FR2738622A1 - LIGHT SOURCE LIGHTING ASSEMBLY, EQUIPPED WITH A THERMAL CHICANE, AND CANDELABRE INCORPORATING SUCH A LIGHTING ASSEMBLY - Google Patents

Abstract

A lighting assembly has a warm light source (S), a light guide (2) for optically connecting said source and a cold light source region, a heat deflector (3) with a cavity partially defined by dichroic surfaces (7) reflecting visible light and transmitting infrared light, adapted for filtering light radiation emitted by the source to be introduced into the guide, characterised in that substantially cylindrical surfaces (5, 6) reflecting visible light define the remaining portion of the cavity and are adapted, with the dichroic surfaces, to reflect at the input of the guide substantially the whole of a divergent light beam emitted by the source while reflecting at least once on said dichroic surfaces any light ray input into the guide at an angle with the axis of the lower guide at the digital half beamwidth of said guide. The source and the guide are arranged in such a way that the cylindrical surfaces can be formed by the intersection of two or more tubular cylinder segments.

Description

 The present invention relates to lighting over traffic or intervention zones, most often outside, by luminaires, but not exclusively, by luminaires with specific supports such as candelabras for public roads or industrial zones; they can also be luminaires integrated into supports and having a different function, such as in traffic tunnels or facade luminaires.

 In one of its applications, the present invention relates to equipment for lighting from above a circulation or intervention zone, the light source of which is located near this zone (at maximum at height of man) and whose head located at a distance in height relative to this same area is optically connected to the light source.

 Such remote source lighting equipment is known in particular from the international patent application WO-9511 0792.

 This type of equipment includes a light generator which injects a large amount of light energy into a light guide.

The light emerging from the light guide at its other end is either reflected by a reflector or diffuser with a reflecting surface towards the area to be illuminated, or focused on this same area, by means of an appropriate optical system, depending on the envisaged application. In other applications, the zone forming a cold light source, as opposed to the hot light source formed by the generator, can be constituted by a lateral portion of this guide.

The light guides currently used are of several types:
- bars or fibers based on quartz or silica: they absorb very little light energy, withstand very high temperatures, but are fragile and above all very expensive;
- glass fibers: they are less expensive, withstand high temperatures, but have significant line losses and rapidly distort the light spectrum. In addition, they are fragile and relatively complex to use;
- plastic-based fibers or bars, such as PMMA (polymethylmethacrylate). They are much less expensive than glass fibers, have much less loss in line than glass and are not fragile. They are also easy to implement.

However, the use of this last type of plastic bars or fibers remains limited due to their poor temperature resistance (80 "C for conventional PMMA sheathed fibers, 150eC for bars in
PMMA of type ALTUGLASS @). Placed directly in front of a source generating a narrow, high-power light beam (typically, in the case of remote source lighting, a beam with a maximum aperture of 40 to 50, presenting a light flux of 6000 to 7000 Lm through a circular surface with a diameter equal to 30 mm), it degrades quickly by melting and then charring.

 This degradation is observed even if the light guide is isolated from direct contact with the heat radiated by the light source, by interposing, for example between this light source and the guide, a quartz window and removing the hot air. ambient by ventilation. The degradation is then slowed down, but nevertheless occurs in the long term, because even if the ambient air does not reach an excessive temperature, the plastic material constituting the bar itself absorbs part of the light energy which is transforms into heat energy in the bar.

 In practice, it turns out to be the same when the light generator comprises a light source placed within an enclosure with a reflecting surface, letting pass the infrared radiation, or even when the dichrnic selector treatment of inside such an enclosure by the interposition, perpendicular to the beam emerging from the generator, of dichroic filters returning towards the interior of the generator the infrared radiation of the beam of light emerging from that.

 The present invention proposes in particular to overcome these drawbacks.

