FR2842437A1 - Hose for hydroponic plant culture forcing tray comprises tubular body with internal surface defining flow channel and provided with helicoidal left hand thread rib - Google Patents

Abstract

The hose (30) with a vortex flow comprises a tubular body consisting of an upper cylindrical part (31) and a lower truncated part (32) having an internal surface defining a liquid flow channel (35). This internal surface is provided with a helicoidal rib (36) with a left hand thread.

Description

I The present invention relates generally to a forcing tank

  for the hydroponic cultivation of plants, in particular endives, a method of hydroponic cultivation and forcing of plants using such a tank, as well as a hose for the flow of a nutritive solution from one tank to another a stack of bins in a forcing room ensuring

  re-oxygenation of the nutrient solution.

  Conventionally for the cultivation and hydroponic forcing of plants such as endives, as shown in FIG. 1, forcing tanks 2a to 2h are stacked in staggered rows in a forcing room 1, that is to say with the flow hoses 3a to 3h of successive tanks in the stack arranged in opposition to each other. A pump 4 feeds from a vat 6 via a pipe 5, the upper tank 2a in nutritive solution.

  The nutrient solution then passes from tray to tray, via the hoses 3a to 3g to the last tank 2h of the stack where the nutrient solution is then evacuated by the hose 3h and returned to the vat 6 by the pipe 7 connected to the hose 3h.

  The nutrient solution is reoxygenated in the vat by stirring, possibly adjusted to the dosage of fertilizers or trace elements

  before being sent back into the circuit.

  The system which has just been described can, depending on the rooms

  forcing, feed 15 to 30 stacks of 10 to 14 bins each.

  As will be readily understood, it is the height of protrusion from each of the tub hoses that determines the level of the nutrient solution in each of the tubs. Generally, the height of

  exceeding the hose in the tank is about 2 cm.

  The system just described applies more

  particularly in the cultivation and hydroponic forcing of endives.

  Although the following description will be made in connection with the hydroponics of endives, the invention can be applied to any culture.

  for which the same problems are encountered.

  In endive hydroponics, at the start of the cycle, the endive roots are placed for 24 to 36 hours in a fungicidal solution, that is to say that the pump 4 does not work. The level of this fungicidal solution in the tanks is generally maintained

  substantially constant, generally at a level between 0.5 cm and 1.5 cm, preferably about 1 cm, so as to ensure that the fungicide and rooting products have effect.

  After 1 to 3 days, the circulation of the nutrient solution begins.

  The nutrient solution provides the plant with the elements necessary to

  growth of chicory including oxygen. Oxygen is one of the main limiting factors in soilless cultivation techniques.

  Therefore, generally, vegetable and floral productions in hydroponics, are oriented towards the use of lo inert substrates, rock wool type with irrigations at regular intervals. The cultivation and hydroponic forcing of endives is one of the rare productions to have developed in hydroponic culture and forcing without substrate.

  The endive root, for its growth, and the formation of chicory, needs fertilizers, trace elements, water and oxygen. In

  hydroponics, food is provided by the nutrient solution.

  The level of dissolved oxygen in the nutrient solution is decisive for growth of the endive. The roots constantly need oxygen: the root respiration provides the energy necessary for their own metabolism but also for the absorption of

water and nutrients.

  Asphyxiation of the root system does not cause, as in the animal kingdom, the immediate death of the plant, but plants are characterized by an adaptation mechanism, resulting in a slowing down and then in stopping the growth of the aerial part of the plant. It is not uncommon to see, in the forcing tanks, a completely asphyxiated nutritive solution. One can even commonly observe under these conditions the presence of nitrites (NO2) from the removal of an oxygen ion to nitrate ions (NO3) by bacteria in the absence

  oxygen dissolved in the nutrient solution.

  The diagram of the culture and forcing room described above

  has a number of drawbacks.

  The nutrient solution feeds the trays from the top and it descends into the stack as it passes through the trays.

  The rootlets of the plant absorb oxygen dissolved in the nutrient solution. It is then easy to understand that the oxygen level decreases as one goes down in the stack. (Figure 10).

  As indicated previously in the last tank, the nutrient solution s is channeled to the vat where it will be re-oxygenated by a simple

  mixing by means of the pump and reintroduced into the circuit.

