EP2844474B1 - Lighting unit with reflector - Google Patents

Description

The invention relates to a luminaire, comprising a first module and at least one second module, each having a plurality of distributed over a module surface LEDs, the modules are arranged to dissipate heat loss on at least one heat sink, and a reflector, wherein radiated from one of the modules Light is deflected by the reflector in an outlet opening of the lamp.

EP 2 375 133 A2 describes a lamp with an air-cooled heat sink, in which two LED modules are arranged opposite one another. The light from the two LED modules is filtered through collimators mounted individually on the LEDS and deflected by two deflecting mirrors through 90 ° into a common exit direction. The light leaving the light is completely divergent. EP 2 284 006 A2 describes a light source for UV drying with bundled leaving light.

It is the object of the invention to provide a luminaire with which a high irradiation density can be achieved with an optimized design.

This object is achieved by a luminaire according to claim 1.

By bundling with the optics, a large opening angle of the individual LEDs can be bundled into the structure of the target surface. In addition, a high degree of flexibility in terms of shape and size of the luminaire is achieved by the deflection of the light by means of the reflector.

In particular, an installation position and size of the heat sink or the heat sink can be selected so that a height of the lamp is reduced in the exit direction of the light. In the present case, the exit direction is understood to be the geometric main direction of the light after the deflection and when leaving the exit opening.

Generally advantageous, by means of the reflector or a plurality of reflectors, the light from a plurality of differently arranged and / or radiating in different main directions modules in the same exit direction from the light can be deflected, for example, each 90 ° According to the invention, it is the deflection of the light of opposite modules with opposite directions of radiation, wherein the reflector or reflectors are arranged between the modules and deflect the light in the common outlet direction.

Under an optic in the context of the invention, each object located in the beam path to understand, by means of which a defined change in the propagation direction of the geometric light beams is achieved. In particular, these are for the beam path permeable lenses, including cylindrical lenses and Fresnel lenses. But it can also be defined curved reflectors. A defined curvature of the deflecting reflector, by means of which a bundling in the defined structure is achieved, is an optic in the context of the invention.

In a preferred embodiment of the invention, it is provided that the optics comprises a primary optics for focusing the radiated light, which is arranged directly on the LEDs. Such a primary optic makes it possible to transport a particularly large solid angle of the light which is usually emitted by the LEDs over a large angle. For example, these may be a plurality of collecting lenses each arranged above an LED.

In a preferred development, the primary optics is formed as a transparent polymer layer applied to the modules, which integrally engages over at least a plurality of LEDs. Such a polymer layer may be, for example, by the type of in WO 2012/031703 A1 be formed optics described. In this case, an LED module is coated by means of an open mold with a UV-resistant silicone.

In an alternative or supplementary embodiment of the invention, the optics comprises a secondary optic, which is arranged spatially separated from a module in a beam path of the light. In contrast to the concept of primary optics, secondary optics in the present case are generally understood to mean optics that are not seated directly on the LEDs. Embodiments are therefore possible which include secondary optics but no primary optics. In a particularly preferred embodiment, both a primary optic and a secondary optics are arranged in the beam path of the luminaire, resulting in a particularly small design with high illuminance.

In a preferred detailed design, the secondary optics is formed as a transparent polymer layer on a transparent substrate. The secondary optics can be classified according to the type of WO 2012/031703 A1 described optics, wherein instead of an LED module, a transparent substrate, for example glass, is coated by means of an open mold with a UV-resistant silicone.

Generally advantageously, the optic comprises at least one cylindrical lens, by means of which the light of a plurality of LEDs arranged in a row is bundled. Such a cylindrical lens may be formed, in particular, in a secondary optic arranged at a distance from the LEDs.

In a preferred detailed embodiment of the invention, the defined structure is formed as a straight line. Preferably, but not necessarily, the luminaire is parallel to the line in a longitudinal direction and has in this direction a length which is at least twice, preferably at least three times, a height of the luminaire in a vertical direction perpendicular to the longitudinal direction.

