System and method for forming a thermoset golf ball cover

Title

SYSTEM AND METHOD FOR FORMING A THERMOSET GOLF BALL COVER

Technical Field

The present invention relates to an apparatus and method for forming a golf ball cover

layer. More specifically, the present invention relates to an apparatus and method 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 sunounds 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 thermosetting materials, including

thermoplastic resins such as ionomeric, polyester, polyetherester or polyetheramide resins;

thermoplastic or thermoset polyurethanes; natural or synthetic mbbers 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 example of a conventional golf ball manufacturing process is described in U.S.

Patent No. 3,068,522, issued on December 18, 1962 ("the '522 patent"). The manufacturing

process disclosed in the '522 patent uses a molding press having upper and lower die portions

that sunound a golf ball core. A retractable seat contacts the golf ball core to place the same in

the desired orientation within the die cavity. The cover material is then injected into the die

cavity to form the cover of the ball. The '522 patent further discloses that the timing of the

retraction of the retractable seat is critical and depends, in part, on the flow rate of the cover

material into the mold cavity. In order to prevent the retardation of the flow rate or pre-

hardening of the injected coating material, the '522 patent teaches that in some instances, it may

be necessary to heat the molding dies and pre -heat the golf ball core to a temperature slightly

above ambient temperature.

Another example, U.S. Patent No. 5,194,191 ("the ' 191 patent"), issued March 16, 1993

discloses a method of preparing thread-wound golf balls. In the '191 patent, a rubber thread or material is wound around a frozen core of material to form a core. Immediately thereafter, the

core undergoes microwave heating to rapidly thaw the frozen core without heating the rubber

thread layer and without moisture condensation taking place on the surface of the core. The

method of the ' 191 patent allegedly reduces the core thawing time and eliminates the need for a

drying step.

These and other current golf ball manufacturing processes continue to suffer from a

number of disadvantages. For example, when the outer cover of the golf ball is made from a

thermoset material, e.g., thermoset polyurethane, the core and any intermediate boundary layer(s)

tend to undergo thermal expansion during the casting of the outer cover, as heat is generated by

the exothermic reaction of the thermoset processes used in the formation of the cover. As the

cover forms, and before the cover develops sufficient green strength, the thermal expansion of

the core and any intermediate boundary layer, in turn, may cause the outer cover of the golf ball

to fracture or crack. Although this problem is particularly relevant to covers that are formed of

thermoset polyurethane, it is not believed to be limited thereto. Similar problems may arise with

other materials and processes.

Cracking is not the only problem with the current conventional methods of manufacturing

golf balls. Since a temperature gradient exists between the core, intermediate layer, if any, and

the outer cover, the central portion of the ball acts as a heat sink that absorbs heat given off

during the cover-making process. In this regard, the reaction that takes place to cure the outer cover takes longer given the cooler temperature in the inner core of the ball. Production cycle

times are thus adversely increased.

Consequently, there remains a need for methods of manufacturing golf balls that do not

suffer from the above disadvantages. Moreover, a system and method that permits precision

centering of a core in relation to a cover is greatly desired.

Disclosure of the Invention

The present invention provides a method and system for automatically casting a

thermoset layer over a golf ball precursor product, such as a core with a boundary layer. The

present invention allows for a plurality of golf ball precursor products to be simultaneously cast

molded within a plurality of cavities containing the thermoset material. A prefened thermoset

material is a thermoset polyurethane material.

One aspect of the present invention is a method for casting a thermoset layer on each of a

plurality of golf ball precursor products. The method includes dispensing a flowable material

from a stationary dispenser into each of a plurality of cavities disposed on a first mold half and a

second mold half. The flowable material is a thermoset polymer material, precursor thermoset

polymer materials, or a mixture thereof. Next, each of the plurality of golf ball pre; αrsor

products is inserted into a conesponding cavity of the plurality of cavities of the first mold half.

Next, the first mold half is inverted and mated with the second mold half to form a mold

assembly to enclose each of the plurality of golf ball precursor products within a spherical cavity

to form a thermoset layer on each of the plurality of golf ball precursor products. Next, the mold assembly is heated to cure the th rmoset layer on each of the golf ball precursor products. After

curing, the mold assembly is separated into the first mold half and the second mold half to

expose each the plurality of golf ball precursor products with a thermoset layer thereon for

removal from the second mold half.

