U.S. patent application number 09/764110 was filed with the patent office on 2002-07-25 for apparatus and method for molding golf balls.
Invention is credited to Puniello, Paul A., Wilson, Robert A..
Application Number | 20020096801 09/764110 |
Document ID | / |
Family ID | 25069713 |
Filed Date | 2002-07-25 |
United States Patent
Application |
20020096801 |
Kind Code |
A1 |
Puniello, Paul A. ; et
al. |
July 25, 2002 |
Apparatus and method for molding golf balls
Abstract
The present invention is directed to a mold and method for
forming a golf ball with at least a core. The mold and method
comprise or use members with projections for forming multiple
dimples on the core. The members can be retractable pins or sleeves
or vent pins. In the case of the retractable pins, sets of pins
with multiple dimple projections on the ends thereof are used to
center the golf ball core within the mold. The members can have
circular or non-circular cross-sections so that the dimple-forming
projections can conform to any dimple pattern.
Inventors: |
Puniello, Paul A.; (Bristol,
RI) ; Wilson, Robert A.; (Sagamore, MA) |
Correspondence
Address: |
PENNIE & EDMONDS LLP
1667 K STREET NW
SUITE 1000
WASHINGTON
DC
20006
|
Family ID: |
25069713 |
Appl. No.: |
09/764110 |
Filed: |
January 19, 2001 |
Current U.S.
Class: |
264/278 ;
264/279; 264/279.1; 425/116; 425/125; 425/577 |
Current CPC
Class: |
A63B 37/0018 20130101;
A63B 37/002 20130101; A63B 37/0037 20130101; B29C 45/14819
20130101; A63B 37/0021 20130101; B29L 2031/545 20130101; A63B
37/0075 20130101; A63B 37/0078 20130101; A63B 37/0087 20130101;
A63B 45/00 20130101; A63B 37/0031 20130101; B29C 45/14073 20130101;
Y10S 425/812 20130101; A63B 37/00065 20200801; A63B 37/0003
20130101 |
Class at
Publication: |
264/278 ;
264/279; 264/279.1; 425/116; 425/125; 425/577 |
International
Class: |
B29C 033/12; B29C
070/70 |
Claims
What is claimed is:
1. A mold for forming a golf ball having a core, the mold
comprising: (a) at least one internal molding cavity for receiving
said core, said cavity defining an outer spherical surface; and (b)
at least two sets of members associated with each cavity, said
first set of members for contacting a first side of the core and
said second set of members for contacting a second side of the
core, each set further including at least two, separate parts where
each part has at least two projections at a free end for contacting
the core, said parts being movable between an extended position
where the projections are spaced from the outer spherical surface
and contact the core, and a retracted position where the
projections form a portion of the outer spherical surface of the
cavity.
2. The mold of claim 1, wherein the projections are hemispherical
in shape.
3. The mold of claim 1, wherein each projection forms a portion of
a hemispherical shape.
4. The mold of claim 1, further including: (a) a first mold plate
having at least one first hemispherical cavity and said first set
of members associated therewith; (b) a second mold plate having at
least one second hemispherical cavity and said second set of
members associated therewith such that upon mating the first mold
plate with the second mold plate, each first hemispherical cavity
and each second hemispherical cavity form each molding cavity, each
first set of members movable through the first mold plate and each
second set of members movable through the second mold plate.
5. The mold of claim 4, wherein each part is a pin.
6. The mold of claim 5, wherein each pin of the first set is
unaligned with each pin of the second set.
7. The mold of claim 5, wherein each pin of the first set is
aligned with each pin of the second set.
8. The mold of claim 4, wherein each set of members includes at
least three parts.
9. The mold of claim 1, wherein each part is a portion of a
sleeve.
10. The mold of claim 10, wherein the sleeve has a circular
perimeter.
11. The mold of claim 1, wherein the projections on each part are
spaced from one another.
12. The mold of claim 1, wherein the projections on each part are
spaced from the perimeter of the member.
13. The mold of claim 1, further including at least one runner
terminating in at least one gate for flowing a molten material into
said cavity; and an injection unit for injecting said molten
material through each runner into each cavity.
14. A mold for forming a golf ball having a core, the mold
comprising: (a) at least one internal molding cavity for receiving
said core; and (b) at least one pin having a first end, a spaced,
second end, and at least two projections at the second end for
contacting the core, each pin has a non-circular cross-sectional
shape between the first end and the second end.
15. The mold of claim 14, wherein the cross-sectional shape
includes at least two substantially circular portions.
16. The mold of claim 14, wherein the cross-sectional shape
includes three substantially circular portions arranged in a
triangle.
17. The mold of claim 14, wherein the cross-sectional shape
includes four substantially circular portions arranged in a
rectangle.
18. The mold of claim 14, wherein the circles are overlapping.
19. The mold of claim 14, further including at least one first pin
and at least one second pin diametrically opposed to the first
pin.
20. The mold of claim 14, wherein the cavity further defines an
outer spherical surface, and the pins are movable between an
extended position where the projections are spaced from the outer
spherical surface and a retracted position where the projections
form a portion of the outer spherical surface.
21. The mold of claim 14, wherein each pin projection has a
hemispherical shape with an apex and the apex of each pin is at a
different vertical position than the remaining apexes.
22. The mold of claim 14, further including at least one runner
terminating in at least one gate for flowing a molten material into
said cavity; and an injection unit for injecting said molten
material through each runner into each cavity.
