JPH10246A - Golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a lower and flat flying path and improve flight distance by making the resistance less, by processing two kinds of dimples with different diameters on the ball surface. SOLUTION: Dimples processed on the surface of a golf ball summing up 384±3% are placed even at regular intervals. The dimples are arranged by forming approximately equilateral round triangles forming 392 apex and making each apex as the center point of each dimple, and these dimples draw a 20-hedral pattern on the ball surface. Diameters of those dimples have two variations such as either approx. 0.140 inch or approx. 0.160 inch so that the player can fly it in lower and flat path and considerably improved its flight distance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to golf balls and, more particularly, to golf balls that have a greater flight distance than currently marketed golf balls without breaking any of the rules set by the United States Golf Association (USGA). About.

[0002]

BACKGROUND OF THE INVENTION Over the years, golf balls have had no technical development, with only minor improvements in their manufacture. In practice, all golf balls are so-called wound types. This type of golf ball is composed of an elastic rubber ball or a liquid-filled hollow sphere having a diameter of 1-1 / 16 inch (2.54 to 2.54 mm).
It has a small center of 2.69875 cm). Elastic windings surround this center, from 1.45 (3.683 cm) to 1.65
Form a core with a diameter of (4.191 cm) inches. A shell cover, usually made of balata, is formed by compression molding around the core, ultimately resulting in a 1.68 inch diameter ball.

[0003] Since the mid-1960s, many improvements have been made to golf balls that have been valued by the industry. The first major improvement is the new cover material Surlyn
The introduction of ionomer resin. It was the first plastic material widely accepted by the golf industry.
Surlyn resin has gained many markets, but balata is still heavily used, much by advanced players.

[0004] A second major improvement is the so-called two-piece golf ball. This is between 1.45 and 1.61 inches (3.6
83 to 4.0894 cm) is a golf ball having a polymer unit spherical core having substantially the same size as a wound core. Around the core is another polymer cover, which is typically made of a Surlyn ionomer resin. The core is usually compression molded, and the cover is made by either injection molding or compression molding.

A third achievement is an improvement in the aerodynamic shape of the golf ball to make the ball fly more. Since the early days of golf, improvements in the flight distance of golf balls have always been attempted, which has been significantly noticeable in the last decade. Aerodynamic improvements are clearly the largest contributors to date to extend golf ball flight without breaking USGA rules.

[0006] The USGA has published rules for golf games, which include specifications for golf balls. Compliance with the USGA rules is not an obligation, and in fact some companies have declared that they sell "hot" balls that break the USGA rules. If you are a major golf ball maker, you can easily make "hot" balls that break the USGA rules,
All the leading manufacturers humbly adhere to the USGA rules as the ball is locked out of all USGA play. This lockout is not only for Prozer,
Most club play is similar, resulting in stigma close to crime. Even duffry players who play on public golf courses for $ 2 Nassau will protest loudly when anyone in their quartet tries to play with a breached ball.

The USGA defines two static tests: weight and size. The weight of the golf ball must not exceed 1.620 oz (45.927 g) and its size must not be less than 1.680 inches (4.2672 cm) in diameter. These tests are
Used by the USGA for many years, most golf ball manufacturers have approached these with acceptable limits. There are three performance tests imposed by the USGA, one is speed, the other is total flight distance, and the last is the symmetry of the golf ball.

[0008] The demand for speed, commonly referred to as the maximum initial speed, is such that a golf ball, when measured on a device approved by the USGA, can load 250 feet (76.2 feet) per second.
m) must not be exceeded. A 2% error in speed has been observed, so the maximum allowable speed is 255 feet (77.724 m) per second. This rule has been in effect for many years, and most top manufacturers of wound golf balls have been following this maximum speed for very many years. This is relatively easily accomplished by tightly winding the windings to achieve high compression or by winding them with "fast" yarns well known in the golf ball manufacturing art. Most manufacturers have 255 feet per second (77.724
m) is not actually trying to achieve the maximum speed allowed, which is a statement that the ball is too likely to exceed the allowable value and breaks the USGA rules. It is pointed out that this is the case. Most manufacturers have a safety factor, which reduces the risk of "breaking the rule" by 250-253 feet (76.2-77.1).
A slightly smaller value as in the range of m) is set as the average maximum initial velocity.

