WO1979000574A1

WO1979000574A1 - A method and apparatus for killing insects

Info

Publication number: WO1979000574A1
Application number: PCT/SE1979/000022
Authority: WO
Inventors: J Cederstroem; W Herthnek
Original assignee: Redec Ab; J Cederstroem; W Herthnek
Priority date: 1978-02-01
Filing date: 1979-01-31
Publication date: 1979-08-23
Also published as: FI790339A; NO790316L; DK406979A; NO142281C; NO142281B; SE409805B

Abstract

A method and apparatus for killing insects, particularly insects which fly, comprising electrodes (17, 18), between which an electric voltage field is created. The invention also comprises an attractant (19) by which insects are enticed to pass into said field. The voltage field created is of such magnitude that when insects fly through said field a spark is formed between said electrodes may have the form of a multiplicity of wires or rods arranged in mutual, uniform spaced relationship, adjacent electrodes being connectable to opposite poles of a high voltage source (11). The invention further comprises an electronic control means including a detector (2) which is arranged to detect power or energy fluctuations in the voltage field as a result of objects, such as insects, entering said field. A switch (6) is controlled by said control means to automatically interrupt the supply of power to the electrodes when a certain maximum power is reached or exceeded. This interruption in power supply is maintained over a predetermined time with the aid of electronic means (3, 4, 5). These latter means may be operable in respect of short circuits and spark-formations between the electrodes which are of a longer period of time than a given period, and are able to determine the time lapse before the power is re-connected. It is possible in this way to limit the amount of thermal energy which can be accumulated in an insect, a piece of straw or some other object which may have fastened to the electrodes, to a value of such low magnitude that the object in question is unable to glow to burning heat or to ignite. In this way the risk of such an invention being the cause of a fire in the vicinity where it is placed is reduced to a minimum.

Description

A METHOD AND APPARATUS FOR KILLING INSECTS

The present invention relates to a method and an apparatus for killing insects, particularly, although not exclusively, to insects which fly, in which method and apparatus insects are enticed through an electric field towards an attraction source, with the result that the insects are killed.

Human beings and animals are often troubled by insects,. Prior re- search has been directed towards exterminating troublesome insects, such as flies, mosquitous, wasps etc., with the use of chemical preparations. This method of extermination, however, is encumbered with a multiplicity of disadvantages, among which can be mentioned that in time the insects become immune to the chemical agents used; that said chemical agents are both expensive to handle and to purchase; that the environment deteriorates as a result of the use of such chemicals; and that people and animals can be inad¬ vertently harmed by the use of such chemical agents.

Prior research has also resulted in an electrical apparatus, a so-called insect exterminator, through which the aforementioned disadvantages prevailing with the use of chemical exterminants are eliminated. One known exterminator comprises at least two electrodes and means for maintaining between said electrodes an electric field of such magnitude that when the air-gap between two adjacent electrodes is decreased as a result of an insect passing therethrough, an electric spark is generated between the electrodes and through the insect, which results in the death thereof. In those instances when the insect exterminator is not so positioned that insects must pass through the air-gaps between the electrodes thereof in order to reach a space which is to be maintained free from insects, the exterminator is provided wi an insect attractant, for example a scent-source or light-sou which attracts insects and which is of a nature harmless to h beings or animals. When this attraction source comprises one more light sources, these light sources are suitably such whi will emit light lying substantially within the wavelength ran of 2000-6000 and preferably 3200-4000 Angstrom, since light o this nature, i.e. ultraviolet light, has been found particula attractive to insects.

The efficiency of the exterminator is increased by arranging multiplicity of electrodes, which may be of wireform or rod f in parallel and uniformly spaced relationship, these electrod being connected to a high - voltage source in a manner such t mutually adjacent electrodes are each connected to a respecti terminal of said source. The known exterminator comprises two pairs of parallel electrically conductive bars which extend su stantially perpendicularly to said electrodes, the electrode- carrying bars of one pair being connected with each alternate electrode and the bars in theoother pair being connected with remaining electrodes, the terminals of the high-voltage sourc being connected to at least one bar in one or the other of sa pairs. The vertical plane in which the electrodes lie is so placed in relation to the insect-attractive media, that the i sects, when approaching said media and flying towards or agai and around the same, pass through the said electrode plane, a therewith the air-gap between said electrodes. The voltage be the electrodes suitably lies within the range of 3000-7000 vo

An important criterion of such an apparatus is that it shall unhar ful to people and to animals. Consequently, it must not possible to touch the electrodes unintentionally,, To this end, the electrodes, and preferably any insect attractant, are accom¬ modated in a box-like casing whose walls are comprised at least partially of a relatively wide-meshed protective net, which whilst protecting human beings and animals from the electric field will allow passage of insects therethrough. Conveniently the net-like walls of the casing are parallel with the plane in which the electrodes lie. The casing is provided with an openable box for collecting dead insects which have fallen from the electrodes, said box having a bottom which is pivotable about one end portion thereof to facilitate removal of the insects kil¬ led by the exterminator.