  It is not uncommon to find technical rooms that do not facilitate the re-oxygenation of the nutrient solution. Due to their layout, these premises are often difficult to access, cramped and above all poorly ventilated. By the very design of the rooms, the vats are generally buried in the ground and the level of the solution is therefore collected relative to the ground. It follows that the nutrient solution does not leave the circuit with the maximum rate of oxygen that could be dissolved.

  This drop in the oxygen level at the end of stacking is not prohibitive at the start of forcing, when the flow rates in nutritive solution are high and consumption low, or even when the stacks have a low number of tanks, 5 with 6 bins.

  On the other hand, the low oxygen level of the nutrient solution at the end of forcing or when the stack has a large number of tanks

is particularly harmful.

  In large forcing rooms where the tanks are stacked on 12, it is not uncommon to notice illnesses development due, in part, to a lack of oxygen.

  The oxygen level can sometimes drop up to 1 mg / l in the last 25 tanks, while the oxygen concentration of the nutrient solution arriving in the stack of tanks can be at most 9 mg / i. (Figure 10).

  The atrophy of oxygen in the solution promotes the development of bacteria, which themselves will consume oxygen and become more rare

plus the oxygen solution.

  It would then be necessary to increase the flows, but the producers are

  forced to lower them in order to avoid overflowing the tanks.

  As indicated above, the tubing flow hoses protrude

  generally about 2 cm inside the bins.

  When disease occurs in the tanks, producers should bring their tanks to level 0, i.e. bring the liquid inlet of the flow hose back to the bottom of the tank, thus eliminating the protrusion of about 2 cm from the hose in the tank.

  This operation allows: - to increase the head and consequently to increase the flow rates; - eliminate as much soil and waste as possible at the bottom of the tank; - to circulate the solution alternately, which allows the io plant to re-oxygenate more easily (indeed, the rootlets in this configuration are no longer in the solution, which facilitates the transfer of oxygen in the plant ); and

  - total emptying of the tanks when circulation is stopped. Unfortunately, this is rarely done. Indeed, it is very difficult to carry it out in a forcing room, without light and where the quantities of trays are sometimes 4000 in number, tight and stacked, over a height of up to 6 meters.

  The present invention therefore aims to provide a tank for the cultivation and hydroponic forcing of plants, in particular endives, making it possible to carry out the leveling operation 0, without human intervention.

  The subject of the invention is also a culture and hydroponic forcing tank ensuring re-oxygenation of the nutritive solution during its flow from tank to tank in a stack.

  The invention also relates to a chamber for the forcing of

  plants, in particular endives, comprising at least one stack of forcing tanks arranged in staggered rows in which the tanks are as defined above.

  Another subject of the invention is a process for hydroponic cultivation and forcing of plants, in particular endives, ensuring better re-oxygenation of the nutritive solution during its flow from tank to tank of a stack and also a leveling operation O not requiring human intervention.

  The invention finally relates to a flow hose with a vortex effect promoting the re-oxygenation of a liquid, in particular a nutritive solution for forcing plants such as endives.

  According to the invention, the forcing tank for the hydroponic cultivation of plants, in particular endives, comprises a bottom, a side wall and a flow hose fixed to the bottom and having an inlet and an outlet for liquid, this tray being characterized by the fact that the liquid inlet of the hose is located at the bottom of the tank (level 0) and in that the forcing tank also comprises a tubular insert 1o connected to the inlet of liquid from the hose and protruding inside the forcing tank, this added element being made of a biodegradable material or soluble in said liquid.

  Preferably, the tubular insert is biodegraded or dissolved in the culture medium within 2 to 5 days after the start of the introduction of the nutrient solution. Preferably also, the biodegradable or soluble element in the nutritive solution protrudes from a height of about 2 cm inside the tank.

  The biodegradable or soluble in the nutrient solution insert can consist of any biodegradable or soluble material in the culture medium, in particular during the introduction of the

nutrient solution.

  Obviously, the biodegradable or soluble element in the nutrient solution must be initially sealed in order to avoid an escape of the fungicidal solution introduced into the tanks,

  prior to the introduction of the nutrient solution.

  It is preferable to use materials which are biodegradable or soluble in nutritive food grade solution. By way of example of materials which are biodegradable or soluble in the nutritive solution which can be used to manufacture the added element, mention may be made of cellulose acetate, polyvinyl alcohols, polysaccharides and starch, in particular

mas starch.

  Preferably, the forcing tank according to the invention further comprises a means for producing a flow of liquid with a vortex effect in the flow hose.

