Abstract:
Lasers are useful for many types of materials processing, including annealing, texturing, hardening, patterning, cutting, welding, and joining. A method is provided for modifying the surface finish and structure of any material, with said materials being used in the construction of golf clubs. The surface modified materials have properties that lead to increased performance of the golf clubs. A secondary benefit is an improved material structure leading to a better feel for the golfer.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to golf club heads, more specifically to golf club heads with striking faces that have been modified with laser radiation. The primary feature of these laser surface modified golf club heads is improved performance and playability with an improvement in the feel received by the golfer.  
         BACKGROUND OF THE INVENTION  
         [0002]    In recent years, there have been a large number of technological innovations in the field of golf club construction in an effort to improve the performance of the clubs. Many of these innovations have focused on optimizing the weight distribution within the golf club&#39;s head in order to correct for off-center hits, thereby expanding the “sweet spot”. These innovations have resulted in golf clubs with dramatic performance improvements that have received excellent success in the marketplace. Similarly, the configuration of the golf clubs has also been modified to optimize the “spin” imparted to the golf ball during impact, since this spin can be utilized to better control the ball.  
           [0003]    More recently, golf club manufacturers have shifted their focus to improving the golf club&#39;s “feel”. Although the feel is a rather individual and subjective characteristic, most golfers equate it with a comfortable sensation received through the hands during contact with the golf ball. Many golf club manufacturers have improved the feel of golf clubs by incorporating secondary materials into the primary material of the golf club&#39;s construction. Some of these multiple material systems have received an excellent reception in the golf club marketplace. There are additional methods, such as the one described in the current invention, which can also be utilized to improve a golf club&#39;s performance and feel.  
           [0004]    An alternative process to tailor the properties of a material is through the application of a laser (Light Amplification through Stimulated Emission of Radiation). Laser surface modification provides an opportunity to specifically tailor the surface of a material to have unique properties when compared to those of the unmodified bulk material. Laser radiation can be used to focus a very intense source of heat in a small area. Some examples of modified surface properties include an increased surface hardness, a decreased surface hardness, and an increased surface roughness. A decrease in surface hardness or an increase in surface hardness from a laser treatment is possible in different materials depending on their chemical structure. In some non-heat treatable iron alloys, for example, the laser radiation can be used to reduce the internal residual stresses, thereby reducing the surface hardness. In heat-treatable alloys, on the other hand, the thermal energy provided by the laser can increase the hardness by changing the crystalline structure of the material. In most instances, there will also be a change in the surface topography of the laser surface modified material. Specifically, the roughness of the surface will increase. A final example of a beneficial change in the surface structure of a material through the application of laser radiation is the creation of a periodic pattern of raised or depressed features on the golf club.  
           [0005]    The difference in these properties is a result of the specific material to be modified by the laser. The increased surface hardness can be particularly beneficial in golf club applications where it is desired to have the ball rebound from the golf club with as much initial velocity as possible, resulting in a ball that travels a great distance. A decreased surface hardness, on the other hand, can be particularly beneficial in the case of a golf club application where a soft feel is required. Additionally, a golf club hitting face with a periodic array of features can advantageously put an increased amount of spin on the golf ball. Finally, an increased surface roughness on the hitting face of the golf club is particularly desirable in the case of a golf club where it is desired to impart a large degree of spin on the golf ball.  
           [0006]    Laser surface modification has been used extensively in different areas of materials science for joining two or more materials, annealing materials to relieve internal stresses, and sintering powders into a unitary mass. These techniques have been used for a wide variety of industrial applications where it is important to have specific properties of the materials, such as high surface hardness, low surface hardness, or resistance to particular types of wear. In the computer disk drive industry, for example, it has been shown that a laser can be used to modify the surface structure of the hard disk in a manner that benefits the wear properties of the disk drive. Examples of laser application to hard disk drives can be seen in the prior art of Wong, et al. in U.S. Pat. No. 6,117,499 and Baernboim, et al. in U.S. Pat. No. 6,103,990. Additional examples of laser applications are evidenced in the prior art of Herren, et al. in U.S. Pat. No. 5,030,551, which details a process for laser marking ceramics and glasses, and Horng et al. in U.S. Pat. No. 5,322,436 which details a process for creating a laser engraved mark on an orthodontic band. There are many additional examples in the prior art, detailing the apparatus for delivering the laser radiation to a work piece. Excellent examples can be found in U.S. Pat. Nos. 5,338,915, 4,156,124, and 4,797,532. Although there are many industrial examples of the use of laser radiation for the benefit of specific applications, there is an absence of said laser processing in application to golf equipment.  
