Abstract:
A safety helmet having a rigid outer shell, a shock absorbing layer inside of the outer shell, and a shield layer fabricated from a strong and lightweight material positioned between the outer shell and the shock absorbing layer. The shield layer is preferably free to move relative to the outer shell in a direction toward the shock absorbing layer.

Description:
This application claims the benefit of prior provisional application No. 60/121,911 filed Feb. 26, 1999. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to safety helmets, and particularly, to safety helmet assemblies providing protection against top impacts, lateral impacts and penetrating impacts. 
     BACKGROUND OF THE INVENTION 
     Many types of protective headgear or safety helmets are worn by individuals to protect against head injuries. For example, safety helmets providing protection from top impacts, lateral impacts and/or penetrating impacts typically include a rigid outer shell, a shock absorbing layer within the outer shell and a suspension system. An example of such a safety helmet is the SUPER V safety helmet available from Mine Safety Appliances Company of Pittsburgh, Pennsylvania. In such safety helmets, the outer shell, the shock absorbing layer, along with the suspension act to absorb the shock of any impact to the safety helmet. 
     Safety helmets providing protection from top impacts, lateral impacts and penetrating impacts are subjected to stringent testing requirements. Those safety helmets are tested under Impact Standard ANSI Z89.1-1997 in the United States and under CSA Z94.1-1992 in Canada. Under CSA Z94.1-1992, for example, safety helmets are subjected to a rigorous penetration test in which a heavily weighted, pointed projectile is accelerated to impact the helmet. To satisfy such penetration tests, manufacturers of safety helmets fabricate the outer shell of the safety helmet from a relatively thick layer of a high impact strength material. The thicker the layer, the heavier the helmet, which makes the helmet uncomfortable for the user to wear. This discomfort can result in fatigue and/or a reluctance to use the safety helmet, either of which can result in safety lapses. Furthermore, use of a relatively thick layer of a very high impact strength material results in substantial manufacturing expense. 
     It is very desirable, therefore, to develop a safety helmet that provides top impact protection, side impact protection and penetration protection that is lightweight and comfortable to wear, as well low cost and simple to manufacture. 
     SUMMARY OF THE INVENTION 
     Generally, the present invention provides a safety helmet assembly comprising: 
     (a) a rigid outer shell; 
     (b) a shock absorbing layer inside of the outer shell; and 
     (c) a shield layer positioned between the outer shell and the shock absorbing layer. 
     The shield layer assists in preventing an object that penetrates the outer shell from contacting the user&#39;s head. The shield layer is thus preferably fabricated from a relatively strong material that is also lightweight and inexpensive. In that regard, the shield layer is preferably fabricated from a polymeric material having a notched impact strength greater than 0.5 ft.lb./in. The polymeric material also preferably has a modulus in the range of approximately 150,000 to approximately 700,000 psi. Polymeric materials used in the present invention, when amorphous, preferably have a glass transition temperature (T g ) of at least approximately 125° C. Semicrystalline or crystalline polymeric materials preferably have a crystalline melting point of at least approximately 95° C. 
     To minimize the size, weight and cost of the safety helmet assembly, the thickness of the shield layer is preferably minimized, particularly when using polymeric materials as described above. The thickness of the shield layer is preferably in the range of approximately 0.015 to approximately 0.040 in. More preferably, the thickness of the shield layer is preferably in the range of approximately 0.025 to approximately 0.035 in. In general, the stronger/more impact resistant the material used in fabricating the shield layer, the thinner the shield layer can be. Regardless of modulus, impact strength and thickness, an appropriate material for the shield layer and the thickness thereof is readily and easily determined using a known standard such as provided in CSA Z94.1-1992. 
     Similarly, the cost and manufacturability of the material are preferably taken into account since there are many strong, lightweight materials which are simply too expensive for use in a helmet or cannot be manufactured easily in a helmet. 
     Preferably, the shield layer is free to move relative to the outer shell in a direction toward the shock absorbing layer. It is believed that forcing the shield layer into the shock absorbing layer upon penetration of the outer shell absorbs some of the energy of the penetrating object and limits the extent of penetration. 
     The present inventors have discovered that placement of a relatively thin shield layer between the outer shell and shock absorbing layer of a safety helmet assembly greatly increases the penetration resistance of the safety helmet assembly. The incorporation of such a shield layer eliminates the need to fabricate the outer shell of the helmet from a thick layer of a relatively high strength material. The weight, size and cost of safety helmet assemblies can be reduced with the use of the shield layer of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a perspective view of an embodiment of a safety helmet assembly of the present invention in an unassembled state. 
     FIG. 2 illustrates an expanded side view of an embodiment of a shield layer section of the present invention. 
