Weed control method and corresponding weed control device

Abstract

The invention relates to a weed control method comprising generating a plasma from a plasma gas and exposing unwanted plants to the plasma in order to eliminate these unwanted plants.

Description

[0001] TITLE: Weeding method and corresponding weeding apparatus

[0002] The present invention relates to the field of weeding, i.e. the elimination of unwanted plants, also called adventitious plants or weeds.

[0003] In agriculture, it is important to try to eliminate unwanted plants, because they capture part of the water necessary for the growth of the planted seeds, and shelter insects harmful to the plants that we want to see grow.

[0004] It may be necessary to completely weed a field before planting, or partially weed a field after planting, between rows of plants, as they grow.

[0005] In urban areas or for public infrastructure (paths, roads, railways, airfields, etc.), unwanted plants must be eliminated so as not to hinder traffic or contribute to the deterioration of infrastructure.

[0006] It is possible to carry out chemical weed control using a chemical herbicide, such as glyphosate.

[0007] However, chemical herbicides have major drawbacks, such as long-term soil contamination, which can also contaminate subsoils and, therefore, groundwater. Over time, their intensive use makes soils increasingly resistant to their action. In addition, glyphosate is now recognized as potentially carcinogenic to humans and carcinogenic to animals.

[0008] Other non-chemical weeding methods are possible, such as thermal weeding, electric weeding, infrared weeding, ultraviolet weeding, microwave weeding or hot water weeding.

[0009] Thermal weeding (or "pyroweeding") is a weeding technique that uses only heat to freeze-dry and ultimately kill unwanted plants by thermal shock. It involves applying intense heat to unwanted plants to kill them, bursting their tissues so that they then dry out within a few days. Thermal weeding can be carried out using heating elements that use electricity or gas to generate heat. Thermal weeding in agriculture is carried out, for example, using gas-powered thermal heaters, which requires carrying one or more gas cylinders.

[0010] Electric weeding involves generating electric arcs that can reach unwanted plants and damage them due to the electric current passing through them.

[0011] Infrared and ultraviolet weeding involve exposing unwanted plants to infrared and ultraviolet radiation, respectively. Infrared and ultraviolet weeding can be combined.

[0012] Infrared radiation can heat the roots of unwanted plants and thus disrupt their functions. Ultraviolet radiation can damage unwanted plants due to the heating of the foliage of unwanted plants following absorption of ultraviolet radiation by the plant tissues of unwanted plants.

[0013] Microwave weeding involves sending microwaves into the soil to damage the roots of unwanted plants.

[0014] Hot water weeding involves spraying hot liquid water or hot steam onto unwanted plants.

[0015] One of the aims of the invention is to propose a weeding method which is effective and easy to implement.

[0016] For this purpose, the invention provides a weeding method comprising generating a plasma from a plasma gas and exposing unwanted plants to the plasma to eliminate these unwanted plants.

[0017] Plasma production can be done easily, for example by using ambient air as the gas to generate the plasma, which avoids the need to carry a gas supply.

[0018] The use of plasma combines the effects of other weed control processes, namely thermal effects (heat), chemical effects (formation of active species such as ozone), and radiant effects (UV light emission, infrared light emission). The use of plasma therefore allows for effective weed control.

[0019] In particular embodiments, the weeding method comprises one or more of the following optional features, taken individually or in any technically possible combination:

[0020] - the plasma gas is air; - the plasma gas is compressed;

[0021] - the generation of a plasma comprises the generation of at least one plasma jet;

[0022] - each plasma jet has the shape of a column or a curtain;

[0023] - it includes the generation of several plasma jets spaced from each other following a distribution direction;

[0024] - the plasma jets are spaced evenly, with a constant pitch between the plasma jets along the distribution direction;

[0025] - it comprises the movement of plasma jets along rows of planting extending in a planting direction, the distribution direction being perpendicular to the planting direction, each plasma jet being located opposite an inter-row of the planting;

[0026] - it comprises the generation of at least one plasma jet by ionization of the plasma gas using microwaves;

[0027] - generating at least one plasma jet comprises generating microwaves in an elongated waveguide between a first end intended to receive the microwaves and a second closed end, and circulating a flow of plasma gas in one or more passages crossing the waveguide transversely, a respective plasma jet being formed at the outlet of each passage;

[0028] - each passage is located at a distance from the second end of the waveguide tube which is substantially equal to λ / 4 + N*λ / 2 where λ is the wavelength in the microwave guide and N is a natural whole number equal to or greater than zero;

[0029] - several waveguides are connected to respective output branches of a branched power divider through which the waveguides receive the microwaves;

[0030] - at least one plasma jet is generated by discharge, in particular by bare electrode discharge, by single dielectric barrier discharge or by double dielectric barrier discharge;

[0031] - it includes the generation of a plasma by ionization of a slice of air located above the ground;

[0032] - ionization is carried out using a power electrode positioned above the ground, with a dielectric layer located under the power electrode, by applying a voltage between the power electrode and the ground.