           [0007]    The prior art in golf club construction and engineering is significant. Thorne and Poplaski, in U.S. Pat. No. 5,800,285, describe a method for producing artwork on a golf club with a photochemical engraving technique. The application of a laser in this process is intended to change the structure of a photoresist chemical, thereby allowing a separate compound to chemically etch the exposed areas. This process is fundamentally different than the one described in the present patent application where the laser is modifying the material composing the striking face of the golf club. The primary purpose of Thorne&#39;s process is to create a customized pattern such as letters, numbers, symbols, or scorelines, thus it is not primarily focused on functionally modifying the surface. In addition, this patent primarily describes an alternative process for detailing the head of a golf club, when compared to traditional metal casting or metal stamping. Finally, Thorne and Poplaski&#39;s patent is focused only on metallic materials, which is dissimilar from the laser modification process which applies equally well to all classes of materials.  
           [0008]    There are additional methods described in the prior art on golf clubs constructed of multiple materials. For example, Chen in U.S. Pat. No. 5,403,007, describes a golf club with a metal body and a ceramic or titanium hitting face. Similarly, Buck in U.S. Pat. No. 5,779,560, describes a golf club head comprised of a metal head with an insert comprised of a fiber-reinforced composite. Anderson, in U.S. Pat. Nos. 5,024,437 and 5,261,663, describes an insert made of a softer material such as a forged carbon steel to improve the feel of the club during impact. Further attempts to improve the feel of a golf club were proposed by Krumme in U.S. Pat. No. 5,807,190 wherein individual pieces of a secondary material (“pixels”) were incorporated into the striking face of the club. Similarly, Igarashi, in U.S. Pat. No. 5,407,202, proposed a golf club incorporating a high strength, low weight material such as titanium for the striking face of a golf club. An additional method to improve the performance of golf clubs was proposed by Mahaffey in U.S. Pat. No. 5,827,131 including multiple-layer inserts for the golf club hitting surface. Additional attempts have been made to improve the performance and feel, such as U.S. Pat. No. 5,154,425 which describes a golf club head composed of a material which is a composite of metal and ceramic components.  
           [0009]    Many of these methods, however, require very expensive processing techniques and can lead to a substantial number of internal interfaces between the dissimilar materials. These internal interfaces are sources of potential manufacturing defects, as well as interruptions to the vibrations translated to the golfer. It is the vibrations transmitted to the golfer that provide the pleasant feel. In the current invention, on the other hand, the laser surface modified material is substantially the same as the base material, with a slight functional, structural, or topographical modification.  
         SUMMARY OF THE INVENTION  
         [0010]    With the present invention, it has been found that a laser can be used to modify the surface structure of a material. The changes can include modification of the crystalline structure of the material, changes to the surface roughness, changes in the surface chemistry of the chemical elements, or can, in some cases, transform a crystalline material into a non-crystalline (i.e., amorphous) material.  
           [0011]    In one aspect, the present invention provides a surface with a greatly increased roughness, thereby dramatically increasing the frictional coefficient of the material. An increase in the level of the friction on the surface of a club hitting face can positively impact the performance of the club by changing the manner in which the golf ball interacts with the club during striking. The increased friction between the golf club and the ball imparts a high degree of spin to the ball during the contact. This high degree of spin can be particularly advantageous in the application of golf clubs with a high degree of loft since it allows control over the golf ball after it lands in the desired location.  
           [0012]    In a golf putting application, the present invention can be particularly advantageous due to the high friction between the ball and the putter&#39;s surface. This high friction causes the ball to immediately roll in a forward direction, as opposed to the problem of skidding evidenced by many of the prior art putters.  
           [0013]    In many applications for golf clubs, the surface modification will be limited to specific areas on the club hitting face. The present invention can be used for a number of different clubs, including putters, irons, specialty clubs, and drivers. Specialty clubs can include any club used for chipping, hitting out of deep rough, hitting out of wet grass, or hitting out of any hazard, such as, but not limited to sand bunkers.  
           [0014]    Although the preferred location of the laser surface modified material is on the hitting face, it can also be used on any surface of the club, such as the face nearest the ground when the ball is being struck. Again, surface material properties can be altered to increase the performance of the golf club.  
