GB2578092A - Apparatus for high density, automated cultivation - Google Patents

Abstract

Apparatus for growing plants comprises an annular or circular growing surface, rotatable about an axis perpendicular to the growing surface with means to move the plants relative to the growing surface. Preferably, the environmental conditions can be varied according to radial distance and angular position. Rotation may be performed automatically. Preferably the growing surface is divided into multiple growing trays 701, the floor of each forming a segment of the growing surface. Multiple growing surfaces may be stacked vertically. The apparatus may feature a transparent surface, light sources supported by a mesh and/or a central air duct that may have vets to control the rate of airflow. Sensing apparatus and/or manipulating devices may be attached to a beam that radially spans the growing area, the apparatus and devices preferably capable of moving along the beams. The plants may be held above the growing surface in a carrier.

Description

Apparatus for High Density, Automated Cultivation This invention relates to a means of growing plants in a controlled environment using space and light more efficiently whilst reducing construction costs and making automation easier.

Background

There are many reasons why plants are grown in a controlled environment as opposed to in the ground, outdoors. The methods for doing so range from the traditional greenhouse or "poly-tunnel" to high-tech "vertical farms". By stacking plants in layers, one above the other, a vertical farm multiplies its effective area many times over. By carefully controlling light (which then has to be provided artificially), nutrients, irrigation, air quality and temperature, plants can be grown as rapidly as possible, throughout the year. The productivity per square metre per annum is therefore many times that of an open field.

However, such vertical farms are not all profitable. They need to command high prices for the produce to make a profit given the rent, labour, seed, growing medium, nutrients, water and energy costs that are incurred. Complex monitoring and control systems are used to fine tune the environment to ensure the maximum yield.

As such high density "farms" have developed, it is obvious that many of the tools, components and mechanisms used are incremental derivatives of long-standing techniques and devices rather than designed for truly optimal production. For example, many LED "grow-lights" are identical in size, shape, fittings and voltage requirements to the fluorescent tubes that they now replace. Lighting manufacturers are, naturally, keen to give existing users a simple "retro-fit" upgrade path -but that is sub-optimal for new builds.

Plants are typically germinated in trays consisting of a grid of many, small "plugs" of growing medium. As the plants start to grow, these are transplanted into a more widely spaced grid -where they stay until harvested. It is obvious that, until fully grown, a rectangular grid of growing plants will have wasted space between the plants. This not only reduces the density of plants below that which could be achieved, it also means that much of the artificial light being provided falls on the tray between the young plants rather than being absorbed by a plant.

Recent advances in robotics (such as W02018119407A1, W02018132814A1) allow for fully automated growing facilities. However, the approach taken there involves two types of robot. One performs the delicate planting/harvesting operations on each plant. Another, large and expensive one brings large trays of plants to the former.

High density racking systems, especially those with moving racks, as used in vertical farms are expensive. A further object of this invention is to provide a low cost apparatus that can be constructed from off-the-shelf parts where possible and by unskilled construction workers. This should make it more viable in poorer countries where the increased productivity is badly needed but capital and construction skills are scarce.

Inspiration has been taken from the low-tech but highly effective rotating irrigation devices used around the world to water a huge circular field with a single motor, some scaffolding and a couple of wheels. Likewise, the simplicity of construction of a "lazy Susan" has been noted.

Statement of Invention

The present invention replaces the static, rectangular grid in which plants are grown in trays with a rotating, annular growing space, within which plants are moved as they grow.

Newly germinated seedlings are added at the inner edge of the annulus where the spacing between plants is at a minimum. As the plants grow, they are moved outwards towards the outer edge of the annulus. This gradually increases the separation between them as their foliage grows. Plants are then harvested from the outer edge.

By rotating the annular growing area once a day, all plants pass any fixed radial line allowing cameras, robotic handlers, sprays and other devices mounted thereon to monitor and act on every plant daily as it passes them.