 According to a first aspect, it provides a lighting assembly comprising a light generator, a light guide intended to optically connect the hot light source constituted by the generator and a zone forming a cold light source, characterized in that it further comprises a thermal baffle interposed between the generator and the entry surface of the light guide, the baffle having reflective and at least partially dichroic surface parts arranged so as to reflect the entire visible part of the light beam incident on said entry surface, and evacuate infrared radiation, by transmission.

 It will be appreciated that the implementation of such a chicane not only makes it possible to alleviate the aforementioned drawbacks, but it is all the more remarkable since the person skilled in the art has had to overcome his reluctance to deflect the beam of light emerging from the generator, forcing it to go through a chicane.

 This is even more remarkable when the chicane is simply made up of two mirrors placed opposite one another, at least one of the mirrors being a cold mirror. Indeed, a person skilled in the art is moreover led to accept a lateral offset of the entry surface of the light guide with respect to its conventional position in which this surface is in line with the light source.

 This is equally remarkable when the generator comprises an enclosure with an internal reflecting surface comprising at least one concave portion of ellipsoid and a light source placed at the focal point of the ellipsoid situated in this portion of ellipsoid, and the assembly is characterized in that said mirrors are parallel plane mirrors, a first of which obliquely cuts the major axis of the ellipsoid defined by the concave portion of ellipsoid and at least one of these mirrors is a cold mirror.

 Here too, the person skilled in the art has been led to accept the lateral offset of the entry surface of the light guide relative to the conventional position where this surface was positioned in the vicinity of the second focal point of ellipsoid defined by said portion of ellipsoid, where the beam of light generated by the light source and reflected by said enclosure converges. In doing so, those skilled in the art also had to overcome their reluctance to break, at least in part, the coaxial positioning of the axis of the guide and the major axis defined by the portion of ellipsoid.

According to preferred arrangements, possibly combined:, - the reflection surface of the first mirror is placed in the vicinity of the second
focus of the concave portion of ellipsoid; - the first mirror, is placed in front of the second focus of the concave portion
of ellipsoid, towards said focal point of ellipsoid, while the surface
reflective of the second mirror is placed in the vicinity of the focal point of the
beam of light reflected by the first mirror; ; - the generator has an enclosure with an internal reflecting surface
comprising at least a concave portion of ellipsoid and a source of
light placed at the focal point of the ellipsoid located in this portion of the ellipsoid, the
first of the two mirrors being a plane mirror obliquely cutting the large
axis of the ellipsoid defined by the concave portion of the ellipsoid, while the
second mirror is a concave mirror converging by reflection the
beam of light returned by the first mirror, towards the entry surface of the
light guide; - the reflective surface parts at least partially dichrnic
form a continuous reflecting surface; - The lighting assembly also includes two non-dichroic mirrors
parallel to said major axis and connected to the other two mirrors so as to
forming a block with a square section and an internal reflecting surface; - the enclosure further comprises an annular portion of hemisphere on the surface
reflective covering from its base the portion of ellipsoid, centered on said
focus, axis coincident with the major axis of the ellipsoid, and having a
opening at the top of the axis also coincides with said major axis, thus
that a tubular section of cylinder with a reflecting surface capping from
from a first of its ends, the opening of the annular portion
hemisphere and having an axis coincident with said major axis.

- the reflective surface parts of said baffle are an integral part
generator; - the reflective surfaces of the generator enclosure are dichroic,
reflecting in the visible range and transmitting radiation
infrared; - the light guide consists of a rigid homogeneous PMMA bar, a
retaining structure extending along this bar while allowing to remain
a layer of air along almost the entire lateral surface of this bar;

- a porthole of a transparent material surmounts the chicane, the entry surface
of the light guide being arranged opposite this window.

 According to another aspect, the present invention relates to a candelabra, characterized in that it comprises a pole inside which is placed a lighting assembly having the aforementioned characteristics, and a diffuser with reflective surface placed near the exit from the guide.

 Preferably, the light guide is curved at its end extending the baffle then straight over the rest of its length, extending substantially along the axis of the barrel.

