Patent Application
20110269576
1. Field of the Invention
The embodiments described herein relate generally to golf balls and are specifically concerned with golf ball dimple patterns to create desired flight characteristics.
2. Related Art
Golf ball dimple pattern design has long been considered a critical factor in ball flight distance. A golf ball's velocity, launch angle, and spin rate is determined by the impact between the golf club and the golf ball, but the ball's trajectory after impact is controlled by gravity and aerodynamics of the ball. Dimples on a golf ball affect both drag and lift, which in turn determine how far the ball flies.
The aerodynamic forces acting on a golf ball during flight may be determined according to well-understood laws of physics. Scientists have created mathematical models so as to understand these laws and predict the flight of a golf ball. Using these models along with several readily determined values such as the golf ball's weight, diameter and lift and drag coefficients, scientists have been able to resolve these aerodynamic forces into the orthogonal components of lift and drag. The lift coefficient relates to the aerodynamic force component acting perpendicular to the path of the golf ball during flight while the drag coefficient relates to the aerodynamic force component acting parallel to the flight path. The lift and drag coefficients vary by golf ball design and are generally a function of the speed and spin rate of the golf ball and for the most part do not depend on the orientation of the golf ball on the tee for a spherically symmetrical or “conforming” golf ball.
The maximum height a golf ball achieves during flight is directly related to the lift generated by the ball, while the direction that the golf ball takes, specifically how straight a golf ball flies, is related to several factors, some of which include spin and spin axis orientation of the golf ball in relation to the golf ball's direction of flight. Further, the spin and spin axis are important in specifying the direction and magnitude of the lift force vector. The lift force vector is a major factor in controlling the golf ball flight path in the x, y and z directions. Additionally, the total lift force a golf ball generates during flight depends on several factors, including spin rate, velocity of the ball relative to the surrounding air and the surface characteristics of the golf ball. However, with respect to surface characteristics, not all the regions on the surface of a spinning golf ball contribute equally to the generation of the total lift force. As an example, if the surface of the ball has a spherically symmetrical dimple pattern and the ball is hit so that the spin axis passes through the poles, the surface region closest to the golf ball equator (i.e., the great circle orthogonal to the spin axis) is more important in generating lift than are the regions close to the poles. However, a golf ball that is not hit squarely off the tee will tend to drift off-line and disperse away from its intended trajectory. This is often the case with recreational golfers who impart a slice or a hook spin on the golf ball when striking the ball.
In order to overcome the drawbacks of a hook or a slice, some golf ball manufacturers have modified the construction of a golf ball in ways that tend to lower the spin rate. Some of these modifications include utilizing hard two-piece covers and using higher moment of inertia golf balls. Other manufacturers have resorted to modifying the ball surface to decrease the lift characteristics on the ball. These modifications include varying the dimple patterns in order to affect the lift and drag on the golf ball.
Some prior golf balls have been designed with non-conforming or non-symmetrical dimple patterns in an effort to offset the effect of imperfect hits, so that the unskilled golfer can hit a ball more consistently in a straighter path. Although such balls are not legal in professional golf, they are very helpful for the recreational golfer in making the game more fun. One such ball is described in U.S. Pat. No. 3,819,190 of Nepela et al. This ball is also known as a Polara™ golf ball, and has regions with different numbers of dimples or no dimples. A circumferential band extending around the spherical ball has a plurality of dimples, while polar areas on opposite sides of the band have few or no dimples. For this asymmetric golf ball, the measured lift and drag coefficients are strongly influenced by the orientation of the golf ball on the tee before it is struck. This is evidenced by the fact that the trajectory of the golf ball is strongly influenced by how the golf ball is oriented on the tee. For this ball to work properly, it must be placed on the tee with the poles of the ball oriented such that they are in the plane that is pointed in the intended direction of flight. In this orientation, the ball produces the lowest lift force and thus is less susceptible to hooking and slicing.
Other golf balls have been constructed of a single or multi-layer core, either solid or wound, that is tightly surrounded by a single or multilayer cover formed from polymeric materials, such as polyurethane, balata rubber, ionomers or a combination. Although some of these golf balls do reduce some hook and slice dispersion, this type of ball construction has the disadvantage of adding cost to the golf ball manufacturing process.
