GB2279619A

GB2279619A - Method of and apparatus for capturing floating objects

Info

Publication number: GB2279619A
Application number: GB9412887A
Authority: GB
Inventors: Peter Michael Bolton
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-07-09
Filing date: 1994-06-27
Publication date: 1995-01-11
Anticipated expiration: 2014-06-27
Also published as: GB9412887D0; GB2279619B

Abstract

An apparatus for capturing floating objects comprising a hook means 1, adapted to engage a towing cable 7, anchor chain or the like, connected to a float and a drogue 2 such that when the hook means is towed the drogue serves to slow the passage of the hook means through the water. A combined float and drogue is described together with the procedures for using this assembly for capturing large vessels (See Figs 3 - 8) as well as smaller objects such as mooring buoys (Fig 14) and personnel. (Fig 15). <IMAGE>

Description

METHOD OF AND APPARATUS FOR CAPTURING FLOATING OBJECTS Field of the Invention This invention relates to an apparatus for and a method of capturing floating objects. It is specifically, but not exclusively, applicable to attaching a towing cable to a vessel, to a method of capturing a drifting vessel and to recovering objects such as people or buoys from the sea.

Backazound to the Invention In recent years, there has been a recurrent problem for salvage vessels when trying to connect towing cables to drifting vessels. As became clear when the total loss of the Braer occurred in January 1993, there is little a tug can do in the open sea if there is no way her towing cable can be secured. The principal reasons for the difficulties are: Extreme Weather Conditions: Salvage crews cannot work on the open deck of the tugs in all weather conditions. For safe operations, an absolute maximum of wind speeds of 50 knots and seas of 25 feet would be applicable to even the most up-to-date vessels except when head to weather.

Power on Casualty: Often the principal cause of the casualty is complete power failure. This means that, in order to establish a tow following the initial rocket line, a complex system of messengers needs to be used, to create an endless loop, so the salvage vessels power can be used to transfer successively heavier lines. There is then the problem of connecting on the deck of the casualty.

Crew on Casualtv: Even allowing for both the above, if the crew on board the casualty are of poor professional standard, are otherwise engaged (e.g. by a fire), or are absent due to abandonment, then any efforts made by the salvage vessel will be severely hampered. Time and the weather do not always permit crew to be transferred to the stricken vessel.

Similar problems exist in capturing smaller objects floating in the water. It is the object of the present invention to provide an assembly and a method that can overcome these problems not only when taking in tow a large vessel, but, in a scaled-down version, in capturing floating objects such as mooring buoys or personnel drifting or floating in the water.

Summarv of the Invention The present invention provides an apparatus for capturing floating objects comprising a hook means, adapted to engage a towing cable, anchor chain or the like, connected to a float and a drogue such that when the hook means is towed the drogue serves to slow the passage of the hook through the water.

Preferably the hook means is connected to a float so that the hook means is suspended beneath the float when in the water, the float being so sized and shaped that, when the hook means is towed, the float tilts over and partsubmerges in the water so as to serve as a drogue to slow the passage of the hook means through the water.

Preferably the hook means takes the form of a grapple.

Preferably the float is in the form of an annular floatation member with a flexible part or complete membrane thereacross. The float is suitably formed from a synthetic rubber fabric of the type used in the construction of inflatable boats or that used for the construction of off-shore bulk transfer hoses.

Preferably the floatation member is divided into a plurality of separately inflatable chambers in the manner of inflatable boat construction for security against the effects of loss of air and whereby the float may be stored folded or rolled into a smaller space and inflated by compressed air only when needed.

Preferably the floatation member incorporates a rigid frame adapted such that the hook means can be secured to the float by means of support wires and so as to give the float sufficient rigiditv.

In a particularly preferred embodiment the frame consists of a pair of metal beams welded or bolted together in a cruciform arrangement.

In a further embodiment the hook means takes the form of a J-type chasing hook.

