Abstract:
The present invention is an improved putter that 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 putter also comprises a hosel with an attached alignment cap has lobes which matingly engage a series of recesses on the clubhead to secure the clubhead to the shaft. 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.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of and is a continuation-in-part of application Ser. No. 10/920,596 filed Aug. 16, 2004 now U.S. Pat. No. 7,041,004 which is a continuation-in-part of application Ser. No. 10/351,495 filed Jan. 23, 2003, now U.S. Pat. No. 6,776,727. Both of which are hereby incorporated herein by reference. 

   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. The putter includes a rotatable hosel and alignment cap that are fixable to the clubhead to form a single unit, in compliance with the USGA Rules of Golf. 
   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 fourteen 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 USGA Rules 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. 
   For putters that are convertible from practice to play, one of the most difficult USGA Rules to comply with relates to “providing a putter with a shaft and a head, fixed to form one unit.” The fit between the clubhead and shaft must be extremely tight as to be essentially one unit. 
   It would also be desirable for a golfer to practice with putters of various weights to determine which weight makes the most accurate puts. Further, as a golfer&#39;s stroke changes over time, the golfer may want to change the weight of the putter. While a golfer can buy several putters each of a different weight, multiple putters are expensive and each one has its own characteristics that require the golfer to practice with to become accurate. It would be desirable to have a single putter that allows the golfer to change its weight. 
   During the putt stroke, the clubhead passes above the solid ground by only a very short distance. The length and density of the grass on each green may vary, causing the friction against the putter to vary accordingly. It would be desirable to have nearly constant friction against the putter on every green, so that a uniform putt stroke could be used from green to green. One way to make the friction as constant as possible is to reduce it as much as possible. 
   Therefore, it is an object of the present invention to provide a putter with a clubhead that is capable of rotating from a first position to strike the ball with a practice face to a second position to strike the ball with play face in which the shaft and clubhead that are fixed so securely that they form essentially one unit. It is another object of this invention to provide a putter that enables the golfer to change its weight. It is another object to provide a putter in which the friction between the clubhead and grass is minimized. It is also 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 a further 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 a putter with a clubhead that rotates from a first position to strike the ball with a practice face to a second position to strike the ball with a play face. The putter includes a hosel with an attached alignment cap that fits in mated recesses defined by the clubhead so that the shaft and clubhead are fixed as essentially one unit. The clubhead of the present invention also enables one or more weights to be inserted within the clubhead to alter the clubhead&#39;s weight. Finally, the putter includes a base plate attached to the bottom of the clubhead to reduce any friction that may be present between the green and the clubhead. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of the putter showing the practice face; 
       FIG. 2  is a perspective view of the putter showing the play face; 
       FIG. 3  is an exploded perspective view of the practice face; 
       FIG. 4  is a top perspective view of the putter showing the alignment cap rotated out of alignment; 
       FIG. 5   a  is a top perspective view of the clubhead with the alignment cap, hosel and shaft removed; 
       FIG. 5   b  shows a weight. 
       FIG. 6  shows a cross section take along line  6 - 6  of  FIG. 1 . 
       FIG. 7  illustrates a partially-exploded bottom perspective view of the putter; 
       FIG. 8  illustrates a golfer practicing a right-handed putt stroke with the practice-face; 
       FIG. 9  illustrates a golfer playing a right-handed putt stroke with the play face. 
       FIG. 10  is a graph of a parabola. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention comprises a putter having a shaft  12  attached to a clubhead  11  with a hosel  13 . See  FIGS. 1-7 . The present device may be used with shafts of any length. The hosel  13  includes an alignment cap  18  that firmly secures clubhead  11  to shaft  12  to form a unit that is not conveniently taken apart. 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 rotate from a practice position to a play position, keeping the shaft in the same position relative to the golfer. See  FIG. 1  which shows the practice face  14  of a clubhead  11  in the play position for a right handed golfer.  FIG. 2  shows the play face  15  of the same putter.  FIG. 8  shows a right-handed golfer  80  making a putt stroke with the practice face  14  and  FIG. 9  shows the same golfer  80  making a putt with a play face  15 . 
