US20070161434A1

US20070161434A1 - Golf ball

Info

Publication number: US20070161434A1
Application number: US11/144,111
Authority: US
Inventors: Douglas DuFaux; Timothy Owens; Glenn Spacht
Original assignee: NANODYNAMICS Inc; NOONAN TECHNOLOGIES LLC
Current assignee: NOONAN TECHNOLOGIES LLC; NanoDynamics Inc USA
Priority date: 2005-06-03
Filing date: 2005-06-03
Publication date: 2007-07-12
Also published as: EP1885461A4; WO2006132999A2; WO2006132999A3; EP1885461A2

Abstract

A golf ball is provided that has a hard sphere core or layer that exhibits a controlled vibrational response. The vibrational response may be controlled by tailoring the stiffness or damping of the sphere with at least one element, such as a groove(s) or any other type of indentation in the hard sphere core. The groove (or grooves) serves to locally reduce the wall thickness of the hollow metal sphere core, thereby reducing the stiffness of the core by allowing larger deformations under a load without significantly reducing the total mass of the core. 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 that also maintains a high moment of inertia, allowing less hooks and slices during play.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation in part of U.S. patent application Ser. No. 10/756,185, filed Jan. 13, 2004, which is a continuation of U.S. Pat. No. 6,705,957, issued Mar. 16, 2004, which is a continuation of U.S. Pat. No. 6,004,225, issued Dec. 21, 1999, which claims priority to U.S. Provisional Patent Application No. 60/036,196, filed Jan. 16, 1997, each of which are hereby incorporated by reference thereto.

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.

