Electric fence

Abstract

A method of forming an electric fence (22) to span a given region (28) between a first (25) and a second (26) substantially opposing sides, said fence including—one or more insulators (1) located about said opposing sides (25, 26);—at least two electrically distinct conductive strands (23, 29) having different voltage potentials applied by an electrical power source, (24) characterised in that said conductive strands (23, 29) extend continuously and repeatedly between said opposing sides (25, 26), each strand passing around or through one or more insulators (1), wherein at least two strands (23, 29) of different voltage potential pass through or around at least one common insulator (1).

Description

TECHNICAL FIELD

The present invention relates generally to a means of producing an electric fence and to the insulators used therein.

BACKGROUND ART

Electric fences are employed for both security purposes and for stock control in countries worldwide. Despite the proliferation of such electrified fences, the basic means of construction and operation are fundamentally the same, whereby a fence used to prevent movement through a given area is normally formed by a plurality of individual spaced apart (typically parallel) electrified wires/strands extending across the said space (either vertically or horizontally). In order to maintain the appropriate electrical connections, a common connector is attached across the individual wires to provide power to each electrified element.

Typically on longer sections this system requires each individual electrified wire to be individually tensioned, to provide both physical and electrical barrier properties, and to be securely affixed and insulated from the end post upon which all the said electrified strands are terminated. This is both time consuming and expensive and requires a certain degree of skill to ensure correct installation. Furthermore, to achieve the above mentioned tension: required for each individual electrified element, typical known systems hard-wire the electrified element to an insulator at one end of the fence enclosure and use a ratchet mechanism at the other end to provide the said tension. This system requires an individual ratchet mechanism for each electrified strand/wire.

It would be clearly advantageous therefore to form an electrified fence from a reduced number of electrified strands, associated insulators, and ratchet/tensioning mechanisms.

In most security applications and some stock control fences, a separate earth or low voltage strand is employed in addition to the high voltage strand. This ensures a potential difference between an individual or stock contacting the two strands.

On fences with shorter sections formed with wires of different potential (e.g. where one wire acts as an earth, or low voltage potential wire and the other as a phase wire, or high voltage potential wire), it is known to use continuous strands of wire alternating between opposing sides of a fence. However, each strand is effectively tied off at each insulator by applying a number of turns of the wire around the insulators on either side.

As the phase and earth wires (for example) typically form alternate spans between the sides of the fence, some means is required to avoid a short-circuit as the strands cross each other at the sides of the fence. In the prior art, this is achieved by bending a earth wire outwards from the plane of the fence between two insulators on the same side of the fence, looping over the intermediate insulator carrying the other wire of different voltage potential.

The same procedure is adopted for the other, though with the looped section of the wire being bent outwards from the plane of the fence in the opposite direction to the first wire to avoid shorting/interference.

However, this configuration produces numerous drawbacks including:

• • difficulties in tensioning/re-tensioning individual spans after the fence is constructed;
  • the vulnerability of the projecting looping sections of wire to being snagged and/or damaged by passing vehicles/people/animals;
  • an aesthetically undesirable appearance; and
  • difficulties in concealing which wire is the low voltage/earth stand.

It is possible for an assailant to scale an electric security fence by only holding the successive earth strands spanning the gate/fence.

Therefore, it is desirable to make it difficult for an assailant to visibly discern the live strand from the earth strand.

Known means of accomplishing this for fences utilising multiple individual strands joined by configuring wires include the use of complex fittings that clamp several live and earth strands in a manner that obscures the electrical continuity of each strand. Such fittings are however difficult to implement and service and expensive to make.

The same principles apply to fences using variants of the high voltage—earth strand combination. Such variants include applying different high voltage potentials to both strands, or offsetting the instance of the high-voltage pulses, as described in European Patent No. 0843954, U.S. Pat. No. 5,973,413, Australian Patent No. 705977 and South African Patent No. 96/6799 stemming from the applicant's patent PCT/NZ0096/00081, incorporated herein by reference.

It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.

Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

DISCLOSURE OF INVENTION

According to one aspect of the present invention there is provided a method of forming an electric fence to span a given region between a first and a second substantially opposing sides, said fence including

• • one or more insulators located about said opposing sides;
  • at least two electrically distinct conductive strands having different voltage potentials applied by an electrical power source, characterised in that said conductive strands extend continuously and repeatedly between said opposing sides, each strand passing around or through one or more insulators, wherein at least two strands of different voltage potential pass through or around at least one common insulator.

Thus, where two conductive strands pass around or through a single insulator in close physical proximity, it is not obvious to an observer/assailant which strand is which. It would thus be difficult to determine for example which strand entering or exiting the insulator is the continuation of the high voltage strand.

The different voltage potential between two or more strands may, according to different embodiments, relate to differences in different time, magnitude and/or polarity.

Thus, provided there is a relative difference between the voltage potential of any two strands, an assailant attempting to scale the fence by holding both strands will still receive a shock.

To make it even more difficult to determine which strand may be safe to grasp, the high voltage and low (or earthed) voltage applied to two strands may be periodically reversed. Offset synchronised high voltage pulses applied to both strands may also be utilised to achieve the same effect.

The term ‘fence’ includes any structure formed to provide a barrier between defined limits, including doors, panels, gates, walls and so forth.

Preferably, each strand passes around or through an insulator via a confined pathway, physically and electrically separated from any other conductive strands.

Preferably, said confined pathway may be formed in an insulator as a groove, channel, notch, passageway, aperture or the like.

Preferably, each said insulator is formed from one or more non-conductive elements, each having one or more confined pathways.

According to one embodiment, said non-conductive elements are substantially disk-shaped with a substantially circular cross section. Preferably, the disk-shaped element is rotatable about a central axis orientated to maintain symmetrical revolution.

According to an alternative embodiment, one or more said insulators each include two or more said disk-shaped non-conductive elements, with each said central axis being substantially co-axial with that of the other disk-shaped elements forming the insulator.

Preferably, said disk-shaped element is provided with one or more confined pathway in the form of grooves about its outer curved surface, concentric with said central axis.

Preferably, said grooves are configured with side walls sufficiently deep to obscure from an observer on either side of the fence at least part of the path of a strand passing either through the insulator tangentially to the disk-shaped element, or passing circumferentially around at least part of the disk shaped element.

Preferably, one end of each conductive strand is fixedly mounted, whilst the other end is securable to an insulator formed with a tensioning mechanism. Preferably, said tensioning mechanism is comprised of said nonconductive disk-shaped rotatable element provided with a series of ratchet teeth and a pawl configured to only permit unidirectional rotation of said rotatable element.

Preferably, at least one of said grooves contains said ratchet teeth.

Preferably, said rotatable element is rotatably attached to a non-conductive bracket.

Preferably, said pawl is releasably attached to said non-conductive bracket.

Preferably, said electric fence is tensioned by winding said conductive strands about the outside of said disk-shaped element rotated in said permitted direction allowed by said ratchet and pawl arrangement.

It will be appreciated that the electric fence may form a variety of configurations dependent on the particular requirements of the environment and/or security threat. Indeed, the present invention need not be restricted solely to security applications and may be equally applicable to animal stock control fences and so forth.

It will also be appreciated that dependent on the lateral spacing required between traversing strands, it would be possible to use either a single insulator as a turning piece to allow the longitudinal axis of a conductive strand to be turned through substantially 180° or to use two spaced apart insulators located on the same side of said region used in combination to turn a conductive strand through substantially 180°.

It will be appreciated that each insulator's non-conductive element need not be rotatable although if configured so, the force required to tension the fence will be attenuated and the stresses imposed on all the non-conductive elements and respective mounting brackets involved reduced.

In the event the given region requiring protection does not permit a direct ‘straight line’ passage between said first and second sides of the fence, intermediate insulators are provide apices between angled individual section of the conductive strand traversing the region.

Clearly, only the end insulator requires the inclusion of the pawl attachment in order to facilitate the ratchet operation whilst tensioning the fence. Therefore, in order to reduce costs of the entire fence, the remaining insulators may be provided with without the detachable pawl attachment. Each rotatable element would nevertheless be provided with the ratchet teeth to aid inter-changeability and due to the minimal increase in manufacturing costs.

