Apparatus for the adjustment of spacing between growing plants

Apparatus for the Adjustment of Spacing between Growing Plants This invention relates to a means of automatically moving plants as they grow so as to minimize wasted space between them.

Background

Plants grown indoors are typically germinated in close proximity to each other but, as they grow, they need to be moved further apart to allow them space to increase in size. There is a conflict between the labour needed to keep adjusting the spacing between them and the desire not to waste space between them -especially under artificial lighting where every photon that falls on the gap between plants is wasted energy and adds to the cost of cultivation.

Many cultivation methods involve growing plants in some form of individual holder, container or support structure that allows the plants to be moved relative to each other as they grow. This approach allows the seed to germinate in a very small space. For example, consider a hydroponics system in which seeds are inserted into a small cube of mineral wool or phenolic foam, 1cm on each side, to germinate. As the plant grows, it may then be transplanted to a larger pot or container. In this case, the small cube is typically placed inside a hole in a larger cube. These seedlings are then typically spaced out in a rectangular grid, giving them sufficient space to grow to the size at which they will be harvested.

When grown indoors, any space between plants is being lit and heated unnecessarily. Rearranging them manually is labour intensive and, in stacked "vertical" farms, it is difficult for a human to reach the plants. Automated mechanisms are typically expensive and require significant space -for example, to manoeuvre a fork-lift truck between the stacks of trays.

Designs exist for a circular or toroidal growing area within which plants are moved radially outwards as they grow. For example, NL 1004974 C2 (BAKKER et al.), JP 2012024076 A (ABE et al.), CN 108207605 A (CUI), EP 0263857 Al (SJOSTRAND). However, these mechanisms are large and typically require a complete circle as they rely on the rotation of the area to drive the slow outward motion of the plants and/or to bring all plants to fixed planting and/or harvesting areas. They also have complex and/or large structures within the growing space to "nudge" the plants outwards.

There is therefore a need for a simple, low-cost mechanism that gradually separates plants as they grow. Preferably, this should be compatible with (and, ideally, retro-fittable to) existing growing systems and scale down cost-effectively to small spaces.

Statement of Invention

Seedlings and, optionally, their growing medium are placed in carriers which are supported on a pair of parallel rails (optionally joined to form a gutter). The pairs of rails or gutters are closely grouped at the planting end where seedlings are inserted but then fan out towards the opposite end. A channel within at least one rail of each pair (or one side of a gutter) allows the insertion, to any required distance, of a carrier moving mechanism that can be optionally engaged with a carrier allowing it to be pulled or pushed along the rails. Repeating this as the plants grow gradually increases the separation between plants as they are moved along the gutter to the harvesting end which they reach when ready to be harvested or transplanted.

Introduction to the Drawings

Figure 1 shows a perspective view of an exemplary plant hanger.

Figure 2 shows a perspective view of a plant hanger holding a seedling in a mineral wool cube.

Figure 3 shows a perspective end-view of an exemplary gutter within which one or more plant hangers will be placed.

Figure 4 shows a more detailed view of an upper edge of one side rail of the gutter of Figure 3.

Figure 5 shows a perspective view (not to scale) of a LED light fitting that can be clipped into the gutter.

Figure 6 shows a perspective end-view of the gutter holding a hanger and fitted with lighting circuits on both sides; light fittings and Bowden cable positioning mechanism on one side.

Figure 7 shows a side view of an exemplary hanger engaging mechanism in the raised (engaging) state.

Figure 8 shows the hanger engaging mechanism of Figure 7 in the lowered (non-engaging) state.

Figure 9 shows a perspective view along a gutter with the retractable protrusion at the end of a Bowden cable positioning mechanism about to engage with a plant hanger.

Figure 10 shows a side view of a horizontally compact positioning mechanism.

Figure 11 shows a plan view of a rectangular growing tray fitted with 8 gutters in two opposing triangles.

Detail of the Invention The plant moving mechanism discussed below support a variety of cultivation methods in which each plant is grown in a dedicated growing medium and/or support, holder or carrier that can be moved relative to that of neighbouring such holders. The terms "support", "holder" and "carrier" are considered interchangeable throughout. "Hangers" are a subset of these.

This scope encompasses both traditional, individual, plant-pots and many forms of hydroponics. Note that the growing medium itself can act as such a holder or carrier in some cases -such as rockwool cubes.

Note that for some crops, each plant holder or carrier may hold more than one plant growing together.

