Golf ball casting mold assembly

[0002] Not Applicable

[0003] Not Applicable

[0004] 1. Field of the Invention

[0005] The present invention relates to a mold for forming a golf ball cover layer. More specifically, the present invention relates to a mold for forming a thermoset polyurethane cover on a golf ball core.

[0006] 2. Description of the Related Art

[0007] Golf balls may comprise one-piece constructions or they may include several layers including a core, one or more intermediate layers and an outer cover that surrounds any intermediate layer and the core. In multi-component golf balls, there exists an inner core. Often, this core is made by winding a band of elastomeric material about a spherical elastomeric or liquid-filled center. Alternatively, the core may be a unitary spherical core made of a suitable solid elastomeric material. One such material that is conventionally used for the core of golf balls is a base rubber, such as polybutadiene, which is cross-linked with a metal acrylate, such as zinc diacrylate.

[0008] In the construction of some multi-component golf balls, an intermediate boundary layer is provided outside and surrounding the core. This intermediate boundary layer is thus disposed between the core and the outer cover of the golf ball.

[0009] Located outwardly of the core and any intermediate boundary layer is a cover. The cover is typically made from any number of thermoplastic or thermosetting materials, including thermoplastic resins such as ionomeric, polyester, polyetherester or polyetheramide resins; thermoplastic or thermoset polyurethanes; natural or synthetic rubbers such as balata (natural or synthetic) or polybutadiene; or some combination of the above.

[0010] Golf balls are typically manufactured by various molding processes, whether one-component or multicomponent balls. Generally, the core of the golf ball is formed by casting, compression molding, injection molding or the like. If an intermediate boundary layer is desired, one or more intermediate boundary layers are added over the core by any number of molding operations, including casing, compression molding, and/or injection molding. The cover is then formed over the core and intermediate boundary layers, if present, through casting, compression molding, and/or injection molding.

[0011] One of the earliest disclosures of manufacturing a golf ball with dimples is set forth in U.S. Pat. No. 721,462 to Richards, which was filed on May 26, 1902. Richards discloses covering a core that is centered with pins within a spherical cavity of a mold, with a fluent gutta percha material. The gutta percha material is subjected to high pressure and then cooled within the mold to form a cover on the core.

[0012] Bowerman et al., U.S. Pat. No. 2,940,128, which was filed on May 14, 1958, discloses a method of manufacturing a rubber covered golf ball. Bowerman discloses separately forming rubber hemispherical covers on the core.

[0013] One of the earliest methods of manufacturing a polyurethane cover is disclosed in Gallagher, U.S. Pat. No. 3,034,791, which was filed on Apr. 26, 1960. Gallagher discloses forming polyurethane disks that are then molded over cores to create a polyurethane cover.

[0014] Another early method of manufacturing a polyurethane cover is disclosed in Ward, U.S. Pat. No. 3,147,324, which was filed on Oct. 20, 1960. Ward discloses using a liquid polyurethane prepolymer, either polyether-type or polyester-type, that is cured with a diamine. The liquid polyurethane is poured into a hemispherical mold cavity of a mold half, and a wound golf ball core is centered therein. Subsequently, a corresponding hemispherical mold cavity of a second mold half is filled with the liquid polyurethane. The first mold half with the wound core is then mated with the second mold half and allowed to cure for a set period of time.

[0015] A second Ward patent directed toward forming a polyurethane cover is U.S. Pat. No. 3,112,521, which was filed on Mar. 8, 1961. The '521 Ward patent discloses a method and apparatus for sensing the center of a wound core prior to placement in a mold filled with liquid polyurethane which is part of a complete casting machine. As with the '324 Ward patent, liquid polyurethane is poured into a hemispherical mold cavity of a mold half. However, in the '521 Ward patent, the wound core is more precisely centered prior to insertion into the polyurethane filled cavity. The entire process of the '521 Ward patent is performed on a rotatable annular platform.

[0016] Another example of a method for making a polyurethane cover is disclosed in Watson et al., U.S. Pat. No. 3,130,102, filed originally in Great Britain on May 19, 1960. Watson discloses a process for partially forming polyurethane half-shells for a golf ball, cooling them, then fusing them together on a core while imparting a dimple pattern thereon. Watson also demonstrates better cutting resistance for its polyurethane covered golf ball. An alternative of the Watson process for making a polyurethane cover on a golf ball is disclosed in a related patent to Ford et al., U.S. Pat. No. 3,177,280, filed originally in Great Britain on May 23, 1960. Ford discloses coating a core until the required thickness is applied, however, it still requires interrupting the curing, to place the coated core into a mold to impart a dimple pattern thereon.

