Patent Publication Number: US-8522418-B2

Title: Protective helmets and method of manufacture thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The application is a divisional application of U.S. patent application Ser. No. 10/916,831, filed Aug. 13, 2004, the disclosure of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to protective helmets and to methods of manufacture thereof, and, particularly, to thermoplastic protective helmets for use by firefighters and to methods of manufacture thereof. 
     BACKGROUND OF THE INVENTION 
     The outer, protective garments worn by firefighters (commonly referred to as turnout gear) typically include a large coat and pants that have three layers: (1) an outer layer, (2) a intermediate layer providing a vapor barrier, and (3) a removable inner layer providing thermal insulation. The outer layer is fabricated from materials that are resistant to heat, flame, abrasion and water. Firefighters also wear other protective gear, including a helmet, thick gloves, and an air tank that is typically part of a self-contained breathing apparatus (SCBA). 
     In the 19 th  century, firefighters in the United States commonly used leather helmets which included a long rear brim and curled up side brims to prevent water from running down the firefighter&#39;s neck and into his coat. Around the beginning of the 20 th  century, firefighters started using aluminum helmets which were molded to look like leather helmets but were less expensive. However, aluminum helmets conducted heat and electricity, causing many firefighters to return to using leather helmets. Leather helmets, which are still popular among firefighters today, are strong enough to provide protection from falling objects, and the large brim of the traditional leather helmets sheds water effectively and prevents objects from dropping down the back of the fire fighter&#39;s neck. Leather helmets, however, are very labor intensive and time consuming to manufacture, making them relatively more expensive. 
     Designers of firefighter helmets must consider a wide array of factors, including, for example, heat, and flame resistance; resistance to electrical current; impact force and acceleration; penetration; chin strap and suspension system effectiveness; flammability and resistance of ear covers; resistance of the face shield to heat and flame; and brightness and surface area of fluorescent markings. In the 1970s, the National Fire Protection Association (NFPA) developed its Standard on Structural Fire Fighter&#39;s Helmets. NFPA certification requires that firefighter helmets meet a number of stringent performance requirements. 
     Modern firefighter helmets are often fabricated from high-tech plastic and composite materials. Such helmets often include a suspension system and energy-absorbing foam impact liners, a face shield and flame-resistant flaps. To satisfy the NFPA standard, firefighter helmets are usually fabricated from highly impact resistant and thermally stable materials such as thermoplastics (for example, a polyetherimide) and thermosets (for example, fiberglass composites including vinylester/polyester thermoset resins). For example, CairnsHELMETS® 1000 and CAIRNS® 1010 helmets, available from Mine Safety Appliances Company (“MSA”), are NFPA approved helmets fabricated from fiberglass composites, which can be reinforced with ballistic-grade KEVLAR® (poly(p-phenyleneterephtalamide, available from Dupont of Wilmington, Del.). Similarly, the CairnsHELMETS® PHOENIX® 660 helmet, available from MSA, is an NFPA approved helmet fabricated from a thermoplastic material. 
     Thermoplastic helmets, however, have generally been limited to a “modern” or jet-fighter pilot” helmet design in which the helmet brim extends out from the helmet to a much lesser extent and at a greater downward angle relative to horizontal than the brims of a “traditional” helmet design. Prior to the present invention, it was not possible to produce thermoplastic helmets having the extending brim of the traditional helmet design (which typically extends away from the helmet dome by at least 2.5 in. (and, more typically, by at least 3 in.) at, for example, the rear of the helmet) to fully satisfy the NFPA 1971 standard, the disclosure of which is incorporated herein by reference. In that regard, such helmets (and particularly the brims thereof) often do not satisfy the current version of the NFPA 1971 standard for resistance to heat, which limits the deformation a helmet can exhibit under extended exposure to highly elevated temperatures (that is, 5 minutes at a temperature of 500° F.; see, for example, paragraphs 5-2.4, 6-6.2 through 6-6.7 and 6-6.12 of the current version of the NFPA 1971 standard). 
     However, many firefighters prefer to use helmets having a traditional design. In part, such firefighters prefer the traditional look of such helmets. Moreover, the extending brim of the traditional helmet provides increased protection from falling water and/or objects. 
     It is desirable, therefore, to develop improved protective helmets (for example, traditional style firefighter helmets) and methods of manufacture thereof. 
