Patent Publication Number: US-7913325-B2

Title: Bicycle helmet with reinforcement structure

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/801,639, filed May 19, 2006, titled BICYCLE HELMET WITH REINFORCEMENT STRUCUTRE, and the benefit of U.S. Provisional Application No. 60/801,668, filed May 19, 2006, titled BICYCLE HELMET WITH REINFORCEMENT STRUCUTRE, the entire contents of both of which are incorporated by reference and should be considered a part of this specification. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to protective helmets and bicycle helmets in particular. More specifically, the present invention relates to a helmet with multiple-density foam parts interconnected by a reinforcement structure. 
     2. Description of the Related Art 
     Conventional bicycle helmets typically employ a layer of crushable material, usually synthetic resin foam, extending over and about the wearer&#39;s head to mitigate the force of an impact, for example, due to a fall. In order to increase the impact strength of the helmet, manufacturers of conventional helmets usually increase the thickness or the density of the crushable material. However, both these approaches tend to increase the overall weight of the helmet. Additionally, increasing the thickness of the layer of crushable material makes the helmet more bulky. 
     Accordingly, there is a need for a helmet design that provides increased impact strength without increasing the overall weight of the helmet. 
     SUMMARY OF THE INVENTION 
     Preferred embodiments of the present invention provide an improved bicycle helmet and methods of making the same. Preferably, the improved helmet includes a body with multiple foam sections having different densities, the foam sections interconnected at least in part by a reinforcement structure. 
     In accordance with one embodiment, a bicycle helmet is provided comprising a body having a concave inner surface configured to permit the helmet to fit a user&#39;s head. The body has a first section with a first material density and a second section with a second material density different from the first material density. The helmet also comprises a reinforcement structure disposed in the body, wherein the reinforcement structure engages the first and second sections of the body. 
     In accordance with another embodiment, a bicycle helmet is provided comprising a body having a plurality of sections, a first material density of one of the sections being different from a second material density of another of the sections. The helmet also comprises a reinforcement structure, at least a portion of which is embedded within said body, wherein the reinforcement structure extends through adjacent sections so that the sections are interconnected at least partially by the reinforcement structure. 
     In accordance with yet another embodiment, a bicycle helmet is provided comprising a body having a first section having a first material density and a second section having a second material density different from the first material density. The helmet also comprises a reinforcement structure comprising at least one shell attached to the first and second sections, wherein the reinforcement structure extends across the sections so that the sections are interconnected at least partially by the reinforcement structure. 
     In accordance with still another embodiment, a method for manufacturing a bicycle helmet is provided, comprising forming a first body section having a first material density, the first section engaging at least a portion of a reinforcement structure. The method also comprises forming a second body section having a second material density different than the first material density. The second body section engages the first body section and at least a portion of the reinforcement structure, and the reinforcement structure interconnects the first and second body sections. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects and advantages of the present protective helmet are described in greater detail below with reference to several preferred embodiments, which are intended to illustrate, but not to limit the present invention. The drawings contain 24 figures. 
         FIG. 1A  is a schematic front perspective view of a bicycle helmet incorporating one embodiment of a reinforcement structure. 
         FIG. 1B  is a schematic front view of the bicycle helmet in  FIG. 1A . 
         FIG. 1C  is a schematic rear view of the bicycle helmet in  FIG. 1A . 
         FIG. 1D  is a schematic left-side view of the bicycle helmet in  FIG. 1A . 
         FIG. 1E  is a schematic top view of the bicycle helmet in  FIG. 1A . 
         FIG. 2A  is a schematic side view of one embodiment of a reinforcement structure used for manufacturing the bicycle helmet of  FIG. 1A . 
         FIG. 2B  is a schematic side view of one embodiment of a fastener used to interconnect different parts of the reinforcement structure in  FIG. 2A . 
         FIG. 3  is a schematic side view of a partially formed bicycle helmet with a bottom foam portion of a pre-selected density molded about the reinforcement structure of  FIG. 2A . 
         FIG. 4A  is a schematic side view of another embodiment of a reinforcement structure used for manufacturing the bicycle helmet of  FIG. 1A . 
         FIG. 4B  is a schematic side view of another embodiment of a reinforcement structure used for manufacturing the bicycle helmet of  FIG. 1A  during an intermediate manufacturing step, the structure having the bottom foam portion molded thereon. 
         FIG. 4C  is a schematic side view of another embodiment of a reinforcement structure used for manufacturing the bicycle helmet of  FIG. 1A  during an intermediate manufacturing step, the structure having the bottom foam portion molded thereon. 
         FIG. 5A  is a schematic perspective front view of a top portion of a mold for forming the reinforcement structure shown in  FIGS. 4A-4C . 
         FIG. 5B  is a schematic perspective front view of a bottom portion of a mold for forming the reinforcement structure shown in  FIG. 4A-4C . 
         FIG. 6A  is a schematic front view of a bottom portion of a mold for forming a foam portion about the reinforcement structure shown in  FIGS. 4A-4C . 
         FIG. 6B  is a schematic front view of a top portion of a mold for forming a foam portion about the reinforcement structure shown in  FIGS. 4A-4C . 