The present invention also includes the fence produced by the above described methods.

BRIEF DESCRIPTION OF DRAWINGS

Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which:

FIG. 1 shows an exploded perspective view of an insulator assembly of a preferred embodiment of the present invention;

FIG. 2 shows an assembled insulator assembly of the embodiment as shown in FIG. 1;

FIG. 3 shows a side elevation of an insulator assembly as shown in FIG. 1;

FIG. 4 shows a plan view of an insulator assembly as shown in FIG. 1;

FIG. 5 shows a sectional view through the line X₁ X₂ of the insulator assembly shown in FIG. 4;

FIG. 6 shows a side elevation of an electric fence formed as a further embodiment of the present invention;

FIG. 7 shows a side elevation of an electric fence formed as a further embodiment of the present invention, and

FIG. 8 shows a side elevation of a fence formed as a further embodiment of the present invention.

BEST MODES FOR CARRYING OUT THE INVENTION

FIGS. 1-5 show a preferred embodiment of an insulator (1) comprised of a non-conductive element in the form of bobbin (2), and insulated bracket (3) and an optional insulated pawl (4).

The bobbin (2) is formed as a substantially disk-shaped element with two substantially opposing circular faces (5, 6) linked by a central aperture (7) located at the geometric centre of both circular faces (5, 6) and extending therebetween. The outer curved surface of the bobbin (2), is sub-divided into four annular ridges (8, 9, 10, 11) spaced apart defining three confined pathways in the form of annular troughs (12, 13, 14). The central trough (13) is formed significantly wider than the two outermost troughs (12, 14) and is equipped with a series of ratchet teeth (15) equidistantly arranged about the circular length of said trough (13). The ridges (9, 10) adjacent the central trough (13), are formed significantly larger than the outer most ridges (8, 11) and the two outermost troughs (12, 14) interposed therebetween are formed substantially narrower than said central trough (13). The central aperture (7) formed through the bobbin (2), with outwardly projecting cylindrical stubs (15, 16) extending outwards along an axis of rotation co-axial with aperture (7) and configured to engage within corresponding apertures (17, 18) on opposing sides of a substantially u-shaped bracket (3). When engaged within said apertures (17, 18), the bobbin (2) is freely rotatable about said axis of rotation.

An optional pawl mechanism (4) may be attached to the bracket (3) about the mid point of said u-shape and includes two elongated resilient extensions (20, 21) configured to engage with the teeth (15) of the bobbin (2) such that rotation about axis (7) is only permissible in one direction. It will be seen that as the bobbin (2) is formed from an insulating medium and possess three distinct pathways, (ie troughs (12, 13, 14)) it is possible to simultaneously pass up to three separate conductive wires/strands around said confined pathways. It will also be appreciated that bobbin (2) configurations with 1, 2, 4, or more confined pathways are possible.

It is also possible to form each insulator (1) from two or more separate bobbins (2) arranged side by side about a common axis of rotation. Again, such a configuration may provide any number of confined pathways capable of engaging with a corresponding number of conductive strands

The insulator assembly (1) may be utilised to form an electrified fence (22) as shown in any one of FIGS. 6-8. The fence (22) may be formed in a variety of embodiments, although all embodiments incorporate the common feature that one or more continuos strands of conductive material may be used to successively span the region requiring electrified barrier protection.

In FIG. 6, a plurality of insulated bobbins (2) are used in a first embodiment of an electric fence constructed in accordance with the present invention. It will be appreciated however that alternative insulators may be utilised without falling outside the scope of the invention.

FIG. 6 shows a single conductive strand (23) connected to a power supply (24), said conductive strand (23) being used to form an electric fence between two substantially opposed vertical posts (25, 26) and utilising the above described insulator (1). It will be appreciated however, that the region defined by the electric fence need not necessarily be between two vertically orientated sides and may equally be formed between two horizontal sides and/or a combination of same. The region need not necessarily be a fence in the strict sense of the word, but could be equally applied to gates, doors and so forth.

