Patent Publication Number: US-2007099723-A1

Title: Putter head

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a putter head with a face insert fitted in a face portion of a head body.  
      2. Description of the Related Art  
      Conventionally, a putter head has been proposed in which a face insert made of a material different from that of a head body is fitted in a face portion of the head body. For example, JP-A-2004-236985 discloses a putter head in which a face insert having a layered structure integrally including a rubber elastic body layer, a sintered metal layer, and a fluororesin layer is fitted in the face portion of the head body. In addition, JP-A-2005-124730 discloses a putter head in which an elastic body-made face insert whose thickness increases gradually from the side of the vicinity of a sweet spot of the head toward a peripheral edge side is fitted in a face portion of a head body.  
     SUMMARY OF THE INVENTION  
      The above-described putter head with the face insert fitted in the head body is generally aimed at softening the hitting sensation when the ball is hit by the face insert.  
      However, with the conventional putter head with the face insert fitted in the head body, while the hitting sensation can be made soft by the face insert, the hitting sound becomes dull (low), so that there have been cases where it is difficult to grasp a sense of distance of the putt.  
      One aspect of the present invention provides a putter head with a face insert fitted in a head body, in which the hitting sensation at the time of hitting a ball is soft and the hitting sound is hard (high), so that it is easy to grasp the sense of distance of the putt.  
      According to a first aspect of the invention, there is provided a putter head including: a head body having a face portion; and a face insert fitted in the face portion of a head body, the face insert including: a high-hardness portion that forms a hitting surface, and a low-hardness portion jointed to the high-hardness portion and having a hardness lower than that of the high-hardness portion, wherein a thickness of the high-hardness portion is decreased from a central portion toward a peripheral portion.  
      According to a second aspect of the invention, there is provided a putter head including: a head body having a face portion; and a face insert fitted in the face portion of a head body, the face insert including: a high-hardness portion that forms a hitting surface, and a low-hardness portion jointed to the high-hardness portion and having a hardness lower than that of the high-hardness portion, wherein a thickness of the high-hardness portion is increased from a central portion toward a peripheral portion.  
      In the putter head in accordance with the first and second aspects of the invention, since the hardness of the high-hardness portion that forms the hitting surface (the surface for directly hitting the golf ball) is high, it is possible to obtain a hard (high) hitting sound by means of this high-hardness portion. Accordingly, it is easy to grasp the sense of distance of the putt. In addition, since the hardness of the low-hardness portion joined to high-hardness portion is lower than that of the high-hardness portion, a soft hitting sensation can be obtained by this low-hardness portion.  
      Furthermore, in the putter head in accordance with the first aspect of the invention, since the thickness of the high-hardness portion becomes smaller from the central portion toward the peripheral portion, the peripheral portion of the face insert is soft. Therefore, even if a golf ball is hit by the peripheral portion of the face insert, it is possible to obtain a soft hitting sensation. In addition, since the high-hardness portion is present in the peripheral portion as well, it is possible to obtain a hard hitting sound. In the putter head in accordance with the second aspect of the invention, since the thickness of the high-hardness portion becomes larger from the central portion toward the peripheral portion, the peripheral portion of the face insert is hard. For this reason, even if the golf ball is hit by the peripheral portion of the face insert, it is possible to obtain a hard hitting sound. In addition, since the low-hardness portion is present in the peripheral portion as well, it is possible to obtain a soft hitting sensation. Therefore, according to the putter head in accordance with the first and second aspects of the invention, it is possible to control the hitting sensation and the hitting sound when the golf ball is hit at the central portion (center) and at the peripheral portion (off center) of the face insert.  
      Hereafter, a more detailed description will be given of the aspect of the invention. In the aspect, as the material of the head body, it is possible to cite, for example, stainless steel, aluminum, an aluminum alloy, brass, copper, a titanium alloy, zinc, a carbon fiber-reinforced resin, and the like, but the material of the head body is not limited to the same.  
      In addition, as the materials of the high-hardness portion and the low-hardness portion of the face insert, it is possible to cite synthetic resins such as an ionomer resin, a urethane resin, a urethane-based elastomer, and a polyester-based elastomer, and rubbers such as a styrene-butadiene rubber and abutadiene rubber, but the materials of the high-hardness portion and the low-hardness portion of the face insert are not limited to the same. As the materials of the high-hardness portion and the low-hardness portion of the face insert, elastomers such as a urethane-based elastomer and a polyester-based elastomer and urethane resins are particularly preferable.  
      In the aspect, the Shore D hardness of the high-hardness portion is set to 30 or more, more preferably 35 to 100, the Shore D hardness of the low-hardness portion is set to 10 or more, more preferably 15 to 60, and the difference in the Shore D hardness between the high-hardness portion and the low-hardness portion is set to 5 or more, more preferably 10 to 85. If the Shore D hardness of the high-hardness portion is less than 30, there are cases where a hard hitting sound cannot be obtained. If the Shore D hardness of the low-hardness portion is less than 10, there are cases where a soft hitting sensation cannot be obtained. If the difference in the Shore D hardness between the high-hardness portion and the low-hardness portion is less than 5, there are cases where the advantages of the invention of making the hitting sensation soft and making the hitting sound hard cannot be obtained.  
