String set, main string, and cross string

Abstract

A string set is a string set strung on a racket as a main string and a cross string, and is configured to include a first string strung as any one of the main string and the cross string and has a small friction force and a small diameter and a second string strung as another one of the main string and the cross string and has a larger friction force and a larger diameter than the diameter and the surface friction force of the first string. This distributes functions to the first string and the second string to obtain both the hairpin performance, which is improved by the large surface friction force and outer diameter of the string, and the cut smash performance, which is improved by the small surface friction force and outer diameter of the string, at the same time.

1 . A string set strung on a racket as a main string and a cross string, the string set comprising:
 a first string strung as any one of the main string and the cross string, the first string having a small surface friction force and a small diameter, and   a second string strung as another one of the main string and the cross string, the second string having a larger surface friction force and a larger diameter than the surface friction force and the diameter of the first string.   
     
     
         2 . The string set according to  claim 1 , wherein
 the first string is the cross string, and   the second string is the main string.   
     
     
         3 . The string set according to  claim 1 , wherein
 a friction force at which the second string moves with respect to the first string is 2.2 [N] or less.   
     
     
         4 . The string set according to  claim 1 , wherein
 the first string has an outer diameter that is 94% or less of an outer diameter of the second string.   
     
     
         5 . The string set according to  claim 1 , wherein
 the first string and the second string form a face of the racket, the face having a surface friction force of 9 [N] or more.   
     
     
         6 . The string set according to  claim 5 , wherein
 the second string includes a coating film, and   at least a superficial layer of the coating film of the second string has a property to increase a grip force corresponding to an increase in film thickness.   
     
     
         7 . The string set according to  claim 6 , wherein
 the at least the superficial layer of the coating film of the second string is formed of polyurethane or rubber.   
     
     
         8 . A cross string strung on a racket while intersecting with a main string, wherein
 the cross string has a smaller surface friction force and a smaller diameter than a surface friction force and a diameter of the main string.   
     
     
         9 . A main string strung on a racket while intersecting with a cross string, wherein
 the main string has a larger surface friction force and a larger diameter than a surface friction force and a diameter of the cross string.