ELASTIC ELECTRIC FENCE

TECHNICAL FIELD The present invention relates to a string suitable for electric fences, comprising one or more uninsulated conductor.

PRIOR ART

Since long it is known to define enclosures for animals with electrically conductive strings or threads attached in a series of posts and in this way an area is defined where the animals may stay and/or from which other wild or domestic animals may be kept out. By light electric shocks at contact with the string or thread the enclosed animals are taught to stay within the enclosure. During a learning period the string or thread will, however, be subject to important stresses when for instance a young animal being inexperienced to the fence tries to escape from the enclosure. The same problems imply to deer or other larger wild animals which may run into the fence. A conventional current carrying string which is fastened between posts should also be stretched to have best possible conductivity and give a good visual impression, but after stresses at contact with an animal it is according to prior art usual that the string is stretched and breaks.

A string for enclosing animals is known through DE3822529A1 (Hoeck), where the string is heavily stretched between posts to maintain function and good visibility to the animals. The string is wide but loosely manufactured so that it shall not flatter in the wind, and at its edges current carrying conductors run which will guarantee electric shocks to the animals at contact. However, there is a risk for damages on the string when an animal has run towards it, either that the band is stretched in spite of its tightening, or that the string indeed breaks. If the string has been stretched and hence hangs slackly between the posts, there is also the risk of impaired electric effect, as a situation may occur where only a minor portion of the string comes into contact with an animal.

WO82/04378 describes an enclosure for animals comprising an electrically conductive string intended to give electric shocks when animals touch it. Also this string is essentially non-flexible in the longitudinal direction and runs therefore the risk of being stretched or break if an animal runs into the fence. Through is tight weaving, wherein the electrically conductive thread is weaved with twill weaving in the weft threads of

the string, so that one side of the string has an essentially higher presence of the conductive thread than the other one, the chance is increased that an animal receives an electric shock at contact with that side. The tight weaving implies, however, a risk that the string is easily soiled by impurities, such as pollen, and that a coating is thus formed on the conductive thread, which impairs the ability of the string. A string blocked up by dirt flatters also easier in the wind, which one wants to avoid.

Through US5201498 (Akins) a system is shown for enclosing animals, where a plurality of panels comprising essentially rectangular, stiff structures with parallel rods are connected via elastic elements so that an enclosure is formed wherein each panel element may move in relation to the others. In this way, the fence may be stretched at a collision with an animal, and then, thanks to the elastic elements, return to the original shape without being permanently stretched or breaking. However, each panel element is in itself not flexible, but consists of stiff structures, which as such may be detrimental for animals to crash into. The panels become also comparatively bulky to transport and mount, and the system contains no element making contact deterrent for the animals, such as electricity.

DISCLOSURE OF THE INVENTION The object of the present invention is to eliminate or at least minimize the above problems, which is achieved with a string suitable for electric fences, containing one or more uninsulated conductors, characterised in that the string is elastic in its longitudinal direction.

Thanks to the invention, enclosures may be created, where there is no risk that the delimiting string will loose shape or break at collision with the animals enclosed. The elastic properties of the string implies that the fence after each stress may resume its original shape and thus always be stretched, which enables a good function of the string and good visibility for the animals.

According to an aspect of the invention, the string comprises at least two elastic threads, preferably of rubber, running in the longitudinal direction of the string. Due to the rubber threads the string may be stretched very heavily repeated times because of collision with animals and then resume its original shape afterwards.

According to another aspect of the invention, at least one conductive thread, preferably of stainless steel, runs in a first loop in the longitudinal direction of the string in zones

