EP2345839A1

EP2345839A1 - Lighting device with LED

Info

Publication number: EP2345839A1
Application number: EP10197095A
Authority: EP
Inventors: Mauro Favalli
Original assignee: Nadlec SRL
Current assignee: Nadlec SRL
Priority date: 2010-01-14
Filing date: 2010-12-27
Publication date: 2011-07-20
Also published as: ITPR20100003A1

Abstract

A LED lighting device (1) comprising a plurality of LED lighting sources (3), each of which exhibits a different focal point, which LED light sources are arranged inclined on a support surface (2), and a multi-faceted filter (20) located such as to cover the lighting sources (3) in order to mix uniformly the light beams (5) emitted thereby.

Description

The present invention relates to a LED lighting device. In particular, the device is applicable in road lighting plants as well as in the sector of civic lighting, internal and external.
As is known, there already exist on the market various lighting devices in which the LEDs, i.e. light-emitting diodes, are used to replace traditional light sources. While up to a few years ago LEDs emitted a sufficient light to be used almost exclusively as indicators in electronic circuits, the advent of high-efficiency LEDs has made it possible to extend their use also to more versatile lighting apparatus.
Indeed, high-efficiency LEDs are devices able to emit light (white or monochromatic) with a greater efficiency, and therefore lower consumption, than incandescent or halogen lamps.
In particular, the main advantages of LED technology lie in energy saving and reduction of light pollution. Further, LED devices have a longer working lifetime than traditional lamps and considerably shorter light-up times with respect thereto. Last but not least, LEDs enable greater lighting uniformity and efficiency.
Some Italian council authorities, in particular, have already set up systems using LED technology. The lighting devices developed up to now comprise lighting bodies of a flat, curved or circular type housing a plurality of LED light sources. Each lighting body, provided with a LED power supply, is mounted on a pole such as to form a street-lamp for lighting a tract of road.
The known devices exhibit an obvious drawback relating to the limited orientability of the light cone generated. LED light sources are in fact mounted in the lighting body in such a way as to emit light beams that are substantially parallel or convergent in a sole axis for illuminating a portion of road of defined dimensions and set at a precise distance from the lamp itself. It is clear that in order to illuminate tracts of road at variable distance from the lamp, the lighting body has to be appropriately directed. For example, the inclination of the light body can be varied with respect to the road surface, or the height thereof can be increased such as to generate a light cone that is directed as required.
However, even when the inclination of the lighting body is varied, a sufficiently homogeneous illumination is not obtained, i.e. the projections (commonly known as "spotlight" projections) of the light beams emanating from the LEDs are often distinguishable on the road surface.
A further drawback of the prior art is the high degree of light dispersion due to which only a percentage of the light emitted (less than 65%) effectively reaches and illuminates the predefined tract of road.
Further, the applicant has recently developed a LED lighting device (Italian patent application for industrial invention no. PR2008A000038 ) in which the light cone generated is appropriately orientated such as to illuminate surfaces (for example tracts of road) located at different distances from the device.
However the need for a homogeneous and uniform lighting, together with the greatest possible energy efficiency, is a particularly sought-after objective.
The aim of the present invention is to obviate the above-mentioned drawbacks and make available a LED lighting device which enables homogeneously and uniformly illuminating a predetermined surface.
A further aim of the present invention is to make available a LED lighting device which has a high degree of efficiency, while limiting as greatly as possible the light dispersion.
The aims are fully attained by the LED lighting device of the present invention, which comprises the characteristics contained in claim 1 and the following claims.
These and other aims will better emerge from the following description of a preferred embodiment, illustrated purely by way of non-limiting example in the accompanying figures of the drawings, in which:

figures 1 and 3 illustrate a LED lighting device and the optical effect generated thereby, according to the present invention, respectively in a perspective view from below and in a lateral view;
figure 2 illustrates the device of figure 1, in a perspective view from above;
figures 4 and 5 illustrate the device of figure 1 (in which some parts have been removed for reasons of clarity), in a perspective view from below;
figure 6 illustrates the device of figure 1, in a perspective view from below;
figure 7 illustrates the device of figure 1, a partly-section perspective view (from below);
figure 8 illustrates the device of figure 1, in a sectioned frontal view;
figure 9 illustrates the device of figure 1, in a view from below;
figure 10 illustrates a further embodiment of the device of figure 1, in an exploded view.