[0009] The total flight distance is overall
Measured by a test known as Distance Standard, 280 yards (256.032m) plus 6
% Error (permissible total flight distance 296.8 yards (271.39
m)). The error was officially 8%, but has recently been reduced to 6%. The error may be reduced to 4% if the test technique is improved (allowable total flight distance 291.2 yards (266.27m)),
This has never been done, nor is it foreseeable in the future. Overall distance
The standard measures carry and rolling. Carry is the distance from the tee to the point where the golf ball first came into contact with the ground, and carry and rolling is the total distance from the tee to the point where the ball last stopped.
Overall Distance Standard is US
Tested with USGA approved equipment outdoors at GA headquarters. This device simulates a club known as a driver.
Whether the error is 6% or 4%, as far as the applicant knows,
Nothing was able to approach the total distance allowed by the Overall Distance Standard, USG
It keeps the initial speed that does not exceed the maximum allowable initial speed of A.

[0010] The Overall Distance Standard is the standard used by the USGA, but the industrial distance standard is often considered the total flight distance (carry and roll) of a ball hit by a driver and a 5-iron. ing. Such a golf ball is
It is necessary to follow the USGA standard, but since the USGA device simulates a shot with a driver, two balls with almost the same overall flight distance on the USGA device differ in the driver plus 5 iron test. Values.

The recently established rules for golf ball symmetry only state that golf balls should be designed and manufactured to be spherically symmetric. Testing to determine symmetry is in the development stage. At this time, the USGA measures the difference between values when the ball hits two different axes. The differences between the currently measured values are the trajectory peak angle, carry distance, and flight time. Golf balls having a uniform dimple pattern will pass the USGA test, while balls having a non-uniform pattern (see, for example, US Pat. No. 3,819,190) will not.

In addition to the distance a golf ball travels, another important factor to consider is its trajectory height. Without headwinds, commercially available golf balls with the greatest carry at the driver tend to have relatively high trajectories. This high trajectory, relatively high spin speed,
This is due to the aerodynamic shape that results in relatively high lift and drag coefficients. There are two problems with high trajectory. First
In addition, a ball with a high trajectory may be hit in a place where the crosswind is strong and the ball misses the intended direction. In addition, elements that raise the ball also tend to produce extremely unfavorable conditions such as so-called tempura (the ball does not climb and fly away), hooks and slices.

[0013]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a golf ball having a relatively low and flat trajectory and a relatively low drag. Golf balls with low drag are U
Fly at a relatively high speed while maintaining the initial speed within the SGA limit. The overall effect of low and flat trajectory and low drag is that golf balls have a greater carry distance than high trajectory balls. In addition, golf balls impact the ground at a shallow angle due to the low and flat trajectory, and impact at a high speed due to low drag, so that the golf ball will bounce and roll more than a high trajectory golf ball, than can be obtained with a carry The distance can be greatly extended in total.

The great results of the foregoing effectiveness are obtained with golf balls having a particular combination of spin rate and aerodynamic shape.

First, regarding the aerodynamic shape of a golf ball, this relates to the number of dimples, the spacing between the dimples, and the depth and diameter thereof. According to the invention, the golf ball has about 384 dimples. While errors of up to about 3% in the number of dimples are acceptable, the number of dimples is preferably between 376 and 392.

