Note: Descriptions are shown in the official language in which they were submitted.
..g~i9
.'
Units and system for hydroponics ¦
The present invention concerns hydroponics~
i.e. the growing of plants without soil.
As far back as the seventeenth century it was
already suggested by Robert Boyle and others that plants
could be grown without soil. Ever since then attempts
have repeatedly been made to develop commercial systems
for the growing of plants in water or on an inert carrier
substrate but so far no satisfactory commercial method
could be developed.
The first attempts at hydroponics were based
on the immersion of the roots of growing plants in a
stati~nary, aqueous, nutrient solution, means having
been provided for holding the plants in position. However,
this method turned out to be impractical, inter alia
because the nutrient solutions did not contain from the
outset a sufficient amount of oxygen. Moreover, after
a short while the little oxygen that had been present in
the starting solution was spent and the solution also
became depleted in essential nutrient ingredients, such
as for example, iron. Furthermore, there occurred an
excessive accumulation of carbon dioxide exuded by the
~ `~
:'
roots, due to insufficient removal thereof.
Furthermore, fastening the plants for holding them
in position with the roots in the nutrient solution
was a c~ersome, labour-consuming operation.
Finally, this method could not be used for budding
or rooting stalks or sticks and it was necessary to
transplant the young plants from a seed bed or
nursery.
In attempts to overcome these difficulties, ;
- 10 methods of hydroponics were developed using an inert
substrate such as sand, gxavel, vermicolite and rockwool.
In these methods the su~strate serves as a hold for the
roots and also as a vehicle for the nutrient solution.
In operation the substrate is soaked with a nutrient
solution which flows therethrough continuously or
intermittently. In the substrate the continuous body
of nutrient solution of the previous method is replaced
by narrow channels, occasionally of capillary dimensions,
in which continuously or intermittently flowing thin
films or layers of nutrient solution are in contact,
on the one hand, with trapped air and, on the other
hand, with the roots. It was believed that in this
way the problems of oxygen supply and carbon ~ioxide
removal would be resolved.
Various specific methods have been developed
on the basis of this general principle but contrary to
expectations the supply of fresh oxygen and withdrawal
of carbondioxide were insufficient. Although various
means have been devised for increasing the oxygen
content of the feed nutrient solution, e~g. by
introduction of the solution into the inert bed by
free-fall, the overall results remained unsatisfactory.
;:
' `
?59
Furthermore, these methods as well are not
suitable for budding or rooting and consequently here
again young plants have to be transplanted from
conventional seed beds or nurseries.
A further shortcoming of the inert substrate
methods is due to the very fact that in the substrate ,
all the root portions are surrounded only by thin layers
of nutrient solution. These thin layers become rapidly
exhausted of nutrients and oxygen and they have, therefore,
to be replaced regularly. If in consequence of a
mechanical failure the regular replacement is interrupted
for a while, the crop is adversely affected and may even
be lost. These methods are thus sensitive to breakdown -
in the supply of fresh nutrient solution which puts
limitations on their commercial applicability.
Yet another drawback of these methods is that
after each harvest it is necessary either to replace
the inert substrate or wash it very thoroughly from root
remnants and debris of the last crop in order to avoid
the occurrence of rot during the growing of the next
crop.
There is also known so-called nutrient film
technique. In accordance with this method of hydroponics
a nutrient solution is continuously flown as a thin film
through tubular or channel-like units in which the stalks
of the growing plants are held with their roots spreading
on the bottom. This method, while solving satisfactorily
the problem of reyular supply of oxygen and nutrients and
of regular withdrawal of carbon dioxide, is also highly
dependent on the regular flow of the nutrient solution
because of the small amounts of solution that are in
contact with the roots. Conseauently, here again, if
for some reason the regular flow of nutrient solution is
s~ ~
interrupted the crop is spoiled within a short while
and this method is thus too sensitive to mechanical
failures to be of commercial applicability. Moreover
this method as well is unsuitable for sowing, budding
and rooting and therefore, as before, young plants
have to be transplanted from conventional seed beds -
or nurseries.
