FIELD OF THE INVENTION

The invention relates to a light source strip, lighting module and luminaire.

BACKGROUND OF THE INVENTION

Currently, the reduced cost and improved performance of LEDs enable their use for general illumination. The small size of LEDs allows for easy integration of LEDs into building materials and furniture. Combining these trends, the general illumination of an indoor space may be done by a luminous ceiling, rather than by discrete fixtures in a dark ceiling or suspending from a dark ceiling. Such diffuse, large-area and low-brightness ceiling sources provide comfortable lighting with low glare and almost no shadows, while creating an aesthetic, clean ceiling without disturbing fixtures. Luminous ceiling panels, also referred to as ceiling tiles, are widely available, mostly based on backlighting technology, either direct lit or side-lit. US3409766 describes a fully luminous, sound absorbing ceiling, in which the light is generated by indirect lighting of sound-absorbing ceiling panels by TL tubes at the side of the panel. Yet, known large-area ceiling sources are not widely applied, because they have several disadvantages. First of all, creating a large area source with conventional luminaire materials is relatively expensive. Furthermore, the large-area light-emitting ceilings interfere with other elements in the ceiling, such as sprinklers, sensors and air-conditioning vents. Frequently, the large-area light sources lead to unwanted acoustic reflections at the ceiling, thus deteriorating the comfort of the people in the room. Finally, there is relatively very limited flexibility in the use of known luminaire ceiling panels as they have to be custom made to size to fit into a specific, existing false ceiling system.

OBJECT AND SUMMARY OF THE INVENTION

It is an object of the invention to provide a light source strip and/or luminaire in which at least one of the disadvantages of the known light source strips and/or luminaries is counteracted. Thereto the light source strip comprises a mutually oppositely arranged base and support portion extending mutually parallel along a length direction of the light source strip, and a reflector having a light reflective front side facing a first concave portion formed by at least the reflector and the base, said reflector connecting the base and the support portion, in a cross-section transverse to the length direction, the light source strip at least substantially has a contour/shape of an S- or Z-curve, and an open, second concave portion formed by at least the support portion and the reflector, which second concave portion is located at a backside of the reflector. The cross-sectional S- or Z-contour or shape refers to a variety of shapes or contours that look like or could be described by layman in the technical field as figures similar to an S-curve or Z-curve. Hence, for example viewed in cross-section transverse to the length direction of the light source strip, the support part may have a different (straight) size and/or different curvature than the base part, the reflector could be straight, or convexly or concavely curved, the height to width aspect ratio of the shape may vary, for example it could be 5: 1 or 1 :5 or any ratio in between. The expression "at least substantially" in this respect means that at least 70% of the cross-sectional contour is according to said S- or Z-curve. The expression "extending mutually parallel" in this respect means that the base and the support portion may mutually be in an angled position of at the most 20°, preferably at the most 10°, more preferably at the most 5°. The expression

"mutually oppositely arranged" in this respect means that in the plane of the cross-section a normal to the base or the support portion (and extending through a location at at least 10% distance from the border of one at least one of the base and the support portion) extends through both the base and support portion. Alternatively the expression "mutually oppositely arranged" in this respect means that along a normal to either the main surface of the support portion or the base, there is an overlap in projection of said support portion and the base of at least 10% of the surface of the smallest one of the surfaces of the support portion and the base.

Quite often the light source strip comprises in the first concave portion and mounted on the base at least one pair of light source contacts accommodating a light source, or which is to be accommodating a light source, for example a LED thus forming a LED strip. In the description the expressions "light source strip" and "LED-strip" are used alternatingly, however, this does not necessarily mean that the light source is comprised in the light source strip and that the light source is a LED. If the light source strip comprises a light source, for example a LED, the LED is located in the first concave portion of the strip formed by at least the reflector and the base. The reflector having a front side for reflecting at least part of the light issued by the LED during operation. A light source could be an array of LEDs, and light source contacts for accommodating a lamp could be a socket with electrical contacts. Said first concave portion of the strip could be formed by the base and the reflector, or by the base, the reflector and the support portion. Usually the LED strip is provided with electrical contacts for contacting to a power supply. Said LED strip is of particular of use in false ceilings. In false ceilings ceiling tiles rest on a frame comprising elongated suspension brackets with a T-shaped cross section, said ceiling tiles can easily removed from the false ceiling via a tilt and shift movement. The LED-strip of the invention can easily be installed in such a false ceiling, for example by lifting a ceiling tile at one side from the T-shaped bracket on which it usually rests, then subsequently insert the LED strip in between the bracket and the tile. The LED strip rests with its base on the T-shaped bracket and carries the ceiling tile with its support portion, finally the LED strip is connected to a power supply. Alternatively a combination of at least two, mutually connected LED strips, forming a lighting module, can be used in combination with a ceiling tile. Thus, the combination of the LED strip/lighting module and ceiling tile forms a relatively unobtrusive luminaire. Since the LED strip or lighting module, when the LED strips are mutually joined via a joint located at the backside of the reflector or via a frame extending between the base and reflector at the front side of the reflector, is a slim, open structure, the visual impact is minimal, which enables a clean ceiling without much distinction between ceiling tiles with or without lighting function.