The dimples are substantially uniformly spaced on the surface of the golf ball. This is achieved by placing an icosahedral pattern on the surface of the golf ball to form approximately equilateral spherical triangles producing 392 vertices. Each vertex is the center point of the dimple. This is the case, for example, in GB 1,381,897, which discloses such an arrangement of dimple centers. When this icosahedron-spherical triangle method is used to form 392 vertices, 392 points are formed at which dimples can be placed and are approximately equally spaced on the golf ball surface. In a top class golf ball, four dimples are removed at each pole, three of which are used for branding and one for identification numbers. This gives a most preferred dimple number of 384.
If necessary, in addition to omitting the dimples for the trademark, other minor changes can be made to the arrangement of the dimples, for example, a golf ball to be molded to facilitate buffing of the parting line The dimples can be separated at the parting line.

The dimple is substantially a part of a spherical surface, and the number of interrelated dimples represented by the following equation:
It has a dimple diameter and a dimple depth.

[554.3 (d−x) −37 (D−y)] ² +
[138.6 (Dy) +926 (dx)] ² = S where d = average dimple depth D = average dimple diameter x = 0.0275-0.0041667Ny = 0.2790-0.0333NN = 100 Exact number of dimples 0 ≦ S ≦ 1 Based on the various test results obtained as follows, the above formula is used to create a curve showing the correlation between dimple diameter and dimple depth. This curve is shown in FIG. An equation representing the parallel-transformed spheroid forming the curve is derived from the following basic equation of the ellipse.

[0019]

(Equation 1)

As a method of converting the above basic formula into the formula of the present invention, a formula conversion by rotation and translation of an ellipse as described in detail in JP-B-58-50744 is used. Since these conversion methods are well known, they will be briefly described below.

In the above equation, a 10d axis (dimple depth) and a D axis (dimple diameter) are used instead of the X axis and the Y axis. Here, 10d is used instead of d because the depth is a very small value, and it is difficult to draw an ellipse if d is used. Therefore, the above equation can be rewritten as:

[0022]

(Equation 2)

The ellipse in FIG. 2 according to the present invention has φ
Is an ellipse rotated only by φ, so if the axes rotated by φ are U axis and V axis respectively,

[0024]

(Equation 3)

When the U axis and V axis are represented by the above 10d and D,

[0026]

(Equation 4)

## EQU1 ## Substituting these into the formula

[0028]

(Equation 5)

Is obtained.

The ellipse according to the present invention is not only rotated, but also translated from the origin. If the moving distances along the 10d axis and the D axis are x and y, respectively, x, y, a The values of x and y vary with the number of dimples, but by plotting these values against the number of dimples, the values of x, y, a, and b can be correlated. The above equation is obtained by rewriting the equation taking these factors into consideration and defining the relation within the limitation as the relational equation between the depth, diameter and number of the dimples according to the present invention.

The method for measuring the dimple diameter and dimple depth is disclosed in the above-mentioned British Patent No. 1,381,897, and is particularly shown in FIGS. 3 to 5 and FIGS. The implications of British Patent 1,381,897 are hereafter incorporated by reference. Preferably, at least 95% of the dimples have a specified diameter and depth for a particular number of dimples, particularly preferably all. However, minor changes for aesthetic or other purposes without particularly affecting the total flight distance of the golf ball do not impair the technical idea of the present invention.

The preferred size of the dimple used in the golf ball of the present invention is from about 0.145 to about 0.155 inch (0.368 inch).
It has an average diameter of about 3 to 0.3937 cm and an average depth of about 0.0103 to about 0.0123 inches (0.02616 to 0.03124 cm).

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments shown in the accompanying drawings.

The drawings show a hemispherical portion of a golf ball according to the present invention. Its outer peripheral edge is a ball equalizing circle 8.

The dimples are arranged in an icosahedral-spherical triangular pattern as described above. According to the invention,
The dimple 10 located at the pole of the ball may be left as a smooth surface for trademark application. The dimples 12 may also be left empty for identification numbers. Dimples 10, 12, and 14 can be left empty as described in Example 8. The dimples 10, 12, and 14 may be present as shown in the ninth embodiment. The dimple 18 can have a different diameter from the other dimples as described in Example 10.

