Patent Publication Number: US-2006010572-A1

Title: Helmet face shield

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application is a continuation of U.S. patent application Ser. No. 10/769,979, filed on Feb. 3, 2004, and which claims priority on US Provisional Patent Application No. 60/444,159, filed on Feb. 3, 2003. The entire contents of both of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD  
      The present invention relates generally to shields for protective helmets used for snowmobiling, motorcycle riding and the like. More particularly, the present invention relates to a protective face shield having a removable lens portion.  
     BACKGROUND OF THE INVENTION  
      Protective helmets such as, for example, those used for snowmobiling and motorcycle riding, are well known. They typically include a generally transparent face shield or lens. Two distinct types of helmet face shields are typically employed. Shields having a single pane lens are generally used in warmer environmental conditions. Face shields having a dual lens construction comprising an inner lens and an outer lens, are most often used in colder and more humid conditions. In cold weather, single pane lenses tend to fog up, consequently impairing the rider&#39;s vision. However, single pane lenses generally provide better visual properties in comparison with double pane lenses, the thinner single lens causing less optical distortion. Nonetheless, double pane lenses are almost universally used in colder climatic conditions, in order to help keep the face shield substantially free of condensation.  
      Many kinds of face shields employ additional techniques to further attempt to prevent fogging. These include lenses having an electrical heating system, wherein an inner lens surface is coated with an electrically conductive film and two electrodes, on opposite edges of the lens, permit an electrical current to flow across the film covering the lens, thereby inhibiting condensation build up thereon. Other anti-condensation methods are also well known, such as those providing directed ventilation along an inner surface of the lens or employing a hydrophilic anti-condensation layer, in the form of a sheet, film or other covering, that is fitted within an outer lens. These additional anti-condensation devices are typically used in combination with a double-paned lens.  
      Most face shields having such a double pane construction comprise two lenses that are contained within a separately constructed perimeter frame, which provides support for the double-paned lens and permits pivotable attachment thereof to the helmet. Double pane lens assemblies are significantly thicker than single paned lenses, and their attachment to some helmets which are not specifically designed to accommodate them can accordingly be difficult without the rather bulky perimeter frame. These face shield perimeter frames can significantly add to the manufacturing cost of the face shield assembly, unduly add bulk and weight to the helmet, and contribute to aerodynamic inefficiencies and increased wind noise.  
      Most known face shields that do not comprise perimeter frames, and have double pane lenses or have a hydrophilic layer superimposed on a single lens, do not permit removal of one of the lens panes or the anti-condensation layer. However, it has been known to provide such a frame-free face shield for a protective helmet having a detachably engaged inner lens. U.S. Pat. No. 5,765,235 issued Jun. 16, 1998 to Derek Leslie Arnold, for example, discloses an anti-condensation visor comprising an outer visor for attachment to a helmet and an inner visor, made of hydrophilic material, detachably fitted against the inside wall of the outer visor and held there against by at least one mechanical retaining element. The inner visor must rest against the inside wall of the outer visor in such a way that no space is left between them. U.S. Pat. No. 4,584,721 issued Apr. 29, 1986 to Tamenobu Yamamoto, discloses a helmet face shield having an electric heating device for preventing fogging. The device comprises a removable inner lens piece attached behind the outer helmet lens. The inner lens piece is generally engaged to the outer lens by a mechanical engagement element such as a snap fastener.  
     SUMMARY OF THE INVENTION  
      It is an object of the present invention to provide an improved face shield for a protective helmet.  
      It is another object of the present invention to provide a face shield having a frameless main lens capable of receiving a second lens portion that can be sealed to the main lens with an air gap therebetween to create a double pane lens.  
      The present invention permits an inner lens to be engaged to an outer lens such that it is offset therefrom but sealed thereto. The present invention further permits the single pane lens to be converted into a double pane lens having improved anti-condensation properties provided by an air gap trapped between the inner and outer lenses of the sealed double pane lens.  
      Therefore, in accordance with the present invention, there is provided a face shield for headgear comprising: a generally transparent main lens adapted for engagement to the headgear; the main lens comprising curved inner and outer main lens surfaces and having a central recessed portion, the recessed portion having a recessed curved inner lens surface and a recessed curved outer lens surface, the recessed inner lens surface and the recessed outer lens surface being respectively offset from the curved inner and outer main lens surfaces; and the recessed portion being adapted to receive a secondary lens therein such that a sealed air gap is formed between the secondary lens and the main lens, thereby forming a sealed double pane lens having anti-condensation properties.  