BACKGROUND OF THE INVENTION

In order to meet United States Golf Association (“U.S.G.A.”) specifications, a golf ball must meet certain test criteria relating to weight, size, initial velocity, overall distance (carry and roll), and spherical symmetry. In general, a golf ball must not weigh more than 1.620 ounces avoirdupois, must have a diameter of not less than 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 U.S.G.A. ball testing machine, must not have an overall distance that exceeds 317 yards (plus a maximum 3 yard tolerance) as measured by the U.S.G.A. overall distance test procedure, and must not be designed, manufactured or intentionally modified to have properties that differ from those of a spherically symmetric ball. The latter symmetry requirement is tested by the U.S.G.A. during the overall distance test and requires that a ball have no statistically significant difference in carry distance greater than 4.0 yards, nor statistically significant in-flight-time difference of more than 0.40 seconds regardless of which axis the ball is spinning around when launched.
Golf balls are generally either wound or molded. Since molded golf balls are cheaper to produce, many of the currently available golf balls are two-piece polymeric balls of uniform density cores. More recent developments in golf ball design have resulted in golf balls that have improved moments of inertia by minimizing the density in the center of the ball and maximizing the density away from the center and near the cover or outer edge of the ball. This can result in a golf ball that has simultaneous characteristics of low spin for maximum distance, as well as maintaining “bite” for shorter shots approaching the putting green. These types of golf balls, however, have a number of shortcomings. Many, for instance, use fillers to increase the weight distribution of the golf ball towards the cover of the ball, which tend to adversely affect the ball's performance, such as with respect to rebound. Accordingly, there is a need for such golf balls that do not exhibit some or all of the shortcomings of these golf balls appearing in the art.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a golf ball having a hard sphere core or layer with at least one feature for controlling or otherwise achieving a desired vibrational response exhibited by the ball, e.g., by controlling the stiffness of the hard sphere. The stiffness of the sphere may be controlled or tuned 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, 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.
In one embodiment, the present invention includes a golf ball having a cover formed of an ionomeric material or any other material that is resistant to damage from external articles of the type normally encountered when playing golf. The cover has an outer surface, defining a dimpled pattern, and an inner surface, defining with the outer surface a cover thickness. The ball also includes a hard sphere core or layer, such as one made from a metal, which has an outer surface and an inner surface, together defining a sphere thickness. In one embodiment, the outer surface of the sphere supports, and is surrounded by, the inner surface of the cover. In one embodiment, the outer sphere surface advantageously includes at least one groove or other indentation for controlling the stiffness of the hard sphere. In another embodiment, the inner sphere surface advantageously includes at least one groove for controlling the stiffness of the sphere. In another embodiment, both the inner sphere surface and the outer sphere surface include at least one groove for controlling the stiffness of the sphere.
In one aspect, the outer sphere surface individually, the inner sphere surface individually, or both the outer sphere surface and the inner sphere surface, may also include a plurality of grooves where the grooves may be in a regularly spaced pattern. The plurality of grooves may include a plurality of regularly spaced horizontal grooves and a plurality of regularly spaced vertical grooves, where the plurality of vertical grooves are essentially perpendicular to the plurality of horizontal grooves. The plurality of grooves may also include a plurality of angled grooves that intersect the plurality of regularly spaced vertical grooves. Further, an intermediate layer or mantle may be disposed between the hard sphere and the cover, the intermediate layer comprising a compressible and/or resilient material selected from the group consisting of natural rubber, synthetic polymer compounds, and a combination of the natural rubber and synthetic polymer compounds.
In another aspect, the present invention provides a hard sphere core for use in a modern golf ball. The hard sphere core has an outer surface and an inner surface, together defining a core thickness, where the outer core surface individually, the inner core surface individually, or both the outer core surface and the inner core surface have at least one groove or any other type of indentation for controlling the stiffness of the sphere core. In one embodiment, the outer core surface individually, the inner core surface individually, or both the outer core surface and the inner core surface may include a plurality of grooves for controlling the stiffness of the metal sphere core. The plurality of grooves may include a plurality of regularly spaced horizontal grooves and a plurality of regularly spaced vertical grooves, where the plurality of vertical grooves are essentially perpendicular to the plurality of horizontal grooves. The plurality of grooves may also include a plurality of angled grooves that intersect the plurality of regularly spaced vertical grooves and the plurality of horizontal grooves.