[0033] The invention also relates to a weeding apparatus comprising a plasma generation system configured to generate a plasma from a plasma gas. In particular embodiments, the weeding apparatus comprises one or more of the following optional features, taken individually or in any technically possible combination:

[0034] - the plasma gas is air.

[0035] - the plasma gas is compressed.

[0036] - it is configured for the generation of at least one plasma jet, each plasma jet having for example the shape of a column or a curtain;

[0037] - it is configured for the generation of several plasma jets spaced from each other following a distribution direction;

[0038] - the plasma jets are spaced evenly, with a constant pitch between the plasma jets along the distribution direction;

[0039] - it is configured for the generation of at least one plasma jet by ionization of the plasma gas using microwaves;

[0040] - it is configured for the generation of at least one plasma jet from microwaves, comprising a microwave generator configured to generate microwaves in at least one elongated waveguide between a first end intended to receive the microwaves and a second closed end, each waveguide having at least one passage crossing the waveguide transversely, and a supply device configured to supply each passage with a flow of plasmagenic gas for the generation of a respective plasma jet at the outlet of each passage when the microwave generator generates microwaves in the waveguide;

[0041] - each passage of each waveguide is located at a distance from the second end of the waveguide which is substantially equal to Δ / 4 + N*Δ / 2 where Δ is the wavelength in the microwave guide and N is a natural whole number equal to or greater than zero;

[0042] - several waveguides are connected to respective output branches of a branched power divider through which the waveguides receive the microwaves;

[0043] - it is configured to generate at least one plasma jet per discharge, in particular by bare electrode discharge, by single dielectric barrier discharge or by double dielectric barrier discharge;

[0044] - it is configured for the generation of a plasma by ionization of a slice of air located above the ground; - the ionization is carried out using a power electrode positioned above the ground, a dielectric layer being located under the power electrode, by applying a voltage between the power electrode and the ground.

[0045] The invention and its advantages will be better understood upon reading the following description, given solely as a non-limiting example, and made with reference to the appended drawings, in which:

[0046] - [Fig 1] Figure 1 is a schematic side view of a tractor equipped with a weeding apparatus configured to produce a plasma for carrying out a plasma weeding method;

[0047] - [Fig 2] Figure 2 is a schematic sectional view of a plasma generation system using microwaves to generate a plasma jet;

[0048] - [Fig 3] Figure 3 is a perspective view of a waveguide of the plasma generation system of Figure 2;

[0049] - [Fig 4] Figure 4 is a schematic top view of a plasma generation system configured to generate multiple plasma jets simultaneously;

[0050] - [Fig 5] Figure 5 is a schematic top view of a plasma generation system configured to generate multiple plasma jets simultaneously using microwaves;

[0051] - [Fig 6] Figure 6 is a schematic sectional view of a torch plasma generation system using microwaves to generate a plasma jet;

[0052] - [Fig 7] Figure 7 is a schematic sectional view of a plasma generation system using electrodes to generate a plasma jet;

[0053] - [Fig 8] Figure 8 is a schematic sectional view of a plasma generation system using electrodes to generate a plasma jet;

[0054] - [Fig 9] Figure 9 is a schematic sectional view of a plasma generation system using electrodes to generate a plasma jet;

[0055] - [Fig 10] Figure 10 is a schematic sectional view of a plasma generation system using an electrode to generate a plasma in a slice of air located between the electrode and the ground;

[0056] As illustrated in Figure 1, a vehicle 2 is equipped with a weeding apparatus 4 configured to eliminate unwanted plants 6 growing on the ground 8 by implementing a weeding method comprising generating a plasma from a plasma gas and exposing unwanted plants to the plasma to eliminate these unwanted plants.

[0057] A plasma is a gas ionized by an input of energy, in particular a gas ionized under the action of an electric field and / or an electromagnetic field, such as an electromagnetic field generated by a laser or by other electrical generators (continuous, alternating, radiofrequency, microwave, pulsed, etc.).

[0058] Plasma gas, for example, is not exclusively air. Using air as plasma gas eliminates the need for a plasma gas reserve. The air required to generate plasma can be taken from the environment and simply compressed using a compressor.

[0059] Soil 8 is, for example, the soil of a field intended for growing crops. Alternatively, soil 8 is a road, a railway line, or other.

