The majority of golf balls commercially available today are of a solid construction. Solid golf balls include one-piece, two-piece, and multi-layer golf balls. One-piece golf balls are inexpensive and easy to construct, but have limited playing characteristics and their use is, at best, confined to the driving range. Two-piece golf balls are generally constructed with a solid polybutadiene core and a cover and are typically the most popular with recreational golfers because they are very durable and provide good distance. These golf balls are also relatively inexpensive and easy to manufacture, but are regarded by top players as having limited playing characteristics. Multi-layer golf balls are comprised of a solid core and a cover, either of which may be formed of one or more layers. These balls are regarded as having an extended range of playing characteristics, but are more expensive and difficult to manufacture than are one- and two-piece golf balls.
Wound golf balls, which typically included a fluid-filled center surrounded by a layer of tensioned elastomeric material and a cover, were preferred for their spin and “feel” characteristics but were more difficult and expensive to manufacture than solid golf balls. Manufacturers are continuously striving to produce a solid ball that concurrently includes the beneficial characteristics of a wound ball.
Golf ball playing characteristics, such as compression, velocity, and spin can be adjusted and optimized by manufacturers to suit players having a wide variety of playing abilities. For example, manufacturers can alter any or all of these properties by changing the materials and/or the physical construction of each or all of the various golf ball components (i.e., centers, cores, intermediate layers, and covers). Finding the right combination of core and layer materials and the ideal ball construction to produce a golf ball suited for a predetermined set of performance criteria is a challenging task.
Efforts to construct a multi-layer golf ball have generally focused on the use of one or two cover layers formed of ionomeric and/or polyurethane compositions. It is desirable, therefore, to construct a golf ball formed of a urethane or urea outer cover layer, at least two interior cover layers, and at least one core layer, according to the present invention. In particular, it is desired that this construction include a stiff, thermoplastic polyurethane or polyurea intermediate cover layer in conjunction with a stiff, resilient thermoplastic inner cover layer and thermosetting castable outer cover layer.