The present invention also provides a method of constructing a metal sphere core with controlled stiffness for use in a modern golf ball, where the metal sphere core has an outer surface and an inner surface, together defining a core thickness. In one embodiment, the method includes forming at least one groove or any other type of indentation in the outer core surface for controlling the stiffness of the metal sphere core. In another embodiment, the method includes forming at least one groove in the inner core surface for controlling the stiffness of the metal sphere core. In another embodiment, the method includes forming at least one groove in the outer core surface and at least one groove in the inner core surface, for controlling the stiffness of the metal sphere core.
The golf ball of the present invention has several advantages that provide a golf ball having a hollow hard sphere core in which the stiffness of the core may be controlled, while maintaining the high overall moment of inertia for the golf ball. The golf ball includes a cover layer and a hard sphere core that has an outer core surface and an inner core surface where the outer core surface has at least one, and preferably a plurality of, regularly spaced horizontal grooves and a plurality of regularly spaced vertical grooves that serves to decrease the stiffness of the hollow metal sphere core. The grooves are regularly spaced in order to maintain a golf ball that will perform similarly about any axis of rotation, such that the golf ball will conform to the current U.S.G.A. golf ball standard. This results in a hollow metal sphere core for a golf ball in which the stiffness may be controlled and the effect on the high moment of inertia of the ball may be minimized.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
FIG. 1 is a partial cross-sectional perspective view of a hollow cored golf ball.
FIG. 2 is a partial cross-sectional perspective view of a golf ball according to one embodiment of the present invention.
FIG. 3 is a front plan view of a metal sphere core of a golf ball according to one embodiment of the present invention.
FIG. 4 is a cross sectional view of grooves disposed on a metal sphere core according of one embodiment of the present invention.
FIG. 5A and FIG. 5B are exemplary cross sectional depictions of groove profiles according to other embodiments of the present invention.
FIG. 6 is a perspective view depiction of groove lines on a metal sphere core according to another embodiment of the present invention.
FIG. 7 is a perspective view depiction of groove lines on a metal sphere core according to another embodiment of the present invention.
FIG. 8 is a perspective view depiction of groove lines on a metal sphere core according to another embodiment of the present invention.
FIG. 9 is a partial cross sectional view of a metal sphere core according to another embodiment of the present invention.
FIG. 10 is a partial cross sectional view of a metal sphere core according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Like numbers refer to like elements throughout.
In U.S. Pat. No. 6,004,225, which is hereby incorporated herein by reference, the present inventors provide a golf ball having a hollow sphere core and an outer layer surrounding the sphere. The hollow sphere core may be solid, e.g., non-perforated, perforated, or porous. According to one embodiment, the sphere has a specific gravity of 2.5 to 20, a diameter range from 0.39 to 1.5 inches, and a thickness of 0.02 to 0.25 inches. The cover material is an ionomer, urethane, balata, or synthetic elastomer (e.g. SURLYN, produced by DuPont Company or IOTEK produced by Exxon Mobil), or any other suitable material. The resulting golf ball design maximizes the density toward the perimeter of the ball and away from the center. Consequently, the moment of inertia is increased and the spin is reduced, thereby, e.g., reducing hooks and slices.
Similarly, U.S. Pat. No. 6,705,957, which is also hereby incorporated herein by reference, provides a three-layer ball with a hollow sphere core. A second layer is disposed between the sphere and the cover. The second layer is a resilient material, preferably a synthetic polymer compound, such as polybutadiene, a natural rubber compound, or a combination thereof. The thickness of the second layer is about 0.05 to 0.65 inches. This design also results in a golf ball that increases the moment of inertia and reduces spin, with the advantage of providing the designer with an additional degree of freedom to tailor the response of the ball to the impact of the golf club.
However in certain instances under high loads, a golf ball with a hard sphere layer or core, whether hollow or otherwise, can be excessively stiff. In spite of the ball's reduced tendency to hook or slice, this produces performance characteristics, including sound, initial velocity, and distance, that may not be attractive to some golfers. In this respect, the present invention provides golf balls having a hard sphere layer or core with at least one feature associated with the hard sphere or with any other layer for controlling or otherwise achieving a desired vibrational response to the impact of the golf club. A feature that controls the vibrational response of the hard sphere or any other layer generally modifies the manner in which the golf ball oscillates in response to an impact as compared to the response of the sphere or layer without the feature. This includes changes with respect to the initial deflection or amplitude, frequency, wavelength, or the period of one or more cycles of the waveform representing the vibrational response of the ball, the number of cycles it takes to dampen out the vibration, etc. In one embodiment, the first half of the sinusoidal waveform representing the vibrational response after impact is tailored to occur in less than or greater than 5 milliseconds, 7 milliseconds, 10 milliseconds, or greater.