Furthermore, the LED strip or lighting module may be applied as a recessed fixture illuminating a slightly elevated conventional ceiling tile, as a surface mounted fixture illuminating a ceiling tile at the normal position, or as a pendant fixture illuminating multiple ceiling tiles. The ceiling panel can be of any type. Large ceiling area's or even the complete ceiling may be equipped with the LED strip or with the lighting module, since it enables the use of ceiling tiles comprising at least one device selected from the group consisting of sprinklers, sensors, narrow beam light sources, loud-speakers, ventilation grill, and air- conditioning vents. Furthermore, the acoustic properties of the suspended ceiling are not deteriorated, because the passage of sound to sound absorbing ceiling tiles is neither hindered by the LED strip nor by the open frame of the lighting module. The light source strip with the support portion and the reflector border a second concave portion, which second concave portion is located at a backside of the reflector and which is accessible for (a part of) the T- shaped bracket. It is thus enabled that the LED strip alternatively can rest at the T-shaped bracket via a backside of the support portion next to the possibility to rest on the T-shaped bracket by its base. Thus a flexible, applicable LED strip is obtained which enables an easy switch between application as an unobtrusive built-in LED strip in the false ceiling and application as a suspended LED strip from the false ceiling. Said second concave portion of the strip could alternatively be formed by the base, the reflector and the support portion. In an embodiment the LED strip is characterized in that the base, the reflector and support portion are made in one piece. This enables the manufacture of a relatively cheap LED strip via, for example, a molding process using isostatic pressing, an extrusion process or from (metal) sheet material. Preferably the material of the LED strip is easily deformable and shapeable and good heat conductive, for example aluminum metal, thus simultaneously enabling easy manufacture and during operation efficient cooling of the LEDs mounted on said strip.

In an embodiment the LED strip is characterized in that the reflector is concavely formed. By choosing a specific concave shape for the reflector, a specific desired light distribution from light issued by the LED strip can be obtained, for example in that only light is issued through a light emission window from the luminaire via the ceiling tile or that direct light is also issued. When viewed in cross section the concave shape of the reflector could be, for example, a complex shape or be shaped as a parabola, ellipse, or hemisphere.

In an embodiment the LED strip is characterized in that a further support portion is provided at an end of the support portion remote from the connection between reflector and support portion, said further support portion extending in a direction essentially transverse to the base. By this further support portion the risk of the LED strip of assuming a tilted position with respect to the plane of the false ceiling is counteracted as it will abut against a side face of the ceiling tile/panel that rests on the support portion. Essentially transverse in this respect means that said parts are mutually angled at an angle that should fall within a range of 90° ± 20°.

In an embodiment the LED strip is characterized in that the base has an extension extending beyond the backside of the reflector. Extending beyond the backside in this respect should be understood as protruding from the backside of the reflector in a direction from front side of the reflector to backside of the reflector when viewed upon projection of the LED strip/Lighting module in the plane of the base along a normal vector to the plane of the base. Ceiling tiles adjacent to the luminaire formed by the combination of the LED strip/lighting module can then be in a slanted position with respect to the plane of the false ceiling. Such an extension thus enables a smooth transition from the plane of the false ceiling to a LED strip/light module suspended and protruding from said plane.

In an embodiment the LED strip is characterized in that circuitry is comprised in the base, thus enabling easy connection of the LED strip to a control system and/or power supply. Optionally at least one (electronic) driver for the light source is provided in the second concave portion, for example mounted on the backside of the reflector or on the base or support portion.

