Racket

Abstract

A racket 2 includes a frame 4, a grip 6, a grommet 10, and a string 12. The frame 4 includes a head 14, a first throat 16a, a second throat 16b, and a shaft 18. A maximum value of a thickness of the frame 4 is less than 26.0 mm. The racket 2 has an in-plane stiffness index Gi of greater than or equal to 5000 and less than or equal to 8000. The in-plane stiffness index Gi is a product of a top pressure stiffness value Git (kgf/cm) and a side pressure stiffness value Gis (kgf/cm). The racket 2 has an out-of-plane stiffness index Go of greater than or equal to 45000 and less than or equal to 60000. The out-of-plane stiffness index Go is a product of a throat stiffness value Gos (kgf/cm) and a ball-hitting face stiffness value Goh (kgf/cm).

What is claimed is: 
     
         1 . A racket comprising:
 a frame including a head; and   a string that is stretched on the head and that forms a ball-hitting face, wherein:   a maximum value of a thickness of the frame is less than 26.0 mm;   an in-plane stiffness index Gi that is a product of a top pressure stiffness value Git (kgf/cm) and a side pressure stiffness value Gis (kgf/cm) is greater than or equal to 5000 and less than or equal to 8000; and   an out-of-plane stiffness index Go that is a product of a throat stiffness value Gos (kgf/cm) and a ball-hitting face stiffness value Goh (kgf/cm) is greater than or equal to 45000 and less than or equal to 60000.   
     
     
         2 . The racket according to  claim 1 , wherein:
 the frame includes a pair of throats that are continuous with the head and a shaft that is continuous with the throats;   the head has a constant thickness T 1  from a top of the head to joints where the head is joined to the respective throats;   the throats have a constant thickness T 2 ;   the shaft has a constant thickness T 3 ; and   the thickness T 2  and the thickness T 3  are each equal to the thickness T 1 .   
     
     
         3 . The racket according to  claim 1 , wherein
 a ratio (Git/Gis) of the top pressure stiffness value Git to the side pressure stiffness value Gis is greater than or equal to 1.0.   
     
     
         4 . The racket according to  claim 1 , wherein:
 the frame includes a damper; and   a vibration damping rate of the racket in an out-of-plane direction thereof is greater than or equal to 0.5%.