23. A mold for forming a golf ball having at least a core, the mold
comprising: (a) at least one internal molding cavity for receiving
said core, said cavity defining an outer spherical surface; and (b)
at least one stationary member associated with each cavity, each
including at least two projections at a free end where the
projections form a portion of the outer spherical surface of the
cavity.
24. The mold of claim 23, wherein the stationary member includes a
non-circular cross-section between the free end and a spaced
end.
25. The mold of claim 23, wherein the stationary member includes at
least three projections.
26. The mold of claim 25, wherein the projections are hemispherical
in shape.
27. The mold of claim 23, wherein the stationary member includes at
least one primary vent cutout in the outer surface.
28. The mold of claim 27, wherein the stationary member further
includes at least one secondary vent in the outer surface extending
from the primary vent.
29. The mold of claim 28, wherein the primary vent has a first
depth and the secondary vent has a second depth greater than the
first depth.
30. The mold of claim 23, further including at least one runner
terminating in at least one gate for flowing a molten material into
said cavity; and an injection unit for injecting said molten
material through each runner into each cavity.
31. A method of molding a golf ball comprising the steps of: (a)
providing a core; (b) providing at least one internal molding
cavity defining an outer spherical surface; (c) providing at least
one pin having at least two projections at a free end of each pin
for contacting the core; (d) placing said core between the pins so
that the core is centered within the cavity; (e) disposing material
in said cavity until the material covers said core and forms a
layer; and (f) solidifying the material of the layer such that the
projections on each pin form corresponding depressions in the
layer.
32. The method of claim 31, further including providing pins with
hemispherical projections such that the resulting depressions are
dimples.
33. The method of claim 31, wherein the step of providing the core
further includes providing the core with at least one layer of
material on a center.
34. The method of claim 31, wherein the step of providing pins
further includes providing non-movable pins.
35. The method of claim 31, wherein the step of providing pins
further includes providing movable pins.
36. The method of claim 31, wherein the layer is a cover having at
least one of a dimple coverage of greater than about 60 percent, a
hardness from about 35 to 80 Shore D, or a flexural modulus of
greater than about 500 psi, and wherein the golf ball has at least
one of a compression from about 50 to 120 or a coefficient of
restitution of greater than about 0.7.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to the manufacture of golf
balls, and more particularly, to an apparatus and method for
molding golf balls including improved components.
BACKGROUND OF THE INVENTION
[0002] Conventional golf balls generally include a core surrounded
by a cover. The cover forms a spherical outer surface of the ball
and the surface includes a plurality of dimples. Typically the term
"land" means the area of the outer surface of the ball not covered
with dimples so that the land area is the outer surface of the ball
between dimples.
[0003] Conventional dimples are circular depressions that act to
reduce drag and increase lift. By using dimples to decrease drag
and increase lift, golf ball flight distances have increased. The
circumference of each dimple is the edge formed where the dimple
wall slopes away from or intersects the land area of the outer
surface. Since the geometry about the dimple circumference
principally determines ball drag and lift, conventional dimple
patterns have been designed to optimize dimple circumberence to
reduce drag and increase lift.
[0004] Injection molding is a conventional method for forming the
cover or an intermediate layer. According to well-known techniques,
injection molding generally utilizes a mold and an injection unit.
Referring to FIG. 1, a lower mold half 5 of a conventional
injection mold is shown. The lower mold half fits into a bottom
mold plate (not shown) and defines a hemispherical molding cavity
10 for receiving the core. The plate defines a runner system (not
shown) for transporting a molten, cover material to one or more
gates 15. The gates 15 allow the material to enter the cavity 10
from the runner system.
[0005] The mold also includes a plurality of separate, retractable
pins 20, a vent pin (not shown) and a cluster block 25. The cluster
block 25 defines bores for each pin 20 so that the pins extend
therethrough and are affixed thereto. The pins 20 and the vent pin
contact the core in generally the pole area of the core. Typically,
the outer surface of the mold cavity includes a plurality of
hemispherical projections 30 for forming the majority of the
dimples on the ball. The vent pin usually does not move and
typically includes a free end shaped to form a dimple or land area
depending on its location with respect to the dimple pattern being
formed. An upper mold half and top plate of a similar configuration
are also used.
[0006] One molding cycle for forming a golf ball includes a number
of steps. When the top and bottom plates and lower and upper mold
halves are separated, the core is placed within the bottom
hemispherical molding cavity 10 on the pins 20, and the mold plates
are closed to form a spherical cavity around the core. The pins
center the core in the spherical cavity during molding. Then, the
injection unit forces the molten, cover material through the runner
system and gates into the molding cavity, until the cavity is
filled and the material surrounds the core. The pins begin to
retract as the material comes into close proximity to the pins. The
material flows and fills the apertures in the material caused by
the pins. As the material cools, it solidifies in the shape of the
molding cavity around the core to form the golf ball. When the
material is sufficiently cool, the mold plates and mold halves are
again separated and the retractable pins are extended to separate
the formed golf ball from the outer surface of the cavity also
known as ejecting the ball from the mold. Then, mold is made ready
for another molding cycle.
[0007] The retractable pins are located where a dimple or land area
will be formed on the ball. If the retractable pins are located in
dimple spaces, which are shaded areas 35 in FIG. 2, the free ends
are substantially hemisphere-shaped (as shown in FIG. 1). In the
retracted position during molding, each hemisphere-shaped, free end
forms a single dimple in the outer surface of the ball. If the
retractable pin is located in the land area, each such free end is
shaped like the land area. As a result, in the retracted position
during molding, these free ends form the associated, land areas.
