Helmet insert

Abstract

An insert for a helmet comprises a plurality of layers, each layer being of a Miura-Ori fold geometry.

1 . An insert for a helmet comprising a plurality of layers, each layer being of a Miura-Ori fold geometry. 
     
     
         2 . An insert for a helmet as claimed in  claim 1 , in which an upper surface of the insert has an overall curvature to conform to an inner surface of a helmet. 
     
     
         3 . An insert for a helmet as claimed in  claim 2 , in which each layer has an overall curvature. 
     
     
         4 . An insert for a helmet as claimed in  claim 1 , comprising a plurality of layers, each layer including a plurality of parallel straight folds and a plurality of transverse folds, each transverse fold being orientated transverse to the plurality of parallel straight folds to intersect the parallel straight folds,
 each transverse fold changing direction at each intersection with a parallel straight fold to form a zigzag and being either a mountain fold along its entire extent or a valley fold along its entire extent, the transverse folds being arranged alternately on the layer so that each mountain fold neighbours two valley folds,   and each parallel straight fold alternating along its extent between being a mountain fold and a valley fold, changing from a mountain fold to a valley fold or from a valley fold to a mountain fold at each intersection with a transverse fold.   
     
     
         5 . An insert for a helmet as claimed in  claim 4 , in which each transverse fold has a fold angle, and in which all of the transverse folds of each layer have the same fold angle. 
     
     
         6 . An insert for a helmet as claimed in  claim 5 , in which the plurality of layers is divided into a first group and a second group, the transverse folds of the layers of the first group having a first fold angle, and the transverse folds of the layers of the second group having a second fold angle, the first fold angle being greater than the second fold angle, the layers being stacked to alternate between layers of the first group and layers of the second group. 
     
     
         7 . An insert for a helmet as claimed in  claim 6 , in which the fold angle of each transverse fold of each layer of the first group is between 30 degrees and 180 degrees but not equal to 180 degrees. 
     
     
         8 . An insert for a helmet as claimed in  claim 7 , in which the fold angle of each transverse fold of each layer of the first group is 95 degrees. 
     
     
         9 . An insert for a helmet as claimed in  claim 6 , in which the fold angle of each transverse fold of each layer of the second group is between 25 degrees and 130 degrees. 
     
     
         10 . An insert for a helmet as claimed in  claim 7 , in which the fold angle of each transverse fold of each layer of the second group is 36 degrees. 
     
     
         11 . An insert for a helmet as claimed in  claim 1 , in which a wall thickness of each layer is between 0.5 mm and 2 mm 
     
     
         12 . An insert for a helmet as claimed in  claim 11 , in which the wall thickness of each layer is 1 mm. 
     
     
         13 . An insert for a helmet as claimed in  claim 1 , which is integrally formed. 
     
     
         14 . An insert for a helmet as claimed in  claim 13 , which is formed by means of an additive manufacturing method, which is optionally a selective laser sintering method or a fused deposition modelling method. 
     
     
         15 . An insert for a helmet as claimed in  claim 1 , which is formed of an ester based thermoplastic polyurethane. 
     
     
         16 . An insert for a helmet as claimed in  claim 1 , in which the insert comprises a viscoelastic material or an elastomeric material. 
     
     
         17 . A method of manufacturing an insert for a helmet as claimed in  claim 1 ,
 the method comprising the step of:   manufacturing a plurality of layers of the insert integrally.   
     
     
         18 . A method as claimed in  claim 17 , in which the step of manufacturing a plurality of layers of the insert integrally includes using an additive manufacturing process, which is optionally selective laser sintering or fused deposition modelling. 
     
     
         19 . A method as claimed in  claim 17 , further comprising the initial steps of:
 using finite element analysis to model the dependence of the performance of the insert in an impact on a property of the insert; and   selecting an optimal value of that property based on the result of the above step.   
     
     
         20 . A method as claimed in  claim 19 , in which the property is one of: a fold angle of one of the folds; a wall thickness of one of the layers; a relative offset between a pair of layers.