GB2242662A - Line coupling sheath - Google Patents

Abstract

A sheath for a coupling on a line intended to be deployed into and hauled out of the sea is made of two halves (12) defining an open passage (10). The external surface (13) of the sheath is smooth to allow the coupling better to be engaged by a line hauling machine with less chance of derailment. The sheath may have recesses (18) adapted to hold the orientations of the coupling members relative to one another. <IMAGE>

Description

LINE COUPLING FITTING This invention relates to couplings joining lengths of line.

When hauling on a line using a powered winching device it is preferable to be able to present an uninterrupted run of the line to the winching device in order to avoid problems associated with the couplings between lengths of line. However, in the event that a long run of line is required couplings are necessary to join shorter lengths of line together.

In one particular application, undersea communication cables are retrieved for repair by means of a grapnel rope. Often these ropes have to be retrieved from very considerable depths, for example up to and in excess of 10 km. In this case lengths of grapnel rope must be coupled together using shackles. A typical coupling comprises a hard eye splice, egg link, hammerlock shackle, egg link and a further hard eye splice between two ends of rope. Sometimes a swivel connection is used in place of the hammerlock shackles.

The grapnel rope is deployed and hauled inboard under considerable tension to and from the seabed by a cable hauling system, typically comprising a capstan and a hydraulic linear cable engine providing controlling tension on the downstream side of the turns of the rope on the capstan. The cable engine has a number of pairs of opposed hydraulically driven wheels, each of which pairs engage the grapnel rope which thus, passes along the pair sets. A typical example of a hydraulic linear cable engine is that sold by BT (Marine) Limited of Central Marine Depot, Bert 203, Western Docks, Southampton, SO1 OHH, England. The number of pairs of wheels may vary from 2 to 18 pairs.

Commonly, linear cable engines have various inherent characteristics which tend to cause problems when a series of coupled lengths of grapnel rope are to be hauled aboard. Generally, they cannot cope well with the couplings between the lengths of rope. In particular, the wheels tend to be driven at slightly different rates, causing bunching of the rope in the machine. While this can be accepted between couplings without undue problems, it is found that the perturbation in the section of the line caused by the coupling exacerbates the bunching problem to the extent that the hauling operation is often interrupted. At the coupling the line tends to form a natural apex when the line is bunched, causing an exaggerated bow in the line which may often lead to derailment of the line from between the sets of wheels. This problem is compounded by the shape of the coupling shackle loops.

Engaged mutually at right angles with adjacent loops, each shackle loop tends towards lying on its side as it passes through the machines. Each loop will tend to lie in an opposite orientation to the adjacent loops, further increasing the chances of derailment.

Another similar problem is that the sets of driven wheels may start to rotate at slightly different moments on start up. Thus, the line is hauled by some of the sets of wheels and not others for a short period in which similar bowing will occur. The chances of derailment are, thus, increased if the coupling is positioned between sets of wheels at that time.

Derailment may include positive ejection of the cable from the machine which is hazardous to both machinery and personnel.

It has been proposed to fit the linear cable machine with deflectors and/or other guides in an attempt to keep the line on track. These have not proved to be successful. The line still tends to bow out and become derailed.

It is an object of the present invention to provide a fitting which serves to reduce the instances of derailment of a line passing through a hauling device, such as a linear cable engine.

According to the present invention there is provided a line coupling fitting comprising a sheath securable over at least part of the coupling and having an internal open passage which is adapted to accommodate the line coupling, the external surface of the sheath providing the coupling with a substantially smooth outer surface.

Thus, the fitting according to the present invention provides the coupling with a smoother external surface which more easily passes through a hauling machine and, thus, improves the handling of the connections through the linear cable engine.

Conveniently, the fitting is formed from two identical halves which may be bolted and/or strapped together over its respective portion of the total coupling The sheath may completely encircle the coupling. The sheath presents a smooth transition between the line itself and the bulge constituted by the coupling which has been the cause of the problems mentioned above.

Preferably, the internal surface of the sheath defining the passage is adapted substantially to retain the coupling components in their respective orientations relative to one another. The sheath may define a channel and/or non-circular portion in the passage adapted to receive, at least partially, the coupling.

The fitting may not enclose the entire coupling. It may have one opening to the passage shaped to receive, at least partially, a further coupling member. In which case the shape of the opening may be adapted to hold the further coupling member in a particular orientation with respect to the covered part of the coupling.

The glove may be left in place on each end of the rope when not in use. It also serves to protect the rope eye from damage from sharp objects or blades as well as making the rope end less likely to snag on objects. It will also reduce the wear and tear on the rope end reducing the frequency of the need for resplicing.

When in use the fitting or glove is designed to limit or prevent bunching and buckling of the coupling passing through the linear cable engine.

One particular shape of fitting which provides a smooth transition between the rope and coupling is that of a sheath tapered towards one or both ends. The sheath may also have an external surface which is circular in cross-section or one which comprises two arcuate portions joined by flat sides.

The present invention can be put into practice in various ways, one of which will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a side view of one half of a cover according to the invention; Figure 2 is an end view of the half of the cover of Figure 1; and Figure 3 is a side view of a pair of covers in situ on couplings between two lengths of line.

