Abstract:
An illuminated display is disclosed which allows characters to be displayed with near type-set like appearance. This is accomplished by using an appropriately formed and placed rib to connect the optically opaque inner member with the optically opaque base.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims priority to Provisional Application No. 60/462295 filed on Apr. 11, 2003. 
     
    
     
       BACKGROUND OF INVENTION  
         [0002]    Illuminated displays for alphanumeric and special characters are typically used in electronic devices and appliances. Examples include digital displays for time and other information typically present on microwave ovens and video cassette recorders. These displays typically have an opaque base with an opening that defines an outline of a letter, a number or a special character such as a symbol or punctuation mark. Light from an electrically-operated light source such as a light emitting diode (LED) is typically projected through the opening.  
           [0003]    If the character being outlined is an open character such as the numeral “2” or the letter “L”, the illuminated display for that character closely represents a typeset version of that character and is aesthetically pleasing to the human eye. However, if the character being outlined is a closed character such as the letter “D” or the numeral “8”, the characters typically have a stenciled appearance that is not aesthetically pleasing to the human eye. A closed character encloses an inner member that must have a means for anchoring to the opaque base.  
           [0004]    Some displays, for example, such as the widely used seven segment numeric display can be switched to represent any of several different characters. The seven segment display typically uses seven different straight line segments to form the numerals zero through nine. Each straight line segment is typically illuminated by a different light source so that different segments may be illuminated as desired to form different numerals. These numerals have an appearance similar to stenciled numerals. For displays that need to be switchable from one character to another, such as a digital time display, this is typically adequate.  
           [0005]    Other displays only show a single character or a sequence of characters having a defined meaning such as a word, for example. An example of such an illuminated display is an electronic display for kitchen appliances that at different times illuminates one or more words such as “BAKE”, “BROIL”, “WARM”, or “HOLD”. It is typically desirable for such characters or sequence of characters to have a typeset character appearance without visible supporting members connecting the base to the inner members of the display for closed characters. For example, in the display for the word “BAKE” the letter “B” is a closed character with two enclosed inner members and the letter “A” is a closed character with one enclosed inner member whereas the letters “K” and “E” are open characters. If the supporting members that support the enclosed inner members of the display for the letters “B” and “A” are not visible then all four characters in the word “BAKE” appear to be typeset when the word “BAKE” is illuminated.  
           [0006]    An approach to the problem of providing illuminated characters a typeset appearance is disclosed in U.S. Pat. No. 6,422,711 issued Jul. 23, 2002 to Chao et al. The Chao et al patent discloses an embodiment having a rib that functions to connect an inner member of a closed character to the opaque base of the display. The rib disclosed in the Chao et al patent protrudes from one surface of the base and therefore limits the usefulness of the approach.  
           [0007]    Hence, an illuminated display where closed characters have a typeset character appearance without any visible members connecting the inner members of closed characters to the base of the display is desirable.  
         SUMMARY OF THE INVENTION  
         [0008]    In accordance with the invention, characters or icons on an illuminated display may be created having a closed character or icon with an inner member that has no supporting member readily visible to the human eye and no support member protruding beyond a surface of the base of the display. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a perspective view of an illuminated display of a substantially round character in accordance with the invention.  
         [0010]    [0010]FIG. 2 is a section view taken along the line  2 - 2  of FIG. 1.  
         [0011]    [0011]FIG. 3 is a perspective view of a portion of one surface of the display shown in FIGS. 1 and 2 with the light source and light source support omitted.  
         [0012]    [0012]FIG. 4 shows an embodiment in accordance with the invention with the rib not sculpted.  
         [0013]    [0013]FIG. 5 shows an embodiment in accordance with the invention with the rib recessed from the inner member.  
         [0014]    [0014]FIG. 6 shows an embodiment in accordance with the invention with the rib recessed from the base.  
         [0015]    [0015]FIG. 7 shows an embodiment in accordance with the invention with a portion of the region filled with light diffusing material.  
         [0016]    [0016]FIG. 8 shows a front view of an embodiment in accordance with the invention having a number of openings for defining alphanumeric characters.  
         [0017]    [0017]FIG. 9 shows an alternative rib cross-section in accordance with the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    Embodiments in accordance with the invention provide for illuminated displays having closed characters where the supporting rib for the inner member is not visible and no support structure extends beyond the surface of the base of the display. Several embodiments in accordance with the invention are depicted and for convenience, elements that are similar from one embodiment to another embodiment carry the same reference numerals and those elements that differ from one embodiment to another are denoted with the same reference numerals with added alphabetic characters to distinguish them.  
         [0019]    [0019]FIGS. 1-3 show an illuminated display in accordance with the invention that has optically opaque base  11  with first surface  13 , second surface  15  and optically transmissive opening  17 , opening  17  defining outer perimeter  19  of display element  21 . Rib  23  is attached to base  11  and positioned within opening  17 . Optically opaque inner member  26  defines inner perimeter  27  of display element  21  and is positioned within opening  17  to define region  29  between inner perimeter  27  and outer perimeter  19 . Inner member  26  is attached to rib  23 . Light source  31 , for example, a light emitting diode (LED), projects light toward first surface  13  of base  11  and toward first surface  33  of inner member  26  so that light is transmitted through region  29 . Electrical conductors  35 , typically copper or aluminum, provide electrical power to light source  31 . Light source  31  is held in position by support  37  (see FIG. 2). Base  11  and inner member  26  are typically made from opaque plastic material.  
