GB1598957A

GB1598957A - Device for the production of ions

Info

Publication number: GB1598957A
Application number: GB9646/78A
Authority: GB
Original assignee: FLECK C M; KNOBLICH C
Current assignee: FLECK C M; KNOBLICH C
Priority date: 1977-03-10
Filing date: 1978-03-10
Publication date: 1981-09-30
Also published as: DE2809054C2; JPS6048879B2; CH626706A5; DE2809054A1; IT7867506A0; FR2383536A1; JPS53112696A; IT1107132B

Abstract

The device is used especially for ionising air. It consists of a wire (5), which is connected to a high-voltage source (7) and consists of electrically conductive material, and of a reflector screen (1) which is arranged at a distance from the wire, is at a high-voltage potential and partially surrounds the wire. In order to increase the ion emission, it is proposed that the reflector screen be insulated from earth and be connected to the high-voltage source, the high-voltage potential on the reflector screen being at least 3000 V, but preferably 5000 to 10,000 V. <IMAGE>

Description

(54) DEVICE FOR THE PRODUCTION OF IONS (71) We, CARL MARIA FLECK of Schnelleingasse 14/2, A.1040, Vienna, Austria, and CAMILLO KNOBLICH of Schleifmuhlgasse 7, A. 1040, Vienna, Austria, both Austrian Citizens, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a device for the production of ions, in particular for the ionisation of air, with a wire of electrically conducting material connected to a source of high potential and a reflector screen spaced from the wire and partly surrounding it, the reflector screen assuming (in operation) a high potential which has the same polarity as the high potential of the wire but which is smaller in magnitude than the high potential of the wire.

In such known ionisers, electrons are emitted from the surface of the wire by field emission and are deposited on gas molecules and dust particles. The electrons emitted by the wire in all directions rapidly bring about charging of supporting surfaces or mounting devices close to the ioniser. Since the high electrostatic potential produced by this unwanted charging significantly decreases the potential gradient round the emission wire, which is essential to emission, a significant decrease occurs in the electron-emission and resulting ionization.

In order to avoid this disadvantage there has been proposed in U.S. Patent Specification 3.234.432 a reflector screen surrounding the wire on one side and which is earthed through a resistor of 1 - 1000 MQ. A potential drop across the resistor is produced by a fraction of the electrons (ions) emitted against the reflector screen and this should bring the reflector screen to the potential necessary for the repulsion of the remaining electrons, that is to say that, in this known device, the high potential of the reflector screen has the same polarity as the high potential of the wire and is intermediate between the potential of earth and that of the wire.However, in practice this known device is functionally effective only to a limited degree because, on the one hand, a high electron- (ion-) current must flow to the reflector screen in order to produce an effective potential drop and, on the other hand, it is necessary to use a very thin wire and a screen at a large distance from it.

From U.S. Patent Specification 3.296.491 there is known a device for the production of charged aerosols in which a liquid is fed in the longitudinal direction relative to a wire, the liquid being torn away by means of a plate or grid-shaped electrode at a potential different from. that of the wire, and thereby atomised. Since in this known device one of the electrodes (wire or plate/grid) is always earthed it is only possible to produce charged drops of liquid by this device. The production of gaseous ions is not possible by this known device since, because of their low mass, gaseous ions are immediately moved towards the counter-electrode to be discharged there.

It is the object of the invention to eliminate the disadvantages of the known device for producing gaseous ions.

According to the present invention, there is provided a device for the production of ions and serving to emit the ions in free space for the ionisation of the air, as defined in claim 1 below.

In the device according to the invention it is possible to use reflector screens of relatively small dimensions without losing the effect of the screen. It is thus possible, without difficulty, to construct the device according to the invention as a convenient table model.