In this embodiment the float can be incorporated into the hook means by way of buoyancy in or around the hook, the buoyancy being so sized, shaped and distributed such that the hook portion of the hook means is suspended beneath the surface of the water and is generally directed away from that surface.

In a further embodiment there is provided a device for attaching a towing cable to or around a floating object comprising an apparatus for capturing floating objects as described above attached to a cable with buoyancy means attached to some or all of a portion of the length of that cable.

Preferably the buoyancy means comprises an inflatable tube connected at points along its length to the cable to provide a substantially continuous form of buoyancy thus keeping that portion of the cable to which the buoyancy aid is attached at or near the surface of the water.

There is further provided a method of capturing floating objects comprising: (i) providing a device for attaching a towing cable to or around a floating object as described above; (ii) towing around the object the cable with the buoyancy means attached to it such that the object becomes encircled by that cable; (iii) engaging the hook means with the cable to form a loop enclosing the floating object; (iv) closing the loop around the object to permit the object to be towed.

In a still further embodiment there is provided a method of capturing floating objects such as a vessel which has an anchor chain or the like which can be lowered into the water comprising: (a) providing a device for attaching a towing cable to or around a floating object as described above; (b) lowering the anchor of the vessel to be towed into the water; (c) towing the cable past the anchor chain such that the hook means engages with said anchor chain; (d) drawing the cable away from the vessel such that it is then under tow.

Brief Description of the Drawings In the drawings, which illustrate exemplary embodiments of the invention: Figure 1 is a perspective view of the grapple and float in water; Figure 2 is a perspective view of the same grapple and float being towed by a cable; tilted over and 70% submerged to give lateral assistance to the pulling force exerted by the towing vessel; Figure 3 is a diagrammatic view of a salvage vessel forming a loop of cable according to one technique; Figure 4 is a similar view showing another technique for forming a loop; Figure 5 shows the formation of a loop around a drifting vessel; Figure 6 shows the completion of the loop ready for towing; Figure 7 is a view of the bow portion of a vessel, showing the capture of the anchor chain using the grapple of the invention; Figure 8 shows schematically how a vessel can be encircled with a tow wire; ; Figure 9 shows a roll of inflatable hose suitable for use as a buoyancy means; and Figure 10 shows diagrammatically how one end of the hose can be clamped between two plates to afford an air-tight seal; Figure 11 shows a further embodiment with a form of floating hook together with a conventional drogue; Figure 12 shows a conventional J-type chasing hook attached to a buoy; Figure 13 shows a floating hook suitable for use when capturing smaller objects; Figures 14 and 15 show diagrammatically a floating hook and non-floating rope being used to capture a buoy and an unconscious person respectively.

Detailed Description of the Preferred Embodiments Where the object to be captured is a vessel, then the apparatus generally consists of a float attached to a grapple. Referring to Figure 1, the grapple 1 is of conventional design, commonly in use by oil rig supply/anchor hauling vessels, typically having a safe working loading of approximately 100 tonnes, and is suspended from a float 2 consisting of an annular inflatable floatation member 3 which may be divided up into a plurality of separately inflatable boat construction for security against the effects of loss of air. The floatation member is formed from a synthetic rubber fabric of the type used in inflatable boats (eg), and has the centre of the annulus wholly or partially closed by a sheet 4 of a suitable fabric stretched across it.A frame 5, consisting of a pair of steel beams welded or bolted together in cruciform arrangement, permits the grapple 1 to be secured to the float by means of four support wires 6. At rest, the float lies generally horizontally on the water, with the grapple suspended beneath it.

As may be seen from Figure 2, the grapple may be connected to a towing cable 7 by means of a shackle, again in conventional manner. The cable is suitably a 2 to 3 inch diameter cable, depending on the size of the vessel to be towed. When the cable is towed, the float 2 flips over on to its side, as illustrated, with approximately 70% of it immersed in the water to serve as a drogue, slowing passage of the grapple through the water, and so permitting a loop of the cable 7 to be formed as it is paid out behind the salvage vessel.

