Lighting equipment, lamps and refrigerators

Abstract

The invention relates to a lighting device comprising a dome-shaped cylindrical lens (7) having an optical focal line (19) and a plurality of light sources (3) arranged along the focal line and configured to emit light during operation. The lens is arranged to receive the light and deflect the light into a beam having an angle y in a transverse direction, wherein 0′≤7≤30′. In transverse cross-section, the cylindrical lens comprises a central portion (21) flanked by a first side portion (23) and a second side portion (25). The lighting device further comprises an axially extending barrier arranged adjacent to the first side portion; and an axially extending diffuser provided at the second side portion.

Description

Technical Field

[0001] The present invention relates to a lighting device, a lamp comprising the lighting device, and a refrigerator comprising the lighting device and / or the lamp. Background Art

[0002] The present invention generally relates to lighting devices for providing uniform light distribution, particularly for evenly illuminating wall-mounted spotlights, wall washers, or merchandise on long shelves in refrigerator compartments. One prominent approach to illuminating long shelves is retrofitting T-LED lamps, which can more economically replace the fluorescent lamps typically used to illuminate refrigerator shelves. Compared to fluorescent tubes, light-emitting diodes (LEDs) offer higher efficiency at the low temperatures typically used in refrigerator applications and a longer lifespan at low temperatures (e.g., 50,000-100,000 hours). The key advantages of longer lifespan, lower power consumption, higher efficacy at lower temperatures, and compact package size make LEDs an ideal light source for supermarket freezer lighting. The linear geometry of T-LED lamps is suitable for long shelves, as the illumination is sufficient to illuminate the merchandise within the compartment. However, due to their relatively large size compared to the frame, providing T-LEDs within the refrigerator frame is cumbersome. Therefore, a need exists to replace T-LEDs with basic LED strips. Such LED strips can be economically provided as low-cost LEDs on a low-voltage ribbon, with the LED dies typically spaced every 10-20 mm.

[0003] Because LEDs typically radiate into a hemisphere, optical lenses are necessary to distribute their light output and collimate / deflect the (typically Lambertian) emission beam of the LED into a relatively narrow beam. Typically, such optical devices are mounted as domes on the LEDs individually. However, cylindrical continuous lenses extending over the multiple LEDs in an LED strip are now also being used. However, even with these cylindrical lenses, the illumination of such LED strips appears to suffer from various drawbacks. For example, when mounted as light sources on refrigerator door frames, this has led to customer complaints about the light source's dot-like appearance, sometimes referred to as a "Christmas tree." This appearance gives potential buyers the impression of a cheap, low-quality refrigerator and can also cause undesirable distraction due to glare. As a countermeasure to avoid the undesirable visible dot-like appearance of the LED strip, it can be shielded from direct view by an additional, relatively large glare shield. However, this has the disadvantage of reducing the lighting device's efficiency, as it also blocks light useful for illuminating the shelves / products, and makes the lighting device relatively expensive and bulky. Summary of the Invention

[0004] It is an object of the present invention to provide a lighting device of the type described in the opening paragraph in which at least one of the above-mentioned disadvantages is eliminated. To this end, the lighting device comprises:

[0005] - a dome-shaped cylindrical lens having an optical focal line defining a principal axis;

[0006] - a plurality of light sources arranged along the main axis and configured to emit light during operation;

[0007] The lens is configured to receive the light and deflect the light into a beam having an angle γ in a direction transverse to the main axis at the FWHM, wherein preferably 0°<=γ<=45°, and in a transverse cross section, the cylindrical lens comprises a central portion flanked by a first side portion and a second side portion;

[0008] - an axially extending barrier disposed adjacent the first side; and

[0009] - an axially extending diffuser provided at the second side,

[0010] wherein the cylindrical lens comprises an inner lens surface facing the plurality of light sources and an outer lens surface facing away from the light sources, and wherein the diffuser is provided at least on the outer lens surface.

