WO1988003754A1

WO1988003754A1 - A barrier device

Info

Publication number: WO1988003754A1
Application number: PCT/AU1987/000391
Authority: WO
Inventors: Iain Godfrey Saul
Original assignee: Consolidated Technology Pty. Ltd.
Priority date: 1986-11-21
Filing date: 1987-11-20
Publication date: 1988-06-02

Abstract

A barrier device (10) comprising an elongated flexible strip (12) on one face (12a) of which are disposed two lengthwise extending conductive tracks (14, 16) arranged in a spaced electrically insulative disposition but being capable of being bridged by a snail, slug or the like moving transversely across the face (12a), the tracks (14, 16) being capable of being energized by an electrical power source (18) such that when a snail, slug or the like bridges the tracks a current passes through the snails, slug or the like thereby deterring the snail, slug or the like from passing over the strip (12).

Description

A BARRIER DEVICE

This invention relates to a barrier device suitable, inter alia, for positioning on a ground surface so as when energized by an electric source, to provide a barrier for deterring slugs, snails and the like from passing the barrier.

In one aspect, the invention provides a barrier device in the form of an elongated flexible strip on one face of which are disposed two lengthwise extending conductive tracks arranged in spaced electrically insulated disposition but being capable of being bridged by a snail, slug or the like moving transversely across the said face. When energized by an electric cell or other electric source, the bridging of the tracks which occurs when the snail or slug crawls across the aforementioned face causes an electric current to pass between the tracks, through the snail or slug. It has been found that this passage tends to deter a snail .or slug from passing over the barrier. Thus, the barrier device can, for example, be positioned on a ground surface to protect portions of a garden from intrusion of snails or slugs. Particularly in accordance with the invention, the aforementioned strip is formed of material of such flexibility that the strip may be wound up so as to provide a convenient means of storage thereof, such as prior to sale. In one form, the so wound up strip is provided in casing together with a battery pre-connected to the strip tracks whereby to permit the strip to be unwound out of the casing for use. Particularly, too, by virtue of its flexibility, the strip may readily be folded to permit it to be disposed in a two dimensional path such as a closed loop on a ground surface so as to partly partition off a portion of a garden or the like against intrusion of snails or slugs. The strip is preferably formed of material of substantial thinness such as in the range .03 mm to .10 mm, and formed free of surface^' projections or edge projections"so as to enable it to be tightly wound in coil-like configuration for easy handling prior to use, and to permit folding to form corners in the barrier. The strip is preferably also arranged with the tracks positioned closer to one edge than the other, so as to leave a substantial portion . of the width of the strip between the other edge thereof clear of tracks. This portion may be buried in the ground to facilitate location of the strip.

The invention is further described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a perspective view of a barrier device constructed in accordance with the invention; Figure 2 is an enlarged side elevational view illustrating the manner of use of the device of Figure 1 to form a barrier;

Figure 3 is a plan view of the barrier of Figure 2;

Figure 4a and 4b comprise respective views showing the manner of formation of corners in a barrier constructed by use of the device of Figure 1;

Figure 5 is a plan view of the barrier corner of Figure 4;

Figure 6 is a transverse section of a device of Figure 1;

Figure 7 is a circuit diagram of an alternating current generating circuit useful in practicing the invention;

Figure 7a is a circuit diagram of a modified alternating current generating circuit;

Figure 7b is a circuit diagram of a further modified alternating current generating circuit;

Figure 8 is a perspective view of a further barrier formed by use of the invention;

Figure 9a and 9b are perspective views showing the manner of affix ent of retaining stakes to the ^" barrier of the invention;

Figures 10a and 10b are respectively a perspective view of a device useful in the invention and a diagram showing the positioning of LED' s for fitting into that device and