           [0015]    Non-limiting examples of some materials that may be included in laser surface modification processing include steel alloys, stainless steel alloys, titanium alloys, aluminum and its alloys, aluminum oxide, zirconium dioxide, silicon carbide, silicon nitride, polymeric materials, and rubber compounds.  
           [0016]    In a major aspect, the present invention provides a method of manufacture for a laser surface modified material. The manufacturing method typically includes treating the material surface with laser radiation. Nonlimiting examples of laser types include carbon dioxide, yttrium aluminum garnet (YAG), or any type of solid-state semiconductor laser. Typical laser power for a carbon dioxide laser ranges from 5-5000 Watts. The focused spot size is typically in the range of 125 microns (0.005 inches).  
           [0017]    One tremendous advantage of the present invention is the multiple methods to functionally modify the surface structure of the material. In one instance, for example, a heat treatable steel alloy can increase in hardness from the thermal energy provided by the laser. In another example, the laser beam can increase the surface roughness of a material. In yet another example, lasers can be used to anneal a metallic alloy to remove residual stresses and decrease the hardness of the material. Each one of these properties can benefit different applications for the striking face of a golf club. In one instance, a softer metallic alloy on the striking face of a golf club delivers a better feel to the player. In another instance, an increase in the surface roughness of the striking face of a golf club provides an increase in the amount of advantageous spin that can be applied to a golf ball. Although the previous examples have focused on metallic materials, the technique for laser surface modification applies equally well to natural materials such as wood, as well as synthetic materials comprising the classes generally known as polymers and ceramics.  
           [0018]    The type and power of the laser depends on the type of material to be treated. For a given material, an increase in laser power will increase the depth of penetration into the material. In general, any laser will cause a small change in the surface structure of a material. In the case of the present invention, however, the power must reach a threshold that depends on the type of material, to give the benefits described for the striking face of a golf club.  
           [0019]    An alternative embodiment for the laser surface modification process can be applied to golf clubs that are composed of multiple materials. For example, the laser surface modified material can be used on the hitting surface of the golf clubs, In an alternative embodiment, a secondary material that is inserted into the primary golf club material, can be treated with laser surface modification. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    [0020]FIG. 1 is a scanning electron microscope image of an aluminum oxide surface that has been modified with laser radiation.  
         [0021]    [0021]FIG. 2 is a scanning electron microscope image of a titanium alloy surface that has been modified with laser radiation.  
         [0022]    [0022]FIG. 3 is a high magnification scanning electron microscope image of a titanium alloy surface that has been modified with laser radiation.  
         [0023]    [0023]FIG. 4 is a schematic showing a putter with a laser surface modified striking face.  
         [0024]    [0024]FIG. 5 is a schematic showing an iron with a laser surface modified striking face.  
         [0025]    [0025]FIG. 6 is a schematic showing a driver with a laser surface modified striking face.  
         [0026]    [0026]FIG. 7 is a cross-sectional view of putter with a laser surface modified striking face. The depth of penetration of the laser modified material is indicated on the drawing.  
         [0027]    [0027]FIG. 8 is a cross-sectional view of a driver with a laser surface modified striking face. The depth of penetration of the laser modified material is indicated on the drawing.  
         [0028]    [0028]FIG. 9 is a cross-sectional view of an iron club with a laser surface modified striking face. The depth of penetration of the laser modified material is indicated on the drawing. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]    With the present invention, it has been found that a laser can be used to advantageously modify properties such as crystallinity, hardness, ductility, elasticity and topography of the surface of a material. These modifications can be particularly beneficial in the case of golf club applications.  
         [0030]    Non-limiting examples of some materials that may be included in laser surface modification processing include steel alloys, stainless steel alloys, titanium alloys, aluminum and its alloys, aluminum oxide, zirconium dioxide, silicon carbide, silicon nitride, polymeric materials, and rubber compounds.  
         [0031]    Nonlimiting examples of laser types include gas lasers, such as Helium-Neon, Helium-Cadmium, Copper vapor, gold vapor, carbon dioxide, nitrogen, argon ion, krypton ion, Excimer, a liquid dye laser, diode laser, free electron laser, or x-ray laser, yttrium aluminum garnet (YAG), Excimer, diode-laser, or any type of solid state semiconductor laser.  
