Luminaire with LED light source and light guide plate

Abstract

A luminaire 100 comprises an LED light source 50 held in a carrier element 60 and arranged at an incident edge 12 of a light guide plate 10 with light emitted at a flat side 11 of the light guide plate. The light guide is supported by a support element 62 and a pressing element 40 between the light guide plate and a supporting element 90 presses the light guide plate towards the support element. Spring elements 45 extend from a planar base 41 of the pressing element and are supported on the supporting element. An end region 42 of the pressing element engages in a positioning opening in the carrier element. The spring elements may be arc-shaped fingers. The end region of the pressing element may comprise a deformable hook. A housing 110 may form a light exit opening 115 containing a disk shaped diffuser 30. The LED light source may be LEDs 51 on an elongated circuit board. The luminaire is typically a floor or pendant luminaire.

Description

Field of invention The present invention relates to a luminaire which comprises a preferably elongated LED light source and a light guide plate, wherein the light of the LED light source is radiated into the light guide plate via an incident edge surface of the light guide plate and is emitted via at least one flat side of the light guide plate. Background to the invention Luminaires of this type, which use this so-called “edge-lit” technology, are designed to emit light over as large an area and as homogeneously as possible. The use of a light guide plate and the associated arrangement of the LED light source on one edge of the light guide plate makes it possible to realize the structural unit responsible for light generation and light emission with an extremely low installation height. Accordingly, such luminaires are preferably used as suspended pendant luminaires or as floor luminaires, since the low installation height can have a particularly positive effect on the appearance of the luminaire. With regard to the efficiency of the light emission in such luminaires, it is crucial that the LED light source and the light guide plate are positioned precisely relative to each other. The arrangement of the components responsible for light distribution and light emission is usually carried out in a so-called sandwich construction, in which several layers are arranged one behind the other in a direction perpendicular to the plane of the light guide plate. These layers include in particular the light guide plate and, if necessary, other plate-shaped components with which the desired light emission can be optimized. Such additional components can be, for example, a diffuser plate, films for controlling the light emission and / or reflective layers. As already mentioned, these are placed on top of each other in a sandwich-like manner and then stored inside the housing of the luminaire. One problem here is that these plate-like components or parts have a certain tolerance in their thickness due to manufacturing. Because these tolerances can vary, it can be difficult to ensure that all the layers are perfectly aligned. In particular, this can lead to the position of the light source shifting slightly relative to the light guide plate within the housing, which would then result in a significant reduction in the efficiency of the light coupling and light distribution. In order to avoid this problem, it is known from the state of the art to additionally use a compressible, plate-shaped element. This element, usually formed by a foam sheet, is placed in the housing in such a way that it compresses the various components responsible for emitting 1 light. The aim is to compensate for the differences in the thickness of the layers and at the same time to exert pressure on the entire sandwich construction to ensure that the individual layers cannot shift relative to each other and, in particular, to maintain the desired positioning of the light guide plate in relation to the LED light source. However, the production of such foam panels involves a certain amount of effort, as they are cut out of a corresponding foam block. This process can in turn lead to higher tolerances, so that the reliable functionality of the foam plate cannot be guaranteed over the lifetime of the luminaire. Another problem is that the corresponding material has to be disposed of at great expense at the end of its service life. From US 2013 / 0169886 A1 a display for an LCD screen is known in which a light guide plate is pressed against a housing surface by means of spring elements. Luminaires or displays with plate-shaped light guides are also described in EP 3 392 551 A1, US 2017,0082795 A1 or US 2007 / 0019440 A1. It would therefore be desirable to provide a novel solution with the help of which a reliable positioning of a light guide plate in relation to an LED light source is ensured with reduced effort. Summary The present invention is defined by the features of claim 1. Advantageous refinements of the invention are the subject of the respective dependent claims. According to the present invention, analogous to the foam plate explained above, it is provided to press the light guide plate in the direction of a support element by means of a corresponding pressing element, so that the light guide plate is correctly positioned in relation to an associated LED light source. According to the present invention, however, a pressing element is now used which forms at least one, preferably several spring elements which extend from a planar base region and are supported on a suitable supporting element or a component of the luminaire arranged in front of the supporting element. In this way, the pressure required for exact positioning is again exerted on the light guide plate, but the design of the pressing element according to the invention allows it to be manufactured simply and inexpensively. At the same time, the pressing element according to the invention can be used more flexibly compared to the foam plate and can be used efficiently in different constructions, wherein correct positioning of the pressing element is achieved in that the luminaire further comprises a carrier element for holding the LED light source and the pressing element has an end region which engages in a positioning opening in the carrier element. According to the present invention, a luminaire is proposed which comprises: at least one preferably elongated LED light source for generating light, a light guide plate, wherein the LED light source is arranged on an incident edge surface of the light guide plate, such that the light generated by the LED light source is radiated into the light guide plate via the incident edge surface of the light guide plate and is emitted