EP0771483A1

EP0771483A1 - Plasma superconfinement generator for producing positive or negative ions in a gaseous medium

Info

Publication number: EP0771483A1
Application number: EP95926407A
Authority: EP
Inventors: Jacques Léon Georges Breton
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-07-20
Filing date: 1995-07-20
Publication date: 1997-05-07
Anticipated expiration: 2015-07-20
Also published as: CA2195343A1; DE69506712T2; FR2722923B1; US5789749A; JPH10503048A; EP0771483B1; AU3081195A; FR2722923A1; DE69506712D1; ES2128068T3; ATE174729T1; GR3029664T3; BR9508416A; WO1996002966A1

Abstract

PCT No. PCT/FR95/00978 Sec. 371 Date Mar. 21, 1997 Sec. 102(e) Date Mar. 21, 1997 PCT Filed Jul. 20, 1995 PCT Pub. No. WO96/02966 PCT Pub. Date Feb. 1, 1996The invention relates to a generator of ions in gaseous medium comprising at least one emissive needle (Ag) disposed in a system of plates (P2, P4, P5) connected to a high voltage electrical source (Al), an insulating plate ensuring the diffusion of the electrons, and is characterized in that the needle (Ag) comprises a coaxial sheath (Gn) of a dielectric material of high resistivity, low loss and relatively high permissivity, extended by a first conical proximal section (Cp) of the same material, leaving exposed the emissive end of the needle, and itself extended by an open conical distal structure (Cd) of the same material as the sheath, in that said distal structure (Cd) is extended by a plate (Pi) of the same material as the sheath and constituting with the distal conical structure (Cd) said diffusion plate of the electrons and in that said extending plate (Pi) is fixed below a plate (P6) of a material of very low electrical conductivity, adapted to form a portion of the external housing of the generator. Use particularly in the depollution/decontamination of localities and in the protection of sites sensitive to static charges.

Description

POSITIVE OR NEGATIVE ION GENERATOR IN GASEOUS MEDIA WITH PLASMA SURFACE

The present invention relates to electronic devices of the "negative or positive ion generator" type. These devices make it possible to maintain inside an enclosure or a local an ion density (for example of negative oxygen ions 0 ₂ in the air) of homogeneous or localized distribution, permanent or temporary, previously determined and also high than necessary, in the absence of any production of aggressive or toxic compounds (Ozone 0 ₃ and / or nitrogen oxides NO _χ among others). Known devices of this kind are based on the "crown" effect (or "tip" effect). Brought for example to a voltage of -6 to -12 kV, a metallic tip then emits a rapidly increasing electron flow (exponentially) with the applied voltage. The known faults of these devices, inherent in their emissive structure, however severely limit their performance, and more particularly the advantage and the possibilities of applications. In particular, the rudimentary emission configuration generally adopted has the following inevitable consequences:

- the compulsory use of very high voltages (8 to 12 kVolts) essential for the production of a sufficient ion flux, but difficult to control or even dangerous for current applications, - the random value of the electric field existing in the vicinity of the tip emissive, the disadvantage of a poor ionic yield, - the existence of an extended plasma zone, created at the end of the tips, favoring an intense production of the peroxidants already mentioned and detracting by screen effect from the intensity of the ionic emission, - the dispersion in the atmosphere of the toxic compounds thus produced, favored by the "electric wind" resulting from the very high voltages used,

- the excessive directivity of the electronic emission, producing a very inhomogeneous ambient ion density, - the quasi obligation to use a "propellant" costly in unnecessary energy, noisy, subject to wear (fan, turbine ...), cause harmful air turbulence (resuspension of the pollutants present) and discomfort, exaggerating the directivity of the device. Such defects were largely attenuated, and some were eliminated in the devices fitted with "electronic optics" according to the patents FR-A-2 603 428 and FR-A-2 687 858. However, several defects specific to the configuration adopted remained. : - initiations difficult to avoid between the emitting needles and the field plate (connected to ground and to the ground), due to the necessarily limited diameter of the openings of said plate (maximum "drawdown" of the zero equipotential), - inevitable capture , by the field plate and the walls, charges from the needles by lateral crown effect (effluvage), resulting in a significant loss of yield, still insufficient limitation of plasma confinement, due to the partial "drawdown" of the zero equipotential , resulting from the large diameter of the openings of the field plate,

