Abstract:
A helmet that ventilates a user&#39;s head more efficiently. The relative movement of the helmet to air in the environment creates an airflow that enters intake openings designed to allow increased amounts of airflow into the helmet. The intake openings are positioned on an inclined plane near a user&#39;s forehead such that the intake openings extend upwardly and outwardly away from a user&#39;s eyes, thereby reducing the impact of a larger intake opening on the user&#39;s field of vision. Inside the intake openings, air is collected in a plenum and then guided into air channels leading into the head cavity. The air channels direct the airflow throughout the head cavity allowing the fresh air from the environment to exchange heat and perspiration from a user&#39;s head and are designed to inhibit obstruction of the air channels by the liner. Air channels also direct airflow to an exhaust such that the airflow can remove heat and perspiration from the helmet cavity and the helmet surface adjacent the exhaust is contoured to facilitate removal of air from the helmet. The liner is designed for easier installation and replacement.

Description:
RELATED APPLICATIONS  
       [0001]     The present application claims priority to U.S. Provisional Patent Application Ser. No. 60/558241, filed Mar. 31, 2004. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     This invention relates to head protection for operators or riders of motorized vehicles.  
         [0004]     2. Description of the Related Art  
         [0005]     Use of head protection is often recommended and sometimes required by law while operating motorized vehicles, such as when riding a motorcycle. Helmets are available in a variety of styles but the principle design consideration for all helmets is protection from serious head injuries during accidents.  
         [0006]     Generally, motorcycle helmets that comply with the safety standards include a thin, hard outer shell and an impact-absorbing, thicker inner shell made of a rigid foam, such as Expanded Polystyrene (“EPS”). While some prior art motorcycle helmets meet the safety standards and provide protection against head injuries, prior art motorcycle helmets are uncomfortable for a number of reasons. For many years, motorcycle riders have complained about the heat retention properties of today&#39;s helmets. Especially for riders in warm climates, motorcycle helmets become very uncomfortable as they trap heat around a person&#39;s head. The problem of heat retention in helmets is amplified for off-road motorcycle riders, who often enjoy riding in desert settings, by the vigorous, athletic exertions involved in the sport. Not only does the heat retention in today&#39;s helmets causes excessive perspiration from the heads of riders, it can lead to heat exhaustion, limiting the length of time a rider can enjoy off-road riding.  
         [0007]     Some helmets on the market today have tried to address these problems with ventilation holes formed through the outer shell and EPS layer for the apparent purpose of allowing air into the head cavity. These holes are often ineffective because they simply do not allow enough air into the head cavity to provide significant cooling to the user.  
         [0008]     Some helmets on the market today offer helmets with air intake scoops at the top of the helmet&#39;s eye opening. The scoops are intended catch air and direct it into the head cavity. Unfortunately, these air scopes typically have very small openings, often about ⅛ inch or ¼ inch, and therefore catch very little air and are similarly less effective in flowing cooling air into the head cavity.  
         [0009]     Further, today&#39;s helmets have limited air flow within the helmet itself. In particular, helmets on the market today have small channels that are easily occluded by the liner. Moreover, the channels are often formed in such a manner that continuous air flow through the channels is disrupted. As such, these helmets have less effective channeling systems such that any air that does enter the head cavity simply cannot create the airflow needed to adequately cool a user&#39;s head.  
         [0010]     Furthermore, today&#39;s helmets are not very effective in removing heated air and perspiration from the head cavity. Most helmets on the market today have small exhaust openings that are not particularly effective in permitting the air from the inside of the helmet to be removed.  
         [0011]     Additional problems with today&#39;s helmets relate to the helmet liners included in helmets as a soft cushion between a user&#39;s head and the helmet&#39;s impact absorbing layer. The liners in today&#39;s helmets are often pressed against the impact absorbing layer by a user&#39;s head such that the liner impedes, or sometimes even blocks, airflow in the head cavity. This problem is amplified when the liner becomes saturated with sweat as a wet liner will adhere to the impact absorbing layer and allow even less air through an air channel than a dry liner. Further, a sweat saturated liner is uncomfortable against a riders head.  