There are several drawbacks to these configurations.
[0008] Generally, golf balls have 300 to 500 circular dimples with
a conventional sized dimple having a diameter that ranges from
about 0.120 inches to about 0.180 inches. The retractable pins have
similar dimensions at the free end to form the dimples. This leads
to small surface areas at the free ends for each of the retractable
pins. During ejection, since the free end surface area of each
retractable pin is so small, the force each pin exerts on the ball
is great. Accordingly, concentrated, high stresses are applied to
the ball by the pins during ejection. These stresses can damage the
ball in these areas so that extensive post-mold finishing, such as
vibration tumbling, is done to make the balls playable. This is
undesirable. In addition, the retractable pins slide with respect
to the mold halves. This sliding forms "witness lines" about the
pins in the retracted position. The clearance between the pins and
the mold that causes these witness lines is about 0.0005 to 0.001
inches.
[0009] Another drawback is related to material flow during
injection. When the material contacts the pins during molding, the
pins are colder than the molten material. As a result, the molten
material contacts the pins and begins to solidify about the pins,
and the remaining molten material forms the cover. This also
results in the formation of witness lines.
[0010] During retraction of the pins, when the material is packed
around the pins, the pins can draw the material into the pin
clearance between the pin and the mold. This material is often
referred to as "flash material." Flash material can also be formed
when there is wear between the pins and the mold.
[0011] Post-mold finishing is conducted to remove the witness lines
and flash material. Finishing to remove witness lines and flash on
the dimple circumference can cause uncontrolled rounding of the
dimple edges that can alter the flight characteristics of the ball
undesirably. One way to reduce forming such material on the dimple
circumference is to configure the pin so that the diameter of the
pin is greater than the maximum dimple diameter. Such a mold is
disclosed in Japanese Publication No. 61-213068. However, this mold
has the drawback of requiring significant ejection force as
discussed above.
[0012] An alternative to centering the core on pins throughout
molding is disclosed in U.S. Pat. No. 3,068,552 entitled "Method
and Apparatus for Molding Covers on Spherical Bodies" to Nickerson
et al. This patent discloses a molding press with hemispherical
cavities and a horizontally movable, retractable seat with an inner
curved surface with the same radius of curvature as that of the
wall of the cavity. The seat further includes a multiplicity of
rectangular or rounded projections to form the checkered or dimpled
outer surface on the completed golf ball. The patent further
requires that the area of the curved surface of the seat be within
certain limits; i.e., not more than 40% nor less than about 10% of
that of the complete cavity wall and hence that of the spherical
resilient, wound core. In the extended position, each retractable
seat holds the core in an eccentric position. During molding, the
patent discloses the core is moved from the eccentric position to
the center of the mold. One drawback is that beginning in the
eccentric position, it would be difficult to complete molding with
a centered core. This would likely be partially due to gravity
acting on the core during molding and moving the core downward.
Another drawback is that no vent is shown in the seat, without this
vent air would be trapped in the seat during molding and would
create a void in the cover that is undesirable.
[0013] Consequently, a need exists for an improved molding
apparatus and method for manufacturing a golf ball. The apparatus
and method should decrease the likelihood of damaging the cover
during ejection, and allow formation of the cover in such a way
that post-mold finishing minimally changes the dimple circumference
and requires less time than in conventional processes.
SUMMARY OF THE INVENTION
[0014] The present invention is directed to a mold for forming a
golf ball having a core. The mold comprises at least one internal
molding cavity for receiving the core. The cavity defines an outer
spherical surface. The mold also comprises at least two sets of
members associated with each cavity. The first set of members
contact a first side of the core and the second set of members
contact a second side of the core. Each set further includes at
least two, separate parts where each part has at least two
projections at a free end for contacting the core. The parts are
movable between an extended position where the projections are
spaced from the outer spherical surface and contact the core, and a
retracted position where the projections form a portion of the
outer spherical surface of the cavity.
[0015] Preferably, the projections on the parts have a
hemispherical shape or form a portion of a hemispherical shape. The
parts can be pins or portions of a sleeve.
[0016] According to another aspect of the present invention, the
inventive mold as discussed above includes at least one internal
molding cavity, and at least one pin having a first end, a spaced,
second end, and at least two projections at the second end for
contacting the core. According to one feature of this invention,
each pin has a substantially non-circular cross-sectional shape
between the first end and the second end. In one embodiment, the
cross-sectional shape of each pin includes at least two
substantially circular portions. These circular portions can be
overlapping or non-overlapping.
[0017] The present invention is also directed to a mold that
comprises at least one internal molding cavity for receiving the
core, and at least one stationary member associated with each
cavity. The member includes at least two projections at a free end,
where the projections form a portion of the outer spherical surface
of the cavity.
[0018] In one embodiment, the stationary member includes a
substantially, non-circular cross-section between the free end and
a spaced end. In another embodiment, the stationary member includes
at least three projections. In this embodiment, the projections are
hemispherical in shape. In still another embodiment, the stationary
member includes at least one primary vent cutout in the outer
surface at the free end, and possibly at least one secondary vent
in the outer surface extending from the primary vent.
[0019] It is possible that the above-described molds are injection
molds and further include at least one runner terminating in at
least one gate for flowing a molten material into the cavity; and
an injection unit for injecting the molten material through each
runner into each cavity.
[0020] The present invention is also directed to a method of
molding a golf ball comprising the steps of: providing a core;
providing at least one internal molding cavity defining an outer
spherical surface; providing at least one pin having at least two
projections at a free end of each pin for contacting the core;
placing the core between the pins so that the core is centered
within the cavity; disposing material in the cavity until the
material covers the core and forms a layer; and solidifying the
material of the layer such that the projections on each pin form
corresponding depressions in the layer.
