Patent Publication Number: US-6905420-B2

Title: Putter head

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   The present application is a continuation application of U.S. patent application Ser. No. 10/707,847 filed Jan. 16, 2004 now U.S. Pat. No. 6,793,588, which is a continuation application of U.S. patent application Ser. No. 10/065,232, filed Sep. 26, 2002 now U.S. Pat. No. 6, 679,782, which is a continuation-in-part application of U.S. patent application Ser. No. 10/063,908, filed on May 22, 2002, now U.S. Pat. No. 6,471,600, which is a continuation-in-part application of U.S. patent application Ser. No. 09/683,125, filed on Nov. 21, 2001, now U.S. Pat. No. 6,506,125, which is a continuation-in-part application of U.S. patent application Ser. No. 29/147,888, filed on Sep. 7, 2001, now U.S. Pat. No. D458,656, and a continuation-in-part application of U.S. patent application Ser. No. 09/693,349, filed on Oct. 20, 2000, now U.S. Pat. No. 6,632,391, which is a divisional application of U.S. patent application Ser. No. 09/389,798, filed on Sep. 3, 1999, now U.S. Pat. No. 6,238,302. 

   FEDERAL RESEARCH STATEMENT 
   [Not Applicable] 
   BACKGROUND OF INVENTION 
   1. Field of the Invention 
   The present invention relates to a putter-type club head. More specifically, the present invention relates to a putter-type club head having a rearward center of gravity. 
   2. Description of the Related Art 
   The golf industry has been inventing putters that make the game of golf easier for the high handicap player. One such putter is disclosed in U.S. Pat. No. 4,688,798 to David Peiz. The Pelz patent discloses a putter with an alignment means to assist a golfer in aiming a golf ball toward a hole during putting. The Pelz patent discloses using two or three golf ball shaped indicators as the alignment means. The golf ball shaped indicators may be circles, hemispheres, or complete spheres. The Pelz patent discloses positioning the indicators along a line extending rearward from the center of percussion. 
   Another patent that discloses an alignment means is U.S. Pat. No. 4,659,083 to Szczepanski. The Szczepanski patent discloses a group of lines that converge toward the center of the face of the putter. 
   Yet another patent that discloses an alignment means is Great Britain Patent Application Number 4,659,083 to Lilley. The Lilley patent also discloses a group of lines that converge toward the center of the face of a putter. 
   Although these inventions have provided new and improved putters for making the game of golf more enjoyable for high handicap players, the prior art has not optimized a putter by making it more forgiving and assisting in alignment. 
   SUMMARY OF INVENTION 
   One aspect of the present invention is a putter with novel inertial properties. 
   Another aspect of the present invention is a putter having a club head, a shaft connected the club head, and a grip attached to shaft. The putter has a center of gravity located at least 1.5 centimeters rearward from a shaft axis of the putter. 
   Yet another aspect of the present invention is a putter having a club head, a shaft connected the club head, and a grip attached to shaft, and the putter has a torsion swing inertia, Ixz, that has an absolute value greater than 10,000 grams-centimeter square. 
   Yet another aspect of the present invention is a putter having a club head, a shaft connected the club head, and a grip attached to shaft, and the putter has a swing static imbalance, Sy, greater than 500 grams-centimeter. 
   Having briefly described the present invention, the above and further objects, features and advantages thereof will be recognized by those skilled in the pertinent art from the following detailed description of the invention when taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is a top perspective view of a putter-type club head. 
       FIG. 2  is a top perspective view from the heel of the putter-type club head of FIG.  1 . 
       FIG. 3  is a perspective view from the bottom of the putter-type club head of FIG.  1 . 
       FIG. 4  is a top plan view of the putter-type club head of FIG.  1 . 
       FIG. 5  is a bottom plan view of the putter-type club head of FIG.  1 . 
       FIG. 6  is a front plan view of the putter-type club head of FIG.  1 . 
       FIG. 7  is a rear plan view of the putter-type club head of FIG.  1 . 
       FIG. 8  is a heel side view of the putter-type club head of FIG.  1 . 
       FIG. 9  is a toe side view of the putter-type club head of FIG.  1 . 
       FIG. 10  is a top perspective view of an alternative embodiment of a putter-type club head. 
       FIG. 11  is a top plan view of putter-type club head of FIG.  10 . 
       FIG. 12  is a bottom plan view of putter-type club head of FIG.  10 . 
       FIG. 12A  is a bottom plan view of putter-type club head of  FIG. 10  with an alternative sole. 
       FIG. 13  is a front plan view of putter-type club head of FIG.  10 . 
       FIG. 14  is a rear plan view of putter-type club head of FIG.  10 . 
       FIG. 15  is a heel side view of putter-type club head of FIG.  10 . 
       FIG. 16  is a toe side view of putter-type club head of FIG.  10 . 
       FIG. 17  is a cross-section view along line  17 — 17  of the putter-type club head of FIG.  10 . 
       FIG. 18  is a front plan view of a putter. 
       FIG. 19  is a side view of the putter of FIG.  18 . 
       FIG. 20  is a front plan view of a putter. 
       FIG. 21  is a side view of the putter of FIG.  20 . 
   

