US20150343270A1

US20150343270A1 - Thermoplastic elastomer composites for stiff core golf balls and method for making same

Info

Publication number: US20150343270A1
Application number: US14/714,203
Authority: US
Inventors: Douglas P. DuFaux
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-05-15
Filing date: 2015-05-15
Publication date: 2015-12-03

Abstract

A golf ball is provided that includes at least one layer of material that is a composite of thermoplastic and a second phase material that is dispersed within the thermoplastic. This material may be a blend of thermoplastic and elastomeric material. Preferably, the golf ball comprises a hard sphere core such as a hollow metal core, a layer of Thermoplastic Elastomer Composite, and a cover layer. This results in a golf ball that is legal for play and capable of drive distances essentially equivalent to those of currently available high performance golf balls, but also provides a ball that has less hook and slice during play, while being durable and economical to produce.

Description

FIELD OF THE INVENTION

The present invention relates generally to an improved multi-piece golf ball, and more particularly, a multi-piece golf ball including a hard spherical core or layer with improved characteristics. More particularly, the present invention relates to an improved golf ball having a blend of an injection moldable polymer and non-injection moldable polymer, in one or more layers of a golf ball.

BACKGROUND OF THE INVENTION

Most golf balls sold in the U.S. are listed on the conforming list of the United States Golf Association—the USGA. Several specifications have been established by the USGA, and a golf ball must meet certain test criteria relating to these specifications for weight, size, initial velocity, overall distance (carry and roll), and spherical symmetry. For acceptance by the USGA a golf ball must not weigh more than 1.620 ounces, must have a minimum diameter of 1.680 inches, must have a maximum initial ball velocity of 250 feet per second (plus a maximum 2% tolerance) as measured on a standard USGA ball testing machine, must have an overall distance maximum of 317 yards (plus a maximum 3 yard tolerance) as measured by the USGA overall distance test procedure. Further, the ball must not be designed, manufactured or intentionally modified to have properties that differ from those of a spherically symmetric ball. The USGA tests for symmetry by inspecting the statistical deviation of the overall distance test data (distance variation and flight time variation) when the ball is struck from various aspects.
In the modern era of golf, a typical golf ball has been either of the ‘wound’ or ‘molded’ type. Since molded golf balls are cheaper to produce, virtually all of the golf balls currently sold today are molded. The major manufacturers have ceased production of wound balls in pursuit of more sophisticated molded type balls. Due to their low price, most golf balls sold today are two-piece polymeric balls with polybutadiene cores and ionomer covers. The process of making this type of ball includes first compression molding the polybutadiene into a solid core and then injection molding a cover onto this core. Dimples are included in the die and so the second step of injection molding produces a nearly finished golf ball—clean up and painting is typically performed to finish the ball. Most development of new golf balls is based on the simple two-piece architecture—employing the solid polybutadiene core, but adding various layers between this core and the outermost cover. First, a two-layer cover appeared, then multiple layers with as many as five or six total layers. Also, new materials have been employed for the various covers. Some balls use an injection molded core or mantle layer (between the core and cover layers) but the majority of even the best selling tour balls employs the proven compression molded polybutadiene core.
One common factor amongst the far majority of golf balls today is the materials of construction. Most commercially available golf balls are made of nonmetallic rubbers and plastics, such as elastomers, ionomers, polyurethanes, polyisoprenes, nylons, and other similar materials. In recent years, however, golf balls incorporating metals have appeared in the market. For example, U.S. Pat. Nos. 6,004,225, 6,705,957, and 6,976,925 disclose a golf ball having a hollow metal core. This design takes advantage of the high stiffness of the metal core (when compared to the stiffness of typical golf ball materials) to achieve a golf ball that has simultaneous characteristics of high accuracy (less hook and slice) as well as excellent putting characteristics. These types of golf balls may have a couple of shortcomings, including hard feel and a small loss of distance compared to more typical molded balls discussed above. Accordingly, there is a need for golf balls that have a hollow metal core that do not exhibit some or all of the shortcomings of these golf balls appearing in the art. Furthermore, there is a need for materials that allow a golf ball designer to control the stiffness of the core, while also avoiding the shortcomings observed in high stiffness cores. Perhaps most importantly, needs should be met in a manner that allows an economical means of production.
Simply using a metal in part of the golf ball is not sufficint to significantly increase the stiffness of the golf ball. A few very old patents discuss a ball having a hollow metal sphere of some type. See U.S. Pat. Nos. 697,816; 700,658; 713,772; 1,568,513; and 1,568,514, each of which is hereby incorporated herein by reference. However, these prior art designs suffer from several shortcomings including a hollow metal sphere design that is not durable enough to withstand impact forces from being struck by a club. For example the '514 patent provides a golf ball having a hollow metal sphere comprising half shells. The half shells are only 0.005 inches in thickness with scalloped edges that are fit together but not securely joined. These patents do not disclose a golf ball design having a hollow metal sphere that can withstand the impact of a golf club without permanent distortion or an efficient or cost effective method of manufacturing the golf balls. Not surprisingly, the golf balls are not believed to have achieved any commercial success.
Other designs have looked at new materials, but have either not attempted or accomplished a design that provides a significantly higher stiffness in the core (i.e., stiffness greater than 5× that of a typical polybutadiene core.) For example, U.S. Pat. No. 6,710,114, which is hereby incorporated herein by reference, provides golf balls having a portion or layer formed from a polymeric composite that includes at least two polymers with distinct microstructures. The polymer composite may include one or more reinforcing agents, such as nanoparticles that are silica-based or carbon-based. According to the '114 patent, increasing the amount of nanoparticles can decrease the amount of crosslinking agent required to provide increased resilience but does not create a core with significantly higher stiffness.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a golf ball with a high stiffness core which is durable and capable of maintaining structural integrity and symmetry and which has good feel, rebound and flight trajectory.
Another objective of the present invention is the manufacture of a hollow metal core golf ball with materials that are compatible for energy transfer between each layer without structural degradation of either material.
These and other objects are provided, according to the present invention, by a golf ball which includes a hollow metal sphere or composite sphere as the core and one or more outer layers surrounding the sphere comprising a durable blended polymer that can withstand the extreme forces when compressed between a golf club and hollow metal sphere encountered during play. The blended polymer is comprised of a blend of at least two components, wherein one of the components is an injection moldable polymer. A hollow metal sphere may be comprised of a steel, steel alloy, a nanostructured steel material, titanium and titanium alloys. A composite core may include silicon nitride, carbon fiber, carbon nanotubes, graphene, and other high stiffness materials.
In one preferred embodiment of the present invention, a hollow metal sphere core is made of a 301 stainless steel alloy and is surrounded by a blended polymer layer, such as a mixture of ethylene (meth)acrylic acid ionomers (such as DuPont's HPF™ resin) and polybutadiene, which is surrounded by an ionomer cover that includes a dimple pattern. Between about 1% and 80% and preferably between about 10% and 60% by weight of the polymer blend is polybutadiene.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of one embodiment of the present invention golf ball including three material layers: (1) an innermost core comprised of a hollow metal sphere, (2) a middle mantle layer comprised of Thermoplastic Elastomer Composite, and (3) cover layer.

