Abstract:
A device designed for modifying the length of a golf club shaft. The device is a three-piece mechanism with a bottom part bonded into the top end of a tubular golf club shaft, a top part provided within the grip, a threaded screw provided within the top part and threadably connected to the bottom part such that movement of the screw will adjust the distance between the top part and bottom part thereby adjusting the club length. The extension device is hidden within the shaft and grip and does not require a custom grip or shaft.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to a device for adjusting the length of a golf shaft. In particular, the invention concerns modifying the length of the shaft by utilizing the device at the gripping end of the club that is not visible and does not require a special grip or shaft. 
     BACKGROUND OF THE INVENTION 
     One of the more important factors in golf club equipment is the club shaft. The shaft transfers the golfer&#39;s power to the club head. Golf club shafts are available in various types of materials and structures. Steel shafts are stronger, last longer, more durable and generally less expensive than graphite or carbon fiber shafts, and are usually made from carbon steel, although stainless steel is sometimes used. The steel shafts are available in stepped or rifle designs. The graphite shafts are more expensive and less durable; however, the lighter weight creates greater swing speed for more power. Also available are multi-material and titanium shafts. 
     When installing a shaft, the proper length must be accurately determined. The length can be as important to a golf shaft as is the flex or torque. Most measurements of the correct shaft length for the player involve a determination of a particular player&#39;s height and distance of his hands to the floor. Shaft length will impact whereon the clubface the ball will be consistently struck, and often, an incorrect shaft length is the main cause of a golfer to alter his natural swing arc in order to make optimum impact. According to most research, if ball impact is but one inch off-center this can equate to a 14% loss of carry distance, so it is vitally important that the length of the club be accurately fitted for each particular player. 
     If it is seen in the fitting process that a player needs to adjust his club length, such as adding or removing a half inch, inch or two inches to the length of the club, it would be highly desirable to lengthen his present club(s) rather buy and install new shafts. Typical driver shaft lengths are from 43 to 47 inches. 
     Prior art shafts having adjustable lengths have been used for many years for a wide variety of applications. Each of these applications has its own functional and aesthetic requirements for the shaft construction which is employed. As a consequence, a number of different mechanisms and devices have been developed to satisfy the particular application requirements. A majority of golf club shaft extension patents are directed to use mainly as putters, or to extending shafts of an existing set of clubs to accommodate growing children. While the teachings of the present invention may be adapted to these types of applications, the focus is rather to make a club adjustment that is rigid, secure, and easily fastened. Additionally, the ability to adjust the shaft length without the need for a custom grip or a custom made shaft is desirable along with the device being hidden within the shaft and grip such that it is not distracting to the player. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides for an extension device for use on the butt-end of a golf club shaft. The device consists of three basic parts: an upper part; a lower part; and a connecting device. The bottom part is secured into the tubular opening in the top of the club shaft. A connecting device is provided within the upper part and extending from a second end of the upper part, a distal portion of the connecting device is threadably connected to the lower part. The connecting device is engageable to adjust the position of the lower part relative to the upper part. 
     In another embodiment, an extension device is provided for use on a butt-end of a golf club shaft. The extension device comprises a grip secured to an upper end of a golf club shaft where the top end of the grip has a threaded cavity. A plurality of grip inserts having different lengths is provided. The inserts have threaded protrusions. The grip insert having the desired length may be selected, whereby the threaded protrusion of the grip insert engages the threaded cavity of the grip such that the grip insert is secured to the grip resulting in a club that has a desired length. 
     The invention can be used to extend or shorten any of the golf clubs in a set, but preferably is designed for use with a driver. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features and advantages of the invention will be apparent from the following description of the invention as illustrated in the accompanying drawings. The accompanying drawings, which are incorporated herein and form a part of the specification, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention. 
         FIG. 1  is a perspective view of a golf club grip, shaft and shaft extension device in accordance with an exemplary embodiment of the present invention and showing all of the assembled internal parts; 
         FIG. 1A  is a perspective view of an end of the golf club grip according to the embodiment of  FIG. 1 ; 
         FIG. 2  is a perspective three-dimensional cross-sectional view of the grip, shaft and shaft extension device according to the embodiment of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of the grip, shaft and the shaft extension device according to the embodiment of  FIG. 1 ; 
         FIG. 4  is perspective view of a portion of the grip, shaft and the shaft extension device showing all of the assembled parts according to the embodiment of  FIG. 1 ; 
         FIG. 5  is perspective view of the upper part and lower part of the shaft extension device according to the embodiment of  FIG. 1 ; 
         FIG. 6  is a plan view of a grip according to another embodiment of the present invention; 
         FIG. 6A  is a plan view of a grip insert according to the embodiment of  FIG. 6 ; 
         FIG. 6B  is a plan view of another grip insert according to the embodiment of  FIG. 6 ; 
         FIG. 6C  is a plan view of another grip insert according to the embodiment of  FIG. 6 ; 
         FIG. 7  is a plan view of a grip according to the embodiment of  FIGS. 6 and 6A ; 
         FIG. 8  is a plan view of a grip according to the embodiment of  FIGS. 6 and 6B ; and 
         FIG. 9  is a plan view of a grip according to the embodiment of  FIGS. 6 and 6C . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims. 