- excessive capture of the charges emitted by the walls of the housing, thereby reducing the efficiency of the device. The new device according to the invention sees the defects noted above disappear, and thus proves to be free from the aforementioned drawbacks. Experimental control

(Faraday cage measurements of the overall flow) of an embodiment of said new device makes it possible to verify the actual disOarition of the aforementioned faults. To this end, the subject of the invention is a generator of positive or negative ions in a gaseous medium, comprising an electronic optic consisting of at least one needle or emissive point arranged in a system of support and acceleration plates, focusing and diffusion of ions comprising a first conductive plate to which the non-emissive end of the needle is fixed, a second conductive plate traversed by said needle and provided, on its face facing said first conductive plate, with an insulating plate , said first and second conductive plates being connected to a suitable high-voltage electrical source and an insulating plate arranged at the height of the emissive end of the needle and ensuring the diffusion of the electrons emitted by the needle, characterized in that the needle has a coaxial sheath made of a dielectric material with high resistivity, low loss and high relative permittivity , in that the part of said sheath situated on the side of the emissive end of the needle is extended by a first conical proximal section made of the same material as the sheath and leaving uncovered said emissive end, in that said proximal section is extended by an open conical distal structure made of the same material as the sheath, in that said distal conical structure is extended by a plate made of the same material as the sheath and constituting with the distal conical structure said electron diffusion plate and in that said plate extension is fixed under a plate of material with very low electrical conductivity, capable of forming a part of the external casing of the generator.

Other characteristics of the device of the invention are defined in the secondary claims.

The generator of the invention is therefore generally characterized by a complete "cladding" of each of the emitting needles, extended by an adaptive emission structure, assembly consisting of a dielectric with high resistivity and low losses, of relative permittivity high, associated with a reorganization of the elements of electronic optics. This cladding, this adaptive structure and the reorganization of the electronic otic then ensure the multiple advantages which follow, making it possible in particular: to minimize the diameter of the openings of the field plate, - to thereby ensure the maximum possible "drawdown" of the zero equipotential (by effect of the configuration of the electric field in the dielectric), to ensure a unique relationship between the parameters chosen and the value fixed to the electric field at the end of the needles,

to thus obtain the value close to the maximum possible of said electric field at the extreme point of the emissive needles,

- to approach as much as possible the electronic emission of needles,

- thus avoiding the use of very high voltages of difficult or dangerous use, in addition inevitable additional generators of the aforementioned toxic compounds, - minimizing the volume of the plasma zone at the free end of the needles ( "over-containment" mechanism),

- to further reduce, or even cancel, the production of the aforementioned peroxidants, - to completely eliminate all risks of priming with the field plate,

- completely cancel the losses by side crown effect of the needles, thus eliminating any additional effluviation generating toxic compounds, thus ensuring the optimum intrinsic ionic yield of the emissive needles,

- then to have the free end of the needles in the optimal geometrical configuration with respect to the outer plate of the box enclosing the device, with a view to the maximum electronic emission efficiency towards the atmosphere,

- thereby reducing the diameter of the openings of said plate, - thus having an increased number of needles emissive on the same surface,

- to exclude any unnecessary "propellant" system from previously ionized air, and thus to remove the inevitable nuisances, - to reduce to the strict minimum, if necessary and without affecting its performance, the external bulk of the device by facilitating its use,

- finally to reduce to the essential minimum the energy consumption of the device. The device according to the invention thus ensures the production, emission and quasi-isotropic diffusion of an intense flow of charges of one and / or the other sign, without emission of toxic compounds, under a voltage of value moderate, without unnecessary expenditure of energy. Such features are absent in whole or in part from all the other emissive point devices currently used.

