FR2466886A1 - Electrode structure for ionised air generator - uses needles as one electrode and flat perforated conducting plate as other to reduce ozone and nitrous oxide production - Google Patents

Abstract

The generator of negatively ionised air generates reduced levels of ozone and nitrous oxides to improve its suitability for application in dwellings and offices. The electrode downstream in the flow of ionised air is a flat perforated conducting wire mesh (2), in contact with a metalised layer on the insulating layer (1), while the electrode upstream of the airflow comprises conducting needles (31,41) which are coaxial with the tubes (11) passing through the phenolic or epoxy insulating layer (1), and project to the face of the insulated layer. The needles are electrically connected by wires (5,6) lying parallel to the flat electrode and electrically insulated from it. A potential of approx. 4.2kV is used to give the required electric field.

Description

 The invention relates to atmospheric negative ion generators, used in residential premises and offices and, more particularly> to those which include a fan, placed upstream of the electrodes and projecting the ions generated by them to a certain distance.

 In this category of atmospheric air ionization devices, the downstream electrode must brake and stop the ions and the air flow as little as possible and this is why it is most often made up of an openwork conductive plate or of a grid. The upstream electrode is generally identical to the downstream electrode.

 With these symmetrical electrode structures of the prior art, it has been found that the production of ions is generally accompanied by a notable production of ozone and nitrogen oxide, polluting substances whose current regulations limit strictly the concentrations allowed.

 The invention provides an electrode structure which provides both increased ion production and reduced production of polluting substances.

 According to the invention, the downstream electrode consists of a flat conductor provided with orifices, while the upstream electrodes consist of conductive needles which pass through said orifices and protrude beyond the downstream face of the planar conductor.

 According to a preferred embodiment, said needles are electrically connected together by conductive wires arranged parallel to the upstream face of the planar conductor and separated from the latter by insulating spacers.

 Other features, as well as the advantages of the invention, will become apparent in the light of the description below.

In the attached drawing:
Figure 1 is a plan view, partially broken away, of an assembly, showing the upstream face of electrodes according to a preferred embodiment of the invention, intended to equip an ionization generator; and
Figure 2 is a section along II - II of Figure 1.

 It can be seen that the figured assembly comprises an openwork plate 1, the face of which visible in FIG. 1 is covered with an insulating plate 2 provided with cells 21 having, in the nonlimiting example described, a hexagonal shape (nest d 'bees).

For example, the plates 1 and 2 are 210 mm long and 75 mm wide; plate 2 at 19 mm thick and plate 1, 2 mm.

 In FIG. 1, the plate 2 has been torn off over most of the surface of the block to show that the plate i, made of an insulating material, is provided with circular orifices 11 (eight in number in 11 example described) and metallized on its face in contact with the plate 2, except on annular portions 12, surrounding each orifice 11.

 In FIG. 2, there has been shown, for greater clarity, an interval between the metallization 12- and the plates 1 and 2.

In reality, the metallization is carried by the surface of the plate 1 (it is, for example, a conductive paint or a layer of copper), while the plate 2 comes into contact with the metallization or is separated by a small interval.

Plate 1 is, for example, made of a: phenolic insulator or epoxy glass.

 By way of example, the orifices II are 20 mm in diameter and the non-metallized region 12 has an external diameter of 30 mm.

 The openings II and the facing cells 21 are concentric and, along the axis of each orifice, penetrates a needle (3 or 4), for example made up of a steel rod a few tenths of a mm in diameter.

 Finally, as many pairs of electrodes were thus formed as there were needles, each needle constituting an upstream electrode and the portion of the plate 1 which it passes through constituting a downstream electrode.

 The high voltage, (for example: 4.2 kilo-volts) necessary for the creation of a high electric field (for example 300,000 volts / meter) between the electrodes, is applied between a wire connected to the metallization 13 (not shown) and mistletoe wires connect together all the ends of needles located upstream of the plate 1 (31 - 41, FIG. 2). There is shown in dotted lines, in Figure 1, two horizontal son 5 and 6, which interconnect the needles corresponding respectively to the first and second rows of guatre orifices.

These two wires are connected together by a vertical wire 7 itself connected to a terminal of the high voltage generator. The wire 7 is supported by an insulating spacer 8, 3mm thick in the example described. The assembly of the supply wires of the upstream electrodes is thus placed in a plane separated by a dielectric thickness of 5 mm from the metallization 13.

 FIG. 1 shows that an identical insulating spacer is fixed on the upstream face of the plate 1, between each of the successive vertical pairs of orifices. All the needle station feed wires are fixed on the upstream face of these spacers.

 In operation, the electric field generated between the metallization 13 and the part of the needles which projects downstream of the plate 1 ionizes the oxygen in the air and the negative ions thus created are projected through the alveoli 21 outside of the device housing. The terms "upstream" and "downstream" used above are therefore defined by reference to the flow of ions.

 Given the fragility and the short lifespan of the ions, it is important not only that the ventilation is energetic (we are limited, in this regard, by the need to use a silent fan) but also, that the 'electrode protection member that constitutes the plate 2 is as transparent as possible to them, hence the interest of the honeycomb structure in the cells of which the needles penetrate.

 I1 was found, moreover, that the particular architecture of the electrodes described is favorable to the production of ions while preventing the production of ozone and nitrogen oxide from reaching excessive amounts. With the apparatus described by way of example, the production of ions reaches 24 × 10 12 per second without the ozone concentration exceeding 0.003 ppm, or 3% of the admissible dose for humans.

 It goes without saying that various modifications may be made to the device described and shown, without departing from the spirit of the invention.

Claims (4)

 1. Structure of electrodes for atmospheric endowment generators, comprising a downstream electrode in the form of a flat conductor, provided with orifices, characterized by at least one upstream electrode comprising a conductive needle passing through one of said orifices and projecting beyond the downstream face of the planar conductor  2. Structure of electrodes according to claim 1, characterized by a plurality of needles interconnected by conductive wires arranged parallel to the upstream face of the planar conductor and separated from the latter by insulating spacers  3. electrode structure according to claim 1 or 2, characterized by a protective honeycomb plate placed opposite the downstream face of said planar conductor, so that the needles penetrate into the cells of said protective plate  4 electrode structure according to one of claims 1 to 3, characterized in that said flat conductor is constituted by a conductive layer formed on the downstream face of a plate of insulating material.  50 electrode structure according to claim 4, characterized in that said orifices are circular and each surrounded by an annular zone not covered with said conductive layer.