Patent Abstract:
The present invention is an improved putter that combines several features to provide a balanced putter, which assists a player in perfecting a putt stroke during practice and repeating it with the same club during play. The shaft is attached to the clubhead such that it can swivel from a practice configuration to a play configuration. The clubhead has tapered top and bottom surfaces such that the angle of the shaft relative to the sole of the putter is no more than 80 degrees. The clubhead has a playing surface on one face that is parabolic and can be flat in the extreme. The clubhead has a practice surface on the other face that is curved, preferably elliptical, to assist the golfer in learning the proper stroke. The putter conforms to the Rules of Golf so that the player does not have to change clubs between practice and play. The club may be used for either a right- or left-handed stroke.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation-in-part of application Ser. No. 10/351,495 filed Jan. 23, 2003 now U.S. Pat. No. 6,776,727 and claims the benefit thereof. 

   FIELD OF INVENTION 
   This invention relates to putters that can be used for practice and play, with either a right or left-handed stroke. Specifically, this invention is a putter rotatable from a first position to strike a golf ball with a practice face of a clubhead to a second position to strike a golf ball with a play face of the clubhead. 
   BACKGROUND 
   Golf is governed by The Rules of Golf as approved by the United States Golf Association and the Royal and Ancient Golf Club of St. Andrews, Scotland, referred to herein as the USGA Rules. The most current rules are available from www.USGA.org. A typical game of golf is played on a course having 18 holes and a golfer may carry up to 14 clubs with him during play. An average golfer uses over 80 strokes to complete the game, and typically half of those stokes are putts. Therefore, the putter is by far the most important of the regulation 14 golf clubs in a golfer&#39;s bag, and improved putting will improve a player&#39;s score more than improvement in any other stroke. 
   Consequently, thousands of devices and methods have been devised to help a golfer improve his putting, ranging from the practical to the absurd. Most of these devices do not conform to the design of clubs specified by the USGA Rules, however, and therefore are used during practice only. The golfer must switch putters to play a round of golf, thus changing the primary tool with which he perfected his stroke. As a result, the putt stokes during play are seldom as good as during practice. It would be advantageous, then, to provide a dual-purpose putter that conforms to the Rules of Golf so that the golfer can use the same putter in practice as in play. 
   Under the USGA Rules, the putter shall have a shaft and a head, fixed to form one unit. When the golf club is in its normal position to address the ball, the shaft shall be aligned so that the projection of the straight part of the shaft onto the vertical plane through the toe and heel shall diverge from the vertical by at least 10 degrees. Further, the projection of the straight part of the shaft onto the vertical plane along the intended line of play shall not diverge from the vertical by more than 20 degrees. The USGA Rules further require that the clubhead meet specific criteria. For example, the distance from the heel to the toe of a putter shall be greater than the distance from the play face to the back. These rules limit the orientation of the shaft to the clubhead, and therefore the balance of the putter, a major factor in aligning the ball and in putting consistently. 
   The penalty for playing a game of golf with a putter that does not conform to the USGA Rules is disqualification from the game. However, with the many rules pertaining to the design of putters, it is difficult to design a club that provides quality training features for practicing and yet can be used for play. It is desirable to provide a single putter that can be converted from a practice putter to a play putter that conforms to USGA Rules. 
   Therefore, it is an object of this invention to provide a putter that enables the golfer to determine which strokes are the best during practice so that he may practice those strokes repeatedly and learn to stroke the ball consistently in play. It is another object of this invention to provide a single putter that can be used for both practice and play. It is another object to provide a single putter that can be converted from a practice putter to a play putter that conforms to the USGA Rules. It is an object of this invention to provide a putter in which the shaft always diverges at least 10 degrees from the sole of the clubhead, regardless which orientation the golfer holds the putter when addressing the ball. 
   SUMMARY OF THE INVENTION 
   The present invention is an improved putter that combines several features to provide a balanced putter, which assists a player in perfecting a putt stroke during practice and repeating it with the same club during play. The shaft is attached to the clubhead such that it can swivel from a practice configuration to a play configuration. The clubhead has tapered top and bottom surfaces such that the angle of the shaft relative to the sole of the putter is no more than 80 degrees. The clubhead has a playing surface on one face that is parabolic and can be flat in the extreme. The clubhead has a practice surface on the other face that is curved, preferably elliptical, to assist the golfer in learning the proper stroke. The putter conforms to the Rules of Golf so that the player does not have to change clubs between practice and play. The club may be used for either a right- or left-handed stroke. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1(   a ) is a perspective view of the practice face of the clubhead with the shaft in position for a right-handed golfer. 