[0021] In one embodiment, the pins have hemispherical projections
such that the resulting depressions are dimples. In another
embodiment, the step of providing the core further includes
providing the core with at least one layer of material on a center.
In yet another embodiment, the step of providing pins further
includes providing non-movable pins or movable pins.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is an enlarged, perspective view of a lower mold half
of a prior art injection mold, wherein a plurality of retractable
pins are in an extended position and a portion is broken away for
clarity;
[0023] FIG. 2 is a perspective view of a prior art golf ball seen
from the bottom showing the locations of contact between the
retractable pins of FIG. 1 and the ball surface;
[0024] FIG. 3 is a perspective view of a golf ball according to the
present invention;
[0025] FIG. 4 is a cross-sectional view of the golf ball of FIG.
3;
[0026] FIG. 5 is a cross-sectional view of another embodiment of a
golf ball of the present invention;
[0027] FIG. 6 is an exploded view of upper and lower mold halves of
the injection mold of the present invention in an open position
with a golf ball core therebetween, wherein the retractable pins
are in an extended position;
[0028] FIG. 7 is an enlarged, perspective view of the lower mold
half of FIG. 6 having a portion broken away for clarity;
[0029] FIG. 8 is a partial, enlarged, perspective view of one pin
of FIG. 7;
[0030] FIG. 9 is a cross-sectional view of the retractable pin
along line 9-9 of FIG. 8;
[0031] FIG. 10 is an enlarged, perspective view of the golf ball of
FIG. 3 as seen from the bottom showing the locations of contact
between the retractable pins of FIG. 7 and the ball surface;
[0032] FIG. 11 is a cross-sectional view of the mold halves of FIG.
6 in a closed position, wherein the pins are in an extended
position and it is prior to molding a cover;
[0033] FIG. 12 is a cross-sectional view of the mold halves of FIG.
11 wherein the pins are in a retracted position and it is after
molding the cover;
[0034] FIG. 13 is an enlarged, perspective view of a second
embodiment of the lower mold half of FIG. 6 having a portion broken
away for clarity;
[0035] FIG. 14 is a partial, enlarged, perspective view of one pin
of FIG. 13;
[0036] FIG. 15 is a cross-sectional view of the retractable pin
along line 15-15 of FIG. 14;
[0037] FIG. 16 is an enlarged, perspective view of the golf ball of
FIG. 3 as seen from the bottom showing the locations of contact
between the retractable pins of FIG. 13 and the ball surface;
[0038] FIG. 17 is an enlarged, perspective view of a third
embodiment of the lower mold half of FIG. 6 having a portion broken
away for clarity;
[0039] FIG. 18 is a partial, enlarged, perspective view of one pin
of FIG. 17;
[0040] FIG. 19 is a cross-sectional view of the retractable pin
along line 19-19 of FIG. 18;
[0041] FIG. 20 is an enlarged, perspective view of the golf ball of
FIG. 3 as seen from the bottom showing the locations of contact
between the retractable pins of FIG. 17 and the ball surface;
[0042] FIG. 20A is a partial, enlarged, perspective view of another
embodiment of a pin of the present invention;
[0043] FIG. 20B is an enlarged, perspective view of the golf ball
of FIG. 3 as seen from the bottom showing the locations of contact
between the retractable pins formed like the pin shown in FIG. 20A
and the ball surface;
[0044] FIGS. 21 and 22 are perspective views of various alternative
embodiments of retractable members according to the present
invention;
[0045] FIGS. 21A and 22A are top views of the retractable members
shown in FIG. 21 and 22, respectively;
[0046] FIG. 23 is an enlarged, cross-sectional view of another
embodiment of a lower mold half of the present invention;
[0047] FIG. 24 is a partial, top view of the lower mold half shown
in FIG. 23 inserted into a bottom mold plate;
[0048] FIG. 25 is a perspective view of a multi-dimple vent pin for
use with the mold half of FIG. 23;
[0049] FIG. 25A is an enlarged, perspective view of a portion of
the pin within the dashed circle 25A of FIG. 25; and
[0050] FIG. 26 is top view of the vent pin of FIG. 25.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0051] Referring to FIGS. 3 and 4, this invention is related to a
golf ball 50 which comprises a core 55 surrounded by at least one
cover layer 60. The cover layer forms the outer surface of the ball
which defines dimples 65 therein.
[0052] Suitable core materials include thermosets, such as styrene
butadiene rubber, polybutadiene, polyisoprene; thermoplastics such
as ionomer resins, polyamides or polyesters; or a thermoplastic
elastomer. Suitable thermoplastic elastomers include but are not
limited to Pebax.RTM., Hytrel.RTM., thermoplastic urethane, and
Kraton.RTM., which are commercially available from Elf-Atochem,
DuPont, various manufacturers, and Shell, respectively. The core
material can also be formed from a castable material. Suitable
castable materials include, but are not limited to urethane,
polyurea, epoxy, and silicone.
[0053] Preferably, the cover 60 is tough, cut-resistant, and
selected from conventional materials used as golf ball covers based
on the desired performance characteristics. The cover may be
comprised of one or more layers. Cover materials can be injection
moldable, such as ionomer resins, blends of ionomer resins,
thermoplastic urethane, and polyisoprene and blends thereof, as
known in the art. However, the present invention is not limited
thereto and other materials such as castable resins can also be
used.
