EP2202445A1

EP2202445A1 - LED lighting electric device and corresponding lamp including a plurality of such LED devices

Info

Publication number: EP2202445A1
Application number: EP08022376A
Authority: EP
Inventors: Tao Lin
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-12-23
Filing date: 2008-12-23
Publication date: 2010-06-30

Abstract

The invention concerns an LED lighting electric device (1) comprising:
- an LED light source (2) mounted and powered on a support card (15);
- a corresponding inverted truncated cone-shaped waveguide (3) associated with the light source (2) to diffuse the light beam generated by said source;
- a lens (4) supported in a predetermined spaced apart relationship with the light source (2);
- transparent support legs (5) formed in one piece with the waveguide (3) and base ends (7) proximal to the light source (2) fixed to the card (15) around the light source (2).

Advantageously, according to the invention, the base ends (7) of the transparent legs (5) are in contact with a resin (9) that does not absorb light radiation.

In this way, a saturation effect of the light beam taken away through the support legs of the waveguide is achieved and the luminosity of the LED lighting device (1) is increased for an equal level of electrical power consumption.

Description

The present invention refers to an LED lighting electric device comprising:

an LED light source mounted and powered on a support card;
a corresponding waveguide associated with the light source to diffuse the light beam generated by said source;
a lens supported in a predetermined spaced apart relationship with said light source;
transparent support legs formed in one piece with the waveguide or with said lens and extending around said light source.
The invention also concerns a lighting apparatus, for instance a lamp or a headlight, including a plurality of said LED lighting electric devices.
The invention also concerns a method for producing said LED lighting electric devices.

Field of application

As is well known in this specific technical field, over the past few years a new artificial lighting technology has become popular, based upon semiconducting light emitting diodes, so-called LEDs. LEDs are powered by means of a suitable electronic circuit and their light is generated by a physical process called "Electron-hole recombination" that results in the emission of light particles, in other words photons.
The average life of an LED is estimated to be tens of times greater than most light bulbs or discharge lamps that, in optimal conditions of continuous use, can respectively reach a maximum of 2000 or 7000 hours of operation. LEDs, on the other hand, can ideally last 50,000 hours or more.
Moreover, LEDs consume much less electrical energy and can play a fundamental role in the reduction of the costs linked to electrical energy consumption.
Currently, LEDs are still relatively expensive, set to fall in the future as they are used more extensively, but LED lighting can already offer savings in the medium and long term thanks to their lower consumption, their greater lifetime and their very low maintenance.

Prior art

In the field of lighting technology LEDs are normally used in lamps or lighting apparatuses that include a plurality of LED light sources and corresponding lighting bodies that can comprise a waveguide or reflector of the light beam produced by the LED and a lens crossed by such a light beam.
Lighting apparatuses of various shapes and sizes are known in which the aforementioned LED light sources and the corresponding lighting bodies are suitably positioned and orientated to obtain a predetermined size of lit area or else a predetermined lighting intensity. It is also known to equip these lighting apparatuses with groups of LED light sources having different lighting powers to one another.
It is also worth noting that increases in lighting intensity normally involve corresponding increases in the electrical power consumed.
Whilst advantageous from various points of view, and substantially achieving their purpose, these lighting apparatuses still have some drawbacks that limit their widespread use.
Firstly, the intensity of the light beam generated by the LED sources and by the corresponding diffusing lighting bodies is not yet satisfactory in terms of energy efficiency and of size of area lit. More specifically, the transparent support legs of the diffusing lighting bodies associated with each LED take away part of the light beam generated.
Secondly, the standard thermal operating conditions of LED lighting apparatuses is close to 70° on the lighting body and it is obviously at an even higher temperature on the LED source reducing the overall useful life of the source. These relatively high standard thermal conditions also oblige the use of metal casings and supports for such lighting apparatuses.
Finally, the drawback remains that the possible increase in lighting area or radius is paid for by an increase in the electrical power used.
The technical problem forming the basis of the present invention is to device a new structure of LED lighting electric device having structural and functional characteristics such as to overcome the aforementioned drawbacks with reference to the prior art.

Summary of the invention

The technical problem is solved by an LED lighting electric device of the type indicated previously and characterised in that a resin that does not absorb light radiation is used in contact with the base ends of the transparent support legs of the lighting body acting as diffuser, so as to obtain a saturation of the light beam inside such transparent legs with a corresponding increase in the light intensity emitted by the LED device for the same electrical power consumed
Advantageously, the aforementioned resin is a silicon epoxy resin with high heat conduction. In this way there is the further advantage that part of the heat produced by the LED light source is taken away through the silicon resin reducing the standard thermal conditions of the lighting device.
Other characteristics and advantages of the LED lighting electric device according to the present invention shall become clearer from the following description of an example embodiment thereof, given for indicating and not limiting purposes with reference to the attached drawings.