      In the aspect, one or both of the high-hardness portion and the low-hardness portion can be provided with a multi-layered structure. In a case where only the high-hardness portion is provided with the multi-layered structure, the Shore D hardness of an outermost layer which comes into contact with the golf ball in the high-hardness portion and the difference in hardness between the outermost layer and the low-hardness portion are set to the aforementioned values. In a case where only the low-hardness portion is provided with the multi-layered structure, the Shore D hardness of an innermost layer which is closest to the head body in the low-hardness portion and the difference in hardness between the innermost layer and the high-hardness portion are set to the aforementioned values. In a case where both of the high-hardness portion and the low-hardness portion are provided with a multi-layered structure, the Shore D hardness of the outermost layer which comes into contact with the golf ball in the high-hardness portion, the Shore D hardness of the innermost layer which is closest to the head body in the low-hardness portion, and the difference in hardness between the outermost layer of the high-hardness portion and the innermost layer of the low-hardness portion are set to the aforementioned values.  
      In the first aspect of the invention, the thickness of the high-hardness portion is made smaller from the central portion toward the peripheral portion. In the second aspect of the invention, the thickness of the high-hardness portion is made larger from the central portion toward the peripheral portion. In this case, the thickness of the high-hardness portion may be varied continuously, or maybe varied in steps. In addition, the thickness of the high-hardness portion may be varied only in the longitudinal cross section of the face insert, or may be varied only in the transverse cross section thereof, or may be varied in both the longitudinal and transverse cross sections.  
      According to the putter head in accordance with the invention, the hitting sensation at the time of hitting a ball is soft, and the hitting sound is hard, so that the sense of distance is easy to grasp. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a rear view illustrating a face insert used in a putter head according to a first embodiment of the invention;  
       FIG. 2  is a cross-sectional view taken along line A-A in  FIG. 1 ;  
       FIG. 3  is a cross-sectional view taken along line B-B in  FIG. 1 ;  
       FIG. 4  is an exploded perspective view illustrating an example of a putter head with the face insert fitted therein;  
       FIG. 5  is a rear view illustrating a face insert used in a putter head according to a second embodiment of the invention;  
       FIG. 6  is a cross-sectional view taken along line A-A in  FIG. 5 ;  
       FIG. 7  is a cross-sectional view taken along line B-B in  FIG. 5 ;  
       FIG. 8  is a cross-sectional view illustrating a face insert used in a putter head according to a third embodiment of the invention;  
       FIG. 9  is a cross-sectional view taken along line B-B in  FIG. 8 ;  
       FIG. 10  is a cross-sectional view illustrating a face insert used in a putter head according to a fourth embodiment of the invention; and  
       FIG. 11  is a cross-sectional view taken along line B-B in  FIG. 10 . 
    
    
     DETAILED DESCRIPTION OF THE PREFFERED EMBODIMENTS  
      Hereafter, a description will be given the embodiments of the invention with reference to the drawings, but the invention is not limited to these embodiments.  
      (First Embodiment)  
       FIG. 1  is a rear view illustrating a face insert used in a putter head according to a first embodiment of the invention.  FIG. 2  is a cross-sectional view taken along line A-A in  FIG. 1 .  FIG. 3  is a cross-sectional view taken along line B-B in  FIG. 1 . A face insert l 0  in accordance with this embodiment includes a high-hardness portion  12  that forms a hitting surface and a low-hardness portion  14  that is joined to an inner surface of the high-hardness portion l 2 . The hardness of the low-hardness portion  14  is lower than that of the high-hardness portion  12 . In addition, in the face insert  10  of this embodiment, the thickness of the high-hardness portion  12  becomes gradually smaller from a central portion toward a peripheral portion in the longitudinal cross section shown in  FIG. 2 . It should be noted that the thickness of the high-hardness portion  12  is fixed in the transverse cross section shown in  FIG. 3 . Furthermore, in the face insert  10  of this embodiment, a frame-like body  16  is provided projectingly along peripheral edges of the inner surface of the high-hardness portion  12 , and the low-hardness portion  14  is disposed in a recessed portion  18  formed by this frame-like body  16 . The face insert  10  in accordance with this embodiment is used by being fitted in a recessed portion  104  formed in a face portion  102  of a head body  100 , as shown in  FIG. 4 .  
      (Second Embodiment)  
       FIG. 5  is a rear view illustrating a face insert used in a putter head according to a second embodiment of the invention.  FIG. 6  is a cross-sectional view taken along line A-A in  FIG. 5 .  FIG. 7  is a cross-sectional view taken along line B-B in  FIG. 5 . A face insert  20  in accordance with this embodiment is similar to the first embodiment except that the frame-like body is not projectingly provided on the peripheral edges of the high-hardness portion  12 . In FIGS.  5  to  7 , the same component portions as those shown in FIGS.  1  to  3  are denoted by the same reference numerals, and a description thereof will be omitted. The use of the face insert  20  in accordance with this embodiment is similar to that of the first embodiment.  