Plants requiring N hours of lighting per day need to be in lit segments of the space for that period. As the plants move under the lights, only N/24ths of the toroid need to be lit. This reduces the number of lights and allows them to be on 24 hours per day giving steady state heat and lighting conditions. This also allows the temperature in the lit ("day") segment of the space to be maintained above that of the dark ("night") segment.

Introduction to the Drawings

Figure 1 shows two different sizes of rockwool growing medium and corresponding carrier frames into which each is placed.

Figure 2 shows a pre-fabricated inner collar component. Four of these are bolted together to form a structure at the inside edge of the annular growing area.

Figure 3 shows the pre-fabricated outer collar component. Twenty of these are bolted together to form a structure at the outside edge of the annular growing area.

Figure 4 shows a bearing block that allows a tray to move over it easily in any direction. Figure 5 shots a support spoke with bearing blocks attached.

Figure 6 shows the completed support assembly for an annular growing area.

Figure 7 shows a single, transparent acrylic growing tray.

Figure 8 shows the support structure of Figure 6 fully loaded with the trays of Figure 7 to form a single annular growing layer.

Figure 9 shows a stack of 3 growing layers of different heights.

Figure 10 shows an Optimal Plant Positioning Robotic Apparatus ("OPPRA") that moves and observes the plants as they pass above and below it.

Figure 11 shows the location of a stack of OPPRAs next to the packing station. Detail of the Invention The spacing, speed, lighting, temperature, air and nutrient requirements for efficient indoor cultivation vary from crop to crop. To provide a concrete example of the invention, the hydroponic farming of Butterhead lettuce (Lactuca sativa var. capitata) is used below. This takes approximately 30-40 days and the lettuce, when harvested, occupies approximately a sphere of 20cm diameter. These parameters influence the optimum dimensions of the apparatus.

The example discussed uses hydroponic "flood and drain" cultivation with a rockwool substrate. The same approach works for several other growing techniques -including more traditional cultivation in which each plant is in a standard plant pot containing soil. This latter approach can be used, for example, in a nursery producing pot plants for sale.

Figure 1 shows how the growing substrate is supported at the desired height, within a framework or "carrier" that can be used to move it around the growing area as the plant grows.

Seeds are typically planted in a hole (9) at the centre of the top face of a tiny rockwool cube (1) -say 25mm on each side. The cubes are normally in trays of 150 or so and have a density of approximately 1600 per square metre.

As the roots reach the outer faces of this cube, the whole cube (1) can be placed in the precut hole (10) in the top face of a larger cube -say 100mm on a side (5).

In existing hydroponic "gutter" systems using the "flood and drain" (also known as "ebb and flow") technique, these cubes (5) are typically placed 200mm apart in plastic troughs into which nutrient solution flows as required, soaking the rockwool -which holds the moisture allowing the plant to absorb the nutrients. Troughs are typically spaced on 200mm centres in rectangular shelves. This gives a density of 25 plants per square metre. The plants remain in that position throughout the several weeks they take to grow from propagated seedlings to harvestable produce.

Multiple such shelves are stacked vertically giving a plant density of (25 x number of shelves per metre high) plants per cubic metre of racking. Very high density systems move racks on rails -in the same way that high density library shelving operates. This avoids the need for space between each rack. In the extreme case with many racks being moved and only space for a single access aisle at a time, the density within the overall growing space approaches that within a single rack (as stated above).

In this invention, however, plants are kept within the small growing cube (1) for longer achieving higher densities in the early stages of growth. This is only viable if the subsequent transfer into larger growing cubes (5) can be automated. To this end, growing cubes (1, 5) are held in metal carriers, designed to hold a cube of specific size at the optimum height and allowing it to be moved by the application of magnetic forces from beneath.

These carriers must therefore be made of magnetic material but also rust-proof -for example: stainless steel, galvanized or otherwise coated steel. They must also allow water and nutrient solution to flow freely into and out of the rockwool cube they support.

