WO2008122942A1

WO2008122942A1 - Radiator and luminary

Info

Publication number: WO2008122942A1
Application number: PCT/IB2008/051266
Authority: WO
Inventors: Louis Montagne
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2007-04-05
Filing date: 2008-04-04
Publication date: 2008-10-16

Abstract

The invention relates to a radiator (2) which may be used in connection with a light-emitting diode (LED) luminary (5). For instance, such a luminary may be installed in a suspended ceiling (7). The radiator element comprises a solid heat conducting body consisting of a succession of at least two segments (22), two consecutive segments having different directions, the proximal end (21) of the radiator element being adapted to be equipped with a LED circuitry (3, 4). A luminary (5) comprises a plurality of adjacent luminary units (1) secured to a luminary frame (6). Each luminary unit comprises a plurality of aligned LEDs (4) connected to a printed circuit board (3) for controlling said LEDs and for transferring heat to a radiator element (2) the proximal end (21) of which is secured to the printed circuit board (3).

Description

RADIATOR AND LUMINARY

TECHNICAL FIELD

The invention relates to a radiator which may be used in connection with a light- emitting diode (LED) luminary. For instance, such a luminary may be installed in a suspended ceiling.

BACKGROUND OF THE INVENTION

A lighting fixture is disclosed in publication No. US 2004/0120152 Al. This lighting fixture comprises a LED array secured to an emitter plate which is unitary with a T-shaped heat transfer mounting bar. The emitter plate separates the lighting fixture into two compartments: a heat transfer compartment which is delimited by the emitter plate and the fixture body, and a LED compartment which is delimited by the emitter plate and the lens cover of the lighting fixture. Air channels are formed between two adjacent heat transfer mounting bars. Air circulates through the air channels in the heat transfer compartment thanks to an inlet fan and an outlet fan disposed in the wall of the fixture body.

SUMMARY OF THE INVENTION When using LEDs in luminaries, the thermal aspect is always an issue. Indeed,

LEDs are more and more efficient, but their light flux decreases with the increase of temperature. Therefore, the use of radiator is compulsory in order to maintain the light flux and to avoid the destruction of the LEDs. However, the location and the orientation of the radiator elements to obtain the best thermal exchange with air is an important question as it has a direct impact on the number of LEDs by surface unit, and as consequence on the miniaturisation of LEDs luminaries.

It is an object of embodiments of the invention to provide a LED luminary with an optimized thermal exchange capacity. In particular, it is an object of embodiments of the invention to provide a radiator for use in a LED luminary, which allows for an improved balance between light flux and thermal exchanges.

Another object of embodiments of the invention is to provide a LED luminary adapted to suspended ceilings. In an embodiment of the invention, the radiator has a further feature of preventing a user from catching a glimpse of the ceiling proper.

A further object of embodiments of the invention is to provide a LED luminary which takes advantage of natural cooling, in particular without the need of a mechanical air circulation.

To this end, an embodiment of the invention proposes a radiator element for use in a LED luminary, said radiator element comprising a solid heat conducting body consisting of a succession of at least two segments, two consecutive segments having different directions, the proximal end of the radiator element being adapted to be equipped with a LED circuitry.

The structure of the radiator element, with at least two consecutive segments which have different directions permits to enclose a greater heat exchange surface in a given volume, than that which would be reached with a single straight segment.

Moreover, provided that the radiator elements all have the same cross-section, stocking or transporting them is quite easy as they can be piled for instance.

A further embodiment of the invention is a luminary unit which comprises a plurality of aligned LEDs connected to a printed circuit board for controlling said LEDs and for transferring heat to a radiator element, the proximal end of said radiator element being secured to said printed circuit board.

Thus, it is possible to associate a plurality of luminary units in order to manufacture a luminary. Therefore, another embodiment of the invention is a luminary comprising a plurality of adjacent luminary units secured to a luminary frame. In a preferred embodiment, the distance between two adjacent luminary units is sufficient to allow the air to flow between said adjacent luminary units.

When the LEDs are under operation, they generate heat. Thus the radiator is hotter at its proximal end than at its distal end. A natural convective air flow installs itself, from the proximal end towards the distal end of the luminary. This leads to a natural cooling of the LEDs, thereby improving their efficiency and preventing overheating or their destruction.