Objects, characteristics and advantages of the invention appear from the following description, given by way of nonlimiting example, with reference to the appended drawings in which:
- Figure 1 is a schematic view in vertical section with interruption of a street lighting candelabra incorporating a lighting assembly according to the invention;
- Figure 2 is an enlarged schematic view in partial vertical section, in more detail, of a lighting assembly according to a first embodiment of the invention, placed in the foot of the candelabrum of Figure 1;
- Figure 3 is a schematic view similar to that of Figure 2 and shows a lighting assembly according to a second embodiment of the invention;
- Figure 4 is also a schematic view similar to Figures 2 and 3 and shows a lighting assembly according to a third embodiment of the invention; and
- Figure 5 is a schematic exploded perspective view of an optical baffle according to the invention.

 It will be noted, first of all, that the same reference numerals used in different figures designate identical or similar elements.

 The lighting assembly according to the invention and shown in Figures 1 to 5 is integrated into a street lighting candelabra, marked 1 as a whole in Figure 1. This candelabrum 1 is to be considered by way of example and of nonlimiting application of the lighting assembly of the present invention and mainly comprises two sub-assemblies: an elongated part or barrel 10, fixed to the ground, extending from the latter upwards, and an upper part or head 20 mounted at the free end of the barrel 10.

 The post 10 of the candelabrum, as shown diagrammatically in FIG. 1, incorporates a lighting assembly 30 according to the invention.

 More specifically, this lighting assembly 30 comprises, first of all, a light generator 31 disposed in the lower part or foot of the barrel 10 and fixed on a support 32, itself fixed to the foot of the barrel in a manner not shown. . The base of the barrel 10 is in practice also equipped with a inspection hatch, not shown here.

 The lighting assembly 30 also comprises a light guide 33 intended to optically connect the hot light source constituted by the generator 31 and a zone forming a cold light source.

In this case, the beam of cold light emerging from the light guide is returned to the ground by a lantern fitted with a reflector and constituting the head 20. In other embodiments, the head 20 may be constituted by any another suitable diffuser, and in particular a diffuser such as that described in the above-mentioned international patent application WO-95! 1,0792. But, as will be described in more detail below, the light guide 33 consisting of an optical bar, the latter could simply be pointed, without the use of any diffuser, towards an area to be highlighted. , or else be connected to a network of optical fibers, or even be frosted over all or part of its lateral surface, at its free end, with a view, for example, to lateral illumination.

 The light guide 33 is, in fact, because of its particularly advantageous characteristics explained above, consisting of an optical bar 34 of plastic material, such as PMMA, a few centimeters in diameter (generally between 3 and 6 cm) surrounded by an air duct 35 whose thickness here is a few millimeters over most of its circumference, and protected by a mechanical protection 36. This mechanical protection 36 is here in the form of a cylindrical tube.

Spacers 37 are arranged between the mechanical protection 36 and the light bar 34 to center and tighten the latter. For further details concerning this light guide 33, reference may also be made to the aforementioned international patent application WO-95/10792. Note, however, that thanks to the two different refractive index media of this light guide 33, namely PMMA and air, the Snell-Descartes law is satisfied.

 So that the PMMA light bar 34 does not degrade while melting and charring, The lighting assembly 30 comprises, in a particularly advantageous manner, an optical baffle 40 interposed between the generator 31 and the light guide 33. Its characteristics will now be described.

 In general, this optical baffle 40 has reflective and at least partially dichroic surface parts arranged so as to reflect the whole of the visible part of the incident light beam on the light guide entry surface 33, and evacuate at least infrared radiation, by transmission.

 More generally, it is interesting to choose reflective and at least partially dichroic surface parts which transmit the entire spectrum of the light beam incident on the mirror, except the visible part. Indeed, radiation such as UV radiation can also be harmful, in the sense that it contributes to the premature aging of the plastic material constituting the optical bar 34.

 Preferably, the baffle is made up of two mirrors placed facing one another, at least one of the mirrors being a cold mirror.

 A cold mirror is a dichroic mirror or semi-reflecting mirror, reflecting visible radiation (wavelengths between 400 and 700 nm) and transmitting all the rest, or almost all the rest, of the spectrum of the light beam incident on the mirror.