A solid steel base (2, 6) with an open cage structure as shown in Figure 1 may be used. Columns (3, 8) project upwards from the base and hold the rockwool cube (or flower-pot if designed for that) firmly in position. A cross-member (4, 7) or protrusions from the columns (3, 8) holds the base of the cube at the desired height above the base (2, 6). Alternatively, spikes projecting up from the base may penetrate the growing medium. This latter approach is preferable for growing media that do not maintain a rigid profile well.

The precise height at which the cube should be held is a function of the height of the plant being grown and the distance of the lights above the floor of the growing area. Preferably, the supporting structure (7) holds the rockwool cube (5) at least a few millimetres off the base (6) of the carrier -so that even if nutrient is not completely drained, none of the rockwool cubes are in contact with the residue. This ensured they only absorb nutrients when the growing area is deliberately flooded and not after it has been drained.

Note that a used tin can may be converted into an effective carrier to reduce costs -and is already food-grade and tolerant of prolonged contact with water.

Figure 2 shows a pre-fabricated aluminium arc (201) that forms one quarter of the inner "collar" of the apparatus. The inner collar (201) subtends 90 degrees with full thickness but slightly more than 90 degrees with asymmetrical flanges (202, 203) at each end. These are drilled to accept bolts such that adjacent section can be firmly joined to form a complete circle. Spoke sockets (204) are welded to the collar -in this example, at 9 degree intervals.

Figure 3 shows a pre-fabricated aluminium arc (301) which is, similarly, flanged at each end -in this case allowing 20 such sections to be bolted together to form the outer edge support structure for the growing space. Each section therefore subtends 18 degrees and connects to the outer ends of two spokes which are held in outer spoke sockets (302).

Figure 4 show a bearing block (401) that allows a tray (701) to move over it easily in any direction. Horizontal hole (402) allows the block (401) to be slipped over the end of a spoke (501). When vertical fixing hole (403) is aligned with a similar hole (502) in the spoke (501), the block can be fixed firmly in place with a single bolt passing through the spoke.

A pair of spherical roller bearings (404) protrude from the top surface of the block (401), supporting the trays (701) just above the level of the head of the bolt used to hold the block (401) to the spoke (501). The overall height of the assembly needs to be minimized so that as many layers as possible can be stacked vertically beneath a given ceiling height.

Alternative means of enabling the trays to move include, but are not limited to; a bed of spherical bearings; bearings built into the base of the tray. In a further variation, the spherical bearings (404) may be replaced with roller bearings aligned to allow tangential movement but not radial movement of the trays. In this case, in one segment of the annulus, additional bearings at 90 degrees to these may be raised (by means of a cam, for example) so as to rise above the level of the main bearings. This lifts the tray sitting above them by a few millimetres, allowing it to be slid into or out of the growing area.

Figure 5 shows a support spoke formed from a standard 4m long aluminium scaffolding pole (501). Holes drilled vertically through it at intervals allow a plurality of bearing blocks (401) to be firmly attached. Note that the separation between bearing blocks is greater towards the end attached to the inner edge of the annulus (502) than that at the outer edge (503).

Figure 6 shows a complete support assembly (601), constructed from the above components. Note that the inner collar is typically a few millimetres above the outer collar. This provides a very gentle slope so that the flooded trays can be almost completely drained of nutrients by a suction pipe at the outer edge of the growing area.

Note that a lower cost alternative is to simply form a level bed of rollers -for example, by mounting a number of bearing blocks or similar at a consistent height throughout the annulus. This obviously only works for a single layer growing space or the bottom level space in a vertical stack.

Figure 7 shows a growing tray (701) formed from transparent acrylic (Perspex/Plexiglass) of which 16 are required to fill the growing area of Figure 6. In this example, the walls (702) of the tray are 150mm high -taller than the top of the larger rockwool blocks (5) when mounted in the carriers of Figure 1. The depth is similar to that of a hydroponic "gulley" suitable for holding the rockwool cube size being used.

