Patent Publication Number: US-9848667-B2

Title: Lens seal for headgear

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage filing under 35 U.S.C. 371 of PCT/US2009/038733, filed Mar. 30, 2009, which claims priority to United States Provisional Application No. 61/042,309, filed Apr. 4, 2008, the disclosure of which is incorporated by reference in its/their entirety herein. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure is directed to headgear having a movable face shield and lens, in particular, to headgear having a lens sealingly engaging the headgear. 
     BACKGROUND OF THE DISCLOSURE 
     One common type of headgear is a respirator system. Respirator systems are frequently worn by people working in areas where the air may be contaminated with toxic or noxious substances such as particulates, gases and vapors. For example, the air in a sanding or grinding area may contain airborne particulates, the air in a painting area may contain droplets of paint or solvent vapors, and the air in a welding area may contain harmful particles or fumes. The respirator system may filter the air or it may provide a supply of uncontaminated air. 
     A respirator system may include a helmet, hardhat or similar device for impact protection. Respirator systems that include helmets are frequently worn by people working in areas where there is a potential for impact from a foreign object. Typically, this type of respirator system includes a helmet, hardhat or another impact resistant head cover with an air inlet, face shield, and a clean air supply. 
     When the respirator system is in use with the face shield lowered, the face shield should form a tight seal to inhibit passage of contaminants, both particulate and gaseous, into the wearer&#39;s air space. Often while being worn, but when the respirator system is not in use, there is a desire by the user to remove the face shield from the field of view. Many face shields are pivotally attached to the head cover, to allow the face shield to be lifted when it is not needed. 
     What is needed is a respirator system that provides good sealing when the respirator system is in use with the face shield lowered, but that also allows the face shield to be lifted when desired. 
     BRIEF SUMMARY OF THE DISCLOSURE 
     In one particular aspect, this disclosure is directed to an article of headgear that has a head-covering article, a lens moveably attached to the head-covering article, and a seal attached to the lens, the seal comprising a first polymeric material and a second polymeric material, the first polymeric material having a greater tensile modulus than the second material. 
     In another particular aspect, this disclosure is directed to an article of headgear having a head-covering article, a lens moveably attached to the head-covering article, the lens having a curve associated therewith, and a seal attached to the lens, the seal being curved and comprising a first polymeric material and a second polymeric material, the first polymeric material having a greater tensile modulus than the second material. 
     In another particular aspect, this disclosure is directed to a method of making an article of headgear. The method includes providing a head-covering article, pivotally connecting to the head-covering article a lens, extruding a polymeric material to form a seal, post-forming the extruded seal to form a curved seal; and mechanically attaching the curved seal to the lens. 
     In yet another particular aspect, this disclosure is directed to a method of making an article of headgear. The method includes providing a head-covering article, pivotally connecting to the head-covering article a lens, extruding a first polymeric material and a second polymeric material to form a seal, the first polymeric material having a greater tensile modulus than the second material, and mechanically attaching the seal to the lens. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a side view of a hardhat respirator system according to the present disclosure, with the lens of the hardhat in a first, closed, position. 
         FIG. 1B  is a side view of the hardhat respirator system of  FIG. 1A  with the lens in a second, open, position. 
         FIG. 2A  is a side view of a helmet respirator system according to the present disclosure, with the lens of the helmet in a first, closed, position. 
         FIG. 2B  is a side view of the helmet respirator system of  FIG. 2A  with the lens in a second, open, position. 
         FIG. 3  is a side view of a visor respirator system according to the present disclosure, with the lens of the visor in a first, closed, position. 
         FIG. 4  is an exploded perspective view of the visor respirator system of  FIG. 3 , illustrating various elements of the system. 
         FIG. 5  is an enlarged perspective side view of a portion of a headgear article according to the present disclosure, focusing on the seal and its engagement with the lens and head-covering article. 
         FIG. 6  is an end view of another embodiment of a seal according to the present disclosure. 