   The shaft  12  is attached to the hosel  13  as shown in  FIG. 4 . In turn, the hosel  13  is attached to the alignment cap  18 , which cooperates with one or more mated structures in the clubhead  11  to align the shaft  12  and the clubhead. As used herein, “attached” means that the parts are integral with each other or are separate components that have been connected to each other. In the preferred embodiment, the alignment cap  18  includes three lobes  24   a ,  24   b , and  24   c  which engage three mated recesses  26   a ,  26   b , and  26   c  which are defined by the clubhead  11 . See  FIG. 4 . In this preferred embodiment, the recesses  26  are connected to each other, but non-connected recesses  26  could be used and fall within the scope of the present invention. In alternative embodiments, the number of mated lobes and recesses can be increased or decreased, and the shape of the lobes and recesses can be changed, for example from circular to square, ovoid, triangular or other shape. Additionally, instead of lobes and recesses, pins, pegs or other types of protrusions could be placed on the alignment cap  18  to engage apertures, holes or any other type of recess located on the clubhead  11 . Alternatively, the clubhead could have protrusions that mate with apertures in the alignment cap. 
   When three lobes  24  are used, a center lobe  24   b  is designed to fit within a center recess  26   b  defined by the clubhead  11 . See  FIGS. 4 and 5   a . The remaining two side lobes,  24   a  and  24   c  in turn engage corresponding recesses  26   a  and  26   c . The mated structures ensure that the shaft  12  and the clubhead  11  are aligned and tightly secured to each other. 
   Several components cooperate to fix the shaft  12  to the clubhead. See  FIG. 6 . A first attachment structure causes the alignment cap  18  to be rotatably retained to the clubhead  11  and the second attachment structure causes the alignment cap  18  to be fixed securely to the clubhead  11 . 
   In the first attachment structure, a retention screw  40  is aligned through a mated retention aperture  41  that extends through the clubhead  11  and into the alignment cap  18 . The retention aperture  41  has smooth sidewalls where it goes through the clubhead  11  but the retention aperture is matedly threaded in the alignment cap  18  to securely receive the retention screw  40 . See  FIG. 6 . As a result, when the retention screw  40  is in place, the alignment cap  18  can be separated from the clubhead  11  distance “A” while still being retained thereto, so that it swivels freely. The retention screw may take the form of a regular screw, a Chicago screw, rivet, detent and socket pair, or other device that allows the alignment cap  18  to be rotatably retained to the clubhead. The distance “A” that the alignment cap  18  can be separated from the clubhead  11  is greater than or equal to the thickness “B” of the alignment cap  18 . This facilitates the rotation of the shaft from a practice position to a play position. 
   In the second attachment structure, a set screw  42  is aligned through one of two mated set apertures  43  that extend through the alignment cap  18  and into the clubhead  11 . The clubhead portion of the set aperture  43  is matedly threaded to securely receive the set screw  42 . See  FIG. 6 . The portion of the set aperture  43  in the alignment cap  18  can be smooth-walled or threaded. As a result, when the set screw  42  is in place, the alignment cap  18  cannot be separated from the clubhead  11 . This prevents the rotation of the shaft  12  and fixes the shaft  12  and the clubhead  11  together to form essentially one unit. Preferably the set screw  42  is a hex screw or some other screw with a head that would be difficult or time-consuming to remove while on a golf course. 
   The clubhead  11  is switched from a practice position to a play position by removing set screw  42  so that the shaft  12  may be pulled away from the clubhead  11 . Once the hosel  13  and alignment cap  18  are free of their seated position in the clubhead  11 , the clubhead  11  is rotated approximately 180 degrees relative to the shaft  12 . The hosel  13  is guided to its seated position by placing lobes  24   a ,  24   b ,  24   c  within recesses  26   a ,  26   b ,  26   c  and the play face  15  is now facing the ball. The process is completed by re-inserting and tightening set screw  42  into the other set aperture  43 . 