         [0012]     While liners are typically removable and replaceable, poor design of today&#39;s liners makes removal and replacement inconvenient. Helmet liners on the market today include a series of ears with holes in the middle designed to mate with clips within helmet&#39;s shell. The clips on today&#39;s helmets are hidden within plastic molding around the helmet&#39;s eye opening and have a small circular protrusion that a user must mate with the hole in the liner&#39;s ear. Because the clips are hidden within the molding, the user must probe the ears under the molding and blindly match the hole to the protrusion. This design makes replacing a helmet liner a time consuming and bothersome chore.  
         [0013]     In sum, today&#39;s helmets are not very effective in addressing the problem of heat retention associated with helmets. The problem of heat retention in helmets often leads riders to loosen the fit of their helmets or even remove their helmets while riding, thereby defeating the safety function. Considering the shortcomings in prior art helmets, there exists a need for a helmet that is better at capturing air from the environment and introducing it into the interior of the helmet. Further, there is a need for a helmet that allows better airflow through the head cavity, and exhausts heated air and perspiration to the environment more efficiently. Moreover, there exists a need for a helmet with a liner that is less likely to obstruct airflow within the head cavity and that can be replaced quickly and easily.  
       SUMMARY OF THE INVENTION  
       [0014]     The aforementioned needs are satisfied by the helmet of the present invention which in one aspect comprises a helmet having an inner and an outer surface that is sized so as to encompass the head of the operator. The outer protective shell defines an eye opening that is positioned proximate the operator&#39;s eyes when the operator is wearing the helmet. The outer protective shell also defines at least one exhaust opening located adjacent the back of the head of the operator when the operator is wearing the helmet.  
         [0015]     In this aspect, the helmet further comprises an inner protective layer that is positioned inward of the outer protective shell so as to substantially cover the inner surface of the outer protective shell. The inner protective layer includes a plurality of air channels extending from the at least one intake positioned adjacent the opening in the eye opening to the exhaust openings. In this aspect, the at least one input is formed in the inner protective layer such that the plane of the intake opening has a component that is perpendicular to the direction of travel of the operator such that the air is injected into the plurality of channels as a result of the operator traveling in the direction of travel.  
         [0016]     Since the at least one opening is formed in the eye opening, the opening can be quite large and capable of gathering a substantial amount of air. Moreover, since the at least one opening has a component that is perpendicular to the direction of travel, air can be injected into the channels at a relatively high rate of speed thereby improving air flow through the helmet.  
         [0017]     In another aspect of the invention, an intake plenum is formed on the intake surface of the helmet. The intake plenum in one embodiment is comprised of a plurality of openings formed along the eye opening so as to be able to gather air for subsequent delivery into the channels. The use of such an intake plenum results in better air flow through the helmet.  
         [0018]     In another aspect of the invention, the helmet further comprises a liner that is interposed between the inner protective layer and the operator&#39;s head. The liner is preferably inhibited from being pushed into the channels at a position proximate the user&#39;s forehead when the user is wearing the helmet so as to allow for better air flow through the channels. Moreover, the liner is attached, in one aspect, to the helmet via attachment tabs that are sized so as to be positioned within mating openings. The attachment tabs include a surface that is perpendicular to the plane of the attachment tab that mates with a mating surface in the helmet. Hence, the liner can be positioned within the helmet and secured therein more easily as a result of the tabs being mated with the openings.  
         [0019]     In yet another aspect of the invention, the outer shell of the helmet defines a first air flow surface and a second air flow surface wherein the air flows over the second surface at a slower rate than the first surface. The exhaust openings are, in this aspect, preferably positioned on the second surface immediately adjacent the interface with the first surface such that a relative vacuum is formed adjacent the exhaust openings to thereby facilitate removal of the air. In this aspect, air flow through the helmet is enhanced as a result of the relative vacuum.  
