# Patent

## Title
Golf ball dimple plan shape

## Abstract

The present invention is directed to golf balls having improved aerodynamic performance due, at least in part, to the selection of the plan shapes of the dimples thereon. In particular, the present invention is directed to a golf ball that includes at least a portion of its dimples having a plan shape defined by low frequency periodic functions along a closed simple path. In addition, the present invention provides methods for designing dimples having a plan shape defined by a low frequency periodic function along a closed simple path.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of U.S. patent application Ser. No. 14/941,841, filed Nov. 16, 2015, the entire disclosure of which is hereby incorporated herein by reference.


FIELD OF THE INVENTION
The present invention relates to golf balls having improved aerodynamic characteristics. The improved aerodynamic characteristics are obtained through the use of specific dimple arrangements and dimple plan shapes. In particular, the present invention relates to a golf ball including at least a portion of dimples having a plan shape defined by low frequency periodic functions, and, more particularly, a low frequency periodic sawtooth function, along a simple closed path.
BACKGROUND OF THE INVENTION
Aerodynamic forces acting on a golf ball are typically resolved into orthogonal components of lift (FL) and drag (FD). Lift is defined as the aerodynamic force component acting perpendicular to the flight path. It results from a difference in pressure that is created by a distortion in the air flow that results from the back spin of the ball. Due to the back spin, the top of the ball moves with the air flow, which delays the separation to a point further aft. Conversely, the bottom of the ball moves against the air flow, moving the separation point forward. This asymmetrical separation creates an arch in the flow pattern, requiring the air over the top of the ball to move faster, and thus have lower pressure than the air underneath the ball.
Drag is defined as the aerodynamic force component acting opposite to the ball flight direction. As the ball travels through the air, the air surrounding the ball has different velocities and, thus, different pressures. The air exerts maximum pressure at the stagnation point on the front of the ball. The air then flows over the sides of the ball and has increased velocity and reduced pressure. The air separates from the surface of the ball, leaving a large turbulent flow area with low pressure, i.e., the wake. The difference between the high pressure in front of the ball and the low pressure behind the ball reduces the ball speed and acts as the primary source of drag.
Lift and drag, among other aerodynamic characteristics of a golf ball are influenced by the external surface geometry of the ball, which includes the dimples thereon. As such, the dimples on a golf ball play an important role in controlling those parameters. For example, the dimples on a golf ball create a turbulent boundary layer around the ball, i.e., the air in a thin layer adjacent to the ball flows in a turbulent manner. The turbulence energizes the boundary layer and helps it stay attached further around the ball to reduce the area of the wake. This greatly increases the pressure behind the ball and substantially reduces the drag.
Accordingly, the design variables associated with the external surface geometry of a golf ball, e.g., influenced by surface coverage, dimple pattern, and individual dimple geometries provide golf ball manufacturers the ability to control and optimize ball flight. However, there has been little to no focus on the plan shape of a dimple, i.e., the perimeter or boundaries of the dimple on the golf ball outer surface, as a key variable in achieving such control and optimization. In particular, since the bifurcation created by the plan shape of a dimple creates a large transition from the external surface geometry, it is considered to play a role in aerodynamic behavior. As such, there remains a need for a dimple plan shape that maximizes surface coverage uniformity and packing efficiency, while maintaining desirable aerodynamic characteristics.
SUMMARY OF THE INVENTION
The present invention is directed to a golf ball having a generally spherical surface and including a plurality of dimples on the spherical surface, wherein at least a portion of the plurality of dimples, for example, about 50 percent or more, or about 80 percent or more, have a non-circular plan shape defined by a low frequency periodic function along a simple closed path. In one embodiment, the periodic function is a smooth sinusoidal periodic function such as a sine function. In another embodiment, the periodic function is a non-smooth function selected from a sawtooth wave, triangle wave, or square wave function. The periodic function may also be a combination of two or more periodic functions including smooth and non-smooth functions. In another embodiment, the periodic function is an arbitrary periodic function. In still another embodiment, the simple closed path is selected from a circle, ellipse, or square. The simple closed path may also be an arbitrary closed curve.
In this aspect, the plan shape is defined according to the following function:

Q(x)=Fpath(l,scl,x)*Fperiodic(s,a,p,x)

where Fpath is a path function of length l, with scale factor scl, defined along the vertices x; and Fperiodic is a periodic function with sharpness factor s, amplitude a, and period p defined at the vertices x. In one embodiment, the low frequency periodic function has a period of about 15 or less.

The present invention is also directed to a golf ball having a generally spherical surface and including a plurality of dimples on the surface, wherein at least a portion of the plurality of dimples, for example, about 50 percent or more, or about 80 percent or more, have a plan shape defined by a low frequency periodic function along a simple closed path according to the following function:

Q(x)=Fpath(l,scl,x)*Fperiodic(s,a,p,x)

where Fpath is a path function of length l, with scale factor scl, defined along the vertices x; and Fperiodic is a periodic function with sharpness factor s, amplitude a, and period p defined at the vertices x. In one embodiment, the periodic function is selected from a sine, cosine, sawtooth wave, triangle wave, square wave, or arbitrary function. In another embodiment, the path function is any simple closed path that is symmetrical about two orthogonal axes. For example, the path function may be selected from a circle, ellipse, or square. In still another embodiment, the period, p, may be about 15 or less, or about 9 or less. In yet another embodiment, the amplitude, a, is about 1 or less. In this aspect, the plan shape has an amplitude A of less than about 0.500.

The present invention is further directed to a golf ball having a surface with a plurality of recessed dimples thereon, wherein at least one of the dimples has a plan shape defined by a low frequency periodic function along a simple closed path symmetrical about two orthogonal axes according to the following function:

Q(x)=Fpath(l,scl,x)*Fperiodic(s,a,p,x)

where Fpath is a path function of length l, with scale factor scl, defined along the vertices x; and Fperiodic is a periodic function with sharpness factor s, amplitude a, and period p defined at the vertices x, wherein the periodic function is selected from a sine, cosine, sawtooth wave, triangle wave, square wave, or arbitrary function. In this aspect, the periodic function may be a sawtooth wave form, a square wave form, a cosine wave form, or a triangle wave form. In another embodiment, the plan shape has an amplitude A of about 0.0005 inches to about 0.100 inches.

The present invention is further directed to a golf ball having a generally spherical surface and comprising a plurality of dimples on the spherical surface, wherein at least a portion of the plurality of dimples have a non-circular plan shape defined by a low frequency periodic sawtooth function mapped along a circular simple closed path resulting in the following function:

Q(x)=Fpath(l,scl,x)*Fperiodic(s,a,p,x)

where Fpath is a circular function of length l, with scale factor scl, defined along the vertices x; and Fperiodic is a periodic sawtooth function with sharpness factor s, amplitude a, and period p defined at the vertices x.




