Abstract:
The present invention provides a method of adjusting a coefficient of restitution (COR) of the face of a golf club head. A metallic assistant device is fixed on a center of a back of the face by friction welding or brazing. The metallic assistant may increases the central thickness of the face that may reduce the COR of the face.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to a method of making golf club, and more particularly to a method of making a golf club head that may adjust the coefficient of restitution of the face. 
         [0003]    2. Description of the Related Art 
         [0004]    In the standards of United States Golf Association (USGA), the coefficient of restitution (COR) of the face must be less than 0.83. The golf club with COR greater than 0.83 is forbidden in the game. The facts of COR of the face include the thickness of the face and the hardness of the face. The thicker or harder face will have less COR. In present days, the new material had introduced in golf clubs that the thinner face can pass the strength test. However, the thinner face usually has the COR greater than 0.83. A solution is making the face thicker. The thicker face increases the cost and shifts the center of gravity of the head forward that is disadvantageous for swing. Now, a new head has a face made by forging. Such face is thicker at center and thinner at margin that may reduce the COR. The forging process is working under a high temperature environment and molded in several molds that the cost of manufacturing such faces is much higher and can not meet the requirement of quick and mass production and making the products with less quantity and more aspects. 
       SUMMARY OF THE INVENTION 
       [0005]    The primary objective of the present invention is to provide a method of adjusting the coefficient of restitution of the face, which has lower cost of manufacture and fit to various types of golf clubs. 
         [0006]    The secondary objective of the present invention is to provide a method of adjusting the coefficient of restitution of the face, which provides various materials with different characters to help the face getting perfect COR. 
         [0007]    According to the objectives of the present invention, a method of adjusting a coefficient of restitution of the face of a golf club head including the step of fixing a metallic assistant device on a back of the face to reduce the coefficient of restitution of the face. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a sectional view of a first preferred embodiment of the present invention; 
           [0009]      FIG. 2  is a sectional view of a second preferred embodiment of the present invention; and 
           [0010]      FIG. 3  is a sectional view of a third preferred embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0011]    As shown in  FIG. 1 , a face  10  of a golf club head may be made of metal and made by casting, forging or punching. In the present invention, the face  10  is made of titanium alloy, more preferred βTi TVC, with a thickness about 2.5 mm and a hardness of HRC42°. An assistant device  20  is made of βTi 15-333 with a thickness about 1.5 mm and a hardness of HRC28°. The assistant device  20  is pressed on a center of a back side of the face  10  and spun in a high speed. The spinning of the assistant device  20  generates heat, and the heat welds the assistant device  20  and the face  10  together, so called friction welding, to form a face thicker at center and thinner at margin. The thickness of the center of the face is about 4 mm that may reduce the ROC. 
         [0012]    As shown in  FIG. 2 , the second preferred embodiment provides a face  30  made of 6-4 titanium and an annular assistant device  40 , which is made of 6-4 titanium also, fixed at a center of a back of the face  30  by friction welding. It has gaps between the assistant device  40  and the face  30  because of the friction welding, so that we perform brazing to the junction between the face  30  and the assistant device  40  to have solder  50  filled in the gaps that enhance the strength of the connection of the face  30  and the assistant device  40 . 
         [0013]    As shown in  FIG. 3 , the third preferred embodiment provides a face  60  made of stainless steel and an assistant device  70  made of titanium alloy. The assistant device  70  has a recess at the side fixed to the face  60 . Brazing is performed to fix the assistant device  70  on a center of a back of the face  60 . 
         [0014]    The assistant device is preferred a round member when it performs friction welding to fix the assistant device on the face. The assistant device may be an elliptical, polygonal or irregular or other shaped member that may perform friction welding. 
         [0015]    The shape of the assistant device has no limitation when it performs brazing to fix the assistant device on the face, except for X shape or other shapes that can&#39;t perform brazing. The condition may not suitable for friction welding, such as when the assistant device and the face are made of different material, may perform brazing to fix the assistant device and the face. Before brazing it may perform spot welding or TIG to pre-fix the assistant device on the face. 
         [0016]    Table 1 shows the test report of the face of the first preferred embodiment. The thickness of the face is measured at four points, shown in the figure as A, B, C, D. First line is the thicknesses of the blank of the face at the four points, and second line is the thicknesses of the face after first grind. The face after the second, third and fourth grinds is thinner at the fourth points and has a greater COR. The CORs of the faces with the assistant devices of the present invention are less than 0.83, and the CORs of the faces without the assistant devices of the present invention are greater than 0.83. It proves the assistant device of the present invention helps the reduction of COR of the face. 
         [0017]    The advantages of the present include fast adjustment of the COR of the face and flexible to every golf club heads made by different manufacture. It provides an easier and low-cost way to adjust the COR of the face. The present invention has no need to change the mold. The present invention may choose the specific material for the assistant devices to adjust the COR. 
         [0018]    The description above is a few preferred embodiments of the present invention and the equivalence of the present invention is still in the scope of the claim of the present invention.