Another aspect of the present invention is a system for casting a thermoset layer on a golf

ball precursor product. The system includes a mold assembly having first and second mold

halves with each having a plurality of hemispherical cavities therein. The system also includes a

dispensing mechanism having a stationary dispenser and an X-Y gantry. The stationary

dispenser dispenses a flowable material into each of the plurality of cavities while the X-Y

gantry moves each of the mold halves in a figure eight pattern below it. The system also

includes an insertion mechanism having a plurality of vacuum cups for suctioning a plurality of

golf ball precursor products from a platen and moving downward along a longitudinal pathway.

The insertion mechanism also has a lifter for lifting the first mold half upward along the

longitudinal pathway toward the vacuum cups. The system also includes a mold assembly

mechanism for inverting the first mold half and mating it with the second mold half. The system

also includes a conveyor for transfening the mold assembly along the system, and a heating oven

for curing a thermoset layer on each of the golf ball precursor products. Finally, the system

includes a de-molding mechanism for separating the first mold half from the second mold half,

and removing each of the thermoset layered golf balls from the first mold half.

Brief Description of the Drawings FIG. 1 is a schematic view of a casting system.

FIG. 2 is a cross-sectional view of a golf ball manufactured using the present invention.

FIG. 3 is a front view of the dispensing station of the present invention.

FIG. 4 is a side view of the dispensing station of the present invention.

FIG. 5 is an isolated view of the figure eight pattern of dispensing into each of the

cavities of the first and second mold halves.

FIG. 6 is an isolated view of the X-Y gantry of the dispensing station.

FIG. 7 is a front view of the insertion station of the present invention.

FIG. 8 is a front view of the mold assembly station of the present invention.

FIG. 9 is a side view of a mold assembly utilized with the present invention.

FIG. 10 is a top plan view of top mold half of the mold assembly of FIG. 9.

FIG. 11 is a cross-sectional view of the top mold half of FIG. 10.

FIG. 12 is a top plan view of a bottom mold half of the mold assembly of FIG. 9.

FIG. 13 is a cross-sectional view of the bottom mold half of FIG. 12.

FIG. 14 is a plan view of a mold insert placed within a mold half of the mold assembly of

FIG. 9.

FIG. 15 is a top plan view of the mold insert of FIG. 14 illustrating the inverse dimple

pattern for creating a thermoset cover with a dimple pattern thereon.

FIG. 16 is a side view of the mold insert of FIG. 14 with a golf ball precursor product therein.

FIG. 17 is a top plan view of FIG. 16.

FIG. 18 is an isolated view of the mold assembly at the de-molding station prior to de-

molding.

FIG. 19 is an isolated view of the mold assembly at the de-molding station during de-

molding.

Best Mode(s) For Carrying Out The Invention

The casting system and method of the present invention is designed to be performed

automatically with minimal user contact. In a prefened embodiment, the present invention is

utilized to form a thermoset polyurethane cover over a core and boundary layer. The present

invention preferably processes ten golf balls simultaneously.

A preferred casting system 20 is shown in FIG. 1. The cycle of the system 20 begins

with mold halves preheated to a predetermined temperature in a preheating oven 22. The pre¬

heating prevents the cooling of the flowable thermoset material. From there, the mold halves are

transported on conveyors 24 and 25 to a dispensing station 26 where each cavity of each mold

half, is filled with the flowable thermoset material, preferably a thermoset polyurethane. The

mixture is allowed to gel, or partially cure for about 30 to 90 seconds, then a golf ball precursor

product is inserted in each of the mold cavities of one mold half at a core insertion station 28,

which will be described below in greater detail. Preferably, the golf ball precursor products are

heated to a predetermined temperature prior to insertion, such as described in co-pending U.S. Patent Application Number 09/296,197, entitled Golf Balls And Methods Of Manufacturing The

Same, which is hereby incorporated by reference. During this time, the cavities of a second mold

half have received a predetermined quantity of the flowable thermoset material, and the material

has been curing or gelling for about 30 to 90 seconds. After about 10 to 30 seconds, the first

mold half is transferred to a mold assembly station 30 to be inverted and mated with the second

mold half to form a mold assembly with each mold cavity of the first mold half aligning with a

conesponding mold cavity of the second mold half. The mold assembly is then transfened on

the conveyor 24 to a curing oven 32 where it is subject to temperatures between 140 to 220

degrees Fahrenheit at pressures of 1/3 to 2 tons per cavity for about 2 to 10 minutes. Then, the

mold assembly is partially cooled in a cooling oven 34. Next, the mold assembly is transfened

to a disassembly station 36 for separating the mold halves. The first mold half is placed on a

second conveyor line 25 and the second mold half is placed on the first conveyor line 24. Then,

the golf balls are removed from the second mold half at a removal station 38. The mold halves

are cleaned and inspected at an inspection station 40, then the process is repeated.

