Conventional helmets typically include a hard exterior shell and a foam liner interior to the shell. There are two widely-used methods of making a helmet with a liner and shell. In one method, the hard outer shell and the foam liner are both made independently of each other. Thereafter, the shell is applied to the liner with glue, rivets, screws or is otherwise attached by physical means. As used throughout this application, “post-applied shell” refers to a shell or shell portion attached to the foam liner, after the foam liner has been pulled from the mold, and such technique is referred to as the “post-applied method.” In a second method, the helmet's hard outer shell is bonded to the helmet's inner foam liner simultaneously with the formation of the liner. The liner is cast with the shell in the mold. The liner material, typically polystyrene, is injected into the mold containing the hard outer shell. As used throughout this application, “in-mold shell” refers to a shell or shell portion that is bonded to the foam liner at the time of formation of the foam liner, and such technique is referred to as the “in-mold method.” The advantage with the latter method is that the in-mold method results in a sturdier attachment between the shell and the liner that can prevent separation of the shell from the liner under a severe impact. The former method, however, is not without advantages.
While the in-mold method has a distinct advantage in strength, the post-applied method also has an advantage that cannot be fully realized in a helmet with an in-mold shell. For example, independently forming the liner and the shell, and thereafter, attaching the shell to the liner, after formation of the liner, permits the creation of channels on the exterior surface of the liner (i.e., the surface facing the shell). Thus, when the shell and liner are brought together, the channels on the liner are converted into conduits between the shell and liner that are useful for providing ventilation. Air flow between the shell and the liner is not possible with a helmet having an in-mold shell, since all the interior surfaces of an in-mold shell are covered with the foam liner as a result of the method used.
Accordingly, there is a need to provide a sturdy in-mold shell helmet with the ventilation advantages of a post-applied shell helmet. Alternatively, there is a need for a sturdy shell to liner attachment in a post-applied shell helmet. The present invention fulfills these needs and has further related advantages.