Patent Publication Number: US-10322326-B2

Title: Golf club hosel detachably coupled in a plurality of rotation positions

Description:
TECHNICAL FIELD 
     The present invention relates to a golf club. 
     BACKGROUND ART 
     Various methods of coupling a golf club head and a shaft have been proposed in recent years. For example, Patent Literature 1 discloses a golf club in which two adapters are attached between the hosel portion of the golf club head and the shaft so as to make it possible to change the angle of attachment of the shaft to the golf club head. 
     Specifically, the golf club disclosed in Patent Literature 1 is configured as follows. First, a shaft adapter attached to the shaft is fixed so as to be inclined relative to the shaft. Ahead adapter attached to the hosel portion is removably attached to the head at one of multiple rotation positions. The shaft adapter is then fitted into the head adapter at an inclined angle relative thereto, and furthermore can be fitted therein at multiple rotation positions. 
     Accordingly, the shaft can be attached to the golf club head at various angles by adjusting the rotation position of the head adapter relative to the hosel portion and the rotation position of the shaft adapter relative to the head adapter. This makes it possible to adjust the lie angle, loft angle, and face angle of the golf club to suit the user&#39;s preference. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP 2013-500059A 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, in the golf club described above, the head adapter is fitted into the hosel portion, and the shaft adapter is fitted into the head adapter, thus fixing the shaft so as to be incapable of axial rotation. For this reason, there has been a problem in that the shapes of the two adapters are limited to shapes that prevent axial rotation of the shaft. 
     One aspect of the present invention has been achieved in consideration of this point, and an object thereof is to make it possible to increase the degree of freedom in adapter design. 
     Solution to Problem 
     A golf club according to one aspect of the present invention includes: a shaft; a golf club head having a hosel portion that includes an attachment hole for attachment of the shaft, a hosel first coupling portion provided on a peripheral edge of the attachment hole, a hosel second coupling portion provided on a side opposite to the attachment hole, and a first opening portion that is formed on a side opposite to the attachment hole of the hosel portion and is in communication with an interior space of the hosel portion; a first adapter that is accommodated in the interior space of the hosel portion from an attachment hole side and has a first end portion and a second end portion, the first adapter having a shaft receiving recessed portion to which the shaft is to be fixed and that is open on a first end portion side, a first coupling portion that is provided on the first end portion side and is coupled to the hosel first coupling portion of the golf club head so as to be incapable of axial rotation, and a second coupling portion provided on a second end portion side; a second adapter that is accommodated in the interior space of the hosel portion from a first opening portion side and has a first end portion and a second end portion, the second adapter having a first coupling portion that is provided on a first end portion side and is coupled to the second coupling portion of the first adapter, and a second coupling portion that is coupled to the hosel second coupling portion of the golf club head; and a fixing member that detachably fixes the first adapter and the second adapter from a second end portion side of the second adapter. Also, the second coupling portion of the first adapter is formed along a first axis, and the shaft receiving recessed portion of the first adapter is formed along a second axis that intersects the first axis of the first adapter, such that the shaft is fixed to the shaft receiving recessed portion so as to be inclined relative to the second coupling portion of the first adapter, the second coupling portion of the second adapter is formed along a first axis, and the first coupling portion of the second adapter is formed along a second axis that intersects the first axis of the second adapter, such that the second coupling portion of the first adapter is coupled to the first coupling portion of the second adapter so as to be inclined relative to the second coupling portion of the second adapter, the first coupling portion of the first adapter and the hosel first coupling portion of the golf club head can be detachably coupled in a plurality of rotation positions, and the second coupling portion of the first adapter and the first coupling portion of the second adapter can be detachably coupled in a plurality of rotation positions. 
     Also, as another mode of the golf club according to the above aspect, a second opening portion that is in communication with the interior space of the hosel portion and exposes at least a portion of an outer peripheral surface of the second adapter to the outside may be formed in a front surface of the golf club head. Furthermore, a position indication portion for indicating a rotation position may be provided on a portion of the second adapter that is exposed through the second opening portion. 
     Also, as another mode of the golf club according to the above aspect, the first adapter may be formed with a tube shape along the first axis of the first adapter such that the first end portion and the second end portion of the first adapter are located on the first axis of the first adapter. Furthermore, the second adapter may be formed with a tube shape along the first axis of the second adapter such that the first end portion and the second end portion of the second adapter are located on the first axis of the second adapter. Moreover, the first coupling portion of the first adapter and the hosel first coupling portion of the golf club head may be able to be coupled in a plurality of rotation positions about the first axis of the first adapter, and the second coupling portion of the first adapter and the first coupling portion of the second adapter may be able to be coupled in a plurality of rotation positions about the second axis of the second adapter. 
     Also, as another mode of the golf club according to the above aspect, the second coupling portion of the first adapter may be configured by an outer peripheral surface having formed thereon a plurality of projections that extend in a direction of the first axis of the first adapter. Furthermore, the first coupling portion of the second adapter may be configured by an inner peripheral surface having formed therein a plurality of grooves that extend in a direction of the second axis of the second adapter and correspond to the plurality of projections so as to receive insertion of the plurality of projections. Moreover, the second coupling portion of the first adapter and the first coupling portion of the second adapter may be able to be coupled so as to be incapable of axial rotation in a plurality of rotation positions due to engagement of the plurality of projections of the first adapter and the plurality of grooves of the second adapter. 
     Also, as another mode of the golf club according to the above aspect, the second coupling portion of the second adapter may be configured by an outer peripheral surface formed with a polygonal shape, and the hosel second coupling portion of the golf club head may be configured by a polygonal inner wall surface on a first opening portion side so as to receive and engage with the second coupling portion of the second adapter, such that the second coupling portion of the second adapter and the hosel second coupling portion of the golf club head can be coupled so as to be incapable of axial rotation. 
     Also, as another mode of the golf club according to the above aspect, the golf club may further include a cover member that detachably closes the first opening portion. 
     Also, as another mode of the golf club according to the above aspect, a through-hole for insertion of a tool that can operate the fixing member may be formed in the cover member. 
     Also, as another mode of the golf club according to the above aspect, the first adapter may further have a position indication portion for indicating a rotation position on the first end portion side of the first adapter. 