   DETAILED DESCRIPTION 
   As shown in  FIGS. 1-8 , a putter-type club head is generally designated  20 . The club head  20  has a body  22  that is preferably composed of a cast metal. A preferred metal for the body  22  is stainless steel. Alternative materials for the body  22  include titanium, titanium alloys, carbon steel, bronze, and the like. The body  22  preferably weighs from 275 grams to 400 grams, more preferably from 300 grams to 350 grams, even more preferably from 315 grams to 335 grams and most preferably 328 grams. 
   The body  22  has a face portion  24 , a crown portion  26 , a sole portion  28  and an aft-mass portion  30 . The face portion  24 , the crown portion  26 , the sole portion  28  and the aft-mass portion  30  define a central aperture  32  that extends through the body  22 . The central aperture  32  has a heel opening  34  at a heel end  23  of the body  22  and a toe opening  36  at a toe end  25  of the body  22 . The central aperture  32  horizontally separates the face portion  24  from the aft-mass portion  30 , and the central aperture  32  vertically separates the crown portion  26  from the sole portion  28 . The central aperture  32 , in connection with the aft-mass portion  30 , allows for the center of gravity of the club head  20 , CG, to be moved rearward from the face portion  24 . In a preferred embodiment, the CG of the club head  20  is positioned within the central aperture  32 , and thus the CG is not positioned within material of the club head  20  but instead the CG lies outside the material in space within the central aperture  32 . Preferably, the CG is located between 0.25 inch and 1.0 inch from an external surface  71  of the sole portion  28 , more preferably 0.50 inch to 0.75 inch, and most preferably 0.73 inch from the external surface  71  of the sole portion  28 . Also, preferably the CG of the club head  20  is located 0.50 inch to 2.5 inches rearward from the external surface  58  of the face portion  24 , more preferably 0.75 inch to 1.5 inches, and most preferably 0.944 inch from the external surface  58  of the face portion  24 . In addition to assisting in the rearward positioning of the CG, the aft-mass portion  30  is a rearward support structure for crown portion  26 . The aft-mass portion  30  extends upward and rearward from a rearward end  29  of the sole portion  28 . The aft-mass portion  30  ranges from 10 to 30 volume percent of the body  22  and ranges from 25 to 75 weight percent of the body  22 . More preferably, the aft-mass portion  30  ranges from 15 to 25 volume percent of the body  22  and ranges from 40 to 60 weight percent of the body  22 . The external surface  64  of the aft-mass portion  30  preferably defines an acute edge  65  (relative to the ground) and a straight edge  67  (relative to the ground). As shown in  FIG. 3 , the aft-mass portion  30  extends outward from the sole portion  28 . An internal surface  62  of the aft-mass portion  30  defines a portion of the central aperture  32 . 
   The sole portion  28  preferably has an approximate T-shape. The external surface  71  of the sole portion  28  contacts the ground when the club head  20  is used with a shaft and grip, both not shown, as a putter. A center section of an internal surface  56  of the sole portion  28  partially defines the central aperture. The CG of the club head  20  preferably lies above the sole portion  28 . 
   The crown portion  26  extends rearward from the face portion  24 . The crown portion  26  has a central elongated section  44  and a front section  46 . The front section  46  has a width w′ that extends from the heel end  23  to the toe end  25  of the face portion  24 , and gradually narrows as the front section  46  transitions into the central elongated section  44 . The width, w′, preferably ranges from 2.5 inches to 5.0 inches, more preferably from 3.5 inches to 4.5 inches, and most preferably 4.25 inches. The central elongated section  44  has a width w″ that is less than the width w′ of the front section  46 . The width, w″, preferably ranges from 1.0 inch to 3.0 inches, more preferably from 1.5 inches to 2.25 inches, and most preferably 1.8 inches. The internal surface  48  of the crown portion  26  partially defines the central aperture  32 . The crown portion preferably has a thickness that ranges from 0.10 inch to 0.50 inch, more preferably 0.15 inch to 0.30 inch. 