Although an insect exterminator of the type described is able to carry out its function satisfactorily, it may constitute a fire risk under unfavourable circumstances. For example, if an insect or some other ignitable object should become fastened in the electrode grid, the body of said insect is able to accumulate so much electrical energy, converted into thermal energy, as to cause said insect to glow with heat or to flare. When this insect subsequently falls down onto the floor of the box or said apparatus to mix with insects previously killed in the apparatus, these insects may also be ignited and when subsequently thrown from the box, cause a fire in the surroundings.

The object of the present invention is to provide a simple and economically viable method of exterminating insects, particularly insects which fly, without any fire risk whatsoever. The invention also relates to an insect exterminator suitable for carrying out the method.

To this end the method according to the invention mentioned in the introduction is mainly characterized by the steps of continuous ly detecting fluctuations in the power or energy of the voltage field as a result of objects, such as insects etc. entering sai field, and automatically interrupting the power supply when a g maximum value thereof is reached or exceeded, and maintaining said interruption over a given length of time.

An exterminator for carrying out the method has the characteris tic features disclosed in the characterizing clauses of the sub ordinate claims relating to such apparatus.

In other words the invention implies that if the current supply to the electrode grid is so controlled that an insect or an ob¬ ject can never cause between two wires or rods of the grid a spark of such duration that said insect or said object begins t glow. Thus, the current consumed by the electrode grid is moni tored, and since this consumption increases greatly when a shor circuit occurs, it is possible to detect any electrically con¬ ductive object which enters the energy field of the grid. When, upon the occurrence of a short circuit, the monitored current increases to an extent such that it reaches a given critical va a detecting unit controlled by said current transmits a signal to a switching apparatus which switches off the supply of curre to the grid. The grid is' kept deenergized for a given period of time, whereafter the grid is automatically again switched on. Should the amount of current consumed still reach the critical value, the grid is again disconnected and the process is contin with the grid being alternately energized and deenergized until the insect, or object, has fallen down or has lost its ability conduct electricity. The time intervals over which the grid is energized and energized are so selected that no object or insec is able to accu mulate sufficient thermal energy to make it glow or ignite.

So that the invention will be more readily understood and op- tional features thereof made more apparent a preferred embodiment thereof will now be described with reference to the accompanying schematic drawings, in which

Figure 1 is a front view of an insect exterminator according to the invention. Figure 2 is a perspective view of a part of the exterminator shown in Figure 1. Figure 3 is a block schematic of the electrical components of the exterminator. Figure 4 shows the electrical circuitry in more detail.

In Figure 1 the reference 10 identifies generally a casing co p- rising side walls 12, 13 and lower and upper walls 14 and 15 respectively. Mounted on the upper parts of the side walls are suspension means (rails) 16, by means of which the insect extermi¬ nator can be mounted on, for example, the roof of a building which is to be kept free of flying insects.

Arranged in the casing 10 are electrodes 17, 18, of which the electrodes 17 are connected to one terminal of an electric high- voltage source, and the electrodes 18 to the other terminal of said source. Maintained between the electrodes 17, 18 is an elec- trie field of such magnitude that if the air-gap defined between a pair of said electrodes decreases as a result of an insect passing therebetween, there occurs between said electrodes a spark which passes over or through the insect, resulting in the death thereof. The electrodes 17, 18 have the form of metal wires or rods, each of which extends between a respective pair of metal rails 23 and 24. The rails 23 are suspended in insulated fashion by means of an insulating bar 25 and two insulated holders 30, whilst the rails 24 are directly connected to the casing of the apparatus, thus earthing the corresponding electrode 18.

Further, the insect exterminator is provided with means for attracting insects into the air-gap between mutually adjacent electrodes 17, 18. Such means may comprise a suitably located scent-source, but in the illustrated embodiment comprises two light tubes 19. Conveniently, the light tubes emit light in the wave length 3200-4000 Angstrom; light of this wave length has proven to be particularly attractive to insects which fly.

