GB2171882A

GB2171882A - Devices for killing insects

Info

Publication number: GB2171882A
Application number: GB08603101A
Authority: GB
Inventors: Gordon Carter; Peter Graham Harry Massey
Original assignee: Birch & Co Ltd H A
Current assignee: Birch & Co Ltd H A
Priority date: 1985-02-08
Filing date: 1986-02-07
Publication date: 1986-09-10
Also published as: GB8503326D0; GB8603101D0

Abstract

A device for killing insects incorporates a housing, a fluorescent tube mounted within the housing and form an attractant member for insects, a pair of spaced parallel generally flat killing grids extending across the recess so as to intercept and kill insects passing through the grids towards the attractant member, and means for applying an electric voltage across the grids. A light permeable screen preferably extends across the opening in the casing between the attractant member and the grids and means is desirably provided to facilitate removal of insect remains from the lower end of the housing. In its preferred form the electric voltage across the killing grids is from a pulsed high voltage AC supply described with reference to Fig. 2. <IMAGE>

Description

SPECIFICATION Apparatus for killing insects This invention relates to apparatus for use in killing flying insects and particularly to electrically operated apparatus incorporating an attractantfor the insects and means for killing insects attracted to the apparatus.

Previously proposed electrically controlled apparatus for killing insects has operated from a low voltage D.C. supply and functions by dehydrating and exploding the insects. The construction of such apparatus as hitherto proposed has produced a number of disadvantages. In particular insect remains have tended to accumulate around the base of the apparatus and in contact with the attractant tube. In addition such previously proposed devices have not been effective in killing large insects such as wasps.

It is an object of the present invention to obviate or mitigate these disadvantages.

According to one aspect of the invention there is provided a device for killing insects incorporating an electrically operated visual attractant member, a killing grid disposed adjacent said attractant member, and means for applying a pulsed high voltage A.C. electrical supply across said grid.

Preferably the attractant member comprises a fluorescent tube. Preferably also said generating means is adapted to produce an output of 2,500 volts and preferably of the order of 10,000 volts. The term "high voltage" is used herein to refer to a voltage in the range 2,000 to 15,000 volts.

According to a further aspect of the invention there is provided a device for killing insects comprising a housing incorporating an electrically operated visual attractant member mounted in a recess therein, a pair of spaced parallel killing grids extending across the mouth of said recess so as to enclose said attractant member within the recess, means for applying an electrical voltage across said killing grids, and a light-permeable screen extending across said opening in the casing between said attractant member and said grids.

Preferably each of said killing grids comprises a series of spaced parallel bars or wires electrically interconnected at their opposite ends, the grids being connected to respective terminals adapted to be connected across a pulsed high voltage A.C.

electrical supply. Preferably also an outer safety grid is provided.

The light-permeable screen preferably comprises a transparent membrane of synthetic plastics material.

Preferably the attractant member is disposed generally vertically, the killing grids being substantially flat and means being provided at the lower end of the housing for collection and removal of insect remains which may accumulate.

Thus according to a further aspect of the invention there is provided a device for killing insects comprising a housing, a fluorescent tube mounted generally vertically within a recess in the housing, means for energizing said tube to illuminate same and form an attractant member for insects, a pair of spaced parallel generally flat killing grids extending across and closing.said recess so as to intercept and kill insects passing therethrough towards the attractant member, means for applying an electrical voltage across said killing grids, and means facilitating removal of insect remains from the lower end ofthe housing.

Preferably said means four removing insect remains comprises 9 collecting tray forming the floor of said recess and slidably mounted relative to said housing for movement to a position outside said killing grids. Advantageously the tray is adapted to be detached from the housing to facilitate removal of insect remains and cleaning.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which: Fig. 1 is an exploded perspective view of one form of insect killing device according to the invention; and Fig. 2 is a diagram of electrical circuitry incorporated in the device of Fig. 1.