      There is also provided, in accordance with the present invention, a face shield for headgear comprising: a generally transparent main lens adapted for engagement to the headgear; the main lens comprising curved inner and outer main lens surfaces and having a central recessed portion, the recessed portion having a recessed curved inner lens surface and a recessed curved outer lens surface, the recessed inner lens surface and the recessed outer lens surface being respectively offset from the curved inner and outer main lens surfaces; and a secondary lens, selectively engageable within the recessed portion of the main lens such that a sealed air gap is formed between the secondary lens and the main lens, thereby selectively forming a sealed double pane lens having anti-condensation properties. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Further features and advantages of the present invention will become apparent from the following detailed description, taken in combination with the appended drawings, in which:  
       FIG. 1  is a perspective view of a face shield according to the present invention engaged to a protective helmet;  
       FIG. 2  is an exploded perspective view of the helmet face shield of  FIG. 1 , showing a main lens and a secondary lens;  
       FIG. 3  is a front elevation view of the helmet face shield of  FIG. 1 ;  
       FIG. 4  is a horizontal cross-sectional view taken along line  4 - 4  of  FIG. 3 ; and  
       FIG. 5  is a perspective view of an alternate embodiment of the secondary lens for engagement with the main lens of  FIG. 2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Referring to  FIG. 1 , the face shield  10  is adapted to be engaged to, and used with, headgear such as a protective helmet  13  as conventionally used for motorcycle riding, snowmobiling, flying and the like. The face shield  10  is also adapted for use with other protective headgear comprising a transparent face shield, such as paintball masks for example. The face shield  10  comprises primarily a generally transparent main lens  12 , thereby providing a single pane lens that does not require a perimeter frame for support or engagement to the protective helmet  13 . The main lens  12  is preferably a moulded plastic one-piece element, having a thickness of approximately 2 mm (about 0.07874 inches). The main lens  12  is preferably injection moulded, however other manufacturing techniques could also be used, such as drape or vacuum moulding for example. One skilled in the art will also appreciate that the main lens  12  can have a non-uniform thickness throughout. Particularly, as is known in the art, the lens can be formed such that it is thickest at a center point thereof and becomes gradually thinner towards each edge of the lens. This causes the least distortion of light passing through the lens, enabling the single paned main lens  12  to provide substantially distortion free optical characteristics. The main lens  12  is preferably formed having a curvature about a substantially vertical axis that substantially corresponds to that of the protective helmet  13  to which it is to be engaged, however it generally comprises a substantially semi-circular shape. The main lens  12  can also be outwardly convex throughout the semi-circular length thereof, having a second curvature about a substantially horizontal axis, creating a complex lens curvature. The curved main lens  12  comprises a curved inner main lens surface  14  and a curved outer main lens surface  16 .  
      The main lens  12  comprises a central recessed portion  18 , having a recessed curved inner surface  20  and a recessed curved outer surface  22 , the recessed portion  18  being preferably outwardly offset from the main lens  12 . The recessed portion  18  preferably comprises most of the main lens  12 , such that the recessed portion  18  substantially covers the entire visual field of the user. The offset edges  24  of the recessed portion  18  are therefore located just at the edge or just outside the viewing field of the user looking through the face shield  10  when it is disposed in a normal operating position on the protective helmet  13 . The size and shape of the recessed portion  18  preferably corresponds to a forward opening  15  in the protective helmet  13 , such that the offset edges  24  of the recessed portion  18  are near the perimeter of the opening  15  in the helmet  13 .  
      As seen in  FIG. 1 , helmet engaging members  28  are fixed to the main lens  12  at remote mounting ends  16  thereof. The helmet engaging members  28  are fixed to the remote ends  26  of the main lens  12 , and are preferably pivotally engageable to the sides of the protective helmet  13 , such that the entire face shield  10  can be pivoted to open or close the opening  15  in the helmet  13 . The main lens  12  can thus be used alone as a single pane helmet visor when required. This may be most desirable in warm environmental operating conditions, and for particular applications, such as for motorcycle riding for example.  
      However, in colder conditions and applications, such as for snowmobiling for example, a single pane helmet lens tends to fog up. As such, the main lens  12  of the face shield  10  can be modified to provide a double pane lens  19 , as seen in  FIGS. 3 and 4 , if desired. A generally transparent secondary lens  30 , best seen in  FIG. 2 , is receivable into the recessed portion  18  of the main lens  12 , such that a sealed double pane helmet lens  19  is formed. The secondary lens  30  comprises an inner curved lens surface  32  and an outer curved lens surface  34 . The secondary lens  30  is generally formed with a radius of curvature somewhat similar to that of the main lens  12 , however the secondary lens  30  is preferably provided with a radius of curvature that is slightly larger than that of the main lens  12 . This requires a slight deflection of the secondary lens  30  for it to fit within the recessed portion  18 , providing a slight pre-tension in the secondary lens  30 , and thereby helping it to remain engaged within the recessed portion  18 . The secondary lens  30  is positioned within the recessed portion  18  such that an air gap  40  remains between the outer curved lens surface  34  of the secondary lens  30  and the curved inner main lens surface  14  of the main lens  12 . The secondary lens  30  preferably has a lens thickness that is less than the offset distance of the recessed portion  18  from the curved lens surfaces  14 , 16  of the main lens  12 . The common distance that the recessed curved inner lens surface  20  and the recessed curved outer lens surface  22  are respectively offset from the inner main lens surface  14  and outer main lens surface  16  is preferably approximately 3 mm (about 0.11811 inch). If a secondary lens  30  having a 2 mm (about 0.07874 inch) thickness is used, for example, the air gap  40  will be approximately 1 mm (about 0.03937 inch) wide. It will be understood, however, that other air gap widths and secondary lens thicknesses can be similarly used to achieve the same effect.  
