1. Field of the Invention
This invention relates generally to the field of golf balls and, more particularly, to golf ball with a weight distribution designed for straighter flight performance.
2. Related Art
The flight path of a golf ball is determined by many factors. Several of the factors can be controlled to some extent by the golfer, such as the ball's velocity, launch angle, spin rate, and spin axis. Other factors are controlled by the design of the ball, including the ball's weight, size, materials of construction, and aerodynamic properties.
A golf ball can be represented in three dimensional space with three orthogonal axes intersecting in the center of the ball. Often these are called the x, y and z axes. It is common to represent the golf ball with two of the axes co-planar with the ball's equatorial plane and the third axis (z axis) perpendicular to the equatorial plane and running through the poles of the ball.
When a golf ball is rotating in space, it is said to be “rotating about its spin axis”. When a golf ball is struck with a club it generally makes the ball rotate with a backward spin. Whether the resulting spin axis coincides to one of the three principle axes of the ball depends on how the ball was oriented before club impact and the type of club impact that occurred (straight, hook or slice club action).
According to one embodiment, a golf ball is designed with an asymmetrical weight distribution causes the ball to exhibit what may be defined as a moment of inertia (MOI) differential between two or three of the orthogonal spin axes or x, y and z axes, where the x and y axes are co-planar with the equatorial plane of the ball and the z axis extends through the poles. In a ball with a differential MOI, the spin axis with the highest MOI is the preferred spin axis and most importantly a golf ball with a MOI differential and preferred spin axis resists tilting of the ball's spin axis when it is hit with a slice or hook type golf club swing. The ball's resistance to tilting of the spin axis means the ball resists hooking and slicing (left or right dispersion from the intended direction of flight). The mechanism for this hook and slice resistance appears to occur on the clubface during club-ball impact. When the preferred spin axis also corresponds to a low aerodynamic lift ball configuration (the ball's lift generated by the dimple pattern can be different in different orientations, even when velocity and spin are identical), the ball has less tendency to slice and hook after the ball leaves the clubface with the preferred spin axis tilted right or left of horizontal orientation (horizontal orientation is defined as parallel to the ground and perpendicular to the intended direction of flight). The lift force is what generates the ball height on a straight shot and it is also responsible for the right and left directional movement (dispersion) of the ball when it is hit with a slice or hook club action.
In one embodiment, a golf ball has a cover and a core. The core may be a single piece or can be made up of two or more parts, for example an inner core covered by an outer core. The cover may also be a single piece or be made up of two or more parts. A layer between the inner core and cover may be defined as a mantle layer, and in some cases may be an outer core layer and in other cases it may be an inner cover layer, depending on materials and construction. In one embodiment, one or more parts of the ball have non-spherical aspects, and the different parts may also have different specific gravities. The different shaped ball parts combined with the different specific gravities of the materials for different ball parts produces the MOI differential between spin axes. The golf ball is spherical, but the inner layers are not necessarily completely spherical or symmetrical layers or parts.
The ball may also have an asymmetrical dimple pattern on the outer surface designed to augment the slice and hook correcting differential MOI properties.
The details of the present invention, both as to its 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:
Certain embodiments as disclosed herein provide for a golf ball which has non-spherical aspects in various combinations of the core and cover parts, so as to provide a moment of inertia (MOI) differential between the spin axes of the ball. In some embodiments, different parts may also have different specific gravities.
After reading this description it will become apparent to one skilled in the art how to implement the invention in various alternative embodiments and alternative applications. However, although various embodiments of the present invention will be described herein, it is understood that these embodiments are presented by way of example only, and not limitation.
It is common to represent the golf ball with two of the axes (x-axis and y-axis) co-planar with the ball's equatorial plane and the third axis (z-axis) perpendicular to the equatorial plane and running through the poles of the ball. In the following description, these three axes are called the principle axes or the orthogonal spin axes.