High potential sources of very low power can be used. Contact with the wire or with the reflector screen is completely free from danger since the potential collapses immediately on contact. Current limiting resistors are preferably provided between the wire or the reflector screen and the source of high potential. The emissive power of the wire can be controlled or stabilised. This is achieved relatively easily in that the screen is brought to a negative (positive) potential while the curve of free potential V (r) about an undistorted wire is given by the formula: V(r) = V0 ln (r/rl)/ln(ra/rl) where rl is the diameter of the wire, ra is the mean corrected distance of the surroundings from the wire and V0 is the potential of the wire.

The reflective action of the screen can be increased in a simple manner by slightly increasing the potential of the screen. A preferred embodiment of the invention thus has the reflector screen connected to a potential which is at least equal to and preferably somewhat higher than the potential due to the electric field produced by the electrical charge on the wire at the position of the edges of the output region when the wire is mounted without a metal shield.

In another convenient embodiment of the invention, the high potential of the wire can be adjusted together with the high potential of the reflector screen. The wire potential is usually 5000 V above that of the reflector screen, that is the potential of the wire is preferably 10,000 to 15,000 V.

It is known that not only atmospheric ions but also electric fields with low frequency modulation have positive effects on human beings. It has already been established that an electric field with a 10 Hz frequency modulation can produce improved learning results in pupils in a class as well as increased attention in test assignments.

It is a subsidiary object of the invention to design ionisers of the type described in such a way that they produce not only atmospheric ions but also an alternating field without the need for the introduction of complex devices. This is achieved in that a high potential pulsating with a frequency of 1 to 20 Hz, preferably 3 - 12 Hz, between a maximum and a minimum value is connected to the reflecting screen.

Wire ionisers have the disadvantage that the exposed emission wire stretched between two mountings cannot be protected against mechanical effects and because of its small diameter (usually less than 50 micron) is easily broken by mechanical action.

It is another subsidiary object of the invention to remove this disadvantage and to apply tension to the wire in such a way that the wire is released when it is contacted mechanically.

For this purpose the device is so designed that a magnetic field can be applied to a magnetic or magnetisable mounting of the wire, the magnetic adhesion being smaller than the tensile strength of the wire.

The invention will now be described in more detail by way of an example with reference to the drawings, in which: Figure 1 shows an embodiment of a device according to the invention for the production of ions, in a schematic representation; Figure 2 is a cross-section through another embodiment of a device according to the invention; Figure 3 is a perspective view of part of a conducting tube for a device according to the invention; Figure 4 shows an embodiment of the device according to the invention designed as table model; Figure 5 shows a schematic representation of another embodiment of a device according to the invention with a reflector screen of cylindrical cross-section; Figure 6 is a diagram showing the distribution of potential around the wire for a device according to Figure 5;; Figures 7 and 8 show two embodiments of circuits for the production of frequency modulated potentials to be applied to the reflector screen; and Figures 9, 10 and 11 show three forms of mountings for the wire of a device according to the invention..

A device according to the invention for the production of ions is shown schematicallv in Figure 1. The device includes a reflector screen 1, of aluminium for example, with two plates 2, 3 converging outwards and a channel 4 of U-shaped cross-section connecting the two plates 2,3. A wire 5 is stretched between two mounting devices 6 in the longitudinal direction of the screen 1. The mounting devices 6 are attached to side sections of the housing (not illustrated). Both the wire 5 and the screen 1 are separately connected to a high potential of the same polarity. A high voltage circuit 7 is provided for this purpose for the wire 5 and the screen 1. The high voltage circuit 7 may be of a known type which produces a d.c. voltage of up to 20 kV from the a.c. mains voltage.The high voltage circuit 7 ils connected through an adjustable resistor 10 to the source of a.c. voltage, for instance 220 V. A voltmeter 9 and an ammeter 8 are provided for measurement of the voltage and the current. In Figure 1 there is applied by means of the high voltage circuit 7 to the wire 5 and to the screen 1 either a positive high potential only or a negative high potential only, according to whether it is desired to produce positive or negative ions. The potential on the screen 1 can be adjusted by moving the tapping 11 on the high voltage circuit 7, and the potential of the wire 5 and of the screen 1 can thus be adjusted to the prevailing conditions.