A second fundamental requirement is the spin rate of the golf ball. Spin speed varies as a function of golf ball compression. The term "compression" as used herein is well known in the golf ball industry. Compression is sometimes used as PGA compression and is expressed as a baseless unit of scale known as the PGA compression scale. A standard compression of 90-100 is used in almost all of the top golf balls. Many manufacturers have 90 compressions and 1
It sells both 00 compression models. In accordance with the present invention, golf balls having a reference compression between 90 and 100 have a spin rate of 230 feet per second (70.1 feet) with a tool having a club face angle of 13 degrees to vertical with a launch angle of about 11 degrees. When hit at a speed of m), the speed falls below about 2900 rpm. As a practical matter, at the lowest spin rate, the golf ball will be about 2000 rp
reach m. The device that determines the hitting parameters is:
It is commercially available from companies such as True Temper Corporation. An apparatus suitable for performing spin rate measurements is disclosed in U.S. Pat. No. 4,063,259. This patent also discusses the correlation between launch angle and spin rate.

The spin rate of the golf ball of the present invention is
Slightly lower than the spin rate of golf balls covered with conventional wound balata. Standard compression 90-100
Such a golf ball has a club face angle of 13 °
About 30 when hit at 230 feet per second
It has a spin speed from 00 to about 3500 rpm. However, it has been found that such balata-coated balls can be spun at the spin rates required in the present invention by increasing the size of the liquid center and the hardness of the coating. The center of a wrapped golf ball is usually 1-1 1/16 inch (2.54-2.698).
75 cm). According to the present invention, it is preferred to increase the center to at least 1/8 inch (2.8575 cm). Such an increase in center diameter relative to a conventional ball is effective in reducing the spin rate of a golf ball.

The coating of a golf ball is commonly known as a balata. Balata can be found in nature, but can also be synthesized. In each case, trans-polyisoprene is a component. It is a relatively hard material, but very expensive and costs 5.50 per pound.
From $ (for synthetic) to $ 12.00 (for natural products). In comparison, natural rubber (100% cis isoprene) costs about $ 0.50 per pound. Natural rubber is a flexible material that is mixed with balata to be 50% or slightly more to reduce the overall cost of the coating. Other materials may be mixed with the balata along with or instead of the rubber to reduce the cost of the coating. Notable among these materials are gutta percha, butadiene and synthetic rubber. To obtain the spin rate of the present invention, at least 90% of trans polyisoprene is used, or more preferably
Use 95% trans polyisoprene, or most preferably, at least 99% trans polyisoprene. The combination of a large liquid center and a hard balata coating has been found to be an excellent way to achieve the spin rate according to the present invention on a balata coated wound ball. Of course, the required spin speed can be obtained by other methods.

The wound core type golf ball according to the present invention has an aerodynamic shape and spin rate and has a lower and flatter trajectory than commercially available wound core type golf balls of similar compression. At the same time, it has been found that it has a larger carry distance and a larger total flight distance (this is a
Can be said about both irons). As for the trajectory,
A half yard (0.4572m) height is considered important when hit at a 13 ° angle at a speed of 230 feet (70.1m) per second. Balls according to the present invention have a trajectory that is at least 1-11 / 2 yards lower than commercially available wound balata-coated golf balls. Regarding carry distance (in driver and 5 iron test), the golf ball according to the present invention
Whether wound or two-piece, balata-coated or Surlyn-coated, a minimum improvement in carry distance of at least 5 yards (4.572 m) over commercially available golf balls can be made. Hereinafter, the configuration of the present invention will be further described with reference to examples.

