Abstract:
Disclosed is a golf ball including a center portion, at least two intermediate tiers sequentially surrounding the center portion, and an outer tier surrounding the intermediate tiers, which comprises: said outer tier having a thickness in a range of 0.8˜1.4 mm, and an a hardness (Shore D) in a range of 40˜50; among the intermediate tiers, said first intermediate tier formed just below the outer tier, having a thickness in a range of 1.0˜2.0 mm and a hardness (Shore D) in a range of 50˜65; each intermediate tier formed just below the first intermediate tier having a thickness in a range of 1.3˜1.5 mm, and a hardness (Shore D) in range of 30˜70; the radius of the center portion is in a range of 5˜18 mm, and a hardness (Shore D) in a range of 30˜70; and a moment of inertia value of the golf ball is less than 83 g·cm 2 . According to the golf ball of the present invention, an iron spin force is excellent as compared to a conventional golf ball for a match, and the flying distance is almost same.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority to Korean Application No. 10-2010-0053604, filed on Jun. 7, 2010, in the Korean Intellectual Property Office, which is incorporated herein by reference in its entirety as if set forth in full. 
       BACKGROUND 
       [0002]    Various embodiments relate to a golf ball, and in particular to a golf ball which is easy to land on a green with the aid of a better spin in an approach shot within 100 yards, and has less elasticity due to lesser spin in a driver shot which serves to increase a run, thus increasing the total flying distance. 
         [0003]    According to a new regulation, R&amp;A of Great Britain and USGA of the USA have prohibited the use of a conventional square type of groove (club face groove) of irons (fifth iron to wedge) of equal to or more than 25 degrees from Jan. 1, 2010. The value obtained by dividing the total cross sectional area of the groove with the pitch of the groove (Pitch=width+interval) is limited to 0.003 square inches (0.0762 square mm), and the sharpness of the groove edge of the groove is limited to 0.010 inches (0.254 mm). 
         [0004]    A U-shaped groove club, compared to a conventional V-shaped groove club, serves to significantly increase spin in a rough, so the difference of spin between a fairway shot and a rough shot is almost similar, thus decreasing accuracy, which has been shown by many researches. 
         [0005]    The purpose of the regulation regarding the club groove can be seen as to increase the benefits of accurate shots, especially due to high technique required in a rough shot, by increasing the difference of the spin between a fairway shot and a rough shot. 
         [0006]    The main focus of the changed regulation regarding the club is to make a spin more difficult, so the development of a ball with better spin is urgently needed. Currently available products for professional golfers have a cover having a hardness of above 50 (units: Shore D). When a golf ball with such hardness is struck with an iron satisfying the changed regulations, it is hard to give the ball enough spin, so it is difficult to hit the ball to a desired position. 
         [0007]    It is possible to produce a desired spin by using a golf ball having a cover of a lower hardness material. But in such a case, a spin can be increased properly, but over-spin occurs with impact by a driver and the forward flying force is dispersed by a reverse rotation force, so generation of over-lifting force causes an increase in elasticity, which leads to an increase of an angle of falling, which decreases a run, and a flying distance is significantly decreased. 
         [0008]    Finally, it is urgently needed to develop a new golf ball which serves to increase a flying distance when impacted by a driver while it is easy to make a spin when impacted by an iron. 
       SUMMARY 
       [0009]    Accordingly, it is an object of the present invention to provide a golf ball which serves to satisfy the above demands and is easy to fly to a green with the aid of a good spin at an approach shot by providing a smooth cover (outer layer). At the same time, spins can be reduced at a driver impact by limiting the value of a moment of inertia, and an elasticity can be reduced since an over lifting force is inhibited, and an angle of falling to the ground can be decreased, thus enhancing a run, which consequently results in increasing a total flying distance. 
         [0010]    To achieve the above objects, there is provided a golf ball including a center portion, at least two intermediate tiers sequentially surrounding the center portion, and an outer tier surrounding the intermediate tiers, comprising the outer tier having a thickness in a range of 0.8˜1.4 mm, and a hardness (Shore D) in a range of 40˜50; a first intermediate tier formed just below the outer tier among the intermediate tier having a thickness in a range of 1.0˜2.0 mm and a hardness (Shore D) in a range of 50˜65; each intermediate tier formed just below the first intermediate tier having a thickness in a range of 1.3˜1.5 mm, and a hardness (Shore D) in range of 30˜70; the length of a radius of the center portion is in a range of 5-18 mm, and a hardness (Shore D) in a range of 30˜70; and a moment of inertia value of the golf ball is less than 83 g·cm 2  value. 
         [0011]    Meanwhile, the outer tier is made of an ionomer resin, and the ionomer resin is made by neutralizing mono-olefin containing at least a part of unsaturated carbonic acid with the number of 3˜8 carbon atoms and the ester of carbonic acid with a 1- or 2-metal. 
