Abstract:
The present invention relates to protective helmets used in activities where there is significant risk for head injuries. More specifically to helmets enhanced with a chin strap and multiple layers which are connected in such a way that compression and torsion forces applied to the helmet as a result of impact are significantly absorbed, reducing the risk of injury to the wearer&#39;s head.

Description:
FIELD OF INVENTION 
       [0001]    The present invention relates generally to protective headgear and, more specifically to a protective helmet with multiple layers, enhanced to reduce and dissipate compression and torsion forces respectively in activities where there is significant potential for head injuries. 
       RELATED ART 
       [0002]    Protective helmets have been used for many years to shield the wearers during activities where there is a risk of head injury. The first helmet ever invented was a monolithic leather structure with three leather straps which secure the helmet to the wearers head. Over the years, different materials became available and the structure of the helmet developed to incorporate padding as well as the implementation of plastics into the design. In more recent times there have been significant concerns over the increasing number of concussions occurring among American football players. This has led to a great deal of research into ways of decreasing the severity of the damages caused from impact while wearing a helmet in hopes of reducing the number of concussions. 
         [0003]    Several improvements have been made in an effort to reduce the risk of head injury in football and other activities where this risk exists. In such an effort various designs have been implemented, which diminish the amount of energy absorbed by the helmet upon impact. For example, U.S. Pat. No. 7,930,771 discloses a multi-layered protective helmet which uses an anisotropic intermediate layer, U.S. Pat. No. 7,328,462 discloses a helmet with a hardened shell and an outer layer comprising of an elastomeric cellular foam material, U.S. Pat. No. 7,089,602 discloses a helmet with a honeycomb layer in contact with a viscoelastic energy absorbent layer, U.S. patent application Ser. No. 13/227,901 discloses a helmet with an inner layer connected to an outer layer by multiple connectors which are stretched along their longitudinal axes. While these helmets are all significant improvements over the traditional monolithic helmets, they only allow limited rotational displacement of the inner shell with respect to the outer shell and consequently they only allow limited dissipation of energy. Therefore, what is needed is a protective helmet which provides greater protection from head injuries by allowing for greater reduction and dissipation of compression and torsion forces. 
       SUMMARY OF THE INVENTION 
       [0004]    It is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of the description and should not be regarded as limiting. 
         [0005]    Various embodiments of the present invention are directed to a protective helmet having a lining layer, which provides cushioning for the wearers head. The lining layer is connected to a hard inner shell which is further connected to a hard outer shell by an intermediate layer. The intermediate layer dissipates compression and torsional forces from impacts. The inner shell is connected to the outer shell in such a way to allow for displacement of the inner shell relative to the outer shell. A chin strap which secures the helmet to wearer&#39;s head is attached to the inner shell. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Embodiments of the present invention will be described by way of example only, and not limitation, with reference to the accompanying drawings in which: 
           [0007]      FIG. 1  shows a vertical cross-section of a helmet according to the present invention. 
           [0008]      FIG. 2  shows a cross-section of a rigid chin strap connection according to the present invention. 
           [0009]      FIG. 3  shows a cross-section of a soft chin strap connection according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0010]    Turning now descriptively to the drawings, in which similar reference characters denote similar elements throughout the several views,  FIG. 1  illustrates a cross sectional view of a protective helmet in accordance with a preferred embodiment of the present invention which includes a hard inner shell  104 , a hard outer shell  100 , an energy absorbing intermediate layer  102  between the inner shell  104  and the outer shell  100 , a lining layer  106  on the surface of the inner shell  104 , which is adjacent to and provides cushioning for the wearer&#39;s head, and a chin strap attached to the inner shell  104  by the use of a spacer  110  where the spacer is of a height that allows the chin strap to be flush with the outer shell  100 . 
         [0011]    Both the inner shell  104  and the outer shell  100  are made of a hard lightweight plastic material such as a polycarbonate alloy. The intermediate layer  102  is located between the inner shell  104  and the outer shell  100  and is attached to both the inner shell  104  and the outer shell  100  by adhesives, rivets, bolts or other attachment means generally known in the art. The intermediate layer  102  absorbs rotational energy applied to the outer shell  100  of the helmet as a result of impact, in such a way that rotational acceleration or deceleration of the head is kept low. The intermediate layer  102  also reduces compression forces applied to the outer layer  100  of the helmet as a result of impact, thereby reducing the risk of head injury to the wearer. 
