Elongated lamp

Abstract

A lamp (1), comprising a metallic carrier (10) having a transverse dimension (T) and a longitudinal dimension (L) and comprising a heat dispersing surface (11) opposite an installation surface (12), and a heat conducting spacer (15) in thermal contact with the installation surface (12) and having a PCB mounting surface (16), a PCB (20) mounted on the PCB mounting surface (16), which PCB (20) carries a row of LEDs (25) in the longitudinal dimension (L) of the lamp (1), and a transparent cover (30) mounted on the metallic carrier (10), the transparent cover (30) having a transversally convex outer surface (31) and an inner surface (33) facing the PCB mounting surface (16).

Description

[0001] ELONGATED LAMP

[0002] Field of the invention

[0003] The present invention relates to a lamp. The lamp is especially suited for use in a greenhouse. The lamp is configured to provide a better distribution of lights directed at a surface where plants can grow in a greenhouse. The present invention also relates to a greenhouse lighting system comprising a plurality of lamps of the invention.

[0004] Background

[0005] Technological advances in climate control and lighting systems have enabled food production indoors. Sunlight is a vital resource in all food production and is needed to provide optimal growing conditions. The emergence of powerful light emitting diodes, LEDs, in the correct light spectrum has allowed food production where natural sunlight is limited or absent, such as in vertical farming or in indoor horticulture in general. Further, it has allowed traditional greenhouses with glass facades to be more efficient because the lighting systems provide artificial daytime conditions after sunset. However, such growing techniques require efficient lighting systems that can deliver uniform lighting conditions while requiring minimal maintenance and support. Conventional greenhouses at industrial scale are commonly 50 to 150 meters long and may extend even further. Lighting systems in such greenhouses are typically supported by a plurality of rafters spaced at least 3 to 4 meters apart. Installing lighting systems on these rafters requires installation of support plates or support beams extending between the rafters in the full length of the greenhouse which makes installation of the lighting systems cumbersome and more costly. Furthermore, lamps used under such conditions typically have power ratings that demand efficient cooling design of the lamp systems or even active cooling such as fans or water cooling which adds to the installation time, cost and complexity. Summary

[0006] With this background, it is therefore an object of the invention to provide a lamp for a greenhouse, which solves or at least alleviates some of these problems.

[0007] The present invention relates to a lamp comprising a metallic carrier having a transverse dimension and a longitudinal dimension and comprising a heat dispersing surface opposite an installation surface, and a heat conducting spacer in thermal contact with the installation surface and having a PCB mounting surface. A PCB is mounted on the PCB mounting surface, which PCB carries a row of LEDs in the longitudinal dimension of the lamp. A transparent cover is mounted on the metallic carrier and the transparent cover has a transversally convex outer surface and an inner surface facing the PCB mounting surface. The heat conducting spacer is sized to provide a spacer distance from the LEDs to an apex of the inner surface of the transparent cover, which distance is in the range of 3 mm to 50 mm. The inner surface of the transparent cover comprises a flank section defined by an angle in a plane normal to the longitudinal dimension of the lamp, which angle is defined from the PCB mounting surface and is in the range of 5° to 60°. The flank section of the inner surface of the transparent cover has a plurality of flank prisms extending in the longitudinal dimension of the lamp, which flank prisms are configured to direct light that reaches the flank section of the inner surface towards a surface opposite the PCB mounting surface.

[0008] The lamp is generally adapted for a greenhouse and / or for agricultural use where natural light is limited, such as for indoor horticulture and / or indoor agriculture. The lamp provides a more uniform distribution of light, in both longitudinal and its transverse direction, than can be obtained from conventional lamps. Several lamps of the disclosure, due to the distribution of the light in the transverse and longitudinal direction, can advantageously be used in combination to provide an even distribution of light in a greenhouse. Thus, in another aspect, the invention relates to a greenhouse lighting system comprising a plurality of lamps of the disclosure, where the lamps are arranged in parallel at a distance from each other in the range of 1 m to 5 m, e.g. 3 m to 4 m. Metallic carrier

[0009] The metallic carrier is generally elongated in shape and is adapted to be installed directly on rafters in a greenhouse which are typically spaced at least 3 to 4 meters apart. The metallic carrier preferably has a length in the longitudinal dimension in the range of 3 to 15 meters, more preferably at least 6 meters. The metallic carrier may be 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, or 15 meters long.

