EP3244124A1

EP3244124A1 - Luminaire and surface covering arrangement

Info

Publication number: EP3244124A1
Application number: EP16169267.8A
Authority: EP
Inventors: designation of the inventor has not yet been filed The
Original assignee: Philips Lighting Holding BV
Current assignee: Signify Holding BV
Priority date: 2016-05-12
Filing date: 2016-05-12
Publication date: 2017-11-15

Abstract

Disclosed is a luminaire (1) comprising a sheet metal housing (100) shaped to include a trench (110) comprising a pair of opposing elongate side walls (111) extending from a trench floor; a pair of optical cavities (120) on opposite sides of the trench, each optical cavity being delimited by one of the elongate side walls (111) of the trench, a first inclining elongate surface portion (121) extending from an edge of the elongate side wall distal to the trench floor and a second inclining elongate surface portion (123) extending from the first inclining elongate surface portion, each optical cavity further comprising a diffuser (130) extending between the second inclining elongate surface portion and the elongate side wall; each optical cavity housing a plurality of solid state lighting elements (141) mounted on the first inclining elongate surface portion such that the solid state lighting elements face the diffuser; and at least one driver circuit (150) of said solid state lighting elements in said trench on the trench floor. A surface covering arrangement including such a luminaire is also disclosed.

Description

FIELD OF THE INVENTION

The present invention relates to a luminaire comprising a housing in which a plurality of solid state lighting elements is housed.
The present invention further relates to a surface covering arrangement including such a luminaire.

BACKGROUND OF THE INVENTION

Solid state lighting such as LED lighting is becoming increasingly popular because of the energy efficient nature of such lighting as well as the lifetime of such lighting. A further advantage of solid state lighting is that the solid state lighting devices may have a configurable luminous output with short response times to configuration changes. This has led to the advent of many luminaires including solid state lighting devices to replace existing luminaires. For example, solid state lighting-based luminaires that can be used as troffers in a surface covering arrangement such as a modular suspended ceiling are gaining popularity because of their superior lifetime and energy efficiency compared to traditional troffers based on fluorescent tubes.
In order to ensure an extended lifetime and desired luminous output of the solid state lighting devices, the solid state lighting devices, e.g. LEDs, are typically mounted or otherwise thermally connected to a heatsink, which absorbs heat generated by the solid state lighting devices and transfers this heat to its surroundings. However, the provision of such an additional heat sink component increases the cost of such luminaires. This is often undesirable given the already high price point of solid state lighting-based luminaires compared to traditional luminaires, which hampers the market penetration of solid state lighting-based luminaires. What is more, additional optical components such as reflectors are typically required to ensure that the luminous output produced by the solid state lighting devices, e.g. LEDs, resembles that of 'known' light sources in order to achieve customer acceptance of the luminaire. This further adds to the cost of such luminaires. FIG. 1 schematically depicts a prior art troffer-style luminaire 1'. The luminaire 1' comprises a centrally located LED arrangement in a central batten 20. Inclining reflective panels 11 extend from the respective elongate edges 15 of the central batten 20 to the elongate support frame edges 13 of the housing 10 of the luminaire 1'. The reflective panels 11 are typically sloped to downwardly reflect the light emitted by the LEDs incident on these surfaces. Although not specifically shown, such a prior art luminaire 1' typically comprises a driver box behind the central batten 20, which is formed in a recess of the housing 10. A drawback of such a luminaire 1' is that its assembly is rather complex, causing the luminaire want to have a high cost of manufacture.
Another example of a luminaire that can be used as a troffer is provided in WO 2012/030387 A2 . The luminaire is a troffer-style fixture for use with solid state light sources, such as LEDs. The troffer comprises a light engine unit that is surrounded on its perimeter by a reflective pan. A back reflector defines a reflective interior surface of the light engine. To facilitate thermal dissipation, a heat sink is disposed proximate to the back reflector. A portion of the heat sink is exposed to the ambient room environment while another portion functions as a mount surface for the light sources that faces the back reflector. One or more light sources disposed along the heat sink mount surface emit light into an interior cavity where it can be mixed and/or shaped prior to emission. Such a luminaire is relatively expensive.

