WO1999044418A1

WO1999044418A1 - Electrical repelling of insects

Info

Publication number: WO1999044418A1
Application number: PCT/GB1999/000646
Authority: WO
Inventors: Philip Edwin Howse; John Farrell Hughes
Original assignee: University Of Southampton
Priority date: 1998-03-05
Filing date: 1999-03-04
Publication date: 1999-09-10
Also published as: GB9804564D0; AU3264699A

Abstract

Method of and apparatus for repelling insects from a predefined space by creating an electric field between the insects and the boundary of the predefined space. A mesh screen (2) provides the boundary of the space and at least one electrode (3) is attached to the screen, with means (4) for applying an electrical potential to the screen (2). Further apparatus comprises a tubular housing (11) of an electrically-insulated material with an open end, an electrode (12) with a pointed tip (14) mounted within the housing (11), a voltage source (13) connected to the electrode (12), and a ring (15) of an electrically-conductive material surrounding the open end of the housing (11).

Description

-1-

FT.FCTRICAL REPELLING OF INS fTS

The present invention relates to methods and apparatus for the electrical repelling of insects. Chemical insect repellents are known in the art and are widely used. For example, N, N-diethyl-m-toluamide (DEE T) is widely used as an insect repellent in formulations for use on clothing and the skin to repel insects which bite, such as mosquitoes. Citronella oil and eucalyptus oil are also used for the same purpose. However, the application of such chemicals has disadvantages in that they need to be frequently reappϋed and they can produce allergic responses in some people.

Pesticides, such as synthetic pyrethroids also have a repellent action and can be used to treat clothing, mosquito nets etc,. However, prolonged or frequent exposure to synthetic insecticides may be hazardous to health.

Alternatively, insects can be excluded from contact with human beings by providing physical barriers, such as netting or fly screens, over windows and doors, or mosquito netting around beds. The disadvantage of such physical barriers is that the entry of air is severely restricted when the barriers are in place because of the small mesh size required to exclude the insects. This leads to discomfort in hot climates.

Ultrasonic devices have also been sold for repelling mosquitoes, but their efficacy has not been scientifically proven. We have now developed a method and apparatus for repelling insects.

Accordingly, in a first aspect the present invention provides a method of repelling insects from a predefined space, which method comprises creating an electric field between the insects and the boundary of the said predefined space.

In a first embodiment of the method of the present invention, the boundary of the predefined space is connected to -2- an electrical potential. Generally the electrical potential will be in the range of from +5 to +20kv, more preferably in the range of from +10 to +15kv. The electrical potential may be applied to at least one mesh screen covering a door and/or window of a room through which air passes from the exterior of the room. The mesh size of the screen may be larger than that conventionally used in mesh screens used as physical barriers to the entrance of insects into a room. Accordingly, therefore, mesh screen having mesh openings in the range of from 10 to 20mm may be used.

In a second embodiment of the method of the invention, an electrical field is generated by placing a charge on the insects which are to be repelled form the predefined space. This may be achieved, for example, by directing a stream of ionized air molecules at the insects. The ionized molecules may be generated by means of an electrode with a pointed tip maintained at a potential of approximately 5 to 20kv.

It is important that the ionized air molecules are generated as a concentrated stream of ionized particles. (Preferably, the concentrated stream of ionized air molecules will have a diameter of 10 - 50cm at 5cm from the source). Preferably, the stream of ionized air molecules will pass through a ring or opening which is oppositley charged to that of the charge which the insects carry. The insects are thus attracted to the ring or opening, but are deflected away from the ionized air stream as they approach the air stream. The operation of this device is in contrast to commercial air ionizing molecules which do not deliver a concentrated stream of ionized air molecules, but rather ionize the air molecules in the entire surrounding space. Accordingly, the prior art devices do not produce a sufficient concentration of charge in any one locality to place a charge on the insects which is sufficient to .affect their orientation. -3-

Electrical fields which are generated in accordance with the methods as detailed above can be used to repel small flying insects and inhibit them from landing. Accordingly, insects of low mass, such as mosquitoes approaching a surface carrying an electrical potential are repelled from the surface and inhibited from landing thereon. Furthermore, an electrical field may also be used to repel crawling insects, such as fleas, ants and cockroaches and other Arthropods, such as ticks and mites. One possible explanation of the manner in which the electrical field repels insects is that the electric field at a close range causes sudden displacement of the fine antennae of the insect and interferes with the orientation mechanism of the insect.