   The external surface  38  of the crown portion  26  preferably has an alignment means  40  thereon. The external surface  38  also preferably has a cylindrical rod  54  extending upward therefrom for engagement with a shaft, not shown. A preferred alignment means  40  is first and second inserts  40   a  and  40   b  disposed within first and second recesses  42   a  and  42   b  in the crown portion  26 . The depth of each of the recesses  42   a  and  42   b  is preferably within 0.05 inch to 0.50 inch, more preferably 0.1 inch to 0.250 inch. Each of the circular inserts  40   a  and  40   b  preferably have a thickness ranging from 0.05 inch to 0.50 inch, more preferably 0.1 inch to 0.250 inch. 
   In a preferred embodiment, each of the circular inserts  40   a  and  40   b  are preferably composed of a thermosetting polyurethane material such as described in U.S. Pat. No. 6,273,831, entitled Golf Club Head with A Polymer Insert, assigned to Callaway Golf (the assignee of the Present Application), which is hereby incorporated by reference in its entirety. Alternatively, each of the circular inserts  40   a  and  40   b  may be composed of a thermoplastic polyurethane. Each of the circular inserts  40   a  and  40   b  is preferably colored white, through painting or doping of the polyurethane with coloring agents, and each circular insert  40   a  and  40   b  preferably has a texture of a golf ball cover. Each of the circular inserts  40   a  and  40   b  preferably has a diameter ranging from 1.62 inches to 1.70 inches, and most preferably 1.68 inches. Those skilled in the art will recognize that more than two circular inserts  40   a  and  40   b  may be utilized without departing from the scope and spirit of the present invention. Alternative alignment means are disclosed in U.S. Pat. No. 4,688,798, entitled Golf Club And Head Including Alignment Indicators, assigned to the Callaway Golf (the assignee of the Present Application), which pertinent parts are hereby incorporated by reference. As disclosed in U.S. Pat. No. 4,688,798, the alignment means assists a golfer in properly aiming a golf ball toward a hole when putting. Alternative alignment means, including a large white strip may be utilized in the present invention. 
   The face portion  24  preferably has a thickness ranging from 0.10 inch to 0.50 inch, more preferably 0.20 inch to 0.35 inch. The face portion  24  has an internal surface  60  that partially defines the central aperture  32 . The external surface  58  of the face preferably has a face recess  52  therein with a face insert  50  disposed therein such as disclosed in U.S. Pat. No. 6,238,302, entitled A Golf Club Head With An Insert Having Integral Tabs, assigned to Callaway Golf (the assignee of the Present Application), which is hereby incorporated by reference in its entirety. As disclosed in U.S. Pat. No. 6,238,302, the face insert is preferably composed of a thermosetting polyurethane material and is preferably colored white. In an alternative embodiment, the face portion  24  is a non-insert blade as is known in the art. 
   The body  22  preferably has a length, L, from the face portion  24  to the rearward most end of the aft mass portion  30  preferably ranging from 2.5 inches to 4.5 inches, more preferably from 3.0 inches to 4.0 inches, and most preferably 3.43 inches. In one alternative embodiment, the body  22  has a length, L, that is equal to the width, w′. 
   As mentioned previously, the central aperture is defined by the internal surface  60  of the face portion  24 , the internal surface  48  of the crown portion  26 , the internal surface  56  of the sole portion  28  and the internal surface  62  of the aft-mass portion  30 . The distance from the internal surface  48  of the crown portion  26  to the internal surface  56  of the sole portion  28  preferably ranges from 0.01 inch to 1.50 inches, more preferably 0.25 inch to 1.0 inch, and most preferably 0.5 inch. The distance from the internal surface  60  of the face portion  24  to the internal surface  62  of the aft-mass portion  30  preferably ranges from 1.0 inch to 3.50 inches, more preferably from 1.5 inches to 3.0 inches, and most preferably 2.00 inches. The body  22  is preferably formed as a single cast structure using known investment casting techniques. However, those skilled in the pertinent art will recognize that alternative forming techniques such as milling, welding forged or formed pieces, and the like may be utilized without departing from the scope and spirit of the present invention. 
