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 ?sec 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.

Abstract: In a golf ball having a core and a cover, the cover is formed primarily of polyurethane, the ball has a diameter of at least 43.0 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 driver to separate is 650 ?sec 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.

Abstract: In a golf ball having a core and a cover, the cover is formed primarily of polyurethane, the ball has a weight of 44.8 g or less 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 driver to separate is 650 ?sec 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.

Abstract: In a golf ball having a core and a cover, the cover is formed primarily of polyurethane, the ball has a weight of 44.8 g or less 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 driver to separate is 650 ?sec 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.

Abstract: In a golf ball having a core and a cover, the cover is formed primarily of polyurethane, the ball has a diameter of at least 43.0 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 driver to separate is 650 ?sec 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.

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 ?sec 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.

Abstract: A multi-piece solid golf ball for professional golfers and skilled amateurs in particular is endowed with an excellent distance, a soft yet good feel at impact and a good durability. In the ball, which includes a core, an envelope layer, an intermediate layer and a cover, the core has a hardness profile which satisfies specific conditions, the envelope layer has a thickness of from 0.3 to 1.2 mm, the intermediate layer has a thickness of from 0.3 to 1.2 mm, and the envelope and intermediate layers have a combined thickness from of 0.8 to 1.7 mm.

Abstract: A multi-piece solid golf ball for professional golfers and skilled amateurs in particular is endowed with an excellent distance, a soft yet good feel at impact and a good durability. In the ball, which includes a core, an envelope layer, an intermediate layer and a cover, the core has a hardness profile which satisfies specific conditions, the envelope layer has a thickness of from 0.3 to 1.2 mm, the intermediate layer has a thickness of from 0.3 to 1.2 mm, and the envelope and intermediate layers have a combined thickness from of 0.8 to 1.7 mm.

Abstract: In a multi-piece solid golf ball having a rubber two-layer core consisting of an inner layer and an outer layer, a cover, and at least one intermediate layer therebetween, the inner core layer has a diameter of at least 22 mm, the difference in JIS-C hardness between the center of the inner core layer and the surface of the outer core layer is at least 25, the ball satisfies the relationship A/B?2.0, where A and B are the deflections of, respectively, the inner core layer and the two-layer core when compressed under specific loading conditions, and the intermediate layer has a higher material hardness than the cover, and the core hardness profile are optimized by the specific conditions. This ball enables mid- to high-level golfers both to achieve even longer distances and to maintain the spin performance on approach shots at a high level.

Abstract: In a golf ball having, in order, a core, an envelope layer, an intermediate layer and a cover, the following conditions are satisfied: (I) ball surface hardness>intermediate layer surface hardness>envelope layer surface hardness<core surface hardness, (II) (Shore D hardness at core surface?Shore D hardness at envelope layer surface)?10, (III) (cover thickness?intermediate layer thickness)>0.05 mm, (IV) (intermediate layer thickness?envelope layer thickness)>0.05 mm, and (V) (Cs?C10)/(C10?Cc)>1.0 (where Cs denotes the JIS-C hardness at the core surface, C10 the JIS-C hardness at a position 10 mm from a center of the core, and Cc the JIS-C hardness at the core center). The ball provides an excellent flight performance when struck by the average golfer, a feel that is both soft and solid, and an excellent durability to repeated impact.

Abstract: In a multi-piece solid golf ball having a rubber two-layer core consisting of an inner layer and an outer layer, a cover, and at least one intermediate layer therebetween, the inner core layer has a diameter of at least 30 mm, the difference in JIS-C hardness between the center of the inner core layer and the surface of the outer core layer is at least 25, the ball satisfies the relationship A/B?1.5, where A and B are the deflections of, respectively, the inner core layer and the two-layer core when compressed under specific loading conditions, and the intermediate layer has a higher material hardness than the cover. This ball enables mid- to high-level golfers both to achieve even longer distances and to maintain the spin performance on approach shots at a high level.

Abstract: In a multi-piece solid golf ball having a rubber two-layer core consisting of an inner layer and an outer layer, a cover, and at least one intermediate layer therebetween, the inner core layer has a diameter of at least 30 mm, the difference in JIS-C hardness between the center of the inner core layer and the surface of the outer core layer is at least 25, the ball satisfies the relationship A/B?1.5, where A and B are the deflections of, respectively, the inner core layer and the two-layer core when compressed under specific loading conditions, and the intermediate layer has a higher material hardness than the cover. This ball enables mid- to high-level golfers both to achieve even longer distances and to maintain the spin performance on approach shots at a high level.

Abstract: The invention provides a mold for injection-molding a golf ball, which mold has a cavity inner wall with a vertical diameter connecting both poles in a vertical direction thereof that is longer than a horizontal diameter connecting both poles in a horizontal direction thereof. A method of manufacturing golf balls using such a mold is also provided. The use of this mold eliminates molding problems that arise when molding the outermost cover layer of a golf ball, enabling the cover to be stably molded and also making it possible to easily and reliably obtain golf balls of high symmetry in which a cover of uniform thickness has been formed.

