Golf Club Head

Abstract

[Object] To provide a golf club head having various performances improved by a disposal of a rib. [Solution] A head 2 includes a face 4, a crown 6 and a sole 8. A rib rb is formed on an inner surface of the sole 8. The rib rb has a sloped extension part ks1 extending to be closer to a face side as approaching from a heel side to a toe side. A center of gravity of the head is positioned on the heel side relative to a face center. The head 2 is hollow. Preferably, the sole 8 has a minimum-thickness region. Preferably, the rib rb has a thin reinforcing part rb2 positioned in the minimum-thickness region. The rib rb may extend linearly. The rib rb may extend curvedly. Preferably, a slope angle of the rib rb relative to a toe-heel direction is equal to or greater than 10.degree. and equal to or less than 45.degree..

Description

TECHNICAL FIELD

[0001] The present invention relates to a hollow golf club head.

BACKGROUND ART

[0002] A hollow golf club head has been known. The hollow structure increases a head volume and a moment of inertia. For example, wood type golf club heads are usually hollow.

[0003] The volume of a hollow part is increased and the thickness of the head is thinned with the increase in size of the head.

[0004] A hollow golf club head having a rib provided on a sole has been proposed. Japanese Patent Application Laid-Open No. 2009-195699 discloses a golf club head in which a dynamic-excitation response can be improved. In the head, a stiffening element is provided on a sole thereof. FIGS. 2, 2A, 2B and 2C of Japanese Patent Application Laid-Open No. 2009-195699 show disposals of the stiffening element. [0005] Patent Literature 1: JP-A-2009-195699

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

[0006] Flight distance and directional stability of a hit ball are required for heads. A head in which flight distance is less likely to decrease even when a hitting point is off a sweet spot is preferable. A good hitting sound is also required particularly in hollow heads. Such demand for performances has been more and more increased.

[0007] It is an object of the present invention to provide a hollow golf club head having performances improved by a disposal of a rib.

Solution to the Problems

[0008] A golf club head according to the present invention includes a face, a crown and a sole. A rib is formed on an inner surface of the sole. The rib has a sloped extension part extending to be closer to a face side as approaching from a heel side to a toe side. A center of gravity of the head is positioned on the heel side relative to a face center. The head is hollow.

[0009] Preferably, the sole has a minimum-thickness region. Preferably, the rib has a thin reinforcing part positioned in the minimum-thickness region.

[0010] Preferably, a first recess part is formed on an outer surface of the sole. Preferably, a recess part for a weight is formed inside the first recess part. Preferably, a weight member can be attached to the recess part for a weight. Preferably, the rib includes a recess-part-reverse-side rib part positioned at the reverse side of the first recess part on an inner surface of the sole.

[0011] Preferably, a second recess part is formed on the outer surface of the sole. Preferably, the second recess part forms a protruding extension part on the inner surface side of the sole. Preferably, the protruding extension part extends along the rib.

[0012] Preferably, the first recess part is continuous to the second recess part.

[0013] Preferably, the head further includes a side part. Preferably, a toe side end part of the rib does not extend up to the side part. Preferably, a heel side end part of the rib extends up to the side part.

[0014] Preferably, in a plan view, the rib extends linearly. Preferably, a slope angle of the rib relative to a toe-heel direction is equal to or greater than 10.degree. and equal to or less than 45.degree..

[0015] The rib may extend curvedly so as to project toward the face side.

[0016] The rib may extend curvedly so as to project toward a back side.

Advantageous Effects of the Invention

[0017] It is possible to obtain a hollow golf club head excellent in performances because of a rib provided on a sole.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 is a perspective view of a head according to a first embodiment of the present invention.

[0019] FIG. 2 is a plan view of the head of FIG. 1.

[0020] FIG. 3 is a bottom view of the head of FIG. 1.

[0021] FIG. 4 is a perspective view of a head body in the head of FIG. 1.

[0022] FIG. 5 is a bottom view of the head of FIG. 1.

[0023] FIG. 5 shows a thickness distribution of a sole.

[0024] FIG. 6 is a plan view of a head according to a second embodiment.

[0025] FIG. 7 is a bottom view of a head according to a third embodiment.

[0026] FIG. 8 is a bottom view of a head according to a fourth embodiment.

