Lighting device with a light mixing chamber

Abstract

: A lighting device (1) comprising a lamp shade (2) and a light engine (3) enclosed in said lamp shade (2), the light engine (3) comprising: - a housing having two opposite side walls (7) extending from a base (4) and delimiting a light exit window (11) located opposite to the base (4), - a first light source comprising a plurality of first LED's (5) arranged on a first 5 carrier (6), the first light source being provided in the housing and arranged to emit light towards the light exit window (11), wherein the lighting device (1) further comprises a light mixing chamber (10) that is formed between the base (4), the two opposite side walls (7) and a cover (8) that is extending between the two opposite side walls (7) and closing the light exit window (11), 10 wherein the cover (8) is (i) part of the lamp shade (2) or (ii) part of the housing of the light engine (3) with the cover (8) facing a portion (2a) of the lamp shade (2), and wherein the light mixing chamber (10) has a spiral or helical shape.

Description

[0001] Lighting device with a light mixing chamber

[0002] FIELD OF THE INVENTION

[0003] The invention relates to a lighting device using a light mixing chamber to provide a particular aesthetic effect.

[0004] BACKGROUND OF THE INVENTION

[0005] The use of light emitting diodes (LED) for illumination purposes continues to attract attention. Compared to incandescent lamps, fluorescent lamps, neon tube lamps, etc., LED’s provide numerous advantages such as a longer operational life, a reduced power consumption, and an increased efficiency related to the ratio between light energy and heat energy. In particular, LED filament lamps are highly appreciated as they are very decorative.

[0006] LED strips or filaments are usually straight. Curling them up into a spiral makes it possible to have long length of LED strips or filaments into a small diameter cylinder when mounted inside a tube.

[0007] For example, US 2015 / 0285472 discloses such an arrangement. The appearance of this lighting device with a curved LED strip is appreciated but not optimized to provide particular esthetic effect.

[0008] US 2022 / 228715 discloses a lighting device having a light-emitting filament comprising a plurality of solid-state light sources and an elongated reflector to reflect light emitted by the light-emitting filament. The reflector has a longitudinal groove in which the light-emitting filament is arranged such that the reflector and the light-emitting filament extend longitudinally along a common path that is curved in three dimensions.

[0009] SUMMARY OF THE INVENTION

[0010] Hence, it is an object of the present invention to produce lighting devices showing improved decorative lighting.

[0011] To this end, a lighting device with a lamp shade enclosing a light mixing chamber with a spiral or helical shape is provided. A first light source, such as a LED strip or a LED filament, is arranged on a carrier, such as a flexible carrier, that is positioned at a base of the light mixing chamber located opposite to a light exit window of the light mixing chamber.

[0012] In operation, the lighting device emits light, such as white light having a correlated color temperature in a range from 1800 K to 6500 K, and / or a color rendering index of at least 80.

[0013] The mixing chamber provides a light effect that is visible on an exterior surface of the lamp shade, the light effect taking the form of a spiral, or a helix, or a swirl, while spottiness of the LEDs is prevented. The light effect may even be a pixelated light effect.

[0014] More specifically, the invention relates to a lighting device comprising a lamp shade and a first light engine enclosed in the lamp shade.

[0015] The first light engine comprises a housing having two opposite side walls (z.e., two side walls opposite from each other) extending from a base and delimiting a light exit window located opposite to the base, and a first light source comprising a plurality of first LEDs arranged on a first carrier, wherein the first light source is at least partly provided in the housing and arranged to emit light towards the light exit window.

[0016] The lighting device further comprises a light mixing chamber that is formed between the base, the two side walls and a cover that extends between the two side walls and that closes the light exit window.

[0017] The cover is either part of the lamp shade or part of the housing of the first light engine. When the cover is part of the lamp shade, the cover is a first portion of the lamp shade. When the cover is part of the housing of the first light engine, the cover faces a first portion of the lamp shade. When, in the remainder of this description, reference is made to ’’the first portion of the lamp shade”, what is meant is either the cover (in the situation that the cover is part of the lamp shade) or the part of the lamp shade that faces the cover (in the situation that the cover is part of the housing of the first light engine).

