Patent Application
20090010026
The present invention relates to a radiating element for light panels and to a light panel manufactured therewith. More particularly, the present invention relates to a radiating element for light panels that includes a face providing a light radiation-emitting surface, a light source for sideward light generation and an element for reflecting and/or scattering the incident light.
Light-emitting elements that are configured to emit light radiation from a surface and that have a substantially constant distribution of intensity over such surface are used as light sources in the manufacture of light panels. Such light panels typically include a thin, box-like member having one or two translucent and inner backlit surfaces, which have transparent films or paper sheets laid thereon and carry a picture or a message to be publicly displayed. Light panels of this kind are widely used in the fields of advertising, interior and exterior lighting, road and highway signs, and also in other fields.
Light-emitting elements suitable for use in light panels are known in the art, for example:
light panels with fluorescent or neon tubes, in which the tubes are disposed behind the light-emitting surface of the panel and illuminate the front of the light-emitting surface of the same panel;
light panels with a plate-like scattering element, in which the light radiation sources illuminate the scattering element from one or more delimiting sides of the scattering element, and in which scattering occurs in the direction of the front surface of the scattering element, causing the scattering element to become the light radiation-emitting surface. The related light sources may be fluorescent tubes, incandescent lamps and light emitting diodes (LEDs); or
light panels with front LEDs emitting light radiation from an emitting head directed towards the user, i.e. perpendicular or approximately perpendicular to the emitting surface of the panel. In this configuration, the LEDs are oriented towards the front and lie on the bottom of the panel, with each LED forming a unit point of minimum size, i.e. some sort of pixel of a luminous picture composed of a number of the LEDs.
All the above systems provide light panels but also suffer from drawbacks deriving from complex construction, inhomogeneous light intensity along the emitting surface, short life and difficult manufacture within industrial environments, causing the panels to be relatively expensive.
The present invention addresses on the problem of providing a light-emitting radiating element for light panels that has a simple and inexpensive construction and a smaller weight, and that requires a lower, simpler, and less time-consuming maintenance, while preserving and improving performance over light-emitting radiating elements and panels of the prior art.
The invention fulfills the above objective by providing a radiating element for light panels, in which a reflection/scattering element forms a tile element, individually or in mosaic form, and includes a half-shell shaped plate with a concave reflection/scattering side facing towards the emitting surface and a convex side opposite said emitting surface. The central area of the shell has an opening for receiving the light source which houses the radiating head within a depression of the concave side and at a focal point of said concave surface, so that the light radiation emitted from the emitting head of the light source in the sideward, i.e. radial direction, relative to the central axis of symmetry of the reflection/scattering element, is reflected/scattered in a predetermined percentage in a direction incident upon an emitting surface oriented along a plane transverse, preferably perpendicular to the central axis of symmetry of the reflection/scattering element.
The convex surface may be a reflective, mirror-like surface or a scattering, for example, white surface.
The half shell element that forms the tile may have any plan shape, e.g. a square or triangular shape or another regular or irregular polygonal shape.
Advantageously, the front concave surface facing towards the emitting side of the half-shell plate and/or the rear convex surface have a paraboloidal curvature.
The plate or sheet that forms the reflection/scattering element with its concave shape, is advantageously, but without limitation, made of a plastic material, preferably a heat deformable plastic material.
The plate forming the reflection/scattering element may be relatively thin and have a typical thickness for a vacuum and thermoforming process. These types of processes are known and widely used, for example in the fabrication of food-grade plastic containers or shaped, expanded fruit trays.
The light source typically consists of a radial or edge-emitting LED with a 360° light pattern as described in greater detail herein.
In one embodiment of the invention, the concave side of the half-shell reflection/scattering element is closed by a transparent or translucent element, which is configured to be coupled to the peripheral edge of the reflection/scattering element.
Preferably, the transparent closing element has the same or substantially the same plan shape as the reflection/scattering element.
