Patent Publication Number: US-2001000507-A1

Title: Ball for baseball

Description:
BACKGROUND OF THE INVENTION  
       1. This invention relates to a ball used in baseball.  
       2. Balls used in pro baseball, high school baseball, etc. are formed, as shown in FIG. 2, by providing a layer  3  of woolen yarn around a rubber core  2  having a baked cork  1  inside and, around the layer  3  an outermost layer  5  of cowhide through a layer  4  comprising cotton yarn.  
       3. With such balls, the cowhide of the outermost layer is liable to be damaged and deformed due to shocks upon batting. Since the cowhide is not uniform in density, strength and restoring force, every time batting is repeated, protrusions or recesses tend to be formed and restoring such protrusions and recesses is difficult. Therefore the life of balls is not so long. Further, the stitched portion of the cowhide is the weakest part in strength. Thus, if a shock upon batting is repeatedly given to this portion, the string may be cut or cowhide therearound may break, thus making the ball unusable.  
       4. Also, into such balls, water such as rainwater tends to infiltrate through the seam of the cowhide. If water infiltrates into the ball, woolen yarn is impregnated with water, thus deteriorating. Thus, shrikage of the ball due to batting occurs. Further, as mentioned above, since water such as rainwater tends to infiltrate into balls through the seam, according to the environment of use, i.e. weather and humidity, moisture enters and exits, so that the weight of the entire ball changes markedly.  
       5. As a solution of this problem, top balls and practice balls having their outermost layers covered with resin are known. A top ball has, as shown in FIG. 3, a baked cork layer  7  provided around a foamed polyurethane core  6 , and a resin elastomer layer  8  provided around the layer  7 . Also, a practice ball is a ball for baseball for practice in the rain, and is provided, as shown in FIG. 4, with a resin elastomer layer  10  on the outer periphery of a core layer  9  of a baked cork.  
       6. Since these balls have a resin elastomer layer on the outermost layer, they have excellent waterproof performance and resistance to deformation due to shocks.  
       7. But the top balls are not accepted for ordinary baseball. Also, the weights of top balls and practice balls are heavy compared with ordinary balls. Thus, these balls give wired feelings to players who use them, so that they are rarely used as an alternative for ordinary balls for baseball. Further, the ratio of the density of the outer peripheral portion of such top balls and practice balls to that of the core is larger than that of ordinary balls. Thus, when a spin is given to the ball, a change such as a curve tends to occur and also the degree of spin is large.  
       8. Also, since such top balls and practice balls are large in the resilience and repulsion of the resin elastomer layer of the outermost layer compared with ordinary balls, flying distance by batting tends to be prolonged and the bound tends to be large.  
       9. Further, if such top balls and practice balls are used with a pitching machine, the resin elastomer layer of their outermost layer is worn due to wear. At this time, urethane wheels of the pitching machine, too, are worn more, so that an unexpected spin is applied to balls themselves and the pitching track tends to be disturbed. Furthermore, as use is repeated, the resin elastomer layer of the outermost layer tends to be heat-deformed or get seized.  
       10. In order to overcome such difference in weight and to make the weights of such top balls and practice balls the same as that of ordinary balls, one may consider reducing the weight of the resin elastomer layer of the outermost layer.  
       11. In this case, the thickness of the outermost layer decreases, so that the strength of the outermost layer decreases correspondingly. Thus, if such balls are used with a pitching machine, as use is repeated, the resin elastomer of the outermost layer may be heat-deformed, seize or break. Thus, waterproofness will be lost.  
       12. An object of this invention is to provide a ball for baseball having properties similar to those of ordinary balls and superior in waterproofness.  
       SUMMARY OF THE INVENTION  
       13. According to this invention, there is provided a ball for baseball comprising a baked cork, a rubber core around the baked cork, a layer of woolen yarn around the rubber core, a layer of cotton yarn around the layer of woolen yarn, and an outermost layer provided around the layer of cotton yarn, the outermost layer being formed from a water-impermeable resin and the total weight of the ball being 142 to 148 g.  
       14. Since it has the above-described structure, the total weight of the ball and the density ratio between the core portion and the outer peripheral portion are equal to conventional balls, and also there will be no difference in change due to spinning of balls. Further, since the outermost layer of the ball is formed from a water-impermeable resin, it has waterproofness and it is possible to suppress deterioration of the ball due to infiltration of water and variation in the weight of the ball.  
       15. Also, this ball can be repeatedly used at least 2500 times in a machine test in which using a two-wheel type pitching machine having two urethane wheels, the ball is thrown at an initial velocity of 130 km/h.  
       16. Further, as a water impermiable resin, it is possible to select one whose degree of taper wear is over 0 mg and 15 mg or under, and the softening temperature is 80 to 300° C.  