The continuous flow approach is particularly suited to rapidly growing crops of modest height that are harvested in their entirety on reaching a target size -such as lettuce. The invention is therefore described with regard to an exemplary hydroponic system in which lettuce seedlings are each grown in mineral wool cubes approximately 5cm on each side and are harvested when approximately 20cm in diameter and spaced 25cm apart. However, the approach is easily adaptable to other crops and other growing systems.

Options for Moving Plants Patent application GB1816403.8 (BLAIR) by the same inventor and hereby incorporated in its entirety by reference describes a mechanism by which plants held in carriers with magnetic material on their bases are individually moved using electromagnetic forces acting through the bottom of the growing tray to drag the carrier holding the plant and its growing medium. This allows for movement in any direction and works in any size or shape of tray or trough but does require sophisticated control and sensing. It also requires space beneath the growing area and constrains the dimensions and materials used to form the tray.

The aforementioned application also discusses an overhead "grab" mechanism not unlike those found in arcade games where children attempt to lift a toy with the X/Y positioned grabber mechanism. This is cost effective for the rotating growing space described there as all plants pass daily beneath the limited range of a single such grabber on each layer. So long as the fingers of the grabber are narrow and open space is maintained between plants as they grow, this is a simple and cost effective approach. The space it requires above each growing space, and the positioning mechanisms needed to add it to an existing system of static growing trays makes it unattractive for retro-fitting to existing schemes.

An alternative to having magnetic carriers is to use simpler holders -such as a rockwool cube and a smaller number of magnetic pusher devices or "pucks" that can be positioned at or around any plant in a tray as needed.

A segmented or totally flexible "puck" consisting of two or more, typically vertically cylindrical magnets in close contact with the supporting surface (bar a nylon or Teflon"' glide layer) and vertical "fins" projecting upwards between. These fins are either hinged together or made from a single highly flexible membrane. The fins project upwards no higher than the top surface of the growing medium so as not to foul the leaves of the growing plants.

By directing electromagnetic fields from below the surface, using electromagnetic coils or small permanent magnets, mounted on a platform with controllable X/Y movement, each of the magnets can be pulled to any desired position.

To move the puck between plant carriers, the magnets can be aligned so that the fins form a straight line. On reaching the plant carrier to be moved, the magnets pass around the outside of the carrier, enveloping it in the fins. Further movement of the magnets thus drags the carrier, wrapped in a jacket of fins typically around at least three sides, pulling it in the direction required (normally towards the unwrapped or partially wrapped side). The magnets are then moved so as to unwrap the fins from around the carrier and it can "snake" its way to the next carrier.

Other mechanisms include a staggered conveyor belt at the bottom of the growing tray or pool. However, this is then in contact with the nutrient solution (less of an issue with flood and drain systems but difficult to keep clean and hygienic in permanently flooded pool). It also restricts movement to a (small) finite number of separate conveyors, each of which moves at a different rate. Taking this to its logical conclusion, a bed of rollers in the bottom of the growing space, each of which moves at a slightly different speed would allow more flexibility but these will not move plant carriers in two dimensions unless each line of growing plants has a separate conveyor angled away from its neighbours.

"Gutter and Inch-worm" Approach This approach is simple, affordable and can be retro-fitted to existing rectangular spaces as well as used in a rotating radial bed.

Figure 11 shows how a number of gutters (34) are arranged in a rectangular growing tray or pool (45). As shown in Figure 9, plants are held within the gutters, each in its own carrier or "hanger" (1) containing the plant (12) and (if using any) its dedicated growing medium (2). The gutters are in contact where seedlings are added (46), typically once a day. The gutters then fan out so as to be significantly further apart at the other end, where plants are harvested (47).

A hanger engaging mechanism (shown in Figures 7 and 8) is moved along the gutter walls by a positioning mechanism shown in Figure 10. This moves the hangers daily or every few days, one at a time, increasing the spacing between them along the gutter slightly each time so as to give each plant the space it needs to continue growing and to transport it to the harvesting areas of the gutter (47) as it reaches the size at which it is to be harvested.

When deployed in a rectangular growing tray (45), a "fan" of gutters occupy a triangular area. An identical but mirror-imaged triangle of gutters allows the same number of plants to be grown whilst being moved in the opposite direction. This increases the number of plants grown per tray to approximately three times that achieved on a static rectangular planting pattern with fixed spacing equal to that at the harvesting areas (47).

The aforementioned components and a number of alternatives to them are described in more detail below.

