The present invention pertains to the art of making golf balls, and, more particularly, golf balls having one or more overlaying deep dimples. The present invention further relates to processes and apparatuses for forming multi-layer golf balls, and more particularly to processes and equipment for forming multi-layer golf balls having one or more deep dimples that extend through the outer cover layer and into one or more matching depressions in the layers or components thereunder.
Golf balls are typically made by molding a core of elastomeric or polymeric material into a spheroid shape. A cover is then molded around the core. Sometimes, before the cover is molded about the core, an intermediate layer is molded about the core and the cover is then molded around the intermediate layer. The molding processes used for the cover and the intermediate layer are similar and usually involve either compression molding or injection molding.
In compression molding, the golf ball core is inserted into a central area of a two piece die and pre-sized sections of cover material are placed in each half of the die, which then clamps shut. The application of heat and pressure molds the cover material about the core.
Blends of polymeric materials have been used for modern golf ball covers because certain grades and combinations have offered certain levels of hardness to resist damage when the ball is hit with a club and elasticity to allow responsiveness to the hit. Some of these materials facilitate processing by compression molding, yet disadvantages have arisen. These disadvantages include the presence of seams in the cover, which occur where the pre-sized sections of cover material were joined, and long process cycle times which are required to heat the cover material and complete the molding process.
Injection molding of golf ball covers arose as a processing technique to overcome some of the disadvantages of compression molding. The process involves inserting a golf ball core into a die, closing the die and forcing a heated, viscous polymeric material into the die. The material is then cooled and the golf ball is removed from the die. Injection molding is well-suited for thermoplastic materials, but has limited application to some thermosetting polymers. However, certain types of these thermosetting polymers often exhibit the hardness and elasticity desired for a golf ball cover. Some of the most promising thermosetting materials are reactive, requiring two or more components to be mixed and rapidly transferred into a die before a polymerization reaction is complete. As a result, traditional injection molding techniques do not provide proper processing when applied to these materials.
Reaction injection molding is a processing technique used specifically for certain reactive thermosetting plastics. As mentioned above, by xe2x80x9creactivexe2x80x9d it is meant that the polymer is formed from two or more components which react. Generally, the components, prior to reacting, exhibit relatively low viscosities. The low viscosities of the components allow the use of lower temperatures and pressures than those utilized in traditional injection molding. In reaction injection molding, the two or more components are combined and reacted to produce the final polymerized material. Mixing of these separate components is critical, a distinct difference from traditional injection molding.
The process of reaction injection molding a golf ball cover involves placing a golf ball core into a die, closing the die, injecting the reactive components into a mixing chamber where they combine, and transferring the combined material into the die. The mixing begins the polymerization reaction which is typically completed upon cooling of the cover material.
The present invention provides a new mold or die configuration and a new method of processing for reaction injection molding a golf ball cover or inner layer which promotes increased mixing of constituent materials, resulting in enhanced properties and the ability to explore the use of materials new to the golf ball art.
For certain applications it is desirable to produce a golf ball having a very thin cover layer. However, due to equipment limitations, it is often very difficult to mold a thin cover. Accordingly, it would be beneficial to provide an apparatus and technique for producing a relatively thin cover layer.
Moreover, retractable pins have been utilized to hold, or center, the core or core and mantle and/or cover layer(s) in place within an injection mold while molding an outer cover layer thereon. In such processes, the core or mantled ball is supported in the mold using retractable pins extending from the inner surface of the mold to the outer surface of the core or mantled ball. The pins in essence support the core or mantled ball while the cover layer is injected into the mold. Subsequently, the pins are retracted as the cover material fills the void between the core or mantle and the inner surface of the mold.
However, notwithstanding, the benefits produced through the use of the retractable pins, the pins sometimes produce centering difficulties and cosmetic problems (i.e. pin flash, pin marks, etc.) during retraction, which in turn require additional handling to produce a golf ball suitable for use and sale. Additionally, the lower the viscosity of the mantle and/or cover materials, the greater the tendency for the retractable pins to stick due to material accumulation, making it necessary to shut down and clean the molds routinely. Accordingly, it would be desirable to provide an apparatus and method for forming a cover layer on a golf ball without the use of retractable pins.
The present invention provides, in a first aspect, a multi-layer golf ball with a plurality of deep dimples. The golf ball comprises a core having an outer surface defining a plurality of depressions in the core. The golf ball also comprises a first layer disposed on the core in which the first layer defines a first plurality of apertures. The first layer is disposed on the core such that the plurality of apertures overlie the plurality of depressions in the core. The golf ball also comprises a second layer disposed on the first layer. The second layer defines a second plurality of apertures and is disposed on the first layer such that the second plurality of apertures overlie the first plurality of apertures. The plurality of depressions in the core, the plurality of apertures in the first cover layer, and the plurality of apertures in the second cover layer are aligned with each other and form the plurality of deep dimples in the resulting golf ball.
In yet another aspect, the present invention provides a multi-layer golf ball having a plurality of deep dimples along its outer surface. The golf ball comprises a core, a first layer disposed on the core, and a second layer disposed on the first layer. The first layer defines a plurality of depressions along its outer surface. The second layer defines a plurality of apertures, and the second layer is disposed on the first layer such that the plurality of apertures overlie the plurality of depressions defined in the first layer. Furthermore, the plurality of depressions defined in the first layer and the plurality of apertures defined in the second layer form the plurality of deep dimples in the resulting golf ball.
In yet another aspect, the present invention provides a multi-layer golf ball having a plurality of deep dimples. The golf ball comprises a core and a first layer disposed on the core. The first layer defines a first plurality of apertures. The golf ball also comprises a second layer disposed on the first layer. The second layer defines a second plurality of apertures. The second layer is disposed on the first layer such that the second plurality of apertures in the second layer overlie the first plurality of apertures defined in the first layer. The first plurality of apertures defined in the first layer and the second plurality of apertures defined in the second layer form the plurality of deep dimples in the resulting golf ball.
One advantage of the present invention is that the constituent materials are mixed thoroughly, thereby providing a more consistent intermediate and/or cover layer, resulting in better golf ball performance characteristics.
Another advantage of the present invention is that the use of new, lower viscosity materials may be explored, resulting in enhanced golf ball properties and performance.
Yet another advantage of the present invention is that increased mixing of lower viscosity materials allows the intermediate layer or cover to be thinner, resulting in increased ball performance.
Still another advantage of the present invention is that a unique venting configuration of the mold reduces the porosity of the material being processed, creating a ball cover or other layer that is substantially free of voids.
A further aspect of the invention is to provide equipment and methods for forming a golf ball having a dimpled cover that is thinner than traditional cover layers.
Another aspect of the invention is to provide equipment and methods for forming a golf ball having dimples in an outer cover layer that extend to, and/or into, at least the next inner layer of the ball.
Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.