       17. If the ball has such structure, damage, breakage, heat deformation, seizure, etc. are less likely to occur in the resin layer of the outermost layer. Thus, it is possible to prolong the life of the ball.  
       18. Other features and objects of the present invention will become apparent from the following description made with reference to the accompanying drawings, in which:  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     19.FIG. 1 is a sectional view showing an embodiment of the ball according to this invention;  
     20.FIG. 2 is a sectional view showing a conventional ball;  
     21.FIG. 3 is a sectional view of a top ball; and  
     22.FIG. 4 is a sectional view of a practice ball.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
     23. Hereinbelow, embodiments of this invention are described with reference to the drawings.  
     24. The ball for baseball according to this invention (hereinafter referred to as a “new ball”) has, as shown in FIG. 1, a layer  13  of woolen yarn provided around a rubber core  12  having a baked cork  11  inside, and a layer  15  as the outermost layer formed of a water-impermeable resin through a layer  14  of cotton yarn.  
     25. The total weight of this new ball is 142 to 148 g. This is the same as the standard for balls normally used in pro baseball and having the outermost layer formed from cowhide (hereinafter referred to as “conventional balls”) as shown in FIG. 2. The rubber core  12  having the baked cork  11 , woolen yarn layer  13  and cotton yarn layer  14  are the same as those of the conventional balls. That is, the rubber core having baked cork, woolen yarn and cotton yarn used in pro baseball are used in the new ball, too. Thus, except for the water-impermeable resin layer  15  of the outermost layer, the new ball is similar to conventional balls. The water-impermeable resin layer  15  of the new ball and the cowhide of the conventional ball have the same weights. The thickness of the water-impermeable resin layer  15  used is limited. Thus, the total weight of the new ball is equal to that of the conventional ball, so that it can be a substitute for the conventional ball. Further, the density ratio between the core portion and the outer peripheral portion of the new ball is equal to that of the conventional ball, so that there will be no difference in change due to spinning of the balls.  
     26. The outermost layer of the new ball comprises the water-impermeable resin layer  15 . Thus, the new ball has waterproofness and can withstand use in the rain. Also, since the density, strength and restoring force are uniform at any part of the water-impermeable resin layer  15 , even after batting is repeated, protrusions and recesses are less likely to be formed.  
     27. It is preferable that this new ball has durability in a machine test. The machine test is a test for measuring how many times the ball can be used repeatedly, by use of a two-wheel type pitching machine having two urethane wheels. It is preferable that the ball can be repeatedly used at least 2500 times when the ball is thrown at an initial velocity of 130 km/h. It is more preferable that it can be repeatedly used at least 3000 times. It is still more preferable that it can be repeatedly used at least 4000 times. The reason why it can be used so many times is because in spite of a limited thickness of the water-impermeable resin layer  15  used in the new ball, it is a material that is less likely to develop damage, breakage, heat deformation, seizure, etc. Thus, the life of the new ball is prolonged dramatically compared with the conventional ball.  
     28. As properties required for the water-impermeable resin forming the water-impermeable resin layer  15 , hardness, breaking strength, taper wear, softening temperature, etc. can be cited.  
     29. Hardness is, in the type A measurement under JIS K 7311, preferably 60 to 100, and more preferably 80 to 100. Under 60, it tends to be deformed by shocks. Over 100, it is too hard and players cannot obtain a feeling similar to the conventional ball.  
     30. Breaking strength is, in the measurement under JIS K 7311, preferably 40 to 100 MPa, and more preferably 50 to 100 MPa. Under 40 MPa, damage may develop or breakage occur in the outermost layer. Although it may exceed 100 MPa, there is no particular need for such high-performance.  
     31. Taper wear is, in the measurement under JIS K 7311, preferably over 0 mg and 15 mg or under, and more preferably 0.1 mg or over and 10 mg or under, and still more preferably 0.1 mg or over and 1 mg or under. Over 15 mg, damage may develop or breakage may occur in the outermost layer.  
     32. Softening temperature is, in the measurement under JIS K 7206, preferably 80 to 300°C., more preferably 90 to 300°C., and still more preferably 105 to 300° C. Under 80° C., seizure tends to occur during the use of a pitching machine. Although it may exceed 300°C., there is no particular need for such high performance.  
     33. If the above properties are met, in normal use of balls in baseball games, batting practices, or practices using pitching machines, the balls will exhibit sufficient strength.  
     34. Among the above properties, if at least the requirements for the taper wear and softening temperature are met, it is preferable because damage, abrasion, breakage, heat deformation, seizure, etc. are prevented even if the water-impermeable resin layer  15  is limited to a predetermined thickness.  