With reference to the figures, 1 denotes a LED lighting device, in particular for use in road lighting.
The device 1 comprises a support surface 2 and a plurality of LED light sources 3 arranged on the support 2 surface. The light sources 3 are singly inclined with respect to the support surface 2 such as to emit light beams 5 destined to intersect in order to define converging volumes. For example, each of the light sources 3 is constituted by a monochromatic LED. Each light source 3 preferably exhibits a different focal point with respect to the focal points of the other light sources 3.
As illustrated in figure 8, the device 1 is provided with a filter 20 located as a cover of the light sources 3 such as to uniformly mix the light beams 5. The filter 20 is preferably made of materials exhibiting refraction indices of between 1.3 and 1.9. The filter 20 is advantageously multi-faceted, i.e. composed of contiguous flat faces 26 present in a number that is equal to the number of light sources 3. Each face 26 of the filter 20 is originally associated to a corresponding light source 3 and is arranged orthogonally with respect to the light beam 5 coming from the corresponding light source 3. An anti-reflection treatment is preferably performed on the filter 20 with the aim of increasing by up to 8% the overall efficiency of the device 1.
The device 1 is further provided with a plurality of optical elements 4 associated to the light sources 3 and coaxial thereto in such a way as to collimate the light beams 5 emitted by the sources 3. The optical elements 4 are preferably constituted by optical collimators which restrict the breadth of the light beams 5 emitted by the LED light sources 3. The LED light sources 3 have a directional opening which is generally comprised between 90° and 120°, while the collimators reduce the aperture range to about 6-40°.
In a first embodiment, illustrated in figures from 1 to 9, the support surface 2 is constituted by a portion 12 of a semi-cylindrical mantle. Such portion 12 is arranged such as to have a concavity 14 thereof substantially tangential to a predefined plane 6. In a further embodiment, illustrated in figure 10, the support surface 2 is substantially flat.
The device 1 is further provided with a plurality of supports 15 arranged on the support surface 2. For example, in the first embodiment, the supports 15 are arranged internally of the portion 12 of the semicylindrical mantle such that the light beams 5 are emitted in an opposite direction to said predefined plane 6. In particular, each support 15 is deputed to support, via a base 15a thereof, one of the light sources 3. Advantageously all the bases 15a have the same surface extension but are differently inclined with respect to the support surface 2. The bases 15a preferably have a rectangular shape.
The supports 15 and the support surface 2 preferably form a single body, i.e. they are obtained by shaping a single sheet of material. For example, in the first embodiment, the supports 15 are obtained by shaping a concave surface 12a of the portion 12 of the semi-cylindrical mantle.
Alternatively, the supports 15 can be mounted on the support surface 2. In this case, the angles formed by each base 15a with respect to the support surface 2 can be modified such as to vary the distance of the convergence volumes with respect to the support surface 2. For example, and still with reference to the first embodiment, the supports 15 are mounted on the concave surface 12a of the portion 12 of the semicylindrical mantle. In this case, the angles formed by each base 15a with respect to the predefined plane 6 are modifiable such as to vary the distance of the convergence volumes with respect to the predefined plane 6.
Each light source 3 is preferably inclined in two directions with respect to the support surface 2. For example, in the first embodiment, each light source 3 is inclined with respect to the predefined plane 6 in a first inclination direction which is parallel to the longitudinal extension of the portion 12 of the semicylindrical mantle. Further, each light source 3, being mounted on the corresponding support 15, is inclined with respect to the predefined plane 6 in a second inclination direction, different from the first inclination direction. Thus, each light source 3 is inclined in two directions with respect to said predefined plane 6 (and therefore also with respect to the support surface). Since the optical elements 4 are coaxial to the light sources 3, the optical elements 4 are also inclined in two directions with respect to the predefined plane 6.
In the first embodiment, the convergence volumes of the collimated light beams 5 preferably identify an area 9 of convergence that is smaller than the area 10 delimited by the light sources 3 on the support surface 2. The convergence volumes of the collimated light beams 5 preferably define a convergence plane which is substantially parallel to the predefined plane 6. In this case, the area 9 of convergence belongs to the convergence plane. As already mentioned, in the embodiment in which the supports 15 are mounted on the concave surface 12a, the angles formed by each base 15a with respect to the predefined plane 6 are modifiable such that it is possible to vary the distance of the convergence volumes with respect to the predefined plane 6. Consequently the distance of the area of convergence 9 with respect the predefined plane 6 is changed.
The device 1 is advantageously provided with a dissipator 21 for dispersing the heat generated by the light sources 3. The junction temperature of the LED light sources 3 must in fact be maintained below the thus-termed cold junction temperature for reasons connected with reliability. The dissipator 21 preferably exhibits dissipating fins 22.
The device 1 preferably comprises a control circuit (not illustrated) of the light sources 3. Such control circuit is subdivided into a plurality of modules destined to command lighting of groups of light sources 3. In particular, each module of the control circuit commands lighting of a group of light sources 3 such that, in a case of malfunctioning of the module, the remaining modules (commanding other groups of light sources 3) continue to function correctly, enabling illumination, however partial.
The support surface 2, the light sources 3, the optical elements 4, the filter 20, the dissipator 21 and the supports 15 are part of a lighting body 23 of the device 1. The device 1 is preferably provided with a support pole 24 for the lighting body 23 in order for the lighting body 23 to be positioned at a determined height with respect to the zone to be illuminated.
The functioning of the LED lighting device of the present invention is substantially as follows.
The light beams emitted by the LED light sources 3 are collimated by the optical elements 4 such as to obtain the collimated light beams 5 which are incident on the filter 20. In the passage through the faces 26 of the filter 20, the collimated light beams 5 are transmitted substantially totally and mixed in a light cone 25 such as to illuminate a predetermined zone.
In particular, the lighting body 23 of the device 1, positioned at a height of 8 metres from the ground, can illuminate a surface of dimensions of 29 metres x 8 metres.
From the above description the characteristics of the LED lighting device of the present invention clearly emerge, as do the advantages afforded thereby.
In particular, thanks to the fact that the surfaces of the filter are arranged perpendicularly with respect to the light beams emitted by the sources, such beams are transmitted substantially totally, thus obtaining a homogeneous and uniform illumination.
Further, the proposed device has a high degree of efficiency (above 80%) as the light dispersion is limited, not only by the use of the collimating optical elements, but also by the multi-faceted profile of the filter and the anti-reflection treatment of the filter itself. Further, the embodiment in which the supports are directly afforded on the support surface by shaping a single sheet of material facilitates the heat dissipation, thus further improving the heat efficiency of the device.

