"STEM LIGHTING DEVICE"

[0001] The present invention relates to a floor or desk lighting device, in particular for lighting medium/large sized rooms .

[0002] The lighting sector is characterised by great efforts to innovate, both from an aesthetic and functional point of view.

[0003] In particular, LED lighting devices are becoming especially popular although having some drawbacks as regards heat dissipation. In fact, high power LEDs develop a lot of heat due to the flow of current in the semiconductor. Consequently, to ensure an optimal light flow and a long life of the bulb, it is important for LEDs not to overheat excessively, especially in the case of continuous functioning.

[0004] The present invention addresses, in particular, stem lighting devices, i.e. provided with a stem which the light source is positioned on. In these devices, specifically due to the reduced dimensions of the stem, which does not allow optimal dissipation of the heat, and of the bulb which easily overheats having to guarantee an elevated flow of light to illuminate rooms of large sizes, the problem of correct heat management becomes critical. [0005] The purpose of the present invention is to overcome the drawbacks of the prior art bearing in mind the requirements of the sector.

[0006] In particular, the purpose of the present invention is to get an LED stem lighting device, able to provide an optimal light flow and to operate, even in the case of continuous functioning, below critical temperatures at all times.

[0007] Such purpose is achieved by a lighting device made according to claim 1. The dependent claims describe preferred or advantageous embodiments of the lighting device .

[0008] The characteristics and advantages of the lighting device according to the present invention will be evident from the description below, made by way of a non-limiting example in accordance with the appended drawings wherein:

[0009] figure 1 shows an axonometric view of a lighting device according to the present invention, in one embodiment ;

[0010] figure 2 shows an axonometric view of a lighting device according to the present invention, in a further embodiment;

[0011] figure 3 shows a cross-section view of the lighting device in figure 1;

[0012] figure 4 shows a view of the detail IV of the lighting device in figure 3;

[0013] figure 5 shows a view from below of the lighting device in figure 3.

[0014] With reference to the appended drawings, reference numeral 1 indicates a floor or desk lighting device for example LED, in particular for lighting medium/large sized rooms.

[0015] The lighting device 1 comprises a hollow stem 2. The stem 2 is made in one piece, or, according to embodiment variants, in separate parts mechanically joined to each other .

[0016] Preferably, the stem 2 is made of metal, preferably aluminium.

[0017] The stem 2 is an elongated cylindrical and slim shape with a circular or polygonal cross-section. The stem 2 is defined by a height H and by a characteristic dimension W, corresponding to the transversal cross- section. The characteristic dimension W of the stem is represented by the diameter, in the case of a circular cross-section, or by the side or diagonal in the case of a polygonal cross-section.

[0018] The stem 2 has a characteristic dimension/height ratio (W/H) less than 1/30, preferably less than 1/40, even more preferably less than 1/60.

[0019] Preferably, the stem 2 extends along a straight vertical axis X, and is provided with a lower end 21 and an opposite upper end 22.

[0020] As shown in Figures 1 and 2, the lighting device 1 comprises a base 3 suitable for supporting the stem 2 and an optical group 5.

[0021] The base 3, positioned at the lower end 21 of the stem, is preferably a circular shape (Figure 1) or polygonal, for example square (Figure 2).

[0022] As shown in figure 4, the optical group 5 is positioned inside the stem 2 at the upper end 22. Preferably, the optical group 5 is inserted in the stem 2 in such a way that between the support 52 of the LED 51 and the inner wall 25 of the stem 2 there is a space 27 (for example in the shape of a circular crown) which surrounds the support 52.

[0023] Preferably, the optical group 5 comprises a LED 51 supported by a support 52 and is electrically powered by means of a power supply cable (not shown) . Preferably, an electronic driver of the LED 51 is housed in the base 3, for example in a compartment 56.

[0024] The power supply cable crosses the stem 2 internally and connects to a power supply 53 housed in the base 3. An input 54 for the exit of the power supply cable or entrance of a plug is provided, also in the base 3.

[0025] The optical group 5 can be turned on/off by means of a switch 55, preferably housed around or above the upper end 22 of the stem 2. Preferably, the switch 55 is a capacitive switch, and the control electronics of the switch are housed in the base 3, for example in a compartment 56.

