LED indicator for producing a light bar in a bargraph

A led indicator has a bargraph and a lighting device arranged behind the bargraph and provided with a row of LEDs controlled to produce a light bar with a length which is variable as a function of the number of LEDs that are switched on along a lighting sense; the LEDs are arranged between screens, which are spaced apart from the lower surface of the bargraph and extend at least to reach an axis which starts from the immediately preceding led orthogonally to such a lower surface.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims priority to published Italian Patent Application TO2012A 001019, filed on Nov. 23, 2012.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a LED indicator for producing a light bar in a bargraph, in particular for an instrument on a motor vehicle.

2. Description of the Related Art

In the instrument panel of motor vehicles, as an alternative to common pointer indicators, it is known in the art to use so-called bargraphs, which are backlit by a row of LEDs to produce a light bar of variable length. The length depends on the number of adjacent LEDs that are switched on and provides visual information of a variable quantity, in particular of a measurement carried out in the motor vehicle (e.g. the measurement of speed, engine RPM, fuel consumption, etc.).

LEDs are usually housed in respective cavities, which are separated from one another by screens. In solutions known in the art, such screens extend orthogonally to the bargraph, up to the lower surface of the bargraph itself, so as to prevent any leakage of light towards the adjacent cavities where the LEDs are off. Due to this configuration, the backlighting of the bargraph produces a series of segments, which are arranged between areas turned off or with dim light due to the presence of the underlying screens. With this configuration, the reading of the measured value on the bargraph is well defined due to the absence of leakages of light from the lighted segments to the dark ones. An example of this kind of solution is shown in published U.S. Pat. No. 5,949,346A.

However, if obtaining a bar of continuous, non segmented light is desired, it would be appropriate to reduce the height and/or thickness of the screens. Further, by operating in this manner with the known solutions, there would be a leaking of light from the last cavity having a switched on led towards the dark side of the bargraph, whereby the visual indication of the measurement would not be accurately perceived by the user.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide a LED indicator for producing a light bar in a bargraph which allows the above drawback to be solved in a simple and cost-effective manner when obtaining a continuous light bar is desired.

According to the present invention, a LED indicator for producing a light bar in a bargraph is provided.

DETAILED DESCRIPTION OF THE INVENTION

InFIG. 1, reference numeral1indicates an instrument of a motor vehicle, which include a LED indicator2for providing a user with information relating to a variable quantity (for example, a measurement carried out in the motor vehicle). The example shown refers to the amount of fuel in a tank, but the LED indicator2may be generally used for any type of quantity.

The LED indicator2includes a bargraph3, which further includes a graduated scale4and a window5made of a light-permeable material and adapted to be backlit, as will be described below. The window5has an elongated (either straight or curved) shape from a starting point6(corresponding to a minimum value of the graduated scale4) up to a final point7(corresponding to a maximum value of the graduated scale4).

With reference toFIG. 2, the LED indicator further includes a lighting device8which further includes an electronic board9arranged behind the window5in a position spaced apart from a lower flat surface10of the bargraph3. The electronic board9supports a plurality of LEDs11, which are arranged in a row along a direction12, each beneath a corresponding area of the window5. The LEDs11are preferably spaced apart from one another by a constant step. The electronic board9has a printed circuit board controlled for powering the LEDs11and light the areas of the window5from the starting point6, so as to produce a light bar15having a length which is variable as a function of the number of LEDs11which are switched on as a sequence in a lighting sense16starting from point6towards point7. The end of the light bar15is indicated by reference numeral13and is lit by the LED indicated by reference numeral11ainFIG. 2: in relation to the graduated scale4, the end13provides visual information of the measured value. Thus, if only some LEDs11are switched on, window5has a dark area18from end13to the final point7.

With reference toFIG. 2, the electronic board9also supports a row of screens20, which are arranged between the LEDs11along direction12and are substantially light-impermeable. The screens20include respective base portions22which extend from the electronic board9, transversely to direction12. The base portions22are preferably flat and are orthogonal to the electronic board9and to direction12. The base portions22are conveniently spaced apart from the LEDs11along direction12and define a series of cavities23therebetween, each of which is delimited at the bottom by the electronic board9and accommodates a corresponding LED11.

The screens20include respective appendixes25, which extend from the base portions22, respectively, and end with an edge26which is spaced from the window5so as to leave an empty space or “gap”27in which light can pass. Due to the presence of the gaps27, the areas lit by the LEDs11are contiguous and not separated from one another, whereby the light bar15is of the continuous, non segmented type.

According to the present invention, the shape of the screens20is such as to prevent the light emitted by the LEDs11from going towards the gaps27forward, but they allow the light emitted by the LEDs11to go through the gaps27only backwards. Herein and hereafter, the terms “forward”, “backward”, “previous”, “next”, “front”, “rear”, “after”, “before”, etc. are indicated with reference to the lighting sense16.