         [0012]    Meanwhile, the outer tier is a polyurethane containing at least one among an ester type polyurethane, ether type polyurethane or ether ester copolymer type polyurethane. It is formed of a poly urethane elastomer made by polymerizing polyol, disocianate, crosslinker, etc. or is formed of a 2-liquid type polyurethane mixed in the course of forming polyol and pole isocianate. 
         [0013]    In addition, the first intermediate tier is formed of an ionomer resin, the ionomer resin being made by neutralizing mono-olefin containing at least a part of unsaturated carbonic acid with the number of 3˜8 carbon atoms and the ester of carbonic acid with a 1- or 2-metal. 
         [0014]    In the golf ball according to the present invention, a spin force by an iron is excellent as compared to a conventional golf ball used in competition, and a driver flying distance is almost the same as a conventional golf ball used in competition. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention. 
           [0016]      FIG. 1  is a schematic cross sectional view of a golf ball according to an embodiment of the present invention; and 
           [0017]      FIG. 2  is a schematic cross sectional view of a golf ball according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0018]    The present invention is basically characterized in that when assuming the center portion of the golf ball as a first tier, the entire construction is formed of four tiers (called a 4-piece ball) or five or more tiers, thus forming a multi-tier golf ball. Various moment of inertia values are obtained by adjusting a thickness and density of each tier, and a spin degree and a flying distance are measured and analyzed using a swing robot and a flying performance measurement device, thus developing a golf ball which satisfies a spin degree and a flying distance. 
         [0019]    Through the above experiments, the value of the moment of inertia of a golf ball needed to be less than 83 g·cm 2 , and optimum conditions on the thickness and hardness of the outer tier, the first intermediate tier and second intermediate tier and the following tiers are found. When the following conditions are satisfied, the moment of inertia value of a golf ball is less than 83 g·cm 2  while obtaining a desired spin amount. 
         [0020]    A golf ball according to the present invention is characterized in that the thickness of the outer tier (cover of outer-most side) is 0.8-1.4 mm, and the hardness (Shore D) is 40˜50, and the thickness of the first intermediate tier (second tier from the outer most tier) is 1.0˜3.0 mm, and the hardness (Shore D) is 50˜65, and the thickness of each tier from the second intermediate tier (third tier from outer most tier) is 1.3˜15 mm, and the hardness (Shore D) is 30˜70. The length of the radius of the center is 5-18 mm, and the hardness (Shore D) is 30˜70. 
         [0021]    A golf ball according to the present invention is characterized in having the moment of inertia value of less than 83 g·cm 2 . 
         [0022]    When the thickness of the outer tier is less than 0.8 mm, the difference of the flying distance between when a ball is hit on a portion with a dimple and the portion without a dimple is large. When the thickness of the outer tier is more than 1.4 mm, the loss of the flying distance increases greatly and is undesirable. 
         [0023]    When the cover hardness (Shore D) of the outer tier is more than 50, the spin generation force of an iron decreases and might result in failing to achieve the objective of the present invention. When the cover hardness is less than 40, the flying distance significantly decreases, which keep consumers from selecting the product. 
         [0024]    When the thickness of the first intermediate tier is less than 1.0 mm, the flying distance is decreased, and when above 3.0 mm, the impact does not feel good. When the hardness (Shore D) of the first intermediate tier is less than 50, the flying distance decreases, and when more than 65, the impact feels bad. 
         [0025]    It is preferred that the thickness of each tier from the second intermediate tier is in a range of 1.3˜15 mm, and it is determined considering the thicknesses of the other tiers, the radius of the center portion, and the entire diameter of the golf ball. The radius of the center portion is determined to be in a range of 5-18 mm, considering the thicknesses of the other tiers and the entire diameter of the golf ball. 
         [0026]    A golf ball according to the present invention, in the case of a four-piece golf ball, the thicknesses of the outer tier and the first intermediate tier and the hardness are determined to meet the above conditions. The thickness of the second intermediate tier is in a range of 1.3˜15 mm, and the radius of the center portion is in a range of 5˜18 mm. The thickness of the second intermediate tier and the size of the center portion are determined considering the entire diameter of the golf ball. 
         [0027]    When the thickness of the second intermediate tier becomes thicker, the radius of the center portion becomes relatively shorter, so the diameter of the golf ball can be in the desired range. The diameter of the golf ball used in competition is regulated to be longer than 42.67 mm. However, since having shorter diameters in most golf balls provide advantageous flying distances, it is preferred that most golf balls are slightly longer than 42.6 mm. The diameters of golf balls according to the first and second embodiments of the present invention are 42.7 mm, respectively. 