between two elastic threads. This thread conducts electric current through the string, and thanks to the shape of the loop a comparatively large portion of the surface of the string is current carrying. Through the shape of the loop it is also possible to utilize the elastic properties of the string, although the conductive as the above mentioned non-conductive thread, which preferably is a monofilament and forms a second loop in the zone, are essentially inelastic. In a preferred embodiment, said loops are meander-shaped, comprising partly curved end portions, in which the conductive and non-conductive threads are mounted with said two elastic threads, partly essentially transverse portions between the end portions. An essential characteristic of the embodiment chosen also is that the transverse portions of the meander-curve of at least the first loop in the non- stretched condition of the string show an inflexion point in the region of each point of intersection with an imaginary central line in the zone, and that the maximal width of the curves of the loop in the non-stretched string is larger than the distance between adjacent inflexion points, a condition promoting the stretchability of the string in the longitudinal direction without simultaneous reduction of the width. Said non-conductive thread of preferably a polymer material has considerable stiffness and contributes to the string also in stretched condition having essentially the same width as in its normal condition. Also for the other loops formed by this non-conductive thread in the non- stretched string, preferably the same conditions are valid as for said other loops that the maximal width of the curves are larger than adjacent inflexion points. As the width of the string may be kept constant, in spite the band being stretched, one may use string holders at the fence posts, which are adapted to the width of the string. Further, it offers a good visual impression, if the string in different portions of the enclosure has a uniform appearance.

According to another aspect of the invention, the string consists of at least two zones as mentioned above and at the outer edge the string comprises at least two, preferably three, parallel elastic threads. In this way, a wider string may be formed and a firm edge established which further contributes to the same shape being maintained in the non- stretched as well as in the stretched conditions.

According to another aspect of the invention, the conductive thread, the non-conductive thread and the elastic thread of the string are kept in place in relation to each other by a warp thread, preferably a multifilament, by tricot weaving, wherein the warp thread forms extendable meshes binding the different types of thread together and giving stiffness to the string.

According to another aspect of the invention, the string has an essentially loose structure. This implies that the tendency of the string to flatter in the wind is low and that a uniform impression is also kept irrespective of weather, and that impurities such as dirt or pollen may pass rather than adhere to the band. Thus, if the band can be kept clean, it will easily be visible to people as well as animals and keep its electrically conductivity. The conductive thread is weaved into one side of the string, but thanks to the loose structure, an animal may easily reach the conductive thread at both the front and back.

According to another aspect of the invention, the elastic, electric string may be part of an electric fence system with post and a current source, and string holders adapted to the width of the string, which holders are mounted at the posts. This system is also easy to mount, and thanks to the elasticity of the string a uniform appearance is easily achieved.

BRIEF DESCRIPTION OF DRAWINGS

The invention will be described more in detail below with reference to the enclosed drawings, of which:

Fig. 1 is a schematic view of a fence system according to the invention; Fig. 2 somewhat schematically shows the principle of the construction of an elastic, electric string according to the invention in its simplest embodiment, comprising only one zone, in a view showing the back of the string in a stretched condition; Fig. 3 shows in an enlarged view a preferred embodiment of the back of the elastic string in the non-stretched condition of the string; Fig. 4 shows a central section of the front side of the string of Fig. 3 in a still larger scale; Fig. 4A shows a section of a meander-shaped loop, in the claims denominated first loop, which is formed by each conductive thread in the non-stretched string of Fig. 3 and Fig. 4; Fig. 4B shows a section of the meander-shaped loop, in the claims denominated second loop, which is formed by said non-conductive thread in the same string; Fig. 5 shows a central section of the front side of the string of Fig. 3 in a stretched condition; Fig. 5 A shows a section of the meander-shaped first loop formed by each conductive thread in the stretched string of Fig. 5;

Fig. 5 B shows a section of the meander-shaped second loop formed by each said non- conductive thread in the stretched string of Fig. 5.

DETAILED DESCRIPTION OF DRAWINGS Fig. 1 shows a fence system according to the invention, wherein an elastic electric string 1, according to any preferred embodiment of the invention, is fixed to posts 8 through engagement in string holders 9 being adapted to the width of the string. The string may be fixed to one post at a time around the enclosure, whereafter finally the two opposing ends may be connected. A current source 10 is placed somewhere along the enclosure, and the current is coupled to the string through a connector 11. The posts 8 are made of an insulated material, preferably wood, and have dimensions, suitably adapted to the size of the pasture or the type of animals which are to be kept in the enclosure. For larger animals it is conceived that heavier posts are preferred, as also the posts may be subject to important force at a collision with an animal. At a certain height from the ground, also adapted to the animals enclosed, the string holders 9 are fixed to the posts. The string holders 8 are like the posts made of an insulated material, preferably a plastic material. As both the posts 8 and the string holders 9 function as insulators for the current, the risk is reduced that the circuit is unintentionally short-circuited or earthed. An embodiment is possible, wherein several strips 1 are stretched parallelly at different heights at the posts 8, so that both large and small animals may be effectively enclosed, such as for instance horses with foals or cows with calves.