FIG. 2 is a cross-sectional view of one embodiment of the present invention golf ball including three material layers: (1) an innermost core comprised of solid core, (2) a middle mantle layer comprised of Thermoplastic Elastomer Composite, and (3) cover layer.

FIG. 3 is a cross-sectional view of one embodiment of the present invention golf ball including two material layers: (1) an innermost core comprised of a hollow metal sphere or solid/porous composite sphere, and (2) a thick cover layer comprised of Thermoplastic Elastomer Composite.

FIG. 4 is a cross-sectional view of one embodiment of the present invention golf ball including one material layer: (1) a single layer comprised of Thermoplastic Elastomer Composite.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention is shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.
U.S. Pat. Nos. 6,004,225, 6,705,957, and 6,976,925 each of which is hereby incorporated herein by reference, discuss a modern golf ball with a one-piece hollow metal sphere surrounded by a cover or a mantle layer and cover. The '225, '957, and '925 patents also discuss several methods for making the golf ball having a hollow metal sphere by hot forming or cold forming two halves of a sphere, which are securely joined together by various welding techniques or other sufficient means. This golf ball design exhibits less hook and slice when miss hit. The one-piece hollow metal sphere, which is surrounded by at least one polymer layer, is capable of withstanding the hardest impacts from current titanium-faced golf clubs. The '225, '957, and '925 patents disclose at least one layer made of polymers typically used in golf balls between the hollow metal sphere and the cover. Due to the presence of the high stiffness hollow metal sphere, the polymer layer and cover are subject to a different set of stresses when compared to a conventional ball when struck by a club, which results in the unique flight characteristics.
During a high-speed collision between a golf ball and club, a golf ball undergoes deformation such that the core of the ball deforms from a spherical shape to an oblong shape. At the point of maximum deflection of the golf ball, the ball and the club head travel together for a moment of time at the same velocity. After this point, the ball projects forward, accelerating off of the face of the club due to the elastic nature of a golf ball. Based on the Coefficient of Restitution (COR) of the golf ball and the relative weight of the club head to that of the golf ball, the golf ball travels at a faster speed than the club head. The initial velocity of the golf ball can be approximated with the following equation:
$\begin{matrix} v = U \times \frac{1 + COR}{1 + (m / M)} & [1] \end{matrix}$

