GB2197840A

GB2197840A - Cable tension relief device

Info

Publication number: GB2197840A
Application number: GB08627324A
Authority: GB
Inventors: Alan Crowe
Original assignee: UK Secretary of State for Defence
Current assignee: UK Secretary of State for Defence
Priority date: 1986-11-14
Filing date: 1986-11-14
Publication date: 1988-06-02
Anticipated expiration: 2006-11-14
Also published as: GB2197840B; GB8627324D0

Abstract

A tension relief device comprises a rotatable capstan body about which a cable or rope 60 can be wound with the surface of the capstan body in contact with the wire or rope being driven by a motor or gearing such that it moves continuously from one axial end of the capstan body to the other. In the preferred arrangement there are four endless conveyor belts 61 formed by a train of linked carriages 62. The carriages 62 are driven by the same motor driving the capstan body at a speed equivalent to the displacement of the turns of cable or rope. The carriages are provided with equispaced transverse grooves 66 separated by a spacing greater than the diameter of the cable or rope such that the turns of cable or rope engage the grooves and are thereby spaced on the capstan. The capstan body may be tapered in the direction 68 from the input towards the output of the cable or rope to allow for contraction of the cable or rope as the tension is relieved. <IMAGE>

Description

A Cable Tension Relief Device The invention relates to the storage of cables, ropes etc and in particular to devices which enable cables to be stored under low tension.

As a cable or rope is reeled in it is desirable that the tension should be relieved prior to storage on the reel otherwise the cumltiv force from each coil of the cable can become unacceptably large, leading to damage of the cable or storage reel. This is particularly true where 8 towed sonar array is being reeled in as the cumulative force could damage the array.

Any solution to overcoming this problem should retain a small tension sufficient to ensure that coils are not dropped and the cable twisted. Ideally a device is required which will recover a cable under high tension and release it under reduced tension to be stored on a storage drum. A common solution has adapted use of a driven capstan around which a cable is partly wound while hauling on the cable. As the cable passes around the capstan there is slippage and rolling of the cable on the capstan. The cable rubs aciainst adjacent coils and this on the capstan leads to abrasion.

The object of the invention is to provide a tension reliever which reduces the wear resulting from conventional devices.

The invention provides: a tension relief capstan comprising a rotatable capstan body about which a cable or rope etc can be wound; and a motor for driving said capstan body about its axis of rotation; the arrangernent being such that the surface of the capstan body in contact with the wire or rope etc is driven by a motor such that it moves continuously from one axial end of the capstan body to the other.

Preferably there are at least two, and advantageously four, endless conveyor belts about which the cable or rope etc is wound in use. The conveyor belts may be driven by the same motor driving the capstan body. The arrangement is such that as the cable or rope etc is driven around the capstan it is conveyed in a direction from one end towards the other by means of the conveyor belts. Ad'7antageously the conveyor belts are provided with equispaced transverse grooves separated by a spacing greater than the diameter of the cable or rope etc such that the turns of cable or rope engage the grooves and are spaced on the capstan thereby. preferably the capstan body is tapered in the direction from the input towards the output of the cable or rope to allow for contraction of the cable or rope as the tension is relieved.

The invention will now be described by way of examp]e only with reference to the attached Drawings of which: Figure 1 is a side elevation of a cable recovery system, Figure 2 is a schematic plan view of the tension relief capstan shown in Figure 1; Fi,oures 3 to 5 illustrate three known prior art arrangements of tension relief system to improve the Figure 2 arrangement; Figure 6 is 8 perspective view, part cut away, of a tension relief drum according to the invention; Figure 7 is a schematic cross section perpendicular to the axis of the drum of Figure 6; Fiaure 8 is a schematic side elevation of part of one conveyor of the drum of Figures 6 and 7; and Figure 9 is a part sectional view taken through the conveyor of Figure 8.

Figure 1 illustrates a cable storage system wherein a cable 10 is recovered under tension by means of a recovery drum 11 for storage under reduced tension on a storage drum 12. The recovery drum 11 and storage drum 12 are rotated in the directions 13 and 14. The cable 10 has a number of turns around the recovery drum determined by the required reduction in tension. The low tension cable is then guided on to the storage drum for neat storage.

Figure 2 is a plan elevation of the recovery drum 11 showing seven coils 20 wound around the barrel 21 of the drum 11.