[0018] The light mixing chamber has a spiral or helical shape.

[0019] The cover extends between the two side walls and closes the light exit window. For this purpose, the cover may either be inserted between the two side walls, or it may be adjacent to the respective ends of the two side walls.

[0020] The first portion of the lamp shade may be transparent. In case the cover is part of the lamp shade, the first portion of the lamp shade is the cover, so hence the cover is transparent. In case the cover is part of the housing of the first light engine, the first portion of the lamp shade is the part of the lamp shade that faces the cover. In that case, not only the first portion but also the cover may be transparent.

[0021] The cover and the two side walls may have different optical properties to change the light effect visible through the lamp shade.

[0022] In a first variant, the cover is a diffuser having a first reflectance R1 and each of the two opposite side walls has a second reflectance R2, wherein the second reflectance R2 is at least 20 % larger than the first reflectance Rl, such as at least 30 % larger than the first reflectance Rl, or at least 40 % larger than the first reflectance Rl, or at least 50 % larger than the first reflectance Rl. In other words, R2 > Rl+20 %, such as R2 > Rl+30 %, or R2 > Rl+40 %, or R2 > Rl+50 %. The second reflectance R2 of the side walls may be at least 70 %, such as at least 80 %, or at least 85 %, or at least 88 %, or at least 90 %.

[0023] The first variant ensures that, in operation, a majority of the light emitted by the plurality of LEDs is emitted out of the mixing chamber and through the lamp shade in such a way that the spiral- or helical-shaped light effect is visible on an exterior surface of the lamp shade in the form of an area of relatively high brightness surrounded by an area of relatively low brightness.

[0024] In a second variant, the cover is a diffuser having a first reflectance Rl and each of the two opposite side walls has a second reflectance R2, wherein the second reflectance R2 is at least 20 % smaller than the first reflectance Rl, such as at least 30 % smaller than the first reflectance Rl, or at least 40 % smaller than the first reflectance Rl, or at least 50 % smaller than the first reflectance Rl. In other words, R2 < Rl-20 %, such as R2 < Rl-30 %, or R2 < Rl-40 %, or R2 < Rl-50 %. The first reflectance Rl of the cover may be in a range from 30 % to 65 %, such as in a range from 35 % to 60 %, or in a range from 40 % to 55 %. The second reflectance R2 of the side walls may be smaller than 28%, such as smaller than 25%, or smaller than 23%.

[0025] The second variant ensures that, in operation, a majority of the light emitted by the plurality of LEDs is emitted out of the mixing chamber and through the lamp shade in such a way that the spiral- or helical-shaped light effect is visible on an exterior surface of the lamp shade in the form of an area of relatively low brightness surrounded by an area of relatively high brightness.

[0026] In each of the first and second variants, part of the light that is emitted by the first light source is not reflected but instead transmitted through the two opposite side walls and / or through the diffusive cover. The absorption of light by the two side walls and / or by the diffusive cover may be less than 3 %, such as less than 2 %, or less than 1 %. In each of the first and second variants, the first reflectance R1 of the cover may be in a range from 25 % to 45 %, such as in a range from 28 % to 42 %, or in a range from 30 % to 40 %.

[0027] In a third variant, the cover is a diffuser and each of the two opposite side walls is transparent. The third variant further improves the visibility of the spiral- or helicalshaped light effect on an exterior surface of the lamp shade.

[0028] The cover is either part of the lamp shade or part of the housing of the first light engine. When the cover is part of the lamp shade, the cover is a first portion of the lamp shade. When the cover is part of the housing of the first light engine, the cover faces a first portion of the lamp shade.

[0029] Next to a first portion (that either constitutes the cover or faces the cover), the lamp shade may comprise a second portion that is separate from the first portion, wherein the first portion and the second portion of the lamp shade have different optical properties.

[0030] The first portion of the lamp shade and / or the cover may be transparent with the second portion of the lamp shade being light diffusive, or the first portion of the lamp shade and / or the cover is light diffusive with the second portion of the lamp shade being transparent.

