Patent Publication Number: US-2009239681-A1

Title: Iron-type golf club head and method for manufacturing the same

Description:
BACKGROUND OF THE INVENTION  
     The present invention relates to an iron-type golf club head and a manufacturing method therefor, more particularly to a segmented structure of a ring-shaped member disposed behind the clubface, and a method for welding the segments to the main body of the club head. 
     In the Japanese utility Model Patent 3,114,961, as shown in  FIGS. 11(   a ) and  11 ( b ), there has been proposed an iron-type golf club head (A 1 ) composed of a main body (a) having a flat back surface (b), and a ring-shaped member (c) welded to the back surface (b) to form an open cavity (e) behind the clubface. 
     In such a club head structure, the interface between the main body (a) and the ring-shaped member (c) appears on the outer peripheral surface of the head as a line (Bo) and appears on the inner surface of the cavity (e) as a line (Bi). Thus, there is a possibility that the welding operation is made along the line (Bo) and line (Bi). 
     The welding along the line (BO) can be made from the outside of the head, therefore, the operation is easy. But, the welding operation along the line (Bi) is difficult because the cavity is narrow and restricts the movements of welding tools. Especially, when the so called pocket cavity CP as shown in  FIG. 3  is formed, the welding operation along the line (Bi) becomes very difficult although such structure requires more joint strength between the main body and ring-shaped member in order to support the mass of the backside wall  14 . Therefore, it is difficult to provide a sufficient joint strength if the welding is made along the line (Bo) only. Furthermore, in the case that the line (Bi) is easily visible as shown in  FIG. 11(   b ), even if the welding can be made along the line (Bi), it is necessary to make finish polishing. But, such operation is difficult for the same reason as above. 
     SUMMARY OF THE INVENTION  
     It is therefore, an object of the present invention to provide an iron-type golf club head and a manufacturing method therefor, in which the joint strength between the ring-shaped member and the head main body can be effectively increased without the need for the above-mentioned difficult operations. 
     According to the present invention, an iron-type metal golf club head comprises: 
     a main body including a hosel portion and a face plate portion having a back surface and a front surface forming a clubface; and 
     a ring-shaped member disposed behind the face plate portion and having an outer periphery surface continuous in the circling direction of the ring, wherein 
     the ring-shaped member is made up of at least two segments parted by at least two parting planes, each parting plane extending crosswise to the circling direction of the ring-shaped member so as to form opposed sections of the adjacent segments, and 
     the segments include: a primary segment attached to the main body by welding along a first line and at least one of second lines; and a secondary segment attached to the main body by welding along the first line but the second lines, wherein 
     the first line is an intersection line of the above-mentioned outer periphery surface and the surface of the main body, and 
     the second line is an intersection line of the back surface of the face plate portion and each of the sections of the segment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         FIG. 1  is a front view of an iron-type golf club head according to the present invention. 
         FIG. 2  is a rear view thereof. 
         FIG. 3  is a cross sectional view taken along line A-A in  FIG. 1 . 
         FIG. 4  is an exploded perspective view showing a first embodiment of the club head. 
         FIGS. 5(   a ) and  5 ( b ) are perspective views for explaining a method for manufacturing the first embodiment of the club head according to the present invention. 
         FIG. 6  is a rear view of a second embodiment of the club head. 
         FIG. 7  is a rear view of a third embodiment of the club head. 
         FIGS. 8(   a ) and  8 ( b ) are perspective views for explaining a fourth embodiment of the club head and a manufacturing method therefor. 
         FIG. 9  is an enlarged cross-sectional view showing an example of a welded portion taken along a perpendicular direction to the second line. 
         FIGS. 10(   a ) and  10 ( b ) are enlarged cross-sectional views showing another example of a welded portion taken along a perpendicular direction to the second line. 
         FIGS. 11(   a ) and  11 ( b ) are an exploded perspective view and a cross sectional view showing an iron-type golf club head according to the a prior art. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     Embodiments of the present invention will now be described in detail in conjunction with accompanying drawings. 
