EP2803907A1

EP2803907A1 - Lighting device

Info

Publication number: EP2803907A1
Application number: EP14166520.8A
Authority: EP
Inventors: Simone Cannella; Fabio Curro'
Original assignee: TCore Srl
Current assignee: TCore Srl
Priority date: 2013-05-14
Filing date: 2014-04-30
Publication date: 2014-11-19
Also published as: ITMI20130787A1

Abstract

A lighting device comprises a containment case (2) internally comprising a first compartment (2a) and a second compartment (2b), at least one light source (3) contained in the first compartment (2a) and at least a plurality of electronic components (4) inserted in the second compartment (2b) of the case (2). At least the second compartment (2b) of the containment case (2) is filled with a coolant, which serves as a thermal fluid.

Description

The object of the present invention is a lighting device that is particularly suited to sports-related, domestic, military and/or industrial use.
In particular, the present invention relates to a lighting device that can be utilised for example on safety helmets for caving and mountain climbing, as a scuba-diving flashlight, or as bicycle lights or also as spotlights in suspended ceilings in apartments/homes, offices or places open to the public.
Currently known lighting devices available on the market comprise a light source housed inside a containment body, substantially having the shape of a socket and that is closed at the only open end by a lens or by a generic transparent surface that permits the passage of light emitted by the light source.
Inside the containment body there is a set of electronic components such as temperature sensors, current sensors, transistors, etc., which must be positioned in very precise positions and preferably on electronic circuit boards for proper operation of the lighting device.
In further detail, the light source preferably comprises one or more LEDs that must be mounted on a supporting electronic circuit board generally arranged in a position parallel to the transparent lens.
The supporting circuit board advantageously divides the containment body into two compartments, a first compartment inside of which the light source is housed, and a second compartment containing the above-mentioned electronic components.
Preferably, the lighting device constituting the object of the present invention finds particular use as an instrument for use in high-level sports, given the particularly sophisticated electronic components thereof.
In fact, a lighting device such as this makes it possible for example to change the intensity of the light emitted by the source, or the light frequency, with programs that can be set by the user and that permit the use of Morse code for example.
Furthermore, given its particular uses, the dimensions of the lighting device must be limited and thus the need arises to have to dissipate the heat produced by the light source so as to prevent damage to the electronic components located in the immediate vicinity of the LEDs.
In particular, the intensity of the light is directly correlated with the temperature reached on the supporting circuit board supporting the light source, and the duration of the LED is affected by the temperature immediately surrounding it.
For this reason, the temperature sensors are necessarily positioned on the supporting circuit board supporting the LEDs, where the heat produced by the LEDs is greatest and thus the temperature is detectable.
Lighting devices of this type comprise an automatic program, based on which the maximum light for a given temperature detected by the temperature sensor is supplied.
This temperature control system also serves to prevent excessive overheating of the external surface of the containment body, and thus possible risks for the user, in addition to preventing internal overheating problems that could damage the internal electronics.
With this aim, the temperature sensors also serve for monitoring the temperature detected outside the containment body and enabling the device to emit the greatest possible brightness for a given detected temperature, preventing an increase in brightness when the detected temperature is already high.
Generally, the actual luminous flux produced (as output from the lenses) is (with the LED technology available today) in the range of 400-10,000 lumens. These values are limited only by heat dissipation due to the current inefficiencies of LEDs.
In order to reduce the overall temperature of the device, facilitate heat dissipation and thus attempt to increase the luminous flux produced, the heat produced needs to be dissipated efficiently; for this purpose the containment body of the prior-art devices has a finned surface in the lateral thickness thereof, specially designed and shaped to increase the heat exchange surface.
Yet, this heat dissipation surface is inefficient given that following prolonged use of the device, externally the containment body has zones varying in temperature, with temperature peaks in some zones and other cooler zones, which evidently participate to a limited extent in the heat exchange process. Internally, the distribution of temperatures is not homogeneous either and this does not make the process of heat exchange with the exterior, and thus the cooling of the entire device, efficient.
The heat produced by the light sources passes by conduction only through the contact bridges between the supporting electronic circuit boards and the external case, thus preventing uniform and rapid distribution of the heat. Internally there are zones that locally reach even 85°C, while externally the temperatures reach about 80°C. It is evident that local temperatures such as these are inevitably hazardous and damaging internally and externally.
In order to be cooled efficiently, the internal electronic circuit boards of the device should be finned in turn. However, this proves to be impossible due to problems relating to the dimensions and internal shape of the device. Moreover, in critical situations, such as underwater use where pressure is higher, the device is negatively affected and the life thereof could be of considerably shorter duration.
The same overheating problems are encountered, to an even more significant and burdensome extent, when using this device in drywall suspended ceilings for indoor lighting. In fact, while for sports-related use, the air flowing against the spotlight during normal use also helps to cool it, when it is stably inserted in a dropped ceiling, there is a greater accumulation of heat.
In this context, the technical task underlying the present invention is to offer a lighting device that overcomes the above-mentioned drawbacks of the prior art.
In particular, an aim of the present invention is to make available a lighting device that ensures efficient heat exchange and thus prevents overheating of the internal electronics and the external containment case.
Lastly, an aim of the present invention is to realise a lighting device that has greater structural strength also in critical situations of use.
The defined technical task and the specified aim are substantially achieved by a lighting device comprising the technical characteristics recited in one or more of the appended claims.
Further characteristics and advantages of the present invention will become more apparent from the approximate and thus non-limiting description of a preferred, but not exclusive, embodiment of a lighting device, as illustrated in the accompanying drawings, in which:

Figure 1 is a perspective view of a lighting device according to the present invention;
Figure 2 is a sectional perspective view of the device appearing in Figure 1, along a horizontal plane B-B;
Figure 3 is a sectional perspective view of the device appearing in Figure 1, along a vertical plane A-A;
Figure 4 is a sectional plan view of the device constituting the object of the present invention.

With reference to the figures attached hereto, a lighting device in accordance with the present invention is represented in its entirety by the number 1.
This device 1 comprises a containment case 2 substantially having the shape of a socket, inside of which there is a light source 3 and a plurality of electronic components 4, for the operation of this light source 3.
The device 1 has an on/off switch 10 on the containment case 2.
Internally, the containment case 2 is subdivided into a first compartment 2a containing the light source 3, and a second compartment 2b containing the electronic components 4.
The first compartment is delimited laterally by the containment case 2, at the top by a transparent surface 5 such as a lens or a reflecting surface, through which the light emitted by the light source 3 passes, and at the bottom, in a position opposite the transparent surface 5, by a supporting electronic circuit board 6, on which the light source 3 is mounted.
An alternative configuration (unillustrated) comprises that the electronic circuit board 6 supporting the light source 3 be arranged transversely to the transparent surface 5. In this case, the case 2 is always subdivided into two compartments 2a and 2b even if a dividing wall is not physically present between the two compartments.
The electronic components 4, which are advantageously housed in the second compartment 2b of the containment case 2, comprise a plurality of electronic circuit boards 7 bearing a plurality of sensors 8.
Among the sensors 8 provided inside the device 1, there is at least one temperature sensor, at least one current sensor and at least one transistor.
The device 1 also has various operating programs, various flashing levels and/or various levels of brightness, with different corresponding levels of duration, which can be selected according to the number of times the on/off switch is pressed.
The light source 3 preferably comprises at least one LED, even more preferably a plurality of LEDS, varying in number according to the size of the device and the intensity of light required.
In fact, devices of this type vary in size and they preferably have a maximum cross-sectional transverse dimension varying between 2 and 25 cm, more preferably between 4 and 20 cm.
The maximum circulating power within the device 1 preferably varies between 3 W and 100W, depending upon the number and dimensions of the LEDs.
Advantageously, the electric power supply is external to the device 1 and through cable sleeves, it arrives inside the device directly to the electronic components; however, the possibility of inserting a particular electric power supply system inside the device is not excluded.
At least the second compartment 2b, the one containing the electronic components 4, is advantageously filled with a coolant.
Advantageously, the coolant is a dielectric fluid that is preferably biodegradable and preferably in liquid form, such as oil, distilled water, etc. Any type of dielectric fluid can be used to fill the case and actively contribute to heat dissipation and improved distribution of the heat throughout the entire volume and on the entire internal surface of the device.
The coolant is a thermal fluid and by rendering the internal temperature uniform, it also increases heat exchange externally, thereby also rendering the external temperature uniform. In this manner, further maximisation of the intensity of the light and achieving more light is also possible.
In this manner, warmer zones and others that are less warm are no longer created and the heat is evenly distributed both internally and externally. Advantageously, the electronic circuit boards have through zones 9 allowing free circulation of the coolant within the second compartment 2b. In Figure 3 for example, these zones are afforded between the electronic circuit boards 7 and the internal surface 2c of the containment case 2, but it is not excluded that these through zones can be realised also as holes in the electronic circuit board 7.
Advantageously, the first compartment 2a can also be filled with coolant, which, in that case, must necessarily consist of a transparent fluid so as not to alter the intensity of the light emitted.
In the case in which the first compartment 2a is also filled with coolant, the supporting circuit board 6 supporting the light source 3 has openings 12 to enable free circulation of the coolant between the two compartments. Given that the containment case 2 is thus filled with fluid, it must necessarily be watertight so as to prevent undesirable leakage.
The presence of the coolant eliminates the need to equip the internal components with fins and it can advantageously lead to a structure of the external case 2 that is slenderer, lighter and less complicated and that could also be without the finned, heat exchange surface 11.
In the attached figures, a containment case is illustrated; it has these finned surfaces 11 and if present, such surfaces synergistically improve heat exchange with the exterior.
The distribution of heat within the device thus takes place not only by conduction, but also by both natural and forced convection.
In fact, if used in sports-related activities, the movement of the device enables re-mixing of the coolant contained therein.
The dimensions of the internal volume of the device 1 are limited and thus the convection motion generated is sufficient to cool the internal electronics as well.
With the devices currently in use, the maximum external temperature that can be reached at maximum brightness reveals zones with a temperature varying between 55°C and 80°C, whereas locally there are temperature peaks varying from 75°C to 85°C. Owing to the presence of the internal fluid, it is possible to make better use of the dissipation affecting the case, which is advantageously made of aluminium, obtaining an increase in heat dissipation by as much as 30-50%.