Figure 11 is a perspective view of a modified form of barrier device constructed in accordance with the invention. The barrier device 10 shown comprises an elongate strip 12 of plastics or other electrically insulative material. This has, on one major face 12a thereof, two parallel conductive strip-like tracks 14, 16 which extend lengthwise along that face in spaced relationship. Typically, the strip may be of the order of two centimetres in width with the tracks 14 and 16 positioned about 3 mm apart. In any event,, the spacing between the tracks 14, 16 should be sufficient that, when a mollusk such as a snail or slug traverses the strip by moving over the face 12a transversely to the direction^'to the extent of strip 12, it will necessarily bridge the tracks 14 and 16. The strip 12 is formed of material of thickness about 0.05 mm so as to enable the strip to be tightly wound in coiled configuration as described later. The tracks 14, 16 may be discretely formed and adhered to the strip 12, or may be otherwise formed such as by electro or electroless deposition or the printing down of conductive compositions. In any event the tracks should be formed of material of sufficient flexibility to prevent cracking or breakage when the strip 12 is . coiled. Suitable materials for forming the tracks include aluminium, copper, nickel and silver.

A battery 18, such as a suitable _.dry cell, contained in housing 21, is connected across the tracks 14, 16 with one terminal 18a of the battery is connected to track 14 and another terminal 18b of the battery 18 connected to the track 16. It has been found that small commercial 9 Volt batteries are suitable for this purpose. The battery housing 21 is physically attached to the strip 12.

Figures 8 illustrate the use of the device 10. Here, the strip 12 is laid flat on the ground, face 12a uppermost, to extend around the area of a garden adjacent, for example, vegetables 22 and located on the ground surface by attaching suitable stakes 26 to the strip 12 and pushing into the ground such as at spaced locations along the length thereof. In order to minimise the possibility of bridging the tracks 14, 16 the stakes 26 may be formed of non-conductive material such as plastics.

In use, the snails are deterred from crossing the barrier provided by the device 10 by virtue of the fact that as they attempt to cross the strip 12, the inevitable bridging of the tracks 14 and 16 which occurs as the snail or slug moves across the strip face 12a causes bridging of the tracks 14, 16 whereby electric current from the battery 18 can flow through the tracks 14, 16 across the snail or slug.

Figures 9a and 9b show a preferred form of stake 26. Here, the stake 26 is an integrally formed plastic component having a stake portion 40 of somewhat "L" shaped transverse cross section, downwardly depending from a transversely extending upper ledge 42. The ledge 42 has, located towards one edge thereof, an integrally hinged retaining element 44 which can be moved from the ^'position shown in Figure 9a where it is hinged away from ledge 42 to the position shown in Figure 9b where it is positioned in an overlying relationship to the ledge 42 and retained in such position by engagement of a free end portion 44a of the element 44 in a resiliently deformable "c" shaped upstanding ridge 48 formed on ledge 42. This ridge is so formed as to enable the element 44 to be snapped into the position shown in Figure 9 and retained therein, whilst also permitting the element 44 to be hinged upwardly to disengage it from the ridge 48 under resilient deformation of the ridge. As shown in Figure 9a the strip 12 is attached to the stake 26 by forming an "S" shaped bend therein so that a first 180° bend 12c is made therein transverse to the directio ^'of extent of the strip so that a portion 12d thereof overlies the "preceding" portion 12c of the strip and a second 180° reversely effected bend 12e is then made so that a further portion 12f of the strip then overlies the portion 12d. Thus, at the location of the portion 12d there are portions of the strip 12 both above and below that portion. At this location, where there are three thicknesses of strip present, the strip is positioned on the ledge 42 (with the element 44 having been hinged outwardly to the position shown in Figure 9a) whereupon the element 4 is then snap fitted into the position shown in 9b so as to be positioned between the overlying portions 12d and 12f of the strip 12. The portion 12d and the underlying portion 12c of strip 12 are thus clamped between ledge 42 and element 44. In order to facilitate the retention, the element 44 has a "V" shaped transverse ridge 44c which extends into a "V" shaped transverse groove 42a in the ledge 42. The resultant assembly shown in 9b is a neat interconnection between the strip 12 and stake 26.

As shown in Figure 5 , due to the thinness of the strip 12, the flexibility of the strip 12 is such as to readily enable folded corners to be formed in the barrier defined by the barrier device 10 when it is in position on a ground surface. One such corner 30 is shown in Figure 5.