In such drawings:

Brief description of the drawings

figure 1 shows a perspective and schematic view of an LED electric device according to the present invention;
figure 2 shows a perspective and partial section view of a detail of the lighting device according to the invention;
figure 3 shows a perspective view of the framework of a lighting apparatus including a plurality of LED lighting devices according to the present invention;
figures 4 and 5 show respective schematic views from above, and from the side of the framework of figure 3;
figures 6 and 7 show respective perspective views from above and from the side of a detail of the lighting apparatus of figure 3;
figure 8 shows a perspective view of a lighting apparatus obtained in accordance with the present invention.

Detailed description

With reference to such drawings, an LED lighting electric device made according to the present invention is globally and schematically indicated with 1.
The device 1 can also be defined as an LED lamp associated with a diffusing optical element of the light beam produced by the lamp.
The device 1 is particularly suitable for being used in the field of civil or industrial lighting technology. In other words bulbs or lights including a plurality of devices 1 can be installed inside or outside, i.e. indoors or outdoors, in homes, offices, shops or warehouses, or else they can be used for public uses like for example street lighting or lighting for public places in general (gyms, schools, hospitals, etc.).
The LED lighting electric device 1 comprising at least one LED (Light Emitter Diode) light source 2 based upon a light emitting semiconductor diode.
The specific type of LED light source 2 is not covered by the present invention in the sense that the source 2 can be a single diode or a multichip LED formed from at least three diodes.
For example, leds are available in a very wide range of "pure" colours, i.e. obtained without the use of filters placed in front of the light source and emitted "naturally" by the led itself. Multichip leds, on the other hand, are formed from three diodes - a red one, a blue one and a green one - that when suitably controlled can create thousands of colour combinations.
For the purposes of the present invention what counts is exclusively that the device 1 comprises at least one LED light source 2 mounted and powered on a support plate 15.
It is commonly said that the LED is a primary optical system that is mounted on a primary reflector, for example a metallic layer, which is fixedly connected to a printed circuit board.
The LED light source 2 has an associated waveguide 3 that acts as a diffusing lighting body intended to transmit, direct and diffuse the light beam generated by the light source 2.
The waveguide 3 has an essentially inverted truncated cone shaped structure extending with the smaller base at the LED light source 2 and the larger base distal from the LED source 2.
The larger base is substantially formed from an optical element intended to interact with a light beam emitted by the LED.
In other words, the larger base of the waveguide 3 comprises a lens 4 arranged in a predetermined spaced apart relationship from the LED light source 2 in a position substantially perpendicular to the main lighting direction of the light source 2.
The lens 4 allows the light beam emitted by the LED light source 2 to be focused keeping it within a predetermined emission angle with the minimum dispersion.
The inverted truncated cone shape of the waveguide 3 has the function of directing and diffusing the light beam emitted by the LED onto the lens 4 operating substantially as a diffusing body of the light beam.
To keep the waveguide 3 in position transparent support legs 5 are provided formed in one piece with the waveguide and extending around said light source 2. In some other embodiments the legs 5 are formed in one piece around the perimeter of the lens 4.
More specifically, there are four of such legs 5 and they extend parallel to one another around the light source 2. The legs 5 are arranged in equally angularly spaced position, 90° apart, around the waveguide 3.
Therefore, the legs 5 have an end formed in one piece with the waveguide 3, at the lens 4, and have the opposite base or foot ends fixedly connected to the support plate 15 of the light source 2.
Even more specifically, the legs 5 are small cylindrical transparent columns, slightly tapered towards their base, and having a base end portion 7 fixed to the support card 15 around the light source 2.
The base end portions 7 have a smaller diameter than the average diameter of the column-shaped legs 5 to each be inserted with pressure in a corresponding hole 8 formed in the plate 15 around the light source 2.
In the example embodiment described here purely for indicative and not limiting purpose, there are four holes 8 arranged with an angular spacing of 90° around the light source 2, as if they were the vertices of a square running around said light source 2.
The waveguide 3 and the corresponding support legs 5, formed in one piece, are made from a transparent synthetic plastic material, for example a polycarbonate.
The lens 4 can also be formed in one piece with the waveguide 3 as larger base of the truncated cone shaped body.
Alternatively, the lens 4 can be fixedly connected as the larger base of the waveguide 3 shaped like a truncated cone.
Again alternatively, the lens 4 may be missing.
The lens 4 can be simply a transparent layer, in the shape of a circular crown with a central through hole.
The lens 4 can also have a more complex structure, for example with a pair of surfaces arranged parallel to one another a predetermined distance apart, a flat surface facing towards the light source 2 and another prism shaped outer surface.
By prism shaped surface we mean to define a surface that has a plurality of prism shaped elements adjacent to one another and equipped with inclined portions 4a or facetings 4b such as to be able to create phenomena of reflection, refraction, diffraction or polarisation of the light beam that passes through the lens 4.
The aforementioned prism shaped elements can be right pyramids or frustums of right pyramid brought close together and having the base parallel to the first flat surface.
