GOLF BALL DIMPLES DEFINED BY SUPERPOSED CURVES
20180207488 ยท 2018-07-26
Assignee
Inventors
Cpc classification
International classification
Abstract
The present invention is a golf ball which comprises dimples having a cross section defined by the superposition of two or more continuous and differentiable functions, and particularly the superposition of a catenary function and a Witch of Agnesi function. Additionally, the dimples preferably have a circular boundary and maintain an axis coincident with the center of the circular boundary.
Claims
1. A golf ball having a surface with a plurality of recessed dimples thereon, including a plurality of axially symmetric cat-witch dimples having a profile defined by a function resulting from the sum of a catenary function and a Witch of Agnesi function, wherein the plurality of cat-witch dimples comprises: at least one cat-witch dimple having a first diameter (D.sub.D1) and a first chord depth, and at least one cat-witch dimple having a second diameter (D.sub.D2) and a second chord depth; wherein D.sub.D1 is at least 0.005 inches greater than D.sub.D2; wherein the chord depth difference, .sub.CD1, between the first chord depth and the second chord depth is at least 0.001 inches; and wherein the profile depth difference, .sub.PD1, between the profile depth of the cat-witch dimple having the first diameter and the profile depth of the cat-witch dimple having the second diameter, at every distance D.sub.C from the center of the dimple, where
2. The golf ball of claim 1, wherein the superposed dimple has a circular plan shape.
3. The golf ball of claim 1, wherein the superposed dimple has a dimple diameter of from 0.100 inches to 0.220 inches.
4. The golf ball of claim 1, wherein the plurality of cat-witch dimples additionally comprise at least one cat-witch dimple having a third diameter (D.sub.D3) and a third chord depth, and wherein D.sub.D3 is at least 0.005 inches less than D.sub.D2.
5. The golf ball of claim 4, wherein the chord depth difference, .sub.CD2, between the first chord depth and the third chord depth is at least 0.002 inches.
6. The golf ball of claim 5, wherein the profile depth difference, .sub.PD2, between the profile depth of the cat-witch dimple having the first diameter and the profile depth of the cat-witch dimple having the third diameter, at every distance D.sub.C from the center of the dimple, where
7. The golf ball of claim 6, wherein the chord depth difference, .sub.CD3, between the second chord depth and the third chord depth is at least 0.001 inches, and wherein the profile depth difference, .sub.PD3, between the profile depth of the cat-witch dimple having the second diameter and the profile depth of the cat-witch dimple having the third diameter, at every distance D.sub.C from the center of the dimple, where
Description
BRIEF DESCRIPTION OF DRAWINGS
[0015] These and other aspects of the present invention may be more fully understood with references to, but not limited by, the following drawings:
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DETAILED DESCRIPTION
[0040] The present invention is a golf ball which comprises dimples having a cross section defined by the superposition of two or more continuous and differentiable functions. Additionally, the dimples preferably have a circular boundary and maintain an axis coincident with the center of the circular boundary.
[0041] Dimples that are defined by superposed curves provide greater opportunity to control the dimple cross-section and therefore, provide dimples that improve the flight characteristics of the golf ball. This method is capable of producing an unlimited number of unique dimple shapes produced using the superposition principle. Since the dimple shape is axially symmetric and maintains a circular boundary, hob, and cavity manufacture remains similar to those for conventionally shaped prior art dimple profiles.
[0042] The Superposition Principle states that for linear homogenous ordinary differential equations, if y1(x) and y2(x) yield valid solutions, then the sum of y1(x) and y2(x) will also yield a valid solution. (Weisstein, Eric W. Superposition Principle) This allows the combination of equations that are continuous and differentiable, and combining their solutions creates unique dimple profiles.
[0043] Several examples of dimple cross sections according to the present invention are illustrated by referencing
[0044]
[0045] Another example of a dimple profile is illustrated by reference to
[0046] Yet another example of the present invention is the superposition of more than 2 functions. For example, a frequency curve, catenary curve and cosine curve as shown in
[0047] Another example of the present invention is the combination of a catenary curve 30 and a spherical curve 21 to form the catenary-spherical curve dimple profile 53 shown in
[0048]
[0049] Each of
[0050] In
where d.sub.CAT is chord depth (in inches), D.sub.D is dimple diameter (in inches), and SF, referred to as shape factor, is a constant selected to alter the steepness of the sidewall. In
[0051] In
where D.sub.D is dimple diameter (in inches); C.sub.1, referred to as steepness factor, is a constant selected to alter the steepness of the sidewall; C.sub.2, referred to as curvature factor, is a constant selected to alter the radius of curvature of the sidewall; and a, referred to as depth factor, is a constant selected to alter the depth of the profile. In
[0052] Golf ball dimple profiles defined using catenary curves are further disclosed, for example, in U.S. Pat. No. 7,641,572, the entire disclosure of which is hereby incorporated herein by reference. Golf ball dimple profiles defined using Witch of Agnesi curves are further disclosed, for example, in U.S. Patent Application Publication No. 2012/0122613, the entire disclosure of which is hereby incorporated herein by reference.