   In the preferred embodiment, the clubhead  11  has recesses  46  to hold removable weights. See  FIGS. 5   a  and  5   b . The recesses are referred to herein as weight cavities  46 . One or more weights  38  may be inserted into each weight cavity  46  to adjust the weight of clubhead  11  to the golfer&#39;s liking. See  FIG. 5   b . Preferably the weights  38  fit snugly in the weight cavities  46 . A golfer can vary the weight of clubhead  11  by using equally-sized weights  38  made of different materials that have different densities. For example, aluminum weights would cause the club to weigh less than brass weights, which would weigh less than lead weights. Preferably only a single weight  38  is placed within each of the cavities, which complies with USGA Rules, but alternatively several weights  38  can be placed in cavities. Preferably the weight cavities  46  are aligned with the recesses  26  such that the weights are retained within the weight cavity by the alignment cap. Aligning the weight cavities will also make it easier to load the weights and to manufacture the clubhead. 
   Further, in the preferred embodiment, the clubhead  11  has one or more apertures on the practice face  14  that allow the golfer to see the weight  38  in the weight cavity  46  without having to remove the alignment cap  18 . By using weights of different colors, whether painted or simply by the nature of the material used, the golfer can quickly determine which weights are in the clubhead and therefore the weight. These apertures are referred to herein as weight windows  51 . 
   As described in the related applications and patent, 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 , and the practice face  14  shape ranges from elliptical to spherical. The curved shape limits the number of points at which the practice face  14  can strike a golf ball in order for the golf ball to move in a straight line perpendicular to the practice face  14 , referred to as the line of putt. Hitting the center of the golf ball with the center of the practice face  14  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  14  other than the center of the practice insert  16 , the golf ball will veer off the perpendicular line. The farther away from the center of the practice insert  16 , the worse the veer angle will be. 
   Preferably the practice insert  16  is an ellipse. With an elliptically practice insert  16 , 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  14 , the “penalty” for a bad stroke increases as the strokes 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  16 , the present invention includes a number of alignment apertures  50  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 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, 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, however more are acceptable. 
   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. 
   See  FIG. 10 . 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  17  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  17  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  10  provides no self-correcting assistance to the golfer. Preferably, the play insert  17  is flat so that the putter  10  conforms to USGA Rules.  FIGS. 1-3  illustrates a preferred embodiment of the clubhead  11  having a curved practice insert  16  and flat play insert  17 . 
   As shown in  FIG. 7 , the clubhead  11  includes a base plate  62  that is attached to the clubhead  11 , preferably by friction fit, although, glue, another adhesive or any other attachment mechanism may suffice. The base plate  62  is preferably has a cross section to minimize the amount of head surface that comes into contact with green. The base plate  62  may be smooth or, preferably, include a series of ridges  66  creating grooves aligned along the line of putt that allow grass to pass through them thereby reducing the amount of friction between clubhead  11  and the ground. The grooves aid in combing the green thus aiding the golfer in holding the head perpendicular to the intended line while the stroke is in the critical phase of moving across the green. 
   The clubhead is made of any durable material, and preferably metal such as aluminum, brass or steel. The practice insert  16  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 DeNemours 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  17  is made of durable materials, metal or composite, and preferably the same material as the practice insert  16  so that the feel of the practice stroke is the same as the stroke during play. 
   One USGA Rule requires that the projection of the straight part of the shaft  12  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  12  and the sole of the club must be less than 80 degrees.  FIGS. 8 and 9  illustrate a golfer  80  practicing a right-handed putt stroke into hole  83 . The golfer uses the practice face  14  to hit the ball and improve his aim. By rotating the putter approximately 180 degrees in his hands, the golfer can use the same putter  10  and the same stance to putt in play.  FIG. 9  illustrates the same golfer putting in play, using the play face  15  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.