SUMMARY OF THE INVENTION

The present invention seeks to provide a luminaire having desirable optical performance that can be produced in a cost-effective manner.
The present invention further seeks to provide a surface covering arrangement including such a luminaire.
According to an aspect, there is provided a luminaire comprising a sheet metal housing shaped to include a trench comprising a pair of opposing elongate side walls extending from a trench floor; a pair of optical cavities on opposite sides of the trench, each optical cavity being delimited by one of the elongate side walls of the trench, a first inclining elongate surface portion extending from an edge of the elongate side wall distal to the trench floor and a second inclining elongate surface portion extending from the first inclining elongate surface portion, each optical cavity further comprising a diffuser extending between the second inclining elongate surface portion and the elongate side wall; each optical cavity housing a plurality of solid state lighting elements mounted on the first inclining elongate surface portion such that the solid state lighting elements face the diffuser; and at least one driver circuit of said solid state lighting elements in said trench on the trench floor.
The luminaire of the present invention is provided by a metal sheet that is shaped to incorporate the heatsink as well as at least part of the luminaire housing, i.e. the optical cavities, in which the solid state lighting elements are mounted. Such a luminaire may be manufactured particularly cost-effectively due to the limited amount of components required, as for example the sheet metal housing further acts as a heating of the solid state lighting elements, thereby obviating the need for a separate heatsink. Furthermore, the particular shape of the sheet metal housing further ensures excellent optical characteristics of the luminaire, for example, because the diffusers acting as the light exit windows are directly illuminated by the solid state lighting elements. This increases the luminous efficiency of the luminaire, for example compared to luminaires in which the one or more light exit windows are indirectly lit.
Advantageously, the design of the luminaire facilitates the use of planar sheet diffusers as the diffusers in the optical cavities. Such planar sheet diffusers typically have a lower cost than for example extrusion or injection diffusers that often are required in such luminaires, thus further reducing the overall cost of the luminaire. Such diffusers may for example be oriented parallel to the first inclining elongate surface portion.
Each optical cavity may have a trapezoid cross-section such that the optical cavity tapers outwardly in the direction in which the solid state lighting elements project their luminous outputs in order to minimize the amount of light incident on the optical cavity walls, i.e. to optimize the luminous efficiency of each optical cavity. In an embodiment, for each optical cavity a normal to first inclining elongate surface portion is oriented under an angle ranging from 20-40° relative to an edge of the diffuser proximal to the elongate sidewall to achieve a particularly good optical efficiency for each cavity whilst at the same time produce a substantially homogeneous luminous output with the luminaire.
To further increase the optical efficiency of the optical cavities, the elongate side wall of the trench and the first and second inclining elongate surface portions delimiting each optical cavity preferably are reflective.
The sheet metal housing preferably comprises two fused metal sheet portions, each portion comprising one of said optical cavities. By assembling the separate optical cavities and subsequently fusing these cavities, the assembly of the luminaire is more straightforward and therefore more cost-effective.
For example, the two metal sheet portions may be fused by screwing, welding or soldering.
In an embodiment, one of the metal sheet portions comprises a protrusion extending from an elongate edge of a floor section of the trench and the other of the metal sheet portions comprises a recess in the elongate edge of a further floor section of the trench, the protrusion extending into said recess. By providing the respective metal sheet portions with mating portions (i.e. a protrusion fitting into a recess on the other metal sheet portion), the separate metal sheet portions may be easily aligned in the assembly process prior to fusing the two metal sheet portions together.
Although preferably the luminaire housing consists of the sheet metal, in some embodiments the luminaire may further comprise a support frame comprising a recess having opposing elongate recess edges, wherein an edge of each second inclining surface portion is secured on one of said opposing elongate recess edges to facilitate the mounting of the sheet metal housing in this support frame. The support frame may be a stamped sheet metal frame, in which case the support frame may be easily manufactured in a cost-effective manner.
The support frame may further comprise a reflective inclining panel extending from each elongate recess edge to an elongate support frame edge. The reflective inclining panels may assist in further shaping the luminous output produced by the respective optical cavities, which for example is particularly advantageous in case the luminaire is to be ceiling-mounted.
Each plurality of solid state lighting elements may be located on a strip mounted on the first inclining surface portion. This has the advantage that the solid state lighting elements can be easily correctly positioned and spaced within each optical cavity, thereby facilitating straightforward manufacturing of the luminaire.
In an embodiment, the luminaire is a troffer.
According to another aspect, there is provided a surface covering arrangement comprising a plurality of surface covering elements; a plurality of frame elements for assembling a frame comprising a plurality of recesses for receiving the plurality of surface covering elements; and a luminaire according to any of the above embodiments, wherein the luminaire is dimensioned to fit in one of said recesses. Such a modular surface covering arrangement may be provided at lower cost than existing modular surface covering arrangements in which more costly luminaires have to be deployed.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described in more detail and by way of non-limiting examples with reference to the accompanying drawings, wherein:

FIG. 1 schematically depicts a prior art luminaire;
FIG. 2 schematically depicts a cross-section of a luminaire according to an embodiment;
FIG. 3 schematically depicts a perspective view of the luminaire of FIG. 2;
FIG. 4 schematically depicts a perspective view of a luminaire according to another embodiment in disassembled form;
FIG. 5 schematically depicts an aspect of a luminaire according to yet another embodiment;
FIG. 6 is a thermal image of an aspect of a luminaire according to an embodiment in operation;
FIG. 7 is a thermal image of another aspect of a luminaire according to an embodiment in operation; and
FIG. 8 schematically depicts a surface covering arrangement according to an embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.
The luminaire according to embodiments of the present invention may be a troffer although embodiments of the luminaire are not limited thereto; the luminaire may be deployed in any suitable application.
Embodiments of the present invention provide a luminaire in which at least a part of the housing is formed by a shaped metal sheet in which a central trench for housing a driver circuit is flanked by a pair of optical cavities in which the solid state lighting (SSL) elements of the luminaire are mounted. The respective mounting surfaces of the SSL elements in these optical cavities typically opposes the mounting surface or floor of the trench and in at least some embodiments may be angled relative to the floor of the trench such that the SSL elements mounted on these respective mounting surfaces within the optical cavities exhibit an optical axis that is directed away from the floor of the trench. This arrangement provides a cost-effective compartmentalized luminaire housing for both the one or more drivers of the SSL elements as well as the SSL elements themselves. The luminaire according to embodiments of the present invention preferably but not necessarily has a symmetrical shape.
FIG. 2 schematically depicts a cross-section and FIG. 3 schematically depicts a perspective view of a luminaire 1 according to a first embodiment. The luminaire 1 comprises a housing 100 formed from a metal sheet that is shaped, e.g. folded, stamped, bent or the like, to form the housing 100. Any suitable metal or metal alloy may be used as the sheet metal. For example, the sheet metal may be aluminium although embodiments of the present invention are not limited thereto.
Central to the housing 100 is a trench 110 for housing the one or more driver circuits 150, ballasts and the like for the SSL elements in the luminaire 1. The trench 100 typically has an elongate shape in which an elongate trench floor 112 is flanked by opposing elongate side walls 111 extending from opposing elongate edges of the trench floor 112. In this embodiment, the opposing elongate side walls 111 extend perpendicularly from the trench floor 112 (i.e. under an angle of 90°) to give the trench 110 a U-shaped profile (with a flat trench floor 112). In alternatively embodiments, the angle between the trench floor 112 and each of the elongate side walls 111 may be larger than 90° to give the trench 110 a V-shaped profile (with a flat trench floor 112). For example, the angle between the trench floor 112 and each of the elongate side walls 111 may be in the range of 90°-120°.
Each elongate side wall 111 delimits part of a respective optical cavity 120. The optical cavities 120 flank, i.e. are positioned adjacent to, the trench 110. Each optical cavity 120 further comprises a first inclining elongate surface portion 121 extending from an edge of the elongate side wall 111 distal to the trench floor 112. In the present application, the first inclining elongate surface portion 121 is inclining in respect of the elongate side wall 111 to which it is attached. In other words, the angle between the elongate side wall 111 and the first inclining elongate surface portion 121 is greater than 90°. In an embodiment, the incline angle between the plane of the cavity floor 112 and the first inclining elongate surface portion 121 is in the range of 25-45°, such as 30°, 35°, or 40°. Under these angles, it has been demonstrated that the luminaire 1 can produce a luminous output of acceptable homogeneity as well as an acceptable luminous efficiency, which is particularly desirable when the luminaire 1 is to be used as a troffer in a surface covering arrangement such as a suspended ceiling arrangement.
Each optical cavity 120 is further delimited by a second inclining elongate surface portion 123 extending from the first inclining elongate surface portion. In the context of the present application, where reference is made to the second inclining elongate surface portion 123, this is intended to mean that this surface portion extends from the first inclining elongate surface portion 121 under an angle of greater than 90°. Consequently, due to the inclining nature of the first inclining surface portion 121 and the second inclining surface portion 123, each optical cavity 120 may have a trapezoidal cross-section.
