EP3292349B1

EP3292349B1 - Strip-shaped lighting device comprising point light emitting sources, provided with means adapted to control the elongation and torsion movements of said strip

Info

Publication number: EP3292349B1
Application number: EP16728375.3A
Authority: EP
Inventors: Massimo Gattari
Original assignee: Iguzzini Illuminazione SpA
Current assignee: Iguzzini Illuminazione SpA
Priority date: 2015-04-29
Filing date: 2016-04-29
Publication date: 2019-06-05
Anticipated expiration: 2036-04-29
Also published as: CN107980087A; ES2741805T3; CN107980087B; WO2016174626A1; EP3292349A1

Description

Field of the invention

The present invention relates to the field of lighting devices comprising point-type lighting source, such as LEDs (Light Emitting Diodes) and the like. In particular, the present invention relates to the field of lighting devices comprising point-type lighting source of the LED strip type.

Background art

The so-called LED strips are lighting devices comprising approximately tubular sheaths made of a flexible material, e.g. silicone plastic material or polyurethane resin, within which a plurality of LEDs is housed.
Said LEDs are usually mounted on a printed circuit, which is also flexible, together with possible configuration circuits and are further connected to power supply wiring, which is normally accessible from one of the ends of the strip and connectable to external power supply means, typically power supplies which output 12V or 24V voltages.
The LEDs of the strip may be of a single color or different colors or changing colors within a given color range. The mechanical and electrical structure of these LED lighting sources may make them suited to be cut to size by the user without compromising the operation thereof, and thus allows to obtain a high flexibility in choosing the length of said LED strips to be made and industrially produced.
In general, the material of which the strip is made is translucent, at least on the front part, so as to let through the light emission of said LEDs. Furthermore, said LED strips are generally provided with fixing means to a wall, comprising holes or slots adapted to accommodate anchoring screws or the like, or an adhesive layer applied on the strip face opposite to that of the light emission.
The availability of high-intensity LED lighting sources, in addition to the simplicity and flexibility of use, has quickly made the LED strips very popular and used for a wide range of applications, including decorative lighting of walkways, walls, floors, furniture, stairs, vehicles, etc.
However, a drawback of the LED strips of the prior art is related to the stress that the printed circuit housing the LEDs undergoes when the strip itself is bent and shaped for the intended use. Indeed, even if the employed printed circuits are flexible and can be curved, when the LED strip is bent and stressed said printed circuit are in all cases subjected to tractions, compressions or flexions which may be such as to damage the components soldered thereto and the soldered joints themselves.
This also occurs because the LED strip, complete with sheath and internal flexible printed circuit, is generally cut to size when flat and then curved during installation. Thereby, when the LED strip must be curved, it occurs that the printed circuit and the sheath which houses it do not curve in the same manner, thus maintaining the same reciprocal position, but instead slide with respect to each other. Indeed, it occurs that the center of gravity of the sheath (defined as the geometric locus of the centers of gravity of the sheath sections) and the center of gravity of the internal printed circuit are distinct and spaced apart and such as to rest on two different radii of curvature when bending the LED strip.
When the curvature of the strip is such that the radius of curvature related to the center of gravity of the sheath is greater than the radius of curvature related to the center of gravity of the printed circuit, then the printed circuit tends to protrude from the edges; in contrast, when the curvature of the strip is such that the radius of curvature related to the center of gravity of the sheath is smaller than the radius of curvature related to the center of gravity of the printed circuit, then it is the sheath which tends to protrude with respect to the printed circuit.
For this reason, since the sheath and the printed circuit are integrally constrained at the ends of the strip, when bending the LED strip, pressures and tractions are created on the printed circuit itself which can damage it or damage the soldered joints or the soldered components thereof, thus compromising the operation.
Moreover, if said LED strips must be used for long length installations, they are often made in two parts to be installed separately: a first part, comprising the LED devices, adapted to be fixed to a support, a wall, a cornice, etc., and a second part comprising an open sheath with forms a semi-transparent covering adapted to diffuse the light beams emitted by the LED devices.
In turn, the part adapted to be fixed to a support may consist of a plurality of printed circuits, housing the LED devices and the respective power supply circuits and connected together by means of respective wiring.
The sheath, on the other hand, may be made as a single piece, so as not to create joints between multiple parts which could make the appearance of the LED strip less pleasant and deteriorate the emitted light beam creating lack of uniformity and unevenness. Silicone materials, which offer the required qualities of flexibility, robustness and UV ray resistance, are often chosen in order to provide a sheath of this type.
The problem which occurs in these cases is related to the different deformations that the different parts of the LED strip undergo because of the temperature changes to which they are subjected. Indeed, the part adapted to be fixed to a support and the related outer sheath comprise mutually different materials having thermal expansion coefficients which may be very different.
Dimensional variations are thus created when the LED strip undergoes a temperature change, which variations create misalignments at the ends, with the sheath tending to protrude with respect to the printed circuit, or vice versa, endangering both the performance and the integrity of the LED strip itself.
The need for a sheath for LED strips which can solve the technical problems described above is thus apparent.
It is thus the object of the present invention to introduce a sheath for LED strips which is adapted to allow bending such as not to stress the printed circuit housed in said sheath with undesired tractions or extensions, said sheath being further adapted to ensure the correct operation of the LED strip even in case of considerable stresses and temperature changes.
It is another object of the present invention to introduce an LED strip which comprises a sheath adapted to maintain correct operation even in case of considerable stresses and temperature changes and to protect the printed circuit inside said LED strip.
Document WO 2014/026976 A1 discloses a lighting device according to the preamble of claim 1.