Plant Carriers Figure 1 shows a perspective view of a typical, reusable plant carrier -in this exemplary case, in the form of a hanger (1). This is preferably formed from a plastic such as medium density polyethylene (MDPE) but alternative materials, such as aluminium could be used. This exemplary hanger is designed to hold a 5cm cube of mineral wool (2). Figure 2 shows

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the hanger (1) filled with the mineral wool cube (2) which, being readily deformable, is pinched in along the top edges by indented collar (3).

Alternative hydroponic methods use no rooting medium -with the roots spreading out into a permanently filled pool of nutrients. In this case, although seeds are also typically germinated in a tiny cube of porous medium -typically 1cm on a side -subsequent root growth is not constrained to a medium. Such bare rooted plants are held in a much smaller hanger -the sides and base of which take the form of a largely open mesh basket. When hung from the gutter, the base of the basket is at the height required to support the plant with its roots just below the surface of the nutrient pool.

The roots are then free to extend in all directions through the mesh of the basket. For many crops, this approach allows a much smaller hanger -the width being dictated by the diameter of the plant stem at harvesting, or the roots at the time of inserting the young plant, whichever is greater.

The hanger is supported on the top rail of the gutter by horizontally projecting tabs (4,5,6,7). The gaps between the pairs of tabs on each side (4, 6 or 5, 7) allow a protrusion to rise up between them and then be pulled against the trailing edge of the leading tab (4 or 5). This allows hangers to be placed into the planting end of the gutter without a gap between them, maximizing the density of plants at that end.

Figure 1 shows a hanger with tabs at both front and back ends of the hanger. Such a hanger can be pushed in either direction along the rail and is supported at all four corners. In cases where the hanger is sufficiently rigid or where the base of the hanger rests on the floor of the gutter (or growing area if using separate rails), the hanger does not need to be supported at both ends. Hence it is possible to use hangers with only one pair of tabs-at the front edge (4,5).

For optimum plant density, the carrier and gutter system should add as little width to the growing medium, plant-pot or bare-rooted plant as possible. Hence the side walls (8,9) are as thin as practical and the bulkier top section of the rails is accommodated inside the gutter. This requires a collar (3) rather than extending further beyond the width of the growing medium.

In cases where the crop has little or no vertical stem, the top of the growing medium (2) needs to be almost level with the top of the hanger (1). If the growing medium is easily compressible, the collar (3) is advantageous as compression of the top edges of the growing medium (2) holds it firmly in place. There is little impact on the root system by restricting the width at the top of the growing medium.

Preferably the front and back of the hanger (1) are largely open so as to allow nutrients to reach the growing medium (2) and the roots to extend along the gutter if required.

The trailing side of the base of the hanger has a raised lip (10) to ensure the mineral wool cube (2) and plant (12) do not slide out of the carrier when it is moved in the direction of the leading edge (11). The leading side is preferably completely open to allow easy insertion and removal of the mineral wool cube (2) containing the seedling (12) growing in the centre of its top face.

Root Spread For crops with roots that will extend beneath the growing medium, the gutter can be deeper than the hanger. To allow the roots to extend into the gutter, the base (13) of the hanger (1) is preferably formed of a substantially open lattice in this case.

For crops with wider root systems than the growing medium or hanger can accommodate, the gutter is advantageously replaced by two independent wall sections or "rails" that are not joined together at the base. These need not extend to the bottom of the pool of nutrients in which they typically hang. They just need to be deep enough and rigid enough to allow the rails to be hung from the edges of the tray or pool without sagging significantly in the middle.

This may require strengthening members such as steel inserts in the walls (16, 17) so as to provide sufficient rigidity without the walls extending far below the top of the hanger. Alternatively, instead of a plastic extrusion, gutters or individual rails may be made from extruded aluminium for additional strength.

In such cases, the side walls (14, 15) of the hangers may also be constructed as largely open lattices. This allows the roots to spread out sideways beneath the lower edge of the rails.

Gutter Extrusion Figure 3 shows a perspective end view of an exemplary gutter (34) which is advantageously formed as an extrusion. Figure 4 shows the detail of the top corner of the same gutter. The gutter shown in Figure 3 is symmetrical, allowing for hanger engaging mechanisms (and their attached positioning mechanisms) and supplementary low-level lighting to be provided on both walls (16, 17) of the gutter.

For lightweight crops, only one wall or rail need have the hanger engaging mechanism. For those not requiring much additional lighting, either or both sides may not require the lighting circuits and channels. In the simplest case, one wall of the gutter may be a simple vertical support and hence cheaper as its only purpose then is to support the (undriven) side of the hangers (1).