     SUMMARY OF THE INVENTION 
     In one aspect, the present invention provides a protective helmet including a generally dome-shaped section and a brim extending outwardly from a lower portion of the dome-shaped section. In the case of a protective helmet of the present invention having the form of a traditional style firefighter helmet, the rear of the brim can extend outwardly from the bottom of the dome-shaped section further and more generally horizontally (or more closely to horizontally) than the rear brim of a modern style firefighter helmet. The sides of the brim of such a traditional style helmet can curve, slope or angle upward, while the rear of the brim can curve, slope or angle downward to provide a water shed. The dome-shaped section and the brim of the helmets of the present invention are formed from a thermoplastic material. The helmet further includes a brim support in operative connection with at least a portion of the brim. The brim support is formed from a material that is more heat resistant than the thermoplastic material. The brim support is sufficiently rigid to limit deformation of the brim upon exposure to high temperature (for example, exposure for a period of time to a temperature above the heat deflection temperature or above the melting temperature of the thermoplastic material). The brim support material can, for example, have a melting point greater than the melting point of the thermoplastic material (for example, above 500° F.). 
     In one embodiment, the brim support conforms generally to a perimeter of the brim. The brim support can, for example, extend along a portion of the perimeter of the brim. Preferably, the brim support extends over more than fifty percent (50%) of the perimeter of the brim. In one embodiment, the brim supports extends along the entire perimeter of the brim. 
     The helmet can further include an edge trim that extends around the brim support and the perimeter of the brim to retain the brim support in operative connection with the brim. The brim support can, for example, be added to the helmet after the helmet is formed. The brim support can alternatively be molded into the brim of the helmet. In one embodiment, the brim support is formed from a metal (for example, steel, aluminum or titanium). 
     In another aspect, the present invention provides a method of manufacturing a protective helmet, including: molding an outer shell of the helmet from a thermoplastic material, the outer shell comprising a generally dome-shaped portion and an outwardly extending brim, the brim preferably extending outwardly from near the bottom of the dome-shaped section; and operatively connecting a brim support to the brim, the brim support being formed from a material that is more heat resistant than the thermoplastic material. 
     The brim supports of the present invention enable the manufacture of protective helmets (for example, traditional style firefighter helmets and modern style firefighter helmets) from thermoplastic materials having a lower melting point than would otherwise be possible. The brim supports of the present invention can increase the resistance to deformation of the brims of protective helmets upon exposure of such helmets to high temperatures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a side, perspective view of one embodiment of a firefighter helmet of the present invention having an extending brim associated with a traditional helmet design 
         FIG. 2  illustrates a bottom perspective view of the helmet of  FIG. 1  wherein the edge trim has been partially removed from connection with the brim to show a portion of the brim support. 
         FIG. 3  illustrates a side, perspective view of the helmet of  FIG. 1  wherein the edge trim has been removed. 
         FIG. 4  illustrates a perspective view of a connector used to connect the brim support to the brim of the helmet of  FIG. 1 . 
         FIG. 5  illustrates a front perspective view of the helmet of  FIG. 1  with the edge trim removed. 
         FIG. 6A  illustrates a side, cross-sectional view of the operative connection of the edge trim, the brim support and the brim of the helmet of  FIG. 1 . 
         FIG. 6B  illustrates a perspective view of a clip member of the edge trim of  FIG. 6A . 
         FIG. 7  illustrates a side cross-sectional view of a portion of another embodiment of a helmet brim of the present invention including a seating into which a brim support can be snap fit. 
         FIG. 8  illustrates another embodiment of a portion of a thermoplastic helmet brim of the present invention wherein the brim support is molded into the brim. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Firefighter&#39;s helmets can take a variety of forms as, for example, disclosed in U.S. Pat. Nos. 5,044,016 and 6,260,212, assigned to the assignee of the present invention, the disclosures of which are incorporated herein by reference.  FIGS. 1 through 5  illustrate one embodiment of a helmet of the present invention that has the general shape of the CairnsHELMETS® 880 Tradition™ firefighter helmet available from Mine Safety Appliances Company (“MSA”). However, as is clear to one skilled in the art of protective helmets, the protective helmets of the present invention can have generally any shape suitable for protective headgear. Firefighter protective helmet  10  typically includes an outer shell  20 . An inner impact attenuation liner assembly (not shown) can be included. Outer shell  20  is formed with a generally dome-shaped section  25  and a radially outward extending brim  30  which can be wider at the back than at the front and at the sides to shield the back of the wearer&#39;s neck. 