In the upper part of the casing there is a space 20 in which mea for generating a high voltage, e.g. a transformer 11, is accomo- dated together with ignition means and the like for the light tubes. The space 20 is defined by the upper wall 15 and the up¬ per parts of the walls 12, 13 and a wall 21 which extends parall with the wall 15. The space 20 also accommodates the electric control means according to the invention. The electrical equip- ment is connectable to the mains network by means of a cable

(not shown) extending from the exterminator. The upper wall 15 forms a lid or cover which is removable from the remainder of the casing 10, thereby to permit access to the electrical equip¬ ment in the space 20. The electrodes 17, 18 are mutually paralle and spaced at a uniform distance apart. In the illustrated embod ment, the spacing between the adjacent electrodes is approximate 1 cm whilst the voltage applied is approximately 4000 V. The electrodes have a circular cross-section and a diameter of appro mately 2 mm. The electrodes are arranged in a vertical plane.

Each of the light tubes 19 is located on a respective side of th said vertical electrode-plane. The electrically conductive rails 23, 24 extend parallel. Vith said electrode plane, substantially at right angles to said electrodes, each of said rails being connected to a respective terminal of the high-voltage source. As will be seen, the rail 23 carries each alternate electrode, namely the electrodes 17, whilst the rail 24 carries the remain¬ ing electrodes 18. The rails 23, 24 are located adjacent the side wall 13 of the casing 10.

As will be seen from Figure 2, each of the rails 23, 24 is pro¬ vided along one edge thereof with recesses 9, the spacing of said recesses along said edge corresponding to the spacing of the electrodes 17, 18. More specifically, the recesses 9 of the earthed rail 24 lie opposite respective wires 17 and the recesses 9 of the insulated rail 23 lie opposite respective wires 18, said rail 23 being suspended by insulating means 30 or holder and the insulating rod 25. The purpose of the recesses is to prevent spontaneous sparking between the electrodes.

The openings in the casing 10 are covered by removable protective grids 26, on the front side and rear side as shown in Figure 1, these protective grids being shown predominantly in a cut-away view. The purpose of the protective grids 26 is to prevent people or animals from touching the electrodes, whilst allowing insects to pass through the electric field.

The lower part of the exterminator forms a collecting chamber 22 for insects killed by the exterminator. In the chamber there is provided a scraper 27, comprising a rod 28 and a plate 29, by means of which dead insects and other material deposited in said chamber 22 can be removed through a side opening -located, although not shown, to the right of the figure, which opening, when the scraper 27 is fully located in the chamber, is closed by a cove 31 which can function as a handle for the scraper. The rod 28 an the plate 29 of the scraper are both made of an electrically in- sulating material.

The electrical control means 1 is illustrated in block schematic form in Figure 3. The mains voltage is taken out over terminals 32-32. A light tube 19 is supplied with mains voltage over a bre contact 33 which is normally closed but which can be actuated by an excess-current protective device in the form of a relay 8 whi is in turn activated when current of a predetermined strength exceeds a. given value. Connected in series with the input termin 32-32 is a series circuit comprising said excess-current protect device 8, the primary winding of the high-voltage transformer 11 a triac 6 (electronically controlled switch) and a current detec tor 2. The electrodes 17, 18 of the exterminator are connected t the secondary coil of the transformer 11, of which electrodes th electrodes 18 are earthed.

The excess-current protective device 8 is an automatic fuse whic breaks the current to the transformer 11 when a permanent fault occurs in the control means 1, causing the detecting or switchin function of the means to cease. Subsequent to the lapse of a pre determined length of time, the protective device 8 will release. The function of the exterminator will then cease, which is indi¬ cated by the light tube 19 being extinguished as a result of bei disconnected at the contact 33 through said protective device 8.

The current detector 2 detects the current consumption in the transformer 11 and controls a spark time-control means 3 which i turn controls α pause-time circuit 4. This latter circuit regulates a static electronic switch 5 which in turn sends energizing sig¬ nals to the triac 6.

As indicated, when there is a short circuit between electrodes 17 and 18, the primary winding of the transformer 11 is deenergized through the triac 6. Subsequent to the lapse of a given period of time, determined by the time circuit 4, the triac 6 re-energizes the primary winding. If the short circuit still prevails, the pri- ary winding of the transformer is again deenergized, thereafter to be re-energized when a given length of time has lapsed. The time interval over which the primary winding is supplied with current may be about 400 s whilst the time over which said pri¬ mary winding is deenergized may be about 3 seconds, during which time the object causing the short circuit is able to give off the energy obtained during the time which the coil was energized, i.e. has had time to cool. As will be readily understood, the grid comprising the electrodes 17 and 18 is conductive during 12 of the time of the switch-off-cycle when the short-circuiting state or state of comprehensive current increase prevails. If, for some reason or other, the electrical control means 1 does not completely fulfil its purpose, the protective device 8 will come into operation after a certain length of time in the place of said device, to permanently disconnect the transformer 11 from the mains, as before mentioned.