[0017] Building upon Ford and Watson, U.S. Pat. No. 3,989,568 to Isaac discloses a process for using curing agents that have different reaction rates to partially cure a polyurethane half shell that is later placed on a core for further processing. Isaac discloses that a cover may be as thin as 0.025 inches using this process which involves two different diisocyanates and different amine curing agents. Dusbiber, U.S. Pat. No. 3,979,126, originally filed in February of 1965, discloses another method of making polyurethane half shells for a golf ball cover.

[0018] Brown et al., U.S. Pat. No. 5,006,297, filed on Feb. 22, 1989, discloses openly curing both halves of polyurethane cover in an initial mold, then compression molding the smooth covered golf ball to form a dimple pattern thereon. The initial molding step may use retractable or non-retractable pins to center the wound core while polyurethane flows about it.

[0019] Wu, U.S. Pat. No. 5,334,673 discloses the multiple step process of Ford and Watson using a slow-reacting polyamine curing agent. Wu et al., U.S. Pat. No. 5,692, 974 discloses the difficulty in manufacturing a commercially viable polyurethane covered golf ball due to the centering of the core within a partially cured mixture of polyurethane. The '974 Wu patent states that the 1993 Titleist® PROFESSIONAL was the first successful polyurethane covered golf ball.

[0020] Calabria et al., U.S. Pat. Nos. 5,733,428; 5,888,437; 5,897,884; and 5,947,843 all originate from an application filed on Jan. 21, 1994 which was a continuation-in-part application of an abandoned application filed on Jul. 6, 1992. The Calabria family of patents disclose a method and apparatus for forming a wound core golf ball with a polyurethane cover. The apparatus of Calabria, similar to that of the '521 Ward patent, inserts a wound core into a half mold cavity of partially cured polyurethane. Calabria discloses using a single insertion device for each individual mold. Calabria introduces the polyurethane mixture into a top mold half and after 50 to 80 seconds later a core is lowered at a controlled rate to prevent air bubbles, and a stop limits the downward movement of the core into the mold cavity. At a later time the bottom mold halves are filled with the polyurethane mixture. After another 50 to 80 seconds, the vacuum holding the core is released and mold halves are removed from the centering fixture. The top mold halves are then mated with the bottom mold halves and excess material resides in sprue channels. The mold halves are heated and pressurized for a predetermined period of time, and then demolded.

[0021] Herbert et al., U.S. Pat. No. 5,885,172, which was filed on May 27, 1997, discloses using the process of Calabria to form a polyurethane cover over a core with an inner layer thereon. Wu, U.S. Pat. No. 5,908,358, which was originally filed on Jun. 7, 1995, discloses using a four mold unit to manufacture golf balls with polyurethane covers.

[0022] Dewanjee, et al., PCT International Publication Number WO 99/43394, claiming priority from U.S. patent application Ser. No. 09/030,332, filed on Feb. 25, 1998 discloses a method for forming a polyurethane cover on a golf ball. Dewanjee discloses using a X-Y table to position mold halves under a mix head that dispenses the polyurethane mixture. The mold halves are then placed on a conveyor for transport to a core insertion station. The cores are then centered over each cavity through use of a pin on the mold half that engages with an aperture on the core holding unit. A second mold half is mated with the first mold half, and the mold is heated under pressure to form a polyurethane cover over the core. De-molding is accomplished through insertion of mold releasing pins into apertures of the mold halves.

[0023] Consequently, there remains a need for methods of manufacturing golf balls that do not suffer from the above disadvantages. Moreover, the methods would preferably decrease the production time to manufacture golf balls.

[0024] The mold assembly of the present invention is able to provide a solution to the problems of the prior art. The present invention is able to accomplish this by providing a novel mold assembly design that allows for a greater number of golf ball precursor products to be processed simultaneously, and allows for a more efficient transfer of heat during the casting process.