In an embodiment the LED strip is characterized in that the reflector is provided with an optically effective coating, preferably the optically effective coating is a diffusive coating and/or a (remote) phosphor. Alternatively the LED strip is characterized in that an optical element/dome extends between an end of the base and the connection between reflector and support portion, further referred to as the strip window, preferably said optical element is refractive, for example a Fresnel lens or prism, or a micro-lens optics, diffusive coating and/or a (remote) phosphor. In such embodiments the distinction by

viewers/observers of discrete LEDs is counteracted as the light issued by a single LED is scattered and mixed with light issued by other LEDs before being issued through the strip window. The risk on glare thus is counteracted. Furthermore, UV/blue light emitting LEDs can be used which issue light through the strip window which is partly unconverted and partly converted by a (remote) phosphor to green, yellow, orange and/or red light.

An embodiment of the LED strip is characterized in that it is provided with end caps extending transverse to a length direction of the strip for closing an end face transverse to the length direction of the first (and optionally also the second) concave portion. Thus the potential occurrence of light losses, or undesired light issued at end portions of the LED strip is counteracted. The length direction could, for example be defined by the arrangement of the at least one LEDs. Preferably said end faces are light reflective to further reduce said light losses. To yet further reduce light losses to above the false ceiling, the end cap is provided with a flap which functions as a lid for closing off the space between ceiling tile and the T-shaped bracket it originally rested on. When the LED strip is installed in the false ceiling, the respective ceiling tile is lifted, and leaves an opening between ceiling tile and the rest of the false ceiling. Said opening is covered by the flap which thereto extends from the end cap in a direction transverse to the length direction at a front side of the reflector and preferably is hingingly, resiliently or bendable be attached to the end cap. The flap preferably is reflective and could have a triangular shape or a rectangular shape.

In an embodiment the luminaire of the invention is further characterized in that the light emission window which extends between either two bases or between one base and a ceiling tile, is provided with a light transmissive plate to further shape the light beam issued by the luminaire. The plate may be transparent, translucent, colored, straight or curved, may comprise optical structures, for example micro-lens optics, or acoustic transparent diffuser like glass fiber-based woven or non- woven cloth. Such a plate may have various aesthetic or practical purposes, comparable to the exit window plates used in conventional luminaries. However, it is noted that the added functionality of the luminaire by said plate involves extra costs and reduces the versatility of the module, since it can no longer be easily combined with other ceiling elements.

Preferably, the indirect lighting module is powered by a low-voltage source, such as 36 Volt, or lower, for example 24 Volt or 12 Volt. This allows for a minimal housing, since no electrical isolation measures are required. Furthermore, for reasons of cost it is preferred to have a single source for multiple lighting modules. The low-voltage source may be integrated into the dropped false ceiling, like in the Emerge standard, as applied in dropped ceilings by Armstrong. In this low voltage powered grid solution, the wiring is integrated in the T-bars. In the recessed application, the indirect lighting module may contain a mechanical and electrical connector to the T-bar, where the electrical connection is made to the conductor on the "bulb" of the T-bar. In a surface mounted or suspended application, the mechanical and electrical connection can be made to the conductor in the "reveal" (in the visible part of the T-bar). This allows for a very easy and flexible installation of the modules.

Generally in the application the expression LED strip is used, however, LED strip could equally be substituted by light source strip in which the light source could be an elongated low/high pressure gas discharge lamp or an elongated halogen lamp, the elongated dimension of the light source generally extending along the length direction along which the light source strip extends.

WO2011019753 discloses an elongated light source strip with a LED light source provided at a base within a concave portion formed by the base and a concavely curved reflector which connects the base to a support portion. BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.

In the drawings:

Fig. 1 shows a LED strip according to the prior art in perspective cross sectional view;

Fig. 2 shows a perspective view of a first embodiment of a LED strip according to the invention;

Fig. 3 shows a perspective end view of a second embodiment of a LED strip according to the invention in a recessed configuration; Fig. 4 shows a surface-mounted, third embodiment of a LED strip according to the invention in perspective cross section;

Fig. 5 shows a cross-section of an embodiment of a lighting module according to the invention;

Fig. 6 shows a cross section of an embodiment of a luminaire according to the invention;

Fig. 7-9 each shows a cross section of a part of a false ceiling comprising various embodiments of luminaire according to the invention.

Fig.lOa-c show a cross-sectional view of a lighting module with two LED strips mutually connected via a joint at their bases.

Fig. 11 show a part of a false ceiling with installed LED strip provided with flaps.

The figures are purely diagrammatic and not drawn to scale. Particularly for clarity, some dimensions are exaggerated strongly. Similar components in the figures are denoted by the same reference numerals as much as possible.