[0031] The first light engine has a housing with two opposite side walls extending from a base and delimiting a light exit window located opposite to the base. The first light engine further has a first light source comprising a plurality of first LEDs. The first light source is at least partly provided in the housing and arranged to emit light towards the light exit window.

[0032] The plurality of first LEDs is arranged on a first carrier. As long as the first light source is at least partly provided in the housing and arranged to emit light towards the light exit window, the first carrier may be at least partly arranged outside the housing, such as at least partly on the base of the housing. This arrangement allows to improve the thermal management, thereby improving reliability and efficiency. The base may be provided with a plurality of holes to accommodate the plurality of first LEDs protruding through the plurality of holes.

[0033] The swirl light effect may have a gradient in intensity and / or color and / or correlated color temperature. This may be obtained by using a pixelated LED strip which provides a gradient in intensity and / or color and / or correlated color temperature. Alternatively, or additionally, this may also be obtained by using a lamp shade or cover in which the reflectivity and transmissivity varies in a given direction. More specifically, the optical properties of the first portion of the lamp shade and / or of the cover may vary along the spiral or helical shape of the light mixing chamber. Additionally or alternatively, the optical properties of the first portion of the lamp shade and / or of the cover may vary in a direction parallel to a longitudinal axis of the lighting device and / or in a direction perpendicular to a longitudinal axis. Such a variation may occur gradually or in a stepwise manner, and serves to further enhance the decorative light effect.

[0034] The light mixing chamber may comprise at least three loops, of which at least one loop has N variations in optical properties, N being equal to or larger than 5.

[0035] To obtain a desired variation of the optical properties, the first portion of the lamp shade and / or the cover may have a thickness that is locally decreased or increased. Additionally or alternatively, the first portion of the lamp shade and / or the cover may comprise reflective particles, wherein a concentration and / or a type of the reflective particles is locally changed,

[0036] The lighting device has a first light source comprising a plurality of first LEDs. Each LED of the plurality of first LEDs may be individually controllable. The lighting device may then further comprise a controller for individually controlling the LEDs of the plurality of first LEDs to vary the intensity and / or color point of the LEDs to obtain a light gradient along the spiral or helical shape of the light mixing chamber.

[0037] The first light source may comprise a LED filament or a LED strip.

[0038] A LED filament typically comprises an array of LEDs that is arranged, mounted and / or mechanically coupled to a carrier or substrate. The term “array” refers to a linear arrangement or chain of LEDs, for example of 20 or more LEDs. The carrier or substrate is configured to support the LEDs, and it may be rigid or flexible. A LED filament typically further comprises an encapsulant enclosing the array of LEDs, wherein the encapsulant comprises a light-transmissive material, and optionally a luminescent material for at least partially converting the light emitted by the LEDs. The term “encapsulant” refers to an elongated material, element, arrangement, or the like, which is configured or arranged to at least partially surround, encapsulate and / or enclose the array of LEDs. The term “light- transmissive material” refers to a material, composition and / or substance which is configured to transmit light.

[0039] The lighting device may further comprise a second light engine comprising a second light source. The second light engine may be at least partly enclosed by the first light engine, and it may also be at least partly enclosed by the first light engine. The second light source may be a LED filament. In other words, the second light engine may be a LED filament lamp.

[0040] The lamp shade and at least part of the housing may be manufactured by 3D printing.

[0041] Further objectives of, features of, and advantages with, the present invention will become apparent when studying the following detailed disclosure, the drawings and the appended claims. Those skilled in the art will realize that different features of the present invention may be combined to create embodiments other than those described in the following.

[0042] BRIEF DESCRIPTION OF THE DRAWINGS

[0043] This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing embodiment(s) of the invention.

[0044] Fig. 1 shows a perspective view of a lighting device,

[0045] Fig. 2 shows a perspective view of part of the light engine enclosed in the lamp shade of the lighting device of Fig. 1,

[0046] Fig. 3 schematically shows a partial cross-sectional view of a first type of lighting device,

[0047] Fig. 4 schematically shows a partial cross-sectional view of a second type of lighting device,

[0048] Fig. 5 shows an arrangement of a LED strip on a carrier.