The coupling of the half-shell reflection/scattering element with the transparent or translucent element may be provided by either continuous or discontinuous extensions, and may be provided by complementarily shaped end portions of the peripheral edge of both the reflection/scattering element and the closing element, such as clips or the like, that engage folded peripheral edges or peripheral edge segments forming peripheral coupling grooves along the peripheral edges of the reflection/scattering element and of the closing element.
Advantageously, the covering element or closing element has a surface area with a lower transmission coefficient, i.e. is less transparent, in a central portion coincident or coaxial with the light source head, as compared with the remaining peripheral portion. This surface area attenuates the intensity of the light radiation emitted at the light source head, at least approximately to the same level as the intensity of the light radiation emitted through the surface area of the transparent closing element with the higher transmission coefficient, i.e. surrounding such central portion. Thus, in addition to the advantage of closing the light source compartment to the external environment and of providing a tile that is externally closed and that has a very low weight and very low material, fabrication and assembly costs, the light intensity is radiated through said closing surface with optimized homogeneity, so that the emitted light radiation is substantially constant throughout the emitting surface, i.e. through the surface of the closing element.
In one embodiment of the invention, this central surface portion with the lower light transmission coefficient is a depressed central portion, i.e. a central depression of the surface of the closing element that is treated to reduce the transmission coefficient.
The closing element may also be formed with a vacuum and hot forming process from a thin plate of transparent plastic material, as discussed with regard to the reflection/scattering element.
The light source, i.e. the radial or edge-emitting LED, may be directly mounted onto the header of a printed circuit board, typically a glass epoxy laminate. Such header supports the printed circuit board that forms the power supply circuit for the light source and may also carry some of the circuit components of a power supply or power regulation circuit for said source, which is provided on one side of said header. The header is coupled or couplable to the half-shell reflection/scattering element whereas, in the mounted condition, said header extends tangent to the convex side of the reflection/scattering element in the area of the central light source receptacle. In this configuration, the light source projects cantilever-wise out of the concave side of the reflection/scattering element towards the focus of the paraboloid.
The LED may be attached to a metal plate, preferably made of aluminum, which provides for heat dissipation and fixation of the light-emitting radiating element to a load bearing structure. The metal plate is placed tangent or parallel to a position tangent to the convex side of the reflection/scattering element in the area of the central light source receptacle, and said light source projects cantilever-wise out of the concave side of the reflection/scattering element in the area of the focus of the paraboloid, whereas said reflection/scattering element is or may be attached to said metal plate.
The header or headers of the printed circuit board of a power supply circuit or a power regulating circuit for said light source may also be mounted onto said metal plate, for example in a slightly offset position and in the area peripherally surrounding the light source, causing the convex side of the reflection/scattering element to be spaced from the metal plate.
Typically, such metal plate is substantially coaxial or concentric with the plan shape of the reflection/scattering element.
The size of the radiation element depends on the type of light source that is used which may be a LED, and on the light intensity to be obtained through the emitting surface, with the side or diameter ranging from 5 cm to 30 cm.
In one alternative embodiment, the reflection/scattering element is formed of a thin metal sheet, for example an aluminum sheet, and has one side, for example the side designed to form the concave side, treated to become reflective and coated with a layer of material providing a scattering effect, for example, white paint. This sheet may be shaped by molding.
In another embodiment of the invention, two or more radiating elements as described above are integrated in a single element and the half-shell reflection/scattering element for two or more light sources is formed from a single sheet of material that is shaped to form two or more half-shells in side-by-side relationship on one or more sides.
Each of the reflection/scattering elements integrated in the radiation assembly may be formed completely or in part as described above with regard to a single radiating element.
A corresponding multiple closing element is provided, composed of an array of side-by-side single closing elements, each having a central portion with a lower light transmission coefficient, coincident with the light source of the corresponding reflection/scattering element of the array in the radiating assembly.
The multiple closing element also may include one or more of the features described above with reference to the closing element of the single radiating element.
The multiple covering element may be coupled to the corresponding array of reflection/scattering elements in a manner substantially identical to the single radiating element, at least along the coincident peripheral edges of the multiple closing element and of the array of reflection/scattering element.