Corner stakes 26 may be used to form the corners 30 in the manner shown in Figures 4a and 4b. ^■ In particular, the strip 12 is affixed to the corner stakes in analogous manner to that shown in Figures 9a and 9b save that, here, the strip 12 is overlaid on the ledge 42 at an angle of 45° to the hinge line between the element 44 and the ledge 42 so that, in the resultant assembly, the portion 12c of the strip 1'2 and the exiting portion 12f therefrom, at the location of the stake extend at 90° to each other. Of course, by varying the angular displacement between the portion 12c and the hinge line of the stake (and thus between that portion and the direction of extent of the end face of the free end 44a and the element 44) corners of angular displacement different to the 90° described in Figures 4a and 4b may be formed.

It is envisaged that the strip 12 may be sold separately of the battery or may, alternatively, be sold in combination with the battery 18. Since the battery may last for a considerable time, bearing in mind that the current flow thereon would, in normal use be minimal, it is feasable to provide the battery 18 integrally or otherwise fixedly secured to the strip.

As shown in figure 7, it is possible to include, in the device according to the invention, an oscillator 60 interposed between the battery 18 and the tracks 14 and 16 and effective to apply an alternating potential to the tracks. As shown, the oscillator 60 includes an oscillator device 62 formed from an inverter 64 having a feed back resistor 66 and a capacitor 68 connected from the input of the inverter 64 to negative supply. Output from this oscillator device is in the form of the alternating potential indicated by wave-form 70 in figure 7.. In particular, this potential rises at time interval t.. from a small positive voltage to a voltage +V which voltage is similar to the positive supply voltage from the battery 18, such as 9 volts, and thence falls at a later time interval t.- back to the small positive voltage. After a further time interval, the voltage then rises at a time t-. again to the voltage +V. The intervals t. to t~ and t₂ to t-, may be equal and to the order of 100 milliseconds in duration. This output is applied to track. 16. The output from the oscillator device 62 is applied via an inverter 72 to the track 14. Thus, the track 14 has applied to it a voltage which is in the inverse of that illustrated by wave form 70, being of the form indicated by wave form 74 in figure 7.

The waveforms 70 and 74 can also be buffered to provide greater power by serially connecting further inverters in parallel as shown in the modified circuit of figure 7a. Thus, parallel inverters 71 and 73 are connected in series with the output of inverter 72. Output from these inverters 71, 73 is connected to track 14. Further parallel inverters 75, 76 are connected in series with the output of oscillator device 62. Output from these inverters 75, 76 is connected to track 16.

A further modified oscillator circuit is illustrated in Figure 7b and includes the oscillator device 62 of Figures 7 and 7A and a second oscillator device 100 and a monostable 102. The second oscillator device 100 comprises a commercially available integrated circuit 102 coupled to the positive terminal of the nine volt supply 18 via a diode 104. The integrated circuit 102 is configured so as to produce an ac waveform having a period of four seconds at its output 106. The output 106 of the second oscillator device 100 is connected to the monostable 102. The monostable 102 comprises an inverter 108 having its input coupled to the positive terminal of the battery 18 via a resistor 110. The monostable 102 also includes a capacitor 112 which is. connected in between the input of the inverter 108 and the output 106 of the second oscillator device 100. The monostable 102 is triggered by negative going edges of the waveform produced by the second oscillator device 100, that is whenever the output 106 initially goes low the input of^-' the inverter 108 is pulled low and therefore its output and the monostables output 114 go high. The output 114 of the monostable 102 remains high for approximately one second until the capacitor 112 becomes sufficiently charged, via the resistor 110, so that the output 114 returns to a low state. Therefore a pulse of one second duration is produced every four seconds at the output 114 of the monostable 102. As in the circuits of Figures 7 and 7a, the track 14 is connected to the output of the oscillator device 62 via an inverter 72 and the track 16 is connected to the output of the oscillator device 62, albeit in the circuit of Figure 7b via a resistor 120 and two inverters 122 and 124 connected in series. Hence, when the oscillator device 62 is enabled 'an ac waveform 74, as shown in Figure 7 is produced on the track 14 and an ac waveform 70 , of opposite polarity to the waveform 74, is produced on track 16. In the circuit of Figure 7b, however, the oscillator device 62 is disabled for approximately one second in -every four -in response to the output 114 of the monostable 102. This is achieved by connecting a first diode 130 between the output 114 and the input of the inverter 64 of the oscillator device 62 and a second diode 132 between the output 114 and the input of the inverter 122 coupled to the track 16. The diodes 130 and 132 have their cathodes connected to the output 114. Therefore when the output 114 is low the diodes 130 and 132 conduct and the input to the inverter 164 is held low and the input to the inverter 122 is held low, this ensures the tracks 14 and 16 are held low. When the output 114 is high, however, the diodes 130 and 132 are non-conductive and the oscillator device 62 is able to function as described with reference to Figure 7. The circuit of Figure 7b gives rise to generation of a waveform 150, as illustrated in Figure 7b, on the track 14 and a similar waveform is generated on the track 16 with the one second oscillating portions 152 of the waveform 150 being opposite in polarity to that produced on the track 14. The circuit of 7b is designed to conserve power. If a conductive element bridges the tracks 14 and 16 power consumption for the circuit of Figure 7b will be 25% of the power consumed if the circuits of Figures 7 and 7a are used. The circuit of Figure 7b also does not diminish the effectiveness of barrier device 10 as mollusks, in traversing the strip 12, would normally bridge the tracks 14 and 16 for a period greater than four seconds. The diode 132 and the resistor 120 are included so as to ensure that the track 16 is simulataneously pulled low with the track 14.