     Advantageous Effects of Invention 
     According to the present invention, the first coupling portion of the first adapter, to which the shaft is fixed, and the hosel first coupling portion of the golf club head are coupled so as to be incapable of axial rotation, and therefore the shaft is attached to the golf club head so as to be incapable of axial rotation. For this reason, at least the second adapter does not need to be configured so as to be incapable of axial rotation. Accordingly, the golf club according to an aspect of the present invention makes it possible to increase the degree of freedom in adapter design. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view illustrating an overall structure of a golf club according to an embodiment; 
         FIG. 2  is a plan view illustrating a golf club head according to the embodiment; 
         FIG. 3  is an exploded view illustrating a coupling structure for coupling the golf club head and a shaft according to the embodiment; 
         FIG. 4  is a front view illustrating a state of the golf club head with a first adapter, a second adapter, a washer, and a fastener mounted thereto, as viewed from the heel side; 
         FIG. 5  illustrates a cross-section taken along line A-A in  FIG. 4 ; 
         FIG. 6  is a bottom view of the golf club head illustrated in  FIG. 4 , as viewed from the sole portion side; 
         FIG. 7  illustrates a cross-section taken along line B-B in  FIG. 5 ; 
         FIG. 8A  is a side view illustrating the first adapter according to the embodiment; 
         FIG. 8B  is a cross-sectional view illustrating the first adapter according to the embodiment; 
         FIG. 9A  is a perspective view illustrating a state of the second adapter according to the embodiment, as viewed from above; 
         FIG. 9B  is a cross-sectional view illustrating the second adapter according to the embodiment; 
         FIG. 9C  is a perspective view illustrating a state of the second adapter according to the embodiment, as viewed from below; 
         FIG. 10A  is a side view of the first adapter according to another embodiment; 
         FIG. 10B  is a side view of the golf club head according to the other embodiment; 
         FIG. 11A  is a side view illustrating the first adapter according to another embodiment; 
         FIG. 11B  is a perspective view illustrating the second adapter according to the other embodiment; 
         FIG. 12  is a perspective view illustrating the second adapter according to another embodiment; 
         FIG. 13A  is a perspective view illustrating the second adapter according to another embodiment; 
         FIG. 13B  is a cross-sectional view illustrating the second adapter according to the other embodiment; 
         FIG. 13C  is a cross-sectional view illustrating the golf club head with the second adapter of  FIG. 13A  ( FIG. 13B ) mounted thereto; 
         FIG. 14A  is a front view illustrating the golf club head with a cap mounted thereto; 
         FIG. 14B  is a cross-sectional view illustrating the golf club head with the cap mounted thereto; 
         FIG. 15  is a cross-sectional view illustrating the golf club head according to another embodiment; 
         FIG. 16A  is a front view illustrating a neck member; 
         FIG. 16B  is a cross-sectional view illustrating the neck member; 
         FIG. 17  is a side view illustrating the first adapter according to another embodiment; 
         FIG. 18  is a perspective view illustrating the second adapter according to another embodiment; 
         FIG. 19A  is a cross-sectional view illustrating a state of the inside of the hosel according to another embodiment; 
         FIG. 19B  illustrates a cross-section taken along line C-C in  FIG. 19A ; 
         FIG. 19C  is a side view illustrating the first adapter according to the other embodiment; 
         FIG. 20A  is a cross-sectional view illustrating a state of the inside of the hosel according to another embodiment; 
         FIG. 20B  is a side view illustrating the first adapter according to the other embodiment. 
     
    
    
     REFERENCE SIGNS LIST 
     
         
         
           
               10  Golf club head 
               20  Shaft 
               5  Hosel portion 
               501  First diameter portion (hosel first coupling portion) 
               6  First adapter 
               613  First coupling portion 
               7  Second adapter 
               9  Fastener (fixing member) 
           
         
       
    
     DESCRIPTION OF EMBODIMENTS 
     An embodiment of a golf club according to the present invention will be described below with reference to the drawings. 
     Note that although the following description uses the orientation shown in the drawings as a reference, this is for the sake of convenience in the description, and this orientation is not intended to limit the invention. Also, the axial direction in the following description is generally the direction in which the shaft extends unless otherwise stated, and is not intended to have a strict definition. 
     1. Overall Structure of Golf Club 
     First, the overall structure of the golf club will be described using  FIGS. 1 and 2 .  FIG. 1  is a perspective view illustrating the overall structure of a golf club  100  according to the present embodiment. Also,  FIG. 2  is a plan view illustrating a golf club head  10  according to the present embodiment. 
     As illustrated in  FIGS. 1 and 2 , the golf club  100  according to the present embodiment includes a shaft  20  and a golf club head  10  (hereinafter, sometimes simply called the “head”) coupled to the end portion of the shaft  20 . Also, the shaft  20  and the golf club head  10  are coupled together by a later-described coupling structure, and are configured such that it is possible to change the axial rotation position of the shaft  20  relative to the head  10 . These members will be described in detail below. 
     The shaft  20  is shaped as a hollow tube, has a lower end portion to which the above-mentioned golf club head  10  is coupled, and has an upper end portion to which a grip (not shown) is fixed. 
     The golf club head  10  is a hollow structure and has outer surfaces formed by a face portion  1 , a crown portion  2 , a sole portion  3 , a side portion  4 , and a hosel portion  5 . The face portion  1  has a face surface, which is the surface for hitting a golf ball. The crown portion  2  is adjacent to the face portion  1  and constitutes the upper surface of the head  10 . The sole portion  3  constitutes the bottom surface of the head  10 , and is adjacent to the face portion  1  and the side portion  4 . Also, the side portion  4  is the portion between the crown portion  2  and the sole portion  3 , and extends from the toe side of the face portion  1 , across the back side of the head  10 , to the heel side of the face portion  1 . 
     Furthermore, the hosel portion  5  is a cylindrical portion provided adjacent to the heel side of the crown portion  2 , and has an attachment hole  51  for the attachment of the shaft  20 . Specifically, a later-described first adapter  6 , which is fixed to the lower end portion of the shaft  20 , is inserted into the attachment hole  51 . Note that although the head  10  described here is a wood head such as a driver (#1) or fairway wood head, it is not limited to being a wood head, and may be a so-called utility head, hybrid head, or the like. 