Each optical cavity 120 further comprises a diffuser 130 extending between the second inclining elongate surface portion 123 and the elongate side wall 111 delimiting the optical cavity 120. From an optical perspective, any suitable type of diffuser 130 may be used for this purpose. From a cost perspective, a planar sheet diffuser 130 is particularly mentioned as such a diffuser may be formed in a cost-effective manner, e.g. by stamping the diffuser 130 to its appropriate dimensions for fitting into the optical cavity 120 from a large sheet of diffusive material, e.g. polycarbonate, poly (methylmethacrylate) or another suitable diffusive material. The diffuser 130 may be an elongate diffuser extending across the full length of the optical cavity 120 such that all substantially all light emitted from the optical cavity 120 passes through the diffuser 130. The diffuser 130 may be mounted such that it is oriented in parallel with the first inclining elongate surface portion 121 of the optical cavity 120 in which the diffuser 130 is fitted, although it should be understood that the diffuser 130 may be mounted in any suitable orientation relative to this surface portion of the metal sheet housing 100. The diffuser 130 may be mounted in the optical cavity in any suitable manner, e.g. using plastic or metal clips or snaps that secure the diffuser 130 to the elongate side wall 111 and the second inclining elongate surface portion 123 of the optical cavity 120.
Each optical cavity houses a plurality of SSL elements 141 mounted on the first inclining elongate surface portion 121 such that the SSL elements 141 face the diffuser 130, i.e. have the optical axis of the luminous distribution they produce extend through the diffuser 130. Any suitable type of SSL element may be used for this purpose, e.g. white LEDs, coloured LEDs arranged to combine their luminous output to produce white light, coloured LEDs arranged to produce a luminous output of a particular colour, and so on. Such SSL elements 141 may be individually addressable such that the luminaire 1 may be configured to produce different lighting effects, e.g. different types of mood lighting, or may be addressable as a single group of SSL elements, for example in case of a luminaire 1 arranged to produce a single type of luminous output only, e.g. white light.
The SSL elements 141 may be mounted on a carrier 140, such as an elongate PCB or strip. The SSL elements 141 for example may be soldered to such a carrier 140. This has the advantage that only the carrier 140 needs to be secured, e.g. screwed or adhered, against the first inclining elongate surface portion 121. A particularly suitable embodiment of such an arrangement is a so-called Level 2 assembly, in which a strip 141 carrying the SSL elements 141 may be glued to a PCB such as a MCPCB. As is well-known per se, this simplifies wiring requirements for the SSL elements 141, thereby further reducing the cost of the luminaire 1.
The inner surfaces of each optical cavity 120 preferably are reflective to ensure that light directed by the SSL elements 141 onto these inner surfaces is reflected back into the optical cavity such that eventually this light can escape the optical cavity 120 through the diffuser 130, thereby minimizing light loss and optimizing the luminous efficiency of the optical cavity 120. Typically, at least the elongate side wall 111 and the second inclining elongate surface portion 123 facing the optical cavity 120 are reflective although in some embodiments the first inclining elongate surface portion facing the optical cavity 120 may also be reflective. These surfaces may be made reflected in any suitable manner, e.g. by application of a reflective film or coating. In an embodiment, these surfaces may be painted with white paint in order to give these surfaces the desired reflectivity in a cost-effective manner.
The inclined mounting of the SSL elements 141 within the optical cavities 120 causes a portion of the luminous output produced by the SSL elements 141 to directly exit the optical cavities 120 through the respective diffusers 130, whereas another portion of this luminous output indirectly exits the optical cavities 120 through reflection from the inner surfaces of these optical cavities. Consequently, each optical cavity 120 produces a widely spread luminous output, which gives the luminaire 1 the appearance of having a large area light exit window (well beyond the combined areas of the diffusers 130), which gives the luminaire 1 an appearance that resembles the appearance of conventional luminaires, e.g. troffers comprising fluorescent tubes as light engines.
