Title
A GOLF BALL CASTING MOLD ASSEMBLY
Technical Field
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.
Background Art
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.
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.
Located outwardly of the core and any intermediate boundary layer is a cover.
The cover is typically made from any number of thermoplastic or thermo setting
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.
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 casting, 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.
One of the earliest disclosures of manufacturing a golf ball with dimples is set
forth in U.S. Patent Number 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.
Bowerman et al., U.S. Patent Number 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.
One of the earliest methods of manufacturing a polyurethane cover is disclosed in
Gallagher, U.S. Patent Number 3,034,791, which was filed on April 26, 1960. Gallagher
discloses forming polyurethane disks that are then molded over cores to create a
polyurethane cover.
Another early method of manufacturing a polyurethane cover is disclosed in
Ward, U.S. Patent 3,147,324, which was filed on October 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.
A second Ward patent directed toward forming a polyurethane cover is U.S.
Patent Number 3,112,521, which was filed on March 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.
Another example of a method for making a polyurethane cover is disclosed in
Watson et al., U.S. Patent Number 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. Patent Number
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.
Building upon Ford and Watson, U.S. Patent Number 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. Patent
Number 3,979,126, originally filed in February of 1965, discloses another method of
making polyurethane half shells for a golf ball cover.
Brown et al, U.S. Patent Number 5,006,297, filed on February 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.
Wu, U.S. Patent Number 5,334,673 discloses the multiple step process of Ford
and Watson using a slow-reacting polyamine curing agent. Wu et al., U. S. Patent
Number 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.
Calabria et al., U.S. Patent Numbers 5,733,428; 5,888,437; 5,897,884; and
5,947,843 all originate from an application filed on January 21, 1994 which was a
continuation-in-part application of an abandoned application filed on July 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.
Herbert et ah, U.S. Patent Number 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. Patent Number 5,908,358, which was originally filed on
June 7, 1995, discloses using a four mold unit to manufacture golf balls with
polyurethane covers.
Dewanjee, et ah, PCT International Publication Number WO 99/43394, claiming
priority from U.S. Patent Application Number 09/030,332, filed on February 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.
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.
Disclosure of the Invention
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.
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.
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.
Brief Description of the Drawings
FIG. 1 is a side view of a mold assembly of the present invention.
FIG. 1A is a cross-sectional view of a golf ball.
FIG. 2 is a top plan view of a first mold half of the mold assembly of FIG. 1.
FIG. 3 is a cross-sectional views of the first mold half of FIG. 2.
FIG. 4 is a top plan view of a second mold half of the mold assembly of FIG. 1.
FIG. 5 is a cross-sectional views of the second mold half of FIG. 4.
FIG. 6 is a schematic top plan view of a mold half of the prior art.
FIG. 6 A is a schematic top plan view of another mold half of the prior art.
FIG. 7 is a schematic side view of the mold half of FIG. 6.
FIG. 8 is a top plan view of a carrier base of a mold half of a mold assembly of
the present invention.
FIG. 9 is a bottom plan view of a carrier plate of a mold half of a mold assembly
of the present invention.
FIG. 10 is a top plan view of a carrier plate of a mold half of a mold assembly of
the present invention.
FIG. 1 1 is a top plan view of a retainer plate of a mold half of a mold assembly of
the present invention.
FIG. 12 is a side view of a mold insert of the mold assembly of the present
invention.
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.
FIG. 14 is a side view of a mold insert of FIG. 12 with a golf ball precursor
product therein.
FIG. 15 is an enlarged top view of the retainer plate with an insert radial locating
plate. 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.
Best Mode(s) for Carrying Out the Invention
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 22a and a second mold half 22b. In a preferred embodiment, the first mold
half 22a is the top mold half and the second mold half 22b is the bottom mold half. The
mold halves 22a-b are mated together during a casting process as set forth in co-pending
U.S. Patent Application Number 09/496,126 filed on an even date herewith, entitled
System And Method For Forming A Thermoset Golf Ball Cover, which is hereby
incorporated in its entirety by reference.
As shown in FIG. 1, a set of golf ball precursor products 25 are placed within the
first mold half 22a which 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 27c of the golf ball 27, however, it may
also be the boundary layer 27b. A preferred thermoset material is polyurethane such as
described in co-pending U.S. Patent Application Number 09/295,635, 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.
Referring again to FIGS. 1-5, each mold half 22a-b is generally composed of a
carrier base 24, a carrier plate 26 and a retainer plate 28. Each mold half 22a-b also 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.
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.
Compared to the solid one-piece body mold halves 1 OOa-b of the prior art
illustrated in FIGS. 6, 6A and 7, each mold half 22a-b of 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-b
allows for a more efficient transfer of heat to the mold halves 22a-b than the prior art
since there is less metal per mold cavity. Further, the mold halves lOOa-b of the prior art
had the cavities 102a-b as part of the body of the mold half lOOa-b. The mold halves 22a-
b are 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.
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-b located in the center for
stopping on a casting apparatus. The body 60 also has two hub apertures 64a-b for
assembling of the mold half 22. The body 60 also has stud spacers 66a-d that elevate the
carrier plate 26 approximately 1.0 inch.
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-d at each corner for mounting locating pins
92a-b and locating bushings 94a-b.
The locating pins 92a-b and bushings 94a-b properly align the mold halves 22a-b
during mating thereof to form the mold assembly 20. In a preferred embodiment, the
locating pins 92a-b are diagonally opposed to each other on the second mold half 22b.
The locating bushings 94a-b are disposed on the first mold half 22a. Each locating pin
92a-b may be extended or retracted for molding and de-molding purposes. The top of
each locating pins 92a-b is tapered or indented for assistance during the de-molding
separation of the first and second mold halves 22a-b. Alternatively, the locating pins 92a-
b may be fixed with a double tapered top.
The hub mechanisms 40 are placed through the afore-mentioned hub apertures
72a-b on each of the mold halves 22a-b. Each hub mechanism 40a-b for the first mold
half 22a has a stud adapter 80, a spring 82, a backing plate 84 and a bolt 86. Each hub
mechanism 40c-d for the second mold half 22b has a stud adapter 80, a spring 82, a
backing plate 84 and a nut 88. When the first mold half 22a is 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
22b and the nuts 88 on the top or first mold half 22a. Further, those skilled in the art will
recognize that each mold half 22a-b may have one nut 88 and one bolt 86.
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-b, which allow for engagement of the bolt 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.
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.
The hemispherical cavity 32 preferably has an inverse dimple pattern thereon if a
cover 27c is 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-b may 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-e are positioned about hub mechanism 40a, five mold inserts
30f-j are positioned about hub mechanism 40b, five mold inserts 30k-o are positioned
about hub mechanism 40c, and five mold inserts 30p-t are 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-d without departing from the scope
and spirit of the present invention.
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-d has 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 co-
pending U.S. Patent Application 09/310,785, entitled Replaceable Mold Inserts For Golf
Balls, which pertinent parts are hereby incorporated by reference.
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-j of the
first mold half 22a. During this time, the cavity 32 of the mold inserts 30k-t of the
second mold half 22b, have received a predetermined quantity of the flowable
polyurethane mixture. The first mold half 22a is then inverted and mated with the second
mold half 22b to form the mold assembly 20 with each mold insert 30a-j of the first mold
half 22a aligning with a corresponding mold insert 30k-t of the second mold half 22b.
The bolts 86 are then preferably threadingly engaged with the nuts 88.