[0040]

EXAMPLE 1 A group of golf balls was obtained. Golf balls are manufactured by the applicant and sold under the trademark Titleist Pro Trajectory. These golf balls have a so-called liquid center that is well known in the golf ball industry. The center of the liquid is a hollow sphere having an outer diameter of 1-11 / 16 inches (2.54-2.69875 cm). The hollow sphere is completely filled with liquid. The center is covered with a 0.22 inch x 1/16 inch (0.5588 cm x 0.15875 cm) elastic thread,
It is wound into a 1.610 inch (4.0894 cm) diameter wound ball. Its upper surface is molded with a coating consisting of the following components: resin; 76.2%, resin component; transpolyisoprene 84
%, Natural rubber 16%, filler; 22.5%, others; 1.3% Molded golf balls are processed and painted in a standard manner. The diameter of the finished golf ball is
It is 1.680 inches (4.2672 cm). This value is an average value. Actual values may vary by as much as 0.003 inches (0.00762 cm).

The golf ball has 324 dimples uniformly distributed on the surface of the golf ball such that the golf ball is centered at the apex of an icosahedral-spherical triangular array as described in GB 1,381,897. The four vertices at each pole of the ball do not have dimples to form a smooth surface for branding and identification, and these vertices are equal to separate the dimples on the molded parting line. Slightly rearranged to form a circle. Dimples are 0.146 inch ± 0.002 inch (0.3
7084 cm ± 0.00508 cm) and 0.0122 inches ± 0.
It has a depth of 0003 inches (0.030988 cm ± 0.000762 cm).

Example 2 A group of golf balls was made according to the method of the present invention. The golf ball has the same type of liquid filling center as the golf ball of Example 1, uses the same elastic system as in Example 1, and has the same diameter of the wound ball.
It was 1.610 inches (4.089 cm).

In this case, however, the golf ball was made to meet the parameters of the present invention.
The size of the center has been increased to 1/8 inch (2.8575 cm). The composition of the coating molded into the wound ball was changed to 100% trans polyisoprene polymer as follows: resin; 76.7%, resin composition; trans polyisoprene 1
00%, 0% natural rubber, filler; 22.0%, others; 1.3% Fillers and other compositions are the same as in Example 1, except that the filler is slightly less. The molded balls are processed and painted in a standard manner. The finished ball diameter is 1.680 inches (4.26 inches)
72 cm). As in Example 1, the diameter error tolerance was up to 0.003 inches (0.00762 cm).

Further, according to the present invention, the golf ball has a icosahedron / spherical surface 3 like the golf ball of the first embodiment.
It has 384 dimples arranged at approximately equal intervals on the surface of the golf ball using a square pattern. As with the golf ball of Example 1, no dimples are used at the four vertices to form a smooth surface for each trademark and identification number on each pole. The tops of the dimples are rearranged with a slight shift so that the molding parting line becomes an even circle. The dimple has a diameter of 0.146 inches ± 0.002 inches (0.37084 cm ± 0.00508 cm) and a depth of 0.0115 inches ± 0.0003 inches (0.02921 cm ± 0.000762 cm).

Comparative Tests The finished golf balls of Examples 1 and 2 were compared for a number of properties. The ball was selected from the examples of size, weight, and initial velocity that were statistically comparable to the USGA standard. Each selected ball is between 1.610 and 1.620
Ounces (45.6435-45.927g) weight, 1.680-1.690
Inch (4.2672-4.2926cm) size and 253.0 per second
It had an initial speed of ~ 253.5 feet (77.1144-77.2668 m). These changes in size, weight and initial velocity
The number of balls tested was not statistically significant. The ball was first examined for spin rate. This was done for both the driver and the 5 iron. The ball hit by the driver
A ball hit with a 5-iron having a launch angle of 11 ° has a launch angle of 21 °. The spin speed is
Determined by mechanical testing at the indicated angles using an apparatus of the type disclosed in U.S. Pat. No. 4,063,259.