In an embodiment, for each optical cavity 120, a normal 122 to first inclining elongate surface portion 121 is oriented under an angle θ ranging from 20-40° relative to an edge of the diffuser 130 proximal to the elongate sidewall as shown in FIG. 2 to achieve a desired optical performance of the optical cavity 120. Each optical cavity 120 may have a width w ranging from 50-100 mm and a depth d ranging from 30-60 mm in selected embodiments.
Compared to the conventional luminaire 1' as shown in FIG. 1, the sheet metal housing 100 of the luminaire 1 according to embodiments of the present invention may further include the inclined reflector panels 11 as shown in FIG. 3, which each may extend from an intermediate portion 125 of the sheet metal housing 100 such that each inclined reflector panel 11 is connected to one of the second inclining elongate surface portions 123 by the intermediate portion 125. Alternatively, the intermediate portion 125 may be omitted such that each inclined reflector panel 11 directly extends from one of the second inclining elongate surface portions 123. Each inclined reflector panel 11 is typically oriented such that at least some of the light escaping the optical cavities 120 in a direction away from the central axis of the luminaire 1 is reflected by the inclined reflector panel 11 such that the angle between the direction of the light and the central axis is reduced. For example, for a ceiling-mounted luminaire 1, each inclined elongate reflector 11 may be arranged to downwardly reflect the light incident on to these reflectors in order to illuminate a surface area below the ceiling-mounted luminaire 1.
The sheet metal housing 100 may further comprise mounting edges 13 along the respective elongate edges of the inclined reflector panels 11 distal to the optical cavities 120 for mounting the luminaire 1 into a support structure. Such mounting edges 13 may have any suitable shape as will be immediately apparent to the person skilled in the art.
In an alternative embodiment of the luminaire 1, a disassembled view of which is schematically depicted in FIG. 4, the inclined elongate reflectors 11 and mounting edges 13 may form part of a mounting frame 10, which for example may be formed as a sheet metal mounting frame 10 by stamping a sheet metal. The support frame 10 comprising a recess 12 having opposing elongate recess edges 15. In this embodiment, the previously described intermediate elongate edges 125 of the sheet metal housing 100 are terminal edges of this housing adapted to engage with, i.e. to be mounted on, respective elongate recess edges 15 to secure the sheet metal housing 100 in the support frame 10, e.g. using screws, clips, staples or the like. In this embodiment, each inclined reflector panel 11 extends between one of the elongate recess edges 15 and an opposing elongate support frame mounting edge 13.
In the above embodiments, the sheet metal housing 100 is made from a single piece of sheet metal. However, in alternative embodiments, the sheet metal housing 100 may be made of a pair of sheet metal portions that are fused together in order to form the sheet metal housing 100. This has the advantage that each half of the sheet metal housing 100 comprising one of the optical cavities 120 may be more easily manufactured compared to a manufacturing process in which the entire sheet metal housing 100 including both optical cavities 120 is formed by shaping, e.g. bending and/or stamping, a single piece of sheet metal.
FIG. 5 schematically depicts an embodiment of such a modular sheet metal housing 100. The modular sheet metal housing 100 comprises a first sheet metal module 101 (only the part of this module for forming the trench 110 is shown for the sake of clarity) and a second sheet module 103 (only the part of this module for forming the trench 110 is shown for the sake of clarity). The first sheet metal module 101 comprises a first section 112' of the trench floor 112 and the second sheet metal module 101 comprises a second section 112" of the trench floor 112. Each of the first section 112' and the second section 112" comprises at least one male or female mating portion along an elongate edge for mating with a female or male mating portion on the elongate edge of the section of the opposing sheet metal module to securely couple the first sheet metal module 101 to the second sheet metal module 103, e.g. through screwing, soldering, welding, gluing and so on.
For example, a male mating portion may comprise a protrusion 105 protruding from the elongate edge of one of the sheet metal modules. A female mating portion may comprise a recess 107 formed in the elongate edge of another one of the sheet metal modules and dimensioned to receive the protrusion 105. For example, the recess 107 may be shaped such that the protrusion 105 may be slid into the recess 107 such that the respective floor sections 112' and 112" are abutted by the respective elongate edges contacting each other. Such male and female mating portions may further comprise a hole or the like, which holes align when the male mating portion is correctly inserted into the female mating portion such that the first sheet metal module 101 and the second sheet metal module 103 may be secured together by extending a screw through the aligned holes and by subsequently engaging a bolt or the like with the screw to keep the first sheet metal module 101 and the second sheet metal module 103 together. Alternatively, such holes may be used for soldering or welding the respective sheet metal modules together although it should be understood that this may also be achieved without the use of such holes, e.g. by gluing, soldering or welding the respective elongate edges of these modules together.