Conductive strand (23) is attached to an upright post (25) at a convenient point typically located at either the top or bottom of the post (25). The conductive strand (23) is connected to a power supply (24) at a detachable connection point (27) attached to a first insulator (reference numeral la) and extends directly across the open region requiring electrified barrier protection (28) until reaching a second insulator (reference numeral 1b) engaging in one of the outer troughs (12, 14) of the bobbin element (2) of the insulator.

The strand (23) extends around the outer curved surface of the trough until re-orientated through an angle of substantially 90° vertically upwards, thereupon engaging with a corresponding outer trough (12, 14) of a third insulator (1c) located directly above the said second insulator (1b). The strand thereupon extends around a similar portion of the trough surface until re-orientated through a further 90° and then traversing back across region (28) in reciprocal direction to the first traverse until encountering a forth insulator (1e) mounted on the first post (25) and engaging again in a outer trough (12, 14) and being realigned vertically upwards until engaging with a further insulator (1e) and thereupon returning to again span the said region (28) and engage with a yet further insulator (1f).

This process is repeated through successive insulators 1g)-1m) until terminating in an end fitting (in). According to the vertical and horizontal dimensions of the region (28) to be covered, the number of insulators (1) and the length of each strand spanning the region (28) may be correspondingly adjusted. In the preferred embodiment shown, either or both of the initial and/or final insulator fittings (1a), 1n)) may take the form of an insulator pawl (1) with insulator pawl (4) fitted to provide uni-directional ratchet action.

After the conductive strand (23) has been interconnected via insulators (1a)-1n)) as described above, rotating either and/or both of said end fittings (1a), 1n)) to tighten the conductive strand (23) wound about the outer curved surface in trough (12, 14) acts upon the entire length of conductive strand (23), thereby applying tension to the entire fence.

In the event any and/or all of insulators (1a)-1n)) are rotatably mounted in said insulated brackets (3), the frictional forces opposing the tensioning action will be correspondingly reduced. By virtue of the single tensioning action, an even and consistent force is applied to all the sections of conductive strand (23) spanning the enclosure (28).

FIG. 7 shows an alternative embodiment in which the use of a pair of insulator (1) attached to either post (25, 26) used to realign the orientation of conductive strand (23) through substantially 180° to span the region (28) (as per the previous embodiment described with reference to FIG. 6) is replaced by a single insulator (1) with a significantly increased diameter of said bobbin (2). This permits a reduced vertical spacing between sections of strand (23) spanning the region (28). This may be desirable in applications where an extremely fine spacing between strands is required.

FIG. 8 shows yet a further embodiment whereby a first conductive strand (23) having a high voltage potential is interconnected through alternate insulators (3a)-3m)) mounted on post (25, 26), whilst a second strand (29) having a low voltage potential is interconnected between the remaining insulators (4a)4n)) in a corresponding manner to the embodiments described with reference to FIG. 6 and 7. In all embodiments, like elements are identically numbered in the drawings. The advantage of using two conductive strands (23, 29) of different voltage potential is the prevention of a potential assailant from insulating themselves from the adjacent terrain, (eg by suitably insulated clothing/footwear) by providing a conductive path when the assailant simultaneously touches the high voltage conductive strand (23) and the low voltage conductive strand (29), or from scaling a fence where all the strands being touched are at the same potential or earthed.

The voltage applied to the separate strands (23, 29) may differ in any number of ways, provided the net result is a potential difference between the strands sufficient to shock an assailant touching both strands (23, 29).

The position of the respective strands (23, 29) as they pass through or around a bobbin (2) is shielded from the view of an observer located on either side of the fence (22). It would be unclear to the observer without very careful scrutiny whether a particular strand entering the bobbin (2) passes straight through, or is turned through an angle (e.g. 90, 180 degrees).

This uncertainty may be further compounded by utilising an irregular pattern to repeatedly traverse the fence (22), and/or alternating the strands in a lateral direction between the opposite sides of the bobbin (2), i.e. moving between the two outer troughs (12, 14). Myriad combinations and permutations of fence configuration are possible using the construction method of the invention and will be understood to fall within the scope and spirit of the invention. In both embodiments shown in FIGS. 7 and 8, a single tensioning means (ie by means of an insulated pawl (4) fitted to the first or last insulator (1) assembly) enables the requisite degree of tension to be applied to the entire fence from a single point.