[0049] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0050] Figure 1 shows a lighting device 1, which comprises a lamp shade 2 and a first light engine 3 enclosed in the lamp shade 2.

[0051] Figure 2 shows part of the first light engine 3 enclosed in the lamp shade 2 of the lighting device 1.

[0052] The first light engine 3 comprises a housing with a base 4 and two opposite side walls 7 extending from the base 4 and delimiting a light exit window 11 located opposite to the base 4.

[0053] The first light engine 3 further comprises a first light source positioned on a carrier 6 which is arranged on the base 4 of the housing. The first light source comprises a plurality of LEDs 5, such as in the form of a LED filament or a LED strip, arranged on the carrier 6. The light exit window 11 is closed by a cover 8.

[0054] In a first variant of the lighting device 1, the cover 8 is a first portion 2a of the lamp shade 2, as schematically shown in Figure 3.

[0055] In a second variant of the lighting device, the cover 8 is distinct from the lamp shade 2 and part of the housing of the first light engine 3, as schematically shown in Figure 4 and as represented in Figure 1. The cover 8 then faces the first portion 2a of the lamp shade 2.

[0056] The distance between the plurality of LEDs 5 and the cover 8 may be between 1 and 5 cm to prevent spottiness in the on-state of the lighting device 1.

[0057] A light mixing chamber 10 is formed between the base 4, the two opposite side walls 7 and the cover 8. The light mixing chamber 10 is shaped in the form of a spiral or a helix, for example with three or more loops or windings.

[0058] The lamp shade 2 may have a conical shape or a cylindrical shape, to accommodate the housing against an inner surface of the lamp shade 2. The lamp shade 2 may be formed of a continuous wall enclosing the housing.

[0059] The housing may have a polygonal cross-section, such as a rectangular crosssection or a square cross-section, or a cross-section of any shape appropriate for arranging the carrier 6 on the base 4. In the example of Figure 2, the side walls 7 extend from the base 4 to form a truncated conical shape with the carrier 6 being located at the smaller base of the truncated cone.

[0060] The carrier 6 is configured to mechanically and / or electrically support the plurality of LEDs 5. The carrier 6 may be a printed circuit board (PCB). The carrier 6 may be light transmissive and / or reflective. Furthermore, the carrier 6 may be flexible, and may for example comprise a foil made from a polymer, such as polyimide (PI) or polyethylene terephthalate (PET). The carrier 6 may comprise one or more thermally conductive layers and one or more insulating layers. The carrier 6 may be attached to the two opposite walls 7 by means of an adhesive and / or a mechanical fasteners.

[0061] The carrier 6 may be at least partly arranged on the base 4 outside the housing, while the first light source as a whole is still at least partly provided inside the housing and arranged to emit light towards the light exit window 11.

[0062] As shown in Figure 5, the base 4 may be provided with a plurality of holes 9 to accommodate the LEDs 5 of the light source such that the LEDs 5 protrude into the housing through the holes 9. In terms of optical properties of the lamp shade and housing, various options are available for changing the light effect that is visible through the lamp shade.

[0063] The cover and the two opposite side walls may have the same optical properties. For example, the side walls and the cover may be transparent. Alternatively, the side walls and the cover may be light diffusive.

[0064] The cover and the two opposite side walls may also have different optical properties.

[0065] In one variant, the cover is a diffuser having a reflectance that is less than that of the side walls. For example, the cover has a first reflectance R1 and the side walls have a second reflectance R2, wherein the second reflectance R2 is at least 20 % larger than the first reflectance Rl, or, in other words, R2 > Rl+20 %.

[0066] In a second variant, the cover is a diffuser having a reflectance that is higher than the reflectance of the side walls. For example, the cover has a first reflectance Rl and the side walls have a second reflectance R2, wherein the second reflectance R2 is at least 20 % smaller than the first reflectance Rl , or, in other words, R2 < Rl -20 %.

[0067] In a third variant, the cover is a diffuser and the two opposite side walls are transparent.