     2. Coupling Structure for Coupling Shaft and Golf Club Head 
     Next, the coupling structure for coupling the shaft  20  and the golf club head  10  will be described using  FIG. 3 .  FIG. 3  is an exploded view illustrating the coupling structure for coupling the shaft  20  and the golf club head  10 . As illustrated in this figure, the shaft  20  and the golf club head  10  are coupled via the first adapter  6  and a second adapter  7 . The first adapter  6  and the second adapter  7  are fixed inside the golf club head  10  by a washer  8  and a fastener  9  (which correspond to a fixing member of the present invention). This coupling structure will be described in detail below. 
     2.1 Coupling-Related Structure of Golf Club Head 
     First, the structure of the golf club head  10  will be described using  FIGS. 4 to 7 .  FIG. 4  is a front view illustrating a state of the golf club head  10  with the first adapter  6 , the second adapter  7 , the washer  8 , and the fastener  9  mounted thereto, as viewed from the heel side.  FIG. 5  is a cross-sectional view illustrating a cross-section taken along A-A in  FIG. 4 .  FIG. 6  is a bottom view illustrating a state of the golf club head  10  illustrated in  FIG. 4 , as viewed from the sole portion  3  side.  FIG. 7  is a cross-sectional view illustrating a cross-section taken along B-B in  FIG. 5 . 
     As illustrated in  FIGS. 4 to 6 , the interior space of the hosel portion  5  extends to the side portion  4  side and the sole portion  3  side in a direction approximately parallel to the axial direction of the shaft  20 . A recessed portion  31  is formed in a portion of the sole portion  3  on the side opposite to the attachment hole  51  of the hosel portion  5 . This recessed portion  31  is constituted by an arc-shaped side surface  311  that extends approximately parallel to the interior space of the hosel portion  5 , and a base surface  312  that extends approximately perpendicularly from the side surface  311 . Also, a lower opening  313  that is in communication with the interior space of the hosel portion  5  is formed in the base surface  312 . The lower opening  313  corresponds to a first opening portion of the golf club head of the present invention. 
     Also, a rectangular window  55  in communication with the interior space of the hosel portion  5  is formed on the attachment hole  51  side relative to the base surface  312 . The window  55  corresponds to a second opening portion of the golf club head of the present invention. The window  55  is formed by cutting out a portion of the base surface  312  and the side portion  4  so as to expose a portion of the interior space of the hosel portion  5  (a third diameter portion  503  that will be described later) to the outside. For this reason, when the later-described second adapter  7  is arranged in the interior space of the hosel portion  5 , a portion of the second adapter  7  is exposed through the window  55 . 
     As shown in the enlarged view in  FIG. 5 , the interior space of the hosel portion  5  according to the present embodiment is constituted by a first diameter portion  501 , a second diameter portion  502 , and a third diameter portion  503 , in order from the attachment hole  51  side. The first diameter portion  501  is provided on the inner peripheral edge of the attachment hole  51 , and has multiple rectangular depressions along the inner peripheral edge. The first diameter portion  501  will be described below using  FIG. 7 . 
       FIG. 7  is a cross-sectional view illustrating a cross-section taken along B-B in  FIG. 5 . As illustrated in  FIG. 7  and the enlarged view in  FIG. 5 , multiple protrusion portions provided on the outer peripheral surface of a first coupling portion  613  of the later-described first adapter  6  engage with the depressions of the first diameter portion  501 . Accordingly, the first adapter  6  (shaft  20 ) and the hosel portion  5  (head  10 ) are coupled so as to be incapable of axial rotation. In other words, the first diameter portion  501  corresponds to a hosel first coupling portion of the present invention. Note that the term “coupled” here need only mean that at least two things are in contact so as to be immobile, and it is not required that the two things do not separate even when external force is applied. The same applies for the term “couple” used hereinafter. 
     Returning to  FIG. 5 , the second diameter portion  502  and the third diameter portion  503  will be described next. The second diameter portion  502  is continuous with the first diameter portion  501  and is formed with a cylindrical shape. Specifically, the second diameter portion  502  is formed with a tapered shape in which the diameter somewhat increases as it extends toward the third diameter portion  503  side. The third diameter portion  503  is continuous with the second diameter portion  502  and is formed with a cylindrical shape having a larger diameter than the second diameter portion  502 . Also, the third diameter portion  503  is in communication with the lower opening  313 . The opening of the third diameter portion  503  on the lower end portion side is provided so as to match the lower opening  313 . 
     During assembly, the first adapter  6  is inserted into the first diameter portion  501  and the second diameter portion  502  from the attachment hole  51  side. Also, the second adapter  7  is inserted into the third diameter portion  503  from the lower opening  313  side. The first adapter  6  and the second adapter  7  are thus detachably coupled in the interior space of the hosel portion  5 , and are removably fixed by the washer  8  and the screw-like fastener  9 . 
     As illustrated in  FIG. 3 , the fastener  9  is formed by a head portion  91  and a threaded portion  92  that is coupled to the head portion  91 . A rectangular recessed portion  911  (see  FIGS. 5 and 6 ) for insertion of a wrench is formed in the head portion  91 . By fitting a wrench into the recessed portion  911  and operating it, a user can fasten and detach the first adapter  6  and the second adapter  7 . 
     Note that when the first adapter  6  and the second adapter  7  have been fixed by the washer  8  and the screw-like fastener  9 , the fastening force of the fastener  9  couples a flange portion  72  of the later-described second adapter  7  to a step formed in the coupling portion between the second diameter portion  502  and the third diameter portion  503 . In other words, the step formed in the coupling portion between the second diameter portion  502  and the third diameter portion  503  corresponds to a hosel second coupling portion of the present invention. 
     2.2 First Adapter 
     Next, the first adapter  6  will be described using  FIGS. 8A and 8B .  FIG. 8A  is a side view illustrating the first adapter  6  according to the present embodiment. Also,  FIG. 8B  is a cross-sectional view illustrating the first adapter  6  according to the present embodiment. 
