A greenhouse top light

Abstract

The top light 1, particularly for installing in a greenhouse, comprises a pair of LED assemblies mounted horizontally on a mounting structure, laterally alongside one another on either side of a longitudinal centre line of the top light. Each LED assembly is tiltable between a downward-facing neutral position and a tilted position. The LED assemblies may be mounted between opposing upright end plates, optionally with an inner and an outer attachment point on each plate, respectively proximal the centre line and an outer edge of the plates. The inner attachment points may comprise pivot points, optionally defined by a through-hole in the end plate through which a bolt is inserted to be received in the LED assembly. The outer attachment points may be located along an adjustment slot, optionally arcuate around the inner attachment point and / or defining a discrete set of locations.

Description

Field The invention concerns greenhouse top lights i.e. top lights of a type suitable for mounting within and illuminating a greenhouse environment. Such top lights tend to be mounted high up, to provide artificial lighting to support crop growth below. Background Provision of suitable artificial lighting can have a considerable impact on greenhouse plant growth, particularly where available natural light is restricted. In the northern hemisphere, where natural light levels are variable and inconsistent, supplementary artificial lighting is frequently used in commercial greenhouses to boost crop growth. A difficulty with top lighting in greenhouses is non-uniform illumination of the crops across the greenhouse depending on placement of the top lights. A further drawback is the concentration of the light on the upper crop canopy, and an absence of light to lower leaf layers. Proposed artificial lighting solutions have utilised inter-canopy lighting to supplement the top lighting, wherein light sources are mounted on fixtures placed lower down, amongst the crops, and beneath the upper crop canopy. The lights are operated to provide a combined lighting effect. Inter-canopy lighting installations can however be expensive to install and operate, and make it more difficult to work with the crops. An alternative solution which is more commercially viable and less restrictive to greenhouse workers is required. Summary In a first aspect of the invention there is provided a top light, for example a greenhouse top light for installing in a greenhouse. The top light comprises a mounting structure configured to enable fixing of the top light in the greenhouse. The top light further comprises a pair of LED assemblies each LED assembly comprising an array of LEDs. The LED assemblies are mounted horizontally on the mounting structure and are positioned laterally alongside one another on either side of a notional longitudinal centre line of the top light. Each LED assembly is configured to tilt with respect to the mounting structure about a rotation axis parallel the longitudinal centre line between a neutral position and a tilted position, wherein when installed in the greenhouse, in the neutral position the array of LEDs is disposed in a horizontal downwards-facing plane, and in the tilted position the array of LEDs is disposed in an angled downwards-facing plane. An LED assembly may be a light engine which will be understood by the skilled person to be an integrated LED assembly comprising an LED driver and array of LEDs. The top light may comprise a plurality of LED assemblies. The top light may comprise a plurality of pairs of LED assemblies. The present invention provides, through the implementation of a pair of adjustable LED assemblies, for example which may form part of a plurality of adjustable LED arrays, improved illumination of crops growing in a greenhouse. In particular, the present invention provides a way of illuminating the entire crop canopy including layers beneath the top canopy, from a single light fixture, without requiring additional lighting. The present invention is therefore of particular benefit for greenhouse lighting of vine growing crops. Providing tiltable LED assemblies enables the optimisation of light intensity within a greenhouse. Light intensity can be increased through either, or a combination of, selecting a suitable mounting height for the top light and selecting a suitable tilt angle for the LED assemblies to take account of different crop types and spacings between rows. Use of tiltable lights as claimed has been found to provide a significant increase in light intensity which in turn increases crop yield. The mounting structure