[0010] The inventors have realised that a metallic carrier of this length can provide a lamp that is easily installed in greenhouses without the need for additional support plates or support beams. By having a lamp that extends at least the typical length between rafters of a greenhouse, the lamp can be directly attached to these rafters. The lamp may extend across multiple rafters. In traditional greenhouses, the lamp installer installs the support beams and thereafter attaches the traditional lamps to the support beams. For retro fit with new LED lamps, the lamp installer is therefore limited to where the support beams have been installed, and it requires substantial effort to rearrange the lighting which may be required when new lamps are installed or when the inventory of the greenhouse is rearranged. By having a lamp that can be directly attached to the rafters the installer is free to rearrange them with minimal effort because only the lamps must be moved.

[0011] Another advantage is that by having lamps of this length, the number of lamps per unit area is reduced which further reduces installation costs and space. Fewer lamps also require fewer LED power supplies which therefore also saves installation costs and time, especially with regards to electrical wiring and connections. The transverse dimension is to be understood as the dimension defined in a plane normal to the longitudinal direction. Correspondingly, the lamp provides light, and the light provided by the lamp has a profile in a transverse direction. A cross-section of the lamp in the transverse dimension is a cross-section in a plane normal to the longitudinal dimension. The transverse dimension is defined by a width dimension and a height dimension.

[0012] The lamp is generally adapted to be installed with the longitudinal dimension and the width dimension extending substantially parallel with a plant surface, where the plant surface is the surface beneath the lamp intended for growing plants and / or vegetables and the height dimension extending normal to the plant surface.

[0013] The metallic carrier preferably has a width in the range of 30 mm to 200 mm, more preferably 50 mm to 100 mm, most preferred 60 mm to 80mm.

[0014] Preferably, the cross-sectional shape of the metallic carrier in the transverse dimension is substantially the same throughout the length of the metallic carrier. This is especially advantageous, because it allows the metallic carrier to be manufactured by metal extrusion. The combination of the same cross-sectional shape throughout the length of the metallic carrier and manufacturing by metal extrusion is advantageous for providing a lamp of the preferred length. Having substantially the same transverse dimension throughout the length of the metallic carrier has the further advantage that the metallic carrier has the same heat dispersing properties throughout the entire length of the metallic carrier. This in turn minimises local build-up of heat in a section of the lamp so that the heat dispersion is more efficient.

[0015] The cross-sectional shape of the metallic carrier in the transverse dimension is preferably substantially T-shaped. Generally, the T-shape is defined by a fin extending from an elongated body. The fin is arranged on the side of the metallic carrier comprising the heat dispersing surface and the surface of the fin is generally comprised in the heat dispersing surface. The fin may extend at any angle relative to the heat dispersing surface, e.g. an angle in the range of 70° to 110°, although a substantially right angle is preferred.

[0016] The fin may be positioned at any position in the heat dispersing surface. Preferably, the fin extends substantially perpendicular from a centre of the elongated body. This has the potential advantage of providing a lamp which is symmetrical around an axis in the transverse dimension which provides a stable and weight balanced lamp. Additionally, the T-shaped cross-section provides stability to the lamp, especially when the lamp is provided in its preferred length of at least 3 m. The T-shape allows the metallic carrier to be by hung from rafters spaced at least 3 m apart without substantial bending of the lamp. It is preferred that the fin is integrally formed with the metallic carrier. For example, the metallic carrier having the fin may be extruded from a metal. The fin may extend from the elongated body closer towards one end of the elongated body. In alternative embodiments, it may be envisioned that the fin extends from the elongated body at an angle between 85° and 45°.

[0017] It has further been realised that a T-shape provides sufficient heat dispersion to the surrounding air. Additional fins extending from the elongated body may be envisioned to increase the heat dispersing surface area, but a single fin is presently preferred as it allows air to flow freely around the fins thereby facilitating further heat exchange between the metallic carrier and the surrounding air. In an example, the lamp comprises a single fin. The fin preferably has a height in the range of 30 mm to 400 m, preferably 70 mm to 100 mm. The height of the fin relative to the width of the metallic carrier may have a ratio in the range of 0.9 to 1 .4, preferably the ratio is at least 1 .

[0018] In preferred embodiments, the heat dispersing surface of the fin and / or the elongated body has a grooved surface in the longitudinal direction of the lamp to further increase the heat dispersing surface area.

[0019] The lamp is preferably configured to be fixed to rafters in a greenhouse by engagement in the metallic carrier. The engagement means is preferably comprised in the fin. The engagement means may be at least 3 meters spaced apart. By having engagement means integrated in the metallic carrier the lamp can be easily installed and may be attached directly to existing rafters of the greenhouse. Engagement means may be arranged for engagement with neighbouring rafters. In some embodiments the metallic carrier extends across multiple rafters and the preferred T-shape allows engagement means to be arranged for engagement with rafters only by the ends of the metallic carrier, or by every second or third rafters.