     As illustrated in  FIGS. 8A and 8B , the first adapter  6  includes a body portion  61  formed in a tubular shape. The body portion  61  has a first axis X 1  (solid line in  FIG. 8B ) as its axial center, has an external shape that extends in a cylindrical manner along the first axis X 1 , and has a shaft receiving recessed portion  611  that is open on the upper end portion side. The shaft receiving recessed portion  611  has a cylindrical inner wall surface that extends along a second axis X 2  (dashed line in  FIG. 8B ) that intersects the first axis X 1  with an angle of approximately 1 degree, and the lower end portion of the shaft  20  is inserted into the shaft receiving recessed portion  611 . The shaft  20  is fixed to the shaft receiving recessed portion  611  by a fixing means such as adhesion. Accordingly, the shaft  20  is fixed such that an axial center S (see  FIG. 1 ) thereof extends along the second axis X 2  of the first adapter  6  and extends at an inclination from the first axis X 1  of the first adapter  6 . 
     Also, the outer diameter of the body portion  61  of the first adapter  6  is smaller than the attachment hole  51  of the hosel portion  5 , but a flange portion  612  that extends outward in the diameter direction with a larger diameter than the attachment hole  51  is formed on the outer peripheral surface of the body portion  61  on the upper end side, and a first coupling portion  613  having multiple protrusion portions with a smaller diameter than the flange portion  612  is formed on the lower surface of the flange portion  612 . 
     The flange portion  612  comes into contact with the peripheral edge of the attachment hole  51  of the hosel portion  5 . Also, the first coupling portion  613  is formed below the flange portion  612 , and is used to couple the first adapter  6  and the hosel portion  5 . Specifically, the protrusion portions of the first coupling portion  613  engage with the depressions of the first diameter portion  501  of the hosel portion  5 , thus coupling the first adapter  6  and the hosel portion  5  so as to be incapable of axial rotation. 
     Note that the first adapter  6  is fixed at one of the rotation positions with an inclination relative to the later-described second adapter  7 . For this reason, the protrusion portions formed on the first coupling portion  613  of the first adapter  6  are formed somewhat smaller than the depressions formed on the first diameter portion  501  of the hosel portion  5  such that the first adapter  6  does not interfere with the inner wall surface of the first diameter portion  501  regardless of the rotation position at which the first adapter  6  is fixed to the second adapter  7 . 
     Due to the first adapter  6  being attached to the hosel portion  5  in this way, the first adapter  6  is accommodated in the interior space of the hosel portion  5  in a state in which the flange portion  612  is arranged outside the attachment hole  51 , and the portion below the flange portion  612  is arranged in the interior space of the hosel portion  5 . In other words, the term “accommodate” used here need only mean that at least a portion of something is inside the interior space, and there is not necessarily a requirement for all portions to be inside the interior space. The same applies for the term “accommodate” used hereinafter. 
     Note that the number of protrusion portions on the first coupling portion  613  and the number of depressions in the first diameter portion  501  are not particularly limited, but are each four in the present embodiment. For this reason, the first adapter  6  can be fitted into the hosel portion  5  in four rotation positions. For example, as illustrated in  FIG. 4 , a position indication portion  65  for displaying the rotation position is provided on the outer peripheral surface of the flange portion  612 . The user can set the head  10  at a desired angle, as will be described later, by selecting the rotation position of the first adapter  6  while referencing the position indication portion  65 . 
     Also, as illustrated in  FIGS. 8A and 8B , the first adapter  6  includes a tube-shaped second coupling portion  62  that is formed as a single body with the lower end portion of the body portion  61  and has a smaller diameter than the body portion  61 . The second coupling portion  62  of the first adapter  6  is formed in the shape of a tube that extends along the first axis X 1 , and has a threaded hole  621  that is open downward. Female threading is formed on the inner wall surface of the threaded hole  621 , and the threaded portion  92  of the fastener  9  is screwed therein. On the other hand, the outer peripheral surface of the second coupling portion  62  is smooth, and the second coupling portion  62  is inserted into a later-described recessed portion  711  of the second adapter  7 . Note that in  FIGS. 8A and 8B , the upper end portion of the first adapter  6  corresponds to a first end portion of the present invention, and the lower end portion of the first adapter  6  corresponds to a second end portion of the present invention. 
     2.3 Second Adapter 
     Next, the second adapter  7  will be described using  FIGS. 9A to 9C .  FIG. 9A  is a perspective view illustrating a state of the second adapter  7  according to the present embodiment, as viewed from above.  FIG. 9B  is a cross-sectional view illustrating a cross-section of the second adapter  7  according to the present embodiment.  FIG. 9C  is a perspective view illustrating a state of the second adapter  7  according to the present embodiment, as viewed from below. 
     As illustrated in  FIGS. 9A to 9C , the second adapter  7  includes a cylindrical body portion  71 . The body portion  71  has a first axis Y 1  (solid line in  FIG. 9B ) as its axial center, has an outer diameter that extends in a cylindrical manner along the first axis Y 1 , and has a recessed portion  711  that is open on the upper end portion side. The recessed portion  711  has a smooth cylindrical inner wall surface that extends along a second axis Y 2  (dashed line in  FIG. 9B ) that intersects the first axis Y 1  at an angle of approximately 1 degree, and the second coupling portion  62  of the first adapter  6  is removably inserted into this recessed portion  711 . In other words, the recessed portion  711  corresponds to a first coupling portion of the second adapter of the present invention. 
     According to this configuration, the second coupling portion  62  of the first adapter  6  attached to the recessed portion  711  extends along the second axis Y 2  of the second adapter  7 , and thus the first adapter  6  is fixed so as to extend at an inclination from the second adapter  7 . Here, the axial center of the second coupling portion  62  of the first adapter  6  is the first axis X 1  of the first adapter  6 , and the shaft  20  is fixed to the first adapter  6  along the second axis X 2  of the first adapter  6 . For this reason, with the golf club  100  of the present embodiment, the user can adjust the attachment angle of the shaft  20  in two stages using the first adapter  6  and the second adapter  7 . 
     Also, as illustrated in  FIGS. 9A to 9C , the second adapter  7  includes a cylindrical flange portion  72  that is integrally coupled to the lower end of the body portion  71  and has a larger diameter than the body portion  71 . The outer peripheral surface of the flange portion  72  is smooth, and the flange portion  72  is fixed to the step between the second diameter portion  502  and the third diameter portion  503  of the hosel portion  5  by the fastening force of the fastener  9 , as described above. In other words, the flange portion  72  corresponds to a second coupling portion of the second adapter of the present invention. 