The result is a definite and decisive improvement in the "crown effect" generator, both with regard to the size of the emitted flux and its spatial distribution (quasi-isotropy), the even greater safety in its use, the total absence and definitive of any nuisance caused to sensitive people or installations, due to the absence of emission of toxic or aggressive compounds (ozone and nitrogen oxides among others), the considerable energy saving in permanent or intensive use. The proof of the reality of such improvements is provided by the measurements made on an experimental model of the device according to the invention:

- Faraday cage measurements of the total flux emitted to the atmosphere,

- reading by electronic probe of the polar diagram of ionic emission in free space,

- chemiluminescence spectroscopy analysis of the air taken in the immediate vicinity of the tips. This set of measures fully verifies and confirms each of the advantages stated characterizing the new device according to the invention.

The accompanying drawings illustrate an embodiment of the device of the invention, namely: - Figure 1 shows the diagram (in principle) of elements of the new electronic optics, with the distribution of the equipotentials and of the emitted ion flux;

Figure 2 shows the diagram (block diagram) of the entire device in the form of the specific functions exercised by each of its parts.

As shown in FIG. 2, the assembly of the device according to the invention comprises two sub-assemblies:

- a sub-assembly (section I) constituted by the electronic optical system, described above, according to FIG. 1.

- a sub-assembly (section II) consisting of a power supply unit (Al) delivering between .the output (S) and the common ground (M) a high voltage (-THT) of the order of 4 to 5 kV under an impedance of the order of a hundred Mohms, intended to supply said electronic optics with the high voltage necessary for ionic production. As shown in FIG. 1, the "electronic optical" part of the device is thus constituted: - a plate (P) made of insulating material, with a thickness of the order of 1 mm, canceling out any electronic emission ( effluvage) towards the rear of the device inside the housing;

- a conductive plate (P ₂ ) on which are fixed on its rear face (welding, crimping, or any other means of fixing) the emissive "points";

- an insulating plate (P ₃ ), integral with the plate (P ₂ ) and located in front of the latter, the integral assembly (P ₂ , P ₃ ) having a thickness of 16/10 mm; - "tips" constituted by long and thin needles of stainless metal (Ag) whose free (emissive) end has a radius of a few micrometers, ^• an adaptive structure of electronic emission made up: * of a "sheath" dielectric (Gn), made of a material with high resistivity (. 10 ¹⁵ m), low losses and high relative permittivity, with an outside diameter of the order of 5 mm, with an inside diameter allowing passage needles. Said sheath is threaded with friction

RECTIFIED SHEET (RULE 91) A / EP soft on each needle, leaving free of it only about 2 mm beyond the first terminal conical section constituting the end of said sheath, and coming into contact with the plate (P ₃ ) at its other end;

* a double conical structure integral with the sheath, made of the same insulating material as the latter, the proximal part (C_) surrounding the end of the needle excluding the last two millimeters remained free, thus completing confinement of the plasma, and of which the flared distal part (C ^) with an angular opening of 45 ° and a depth of 8 mm ensures a first complete and rapid diffusion of the ionic flux towards the surrounding atmosphere;

* an internal planar structure, plate (P ^) integral with the conical structure and in the extension thereof, 2 mm thick, made of the same insulating material, and coming to be fixed on the outer wall of the housing enclosing the device, so that the conical openings of the adaptive structure coincide exactly with the circular openings (base of the chamfer) of said housing; - a composite plate (P ₄ , P ₅ ) 16/10 mm thick, the lower face of which is insulating, the upper face is conductive and connected to ground (ground zero potential). Said plate is pierced with circular openings (O _c ), ensuring exactly the gentle friction passage of the "sheaths" of the emitting needles on which it is threaded;

