Racket string and method for producing the same and racket strung with the same

Abstract

A racket string 10 of the present invention includes a synthetic fiber. The cross section is flattened by heating, compressing, and deforming the string after it has been formed, and an indentation is made in any part of the string. The flattened string is wound in a substantially non-twisted state. A method for producing the racket string includes heating the string at a temperature of Tg (° C.) or more and Tm −10 (° C.) or less, where Tg (° C.) represents a glass transition point and Tm (° C.) represents a melting point of a main synthetic fiber constituting the string, compressing and deforming the string between rollers 7 a and 7 b that are arranged with a predetermined clearance therebetween; and then cooling and winding up the string. In a racket strung with the racket string of the present invention, a principal surface of a hitting surface of the racket is formed of the flat surfaces of the string, and the strings include uneven portions due to torsion that are present partially and non-uniformly on the hitting surface of the racket. Thus, the present invention provides a racket string that can make full use of the features of the flat surface, a method for producing the racket string, and a racket strung with the racket string.

1 . A racket string comprising a synthetic fiber,
 wherein a cross section is flattened by heating, compressing, and deforming the string after it has been formed, and an indentation is made in any part of the string, and   wherein the flattened string is wound in a substantially non-twisted state.   
     
     
         2 . The racket string according to  claim 1 , wherein a ratio of a major axis to a minor axis (degree of flatness) of the cross section of the flattened string is 1.1 to 1.8. 
     
     
         3 . The racket string according to  claim 1 , wherein the synthetic fiber is at least one selected from a thermoplastic polyamide and a thermoplastic polyester. 
     
     
         4 . The racket string according to  claim 1 , wherein the string comprises a core yarn composed of a monofilament, sheath yarns wrapped around the core yarn, and a coating resin joining the core yarn and the sheath yarns together, and
 wherein the core yarn mainly is flattened.   
     
     
         5 . The racket string according to  claim 4 , wherein the monofilament of the core yarn is a thermoplastic polyamide. 
     
     
         6 . The racket string according to  claim 1 , wherein the synthetic fiber is a thermoplastic polyester, and the string has a structure that includes a monofilament alone or a monofilament with coating. 
     
     
         7 . A method for producing a racket string comprising a synthetic fiber,
 the method comprising:   heating the string at a temperature of Tg (° C.) or more and Tm −10 (° C.) or less, where Tg (° C.) represents a glass transition point and Tm (° C.) represents a melting point of a main synthetic fiber constituting the string;   compressing and deforming the string between rollers that are arranged with a predetermined clearance therebetween; and then   cooling and winding up the string,   wherein a cross section is flattened by heating, compressing, and deforming the string after it has been formed, and an indentation is made in any part of the string, and   wherein the flattened string is wound in a substantially non-twisted state.   
     
     
         8 . The method according to  claim 7 , wherein the clearance between the rollers for compressing and deforming the string is 0.55 to 0.90 times a string diameter before the compression, so that a minor axis of the flattened string is 0.65 to 0.95 times the string diameter before the compression. 
     
     
         9 . A racket strung with a racket string comprising a synthetic fiber, wherein a cross section is flattened by heating, compressing, and deforming the string after it has been formed, and an indentation is made in any part of the string, and wherein the flattened string is wound in a substantially non-twisted state,
 wherein a principal surface of a hitting surface of the racket is formed of the flat surfaces of the strings, and   the strings include uneven portions due to torsion that are present partially and non-uniformly on the hitting surface of the racket.   
     
     
         10 . The racket according to  claim 9 , wherein the number of the uneven portions due to torsion is 10 to 100. 
     
     
         11 . The method according to  claim 8 , wherein a ratio of a major axis to the minor axis (degree of flatness) of the cross section of the flattened string is 1.1 to 1.8. 
     
     
         12 . The method according to  claim 8 , wherein the synthetic fiber is at least one selected from a thermoplastic polyamide and a thermoplastic polyester. 
     
     
         13 . The method according to  claim 8 , wherein the string comprises a core yarn composed of a monofilament, sheath yarns wrapped around the core yarn, and a coating resin joining the core yarn and the sheath yarns together, and
 wherein the core yarn mainly is flattened.   
     
     
         14 . The method according to  claim 13 , wherein the monofilament of the core yarn is a thermoplastic polyamide. 
     
     
         15 . The method according to  claim 8 , wherein the synthetic fiber is a thermoplastic polyester, and the string has a structure that includes a monofilament alone or a monofilament with coating. 
     
     
         16 . The racket according to  claim 9 , wherein a ratio of a major axis to a minor axis (degree of flatness) of the cross section of the flattened string is 1.1 to 1.8. 
     
     
         17 . The racket according to  claim 9 , wherein the synthetic fiber is at least one selected from a thermoplastic polyamide and a thermoplastic polyester. 
     
     
         18 . The racket according to  claim 9 , wherein the string comprises a core yarn composed of a monofilament, sheath yarns wrapped around the core yarn, and a coating resin joining the core yarn and the sheath yarns together, and
 wherein the core yarn mainly is flattened.   
     
     
         19 . The racket according to  claim 18 , wherein the monofilament of the core yarn is a thermoplastic polyamide. 
     
     
         20 . The racket according to  claim 9 , wherein the synthetic fiber is a thermoplastic polyester, and the string has a structure that includes a monofilament alone or a monofilament with coating.