     Various inventive features are described below that can each be used independently of one another or in combination with other features. However, any single inventive feature may not address any or all of the problems discussed above or may only address one of the problems discussed above. Further, one or more of the problems discussed above may not be fully addressed by any of the features described below. 
       FIG. 1  of the accompanying drawings shows a golf club shaft  100  and grip  102  having an extension device  104  provided on a golf club head (not shown) according to the present invention. The extension device  104  allows the shaft to be telescopically inserted further under the grip  102  to shorten the overall length of the golf club by shortening the length of exposed shaft  100  extending from the grip  102 . It will be appreciated that the extension device  104  also allows the shaft&#39;s  100  length to be lengthened by sliding the shaft  100  further out from the grip  102  to lengthen the exposed shaft  100  extending from the grip  102 . No special custom grip or shaft is required to operate or use the extension device  104 . 
       FIGS. 2 and 3  illustrate the extension device  104  provided within the grip  102  and shaft  100 . The extension device  104  is for use on a butt-end of the golf club shaft  100  and comprises an upper part  106  provided in the grip  102  and a lower part  108  provided in an upper tubular opening  110  of the golf club shaft  100 . A connecting device  112  is provided within the upper part  106  and extends from a second end  114  of the upper part  106 , and has a distal portion  116  of the connecting device  112  threadably connected to the lower part  108 . The connecting device  112  is engageable to adjust the position of the lower part  108  relative to the upper part  106 . 
     The upper part  106  has a first portion  118  with a first cavity  120  extending from an opening  122  at a first end  124  and a second portion  126  with a second cavity  128  that extends along the length of the upper part  106  from the first cavity  120  through the second portion  126  to an opening  130  at the second end  114  of the upper part  106 . The first portion  118  has an outer surface  132  that is connected to an inner surface  134  of the grip  102 . Preferably the outer surface  132  of the upper part  106  is secured within a second shaft portion  136  provided within the grip  102 . This second shaft portion  136  is then secured to the inner surface  134  of the grip  102 . As will be appreciated, adhesive, glue or other means may be used to secure the upper part  106  to either the grip  102  or second shaft portion  136  and the second shaft portion  136  to the grip  102 . The second portion  126  of the upper part  106  remains unconnected to the grip  102 , and when a second shaft portion  136  is provided, the second portion  126  extends beyond the second shaft portion  136 . 
     The lower part  108  has an upper cavity  138  extending along its length that receives the second portion  126  of the upper part  106  and a lower threaded cavity  140  that extends along the length of the lower part  108  from the upper cavity  138 . The lower part  108  is provided within the upper tubular opening  110  of the golf club shaft  100 . Preferably the lower part  108  is secured within the golf club shaft  100  using adhesive or glue or other suitable means. The second portion  126  of the upper part  106  is at least partially slidably inserted into the upper cavity  138  of the lower part  108 . 
     The connecting device  112  is provided in the first cavity  120  of the first portion  118  of the upper part  106  and extends through the second cavity  128  of the second portion  126  of the upper part  106 , through the upper cavity  138  of the lower part  108  and into the threaded lower cavity  140  of the lower part  108 . Preferably, the connecting device  112  is a threaded screw  142  having a head  144  and a body  146 , the body  146  at least partially having threads  148  to engage with threads  150  of the threaded lower cavity  140  of the lower part  108 . The head  144  fits within the cavity  120  of the first portion  118  of the upper part  106  and is prevented from exiting the upper part  106  by a threaded member  152  that engages threads  154  on sidewalls  156  of the cavity  120  to prevent movement of the screw  142  out of the upper part  106 . A wave washer, nylon or delrin spacer  158  may be provided between the threaded member  152  and the head  144  of the screw  142 . The threaded member  152  has an opening  160 , such that a tool (not shown) may be engaged with the head  144  of the screw  142  for turning the screw  142  to engage it with the threads  150  in the threaded lower cavity  140  of the lower part  108 . 
     As illustrated in  FIGS. 4 and 5 , the second portion  126  of upper part  106  preferably includes at least one protrusion  162  provided along its length. This protrusion  162  is matingly received by a reciprocal slot  164  provided on an inner surface  166  of the upper cavity  138  of the lower part  108 . The engagement of the protrusion  162  in the slot  164  prevents rotation between the upper part  106  and the lower part  108 . It will be understood that more than one set of mating protrusions  162  and slots  164  may be provided on the extension device  104 . 
     Referring now to  FIGS. 2 and 3 , by tightening or loosening the screw  142 , the distance between a first end  168  of the lower part  108  and the second end  170  of the first portion  118  of the upper part  106  may be adjusted. Engaging the screw  142  further into the threaded cavity  140  of the lower part  108  will slide the shaft  100  and lower part  108  further under the grip  102  to shorten the overall golf club shaft  100  length. As illustrated in  FIG. 3 , the second portion  126  of the upper part  106  has a distance L 1  and the upper cavity  138  of the lower part  108  has a length L 2 , preferably L 1  and L 2  are substantially the same, such that substantially the whole of the second portion  126  of the upper part  106  may be fit within the upper cavity  138  of the lower part  108 . By moving the lower part  108  slidably over the upper part  106  the distance D 1  between the lower end  170  of the first portion  118  of the upper part  106  and first end  168  of the lower portion  108  may be shortened or lengthened. Preferably, the distance D 1  may be from 0 to 5 inches, more preferably it may be adjusted from 0 to 3 inches, still more preferably from 0 to 2 inches and most preferably from 0 to 1 inch. It will be appreciated that the distance may be adjustable in increments or continuously adjustable. 