Referring to Fig. 1, the device comprises a housing or casing 5 having a base portion 5A and a detachable cover portion 5B. The base portion 5A incorporates electrical circuitry which will be described in more detail with reference to Fig. 2. The cover portion 5B incorporates a recess or opening 6 having inclined side'walls 6A so as to be narrower at the base or rear 6B than at the mouth. The floor and roof of the recess incorporate mounting brackets (one of which is shown at 6C) adapted to receive electrical connectors (not shown) for connection to the opposite ends of a 6W fluorescent tube 8 arranged to be mounted adjacent the back wall 6B of the housing in a vertical position.

A protective membrane 10 in the form of a transparent sheet of synthetic plastics material is mounted in the recess 6 of the housing 5 in front of the tube 8 and serves to prevent direct impingement of insects on the tube itself. The recess 6 is closed by a pair of wire grids 11 and 12 forming "killing" grids and adapted to be energized from the electrical supply so that the respective grids are at different electrical potentials. Each grid consists of spaced parallel metal wires electrically interconnected at their upper and lower ends. The grids are spaced apart by around 4.5 mm which is wider than the distance across which the supply voltage can discharge. Consequently the passage of an insect between the grids is necessary to complete a circuit and bring about electrical discharge between the grids, thereby killing the insect.An outer safety shield 14 is mounted on the front of the cover portion 5B of the casing Sto prevent human contact with the grids 11 and 12 during or after installation.

A drawer 15 is mounted in the lower portion of the casing 5 beneath the recess 6 and serves to collect insect remains which may thus be withdrawn and disposed of.

Fig. 2 is a diagram illustrating the circuitry incorporated in the device. The circuit consists of two principal portions, the first being a supply circuit for the fluorescent tube 8 incorporating a choke CH1 and capacitors C1 and C2 and being of generally conventional form. The second portion is a timing/switching circuit serving to supply an input voltage to a transformer TR1. This circuit consists of resistors R1 to R5, capacitors C3, and C4, a diac D1 and triac T1. The circuits are supplied from a normal 240 voltAC. supplythrough terminals Land N and the transformer is a step-up transformer serving to boost the supply voltage to 10,000 volts. This high voltage output is applied across the killing grids.

The timing/switching circuit supplies voltage pulses to the primary coil of the transformer TR1.

Resistor R1 is a load resistor which drops the supply voltage to line 20 to 200 V. Resistors R2, R3 and R4 form a voltage divider supplying a voltage of 36 V across capacitor C3. Due to variations in manufacturing tolerances in the transformer the value of resistor R3 may require to differ from one unit to another to ensure accurate control of the voltage applied across the primary coil of transformerTR1 and hence of the output from the transformer secondary coil which is applied to the killing grids.

Capacitor C4 discharges across the primary coil of transformer TR1 at timed intervals determined by the switching of triac T1. This in turn is triggered from diac D1 via capacitor C3 the charging of which builds in a time delay. The winding ratio of the transformer is 50:1 and hence the voltage is stepped up from 200 Vat the primary coil to 10,000 Vat the secondary coil which is applied across the killing grids. The capacitor C4 discharges rapidly and hence the voltage pulse has a duration of only one millisecond. The capacitor C4 discharges every 10 milliseconds thereby providing a pulsed supply to the transformer.

In this way the high voltage applied across the killing grids is pulsed to a set time and frequency so that although the voltage is high the risk of electrocution of anyone touching the killing grids is eliminated. The device therefore operates at a high working voltage, which enables large insects such as wasps to be killed, without any danger of electrocution of installers or users.

In operation of the device the casing 5 is mounted in a suitable position in an area to be kept free of flying insects and the unit is connected to a normal 240 volt A.C. electrical supply. The fluorescent tube 8 is illuminated forming an attractant for insects which therefore fly towards the tube. Because of the wide spacing of the bars on the safety shield 14 most insects will pass through the safety shield into contact with the killing grids. On passing between the grids 11 and 12 the insects cause an electrical discharge between the adjacent grids, thereby subjecting the insects to a high electrical voltage resulting in electrocution. Insects travelling rapidly are prevented from contacting the tube 8 itself impingement on the protective membrane or screen 10.

Insects killed by the device either fall to the ground or fall to the bottom of the casing 5 where they are collected in the tray 15. Periodically this can be removed and the insect remains disposed of thereby enabling the device to be kept clean.