         [0028]    In the case of a five-piece golf ball, it is constituted to have the thickness and hardness of the outer tier and the first intermediate tier as described above, and the thicknesses of the second intermediate tier and the third intermediate tier are determined to be in a range of 1.3˜15 mm, and the length of the radius of the center portion is in a range of 5˜18 mm. The thicknesses of the second and third intermediate tiers and the size of the center portion must be properly adjusted to obtain a desired size in the entire diameter of the golf ball. 
         [0029]    In case of the six-piece or seven-piece golf ball, the thicknesses of the outer tier and the first intermediate tier are determined to meet the above conditions, and the thicknesses of the second, third and fourth or fifth intermediate tiers are determined to be in a range of 1.3˜15 mm in consideration of the diameter of the entire golf ball, and the radius of the center portion is in a range of 5˜18 mm. 
         [0030]    In the second and subsequent intermediate tiers, it cannot affect a moment of inertia when the respective thickness is less than 1.3 mm, and when the thickness is above 15 mm, it is impossible to obtain an enough thickness in other tiers in relation with the other tiers. 
         [0031]    In the second and subsequent intermediate tiers and the center part, the flying distance becomes significantly decreased when each tier is less than 30 in its hardness (Shore D), and provides a bad impact feeling when each tier is more than 70 in its hardness, so it is preferred to use the material having a hardness in a range of 30˜70. 
         [0032]      FIG. 1  is a cross sectional view illustrating a golf ball according to a first embodiment of the present invention. 
         [0033]    The golf ball  1  of the first embodiment is a four-piece golf ball. The golf ball  1  is formed of an outer tier  10 , a first intermediate tier  20 , a second intermediate tier  22 , and a center part  30 . 
         [0034]    The outer tier  10  has a thickness of 1.325 mm, and the hardness (Shored D) is 48. According to another embodiment of the present invention, the thickness may be in a range of 0.8-1.4 mm, and the hardness in a range of 40˜50. 
         [0035]    The outer tier  10  is formed of an ionomer resin, and the ionomer resin is made by neutralizing mono-olefin containing at least a part of unsaturated carbonic acid with a number of 3˜8 carbon atoms and an ester of carbonic acid with a 1- or 2-metal. 
         [0036]    According to another embodiment of the present invention, the outer tier is made of polyurethane containing at least one of ester type polyurethane, ether type polyurethane or ether ester copolymer type polyurethane. 
         [0037]    The polyurethane may be formed of polyurethane elastomer made by polymerizing polyol, disocianate, crosslinker, etc. or may be formed of 2-liquid type polyurethane mixed in the course of forming polyol and pole isocianate. 
         [0038]    The first intermediate tier  20  has a thickness of 1.45 mm and a hardness (Shore D) of 45. According to another embodiment of the present invention, the thickness may be in a range of 1.0˜2.0 mm, and the hardness in a range of 50˜65. 
         [0039]    The first intermediate tier  20  is formed of ionomer resin, and the ionomer resin is made by neutralizing mono-olefin with a 1- or 2-metal, the mono-olefin containing at least a part of unsaturated carbonic acid of 3˜8 carbon atoms and an ester of the carbonic acid. 
         [0040]    The second intermediate tier  22  has a thickness of 6.55 mm and hardness of (Shore D) of 45. According to another embodiment of the present invention, the thickness may be in a range of 1.3˜15 mm, and the hardness in a range of 30˜70. 
         [0041]    The radius of the center portion  30  is 12.05 mm, and the hardness (Shore D) is 52. According to another embodiment of the present invention, the thickness may be in a range of 5˜8, and the hardness in a range of 30˜70. 
         [0042]    The detailed materials of the second intermediate tier and the center portion are shown in the following table, provided that the materials may be properly selected depending on the hardness, density, etc. 
         [0043]    The moment of inertia of the golf ball  1  according to an embodiment of the present invention is 83 g·cm 2 , the computation of which will be described later. 
         [0044]      FIG. 2  is a schematic cross sectional view of a golf ball according to a second embodiment of the present invention. 
         [0045]    The golf ball  1   a  of the second embodiment of the present invention is a five-piece golf ball. The golf ball  1   a  is formed of an outer tier  10 , a first intermediate tier  20 , a second intermediate tier  22 , a third intermediate tier  24 , and a center part  30 . The description of each element is the same as or similar to the description of the first embodiment. 
         [0046]    As further embodiments of the present invention, there are third and fourth embodiments which are each five-piece golf balls. Golf balls according to the third and fourth embodiments of the present invention, as compared to the second embodiment, each comprise a five-piece ball as does the second embodiment, but the value of the physical properties of each tier and the center part are different. In case of the third and fourth embodiments, the entire appearance is similar with the second embodiment, so drawings are not separately provided. 
         [0047]    The diameters, weights and hardness of the outer tier, the intermediate tier and the center part of each golf ball according to the first, second, third and fourth embodiments of the present invention are shown in the table below. 
         [0048]    The following table also shows the comparisons between comparisons 1, 2, 3 and 4 and the embodiments of the present invention. 
         [0000]    
       