Referring to FIG. 1, a golf ball 10 having a cover 11 and a one-piece hollow core 12 is shown. During a high-speed collision with the face of a clubhead (or the face of a rigid member), 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, the ball and the clubhead travel together for a moment of time. After this point, the ball projects forward, pushing itself off of the face of the club. Based on the relative weight of the clubhead to that of the golf ball, the golf ball travels at a faster speed than the clubhead. The initial velocity of the golf ball can be approximated with the following equation: $v = U \times \frac{1 + COR}{1 + (m / M)}$
where v is the velocity of the ball immediately after impact, U is the velocity of the clubhead immediately before impact, m is the mass of the ball, M is the mass of the clubhead, and COR is the coefficient of restitution of the ball.
With respect to the coefficient of restitution (‘COR’) of the golf ball, in general, if the COR in 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. The COR of a typical polymeric golf ball is around 70-85%, with the losses resulting 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.
The inventors have observed that in some instances, depending on the materials used for construction, the COR of golf balls with hollow metal cores having a smooth surface or surfaces, such as that shown in FIG. 1, can be much less than 100%, in some cases ranging as low as 40%. The inventors have also determined that a large fraction of the energy losses after impact are attributed at least in part to vibrations. That is, after impact the metal sphere can be seen as being displaced about an equilibrium position (e.g., from an essentially perfect sphere to an elongated sphere) and will oscillate about this equilibrium position until internal and external frictional forces cause the vibration to decay. These vibrations are generally converted to thermal energy.
One parameter that plays a role in the vibrational response of a golf ball having a hard sphere core or layer is the stiffness of the sphere. The stiffness may be attributed to either the properties of the material used to construct the sphere, 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, etc. In addition, the properties of the polymers or other materials surrounding the sphere, as well as any materials within the sphere, affect the vibrational response. The ability to minimize or otherwise reduce vibrational losses will generally reduce the kinetic energy from the impact that is lost to heat, thereby increasing the COR of the ball. Another parameter that plays a role in the vibrational response of a golf ball is the ball's ability to dampen the vibrations caused by impact. Damping may be attributed to the properties of the materials surrounding or disposed within the hard sphere, such as the density, viscosity, modulus of elasticity, coefficients of friction, etc., of the materials. The materials may be gases, pressurized or otherwise, liquids, gels, foams, solids, etc. Additionally, the state of the materials is also a consideration, such as whether the materials are prestressed, etc. Any one of these parameters may be modified to tailor the vibrational response of the golf ball.
The following equation describes the deflection response of a three piece golf ball when struck during a high impact collision. It should be noted that although the equation describes the deflection of a three piece ball, the analysis is equally valid for a two piece ball by setting the portion relating to the mantle layer to zero.
D=(d _cover +d _mantle +d _core)
where D=the total deformation of the ball, d_cover=the deflection of the cover layer, d_mantle=the deflection of the mantle layer, and d_core=the deflection of the hollow sphere core, each of which is a function of the force F applied to the ball. The deflections of the cover, mantle, and core are all non-linear functions of the applied force, thickness of the layer, configuration, and materials of construction, respectively.
The hard hollow sphere core and a resilient mantle layer of a three piece golf ball tends to deflect in a linear manner for small loads, and becomes increasingly stiff and therefore non-linear as the load increases. A metal core is linear in its response to much higher loads. As a result, for shorter shots approaching the green, which are not struck as hard as drives, the cover and the mantle provide proportionately more of the deformation of the ball than they do in a drive which exerts much higher forces to the ball. Therefore, a golf ball can be thought of exhibiting a variable spring constant, with the constant being primarily defined by the cover and mantle layers for low energy impacts and defined primarily by the hollow metal core for high energy impacts.
Stiffness is directly related to the vibrational response of an object. The following equation for a simple harmonic oscillator relates the stiffness of a spring to various damping factors (including certain frictional forces) and the resulting vibrational response: $\frac{ⅆ^{2} x}{ⅆ t^{2}} + b \frac{ⅆ x}{ⅆ t} + ω_{o}^{2} x = A_{o} \cos (ω t)$
