GB2175752A

GB2175752A - Cable laying device and process

Info

Publication number: GB2175752A
Application number: GB08511512A
Authority: GB
Inventors: Dr P H Morgan
Original assignee: University College Cardiff Consultants Ltd; Cardiff University
Current assignee: University College Cardiff Consultants Ltd; Cardiff University
Priority date: 1985-05-07
Filing date: 1985-05-07
Publication date: 1986-12-03
Also published as: GB8511512D0

Abstract

A device for laying cables in a pipe comprises a brush having radially projecting stiff bristles 2, a swivel eye 7 centrally located on one face or end of the brush for attaching a rope thereto and, on an opposite face or end of the brush, means 5 for attaching one or more cables. The brush may be planar, similar to a chimney sweep's brush, or cylindrical, similar to a flue brush. The device, with the leading end of cable attached thereto, is drawn through the pipe by means of a rope attached to the swivel eye. The brush is of larger diameter than the internal diameter of the pipe so that the bristles are bent backwards (Fig. 4) against the interior wall of the pipe and so prevent or substantially reduce twisting of the cable in the laying process. The device is particularly advantageous when the pipe has cables in it already. <IMAGE>

Description

SPECIFICATION Cable laying device and process This invention relates to a device for and a process of laying cables in pipes.

It is a common practice to lay a cable in a pipe by drawing the cable into and through the pipe by means of a rope attached to the leading end of the cable. However in this process it frequently occurs that the cable becomes twisted during its passage through the pipe. This causes difficulties when additional cables are to be laid in the pipe in the same way, so much so that often no more cables than occupy 25% of the cross sectional area of the pipe can be laid.

This invention provides a device which, when used to connect a rope for drawing a cable through a pipe to the leading end of the cable, makes it possible to reduce or even eliminate twisting of the cable so laid in the pipe.

The device comprises a brush having radially-projecting stiff bristles, a swivel eye centrally located on one face or end of the brush for attaching a rope thereto and, on an opposite face or end of the brush, means for attaching one or more cables. The brush may be substantially planar, similar to a chimney sweep's brush, in which case the swivel eye is provided at or near the centre point of one face of the brush. Preferably the brush is cylindrical similar to a flue brush, in which case the swivel eye is provided at or near one end of the central axis of the cylindrical brush.

The cable attachment means on the opposite face or end of the brush may be an eyelet or hook or other means suitable for attachment of the end of a cable. Another means may be a strip of metal having a pair of adjacent holes in which the cable may be gripped by threading the end first through one hole and then through the other. Preferably, when a number of cables are to be attached to the device, the cable connecting means comprises a perforated plate having a multiplicity of holes, through pairs of which the leading end of cables may be threaded and so secured to the plate.

For laying a cable or cables in a pipe, the end of a rope previously laid in the pipe is attached to the swivel eye of a device of this invention, the end of a cable, or of each cable, is attached to the cable attachment means on the other side or end of the brush and the device, with the cable or cables attached thereto, is then drawn into and through the pipe by pulling on the other end of the rope, the brush being of greater diameter than the pipe so that when in the pipe the bristles are bent in a backwards direction against the interior wall of the pipe.

The bristles of the brush must be so bendable but must be stiff enough to appreciably resist such bending. It is believed that the appreciable resistance to bending of the bristles in contact with the pipe wall reduces or even eliminates any tendency of the device to twist during its passage through the pipe, in which case the attached cable or cables remain untwisted.

Preferably the brush is cylindrical so that a greater number of bristles can be in contact with the inner surface of the pipe.

The bristles may be of natural origin but preferably are of a synthetic material which retains its stiffness even when wet. Nylon or polypropylene are particularly suitable.

The diameter of the brush should be at least 10% greater than the internal diameter of the pipe so that the bristles are bent backwards when the brush is pulled through the pipe.

For example, in a standard telephone cable pipe of 4" internal diameter a suitable cylindrical brush is made up of nylon bristles 6" long of the type used in a stiff yard brush. Where the pipe is of larger diameter the bristles may be of larger diameter to compensate, from the stiffness point of view, for the longer length of bristle needed.

A feature of the device is that since the bristles are displaceable, the device can be used to draw a cable through a pipe which already contains one or more cables. An inpipe cable displaces the bristles of the brush sideways, i.e. parts them, so enabling the device to ride along it.

The brush of the device may also serve a useful function in sweeping out the pipe.

One embodiment of the invention is now described with reference to the accompanying drawings in which: Figure 1 is a diagram of a device in which the brush is cylindrical; Figure 2 is an end view of the brush of Fig.

1; Figure 3 is an illustration of a suitable towing plate for attachment of several cables to the device; Figure 4 is a diagrammatic representation of the configuration of the bristles of a device when it is being pulled through a pipe.

In Fig. 1, the cylindrical brush 1 is of conventional structure in which bristles 2 are gripped at their centre between twisted wires 3. At one end of the wires 3 there is clamped by means of a U-bolt 4, a strip of metal 5 having a pair of holes through which the leading end of a cable 6 is threaded to attach it to the device. At the other end of the wires 3 is fixed a swivel eye 7 to which is attached the end of a rope 8.

Fig. 2 shows the radial arrangement of bristles 2 around the axis provided by the wires 3.

Fig. 3 shows a plate 9 which when secured by projection 10 to one end of the brush 1 can be used for attachment of up to five cables, by threading the leading end of the cables through each of a pair of holes 11.

Fig. 4 illustrates the configuration of the bristles 2 of a device when being pulled in the direction shown by the arrow through a pipe 12.

Claims

1. A device for laying cables in pipes comprising a brush having radially-projecting stiff bristles, a swivel eye centrally located on one face or end of the brush for attaching a rope thereto and, on an opposite face or end of the brush, means for attaching one or more cables.

2. A device as claimed in claim 1 in which the brush is cylindrical, the swivel eye being provided at or near one end of the axis of the cylindrical brush and the means for attaching one or more cables being provided at the other end of the axis.

3. A device as claimed in claim 1 or claim 2 in which the means for attaching one or more cables is a strip or plate having one or more pairs of adjustment holes through which the end of a cable may be threaded.

4. A method of laying a cable in a pipe in which the leading end of the cable is attached to a device as claimed in claim 1, 2 or 3 and the device and cable are drawn through the pipe by means of a rope attached to the swivel eye of the device, the brush being of greater diameter than the internal diameter of the pipe so that when the device is drawn through the pipe the bristles are bent in a backwards direction against the interior wall of the pipe.

5. A method as claimed in claim 4 in which the diameter of the brush is at least 10% greater than the internal diameter of the pipe.