         FIG. 7  is an end view of yet another embodiment of a seal according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     In the following description, reference is made to the accompanying set of drawings that form a part hereof and in which are shown by way of illustration several specific embodiments. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense. While the present invention is not so limited, an appreciation of various aspects of the invention will be gained through a discussion of the examples provided below. 
     The present disclosure is directed to articles of headgear, such as respirator systems, which may include a face shield movable from a first, lowered position to a second, raised position. The face shield includes a lens having a seal at its top edge that sealingly engages the surface of the headgear when the face shield is in its lowered or closed position. In some embodiments, the seal is fluid tight, e.g., air tight. The seal present between the face shield and the head-covering article may be curved or radiused, to follow the contours of the face shield and the head-covering article. Such a face shield and seal is particularly suited for use with respirator systems. 
     Various embodiments are provided below of seals, such as extruded seals, that inhibit puckering when formed to a radiused shape, such as a curved shape. Also provided below are various embodiments of seals, such as extruded seals, that sealingly conform to a radiused surface and/or when mounted to a radiused lens. In some embodiments, the seals are composed of at least two different polymeric materials, the materials having different tensile modulus. In other embodiments, the seals are thermally post-processed. The seals engage their sealing surface with minimal puckering that might provide an unsealed area. 
     Referring to the figures, a first embodiment of an article of headgear according to this disclosure is illustrated in  FIGS. 1A and 1B . The particular article of headgear illustrated is an embodiment of a hardhat respirator system  100 . Hardhat respirator system  100  includes a head-protecting head-covering article or shell  10  with a moveable face shield  20  pivotally attached thereto.  FIG. 1A  illustrates face shield  20  in a first, closed or lowered position, configured for protecting the user&#39;s face.  FIG. 1B  illustrates face shield  20  in a second, open or raised position. Hardhat respirator system  100  includes an air inlet  11 , configured to be connected to an air supply for providing a source of breathing air, such as purified air, to the user of hardhat respirator system  100  and an outlet (not shown) configured to be disposed proximate a user&#39;s face when the respirator system  100  is worn. 
     Shell  10  of hardhat respirator system  100  has an outer surface  12 , typically configured to resist impact. Shell  10  extends over the user&#39;s head and includes a frontal area surface  15 . A suspension system  16 , e.g., an adjustable suspension system, secures hardhat respirator system  100  to the user&#39;s head. In this exemplary embodiment, face shield  20  is pivotally attached to shell  10  via pivot mechanism  18 . Face shield  20  has a generally curved lens  22  and a lens frame  24 . Lens frame  24  supports lens  22  and allows pivoting of face shield  20  via pivot mechanism  18 . Lens  22  may be attached to the head-covering article or shell  10  using the lens frame  24 . Face shield  20  includes a seal  25 . Seal  25  typically engages, e.g., sealingly engages, frontal area surface  15  of shell  10  when face shield  20  is in its lowered or closed position ( FIG. 1A ). In some embodiments, the seal may be fluid tight, e.g., air tight. When face shield  20  is in a raised or open position ( FIG. 1B ), seal  25  usually does not contact shell  10  but other configurations are possible. 
     A second embodiment of an article of headgear according to this disclosure is illustrated in  FIGS. 2A and 2B . The particular article of headgear illustrated is an embodiment of a helmet respirator system  110 . Helmet respirator system  110  includes a head-covering article or head-protecting shell  40  with a moveable face shield  50  pivotally attached thereto.  FIG. 2A  illustrates face shield  40  in a first, closed or lowered position, configured for protecting the user&#39;s face.  FIG. 2B  illustrates face shield  50  in a second, open or raised position. Helmet respirator system  110  includes an air inlet  41 , configured to be connected to an air supply for providing a source of breathing air, such as filtered air, to the user of helmet respirator system  110  and an outlet (not shown) configured to be disposed proximate a user&#39;s face when the respirator system  110  is worn. 