[0060] Vehicle 2 is, for example, a tractor intended for carrying out agricultural work, particularly in fields. Alternatively, vehicle 2 is a road vehicle, a rail vehicle or other.

[0061] The weeding device 4 comprises for example an axle 10, here two axles 10, and a coupling device 12 making it possible to couple the weeding device 4 to the vehicle 2 so that the weeding device is towed by the tractor 2.

[0062] Alternatively, the weeding device 4 is for example configured to be mounted on the vehicle 2, and in particular suspended from the vehicle 2. Such a weeding device 4 is for example mounted or suspended at the rear of the vehicle 2, at the front of the vehicle 2 or under the vehicle 2.

[0063] In another variant, the weeding device can be attached to the vehicle (if integrated during the design of the latter).

[0064] The weeding apparatus 4 has at least one plasma generation system 14 configured to generate a plasma to eliminate unwanted plants 6 growing on the soil 8.

[0065] In particular, the plasma generation system 14 is configured to generate one or more plasma jets 16

[0066] The weeding apparatus 4 is preferably configured to, when fitted to the vehicle 2, be located above the ground 8 in such a way that the plasma generation system 14 generates one or more plasma jets 14 directed towards the ground 8 to eliminate unwanted plants 6 growing on the ground 8.

[0067] The weeding device 4 configured to equip the vehicle 2, for example by being towed by the vehicle 2 or mounted on the vehicle 2, makes it possible to quickly and efficiently treat large areas, such as a field, a road or a railway line.

[0068] The generation of one or more plasma jets 16 allows targeted elimination of unwanted plants, for example by eliminating unwanted plants located between rows of planting, also called “intra-row” weeds. Advantageously, the plasma generation system 14 is configured to use air as a plasma gas, i.e. to generate a plasma from air, in particular air taken from the environment of the plasma generation system 14, and which can be compressed using a compressor, for example.

[0069] Using air as a plasma gas, particularly to generate the plasma jet(s), allows air to be taken from the environment and avoids the need to carry a gas reserve. It advantageously simplifies the system, avoiding the time required to change gas reserves (for other gases) and reducing the risk of accidents. In addition, it is the least expensive of the gases.

[0070] As illustrated in Figures 2 and 3, a plasma generation system 14 is configured to generate at least one plasma jet 16 using microwaves to ionize the gas.

[0071] The plasma generation system 14 comprises at least one microwave generator 18 configured to generate microwaves, at least one waveguide 20 configured to guide the microwaves generated by the microwave generator(s) 18, each waveguide 20 having a passage 22 passing through the waveguide 20 and having an inlet 24 for receiving the plasma gas flow and an outlet 26 at which the plasma gas flow is transformed into a plasma jet 16.

[0072] Each waveguide 20 is tubular. It comprises a side wall 30 and has a first end 32 intended to receive the microwaves and a second closed end 34. Each waveguide 20 is preferably straight between its first end 32 and its second end 34. The side wall 30 is preferably metallic.

[0073] Each waveguide 20 extends longitudinally between its first end 32 and its second end 34, and, preferably, each passage 22 of the waveguide 20 extends transversely across the waveguide 20.

[0074] The inlet 24 and the outlet 26 of each passage 22 are for example defined by openings provided in the side wall 30 of the waveguide 20 and located opposite each other.

[0075] The inlet 24 and the outlet 26 are defined by openings provided in the side wall 30 of the waveguide 20, being located at the same location along the waveguide 20.

[0076] Preferably, the waveguide 20 has a rectangular cross-section (Figure 3), such that the side wall 30 has two opposite first faces 30A and two opposite second faces 30B. The inlet 24 is provided in one of the two opposite first faces 30A and the outlet 26 is provided in the other of the two opposite first faces 30A, being located opposite the inlet 24.

[0077] The second end 34 is for example closed by a bottom 35, which is preferably metallic. The bottom 36 is for example a plate, in particular a metal plate.

[0078] Alternatively, as illustrated in chain lines in Figure 3, the waveguide 20 has for example a beveled shape near its second end 34, the cross-section of the waveguide 20 gradually decreasing until its second end 34 which ends in a point.

[0079] Preferably, the length of the waveguide 20 taken between the first end 32 and the second end 34 is equal to M*À where À is the wavelength of the microwaves in the guide and M is a natural integer equal to or greater than 1.

[0080] Preferably, the inlet 24 and the outlet 26 of each passage 22 are arranged at a distance D from the second end 34 of the waveguide 20 which is substantially equal to λ / 4 + N*λ / 2 where λ is the wavelength of the microwaves in the guide and N is a natural whole number equal to or greater than zero.