       FIG. 1(   b ) is a perspective view of the play face of the clubhead, with the shaft in position for a right-handed golfer. 
       FIG. 2(   a ) is a top view of the clubhead. 
       FIG. 2(   b ) is a bottom view of the clubhead. 
       FIG. 2(   c ) is a cross-section view of the clubhead  11  along line c—c of  FIG. 2(   a ). 
       FIG. 2(   d ) is an end view of the clubhead; each end is symmetric to the other. 
       FIG. 3  is an exploded, perspective view of the clubhead with a curved practice face and a flat play face. 
       FIG. 4  illustrates an exploded view of the clubhead, illustrating the hosel and its alignment with the receiving holes. 
       FIG. 5(   a ) illustrates the angle of the shaft to the sole of the putter when the putter is standing upright. 
       FIG. 5(   b ) illustrates the angle of the shaft to the sole of the putter for a right-handed stroke. 
       FIG. 5(   c ) illustrates the angle of the shaft to the sole of the putter for a left-handed stroke. 
       FIG. 6  is a perspective schematic view of the clubhead, indicating the sides and faces of the preferred embodiment. 
       FIG. 7  illustrates the center of the clubhead aligned with the center of the golf ball at the instant the clubhead strikes the golf ball during a putt stroke. 
       FIG. 8(   a ) is a plan view of the practice face of the preferred embodiment, having a convex practice insert. 
       FIG. 8(   b ) is a plan view of the play face of the preferred embodiment, having a flat play insert. 
       FIG. 9(   a ) is a plan view of the practice face of an alternate embodiment, having a convex practice insert. 
       FIG. 9(   b ) is a plan view of the play face of an alternate embodiment having a parabolic, concave play insert. 
       FIG. 9(   c ) is a side view of the alternate embodiment, showing a convex practice face and a concave play face. 
       FIG. 10(   a ) illustrates a golfer playing a left-handed putt stroke with the play face. 
       FIG. 10(   b ) illustrates a golfer practicing a left-handed putt stroke with the practice face. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A clubhead  11  of an improved putter  10  is attached to a shaft  12  with a hosel  13 . The present device may be used with shafts of any length. The clubhead  11  has two faces, a practice face  14  and a play face  15 . Only the play face is used as a striking surface during play, thereby conforming with a USGA Rule that a clubhead have only one striking face. The shaft is attached to the clubhead in such a way that the clubhead can swivel from a practice position to a play position, keeping the shaft in the same position relative to the golfer. See  FIG. 1   a  which shows the clubhead in the practice position for a right handed golfer and  FIG. 1   b  which shows the clubhead after it has been swiveled into the play position. 
   In the preferred embodiment, the shaft is affixed to the hosel or integral with it. The hosel  13  is attached to a spring  9  that is biased to keep the hosel substantially flush with the top surface of the clubhead. See  FIG. 2   c . The clubhead is switched from a practice position to a play position by pulling the shaft away from the clubhead, thereby extending the spring  9 . Once the hosel is free of its seated position in the clubhead, the clubhead is rotated 180 degrees relative to the shaft. The shaft is released, thereby allowing the hosel to be drawn back to the clubhead again as the spring  9  contracts. See  FIG. 4 . The hosel is guided to its seated position and the playface is now facing the ball. 
   In the preferred embodiment, the hosel has two pins  7  that extend toward the clubhead that rest inside two receiving holes  8 . The hosel can be firmly seated in the clubhead in other ways, for example using a detente system having hemispherical projections and mated recesses. 
   The practice face  14  has a substantially circular insert, referred to as a practice insert  16 . The practice insert  16  is convex relative to the practice face  14 , as best illustrated in  FIGS. 2   a–d , and the practice face shape ranges from elliptical to spherical. The curved shape limits the number of points at which the practice face can strike a golf ball in order for the golf ball to move in a straight line perpendicular to the practice face, referred to as the line of putt. Hitting the center of the golf ball with the center of the practice face will cause the golf ball to move on the perpendicular line. However, if the golfer hits the golf ball with any part of the practice face other than the center of the practice insert, the golf ball will veer off the perpendicular line. The farther away from the center of the practice insert, the worse the veer angle will be. 