[0020] The lamp comprises a heat conducting spacer. The heat conducting spacer may also be referred to as a “spacer”, and the terms “heat conducting spacer” and “spacer” are used interchangeably throughout this document. The heat conducting spacer is in thermal contact with the PCB and transfers heat from LEDs mounted on the PCB to the metallic carrier. Correspondingly, the heat conducting spacer may be in thermal contact with the metallic carrier via the installation surface. The heat conducting spacer may be made from any material than can transfer heat from the LED to the metallic carrier. For example, the heat conducting spacer may be made from a metal or SiC. The heat conducting spacer is sized to provide a distance from the LEDs to an apex of the inner surface of the transparent cover, which distance is in the range of 5 mm to 100 mm, preferably in the range of 10 mm to 50 mm. The spacer ensures that the LEDs are spaced correctly relative to the prisms of the transparent cover.

[0021] The spacer is sized to have an extension from the installation surface in the range of 0 mm to 100 mm. In presently preferred embodiments, the spacer extends 5 mm to 20 mm from the installation surface. LEDs generally emit light, e.g. when viewed in a plane normal to the longitudinal dimension of the metallic carrier, in a 180° semicircle. One advantage of having the LEDs positioned at a distance to the installation surface as provided by the spacer, e.g. in the range of 5 mm to 20 mm, is that it allows light that is emitted in a 180° semicircle in the transverse dimension from each LED comprised in the row of LED’s to directly hit the transparent cover with a light intensity matching the design of a transparent cover, e.g. with respect to the positioning of light directing prisms in the transparent cover. One advantage of this is that no reflectors are needed to direct the light, and thereby a lamp is provided where reflectors are not needed. This is an advantage since reflectors always lead to optical loss that becomes heat. In an example, the lamp does not comprise reflectors.

[0022] A further advantage of having a spacer sized to provide a spacer distance in the range of 3 mm to 50 mm, in particular a spacer integrally formed with the metallic carrier, is that it provides room for the transparent cover to be mounted by press-fitting between longitudinal rim sections of the metallic carrier, e.g. without permanently fixing the transparent cover to the metallic carrier, which in turn allows the transparent cover and the metallic carrier to thermally expand independently of each other. This is especially advantageous for a long lamp, e.g. when the lamp has a length of at least 3 m. Thus, the combination of a spacer sized to provide a spacer distance in the range of 3 mm to 50 mm and the flank prisms in the transparent cover together provide better utilisation of light emitted by the LEDs and flexibility with respect to thermal expansion of the transparent cover and the metallic carrier for a long lamp. A gasket is preferably arranged in the connection between the metallic carrier and transparent cover. The gasket provides a watertight seal to protect the LEDs, PCBs, and other electronic components from the moist environment in the greenhouse.

[0023] The heat conducting spacer and the metallic carrier are preferably integrally formed. Alternatively, the heat conducting spacer is fixed to the metallic carrier. The heat conducting spacer is preferably made of aluminium, in particular the metallic carrier and the heating spacer may be integrally formed from aluminium. The spacer therefore has the advantages of providing the correct distance from the LEDs to the apex of the transparent cover, of providing a distance to the installation surface allowing light emitted substantially from a 180° semicircle in the transverse dimension from each LED comprised in the row of LED’s to directly hit the transparent cover and providing heat dispersion.

[0024] The metallic carrier is preferably made of aluminium. The spacer is also preferably made of aluminium. Aluminium is known to be both light weight and has shown to have sufficient strength for a lamp of the preferred length. The metallic carrier is preferably manufactured by extrusion. When the metallic carrier is manufactured by extrusion, the metallic carrier, preferably with the integrally formed heat conducting spacer, and preferably also the fin, the metallic carrier may be made of aluminium, magnesium, copper, titanium, or steel, although aluminium is preferred. Manufacturing of the metallic carrier by extrusion has shown to be advantageous as it allows the metallic carrier and spacer, and optionally also the fin, to be integrally formed. This provides better heat conduction between the spacer and the heat dispersing surface of the metallic carrier and therefore allows for better cooling of the lamp.

[0025] The metallic carrier may comprise first and a second longitudinal rim sections along longitudinal edges of the metallic carrier, wherein the transparent cover is mounted by press-fitting between the first and the second longitudinal rim sections. Heat is generated when the lamp is operated, i.e. from the LEDs, which results in the metallic carrier and transparent cover to expand according to the respective thermal expansion coefficients of the materials that they are made of. For a long lamp, i.e. a lamp having a length of at least 3 m, the transparent cover and metallic carrier may experience substantially different length changes due to the expansion of the different materials caused by changes in temperature. This is especially relevant in environments with relatively high temperatures such as in greenhouses where it is difficult to get rid of excess heat. It is therefore important that the parts can move freely relative to each other at least in the longitudinal direction. The inventors have realised that attaching the transparent cover to the metallic carrier via pressfitting allows sufficient relative movement between the parts. Alternatively and / or additionally, the transparent cover is attached to the metallic carrier via a snap lock mechanism or configured to slide into engagement with the metallic carrier such as by sliding the cover onto the carrier in the longitudinal direction. It is preferred that the mounting of the transparent cover to the metallic carrier does not involving fastening means that permanently fix the transparent cover to the metallic carrier.

