EP2206945A1

EP2206945A1 - LED lighting device for outdoors and large covered areas having opitmized heat dissipation

Info

Publication number: EP2206945A1
Application number: EP09180160A
Authority: EP
Inventors: Massimo Viglione; Marco Ezio Enea Lamperti; Antonio Macchi Cassia; Pietro Maria Castiglioni
Original assignee: Ibt Lighting SpA
Current assignee: Ibt Lighting SpA
Priority date: 2008-12-30
Filing date: 2009-12-21
Publication date: 2010-07-14
Anticipated expiration: 2029-12-21
Also published as: ITMI20082349A1; IT1392500B1; NZ582311A; AU2009251130A1; EP2206945B1

Abstract

The present invention refers to an LED lighting device for use outdoors and in large covered areas, in the public and private sectors, which comprises a plurality of LED light sources (11) constrained to a lamp body (13), said lamp body (13) has a finned ring shape, at least one substantially flat optical element (12) being constrained at the bottom to the finned ring lamp body (13), the finned ring lamp body (13) and the optical element (12) defining a first chamber (11a) for housing the plurality of LED light sources (11) and circuitry for managing them (11).

Description

The present invention refers to a lighting device for use outdoors and in large covered areas, in the public and private sectors, distinguished by an optimized heat dissipation. The lighting device for outdoors and large covered areas according to the present invention is based on the use of preferably high power LEDs as the light source.
High power LEDs have seen continuous and progressive improvements, over the last years, in terms of light efficiency and they are considered the light source of the next generation for general lighting applications. Moreover, the absence of light pollution and the drastic reduction of maintenance costs, ensured by this type of light source, opens the doors to a rapid penetration on the market, with a gradual replacement of conventional lighting sources for outdoors and large covered areas, like high pressure sodium and metal iodides.
One of the main advantages of the high power LED light source comes from the fact that, if correctly managed, it can have a useful life which is greater than 50.000 hours, with consequent advantages for the maintenance of the lighting device.
However, such an LED light source, in particular if it is high power, although it offers high light efficiency, has an intrinsic amount of power which is not converted into light but consists of heat to be disposed of.
Therefore, in the absence of suitable dissipation elements that are suitably sized so as to have a sufficient heat exchange surface, there is a rapid deterioration of the LED devices themselves, in particular if the junction temperature of such devices exceeds a predetermined limit value.
The performance of the dissipation elements is thus fundamental in order to reach the useful life objectives in the final product. Its purpose is to keep the temperature of the lighting device at values which are not dangerous for the life of the LED light sources.
An optimal sizing of the dissipating elements makes it possible to increase the service life of the product and thus to reduce the costs and maintenance time it requires.
On the contrary, an inadequate dissipator causes the performance to decrease rapidly or causes the lighting device to break.
The lighting devices for outdoors and large covered areas known to this day, having one or more LEDs as their light source, are thus designed in a way such as to foresee at least one suitably sized dissipator element in contact with the LED light sources.
However, the solutions adopted nowadays, for making the dissipator elements do not make it possible to achieve satisfactory performance in terms of dissipation, in particular in the case in which there are many sources, in relation to the homogeneity and the efficiency of the cooling effect.
This is often due to the fact that in the dissipators used in the known LED lighting devices for outdoors and large covered areas, the cooling air is not typically able to reach the centre of the dissipator.
The purpose of the present invention is that of avoiding the aforementioned drawbacks and in particular that of conceiving an LED lighting device for outdoors and large covered areas that, for the same dissipating surface of the dissipating element used, offers improved dissipation performance.
A further purpose of the present invention is that of making an LED lighting device for outdoors and large covered areas, which is able to produce a homogeneous and efficient cooling effect on the LEDs.
Last but not least purpose of the present invention is that of conceiving an LED lighting device for outdoors and large covered areas, which offers a particularly long service life.
These and other purposes according to the present invention are achieved by making an LED lighting device for outdoors and large covered areas as outlined in claim 1.
Further characteristics of the LED lighting device for outdoors and large covered areas are object of the dependent claims.
The characteristics and the advantages of an LED lighting device for outdoors and large covered areas according to the present invention shall become clearer from the following description, given as an example and not for limiting purposes, with reference to the attached schematic drawings in which:

figure 1 is a perspective view from below of a first embodiment of the LED lighting device for outdoors and large covered areas according to the present invention;
figure 2 is a perspective view from above of the LED lighting device for outdoors and large covered areas of figure 1;

figure 3 is a section view of the LED lighting device for outdoors and large covered areas of figure 1, in which the arrows represent the direction in which the air passes through the device;
figure 4 is an enlarged detail of figure 3;
figure 5 is a perspective view from above of a second embodiment of the LED lighting device for outdoors and large covered areas according to the present invention;
figure 6 is an enlarged detail in section of the LED lighting device for outdoors and large covered areas of figure 5, in which the arrows represent the direction in which the air passes through the device;
figure 7 is a perspective view from above of a third embodiment of the LED lighting device for outdoors and large covered areas according to the present invention;
figure 8 is an enlarged detail in section of the LED lighting device for outdoors and large covered areas of figure 7, in which the arrows represent the direction in which the air passes through the device;
figure 9 is a perspective view from above of a fourth embodiment of the LED lighting device for outdoors and large covered areas according to the present invention;
figure 10 is an enlarged detail in section of the LED lighting device for outdoors and large covered areas of figure 9, in which the arrows represent the direction in which the air passes through the device.

With reference to the figures, an LED lighting device for outdoors and large covered areas is shown, wholly indicated with reference numeral 10.
According to the present invention, the LED lighting device for outdoors and large covered areas 10 comprises a plurality of, preferably high power, LED light sources 11 directly constrained to a finned body which constitutes the lamp body 13.
The finned ring lamp body 13, to which the plurality of LED light sources 11 is constrained underneath, has a substantially flat ring base 13a from the top of which a plurality of fins 13b, substantially arranged along the entire ring defined by the lamp body 13, projects upwards.
By ring shape it is not only referred to a perfectly circular flat plan shape, but generic shapes are meant which are centrally hollow, for example having a an elliptical, square or rectangular base and so forth, the said shapes following the profile of surfaces which are not necessarily flat, such as for example curved surfaces, or surfaces having a profile corresponding to a broken line.
The ring base 13a acts as a surface for coupling with at least one lower optical element 12, on which there is a plurality of lenses 18 arranged in matrixes.
The optical element 12 below is in general constrained to the lamp body 13 through suitable constraining means 20.
The group made of the lamp body 13 and the optical element 12 forms a toroid 12,13.
The lamp body 13 and the optical element 12 define inside the toroid 12,13 a substantially flat first chamber 11a, in which the LED light sources 11 are housed.
The LED light sources 11 with the relative circuitry 11b, are also constrained to the finned ring lamp body 13 through the action of the constraining means 20 which keep the optical element 12 constrained to the lamp body 13.
Particularly, the plurality of LED light sources 11 and the relative circuitry 11b are directly constrained to the bottom of the ring base 13a of the lamp body 13, whereas from the top of the ring base 13a the plurality of fins 13b projects upwards.
Further, next to both sides of the optical element 12 there is a mask element 14 that, along with the lamp body 13, defines a second chamber 14b for housing the cables for supplying power to the LED light sources 11. The mask element 14 is also constrained to the lamp body 13 through suitable constraining means (not illustrated).
The mask element 14, joining up with the lenses 18 so as to form a lower transparent surface of a material similar to that of the lenses 18 themselves, offers a homogeneous visual effect.
The positioning and the distribution of the light sources 11 follow the profile outlined by the finned ring lamp body 13.
Preferably, the LED light sources 11 are arranged in groups of matrixes in which each matrix is associated with an optical element 12, in such a manner that the single LED light source 11 is optically coupled with a single lens 18, forming part of the optical element 12. The resulting light distribution on the ground is thus made up of the sum of all the single flows coming out from every optical element 12, which therefore equally contribute to lighting up the street area to be lit.
Moreover, the mask element 14 makes it possible to have a homogeneous visual appearance of the lighting apparatus for outdoors and large covered areas, due to the fact that it gathers the light emitted laterally by the optical elements 12 and diffuses it through a plurality of prisms 14a formed on the mask element 14. The effect obtained is that, when turned on, the lighting device seems like a uniform ring of light thus masking the plurality of single spot lights.