- A plate (P _g ), the thickness of which is of the order of 3 mm, constitutes the housing containing the device, is made of a very weakly conductive material (resistivity of the order of 10 square ohms). Said plate constituting said housing is connected to the conductive plate (P ₅ ). The "leakage" resistance (R _f ) symbolizes the real resistance of the plate (P ₅ ) responsible for draining the charges (I _f ) taken from the local space charge resulting from the electronic emission of the tips. Said plate (Pg) is pierced with circular openings (Open) provided with a chamfer (Ch) with an angular opening of the order of 60 °, hollowed out over its entire thickness, so that its underside fits exactly on the open end of the cone (C _d ) carried by the internal plate (P ^ _), the wall of the chamfer (Ch) lying in the extension of the conical surface of the distal structure (C _d ).

FIG. 2 represents a possible exemplary embodiment of the electronic optical system intended for the production and the emission towards the atmosphere of the ionic flux emitted by the "tips".

A set of needles, the length of which is of the order of 25 to 30 mm for a diameter of the order of 1 mm and a terminal radius of the order of a few micrometers, is fixed to the conductive plate (P ₂ ), subjected by the aforementioned power supply (Al) to a negative voltage (case of the production of ions

Negative oxygen in the air) close to 4.5 kv maximum.

The conductive field plate (P ₅ ) carried by the insulating plate (P ₄ ) is connected to ground (zero potential). The emissive needles are sheathed with dielectric. It follows that the zero equipotential is imposed by the field plate (P ₅ ), its distribution then depending on the position and the length of the needles as well as the characteristics of the dielectric sheath and its distal cone (C _d ) . In fact, because of the high relative permittivity of the sheath and of its distal cone, the "drawdown" of the zero equipotential is practically done on the external surface of said sheath and ensures the presence of an electric field of maximum value. very high at the free end of the needle, a prerequisite for the most intense primary electronic emission possible.

The plate (Pg) constituting the device housing has a low but not zero conductivity. This characteristic greatly reduces the capture of the charges emitted, while ensuring their evacuation to the common ground. The optimum dynamic balance between capture and evacuation then results from the choice of the value of said conductivity and the characteristics of the adaptive structure. The surface charge acquired by the cone distal (C _d ) exerts a strongly repulsive effect on the local space charge, ensuring the emission towards the outside of the maximum ion flux of which only a very small part is captured by the housing. The measurement of said "capture current" on the aforementioned experimental model confirms the accuracy of the approach and the effectiveness of the device.

Such an exemplary embodiment does not exhaust the invention, the various constituent elements of which can be produced, as required, in several parts of suitable dimensions and materials, assembled in the final device, or produced in whole or in part in the form of molded parts having the characteristics and functions of the aforementioned parts, in the functional form of a "unitary electronic optics module". The assembly of a determined number of such "unit modules" by simple juxtaposition or by an overall molding makes it possible to have a "composite electronic sheet optic" adapted to previously defined needs.

An example of application is given by the implementation of the device in all places subject to air pollution or biocontamination; this is particularly the case for nurseries. Tests carried out within the framework of numerous establishments have shown that the injection of a sufficient negative ionic flux then ensures the precipitation of the polluting particles and of the germs present, as well as the death of the latter, with the corollary a significant and lasting improvement. occupant health status.

Another example of application relates to places subject to strong influences from existing static charges or created by certain devices: this is among others the case of computer rooms in general, places of manipulation or processing of photographic films as well as sensitive electronic components. The injection of a sufficient permanent flow of negative charges makes it possible to almost completely eliminate the nuisances observed, without prejudice to those present and sensitive equipment.

Another example of application is given by the injection of an intense negative ionic flux into the air intake pipes of combustion or combustion engines. internal. The negatively charged air ensures better stability and more complete combustion of the hydrocarbon aerosol, and therefore a lower emission of pollutants in the exhaust gases. Such examples in no way exhaust the applications of the invention, which can be used in all circumstances requiring the production of intense fluxes of ions

(in particular negative) in air or other gaseous medium, in the complete absence of compounds (Ozone or nitrogen oxides) aggressive or toxic for people and goods.

