EP0048102A1

EP0048102A1 - Air ionization devices

Info

Publication number: EP0048102A1
Application number: EP81303932A
Authority: EP
Inventors: Jolyon Michael Crane
Original assignee: PENNY AND GILES POTENTIOMETERS Ltd
Current assignee: PENNY AND GILES POTENTIOMETERS Ltd
Priority date: 1980-09-11
Filing date: 1981-08-27
Publication date: 1982-03-24

Abstract

An air ionization device for generating negative ions comprises an electrode (14), and a circuit including a transformer (5) and voltage-doubler rectifier circuits (7,8) for producing from a relatively low voltage source (1,2) a negative voltage for application to said electrode (14) of sufficient magnitude to cause a corona discharge and produce negative ions at said electrode (14), said electrode (14) being formed of carbon fibre filaments (16).

Description

This invention relates to air ionization devices for producing negative ions by corona discharge.
It is well known that many articles of modern living, for example, things made of plastics materials and television receivers decrease the relative number of negative ions in the air, either by preferentially absorbing negative ions or by preferentially producing positive ions. Modern heating and ventilating systems, particularly air-conditioning systems, also commonly have a similar effect. Moreover, it is now well established that a deficiency of negative ions in the air has a detrimental effect on a person's feeling of well-being or even on their health. For example, a deficiency of negative ions may reduce the ability of the body to absorb oxygen into the bloodstream and this in turn reduces the efficiency of all the bodily functions associated with respiration.
It has therefore been proposed to provide air ionization devices for producing large numbers of negative ions for dissemination into the air in homes and workplaces. Unfortunately there is some difficulty in producing such devices which are both mechanically and electrically safe. Thus, some previously proposed air ionization devices include an electrode at which the corona discharge takes place and which is in the form a sharp needle or a stainless steel brush. In the case of a needle, the efficiency of the discharge is very dependent on the sharpness of the point, but clearly a very sharp point, which must necessarily be exposed to the air, is ,a safety hazard particularly to young children. A stainless steel brush is safer, but substantially less efficient as an ion emitter, because the brush quickly becomes clogged with dirt and also the closely adjacent metallic points have a mutual screening effect.
To cause a corona discharge, a voltage of several kilovolts is necessary, and to avoid electrical hazards resulting from a voltage of that magnitude being present on an exposed electrode, it has been proposed that the drive circuit which supplies the high voltage to the electrode should include a current limiting resistor. If, however, this resistor is short circuited for any reason, the necessary electrical safety is lost.
According to the present invention there is provided an air ionization device comprising an electrode and means for applying to said electrode a negative voltage of sufficient magnitude to cause a corona discharge and produce negative ions at said electrode, said electrode being formed of carbon fibre filaments.
Such devices can be associated with other equipment in many different ways, for example by being incorporated in air or gas cleaners, or in air conditioning systems or air circulating systems. Such devices can also be used in association with equipment such as fan heaters or cathode ray tubes which tend to produce an excess of positive ions.
The invention also provides air ionization devices suitable for use to increase the number of negative ions in a room or other living space, such as a workplace or a car, without being specifically associated with any other equipment except a suitable power supply.
According to the present invention, therefore, there is also provided an air ionization device comprising an electrode, and a circuit for producing from a relatively low voltage source a negative voltage for application to said electrode of sufficient magnitude to cause a corona discharge and produce negative ions at said electrode, said electrode being formed of carbon fibre filaments.
The relatively low voltage source may be an alternating current mains source in which case said circuit may include a transformer and one or more voltage-doubler rectifer circuits, or it may be a battery or solar cells, in which case said circuit may include an inverter circuit to produce an alternating current for subsequent voltage step-up.
Preferably said circuit includes a series connection of a plurality of current limiting resistors, so that if one of the resistors becomes shortcircuited, the remaining resistor or resistors are effective to limit to the current that can be derived from said electrode.
In one embodiment the carbon fibre filaments comprise a bundle or bunch of some forty-thousand filaments each some 7 or 8 microns in diameter. Such an electrode is soft to the touch and moreover is very readily cleaned of dirt simply by blowing on it.
The invention will now be further described by way of example with reference to the accompanying drawing, in which:

Figure 1 shows the circuit of an embodiment of air ionization device according to the invention;
Figure 2 is a diagrammatic side view of an electrode of the embodiment; and
Figure 3 is a diagrammatic plan view of part of another embodiment.

