WO2004001903A2

WO2004001903A2 - Knitted electrical conductor fabric

Info

Publication number: WO2004001903A2
Application number: PCT/US2003/019256
Authority: WO
Inventors: Josef Sorgen
Original assignee: Beacon Looms, Inc.
Priority date: 2002-06-20
Filing date: 2003-06-20
Publication date: 2003-12-31
Also published as: WO2004001903A3; AU2003251561A8; AU2003251561A1

Abstract

A warp-knittted current-carrying fabric (210) having a plurality of current-carrying wires (201) that cross each other is disclosed. The fabric is capable of carrying current in the presence of breakage in all but one of the wires in any given place.

Description

KNITTED ELECTRICAL CONDUCTOR FABRIC

SPECIFICATION

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to and claims priority from U.S. Provisional Application Serial No. 60/391,076, filed on June 20, 2002.

BACKGROUND OF THE INVENTION Field of the invention. The present invention relates to materials suitable for use in an electrified fence, and more particularly, to fabrics that may be used to conduct electricity and to techniques for using such fabrics.

Description of related art. Prior electrical conductor fabrics have generally fallen into one of two categories: woven fabrics or braided materials such as rope. Although commercially viable, there are drawbacks to each category, including: breakage in electrical current, insulation, structural stability, wind stress, and ultraviolet degradation.

One of the problems addressed in prior products is continuation of electrical current after breakage somewhere in the line. Low-resistance wires are needed to carry the current effectively, but such wires are generally weak and relatively susceptible to working stress. Stronger wires have higher electrical resistance, and therefore do not carry the current well across long distances. U.S. Patent No. 5,036,166 attempts to address this problem by incorporating a high- strength, high-resistance line throughout the fence line, to serve as a connector between any breaches in the low-resistance line. While this solution solves the problem, it does so at the expense of incorporating a wire that is not needed most of the time. Furthermore, if both break in the same spot the circuit is broken at that spot. Another attempted solution presented by woven tape-type products is the insertion of a wire in the weft direction, across the entire width of the material. Unfortunately, this necessitates the use of an inordinate amount of wire to accomplish the task. Furthermore, the movements of the weaving shuttle necessary to create such a weft cause inefficiencies in the manufacturing process. In both wovens and braided products, the current-carrying wire moves through the fabric to emerge on both faces of the product, or, in the case of a rope product, all around the product. As such, no side is electrically insulated. Furthermore, this is an inefficient use of the wire as much of it is buried inside the fabric while moving from one face to another. This necessitates the need for more wire to cover one surface of the fabric than would wire disposed on one face of such fabric. For example, as shown in Fig. 1, when electrically conductive wires 101, 102 are incorporated into a woven fabric 110, the wires 101, 102 must move in and out of the fabric, rather than always being on one face thereof. Further, in existing products, non-conductive clips must be used to affix the product to a post or other support. This is necessary in order to prevent current from flowing into the post, diminishing the current in the current carrying product, and presenting a potential hazard by electrifying the post or support. These clips are expensive, and time-consuming to install. Moreover, it is a well known property of woven fabrics that they are, by nature, structurally unstable in the direction of the weft and vulnerable to skewing or bowing distortions unless enough yarn is used to hold the strands together by friction. Existing products have been very loosely woven, leaving them vulnerable to distortion. Since even the most loosely woven fabrics must still be relatively dense, they are susceptible to stresses due to high wind resistance. This density also makes it hard to separate electrically conductive wires from each other in the fabric since moisture adheres to the yarns in the fabric.

Further, most electrical fences only run one side of the circuit through the fabric, relying on the earth to provide the ground side of the circuit once the animal completes the circuit by touching the fabric while standing on the earth. This arrangement requires a considerable amount of time, effort and cost, since it requires placing a series of metal stakes and wires in the earth, and requires very high voltages to overcome the resistance in the earth, particularly when it is dry. In addition, many of the products in the marketplace are made of polypropylene, which is susceptible to chemical breakdown from exposure to ultraviolet sunlight, and therefore requires expensive extra treatment. Accordingly, there exists a need for a current-carrying fabric which overcomes the problems identified above.

SUMMARY OF THE INVENTION The foregoing problems are solved by the present invention. One object of the present invention is to provide a current-carrying fabric in which electrical current is carried after substantial breakage anywhere in the fabric, without loss or diminishment of current downstream of the break.

Another object of the invention is to provide a current-carrying fabric which can be insulated on one side and which provides the maximum efficiency and effectiveness of the electrically conductive wires incorporated in the fabric.