In one embodiment of the invention, an array of single or multiple radiating elements is provided to cover various shapes and sizes of the surfaces to be illuminated. More particularly, an array of radiating elements is provided that has one or more single radiating elements, one or more double radiating elements, one or more triple radiating elements, one or more quadruple radiating elements, or one or more sextuple radiating elements, or a combination of such single or multiple radiating elements. For example, the single radiating elements may have a square plan shape.
The multiple radiating elements advantageously improves the efficiency of the construction, further reducing costs, weight, as well as construction and assembly complexity.
More particularly, the light sources may be mounted onto a common metal support sheet or the like, each light source being coincident with the receptacle of the corresponding reflection/scattering element. Printed circuit boards may be provided that are formed of an element shared by two or more light sources.
The combination of single radiating elements into multiple radiating elements provides various advantages, namely:
easier and less costly assembly of the radiating elements in the light panel;
easier and less costly power supply to the light sources. In particular, a combination of six single radiating elements having six 2 Watt LEDs enables a sextuple radiating elements to be powered by a 24 Volt direct current source and, by particular arrangements, other single or multiple elements can be also powered with a predetermined reference voltage;
less costly assembly of the multiple radiating elements; and
better storage conditions before assembly into a light panel.
In one embodiment the transparent covering element may include stiffening ribs arranged in a predetermined pattern over the surface of said covering element.
In another embodiment, the multiple covering element has a plurality of projecting spacers on a transparent or translucent plate of a light panel, which is illuminated by a radiating assembly of the above type.
The spacer elements are optional and their provision depends on the width of the plate, which can be very large and possibly cause buckling of the plate under its own weight.
These projections may be other than the ribs or at least partly formed of the above stiffening ribs.
The invention also relates to a light panel having at least one bearing frame for supporting a plurality of light emitting elements mounted onto the back of at least one translucent or transparent plate, which bears or supports graphical information formed by a combination of transparent and/or translucent surfaces having different colors and/or light transmission coefficients, the light emitting means including, according to the present invention, one or more single or multiple radiating elements as described above.
Further features of embodiments or the invention can be found in the detailed description and in the claims.
The drawings constitute a part of this specification and include exemplary embodiments of the invention, which may be embodied in various forms. It is to be understood that in some instances various aspects of the invention may be shown exaggerated or enlarged to facilitate an understanding of the invention.
The characteristics of the invention and the advantages deriving therefrom will appear more clearly from the following description of a few non-limiting embodiments which are illustrated in the accompanying drawings, in which:
Detailed descriptions of embodiments of the invention are provided herein. It should be understood, however, that the present invention may be embodied in various forms. Therefore, the specific details disclosed herein are not to be interpreted as limiting, but rather as a representative basis for teaching one skilled in the art how to employ the present invention in virtually any detailed system, structure, or manner.
Referring to
Concave surface 202 is rotationally symmetrical with respect to a central axis perpendicular to the plan shape of reflection/scattering element 2 and, for example, may have a paraboloidal shape.
The front side has a curvature that forms a reflection/scattering surface to reflect/scatter the light radiation coming in a direction radial to the central axis of symmetry of the half-shell and hence of the concave surface 202, so that the light rays having such radial direction and also having a predetermined orientation in relation to the central axis of symmetry (which might be defined as an opening in the azimuth direction) are reflected/scattered in a direction incident upon a plane oriented transversally, preferably perpendicularly, in relation to the axis of symmetry of concave surface 202.
The half-shell has a central receptacle 102 at its central portion, which is coaxial with the central axis of symmetry of concave surface 202, and which is configured for receiving socket 205 of a light source 5, whose light radiation emitting head 105 projects into the space defined by concave surface 202. Light source 5 is an edge-emitting source operating over a 360° range, i.e. a light source that emits light radiation with an intensity distribution, in which intensity is higher or concentrated in a direction radial to a central axis oriented in a desired light radiation emitting direction, with a predetermined opening in the plane containing said axis and with an angular extension corresponding to a round angle, i.e. 360°. In the embodiment of FIG. 1, light radiation is emitted at head 105 and the light radiation distribution is coaxial with the central axis of symmetry of reflection/scattering element 2, and particularly of concave surface 202.
