Double-rope structure

Abstract

Provided is a double rope structure which comprises an inner core and an outer cover. In the double rope structure, the inner core includes high strength and high modulus fibers with a yarn tenacity of 20 cN/dtex or more and yarn elastic modulus of 400 cN/dtex or more, and an inner-and-outer-layer suitability represented by the following formula (1) is 0.70 to 1.20. Formula (1): (a 2 /b 2 )/Vf×100. In the formula (1), a represents the diameter of the outer periphery of the inner core, b represents the diameter of the outer periphery of the outer cover, and Vf represents the volume ratio (%) of the volume of the inner core to the total volume of the inner core and the outer cover.

What is claimed is: 
     
         1 . A double rope structure comprising an inner core and an outer cover, wherein the inner core comprises high strength and high modulus fibers with a yarn tenacity of 20 cN/dtex or more and a yarn elastic modulus of 400 cN/dtex or more, and
 an inner-and-outer-layer suitability represented by the following formula (1) is 0.70 to 1.20,   
       
         
           
             
               
                 
                   
                     
                       
                         ( 
                         
                           
                             a 
                             2 
                           
                           / 
                           
                             b 
                             2 
                           
                         
                         ) 
                       
                       / 
                       Vf 
                     
                     × 
                     100 
                   
                 
                 
                   
                     ( 
                     1 
                     ) 
                   
                 
               
             
           
         
         wherein a represents a diameter of an outer periphery of the inner core, b represents a diameter of an outer periphery of the outer cover, and Vf represents a volume ratio (%) of a volume of the inner core to a total volume of the inner core and the outer cover. 
       
     
     
         2 . The double rope structure according to  claim 1 , wherein the volume ratio Vf of the volume of the inner core to the total volume of the inner core and the outer cover is 10% or larger. 
     
     
         3 . The double rope structure according to  claim 1 , wherein the double rope structure has a ratio of yarn length/rope length of 1.005 or more and 1.400 or less, the rope length being determined as a length of a cut section of the double rope structure cut to a certain length, the yarn length being determined as an average value of lengths of yarns constituting the inner core of the cut section. 
     
     
         4 . The double rope structure according to any one of  claims 1 to 3 , wherein a tensile strength per cross-sectional area of the double rope structure is 180 N/mm 2  or more, the tensile strength being measured in accordance with JIS L 1013:2021. 
     
     
         5 . The double rope structure according to any one of  claims 1 to 4 , wherein the high strength and high modulus fibers have a yarn elongation of 1 to 6%. 
     
     
         6 . The double rope structure according to any one of  claims 1 to 5 , wherein the high strength and high modulus fibers are at least one selected from the group consisting of liquid crystal polyester fibers, ultra-high molecular weight polyethylene fibers, aramid fibers, and poly(para-phenylene benzobisoxazole) fibers. 
     
     
         7 . The double rope structure according to any one of  claims 1 to 6 , wherein a ratio of a tenacity of fibers used for the outer cover to a tenacity of fibers used for the inner core is 0.10 to 0.40. 
     
     
         8 . The double rope structure according to any one of  claims 1 to 7 , wherein the outer cover substantially comprises non-high strength and non-high modulus fibers. 
     
     
         9 . The double rope structure according to any one of  claims 1 to 8 , wherein the outer cover comprises multifilaments. 
     
     
         10 . The double rope structure according to any one of  claims 1 to 9 , wherein a ratio of a tensile strength of the double rope structure after a bending test to a tensile strength of the double rope structure before the bending test is 90% or more, in which the bending test, the double rope structure is subjected to repeated bending of 10,000 times under a load of 1% of a tensile break strength of the double rope structure at a bending angle of 240° with a bending R of 7.5 mm.