DESCRIPTION

Scope of the invention

The present invention relates to the field of lighting devices, mainly for outdoor, and in particular it relates to a light unit for a lighting apparatus used for example for lighting streets, tunnels, galleries, parking lots etc. The light unit according to the present invention can also be applied for lighting indoor spaces having large size.

In addition, the invention refers to a lighting apparatus which implements the light unit and to a lens comprised in the light unit.

State of the art

As known, the designing of outdoor lighting devices, in particular for street lighting, is made with the aim of improving the safety of both vehicle and pedestrian traffic, in compliance with the technical rules and laws, ensuring the conditions of obstacle visibility on the roadbed and in potential hazard situations in case of intersections with other vehicles or pedestrian crossings.

The conventional technical solution in street lighting is the application of a plurality of supporting poles placed at the edge of the carriageway, provided with respective light units or projectors for the lighting, able to light a corresponding portion of the underlying street field.

Among different typologies of projectors, the most effective are those using LED lighting sources. Such sources in fact provide a more homogeneous lighting from both the light hue point-of-view and the color rendering point-of- view, as well as having an optimal lighting efficiency which ensures a reduction in power consumptions with respect to the conventional sources.

An example of street lighting device which adopts the LED technology is described in EP 2405181 . The device comprises a plurality of LED sources adapted to light a corresponding area of the street field. More in particular, each source has its own spatial orientation which can be different from the orientation of the other sources. Thereby, the entire carriageway can be lighted transversally. In addition, each LED source is combined with a lens or light unit able to convey the produced light beam in a certain direction and with a predetermined divergence.

In the known art different geometries of the light unit are present in order to realize a predetermined light distribution.

For the purpose of outdoor lighting, and in particular of street lighting, indeed there is the need of obtaining a light beam having a predetermined longitudinal spread encompassing a carriageway region having the maximum allowed length without however impairing the lighting quality, preferably the performances in the transverse direction remaining the same.

In order to obtain such an object, light units having particular geometry have been developed. For example, US 2009/225543 describes a lens formed by two shell portions coupled together with respect to a symmetry axis. The assembly of the two shell portions forms a V-shaped depression. This way, the light radiation emitted by the LED source placed at the lens center, is refracted by the lens surface which widens the beam in a substantially longitudinal direction.

However, such a geometry has the drawback that the produced light beam does not have optimal divergence and lighting uniformity. This has to be ascribed to the presence of the lens causing a light dispersion outside the target of interest, that is to say towards outer areas, for example areas extending excessively beyond the carriageway.

The light beam which crossed the lens has areas having a lighting intensity more or less strong in certain points with respect to other points, according to an actually not optimal "spot" pattern.

Among other things, the light dispersion along the longitudinal direction of the light beam yields a smaller intensity towards edge areas of the light profile created by the single projector. Therefore, between two adjacent projectors along the carriageway, an area of partial shadow is found.

Summary of the invention

It is therefore an object of the present invention to provide a light unit preferably for an outdoor lighting use, which allows obtaining an uniform light beam and having a good intensity in almost all the directions required for obtaining the lighting of the area of interest, and which at the same time minimizes the light dispersed outside the area of interest itself.

It is also an object of the present invention to provide a light unit preferably for an outdoor lighting use, which allows obtaining a minimization of power consumptions for the benefit of the lighting power which can be dedicated to the area to be lighted.

It is also an object of the present invention to provide a light unit which is easy and cheap to realize.

It is a further object of the present invention to provide a lighting apparatus comprising said light unit.

It is again an object of the present invention to provide a lens which can be applied to a light unit which achieves the same objects.

These and other objects are obtained by a light unit, according to claim 1, for a preferably outdoor lighting apparatus.

In particular, the light unit comprises a light source and a related lens.

The lens comprises a first face facing towards a plane to be lighted and a second face, opposite to the first face and facing towards the light source. The first face is substantially rounded towards the plane to be lighted. At the second face of the lens an optical diffuser is obtained consisting in a recess having a substantially drop shape.

The above described lens geometry allows obtaining a light beam hitting on the plane to be lighted with a wide longitudinal and transverse spread. The so-obtained light beam has reduced light dispersions outside the area of interest and a good uniformity. This allows taking advantage optimally and effectively of the overall lighting power of the light source, for the benefit of the consumption minimization.

Preferably the first face of the lens develops according to a main longitudinal direction.

Preferably the second face of the lens is flat and the optical diffuser is obtained in correspondence thereof.

Preferably the optical diffuser develops substantially along the main longitudinal direction or alternatively along a main direction transverse or skew with respect to the latter.

The drop shape of the optical diffuser provides at least one substantially hemispherical portion from which a tapered portion extends, for example constituted by the half of a cone intended as sectioned along its own longitudinal axis. Additional alike shapes of diffuser can be encompassed in the definition of drop configuration, such as for example a mushroom shape or still a cone shape or other like shapes. Such a geometry, which combines the hemispherical portion and the cone portion, allows making the light beam asymmetrical by widening it, for example, in the developing direction of the cone itself.