BRIEF DESCRIPTION OF THE DRAWINGS
Further features and advantages of the invention can be ascertained from the following detailed description that is provided in connection with the drawings described below:
FIG. 1 illustrates the waveform of a cosine periodic function for use in a dimple plan shape according to the present invention;
FIG. 2 illustrates the waveform of a sawtooth wave periodic function approximated by a Fourier series for use in a dimple plan shape according to the present invention;
FIG. 3 illustrates the waveform of a triangle wave periodic function approximated by a Fourier series for use in a dimple plan shape according to the present invention;
FIG. 4 illustrates the waveform of a square wave periodic function approximated by a Fourier series for use in a dimple plan shape according to the present invention;
FIG. 5 illustrates the waveform of an arbitrary periodic function for use in a dimple plan shape according to the present invention;
FIG. 6 is a flow chart illustrating the steps according to a method of the present invention;
FIGS. 7A-7F illustrate various embodiments of a golf ball dimple plan shape defined by a cosine periodic function along a circular path;
FIGS. 8A-8F illustrate various embodiments of a golf ball dimple plan shape defined by a sawtooth wave periodic function along a circular path;
FIGS. 9A-9F illustrate various embodiments of a golf ball dimple plan shape defined by a triangle wave periodic function along a circular path;
FIGS. 10A-10F illustrate various embodiments of a golf ball dimple plan shape defined by a square wave periodic function along a circular path;
FIGS. 11A-11F illustrate various embodiments of a golf ball dimple plan shape defined by a square wave periodic function along an elliptical path;
FIGS. 12A-12F illustrate various embodiments of a golf ball dimple plan shape defined by a square wave periodic function along a square path;
FIGS. 13A-13F illustrate various embodiments of a golf ball dimple plan shape defined by an arbitrary periodic function along a circular path;
FIGS. 14A-14F illustrate various embodiments of a golf ball dimple plan shape defined by an arbitrary periodic function along an arbitrary path;
FIG. 15 illustrates a golf ball dimple pattern constructed from a plurality of dimple plan shapes according to the present invention;
FIG. 16A is a graphical representation illustrating dimple surface volumes for golf balls produced in accordance with the present invention;
FIG. 16B is a graphical representation illustrating preferred dimple surface volumes for golf balls produced in accordance with the present invention;
FIG. 17 illustrates a golf ball dimple plan shape produced in accordance with the present invention;
FIG. 18 illustrates a golf ball dimple plan shape produced in accordance with the present invention;
FIG. 19 is a graphical representation illustrating the range of the ratio of sharpness factor to amplitude for a periodic function for a given radius of a circular path in accordance with the present invention;
FIG. 20 illustrates a golf ball dimple plan shape defined by a periodic sawtooth function mapped along a circular path in accordance with the present invention and a golf ball dimple profile shape defined by a parabolic function;
FIG. 21 illustrates a golf ball pattern having a plurality of dimple plan shapes produced in accordance with the present invention;
FIG. 22 illustrates a golf ball dimple plan shape defined by a periodic sawtooth function mapped along a circular path in accordance with the present invention and a golf ball dimple profile shape defined by an exponential function;
FIG. 23 illustrates a golf ball pattern having a plurality of dimple plan shapes produced in accordance with the present invention;
FIG. 24 illustrates a golf ball dimple plan shape defined by a periodic sawtooth function mapped along a circular path in accordance with the present invention and a golf ball dimple profile shape defined by a trigonometric function;
FIG. 25 illustrates a golf ball pattern having a plurality of dimple plan shapes produced in accordance with the present invention;
FIG. 26 illustrates a golf ball dimple plan shape defined by a periodic sawtooth function mapped along a circular path in accordance with the present invention and a golf ball dimple profile shape defined by a polynomial function;
FIG. 27 illustrates a golf ball pattern having a plurality of dimple plan shapes produced in accordance with the present invention;
FIG. 28 illustrates a golf ball dimple plan shape defined by a periodic sawtooth function mapped along a circular path in accordance with the present invention and a golf ball dimple profile shape defined by a mixed function containing exponential and polynomial terms; and
FIG. 29 illustrates a golf ball pattern having a plurality of dimple plan shapes produced in accordance with the present invention.



DETAILED DESCRIPTION
The present invention is directed to golf balls having improved aerodynamic performance due, at least in part, to the use of non-circular dimple plan shapes. In particular, the present invention is directed to a golf ball that includes at least a portion of its dimples having a plan shape defined by low frequency periodic functions along a simple closed path.
Advantageously, the dimple plan shapes in accordance with the present invention allow for greater control and flexibility in defining the dimple geometry. For example, when dimple shapes or boundaries of the golf ball are circular, the packing efficiency and number of the dimples is limited. In fact, dimple patterns that provide a high percentage of surface coverage as disclosed, for example, in U.S. Pat. Nos. 5,562,552, 5,575,477, 5,957,787, 5,249,804, and 4,925,193 disclose geometric patterns for positioning dimples on a golf ball that are based on circular dimples. Since a number of dimple shapes are possible using the present invention, the present invention, in turn, provides for improved dimple packing efficiency and uniformity of surface coverage. As a result, the present invention provides a golf ball manufacturer the ability to fine tune golf ball aerodynamic characteristics by controlling the external surface geometry of the dimple.
Additionally, the plan shapes of dimples according to the present invention are unique in appearance. For example, in one embodiment, the low frequency periodic functions defining the plan shapes of the present invention provide perimeters having a distinct appearance. In turn, the plan shapes of the present invention provide for golf ball surface textures having distinct visual appearances as well as golf balls having improved aerodynamic characteristics.
Further, advantageously, dimples having plan shapes according to the invention and the golf balls incorporating such dimples provide a means to fine tune golf ball aerodynamic characteristics by specifically controlling the perimeter or boundary of each dimple. This allows the dimples to create the turbulence in the boundary layer. “Micro” adjusting the dimple plan shapes in accordance with the present invention allows for further agitation and/or tuning of the turbulent flow over the dimples. This, in turn, reduces the tendency for separation of the turbulent boundary layer around the golf ball in flight, and thus improves the aerodynamic performance of the golf ball. Further, plan shapes of the present invention allow for improved regularity of the undimpled golf ball surface. This allows the golf ball to remain resistant to premature wear and tear.
Dimple Plan Shapes
The present invention contemplates dimples having a non-circular plan shape defined by low frequency, low amplitude periodic functions or linear combinations thereof along a simple closed path. In particular, golf balls formed according to the present invention include at least one dimple having a plan shape defined by low frequency, low amplitude periodic functions or linear combinations thereof along a simple closed path. By the term, “plan shape,” it is meant the shape of the perimeter of the dimple, or the demarcation between the dimple and the outer surface of the golf ball or fret surface.
According to the present invention, at least one dimple is formed using a simple closed path, i.e., a path that starts and ends at the same point without traversing any defining point or edge along the path more than once. For example, the present invention contemplates dimples formed using any simple cycle known in graph theory including circles and polygons. In one embodiment, the simple closed path is any path that is symmetrical about two orthogonal axes. In another embodiment, the simple closed path is a circle, ellipse, square, or polygon. In still another embodiment, the simple closed path is an arbitrary path. In this aspect, a suitable dimple shape according to the present invention may be based on any path that starts and ends at the same point without intersecting any defining point or edge.
The present invention contemplates the use of periodic functions to form the dimple shape including any function that repeats its values at regular intervals or periods. For the purposes of the present invention, a function ƒ is periodic if

ƒ(x)=ƒ(x+p)  (1)

for all values of x where p is the period. In particular, the present invention contemplates any periodic function that is non-constant, non-zero.

In one embodiment, the periodic function used to form the dimple shape includes a trigonometric function. Examples of trigonometric functions suitable for use in accordance with the present invention include, but are not limited to, sine and cosine. FIG. 1 illustrates the waveform of a cosine periodic function that may be used to form a dimple shape in accordance with the invention. As shown in FIG. 1, the cosine wave 2 suitable for use in accordance with the present invention has a shape identical to that of a sine wave, except that each point on the cosine wave occurs exactly 1⁄4 cycle earlier than the corresponding point on the sine wave.
In another embodiment, the periodic function suitable for use in forming a dimple shape in accordance with the present invention includes a non-smooth periodic function. Non-limiting examples of non-smooth periodic functions suitable for use with the present invention include, but are not limited to, sawtooth wave, triangle wave, square wave, and cycloid. In one embodiment, a sawtooth wave is suitable for use in forming a dimple shape in accordance with the present invention. In particular, a dimple in accordance with the present invention may have a shape based on a non-sinusoidal waveform that ramps upward and then sharply drops.
In another embodiment, a triangle wave is suitable for use in forming a dimple shape in accordance with the present invention. The triangle wave suitable for use in forming a dimple shape in accordance with the present invention is a non-sinusoidal waveform that is a periodic, piecewise linear, continuous real function.
In yet another embodiment, a square wave is suitable for use in forming a dimple shape in accordance with the present invention. For example, the square wave suitable for use in forming a dimple shape in accordance with the present invention is a non-sinusoidal periodic waveform in which the amplitude alternates at a steady frequency between fixed minimum and maximum values, with the same duration at minimum and maximum.
In this aspect of the invention, any of the above-mentioned periodic functions may be constructed as an infinite series of sines and cosines using Fourier series expansion for use in forming a dimple shape in accordance with the present invention. In particular, the Fourier series of a function, which is given by equations (2)-(5), is contemplated for use in forming the dimple shape according to the present invention:




  
    
      
        
          
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In addition, the following Fourier series are contemplated for use in forming the dimple shape in accordance with the present invention.