The casing 21 which houses the battery 18 is preferably formed as shown in Figure 6 , having a hollow housing portion 80 removably closed at one end by a closure element 82 so as to permit the battery 18 to be replaced, when necessary. The battery 18 when . positioned in the housing is maintained in a position between the closure 82 and a retaining plate 84 within the housing. Plate 84 may comprise a printed circuit board housing the aforedescribed oscillator 70. Connections are made via the oscillator circuit board or by wires (not shown) from the battery to terminals 90 on the exterior of the housing at the end remote from closure 82. A hinged clip 94 is provided effective to hold the strip 12 to the housing in such a fashion that the two tracks of the strip 12 are brought into and retained in firm engagement with the terminals 90. Clip 94 comprises a rectangular planar element hinged at one edge 94a to casing 21 and having at its opposed edge an inturned edge portion 94b which cooperates with a ridge 21a on the casing 21 to act as a snap fastener for holding the clip 94 in closed position. The strip 12 may, as shown, be doubled back at its end to enable the tracks 14, 16 to be brought into engagement with terminals 90. For securing the strip, the end portion of the strip is led into the space between ^'the clip 94 and casing 21 adjacent ridge 21a so that when the clip 94 is moved to its closed position the strip is securely engaged and held between the ridge 21a and the edge portion 94a of the clip 94, with the doubled over end portion of the strip correctly positioned to bring tracks 14, 16 into contact with the terminals 90.

It is desirable that some means be provided to enable testing of the state of the battery 18 in order to determine when the battery needs to be replaced and to check if tracks 14, 16 are broken. Figure 10a shows a suitable testing unit formed of a plastics housing 50 hinged at one end 50a and suitably grooved on opposed faces of the two halves of the casing to either side of the hinge so as to retain therewithin three LEDs 51, 52, 53. These are connected in series as illustrated in Figure 10b and are maintained in the housing by being clamped between the two housing halves, the housing halves being provided with cooperating snap fastener means whereby once assembled, the two halves are retained together. Projecting leads from the outermost LEDs 51, 53/ designated by reference numeral 55 and 57 in Figures 10a and 10b, extend from the housing and are spaced apart a distance enabling them to be readily positioned in contact with the two contacts 90 of the housing 21 to place the three LEDs in series across the battery 18, such as by bringing these projecting leads into contact with respective tracks 14, 16. Thus, if the LEDs are illuminated under this condition it is determined that the battery is still operative, otherwise determined that the battery requires replacement.

As shown in Figure 10b, it is not necessary to , physically solder together leads of the LEDs 51, 52, 53 in order to permit the series connection requires adjacent leads merely being crossed as shown in Figure 10b and retained in position, in electrical contact, when the two housing halves are clamped together.

As shown in Figure 6, the housing 21 may, conveniently, be provided with an integral stake 21b which may be placed in the ground in the same manner . as the stakes 26, in this case, however, to retain the housing 21 in any convenient location adjacent the ground surface.