via at least one flat side of the light guide plate, a support element for supporting the light guide plate and a pressing element which is arranged between the light guide plate and a supporting element opposite the support element with respect to the light guide plate and is designed to press the light guide plate in the direction of the support element, wherein, according to the invention, the pressing element forms at least one, preferably several spring elements, which extend from a planar base region and are supported on the supporting element or a component arranged in front of the supporting element, and wherein the luminaire further comprises a carrier element for holding the LED light source and the pressing element has an end region which engages in a positioning opening in the carrier element. The spring elements of the pressing element according to the invention are preferably formed by fingers which extend in an arc from the planar base region in the direction of the supporting element. In particular, it can be provided that the pressing element is formed in one piece, wherein the pressing element is particularly preferably formed by a plastic part, preferably by an injection-molded plastic part. This provides a relatively simple way of producing the pressing element, whereby the manufacturing tolerances are significantly lower compared to the foam plate used previously and, due to the corresponding design of the spring elements, larger tolerances of the sandwich-like arrangement of the luminaire can be compensated. The base region of the pressing element preferably rests flat on the light guide plate or a reflector element resting on the light guide plate. In this way, a flat pressure application is exerted on the sandwich construction and the occurrence of point loads can be avoided. This ensures that a homogeneous light distribution is still ensured and that local differences in brightness cannot occur. The supporting element of the luminaire is preferably formed by a heat sink element which is arranged on a rear side of the luminaire. If necessary, at least one further flat cover element can be arranged between the supporting element and the pressing element. This can prevent light from escaping to the back. However, it may also be possible for the cover element to have one or more openings that allow indirect light emission, for example towards the topside. The carrier element for holding the LED light source can in particular be designed to be angled and in this case have a first web on which the LED light source is arranged, as well as a second web which is aligned, for example, at right angle with respect to the first web and forms a support surface for the light guide plate. According to the invention, as explained above, it is further provided that the pressing element has an end region which engages in a positioning opening in the carrier element This enables precise positioning of the pressing element and ultimately further simplifies the installation of the luminaire. Furthermore, it is ensured that the pressing element remains in the desired position throughout the duration of use of the luminaire and thus performs its function permanently and reliably. Particularly preferably, it can be provided that the end region of the pressing element is at least slightly deformable in a plane parallel to the light guide plate. If changes in the dimensions of individual components of the luminaire occur due to temperature fluctuations, these can be absorbed by the pressing element without the risk of it leaving its desired position. The LED light source preferably includes an elongated circuit board on which several LEDs are distributed. In particular, the length of the circuit board can correspond to the length of the incident edge surface of the light guide plate. The luminaire according to the present invention preferably further comprises a housing which forms a light exit opening. A further disc-like diffuser element can be arranged within the light exit opening, through which the light is ultimately emitted by the luminaire. As already mentioned at the beginning, it can be a pendant luminaire or a floor luminaire. Brief description of the drawings The invention will be explained in more detail below with reference to the accompanying drawing. In the drawings: Figure 1 shows a sectional view of a lateral region of a luminaire designed according to the invention; Figure 2 shows a plan view of the luminaire opened at the top; Figures 3 and 4 are views of the pressing element used in the luminaire according to the invention; and Figures 5 to 7 are views of a second embodiment example of a luminaire according to the invention. Detailed description Figures 1 and 2 show views of a luminaire 100 designed according to the invention, which in the present case is a floor luminaire. Strictly speaking, Figures 1 and 2 only show the so-called luminaire head of a floor luminaire. This luminaire head is located at the upper end of a column, which is not shown for reasons of clarity, since the solution according to the invention concerns in particular the design of the components responsible for light generation and light emission. Accordingly, the arrangement of the luminaire head can be provided in any manner on a corresponding carrier. In the same way, however, the luminaire 100 could also be arranged in the form of a pendant luminaire suspended from the ceiling of a room to be illuminated, or it could also be implemented as a surface-mounted or recessed luminaire, using appropriate measures. The inventive concept is therefore not limited to a specific type of luminaire. The housing 110 of the luminaire 100, which in the present case is approximately rectangular, accommodates all the essential components for light generation and light emission. It forms a light exit opening 115 towards the front or bottom, through which the (primary) light emission of the luminaire 100 takes place. The luminaire housing 110 is designed like a frame and is closed or covered at the rear by further components, which are only partially shown in Figures 1 and 2. The luminaire frame itself is formed by circumferential walls which are angled and form, on the one hand, vertical side walls 111 and, on the other hand, a web 112 which projects inwards on the underside and frames the light exit opening 115. This circumferential web 112 here serves as a support surface for numerous components of the luminaire 100, wherein additional components can also be attached directly to the inner sides of the side walls 111 by means of suitable carrier elements. Particularly noteworthy here are the operating devices 120, which can be seen in Figure 2, which shows the luminaire 100 in a partially open state towards the