Another object of the invention is to provide a current-carrying fabric which reduces or eliminates the need for non-conductive clips to be used to prevent current from draining into the attachment posts. Another object of the present invention is to provide a current-carrying fabric which is substantially less susceptible to distortion than other products.

Another object of the present invention is to provide a current-carrying fabric which is substantially less susceptible to wind-stress than other products.

Another object of the present invention is to provide a current-carrying fabric which reduces or eliminates the need to provide the ground side of the circuit through the earth.

Another object of the present invention is to provide a current-carrying fabric which is not susceptible to chemical breakdown from exposure to ultra-violet sunlight. In order to meet these and other objects of the present invention which will become apparent with reference to the disclosure belpw, the present invention employs warp-knitting in novel ways to provide particular advantages. The fabric of the invention differs from known products, which are made by a weaving or braiding process. The present invention provides a current-carrying fabric havinga plurality of current-carrying wires in which knitting is used to cross the wires of the fabric at regular intervals so that the fabric is capable of carrying current in the presence of breakage of the majority of wires without loss of electrical performance. Such crossing methods are not available in the weaving art or braiding arts. Other methods that are available in the weaving arts are less efficient.

The present invention provides a current-carrying fabric havinga plurality of current-carrying wires in which the knitting art is used to keep the wires on the front face of the fabric thus electrically insulating the back face, reducing the need for added insulating devices to insulate the fabric against supports to which the fabric is attached. Such insulation of a side of the fabric is only available usingweaving technologythrough the use of an inordinate amount of yarn creating an entire second layer of fabric under the first. By the same method of using knitting to keep the wires on the front face of the fabric, the present invention utilizes the current carrying wires in the most efficient way by presenting a greater surface area of current carrying wire than is possible in woven or braided products.

The present invention also provides a current-carrying fabric havinga plurality of current-carrying wires where warp-knitting defines a warp direction and an lay-in direction, where the knitting art is used to create a fabric, and where heat- setting is used to fix the shape of that fabric so that it is capable of resisting skewing and bowing distortions in the warp direction and in the lay-in direction.

The present invention utilizes knitting to provide an open current- carrying fabric comprising a plurality of current-carrying wires which is capable of allowing air to pass through the fabric in a way that is unavailable withweaving or braiding, thereby reducing wind resistance and consequent wear on the fabric.

The present invention utilizes knitting to provide an open current- carrying fabric havinga plurality of current-carrying wires where two separate bands of a plurality of current-carrying wires are carried through the same fabric, and the two separate bands are held apart from each other with an open fabric such that current will not pass from one band to another, even in more wet conditions than is possible with woven or braided products. As a result, the present invention provides a method for creating a circuit with both sides of the circuit embodied in the fabric. This facilitates the generation of a fence across or enclosing an area of ground, including surrounding the area with a fence including at least two supports and a current- carrying fabric attached to the supports, where each support contacts the earth and no current is carried through the earth as part of the circuit. The present invention also uses polyester fibers which are more resistant to degradation due to ultra-violet rays than are the current woven and braided products made of polypropylene unless such polypropylene products are specially treated, adding unnecessary cost. The fabric described herein can be used in a variety of applications.

One category of use lies in agricultural fencing, in order to corral or otherwise contain or control farm livestock (electrical side faces inward), to enclose and protect areas such as planted fields and gardens, open storage silos, an honey bee hives, from wildlife (electrical side faces outward), or to protect trees from wildlife. In the latter case, the insulation of one side of the fabric allows the fabric to be wrapped around the tree without discharging electricity into the tree.

A second category of use is as a portable, flexible, "power strip." Light emitting diodes (LED's) can be attached to the fabric by means of clips. Such a system would be useful at accident scenes, construction sites and any other kind of situation which requires temporary or short-term marking. Such applications may require variations in construction, including removal or rearrangement of a wire, but with the same basic concept.

A third category of use is for static absorption and protection. The fabric of the invention can be used to absorb static electricity in the manufacturing of certain products, such as in the textile industry. Warp-knit fabrics are commonly used as a reinforcement substrate. This fabric can be used in construction materials such as concrete, sheetrock, or plywood to create a static-free environment, for example, in rooms or buildings.