   The golf club putter of the present invention may alternatively have an embodiment as shown in  FIGS. 10-17 , wherein a putter-type club head of the present invention is generally designated  20 . The club head  20  has a body  22  that is preferably composed of a cast metal. A preferred metal for the body  22  is stainless steel. Alternative materials for the body  22  include titanium, titanium alloys, carbon steel, bronze, and the like. The body  22  preferably weighs from 275 grams to 400 grams, more preferably from 300 grams to 350 grams, even more preferably from 315 grams to 335 grams and most preferably 328 grams. 
   The body  22  has a face portion  24 , a crown portion  26 , a sole portion  28  and an aft-mass portion  30 . The face portion  24 , the crown portion  26 , the sole portion  28  and the aft-mass portion  30  define a central aperture  32  that extends through the body  22 . The central aperture  32  has a heel opening  34  at a heel end  23  of the body  22  and a toe opening  36  at a toe end  25  of the body  22 . The central aperture  32  horizontally separates the face portion  24  from the aft-mass portion  30 , and the central aperture  32  vertically separates the crown portion  26  from the sole portion  28 . The central aperture  32 , in connection with the aft-mass portion  30 , allows for the center of gravity of the club head  20 , CG, to be moved rearward from the face portion  24 . In a preferred embodiment, the CG of the club head  20  is positioned within the central aperture  32 , and thus the CG is not positioned within material of the club head  20  but instead the CG lies outside the material in space within the central aperture  32 . Preferably, the CG is located between 0.25 inch and 1.0 inch from an external surface  71  of the sole portion  28 , more preferably 0.50 inch to 0.75 inch, and most preferably 0.615 inch from the external surface  71  of the sole portion  28 . Also, preferably the CG of the club head  20  is located 0.50 inch to 2.5 inches rearward from the external surface  58  of the face portion  24 , more preferably 0.75 inch to 2.0 inches, and most preferably 1.2 inches from the external surface  58  of the face portion  24 . In addition to assisting in the rearward positioning of the CG, the aft-mass portion  30  is a rearward support structure for crown portion  26 . The aft-mass portion  30  extends upward and rearward from a rearward end  29  of the sole portion  28 . The aft-mass portion  30  ranges from 10 to 30 volume percent of the body  22  and ranges from 25 to 75 weight percent of the body  22 . More preferably, the aft-mass portion  30  ranges from 15 to 25 volume percent of the body  22  and ranges from 40 to 60 weight percent of the body  22 . The external surface  64  of the aft-mass portion  30  preferably defines an acute edge  65  (relative to the ground) and a straight edge  67  (relative to the ground). As shown in  FIG. 3 , the aft-mass portion  30  extends outward from the sole portion  28 . An internal surface  62  of the aft-mass portion  30  defines a portion of the central aperture  32 . 
   The sole portion  28  preferably has an approximate semi-circular shape and is substantially planar. The external surface  71  of the sole portion  28  contacts the ground when the club head  20  is used with a shaft and grip, both not shown, as a putter. A center section of an internal surface  56  of the sole portion  28  partially defines the central aperture, and such center section of the internal surface  56  is covered by the crown portion  26 . A heel section  56   a  and a toe section  56   b  of the internal surface  56  of the sole portion  28  are not covered by the crown portion, and are exposed as shown in FIG.  2 . The CG of the club head  20  preferably lies above the sole portion  28 . 
