Golf Club Head and Method of Varying Moment of Inertia of Same

Abstract

Methods of optimizing mass characteristics of golf club heads, particularly moment of inertia and the position of center of gravity, and a golf club head with an optimized moment of inertia are disclosed. In one embodiment of the invention, the moment of inertia of the club head is controlled by allocating the mass of the club head relative to the location of a centroid radius of the sole. In another embodiment of the present invention, a sole is modeled on two-dimensional matrices to determine the change in moment of inertia due to shifts in mass concentration around the sole. In another embodiment of the present invention, a sole is modeled on two-dimensional matrices to determine the shift in position of the center of gravity of the sole due to shifts in mass concentration around the sole.

1 . A golf club head comprising a face, a crown, a skirt, and a sole,
 wherein the sole comprises at least a first weight located radially outside of a centroid radius of the sole, and wherein said first weight is denser or thicker than the rest of the sole so that the moment of inertia of the club head is higher than a baseline moment of inertia where the sole has a uniform mass, and   wherein the centroid radius is calculated from a predetermined reference axis.   
     
     
         2 . The golf club head of  claim 1 , wherein the first weight has an arc-like shape that is similar to a rear contour of the club head, and the predetermined reference axis comprises a vertical axis extending through a center of gravity of the club head with the sole with uniform mass. 
     
     
         3 . The golf club head of  claim 1 , wherein at least a portion of the sole located inside the centroid radius is composed of lightweight materials. 
     
     
         4 . The golf club head of  claim 1 , wherein the weight of has an arc-like shape that is similar to the contour of the rear-toe region of the club head, and the predetermined reference axis is a vertical axis going through a hosel. 
     
     
         5 . The golf club head of  claim 3 , wherein said portion of the sole located inside the centroid radius is composed of titanium. 
     
     
         6 . A method for increasing the moment of inertia of a golf club head, comprising the steps of (a) determining a centroid radius for a sole of the golf club head; and (b) reallocating a portion of the mass of the golf club head to a location radially outside of the centroid radius. 
     
     
         7 . The method of  claim 6 , wherein in step (b), a portion of the sole is reallocated to said location. 
     
     
         8 . The method of  claim 6 , wherein step (a) comprises the steps of
 (i) selecting a reference axis;   (ii) determining a baseline moment of inertia of the sole relative to said reference axis;   (iii) reallocating a portion of the mass of the sole radially outward from a designated location on the sole through which an axis of rotation runs;   (iv) determining a moment of inertia of the sole of step (iii);   (v) repeating steps (iii)-(iv) for a predetermined number of iterations, wherein the radial distance of the reallocated portion of mass from the center of gravity changes with each iteration; and   (vi) selecting the centroid radius at the radial location where the moment of inertia of step (iii) changes from being less than the baseline moment of inertia to being greater than the baseline moment of inertia.   
     
     
         9 . The method of  claim 6 , wherein the calculations are performed on two-dimensional matrices. 
     
     
         10 . A method of determining the center of gravity of a sole of a golf club head comprising the steps of
 (i) dividing the sole into portions of equal size;   (ii) assigning each portion a value in the x, y and z directions corresponding to the position of each portion relative to the entire sole;   (iii) assigning each portion a mass;   (iv) finding the products of the mass of each portion and its corresponding x value, finding the sum of said products, and dividing the sum by the total mass of the sole to find the center of gravity in the x-direction;   (v) repeating step (iv), substituting the x-value for the y-value to find the center of gravity in the y-direction; and   (vi) repeating step (iv), substituting the x-value for the z-value to find the center of gravity in the z-direction.   
     
     
         11 . A method of optimizing the mass characteristics of a golf club head comprising the steps of
 (i) finding the moments of inertia of a sole according to the method of  claim 8 ;   (ii) finding the center of gravity in the vertical z-direction according to the method of  claim 10  for each distribution of mass around the sole for which moment of inertia was calculated in step (i); and   (iii) plotting the change in center of gravity in the vertical z-direction and the change in moment of inertia against the average value of distance from a designated axis of rotation of each portion of the sole that comprised the area in which mass was concentrated   
     
     
         12 . The golf club head of  claim 3 , wherein said portion of the sole located inside the centroid radius is composed of composite. 
     
     
         13 . The golf club head of  claim 1 , further comprising at least two weights located outside of the centroid radius of the sole. 
     
     
         14 . The golf club head of  claim 1 , further comprising at least three weights located outside of the centroid radius of the sole. 
     
     
         15 . The golf club head of  claim 1 , wherein said weight is composed of tungsten. 
     
     
         16 . A golf club head comprising a face, a crown and a sole, the sole comprising:
 at least two points, each point having an area of  4 . 5  mm by  4 . 5  mm and each point having a point-mass;   at least a first zone having at least one point with a first point-mass; and   at least a second zone having at least one point with a second point-mass, wherein the first point-mass is at least two times the second point-mass.   
     
     
         17 . The golf club head of  claim 16  wherein the first zone has an arc-like shape that is similar to the contour of the rear-toe region of the club head. 
     
     
         18 . The golf club head of  claim 16 , wherein the first zone has an arc-like shape that is located radially outside of a centroid radius of the sole, wherein the centroid radius is calculated from a pre-determined reference axis. 
     
     
         19 . The golf club head of  claim 16 , wherein the first zone is a weight that is denser or thicker than the remainder of the sole. 
     
     
         20 . The golf club head of  claim 16 , wherein the first point-mass is at least  2 . 3  times the second point-mass.