      Unlike many double paned lens assemblies of the prior art, the present double pane lens  19  does not require a separately constructed perimeter frame which provides support for the double paned lens assembly, as the secondary lens  30  is retained within the recessed portion  18  of the main lens  12 . The elimination of the perimeter frame results in reduced manufacturing, and subsequently retail, costs, a reduction in the overall weight and size of the face shield  10  having the double pane lens  19 , and improved aerodynamics. By smoothly integrating the frameless main lens  12  into the helmet  13  such that the outer main lens surface  16  is substantially flush with an outer surface of the helmet  13 , reduced aerodynamic drag and noise is provided.  
      The secondary lens  30  preferably has a gasket seal  36  disposed around the perimeter thereof. The gasket seal  36  is preferably disposed on one of the outer curved lens surface, and a peripheral edge defined between the inner curved lens surface  32  and the outer curved lens surface  34 . When disposed on the outer curved lens surface, the perimeter gasket seal  36  helps to space the secondary lens  30  away from the main lens  12  when positioned within the recessed portion  18 , ensuring that a fairly constantly spaced air gap  40  is maintained therebetween. The gasket  36  also seals the air gap  40 , ensuring that a sealed double pane lens  19  is maintained. While the gasket seal  36  is preferably disposed on the secondary lens  30  before insertion of the secondary lens  30  into the recessed portion  18  of the main lens  12 , it can similarly be inserted independently into the recessed portion  18  before the secondary lens  30  is positioned therein. The gasket seal  36  is preferably made of generally transparent material, such that vision at the offset edges  24  between the secondary lens  30  and the main lens  12  is not obscured. The gasket seal  36  is preferably as transparent as possible, but materials that are merely translucent can also be employed. A generally transparent silicone bead, for example, can be used as the gasket seal  36 . Such a silicone bead is preferably sufficiently compressible when the secondary lens  30  is engaged within the recessed portion  18 , such that a slight vacuum is created between the secondary lens  30  and the main lens  12 , thereby holding the secondary lens  30  in place therein. The slightly larger radius of curvature of the secondary lens  30  relative to the main lens  12  further provides frictional retention of the secondary lens  30  within the recessed portion  18  of the main lens  12 . Other substantially permanent retention means, such as adhesives or sealing tape for example, can be used to fix the secondary lens  30  within the recessed portion  18  and to seal the air gap  40  therebetween.  
      Alternately, other temporary retention means can be used which permit the user to add and/or remove the secondary lens  30  from the main lens  12  whenever required. This may be desirable, for example, if a protective helmet  13  having the face shield  10  is to be used both for motorcycle riding in warm weather and snowmobile riding in cold weather. In such a case, the main lens  12  is preferably used by itself in the warmer conditions to provide improved visibility. The secondary lens  30  may be subsequently inserted within the recessed portion  18  of the main lens  12  to form the double pane lens assembly  19  in colder conditions, to provide improved anti-condensation properties. In such a case, the secondary lens  30  is therefore engaged within the recessed portion  18 , using removably fastenable members such as temporary adhesives, removable two-sided tape, or hook and loop fasteners for example. With such temporary fastening means, the secondary lens  30  nonetheless preferably forms a seal with the main lens  12  such that the sealed air gap  40  is provided therebetween in the recessed portion  18 . The temporary fastening means may provide the sealing themselves, or an additional seal may be provided in addition to the temporary fastening means.  
      The addition of the secondary lens  30  to the main lens  12  can be done either by the user as an after-market upgrade, or by the manufacturer, permitting a more cost effective way of producing different face shields for various applications. Particularly, rather than producing two distinct product lines, a common main lens  12  can be used alone or in combination with a secondary lens  30  to create a double pane lens  19 . For example, the main lenses  12  can be either sold alone as a single pane face shield, or be permanently assembled with the secondary lens  30  in the factory for sale as a sealed double pane lens  19  particularly adapted for cold climatic applications. The secondary lenses  30  could also be sold independently, for selected assembly by the user for converting a single pane lens into a cold weather, sealed double pane lens  19 . The secondary lens  30  can either be as transparent as the main lens  12 , or can comprise a tint, such that a shaded double pane lens  19  is created.  