may comprise two opposing upright end plates . The LED assemblies may be mounted horizontally between the two end plates. Each LED assembly at each longitudinal end may be mounted to a respective end plate at an inner attachment point towards the longitudinal centre line. Each LED assembly at each longitudinal end may be mounted to a respective end plate at an outer attachment point towards an outer edge of the end plates. The inner and outer attachment points of each end plate may be symmetrically disposed about a notional vertical centre line of the end plate. The inner attachment points may comprise pivot points. The rotation axis of each LED assembly may extend between corresponding inner attachment points on the opposing end plates. Each pivot point may be defined by a through-hole in the respective end plate through which a bolt is inserted and received in a recess in a longitudinal end of the corresponding LED assembly. Each adjustment slot may be shaped to enable free movement of the bolt from a lowermost position at a bottom end of the slot to an uppermost position at a top end of the slot. Each end plate may comprise an adjustment slot. The outer attachment point may have a location along the adjustment slot. There may be a discrete set of locations for the outer attachment point along the adjustment slot. Each LED assembly may comprise a recess at each longitudinal end for receiving a bolt inserted through the respective adjustment slot at the outer attachment point. Each adjustment slot may be defined by a circular arc around a centre point corresponding to the respective inner attachment point. Each adjustment slot may extend up from a notional horizontal base line of the end plate, wherein the horizontal base line passes through the inner attachment points. There may be two, three, or more locations for outer attachment points along each adjustment slot. There may be four locations for outer attachment points along each adjustment slot. There may be multiple locations for outer attachment points along each adjustment slot. The outer attachment points may be disposed between 0-90 degrees, for example between 0-45 degrees, from a notional horizontal base line of the end plate. A first location may be at 0 degrees from the notional horizontal base line of the end plate. A second location may be at 15 degrees from the notional horizontal base line of the end plate. A third location may be at 30 degrees from the notional horizontal base line of the end plate. A fourth location may be at 45 degrees from the notional horizontal base line of the end plate. In use, the degree of tilt is selectable by an operator. The degree of tilt can be selected to optimise the light intensity and coverage within the greenhouse. The degree of tilt can be varied to enable different mounting heights of the greenhouse top light. In a second aspect of the invention there is provided a method of adjusting a greenhouse top light including the steps of: providing a greenhouse top light comprising two LED assemblies mounted horizontally on a mounting structure, the LED assemblies each being mounted to rotate with respect to the mounting structure about a notional horizontal rotation axis; and rotating the LED assemblies in opposing directions, so that the LED assemblies move from a neutral position wherein the LED assemblies face downwards, to a tilted position wherein the LED assemblies are angled downwards by equal and opposite angles. In a third aspect of the invention there is provided a method of adjusting a greenhouse top light including the steps of: providing a greenhouse top light comprising two LED assemblies disposed horizontally between two upright end plates, wherein the LED assemblies are attached at each end to a respective end plate by a rotating bolt and a sliding bolt; loosening the sliding bolts; tilting at least one of the LED assemblies and simultaneously sliding the sliding bolts within a slot in each end plate, to thereby rotate the LED assembly about a pivot point defined by the rotating bolt; fixing the sliding bolts in place at a corresponding attachment point on each slot. The end plates may be substantially vertically arranged. Drawings An embodiment of the present invention will now be described by way of example only with reference to the accompanying schematic drawings: Figure 1 is a perspective view of a greenhouse top light according to the example embodiment; Figure 2 is a perspective view of the greenhouse top light according to the example embodiment; Figure 3 is an end view of the greenhouse top light according to the example embodiment in a neutral