GB2040658A - Cultivating plants - Google Patents

Abstract

In a method of and apparatus for plant cultivation, the growth medium in which the plants are to be grown, in trays (42), is moved continually around an endless path, the movement of the trays thereby creating movement of the ambient air relative to the plants and the growth medium to promote growth. The apparatus includes means for conveying the trays (42) around the endless path and may additionally include means for supplying water and/or steam to the growth medium. <IMAGE>

Description

SPECIFICATION Method of and apparatus for plant cultivation The invention relates to the cultivation of plants, in particular plants which require a closely controlled environment in which to propagate.

One example of a plant which requires a closely controlled environment is mushrooms. Mushrooms require a continual supply of clean, fresh air; a highly humid atmosphere; a controlled supply of fresh water; a closely controlled temperature; and, in some cases, controlled exposure to light It is well known to fill a number of trays with the growth medium in which the mushrooms are to be grown and to stack the trays on shelves in an enclosed growing room. Air is circulated within the growing room buy a number of fans but, in order to achieve good and even air circulation in a room of standard height, the trays must not be stacked more than five or six feet high. Watering is done entirely by hand and thus it is almost impossible to water each tray equally or evenly.

Furthermore, there is usually a temperature variation between the bottom tray and the top tray of between 10 and 12" C, and this means that only the trays near the centre of the stack will be at the optimum temperature. Finally, if the growth medium must be exposed to a controlled amount of light, this will also be difficult if the trays are stacked.

In order to overcome these problems and in accordance with the present invention, a method of plant cultivation comprises moving the growth medium in which the plants are to be grown in trays or baskets continually about an endless path, the movement thereby creating movement of the ambient air relative to the plants and growth medium to promote growth.

With this method the problem of air circulation is overcome since the trays or baskets themselves create air movement and each tray or basket moves through the same air space.

Preferably, the trays or baskets are moved con tinuouslyaboutthe endless path although a stepwise movement may be appropriate in some cases.

The invention includes mushrooms which have been cultivated by the above method.

The invention also includes apparatus for use in the cultivation of plants, the apparatus comprising a plurality of trays or baskets for holding a growth medium in which the plants are to be grown, and means for conveying the trays or baskets around an endless path.

Preferably the conveying means comprises a pair of horizontally spaced, endless driven belts between which the trays or baskets are supported. In particular, the path of the trays may lie in a vertical plane.

With this arrangement, the column of trays may extend from the floor to the ceiling of the growing room and thus the ratio of growing area to floor area can be considerably increased over the known system.

The endless belts may be trained around two spaced-apart shafts, one of which may be connected to an air supply means for supplying air to the plants, and the other of which may be a drive shaft, having spaced thereabout extraction nozzles for extracting air, and including means for conveying the extracted air away from the trays. The quantity of fresh air in the system can therefore be closely controlled and the air speed across each tray, which in the case of mushrooms is ideally 0.5 feet per second, can also be controlled.

It is particularly convenient if the apparatus includes means for supplying water to the growth medium from the vicinity of the endless path. The water and/or steam may be sprayed as a mist into the path of the trays or baskets, the continual movement of the trays creating uniform exposure to the mist. It is useful if the water is preheated to a temperature just above that of the growth medium since this prevents the growth medium being "shocked" as would happen if cold water were used, and this also helps to maintain the overall temperature in the growing room and also its eveness.

The temperature and humidity of the atmosphere in the growing room may be additionally controlled during the growing process by supplying steam to the growth medium from the vicinity of the endless path. If the temperature in the growing room drops, a small amount of steam may be injected to raise it again. The supply of steam is preferably also used, prior to the growth medium being put into the baskets, to sterilize the apparatus. Once the growth medium is in place then it can be pasteurized by raising the temperature to about 60"C. The continual mixing of the air by the moving trays also decreases the temperature variation between the bottom and top of the apparatus to about 2" - 4"C. Temperature control is aided if the growing room is well insulated.

Uniform exposure to light is very simply arranged by having a single source adjacent to the apparatus and past which each tray moves at a uniform speed.

It will be appreciated that the apparatus of this invention is labour saving, the rotation of the trays saving an operator from having to move the trays around, not only during growing, but also during filling of the trays with the growing medium.

One example of an apparatus constructed in accordance with the present invention will now be described with reference to the accompanying drawings, in which: Figure lisa side-elevation of the apparatus; Figure 2 is an axial section through a drive shaft bearing; Figure 3 is a plan view of a pulley wheel; Figure 4 is an axial section through an upper shaft bearing; Figure 5 is a front elevation of the apparatus; Figure 6 is a side elevation of a tray and basket; Figure 7 is a partial front elevation of a tray and basket connected to an endless belt; Figure 8 is a diagrammatic view of an air diffuser; Figure 9 is a diagrammatic view of an air extractor; Figure 10 is a diagrammatic view of a pair of water nozzles; and Figure 11 shows two diagrammatic views of a steam pipe of the apparatus.

