Patent Publication Number: US-2004043831-A1

Title: Striking plate of a golf club head

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to a striking plate for a golf club head and, more particularly, to such a striking plate which has an inner surface highly polished so as to eliminate surface defects that may otherwise cause concentration of impact stress in the striking plate during its hitting a ball.  
       [0003] 2. Description of Related Art  
       [0004] A prior art striking plate  90  for a golf club head is shown in FIG. 4. It is a curved metal piece typically made of high strength special steel or titanium alloy by a procedure of forging, punching or machining. Because the outer surface  91  i.e. the striking face of the striking plate  90  has much influence over friction, accuracy and a traveling distance of a ball, the resulting outer surface  91  is usually finish processed, for example, polished before grooves  93  are made in it.  
       [0005] Irrespective of the procedure the striking plate  90  is formed, fine textures of the metal material can never be disposed as uniform as desired during the formation process, thus leaving in the outer and inner surfaces  91  and  92  a number of surface defects  94  that will lead to micro-cracks when the plate  90  hits a ball.  
       [0006] In detail, if the striking plate  90  is formed by forging, the hot, ductile metal will produce lines of fine textures, as shown in FIGS. 5 and 6, in the surfaces  91  and  92  at where the metal makes contact with the cool die. If the striking plate  90  is formed by punching, lines of fine textures in the raw material or the rolled metal plate will remain in the surfaces  91  and  92  of the striking plate  90 . And if the striking plate  90  is made by machining, the cutting tool will leave lines of fine incisions in the surfaces  91  and  92  of the striking plate  90 .  
       [0007] Although the fine processing mentioned above will remove the surface defects from the outer surface  91  of the striking plate  90 , the defects  94  are still kept intact in the inner surface  92  which is not fine processed. These residual defects  94  causes concentration of impact stress in the striking plate  90  during its hitting a ball and so degenerates the fatigue endurance of the same plate  90 , for the worse, leading to micro-cracks in the striking plate  90  and shorting its life. Therefore, there is really a need to improve such a striking plate  90 .  
       SUMMARY OF THE INVENTION  
       [0008] The object of the present invention is to provide a striking plate which has an inner surface highly-polished so as to eliminate concentration of impact stress, thereby providing an improved fatigue endurance and prolonged life for the striking plate.  
       [0009] To achieve the aforementioned object, the present invention provides a striking plate having an outer surface and an inner surface. The outer surface serves as a striking face formed with a plurality of grooves, and the inner surface is a highly-polished face with a surface roughness below 6.3 μm so as to eliminate surface defects that may otherwise cause contraction of impact stress. The striking plate can be integrated with a sole plate and a crown plate into a golf club head.  
       [0010] Other objects, advantages and novel features of this invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0011]FIG. 1 is an exploded perspective view of a club head provided with a striking plate constructed in accordance with the present invention;  
     [0012]FIG. 2 is a cross-sectional view of the striking plate taken along lines  2 - 2  in FIG. 1;  
     [0013]FIG. 3 is a diagram showing surface roughness on the inner surfaces of the striking plates of the present invention and of the prior arts;  
     [0014]FIG. 4 is a cross-sectional view of a prior art striking plate, shown a number of surface defects in an inner surface thereof;  
     [0015]FIG. 5 is a photograph, taken through an electro microscope, showing lines of surface defects presented as fine texture in the inner surface of the prior art striking plate; and  
     [0016]FIG. 6 is another photograph, also taken through an electro microscope, showing lines of surface defects presented as much finer texture in the inner surface of the prior art striking plate. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0017] The present invention is now to be described hereinafter by way of a preferred embodiment in reference to drawings.  
     [0018] Referring to FIGS.  1  to  3 , a striking plate  10  in accordance with the present invention includes an outer surface  11  and an inner surface  12 . The striking plate  10  is a curved metal piece made of high strength special steel or titanium alloy by means of forging, punching or machining. The outer surface  11 , which serves as a striking face, is formed with a plurality of grooves  13  to improve the friction, accuracy and traveling distance for a golf ball.  
     [0019] In the present invention, the inner surface  12  is a highly-polished face, as shown in TABLE 1, which is optionally formed by electrolytic polishing, chemical polishing or shake-and-grind polishing. The highly-polished face preferably has a roughness below 1 6.3 μm and, more preferably, below 3.5 μm, so as to eliminate as more surface defects (as those designated with the reference numeral  94  in FIGS. 4 and 6) from the inner surface  12  as possible and therefore to improve the fatigue strength of the striking plate  10 .  
     [0020] The outer surface  11  of the striking plate  10  may also be polished so. After the surfaces  11  and  12  are finished, as shown in FIG. 1, the striking plate  10  is integrated with a sole plate  20  and a crown plate  30  into a club head of a normal or super-large size. Furthermore, the resulting club head may be provided with an additional sleeve  40  that extends from the head for receiving a shaft (not shown).  
               TABLE 1                       Available Roughness for the Inner surface of the striking plate                                                                                 
 
     [0021] Referring again to FIGS. 2 and 4, the inner surface  12  of the inventive striking plate  10  in FIG. 2 is a highly-polished face with a surface roughness below 6.3 μm. This eliminates surface defects from the inner surface  12  and hence reduces the possibility of micro-cracks in the striking plate  10 .  
     [0022] In contrast to the prior art striking plate  90  of FIG. 4, in which the inner surface  92  has a number of residual defects  94  that causes concentration of impact stress in the plate  90  during its hitting a ball and degenerates the fatigue endurance of the plate  90 , the inventive striking plate  10  in FIG. 2 surely has an improved fatigue endurance and a prolonged life.  
     [0023] While the principles of this invention have been disclosed in connection with specific embodiments, it should be understood by those skilled in the art that these descriptions are not intended to limit the scope of the invention, and that any modification and variation without departing the spirit of the invention is intended to be covered by the scope of this invention defined only by the appended claims.