Moreover, the presence of a fluid dampens any vibrations and impacts that could have negative effects on the internal electronics.
In other words, in addition to serving as a thermal fluid, the coolant also functions as a shock absorber.
Moreover, the thermal capacity of the coolant is greater than that of the air normally contained in the light, and this therefore allows the fluid to function also as a heat reservoir and therefore the device remains lit at maximum brightness for a longer period of time.
The prior-art device utilized for sports has a further drawback: when it remains stationary following more or less prolonged use, it no longer receives the forced heat exchange generated by the air stream flowing against it and thus the temperature of the LED undergoes a sharp increase with a resulting progressive and fairly sharp drop in the intensity of the light.
On the other hand, the lighting device that is filled with thermal fluid has a heat flux that is delayed in reaching the surface, given that the fluid also functions as a heat reservoir and during that interval of time, the brightness of the light source does not drop sharply, but rather it diminishes gradually as the thermal fluid is heated. In other words, in lighting devices of the prior art, if the light of the light source is set at maximum intensity, the internal temperature of the LED immediately rises sharply and it is thus necessary to dampen the intensity immediately. In the device constituting the object of the present invention, the thermal fluid, which has a thermal capacity greater than that of air, enables cooling of the LEDS immediately, before the heat reaches the external surface (solely by conduction through the solid material). This increases the duration of the thermal transient of the LEDs, which, given that they reach the maximum operating temperature more slowly, can offer maximum light for a longer period of time. Therefore, the increase in the temperature of the LEDS is actually delayed, while the thermal wave reaches the surface first, following the presence of the thermal fluid, and dampened in amplitude given that the heat is more distributed; even in the case of particularly unfavourable external conditions, the thermal fluid makes it possible to accumulate heat at least temporarily and thus functions as a heat reservoir, preventing this increase, even a temporary increase, from damaging the electrical connections and the electronic components.
The presence of a coolant also makes it possible to position the temperature sensors at a distance from the light source 3, given that the heat is now distributed evenly and the supporting circuit board of the light source is no longer the hottest point to be monitored for adjustment of the light intensity accordingly.
In other words, the temperature sensors, just as any other sensors, no longer necessarily need to be positioned directly on the supporting circuit board 6 supporting the light source 3, for they can also be positioned in the proximity of the point of insertion of the electrical connections from the outside into the case 2, for example on the base of the socket of the case 2, opposite the transparent surface 5.
Given that not only the temperature sensors, but also all the other sensors in general, can be positioned in any position, structural complications involving the positioning of the electrical connection wires can be avoided. The structural simplicity of the device is thus improved and enhanced, also in terms of the complexity of the internal electrical connections, which are more direct and therefore shorter.
The intensity of the light produced depends on the number of LEDs present and this inevitably affects the dimensions of the device.
With the device constituting the object of the present invention, with the intensity of the light produced being the same, the volume of the device can be reduced by 15-25% compared to current realisations; the weights thereof are also lower by similar percentages. This is made possible owing to the fact that the extension or the thickness of the finned surface 11 present on the lateral surface of the containment case 2 can be reduced or even eliminated.
The reduction of the thickness of the walls, especially in scuba-diving devices, is quite advantageous, for the device proves to be lighter, more manageable and less cumbersome, and the structural strength of the device is not compromised in any manner whatsoever, as the fluid withstands the ambient pressure as well and contrasts it, maintaining a perfect equilibrium between internal pressure and external pressure.
Therefore, structurally the internal fluid serves to give the device greater robustness, with particular reference to underwater uses.
The invention achieves the proposed aims and makes it possible to obtain numerous advantages with respect to the prior art.
In fact, the presence of the internal coolant allows for limiting the thermal drift of the active components and for minimising the internal thermal gradient, given that it is distributed internally.
The fluid also makes it possible to obtain stabilisation of the measurement sensors and to prolong the duration of the LEDs because the local thermal gradients are lowered and the LED remains cooler.
Furthermore, in limited spaces there can be more light, more efficient cooling, and the structure of the entire device, including the electrical connections, proves to be simpler.
The structural simplicity and the improved thermal uniformity also permit reductions in the space occupied, dimensions and weight, to the advantage of portability, even in critical situations.
Furthermore, in the event of a temporary drop in heat exchange externally, the thermal transients increase, enabling a more gradual lowering of the light.
The active components undergo less wear, which is to the benefit of the duration thereof, which is inevitably prolonged.
Lastly, the internal temperatures reached are such that the coolant does not undergo any physical degradation, not does it produce any waste, with the advantage that there is no need for it to be replaced.