In the embodiment illustrated in
Advantageously, the plate that forms reflection/scattering element 2 is made of a thermoformable plastic material and preferably has a thickness that enables shaping by a simple vacuum and hot forming process, also known as thermoforming. Such forming process is known to be used, for example, with food-grade packaging containers, expanded fruit trays, or the like.
The plate forming reflection/scattering element 2 may also be metal, such as aluminum. In this case, thickness is selected to enable the plate to be shaped by molding while ensuring that the half-shell has some structural stability.
Composite material plates can also be used, for example, multilayer plates having a composition that affords structural stability, formability, low weight and low cost.
Reflection/scattering element 2 has the concave side closed by a cover element 4 of transparent material which forms the light radiation emitting surface, on which the light radiation is directed that is emitted by source 5 laterally from the central axis of symmetry and deflected by concave surface 202. Cover element 4 is made of a transparent and/or translucent material and particularly of a transparent or translucent plastic material. As for reflection/scattering element 2, cover element 4 may include a thin thermoformable plate.
Cover element 4 may be coupled to the half-shell and as a reflection/scattering element to form a box-like radiating element containing emitting head 105 of the light source 5 in a predetermined position relative to concave surface 202. In particular, cover element 4 has a plan shape substantially identical to the plan shape of the reflection/scattering element 4 and is approximately congruent therewith. Cover element 4 and the half-shell that acts as reflection/scattering element 2 are mutually coupled along the peripheral edges, for example, with matching peripheral fixation flanges 502.
Such coupling may be continuous or discontinuous all along flanges 502 and may be attained, for example, by chemical/physical bonding, such as by welding, gluing or the like, or by detachable fastening, such as interlocking, or mutual clamping with screws and bolts or the like, or by clipping.
In the embodiment illustrated in
In both variants, clips 3 may be either elastically deformed for snap engagement with flanges 502 or the clips may be inelastically deformed and then applied by shaping around flanges 502, so to clamp them together.
Still with regard to cover element 4, this element has a central portion 402, i.e. a portion coincident and/or possibly coaxial emitting head 105 of light source 5, that is provided with a lower light radiation transmission coefficient as compared with the rest of cover element 4. This arrangement has the purpose of attenuating a light radiation intensity peak towards the central axis of symmetry and of generating non-homogeneous distribution of the light intensity radiated from the surface of cover element 4.
According to the present embodiment, central portion 402 that is treated for radiation intensity attenuation includes a central depression 302 concentric and possibly coaxial with head 105 of light source 5, and the bottom and/or possibly the lateral parts of depression 302 are treated with processes of the type described above.
Light source 5 is supported by a base plate, which may be the header of the printed circuit board that forms the power supply circuit and/or the power regulation circuit or at least part of the power supply and/or power regulation circuits of light source 5. Such header bears, in the present embodiment, at least some of the circuit components, and may be further supported by a base plate that also acts as a heat sink.
The base plate may also act as a cooling plate and may be made of metal, aluminum or any other material with a high heat transmission coefficient. The base plate has the function of dissipating the heat generated by light source 5 and may in turn have, alongside light source 5, one or more printed circuit board headers for power supply and/or power regulation devices or for part of such devices or circuits.
Heat dissipation plate 6 and/or the header also support reflection/scattering element 2 and cover element 4 that are or can be fixed, preferably in a detachable manner, to source 5 and/or header 7 and/or heat dissipation plate 6.
Depending on the construction variant selected from the above options, header 7 and/or heat dissipation plate 6 also act as a socket for connecting single radiating element 1 to a bearing structure of a device, in which radiating element 1 is used or located, like the light panel of
Referring to
These figures also show, on the right side, the intensity distribution pattern of the radiation emitted by the light source in various conditions and variants, as described in greater detail below.
