GB2112093A - Strand tensioning device - Google Patents

Abstract

A strand tensioning device for attachment to a fence-post 17 is free from corrodible screw-threaded members, and has a shank 25 with end plates 3 bent to lie parallel so that orifices 4 in each plate 3 are aligned. Each orifice is generally in the shape of a square with internally radiussed rearward corners, a recess at the top forward corner and a step at the bottom forward corner. Spindle 1 for a strand 2 is loosely held in orifice 4. It can be rotated one way so that its corners pass over the step, and the strand is tensioned. On rotation the other way it jams, one edge lodging on the step and the opposite edge lodging at the top edge of the orifice 4. Thus, the tensioned strand is held. <IMAGE>

Description

SPECIFICATION Strand tensioning device This invention relates to strand tensioning devices, i.e. which as can place a strand such as a wire rope or cable under tension for structural purposes or for load-supporting or lifting. In particular it relates to a tensioning device for wire fencing strands, and it will for convenience be described primarily with reference to this particular purpose.

It is commonplace to provide fencing comprising a number of spaced posts jointly carrying several parallel wire strands. The wire strands can constitute the whole of the fence material (other than the posts) or may themselves be support strands for other material such as chain link wire mesh. In either instance they are typically supported and directed every few metres by a succession of posts, but only attached every sixty metres or so, often at a more substantial braced post or corner post. At this point of attachment the wires are pulled tight before being fixed.

Most tensioning means used at such points of attachment depend in some way on a screwthreaded member. This has the disadvantage that such members can become damaged or corroded, either on transport or storage, or during assembly.

They thus become difficult to use. Also, after a period in situ, the wires may become slack e.g.

due to settlement of support posts or vandalism.

Threaded tensioning members by this time may have become too corroded for ready use or may have reached the end of their adjustment travel.

The present invention sets out to provide a tensioning device which does not utilise an adjustable threaded movement, which can be operated with simple tools even after a period in situ, which resists careless usage and storage, and which has a substantial adjustment facility.

In one aspect the invention provides a strand tensioning device having a winding spindle for the strand held in like oversized orifices in parallel support members, the spindle having a square cross-section at least at those regions lying within the orifices: one edge of each orifice being provided with a step which traps the square section of spindle against rotation in one direction but allows the square section to roll down over the step and continue rotation in the other direction so as to tension the strand.

Preferably the spindle is of uniform square section throughout its length, and protrudes from the supports at one end to facilitate turning.

The orifice can, for example, be of generally square shape with a step in a lower corner which thereby defines a minor area of the orifice somewhat higher than necessary to accommodate one edge region of the spindle square section. In these conditions if the square starts to rotate to release the tension, one corner of the square engages with the platform, one with the forward face of the orifice, and one with the top edge of the orifice so that no such release is possible. The step should be low enough, however, that rotation of the spindle in the "tightening" direction allows the spindle to roll over the edge of the shelf without its topmost corner hitting the top edge of the orifice.

It is preferred in practice, even if not geometrically necessary in theory, for an additional shallow recess to be provided at one end of the top edge of the orifice, so as to accommodate any "chattering" displacement and undesired contact of the topmost spindle edge with the orifice edges during tightening.

The tension device can be embodied as an T-shaped metal bracket member with the arms of the T folded parallel out of the plane of the T and provided with like orifices to hold a spindle of square section (at least over part of its length) as described above, and with the shank of the T adapted for securing to a post or the like.

Such a bracket when assernbled to a suitable fence post also constitutes an aspect of the invention.

The invention will be further described with reference to the accompanying drawings, in which: Figure 1 shows diagrammatically an end view of the spindle of a strand tensioning device immobilised in relation to its support, Figure 2 shows diagrammatically an end view of the spindle of a strand tensioning device in a position capable of rotation in relation to its support.

Figure 3 is a composite diagram showing a number of possible spindle positions, and Figure 4 shows in perspective view a practical embodiment of strand tensioning device by way of example.

Figures 1 and 2 show a square-section spindle 1, a strand 2 wrapped around the spindle, and an end support plate 3 within which is formed a specially shaped orifice 4. There are two or more of such support plates, aligned and parallel, with the spindle extending between them.

Orifice 4 is generally in the shape of a square with internally radiused rearward corners 5 and 6, a recess 7 at the top forward corner and a step 8 at the bottom forward corner, forming a flat platform 9.

The relative dirnensions of the spindle 1 and orifice 4 are such that: (a) to lock the spindle under tension from the strand, corner 1 a of the spindle engages with the platform 9, corner, 1 b with the forward edge of the orifice 10 and corner 1 c with the top edge of the orifice 11, all as shown in Figure 1, (b) to rotate the spindle so as to increase the tension, the corner 1 b just clears the top edge at 12 at a time when corner 1 a engages with the forward edge of the orifice at 13 and the face 14 of the spindle engages with the end 1 5 of the platform 9, all as shown in Figure 2.