This allows the rockwool cubes (5) held in their carriers within the tray to be completely saturated if the tray is filled with nutrient solution to a depth of just over 100mm. The solution can then be drained from the tray with a suction pump using a pipe lowered into the tray. Preferably the pipe is surrounded by a filter that blocks particles from entering the pipe. The filter may be cleaned as required by lowering the pipe into a waste receptacle and reversing the flow of liquid (in this case water rather than nutrient solution) so as to blow debris off the filter and into the waste outlet.

The tray (701) is made of food-grade, non-leaching material. Preferably, especially if trays are being stacked vertically (see later), the tray is made of a transparent material. This allows light that falls between plants to reach other levels in a stacked system where it may be absorbed by a plant. Acrylic (Perspex/Plexiglass) is a good choice as it can be easily thermoformed into shape and it is easy to incorporate metal inserts.

Figure 8 shows sixteen trays forming a rectangular toroid directly above the annular growing area formed by the top face of the annular support structure of Figure 6.

Figure 9 show a vertical stack of 3 growing spaces (more can be added), supported by columns around the inner (901) and outer (902) edges of the support structure of Figure 6. Note that there are fewer columns (902) in the outer edge than there are trays (701) in each layer. A tray (701) can therefore be inserted or removed easily without fouling these columns (902).

Note that this also supports a mode of operation in which trays are slid out of the annulus at which point they can be manually cleaned, inspected and plants moved if manual labour is available and more cost effective than the automated alternatives.

Fixing holes every 25mm up the length of each column (901, 902) allow the position of any layer and hence its separation from the ones above and below to be adjusted to suit the crop being grown. Different layers may contain different crops and be positioned at different heights. The limit on the number of layers is a function of the interior height of the building.

Optionally, automated means of adjusting the height of each layer may be provided. For example, ceiling mounted winches with chains that attach to the inner and/or outer collars; hydraulic rams; manual winches.

This can be useful for maintenance tasks, for fine-tuning height as a result of ongoing observations and experiments and for changing crops on each layer.

The height between layers is determined by the height of that crop when harvested plus a space for lighting. When a single layer is used inside a greenhouse or under a transparent roof section, natural light can reach the plants. In this case, supplemental lighting may be provided if required. When multiple layers are used, artificial lighting -normally in the form of LEDs -must be provided. Other lighting mechanisms (e.g. HID lamps) may be used but LED is normally preferred for the lower heat output.

When stacked as in Figure 9, the stationary framework (601) supporting the layer above and/or the columns can be used to hang LED lighting from (not shown). Flat panels may be used but a wire mesh of individual point light sources allows for better cooling; lets light travel through the layers and allows the height of the lights above the trays to be varied easily.

This allows lights to be lower and hence closer to the smaller plants in the inner edge and at the full height of the layer towards the outer edge where the plants are taller. This allows light sources with wider angles of emission to be used -letting some light reach leaves from the sides that would normally be shaded from more directional lights hung further above the plants.

As well as the vertical position of the lights, the exact radial and tangential position of each point source can be aligned so as to provide optimum lighting to a single plant directly beneath it -taking into account the dimensions of the substrate cages (2, 6) and the spacing between these that is used at a given radius from the centre. At the inner edges this may be a single LED directly above the centre of the spot where the plant will be positioned. Towards the outer edge, this may change to a cluster of lights spread around an area comparable to the size of the plant beneath it.

To allow the system to place the pots precisely under a light or light cluster, a number of approaches may be used. For example, markers or a grid can be printed onto, etched into or affixed to the underside of the trays (701) so that a camera (1005) moving beneath the tray can precisely align the bottom of the plant cages (2, 6) that it sees through the transparent floor of the tray (701) with these markers.

The above approach only works well if the lighted portion has precisely aligned lights -yet a wire mesh may not be precisely aligned and/or some lights may not be pointing straight down. The exact pattern of lighting can be determined during commissioning of the system by placing a small wheeled robot into an empty tray (701) and letting it pass beneath the lit area -preferably at a rotational speed higher than the normal 1 revolution per day rate.

