The invention relates generally to a golf ball and, more specifically, to a golf ball incorporating an intermediate layer designed to improve ball performance. The invention also relates to methods of making such golf balls.
Golf balls generally have a core and at least one cover layer surrounding the core. Balls can be classified as two-piece, wound, or multi-layer balls. Two-piece balls include a spherical inner core generally made from rubber and an outer cover layer. Two-piece balls generally have high durability and good ball speed when hit, leading to good ball distance. However, these balls also generally have low spin rates, which results in poor ball controllability. High spin rate is a desirable property of golf balls, particularly for advanced players who can take particular advantage of the improved controllability of balls exhibiting high spin. Two-piece balls also provide poor “feel,” or overall sensation transmitted to the golfer while hitting the ball. Wound balls generally include a core, a rubber thread wound under tension around the core to a desired diameter, and a cover layer, typically of balata material. Wound balls generally provide high spin, and therefore greater controllability, than two-piece balls, and they also generally provide superior feel. However, these balls generally have a relatively low coefficient of restitution (C.O.R.), which leads to reduced ball speed and therefore distance, and also are less durable than two-piece balls.
A good way to optimize the requirements of good speed, spin, feel, and durability is through a multi-layer construction. Multi-layer balls include a core, a cover layer, and one or more intermediate layers situated between the core and the cover layer. U.S. Pat. No. 6,012,991 to Kim et al. discloses a multi-layer golf ball having good distance, feel, and spin. Multi-layer balls generally have performance characteristics between those of two-piece and wound balls; that is, multi-layer balls exhibit distance and durability inferior to two-piece balls but superior to wound balls, and they exhibit feel and spin rate inferior to wound balls but superior to two-piece balls. In particular, use of an intermediate layer to improve spin rate often can lead to substantial loss of ball speed, and therefore distance. In particular, balls preferably should exhibit high spin rate when hit by an iron for enhanced controllability of short- and medium-distance shots, but the balls preferably should exhibit lower spin rate when hit by a driver to maximize distance for long shots. Therefore, efforts have been focused in designing intermediate layers for golf balls on producing layers that provide high spin rate without loss of ball distance or durability. These efforts have not met with complete success.
In view of the above, there remains a need for golf balls having intermediate layers that provide for high spin rate without substantial loss of ball speed and distance. The present invention fulfills this need and provides several related advantages.