topside, via which the luminaires are supplied with power, as well as corresponding connection components 121 for supplying power to the operating devices 120. However, the present invention relates in particular to the lighting means and other optical components responsible for light generation and light emission, as well as the problem of positioning these reliably and permanently in a suitable manner relative to one another. It is provided that the light guide technology already known from the prior art is used in the luminaire 100 according to the invention, in which the light from luminaires is distributed by means of a plate-like light guide element and is emitted as homogeneously and over as large an area as possible. The central component of the so-called light engine of the luminaire 100 is therefore a light guide plate 10, which is arranged in the lower region of the luminaire housing 110. The underside 11 of this light guide plate 10 forms the flat side via which the light is coupled out and thus emitted. The coupling of the light into the light guide plate 10 takes place via an edge surface 12 aligned perpendicularly thereto, in the illustrated embodiment example via the surface provided at the left end region of the light guide plate 10. Depending on how much light is to be emitted by the luminaire 100 in total, an arrangement of lighting means and thus a coupling of light can of course also take place at other edge regions of the light guide plate 10. The number of LED light sources used then increases accordingly, and these are then distributed along the various edges. For the present case, it is sufficient to consider the left end region of the luminaire 100 shown in Figure 1. The light is thus coupled into the light guide plate via the edge surface 12, wherein the light comes from an LED light source which is arranged in the luminaire housing 110 and associated with this edge region 12. The LED light source is here preferably formed by an elongated LED circuit board 50 on which several LEDs 51 are distributed. The arrangement of the LEDs 51 preferably extends over the entire length of the associated edge surface 12 of the light guide plate 10, so that the most uniform possible light coupling can be realized. In this case, additional structures can be provided in the region of the edge surface 12 of the light guide plate 10, which are not shown in the figures, but which contribute to achieving a more efficient and homogeneous light coupling, which ultimately has a positive effect on the homogeneous light emission of the luminaire 100 as a whole. In this case, suitable lens-like structures or the like can be considered, with the aid of which the light emitted by the LEDs 51 is radiated into the light guide plate 10 as homogeneously as possible. The arrangement of the LED lighting means 50 within the luminaire housing 110 is carried out with the aid of a carrier element 60, which is arranged in the edge region of the luminaire housing 110. The carrier element is angled as shown and forms on the one hand a vertical wall 61 on which the LED circuit board 50 is arranged, as well as a horizontal web 62 formed on the underside. As can be seen in Figure 1, the light guide plate 10 rests with its underside on this web 62, so that this web or the carrier element 60 as a whole simultaneously forms a support element for the support of the light guide plate 10. The luminaire 100 shown in Figures 1 and 2 also comprises components for emitting light towards the topside. As can be seen in particular from the illustration in Figure 1, an LED circuit board 80 with several LEDs 81 is arranged in the upper region of the luminaire housing 110. A cover element 85 arranged on this circuit board 80 is provided with corresponding openings 86 through which the light of the LEDs 81 is emitted towards the upper side. Further components of the luminaire 100 arranged above these additional LEDs 81 then also comprise corresponding 6 openings or are designed to be translucent in such a way that the light of these LEDs 81 is emitted towards the topside in the sense of indirect lighting. However, this is merely a supplementary measure for light emission, which plays no role in the inventive concept and is therefore optional. With regard to the primary light emission via the light guide plate 10 towards the underside, it must be taken into account that this light guide plate must be positioned exactly with regard to the LEDs 51 in order to enable efficient coupling of the LED light. Even small deviations in positioning could lead to inhomogeneous coupling in terms of light intensity and / or light color, which then leads to a negative appearance and a qualitatively unacceptable light emission. It should be noted that, in addition to the light guide plate 10, additional (flat) components are required to enable the most efficient and homogeneous light distribution and light emission possible. As a rule, a plate- or foil-like reflector element 20 is provided on the rear side, i.e. on the upper side of the light guide plate 10, which prevents unwanted light from escaping to the rear side. This reflector element 20 ensures that the light coupled into the light guide plate 10 is emitted essentially completely towards the underside. On the underside of the light guide plate 10, a scattering foil or another structured foil or plate can be provided again in order to increase the efficiency of the planar light outcoupling. Furthermore, in the present case, a plate-shaped diffuser 30 is additionally provided, via which the actual emission of the light takes place. All of the components just explained, including the light guide plate 10, are therefore flat elements which are arranged one above the other in a sandwich-like manner within the luminaire housing 110 and at least partially lie directly on top of one another. Since these elements have certain tolerances with regard to their thickness during their manufacture, there is a risk that simply arranging the components one above the other will result in the light guide plate 10 not being positioned exactly with regard to the LED lighting means 50. In order to avoid this, it is provided to press the light guide plate 10 onto a support that is fixedly aligned with respect to the LEDs 51, in the present case therefore to press the light guide plate 10 onto the web 62 of the carrier element 60. This ensures a defined positioning of the light guide plate 10, which at the same time, due to the known positional relationship of the surface of the web 62 with respect to the position of the LEDs 51, leads to the edge surface 12 used for the light irradiation into the light guide plate 10 being positioned in the correct manner. This pressing of the light guide plate 10 onto the support