where t is time, b is the damping constant, ω_ois the characteristic angular frequency (equal to 2πf_O, where f is frequency in cycles per second), A_ocos(ωt) (=A_Ocos(2πft)) is the driving force with an amplitude of A_Oand an angular frequency of ω, and x is the position.
Because the force exerted on a golf ball may be considered an impact or impulse force, the initial conditions (t=0) are such that the right hand side of the equation is zero. Focusing on the left hand side of the equation, the damping coefficient and characteristic angular frequency will be important variables for design considerations in terms of controlling the vibrational response of the ball. Since the damping coefficient will not determine the amount of energy coupled to the vibrational losses of the system, only the rate at which it is dissipated as heat, this shows that the characteristic frequency will be the primary variable for designers to reduce energy losses associated with vibration. Characteristic frequency is a function of the stiffness or spring constant of the sphere or ball, as well as the state of the prestress (compression or tension forces) on the sphere.
The inventors have determined that by increasing the amount of deflection that the hard sphere core or layer of the golf ball exhibits for a given impact, without decreasing the diameter of the core, e.g., by decreasing the stiffness of the golf ball or the hard sphere, or the spring constant of the hard sphere, the COR of the ball may be increased preferably to greater than about 70%, or more preferably to greater than about 85% or about 90%, or even more preferably close to unity, with a minimal affect on the ball's high moment of inertia. Thus, increasing the defection of the hard sphere core or layer of the golf ball would provide additional design parameters and an ability to increase the total deflection of the ball without an associated increase in the ball's tendency to hook or slice. 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 that also maintains a high moment of inertia, allowing less hooks and slices during play.
The present invention therefore generally provides golf balls having an outer cover with a dimpled pattern and a hard sphere layer or core having at least one feature associated with the hard sphere or with any other layer for controlling the vibrational response of the hard sphere or the ball. The present invention may be applied toward two-piece golf balls in which instance the ball will consist of the cover with a hard sphere core, hollow or otherwise. The invention may also be applied toward other multi-piece designs using greater than two pieces, e.g., three, four, five, etc. pieces, in which instance the hard sphere may serve as an intermediate layer or as a sphere core, hollow or otherwise. The feature that controls the vibrational response of the hard sphere or of any other layer may be any feature that modifies the manner in which the golf ball responds to an impact as compared to the response of the sphere without the feature. The feature may be one that modifies, e.g., reduces or increases, as the case may be, the stiffness, the amount of deflection for a given impact, the spring constant, the damping coefficient associated with the ball or sphere, or a combination thereof. The modification may be accomplished by varying any parameter attributing to the stiffness, deflection, spring constant, or damping coefficient noted above.
Referring to FIG. 2, in one embodiment of, the present invention provides a golf ball 20 having a metal or other hard material sphere core or layer 27 surrounded by a cover layer 21, where the sphere core 27 has at least one indentation or groove 23 or other means for controlling the vibrational response of the sphere, such as for reducing the stiffness or spring constant, or increasing the deflection response of the hard sphere core or layer 27 or increasing the damping coefficient against the hard sphere core or layer as compared to core or layer without the feature. Hereinafter, the term “core” shall be used to include the term “layer”. The sphere may also be a one-piece design. Although the invention is described by way of example in relation to certain types of materials, such as a metal sphere core, it is understood that the invention is equally applicable with other hard materials that do not appreciably deform under loads, such as plastics, e.g., polypropylene, ceramics, e.g., silicon carbide, composites, e.g., carbon fiber and graphite, etc., and is thus not limited thereto. Additionally, 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 to reduce the stiffness of the core thereby allowing larger deflections at impact, e.g., elastic deformations, and is also not limited thereto.
The cover layer 21 has a cover outer surface 22 and a cover inner surface 24. The cover outer surface 22 and the cover inner surface 24 together define a cover thickness 25, 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 21 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. The cover layer 21 also forms the golf ball diameter 26. The golf ball diameter is preferably 42.67 mm (1.68 inches), but may be any diameter equal to, greater or less than 42.67 mm, preferably between about 40 mm and about 45 mm. It should be noted that the golf ball 20 of the present design may also include at least one intermediate layer (not shown) disposed between the cover layer 21 and the metal sphere core 27.