position; Figure 4 is an end view of the greenhouse top light according to the example embodiment in a tilted position; Figure 5 is a perspective view of the greenhouse top light according to the example embodiment in the neutral position; and Figure 6 is a perspective view of the greenhouse top light according to the example embodiment in the tilted position. Detailed Description A greenhouse top light 1 according to the example embodiment of the invention (Figures 1 and 2) comprises two horizontally disposed LED assemblies 5 attached between two vertically disposed end plates 3. The LED assemblies 5 each comprise an array of LEDs 7 mounted in a frame 9, as is known in the art. The LED assemblies 5 are powered via a cable assembly 11 (best shown in Figure 2) which connects the LED assemblies 5 to a power supply (not shown). The cable assembly 11 comprises a top cable 13, arranged between an external power supply (not shown) and the right side end plate 3a (in an alternative embodiment, it could be the left side end plate 3b). The top cable 13 at its upper end is fitted with a connector 17 for attaching to a power supply, and at its lower end is connected to a power splitting box 19. The cable assembly 11 further comprises two lower cables 15, arranged between the right side end plate 3a and the LED assemblies 5. Each lower cable 15 is connected at an upper end to the power splitting box 19, and at a lower end, through the right side end plate 3a to a respective LED assembly 5. The LED assemblies are powered from an AC or a DC supply. Each end plate 3 (Figure 3) comprises a number of cut-out portions as will be described in more detail below. Each end plate 3 is symmetrical about a notional vertical centre line. In the example embodiment, each end plate 3 is identical, which simplifies manufacturing, although in an alternative embodiment the right and left end plates 3a, 3b could be different. The LED assemblies 5 fix in a similar manner to each of the end plates 3a, 3b. The cable assembly only attaches on one of the end plates, in the example embodiment of the invention to the right side end plate 3a. In the example embodiment, each end plate 3 comprises a mounting recess 21 in each upper corner (when held in an orientation ready for installation) in which brackets can be inserted for mounting the top light 1 within a greenhouse, for example to the trusses or supporting profiles of the greenhouse. Each end plate 3 further comprises a plurality of small bores 23 disposed towards the top edge 24 of the end plate 3, for attaching the power splitting box 19 to the end plate for example with a nut and bolt in each small bore 23. Each end plate 3 further comprises a pair of larger holes 25, through which the lower cables 15 extend, to connect with the power splitting box 19. The holes 25 are disposed centrally between the bores 23, towards the top edge 24 of the end plate 3. Each end plate 3 further comprises a pair of curved channels 27 through which the lower cables 15 extend, to connect with the respective LED assemblies 5. The channels 27 are disposed towards the bottom edge 29 of the end plate 3. Each channel 27 has the shape of an arc, forming part of a circle about a respective pivot point 37. The right 27a, and left 27b channels form mirror reflections in the notional vertical centre line of the end plate. The channels have a width sufficient to enable the lower cables 15 to move within the channels from top to bottom. Each channel 27 extends a distance vertically above and below the respective pivot point 37. Each pivot point 37 is formed by a pivot bolt 36 within a bolt hole. The pivot bolts 36 attach an inner edge of each LED assembly 5 to the end plate 3. The pivot bolts 36 comprise a non-threaded portion extending through the end plate, thereby being configured to rotate within the bolt holes. The LED assemblies 5 tilt about a rotation axis passing through the pivot points 37 of opposing end plates 3. Each end plate 3 further comprises a pair of curved slots 31, disposed towards the left edge 33 and right edge 35 of the end plate 3. Each slot 31 has the shape of an arc, forming part of a circle about the respective pivot points 37. The slots 31 form mirror reflections in the notional vertical centre line of the end plate. The slots 31 are disposed radially outside of the channels 27 on each end plate 3. Each slot 31 extends up towards the top edge 24 of the end plate 3 from a notional horizontal base line of the end plate 3 which incorporates the pivot points 37. Inserted in each slot 31 is an adjustment bolt 39. Each adjustment bolt 39 attaches an outer edge of a respective