         [0012]    The intermediate layer  102  comprises of an elastomeric material selected for its energy dissipation properties such as Teflon, rubber or cellular foam. In accordance with an embodiment of the present invention a high level of anisotropy of the elastomeric material is preferred. A material is anisotropic when it is directionally dependent, more specifically, when its physical or mechanical properties are different when measured along different axes. The intermediate layer  102  is arranged in such a way that the direction in which the material exhibits a low resistance against deformation is in line with the direction in which tangential forces are likely applied as a result of impact. This ensures that the rotational acceleration and deceleration of the wearer&#39;s head is kept low. An example of this is an elastomeric material arranged in a honeycomb structure, where the walls are perpendicular to the outer shell. The height and widths of honeycomb structure&#39;s cells may vary to produce the preferred level of anisotropy. 
         [0013]    The lining layer  106  is made of a material, which provides comfort for the wearer by preventing the wearer&#39;s head from coming into contact with the hard inner shell  104 , such as foam or rubber. The lining layer  106  is attached to the inner shell  104  using adhesives, rivets, bolts or other attachment means generally known in the art, preventing the inner shell  104  from moving separately from the wearer&#39;s head. 
         [0014]    In one embodiment of the present invention the intermediate layer comprises a combination of layers of isotropic and anisotropic materials. For example the intermediate layer can comprise a first layer of elastomeric isotropic materials such as Teflon, rubber or cellular foam and a second layer of elastomeric anisotropic material arranged in a honeycomb structure. Different materials can be selected to suit the particular activity that the helmet will be used for. 
         [0015]    In another embodiment the intermediate layer  102  comprises a plurality of structures selected specifically for their energy dampening properties such as springs, pistons and other suitable devices generally known in the art. 
         [0016]    In an embodiment of the present invention the lining layer is used to provide cushioning for the wearer&#39;s head as well as to obtain a proper fit. This is done by having either an inflatable lining layer  106  or a lining layer  106  divided into multiple sections of varying size and thickness selected specifically for the individual wearer. 
         [0017]    In an embodiment of the present invention a face mask it attached to the helmet&#39;s outer shell  100  on opposite sides using snaps, bolts, screws, adhesives or other attachment means generally known to the art. Where tangential forces are applied to the face mask, energy is transferred from the face mask to the outer shell  100 . The intermediate layer  102  absorbs rotational energy from the outer shell  100  reducing the rotational acceleration and deceleration of the wearer&#39;s head. 
         [0018]    In an embodiment of a protective helmet according to  FIG. 2 , the inner shell  104  is connected to the outer shell  100  by means of a spacer on each side of the helmet, each spacer having two ends where one end is rigidly attached to the inner shell  104  and the other end has an attachment for the chin strap. The purpose of the chin strap is to secure the helmet on the wearer&#39;s head by preventing the inner shell  104  from moving relative to the wearer&#39;s head and allowing the outer shell  100  to be displaceable relative to the inner shell  104 . Spaces  108  through the intermediate layer  102  and the outer shell  100  allow the spacer  110  to be accessed through the outer shell  100 . 
         [0019]    In an embodiment of a protective helmet according to  FIG. 3 , the inner shell  104  is connected to the outer shell  100  by means of a spacer on each side of the helmet, each spacer having two ends where one end is elastically attached to the inner shell  104  and the other end has an attachment for the chin strap. The elastic attachment is accomplished by shrouding the spacer  110  in a tough elastomeric material. One groove is created on each side of the shroud at the end of the shroud that is connected to the inner shell  104 . A hole is made in the inner shell  104  through which the shroud can be placed. The size of the hole is calculated by adding the lengths of the grooves in the shroud and subtracting the total from the width of the shroud. The spacer is forced through the inner shell  104  whereby the groove and the inner shell are mated  112 . On the other end of the spacer an adhesive, snap, screw, bolt or other attachment means generally known in the art is used to join the chinstrap to the shroud.