Abstract:
A method of imparting a directional corrective horizontal spin component to a golf ball includes providing a plurality of golf clubs each having a golf club head with a ball striking face having grooves angled relative to a sole of the club. Each club has a select loft angle and a groove angle which varies as a function of the select loft angle. The method further includes selecting a club having a desired loft angle for striking a golf ball, aligning the club head with the sole perpendicular to a desired line between the ball and the target and striking the golf ball with the sole perpendicular to the desired line between the ball and the target.

Description:
FIELD OF THE INVENTION  
       [0001]    This application is a continuation-in-part of copending U.S. application Ser. No. 09/328,984 filed on Jun. 9, 1999. The present invention relates to the field of golf, and more particularly to golf clubs that impart corrective spin on a golf ball to impart desired flight characteristics. 
     
    
     
       BACKGROUND  
         [0002]    The sport of golf has a long history and is enjoyed by many participants throughout the United States and the world. The sport is well known and need not be described in detail except as is necessary to describe the present invention. Briefly, a player strikes a golf ball with a golf club. The golf club includes a shaft gripped by the player (“golfer”), to which is attached a golf club head which strikes the ball. The portion of the head that strikes the ball is called the “face,” which is a generally planar surface. The bottom perimeter of the golf club face (as defined when the club is used in its intended manner to strike the ball) is called the “sole.” It is noted here that the golf clubs relevant to the present invention are all “distance” clubs, as opposed to “putters,” which are used in a substantially different manner from distance clubs and which are not relevant to the present invention.  
           [0003]    A phenomenon all too familiar to most recreational golfers and even professional golfers is the “slice,” which is a description of the path of a golf ball that moves in an increasing curve away from a golfer in the direction the golfer is facing. While it is in some cases be desirable to slice the ball, a slice is much more commonly the result of flaws in the golfer&#39;s swing. Slicing the ball misdirects the ball from its intended trajectory, which can frustrate the golfer and prevent the golfer from obtaining a satisfactory score.  
           [0004]    A slice is caused by a horizontally glancing blow of the club, which imparts spin. Such a glancing blow is influenced by the club face angle and by the swing path at the moment of impact. To avoid a slice, the face angle and the swing path should be at right angles at the absolute point of impact, which imparts a back spin about a horizontal axis perpendicular to the desired line of travel. The ball therefore rotates in a clockwise manner in relation to the vertical axis of the golfer, from the golfer&#39;s perspective. However, because the club head carries the ball somewhat during and immediately after impact, there is a high likelihood of imparting a horizontal component to the spin, in essence tipping the desired horizontal axis clockwise from a perspective behind the ball facing the direction of travel so that a slicing spin results.  
           [0005]    A related phenomenon is the “hook,” which is a description of the path of a golf ball that moves in a curve away from the direction the golfer is facing. With a hook, axis of rotation is tipped counter-clockwise when viewed from behind the ball facing the direction of travel. Because of the swing path of a typical golfer, hooking is much less common than slicing. Like the slice, the hook is sometimes intended but it more often unintended, and can also prevent a golfer from achieving a good score. However, the difficulty of hooking the ball and its perceived aesthetics are such that sometimes a golfer will attempt to hook the ball, in a shot called a “draw.” The ability to make a draw show is often a source of accomplishment to the golfer.  
           [0006]    As discussed above, in addition to a horizontal spin component that would cause a slice or hook, a struck golf ball generally also has a backspin. The spinning ball rises because of the Magnus Effect (as described in more detail herein), thus affecting the trajectory. More backspin results in a higher trajectory. Additionally, backspin aids in the ability to stop the ball on the green without excess roll.  
           [0007]    A number of different golf clubs are used by a golfer depending upon the position of the ball on the course and its distance to the hole. Typical golf clubs are a set of “woods,” a set of “irons” in the range of 1-9, and several of wedges. The difference between the clubs (within a class of clubs) are the “loft” of the golf head, which is the angle between the club head face and the axis of the shaft, and the length of the shaft. The higher lofted clubs typically have shorter shafts; the combination of high loft and a short shaft results in greater backspin.  
           [0008]    A consequence of the longer shaft lengths of the lower lofted clubs is increased head speed. This is because such a club is swung in an arc of greater radius than a shorter club. The increased head spin increases the horizontal spin and exaggerates a slice (or a hook).  
