Abstract:
An improved vacuum fluorescent (VF) display panel includes a VF display device having an integral VF light source that is shielded from viewer of the display, and that provides illumination for panel indicia formed in the vicinity of the VF display. The integral light source for indicia illumination is produced at one or more marginal areas of the VF display by secondary anode segments and an integral reflector structure that directs the light produced by the secondary anode segment(s) laterally through a transparent side glass of the display housing. A light-pipe structure adjacent the VF display receives the laterally directed light, and uses the received light to illuminate the panel indicia.

Description:
TECHNICAL FIELD 
     This invention relates to instrument panels incorporating a vacuum fluorescent (VF) display, and more particularly to illumination of instrument panel indicia by the VF display. 
     BACKGROUND OF THE INVENTION 
     Vacuum fluorescent (VF) displays are generally manufactured in the form of a glass housing having an evacuated central cavity containing phosphored anode segments arranged in a suitable display pattern, and a grid disposed between the anode segments and a filament (cathode). The filament is electrically heated to generate a cloud of electrons, which are attracted by the grid and driven into the phosphored anode segments, resulting in emission of light at the phosphor surface. The emitted light is very bright, but is usually extensively filtered so that a viewer of the panel only sees the illuminated anode segments. Frequently, the instrument panel is also provided with separate light sources for illumination of other indicia formed on the panel. In an automotive radio or HVAC control panel, for example, a VF display is used to communicate certain parameters to the operator, and various incandescent light sources are used to illuminate legends or other indicia on adjacent control knobs or buttons. The indicia light source and associated light-piping can significantly increase the size, complexity and cost of the display panel, and a considerable effort is typically entailed in matching the color of the indicia illumination with that of the display illumination. Accordingly, what is needed is a way of using light from the VF display to illuminate other indicia of the instrument panel. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an improved display panel including a VF display having an integral VF light source that is shielded from viewer of the display, and that provides illumination for display panel indicia formed in the vicinity of the VF display. According to the invention, the integral light source for indicia illumination is produced at marginal areas of the VF display by one or more secondary anode segments and associated reflector structures that direct the light produced by the secondary anode segments laterally through a transparent side glass of the display housing. A light-pipe structure adjacent the VF display receives the laterally directed light, and uses the received light to backlight the panel indicia. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a frontal view of a VF display panel according to this invention. 
     FIG. 2 is an exploded view of the VF display panel of FIG.  1 . 
     FIG. 3 is a partial isometric view of a VF display device according to a preferred embodiment of this invention. 
     FIG. 4 is a partial cross-sectional view of the VF display device of FIG.  3 . 
     FIG. 5 is a partial isometric view of a VF display device according to an alternate embodiment of this invention. 
     FIG. 6 is a partial cross-sectional view of the VF display device of FIG.  5 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention is illustrated in the context of a motor vehicle automatic climate control head, generally designated by the reference numeral  10  in FIGS. 1 and 2. The control head  10  is designed to be mounted in the instrument panel of a motor vehicle for receiving operator inputs relating to fan speed and set temperature, and for displaying system parameters of interest, such as fan speed, set temperature, and outside temperature. In the illustrated embodiment, a pair of momentary contact pushbuttons  11 ,  12  protrude through openings  14   a ,  14   b  in the control head housing  14  for operator entry of the desired fan speed and set temperature, respectively. The pushbutton  11  has a fan indicator  16 , and a pair of directional indicia  18   a ,  18   b ; the indicator  16  denotes the function controlled by the pushbutton  11 , while the directional indicia  18   a ,  18   b  denote the manner and direction of fan speed adjustment. Similarly, the pushbutton  12  has a TEMP indication  20  to denote the controlled function (set temperature), and a pair of directional indicia  22   a ,  22   b  to denote the manner and direction of temperature adjustment. A VF display generally designated by the reference numeral  24  in FIG. 1 is aligned with a housing opening  14   c  between the pushbuttons  11  and  12 , and includes a vacuum fluorescent (VF) display device  26  and a tinted lens  28 . The VF display device  26  has a number of primary anode segments  30  that are selectively activated to display the system parameters, as mentioned above. The reference numerals  32  and  34  in FIG. 1 designate marginal areas of the display device  26  that are concealed from the viewer, but that produce light that is directed into the pushbuttons  11 ,  12  by light-pipe structures  36 ,  38  for illuminating the indicia  16 ,  18   a ,  18   b ,  20 ,  22   a ,  22   b , as explained below. 