In order to reach a maximum thermal exchange, the luminary units have a structure which has a minimum impact on the air flow. In particular, the luminary units are provided so that they have a minimum projected area.

Moreover, depending on the number of segments of the radiator elements and on their respective directions, they contribute to hiding the ceiling above the luminary, when the latter is installed in a suspended ceiling. Thus, someone glancing above one's head should not catch a glimpse of the ceiling proper. These and other aspects, features and advantages of the invention will become apparent to those skilled in the art upon reading the disclosure provided here in connection with the attached drawings. The detailed description, while indicating preferred embodiments of the invention, is only given by way of illustration. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more details by way of example with reference to the accompanying drawings, in which:

- Figure 1 shows a perspective view of an assembly of luminary units comprising radiator elements according to a first embodiment of the invention.

- Figure 2 depicts a cross-section of the assembly of figure 1.

- Figure 3 depicts a detail of a cross-section of an assembly of luminary units comprising radiator elements according to a second embodiment of the invention.

- Figure 4 shows a perspective view of a luminary comprising radiators according to a third embodiment of the invention.

- Figure 5 depicts a cross-section of the luminary of figure 5 installed in a suspended ceiling.

DETAILED DESCRIPTION OF THE INVENTION It must be noted that as used in this specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The term "segment" is used herein to encompass a portion of a line, be it straight or curved. A curved line portion may be a circle arc for instance. In the latter case, and more generally in the case of any curved line, if the curve portion (or curved line portion) is greater than a quarter of circle, it will be considered as two curve segments for the purpose of this specification. For instance, an S-shaped curve portion will be considered as comprising three segments. In the case of a curve segment, its direction will be taken as the direction of the chord of this curve segment.

In the specification, the LED luminary will be described as a ceiling luminary installed in a suspended ceiling. However, it is emphasized that a LED luminary according to the invention may also be installed, for instance, on a wall.

Figure 1 shows five luminary units 1. Each luminary unit 1 comprises a solid radiator element 2 and a printed circuit board 3 to which LEDs 4 are connected. In this embodiment, one radiator element is associated to six LEDs, however, this is not an essential feature of the invention. For instance, the LEDs 4 are surface-mounted to the printed circuit board 3.

In this embodiment, the proximal end 21 of the radiator element 2 is secured to the printed circuit board 3 on the same face 31 as the face to which the LEDs 4 are connected. However, the LEDs 4 can also be connected to the opposite face 32 of the printed circuit board 3, as illustrated on figure 3.

The radiator element 2 comprises a solid heat conducting body which consists of a succession of radiator segments 22. Two consecutive segments have different directions: they are at an angle. As illustrated, the radiator segments 22 have a substantially straight cross-section. It should be noted however that the radiator segments 22 could be curved, the junction between two segments corresponding to a curve change for instance. Therefore, the general aspect of the cross-section of a radiator elements 2 may be among others a V-shape, a W-shape, a Z-shape, a U-shape, a S-shape, or an assembly thereof. Preferably, when the directions of two consecutive segments 22 of the radiator element 2 form an obtuse angle, as illustrated on figures 1-3, the body of the radiator element consists of at least three segments. The main reason is that having three segments in such a case prevents people walking below the luminary from catching a glimpse of the ceiling proper. Otherwise, when there are only two radiator segments at an obtuse angle, there are some positions where seeing the ceiling might be possible. The number of segments is only limited by the configuration of the place where the luminary will be installed, inter alia by the depth of the suspended ceiling 7 where it will be installed. For instance, on figures 1 and 2, the radiator element 2 has four consecutive segments 22. As illustrated on figures 4 and 5, when the radiator segments 22 are at an acute angle (or their directions are at an acute angle), two segments may be sufficient to prevent people from catching a glimpse of the ceiling.

More generally, in a luminary units assembly, when the luminary units 1 are close enough together, or when the bent junction of a radiator element overlaps the proximal end of an adjacent radiator element, then two radiator segments 22 are enough to prevent people from catching a glimpse of the ceiling.

In a preferred embodiment of the invention, the outer surface of the radiator elements 2, or part thereof, is dark and/or matt. Both features improve the dispersion or absorption of parasite light coming from the ceiling. Therefore, they contribute to preventing people from seeing the ceiling. If only part of the outer surface of the radiator elements 2 is dark and/or matt, preferably it is the zone close to the distal end of the radiator element 2.