[0081] These locations along the waveguide 20 at such distances from the second closed end 34 of the waveguide 20 are where the microwave energy is strongest.

[0082] In an exemplary embodiment, several passages 22 are provided along the waveguide 20.

[0083] Advantageously, as illustrated in Figure 3, the outlet 26 of each passage 22 has an elongated shape along a direction of elongation E. This makes it possible to generate a plasma jet 16 of elongated shape. The plasma jet 16 has the shape of an elongated blade along the direction of elongation E, as illustrated in dotted lines in Figure 3.

[0084] Preferably, in this case, the inlet 24 also has an elongated shape along the elongation direction E.

[0085] In particular, the inlet 24 has the same shape and dimensions as the outlet 26. This allows an identical flow rate of the gas flow at the inlet 24 and the outlet 26 of the passage 22.

[0086] Preferably, the plasma generation system 14 is configured to supply each passage 20 with compressed plasma gas, in particular to supply each passage 20 with compressed air. The plasma generation system 14 comprises a gas supply device 36 configured to supply compressed plasma gas.

[0087] The gas supply device 36 is, for example, a compressed gas source or a compressor.

[0088] In particular, the gas supply device 36 is for example an air compressor configured to supply each passage 22 with compressed air, preferably by taking air from the environment of the weeding device 4. Alternatively, the gas supply device 36 comprises a reservoir of compressed plasma gas.

[0089] Optionally, as illustrated in Figure 2, the plasma generation system 14 includes, in each passage 22, at least one conduit 38, each conduit extending in the passage 22 from the inlet 24 to the outlet 26.

[0090] Each channel duct 38 makes it possible to channel the flow of plasma gas between the inlet 24 and the outlet 26, without the plasma gas circulating in the waveguide 20. The plasma gas is in particular confined in the zone where the microwave energy is the strongest.

[0091] The plasma generation system 14 comprises, for example, in at least one passage 22 or in each passage 22, a single pipe conduit 38 whose cross-section corresponds to that of the inlet 24 and the outlet 26. In operation, the plasma jet 16 is generated at the outlet of the pipe conduit 38.

[0092] Alternatively, the plasma generation system 14 comprises, for example, in at least one passage 22 or in each passage 22, a plurality of channeling conduits 38 arranged side by side.

[0093] In operation, an elementary plasma jet is generated at the outlet of each pipeline conduit 38, the elementary plasma jets defining the plasma jet 16.

[0094] The pipeline conduits 38 are, for example, conduits of circular cross-section arranged side by side to take together the elongated shape of the inlet 24 and the outlet 26 of the passage 22.

[0095] In operation, the microwave generator 18 generates microwaves propagating from the waveguide 20, and the gas supply device supplies each passage 22 with gas, in particular air. By passing through the passage 22, the gas is ionized by the microwaves propagating in the waveguide 20, and a plasma jet 16 is thus generated at the outlet 26 of each passage 22. The plasma jet 16 damages unwanted plants located in the vicinity of the plasma jet 16. Advantageously, as illustrated in Figure 4, a weeding apparatus 4 comprises a plasma generation system 14 and is configured to simultaneously generate several plasma jets 16.

[0096] Preferably, the plasma jets 16 are distributed along a distribution direction DD while being spaced from each other, preferably uniformly, i.e. with a constant pitch between the plasma jets 16.

[0097] Such an arrangement of the plasma jets 16 makes it possible, for example, to simultaneously treat several spaces between rows of plantations (or “inter-rows”) extending in parallel, the weeding apparatus 4 being arranged so that the distribution direction DD is perpendicular to the rows of plantations and each plasma jet 16 is located in an inter-row, the weeding apparatus 4 being moved along the rows of plantations.

[0098] In an exemplary embodiment, several plasma jets 16 distributed along a distribution direction DD are generated using microwaves, preferably generated by a single microwave generator 18.

[0099] To do this, the plasma generation system 14 comprises, for example, at least one waveguide 20 provided with several passages 20 arranged along this same waveguide 20.

[0100] In such a case, the spacing between each plasma jet 16 and the next is approximately λ / 2, λ being the wavelength in the microwave guide generated by the microwave generator.

[0101] Each waveguide 20 has, for example, one passage 22, two passages 22, three passages 22, four passages 22 or more.

[0102] Alternatively or as an optional addition, the plasma generation system 14 comprises several waveguides 20 receiving microwaves generated by a single microwave generator 18.

[0103] The plasma generation system 14 of Figure 5 is analogous to that of Figure 3 in being configured to simultaneously generate multiple plasma jets 16 using a single microwave generator 18, with multiple waveguides 20.