Also advantageous is the reflector relative to the LED module arranged at an angle between 30 ° and 60 °. In particular, the angle may be about 45 °, so that a total of a deflection of the light rays by about 90 °. which favors a low height of the lamp. The angled arrangement of the reflector refers in the context of the invention to a deflection of a main beam of the light beam by twice the angle. In this sense, not only flat, but also curved reflectors are arranged at a certain angle.

The luminaire is preferably designed so that an irradiance on the structure is at least 2 W / cm ² . This allows in particular the use for drying applications such as paint drying with UV light as part of a printing process.

Advantageously, at least 50% of the light emitted by the LEDs is present in a wavelength range of less than 470 nm. This allows at least a predominant design of the lamp as a UV lamp. Due to the further combination of the features according to the invention, the UV radiator can be flexibly installed in a technical device, for example a printing machine.

Alternatively, at least 50% of the light emitted by the LEDs is in a wavelength range of more than 780 nm. This allows at least a predominant interpretation of the lamp as IR emitters. As a result of the further combination of the features according to the invention, the IR radiator can be flexibly installed in a technical device, for example a printing press.

Depending on the design, the lacquers or inks of printing presses are dried by UV light, in which case crosslinking of the substance to be dried usually takes place, or else by heat, with IR emitters preferably being used.

Generally, preferably, an amount of heat emitted to the cooling body is absorbed via a liquid coolant, so that overall a particularly large amount of waste heat can be dissipated even in the case of unfavorable installation conditions of the luminaire. Liquid coolants have a higher heat capacity than gaseous ones and allow high cooling capacities. The removal can be done by shifting the coolant in the liquid phase, for example by means of a circulating cooling circuit. It may alternatively or additionally also be the use of heat pipes, in which heat absorption first leads to a phase change of the liquid coolant.

The object of the invention is also achieved by a device for drying a coating, comprising a luminaire according to the invention. The luminaire according to the invention is particularly well suited for this purpose, since it combines high irradiation intensities with a flexible and, in particular, compact design.

In a preferred development, a planar substrate with the coating to be dried and the luminaire are movable relative to one another in a conveying direction, wherein the luminaire extends in a transverse direction at least partially over a width of the substrate and is arranged at a defined distance above the substrate. This is also to be understood as meaning a scanning down of the substrate surface in several webs. For example, the substrate may be a printed product that is coated in a printing press with printed paint or other substance.

The object of the invention is also achieved by the use of a luminaire according to the invention for drying a coating, preferably in a printing process.

Further advantages and features of the invention will become apparent from the embodiment described below and from the dependent claims.

Fig. 1

zeigt eine schematische Darstellung eines ersten Ausführungsbeispiels der Erfindung.

Fig. 2

zeigt eine schematische Darstellung eines zweiten Ausführungsbeispiels der Erfindung.

Hereinafter, two preferred embodiments of the invention will be described and explained in more detail with reference to the accompanying drawings.

Fig. 1

shows a schematic representation of a first embodiment of the invention.

Fig. 2

shows a schematic representation of a second embodiment of the invention.

A luminaire according to the invention Fig. 1 comprises two LED modules 1, wherein each of the modules 1 is applied to a heat sink 2 in a flat, thermally conductive connection. The modules 1 each comprise a plurality of LEDs 3, which are distributed in a grid over a plane perpendicular to the plane of the module surface. The LEDs 3 are applied together with other electronic components (not shown) on a planar support 4, whereby a total of one chip on-board module (COB) is formed in each case. The modules 1 extend in a direction perpendicular to the plane of the drawing longitudinal direction and in a vertical direction, in the drawing Fig. 1 from top to bottom and corresponds to an exit direction of the lamp. A main emission direction of the LEDs thus corresponds to a transverse direction, which in the drawing Fig. 1 from left to right.

The equipped with LEDs sides of the modules 1 are opposite, with a reflector 5 is disposed between the modules. The reflector 5 comprises two reflector surfaces 5a, 5b, wherein each of the reflector surfaces is planar and is inclined at an angle of 45 ° to the plane of the respective opposite module. Thus, a light beam emanating from an LED below 90 ° to the respective module plane (main emission direction) is deflected by the respective reflector surface 5a, 5b at an angle of 90 ° and leaves the luminaire through an exit opening 6 in an exit direction parallel to the vertical direction. The design of the reflector can be arbitrary, for example, as a prism, as a glass mirror or mirror plate. In order to minimize losses, in each case a corresponding surface compensation can be present.