[0011] In this context, full width at half maximum (FWHM) is the width of a beam measured between points at half the beam's maximum intensity. The present invention is preferably based on LED strips and addresses the shortcomings of the prior art for suitable illumination of uniformly illuminated LED shelf lights. The inventors discovered that the undesirable point-like appearance is the result of reflections of the individual LED dies at the surface of the cylindrical lens on the second side, required to shape the light emitted by the LEDs into the desired narrow beam. Consequently, the customer cannot directly view the individual LEDs, as they are shielded from direct viewing by a barrier formed, for example, by the frame of the refrigerator door. However, the customer is typically exposed to glare caused by viewing the images reflected by the individual LEDs in the surface on the second side of the cylindrical lens. This second side is typically not shielded from direct viewing by the refrigerator door frame, as this would make the frame too large. Providing an axially extending reflective diffuser on the second side of the lens blurs or diffuses the point-like appearance of the LED reflected image, thereby reducing the undesirable "Christmas tree" effect and lowering glare. Providing a diffuser at the collimating lens is counterintuitive, as a diffuser typically causes the beam to widen, whereas a collimator is intended to narrow the beam from a Lambertian light emitter. However, it appears that by providing the diffuser at the designated location of the lens, i.e. at the second side, the widening effect of the diffuser is acceptably small, and a satisfactory blurring effect of the LED dot-like appearance is also achieved. The transverse direction can, for example, be a direction perpendicular to the main axis, such as a transverse cross-section can be a cross-section perpendicular to the main axis. In the context of the present invention, the expression extending along the main axis can be interpreted as being close to, such as extending parallel to, the main axis, or can be interpreted as coinciding with the main axis. Typically, suitable lens materials are, for example, polymethyl methacrylate (PMMA), polycarbonate (PC), polyethylene terephthalate (PET), and polyethylene (PE). The beam having an angle γ at FWHM in a direction transverse to the main axis is preferably 0° <= γ <= 45°, as being wider than 45° increases the risk of excessive spillover light.

[0012] The lighting device is characterized in that the cylindrical lens comprises an inner lens surface facing the plurality of light sources and an outer lens surface facing away from the light sources, and wherein the diffuser is provided at least on the outer lens surface. It appears that this specific location of the diffuser region on the outer surface advantageously combines the effect of counteracting the point-like appearance with only a slight widening of the deflected narrow light beam. Furthermore, it makes the lighting device relatively compact while still achieving the desired combined effect. The diffuser may be provided only on the outer surface of the lens, but in addition, the lighting device may be characterized in that, for example, it further comprises a reflector having a reflective surface facing the lens, wherein the reflector is arranged adjacent to the second side portion, and wherein the diffuser is provided on the reflective surface.

[0013] The lighting device may be characterized in that each of the plurality of light sources is located on a focal line, and each light source has a respective optical axis extending through the cylindrical lens in a direction transverse to the main axis. Deflection of the Lambertian beam profile emitted by the LED is then relatively effective for converting the beam into a desired narrow beam.

[0014] The lighting device may have the following features: A dome-shaped lens extends over the plurality of light sources within an angle α, with respect to rotation relative to the focal line, where 90° <= α <= 160°. A larger angle α improves the lens's ability to capture and deflect the light emitted by the LEDs, thereby increasing the lighting device's efficiency. For example, the lens can extend up to 180°, though in practice 160° is sufficient. However, the lens is preferably as small as possible, i.e., no less than 90°, to save cost and weight and make the lighting device compact.

[0015] The lighting device may have the following features: the first side has an axially extending first outer edge, and the barrier shields the dome from the first outer edge within an angle β for rotation relative to the focal line, where 10°<=β<=50°. Such shielding at angle β makes the barrier relatively small, but effectively shields the LED from direct viewing. A larger barrier is not necessary because distracting indirect viewing (i.e., visibility of a point reflected image of the LED at the second side of the cylindrical lens) is offset by the axially extending diffuser at the second side.

[0016] The lighting device may have the following feature, the second side portion has an axially extending second outer edge, and wherein the diffuser forms a second outer edge extending from the second outer edge at an angle of 100° with respect to the rotation relative to the focal line. The diffuser area where and wherein the diffuser area extends within an angle Θ, wherein 5° <= Θ <= 15°. It appears that in particular this designated diffuser area effectively counteracts the dot-like appearance, combined with a slight widening of the deflected narrow light beam. Specifically, in some embodiments, And 8°<=Θ<=12° seems to provide a well-balanced and effectively desired result in terms of lighting, shielding, and offset dotted appearance.

[0017] The lighting device may be characterized by the diffuser comprising at least one of: a white powder coating, white tape, white spray coating, frosted portions, and etched surface structures. These are typical and convenient forms of providing and applying the diffuser on and near the optical surface.