[0027] FIG. 9 is a bottom view of a head according to a fifth embodiment.

[0028] FIG. 10 is a cross-sectional view of a rib.

DESCRIPTION OF EMBODIMENTS

[0029] Hereinafter, the present invention will be described in detail according to the preferred embodiments with appropriate references to the accompanying drawings.

[0030] FIG. 1 is a perspective view of a golf club head 2 according to a first embodiment of the present invention. FIG. 2 is a plan view of the head 2. FIG. 3 is a bottom view of the head 2.

[0031] The head 2 has a face 4, a crown 6, a sole 8, a side part 10 and a hosel 12. The face 4 has a face surface fs. The face surface fs is a ball hitting face. The crown 6 extends toward the back of the head from the upper edge of the face 4. The sole 8 extends toward the back of the head from the lower edge of the face 4. The side part 10 extends between the crown 6 and the sole 8. The side part 10 extends to a heel side from a toe side via a back side in the head 2. As shown in FIG. 4 to be described later, the head 2 is hollow. The head 2 is a so-called wood type golf club head.

[0032] The side part 10 may not be present. When the sole 8 and the crown 6 are continuous with a smooth curved surface, the side part 10 is not present. In this case, the curved surface extending to the crown 6 is the sole 8. In the embodiment, a ridge line rs1 showing a boundary between the sole 8 and the side part 10 is present (See FIG. 3).

[0033] The head 2 has a two-piece structure. The head 2 is constituted by joining a face member Fp1 and a head body Hp1. A joining method is welding. Although not shown in the drawings, the face member Fp1 is also referred to as a cup face. A boundary k1 between the face member Fp1 and the head body Hp1 is shown by a two-dot chain line in FIG. 1. Welding is performed at the boundary k1. The boundary k1 is not visually recognized in a completed head 2 after coating.

[0034] The face member Fp1 constitutes the whole face 4. Furthermore, the face member Fp1 constitutes a part of the crown 6, a part of the sole 8 and a part of the side part 10.

[0035] FIG. 4 is a perspective view of the head body Hp1. The head body Hp1 has an opening a1. In the head 2, the opening a1 is blocked with the face member Fp1.

[0036] As shown in FIG. 4, the head body Hp1 constitutes a part of the crown 6, a part of the sole 8, a part of the side part 10, and the whole hosel 12. Most parts of the crown 6, the sole 8 and the side part 10 are constituted with the head body Hp1.

[0037] The hosel 12 has a shaft hole 14 to which a shaft is mounted. The shaft, not shown in the drawings, is inserted into the shaft hole 14. Although not shown in the drawings, the shaft hole 14 has a center axial line Z1. The center axial line Z1 conforms to a shaft axial line of a golf club having the head 2.

[0038] As shown in FIG. 4, a rib rb is formed on an inner surface of the sole 8. The rib rb is formed on the head body Hp1. The head body Hp1 is manufactured by casting. The rib rb is integrally formed with the head body Hp1. The casting is a lost-wax process. The head body Hp1 having a complicated shape including the rib rb can be integrally formed by casting. The face member Fp1 is manufactured by forging. The rib rb may be welded to a separately formed sole body.

[0039] As shown in FIGS. 2 and 3, the rib rb is linear in the plan view.

[0040] As shown in FIG. 3, the rib rb reaches to the side part 10 of the toe side. The rib rb reaches to the side part 10 of the heel side.

[0041] In the present application, a reference vertical plane, a face-back direction and a toe-heel direction are defined. A reference state denotes a state that the center axial line Z1 is contained in a plane P1 perpendicular to a horizontal plane H and the head 2 is placed on the horizontal plane H at a prescribed lie angle and real loft angle. The reference vertical plane denotes the plane P1. The prescribed lie angle and real loft angle are appeared, for example, in a product catalog.

[0042] In the present application, the toe-heel direction is a direction of an intersection line between the reference vertical plane and the horizontal plane H.

[0043] In the present application, the face-back direction is a direction perpendicular to the toe-heel direction and parallel to the horizontal plane H.

[0044] In the present application, a face center is defined. A maximum width Wx of the face surface in the toe-heel direction is determined. Furthermore, a middle position Px of the maximum width Wx in the toe-heel direction is determined. At the position Px, a middle point Py of the face surface in an up-down direction is determined. The point Py is defined as the face center.