     35. As specific examples of the resin used for the water-impermeable resin layer  15 , thermoplastic resins and thermosetting resins such as polyethylene, polypropylene, polystyrene, polyamide resin, epoxy resin, thermoplastic polyurethane resin, polyester resin, vinyl acetate resin, ABS resin and acrylic resin, and elastomers of thermoplastic resins can be cited. Among them, polyamide resin, epoxy resin, thermoplastic polyurethane resin, polyamide elastomers, thermoplastic polyurethane vulcanized elastomers, etc. are more preferable, and thermoplastic polyurethane resin and thermoplastic polyurethane vulcanized elastomers are particularly preferable.  
     36. Also, as the water-impermeable resin layer  15 , a resin itself may be used or it may be used in the form of synthetic leather or artificial leather.  
     37. Further, as the method of providing the water-impermeable resin layer  15  as the outermost layer, injection molding using a mold, or bonding synthetic leather or artificial leather portions together to cover as the outermost layer and fusing its boundary with the same resin can be adopted. Since the new ball of this invention has no seam, no portion that is weak in strength is formed. Thus there will be no cutting of stitch yarn due to batting or breakage of the outermost layer therearound. Thus, the life as the ball is prolonged.  
     EXAMPLES  
     38. Hereinbelow, this invention is described with reference to examples.  
     Manufacture of Balls  
     Manufacturing Example 1  
     39. Using a rubber core having a baked cork, woolen yarn and cotton yarn used for balls for pro baseball, as shown in FIG. 1, woolen yarn was wound around the rubber core and the cotton yarn was wound therearound. This was placed in a mold, a molten thermoplastic polyurethane resin (3537 made by KURARAY Co.,Ltd.) was poured around it, and was cooled to manufacture balls having the structure as shown in FIG. 1.  
     40. The average weight of 10 balls obtained was 146 grams and all the balls were within the range of 142 to 148 grams.  
     41. The hardness (JIS K 7311 Type A) of the thermoplastic polyurethane resin used was 90, breaking hardness (JIS K 7311) was 57 MPa, taper wear (JIS K 7311) was 1 mg, and the softening temperature (JIS K 7206) was 116° C.  
     Manufacturing Example 2  
     42. Except that a thermoplastic polyurethane resin (Clarino made by KURARAY Co.,Ltd.) was used as the resin for the outermost layer, balls were manufactured in the same manner as in Manufacturing Example 1.  
     43. The average weight of 10 balls obtained was 146 grams and all the balls were within the range of 142 to 148 grams.  
     44. The hardness (JIS K 7311 Type A) of the thermoplastic polyurethane resin used was 90, breaking hardness (JIS K 7311) was 57 MPa, taper wear (JIS K 7311) was 35 mg, and softening temperature (JIS K 7206) was 93° C.  
     Machine Test  
     45. For the balls manufactured in Manufacturing Examples 1 and 2, conventional balls (balls for pro baseball) and top balls, a machine test was conducted.  
     46. For the machine test, using a two-wheel type all-round pitching machine (made by MIDZUNO) having two urethane wheels, under the conditions of throwing balls at an initial velocity of 130 km/h, how many times they could be used was examined. The test was conducted using 10 balls for each.  
     Example 1  
     47. Using balls manufactured in Manufacturing Example 1, the above machine test was conducted. As a result, even after they were repeatedly used 4000 times, for all of the 10 balls, no damage, seizure or breakage was observed on the surface. Also, no deformation of balls was observed. Thus, the test was interrupted after repetitions of 4000 times.  
     Example 2  
     48. Using balls manufactured in Manufacturing Example 2, the above machine test was conducted. As a result, when the number of repetitions reached 3500 times on the average, the surface was damaged and got worn severely to continue repeated use.  
     Comparative Example 1  
     49. Using balls used in pro baseball as conventional balls, the machine test was conducted. As a result, when the number of repetitions reached 1000 times on the average, the cowhide peeled and repeated use became impossible.  
     Comparative Example 2  
     50. Using commercial top balls, the machine test was conducted. As a result, when the number of repetitions reached 2000 times on the average, the cowhide peeled and repeated use became impossible.  
     51. According to this invention, the balls obtained are less likely to develop damage or breakage on the surface, and heat deformation or seizure in the balls themselves, so that it is possible to prolong the life of the balls.  
     52. Also, for the weight of the balls and the density ratio between the core portion and the outer peripheral portion too, there is no difference from conventional balls. Thus no uncomfortable feeling will be given to players using them. Thus, they can be used for practice as a substitute for conventional balls.  
     53. Further, since except for the outermost layer, parts used in pro baseball and high school baseball are used, except for the performance resulting from the outermost layer, one can expect the same performance as conventional balls.  
     54. Furthermore, since they have waterproofness, it is possible to suppress deterioration of the balls and variation in the ball weight due to infiltration of water. Thus, it is possible to use them for practice in the rain.