[0054] Referring to FIG. 5, this invention is also related to a
golf ball 70 that includes a core 75 surrounded by a cover layer
80, and at least one intermediate layer 85 disposed therebetween.
Although the golf balls 50 and 70 are shown with solid cores the
present invention can also be used with fluid-filled cores. The
fluid within the core can be a wide variety of materials including
air, water solutions, liquids, gels, foams, hot-melts, other fluid
materials and combinations thereof, as known by those of ordinary
skill in the art. The intermediate layer 85 can be formed by
molding conventional core, mantle layer or cover layer materials on
the core or the intermediate layer can be formed by winding
non-elongated or elongated thread on the core. Examples of
materials for forming the thread include thermoset materials,
synthetic cis-1,4 polyisoprene rubber, natural rubber, blends of
synthetic and natural rubber, thermoplastic materials,
poly(p-phenylene terephthalamide), natural fibers, glass fiber,
mineral fibers such as silicates, vegetable fibers such as
cellulosic and animal fibers, or metallic materials. The present
invention is not limited to these materials and any material known
by those of ordinary skill in the art can be used. In an
alternative embodiment, the ball 70 can be formed with any number
of intermediate layers formed in any manner. These layers can be
solid or wound.
[0055] Referring to FIGS. 6-11, this invention is directed to
molds, and more specifically injection molds, such as mold 100 that
generally includes members that form more than one dimple on a
sphere, such as a golf ball. This invention, however, is not
limited to injection molds and can be used for example with
non-injected materials. The present invention can be utilized with
various configurations of molds and dimples, and thus the present
invention is not limited to any particular types of molds or
dimples shown and discussed below.
[0056] The mold 100 according to the present invention includes
upper and lower mold halves 110 and 115 located within
conventional, top and bottom mold plates (not shown). Each half 110
and 115 defines a hemispherical molding cavity 120 and 125 (best
seen in FIG. 11), respectively. The halves 120 and 125 each further
include hemispherical outer surfaces 130 and 135, respectively. The
hemispherical surfaces 130 and 135 include a plurality of
hemispherical projections 136 for forming the majority of the
dimples 65 (as shown in FIG. 3) on the ball 50. Although the mold
is shown with one pair of upper and lower mold halves forming one
spherical cavity, molds can include more than one pair of mold
halves to form a plurality of spherical cavities.
[0057] As best seen in FIGS. 7 and 11, the halves 110 and 115
define bores there through for receiving sets 140 and 145 of
separate, retractable pins or members. Each set of pins 140, 145
includes five retractable pins. The sets of pins are coupled
together with a cluster block 150. A non-movable, vent pin (not
shown) is also used with the mold halves as know by those of
ordinary skill in the art.
[0058] Referring to FIG. 11, the first set of retractable pins 140
extend from the top half 110 in a first direction into the cavity
120. The second set of retractable pins 145 extend from the bottom
half 115 in a second direction opposite the first direction into
the cavity 125. The pins of set 140 are aligned with the associated
pins of the set 145. In another embodiment, the sets of pins can be
unaligned. For example, when molding an icosahedron pattern with
392 dimples, with the appropriate dimple layout three pins can be
in each set and the pins of each set can be 180.degree. out of
phase with one another.
[0059] Referring to FIGS. 7 and 8, free ends 155 of each of the
retractable pins in the set 145 have a surface 160, which is planar
and angularly offset from the vertical outer surface 170 of the
pin. Each pin in the set 145 further includes a plurality of
projections 175 extending outwardly from the surface 160. The
projections 175 in this embodiment are hemispherical and spaced
from one another. The projections have the opposite curvature than
the outer spherical surfaces 130, 135 of the cavity lacking the
projections 136. There are three projections 175 on each pin, which
are arranged in a triangular configuration. Each of the pins in the
sets 140 and 145 have a similar configuration. Referring to FIG. 9,
each of the pins in the sets 140, 145 has a circular,
cross-sectional shape between the ends.
[0060] During use, as discussed below, the projections 175 form a
plurality of dimples and the surface 160 of the pins without
projections 175 is configured to form the land area between
dimples. Thus, the tips of the pins are shaped or textured to
conform to the radius and negative dimple pattern of the golf ball
mold cavity.
[0061] The retractable pins 140, 145 center the golf ball core 55
within the spherical cavity so that the core 55 is spaced from the
cavity surfaces 130, 135. The retractable pins 140 and 145 are
movable between an extended position (as shown in FIG. 11) and a
retracted position (as shown in FIG. 12). In the extended position,
the projections 175 (as shown in FIG. 8) are spaced from the outer
surface 135 of the mold half 115 and contact core 55. In the
retracted position, the pins 140 and 145 are flush with the cavity
surfaces 130, 135 to form a portion thereof. In the retracted
position, the pins 140, 145 are also spaced from the core 55.
[0062] Referring again to FIG. 6, the mold halves 110, 115 and top
and bottom plates have planar surfaces 180. The halves 110, 115 and
top and bottom mold plates move between open and closed positions.
In the open position (shown in FIG. 6), the halves and mold plates
(not shown) are spaced apart.
[0063] Referring to FIG. 11, in the closed position, the surfaces
180 of the halves 110, 115 and mold plates are in contact except at
gates 185. In this position, the hemispherical cavities 120, 125
form an internal, spherical molding cavity. Runners or passages 190
are formed between the halves and the plates. The runners 190
terminate at the outer surfaces 130, 135 of the halves at gates
185. The gates 185 are openings through which molten material
enters the spherical cavity from the runners 190.
