Golf ball

Abstract

A golf ball 2 has a spherical core 4, a mid layer 6 situated on the external side of the core 4, and a cover 8 situated on the external side of the mid layer 6. The core 4 has a spherical center 10 and an envelope layer 12 situated on the external side of the center 10. At all points P included in a zone away from the central point of the core 4 at a distance of 1 mm or greater and 15 mm or less, the following mathematical expression is satisfied.H2−H1≦5In the above mathematical expression, H1 represents the JIS-C hardness at a point P1 that is located inside the point P along the radial direction and away from the point P at a distance of 1 mm, and H2 represents the JIS-C hardness at a point P2 that is located outside the point P along the radial direction and away from the point P at a distance of 1 mm.

Description

[0001]This application claims priority on Patent Application No. 2009-297651 filed in JAPAN on Dec. 28, 2009. The entire contents of this Japanese Patent Application are hereby incorporated by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to golf balls. More particularly, the present invention relates to multi-piece golf balls having a core, a mid layer and a cover.[0004]2. Description of the Related Art[0005]Top requirement for golf balls by golf players is their flight performances. The golf players place great importance on flight performances achieved upon shots with a driver, a long iron and a middle iron. The flight performances correlate with resilience performances of the golf ball. Hitting of a golf ball that is excellent in resilience performance leads to a high-speed flight, whereby a great flight distance is attained.[0006]For attaining a great flight distance, an appropriate trajectory height is required. The tra...

AI Technical Summary

Benefits of technology

"The present invention relates to a golf ball with a core, mid layer, and cover. The core has a specific hardness distribution that results in less energy loss and a great flight distance when hit with a driver. The cover has a hardness that is lower than the core, but higher than the mid layer. The mid layer has a specific hardness that is greater than the hardness of the cover. The cover is made of thermoplastic polyurethane with a specific hardness difference between the center and the envelope layer. The technical effects of this invention include improved flight distance, better control performance, and a more stable feel when hitting the ball with a short iron."

Problems solved by technology

Golf balls which achieve a high trajectory due to a high spin rate are accompanied by insufficient flight distance.

A great back spin rate results in small run.

Great side spin rate results in easily curved trajectory of the golf ball.

When a core having an outer-hard / inner-soft structure and having an excessively large hardness distribution is hit with a driver, great energy loss occurs at this core.

The energy loss results in deterioration of the resilience performance.

The low spin rate results in deterioration of the control performance.

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