GB2242603A

GB2242603A - Hydroponic unit

Info

Publication number: GB2242603A
Application number: GB9007592A
Authority: GB
Inventors: John Rattenbury
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-04-04
Filing date: 1990-04-04
Publication date: 1991-10-09
Also published as: GB9007592D0

Abstract

The unit includes a housing for containing seed germination trays, and having an array of misting sprays, the walls of the housing being formed of triple-wall polycarbonate for improved stabilisation of the internal temperature of the housing. Cantilevered doors 17, 18 help to reduce the occurrence of dirt traps. Air is recirculated from the housing through an environmental control system which adjusts the temperature and humidity of the recirculated air. The air is re-introduced into the housing via a sock, and a proportion of external air may be added to the recirculated air. Air recirculation ceases during misting of the housing. <IMAGE>

Description

HYDROPONIC UNIT TECHNICAL FIELD OF THE INVENTION This invention relates to a hydroponic unit for the soil-free germination of seed and/or propagation of plant material.

BACKGROUND Hydroponic enclosures containing a water spray systems have been proposed in the past, but in general these are not capable of maintaining a stable internal internal environment in the face of wide fluctuations in external conditions.

SUMMARY OF THE INVENTION The present invention proposes a hydroponic unit comprising a housing for containing plant material and spray means for introducing a water into the housing, in which the walls of the housing comprise three mutually spaced skins of light-transmitting plastics material.

Such an arrangement has been found to dramatically improve the stabilisation of the internal temperature of the housing.

For improved heat insulation properties the gaps between the respective skins are preferably divided by a series of spacer walls formed integrally with the three skins. This prevents circulation of cooling air currents between the skins.

The housing is preferably provided with cantilevered doors for ease of cleaning.

The housing preferably has an air inlet and an air outlet, and the unit includes means for recirculating air from the outlet back to the inlet via an environmental control system which operates to adjust the temperature of the recirculated air.

The control system preferably also controls the humidity of the recircularted air.

The air inlet preferably includes a porous sock through which recirculated air is re-introduced into the housing. This substantially reduces the risk of draughts impinging on the germinating seed.

The control system is preferably arranged such that air is not recirculated whilst the spray means is operating to introduce water into the housing, and preferably also for a predetermined period thereafter. The spray means are preferably arranged to operate to introduce water into the housing for an adjustable period.

The environmental control system preferably includes a further inlet for introducing a proportion of external air into the recirculated air. The further inlet preferably has an adjustable aperture to permit adjustment of the proportion of air which is introduced. Preferably heating means are provided for heating the external air prior to introduction into the recirculated air flow.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is exemplified in the accompanying drawings, in which: Figure 1 is a schematic representation of a hydroponic unit of the invention, Figure 2 is a more detailed perspective view of the housing incorporated in the unit, Figure 3 is a sectional view of the wall of the housing on an enlarged scale, and Figure 4 is a block diagram of the environmental control system which is incorporated in the unit.

DETAILED DESCRIPTION OF THE DRAWINGS Referring firstly to Fig. 1, the hydroponic unit comprises a housing 1 for containing trays of seed, and an environmental control module 2. The housing includes a spray system 3 for humidifying the internal environbment of the housing by introducing a fine mist of water. Drainage channels 4 are also provided for collecting condensed water in the housing and conducting it to waste. In addition, the housing is provided with an air outlet 5 through which humidified air can pass out of the housing, and after passing through the control module 2 the air passes through an air inlet 6 to be is re-introduced into the housing via a porous sock 7.

The housing 1 is shown in more detail in Fig. 2. The housing is formed of a sectional lightweight metal frame to which are bolted a number of lightweight heat insulating panels (see below) so that the housing can be easily dismantled for transporation. The housing includes end walls 14 and 15, one of which 14 contains the inlet and outlet 6 and 5, and a top wall 16. Two opposite sides of the housing are formed by doors 17 and 18 which are pivotally coupled to the frame by pairs of tie rods 19. Springs 20 extend between the upper edge of each door and the top of the housing to counteract the weight of the doors and assist in their closure. Thus, each door can easily be raised in a cantilever or up-and-over fashion to a raised position in which the door partially overlies the top wall 16 as shown.By omitting one of the end walls 15 a number of such housing sections can be connected together in endto-end relation to increase the total size of the housing.