[0026] The LED light source 51 must ensure an optimal light flow able to correctly illuminate even large rooms. Consequently, the LED 51 is the high power type, for example with 50W of power, colour temperature 2700K, light flow of 40001m in all, Color Rendering Index (CRI) 93.

[0027] The main problem related to the use of high power LEDs which rapidly overheat inside a stem lighting device concerns the correct dissipation of heat.

[0028] Consequently, the lighting device 1 comprises a liquid cooling system 6 integrated inside the stem 2, suitable for cooling the optical group 5.

[0029] The cooling system 6 comprises a dissipating liquid, preferably water, flowing inside ducts 62, 63 provided in the stem 2.

[0030] As shown in figure 3, the ducts 62, 63 for the circulation of the dissipating liquid are made inside the stem 2.

[0031] Preferably, the ducts 62, 63 run parallel to the inside of the stem 2. [0032] The ducts 62, 63 of the cooling system 6 are: a delivery duct 62 for the supply of the dissipating liquid, and a return duct 63 for the drainage of the dissipating liquid.

[0033] Preferably, the delivery duct 62 of the dissipating liquid has a smaller cross-section than the return duct 63.

[0034] A pump 61, for pumping the dissipating liquid inside the ducts 62, 63 is provided to increase the speed of circulation of the liquid and thus the dissipating power of the cooling system 6.

[0035] Preferably, the pump 61 is placed inside the base 3. In particular, the two ducts 62, 63 join at the base 3 in a collection container connected to the pump 61.

[0036] In use, the pump 61 pushes the dissipating liquid (cooled) inside the delivery duct 62 from the base 3 as far as the upper end 22 of the stem 2. The dissipating liquid comes out of the delivery duct 62 inside the space 27, accumulates the heat produced by the LED 51 through contact with the support 52, and goes back down (heated) through the return duct 63 as far as the base 3. The dissipating liquid thus passes through the space 27 and by taking away the heat efficaciously cools the optical group 5 preventing it from overheating.

[0037] Along its descent route to the base 3 the dissipating liquid loses heat through the duct walls 63, that is to say, through the walls of the stem 2 made in metal, and cools.

[0038] The presence of the pump makes it possible to increase the speed of circulation of the liquid, and thus the dissipating power of the cooling system 6.

[0039] As shown in figure 3, the stem 2 is provided internally with a further duct, and in particular with a passage 64 for housing the power supply cable of the optical group 5.

[0040] Preferably, the three ducts 62, 63, 64 run parallel to the inside of the stem 2.

[0041] Preferably, the passage 64 for the power supply cable is hermetically separate from the two ducts 62, 63 of the dissipating liquid.

[0042] Preferably, at least two ducts (for example the passage 64 for the power supply cable and the delivery duct 62 of the dissipating liquid) are made by means of tubular elements 66 inserted inside the stem 2.

[0043] Preferably, at least one duct (for example the return duct 63 of the dissipating liquid) is made in the free cross-section of the stem 2.

[0044] In one embodiment variant, the lighting device 1 comprises a diffuser 4, positioned at the upper end 22 of the stem 2, around the optical group 5. [0045] Preferably, the diffuser 4 is a truncated cone, an overturned bell (Figure 1), ball, bulb (Figure 2) or disc shape.

[0046] Preferably, the diffuser 4 is opaque- to the light, or semi-opaque or transparent.

[0047] Preferably, the diffuser 4 is colourless or coloured, so that the light emitted outside said diffuser 4 has the desired colour.

[0048] The diffuser 4 is made for example in plastic or in glass.

[0049] Innovatively, the lighting device according to the present invention provides an optimal luminous flow without overheating.

[0050] Advantageously, the lighting device according to the present invention is able to light rooms of large sizes without overheating.

[0051] Advantageously, the lighting device according to the present invention is particularly suitable in the case of continuous functioning.

[0052] Advantageously, the lighting device according to the present invention has an elevated aesthetic impact given the presence of the extremely elongated slim stem, and at the same time provides excellent lighting performance thanks to the presence of the integrated cooling system able to dissipate the considerable heat produced by the high power LEDs.

[0053] Advantageously, the lighting device according to the present invention is provided with a particularly effective and discreet cooling system which does not jeopardise the aesthetic appearance of the device.

[0054] It is clear that a person skilled in the art may make modifications to the device described above while remaining within the sphere of protection as defined by the following claims.