     Shell  40  of helmet respirator system  110  has an outer surface  42 , typically configured to resist impact. Shell  40  extends over the user&#39;s head and includes a frontal area surface  45 . A suspension system  46 , e.g., an adjustable suspension system, secures helmet respirator system  110  to the user&#39;s head. Face shield  50  is pivotally attached to shell  40  via pivot mechanism  48 . Face shield  50  has a generally curved lens  52  and a lens frame  54 . Lens frame  54  supports lens  52  and allows pivoting of face shield  50  via pivot mechanism  48 . Lens  52  may be attached to the head-covering article or shell  40  using the lens frame  54 . Face shield  50  includes a seal  55  on lens  52 . Seal  55  engages, e.g., sealingly engages, frontal area surface  45  of shell  40  when face shield  50  is in its lowered or closed position ( FIG. 2A ). In some embodiments, the seal is fluid tight, e.g., air tight. When face shield  50  is in a raised or open position ( FIG. 2B ), seal  55  usually does not contact shell  40 , but other configurations are possible. Fixedly positioned in relation to shell  40  is a jaw frame  56 . When closed (i.e., as in  FIG. 2A ), lens frame  54  contacts and usually seals against jaw frame  56 . 
     A third embodiment of an article of headgear according to this disclosure is illustrated in  FIG. 3 . The particular article of headgear illustrated is an embodiment of a visor respirator system  120 . Visor respirator system  120  includes a head covering article or shell  70 , that although it covers a portion of the user&#39;s head, it is not intended to provide as high of a degree of impact protection as the previously described embodiments. Pivotally connected to shell  70  via mechanism  78  is a moveable face shield  80 . Visor respirator system  120  includes an air inlet  71 , configured to be connected to an air supply for providing a source of breathing air, such as purified air, to the user of visor respirator system  120  and an outlet (not shown) configured to be disposed proximate a user&#39;s face when the respirator system  120  is worn. 
     Shell  70  of visor respirator system  120  has an outer surface  72  and extends over the user&#39;s head and includes a frontal area surface  75 . A suspension system  76 , e.g., an adjustable suspension system, secures visor respirator system  120  to the user&#39;s head. Face shield  80  is pivotally attached to shell  70  via pivot mechanism  78 . Face shield  80  has a generally curved lens  82  and a lens frame  84  that supports lens  82  and allows pivoting of face shield  80  via pivot mechanism  78 . Lens  82  may be attached to the head-covering article or shell  70  using the lens frame  84 . Face shield  80  includes a seal  85  on lens  82 . Seal  85  engages, e.g., sealingly engages, frontal area surface  75  of shell  70  when face shield  80  is in its lowered or closed position. In some embodiments, the seal is fluid tight, e.g., air tight. When face shield  80  is in a raised or open position, seal  85  does not contact shell  70 , although other configurations are possible. 
       FIG. 4  illustrates visor respirator system  120  with various pieces exploded to provide a better understanding of the construction of visor respirator system  120  and also of hardhat respirator system  100  and helmet respirator system  110 . Illustrated in  FIG. 4  are shell  70  and its outer surface  72  including frontal area surface  75 , lens  82  and lens frame  84 , and seal  85 . Also illustrated are the various pieces of an exemplary pivot mechanism  78 . Shell  70  includes an engagement region  78   a  which includes an aperture through shell  70 . Positioned on the inside of shell  70  is a cam socket  78   b  that seats within engagement region  78   a  and that extends into the aperture. Lens frame  84  includes an aperture  78   d  therethrough that forms a pivot axis for face shield  80  ( FIG. 3 ). A cam post  78   e  passes through aperture  78   d  in lens frame  84  and through the aperture in engagement region  78   a  of shell  70  and engages with cam socket  78   b . A spring  78   c , in this embodiment, is positioned within engagement region  78   a  in shell  70  between a flange on post  78   e  and an inner surface of the aperture in shell  70 . Other exemplary embodiments may include completely different pivoting mechanisms, or pivoting mechanisms having different pieces, e.g., different springs  78   c  or different posts  78   e  and sockets  78   b.    
     Each of the headgear respirator systems discussed above (i.e., hardhat respirator system  100 , helmet respirator system  110  and visor respirator system  120 ) includes a seal on the face shield lens that forms a seal (e.g., a fluid tight seal) against the shell of the headgear. The following discussion provides various embodiments of seals suitable for use in articles of headgear according to the present disclosure, particularly for those that have a curved lens. 