Carry distance and rolling distance (carry and rolling) were determined by field tests using a device commonly known in the golf ball industry as a dual pendulum. The dual pendulum device has pendulums on both sides of the motor to draw a pendulum locus, and strikes two pendulums, one for each pendulum. The ball is 70 ° F (21.111…
(° C). Two balls at a time are hit into the open field by the pendulum and the carry distance and total flight distance are individually observed and recorded by the operator. Eight balls are hit on both sides of the device. In this case, the series of eight balls of Example 1 are hit on one side of the device, and the series of eight balls of Example 2 are hit simultaneously on the other side. 16 after rolling
The balls are collected and returned to the device. They are,
Replaced assorted and struck pendulum. The measurements are taken again, the balls are collected, and this procedure
It is repeated twice more. Thus, each of the eight balls of each embodiment is hit four times, and a total of 32 hits for both pendulums, and 16 hits for each pendulum. The number of hits produces statistically significant results and almost cancels out winding changes, temperature differences, device or pendulum differences, and the like. This is especially so because the balls of the two embodiments are hit simultaneously and the pendulum is changed over a series of four tests.

The procedure just described was used for both driver and 5-iron distance tests. The dual pendulum has an adjustable hitting surface. A launch angle of 11 ° was used to trace the driver.
A launch angle of 11 ° is obtained by using a striking surface having an angle of 13 ° to the vertical. A launch angle of 21 ° was used to trace the 5 iron. twenty one
A launch angle of ° was obtained by using a striking face with an angle of 26 ° to the vertical. The results of the spin speed and drive distance tests are as follows.

Ball of Example 1 (Titleist, Ball Pro Trajectory of Example 2) (Invention) Spin Speed (rpm) 11 ° 3135 2799 21 ° 5310 4788 Carry Distance (Yard) 11 ° 251.3 253.7 (229.78872m (231.98328m) 21 ° 168.8 172.3 (154.35072m) (157.55112m) 11 ° + 21 ° 420.1 426.0 (384.13944m) (389.5344m) Total flight distance (carry + rolling) (yard) 11 ° 268.5 276.3 (245.5164m) (252.64872m) 21 ° 179.1 184.7 (163.76904m) (168.88968m) 11 ° + 21 ° 447.6 461.0 (409.8544m) (421.5384m) Example 3 The golf ball made in Example 2 is described in the previous page. Using the distance test set as "test", it is compared to top balata coated golf balls from various manufacturers. Because the tests were performed under different environmental conditions, there are significant differences between the tests. The golf ball to compare was the current manufactured ball provided by the manufacturer to Prozer. The test results are as follows.

[0049]

[Table 1]

Examples 4 and 5 These examples show that the present invention can employ coatings such as ionomer resins, for example, Du Pont's Surlyn resin. A series of golf balls were made in the same manner as Examples 1 and 2, and Examples 4 and 5
Was called. In each case, the ionomer resin was obtained by replacing the coating material with the resin of Examples 1 and 2. The size of the wound ball is 1.58 inches (4.
The cores of Examples 4 and 5 were made in the same manner and from the same material. The total distance (carry and roll) of these balls is determined by the procedure described above.
Were compared, and the results are as follows.

Example 4 Ball Example 5 Total Ball Flying Distance (Carry + Roll ) Yard 11 ° 246.6 251.0 (225.49104m) (229.5144m) 21 ° 183.6 184.3 (167.88384m) (168.52392m) 11 ° + 21 ° 430.2 435.3 (393.37488 m) (398.03832 m) Examples 6 and 7 These examples show that the invention can also be used with rigid cores. A series of golf balls were made similar to Examples 4 and 5, and are referred to as Examples 6 and 7.
In both cases, the rigid core is replaced with the wound core of Examples 4 and 5. Rigid core, British Patent 1,36
Made according to the suggestions of 4,138. These balls were compared in total flight distance (carry and rolling) according to the procedure described above, and the results are shown below.

