An impact absorbing structure and a helmet comprising such a structure

Abstract

An impact absorbing structure comprises a unitary material formed as a stretch-dominated hollow cell structure and a helmet comprising such a structure as an inner impact resistant liner.

1 . An impact absorbing structure, comprising a unitary material formed as a stretch-dominated hollow cell structure wherein at least a plurality of cells are configured to tessellate with a cell axis normal to the surface or out-of-plane and the unitary material has a relative density substantially between 0.05 and 0.15. 
     
     
         2 . An impact absorbing structure as claimed in  claim 1  wherein substantially all the cells of the hollow cell structure are 2D hollow-cells. 
     
     
         3 . An impact absorbing structure as claimed in  claim 2  wherein substantially all the cells are aligned substantially out of plane. 
     
     
         4 . An impact absorbing structure as claimed in  claim 1  wherein the cells are formed as a micro-truss lattice. 
     
     
         5 . An impact absorbing structure as claimed in  claim 1  wherein the cells are formed as a crystal lattice structure. 
     
     
         6 . (canceled) 
     
     
         7 . (canceled) 
     
     
         8 . An impact absorbing structure as claimed in  claim 1  wherein at least a plurality of the cells are hexagonal. 
     
     
         9 . An impact absorbing structure as claimed in  claim 1  wherein at least a plurality of the cells are triangular. 
     
     
         10 . An impact absorbing structure as claimed in  claim 1  wherein at least a plurality of the cells are square. 
     
     
         11 . An impact absorbing structure as claimed in  claim 1  wherein at least a plurality of the cells are a combination of octagons and squares co-located in a tessellating pattern. 
     
     
         12 . (canceled) 
     
     
         13 . (canceled) 
     
     
         14 . An impact absorbing structure as claimed in  claim 1  wherein the ratio of cell wall thickness to cell length is significantly small. 
     
     
         15 . An impact absorbing structure as claimed in  claim 14  wherein the wall has a maximum thickness of substantially 1 mm. 
     
     
         16 . An impact absorbing structure as claimed in  claim 1  wherein the unitary material is a polymer material. 
     
     
         17 . An impact absorbing structure as claimed in  claim 16  wherein the unitary material is an elastomer. 
     
     
         18 . An impact absorbing structure as claimed in  claim 16  wherein the unitary material is elastic-plastic and elastic-brittle. 
     
     
         19 . An impact absorbing structure as claimed in  claim 16  wherein the unitary material is selected from the group consisting of Nylon 11 and ST Elastomer. 
     
     
         20 . (canceled) 
     
     
         21 . (canceled) 
     
     
         22 . A helmet, comprising an inner impact resistant liner at least partly formed from an impact absorbing structure as claimed in  claim 1 . 
     
     
         23 . A helmet as claimed in  claim 22  further comprising an outer shell formed to substantially cover the inner impact resistant liner. 
     
     
         24 . A helmet as claimed in  claim 22  further comprising an outer shell formed to substantially cover the inner impact resistant liner wherein the outer shell is at least partly formed from a composite material. 
     
     
         25 . A helmet as claimed in  claim 22  further comprising an outer shell formed to substantially cover the inner impact resistant liner wherein the outer shell is at least partly formed from a thermoplastic material. 
     
     
         26 . A helmet as claimed in  claim 22  further comprising an outer shell formed to substantially cover the inner impact resistant liner wherein at least one vent slot is formed in the outer shell. 
     
     
         27 - 50 . (canceled)