Advantageously, according to the present invention, the base ends 7 of said legs 5 are in contact with a resin 9 that does not absorb light radiation.
For the purposes of the present invention it is sufficient that the ends of the legs 5 be covered or in any case darkened by the resin 9 so that the light radiation channelling along the small transparent columns is unable to leave by the base.
Preferably, however, the base ends 7 of the legs 5 are embedded in the resin 9 on the opposite side of the plate 15 with respect to where the light source 2 is located.
The resin 9 is a silicon resin that is a good heat conductor.
Advantageously, moreover, the resin 9 is an epoxy resin that lends itself to being shaped through injection moulding.
Purely as a non-limiting example we point out that the resin 9 can be of the type commercially known by the trade name FT0610 that defines a specific resin for insulating, sealing and protecting electrical transformers.
The low exothermy of this resin avoids damaging the components during polymerisation thanks to the low heat production. Moreover, this epoxy resin FT0610, offers excellent heat dissipation.
The high dielectric, mechanical, physical and chemical characteristics of this resin give the components coated with it total protection against humidity and chemical agents.
The presence of the resin 9 on the base ends 7 of the transparent support legs 5 of the waveguide 3 allows the light radiation emitted by the source 2 and diffused by the waveguide 3 not to be attenuated or damped in its intensity by the presence of the transparent legs 5.
The phenomenon that occurs in the device according to the present invention is relatively complex and we can define it as light "saturation".
Basically, the light beam that crosses the legs 5 in the opposite direction, i.e. in the direction of the source, with respect to the desired and main direction of emission of the beam itself, finds its path blocked by the silicon resin 9.
It is as if each of the legs 5 were in a situation of saturation of the light beam with the result that none of them any longer absorbs part of the light beam produced by the source 2.
Thus, unlike what currently occurs for the solutions of the prior art, the transparent support legs 5 of the waveguide 3 do not in any way take away light from the main light beam emitted by the source 2 and do not contribute to reducing the light intensity of the source 2.
To use a plumbing analogy, it is as if there was a main pipe carrying a fluid that has branches along which the fluid finds its path blocked. In this case the branches could not in any way contribute to taking fluid away from the main pipe.
By analogy, the light beam that passes through each of the transparent legs 5 has no way to pass or be absorbed at the ends thereof located near to the source 2 and it reaches a state of saturation that prevents other arriving light from passing back through the small transparent column.
In other words, the electromagnetic light wave that passes through the transparent support legs 5 of the waveguide 3 reaches the ends 7 coated with resin 9 and saturates the corresponding transparent leg with light.
Tests carried out by the Applicant have demonstrated that the light intensity of the device according to the invention is surprisingly increased by 40% and more compared to the same device made according to the prior art placed in the same operating conditions.
This configuration of the device 1 according to the invention achieves a further important advantage represented by the fact that the silicon resin 9 takes away the heat produced at the base of the LED light source 2 and thus allows full performance operating conditions to be reached that substantially coincide with those theoretically foreseen for the regular and correct operation of a semiconductor LED.
With the device according to the invention the operating temperature at the base of the LED is around 45°C whereas that of the light source is around 70°C, which represents the optimal theoretical combination of operation for a semiconductor LED.
This gives the great advantage that the LED device according to the invention can operate for a period that substantially coincides with the theoretical operating time equal to 100,000 hours.
It can therefore be understood how important and far-reaching the present invention is, making it possible to provide an LED lighting electric device in which the totality of the light beam emitted by the source is exploited and directed for lighting purposes whilst, at the same time, the light source is kept at a regular operating temperature foreseen by the theoretical specifications of semiconductor LEDs.
It follows from this that with the lighting devices according to the invention it is possible to obtain better optical performance, an increase in luminosity of the source and a reduction in the standard thermal conditions, if compared with the devices currently proposed by the prior art.
The LED lighting electric device according to the invention can be used to make LED headlights or lamps in general by associating them together and feeding power, for example in parallel, to a plurality of devices 1 in the same lighting apparatus.
An example of application of a plurality of devices made in accordance with the present invention and mounted on a headlight for use on the road shall now be described.
Of course, there is no reason why various types of lighting apparatuses should not be made, for example by associating or combining a plurality of devices 1 in order to obtain lighting apparatuses for indoor or outdoor uses, both for public or private use.
For indicative but not limiting purpose, figure 3 schematically illustrates a lighting apparatus 10 including a plurality of LED lighting electric devices 1 according to the present invention.
The apparatus 10 is substantially a headlight having an essentially open truncated cone shaped framework 11 with the smaller base 13 plate-shaped and substantially round and the larger base 14 open to give access to an inner cavity 12 in which the lighting devices 1 are housed, to all face towards an area to be lit when the apparatus 10 is installed.
