Helmet

Abstract

A helmet (10) comprising: an airbag (1) having an airbag wall surrounding an internal cavity; and one or more tensional reinforcements (2) extending through the internal cavity between different points on the airbag wall.

1 . A helmet comprising:
 an airbag having an airbag wall surrounding an internal cavity; and   one or more tensional reinforcements extending through the internal cavity between different points on the airbag wall.   
     
     
         2 . A helmet according to  claim 1 , wherein the tensional reinforcements are arranged to reduce the rotational energy that would otherwise be transmitted to the head in the event of an impact. 
     
     
         3 . A helmet according to  claim 1 , wherein the airbag is pre-inflated. 
     
     
         4 . A helmet according to  claim 3 , further comprising an outer shell, provided radially outward of the airbag. 
     
     
         5 . A helmet according to  claim 1 , wherein the airbag is a dynamic airbag that inflates in the event of an impact. 
     
     
         6 . A helmet according to  claim 5 , further comprising a pressurised gas canister or gas generator for providing gas to the internal cavity in the event of an impact. 
     
     
         7 . A helmet according to  claim 6 , further comprising a controller for detecting an impact or imminent impact and instigating the provision of gas from the pressurised gas canister or gas generator to the internal cavity. 
     
     
         8 . A helmet according to  claim 6 , wherein the controller comprises an accelerometer, preferably a microelectromechanical systems (MEMS) accelerometer, to detect an impact or imminent impact. 
     
     
         9 . A helmet according to  claim 1 , further comprising an inner shell provided radially inwards of the airbag. 
     
     
         10 . A helmet according to  claim 9 , wherein the inner shell is a hard shell, or is made from a foam material, optionally EPP or EPS, for absorbing some or all of the compressive force in an impact. 
     
     
         11 . A helmet according to  claim 9 , further comprising a sliding facilitator provided between the inner shell and the airbag, to facilitate rotation between the airbag and the inner shell in the event of an oblique impact on the helmet. 
     
     
         12 . A helmet according to  claim 1 , wherein the tensional reinforcements are flexible or stiff. 
     
     
         13 . A helmet according to  claim 1 , wherein the tensional reinforcements are threads, membranes, beams or tubes. 
     
     
         14 . A helmet according to  claim 1 , wherein the outermost airbag wall comprises a material, or is treated, for facilitating sliding of the airbag with respect to an object being impacted upon. 
     
     
         15 . A helmet according to  claim 1 , wherein, in the event of an impact, the arrangement of the tensional reinforcements reduces the rotational energy that would otherwise be transmitted to the head of a wearer of the helmet, but allows for local compression of the airbag in the region impacted upon.