         FIG. 7A  is a schematic front view of a bottom portion of the mold in  FIG. 6A , with a reinforcement structure disposed therein, prior to formation of the foam portion about the reinforcement structure. 
         FIG. 7B  is a schematic front view of the bottom portion in  FIG. 7A , following the formation of the foam portion about the reinforcement structure. 
         FIG. 8A  is a schematic rear view of another embodiment of a reinforcement structure for a bicycle helmet. 
         FIG. 8B  is a schematic top and rear side view of the reinforcement structure in  FIG. 8A . 
         FIG. 8C  is a partial schematic view of a front portion of a helmet body incorporating the reinforcement structure of  FIG. 8A . 
         FIG. 8D  is a partial schematic view of a front portion of a helmet body incorporating the reinforcement structure of  FIG. 8A . 
         FIG. 8E  is a partial schematic view of a rear portion of a helmet body incorporating the reinforcement structure of  FIG. 8A . 
         FIG. 8F  is a partial schematic view of a rear portion of a helmet body incorporating the reinforcement structure of  FIG. 8A . 
         FIG. 9  is a rear view of another embodiment of a reinforcement structure for a bicycle helmet. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the following detailed description, terms of orientation such as “top,” “bottom,” “upper,” “lower,” “front,” “rear,” “left,” “right” and “center” are used herein to simplify the description of the context of the illustrated embodiments. Likewise, terms of sequence, such as “first” and “second,” are used to simplify the description of the illustrated embodiments. However, because other orientations and sequences are possible, the present invention should not be limited to the illustrated orientation. Those skilled in the art will appreciate that other orientations of the various components described above are possible. As used herein, “front”, “rear”, “left” and “right” are interpreted from the point of view of a user of a protective helmet. Likewise, “top”, “bottom”, “upper” and “lower” are interpreted from the point of view of the wearer of the helmet. 
       FIGS. 1A-1E  illustrate one preferred embodiment of a protective helmet, which is especially well suited for use as a bicycle helmet  100 . The helmet  100  includes a body  10 , which preferably is a composite structure. The helmet body  10  preferably makes up the protective, impact resistant portion of the helmet  100 . In the illustrated arrangement, the body  10  includes a front end  12 , a rear end  14 , a bottom edge  16  and a top end  18 . Additionally, the body includes a left side  20  and a right side  30 . The helmet body  10  also preferably defines a cavity sized to permit the body  10  to fit on a user&#39;s head. For example, the cavity can have a concave surface that at least partially surrounds a portion of the user&#39;s head when wearing the helmet  100 . In one preferred embodiment, the body  10  is sized so that the bottom edge  16  on the left and right sides  20 ,  30  sits proximal the user&#39;s ears, and so the rear end  14  sits at or below the user&#39;s skull when wearing the helmet  100 . Further, as known in the art, the helmet body  10  can have a variety of sizes in order to fit the variety of head-sizes in the user population. For example, in one embodiment the helmet  100  can be sized to fit children. In another embodiment, the helmet  100  can be sized to fit adults. In still another embodiment, the helmet  100  can be sized to fit a range of head sizes. 
     The helmet body  10  preferably defines a bottom section  40  and a top section  50 . In the illustrated embodiment, the bottom section  40  is defined below a dotted line (See  FIG. 1D ) and extends from the rear end  14  to a point P proximal the front end  12  of the body  10 . The helmet body  10  is preferably symmetrical about a longitudinal axis X, as shown in  FIGS. 1B ,  1 C and  1 F, so that the left side  20  and right side  30  of the body  10  are mirror images of each other. In another embodiment, the bottom section  40  extends from the rear end  14  to the front end  12 . 
     With continued reference to  FIGS. 1A-1E , a number of openings  60  are formed in the helmet body  10 , where the openings  60  are configured to allow air to flow therethrough to advantageously cool the head of a user wearing the helmet  100 . In the illustrated embodiment, the helmet body  10  has at least one air opening  62  formed between the bottom and top sections  40 ,  50  of the body  10 . In the illustrated embodiment, two openings  62  are formed at a boundary between the bottom and top sections  40 ,  50 . The openings  62  are preferably elongated and are arranged in a longitudinal direction between the front end  12  and the rear end  14  of the body  10 . Additionally, a recess  62   a  in the body  10  is disposed adjacent each opening  62  and configured to guide air toward the opening  62 . However, the openings  62  can be arranged in other suitable patterns. 
       FIG. 1D  also illustrates a plurality of openings  64  formed in the top section  50  of the body  10 . Preferably, the openings  62 ,  64  are sized to direct a desired amount of airflow to a user&#39;s head. The openings  64  are likewise elongated and arranged in a longitudinal direction between the front end  12  and the rear end  14  of the body  10 . However, the openings  64  can be arranged in other suitable patterns. The top section  50  also has recesses  64 a formed therein, one of said recesses  64 a disposed adjacent each opening  64 . As discussed above, the recesses  64 a are configured to guide airflow to the openings  64  and onto a user&#39;s head. The top section  50  includes at least one elongated support member  52  between adjacent series of openings  64 . The support member  52  preferably extends longitudinally between the front end  12  and the rear end  14  of the helmet body  10 . 
