GB2166704A

GB2166704A - Winch mechanism

Info

Publication number: GB2166704A
Application number: GB08427823A
Authority: GB
Inventors: James Justinian Hancock; Ronald Wallace
Original assignee: INNOVA ENGINEERING Ltd
Current assignee: INNOVA ENGINEERING Ltd
Priority date: 1984-11-02
Filing date: 1984-11-02
Publication date: 1986-05-14
Also published as: GB2166704B; GB8427823D0

Abstract

A winch mechanism for hauling a flexible elongate element comprises a first pulley 11, an inlet guide 15 for the elongate element which is spaced from the first pulley 11 to define a feed path from the guide to the pulley, a second pulley 12 arranged to cooperate with the first pulley 11 in such a way that the elongate element engages throughout an arc of the first pulley which subtends an angle of at least 180 DEG before passing to the second pulley, an outlet guide 18 which is arranged relative to the second pulley 12 in such away that the elongate element 16 engages throughout an arc of the second pulley which subtends an angle of at least 180 DEG before passing to the outlet guide, a take-up drum 13 arranged to receive the elongate element from the outlet guide 18, first drive means 24 for driving at least one of the first and second pulleys, second drive means for driving the take-up drum 13, and a tension monitoring device 19 arranged along the feed path to monitor the tension in the elongate element 16, the device 19 being coupled with the first drive means 24 in such a way as to control the operation of the drive means and thereby maintain a predetermined tension in the elongate element. <IMAGE>

Description

SPECIFICATION Winch mechanism This invention relates to a winch mechanism for hauling a cable, flexible pipe or other elongate flexible element when it is required to draw the leading end of such an element from a starting position to a final position whereby a length or run of the element extends between the two positions.

Telecommunication and other electric cables have been hauled through underground conduits by winch mechanisms for many years. Such winch mechanisms have been relatively unsophisticated, using a winch drum which is driven in order to haul the cable, and whose operation is manually controlled in order to adjust the tension applied to the cable when circumstances require i.e. if the cable encounters an unexpected obstacle or resistance during haulage.

However, with the advent of cable television, and the use of optical fibre cables for the transmission of data, there is a requirement to provide a generally improved construction of winch mechanism for hauling such less robust cables satisfactorily, without risk of damage to the constituent parts of the cable. Thus, in the haulage of an electrical power cable underground, a relatively unsophisticated winch mechanism is satisfactory, since the cable is of robust internal and external construction, so that ther is only small risk of internal rupture of the core constitutents of the cable during haulage.

However, an optical fibre cable is composed of a very great number of very fine optical fibres stranded together, and therefore the application of excessive traction forces to an optical fibre cable (caused for example by the cable encountering an unexpected obtacle or resistance during hauling) could result in serious internal damage to the optical fibres, even although external inspection of the cable may not reveal any apparent damage.

It will be evident that the detection of (a) the presence of an internal fracture and (b) its location, and the subsequent repair or replacement of a damaged section, will be a difficult and time-consuming task. Therefore, there exists a need to provide a winch mechanism for hauling cables and other elongate elements, which have relatively sensitive internal constituents, such as optical fibre cable, in such a way as to avoid the application of excessive or sudden tensile stresses when an unexpected obstacle or resistance is encountered during cable haulage.

The invention has therefore been developed primarily in relation to the provision of a winch mechanism for hauling sensitive cables underground, though the invention is not limited exclusively to such use. Indeed, it is envisaged that a winch mechanism according to the invention may have application in other areas of cable or pipe haulage where a substantially constant hauling force is required. Examples of such alternative use include marine pipe laying, where a substantially constant hauling tension is desirable to obtain the required"catenary" shape of the pipe as it runs from the rear of a pipe laying barge or the like down to the sea bed. Another possible use is in the overhead haulage of electrical power cables between pylons.

According to the invention there is provided a winch mechanism for hauling a flexible elongate element and comprising: a first pulley; an inlet guide for the elongate element which is spaced from the first pulley to define a feed path from the guide to the pulley; a second pulley arranged to cooperate with the first pulley in such a way that the elongate element engages throughout an arc of the first pulley which subtends an angle of at least 1800 before passing to the second pulley; an outlet guide for the elongate element which is arranged relative to the second pulley in such a way that the elongate element engages throughout an arc of the second pulley which subtends an angle of at least 1800 before passing to the outlet guide; a take-up drum arranged to receive the elongate element from the outlet guide;; first drive means for driving at least one of the first and second pulleys to apply traction to the elongate element; second drive means for driving the take-up drum so as to apply a small but sufficient tractive force to draw the elongate element from the second pulley to the take-up drum via the outlet guide; and a tension monitoring device arranged along said feed path to monitor the tension in the elongate element, such device being coupled with said first drive means in such a way as to control the operation of the drive means and thereby maintain a predetermined tension in the elongate element.