On the modules 1, a primary optics 8 is arranged, which in the present case is designed as a full-area coating of the modules 1. The primary optics has directly on the individual LEDs 3 in each case lenses 9, by means of which a large opening angle of the emitted light bundled and the deflection by the reflector 5 on a target surface 10 (see illustration and analogous beam paths in Fig. 2 ). In this case, a predominant concentration of the rays into a structure takes place in the form of a straight, longitudinally extending line in the target surface 10. On this structure, the irradiation intensity through the luminaire is significantly more than 2 W / cm ² .

The outlet opening 6 is covered by a transparent protective screen 7, which in the present case has no distracting effect on the beam path. In principle, however, the protective screen may be formed as part of the optics.

The heat sink 2 each have connections 2a for the inlet and outlet of a liquid coolant, which flows through the heat sink for the removal of heat. The coolant can be in a closed circuit and release the heat elsewhere through a heat exchanger. In the present luminaire dissipated heat outputs in the range of much more than 1 kW.

The second embodiment according to Fig. 2 differs from the first example in that in addition to the primary optics 8. In addition, a secondary optics 11 is provided in front of the modules, whereby the bundling of the largest possible exit angle from the LEDs in the structure on the target surface is further improved. It is understood that the primary optics 8 according to the combined effect with the secondary optics may have a different interpretation, for example, in terms of size and focal lengths of the lenses 9 than in the first example, but otherwise constructed on the same principle.

The secondary optics 11 are each spaced in front of one of the modules 1, but arranged between the module 1 and the respective reflector plane 5a, 5b to act as early as possible bundling on the beam path.

The secondary optics each include a plurality of parallel cylindrical lenses 12 extended in the longitudinal direction. Thus, the light of at least one row of LEDs is detected by one of the cylindrical lenses 12 and bundled into the line or structure of the target surface 10 (printed product). Exemplary are in Fig. 2 Three different light beams are drawn by three LEDs, each with a different beam angle, all of which are focused into the structure in the target area.

In the present case, the primary optics are according to one in the WO 2012/031703 A1 prepared in principle by the COB modules are coated by silicone in an open mold. The present secondary optics are produced by an analogous method in which, instead of the COB modules, a transparent, flat substrate 13 is coated with UV-resistant silicone in order to produce the optically active structures 12 (cylindrical lenses).

A lamp according to the embodiments described above is used for purposes of UV drying of paint or ink in a printing press, in this case offset sheet-fed press. An extension of the luminaire in the longitudinal direction is typically more than 1 meter, in the present example 1.6 meters, which corresponds to the sheet width of the printed product. To realize such lengths, several modules 1 and optics 8 are typically arranged one behind the other in the longitudinal direction.

The components of the luminaire described above are accommodated in a housing 14 which is optimized with respect to the construction space.

An irradiance on the target plane with respect to the longitudinal direction is presently about 10 watts per cm. The majority of the light is in the range of a wavelength of less than 470 nm.

In order to produce LED luminaires with very high optical output powers, 0.1-200 mm ² , typically 1-2 mm ² LEDs are built in the chip-on-board (COB) method. In doing so, who several LEDs, typically 4-200 chips, are assembled into a module on a common substrate having an area on the order of 5 to 50 cm ² . By stringing modules equipped with LEDs, the desired lamp size is generated.

The heat generated during operation, due to the non-100% efficiency of the LEDs (optical output power in relation to fed-in electrical power, <100%, typ.5-60% for UV-A and blue LED chips), must by the Heatsink be discharged as a cooling system.

The cooling bodies 8, which are cooled with liquid, are three-dimensional bodies having a flat side to which the substrates are applied. Inside, the heat sink 8 may be completely hollow, or may have a channel or micro channel system. The finer the structure within the heat sink 8, the greater the surface area between the heat sink and the cooling liquid, via which heat can be released from the system to the cooling liquid.