[0026] An integrally formed metallic carrier of the preferred length and with the preferred T-shape provides several advantages as a heat dispersing surface.

[0027] The fin extending the entire length of the integrally formed metallic carrier provides efficient cooling and improved cooling compared to multiple separated lamps installed in extension of each other. The preferred single fin allows the same low operating temperature for all LEDs as heated air can be easily led away from the lamp compared to normal heatsinks where fins are typically packed closely together allowing dead spaces of still heated air. Combined with the integrally formed metallic carrier the lamp provides a minimal thermal gradient across the length of the lamp. This also allows a lamp with a relatively high power density in the range of 1000 W to 3500 W per m2without the need of active cooling systems.

[0028] PCB and LEDs

[0029] The PCB is mounted on the PCB mounting surface of the metallic carrier. The PCB is preferably an aluminium based PCB. To reduce the total amount of PCBs and reduce assembly time and cost, each PCB preferably has a length of 50 cm to 150 cm in the longitudinal direction. Preferably, each PCB carries one row of LEDs in the longitudinal dimension of the lamp. This has the potential advantage that each LED can be placed optimally relative to the prisms of the transparent cover for directing light in the straight line from the outer surface of the transparent cover. Thereby, when the lamp has a PCB with a single row of LEDs, the positioning of the LEDs, i.e. with respect to the spacer distance from the LEDs to an apex of the inner surface of the transparent cover being in the range of 3 mm to 50 mm, allows better utilisation of the light emitted from the LEDs, as all LEDs are positioned optimally relative to the flank prisms. It may be envisioned that at least two rows of LEDs can be placed sufficiently close to the optimal position relative to the prisms and still provide a relatively good redirection of the light, It may further be envisioned that the flank sections on opposite sides of the apex of the transparent cover are configured to match one of the two rows of LEDs.

[0030] The LEDs are preferably arranged in the range of 3 mm to 100 mm apart in the longitudinal dimension, preferably in the range of 8 mm to 12 mm. This has the advantage of providing a homogeneous light distribution in the longitudinal dimension.

[0031] The LEDs may emit light of any wavelength as useful for the specific lamp. For example, the LEDs may emit white light, or when the lamp is intended for use in a greenhouse, the LEDs may emit light of wavelength appropriate for plants in the greenhouse. The desired spectrum can be achieved by combining different LEDs.

[0032] Generally, each LED is connected to a power source via the PCB allowing the LEDs to be operated. For example, the lamp may include a power supply providing power to the PCB.

[0033] The lamp may further comprise a control unit. The control unit may comprise control circuitry configured to control the LEDs. Such control circuitry may, for instance, comprise one or more LED drivers for driving the LEDs of the light sources, power electronics, and / or a communication interface for wireless and / or wired connection. A communication interface may comprise a wireless module configured to allow communication over wireless connections, such as an infrared (IR) communication, 2.4 GHz or 5 GHz communication, such as Bluetooth, ZigBee, Z-Wave, Wi-Fi, or the like, or by a wired connection, such as a wired electrical connection.

[0034] The control unit may comprise a processing unit in operational connection with the light sources and / or the control circuitry. The control unit may be any processing unit, such as a central processing unit (CPU), a microcontroller unit (MCU), a field-programmable gate array (FPGA), a programmable logic controller (PLC), a digital signal processor (DSP), or the like. The control unit may be configured to control the LEDs, potentially via the control circuitry.

[0035] Alternatively or additionally, the control unit may comprise a memory unit, such as a non-transitory memory, on which instructions are stored, which, when carried out by the processing unit, causes the processing unit to control the LEDs.

[0036] The memory unit may be operably connected to the processing unit. The memory unit may be a random access memory (RAM), a read-only memory (ROM), a Flash memory, or the like.

[0037] The lamp may have a power rating in the range of 10 W to 24 W per 10 cm of the metallic carrier. The power supply, when included with the lamp, provides power to match the power rating depending on the length of the lamp. Preferably, the lamp has a power rating of 17 W per 10 cm of the metallic carrier.