- where v is the velocity of the ball immediately after impact, U is the velocity of the club head immediately before impact, m is the mass of the ball, M is the mass of the club head, and COR is the coefficient of restitution of the ball.

The COR of a golf ball is determined empirically. The ball is launched at a predetermined velocity (v_(initial)) toward a flat rigid object, such as a large steel plate fixed to a wall, and the velocity is measured after the ball bounces off of the plate (v_(final)) in a manner such that the impact is perpendicular to the plate. The COR is calculated as shown in equation 2:
COR=v _(final) /v _(initial) [2]
Basically, COR determines the elasticity of a golf ball and the value lies between an ideal case where all the energy at impact is returned to the ball and the final velocity matches the initial velocity, with COR equal to 100% or 1.0 and the case where none of the energy at impact is returned to the ball and the final velocity is zero (i.e., simply drops to the floor) and COR equals 0% or 0. The COR of a typical polymeric golf ball is around 70-85%. COR may change over the range of initial velocities—i.e., COR at an impact velocity of 10 meters per second may be different than the COR at an impact speed of 50 meters per second.
If the COR of the golf ball for a given collision is high (i.e. near 1.0 or 100%), then very little of the kinetic energy is lost during the collision. However, if the COR in a given collision is low, then more kinetic energy is lost during the collision. This energy loss results from internal friction between the polymeric molecules as the ball deforms from the spherical shape to an elongated sphere during maximum deflection, and back to the spherical shape after impact.
It has been observed that in some instances, depending on the materials used for construction, the COR of golf balls with stiff metal cores having a smooth surface or surfaces can be much less than that of a typical golf ball, in some cases ranging as low as 40%.
For COR, the key parameters are the properties of the core, such as the stiffness of the core, and the properties of the mantle layer. The stiffness may be attributed to either the properties of the material used to construct the core, such as the hardness, modulus of elasticity, toughness, etc., or properties associated with the shape and size of the sphere, such as the moment of inertia, the section modulus, surface features, etc. In addition, the properties of the polymers or other materials surrounding the sphere, as well as any materials within the sphere are important. The ability to minimize or otherwise reduce losses upon impact will generally reduce the kinetic energy from the impact that is lost to heat, thereby increasing the COR of the ball.
Further, it has been observed that some thermoplastic materials, such as DuPont HPF™ materials perform very well in golf balls with a hollow metal core with respect to durability, but often players complain about the hard feel of these golf balls. It has also been found that some formulations of polybutadiene have excellent performance characteristics and feel to a golfer, but durability is very poor, with cracks forming in hollow metal core balls after just a few high-speed impacts.
A blend of materials that provides the benefits of both materials as well as a suitable COR is provided herein.
The present invention therefore generally provides golf balls having an outer cover with a dimpled pattern and a stiff spherical core, where intermediate layer between the outer cover and the core is made from a blend of a thermoplastic material and a second phase elastomeric material that is dispersed within the thermoplastic material to provide material characteristics that are a combination of the two materials. This material is referred to as a Thermoplastic Elastomer Composite, or TEC.
Referring now to FIG. 1, an improved golf ball according to one embodiment of the present invention is illustrated in cross section. The golf ball 100 includes a hollow metal sphere 110, with internal void space 115, surrounded by the Thermoplastic Elastomer Composite layer 120, and cover layer 130. The outer surface 140 may include surface features such as dimples to increase flight characteristics, as is well known in the art.
As discussed more thoroughly in the '225, '957, and '925 patents, the hollow metal sphere 110 may be made of titanium, titanium alloys, or steel, including carbon steel, stainless steel and steel alloys. The hollow metal sphere 110 has an outside diameter ranging from about 0.50 to 1.50 inches (about 1.27 to 3.8 centimeters), and a thickness of about 0.02 to 0.16 inches (0.05 to 0.41 centimeters) and more preferably about 0.02 to 0.08 inches (0.05 to 0.20 centimeters). Preferred steels include the 300 series stainless steels, the 400 series stainless steels and alloy steels, and more preferably 301 stainless steel, 302 stainless steel, 304 stainless steel, 430 stainless steel, and ***