Claims

Lighting device comprising a containment case (2) internally comprising at least one light source (3) and a plurality of electronic components (4), characterised in that said containment case (2) internally contains a coolant.
Device according to the preceding claim, characterised in that said coolant is a dielectric fluid.
Device according to one of the preceding claims, characterised in that said containment case (2) internally contains a first compartment (2a), containing said light source (3), and a second compartment (2b), within which said plurality of electronic components (4) is housed; said coolant being present at least in said second compartment (2b), surrounding said electronic components (4).
Device according to the preceding claim, characterised in that said coolant is also present in said first compartment (2a).
Lighting device according to the preceding claim, characterised in that said light source (3) is connected to a support board (6); said support board (6) being interposed between said first (2a) and said second (2b) compartment.
Device according to the preceding claim, characterised in that said support board (6) supporting the light source (3) has openings (12) for the circulation of the coolant between said first (2a) and said second (2b) compartment.
Device according to one of the preceding claims, characterised in that said light source (3) comprises at least one LED, preferably a plurality of LEDs.
Lighting device according to one of the preceding claims, characterised in that said electronic components (4) comprise a plurality of electronic boards (7) and a plurality of sensors (8); said electronic boards (7) having through zones (9) to allow the free circulation of the coolant within the second compartment (2b).
Device according to the preceding claim, characterised in that said sensors (8) can be connected at a distanced position with respect to the support board (6) supporting said light source (3).
Device according to one of the preceding claims, characterised in that said case (2) is watertight.