As shown in FIG. 2, a golf ball 50 has a core 52, an optional boundary layer 54 and a

cover 56. The golf ball precursor products 58 may be the core 52 alone (solid, liquid or hollow,

and wound or non- wound). However, preferably the golf ball precursor product 58 is the core 52

with one or more intermediate or boundary layers 54 over the core portion. The cover 56 is

preferably the thermoset material layer that is casted using the casting process mentioned above.

However, the boundary layer 54 may be the thermoset layer, and a cover may be formed over it. A prefened thermoset material i:i a thermoset 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 present invention without

departing from the scope and spirit of the present invention.

The dispensing station 26 is illustrated in FIGS. 3-6. The dispensing station 26 has a

stationary dispenser 41 for dispensing the flowable material from a mixing chamber to each of

the plurality of cavities 132 of each of the mold halves 122a-b. The mold halves 122a-b are

conveyed on conveyors 24 and 25 to an X-Y gantry 42. The X-Y gantry 42 moves each of the

mold halves 122a-b in a X direction and a Y direction making a figure eight pattern 44, as shown

in FIG. 5, to dispense a predetermined quantity of the flowable thermoset material into each of

the plurality of cavities 132. In a prefened embodiment, the flowable thermoset material is a

thermoset polyurethane that is dispsensed in an uncured flowable form in an amount ranging

from 1.0 to 4.0 grams, most preferably in an amount ranging from 2.0 to 3.5 grams, and most

preferably 2.5 grams. In operation, the stationary dispenser 41 begins with the first mold half

122a, and delivers a shot of the flowable thermoset material into a cavity 132, then the X-Y

gantry 42 moves the mold halves 122a-b to place another cavity 132 under the stationary

dispenser 41. The stationary dispenser 41 then delivers another shot of the flowable thermoset

material, and the operation is repeated until all of the plurality of cavities 132 have received the

flowable thermoset material. The dispensing of the flowable material into each cavity and the movement of the each cavity is preferably accomplished within 1.0 second. The operation is

preferably accomplished within 10 to 30 seconds, and most preferably within 22 seconds. After

the dispensing station 26, the first mold half 122a is conveyed to the insertion station 28 while

the second mold half is conveyed to the mold assembly station 30.

The insertion station 28 is illustrated in FIG. 7. The insertion station has a system 60 that

is mounted on a frame 62. The system 60 includes a source 64 of golf ball precursor products.

The source 64 is preferably a hopper that receives golf ball precursor products that have been

manufactured outside of the system 60 and heated as discussed above. The source 64 delivers

the golf ball precursor products in a predetermined pattern to a platen 66. The platen 66 moves

along a horizontal plane from a hopper position 70 to a removal position 72. The removal

position 72 is along a longitudinal pathway 74. In this manner, golf ball precursor products are

delivered from the source 64 to insertion mechanism 80.

The insertion mechanism 80 is disposed along the longitudinal pathway 74, and is

operable along this pathway 74. The insertion mechanism 80 includes a locating plate 82 with a

plurality of vacuum cups 84 connected thereto. The locating plate 82 has its movement

controlled by a servo motor 86 disposed within the mechanism 80. The servo motor 86 allows

the vertical movement of the locating plate 82 to be precisely controlled to effect precision

centering of each of the golf ball precursor products 58 within a cavity containing a thermoset

material. This precision centering allows for concentricity of the core 52 in relation to the cover

56, and possible boundary layer 54. A conventional computer processing unit ("CPU") 88, not shown, is programmed to control the activation and deactivation of the servo-motor 86. Thus,

the servo-motor 86 can be programmed to operate for a set time period, then stop, to effect

precision centering. This allows the present invention to center a golf ball precursor product 58

within a cavity without the need for a stop or other accessories for limiting the downward

progression of the golf ball precursor products. In one prefened embodiment, the servo-motor

86 controls a threaded screw 90 which is threadingly connected to the locating plate 82.