  A first means for imparting a vortex effect in the flow of liquid in the hose consists of a barrier, generally in the form of an arc, projecting from the bottom inside the tank and located in front of the liquid inlet. of the hose. However, preferably, the means for imparting a vortex effect to the flow in the hose consists of at least one helical rib, with left-hand pitch, formed on the internal surface of the flow channel of the hose. Preferably, the means for imparting the vortex effect is constituted by a set of helical ribs, parallel, left-handed, formed on the surface

  internal lo of the hose flow channel.

  Preferably, the number of helical ribs of the hose is

  6 to 12, and most preferably 4 to 8.

  The invention also relates to a hydroponic forcing room for plants, in particular endives, comprising at least one stack in

  staggered trays according to the invention.

  The invention also relates to a method of hydroponically growing and forcing plants, in particular endives, in which the plants are in a stack of forcing tanks in fluid communication with each other from a first tank at the top. from the stack to a last tank in fluid communication with the outside, the method comprising: - the introduction into the tanks of a fungicidal solution; and subsequently - the introduction into the tanks of a nutritive solution; said method being characterized in that the tanks are as defined above so that the insert made of biodegradable material or soluble in the nutritive solution is degraded within two to five days, preferably two to three days , following the introduction of the nutritive solution thus bringing the tanks to level O without any

3 0 human intervention.

  The rest of the description refers to the appended figures which

  represent respectively: Figure 1, a diagram of a conventional hydroponic forcing and growing room; Figure 2, a schematic sectional view of a first embodiment of a biodegradable insert according to the invention; Figure 3, a front view of a second embodiment of an insert biodegradable or soluble in the nutrient solution according to the invention, particularly suitable for use with a hose with vortex effect; Figure 4, a diagram of part of a forcing tank comprising a dam imparting a vortex effect to the flow in the hose; Figures 5 to 7, front views, in section and from above 1o respectively of a vortex-effect hose according to the invention; Figures 8 and 9, photographs of the flow of liquid at the outlet of a conventional hose (GODE) and a hose with a vortex effect according to the invention; Figures 10 and 11, graphs of the oxygen level of the nutrient solution at the inlet and outlet of tanks fitted with a hose according to the art

  anterior and a vortex hose according to the invention.

  There is shown in Figure 2, a first embodiment of a tubular insert biodegradable or soluble in the nutrient solution 10 according to the invention. As shown in the figure, this insert made of biodegradable material 10 has the shape of a truncated cone with a total height generally of 5 to 6 cm. This insert 10 is easily adaptable in the liquid inlet of a hose by simple fitting of this frustoconical element in the liquid inlet of the hose by its end of smaller diameter. The nesting thus produced allows a projection of the insert in the tank of the order of 2 to 3 cm, of

preferably 2 cm.

  There is shown in Figure 3, a second embodiment of an insert 10 according to the invention, particularly suitable for use with the hoses with vortex effect according to the invention, as will be

explained below.

  As shown in FIG. 3, this added element 10 is a tube element with a height of the order of 5 to 6 cm, the inner part of the external lateral surface of which is provided with helical threads (grooves) with left pitch 11. As seen in Figure 3, these grooves 11 extend from about the middle of the outer side surface of the element 10 to terminate at its lower end. The threads 11 are produced so as to cooperate with left-hand helical ribs formed on the internal surface of the hose when the lower part of the insert 10 is fitted into the liquid inlet of the vortex-effect hose.

  Figure 4 is a schematic top view of a tank 2a according to the invention comprising a conventional hose 3a disposed at level O (that is to say with its liquid inlet flush with the bottom of tank 2a). As is conventional, the hose 3 is arranged near a corner of the tank 2a.

  1o According to the invention, a barrier 4a has been formed on the bottom of the tank in front of the hose 3a intended to impart a vortex effect to the flow of liquid in the hose 3a. As shown in FIG. 4, this dam 4a can consist of an arc-shaped barrier in front of the hose 3a, the ends of which define flow passages with the sides of the

side wall of the tank.

  The height of this dam is generally of the order of 2 cm. This dam has the effect of accelerating the liquid around the hose 3a thus accentuating the swirl effect (vortex) when passing through the hose 3a.

