1. Field of the Invention
The present invention relates to articulating fencing systems and, more particularly, to a radially articulating fencing system.
2. Description of the Related Art
Farmers and ranchers use fences, walls, hedgerows and other boundary markers to demarcate territory, and to control ingress and egress of persons and animals from and to the boundaries territory. With the advent of large cattle and sheep ranches, particularly in the Western United States, fences are used primarily to restrain domestic livestock from leaving a fenced in area. These western style fences are typically built from four or five horizontally spaced strands of barbed wire, mounted on wooden fence posts that are driven into the ground. A single fence, often stretching for miles, is used to delineate a xe2x80x9crangexe2x80x9d or xe2x80x9cpasturexe2x80x9d where herds of cattle, or other grazing animals, are confined.
Multi-purpose land use methods have brought crop cultivation and the raising of livestock together on the same land. These multi-use methods involve dividing a tract of land into several parcels and rotating the function of the parcels between crop cultivation and livestock feeding. These methods typically involve concentrating dense populations of livestock, such as feeder cattle and dairy cattle, on one parcel while crops, such as grains and seeds, are being cultivated on the others. Since cattle fed in this manner are in high density, barbed wire fences, and fences that have electrified strands of wire, are needed to confine the cattle in the parcel. Multi-purpose land use methods have gained widespread acceptance in the agriculture business because they generate increased yields of table meat from cattle by providing abundant food supplies for fattening cattle prior to slaughter.
With the requirement for increased agriculture production, especially in arid climes, sophisticated irrigation systems and methods have become a necessity to increase acreage yields. Today, these systems are usually automated, using computers, and can cover extended acreage without being manned. Water pressure and electricity are commonly used to provide the energy to move these systems. The irrigation systems which have mechanized means of movement such as drive wheels mounted under spray irrigation carriages. A pivotal irrigation system, for example, is anchored at a center point and rotates about that point on large cleated wheels, mounted under a spray irrigation carriage, to sweep out an irrigation circle which can be a mile or more in diameter.
The close proximity of cattle pastures and domestic crops created by modern, multi-purpose land use methods have put an unforseen burden on irrigation systems. The fences, necessary for separating cattle pastures from growing crops, greatly hinder the mobility of irrigation systems over a tract of multi purpose farmland. Large irrigation systems designed to efficiently irrigate large tracts of land, such as a pivotal irrigation systems, become impractical if they are obstructed by fences.
One approach to allow a fenced area to be irrigated, has been to place gaps in the fence which are wide enough for the cleated wheels of the irrigation system to pass. Unfortunately, the cleated wheels are so wide that the gaps in the fence are large enough to let livestock, including cattle, pass as well.
Another approach is to have crews move the fence in the path of the irrigation system and then replace it. This is labor intensive and expensive. It would therefore be advantageous to have fencing system that could articulate under the force of the moving irrigation system wheels, yet be resilient enough to retain livestock. Unfortunately, there are a number of problems associated with such a system. First, the fence must be able to yield to the force of the cleated wheels and articulate from its upright position, perpendicular to the ground, to a substantially flattened position that is parallel with the ground. Second, the fence system must maintain the strand integrity to keep from snapping wire strands as the fence articulates.
Articulating fence systems have been suggested for varying uses, such as flood-fences built along river banks that are prone to regular flooding. U.S. Pat. No. 567,333 issued to Chandler, for example, discloses fence posts and fences that can pivot on a hinge from an upright position normal to the ground, to a flattened position parallel with the ground. Unfortunately, a number of problems arise when attempts are made to adapt these fence systems to use with mobile irrigation systems on farmland.
Many hinged fence systems disclosed in the prior art are designed to remain parallel with the ground after being knocked down, and must be re-erected by hand to their upright positions. Such systems defeat the benefit of having a computer-controlled, self-propelled irrigation system, since they must be monitored and re-erected. Moreover, fences which are down for even a short time create a possibility that livestock will migrate from their designated pastures. In addition, they are labor intensive and thus expensive.
