Shaft for golf club

Abstract

A shaft for a golf club includes a tip end configured to couple to a golf club head; a butt end opposite to the tip end; and a butt end portion that extends in a butt-to-tip direction from the butt end by at least 50 mm and has an average rate of change of bending stiffness in a tip-to-butt direction, wherein a greatest rate of change of bending stiffness of the shaft in the tip-to-butt direction is at least 2.7 times the average rate of change of bending stiffness of the butt end portion.

What is claimed is: 
     
         1 . A shaft for a golf club, comprising:
 a tip end configured to couple to a golf club head;   a butt end opposite to the tip end; and   a butt end portion that extends in a butt-to-tip direction from the butt end by at least 50 mm and has an average rate of change of bending stiffness in a tip-to-butt direction,   wherein a greatest rate of change of bending stiffness of the shaft in the tip-to-butt direction is at least 2.7 times the average rate of change of bending stiffness of the butt end portion.   
     
     
         2 . The shaft of  claim 1 , wherein the greatest rate of change of bending stiffness of the shaft in the tip-to-butt direction is at least 5.0 times the average rate of change of bending stiffness of the butt end portion. 
     
     
         3 . The shaft of  claim 2 , wherein the greatest rate of change of bending stiffness of the shaft in the tip-to-butt direction is at least 10.0 times the average rate of change of bending stiffness of the butt end portion. 
     
     
         4 . The shaft of  claim 1 , wherein the butt end portion extends in the butt-to-tip direction from the butt end by at least 150 mm. 
     
     
         5 . The shaft of  claim 1 , wherein the shaft has a tip end portion extending in the tip-to-butt direction from the tip end by at least 150 mm, and
 wherein a ratio of the average bending stiffness of the butt end portion to the average bending stiffness of the tip end portion is at least 4.0.   
     
     
         6 . The shaft of  claim 5 , wherein the ratio of the average bending stiffness of the butt end portion to the average bending stiffness of the tip end portion is at least 5.0. 
     
     
         7 . The shaft of  claim 1 , wherein a diameter of the shaft at the tip end is less than 0.300 inches. 
     
     
         8 . A golf club, comprising:
 the shaft of  claim 1 ;   a golf club head coupled to the tip end of the shaft; and   a grip coupled to the butt end portion of the shaft.   
     
     
         9 . The golf club of  claim 8 , wherein a mass ratio of the mass of the shaft to the mass of the grip is within a range of 1.1 to 1.3. 
     
     
         10 . A shaft for a golf club, comprising:
 a tip end configured to couple to a golf club head;   a butt end opposite to the tip end; and   a butt end portion that extends in the tip-to-butt direction from 800 mm from the tip end to 950 mm from the tip end and has an average rate of change of bending stiffness in the tip-to-butt direction,   wherein a rate ratio is at least 2.7 and is defined as a ratio of:
 the rate of change of bending stiffness of the shaft in the tip-to-butt direction at any point within a portion of the shaft extending at least 10 mm along the tip-to-butt direction and being centered at a point having a maximum rate of change of bending stiffness; to 
 the average rate of change of bending stiffness of the butt end portion. 
   
     
     
         11 . The shaft of  claim 10 , wherein the rate ratio is at least 3.5. 
     
     
         12 . The shaft of  claim 11 , wherein the rate ratio is at least 7.5. 
     
     
         13 . The shaft of  claim 10 , wherein the portion of the shaft extends at least 50 mm along the tip-to-butt direction. 
     
     
         14 . The shaft of  claim 10 , wherein the portion of the shaft extends at least 100 mm along the tip-to-butt direction. 
     
     
         15 . The shaft of  claim 10 , wherein the shaft has a tip end portion extending in the tip-to-butt direction from 150 mm from the tip end to 300 mm from the tip end, and
 wherein a ratio of the average bending stiffness of the butt end portion to an average bending stiffness of the tip end portion is at least 5.0.   
     
     
         16 . The shaft of  claim 10 , wherein a diameter of the shaft at the tip end is less than 0.290 inches. 
     
     
         17 . A golf club, comprising:
 the shaft of  claim 10 ;   a golf club head coupled to the tip end of the shaft; and   a grip coupled to the butt end portion of the shaft.   
     
     
         18 . The golf club of  claim 17 , wherein a mass of the shaft is less than 50 g, a mass of the grip is less than 40 g, and a mass ratio of the mass of the shaft to the mass of the grip is within a range of 1.1 to 1.3. 
     
     
         19 . A shaft for a golf club, comprising:
 a tip end configured to couple to a golf club head;   a butt end opposite to the tip end;   a tip end portion that extends in a tip-to-butt direction from the tip end by at least 50 mm;   a butt end portion that extends in a butt-to-tip direction from the butt end by at least 50 mm and has an average rate of change of bending stiffness in a tip-to-butt direction; and   a middle portion between the tip end portion and the butt end portion,   wherein a rate of change of bending stiffness in the tip-to-butt direction at a point in the middle portion is at least 2.7 times the average rate of change of bending stiffness of the butt end portion, and   wherein a diameter of the shaft at the tip end is less than 0.300 inches.   
     
     
         20 . The shaft of  claim 19 , wherein the rate of change of bending stiffness in the tip-to-butt direction at the point in the middle portion is at least 5.0 times the average rate of change of bending stiffness of the butt end portion, and
 wherein the diameter of the shaft at the tip end is less than 0.285 inches.