     The body  10  also has an opening  66  formed at the front end  12  thereof. In the illustrate embodiment, three openings  66  are shown. However, any the body  10  can have any suitable number of openings  66 . The opening  66  preferably defines a slot above the bottom edge  16  that extends laterally from the left side  20  to the right side  30  of the body  10 . Preferably, the opening  66  allows air to flow therethrough at least partially onto a user&#39;s forehead when the helmet  100  is worn by the user. In one embodiment, the body  10  also preferably has an opening  68  formed at the rear end  14  thereof, as shown in  FIG. 1C . In the illustrated, the body  10  has three openings  66  at the front end  12  and five openings  68  at the rear end  14 . In another embodiment, more or fewer than three openings  66  can be provided at the front end  12  and more or fewer than five openings  68  can be provided at the rear end  14 . In the illustrated embodiment, the openings  66  at the front end  12  are elongated and extend between the left and right sides  20 ,  30  of the helmet body  10 . Likewise, the openings  68  at the rear end  14  are preferably elongated. 
     The helmet body  10  is preferably manufactured with an energy absorbing material, such as an expanded foam material. However, other suitable materials may also be used. More preferably, the helmet body  10  is constructed of different parts of expanded foam material, each part having a different foam density. In the illustrated embodiment, the bottom section  40  defines one part having a first foam density and the top section  50  defines a second part having a second foam density different than the first foam density. In one embodiment, the first foam density is greater than the second foam density. In another embodiment, the second foam density is greater than the first foam density. In still another embodiment, the bottom section  40  defines a plurality of foam parts, each having a different foam density. Likewise, in another embodiment the top section  50  defines a plurality of foam parts, each having a different foam density. Advantageously, the helmet body  10  constructed with said areas of different foam density provides a lighter helmet  100 , while satisfying the impact resistance standards of the helmet  100 . In a preferred embodiment, the helmet body  10  has a first foam density of between about 60 grams/liter and about 112 grams/liter. In another embodiment, the first foam density is between about 98 grams/liter and about 112 grams/liter. In still another embodiment, the first foam density is about 104 grams/liter. In another embodiment, the helmet body  10  has a second foam density of between about 60 grams/liter and about 112 grams/liter. In another embodiment, the second foam density is between about 60 g grams/liter and bout 98 grams/liter. In still another embodiment, the second foam density is about 72 grams/liter. 
       FIG. 2A  illustrates one embodiment of a frame  70  for use in constructing a helmet, such as the helmet  100  discussed above. The frame  70  preferably includes a tray having a cavity sized to receive foam thereabout, as further described below. In the illustrated embodiment, the frame  70  includes a right-side tray  72  and a left-side tray  74 . In a preferred embodiment, the right-side and left-side trays  72 ,  74  are mirror images of each other. In one embodiment, the trays  72 ,  74  are made of a plastic material. However, the trays  72 ,  74  can be made of other suitable light-weight materials. Preferably, the trays  72 ,  74  have a shape corresponding to the section of the helmet body  10  to be molded. In the illustrated embodiment, the right and left trays  72 ,  74  have the same shape as the right and left sides of the bottom section  40  of the helmet body  10 , respectively. 
     The right-side and left-side trays  72 ,  74  preferably include openings  72   a ,  74   a , respectively, through which straps  75  can extend. The straps  75  can be made of nylon or other suitable materials for use with protective helmets. Additionally, the straps  75  can be arranged to securely fasten the constructed helmet  100  on a user&#39;s body. For example, the straps can include front straps  75   a  and rear straps  75   b , wherein the front and rear straps  75   a ,  75   b  together maintain the constructed helmet  100  in generally fixed relationship to the user&#39;s head. The straps  75   a ,  75   b  of the right-side and left-side trays  72 ,  74  can be fastened to each other in any suitable manner to maintain the constructed helmet generally in place on a user&#39;s head. Each of the straps  75   a ,  75   b  preferably has a closed end  75   c  at one end thereof. In the illustrated embodiment, the closed end  75   c  of the strap  75   a ,  75   b  is disposed in the cavity of the tray  72 ,  74 . In one embodiment, the closed end  75   c  includes a passage defined by portions of the strap  75   a ,  75   b  fastened together with stitches. However, the closed end  75   c  can be defined by fastening the strap  75   a ,  75   b  in other suitable ways, such as with an adhesive. 
     With continued reference to  FIG. 2A , the frame  70  includes a reinforcement structure  80 . In the illustrated embodiment, the reinforcement structure  80  includes a structure of flexible linear material  81 . For example, in one arrangement, the reinforcement structure  80  includes a structure of composite material, preferably having unidirectional fiber orientation. One suitable flexible linear material reinforcement structure is discussed in co-pending application Ser. No. 11/425,331, titled BICYCLE HELMET WITH REINFORCEMENT STRUCTURE and filed on Jun. 20, 2006, the entire contents of which are hereby incorporated by reference and should be considered a part of this specification. However, the reinforcement structure  80  can additionally or alternatively include other suitable structures, such as reinforcement shells or panels, as further discussed below. In the illustrated embodiment, the reinforcement structure  80  includes a right-side frame  82 , a left-side frame  84  and a top frame  86 . In one preferred embodiment, the frames  82 ,  84 ,  86  are defined by a continuous filament. In another embodiment, the reinforcement structure  80  can consist of the right-side frame  82  and the left-side frame  84 , without a top frame  86 . 
