Abstract:
A light filter for dental use having: a transparent planar member ( 20 ) coloured so as to filter-out visible radiation in the range of 400 nm to 520 nm, the range being that to which dental light-cured materials are sensitive; a base ( 22 ) of a magnetic material attached to the underside of the planar member ( 20 ); and an attachment device ( 36 ) having a shell ( 34 ) of a magnetic material containing a permanent magnet ( 30 ), the attachment device ( 36 ) being attached to the lens ( 16 ).

Description:
RELATED PATENT  
       [0001]    This invention is related to our earlier U.S. Pat. No. 5,509,800 issued April 1996, the contents of which are herein incorporated by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    Present invention relates to a light filter for dental use and refers particularly, though not exclusively, to a light filter for dental use which is releasably attachable to a dental lamp to enable light of a particular frequency to be filtered out.  
         BACKGROUND OF THE INVENTION  
         [0003]    In our aforesaid US Patent specification we describe and define a light filter for dental use. It has been found that a similar filter can be more easily attached to the dental lamp. It has also been found that by the new form of attachment, it is possible to provide improved filtration of the light emanating from the lamp.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention provides a light filter for dental use including a transparent planar member coloured so as to filter-out visible radiation in the range of 400 nm to 520 nm the range being that to which dental light-cured materials are sensitive; and an attachment device configured to enable the transparent planar member to be directly attached to a dental lamp immediately adjacent a lens of the dental lamp.  
           [0005]    Preferably, the transparent planar member has attached to the underside thereof a base. Advantageously, the base is of a magnetic material such as, for example, iron, steel or ferrite.  
           [0006]    Preferably, the attachment device is a permanent magnet attached to the dental lamp immediately in front of the lens. More preferably, the permanent magnet is a solid or hollow cylinder. More advantageously, the permanent magnet is enclosed in a shell, the shell being attached to the dental lamp. More preferably, the shell is made of a magnetic material such as, for example, iron, steel or ferrite.  
           [0007]    Advantageously, the base is of a similar surface shape and size as the permanent magnet. More advantageously, the base is annular.  
           [0008]    The light filter is preferably of a size and shape to enable it to completely cover the lens of the dental lamp, the light filter preferably being made so that it is disposable. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0009]    In order that the invention may be fully understood and readily put into practical effect, there shall now be described a preferred construction of a light filter for dental use incorporating the principal features of the present invention, the description being with reference to the accompanying illustrative drawings in which:  
         [0010]    [0010]FIG. 1 is a front perspective view showing the light filter attached to a dental lamp;  
         [0011]    [0011]FIG. 2 is an exploded perspective view corresponding to FIG. 1;  
         [0012]    [0012]FIG. 3 is a front view corresponding to FIG. 1; and  
         [0013]    [0013]FIG. 4 is a partial cross-sectional view along the lines and in the direction of arrows  4 - 4  on FIG. 3. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0014]    In the drawings there is shown a dental lamp  14  which is attached to a mounting bracket (not shown) which is in turn mounted to a pivotal arm (not shown). This is standard form of dental lamp, and is well known in the dental industry and profession.  
         [0015]    Dental lamp  14  has a lens  16  at its front. In the centre of front surface  12  of lens  16  is a centre piece  18 , which is intended to block a direct view of the illuminating globe (not shown), and/or to indicate the manufacturer of the lamp  14 .  
         [0016]    Adapted to be mounted on lamp  14  over lens  16  is a light filter  20 , which has a central mounting base  22 . The light filter  20  is in accordance with the light filter of the aforesaid U.S. Pat. No. 5,509,800 and thus further description of that filter will not be made here. However, by virtue of the placement of the filter  20  directly in front of the lens  16  of the lamp  14 , the filter  20  may be made of a slightly thicker material to allow for the heat generated by the lamp. Alternatively, it may be made relatively thin so that it is disposable.  
         [0017]    The filter  20  is sized and shaped to fit over the lens  16  and is preferably substantially the same size as or slightly larger than lens  16 . Preferably, it is not smaller. In this way, effectively all of the light emanating from lamp  14  through lens  16  is filtered by the filter  20 . Although the filter  20  is shown as being rectangular, it may be any shape required such as, for example, circular, pentagonal, hexagonal, ovular, elliptical, octagonal, or otherwise.  
         [0018]    Base  22  is secured to the under surface of lens  20 . Base  22  is preferably made of a magnetic material such as iron, steel or ferrite. It may be of any appropriate size or shape although, as illustrated, it is in the form of an annular disc, having a central opening  24 .  
         [0019]    Mountable to centre piece  18  is the attachment device generally designated  36 . In a preferred form, the attachment device  36  includes a shell  34  which is approximately cup shaped. Mounted within shell  34  is a permanent magnet  30  which may be in the form of solid cylinder, as shown, or a hollow cylinder. The magnet  30  will, upon assembly, be substantially co-axial with base  22  and opening  24 . If the centre piece  18  is of a magnetic material, by having permanent magnet  30  within a shell  34  of a magnetic material, the attachment device  36  will be able to be attached to the centre piece  18  by virtue of its own magnetism. If centre piece  18  is not of a magnetic material, as an alternative shell  34  may be attached to centre piece  18  or front surface  12  of lens  16  by gluing, screwing, double-sided adhesive tape  38 , or any other suitable method or means known.  
         [0020]    In use, the attachment device  36  is attached to the centre piece  18 . The filter  20  can then be placed over lens  16  such that base  22  contacts and is attached to magnet  30 . This provides for minimal spacing between filter  20  and lens  16 , and also provides for secure attachment of the filter  20  to the lamp  14 . By using a permanent magnet  30 , and an annular disc for the base  22 , a continuous path for magnetic flux is formed. This minimises the loss of magnetic flux to the atmosphere to thus enhance the magnetic attraction.  
         [0021]    Base  22  is attached to filter  20  by any suitable means such as, for example, gluing, sonic welding, screwing, or any other suitable ways. If desired, a name-plate (not shown) may be placed on the upper surface of filter  20  above base  22 .  
         [0022]    Base  22  may be made as a permanent magnet so the ‘north’ pole of base  22  aligns with ‘south’ pole of attachment device  36 , to thus provide secure yet releasable attachment. This would enable base  22  to be attached directly to centre piece  18  if desired. Furthermore, the base  22  may be of any suitable size or shape, as may be the attachment device  36 . Although circular as shown, square, rectangular, or any other suitable shape may be used, including bar shaped.  
         [0023]    Attachment device  36  may be attached to centre piece  18  in a permanent or semi-permanent manner, and the filter  20  replaced as required. In this way the filter  20  may be made disposable, yet the attachment device  36  may be reusable.  
         [0024]    Dental lamps are generally made as being somewhat elliptical or rectangular, and are normally oriented either somewhat horizontally or vertically. By having the filter  20  made as a general rectangular shape, it will be suitable for either form of dental lamp. The rectangular shape will cover the entirety of the lens  16  to minimise the likelihood of light impacting upon the light-cured dental material in use to thus delay the curing of that material, and thus prolong the time available to the dentist or dental surgeon in using that material.  
         [0025]    Whilst there has been described in the foregoing description a preferred construction of a light filter for dental use, it will be understood by those skilled in the technology concerned that many variations or modifications in details of design or construction may be made without departing from the essential features of the present invention.  
         [0026]    It will be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.  
         [0027]    It will also be understood that where the term “comprises” or its grammatical variants, is employed herein, it is equivalent to the term “includes” and is not to be taken as excluding the presence of other elements or features.