[0018] The lighting device may be characterized by an extruded cylindrical lens and a co-extruded diffuser. This is a preferred manufacturing method, for example, in injection molding of the lens, where the diffuser is subsequently applied in a separate process step, as it is a relatively inexpensive, accurate, and fast method for producing a continuous, elongated cylindrical lens. This method has the further advantage of being able to cut the cylindrical lens to size. Suitable lens materials that are typically extrudable are PMMA and PC, with the co-extruded diffuser having the same carrier material as the lens but subsequently doped with scattering particles, such as TiO2, Al2O3, ZrO2, or SiO2 particles.

[0019] The lighting device may be characterized in that the diffuser is an anisotropic diffuser having a higher degree of diffusion in a main direction than in a lateral direction. This provides the lighting device with the advantage that only the point-like appearance of the lighting device is substantially offset, while there is substantially no beam broadening in the lateral direction, thereby making the lighting device more efficient.

[0020] The lighting device may be characterized in that the diffuser has a beam widening effect that widens the light beam by an angle δ, where 1° <= δ <= 5°. It appears that in practical cases such beam widening is effective in counteracting the spot-like appearance, while the negative impact of the beam widening on the desired lighting distribution of the merchandise on the shelf may be acceptably low.

[0021] The present invention also relates to a luminaire comprising a housing containing the lighting device according to the present invention and a fixing device for mounting the luminaire to a carrier. The luminaire can be mounted, for example, on a refrigerator door frame or on a wall or ceiling for use as a lightweight wall washer.

[0022] The invention further relates to a refrigerator comprising a refrigerator door frame, a refrigerator compartment comprising at least one shelf and covered by the refrigerator door, wherein a lighting device according to the invention or a lamp according to the invention is mounted on a first vertical upright of the door frame for illuminating the front of the shelf closest to the refrigerator door from a first direction.

[0023] The refrigerator may have the following features: it includes additional lighting devices and / or lamps according to the present invention, which are mounted on a second vertical column opposite the first vertical column and are used to illuminate the front of the shelf closest to the refrigerator door from a second direction opposite the first direction. Thus, the merchandise on the refrigerator shelf can be illuminated from both sides, thereby presenting the merchandise in a more attractive manner for customers. Each lighting device, including each LED, can be individually controlled, allowing the desired color distribution and light intensity distribution to be selected to achieve optimal illumination of the displayed merchandise. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention will now be further explained by means of schematic diagrams which are not drawn to scale, wherein the dimensions of some features may be exaggerated for the purpose of explanation. The accompanying drawings are in no way intended to limit the scope of the invention, but rather to illustrate the numerous possibilities of the invention. In the drawings:

[0025] Figure 1A-1B Shows a prior art lighting device and its appearance when used in a refrigerator application;

[0026] Figure 2A-2B The first embodiment of the lighting device according to the present invention and its appearance when applied to a refrigerator are shown;

[0027] Figure 3A-3B A perspective view and a transverse cross-sectional view respectively show a luminaire comprising a second embodiment of a lighting device according to the present invention;

[0028] Figure 4A-4B A refrigerator comprising two lighting devices according to the present invention is shown, and

[0029] Figure 5 A luminaire comprising a lighting device according to the invention is shown. DETAILED DESCRIPTION

[0030] Figure 1A-1B The figure shows a prior art lighting device 1 and its appearance in a refrigerator application. The lighting device comprises a plurality of light sources 3, which in the figure are LED strips, which emit light 5 having a Lambertian beam profile during operation, i.e., the light source light. A cylindrical lens 7 is mounted above the LED strips. The cylindrical lens has a dome-shaped cross section and deflects the light source light into a (relatively) narrow beam 9 that is deflected from the LED strips towards an object 11. Figure 1A-1B In the example, the object is merchandise, but it could alternatively be a wall, a shelf, or a painting. The customer 13 can see the merchandise illuminated by the light source. However, due to the negative side effect of the merchandise lighting, the customer is also distracted by the light source, which is visible to the customer as well as its image 15 reflected in the lens. This negative effect is as follows: Figure 1B shown in , and is often referred to by customers as the “Christmas Tree” effect due to its dotted appearance.