For convenience hereinafter a flexible elongate element will be referred to as a "cable".

If, during operation of the winch mechanism according to the invention, an unexpected obstacle or resistance is encountered by the cable during haulage, which might otherwise give rise to application of a shock or excessive tensile loading to the cable, the mechanism can respond immediately to this and automatically reduces the driving force applied by the first drive means. Accordingly, a substantially constant tractive force can be applied to the cable during haulage, giving a generally smooth passage of the cable and without risk of internal damage occurring even when unexpected resistance is encountered.

Preferably, the second pulley is arranged at a higher level than the first pulley, and the cable engages throughout an arc which subtends an angle of at least 270".

The first and second pulleys preferably comprise wheels having generally V-shaped grooves which have such a size and shape, in relation to the cable, that the cable is gripped smoothly and in substantially non-slip manner as it passes along the respective part of the circumference of each wheel.

The tension monitor may comprise conveniently a pulley wheel which is biased to a position of en gagement with the cable, whereby it deflects the cable from a straight path to the first pulley, and therefore is able to monitor variations in cable tension by moving relative to its biasing.

When the winch mechanism is used to haul an optical fibre cable, usually a tractor cable will be coupled with the leading end of the optical fibre cable, and it will be the tractor cable which is coupled with the winch mechanism. In order to monitor progress of cable hauling, a length monitor may be provided, also located on the feed path, and conveniently comprising a wheel or pulley arranged to be rotated by the cable as the latter passes to the first pulley.

The preferred form of first drive means is an hydraulic motor-drive, since this can readily be controlled by the tension monitor, when fluctuation occurs in cable tension, in order to maintain any desired cable tension, which can be set to any required pre-set value before cable hauling commences. The second drive means may also be an hydraulic motor-drive. However, electrical drive arrangements may be provided instead.

One embodiment of winch mechanism according to the invention will now be described in detail with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of the winch mechanism; and Figure 2 is an end view of the winch mechanism.

Referring now to the drawing, a winch mechanism according to the invention is provided which is suitable for hauling a cable, flexible pipe or other elongate flexible element, when it is required to draw the leading end of such an element from a starting position to a final position, whereby a length or run of the element extends between the two positions.

The winch mechanism is mounted on a base frame 10 and comprises a first pulley 11, a second pulley 12 and a take-up drum 13. The first and second pulleys 11 and 12 are mounted for rotation about horizontal axes on a support plate 14 upstanding from the base frame 10.

An inlet guide 15 is mounted on the support plate 14 and comprises a pair of vertical guide rollers (not shown in detail) which define therebetween a space through which is fed a cable 16 which is to be hauled. The inlet guide 15 is spaced from the first pulley 11 to define a feed path 17 for the cable 16 from the guide 15 to the pulley 11.

An outlet guide 18 is mounted on the base frame 10 and serves to guide the passage of the cable 16 to the take-up drum 13.

It will be noted from the drawing that the arrangement of the first and second pulleys 11 and 12, and the inlet guide 15 and the outlet guide 18 is such that the cable engages throughout an arc of the first pulley 11 which subtends an angle a' of at least 1800 before passing to the second pulley 12. During passage around the second pulley 12, the cable 16 engages throughout an arc of the second pulley 12 which subtends an angle b' of at least 270 before passing to the outlet guide 18.

However, a different arrangement of the pulleys 11 and 12 may be provided, in which the cable extends over the pulleys throughout an angle of at least 180 for each pulley.

First drive means, in the form of an hydraulic motor-drive unit (not shown in detail), is, provided for driving at least one of the first and second pulleys 11, 12, to apply traction to the cable 16. As shown in Figure 2, a hydraulic motor 24 is arranged to drive each pulley, and the motors 24 have the same rating and are supplied by a common hydraulic pump (not shown). Second drive means, also in the form of an hydraulic motordrive unit (not shown), is provided for driving the take-up drum 13 so as to apply a small but sufficient tractive force to draw the cable 16 from the second pulley 12 to the take-up drum 13 via the outlet guide 18.

