaft structure that has a selectable stiffness. Hence, a single shaft structure can replace many different combinations and permutations of golf shafts, golf clubs, and manufacturing procedures and can avoid the need for large inventories of golf clubs with golf club shafts pre-set to different stiffness values, thereby generating a savings of what would otherwise be an expenditure of substantial amounts of money. 
         [0015]    Another object of the present invention is to provide a device which allows manufactures to utilize their current stock of golf shafts so as to provide adjustability to the stock golf shafts. 
         [0016]    Yet another object of the present invention is to provide a golf club shaft structure which allows a golfer to customize the stiffness of each shaft of a set of clubs, or of a, fishing pole, according to his ability or wishes without being dependent upon the shaft stiffness that happens to result from purchasing a set of clubs such as woods or a set of irons. 
         [0017]    Another object of the present invention is to provide a golf club shaft structure which allows a golfer to customize the stiffness of an existing golf club or clubs. The present invention easily adapts to a golfer&#39;s existing golf club and provides the ability to enhance both the stiffness of a set of clubs, fishing poles and like apparatuses. 
         [0018]    Another object of the present invention is to provide a golf club shaft structure that requires minimum force to adjust the stiffness of golf shaft Seniors especially need to be able to adjust their club stiffness without requiring an extraordinary amount of physical effort. 
         [0019]    Yet another object of the present invention is to provide a golf club shaft that would drastically reduce the probability that a rupture would occur were the fluid would leak out. Given the shaft-in-a-shaft structure it is unlikely that the inner shaft structure would be damaged as well when the overall golf shaft is subjected to a blunt force. 
         [0020]    Another object of the current invention is to provide a golf club shaft structure that provides a significant safety factor by providing a device which utilizes the compounded action of a shaft-in-a-shaft, structure such that the inner shaft can be made from material with a low Young&#39;s modulus such as plastics and, as such requires significantly lower and safe pressures to effect a stiffness change. 
         [0021]    Other and further objects, aims, features, advantages, applications, embodiments and the like regarding the present invention will be apparent to those skilled in the art from the present specification, attached drawings, and appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which: 
           [0023]      FIG. 1  illustrates a perspective view of one embodiment of a golf club which incorporates a shaft structure of the present invention; 
           [0024]      FIG. 2  illustrates a diagrammatical view of the inner shaft structure of the shaft structure of  FIG. 1 ; 
       
    
    
     DETAILED DESCRIPTION 
       [0025]      FIG. 1  reveals an illustrative golf club  2  that incorporates an embodiment of a shaft structure  4  of the present invention. In the preferred embodiment, shaft structure  4  includes an inner shaft structure  6  and outer shaft structure  8 . Outer shaft structure  8  is fashioned as a conventional golf shaft with an associated stiffness. Those skilled in the art will recognize that a multitude of materials may be used for both the inner and outer shaft structure and that using alternative materials does not deviate from the scope or spirit of the present invention. Stiffness is indicated by stiffness indicator  5  which is affixed firmly to the butt and of the grip. Indication of stiffness is demonstrated by the dial markings of stiffness indicator  5  and by the relative position of the capstan  20 . 
