Games using tangible projectile – Golf – Ball
Reexamination Certificate
1999-08-20
2001-06-26
Chapman, Jeanette (Department: 3711)
Games using tangible projectile
Golf
Ball
Reexamination Certificate
active
06251031
ABSTRACT:
This invention relates to a multi-piece solid golf ball comprising at least four layers, a solid core, an enclosure layer, an intermediate layer, and a cover and having high resilience, durability and a very soft pleasant feel.
BACKGROUND OF THE INVENTION
Many solid golf balls such as two-piece golf balls are known in the art. As compared with the wound golf balls, solid golf balls have the advantage of an increased total flight distance on both driver and iron shots, because of a so-called straight line trajectory and a low spin rate due to their structure, which allows for a long run. On the other hand, the solid golf balls are more difficult to control than the wound golf balls in that they do not stop short on the green because of low spin receptivity on iron shots.
Like flight distance, a pleasant feel when hit is essential for golf balls. The absence of a pleasant feel represents a substantial loss of commodity value of the golfball. As compared with the solid golf balls, wound golf balls have the structural characteristics ensuring a soft and pleasant feel.
On two-piece solid golf balls consisting of a core and a cover, attempts have been made to soften the ball structure in order to accomplish a soft feel upon impact. However, such attempts fail to fully meet the demand. By providing an intermediate layer between the core and the cover, three-piece solid golf balls were obtained. Although many proposals were made, it was still difficult to provide a golf ball having both the flight distance of two-piece solid golf balls and the feel of wound golf balls.
Recently, multi-piece solid golf balls having at least four layers were proposed (see JP-A 9-266959, 10-127818, and 10-127819). One solid golf ball proposed is of the four-layer structure in which a three-layer structure solid core consisting of an internal layer, an intermediate layer and an outer layer is enclosed with a cover. The ball is improved in hitting feel and control by providing a difference in hardness between the respective layers.
However, if the difference in hardness between two adjacent layers is reduced, little improvement in hitting feel is achieved. If the difference in hardness between two adjacent layers is significant or if the selection of the thickness or material of the adjacent layers is inappropriate, the deflection or deformation upon impact becomes largely different between the adjacent layers. This causes an energy loss at the interface therebetween and thus detracts from resilience, resulting in a reduced flight distance. The durability of the ball against consecutive strikes is also lost. This tendency becomes outstanding particularly when two adjacent layers are formed of different materials which cannot be strongly joined.
SUMMARY OF THE INVENTION
An object of the invention is to provide a multi-piece solid golf ball comprising a solid core, an enclosure layer, an intermediate layer, and a cover which has a very soft feel and high durability against consecutive strikes while maintaining the flight performance of solid golf balls.
The invention is directed to a multi-piece solid golf ball of at least four-layer structure comprising a solid core, an enclosure layer of at least one layer surrounding the core, an intermediate layer surrounding the enclosure layer, and a cover of at least one layer surrounding the intermediate layer. The inventor has found that by properly selecting the hardness, thickness and material of the respective layers, the multi-piece solid golf ball can be improved in resilience and durability and provided with a very soft, pleasant feel. More particularly, the inventor has found the following. (1) The intermediate layer and the cover are formed mainly of thermoplastic resins of the same type, especially ionomer resins. This strengthens the bond between these layers, contributing to durability. (2) The intermediate layer is made softer than the cover, and the enclosure layer is made softer than the intermediate layer. That is, the ball is constructed such that the layers are made softer as they are positioned more inside. This order of hardness minimizes the energy loss by deformation upon impact, prevents any loss of resilience, improves the durability of the ball, and imparts a soft feel. (3) The enclosure layer surrounding the core is formed mainly of a thermoplastic resin characterized by softness and resilience, especially a thermoplastic polyester elastomer or polyurethane elastomer. (4) An inorganic filler is added to at least one of the intermediate layer and the cover. Owing to the reinforcing effect of the filler, the ball is improved in durability.
In a first aspect, the invention provides a multi-piece solid golf ball comprising a solid core, an enclosure layer of at least one layer around the core, an intermediate layer around the enclosure layer, and a cover of at least one layer around the intermediate layer. According to the invention, the solid core has a hardness corresponding to a deflection of 2.5 to 7.0 mm under an applied load of 100 kg, the cover has a Shore D hardness of at least 53, and the Shore D hardness of the cover is higher than the Shore D hardness of the intermediate layer. The intermediate layer and the cover are formed mainly of thermoplastic resins of the same type. In addition to the above requirements, a second aspect requires that at least one of the intermediate layer and the cover contains an inorganic filler. Preferably the enclosure layer has a Shore D hardness of 10 to 50, and the Shore D hardness of the enclosure layer is lower than the Shore D hardness of the intermediate layer. Since the hardness, thickness and material of the respective layers are properly selected so that the respective layers may cooperate synergistically to construct a minimized energy loss ball structure, the multi-piece solid golf ball of the invention exhibits favorable flight performance by virtue of improved resilience and gives a very soft, pleasant feel. Moreover, owing to the reinforcing effect of the filler which is added to either one of the intermediate layer and the cover, the ball is outstandingly improved in durability against consecutive strikes.
REFERENCES:
patent: 5733205 (1998-03-01), Higuchi et al.
patent: 5743816 (1998-04-01), Ohsumi et al.
patent: 5772531 (1998-06-01), Ohsumi et al.
patent: 2 302 037 (1997-01-01), None
patent: 2 302 035 (1997-01-01), None
patent: 2 302 036 (1997-01-01), None
patent: 9-266959 (1997-10-01), None
patent: 10-127819 (1998-05-01), None
patent: 10-127818 (1998-05-01), None
Hayashi Junji
Higuchi Hiroshi
Shimizu Yasumasa
Yamagishi Hisashi
Bridgestone Sports Co. Ltd.
Chapman Jeanette
Gorden Raeann
Sughrue Mion Zinn Macpeak & Seas, PLLC
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