Golf ball
AssigneeBridgestone Sports Co., Ltd.
InventorsHideo Watanabe, Atsuki Kasashima
Life of this patent
Estimating the term…
Abstract
In a golf ball having a core and a cover with a plurality of dimples on the surface, the cover is formed primarily of polyurethane, the dimples have a specific volume occupancy ratio and the ball has a diameter of at least 42.8 mm. In an impact test carried out by hitting the ball with a driver at a head speed of 40 m/s, the sum t1+t2 of the time t1 required from initial contact by the driver with the ball for deformation of the ball to reach a maximum and the time t2 required from the state of maximum ball deformation for the ball and driver to separate is 660 μsec or less. This golf ball makes it possible for golfers who have a high head speed and ordinary golfers who do not to compete without relying excessively on superiority in terms of distance.
Claims10
A golf ball comprising a core and a cover, which cover has a plurality of dimples on a surface thereof, wherein the cover is formed primarily of polyurethane and the dimples thereon have a volume occupancy ratio VR within the range of 0.80 to 0.92%, the ball has a diameter of at least 42.8 mm and, in an impact test carried out by hitting the ball with a driver at a head speed of 40 m/s, the sum t1+t2 of the time t1 required from initial contact by the driver with the ball for deformation of the ball to reach a maximum and the time t2 required from the state of maximum ball deformation for the ball and the driver to separate is 660 μsec or less,
- wherein the core has a diameter of at least 37.0 mm and a hardness profile in which, letting Cc be the Shore C hardness at a center of the core, Cs be the Shore C hardness at a surface of the core, Cm be the Shore C hardness at a midpoint M between the core center and the core surface, Cm−2, Cm−4, Cm−6 and Cm−8 be the respective Shore C hardnesses at positions 2 mm, 4 mm, 6 mm and 8 mm inward from the midpoint M and Cm+2, Cm+4 and Cm+6 be the respective Shore C hardnesses at positions 2 mm, 4 mm and 6 mm outward from the midpoint M, and defining surface areas X and A to F as follows
- surface area X:
- ½×2×(Cm−6-Cm−8)
- surface area A:
- ½×2×(Cm−4-Cm−6)
- surface area B:
- ½×2×(Cm−2-Cm−4)
- surface area C:
- ½×2×(Cm-Cm−2)
- surface area D:
- ½×2×(Cm+2-Cm)
- surface area E:
- ½×2×(Cm+4-Cm+2)
- surface area F:
- ½×2×(Cm+6-Cm+4),
- the core satisfies the condition:
- (surface area D+surface area E+surface area F)−(surface area A+surface area B+surface area C)>0, and wherein an intermediate layer made of a resin material is formed between the core and the cover, and the sphere obtained by encasing the core with the intermediate layer (intermediate layer-encased sphere) and the ball satisfy the following surface hardness (Shore C hardness) relationship;
- 9≤(surface hardness of intermediate layer-encased sphere)−(surface hardness of ball)≤15, and the surface hardness of the intermediate layer-encased sphere is from 70 to 78, expressed on the Shore D hardness scale.
A golf ball comprising a core and a cover, which cover has a plurality of dimples on a surface thereof, wherein the cover is formed primarily of polyurethane and the dimples thereon have a volume occupancy ratio VR within the range of 0.80 to 0.92%, the ball has a diameter of at least 42.9 mm and, in an impact test carried out by hitting the ball with a driver at a head speed of 40 m/s, the sum t1+t2 of the time t1 required from initial contact by the driver with the ball for deformation of the ball to reach a maximum and the time t2 required from the state of maximum ball deformation for the ball and the driver to separate is 660 μsec or less, wherein the core has a diameter of at least 37.0 mm and a hardness profile in which, letting Cc be the Shore C hardness at a center of the core, Cs be the Shore C hardness at a surface of the core, Cm be the Shore C hardness at a midpoint M between the core center and the core surface, Cm−2, Cm−4, Cm−6 and Cm−8 be the respective Shore C hardnesses at positions 2 mm, 4 mm, 6 mm and 8 mm inward from the midpoint M and Cm+2, Cm+4 and Cm+6 be the respective Shore C hardnesses at positions 2 mm, 4 mm and 6 mm outward from the midpoint M, and defining surface areas X and A to F as follows
- surface area X:
- ½×2×(Cm−6-Cm−8)
- surface area A:
- ½×2×(Cm−4-Cm−6)
- surface area B:
- ½×2×(Cm−2-Cm−4)
- surface area C:
- ½×2×(Cm-Cm−2)
- surface area D:
- ½×2×(Cm+2-Cm)
- surface area E:
- ½×2×(Cm+4-Cm+2)
- surface area F:
- ½×2×(Cm+6-Cm+4),
- the core satisfies the condition:
- (surface area D+surface area E+surface area F)−(surface area A+surface area B+surface area C)>0.
Dependencies are inferred from the claim text.