Abstract:
A protective cover ( 13 ) for windscreens of vehicles comprises a single layer polypropylene base sheet ( 16 ) and an acrylate adhesive layer ( 18 ). The cover extends over the glazed windscreen and at least a portion of the surrounding frame. The film ( 13 ) serves to protect the windshield against damage during transport from factory to showroom and can be easily removed on arrival.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the invention 
     This invention relates to means for protection of vehicle windscreens, particularly during transit. 
     2. Prior Art 
     It is known, for example from EP-A-519278 (Nitto Denko) to cover the bodywork and attachments such as fenders of vehicles with adhesive film or cloth sheets to protect against damage during transport or shipping of the vehicle. 
     It has been found that in practice, when transporting vehicles in long ocean voyages, it is inevitable that water will find its way into the hold, and drip onto the windscreen of a vehicle. Such water will contain iron oxide due to contact with rusted surfaces within the ship and this oxide can permanently stain and damage a windscreen, particularly when a horizontal trap associated with the windscreen, such as a lower edge seal, catches the dripping water and holds it for a long time to leave behind an iron oxide residue. 
     Currently available protractive films or cloths are not suitable for use, since it is impracticable to apply them onto the windscreens after the vehicles have been loaded onto the ship. it is the usual procedure to apply all protective films or sheets just before leaving the factory. Since the vehicles have to be driven onto and from the ship, a typical protective film or cloth is unsuitable for use to cover the windscreen since it obscures the driver&#39;s vision. 
     It is a further requirement that any cover applied to the windscreen should be sufficiently abrasion resistant to withstand wiper action, in case the car is unloaded or loaded in bad weather. Ruching or peeling of the cover by the windscreen wipers will damage or remove the cover and compromise its effectiveness. 
     U.S. Pat. No. 5,002,326 proposes a windscreen cover of a multiplicity of polycarbonate film sheets non-permanently bonded by pressure sensitive adhesive. 12 to 16 sheets are suggested. As each exposed film is worn and degraded by exposure it is removed to expose the next film below. The initially rather thick layer is not suitable for use as a temporary cover for vehicles in transit and also the material chosen is likely to degrade due to UV exposure. 
     Any adhesive used must be strong enough to stick the cover to the windscreen during use of the wipers, yet be sufficiently easily releasable to remove the cover without leaving an adhesive residue on the glass. 
     SUMMARY OF THE INVENTION 
     No windscreen cover has so far been produced which is able to satisfy all these requirements, and it is an object of the invention to provide such a windscreen cover. 
     EP-A-770654 describes a coloured film comprising a transparent film with a coloured adhesive layer. In dim light such as obtaining in a ship&#39;s hold, such a film will unduly impair the driver&#39;s vision. 
     The invention therefore provides a vehicle windscreen having a cover, for use in transit which covers the entire glass area of the windscreen, and overlaps the surrounding frame area and which comprises a transparent thermoplastic film, said film having a coating of a pressure-sensitive adhesive on one facer of the film, to contact the windscreen. 
     The transparent thermoplastic film may be a propylene polymer. 
     The pressure-sensitive adhesive is preferably an acrylic based material. 
     The film is preferably sufficiently large to cover not only the windscreen glass area, but also at least part of the surrounding frame area, to prevent access of dirty water to any corners, cracks or channels which might cause such water to accumulate. 
     These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An embodiment of the invention is described by way of example, with reference to the accompanying drawings, wherein: 
     FIG. 1 is a view of a vehicle wind screen protected by a windscreen cover according to this invention; 
     FIG. 2 is a fragmentary cross section of the windscreen and windscreen cover; and 
     FIG. 3 is an enlarged sectional view of the cover itself. 
    
    
     DESCRIPTION OF THE INVENTION 
     Although only one preferred embodiment of the invention is explained in detail, it is to be understood that other embodiments are possible. Accordingly, it is not intended that the invention is to be limited in its scope to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways. Also, in describing the preferred embodiment, specific terminology will be resorted to for the sake of clarity. It is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. 
     As shown in FIG. 1 a vehicle  10  (only partially shown) has a windscreen  121 , surrounded by a frame  12 , by means of which the windscreen is held in the bodywork of the vehicle. The windscreen  11  is protected by a removable cover  13 , the edges  13   a  of which extend beyond the frame  12  to partially overlie the bodywork. The cover  13  is also provided below windscreen wipers  14 , which can be used over the screen cover  13 . 
     This latter feature is more clearly shown in FIG. 2, where the edges of the screen  11  are shown to be received in seals  15 , received in the frame  12 . The edges  13   a  extend sufficiently beyond the frame  12  to cover any cracks, channels or water-retaining angles arising between the screen  11  and the seal  15  or frame  12 , so that accumulation of water in any such water traps is avoided. 
     The screen cover  13 , as shown in FIG. 3, comprises a film  16  of a propylene polymer or co-polymer, which is transparent and thermoplastic and provides a smooth outer surface  17  which provides no resistance to the operation of a wiper blade  14  and thus has no tendency to peel, ruche or tear under the action of the wiper blade. 
     This enables the vehicle to be driven, e.g. to and from a storage location or onto and from a ship during transit of the vehicle for delivery, with the windscreen cover  13  in place. The windscreen cover can thus be placed on the windscreen at the factory before despatch, without impairing the usual delivery routines which require the vehicle to be driven occasionally. 
     The film  16  has an adhesive backing  18 , comprising a pressure-sensitive acrylic-based adhesive, which is sufficiently strong enough to resist any loading imposed by operation of wiper blades  14 , but can nevertheless be easily removed by peeling from the windscreen  11  when it is necessary to remove the cover  13 . 
     A suitable film for the film  16  by way of example comprises a polypropylene film with the following properties: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Density 
                 0.91 g/cm 3   
               
               
                   
                 Thickness 
                 47 microns 
               
               
                   
                 Load at break 
                 70N/25 mm (machine direction) 
               
               
                   
                 Elongation at break 
                 600% (machine direction) 
               
               
                   
                 Coefficiemt of friction 
                 0.2 
               
               
                   
                 Gloss 
                 85% 
               
               
                   
                 Peel adhesion strength 
                 100 g/25 mm 
               
               
                   
                   
               
             
          
         
       
     
     The adhesive backing  18  is in a preferred embodiment a coating on one side of the film  16  comprising 15.7 g/m 2  of a solvent-based acrylic pressure sensitive adhesive using dimethylene diisocyanate (MDI) in a toluene solvent as a curing reagent. 
     The film preferably has a density in the range 0.75-1.0 g/cm 3 ; a thickness in the range 20-1.50 microns; load at break in the range 30-100 N/25 mm; elongation at break in the range 300-800%; coefficient of friction 0.05-0.8; and peel adhesion strength 30-150 g/25 mm, 
     A windscreen cover as described will prevent dirty, e.g. rust containing water from accumulating on or about the edges of the windscreen and thus prevent the occurrence of unsightly and potentially damaging rust stains on the windscreen or its immediate frame. 
     The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and, accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.