     Outer shell  20 , dome-shaped section  25  and brim  30  are preferably fabricated from a thermoplastic material exhibiting strength, impact resistance, heat resistance and chemical resistance. An example, of a suitable thermoplastic material for use in the present invention is ULTEM®, available from GE Plastics of General Electric Company Corporation of New York, N.Y. ULTEM is an amorphous thermoplastic polyetherimide providing high heat resistance, high strength, high stiffness and broad chemical resistance. 
     Upon exposure to an elevated temperature for an extended period of time (for example, to a temperature of 500° F. for five minutes such as is required under the current version of the NFPA 1971 standard), the brim of a helmet fabricated from certain thermoplastic materials can deform. As described above, the NFPA standard limits the amount of deformation a helmet brim can undergo during testing. The present inventor has discovered that inclusion of a brim support  40  around the perimeter of brim  30  significantly limits deformation of brim  30  and enables helmet  10  to fully satisfy the requirement of the current version of the NFPA 1971 standard, even with the extending brim of a traditional helmet design. Brim support  40  can be formed in the general shape of the perimeter of brim  30  and is formed from a heat resistant material. In general, such materials should be sufficiently rigid to support (that is, limit deformation of) brim  30  at high temperature and have a melting temperature above 500° F. Such materials include, but are not limited to various metals, polymers and ceramics. In the embodiment of  FIGS. 1 through 5 , brim support  40  is fabricated from a metal such as steel. Steel, for example, is quite malleable and can be readily formed in the shape of the perimeter of brim  30 . 
     Brim support  40  can, for example, be in the form of a wire having a structural weight of approximately 1 oz. to approximately 3 oz in the case of a steel wire. In the case of an aluminum wire, the structural weight of brim support  40  can, for example, be in the range of approximately 0.33 oz. to approximately 1 oz. As is clear to one skilled in the art, various structural weights for various other structural materials (for example, titanium, ceramic, etc.) are suitable for use in the present invention. 
     In one embodiment, brim  30  of helmet  10  (a traditional style helmet similar to the CairnsHELMETS 880 TRADITION™ helmet available from MSA) extended outwardly near the bottom of shell  20  approximately 1.75 in. in the front, approximately 1.25 in. on the sides and approximately 3.5 in. at the back of helmet  10 . The weight of brim  40  in this embodiment was approximately 193 grams or approximately 6.8 oz. In this embodiment, brim  30  had an overall length (that is, a measurement from front to back) of approximately 15.25 in, and an overall width (that is, a measurement from side to side) of approximately 11.5 in. For comparison, a modern style helmet such as the PHOENIX 660® helmet available from MSA, the brim had an overall length of approximately 14 in. and an overall width of approximately 10.5 in. The brim of that helmet extended away from the shell by approximately 1 in. on the front and sides and by approximately 2.5 in. at the rear of the helmet. In the case of the modern style helmet, the rear of the brim also extends away from the bottom of the dome-shaped section of the shell at approximately a 45° angle downward, whereas the rear brim of traditional style helmet  10  extended generally horizontally from the bottom of the dome-shaped section of shell  20  and curved gently downward near the perimeter of brim  30 . The greater extension of the brim of a traditional style helmet and the generally horizontal extension of brim  30  of such helmets from near the bottom of dome-shaped section  25  can result in greater torque and potentially lead to greater deformation of the brim as compared to a modern style helmet upon exposure to temperatures above the heat deflection temperature or above the glass transition temperature of the thermoplastic material of the helmet for an extended period of time. 
     As recognized by one skilled in the art, the stiffness, shape, dimensions, etc. of brim support  40  can vary widely depending upon the specific properties of the material chosen for brim support  40 , the brim conformation, and the specific properties of the thermoplastic material of helmet  10 . Typical stiffness values measured for one half of the space-frame width or length of brim support  40  can, for example, be in the range of approximately 1 lbs./in. to approximately 10 lbs./in. (or even approximately 1 lbs./in. to approximately 5 lbs./in.). A variety of combinations of material, diameter and cross-section shape can, for example, create an infinite combination of suitable stiffness along each of the three axes. In the representative embodiment of a steel brim support  40  of a generally circular cross-section, the diameter of brim support  40  can, for example, be in the range of approximately 0.032 in to approximately 0.180 in. 
