EP2107621A1

EP2107621A1 - Light module

Info

Publication number: EP2107621A1
Application number: EP08006793A
Authority: EP
Inventors: Michiel Bekker; Bernardus Anthonius Maria Elfrink
Original assignee: Bekker & Business Holding Bv
Current assignee: Bekker & Business Holding Bv
Priority date: 2008-04-03
Filing date: 2008-04-03
Publication date: 2009-10-07

Abstract

The invention relates to a light module comprising:
- a housing;
- a heat dissipating mounting plate arranged in the housing;
- a plurality of LED's mounted on a first side of the heat dissipating mounting plate, wherein each junction of the LED's is in heat conducting contact with the mounting plate;
- opposed first and second ventilation openings arranged in the housing for allowing natural convection along the mounting plate.

Description

The invention relates to a light module.
Light modules are used in a number of applications, such as for use in head lights of vehicles or for the lighting of a room.
One of the applications in particular is in use for a light pipe. Such a light pipe comprises a light module, which directs a light beam into a tube, which tube has a transparent or translucent wall portion. In the light tube a foil is arranged, which reflects the light an ensures that the light beam of the light module exits the tube through the transparent wall portion in an even tempered way.
It is known to use for such a light pipe a light module, which comprises a gas discharge lamp. The disadvantage of such gas discharge lamps is that a considerable time must be present between switching off the light and turning the light back on. Another disadvantage is that such lights cannot be dimmed. On the other hand, gas discharge lamps can produce a considerable amount of light compared to for example incandescent lamps.
Other light sources known in the prior art are LED's (light emitting diodes). Up to recent, LED's did not provide much light power and were not suitable for lighting a room or for use as head lights in a vehicle. However, LED's have been recently developed, which produce a substantial higher amount of light. Such LED's are also called power LED's. Although these LED's produce a substantial amount of light, the disadvantage is that they also produce a substantial amount of heat. In particular at the junction of the LED's the temperatures could rise substantially, which decreases the life span of such LED's.
It is therefore necessary when using such power LED's to have a good dissipation of the heat generated by the LED's. These requirements are contradictory to applications in which a substantial amount of light has to be produced while keeping the dimensions of such a light module small.
It is however an object of the invention to combine the advantages of LED's in a light module and be able to keep the dimensions of the light module small.
This object is achieved according to the invention with a light module comprising:

a housing;
a heat dissipating mounting plate arranged in the housing;
a plurality of LED's mounted on a first side of the heat dissipating mounting plate, wherein each junction of the LED's is in heat conducting contact with the mounting plate;
opposed first and second ventilation openings arranged in the housing for allowing natural convection along the mounting plate.

By arranging the plurality of LED's on a heat dissipating mounting plate, the heat generated by the LED's can be dissipated into the mounting plate. This heat which is dissipated into the mounting plate is than discharged by natural convection, which is possible as a result of the ventilation openings arranged in the housing of the light module. This arrangement makes it possible to have a large number of LED's packed together and still keep the temperature of the junction of a LED within reasonable limits.
As a large amount of LED's can be placed close to each other a high amount of light can be produced by the light module. Furthermore, LED's can easily be dimmed and switched on and off at desired intervals.
In a preferred embodiment of the light module according to the invention, the first ventilation openings are in use located higher, and seen in gravitational direction, than the second ventilation openings. This will promote the natural convection.
In another preferred embodiment of the light module according to the invention, the mounting plate is provided on the second side with heat dissipating means. Preferably these heat dissipating means comprise fins or ribs. With such fins or ribs, the surface area is increased, which allows for a better contact between the air flow generated by natural convention and the heat dissipating mounting plate.
In yet another embodiment of the light module according to the invention each LED is provided with a lens for focusing the light of the LED. In addition the light module could furthermore comprise a lens arranged in the housing for focusing the light of the plurality of LED's.
LED's produce a very wide angled diverging light beam. For some applications a more focused light beam is required. By arranging a lens for each LED and/or by arranging a lens in the housing the wide angled light beams of the LED's can be focused towards a more focused light beam.
The invention further relates to a modular lamp, comprising:

a hollow mounting beam, having at least one longitudinal channel;
at least one light module according to the invention, mounted in the mounting beam such that the light beam is parallel to the mounting beam;
a tube mounted in the mounting beam adjacent and inline with the at least one light module, wherein the tube has a translucent wall portion and comprises means for reflecting the light beam through the translucent wall portion;