     Referring particularly to FIG. 2, the control head  10  comprises three principle components assembled into the housing  14 —the tinted lens  28 , a pushbutton and light-pipe assembly  40 , and a display and circuit board assembly  42 —and a rear cover plate  44  for retaining the components within the housing  14 . The assembly  40  includes the pushbuttons  11 ,  12 , the light-pipe structures  36 ,  38 , a support frame  46  for supporting the tinted lens  28 , and a set of spacer elements  48 ,  49 ,  50 ,  52  for locating the pushbutton and light-pipe assembly  40  with respect to the display and circuit board assembly  42 . The display and circuit board assembly  42  includes a circuit board  54  supporting the VF display device  26  and first and second pairs of micro-switches  56   a ,  56   b  and  58   a ,  58   b . The display device  26  is centered relative to the support frame  46 , the micro-switches  56   a ,  56   b  are located for activation by the pushbutton  11 , and the micro-switches  58   a ,  58   b  are located for activation by the pushbutton  12 . 
     In operation, the light emanating from the primary anode segments  30  is attenuated by the tinted lens  28  for viewing by the vehicle occupants, whereas the light emanating from secondary anode segments  30 ′ disposed in the marginal areas  32  and  34  is shielded from view and directed laterally by the reflector structures  60 ,  62 . The light that is laterally directed by reflector structure  60  impinges on the inboard face  36   a  of light-pipe  36 , while the light that is laterally directed by reflector structure  62  impinges on the inboard face  38   a  of light-pipe  38 . The light-pipes  36  and  38  are formed of poly-carbonate or other suitable light conducting material, and direct the light into the respective pushbuttons  11 ,  12  which are formed of a similar material. The front faces of light-pipes  36 ,  38  and pushbuttons  11 ,  12  are coated with an opaque material except in the areas defined by the indicia  16 ,  18   a ,  18   b ,  20 ,  22   a ,  22   b  so that the light received by light-pipes  36 ,  38  is visible to the operator only in the areas defined by the indicia  16 ,  18   a ,  18   b ,  20 ,  22   a ,  22   b.    
     Referring to FIGS. 3 and 4 it will be seen that the VF display device  26  comprises three glass layers: a planar bottom layer  64 , a transparent planar top layer  66 , and a transparent marginal spacer layer  68 . The spacer layer  68  separates the top and bottom layers  66 ,  64 , creating a sealed cavity  70  in which the electrical elements (anodes, cathodes and grid) of the display  26  are disposed. The primary and secondary anode segments  30  and  30 ′ are formed on bottom layer  64  by successive deposition. Anode conductors  72 , which are electrically coupled to respective terminals  74  of the VF display device  26 , are deposited directly on the bottom layer  64  as seen in FIG. 4, and an insulation layer  76  is deposited over the bottom layer  64  and conductors  72 , leaving through-holes  78  over the conductors  72  in the areas where the anode segments  30 ,  30 ′ are to be formed. The anode segments  30 ,  30 ′ and phosphor material  80  are then deposited in the area of the through-holes  78 , completing the formation of anode segments  30 ,  30 ′. Thereafter, the reflector structures  60 ,  62  are then placed on and adhered to the insulation layer  76  so as to cover the secondary anode segments  30 ′. The reflector structure  62  (as well as the reflector structure  64 ) is preferably formed of metal having a highly reflective inboard surface  62   a  and dark non-reflective outboard surface  62   b  and triangular side elements  62   c ,  62   d ; its function is to direct the light emanating from the secondary anode segment  30 ′ laterally through the transparent spacer layer  68  as indicated by the arrow  82 , while shielding such light from the view of the vehicle occupants. 
     An alternative embodiment of the reflector structure  62  is depicted in FIGS. 5-6, where the reference numerals of FIGS. 3-4 have been repeated to identify common elements. Here, the reflector structure is identified by the reference numerals  62 ′,  62   a ′,  62   b ′,  62   c  and  62   d , the principle difference being that the side surfaces  62   c ′,  62   d ′ are rectangular in shape, and may be adhered to both the insulation layer  76  and the top glass layer  66  as shown. 
     In summary, the display of this invention provides an improved and cost effective way of using a VF display to illuminate panel indicia disposed adjacent to the display. The requirement for separate panel illumination light sources is eliminated, and the color of the light illuminating the panel indicia is inherently matched to the color of the light emanating from the primary display segments. While the present invention has been described in reference to the illustrated embodiments, it is expected that various modification in addition to those mentioned above will occur to those skilled in the art. Thus, it will be understood that displays incorporating these and other modifications may fall within the scope of this invention, which is defined by the appended claims.