Still another category of use is for heat dispersion, collection, and/or distribution. The fabric can be spread across a large area to allow heat from a single source-point to be dispersed across the metal surface areas. The fabric can be spread across a wide area to capture heat and transmit it to a point. The fabric can be used to distribute heat through materials, e.g., in clothing such as winter or ski- wear, in concrete blocks as a substrate to both strengthen the concrete and permit heating thereof melt snow or ice, in heated seat-pads for ski-lifts, or in heated sheets of material to melt snow off cars.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects of this invention, the various features thereof, as well as the invention itself, may be more fully understood from the following description, when read together with the accompanying drawings in which: Fig. 1 is a diagram of a prior art woven fabric; Fig. 2 is a diagram of a warp-knitted fabric in accordance with the present invention;

Fig. 3 is a diagram showing two bands of wires for a warp-knitted fabric in accordance with the present invention;

Fig. 4 is a stitch diagram of a fabric in accordance with an exemplary embodiment of the present invention;

Fig. 5 is an illustrative diagram illustrating guide bar threading in accordance with an exemplary embodiment of the present invention; and

Fig. 6 is a an illustrative diagram showing an edge-on view of a fabric in accordance with an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS Referring to Fig. 2 the fabric of the present invention advantageously includes, current-carrying wires 201, 202 crossed at regular intervals 221, 222 in the fabric 210. The current-carrying wires 201, 202 cross and contact each other at the regular intervals, which may be, for example, intervals of approximately V-.-inch, allowing electrical current to be conducted from one wire to another. The arrangement of Fig. 2 permits the fabric 210 to withstand even substantial breakage of the wires 201, 202, without compromising the ability of the fabric to carry electrical current. In figure 2, any two of the three wires can be cut at a given point in the fabric and the current will be restored to those wires at the next contact point with the uncut wire without loss of current carrying performance in the fabric. Multiple such breaks in the wire can occur in the fabric without loss of performance. Note that while there is a minimum of two wires, the maximum is limited only by the width of the machine, hi any case if all but one wire are cut at a given point, the fabric will still retain its ability to convey the full amount of current. Only if all the electrically conductive wires are cut at the same spot is the capability of the fabric to carry full current comprimised. Note also that the number of crossings of the wire and the intervals between them may be adjusted. The warp-knitted, current-carrying fabric 210 has two sides, one of which may carry the current-carrying wires 201, 202, and one side which may be electrically insulated. The electrically insulating material is preferably in the form of the plurality of electrically insulating yarns. The insulated side (603 in Figure 6) allows for greater safety for people or objects on that side. Furthermore, the insulation helps to insulate the fabric against the supports (not shown) to which the fabric is attached. A polyester coating (not shown) may also be laminated onto the electrically insulating material to further insulate the fabric. The fabric may then be attached to two or more supports in order to form an electrical fence. For example, the second side of the fabric may be attached to the supports with staples, where the staples do not contact the current-carrying wires in the fabric (404 in Figure 3). As a result, it is unnecessary to insulate the fabric by connecting the fabric to the post using non-conductive elements, such as pieces of molded non-conductive plastic which can be expensive, and time-consuming to erect. The number of supports will depend on the configuration of the space to be enclosed or separated by the fence.

Between the points at which they are attached to the fabric (221 and 222) the current-carrying wires 201, 202 are raised up to lie on top of the non- conductive fabric. The current-carrying wires are warp-knitted together with a plurality of electrically insulating yarns to form the fabric. Figure 6 demonstrates the electrical wires being raised off the surface of the fabric (602). By raising the wire off the surface of the fabric we create a greater surface area than do woven products.

The fabric of the present invention, like warp-knitted fabrics in general, resists distortion in both the warp and the in-lay direction, commonly referred to as bowing and skewing. This fabric is more resistant when it is heat-set. As used herein, the term "heat-set current-carrying fabric" refers to a current-carrying fabric which is treated by heat-setting. As used herein, the term "heat-setting" refers to a process of forming the fabric into a desired shape and baking the fabric to set the fabric into the desired shape. The fabric may be baked at a temperature of about 300- 450 °F, such as, for example, 360-385 °F, to give the fabric the stiffness to resist distortion further.