The wire 5 has a diameter of 50 micron or less and preferably consists of tungsten or tantalum. In order to increase the emissivity of the wire, the wire 5 may be surface-treated with caesium or barium and/or alloyed with thorium. The electron emission of the wire 5 can be further increased by decreasing the diameter of the wire 5, by increasing the length of the wire 5 or by raising the high potential applied to the wire (by adjustment of the potentiometer 10). The emissivity of the wire 5, and at the same time the number of ions produces, can be read off from the ammeter 9. The screen 1 is connected to a high potential source, of between 5 and 10 kV. On switching-on the device, continuous production of ions takes place round the wire 5 and the ions are repelled by the screen 1 and move into the open air.

In the embodiment according to Figure 2 the screen 1 includes two fins 12 for projecting from the upper edge of the plates 2,3, which serve to attach the screen to the walls (not illustrated) of a housing of synthetic material. A conduit 18 of synthetic material (Figure 3) is inserted in the channel 4 and includes a number of outlet slots 14 directed outwards. A blower and/or an aerosol producer (not illustrated) can be connected to the conduit 18 so that a stream of ionised air, or an electrically charged aerosol stream emerging continuously into the atmosphere can be produced. Fluorescent tubes (not illustrated) may also be mounted in the channel 4 so that a lamp combined with an ioniser is produced.

A table model with a housing of synthetic material 17 is shown in Figure 4 and is combined with a light 13. A voltmeter 19, a safety signal lamp 20, a control 15 for adjustment of the potential of the wire 5 and a switch 16 for switching the fluorescent tube 13 on and off are provided.

The device according to the invention can be used for the production of both positive and negative ions. For this purpose the high potential on the emission wire is reversed in polarity in an adjustable rhythm by means of a timing device or two devices according to the invention, combined to form a unit, may be provided in which the two wires have opposite polarities.

In Figure 5 the emission wire 5 is partially surrounded by a reflector screen by 1. The reflector screen 1 has an outlet region 21 extending parallel to the axis of the emission wire 5, the outlet region being bounded by edges 22 and having an angular aperture preferably between 60 and 1600. The diagram of Figure 6 shows the distribution of potential round the undisturbed emission wire 5 that is in the absence of the screen 1, by a curve in which the distance r from the emission wire 5 is plotted as abscissa and the absolute potential U as ordinate. At a distance r from the emission wire 5, when the screen 1 is absent, the potential is Ur. The cylindrical metal screen is raised to a potential which is at least equal to the potential Ur. In Figure 5 the screen 1 is raised to the potential Us.The screen thus has a potential greater than Ur by an amount AUr.

In order for atmospheric ions to emerge from the outlet region 21 (Figure 5) the potential at the edges 22 of the screen 1 is, in the first instance, decisive, where for an imaginary screen 1 of cylindrical form with the emission wire 5 arranged along the axis of the cylinder the potential in an undistorted field is the same at the edges as at all other parts of the screen. Either the emission wire 5 may be moved away from the cylinder axis to the position 5' or the edges 22 may be bent inward closer to the wire 5 (see dot-dash line in Figure 5).

Since the screen 1 is made from metal, the potential is Us over the whole screen 1. This means that the edges 22 (distance r2) and the central region of the screen 1 are at a potential greater than that potential (U2 or U1) which would prevail in these positions respectively on the imaginary screen with undistorted field by a potential difference AU2 at the edges 22 (distance r2) and by a potential difference AU1 in the central region of the screen 1. Since the potential difference AU2 is greater than the potential difference AU1 a useless flow of current between the screen 1 and the emission wire 5 is prevented and a good emission efficiency is achieved.

In the embodiment according to Figure 5, the screen 1 is connected to a high potential - U through two series resistors 23, 24 of high resistance, the potential -U being so adjusted that it corresponds with the undistorted potential round the wire at the position of the screen 1..