element, in the present case onto the web 62, is achieved according to the invention with the aid of a pressing element which is 7 provided with the reference numeral 40 in the figures and is shown in isolation in Figures 3 and 4. This is preferably a one-piece plastic part, which can be manufactured in particular by injection molding. As can be seen from Figures 3 and 4, this pressing element 40 initially has an elongated, approximately rectangular configuration, wherein, according to the lateral representation of Figure 4, a flat or planar base region 41 is initially formed. Starting from this base region 41, several arcuately curved fingers 45 then extend towards the upper side, which form flexible spring elements which are supported on a supporting element of the luminaire 100 provided above the light guide plate 10. The configuration shown is selected such that the pressing element 40 can be manufactured relatively easily using the injection molding process. Accordingly, the arcuate fingers 45 extend above corresponding openings or recesses in the plate-shaped base region 41 of the pressing element 40 in order to enable easy demolding of the pressing element 40 from the injection molding tool. The pressing element 40 according to the invention is then positioned, as can be seen in the figures, above the light guide plate 10, in the present case in particular above the reflector foil 20 in the luminaire housing, so that the fingers 45 extend towards the topside as shown. Here, the fingers 45 are supported with their end regions on a corresponding supporting element. In the present case, this is formed by a metal plate 90 provided on the underside of the further LED circuit board 80, which at the same time also serves to dissipate the heat generated during operation. Because this supporting element 90 is firmly installed in the housing 110 of the luminaire 100, the pressing element 40 is clamped between the supporting element 90 and the light guide plate 10 by means of the fingers 45, so that the light guide plate 10 is pressed downwards in the direction of the corresponding support surface of the web 62 as desired. The pressing element 40 rests with the base region 41 flat on the upper side of the light guide plate 10 or the reflector foil 20, so that a relatively uniform pressure is exerted on the light guide plate 10. This also represents an advantageous effect of the pressing element 40 according to the invention, since local voltage peaks, which would negatively affect a uniform distribution of the light, are avoided. As can be seen in particular in Figure 3, the pressing element 40 further comprises a hook-like end region 42 with a projection 43 at both of its ends. This projection 43 can engage in a corresponding recess of the carrier element 60 for the LED circuit board 50, as can be seen in Figure 1. This engagement results in the pressing element 40 being able to be positioned precisely in a direction parallel to the longitudinal direction of the luminaire housing 110 and this alignment is permanently maintained. The hook-like configuration of the end region 42 also means that this region can deform slightly if necessary and, in particular, can accommodate 8 temperature-related changes in length. This makes it possible to ensure a reliable arrangement and alignment of the pressing element 40 according to the invention in the luminaire housing 110 even in the event of larger temperature differences. This defined arrangement of the pressing element 40 takes place in an analogous manner on the side opposite the LED light source, whereby here - depending on the number of LED circuit boards used - a further LED light source with associated carrier element 60 or another component can be provided which enables a corresponding engagement of the end region 42 of the pressing element 40. The luminaire 100 is therefore assembled with regard to the components responsible for light generation and light emission in such a way that after the LED lighting means 50 have been arranged in the luminaire housing 110, in a subsequent step all of the flat components responsible for light distribution and light emission are loosely inserted into the luminaire housing 110. Subsequently, one or more of the pressing elements 40 according to the invention are placed on the sandwich-like structure and arranged in a defined manner on the LED carrier element 60 with the aid of the end regions 42. The subsequent arrangement of additional elements on the upper side then leads to the pressing element 40 being clamped in and thus exerting pressure on the light guide plate 10 so that it is arranged in the desired exact alignment and position with respect to the LED lighting means. This results in a simple installation of the luminaire, whereby an efficient and uniform light distribution is ensured by means of the pressing element according to the invention, since a desired exact alignment with regard to the light sources is ensured. Figures 5 to 7 show a second embodiment example of a luminaire 100 according to the invention, in which the same elements are provided with the same reference numerals. Figures 5 and 6 here show two different sections in the longitudinal direction, while Figure 7 again shows a perspective sectional view of a lateral region of the luminaire 100. This second embodiment is very similar to that of Figures 1 and 2. In particular, the pressing element 40 shown in Figures 3 and 4 is also used here. The main difference is that no additional indirect light emission is now provided, i.e. the components explained above for light emission towards the topside are no longer required. However, in this case too, the pressing element 40 is of course clamped on the one hand between the light guide plate 10 or the reflector foil 20 possibly provided on the topside of the light guide plate 10 and on the other hand between a supporting element 90 provided on the topside of the housing in order to ultimately press the light guide plate 10 in the direction of the associated support element in accordance with the invention and thus position it correctly in relation to the lighting means. This further example illustrates that, depending on the design of the luminaire 100, the supporting element 90 can be formed by different components. It is only 9 necessary that the supporting element 90 is installed sufficiently stably in the luminaire housing 110 in order to ensure that the pressing element 40 can be clamped in place. However, an exact positioning of the supporting element 90 is not absolutely necessary, since any tolerances are compensated by the flexibility of the pressing element 40. Ultimately, the inventive solution helps to ensure optimized light emission in luminaires that use the “edge-lit” technology.