   In an alternative sole embodiment shown in  FIG. 12A , the sole portion  28  has a medial ridge  81  along the center of the sole portion  28  that is connected to an arc-heel ridge  83   a  and an arc-toe ridge  83   b  at a juncture  87 . A front ridge  82  is perpendicular to the medial ridge  81  and is connected to the arc-heel ridge  83   a  at one end and the arc-toe ridge  83   b  at the other end of the front ridge  82 . The medial ridge  81 , the front ridge  82  and the arc-heel ridge  83   a  define a heel recess  85   a  having a surface  71   a . The medial ridge  81 , the front ridge  82  and the arc-toe ridge  83   b  define a toe recess  85   b  with a surface  71   b . The medial ridge  81 , the arc-heel ridge  83   a  and the toe-heel ridge  83   b  are preferably 0.125 inch above the surfaces  71   a  and  71   b  of the recesses  85   a  and  85   b . This structure of the sole portion  28  moves mass to the perimeter of the body  22  and allows for greater stabilization of the putter-type club head  20  during a putt by a golfer. 
   The crown portion  26  extends rearward from the face portion  24 . The crown portion  26  has a central elongated section  44  and a front section  46 . The front section  46  has a width w′ that extends from the heel end  23  to the toe end  25  of the face portion  24 , and gradually narrows as the front section  46  transitions into the central elongated section  44 . The width, w′, preferably ranges from 2.5 inches to 4.5 inches, more preferably from 3.0 inches to 3.75 inches, and most preferably 3.5 inches. The central elongated section  44  has a width w″ that is less than the width w′ of the front section  46 . The width, w″, preferably ranges from 1.0 inch to 3.0 inches, more preferably from 1.5 inches to 2.25 inches, and most preferably 1.8 inches. The internal surface  48  of the crown portion  26  partially defines the central aperture  32 . The crown portion preferably has a thickness that ranges from 0.10 inch to 0.50 inch, more preferably 0.15 inch to 0.30 inch. 
   The external surface  38  of the crown portion  26  preferably has an alignment means  40  thereon. The external surface  38  also preferably has a cylindrical rod  54  extending upward therefrom for engagement with a shaft, not shown. A preferred alignment means  40  is first and second inserts  40   a  and  40   b  disposed within first and second recesses  42   a  and  42   b  in the crown portion  26 . The depth of each of the recesses  42   a  and  42   b  is preferably within 0.05 inch to 0.50 inch, more preferably 0.1 inch to 0.250 inch. Each of the circular inserts  40   a  and  40   b  preferably has a thickness ranging from 0.05 inch to 0.50 inch, more preferably 0.1 inch to 0.250 inch. 
   In a preferred embodiment, each of the circular inserts  40   a  and  40   b  is composed of a thermosetting polyurethane material such as described in U.S. Pat. No. 6,273,831, entitled Golf Club Head with A Polymer Insert, assigned to Callaway Golf (the assignee of the Present Application), which is hereby incorporated by reference in its entirety. Each of the circular inserts  40   a  and  40   b  is preferably colored white, through painting or doping of the polyurethane with coloring agents, and each circular insert  40   a  and  40   b  preferably has a texture of a golf ball cover. Each of the circular inserts  40   a  and  40   b  preferably has a diameter ranging from 1.62 inches to 1.70 inches, and most preferably 1.68 inches. Those skilled in the art will recognize that more than two circular inserts  40   a  and  40   b  may be utilized without departing from the scope and spirit of the present invention. Alternative alignment means are disclosed in U.S. Pat. No. 4,688,798, entitled Golf Club And Head Including Alignment Indicators, assigned to Callaway Golf (the assignee of the Present Application), which pertinent parts are hereby incorporated by reference. As disclosed in U.S. Pat. No. 4,688,798, the alignment means assists a golfer in properly aiming a golf ball toward a hole when putting. Alternative alignment means, including a large white strip may be utilized in the present invention. 