[0025] One aspect of the present invention is a mold assembly for forming a layer on a golf ball precursor product. The mold assembly includes a first mold half and a second mold half. The first mold half includes a first central hub mechanism having a first plurality of hemispherical cavities disposed circularly equidistant about the first central hub mechanism, and a second central hub mechanism having a second plurality of hemispherical cavities disposed circularly equidistant about the second central hub mechanism. The second mold half includes a third central hub mechanism having a third plurality of hemispherical cavities disposed circularly equidistant about the third central hub mechanism, and a fourth central hub mechanism having a fourth plurality of hemispherical cavities disposed circularly equidistant about the fourth central hub mechanism. The first and second central hub mechanisms engage with the third and fourth central hub mechanisms during mating of the first mold half with the second mold half.

[0026] Another aspect of the present invention is mold assembly that includes multiple-component first and second mold halves. The first and second mold halves each include a carrier base, a carrier plate, a plurality of mold inserts and a retainer plate. Each carrier base has a plurality of studs extending from an interior surface. Each carrier plate has a plurality of insert apertures with each having a first diameter and a plurality of hub apertures therein. Each carrier plate is mounted on the plurality of studs of the carrier base. Each of the plurality of mold inserts is disposed within a corresponding insert aperture of the plurality of insert apertures. Each retainer plate has a plurality of insert apertures with each having a second diameter. Each retainer plate is mounted on the carrier plate, and each of the plurality of insert apertures is positioned above a corresponding mold insert of the plurality of mold inserts.

[0027] Having briefly described the present invention, the above and further objects, features and advantages thereof will be recognized by those skilled in the pertinent art from the following detailed description of the invention when taken in conjunction with the accompanying drawings.

[0028] FIG. 1 is a side view of a mold assembly of the present invention.

[0029] FIG. 1A is a cross-sectional view of a golf ball.

[0030] FIG. 2 is a top plan view of a first mold half of the mold assembly of FIG. 1.

[0031] FIG. 3 is a cross-sectional view of the first mold half of FIG. 2.

[0032] FIG. 4 is a top plan view of a second mold half of the mold assembly of FIG. 1.

[0033] FIG. 5 is a cross-sectional view of the second mold half of FIG. 4.

[0034] FIG. 6 is a schematic top plan view of a mold half of the prior art.

[0035] FIG. 6A is a schematic top plan view of another mold half of the prior art.

[0036] FIG. 7 is a schematic side view of the mold half of FIG. 6.

[0037] FIG. 8 is a top plan view of a carrier base of a mold half of a mold assembly of the present invention.

[0038] FIG. 9 is a bottom plan view of a carrier plate of a mold half of a mold assembly of the present invention

[0039] FIG. 10 is a top plan view of a carrier plate of a mold half of a mold assembly of the present invention.

[0040] FIG. 11 is a top plan view of a retainer plate of a mold half of a mold assembly of the present invention.

[0041] FIG. 12 is a side view of a mold insert of the mold assembly of the present invention.

[0042] FIG. 13 is a top plan view of the mold insert of FIG. 12 illustrating the inverse dimple pattern of the cavity of the mold insert

[0043] FIG. 14 is a side view of a mold insert of FIG. 12 with a golf ball precursor product therein.

[0044] FIG. 15 is an enlarged top view of the retainer plate with an insert radial locating plate.

[0045] FIG. 16 is an enlarged view of a hub mechanism and mold inserts of a mold half of the mold assembly of the present invention.

[0046] As shown in FIGS. 1-5, a mold assembly for casting a layer of a thermoset material on a golf ball precursor product is generally designated 20, and is composed of a first mold half 22aand a second mold half 22b. In a preferred embodiment, the first mold half 22ais the top mold half and the second mold half 22bis the bottom mold half. The mold halves 22a-bare mated together during a casting process as set forth in co-pending U.S. patent application Ser. No. 09/496,126 filed Feb. 1, 2000, entitled System And Method For Cast Molding A Golf Ball, which is hereby incorporated in its entirety by reference.

[0047] As shown in FIG. 1, a set of golf ball precursor products 25 are placed within the first mold half 22awhich is inverted for mating with the second mold half 22b. The golf ball precursor products 25 may be a core (solid, liquid or hollow) that is wound or non-wound. Each golf ball precursor product 25 may also have one or more intermediate or boundary layers over the core portion. The thermoset material layer that is casted in the mold assembly 20 is preferably the cover layer 27cof the golf ball 27, however, it may also be the boundary layer 27b. A preferred thermoset material is polyurethane such as described in U.S. Pat. No. 6,117,024, entitled Polyurethane Cover For A Golf Ball, which pertinent parts are hereby incorporated by reference. However, those skilled in the relevant art will recognize that other thermoset materials may be used with the mold assembly 20 without departing from the scope and spirit of the present invention.