Referring to Figure 1, the air ionization device is intended to be powered from the usual 240 volts ac mains and line and neutral input terminals 1 and 2 are provided for this purpose. The terminals 1 and 2 are connected by way of a thermal fuse 3 and directly to the primary winding 4 of a step-up transformer 5, which develops an output voltage of some 1.2 kilovolts across a secondary winding 6.
The secondary winding 6 is connected to two series-connected voltage-dealer rectifier circuits 7 and 8, the rectifier circuit 7 comprising rectifier diodes Dl and D2 and capacitors Cl and C3, and the rectifier circuit 8 comprising rectifier diodes D3 and D4 and capacitors C2 and C4. A 1 megohm resistor 9 is connected between the neutral input terminal 2 and the junction of one end of the secondary winding 6, and the diode D1 and the capacitor C3 in the rectifier circuit 7, so the neutral input terminal 2 forms the circuit earth point.
The voltage-doubler rectifier circuits 7 and 8 operate to produce a negative output voltage of some 6.8 kilovolts dc at an output terminal 10. The output terminal 10 is connected to a socket 11 by way of a series- connection of a plurality of current-limiting resistors 12, there being nine resistors 12 in the present case. Each resistor 12 is of 10 megohms resistance and 0.5 watt capacity. Mating with the socket 11 is a plug 13 to which is attached an electrode 14 shown in more detail in Figure 2.
The thermal fuse 3 is provided to provide a safety cut-out should the primary winding 4 become over-heated due to malfunction of components in the voltage-doubler rectifier circuits 7 and 8 or of the transformer 5.
Referring to Figure 2, the electrode 14 comprises a moulded body 15 of plastics material from one end of which projects the plug 13 comprising tinned copper connectors. From the other end of the body 15 projects a bundle or bunch of carbon fibre filaments 16 at which the actual corona discharge and production of negative ions takes place for dissemination into the surrounding air.
In one particular embodiment the carbon fibre filaments 16 comprises some forty-thousand filaments 16 each some 12 mm in length and 7 to 8 microns in diameter. The base of the bundle is some 2 mm in diameter and the body 15 some 5 mm in diameter and 7.5 mm in length. If desired a tapered member may be pressed into the centre of the bundle to cause the carbon fibre filaments 16 to fan out to some extent. The plug 13 projects by a further 5 mm or so and is readily connectable to and disconnectable from the socket 11 to enable the electrode 14 to be removed for cleaning. Such cleaning is very readily effected, simply by blowing on the bundle of carbon fibre filaments 16.
The circuit is contained in a suitable housing from which only the electrode 14 and a flex which may include a fused switch with a neon indicator projects. The housing which may, for example, be generally spherical, may be made of a ceramic material and the circuit may be held in the interior of the housing by a flexible potting medium.
The air ionization device described has a number of advantages. In particular, the diameter of each of the carbon fibre filaments 16 is comparable to the diameter of a very sharp point, and remains so even after erosion, so the production of a corona discharge and negative ions is very efficient. Moreover, the very large number of carbon fibre filaments 16 and their diameter is such as to reduce erosion problems. At any one time only a few of the carbon fibre filaments 16 are actually effective as negative ion emitters and if these carbon fibre filaments 16 erode or are broken their function is taken over by others, so in view of the very large number of carbon fibre filaments 16, the electrode 14 has a long life. The few operating carbon fibre filaments 16 are repelled by electrostatic force from the main bunch, thus providing the necessary voltage gradient around each tip to promote corona discharge and ion production. The electrode 14 is readily cleaned to remove dust, and indeed it can even be washed if necessary. The bundle of carbon fibre filaments 16 feels quite soft to the touch and hence the air ionization device can more readily be used in an exposed position and hence be more efficiently used.
As negative ions are repelled from the electrode 14 a reaction force acts on the electrode 14, and this can be used as a driving force to produce movement. For example, as indicated in Figure 3, if two electrodes 14 are mounted horizontally and facing in opposite directions at respective ends of a conductive arm 17 which is mounted horizontally and is rotatable about a vertical axis 18, the arm 17 will rotate.

Claims

1. An air ionization device comprising an electrode (14) and means for applying to said electrode (14) a negative voltage of sufficient magnitude to cause a corona discharge and produce negative ions at said electrode (14), said electrode (14) being formed of carbon fibre filaments (16).

2. An air ionization device comprising an electrode (14), and a circuit (5, 7, 8) for producing from a relatively low voltage source (1, 2) a negative voltage for application to said electrode (14) of sufficient magnitude to cause a corona discharge and produce negative ions at said electrode (14), said electrode (14) being formed of carbon fibre filaments (16).

3. A device according to claim 2 wherein said circuit includes a transformer (5) and one or more voltage-doubler rectifier circuits (7, 8) coupled between the output of said transformer (5) and said electrode (14).

4. A device according to claim 2 or claim 3 wherein said circuit includes a series connection of a plurality of resistors (12) coupled to said electrode (14) so as to limit the current that can-be drawn from said electrode (14).

5. A device according to any one of the preceding claims wherein the reaction force acting in use of the device on said electrode (14) is used as a driving force.

6. A device according to claim 5 wherein two said electrodes (14) are mounted back-to-back at respective ends of an arm 17 which is rotatable about an axis (18).

7. A device according to any one of the preceding claims wherein each said filament (16) is some 7 to 8 microns in diameter.

8. A device according to any one of the preceding claims wherein said negative voltage is some 6.8 kilovolts.