A tension monitoring device is arranged along the feed path 17 to monitor the tension in the cable 16, and comprises a wheel 19 which is biased to a position of engagement with the cable 16, whereby it deflects the cable from a straight path to the first pulley 11. The wheel 19 is able to monitor variations in cable tension by moving relative to its biasing. For illustration purposes only, the wheel 19 is shown carried by a bracket 20 which is pressed in a direction towards the cable 16 by the pressure in a cylinder 21 acting on a piston 22.

The tension monitoring device (19 to 22) is coupled with the first drive means in such a way as to control the operation of the latter and thereby maintain a predetermined tension in the cable as the latter is hauled by the winch mechanism.

Also along the feed path 17, there is located a length monitor which comprises a wheel 23 which is arranged to be rotated by the cable 16 as it passes from the inlet guide 15 to the first pulley 11. This enables the progress of cable haulage to be monitored.

Although not shown in detail, the winch mechanism will be provided with a control and monitoring station at which an operative may be located, who can set initial operating parameters for the mechanism, according to circumstances, e.g. pulley wheel speed and driving torque, take-up drum speed and torque etc., and thereafter the winch mechanism will control its operation automatically to maintain any desired pre-set cable tension required.

The following are the parameters of one detailed embodiment of winch mechanism according to the invention: Cable 6 millimetre steel wire rope for pulling fibre optic cable Diameter of pulley wheels 11 and 12 700 millimetres Linear haulage speed of cable 25 to 50 metres per minute Power supply 115 horse power diesel engine generating up to 15 kN Tractive effort I up to 2 kilometres of cable (equivalent to 2 tonnes tension) Drive to the pulley 11 and 12 I same rating hydraulic motors driven from common pump Drive to take-up drum I variable speed small hy draulic motor (sufficient just to maintain tension in the cable between second pulley 12 and take up drum 13) Construction of pulley wheel 11 and 12 I two pulley halves bolted together with a V angle minimum 14" up to 18 or 19 , depending on the nature of the cable.

Claims

1. A winch mechanism for hauling a flexible elongate element and comprising: a first pulley; an inlet guide for the elongate element which is spaced from the first pulley to define a feed path from the guide to the pulley; a second pulley arranged to cooperate with the first pulley in such a way that the elongate element engages throughout an arc of the first pulley which subtends an angle of at least 1800 before passing to the second pulley; an outlet guide for the elongate element which is arranged relative to the second pulley in such a way that the elongate element engages throughout an arc of the second pulley which subtends an angle of at least 180 before passing to the outlet guide; a take-up drum arranged to receive the elongate element from the outlet guide;; first drive means for driving at least one of the first and second pulleys to apply traction to the elongate element; second drive means for driving the take-up drum so as to apply a small but sufficient tractive force to draw the elongate element from the second pulley to the take-up drum via the outlet guide; and a tension monitoring device arranged along said feed path to monitor the tension in the elongate element, such device being coupled with said first drive means in such a way as to control the operation of the drive means and thereby maintain a predetermined tension in the elongate element (cable).

2. A winch mechanism according to claim 1, in which the second pulley is arranged at a higher level than the first pulley, and the cable engages throughout an arc which subtends an angle of at least 270 .

3. A winch mechanism according to claim 1 or 2, in which the first and second pulleys comprise wheels having generally V-shaped grooves which have such a size and shape, in relation to the cable, that the cable is gripped smoothly and in substantially non-slip manner as it passes along the respective path of the circumference of each wheel.

4. A winch mechanism according to any one of the preceding claims, in which the tension monitor comprises a pulley wheel which is biased to a position of engagement with the cable, whereby it deflects the cable from a straight path to the first pulley, and therefore is able to monitor variations in cable tension by moving relative to its biassing.

5. A winch mechanism according to any one of the preceding claims, including a length monitor located on the feed path to monitor progress of cable hauling.

6. A winch mechanism according to claim 5, in which the length monitor comprises a wheel or pulley arranged to be rotated by the cable as the latter passes to the first pulley.

7. A winch mechanism according to any one of the preceding claims, in which the first drive means is an hydraulic motor-drive.

8. A winch mechanism according to any one of the preceding claims, in which the second drive means is an hydraulic motor-drive.