It is moreover inherent in this method that I
there occurs a concentration gradient of all ingredients ¦
of the nutrient solution along the unit in the direction
of flow with a consequential plant performance gradient. ~
It is the object of the present invention to ~ ,
provide a new, improved method of hydroponics in which
the regular supply of nutrients and oxygen and the
regular withdrawal of carbon dioxide is ensured; in
which plant performance is uniform; which at the same
time is suita~le for sowing, budding and rooting; and j
which has a large absorpt~on capacity for technical ¦
failures such that if the supply of fresh nutrient
solution is interrupted for a long period, say two days
or even more, the crop is not at all or not significantly
affected.
In accordance with the present invention there
is provided a hydroponics unit comprising in ¦~
combination: ,
~a) a covered trough adapted for holding a
body of nutrient solution and an air
space above it;
(b) means for the continuous injection of an
aqueous plant nutrient solution in
atomi~ed form into said air space;
., .
59
(c) plant holders penetrating into the
trough through the cover thereof, which
plant holders are adapted each to hold
the lower stalk portion Qf a growing
plant and comprise each means for
supporting the lower stalk end of the-
plant at or above the surface level of
the nutrient solution in the trough while
at the same time allowing the roots to
, depend dow~-~rom-the~ ~d--reach-in-to
the solution; and
~d) adjustable overflow means for the
continuous discharge of solution from the
trough, such that by adjustment of said
overflow means the level of liquid within
the trough is controlled.
During operation the air spa~e within the
trough is filled with a mist or fog of the atomi~ed
nutrient solution. In consequence of the atomization
the injected nutrient solution a]bsorbs oxygen from the
surrounding air and in this way the required amouni of
oxygen in the nutrient solution is ensured. As the
solution flows continuously through the trough a
sufficient amount of oxygen is ensured at all times.
The flowing solution in the trough is in-
direct contact with the roots without the formaticn o~any barrier layer and consequently the constant supply
of oxygen to the-roots and the withdrawal of e~uded
carbon dioxide from their vicinity is ensured. The
flowing solution also ensures a steady supply of the
nutrients.
The amount of nutrient solution in the unit
at any time is relatively large so that at all times a
` :.
-- 6 --
large excess of oxygen and nutrient ingredients is
present. Because of this the plants will continue to
grow and not suffer any significant damage even if due
to some technical failure the regular flow of nutrient
solution is stopped for some time~ In experiments
conducted in accordance with the present invention with
various plants, e.g. tomatoes, at l9~C the regular flow
of nutrient solution was interrupted for as much as five
days without any permanent adverse e~fect on the crop.
Due to t~e specific design of the plant holder
with said supporting means, it is in accordance with the
present invention for the first time possible to raise
plants hydroponically from the start, i.e. from seeds, --
bulbs, buds or stalks. In case of budding a seed, bulb
or bud, as the case may be, is placed on a support within
a plant holder and the level of the nutrient solution in
the trough and/or the position of the holder in the -
cover is so adjusted that the solution touches the support
from below. Due to surface tension phenomena the upper
face o~ the supporting means will be covered by a thin
film of nutrient solution and in this way the seed, bud
or bulb will be in constant contact with the solution and
the budding sets on. With the emergence of a plant and
the formation of roots the contact between the solution !.
and the support will be severed by lowering the level of
the solution in the trough and/or raising the holder and
in this way any rotting of the lower stalk portion of the
developing seeding or shoot is prevented.
Rooting of stalks proceeds in a similar way. The
stalk is inserted into the plant holder with its lower end
abutting said supporting means and as the roots develop the
direct contact between the supporting means and solution
is severed in the same manner as above.
. .
5~
-- 7 --
If desired, said supporting means may be
arranged to be vertically reciprocable within the
plant holder between an upper and lower position. In
this way, as long as the relative positions of the
plant holder and the level of the solution in the trough
is such that the supporting means are at intermediary
positions, they float on the surface of the solution
and in this way constant contact between the solution
and the budding or rooting plants is ensured for as
long as this is required. When the contact has to be
severed, the holder is raised and~or the level of the
solution in the trough is lowered and thereby the
support is arrested in its lowermost position from
where the contact can be severed as explained before.