         
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                   
                   
                 third 
                 second 
                 first 
                   
               
               
                   
                 physical 
                   
                 intermediate 
                 intermediate 
                 intermediate 
               
               
                   
                 property 
                 center 
                 tier 
                 tier 
                 tier 
                 outer tier 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 comparison1 
                 diameter (mm) 
                 40.1 
                   
                   
                   
                 42.75 
               
               
                 (2PC) 
                 weight (g) 
                 38.936 
                   
                   
                   
                 45.508 
               
               
                   
                 hardness 
                 43 
                   
                   
                   
                 48 
               
               
                 comparison2 
                 diameter (mm) 
                 29.8 
                   
                   
                 40.1 
                 42.75 
               
               
                 (3PC) 
                 weight (g) 
                 15.184 
                   
                   
                 38.680 
                 45.452 
               
               
                   
                 hardness 
                 52 
                   
                   
                 43 
                 48 
               
               
                 comparison3 
                 diameter (mm) 
                 29.62 
                   
                   
                 40.1 
                 42.75 
               
               
                 (3PC) 
                 weight (g) 
                 13.037 
                   
                   
                 38.705 
                 45.540 
               
               
                   
                 Hardness 
                 47 
                   
                   
                 45 
                 48 
               
               
                 first 
                 diameter (mm) 
                 24.1 
                   
                 37.2 
                 40.1 
                 42.75 
               
               
                 embodiment 
                 weight (g) 
                 7.965 
                   
                 32.412 
                 38.937 
                 45.621 
               
               
                 (4PC) 
                 Hardness 
                 52 
                   
                 45 
                 45 
                 48 
               
               
                 comparison4 
                 diameter (mm) 
                 29.55 
                   
                 37.1 
                 40.1 
                 42.75 
               
               
                 (4PC) 
                 weight (g) 
                 12.945 
                   
                 32.072 
                 38.951 
                 45.699 
               
               
                   
                 Hardness 
                 47 
                   
                 50 
                 45 
                 48 
               
               
                 second 
                 diameter (mm) 
                 29.9 
                 34.1 
                 37.1 
                 40.1 
                 42.75 
               
               
                 embodiment 
                 weight (g) 
                 15.295 
                 24.952 
                 32.070 
                 38.868 
                 45.604 
               
               
                 (5PC) 
                 Hardness 
                 52 
                 48 
                 43 
                 45 
                 48 
               
               
                 comparison5 
                 diameter (mm) 
                 29.4 
                 34.2 
                 37.2 
                 40.1 
                 42.75 
               
               
                 (5PC) 
                 weight (g) 
                 12.564 
                 23.433 
                 32.247 
                 38.997 
                 45.746 
               
               
                   
                 Hardness 
                 55 
                 43 
                 49 
                 45 
                 48 
               
               
                 comparison6 
                 diameter (mm) 
                 29.4 
                 35.2 
                 37 
                 40.1 
                 42.75 
               
               
                 (5PC) 
                 weight (g) 
                 12.664 
                 23.851 
                 29.461 
                 38.448 
                 45.264 
               
               
                   
                 Hardness 
                 55 
                 44 
                 46 
                 44 
                 48 
               
               
                 comparison7 
                 diameter (mm) 
                 29.9 
                 34.1 
                 37.1 
                 40.1 
                 42.75 
               
               
                 (5PC) 
                 weight (g) 
                 15.241 
                 22.900 
                 31.753 
                 38.959 
                 45.516 
               
               
                   
                 Hardness 
                 49 
                 43 
                 45 
                 45 
                 48 
               
               
                 third 
                 diameter (mm) 
                 29.9 
                 34 
                 37 
                 40.1 
                 42.75 
               
               
                 embodiment 
                 weight (g) 
                 15.235 
                 23.611 
                 31.931 
                 38.762 
                 45.521 
               
               
                 (5PC) 
                 Hardness 
                 49 
                 42 
                 48 
                 45 
                 48 
               
               
                 fourth 
                 diameter (mm) 
                 29.9 
                 34 
                 37 
                 40.1 
                 42.75 
               
               
                 embodiment 
                 weight (g) 
                 15.257 
                 25.435 
                 31.935 
                 38.770 
                 45.503 
               
               
                 (5PC) 
                 Hardness 
                 49 
                 50 
                 40 
                 45 
                 48 
               
               
                   
               
             
          
         
       
     
         [0049]    The following table shows the specific mixing ratios of the first embodiment and the first to fourth comparisons. 
         [0000]    
       
         
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                   
                   
                   
                   
                 First 
                   
               
               
                   
                   
                 comparison1 
                 comparison2 
                 comparison3 
                 embodiment 
                 comparison4 
               
               
                   
                 Mixed chemicals 
                 2PC 
                 3PC 
                 3PC 
                 4PC 
                 4PC 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 center 
                 cis-1,4-poly butadiene 
                 100 
                 100 
                   
                 100 
                   
               
               
                   
                 rubber 
               
               
                   
                 2,2′-methylenebis(4-ethyl- 
                 0.5 
                 0.5 
                   
                 0.5 
               
               
                   
                 6-tertiarybutyl phenol) 
               
               
                   
                 zinc oxide 
                 16.6 
                 7 
                   
                 7 
               
               
                   
                 Sub-creamic acid zinc 
                 30 
                 31 
                   
                 31 
               
               
                   
                 dicumyl peroxide (40%) 
                 3 
                 3 
                   
                 3 
               
               
                   
                 surlyn HPF2000(product 
                   
                   
                 100 
                   
                 100 
               
               
                   
                 name of ionomer resin) 
               
               
                 second 
                 cis-1.4-poly butadiene 
                   
                 100 
                 100 
                 100 
                 100 
               
               
                 intermediate 
                 rubber 
               
               
                 tier 
                 2,2′-methylenebis(4-ethyl- 
                   
                 0.5 
                 0.5 
                 0.5 
                 0.5 
               
               
                   
                 6-tertiarybutyl phenol) 
               