 Such a mirror can be obtained by dichroic selective treatments, for example by depositing multi-electric layers on a glass plate.

 More particularly, according to a first embodiment illustrated in FIG. 1 and in more detail in FIG. 2, the lighting assembly comprises a baffle 40 which is made up of two cold mirrors and planes 41, 42, transmitting at least the infrared radiation and reflecting the visible part of a light beam emerging from the generator 31, of which only the reflecting enclosure has been shown in FIG. 2.

 In this case, this enclosure 43 with a reflecting internal surface comprises: - a concave portion of ellipsoid 44; a light source 45, such as a short arc discharge lamp, of the metal iodide type, approximately placed at the first focal point F1 situated in this portion of ellipsoid; an annular hemisphere portion 46 with a reflecting surface, covering from its base the half-ellipsoid portion 44, centered on said focal point F1, with an axis coinciding with the major axis 48 of the ellipsoid defined by said portion of semi-ellipsoid , and having an opening at its top of axis also coincident with said major axis 48; and a tubular section of cylinder 47 with a reflecting surface, covering from a first of its ends the opening of the annular portion of hemisphere 46 and having an axis also coincident with said major axis 48.

 Such an enclosure 43 may be surrounded by a heat shield and include a housing containing a socket for the lamp, the housing itself being tightly connected to a ballast connected to an electrical energy supply network.

 We can also refer in this regard to the intemationa patent application! cited above WO-95/10792.

In the present embodiment, the mirrors 41 and 42 are parallel and extend, diametrically opposite and in one piece,
The opening, here circular, located at the free end of the cylinder section 47.

 The free ends of these two mirrors 41 and 42 are also also placed diametrically opposite with respect to the circular entry surface 49 of the light guide 33.

 In addition, the incidence of use of these mirrors being, in practice, between 0 and 45, a first 41 of these two mirrors is arranged so as to obliquely cut the major axis 48, also constituting the axis of the beam of light emerging from the reflecting enclosure 43, with an angle of 45.

 In addition, most of this beam of light converging at the second focal point F2 of the ellipsoid defined by the concave portion of the semiellipsoid 44, the reflecting surface of this mirror 41 has been placed in the vicinity of this focal point F2.

 Thanks to these arrangements, and as shown in FIG. 2 using an envelope of a light beam given by way of example, the first mirror 41 intercepts the light beam, returns it by reflection on the second mirror 42 which itself returns it by reflection towards the entry surface 49 of the light guide 33. In so doing, the beam of light produced by the light generator 31 is deflected from its path from side to side. other of the major axis 48 and subjected to a zig-zag path in the baffle 40, the whole of the visible part of the beam of cold light incident on the entry surface 49 having been subjected to reflection and the infrared radiation having has been evacuated from this entry surface 49 by transmission. It will be noted, in this regard, that the second mirror 42 is here also dichroic, in order to evacuate any residual infrared radiation that may possibly be reflected by the first mirror 41.

 It will also be noted that the infrared radiation has been shown diagrammatically in the drawings with the aid of an arrow accompanied by the mention "IR".

 In a second embodiment, illustrated in FIG. 3, the mirror 41 which cuts the long axis 48 with an angle of 45, is placed in front of the second focal point F2 defined by the concave portion of ellipsoid, in the direction of the first focal point of ellipsoid F1, while the reflecting surface of the other mirror 42 is placed in the vicinity of the focal point F3, the point of concentration of the light beam reflected by the mirror 41.

 Compared to the embodiment of FIG. 2, the virtual concentration point Fq of the beam of light incident on this surface has thus been brought closer to the input surface 49. To collect the same amount of light, a light guide 33 of smaller section can thus be used.

 However, this is not really prohibitive, because of the lower cost of guides made of plastic, such as PMMA.

 Light guides with smaller sections are, however, more advantageous in terms of space.