         [0020]     Hence, from the foregoing, the design of the helmet in each of these aspects is adapted to facilitate air flow through the helmet. As such, the user is provided with greater cooling than with prior art helmets. These and other objects and advantages will become more apparent from the following description taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]     The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings. A part that appears in more than one drawing is in many instances identified by the same reference numeral throughout the drawings to facilitate cross-reference among the various views represented. In some of the Figures, for improved clarity of presentation, not all of the parts that appear in the figure are identified by their respective numerals.  
         [0022]      FIG. 1  is an exploded perspective view of one embodiment of the helmet.  
         [0023]      FIG. 2  is a front view of one embodiment of the helmet of  FIG. 1 .  
         [0024]      FIG. 3  is a cross section of one embodiment of the helmet of  FIG. 1 .  
         [0025]      FIG. 4  is front view of the inner protective layer and intake cover of one embodiment of the helmet of  FIG. 1 .  
         [0026]      FIG. 5A  is a cross section view of one embodiment of the helmet of  FIG. 1  showing the liner attachment mechanism.  
         [0027]      FIG. 5B  is a bottom view of the liner attachment assembly of  FIG. 5A .  
         [0028]      FIG. 6  is a side view of one embodiment of the helmet of  FIG. 1 . 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0029]     Reference will now be made to the drawings wherein like numerals refer to like parts throughout.  FIG. 1  illustrates an exploded view of the disclosed helmet  100  according to one embodiment.  FIG. 1  illustrates an outer protective shell  102  and an inner protective layer  104  which combine to form a head cavity  106 . The outer shell  102  includes an eye opening  110 , through which a user can see while wearing the helmet, an eye opening perimeter  112 , and at least one exhaust opening  114 , not shown in  FIG. 1 . The outer shell may also include a forehead member  116  located at or near the eye opening perimeter  112 .  
         [0030]     As illustrated in  FIG. 1 , the outer shell  102  includes a skull protection section  117  and a chin protector  119  with the eye opening  106  interposed therebetween. The chin protector  119  is integrally attached to the skull protection section  117  and extends outward therefrom in a known manner and is positioned so as to provide protection to the lower face of the user when the user is wearing the helmet  100 . The chin protector  119  substantially covers an operator&#39;s jaw when the helmet  100  is worn. The chin protector  119  and skull protection section  117  communicate with the eye opening perimeter  112  to define the eye opening  110 .  
         [0031]     When the helmet is worn by an operator, the eye opening perimeter  112  and skull protection section  117  generally meet at a location near the operator&#39;s forehead, slightly above the operator&#39;s eyes. The eye opening perimeter  112  and chin protector  119  generally meet at a location slightly below the operator&#39;s nose. In this orientation, the eye opening  110  is approximately the same shape as typical eye goggles worn by many operators of motorized vehicles, such that typical goggles substantially cover the exposed portion of an operator&#39;s face, with the exception of the nose, and generally substantially occupy the eye opening. In this arrangement, intake openings  120  generally spaced along an eye opening surface  131  of an inner protective layer  104  adjacent the forehead member  116  are generally above a user&#39;s goggles and not obstructed by a user&#39;s goggles. As will be discussed below, this arrangement can help direct airflow to the intake openings  120 .  
         [0032]     The skull protection section  117  is integrally formed of a rigid material such as plastic, fiberglass, carbon fiber, and/or Kevlar and is sized so as to cover substantially the skull of the user. As will be described in greater detail hereinbelow, the skull protection section  117  defines an upper air flow surface  121  and a lower air flow surface  123  with an interface comprising a raised ridge  125 . The air flow surfaces  121  and  123  along with the interface  125  assist in removing air from the interior of the helmet  100  in the manner that will be described in greater detail hereinbelow.  