TABLE 1







FOURIER SERIES OF NON-SMOOTH PERIODIC FUNCTIONS










Periodic Function
Fourier Series







Sawtooth wave




  
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Triangle wave




  
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Square wave




  
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For example, FIG. 2 illustrates the waveform of a sawtooth wave approximated by a Fourier series. In particular, FIG. 2 illustrates a sawtooth wave 4 approximated by a four-term Fourier series expansion for use in forming a dimple shape in accordance with the present invention. The four term sawtooth expansion can be described by:




  
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        .
      
    
  




In addition, FIG. 3 illustrates the waveform of a triangle wave approximated by a Fourier series. FIG. 3 illustrates a triangle wave 6 approximated by a four-term Fourier series expansion for use in forming a dimple shape in accordance with the present invention. Further, FIG. 4 illustrates the waveform of a square wave approximated by a Fourier series. For example, FIG. 4 illustrates a square wave 8 approximated by a four-term Fourier series expansion for use in forming a dimple shape in accordance with the present invention.
While the above examples demonstrate four-term Fourier series expansions, it will be understood by those of ordinary skill in the art that more than or less than four terms may be used to approximate the non-sinusoidal waveforms. In addition, any method of approximation known to one of ordinary skill in the art may be used in this aspect of the invention.
In yet another embodiment, the present invention contemplates arbitrary periodic functions, or linear combinations of periodic functions for use in forming a dimple shape in accordance with the present invention. Accordingly, in one embodiment of the present invention, an arbitrary periodic function may be created using a linear combination of sines and cosines to form a dimple shape in accordance with the present invention. In this aspect, FIG. 5 illustrates the waveform of an arbitrary periodic function contemplated by the present invention. As shown in FIG. 5, the arbitrary wave 10 represents a linear combination of sines and cosines.
According to the present invention, the plan shape of the dimple may be produced by projecting or mapping any of the above-referenced periodic functions onto the simple closed path. In general, the mathematical formula representing the projection or mapping of the periodic function onto the simple closed path is expressed as equation (6):

Q(x)=Fpath(l,scl,x)*Fperiodic(s,a,p,x)  (6)

where Fpath represents the simple closed path on which the periodic function is mapped or projected with length l, scale factor scl, defined along the vertices x; and Fperiodic is any suitable periodic function with sharpness factor s, amplitude a, and period p defined at the vertices x.

In one embodiment, the projection may be described in terms of how the path function is altered by the periodic function. For example, the resulting vector Q(x) represents the altered coordinates of the path. Indeed, the “path function” contemplated by the present invention includes any of the simple paths discussed above.
In this aspect of the invention, the resulting vector, Q(x), may also be a suitable path for a dimple plan shape according to the present invention. That is, the resulting vector, Q(x), could itself become a path to which another periodic function is mapped. Indeed, any of the periodic functions disclosed above may be mapped to the resulting vector, Q(x), to form a dimple plan shape in accordance with the present invention.
The “length,” l, and “scale factor,” scl, may vary depending on the desired size of the dimple. However, in one embodiment, the length is about 0.150 inches to about 1.400 inches. In another embodiment, the length is about 0.250 inches to about 1.200 inches. In still another embodiment, the length is about 0.500 inches to about 0.800 inches.
The variable, Fperiodic, of equation (6) will vary based on the desired periodic function. The term, “sharpness factor,” is a scalar value and defines the mean of the periodic function. Generally, small values of s produce periodic functions that greatly alter the plan shape, while larger values of s produce periodic functions having a diminished influence on the plan shape. Indeed, as will be apparent to one of ordinary skill in the art, once an amplitude value is chosen, the sharpness factor, s, may be varied depending on the desired amount of alteration to the plan shape. In one embodiment, the sharpness factor ranges from about 10 to about 60. In another embodiment, the sharpness factor ranges from about 15 to about 55. In still another embodiment, the sharpness factor ranges from about 20 to about 50.
The amplitude of the plan shape, A, is defined as the absolute value of the maximum distance from the path during one period of the periodic function. The amplitude of the periodic function, a, affects the dimple plan shape in the opposite sense as sharpness factor, s. In this aspect, the “sharpness factor,” s, and “amplitude,” a, parameters are both used to control the mapped periodic function used to define Q(x). For example, the sharpness factor, s, and amplitude, a, parameters control the severity of the perimeter of the final plan shape.
In one embodiment, the amplitude, a, of the periodic function ranges from about 0.1 to about 1. In another embodiment, the amplitude, a, ranges from about 0.2 to about 0.8. In still another embodiment, the amplitude, a, ranges from about 0.3 to about 0.7. In yet another embodiment, the amplitude, a, ranges from about 0.4 to about 0.6. For example, the amplitude, a, may be about 0.5.
In one embodiment, the ratio of the sharpness factor, s, to the amplitude, a, defined as s divided by a, is within a range shown as region 1 or region 2 in FIG. 19 for a periodic function mapped along a circular path having a radius, r.
In another embodiment, the amplitude of the plan shape, A, i.e., the amplitude of function Q(x), is related to the period, p, and the dimple diameter, d, by equation (7):

A=πd/2p  (7)

For example, FIG. 17 illustrates a plan shape constructed in accordance with the present invention having amplitude, A. As shown in FIG. 17, the amplitude A defines the maximum variation between the plan shape 90 from the path 95 (represented by the dashed line) during one period of the periodic function.
Low amplitude periodic functions are contemplated for use in forming a dimple shape in accordance with the present invention. In one embodiment, the amplitude A is less than about 0.500. In another embodiment, the amplitude A is about 1×10−7 to about 0.100. In still another embodiment, the amplitude A is about 1×10−6 to about 0.070. In yet another embodiment, the amplitude A is about 1×10−5 to about 0.040. In still another embodiment, the amplitude A is about 0.0001 to about 0.002. For example, the amplitude A is about 0.078.
The amplitude of the plan shape, A, can be expressed as the maximum distance of any point on the plan shape from the path. In one embodiment, the maximum distance ranges from about 0.0001 inches to about 0.035 inches. In another embodiment, the maximum distance ranges from about 0.001 inches to about 0.020 inches. In another embodiment, the maximum distance ranges from about 0.001 inches to about 0.015 inches. In another embodiment, the maximum distance ranges from about 0.002 inches to about 0.010 inches. In another embodiment, the maximum distance ranges from about 0.002 inches to about 0.008 inches. In another embodiment, the maximum distance ranges from about 0.003 inches to about 0.008 inches.
FIG. 18 illustrates a plan shape constructed in accordance with the present invention, wherein a periodic function is mapped along a circular path. The absolute distance, d, of any point on the plan shape 100 from the circular path 105 (represented by the dashed line) is defined by the following equation:

d=√{square root over ((xcircle−xplan)2+(ycircle−yplan)2)},

where d is a directed distance calculated along a line from the plan shape centroid through corresponding points on the plan shape and circular path. The amplitude of the plan shape, A, is expressed as the maximum value, dmax, for all calculated distances, d. In a particular embodiment of the present invention, a periodic function is mapped along a circular path having a radius of from about 0.025 inches to about 0.150 inches, and the maximum value, dmax, for all calculated distances, d, of any point on the plan shape from the circular path is from about 0.001 inches to about 0.015 inches.

