GB2275827A - Air ioniser - Google Patents

Abstract

An air ioniser has a plastics case (30) containing a primary ion emitter (36) connected to a high voltage source and means such as a secondary ion emitter (38) to neutralise charge build up on the inner surfaces of the plastics case. The secondary ion emitter (38) is connected to earth and produces ions of opposite charge to those from the emitter (36). The ioniser may include a fan (32). <IMAGE>

Description

TITTLE: Improvements in and relating to air ionisers 3ESCRIPTION This invention concerns improvements in and relating to air ionisers.

Air ionisers operate bv raisina one or more sharp points to a high voltage whereby ions. normally negative ions are emitted into the surrounding atmosphere. in a fan-driven ioniser, the emitter points are enclosed within a chamber and the fan is used to drive the ions out into the surrounding atmosphere. In such ionisers it is possible to eliminate substantial iv the effect of the external electric field and to reduce substantially the troublesome dirt precipitation experienced with simper air ionisers.

The chamber for such ionisers is commonly fabricated from metal and the chamber is earthed. This resuits in a Faradav Caae. However. due to the relatively high cost of usina metal. attempts have been made to produce such ionlsers with a plastics chamber.

Unfortunately, surface charge buiids up in a plastics chamber to an extent that neaative ion emission can become severely reduced and even stopped completely.

An object of this invention is to provide an air ioniser having a plastics case, wherein the above mentioned disadvantage mav be overcome.

According to this invention, there is provided an air ioniser comprising a plastics chamber. a primary ion emitter in the chamber connected to a source of high voltage for producing ions, one or more apertures in the chamber whereby produced ions may pass from the chamber and a secondary ion emitter in the chamber and means for neutralising charge build up on inner surfaces of the chamber. The means for neutralising charge build up is preferabiy a secondary ion emitter in the camber for emitting ions of opposite charge to those emitted by the primary emitter. The secondary emitter is preferably connected to earth.

The air ioniser is preferably a fan-driven ioniser and the one or more apertures are preferably provided by a grill preferably situated opposite the fan.

The primary ion emitter is preferabiy connected to a negative source of high voltage. whereby negative ions are produced. as these are physiologically beneficial, The secondary emitter then due to the high electric field subsisting between the primary and secondary emitter will produce positive ions but in a much lower amount than the negative ions produced but nevertheless in a sufficient amount to neutralise negative charge build up on the plastics case.

Typically the primary emitter will be at -6000 voits with respect to earth and will produce about 500.000 negative ions per c.c. at one metre from the ioniser.

whereas the secondarv emitter will produce 20.000 positive ions per c.c. at one metre from the ioniser.

Thus the amount of positive ions produced by the secondary emitter is relatively small and so sufficient to neutralise negative charge build up on the plastics case of the ioniser but insufficient to hinder to any great extent the emission of negative ions from the ioniser.

The positioning of the secondary emitter relative to the primary emitter is of importance in ensuring a stable output of required ions. if the secondary emitter is too close to the primary embitter, negative ion output may be severely affected and if the secondary emitter is too far from the primary emitter. posItIve ion emission may be too low to neutraiise negative charge build up in the chamber.

This invention will now be further described, by way of example onlv. with reference to the accomDanylng drawings, in which: - Figure 1 shows schematically a prior art fandriven air ioniser having a metal case: Figure 2 shows schematically a prior art fandriven air ioniser havinq a plastic case: Figure 3 shows schematicaily a fan-driven air ioniser according to the invention; and Figure 4 is a schematic front view of a fandriven air ioniser according to the invention.

Referrina to figure 1 of the accompanying drawings, a prior art air ioniser 10 comprises a metal case 12 which is earthed, a fan 14 at one side and a grill 16 at the side opposite the fan. On anintermediate side is an ion emitter 18 in the form of a pin, connected to a high voltage source fnot shown) so that it emits negative ions. The negative ions produced by the emitter 18 are driven out of the metal case 12 through the grill 16 by the fan 14. Because the metal case is earthed, there is no build up of negative ions on the surface of the case and a stable emission of negative ions is produced.

To reduce one cost of such an air ioniser, as shown in Figure 2, a plastics case 20 nas been used in place of the metal case of the ioniser of Inure 1.

Again at one side of the case there is a fan 22 and at the opposite side a grill 24. On an intermediate side is an emitter 26 connected to a high voltage source (not shown) for emission of negative ions. The fan drives the negative ions out of the case through the grill.

The plastics case 20 cannot be effectively earthed so that as negative ions are emitted from the emitter, initially there is a reasonably stable production cf negative ions but eventually negative ions in the ioniser cause a build of negative sur-ace charge on the plastics case, so that further negative ion emission IS suncressed.

This problem is overcome bv an air ioniser according to the invention as shown In Figure 3 of the accompanying drawings. which comprises a plastics case 30 having a fan 32 at one side, a grill 34 at the opposite side thereto, a primary emitter 36, in the form of a pin, on an intermediate side connected to a source of hiah voltage (not shown). On another side of the ease 30 is a secondary emitter 38, in the form of a pin.

connected to earth.

The air ioniser of Figure 3 operates in the same way as the ionisers of Figures 1 and 2 except that the secondary emitter emits a small amount of positive ions due to the high electric field that subsists between the two emitters. The positive ions produced are sufficient to neutralise negative charge build ut on the case 30. so that emission of negative ions from the air ioniser can remain stable.

The production of positive ions may be controlled bv the positioning of the secondary emitter relative to the primary emitter and a typical example is shown in Figure 4, which is a view from the exit grill of an ioniser. Hence. the plastics case 40 is approximately 150x35mm insection, with the primary emitter 42 of approximately 20mm in length positioned midway up side wali 44. The secondary emitter 46 is positioned on top wall 48 approximately 87mm in from side wall 44 and 16mm to the rear of the plane of the primary emitter.

Typicaily the primary emitter will be at -6000 voits witn respect to earth and the primary emitter current will be 435x10-iA. The secondary emitter current will typically be 360x10'9A.

Thus, by the present invention it is possible to produce an air ioniser in a plastics case in which negative charge build up is effectively neutralised by positive ion emission from the secondary emitter induced by the high electric field between the primary and secondary emitters.

Claims (9)

1. An air ioniser comprising a plastics chamber, a primary ion emitter in the chamber connected to a source of high voltage for producing ions, one or more apertures in the chamber, whereby produced ions pass from the chamber, and means for neutralising charge build up on inner surfaces of the chamber.

2. An air ioniser as claimed in claim 1, wherein the means for neutralising charge build up is a secondary ion emitter in the chamber for producing ions of opposite charge to those produced by the primary ion emitter.

3. An air ioniser as claimed in claim 2, wherein the secondary ion emitter is connected to earth.

4. An air ioniser as claimed in claim 1, 2 or 3, wherein the air ioniser is fan-driven.

5. An air ioniser as claimed in any one of claims 1 to 4, wherein the one or more apertures are provided by a grill.

6. An air ioniser as claimed in claim 5, wherein the grill is situated in an airstream produced by a fan.

7. An air ioniser as claimed in any one of claims 1 to 6, wherein the primary ion emitter is connected to a negative source of high voltage.

8. An air ioniser as claimed in claim 7, wherein the primary ion emitter is at -6000 volts with respect to earth.

9. An air ioniser substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.