[0104] The plasma generation system 14 comprises an input tube 40 having a first end 42 provided to receive the microwaves generated by the microwave generator 18 and a second end 44, and several waveguides 20, each waveguide 20 having its first end 32 connected to the second end 44 of the waveguide 20 to receive the microwaves propagating in the input tube 40. The first end 32 of each waveguide 20 is for example connected to the input tube 40 by a power divider 46. The power divider 46 is a branched conduit comprising an input branch 48 connected to the second end 44 of the input tube 40 and several output branches 50, each output branch 50 being connected to a waveguide tube 28.

[0105] As illustrated in Figure 5, the plasma generation system 14 includes two waveguides 20, and the power divider 46 includes two output branches 50. The power divider 46 has a “T” shape.

[0106] Preferably, the waveguides 20 have the same cross-section, and the input tube 40 and each branch of the power divider 46 (i.e. the input branch 48 and each output branch 50) have the same cross-section as the waveguides 20.

[0107] Each waveguide 20 includes one or more passages 22 for passing plasma gas through the waveguide 20 and generating a plasma jet 16. Each passage 22 is connected to the gas supply device 36 (not shown in Figure 4) for its supply of plasma gas.

[0108] Advantageously, each waveguide 20 comprises several passages 22 distributed along the waveguide 20.

[0109] In Figure 5, each waveguide 20 comprises three passages 22. The passage 22 closest to the second end 34 of the waveguide 20 is located at a distance λ / 4 from this second end 34, the next passage 22 is located at a distance λ / 4 + λ / 2 from this second end 34, and the next passage 22 is located at a distance λ / 4 + λ from this second end 34.

[0110] In possible variants, each waveguide 20 has a different number of passages 22, for example one passage 22, two passages 22, four or more passages 22.

[0111] The plasma generation system 14 comprises, for example, a pair of collinear waveguides 20 following a distribution direction DD. This makes it possible to have a large number of passages 22 distributed along the distribution direction DD.

[0112] In operation, the microwave generator 18 generates microwaves entering the waveguide 20 through the first end 42 of the inlet tube 40 and propagating in each waveguide 20 via the power divider 46. The gas supply device 36 supplies each passage 22 with gas, in particular air. In each passage 22, the gas passing through the passage 22 is ionized by the microwaves and a plasma jet 16 is generated at the outlet 26 of the passage 22. The provision of several passages 22 along a waveguide 20 and / or several waveguides 20 makes it possible to treat several areas in a single pass.

[0113] The generally "T"-shaped configuration comprising two collinear waveguides 20 is given as an example. Other configurations are possible, for example a generally "L"-shaped, comb-shaped or rake-shaped configuration.

[0114] The microwaves used to generate plasma, for example, have a frequency between 300 MHz and 300 GHz, in particular a frequency between 2.4 GHz and 2.5 GHz.

[0115] The microwaves used to generate plasma thus have a wavelength between 1 mm and 1 m, in particular a wavelength between 17 cm and 18 cm.

[0116] When a waveguide 20 has a rectangular cross-section, the latter has, for example, a height of between 5 mm and 75 mm, in particular between 42 mm and 44 mm, and / or a width of between 10 mm and 150 mm, in particular between 84 mm and 88 mm.

[0117] In an exemplary embodiment, the microwaves have a frequency between 2.4 GHz and 2.5 GHz and / or each waveguide 20 has a rectangular cross-section having a height of 43 mm and a width of 86 mm.

[0118] In this case, when several passages are provided along a waveguide 20, the spacing between one plasma jet 16 and the next is a multiple of the half wavelength in the guide (approximately 8.7 cm), which makes it possible to obtain a value corresponding to a usual spacing between rows of plantations.

[0119] Other plasma generation systems 14 are conceivable.

[0120] In one example, as illustrated in Figure 6, a microwave plasma generation system 14 is of the torch type.

[0121] The plasma generation system 14 comprises for example a microwave generator 18 configured to generate microwaves, a waveguide 20 configured to guide the microwaves generated by the microwave generators 18, the waveguide 20 having a passage 22 passing through the waveguide 20 and having an inlet 24 and an outlet 26, and a torch 51 extending in the passage 22 passing through the waveguide 20, a space being provided between the torch 51 and the inner wall 24A, 26A of each of the inlet 24 and the outlet 26. The gas supply device 36 is connected to the torch 51 to supply the torch 51 with plasma gas, the plasma gas being for example air, and the plasma gas preferably being compressed.