In this aspect, the amplitude of the plan shape, A, can also be expressed as a ratio of amplitude of the plan shape, A, to effective dimple diameter. For example, the ratio of amplitude of the plan shape, A, to effective dimple diameter is about 10:1 or less. In another embodiment, the ratio of amplitude of the plan shape, A, to effective dimple diameter is about 7.5:1 or less. In yet another embodiment, the ratio of amplitude of the plan shape, A, to effective dimple diameter is about 5:1 or less.
The “period,” p, refers to the horizontal distance required for the periodic function to complete one cycle. For example, as shown in FIG. 1, one period p of the waveform is depicted by the dotted line. As will be apparent to one of ordinary skill in the art, the period may vary based on the periodic function. However, in one embodiment, the present invention contemplates periodic functions having a period of about 15 or less. In another embodiment, the present invention contemplates periodic functions having a period of less than about 15. In another embodiment, the present invention contemplates periodic functions having a period of less than about 12. In another embodiment, the present invention contemplates periodic functions having a period of about 10 or less. In another embodiment, the present invention contemplates periodic functions having a period of less than about 9. In another embodiment, the present invention contemplates periodic functions having a period of about 8 or less. In another embodiment, the present invention contemplates periodic functions having a period of less than about 6. In another embodiment, the present invention contemplates periodic functions having a period of about 5 or less. For example, the present invention contemplates periodic functions having a period of less than about 5.
The period of the wave function is inversely proportional to the function frequency. Indeed, the frequency refers to the number of periods completed over the path function. For example, the frequency of a periodic function having a period p is represented by 1/p. In one embodiment, the present invention contemplates low frequency periodic functions. That is, the present invention contemplates periodic functions having a frequency of about 1/15 or more. In one embodiment, the periodic function has a frequency of about 1/12 or more. In another embodiment, the periodic function has a frequency of about 1/9 or more. In still another embodiment, the periodic function has a frequency of about 1⁄6 or more. In yet another embodiment, the periodic function has a frequency of about 1⁄5 or more.
Accordingly, by manipulating the variables of equation (6), the present invention provides for golf ball dimples having various plan shapes defined by low frequency periodic functions along simple closed paths. By using the low frequency, low amplitude periodic functions and simple closed paths disclosed herein, the present invention allows for numerous dimple plan shapes.
FIG. 6 illustrates one embodiment of a method of forming a dimple plan shape in accordance with the present invention. For example, step 101 includes selecting the simple closed path on which the periodic function is to be projected. In this aspect, the present invention contemplates the use of any of the simple closed paths discussed above. Step 102 includes selecting the desired periodic function. Indeed, any of the periodic functions disclosed above are contemplated in this aspect of the invention.
At step 103, the amplitude, sharpness, period, or frequency of the periodic function is selected based on the desired periodic function and path. In one embodiment, the present invention contemplates dimple plan shapes defined by a low frequency, low amplitude periodic function. Accordingly, the amplitude, sharpness, period, or frequency should be selected such that the values are in accordance with the parameters defined above.
At step 104, the variables selected above, including the path, periodic function, amplitude, sharpness, and period, are inserted into equation (6), reproduced below:

Q(x)=Fpath(l,scl,x)*Fperiodic(s,a,p,x)  (6)

The resultant function is then used to project the periodic function onto the simple closed path in order to generate the dimple plan shape. The resultant function will vary based on the desired path and periodic function. For example, if the desired periodic function is a cosine function, Fperiodic may be represented by equation (8), depicted below:

f(x)=s+a*cos (p*pi*x)  (8)

As discussed above, the resultant dimple plan shape (e.g., the resulting vector Q(x)) may also be used as the path to which another periodic function is mapped. For example, a periodic function having a different period or a different periodic function may be projected onto the resultant dimple plan shape to form a new dimple plan shape in accordance with the present invention.
After the dimple plan shape has been generated, at step 105, the plan shape can be used in designing geometries for dimple patterns of a golf ball. For example, the plan shape paths generated by the methods of the present invention can be imported into a CAD program and used to define dimple geometries and tool paths for fabricating tooling for golf ball manufacture. The various dimple geometries produced in accordance with the present invention can then be used in constructing a dimple pattern that maximizes surface coverage uniformity and dimple packing efficiency.
Golf ball dimple patterns using plan shapes produced in accordance with the present invention can be modified in a number of ways to alter ball flight path and the associated lift and drag characteristics. The plan shapes can be scaled and weighted according to proximity to neighboring dimples. For example, the plan shapes of the present invention may be enlarged or reduced based on the neighboring dimples in order to allow for greater dimple packing efficiency. Likewise, the profile can be ‘micro’ altered to tailor desired dimple volume, edge angle, or dimple depth to optimize flight performance.
Dimple Patterns & Packing
The present invention allows for improved dimple packing over previous patterns so that a greater percentage of the surface of the golf ball is covered by dimples. In particular, each dimple having a plan shape in accordance with the present invention is part of a dimple pattern that maximizes surface coverage uniformity and packing efficiency.
In one embodiment, the dimple pattern provides greater than about 80 percent surface coverage. In another embodiment, the dimple pattern provides greater than about 85 percent surface coverage. In yet another embodiment, the dimple pattern provides greater than about 90 percent surface coverage. In still another embodiment, the dimple pattern provides greater than about 92 percent surface coverage.
In this aspect, the golf ball dimple plan shapes of the present invention can be tailored to maximize surface coverage uniformity and packing efficiency by selecting a period for the periodic function that is a scalar multiple of the number of neighboring dimples. For example, if the number of neighboring dimples is 4, the present invention contemplates a dimple plan shape having a period of 8 or 12. In another embodiment, the period is equal to the number of neighboring dimples. For example, if the dimple plan shape is constructed using a period of 5, the present invention contemplates that the dimple will be surrounded by 5 neighboring dimples.
FIG. 15 illustrates an example of a dimple pattern created in accordance with the present invention. In particular, FIG. 15 illustrates a golf ball dimple pattern 110 made up of non-circular dimple plan shapes (represented by 115) defined by low frequency periodic functions and produced in accordance with the present invention. As demonstrated in FIG. 15, the present invention provides for the possibility of interdigitation amongst neighboring dimples, a characteristic not possible with conventional circular dimples. This creates the opportunity for additional dimple packing arrangements and dimple distribution on the golf ball surface.
While the plan shapes of the present invention may be used for at least a portion of the dimples on a golf ball, it is not necessary that the plan shapes be used on every dimple of a golf ball. In general, it is preferred that a sufficient number of dimples on the ball have plan shapes according to the present invention so that the aerodynamic characteristics of the ball may be altered and the packing efficiency benefits realized. For example, at least about 30 percent of the dimples on a golf ball include plan shapes according to the present invention. In another embodiment, at least about 50 percent of the dimples on a golf ball include plan shapes according to the present invention. In still another embodiment, at least about 70 percent of the dimples on a golf ball include plan shapes according to the present invention. In yet another embodiment, at least about 90 percent of the dimples on a golf ball include the plan shapes of the present invention. In still another embodiment, all of the dimples (100 percent) on a golf ball may include the plan shapes of the present invention.
While the present invention is not limited by any particular dimple pattern, dimples having plan shapes according to the present invention are arranged preferably along parting lines or equatorial lines, in proximity to the poles, or along the outlines of a geodesic or polyhedron pattern. Conventional dimples, or those dimples that do not include the plan shapes of the present invention, may occupy the remaining spaces. The reverse arrangement is also suitable. Suitable dimple patterns include, but are not limited to, polyhedron-based patterns (e.g., icosahedron, octahedron, dodecahedron, icosidodecahedron, cuboctahedron, and triangular dipyramid), phyllotaxis-based patterns, spherical tiling patterns, and random arrangements.
Dimple Dimensions
The dimples on the golf balls of the present invention may include any width, depth, depth profile, edge angle, or edge radius and the patterns may include multitudes of dimples having different widths, depths, depth profiles, edge angles, or edge radii.
Since the plan shape perimeters of the present invention are noncircular, the plan shapes are defined by an effective dimple diameter which is twice the average radial dimension of the set of points defining the plan shape from the plan shape centroid. For example, in one embodiment, dimples according to the present invention have an effective dimple diameter within a range of about 0.005 inches to about 0.300 inches. In another embodiment, the dimples have an effective dimple diameter of about 0.020 inches to about 0.250 inches. In still another embodiment, the dimples have an effective dimple diameter of about 0.100 inches to about 0.225 inches. In yet another embodiment, the dimples have an effective dimple diameter of about 0.125 inches to about 0.200 inches.
The surface depth for dimples of the present invention is within a range of about 0.003 inches to about 0.025 inches. In one embodiment, the surface depth is about 0.005 inches to about 0.020 inches. In another embodiment, the surface depth is about 0.006 inches to about 0.017 inches.
The dimples of the present invention also have a plan shape area. By the term, “plan shape area,” it is meant the area based on a planar view of the dimple plan shape, such that the viewing plane is normal to an axis connecting the center of the golf ball to the point of the calculated surface depth. In one embodiment, dimples of the present invention have a plan shape area ranging from about 0.0025 in2 to about 0.045 in2. In another embodiment, dimples of the present invention have a plan shape area ranging from about 0.005 in2 to about 0.035 in2. In still another embodiment, dimples of the present invention have a plan shape area ranging from about 0.010 in2 to about 0.030 in2.
Further, dimples of the present invention have a dimple surface volume. By the term, “dimple surface volume,” it is meant the total volume encompassed by the dimple shape and the surface of the golf ball. FIGS. 16A and 16B illustrate graphical representations of dimple surface volumes contemplated for dimples produced in accordance with the present invention.
For example, FIGS. 16A and 16B demonstrate contemplated dimple surface volumes over a range of plan shape areas. In one embodiment, dimples produced in accordance with the present invention have a plan shape area and dimple surface volume falling within the ranges shown in FIG. 16A. For example, a dimple having a plan shape area of about 0.01 in2 may have a surface volume of about 0.20×10−4 in3 to about 0.50×10−4 in3. In another embodiment, a dimple having a plan shape area of about 0.025 in2 may have a surface volume of about 0.80×10−4 in3 to about 1.75×10−4 in3. In still another embodiment, a dimple having a plan shape area of about 0.030 in2 may have a surface volume of about 1.20×10−4 in3 to about 2.40×10−4 in3. In yet another embodiment, a dimple having a plan shape area of about 0.045 in2 may have a surface volume of about 2.10×10−4 in3 to about 4.25×10−4 in3.
In another embodiment, dimples produced in accordance with the present invention have a plan shape area and dimple surface volume falling within the ranges shown in FIG. 16B. For example, a dimple having a plan shape area of about 0.01 in2 may have a surface volume of about 0.25×10−4 in3 to about 0.35×10−4 in3. In another embodiment, a dimple having a plan shape area of about 0.025 in2 may have a surface volume of about 1.10×10−4 in3 to about 1.45×10−4 in3. In yet another embodiment, a dimple having a plan shape area of about 0.030 in2 may have a surface volume of about 1.40×10−4 in3 to about 1.90×10−4 in3.
Since, as discussed above, the dimple patterns useful in accordance with the present invention do not necessarily include only dimples having plan shapes as described above, other conventional dimples included in the dimple patterns may have similar dimensions.
Dimple Profile
In addition to varying the size of the dimples, the cross-sectional profile of the dimples may be varied. The cross-sectional profile of the dimples according to the present invention may be based on any known dimple profile shape. In one embodiment, the profile of the dimples corresponds to a curve. For example, the dimples of the present invention may be defined by the revolution of a catenary curve about an axis, such as that disclosed in U.S. Pat. Nos. 6,796,912 and 6,729,976, the entire disclosures of which are incorporated by reference herein. In another embodiment, the dimple profiles correspond to polynomial curves, ellipses, spherical curves, saucer-shapes, truncated cones, trigonometric, exponential, or logarithmic curves, and flattened trapezoids.
The profile of the dimple may also aid in the design of the aerodynamics of the golf ball. For example, shallow dimple depths, such as those in U.S. Pat. No. 5,566,943, the entire disclosure of which is incorporated by reference herein, may be used to obtain a golf ball with high lift and low drag coefficients. Conversely, a relatively deep dimple depth may aid in obtaining a golf ball with low lift and low drag coefficients.
The dimple profile may also be defined by combining a spherical curve and a different curve, such as a cosine curve, a frequency curve or a catenary curve, as disclosed in U.S. Patent Publication No. 2012/0165130, which is incorporated in its entirety by reference herein. Similarly, the dimple profile may be defined by a combination of two or more curves. For example, in one embodiment, the dimple profile is defined by combining a spherical curve and a different curve. In another embodiment, the dimple profile is defined by combining a cosine curve and a different curve. In still another embodiment, the dimple profile is defined by combining a frequency curve and a different curve. In yet another embodiment, the dimple profile is defined by combining a catenary curve and different curve. In still another embodiment, the dimple profile may be defined by combining three or more different curves. In yet another embodiment, one or more of the curves may be a functionally weighted curve, as disclosed in U.S. Patent Publication No. 2013/0172123, which is incorporated in its entirety by reference herein.
Golf Ball Construction
The dimples of the present invention may be used with practically any type of ball construction. For instance, the golf ball may have a two-piece design, a double cover, or veneer cover construction depending on the type of performance desired of the ball. Other suitable golf ball constructions include solid, wound, liquid-filled, and/or dual cores, and multiple intermediate layers.
Different materials may be used in the construction of the golf balls made with the present invention. For example, the cover of the ball may be made of a thermoset or thermoplastic, a castable or non-castable polyurethane and polyurea, an ionomer resin, balata, or any other suitable cover material known to those skilled in the art. Conventional and non-conventional materials may be used for forming core and intermediate layers of the ball including polybutadiene and other rubber-based core formulations, ionomer resins, highly neutralized polymers, and the like.
EXAMPLES
The following non-limiting examples demonstrate plan shapes of golf ball dimples made in accordance with the present invention. The examples are merely illustrative of the preferred embodiments of the present invention, and are not to be construed as limiting the invention, the scope of which is defined by the appended claims.
Example 1
The following example illustrates golf ball dimple plan shapes defined by a low frequency cosine periodic function mapped to a circular path. Table 2, depicted below, describes the mathematical parameters used to project the periodic function onto the simple closed path.