   Preferably the practice insert  16  is an ellipse. With an elliptically curved practice insert, the veer is relatively small at short radii from its center, thereby being somewhat forgiving to a less-than-perfect stroke. This approximates the amount of forgiveness of putts in play, because slight deviations for a perfect line of putt will not prevent the golf ball from falling in the hole. However, as the veer angle grows increasingly larger farther away from the center of the practice face, the “penalty” for a bad stroke increases as the stokes become increasingly off-center. A spherical practice insert may also be used; it provides a less forgiving center, but a more forgiving perimeter, as the veer angle changes relatively less than at the perimeter of an elliptical practice insert. The “penalty” for a bad stroke is constant regardless of how off-center the stroke is. It is likely that a better golfer will use the spherical practice insert to fine tune his putt stroke. 
   In addition to the curvature of the practice insert, the present invention includes alignment apertures for assisting the golfer in visualizing a straight line to the ball or other desired point. Each alignment aperture is made in the clubhead  11  to receive a lightweight post  30  that extends substantially perpendicularly from the practice face  14 . A conventional drinking straw is suitable for the post, as is it extremely lightweight and most convenient to obtain at a golf course. Preferably, therefore, the diameter of each aperture is made to enable a drinking straw to be inserted and held in place snugly simply by friction. A post can be inserted in any one or more of the alignment apertures, in whichever placement the golfer finds it assists his alignment the best. In the preferred embodiment, the practice face  14  has two alignment apertures,  18  and  20 , however more are acceptable, as indicated by aperture  21  and the aperture into which post  30  is inserted. 
   The play face  15  also has a substantially circular insert, referred to as a play insert  17 . The play insert  17  is inwardly parabolic relative to the play face  15 , ranging from flat to concave. A flat striking face is required under USGA Rules, so a flat play insert should be used when playing a round of golf. 
                              
A parabolic-shaped play insert is self-correcting to some degree, because the curve of the insert will urge the golf ball to the center of the parabola before redirecting the ball away from the play face. A parabola is the set of all points in a plane equidistant from a fixed point (called the focus) and a fixed line (called the directrix). The formula for a parabola is generally:
 
           y   =       x   2       4   ⁢   p             
Thus, when p is large, the curvature of the play insert is great and the ball is strongly urged to the center of the parabola. As the parabola flattens out, that is, as p becomes small, the play insert provides less assistance in getting the ball to travel on the putt line perpendicular to the play face. When the parabola is flat, that is, when y is constant, the striking face is flat, and the putter provides no self-correcting assistance to the golfer. Preferably, the play insert  17  is flat so that the putter conforms to USGA Rules.
 
     FIG. 3  illustrates a preferred embodiment of the clubhead having a core  91 , curved practice insert  92  and flat play insert  93 . The top and the bottom of the clubhead are substantially v-shaped with flattened apexes, the tapered sides serving to position the shaft at an appropriate angle to the ground during practice and play, as described in more detail below. The clubhead is operable with sharp edges where the various faces meet, but preferably the edges are rounded. Preferably the clubhead  11  is manufactured as a core having apertures into which the hosel and shaft assembly, practice insert and play insert are inserted to form an integral unit. The inserts must be firmly fixed so that there is little likelihood of them working loose during a round of golf. The inserts may be integral with the core  91  of the clubhead  11 , or may be separate pieces that are attached to the core or face of the clubhead, with adhesive or friction fit. Preferably the practice inserts and play inserts are changeable to accommodate the needs of the golfer and preferably the insets are threaded to mate with a threaded aperture in the core  91 . They also may be attached in other ways, such as friction fit. 
   The core is made of any durable material, and preferably metal such as aluminum, brass or steel. The practice insert is also made of a durable material, but preferably a hard composite material such as a polymer that provides for a satisfying “thunk,” such as Surlyn® thermoplastic resin sold by the E.I. DuPont De Nemours and Company, which was the first and most durable cover material that revolutionized the construction of the golf ball when it was introduced in the 1980s. The play insert is made of durable materials, metal or composite, and preferably the same material as the practice insert so that the feel of the practice stroke is the same as the stroke during play. 