The fins 13b of the finned ring body 13 can take on any profile, even different from one another, according to the overall shape which is wished to be given to the lighting device for outdoors and large covered areas 10, as well as according to the type (conduction and/or convection) and quantity of heat transmission that is wished to be obtained through the finned ring body 13. In order to ensure an optimal conduction, the plurality of fins 13b is uniformly distributed along the entire extension of the ring base 13a. Moreover, the single fins 13b are made with a thickness which is as thin as possible, where the limit of the choice of thickness depends on the type of material used as well as on the technology used for making the finned body 13.
In the embodiments illustrated, in which the lamp body 13 has a circular shape, the fins 13b are arranged along radiuses whose geometrical centre coincides with the centre of the lamp body 13.
This geometry promotes uniformity of the thermal path. Moreover, such an arrangement does not have a single preferential direction, and thus expresses a better behaviour, in operating conditions, when there is wind. The spacing between the fins 13b is defined according to a volumetric approach to the natural convection. Indeed, if two fins 13b are too close together they affect each other negatively whereas, if they are too far apart the overall number of fins 13b of the finned ring lamp body 13 and thus the total surface of heat exchange is reduced.
The optimal spacing is that which maximises the coefficients of heat exchange and thus the total power transmitted to the environment, according to the sizes of the dissipator, in turn depending on the overall sizes of the lighting device 10 and depending on the limit temperature one wishes to have at the lamp body 13 itself.
Therefore, in the embodiment illustrated, fins 13b extending for the entire thickness of the lower ring base 13a, are alternated with fins 13b' which extend for only a portion of such a thickness, in particular arranged in the outermost portion of the finned ring lamp body 13. This is done so as to exploit the fact that, at the outermost portion, the circular-shaped finned ring lamp body 13 has a circumference which is greater and thus has more space for housing such fins 13b without having them excessively close to one another.
The finned ring lamp body 13, being configured according to a closed profile, creates a central cavity that, for the same overall size of the lighting device, makes it possible to have a cool air flow towards the fins 13b, coming both from the outer perimeter of the device, and from the inner perimeter corresponding to the perimeter of the cavity, as illustrated in figures 3, 4, 6 and 8.
In such a way, the fins 13b have a marked phenomenon of thermal convection which takes the heat away from the lamp body 13.
The heat dissipation is thus improved with respect to the condition of dissipators known nowadays, in which the cooling air is typically not able to reach the centre of the dissipator causing the cooling effect to be heterogeneous and inefficient.
In the LED lighting device for outdoors and large covered areas 10 according to the present invention provided with a central cavity, there are two directions in which the air can flow through the fins 13b cooling them on both sides, inside and outside, with consequent increase of the heat dissipation performance.
The fins 13b, 13b' of the finned lamp body 13 are preferably interrupted in one or more sectors of such a body 13 in which hollow compartments 13c, 15 are arranged.
As shown in figure 2, it is possible to foresee a single hollow compartment 15 suitable for housing electronic means (not illustrated) inside of it, necessary for supplying power and, preferably, also for managing the lighting device 10, such as a power supply unit and a plurality of sensors and/or actuators. Alternatively, as illustrated in figure 5, it is possible to conceive making, in predetermined positions, an additional plurality of hollow compartments 13c suitable for the same purpose.
The power supply unit dispenses the correct power supply to both the LED light sources 11 of the lighting device 10, and the further electronic means.
Such electronic means are used to manage the communication between the lighting device for outdoors and large covered areas 10 and a remote control unit, which verifies the correct operation of the device 10 and records the sent data (signals, anomalies, images and so forth).
The communication is managed through a control unit integrated in the power supply unit of the lighting device for outdoors and large covered areas 10 suitable for recording possible anomalies and for transmitting the operation parameters to a connection unit installed in the electrical distribution cabin, which in turn is connected to a remote control station.