The apparatus comprises two A-frames 1 which may be made from mild steel and one of which is shown in Figure 1. The frame has four equally spaced cross-struts 2,3,4 and 5 and a base strut 6 which may be welded or bolted to the frame 1. The cross struts 5, which are additionally supported by reinforcing posts 7,8, support a bearing block 9. A drive shaft 10 is rotatably held at each end in respective bearing blocks 9.

The bearing arrangement is illustrated more clearly in Figure 2. Each end of the drive shaft loins surrounded by a stainless-steel sleeve 11 upon which an annular flange element 12 is non-rotatably mounted, held by a pin 13. The drive shaft 10 is supported in the bearing block 9 by a bush 14 and an annular bracket 15. Four annular steel spacers 16 are non-rotatably connected to the drive shaft 10 by pins 17.

The pins 13, 17 are designed to shear if there is a malfunction and thus the major components of the apparatus are protected from damage. In use, the bearings may have to support a load of 2.34 tons which produces a pressure of 2341bs per square inch. Also, as the apparatus is likely to be used in an atmosphere with a temperature of substantially 100"C (for reasons explained later) the bush 14 and washer 18 may be made of Tufnel which is a hard carbon-fibre material having a low coefficient of expansion and the property that the bearing surface improves with use. Lubrication is not required for these bearings because the speed of rotation is slow.

One end of the drive shaft 10 may be non-rotatably connected by a pin 19 to a further annular flange 20 which may be connected to a drive motor (not shown).

Between the two frames 1, the drive shaft 10 carries, adjacent to its ends, a pair of pulleys 21. Each pulley 21 comprises a single plate which is attached to the annular flange element 12. As may be seen from Figures 1 and 3, the pulley 21 has a plurality of equally spaced notches 41 spaced around its periphery.

Each cross-strut 2 supports a further bearing block 22 which is slidable on two rods 23 and can be fixed at any desired point along the rods 23 by means of an adjusting rod 24 connected to an adjusting nut 25.

Atop shaft 26 is connected between the two bearing blocks 22.

The arrangement is very similar to that for the bottom shaft 10 except that the top shaft 26 is non-rotatable in the bearing block 22. This may be seen best in Figure 4, which shows that a stainless steel sleeve 27 non-rotatably surrounds an end of the shaft 26. The sleeve 27 is rotatable in a bush 28 which is surrounded by an annular flange element 29. The bush 28 and the annular flange element 29 abut on each side a washer 30 one of which is held on the stainless steel sleeve 27 by two screw threaded locking rings 31. The top shaft 26 is supported between two brackets 32,33 of the bearing-block 22 which are spaced from the bush 28 by a spacer 34.

As with the lower bearing it is preferable that the bush 28 and the washers 30 are made from Tufnel and nylon.

The top shaft 26 carries, between the two frames 1, and at each end a pulley 21. Each pulley 21 is secured to the flange element 29 and is thus rotatable on the sleeve 27 and hence on the shaft 26.

The pulleys 21 on the top shaft 26 are identical with and aligned with the respective pulleys 21 on the bottom shaft 10. This may best be seen in Figure 5.

The rigidity of the apparatus is increased by a V-shaped supporting bracket 35 extending from the cross strut 4 to a central connecting beam 36, as shown in Figure 5.

Each pair of upper and lower pulleys 21 is connected by an endless belt 37. Each belt 37 is formed by a double chain of alternating steel links 38,39, the links 38 being straight and the links 39 generally triangular. As may be seen from Figures 6 and 7, the links 39 each support one of a plurality of trays 42, whilst the links 38 are merely spacing links.

The links 38,39 are connected together by link pins 40 and the links 39 have the foot of the triangle directed in the same direction outwardly of the path of movement. The link pins 40 engage in the notches 41 in each pulley 21. Each chain 37 is tensioned or loosened by adjusting the position of the bearingblock 22 with the adjusting nut 25 accordingly.

A plurality of trays 42 are suspended horizontally between the two chains 37 at equally spaced intervals along each chain. Each tray 42 has a rectangular base the long sides of which are formed buy a pair of stainless steel tubes 43 and the short sides of which are formed buy a pair of triangular end plates 44 welded to the tubes 43 as may be seen in Figures 6 and 7. The end plates 44 are connected to the triangular links 39 by pins 45 as shown in Figure 7 and the triangular shape of the links 39 provides additional clearance as the trays change direction at the top and bottom of their path.