[0045] As shown in FIGS. 2 and 3, the rib rb has a sloped extension part ks1 extending to be closer to a face 4 side as approaching from the heel side to the toe side. In the embodiment, the entire rib rb is the sloped extension part ks1. That is, the rib rb extends to be closer to the face 4 side as approaching from the heel side to the toe side.

[0046] [Rib Sloping Effect]

[0047] A toe side end part of the rib rb can be positioned at a vicinity of the face 4 due to the sloped extension part ks1. When a ball is hit at the toe side of the face 4, the rib rb suppresses a deformation in the toe side of the sole 8. Therefore, a deformation in the toe side of the face 4 is also suppressed (toe-deformation suppressing effect). For this reason, directivity of a ball hit at the toe side of the face 4 can be improved. Due to the sloped extension part ks1, the rib rb can extend to a vicinity of the face 4 on the toe side and to a center part of the sole 8. The center part of the sole 8 is likely to be an antinode of sole vibration. By the presence of the rib rb at a portion likely to be the antinode, the vibration of the sole 8 can be effectively suppressed (antinode-vibration suppressing effect). For this reason, high-pitched hitting sound is likely to be obtained. Thus, both the toe-deformation suppressing effect and the antinode-vibration suppressing effect can be effectively achieved by the sloped extension part ks1. This is the rib sloping effect. In the embodiment, since the entire rib rb is the sloped extension part ks1, the rib sloping effect is further enhanced.

[0048] As shown in FIG. 3, a first recess part r1 is formed on an outer surface of the sole 8. In the plan view of FIG. 3, the first recess part r1 has a substantially triangle shape. As shown FIG. 4, a first protruding part p1 corresponding to the first recess part r1 is formed on the inner surface of the sole 8.

[0049] A recess part rw1 for a weight is formed inside the first recess part r1. The recess part rw1 for a weight is formed on a bottom surface of the first recess part r1. A weight fixing part fx1 is provided on the recess part rw1 for a weight. In the embodiment, a screw hole is formed on an inner surface of the weight fixing part fx1. A male screw of a weight, not shown in the drawings, is fastened to the screw hole. The weight, not shown in the drawings, is detachably fixed to the recess part rw1 for a weight.

[0050] As shown in FIG. 4, a protruding part pw1 for a weight corresponding to the recess part rw1 for a weight is formed on the inner surface of the sole 8.

[0051] Since a weight is disposed inside the first recess part r1, mass is concentrated. Due to this concentrated mass, the first recess part r1 is likely to vibrate. Hereinafter, this vibration is also referred to as a sole vibration Vm. A recess-part-reverse-side rib part rb1 to be described later has an effect of effectively suppressing the sole vibration Vm. Therefore, it is possible to make a hitting sound higher-pitched.

[0052] The first recess part r1 is provided on the heel side relative to the face center. The recess part rw1 for a weight is provided on the heel side relative to the face center.

[0053] In the head 2 increased in size, the sole 8 is made thin, and a thickness thereof is usually set to equal to or less than 3 mm. Therefore, in the thinned sole 8, forming a recess part on the outer surface involves forming a protruding part on the inner surface. Because of the circumstances, usually, when a recess part is formed on the outer surface of the sole 8, a corresponding protruding part is formed on the inner surface of the sole 8. In this case, the weight of the recess part is larger as compared with a case where the recess part is replaced with a flat part. This is because the weight of the side surfaces of the recess part is added by forming the recess part. Weight distribution to the heel side of the sole 8 is increased by recess parts, such as the recess part rw1 for a weight and the first recess part r1. Furthermore, a weight is mounted to the recess part rw1 for a weight. The weight contributes to locating the center of gravity of the head on the heel side.

[0054] The center of gravity of the head 2 is positioned on the heel side relative to the face center. Therefore, a distance of the center of gravity is short. The distance of a center of gravity denotes a distance between the shaft axial line and the center of gravity of the head. For this reason, the head is likely to be turned at impact and the ball is likely to be caught. In other words, the opening of the face at impact is suppressed, and the hit ball is less likely to be a slice. Therefore, the force of the hit ball is likely to be strong.