         [0033]     The inner protective layer  104  shown in  FIG. 1  fits within the outer shell  102  and is permanently attached therein. A first surface  105  of the inner protective layer  104  substantially covers an inner surface  122  of the skull protection section  117  of the outer shell  102 . In this arrangement, the inner protective layer  104  is positioned between the outer shell  102  and an operator&#39;s skull when the helmet  100  is worn. The inner protective layer  104  is preferably constructed of an impact absorbing material such as molded expended polystyrene (“EPS”). As is also illustrated in  FIG. 1 , the inner protective layer also defines a eye opening surface  131  that is positioned immediately adjacent the eye opening  110 . As will be discussed in greater detail below, the eye opening surface  131  is preferably angled and has plenums formed therein so as to facilitate air flow through the helmet  100 .  
         [0034]     Air channels  124  are formed on a second surface  107  of the inner protective layer  104 . At least one of the air channels  124  extends along the curved second surface  107  from a location at or near the forehead member  116 , e.g., initiating at the eye opening surface  131  to a location preferably near the rear of an operator&#39;s skull. A plurality of air channels  124  can be included with more than one extending from the forehead member  116 . One or more optional plenum  134 , formed on the eye opening surface  131  of the inner protective layer  104 , are also shown in  FIG. 1 . The air channels  124  and plenum  134  will be described in greater detail below.  
         [0035]      FIG. 1  also shows a liner member  126 . The liner member  126  can be any shape, but the preferred liner member  126  is generally thin with a rectangular shape, such as that shown in  FIG. 1 . The liner member  126  is preferably permanently attached to the second surface  107  of the inner protective layer  104  and generally follows the curved shape of the second surface  107 , spanning over one or more air channels  124 . Placement of the liner member  126  on the second surface  107  can vary, but the typical location of attachment is at or near the forehead member  116  with a lateral orientation, substantially parallel to an operator&#39;s forehead. More than one liner member could be utilized at different locations on the second surface  107 . The liner member  126  can be made from a variety of suitable materials such as plastic or other somewhat rigid, preferably waterproof, materials. The liner member  126  serves a number of functions described in greater detail hereinbelow.  
         [0036]      FIG. 1  also depicts a liner  132 . The liner  132  is generally shaped to substantially cover the second surface  107  of the inner protective layer  104 . The liner  132  is preferably air permeable and typically constructed of material and/or foam or padding. The liner  132  is positioned between the relatively hard inner protective layer  104  and an operator&#39;s head to provide cushioning. The liner  132  is removably attached to the helmet  100  with attachment mechanisms such as snaps, buttons, or other known mechanical attachment devices generally positioned near the forehead member  116  and near the rear of an operator&#39;s head. The liner  132  shown in  FIG. 1  also includes a liner connector  147 . The liner connector  147  includes a liner rim  148  that traces along a forehead section  133  of the liner  132  and at least one liner tab  149  extending from the liner connector  174 . The liner rim  148  is curved with roughly the same curvature as the eye opening perimeter  112 .  FIG. 1  shows a series of liner tabs  149  spaced generally symmetrically along the liner rim  148 . The liner connector  147  is part of a novel retention mechanism  144 , which will be described in detail below.  
         [0037]      FIG. 1  also shows an intake covering  130 . The intake covering  130  generally covers the eye opening surface  131  and is positioned adjacent to the eye opening  110  and eye opening perimeter  112 . As depicted in  FIG. 1 , the air intake covering  130  is preferably a thin plastic piece with a crescent shape, with a curvature generally the same as the eye opening perimeter  112 . The intake covering  130  includes at least one air intake opening  120 . The intake covering  130  shown in  FIG. 1  includes screen members  133  that span across a series of intake openings  120  to filter out dirt and debris. In some preferred embodiments, the intake covering  130  curves following the eye opening perimeter  112  and is approximately ¾ inch by 8 inches. The intake cover  130  shown in  FIG. 1  also includes a liner attachment  145  described in greater detail herein below in reference to  FIG. 5A  and  FIG. 5B . The liner attachment receiver  145  includes liner attachment retainers  150 , a receiver rim  151 , and receiver openings  146  (not shown) which are also part of the retention mechanism  144  described below. The receiver rim  151  has generally the same shape and dimensions as the liner rim  148  such that the receiver rim  151  and the liner rim  148  mate when the liner  132  is attached to the helmet  100 . Further, the receiver openings  146  are spaced along the attachment receiver  145  at locations corresponding to the liner tabs  149 .  