Brief description of the drawings

Further objects, features and advantages of the present invention will become more apparent from the following detailed description provided by way of non-limitative example and shown in the accompanying drawings, in which:

Fig. 1 shows a section of an unclaimed aspect of the LED strip;
Fig. 2 shows a section of a second preferred embodiment of the LED strip according to the present invention;
Fig. 3 shows a section of a third preferred embodiment of the LED strip according to the present invention.

Detailed description of the invention

With reference to the drawings accompanying the present application, the LED strip according to the present invention comprises an elongated body 10 comprising, in turn, an inner compartment 11 adapted to house a printed circuit 12 or similar support for LED devices 13 or for similar point light emitting devices.
With reference to accompanying figure 1, a first aspect comprises a strip-shaped lighting device comprising an elongated body 10 comprising, in turn, an inner compartment 11 adapted to house a support for point light emitting devices 13, e.g. a printed circuit 12 preferably of flexible type. Said elongated body 10 comprises an upper part adapted to diffuse the light emitted by said point light emitting devices 13. Said point light emitting devices 13 may consist of light emitting diodes (LED).
Furthermore, said elongated body 10 advantageously comprises at least one flexible element which is integral with said elongated body 10 and arranged over the whole length of said elongated body 10 at the printed circuit on which the point light emitting devices 13 are mounted.
Said flexible element preferably consists of at least one rigid wire 15 made of steel or other similar material which offers features of high flexibility and robustness, together with the possibility of being made with even very small diameters.
Said flexible element is preferably arranged inside said elongated body 10 and integrally constrained thereto. Said flexible element may be inserted, for example, inside said elongated body 10 during the extrusion process thereof or later inserted into a specific cavity made in said elongated body 10 and then appropriately glued so as to constrain it integrally and irreversibly to said elongated body 10.
The presence of said flexible element in said elongated body 10 and at the printed circuit 12 constrains the neutral axis of the sheath approximately at the printed circuit so as to avoid traction or compression stresses on the printed circuit itself due to the curvatures and torsions that the LED strip undergoes.
In essence, the presence of said flexible element which is rigidly integral with said elongated body 10 will allow said elongated body 10 and said printed circuit 12 to follow always corresponding curvatures such that said elongated body 10 cannot apply undesired stresses on said printed circuit 12 by virtue of different curvatures and tractions that it undergoes with respect to the curvatures and tractions that said printed circuit 12 undergoes.
In the aspect shown in accompanying figure 1, said body 10 has a section tapering towards the bottom comprising an inner compartment 11 adapted to house the printed circuit 12. Instead, the front part of said elongated body 10, adapted to emit the light radiation of the LEDs 13 has a quasi-triangular cross section which departs from said inner compartment to ensure the desired amount of light emission. In this case, said flexible element is preferably obtained by means of a single rigid steel wire 15 arranged at the bottom of said elongated body 10 and aligned with said printed circuit 12.
Instead, the preferred embodiment of the present invention shown in accompanying figure 2 comprises a section of substantially rectangular or trapezoidal shape, the rear part of which comprises an inner compartment 11 adapted to house the printed circuit 12. Advantageously, two grooves are present on the walls of said inner compartment, adapted to house the ends of the printed circuit 12. The front part of said elongated body 10, adapted to emit the light radiation of the LEDs 13, has a trapezoidal cross section which departs from said inner compartment to ensure the desired amount of light emission. In this case, said flexible element consists of a pair of rigid steel wires 15 arranged inside said elongated body 10 by the sides of said printed circuit 12 and aligned therewith.
With reference to accompanying figure 3, a third preferred embodiment of the present invention comprises an elongated body 10, in turn comprising two separate parts provided with reciprocal engagement means: a base 17 and a cover 16 which delimit an inner compartment 11 adapted to house the printed circuit 12. Said base 17 is provided with fixing means to a support, e.g. a wall, a cornice, etc. Said cover 16 is made of a material adapted to diffuse the light emitted by the point light emitting devices 13 mounted on said printed circuit 12. The reciprocal engagement means between base 17 and cover 16 could advantageously consist of a pair of teeth 18, 19.
In this case, said flexible element consists of a pair of rigid wires 15 arranged inside said cover 16 by the sides of said printed circuit 12 and substantially aligned therewith.
Advantageously, the elongated body 10 of the strip-shaped lighting device according to the present invention may consist of extrudates of appropriate material. The cover 16 of said elongated body 10 may consist of an element or a plurality of elements made of a silicone plastic material extrudate appropriately treated so as to enhance its light radiation transmission properties and may be either transparent or opaque. The base 17 of said elongated body 10 may consist of an element or a plurality of elements made of a metal material extrudate, e.g. aluminum, so as to ensure the required consistency and offer the possibility of rigid fixing to a support, such as for example a wall.
In this case, the thermal expansion coefficients of the cover 16 and the base 17 of said elongated body 10 are very different. Considering the aforesaid examples, it occurs that aluminum, and thus said base 17, has a thermal expansion coefficient of about 23*10^-6 m/°C, while said silicone plastic material cover 16 has a thermal expansion coefficient of about 146*10^-6 m/°C.
For this reason, the parts of said elongated body will undergo considerably different deformations, due to the temperature to which they are exposed, which will cause dissymmetries, misalignments and tensions which are detrimental to the performance and integrity of the LED strip itself.
With the addition of said flexible element, consisting of a pair of rigid steel wires 15, arranged inside said cover 16 by the sides of said printed circuit 12 and substantially aligned therewith, it occurs that the thermal deformation of said cover 16, integrally associated with said rigid steel wires 15, is controlled and limited by said rigid steel wires 15. Since steel has a thermal expansion coefficient of about 15*10^-6 m/°C, which is much closer to the thermal expansion coefficient of aluminum than to the thermal expansion coefficient of silicone plastic material, it occurs that, by virtue of said steel wires 15, the parts of said elongated body will undergo deformations substantially of the same entity because of the temperature to which they are exposed, which deformations are such as not to cause dissymmetries, misalignments or tensions which could be detrimental to the performance and integrity of the LED strip itself.