In addition, the electronic means housed in the hollow compartment 15 can comprise a webcam, for recording and sending images to a remote unit, and/or a pollution sensor for recording the air quality, and/or temperature sensors and/or smoke sensors for fire safety and/or anti-intrusion movement sensors for private use.
Moreover, at a higher level of integration, the electronic means can be active devices, amongst which, for example, an extinguisher system which operates in the case of fire, detected by the temperature and/or smoke sensors.
For hooking the LED lighting device for outdoors and large covered areas 10 onto a respective support pole, suitable hooking means 16 are foreseen comprising a first portion 16a integral with the finned ring lamp body 13 connected by means of a pivot to a second hollow tube-shaped portion 16b, suitable for cooperating with the support pole of the lighting device for outdoors and large covered areas 10.
In the case in which the first portion 16a of the hooking means 16 is integral with a hollow compartment 15, 13c of the lamp body 13, it preferably has a finning 16c intended for the thermal dissipation of the electronic means contained in the compartment 15, 13c itself, as illustrated in figures 5, 7 and 9.
In the embodiments illustrated in figures 7-10, a screen 19 is also advantageously foreseen, above the finned ring lamp body 13, having the same ring shape and a suitably shaped profile which further improves the dissipation performance of the finned ring lamp body 13.
The upper screen 19 constitutes a protection from direct solar radiation, for all the electronic components of the lighting device 10.
Indeed such a radiation has a negative effect on the electronic components even when they are turned off, since it could cause limit temperature thresholds to be exceeded, causing the life of the components themselves to be shortened.
The advantage of using a solar screen 19 is even more obvious at sunset, which is the moment when the lighting device is turned on and, depending on the geographical location in which it is installed and on the season, it could be operating in critical environmental conditions, if it did not have the screen.
The protection offered by the screen 19 against solar radiation indeed keeps the lighting device, and thus the LED light sources 11 and the finned lamp body 13, at a lower temperature with respect to what it would be without the screen 19, positively contributing to the thermal dissipation and to the useful life of the device 10.
The screen 19 can advantageously be connected to a hollow body 15, 13c through suitable connection means 21.
Specifically, the screen 19 has a profile which at least partially follows the profile of the fins 13b, 13c and on top of it, it can have some slits 22 for disposing of the heat released by the fins 13b, 13c. The arrangement of the slits 22 shown in figures 7 and 8 is not restricted to the number, size and shape of the slits 22 themselves.
If there are no slits 22, the screen 19 is configured in such a manner that the fins 13b, 13c themselves create a channel 17 with parallel walls having a substantially ascending direction or, at least, having an inlet 17a and an outlet 17b, in which the inlet of the channel 17a is positioned in a lower position with respect to the outlet 17b.
The screen 19 thus makes it possible to obtain an increased air flow through the fins 13b of the finned body 13, as illustrated in figure 10.
Indeed, at the inlet 17a of the channel 17 formed by the finned lamp body 13 and by the screen 19 there is cool air at atmospheric pressure. Inside the channel 17, on the other hand, there is a low pressure area and a high temperature.
A pressure difference is thus created between the inner and outer area of the channel 17, which accentuates even more the cool air flow entering in the finned body 13 in at least one of the two flow directions outlined in relation to the embodiments without a screen 19.
This flow can be amplified by the presence of wind which impacts the surface of the screen 19.
From the description made, the characteristics of the electronic system object of the present invention as well as the relative advantages should be clear.
The LED lighting device for outdoors and large covered areas according to the present invention is indeed able to offer an increased dissipation effect for the same dissipation surface of the dissipation element used, obtaining a homogeneous and efficient cooling effect on the LEDs. In such a way, a long service life of the lighting device for outdoors and large covered areas according to the present invention is ensured.
It should finally be clear, that the LED lighting device for outdoors and large covered areas thus conceived can undergo numerous modifications and variants, all covered by the invention; moreover, all the details may be replaced by technically equivalent elements. In practice the materials used, as well as the sizes, can be any according to the technical requirements.