By moving back and forward radially between inner and outer edges of the tray as it is rotated, an upward facing camera and, preferably, light spectrum meter, can record the actual light intensity throughout the lit area. Preferably, the camera and/or light sensor can be raised or lowered and oriented in any direction to measure light falling on it from every angle at every possible position.

The results can later be used to correct any dark or hot spots before use; to calibrate the control system and to fine tune the placement of a plant of any given shape and height so as to maximize the light falling on it.

LEDs are typically provided around only a portion -typically no more than 18/24 -of the 360 degrees. As the layers are rotated daily, trays (701) pass beneath the areas where LEDs are present before moving into the area where there are none. All plants thus experience "day" of up to 18 hours (in this example) and "night" of 6 hours -yet only 75% of the area has to be equipped with lights.

On the radial boundaries between lit and non-lit areas, opaque vertical barriers may be hung down from the support structure above to just above the maximum height that the crop reaches. Black on the "night" side and reflective on the "day" side, these prevent significant light leakage from day to night spaces, bouncing the light back into the "day" area.

Note that this approach advantageously ensures that there is at least one segment of the annulus where lighting is not present -allowing automated plant handlers to operate unencumbered in this space. So, in the lit area, the lighting mesh can hang an LED a centimetre or two above the surface of the rockwool cube giving very precise, localised light as the first leaf appears. In the dark area, the space directly above the rockwool is open and available for automated plant handlers to operate there.

Preferably, the lighting mesh is run at low voltage (SELV levels) rather than mains. LED drivers -which are never 100% efficient -can be sited outside the annulus. Insulating panels can be built between adjacent columns (901, 902) to separate the toroidal volume within the growing area from the rest of the building.

Adjustable vents can be incorporated in such panels at the inner and/or outer edges of tha annulus. For example, an arrays of vents each spanning 10 degrees and a height of 200mm allows precise control over the radial flow of air through each segment of the circle and for each layer independently.

Thus, different temperatures and air flow rates can be achieved for the different crops in different layers and for the "day" and "night" segments of the annulus.

Some of these vents may direct air out and over LED drivers, cooling them to the outside or, when reversed, pull air in, warming it as it enters the growing space.

If the temperature within the stack is too high, colder air is blown so as to leave the stack and then pass over the heatsinks of the LED drivers. If the stack is too cool, however, the air flow can be reversed, pulling in pre-warmed air over the LED drivers into the annulus.

Using these vents, in conjunction with sensors, fans, mist-sprays, carbon-dioxide pipes and so forth (which can easily be hung from the rigid and stationary supporting structure of the layer above) a wide range of environmental conditions can be monitored and manipulated. This allows plants to be given different conditions according to the stage of their growth as they are gradually moved from inner to outer edges and within daily cycles as they rotate once around the structure each day.

Thus temperature, humidity, air-flow rate, carbon dioxide concentration, nutrients, light level and spectrum may be observed and finely controlled.

As the trays form a complete toroid, the trays in a layer can all be rotated about the vertical axis perpendicular to the centre of the annulus by applying a tangential force to any one of them. However, there are times when one or more trays is not present-when being cleaned for example, or if production at 100% of capacity is not required temporarily. In this case, it is important that neighbouring trays can be attached to each other so that the set of conjoined trays move together around the annulus when required.

This can be achieved by a variety of means, including but not limited to: U-shaped clips/brackets that fit over the tops of adjacent walls of two trays (701); by hook and eye or similar latches at adjacent corners of the inner and outer faces; by interlocking projections on the walls (such as dove-tail joints, allowing adjacent trays to be locked together and unlocked by raising one relative to the other, aligning the joints and lowering the raised tray again); holes in the walls through which bolts can be inserted and tightened onto washers using nuts.

The annulus (or partial annulus) of one or more trays needs to be rotated about the vertical axis through its centre. This is most easily achieved by means of a horizontal, tangential force applied towards the outer edge. A rotational speed of only one revolution in 24 hours is required to move plants from lit to dark space and back again each day. Faster operation is occasionally required -for maintenance operations for example.