[0122] The waveguide 20 comprises a first end 32 intended to receive the microwaves generated by the microwave generator 18 and a second end 34 closed by a short-circuit plug 52 - also called a "short-circuit".

[0123] Preferably, the shorting plug 52 is inserted into the waveguide 20 by being slidably movable in the waveguide 20 such that the position of the plug 52 in the waveguide 20 is adjustable.

[0124] The inlet 24 of the passage 22 is provided with an initiator plug 54 - also called an "initiator" - through which the torch 51 extends.

[0125] Preferably, the priming plug 54 is inserted into the inlet 24 of the passage 22 by being slidably movable in the inlet 24 of the passage 22 such that the position of the priming plug 54 in the inlet 24 of the passage 22 is adjustable.

[0126] The torch 51 and the waveguide 20 are preferably metallic, the plasma generation system 14 comprises a voltage generator 56 configured to apply an electrical voltage between the torch 51 and the waveguide 20.

[0127] In operation, the microwave generator 18 generates microwaves propagating from the waveguide 20, and the gas supply device supplies the torch 51 with plasma gas. The plasma gas is ionized by the microwaves propagating in the waveguide 20, and a plasma jet 16 is thus generated at the outlet of the torch 51.

[0128] Adjusting the position of the short-circuit plug 52 and / or adjusting the position of the initiator plug 54 makes it possible to modify the propagation of the microwaves in the waveguide 20 to ensure the generation of the plasma jet 16 at the outlet of the torch 51.

[0129] The weeding apparatus 4 comprises one or more plasma generation systems 14 of this type.

[0130] In particular, several plasma generation systems 14 can be arranged to generate plasma jets 16 distributed along a distribution direction DD as mentioned above.

[0131] Alternatively or optionally, the plasma generation system 14 is configured to generate at least one plasma jet by discharge, in particular by bare electrode discharge, by single dielectric barrier discharge or by double dielectric barrier discharge. In one example, the weeding apparatus 4 comprises at least one plasma generation system 14 by discharge, in particular a plasma generation system 14 by single dielectric barrier discharge, by double dielectric barrier discharge or by bare electrode discharge.

[0132] As illustrated in Figure 7, a bare electrode discharge plasma generation system 14 comprises a conduit 60 having a first end 62 connected to the gas supply device 36 for its supply of plasma gas and a second end 64 where the plasma is generated in operation, and an electrode 66, preferably thread-like, extending in the conduit 60 and terminating near the second end 64, and a voltage generator 68 connected to the electrode 66 for applying an electrical voltage thereto. Plasma gas flowing in the conduit 60 is in contact with the electrode 66.

[0133] In operation, the gas supply device 36 supplies the conduit with plasma gas and the voltage generator 68 applies a voltage to the electrode 66 which generates an electric field around the electrode 66, the plasma gas passing through this electric field being ionized, so that the plasma jet 16 is generated at the outlet of the conduit 60.

[0134] Other systems for generating plasma 14 by bare electrode discharge are conceivable.

[0135] As illustrated in Figure 8, a plasma generation system 14 by single dielectric barrier discharge differs from the plasma generation system 14 by bare electrode discharge of Figure 5 in that the electrode 66 constitutes a first electrode, the plasma generation system 14 comprising a second electrode 70 located outside the conduit 60, here around the second end 64 of the conduit 60, the voltage generator 68 being connected to the two electrodes 66, 70 to generate an electrical voltage between the two electrodes 66, 70.

[0136] The conduit 50 is made of a dielectric material. Plasma gas flowing in the conduit 60 is in contact with the electrode 66 and is not in contact with the electrode 70.

[0137] In operation, the gas supply device 36 supplies the conduit 60 with plasma gas and the voltage generator 68 applies a voltage between the two electrodes 66, 70 which generates an electric field between the two electrodes 66, 70, the plasma gas passing through this electric field being ionized, so that the plasma jet 16 is generated at the outlet of the conduit 60.

[0138] Other systems for generating plasma 14 by single dielectric barrier discharge are conceivable. As illustrated in Figure 9, a system for generating plasma 14 by double dielectric barrier discharge differs from the system for generating plasma 14 by bare electrode discharge of Figure 6 in that the first electrode 66 is separated from the gas flow by a dielectric material. The first electrode 66 is here covered with a dielectric material 71.

[0139] Plasma gas flowing in the conduit 60 is not in contact with the first electrode 66 and the second electrode 70.

[0140] In operation, the gas supply device 36 supplies the conduit 60 with plasma gas and the voltage generator 68 applies a voltage between the two electrodes 66, 70 which generates an electric field between the two electrodes 66, 70, the plasma gas passing through this electric field being ionized, so that the plasma jet 16 is generated at the outlet of the conduit 60.