[0038] Transparent cover

[0039] The transparent cover of the lamp is adapted to direct the scattered light emitted by the LEDs towards a surface opposite the PCB mounting surface. This is achieved by the prisms, i.e. flank prisms and optionally also central prisms, comprised in the cover. Without the prisms, the light intensity is higher on the surface directly below the LEDs and decreases steadily when moving to the side. The light intensity therefore normally either varies significantly or the LEDs are packed very close to each other such that their light profiles overlap.

[0040] The prisms in the transparent cover are arranged to redirect light emitted by the LEDs to provide an area of substantially homogenous light intensity on the plant surface opposite the PCB mounting surface. The transparent cover has flank prisms and optionally also central prisms, and as such the transparent cover is comparable to what is commonly known as a Fresnel lens. The prisms, i.e. the flank prisms and the central prisms, when present, direct light towards a surface opposite the PCB mounting surface. In general terms, the prisms may be considered to angle the light emitted from the LEDs, e.g. the prisms may have an angle of deflection, and when the lamp comprises both flank prisms and central prisms, the flank prisms have a larger angle of deflection than the angle of deflection of the central prisms. Thereby, a more even distribution of the light from the LEDs is obtained compared to light emitted from a lamp not having prisms, or the embodiment where the lamp only has flank prisms.

[0041] The prisms may be configured by the skilled person by use of any optical simulation software such as TracePro (Lambda Research Corporation of Littleton, Massachusetts, USA).

[0042] The transparent cover has a generally convex shape in the transverse dimension and extends in the longitudinal dimension. The transparent cover is preferably substantially the same length as the metallic carrier.

[0043] The prisms extend in the longitudinal direction of the transparent cover.

[0044] A cross-section of the transparent cover in the transverse dimension is a cross-section in a plane normal to the longitudinal dimension. Preferably, the cross-sectional shape of the transparent cover in the transverse dimension is the same throughout the length of the metallic carrier. The prisms are preferably integrally formed with the transparent cover and extend along the longitudinal direction of the transparent cover. For example, the transparent cover with integrally formed prisms may be extruded from an appropriate transparent polymer. Extrusion of the transparent cover advantageously provides a simple way to manufacture very long transparent covers to match the preferred length of the lamp of the disclosure.

[0045] The number of prisms is generally only limited by the manufacturing method.

[0046] The prisms are arranged in the flank section, although the central section may also comprise prisms. The flank section preferably comprises 3 to 25 prisms, preferably ? to 15. The angle defining the flank section is in the range of 5° to 60°. The angle defining the flank section may be in the range of 10° to 40°.

[0047] A flank section may be arranged on both sides of the apex.

[0048] The inner surface of the transparent cover may further comprise a central section between the flank section and the apex of the inner surface of the transparent cover, which central section comprises a plurality of central prisms extending in the longitudinal dimension of the lamp, which central prisms are configured to direct light that reaches the central section of the inner surface towards a surface opposite the PCB mounting surface.

[0049] In an example, the transparent cover comprises additional section between the flank section and the central section. Additional sections may comprise prisms, and the prisms may provide another angle of deflection than the flank prisms or the central prisms. For example, the prisms of additional sections may have an angle of deflection between the angle of deflection of the flank prisms and the central prisms.

[0050] The central section generally scatters the light emitted from the LEDs, such that the light intensity on the plant surface directly below the LEDs is reduced.

[0051] A central section may be arranged on both sides of the apex of the transparent cover.

[0052] The combined effect of the flank section and the central section has the advantage of reducing the light intensity directly under the LEDs and increase the light intensity at a distance to the side.

[0053] The width of the transparent cover is preferably in the range of 20 mm to 200 mm, more preferred in the range of 30 mm to 100 mm.

[0054] The transparent cover is made of a suitable transparent material, preferably an acrylic based material.

[0055] The convex outer surface of the transparent cover further provides optimal flow conditions for an airflow in the upwards direction of the lamp with minimal turbulence. This airflow contributes to the heat dispersing properties of the lamp by passive cooling via a continuous replenishment of cooler air from under the lamp and with minimal dead spaces for hot air to accumulate. The convex outer surface of the transparent cover is beneficial with the preferred T- shaped metallic carrier which in combination provides optimal heat dispersing properties.

[0056] The heat conducting spacer and the transparent cover has the combined advantage of providing a lamp adapted to emit light towards the surface opposite the PCB mounting surface. Each LED emits light in a substantially 180° angle and some of the emitted light is therefore not directed towards the plant surface substantially below the lamp or at such a sharp angle relative to the PCB mounting surface that this light does not contribute significantly to plant growth. The flank sections of the prisms may be configured to direct light emitted from each LED at an angle in the range of 5° to 60° from the PCB mounting surface towards the plant surface under the lamp. The prisms and LEDs are preferably configured to direct the light towards a plant surface in the range of 0 m to 2 m in the width direction from the row of LEDs when the lamp is arranged at 1 .6 m to 4 m above the plant surface.