In a preferred embodiment, the first rounded face of the lens substantially defines a cap. This is axially symmetric with respect to a transversal symmetry axis of the lens; preferably it is axisymmetric (axially symmetric) with respect to the transverse symmetry axis and to a lens longitudinal symmetry axis orthogonal to the transverse symmetry axis.

Preferably, the cap is positioned so that its own center, located by the intersection of the transverse and longitudinal symmetry axes, is aligned with the light source.

In a preferred embodiment the cap comprises a first and a second cap portions coupled together and forming a substantially V-shaped groove extending along the transverse symmetry axis of the lens. In other words, the first and the second cap portions create a V-shaped depression at the lens center geometrically defined by the intersection and merging of two almost hemispherical portions. The afore said cap configuration allows widening the light beam in the longitudinal direction, located by the longitudinal symmetry axis. The obtained angular width of the light beam is about 130°.

The light source is preferably a high intensity LED source, or LED clusters.

Preferably, the lens is a solid single-piece realized in clear material, more preferably in plastic material such as for example polycarbonate or PMMA, and the drop-shaped optical diffuser, as described, is hollow on the second face thereof by material removal; alternatively, the diffuser is provided in the lens already during the production step, for example during the molding step.

According to another aspect of the invention, a lighting apparatus comprises a plurality of light units prearranged on a supporting panel according to a predetermined layout. A preferred layout provides for a supporting panel having elongated shape, to form a supporting strip, wherein the plurality of light units is aligned and spaced one from each other according to a certain pitch.

Advantageously, according to the application, the lighting apparatus can be composed of a variable number of supporting strips each one provided with a number of light units comprised, for example, between one and eight or yet alternatively by a single board comprising a plurality of light units.

In a preferred embodiment, a light reflector is provided mounted on said supporting panel surrounding said light units. The light reflector, preferably made of ABS with a reflective material coating, contributes to render substantially rectangular the distribution of the light flux on the plane to be lighted by reducing the light rays outgoing from the area of interest.

In particular, the reflector comprises a first and a second wall developing parallel to the longitudinal axis. Preferably, the two walls have curved shape facing towards the lens, and in particular the first wall has a curvature radius greater than the curvature radius of the second wall. In particular, both walls have a convex curved shape. The convexity of each wall is facing towards the light units prearranged inside the light reflector.

According to a further aspect of the invention a lens combined with a light source of a light unit for an outdoor lighting apparatus comprises a first face facing towards a plane to be lighted and a second face facing towards the light source, wherein the first face is substantially rounded towards the plane to be lighted, and wherein at the second face of the lens an optical diffuser is obtained consisting in a recess having a substantially drop shape.

Description of the Drawings

Further characteristics and advantages of the present invention will be more evident from a review of the following specification of a preferred, but not exclusive, embodiment, shown for illustration purposes only and without limitation, with the aid of the attached drawings, in which:

• figure 1 shows a sectional view of a light unit, according to the invention, for an outdoor lighting apparatus;

• figure 2 shows a perspective view of the light unit of figure 1;

• figure 2A shows a further perspective view of the light unit of figure 2;

• figure 3 shows a plan view of the light unit and respective sectional views of the latter identified with A-A and B-B, which highlight the shape of an optical diffuser;

• figure 4 shows a perspective view of the deflector of figure 3;

• figure 5 shows a perspective view of an outdoor lighting apparatus comprising the light unit, according to the invention;

• figure 6 shows a schematic view of the light beam produced by the lighting apparatus of figure 5;

• figure 7 shows a plot wherein an array of isolines is represented which identify the power distribution of the light beam produced by the light unit, according to the invention;

• figures 7A and 7B show respective plots which highlight a different distribution of the light beam.

Detailed description of the invention

Referring to figure 1 a light unit 10 is represented for an outdoor lighting apparatus 100 (Fig. 5) used, for example, for lighting streets, galleries or parking lots, but also for lighting building facades.

In particular, the light unit 10 comprises a light source 30 (shown schematically) combined with a lens 15 which produces a light beam 50 directed towards a plane to be lighted 150 (Fig. 6). The light source 30 is preferably a high intensity LED source.

More in particular, the lens 15 comprises a first face or an outer face

15' facing towards the plane to be lighted 150 and a second face or an inner face 20' facing towards the source 30. The first face 15' has a rounded shape to form substantially a cap 15' surrounding at least partially the light source 30.

The inner face 15' of the lens 15, as shown in figure 2, has conversely an optical diffuser 20 consisting in a drop-shaped recess. In particular, the lens 15 is a single-piece in clear material and the optical diffuser 20 is hollow on the inner face 20', preferably flat, of the lens 15 and fills a predetermined central area. The concavity of the outer cap 15' and the optical diffuser 20 are therefore concordant one to another. In other words, the lens 15 is a single piece with the rounded outer face 15' and the flat inner face 20' in which the optical diffuser 20 is obtained.

Such a geometry of the lens 15 allows obtaining a light beam 50 concentrated on the plane to be lighted without light dispersions outside the area of interest, as visible by the plots of figures 7 A and 7B and as described in detail in the following.