At the top of side walls (16, 17), at a height just above the walls of the nutrient holding tray or pool into which the gutters are to be placed, the walls are thickened to hold the plant moving mechanism and, optionally, lighting system. The former moves along an open channel (19) in the upper surface of the gutter -formed from a tapered substantially vertical slot (20) intersecting a circular hole (18) of slightly larger diameter than the bottom, wider edge of the tapered slot (20).

Artificial Lighting Preferably plants are moved (in their hangers) so that as one is harvested, those behind it in the gutter (34) are moved along one (variable distance) position to occupy the site previously taken by their slightly older and larger predecessor. Thus the locations of hangers (1) remains constant from day to day. This allows focused down-lighting to be aimed at these hanger positions to suit the size and shape of the plant at that position and hence stage in its growth.

For example a single focused spotlight aimed at the centre of the first hanger (1) avoids wasting light on the rest of the growing medium (2) as the recently sprouted seedling (12) is only present there. This may be further optimised by being mounted just above the seedling. With several gutters side by side, a grid of such spotlights can be positioned across the first few carrier positions.

Conversely, as the plants grow to occupy the bulk of the space, the lights need to be raised higher and cover a wider area about the centre of each carrier.

Supplementary Low-level Lighting Optionally, for crops that benefit from it, additional LED lights can be included in the guttering to provide lighting underneath and beside the plant. This can achieve additional growth and can modify the shape of the plants as well as the health of the lowest leaves that are otherwise shaded from light sources above the plant.

Holes at regular intervals along the top surface of the gutter would allow LED holders to be inserted so as to make contact with power rails but for simpler construction and more flexible light positioning, channel (23) is formed in the extrusion profile. This allows LED holders (28) to be inserted anywhere along the gutter (34) with access to the power rails. LED holders (28) can therefore be placed as needed to match the precise locations to which hangers will be moved. This also allows clusters of LEDs to be grouped close together, providing more intense light if needed.

The lighting circuit uses wires (35,36 on one side, 37, 38 on the others) that are embedded within the gutter extrusion in circular holes (21, 22) and one or more LED fittings (28) as shown in Figure 5 (not to scale) and in position in Figure 9. Preferably, these holes allow bare metal power rail wires to be inserted -across which an LED driver circuit provides the voltage necessary to light the LEDs. In the case of an aluminium or steel gutter, only one such wire and hole is needed as the gutter itself can act as the earth return path. However the walls of the hole (21 or 22) or the wire must be electrically insulated in this case. If the wire is insulated, positive contact (30 or 32) is replaced with an insulation displacement connector as used in telephone "punch-down" wiring.

Peg (33) on a light fitting (28) is pushed downwards through open channel (23) in the top surface of a gutter wall or rail. This channel (23) is beyond the extent of the hanger's tabs (5, 7) so does not foul them. The side walls of this channel (23) are substantially vertical and parallel except for an indent (24) used to "click-fit" with a complementary protrusion on the light holder's peg (33) when the peg is fully pushed into the channel (23).

The angled bottom face (26) of the channel, combined with a correspondingly angled bottom edge (31) of the peg (33) ensures that the light fitting cannot be pushed fully home unless oriented correctly. This ensures that metallic contacts (30, 32), at different heights on the peg (33), each make contact with the appropriate power wire where channel (23) intersects wiring holes (21, 22). The contacts (30, 32) are connected to the appropriate terminals of the LED light (29) which is mount in angled face (27) so as to direct the light as required.

The holder shown has the LED (29) angled at 45 degrees but this may vary according to the plant type and stage of growth that is present at this location along the rail. Some plants will hang over the LED holder and lighting directly upwards may be advantageous. Similarly, light may be focused using a lens over the LED source -particularly where the plant is still very small -only a few centimetres in size -thus avoiding wasting light that would otherwise fall elsewhere.

If the gutter or rail extrusion is made of a flexible plastic, outer corner (25) acts as a spring, pressing contacts (30, 32) onto the wires (35, 36) present in holes (21, 22) thus ensuring a good electrical contact and allowing reliable and positive "click-fit" insertion of deliberately tight-fitting peg (33).

Where lighting needs are known and static, gutters can be manufactured with LED lights already and permanently inserted rather than requiring the addition of light fittings (28).