               
                   
                 zinc oxide 
                   
                 22.8 
                 38.9 
                 29.8 
                 67.4 
               
               
                   
                 Sub-creamic acid zinc 
                   
                 30 
                 30 
                 30 
                 30 
               
               
                   
                 dicumyl peroxide (40%) 
                   
                 3 
                 3 
                 3 
                 3 
               
               
                 first 
                 surlyn HPF1000(product 
                   
                   
                   
                 100 
                 100 
               
               
                 intermediate 
                 name of ionomer resin) 
               
               
                 tier 
                 zinc oxide 
                   
                   
                   
                 5 
                 5 
               
               
                 outer 
                 surlyn #8320(product name 
                 73 
                 73 
                 73 
                 73 
                 73 
               
               
                 tier 
                 of ionomer resin) 
               
               
                   
                 surlyn #9910(product name 
                 27 
                 27 
                 27 
                 27 
                 27 
               
               
                   
                 of ionomer resin) 
               
               
                   
                 titanium oxide(Rutile type) 
                 2 
                 2 
                 2 
                 2 
                 2 
               
               
                   
                 zirconium oxide 
                 3 
                 3 
                 3 
                 3 
                 3 
               
               
                   
               
             
          
         
       
     
         [0050]    The following shows the mixing ratios of the second to forth embodiments and the fifth to seventh comparisons. 
         [0000]    
       
         
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                   
                 secod 
                 Fifth 
                 Sixth 
                 Seventh 
                 third 
                 fourth 
               
               
                   
                   
                 embodiment 
                 comparison 
                 comparison 
                 comparison 
                 embodiment 
                 embodiment 
               
               
                   
                 Mixed chemicals 
                 5PC 
                 5PC 
                 5PC 
                 5PC 
                 5PC 
                 5PC 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 center 
                 cis-1.4-poly butadiene 
                 100 
                   
                   
                 100 
                 100 
                 100 
               
               
                   
                 rubber 
               
               
                   
                 2,2′-methylenebis(4-ethyl- 
                 0.5 
                   
                   
                 0.5 
                 0.5 
                 0.5 
               
               
                   
                 6-tertiarybutyl phenol) 
               
               
                   
                 zinc oxide 
                 7 
                   
                   
                 7 
                 7 
                 7 
               
               
                   
                 Sub-creamic acid zinc 
                 31 
                   
                   
                 31 
                 31 
                 31 
               
               
                   
                 dicumyl peroxide (40%) 
                 3 
                   
                   
                 3 
                 3 
                 3 
               
               
                   
                 surlyn HPF{circumflex over ( )}OO(product 
                   
                 100 
                 100 
                 100 
               
               
                   
                 name of ionomer resin) 
               
               
                 Third 
                 cis-1.4-poly butadiene 
                 100 
                 100 
                 100 
                 100 
                 100 
                 100 
               
               
                 intermediate 
                 rubber 
               
               
                 tier 
                 2,2′-methylenebis(4-ethyl- 
                 0.5 
                 0.5 
                 0.5 
                 0.5 
                 0.5 
                 0.5 
               
               
                   
                 6-tertiarybutyl phenol) 
               
               
                   
                 zinc oxide 
                 63.2 
                 67.8 
                 27.4 
                 14.2 
                 31.4 
                 85.6 
               
               
                   
                 Sub-creamic acid zinc 
                 30 
                 30 
                 30 
                 30 
                 30 
                 30 
               
               
                   
                 dicumyl peroxide (40%) 
                 3 
                 3 
                 3 
                 3 
                 3 
                 3 
               
               
                 second 
                 cis-1.4-poly butadiene 
                 100 
                 100 
                 100 
                 100 
                 100 
                 100 
               
               
                 intermediate 
                 rubber 
               
               
                 tier 
                 2,2′-methylenebis(4-ethyl- 
                 0.5 
                 0.5 
                 0.5 
                 0.5 
                 0.5 
                 0.5 
               
               
                   
                 6-tertiarybutyl phenol) 
               
               
                   
                 zinc oxide 
                 19.1 
                 69.2 
                 43.2 
                 75.8 
                 53.9 
                 0 
               
               
                   
                 Sub-creamic acid zinc 
                 30 
                 30 
                 30 
                 30 
                 30 
                 30 
               
               
                   
                 dicumyl peroxide (40%) 
                 3 
                 3 
                 3 
                 3 
                 3 
                 3 
               
               
                 first 
                 cis-1.4-poly butadiene 
                   
                   
                 100 
               
               
                 intermediate 
                 rubber 
               
               
                 tier 
                 2,2′-methylenebis (4-chil- 
                   
                   
                 0.5 
               
               
                   
                 6-tertiarybutyl phenol) 
               
               
                   
                 zinc oxide 
                   
                   
                 45 
               
               
                   
                 Sub-creamic acid zinc 
                   
                   
                 30 
               
               
                   
                 dicumyl peroxide (40%) 
                   
                   
                 3 
               
               
                   
                 surlyn HPFIOOO 
                 100 
                 100 
                   
                 100 
                 100 
                 100 
               
               
                   
                 (product name of ionomer 
               
               
                   
                 resin) 
               