[0053] Dimples having a profile shape defined by the superposition of a catenary curve and a Witch of Agnesi curve, herein referred to as cat-witch dimples, preferably have a circular plan shape and a dimple diameter of from 0.100 inches to 0.220 inches. The chord volume of the cat-witch dimple profile is calculated by summing the individual chord volume contributions of the catenary profile and the Witch profile. The chord volume of a catenary dimple profile, V.sub.CAT, is defined as:
where D.sub.D is dimple diameter (in inches).
The chord volume of a Witch of Agnesi dimple profile, V.sub.W, is defined as:
Thus, the chord volume of the cat-witch dimple profile, V.sub.D, is equal to V.sub.CAT+V.sub.W.
[0060]
v.sub.1=407.14D.sub.D.sup.217.79D.sub.D0.09
curve 2 is defined by the equation:
v.sub.2=66.67D.sub.D.sup.2+35.33D.sub.D2.80
curve 3 is defined by the equation:
v.sub.3=319.05D.sub.D.sup.23.76D.sub.D0.81
and curve 4 is defined by the equation:
v.sub.4=152.86D.sub.D.sup.2+20.59D.sub.D1.93
where D.sub.D is the dimple diameter and v is the respective chord volume. In a particular embodiment, the cat-witch dimples have a chord volume within a range having a lower limit defined by curve 2 and an upper limit defined by curve 1. In another particular embodiment, the cat-witch dimples have a chord volume within a range having a lower limit defined by curve 4 and an upper limit defined by curve 3.
[0061] Cat-witch dimples of the present invention preferably have a surface depth, defined herein as the distance from the phantom ball surface to the bottom of the dimple, of 0.020 inches or less, or 0.015 inches or less.
[0062] Cat-witch dimples of the present invention preferably have a chord depth, defined herein as the distance from the chord plane to the bottom of the dimple, of from 0.004 inches to 0.013 inches.
[0063] In a particular embodiment, the present invention provides a golf ball comprising cat-witch dimples of two or more different diameters. For purposes of the present invention, dimple diameters are generally considered to be different if they differ by at least 0.005 inches. It should be understood that manufacturing variances are to be taken into account when determining whether two dimples have different diameters. In a preferred aspect of this embodiment, at least two cat-witch dimples having different diameters have a consistent depth variation, i.e., have a similar shape. The cat-witch dimples of this preferred aspect of the invention have a circular plan shape and are axially symmetric. The determination of consistent depth variation between two cat-witch dimples having different diameters is conducted on the profile of the dimples according to the following procedure. An evaluation zone is defined as the portion of the two dimple profiles extending from the center of the dimple to a distance
measured radially outward from the center, where D.sub.D is the diameter of the dimple having the smaller diameter of the two dimples being evaluated for consistent depth variation. The difference in the chord depth of the two dimples being evaluated, .sub.CD, is calculated, and is typically at least 0.001 inches. If, within the evaluation zone, at every given distance from the center of the dimple, the difference in the profile depth of the two dimples being evaluated, .sub.PD, falls within a range having a lower limit of
and an upper limit of
then the dimples have consistent depth variation. For purposes of the present invention, profile depth is defined herein as the distance from the chord plane to the profile of the dimple at a given distance from the center of the dimple.
[0064] For example,
[0065] In a particular aspect of the embodiment shown in
where d.sub.CAT is 0.0027 inches and SF is 100. The value for D.sub.D is different for each of profiles 210, 220, and 230, and is given in Table 1 below. The Witch of Agnesi curve is defined by the equation:
where C.sub.1 is 4 and C.sub.2 is 4. The values for D.sub.D and a are different for each of profiles 210, 220, and 230, and are given in Table 1 below.