The golf ball 20 also includes a sphere core 27 having a diameter 31 and an outer core surface 28 and an inner core surface 29. Preferably, the diameter 31 of the metal sphere core 27 is about 31.75 mm (1.25 inches), 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 28 and the inner core surface 29 together define a core thickness 30. The core thickness 30 is preferably about 1.82 mm, however the core thickness 30 may be any thickness from about 0.5 mm to about 6.4 mm. The metal sphere core 27 is preferably made of titanium or titanium alloy, but may also be made of another metal alloy including stainless steel, or an intermetallic material such as aluminum. The metal sphere core 27 may also be made of iron, carbon steel, nickel, molybdenum, aluminum, tungsten or alloys of steel, nickel, aluminum, molybdenum, or tungsten.
Advantageously, in one embodiment of the present invention, the outer core surface 28 of the metal sphere core 27 includes at least one groove 23 for controlling or otherwise reducing the stiffness of the metal sphere core 27. The outer core surface 28 may include at least one horizontal groove, and more preferably includes a plurality of regularly or randomly spaced horizontal grooves 32. The outer core surface 28 may also include at least one vertical groove, and more preferably includes a plurality of regularly or randomly spaced vertical grooves 35. The material displaced by the grooves may be replaced with a filler material having a density greater than that of the cover layer or intermediate layer, as the case may be. In the embodiment depicted in FIG. 3, the outer core surface 28 of the metal sphere core 27 includes a plurality of regularly spaced horizontal grooves 32 and a plurality of regularly spaced vertical grooves 35. The plurality of regularly spaced vertical grooves 35 intersect and are substantially perpendicular to the plurality of regularly spaced horizontal grooves 33. In the depicted embodiment, the horizontal grooves 32 and the vertical grooves 35 are spaced at increments of about every ten degrees and may be manufactured by any method suitable to form grooves in metal, including, but not limited to laser cutting, mechanical stamping, casting, and chemical etching.
Referring to FIG. 4, the horizontal grooves 32 and the vertical grooves 35 define a groove width 33 and a groove depth 34. The groove width 33 is preferably about 0.30 mm, or any width from about 1 nm to about 5 mm, and the groove depth 37 is preferably about 0.91 mm, but may be any depth between 1 nm and 5 mm, depending on the thickness of the metal sphere core 27. The profile of the horizontal grooves 32 and vertical grooves 35 is preferably u-shaped with right angles defining the maximum depth, but may be any other profile or combinations of profiles suitable for controlling the stiffness of the metal sphere core 27, including but not limited to a profile having a u-shape with filleted angles defining the maximum depth as shown in FIG. 5A, or a profile having a v-shape as shown in FIG. 5B.
It should be noted that the golf ball 20 of the present invention may include other groove configurations or combinations of configurations that serve to control the vibrational response or stiffness of the metal sphere core 27. For example, at least one angled groove (not shown), and preferably, a plurality of angled grooves may intersect the plurality of vertical grooves 32. The groves or indentations may also be disposed or oriented in a random or an apparently random manner. In another embodiment, the plurality of horizontal grooves 32 and the plurality of vertical grooves 35 may be configured along lines similar to latitudinal and longitudinal lines of a globe, as shown in FIG. 6, which shows a latitude and longitude lines oriented around a single axis. A plurality of latitude and/or longitude lines may also be oriented around a plurality of axes, such as two axes, three axes, etc. The axes may be oriented at any angle from about 0 degrees to about 360 degrees from each other. In another embodiment, the plurality of horizontal grooves 32 and the plurality of vertical grooves 35 may be configured along horizontal and vertical lines on each of the two or three axes of the metal sphere core 27, as shown in FIG. 7. In another embodiment, grooves 23 may be configured along an icosahedron pattern as shown in FIG. 8.
In another embodiment, the inner core surface 29 of the metal sphere core 27 includes at least one groove 23 for controlling the stiffness of the metal sphere core 27. The inner core surface 29 may include at least one horizontal groove, and more preferably includes a plurality of regularly or randomly spaced horizontal grooves 32. The inner core surface 29 may also include at least one vertical groove, and more preferably includes a plurality of regularly or randomly spaced vertical grooves 35. In the embodiment depicted in FIG. 9, the inner core surface 29 includes a plurality of regularly or randomly spaced horizontal grooves 32 and a plurality of regularly or randomly spaced vertical grooves 35. In another embodiment, both the outer core surface 28 and the inner core surface 29 may include at least one groove 23 for controlling the stiffness of the metal sphere core 27. In the embodiment depicted in FIG. 10, both the inner core surface 29 and the outer core surface 28 include a plurality of regularly spaced horizontal grooves 32 and a plurality of regularly spaced vertical grooves 35. The orientation of the groves or indentation in the inner core surface may be any described above with relation to the outer core surface. It should further be noted that one skilled in the art may conceive other possible groove configurations that may be included on the inner core surface 29, the outer core surface 28, or both the inner core surface 29 and the outer core surface 28, including, but not limited to the examples shown in FIG. 6, FIG. 7, and FIG. 8, and combinations thereof.