Ball of Example 6 Ball of Example 7 (having a rigid core (ball of Example 4 having a rigid core) Ball of Example 5) Total flight distance (carry + rolling) yard 11 ° 274.8 275.8 (251.27712m) (252.9152m) 21 ° 171.9 175.6 (157.18536m) (160.56864m) 11 ° + 21 ° 446.7 451.4 (408.48248m) (412.76016m) Example 8 Ball with 372 dimples instead of 384 dimples Made in the manner of Example 2. This number of dimples is obtained by omitting the dimple indicated by 14 in the drawing. Although only one dimple on one hemisphere of the golf ball is shown in the drawing, the total number of dimples omitted is 12, leaving 372 dimples on the golf ball. The dimple is 0.155
± 0.002 inch (0.3937 ± 0.00508 cm) diameter and 0.0120
It has a depth of ± 0.0003 inches (0.03048 ± 0.000762 cm). The spin rate of the golf ball was the same as that of Example 2, and in the distance test, the result was that of Example 2.
There was no statistical difference from the one.

Example 9 The procedure of Example 2 was repeated, except that the number of dimples was changed from 384 to 392. This is achieved by including 10 dimples in the trademark identification area on each hemisphere surface of the golf ball and 12 dimples in the number identification area. The spin rate of the golf ball is the same as that of the golf ball of the second embodiment. The results of the distance test were not statistically different from the results of Example 2.

Example 10 A golf ball was made in the manner of Example 2 except that the dimple marked 18 in the drawing had a diameter of 0.140 ± 0.002 inches (0.3556 ± 0.00508 cm) and the remaining dimples But 0.160 ± 0.002 inch (0.4064 ± 0.00508c
m). The average diameter of the entire dimple is 0.151 ± 0.002 inches (0.38354 ± 0.00508)
cm). Example 2
It is the same as that of In the distance test, the golf ball of this example was statistically superior to the golf ball of Example 2.

Example 11 (Production of Comparative Control Golf Ball) For comparison, TI, which is the golf ball flying the most at that time, was used.
As a result of selecting TLEIST K-2 and conducting extensive tests,
This ball was found to fly farther than any other ball.

In conducting the first test using the wind tunnel, solid nylon golf balls were used. Nylon balls were used instead of actual molded balls because nylon can be cut very well, but the molded cover is elastic and tends to be unevenly cut and melted during high-speed cutting.

Each golf ball was tested for aerodynamic properties in a wind tunnel. The reason for using the wind tunnel test instead of the actual driving test is that it can be accurately reproduced.
Extensive golf ball testing has shown that the wind tunnel test and the actual driving test are correlated. In other words, if a wind ball test indicates that a certain golf ball flies over another ball, it means that the golf ball flies well at the same ratio in an actual driving test.

In the analysis of the golf ball, many factors were varied. These factors include the number of dimples, dimple shape, dimple arrangement, dimple depth, and dimple diameter. From this initial data analysis, it was found that placing dimples as evenly as possible on the surface of the golf ball was one of the first considerations. The improved icosahedral pattern was chosen as the best way to do this. A regular icosahedral pattern, which has dimples at the dividing line of the golf ball mold and cannot be buffed, was not used.

With the improved icosahedral pattern, 252,332 and
392 dimples were uniformly arranged, and these dimple numbers were used in the following tests. Many golf balls having these dimple numbers were made by changing the dimple depth and dimple diameter. A set of six golf balls was prepared for each parameter. Each set of golf balls was subjected to a wind tunnel test. The results of the wind tunnel test were analyzed to determine the flight distance of each golf ball.

As a result, the number of dimples, dimple diameter,
It has been found that there is a correlation between dimple depth and dimple spacing. Applications relating to this interrelationship have been filed in several countries, one of which is Japanese Patent No. 1,31.
No. 3,596 (Japanese Patent Publication No. 58-50744). Up to now, the golf balls according to the above patent have been the most excellent in aerodynamic properties.

Example 12 Analysis of various test data showed that a ball with 392 dimples had a lower trajectory and a higher terminal velocity than balls with 252 and 332 dimples.