Certain embodiments as disclosed herein provide for a golf ball having a dimple pattern which results in reduced hook and slice dispersion.
In one aspect, a golf ball is designed with a dimple pattern which has reduced or no dimple volume in a selected circumferential band around the ball and more dimple volume in other regions of the ball. This causes the ball to have a “preferred” spin axis because of the weight differences caused by locating different volume dimples in different areas across the ball. This in turn reduces the tendency for dispersion of the ball to the left or right (hooking and slicing) during flight. In one example, the circumferential band of lower dimple volume is around the equator with more dimple volume in the polar regions. This creates a preferred spin axis passing through the poles. In one embodiment, the dimple pattern is also designed to exhibit relatively low lift when the ball spins in the selected orientation around its preferred spin axis. This golf ball is nonconforming or non-symmetrical under United States Golf Association (USGA) rules.
A golf ball's preferred or selected spin axis may also be established by placing high and low density materials in specific locations within the core or intermediate layers of the golf ball, but has the disadvantage of adding cost and complexity to the golf ball manufacturing process.
Where a circumferential band of lower or zero dimple volume is provided about the equator and more dimple volume is provided in the polar regions, a ball is created which has a large enough moment of inertia (MOI) difference between the poles horizontal (PH) orientation and other orientations that the ball has a preferential spin axis going through the poles of the ball. The preferred spin axis extends through the lowest weight regions of the ball. If these are the polar regions, the preferred axis extends through the poles. If the ball is oriented on the tee so that the “preferred axis” or axis through the poles is pointing up and down (pole over pole or POP orientation), it is less effective in correcting hooks and slices compared to being oriented in the PH orientation when struck.
In another aspect, the ball may have no dimples in a band about the equator (a land area) and deep dimples in the polar regions. The dimpleless region may be narrow, like a wide seam, or may be wider, i.e. equivalent to removing two or more rows of dimples next to the equator.
By creating a golf ball with a dimple pattern that has less dimple volume in a band around the equator and by removing more dimple volume from the polar regions adjacent to the low-dimple-volume band, a ball can be created with a large enough moment of inertia (MOI) difference between the poles-horizontal (PH) and other orientations that the ball has a “preferred” spin axis going through the poles of the ball and this preferred spin axis tends to reduce or prevent hooking or slicing when a golfer hits the ball in a manner which would generate other than pure backspin on a normal symmetrically designed golf ball. In other words, when this ball is hit in manner which would normally cause hooking or slicing in a symmetrical or conforming ball, the ball tends to rotate about the selected spin axis and thus not hook or slice as much as a symmetrical ball with no selected or “preferred” spin axis. In one embodiment, the dimple pattern is designed so that it generates relatively low lift when rotating in the PH orientation. The resulting golf ball displays enhanced hook and slice correcting characteristics.
The low volume dimples do not have to be located in a continuous band around the ball's equator. The low volume dimples could be interspersed with higher volume dimples, the band could be wider in some parts than others, the area in which the low volume dimples are located could have more land area (lack of dimples) than in other areas of the ball. The high volume dimples located in the polar regions could also be inter-dispersed with lower volume dimples; and the polar regions could be wider in some spots than others. The main idea is to create a higher moment of inertia for the ball when it is rotating in one configuration and to do this by manipulating the volume of the dimples across the surface of the ball. This difference in MOI then causes the ball to have a preferred spin axis. The golf ball is then placed on the tee so that the preferred spin axis is oriented approximately horizontally so that when the ball is hit with a hook or slice action, the ball tends to rotate about the horizontal spin axis and thus not hook or slice as much as a symmetrical ball with no preferred spin axis would hook or slice. In some embodiments, the preferred spin axis is the PH orientation.
Another way to create the preferred spin axis would be to place two or more regions of lower volume or zero volume regions on the ball's surface and make the regions somewhat co-planar so that they create a preferred spin axis. For example, if two areas of lower volume dimples were placed opposite each other on the ball, then a dumbbell-type weight distribution would exist. In this case, the ball has a preferred spin axis equal to the orientation of the ball when it is rotating end-over-end with the “dumbbell areas”.