Claims

CLAIM SB + - »+ β +" + β + "+ β + = + = + a + - + β + - + -s

1. Generator of positive or negative ions in a gaseous medium, comprising an electronic optic (EO) consisting of at least one needle or emissive point (Ag) disposed in a system of support and acceleration, focusing and diffusion plates. ions comprising a first conductive plate (P ₂ ) to which the non-emissive end of the needle is fixed, a second conductive plate

(P ₅ ) traversed by said needle and provided, on its face facing said first conductive plate (P ₂ ), with an insulating plate (P ₄ ), said first and second conductive plates being connected to an appropriate high voltage electrical source (Al) and an insulating plate arranged at the emissive end of the needle and ensuring the diffusion of the electrons emitted by the needle, characterized in that the needle (Ag) comprises a coaxial sheath (Gn) in one dielectric material with high resistivity, low loss and high relative permittivity, in that the part of said sheath (Gn) situated on the side of the emissive end of the needle (Ag) is extended by a first conical proximal section (Cp) in the same material as the sheath and leaving uncovered said emissive end, in that said proximal section (Cp) is extended by an open conical distal structure (Cd) in the same material as the sheath, in that the said distal conical structure (Cd) is extended by a plate (Pi) made of the same material as the sheath and constituting with the distal conical structure (Cd) said electron diffusion plate and in that said extension plate (Pi) is fixed under a plate (P6) made of a material with very low electrical conductivity, capable of forming part of the external casing of the generator.

2. Generator according to claim l, characterized in that it comprises a plate (P-_) attached under said first conductive plate (P ₂ ) for protection purposes against possible effluvage from said conductive plate.

3. Generator according to claim 1 or 2, characterized in that said first conductive plate (P ₂ ) has an insulating plate (P3) on its side facing the needle.

4. Generator according to one of claims 1 to 3, characterized in that said second conductive plate (P ₅ ) comprises an insulating plate (P ₄ ) on its face facing towards said first conductive plate (P ₂ ).

5. Generator according to one of claims 1 to 4, characterized in that said second conductive plate (P ₅ ) and any associated insulating plate (P ₄ ) are provided with openings (Oc) of diameter corresponding to that of the sheath of the needle (Ag) so as to allow the passage with gentle friction of the sheath on which said plates (P ₅ , P ₄ ) are threaded.

6. Generator according to one of claims 1 to 5, characterized in that said plate (Pg) with very low electrical conductivity capable of forming a part of the outer casing of the generator is provided with a chamfered opening (Ouv, Ch) of which the frustoconical wall is an extension of the conical surface of said distal conical structure (Cd).

7. Generator according to one of claims 1 to 6, characterized in that said second conductive plate (Pc) is brought to zero potential of the general mass of the device.

8. Generator according to claim 7, characterized in that said plate (Pg) with very low electrical conductivity capable of forming a part of the outer casing of the generator is electrically connected to said second conductive plate (P ₅ ) by an equivalent leakage resistance (R _F ).

9. Generator according to one of claims 1 to 8, characterized in that the sheath material (Gn) has a resistivity greater than or equal to 10 ¹⁵ -fλ.m.

10. Generator according to one of claims 1 to 9, characterized in that said needle (Ag) is left uncovered by said conical proximal section (Cp) over a length of the order of two mm.

11. Generator according to one of claims 1 to 10, characterized in that said distal conical structure (Cd) has an angular opening of the order of 45 ° and a depth of the order of 8 mm.

12. Generator according to one of claims 1 to 11, characterized in that said plate (Pg) with very low electrical conductivity is made of a material whose resistivity is of the order of 10 'Ohm.carré.

13. Generator according to one of claims 1 to 12, characterized in that said high voltage electrical source provides a voltage of the order of 4Kv.