When trays are flooded with nutrient solution, they are much heavier than they are once it has been pumped out again. Rotation is therefore easiest when all trays are empty of nutrient solution -as occurs after draining all trays. This is another reason to keep tray wall thickness to a minimum so as to minimize the mass and hence inertia of the annulus.

The tangential force may be applied to the outer wall of the tray or, preferably, to the underside of the tray -towards to the outer edge for maximum moment about the axis of rotation. This uses the weight of the tray itself to press onto the drive mechanism. This may be as simple as one or more rubber tyres on an axle driven by a highly reducing gearbox from a low power electric motor. This is the same drive mechanism as is commonly used on roller coasters -with a fixed rubber drive wheel over which the trays (701) pass.

Such a mechanism can easily by clamped between a pair of spokes beneath the trays it is to move. Alternatively, the underside and/or wall of the tray may incorporate teeth that engage with a drive cog. A belt in tension around the outside of the annulus could be used but makes it difficult to add or remove trays.

There may be multiple such drive mechanisms, distributed around the perimeter of the annulus, providing fault tolerance; more even movement and load sharing.

At least one inner (901) and outer columns (902) are positioned directly facing each other. Between these are strung a set of robotic plant tenders or "Optimal Plant Positioning Robotic Apparatus" (OPPRA) (1004). One of these is shown in Figure 10.

As shown in Figure 11, one runs beneath the bottom layer, one between each pair of layers and one above the top layer -giving one above and below every layer. These place new seedlings into the centre of the annulus; monitor each plant daily; (optionally) control the flooding and draining of each tray daily and move each plant as needed.

A parallel pair of taut cables or rails 300mm apart (1002, 1003) is hung (via insulators) from brackets (1001) attached to a pair of facing columns (901, 902) and thus spanning a 300mm wide strip of the annular growing space.

This "tramline" should be situated at the start of the dark ("night") segment of the annulus so that the lights it uses for its cameras do not interrupt the truly dark period that the plants require.

One or more electric stepper motors within the OPPRA (1004) acts to drive rubber wheels inside it that run on the top of the cables (1002, 1003) and propel it along the guide cables. This allows it to position itself anywhere between inner and outer edges of the annulus.

Microswitches or optical proximity sensors (1009) on front and back faces of the OPPRA (1004) detect the end brackets (1001) allowing the device to stop before it hits them and to recalibrate its position at the end of a traversal of the cables.

These cables (1002, 1003) act as both supports and power supply for this robotic device. A 24V D.C. supply is provided across the wires to avoid the need for a battery.

The OPPRA contains two cameras-one (1005) facing up to look at the underside of the tray above it. The other camera (1006) looks down on the foliage of the tray below it. Preferably, at least the downward facing camera includes depth sensors (as used by recent smartphones for facial recognition) so it can build up a 3-D picture of foliage growth as it passes over the plants.

A computer controller (1008) -for example an Arduino or Raspberry Pi computer -or a smartphone (which provides the cameras in a handily thin package) controls the device. This is in wireless communication with the other OPPRAs above and below it as well as the overall room controller (not shown).

A further electric stepper motor within the OPPRA drives a horizontal threaded rod perpendicular to the cables (1002, 1003) on which is mounted a powerful electromagnet (1007). This can therefore be moved tangentially approximately 150mm either side of the centre of the OPPRA (1004).

The bracket (1001) is positioned vertically such that, when not energised, the top of the electromagnet (1007) is a few millimetres below the base of the tray (701) above it. This allows the trays to move over it freely until a plant is to be moved. The upwards facing camera (1005) can locate the base of a plant carrier (2, 6) thanks to the trays (701) being transparent.

By positioning the electromagnet (1007) directly beneath the centre of the carrier (6) and energising the electromagnet (1007), the OPPRA is attracted to the plant carrier above, lifting it into contact with the bottom of the tray (701). By then moving along the radial wires (1002, 1003) and/or tangentially between them on its threaded rod, it can move the plant carrier-and its contained rockwool and plant-to the required location.