[0057] Preferably, the lamp is configured to direct light towards a surface opposite the PCB mounting surface, wherein said opposite surface spans in the range of 2 to 8 meters.

[0058] The prisms extend in the longitudinal dimension and a single row of LEDs in the longitudinal direction is advantageous because each LED can be arranged optimally relative to the prisms to achieve the desired redirection of light by the prisms. This is advantages over other lamps having the LEDs in closely positioned rows next to each other in the same lamp.

[0059] Any embodiment of the invention may be used in any aspect of the invention, and any advantage for a specific embodiment applies equally when an embodiment is used in a specific aspect.

[0060] Brief description of the drawings

[0061] In the following the invention will be explained in greater detail with the aid of an example and with reference to the schematic drawings, in which:

[0062] Figure 1 shows an embodiment of a lamp according to the invention from a view in the transverse dimension. Figure 2 is a perspective view of a lamp in an embodiment of the invention showing primarily the lamp in the longitudinal dimension.

[0063] Figure 3 shows an embodiment of a lamp according to the invention from a view in the transverse dimension.

[0064] Figure 4 shows an embodiment of a lamp according to the invention from a view in the transverse dimension.

[0065] Figure 5 shows an embodiment of a lamp according to the invention from a view in the transverse dimension.

[0066] Figure 6A shows an embodiment of a lamp according to the invention from a view in the transverse dimension with flank sections and central sections.

[0067] Figure 6B shows an embodiment of a lamp according to the invention from a view in the transverse dimension showing the redirection of the light for a transparent cover according to the invention.

[0068] Figure 7 shows an embodiment of a lamp according to the invention showing in the longitudinal dimension.

[0069] Figure 8 shows an embodiment of a lamp according to the invention showing in the transverse dimension.

[0070] Figure 9 shows a simulated light profile for an embodiment of a lamp according to the invention.

[0071] Figure 10 shows data for a light profile for an embodiment of a lamp according to the invention.

[0072] Figure 11 shows a light profile of a lamp without prisms in the transparent cover. Figure 12 shows a light profile for an embodiment of a lamp according to the invention.

[0073] Figure 13 shows a light profile of three lamps without prisms in the transparent cover.

[0074] Figure 14 shows a light profile for an embodiment of three lamps according to the invention.

[0075] Figure 15 shows a perspective view of an embodiment of a lamp according to the invention.

[0076] Figure 16 shows a flow simulation of an embodiment of a lamp according to the invention. The invention is not limited to the embodiment / s illustrated in the drawings. Accordingly, it should be understood that where features mentioned in the appended claims are followed by reference signs, such signs are included solely for the purpose of enhancing the intelligibility of the claims and are in no way limiting on the scope of the claims.

[0077] The term “comprising” as used in this specification and claims means “consisting at least in part of”. When interpreting statements in this specification and claims which include the term “comprising”, other features besides the features prefaced by this term in each statement can also be present. Related terms such as “comprise” and “comprised” are to be interpreted in a similar manner.

[0078] Detailed Description

[0079] The present invention relates to a lamp 1 as shown in Fig. 1. The lamp 1 is for a greenhouse such as greenhouses where natural light is a limited resource. The lamp comprises a metallic carrier 10 having a transverse dimension T and a longitudinal dimension L. The metallic carrier 10 has a heat dispersing surface 11 opposite an installation surface 12 and a heat conducting spacer 15 in thermal contact with the installation surface 12. A printed circuit board, PCB, 20 is mounted on a PCB mounting surface 16 of the heat conducting spacer 15 and carries a row of LEDs 25 in the longitudinal dimension L of the lamp 1 .

[0080] The metallic carrier has a T-shape provided by an elongated body 10i and a fin 17.

[0081] A transparent cover 30 is mounted on the metallic carrier 10 and has a transversally convex outer surface 31 and an inner surface 33 facing the PCB mounting surface 16. The transparent cover 30 further has a plurality of prisms 32 extending in the longitudinal dimension L of the lamp 1 , which prisms are configured to redirect light that reaches the prisms from the LED towards a surface opposite the PCB mounting surface. The prisms are comprised in a flank section of the transparent cover, and the flank section is defined by an angle a in a plane normal to the longitudinal dimension L of the lamp. Thereby, light that would otherwise be direct substantially parallel with a plant surface opposite the PCB mounting surface is directed towards the plant surface under the lamp.

[0082] The redirected light is shown as the dotted line in Fig. 1 .

[0083] Turning to Fig. 2, a sketch of an embodiment of a side a lamp 1 according to the invention is shown in a perspective view. The figure is not considered as showing the correct relation between length, width, and height but serves merely as representative drawing. A fin 17 of the metallic carrier is shown to comprise engagement means 13 for installing the lamp 1.