In other embodiments, the ball may have non-spherical aspects of various combinations of the core and cover parts which have different specific gravities. The different shaped ball parts combined with the different specific gravities of the materials for different ball parts is what causes the MOI differential between spin axes. The golf ball is spherical, but the inner layers are not necessarily completely spherical or symmetrical layers or parts.
In the embodiments illustrated in
In the embodiments of
In each embodiment, at least two components of the ball have different specific gravities. One is denser than the other. The cover can be more or less dense than the core. The mantle layer can be more of less dense than the cover, the mantle layer can be more or less dense than the core, two mantle layers can differ in density, two cover layers can differ in density, etc. In any case, the ball will have a MOI differential depending upon the shape of the core, cover and mantle layers and the density differences among them. A spherical inner core or uniform thickness cover or uniform thickness mantle layer can be higher or lower specific gravity compared to any of the other mantle, cover or core layers.
As illustrated in
This embodiment and all other ball construction embodiments described below in connection with
In the case of the Polara Ultimate Straight dimple pattern combined with design “A1”, if the flat spot on the core was centered with the pole of the dimple pattern (the deep dimpled region), and the density of the materials for the core and cover mantle layer we chosen so that core was higher specific gravity than the cover, then the MOI differentials caused by the ball construction and dimple pattern would reinforce each other and create a larger MOI differential than when just the Polara dimple pattern was used on a symmetrical ball construction or when a symmetrical dimple pattern was combined with the ball construction of
Another example similar to the ball 10 of
In the above embodiments, the mantle density or specific gravity may be greater than the cover layer density, but that does not have to be the case in all embodiments. The cover density may also be higher than the mantle density in the above embodiments, and this structure still results in a MOI differential. As long as there is a difference in the core and mantle densities in any of designs A1 to E1 of
One consideration when having more than one band or recess in a core, mantle or cover is that the shape would be easier to injection mold and then remove from the mold if there were no undercut portions of the shape such that when the part was removed from the mold that it was caught on a protruding part of the mold that was closer to the parting line of the mold. The dimensions for some specific examples of Designs “A1” through “E1” are provided below. There could be many other examples, with an almost infinite combination of dimensions and the examples discussed above are just a few simple designs selected for illustration of the invention and some of its various aspects.
Table 1 below shows the dimensions of a 1.68″ outer diameter golf ball of embodiments A1 through E1 (labeled A1, B1 . . . E1, respectively. In Table 1 the outer core is referred to as the “mantle”. The numbers in Table 1 are expressed in “inches”. For these particular examples, the width of the raised band for the mantle in ball designs D1 and E1 is 0.50 inches and the width of the flat area for the mantle on ball design B1 is 0.50 inches.
Tables 2 and 3 below provide the differential MOI data between the x, y and z spin axes for a combination of different specific gravity materials used with designs A1-E1. Any combination of specific gravities of materials could be used and this would in turn change the resulting MOI differential for the ball. It may be higher or lower than what is shown below.
Tables 2 and 3 above provide the MOI Differential for Designs A1-E1. The MOI for rotation about the x and y axes are the same, but the MOI for rotation about the z axis is different. The actual MOI differential for the entire ball design is given in the far right column of the last row for each ball design. The far right column is labeled “Ix vs Iz”. This is the MOI Differential defined as the MOI percent difference between the ball rotating around the X-axis versus rotating around the Z-axis. Whether the value is positive or negative does not matter, this is just a matter of which axis MOI value was subtracted from the other. What matters is the absolute value of the “Ix vs Iz” value. For example, E-1 design has almost 10× the Moment of Inertia Differential (MOI differential) as A-1 design. The formula for calculating the MOI differential is as follows:
Moment of Inertia Differential=(MOI X-axis−MOI Z-axis)/((MOI X-axis+MOI Z-Axis)/2).