The growth medium such as compost is placed in a number of baskets 46 which are then seated on respective trays 42. The baskets are formed by a number of rods 47 into the shape of a right-angled cage the base of which has similar dimensions to the base of the tray 42. The short ends of the basket are provided with handles 48. Nylon orwire mesh 49 provides the sides and base of the basket 46 and is connected to the rods 47 as shown in Figures 6 and 7.

The chains 37 are driven via the lower pulleys 21 by the drive shaft 10. Up to four apparatuses may be connected in series by their respective drive shafts 10 and all being driven by the same motor. In one example each apparatus has a torque load of 2 tons and the shaft 10, can endure a 2" twist. An electric motor of 15hp would be needed, in this case, to drive a set of four apparatuses and it is important that the first apparatus has a drive shaft 10 with a wall thickness twice that of the other three drive shafts.

This is necessary in view of the very high initial torque load.

A typical rate of rotation is 3 revolutions per minute which, for a A-frame height of twelve feet, is slow enough for the baskets 46 to be placed on and removed from the respective trays 42 while the trays are moving. In the example illustrated there are twenty two trays each having a base area of 10 square feet thus providing a total growing area of 220 square feet.

In the cultivation of speciality food products for example mushrooms, the environment in which they are grown is critical. In particular, they require clean, fresh air; high humidity; some light (depending on the strain); fresh water; and accurate temperature control varying from 100"C to 10 C.

In use the apparatus is set up in a closed growing room and the atmospheric conditions can be controlled remotely as will now be described.

The top shaft 26 of the apparatus is hollow and acts as an air supply pipe. The shaft 26 is provided with five equally spaced outlets 54 opening towards the bottom shaft 10, each opening 54 being connected to a respective air diffuser 55. One diffuser 55 is illustrated in more detail in Figure 10. The diffuser 55 comprises a spherical plastic or PVC container filled with wire wool 56 and has a number of apertures 57 through which air can escape. The diffuser 55 is connected to the shaft 26 by an air duct 58 passing through the hole 54, the end of the air duct 58 inside the shaft 26 being shaped to face towards the incoming air. The air duct 58 is sealed in the hole 54 by a rubber seal 59.

Fresh, filtered air is blown into the shaft 26 by axial flow fans, passes through the air duct 58, and is dispersed in the wire wool 56 to be emitted uniform lythrough the apertures 57. It has been shown that the ideal air speed across a mushroom tray is 0.5 feet per second. This is achieved in this case by the movement of the trays through the band of fresh air around the upper shaft. Thus the motion of each tray relative to the air creates an even flow of filtered fresh air across it creating a uniform air distributions.

The end of the shaft 26 remote from the air inlet is plugged and the air flow can be damped or stopped by a butterfly or ball valve located in the air stream prior to the shaft 26.

The fan or fans are arranged to produce a minimum of two complete changes of air per hour but are capable of up to six air changes per hour.

The bottom shaft 10 is also hollow and is used to extract air from the lower region of the growing room. It will also extract carbon dioxide which is produced during cultivation and which, due to its greater density, sinks to the bottom of the room. The shaft 10 is provided with five nozzles 60 made from GRP or fibre glass and spaced equally along the shaft as may be seen in Figure 5. One nozzle 60 is illustrated in more detail in Figure 11 which shows that the nozzle has an integral extraction duct 61 passing through a hole 62 in the shaft 10 and opening towards an extraction fan (not shown). The outlet duct 61 is sealed in the hole 62 with a rubber seal 63. The outlet end of the shaft 10 is connected to a matched axial flow fan identical to that used to inject air but with the direction of rotation reversed to create a suction.A butterfly or ball valve may also be provided to throttle the output stream.

A water pipe 64 is connected, between the two A-frames 1 to the cross struts 3 (see Figures 1 and 5) the pipe 64 having five pairs of atomizing nozzles 65 spaced at equal intervals along the pipe and with one nozzle of each pair pointing towards the top shaft 26 and the other of the pair pointing towards the bottom shaft 10. As may be seen from Figure 1, each one of a pair of nozzles 65 has an inlet duct 66 extending parallel to the cross strut 3 and an atomizer 67 attached to the duct 66. The ducts 66 are welded in holes 68 in the pipe 64 (see Figure 11).

The water is preferably pre-heated in a pressure tank outside the growing room by using an immersion heater and the temperature is controlled to be at least 2" or 3"C above the growth medium temperature. The water emerges from the atomizers 65 as a fine mist which permeates the entire surface of each tray 42. Typically the pressure at each nozzle is 100 Ibs per square inch. Since the atomising nozzles 65 point in two directions both the top surface and the bottom surface of each tray are watered equally.

Some strains of mushrooms require a certain degree of light to stimulate growth and to control colour. A uniform exposure to light is easily achieved by having one light source past which each of the trays passes in turn.