     FIG. 3A and 3B illustrate expanded side views of the shield layer section of FIG. 2 as positioned within the safety helmet assembly of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As illustrated in FIG. 1, safety helmet assembly  10  of the present invention preferably includes a rigid outer shell  20  fabricated from a relatively rigid, strong material. Safety helmet assembly  10  also preferably includes a shock absorbing layer  30  formed generally to the shape of the interior of outer shell  20 . Shock absorbing layer  30  is preferably fabricated from a collapsible material such as a foamed polymeric material suitable to absorb the shock of a lateral or side impact upon outer shell  20 . Since shock absorbing layer  30  protects predominantly against side impacts, shock absorbing layer  30  typically need not extend to the top of outer shell  20  when safety helmet assembly  10  is assembled. 
     Safety helmet assembly  10  also preferably comprises a suspension  40  as disclosed, for example, in U.S. patent application Ser. No. 08/838,004, filed Apr. 4, 1997, now U.S. Pat. No. 5,950, 245, the disclosure of which is incorporated herein by reference. In that regard, suspension  40  may include strips  44  of, for example, webbing material arranged to cross each other. The ends of webbing strips  44  are preferably attached at four or more points around the circumference of the outer shell  20 . Webbing strips  44  form the crown portion of suspension  44 . A headband  46  is then typically attached at four or more points to suspension  40  to permit safety helmet assembly  10  to be worn by the worker. To securely position safety helmet assembly  10  on the worker&#39;s head, it is preferable that the circumference of headband  46  be adjustable to fit the appropriate head size. In that regard, an adjustable napestrap  48  may be attached at a rearward end of headband  46  to achieve these results. In the embodiment of FIG. 1, a ratchet mechanism  50  adjusts the fit of suspension  40 . 
     As illustrated in FIG. 1, the ends of webbing strips  44  are preferably attached to tabs  60  that preferably pass through passages  32  in shock absorbing layer  30  to be removably seated in cooperating ports  22  formed around the circumference of outer shell  20 . 
     Unlike prior safety helmet assemblies, safety helmet assembly  10  further includes a shield layer  70  preferably comprising one or more sections  72  formed from a relatively structurally strong polymeric material such as nylon or polycarbonate. Shield sections  72  are preferably positioned between outer shell  20  and shock absorbing layer  30 . Shield sections  72  are also preferably relatively thin to prevent a substantial increase in the overall size and weight of safety helmet assembly  10 . In one embodiment, outer shell  20  was fabricated from polyethylene and shield sections  72  were fabricated from nylon of a thickness of approximately 0.030 in. 
     Likewise, shield sections  72  are also preferably limited in size (area) and positioned adjacent to only those sections of outer shell  20  and shock absorbing layer  30  requiring reinforcement for protection against puncturing impacts. In that regard, certain regions of outer shell  20  may be less resistant to penetration than other regions or the distance between the outer shell and the head of the user may be less than in other regions. The curvature of outer shell  20  at the forward and rearward ends thereof and the distance from outer shell  20  to the head of the user at the top portion of outer shell  20  make contact of a penetrating object with the head of the user less likely in those regions. On the other hand, the reduced amount of curvature on the sides of outer shell  20  may result in less resistance to penetration. Likewise, it is in the area of the lower sides of outer shell  20  that the user&#39;s head is closest to outer shell  20 . Furthermore, in the embodiment of FIG. 1, passages  32  in shock absorbing layer  30  may increase the likelihood that a penetrating object may contact the user&#39;s head in the vicinity thereof. Shield sections  72  are thus preferably positioned on each side of safety helmet assembly  10  and cover passages  32 . 
     As best illustrated in FIGS. 2,  3 A and  3 B, shield sections  72  may be provided with slots  74  at each end thereof through which webbing strips  44  may pass when shield sections  72  are positioned within safety helmet assembly  10 . Shield sections  72  are thereby held securely within safety helmet assembly  10  but are allowed to float or move relatively freely (that is, in a generally radial direction relative to the circumference of outer shell  20 ) between outer shell  20  and shock absorbing layer  30 . Shield sections  72  preferably are not attached to outer shell  20  so that in the case of a penetration of outer shell  20 , the penetrating object will contact one of shield sections  72  and displace shield section  72  in the direction of shock absorbing layer  30 . Shield section  72  will be forced into shock absorbing layer  30  which will compress to absorb some of the energy of the penetrating object. 
     Although the present invention has been described in detail in connection with the above embodiments, it is to be understood that such detail is solely for that purpose and that variations can be made by those skilled in the art without departing from the spirit of the invention except as it may be limited by the following claims.