[0084] Fig. 3 shows an embodiment of the lamp 1 according to the invention with spacers 15 arranged between the installation surface 12 and the PCB 20. In the shown embodiment, the transparent cover 30 comprises attachment means 40 at both ends. Each attachment means 40 is fixed to the metallic carrier by being press fitted between the spacer 15 and the metallic carrier 10. The attachment means 40 are in this embodiment comprised in the transparent cover 30 and is received by the metallic carrier 10.

[0085] The spacer 15 provides a distance Y to the installation surface 12. The LED 25 is arranged in a PCB 20 on the spacer 15 and the LED is thereby arranged such that light emitted substantially from a 180° semicircle in the transverse dimension directly hits the transparent cover.

[0086] The spacer further provides the correct distance X between the LED and an apex of the transparent cover 36.

[0087] In Fig. 4 a preferred embodiment of a lamp according to the invention is shown wherein the metallic carrier 10 comprises first and second longitudinal rim sections 14 along longitudinal edges 10i of the metallic carrier 10 and the transparent cover 15 is mounted by press-fitting between the first and second longitudinal rim sections. Fig. 4 further shows a gasket 37 arranged between the transparent cover 30 and the metallic carrier 10 to provide a watertight seal to the surrounding environment.

[0088] Fig. 5 shows an embodiment of the lamp in the transverse dimension, where a flank section 34 defined by angle a is shown. Flank sections are shown on both sides of the apex 36 defined by angle ai and 02, respectively. Angles on and 02 may vary. The lamp shown in Fig. 5 further shows a centre section 35 defined by angle |3i , and a centre section 35 defined by angle P2.

[0089] Fig. 6A shows an embodiment of the transparent cover where the flank prisms 32 ii of the flank sections 34 and the centre prisms 32ii are shown.

[0090] Fig. 6B shows is schematic view of how light is directed by the prisms 32 of the transparent cover 30. The flank prisms are shown to direct light towards the plant surface 50. Light is visualized by the dotted lines. The LED 25 is shown to emit light in a 180° angle. Light hitting the flank section 34 is directed towards the surface opposite the PCB mounting surface 50 and light hitting the central section 35 is shown to be spread. The combination of the flank section 34 and central section 35 provides a more homogenous light field on the surface opposite the PCB mounting surface 50.

[0091] Figs. 7 to 8 are illustrations of the light profiles of the lamp. Fig. 7 shows a lamp in the longitudinal dimension. A light profile for an LED from this direction is a light profile in the longitudinal dimension. The angular light profile in this dimension is referred to as a light profile at a longitudinal angle LA relative to the PCB mounting surface. Fig. 8 shows the light profile in the transverse dimension. The light profile in the width direction is referred to as the light profile in the width direction and the angular light profile is referred to as the light profile in transverse angle TA relative to an axis normal to the PCB mounting surface.

[0092] Figs. 9 and 11 to 14 show simulation results of light intensity of lamps with different transparent covers. The behaviour of light as it interacts with the lens formed by prisms in the transparent cover has been characterized through simulation using well-known computerized optical ray tracing methods. Fig. 9 shows a simulation of the light profiles in the width direction and longitudinal direction for a lamp according to this invention with prisms provided in a central section and a flank section on both sides of the apex. The x-axis shows the distance from right underneath the LED. The star-dotted line shows the lighting profile in the longitudinal direction and the light intensity drops of as you move to either side of the LED in the longitudinal direction, showing that the light is not substantially redirected by the prisms extending the longitudinal direction. Looking in the width direction i.e. the transverse dimension, the light profile represented by the star-dotted line shows that the light profile has a dip in the middle right underneath the LED and a small increase in light intensity on both sides of the dip caused by the prisms in the central section and the flank section.

[0093] Fig. 10 shows a measurement of the light intensity of a lamp with a transparent cover as shown in Fig. 6B. The light intensity is shown to be relatively homogenous in a width of approximately 1250 mm on both sides of the LED.

[0094] Figs. 11 - 12 show the light profiles for lamps in the transverse angle TA and the longitudinal angle LA. Fig. 11 shows the light profiles for a lamp without prisms in the transparent cover. The light profile in the transverse angle and longitudinal angle is shown to be similar. Turning to Fig. 12, light profiles are shown for a lamp with prisms in the transparent cover as depicted in Fig. 6B, with the redirection of the light in the transverse angle TA.