TABLE 2





PLAN SHAPE PARAMETERS OF EXAMPLE 1


















Path
Circular



Periodic Function
Cosine



Function (f(x))
f (x) = s + a * cos(πpx)



Sharpness Factor, s
about 15



Amplitude, a
about 1










FIGS. 7A-7F demonstrate the golf ball dimple plan shapes produced in accordance with the parameters of Table 2. In particular, FIG. 7A shows a dimple plan shape 11 defined by a cosine periodic function having period, p=3, mapped to a circular path. FIG. 7B shows a dimple plan shape 12 defined by a cosine periodic function having period, p=4, mapped to a circular path. FIG. 7C shows a dimple plan shape 13 defined by a cosine periodic function having period, p=5, mapped to a circular path. FIG. 7D shows a dimple plan shape 14 defined by a cosine periodic function having period, p=6, mapped to a circular path. FIG. 7E shows a dimple plan shape 15 defined by a cosine periodic function having period, p=7, mapped to a circular path. FIG. 7F shows a dimple plan shape 16 defined by a cosine periodic function having period, p=8, mapped to a circular path.
Example 2
The following example illustrates golf ball dimple plan shapes defined by a low frequency sawtooth wave periodic function mapped to a circular path. The non-uniform sawtooth wave function is approximated by a four-term Fourier series. Table 3, depicted below, describes the mathematical parameters used to project the periodic function onto the simple closed path.







TABLE 3





PLAN SHAPE PARAMETERS OF EXAMPLE 2
















Path
Circular


Periodic Function
Sawtooth Wave (4-term Fourier expansion)


Function (f(x))
f (x) = s + a/π * (sin(πpx) + sin(2πpx)/2 +



sin(3πpx)/3 + sin(4πpx)/4)


Sharpness Factor, s
about 15


Amplitude, a
about 0.5









FIGS. 8A-8F demonstrate the golf ball dimple plan shapes produced in accordance with the parameters of Table 3. In particular, FIG. 8A shows a dimple plan shape 21 defined by a sawtooth wave function approximated by a four-term Fourier series having period, p=3, mapped to a circular path. FIG. 8B shows a dimple plan shape 22 defined by a sawtooth wave function approximated by a four-term Fourier series having period, p=4, mapped to a circular path. FIG. 8C shows a dimple plan shape 23 defined by a sawtooth wave function approximated by a four-term Fourier series having period, p=5, mapped to a circular path. FIG. 8D shows a dimple plan shape 24 defined by a sawtooth wave function approximated by a four-term Fourier series having period, p=6, mapped to a circular path. FIG. 8E shows a dimple plan shape 25 defined by a sawtooth wave function approximated by a four-term Fourier series having period, p=7, mapped to a circular path. FIG. 8F shows a dimple plan shape 26 defined by a sawtooth wave function approximated by a four-term Fourier series having period, p=8, mapped to a circular path.
Example 3
The following example illustrates golf ball dimple plan shapes defined by a low frequency triangle wave periodic function mapped to a circular path. The non-uniform triangle wave function is approximated by a four-term Fourier series. Table 4, depicted below, describes the mathematical parameters used to project the periodic function onto the simple closed path.