The dimensions of the fabric may vary over a wide range. As an example, the fabric may be about 1 centimeter in thickness and have a width from about 0.5" up to the width of the knitting machine (230"). The length of the fabric may be of any length necessary for the application in which the fabric is used. However, the generally open knitting confers an advantage over woven and braided products in that wind can pass through the product without unduly stressing the fabric. In one preferred embodiment of the invention, the current-carrying wires form two separate bands. As used herein, the term "band" refers to at least two current-carrying wires running lengthwise along the fabric across on at least a portion of one side of the fabric. As shown in Fig. 3, two separate bands (301 and 302) are bands in which none of the wires of each band contacts any of the wires of the other band. Each separate band is warp-knitted with the electrically insulating yarns of the fabric. A fabric may be waφ-knitted with both separate bands or with only one of the two separate bands. Each band may be used as either the line side of the circuit or the ground side of the circuit. The two bands may be separated from each other by a sufficiently large separation zone which contains a sufficiently low density of intervening yarns that current does not pass between the bands, even in the presence of moisture in the separation zone, which may be due to, for example, wet weather. At the same time, the separation zone is small enough that a person or an animal that touches the fence generally completes the circuit and receives a shock. Such a separation is generally not available in the weaving art, particularly in wet weather.

The resistance to distortion of the fabric is sufficiently high in both the warp direction and the in-lay direction that the fabric does not fold in on itself creating a short circuit. This embodiment offers significant savings in cost and effort over generally available fences because there is no need to construct a separate return side of the circuit through the earth. It also means that far less voltage is needed to complete the circuit since it is not necessary to overcome resistance in the earth. The strands of the wires which are raised off the surface may effectively provide electrical shocks to animals coming in contact with them, or may be used to attach other electrical devices such as small lights.

The present invention takes advantage of the tensile strength offered by the electrically insulating yarns and by the knitted structure to remove any tensile burden from the current-carrying wires. This allows the usage of thinner, less expensive current-carrying wires in the product. When lamination is added, for example, to increase insulation, as noted above, it also increases the tensile strength of the fabric. 600 and 1200 denier yarns are preferably used in the stitches to remove the tensile burden from the current-carrying wires. The use of polyester as the electrically insulating material in the yarns also makes the fabric more colorfast and more resistant to chemical breakdown in ultra-violet sunlight than is the case for previous fabrics made with polyurethane or polypropylene. Polyester is also more weather resistant and is therefore more suitable for preventing fading and disintegration due to bacteria and weathering.

Referring to Figs. 4-6 an exemplary embodiment utilizes a combination of electrically insulating synthetic polyester yarns and electrically conductive wires that are knitted via a guide-bar threading in accordance with Fig. 5, to construct a material in accordance with Fig. 4. An edge-on view of such a fabric is shown in Fig. 6.

The yarns may be of any color, but ideally, should be of three different colors for best visibility by livestock, wildlife and humans. The colors of the yarns may be, for example, black, white, and a fluorescent yellow or red or any bright color. Black and/or white are visible to animals under varied color conditions including green backgrounds (grass), brown backgrounds (dirt), white backgrounds (snow), or sand backgrounds. Bright colors are visible to humans. Reflective yarns may also be included in the fabric, lending even more visibility under various weather and light conditions. Glow-in-the-dark and other luminescent yarns may also be used to make the fabric more visible in the dark.

For applications where the electrical current output is critical, as is the case, for example, for wires used in electrical fences or in a "power strip", current- carrying wires should be highly electrically conductive and of low resistance. For applications where heat output is critical, as is the case, for example, in heated ski-lift seats, more electrically resistant current-carrying wires may be used.

Figures 4-6 illustrate an exemplary machine layout for the production of a fabric on a "Raschel-type" flat warp-knitting machine. Figure 4 (the "stitch diagram") shows the movement of different threads or "ends" of electrically insulating yarn or electrically conductive wire through the fabric as the fabric is constructed. Same-color yarns move in the same pattern through the fabric. Figure 4 shows at least one of each different motion pattern. The motion of the yarns is controlled by guide-bars which are shown as 501 in Figure 5. Each guide-bar guides the ends of yarn back and forth horizontally in a pattern which may be different for different yarns. All the yarns threaded into a given guide-bar make the same motion in different locations across the width of the fabric. Figure 5 shows each of the guide bars as a separate row. The presence of a square in a column of that row indicates that a yarn must be threaded at that point in the guide bar. If there is no square, no yarn is present in that guide bar at that point.

A portion or "course" of the fabric, shown as 405 in Figure 4, is formed during each warp-knitting cycle. During each cycle, a stitch of yam is formed and the fabric is moved forward by the machine. As shown in Figure 4, rows of knitting needles, shown as 406 in Figure 4, are present across the warp-knitting machine. Each row of needles in Figure 4 represents one course. Figure 4 shows a sufficient number of courses, equal to sixteen courses for the fabric shown in the figure, to take the fabric through one full length "repeat." Figure 4 shows only one full width "repeat" or one full width of the fabric. Accordingly, it will be readily understood by persons skilled in the art that there are more needles on the machine than are shown in Figure 4.