[0048] Referring again to FIGS. 1-5, each mold half 22a-bis generally composed of a carrier base 24, a carrier plate 26 and a retainer plate 28. Each mold half 22a-balso has a plurality of mold inserts 30 positioned within mold insert apertures 31 of the retainer plate 28 and mold insert apertures 33 of the carrier plate 26.

[0049] The carrier plate 26 is sandwiched between the carrier base 24 and the retainer plate 28. The carrier plate 26 carries the mold inserts 30 during the casting process. The retainer plate 28 is designed to lock each of the mold inserts 30 in the carrier plate 26. The carrier base 24 is the mold assembly's 20 contact surface during conveyance through a casting system.

[0050] Compared to the solid one-piece body mold halves 100a-bof the prior art illustrated in FIGS. 6, 6A and 7, each mold half 22a-bof the present invention is composed of multiple stacked components that minimize the mass of the mold assembly 20 while providing sufficient structural support to withstand the high pressure forces during the casting process. The multiple component structure of each mold half 22a-ballows for a more efficient transfer of heat to the mold halves 22a-bthan the prior art since there is less metal per mold cavity. Further, the mold halves 100a-bof the prior art had the cavities 102a-bas part of the body of the mold half 100a-b. The mold halves 22a-bare heated to prevent problems with the dispersion of the exothermic thermoset material into each mold cavity. Further, the mold assembly 20 is capable of casting a layer on a greater number of golf ball precursor products 25 than the prior art mold assemblies.

[0051] As shown in FIG. 8, the carrier base 24 has a substantially flat body 60 and is preferably composed of a rolled steel material. The thickness of the carrier base 24 is between 0.2 and 1.0 inches. The body 60 has two cut-outs 62a-blocated in the center for stopping on a casting apparatus. The body 60 also has two hub apertures 64a-bfor assembling of the mold half 22. The body 60 also has stud spacers 66a-dthat elevate the carrier plate 26 approximately 1.0 inch.

[0052] As shown in FIGS. 9 and 10, the carrier plate 26 is mounted on top of the carrier base 24. The carrier plate 26 has a body 70 has a thickness that is preferably between 0.3 and 1.0 inches. The body 70 is preferably composed of a mild steel material. The body 70 has two equal sets of insert apertures 33 for housing each of the mold inserts 30. Each set of insert apertures 33 is positioned about a hub aperture 72a-b. The insert apertures 33 are equidistant from their respective hub aperture 72, and equidistant from each other within the set. Preferably, the insert apertures each have a diameter that ranges from 2.00 to 3.00 inches, and each diameter is larger than the diameter of the mold insert 30. The body 70 also has locating apertures 74a-dat each corner for mounting locating pins 92a-band locating bushings 94a-b.

[0053] The locating pins 92a-band bushings 94a-bproperly align the mold halves 22a-bduring mating thereof to form the mold assembly 20. In a preferred embodiment, the locating pins 92a-bare diagonally opposed to each other on the second mold half 22b. The locating bushings 94a-bare disposed on the first mold half 22aEach locating pin 92a-bmay be extended or retracted for molding and de-molding purposes. The top of each locating pins 92a-bis tapered or indented for assistance during the de-molding separation of the first and second mold halves 22a-b. Alternatively, the locating pins 92a-bmay be fixed with a double tapered top.

[0054] The hub mechanisms 40 are placed through the afore-mentioned hub apertures 72a-bon each of the mold halves 22a-b. Each hub mechanism 40a-bfor the first mold half 22ahas a stud adapter 80, a spring 82, a backing plate 84 and a bolt 86. Each hub mechanism 40c-dfor the second mold half 22bhas a stud adapter 80, a spring 82, a backing plate 84 and a nut 88. When the first mold half 22ais mated with the second mold half 22b, each bolt 86 is connected with a corresponding nut 88. Preferably, the bolts 86 are threadingly connected to the nuts 88, and each bolt 86 has a spring 90 attached thereto to keep the bolt 86 extended through the carrier plate 26. Those skilled in the art will recognize that the bolts 86 may be used on the second or bottom mold half 22band the nuts 88 on the top or first mold half 22a. Further, those skilled in the art will recognize that each mold half 22a-bmay have one nut 88 and one bolt 86.