     In the drawings, iron-type golf club head  1  according to the present invention has a clubface  2  for striking a ball, a top face  3  intersecting the clubface  2  at an upper part of the clubface edge, a sole face  4  intersecting the clubface  2  at a lower part of the clubface edge, and a toe face  5  intersecting the clubface  2  at a toe-side part of the clubface edge and extending between the top face  3  and sole face  4 . The top face  3  is inclined downward toward the heel from the toe. A major part of the sole face  4  extends substantially horizontally in the heel-and-toe direction. The toe face  5  is curved convexly towards the outside. The head  1  comprises a heel portion  6  provided with a tubular hosel portion  7  protruding upwardly therefrom and having a shaft inserting hole  7   a  into which a clubshaft (not shown) is inserted. 
     In this specification, positions, directions and the like relating to the club head refer to those under a standard state of the club head unless otherwise noted. Here, the standard state of the club head is such that the club head is set on a horizontal plane HP so that the center line CL of the club shaft (not shown) is inclined at the lie angle (alpha) while keeping the club shaft center line CL on a vertical plane, and the clubface forms its loft angle (beta) with respect to the horizontal plane HP. Incidentally, in the case of the club head alone, the center line of the shaft inserting hole can be used instead of the center line of the club shaft. As shown in  FIG. 1 , the above-mentioned top face  3  is defined as extending between vertical planes VP 1  and VP 2 . The sole face  4  is defined as extending between the vertical planes VP 1  and VP 2 . The toe face  5  is defined as existing on the toe-side of the vertical plane VP 1 . The heel portion  6  including the hosel portion  7  is defined as existing on the heel-side of the vertical plane VP 2 . The vertical plane VP 1  is defined as being perpendicular to the clubface  2  and including the highest point P 1  of the clubface  2 . The vertical plane VP 2  is defined as being perpendicular to the clubface  2  and including the intersecting point P 2  of the center line CL and the horizontal plane HP. 
     The clubface  2  can be provided with so called impact area marking M, namely, small grooves extending horizontally to increase the frictional force between the ball and clubface  2  at impact. Otherwise, the clubface  2  is flat. Therefore, the edge of the clubface  2  can be determined as the edge of the flat surface. 
     The club head  1  is composed of a main body  1 A and a ring-shaped member  1 B which are welded to each other. Therefore, as shown in  FIG. 2 , an open cavity is formed behind the clubface  2 . 
     The main body  1 A is made of a single metal material which preferably has a specific gravity of not more than 10.0, more preferably not more than 9.0, still more preferably not more than 8.0, but not less than 2.0, more preferably not less than 3.0, still more preferably not less than 4.0, especially preferably not less than 4.5. For example, magnesium alloys, aluminum alloys, titanium alloys, stainless alloys, soft irons (or low-carbon steel whose carbon content is less than 0.3 wt %) and the like can be used suitably for such metal material. 
     The weight or mass of the main body  1 A is preferably set in a range of not less than 120 grams, more preferably not less than 130 grams, but not more than 220 grams, more preferably not more than 210 grams, still more preferably not more than 200 grams. 
     The main body  1 A integrally includes a face plate portion  8  and the above-mentioned hosel portion  7  on the heel-side of face plate portion  8 . 
     The face plate portion  8  has the front surface which includes the entirety of the clubface  2  and the back surface  8   b  which is a single flat surface, and the thickness of the face plate portion  8  is substantially constant. 
     The ring-shaped member  1 B is provided at the front thereof with an engaging surface  13  which is a flat surface capable of closely contacting with the back surface  8   b  of the face plate portion  8 . In the closely contact state, the ring-shaped member  1 B is welded to the back surface  8   b  so that it has a continuous annular outer periphery surface  10  which surface  10  forms rear parts of the above-mentioned top face  3 , toe face  5  and sole face  4 , respectively, and a rear part of the outer surface of the heel portion  6 , as shown in  FIG. 2  and  FIG. 3 . 
     In the following embodiments, the ring-shaped member  1 B is provided with a backside wall  14  in order to deepen the center of gravity of the head. The backside wall  14  extends upwardly from the sole face  4 , while leaving a space from the back surface  8   b  of the face plate portion  8 , therefore, a pocket cavity CP is formed between the face plate portion  8  and the backside wall  14 . The backside wall  14  is formed along only the sole face  4 , but it is also possible to form the backside wall along the entire circumference of the ring-shaped member  1 B, or along the sole face  4  and the top face  3 , or any suitable combination. 
     In order to deepen the center of gravity of the head and to increase the moment of inertia, the total mass of the ring-shaped member  1 B is preferably set in a range of not less than 70 grams, more preferably not less than 80 grams, still more preferably not less than 90 grams, but not more than 130 grams, more preferably not more than 120 grams, still more preferably not more than 110 grams. If the total mass is less than 70 grams, the depth of the center of gravity and the moment of inertia become decreased, and as a result, directionality of the hit balls tends to become worse. If more than 130 grams, the weight available for the main body  1 A is relatively decreased, and as a result, it becomes necessary to downsize the head or the weight balance of the head becomes worse. 