               
                   
                 zinc oxide 
                 5 
                 5 
                   
                 5 
                 5 
                 5 
               
               
                 outer 
                 Surlyn #8320 (product 
                 73 
                 73 
                 73 
                 73 
                 73 
                 73 
               
               
                 tier 
                 name of ionomer resin) 
               
               
                   
                 surlyn #9910 
                 27 
                 27 
                 27 
                 27 
                 27 
                 27 
               
               
                   
                 (product name of ionomer 
               
               
                   
                 resin) 
               
               
                   
                 Titanium oxide(Rutile 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
               
               
                   
                 type) 
               
               
                   
                 zirconium oxide 
                 3 
                 3 
                 3 
                 3 
                 3 
                 3 
               
               
                   
               
             
          
         
       
     
         [0051]    The computations for the moment of inertias are derived from the following two articles “Fundamentals of Physics 7/e by David Halliday, 2006, p 302-p 305” and “Physics for Scientists and Engineers with Modern Physics 6/e by Raymond A. Serway, 2004, p 211-p 217”. 
         [0052]    In the common formula, the moment of inertia I of the golf ball of four non-uniform tiers can be computed from the following formula. The radius of each tier from the portion of the outer to the outer side is r i , and the density of each tier is ρ i . 
         [0053]    The moment of inertia (I) is, 
         [0000]    
       
         
           
             
               ∫ 
               
                 
                   r 
                   2 
                 
                  
                 
                    
                   m 
                 
               
             
             = 
             
               
                 
                   8 
                   15 
                 
                  
                 
                   πρ 
                   1 
                 
                  
                 
                   r 
                   1 
                   5 
                 
               
               + 
               
                 
                   8 
                   15 
                 
                  
                 
                   
                     πρ 
                     2 
                   
                    
                   
                     ( 
                     
                       
                         r 
                         2 
                         5 
                       
                       - 
                       
                         r 
                         1 
                         5 
                       
                     
                     ) 
                   
                 
               
               + 
               
                 
                   8 
                   15 
                 
                  
                 
                   
                     πρ 
                     3 
                   
                    
                   
                     ( 
                     
                       
                         r 
                         3 
                         5 
                       
                       - 
                       
                         r 
                         2 
                         5 
                       
                     
                     ) 
                   
                 
               
               + 
               
                 
                   8 
                   15 
                 
                  
                 
                   
                     πρ 
                     4 
                   
                    
                   
                     ( 
                     
                       
                         r 
                         4 
                         5 
                       
                       - 
                       
                         r 
                         3 
                         5 
                       
                     
                     ) 
                   
                 
               
             
           
         
       
     
         [0054]    The moment of inertia values of the first to four embodiments and the comparisons are computed using the above formula. In the following formula, since the moment of inertia value I uses the unit of g·cm 2 , the lengths in the above table is converted into the values by the units of cm. 
         [0000]    
       
         
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                   
                 third 
                 second 
                 first 
                   
                   
               
               
                   
                   
                 intermediate 
                 intermediate 
                 intermediate 
                   
                 Moment 
               
               
                   
                 center 
                 tier 
                 tier 
                 tier 
                 outer tier 
                 of inertia 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 comparison1 
                 Radius (cm) 
                 2.005 
                   
                   
                   
                 2.1375 
                 82.55 
               
               
                   
                 density(g/cm 3 ) 
                 1.153 
                   
                   
                   
                 0.974 
               
               
                   
                 volume 
                 33.762 
                   
                   
                   
                 40.508 
               
               
                   
                 partialvolume 
                 33.762 
                   
                   
                   
                 6.746 
               
               
                   
                 weight 
                 38.936 
                   
                   
                   
                 45.508 
               
               
                   
                 partialweight 
                 38.936 
                   
                   
                   
                 6.572 
               
               
                 comparison2 
                 Radius (cm) 
                 1.49 
                   
                   
                 2.005 
                 2.1375 
                 83.59 
               
               
                   
                 density(g/cm 3 ) 
                 1.096 
                   
                   
                 1.180 
                 1.004 
               
               
                   
                 volume 
                 13.856 
                   
                   
                 33.762 
                 40.508 
               
               
                   
                 partialvolume 
                 13.856 
                   
                   
                 19.906 
                 6.746 
               
               
                   
                 weight 
                 15.184 
                   
                   
                 38.68 
                 45.452 
               
               
                   
                 partialweight 
                 15.184 
                   
                   
                 23.496 
                 6.772 
               
               
                 comparison3 
                 Radius (cm) 
                 1.481 
                   
                   
                 2.005 
                 2.1375 
                 86.12 
               
               
                   
                 density(g/cm 3 ) 
                 0.958 
                   
                   
                 1.273 
                 1.013 
               
               
                   
                 volume 
                 13.607 
                   
                   
                 33.762 
                 40.508 
               
               
                   
                 partialvolume 
                 13.607 
                   
                   
                 20.156 
                 6.746 
               
               
                   
                 weight 
                 13.037 
                   
                   
                 38.705 
                 45.54 
               
               
                   