The present invention also includes within its scope an apparatus for repelling insects from a predefined space, which apparatus comprises:

(i) a mesh screen to provide a boundary of the said predefined space; (ii) at least one electrode attached to the screen; and (iii) means to apply an electrical potential to the screen. The present invention further includes within its scope an apparatus for repelling insects from a predefined space which apparatus comprises: a) a tubule housing of an electrically insulated material with an open end; b) an electrode with a pointed tip mounted within the housing; c) a voltage source connected to the electrode; and d) a ring of an electrically conductive material surrounding the said open end of the tubular housing. -4-

The present invention will be further described with reference to the accompanying drawings, in which:

Figure 1 is a diagrammatic perspective view of an apparatus according to a first embodiment of the invention; Figure 2 is a diagrammatic perspective view of an apparatus according to a second embodiment of the invention; and

Figure 3 is a diagrammatic view of an apparatus according to a third embodiment of the invention which can be used for experiments.

Referring to Figure 1, the apparatus as illustrated comprises a fly screen 1 for a window or door. The fly screen 1 is constructed from a mesh 2 of glass fibre threads coated with a plastic material such as polyvinylchloride (PVC). The mesh 2 has a low electrical conductivity and the mesh openings are in the range of from 10 to 20mm. This permits a good flow of air through the screen from the external surroundings.

A high voltage electrode 3 is attached to the centre of the screen 1 and is powered from a mains AC supply 4 through a rectifier 5, a resettable trip switch 6 and a cable connection 7. The rectifier 5 has an output voltage in the range of from +10 to +20kv and the electrode 3 is maintained at the source potential. Since the mesh 2 has a low electrical conductivity, the voltage applied to electrode 3 reduces in intensity across the mesh 2 with increasing distance from the electrode. The screen 1 and mesh 2 are not connected to earth.

The screen is well insulated for safety reasons. To guard against a possible breakdown in insulation with rain or other particles or debris hitting the screen, or with high humidity in some climates, a resettable trip switch 6 is included between the rectifier 5 and the electrode 3.

The voltage applied to the electrode 3, which reduces in intensity across the mesh 2 with increasing distance from -5- electrode 3, generates an electric field in the region of the screen. Uncharged insects approaching the screen 1 are repelled by the high voltage electric field. Any contact of the insects with the mesh 2 of the screen will not normally result in an electrical breakdown, since the mesh has a high electrical resistivity.

According to this embodiment of the invention, an electrical field is generated on the fixed screen 1 and insects are repelled from the screen. Thus, by placing the screen in a selected space from which insects are to be repelled, any insect approaching the screen will be repelled from the selected space. Referring to Figure 2, the apparatus comprises a tube 11 of an electrically insulated material which provides a housing for an electrode 12 with a pointed end 14 connected to a voltage source 13. As illustrated, the pointed end 14 of the electrode is positioned within the tube 11 and points towards an open end of the tube 11 which has a ring 15 of an electrically conductive material surrounding the opening. The ring 15 is connected to earth. When a voltage from the voltage source 13 is applied to the electrode 12, a stream of ionized air molecules 16 will leave the pointed end 14 of the electrode 12, pass through the ring 15 and be emitted from the tube 11.

The cuticle (outer surface) of an insect has a high electrical resistivity and is permanently electrically polarised. This surface charge can be artificially enhanced by exposing the insect to ionized air molecules of appropriate polarity.

The stream of ionized air molecules 16 emitted from the tube 11 can be directed towards a small insect 17, such as a mosquito, and this will cause the charge on the insect to be enhanced. It is found that, when this enhancement occurs, the insect will deviate in its flight path towards an earthed surface or a surface carrying a charge of opposite polarity. In addition, the insect becomes disorientated. A possible explanation for this is that the antennae of the insect, or the fine wind sensitive hairs on the insect which monitor its flight direction or velocity, .are deflected by the electrical field and create an imbalance in the nervous flight control mechanism of the insect.

Accordingly, the natural charge on the surface of an insect is enhanced by exposing the insect to a stream of ionized air molecules 16. Thus by directing the stream of ionized air molecules into a selected space from which the insects are to be repelled, any insects entering the selected space will become charged and will thus be repelled from the space.