  The jet of liquid at the outlet of the hose 3a is then transformed by the vortex effect into a column of hollow water (see FIG. 9) which is not the case when using only a conventional hose ( see figure 8). Obtaining a hollow column of liquid increases the exchange surfaces, which allows an easier transfer of oxygen in the

  liquid, in particular, in a nutritive solution.

  FIGS. 5 to 7 show a hose 30 according to the invention, which comprises means imparting a vortex effect to the flow of the liquid in the hose.

  As shown in the figures, the hose 30 comprises a body 30 consisting of a cylindrical upper part 31 and a frustoconical lower part 32. This hose 30 is, in its general constitution, similar to conventional hoses and in particular to the hose described in patent FR-2,761,174.

  According to the invention, a set of parallel helical ribs 36, 35, with left pitch, are formed on the internal surface of the channel

  flow 35 of the hose 30. As can be seen in FIG. 6, the ribs 36 extend from the liquid inlet 33 of the hose 30 and terminate in a horizontal plane at the end of the part cylindrical 31 of the hose body.

  Preferably, the thickness of the ribs 36 increases

  gradually from the liquid inlet 33 of the hose to their terminal end to facilitate the flow of liquid and, in the case where the hose 30 is obtained by molding of plastic material, facilitate the demolding of the latter.

  Obviously, the height, number and pitch of the ribs 36

  must be sufficient to divide the flow of liquid and contain the volume of the multiple streams of solution thus created. Likewise, the pitch of the ribs is determined so as to induce an optimum rotational movement of the liquid while preventing it from falling.

  Preferably, the pitch of the ribs is on the left so as to

  use the Coriolis effect, caused by the rotation of the earth.

  For use in the southern hemisphere, you can use

ribs with a step to the right.

  Preferably, the helical ribs 36 extend above the liquid inlet 33 by radial ribs 38 which ensure a division of the liquid even before it enters the hose 30. These radial ribs 38 also allow, when the hose 30 is made of plastic by molding, to prevent the hose 30 from turning during

  demolding and in particular during the pitting operation.

  Although the vortex-effect hose 30 has been described in connection with the cultivation and hydroponic forcing of plants, in particular endives, its use is not limited to this single application. This vortex-effect hose can find numerous applications in which a liquid must be re-oxygenated, for example in the food industry,

  treatment plants, chemical industry, fish farming, etc ...

  As indicated above, the vortex hose 30 which has just been described is preferably used with the biodegradable insert, or soluble in the nutrient solution 10, the threads of which

  helical l 1 (Figure 3) are made to receive an upper portion of the helical ribs 36 of the hose 30 with a vortex effect.

Example

  We made two stacks A and B of endive forcing tanks

  each comprising eleven bins arranged in staggered rows.

  In the first stack A, the hoses were standard hoses (GODE) bet at level 0, while in stack B the hoses were hoses with a vortex effect according to the invention described above.

  The test was carried out for forcing endives of the EUREKA variety. The forcing was carried out in a conventional manner and under the same conditions for the two stacks A and B, in particular the flow rates of nutrient solution were the same for the two stacks. (8 1 / min.). The oxygen level in the nutrient solution entering and leaving the tanks of the two stacks was measured after seventeen days of forcing, that is to say seventeen days after the start of the circulation of the

  nutrient solution. The results are shown in Figures 10 and 1 1.

  The measurement of the oxygen level was carried out with an HI 9142 type oximeter sold by the company HANNA Instruments, according to the manufacturer's recommendations.

  As can be seen in these figures, the level of oxygen dissolved in the nutrient solution entering the tanks decreases in stack A, the tanks of which have a traditional hose compared to stack B in which the tanks have the hose vortex effect according to the invention o the oxygen level is kept constant at around 6 - 6.5 mg / l. Likewise, the level of oxygen dissolved in the nutrient solution drops sharply in stack A of tanks fitted with a traditional hose, the last six tanks being practically asphyxiated (oxygen level below 1 mg / l) whereas in stack B of tanks fitted with the vortex-effect hose according to the invention, the level of oxygen dissolved in the nutritive solution is practically constant at 5 mg / l.

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Claims (2)

  1. Vortex effect flow hose (30) comprising a tubular body having an internal surface defining a liquid flow channel (35), characterized in that the internal surface is provided with at least one helical rib (36) step to the left, preferably one   set of helical ribs, parallel, left-hand.   2. Hose according to claim 1, characterized in that the (or) rib (s) (36) is (are) wider (s) at its (their) base (s) than at its (their) top (s).