     According to the present invention, the ring-shaped member  1 B is, before welded to the main body  1 A, made up of at least two separate segments  12  which are parted by at least two parting planes each extending crosswise to the circling direction C of the ring. Accordingly, the segments  12  each have two sections  11  one on each side in the circling direction C. 
     Each of the segments  12  is made of a metal material having a specific gravity which is in a range of not less than 5.0, preferably not less than 6.0, more preferably not less than 7.0, but not more than 20.0, preferably not more than 18.0, more preferably not more than 15.0. For example, aluminum alloys, titanium alloys, stainless alloys, tungsten alloys and the like can be used. Thus, the ring-shaped member  1 B as a whole can be made of a singe metal material or alternatively plurality kinds of different metal materials. Preferably at least one of, more preferably each of the segments  12  has a specific gravity larger than that of the main body  1 A. In this case, it is preferable that the difference in the specific gravity from the main body  1 A is not less than 1.0, more preferably not less than 2.0, still more preferably not less than 3.0, but not more than 10.0, more preferably not more than 9.0, still more preferably not more than 8.0. 
       FIGS. 4 ,  5 ( a ) and  5 ( b ) show a first embodiment made up of two segments  12  parted by two parting planes. 
       FIG. 6  shows a second embodiment made up of two segments  12  parted by two parting planes. 
       FIG. 7  shows a third embodiment made up of three segments  12  parted by three parting planes. 
       FIGS. 8(   a ) and  8 ( b ) show a fourth embodiment made up of four segments  12  parted by four parting planes. 
     It is preferable that the number of the segments  12  is not more than 8, more preferably not more than 7, still more preferably not more than 6 since the production efficiency is lowered with the increase in the number of the segments. 
     According to the present invention, the segments  12  can be classified into primary segments  12   a  and secondary segments  12   b  by the positions of the segment welded to the main body  1 A. Specifically, the primary segment  12   a  is defined as being welded to the main body  1 A along both of a first line j 1  and a second line j 2 . The secondary segment  12   b  is defined as being welded to the main body  1 A along the first line j 1  but the second line j 2 . Here, the first line j 1  is the intersection line of two surfaces which are the periphery surface  10  of the ring-shaped member  1 B and the outer surface of the main body which is the periphery surface  8 P of the face plate portion  8  in the 1st to 4th embodiments. The second line j 2  is the intersection line of two surfaces which are the back surface  8   b  of the face plate portion  8  and each of the sections  11  (parting planes). 
     Each of the segments  12  has two second lines j 2  since there are two sections  11  (or parting planes) one on each side thereof. In the case of the primary segment  12   a , the welding is made along at least one of the two second lines j 2 . In the case of the secondary segment  12   b , the welding is made along neither one of nor both of the two second lines j 2 . 
     The expression “welding along the line j 1 /j 2 ” means that the welding is made continuously or discontinuously along the line, more specifically, the welding is made continuously along the entire length of the line or the welding is made at certain intervals along the entire length of the line. 
     The sole face  4  is very liable to be subjected to a large impulsive force when contacting the ground during swing, therefore, it is preferable that the primary segment  12   a  forms at least a part of the sole face  4  in order to increase the joint strength between the segment and the main body and thereby to improve the durability of the head. 
     As the segment  12  becomes heavier, a larger joint strength is required, therefore, it is preferable that the weight of the primary segment  12   a  which can exert a larger joint strength is increased more than the secondary segment  12   b , whereby the joint strength of the ring-shaped member  1 B as a whole can be improved well-balancedly to further improve the durability. 
     In the first embodiment shown in  FIGS. 4 ,  5 ( a ) and  5 ( b ), the two parting planes (sections  11 ) are substantially-vertical flat planes extending at such positions that substantially bisect the ring-shaped member  1 B in the heel-and-toe direction. In this example, the heel-side segment is the above-mentioned primary segment  12   a.    
     In the second embodiment shown in  FIG. 6 , the two parting planes (sections  11 ) are substantially-flat planes extending across a midpoint of the toe and a midpoint of the heel such that the ring-shaped member  1 B is divided into an upper segment and a lower segment. In this example, the lower segment is the primary segment  12   a . The lower segment forms the entirety of the sole face  4  and is heavier than the upper segment. 