     Referring to  FIG. 5 , an enlarged perspective side view of a face shield engagement with generic head covering article is shown. This face shield and head covering article may be from any of the headgear discussed above (i.e., hardhat respirator system  100 , helmet respirator system  110  and visor respirator system  120 ) or from another exemplary article of headgear. Illustrated is headgear having a surface  130  with a lens  132  making a sealed connection thereto by seal  140  present at edge  134  of lens  132 . Exemplary lens  132  includes a groove  135  for receiving a part of seal  140  therein. Seal  140  may represent any or all of seal  25 , seal  55 , and seal  85 . 
     In an exemplary embodiment, seal  140  includes a body  142  having a length L ( FIG. 4 ) that has a sealing portion  144  and an attachment portion  146  extending the length L. Sealing portion  144  includes a sealing surface  143  at least proximate a distal end  145  of body  142  that, when disposed against surface  130  of the headgear, creates a seal, e.g., a fluid tight seal, with surface  130 . Opposite sealing surface  143  is an opposite, upper surface  141 . Upper surface  141  is configured to facilitate the removal of solid (e.g., particulate) contaminants from the headgear by providing a surface from which the contaminants can readily slide off when lens  132  is in its lowered position. In some embodiments, upper surface  141  provides a smooth transition from head covering article surface  130  to lens edge  134 . 
     In this embodiment, the attachment of seal  140  to lens  132  is a mechanical attachment via attachment portion  146 , which includes a stem  147  with one or more projections, such as a plurality of barbs  148  extending therefrom. In most embodiments, attachment portion  146  is press-fit into groove  135 , without the use of secondary attachment systems such as clips, pins, screws, or the like. In some exemplary embodiments, seal  140  may be removably received in groove  135  of lens  132  or otherwise removably attached to lens  132  or the face shield. In some embodiments, the seal is attached to the lens after pivotally connecting the lens to the head-covering article, whereas in other embodiments the seal is attached to the lens prior to connecting the lens to the head-covering article. 
     As seen best in  FIG. 4 , seal  85  follows the shape of both lens  82  and frontal surface  75 . In typical embodiments, seal  85  is curved along its length L; e.g., seal  85  has an arcuate shape. In some embodiments, seal  85  is not semi-circular, but is a portion of an ellipse (e.g., seal  85  is elliptical) or other shape having a non-constant radius. Although not discernible in  FIG. 5 , seal  140  may be configured to follow the shape of surface  130  and lens  132 . In some exemplary embodiments, the seal  140  may have a curved shape, as previously described. Various embodiments are provided below in this disclosure of seals that inhibit puckering when formed to a radiused shape, such as a curved shape. Also provided below are various embodiments of seals that may be configured to sealingly conform to a radiused surface, such as a curved surface  130 , when mounted to a radiused lens, such as a curved lens  132 . The seals engage their sealing surface with relatively minimal puckering that might otherwise provide an unsealed area. In some embodiments, there is no puckering. 
     The seals of this disclosure (e.g., seals  25 ,  55 ,  85 ,  140 , etc.) can be formed from a flexible, conformable, and generally polymeric material. The seals can be made from a variety of materials including, e.g., organic polymers, inorganic polymers, metals, composites of organic polymers, and combinations thereof. Examples of suitable polymeric materials include thermoplastic and thermosetting materials. Suitable thermoplastic polymer materials include polyesters, polyurethanes, polystyrenes, polyolefins, polystyrene, polyperfluoro olefins, vinyls and polyvinyl chlorides, nylons, and copolymers thereof. Suitable thermosetting polymers include epoxies, polyimides, polyesters, silicones, and copolymers thereof (i.e., polymers containing at least two different monomers including, e.g., terpolymers and tetrapolymers). Elastomers are particularly suitable for seals of this disclosure. Examples of elastomers or elastomeric materials include styrene-butadiene copolymer, polychloroprene (neoprene), nitrile rubber, butyl rubber, polysulfide rubber, polyisoprene, ethylene-propylene terpolymers (EPDM rubbers), silicone rubber, and polyurethane rubber. Rubber (e.g., natural rubber) is also a suitable material. 
