Helmet System

Abstract

A protective helmet includes a head cap, which surrounds and moves with a wearer's head, and an outer shell which surrounds the head cap. The outer shell is movable both radially and circumferentially relative to the head cap. An energy absorbing flexible liner is located between the head cap and the outer shell. The liner is attached to the outer shell and the head cap so that neither the head cap nor the head of the wearer is otherwise attached to the outer shell. The liner establishes a preset initial relative position and spacing between the head cap and the outer shell and compliantly absorbs energy imparted to the outer shell during a helmet impact to enable the outer shell to move relative to the head cap during the helmet impact and to be returned to the initial relative position with the head cap following the impact.

I/We claim: 
     
         1 . A method for protecting a wearer's brain from injury resulting from an impact to a helmet that surrounds the wearer's head by reducing two potential contributors to damaging head angular acceleration that may result from such an impact, the first contributor substantially arising from a head horizontal component of a normal force of the impact and the second contributor substantially arising from a tangential force component of the impact, the method utilizing the helmet which provides protection for successive helmet impacts, the helmet having an outer shell, a head cap, and a compliant liner between and attached to the outer shell and the head cap, the outer shell and the head cap having an initial pre-impact relative position established by the liner, the method comprising the steps of:
 before the impact, donning and securing the helmet to a portion of the wearer's head such that the head cap substantially follows the motion of an underlying cranial portion of the head during the impact to the helmet;   during the impact, the compliant liner temporarily deforming to enable the outer shell to locally and temporarily deform inwardly and to also move globally both radially and circumferentially relative to the head cap, the liner absorbing energy in the process to reduce both the first and second contributors to the angular acceleration of the wearer's head; and   after the impact, the liner automatically returning the outer shell to the initial pre-impact relative position with respect to the head cap so that the helmet remains protective to the wearer for a subsequent impact.   
     
     
         2 . A method for protecting a wearer's brain from injury resulting from an impact to a helmet that surrounds the wearer's head by reducing two potential contributors to damaging head angular acceleration that may result from such an impact, the first contributor substantially arising from a head horizontal component of a normal force of the impact and the second contributor substantially arising from a tangential force component of the impact, the method utilizing the helmet which provides protection for successive helmet impacts, the helmet having an outer shell, a head cap, and a compliant liner between and attached to the outer shell and the head cap, the outer shell and the head cap having an initial pre-impact relative position established by the liner, the method comprising the steps of:
 before the impact, donning and securing the helmet to a portion of the wearer's head such that the head cap will substantially follow the motion of the underlying cranial portion of the head during the impact to the helmet;   during the impact, the compliant liner temporarily deforming to enable the outer shell to locally and temporarily deform inwardly and to also move globally radially inwardly relative the head cap, the liner absorbing energy in the process to reduce the first potential contributor to the resultant angular acceleration of the wearer's head, the liner also potentially sliding between portions of itself by displacing from locating features within the sliding portions to enable the outer shell to move globally circumferentially relative to the head cap, the liner absorbing energy in the process to reduce the second contributor to the resultant angular acceleration of the wearer's head; and   after the impact, the liner being manually returned by the wearer or a third party by re-engaging the locating features within the sliding portions of the liner which returns the outer shell to the pre-impact relative position so that the helmet remains protective to the wearer for a subsequent impact.   
     
     
         3 . A method for protecting a wearer's brain from injury resulting from an impact to a helmet that surrounds the wearer's head by reducing two potential contributors to damaging head angular acceleration that may result from such an impact, the first contributor substantially arising from a head horizontal component of a normal force of the impact and the second contributor substantially arising from a tangential force component of the impact, the method utilizing the helmet which provides protection for successive helmet impacts, the helmet having an outer shell, a head cap, and a compliant liner between and attached to the outer shell and the head cap, the outer shell and the head cap having an initial pre-impact relative position established by the liner, the method comprising the steps of:
 before the impact, donning and securing the helmet to a portion of the wearer's head so that the head cap will follow the motion of the underlying cranial portion of the head during the impact to the helmet;   during the impact, the compliant liner temporarily deforming to enable the outer shell to locally and temporarily deform inwardly and to also move globally radially inwardly relative to the head cap, the liner absorbing energy in the process to reduce the first potential contributor to a resultant angular acceleration of the wearer's head, the liner also potentially sliding between portions of itself by displacing from locating features within the sliding portions to enable the outer shell to move globally, circumferentially relative to the head cap, the liner absorbing energy in the process to reduce the second contributor to the resultant angular acceleration of the wearer's head and for certain impacts, which, because of their unique location and direction, cause the second contributor to beneficially subtract from the first contributor to reduce the resultant angular acceleration of the wearer's head, the locating features in the liner portions in proximity of the impact being compressed to act like a one-way abutment in a direction of a sliding motion to preclude some of the sliding motion between the liner portions and that lessens the reduction of the second contributor so that it may better reduce the resultant angular acceleration of the wearer's head in that case; and   after the impact, the liner being manually returned by the wearer or a third party by re-engaging the locating features within the sliding portions of the liner which returns the outer shell to the pre-impact relative position with the head cap and restores the liner to its pre-impact condition so the helmet remains protective to the wearer for a subsequent impact.