Multi-piece solid golf ball

Abstract

The invention provides a multi-piece solid golf ball having a solid core, an inner cover layer and an outer cover layer, which outer cover layer has a plurality of dimples on a surface thereof. The value obtained by subtracting a material hardness (Shore D) of the outer cover layer from a material hardness (Shore D) of the inner cover layer is greater than −5 and less than +5. The dimples number at least 250 and not more than 500, have a surface coverage (SR) of at least 70% and a volume ratio (VR) of at least 1.0%, are of at least three types of mutually differing dimple diameter (DM) and / or dimple depth (DP), and have an average depth of at least about 0.18 mm and a diameter-to-depth ratio (DM / DP) of not more than about 23. The ball has a coefficient of lift CL at a Reynolds number of 70,000 and a spin rate of 2,000 rpm which is maintained at 60% or more of the coefficient of lift CL at a Reynolds number of 80,000 and a spin rate of 2,000. This multi-piece solid golf ball is able to substantially reduce the distance traveled by the ball when struck at a high HS, while at the same time holding down the reduction in distance when struck at a low HS.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to a multi-piece solid golf ball having a solid core, an inner cover layer and an outer cover layer, and having a plurality of dimples on a surface of the outer cover layer. More specifically, the invention relates to a multi-piece solid golf ball which substantially reduces the distance traveled by the ball when struck at a high head speed (head speed is sometimes abbreviated below as “HS”) while at the same time undergoing little reduction in distance when struck at a low HS.[0002]With recent advances in golfing equipment such as balls and clubs, golf balls have come to travel increasing distances. For this reason, to keep play fair, strict rules have been adopted which establish, in the case of a golf club, for example, the size of the head and the length of the shaft. Similarly, limitations have been placed on certain characteristics of the golf ball, such as its size, weight and initial velocity, so as to restrict e...

AI Technical Summary

Benefits of technology

[0008]The inventors have conducted extensive investigations in order to achieve the above object. As a result, they have found that, in a multi-piece solid golf ball composed of a solid core, an inner cover layer and an outer cover layer, which outer cover layer has a plurality of dimples on a surface thereof, by specifying the size relationship between the material hardnesses (Shore D) of the inner cover layer and the outer cover layer; by specifying, for the dimples formed on the surface of the outer cover layer, the number of dimples, dimple surface coverage (SR), dimple volume ratio (VR), dimple types, average dimple depth, and dimple diameter-to-depth ratio (DM / DP); and by having the coefficient of lift CL at a Reynolds number of 70,000 and a spin rate of 2,000 rpm maintained at 60% or more of the coefficient of lift CL at a Reynolds number of 80,000 and a spin rate of 2,000, synergistic effects arising from dimple optimization and the suitable hardness relationship between the inner cover layer and the outer cover layer make it possible to substantially reduce the distance traveled by the ball when struck at a high HS while at the same time holding down the decrease in distance when the ball is struck at a low HS.

[0009]That is, unlike conventional methods of lowering the ball initial velocity or core initial velocity, the golf ball of the present invention is able, by combining low-trajectory dimples with the interior structure (multilayer structure) of the ball, to substantially reduce the distance of the ball when struck at a high HS while at the same time holding down to the extent possible, relative to the reduction in distance at high HS, the reduction in distance on low HS shots. As used herein, “distance” refers to the total distance traveled by a golf ball, including both the carry and the run.

Problems solved by technology

Similarly, limitations have been placed on certain characteristics of the golf ball, such as its size, weight and initial velocity, so as to restrict excessive ball travel of the sort that would result in a loss of fair play.

As a result, such balls have significant drawbacks for low HS players.

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