Claims

A strip-shaped lighting device comprising an elongated body (10) comprising, in turn, an inner compartment (11) adapted to house a printed circuit (12) for point light emitting devices (13), said elongated body (10) comprising an upper part adapted to diffuse the light emitted by said point light emitting devices (13), wherein the lighting device further comprises at least one flexible element arranged within said elongated body (10) and integral therewith, in a position by the side of said printed circuit (12), characterized in that said at least one flexible element comprises two wires (15) made of steel, arranged within the side walls of said elongated body (10), at said printed circuit (12).
A device according to claim 1, characterized in that said elongated body (10) comprises two separate parts provided with reciprocal engagement means: a base (17) comprising means for the attachment to a support and a cover (16) adapted to diffuse the light emitted by said point light emitting devices (13).
A device according to one or more of claims from 1 to 2, characterized in that said inner compartment (11) comprises means for the engagement with said at least one printed circuit (12).
A device according to claim 3, characterized in that said means for the engagement with said at least one printed circuit (12) comprise a groove (14) adapted to house the edges of said printed circuit (12).
A device according to one or more of the claims from 1 to 4, characterized in that said at least one flexible element is adapted to be inserted into a specific recess obtained in said elongated body (10) and to be glued to said elongated body (10).
A device according to one or more of the claims from 1 to 5, characterized in that said elongated body (10) is made of an extruded material.
A device according to one or more of the claims from 2 to 6, characterized in that said base (17) comprises at least one element made of an aluminum extrudate and said cover (16) comprises at least one element made of an extrudate of plastic silicone material.
A device according to one or more of the claims from 1 to 7, characterized in that said point light emitting devices (13) comprise LEDs.
A device according to one or more of the claims from 1 to 8, characterized in that the front part or cover (16) of said elongated body (10) is made of a plastic silicone material adapted to transmit the light radiation.