      The seal formed between the secondary lens  30  and the main lens  12 , ensuring the sealed air gap  40  therebetween, maintains thermal properties of the double pane lens  19  formed by the assembly of the main lens  12  and the secondary lens  30 . Such a sealed, dual plane lens  19  is much more effective at preventing condensation at low temperatures than single paned lenses or double lenses that do not form a sealed air gap therebetween.  
      A secondary lens  50  of an alternate embodiment, shown in  FIG. 5 , is alternately used in place of the secondary lens  30  for engagement with the main lens  12  to form the sealed dual plane lens  19 . The alternate secondary lens  50  is similarly shaped to the secondary lens  30 , and is equivalently receivable into the recessed portion  18  of the main lens  12 . The secondary lens  50  is generally transparent, although can comprise a tint if desired, and comprises a curved inner lens surface  52  and a curved outer lens surface  54 . The secondary lens  50  preferably includes a perimeter seal  56  thereon, disposed either about a perimeter of the curved outer lens surface  54  or on the perimeter edge between the inner curved lens surface  52  and the curved outer lens surface  54 . The secondary lens  50  differs from the secondary lens  30  in that it comprises an electrical heating system  60  which provides additional anti-fogging capabilities. The electrical heating system  60  generally includes at least two elongated electrodes, normally an upper electrode  62  extending along an upper margin of the secondary lens  50  and a lower electrode  64  extending along a lower margin of the secondary lens  50 . While the upper and lower electrodes  62 , 64  are preferably located on the outer lens surface  54 , they can be alternately disposed on the inner lens surface  52  without significantly altering their anti-condensation effect. Between the upper and lower electrodes  62 , 64  is provided a transparent electro-conductive film  68  substantially covering the entire outer lens surface  54 . The transparent electro-conductive film  68  is preferably a thin layer of indium tin oxide (ITO), applied by sputter coating on the outer curved lens surface  54 . Such an ITO coating provides high visible light transmission, low reflectivity and substantially uniform electrical conductivity. Insulated electrode contacts  66  are in electrical contact with the upper and lower electrodes  62 , 64  and extend through the secondary lens  50  to the inner lens surface  52 . Conductors (not shown) linked to a power supply can then be engaged to the electrode contacts  66 , such that power is supplied across the upper and lower electrodes  62 , 64 , resulting in an electrical flow across the electro-conductive film  68 . The conductors can comprise wires or another electro-conductive film, such as an electrically conductive silk screen ink, for example, formed on the inner lens surface  52 . Another transparent electro-conductive film on the inner lens surface  52  may be used as the conductor linking the power supply to the electrode contacts  66 . This eliminates any possible vision impeding elements being located on the lens surfaces. Such a strip of transparent ITO film extends along the inner main lens surface  14  of the main lens  12  and inner lens surface  52  of the secondary lens  50 , linking a connection to the power supply within the helmet attachment members  28  to the electrode contacts  66  on the secondary lens  50 . Resistance to the flow of electricity across the electro-conductive film  68 , between the upper and lower electrodes  62 , 64  on the outer lens surface  54 , causes heat. This heating of the secondary lens  50  thereby further helps to prevent or reduce the formation of fog, frost and ice on the sealed double pane lens assembly  19 , comprising the main lens  12  and the secondary lens  50 . Much as the secondary lens  30 , the alternate secondary lens  50  having the electrical heating system  60  can be either permanently fixed within the recessed portion  18  of the main lens  12 , or can be selectively removable therefrom as described above. Although the electrical heating system  60  is described herein as being preferably engaged on the secondary lens  50 , it is to be understood that it can also be disposed on the main lens  12 , and particularly on the recessed curved inner surface  20 .  
      The frame-less face shield  10  according to the present invention has great versatility. The main lens  12  can be used alone as a single pane, warm weather shield. When required, this can be converted into a cold weather, sealed double pane lens  19  with the addition of one of the secondary lenses  30  or  50  into the central recessed portion  18  of the main lens  12 , providing a sealed air gap  40  therebetween. This provides a face shield having a thermal barrier, the double pane lens  19  providing improved anti-condensation properties at low temperatures. The best anti-condensation abilities of the face shield  10  are provided when using the alternate secondary lens  50  having the electrical heating system  60  therein, which may be suited for very cold environmental conditions. The face shield  10  can therefore be selectively adapted for different uses and different environmental conditions as required, whether before consumer sale or after-market.  
      It is understood that numerous modifications to the face shield according to the present invention will be evident to those skilled in the art. Accordingly, the above description and accompanying drawings should be taken as illustrative of the preferred embodiments of the invention and not in a limiting sense. It will be further understood that the present invention is intended to cover any variation, use or adaptation of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains, and as may be applied to the essential features herein set forth and as follow in the scope of the appended claims.