Abstract:
A face shield or visor for a helmet which has a second lense fitted into a gapped space underneath the first lense and has improved anti fogging properties.

Description:
[0001]    The present invention claims benefit of priority to U.S. patent application Ser. No. 61/302,204, which was filed on 8 Feb., 2010 and which is incorporated by reference as if fully recited herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to face shields or visors for helmets of a type worn by operators of snowmobiles, motorcycles and the like. In particular, the invention relates to adapting the face shield with a second lense to thereby improve the anti fogging properties thereof. 
       BACKGROUND OF THE INVENTION 
       [0003]    Typically, the face shield is rotatably attached at each side of the helmet to allow pivotal rotation of the face shield from a closed position covering the face portion to an open position exposing the face. A rubber gasket liner is fitted along the periphery of the face portion of the helmet which frictionally engages the inner surface of the frame portion of the face shield to create an environmental seal against air and noise flow into the helmet when the face shield is in the closed position. 
         [0004]    A common problem associated with helmet face shields used in cold and humid environments is fogging. One solution is to attach an inner lense on the inside surface of the outer lense and in spaced apart relationship thereto whereby an air space is created therebetween. 
         [0005]    A disadvantage of this approach is that the inner lense adds a layer of thickness on the inside surface of the face shield which interferes with the upward rotation of the face shield. To alleviate the interference problem, the inner lense must be sized smaller than the face portion in order to clear the rubber gasket when the face shield is rotated upwardly. This interferes with and reduces the field of vision through the face shield. 
         [0006]    Another disadvantage is that the inner lense is not made of the same material as the outer lense and typically consists of a flexible plastic sheet material. The inner lense is not optically correct to the outer lense which affects clear vision through the face shield. 
         [0007]    Another solution is to install a secondary market replacement face shield having a double lense arrangement. The lenses used in the replacement face shield are not the same as the original lense material and typically consist of thin plastic sheet material. A disadvantage of this ad hoc solution is that the replacement face shield is inferior in strength when compared to the original face shield, the optics are inferior and the face shield fit against the liner gasket is not exact. 
       SUMMARY OF THE INVENTION 
       [0008]    It is an object of the present invention to adapt a face shield or visor for a helmet with a second spaced apart lense to thereby improve the anti-fogging property of the face shield. According to the invention, an inner lense is fitted into a uniform gapped space which is formed underneath the outer lense of the face shield. 
         [0009]    It is a further object of the present invention to provide a face shield for a helmet having a face opening with a lense viewing area having an outer lense and an inner lense spaced apart therefrom and a surrounding frame portion. The inner lense is attached to the outer lense substantially along its perimeter defining a uniform air space between the inner surface of the outer lense and the outer surface of the inner lense. The lense viewing area is coterminous with the frame portion and the defines a common inner surface area for the face shield. 
         [0010]    According to an aspect of the invention, the outer lense is elevated above the frame portion to define a uniform gapped space thereunder for attachment therein of the second lense. The thickness of the uniform gapped space is at least equal to the thickness of the inner lense and the thickness of the air space between the lenses. 
         [0011]    According to yet another aspect of the invention, the helmet has an integral chin portion and a periphery of the face opening is lined with a gasket material. The face shield is adapted to rotate on the helmet between the first open position exposing the face opening and a second closed position covering the face opening wherein the inner surface of the face shield frictionally engages the gasket material to thereby environmentally seal the face opening. According to the invention, the inner lense may be adhesively attached to the outer lense. Further, the inner and outer lenses may be made of the same material and the lenses are optically correct with each other. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    In order that the invention may be more clearly understood, a preferred embodiment thereof will now be described in detail by way of example, with reference to the accompanying drawings, in which: 
           [0013]      FIG. 1  is an illustration of a helmet and face shield according to this invention. 
           [0014]      FIG. 2  is a face shield according to this invention. 
           [0015]      FIG. 3  is a cross-sectional view of  FIG. 2  taken at AA. 
           [0016]      FIG. 4  is a cross sectional exploded view of another embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0017]    The invention will be described with reference to a full face helmet and face shield shown in  FIGS. 1 and 2  which has an integrally formed protective chin portion  1 . There is a cut out face portion  2  over the eyes and nose which may be optionally covered by a face shield  3  which is rotatable upwardly to expose the face portion and allow access to the face. The portion of the face shield covering the cut out face portion will be hereinafter referred to as the lense or outer lense  6  and the surrounding face shield as the frame portion  9 . 
         [0018]    Referring to  FIG. 3 , a gapped uniform space gap is formed underneath the outer lense  6  having an equal thickness t and perimeter shape substantially equal to the perimeter shape of the lense area covering the face portion of the helmet. 
         [0019]    According to one embodiment, the gapped space is formed by uniformly raising the outer lense  6  of the face shield a distance t with reference to the surrounding frame portion  9  of the face shield, as shown in  FIG. 3 . 
         [0020]    An inner lense  7  having a perimeter shape identical to but slightly smaller than the lense portion is fitted into the gapped space and adhesively secured in place along its perimeter with two sided tape  8  in spaced apart relationship to the outer lense. The air space distance d between the lenses is preferably approximately one (1) mm. It can be appreciated that the thickness of the gapped space t must be at least equal to the thickness of the inner lense and air space thickness d. 
         [0021]    The inner lense is made of the same material as the outer lense. The field of vision through the face shield is unaffected and the strength of the face shield is unaltered. The compound curvature of the inner lense is made identical to the compound curvature of the outer lense so that the optical characteristics of the face shield are unaffected. 
         [0022]    Another approach to forming the gapped space underneath the outer lense is to start with a thicker face shield and remove lense material to a thickness t from underneath the lense. In any event, the objective is to create a smooth uninterrupted inner surface for the face shield. The inside surface of the inner lens is coterminous with the inside surface of the frame portion. By this means the pivoting action of the face shield from a first closed position covering the face opening to a second open position exposing the face is not impeded or interfered with by the inner lense. It is accordingly important to ensure that the inside surface of the inner lense does not extend outwardly beyond the inner surface of the frame portion of the face shield. 
         [0023]    According to the present invention, the outside surface of the outer lense may be coated for hardness The inside surface of the outer lense is uncoated as is the outside surface of the inner lense. In other words, the facing surfaces across distance d in the air space are uncoated which facilitates adhesion of the lenses along the common perimeter with double sided tape. The inner surface of the inner lense is preferably coated with an antifogging solution. 
         [0024]    Another advantage of the present invention is the resulting strength and rigidity of the face shield enables the helmet to pass standardized impact tests in the US and UK. 
         [0025]    According to another aspect of the invention, the inner lense can be replaced with a combination lense that has electrical conductivity features which further improve anti-fog characteristics. 
         [0026]    As shown in  FIG. 4 , the inner lense is comprised of two layers of materials. A first layer of lense material  7  and a thin layer of indium tin oxide (ITO) material  10  is bonded to the outside of the inner lense. The ITO material is very delicate and requires special handling and needs to be applied in a sterilized clean room. The thickness of the combined ITO and inner lense is the same as the thickness of the inner lense without the coating. The ITO material is electrically conductive. Thus the application of ITO creates an electrically conductive lense for fog prevention. 
         [0027]    Other advantages which are inherent to the invention are obvious to one skilled in the art. The embodiments are described herein illustratively and are not meant to limit the scope of the invention as claimed. Variations of the foregoing embodiments will be evident to a person of ordinary skill and are intended by the inventor to be encompassed by the following claims.