Abstract: In a golf ball having, in order, a core, an envelope layer, an intermediate layer and a cover, the following conditions are satisfied: (I) ball surface hardness>intermediate layer surface hardness>envelope layer surface hardness<core surface hardness, (II) (Shore D hardness at core surface?Shore D hardness at envelope layer surface)?10, (III) (cover thickness?intermediate layer thickness)>0.05 mm, (IV) (intermediate layer thickness?envelope layer thickness)>0.05 mm, and (V) (Cs?C10)/(C10?Cc)>1.0 (where Cs denotes the JIS-C hardness at the core surface, C10 the JIS-C hardness at a position 10 mm from a center of the core, and Cc the JIS-C hardness at the core center). The ball provides an excellent flight performance when struck by the average golfer, a feel that is both soft and solid, and an excellent durability to repeated impact.

Abstract: In a multi-piece solid golf ball having a core, an envelope layer, an intermediate layer and a cover, the surface hardnesses of the respective layers are set so as to satisfy specific relationships. Also, the initial velocities measured for the core, for a sphere obtained by forming the envelope layer over the core (envelope layer-encased sphere), for a sphere obtained by forming the envelope layer and the intermediate layer over the core (intermediate layer-encased sphere) and for the ball are set so as to satisfy specific relationships. In addition, the deflection (mm) of the ball when compressed under a given load and the deflection (mm) of the intermediate layer-encased sphere when compressed under a given load are set so as satisfy a specific relationship.

Abstract: In a multi-piece solid golf ball which has a core with a two-layer structure composed of an inner layer and an outer layer, and has over the core a cover of two or more layers that includes an intermediate layer and an outermost layer, the core inner layer is formed primarily of a specific thermoplastic elastomer, the core outer layer is formed of a rubber composition consisting primarily of a rubber material, and the hardness relationship between the core inner layer and the core outer layer and the hardness relationship between the intermediate layer and the outermost layer have been optimized. This golf ball has an excellent flight performance on full shots with a driver (W#1) and also has good controllability in the short game and a good durability.

Abstract: In a multi-piece solid golf ball having a core, an envelope layer, an intermediate layer and a cover, the surface hardnesses of the respective layers are set so as to satisfy specific relationships. Also, the initial velocities measured for the core, for a sphere obtained by forming the envelope layer over the core (envelope layer-encased sphere), for a sphere obtained by forming the envelope layer and the intermediate layer over the core (intermediate layer-encased sphere) and for the ball are set so as to satisfy specific relationships. In addition, the deflection (mm) of the ball when compressed under a given load and the deflection (mm) of the intermediate layer-encased sphere when compressed under a given load are set so as satisfy a specific relationship.

Abstract: In a multi-piece solid golf ball having a core, an envelope layer, an intermediate layer and a cover, the core is formed primarily of a thermoplastic elastomer, the envelope layer is formed of a rubber composition containing primarily a rubber material, the intermediate layer is formed of a resin composition containing primarily an ionomer, and the cover is formed of a resin composition containing primarily a urethane. The relationships among the specific gravities and the surface hardnesses of the respective layers are optimized. This golf ball enables an increased distance on full shots with a driver and improved controllability in the short game to be achieved, and also makes it possible to obtain a further reduction in the spin rate on full shots.

Abstract: In a multi-piece solid golf ball having a core, an intermediate layer and a cover, the ball and the intermediate layer have respective surface hardnesses which are set so as to satisfy a specific relationship. Also, the respective initial velocities measured for the core, a sphere composed of the core over which an envelope layer and the intermediate layer have been formed (intermediate layer-encased sphere) and the ball are set so as to satisfy a specific relationship. In addition, the hardness relationship between the surface and the center of the core has been adjusted in a specific range. This golf ball is able to exhibit an excellent flight performance not only when struck by mid head-speed golfers, but even when struck by low head-speed golfers, in addition to which it has both a good feel at impact and an excellent durability to repeated impact.

Abstract: A golf ball has a core, an envelope layer, an intermediate layer and a cover whose respective surface hardnesses have been set so as to satisfy certain specific relationships. In addition, the respective initial velocities measured for the core, a sphere composed of the core peripherally covered by the envelope layer (envelope layer-encased sphere), a sphere composed of the core peripherally covered by the envelope layer and the intermediate layer (intermediate layer-encased sphere), and the ball itself have been set so as to satisfy certain specific relationships. This golf ball is able to exhibit an excellent flight performance not only when struck by mid head-speed golfers, but even when struck by low head-speed golfers, in addition to which it also has a good feel at impact and an excellent durability to repeated impact.