It will be apparent to those skilled in the art that any of the aforesaid embodiments may be implemented with the side posts (25, 26) in a substantially horizontally opposed configuration.

Due to the three distinct troughs (12, 13, 14) of bobbin (2) it will be apparent that in fact three electrically distinct wires may be simultaneously used on a pair of given fence assembly and that the same concept could be extended to any number of conductive strands by providing the bobbin (2) with the corresponding number of troughs.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof.

Claims

1. A method of forming an electric fence to span a given region between a first and a second substantially opposing sides, said fence including one or more insulators located about said opposing sides; at least two electrically distinct conductive strands having different voltage potentials applied by an electrical power source, characterised in that said conductive strands extend continuously and repeatedly between said opposing sides, each strand passing around or through one or more insulators, wherein at least two strands of different voltage potential pass through or around at least one common insulator.

2. The method claimed in claim 1, characterised in that different voltage potential between two or more strands relate to differences in different time, and/or magnitude and/or polarity.

3. The method claimed in claim 1, characterised in that each strand passes around or through an insulator via a confined pathway, physically and electrically separated from any other conductive strands.

4. The method claimed in claim 3, characterised in that said confined pathway may be formed in an insulator as a groove, channel, notch, passageway, aperture or the like.

5. The method claimed in claim 1, characterised in that each said insulator is formed from one or more non-conductive elements, each having one or more confined pathways.

6. The method claimed in claim 5, characterised in that said non-conductive elements are substantially disk-shaped with a substantially circular cross section.

7. The method claimed in claim 6, characterised in that the disk-shaped element is rotatable about a central axis orientated to maintain symmetrical revolution.

8. The method claimed in claim 6, characterised in that one or more said insulators each include two or more said disk-shaped non-conductive elements, with each said central axis being substantially co-axial with that of the other disk-shaped elements forming the insulator.

9. The method claimed in claim 6, characterised in that said disk-shaped element is provided with one or more confined pathway(s) in the form of grooves about its outer curved surface, concentric with said central axis.

10. The method claimed in claim 9, characterised in that said grooves are configured with side walls sufficiently deep to obscure from an observer on either side of the fence at least part of the path of a strand passing either through the insulator tangentially to the disk-shaped element, or passing circumferentially around at least part of the disk shaped element.

11. The method claimed in claim 1, characterised in that one end of each conductive strand is fixedly mounted, whilst the other end is securable to an insulator formed with a tensioning mechanism.

12. The method claimed in claims 11, characterised in that said tensioning mechanism includes a non-conductive disk-shaped rotatable element configured to only permit unidirectional rotation of said rotatable element.

13. The method claimed in claim 12, characterised in that said unidirectional rotation of said rotatable element is controlled by a series of ratchet teeth and a pawl.

14. The method claimed in claim 13, characterised in that at least one of said confined pathways contains said ratchet teeth.

15. The method claimed in claim 14, characterised in that said rotatable element is rotatably attached to a non-conductive bracket.

16. The method claimed in claim 15, characterised in that said pawl is releasably attached to said non-conductive bracket.

17. The method claimed in claim 13, characterised in that said electric fence is tensioned by winding said conductive strands about the outside of said disk-shaped element rotated in said permitted direction allowed by said ratchet and pawl arrangement.

18. The method claimed in claim 1 characterised in that if the given region requiring protection does not permit a direct passage between said first and second sides of the fence, intermediate insulators provide apices between angled individual sections of the conductive strand traversing the region.

19. An electric fence to span a given region between a first and a second substantially opposing sides, said fence including one or more insulators located about said opposing sides; at least two electrically distinct conductive strands having different voltage potentials applied by an electrical power source, characterised in that said conductive strands extend continuously and repeatedly between said opposing sides, each strand passing around or through one or more insulators, wherein at least two strands of different voltage potential pass through or around at least one common insulator.