Fig. 2 shows a clear, somewhat schematic view of an elastic, electric string 1 according to the invention, wherein an electrically conductive thread 4 and a non-conductive thread 3 form a first meander-shaped loop 4a with curves 4b and transverse portions 4c between the curves 4b and the elastic threads 2, and a second meander-shaped 3a with curves 3b and transverse portions 3 c between two elastic threads 2, respectively, and together they form a zone 7. The thread 4 is made of a material with good electric conductivity, preferably stainless steel, and has a diameter of 0.10 to 0.50 mm, most preferred 0.20 mm. The non-conductive thread 3 is made of an insulating material, preferably a thread of monofilament, polymer material with a diameter of 0.10 to 0.40 mm, most preferred 0.20 mm, while the elastic thread, which is preferably made of rubber, has a diameter of 0.20 to 0.50 mm, most preferred 0.40 mm. The loops 4a and 3 a of the conductive thread 4 and the non-conductive thread 3 are fixed to the elastic threads 2 through warp threads 5 forming meshes around the threads. The warp thread 5 is preferably made of a multifilament thread with a diameter of 0.10 to 0.50 mm, most preferred 0.2 mm. From a terminological point of view, a more correct denomination of

the warp thread 5 is multifilament yarn, but nevertheless the term thread is used here, but no limiting meaning is to apply for this denomination. The materials present are preferably resistant to UV-radiation, so that the string may hang outdoors all the year round without being destroyed by the sunbeams.

The four different types of threads 2, 3, 4, 5, which together form the string 1, are of different nature and function. The elastic rubber threads 2 guarantee the elasticity of the string 1 but are also components of the two selvages of the zone 7/string 1. The main task of the electric thread 4 is to make the string 1 electrically conductive. Besides the electric conductivity it also has an important stiffness. Also the non-conductive thread 3 of the monofilament polymer material is comparatively stiff, but not as stiff as the conductive thread 4. The stiffening threads 3 and 4 function together as construction elements in the string and form as such spacers with enough stiffness between the elastic threads 2 to prevent that the width of the string is reduced to an unacceptable degree when the string is stretched. Finally, the task of the warp thread 5 is to secure the conductive thread 4 and the non-conductive thread 3 to the elastic threads 2. Therefore, it consists of a multifilament polymer material having great tensile strength, but also being so flexible and missing springiness that it may easily be used in a warp tricot machine to form first and second meshes 13, 14 around the elastic threads 2 and around the stiff, conductive and non-conductive threads 4, 3, so that the latter ones are bound to the former ones.

Fig. 2 shows the string 1 in a stretched condition. In the string said first, meander- shaped loops 4a of the conductive thread 4 form only half as many curves 4b by each length unit of the string 1 as the loop 3 a of the non-conductive thread 3. This depends on the fact that the conductive thread 4 already with its limited number of curves by each length unit of the string provides an important stiffness contribution to the string, that it, because its fewer number of curves 4b by each length unit, with its transverse portions 4c will cross the transverse portions 3c of the conductive thread 3, which implies that the electric thread is well exposed in the string, and above all that the length of the electric thread 4 and hence its electric resistance as well as the manufacturing costs of the string are heavily reduced.

In Fig. 2, which shows the string 1 in a stretched condition, the meshes 13 and 14 are also shown in a condition which is stretched as compared to an original, compressed initial condition. The first meshes 13 bind the conductive thread 4 as well as the non- conductive thread 3 to the elastic thread 2, while the other meshes 13 only bind the non-

conductive thread 4 to the elastic thread 2. It should be mentioned that the first and second meshes 13 and 14 from a tricot technical point of view are in themselves identical but they do not have identical tasks in the string 1.