Inside the housing, open racks 22 are arranged for supporting seed germination trays formed of plastics material such as polypropylene composit. The racks are arranged such that the trays slope downwardly towards the adjacent door openings.

The sock 7 is in the form of a closed sleeve of woven polypropylene or other synthetic material which is suspended from the top wall 16 and runs lengthwise along the upper region of the housing above the racks 22. The spray system 3 incorporates a number of fine spray outlets for producing a very fine mist. The sprays are arranged between the sock 7 and the racking 22 and are supplied by suitable pipework 23.

The panels of the housing are formed of lighttransmitting triple wall polycarbonate having good heat-insulating properties. As shown in Fig. 3, the panels each include three walls 25, 26 and 27 which are held in a spaced relationship by numerous parallel internal dividing walls 28. The panels thus include a series of parallel elongate cells 29 which are arranged vertically and are open at the bottom to ensure good drainage of condensation.

Referring now to Fig. 4, the envoronmental control module comprises an electrically operated air blower 30 which creates an air flow through the module via a heat exchanger 31. Sensors 33 monitor the temperature of the incoming air and control the heat exchanger via a switching circuit 34 such that the incoming air is either heated or cooled as appropriate to maintain the air temperature within a predetermined range. In the case of cooling of the incoming air, the humidity of the air will also be reduced accordingly by condensation of excess water vapour. The temperature and humidity of the air re-entering the housing 1 via the sock 7 are thus controlled within the limits required for most efficient germination of seed.

An inlet 37 is provided for introducing a proportion of external air into the recirculated air prior to the sensors 33. The inlet has a manually adjustable aperture 38 providing adjustment of the proportion of air which is introduced. A pre-heater 39 is provided for pre-heating the external air prior to introduction into the recirculating air flow.

The water supply to the spray system 3 is controlled by an electrically operable valve 42. A timer 43 controls the valve 42 to permit water to be fed to the housing at preset intervals and for preset period. Both the spray periods and the intervals between the spray period are adjustable. The timer 43 also controls the blower 30 such that the blower is switched off whilst the spray system is operating and for a predetermined period thereafter, thereby ensuring that the water mist is not immediately drawn out of the housing.

Trays of seed to be germinated are pre-soaked and stacked in the racks 22. The fine misting of the housing rather than the use of a spray means that the seed is moistened evenly. Water drains through openings in the bottom of the seed trays and eventually drains into the channels 4. The air sock 7 substantially reduces the risk of draughts impinging on the germinating seed. Thus, the equipment ensures that a stable environment is maintained for the optimum germination of seed and for maintaining healthy growth of the seedlings thereafter.

The machine may incorporate a pressure washer for cleaning down the machine after use. The use of cantilevered doors as opposed to sliding doors for example eliminates the need for runners which can act as dirt traps.

The apparatus could also be used for the propagation of cuttings.

Claims

1. A hydroponic unit comprising a housing for containing plant material and spray means for introducing a water into the housing, in which the walls of the housing comprise three mutually spaced skins of light-transmitting plastics material.

2. A hydroponic unit according to Claim 1, in which the gaps between the respective skins are divided by a series of spacer walls formed integrally with the three skins.

3. A hydroponic unit according to Claim 1 or 2, in which the housing is provided with cantilevered doors.

4. A hydroponic unit according to any preceding claim, in which the housing has an air inlet and an air outlet, and the unit includes means for recirculating air from the outlet back to the inlet via an environmental control system which operates to adjust the temperature of the recirculated air.

5. A hydroponic unit according to Claim 4, in which the air inlet includes a porous sock through which recirculated air is re-introduced into the bousing.

6. A hydroponic unit according to Claim 4 or 5, in which the control system is arranged such that air is not recirculated whilst the spray means is operating to introduce water into the housing.

7. A hydroponic unit according to Claim 6, in which the control system is arranged such that air is not recirculated for a predetermined period after the spray means operates to introduce water into the housing.

8. A hydroponic unit according to any of Claims 4 to 7, in which the environmental control system includes a further inlet for introducing a proportion of external air into the recirculated air.

9. A hydroponic unit according to Claim 8, in which the further inlet has an adjustable aperture.

10. A hydroponic unit according to Claim 8 or 9, in which pre-heating means are provided for heating the external air prior to introduction into the recirculated air flow.

11. A hydroponic unit substantially as described with reference to the drawings.