Golf ball having a hollow center

Abstract

A hollow golf ball includes a spherical inner core shell layer formed from a first thermoplastic composition, the shell layer having an outer surface, an inner surface, and an inner diameter to define a hollow center. An outer core layer is formed about the shell layer and includes a thermoset rubber composition. An inner cover layer is formed about the outer core layer and includes an ionomeric material. An outer cover layer is formed about the inner cover layer. The outer cover includes a polyurea or a polyurethane and has a hardness less than the inner cover layer. The hollow center has a diameter of about 0.15 to 1.1 inches, the shell layer has a surface hardness greater than an inner surface hardness by about 0 to 5 Shore C to define a first hardness gradient, and the thermoset outer core layer has a second hardness gradient.

Description

FIELD OF THE INVENTION[0001]This invention relates generally to golf balls with a core having a hollow center surrounded by one or more core layers and one or more cover layers. Any of the core or cover layers may have a ‘negative’ or ‘positive’ hardness gradient, depending on the desired construction. More particularly, the golf ball includes a core having a hollow center surrounded by a thermoplastic ‘shell layer’ and at least one additional core layer that is thermoset.BACKGROUND OF THE INVENTION[0002]In recent years, virtually all golf balls are of a solid construction, typically including with a solid core encased by a cover, both of which can have multiple layers, such as a dual core having a solid center and an outer core layer, or a multi-layer cover having an inner and outer cover layer. Golf ball cores and / or centers are formed from a thermoset rubber composition with polybutadiene as the base rubber. The cores are usually heated and crosslinked to create a core having cer...

AI Technical Summary

Benefits of technology

This patent describes a new design for a golf ball with a hollow core. The ball has a shell layer made from a thermoplastic material and a thermoset outer core layer made from another thermoset material. There is also an optional inner cover layer made from ionomeric material, and an outer cover layer made from polyurea or polyurethane. The hollow center has a diameter of 0.15 to 1.1 inches, and the shell layer has a surface hardness greater than the inner surface hardness by 0 to 5 Shore C. The thermoset outer core layer has a second hardness gradient, which can be either positive or negative. The patent also describes a shallow positive hardness gradient for the thermoset outer core layer or thermoset intermediate core layer. The technical effect of this design is to improve the performance and feel of the golf ball.

Problems solved by technology

While, in the past, many commercially-available golf balls have been constructed with non-solid centers, such as liquid centers, very few golf balls having hollow centers have ever been constructed.

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