Fig. 3 shows in an enlarged view a preferred embodiment of the string 1 according to the invention, wherein the back of the string can be seen in the non-stretched condition of the string. The preferred embodiment shows the string 1 constructed of four central zones 7 and two outer zones T, wherein the outer zones 7' have a selvage 6 with elastic threads 20, 21, 22. The elastic threads 20, 21, 22 are tighter arranged in the selvages 6 than in the remainder of the string and provide therefore additional stiffness to the band. The elastic thread 22 in respective selvage 6 is arranged in the middle of the edge zones 7'. An additional elastic thread 22 is also provided in the middle of the central zones - the centre lines are designated 23.

Figs. 4 and 5 show detailed views of the front side of the string in a preferred embodiment. In each central zone 7 there are two elastic threads 2 forming zonal boundaries, which threads are common with an adjacent zone 7 or edge zone T . The meshes are stitched around the elastic threads 2 which are common for the adjacent zones, in a manner most clearly shown in Fig. 5. Here the term stitch is used, whether it is a correct tricot technical term or not. Particularly, in the zigzag-pattern formed by the meshes around the elastic threads 2, the stitches sloping to the right in this pattern are designated 15 and the stitches sloping to the left are designated 16. Thus, a first stitch 15 around the elastic thread 2, which is common for the zones 7a and 7b, is the stitch also around the conductive thread 4 and the non-conductive thread 3 in the zone 7a as well as around the conductive thread 4 and the non-conductive thread 3 in the zone 7b. The next stitch 16 is the stitch around the conductive thread 4 and the non-conductive thread 3 in the zone 7b but only around the non-conductive thread 3 in the zone 7a, etc.

In a similar manner, the conductive and non-conductive threads 4 and 3, respectively, are fixed to the elastic threads 22 in the region of the centre lines 23 of all zones, wherein the meshes besides the elastic threads alternately include both non-conductive and conductive threads, and only non-conductive threads, respectively.

In the non-stretched condition of the string, Fig. 4, the meshes 13, 14 are tightly pressed towards each other, which in a manner typical for tricot allows that they may be stretched together with the elastic threads, when the string is stretched, Fig. 5.

Now, with reference to Figs. 4A and Fig. 4B, the meander-shaped loops 4' and 3' are shown, which are formed by the conductive 4 and non-conductive threads 3, respectively, in the non-stretched string 1 shown in Fig. 4. The loops may be compared to a wave-shaped curve with inflexion points 17 and 18, respectively. Typical for the curves formed by the waves also is that the maximal width of the curves in the non- stretched string, i.e. the maximal width of the individual wave-halves in the translation direction of the wave corresponding to the longitudinal direction of the string, is larger than the distance between adjacent inflexion points in the respective loop. This implies that the rounded curves in the non-stretched string consist of reserves of threads which are utilized and more or less emptied when the string is stretched. This is of great importance, as it allows the string to be stretched without loosing its width. In other words, with reference to the wave motion teachings, the wave length of the meander- loops 4' and 3 'may be increased to a great extent as well as the distance between the inflexion points 17 and 18 - which corresponds to an elongation of the string 1 - without the wave height decreasing at all, which corresponds to a constant width of the string. Thanks to the shape of the loops 4' and 3' it is thus possible to utilize the elasticity of the elastic threads maximally without the width of the string shrinking.

It can also be seen, clearest in Fig. 4 and Fig. 5, that both loops 3' and 4' of the threads 3 and 4 are arranged on the front side of the string 1, but that the electrically conductive threads 4 thanks to the loose structure of the string are accessible also from the back of the string, which especially is true when the string is stretched, which it normally is to an essential degree when used. In this way it is possible to give electric shocks to enclosed animals independent of which side of the string is mounted inwards.

A man skilled in the tricot production technique will realize how the manufacture of the string is performed.

The invention is not limited to the above description but may be varied within the scope of the appending claims. For example, it should be understood that you can choose to weave conductive threads also into the back of the string, or that the loops in the different zones of the string may be displaced to each other so that the conductive threads come into contact with each other and contribute to a safe current supply in the string. Different types of current sources may be conceived to provide the string with current or that both ends of the string may be coupled together in different ways. It is conceivable that the width of the string may be varied from narrow string with only one zone to very wide ones, or that an enclosure system is constructed where there are

parallel strings at different heights above the ground. Nor is the invention limited to being manufactured using a tricot technique but other methods of production, such as for instance weaving, are possible.