Abstract: An iron type golf club head includes a head main body, a toe-side weight member made of a metal material having specific gravity ?2 larger than that of the head main body and disposed on a toe-side of the head main body, and a heel-side weight member made of a metal material having specific gravity ?3 larger than that of the head main body and disposed on a heel-side of the head main body. The head main body includes a face main portion having a face to hit a golf ball, and a tubular hosel portion provided continuously on a heel-side of the face main portion and having a shaft inserting hole. A distance from the center of gravity Gt of the toe-side weight member to the center of gravity Gh of the heel-side weight member ranges from 50 to 120 mm.

Abstract: On the basis of a surface shape appearing at a predetermined point moment by moment during rotation of a golf ball having numerous dimples on its surface, a data constellation regarding a parameter dependent on a surface shape of the golf ball is calculated. A preferable parameter is a distance between an axis of the rotation and the surface of the golf ball. Another preferable parameter is a volume of space between a surface of a phantom sphere and the surface of the golf ball. Fourier transformation is performed on the data constellation to obtain a transformed data constellation. On the basis of a peak value and an order of a maximum peak of the transformed data constellation, an aerodynamic characteristic of the golf ball is determined. The peak value and the order of the maximum peak are calculated for each of PH rotation and POP rotation.

Abstract: An object of the present invention is to provide a golf ball that decrease the spin rate on the driver shots while suppressing the decrease in the spin rate on the approach shots in a golf ball having a urethane cover. The present invention provides a golf ball having a core consisting of a center and at least one intermediate layer covering the center, and a cover covering the core, wherein the cover contains polyurethane, and has a slab hardness of 85 or less in JIS A hardness, the core has a surface hardness of 60 or more in Shore D hardness, the intermediate layer has a thickness ranging from 0.5 mm to 2.0 mm, and a resin component constituting the intermediate layer has a hardness from 62 to 68 in Shore D hardness, a flexural modulus from 300 MPa to 500 MPa, and a maximum storage modulus E? between ?30° C. to 0° C. ranging from 1,000 MPa to 2,000 MPa.

Abstract: A golf club head 1 comprising a hollow head body 1b and a gravity center adjuster 14 fixed to the head body 1b and comprising a first weight member 15 and a second weight member 16 having a lower specific gravity than the first weight member 15, wherein the first and second weight members are provided in the head body 1b so that the locations thereof are exchangeable with each other, and a depth GL of the center of gravity which is a distance from the head's center of gravity G to a sweet spot SS of a face 2 can be changed by location exchange between the first and second weight members 15 and 16 without substantially changing a distance GK of the center of gravity which is the shortest distance from an axial center line of a shaft-inserting hole 7a to the head's center of gravity G.

Abstract: A golf ball 2 has a core 4, an inner cover 6 positioned outside this core 4 and an outer cover 8 positioned outside the inner cover 6. The core 4 has a spherical center 10 and a mid layer 12 positioned outside this center 10. The center 10 is formed by crosslinking a rubber composition. The mid layer 12 is formed by crosslinking a rubber composition. The inner cover 6 is made of a thermoplastic resin composition. The outer cover 8 is made of a thermoplastic resin composition. The center 10 has a diameter of 1 mm or greater and 15 mm or less. The center 10 has a central point having JIS-C hardness H1 of 20 or greater and 50 or less. A difference (H4?H3) between a hardness H4 of a surface of the core and a hardness H3 of an innermost part of the mid layer is equal to or greater than 10. A hardness H5 of the inner cover is smaller than a hardness H6 of the outer cover.

Abstract: An object of the present invention is to provide a novel technology to improve the resilience of the ionomer resin while keeping the material strength of the ionomer resin. That is, the object of the present invention is to provide a golf ball excellent in the durability and resilience in a golf ball using an ionomer resin. The present invention provides a golf ball comprising a core having a center and at least one intermediate layer disposed around the center, and a cover disposed around the core, wherein at least one of the center, the intermediate layer, and the cover is formed from an ionomer resin composition which comprises 100 parts by mass of (A) an ionomer resin of a ternary copolymer composed of ethylene, ?,?-unsaturated carboxylic acid having 3 to 8 carbon atoms and ?,?-unsaturated carboxylic acid ester, and from 0.05 part to 10 parts by mass of (B) a metal salt of an unsaturated carboxylic acid.