[0068] Irrespective of the optical properties of the side walls, the cover may be transparent. The cover is either part of the lamp shade, in which case it is a first portion of the lamp shade, or the cover is part of the housing, in which case it faces a first portion of the lamp shade. In the former situation, the first portion, and hence the cover, may be transparent. In the latter situation, the cover and the first portion may both be transparent.

[0069] Next to a first portion (that either constitutes the cover or faces the cover), the lamp shade may comprise a second portion that is separate from the first portion, wherein the first portion and the second portion of the lamp shade have different optical properties.

[0070] The first portion of the lamp shade, which is either the cover or the part of the lamp shade that faces the cover, and the second portion of the lamp shade may have different optical properties.

[0071] The first portion of the lamp shade may be transparent and the second portion of the lamp shade may be light diffusive. Alternatively, the first portion of the lamp shade may be light diffusive and the second portion of the lamp shade may be transparent.

[0072] The optical properties of the cover and / or of the first portion of the lamp shade may vary along the spiral or helical shape of the housing. Additionally or alternatively, the optical properties may also vary in a direction along a longitudinal axis of the lighting device and / or in a direction perpendicular to a longitudinal axis of the lighting device. For example, for at least one loop of the spiral or helical shape, there may be at least five variations in the optical properties along the loop. The variations may occur gradually or in a stepwise manner. The variation may result from a change in the thickness of the cover and / or of the first portion of the lamp shade facing the cover, with a local increase or decrease of the thickness to obtain the desired variation. This variation may also result from a local change in the chemical composition of the cover and / or of the first portion of the lamp shade facing the cover.

[0073] The cover and / or the first portion of the lamp shade facing the cover may comprise reflective particles such as Ba2SO4, TiCh, AI2O3 or SiCh particles with a concentration and / or type of particles being variable along the spiral or helical shape of the housing, and / or in a direction parallel to the longitudinal axis of the lighting device, and / or in a direction perpendicular to the longitudinal axis of the lighting device.

[0074] The lighting device has a first light source comprising a plurality of first LEDs. Each LED of the plurality of first LEDs may be individually controllable. The lighting device may then further comprise a controller for individually controlling the LEDs of the plurality of first LEDs to vary the intensity and / or color point of the LEDs to obtain a light gradient along the spiral or helical shape of the light mixing chamber.

[0075] The lighting device may comprise a second light engine at least partly enclosed in the housing. The second light engine may also be at least partly enclosed by the first light engine. The second light engine has a second light source. The second light source may be a LED filament. In other words, the second light engine may be a LED filament lamp.

[0076] The lamp shade and at least a part of the housing may be manufactured by 3D printing.

[0077] The lamp shade, the housing, and the cover may be manufactured by 3D printing as separate components, but they may also be manufactured by 3D printing as a single, monolithic, component.

[0078] Different 3D printing techniques may be used, such as any one of fused filament fabrication, stereolithography, UV LCD, polyjet printing, multijet printing, colorjet printing, binder jetting, selective laser sintering, selective laser melting, direct metal laser sintering, electron-beam additive manufacturing, multi -jet fusion techniques, and any combination thereof. When choosing fused filament fabrication as 3D printing technique, the lamp shade and at least part of the housing may be made from polycarbonate, polyethylene terephthalate or polyethylene terephthalate glycol, but any other material suitable for use as printable material in fused filament fabrication may be employed. A method for manufacturing the spiral- or helical-shaped housing by means of fused deposition modelling may comprise the following steps. In a first step, a computer- aided design (CAD) of a straight version of the housing is prepared. In other words, the housing is designed as a straightened or rolled-out version of the desired spiral or helical shape. In a second step, the CAD of the straightened (or rolled-out) version of the housing is sliced with a G-code slicing program, to provide process settings and coordinates in an XYZ space. In a third step, the XYZ coordinates are transformed into X-Rotation-Z coordinates. In a fourth step, the transformed coordinates are used to print the housing with a printer having a rotating cylindrical mandrel as building platform. In such a printer, the printer head moves along an X-axis gantry, which can move up and down along the Z-axis. The Y-axis has been replaced by a rotation axis around which the cylindrical mandrel can rotate. This results in the housing, which was designed in a straightened (or rolled-out) version, being printed with a spiral- or helical shape onto the rotating cylindrical mandrel. In a fifth step, the spiral- or helical-shaped housing can be removed from the cylindrical mandrel, ready to be assembled together with a lamp shade to form a lighting device.