 In this regard, it will also be noted that the thermal baffle 40 proves to be relatively advantageous in terms of vertical bulk with respect to a section of cylinder 47 of the reflecting enclosure 43, the reflecting surface of which would be dichrolic so as to also remove infrared radiation. , as is the case for a conventional light generator such as that which is the subject of intemational patent application WO-95/1 0792.

 It will also be observed that, in the embodiment of FIG. 3, the thermal baffle 40 does not extend in one piece the reflective enclosure 43. A person skilled in the art will, in this regard, be able to produce the fixing means and for maintaining such a baffle 40 on the reflecting enclosure 43 or the generator 31, but also within a candelabrum barrel, just as it will be able to produce the means for fixing and maintaining the light guide 33 within it was candelabra. In the case of the candelabrum I of FIG. 1, it will be observed that the light guide is fixed and maintained at its upper end in the barrel of the candelabrum using openwork brackets 51, while its base is arranged opposite d 'a porthole 52 surmounting the thermal baffle 40. This porthole 52 is made of a transparent material treated with anti-reflection to avoid any light loss. For the sake of clarity, it has not been shown in FIG. 2. This window 52 also makes it possible to close the reflective enclosure 43-thermal baffle 40 assembly to isolate the light guide 33 from the ambient heat prevailing in this enclosure 43. It will be noted, in this regard, that the internal reflecting surfaces of enclosure 43 may also be dichroic, reflecting in the visible range and transmitting infrared radiation. The heat leaving the reflecting enclosure 43 will then be stopped by the heat shield mentioned above, then evacuated by chimney effect through the tubular space constituting an air passage, delimited by the barrel of the candelabrum around the light guide 33 .

 For further details on this subject, reference may also be made to the international patent application WO95 / 10792.

 It will also be noted that an air gap remains between the window 52 and the inlet surface 49 in order to avoid any transmission of heat to the light guide 33 by conduction.

 It will also be observed in FIG. 1 that the light guide 33 is curved at its base extending the baffle 40 and straight over the rest of its length, extending substantially along the axis of the barrel 10 of the candelabrum 1, making it possible to catch up with the lateral offset of the entry surface 49 induced by the thermal baffle 40, while ensuring an optimal chimney effect.

 As shown in FIG. 5, as a variant, two simple non-dichroic mirrors 60 and 61 can be connected to the other two dichroic mirrors 41 and 42 of the thermal baffle 40 so as to form a block with a square section and an internal reflecting surface. In other words, the dichroic mirrors 41 and 42 are placed at 45C with respect to the axis of the light beam, marked 70, while the simple mirrors are parallel to this axis 70. The losses of diverging rays are thus limited according to a direction XX 'shown diagrammatically in this FIG. 5 and perpendicular to the plane containing the trajectory of the axis 70 of the light beam. The light beam then moving between two parallel reflecting planes, it can deviate in the direction XX'.

 Finally, in a third embodiment of the lighting assembly according to the invention, illustrated in FIG. 4, the second plane mirror parallel to the first mirror obliquely cutting the major axis 48 of the ellipsoid defined by the concave portion ellipsoid 44, has been replaced by a concave mirror 42 '. It has been shown, in this FIG. 4, using two standard paths of light rays that it is thus possible to make the beam of light reflected by reflection by the first mirror 41 converge towards the entry surface 49 of the guide. light 33. Consequently, it is also possible here to use light guides with a small section.

 Mirrors 41 and 42 'are here both cold mirrors but, as a variant, provision may be made for only one of these two mirrors to be a cold mirror.

 They may also, as a variant, form an integral part of the generator, by extending, in one piece, the reflective surfaces of the enclosure 43.

 It goes without saying that the above description has been offered only by way of nonlimiting example and that numerous variants can be proposed by a person skilled in the art without departing from the scope of the invention.

 In particular, a person skilled in the art will be able, on the basis of the teachings of the international patent application WO-95/10792 and of the above description, to produce a light generator with a totally waterproof reflective enclosure.

