GB2233312A - Strain relief reeling system - Google Patents

Abstract

A strain relief system (1) which overcomes the problems associated with strain development in cables and the like when wound onto a storage drum. The system comprises a modified storage drum (4) which consists of four curved steel plates (2) positioned around drum core (3), the plates having a radius of curvature substantially the same as the drum core (3). Disposed between the plates (2) and drum core (3) are four bags which may be inflated or deflated by the introduction or expulsion of water. With the bags inflated and the plates positioned away from the drum core a cable is wound onto the drum. Any strain which develops in the cable during when wound is released by releasing water from the bags and allowing the effective drum core diameter to decrease. A typical use of this device is for relief of strain in towed sonar arrays. <IMAGE>

Description

STRAIN RELIEF REELING SYSTEM This invention relates to a device for preventing strain damage occurring to cables and the like when wound upon a storage drum. Ihe invention is particularly aimed at preventing strain damage to towed sonar arrays.

When sonar arrays are not in use they are removed fran the sea by winding onto a drum and stored there until further use is required. Because of length and other dimensions of towed sonar arrays and speed at which they are towed through the sea they tend to exhibit high drag which because of the nature of construction of towed sonar arrays results in them being stretched. m This may be especially so where the vessel is moving at speed whilst reeling a sonar array onto the drum. The array itself needs to be sensitive to vibration and requires the use of materials which because of this will stretch if force is applied.

It is undesirable to store these arrays when stressed as this can result in damage occurring to the sensitive arrays.

Consequently the present invention seeks to overcome or mitigate the problem of strain in the storage of towed sonar arrays and the like by providing a strain relief reeling system.

Accordingly there is provided a strain relieving system having a rotatable drum wherein the drum comprises; (a) a central core with a side wall at each end, (b) at least one plate extending along the axis of the drum core and having a radius of curvature in parallel alignment with and substantially the same as that of the drum core, (c) at least one inflatable bag disposed between the plate and the drum core, and (d) means to inflate and deflate each bag, whereby deflation of each bag and hence plate movement towards the central core takes place mostly or entirely after the drum is wound.

When the array is wound onto the drum core deformation of the core reduces its circumference and relieves strain which develops in winding the array onto the drum.

Whilst this invention is particularly directed towards the efficient storage of towed linear sonar arrays it is not to be limited by this and reference to arrays herein can be taken to include ant situation where storage of cable etc upon a drum may involve unwanted strain.

Preferably the amount of deformation of the drum is controlled so that the deformation takes place mostly or entirely after the drum is completely wound. This is preferred as lack of control in the procedure can lead to improper storage e.g. the layers of coils not overlaying each other properly, and consequent difficulties in subsequently removing the coils fran the drum.

Preferably the at least one inflatable bag when inflated is substantially incompressible. To achieve this each bag is filled with a fluid which is either a gas under high pressure or a liquid which is substantially incompressible.

This has the particular advantage of allowing a towed sonar array to be wound onto the drum with the bag inflated and the plate displaced away fran the drum core and when winding is complete the bag can be deflated to reduce the effective cross-sectional area of the drum by movement towards the drum core surface. This relieves the strain within the array and helps to prevent strain damage by allowing the array length to decrease. Because the movement of each plate is controllable by virtue of fluid pressure control the system overcomes prior art problems of allowing the arrays to become too slack which can give rise to difficulties when redeploying the array.

The e use of a substantially incompressible fluid within each bag prevents any substantial movement of the plates towards the drum core when an array is wound tightly around the drum. Preferably the liquid used for inflation of each bag is water for ease of use. This may be introduced by a system of pipes. Preferably one bag is provided adjacent to each plate and a plurality of plates is used substantially forming a shell around the drum core.

Advantageously the bags cover a substantial surface area of the plates used so that good control and if necessary high pressures can be exerted upon the plates. Preferably the bags should also be of uniform thickness to aid good control over the plate movement.

To prevent the bags slipping they are preferably held in place against the plates by a suitable adhesive.

Preferably the bags are constructed of a flexible, resilient material.

This is so that they do not distort substantially when external pressures are applied. Because of the possibility of high pressures being exerted the material of the bags construction should be sufficiently strong. There are preferably four plates which are equally spaced around the winding core of the drum and which together substantially cover the core and are a close fit with the side walls of the drum. The plates ensure that the winding of the array on the drumdoes not cause bulging of the bags and help to ensure even application of pressure applied by the array.The overall shape adopted by the plates can therefore be of substantially circular section, like the core, which helps to ensure the array is properly wound and presents the further advantages of increased control as the overall plate displacement is greater and also that the displacement can be controlled evenly relative to the core surface.