         [0038]      FIG. 2  shows a front view of the helmet  100 . As can be appreciated from  FIG. 2 , the eye opening surface  131  is angled such that the air intake openings  120  communicate with air in the environment near the eye opening  110 . The eye opening surface  131  of the inner layer  104  is preferably angled such that the surface  131  has a component that is normal to the direction of travel. When a user operates a motorized vehicle while looking in the direction of travel, movement of the helmet  100  relative to the environment creates a flow of air in the direction opposite the direction of travel. Intake openings  120  oriented normal or oblique to the airflow therefore capture airflow. Generally, larger and increased numbers of intake openings  120  can catch larger amounts of airflow. In embodiments in which the forehead member  116  curves around the operator&#39;s forehead, intake openings  120  can be spaced along the eye opening surface  131 . The embodiment depicted in  FIG. 2  shows five intake openings  120  spaced along the eye opening surface  131  and the intake opening cover  130  with screen members  133  spanning over each one.  
         [0039]      FIG. 2  also shows optional intake openings  120  located in the skull protection portion  117  of the outer shell  102  and in the chin protector  119 .  FIG. 2  also shows exhaust openings  114  which communicate with the environment near lower airflow surface  123 , not shown in  FIG. 2 , and with air within the head cavity  106 . Further details of the exhaust openings will be provided below.  
         [0040]     Considering the front view shown in  FIG. 2 , airflow created from a forward movement of the helmet would be generally normal to the page. As can be appreciated from  FIG. 2 , airflow near the eye opening  110  contacts the helmet  100  and a user&#39;s face or eye goggles (not shown) and to at least some extent is rebounded upwards towards the openings  120 .  FIG. 3  illustrates this air flow pattern in greater detail. As illustrated, a portion of the air  211  flows directly into the openings  120 . Similarly, the angled surface  131  is positioned immediately proximate the goggles  212  of the user such that a portion of the air  214  hitting the goggles  212  is rebounded into the openings  120 . In this sort of arrangement, the amount of airflow captured by the intake openings  120  can be significant. The embodiment shown in  FIG. 2  includes five air intake openings  120  in the forehead member  116  with a total surface area of approximately 3 square inches.  
         [0041]      FIG. 3  also shows the forehead member  116  and intake opening  124  on a plane oriented at an angle Θ from horizontal. By orienting the eye opening surface  131  on an upwardly angled plane above a rider&#39;s forehead, the surface area of the intake opening  120  can be increased with little or no decrease in the user&#39;s field of vision. In this arrangement, the effective size of the intake opening  120  can be increased by increasing the width of the surface  131  and, thus, the openings  120  upwardly and outwardly relative to a user&#39;s face and eyes. In one particular implementation, the surface  131  is angled at an angle Θ within the range of 35 degrees to 45 degrees from horizontal when the helmet  100  is sitting on the flat surface in the manner shown in  FIG. 3 , and in a more specific implementation is angled at about 40 degrees from horizontal when the helmet  100  is sitting on a flat surface. In one implementation, the width of the surface  131  is in the range of ¾ inch to 1 inch and is more specifically ⅞ inch.  
         [0042]      FIG. 3  also shows the plenums  134  formed in the surface with a width B and depth C. The plenum  134  is generally a cavity formed in the surface  131  of the inner protective layer  104  that collects air entering the air intake openings  124 . In this arrangement, the plenum  134  is curved, generally following the forehead member  116  or eye opening perimeter  112 . The width and depth of the plenums  134  can vary, with greater values for these dimensions allowing the plenum  134  to hold more air, in general. In preferred embodiments, plenum width is greater than or equal to air intake opening width  120 , and the intake opening  120  is generally aligned with the plenum  134  such that air can flow through the intake opening  120  into the plenum  134 . In some preferred embodiments, the total volume of the plenum  134  is approximately 40 cubic centimeters.  
