Hybrid golf club shaft

Abstract

A hollow golf club shaft of circular cross-section comprises a tubular core layer, a tubular outer layer, and a tubular intermediate member juxtaposed to both the core layer and the outer layer, wherein the core layer and the outer layer coextend substantially the entire length of the shaft.

What is claimed is:  
     
         1 . A hollow golf club shaft of circular cross-section comprising a tubular core layer, a tubular outer layer, and a tubular intermediate member juxtaposed to both the core layer and the outer layer, wherein the core layer and the outer layer coextend substantially the entire length of the shaft.  
     
     
         2 . The shaft of  claim 2 , wherein the intermediate member is substantially embedded in an outer surface of the core layer.  
     
     
         3 . The shaft of  claim 2 , wherein the outer layer is formed of a first isotropic material, the intermediate member is formed of a second isotropic material, and the core layer is formed of a non-isotropic material.  
     
     
         4 . The shaft of  claim 3 , wherein the first and second isotropic materials are independently selected from metal matrix composites, metals or alloys thereof, comprising titanium, steel, stainless steel, aluminum, tungsten, nickel, copper, zinc, brass, bronze, magnesium, tin, gold, or silver.  
     
     
         5 . The shaft of  claim 3 , wherein the non-isotropic material comprises a vibration damping thermosetting or thermoplastic resin.  
     
     
         6 . The shaft of  claim 5 , wherein the non-isotropic material further comprises a reinforcement material comprising carbon fibers, graphite fibers, glass fibers, quartz fibers, boron fibers, ceramic fibers, ceramic whiskers, metal-coated fibers, ceramic-coated fibers, diamond-coated fibers, carbon nanotubes, extended-chain polyethylenes, poly-p-phenylenebenzobisoxazole fibers, metal fibers, polythenes, polyarylates, polyacetals, liquid crystalline polymers, aromatic polyesters, or polyallylates.  
     
     
         7 . The shaft of  claim 1 , wherein the intermediate member is a porous grid, web, mesh, cloth, woven member, braided member, wound member, coil member, continuous member, discontinuous member, or lattice network member formed from fibers, filaments, wires, strips, or ribbons.  
     
     
         8 . The shaft of  claim 1 , further comprising a vibration damping layer between the core layer and the outer layer, wherein the vibration damping layer is integrated with and coextensive to the intermediate member.  
     
     
         9 . The shaft of  claim 8 , wherein the vibration damping layer comprises a viscoelastic material.  
     
     
         10 . The shaft of  claim 9 , wherein the core layer comprises as a vibration damping thermosetting or thermoplastic resin that is substantially the same as the viscoelastic material.  
     
     
         11 . The shaft of  claim 1 , wherein the outer layer has a thickness of less than about 0.05 inches.  
     
     
         12 . The shaft of  claim 1 , wherein the intermediate member has a first thickness of less than about 0.2 inches, and the core layer has a second thickness no less than the first thickness.  
     
     
         13 . The shaft of  claim 1 , further comprising a reinforcing layer embedded in or disposed on an inner surface of the core layer, wherein the reinforcing layer has a thickness of less than about 0.1 inches and a length of at least about 5% of the shaft length.  
     
     
         14 . The shaft of  claim 13 , wherein the reinforcing layer comprises an isotropic or quasi-isotropic material.  
     
     
         15 . A hollow golf club shaft of circular cross-section comprising a tubular core layer, a tubular outer layer, and a tubular intermediate member juxtaposed to both the core layer and the outer layer, wherein the core layer has a thickness of less than about 0.3 inches.  
     
     
         16 . The shaft of  claim 15 , wherein the intermediate member has a thickness of less than about 0.2 inches and a length of at least about 5% of the shaft length.  
     
     
         17 . The shaft of  claim 15 , wherein the thickness of the core layer ranges from about 0.01 inches to about 0.18 inches.  
     
     
         18 . The shaft of  claim 15 , wherein the cover layer has a thickness of less than about 0.05 inches.  
     
     
         19 . The shaft of  claim 15 , wherein the outer layer and the intermediate member independently comprise a metallic material, and the core layer is formed from a non-isotropic material comprising a reinforcement material impregnated with a vibration damping thermosetting or thermoplastic resin.  
     
     
         20 . The shaft of  claim 19 , wherein the vibration damping thermosetting or thermoplastic resin has a loss factor of between about 0.2 and about 1.2 at 100 Hz and 68° F., a shear storage modulus of at least about 1,000 psi, and a Young's modulus of at least about 0.01 Mpsi.  
     
     
         21 . The shaft of  claim 19 , wherein the reinforcement material is present in an amount ranging from 10% to 80% by volume and from about 5% to about 90% by weight of the non-isotropic material.  
     
     
         22 . The shaft of  claim 15 , further comprising a vibration damping layer formed of a viscoelastic material having a Young's modulus of at least about 15 psi, a shear storage modulus of at least about 10 psi, a strain energy ratio of at least about 2%, and a loss factor of at least about 0.01 at a temperature range of −40° C. to 100° C. and a frequency range of 1 Hz to 10,000 Hz.  
     
     
         23 . The shaft of  claim 15 , further comprising a reinforcing layer formed of an isotropic or quasi-isotropic material, wherein the reinforcing layer has a thickness ranging from about 0.001 inches to about 0.05 inches.  
     
     
         24 . The shaft of  claim 15 , wherein the shaft has an overall length ranging from about 30 inches to about 65 inches, and an overall weight of less than about 130 grams.  
     
     
         25 . A hollow golf club shaft of circular cross-section comprising a tubular core layer, a tubular outer layer, and a tubular intermediate member juxtaposed to both the core layer and the outer layer, wherein the intermediate member comprises at least one isotropic or non-isotropic material having a Young's modulus of at least about 10 Mpsi.