   The face portion  24  preferably has a thickness ranging from 0.10 inch to 0.50 inch, more preferably 0.20 inch to 0.35 inch. The face portion  24  has an internal surface  60  that partially defines the central aperture  32 . The external surface  58  of the face preferably has a face recess  52  therein with a face insert  50  disposed therein such as disclosed in U.S. Pat. No. 6,238,302, entitled A Golf Club Head With An Insert Having Integral Tabs, assigned to Callaway Golf (the assignee of the Present Application), which is hereby incorporated by reference in its entirety. As disclosed in U.S. Pat. No. 6,238,302, the face insert is preferably composed of a thermosetting polyurethane material and is preferably colored white. In an alternative embodiment, the face portion  24  is a non-insert blade as is known in the art. 
   The body  22  preferably has a length, L, from the face portion  24  to the rearward most end of the aft mass portion  30  preferably ranging from 2.5 inches to 4.5 inches, more preferably from 3.0 inches to 3.5 inches, and most preferably 3.25 inches. In one alternative embodiment, the body  22  has a length, L, that is equal to the width, w′. 
   One aspect of the club head  20  is the concentration of mass in the center section  95  of the club head  20 , as shown in FIG.  12 . In a preferred embodiment, 210 grams to 250 grams of the mass of the club head  20  is located within the center section  95 . In a most preferred embodiment, 232 grams of the mass of the club head  20  is located within the center section  95 . Preferably 60% to 80% of the mass of the club head  20  is located within the center section  95 . 
   As mentioned previously, the central aperture is defined by the internal surface  60  of the face portion  24 , the internal surface  48  of the crown portion  26 , the internal surface  56  of the sole portion  28  and the internal surface  62  of the aft-mass portion  30 . The distance from the internal surface  48  of the crown portion  26  to the internal surface  56  of the sole portion  28  preferably ranges from 0.01 inch to 1.50 inches, more preferably 0.25 inch to 1.0 inch, and most preferably 0.5 inch. The distance from the internal surface  60  of the face portion  24  to the internal surface  62  of the aft-mass portion  30  preferably ranges from 1.0 inch to 3.50 inches, more preferably from 1.5 inches to 3.0 inches, and most preferably 1.87 inches. The body  22  is preferably formed as a single cast structure using known investment casting techniques. However, those skilled in the pertinent art will recognize that alternative forming techniques such as milling, welding forged or formed pieces, and the like may be utilized without departing from the scope and spirit of the present invention. 
   A preferred embodiment of a putter  100  is shown in  FIGS. 18 and 19 , and an alternative embodiment is shown in  FIGS. 20-21 .  FIGS. 18-21  also illustrate a reference frame for measuring the center of gravity of the putter  100 , which is different than the center of gravity for the club head  20 . The putter  100  generally includes the putter club head  20 , a shaft  102  and a grip  104 . In one embodiment, the putter  100  has a conventional club length that preferably ranges from 33 inches to 36 inches, and a mass that preferably ranges from 475 grams to 525 grams. 
   In another embodiment, the putter  100  has a mid-club length that preferably ranges from 41 inches to 45 inches, and a mass that preferably ranges from 665 grams to 700 grams. In this mid-length embodiment, the shaft  102  preferably has a mss that ranges from 160 grams to 175 grams and the grip  104  preferably has a mass that ranges from 135 grams to 145 grams. The loft angle is preferably three degrees and the lie angle is preferably 72 degrees. 
   In yet another embodiment, the putter  100  has a long-club length that preferably ranges from 46 inches to 50 inches, and a mass that preferably ranges from 730 grams to 775 grams. In this long-length embodiment, the shaft  102  preferably has a mass that ranges from 160 grams to 175 grams. This long-length embodiment preferably has two grips  104  (the second grip not shown) with the top grip  104  preferably having a mass that ranges from 45 grams to 50 grams, and a bottom grip (not shown) having a mass that preferably ranges from 95 grams to 105 grams. The loft angle is preferably three degrees and the lie angle is preferably 78 degrees. 
   