In the embodiments of
In all of the embodiments of
The density, mass, volume and MOI values for a ball made with the wide X-band mantle or outer core layer 170 of
In the embodiments of
In the above embodiments, at least one inner layer or part of the ball is non-spherical and is asymmetrical in such a way that the MOI measured in three orthogonal axes is different for at least one of the axes. The non-spherical part in many of the above embodiments is described as an outer core layer or mantle, but could also be an inner cover layer of a two part cover. The design is such that at least one layer of the cover or core is non-uniform in thickness and non-uniform in radius. In one embodiment, the diameter of the entire core (including the inner core and any outer core layer) may be greater than 1.61 inches. At least one core or cover layer has a higher specific gravity than other layers. In one embodiment, the difference in the MOI of any two axes is less than about 3 gm cm2.
As noted above, various types of symmetric or asymmetric dimple patterns may be provided on the outer cover of the golf balls described above. Golf balls with asymmetric dimple patterns are described in described in co-pending patent application Ser. No. 13/097,013 of the same Applicant filed on Aug. 28, 2011, the entire contents of which are incorporated herein by reference. Any of the dimple patterns described in that application may be combined with any of the golf balls described above with different MOI on at least two of the three perpendicular spin axes or principal axes. Two examples of dimple patterns described in application Ser. No. 13/097,013 are illustrated in
Alternatively, the differential may result only from the asymmetry of the dimple pattern, as described application Ser. No. 13/097,013 referenced above. The MOI variations in several such balls are provided in Table 4 below.
With the original Polara™ golf ball dimple pattern (deep spherical dimples around the equator and shallow truncated dimples on the poles) as a standard, the MOI differences between each orientation of balls with different asymmetric dimple patterns are compared to the original Polara golf ball in addition to being compared to each other. In Table 4, the largest difference between any two orientations is called the “MOI Delta”. In this case the MOI Delta and the previously defined MOI Differentials are different quantities because they are calculated differently. However, they both define a difference in MOI between one rotational axis and the other. And it is this difference, no matter how it is defined, which is important to understand in order to make balls which will perform straighter when hit with a slice or hook type golf swing.
In Table 4, 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 original Polara ball. Because the density value used to calculate the mass and MOI (using the solid works CAD program) was lower than the average density of a golf ball, the predicted weight and MOI for each ball are 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 4. Generally a golf ball weighs about 45.5-45.9 g. Comparing the MOI values of all of the balls in Table 4 is quite instructive, in that it predicts the relative order of MOI difference between the different designs.
Design 25-1 of
Table 5 shows that a ball's MOI Delta does strongly influence the balls dispersion control. In general as the relative MOI Delta of each ball increases, for a slice shot the dispersion distance decreases. 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 is shown in Table 5 below.
Golf balls of the embodiments with asymmetrical dimple patterns described above exhibit lower aerodynamic lift properties in one orientation than in another. If these dimple patterns are provided on balls with core and cover layers constructed as described above in connection with the embodiments of
Any combination of symmetrical or asymmetrical dimple patterns, such as the dimple patterns of
The dimple co-ordinates for one embodiment of dimple pattern 95-3 of
The balls of
Any of the balls of
Tables 8, 9 and 10 contain the density, volume and mass information for each of the individual layers and the complete balls for all of the ball designs of
Tables 11, 12 and 13 contain the moment of inertia values for each of the principle axes of rotation for all of the individual layers of each ball design in
Tables 14, 15 and 16 contain the ball mass, ball volume, ball moment of inertia values for each of the principle axes of rotation and the MOI Differential for each of the complete ball designs of
If a ball is designed with an internal construction providing a preferred spin axis due to differential MOI between the spin axes, the dimple pattern can be designed to have the lowest lift or lift coefficient (CL) and drag or drag coefficient (CD) when the ball is spinning about the preferred spin axis, i.e. the spin axis corresponding to the highest MOI. This decouples the dimple pattern from the mechanism for creating a preferred spin axis. The differential MOI may be achieved by different specific gravity layers in the ball or by different non-spherical geometry in at least one layer, or both, as described in the above embodiments.
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.
The present application claims the benefit of co-pending U.S. Provisional Pat. App. Ser. No. 61/453,230 filed on Mar. 16, 2011, the contents of which are incorporated herein by reference.
Number | Date | Country | |
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61453230 | Mar 2011 | US |