     In the illustrated embodiment, the right-side and left-side frames  82 ,  84  preferably have a same layout L. Accordingly, the following description of the layout L is applicable to both the right-side and left-side frames  82 ,  84 . The layout L preferably includes a plurality of elongated members, with at least one extending longitudinally along at least a portion of the length of the tray  72 ,  74  and at least one extending generally transverse thereto. In the illustrated embodiment, the layout L includes a first elongated member  80   a  extending generally longitudinally along substantially the entire length of the tray  72 ,  74 . As shown in  FIG. 2A , the first elongated member  80   a  extends through the passages in the straps  75   a ,  75   b . Accordingly, the straps  75   a ,  75   b  are coupled to the reinforcement structure  80  via the first elongated members  80   a . The layout L also includes a second elongated member  80   b  extending generally longitudinally along substantially the entire length of the tray  72 ,  74  and generally parallel to the first elongated member  80   a . The second elongated member  80   b preferably attaches to the first elongated member  80   a  via transverse members  80   c  extending therebetween. The layout L also includes a third elongated member  80   d  extending generally longitudinally along a portion of the length of the tray  72 ,  74  and generally parallel to the second elongated member  80   b . The third elongated member  80   d  preferably attaches to the second elongated member  80   b  via second transverse members  80   e  extending therebetween. As shown in  FIG. 2A , the layout also includes junctions  80   f  along the length of the second and third elongated members  80   b ,  80   d , as well as at a junction between the second elongated member  80   b  and the transverse members  80   c ,  80   e . Preferably, the elongated members  80   a ,  80   b ,  80   d  and transverse members  80   c ,  80   e  at least partially define the openings  60  in the completed helmet body  10 . 
     In one embodiment, a reinforcement member  88  extends between the third elongated member  80   d  and the second elongated member  80   b  (see  FIG. 3 ). The reinforcement member  88  is preferably positioned proximal a front end of the layout L. In the illustrated embodiment, the reinforcement member  88  has an upside-down Y shape. However, the reinforcement member  88  can have other suitable shapes. Advantageously, the reinforcement member  88  provides additional stiffness to the right-side and left-side frames  82 ,  84 . Preferably, the reinforcement member  88  is made of a light-weight and stiff material, such as a hard plastic. In one embodiment, the reinforcement member  88  fastens to the right-side and left-side frames  82 ,  84  via the junctions  80   f  , as further described below. In other embodiments, other suitable mechanisms can be used to fasten the reinforcement member  88  fastens to the right-side and left-side frames, such as an adhesive. However, the reinforcement member  88  is optional, and in other embodiments the reinforcement structure  80  can be constructed without the use of such a reinforcement member  88 , as shown in  FIGS. 4A-4C  below. 
     In one embodiment, shown in  FIG. 2A , the elongated members  80   a ,  80   b ,  80   d  and transverse members  80   c ,  80   e  are preferably made of a single unidirectional linear material, which can be a single continuous filament. For example, the linear material can be shaped to define the elongated members  80   a ,  80   b ,  80   c  and the transverse members  80   c ,  80   e . In one embodiment, the linear material is bent or twisted to form said members  80   a - 80   e . Additionally, the linear material can be bent or twisted to form the junctions  80   f . For example, the linear material can be looped onto itself to form said junctions  80   f . However, in other embodiments, the reinforcement structure  80  can consists of a plurality of individual sections that overlap each other. For example, the reinforcement structure  80  can consist of a number of loops made of unidirectional linear material, wherein the loops overlap each other to define the layout of the reinforcement structure  80 , as shown in  FIG. 4C  and discussed further below. 
     In the illustrated embodiment, the reinforcement structure  80  also includes a top frame  86 , as shown in  FIG. 2A , though as noted above, the top frame  86  is optional. The top frame  86  preferably has an elongated shape and includes a first elongated member  86   a  and a second elongated member  86   b . Both members  86   a ,  86   b  extend generally longitudinally and are attached to each other via generally transverse members  86   c . In the illustrated embodiment, the top frame  86  has a generally oval shape. However, the top frame  86  can have other suitable shapes, such as rectangular. The top frame  86  also preferably defines at least one junction  86 f along the elongated members  86   a ,  86   b . In the illustrated embodiment, the top frame  86  defines four junctions  86   f , two along the first elongated member  86   a  and two along the second elongated member  86   b . However, the top frame  86  can have any suitable number of junctions  86   f.    
     In one embodiment, the right-side and left-side frames  82 ,  84  are attached to the top frame  86  via the junctions  80   f  ,  86   f . For example, in one embodiment the junctions  80   f  on the second elongated member  80   b  of the right-side frame  82  can be attached to the junctions  86   f  on the first elongated member  86   a  of the top frame  86 . Additionally, in one embodiment the junction  80   f  on the third elongated member  80   d  of the right-side frame  82  can be attached to one of the junctions  86   f  on the second elongated member  86   b  of the top frame  86 . Likewise, in one embodiment the junctions  80   f  on the second elongated member  80   b  of the left-side frame  84  can be attached to the junctions  86   f  on the second elongated member  86   b  of the top frame  86 . Additionally, in one embodiment the junction  80   f  on the third elongated member  80   d  of the left-side frame  84  can be attached to one of the junctions  86   f  on the first elongated member  86   a  of the top frame  86 . However, the right-side and left-side frames  82 ,  84  can be fastened to the top frame  86  using any suitable combination of junctions  80   f  ,  86   f . For example, in another embodiment, the top frame  86  can be fastened to the second elongated members  80   d  of the right-side and left-side frames  82 ,  84  via the junctions  80   f  ,  86   f.    