           [0009]    Presently, all commercially available clubs known to the inventor have grooves in the club face that are parallel to the club face sole. Such grooves increase the friction between the club face and the ball and therefore increase the spin imparted to the ball. While such grooves are useful for increasing backspin, they do not assist in imparting a desired horizontal spin that could correct for a hook or slice.  
           [0010]    U.S. Pat. No. 5,785,610 of Birmingham (1998) describes a golf club having grooves in a what is a described as a “chevron” pattern. The chevron pattern grooves may serve to impart horizontal spin to the ball. However, the chevron pattern is not believed to be useful because it assumes that horizontal spin that is imparted on the ball is solely a function of the portion of the club face that the impacts the ball. It therefore has grooves of different angular slopes across the club face. It is believed that the chevron pattern is not effective in reducing slice, and further, even if grooves of different slope across the club face are used, the slopes should not be as shown in the Birmingham patent.  
           [0011]    Japanese patent publication no. JP9299518 A2 to Hideaki discloses a set of iron clubs having grooves on the club face which are inclined plus or minus 15° from a phantom horizontal reference line. The angle of the grooves decreases by 1° to 3° successively as the club number (or loft angle) increases. Hideaki teaches that the inclined grooves are used as an alignment device by a golfer to help compensate for errors in the golfer&#39;s swing. When a golfer addresses a ball, the parallel lines are aligned perpendicular to a line between the ball and an intended target area. The intent is that when a golfer makes an ordinary swing the club face will be properly aligned to drive a golf ball closer to the intended target area. Because the grooves of the Hideaki reference are intended for use as an alignment aid, there is no teaching or suggestion of stroking a ball with the grooves at an angle relative to a leading edge or sole of the club for imparting a corrective spin on a ball.  
           [0012]    Japanese patent publication JP2005980 A2 to Sheihei discloses a wood golf club head having inclined grooves forming an angle of about 90° with a golf club shaft. This provides grooves which are inclined between a lower heel portion and lower toe portion about 37 20  -35° from a leading edge of a club. The &#39;980 publication teaches that the purpose of these grooves is to minimize slicing and induce a high trajectory, draw type drive. The &#39;980 publication teaches only providing a single club with a select groove angle. Thus, the &#39;980 publication does not teach varying the groove angle to vary the amount of corrective spin applied to a ball as between clubs of different loft angles.  
           [0013]    An understanding of the principles behind the present invention requires an understanding of the “Magnus Effect.” This well understood effect is a particular manifestation of Bernoulli&#39;s theorem that fluid pressure decreases as fluid speed increases. This effect explains the “curve” of rotating balls such as baseballs and golf balls. Pressure differences develop in a fluid through which a spinning sphere moves. Greater pressure on the side where the airflow is slowed down forces the ball in the direction of the low-pressure region on the opposite side, where there is a relative increase in airflow.  
           [0014]    Finally, it should be noted that while the principles on which the present invention is based are believed to be well understood, the effectiveness of the present invention has been verified through experiment and therefore the scope the invention should not be limited by the validity of any scientific theory.  
         SUMMARY  
         [0015]    The present invention is directed to a method of imparting a corrective spin to a golf ball as well as a set of golf clubs for imparting a corrective spin. Each club includes a golf club head having a golf club face with a plurality of grooves. At least two of the clubs have grooves which are angled across the face at an angle that is substantially non-parallel with the club sole, the grooves being sloped in the same direction as one another. The purpose of the angled grooves is to impart a corrective spin on a struck golf ball that counteracts a horizontal spin component imparted by a glancing blow to a golf ball. The angle of the grooves is preferably varied depending upon the loft angle of the club. An advantage of the present invention is that slicing is eliminated or greatly reduced, and a golfer can much more easily draw the ball if desired. Alternatively, the grooves can be angled to eliminate or reduce an unwanted hook. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    FIGS.  1 A- 1 L are elevation views of the faces of a set of golf clubs according to an embodiment of the present invention.  
         [0017]    [0017]FIG. 2 is a schematic view illustrating the gear effect according to an embodiment of the present invention.  
         [0018]    [0018]FIG. 3 is a perspective view of a golfer illustrating different swing arcs for different club heads.  
         [0019]    [0019]FIG. 4 is an elevational view depicting decreasing shaft length as the loft angle of club heads increases.  
         [0020]    [0020]FIG. 5 is a view of a club head in accordance with the present invention from the perspective of a golfer preparing to strike a ball illustrating alignment of the club head before striking the ball.  