By using transparent growing trays, lights can be built into the bottom face of the gutter so as to shine through the tray onto the plants beneath (assuming trays are stacked). When aligned with the tray below, this can eliminate the need for separate light fittings and ensure light is concentrated along the lines of the gutters where it is most needed. By fitting LEDs with different lenses, the light shining on the gutter beneath can be optimized to the size of the plant at that point along the gutter.

Spacers, Barriers and Reflectors Slotted channel (23) and its indent (24) allow other components to be click-fitted into it along the gutter as required. It can therefore be advantageous to have channel (23) present in both rails even if lighting is not required.

Spacing brackets (61) of various lengths can be clipped into the channels of adjacent gutters to hold the gutter at an appropriate distance from its neighbours. This is shown in a pair of 4 gutter fan-outs in Figure 11.

However, where crops tend to overhang the edge of the gutter, spacers may be better connected between the sides or at the bottom of the gutters so as not to foul the leaves when the plants are pushed along the gutters. Holes at regular intervals along the gutter allow click-fit pegs to be inserted lower down the gutter walls.

Vertical barriers can be clipped into the channels along some or all of the length of the gutter and/or edge(s) of the growing tray (45). For example, where larger plants would otherwise spread over adjacent seedling in the neighbouring gutter (59, 60), a barrier can prevent this. Optionally barriers may have one or more mirrored surfaces so as to reflect light back into the plants thus providing additional side lighting. This is advantageous where the spread of light from light fittings extends beyond the plant at this stage of its growth.

Note that during early growth, concave mirrored surfaces can be used to focus light into the centre or the gutter -directly onto the tiny seedlings. During later growth, where the plants typically extend beyond the gutter, vertical barriers (62) with mirrors on both faces are placed down the centre line of the spacers (61) instead of along the gutter channel.

Alternatives to Gutters If a variety of plants and hence different widths of plant hanger (1) are needed, a more flexible alternative to a gutter is a pair of separate side walls or "rails" that can then be held at the required separation by cross members between them at intervals.

Where different heights of plant hanger are needed, rather than keep multiple heights of such rails, the top section of the wall may be strengthened and/or variable height vertical supports provided at intervals allowing the top rail to be hung from the edge of a growing tray or held at any desired height above the base of the growing surface.

When using a gutter or rails with solid vertical walls that reach the floor of the tray or pool, these will substantially restrict the flow of nutrient solution across them. This allows different nutrients to be directed to different "tracks" of plants within the same tray.

Equipped Gutter Figure 6 shows an end view of gutter (34) holding hanger (1) containing mineral wool cube (2) in which seedling (12) is growing. Light fittings (28) are inserted at intervals along the gutter. Wires (35,36 and 37, 38) provide power to both sides, thus allowing lights to be inserted on either or both sides of this gutter.

In this example, a plant moving mechanism is provided on one side only. This mechanism, shown in Figure 7, consists of a positioning mechanism using a Bowden cable that is inserted or retracted to align the hanger engaging mechanism, in this case formed from a simple flexible filament (41) attached to the inner cable (40).

Exemplary "Inch-worm" Hanger Engaging Mechanism Cylindrical hole (18) allows a Bowden cable (39, 40) of slightly smaller diameter than said hole to be inserted to any desired distance along the gutter (34). Such cables allow a force to be transmitted via their inner cable (40) to wherever the far end of the cable is located. They are commonly used to activate bicycle brakes and, closer to the lengths of several metres being used here, flight surfaces on light aeroplanes.

In most such applications, the outer sheath (39) is fixed in position. Here, however, it is extended into the gutter as required so as to apply the force at different distances along the gutter. Advantageously therefore, to avoid chafing and wear, the outer sheath (39) and/or the surfaces it contacts are made from or coated in a hard-wearing, low friction material such as Teflon"' or nylon.

Note that if the walls (16, 17) of the gutter (34) are only slightly taller than the hanger (1), it is acceptable for the hanger (1) to be weighed down by its contents-namely growing medium (2), absorbed nutrient solution and increasingly heavy plant (12) -so as to contact the floor of the gutter. The hanger (1) need only be rigid enough to allow it and its contents to be pushed (slowly) along the gutter (34) by the forces that can be applied to the trailing edges of the hanger's front tabs (4, 5). To aid this, the upper surfaces of the gutter walls (16, 17) and/or bottom surfaces of the hanger tabs (4, 5, 6, 7) may be made from or coated in a low friction material such as, for example, nylon or TeflonTM.