     It will be appreciated that the upper end  106  of the grip  102  may have an opening  172 , such that a tool, such as a screw driver, may be used to engage with the screw head  146  to turn the screw  142  in the desired direction to either move the lower part  108 , and thus the shaft  100 , further under or out of a lower end  174  of the grip  102 . This allows the length of the shaft  100  to be adjusted without having to modify the grip  102 . This allows for easy adjustment of shaft  100  length without having to change the grip  102  or use a specialized grip to adjust for a change of length. As shown in  FIG. 1A , the opening  172  in the upper end of the grip  102  may include a cap  176  to cover the opening  172  when adjustment of the club length is not needed. It will be appreciated that a traditional grip may use the desired cap  176 . It will be appreciated that the present shaft extension device  104  may be used on any type of club, including drivers, fairways, hybrids, irons, wedges and putters. 
       FIG. 6  illustrates another shaft extension device  216  design for lengthening or shortening a golf club. In this embodiment, a shaft  200  is engaged with a grip  202  in a traditional manner. The grip  202  features a cavity  204  at an upper end  206 . Preferably, the cavity  204  features threaded sidewalls  208 . A plurality of grip extenders or inserts  210 ,  212 ,  214  may be provided for attachment to the upper end  206  of the grip  202 . For example, as shown in  FIGS. 6A through 6C , three different sized grip inserts  210 ,  212  and  214  are provided. The first grip insert  210  has a length L 2 , the second grip insert  212  has a length L 3  and the third grip insert  214  has a length L 4 . The grip  202  has a length L 1 . A grip insert  210 ,  212  and  214  may be selected to be attached to the grip  202  to provide a desired length golf club. For example, as shown in  FIG. 7 , the length L 1  of the grip  202  with the grip insert  210  having a length L 2  may together form a desired length club. As illustrated in  FIG. 8 , the length L 1  of the grip  202  with the grip insert  212  having a length L 3  may together form a shorter length club. Finally, as illustrated in  FIG. 9 , the length L 1  of the grip  202  with the grip insert  214  having a length L 4  may together form a longer length club. It will be appreciated that more than three shaft grip inserts  210 ,  212  and  214  may be provided to modify the overall length of the club. It will be appreciated that the lengths L 1 , L 2 , L 3  and L 4  may be any desired lengths. In a preferred embodiment, the length L 2  brings the club to a standard length club, while the length L 3  shortens the club length by 0.5 to 2 inches and the length L 4  lengthens the club length by 0.5 to 2 inches. Most preferably, the grip insert  212  with a length L 3  shortens the club length by 0.5 inches, while the grip insert  214  with a length L 4  lengthens the club by 0.5 inches. It will be appreciated that the present grip extension device  216  may be used on any type of clubs, including drivers, fairways, hybrids, irons, wedges and putters. 
     It will be appreciated that any means of attachment may be used to secure the grip inserts  210 ,  212  and  214  to the upper end  206  of the grip  202 . In a preferred embodiment, the cavity  204  in the grip  202  features threaded sidewalls  218  and the grip inserts  210 ,  212  and  214  have extensions  220  with reciprocating threads  222  that engage with the sidewall threads  218  to removably secure the grip insert  210 ,  212  and  214  to the grip  202 . Alternatively, the grip inserts  210 ,  212  and  214  and grip cavity  204  may feature a snap-fit feature or other mechanism to secure the grip inserts  210 ,  212  and  214  to the grip  202 . It will be appreciated that a change in swing weight with the different grip inserts  210 ,  212  and  214  may be accounted for by having the grip inserts  210 ,  212  and  214  be different weights by using different materials of different densities or by the construction of the grip inserts  210 ,  212  and  214  by making them hollow or filled. Additionally, the grip inserts  210 ,  212  and  214  may accommodate different weight mechanisms so that the grip inserts  210 ,  212  and  214  may additionally add or remove weight from the grip  202 . Generally the mass of the inserts may alter the weight of the grip by 1 to 60 grams, preferably between 5 and 40 grams. Additionally or alternatively, the club head itself may be designed such that it has adjustable weights. 
     Unless otherwise expressly specified, all of the numerical ranges, amounts, values and percentages may be read as if prefaced by the word “about” even though the term “about” may not expressly appear in the value, amount, or range. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. 
     Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting form the standard deviation found in their respective testing measurements. Furthermore, when numerical ranges of varying scope are set forth herein, it is contemplated that any combination of these values inclusive of the recited values may be used. 
     It should be understood, of course, that the foregoing relates to exemplary embodiments of the present invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.