     Also, a through-hole is formed between the flange portion  72  and the body portion  71 . This through-hole is defined by a circular large-diameter portion  731  that is open on the flange portion  72  side and a circular small-diameter portion  732  that is continuous with the large-diameter portion  731  and has a smaller diameter than the large-diameter portion  731 , and is also in communication with the recessed portion  711 . The previously-mentioned circular washer  8  is arranged in the large-diameter portion  731 , and the fastener  9  is arranged therein along with the washer  8 . The fastener  9  presses the washer  8  with the head portion  91 , and the threaded portion  92  passes through the small-diameter portion  732  and extends into the recessed portion  711 . The threaded portion  92  is then screwed to the second coupling portion  62  of the first adapter  6 , which has been inserted into the recessed portion  711 . 
     The large-diameter portion  731  is formed such that the surface on which the washer  8  is arranged is orthogonal to the second axis Y 2 . That is to say, since the first adapter  6  extends along the second axis Y 2  when it is coupled to the second adapter  7 , the washer  8  and the fastener  9  firmly fix them together along the direction in which the first adapter  6  extends. Note that the upper end portion of the second adapter  7  in  FIG. 8B  corresponds to a first end portion of the present invention, and the lower end portion of the second adapter  7  corresponds to a second end portion of the present invention. 
     When the second adapter  7  is fixed in this way, the body portion  71  of the second adapter  7  is arranged in a state of being coupled to the first adapter  6  in the second diameter portion  502  of the interior space in the hosel portion  5  (see  FIG. 5 ). On the other hand, the flange portion  72  of the second adapter  7  is arranged in the third diameter portion  503  in the interior space. The second adapter  7  is accommodated in the interior space of the hosel portion  5  in this state. 
     When the second adapter  7  is accommodated in the interior space of the hosel portion  5  in this way, the second adapter  7  is coupled to the first adapter  6  and the hosel portion  5  by the fastening force of the fastener  9  as described above. The second coupling portion  62  of the first adapter  6 , the recessed portion  711  of the second adapter  7 , the third diameter portion  503  of the hosel portion  5 , and the flange portion  72  of the second adapter  7  are each not shaped such that the second adapter  7  is fixed so as to be incapable of axial rotation in a predetermined rotation position. For this reason, the second adapter  7  can be fitted into the third diameter portion  503  of the hosel portion  5  in any rotation position. 
     It should be noted that since each of the above is shaped in such a way, when external axial rotational force is applied to the second adapter  7 , it is possible for the second adapter  7  to rotate about the axis even in the state of being fixed by the fastener  9 . However, the protrusion portions formed on the first coupling portion  613  of the first adapter  6 , to which the shaft  20  is fixed, are engaged with the depressions formed in the first diameter portion  501  of the hosel portion  5 , and the first adapter  6  and the hosel portion  5  are coupled so as to be incapable of axial rotation. For this reason, it is envisioned that external axial rotational force generated in normal use of the golf club  100  will be canceled out by this portion. Accordingly, it is envisioned that there is a very low possibility of the second adapter  7  rotating about its axis in normal use of the golf club  100 . 
     Accordingly, the second adapter  7  does not need to be coupled to the hosel portion  5  and the first adapter  6  so as to be incapable of axial rotation, and may be designed with any shape as long as it can be coupled to the hosel portion  5  and the first adapter  6 . In other words, according to the present embodiment, it is possible to increase the degree of freedom in adapter design. 
     Note that a position indication portion  722  for indicating multiple rotation positions is provided on the side surface and the lower end surface of the flange portion  72  of the second adapter  7  of the present embodiment. The position indication portion  722  provided on the lower end surface of the flange portion  72  is exposed through the lower opening  313  and visible to the user through the recessed portion  31 . Also, in the present embodiment, a portion of the flange portion  72  is exposed through the above-described window  55 . For this reason, the position indication portion  722  provided on the side surface of the flange portion  72  is visible to the user through the window  55 . Furthermore, a reference indicator  52  serving as indicator of the rotation position of the second adapter  7  is provided on the side surface of the peripheral edge of the opening of the window  55 . The user can determine the rotation position of the second adapter  7  by matching one of the indicators of the position indication portion  722  provided on the second adapter  7  with the reference indicator  52 . 
     Also, the first adapter  6  and the second adapter  7  used in the coupling structure can be formed using various materials, and can be formed using Ti(6-4Ti), Al (Al5052), or the like. 
     3. Assembly of Shaft and Golf Club Head 
     Next, a method of assembling the golf club  100  having the above configuration will be described. Specifically, a method for attaching the shaft  20  to the golf club head  10  will be described. 
     First, the user inserts the first adapter  6 , which has the shaft  20  fixed thereto, into the attachment hole  51  of the hosel portion  5  in a state in which the second coupling portion  62  faces downward. At this time, the user appropriately determines the rotation position of the first adapter  6  relative to the hosel portion  5  by referencing the position indication portion  65 . The user then fits the first coupling portion  613  of the first adapter  6  into the first diameter portion  501  of the hosel portion  5  in the desired rotation position. 
     Subsequently, the user inserts the second adapter  7  through the lower opening  313  on the sole portion  3  side. At this time, the user appropriately determines the rotation position of the second adapter  7  relative to the first adapter  6  by referencing the position indication portion  722  and the reference indicator  52 . The user then couples the second coupling portion  62  of the first adapter  6  and the recessed portion  711  of the second adapter  7  such that the flange portion  72  is fitted into the third diameter portion  503  of the hosel portion  5  in the desired rotation position. 
     Lastly, the user arranges the washer  8  in the large-diameter portion  731  of the flange portion  72  of the second adapter  7 , and inserts the threaded portion  92  of the fastener  9  into the small-diameter portion  732  and screws it to the second coupling portion  62  of the first adapter  6 . Accordingly, the first adapter  6  and the second adapter  7  are fixed in the interior space of the hosel portion  5 , and the shaft  20  is attached to the golf club head  10 . 
     When the shaft  20  and the head  10  have been fixed as described above, the shaft  20  is fixed so as to be inclined at an angle of 1 degree relative to the first adapter  6 . Also, the first adapter  6  is fixed so as to be inclined at an angle of 1 degree relative to the second adapter  7 . Accordingly, the shaft  20  is fixed so as to be inclined at a maximum of 2 degrees relative to the second adapter  7 . 
