Type of safety helmet impact indicator

Abstract

A strap with a failure indicator and a safety device including the strap. The strap comprises: a main body structure formed by knitting; and one or more second yarns integrated straight into the main body structure in the length direction of the main body structure along the entire length of the main body structure and at least partially fixed to the main body structure, wherein the main body structure and the second yarn are selected such that the main body structure and the second yarn are elongated and do not break under a predetermined amount of a tensile force, and after the tensile force is released, the main body structure retracts, such that at least one second yarn at least partially protrudes from a plane of the main body structure to form a failure indicating loop. The safety device comprises a component formed by the strap with a failure indicator.

What is claimed is: 
     
         1 . A strap with a failure indicator, comprising:
 a main body structure formed by knitting; and   one or more second yarns integrated straight into the main body structure in a length direction of the main body structure along the entire length of the main body structure and at least partially fixed to the main body structure,   wherein the main body structure and the second yarn are selected such that the main body structure and the second yarn are elongated and do not break under a predetermined amount of a tensile force, and after the tensile force is released, the main body structure retracts, such that at least one second yarn at least partially protrudes from a plane of the main body structure to form a failure indicating loop.   
     
     
         2 . The strap according to  claim 1 , wherein under the predetermined amount of the tensile force, an elongated length of the main body structure is greater than an elongated length of the second yarn, such that the second yarn detaches from the fixation to the main body structure and can slide in the main body structure; when the tensile force is released, the main body structure retracts, and the second yarn does not retract due to occurred plastic deformation, such that the length of the main body structure is smaller than the length of at least one second yarn that has slid, thereby the at least one second yarn at least partially protruding from the plane of the main body structure. 
     
     
         3 . The strap according to  claim 1 , wherein under the predetermined amount of the tensile force, the second yarn deforms synchronously with the main body structure, and after the tensile force is released, the length of the main body structure after retraction is smaller than the length of at least one second yarn that has deformed plastically, such that the at least one second yarn at least partially protrudes from the plane of the main body structure. 
     
     
         4 . The strap according to  claim 1 , wherein material of a first yarn forming the main body structure may be any of the following: polyester fiber, polyester low-elastic yarn, polyester high-elastic yarn, spandex core-spun material, polyester, polyamide, natural fiber, viscose fiber, acrylic fiber and acetate fiber, and the first yarn is of a different color from the second yarn. 
     
     
         5 . The strap according to  claim 1 , wherein the second yarn has a tensile strength of at least 2.0 N/Tex, and the elongation at break in the range of 2˜5%; the main body structure has the maximum tensile force of not less than 800 N, and the elongation in the range of 15%˜35%. 
     
     
         6 . The strap according to  claim 3 , wherein material of the second yarn may be medium-density polyethylene, high-density polyethylene yarn, or polyethylene. 
     
     
         7 . The strap according to  claim 1 , wherein the strap has a compensating portion, which can compensate for the difference in elongated lengths between the main body structure and the second yarn under the predetermined amount of the tensile force. 
     
     
         8 . The strap according to  claim 7 , wherein the compensating portion is formed by forming a bending portion at an end of the main body structure. 
     
     
         9 . The strap according to  claim 1 , wherein the one or more second yarns are formed by a single yarn which is in a serpentine arrangement and turns at the ends of the main body structure. 
     
     
         10 . The strap according to  claim 1 , wherein the fixation of the second yarn to the main body structure is realized by winding a thermal fuse at least partially around the second yarn with a twist of 6˜10 turns/cm or by using an adhesive. 
     
     
         11 . A safety device comprising a component formed by the strap with a failure indicator according to  claim 1 , to facilitate determining whether the safety device has been damaged. 
     
     
         12 . A safety helmet, comprising a helmet body and a suspension system attached to the inside of the helmet body, the suspension system comprising a plurality of straps connected with a cushion pad to form a structure covering a head, wherein at least one of the plurality of straps is formed by the strap according to  claim 1 , such that the suspension system can not only act as a buffer when subjected to a tensile force, but also can indicate whether the suspension system has experienced impact. 
     
     
         13 . A method for manufacturing a strap with a failure indicator, comprising:
 a) providing a first yarn;   b) providing a second yarn;   c) knitting the first yarn to form a main body structure, and integrating the second yarn straight into the main body structure and extending the entire length of the main body structure, and   d) at least partially fixing the second yarn to the main body structure,   wherein the main body structure and the second yarn are selected such that the main body structure and the second yarn are elongated and do not break under a predetermined amount of a tensile force, and after the tensile force is released, the main body structure retracts, such that at least one second yarn can at least partially protrude from a plane of the main body structure to form a failure indicating loop.   
     
     
         14 . The method according to  claim 13 , wherein in step c, knitting the first yarn in a manner of plain weave, double-sided weave or jacquard weave to form the main body structure. 
     
     
         15 . The method according to  claim 13 , further comprising: in step b, winding a thermal fuse around the second yarn along at least part of the length of the second yarn and, in step d, melting the thermal fuse by heating the strap to at least partially fix the second yarn to the main body structure. 
     
     
         16 . The method according to  claim 15 , wherein a melting point of the thermal fuse is 80˜130° C. and its twist is 6˜10 turns/cm. 
     
     
         17 . The method according to  claim 15 , wherein the fixation of the second yarn to the main body structure is realized by winding a thermal fuse at least partially around the second yarn with a twist of 6˜10 turns/cm or by using an adhesive. 
     
     
         18 . The method according to  claim 13 , after step d, folding each end of the strap and fixing it in the middle with a suture to form a first bending portion and a compensating portion. 
     
     
         19 . The method according to  claim 13 , wherein the elongated length of the main body structure under the predetermined amount of the tensile force is substantially caused by the deformation of the orientation of the knitted loops and the straightening of arcs of the loops. 
     
     
         20 . The method according to  claim 13 , wherein under the predetermined amount of the tensile force, the second yarn deforms synchronously with the main body structure, and after the tensile force is released, the length of the main body structure after retraction is smaller than the length of at least one second yarn that has deformed plastically, such that the at least one second yarn at least partially protrudes from the plane of the main body structure.