     
       
         
             
             
             
             
             
             
           
             
               TABLE ONE 
             
             
                 
             
             
                 
                 
               100 
                 
                 
                 
             
             
               Club Parameter 
                 
               Pres. 
               White Hot 
               White Hot 
             
             
               Name 
               Units 
               Inv. 
               #1 
               #8 
               Description 
             
             
                 
             
           
          
             
                 
             
          
         
         
             
             
             
             
             
             
          
             
               Total Mass 
               Grams 
               497.8 
               496.8 
               501.3 
               Total mass of club 
             
             
                 
                 
                 
                 
                 
               including head, shaft and 
             
             
                 
                 
                 
                 
                 
               grip 
             
             
               Length 
               Cm 
               34 
               34 
               34 
               Nominal length of club 
             
             
               Lie Angle 
               Degrees 
               70 
               70 
               72 
             
             
               Xcg 
               Cm 
               −66.149 
               −66.010 
               −64.915 
               Shaft Axis cg position 
             
             
               Ycg 
               Cm 
               0.150 
               0.824 
               2.224 
               CG offset normal to the 
             
             
                 
                 
                 
                 
                 
               swing plane 
             
             
               Zcg 
               Cm 
               −1.797 
               −0.946 
               −0.695 
               Target Direction cg 
             
             
                 
                 
                 
                 
                 
               position 
             
             
               Sx 
               gm cm 
               — 
               — 
               — 
               Torsional Static Imbalance 
             
             
               Sy 
               gm cm 
               −894.5 
               −470.0 
               −348.4 
               Swing Static Imbalance 
             
             
               Sz 
               gm cm 
               11332.5 
               11600.8 
               11116.3 
               Toe Down Static 
             
             
                 
                 
                 
                 
                 
               Imbalance 
             
             
               Ixx 
               Gm cm 2   
               4622 
               3499 
               4293 
               Torsional Inertia 
             
             
               Iyy 
               Gm cm 2   
               456130 
               470200 
               462440 
               Swing Inertia 
             
             
               Izz 
               Gm cm 2   
               454990 
               472810 
               465980 
               Toe Down Inertia 
             
             
               Ixy 
               Gm cm 2   
               1975 
               9235 
               23639 
               Torsion/Toe Down Inertia 
             
             
                 
                 
                 
                 
                 
               Coupling 
             
             
               Ixz 
               Gm cm 2   
               −17065 
               −9471 
               −7275 
               Torsion/Swing Inertia 
             
             
                 
                 
                 
                 
                 
               Coupling 
             
             
               Iyz 
               Gm cm 2   
               130 
               223 
               653 
               Swing/Toe Down Inertia 
             
             
                 
                 
                 
                 
                 
               Coupling 
             
             
                 
             
          
         
       
     
   
   In Table One, a putter  100  (conventional length) of the present invention is compared to two different ODYSSEY®WHITE HOT® putters. Xcg, Ycg and Zcg reference the location of the center of gravity of the putters. The static imbalance is a measure of the distance (parallel to the ground) of the center of gravity of the putter  100  from the position of the golfer&#39;s hands on the grip  104  multiplied by the mass of the putter. One component of the static imbalance is the swing static imbalance Sy, which is the product of the putter mass and the offset distance of the center of gravity of the club head  20  behind the golfer&#39;s hands in the target direction. Swing static imbalance results in a torque at the hands that tends to swing the putter for a putter held motionless in the address position under the acceleration of gravity. The putter  100  has a much larger (almost twice as much) swing static imbalance, Sy, then conventional putters. 
   The location of the center of gravity of the putter  100  is measured using the reference frame through the straight portion of the shaft  102 . The Xcg location is measured from the butt end of the shaft  102 . As shown in  FIGS. 18-21 , the center of gravity of the putter  100  is located above the club head  20  and rearward from the face portion  24 . As shown in Table One, the Zcg location of the putter  100  is much further rearward than the conventional putters, 1.797 cm for the putter  100  as compared to 0.946 cm and 0.695 cm for the conventional putters. It is believed that this rearward position of the center of gravity allows for the putter  100  to have a much larger absolute product of inertia, Ixz ( the torsion swing inertia) than the conventional putters, and a much smaller absolute product of inertia, Ixy (the torsion/toe down inertia) than the conventional putters. The torsion swing product of inertia couples angular accelerations about the shaft axis and the swing axis. As a result of this coupling a torque about a single axis will result in angular accelerations and velocities about both axes. Of, conversely, motion about two axes can be affected by a single torque. These club rotations in turn effect the putting of a golf ball. A more detailed discussion is found in Beer, F. P., Johnston, E. R. Jr.,  Vector Mechanics for Engineers  5 th Edition,  McGraw Hill, pp. 890-910, 1988, which is hereby incorporated by reference in its entirety. 
   From the foregoing it is believed that those skilled in the pertinent art will recognize the meritorious advancement of this invention and will readily understand that while the present invention has been described in association with a preferred embodiment thereof, and other embodiments illustrated in the accompanying drawings, numerous changes, modifications and substitutions of equivalents may be made therein without departing from the spirit and scope of this invention which is intended to be unlimited by the foregoing except as may appear in the following appended claims. Therefore, the embodiments of the invention in which an exclusive property or privilege is claimed are defined in the following appended claims.