Claims (15)

 1. Lighting assembly comprising a light generator (31), a light guide (33) intended to optically connect the hot light source constituted by the generator and a zone forming a cold light source, characterized in that it further comprises a thermal baffle (40) interposed between the generator and the entry surface (49) of the light guide, the baffle having reflective and at least partially dichroic surface portions arranged so as to reflect the whole of the visible part of the beam of light incident on said input surface, and discharging infrared radiation, by transmission.  2. Lighting assembly according to claim 1, characterized in that the baffle consists of two mirrors (41, 42; 42 ') placed opposite one another, at least one of the mirrors being a cold mirror.  3. Lighting assembly according to claim 2, in which the generator comprises an enclosure (43) with an internal reflecting surface comprising at least one concave portion of ellipsoid (44) and a light source (45) placed at the focal point of ellipsoid (F1) located in this portion of ellipsoid, characterized in that said mirrors are parallel plane mirrors (41, 42), a first of which obliquely cuts the major axis (48) of the ellipsoid defined by the concave portion of ellipsoid.  4. Lighting assembly according to claim 3, characterized in that the reflection surface of the first mirror is placed in the vicinity of the second focus (F2) of the concave portion of ellipsoid.  5. Lighting assembly according to claim 3, characterized in that the first mirror (41) is placed in front of the second focus (F2) of the concave portion of ellipsoid, in the direction of said ellipsoid focus (F1), while the reflecting surface of the second mirror (42) is placed in the vicinity of the focal point (F3) of the light beam reflected by the first mirror (41).  6. The lighting assembly as claimed in claim 2, in which the generator comprises an enclosure (43) with an internal reflecting surface comprising at least one concave portion of ellipsoid (44) and a light source (45) placed at the focal point. ellipsoid (F1) located in this portion of ellipsoid, characterized in that a first (41) of the two mirrors is a plane mirror obliquely cutting the major axis (48) of the ellipsoid defined by the concave portion of ellipsoid, while the second mirror (42) is a concave mirror converging by reflection the beam of light returned by the first mirror, towards the entry surface (49) of the light guide (33).  7. Lighting assembly according to any one of claims 3 to 5, characterized in that it further comprises two mirrors (60, 61) non-dichroic, parallel to said major axis and connected to the other two mirrors so as to form a block with a square cross section and internal reflective surfaces.  8. Lighting assembly according to any one of claims 3 to 7, characterized in that the enclosure further comprises an annular portion of hemisphere (46) with reflective surface covering from its base the portion of ellipsoid , centered on said focal point (F1), of axis coincident with the major axis of the ellipsoid, and having an opening at its apex of axis also coincident with said major axis, as well as a tubular section of cylinder (47) to reflecting surface covering from a first of its ends the opening of the annular hemisphere portion and having an axis coincident with said major axis.  9. Lighting assembly according to any one of claims 3 to 8, characterized in that the reflecting surfaces of the enclosure of the generator are dichroic, reflecting in the visible range and transmitting infrared radiation.  10. Lighting assembly according to any one of claims 1 to 9, characterized in that the at least partially dichroic reflecting surface portions form a continuous reflecting surface.  11. Lighting assembly according to any one of claims 1 to 10, characterized in that the reflective surface portions of said baffle are an integral part of the generator.  12. Lighting assembly according to any one of claims 1 to 11, characterized in that the light guide consists of a rigid homogeneous PMMA bar, a holding structure (36) extending along this bar by leaving a layer of air (35) along almost the entire lateral surface of this bar (34).  13. Lighting assembly according to any one of claims 1 to 12, characterized in that a window (52) of a transparent material surmounts the baffle, the entry surface (49) of the light guide being disposed next to this porthole.  14. Candelabra, characterized in that it comprises a barrel inside which is placed a lighting assembly according to any one of claims 1 to 13, and a diffuser (20) with reflective surface placed near the outlet of the guide.  15. Candelabra according to claim 14, characterized in that the light guide is curved at its end extending the baffle then straight over the rest of its length, extending substantially along the axis of the barrel.