The golf ball 20 of the present invention has several advantages that provide a golf ball having a hollow metal or other hard material sphere core or layer in which the vibrational response stiffness may be controlled, while maintaining a high overall moment of inertia for the golf ball. The golf ball 20 includes a cover layer 21 and a hollow metal sphere core 27 that has an outer core surface 28 and an inner core surface 29 where the outer core surface 28 has a plurality of regularly spaced horizontal grooves 32 and a plurality of regularly spaced vertical grooves 35 that serve to decrease the stiffness of the metal sphere core 27. Additionally, the grooves are regularly spaced in order to maintain a golf ball that will perform similarly about any axis of rotation, such that the golf ball will conform with the current U.S.G.A. golf ball standard. This results in a hollow metal sphere core 27 for a golf ball 20 in which the stiffness may be controlled and the effect on the high moment of inertia of the ball may be minimized.
The inventors have determined that a golf ball with a titanium metal core having a 34.64 mm diameter, a 1.82 mm wall thickness, and one degree thick grooves 0.91 mm deep spaced every ten degrees, and a 4 mm Surlyn cover, deformed 2.75 times more than a similar ball without the grooves. Accordingly, the stiffness of the hard sphere may be reduced to as low as about 36% as compared with the sphere without the grooves. It is understood that the depth, width, and number of grooves may be varied to achieve a desired stiffness. The reduced stiffness may also be achieved by one or more of the following: selecting materials and/or processing conditions for the mantle and/or cover to create a prestressed condition on the hard sphere, selecting materials with suitable characteristics, altering the physical properties of the material used to construct the hard sphere, such as by annealing, hot working, or cold working prior to or after hemisphere formation, preferentially etching material located within the grain boundaries of the metal sphere to remove material located with the grain boundaries of the bulk material, pressurizing the interior of the sphere, e.g., to create positive or negative pressure therein (to prestress the sphere either positively or negatively), uniformly altering the gauge thickness of the hard sphere, having the hard sphere consist of two or more concentric or layered hard spheres having preferred properties, or a combination thereof.
The material sets, polymer layers, and processing conditions may also be tailored to achieve the desired vibrational response. The response and performance of a finished golf ball is generally related to the combination of materials used in construction. Each layer of the golf ball will generally contribute to the overall response. That is, the final response will generally be the sum of the responses from the individual layers and any interplay between the layers. The vibrational response may therefore also be tailored by controlling the interplay between the layers of the golf ball of the present invention. For example, the cover layer or intermediate layer may be applied over the hard sphere core to prestress the sphere. This may be accomplished with rubber winding technology used with solid core golf balls, which winds polymers or rubber materials around the hard sphere to prestress the sphere. Other methods may be used to prestress the sphere, such as by using oversized, undersized, or out of round metal hemispheres that are forced into the proper spherical form and size prior to welding.
Nano-materials may also be used as the feature to tailor the vibrational response or other characteristics of the golf ball. 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. For example, materials, such as metal, e.g., titanium, with controlled grain sizes may be used for the hard sphere core with beneficial characteristics based on grain size. For example, grain sizes may be increased to reduce stiffness or the reverse. Composite materials may also be used to control the vibrational response or other characteristic of the golf ball. For example, by varying the amount of second phase dispersions within a metal matrix composite, the strength and stiffness of the base material used for the sphere may be tailored. For example, alloying elements may be introduced into the metal matrix to restrict dislocation movement thereby stiffening the material. Conversely, using essentially pure metals reduces the stiffness of the material. Additionally, nanomaterials may be used to control dispersoid-dislocation interactions, e.g., Orowan bypassing, and Hall-Petch strengthening. 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 on the hard sphere or any other layer, but may also interact with the matrix material dislocations or grain boundaries to tailor the strength or stiffness of the sphere or any other layer. For example, nano-ceramic or clay powders may be introduced into a polymer mantle layer to achieve a desired vibrational response from the ball.
The present invention generally provides golf balls that exhibit a desired vibrational response. Other hardware may similarly be tuned to the vibrational response of the golf balls tuned in accordance with the present disclosure. For example, golf clubs, such as woods, irons, wedges, putters, etc., may be tuned to the golf ball to maximize the beneficial characteristics of the golf balls.
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.