                 partialweight 
                 13.037 
                   
                   
                 25.668 
                 6.835 
               
               
                 first 
                 Radius (cm) 
                 1.205 
                   
                 1.86 
                 2.005 
                 2.1375 
                 82.36 
               
               
                 embodiment 
                 density(g/cm 3 ) 
                 1.087 
                   
                 1.246 
                 0.958 
                 0.991 
               
               
                   
                 volume 
                 7.329 
                   
                 26.954 
                 33.762 
                 40.508 
               
               
                   
                 partialvolume 
                 7.329 
                   
                 19.625 
                 6.808 
                 6.746 
               
               
                   
                 weight 
                 7.965 
                   
                 32.412 
                 38.937 
                 45.621 
               
               
                   
                 partialweight 
                 7.965 
                   
                 24.447 
                 6.525 
                 6.684 
               
               
                 comparison4 
                 Radius (cm) 
                 1.4775 
                   
                 1.855 
                 2.005 
                 2.1375 
                 85.07 
               
               
                   
                 density(g/cm 3 ) 
                 0.958 
                   
                 1.446 
                 0.979 
                 1.000 
               
               
                   
                 volume 
                 13.510 
                   
                 26.737 
                 33.762 
                 40.508 
               
               
                   
                 partialvolume 
                 13.510 
                   
                 13.227 
                 7.025 
                 6.746 
               
               
                   
                 weight 
                 12.945 
                   
                 32.072 
                 38.951 
                 45.699 
               
               
                   
                 partialweight 
                 12.945 
                   
                 19.127 
                 6.879 
                 6.748 
               
               
                 second 
                 Radius (cm) 
                 1.495 
                 1.705 
                 1.855 
                 2.005 
                 2.1375 
                 82.72 
               
               
                 embodiment 
                 density(g/cm 3 ) 
                 1.093 
                 1.427 
                 1.191 
                 0.968 
                 0.999 
               
               
                   
                 volume 
                 13.996 
                 20.762 
                 26.737 
                 33.762 
                 40.508 
               
               
                   
                 Partialvolume 
                 13.996 
                 6.765 
                 5.976 
                 7.025 
                 6.746 
               
               
                   
                 weight 
                 15.295 
                 24.952 
                 32.070 
                 38.868 
                 45.604 
               
               
                   
                 Partialweight 
                 15.295 
                 9.657 
                 7.118 
                 6.798 
                 6.736 
               
               
                 comparison5 
                 Radius (cm) 
                 1.47 
                 1.71 
                 1.86 
                 2.005 
                 2.1375 
                 85.46 
               
               
                   
                 density(g/cm 3 ) 
                 0.944 
                 1.423 
                 1.467 
                 0.991 
                 1.001 
               
               
                   
                 volume 
                 13.306 
                 20.945 
                 26.954 
                 33.762 
                 40.508 
               
               
                   
                 Partialvolume 
                 13.306 
                 7.639 
                 6.009 
                 6.808 
                 6.746 
               
               
                   
                 weight 
                 12.564 
                 23.433 
                 32.247 
                 38.997 
                 45.746 
               
               
                   
                 Partialweight 
                 12.564 
                 10.869 
                 8.814 
                 6.750 
                 6.749 
               
               
                 comparison6 
                 Radius (cm) 
                 1.47 
                 1.76 
                 1.85 
                 2.005 
                 2.1375 
                 85.86 
               
               
                   
                 density(g/cm 3 ) 
                 0.952 
                 1.174 
                 1.522 
                 1.241 
                 1.010 
               
               
                   
                 volume 
                 13.306 
                 22.836 
                 26.522 
                 33.762 
                 40.508 
               
               
                   
                 Partialvolume 
                 13.306 
                 9.531 
                 3.686 
                 7.240 
                 6.746 
               
               
                   
                 weight 
                 12.664 
                 23.851 
                 29.461 
                 38.448 
                 45.264 
               
               
                   
                 Partialweight 
                 12.664 
                 11.187 
                 5.610 
                 8.987 
                 6.816 
               
               
                 comparison7 
                 Radius (cm) 
                 1.495 
                 1.705 
                 1.855 
                 2.005 
                 2.1375 
                 83.38 
               
               
                   
                 density(g/cm 3 ) 
                 1.089 
                 1.132 
                 1.481 
                 1.026 
                 0.972 
               
               
                   
                 volume 
                 13.996 
                 20.762 
                 26.737 
                 33.762 
                 40.508 
               
               
                   
                 Partialvolume 
                 13.996 
                 6.765 
                 5.976 
                 7.025 
                 6.746 
               
               
                   
                 weight 
                 15.241 
                 22.900 
                 31.753 
                 38.959 
                 45.516 
               
               
                   
                 Partialweight 
                 15.241 
                 7.659 
                 8.853 
                 7.206 
                 6.557 
               
               
                 third 
                 Radius (cm) 
                 1.495 
                 1.7 
                 1.85 
                 2.005 
                 2.1375 
                 82.97 
               
               
                 embodiment 
                 density(g/cm 3 ) 
                 1.089 
                 1.272 
                 1.400 
                 0.943 
                 1.002 
               
               
                   
                 volume 
                 13.996 
                 20.580 
                 26.522 
                 33.762 
                 40.508 
               