     In this way, the first adapter  6  is fixed so as to be inclined relative to the second adapter  7  in one of the rotation positions, and since the second diameter portion  502  of the interior space accommodating the first adapter  6  is tapered, the first adapter  6  does not interfere with the inner wall surface of the second diameter portion  502  regardless of the rotation position in which the first adapter  6  is fixed to the second adapter  7 . Also, the protrusion portions formed on the first coupling portion  613  of the first adapter  6  are formed somewhat smaller than the depressions formed in the first diameter portion  501  of the hosel portion  5  such that the first adapter  6  does not interfere with the inner wall surface of the first diameter portion  501  regardless of the rotation position in which the first adapter  6  is fixed to the second adapter  7 . 
     Accordingly, by changing the orientation in which the first adapter  6  is fitted into the hosel portion  5  so as to change the rotation position of the first adapter  6  relative to the hosel portion  5 , the user can change the attachment angle of the shaft  20  relative to the head  10  so as to change the lie angle, the loft angle, and the face angle of the head  10 . Also, by changing the rotation position of the second adapter  7  relative to the first adapter  6  while keeping the rotation position of the first adapter  6  fixed, the user can more finely change the lie angle, the loft angle, and the face angle of the head  10 . Here, with the golf club  100  of the present embodiment, the user can attach the second adapter  7  in any rotation position. For this reason, with the golf club  100  of the present embodiment, the user can determine the attachment angle of the head  10  by selecting a desired combination from among countless combinations of a lie angle, a loft angle, and a face angle for the head  10 . 
     At this time, the position indication portion  65  (see  FIG. 3 ) indicating the rotation position is provided on the flange portion  612  of the first adapter  6 , and is exposed to the outside. For this reason, the user can view the rotation position of the first adapter  6  without detaching the first adapter  6 . Also, in the present embodiment, a portion of the interior space of the hosel portion  5  is exposed to the outside through the window  55 . Specifically, a portion of the third diameter portion  503  of the hosel portion  5  is exposed to the outside, and a portion of the flange portion  72 , which is provided with the position indication portion  722  (see  FIG. 4 ) that indicates the rotation position of the second adapter  7 , can be viewed from the outside. For this reason, the user can check the rotation position of the second adapter  7  without detaching the second adapter  7 . Accordingly, with the golf club  100  of the present embodiment, the user can check the rotation position of the first adapter  6  and the rotation position of the second adapter  7  and thus check the lie angle, the loft angle, and the face angle of the golf club  100 , without disassembling the coupling structure. 
     4. Variations 
     Although an embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and various modifications can be made without departing from the gist of the invention. The following are examples of modifications that can be made. 
     4.1 
     In the above embodiment, multiple protrusion portions are formed on the first coupling portion  613  of the first adapter  6 , and multiple depressions are formed in the first diameter portion  501  of the hosel portion  5 , and thus the first adapter  6  and the hosel portion  5  are coupled so as to be incapable of axial rotation. However, the mode in which the first adapter  6  and the hosel portion  5  are coupled so as to be incapable of axial rotation is not limited to this mode, and various modes are possible. For example, although protrusion portions (first coupling portions  613 ) with a smaller diameter than the flange portion  612  of the first adapter  6  are provided in the above embodiment, protrusion portions  613  with the same diameter as the flange portion  612  may be provided below the flange portion  612  as shown in  FIG. 10A . In this case, as shown in  FIG. 10B , multiple cutout portions  511  into which the protrusion portions  513  fit are provided in the peripheral edge of the attachment hole  51  of the hosel portion  5 . Even with this configuration, the first adapter  6  and the hosel portion can be coupled so as to be incapable of rotation. Alternatively, it is possible to provide protrusion portions that protrude in the axial direction on the peripheral edge of the attachment hole  51  of the hosel portion  5  and provide recessed portions into which the protrusion portions fit in the lower portion of the flange portion  612  of the first adapter. Alternatively, the first adapter  6  and the hosel portion  5  can have various configurations, as long as they can be detachably coupled so as to be incapable of rotation. 
     4.2 
     Also, in the above embodiment, the second adapter  7  is configured so as to be able to be fitted in any rotation position relative to the first adapter  6 . However, the second adapter  7  need not be limited to this shape, and a rotation position that allows the second adapter  7  to fit into the first adapter  6  may be specified. 
     In this case, for example, as illustrated in  FIG. 11A , the second coupling portion  62  of the first adapter  6  may be configured with an outer peripheral surface having formed thereon multiple projections  622  that extend in the first axis X 1  direction. As illustrated in  FIG. 11B , the recessed portion  711  of the second adapter  7  may be configured with an inner peripheral surface having formed thereon multiple grooves  712  that extend in the direction of the second axis Y 2  of the second adapter and correspond to the projections  622  formed on the second coupling portion  62  of the first adapter  6 , such that the grooves  712  receive the projections  622 . At this time, the second coupling portion  62  and the recessed portion  711  are splined together, and therefore the first adapter  6  and the second adapter  7  are coupled so as to be incapable of axial rotation. Here, the first adapter  6  and the second adapter  7  can be coupled in the same number of rotation positions as the number of projections  622 . Note that the number of projections  622  and grooves  712  is 2 to 12, for example, but there is no particular limitation on the number thereof. 
     In this way, by configuring the first adapter  6  and the second adapter  7  to be connected so as to be incapable of axial rotation, the rotation position in which the second adapter  7  can be fitted into the first adapter  6  is specified. Accordingly, the types of rotation positions that can be selected by the user are fixed, thus making it easier for the user to select a rotation position for the second adapter  7 . 
     Note that in the above variation, the first adapter  6  and the second adapter  7  are coupled so as to be incapable of axial rotation due to the first adapter  6  and the second adapter  7  being splined together. However, the mode in which the first adapter  6  and the second adapter  7  are coupled about their axes need not be limited to this mode. For example, a configuration is possible in which the first adapter  6  and the second adapter  7  are coupled so as to be incapable of axial rotation due to forming the outer peripheral surface of the second coupling portion  62  of the first adapter  6  with a polygonal shape, and forming the recessed portion  711  of the second adapter  7  so as to have a polygonal inner wall surface that receives the second coupling portion  62 . 