LED assembly 5 to the end plate 3. The LED assemblies are therefore attached to the opposing end plates via the pivot bolts 36, and the adjustment bolts 39. The adjustment bolts 39 are at least partly straight sided so that they can move freely in the slots 31 from top to bottom. Each slot 31 comprises a plurality of fixing points 41 along the arc, wherein the adjustment bolts 39 can be tightened at each fixing point 41 to secure the LED assembly 5 in position with respect to the end plate 3. An operator can select a degree of tilt for each LED assembly 5 by tightening the adjustment bolts 39 at a desired fixing point 41. The series of fixing points 41 enables a progressive tilt of each LED assembly 5 about the respective pivot point 37. In the example embodiment of the invention, the fixing points 41 in each slot 31 are disposed at 0 degrees, 15 degrees, 30 degrees and 45 degrees from the notional horizontal base line of the end plate. The LED assemblies 5 can be tilted by the same, or by differing angles depending on the application. In a neutral position (as shown in Figures 3 and 5) the LED assemblies 5 are in a horizontal position at 0 degrees from the notional baseline defined through the pivot points 37. The LED assemblies 5 are fixed in place with respect to the end plates 3 by the adjustment bolts 39 at the lowermost fixing points 41 of each end plate 3a, 3b. In a tilted position (as shown in Figures 4 and 6) the LED assemblies 5 are in a tilted position, at 45 degrees from the notional baseline defined through the pivot points 37. The LED assemblies 5 are fixed in place with respect to the end plates 3 by the adjustment bolts 39 at the uppermost fixing points 41 of each end plate 3a, 3b. In another tilted position (not shown) the LED assemblies 5 may be tilted at 15 degrees or 30 degrees from the notional horizontal baseline. In use, to adjust the position of the LED assemblies 5, the adjustment bolts 39 on each end plate 3a, 3b, are loosened. The LED assemblies 5 are moved, for example one at a time, by tilting the LED assembly 5 such that the adjustment bolts 39 slide within the respective slots 31 on each end plate 3a, 3b. When the adjustment bolts 39 are at the relevant fixing point 41 for the required tilt position, the bolts 39 are tightened on each end plate 3a, 3b. Frequently a symmetric illumination of the crops is optimal, but the LED assemblies 5 do not necessarily have to be adjusted to the same tilt angle, and can be adjusted to different tilt positions if required, for example, to target different crop areas. During tilting, at the same time as the adjustment bolts 39 slide within the respective slots 31, the lower cables 15 move up or down within the channels 27. Experiments have shown that light intensity is considerably higher at all measured heights above floor level when a top light according to the example embodiment is used to illuminate a greenhouse growing cucumber vines, compared to conventional and LED standard top lights. 5 Light intensity, PPFD (umol / m2 / s) provided by top light according to the example embodiment measured in horizontal planes at various measurement heights above floor level Measurement height (m) Vine number Data comparison V1 V3 V5 Average Increase compared to conventional toplight (%) Increase compared to standard LED toplight (%) 3 534.2 575.4 535.8 548.5 57 50 2.5 436.9 452.7 437.3 442.3 52 45 2 308.7 327.1 334.2 323.3 42 46 1.5 261.1 263.4 267.7 264.1 95 93 1 200.3 204.8 195.3 200.1 93 77 10 The increase in light intensity over the cucumber vine provided by the present top light compared to a conventional top light averaged over all measurement heights is 68%. The increase in light intensity over the cucumber vine compared to an industry standard LED top light averaged over all measurement heights is 62%. Light intensity, PPFD (umol / m2 / s) provided by top light according to the example 15 embodiment measured in vertical planes at various measurement heights above floor level Measurement height (m) Vine number Data comparison V1 V3 V5 Average Increase compared to conventional toplight (%) Increase compared to standard LED toplight (%) 3 245.9 251.0 257.1 251.3 51 42 2.5 186.0 180.3 187.4 184.6 37 29 2 151.0 148.5 149.9 149.8 37 42 1.5 112.6 117.3 116.1 115.3 59 68 1 84.2 79.3 82.4 81.9 31 30 The increase in light intensity over the cucumber vine provided by the present top light compared to a conventional top light averaged over all measurement heights is 43%. The increase in light intensity over the cucumber vine compared to an 5 industry standard LED top light averaged over all measurement heights is 42%. 10