         [0020]    In an embodiment in accordance with the invention, rib  23  is recessed into opening  17  with respect to first surface  13  and second surface  15  of base  11 . Inner member  26  is typically about 0.8 mm thick. Base  11  adjacent to opening  17  is also typically about 0.8 mm thick. Rib  23  is typically recessed about 0.05 mm to about 0.1 mm from first surface  13  and should not be recessed so far as to weaken the display to the extent that it is not reproducible using a standard molder. Rib  23  typically needs to be recessed from second surface  15  sufficiently far to allow the encapsulating material such as epoxy to flow over rib  23  and hide it from view while still allowing sufficient illumination. Adjacent to second surface  15 , rib  23  is typically sculpted and recessed between about 0.3 mm and about 0.4 mm from second surface  15 . Sculpting rib  23  typically involves forming rib  23  so that it is less perceptible to the human eye. Ideally, when the surface of rib  23  is recessed from second surface  15 , rib  23  presents a line to the human eye. Typical requirements for sculpted rib  23  are that sculpted rib  23  be thinner or smaller in the direction of second surface  15  that is typically visible to the human eye and thicker or bigger in the direction of first surface  13  which is typically hidden from the human eye. The tapering of rib  23  ensures structural strength. The recited dimensions are not critical to the invention and may be varied as appropriate according to the requirements for display element embodiments such as the size and the number of display elements desired.  
         [0021]    In an embodiment in accordance with the invention shown in FIG. 4, rib  23 A is not sculpted adjacent to second surface  15  of base  11 .  
         [0022]    In an embodiment in accordance with the invention shown in FIG. 5, rib  23 B is coplanar with first surface  13  of base  11  and is slightly recessed and not coplanar with respect to first surface  33  of inner member  26 .  
         [0023]    In an embodiment in accordance with the invention shown in FIG. 6, rib  23 C is substantially coplanar with first surface  33  of inner member  26  but is slightly recessed and not coplanar with respect to first surface  13  of base  11 .  
         [0024]    In an embodiment in accordance with the invention, light source  31  includes at least one LED. Depending on the desired configuration, a plurality of light sources  31  such as LEDs may be used. Other choices for illumination include incandescent lamps, fluorescent lamps, lasers and the like.  
         [0025]    In accordance with the invention, diffusing material  39  such as, for example, a translucent filter, may be positioned in region  29  as shown in FIG. 7. While only a portion of region  29  is shown as being filled, all of region  29  may be filled with diffusing material  39  to diffuse the light and provide a more uniform appearance to the displayed alphanumeric element or icon. Alternatively, diffusing film  41  may be applied to surface  15  of base  11  and second surface  25  of inner member  26  to cover opening  17 . While only a portion of opening  17  as shown in FIG. 7 is covered by diffusing film  41 , it is clear that all of opening  17  may be covered with diffusing film  41 . If desired, both diffusing film  41  and diffusing material  39  may be used. With respect to FIG. 7, rib  23 D is shown as sculpted such that rib  23 D is coplanar with second surface  15  of base  11  at the point where rib  23 D and base  11  meet and elsewhere rib  23 D is recessed into opening  17  in relation to second surface  15  of base  11 .  
         [0026]    Rib  23  has been depicted as being triangular in cross-section and oriented such that the apex of the substantially triangular cross-section of rib  23  is located adjacent to second surface  15  of base  11 . The shape of rib  23  is not typically critical and other shapes may be used as desired. For example, rib  23  may have a substantially triangular cross-section with curved sides that are either convex or concave. Also, rib  23  may have a polygonal shape having a cross-section resembling a triangle positioned over the side of a rectangle as shown in FIG. 9.  
         [0027]    In some embodiments in accordance with the invention, base  11  has a plurality of optically transmissive openings, each opening defining a display element such as an alphanumeric character or icon. The display elements are typically arranged in a sequence having a predefined meaning. For example, in FIG. 8 base  11  has openings  43 ,  45 ,  47  and  49  that define alphanumeric characters “H”, “O”, “L” and “D”, respectively. At least one of openings  43 ,  45 ,  47  and  49  defines a closed alphanumeric character that encloses an inner member. In particular with respect to FIG. 8, openings  45  and  49  define closed characters “O” and “D”, respectively, opening  45  enclosing an inner member  51  and opening  49  enclosing inner member  53 . The four alphanumeric characters defined by openings  43 ,  45 ,  47  and  49  together spell the word “HOLD”. One or more light sources as desired may be activated so as to light up all four characters when the word “HOLD” is displayed.  
         [0028]    While the invention has been described in conjunction with specific embodiments, it is evident to those skilled in the art that many alternatives, modifications, and variations will be apparent in light of the foregoing description. Accordingly, the invention is intended to embrace all other such alternatives, modifications, and variations that fall within the spirit and scope of the appended claims.