FIELD OF THE INVENTION
The present invention involves a process for modifying the surface of a material with a laser, and incorporating said material into a golf club. The primary feature of the laser surface modified material involves incorporating it into the striking face of the golf club.
BACKGROUND OF THE INVENTION
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 optimizing the weight distribution within the golf club'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.
More recently, golf club manufacturers have shifted their focus to improving the golf club'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'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, that can also be utilized to improve a golf club's performance and feel.
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. 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.
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 ball 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. 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.
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. 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.
The pricr 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'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's patent is focused on metallic materials, which is dissimilar from the laser surface modification process which applies equally well to all classes of materials.
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.
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 modification.
SUMMARY OF THE INVENTION
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.
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 a high degree of control over the golf ball after it lands in the desired location.
In a golf putting application, the present invention can be particularly advantageous due to the high friction between the ball and the putter'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.
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.
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.
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.
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 dixoide laser ranges from 5-100 Watts. The focused spot size is typically in the range of 125 microns (0.005 inches).
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.
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.
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.