[0055] As shown in FIG. 4, the rib rb includes the recess-part-reverse-side rib part rb1 positioned at the reverse side of the first recess part r1 on the inner surface of the sole. In the embodiment, the recess-part-reverse-side rib part rb1 is provided on the first protruding part p1. It is sufficient that the recess-part-reverse-side rib part rb1 is position at the reverse side of the first recess part r1. The recess-part-reverse-side rib part rb1 may not be positioned on the first protruding part p1.

[0056] The recess-part-reverse-side rib part rb1 is not positioned at the reverse side of the recess part rw1 for a weight on the inner surface of the sole. The recess-part-reverse-side rib part rb1 is positioned on the face side relative to the reverse side of the recess part rw1 for a weight on the inner surface of the sole. The recess-part-reverse-side rib part rb1 is not positioned on the protruding part pw1 for a weight. The recess-part-reverse-side rib part rb1 is positioned on the face side relative to the protruding part pw1 for a weight.

[0057] It is necessary that a weight is securely fixed to the weight fixing part fx1. Particularly high dimensional accuracy is required for the weight fixing part fx1. The rib rb can affect forming accuracy of the protruding part pw1 for a weight. For example, when the rib rb is integrally formed with the sole 8 by casting, the existence of the rib rb having a protruding shape may cause shrinkage during the casting, and/or affect molten metal flow. When the rib rb is separately welded to a sole body, the weight fixing part fx1 can be deformed by heat during the welding. Since the rib rb is not positioned on the protruding part pw1 for a weight, the dimensional accuracy of the weight fixing part fx1 is likely to be improved.

[0058] As shown in FIG. 3, a second recess part r2 is formed on the outer surface of the sole 8. The second recess part r2 in the embodiment has a shape of elongated triangle in the plan view of FIG. 3. The second recess part r2 extends to be closer to the face 4 side as approaching from the heel side to the toe side. As shown in FIG. 3, the width of the second recess part r2 in the plan view becomes narrower as approaching from the heel side to the toe side.

[0059] As shown in FIG. 4, a protruding extension part p2 is formed at the reverse side of the second recess part r2 on the inner surface of the sole. The protruding extension part p2 is formed corresponding to the second recess part r2. The shape of the protruding extension part p2 in the plan view is similar to the shape of the second recess part r2, although this is difficult to recognize in FIG. 4.

[0060] The rigidity of the sole 8 is enhanced by the second recess part r2 (the protruding extension part p2). The effect of suppressing the vibration of the sole 8 can be exhibited by the second recess part r2. A high-pitched hitting sound is likely to be obtained by the second recess part r2.

[0061] In the embodiment, the rib rb is not provided on the protruding extension part p2. The rib rb may be provided on the protruding extension part p2.

[0062] The protruding extension part p2 is positioned on the backside of the rib rb. The protruding extension part p2 may be positioned on the face side of the rib rb.

[0063] [Rib Substitution Effect]

[0064] The protruding extension part p2 extends along the rib rb. The rigidity of the sole 8 is enhanced by the protruding extension part p2 extending along the rib rb. The protruding extension part p2 extends along the rib rb, and thereby can exhibit a sole-rigidity improving effect (rib substitution effect) as in the rib rb. The rigidity of the sole 8 can be enhanced by the rigidity improving effect exhibited by the protruding extension part p2, even when the rib rb is lowered. Therefore, it is possible to lower the center of gravity of the head (low-center-of-gravity effect). In this respect, the height of the protruding extension part p2 is preferably lower than the height of the rib rb.

[0065] The protruding extension part p2 extends along the rib rb. That is, the protruding extension part p2 extends so as to slope along the rib rb. Therefore, the rib sloping effect discussed above can be further enhanced by the protruding extension part p2.

[0066] A center line L2 in the width direction of the protruding extension part p2 is shown by a one-dot chain line in FIG. 3. In respect of enhancing the rib substitution effect, a distance Dr in the face-back direction between the center line L2 in the width direction and the rib rb is preferably equal to or greater than 0 mm and preferably equal to or less than 10 mm at any position in the toe-heel direction. The distance Dr is indicated in the enlarged part of FIG. 3. As discussed above, the rib rb may be formed on the protruding extension part p2. In this case, the distance Dr is 0 mm.