Abstract: The present invention relates to a putter-type golf club head with a face on a front side to hit a golf ball comprising a head main portion provided with a concave portion on a side of the face, and a face insert made of elastic material attached to the concave portion of the head main portion, the face insert having a three-layer structure comprising of a first layer disposed at the front, a third layer disposed at the rear, and a second layer disposed between the first layer and the third layer, each of the first layer, the second layer, and the third layer having a hardness of h1, h2, and h3 and a rebound resilience of r1, r2, and r3, and the first layer, the second layer, and the third layer satisfying the following relations: h2<h1<=h3, r1>r2, and r1>r3.

Abstract: In a shaft 6, a shaft full length is defined as Ls, and a distance between a tip end of the shaft and a center of gravity G of the shaft is defined as Lg. Lg/Ls is 0.52 or greater and 0.65 or less. A shaft weight is equal to or less than 52 g. Preferably, the shaft 6 has butt partial layers a5 and a6. When a point separated by 250 mm from a butt end Bt is defined as P2; a range from the point P2 to the butt end Bt is defined as a specific butt range; the total weight of the butt partial layers a5 and a6 existing in the specific butt range is Wa gram; and a weight of the shaft in the specific butt range is defined as Wb gram, Wa/Wb is preferably equal to or greater than 0.4.

Abstract: An object of the present invention is to provide a golf ball which travels a great distance on the driver shots and stops quickly on the green on the approach shots. The present invention is directed to a golf ball material having a shear loss modulus G? of 2.11×107 Pa or less, and a ratio (E?/G?) of a tensile loss modulus E? to the shear loss modulus G? of 1.78 or more, when measuring the shear loss modulus G? in a shear mode and the tensile loss modulus E? in a tensile mode at conditions of a temperature of 0° C., oscillation frequency of 10 Hz using a dynamic viscoelasticity measuring apparatus.

Abstract: A method for surface treating a golf club head, includes: (a) forming a depression unit in the golf club head, the depression unit being indented inwardly from an outer surface of the golf club head, the outer surface being divided into a working area and a non-working area, the depression unit being formed in the working area; (b) filling the depression unit with a shielding material and covering the non-working area with a covering material; and (c) sandblasting the golf club head after step (b) and removing subsequently the shielding material from the depression unit and the covering material from the non-working area so as to form the working area into sandblasted and non-sandblasted regions that differ in gloss intensity.

Abstract: A golf ball 2 includes a spherical core 4 and a cover 6 positioned outside the core 4. The golf ball 2 further has dimples 8 on a surface thereof. The core 4 is obtained by crosslinking a rubber composition. The difference between a hardness H(5.0) at a point that is located at a distance of 5 mm from the central point of the core 4, and a hardness Ho at the central point is equal to or greater than 6.0. The difference between a hardness H(12.5) at a point that is located at a distance of 12.5 mm from the central point, and the hardness H(5.0) is equal to or less than 4.0. The difference between a hardness Hs at the surface of the core 4 and the hardness H(12.5) is equal to or greater than 10.0. The difference between the hardness Hs and the hardness Ho is equal to or greater than 22.0. There is no zone in which a hardness decreases from the central point to the surface. The rubber composition of the core 4 includes 2-naphthalenethiol. A cross-sectional shape of each dimple 8 is a wave-like curve.

Abstract: An object of the present invention is to provide a golf ball having an improved controllability and shot feeling while maintaining a flight distance on driver shots. The present invention provides a golf ball having a core, an intermediate layer disposed around the core, and a cover disposed around the intermediate layer, wherein the core has a center and an envelope layer disposed around the center, and has a specific hardness distribution, and the intermediate layer is formed from an intermediate layer composition comprising, as a resin component, (A) a modified polyester elastomer and (B) a binary ionomer resin, and having a flexural modulus ranging from 150 MPa to 450 MPa, a maximum loss factor (tan ?) between ?20° C. and 0° C. of 0.08 or less, a repulsive modulus of 55% or more, and a slab hardness ranging from 60 to 90 in JIS-hardness.

Abstract: A golf club according to one or more aspects of the present invention may have a mass less than 300 g, a length greater than about 45 inches, a swing weight between D0 and D6, a head weighing less than about 200 g, a club-head volume of at least about 360 cm3, a grip weighing less than about 50 g, and a shaft having a tip end, a butt end, and a shaft balance point located no more than 24 inches from the butt end. The shaft may have a torsional displacement angle greater than about 5.5° and a mass less than about 50 g. A coordinate system having x-, y-, and z-axes may have its origin at the center of gravity of the club head. The golf club head may have a moment of inertia of at least about 4500 g·cm2 about the z-axis and a moment of inertia of at least about 3000 g·cm2 about the y-axis.