     The junctions  80   f  ,  86   f  can be attached with a fastener. For example, the junctions  80   f  ,  86   f  can be fastened together with a rivet, such as the snap rivet  90  shown in  FIG. 2B . However, other types of rivets and other types of fasteners can also be used, such as screws, clamps, pins, nails and the like. Preferably, the fasteners are made of a rigid and light-weight material. In one embodiment, the fasteners are made of a hard plastic, such as polyethylene. In another embodiment, the junctions  80   f  ,  86   f  can be fastened together via an adhesive. Once fastened together, the right-side frame  82 , left-side frame  84  and top frame  86  define an assembled reinforcement structure  80 . 
       FIG. 3  illustrates a partially formed helmet body  10 . Specifically,  FIG. 3  shows right and left bottom foam portions  40  of the right-side and left-side frames  82 ,  84 . In the illustrated embodiment, the helmet body  10  is injection molded about the bottom portions of the right-side and left-side frames  82 ,  84 , as well as about the right-side and left-side trays  72 ,  74 . The foam molding process is can be any process known in the art. One suitable process is discussed further below with reference to  FIGS. 6A-7B , which illustrate one embodiment of a mold used to form the foam portions about the right and left side frames  82 ,  84 . Preferably, the first elongated member  80   a , and at least a portion of the transverse members  80   c  connecting the first and second elongated members  80   a ,  80   b  are insert molded into said bottom foam portions, while the remainder of the right-side and left-side frames  82 ,  84  remain exposed. As used herein, “insert molded” means embedding at least a portion of the reinforcement structure  80  in foam so that the foam envelops said portion of the structure  80 . In another embodiment, a different portion of the right-side and left-side frames  82 ,  84  can be insert molded or embedded in the foam portion. For example, in one embodiment said first and second elongated members  80   a ,  80   b  and transverse members  80   c  can be substantially entirely embedded within the bottom foam portions. In one embodiment, the right and left sides of the partially formed helmet body  10  are removed from the mold so that the bottom portions are allowed to partially stiffen. In another embodiment, the bottom portions are allowed to fully harden. The partially formed helmet body  10  can then be inserted into another mold, and the injection molding process resumed to form the remaining portion of the helmet body  10 . For example, foam can be molded onto the exposed portions of the right-side and left-side frames  82 ,  84  to form the top section  50  of the completed helmet body  10 , as shown in  FIGS. 1A-1E . 
     In one embodiment, the bottom foam portions form the bottom section  40  of the helmet body  10  and interconnect with the subsequently formed top section  50  at least partially via the reinforcement structure  80 . In another embodiment, the combination of the bottom foam portions of the right-side and left-side frames  82 ,  84  and the exposed portions of the same are insert molded into a foam part that defines the top section  50  of the completed helmet body  10 . Accordingly, in a preferred embodiment the helmet body  10  includes multiple foam parts formed as individual layers of a unitary structure molded in successive steps to form said unitary structure. Advantageously, the right-side and left-side frames  82 ,  84  engage and fasten the different foam portions together. 
     Though the molding process described above involves molding the bottom portion  40  of the helmet body  10  first, and then molding the top portion  50  of the helmet body  10 , other suitable sequences can be used to mold the helmet body  10 . For example, in one embodiment, foam can be injection molded about the top portions of the right and left side frames  82 ,  84 , while leaving the bottom portions of said frames  82 ,  84  exposed. Then, foam having a different density can be injection molded about the exposed bottom portions of the right and left side frames  82 ,  84 , as well as about the previously formed foam part molded about the top portions of the frames  82 ,  84 . 
     In a preferred embodiment, the foam used to form the bottom section  40  of the body  10  has a different density than the foam used to form the top section  50 . In one embodiment, the foam used to form the bottom section  40  has a higher density than the foam used to form the top section  50 . In still another embodiment, the bottom section  40  can be formed with a plurality of foam sections of different densities. For example, in one embodiment a first portion of the frames  82 ,  84  can be insert molded into a first foam section having a first density. Similarly, a second portion of the frames  82 ,  84  can be insert molded into a second foam section having a second density. Additionally, a third portion of the frames  82 ,  84  can be insert molded into a third foam section having a third density. The first, second and third foam sections can then be interconnected with each other via the frames  82 ,  84  or subsequent foam sections injection molded about the frames  82 ,  84  and at least one of the first, second and third foam sections. Likewise, the top section  50  can be formed with a plurality of foam sections of different densities. Accordingly, different portions of the helmet body  10  can be constructed having a selected foam density. Advantageously, the foam density of specific areas of the helmet body  10  can be optimized to reduce weight and provide a unitary composite structure. 