Claims

1. A luminaire comprisingat least one preferably elongated LED light source for generating light,a light guide plate, wherein the LED light source is arranged on an incident edge surface of the light guide plate, such that the light generated by the LED light source is radiated into the light guide plate via the incident edge surface of the light guide plate and is emitted via at least one flat side of the light guide plate,a support element for supporting the light guide plate , anda pressing element which is arranged between the light guide plate and a supporting element opposite the support element with respect to the light guide plate and which is designed to press the light guide plate in the direction of the support element,wherein the pressing element forms at least one, preferably several spring elements which extend from a planar base region of the pressing element and are supported on the supporting element or a component arranged in front of the support element, andwherein the luminaire further comprises a carrier element for holding the LED light source and the pressing element comprises an end region which engages in a positioning opening in the carrier element.

2. The luminaire according to claim 1, wherein the spring element(s) is / are formed by fingers which extend in an arc from the planar base region in the direction of the supporting element.

3. The luminaire according to claim 1 or 2, wherein the pressing element is formed in one piece.

4. The luminaire according to any one of the preceding claims, wherein the pressing element is formed by a plastic part, preferably by an injection-molded plastic part.

5. The luminaire according to any one of the preceding claims, wherein the base region rests flat on the light guide plate or on a reflector element resting on the light guide plate.

6. The luminaire according to any one of the preceding claims, wherein the supporting element is formed by a heat sink element or another component which is arranged on a rear side of the luminaire and fastened there.

7. The luminaire according to any one of the preceding claims, wherein the carrier element comprises a first web on which the LED light source is arranged, and a second web which is angled with respect to the first web (61) and forms a support surface for the light guide plate.

8. The luminaire according to any one of the preceding claims, wherein the end region of the pressing element is deformable in a plane parallel to the light guide plate, wherein the end region is preferably designed like a hook.5 9. The luminaire according to any one of the preceding claims, wherein the LED light sourceincludes an elongated circuit board on which LEDs are distributed, wherein the length of the circuit board preferably corresponds to the length of the incident beam edge surface of the light guide plate.io 10. The luminaire according to any one of the preceding claims, wherein the luminaire comprises a housing which forms a light exit opening, wherein a disk-like diffuser element is preferably arranged in the region of the light exit opening, via which light is emitted by the luminaire.is 11. The luminaire according to any one of the preceding claims, wherein the luminaire is a floor luminaire or a pendant luminaire.

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