Each of the vacuum cups 84 are themselves movable between an insertion position and a

retraction position. The movement of the vacuum cups is preferably actuated by pneumatic

cylinders. However, a series of servo-motors may also be used to actuate the movement of the

vacuum cups 84. Each of the vacuum cups 84 has a recess, not shown, that is in flow

communication with a vacuum line, not shown, for exerting a vacuum on the golf ball precursor

product 58 for suctioning thereof into the recess, and for retaining the golf ball precursor product

58 therein during the insertion step.

A spacer plate 96 is mounted on the frame 62 along the longitudinal pathway 74. The

spacer plate 96 has a central aperture 98 therein for allowing the vacuum cups 84, with golf ball

precursor products attached thereto, to engage the cavities with the thermoset material therein.

A lifter mechanism 110 is disposed below the line of conveyance 24. The lifter

mechanism 110 has a pneumatic cylinder 112 for lifting a lifter plate 114 along the longitudinal

pathway 74. A first mold half 122a is disposed on the lifter plate 114 during its vertical

movement. A set of hooks, or other conventional locking means, engage the first mold half 122a to restrain its lateral movement during vertical movement along the longitudinal pathway 74.

The first mold half 122a, with the plurality of mold cavities 132 that each have previously

received a predetermined quantity of the thermoset flowable material from a dispenser at the

dispensing station 26, is transferred from the dispensing station 26 to the insertion station 28 by

the conveyor 24. A retractable limiting member is preferably utilized to limit movement of the

first mold half at the insertion station 28. The lifter mechanism 74 then lifts the first mold half

122a to an insertion position at the spacer plate 92. The lifter is set to elevate the first mold half

122a to a position for receiving each of the golf ball precursor products 58 into conesponding

cavities 132. A more detailed explanation of the insertion mechanism is set forth in co-pending

U.S. Patent Application Number 09/495,588, filed on an even date herewith, and entitled A Cast

Molding Insertion Apparatus, which is hereby incorporated by reference in its entirety.

From the insertion station 28, the first mold half is conveyed to the mold assembly station

30. At the mold assembly station 30, the first mold half, with the golf ball precursor products 58

therein, is positioned about an inverting mechanism 45. The inverting mechanism 45 has a pair

of grips 46 that grasp the sides of the first mold assembly 122a and invert and move it above the

second mold half 122b. The first mold half 122a is lowered for engagement with the second

mold half 122b. Preferably only 30 to 60 seconds elapse from the departure from the dispensing

station 26 to the assembly of the mold halves 122a-b, and most preferably only 42 seconds. A

pair of studs are then rotated to threadingly engage a pair of bolts for locking of the mold

assembly 120, and for exerting a predetermined pressure on each of the mold cavities 132. The mold assembly 120 is then convoyed to an oven for heating under pressure, and then to a cooling

oven.

As shown in FIGS. 9-13, a mold assembly for casting a layer of a thermoset material on a

golf ball precursor product is generally designated 120, and is composed of the first mold half

122a and a second mold half 122b. In a prefened embodiment, the first mold half 122a is the top

mold half and the second mold half 122b is the bottom mold half. A preferred mold assembly

120 is described in co-pending U.S. Patent Application Number 09/495,583 filed on an even date

herewith, entitled Golf Ball Casting Mold Assembly, which is hereby incorporated in its entirety

by reference. However, those skilled in the pertinent art will recognize that other mold

assemblies may be utilized with the present invention without departing from the scope and spirit

of the present invention.

Each mold half 122a-b is generally composed of a carrier base 124, a carrier plate 126

and a retainer plate 128. Each mold half 122a-b also has a plurality of mold inserts 130

positioned within mold insert apertures 131 of the retainer plate 128 and mold insert apertures

133 of the carrier plate 126. The canier plate 126 is sandwiched between the carrier base 124

and the retainer plate 128. The carrier plate 126 carries the mold inserts 130 during the casting

process. The retainer plate 128 is designed to lock each of the mold inserts 130 in the carrier

plate 126. The carrier base 124 is the mold assembly's 120 contact surface during conveyance

through a casting system.