Claims

CLAIMS:

1. A lighting device (1) comprising a lamp shade (2) and a first light engine (3) enclosed in the lamp shade (2), the first light engine (3) comprising: a housing having two opposite side walls (7) extending from a base (4) and delimiting a light exit window (11) located opposite to the base (4), and a first light source comprising a plurality of first LEDs (5) arranged on a first carrier (6), the first light source being at least partly provided in the housing and arranged to emit light towards the light exit window (11), wherein the lighting device (1) further comprises a light mixing chamber (10) that is formed between the base (4), the two side walls (7) and a cover (8) that extends between the two side walls (7) and closes the light exit window (11), wherein the cover (8) is (i) a first portion of the lamp shade (2) or (ii) part of the housing of the first light engine (3) and facing a first portion (2a) of the lamp shade (2), wherein the light mixing chamber (10) has a spiral or helical shape, wherein the cover (8) and the two side walls (7) have different optical properties, wherein the cover (8) is a diffuser having a first reflectance Rl, and wherein (i) the two side walls (7) have a second reflectance R2 with R2 < Rl- 20 % or (ii) the two side walls (7) are transparent.

2. The lighting device (1) according to claim 1, wherein the first portion (2a) of the lamp shade (2) is transparent.

3. The lighting device (1) according to any one of the previous claims, wherein the lamp shade (2) comprises a second portion separate from the first portion (2a), and wherein the first portion (2a) and the second portion have different optical properties.

4. The lighting device (1) according to claim 3, wherein the first portion (2a) of the lamp shade (2) is transparent and the second portion of the lamp shade (2) is lightdiffusive, or wherein the first portion (2a) of the lamp shade (2) is light diffusive and the second portion of the lamp shade (2) is transparent.

5. The lighting device (1) according to any one of the previous claims, wherein the first carrier (6) is at least partly arranged on the base (4) outside the housing.

6. The lighting device (1) according to claim 5, wherein the base (4) is provided with a plurality of holes (9) to accommodate the portion of the plurality of first LEDs (5) protruding through the plurality of holes (9).

7. The lighting device (1) according to any one of the previous claims, wherein at least one of the first portion (2a) of the lamp shade (2) and the cover (8) has optical properties that vary (i) along the spiral or helical shape of the light mixing chamber (10), and / or (ii) in a direction parallel to a longitudinal axis of the lighting device (1), and / or (iii) in a direction perpendicular to a longitudinal axis of the lighting device (1).

8. The lighting device (1) according to claim 7, wherein the light mixing chamber (10) comprises at least three loops, wherein at least one loop has N variations in optical properties, and wherein N is at least 5.

9. The lighting device (1) according to any one of claims 7 and 8, wherein, for obtaining the varying optical properties, at least one of the portion (2a) of the lamp shade (2) and the cover (8) (i) has a thickness that is locally decreased or increased, and / or (ii) comprises reflective particles, wherein a concentration and / or a type of the reflective particles is locally changed.

10. The lighting device (1) according to any one of the previous claims, wherein the first light source comprises a LED filament or a LED strip.

11. The lighting device (1) according to any one of the previous claims, wherein each LED of the plurality of first LEDs (5) is individually controllable, and wherein the lighting device (1) comprises a controller for individually controlling the LEDs of the plurality of first LEDs (5) to vary the intensity and / or color point of the LEDs to obtain a light gradient along the spiral or helical shape of the light mixing chamber (10).

12. The lighting device (1) according to any one of the previous claims, wherein the lighting device (1) further comprises a second light engine at least partly enclosed by the first light engine (3).

13. The lighting device (1) according to any one of the previous claims, wherein the lamp shade (2) and at least part of the housing are manufactured by 3D printing.

Images