Baseball

Abstract

A baseball includes an inner core, and an outer layer covering the outer circumferential surface of the inner core. The inner core has a surface hardness of not less than 60 and not more than 80 in Asker C hardness, and has an elastic modulus of not less than 0.6 MPa and not more than 1.0 MPa. In this way, a baseball can be obtained which can achieve a trajectory comparable to that of a ball for hardball after hitting and which can achieve an impact force comparable to a ball for rubber-ball baseball.

1 . A baseball comprising:
 an inner core; and   an outer layer covering an outer circumferential surface of said inner core,   said inner core having a surface hardness of not less than 60 and not more than 80 in Asker C hardness, and having an elastic modulus of not less than 0.6 MPa and not more than 1.0 MPa.   
     
     
         2 . The baseball according to  claim 1 , wherein said inner core has a loss coefficient (tan δ) of not less than 0.15 and not more than 0.31. 
     
     
         3 . The baseball according to  claim 1 , wherein an impact force when said baseball hits against a dummy at a speed of 26.82 m/s is 80 G or smaller. 
     
     
         4 . The baseball according to  claim 1 , wherein a restitution coefficient when said baseball hits against an iron plate at a speed of 26.82 m/s is not less than 0.50 and not more than 0.55. 
     
     
         5 . The baseball according to  claim 1 , wherein a load when compressing an outer diameter of said baseball by 6.35 mm is 16 lbs or more and is less than 30 lbs. 
     
     
         6 . A baseball comprising:
 an inner core;   a thread-wound layer obtained by winding a yarn to cover an outer circumferential surface of said inner core; and   an outer layer covering an outer circumferential surface of said thread-wound layer,   said inner core having a surface hardness of not less than 71 and not more than 75 in Asker C hardness, having an elastic modulus of not less than 0.9 MPa and not more than 1.0 MPa, and having a loss coefficient (tan δ) of not less than 0.25 and not more than 0.27,   said inner core being made of urethane foam,   said inner core having an outer diameter of 70.7 mm, and   said outer layer having an outer diameter of 73.2 mm.