     In most embodiments, seal  140  is extruded. Because of the manufacturing technique (i.e., extrusion), a typical seal is generally straight and non-directional, typically not having a tendency to curl or bend beyond normal manufacturing tolerances. Prior to the various embodiments in according to this disclosure, bending an extruded piece (e.g., a seal) to follow a desired radius usually resulted in puckering, which is not conducive to a fluid-tight seal. The present disclosure provides various embodiments of extruded seals that readily form to a curved shape and/or that sealingly conform to a curved surface. 
     A first embodiment of a seal that readily forms a curved shape and/or that sealingly conforms to a curved surface is illustrated in  FIG. 6 . This seal  160  has a body  162  that has a sealing portion  164  and an attachment portion  166 . Sealing portion  164  includes a sealing surface  163  at least proximate a distal end  165  of body  162  that, when disposed against a curved surface, can create a seal, e.g., a fluid tight seal, with the surface. Opposite sealing surface  163  is an opposite, upper surface  161 . Attachment portion  166  includes a stem  167  with one or more projections, such as plurality of barbs  168  extending therefrom. When positioned in a curved shape, e.g., whether in a groove of a curved face shield lens and/or against a curved headgear surface, the inner surface of body  162  (e.g., sealing surface  163 ) is shorter than the opposite, outer surface of body  162 . 
     To facilitate bending seal  160  to the curved shape, seal  160  may be composed of two different materials; a first material  171  and a second material  172 . First and second materials  171 ,  172  are selected to have different tensile moduli. In one embodiment, a relative tensile modulus between the two materials is at least about 3×, at least about 5× in some embodiments, and in some other embodiments, at least about 10×. Tensile modulus is related to the hardness or durometer of a material. Durometer is a measurement of the relative hardness of an elastomeric material. Two durometer scales exist, which have some overlap: Shore A for the very softest of rubbery materials (e.g., skin or silicone caulk), and Shore D. Examples of materials measured in the Shore A scale include door weather-stripping materials and examples of materials measured in the Shore D scale include solid tires (e.g., on a lawn mower or caster wheels). 
     In this embodiment, first material  171  has a lower durometer than second material  172 . Also in this embodiment, first material  171  has a lower tensile modulus than second material  172 . In this embodiment, second material  172  is proximate sealing surface  163 . First material  171 , present in attachment portion  166  and the outer surface of body  162 , is more stretchable and conformable than second material  172 . When seal  160  is bent (so that sealing surface  163  is an inner surface of a curved shape), second material in sealing portion  164  bends and conforms to the desired shape. First material  171  in sealing portion  164  and in attachment portion  166  stretches to accommodate the longer length that results when sealing portion  164  is curved around front surface area  15 ,  45 ,  75 . 
     An exemplary embodiment of a seal, such as seal  160 , has an overall height of about 0.5 inch (about 1.27 cm), with the sealing portion  164  being about 0.3 inch (about 0.76 cm) and the attachment portion  166  being about 0.23 inch (about 0.58 cm). Sealing portion  164  is tapered and very slightly curved; sealing surface  163  is defined by a radius of about 0.9 inch (about 2.3 cm), and upper surface  161  is defined by a radius of about 0.6 inch (about 1.5 cm). At distal end  165 , the thickness of sealing portion  164  is about 0.024 inch (about 0.6 mm), and that thickness gradually increases to a thickness of about 0.045 inch (about 1.14 mm) prior to flaring to 0.117 inch (about 3 mm) at attachment portion  166 . 
     In an exemplary embodiment, present within sealing portion  164  is an insert of second material  172 , which is about 0.02 inch (about 0.5 mm) thick and 0.185 inch (about 4.7 mm) long. The overall width or thickness of attachment portion  166  is about 0.110 inch (about 2.8 mm), with the thickness of stem  167  about 0.03 inch (about 0.76 mm) with four barbs  168 , each about 0.018 inch (about 0.45 mm) thick, extending from stem  167 . Seal  160  is intended to be used with headgear such as respirator systems  100 ,  110 ,  120 . In one embodiment, seal  160  is about 12 inches (about 30.5 cm) long and conforms to an elliptical shape (best seen in  FIG. 2 ) having a minimum radius of about 2.93 inches (about 7.44 cm) and a maximum radius of about 7.3 inches (about 18.5 cm). 