FIG. 6 and FIG. 7 depict the results of a thermal simulation of an embodiment of the luminaire 1, a cross-section of which is shown in FIG. 6, whilst FIG. 7 shows a perspective view of the luminaire 1. The dark areas in this thermal simulation indicate regions of elevated temperature. The simulation was performed at a simulated operating temperature of 25°C. At this operating temperature, a maximum operating temperature for the SSL elements 141 of 44°C was obtained. It is noted that in order for the SSL elements 141 to have lifetime expectancy in excess of 50,000 hours, the maximum operating temperature of the SSL elements should be below 85°C. This therefore clearly demonstrates the effectiveness of the sheet metal housing 100 of the luminaire 1 as a heat sink, as the heat generated by the SSL elements 141 is effectively dissipated as indicated by the maximum operating temperature of these elements.
Similarly, the maximum operating temperature of the driver circuit 150 was observed to be 37°C whereas typical driver specifications require an operating temperature of below 75°C. It can therefore be expected that the luminaire 1 according to embodiments of the present invention will have excellent lifetime expectancy well in excess of 50,000 hours.
FIG. 8 schematically depicts a front view of a modular surface covering arrangement 200 having a plurality of surface tiles 210 suspended in a support frame 220. The surface tiles 210 and the support frame 220 may be made of any suitable material depending on the application of the modular surface covering arrangement 200.
For example, where the modular surface covering arrangement 200 implements a modular ceiling, the surface tiles 210 and the support frame 220 do not need to be load-bearing and may be made of cheap lightweight materials such as polystyrene surface tiles 210 or the like and a plastics or aluminium the support frame 220 or the like. For example, where the modular surface covering arrangement 100 implements a modular floor, the surface tiles 110 and the support frame 120 may need to be load-bearing and may be made of more sturdy materials, e.g. resilient materials having a minimum thickness.
The modular surface covering arrangement 200 further comprises at least one luminaire 1 according to any of the above embodiments and preferably comprises a plurality of such luminaires 1 for instance to achieve a homogeneous illumination pattern across an enclosed space in which the modular surface covering arrangement 200 is fitted or to deliver illumination in target areas within such an enclosed space, e.g. in walkways, over desks or shopping display areas, and so on. The surface tiles 210 and at least one luminaire 1 may be fitted in the support frame 220 in any suitable manner. For example, the tiles 210 and/or the at least one luminaire 1 may have a lip around an outer perimeter that extends over the support frame 220 such that the lip rests on the support frame 220.
Alternatively, the tiles 210 and/or the at least one luminaire 1 may be dimensioned such that they are larger than an aperture for receiving the tiles 210 and/or the at least one luminaire 1 delimited by the support frame 220. The tiles 210 and/or the at least one luminaire 1 may have a recessed perimeter portion for receiving the support frame 220, with this recess preferably matching the thickness of the support frame 220 to obtain excellent planarity in the overall modular surface covering arrangement 200.
Many other suitable mounting arrangements will be immediately apparent by the skilled person. It is further noted that the surface tiles 210 and the luminaires 1 are shown to have the same dimensions in the modular surface covering arrangement 200 by way of non-limiting example only. It is equally feasible that the surface tiles 210 and the luminaires 1 have different sizes, e.g. the surface tiles 210 having a size that is a multiple of the size of a luminaire 1 or the luminaire 1 having a size that is a multiple of the size of a surface tile 210.
It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps other than those listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several distinct elements. In the device claim enumerating several means, several of these means can be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