For example, the apparatus of Figure 2 can be located near a bed and the stream of ionised air molecules 16 can be directed over a person sleeping in the bed. This will result in any insects approaching the space above the sleeping person being repelled from that space. Alternatively, the stream of ionized air molecules 16 can be directed at an open window or other points of entry into a room. Insects trying to enter the room will become charged and will be repelled from the source of the ions.

The stream of ionized air molecules 16 generated by the apparatus of Figure 2 can be aided by a fan, if desired.

Figure 3 illustrates an apparatus for illustrating the efficacy of the present invention in which an electrical field is generated. The apparatus comprises a cubical perspex box 21 having six sides 22a, 22b, 22c, 22d, 22e and 22f and edges approximately 60cm in length. The inner surfaces of the sides 22a, 22b, 22c, 22d and 22e are lined with white paper so as to obscure these sides. The remaining side 22f is unlined so that the inside of the box can be viewed through this side. A dish 24, 9cm in diameter, is suspended within the box 11 from the middle of the side 22a. The dish 24 can be electrically charged. A selected number of mosquitoes can be inserted into the box •7- and their activities viewed through side 22f from outside the box.

The present invention is further described in the following Examples.

EXAMPLE 1

The apparatus as described above with reference to Figure 3 was used. In a first experiment the dish 24 was maintained electrically uncharged.

In a second experiment the surface of the dish 24 was charged by friction to a surface potential of approximately -30kv.

For each experiment a selected number (20) of mosquitoes (Aedes aegypti) were introduced into the box 21 and the number of landings on the dish 24 attempted by the mosquitoes was compared for each of the two experiments. It was found that the percentage of successful landings was greatly reduced when the dish 24 was charged.

EXAMPLE 2

In a further experiment the dish 24 was replaced by two 15 cm square mesh screens as illustrated in Figure 1. The electrode 3 on the mesh of one screen was connected to either +20kv or -201cv, whilst the electrode on the other screen was unconnected. 30 mosquitoes were introduced into the box 21 and the percentage of successful landings on the mesh of the charged screen as compared with the successful landings on the mesh of the uncharged screen was noted. The landings on the charged mesh were inhibited completely with a -20kv potential and almost completely with a +20kv potential.

Claims

CLAIMS;

1. A method of repelling insects from a predefined space, which method comprises creating an electric field between the insects and the boundary of the said predefined space.

2. A method as claimed in claim 1 wherein the boundary of the said predefined space is connected to an electrical potential.

3. A method as claimed in claim 2 wherein the electrical potential is in the range of from +5 to +20kv.

4. A method as claimed in cl-aim 1 or cl m 2 wherein the electrical potential is applied to at least one mesh screen covering a door and/or a window of a room.

5. A method as claimed in claim 4 wherein the mesh screen has mesh openings in the range of from 10 to 20mm.

6. A method as claimed in claim 1 wherein an electric field is generated by placing a charge on the insects which are to be repelled from the predefined space by directing a stream of ionized air molecules at the insects.

7. A method as claimed in claim 6 wherein the ionized air molecules are generated by means of an electrode with a pointed end maintained at a potential of 5 - 20kv.

8. An apparatus for repelling insects from a predefined space, which apparatus comprises: i) a mesh screen to provide a boundary of the said predefined space; ii) at least one electrode attached to the screen; ╧ïi) means to apply an electrical potential to the screen.

9. An apparatus as claimed in claim 8 wherein the mesh screen has mesh openings in the range of from 10 to 20mm.

10. An apparatus as claimed in claim 8 or claim 9 wherein the mesh comprises glass fibre threads coated with a plastic material.

11. An apparatus as claimed in any one of the claims 8 to 10 wherein the electrode attached to the screen is powered from a mains supply via a rectifier. -9-

12. An apparatus for repelling insects from a predefined space which apparatus comprises: a) a tubular housing of an electrically insulated material with an open end; b) an electrode with a pointed tip mounted within the housing; c) a voltage source conne╬▒ed to the electrode; and d) a ring of an electrically conductive material surrounding the said open end of the tubular housing.

13. An apparatus as claimed in claim 12 wherein the ring of electrically conductive material is connerted to earth.