LIGHTING FIXTURES

The present invention relates generally to a watertight LED lighting device for public or private lighting fixtures.

More particularly, the invention relates to a technology solution for dissipating heat in a LED lighting device, which can be used for public or private lighting fixtures, where the LEDs are protected from the atmosphere by a tube of glass and are mounted inside the same tube.

LED lighting devices for public or private lighting fixtures are known (as shown in the enclosed figures 1, 2 and 3) and substantially comprise a glass tubular element 0, with a cap 14 at one end for covering the fixing screw of a heat dissipation element and with the LED lights or LEDs placed inside the tubular element 10 so that they are protected from the atmosphere; the LED lights 11 are also mounted on a heat sink 12, which is generally made of aluminum and which is also placed inside the glass tube 10.

The heat sink 12 is usually constituted by a extruded bar having a hexagonal cross-section and with a length almost equal to the length of the lighting ^{^} clevice, so that the LEDs 11 can be fitted on each side of the hexagon.

Furthermore, the internal volume 13 which divides the heat sink 12, on which the LEDs 11 are mounted, from the glass tube 10 can be filled with air or transparent resin, or generally with an insulating material.

The heat is conveyed inside the lighting device by conduction, both from the light source towards the outside, through the interspace or internal volume 13 filled with air or resin and the glass of the tube 10, and from the light source towards the ends of the device, through the extruded bar of the aluminum heat sink 12.

In both cases, at the end of the heat conduction, the surface of the lighting device exchanges heat with the surrounding air by free convection.

However, the main drawbacks of this technical solution derive from the fact that a high thermal resistance of air or of the resin used for filling the volume 13 inside the tube 10 arises, as well as a limited area for heat exchange with the external environment is provided.

The object of the present invention is, therefore, to obviate the above mentioned drawbacks and, in particular, is to realize a watertight LED lighting device for public or private lighting fixtures, that allows to improve the heat dissipation of LED light sources, with respect to the prior art.

Another object of the present invention is to indicate a watertight LED lighting device for public or private lighting fixtures, which is easy and inexpensive to manufacture, thus also avoiding the use of complex and/or expensive technologies.

These and other objects are achieved by a LED lighting device for public or private lighting fixtures according to the enclosed claim 1 ; other detailed technical features are also present in the dependent claims.

Advantageously, the lighting device according to the invention employs a heat sink which is hollow and internally finned, so as to improve the heat exchange with the external environment.

Therefore, a duct is provided which puts the heat generated by the LED light sources directly in communication with the external environment.

Further objects and advantages of the present invention will become apparent from the description that follows, which refers to a preferred, but not limiting, embodiment of the LED lighting device, which is the object of the invention, and from the enclosed drawings, in which:

- figure 1 is a perspective view of a LED lighting device for public or private lighting fixtures, according to the prior art;

- figure 2 shows an enlarged detail of the LED lighting device of figure 1 , according to the prior art;

- figure 3 is a cross section of the LED lighting device of figure 1 , according to the prior art;

- figures 4 and 5 show perspective views of a LED lighting device for public or private lighting fixtures, according to the present invention; - figure 6 shows an enlarged detail of the LED lighting device as shown in figures 4 and 5, according to the present invention;

- figure 7 is a middle cross section of the LED lighting device as shown in figures 4 and 5, according to the present invention;

- figures 8A, 8B, 8C, 8D show a series of perspective views of an enlarged detail of the LED lighting device as shown in figures 4 and 5, according to the present invention;

- figure 9 is a longitudinal section of the detail shown in figures 8A, 8B, 8C, 8D, according to the present invention;

- figure 10 is a complete longitudinal section of the LED lighting device of figures 4 and 5, according to the present invention.

Referring particularly to figures from 4 to 10, which show the LED lighting device according to the present invention, 20 indicates a tubular element, made of glass, within which, in the inner volume 30, a shaped extruded section 21 is positioned; a series of LED 22 are also mounted on said extruded section 21 and the extruded section 21 acts as a heat sink and dissipates the heat generated by the LED light sources 22.