In
In
The same effect is obtained using an annular lens of rectangular or square cross section, as shown in
It can be noted, with reference to
According to another feature of the present embodiment, the side of annular lens 10 that is designed to contact, be coupled or at least face towards the area of the reflective surface all around the through hole for light source 5 may be treated to become reflective. More particularly, such side of annular lens 10 may be covered with a white adhesive film and/or be subjected to pad printing or coated with a layer of white paint. Said surface of the annular lens 10 may also be subjected to any alternative treatment for providing said reflective surface on the side facing the inside of lens 10.
Referring to
A very simple light panel embodiment is shown in
The plan size of container or tray 12, i.e. the plan size of the surface to be illuminated, and the plan shape of container or tray 12 are exact multiples of the size of radiating element 1. The front side of the light panel is equipped with a plate 14 of transparent or translucent material, in direct contact with the front side, i.e. the covering elements of the array of radiating elements 1, or somewhat spaced therefrom by means of spacer elements. Plate 14 bears a communication message drawn directly thereon or on a support separate from plate 14. A cover 15 with a window 115 closes the front of the light panel to overlie a peripheral strip of plate 14 in a frame-like fashion, and may include side walls 215 overlying side walls 212 of container or tray 12.
Container or tray 12 has elements 16 at its back for coupling to a support, such as a wall, a post or other means. Furthermore, container or tray 12 has a tight opening for receiving power leads 17. These leads may be connected to any power source, power being transformed by a power supply unit 18, which may be located wholly or partly outside or inside the panel.
Arrays may be further provided with single and multiple radiating elements having different plan shapes. For instance, arrays of single and multiple radiating elements may include single radiating elements of isosceles triangular and square plan shapes, each triangular radiating element being identical to the diagonal half of the square element, whereas the multiple radiating elements are composed of one or more square radiating elements and one or more single triangular radiating elements or combinations of one or more of said square and triangular radiating elements.
The reflection/scattering assembly designated by numeral 20 includes a half-shell which is shaped to include six depressions in side-by-side relationship, disposed in one or both directions of extension of such half-shell, each of the six depressions providing the convex side 202 of one reflection/scattering element 2 for a single radiating element. Such radiation/scattering assembly defines a multiple reflection/scattering element that may be coupled to a multiple light radiation emitting element (such as a transparent or translucent plate that carries a message to be displayed) to form a multiple radiating element. Advantageously, reflection/scattering assembly 20 is also formed as a relatively thin plate made of plastic or other material as described above with regard to single radiating element 1 of
Accordingly, plate 14 has a single-piece construction, whereas the central portion, coaxial with the central axis of the plan shape (still as described above for single radiating element 1), includes the receptacle of light source 5, which is also of the radial or edge-emitting type relative to the central axis of symmetry. In the variant of
Still with reference to
In the present embodiment, header 7 is formed as an elongate element having an extension that overlie three receptacles 102 of the three light sources 5 of three adjacent single radiating elements aligned along a longitudinal direction of radiation/scattering assembly 20. Particularly, as shown in
During assembly, light sources 5 (here embodied as LEDs) are mounted onto header 7 by connecting the LED contacts to the corresponding tracks and, in the position illustrated in
According to yet another feature of the present invention, header 7 may be selected to obtain 2 and 1 LED elements.
Frustoconical annular lenses 11, with head 105 of light source 5 held therein, are associated with receptacles 102.
The embodiment of
In this variant the radiation emitted by the LED in the direction of the central axis of symmetry is attenuated by an attenuation element with a predetermined transmission coefficient, which is integrated, or is or can be coupled, possibly in a detachable manner, to annular lens 11. Particularly, in the embodiment of
Nevertheless, the radiation/scattering assembly may be similar to the single radiating element of
Such multiple closing or covering element 40 preferably has a plan shape corresponding to the plan shape of reflection/scattering assembly 20 and is formed of single covering or closing elements having a shape and size that corresponds to those of single reflection/scattering element 2 integrated in reflection/scattering assembly 20 and located in a position coincident, centered and coaxial therewith.