Many tests were performed in the same manner as in the test of Example 11 except that the dimple diameter and the dimple depth were changed.
Here, the number of dimples was 392 (this golf ball actually had 384 dimples because the dimples were removed from the nameplate and number areas to obtain a smooth surface for stamping. According to the previous investigation, it has been found that a change in the number of dimples of 3% does not significantly affect the flight distance.)

In addition to changing the dimple diameter and dimple depth, the test was performed by changing the spin rate of the ball.
Spin speed is the number of revolutions per minute of the ball immediately after the ball has been hit with a golf club. The spin rate is affected by the composition of the cover, the hardness of the cover, the overall mass distribution of the ball, the type of ball structure, and other factors.
However, spin speed is virtually unaffected by dimples on the ball surface.

The aforementioned patent No. 1,313,596 (Japanese Patent Publication No. 58-5074)
A comparison of the flight distance between the ball according to 4) and the ball according to the present invention is shown below. Here, the ball according to Patent No. 1,313,596 has 324 dimples and 0.151 inch (0.384 inch).
cm) average dimple diameter and 0.0126 inch (0.0320c)
m), the ball according to the invention had a dimple number of 384, an average dimple diameter of 0.150 inches (0.381 cm) and an average dimple depth of 0.011 inches (0.0279 cm).

Distance (yard) ^* Carry Total Test 1 (a) Ball according to Patent No. 1,313,596 188.3 203.5 (b) Ball according to the present invention 190.4 206.1 Test 2 (a) Ball according to Patent No. 1,313,596 190.4 212.4 (b) Present invention Ball due to 192.6 215.7 ^{* The} relatively short flight distance overall is due to tests conducted by amateur golfers. The test was performed by different amateur golfers on different days. The golf ball according to the invention was shown to be excellent (the golf ball according to the invention flew at least 2 yards away).

After optimizing the size of the dimples, further tests were performed with varying spin rates. The results are shown below. Here, each golf ball had dimples having the same average dimple diameter and the same average dimple depth.

Distance (yards) Spin Speed (rpm) Carry Total Ball A 3055 234.7 244.1 Ball B 2865 236.5 245.7 Ball C 2728 236.8 246.3 As is clear from the above, when the spin speed is controlled to be less than 2900 rpm, 1.5 The flight distance increased by more than yards. Combining the control of the dimple size and the spin rate results in a flight distance increase of 4 yards or more compared to the golf ball according to the above-mentioned Japanese Patent No. 1,313,596.

Although several embodiments have been described above, variations and modifications of these embodiments can be easily made without departing from the technical concept of the present invention.

[Brief description of the drawings]

FIG. 1 is a diagram showing a hemisphere portion of a golf ball according to the present invention.

FIG. 2 is a graph showing a correlation between a dimple diameter and a dimple depth of a golf ball according to the present invention.

[Explanation of symbols]

 8 Equator 10, 12, 14, 18 dimples

 ──────────────────────────────────────────────────続 き Continued on front page (72) Robert A. Brown, Inventor Ma Tapoiset Foster Street, Mass., USA 8 (72) John W. Jeffson, Inventor Marion Ord Chlor Road 56, Mass., USA

Claims (5)

[Claims] 1. A golf ball having dimples having two different dimple diameters. 2. The golf ball of claim 1, wherein one dimple diameter is about 0.140 inches and another dimple diameter is about 0.160 inches. 3. The golf ball according to claim 2, wherein the total number of the dimples is 384 ± 3%. 4. It has a total of 384 ± 3% of dimples,
The dimples have two sets of dimples, each set of dimples having the same diameter within that set, one set of dimples being larger than the other set of dimples, and the larger dimple having a nominal diameter of 0.160. A golf ball characterized by being inches. 5. It has a total of 384 ± 3% of dimples,
The dimple has two sets of dimples, each set of dimples having the same diameter within that set, one set of dimples being larger than the other set of dimples, and the smaller dimple having a nominal diameter of 0.140. A golf ball characterized by being inches.