The ball can also be oriented on the tee with the preferred spin axis tilted up to about 45 degrees to the right and then the ball still resists slicing, but does not resist hooking. If the ball is tilted 45 degrees to the left it reduces or prevents hook dispersion, but not slice dispersion. This may be helpful for untrained golfers who tend to hook or slice a ball. When the ball is oriented so that the preferred axis is pointing up and down on the tee (POP orientation for a preferred spin axis in the PH orientation), the ball is much less effective in correcting hooks and slices compared to being oriented in the PH orientation.
Other features and advantages will become more readily apparent to those of ordinary skill in the art after reviewing the following detailed description and accompanying drawings.
The details of the present embodiments, both as to structure and operation, may be gleaned in part by study of the accompanying drawings, in which like reference numerals refer to like parts, and in which:
After reading this description it will become apparent to one skilled in the art how to implement the embodiments in various alternative implementations and alternative applications. Further, although various embodiments will be described herein, it is understood that these embodiments are presented by way of example only, and not limitation. As such, this detailed description of various alternative embodiments should not be construed to limit the scope or breadth of the appended claims.
In the embodiments of
It should also be understood that the terms equator or equatorial region and poles can be defined with respect to the gyroscopic center plane. In other words, the equator is in the gyroscopic center plane and the preferred spin axis goes through the poles.
In fact it has been determined that making dimples more shallow within the region inside the approximately 45 degree point 1803 on the circumference of the ball 10 with respect to the gyroscopic center plane 1801, as illustrated in
Shown in Table 1 below are the dimple radius, depth and dimple location information for making a hemispherical injection molding cavity to produce the dimple pattern 28-1 on one hemisphere of the ball, with the other injection molding cavity being identical. As illustrated in Table 1, the ball has a total of 410 dimples (205 in each hemisphere of the ball). The truncated dimples 12 are each of the same radius and truncated chord depth, while the larger and smaller spherical dimples are each of three different sizes (Smaller dimples 1, 2 and 3 and larger dimples 5, 6, 7 in Table 1). Table 1 illustrates the locations of the truncated dimples and each of the different size spherical dimples on one hemisphere of the ball,
As seen in
With this dimple arrangement, significantly more material is removed from the polar regions of the ball to create the larger, deeper spherical dimples, and less material is removed to create the band of shallower, truncated dimples around the equator. In testing described in more detail below, the 28-1 dimple pattern of
Shown in Table 2 are the dimple radius, depth and dimple location information for making an injection molding cavity to produce the dimple pattern 25-1 of
As indicated in Table 2, ball 25-1 has only two different size smaller spherical dimples 22 in the polar region (dimples 1 and 2 which are the same size as dimples 1 and 2 of the 28-1 ball), and only one size larger spherical dimple 20, i.e. dimple 4 which is the same size as dimple 5 of the 28-1 ball. Thus, the 28-1 ball has some spherical dimples, specifically dimples 6 and 7 in Table 1, which are of larger diameter than any of the spherical dimples 20 of the 25-1 ball.
It will be understood that a similar type of mold, or set of molds, is used for all of the embodiments described herein, and that mold 23 is shown by way of example only.
Table 4 below lists dimple shapes, dimensions, and coordinates or locations on a ball for a dimple pattern 28-2 which is very similar to the dimple pattern 28-1 and is therefore not shown separately in the drawings. The ball with dimple pattern 28-2 has three larger spherical dimples of different dimensions, numbered 5, 6 and 7 in Table 4, and three smaller spherical dimples of different dimensions, numbered 1, 2 and 3, and the dimensions of these dimples are identical to the corresponding dimples of the 28-1 ball in Table 1, as are the dimensions of truncated dimples numbered 4 in Table 4. The dimple pattern 28-2 is nearly identical to dimple pattern 28-1, except that the seam that separates the two hemispheres of the ball is wider in the 28-2 ball, and the coordinates of some of the dimples are slightly different, as can be determined by comparing Tables 1 and 4.
The dimple coordinates for pattern 28-2 are shown in table 4 below.