[0064] Now, the operation of the apparatus will be discussed with
reference to FIGS. 11 and 12. With the pins 140 and 145 in the
extended position, the core 55 is placed between the pins 140 and
145 so that the core is centered within the cavities 120, 125. An
injection unit (not shown) forces the molten material 195 into the
spherical cavity. This continues until enough of the molten
material has been injected to cover the core 55. After the molten
material 195 contacts the core 55, the pins 140 and 145 are
retracted in the direction of the arrows A. Retraction continues
until the projections 175 (best seen in FIG. 8) form a portion of
the spherical surfaces 130, 135. Then, the molten material 195 is
solidified to define the cover layer 60 (as shown in FIG. 4).
[0065] Once the cover layer is formed, it can be seen in FIG. 10,
where the retractable pins 145 contact the ball 50 about the lower
pole P. The contact areas of the pins is shaded within the circle
C. The diameter of the contact circle d.sub.C is equal to the
diameter of each pin d.sub.p (as shown in FIG. 9). The projections
175 are within the contact circle C and form the non-overlapping
dimples 200, 205, and 210. Within each contact area, where the pins
145 contact the ball, three dimples are formed by the projections
on the end of each pin.
[0066] The total surface area of the free ends of all of the pins
is less than about 10% of the ball surface area. This total surface
area is calculated using the surface area of the projections for
each pin combined. More preferably, the total surface area of the
free ends of all of the pins is less than or equal to about 5% of
the ball surface area. In a ball with a 300 dimple pattern with
about 70% dimple coverage of the ball surface area, if four dimples
are formed by two pins with two projections each, the total surface
area of the pins free ends is about 1% of the ball surface area. In
a ball with a 500 dimple pattern with about 80% dimple coverage of
the ball surface area, if thirty dimples are formed by ten pins
with three projections each, the total surface area of the pins
free ends is about 5% of the ball surface area. The above
calculations based on dimples assume that the all of the dimples
have the same diameter.
[0067] Referring to FIG. 8, thus the projections 175 form dimples
in the cover and the remaining area of the free ends 160 forms land
area of the ball about the dimples. The pins 140 (as shown on FIG.
11) similarly contact the ball at an upper pole to form groups of
dimples there about.
[0068] Referring to FIGS. 7, 10, and 11, preferably, the pins 140,
145 are for use in forming a ball with a dimple pattern of which at
least two dimples and surrounding land area are within the contact
circle C without bisecting any adjacent surrounding dimples. In the
dimple pattern on ball 50, three dimples 200, 205, and 210 are
within contact area C. In another embodiment, at least two
projections can be formed on each pin such projections form dimples
and bisect and/or contact dimples outside a contact circle.
[0069] Referring to FIGS. 13 and 14, an alternative embodiment of a
lower mold half 215 is shown. The mold half 215 includes a set of
retractable pins 245 slidable therethrough. Each pin 245 in set
includes a planar free end surface 260 having outwardly extending
projections 275a, 275b, and 275c thereon. The projections 275a-c
are spaced from one another. The projections 275a and 275b are
shaped like half of a hemisphere. The projection 275c is shaped
like a complete hemisphere. The pins 245 have a circular diameter
d.sub.p (as shown in FIG. 15). The lower mold half 215 is used with
a similarly configured upper half, as disclosed above to form the
cover layer on ball 280 (as shown in FIG. 16).
[0070] Referring to FIGS. 13-16, the contact area of the pins 245
is shaded and within the contact area circle C. The diameter of the
contact area d.sub.C is equal to the diameter of each pin d.sub.p.
The other pins in the upper half similarly contact the ball at an
upper pole. The partial projection 275a forms a portion of the
dimple 300. The partial projection 275b forms a portion of the
dimple 305. The completely hemispherical dimple 275c forms the
entire dimple 310 (shown in phantom). The remaining portions of the
dimples 300 and 305 not formed by the pins are formed by
projections on the outer surface of the mold half 215. Thus, in the
dimple pattern on ball 280, the contact area C bisects dimples 300
and 305. The remaining surface of end surface 260 forms the land
area between dimples.
[0071] Referring to FIGS. 17 and 18, a preferred embodiment of a
lower mold half 415 is shown. The mold half 415 includes a set of
retractable pins 445 slidable therethrough. Each pin 445 in the set
includes three substantially cylindrical portions 445a-c (as best
shown in FIG. 19) so that the cross-sectional shape of the pins
between its ends is non-circular. Since the cross-section of each
portion 445a-c is a non-overlapping circle, the cross-sectional
area of each pin has a substantially three-leaf, clover shape
between the ends. The perimeter of each pin is indicated as P. The
bore through the mold halves for use with pins 445 have the same
clover shape as the pin perimeter P to allow passage of the pins
therethrough. The bores can be formed by either conventional or
wire electrical discharge machining. The bores can alternatively be
formed by other processes such as milling, honing and drilling, but
the present invention is not limited to formation be the
above-mentioned processes. The dimensions of the bores and pins can
be selected as known by those of ordinary skill in the art to allow
the necessary sliding fit and the minimize flash.
[0072] Each pin with a non-circular cross-sectional shape includes
at least two substantially circular portions. When three
substantially circular portions form the cross-sectional shape,
these portions can be arranged in various ways depending on the
dimples being formed and the dimple pattern. For example, the
circular portions can be arranged in a line or triangle, but the
present invention is not limited to these arrangements. When four
substantially circular portions form the cross-sectional shape,
these portions can be arranged in various ways depending on the
dimples being formed and the dimple pattern. For example, the
circular portions can be arranged in a line, triangle, or rectangle
but the present invention is not limited to these arrangements.