     In the third embodiment shown in  FIG. 7 , the above-mentioned lower segment shown in  FIG. 6  is further divided into two parts, and the third parting plane (sections  11 ) is a substantially-vertical flat plane extending at such a position that substantially bisects the lower segment in the heel-and-toe direction. In this example, the toe-side and heel-side segments or parts divided from the lower segment are the primary segment  12   a.    
     In the fourth embodiment shown in  FIGS. 8(   a ) and  8 ( b ), the lower segment shown in  FIG. 6  is further divided into three parts, and the third and fourth parting planes (sections  11 ) are substantially-vertical flat planes extending at such positions that substantially trisect the lower segment in the heel-and-toe direction. In this example, each of the segments or parts divided from the lower segment are the primary segment  12   a.    
     The method for manufacturing the club head  1  according to the present invention will now be described in detail, mainly taking the first embodiment as an example, in conjunction with  FIG. 5(   a ) and  5 ( b ). 
     Firstly, the main body  1 A and the segments  12  are prepared. Various methods may be employed in order to make these metal parts. In view of the production efficiency, casting, forging and/or press molding are preferred. 
     In the first embodiment, it is possible to treat one of the two segments  12  on the heel-side as the primary segment  12   a , and the segment  12  on the toe-side as the secondary segment  12   b  as mentioned above. As shown in  FIG. 5(   a ), the primary segment  12   a  is fixed to the main body  1 A by welding these two parts along the first line j 1  and the two second lines j 2 . In this example, the welding is made continuously along the entire length of the first line j 1  and along the entire length of each of the second lines j 2 . 
     Because the first line j 1  appears on the outer surface of the club head  1 , the welding operation can be made from the outside of the head and, thus the operation is easy. Also the second line j 2  appears on the back surface  8   b  of the face plate portion  8  which is exposed to the outside of the head and thus easily accessible, therefore, the welding operation along the second line j 2  can be made from the outside of the head and, thus, this operation is also easy. 
     As to the sequence of the welding operation, it is possible to weld along the first line j 1  ahead of the second line j 2  or vice versa. 
     The primary segment  12   a  is thus fixed to the main body  1 A. 
     Next, in the case of the first embodiment, the secondary segment  12   b  is fixed to the main body  1 A, as shown in  FIG. 5(   b ). Firstly, the secondary segment  12   b  is set such that the sections  11  thereof are substantially fitted to the sections  11  of the primary segment  12   a , and thereby the welded portions along the second lines j 2  of the primary segment  12   a  are hidden by the secondary segment  12   b.    
     Then, the secondary segment  12   b  is welded along the first line j 1 . In this example, the welding is made continuously along the entire length of the first line j 1 . 
     Incidentally, during welding, in order to prevent displacement of the segments  12   a  and  12   b  from the main body  1 A, an adhesive and/or a device, e.g. clamp, holder or the like can be used for temporarily fixation. 
     As to the kinds of welding, various welding methods, for example, TIG welding, plasma welding, laser welding and the like can be employed, but in order to prevent the formation of unfavorable large weld beads, plasma welding or laser welding is preferably employed. 
     In some combinations of metal materials where it is difficult to join one metal material directly to the other metal material (for example, titanium alloy and stainless alloy, magnesium alloy and stainless alloy, titanium alloy and tungsten alloy), an intermediate or filler metal can be used to join such materials each other. As understandable from this, what is called “soldering” can be employed as the welding in a broad sense. 
     Optionally, further welding which can be made from the outside of the club head, is made along an intersection line j 3  of the outer surfaces of the adjacent segments  12  (or a small gap (j 3 ) between the opposed sections  11  thereof). 
     Furthermore, it is possible to make welding along an intersection line which is substantially invisible after the completion of the head but easily accessible during assembling the head. An example of such invisible intersection line is shown in  FIG. 5(   a ) as line “js”. This intersection line “js” is that of the back surface  8   b  of the face plate portion  8  and the inner circumferential surface of the segment  12  ( 12   a ), and the line “js” is hidden behind the backside wall  14  in the backside view of the club head  1  under the standard state. In such case, as the welded part is located in a blind spot, the finishing work such as polishing for improving the appearance can be omitted to increase the manufacturing efficiency. 
     In the case of the ring-shaped member  1 B made up of three or more segments  12 , it is preferable that one of the segments  12  is the secondary segment  12   b  and all of the remaining segments  12  are the primary segment  12   a.    