Ball 30 or 25-2 of
Ball 40 or 25-3 of
Ball 50 or 25-4 of
As indicated in Tables 5, 6, and 7 below, the balls 25-2 and 25-3 each have three different sizes of truncated dimple in the equatorial region and two different sizes of spherical dimple in the polar region, while ball 25-4 has three different sizes of truncated dimple as well as three different sizes of spherical dimple. The polar region of dimples is largest in ball 25-2, which has four rows of truncated dimples (two rows per hemisphere) in the equatorial region, and smallest in ball 25-3, which has eight rows of truncated dimples in the equatorial region. In alternative embodiments, balls may be made with a single row of truncated dimples in each hemisphere, as well as with a land area having no dimples in an equatorial region, the land area or band having a width equal to two, four or more rows of dimples, or with a band having regions with dimples alternating with land regions with no dimples spaced around the equator.
Dimple patterns 25-2, 25-3 and 25-4 are similar to pattern 2-9 in that they have truncated dimples around the equatorial region and deeper dimples around the pole region, but the truncated dimples in patterns 25-2, 25-3 and 25-4 are of larger diameter than the truncated dimples of patterns 28-1, 25-1 and 2-9. The larger truncated dimples near the equator means that more weight is removed from the equator area. With all other factors being equal, this means that there is a smaller MOI difference between the PH and POP orientations for balls 25-2, 25-3 and 25-4 than for balls 28-1, 28-2, 25-1 and 2-9.
As indicated in Table 8 and
The dimple parameters and coordinates for making one hemisphere of the 28-3 ball are listed below in Table 8,
In one example, the seam widths for balls 28-1, 28-2, and 28-3 was 0.0088″ total (split on each hemisphere), while the seam widths for balls 25-2, 25-3, and 25-4 was 0.006″, and the seam width for ball 25-1 was 0.030″.
Each of the dimple patterns described above and illustrated in
V1=volume of truncated dimple,
V1+V2=volume of spherical dimple,
V1+V2+V3=volume of cover removed to create spherical dimple, and
V1+V3=volume of cover removed to create truncated dimple.
For dimples that are based on the same radius and spherical chord depth, the moment of inertia difference between a ball with truncated dimples and spherical dimples is related to the volume V2 below line or plane A-A which is removed in forming a spherical dimple and not removed for the truncated dimple. A ball with all other factors being the same except that one has only truncated dimples and the other has only spherical dimples, with the difference between the truncated and spherical dimples being only the volume V2 (i.e. all other dimple parameters are the same), the ball with truncated dimples is of greater weight and has a higher MOI than the ball with spherical dimples, which has more material removed from the surface to create the dimples.
The approximate moment of inertia can be calculated for each of the balls illustrated in
The MOI for each ball was calculated based on the dimple pattern information and the physical information in Table 9. Table 10 shows the MOI calculations.
With the Polara™ golf ball as a standard, the MOI differences between each orientation were compared to the Polara golf ball in addition to being compared to each other. The largest difference between any two orientations is called the “MOI Delta”, shown in table 10. The two columns to the right quantify the MOI Delta in terms of the maximum % difference in MOI between two orientations and the MOI Delta relative to the MOI Delta for the Polara ball. Because the density value used to calculate the mass and MOI was lower than the average density of a golf ball, the predicted weight and MOI for each ball is relative to each other, but not exactly the same as the actual MOI values of the golf balls that were made, robot tested and shown in Table 10. Generally a golf ball weighs about 45.5-45.9 g. Comparing the MOI values of all of the balls in Table 10 is quite instructive, in that it predicts the relative order of MOI difference between the different designs, with the 25-3 ball having the smallest MOI difference and ball 28-2 having the largest MOI difference.
Table 11 shows that a ball's MOI Delta does strongly influence the ball's dispersion control. In general as the relative MOI Delta of each ball increases, the dispersion distance for a slice shot decreases. The results illustrated in Table 11 also include data obtained from testing a known TopFlite XL straight ball, and were obtained during robot testing under standard laboratory conditions, as discussed in more detail below.
As illustrated in Table 11, balls 28-3, 25-1, 28-1 and 28-2 all have higher MOI deltas relative to the Polara, and they all have better dispersion control than the Polara. This MOI difference is also shown in
The aerodynamic force acting on a golf ball during flight can be broken down into three separate force vectors: Lift, Drag, and Gravity. The lift force vector acts in the direction determined by the cross product of the spin vector and the velocity vector. The drag force vector acts in the direction opposite of the velocity vector. More specifically, the aerodynamic properties of a golf ball are characterized by its lift and drag coefficients as a function of the Reynolds Number (Re) and the Dimensionless Spin Parameter (DSP). The Reynolds Number is a dimensionless quantity that quantifies the ratio of the inertial to viscous forces acting on the golf ball as it flies through the air. The Dimensionless Spin Parameter is the ratio of the golf ball's rotational surface speed to its speed through the air.