   For aligning the ball and for putting consistently, it is advantageous to have a puffer that is balanced in as many dimensions as possible. One USGA Rule requires that the projection of the straight part of the shaft onto the vertical plane through the toe and heel shall diverge from the vertical by at least 10 degrees. In other words, the angle between the shaft and the sole of the club must be less than 80 degrees. To achieve both a balanced clubhead and this angle, the bottom of the clubhead is tapered in a V, upward from the midpoint of the bottom to the toe and heel. When putting, one side of the bottom of the club will be resting on or parallel to the playing surface. This portion of the bottom becomes the sole of the club. Due to the taper and the shaft&#39;s orientation to the clubhead, the shaft is then atways tilted at least 10 degrees from vertical. The clubhead can be rotated to accommodate for either a right-handed or left-handed golfer.  FIG. 5  illustrates the resultant effect, where α is the angle between the vertical and the shaft. In  FIG. 5(   a ), the putter is shown in its upright position with the shaft  12  perpendicular to the playing surface  60 .  FIG. 5(   b ) illustrates the putter in the position as a right-handed golfer addresses the ball. Note that α is at least 10 degrees, making the shaft  12  at least 10 degrees off vertical; in other words, the angle between the shaft and the sole  31  of the club is less than 80 degrees.  FIG. 5(   c ) illustrates the putter in the position as a left-handed golfer addresses the ball. Note again that the shaft  12  is at least 10 degrees off vertical, so that the angle between the shaft  12  and the sole  32  is less than 80 degrees. Since the clubhead is tapered by at least 10 degrees, the shaft will always diverge at least 10 degrees from the plane through the toe and heel, regardless of which orientation the golfer uses to address the ball. To maintain symmetry and weight balance in the clubhead, the top should be similarly tapered. That is, the top of the clubhead is tapered in a V, downward from the midpoint of the top to the toe and heel. 
   The clubhead  11  is a polyhedron. Preferably the perimeter of the practice face  16  and play face  17  are octagons as shown in  FIG. 6 . The perimeter of the practice face has sides a, b, d, c, e, f, g and h. The perimeter of the play face has sides i, j, k, l, m, n, o and p. The practice face and play face are substantially parallel to each other, and connected to each other with a top and a bottom. The top of the polyhedron has three faces, P, Q and R that are attached to sides of the practice face a, b, c and the play face i, j, and k, respectively. The bottom has three faces, S, T and U that are attached to sides of the practice face e, f, g and play face m, n and o, respectively. The ends of the clubhead  11  are parallel to each other and perpendicular to face Q and face T of the bottom. The taper of the clubhead is the effect of the relationship of the sides to the top and bottom. In  FIG. 6 , the taper is therefore indicated by angle β. The angles between sides a and b, b and c, d and e, e and f, are equal and no more than 170 degrees, and the angles between sides i and j, j and k, m and n, n and o, are equal and no more than 170 degrees. 
   To best control and eliminate spin on the golf ball, it is desirable to be able to strike the ball along the horizontal plane bisecting the center of the ball.  FIG. 7  illustrates the centerline l—l of the play face  15  aligned with the center of a golf ball  79  upon impact with the golf ball. Consistent with good clubhead balance, preferably the practice and play faces are centered along the horizontal centerline of the clubhead  11 . For good visual alignment, the practice and play faces are preferably about the same size as a golf ball. Preferably, therefore, the practice and play faces are centered on the clubhead so that the center of the practice and play faces meet the centerline of the ball when it is struck. The actual dimensions of the clubhead can be customized to take into account various factors including the player&#39;s stroke, the lay of the ball on the putting surface, and the length of the nap of the grass. 
   Many combinations of the shapes of the clubhead, play and practice faces are possible while still achieving the objective of this invention, as illustrated in  FIGS. 8 and 9 .  FIG. 8  illustrates the preferred embodiment, wherein the practice face  50  ( FIG. 8(   a )) and play face  51  ( FIG. 8(   b )) are octagons and the taper angle α is about 10 degrees. The practice insert  52  is outwardly convex in an elliptical curve. The play insert  53  is flat.  FIG. 9  illustrates an alternate embodiment, wherein the practice face  70  ( FIG. 9(   a )) and play face  71  ( FIG. 9(   b )) are octagons, but the taper angle α has been increased to about 20 degrees. The practice insert  72  is outwardly convex in a spherical curve and the play insert  73  is convex in a parabolic curve.  FIG. 9(   c ) is a side view illustrating a convex practice face and a concave play face. 
     FIG. 10(   a ) illustrates a golfer  80  practicing a left-handed putt stroke into hole  83 . The golfer uses the practice face  81  to hit the ball and improve his aim. By rotating the putter 180 degrees in his hands, the golfer can use the same putter and the same stance to putt in play.  FIG. 10(   b ) illustrates the same golfer putting in play, using the play face  82  as the striking face. 
   While there has been illustrated and described what is at present considered to be the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made and equivalents may be substituted for elements thereof without departing from the true scope of the invention. Therefore, it is intended that this invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Technology Classification (CPC): 0