     In one embodiment, the lower-density foam is first injection molded about a portion of the frames  82 ,  84 , and then the higher-density foam is injection molded about another portion of the frames  82 ,  84 . In another embodiment, the higher-density foam section is first injection molded about a portion of the frames  82 ,  84 , then the lower-density foam is injection molded about another portion of the frames  82 ,  84 . This process can be repeated until the helmet body  10  has been fully formed. 
     As discussed above, and shown in  FIG. 4A , in one embodiment, the structure of linear material  81  can be formed without a reinforcement member  88 . In the illustrated embodiment, the structure of linear material  81  includes a least one loop  83  of linear material. Preferably, the loops  83  are disposed on the structure  81  at locations where one foam part having a first density will meet with a second foam part having a second density different from the first density. Accordingly, the loops  83  are preferably positioned along the foam density “border”. Advantageously, the loops  83  strengthen the engagement between the structure of linear material  81  and the foam parts in the completed helmet body  10 . 
       FIG. 4B  illustrates another embodiment of the reinforcement structure  80  with a frame  82 ′ of linear material, without a reinforcement member  88 . In the illustrated embodiment, the frame  82 ′ corresponds to a right-side frame of a helmet body and is defined by a unidirectional continuous filament. In the illustrated embodiment, the helmet body is in an intermediate manufacturing step, where the bottom foam portion  40  has been molded onto the frame  82 ′, as further discussed below. A left-side frame is preferably a mirror image of the frame  82 ′ and is therefore not shown. 
     As discussed above, the frame  82 ′ of the helmet body  80  can be made of a continuous unidirectional filament. In another embodiment, shown in  FIG. 4C , the frame  82 ″ can consist of multiple loops  82   a ′ of linear material, wherein each of the loops  82   a ′ is attached to at least another of the loops  82   a ′, so that the loops  82   a ′ of linear material overlap with each other. In a preferred embodiment, the loops  82   a ′ overlap over a length of between about 3 cm and about 4 cm. However, the loops  82   a ′ can overlap over a longer or shorter distance. 
       FIGS. 5A-5B  illustrate a mold  200  used to form the structure of linear material  81 . In the illustrated embodiment, the mold  200  is used to form a right-side reinforcement frame  82 ′,  82 ″ for a helmet body. However, a similarly constructed mold can be used to form a left-side reinforcement frame of the helmet body. 
     The mold  200  includes a top portion  210  and a bottom portion  250 . The top portion  210  defines an outer frame surface  220  and an inner frame surface (not shown) on a side opposite the outer frame surface  220 . The top portion  210  also has an outer edge  230 . 
     The bottom portion  250  defines an inner frame surface  260 , which includes a plurality of grooves  270  formed thereon. The grooves  270  are oriented to provide a desired layout L′, which preferably corresponds to the layout L of the frame  82 ′ of linear material. However, one of ordinary skill in the art will recognize that the grooves  270  can be oriented to provide any desired layout, such as the layout L of the right-side frame  82  and left-side frame  84  described above. The bottom portion  250  also includes and outer edge  280 . The top and bottom portions  210 ,  250  of the mold  200  preferably couple to each other along their edges  230 ,  280  to form a closed mold. 
     In one embodiment, continuous linear material is preferably disposed in the grooves  270  of the bottom portion  250  and wound around junctions between intersecting grooves  270 , in order to define the desired layout L. In one embodiment, pins are inserted at the junctions J between grooves  270 , and the linear material wound around the pins to aid in laying the linear material along the grooves  270 . Once the desired layout L is obtained, and the frame  82 ′ cured, said pins can be removed. Such a process can be used to form, for example, the frame  82 ′ shown in  FIG. 4B . 
     In another embodiment, discrete loops of linear material can be disposed along the grooves  270  so as to define the desired layout L. For example a loop of linear material can be laid along a set of grooves  270  that define one section  272  of the layout L. Another loop of linear material can then be laid along another set of grooves  270  that define another section  274  of the layout L. Preferably the loops of linear material are laid within the grooves  270  so that at least a portion of each loop overlaps with a portion of another loop. In a preferred embodiment, said loops of linear material overlap between about 3 cm and about 4 cm. However, in another embodiment, the loops of linear material can overlap less than 3 cm, or more than 4 cm. Such a process can be used to form, for example, the frame  82 ″ shown in  FIG. 4C . 
     After the linear material has been laid within the grooves  270   250 , the top portion  210  is coupled to the bottom portion  250  of the mold  200 . The linear material within the grooves  270  can then be cured to provide a frame  81 ,  82 ′,  82 ″ that is substantially rigid. For example, the linear material with the grooves can be heated to harden the linear material into a substantially rigid structure. 
       FIGS. 6A-6B  illustrate one embodiment of a mold  300  used to form a foam section about the structure of linear material  81  or frame  82 ,  82 ′,  82 ″. Specifically, the mold  300  is sized to form the bottom foam portion  40  about the structure of linear material  81 . 