When ion emission commences, a large percentage of the ions will flow to the screen 1 at first. Thus a potential drop across the high resistance resistors 23, 24 is produced which decreases the field strength between the wire 5 and the screen 1 or changes the potential of the screen 1 in the direction of the potential of the wire so that more ions are guided through the outlet region 21. The case in which emission is completely extinguished cannot occur since in this case no drop in the potential would be produced across the resistors 23, 24.

In Figure 5 parts of the screen are constructed as bars 25 which are connected to the source of high potential - U through the high resistance resistor 23 along. Thus that part of the screen 1 which forms the casing is at a higher potential than that of the rods 25 so that the flow of ions to part 1 is suppressed. With the potential of the source - U equal to -6 KV and a wire potential of -10 KV the potential of part 2 is about -6.3 KV and the potential of the rods 23 is 6.2 KV.

The screen 1 may also be constructed as a grid or as a complete cylinder in which case slots forming the outlet region 21 are provided.

In the embodiment according to Figure 7 the reflector screen 1 is connected to a high potential Usch through a spark gap 26. A capacitor 27 is connected in parallel with the spark gap 26. The wire 5 is connected to a high potential UD. In the circuit according to Figure 8 the reflector screen 1 is connected to earth through a capacitor 28 and a spark gap 29 in parallel. A resistor 30 is connected in series with the spark gap 29. The screen 1 is connected through a resistor 31 to a high potential U to which the wire 5 is also connected.Because of the charging of the screen 1 produced by the stream of ions and owing to a suitable choice of the sparking or the extinction potential of the spark gap 26 or 29 and of the capacitor 27 or the capacitor 28 and the resistance 30, a high potential is produced which pulsates between an upper value (about 7 KV) and a lower value (about 5 KV) and is maintained on the screen 1 with a frequency of pulsation from 1 - 20 Hz, preferably 3 - 12 Hz.

Three embodiments of a device to tension or support one end of the emission wire 5 are illustrated in Figures 9, 10 and 11.

In the embodiment of Figure 9 a permanent bar magnet 32 is guided in a guide bush 34 of non-magnetic material, preferably PTFE. The guide bush 34 is surrounded by a metal bush 35. At one end of the wire 5 a sphere 33 is provided which adheres to the bar magnet. If a force greater than the force of adhesion of the sphere 33 to the bar magnet 32 is applied to the wire 5 the sphere 33 is separated from the bar magnet. The force of adhesion to the bar magnet can, for example, be fixed in a simple manner by a suitable choice of the thickness of the guide bush 34, where adjustment is made in such a way that the adhesive or attractive force exerted on the sPhere 33 by the bar magnet 32 is less than the tensile strength of the wire 5. Breaking of the wire on unintentional contact with the stretched wire 5 is thus prevented.

In the embodiment according to Figures 10 and 11 the end of the wire 5 is clamped between a cone socket 36 and a cone body 37. The mounting 39 formed by the cone socket 36 and the cone body 37 is movable within a guide bush 38 against a permanent magnet 40.

In the embodiment according to Figure 10 a small plate 41 of synthetic material is provided between the mounting 39 and the permanent magnet 40. The adhesive force or elastic force exerted by the magnet 40 on the mounting 39 can be adjusted by a suitable choice of the thickness of the small plate 41. One of the two parts 36 or 37 must consist of a magnetisable material, for example. a suitable metal, where the supply of current to the wire 5 may also take place through this part.

Similarly in the embodiment according to Figure 10, a metallic cone body 37 is clamped in a cone socket 36. On the other hand, in the embodiment of Figure 11, the cone body 37' consists of a synthetic material and the socket 36' of metal. In order to maintain a suitable tensioning of the wire 5 the mounting 39 is arranged, at least at one end of the wire 5, at a distance a from the magnet (Figure 10). On the other hand the magnet 40' may be in direct contact with the mounting 39' at the other end. The supply of current to the wire 5 can, in this case, take place directly through the magnet 40' and the socket 36'.