More in particular, as shown in figures 2A and 2B, the outer cap 15' of the lens 15 has elongated shape and develops substantially in a longitudinal direction L. Conversely, the optical diffuser 20 develops in a transverse direction T (Fig. 2A), substantially orthogonal or skew with respect to the longitudinal direction L. Alternatively and in a not shown way, the optical diffuser 20 can develop in the longitudinal direction L.

Geometrically, as better shown referring to figures 3 and 4 and respective sections A-A and B-B, the optical diffuser 20 is composed by a substantially spherical portion 22 from which a conical portion 24 extends. The drop shape of the optical diffuser 20 can be alternatively equalized also to other configurations such as for example a mushroom shape or a cone shape or other alike shapes.

Such a geometry allows obtaining a light beam 50, outgoing from the lens 15, substantially asymmetric along the transverse direction T, in accordance with the direction along which the optical diffuser 20 develops. In particular, in the embodiment represented in figure 2A, the transverse direction T corresponds to the direction identified by the median plane cutting the optical diffuser 20 and passing through the vertex of the cone portion 24. An optimal arrangement of the optical diffuser 20 further provides that the vertex of the cone portion 24 is preferably directed from the side in which the plane 150 to be lighted lies.

In particular, referring to figure 3, the cap 15' is preferably axially symmetric with respect to a transverse symmetry axis 13 and to a longitudinal symmetry axis 14 orthogonal each other. More in particular, as better shown in figure 2A, the cap 15' comprises a first 15a and a second 15b cap portions coupled together forming a substantially V-shaped groove 17 extending transversally along the transverse symmetry axis 13. The V-shaped groove is formed by the intersection of two hemispherical portions. Such a configuration of the cap 15 allows obtaining a light beam diverging in a longitudinal direction along the longitudinal symmetry axis 14 (Fig. 7).

The cap 15 is further positioned so that its own center detected by the intersection of the transverse 13 and longitudinal 14 symmetry axes, is coaxial with the axis of the light source 30.

Figure 5 shows the lighting apparatus 100 wherein a plurality of the afore said light units 10 are provided as arranged on a supporting panel 45. In a preferred embodiment, the supporting panel has a preferably elongated shape and the light units 10 are spaced one from each other according to a predetermined pitch p so that to form a respective strip of light units. Additional parallel strips of light units 10 can also be provided according to the intended application.

The supporting panel, in a not shown way, can also be shaped as a single board where differing rows of light units are prearranged.

The supporting element 45 is preferably an electronic panel PCB. The PCB allows controlling the functionalities of the single light units, for example the switching on or off, but also the light intensity and other parameters.

In addition, an optical reflector 70 is provided as prearranged on the supporting panel 45. The optical reflector 70 contributes to make rectangular the distribution of the luminous flux on the plane 150 to be lighted (Fig. 7) by reducing the light rays outgoing from the area of interest (comparison between Fig. 7A and 7B). In such a case the produced light beam 50 is given by the multiple reflections and refractions the light undergoes with the inner face 20' and outer face 15' of the lens 15 and with the reflecting surfaces of the reflector 70.

In particular, as shown in figure 7B, the light beam 50 is substantially specular and has a larger longitudinal width. The beam is therefore wider, at approximately 130°. In addition, the beam is more intense and concentrated towards the area to be lighted and with reduced light dispersions.

More in detail, the reflector 70 is box shaped and comprises a first 72 and a second 74 main walls which develop parallel to the longitudinal axis 14. Advantageously, the two walls 72, 74 have a curved profile. In particular, the first wall 72 has a curvature, with radius Ri (Fig.1) greater than the curvature, with radius R ₂ of the second wall 74. The first wall 72 is further tilted of an angle measured with respect to the supporting panel 45. The angle has a value comprised between 100° and 140° degrees and is preferably of about 130° degrees. In addition, a glass or polycarbonate cover with antiglare treatment covers the lenses 15 in order to further improve the characteristics of the produced light beam 50.

Figure 7 shows a spectrum of the light beam which can be obtained with the lighting apparatus 100 including the light units 10, according to the invention. The light beam 50 has a higher intensity in a center area 55 and a lower intensity in side areas 56 and 57 which develop from sides opposite with respect to the center area 55, as also visible in figure 7. The longitudinal length D _L of the light profile 50 is of about 40 meters with an overall width D _T of about twelve meters, if positioned at a height of about eight meters from ground.

As better shown in figure 6, the center area 55 has a transverse extension able to uniformly encompass the whole carriageway of a street length with a dimension Dc of about eight meters. Conversely, the side areas 56 and 57 allow lighting the side areas of the carriageway, each one with a width Dm of about four meters.

Further object of the invention is a lens 15 combined with a light source 30 of a light unit 10 for the outdoor lighting apparatus 100, wherein the lens 15 comprises an outer face 15' facing towards a plane 150 to be lighted and an inner face 20' facing towards the light source 30. The outer face 15' is substantially rounded towards the plane 150 to be lighted. At the inner face 20' of the lens 15 an optical diffuser 20 is obtained, consisting in a recess having a substantially drop shape.