A luminaire (1) comprising:
a sheet metal housing (100) shaped to include:
a trench (110) comprising a pair of opposing elongate side walls (111) extending from a trench floor;

a pair of optical cavities (120) on opposite sides of the trench, each optical cavity being delimited by one of the elongate side walls (111) of the trench, a first inclining elongate surface portion (121) extending from an edge of the elongate side wall distal to the trench floor and a second inclining elongate surface portion (123) extending from the first inclining elongate surface portion, each optical cavity further comprising a diffuser (130) extending between the second inclining elongate surface portion and the elongate side wall;

each optical cavity housing a plurality of solid state lighting elements (141) mounted on the first inclining elongate surface portion such that the solid state lighting elements face the diffuser; and

at least one driver circuit (150) of said solid state lighting elements in said trench on the trench floor.
The luminaire (1) of claim 1, wherein each diffuser (130) is a planar sheet diffuser.
The luminaire (1) of claim 1 or 2, wherein the diffuser (130) of each optical cavity (120) is oriented parallel to the first inclining elongate surface portion (121).
The luminaire (1) of any of claims 1-3, wherein each optical cavity (120) has a trapezoid cross-section.
The luminaire (1) of any of claims 1-4, wherein for each optical cavity (120) a normal (122) to first inclining elongate surface portion (121) is oriented under an angle (θ) ranging from 20-40° relative to an edge of the diffuser (130) proximal to the elongate sidewall.
The luminaire (1) of any of claims 1-5, wherein the elongate side wall of the trench (111) and the first and second inclining elongate surface portions (121, 123) delimiting each optical cavity (120) are reflective.
The luminaire (1) of any of claims 1-6, wherein the sheet metal housing (100) comprises two fused metal sheet portions (101, 103), each portion comprising one of said optical cavities (120).
The luminaire (1) of claim 7, wherein the two metal sheet portions (101, 103) are fused by welding or soldering.
The luminaire (1) of claim 7 or 8, wherein one of the metal sheet portions (101) comprises a protrusion (105) extending from an elongate edge of a floor section (112') of the trench and the other of the metal sheet portions comprises a recess (107) in the elongate edge of a further floor section (112") of the trench, the protrusion extending into said recess.
The luminaire (1) of any of claims 1-9, further comprising a support frame (10) comprising a recess having opposing elongate recess edges (15), wherein an edge (125) of each second inclining surface portion (123) is secured on one of said opposing elongate recess edges.
The luminaire (1) of claim 10, wherein the support frame (10) is a stamped sheet metal frame.
The luminaire of claim 10 or 11, wherein the support frame (10) further comprises a reflective inclining panel (11) extending from each elongate recess edge (15) to an elongate support frame edge (13).
The luminaire (1) of any of claims 1-12, wherein each plurality of solid state lighting elements (141) is located on a strip (140) mounted on the first inclining surface portion (121).
The luminaire (1) of any of claims 1-13, wherein the luminaire is a troffer.
A surface covering arrangement (200) comprising:
a plurality of surface covering elements (210);

a plurality of frame elements for assembling a frame (220) comprising a plurality of recesses for receiving the plurality of surface covering elements; and

a luminaire (1) according to any of claims 1-14, wherein the luminaire is dimensioned to fit in one of said recesses.