[0067] When the protruding extension part p2 has an excessively large width, the rib substitution effect can be deteriorated. In respect of enhancing the rib substitution effect, the width in the face-back direction of the protruding extension part p2 is preferably equal to or less than 15 mm, and more preferably equal to or less than 12 mm. When the protruding extension part p2 has a too small width, the rib substitution effect can also be deteriorated. In respect of enhancing the rib substitution effect, the width in the face-back direction of the protruding extension part p2 is set to be greater than 0 mm, preferably equal to or greater than 3 mm, and more preferably equal to or greater than 6 mm.

[0068] FIG. 5 shows a thickness distribution of the sole 8. A plurality of regions of the sole 8 are shown by using different kinds of hatching and existence or nonexistence of hatching. In the embodiment, the thickness of each region is as follows. [0069] Region A: greater than 0.7 mm and equal to or less than 2 mm [0070] Region B: greater than 0.7 mm and equal to or less than 3.1 mm [0071] Region J: equal to or greater than 0.60 mm and equal to or less than 0.70 mm

[0072] In the sole 8, a region in which hatching is not shown in FIG. 5 is a region J. The region J is a minimum-thickness region of the sole 8.

[0073] A minimum value of the thickness of the sole 8 is defined as Tmin. In the present application, the minimum-thickness region denotes a region having a thickness of equal to or less than [Tmin+0.1 mm]. The entire region J is the minimum-thickness region.

[0074] In respect of enlargement of a head volume, the minimum thickness Tmin is preferably equal to or less than 0.8 mm, more preferably equal to or less than 0.75 mm, still more preferably equal to or less than 0.7 mm, and yet still more preferably equal to or less than 0.65 mm. In respect of strength, the minimum thickness Tmin is equal to or greater than 0.4 mm, more preferably equal to or greater than 0.45 mm, and still more preferably equal to or greater than 0.5 mm.

[0075] The minimum-thickness region J contributes to weight saving and enlargement of a head. The minimum-thickness region J increases the flexure of the sole 8, and thereby can contribute to rebound performance.

[0076] A distance in the face-back direction between a forefront point Pf of the head 2 and a center minimum region Jc is shown by a double-pointed arrow J1 in FIG. 5. In respect of enhancing strength against the impact of hitting a ball, the distance J1 is preferably equal to or greater than 20 mm, and more preferably equal to or greater than 30 mm. In respect of securing the area of the region J, the distance J1 is preferably equal to or less than 50 mm, and more preferably equal to less than 40 mm. The center minimum region Jc is a portion positioned in a center area Rx of the minimum-thickness region J.

[0077] A distance in the face-back direction between a backmost point Pb of the head 2 and the center minimum region Jc is shown by a double-pointed arrow J2 in FIG. 5. In respect of strength, the distance J2 is preferably equal to or greater than 20 mm, and more preferably equal to or greater than 30 mm. Rebound performance can be improved by increase of the center minimum region Jc. In respect of rebound performance, the distance J2 is preferably equal to or less than 50 mm, and more preferably equal to or less than 40 mm.

[0078] A region A having a greater sole thickness than that of the minimum-thickness region J is present on the face side of the minimum-thickness region J. Head strength can be enhanced by the region A while allowing the minimum-thickness region J to exist.

[0079] A region B having a greater sole thickness than that of the minimum-thickness region J is present on the back side of the minimum-thickness region J. A depth of the center of gravity is deepened by the region B.

[0080] Thus, a region having a greater sole thickness than that of the minimum-thickness region J is present on the face side and the back side of the minimum-thickness region J. For this reason, a moment of inertia in the up-down direction of the head is improved.

[0081] As shown in FIG. 5, the rib rb has a thin reinforcing part rb2 positioned in the minimum-thickness region J. The minimum-thickness region J is thin and has a low rigidity. Therefore, the minimum-thickness region J is likely to be an antinode of vibration. The antinode-vibration suppressing effect discussed above is further enhanced by the thin reinforcing part rb2. Therefore, hitting sound is likely to be high-pitched.

[0082] A center area in the toe-heel direction is shown by a double-pointed arrow Rx in FIG. 5. The center area Rx is an area having a width of 40 mm in the toe-heel direction. The center area Rx is an area between a position t20 having a distance of 20 mm from the face center toward the toe side and the position h20 having a distance of 20 mm from the face center toward the heel side.

[0083] The rib rb crosses the center region Rx. The rib rb extends from a position on the toe side relative to the center area Rx to a position on the heel side relative to the center area Rx.