Figure 4 illustrates in more detail a coupling schematic of the blocks 2-5 shown in Figure 3 and also illustrates a block 7 through which voltage is supplied to the electronic parts of the control means.

A mains fuse is referenced S1 and a surge-voltage-arrester, varis- tor, R28 is in parallel across the terminals 32-32. Parallel wit the electronically controlled switch (the triac) 6 is an RC- link, comprising a resistance R27 and a capacitor C9 preventing self-triggering of the triac 6. The resistance R23 in series with the triac is a resistance in which the current increases with a short circuit between the electrodes 17, 18 and which is incorporated as an input in the current detector 2. The current detector includes a series resistance R9 which is arranged to dampen high voltage peaks, and a rectifier D1 connected in se- ries with R9 to the base of a transistor Tl. A capacitor C4 connected from the base to earth is a smoothing capacitor. The emitter in Tl is directly earthed and the collector obtains voltage across a resistance RIO. The transistor T1 is arranged t open with an increase in current and thus controls the spark- time-control circuit 3.

The circuit 3 comprises a transistor T2 and a double-base diode T3. The base of the transistor T2 is connected to the collector of the transistor Tl through a resistance R11, the emitter in th transistor T2 obtains voltage over the resistance R12 and the co lector of the transistor T2 is connected to earth over a capacit C5. The transistor T2 is an amplifier and a phase reverser. The charging time of the capacitor C5 is determined by the resistanc R12 and its discharge is determined by the resistance R12 in a manner such that the odd sparks between the electrodes 17 and 18 are not accumulated in C5« The emitter of the diode T3 is con¬ nected directly to the collector of the transistor T2. One base of T3 obtains a voltage over the resistance R14 and the other base is earthed over the resistance R15 and is connected through a resistance R16 to the base of a transistor T4 in the pause circuit 4 which includes a further transistor T5. The emitter of the transistor T4 is connected directly to earth and its col¬ lector is connected firstly to the base of the transistor T5 over two series-connected resistances R17, R19 and secondly to the voltage supply source over the resistance R17 in series with resistance R18. The node between resistances R17 and R19 is con¬ nected to earth over a capacitor Co. The collector of the transis¬ tor T5 is connected directly to earth and its emitter is connec¬ ted to the voltage supply over a resistance R20.

The circuit 7 is a voltage supply circuit which is supplied from the mains over a resistance R25 and a rectifier D2 and which in¬ cludes a parallel circuit connected in series to the last men¬ tioned, said parallel circuit comprising a Zener diode D4 and two smoothing and spark-eliminating capacitors C7, C8. The side of the parallel circuit facing the rectifier D2 is con¬ nected to the common connecting point of the resistances RIO, R12, R14, R18 and R20 for supplying the circuits 2,3 and 4, and the opposite side is earthed,

The output (the emitter of transistor T5) of the circuit 4 is connected, via a resistance R21, to the static switch 5 to supply a switching voltage thereto. The voltage is supplied to the cir¬ cuit 5 from the mains over a resistance R24 and a rectifier D3₀ Incorporated in the circuit is a voltage regulator and an IC- circuit (for example of the type designated TCA280A, or the like) resistances R1-R7 and R26, capacitors C1-C3 and the output sig¬ nals thereof are supplied over resistance R26 and a diode D5 to the triac 6 to trigger the same through zero-throughput con¬ trol.

The control means has the following mode of operation: When the exterminator is in operation, the triac 6 obtains triggering si nals from IC and a voltage lies over the primary winding of the transformer 11. Current from the transformer flows through the resistance R23. The drop in voltage across R23 caused by said current is insufficient to make the transistor Tl conductive.