[0031] Figure 2A-2BA first embodiment of a lighting device 1 according to the present invention and its appearance when used in a refrigerator application is shown. The lighting device includes a plurality of light sources 3 that, during operation, emit light having a Lambertian beam profile, namely, source light 5. The light source is an LED strip extending axially along a principal axis 17 (perpendicular to the paper). An axially extending cylindrical lens 7 is mounted above the LED strip such that the LED strip lies on a focal line 19 of the cylindrical lens, coinciding with the principal axis, which collimates or deflects the Lambertian beam profile into a deflected beam 9 having a beam angle γ of approximately 15° at full width half maximum (FWHM). The lens has a central portion 21 flanked by a first side portion 23 and a second side portion 25. In a transverse direction, the cylindrical lens has a dome-shaped cross-section extending at an angle α of approximately 90° across the LED strip and deflects the source light into a (relatively) narrow beam 9 that is deflected from the LED strip toward a product 11. The product illuminated by the light source is visible to a customer 13. The customer's direct view of the light source is blocked by an axially extending barrier 27 provided adjacent the first side of the lens, which shields the dome from the first outer edge 29 at an angle β of approximately 15°. The cause of glare to the customer by the sharp reflected image 15 of the light source (LED die) in the second side of the lens is counteracted because an axially extending diffuser 33 (white tape in the figure) is provided at the outer surface 35 of the lens at the second side. The white tape extends from the second outer edge 31 of the lens at an angle of approximately 20° to the outer surface 35 of the lens. and extends within an angle Θ of approximately 10°. Angles α, β, and Θ are determined with respect to the rotation relative to the focal line. The white tape diffuses a portion of the deflected light from the source and causes a beamlet widening δ of about 3° (determined with respect to the rotation of the white tape). Figure 2B As shown, a more visually appealing reflected image 15 is thus obtained in which the continuous light is formed as strips, rather than distracting visible dotted lines.

[0032] Figure 3A-3B A perspective view and a transverse section, respectively, of a luminaire 37 comprising a second embodiment of a lighting device 1 according to the invention are shown.

[0033] The luminaire includes an elongated housing 39 extending along a principal axis 17. The housing houses the lighting device and includes a fixing device 41, which is shown as a mounting ridge, but could alternatively or additionally be a screw, bolt, magnet, or snap-on feature. The luminaire includes an axially extending LED strip 3, arranged on the focal line 19 of an axially extending cylindrical lens 7. The LED strip 3 is dome-shaped in transverse cross-section and extends axially above the LED strip. Viewed in cross-section, the dome shape extends over an angle α of approximately 115°, wherein the Lambertian emission profile of the LED is converted into a deflected beam having a beam angle γ of approximately 45° at full width half maximum (FWHM). The luminaire also includes an axially extending shield 27 on a first side 23 of the cylindrical lens, which is an integral part of the luminaire housing. The shield shields the cylindrical lens over an angle β of approximately 25° of the dome-shaped cross-section. The lens includes a sprayed coating on its second side 25, on its outer surface 35 facing away from the LED strip, as an axially extending diffuser 33. The sprayed layer is sprayed from the second outer edge 31 of the lens at an angle of about 25 degrees. Starts and extends within an angle Θ of approximately 10°.

[0034] Figure 4A-4B A refrigerator 43 is shown comprising two lighting devices 1 according to the invention. Figure 4A In the illustration, lighting fixtures, each comprising an LED strip 3, are shown attached to a refrigerator door frame 45. Refrigerated merchandise 11 is stored on a shelf 47 inside the refrigerator behind a glass display door 49 for display to a customer 13. When a customer approaches the refrigerator, the refrigerator's built-in sensors detect their presence and send a signal to a controller (not visible) to activate the lighting fixtures to illuminate the merchandise. In the figure, the LEDs are shown as individual points of light because the door is slightly open, but when the refrigerator door is closed, the LEDs appear as a continuous beam of light because the lighting fixtures include a barrier 27 and a diffuser (not shown). Two lighting fixtures are mounted on the door frame between each refrigerator door, typically approximately 1.20 meters from the adjacent door studs 51. In the illustrated embodiment, light is emitted from each individual LED carried by the lighting fixtures and refracted by a lens (not shown) to provide an evenly distributed and ideal light pattern for uniformly illuminating the merchandise displayed in the refrigerator. Typically, refrigerator doors are lined with glass, allowing customers to inspect the contents before opening them. Multiple LEDs are usually required to provide enough lighting to evenly illuminate the interior of the refrigerator. Figure 4B The lighting devices shown are mounted on both sides of the door frame, and the merchandise can be illuminated from two opposite directions. Since each lighting device is individually controllable, wherein each LED is individually controllable, the desired color distribution and light intensity distribution can be selected to achieve the best lighting for the displayed merchandise.