[0084] The first recess part r1 is positioned on the heel side relative to the center area Rx. The first protruding part p1 is positioned on the heel side relative to the center area Rx.

[0085] The minimum-thickness region J has the center minimum region Jc positioned in the center area Rx. There is high possibility that the ball is hit at the vicinity of the face center. The center minimum region Jc is likely to be bent by the hit. The center minimum region Jc can improve rebound performance in a hit at the vicinity of the face center.

[0086] As shown in FIG. 5, the thin reinforcing part rb2 has a center reinforcing part rb3 positioned in the center minimum region Jc. As understood from the position of the second recess part r2 in FIG. 5, the protruding extension part p2 is present on the center minimum region Jc.

[0087] The center minimum region Js is positioned on a center part of the sole 8 and is thin, thereby being likely to be an antinode of the sole 8. The antinode-vibration suppressing effect discussed above is still further enhanced by the center reinforcing part rb3. Therefore, hitting sound is further likely to be high-pitched. The protruding extension part p2 enhances the rigidity of the center minimum region Jc, and thereby can achieve a high-pitched hitting sound.

[0088] As shown in FIG. 5, the region A having a thickness greater than that of the center minimum region Jc is positioned forward of the center minimum region Jc. The minimum-thickness region J is present on the toe side of the region A. The minimum-thickness region J on the toe side of the region A is a toe thin region Jt. The minimum-thickness region J has the toe thin region Jt. The rib rb has a portion rb4 positioned in the toe thin region Jt. The toe thin region Jt is positioned close to the face 4 and is thin, thereby being likely to be deformed. The portion rb4 still further enhances the toe-deformation suppressing effect.

[0089] As shown in FIG. 3, the first recess part r1 is continuous to the second recess part r2. In other words, the first recess part r1 is connected to the second recess part r2. As already discussed, the first recess part r1 is likely to vibrate due to the existence of a weight. The vibration of the first recess part r1 is suppressed by the second recess part r2 (protruding extension part p2) which is continuous to the first recess part r1. Therefore, the effect of suppressing the sole vibration Vm is further enhanced.

[0090] As shown in FIG. 2, the rib rb extends linearly in the plan view. FIG. 6 shows a head 20 of the second embodiment, which is another example of the rib rb extending linearly. In the present application, the rib rb shown in FIG. 6 is also considered as linear. The "linear" means that a deviation range Wz of the rib rb with respect to a straight line Lz connecting the both ends of the rib rb is equal to or less than 10 mm. In respect of taking advantage of being linear, the deviation width Wz is preferably equal to or less than 5 mm. The deviation width Wz is measured along a perpendicular direction with respect to the straight line Lz.

[0091] A slope angle of the rib rb relative to the toe-heel direction is shown by a double-pointed arrow .theta.1 in FIGS. 2 and 6. As shown in FIG. 2, the angle .theta.1 is measured in the plan view. In respect of enhancing the rib sloping effect discussed above, the angle .theta.1 is preferably equal to or greater than 10.degree., more preferably equal to or greater than 15.degree., and still more preferably equal to or greater than 20.degree.. When the angle .theta.1 is excessive, a middle part of the rib may be too far from the face 4, which may reduce the effect of suppressing vibration in hitting a ball. In this respect, the angle .theta.1 is preferably equal to or less than 45.degree., more preferably equal to or less than 40.degree., and still more preferably equal to or less than 35.degree.. In case of a rib rb extending linearly, the angle .theta.1 is an angle between the straight line Lz and the toe-heel direction.

[0092] FIG. 7 is a bottom view showing a head 30 of the third embodiment. The head 30 is the same as the head 2 except the disposal of the rib rb. The rib rb is non-linear. In the head 30, the rib rb extends curvedly so as to project toward the face 4 side. Thus, a portion positioned on the toe side and at the vicinity of the face is increased. Therefore, the toe-deformation suppressing effect discussed above is enhanced. In the head 30, the toe-deformation suppressing effect is enhanced while the rib sloping effect is exhibited.