The appendixes25extend in a cantilever fashion from the respective base portions22and backwards (i.e. in the sense opposite to the lighting sense16) so as to close at the top an immediately preceding part of the cavity23. The width or extent of each appendix25along direction12is such as to reach, with the edge26, at least the position of an axis28which extends orthogonally to the window5from the immediately preceding LED11.

Thereby, considering the above-mentioned LED11a, the latter is followed by a screen20awhich covers and blocks at least the front half of the light beam emitted by LED11a. The other part of the light beam emitted by LED11areaches the surface10, but its rays cross the window5or are reflected back, due to their inclination with respect to the surface10itself. In other words, the appendix25of the screen20aprevents the surface10from being reached by light rays inclined forward with respect to axis28, to avoid reflections in the dark area18and clearly define the end13.

InFIG. 2, the axis28of LED11atouches or lies on the edge26of the screen20a. However, the appendixes25may extend backward beyond such a position, so as to be intersected by axis28.

The edge26of each appendix25is defined by a flat surface which is relatively small and extends orthogonally to direction12and to the surface10. According to the embodiment shown inFIG. 3, the edge26is defined by a sharp edge, which extends orthogonally to direction12and to axis28.

Again with reference toFIG. 2, each appendix25is delimited at the top by a surface30facing the surface10and extending from edge26up to an edge31, which joins the surface30to a lateral surface32of the base portion22. In other words, the lateral surface32of each base portion22faces the immediately following LED11. In particular, the edge31extends orthogonally to direction12and parallel to surface10.

According to one embodiment of the present invention, the surface30, the edge31, and the lateral surface32remain below the light beam emitted by the immediately following LED11. In this regard, the LEDs11are regarded as dot-like light sources (for simplicity) and each emits a respective light beam which is symmetrical and has a predetermined maximum width with respect to the optical axis of the LED11itself. In particular, the optical axis of each LED11substantially coincides with axis28if the direction12and the electronic board9are parallel to the surface10. For example, LEDs are available on the market providing a light beam of conical shape having a maximum width of ±30° or ±60° with respect to the optical axis. Below such a width, the LED produces no light. By selecting the category of LEDs to be installed in the LED indicator2, the maximum width of their light beam is known, and it is thereby possible to design the height of the surface32and the inclination of the surface30so as to prevent such surfaces from receiving the rays of the light beam emitted by the immediately following LED11. Thus, that part of the light beam emitted by the LEDs11awhich is not blocked by screen20a, directly reaches the surface10without affecting the immediately preceding screen22. Therefore, the surfaces30,32do not reflect light rays towards the window5and/or towards the gap27. In other words, there are no reflected rays which can pass over the screen20atowards the dark area18. The lateral surface32preferably extends from the electronic board9orthogonally to direction12. As mentioned above, it is sufficient to limit the height of the lateral surface32with respect to the electronic board9to prevent the lateral surface32from being hit by light rays.

Again with reference toFIG. 2, on the lower side (i.e. on the opposite side with respect to surface30), the appendix25of each screen20is delimited by a surface34facing the immediately preceding LED11, and it is thus irradiated by such a LED11. The surface34preferably has such an inclination and/or shape as to reflect the light emitted by the underlying LED11towards the electronic board9and/or towards the corresponding base portion22, and not towards the base portion22of the immediately preceding screen20. In the embodiment ofFIG. 2, the surface34is flat and substantially has the same inclination as the surface30. According to the variants inFIGS. 4 and 5, in order to more effectively retain the reflections of the surface34, the latter has a concave shape or a planar shape, respectively, orthogonal to axis28of the immediately preceding LED11.

It is apparent from the foregoing description that the configuration of screens20allows a continuous, non segmented light bar15to be obtained, due to gaps27; light emissions and reflections towards the dark area18to be limited as much as possible, due to the extension, position, and shape of the appendixes25. In particular, the backward extension of the appendixes25, up to reach the immediately preceding axis28with the edge26, allows the end13to be clearly marked. In fact, the surface10reflects the direct light rays from the LEDs11(only backwards), thus the disclosed configuration prevents reflections of light directed towards the dark area18. Moreover, the other geometrical and dimensional features of the screens20contribute to preventing the reflected light rays from reaching the dark area18through the gaps27. Further, the LED indicator2may be implemented in a relatively simple manner, only changing the shape and size of the screens20as compared to solutions known in the art.

Finally, it is apparent that the LED indicator2described with reference to the accompanying drawings may be subject to modifications and variants which do not depart from the scope of protection of the present invention as defined in the appended claims. In particular, the shape of the appendixes25and/or the base portions22may be different from those indicated by way of example; and/or the LED indicator2, instead of forming part of an instrument on board of a motor vehicle, may form part of any measuring instrument or of an electronic device (such as a satellite navigation system, a car radio, etc.) where providing a visual indication about a quantity is needed.