The arrangement described produces a number of advantages compared with previously proposed electrically operated insect killing devices. In particular the use of a high voltage pulsed A.C.

supply enables large insects to be killed effectively without danger to persons who might inadvertently contactthe killing grids. Such contact should be prevented by the safety grid 14 but the pulsed nature of the supply ensures that although the voltage is high and a person touching the grids would receive an electric shock, the person would not be electrocuted. The construction of the unit is also advantageous in that the provision of generally flat killing grids and the removable lower tray avoid problems of accumulation of insect remains within the device as has occurred with previous cylindrical devices. The provision of the membrane 10 also ensures that insects do not penetrate the device to the extent that they come into contact with the fluorescent tube 8.

Various modifications may be made without departing from the invention. For example devices constructed in the manner described could be energized by different A.C. or D.C. supplies.

Conversely a pulsed high voltage A.C. supply of the kind described could be applied to devices constructed in a different manner. The voltage applied across the killing grids may be varied dependent on the sizes of insect the device is designed to killzbut in the case of a pulsed A.C.

supply the voltage is preferably not less than 2,500 V and desirably in excess of 5,000 V. The construction and arrangement of the killing grids, safety shield and protective membrane may also be altered and the killing grids may be energized using alternative electrical circuitry The spacing between the killing grids will vary dependent on the electrical supply and other factors but will generally be in the region of 2.00 to 6.00 mm and preferably in the region of 4.00 to 6.00 mm.

Claims

1. A device for killing insects incorporating an electrically operated visual attractant member, a killing grid disposed adjacent said attractant member, and means for applying a pulsed high voltage A.C. electrical supply across said grid.

2. A device according to claim 1 wherein said attractant member is mounted in an opening in a housing enclosed buy a pair of spaced parallel killing grids connected to said electrical supply.

3. A device for killing insects comprising a housing incorporating an electrically operated visual attractant member mounted in a recess therein, a pair of spaced parallel killing grids extending across the mouth of said recess so as to enclose said attractant member within the recess, means for applying an electrical voltage across said killing grids, and a light-permeable screen extending across said opening in the casing between said attractant member and said grids.

4. A device according to claim 3 wherein said means for applying an electrical voltage across said grids is adapted to generate a pulsed high voltage A.C. supply.

5. A device according to claim 3 or 4 wherein said attractant member is disposed generally vertically, the killing grids being substantially flat and means being provided at the lower end of the housing for collection and removal of insect remains which may accumulate.

6. A device for killing insects comprising a housing, a fluorescent tube mounted generally vertically within a recess in the housing, means for energizing said tube to illuminate same and form an attractant member for insects, a pair of spaced parallel generally flat killing grids extending across and closing said recess so as to intercept and kill insects passing therethrough towards the attractant member, means for applying an electrical voltage across said killing grids and means facilitating removal of insect remains from the lower end of the housing.

7. A device according to claim 5 or 6 wherein said means for removing insect remains comprises a collecting tray forming the floor of said recess and slidably mounted relative to said housing for movement to a position outside said killing grids.

8. A device according to claim 7 wherein said tray is adapted to be detached from the housing to facilitate removal of insect remains and cleaning.

9. A device according to any of claims 3 to 8 wherein each of said killing grids comprises a series of spaced parallel bars or wires electrically interconnected at their opposite ends, the grids being connected to respective terminals adapted to be connected across said electrical supply.

10. A device according to any of claims 3 to 9 wherein said killing grids are spaced apart by a distance of between 2.00 mm and 6.00 mm.

11. A device according to any of claims 3 to 10 including an outer safety grid.

12. A device according to any of claims 2 to 11 including a light permeable screen disposed between said attractant member and said killing grids.

13. A device according to claim 12 wherein said light permeable screen comprises a transparent synthetic plastics material.

14. A device according to any preceding claim wherein said attractant member comprises a fluorescent tube.

15. A device according to any preceding claim wherein said generating means is adapted to produce a voltage of the order of 10,000 volts.

16. A device for killing insects substantially as hereinbefore described with reference to Fig. 1 of the accompanying drawings.

17. A device for killing insects substantially as hereinbefore described with reference to Fig. 2 of the accompanying drawings.

18. Any novel subject matter or combination including novel subject matter herein disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.