This invention relates to fence tensioners especially designed for use with flexible polymer fence slats.
Fences are the most commonly employed means for confining that which would otherwise escape and excluding that which would otherwise intrude. Fences may vary greatly in both structure and materials of composition. Common fence structures include wire fences, such as barbed wire and chain link, and wood fences such as, picket fences and split rail fences. Common fence materials include metal, wood and stone. Fence structure and composition are selected on the basis of initial and upkeep costs, durability, strength, aesthetic characteristics, and safety desired or required.
One very common form of fencing is barbed wire. The relatively low cost of purchasing, installing, and maintaining barbed wire fencing has made it the preeminent fencing material for enclosing livestock areas. Barbed wire suffers from the disadvantage, however, that its sharp barbs may cut or gouge the hide of valuable livestock. Furthermore, barbed wire has a very thin cross-section so that it is not easy to see; and an animal is correspondingly more apt to contact a barbed wire fence than it would be to contact a more visible barrier. Other types of wire fencing known in this art, such as web wire fencing, and cyclone wire fencing, suffer from similar limitations. These wire fences also tend to have poor aesthetic qualities and they tend to rust or corrode after a few years of service. Fences made entirely of wood, on the other hand, are typically safer and more pleasing to the eye, but are expensive to install and maintain.
Over the past several years, composite metal and plastic fence systems have become increasingly accepted for the confinement of livestock, thoroughbred horses and the like. Typically, the fence slats are comprised of at least two wires or other high strength fibers encased in a polymer such as vinyl or other suitable plastic web. Depending on the width of the fence slat, two wires may extend along the opposite edges of the slat or, for wider slats, a third wire may be added intermediate the edge wires. Examples of such fencing construction can be found in U.S. Pat. Nos. 4,465,263 and 4,706,942.
To maximize the effectiveness of the flexible fence slats, tensioning devices must be utilized to insure that the individual slats do not sag between posts. Fence tensioners have long been used to tighten individual strands in wire fence systems. Examples may be found in U.S. Pat. Nos. 393,504; 420,819; 473,899; 516,040; 596,987; 658,671. A fence tensioner for polymer fence slats is disclosed in the more recently issued U.S. Pat. No. 6,152,429.
The present invention relates to an improved fence tensioner designed especially for use with flexible polymer fence slats with reinforcing wires embedded therein. In one exemplary embodiment, a tensioning cylinder is mounted for rotation in a pair of bracket flanges formed in respective discrete attachment webs. The attachment webs are designed for adjustment at the manufacturing stage to change the distance between the bracket flanges to accommodate tensioning cylinders of different lengths, thus allowing the tensioning device to be used with fence slats of different widths. Once the appropriate cylinder has been located between the flanges, with integral axle stubs received in aligned holes in the flanges, the attachment webs of the bracket assembly are riveted or otherwise permanently secured to each other.
The tensioning cylinder has a smooth peripheral surface with annular grooves located so as to corresponding with the location of the embedded wires in the fence slat. A longitudinal slot through the cylinder is designed to receive a free end of the fence slat, without having to strip the plastic from the ends of the reinforcing wires. An integral ratchet wheel is formed on the cylinder, inside and adjacent one of the bracket flanges. Teeth on the ratchet wheel are adapted to be engaged by a pawl pivotally mounted on the bracket flange. This is a conventional ratchet and pawl arrangement that permits rotation of the ratchet wheel in a tensioning direction but prevents rotation in an opposite or tension release direction. In this regard, the pawl may be spring biased into engagement with the ratchet wheel, or may be manually moved into or out of engagement by means of a finger tab.
In another embodiment of the invention, a larger bracket assembly is provided that mounts a pair of tensioning cylinders at opposite ends thereof. The adjustability feature at the manufacturing stage for accommodating cylinders of different lengths is maintained.
Accordingly, in its broader aspects, the invention relates to a tensioner device for applying tension to a flexible fence slat comprising a bracket assembly having attachment webs for attachment to a fence post and a pair of vertically spaced, horizontally oriented flanges; a tensioning cylinder mounted for rotation within a pair of apertures provided, respectively, in the horizontally oriented flanges, the tensioning cylinder formed with a through-slot extending longitudinally between a pair of radial flanges, the through-slot having a length substantially equal to a width of the flexible fence slat and adapted to receive one end of the fence slat; a ratchet wheel at one end of the cylinder, between one of the radial flanges and one of the horizontally oriented flanges; a one-way pawl pivotably mounted on the one of the horizontally oriented flanges for engagement with the ratchet so as to permit rotation of the tensioning cylinder in a tensioning direction but to prevent rotation of the tensioning cylinder in an opposite direction; and a finger tab on the pawl for moving the pawl into or out of engagement with the ratchet.
In another aspect, the invention relates to fence tensioner device for applying tension to a flexible fence slat comprising a bracket assembly having a pair of vertically adjustable webs for attaching the device to a fence post and a first pair of vertically spaced, horizontally oriented flanges; a first tensioning cylinder mounted for rotation within a pair of apertures provided, respectively, in the horizontally oriented flanges, the tensioning cylinder formed with a through-slot extending longitudinally between a pair of radial flanges, the through-slot having a length substantially equal to a width of the flexible fence slat and adapted to receive one end of the fence slat; wherein the bracket assembly comprises two mirror image half sections, with one vertical web on one half section in back-to-back relationship with another vertical web on the other half section, each half section formed with a respective one of the pair of horizontally oriented flanges, the half sections being fixed to each other after the tensioning cylinder is mounted within the apertures.
In still another aspect, the invention relates to fence tensioner assembly for applying tension to a pair of flexible fence slats comprising a bracket assembly having a pair of mirror-image half portions, including a pair of attachment webs in back-to-back relationship, one half portion having a first pair of laterally spaced horizontally oriented flanges along an upper edge thereof, vertically alignable with a second pair of laterally spaced horizontally oriented flanges along a lower edge of the other half portion; and a pair of tensioning cylinders mounted between the first and second pair-of horizontally oriented flanges, the pair of tensioning cylinders each having a slot for receiving a free end of a fence slat, and means facilitating rotation of said pair of tensioning cylinders to tension the fence slats and means for locking the fence slats in a tensioned position.
The invention will now be disclosed in further detail in connection with the drawings described below.