Claims

1. A greenhouse top light for installing in a greenhouse, the top light comprising:a mounting structure configured to enable fixing of the top light in the greenhouse;a pair of LED assemblies each comprising an array of LEDs, the LED assemblies being mounted horizontally on the mounting structure and being positioned laterally alongside one another on either side of a notional longitudinal centre line of the top light;each LED assembly each being configured to tilt with respect to the mounting structure about a rotation axis parallel the longitudinal centre line between a neutral position and a tilted position, wherein when installed in the greenhouse, in the neutral position the array of LEDs is disposed in a horizontal downwards-facing plane, and in the tilted position the array of LEDs is disposed in an angled downwards-facing plane.

2. A top light according to any preceding claim, wherein the mounting structure comprises two opposing upright end plates , the LED assemblies being mounted horizontally between the two end plates.

3. A top light according to claim 2, wherein each LED assembly at each longitudinal end is mounted to a respective end plate at an inner attachment point towards the longitudinal centre line, and at an outer attachment point towards an outer edge of the end plates.

4. A top light according to claim 3, wherein the inner and outer attachment points of each end plate are symmetrically disposed about a notional vertical centre line of the end plate.

5. A top light according to claim 3 or 4, wherein the inner attachment points comprise pivot points, and wherein the rotation axis of each LED assembly extends between corresponding inner attachment points on the opposing end plates.

6. A top light according to claim 5, wherein each pivot point is defined by a through-hole in the respective end plate through which a bolt is inserted and received in a recess in a longitudinal end of the corresponding LED assembly.

7. A top light according to any of claims 3 to 5, wherein each end plate comprises an adjustment slot the outer attachment point having a location along the adjustment slot.

8. A top light according to claim 7, wherein there are a discrete set of locations for the outer attachment point along the adjustment slot.

9. A top light according to claim 7 or 8, wherein each LED assembly comprises a recess at each longitudinal end for receiving a bolt inserted through the respective adjustment slot at the outer attachment point.

10. A top light according to any of claims 7 to 9, wherein each adjustment slot is defined by a circular arc around a centre point corresponding to the respective inner attachment point.11 .A top light according to any of claims 7 to 10, wherein each adjustment slot extends up from a notional horizontal base line of the end plate, wherein the horizontal base line passes through the inner attachment points.

12. A top light according to any of claims 7 to 11, there being four locations for outer attachment points along each adjustment slot disposed between 0-90 degrees, for example between 0-45 degrees, from a notional horizontal base line of the end plate.

13. A top light according to claim 12, wherein a first location is at 0-5 degrees from the notional horizontal base line of the end plate, a second location is at 12-18 degrees from the notional horizontal base line of the end plate, a third location is at 27-33 degrees from the notional horizontal base line of the end plate, and a fourth location is at 42-48 degrees from the notional horizontal base line of the end plate.

14. A top light according to claim 9 or any of claims 10 to 13 when dependent on claim 9, wherein each adjustment slot is shaped to enable the bolt to move from a lowermost position at a bottom end of the slot to an uppermost position at a top end of the slot.

15. A method of adjusting a greenhouse top light including the steps of:providing a greenhouse top light comprising two LED assemblies mounted horizontally on a mounting structure, the LED assemblies each being mounted to rotate with respect to the mounting structure about a notional horizontal rotation axis;rotating the LED assemblies in opposing directions, so that the LED assemblies move from a neutral position wherein the LED assemblies face downwards, to a tilted position wherein the LED assemblies are angled downwards by equal and opposite angles.

16. A method of adjusting a greenhouse top light including the steps of:providing a greenhouse top light comprising a pair of LED assemblies disposed horizontally between two upright end plates, wherein the LED assemblies are attached at each end to a respective end plate by a rotating bolt and a sliding bolt;loosening the sliding bolts;tilting at least one of the LED assemblies and simultaneously sliding the sliding bolts within a slot in each end plate, to thereby rotate the LED assembly about a pivot point defined by the rotating bolt;5fixing the sliding bolts in place at a corresponding attachment point on each slot.10

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