Such an embodiment is of particular advantage in case
of sprouting from seeds.
The supporting means of the plant holder may,
for example, be in form of a panel extending within
the holder between two opposite walls thereof; or by
way of a further example, in form of a bracket
projecting from one of the walls of the holder; and it
may, i~ desired, be perforated or in form of a grid
or net.
The plant holders offer adequate and
sufficient support for the young plants to enable them
to emerge from the trough. Depending on the nature of
the plant, as it continues to grow, there may be
required additional outside support means in order to
raise it in upright position, which may, for example,
be the case with grapes, tomatoes and the like. In
other cases, for example, certain ornamental plants
and flowers, outside support may not be required.
~.. ~;;~ , .
~ '
:: `
359
-- 8 --
Preferably the trough of a hydroponicsunit
according to the invention is made accessible from
the outside 'in oxder to enable servicing during-
opPration and removal of roots and bulbs from the
trough at the end of the growing period (which roots
and bulbs do in many instances constitute the actual
product). For this purpose the cover may be totally
or partially removable or swingable by being hinged to
one o~ the side walls.
The plant holders may be made integral with
the cover, be'slidably inserted therein or rest on the
bottom of the trough. In the second case the ~osition
of the plant holder inside the trough is adjustable
without it being necessary to raise or lower the level ,
of the solution within the trough.
The overflow means for the discharge of
solution from the trough may be adjustable mechanically
or manually. ~anual adjustment is best effected from
within the trough and to this end at least part of the
cover has to be removable or swingable,
In order to prevent the formation of concentration
gradients in the nutrient solution within the trough it ,
is preferred to provide several injectors axially spaced
from each other. Thus in accordance with one embodiment
of the invention the hydroponics unit comprises at least
one obl,ong feeder tube extending within the trough in
essentially axial direction and provided with a plurality
of atomizing ejectors. ~They are "ejectors" when
considered with reference to said tube and "injectors"
when considered with reference to the trough). Preferably
the ejectors are so oriented that the atomized solution
is ejected into the trough upwards. In this way the
duration of contact of each droplet with the surrounding
.
.
- ~ :
.
- ~ :
;, ~,. ~:
- 9 -
air and the consequential absorption of oxygen
therefrom is maximized. Preferably the bores in the
tube are c~nically shaped, opening towards the
outside, and are slanted in the direction of flow.
Pipes with such bores are commercially available,
e.g. from Plassim, Kibbutz Merhavia, Israel, and can
be used to advantage for the purpose of the present
nventlon.
In operation nutrient solution flows under a
selected pressure through these feeder tubes and is
ejected therefrom in atomized form into the ai~ space
in the trough as specified.
The invention further provides a hydroponics
installation comprising at least one unit of the kind
specified connected, on the o`ne hand, to nutrient
solution feeder means and, on the other hand, to nutrient
solution drainage means; a reservoir of nutrient
solution; and means for circulating the nutrient solution
in closed cycle between said unit(s) and reservoir.
In such an installation each unit is linked to
said drainage means through the overflow tube.
Preferahly the connection between the overflow tube and
the drainage means is so-designed that there occurs a
free-fall of the discharged solution into the drainage
means. During such free-fall excess carbon dioxide is
removed and some fresh oxygen is absorbed from the
surrounding air.
The invention also provides for use in an
unit of the kind specified a plant holder comprising
means ~or holding a stalk in an upright positi~n and a
support for the lower end of the stalk so designed as
to allow the roots to depend freely from the stalk and
reach down.
S~
-- 10 --
The trough and cover of a hydroponics unit
according to the invention may be of any suitable
material resistant to the nutrient solution. Where it
is desired to maintain a substantially constant
temperature within the trough it is preferable to make
the trough and the cover of insulating material. For
example, a two-sheet plastic board with reinforcing ~ -
ribs between the sheets has been found suitable.
