Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-06-01
2002-10-22
Silbaugh, Jan H. (Department: 1732)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S245000, C156S293000, C264S248000, C264S275000, C264S279100, C264S297500, C264S297800, C425S408000, C425S411000, C425S414000, C425S423000
Reexamination Certificate
active
06468381
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to an improved method of compression molding a multi-layered golf ball core.
BACKGROUND OF THE INVENTION
Generally, golf balls have been classified as solid balls or wound balls. Solid balls are typically comprised of a solid, polymeric core and a cover. These balls are generally easy to manufacture, but are regarded as having non-optimal or limited playing characteristics. Wound balls are comprised of a solid or liquid-filled center surrounded by tensioned elastomeric material and a cover. Wound balls generally have good playing characteristics, but are more difficult to manufacture than solid balls.
The prior art is comprised of various golf balls that have been designed to provide optimal playing characteristics. These characteristics include the initial velocity and spin of the golf ball, which can be optimized for various caliber of players. For instance, certain players prefer to play a ball that is softer feeling and have a high spin rate that allows the player to control or “work” the ball. However, balls of this nature tend to exhibit slight decrease in distance due to the high spin rate. Other players prefer to play a ball that has a low spin rate to maximize distance. These balls, however, tend to be hard feeling and difficult to control around the greens.
Methods for producing golf balls having an ideal combination of the above mentioned desirable characteristics have been many. Manufacturers have molded layers around a solid center by placing a preformed center between two blocks of core material in a spherical compression mold, and closing the mold. This process, however, provides little control over the ultimate placement of the center within the golf ball core. Large variations in the location of the center can result and are extremely detrimental to ultimate golf ball performance. Another method that improves the centering of a solid center involves forming two hemispherical polymer cups with two mold halves that, when placed together, create a hollow cavity in which the solid center rests. The two cups are then heated above the curing temperature of the polymeric material, under compression, to form the golf ball core. However, although centering is improved, at certain desirable temperatures (typically higher) and material compositions (low levels of reinforcing polymer), the cups tend to pull away from the surface of the molds, which can result in a slightly off-center solid center because of displaced shell material.
The prior art also provides for the manufacture of double cover golf balls. This is generally accomplished by injection molding a first cover layer followed by a second cover layer, both around a core. This system, however, requires complex injection molds, usually with retractable pins within the mold to properly position the core. Moreover, this system generally works better with and is, therefore, more ideally suited for use with thermoplastic materials.
Therefore, what is desired is an improved method of molding multi-layer cores that employs a center plate for compression molding that ensures properly centered cores, allows cup or mantle layer formation at higher temperatures, and allows the use of improved formulations by reducing the amount of reinforcing polymer required.
SUMMARY OF THE INVENTION
The invention provides a method for making a golf ball, particularly suited for golf balls that have a multi-layer core with a solid or fluid center. The method comprises forming a solid or fluid-filled center, and then molding from elastomeric material, preferably of a thermoset material such as a polybutadiene-based material, core parts, such as hemispherical cups, that when combined form a hollow sphere.
The hemispherical cups each have a hemispherical cavity, formed by a combination of a first mold plate having a hemispherical cavity and a second mold plate with a hemispherical protrusion. The first mold plate cavity has a cavity diameter and, additionally, a circumferential groove surrounding the cavity, the groove having an inner and outer diameter. The inner diameter of the groove is preferably greater than the cavity diameter in the first mold plate. The second mold plate has a channel disposed concentrically around the hemispherical protrusion, the channel having an inner, outer, and center diameter. The channel inner diameter is preferably less than the cavity diameter. Additionally, the channel outer diameter is greater than inner groove diameter on the first mold plate.
The hemispherical cups are formed from elastomeric material by placing a predetermined amount of the material in the cavity of the first mold plate, locating the second mold plate juxtaposed to the first plate, and compressing the mold plates to form a cup, having a substantially hemispherical cavity and a lip extending into the groove on the first mold plate. The center is placed between the cups. The cups are then joined around the center to form a substantially spherical core with a substantially concentric center. Since the lip maintains the cups uniformly thick shape, the center is positioned concentrically within the finished core. Finally, a cover is molded around the core.
In one embodiment, the channel has a center diameter that is substantially the same as the cavity diameter. The channel has a depth that is preferably greater than about 0.01 inches. More preferably, the depth is from about 0.01 to 0.05 inches. Most preferably, the depth is from about 0.02 to 0.03 inches. In another embodiment, the channel inner diameter is between about 55% and 99.5% of the cavity diameter. The channel outer diameter is preferably between about 100.5% and 105% of the groove inner diameter.
The channel has a first and second sidewall, each having angles that are less than 90 degrees from horizontal, as measured from the center of the channel. More preferably, the angle is from about 30 to 60 degrees from horizontal. Most preferably, the angle is from about 40 to 50 degrees from horizontal. The channel, therefore, can be defined, in one embodiment, by a truncated cone cross-section. In another embodiment, the first and second sidewalls are each defined by an arc having a radius.
Additionally, the channel has a top width and a bottom width smaller than the top width. The bottom width is preferably from about 0.1 to 0.15 inches. More preferably, the bottom width is from about 0.12 to 0.13 inches.
In a preferred method according to the invention, the two cups are a thermoset material and the step of joining the cups comprises elevating the temperature of the cups to cause cross-linking. In the step of joining the cups further comprises compressing the cup edges together when crosslinking to join the cups.
The present invention also discloses a mold for making a golf ball having a multi-layer core comprising a bottom mold plate with a plurality of hemispherical cavities having a cavity diameter and a circumferential groove surrounding each cavity having an inner and outer diameter, the inner diameter being greater than the cavity diameter; a top mold plate with a plurality of hemispherical cavities having a cavity diameter and a circumferential groove surrounding each cavity having an inner and outer diameter, the inner diameter being greater than the cavity diameter; and a center mold plate with a plurality of hemispherical protrusions and a corresponding channel disposed concentrically around the protrusions, the channel having an inner diameter being less than the cavity diameter and an outer diameter greater than the groove inner diameter.
In a preferred method, the mold above is used to form a plurality of core hemispherical cups from elastomeric material by placing the elastomeric material in the cavities of the bottom mold plate and the top mold plate, locating the center mold plate between the top mold plate and the bottom mold plate; and compressing the mold plates to form the cups in the bottom and top mold plate cavities, the cups having substantially hemispherical cavities and a lip extending into the groove
Acushnet Company
Lee Edmund H.
Silbaugh Jan H.
Swidler Berlin Shereff & Friedman, LLP
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