Thus, the perimeter of the pins can have any desired shape.
Furthermore, these portions can be overlapping or non-overlapping.
It is preferable that the perimeter of the pin corresponds to the
dimple projections thereon.
[0073] Each portion 445a-c of each pin 445 in the set includes a
substantially hemispherical projection portion 475a-c. The general
shape of the pins 445 are formed then the projections are machined
thereon.
[0074] Each projection 475a-c has an apex labeled A1-A3,
respectively. The apex A1 of projection 475a defines a reference
plane R. The other portions 445b and 445c of each pin are formed so
that the apex A2 of projection 475b is below the reference plane R
and apex A3 of projection 475c is above the reverence plane R. As a
result, the apex of each pin is at a different vertical
position.
[0075] Of all the embodiments shown, the pins 445 are preferable,
because their cross-sectional shape or shape of perimeter P allows
these pins to be used with any dimple pattern without bisecting or
contacting dimples outside shaded, contact area outlined by C (as
shown in FIG. 20) on ball 550. The shape of contact area conforms
to the outline of adjacent dimples. Thus, pins 445 can be used with
conventional dimple patterns based on an icosahedron, cuboctahedron
or the like.
[0076] Referring to FIG. 20A, another embodiment of a pin 445' is
shown. This pin is used in sets with lower and upper mold halves,
as discussed above. Pin 445' includes two substantially cylindrical
portions 445'a-b so that the cross-sectional shape of the pin
between its ends is non-circular. The cross-section of each portion
445'a-b is a non-overlapping circle. Each portion 445'a-b of each
pin 445' further includes a substantially hemispherical projection
portion 475'a-b at the free end. The bore through the mold halves
for use with pin 445' has the same non-circular cross-sectional
shape as the perimeter of the pin. The pins 445' and the bores are
formed as discussed above with respect to FIGS. 17-19.
[0077] Each projection 475'a-b has an apex labeled A1-A2,
respectively. The apex A1 of projection 475'a defines a reference
plane R. The other portion 445'b of pin 445' is formed so that the
apex A2 of projection 475b is below the reference plane R. As a
result, the apex of each pin is at a different vertical
position.
[0078] Pins 445' have a cross-sectional shape or perimeter shape
that allows these pins to contact dimples without bisecting dimples
as shown by contact area outlined by C (as shown in FIG. 20B) on
ball 550'. The shape of contact area conforms to the outline of
adjacent dimples. As shown by the contact areas on ball 550' in
this embodiment, the dimple pattern is readily useful with five
pins about the pole, however a different number of pins can be
used. With another dimple pattern the pin 445' can be configured to
bisect dimples or form other groups of dimples on the ball.
[0079] Referring to FIG. 21, a substantially annular, retractable
member 600 includes two segments 601 and 602 that are mated in use.
The member 600 is for use with mold halves similar to those shown
in FIG. 6, but modified to receive the member 600. The segment 601
has two dimple projections 604a-b formed on the free end. The
segment 602 has three dimple projections 604c-e formed on the free
end. As best seen in FIG. 21A, the perimeter P of member 600 is
spaced from the dimple projections 604a-e. The member 600 has a
non-circular cross-sectional shape. A vent pin (not shown) and
optionally a core pin are received within the bore 606 formed
through the member 600. In use, member 600 is slidably engaged with
the upper and lower mold halves and coupled together with a cluster
block. Thus, each member 600 and 602 forms a plurality of dimples
during molding similar to the embodiments discussed above.
[0080] Referring to FIGS. 22 and 22A, a substantially annular,
retractable member 700 includes a plurality of segments 701, 702,
704, 706, and 708. The member 700 is for use with mold halves
similar to those shown in FIG. 6, but modified to receive the
member 700. These modifications can include forming features in the
mold half and the member to properly locate the member in the mold
half. The segment 701 has two dimple projections 710a-b formed on
the free end. The projection 710a is semi-hemispherical and the
projection 710b is hemispherical. The members 702-708 also each
have two dimple projections 712a-b, 714a-b, 716a-b, and 718a-b,
respectively, formed on the free end. The projections 712a-b,
714a-b, 716a-b, and 718a-b are formed similar to the projections
710a-b. As best seen in FIG. 22A, the perimeter P of the member 700
intersects dimple projections 710a-718b. The perimeter P is spaced
from the dimple projections 710b -718b. A vent pin (not shown) and
optionally a core pin are received within the bore 720 formed
through the member 700. The member 700 has circular cross-sectional
shape. In use, the member 700 is slidably engaged with the upper
and lower mold halves and coupled together with a cluster block.
Thus, each member 700-708 forms a plurality of dimples during
molding similar to the embodiments discussed above.
[0081] Turning to FIGS. 23-25, an alternative embodiment of a mold
half 800 and vent pin 802 according to the present invention is
shown. The mold half 800 defines a hemispherical cavity 804 with a
plurality of dimple projections 806 formed thereon. The mold half
800 further defines a bore 808 for receiving the vent pin 802.
[0082] Referring to FIGS. 25 and 26, vent pin 802 includes a
plurality of substantially cylindrical segments 810a-d that are
joined together so that the cross-sectional shape of the pin 802
between the ends along the cylindrical segments 810a-d is
non-circular. The four segments form generally a rectangle. Each of
the segments 810a-d includes a projection 812a-d, respectively
extending outwardly from the free end. An optional bore 814 is
disposed within a centrally area between the projections 812a-d.