Knowing exactly when and where to move each plant requires a view from above. In a stacked system, this can be from a second, downward-facing camera (1006) on the OPPRA (1004) of the layer above. This camera -ideally equipped with depth-sensing capabilities not only senses where there are gaps between plants, it also allows the controller to gauge how well each plant is growing.

These factors together allow the control software to decide when and where to move the plant. If it needs more space it is moved towards the outer edge of the annulus. If it is not growing so well, it may be overtaken by the rest of its cohort. In extreme cases, a dead or dying plant and its carrier (6) may be moved right to the outer edge of the annulus and removed by the harvesting robot at the picking station rather than continue to waste space.

The thickness of the tray floor and walls is a trade-off between robustness versus weight and cost. A thinner floor is preferred as the OPPRA's electromagnets beneath it are used to act on the steel carriers (2, 6) holding the rockwool cubes (1, 5) and plants within them.

As the system rotates daily, automated tasks can be performed (once a day) on all plants by robotic equipment at one location on the outside edge of the annulus -the "picking station" (1101). The fully grown plants that have been moved to the outside edge are harvested as they pass this picking station. In this example, the growing areas are rotating clockwise (viewed from above) in Figure 11 -so approach the OPPRAs (1004) after passing the picking station (1101).

The robotic arm of the picking station may also deposit new seedlings in the outer edge of the tray for the plant tenders to move inwards as they reach them. However this may mean that many other growing plants have to be moved out of the way and back again to let the seedling head inwards.

Where plants are staged between two (or more) different sizes of growing medium (and hence carriers), an OPPRA may slide them through a gap they find or create in the outer part of the annulus so that a robotic arm can remove them from the outer edge, pull off the existing carrier and insert the rockwool cube into the hole in the middle of the larger cube and carrier before replacing it. The OPPRA then slides the plant back into the appropriate position in the annulus.

Using this mode of insertion, the picking station (1101) is prefrably positioned directly in line with the OPPRAs (1004) allowing a single robot to harvest fully grown plants, insert new seedlings and repot those needing larger grow cubes.

Alternatively, newly propagated seedlings and/or re-potted plants may be transported to the inner edge of the annulus by the OPPRA (1004) above the tray. The plant tenders are optimally positioned next to the picking station (1101) such that produce is removed from the tray at the picking station (1101) and the gap thus left at the outer edge of the tray then appears beneath the plant tender (1004) shortly afterwards. The plant tender notes the available space and moves the remaining plants outwards to fill the growing space optimally - with minimum space between the plants. This then leaves a gap at the inner edge of the annulus.

A grabber mechanism (not dissimilar to those that lift cuddly toys in penny arcade machines - but less likely to let go till told to) is affixed to a threaded rod in a similar manner to the electromagnet (1007) but hangs down beneath the device (1004). It too can therefore be positioned over any point beneath the guide cables (1002, 1003). At the outer extremity of the cables a seedling can be presented beneath the grabber. The grabber lifts the seedling's carrier, moves it to the gap in the inner edge and lowers it into place before releasing it.

Note that, as plants grow and the foliage becomes larger (obscuring the carrier from above) and taller (limiting the ability to fit between the tops of the walls of the trays and the bottom of the OPPRA), it becomes harder to lift and move them in this way. Hence the need for electromagnetic dragging of carriers from beneath.

In a further refinement, a more sophisticated electromagnet may be added to the top of the OPPRA. This creates a rotating magnetic field which, when applied beneath a suitably non-radially symmetric steel brush-carrier within the tray (701) overhead will both pull the brush down and spin it -cleaning the bottom of the tray.