The fabric shown in Figure 4 is made on a machine with 9 needles per inch or one needle per 0.111 inches. In Figure 4, there are 15 needles across the width "repeat," coπesponding to a fabric width of 15 x 0.111 inches or 1.667 inches. Those skilled in the art will appreciate that other widths can be implemented. Thus, wider fabrics up to 120 inches will include more strands of yarn and electrical wire, and slight concomitant variations in the stitch construction, but the above-described elements of crossing wires, raised wires, and an electrically insulated side remain featured regardless of the fabric width.

In wider fabrics, where wind-resistance may be an issue, the fabric may be less tightly knitted than in narrower fabrics so as to allow for the passage of air without creating unnecessary tension on the fabric. It is also noted that different applications will offer the opportunity to use different wires. Where only short distances need to be covered, the product can use wires with greater resistance.

The fabric of Figure 4 includes a right edge and a left edge. The edges do not include current-carrying wires. Therefore, at least one of the right edge and the left edge may be attached to one or more attachment regions on each of at least two supports without requiring the current in the current-carrying wires of the fabric to be grounded. The foregoing merely illustrates the principles of the invention. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in view of the teachings herein. It will thus be appreciated that those skilled in the art will be able to devise numerous systems and methods which, although not explicitly shown or described herein, embody the principles of the invention and are thus within the spirit and scope of the invention.

Claims

WE CLAIM:

1. A warp-knitted current-carrying fabric comprising a plurality of current- carrying wires, wherein the wires cross periodically.

2. The fabric of claim 1, wherein the plurality of crossed current-carrying wires are warp-knitted together with a plurality of electrically insulating yarns.

3. The fabric of claim 2, wherein the electrically insulating yarns are polyester yarns.

4. The fabric of claim 2, wherein the current-carrying wires and the electrically insulating yams which are warp-knitted together form a surface, wherein strands of at least some of the current-carrying wires are raised off the surface.

5. The fabric of claim 1, wherein the fabric comprises at least one electrically insulated side.

6. The fabric of claim 1, wherein the fabric comprises current-carrying wires only on a one side of the fabric, and wherein a second side of the fabric is electrically insulated.

7. The fabric of claim 5, wherein the electrically insulated face is made of an electrically insulating material.

8. The fabric of claim 7, wherein the electrically insulating face is coated or laminated..

9. The fabric of claim 6, wherein the fabric is capable of being attached to at least two supports by attaching the back face of the fabric to the supports.

10. The fabric of claim 1, wherein the current-carrying wires form two separate bands.

11. The fabric of claim 10, wherein the two separate bands of current-carrying wires are warp-knitted with a plurality of electrically insulating yarns.

12. The fabric of claim 11, wherein the two bands are separated by a separation zone which is sufficiently large and which contains a sufficiently low density of intervening electrically insulating yams that current does not pass between the bands.

13. The fabric of claim 1, wherein the fabric includes a right edge and a left edge, wherein each of the right edge and left edge does not comprise current-carrying wires.

14. The fabric of claim 13, wherein at least one of the right edge and the left edge is capable of being attached to one or more regions on a support.

15. The fabric of claim 1, wherein the current-carrying wires cross and contact each other at approximately ' .-inch intervals.

16. The fabric of claim 1, wherein the fabric is heat-set at a temperature between 300 and 400 °F.

17. A current-carrying fabric constructed by warp-knitting, wherein the warp- knitting defines a warp direction and an in-lay direction, wherein the fabric is sufficiently resistant to distortion in the waφ direction and in the in-lay direction that the fabric does not fold on itself.

18. The fabric of claim 13, wherein the electrically insulating face is coated or laminated.

19. The fabric of claim 7, wherein the electrically insulating face is coated or laminated.

20. A method for enclosing an area of ground, comprising the steps of

(a) surrounding the area with a fence comprising at least two supports each of which contacts the ground, and (b) attaching a warp-knitted current-carrying fabric to each of the at least two supports, wherein the method does not comprise carrying current through the earth.

21. The method of claim 19, wherein the fabric is attached to each of the at least two supports at one or more attachment regions on each support, and the method does not comprise providing non-conductive elements contacting the fabric and the one or more attachment regions on the support.

22. The method of claim 21, wherein the fabric comprises an insulated face and step (b) comprises attaching the insulated face of the fabric to the supports.