Multiple covering or closing element 40 has a portion 420 coincident with each of the light sources, with a predetermined transmission coefficient for attenuating the emission of said sources in the direction of the central axis of symmetry of each concave reflection/scattering surface of the single reflection/scattering elements that form the multiple radiating element.
Portion 420 may include a depression 320 as described for the single radiating element embodiment.
Concerning closing and covering element 40 of the reflection/scattering assembly, means may be provided coupling the reflection/scattering assembly 20 therewith that are formed in the same manner as those of the single radiating element, reference being made here to the description thereof.
Closing and covering element 40 may be also constructed like covering element 4 for a single radiating element, i.e. may be produced from a thin plate or sheet of transparent or translucent plastic material, which is shaped by a molding process. Once again, the sheet or plate has such thicknesses and is made of such materials as to preferably enable vacuum and hot forming.
In
Still in
In addition to or instead of stiffening ribs 41, the closing or covering element 40 may have projecting spacers 42 for spacing a translucent or transparent plate of a light panel like the one designated by numeral 14 in
In the example of
Referring now to the example of
A solution was found to be provided by a relative arrangement of the LEDs or light sources 5, particularly heads 105 thereof (considered here as point light sources) and by a distance of heads 105 from the emitting surface that fulfill the following condition:
angle A<arctg (2x/D)
wherein:
D is the distance between the points that define the position of the emitting heads 105 of two adjacent light sources 5; and
x is the distance of the plane containing said points from the emitting surface, and more particularly from the facing side of a plate that acts as an emitting surface.
Therefore, in accordance with the above description, a construction may be provided for single or multiple radiating elements, with a light source supporting plate that has a radial or edge-wise light emitting source at its center (as defined herein). The plate has a size such that the radius of said plate or of a circle inscribed in the plan shape of said plate or inscribing the plan shape of said plate is equal to D/2, whereas a covering surface is associated with the plate at such a distance therefrom as to fulfill the above condition.
In one embodiment, the LED supporting plate may be heat dissipating plate 6 and/or header 7 according to one or more of the variants described for one or more of the above embodiments, whereas the emitting surface may be formed as a concavo-convex dome, in which the concave side faces towards supporting plate 6, thereby forming a closed compartment. This configuration also provides for a box-like radiating element. Once again, the dome-shaped element may be detachably or permanently coupled to the supporting plate, which may be configured as described above for one or more of the previous embodiments.
It will be appreciated that multiple radiant elements may be also provided that integrate two or more single radiating elements having constructive features of one or more of the previous embodiments of multiple radiating elements.
More particularly, a multiple radiating element may include at least two light sources mounted onto a supporting plate in a central position relative to two adjacent areas of said plate, each of which areas having such a size that the radius of said area, i.e. of a circle inscribed in the plan shape of said area or inscribing the plan shape of said area, is equal to D/2.
The emitting surface may be associated to the plate, or the plate may be equipped with spacer elements for spacing an emitting surface or be provided in combination with a structure having such spacer elements, with the distance of the emitting surface being equal to a distance x that fulfills the above condition.
Finally, the embodiment of
Still further, a number of variant embodiments may be provide with regard to the construction of the headers and/or the LED supporting plate.
Therefore, a panel as disclosed above has a support element for one or more plates, each carrying one or more LEDs in mutually offset positions, with the emitting heads contained in a common plane and with a transparent or translucent plate, provided at a predetermined distance from said emitting head containing plane. In this panel, the distance D between the emitting heads and the distance x of the emitting heads from the transparent or translucent plate is determined by the following condition:
angle A<arctg (2x/D).
Finally, concerning the radiating element of
While the invention has been described in connection with a number of embodiments, it is not intended to limit the scope of the invention to the particular forms set forth, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be included within the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| GE2007A000073 | Jan 2007 | IT | national |