[0141] Other systems for generating plasma 14 by double dielectric barrier discharge are conceivable.

[0142] The weeding apparatus 4 comprises one or more discharge plasma generation systems 14.

[0143] In particular, several discharge plasma generation systems 14 can be arranged to generate plasma jets 16 distributed along a distribution direction DD as mentioned above.

[0144] In one example, the weeding apparatus 4 includes a double dielectric barrier discharge plasma generation system 14 using the unwanted plants as one of the dielectric barriers, to generate a plasma in an air gap located between an electrode and the soil 8.

[0145] As illustrated in Figure 10, such a plasma generation system 14 comprises for example a power electrode 72 configured to be disposed above the ground, a dielectric layer 74 disposed under the power electrode 72, and a voltage generator 76 configured to apply a voltage between the ground and the power electrode 72 so as to ionize the slice of air located between the ground and the power electrode 72.

[0146] In operation, the voltage generator 76 applies a voltage between the soil and the power electrode 72 so as to ionize the air gap between the soil and the power electrode 72. The power electrode 72 is separated from the soil by the dielectric layer 74 and by the unwanted plants which define another dielectric layer.

[0147] Such a plasma generation system 14 makes it possible to efficiently weed a large area of ​​soil. The weeding apparatuses 4 and the plasma generation systems 14 described above make it possible to carry out a weeding method comprising generating a plasma from a plasma gas and exposing unwanted plants to the plasma to eliminate these unwanted plants.

[0148] Preferably, the plasma gas used to generate the plasma is compressed. Advantageously, the plasma gas is not exclusively air, in particular compressed air.

[0149] The generation of a plasma comprises for example the generation of at least one plasma jet, each plasma jet 16 having for example the shape of a column or a curtain.

[0150] The weeding method advantageously comprises the generation of several plasma jets 16 spaced from each other in a distribution direction DD, the plasma jets 16 preferably being spaced uniformly, with a constant pitch between the plasma jets in the distribution direction DD.

[0151] In this case, the weeding method preferably comprises moving the plasma jets 16 along rows of planting extending in a planting direction, the distribution direction DD being perpendicular to the planting direction, each plasma jet 16 being located opposite an inter-row of the planting.

[0152] The weeding method comprises, for example, the generation of at least one plasma jet 16 by ionization of the plasma gas using microwaves.

[0153] The generation of at least one plasma jet comprises the generation of microwaves in at least one waveguide 20 elongated between a first end 32 intended to receive the microwaves and a second closed end 34, and, for each waveguide 20, the circulation of a flow of plasmagenic gas in at least one passage 22 passing transversely through the waveguide 20, a plasma jet 16 being formed at the outlet of each passage 22.

[0154] Each passage 22 is located at a distance from the second end of the waveguide tube which is substantially equal to λ / 4 + N*λ / 2 where λ is the wavelength in the microwave guide and N is a natural integer equal to or greater than zero.

[0155] The weeding method comprises, for example, supplying microwaves to a plurality of waveguides 20 from a microwave generator 18, the first ends 32 of the waveguides 20 being connected to respective output branches of a branched power divider 46 through which the waveguides 20 receive the microwaves.

[0156] Alternatively or optionally, as illustrated in Figures 7 to 9, depending on the weeding method, at least one plasma jet 16 is generated by discharge, in particular by bare electrode discharge, by single dielectric barrier discharge or by double dielectric barrier discharge.

[0157] Alternatively or optionally, as illustrated in Figure 10, the weeding method comprises generating a plasma by ionizing a slice of air located above the ground. The ionization is carried out for example using a power electrode 72 positioned above the ground, a dielectric layer 74 being located under the power electrode 72, by applying a voltage between the power electrode 72 and the ground.

[0158] Plasma production can be done easily, for example by using ambient air as the gas to generate the plasma, which avoids the need to carry a gas supply.

[0159] The use of plasma combines the effects of other weed control processes, namely thermal effects (heat), chemical effects (formation of active species such as ozone), and radiant effects (UV light emission, infrared light emission). The use of plasma therefore allows for effective weed control.

[0160] Several plasma jets can be generated simultaneously, for example using microwaves and / or by discharge, to carry out inter-row weeding in a plantation.

Claims

CLAIMS 1. A method of weed control comprising generating a plasma from a plasma gas and exposing unwanted plants to the plasma to eliminate the unwanted plants.

2. A weeding method according to claim 1, wherein the plasma gas is air.

3. A weeding method according to claim 1 or 2, wherein the plasma gas is compressed.

4. A weeding method according to any one of the preceding claims, wherein the generation of a plasma comprises the generation of at least one plasma jet (16).