Clearly, it is possible to rotate the spindle for the required number of times needed for the desired tension. The composite diagram of Figure 3 shows four typical orientations of the spindle 1 in the orifice 4 during one-quarter of a complete revolution. Although in practice the spindle chatters in the orifice, due to the inevitable incidental forces other than strictly rotary, the approximate locus of spindle corners is as shown by the dotted line.

The shape of the rearward part of the orifice generally indicated at 1 6 is therefore not critical, and can be of any non-interfering rounded shape.

Provision of recess 7, however, while theoretically unnecessary is much preferred in practice since it allows for initial or incidental non-rotary displacement of the spindle 1, without corner 1 b (Figure 2) thereby binding in the corner at an orientation whereat the strand tension jams the spindle.

By way of example only the combination of spindle 1 and end plates 3 can comprise the following dimensions and material.

Spindle 1-13 mm square section, bright drawn steel.

End plates 3-4 mm thick, mild steel, 38 mm wide.

Orifice 4 - length (A) 22 mm - height (B) 21 mm Recess 7-2 mm deep, 8 mm opening step 8 - 5 mm platform length, 6 mm high radiussing orifice corner - 5 mm radiussing recess 7 cornerZ mm.

Figure 4 shows one example of the use of such a strand tensioning device, as a tensioner for wires attached to fence posts.

A fence post 1 7 is formed, as known per se, from a cold-rolled mild steel strip deformed to exhibit a dove-tail section groove 1 8 on flat face 19, and two curved portions 20 meeting at 21 at a joint which can be suitably welded for strength.

Frequently, a cap is placed or welded over such a post, but in the drawing any such cap is omitted for clarity of illustration.

In use, such posts are fixed every few metres to space and support wires which are attached to posts at say 20 metre intervals, by some tensioning arrangement. These support posts are typically provided with angled side braces.

Groove 1 8 contains and secures against rotation a nut, not shown, which can be slid to a desired height and then used to position a projecting bolt 22. This in turn can carry a nut 23 serving to secure a tensioning bracket 24.

Tensioning bracket 24 possesses a shank 25, an eye 26 at one end, and an inwardly bent lug 27 projecting from one side of shank 25 so as to lie within the walis of groove 1 8. At the other end it is bent to define two parallel supports each constituting an end plate 3 as shown in Figures 1, 2 or 3. Orifices 4 are provided in these end plates 3 as shown, to hold spindle 1 supporting tensioning wire 2 (typically with one end thereof held in a through bore in the spindle). Spindle 1 has a circular disc 28 welded thereto to facilitate initial assembly.

Operation of the device will be apparent from the discussion of Figures 1, 2 and 3. A squaresection special tool, or suitable wrench or spanner, is used to turn the spindle 1 in order to tension the wire 2. If the wire becomes slack in use, it can be readily re-tightened even after lengthy external weathering, since there is no screw-thread to rust.

If desired, instead of, or as well as, securing the bracket 24 to a post 1 7 it can be secured via eye 26 to a second strand extending in the opposite direction.

Lug 27, immobilised in groove 18, acts to prevent any tendency to rotate about bolt 22, which can arise when the tensioning wire meets the spindle 1 at or near one end.

Claims (9)

1. A strand tensioning device having a winding spindle for the strand held in like oversized orifices in parallel support members, the spindle having a square cross-section at least at those regions lying within the orifices: one edge of each orifice being provided with a step which traps the square section of spindle against rotation in one direction but allows the square section to roll down over the step and continue rotation in the other direction so as to tension the strand.

2. A strand tensioning device as claimed in claim 1 in which the spindle is of uniform square section throughout its length, and protrudes from the supports at one end to facilitate turning.

3. A strand tensioning device as claimed in claim 1 or 2 in which the orifice is of generally square shape with a step in a lower corner which thereby defines a minor area of the orifice somewhat higher than necessary to accommodate one edge region of the spindle square section, the step being low enough that rotation of the spindle back over the edge of the step can take place without a spindle edge hitting the further edge of the orifice.

4. A strand tensioning device as claimed in claim 1, 2 or 3 in which an additional shallow recess is provided at one end of the top edge of the orifice.

5. A strand tensioning device as claimed in any one preceding claim embodies as a T-shaped metal bracket member with the arms of the T folded parallel out of the plane of the T and provided with like orifices to hold the spindle at its square section, with the shank of the T adapted for securing to a post or the like.

6. A strand tensioning device as claimed in claim 1 and substantially as herein described.

7. The assembly of a fence post and strand tensioning device as claimed in any one of preceding claim.

8. The assembly as claimed in claim 7, in which the fence post has a groove along a front face, and in which a member protruding from the strand tensioning device can locate in the groove to prevent rotation of the strand tensioning device.

9. A fence including one or more assemblies as claimed in claim 7 or 8.