     The mold  300  preferably includes a bottom portion  310  and a top portion  340 . The bottom portion  310  is symmetrical about an axis Y, which divides the bottom portion  310  into two identical halves, and includes fastening members  312  for fastening the bottom portion  310  to the top portion  340 . Preferably, each half of the bottom portion  310  includes a concave surface C with grooves  320  formed therein. The grooves  320  form a layout L″ equal to the layout L of the structure of linear material  81  or reinforcement frames  82 ,  82 ′,  82 ″,  84 . Each half of the bottom portion  310  also has a recessed portion  330  formed adjacent the layout L″ of grooves  320 . The recessed portion  330  is preferably recessed relative to the concave surface C. 
     The top portion  340  of the mold  300  is likewise symmetrical about an axis Z, which divides the top portion  340  into identical halves, and includes fastening members  342  sized to engage the fastening members  312  of the bottom portion  310 , so as to form the assembled mold  300 . The top portion  340  preferably includes a convex surface  350  with a contour corresponding to the contour defined by the concave surface C. The top portion  340  also includes protrusions  360 , which extend out from the contour of the convex surface  350 . 
     Once the structure of linear material  81  has been formed using the mold  200 , the structure  81  is placed in the grooves  320  of the bottom portion  310  of the mold  300 . As the layout L″ of the grooves  320  is substantially equal to the layout L of the structure  81 , the structure  81  readily fits within the grooves  320 . Preferably, the structure  81  fits within the layout L″ of the grooves  320  such that a portion of the structure  81  is not disposed in the grooves  320 , but instead extends over the recessed portion  330 , as shown in  FIG. 7A . 
     The top portion  340  is coupled to the bottom portion  310 . In one embodiment, the convex surface  350  of the top portion  340  contacts the concave surface C of the bottom portion  310 , which maintains the structure  81  in place and inhibits its withdrawal from the layout L″ of the grooves  320 . Foam of a desired density is then injected into the recessed portion  330  so as to form the bottom portion  40  of the helmet body  10 . As shown in  FIG. 7B , the bottom portion  40  is formed about the exposed portion of the structure  81  that extended over the recessed portion  330 . 
     The assembly of the frame  82 ,  82 ′,  82 ″ and bottom portion  40  can then be withdrawn from the mold  300  and transferred to another mold (not shown) to form the top portion  50  of the helmet body  10 . This mold can be similar in construction to the mold  300  and include a recessed portion over which the exposed portion of the structure  81  can be placed, so that foam can similarly be injection molded about the exposed portions of the structure. 
       FIG. 8A-H  illustrate another embodiment of a reinforcement structure  80 ′, As shown in  FIG. 8A , the reinforcement structure  80 ′ includes a structure of flexible linear material  81  about which a bottom foam section  40  has been molded, as described above. In the illustrated embodiment, the bottom foam section  40  includes a high density foam. However, in other embodiments, the bottom foam section  40  can include a lower density foam. In the illustrated embodiment, the reinforcement structure  80 ′ is for a left-side frame  84  of the helmet body  10 . However, as discussed above, the reinforcement structure  80 ′ for a right-side frame  82  would be a mirror image of the structure illustrated in  FIG. 8A . Accordingly, the reinforcement structure  80 ′ for a right-side frame is not shown. 
     With continued reference to  FIG. 8A , the reinforcement structure  80 ′ also includes shells or panels  400  attached to the foam portion  40 . In the illustrated embodiment, a front shell  410  is attached to a surface of the bottom foam portion  40  at the front end  12 , such that at least a portion of the front shell  410  is in contact with the surface of the bottom foam portion  40  while another portion of the shell  410  is free. In one embodiment, about ½ of the front shell  410  is bonded to the surface of the bottom foam portion  40  and about ½ of the front shell  410  is unbonded (e.g., exposed). Likewise, a rear shell  430  is attached to a surface of the bottom foam portion  40  at the rear end  14 , such that at least a portion of the rear shell  430  is in contact with the surface of the bottom foam portion  40 , while another portion of the shell  430  is free. In one embodiment, about ½ of the rear shell  430  is bonded to the surface of the bottom foam portion  40  and about ½ of the shell  430  is unbonded (e.g., exposed). Though the illustrated embodiment includes two shells, the front and rear shells  410 ,  430 , one or ordinary skill in the art will recognize that the reinforcement structure  80 ′ can include more or fewer shells. 
     In the illustrated embodiment, the shells  410 ,  430  are attached to an inner surface  40 a of the bottom foam portion  40 , which is the generally concave surface facing a user&#39;s head once the helmet body  10  is complete. However, in another embodiment, the shells  410 ,  430  can be attached to an outer surface of the bottom foam portion  40  of the helmet body  10 . 
     As shown in  FIGS. 8A-8B , the front shell  410  preferably has a contour  412  that allows the shell  410  to be bonded to other sections of the helmet body  10 .  FIGS. 8C-8D , for example, show the front shell  410  attached to different sections of a completed helmet body  10 . In the illustrated embodiment, the front shell  410  is bonded to the bottom foam section  40 , which preferably includes foam having a first density, and is bonded to the top foam section  50 , which preferably includes foam having a second density different from the first density. Accordingly, the front shell  410  can be a bridge between different sections of the helmet body  10  having different densities, and provide further structural support to the helmet body  10 . Additionally, the contour  412  of the front shell  410  preferably helps define at least some of the vent openings  60  in the helmet body  10 . 