Alternatively to the bore, the vent pin can be split. The
projections 812a-d, in this embodiment, are hemispherical and
spaced from one another. The projections 812a-d are also spaced
from the perimeter P of the pin 802. In use, the projections 812a-d
are used to form indentations in the shape thereof during molding,
be it in a cover or in an intermediate layer.
[0083] Each pin 802 further includes at least one primary vent 816
and at least one secondary vent 818 in fluid communication
therewith in the outer surface of the pin. In this embodiment, each
segment 810a-d includes three primary vents 816 disposed along the
perimeter of the pin 802 at the free end. Each segment 810a-d also
includes three secondary vents 818 extending from the associated
primary vent 810a-d downward. The primary vents 816 are cutouts and
the secondary vents 818 are flat segments in the otherwise curved
surface of the pin. The secondary vents 818 form clearance spaces
between the wall of the bore 808 (as shown in FIG. 24) and the pin
that allow trapped gases during the molding process to escape the
cavity.
[0084] Preferably, as shown in FIGS. 25 and 25A, the primary vents
816 have a depth dl less than the depth d2 of the secondary vents
818. More preferably, the depth of the primary vents 816 is less
than about 0.005 inch and the depth of the secondary vents 818 is
greater than about 0.005 inch. Most preferably, the depth of the
primary vents 816 is between about 0.0005 and about 0.002 inch and
the depth of the secondary vents 818 is between about 0.005 and
about 0.010 inch.
[0085] The geometry of the vent pin can be varied, as discussed
with respect to the retractable members, such that for example the
dimples are non-hemispherical in shape or so that the
cross-sectional shape of the vent pin is circular. Furthermore, the
vent pin 802 can be used in combination with the various
retractable pin and sleeve embodiments discussed above.
[0086] When golf balls are prepared according to the invention,
they typically will have dimple coverage greater than about 60
percent, preferably greater than about 65 percent, and more
preferably greater than about 70 percent. The flexural modulus of
the cover on the golf balls, as measured by ASTM method D-790, is
typically greater than about 500 psi, and is preferably from about
500 psi to 150,000 psi. The hardness of the cover is typically from
about 35 to 80 Shore D, preferably from about 40 to 78 Shore D, and
more preferably from about 45 to 75 Shore D.
[0087] The resultant golf balls typically have a coefficient of
restitution of greater than about 0.7, preferably greater than
about 0.75, and more preferably greater than about 0.78. The golf
balls also typically have an Atti compression of at least about 40,
preferably from about 50 to 120, and more preferably from about 60
to 100.
[0088] In other embodiments, the mold can include various
combinations of retractable elements depending on the dimple
pattern and flow characteristics of the material. For example, the
mold can include two sets of retractable pins of the present
invention associated with each mold half, where the pins on one
half are about 90.degree. out of phase with the other pins to
securely hold the core in the center of the cavity. In another
embodiment, the pins of the present invention can be used with one
mold half and an annular retractable member such as shown in FIGS.
21 and 22 can be used with the other mold half. In this embodiment,
it is preferable that the annular, retractable member be used with
the lower mold half so that it can eject the core. Alternatively,
the pins or annular, retractable members of the present invention
can be used in combination with the sleeves disclosed in U.S. Pat.
No. 6,129,881 issued Oct. 10, 2000, entitled "RETRACTABLE SLEEVE
FOR INJECTION MOLDING," which is incorporated by reference herein
in its entirety.
[0089] While it is apparent that the illustrative embodiments of
the invention herein disclosed fulfill the objectives stated above,
it will be appreciated that numerous modifications and other
embodiments may be devised by those skilled in the art. The process
applies to forming the cover layer and/or any intermediate layers
between the core and cover. After one layer is formed and
solidified according to the method of the present invention
additional layers can be formed. Thus, the invention is equally
applicable to any or all molding processes for thermoplastic and
other material layers in multilayer component golf balls.
Specifically in solid, three piece balls where the intermediate
layer and cover are injection molded. In the present invention, the
general principles of the invention can be used with any dimple
patterns by configuring the pins to match the dimple pattern. For
example, the present invention can be used with golf balls having
an icosahedron pattern, octahedron pattern, quadrilateral pattern,
a cuboctahedron pattern, or a dodecahedron pattern. Another dimple
pattern that can be used involves dividing the ball along equally
spaced longitudinal lines to form segments of the ball shaped like
orange slices. There are usually 5 or 6 such segments and the same
dimple pattern is repeated within each segment. The present
invention is not limited to golf balls having the above-identified
patterns and can be used with other less common dimple patterns.
The number of pins or segments of annular, retraction members in
each embodiment can be varied as needed. The perimeter of the pins
or annular, retractable members may intersect one on more dimples
in the various embodiments. Furthermore, the projections on the
pins are not limited to the hemispherical or semi-hemispherical
shapes. For example, the projections can be configured so that they
produce dimples shaped like octagons, squares, ellipses,
hemispheres with different sections with different radii, or
saucer-shaped. Saucer-shaped dimples have a flattened bottom wall
and steeper sides than conventional dimples. Additionally, the
present mold or method can be used with compression molding, liquid
or reaction injection molding techniques or other conventional
techniques used with the materials disclosed above. In addition,
the features of one embodiment can be used with the features of any
other embodiment. Therefore, it will be understood that the
appended claims are intended to cover all such modifications and
embodiments which come within the spirit and scope of the present
invention.
* * * * *