Steel golf shaft with a composite pivot area

Abstract

A golf club shaft having an upper hollow portion with a handle end and a lower hollow portion with a head end and an intermediate flex portion therebetween. The upper portion has a lower end with a joining region extending into the flex portion. The lower portion has an upper end with a joining region extending into the flex portion. A connector in the flex portion has a central enlarged cylindrical section with a diameter extending outwardly to a diameter essentially equal to the exterior surface of the adjacent shaft portions, the connector also having an upper cylindrical section with a reduced diameter in interference contact with the interior surface at the lower end of the upper portion, the connector also having a lower cylindrical section with a reduced diameter in interference contact with the interior surface at the upper end of the lower portion of the shaft.

What is claimed as being new and desired to be protected by Letters Patent of the United States is as follows:  
     
         1 . A new and improved golf club comprising a shaft having a handle end with a grip thereon and a head end with a head thereon and an intermediate flex portion therebetween comprising, in combination: 
 a shaft including an upper hollow steel portion about 26 inches in length constituting between about 55 and 65 percent, preferably 59.6 percent, of the length of the shaft and a lower hollow steel portion about 12.5 inches in length constituting between about 25 and 33 percent, preferably 28.8 percent of the length of the shaft with an intermediate flex portion about 9 inches in length with about 2 inches at each end within the upper and lower portions leaving about 5 inches therebetween constituting between 9 and 14 percent, preferably 11.6 percent, of the length of the shaft,    the lower end of the upper portion of shaft remote from the handle having an undercut region extending into the intermediate flex portion with the upper end of the lower portion of the shaft remote from the head having an undercut region extending into the intermediate flex portion; and    a cylindrical sleeve formed of a plurality of layers of a composite material having an upper and lower radial abutment surface in contact with the lower end of the upper portion of the shaft and the upper end of the lower portion of the shaft and having an upper end of a reduced diameter in contact with the undercut region of the lower end of the upper portion of the shaft and a lower end of a reduced diameter in contact with the undercut region of the upper end of the lower portion of shaft, and with the exterior surface of the cylindrical sleeve between the upper and lower portion of the shaft forming a smooth continuation of the shaft through the intermediate flex portion with the sleeve forming a region of greater flexibility than the portions of the shaft thereabove and therebelow for tailoring the playing characteristics of the golf clubs.    
     
     
         2 . A golf club shaft having an upper hollow portion with a handle end and a lower hollow portion with a head end and an intermediate flex portion therebetween comprising: 
 the upper portion having a lower end with a joining region extending into the flex portion, the lower portion having an upper end with a joining region extending into the flex portion; and    a connector in the flex portion having a central enlarged cylindrical section with a diameter extending outwardly to a diameter essentially equal to the exterior surface of the adjacent shaft portions, the connector also having an upper cylindrical section in interference contact with the lower end of the upper portion, the connector also having a lower cylindrical section in interference contact with the upper end of the lower portion of the shaft.    
     
     
         3 . The shaft as set forth in    claim 2    wherein the upper and lower portions of the shaft are fabricated of steel.  
     
     
         4 . The shaft as set forth in    claim 2    wherein the upper portion of the shaft constitutes between about 55 and 65 percent of the length of the shaft.  
     
     
         5 . The shaft as set forth in    claim 2    wherein the intermediate flex portion constitutes between about 9 and 14 percent of the length of the shaft.  
     
     
         6 . The shaft as set forth in    claim 2    wherein the intermediate flex portion constitutes up to about 65 percent of the total shaft length.  
     
     
         7 . The shaft as set forth in    claim 2    wherein the lower portion of the shaft constitutes between about 9 and 14 percent of the length of the shaft.  
     
     
         8 . The shaft as set forth in    claim 2    wherein the connector is formed of a non-metallic material.  
     
     
         9 . The shaft as set forth in    claim 2    wherein the connector is formed of a composite material with inextensible strands from between about 0 degrees and 45 degrees with respect to the axis of the shaft.  
     
     
         10 . The shaft as set forth in    claim 2    wherein the connector is formed of plastic.  
     
     
         11 . The shaft as set forth in    claim 2    wherein the upper end and lower end are selected from the class of metals including aluminum, titanium and other metal alloys.