Illuminated control panel for communication apparatus, particularly for car radio or radio-recorder combination

To provide for easy identification of the location of pushbuttons or other similar operating elements of an automobile radio, even in the dark, light guides which provide for function indication and positioned above the respective pushbuttons extend laterally beyond the respective pushbuttons, and the front surface of the panel is formed with a recessed surface having an inclined portion (23), in light transmitting location to an auxiliary light emitting surface (21) shining, from the light guides, downwardly on the inclined portion (23) to provide for lateral illumination of the push buttons which, then, will appear as shadows between the light emitted from the auxiliary light surfaces.

The present invention relates to an illuminated control panel for 
communication apparatus, and more particularly to a control panel for a 
car radio, in which control buttons, typically station selector or 
function selector pushbuttons are illuminated so that their position on 
the apparatus can be readily determined. 
BACKGROUND 
Various types of communication equipment, typically car radios, car 
radio-cassette recorders and the like, have control elements which should 
be readily operable even though the interior of the vehicle is dark. The 
various operating elements should be easily and readily accessible and so 
indicated that finding the respective position of a selected control 
element is simple and can be determined by visual checking, without 
relying, only, on "feel". It is well known to install light guides on the 
front plate of a car radio above the operating elements which carry, at 
the front, an opaque coating or cover with the respective functions left 
off, or being transparent, so that the control buttons located beneath the 
light guide which carries the operating indicia can be easily determined. 
This arrangement, however, does not positively locate the control buttons 
which, then, must be found by "feel" if there is no other external 
illumination available. Arrangements in which light guides provide 
indication of the function of selected control buttons are difficult to 
operate in darkness, particularly without distractihg the driver of the 
vehicle from traffic conditions, rather providing for the driver a clearly 
marked operating location to press a selected button, for example. In the 
dark, such buttons cannot be found visually. 
It has previously been proposed to supply light guides to the operating 
buttons themselves, in which the function indications are shown on the 
buttons themselves. Such arrangements permit immediate accessing of the 
specific buttons by the operator, for example by an operator's finger, but 
are complex to make due to the required light coupling to the respective 
buttons. The additional cost and complexity of such arrangements usually 
is not warranted. 
THE INVENTION 
It is an object to provide a control panel for communication apparatus, 
particularly for car radios, or car audio systems in general, in which 
control elements, such as control buttons or the like, can be readily 
located although the buttons themselves are not illuminated. 
Briefly, light guides which at their end faces provide for operating 
indicia, extend laterally beyond the operating elements. The light guides 
are formed with an auxiliary light emitting surface, positioned below the 
light emitting facing surface and carrying the indicia. The front plate is 
formed with a recess having inclined reflective surfaces, laterally 
adjacent to operating elements, typically pushbuttons, and in the path of 
light emitted from the auxiliary light emitting surface of the light 
guide. 
The system has the advantage that, without additional structural 
requirements, the position of the operating elements can readily be 
determined since they will appear as shadows adjacent the illuminated 
reflective surface of the front plate, next to the operating elements 
themselves. The vehicle operator, thus, is not distracted from attention 
to traffic conditions, nor is the light so bright as to interfere with 
operation of the vehicle, for example at night time. The operating 
elements and the associated function indications can be illuminated by a 
single light guide, so that the overall system is simple and, in effect, 
can utilize presently used structural arrangements.

DETAILED DESCRIPTION 
The front plate 1 of a car radio--not further shown--has three rows of 
operating pushbuttons, located in three vertically staggered groups, 
namely operating elements 2, 3 in the top row, elements 4-8 in the center 
row, and elements 9-15, in the bottom row. These elements, typically, are 
pushbuttons, and/or rocker switches. Light guides 16, 17, 18, 19 are 
located above the respective operating elements 2, 3; 4-8; and 9-15, 
associated with the respective operating elements, and, if desired, 
extending over a portion of a group of operating elements. The width of 
the end face of the respective light guides 16-19, which is essentially 
rectangular in cross section, is so dimensioned that the associated 
operating element 2, 3 or one of the operating elements 4-8; 9-15 is 
covered and, further, the light guide extends laterally thereover. The 
entry of light into the light guides themselves is shown and may be in 
accordance with any suitable arrangement, well known in the art. At the 
front side of the light guides, that is, at the side terminating at the 
panel 1, the light guides 16-19 are covered with an opaque coating, from 
which only the function indication for the respective operating elements 
2-15 is left out. The light guides are embedded with their back side and 
top side in the front plate 1. 
In accordance with a feature of the invention, the light guides 16-19 are 
formed with an auxiliary light emitting surface 21--best seen in FIG. 3, 
and located at the bottom side thereof. The auxiliary light emitting 
surface 21 permits only that light to be emitted freely which is not 
covered by the operating elements 2-15 immediately beneath the respective 
light guide. 
The front plate 1 is formed with a cup-shaped or bowl-shaped recess 
adjacent the respective operating elements or pushbuttons 2-15. The recess 
has an essentially straight upper portion extending, for example, over 
about half the height of the operating pushbuttons 2-15; this portion is 
joined by an inclined portion 23. The upper portion 22 extends essentially 
vertically downwardly, and the inclined portion 23, joining the upper 
portion 22 is formed with a reflective surface. The reflective surface 
need not be a mirror surface, smooth plastic is sufficient. 
OPERATION 
Light fed into the light guides 16-19, in any well known and suitable 
manner, is emitted on the front face where the front is not opaquely 
coated, so that the indicia 20 for the respective functions will be 
apparent. This light is emitted in accordance with the arrows A, see FIG. 
2. Additional light is emitted according to the arrows R from the 
auxiliary light exit surfaces 21. The light which is emitted from the 
auxiliary surfaces 21 is so reflected by the inclined surface 23 that the 
operating elements, typically pushbuttons 2-15, will clearly appear as 
shadows adjacent the illuminated surface 23, and thus can be easily 
visually localized. 
The specification describes the light guides as being located above the 
operating elements. This is the usual location, since light so emitted 
then will not blind the driver. In other installations, however, light 
guides may be located below the pushbuttons or operating elements 2-15, 
and this mere reversal is within the scope of the invention, forming a 
mere reversal modification thereof. 
Various other changes and modifications may be made within the scope of the 
inventive concept. For example, surfaces 23 need not be flat but may be 
curved or part-spherical, or part bowl-shaped.