TABLE 4





PLAN SHAPE PARAMETERS OF EXAMPLE 3
















Path
Circular


Periodic
Triangle Wave (4-term Fourier expansion)


Function


Function
f (x) = s + 8a/π2 * (sin(πpx) − sin(3πpx)/9 + sin(5πpx)/


(f(x))
25 − sin(7πpx)/49)


Sharpness
about 15


Factor, s


Amplitude, a
about 0.4









FIGS. 9A-9F demonstrate the golf ball dimple plan shapes produced in accordance with the parameters of Table 4. In particular, FIG. 9A shows a dimple plan shape 31 defined by a triangle wave function approximated by a four-term Fourier series having period, p=3, mapped to a circular path. FIG. 9B shows a dimple plan shape 32 defined by a triangle wave function approximated by a four-term Fourier series having period, p=4, mapped to a circular path. FIG. 9C shows a dimple plan shape 33 defined by a triangle wave function approximated by a four-term Fourier series having period, p=5, mapped to a circular path. FIG. 9D shows a dimple plan shape 34 defined by a triangle wave function approximated by a four-term Fourier series having period, p=6, mapped to a circular path. FIG. 9E shows a dimple plan shape 35 defined by a triangle wave function approximated by a four-term Fourier series having period, p=7, mapped to a circular path. FIG. 9F shows a dimple plan shape 36 defined by a triangle wave function approximated by a four-term Fourier series having period, p=8, mapped to a circular path.
Example 4
The following example illustrates golf ball dimple plan shapes defined by a low frequency square wave periodic function mapped to a circular path. The non-uniform square wave function is approximated by a four-term Fourier series. Table 5, depicted below, describes the mathematical parameters used to project the periodic function onto the simple closed path.







TABLE 5





PLAN SHAPE PARAMETERS OF EXAMPLE 4
















Path
Circular


Periodic
Square Wave (4-term Fourier expansion)


Function


Function (f(x))
f (x) = s + 4a/π * (sin(πpx) + sin(3πpx)/3 + sin(5πpx)/



5 + sin(7πpx)/7)


Sharpness
about 15


Factor, s


Amplitude, a
about 0.2









FIGS. 10A-10F demonstrate the golf ball dimple plan shapes produced in accordance with the parameters of Table 5. In particular, FIG. 10A shows a dimple plan shape 41 defined by a square wave function approximated by a four-term Fourier series having period, p=3, mapped to a circular path. FIG. 10B shows a dimple plan shape 42 defined by a square wave function approximated by a four-term Fourier series having period, p=4, mapped to a circular path. FIG. 10C shows a dimple plan shape 43 defined by a square wave function approximated by a four-term Fourier series having period, p=5, mapped to a circular path. FIG. 10D shows a dimple plan shape 44 defined by a square wave function approximated by a four-term Fourier series having period, p=6, mapped to a circular path. FIG. 10E shows a dimple plan shape 45 defined by a square wave function approximated by a four-term Fourier series having period, p=7, mapped to a circular path. FIG. 10F shows a dimple plan shape 46 defined by a square wave function approximated by a four-term Fourier series having period, p=8, mapped to a circular path.
Example 5
The following example illustrates golf ball dimple plan shapes defined by a low frequency square wave periodic function mapped to an elliptical path. The non-uniform square wave function is approximated by a four-term Fourier series. Table 6, depicted below, describes the mathematical parameters used to project the periodic function onto the simple closed path.







TABLE 6





PLAN SHAPE PARAMETERS OF EXAMPLE 5
















Path
Elliptical


Periodic
Square Wave (4-term Fourier expansion)


Function


Function (f(x))
f (x) = s + 4a/π * (sin(πpx) + sin(3πpx)/3 + sin(5πpx)/



5 + sin(7πpx)/7)


Sharpness
about 15


Factor, s


Amplitude, a
about 0.2









FIGS. 11A-11F demonstrate the golf ball dimple plan shapes produced in accordance with the parameters of Table 6. In particular, FIG. 11A shows a dimple plan shape 51 defined by a square wave function approximated by a four-term Fourier series having period, p=3, mapped to an elliptical path. FIG. 11B shows a dimple plan shape 52 defined by a square wave function approximated by a four-term Fourier series having period, p=4, mapped to an elliptical path. FIG. 11C shows a dimple plan shape 53 defined by a square wave function approximated by a four-term Fourier series having period, p=5, mapped to an elliptical path. FIG. 11D shows a dimple plan shape 54 defined by a square wave function approximated by a four-term Fourier series having period, p=6, mapped to an elliptical path. FIG. 11E shows a dimple plan shape 55 defined by a square wave function approximated by a four-term Fourier series having period, p=7, mapped to an elliptical path. FIG. 11F shows a dimple plan shape 56 defined by a square wave function approximated by a four-term Fourier series having period, p=8, mapped to an elliptical path.
Example 6
The following example illustrates golf ball dimple plan shapes defined by a low frequency square wave periodic function mapped to a square path. The non-uniform square wave function is approximated by a four-term Fourier series. Table 7, depicted below, describes the mathematical parameters used to project the periodic function onto the simple closed path.







TABLE 7





PLAN SHAPE PARAMETERS OF EXAMPLE 6
















Path
Square


Periodic
Square Wave (4-term Fourier expansion)


Function


Function (f(x))
f (x) = s + 4a/π * (sin(πpx) + sin(3πpx)/3 + sin(5πpx)/



5 + sin(7πpx)/7)


Sharpness
about 55


Factor, s


Amplitude, a
about 1









FIGS. 12A-12F demonstrate the golf ball dimple plan shapes produced in accordance with the parameters of Table 7. In particular, FIG. 12A shows a dimple plan shape 61 defined by a square wave function approximated by a four-term Fourier series having period, p=3, mapped to a square path. FIG. 12B shows a dimple plan shape 62 defined by a square wave function approximated by a four-term Fourier series having period, p=4, mapped to a square path. FIG. 12C shows a dimple plan shape 63 defined by a square wave function approximated by a four-term Fourier series having period, p=5, mapped to a square path. FIG. 12D shows a dimple plan shape 64 defined by a square wave function approximated by a four-term Fourier series having period, p=6, mapped to a square path. FIG. 12E shows a dimple plan shape 65 defined by a square wave function approximated by a four-term Fourier series having period, p=7, mapped to a square path. FIG. 12F shows a dimple plan shape 66 defined by a square wave function approximated by a four-term Fourier series having period, p=8, mapped to a square path.
Example 7
The following example illustrates golf ball dimple plan shapes defined by a low frequency arbitrary periodic function mapped to a circular path. The arbitrary periodic function is created using a linear combination of sines and cosines. Table 8, depicted below, describes the mathematical parameters used to project the periodic function onto the simple closed path.







TABLE 8





PLAN SHAPE PARAMETERS OF EXAMPLE 7
















Path
Circular


Periodic Function
Arbitrary


Function (f(x))
f (x) = s + a * (cos(πpx)3 * sin(3πpx) + sin(7πpx)/7)


Sharpness Factor, s
about 20


Amplitude, a
about 0.8









FIGS. 13A-13F demonstrate the golf ball dimple plan shapes produced in accordance with the parameters of Table 8. In particular, FIG. 13A shows a dimple plan shape 71 defined by an arbitrary periodic function having period, p=3, mapped to a circular path. FIG. 13B shows a dimple plan shape 72 defined by an arbitrary periodic function having period, p=4, mapped to a circular path. FIG. 13C shows a dimple plan shape 73 defined by an arbitrary periodic function having period, p=5, mapped to a circular path. FIG. 13D shows a dimple plan shape 74 defined by an arbitrary periodic function having period, p=6, mapped to a circular path. FIG. 13E shows a dimple plan shape 75 defined by an arbitrary periodic function having period, p=7, mapped to a circular path. FIG. 13F shows a dimple plan shape 76 defined by an arbitrary periodic function having period, p=8, mapped to a circular path.
Example 8
The following example illustrates golf ball dimple plan shapes defined by a low frequency arbitrary periodic function mapped to an arbitrary path. The arbitrary periodic function is created using a linear combination of sines and cosines. Table 9, depicted below, describes the mathematical parameters used to project the periodic function onto the simple closed path.