Alternatively, the apparatus 10 can be made through a parabola or spherical cap-shaped framework in which the LED lighting devices are mounted in the concavity of the parabola or of the spherical cap.
For the purposes of the present invention the shape of the framework of the lighting apparatus can be whatever; what cunts is that the lighting devices can be mounted in the cavity 12 of the framework of the lighting apparatus with the electrical connections going to each light source 2 arranged on the opposite side with respect to the cavity 12, in other words on the outer surface of the framework 11.
In the example embodiment described here for indicating and not limiting purposes, the outer surface of the framework 11 comprises a plurality of plate-shaped portions 16, essentially shaped like an elongated isosceles trapezium, adjacent to one another along a longer oblique side of the trapezium shape to form, as a plurality of trapezium shaped sectors, the inclined or oblique walls of the truncated cone shape and all joined in their shorter round base side 13 of the truncated cone shaped framework 11.
There can be sixteen or twenty portions 16 according to the configuration requirements of the framework 11, both in terms of area covered, and in terms of inclination of the oblique side wall. However, there is no reason why a greater or smaller number of portions 16 should not be used, just as there is nothing to stop such portions 16 being suitably sized so as to modulate the size of their larger and smaller bases and of the oblique sides.
The larger base sides of the trapezium shaped portions 16 are joined with an annular edge portion 17 of the lighting apparatus 10.
Conventional fastening means 18 to hang or fasten the lighting apparatus 10 to a support or to a wall or ceiling are provided on such an annular edge 17.
Advantageously, according to the invention, in the cavity 12 of the lighting apparatus 10 the portions 16 are intended to house a plurality of LED lighting devices 1, arranged in an orderly fashion.
The surface facing towards the cavity 12 of the round smaller base 13 of the framework 11 is in turn also intended to receive a predetermined group of LED lighting devices 1.
In particular, the smaller base 13 is structured substantially like the support card 15 of the light source 2, in the sense that some light sources 2 are mounted and fed with power on it, associated with the respective waveguides 3.
Each light source 2 is encircled by a group of through holes 8 through the base 13 and intended to receive the respective base ends 7 of the support legs 5 of each waveguide 3.
Around each light source there are preferably four holes 8, angularly spaced apart by 90°, each intended to receive, by coupling or by pressure, a corresponding base end 7 of a transparent leg 5.
Outside of the framework 11, in other words on the opposite side to the cavity 12 in which the lighting devices 1 are housed, it is possible to see the holes 8 for housing the base ends 7 and that cross both the smaller base 13 and the portions 16 that form the oblique walls of the framework 11.
These holes 8 are identifiable or groupable in homogeneous groups 20 of four holes each, corresponding to the support legs 5 of the same waveguide 3 associated with a given light source 2.
Each sector 16 has at least six groups 20 of four holes, whereas the smaller base 13 has ten groups 20 of four holes.
So, each group 20 of four holes is defined by a side wall 21 for containing said silicon epoxy resin.
The side walls 21 form substantially a square edge around the holes 8 associated with the support legs 5 of the waveguide 3 of each LED lighting device 1.
In other words, on the rear of the support plate of each light source 2, a plate that can be represented by the smaller base 13 or by any of the portions 16 with trapezium shaped sector, side walls 21 for containing the silicon resin placed in contact with the base ends 7 of the supports of the waveguides 3 are foreseen.
The resin that does not absorb light radiation through injection moulding occupies the space enclosed and defined by the quadrangular side walls 21. The injection is carried out according to per sé conventional ways.
In this way, the base ends 7 of the legs 7, forcibly inserted into the holes 8 and projecting on the rear of the support plates, be they 13 or 16, are coated and substantially embedded inside the layer of resin that has occupied each square portions defined by the side walls 21.
In this way the resin is associated with each lighting device 1 without wastage and avoiding the entire framework 11 being covered by an excessively expensive casting of resin that is of little use in the areas where it is not necessary.
The method for making the lighting apparatus 10 substantially coincides with the method for making even just one of the LED lighting electric devices 1.
Basically, on the rear of the support plate 15 of the light source 2 a layer of resin that does not absorb light radiation is deposited.
Since the silicon resin is an epoxy resin, it lends itself to being deposited through an injection moulding technique that can cover the rest of the support plate 15 or a portion thereof, for example a portion that through the side wall 21 defines a homogeneous group of holes 8 through which the base ends 7 of the support legs 5 of the waveguide 3 are fixed.
Thus the lighting device 1 according to the invention can be made with relatively small investments by providing side walls for containing the resin associated with each lighting device on the rear of the support plate of the corresponding LED light source.
The epoxy resin that is injected into the areas defined by the side walls 21 contributes to firmly fixing the support legs of the waveguides 3 and also covers the electrical connections that go to each semiconductor LED of each light source 2.
The end result is a lighting apparatus 10 of any shape and size in which each LED lighting device 1 has been fixedly connected with the lighting apparatus and, at the same time, takes advantage of the heat dissipating effect carried out by the silicon epoxy resin that greatly contributes to keeping a constant and optimal standard thermal conditions during operation, in other words while the lamp is on.