Figure 11 shows a modified strip 12 in which the two tracks 14, 16 are positioned adjacent one side edge 12d of the strip 12. Thus' there is a strip portion 12f of substantial width between track 14 and the opposite edge 12e of the strip. This portion 12f may be buried in the ground surface to better locate strip 12 and to minimize the possibility of snails or slugs passing under the strip.

The described arrangement has been advanced merely by way of explanation. Many modifications may be made thereto without departing from the spirit and scope of the invention which includes every novel feature and combination of novel features herein disclosed.

Claims

1. A barrier device (10) comprising an elongated flexible strip (12) on one face (12a) of which are disposed two lengthwise extending conductive tracks (14, 16) arranged in a spaced electrically insulative disposition but being capable of being bridged by a snail, slug or the like moving transversely across the said face (12a), said tracks (14, 16) being capable of being energized by an electric power source (18) such that when said snail, slug or the like bridges said tracks (14, 16) a current passes through said snail, slug or the like thereby deterring said snail, slug or the like from passing over said strip 12.

2. A barrier device (10) as claimed in claim 1 wherein said device (10) is configured so that' it may be positioned on a ground surface to protect a portion of said surface from intrusion by snails, slugs or the like.

3. A barrier device (10) as claimed in claim 2, wherein said strip (12) is formed of material of such flexibility that the strip (12) may be wound up for storage thereof.

4. A barrier device (10) as claimed in claim 3, wherein the flexibility of said strip (12) is such that the strip (12) may be readily folded to permit it to be disposed in a two dimensional path.

5. A barrier device (10) as claimed in claim 4, wherein the thickness of said strip (12) is in the range 0.03-T_m to 0.limr

6. A barrier device (10) as claimed in any one of the preceding claims, wherein said tracks (14, 16) are positioned closer to one edge (12d) of the strip (12) than the other edge (12e) so as to provide a substantial portion (12f) of the width of the strip (12) clear of said tracks (14, 16) and which may be buried in the ground to facilitate location of the strip (12).

7. A barrier device (10) as claimed in any one of the preceding claims, further comprising a stake (26) to facilitate location of said strip (12), said stake (26) comprising a stake portion (40), a transversely extending upper ledge (42) from which said stake portion (4) downwardly depends and a retaining element (44 ) hinged at one end thereof to said ledge (42), said ledge (42)"being adapted to engage said element (44) so that said flexible strip (12) may be retained between said element (44) and said ledge (42) .

8. A barrier device (10) as claimed in claim 7, wherein said stake (26) is an integrally formed plastic component.

9. A barrier device (10) as claimed in claim 8, wherein said element (44) overlies said ledge (42), which includes a resiliently deformable ridge (48) adapted to resiliently engage a free end of said element (44) .

10. A barrier device (10) as claimed in any one of claims 7 to 9, wherein said ledge (42) and element (44) are adapted to retain a portion of said stri (12) which has been folded to form a corner.

11. A barrier device (10) as claimed in any one of the preceding claims, further comprising a casing (21) for housing a dc voltage supply (18), including two terminals (90) adapted for electrical connection to said tracks (14, 16), respectively.

12. A barrier device (10) as claimed in claim 11, wherein said casing (21) further includes means for electrically connecting said supply (18) across said tracks (14, 16).

13. A barrier device (10) as claimed in claim 11, wherein said casing (21) includes an oscillator circuit (60) which, in use, is coupled to said supply (18) and outputs first and second ac voltages (70, 74) to said tracks (14, 16), respectively, via said terminals (90), said ac volages (70, 74) being opposite in plurality and being of a level sufficient to induce a deterring current in a snail, slug or the like which bridges said tracks (14, 16).

14. A barrier device (10) as claimed in claim 13, wherein said oscillator circuit (60) is such that said ac voltages (70, 74) are only ouptutted for approximately 1 second every 4 seconds.

15. A barrier device (10) as claimed in claim 13 or 14, wherein said ac voltages (70, 74) have a period of approximately 200 ms.

16. A barrier device (10) as claimed in any one of claims 11 to 16, further comprising means (51, 52, 53) for indicating the strength of said supply (18) .

17. A barrier device (10) substantially as hereinbefore described with reference to the accompanying drawings.