WHAT WE CLAIM IS: 1. A device for the production of ions and serving to emit the ions in free space for the ionisation of the air, with a wire of electrically conducting material connected to a source of high potential and a reflector screen spaced from the wire and partly surrounding it, wherein the reflector screen is insulated from earth and is connected to the source of high potential or to a separate source of high potential, such that, in operation the high potential on the reflector screen is from 5,000 to 10,000 V and has the same polarity as the potential on the wire but is smaller in magnitude than the potential on the wire, and wherein, in operation, the reflector screen is at a potential which is at least equal to the potential which would prevail at the position of the edges of the outlet region of the screen on account of the electrical field due to the electrical charge on the emission wire when the emission wire is assembled without the reflector screen.

2. A device according to claim 1, wherein the edges of the outlet region of the reflecting screen are situated closer to the emission wire than is the remaining part of the screen.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the screen 1 in the direction of the potential of the wire so that more ions are guided through the outlet region 21. The case in which emission is completely extinguished cannot occur since in this case no drop in the potential would be produced across the resistors 23, 24. In Figure 5 parts of the screen are constructed as bars 25 which are connected to the source of high potential - U through the high resistance resistor 23 along. Thus that part of the screen 1 which forms the casing is at a higher potential than that of the rods 25 so that the flow of ions to part 1 is suppressed. With the potential of the source - U equal to -6 KV and a wire potential of -10 KV the potential of part 2 is about -6.3 KV and the potential of the rods 23 is 6.2 KV. The screen 1 may also be constructed as a grid or as a complete cylinder in which case slots forming the outlet region 21 are provided. In the embodiment according to Figure 7 the reflector screen 1 is connected to a high potential Usch through a spark gap 26. A capacitor 27 is connected in parallel with the spark gap 26. The wire 5 is connected to a high potential UD. In the circuit according to Figure 8 the reflector screen 1 is connected to earth through a capacitor 28 and a spark gap 29 in parallel. A resistor 30 is connected in series with the spark gap 29. The screen 1 is connected through a resistor 31 to a high potential U to which the wire 5 is also connected.Because of the charging of the screen 1 produced by the stream of ions and owing to a suitable choice of the sparking or the extinction potential of the spark gap 26 or 29 and of the capacitor 27 or the capacitor 28 and the resistance 30, a high potential is produced which pulsates between an upper value (about 7 KV) and a lower value (about 5 KV) and is maintained on the screen 1 with a frequency of pulsation from 1 - 20 Hz, preferably 3 - 12 Hz. Three embodiments of a device to tension or support one end of the emission wire 5 are illustrated in Figures 9, 10 and 11. In the embodiment of Figure 9 a permanent bar magnet 32 is guided in a guide bush 34 of non-magnetic material, preferably PTFE. The guide bush 34 is surrounded by a metal bush 35. At one end of the wire 5 a sphere 33 is provided which adheres to the bar magnet. If a force greater than the force of adhesion of the sphere 33 to the bar magnet 32 is applied to the wire 5 the sphere 33 is separated from the bar magnet. The force of adhesion to the bar magnet can, for example, be fixed in a simple manner by a suitable choice of the thickness of the guide bush 34, where adjustment is made in such a way that the adhesive or attractive force exerted on the sPhere 33 by the bar magnet 32 is less than the tensile strength of the wire 5. Breaking of the wire on unintentional contact with the stretched wire 5 is thus prevented. In the embodiment according to Figures 10 and 11 the end of the wire 5 is clamped between a cone socket 36 and a cone body 37. The mounting 39 formed by the cone socket 36 and the cone body 37 is movable within a guide bush 38 against a permanent magnet 40. In the embodiment according to Figure 10 a small plate 41 of synthetic material is provided between the mounting 39 and the permanent magnet 40. The adhesive force or elastic force exerted by the magnet 40 on the mounting 39 can be adjusted by a suitable choice of the thickness of the small plate 41. One of the two parts 36 or 37 must consist of a magnetisable material, for example. a suitable metal, where the supply of current to the wire 5 may also take place through this part. Similarly in the embodiment according to Figure 10, a metallic cone body 37 is clamped in a cone socket 36. On the other hand, in the embodiment of Figure 11, the cone body 37' consists of a synthetic material and the socket 36' of metal. In order to maintain a suitable tensioning of the wire 5 the mounting 39 is arranged, at least at one end of the wire 5, at a distance a from the magnet (Figure 10). On the other hand the magnet 40' may be in direct contact with the mounting 39' at the other end. The supply of current to the wire 5 can, in this case, take place directly through the magnet 40' and the socket 36'. WHAT WE CLAIM IS:

1. A device for the production of ions and serving to emit the ions in free space for the ionisation of the air, with a wire of electrically conducting material connected to a source of high potential and a reflector screen spaced from the wire and partly surrounding it, wherein the reflector screen is insulated from earth and is connected to the source of high potential or to a separate source of high potential, such that, in operation the high potential on the reflector screen is from 5,000 to 10,000 V and has the same polarity as the potential on the wire but is smaller in magnitude than the potential on the wire, and wherein, in operation, the reflector screen is at a potential which is at least equal to the potential which would prevail at the position of the edges of the outlet region of the screen on account of the electrical field due to the electrical charge on the emission wire when the emission wire is assembled without the reflector screen.

3. A device according to claim 1 or 2, wherein the screen is designed as a part cylindrical

casing the axis of which coincides with or is parallel to the axis of the wire.

4. A device according to claim 3, wherein the wire is displaced from the axis of the cylinder in the direction of the outlet opening of the screen.

5. A device according to any of the claims 1 to 4, wherein the screen is partly or wholly designed as a grid.

6. A device according to any of claims 1 to 5, wherein the high potential of the wire can be adjusted together with the high potential of the reflector screen.

7. A device according to any of claims 1 to 6, wherein the reflector screen is insulated from earth by mounting it in an insulating housing of synthetic material.

8. A device according to any of claims 1 to 7, wherein a source of high potential pulsating between an upper and a lower value at a frequency of 1 to 20 Hz is connected to the reflector screen.

9. A device according to claim 8, wherein a spark gap with a capacitor in parallel is connected between the source of high potential and the reflector screen or between the reflector screen and earth.

10. A device according to any of claims 1 to 9, wherein the wire is stretched at least at one end by the adhesive or tensile force of a magnet.

11. A device according to claim 10, wherein the adhesive or tensile force of the magnet is less than the tensile strength of the wire.

12. A device according to claim 10 or 11, wherein at least one end of the wire has an enlargement attached to a permanent magnet.

13. A device according to claim 12, wherein the enlargement is spherical.

14. A device according to claim 10 or 11, wherein at least one end of the wire is clamped between a cone socket and a cone body where the cone socket and/or the cone body consists of a magnetisable and/or electrically conducting material.

15. A device according to claim 14, wherein the electrically conducting part of the cone mounting for the wire can be pressed by the magnetic force against a permanent magnet which is connected to the source of high potential.

16. A device according to claim 1 and substantially as hereinbefore described with reference to and as illustrated in Fig. 1 of the accompanying drawings.

17. A device according to claim 1 and substantially as hereinbefore described with reference to and as illustrated in Figs. 2 and 3 of accompanying drawings.

18. A device according to claim 1 and substantially as hereinbefore described with reference to and as illustrated in Fig. 4 of accompanying drawings.

19. A device according to claim 1 and substantially as hereinbefore described with reference to and as illustrated in Fig. 5 of the accompanying drawings.

20. A device according to claim 1 and substantially as hereinbefore described with reference to and as illustrated in Fig. 7 of accompanying drawings.

21. A device according to claim 1 and substantially as hereinbefore described with reference to and as illustrated in Fig. 8 of the accompanying drawings.