FIGS. 14-17 illustrate prefened mold inserts 130 that are used with the mold assembly 120. Each mold insert 130 has a hemispherical cavity 132 within a body 134. Around a center

height of the body 134 is an annular flange 136 that has an alignment flat 138 along a portion

thereof. The flange 136 is used for mounting each mold insert 130 on the carrier plate 126.

The hemispherical cavity 132 preferably has an inverse dimple pattern thereon if a cover

56 is formed in the mold insert 130. However, the hemispherical cavity 132 will have a smooth

surface if a boundary layer 54 is formed in the mold insert 130. The number of mold inserts 130

used for each mold half 122a-b may preferably range from eight to twelve, and is most preferably

ten. In the prefened embodiment, as shown in FIGS. 10 and 12, five mold inserts 130a-e are

positioned about hub mechanism 140a, five mold inserts 13 Of-j are positioned about hub

mechanism 140b, five mold inserts 130k-o are positioned about hub mechanism 140c, and five

mold inserts 130p-t are positioned about hub mechanism 140d. Those skilled in the art will

recognize that more or less than five inserts may be positioned about each hub mechanism 140a-

d without departing from the scope and spirit of the present invention.

FIGS. 18 and 19 illustrate the mold disassembly mechanism 220 of the disassembly

station 214. The mechanism 220 has a top plate 222 and a bottom plate 224. The top plate has at

least two locking hooks 226a-b that engage the first mold half 22a. The top plate 222 also has a

pair of bolt disassemblers 228 for reversing the threaded engagement of bolts to the nuts. The

bottom plate 224 has at least two locking hooks 230a-b for engaging the second mold half 22b

during de-molding. The bottom plate 224 has a pneumatic cylinder 232 for vertical movement.

Both the top plate 222 and the bottom plate 224 have pneumatic cylinders 234 for lateral movement. In a prefened embodiment, the bottom plate 224 will have the pneumatic cylinders

234 on one side, and the top plate 222 will have the pneumatic cylinders on the opposite side to

create a shearing effect. An alternative embodiment has pneumatic cylinders 234 on both sides

of the bottom plate 224 and both sides of the top plate 222 with one side having a greater lateral

force than the other side for each of the plates 222 and 224.

During the disassembly operation, the mold assembly 20 enters the disassembly

mechanism 220 where the hooks 230a-b of the bottom plate engage and lock with the second

mold half 22b. The bottom plate 224 with the mold assembly 20 thereon, is then lifted for

engagement with the top plate 222. The hooks 226a-b of the top plate 222 engage and lock with

the first mold half 22a. The bolt disassemblers 228 engage and reverse the threaded engagement

of bolts 86a-b to the nuts 88a-b. The pneumatic cylinders 234 then exert a lateral force on the

top plate 222 in a first direction and a lateral force on the bottom plate 224 in a second direction

opposite the first direction allowing for the shearing of the mold assembly 20. A lateral force in

a third direction, opposite the first direction, may also be exerted on the top plate 222, however,

the lateral force in the third direction will be less than the lateral force in the first direction.

Similarly, a lateral force in a fourth direction, opposite the second direction, may also be exerted

on the bottom plate 224, however, the lateral force in the fourth direction will be less than the

lateral force in the second direction. The shearing effect allows for the golf balls to be pinched or

rolled out of the cavities 132 of the first mold half 122a while remaining in the cavities 132 of

the second mold half 122b. The first mold half 122a is also angled upward due to the tapered pin which may be retractable between a molding and de-molding position, or may be fixed with

double tapers. The angle of the tapered pin angles the cavities 132 of the first mold half 122a

relative to the cavities 132 of the second mold half 122b allowing for the rolling of the golf balls

from the cavities 132 of the first mold half 122a. A more detailed explanation of the de-molding

mechanism is set forth in co-pending U.S. Patent Application Number 09/495,879, filed on an

even date herewith, and entitled A De-Molding Apparatus For A Golf Ball, which is hereby

incorporated by reference in its entirety.

After the de-molding of the golf balls from the first mold half 122b, the bottom plate 224

is lowered with the second mold half 122b thereon which is then conveyed to the ball removal

station 216. The first mold half 122a remains engaged with the top plate 222 until a grip

mechanism, not shown, engages the first mold half 122b and removes it to a second conveyance

line 25. The de-molding system of the present invention allows for the golf balls to be removed

while they are still relatively hot, allowing for reduced production time.