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 non-perforated hard sphere layer or core disposed within the cover layer, the hard sphere having an outer surface and an inner surface together with the outer surface defining a sphere thickness, wherein the hard sphere comprises at least one feature for controlling a vibrational response of the hard sphere.

2. A golf ball according to claim 1, wherein the at least one feature for controlling the vibrational response of the hard sphere comprises at least one indentation for controlling a stiffness of the hard sphere.

3. A golf ball according to claim 1, wherein the at least one indentation comprises a groove.

4. A golf ball according to claim 3, wherein at least one of the outer sphere surface individually, the inner sphere surface individually, and both the outer sphere surface and the inner sphere surface further comprises a plurality of grooves.

5. A golf ball according to claim 4, wherein the plurality of grooves further comprise a plurality of regularly spaced horizontal grooves and a plurality of regularly spaced vertical grooves, the plurality of vertical grooves being essentially perpendicular to the plurality of horizontal grooves.

6. A golf ball according to claim 4, wherein the plurality of grooves further comprise a plurality of regularly spaced angled grooves that intersect a plurality of regularly spaced vertical grooves and a plurality of horizontal grooves.

7. A golf ball according to claim 3, wherein at least one of the outer sphere surface individually, the inner sphere surface individually, and both the outer sphere surface and the inner sphere surface further comprises a plurality of regularly spaced grooves.

8. A golf ball according to claim 3, wherein the groove defines a groove width and a groove depth, wherein the groove width is between about 1 nm to about 5 mm and the groove depth is between about 1 nm and about 5 mm.

9. A golf ball according to claim 1, further comprising a resilient intermediate layer disposed between the hard sphere and the cover.

10. A golf ball according to claim 1, wherein the hard sphere is a metal sphere of a metal selected from the group consisting of titanium and titanium alloys.

11. A golf ball according to claim 1, wherein the at least one feature for controlling the vibrational response of the hard sphere comprises a plurality of indentations disposed randomly on at least one of the outer sphere surface and the inner sphere surface.

12. A golf ball according to claim 1, wherein the thickness of the hard sphere core is between about 0.5 mm to about 6.4 mm.

13. A golf ball according to claim 1, wherein the hard sphere is a hollow core.

14. A golf ball according to claim 13, wherein the hollow sphere comprises a material disposed within the hollow sphere to at least one of dampen impact vibrations and prestress the hollow sphere.

15. A golf ball according to claim 1, further comprising a resilient intermediate layer disposed between the hard sphere and the cover to prestress the hard sphere.

16. 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;

a hard sphere layer or core disposed within the cover layer, the hard sphere having an outer surface and an inner surface together with the outer surface defining a sphere thickness, wherein the hard sphere comprises at least one feature for controlling a vibrational response of the hard sphere; and

a resilient intermediate layer disposed between the hard sphere and the cover.

17. A golf ball comprising:

a metal sphere layer or core disposed within the cover layer, the metal sphere having an outer surface and an inner surface together with the outer surface defining a sphere thickness, wherein the metal sphere comprises at least one indentation for reducing a stiffness of the metal sphere; and

a resilient intermediate layer disposed between the metal sphere and the cover.

18. A metal sphere core for use in a modern golf ball, the metal sphere core having an outer surface and an inner surface, together defining a core thickness, wherein the outer core surface individually, the inner core surface individually, or both the outer core surface and the inner core surface have at least one grove for controlling the stiffness of the metal sphere core.

19. A metal sphere core according to claim 18, comprising a plurality of grooves, and wherein the outer core surface individually, the inner core surface individually, or both the outer core surface and the inner core surface comprise the plurality of grooves.

20. A metal sphere core according to claim 18, comprising a plurality of grooves, and wherein the outer core surface individually, the inner core surface individually, or both the outer core surface and the inner core surface comprise the plurality of regularly spaced grooves.

21. A metal sphere core according to claim 18, comprising a plurality of grooves, and wherein the outer core surface individually, the inner core surface individually, or both the outer core surface and the inner core surface includes a plurality of regularly spaced angled grooves that intersect the plurality of regularly spaced vertical grooves and the plurality of horizontal grooves.

22. A metal sphere core according to claim 18, wherein the metal is selected from the group consisting of titanium and titanium alloys.

23. A method of constructing a metal sphere core with controlled stiffness for use in a modern golf ball, the metal sphere core having an outer surface and an inner surface defining with the outer surface a core thickness, the method comprising:

forming at least one indentation in the outer core surface individually, the inner core surface individually, or both the outer core surface and the inner core surface for controlling the stiffness of the metal sphere core.

24. A method for constructing a golf ball comprising forming an intermediate layer over a hard sphere layer or core, and forming a cover layer having an outer surface defining a dimpled pattern over the intermediate layer, wherein at least one of the cover layer, intermediate layer, and sphere layer or core comprise at least one of a material selected to achieve a desired vibrational response from the ball and a property associated with a shape, size, and damping of the sphere or layer to achieve the desired vibrational response from the ball.

25. A method for constructing a golf ball according to claim 24, wherein a plurality of the cover layer, intermediate layer, and sphere layer or core, comprise a material set tailored to achieve the desired vibrational response.