      (Third Embodiment)  
       FIG. 8  is a longitudinal cross-sectional view illustrating a face insert used in a putter head according to a third embodiment of the invention.  FIG. 9  is a transverse cross-sectional view taken along line B-B in  FIG. 8 . It should be noted that a rear view is the same as  FIG. 1 . A face insert  30  in accordance with this embodiment includes a high-hardness portion  32  that forms a hitting surface and a low-hardness portion  34  that is joined to the inner surface of the high-hardness portion  32 . The hardness of the low-hardness portion  34  is lower than that of the high-hardness portion  32 . In addition, in the face insert  30  of this embodiment, the thickness of the high-hardness portion  32  becomes gradually larger from the central portion toward the peripheral portion in the longitudinal cross section shown in  FIG. 8 . It should be noted that the thickness of the high-hardness portion  32  is fixed in the transverse cross section shown in  FIG. 9 . Furthermore, in the face insert  30  of this embodiment, a frame-like body  36  is provided projectingly along peripheral edges of the inner surface of the high-hardness portion  32 , and the low-hardness portion  34  is disposed in a recessed portion  38  formed by this frame-like body  36 . The use of the face insert  30  in accordance with this embodiment is similar to that of the first embodiment.  
      (Fourth Embodiment)  
       FIG. 10  is a longitudinal cross-sectional view illustrating a face insert used in a putter head according to a fourth embodiment of the invention.  FIG. 11  is a transverse cross-sectional view taken along line B-B in  FIG. 10 . It should be noted that a rear view is the same as  FIG. 5 . A face insert  40  in accordance with this embodiment is similar the third embodiment except that the frame-like body is not projectingly provided on the peripheral edges of the plate-like high-hardness portion  32 . In  FIGS. 10 and 11 , the same component portions as those shown in  FIGS. 8 and 9  are denoted by the same reference numerals, and a description thereof will be omitted.  
     EXAMPLE  
      A putter was fabricated by using a putter head in which the face insert  10  in accordance with the first embodiment shown in FIGS.  1  to  3  was fitted in the head body  100  shown in  FIG. 4 . In this case, an aluminum alloy was used as the material of the head body; a urethane resin (Shore D hardness: 60) as the material of the high-hardness portion  12 ; a urethane resin (Shore D hardness: 40) as the material of the low-hardness portion  14 ; and steel as the material of the shaft. In addition, the height h of the face insert  10  was set to 20 mm; the width w, 70 mm; the thickness d, 4 mm; the thickness ml of the high-hardness portion  12  in the central portion, 3 mm; the thickness m 2  of the high-hardness portion  12  in the peripheral portion, 2 mm; the width n of the frame-like body  16 , 2 mm; the area of the face surface f, approximately 1290 mm 2 ; and the area of the horizontal cross section of the low-hardness portion  14  (the surface area of the recessed portion  18 ), approximately 930 mm 2 .  
      Next, putting was performed by using the putter (embodiment) obtained, and the hitting sensation and the hitting sound were evaluated. As the golf balls, Tourstage X-01 manufactured by BRIDGESTONE SPORTS CO., LTD. was used. In addition, by way of comparison, similar tests were conducted by using a putter (Comparative Example 1) similar to that of the embodiment except that a recessed portion was not provided in the head body and the face insert was not fitted, a putter (Comparative Example 2) similar to that of the embodiment except that a face insert having a single-layer structure made of a urethane resin (Shore D hardness: 25) was used as the face insert, and a putter (Comparative Example 3) similar to that of the embodiment except that a urethane resin with a Shore D hardness of 60 was used for the high-hardness portion and that a urethane resin with a Shore D hardness of 56 was used for the low-hardness portion. In Comparative Example 3, the difference in the Shore D hardness between the high-hardness portion and the low-hardness portion was less than 5. The evaluation of the hitting sensation and the hitting sound was made on the basis of sensory evaluation by a plurality of golfers. The results are shown in Table 1. 
                               TABLE 1                                   Hitting                   Sensation   Hitting Sound   Sense of Distance                                                    Embodiment   Soft   Hard (high)   Easy to grasp       Comparative   Hard   Hard (high)   Easy to grasp       Example 1       Comparative   Soft   Dull (low)   Difficult to grasp       Example 2       Comparative   Hard   Hard (high)   Easy to grasp       Example 3                  
 
      From the results of Table 1, it was confirmed that, as for the putter head in accordance with the invention, the hitting sensation at the time of hitting the ball is soft, and the hitting sound is hard, so that the sense of distance is easy to grasp. In addition, with the putter of the embodiment, even in cases where the golf ball was hit at a peripheral portion (off center) of the face surface, it was possible to obtain a satisfactory hitting sensation and a hard hitting sound.