TABLE 9





PLAN SHAPE PARAMETERS OF EXAMPLE 8
















Path
Arbitrary


Periodic Function
Arbitrary


Function (f(x))
f (x) = s + a * (cos(πpx)3 * sin(3πpx) + sin(7πpx)/7)


Sharpness Factor, s
about 20


Amplitude, a
about 0.8









FIGS. 14A-14F demonstrate the golf ball dimple plan shapes produced in accordance with the parameters of Table 9. In particular, FIG. 14A shows a dimple plan shape 81 defined by an arbitrary periodic function having period, p=3, mapped to an arbitrary path. FIG. 14B shows a dimple plan shape 82 defined by an arbitrary periodic function having period, p=4, mapped to an arbitrary path. FIG. 14C shows a dimple plan shape 83 defined by an arbitrary periodic function having period, p=5, mapped to an arbitrary path. FIG. 14D shows a dimple plan shape 84 defined by an arbitrary periodic function having period, p=6, mapped to an arbitrary path. FIG. 14E shows a dimple plan shape 85 defined by an arbitrary periodic function having period, p=7, mapped to an arbitrary path. FIG. 14F shows a dimple plan shape 86 defined by an arbitrary periodic function having period, p=8, mapped to an arbitrary path.
Example 9
The following example illustrates golf ball dimple plan shapes defined by a low frequency periodic sawtooth function mapped to a circular path. The sawtooth function is approximated by a four-term Fourier series. Table 10 below describes the mathematical parameters used to project the periodic sawtooth function onto the simple closed path.







TABLE 10





PLAN SHAPE PARAMETERS OF EXAMPLE 9
















Path
Circular


Periodic Function
Sawtooth (4-term Fourier expansion)


 


Function (f(x))




  
    f
    ⁡
    
      (
      x
      )
    
  
  =
  
    s
    -
    
      
        a
        π
      
      ⁢
      
        (
        
          
            sin
            ⁡
            
              (
              
                π
                ⁢
                
                  
                
                ⁢
                p
                ⁢
                
                  
                
                ⁢
                x
              
              )
            
          
          +
          
            
              1
              2
            
            ⁢
            sin
            ⁢
            
              
            
            ⁢
            
              (
              
                2
                ⁢
                
                  
                
                ⁢
                π
                ⁢
                
                  
                
                ⁢
                p
                ⁢
                
                  
                
                ⁢
                x
              
              )
            
          
          +
          
            
              1
              3
            
            ⁢
            
              sin
              ⁡
              
                (
                
                  3
                  ⁢
                  
                    
                  
                  ⁢
                  π
                  ⁢
                  
                    
                  
                  ⁢
                  p
                  ⁢
                  
                    
                  
                  ⁢
                  x
                
                )
              
            
          
          +
          
            
              1
              4
            
            ⁢
            
              sin
              ⁡
              
                (
                
                  4
                  ⁢
                  
                    
                  
                  ⁢
                  π
                  ⁢
                  
                    
                  
                  ⁢
                  p
                  ⁢
                  
                    
                  
                  ⁢
                  x
                
                )
              
            
          
        
        )
      
    
  






 


Sharpness Factor, s
10


Amplitude, a
1


Period
3









FIG. 20 illustrates a golf ball dimple plan shape 120 produced in accordance with the parameters of Table 10. FIG. 20 also illustrates a dimple profile shape 125 defined by the parabolic function ƒ(x)=x2. FIG. 21 illustrates a golf ball pattern utilizing the dimple plan shape and profile shape of FIG. 20.
Example 10
The following example illustrates golf ball dimple plan shapes defined by a low frequency periodic sawtooth function mapped to a circular path. The sawtooth function is approximated by a four-term Fourier series. Table 11 below describes the mathematical parameters used to project the periodic sawtooth function onto the simple closed path.







TABLE 11





PLAN SHAPE PARAMETERS OF EXAMPLE 10
















Path
Circular


Periodic Function
Sawtooth (4-term Fourier expansion)


 


Function (f(x))




  
    f
    ⁡
    
      (
      x
      )
    
  
  =
  
    s
    -
    
      
        a
        π
      
      ⁢
      
        (
        
          
            sin
            ⁡
            
              (
              
                π
                ⁢
                
                  
                
                ⁢
                p
                ⁢
                
                  
                
                ⁢
                x
              
              )
            
          
          +
          
            
              1
              2
            
            ⁢
            sin
            ⁢
            
              
            
            ⁢
            
              (
              
                2
                ⁢
                
                  
                
                ⁢
                π
                ⁢
                
                  
                
                ⁢
                p
                ⁢
                
                  
                
                ⁢
                x
              
              )
            
          
          +
          
            
              1
              3
            
            ⁢
            
              sin
              ⁡
              
                (
                
                  3
                  ⁢
                  
                    
                  
                  ⁢
                  π
                  ⁢
                  
                    
                  
                  ⁢
                  p
                  ⁢
                  
                    
                  
                  ⁢
                  x
                
                )
              
            
          
          +
          
            
              1
              4
            
            ⁢
            
              sin
              ⁡
              
                (
                
                  4
                  ⁢
                  
                    
                  
                  ⁢
                  π
                  ⁢
                  
                    
                  
                  ⁢
                  p
                  ⁢
                  
                    
                  
                  ⁢
                  x
                
                )
              
            
          
        
        )
      
    
  






 


Sharpness Factor, s
8


Amplitude, a
1


Period
4









FIG. 22 illustrates a golf ball dimple plan shape 130 produced in accordance with the parameters of Table 11. FIG. 22 also illustrates a dimple profile shape 135 defined by the exponential function ƒ(x)=exp(x3). FIG. 23 illustrates a golf ball pattern utilizing the dimple plan shape and profile shape of FIG. 22.
Example 11
The following example illustrates golf ball dimple plan shapes defined by a low frequency periodic sawtooth function mapped to a circular path. The sawtooth function is approximated by a four-term Fourier series. Table 12 below describes the mathematical parameters used to project the periodic sawtooth function onto the simple closed path.







TABLE 12





PLAN SHAPE PARAMETERS OF EXAMPLE 11
















Path
Circular


Periodic Function
Sawtooth (4-term Fourier expansion)


 


Function (f(x))




  
    f
    ⁡
    
      (
      x
      )
    
  
  =
  
    s
    -
    
      
        a
        π
      
      ⁢
      
        (
        
          
            sin
            ⁡
            
              (
              
                π
                ⁢
                
                  
                
                ⁢
                p
                ⁢
                
                  
                
                ⁢
                x
              
              )
            
          
          +
          
            
              1
              2
            
            ⁢
            sin
            ⁢
            
              
            
            ⁢
            
              (
              
                2
                ⁢
                
                  
                
                ⁢
                π
                ⁢
                
                  
                
                ⁢
                p
                ⁢
                
                  
                
                ⁢
                x
              
              )
            
          
          +
          
            
              1
              3
            
            ⁢
            
              sin
              ⁡
              
                (
                
                  3
                  ⁢
                  
                    
                  
                  ⁢
                  π
                  ⁢
                  
                    
                  
                  ⁢
                  p
                  ⁢
                  
                    
                  
                  ⁢
                  x
                
                )
              
            
          
          +
          
            
              1
              4
            
            ⁢
            
              sin
              ⁡
              
                (
                
                  4
                  ⁢
                  
                    
                  
                  ⁢
                  π
                  ⁢
                  
                    
                  
                  ⁢
                  p
                  ⁢
                  
                    
                  
                  ⁢
                  x
                
                )
              
            
          
        
        )
      
    
  






 


Sharpness Factor, s
13


Amplitude, a
0.8


Period
7









FIG. 24 illustrates a golf ball dimple plan shape 140 produced in accordance with the parameters of Table 12. FIG. 24 also illustrates a dimple profile shape 145 defined by the trigonometric function ƒ(x)=cos h(3×)−sin h(x). FIG. 25 illustrates a golf ball pattern utilizing the dimple plan shape and profile shape of FIG. 24.
Example 12
The following example illustrates golf ball dimple plan shapes defined by a low frequency periodic sawtooth function mapped to a circular path. The sawtooth function is approximated by a four-term Fourier series. Table 13 below describes the mathematical parameters used to project the periodic sawtooth function onto the simple closed path.