Claims

LED lighting device (1) comprising:
a support surface (2);

a plurality of LED light sources (3) positioned on said support surface (2), said light sources (3) being individually inclined relative to said support surface (2) so as to emit intersecting light beams (5) which define convergence volumes;

a filter (20) positioned to cover the light sources (3) to mix uniformly the light beams (5), said filter (20) being faceted, that means formed by a number of contiguous plane faces (26) that equals at least the number of the light sources (3), each of said faces (26) being associated to a corresponding light source (3) and

being orthogonally positioned relative to the light beam (5) coming from said corresponding light source (3), characterised in that each light source (3) has a focal point which is different from the focal points of the other light sources (3).
Device (1) as claimed in claim 1, further comprising a plurality of optical elements (4) associated with said light sources (3) and coaxial thereto so as to collimate the light beams (5) emitted by the light sources (3).
Device (1) as claimed in any of the previous claims, wherein said support surface (2) is substantially plane.
Device (1) as claimed in any of the previous claims, further comprising a plurality of supports (15) positioned on said support surface (2), each of said supports (15) being appointed for supporting one of the light sources (3) by means of a base (15a), said bases (15a) having the same superficial extension but different inclination relative to the support surface (2).
Device (1) as claimed in claim 4, wherein said supports (15) and said support surface (2) form a single body, indeed they are obtained by shaping a single sheet of material.
Device (1) as claimed in claim 4, wherein the angles formed by each base (15a) relative to the support surface (2) are modifiable such as to vary the distance of the convergence volumes relative to the support surface (2).
Device (1) as claimed in any of the previous claims, each light source (3) is inclined according to two directions relative to the support surface (2).
Device (1) as claimed in any of the previous claims, further comprising a dissipator (21) to disperse the heat generated by the light sources (3).
Device (1) as claimed in any of the previous claims, further comprising a control circuit of the light sources (3), said control circuit being subdivided into a plurality of modules able to drive the lighting of groups of said light sources (3).