The cover layer 130 has a cover outer surface and a cover inner surface, which together define a cover thickness, which is about 4 mm, but may be any thickness between about 1 mm and about 6 mm or between about 2 mm and about 5 mm. The cover has a surface dimple pattern and is preferably made of SURLYN, but may be also be made of an ionomer, urethane, balata, polybutadiene, or other synthetic elastomer, or any other material suitable for a golf ball cover, as is known in the art. The cover layer also forms the golf ball diameter, which is preferably 42.67 mm (1.68 inches), to meet USGA and industry standards, but may be any diameter equal to, greater or less than 42.67 mm, preferably between about 40 mm and about 45 mm.
The hollow metal core 110 has an outer diameter and is preferably about 22.86 mm (0.90 inches) or less to comply with new rules issued by the United States Golf Association (USGA) but the diameter may be any diameter from about 10 mm (0.39 inches) to about 38 mm (1.50 inches), or from about 25.4 mm (1.0 inches) to about 35.6 mm (1.4 inches). The outer core surface and the inner core surface together define a core thickness, which is preferably about 1.82 mm, however the core thickness may range from about 0.5 mm to about 6.4 mm.
Referring now to FIG. 2, an improved golf ball according to another embodiment of the present invention is illustrated in cross section. The golf ball 200 includes a solid spherical core 210, surrounded by a Thermoplastic Elastomer Composite layer 220, and cover layer 230. The outer surface 240 may include surface features such as dimples to increase flight characteristics, as is well known in the art.
The spherical core 210 may be made of various materials and is preferably designed to have high stiffness. One set of materials that can be used to create high stiffness cores is a blend of polymer-ceramic composites, as described in more detail in the related pending U.S. patent application Ser. No. ______ Many polymers and ceramics may be used for this type of composite. Injection molding polymers for the core composites include, but are not limited to nylon, polyethylene, and polystyrene, and ABS. Ceramics that can be used as the strengthening phase in the polymer matrix composite include, but are not limited to Silicon Nitride (Si3N4), Silicon Carbide (SiC), Titanium Diboride (TiB2), Titanium Carbide (TiC), Aluminum Oxide (Al2O3), Zirconium Oxide (ZrO2), and Boron Carbide (B4C). Other materials may be as the strengthening phase in the polymer matrix composite as well. For example, carbon fiber, carbon nanotubes (CNTs), graphene, and other recent materials may provide significant stiffening of a polymer or elastomer when used in a composite as described above. Furthermore, elastomers may also be employed as the matrix or mixed with a polymer to provide the matrix.
Referring now to FIG. 3, an improved golf ball according to another embodiment of the present invention is illustrated in cross section. The golf ball 300 includes a hollow metal sphere 310, with internal void space 315, surrounded by a Thermoplastic Elastomer Composite layer 320. The outer surface 340 may include surface features such as dimples to increase flight characteristics, as is well known in the art. The outer surface 340 may also be painted with various materials, as is known in the art.
The Composite Thermoplastic Elastomer (TEC) materials may be used in a golf ball without a separate core. For example, referring now to FIG. 4, an improved golf ball according to another embodiment of the present invention is illustrated in cross section. The golf ball 400 is comprised of Thermoplastic Elastomer Composite 420. The outer surface 340 may include surface features such as dimples to increase flight characteristics, as is well known in the art. The outer surface 340 may also be painted with various materials, as is known in the art. Optionally, this ball may include a separate cover made of SURLYN, but may be also be made of an ionomer, urethane, balata, polybutadiene, or other synthetic elastomer, or any other material suitable for a golf ball cover, as is known in the art.
In addition to the embodiments shown in FIGS. 1 through 4, the present invention may be applied toward other multi-piece designs using greater than three pieces, e.g., three, four, five, etc. pieces, in which instance the hard sphere may serve as an intermediate layer or as a spherical core, hollow or otherwise. Many multi-layer golf balls today include several layers near the cover, to control spin and other playing characteristics. The present invention may be employed in these designs as well.
The resulting hollow metal sphere will have a yield strength greater than about 350 MPa, more preferably 450 MPa, and more preferably greater than about 650 MPa.

