GB2093198A - Indicating tension in a line - Google Patents

Abstract

An indicating device for indicating tension in a line, such as a guy rope supporting a radio mast, comprises two overlapping stirrup- shaped coupling elements 11 between the cross links 13 of which is disposed a rubber slug 16 which is compressed upon movement of the coupling members away from one another. The device connects together two parts of the line so that the compression of the rubber slug indicates the tension applied to the line. The compression may be determined by measurement or from a scale marked on one of the coupling elements. <IMAGE>

Description

SPECIFICATION Method and device for indicating the tension in a line The invention relates to a method and device for indicating the tension in a line and sets out, in particular, to provide a means of resolving the problem of correctly tensioning guy ropes, such as are used for supportiong radio masts and similar structures, wire antennae and catenaries.

The designer of a radio mast or antenna normally specifies initial tensions to be applied to the supporting guy ropes at the installation stage, and inaccuracies in the application of these tensions can invalidate the design and present problems of maintaining verticality and straightness and, in extreme cases, erosion of safety factors.

The problem facing riggers erecting such masts arises because of the difficulty of determining at all times the tension in a multiplicity of guy ropes.

Devices are available for measuring tensions but their use is expensive, particularly in a complex array where scores or even hundreds of tension points occur. Furthermore, these devices are usually only temporarily applied to a particular rope, and are usually moved from one point to another before being finally removed. There is thus a requirement for a tension indicating device which is permanently incorporated in each guy rope so that the tensions in the multiplicity of guy ropes can all be determined readily at any one time.

The initial tension called for, upon installation of a guy rope supporting a radio mast or similar structure, is usually of the order of 10% of the breaking load and is measured in still air. Later, when under wind load, the tension may increase up to one third of the breaking load and therefore a device permanently incorporated in the guy rope must not only be capable of indicating the initial tension, but must be as strong as the rope in which it is incorporated. A reasonable latitude is available in the tension called for, but assessment by "twanging" a taut rope is not sufficiently accurate and an excessive initial tension will then not leave sufficient strength capacity to accord with the designer's intentions.

According to the invention a method for indicating the tension in a line, such as a guy rope supporting a radio mast, comprises forming the line in two parts connected together by an indicating device comprising a resilient member connected between the adjacent ends of the said two parts, and providing means to indicate the change in dimensions of the resilient member upon application of tension to the line.

Preferably the resilient member is put in compression upon application of tension to the line and preferably also means are provided to indicate the change in length of the resilient member, longitudinally of the line.

The invention also provides an indicating device for indicating tension in a line, comprising a first coupling element for connection to an end of one part of the line, a second coupling element for connection to the adjacent end of another part of the line, a resilient member connecting said coupling elements, and means to indicate changes in dimensions of the resilient member.

Preferably said resilient member is so connected to the coupling elements as to be put in compression upon movement of the coupling elements away from one another. The resilient member may comprise a body of resilient material such as natural rubber, synthetic rubber or resilient plastics material.

Preferably the coupling elements are formed with respective abutments which come into engagement with one another to limit the movement of the elements away from one another.

The means for indicating changes in dimensions of the resilient member may comprise edges or markings on the respective coupling elements, the relative positions of which change upon deformation of the resilient member. The extent of the relative movement under tension of the line may be noted by applying a separate scale to the device to measure the distance between the edges or markings. Alternatively a scale may be permanently provided on one of the coupling elements to cooperate with an indicator on the other coupling element.

The following is a detailed description of an embodiment of the invention, reference being made to the accompanying drawings in which: Figure 1 is a perspective view of a tension indicating device, Figure 2 is a section through the device of Figure 1, and Figure 3 is a plan view of the device.

The tension indicating device 10 comprises two interconnected coupling elements 11. Each coupling element 11 is in the form of a stirrup comprising two side links 12 connected by a square cross link 13. The cross link of each stirrup is connected by screws 14 to its associated side links and extends slideably between the side links of the other coupling element.

The opposed faces of the two cross links 1 3 are formed with circular recesses 1 5 having chamfered edges and a cylindrical slug 1 6 of synthetic rubber is located in the recesses and extends between the cross links.

In use, one end of one part of a line, such as a guy rope, is connected to one stirrup-shaped coupling element and the adjacent end of the other part of the line is connected to the other coupling element. It will thus be seen that tensioning of the line will cause the coupling elements 11 to be pulled apart, thereby compressing the rubber slug 1 6.

The compositions and dimensions of the rubber slug 1 6 are carefully controlled in manufacture so that the compression of the slug bears a predetermined relation to the tension in the line.

The initial tension compresses the rubber and the resultant degree of compression indicates the tension load in the line.

In order to indicate the compression of the rubber slug, adjacent side links 12 of the two coupling elements may be provided with marks or edges which move relatively to one another as the slug is compressed. Thus the degree of compression of the slug may be ascertained by measuring the distance between the marks or edges and obtaining from a table the corresponding tension load in the cable.

Alternatively, an indicating mark on one coupling element may cooperate with a scale on the other coupling element, the scale being calibrated to give a direct reading of the tension in the cable.

At a predetermined higher tension the compression of the rubber slug will be such that the initial gap between the cross links 13 closes and the device "bottoms out. At this stage further compression and consequent damage to the rubber is mechanically prevented and the increasing tension is transmitted through the device by metal-to-metal contact between the cross links. When the load is released the compressed rubber separates the links and again the aforementioned calibrated scale provides a reading of the tension in the line.

Claims (11)

1. A method for indicating the tension in a line, such as a guy rope supporting a radio mast, comprising forming the line in two parts connected together by an indicating device comprising a resilient member connected between the adjacent ends of the said two parts, and providing means to indicate the change in dimensions of the resilient member upon application of tension to the line.

2. A method according to claim 1, wherein the resilient member is put in compression upon application of tension to the line.

3. A method according to claim 1 or claim 2, wherein means are provided to indicate the change in length of the resilient member, longitudinally of the line.

4. An indicating device for indicating tension in a line, comprising a first coupling element for connection to an end of one part of the line, a second coupling element for connection to the adjacent end of another part of the line, a resilient member connecting said coupling elements, and means to indicate changes in dimensions of the resilient member.

5. A device according to claim 4, wherein said resilient member is so connected to the coupling elements as to be put in compression upon movement of the coupling elements away from one another

6. A device according to claim 4 or claim 5, wherein the resilient member comprises a body of resilient material.

7. A device according to claim 6, wherein the resilient material is natural rubber, synthetic rubber or resilient plastics material.

8. A device according to any of claims 4 to 7, wherein the coupling elements are formed with respective abutments which come into engagement with one another to limit the movement of the elements away from one another.

9. A device according to any of claims 4 to 8, wherein the means for indicating changes in dimensions of the resilient member comprise edges or markings on the respective coupling elements, the relative positions of which change upon deformation of the resilient member.

10. A device according to claim 9, wherein a scale is permanently provided on one of the coupling elements-to cooperate with an indicator on the other coupling element.

11. An indicating device for indicating tension in a line, substantially as hereinbefore described with reference to the accompanying drawings.