TABLE-US-00001 TABLE 1 Dimple Profile 210 220 230 Dimple Diameter 0.200 inches 0.150 inches 0.100 inches Chord Depth 0.0124 inches 0.0106 inches 0.0076 inches d.sub.CAT value for catenary curve 0.0027 0.0027 0.0027 SF value for catenary curve 100 100 100 C.sub.1 value for Witch of Agnesi curve 4 4 4 C.sub.2 value for Witch of Agnesi curve 4 4 4 a value for Witch of Agnesi curve 0.0101 0.0083 0.0051
[0066]
D.sub.D being me diameter of the dimple having the smaller diameter of the two dimples being evaluated. Thus, distance 226 is
or 0.0375 inches. The difference in the chord depth of the two dimples being evaluated, .sub.CD, is calculated as 0.0018 inches. For the dimple having the profile 210 and the dimple having the profile 220 to be considered as having consistent depth variation, the difference, .sub.PD, between the profile depth of profile 210 and the profile depth of profile 220 must be within a range having a lower limit of
0.0009 inches in this example, and an upper limit of
0.0027 inches in this example, at every distance from the center axis 202 that is within the evaluation zone 206. The maximum difference between the profile depth of profile 210 and the profile depth of profile 220, within the evaluation zone 206, was determined to be 0.0018 inches. The minimum difference between the profile depth of profile 210 and the profile depth of profile 220, within the evaluation zone 206, was determined to be 0.0009 inches. Thus, within the evaluation zone 206, at every given distance from the center axis 202, the profile depth difference, .sub.PD, falls within a range of from 0.0009 inches to 0.0027 inches. The cat-witch dimple having the profile 210 and the cat-witch dimple having the profile 220, therefore, have consistent depth variation.
[0067]
D.sub.D being the diameter of the dimple having the smaller diameter of the two dimples being evaluated. Thus, distance 236 is
or 0.0250 inches. The difference in the chord depth of the two dimples being evaluated, .sub.CD, is calculated as 0.0048 inches. For the dimple having the profile 210 and the dimple having the profile 230 to be considered as having consistent depth variation, the difference, .sub.PD, between the profile depth of profile 210 and the profile depth of profile 230 must be within a range having a lower limit of
0.0024 inches in this example, and an upper limit of
0.0072 inches in this example, at every distance from the center axis 202 that is within the evaluation zone 206. The maximum difference between the profile depth of profile 210 and the profile depth of profile 230, within the evaluation zone 206, was determined to be 0.0048 inches. The minimum difference between the profile depth of profile 210 and the profile depth of profile 230, within the evaluation zone 206, was determined to be 0.0024 inches. Thus, within the evaluation zone 206, at every given distance from the center axis 202, the profile depth difference, .sub.PD, falls within a range of from 0.0024 inches to 0.0072 inches. The cat-witch dimple having the profile 210 and the cat-witch dimple having the profile 230, therefore, have consistent depth variation.
[0068] The superposition method disclosed herein has the potential to generate dimple profiles that have not been utilized on prior art golf balls. Since the dimple boundaries of the golf ball are preferably circular, previously developed patterns can be utilized, refined and optimized for potentially improved distance and flight control. The visual appearance of golf balls produced from this method can be significantly different. The present invention may be used with any type of ball construction. For instance, the ball may have a 2-piece construction, a double cover or veneer cover construction or other multi-layer constructions depending on the type of performance desired of the ball. Examples of these and other types of ball constructions that may be used with the present invention include those described in U.S. Pat. Nos. 5,713,801, 5,803,831, 5,885,172, 5,919,100, 5,965,669, 5,981,654, 5,981,658, and 6,149,535, for example, the construction and materials disclosed in the patents being expressly incorporated herein. Different materials also 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 polyurethane, ionomer resin, balata or any other suitable cover material known to those skilled in the art. Different materials also may be used for forming core and intermediate layers of the ball.
[0069] After selecting the desired ball construction, the flight performance of the golf ball can be adjusted according to the design, placement, and number of dimples on the ball. As explained above, the use of a variety of dimples, based on a superposition profile, provides a relatively effective way to modify the ball flight performance without significantly altering the dimple pattern. Thus, the use of dimples based on the superposition profile allows a golf ball designer to select flight characteristics of a golf ball in a similar way that different materials and ball constructions can be selected to achieve a desired performance.
[0070] Each dimple of the present invention is part of a dimple pattern selected to achieve a particular desired lift coefficient. Dimple patterns that provide a high percentage of surface coverage are preferred, and are well known in the art. For example, 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. In one embodiment of the present invention, the dimple pattern is at least partially defined by phyllotaxis-based patterns, such as those described in co-pending U.S. patent application Ser. No. 09/418,003, which is incorporated by reference in its entirety. Preferably a dimple pattern that provides greater than about 70% surface coverage is selected. Even more preferably, the dimple pattern provides greater than about 80% surface coverage. Once the dimple pattern is selected, several alternative dimple profiles can be tested in a wind tunnel or indoor test range to empirically determine the properties of the profiles that provide the desired lift and drag coefficients at the desired launch conditions.
[0071] While the invention has been described in conjunction with specific embodiments, it is evident that numerous alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description.