Claims

LED lighting electric device (1) comprising:
- an LED light source (2) mounted and powered on a support card (15);

- a corresponding inverted truncated cone-shaped waveguide (3) associated with the light source (2) to diffuse the light beam generated by said source;

- a lens (4) supported in a predetermined spaced apart relationship with said light source (2);

- transparent support legs (5) formed in one piece with the waveguide (3) and base ends (7) proximal to the light source (2) fixed to said card (15) around the light source (2);
characterised in that said base ends (7) of said transparent legs (5) are in contact with a resin (9) that does not absorb light radiation.
Device according to claim 1, characterised in that said resin is a silicon epoxy resin.
Device according to claim 2, characterised in that said silicon resin is a heat conductor.
Device according to claim 1, characterised in that said base ends (7) are embedded in said resin (9).
Device according to claim 1, characterised in that said legs (5) extend parallel to one another around said light source (2).
Device according to claim 1, characterised in that said base ends (7) of the legs (5) have a reduced diameter compared to the diameter of the corresponding legs (5) each to be forcibly inserted in a corresponding hole (8) formed in said plate around said light source (2).
Device according to claim 1, characterised in that
Lighting apparatus (10) of the type comprising a support framework (11) for a plurality of LED lighting electric devices (1) each of which is structured according to claim 1.
Lighting apparatus (10) according to claim 8, characterised in that said framework (11) is structured like an open truncated cone with the larger base open to give access to an inner cavity (12) in which the lighting devices (1) are housed on at least one plurality of plate-shaped portions (16) with trapezoidal sector associated together to form the inclined wall of the truncated cone; a side wall (21) for containing said resin (9) being provided on the opposite surface of each plate-shaped portion (16) with at least one device present.
Lighting apparatus (10) according to claim 9, characterised in that said side wall (21) defines a group (20) of through holes (8) formed in said plate-shaped portion (16) and receiving the base ends (7) of corresponding support legs (5) of the waveguide (3) of one of said LED lighting devices (1).
Method for making an LED lighting electric device comprising:
- an LED light source (2) mounted and powered on a support card (15);

- a corresponding inverted truncated cone-shaped waveguide (3) associated with the light source (2) to diffuse the light beam generated by said source;

- a lens (4) supported in a predetermined spaced apart relationship with said light source (2);

- transparent support legs (5) formed in one piece with the waveguide (3) and base ends (7) proximal to the light source (2) fixed to said card (15) by means of through holes (8) in said card (15) around the light source (2);
characterised in that a side wall (21) is provided defining said holes (8) on the side of said card (15) opposite said waveguide (3) and injecting into the area defined by said side wall a resin (9) that does not absorb light radiation that is in contact with the base ends (7) of said legs (5).