TABLE 13





PLAN SHAPE PARAMETERS OF EXAMPLE 12
















Path
Circular


Periodic Function
Sawtooth (4-term Fourier expansion)


 


Function (f(x))




  
    f
    ⁡
    
      (
      x
      )
    
  
  =
  
    s
    -
    
      
        a
        π
      
      ⁢
      
        (
        
          
            sin
            ⁡
            
              (
              
                π
                ⁢
                
                  
                
                ⁢
                p
                ⁢
                
                  
                
                ⁢
                x
              
              )
            
          
          +
          
            
              1
              2
            
            ⁢
            sin
            ⁢
            
              
            
            ⁢
            
              (
              
                2
                ⁢
                
                  
                
                ⁢
                π
                ⁢
                
                  
                
                ⁢
                p
                ⁢
                
                  
                
                ⁢
                x
              
              )
            
          
          +
          
            
              1
              3
            
            ⁢
            
              sin
              ⁡
              
                (
                
                  3
                  ⁢
                  
                    
                  
                  ⁢
                  π
                  ⁢
                  
                    
                  
                  ⁢
                  p
                  ⁢
                  
                    
                  
                  ⁢
                  x
                
                )
              
            
          
          +
          
            
              1
              4
            
            ⁢
            
              sin
              ⁡
              
                (
                
                  4
                  ⁢
                  
                    
                  
                  ⁢
                  π
                  ⁢
                  
                    
                  
                  ⁢
                  p
                  ⁢
                  
                    
                  
                  ⁢
                  x
                
                )
              
            
          
        
        )
      
    
  






 


Sharpness Factor, s
12.5


Amplitude, a
1.2


Period
6









FIG. 26 illustrates a golf ball dimple plan shape 150 produced in accordance with the parameters of Table 13. FIG. 26 also illustrates a dimple profile shape 155 defined by the polynomial function ƒ(x)=x4−3⁄5x3+1⁄2x. FIG. 27 illustrates a golf ball pattern utilizing the dimple plan shape and profile shape of FIG. 26.
Example 13
The following example illustrates golf ball dimple plan shapes defined by a low frequency periodic sawtooth function mapped to a circular path. The sawtooth function is approximated by a four-term Fourier series. Table 14 below describes the mathematical parameters used to project the periodic sawtooth function onto the simple closed path.







TABLE 14





PLAN SHAPE PARAMETERS OF EXAMPLE 13
















Path
Circular


Periodic Function
Sawtooth (4-term Fourier expansion)


 


Function (f(x))




  
    f
    ⁡
    
      (
      x
      )
    
  
  =
  
    s
    -
    
      
        a
        π
      
      ⁢
      
        (
        
          
            sin
            ⁡
            
              (
              
                π
                ⁢
                
                  
                
                ⁢
                p
                ⁢
                
                  
                
                ⁢
                x
              
              )
            
          
          +
          
            
              1
              2
            
            ⁢
            sin
            ⁢
            
              
            
            ⁢
            
              (
              
                2
                ⁢
                
                  
                
                ⁢
                π
                ⁢
                
                  
                
                ⁢
                p
                ⁢
                
                  
                
                ⁢
                x
              
              )
            
          
          +
          
            
              1
              3
            
            ⁢
            
              sin
              ⁡
              
                (
                
                  3
                  ⁢
                  
                    
                  
                  ⁢
                  π
                  ⁢
                  
                    
                  
                  ⁢
                  p
                  ⁢
                  
                    
                  
                  ⁢
                  x
                
                )
              
            
          
          +
          
            
              1
              4
            
            ⁢
            
              sin
              ⁡
              
                (
                
                  4
                  ⁢
                  
                    
                  
                  ⁢
                  π
                  ⁢
                  
                    
                  
                  ⁢
                  p
                  ⁢
                  
                    
                  
                  ⁢
                  x
                
                )
              
            
          
        
        )
      
    
  






 


Sharpness Factor, s
21.2


Amplitude, a
0.95


Period
9









FIG. 28 illustrates a golf ball dimple plan shape 160 produced in accordance with the parameters of Table 14. FIG. 28 also illustrates a dimple profile shape 165 defined by the following mixed function containing exponential and polynomial terms f(x)=exp(x2)−x5. FIG. 29 illustrates a golf ball pattern utilizing the dimple plan shape and profile shape of FIG. 28.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Furthermore, when numerical ranges of varying scope are set forth herein, it is contemplated that any combination of these values inclusive of the recited values may be used.
The invention described and claimed herein is not to be limited in scope by the specific embodiments herein disclosed, since these embodiments are intended as illustrations of several aspects of the invention. Any equivalent embodiments are intended to be within the scope of this invention. Indeed, various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description. Such modifications are also intended to fall within the scope of the appended claims. All patents and patent applications cited in the foregoing text are expressly incorporate herein by reference in their entirety.

## Claims

1. A golf ball having a generally spherical surface and comprising a plurality of dimples on the spherical surface, wherein at least a portion of the plurality of dimples have a non-circular plan shape defined by a low frequency periodic sawtooth function mapped along a circular simple closed path resulting in the following function:


Q(x)=Fpath(l,scl,x)*Fperiodic(s,a,p,x)


where Fpath is a circular function of length l, with scale factor scl, defined along the vertices x;
and Fperiodic is a periodic sawtooth function defined by the equation:




  
    
      f
      ⁡
      
        (
        x
        )
      
    
    =
    
      s
      -
      
        
          a
          π
        
        ⁢
        
          (
          
            
              sin
              ⁡
              
                (
                
                  π
                  ⁢
                  
                    
                  
                  ⁢
                  px
                
                )
              
            
            +
            
              
                1
                2
              
              ⁢
              
                sin
                ⁡
                
                  (
                  
                    2
                    ⁢
                    π
                    ⁢
                    
                      
                    
                    ⁢
                    px
                  
                  )
                
              
            
            +
            
              
                1
                3
              
              ⁢
              
                sin
                ⁡
                
                  (
                  
                    3
                    ⁢
                    π
                    ⁢
                    
                      
                    
                    ⁢
                    px
                  
                  )
                
              
            
            +
            
              
                1
                4
              
              ⁢
              
                sin
                ⁡
                
                  (
                  
                    4
                    ⁢
                    π
                    ⁢
                    
                      
                    
                    ⁢
                    px
                  
                  )
                
              
            
          
          )
        
      
    
  
  ,




with sharpness factor s, amplitude a, and period p defined at the vertices x, and wherein period p is about 15 or less and amplitude a is about 1 or less.

2. The golf ball of claim 1, wherein at least a portion comprises about 50 percent or more of the dimples on the golf ball.

3. The golf ball of claim 1, wherein at least a portion comprises about 80 percent or more of the dimples on the golf ball.

4. The golf ball of claim 1, wherein the low frequency periodic sawtooth function has a period of about 10 or less.

5. The golf ball of claim 1, wherein the low frequency periodic sawtooth function has a period of about 8 or less.

6. The golf ball of claim 1, wherein the low frequency periodic sawtooth function has a period of about 5 or less.

7. The golf ball of claim 1, wherein the plan shape has an amplitude, A, of less than about 0.500 inches.

8. The golf ball of claim 1, wherein the circular path has a radius of from about 0.025 inches to about 0.150 inches.

9. The golf ball of claim 8, wherein the maximum distance at any point on the plan shape from the circular path is from about 0.001 inches to about 0.015 inches.

10. The golf ball of claim 8, wherein the maximum distance at any point on the plan shape from the circular path is from about 0.002 inches to about 0.008 inches.

11. The golf ball of claim 1, wherein the plan shape has an amplitude A of about 0.0005 inches to about 0.1000 inches.