         [0043]     The plenum  134  of some preferred embodiments also includes a transition corner  136  that is optionally rounded, creating a relatively smooth corner between the plenums  134  and the air channels  124 . This rounded transition  136  provides a less abrupt change to the direction of the airflow as it moves from the plenum  134  to the air channels  124 . In embodiments that do not include a plenum  134 , the rounded transition  136  may be positioned on the air channels  124  between the intake opening  120  and the air channels  124 .  
         [0044]      FIG. 3  also shows the liner member  126  positioned against the inner protective layer  104 . The liner member  126  is secured to the inner protective layer  104  and extends across the air channels  124  to generally enclose the portion of the air channel  124  proximate the plenums  134 . The liner member  126  is preferably secured to the inner layer  104  at a position such that it is interposed between the user&#39;s forehead and the inner layer  104 . Generally, the user&#39;s forehead is positioned flush against the inner layer when the user is wearing the helmet and the liner member  126  provides a rigid barrier that inhibits the user&#39;s forehead from pushing the liner  132  into the channels  124 . Glue or other connectors, such as rivets, can be used to attach the liner member  126  to the inner protective layer  104 . In one implementation, the width of the liner member  126  is approximately 1¼ inches, but it will be appreciated that this width can vary depending on the helmet configuration. The liner member  126  may optionally include ventilation openings  142  that allow some airflow through the liner member  126 . Also, the liner member  126  could be attached to the liner  132  as an alternative to, or in addition to, attachment to the inner protective layer  104 .  
         [0045]     In the arrangement shown in  FIG. 3 , enclosing the air channel  124  at the location where the plenum  134  and air channels  124  has additional advantages. At this location, the airflow passes from the plenum  134  into the air channels  124 , changing direction as the airflow passes around a transition corner  136 . In this arrangement, the liner member  126  aids in this transition by reducing the tendency for the air to continue to flow along the plane of surface  131  and/or disperse. In other words, by covering the beginnings of air channels  124 , the liner member  126  compliments the air channels  124  in restricting the directions in which the air can pass, thereby directing air into and through the air channels  124 .  
         [0046]     Directing the airflow in the air channels is similarly assisted by side walls  140  in the air channels  124 , shown in  FIG. 3 . The side walls  140  restrict airflow in lateral directions and thus facilitate air flowing in the direction toward the back of a user&#39;s head. By flowing the air through the channels  124  of the helmet  100  at a high rate of speed, e.g., the speed of travel of the motorcycle, a substantial amount of convection cooling can occur within the helmet. Some embodiments include channels  124  having side walls  140  with increased heights near the air intake opening  120  or plenum  134 , creating a relatively deep portion of the air channel  124 . Testing has shown that side walls  140  with heights of approximately ¼ inch and widths of approximately ⅝ inch are effective in facilitating air flow through the channels  124 . These arrangements generally form channels  124  with three-sided, rectangular cross sections or a semi-circular cross section. Typically, the side walls  140  taper from the transition  136  towards the crown of the helmet.  
         [0047]     Referring now to  FIG. 4 , in one implementation, the helmet includes five air channels  124  spaced along the plenum  134  so as to be distributed over the surface  107  of the inner layer  104 . In some embodiments, these channels  124  are spaced approximately ¾ inch apart. As is illustrated in  FIG. 4 , the plenums  134  in this embodiment comprise left and right plenums  134   a ,  134   c  and a center plenum  134   b . The left and right plenums  134   a,    134   c  provide air to two of the channels  124  that extend along the side of the user&#39;s head and the center plenum  134   b  provides air to a channel  127  that extends along the top of the user&#39;s head.  