Referring to Figures 1 and 2, a rigid polyethylene coupling sheath fitting for a shackle coupling between two lengths of grapnel rope comprises two of the halves shown in the figures mated together along the flat surface 9. For convenience, the description will refer to two such halves when joined together to form the sheath.

The two halves define a passage 10 in the sheath made from the two halves 12. The sheath has a smooth outer surface 13 which is tapered towards both ends. The left hand taper (as depicted in Figure 1) is steeper than that to the right.

The left hand end of the sheath is formed with a circular opening 14 to the passage 10. The circular opening is truncated abruptly in a shoulder 16 which constricts the passage 10 to a laterally elongate slot 18 extending across the axis of the opening 14. The curved lateral ends of the slot 18 are shaped to complement that of a coupling member received therein.

Typically, the ends are parallel or diverge from the opening 14.

At the end of the slot 18 the passage expands into a main chamber 20. A curved forward wall portion 20a extends into a straight sided tapered rear wall portion 20b having arcuate upper and lower surfaces. The tapered rear wall portion 20b is terminated in a circular cross section cylindrical wall portion 20c, which constitutes the other opening to the passage, at the extreme right hand end of the sheath.

Each of the halves is formed with a set of three bolt holes. Two of the bolt holes 22 are formed in the body of the material which mates with the other half to define the sheath. The other hole 24 is formed in the portion of the half defining the main chamber 20.

The sheath is formed with a first channel 26 extending generally about the middle of the outside of the sheath between the two tapers. A second annular recess 28 is formed to the right hand end of the sheath also about the outside. This second recess 28 is, in part, defined at its extreme right hand end by an annular lip 30 formed in the halves of the shroud.

Each half of the sheath is formed with a generally central flat area 29 formed on the outer surface as an elongate oval shape extending from over the slot 18 to the rear of the rear wall portion 20b.

When the two halves of the shroud are brought together over a coupling, a stainless steel packing band is wrapped around them, following each of the recesses to assist in retaining the shape of the sheath. In addition, the halves are held relative to one another by means of nuts and bolts extending through the bolt holes 22 and 24.

Referring now to Figure 3, the manner in which this form of sheath is fixed to a particular coupling pair is illustrated. Here, the coupling comprises a double shackle pair 31 and 32 connected to an eye 34 formed in the end of each of a pair of ropes to be joined by means of a respective egg-shaped link 36. The sheath to the left in the drawing is illustrated cut away to show the position of the coupling in place. In this case, the lateral curved ends of the slot 18 are divergent, as described above, to accommodate the eggshaped link 36.

The eye 34 is received in the main chamber 20 of its respective sheath and held generally in an axial position relative to the sheath by virtue of the noncircular section of the inner wall 20a and 20b conforming generally to the overall section of the eye 34. The forward end of the eye abuts against the arcuate portion of the forward wall portion 20a of the main chamber 20. The greatest dimension of the eye 34 coincides with that of the sheath between the tapers.

The connecting egg-shaped link 36 is received in the slot 18 between the main chamber 20 and the circular opening 14 such that the end of the shackle 31 or 32 is braced against the shoulder 16.

The halves of the sheath are held together by the strap 38 and bolts 40. Thus, the sheath holds the coupling members, up to the central double shackle, in positions relative to one another by the form retaining nature of the inner passage 10.

In an alternative form, the circular opening 14 is replaced with a more oval opening, having a lateral section conforming generally to that defined by the shackle at that point to hold it more firmly in its orientation relative to the link 36.

Clearly, the inner passage has to be adapted to suit different shapes and sizes of shackle combinations.

Each must hold substantially the constituent parts relative to one another.

It is also found that the shroud serves to protect the end of the rope where it is formed into the eye 34.

This bulged portion would otherwise be exposed to excessive wear.

Claims (12)

1. A line coupling fitting comprising a sheath securable over at least part of a line coupling and having an internal open passage (10) which is adapted to accommodate the line coupling (34, 36), the external surface (13) of the sheath providing the coupling with a substantially smooth outer surface.

2. A fitting as claimed in claim 1 in which the internal surface of the sheath defining the passage is adapted substantially to retain the coupling components in respective orientations relative to one another.

3. A fitting as claimed in claim 2 in which the internal surface of the sheath is formed with a recess (18) adapted to receive the side of a coupling member to hold it in position.

4. A fitting as claimed in claim 1, 2 or 3 in which the sheath comprises two identical halves (12).

5. A fitting as claimed in claim 4 in which the halves are bolted and/or strapped together.

6. A fitting as claimed in any preceding claim in which an opening (14) in one end of the passage is shaped to receive, at least partially, a further coupling member (32) attached to the line coupling inside the sheath.

7. A fitting as claimed in claim 6 in which the opening is adapted substantially to retain the further member in its orientation relative to the line coupling.

8. A fitting as claimed in any preceding claim in which the external surface of the sheath is tapered towards either or both ends.

9. A fitting as claimed in any preceding claim in which the external surface of the sheath comprises, in lateral section, a pair of arcuate portions joined by a pair of straight sided portions.

10. A fitting as claimed in any preceding claim in which the sheath is adapted to accommodate and retain the relative orientations of an eye (34) in a rope end coupled to a shackle (31, 32) partially received within the sheath by means of an intermediate coupling link (36).

11. A fitting as claimed in any of the preceding claims in which the sheath encircles all the coupling

12. A line coupling including a fitting as claimed in any preceding claim.