Temperature and moisture control is aided by injecting steam as required through a steam inlet pipe 69 attached, between the two A-frames 1, to the cross struts 4. The steam pipe 69 has along the majority of its length an umbrella section or baffle 70 (see Figure 11). Steam emitted through apertures in the pipe 69 first impinges on the baffle 70 so that high velocity steam is prevented from being directed on to the trays as they pass. The steam flow is controlled by a simple valve remote from the apparatus.

Prior to the start of the mushroom growing process the temperature of the surrounding atmosphere is raised to 1000C in order to sterilize the apparatus. This temperature is achieved by injecting steam through the pipe 69. The growth medium can then be laid in the baskets which are positioned in the trays and pasteurization effected by raising the temperature again, this time to about 60"C. The temperature of the atmosphere will then gradually reduce to 34"C which is the lowest temperature that is required for actual growing. This temperature is maintained by periodically injecting steam to raise the temperature when required.

In previous systems the difference in temperature between the bottom tray of a stack and a top tray twelve feet above has been about 10 - 12"C but with this apparatus the relative movement of the trays mixes the surrounding air so that the overall temperature difference is reduced to about 2"C.

Claims (26)

1. A method of plant cultivation which comprises moving the growth medium in which the plants are to be grown, in trays or baskets, continually about an endless path, the movement thereby creating movement of the ambient air relative to the plants and growth medium to promote growth.

2. A method according to claim 1, wherein the trays or baskets are moved continuously about the endless path.

3. A method according to claim 1 or claim 2, wherein the growth medium is contacted with water which is provided in the vicinity of the path.

4. A method according to any of claims 1 to 3, wherein steam is injected into the vicinity of the path.

5. A method according to claim 3 or claim 4, wherein the water and/or steam are provided in a spray mist.

6. A method according to any of the preceding claims, wherein the plants to be grown are mushrooms.

7. A method according to claim 1, substantially as described with reference to the accompanying drawings.

8. Mushrooms which have been cultivated by a method according to any of the preceding claims.

9. Apparatus for use in the cultivation of plants, the apparatus comprising a plurality of trays or baskets for holding a growth medium in which the plants are to be grown, and means for conveying the trays or baskets around an endless path.

10. Apparatus according to claim 9, including means for supplying water to the growth rnedium from the vicinity of the endless path.

11. Apparatus according to claim 9 or claim 10, including means for supplying steam to the vicinity of the endless path.

12. Apparatus according to claim 10 or claim 11 wherein the steam and/or water is sprayed as a mist into the path of the trays or baskets.

13. Apparatus according to any of claims 9 to 12, wherein the conveying means comprises a pair of horizontally spaced, endless, driven belts between which the trays or baskets are supported.

14. Apparatus according to any of claims 9 to 13, including means for supplying air to the apparatus.

15. Apparatus according to any of claims 9 to 14, in which the path of the trays lies in a vertical plane.

16. Apparatus according to claim 15, when de pendent on claim 13, including two spaced-apart shafts around which the belts travel, one of the shafts being connected to the air supply means and being provided with air diffusers for supplying air to the plants.

17. Apparatus according to claim 16, wherein the other of the shafts is a drive shaft for driving the endless belts and includes, spaced thereabout, extraction nozzles for extracting air, and including means for conveying the extracted air away from the trays.

18. Apparatus according to claim 16, wherein each diffuser comprises a container having a filling of wire wool to filter the air supplied thereto and a plurality of apertures through which the air is diffused.

19. Apparatus according to any one of claims 16 to 18, wherein the shafts are adjustably supported one above the other.

20. Apparatus according to claim 10 or claim 12, wherein the means for supplying water to the growth medium comprises a pipe extending transversely to the plane of the endless path, and a plurality of apertures or nozzles through which the water issues into the vicinity of the endless path.

21. Apparatus according to claim 20, wherein the pipe has a plurality of atomising nozzles connected thereto, the nozzles being arranged in pairs pointing in opposite directions substantially parallel to the plane of the endless path.

22. Apparatus according to claim 11 or claim 12, including a steam supply pipe extending transverseliy to the plane of the endless path and having a plurality of apertures through which, in use, steam is injected into the vicinity of the trays.

23. Apparatus according to claim 22, wherein the pipe is partially surrounded along the majority of its length by an umbrella member against which, in use, steam emitted from the apertures initially impinges.

24. Apparatus according to claim 13 or any claim dependent thereon, wherein each of the endless belts comprises a chain.

24. Apparatus according to claim 23, wherein the links of the chain are alternately substantially straight and L-shaped.

25. Apparatus according to claim 23, wherein the links of each chain are substantially triangular.

26. Apparatus according to claim 9, substantially as described with reference to the accompanying drawings.