DESCRIPTION OF EMBODIMENTS

Fig. 1 shows a basic embodiment of the LED strip 1 according to the prior art in perspective cross sectional view. The LED strip comprises a plurality of LEDs 3 on a PCB 10 in a first concave portion 5 of the strip 7 and mounted on a base 9, a support portion 11 extending parallel to the base, and a straight reflector 13 having a front side 15. The reflector connects the base and the support portion. Said reflector is coated with an optically effective coating 17, in the figure a diffuse reflective layer 19, for example, aluminium oxide to diffusely scatter light rays 4 issued by the LEDs and impinging on the layer. The first concave portion is formed by the base, reflector and support portion.

Fig. 2 shows a perspective view of a first embodiment of the LED strip 1 according to the invention, comprising only a single LED 3 mounted on a base 9. The strip 7 is made in one piece via an extrusion process from synthetic resin material, for example PMMA or polyethylene, and comprises the base 9, a support portion 11 and a concavely shaped reflector 13 connecting the base and the support portion. A first concave portion 5 is formed by the base, support portion and the reflector. A second concave portion 35 is provided at a backside 37 of the reflector, which second concave portion can accommodate a branch of a T-shaped bracket (not shown). Fig. 3 shows a perspective end view of a second embodiment of the LED strip 1 according to the invention. The strip is made in one part by cutting and folding aluminium metal sheet, but alternatively could be made of steel, or plastic if the PCB provides for sufficient cooling of the LEDs. The LED strip rests with its base 9 on a suspension bracket 23, said bracket having a T-shaped cross section with two branches 24. On the base a plurality of LEDs 3 are mounted and arranged in a row, defining a length direction or length axis 25. The LEDs 3 are located inside a first concave portion 5 of the strip, said first concave portion being formed by the base and the reflector 13. The reflector has a cross-section transverse to the length direction shaped as a branch of a parabola 39, the LEDs being positioned in the vicinity of a focal point 41 of said parabola branch. The LEDs may be positioned just before (closer to the reflector) or just behind the focal point, in order to aim the light slightly above or slightly below the horizon, respectively, above the horizon is mostly preferred to avoid looking into the source via the reflector. Right at the focal point, the optical axis of the light will be horizontal after reflection, but the beam will be partly above and partly below the horizon. With a first reflector end 27 the reflector is connected to the base and with a second reflector end 29 the reflector is connected to the support portion 11. The LED strip has an end face 31 which is closed by an end cap 33, in the figure made of translucent polyethylene. The support portion and the reflector border a second concave portion 35, which second concave portion is located at a backside 37 of the reflector. In Fig. 4 a LED strip 1 is shown having practically the same S- or Z-shaped cross section as the LED strip of Fig. 3, except for a further support portion 12, extending in a direction transverse to the support portion. The support portion could be made bendable with respect to the base and reflector to adjust its position to the slanted orientation of the ceiling tile for better supporting said ceiling tile. Fig 4 further shows that said second concave portion 35 enables the LED strip to rest with its support portion 11 on the T-shaped bracket 23, and thus forming a LED strip suspending and protruding from a false ceiling (not shown). In fig. 4 further is shown that a light transmissive plate 43 is provided to the LED strip in a light emission window 51 , said plate resting on the base 9 of the LED strip and practically abutting the LEDs 3.

Fig. 5 shows a cross-section of an embodiment of a lighting module 21 according to the invention. The lighting module comprises two LED strips 1 connected to each other via a joint 45 at the backside 37 of the reflector 13, each LED strip being independently on/off switchable. This embodiment is only suitable for suspended

applications not as a recessed version. The module rests via the support portions 11 from a T- shaped bracket 23, adjustable in height, and suspends from a false ceiling 47 of which only one T-shaped bracket and two ceiling panes 49 or ceiling tiles 49 are shown. One side of each of the ceiling panes shown rests also on the T-shaped bracket. In the figure, plane P extend transverse to the plane of the drawing and through the light emission window 51. Light rays 4 issued by the LEDs 3 and impinging on a specular reflective coating 17 of the reflector are either reflected to a respective ceiling panel or are reflected towards a light emission window 51 and subsequently to the exterior. Care should be taken that at least one diffusing step occurs for each ray issued by the LED before said light ray is issued to the exterior. This diffusion step could be either at the reflector, ceiling tile, or if not at none of these two, at a diffuser plate which then should be provided in the light emission window. In the figure light rays impinging on the ceiling pane are diffusely reflected to the light emission window by said ceiling pane, which thereto could be provided with a diffusely reflective coating.