Figures 7 and 8 show a flexible member (41) that can be raised (Figure 7) or lowered (Figure 8) by moving inner cable 40 relative to outer sheath 39. Flexible member (41) is formed of a flexible ribbon, plastic filament or braided wire rope, preferably made or coated in a high friction material or with a roughened surface so as not to slide under the hanger's tabs (4, 5) when pulled against them.

This flexible member (41) is rigidly attached to near-end collar (42) -typically by crimping it thus deforming collar (42) into an oval. This still encircles the inner cable (40) but is not attached to it and is kept open enough in its lower half to allow inner cable (40) to pass through this collar (42) unhindered. The inner radius of collar (42) is, however, too small to allow it to be pulled over the outer sheath (39). The flexible member (41) will naturally push this collar (42) back against the face of the sheath (39) unless the flexible member (41) is almost fully extended -as shown in Figure 8. There is therefore no need to affix collar (42) to sheath (39).

Far-end collar (43) is rigidly affixed to both the inner cable (40) and flexible member (41) -again, typically by crimping it into an oval shape such that when inner cable (40) is extended, as shown in Figure 8, flexible member (41) is pulled taut and lies almost parallel with the inner cable (40).

In this state, although protruding slightly above the top of sheath (39) -and hence advantageously constraining its movement at all times to within the tapered slot (20) above the circular section (18) of the channel (19), flexible member (41) does not protrude above the top of the channel (19). It can thus pass beneath hangers' tabs (4, 5, 6, 7).

By retracting the inner cable (40) relative to outer sheath (39), as shown in Figure 7, the flexible member (41) is forced to rise -in the same way an inch-worm arches its back when pulling its front and back legs together. It will therefore engage with hangers' tabs (4, 5, 6, 7).

Alternative Hanger Engaging Mechanisms Where smaller hangers are used and the tabs (4, 5, 6, 7) extend substantially along the whole length of the hanger (1), a single, small circular hole within a single tab is preferred to a gap between two tabs. The inch-worm mechanism is replaced by a pin of slightly smaller diameter than said hole. This requires more precise alignment of the pin and hole which can be accomplished by means of an optical sensor next to the pin. This can detect where the hole is and, knowing the distance between sensor and retractable pin can adjust its position so the pin engages with the hole.

This more "high-tech" approach can be achieved using derivatives of instruments normally used in medical key-hole surgery instruments -i.e. long retractable instruments with sensors and actuators on the distal end and power and/or control wires along their length.

Alternative Flexible Positioning Mechanisms There are many alternatives to the described "Bowden cable and inch-worm" approach. For example, a hydraulic cable may be used, with pressure being applied at the proximal end to force a hinged element on the distal end to form a right angle and thus protrude through the channel (19). On releasing the pressure this falls or is actively pulled back to the horizontal.

A small, preferably cylindrical, balloon on the end of a hollow tube could be inflated so as to protrude above the surface of the channel (19) when needed to move a hanger or retract fully into the slot when deflated to pass under the hangers.

A miniature electric actuator attached to the end of a flexible cable containing power and control wires is a further alternative.

Rigid versus Flexible Positioning Rods/Cables/Pipes Where space at the end of the gutters is limited, flexible positioning members are preferred but otherwise a rigid rod can be used instead. If access is available to both ends of the gutter, the hanger engaging mechanism need only be inserted up to the mid-point of the gutter -so the member need only be half the length of the longest such gutter.

In this case, cheaper devices on the end of rigid rods can be used. For example, these can be modelled on straight laparoscopic instruments with mechanical actuators.

A further alternative would be a threaded rod extending the full length of the circular hole (18). This needs a deep screw-thread cut into it and into which a protrusion on the underside of the lip of the hanger (4, 5, 6, and/or7) extends via the channel (19) and tapered slot (20). By gradually increasing the pitch of the thread along the length of the rod, a fixed number of turns will move each of the hangers a distance corresponding to the average pitch of the thread that at the point they are traversing.

An alternative topology has the moving mechanism in the floor of the gutter rather than the top edge(s). However, this exposes the mechanism to the nutrient solution.

Positioning the Hanger Engaging Mechanism Preferably the Bowden cable's outer sheath (39) is marked with stripes at regular intervals allowing it to be inserted or withdrawn a known distance by use of an optical sensor observing the passage of these stripes beneath it.

Alternatively, for example, a stepper motor may drive a spindle onto which the Bowden cable (or hydraulic pipe or wired cable in the case of alternative flexible options) is wound or unwound a calculated number of steps to reach a specific position. This, however typically requires the actuator -which pulls or pushes the inner cable (40) -to be mounted in the spindle.