         [0032]    The head of the golf club can be manufactured through one of the methods well known in the prior art. Some examples include casting, forging, and powder metallurgical methods. A typical casting process, for example, consists of heating a metal alloy above its melting temperature, thereby rendering a liquid metal. The club can be cast into a hollow ceramic mold with the dimensions that are desired in the finished piece. Alternatively, a unitary mass of a ductile metal alloy can be forced into a mold cavity while in a solid state, as in the forging process. After one of these initial forming processes, the club can be finished by sand blasting, plating, or some other surface finishing treatment, dependent on the finish desired for the club. Furthermore, the specific demarcations on the golf club, such as the company logo or the club number, can be highlighted with paint for aesthetic purposes.  
         [0033]    In the current invention, the golf club head produced by any of the above processes will then be subjected to laser surface modification. In a typical process, the laser beam will be focused onto the surface of the material to be treated. The laser beam is turned on by means of an electronic controller that initiates the laser power. In a general laser process, the laser beam is emitted from the laser cavity and manipulated by a series of lenses and mirrors to be focused onto the working surface of the material to be modified. In a preferred embodiment, the laser is pulsed on and off from 1 to 200 times per second. Each one of these individual laser pulses modifies the surface of the material in a very localized region, typically 0.1-100 microns. It is particularly advantageous to move either the laser beam or the material to be modified, in an effort to modify the surface of the material in a large pattern. Several commercially available laser systems have a computer-controlled table for mounting the sample. The sample is then moved with the computer software, thereby inscribing a pattern onto the surface of the sample. In most instances for the present invention, the spacing between the individual laser pulses is very small, thereby making the pattern indistinct. In other embodiments of the current invention, individual pulses are separated by an area of 1 to 10 times the size of the pulse, in order to produce a periodic area of surface features.  
         [0034]    There are several elements of the laser process that can be varied to modify the degree of surface modification. Some examples include ambient atmosphere and temperature, pulse period, pulse width, gas pressure, and cone size. Each of these variables can be tuned for the specific material to be modified. The type and power of the laser depends on the type of material to be treated. For a given material, an increase in laser power will increase the depth of penetration into the material. In general, any laser will cause a small change in the surface structure of a material. In the case of the present invention, however, the power must reach a threshold that depends on the type of material, to give the benefits described for the striking face of a golf club. In some instances, sufficient laser power can be applied to golf club causing a localized melting of the surface material. This melting process can produce unique new material characteristics when the surface is re-solidified.  
         [0035]    An alternative embodiment for the laser surface modification process can be applied to golf clubs composed of multiple materials. It is well known in the prior art that multiple materials can be beneficially incorporated into a single golf club to improve the performance and feel. A secondary material, generally referred to as an insert, can be modified similar to a golf club composed of a single material. The laser settings must be adjusted to an appropriate level depending on the material in the insert. Too much laser power can cause excessive damage to the material, while too little laser power can cause no beneficial effect.  
         [0036]    In a major aspect, the present invention provides golf clubs with surfaces that have been modified with laser radiation. The following examples should serve to provide sufficient information to allow anyone skilled in the art to reproduce the current invention.  
       EXAMPLE 1  
     Ceramic Material  
       [0037]    Is A commercially available aluminum oxide (Al 2 O 3 ) material (AD-996, CoorsTek, Inc., Golden, CO) with a thickness of 0.025 inches was selected for the laser surface modification experiments. The aluminum oxide substrate was placed on an anodized aluminum fixture on a carbon dioxide (CO 2 ) laser system with computer-controlled position head and manually adjusted laser settings (Epilog Laser, Golden, Colo.). The laser was operated in a raster mode with powers ranging from 2.5 Watts to 25 Watts and speeds of 2.5 inches per second to 25 inches per second. The surface of the material was characterized with a scanning electron microscope (840-JXA, JEOL Instruments, Ltd.) at an accelerating voltage of 15 kV and a probe current of 3×10 −10  amps. FIG. 1 shows the SEM image of the surface of the aluminum oxide material clearly highlighting the microfeatures on the surface. Additionally, the crystalline material has been changed to an amorphous material, as evidenced by the smooth region within the laser surface modified region.  
       EXAMPLE 2  
     Titanium Alloy  
       [0038]    A commercially available titanium alloy (Ti—6Al—4V, Titanium Industries, Inc.) was selected for the laser surface modification experiments. The titanium material was placed on a xy-fixture on a Nd:YAG laser (Hobart MM1200) system with computer-controlled z-height head and manually adjusted laser settings. The laser was operated in a continuous wave mode with powers ranging from 100 Watts to 1200 Watts and material speeds of 1 inch per second to 10 inches per second. The laser surface modification experiments were conducted in a variety of different atmospheres, including air, methane, nitrogen, and argon. The surface of the material was characterized with a scanning electron microscope (840-JXA, JEOL Instruments, Ltd.) at an accelerating voltage of 15 kV and a probe current of 3×10 −10  amps. FIG. 2 shows a low magnification scanning electron microscope image of the surface of the laser modified titanium alloy. The raised horizontal features are the result of melted and re-solidified material that was treated under the laser beam. FIG. 3 shows a higher magnification scanning electron microscope image of the surface of the laser modified titanium alloy, indicating the presence of the laser microfeatures.  