The lift and drag coefficients of a golf ball can be measured using several different methods including an Indoor Test Range such as the one at the USGA Test Center in Far Hills, N.J. or an outdoor system such as the Trackman Net System made by Interactive Sports Group in Denmark. The test results described below and illustrated in
For right-handed golfers, particularly higher handicap golfers, a major problem is the tendency to “slice” the ball. The unintended slice shot penalizes the golfer in two ways: 1) it causes the ball to deviate to the right of the intended flight path and 2) it can reduce the overall shot distance. A sliced golf ball moves to the right because the ball's spin axis is tilted to the right. The lift force by definition is orthogonal to the spin axis and thus for a sliced golf ball the lift force is pointed to the right.
The spin-axis of a golf ball is the axis about which the ball spins and is usually orthogonal to the direction that the golf ball takes in flight. If a golf ball's spin axis is 0 degrees, i.e., a horizontal spin axis causing pure backspin, the ball does not hook or slice and a higher lift force combined with a 0-degree spin axis only makes the ball fly higher. However, when a ball is hit in such a way as to impart a spin axis that is more than 0 degrees, it hooks, and it slices with a spin axis that is less than 0 degrees. It is the tilt of the spin axis that directs the lift force in the left or right direction, causing the ball to hook or slice. The distance the ball unintentionally flies to the right or left is called Carry Dispersion. A lower flying golf ball, i.e., having a lower lift, is a strong indicator of a ball that has lower Carry Dispersion.
The amount of lift force directed in the hook or slice direction is equal to: Lift Force*Sine (spin axis angle). The amount of lift force directed towards achieving height is: Lift Force*Cosine (spin axis angle).
A common cause of a sliced shot is the striking of the ball with an open clubface. In this case, the opening of the clubface also increases the effective loft of the club and thus increases the total spin of the ball. With all other factors held constant, a higher ball spin rate in general produces a higher lift force and this is why a slice shot often has a higher trajectory than a straight or hook shot.
The table below shows the total ball spin rates generated by a golfer with club head speeds ranging from approximately 85-105 mph using a 10.5 degree driver and hitting a variety of prototype golf balls and commercially available golf balls that are considered to be low and normal spin golf balls:
Table 13 below illustrates results from slice testing the 25-1, 28-1, and 2-9 balls as well as the Titleist ProV1 and the TopFlite XL Straight balls, with the 25-1, 28-1 and 2-9 balls tested in both the PH and POP orientations. In this table, the average values for carry dispersion, carry distance, total dispersion, total yards, and roll yards are indicated. This indicates that the 25-1, 28-1 and 2-9 balls have significantly less dispersion in the PH orientation than in the POP orientation, and also have less dispersion than the known symmetrical ProV1 and TopFlite balls which were tested.
Golf balls 25-1, 28-1, 2-9, Polara 2p 4/08, Titleist ProV1 and TopFlite XL Straight were subjected to several tests under industry standard laboratory conditions to demonstrate the better performance that the dimple patterns described herein obtain over competing golf balls. In these tests, the flight characteristics and distance performance of the golf balls 25-1, 28-1 and 2-9 were conducted and compared with a Titleist Pro V10 made by Acushnet and TopFlite XL Straight made by Callaway Golf and a Polara 2p 4/08 made by Pounce Sports LLC. Also, each of the golf balls 25-1, 28-1, 2-9, Polara 2p 4/08, were tested in the Poles-Forward-Backward (PFB), Pole-Over-Pole (POP) and Pole Horizontal (PH) orientations. The Pro V1® and TopFlite XL Straight are USGA conforming balls and thus are known to be spherically symmetrical, and were therefore tested in no particular orientation (random orientation). Golf balls 25-1 and 28-1 were made from basically the same materials and had a DuPont HPF 2000 based core and a Surlyn™ blend (50% 9150, 50% 8150) cover. The cover was approximately 0.06 inches thick.