When a spark occurs in the grid formed by the electrodes 17, 18 the current through R23 increases, and therewith also the drop in voltage. As a result hereof the transistor Tl becomes conduc tive and the voltage on its collector falls so that the transis tor T2 becomes conductive and the capacitor C5 begins to charge through the resistance R12. The time taken to charge C5 is de¬ pendent upon the voltage drop across R23, the charging current through R12 and the discharging current through R13. The resist R23, R12 and R13 are so dimensioned that the transformer is not deenergized when the spark time is of a given magnitude and the spark interval is of a given value, for example about 10 ms and about 0.5 seconds respectively. If the spark time is longer and the spark interval shorter, the punch-through voltage is obtain for T3 over C5 and the pause function will come into operation. Thus, when the throughput voltage for T3 is reached, e.g. about 15 volts, and C5 is then discharged through T3 a brief an heavy current passes through R15 and through R16 to T4, which is then opened, resulting in the discharge of C6. The voltage across C6 will then fall and T5 will become conductive. The tra sistor T5 is namely choked when C6 is fully charged across R18 but becomes conductive when C6 is discharged. The emitter of tr sistor T5 is in rest position at a high positive potential leve but when C6 is discharged this level is changed and therewith t voltage on the line from R21 to IC which as a result thereof ob a stop signal and sends as a result thereof no trigger pulses t the triαc 6. This state prevails until C6 is recharged over R18 and blocks T5, for a period of about 3 seconds. Thus, the capa¬ citor C6 determines the length of the pause of circuit 4. The capacitor C6 is quickly discharged and has a slower charging time determined by R18. The voltage on the line from R21 into IC then increases and the triggering of the triac 6 is reestab¬ lished, whereafter the sequence of events are repeated with perio¬ dic switching on and switching off of the voltage to the pri¬ mary coil of the transformer 11, if the short circuit or the like causing the voltage means 1 to become operative* remains between two electrodes 17, 18.

The invention is not restricted to the described and illustrated embodiment, but can be modified within the scope of the following claims.

Claims

CLAIMS :-

1. A method of killing insects, particularly insects which fly in which the insects are enticed to pass towards an attraction source through an electric voltage field, thereby to kill said insects, characterized by continuously sensing the fluctuations in energy or power of the voltage field as a result of objects, such as insects etc., entering said field; automatically inter¬ rupting the power supply to said field when a given maximum val thereof is reached or exceeded; and maintaining said interrup¬ tion over a given length of time.

2. A method according to claim 1, in which said attraction sou emits visible or white light, characterized in that the power s ly is permanently interrupted after a given length of time whic is considerably longer than said predetermined length of time, if said automatic interruption should not function as a result an apparatus fault; and that theattraction source is also de¬ energized as an indication of such a permanent fault.

3. A method according to claim 1 or claim 2, characterized by monitoring variations in the current to a high-voltage trans¬ former creating said voltage field.

4. A method according to claim 3, characterized by monitoring the duration of sparks between electrodes creating said voltage field and the interval between said sparks; and by interrupting said current when said duration and said interval exceeds or falls below a given associated value.

5. A method according to claim 4, characterized by re-coupling the current subsequent to said interruption and subsequent to the lapse of a given length of time and - if the duration of sa

( -_ __ v vvir ' spark or the spark interval still exceeds or falls below their given associated values - re-interrupting the current, etc., until said duration or said interval are maintained within said values.

6. An apparatus for killing insects, particularly insects which fly, for carrying out the method according to any one of the preceding claims, said apparatus including a source towards which insects are attracted and a device which generates an electric voltage field by which said insects are killed, said insects passing through said device during their passage towards said attraction source, characterized by an electronic control means (1) having a detector (2) arranged to detect power or ener¬ gy fluctuations of the voltage field resulting from objects, such as insects etc., entering thereinto; a switch (6) controlled by said control means (1) for automatically interrupting the power supply when a given maximum value of said power is reached or exceeded; and a means (3,4,5) for maintaining said interrup¬ tion over a given length of time.

7. An apparatus according to claim 6, characterized by an over- current protective means (8) which is arranged to permanently dis¬ connect said power supply when a given length of time has lapsed in the event of a fault of said electronic control means (1).

8. An apparatus according to claim 7, in which the attraction source comprises a light tube, characterized in that the over- current protective means (8) in the event of a permanent fault is arranged also to deenergize said light tube (19) through a relay - control switch (33) as a visual indication of said fault.

9. An apparatus according to anyone of claims 6-8, characterized in that the input of the detector (2) comprises a resistance (R23) through which the current to the primary winding of a hig voltage transformer (11) passes, said transformer creating the said electric voltage field.

10. An apparatus according to claim 9, characterized in that th detector (2) has connected therebehind a spark-time-control cir¬ cuit (3) which is arranged to be functionable when the detector (2) detects a short circuit or spark formation of a duration which exceeds a given length of time.

11. An apparatus according to claim 10, characterized in that the spark-time-control circuit (3) has connected therebehind a pause-time circuit (4) which is arranged to determine a given pause before the renewed closing of said switch (6) takes place.

12. An apparatus according to anyone of claims 9-11, characteri in that the pause-circuit (4) is arranged to control a static, electronic switch (5) which in turn is arranged to transmit trigger pulses to the electronically controlled switch (6).