An alternative approach that conserves floor-space is shown in Figure 10. This turns the Bowden cable (39, 40) (or other flexible alternative) via an articulated (typically nylon) cable tray or guide wheels (48) so as to run vertically rather than horizontally. As the outer sheath has to move through this bend, a static bend would wear the outer surface over time hence the need for wheels or rollers.

The cable is then turned (49) through 180 degrees close to the floor (58) so as to run vertically upwards, to a height equal to approximately half the length of the gutter. A further 180 degree turn round a further set of guide wheels (50) points it down again to the actuator (57) fixed near ground level. This actuator (57) and the can be fixed in position as can the outer sheath of the Bowden cable (39) using fixed bracket (56).

The axle of the upper guide wheels (50) is raised or lowered by a stepper motor to any height within a range equal to approximately half the length of the gutter. Given the 2 to 1 mechanical advantage of the up and down path, this pushes the far end of the Bowden cable (39, 40) in and out over the full length of the gutter.

Throughout their lengths, the Bowden cables are constrained to run straight rather than bend by outer conduits or cable guides (54, 55, 52, 53). In the case of the variable height sections, telescoping guides are required (52, 53).

Operating the Hanger Engaging Mechanism On arrival between the tabs (5 and 7 -or 4 and 6 according to which side of the gutter is being considered), the actuator (57) pulls on the inner cable (40) so as to bring its end almost in line with that of the outer sheath -as shown in Figure 7. This causes the flexible member (41) to rise up through the tapered slot (20) and protrude through the channel (19) in the top of the gutter (34).

Movable guide wheels (50) are then raised a few millimetres, pulling the outer sheath (39) slightly out of the gutter. The flexible member (41) contacts the tab (5) of the hanger (1) and moves the hanger (1) and contents (2, 12) to the desired position. Depending on the size and weight of the plants, this may require such a mechanism to be used on only one or both upper edges of the gutter.

Having repositioned a hanger (1) as required, actuator (57) pushes the inner cable (40) out again, as shown in Figure 8, flattening the flexible member (41) which again drops beneath the top surface of channel (19) allowing the outer sheath (39) to be inserted further or withdrawn as required by, respectively, lowering or raising guide wheels (50) and thus passing under the tabs (4, 5, 6, 7) to reach the next hanger (1) where the process is repeated.

By inserting the hanger engaging mechanism to the far end of the gutter and then alternately raising and lowering the flexible member (41) as it is gradually withdrawn, each of the hangers (1) can be moved by the required increment. This increment increases as the plants grow.

Lifting Plants from Gutter In a further refinement, such a plant moving mechanism can also remove the fully grown plants from the gutter as follows. This uses a modified gutter end section in which the upper surface and channel (19) ramp up to a height at which the bottom of the hanger is above the wall of the growing tray or pond (45).

The final movement of each hanger thus pulls it up the ramp and out of the tray. Preferably, the stem is severed allowing the hanger (1), used growing medium (2) and roots to fall into a receptacle from where the hangers are recovered, cleaned and reused. The head of the plant is then packed for shipment.

Inserting Plants into Gutter Similarly, at the opposite end of the gutter, an automated planting unit can slide hangers containing seedlings over the wall of the tray and down a ramped end section before merging into the horizontal rails along the rest of the length of the gutter. In this case, the hanger that was previously at the start of the gutter should already have been dragged further along the rails so there is no need to push it out of the way.

Optimizations for Multiple Gutters Since plants typically need only be moved every day or two, whilst it is perfectly possible to have separate positioning and hanger engaging mechanisms on each edge of every gutter, it is more cost effective to have a shared mechanism across many.

Two main approaches can be used. Either can be used at the planting and/or harvesting end where it may share components (microprocessor, memory, power supply, sensors, actuators etc.) with an automated planting or harvesting mechanism respectively.

Shared, Movable Mechanism A mechanism able to insert and withdraw a single Bowden cable and hanger engaging mechanism can be mounted on a platform that is aligned with and then inserted into each gutter edge, one at a time. A tapered funnel is used. This can be on the movable device containing the Bowden cable and/or the end of each gutter itself may be machined to open out a tapered access to the circular hole (18) and tapered slot (20) into which the end of the hanger engaging mechanism must be inserted.