     One or both of the first material and the second material could be a polyolefin-based thermoplastic elastomer. In a first variant of this example, first material  171 , having the lower durometer, is SANTOPRENE™ TPV 101-55 polyolefin-based thermoplastic elastomer from Exxon Mobil Chemical, having a Shore A hardness of 59-64. Second material  172  is SANTOPRENE™ TPV 223-50 polyolefin-based thermoplastic elastomer from Exxon Mobil Chemical, having a Shore D hardness of 51. For these materials, the relative tensile modulus is about 12.3×. Particular properties of these two materials are provided below:
     Santoprene TPV 101-55   Durometer: Shore A 59   Durometer range Shore A 45 to 65   Examples of similar durometer parts: automotive radiator hose, pneumatic auto tire tread   Linear tensile modulus: 2,365 psi   Santoprene TPV 223-50   Durometer: Shore D 51   Durometer range Shore D 45 to 55   Examples of similar durometer parts: molded electrical cable ends, solid tires   Linear tensile modulus: 29,095 psi   

     In a second variant of this example, first material  171 , having the lower durometer, is either SANTOPRENE™ TPV 101-55 polyolefin-based thermoplastic elastomer, or SANTOPRENE™ TPV 223-50 polyolefin-based thermoplastic elastomer. Second material  172  is a polypropylene; one particular polypropylene, PRO-FAX™ 7823 polypropylene from LyondellBasell has a tensile modulus of about 86,700 psi. In this example, the relative tensile modulus is about 36× for Santoprene TPV 101-55, and about 3× for Santoprene TPV 223-50. 
     In a variant embodiment of seal  160 , first and second materials  171 ,  172  may be selected based on relative curing qualities (i.e., from a molten to a solid phase) of the materials. A material for second material  172  could be selected that shrinks or contracts upon curing, relative to first material  171 . With such materials, first material  171  in sealing portion  164  and in attachment portion  166  maintains the longer length needed by the outer surface of the curved seal than needed by sealing surface  163  and second material  172 . 
     A second embodiment of a seal that readily forms a curved shape and/or that sealingly conforms to a curved surface is illustrated in  FIG. 7 . This seal  180  has a body  182  that has a sealing portion  184  and an attachment portion  186 . Sealing portion  184  includes a sealing surface  183  at least proximate a distal end  185  of body  182  that, when against radiused surface, creates a seal, e.g., a fluid tight seal, with the surface. Opposite sealing surface  183  is an upper surface  181 . Attachment portion  186  includes a stem  187  with one or more projections, such as a plurality of barbs  188  extending therefrom. When positioned in a curved shape, e.g., whether in a groove of a curved face shield lens and/or against a curved headgear surface, the inner surface of body  182  (e.g., sealing surface  183 ) is shorter than the opposite, outer surface of body  182 . 
     To facilitate bending seal  180  to the curved shape, seal  180  is composed of two different materials; a first material  191  and a second material  192 . In this embodiment, first material  191  has a lower durometer than second material  192 . In a variant embodiment, first material  191  has a lower tensile modulus than second material  192 . In this embodiment, second material  192  forms at least a portion of stem  187  of attachment portion  186 . First material  191 , present in sealing portion  184  and barbs  188 , is more stretchable and conformable than second material  192 . When seal  180  is bent (so that sealing surface  183  is an inner surface of a curved shape), second material  192  in stem  187  bends and conforms to the desired shape. First material  191  in sealing portion  184  stretches, contracts or otherwise deforms to accommodate the shape and dimensions needed. In some embodiments, seal  180  may be thermally post-processed to improve the sealing engagement to a curved surface, e.g., to surface  130 . 