A suction duct 23 is placed at one end of the tubular element 20, while, at the opposite end, there is provided an exhaust manifold 24, equipped with an air inlet 31 and relative air outlets 25, which is connected to a terminal 26, able to house the LEDs power supply 22 and equipped with a radio antenna 27.

In particular, according to the invention, the heat sink extruded section 21 , which is positioned between the exhaust manifold 24 and the suction duct 23, is hollow and has a profile which is internally finned starting from the manifold 24 and up to the inlet 28 of the external air suction duct 23; the enclosed figures 6 and 7 show clearly the dissipation fins 29 of the cavity 32 which are provided within the extruded section 21.

Therefore, the heat exchange with the outer environment is improved with respect to the prior art, since a duct which puts the heat directly in communication with the outside is provided.

The working principle of the lighting device of the invention is based, in fact, on the heat exchange, which takes place by means of the finned surfaces provided in the heat sink 21 , which allow to increase the exchange surface; moreover, the physical phenomenon of the gas expansion, together with the heating produced by the heat sink 21 , gives rise to move the air existing in the glass tube 20, so that said air, starting from the suction inlet 28 of the terminal 23, goes up again along the internal cavity 32 and the inlet conduit 31 of the manifold 24 and reaches the outside atmosphere through the outlet conduits 25 of the manifold 24, thus draining the heat generated by LED light sources 22 (as shown in detail in the enclosed figure 10, where the path of the air flow drawn from outside that goes up again inside the heat sink 21 and goes out of the conduits 25 of the manifold 24 is shown and indicated by the arrows F).

Then, the finned cavity 32, which is provided internally to the heat sink 21 , performs a function similar to that of a flue, in which the air is sucked at one end.

Moreover, since the inner surface of the cavity 32 is covered with dissipation strip or radial fins 29, the exchange surface between the heat sink 21 and the air is greatly increased.

Finally, unlike a flue, which must be isolated from the outside to prevent the heat dispersion, the cavity 32 is positioned inside the heat sink 21 , which acts as a heat generator.

At the lower end of the duct corresponding to the cavity 32, the air is directly sucked from outside! while, at the upper end, a terminal 26 containing the power supply of the LEDs 22 is-positioned; also, between the supply terminal 26 and the lighting portion of the device an exhaust manifold 24 is inserted, which connects the cavity 32 with the outside atmosphere.

In particular, the exhaust manifold 24 includes a cylindrical or conical element 33 having a central cavity 34 of circular cross section, communicating with the cavity 32 which is provided inside the heat sink 21 via the inlet conduit 31, and a series of outlet ducts 25, generally equal to six and also normally having a circular section.

Finally, to minimize the pressure drop inside the manifold 24, the conduits 25 and 31 are dimensioned such that the air flow F does not meet section reductions and, in particular, the outlet conduits 25 have a minimum inclination which is allowed by the presence of the power supply terminal 26, in order to minimize the pressure drop due to the change of direction of the air flow F.

The above description clearly outlines the characteristics of the LED lighting device for lighting public or private fixtures, which is the object of the present invention, as well as the relative advantages.

In particular, said advantages are:

- total tightness of the device;

- low thermal resistance of the filling insulation provided in the volume inside the lighting device, with respect to the prior art;

- high coefficient of convective exchange due to an increase of the dissipating surface and to a maximization of the fluid speed;

- flexibility, simplicity and quickness in assembling and mounting the device;

- reduction, with respect to the prior art, of the pressure drop within the device due to section reductions and/or changes in direction of the air flow. -

It is finally clear that numerous other variants can be made to the LED lighting device of the invention, without departing from the novelty principles of the inventive idea, as it is clear that, in the practical embodiment of the invention, the materials, forms and the dimensions of the details as illustrated may be any according to requirements and they can be replaced with other details that are technically equivalent.