         [0048]     Referring again to  FIG. 3 , the thickness of the inner protective layer  104  can vary at different locations within the helmet  100 , but generally a minimum thickness is needed for safety considerations. As such, an increased thickness may be necessary to compensate for the channeling  124 . In one implementation, the minimum thickness is approximately 1 3/10 inches to 1½ inches.  
         [0049]     As shown in  FIG. 3 , at least one exhaust opening  114  is formed in the inner layer  104  and the outer shell  102 . The exhaust openings  114  are located in the skull protection portion  117  of the outer shell  102 . Typically, the exhaust openings  114  communicate with at least one air channel  124  and the environment. Exhaust channels  125  extend through the inner protective layer  104  from some location in the head cavity  106  or air channel  124  to an exhaust opening  114 . The exhaust channels  125  typically have a circular cross-section and may be drilled or molded into the helmet  100 . Any cross-sectional shape would suffice. An exhaust plenum  118  is optionally located between the exhaust opening  114  and the exhaust channel  125 . Further,  FIG. 3  shows air channels  124  situated near the neck opening  108  of the helmet such that neck exhaust openings  129  communicate with air channels  124  and the environment allowing air to flow from the air channels and/or head cavity  106  to the environment.  
         [0050]     The airflow within the helmet  100  will now be described in reference to  FIGS. 3 and 4 . The plenum  134  allows an increased amount of air from the environment to enter the intake openings  120 . The difference in size of the plenum  134  and air channels  124  can in turn enhance the airflow into the air channels  124  by producing a venturi effect. As air flows through the relatively large plenum into the relatively narrow air channels, the flow rate increases into the more narrow air channels  124 . The air channels  124  generally channel air through the head cavity in a distributed fashion, preferably with at least one of the air channels  124  extending to locations behind an operator&#39;s head.  
         [0051]     As the airflow continues through the air channels  124  toward the exhaust openings  114 , the fresh air combines with perspiration and air warmed by an operator&#39;s head within the head cavity. In embodiments in which the side walls  140  taper, the tapering allows some lateral movement of airflow and further facilitates the interchange of air from the environment with heated air and perspiration. This interchange of air increases the comfort of a user by removing perspiration and heat from a user&#39;s head. Similarly, airflow through the channels  124  may also serve to remove perspiration and heat from the liner  132 , providing further comfort to users. The exhaust openings  114  located behind a user&#39;s head assist in removing the heated air and perspiration. The exhaust function will be discussed in more detail below.  
         [0052]      FIGS. 5A and 5B  illustrate a retention mechanism  144  that holds the liner  132  in contact with the intake covering  130 . Specifically, the retention mechanism  144  comprises a receiver structure  145  formed on the intake covering  130  and a liner attachment member  148  attached to the liner. The receiver structure has three walls  149 ,  150 ,  153  positioned orthogonal to each other so as to define a recess  152  with a generally U-shaped cross section. A tab  151  is positioned at the end of the wall  150  which aids in retaining the liner attachment member  148  in contact with the intake covering  130  in the manner that will be described herein below. The wall  153  defines an opening  146  that is adapted to receive the liner attachment member  148 .  
         [0053]     The liner attachment member  148  includes a main section  157  that has a cross-section which matches the cross section of the U-shaped recess  152 . At one end of the main section  157 , a flanged protrusion  154  is attached. The flanged protrusion  154  preferably has a cross sectional area that is greater than the opening  146  but is formed of a deformable material such as plastic.  
         [0054]     In operation, the flanged protrusion is positioned adjacent the opening  146  in the recess  152  and the flanged protrusion is forced through the opening thereby elastically deforming the flanged protrusion  157 . The rear surface  156  of the main section  157  of the liner attachment member  148  is urged passed the tab  151 , which is preferably made of an elastically deformable material e.g., plastic, such that the main body  157  is flushly positioned within the recess  152  when the flanged protrusion  154  is inserted through the opening  146 .  
