Golf club shaft with adjustable flex

Abstract

A hollow golf club shaft and a moveable solid shaft insert about 6 to 24 inches long wherein the depth of insertion of the shaft insert into the shaft may vary from about 1 to 10 inches. Changing the location of the shaft insert allows a player to change the flex of the shaft and thereby optimize the performance of the club dynamics to the player. The shaft insert is initially held in place by friction between the shaft and the shaft insert, optionally with a joining agent located therebetween, until a final setting of the shaft insert is determined. Then the shaft insert is permanently located within the shaft to make the club legal for play under U.S.G.A. Rules. Shaft fitting can be administered by a player with or without coaching and can be revisited at any time prior to permanent attachment by a simple adjustment. The shaft inserts are useful on all hollow shaft clubs, from putter to driver, and can be retrofitted to existing clubs without removing the grip.

1 . A method of adjusting the flex of a golf club shaft to produce a golf club which has radially equal shaft flex and is acceptable for play by the rules of the U.S. Golf Association, wherein said golf club comprises a golf club shaft having a first end attached to a grip section and a second end attached to a club head, said golf club shaft being of tubular cross section and containing an elongated cavity extending from about the grip section to about the club head; 
 said method comprising (i) placing a rigid tubular shaft insert having a length of about 6 to 24 inches inside the golf club shaft from the first end, (ii) adjusting the penetration of the tubular shaft insert within the shaft from about 1 inch to about 10 inches to obtain a desired amount of flex for a player, and (iii) attaching the shaft insert within the shaft so that it can not be moved during play of a round of golf.    
   
   
       2 . The method of  claim 1 , wherein the rigid tubular shaft insert is hollow.  
   
   
       3 . The method of  claim 2 , wherein the rigid tubular shaft insert is made of a material selected from the group consisting of aluminum, titanium, and graphite.  
   
   
       4 . The method of  claim 1 , wherein the rigid tubular shaft insert in solid.  
   
   
       5 . The method of  claim 4 , wherein the rigid solid tubular shaft insert is made of graphite.  
   
   
       6 . The method of  claim 1 , wherein a compressible joining agent is located between the golf club shaft and the shaft insert.  
   
   
       7 . The method of  claim 6 , wherein the compressible joining agent is a silicone adhesive.  
   
   
       8 . The method of  claim 7 , wherein the silicone adhesive is placed on a portion of the shaft insert outer surface before the shaft insert is inserted into the golf club shaft.  
   
   
       9 . The method of  claim 8 , wherein the silicone adhesive on the shaft insert outside surface is allowed to cure before the shaft insert is inserted into the golf club shaft.  
   
   
       10 . The method of  claim 1 , wherein the shaft insert is about 10 to 18 inches long.  
   
   
       11 . The method of  claim 10 , wherein the shaft insert is located about 2 to 6 inches from the grip end.  
   
   
       12 . The method of  claim 1 , wherein after an adjustment of the extent of penetration of the shaft insert, a player uses the club to hit golf balls.  
   
   
       13 . The method of  claim 12 , wherein after an adjustment of the extent of penetration of the shaft insert, the flex of the club is determined.  
   
   
       14 . The method of  claim 13 , wherein additional golf clubs are prepared having the determined flex.  
   
   
       15 . The method of  claim 1 , wherein after an adjustment of the extent of penetration of the shaft insert, the flex of the club is determined.  
   
   
       16 . The method of  claim 15 , wherein additional golf clubs are prepared having the determined flex.  
   
   
       17 . The method of  claim 1 , wherein the shaft insert is selected from a group of shaft inserts of varying lengths, stiffness, longitudinal shape, cross section, and material.  
   
   
       18 . The method of  claim 1 , wherein the shaft insert is of sufficient diameter and purchase to hold itself in place during practice when said golf club shaft and said shaft insert are used as an assembly in a finished golf club.  
   
   
       19 . The method of  claim 1 , wherein the golf club shaft has a grip on the grip end and a central portion of the grip at the grip end is removed prior to inserting the shaft insert.  
   
   
       20 . The method of  claim 1 , wherein the shaft insert is shaped so that during bending of the golf club shaft during a golf swing, a central section of the shaft insert contacts the golf club shaft.  
   
   
       21 . A golf club prepared by the method of  claim 1 .  
   
   
       22 . A golf club comprising a tubular hollow shaft with a grip end and a club head end, a rigid tubular shaft insert inserted into the grip end of the hollow shaft, said shaft insert being about 6 to 24 inches long and shaped so fit within the shaft beginning at a distance of 1 to about 10 inches from the grip end, and is held in place by friction.  
   
   
       23 . The golf club of  claim 22 , wherein the shaft insert is movable within the shaft from a first location to a second location and changes the flex of the club.  
   
   
       24 . The golf club of  claim 22 , further containing a compressible joining agent between the shaft interior surface and the shaft insert exterior surface.  
   
   
       25 . The golf club of  claim 24 , wherein the compressible joining agent is a silicone adhesive.  
   
   
       26 . The golf club of  claim 22 , wherein the shaft insert is permanently attached to the shaft.  
   
   
       27 . The golf club of  claim 22 , wherein the shaft insert is about  10  to  18  inches long.  
   
   
       28 . The golf club of  claim 22 , wherein the shaft insert is attached to the golf club shaft within the shaft by means of an adhesive.  
   
   
       29 . The golf club of  claim 22 , wherein the shaft insert is shaped so that during bending of the golf club during a golf swing a central section of the shaft insert contacts the golf club shaft.  
   
   
       30 . A method of retrofitting a golf club to change the flex of the club, said club having a tubular hollow shaft with a grip end and a club head end, a grip attached onto the grip end, a club head attached to the club head end, said method comprising the steps of: 
 (i) cutting a plug hole having a diameter of about 0.55 inches out of the grip surface abutting the tubular hollow shaft grip end, (ii) inserting, a rigid tubular shaft insert through the plug hole into the grip end of the hollow shaft, said shaft insert being about 6 to 24 inches long and shaped to fit within the shaft a distance of 1 to about 10 inches from the grip end, and is held in place by friction.