       EXAMPLE 2  
     Titanium Metal  
       [0039]    A commercially pure titanium metal (CP-Grade II, Titanium Industries, Inc.) was selected for the laser surface modification experiments. The tubular titanium material was placed on an anodized aluminum fixture on a carbon dioxide (CO2) laser system with computer-controlled position head and manually adjusted laser settings (Epilog Laser, Golden, Colo.). The laser was operated in a raster mode with powers ranging from 2.5 Watts to 25 Watts and speeds ranging from 2.5 inches per second to 25 inches per second. A black paint coating was applied to the surface to increase the heat absorbed by the material. The laser surface modification experiments were conducted in air at ambient temperatures.  
       EXAMPLE 3  
     Stainless Steel Alloy  
       [0040]    A stainless steel material (17-4PH alloy, ARMCO Steel Corporation) in a solution-treated condition was selected for the laser surface modification experiments. The stainless steel material was placed on a xy-fixture on a Nd:YAG laser (Hobart MM1200) system with computer-controlled z-height head and manually adjusted laser settings. The laser was operated in a continuous wave mode with powers ranging from 100 Watts to 1200 Watts and material speeds of 1 inch per second to 10 inches per second. The laser surface modification experiments were conducted in a variety of different atmospheres, including air, methane, nitrogen, and argon. The hardness of the laser modified coating was measured by cutting the sample transverse to the laser surface, mounting in a resin material (polyoxybenzylmethylenglycolanhydride, trade name Bakelite), and polishing with silicon carbide and diamond abrasives. The hardness was then measured on the surface layer and bulk material showing an increase from 350+/−6 to 400+/−5 on a Brinell hardness scale.  
       EXAMPLE 4  
     Polymeric Material  
       [0041]    A commercially available polymer material (ethylene/methacrylic acid copolymer, Trade Name: Surlyn, Dupont Packaging and Industrial Polymers, Inc.) was selected for the laser surface modification experiments. A block of the polymeric material was placed on an anodized aluminum fixture on a carbon dioxide (CO2) laser system with computercontrolled position head and manually adjusted laser settings (Epilog Laser, Golden, Colo.). The laser was operated in a raster mode with powers ranging from 2.5 Watts to 25 Watts and speeds of 2.5 inches per second to 25 inches per second. Material was selectively ablated from the surface of the polymer to form a two dimensional periodic array of microfeatures ranging in size from 50 to 1000 microns.  
         [0042]    Golf Club Construction  
         [0043]    After the surface of the material of the golf club head has been modified with the laser, the club head can be attached to a shaft. Typical shaft materials can be composed of aluminum alloys, titanium alloys, graphite reinforced polymers, or chrome-coated steel. The final stage of the golf club assembly is to secure a grip to the opposite end of the club from the club head. Typical grips are composed of molded rubber or leather.  
         [0044]    Referring now to FIG. 4, a golf putter is indicated with a laser surface modified region  2 , a club head  4 , and a golf shaft  6 . The laser surface modified region can be any size relative to the putter head, but will typically occupy 30-90% of the region on the hitting face. Referring now to FIG. 5, a golf driver is indicated with a laser surface modified region  8 , a club head  10 , and a golf shaft  12 . The laser surface modified region can be any size relative to the driver head, but will typically occupy 25-95% of the region on the hitting face. Referring now to FIG. 6, a golf iron is indicated with a laser surface modified region  14 , a club head  16 , and a golf shaft  18 . The laser surface modified region can be any size relative to the iron head, but will typically occupy 25-95% of the region on the hitting face. FIGS.  7 - 9  show cross-sectional views of the three different clubs with laser surface modified striking faces. The depth of the laser surface modification  20  for the putter  22  in FIG. 7 can vary from 0.001-1000 micrometers. The depth of the laser surface modification  24  for the driver  26  in FIG. 8 can vary from 0.001-1000 micrometers. The depth of the laser surface modification  28  for the putter  30  in FIG. 9 can vary from 0.001-1000 micrometers.