5. A weeding method according to claim 4, wherein each plasma jet (16) has the shape of a column or a curtain.

6. Weeding method according to claim 4 or 5, comprising the generation of several plasma jets (16) spaced from each other in a distribution direction (DD).

7. A weeding method according to claim 6, wherein the plasma jets (16) are uniformly spaced, with a constant pitch between the plasma jets along the distribution direction.

8. Weeding method according to claim 6 or 7, comprising moving the plasma jets along rows of planting extending in a planting direction, the distribution direction (DD) being perpendicular to the planting direction, each plasma jet (16) being located opposite an inter-row of the planting.

9. A weeding method according to any one of the preceding claims, comprising generating at least one plasma jet (16) by ionization of the plasma gas using microwaves.

10. A weeding method according to any one of the preceding claims, wherein the generation of at least one plasma jet (16) comprises the generation of microwaves in a waveguide (20) elongated between a first end intended to receive the microwaves and a second closed end, and the circulation of a flow of plasmagenic gas in one or more passages (22) crossing the waveguide transversely, a respective plasma jet (16) being formed at the outlet of each passage (22).

11. A weeding method according to claim 10, wherein each passage (22) is located at a distance from the second end of the waveguide tube which is substantially equal to λ / 4 + N*λ / 2 where λ is the wavelength in the microwave guide and N is a natural integer equal to or greater than zero.

12. A weeding method according to claim 10 or 11, wherein a plurality of waveguides (20) are connected to respective output branches of a branched power divider through which the waveguides (20) receive the microwaves.

13. A weeding method according to any one of the preceding claims, wherein at least one plasma jet is generated by discharge, in particular by bare electrode discharge, by single dielectric barrier discharge or by double dielectric barrier discharge.

14. A weeding method according to any one of the preceding claims, comprising generating a plasma by ionization of a slice of air located above the ground.

15. A weeding method according to claim 14, wherein the ionization is carried out using a power electrode (72) positioned above the ground, a dielectric layer (74) being located under the power electrode, by applying a voltage between the power electrode and the ground.

16. A weeding apparatus comprising a plasma generation system (14) configured to generate a plasma from a plasma gas.

17. A weeding apparatus according to claim 16, wherein the plasma gas is air.

18. A weeding apparatus according to claim 16 or 17, wherein the plasma gas is compressed.

19. Weeding apparatus according to any one of claims 16 to 18, configured for the generation of at least one plasma jet (16), each plasma jet (16) having for example the shape of a column or a curtain.

20. Weeding apparatus according to any one of claims 16 to 19, configured for the generation of several plasma jets (16) spaced from each other in a distribution direction (DD).

21. A weeding apparatus according to claim 20, wherein the plasma jets (16) are uniformly spaced, with a constant pitch between the plasma jets along the delivery direction.

22. Weeding apparatus according to any one of claims 16 to 21, configured for the generation of at least one plasma jet (16) by ionization of the plasma gas using microwaves.

23. Weeding apparatus according to any one of claims 16 to 22 configured for the generation of at least one plasma jet from microwaves, comprising a microwave generator (18) configured to generate microwaves in at least one waveguide (20) elongated between a first end intended to receive the microwaves and a second closed end, each waveguide (20) having at least one passage (22) passing transversely through the waveguide (20), and a supply device (36) configured to supply each passage (20) with a flow of plasmagenic gas for the generation of a respective plasma jet (16) at the outlet of each passage (22) when the microwave generator (18) generates microwaves in the waveguide (20).

24. A weeding apparatus according to claim 23, wherein each passage (22) of each waveguide (20) is located at a distance from the second end of the waveguide (20) which is substantially equal to λ / 4 + N*λ / 2 where λ is the wavelength in the microwave guide and N is a natural integer equal to or greater than zero.

25. A weeding apparatus according to claim 23 or 24, wherein a plurality of waveguides (20) are connected to respective output branches of a branched power divider through which the waveguides (20) receive the microwaves.

26. Weeding apparatus according to any one of claims 16 to 25, configured to generate at least one plasma jet by discharge, in particular by bare electrode discharge, by single dielectric barrier discharge or by double dielectric barrier discharge.

27. Weeding apparatus according to any one of the preceding claims, configured for the generation of a plasma by ionization of a slice of air located above the ground.

28. A weeding apparatus according to claim 27, wherein the ionization is carried out using a power electrode (72) positioned above the ground, a dielectric layer (74) being located under the power electrode, by applying a voltage between the power electrode and the ground.

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