Preferably, the reflector is specular reflective, but a alternatively, the reflector could be provided with a diffuse reflective coating, or high gloss white surface as an intermediate between specular and diffuse reflective coating or as a further alternative a specular ripple as an anisotropic diffuse reflector specular in the direction of the cross-section, and diffuse in extrusion direction.

Fig. 6 shows a cross section of an embodiment of a luminaire 53 according to the invention, said luminaire being formed by a combination of a lighting module 21, comprising two LED strips 1 connected to each other via a frame 55 connecting the front side 15 of the reflectors 13 of the respective LED strips, and at least one ceiling tile 49. The lighting module rests with it support portion 11 on the T-shaped brackets 23, the ceiling tile on its turn rests on the support portions of the LED strips. The LED strips each have a further support portion 12 that confines the ceiling tile and limits the possibility of the LED strips getting tilted with respect to the plane P of the false ceiling 47. The luminaire further has a light transmissive plate 43 provided in the light emission window 51. As shown in Fig. 6 the light source strip 1 has at least for about 90% the typical S- or Z-contour in cross-section with a further support portion 12 forming part of the cross-section as well.

Fig. 7-9 each shows a cross section of a part of a false ceiling comprising various embodiments of luminaire according to the invention. In Fig. 7 the luminaire 53 suspends and protrudes from the false ceiling 47 because its rests with its support portions 11 on the T-shaped-brackets 23, the T-shaped brackets form a grid and are all being suspended from the real ceiling at the same height. A smooth transition between the plane P of the false ceiling and the light emission window 51 of the luminaire has been attained by a slanted position of an adjacent ceiling tile 50 by making it rest with one side on an extension 57 of the base 9.

In Fig. 8 a luminaire 53 according to the invention is shown comprising two (bare) light source strips 1, i.e. light source strips yet without a light source and without light source contacts. Said luminaire is in a recessed position with respect to the plane P of the false ceiling. The originally present ceiling pane 49 has been lifted somewhat with respect to the T-shaped brackets 23 and the luminaire has been inserted in between. Between the luminaire and the T-shaped bracket a light transmissive plate 43, in the figure a lamellae like, open grid structure, has been inserted. Hence, the ceiling tile rests on the support portion 11 , the luminaire rests on the plate and the plate rests on the T-shaped bracket. The ceiling tile is an acoustic tile, i.e. it has an open, more or less porous structure, to enable air and

sound/noise to pass and to reflect light, and further comprises a device 59, in the figure a motion sensor. In a later stage light sources can be easily mounted on bases 9, thereto the light transmissive plate 43 needs to be temporarily removed.

Fig. 9 shows in cross section an asymmetric luminaire 53, with an elongated, low pressure, mercury, fluorescent, discharge lamp 3 as a light source. The light source strip 1 is inserted in between the ceiling tile 49 and the T-shaped bracket 23 at only one side of a ceiling tile, resulting in the ceiling tile to assume a slanted orientation with respect to the plane P of the false ceiling. The light source illuminates the ceiling tile from one side 59. The asymmetric luminaire creates a lighting effect similar to that of a traditional "factory roof, i.e. slanted roof panels with light entering the room by vertical windows between the slanted roof elements. The orientation of the slanted ceiling tile enables use by an interior designer or architect to create a specific, desired effect in the room.

Fig.lOa-c show a cross-sectional view of a lighting module 21 with two LED strips 1 mutually connected via a joint 45 located at the backside 37 of the reflector 13 at their bases 9 at various stages of their mounting on the T-shaped bracket 23 of the false ceiling. The LED strips are made of flexible bendable or resilient material to enable insertion of the T-shaped bracket into the second concave portion 35. The lighting module can either rest with its support portion 11 or with its base on the T-shaped bracket. As shown in Fig. 10c the light source strip 1 has at least for about 70% the typical S- or Z-contour in cross-section with the joint 45 forming part of the cross-section as well.

Fig. 11 show a part of a false ceiling 47 with only one installed LED strip 1, which LED strip is provided with two flaps 61 on either end face 31 of the LED strip. The false ceiling comprises a grid 65 of T-shaped brackets on which the ceiling tiles rest. By insertion of one LED strip in between the T-shaped bracket and the ceiling tile (said ceiling tile is not shown), said ceiling tile is somewhat lifted, thus leaving an opening 63 between said ceiling tile and the grid of T-shaped brackets. The flaps, in the figure of a triangular shape, are bendable attached to the end caps of the LED strip and are oriented in a transverse direction to the length direction 25 of the LED strip to function as a lid and to close these openings.