Abstract: A core 4 of a golf ball 2 includes a center 10 and an envelope layer 12 positioned outside the center 10. The ratio of the volume of the core 4 to the volume of a phantom sphere of the golf ball 2 is equal to or greater than 78%. The difference (He?Ho) between a JIS-C hardness He at the surface of the core 4 and a JIS-C hardness Ho at the central point of the core 4 is equal to or greater than 15 but equal to or less than 40. The difference (H1?Ho) between a JIS-C hardness H1 at a point P1 that is located radially outward of the boundary between the center 10 and the envelope layer 12 and whose distance from the boundary is 1 mm and the JIS-C hardness Ho is equal to or greater than 0 but equal to or less than 2.

Abstract: An object of the present invention is to provide a golf ball resin composition excellent in resilience. Another object of the present invention is to provide a golf ball excellent in a shot feeling and resilience. The golf ball resin composition of the present invention is characterized in that a storage modulus E? (Pa) and a loss modulus E? (Pa) satisfy a following expression; log(E?/E?2)??6.08 when measured at the conditions of the temperature of 12° C., the oscillation frequency of 10 Hz, and a strain of 0.05% in a tensile mode using a dynamic viscoelasticity measuring apparatus.

Abstract: A golf club shaft is manufactured using a plurality of prepreg sheets a1 to a8. The plurality of prepreg sheets a1 to a8 includes full length sheets a2 to a7 disposed all over in a shaft axis direction and partial sheets a1 and a8 partially disposed in the shaft axis direction. The number of plies is substantially an integer in all the full length sheets a2 to a7. The full length sheets a2 to a7 include four or more bias sheets a2 to a5. Circumferential winding start positions of the bias sheets a2 to a5 are dispersed in four or more positions. Preferably, the circumferential winding start positions of the full length sheets a2 to a7 are dispersed in five or more positions.

Abstract: An object of the present invention is to provide a golf ball having high resilience. The present invention provides a golf ball having a constituting member, wherein at least a part of the constituting member is formed from a rubber composition containing (a) a base rubber, (b) a co-crosslinking agent, (c) a crosslinking initiator, and (d) an organic sulfur compound, the organic sulfur compound being derivatives of thiophenols and disulfide with a strong electron withdrawing substituent.

Abstract: A cross-sectional shape of each of dimples 8 of a golf ball 2 is a wave-like curve. The wave-like curve has two first curves 14, two second curves 16, two third curves 18, and one fourth curve 20. Each first curve 14 and each third curve 18 are upwardly convex. Each second curve 16 and the fourth curve 20 are downwardly convex. Each first curve 14 is connoted to a land 10 at an edge Ed. Each second curve 16 is connected to the first curve 14 at a first inflexion point 22. Each third curve 18 is connected to the second curve 16 at a second inflexion point 24. The fourth curve 20 is connected to the third curves 18 at third inflexion points 26. In the wave-like curve, the upwardly convex curves 14 and 18 and the downwardly convex curves 16 and 20 are alternately arranged.

Abstract: A golf ball 2 includes a core 4, a mid layer 6, and a cover 8. The core 4 includes a center 10 and an envelope layer 12. The ratio (Do/De) of an amount of compressive deformation Do of the center 10 to an amount of compressive deformation De of the core 4 is equal to or greater than 1.5 but equal to or less than 2.5. The ratio (Do/Dc) of the amount of compressive deformation Do of the center 10 to an amount of compressive deformation Dc of the golf ball 2 is equal to or greater than 1.8. The diameter of the center 10 is equal to or less than 20 mm. The difference (He?Ho) between a surface hardness He of the core 4 and a central hardness Ho of the center 10 is equal to or less than 40.

Abstract: An object of the present invention is to provide a golf ball which has an increased dry spin rate and wet spin rate on approach shots without sacrificing the processability into the cover. The present invention provides a golf ball cover material having shear loss moduli G1? (Pa), G2? (Pa), and G3? (Pa) that satisfy following equations when measured using a dynamic viscoelasticity measuring apparatus at following conditions. log G1??7.09??(1) log G2??7.17??(2) log G3??7.14??(3) G1? measuring conditions: shear mode, oscillation frequency: 10 Hz, temperature: 0° C., strain: 0.05%; G2? measuring conditions: shear mode, oscillation frequency: 10 Hz, temperature: ?30° C., strain: 0.05%; and G3? measuring conditions: shear mode, oscillation frequency: 10 Hz, temperature: 0° C., strain: 5%.