     Using a fundamental engineering formula for spring force, spring stiffness, and spring deflection according to the formula F=Kx one can readily determine the deflection x of brim  30  using brim support  40  having a known stiffness K. In that regard, F can be defined as the weight of one half of the brim. K can be defined as the stiffness of one half of the space-frame structure or wire of brim support  40 . X can be defined as the deflection of brim  40  assuming that thermoplastic brim  40  is “dead weight” and has no structural stiffness. If F=Kx, the deflection x=F/K. For a brim weight (F) of 4 oz. (0.25 lbs.) and a stiffness (K) of 4 lbs./in., deflection x=(0.25 lbs.)/(4 lbs./in.)=0.0625 in (or 1/16 in.). 
     It is thus demonstrated that even if the thermoplastic material for brim  30  reaches its melting point, brim support  40  is capable of supporting the brim  40  (treated as dead weight, with no structural stiffness) with only 1/16 in deflection at the location of brim support  40 , which is below the deformation limits set forth in the current version of the NFPA 1971 Standard (typically 1⅜ in. to 1⅝ in.). 
     A number of thermoplastic materials suitable for use in the present invention have a heat deflection temperature (at 264 psi) in the range of approximately 235° F. to approximately 400° F., and a melting point in the range of approximately 500° F. to approximately 700° F. At temperatures between the heat deflection temperature and the melting temperature, the material may deflect under a load (even under the load of its own weight), but the material has some structural stiffness. Such materials also have an elastic modulus of approximately 100,000 psi to in excess or 500,000 psi depending on material type. Fillers and/or reinforcements can be added to the materials to provide an elastic modulus of approximately 250,000 psi to in excess of 1,000,000 psi depending on the material type as well as filler and/or reinforcement type and percent composition. 
     In the embodiment of  FIGS. 1 through 5 , brim support  40  is also preferably attached to helmet  10  via a metal clip  50  at the rear of helmet  10  (see, for example,  FIG. 4 ). Brim support  40  is retained in position around the perimeter of brim  30  via an elastomeric or resilient edge trim  60 , which can, for example, be formed from a heat resistant thermoplastic rubber. As illustrated in  FIGS. 6A and 6B , edge trim  60  can have a generally U-shaped cross section that fits snugly around brim  30  to retain brim support  40  in position adjacent to and around the perimeter of brim  30 . Edge trim  60  can, for example, include a clip  62  having a generally U-shaped cross-section. Such metallic clips are sometimes used in edge trim of currently available helmets to maintain the edge trim in snug connection with the brim of the helmet without the use of adhesives. However, the structural stiffness of such clips is compromised by open or cutout sections  64  formed therein to facilitate bending of clip  62  to the shape of the perimeter of the helmet, thereby making such clips unsuitable for use as brim support  40  of the present invention. However, brim support  40  can be formed in the shape of clip  62  as long as the structural stiffness is made sufficient to adequately support brim  30  as described above. For example, open sections  64  can be of reduced width and/or length, provided in reduced number or eliminated. As is clear to one skilled in the art, existing thermoplastic protective helmets are readily retrofitted with the brim support of the present invention to greatly improve the heat resistance of the brim of such helmets. 
       FIG. 7  illustrates another embodiment of a helmet brim  30 ′ including a seating  32 ′ into which a brim support  40 ′ can be snap fit, thereby potentially eliminating the need for a separate attachment member (such as edge trim  60 ) to maintain brim support  40  in operative connection with brim  30 ′. Adhesives and other attachment mechanisms can also be used to maintain the brim supports of the present invention in operative connection with the helmet brims thereof.  FIG. 8  illustrates another embodiment of a helmet brim  30 ″ of the present invention in which a brim support  40 ″ has been molded within brim  30 ″. 
     The foregoing description and accompanying drawings set forth preferred embodiments of the invention at the present time. Various modifications, additions and alternative designs will, of course, become apparent to those skilled in the art in light of the foregoing teachings without departing from the scope of the invention. The scope of the invention is indicated by the following claims rather than by the foregoing description. All changes and variations that fall within the meaning and range of equivalency of the claims are to be embraced within their scope.