The tests were conducted with a “Golf Laboratories” robot and hit with the same Taylor Made® driver at varying club head speeds. The Taylor Made® driver had a 10.5° R9 460 club head with a Motore 65 “S” shaft. The golf balls were hit in a random order. Further, the balls were tested under conditions to simulate an approximately 15-25 degree slice, e.g., a negative spin axis of 15-25 degrees.
The curves in
CL
Regression
=a
1
*Re+a
2
*W+a
3
*Rê2+a4*Ŵ2+a5*ReW+a6
CD
Regression
=b
1
*Re+b
2
*W+b
3
*Rê2+b4*Ŵ2+b5*ReW+b6
Where ai with i=1-6 are regression coefficients for Lift Coefficient and
bi with i=1-6 are regression coefficients for Drag Coefficient
Typically the predicted CD and CL values within the measured Re and W space (interpolation) were in close agreement with the measured CD and CL values. Correlation coefficients of 96-99% were typical.
Below in Tables 14A and 14B are the regression constants for each ball shown in
As can be determined from
Under typical slice conditions, with spin rates of 3,000 rpm or greater, the 2-9, 25-1, 28-1 in PH orientation and the Polara 2p in PFB orientation exhibit lower lift coefficients than the commercial balls: ProV1 and TopFlite XL Straight. Lower lift coefficients translate into lower trajectory for straight shots and less dispersion for slice shots. Balls with dimple patterns 2-9, 25-1, 28-1 in PH orientation have approximately 10-40% lower lift coefficients than the ProV1 and TopFlite XL Straight under Re and spin conditions characteristics of slice shots.
Tables 15-17 are the Trackman Report from the Robot Test. The robot was set up to hit a slice shot with a club path of approximately 7 degrees outside-in and a slightly opened club face. The club speed was approximately 98-100 mph, initial ball spin ranged from about 3,800-5,200 rpm depending on ball construction and the spin axis was approximately 13-21 degrees,
The non-conforming golf balls described above which have dimple patterns including areas of less dimple volume along at least part of a band around the equator and more dimple volume in the polar regions have a large enough moment of inertia (MOI) difference between the poles horizontal (PH) or maximum orientation and other orientations that the ball has a preferred spin axis extending through the poles of the ball. As described above, this preferred spin axis helps to prevent or reduce the amount of hook or slice dispersion when the ball is hit in a way which would normally produce hooking or slicing in a conventional, symmetrically designed golf ball. This reduction in dispersion is illustrated for the embodiments described above in
Although the illustrated embodiments all have reduced dimple volume in a band around the equator as compared to the dimple volume in the polar regions, other dimple patterns which generate preferred spin axis may be used in alternative embodiments to achieve similar results. For example, the low volume dimples do not have to be located in a continuous band around the ball's equator. The low volume dimples could be interspersed with larger volume dimples about the equator, the band could be wider in some parts of the circumference than others, part of the band could be dimpleless around part or all of the circumference, or there may be no dimples at all around the equatorial region. Another embodiment may comprise a dimple pattern having two or more regions of lower or zero dimple volume on the surface of the ball, with the regions being somewhat co-planar. This also creates a preferred spin axis. In one example, if the two areas of lower volume dimples are placed opposite one another on the ball, then a dumbbell-like weight distribution is created. This results in a ball with a preferred spin axis equal to the orientation of the ball when rotating end-over-end with the “dumbbell” areas.
Although the dimples in the embodiments illustrated in
The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles described herein can be applied to other embodiments without departing from the spirit or scope of the invention. Thus, it is to be understood that the description and drawings presented herein represent a presently preferred embodiment of the invention and are therefore representative of the subject matter which is broadly contemplated by the present invention. It is further understood that the scope of the present invention fully encompasses other embodiments that may become obvious to those skilled in the art and that the scope of the present invention is accordingly limited by nothing other than the appended claims.
This application claims the benefit under §119(e) of U.S. Provisional Application Ser. No. 61/328,927 filed Apr. 28, 2010 and entitled “Nonconforming Anti-Slice Ball,” which is incorporated herein by reference in its entirety as if set forth in full.
| Number | Date | Country | |
|---|---|---|---|
| 61328927 | Apr 2010 | US |