     
    
     DETAILED DESCRIPTION  
       [0021]    The present invention includes golf clubs having grooves that are angled across the club face with respect to the sole of the club. Currently used clubs have parallel grooves with respect the sole of the club, which is defined to be an angle of zero degrees herein.  
         [0022]    Representative groove angles for a first embodiment of golf clubs are shown in FIGS.  1 A- 1 L, with reference to Table I below.  
                                             TABLE I                       FIGURE   CLUB   LOFT ANGLE (°)   GROOVE ANGLE (°)                                1B   1 Iron   17   45       1C   2 Iron   20   45       1D   3 Iron   24   45       1E   4 Iron   28   45       1F   5 Iron   32   40       1G   6 Iron   36   35       1H   7 Iron   40   30       1I   8 Iron   44   25       1J   9 Iron   48   20       1K   P   52   10       Not Shown   A   54   10       Not Shown   S   56   10       1L   L   60   −20       1A   Woods   6-32   45                  
 
         [0023]    With reference to FIG. 1A, a club  10  having a face  12  with an intended impact area  14  is shown. The intended impact area  14  is the primary portion of the face  12  that would normally strike a golf ball, and may be relatively larger or smaller than shown. A plurality of grooves  16  traverse the impact area. In FIG. 1A, the grooves angle from an upper toe section  18  toward a lower heel section  20  at a 45 degree angle. In FIGS.  1 B- 1 L, a number of additional clubs are shown having grooves of different angles, as can be determined with reference to TABLE I. For the loft wedge of FIG. 1L, a negative slope (meaning the lines angle in the opposite direction) is shown.  
         [0024]    Table II below sets forth club number, loft angle and groove angle for a second embodiment of golf club irons. Likewise, Table III below sets forth the club number, loft angle and groove angle for a third embodiment of golf club irons. Table IV sets forth preferred groove angles for a driver for use by an amateur golfer and a highly skilled or professional golfer. Table V sets forth preferred ranges of groove loft angles for irons, drivers and fairway woods.  
                       TABLE II                       CLUB   LOFT ANGLE (°)   GROOVE ANGLE (°)                   2   15   25       3   18   25       4   21   25       5   24   25       6   27   25       7   32   25       8   34   20       9   38   15       PW   42   10                  
 
         [0025]    [0025]                                     TABLE III                       CLUB   LOFT ANGLE (°)   GROOVE ANGLE (°)                                1   18   33       2   20   32       3   23   31       4   26   30       5   30   29       6   34   28       7   38   25       8   42   20       9   46   15       PW   50   10       AW   52   5       SW   56   −10       LW   60   −20                    
         [0026]    [0026]                                     TABLE IV                       CLUB   LOFT ANGLE (°)   GROOVE ANGLE (°)                                Driver (Amateur)   10.5   28       Driver (Professional)   9.5   18                    
         [0027]    [0027]                               TABLE V                                   CLUB   LOFT ANGLE (°)   GROOVE ANGLE (°)                           Irons:   40-55   10-20               30-40   10-30               15-30   25-45           Drivers:    5-20   10-30           Fairway Woods:   &gt;15   20-45                        
         [0028]    The angular groove design imparts a corrective horizontal spin component to the ball, while still providing for the availability of backspin. With reference to the schematic diagram of FIG. 2, the angled grooves induce a gear effect as the club impacts the ball. The ball is depressed into the grooves creating a meshing of the grooves with the contacting portion of the ball. As the club carries the ball forward, this gear effect causes an angular spin which counteracts the golfer&#39;s slice. Whereas a glancing blow of a slice tips the ideal horizontal axis of a backspin clockwise from a perspective behind the ball facing the target, the angled grooves and resulting gear effect essentially tips the axis counter-clockwise from this same perspective, thereby counteracting the effect of the slice and even possibly imparting a draw. The higher degree of groove angle with the lower irons and woods is generally desirable because the club head speed is faster and greater corrective spin must be induced (the difference is swing path between clubs is shown in FIG. 3). The mid irons (#4-6) require a less steep groove angle because the swing place is steeper and the club head speed is less. The approach irons and wedges are the shortest length clubs and have the steepest swing plane of the clubs. Therefore, the groove angle may be the least, thus providing relatively more backspin and less corrective horizontal spin.  