     An exemplary embodiment of a seal, such as seal  180 , has an overall height of about 0.5 inch (about 1.27 cm), with the sealing portion  184  being about 0.3 inch (about 0.76 cm) and the attachment portion  186  being about 0.23 inch (about 0.58 cm). Sealing portion  184  is tapered and very slightly curved. Sealing surface  183  is defined by a radius of about 0.9 inch (about 2.3 cm), and upper surface  181  is defined by a radius of about 0.6 inch (about 1.5 cm). Sealing portion  184  has a thickness of about 0.024 inch (about 0.6 mm) at distal end  185  that increases gradually to a thickness of about 0.045 inch (about 1.14 mm) prior to flaring to 0.117 inch (about 3 mm). Stem  187 , of second material  192  has a thickness of about 0.03 inch. Four barbs  188  of first material  191  extend about 0.04 inch (about 1 mm) from stem  187 . 
     One or both of the first material and the second material could be a polyolefin-based thermoplastic elastomer. In this embodiment, first material  191 , having the lower durometer, is SANTOPRENE™ TPV 101-55 polyolefin-based thermoplastic elastomer and second material  192  is SANTOPRENE™ TPV 223-50 polyolefin-based thermoplastic elastomer, described above. 
     An alternate exemplary embodiment of the seal described above, has first material  191  as the lower durometer, SANTOPRENE™ TPV 101-55 polyolefin-based thermoplastic elastomer and second material  192  as PRO-FAX™ 7823 polypropylene. 
     In another embodiment, not specifically illustrated, a seal similar to seal  180  includes a thin layer (0.003 inch (about 0.07 mm) thick) of SANTOPRENE™ TPV 223-50 thermoplastic elastomer across sealing surface  183  of sealing portion  184 . 
     In a variant embodiment of seal  180 , first and second materials  191 ,  192  may be selected based on relative rigidity of the materials. A material for second material  192  could be selected that is more rigid than first material  191  when in the cured state. With such materials, the more rigid material  192  facilitates the insertion and engagement of attachment portion  186  with the lens, e.g., into groove  135  of  FIG. 5 , while the less rigid material  191  in sealing portion  184  better conforms to the curved headgear. 
     Seal  160 ,  180  and other embodiments may be co-extruded, with both first material  171 ,  191  and second material  172 ,  192  shaped by the same extruder and die. The two materials  171 ,  191 ,  172 ,  192  may be extruded simultaneously or sequentially within the same extruder and die. Alternately, seal  160 ,  180  may be extruded using an insert-extrusion technique, where an insert (e.g., second material  172 ,  192 ) is provided in its final shape and the remainder of seal  160 ,  180  (e.g., first material  171 ,  191 ) is extruded around the insert. 
     In yet another embodiment, a seal, e.g., seal  140  of  FIG. 5 , is formed from a single polymeric material that is post-processed after extrusion. As discussed above, after extrusion of a seal, the seal usually has a straight, non-directional orientation. To impart a desired curvature to the seal, the seal can be thermoformed (i.e., heated) to create a curved or arcuate shape. The thermoforming can be done by immersing the entire seal in heat (e.g., in an oven or water bath) or by directing controlled heat (e.g., by a heat gun). Seals composed of at least two materials, e.g., seals  160 ,  180 , could also be post-processed after extrusion. 
     As one example of post-processing, an extruded seal, optionally cut to the desired length, is placed in a holder that replicates the desired curvature of the final product. The holder includes a groove that generally matches the curvature of groove  135  of lens  132 . After placing the untreated seal into the holder, sealing portion  144  may have a rippled, puckering shape proximate tip  145 . A hot air gun (heating air to approximately 350° F.) may be swept back and forth across the rippled, flexible tip  145  for approximately 10 to 15 seconds until the ripples disappear. The heated piece can be removed after cooling from the fixture plate. The resulting seal retains the approximate curvature of the holder and exhibits essentially no ripples or reduced ripples. 
     Thus, embodiments of the LENS SEAL FOR HEADGEAR are disclosed. One skilled in the art will appreciate that the present disclosure can be practiced with embodiments other than those disclosed. The disclosed embodiments are presented for purposes of illustration and not limitation, and the present invention is limited only by the claims that follow.