               
                   
                 Partialvolume 
                 13.996 
                 6.583 
                 5.942 
                 7.240 
                 6.746 
               
               
                   
                 weight 
                 15.235 
                 23.611 
                 31.931 
                 38.762 
                 45.521 
               
               
                   
                 Partialweight 
                 15.235 
                 8.376 
                 8.320 
                 6.831 
                 6.759 
               
               
                 fourth 
                 Radius (cm) 
                 1.495 
                 1.7 
                 1.85 
                 2.005 
                 2.1375 
                 82.18 
               
               
                 embodiment 
                 density(g/cm 3 ) 
                 1.090 
                 1.546 
                 1.094 
                 0.944 
                 0.998 
               
               
                   
                 volume 
                 13.996 
                 20.580 
                 26.522 
                 33.762 
                 40.508 
               
               
                   
                 Partialvolume 
                 13.996 
                 6.583 
                 5.942 
                 7.240 
                 6.746 
               
               
                   
                 weight 
                 15.257 
                 25.435 
                 31.935 
                 38.770 
                 45.503 
               
               
                   
                 Partialweight 
                 15.257 
                 10.178 
                 6.500 
                 6.835 
                 6.733 
               
               
                   
               
             
          
         
       
     
         [0055]    The following table shows flying performances of the first to fourth embodiments of the present invention and the first to seventh comparisons. The equipment used in the test were the measurement instruments of Iron Byron Robot, Trackman, and the test impacting club was Callaway Driver-‘R’SHAFT-10.5°, and the test place was R&amp;D center of the applicant of the present invention. 
         [0000]    
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Moment of 
                 Spin 
                   
                   
                 Total flying 
               
               
                   
                 inertia 
                 amount 
                 carry 
                 Run 
                 distance 
               
               
                   
                 (g -cm 2 ) 
                 (rpm) 
                 (yd) 
                 (yd) 
                 (yd) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 comparison 1(2PC) 
                 82.55 
                 2219 
                 229.6 
                 34.7 
                 264.3 
               
               
                 comparison2(3PC) 
                 83.59 
                 1964 
                 231.9 
                 37.5 
                 269.4 
               
               
                 comparison3(3PC) 
                 86.12 
                 2486 
                 237.1 
                 31.1 
                 268.2 
               
               
                 First 
                 82.36 
                 2001 
                 234.5 
                 37 
                 271.5 
               
               
                 embodiment(4PC) 
               
               
                 comparison4(4PC) 
                 85.07 
                 2277 
                 238.6 
                 32.4 
                 271 
               
               
                 Second 
                 82.72 
                 1969 
                 234.1 
                 37.3 
                 271.4 
               
               
                 embodiment(5PC) 
               
               
                 comparison5(5PC) 
                 85.46 
                 2267 
                 237.5 
                 33.4 
                 270.9 
               
               
                 comparison6(5PC) 
                 85.86 
                 2646 
                 239.8 
                 28.1 
                 267.9 
               
               
                 comparison7(5PC) 
                 83.38 
                 2058 
                 234.7 
                 36.2 
                 270.9 
               
               
                 Third 
                 82.97 
                 2024 
                 235.9 
                 36.3 
                 272.2 
               
               
                 embodiment(5PC) 
               
               
                 Fourth 
                 82.18 
                 1961 
                 235.7 
                 37.1 
                 272.8 
               
               
                 embodiment(5PC) 
               
               
                   
               
             
          
         
       
     
         [0056]    The following results are obtained from the above tables. 
         [0057]    First, comparing the first to third comparisons (2PC, 3PC and 3PC), the spin amount of the second comparison (3PC) is smallest at 1964 and has the longest flying distance. So, it can be shown that when the value of the moment of inertia is small, and the spin amount is small, the flying distance becomes longer. In the case of 2PC and 3PC, since the cover on the core is respectively formed of one tier, the flying distance becomes shorter as compared to 4PC and 5PC, which is not appropriate for a golf ball of the present invention. 
         [0058]    Second, comparing the first (4PC) and the fourth comparisons (4PC), the spin amount of the first embodiment is small at 2001, and the flying distance is longer by 0.5 yards, which shows the effects of the moment of inertias of the present invention. 
         [0059]    Third, the second to fourth embodiments (all 5PC) have the moment of inertias of less than 83 g·cm 2 , and the fifth to seventh comparisons (all 5PCs) have the moment of inertias of above 83 g·cm 2 , and the average flying distance of the second to fourth embodiments (all 5PCs) were 2.2 yards longer when compared to the average flying distance of the fifth to seventh comparisons (all 5PCs), which prove the moment of inertia effects of the present invention. 
         [0060]    The terminologies used in the detailed descriptions of the present invention are described as follows. 
         [0061]    A cover means an outer tier of a golf ball made of resin. A spin means a rotation of a golf ball. A driver is a type of club. A run mean a distance that a golf ball rolls. A carry means the distance that a golf ball flies. A iron is a type of club. A groove means a groove formed on the head part of a golf club. A wedge is a type of club. Ionomer means a resin containing metallic ions. 
         [0062]    As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described examples are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims.