Patent Application
20070259734
This invention generally relates to golf clubs and specifically to clubs for putting a golf ball into a hole.
Putting is a major component of scoring in the game of golf, often comprising about 40% of the strokes used. Putting is a precise activity with a very low error required for holing most putts. The degree of achieving high accuracy will vary with the skill level of the player. Many players have repeated difficulty aiming the putter in the intended direction and/or in stroking the putter on the intended aimline, resulting in misalignment and missed putts.
When the putter face is misaligned with the stroke path, the strike force is not normal to the ball and does not pass through its center. This condition could be due either to twisting of the putter face or from misalignment of the stroke path with the aimline. This misaligned condition results in the ball traveling off the aimline. The actual path of ball travel is determined by the type and amount of misalignment, the friction and energy transfer characteristics of the striking face, and by the forces delivered by the striking face. These stroking errors are subject to compensation in the putter configuration to reduce the misalignment and the effects of misalignment, and thereby improve putting accuracy.
Stroking errors with a putter can generally be classified in three areas: aligning the putter at an error angle to the aimline when setting up; stroking at an error angle to the aimline during the backstroke and/or forward stroke of the putter; and twisting of the putter face prior to striking the ball. Any of the three errors can be experienced only on short putts, only on long putts or on all putts. These errors may be due to problems with a player's grip on the club, with the player's posture, or with the method of stroking the putter. Eyesight and perception can also be causes for errors. Sometimes stroking errors are developed in experienced players and, although recognized, cannot be corrected. These are sometimes referred to as the yips. As putting errors are mainly the result of physical reaction, muscle habits, or directional misperception, they are sometimes repeatable and therefore subject to compensation. Which errors are prevalent, and when, can be tested by an expert.
The putter disclosed herein has an aiming mark that compensates for a player's misalignment of the putter with the aimline. Further, this putter has a face with friction and energy transfer characteristics that corrects for errors in club face orientation or for directional errors in stroking the putter. Also, the putter can be configured with a weight distribution that causes the compensations to vary with stroking force.
Misalignment of the putter with the aimline during setup is the result of the player's perception of direction being inaccurate. This is due to having insufficient perspective of the aimline as the player's eyes are either in front of the ball or insufficiently behind the ball. As disclosed in U.S. Pat. No. 6,988,959, moving the putter grip location (and therefore the player's eyes) substantially behind the putter face is helpful in gaining perspective, but is not sufficient for all players. Putter misalignment at set-up may be consistent with each putt. Consistent misalignment of the putter with the aimline may be compensated for with an aiming mark on the putter that is oblique with the face by a similar angular amount.
Stroking off the aimline results in misalignment of the stroking force with the aimline and misdirection of the ball when struck. Stroking off the aimline is also a directional perception problem and can be player muscle related as well as sight related. This stroking error can be the result of taking a misaligned stance or of a habitual stroking pattern that feels correct but is not. In either case, the putter stroke path is off the intended aimline resulting in putts that are off the intended aimline. The amount that putts deviate from the intended aimline is a function of the friction and energy transfer characteristics of the putter face. This is explained in U.S. Pat. No. 6,988,959. Low friction, high energy transfer face construction tends to influence the ball direction toward a normal to the putter face when struck. This compensates and reduces the effect of stroking off the aimline, improving the directional accuracy of the putt.
There are players that twist the putter involuntarily prior to striking the ball, causing the ball direction to be off the intended aimline. This condition is muscle control related and frequently happens only on short putts. However, it can occur on long putts and the degree can be variable. The amount that putts deviate from the intended line is a function of the friction and energy transfer characteristics of the putter face. This is explained in U.S. Pat. No. 6,988,959. High friction, low energy transfer face construction tends to influence the ball direction toward the stroke path when struck. This compensates for and reduces the effect of twisting the putter, improving the directional accuracy of the putt.
For a particular player, long putts may have a different degree of error than short putts, requiring a different degree of compensation. This may be accommodated with a putter head weight distribution that changes the effect on ball direction with the stroke force. By offsetting the center of gravity of the putter head transversely so that it is not in line with the ball strike point, the putter will tend to twist when the ball is struck. The ball strike force and the inertia force create a twisting couple that is proportional to the strike force. This twisting couple may be combined with the face friction/energy transfer compensation or with an oblique aiming mark, in either a clockwise or counterclockwise manner. The total effect is to have compensation for off-line stroking or for putter twist that varies with strike force.
It is therefore an objective to provide an improved putter that compensates for stroking errors by the player using the putter. A further objective of this putter is for it to be easily used by people of various skill levels and enhance their ability to reduce the number of putts required to hole a golf ball. It is also an objective of this putter to conform to “The Rules of Golf” as published by the United States Golf Association. These and other objectives will be apparent to those skilled in the art.
With reference to
The weight of head 1 varies with the player preference and the type of putter, and may be about 325 g. for conventional free held putters. There may be higher weight values, especially for stomach supported and pendulum-style putters. Head 1 includes a body 44 with the possibility of adding a separate face structure such as a layer 21, and/or a selectable weight 40 or 41. Body 44 may be cast and/or machined. Body 44 is preferably one-piece and may be made from a number of materials including lightweight alloys of titanium or aluminum or of other materials including zinc alloy, stainless steel or a hard polymer. The material selection depends on the size and weight of head 1, and potentially the friction and energy transfer characteristics of face 5. Face 5 may have a surface treatment to change its frictional or energy transfer characteristics. Various other constructions of head 1 are possible including structures with an intermittent surface on top or the bottom, or where body 44 is more than one piece construction.
Weight 23 is sized to locate a center of gravity 8 at a longitudinal location X behind face 5. As location X is also used to establish the pivot point of the stroke, center of gravity 8 is located far enough behind strike face 5 to allow a player's eyes to be behind the ball when taking a stance. For this configuration of head 1, location X is about 68% of head length A. Center of gravity 8 may be offset transversely by adjusting weights 40 and 41.
A hosel 9 is located near to, but offset from, the transverse center of head 1, enough to keep an aiming mark 7 continuous, and contains a bore for a shaft 2. Hosel 9 may be located longitudinally wherever it is convenient, provided dimensional conditions relating to center of gravity 8 are met. Hosel 9 would be on the opposite side of aiming mark 7 for a left-handed player. Face 5 has a loft angle P that is shown positive but which may be zero or negative. Loft angle P would not exceed 10° in conformance with USGA rules. The selection of loft angle P is influenced by the friction and energy transfer characteristics of face 5, and by the stroking arc of face 5.
Aiming mark 7 is located near the transverse center of head 1, substantially in the intended direction of stroking, and may be perpendicular to or at an oblique angle to face 5. Aiming mark 7 is recessed in or flush to a top surface 30 of head 1. In use, aiming mark 7 would normally be aligned with an imaginary aimline 32 of the putt. Aimline 32 is the intended direction of the ball immediately after being struck by the putter. Aiming mark 7 is generally rectangular in shape, and is of sufficient proportions to facilitate a clear image. Aiming mark 7 is not too large to prevent easy focusing and establishment of direction, and is a simple pattern to provide clear information. Except for potential small construction related gaps at the ends, aiming mark 7 establishes head length A, and is preferably between 3.0 in. and 6.0 in. long. A width Z of aiming mark 7 is at least 0.12 in. Aiming mark 7 has a length to width ratio A/Z at least 18:1, and a minimum area A×Z of 0.50 in2. Aiming mark 7 is a bright color that reflects a high percentage of incident light. This would include colors such as safety yellow, iridescent yellow, or white, and preferably with a glossy finish. The balance of the visible top surface 30 of head 1 is a dark, dull color that absorbs a high percentage of incident light. This would include colors such as black, dark gray, or dark green and preferably with a flat or satin finish. Aiming mark 7 has generally parallel sides but may be tapered. Aiming mark 7 is preferably continuous. A regular pattern of small dots or stripes, with minimal open space, would be considered continuous.
In
A face 5 height C is about 1.0 in. Intended strike point 17 is located about halfway up face height C and is vertically below aiming mark 7. Center of gravity 8 is normally positioned in line with shaft longitudinal plane 3, causing both head 1 momentum force and the player's applied strike force to be aligned with each other. The ball resisting force at strike point 17 may not be aligned with center of gravity 8 for some configurations of head 1 in order to create a compensating twisting force. A strike area 19 surrounds strike point 17 and is about 1.0 in. wide and about 0.5 in. high. Strike area 19 encloses the pattern of strike points of a golf ball.
There are several alternate constructions for face 5 shown in
In
Faces 21, 24, 50/51 and 52/53, or similar functioning faces can be achieved on configurations similar to head 1, or on other head configurations. The particular construction is not important. The surface of these faces may be smooth or be textured. Features from some of the faces may be incorporated into other of the faces. The friction and energy transfer characteristics are the requirements to be achieved, together with any other characteristics that are desired.
A swing pivot point 18 is located in a vertical transverse plane 20 that also passes through center of gravity 8. Regardless of where shaft 2 is attached to head 1, this locates pivot point 18 the same distance as c.g. 8 location X behind strike point 17. Transverse plane 20 also passes through the midpoint of grip 11 at the hand position of a player. This ensures that no side force is required to hold putter 28 for use. While transverse plane 20 would normally bisect shaft 2, this is not a necessary condition as the shaft configuration could be unusual. Having center of gravity 8 under the mid-point of grip 11 and in line with shaft plane 3 ensures that there is no dynamic twisting moment on face 5 whether stroking backward or forward.
A height T locates swing pivot point 18 above strike point 17. Height T can be approximated by club 28 length plus dimension H for purposes of determining a lift angle N. Lift angle N is used, along with the frictional and energy transfer characteristics of face 5, to influence face loft angle P. For putter 28 with a c.g. location X of 2.8 in. and height T of 50 in., lift angle N would be 3.2°.
The force actually transmitted to the ball is affected by losses, primarily impact losses in the kinetic energy portion of the putter strike force. Impact losses are determined with a coefficient of restitution r. Coefficient of restitution r is defined as the velocity after impact divided by the velocity before impact with one body stationary. As kinetic energy force varies with the square of velocity, it would vary with coefficient of restitution squared (r)2. Coefficient of restitution r would typically be in the range of 0.71 to 0.85 for a commercially available putter face. The maximum value is established by the available materials and is about 0.85. The minimum value is influenced by the USGA minimum hardness value of 85 Shore A.
Static coefficient of friction f is defined as the tangential force divided by the normal force under conditions of impending motion. A dynamic coefficient of friction would be less than static coefficient f, and would be subject to variations that depend on the conditions. Static coefficient f varies between about 0.23 and 0.32 for commercially available putter faces and it depends on the material. The minimum value for coefficient f is about 0.12 and could be more than 0.40 if desired.
In
In
A drag angle K measurers the difference between normal line 34 and ball motion line 33. As disclosed in U.S. Pat. No. 6,988,959, line 33 direction would be near to normal 34 for low friction, high energy transfer surfaces, and drag angle K would be low. For low force putts, drag angle K could be negative. For high friction, low energy transfer surfaces, ball motion line 33 would near to stroke path 31 and drag angle K would be high. Drag angle K is proportional to error angle L and coefficient of friction f. Also, drag angle K varies inversely with coefficient of restitution r. The resulting translation motion of ball 14 can be determined by measuring angles L and K with a range of values for coefficients f and r, and at different stroke force levels.
In
Stroking errors may also be compensated for by changing other structural characteristics of putter 28.
In some cases, the player has a stroking error in addition to a setup aiming error. In
Some players rotate the putter head by twisting the shaft prior to striking the ball. A counterclockwise twist 54 is indicated on hosel 9. If the ball were struck with the face rotated, there would be a tendency for the ball direction to follow the rotation and move to the left. This can be compensated for by making layer 51 from a high friction, low energy transfer material. This face construction has a tendency to promote ball motion in the direction of the stroke path. A further compensation is to transversely offset center of gravity 8A to the left of aiming mark 7 and strike point 17 by a distance Y. When the ball is struck with offset c.g. 8A, a clockwise twisting moment 55 is created at face 5 that compensates for the player induced twist 54. The compensating effect of the offset center of gravity 8A is proportional to strike force and therefore to putt distance. The direction of c.g. offset is opposite to the direction of corrected ball motion. Offset Y may be adjusted with selectable weights 40 and 41 to change the amount of corrective countertwist. Oblique angle E may also be adjusted to compensate for a twist of putter face 5. As shown in
When a player is ready to stroke putter 28, the intent is for stroke path 31 and aiming mark 7 to be in alignment with aimline 32, and to remain in alignment as the putter is stroked and ball 14 is struck. Head 1 speed should be the correct amount. Accomplishing this requires precise control of the muscles supporting and stroking putter 28 and that some players have difficulty accomplishing. The putter disclosed herein may be configured to compensate for stroking errors as summarized in Table 1. Table 1 shows the configurations available to compensate for the player's errors listed in the left column. The middle column of compensating configurations for short putts are used when the error only occurs on short putts. The right column may be used for putts of all distances, as the offset c.g compensation is variable with force level. Use of these configurations requires testing and evaluation of a player's stroke, and combining the configurations in appropriate proportions.
When using putter 28, ball 14 deviation from aimline 32 resulting from stroking errors is reduced by selecting the correct combination of compensation configurations. When the configurations are matched to the particular swing errors of the player, the percentage of golf balls holed is increased. While the player's error and compensation configurations shown in Table 1 are specifically outlined, other combinations of errors and compensations are possible. Testing and evaluation of a player's putts may suggest combinations and proportions that produce improved results.
It is therefore seen that this invention will achieve at least all of its stated objectives. Although the description contains specific configurations, these should not be construed as limiting the scope of the invention but merely providing illustrations of some of the present embodiments. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.