     4.3 
     Also, in the above embodiment, the second adapter  7  is configured so as to be able to be inserted in any rotation position relative to the hosel portion  5 . However, the second adapter  7  need not be limited to this shape, and a rotation position that allows the second adapter  7  to be inserted into the interior space of the hosel portion  5  may be specified. 
     In this case, for example, as illustrated in  FIG. 12 , the flange portion  72  of the second adapter  7  may be configured with an outer peripheral surface formed in a polygonal shape (a quadrangular shape in the figure). The third diameter portion  503  of the hosel portion  5  receiving the flange portion  72  may be configured with a polygonal inner wall surface so as to engage with the flange portion  72  of the second adapter  7 . At this time, the polygonal outer peripheral surface of the flange portion  72  engages with the polygonal inner wall surface of the third diameter portion  503 , and therefore the second adapter  7  and the hosel portion  5  are coupled so as to be incapable of axial rotation. Here, the second adapter  7  and the hosel portion  5  can be coupled in different rotation positions according to the shape of the flange portion  72 . In the present embodiment, the flange portion  72  and the third diameter portion  503  are formed with a quadrangular column shape, and therefore the second adapter  7  can be inserted in the interior space of the hosel portion  5  in four types of rotation positions. 
     Configuring the second adapter  7  so as to be incapable of axial rotation relative to the hosel portion  5  in this way specifies the rotation positions in which the second adapter  7  can be fitted into the hosel portion  5 . Accordingly, the types of rotation positions for the second adapter  7  that can be selected by the user are fixed, thus making it easier for the user to select a rotation position for the second adapter  7 . Note that a configuration is possible in which the second adapter  7  is configured to be coupled to the first adapter  6  so as to be incapable of axial rotation as in the above variation, and also configured so as to be incapable of axial rotation relative to the hosel portion  5  as in the present variation. 
     Also, in the case of forming the second adapter  7  so as to be incapable of axial rotation relative to the hosel portion  5 , the second adapter  7  may be formed in a polygonal column shape (a quadrangular column shape in the figures) as illustrated in  FIGS. 13A and 13B . Specifically, rather than forming the second adapter  7  so as to have portions with different outer diameters, the second adapter  7  may be formed such that the outer diameter is constant. With the exception of the constant outer diameter being constant, this second adapter  7  is the same as the second adapter  7  described in the above embodiment and variations. In this variation, rather than providing the flange portion  72  (second coupling portion) separately, the entirety of the outer peripheral surface of the second adapter  7  is formed with a rectangular shape, and this outer peripheral surface corresponds to a second coupling portion of the second adapter in the present invention. 
     In this case, the interior space of the hosel portion  5  may be formed by an inner wall surface  504  that is rectangular and has a constant diameter, as illustrated in  FIG. 13C . It should be noted that a flange portion  505  that extends radially inward may be provided on the inner wall surface  504  in order to prevent the first adapter  6  and the second adapter  7  from coming out of the interior space. Here, the upper end surface of the second adapter  7  and the step between the body portion  61  and the second coupling portion  62  of the first adapter  6  engage with the flange portion  505 , thus fixing the first adapter  6  and the second adapter  7  so as to not come out of the interior space. In other words, the inner wall surface  504  and the flange portion  505  correspond to the hosel second coupling portion of the present invention. Note that the second adapter  7  may be formed with a circular column shape rather than a polygonal column shape. 
     4.4 
     Also, although the second coupling portion  62  of the first adapter  6  is formed as a cylindrical protruding portion, and a recessed portion  711  for reception thereof is formed in the second adapter  7  in the above embodiment, the coupling structure for the two adapters is not limited to this. For example, it is possible to form a tube-shaped protruding portion on the upper end portion of the second adapter  7 , and form a recessed portion for receiving the protruding portion on the lower end portion of the first adapter  6 . 
     4.5 
     In the above embodiment, the shaft  20  is inclined at an angle of 1 degree relative to the first adapter  6 , and the first adapter  6  is inclined at an angle of 1 degree relative to the second adapter  7 , but there are no particular limitations on these angles. Also, the two angles may be different. 
     4.6 
     The lower opening  313  in communication with the interior space is exposed via the recessed portion  31  formed in the surface of the golf club head  10  in the above embodiment, and a cap for blocking the recessed portion  31  may be provided. For example, as illustrated in  FIGS. 14A and 14B , a cap  85  is formed by a side wall surface  851  that extends along the side surface  311  of the recessed portion  31 , an outer wall surface  852  that extends along the outer peripheral surface of the golf club head  10 , and an end surface  853  that opposes the base surface  312  of the recessed portion  31 . The length of the side wall surface  851  in the axial direction is shorter than that of the side surface  311  of the recessed portion  31 , and thus a gap is formed between the base surface  312  of the recessed portion  31  and the end surface  853 . Also, a through-hole  854  that extends in the axial direction is formed between the outer wall surface  852  and the end surface  853 , and a tool such as a wrench can be inserted through this through-hole  54  from outside the cap  85 . It is then possible to engage the tool with the head portion  91  of the fastener  9  and detach the fastener  9  while the cap  85  is closed. According to this configuration, the recessed portion  31  is blocked by the cap  85 , thus making it possible to improve the designability of the head  10  and prevent loss of the fastener  9  when it is detached. Note that since a gap exists between the cap  85  and the base surface  312 , the rotation position of the second adapter  7  can be changed by inserting a finger through the gap, for example. Accordingly, even if the cap  85  is attached, the rotation position of the second adapter  7  can be checked through not only the gap, but also through the window  55  formed in the surface of the head  10 . 
     4.7 
     There are no particular limitations on the shape of the window  55 , and as long as a cutout is formed in the inner wall surface of the interior space in the hosel portion  5 , and the outer peripheral surface of the second adapter  7  can be checked, there are no particular limitations on the width, the axial length, the shape, and the like of the window. Also, the recessed portion  31  and the window  55  are not necessarily required to be in communication, and it is possible for them to be separated. In other words, the window  55  may be formed separately from the recessed portion  31  and the lower opening  313 , and may be formed as an independent window in the surface of the head  10 . Also, the window  55  can be made even larger so as to expose not only the second adapter  7  but also the position of coupling with the first adapter  6  to the outside. If a rotation position indicator is provided in the vicinity of the position at which the first adapter  6  is coupled to the second adapter  7 , it is possible to observe the relationship between the rotation positions of the two adapters  6  and  7 . Note that the window  55  is not necessarily required to be provided, and it is sufficient that the lower opening  313  capable of receiving at least the second adapter  7  is formed on the side of the head opposite to the attachment hole  51 . 