         [0055]     Hence, both the engagement between the flanged protrusion  154  and the inner surface of the wall  153  and the tab  151  securely retain interconnection between the liner  126  and the intake covering  130 . However, the use of deformable elastic material allows disengagement between the liner member  148  and the receiver structure  145  by pulling with sufficient force to deform the flange protrusion  154  sufficiently to extract it out of the opening  146  and also with sufficient force to simultaneously deform the tab  151  to remove the main body  157  from the recess  152 .  
         [0056]     As is illustrated in  FIG. 5B , the receiver structure  145  and the liner attachment member  148  extend in a direction parallel to the perimeter of the eye opening  110 . Moreover, in this embodiment, the flange protrusion member  154  and the tab  151  inhibit movement in a direction that is generally perpendicular to the direction of the perimeter. Advantageously, the opening  146  and, in this embodiment, the recess  152  are sized so as to correspond to the size of the tab  148 . Hence, the user can more easily position the tab  148  within the appropriate recess  152  as the mating structures are preferably similar sizes. As is illustrated in  FIG. 5B , in this implementation there are three tabs  148   a - 148   c  and three similarly sized openings  145   a - 145   c  spaced about the upper perimeter of the eye opening  110  to thereby retain the liner  126  in the interior surface of the helmet  100 .  
         [0057]      FIG. 6  shows the upper airflow surface  121  and the lower airflow surface  123  located on the skull protection section  117  of the outer shell  102 . The raised ridge  125  generally defines the interface of the upper and lower air flow surfaces  121  and  123 . Exhaust openings  114  are located on the lower airflow surface, preferably immediately adjacent the raised ridge  125 .  
         [0058]     Movement of the helmet during operation of a motorized vehicle also creates airflow against and around the outer shell  102 . The upper airflow surface  121  will experience airflow at a first flow rate X and the lower airflow surface  123  will experience airflow at a second flow rate Y. Generally, the first flow rate X will be greater than the second flow rate Y. The difference between the second flow rate Y and the first flow rate X creates an area  171  of decreased pressure near the interface  125  of the airflow surfaces  121  and  123 . In one aspect of the invention, exhaust openings  114  are positioned at or near the interface  125  such that the exhaust openings  114  experience a vacuum from the area of decreased pressure  171 . In this arrangement, air is drawn from within the exhaust plenum  118  ( FIG. 3 ) and/or exhaust channels  125 , through the exhaust opening  114 . This suction of air compliments the airflow within the head cavity  106  to exhaust heat and perspiration. In other words, airflow within the head cavity  106  generally continues toward and through the exhaust openings  114 , and, at the same time, the pressure differential near the exhaust openings  114  pulls air through the exhaust openings  114 . By exhausting air from the head cavity  106 , heat and moisture are effectively removed. This function can be achieved with a number of designs and arrangements of ridges and exhaust openings.  
         [0059]     Hence, from the foregoing, it will be appreciated that the helmet is better adept at circulating air through the interior to cool the user when riding. The openings to allow the air in are larger due at least in part to their placement on the exposed angled edge of the inner protective layer at the eye opening. Moreover, the use of plenums greatly facilitates gathering of air to increase airflow through the channels and this air flow is less likely to be impeded by the liner as the channels are better protected. The air is more easily removed due to the configuration of the outer shell of the helmet and the placement of the exhaust opening.  
         [0060]     Advantageously, the liner is also easier to remove for cleaning and replacement purposes. Thus, the illustrated embodiment of the helmet represents an improvement over helmets of the prior art in a number of different manners.  
         [0061]     Although the preferred embodiments of the present invention have shown, described and pointed out the fundamental novel features of the invention as applied to those embodiments, it will be understood that various omissions, substitutions and changes in the form of the detail of the device illustrated may be made by those skilled in the art without departing from the spirit or scope of the present invention. Consequently, the scope of the invention should not be limited to the foregoing description but should be defined by the appended claims.