Thermoplastic Elastomer Composites

The Thermoplastic Elastomer Composite (TEC) is a multi-component polymer m material, comprised of at least one injection moldable thermoplastic material, also referred to as the injection moldable fraction, and a second phase material dispersed throughout the injection moldable thermoplastic. Preferably, the second phase material is an elastomeric material, but may be any other material that is highly resilient.
In one embodiment, the TEC is comprised of a thermoplastic material and polybutadiene as the second phase. The thermoplastic material may comprise one or more polymers from the following group, an ethylene (meth)acrylic acid ionomer (such as HPF™ resin made by DuPont), a polyether block amide (such as Pebax® resin made by Arkema Group), urethane/polyurethane, and/or other commercially available thermoplastics. The polybutadiene may be blended into the injection moldable fraction by adding particles, fragments, and other forms into a blending extruder or mixed with the polymer in the injection molder hopper just prior to injection molding. With this second phase (or multiple additional phases) material is incorporated into to the thermoplastic to from the TEC that is injection molded, increasing the screw and backpressure during injection molding may improve dispersion of the material into the polymer.
Optionally, other materials may be added to the two-component mix to further enhance material properties. One such material is clay of various sizes, including nanometer sized materials. The nanoclay material may be added in the form of a nanocomposite, i.e. nanoclay particles contained in a polymer carrier such as polypropylene (such as Nanoblend™ Concentrate 1001 made by PolyOne Corporation). The weight percent of the nanoclay material is determined by including the weight of the clay and any polymer carrier. Between about 0.1% and 10% and preferably about 0.1% to 5% by weight of a nanoclay material may be added to the injection moldable fraction.
Nano-materials may also be used to tailor the characteristics of the TEC. Nanomaterials are generally those that exhibit characteristics based on controlling the composition of the material at a sub-micrometer level, to vary the strength, ductility, hardness, formability, crack propagation resistance, etc., or a combination thereof. By varying the amount of dispersions within the TEC, the durability, resilience and other properties may be tailored. Thus, nanosize materials, such as metallic, ceramic, or clay powders, carbon-nanotubes, etc., may be used as the second phase may not only to carry a portion of the load, but may also interact with the matrix material dislocations or grain boundaries to tailor the strength or stiffness.
Between about 1% and 80% and preferably between about 10% and 60% by weight of the Thermoplastic Elastomer Composite is polybutadiene or other dispersed phase.
The TEC allows the golf balls of the present invention to be made using conventional economical processes and techniques as are presently employed in the art such as injection molding so that the ball will be spherical in shape, have equal aerodynamic properties, and have equal moments of inertia about any axis through its center.

Multi-Layer Cores and Mantles

The material sets, polymer layers, and processing conditions may be tailored to achieve the desired final characteristics. Therefore, the final design will generally be the sum of the responses from the individual layers and any interplay between the layers. The performance may therefore also be tailored, to some degree, by controlling the interplay between the layers of a golf ball.
The normal force at impact between a golf ball and a golf club when the average golfer strikes the ball can be on the order of 2000 lb. Thus, durability of the materials that comprise a golf ball must be able to withstand this impact force many times while retaining their original shape following impact and without degradation of the ball's coefficient of restitution. For golf balls with highly stiff cores, achieving a golf ball with good energy transfer between layers and sufficient durability is a challenge.
For example, it has been observed that the layer or layers surrounding the core in a golf ball incorporating a highly stiff core, such as a hollow metal core, may fracture upon repeated impact by a golf club at swing speeds that are typical of the average golfer. More specifically, the transfer of useful energy upon impact between the layers may be reduced due to the fracturing or otherwise degradation of materials. One contributing factor for this degradation is the large differential elastic modulus between the separate layers. It would be preferable to design a golf ball such that the elastic modulus is within two (2) orders of magnitude, of an adjacent layer.
The elastic modulus of the metal is much higher than the typical modulus range of polymeric materials. It is thus necessary to have a transition from the metal to the polymeric materials such that the modulus difference between the innermost layer and the hollow metal core is not greater than two orders of magnitude. Molding materials in several steps to produce a multi-component ball with several TEC layers, where each layer is comprised of a different combination of dispersions and results in decreasing stiffness from each layer moving out from the stiff core, is one example of a golf ball that achieves this objective. The selection for each layer will generally be determined through experimental means, testing each layer individually as well as variations of completed balls.
Optionally, it may be desired to reduce the stiffness of a stiff metal core to some degree or to increase the stiffness. One method to modify the stiffness of the hard sphere or of any other layer may be any feature that modifies the manner in which the golf ball responds to a force as compared to the response of the sphere without the feature. The stiffness of the sphere may be controlled by including at least one groove or any other indentation in the hard sphere core or layer. The groove or grooves serve to locally reduce the wall thickness of the sphere, or reducing the thickness of the layer near the outer surface of a solid core, thereby reducing the stiffness of the hollow metal sphere core by allowing larger deformations under a given load without significantly reducing the total mass of the sphere.
One embodiment of the present invention provides a golf ball having a metal or other hard material sphere core or layer surrounded by a mantle layer and a cover layer, where the sphere core has at least one indentation or groove. Although the invention is described by way of having vertical or horizontal grooves, it is understood that a similar result may be achieved with other regularly patterned indentations, such as with perforations, protrusions, or a combination thereof, that reduce the wall thickness of the hard sphere core at the desired locations and depth to reduce the stiffness of the core thereby allowing larger deflections at impact, e.g., elastic deformations, and is also not limited thereto.
Preferably, the golf balls of the present invention meet the specifications of the USGA.