[0095] Figs. 13 - 14 show the result of simulations of three lamps installed next to each other spaced 3.5 m apart in the width direction and 2 meters above the plant surface. The light profile in the longitudinal direction is shown for a single LED in the middle lamp by the star-dotted line. The light profile in the width direction in shown by the solid line. Fig. 13 shows three lamps with a transparent cover without prisms. The light intensity is shown to be larger directly underneath each LED with dips in light intensity between the lamps. Turning to Fig. 14 each lamp has a transparent cover with prisms as shown in Fig. 6B. The peaks and dips in light intensity are still present but a diminished due to the redirected light.

[0096] Fig. 15 shows an embodiment of a lamp according to the invention with engagement means 13 in the metallic carrier 10 for hanging on rafters.

[0097] Fig. 16 shows a flow simulation of one side of a lamp 1 in a preferred embodiment with the curved transparent cover 30 and the metallic carrier 10 with a fin 17 which in combination provides optimal conditions for passive cooling. Reference signs list

[0098] Lamp 1

[0099] Metallic carrier 10

[0100] Longitudinal edge 10i

[0101] Heat dispersing surface 11

[0102] Installation surface 12

[0103] Engagement means 13

[0104] Rim section 14

[0105] Spacer 15

[0106] PCB mounting surface 16

[0107] Fin of metallic carrier 17

[0108] Drip edge 18

[0109] PCB 20

[0110] LED 25

[0111] Transparent cover 30

[0112] Convex outer surface 31

[0113] Prisms 32

[0114] Flank prisms 32 i

[0115] Centre prisms 32ii

[0116] Inner surface 33

[0117] Flank section 34

[0118] Central section 35

[0119] Apex of transparent cover 36

[0120] Gasket 37

[0121] Attachment means 40

[0122] Plant surface 50

[0123] Longitudinal dimension L

[0124] Height dimension H

[0125] Width dimension W

[0126] Transverse dimension T

[0127] Spacer distance X

Claims

P A T E N T C L A I M S1. A lamp (1 ), comprising a metallic carrier (10) having a transverse dimension (T) and a longitudinal dimension (L) and comprising a heat dispersing surface (11 ) opposite an installation surface (12), and a heat conducting spacer (15) in thermal contact with the installation surface (12) and having a PCB mounting surface (16), a PCB (20) mounted on the PCB mounting surface (16), which PCB (20) carries a row of LEDs (25) in the longitudinal dimension (L) of the lamp (1 ), and a transparent cover (30) mounted on the metallic carrier (10), the transparent cover (30) having a transversally convex outer surface (31 ) and an inner surface (33) facing the PCB mounting surface (16), which heat conducting spacer (15) is sized to provide a spacer distance (X) from the LEDs (25) to an apex (36) of the inner surface (33) of the transparent cover (15), which distance is in the range of 3 mm to 50 mm, wherein the inner surface (33) of the transparent cover (30) comprises a flank section (34) defined by an angle (a) in a plane normal to the longitudinal dimension (L) of the lamp (1 ), which angle is defined from the PCB mounting surface (16) and is in the range of 5° to 60°, the flank section (34) of the inner surface (33) of the transparent cover (30) having a plurality of flank prisms (32 i) extending in the longitudinal dimension (L) of the lamp (1 ), which flank prisms (32i) are configured to direct light that reaches the flank section (34) of the inner surface (33) towards a surface opposite the PCB mounting surface (16).

2. A lamp according to claim 1 , wherein the heat conducting spacer (15) and the metallic carrier (10) are integrally formed.

3. A lamp according to any one of the preceding claims, wherein the metallic carrier has a length of at least 6 meters in the longitudinal direction.

4. A lamp according to any one of the preceding claims, wherein the PCB (20) carries one row of LEDs (25) in the longitudinal dimension (L) of the lamp.

5. The lamp according to any of the preceding claims, wherein the metallic carrier (10) comprises a first and a second longitudinal rim sections (14) along longitudinal edges (1 Oi) of the metallic carrier, and wherein the transparent cover (15) is mounted by press-fitting between the first and the second longitudinal rim sections (14).

6. The lamp according to any one of the preceding claims, the LEDs having a power rating in the range of 10 W to 24 W per 10 cm of the metallic carrier.

7. The lamp (1 ) according to any one of the preceding claims, wherein the inner surface (33) of the transparent cover (30) further comprises a central section (35) between the flank section (34) and the apex (36) of the inner surface (33) of the transparent cover (15), which central section (35) comprises a plurality of central prisms (32ii) extending in the longitudinal dimension (L) of the lamp (1 ), which central prisms (32ii) are configured to direct light that reaches the central section (35) of the inner surface (33) towards a surface opposite the PCB mounting surface (16).

8. A greenhouse lighting system comprising a plurality of lamps (1 ) according to any one of claims 1 to 7, wherein the lamps (1 ) are arranged in parallel at a distance from each other in the range of 1 m to 5 m.

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