[0055] As shown in FIG. 11, the retainer plate 28 has a body 110 with a curved perimeter to reduce mass. The body is preferably composed of cold-rolled steel, and preferably has a thickness between 0.1 and 0.2 inches. The retainer plate 28 is designed to secure the mold inserts 30 within the carrier plate 26 with the minimum amount of mass. The retainer plate 28 has an equal number of insert apertures 31 as the insert apertures 33 of the carrier plate 26. Further, the insert apertures 31 are smaller in diameter than the insert apertures 33 of the carrier plate 26. The retainer plate 28 also has two hub apertures 112a-bwhich allow for engagement of the bolts 86 with the nuts 88. Each set of insert apertures 31 is positioned about a hub aperture 112a-b. The insert apertures 31 are equidistant from their respective hub aperture 112, and equidistant from each other within the set. Preferably, each of the insert apertures 31 has a diameter that ranges from 2.00 to 3.00 inches. The retainer plate 28 is secured to the carrier plate 26 using conventional methods.

[0056] FIGS. 12-14 illustrate the mold inserts 30 used with the mold assembly 20 of the present invention. Each mold insert 30 has a hemispherical cavity 32 within a body 34. Around a center height of the body 34 is an annular flange 36 that has an alignment flat 38 along a portion thereof The flange 36 is used for mounting each mold insert 30 on the carrier plate 26.

[0057] The hemispherical cavity 32 preferably has an inverse dimple pattern thereon if a cover 27cis formed in the mold insert 30. However, the hemispherical cavity 32 will have a smooth surface if a boundary layer 27b is formed in the mold insert 30. The number of mold inserts 30 used for each mold half 22a-bmay preferably range from eight to twelve, and is most preferably ten. In the preferred embodiment, as shown in FIGS. 2 and 4, five mold inserts 30a-eare positioned about hub mechanism 40a, five mold inserts 30f-jare positioned about hub mechanism 40b, five mold inserts 30k-oare positioned about hub mechanism 40c, and five mold inserts 30p-tare positioned about hub mechanism 40d. Those skilled in the art will recognize that more or less than five inserts may be positioned about each hub mechanism 40a-dwithout departing from the scope and spirit of the present invention.

[0058] As shown in FIGS. 15-16, each mold insert 30 of a set of mold inserts 30 is properly oriented using a insert radial locator plate 44 that is placed about the hub mechanism 40. Each insert radial locator plate 44a-dhas straight edges to oppose the alignment flat 38 of each of the mold inserts 30. Once the locator plate 44 and the respective mold inserts 30 are aligned, the mold inserts 30 and the locator plate 44 are locked together to prevent rotation thereby ensuring that the top and bottom mold inserts 30 are oriented properly when mated, to produce the correct dimple pattern on the golf ball. Further, each mold insert may be a replaceable mold insert as set forth in U.S. Pat. No. 6,171,091, entitled Replaceable Mold Inserts For Golf Balls, which pertinent parts are hereby incorporated by reference.

[0059] In a preferred casting process, each cavity 32 of each mold insert 30a-j, is filled with a flowable polyurethane mixture. The mixture is allowed to gel, or partially cure, then a golf ball precursor product 25 is inserted in each of the mold inserts 30a-jof the first mold half 22a. During this time, the cavity 32 of the mold inserts 30k-tof the second mold half 22b, have received a predetermined quantity of the flowable polyurethane mixture. The first mold half 22ais then inverted and mated with the second mold half 22bto form the mold assembly 20 with each mold insert 30a-jof the first mold half 22aaligning with a corresponding mold insert 30k-tof the second mold half 22b. The bolts 86 are then preferably threadingly engaged with the nuts 88.

[0060] From the foregoing it is believed that those skilled in the pertinent art will recognize the meritorious advancement of this invention and will readily understand that while the present invention has been described in association with a preferred embodiment thereof, and other embodiments illustrated in the accompanying drawings, numerous changes, modifications and substitutions of equivalents may be made therein without departing from the spirit and scope of this invention which is intended to be unlimited by the foregoing except as may appear in the following appended claims. Therefore, the embodiments of the invention in which an exclusive property or privilege is claimed are defined in the following appended claims.