         [0026]    With reference to  FIG. 2  inner shaft structure  6  is comprised of a proximal end and a distal end. Proximal end of inner shaft structure  6  is further comprised of pressurization unit  9 . Distal end of inner shaft structure  6  outside diameter is received by the inside diameter of the outer shaft structure  8 . Distal end of inner shaft structure  6  is sealed in order to form a seal-tight compartment. Spacers  12 ,  14  and  16  serve to mechanically communicate the bending behavior of the outer shaft structure  8  to the inner shaft structure  6 . Those skilled in the art will recognize that a plurality of spacers may be used as well as choosing different locations for the spacers in a more advantageous manner and in doing so does not deviate from the spirit or scope of the present invention. In turn the resistance to the load imposed upon outer shaft structure  8  during a golf swing is influenced by both the stiffness of the inner shaft structure  6  and the stiffness of the outer shaft structure  8 . When outer shaft structure  8  is under load the unique bending profile is transferred to the inner shaft structure  6  via spacers  12 ,  14  and  16 . Inner shaft structure  6  then has an opportunity to influence the resistance to bending of outer shaft structure  8 . Since the stiffness of inner shaft structure  6  is adjustable so then is the overall shaft structure  4 . Due to the shaft-in-a-shaft structure inner shaft structure  6  is isolated from potential damage that may occur from damage to the outer shaft structure  8 . Additionally, due to the shaft-in-a-shaft structure and due to the lack of need of extreme force in order to affect a change in stiffness inner shaft structure  6  can be fashioned from plastics which require very low forces to enact a stiffness change. 
         [0027]    Pressurization unit  9  is comprised of piston  10 , seal  12 , jackscrew  16 , bulkhead  18  and capstan  20 . Capstan  20  has at one end a hex cap that allows for the inserting of a hex wrench in order to facilitate the turning of jackscrew  16 . Fluid  22  resides within the entire length of inner shaft structure  6 . Fluid  22  many be a gas such as helium or a liquid, or the like. It should be noted that relatively speaking inner shaft structure  6  is small in comparison to the outer shaft structure  8 . The small diameter of inner shaft structure  6  requires a minimal amount of fluid  22  to effect a relatively large change in the overall stiffness of shaft structure  4 . The combination of the outer shaft structure  8 , inner shaft structure  6  and fluid  22  results in an overall shaft  4  weight that is comparable to conventional shaft structures. Additionally, inner shaft structure  6  can be fashioned from materials with a very low Young&#39;s modulus since the overall structural integrity of shaft structure  4  is not dependent upon the structural integrity of inner shaft structure  6  but rather it is dependent upon the outer shaft structure  8 . The very low Young&#39;s modulus provides the opportunity to use materials that would otherwise not be considered such, thermoplastics. 
         [0028]    Clockwise rotation of jackscrew  16  causes piston  10  to traverse longitudinally downward thereby reducing the volume and hence increasing the pressure of fluid  22 . The increase in pressure of fluid  22  promotes an axial stress upon inner shaft structure  6  causing inner shaft structure  6  to stiffen. The axial stress provided, by the pressure of fluid  22  is accommodated by the sealed distal end of inner shaft structure  6  and by bulkhead  18  at the proximal end of inner shaft structure  6 . By working in tandem, the increase in stiffness of inner shaft structure  6  complements the static stiffness of outer shaft structure  8  by virtue of the mechanically cooperative nature of spacers  12 ,  14  and  16 . Counter-clockwise rotation of jackscrew  16  causes piston  10  to travel longitudinally upward thereby decreasing the pressure of fluid  22 . Reduction in pressure of fluid,  22  reduces the axial stress imposed upon inner shaft structure  6  and thereby reduces the overall stiffness of shaft  4  due to the compounded nature of the stiffness of both the inner shaft structure  6  and the outer shaft structure  8 . Those skilled in the art will recognize that a multitude of other materials may be used as fluid  22  and that using other materials does not deviate from the scope or the intention of the current inventions. 
         [0029]    While at practice, a golfer would evaluate the performance of the golf club  2 . While hitting practice shots the golfer would notice ball flight and would tune the golf shaft  4  according to their preference which is predicated upon their physical limitations, course and weather conditions for the day. If a more tighter shot dispersion is needed, the golfer would, turn jackscrew  16  via hex capstan  20  clockwise causing piston  10  to move downward thereby compressing fluid  22  and enacting a greater axial stress upon inner shaft structure  6 . Conversely, if more distance is needed the golfer would turn jackscrew  16  via hex capstan  20  counter-clockwise causing piston  10  to move upward thereby decompressing fluid  22  and enacting less axial stress upon inner shaft structure  6 .