The e plates are preferably constructed of steel. Preferably there is provided a means for ensuring that the plates only move outwards or towards the drum core. This may be conveniently provided by at least one flange at the ends of each plate engaging with a corresponding hole or slot in the side walls of the drum allowing travel upon inflation or deflation of the bags.

Because of the pressure which can be exerted by the inflated bags it is important to select the correct thickness of steel for the plates as high pressures can be exerted by the inflated bags which can cause damage to the plates or drums. Pressure transducers are preferably provided with each bag so that constant monitoring of pressure in each bag can be achieved.

Preferably the maximum working pressure within the bags does not exceed 4.8 bar (70 psi).

It will be appreciated that the invention can be performed by various designs of equipment which are derrivable from the information herein and also in accordance with the thoughts of a person skilled in the art.

The e invention will now be described by way of example only and with reference to the acooeçanying Drawings of which: Figure 1 shows a plate with inflatable bag; Figure 2 shows a drum to which four plates have been fitted.

With reference to Figures 1 and 2 the strain relief reeling system (1) comprises four steel plates (2) which are shaped with a radius of curvature slightly greater than that of a drum core (3) of a drum (4). The plates (2) when in position virtually surround the surface of core (3). The plates (2) have a flange (5) at each end which fit into corresponding holes (6) in the drum walls (7). Adhered to the underside of each plate (2) is an inflatable bag (8) which is of uniform thickness and covers the entire surface area of the plate underside except the edges where it is crimped by rails (9) along the side of the plate (2). Each bag is fitted with a spout (10) for inflating or deflating the bag with water (not shown).The spouts are connected via pressure lines (not shown) to a pressure control system (not shown) situated on the outside of the drum walls and which controls the water pressure in each of the four bags. Each of the bags is provided with a pressure transducer and complementary circuitry (not shown) to monitor pressure.

In use of the strain relief reeling system (1) the bags (7) are first inflated to a pressure of 4.8 bar (70 psi). A linear towed sonar array (not shown), which is deployed at sea from a ship and connected at one end to the drum core (3), is then rotated to wind the sonar array under tension onto the drum.

Finally the tension in the sonar array is relieved by release of water from the bags (8) via the pressure lines and pressure control system. me decrease in the effective size of the drum core (3) allows the sonar array to resume its normal length by contraction towards the drum core and relieves the tension.

The e release of water and cosequential removal of tension is controlled by monitoring of the pressures recorded by the transducers until the pressure reaches a predetermined limit to ensure that the surface of the drum plates (2) remain in contact with the array. The e sonar array may be re-deployed and the tension relief process repeated for storage.

Claims (1)

1. gE

   1. A strain relief reeling system having a rotatable drum wherein the drum comprises; (a) a central core with a side wall at each end, (b) at least one plate extending along the axis of the drum core and having a radius of curvature in parallel alignment with and substantially the same as that of the drum core, (c) at least one inflatable bag disposed between the plate and the drum core, and (d) weans to inflate and deflate each bag, whereby deflation of each bag and hence plate movement towards the central core takes place mostly or entirely after the drum is wound.

   2. A strain relief reeling system as claimed in claim 1 wherein the at least one inflatable bag when inflated is substantially incompressible.

   3. A strain relief reeling system as claimed in claim 1 wherein in use each bag is filled with a fluid which is either a gas under high pressure or a liquid which is substantially incompressible.

   4. A strain relief reeling system as claimed in claim 4 wherein the liquid is water.

   5. A strain relief reeling system as claimed in claim 4 wherein the movement of each plate is contolled by fluid pressure control.

   6. A strain relief reeling system as claimed in claim 1 wherein there is a plurality of plates forming a shell around the drum core and a bag is adjacent to each plate.

   9. A strain relief reeling system as claimed in claim 8 wherein the shell is of substantially circular section.

   10. A strain relief reeling system as claimed in claiml wherein the bags cover a substantial area of the plates.

   11. A strain relief reeling system as claimed in claim wherein the bags are constructed of a flexible, resilient material.

   12. A strain relief reeling system as claimed in claim 1 wherein there are 4 plates which are equally spaced around the core of the drum.

   13. A strain relief reeling system as claimed in claim 1 wherein the plates are constructed of steel.

   14. A strain relief reeling system as claimed in claim 1 wherein the plates are provided with means to ensure that they only move outwards or towards the drum core.

   15. A strain relief reeling system as claimed in claim 14 wherein the means is at least one flange at the ends of each plate engaging with a corresponding hole or slot in the side walls of the drum.

   16. A strain relief reeling system as claimed in claim 1 wherein pressure tranducers are provided with each bag.

   17. A strain relief reeling system substantially as herein described and with reference to the acccmçlnying drawings.