     Likewise, as shown in  FIGS. 8A-8B , the rear shell  430  preferably has a contour  432  that preferably allows the rear shell  430  to be bonded to other sections of the helmet body  10 .  FIGS. 8E-8F , for example, show the rear shell  430  attached to different sections of the completed helmet body  10 . Specifically,  FIGS. 8E-8F  show the rear shell  430  bonded to the bottom foam section  40  and to the top foam section  50 . As noted above, the bottom and top foam sections  40 ,  50  of the helmet body  10  can have different densities. Accordingly, the rear shell  430  can provide additional structural support to the helmet body  10  and function as a bridge between different foam sections having different densities. Additionally, the rear shell  430  preferably helps define at least one of the vent openings  60 . 
     In the illustrated embodiment, the front and rear shells  410 ,  430  have predetermined contours  412 ,  432  corresponding to the shapes of the different foam sections  40 ,  50  to which the shells  410 ,  430  attach. However, in another embodiment, the shells  410 ,  430  can be flexible panels having a generally planar shape that can be bent to conform to the shape of the different foam sections  40 ,  50 . 
     In one embodiment, the shells  410 ,  430  are insert molded to the bottom foam portion  40  having a first density, using a similar process for insert molding the structure of linear material, as described above, to obtain the assembly shown in  FIG. 8A . This assembly can then be insert molded into a second foam part, such as the top foam portion  50 , having a second density different than the first density. Accordingly, a completed helmet body  10 , as shown in  FIGS. 8D-8F , can be obtained. 
     In another embodiment, the shells  410 ,  430  can be attached to the helmet body  10  after the different foam sections, such as the bottom and top foam portions  40 ,  50 , have been insert molded about the structure of linear material  81 . For example, once the completed helmet body  10  is formed, the shells  410 ,  430  can be applied to the body  10  so that the shells  410 ,  430  bridge across and connect the different foam sections  40 ,  50  having different foam densities. The completed helmet body  10  assembly can then be heated to bond the shells  410 ,  430  to the foam sections  40 ,  50 . In one embodiment, the shells  410 ,  430  bond to the foam portions  40 ,  50  via an adhesive or ink on a surface of the shells  410 ,  430  which is activated upon heating. In another embodiment, an adhesive can be applied to the surface  40   a  of the foam portion  40 , and the shells  410 ,  430  applied to said surface  40   a . However, other suitable methods for bonding the shells  410 ,  430  to the foam portion  40 ,  50  can be used. For example, the injection molding process can alter the surface of the shells  410 ,  430 , allowing it to bond to the foam portion  40 ,  50 . 
     In one embodiment, the shells  410 ,  430  can comprise a polycarbonate material configured to withstand temperatures commonly present during the foam molding process. In another embodiment, the shells  410 ,  430  can comprise a polyvinyl chloride (PVC) material, or a polyethylene terephtalate glycol (PETG) material. However, other suitable materials having a desired strength, rigidity and weight can be used, including other plastic materials. 
     In the embodiment illustrated in  FIGS. 8A-8F , the shells  400  are used in addition to the structure of linear material  81  to form the reinforcement structure  80 ′. In another embodiment, a reinforcement structure  80 ″ includes only the shells  400 , without the structure of linear material  81 , as shown in  FIG. 9 . In the illustrated embodiment, the front and rear shells  410 ,  430  are attached to the bottom foam portion  40 , which has a first density, to form an intermediate assembly. As described above, this intermediate assembly can then be insert molded into another foam section having a second density, which may differ from the first density. 
     In one embodiment, shown in  FIG. 1B , an outer shell  500  preferably covers at least a portion of an outer surface of the body  10  and, thus, defines at least a portion of the outer surface of the helmet  100 . In one embodiment, the shell is continuous and overlays an outer surface of the body  10 . The shell can provide protection to the body  10  and improve the overall appearance of the helmet  100 . In addition, the shell may also provide an energy-absorbing function. Further, the shell can function as an external frame of the helmet body  10 . In one embodiment, the shell can be a relatively thin layer of a plastic material. Additionally an average thickness of the shell can desirably be substantially less than an average thickness of the body  10 . In one arrangement, the shell may be injection molded onto the helmet body  10  after it has been formed in a previous process step. 
     Although this invention has been disclosed in the context of certain preferred embodiments and examples, it will be understood by those skilled in the art that the present invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. In particular, while the present helmet has been described in the context of particularly preferred embodiments, the skilled artisan will appreciate, in view of the present disclosure, that certain advantages, features, and aspects of the helmet may be realized in a variety of other applications, many of which have been noted above. Additionally, it is contemplated that various aspects and features of the invention described can be practiced separately, combined together, or substituted for one another, and that a variety of combination and sub-combinations of the features and aspects can be made and still fall within the scope of the invention. Additionally, it is contemplated that the sequence of steps in the construction of the helmet can be varied and still fall within the scope of the invention. For example, the different sections of the helmet body can be formed in any desirable sequence, such as forming the top section of the helmet first and then forming the bottom section of the helmet. Thus, it is intended that the scope of the present invention herein disclosed should not be limited by the particular disclosed embodiments described above, but should be determined only by a fair reading of the claims.