Protective helmet

Abstract

A helmet is formed with a rigid outer shell and three energy-absorbing layers made of two types of CONFOR™ ergonomic, open-celled polyurethane foams. The first layer adjacent the rigid outer shell is a CONFOR™ CF-40 yellow foam and the middle layer is a CF-47 green foam, which is of greater stiffness than the outer layer. The inner-most layer is also a CF-40 yellow foam and, therefore, identical to the outer energy-absorbing layer. The three layers are 0.5″ thick. The helmet body is secured to a user's head with straps, affording a helmet design capable of continuously absorbing energy from multiple impacts while retaining the property of returning completely to its original shape. The multiple layering of materials having different stiffnesses results in the reflection of propagating stress waves through the materials, ultimately absorbing larger amounts of energy than the same materials not layered with alternating stiffnesses could absorb.

1 . A helmet, comprising: 
 a) a stiff shell having an inner surface; and    b) a plurality of impact-energy-absorbing material layers disposed within said shell in superposed position to each other, the layers having differing dynamic impedances;    all of said layers being continuous; and one of said layers being adjacent to and coextensive with substantially the majority of said inner surface of said shell; said shell having a stiffness greater than said layers.    
     
     
         2 . The helmet of  claim 1 , further comprising straps operatively connected to at least one of the shell and plural layers to secure the helmet to a user's head.  
     
     
         3 . The helmet of  claim 1 , wherein at least one of the impact-energy-absorbing material layers are made of polymeric material.  
     
     
         4 . The helmet of  claim 1 , further comprising vents formed in said helmet.  
     
     
         5 . The helmet of  claim 1 , wherein the dynamic impedances of the layers are in a pattern of low, high, low with respect to each other.  
     
     
         6 . A protective device, comprising a stiff outer shell having an inner surface, and inner layers of energy-absorbing material, said layers superposed on each other; 
 one of said layers being in direct contact with the shell;    the layers having differing dynamic impedances;    said shell having a stiffness greater than said inner layers.    
     
     
         7 . The protective device of  claim 6  wherein the energy-absorbing material layers are co-extensive with substantially the majority of the inner surface of the shell.  
     
     
         8 . The protective device of  claim 6 , wherein the device contains at least three inner layers of energy-absorbing material.  
     
     
         9 . The protective device of  claim 6 , wherein the energy-absorbing material is a foamed polymeric material.  
     
     
         10 . The protective device of  claim 6  wherein the layers of energy-absorbing material are positioned with respect to one another so a layer of low dynamic impedance is adjacent to a layer of high dynamic impedance.  
     
     
         11 . An energy-absorbing system comprising alternating layers of energy-absorbing material having different dynamic impedances.  
     
     
         12 . The energy-absorbing system of  claim 11 , wherein the device contains at least three layers of energy-absorbing material.  
     
     
         13 . The energy-absorbing system of  claim 11 , wherein the energy-absorbing material is a foamed polymeric material.  
     
     
         14 . The energy-absorbing system of  claim 11 , wherein the layers of energy-absorbing material are positioned with respect to one another so a layer of low dynamic impedance is adjacent to a layer of high dynamic impedance.  
     
     
         15 . The energy-absorbing system of  claim 11  wherein outer surfaces of the energy-absorbing system comprises an energy-absorbing material layer having a lower dynamic impedance than the layers adjacent to the outer surfaces.  
     
     
         16 . The energy absorbing system of  claim 11 , wherein the system reduces the amplitude of any applied stress wave to the outer surface of the system.  
     
     
         17 . The energy-absorbing system of  claim 11 , wherein the system allows for numerous internal reflections of any applied stress wave to the outer surface of the system.