Claims

LED lighting device (10) for outdoors and large covered areas comprising a plurality of LED light sources (11) constrained to a lamp body (13) characterised in that said lamp body (13) has a finned ring shape, at least one substantially flat optical element (12) being constrained at the bottom to said finned ring lamp body (13), said finned ring lamp body (13) and said at least one optical element (12) defining a first chamber (11a) for housing said plurality of LED light sources (11) and circuitry (11b) for managing said plurality of LED light sources (11).
LED lighting device (10) for outdoors and large covered areas according to claim 1 characterised in that said at least one optical element (12) comprises a plurality of lenses (18) arranged in matrixes.
LED lighting device (10) for outdoors and large covered areas according to claim 2 characterised in that said plurality of LED light sources (11) is arranged in groups of matrixes distributed along the development of said finned ring lamp body (13), each of said LED light source matrixes (11) being associated with a lens matrix (18) such that each light source (11) of said plurality of LED light sources (11) is optically coupled with a lens (18) of said plurality of lenses (18).
LED lighting device (10) for outdoors and large covered areas according to any one of the previous claims characterised in that said finned ring lamp body (13) comprises a ring base (13a) from which a plurality of fins (13b) extends.
LED lighting device (10) for outdoors and large covered areas according to claim 4 characterised in that said fins (13b) are uniformly distributed along the development of said ring base (13a).
LED lighting device (10) for outdoors and large covered areas according to one of claims from 4 to 5 characterised in that said finned ring body (13) has a circular shape, said fins (13b) being arranged along radiuses whose geometrical centre coincides with the centre of said finned ring body (13).
LED lighting device (10) for outdoors and large covered areas according to claim 6 characterised in that first fins (13b) alternate along the development of said ring base (13a), which fins extend for the entire thickness of the ring base (13a) below, and second fins (13b') which extend only for part of such thickness, said second fins (13b') being arranged in an outermost portion of said finned ring body (13).
LED lighting device (10) for outdoors and large covered areas according to any one of claims from 4 to 7 characterised in that said succession of fins (13b,13b') is interrupted at least at one sector (15,13c) of said finned ring body (13), a hollow compartment (15,13c) being arranged in said at least one sector (15, 13c) .
LED lighting device (10) for outdoors and large covered areas according to claim 8 characterised in that electronic means are arranged within said at least one hollow compartment (15,13c).
LED lighting device (10) for outdoors and large covered areas according to any one of the previous claims characterised in that support pole hooking means (16) are connected to said finned ring lamp body (13), said hooking means (16) comprising a first portion (16a) integral with said lamp body (13) connected by means of one pivot to a second hollow tube-shaped portion (16b).
LED lighting device (10) for outdoors and large covered areas according to claim 10 characterised in that said first portion (16a) of said hooking means (16) integral with said lamp body (13) is finned.
LED lighting device (10) for outdoors and large covered areas according to any one of the previous claims characterised in that a mask element (14) is further constrained at the bottom to said finned lamp body (13), said mask element (14) defining with said finned lamp body (13) a second chamber (14b) for the passage of power cables of said plurality of LED light sources (11).
LED lighting device (10) for outdoors and large covered areas according to claim 12 characterised in that said mask element (14) comprises a plurality of prisms (14a) for the diffusion of light emitted laterally by said at least one optical element (12).
LED lighting device (10) for outdoors and large covered areas according to any one of claims from 4 to 13 characterised in that it comprises, on top of said finned ring lamp body (13), a screen (19) having the same ring plan, and having a section profile corresponding to at least part of the profile of said fins (13b), said screen (19) forming with said finned ring lamp body (13) a channel (17) having an inlet (17a) and an outlet (17b) for an air flow, said inlet (17a) being placed in a lower position with respect to said outlet (17b).
LED lighting device (10) for outdoors and large covered areas according to claim 14 characterised in that said screen (19) has a plurality of slits (22).