         [0029]    The angled grooves  16  run across the impact area  14  of the of the club face from an alignment line  21  which is generally parallel to the sole or leading edge  22  to the top edge  24  of the face  12 . Alternatively, the angled grooves may extend from the sole or leading edge  22  itself to the top edge  24 . As an alternative to the reference line  21 , alignment dashes  26  or other indicia defining a horizontal line corresponding to the alignment line may be used (see FIG. 5). The angled grooves  16  are parallel with one another. It can be appreciated that the grooves can traverse the entirety of the club face  10 , or a smaller portion of the club face that corresponds to the impact area. They are preferably inclined relative to the alignment indicia.  
         [0030]    In one embodiment of the invention, the grooves are structured to conform to the United States Golf Association rules, the contents of which are incorporated by reference. Briefly summarizing the rules as they currently stand, any rounding of the groove edges shall be in the form of a radius which does not exceed 0.020 inches (0.5 mm); the groove width shall not exceed 0.035 inches (0.9 mm) using the thirty degree measurement method; the distance between edges of adjacent grooves must not be less than three times the width of a groove, and not less than 0.075 inches (1.9 mm); and the depth of the grooves must not exceed 0.020 inches (0.5 mm). It will be readily understood that these rules may be changed over time, and thus the structure of a club according to this embodiment could be correspondingly changed. While the above parameters describe the maximum size and density of grooves, a club according this embodiment could have smaller and/or less dense grooves. The grooves may have any allowable shape, such as what are known as “U” shaped grooves or “V” shaped grooves. Of course, the standards of any other golfing organization besides the USGA could also be adopted, so long as such rules do not prohibit grooves that are angled with respect to the sole of the club.  
         [0031]    In another embodiment of the invention, the grooves may be structured so that they do not conform to the United States Golf Association rules. In such an embodiment, the grooves could have any shape, size, and density.  
         [0032]    It should be appreciated that groove angles listed in the above tables are merely illustrative embodiments of the invention and are not intended to limit the scope of the invention, except as to the specified embodiments. The precise angles are not necessarily critical and deviations should also produce acceptable results. Thus, it is contemplated that a club of a given loft might be manufactured in a number of different versions of differing groove angles, because the amount of corrective spin that is desirably imparted on the ball depends to some extent upon the swing of an individual golfer. However, it is believed that a groove angle of at least 15° is necessary to apply a corrective spin to balls struck with an iron ranging from a two iron (18°-20° loft) to a nine iron (42°-48° loft). The present invention also contemplates that a testing device could be provided to measure the amount of unwanted side spin (slice or draw) imparted by a golfer, and then corrective groove angles in the ranges set forth in Table V could be provided on a customized basis to provide a required amount of corrective spin. This could be accomplished by determining groove angles necessary to impart a given corrective spin as a function of unwanted spin and factors such as club head speed or by trial and error in varying groove angles. The deviations from the parameters listed in the tables may be minor, such as several degrees, or major. In an example of a major change, the groove angles may be sloped in the opposite direction (at any angle) from that shown in FIG. 1A-K, as illustrated in FIG. 1L, which would be useful for golfers who have an unusual tendency to hook the ball. It will also be apparent that the depicted clubs are “right-handed,” and that the invention has equal applicability to “left-handed” clubs.  
         [0033]    The use of the clubs to impart a corrective spin is illustrated in part by reference to FIG. 5. FIG. 5 is a view of a club head from the perspective of a standing golfer addressing a ball (not shown). The club head  10  is oriented with the alignment dashes  26  (and the leading edge or sole of the club head) defining a straight line illustrated by phantom line  28  perpendicular to an intended line of travel  30  of the golf ball. Therefore, in use the golfer would view an intended target area along the intended line of travel  30  and orient the club with the alignment dashes perpendicular to this intended line of travel. In this manner, the grooves  24  are at an angle relative to the ball so as to impart the corrective spin as discussed above when a golf ball is struck.  
         [0034]    It will also be appreciated that a club could be constructed according to the present invention but could have a different appearance from these shown in FIGS.  1 A- 1 L. For example, the grooves  16  could be replaced with grooves that are not continuous. Grooves could be used that would have some degree of curvature (i.e., are not straight line segments). Or, a plurality of grooves could be used that are not identical to one another in some respects. None of these variations (or other variations that may be apparent to those skilled in the art) should necessarily be deemed to place such a club outside of the scope of the present invention. The above described invention provides means of a club face to achieve a corrective horizontal spin component to a golf ball, and other equivalent means may fall within the inventive scope.