[0093] FIG. 8 shows a bottom view showing a head 40 of the fourth embodiment. The head 40 is the same as the head 2 except the disposal of the rib rb. The rib rb is non-linear. In the head 40, the rib rb extends curvedly so as to project toward the back side. Thus, rib rb positioned on a portion which is likely to be an antinode is increased. Therefore, the antinode-vibration suppressing effect discussed above is enhanced. In the head 40, the antinode-vibration suppressing effect is enhanced while the rib sloping effect is exhibited. In this case, rebound performance by the deformation of the toe part is enhanced, although the toe-deformation suppressing effect is reduced. Therefore, rebound performance in hitting at the toe side of the face can be improved.

[0094] FIG. 9 is a bottom view showing a head 50 of the fifth embodiment. The head 50 is the same as the head 2 except the disposal of the rib rb. A toe side end part of the rib rb does not extend up to the side part 10. A heel side end part of the rib rb extends up to the side part 10. That is, in contrast to the head 2, in the head 50, the rib rb does not disposed on the side part 10 of the toe side. The disposal of the rib rb enables the center of gravity of the head to be closer to the heel side.

[0095] FIG. 10 is a cross-sectional view of the rib rb. In light of making a hitting sound high-pitched, the average value of rib height HR is preferably equal to or greater than 2 mm, more preferably equal to or greater than 2.5 mm, and still more preferably equal to or greater than 3 mm. In light of saving a rib weight, the average value of the rib height HR is preferably equal to or less than 6 mm, and more preferably equal to or less than 5 mm.

[0096] In light of making a hitting sound high-pitched, the maximum value of the rib height HR is preferably equal to or greater than 3 mm, more preferably equal to or greater than 3.5 mm, and still more preferably equal to or greater than 4 mm. In light of saving a rib weight, the maximum value of the rib height HR is preferably equal to less than 10 mm, more preferably equal to or less than 9 mm, and still more preferably equal to or less than 8 mm.

[0097] A width of the rib is shown by a double-pointed arrow BR in FIG. 10. In light of making a hitting sound high-pitched, the average value of the rib width BR is preferably equal to or greater than 0.5 mm, more preferably equal to or greater than 0.7 mm, and still more preferably equal to or greater than 0.9 mm. In light of saving a rib weight, the average value of the rib width BR is preferably equal to or less than 1.5 mm, more preferably equal to or less than 1.3 mm, and still more preferably equal to or less than 1.1 mm. A length of a portion which has a rib width BR of equal to or greater than 0.5 mm and equal to or less than 1.5 mm is preferably equal to or greater than 50% of the total length of the rib, more preferably equal to or greater than 80%, and particularly preferably 100%.

[0098] A head volume is not restricted. In light of increase in moment of inertia and enlargement of sweet area, the head volume is preferably equal to or greater than 400 cc, more preferably equal to or greater than 420 cc, and still more preferably equal to or greater than 440 cc. In light of compliance with regulations regarding golf clubs, the head volume is preferably equal to or less than 470 cc, and in view of a measurement error of 10 cc, particularly preferably 460 cc.

[0099] A head weight Wh is not restricted. In light of swing balance, the head weight Wh is preferably equal to or greater than 175 g, more preferably equal to or greater than 180 g, and still more preferably equal to or greater than 185 g. In light of swing balance, the head weight Wh is preferably equal to or less than 205 g, more preferably equal to or less than 200 g, and still more preferably equal to or less than 195 g.

[0100] A rib weight Wr is not restricted. In light of obtaining a high-pitched hitting sound, the rib weight Wr is equal to or greater than 1.0 g, more preferably equal to or greater than 1.2 g, and still more preferably equal to or greater than 1.5 g. When the rib weight is excessive, weight which can be distributed to parts other than the rib is decreased, thereby deteriorating a design freedom degree of the head. In this respect, the rib weight Wr is preferably equal to or less than 5.0 g, more preferably equal to or less than 4.0 g, and still more preferably equal to or less than 3.0 g.

[0101] A ratio (Wr/Wh) of the rib weight Wr to the head weight Wh is not restricted. In light of obtaining a high-pitched hitting sound, the ratio (Wr/Wh) is preferably equal to or greater than 0.008, more preferably equal to or greater than 0.009, and still more preferably equal to or greater than 0.010. When the rib weight is excessive, weight which can be distributed to the head body is decreased, thereby decreasing a moment of inertia. In this respect, the ratio (Wr/Wh) is preferably equal to or less than 0.025, more preferably equal to or less than 0.020, and still more preferably equal to or less than 0.015.