[0035] Figure 5A luminaire 37 is shown that includes a lighting device 1 according to the present invention. The luminaire is mounted on a wall 53 having a housing 39 that houses the lighting device. The lighting device is oriented in the housing so that it provides glancing light 55 toward the wall for a wallwashing effect and for illuminating an object 11, such as a painting, hung on the wall. Because the lighting device includes a barrier and a diffuser (which are not visible), an observer 13 cannot see either the individual LEDs or the reflected images of the LEDs of the lighting device's LED strips.

Claims

1. A lighting device comprising: - a dome-shaped cylindrical lens having an optical focal line defining a principal axis; - a plurality of light sources arranged along the main axis and configured to emit light during operation; The dome-shaped cylindrical lens is configured to receive the light and deflect the light into a light beam having an angle γ at a full width at half maximum in a direction perpendicular to the main axis, wherein 0°<=γ<=45°, and in a cross section perpendicular to the main axis, the dome-shaped cylindrical lens includes a central portion, and two sides of the central portion are a first side portion and a second side portion; - an axially extending barrier disposed adjacent said first side; and - an axially extending diffuser provided at said second side, wherein the dome-shaped cylindrical lens comprises an inner lens surface facing the plurality of light sources and an outer lens surface facing away from the light sources, and wherein the diffuser is provided at least on the outer lens surface, wherein the second side has an axially extending second outer edge, and wherein, with respect to rotation relative to the focal line, the diffuser forms a diffuser region extending from an angle of about 100° to about 100° from the second outer edge. Starting from the position where And wherein the diffuser region extends within an angle Θ, wherein 5°<=Θ<=15°. 2 . The lighting device of claim 1 , wherein each of the plurality of light sources is positioned on the focal line, and each light source has a corresponding optical axis extending through the dome-shaped cylindrical lens in a direction perpendicular to the main axis. 3 . The lighting device according to claim 1 , wherein the dome-shaped cylindrical lens extends over the plurality of light sources within an angle α with respect to rotation relative to the focal line, wherein 90°<=α<=160°.

4. The lighting device according to claim 1 , wherein the first side portion has an axially extending first outer edge, and wherein the barrier blocks the dome-shaped cylindrical lens starting from the first outer edge within an angle β with respect to rotation relative to the focal line, wherein 10°<=β<=50°.

5. The lighting device according to claim 1 or 2, wherein And among them 8°<=Θ<=12°.

6. The lighting device of claim 1 or 2, wherein the diffuser comprises at least one of: a white powder coating, white tape, white spray painting, a frosted portion, and an etched surface structure.

7. The lighting device of claim 1 or 2, wherein the dome-shaped cylindrical lens is an extruded lens, and wherein the diffuser is a co-extruded component.

8. The lighting device according to claim 1 or 2, further comprising: A reflector having a reflective surface facing the dome-shaped cylindrical lens, wherein the reflector is arranged adjacent to the second side portion and wherein the diffuser is additionally provided on the reflective surface.

9. The lighting device according to claim 1 or 2, wherein the diffuser is an anisotropic diffuser having a higher degree of diffusivity in the direction of the main axis than in the direction perpendicular to the main axis.

10. The lighting device according to claim 1 or 2, wherein the diffuser has a beam widening effect that widens the light beam by an angle δ, wherein 1°<=δ<=5°.

11. A luminaire comprising a housing accommodating a lighting device according to any one of the preceding claims, and further comprising fixing means for mounting the luminaire to a carrier.

12. A refrigerator comprising: refrigerator door frames; A refrigerator compartment comprising at least one shelf and covered by a refrigerator door, wherein a lighting device according to any of the preceding claims 1 to 10 and / or a luminaire according to claim 11 is mounted on a first vertical upright of the door frame for illuminating the front of the shelf closest to the refrigerator door from a first direction.

13. The refrigerator according to claim 12, comprising: The lamp according to claim 11 or another lighting device according to any one of the preceding claims 1 to 10, wherein the lamp or the other lighting device is mounted on a second vertical column opposite to the first vertical column, so as to illuminate the front of the shelf closest to the refrigerator door from a second direction opposite to the first direction.

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