There are additional problems with fence systems disclosed in the prior art. Those that have some kind of resilient means, such as a spring mechanism, which allow the fence to spring back to an upright position after being knocked down by the irrigation system, are hinged at their base so as only to pivot in a single plane. If an irrigation system does not approach the fence in a direction that is perfectly aligned with the articulation direction of the fence system, then the irrigation system imparts side loads on the fence and can cause permanent damage to both systems. This problem is particularly acute for the widely used irrigation systems that rotate around a fixed center point. These systems commonly exert side load forces on the fence, causing either the posts or the wire strand to break or to be damaged.
Presently, there is a need for an articulating fencing system that can allow passage of the irrigation system and accommodate the side loads exerted on the fence by the irrigation system. This need is especially great for fence systems which have delicate strands of electrified fencing wire which are easily snapped under the strain of an impinging irrigation system that moves along an arc that is not perpendicular to the fence line.
It has now been discovered that the problems encountered with prior art fencing systems can be overcome by the present invention. In the broad aspect of the present invention, a fencing system is provided that comprises at least two fence posts, wherein at least one of the fence posts is a resilient, isotropically articulating member, and the posts have strung there between at least one strand of flexible fencing material, such as a wire or cord. In accordance with the present invention, the system resiliently yields to forces exerted in substantially all directions, including directions other than those perpendicular to the fence line.
In accordance with the broad aspect of the present invention, the fencing system contains at least one isotropic fence post that resiliently yields to an object (e.g., a mobile irrigation system) approaching the fencing system from any direction, even a direction substantially parallel to the fence line. The fencing system yields to objects resistively. For example, the system will resiliently yield to a mobile irrigation system, but not to the force of a cow moving against the fence. In a preferred aspect, the resistance to a force pressing against the fence system is variably set, causing the fence posts to substantially yield only when a preset amount of force is applied. For example, the resistance can be set such that the force of a strong wind or a herd of cows will not cause the fence posts to articulate, but the force of an impinging irrigation system will.
Preferably, the fence system of the present invention has at least three posts, including at least one resiliently articulating center post that is aligned between a pair of end posts, wherein a flexible fencing material is strung between adjoining posts. The at least one center post of the present invention is a resilient, isotropically articulating member that preferably includes a shaft adapted for affixing flexible fencing material; a resilient, isotropically flexible member having a top end for rigid communication with the shaft and a bottom end for rigid communication with a base element; and an anchor element, connected to the base element, for anchoring the base. The flexible fencing material preferably comprises strands of wire, either single strand or braided, including strands of electrically conducting metal for electric fences, and strands of barbed wire.
The end post elements of the system of the instant invention can be resiliently articulating, or they can be rigid, non-articulating supports. In a preferred aspect, the end posts are non-articulating. It will be realized that in accordance with the invention the end post elements may also form the apex of a corner that is formed from two linear segments of fence which are joined together at an angle (i.e., the end post is a corner post). At least one segment so joined is radially articulating.
In accordance with a preferred aspect of the present invention, the resilient, isotropically articulating posts have an isotropically flexible member for allowing a shaft to resiliently articulate between a position substantially perpendicular to the ground, and a position substantially parallel to the ground. In a preferred embodiment, the isotropically articulating member is a spring, and preferably a coil spring, that is able of radial, resilient articulation. In another embodiment, the isotropically flexible member is a segment of flexible hose, preferably made from plastic or rubber.
Preferably, a fence material tensioning means, such as a coil spring, is used to attach a strand of fencing material to at least one post element of the fencing system. The tensioning means provides flexibility to assure the integrity of the fence material when the fence is under stress. This is to further assure that strands of fencing material in the fencing system will not break when the fence posts are articulated.
In one preferred embodiment, the tensioning means includes at least one spring element connected at one end to a strand of fencing material and on the other to a variable set tensioning means, such as a turnbuckle, which adjusts the amount of tension on the strand. In another embodiment, the tensioning means comprises two spring segments having a variable set tensioning means there between. In another embodiment, the tensioning means comprises a spring loaded pulley assembly rotatably attached to the end post assembly. A strand of fencing material is spooled on the pulley and held in tensioned engagement therewith.