The cable 10 leaves the drum 11 at a position axially displaced by a distance d from the position at which the cable first engages the drum. The cable thus has to slip or roll or both during the movement d(= 7 x cable diameter) along the drum barrel. During rolling movement the cable twists which is undesirable.

Slippage of the cable on the drum barrel due to the movement d and contraction because of tension relief and the rubbing of one coil against the adjacent coils leads to abrasion.

Figure 3 illustrates a modified recovery drum 30 which incorporates a fleeting knife 31 to urge the cable in the direction 32 along the drum barrel. This arrangement can eliminate roll but sliding and the rubbing together of coils is still present.

A diabolo-shaped capstan 41, as shown in Figure 4, has also been used. The shape of the barrel is such that the cable remains located near the axial centre of the drum without the coils falling off. The capstan arrangement suffers from similar slip and roll problems to the Figure 2 arrangement. An alternative known approach has been to use two capstans 50,51, one of which is driven, as shown in Figure 5. In this arrangement the effect of roll can be reduced by angling the two capstans however there is still slip and roll of the cable. This device is also inherently large by comparison with a single capstan.

Figure 6 shows a cable recovery drum according to the invention. The drum is mounted such that it can be rotated by a motor (not shown) about a horizontal axis in the direction D.

The drum is generally cruciform shaped tapering from left to right as shown with a number of turns of the cable 60 wrapped around it. As can be seen with further reference to Figures 7 and 8 the cable engages endless conveyors 61 located one on each arm of the drum. Each conveyor 61 comprises a plurality of linked carriages 62 which are driven around tracks 63 by means of suitable gearing (not shown) to the drum motor. Each track 63 is sectioned such that the carriages are constrained by means of perpendicular sets of rollers64,65 engaging respective parts of the track 63, as will be described in greater detail in relation to Figure 9. Each carriage 62 has a number of transverse radiused channels 66 which are engaged by the cable 60. The channels are dimensioned such that successive coils of the cable 60 are separated.

In use, cable 60 under high tension engages the topmost conveyor at the point 67 and during rotation of the drum in the direction 60 each conveyor 61 is driven in the direction 68. The cable leaving the conveyor at the point 69 has a reduced tension depending among other things, on the number of coils engaging the drum. The tapering of the drum is arranged such that there is no slipping of the cable on the conveyors 61 as the cable contracts as its tension is relieved.

As can be seen by reference to Figure 9 each conveyor carriage 62 has an arcuate upper profile over which the cable 90 bends. The carriages 62 are linked together by chain links 91 engaging the axles of respective rollers 64.

With the cable 90 being hauled in the direction 92 and the drum rotated in the direction 93 the forward side of the carriage 62 is provided with one pair of rollers 64 engaging a "U" sectioned rail 94. The rearward side of the carriage 62 is seated on an "L" sectioned rail 63 with a pair of rollers 64 engaging on limb 95 of the rail and a horizontal pair of rollers 65 engaging the other limb 96 of the rail. The rollers are arranged so as to balance the reaction forces imposed during operation while constraining the carriage to remain in position.

Although the invention has been described in relation to a drum having four conveyors which is a convenient arrangement, other numbers could be used. The smallest number is two and the largest number depends upon fitting together the gearing and return tracks of the conveyors within the drum design size.

Various modification and design details not described herein will be apparent to those skilled in the art, all falling within the scope of the invention described.

Claims

1. A tension relief device comprising a rotatable capstan body about which a cable or rope etc can be wound; and a motor for driving said capstan body about its axis of rotation; the arrangement being such that the surface of the capstan body in contact with the wire or rope etc is driven by a motor or gearing such that it moves continuously from one axial end of the capstan body to the other.

2. A tension relief device as claimed in claim 1 wherein there are at least two endless conveyor belts about which the cable or rope etc is wound in use.

3. A tension relief device as claimed in claim 2 wherein there are four endless conveyor belts.

4. A tension relief device as claimed in claim 2 or 3 wherein the conveyor belts are driven by the same motor driving the capstan body at a speed equivalent to the displacement of the turns of cable or rope.

5. A tension relief device as claimed in any one of claims 2 to 4 wherein the conveyor belts are provided with equispaced transverse grooves separated by a spacing greater than the diameter of the cable or rope etc such that the turns of cable or rope engage the grooves and are spaced on the capstan thereby.

6. A tension relief device as claimed in any one preceding claim wherein the capstan body is tapered in the direction from the input towards the output of the cable or rope to allow for contraction of the cable or rope as the tension is relieved.