     For example, in the fourth embodiment shown in  FIGS. 8(   a ) and  8 ( b ), one of the four segments  12  is the secondary segment  12   b , and the remaining tree segments  12  are the primary segment  12   a  ( 12   a   1 ,  12   a   2 ,  12   a   3 ). 
     The lower middle primary segment  12   a   1  which forms the rear middle part of the sole face  4  is liable to be subjected to large impulsive forces, therefore, it is preferable that the welding is made along the first line j 1  and both of the two second lines j 2 , more preferably further along the hidden line The toe-side primary segment  12   a   2  which partially forms the sole face  4  and toe face  5 , is connected to the lower middle primary segment  12   a   1  in the sole, and welded along the third line j 3 , the first line j 1 , and one of the second lines j 2  located in the toe. 
     The heel-side primary segment  12   a   3  which forms partially the sole face  4  and heel portion  6 , is connected to the lower middle primary segment  12   a   1  in the sole, and welded along the third line j 3 , the first line j 1 , and one of the second lines j 2  located in the heel. 
     After all of the primary segment  12   a  ( 12   a   1 ,  12   a   2 ,  12   a   3 ) are welded to the main body  1 A, the only one secondary segment  12   b  which forms the rear part of the top face  3 , is welded along the first line j 1  and the two third lines j 3 . 
     In either case, as shown in  FIG. 9 , in order to prevent the weld bead w formed along the second line j 2  of the primary segment  12   a  from contacting with the section  11  of the adjacent segment  12  ( 12   a ,  12   b ), it is possible to chamfer the corner  15  between the section  11  and the engaging surface  13  of the afterward welded segment  12 . Such chamfering of the corner  15  is especially preferable in the case of TIG welding where the size of the weld bead w is liable to become increased. 
     On the other hand, as shown in  FIG. 10(   a ), it is also possible to position the afterward welded segment  12  such that a certain small gap Gp is intentionally formed between the adjacent sections  11  in order to prevent the weld bead w from contacting with the opposed section  11 . In this case, the gap Gp functions like a groove during making so called groove welding, and the molten metal fills and bridges the gap as shown in  FIG. 10(   b ). 
     Upon the completion of the welding of the final segment, the weld bead or weld line arising on the outer surface of the club head along the first line j 1  and third lines j 3  is final polished to improve the appearance of the club head. As to the second line j 2  and intersection line “js”, it is not necessary to make finish polishing. 
     Comparison Tests 
     Five-iron&#39;s heads (loft 26 degrees, weight 240 grams) were prepared and tested for the durability. 
     All of the heads had the same structure shown in  FIGS. 1-3 , excepting the parting and welding of the ring-shaped member. The main body (weight 140 grams) was manufactured by precision casting from a stainless steel (SUS630, specific gravity 7.8). The ring-shaped member (weight  100  grams) was manufactured by precision casting from a single material, tungsten alloy (W:Fe:Ni=35:40:15 in weight %, and specific gravity of 10.0). In order to weld these parts, TIG welding was employed. The specifications of the heads are shown in Table 1. 
     In the durability test, the club heads were attached to identical FRP shafts (“MP-400” manufactured by SRI Sports Limited) to make 38-inch five-iron clubs, and each club was mounted on a swing robot and hit golf balls 10,000 times (maximum) at the head speed of 40 m/s, while visually checking the club head every 100 times. If any damage was occured, the number of hits was recorded. The test results are shown in Table 1. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Head 
                 Ref. 1 
                 Ex. 1 
                 Ex. 2 
                 Ex. 3 
                 Ex. 4 
               
               
                   
               
             
            
               
                 Ring-shaped member 
                   
                   
                   
                   
                   
               
               
                 Structure 
                 — 
                 Fig. 6 
                 Fig. 5 
                 Fig. 7 
                 Fig. 8 
               
               
                 Number of segments 
                 — 
                 2 
                 2 
                 3 
                 4 
               
               
                 Durability 
               
               
                 Number of hits 
                 1800 
                 7000 
                 8000 
                 10000 
                 10000 
               
               
                 Damage 
                 yes *1 
                 yes *1 
                 yes *1 
                 no 
                 no 
               
               
                   
               
               
                 *1 Ring-shaped member was separated from Main body in Sole region 
               
            
           
         
       
     
     From the test results, it was confirmed that the heads according to the present invention can be remarkable improved in the durability.