Golf club shaft formed from metal-containing prepreg and non-metal fiber prepreg and method of making the same

Abstract

Disclosed is a golf club shaft of sheet-wound construction that approximates the characteristics of a steel shaft. The golf club shaft is formed using metal-containing prepreg and non-metal fiber prepreg in order to provide a sheet-wound club having an elasticity index (EI) value of 3.0˜4.5 kgf·m 2 , a mass 80˜130 g, and a center of mass that is 45˜51% of the overall length of the shaft. The metal-containing prepreg is wrapped around a mandrel near the tip of the shaft in order to position the center of mass where desired. The non-metal fiber prepreg is wrapped around the mandrel to provide the desired EI value and overlal mass. Additional layers of metal-containing prepreg may be wrapped beyond the metal-containing prepreg wrapped near the tip in order to vary the characteristics of the golf club shaft. The golf club shaft is preferably formed on a mandrel that includes an annular recess at its tip in order to accommodate the metal-containing prepreg that is wrapped near the tip.

1 . A golf club shaft formed by winding a plurality of layers around a mandrel that is removed after curing comprising: 
 a layer of metal-containing prepreg wrapped at a tip of the shaft; and    a layer of non-metal fiber prepreg wrapped adjacent to the layer of metal-containing prepreg throughout a length of the shaft.    
     
     
         2 . The golf club shaft of  claim 1  wherein the layer of metal-containing prepreg wrapped at the tip of the shaft comprises a first layer of metal-containing prepreg and a second layer of metal-containing prepreg  
     
     
         3 . The golf club shaft of  claim 1  wherein the golf club shaft has a mass of about 80-130 g.  
     
     
         4 . The golf club shaft of  claim 1  wherein the golf club shaft has a center of mass located at about 45˜51% when measured from the tip and expressed as a ratio to an overall length of the golf club shaft.  
     
     
         5 . The golf club shaft of  claim 1  wherein the gold club shaft has an elasticity index (EI) value about 3.0˜4.5 kgf·m 2  at 200 mm from the tip.  
     
     
         6 . The golf club shaft of  claim 1  wherein the layer of metal-containing prepreg located at the tip of the shaft is an inner-most layer.  
     
     
         7 . The golf club shaft of  claim 6  wherein the inner-most layer of metal-containing prepreg is located along a length of the shaft between a tip of the shaft and 40% of an overall length of the shaft.  
     
     
         8 . The golf club shaft of  claim 6  wherein the layer of non-metal fiber prepreg is wrapper over the inner-most layer of metal-containing prepreg.  
     
     
         9 . The golf club shaft of  claim 1  wherein the layer of metal-containing prepreg comprises a metal having a specific mass greater than 7 g/cm 3 .  
     
     
         10 . The golf club shaft of  claim 1  wherein the layer of metal-containing prepreg contains a metal fiber.  
     
     
         11 . The golf club shaft of  claim 1  wherein the layer of metal-containing prepreg contains a metal powder.  
     
     
         12 . The golf club shaft of  claim 11  wherein the metal powder is dispersed in a synthetic resin sheet.  
     
     
         13 . The golf club shaft of  claim 12  wherein the metal powder comprises tungsten.  
     
     
         14 . The golf club shaft of  claim 12  wherein the synthetic resin sheet comprises epoxy resin.  
     
     
         15 . A method of making a golf club shaft comprising the steps of: 
 providing a mandrel that tapers from a butt end to a tip end;    wrapping a layer of metal-containing prepreg around the mandrel from the tip end thereof toward and toward but not all the way to the butt end thereof;    wrapping a layer of non-metal fiber prepreg adjacent to the layer of metal-containing prepreg from the tip end thereof all the way to the butt end thereof;    curing the prepreg; and    removing the mandrel from the prepreg.    
     
     
         16 . The method of making a golf club shaft of  claim 1  wherein the mandrel has a nonlinear taper along its length that creates an annular recess at the tip end thereof and wherein the step of wrapping a layer of metal-containing prepreg around the mandrel from the end thereof toward but not all the way to the butt end thereof is accomplished by wrapping the layer of metal-containing prepreg around the mandrel along the annular recess.