     4.8 
     Although a portion of the head  10  forms the interior space in the hosel portion  5  in the above embodiment, the hosel portion  5  may be constituted by attaching a tube-shaped neck member  50  to the golf club head  10  as shown in  FIG. 15 , for example. For example, an attachment through-hole  21  that extends substantially parallel to the axial direction of the shaft is formed at a position in the golf club head  10  where the hosel portion  5  is to be formed (a position on the heel side of the crown portion  2 ). This attachment through-hole  21  extends toward the sole portion  3  side. Also, the above-described recessed portion  31  is formed in a portion of the sole portion  3  on the side opposite to the hosel portion  5 . 
     The neck member  50  is fixed in the thus-formed attachment through-hole  21  as illustrated in  FIGS. 16A and 16B . Similarly to the hosel portion  5  of the above embodiment, the neck member  50  is constituted by a first diameter portion  501 , a second diameter portion  502 , and a third diameter portion  503 . Also, a flange portion  506  is formed on the outer peripheral surface of the first diameter portion  501  and the second diameter portion  502 , and engages with the peripheral edge of the opening of the attachment through-hole  21  on the crown portion  2  side. The portion of the neck member  50  below the flange portion  506  is then inserted into the attachment through-hole  21 , and the neck member  50  is fixed such that the opening on the lower end portion side of the third diameter portion  503  coincides with the lower opening  313 . In this way, the interior space of the hosel portion  5  is formed by the neck member  50 , and the opening of the first diameter portion  501  on the upper end portion side constitutes the attachment hole  51  of the hosel portion  5 . 
     4.9 
     In the above embodiment, the outer peripheral surface of the first adapter  6  is formed to be parallel with the first axis X 1 , and the shaft receiving recessed portion  611  is formed along the second axis X 2  that intersects the first axis X 1 . However, the first adapter  6  is not limited to this shape, and may be formed as illustrated in  FIG. 17 , for example. As illustrated in this figure, in this example, the body portion  61  of the first adapter  6  is formed to be inclined relative to the second coupling portion  62 . Specifically, in this example, the second coupling portion  62  is formed along the first axis X 1 , and the outer peripheral surface of the body portion  61  is formed along the second axis X 2 . Also, the shaft receiving recessed portion  611  formed in the body portion  61  is also formed so as to extend along the second axis X 2 . Even when the first adapter  6  is configured in this way, the axial center S of the shaft  20  follows the second axis X 2 , and therefore the shaft  20  can be fixed at an inclination relative to the first adapter  6 . Note that in order for the entirety of the flange portion  612  to come into contact with the attachment hole  51  of the hosel portion  5 , the flange portion  612  is formed so as to be inclined relative to the body portion  61 . 
     4.10 
     Also, although the position indication portion  65  of the first adapter  6  and the position indication portion  722  of the second adapter  7  indicate the rotation positions with lines in the above embodiment, they may indicate the rotation positions with something else, such as figures or numbers. Also, the position indication portion  65  of the first adapter  6  and the position indication portion  722  of the second adapter  7  may indicate the rotation positions with a method such as providing protruding portions by processing (e.g., cutting out (see  FIG. 18 )) portions of the first adapter  6  and the second adapter  7 .  FIG. 18  shows an example in which cutouts are used as the position indication portion  722 . Note that there are no particular distinctions between the position indication portion  65  and the reference indicator  52 , and there are no particular limitations on them as long as rotation position alignment can be performed. In other words, it is sufficient that some sort of indicator is provided, and it is possible to provide the reference indicator on the first adapter  6  and provide the position indication portion on the second adapter  7 . 
     4.11 
     Also, in the above embodiment, the depressions in the first diameter portion  501  of the hosel portion  5  and the protrusion portions on the first coupling portion  613  of the first adapter  6  are formed with rectangular shapes. However, the depressions in the first diameter portion  501  and the protrusion portions on the first coupling portion  613  are not limited to this shape, and may be formed as illustrated in  FIGS. 19A to 19C , for example. In the example illustrated in  FIGS. 19A to 19C , the inner peripheral surface of the depressions in the first diameter portion  501  and the outer peripheral surface of the protrusion portions on the first coupling portion  613  are formed so as to be spherical on the contact surface in the direction perpendicular to the axis and protrude in the direction perpendicular to the axis. Accordingly, it is possible to improve the force of adhesion between the hosel  5  and the first adapter  6 . 
     Note that as illustrated in  FIGS. 19A and 19C , the spherical contact surfaces of the depressions in the first diameter portion  501  and the protrusion portions on the first coupling portion  613  do not need to be continuous with the contact surfaces of the second diameter portion  502  and the body portion  61 . In this case, the depressions in the first diameter portion  501  and the protrusion portions on the first coupling portion  613  are formed such that a step is provided in the connection portion between the first diameter portion  501  and the second diameter portion  502 . Also, as illustrated in  FIGS. 20A and 20B , the spherical contact surfaces of the depressions in the first diameter portion  501  and the protrusion portions on the first coupling portion  613  may be continuous with the contact surfaces of the second diameter portion  502  and the body portion  61 . In this case, the depressions in the first diameter portion  501  and the protrusion portions on the first coupling portion  613  are formed such that the first diameter portion  501  and the second diameter portion  502  are continuous, without the formation of a step. 
     4.12 
     Note that since the golf club head configured as described above is a hollow structure, it can be manufactured by joining two or more members together. Specifically, it can be manufactured by joining together a head body provided with one or two or more openings in communication with a hollow portion, and a separate member that blocks these openings. For example, it is possible to constitute the head by constituting only the crown portion  2  and the face portion  1  as separate members and combining them with the head body, or forming the head body such that an opening is provided in the sole portion  3  and the side portion  4  and blocking this opening with a separate member. Also, this head body can be manufactured by casting using a known lost-wax precision casting method, for example.