The invention is illustrated, by way of
example only, in the accompanying drawings in which:
Fig. 1 is a plan view of a hydroponics unit
according to the invention;
Fig. 2 is a section along line II-II of -
Fig. 1 drawn to a larger scale;
Fig. 3 is a section along line III-III of
Fig. 1 drawn to a larger scale;
Fig. 4 is a perspective view, partly broken
open, of a plant holder according to the invention;
Fig. 5 is a wall fragment of a unit
according to the invention;
Fig. 6 is a diagrammatic illustration of a
hydroponics installation employing a plurality of units
according to Figs. 1 to 5; and
- Fig. 7 is a partial elevation of an
installation according to Fig. 6 showing the arrange-
ment of the units.
The unit shown in Fiys. 1 to 5 comprises a
trough 1 with a removable cover 2. Near one of its ends "
trough 1 is fitted with an overflow tube 3, slidably
inserted within a rubber sleeve 4 which in turn is
inserted within a sleeve 5 on which is screwed the
upper, funnel shaped end 6 of a drainage pipe 7 with
the interposition of an annular gasket 8. Tube 3 can be
` ' ' ~
5~
lowered or raised manually and by doing so the level
of the body of liquid 9 inside trough 1 is lowered or
raised, as the case may be. In order to gain access to
the over~low tube 3 cover 2 has to be slightly lifted
or shifted. Preferably the diameter of the overflow
tube 3 is such that the overflowing solution flows in a
laminar flow along the inner wall of the tube and in
this way the overflowing solution may absorb oxygen from
and deliver excessive carbon dioxide to the air present
in the central portion of tube 3.
Drainage pipe 7 leads to a collector pipe
tnot shown) and preferably the arran gment is such that
the solution drops from tube 3 through pipe 7 into the
collector pipe by free-fall whereby the above absorption
of oxygen from and delivery of carbon dioxide to the
atmosphere is further enhanced.
From the upper, longitudinal e~ges of trough 1
there are suspended at regular intervals, a plurality
of bent wire braces 11 one of which is shown in Fig. 3.
As shown the ends of each brace 11 are hook-shaped in
order to enable its suspension. In order to avoid a
clearance between the cover 2 and the trough, notches
or cut-outs are provided in the upper edges of the
trough and/or cover 2 to receive the hook-shapea ends
of each brace 11.
Braces 11 serve for supporting a solution
feeder tube 12 connected in a manner not shown in
Figs. 1-5 to solution supply means. Fèeder tube 12 is
partle immersed in the solution with its upper portion
being e~posed to the air space above solution 9. In
this way portion feeder tube 12 comprises a plurality
of bores 13 through which the pressurized solution 14
flowing through the tube is ejected in atomized form.
S~
- 12 -
Preferably each bore 13 is concially shaped, widening
towards the outside of tube 12 and is slanted in the
direction of flow of solution 14. The atomi~ed solution
is ejected through bore ]3 in the di~ection of cover 2
and in this way the entire air space of the trough above
the level of the body of solution 9 is filled with a
mist or fog of solution which drops gradually and
constantly into the body of solution while at the same
time being continuously reconstituted by ejection from
tube 12.
Cover 2 of unit 1 comprises a plurality of
rectangular cut-outs 16 each of which receives snugly a
plant holder 17. As shown in Figs. 3 and 4 each holder 17
comprises a prismatic body 18 with one larger cut-out 1
and three smaller cut-outs 20. The cut-outs 19, 20
de~ine between them four legs 21. From the upper edye
of cut-out 19 there extends a horizontal plate 22 serving
as support for the lower end of the stalk of a plant 23.
Between the two longitudinal edges of plate 22 and the
opposite walls of body 18 there are clearances
sufficiently wide to enable the depending roots 24 to
reach freely into the body of solution 9 (see Fig. 3).
As can be seen from Fig. 3, plate 22 is located above
the surface of solution 9 and in this way any sliding
of the plant into the solution and rotting of the stalk
is avoided. If during operation conta~t between plate 22
and the surface of solution 9 is desirea, the holder 17
may be lowered and/or the surface of the solution inside
the trough may be raised. Where a higher level of ~he
solution inside the trough 1 is required, braces 11 may
have to be replaced so as to ensure that the upper
portion of tube 12 is at no time submerged.