The use of a hollow mounting beam is that the air flow generated by natural convention of the light modules can be guided such that contamination of the modular lamp is reduced. Also due to the length of the longitudinal channel a natural draft will occur which further improves the discharge of heat from the light modules.
In a preferred embodiment of the modular lamp according to the invention, the hollow mounting beam comprises a longitudinal air supply channel and a longitudinal air discharge channel, wherein the longitudinal air supply channel is in flow contact with the first ventilation openings of a light module and wherein the longitudinal air discharge channel is in flow contact with the second ventilation openings of the light module. This furthermore improves the natural air flow as a result of draft and convention, but makes it also possible to have a central ventilation system which cools the light modules.
In another embodiment of the modular lamp according to the invention, the reflecting means comprise a foil with predetermined reflective properties. Such a foil is designed in particular for the light beam generated by the light module. The foil ensures that the light of the light module is evenly distributed over the tube and the light exits the tube through the transparent or translucent wall portion evenly.
These and other advantages of the invention will be elucidated in conjunction with the accompanying drawings.
Figure 1 shows a embodiment of a modular lamp according to the invention.
Figure 2 shows the modular lamp according to figure 1 with some parts removed.
Figure 3 shows a perspective view of a light module according to the invention as used in the modular lamp according to figure 1.
Figure 4 shows the light module according to figure 3 with some parts removed.
Figures 5 and 6 show two examples of the airflow inside a modular lamp according to the invention.
In figure 1 a modular lamp 1 according to the invention is shown. This modular lamp has a mounting beam 2 in which two light modules 3 and respective tubes 4 are mounted. The portion of the tube 4 not covered by the mounting beam 2 is translucent.
Furthermore, a control unit 5 is mounted in the mounting beam 2. Finally, both ends of the modular lamp are covered by covering plates 6, 7.
In figure 2 the modular lamp 1 according to figure 1 is shown with the control unit 5, covering plate 6, one light module 3 and one tube 4 removed. From figure 2 it is clear that the mounting beam 2 is hollow and has two separate longitudinal channels 8, 9. These longitudinal channels 8, 9 can be used to supply air to a light module 3 and to discharge heated air from a light module 3.
In figure 3 a light module 3 according to the invention is shown. The light module 3 has a housing 10 with cooling ribs 11. One side of the housing is provided with a transparent surface 12, which could be a lens. In the housing 10 a number of ventilation openings 13 and 14 are arranged.
In figure 4 the light module 3 of figure 3 is shown with the housing 10 removed.
In the housing a heat dissipating mounting plate 15 is arranged on which a plurality of LED's 16 are arranged. The LED's 16 shown are typical power LED's which have a support 17 which is in heat dissipating contact with the junction of the LED. This support 17 is glued or soldered or welded to the heat dissipating mounting plate 15 such that the heat generated by the junction of the LED's 16 is easily dissipated into the mounting plate 15. Each LED 16 is furthermore provided with a lens 18 to focus the light of the LED.
On the backside of the mounting plate 15 grooves are arranged, which result in ribs 19 increasing the heat dissipating surface and improving the heat discharge capabilities of the mounting plate 15. Figure 4 shows furthermore a back cover plate 20.
Figure 5 shows in perspective view the light module 1 in use. Cold air Ac is supplied through channel 8 in the mounting beam 2 then through an opening 21 the air flows along the backside of the mounting plate 15 and the ribs 19 and after the air is heated it returns through the channel 9 as hot air Ah.
Figure 6 shows an alternative flow of the air for a light module 3. Cold air Ac is again supplied through channel 8 and enters a light module 3 through a back cover plate (not shown) at a distance from the mounting beam 2. The cold air Ac then flows back along the heat dissipating mounting plate 15 through the opening 13, 14 (as shown in figure 3) and back through channel 9.

Claims

Light module comprising:
- a housing;

- a heat dissipating mounting plate arranged in the housing;

- a plurality of LED's mounted on a first side of the heat dissipating mounting plate, wherein each junction of the LED's is in heat conducting contact with the mounting plate;

- opposed first and second ventilation openings arranged in the housing for allowing natural convection along the mounting plate.
Light module according to claim 1, wherein the first ventilation openings are in use located higher, as seen in gravitational direction, than the second ventilation openings.
Light module according to claim 1 or 2, wherein the mounting plate is provided on the second side with heat dissipating means.
Light module according to claim 3, wherein the heat dissipating means comprises fins or ribs.
Light module according to any of the preceding claims, wherein each LED is provided with a lens for focusing the light of the LED.
Light module according to any of the preceding claims, wherein a lens is arranged in the housing for focusing the light of the plurality of LED's.
Modular lamp comprising:
- a hollow mounting beam, having at least one longitudinal channel;

- at least one light module according to any of the preceding claims, mounted in the mounting beam, such that the light beam is parallel to the mounting beam;

- a tube mounted in the mounting beam adjacent and inline with the at least one light module, wherein the tube has a translucent wall portion and comprises means for reflecting the light beam through the translucent wall portion;
wherein the ventilation openings are in flow contact with the longitudinal channel of the hollow mounting beam.
Modular lamp according to claim 7, wherein the hollow mounting beam comprises a longitudinal air supply channel and a longitudinal air discharge channel, wherein the longitudinal air supply channel is in flow contact with the first ventilation openings of a light module, and
wherein the longitudinal air discharge channel is in flow contact with the second ventilation openings of the light module.
Modular lamp according to claim 7 or 8, wherein the reflecting means comprise a foil with predetermined reflective properties.