To further improve light dispersion, the outer surface of the radiator elements 2, or part thereof, presents embossments. Moreover, this also increases the overall exchange surface of the radiator element, thereby improving its heat exchange properties. These embossments may be irregular or regular. In the latter case, their geometry may be quite varied: points, lines, in staggered rows etc.

Various methods may be cited for manufacturing a radiator element as described here. For instance, a leaf of a heat conducting material such as aluminium is provided with the appropriate thickness. Then the desired shape is imparted to the leaf by compression, together with optional embossments. A surface treatment may also be chosen in order to provide a dark surface, or a matt surface, of both. Such a surface treatment may take place before, or after, shaping of the leaf.

A illustrated on the various figures, a luminary unit 1 comprises a plurality of aligned LEDs 4 connected to a printed circuit board 3. The printed circuit board 3 comprises a LED circuitry controlling the LEDs 4, i.e. supplying the LEDs 4 with power and turning them on and off when desired. The printed circuit board 3 is made of a heat resistant material which permits transferring the heat generated while the LEDs are under operation to a radiator element 2 as described in the foregoing. To the effect, the proximal end 21 of said radiator element 2 is secured to the printed circuit board 3.

Preferably, the direction of the light beams which may be emitted by said LEDs 4 is substantially parallel to the direction between the proximal end 21 and the distal end 23 of the radiator element 2.

A luminary 5 comprises a plurality of adjacent luminary units 1 secured to a luminary frame 6. The distance between two adjacent luminary units 1 is sufficient to allow the air to flow between said adjacent luminary units, as represented with arrows 8 on the various figures. When the LEDs 4 are under operation, they generate heat. Thus the radiator element 2 is hotter at its proximal end 21 than at its distal end 23. A natural convective air flow installs itself, from the proximal end 21 towards the distal end 23 of the luminary unit 1. This leads to a natural cooling of the LEDs, thereby improving their efficiency and preventing overheating or their destruction. Preferably, the distance between two adjacent luminary units 1 is of the same order as the thickness of one luminary unit. The thickness of a luminary unit 1 may be defined for instance as the greatest thickness between the thickness of the radiator element 2 and the thickness of the printed circuit board 3 and a LED 4.

It is preferred that the thickness of a luminary unit 1 is as low as possible. Indeed, this allows for a greater number of luminary units per luminary. Therefore, a greater light intensity may be achieved as well as a sufficient air flow in order to cool the LEDs when they are operated.

The foregoing description of preferred embodiments of the invention is not intended to be exhaustive or to limit the invention to the disclosed embodiments. Various changes within the scope of the invention will become apparent to those skilled in the art and may be acquired from practice of the invention.

Claims

C L A I M S

1. A radiator element (2) for use in a LED luminary, said radiator element (2) comprising a solid heat conducting body consisting of a succession of at least two segments (22), two consecutive segments having different directions, the proximal end (21) of the radiator element (2) being adapted to be equipped with a LED circuitry (3, 4).

2. The radiator element of claim 1 wherein the directions of two consecutive segments form an acute angle.

3. The radiator element of claim 1 wherein the solid body consists of a succession of at least three segments and wherein the directions of two consecutive segments form an obtuse angle.

4. The radiator element of claim 1 wherein the body, or a part thereof, presents a dark and/or matt outer surface.

5. The radiator element of claim 1 wherein the outer surface of the body, or part thereof, presents embossments.

6. A luminary unit (1) comprising a plurality of aligned LEDs (4) connected to a printed circuit board (3) for controlling said LEDs and for transferring heat to a radiator element (2) as claimed in claim 1, the proximal end (21) of said radiator element being secured to said printed circuit board (3).

7. The luminary unit of claim 6, wherein the direction of the light beams which may be emitted by said LEDs is substantially parallel to the direction between the proximal end (21) and the distal end (23) of the radiator element.

8. A luminary (5) comprising a plurality of adjacent luminary units of claim 6 or 7 secured to a luminary frame (6), the distance between two adjacent luminary units being sufficient to allow the air to flow between said adjacent luminary units.

9. The luminary of claim 8 wherein the distance between two adjacent units is of the same order as the thickness of one luminary unit.