[0102] A rib length Lr (See FIG. 2) is not restricted. In order to obtain the plurality of effects discussed above, a longer rib distance Lr is more advantageous. In this respect, the rib length Lr is preferably equal to or greater than 50 mm, more preferably equal to or greater than 60 mm, and still more preferably equal to or greater than 70 mm. Due to a limitation on a sole area, the rib length Lr is preferably equal to or less than 150 mm, more preferably equal to or less than 140 mm, and still more preferably equal to or less than 130 mm.

[0103] The material for the head is not restricted. As the material of the head, metal and CFRP (Carbon Fiber Reinforced Plastic) or the like are exemplified. As the metal used for the head, one or more kinds of metals selected from pure titanium, a titanium alloy, stainless steel, maraging steel, an aluminium alloy, a magnesium alloy and a tungsten-nickel alloy are exemplified. SUS630 and SUS304 are exemplified as stainless steel. As the specific example of stainless steel, CUSTOM450 (manufactured by Carpenter Company) is exemplified. As the titanium alloy, 6-4 titanium (Ti-6Al-4V) and Ti-15V-3Cr-3Sn-3Al or the like are exemplified. When the volume of the head is great, the hitting sound is likely to be increased. The present invention is particularly effective in a head having a great hitting sound. In this respect, the material of the head is preferably the titanium alloy. In this respect, the material of the sole is preferably the titanium alloy.

[0104] A method for manufacturing the head is not restricted. Usually, a hollow head is manufactured by joining two or more members. A method for manufacturing the members constituting the head is not restricted. As the method, casting, forging and press forming are exemplified.

[0105] Examples of the structures of the heads include a two-piece structure in which two members integrally formed separately are joined, a three-piece structure in which three members integrally formed separately are joined, and a four-piece structure in which four members integrally formed separately are joined.

INDUSTRIAL APPLICABILITY

[0106] The present invention is applicable to all types of golf club heads such as wood type heads, utility type heads, and hybrid type heads or the like.

DESCRIPTION OF THE REFERENCE CHARACTERS

[0107] 2, 20, 30, 40, 50 . . . head [0108] 4 . . . face [0109] 6 . . . crown [0110] 8 . . . sole [0111] 10 . . . side part [0112] 12 . . . hosel [0113] 14 . . . shaft hole [0114] rb . . . rib [0115] ks1 . . . sloped extension part [0116] r1 . . . first recess part [0117] p1 . . . first protruding part [0118] r2 . . . second recess part [0119] p2 . . . protruding extension part [0120] J . . . minimum-thickness region

Claims

1. A hollow golf club head comprising: a face; a crown; and a sole, wherein a rib is formed on an inner surface of the sole, the rib has a sloped extension part extending to be closer to a face side of the head as approaching from a heel side to a toe side, and a center of gravity of the head is positioned on the heel side relative to a face center.

2. The golf club head according to claim 1, wherein the sole has a minimum-thickness region, and the rib has a thin reinforcing part positioned in the minimum-thickness region.

3. The golf club head according to claim 1, wherein a first recess part is formed on an outer surface of the sole, a recess part for a weight is formed inside the first recess part, a weight member can be attached to the recess part for a weight, and the rib has a recess-part-reverse-side rib part positioned at a reverse side of the first recess part on the inner surface of the sole.

4. The golf club head according to claim 1, wherein a second recess part is formed on an outer surface of the sole, the second recess part forms a protruding extension part on an inner surface side of the sole, and the protruding extension part extends along the rib.

5. The golf club head according to claim 1, wherein the first recess part is continuous to the second recess part.

6. The golf club head according to claim 1 further comprising a side part, wherein a toe side end of the rib does not extend up to the side part, and a heel side end of the rib extends up to the side part.

7. The golf club head according to claim 1, wherein the rib extends linearly in a plan view, a slope angle of the rib relative to a toe-heel direction is equal to or greater than 10.degree. and equal to or less than 45.degree..

8. The golf club head according to claim 1, wherein the rib extends curvedly so as to project toward a face side.

9. The golf club head according to claim 1, wherein the rib extends curvedly so as to project toward a back side.

10. The golf club head according to claim 1, wherein a length of the rib is equal to or greater than 50 mm and equal to or less than 150 mm.