The upper portion of the stalk of plant 23 is
held by a foam 25 snugly inserted into body 18.
~:
- 13 -
Fig. 5 shows to a larger scale the encircled
portion of Fig. 3. As shown the walls of trough 1 are
made of a two-ply sheet in which the plies are inter- - ¦
connected by reinforcing ribs 50. In this way there is
S provided an insulating air layer within the wall.
Fig. 6 illustrates diagrammatically a hydroponics
installation employing five units according to the ;
invention of t~e kind illustrated in Figs. 1 5. As shown
in a battery 27 units 28 are connected in parallel, on ¦
the one hand, to a distributor 29 of feed solution and,
on the other hand, to a collector 30 of spent solution. -
The installation further comprises a tank 31
holding a body of solution 32 and fitted with a float 33
capable of actuating a valve 34 inserted in a duct 35
which leads to a supply line 36 of fresh water controlled
by means of a valve 37.
There is moreover provided a pump 38 whose
intake end is linked by means of a duct 39 to the body
of solution 32 inside tank 31 and its delivery end is
linked through duct 4~, valve 41, duct 42 and filter 43
to distributor 29. Collector 30 :is linked to the air
space inside tank 31 through a duct 44 fitted with a
filter 45.
For the event that the delivery of pump 3B
exceeds the reguirements of battery 27, e.g. if some of
the units 28 are disconnected, a return duct 46 is
provided itted with a pressure reducer 47.
There is further provided a discharge pipe 48
fitted with a control valve 49 for the rejection of
spent solution.
The operation of this installation is as
` follows:
~, , .
.
,
35'9
- 14
Solution is continuously withdrawn from
tank 31 by means of pump 38 and is delivered through
duct 40, valve 41, duct 42 and filter 43 to the
distributor 29 from where it is evenly distributed
among the five units 28 of battery 27. Within each
unit 28 the solution is delivered by injection in the I
manner described with reference to Fig. 3 and excess ,
solution is continuously discharged from each unit 28 by
overflow, again as described with reference to Fig. 3. i
The discharged solution is drained into collector 30 from
where it flows through drain pipe 44 and filter 45 back
into tank 31.
If during operation one or more of units-28
has to be serviced and is therefore cut off from the
circulation of solutiGn, it may occur that the delivery
of pump 38 exceeds the requirement. In such cases the
excess solution is returned through duct 46 and pressure
reducer 47 to the intake end of pump 38.
During operation the solution is repeatedly used
and gradually depleted of its nutrient ingredients. It is
therefore necessary from time to time to replace the
solution. For this purpose valve 41 is shut and valve 49
is opened and solution from tank 31 is now rejected through
discharge pipe 48.
- For the preparation of new nutrient solution
the nutrient ingredients are introduced into tank 31,
valve 37 is opened and valve 48 is shut. Fresh llne
water now ~lows on the one hand, directly into tank 31
through line 35 and valve 34 and on the other hand through
30 line 42, filter 43 and distributor 29 into units 28 which
are thus flushed. The flushing water discharged from
units 28 flows into tank 31 in the manner specified
hereinbefore.
.
~ . .
;. ~
.
., ~
~{~s~
- 15 -
The fresh water arriving in tank 31 dissolves
the nutrient ingredients and the inflow of fresh water
continues until valve 34 is shut by float 33. Thereupon
valve 37 is shut, valve 41 is opened and the installation
is ready for a new cycle of operation.
As shown in Fi~. 7, the units 28 in battery 27
are arranged in pyramidal foxm which reduces the mutual
interference of the plants in the different units with
their exposure to solar radiation, which exposure is
thus maximized.
Hydroponics installations employing units
according to the lnvention are very versatile and can
be employed for various different purposes in
agriculture, horticulture, research and the like; and
they can be used for large-scale production, for small
scale domestic purposes and also in the laboratory.
. .
.~ .. ,
: , .
' .
' ~ ' . ' '