The movable platform containing the positioning and inner cable actuator assembly is moved such that the end of the hanger engaging mechanism (41) is positioned using standard robotic X,Y,Z positioning so as to align with the hole and slot (18, 20) on a gutter (or the tray and gutter may come to it as in the case of a "lazy Susan" rotating growing bed). The Bowden cable is thus guided into the slotted channel without needing to be precisely aligned. Note the tapered end cap (or "nipple") (44) on the inner cable (40). Preferably this end cap (44) and or the funnel is made of or is covered in a low friction material such as nylon or Teflon"' so as to avoid snagging as it is inserted.

This approach requires precise alignment with the gutters but is small and gives ultimate flexibility in how the gutters are used. It can move the plants in different gutters by different amounts. For example, it can be used to push a hanger, in which the plant has died, right up against the next one rather than giving it the normal spacing. It can also bunch up or space out hangers more than normal in any particular gutter if demand for the crop varies or the growth rate is not as planned.

Shared Static Mechanism and "Cable Loom" However, since the Bowden cables and "inch-worm" mechanisms are cheap, an alternative approach is to use a static mechanism as shown in Figure 10 for a single gutter -running the cable down then up to a variable height and down again to a fixed actuator -but have this act on multiple Bowden cables, each of which is manually and permanently inserted into a given gutter rail.

This is simpler but typically larger and requires more initial "cabling" as the many Bowden cables have to be routed via cable ladders or guides with acceptable bend radii and low friction or rollers to reach the insertion/retraction and actuating mechanisms. Routing these carefully to one side and then combining those from other layers into a common trunking conduit allows automated planters/pickers to access the gutters without significant obstruction.

The guide wheels (48, 49, 50) that turn the Bowden cables up and then down again can be extended (perpendicular to the diagram) into rollers with a slot for each cable (requiring approximately 7mm per cable). Moving upper roller (50) vertically then inserts or retracts multiple cables across multiple gutters. Only a single such mechanism is required even if different gutters require different movements as it is only necessary to insert the cables to the far end of the gutter and then retract them all slowly -say, 2mm at a time, pausing to allow any actuators to raise or lower the appropriate flexible members (41) at each step.

Which hangers get moved how far in which gutter is still completely flexible if the actuators (57) pulling on the end of each gutter's inner cable(s) are independent. If this flexibility is not required, inner cables (40) from multiple gutters can be attached to a common actuator bar that pulls equally on all of them.

Gutter Assembly Figure 9 shows a cross-section of a gutter (34) holding seedlings (12) in hangers (1). These gutters may be used in a variety of ways: on a slight slope with continuous nutrient flow down them; with their ends sealed in a flood and drain approach or set inside a larger growing tank (45) or pool which may be flooded and drained as a whole.

In Figure 9, flexible member (41) has been inserted as far as the second hanger and raised ready to push this hanger into the gap beyond it (to the top right in the diagram).

Arrangement of Gutters Figure 11 shows a simplified plan view of a typical arrangement of 8 gutters (34) fitted to a typical existing tray (45) measuring 1.25m x 4m. Two triangles of 4 gutters each extend from opposite corners. Seedlings are planted where the gutters are tightly packed (46) and are then separated as they grow and are moved along the gutters every day or two till they reach the harvesting areas (47).

A typical arrangement is shown with 6cm wide gutters fanning out to 25 cm spacing at the harvesting end. Thus a tray 1.25m wide accommodates 4 full grown lettuce and 4 seedlings at each end. As the average spacing along the gutters is similarly less than the 25cm that would be allowed with static planting, a similar increase in the number of lettuce in each row is obtained. Thus the capacity of the tray (45) is more than doubled and it no longer produces a batch of 80 lettuces every 30 days. Instead, 8 lettuces per day are produced continuously -3 times the productivity.

Not that towards the ends of the tray, there is a full-grown lettuce next to a seedling. For some crops this may require a vertical barrier (59, 60) between the two triangles so as to prevent leaves from the fully grown plant spilling over and shading the nearest seedling. It is also important that lighting is provided directly above or from the side of the tray where the seedling may otherwise be shaded by the neighbouring fully-grown plant and/or vertical barrier.

Note that this scheme allows these gutters to be retro-fitted to existing trays. It also allows an arbitrary rectangular space to be configure for continuous production flow in both directions. Alternating triangles of gutters interleave to fill one the width. The length of each gutter determines how far the plants need to be moved in order to traverse it during their growing period. Thus the longer the gutter, the more plants are harvested at one end and added at the other each day.

In the case of a rotary, toroidal growing bed, all gutters simply fan out radially. This preserves the ability of such arrangements to bring all plants (in a given layer) past a common point on the inner rim for insertion of new seedlings and a second point, on the outer rim, for harvesting.