Due to this structure, which includes the COB modules 1 to the cooling system, and which is necessary to protect the lamp from overheating during operation, resulting in a technically related height of the lamp between the emission level of the modules to the termination level of the heat sink 8. This leads to given requirements on the light output of the lamp to minimum heights in the direction of emission of the modules 1 of typically up to 20 cm. In many applications, such as in sheetfed printing by means of UV-curing inks and inks, luminaires with this overall height can not be used, since the available installation space in the machine is insufficient, e.g. because gripper systems that promote the bows limit the space.

By the above-described, inventive arrangement of modules 1 and reflector 5, the overall height for a lamp of the required power density can be significantly reduced. The luminaire according to the invention fulfills the specifications for the realization of an LED dryer (LED luminaire) with high specific optical power (radiated total power of> 10 W per cm length), which has the need for efficient cooling and efficient optics to achieve high peak irradiance (> 2 W / cm ² , at> 40 mm distance, with target values of 4-10 W / cm ² at intervals of 40-100 mm between luminaire and target plane) combined, while the smallest possible height in the exit direction of <80 mm.

Claims (16)

1. Lamp comprising a first module (1) and at least one second module (1) each having a plurality of LEDs (3) distributed over a module surface, whereby the modules (1) are arranged on at least one cooling element (2) for dissipation of lost heat, and a reflector (5), whereby light emitted from one of the modules (1) is deflected by the reflector (5, 5a, 5b) into an exit opening (6) of the lamp, characterised in that an optical system (8, 9, 11, 12) through which the light of the LEDs (3) is bundled into a defined structure in a target surface (10) is provided between at least some of the LEDs (3) and the exit opening (6), whereby the first module (1) and the second module (2) have opposite emission directions, whereby the reflector (5, 5a, 5b) is arranged between the modules.
2. Lamp according to claim 1, characterised in that the optical system comprises a primary optical system (8, 9) for bundling the emitted light that is arranged right on the LEDs (3).
3. Lamp according to claim 2, characterised in that the primary optical system (8, 9) is provided as a transparent polymer layer that is applied to the modules and extends, as a single part, over at least multiple LEDs (3).
4. Lamp according to any one of the preceding claims, characterised in that the optical system comprises a secondary optical system (11, 12) that is arranged in an optical path of the light while being spatially separated from a module (1).
5. Lamp according to claim 4, characterised in that the secondary optical system (11, 12) is provided as a transparent polymer layer on a transparent substrate (13).
6. Lamp according to any one of the preceding claims, characterised in that the optical system comprises at least one cylindrical lens (12) by means of which the light of a plurality of LEDs (3) that are arranged in a row can be bundled.
7. Lamp according to any one of the preceding claims, characterised in that the defined structure is provided as a straight line.
8. Lamp according to claim 7, characterised in that the lamp extends parallel to said line in a longitudinal direction and has a length in said direction that is at least two times an installed height of the lamp in an upward direction that is perpendicular to the longitudinal direction.
9. Lamp according to claim 7 or 8, characterised in that the reflector (5a, 5b) is arranged opposite from the module (1) at an angle between 30° and 60°.
10. Lamp according to any one of the preceding claims, characterised in that an irradiation intensity on the structure is at least 2 W/cm2.
11. Lamp according to any one of the preceding claims, characterised in that at least 50% of the light emitted by the LEDs (3) is in a wavelength range below 470 nm.
12. Lamp according to any one of the claims 1 to 10, characterised in that at least 20 50% of the light emitted by the LEDs (3) is in a wavelength range above 780 nm.
13. Lamp according to any one of the preceding claims, characterised in that an amount of heat transferred to the cooling element (2) is taken up by a liquid coolant.
14. Device for drying a coating, comprising a lamp according to any one of the preceding claims.
15. Device according to claim 14, characterised in that a two-dimensional substrate bearing the coating to be dried and the lamp can be moved towards each other in a conveying direction, whereby the lamp extends over a width of the substrate in a transverse direction and is arranged at a defined distance above the substrate.
16. Use of a lamp according to any one of the claims 1 to 13 for drying a coating, in particular in a printing procedure.

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