EXAMPLES

Examples of golf balls made according to the present invention are shown below:

Example 1

Three piece ball: hollow 301 stainless steel core having an elastic modulus of 193 GigaPascals (GPa) and a thickness of approximately 0.039 inches and a diameter of 1.1 inches, surrounded by a polyether block amide as the transition agent which has an elastic modulus of 290 MegaPascals (MPa), and then further surrounded by a layer of polymeric resin having an elastic modulus of 86 MPa, and covered with an ionomer with an elastic modulus of approximately 350 MPa and a thickness of 0.063 inches.
Other materials, such as polybutadiene, urethanes, and various resins may be used as layers, provided the constraint is met that no two adjacent layers have no more than two orders of magnitude difference in their respective elastic modulus.

Example 2

Three piece ball: hollow metal core, second polymer layer comprising a DuPont HPF 1000 or HPF 2000 resin blended with 0.25-1.0 mm particulate polybutadiene and a Surlyn cover. The hollow sphere comprising a 301 stainless steel core with an inside diameter of 21.21 mm (0.835 inches) and an outside diameter of 22.86 mm (0.9 inches), the specific gravity of the stainless steel of 7.8 and a core mass of 10.125 grams. HPF resin (base resin specific gravity=0.96) with a layer thickness of 8.32 mm (0.3275) inches blended with 25% polybutadiene in particulate form with a size of 0.25-1.0 mm, and 1% by weight of nanoclay material in a polypropylene carrier (such as PolyOne® Nanoblend™ Concentrate 1001—specific gravity of about 1.1) with a total layer mass of 27.4 grams. Further comprising a SURLYN (specific gravity of about 0.95) cover of thickness 1.59 mm (0.0625 inches), and a mass of 7.95 grams. The pressure of the residual gas or air in the hollow metal sphere is less than about 1 mbar above atmospheric pressure. The total mass of the ball is 45.5 grams.
As described above, the improved golf ball of the present invention provides improved performance characteristics including high accuracy, minimization of hook and slice when improperly hit, long distance, and bite without adversely affecting rebound characteristics. The design of the golf ball allows variations in the material and the size of the core, mantle layer(s), and outer cover or multiple cover layers in order to optimize performance characteristics.
Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
In the drawings and specification there has been set forth preferred embodiments of the invention and although specific terms are employed, the terms are used in a generic and descriptive sense only and not for the purpose of limiting the scope of the invention being set forth in the claims.

Claims

1. A golf ball comprising:

a cover layer having an outer surface defining a dimpled pattern and an inner surface defining with the outer surface a cover thickness; and

a stiff sphere core disposed within the cover layer, wherein the hard sphere has a stiffness of at least 1 GPa; and

a mantle layer having an inner surface mating with the outer surface of the spherical core and a outer surface mating with the inside surface of the cover layer, comprised of a mixture of a thermoplastic and elastomer.

2. A golf ball according to claim 1, wherein the hard spherical core is made of a hollow metal core.

3. A golf ball according to claim 1, wherein the mantle layer is comprised of a mixture of a thermoplastic and elastomer, wherein the elastomer is in particulate form.

4. A golf ball according to claim 3, wherein the mantle layer is comprised of a mixture of a thermoplastic and elastomer, wherein the elastomer is in particulate form.

5. A golf ball according to claim 4, wherein the mantle layer is comprised of a mixture of a thermoplastic and elastomer, wherein the elastomer is in particulate form and has a mass fraction of less than 60%.