Claims (25)

1. CLAIMS1. An apparatus for the cultivation of plants in which said plants are placed on an annular or circular growing surface, rotatable about an axis perpendicular to said surface forming a cylindrical or toroidal growing space and a means of moving said plants within said growing space.
2. 2. An apparatus of Claim 1 further characterised in that the environmental conditions including but not limited to temperature, humidity, air-flow rate, carbon dioxide concentration, nutrients, light level and spectrum are controlled so as to vary according to radial distance and/or angular position.
3. 3. An apparatus of Claim 1 further characterised in that rotation is performed automatically.
4. 4. An apparatus of Claim 1 further characterised in that multiple such growing spaces are stacked vertically.
5. 5. An apparatus of Claim 1 further characterised in that said growing area is subdivided into multiple growing trays, the floor of each of which forms a segment of the said growing space.
6. 6. An apparatus of Claim 1 further characterised in that the substantially horizontal surface of said growing space is transparent.
7. 7. An apparatus of Claim 1 further characterised in that lighting is provided above said growing area using light sources supported by a mesh allowing light to pass through them and air to pass around them.
8. 8. An apparatus of Claim 1 further characterised by having a central air duct through which air may be forced in either direction.
9. 9. An apparatus of Claim 8 further characterised in that the rate of flow of air from said duct is controlled by vents that can be adjusted independently for a plurality of segments around the inner and/or outer edges of said growing area.
10. 10. An apparatus of Claim 1 further characterised in that sensing and/or manipulating devices including one or more of camera, depth sensing camera, electromagnet, grab-hoist are attached to a fixed beam, rod, track or rail that radially spans said growing area.
11. 11. An apparatus of Claim 10 further characterised in that devices are moved radially along said means of attachment.
12. 12. An apparatus of Claim 1 further characterised in that said plants and growing medium are held above said growing surface in a carrier.
13. 13. An apparatus of Claim 12 further characterised in that at least part of said carrier in close proximity to said growing surface consists of a magnetic material.
14. 14. An apparatus of Claim 13 further characterised in that electromagnetic forces acting on said carrier are used to move said carrier and the growing medium and plant that it supports.
15. 15. An apparatus of Claim 5 further characterised in that said trays are mounted on spherical roller bearings allowing them to be easily moved in a horizontal plane.
16. 16. An apparatus of Claim 5 further characterised in that said trays are placed on a bed of roller bearings oriented radially with respect to said growing space, allowing them to be easily rotated around said growing space.
17. 17. An apparatus of Claim 5 further characterised in that said trays are raised when required on an array of roller bearings oriented tangentially to said growing space, allowing them to be easily inserted into and removed from said growing space.
18. 18. An apparatus of Claim 5 further characterised in that said trays incorporate means of attachment to an adjacent tray, including but not limited to: clips, bolts, interlocking profiles or adhesives, allowing two or more such conjoined trays to be rotated about the centre of said growing area via a tangential force applied to any of said conjoined trays.
19. 19. An apparatus of Claim 5 further characterised in that said tray incorporates means of applying a tangential force so as to rotate said tray about the centre of said annular growing area, wherein said means may be any of toothed rail or plane; high friction coating; high friction surface treatment or profiling so as to engage with complementarily shaped drive wheels, belts or cogs.
20. 20. An apparatus of Claim 7 further characterised in that the height of the light sources above said annular growing space increases towards the outer edge of said annular growing space.
21. 21. An apparatus of Claim 5 further characterised in that the inner surface of the tray is cleaned by means of a brush mounted under or made from a magnetic material that is moved across the surface and pulled towards it by means of a magnetic field applied from beneath said tray.
22. 22. An apparatus of Claim 7 further characterised in that the strength, direction and/or spectrum of light received at any point within said growing space is measured by a device moving at least radially beneath said lights as said growing area is rotated.
23. 23. An apparatus of Claim 22 further characterised in that the light sensing element can be automatically positioned at any height above the surface of said tray.
24. 24. An apparatus of Claim 22 further characterised in that the light sensing element can be automatically rotated about one or more axes so as to measure light arriving from different directions.
25. 25. An apparatus of Claim 3 further characterised in that rotational force is applied to the underside of said growing surface via one or more driven wheels supporting at least some of the weight of said growing surface.