Figure 3 shows one way in which the salvage vessel may form the cable into a loop. The cable 7 is provided with floats 8 spaced along its length at intervals such that the cable forms shallow bights close enough to the surface to ensure contact with the drifting vessel, and to ensure that the grapple can capture the cable. Typically, the floats will be of approximately 1 tonne buoyancy and spaced at intervals of approximately 50 feet. The salvage vessel 9 completes a loop around the drifting vessel, with the drogue effect of the float 2 ensuring that the cable pays out to form the loop rather than the grapple simply following the salvage vessel.After drawing the cable 7 across the grapple 1 and float 2, as shown in Figure 3, using the crash rail 9a to elevate the cable over the float 2, the salvage vessel 9 then steers ahead and then in the opposite direction to bring the cable into engagement with the grapple to close the loop.

In an alternative manoeuvre, as illustrated in Figure 4, the salvage vessel 9, on its approach to the grapple 1 and float 2, pays out enough of the cable 7 without attached floats 8 to form a loop beneath the grapple. Heaving up on the cable then pulls it into engagement with the grapple to complete the loop, as before.

Figure 5 shows the completed loop around the drifting vessel 10. The salvage vessel 9 then pulls the cable tight to draw the loop into contact with the hull of the vessel 10 so that towing can commence, as shown in Figure 6. The floats 8 supporting the cable 7 nearest to the salvage vessel 9 are attached with a single turn of wire, permitting them to slide along the cable 7 so as not to impede the closing of the loop on to the vessel 10. The other floats 8 are attached using two or three round turns to ensure that they do not slide, but remain evenly spaced along the cable. More floats may be needed in areas where flared hull sections of the drifting vessel's hull could cause the line to slip off.

The method of encircling a vessel with a tow wire is further illustrated in Figure 8.

Figure 7 illustrates how the grapple can be used to capture the anchor chain 11 of the drifting vessel 10, to permit it to be towed thereby. The grapple 1 is drawn by the salvage vessel obliquely across the bows of the vessel 10 so that it drifts into the side of the vessel. Continued towing then draws the grapple into engagement with the anchor chain, further motion permitting towing of the vessel 10 to commence.

To deploy the grapple and drogue from the salvage vessel, one can either use tugs with wires led through the stern fairleads, or deploy a slave drogue and use ship's power ahead to drag the whole assembly over the stern. With the salvage vessel heading into the weather, the crew can safely work in up to 35 feet seas and 70 knots wind.

As an alternative to individual floats 8 attached at intervals to the cable 7, a form of inflated hose 20 can be attached to the cable 7 to provide continuous buoyancy along a portion or portions of its length. Such a hose is shown in figure 9 and is generally sealed at one end by any conventional means. One such means is shown in figure 10 where two flat plates 21 are bolted or otherwise clamped on either side of the hose 20. The plates can be ribbed (not shown), the ribs on opposing plates co-operating together to improve the effectiveness of the seal.

A further embodiment of the invention could also be used for recovering buoys in more difficult conditions than are allowed by present techniques.

Again, a loop of cable around the buoy is achieved by circling the buoy in the recovery vessel, while paying out cable attached to the grapple and float.

The grapple then hooks the cable, as hereinbefore described, and the loop is drawn closed to capture the buoy; alternatively towing the grapple so as to engage the buoy riser pennant.

Further embodiments of the invention are shown in figures 11 and 12.

Referring to figure 11, it shows a conventional drogue 30 attached by a line 31 to a floating hook 32. The buoyancy in the hook 33, which in this example is an integral part of the hook, is deployed in such a way that the tip of the hook points downwards away from the surface of the water. Additional buoyancy 34 may well be required to retain the hook in the desired orientation.

The jaw 30 of the hook 32 is sufficiently radiused to prevent damage to any cable or wire that the hook engages in use.

It is not essential that the hook incorporates its own buoyancy. Referring to figure 12, this illustrates a standard J-type chasing hook 41 with a buoy 42 attached to it, the assembly being attached to a cable 47.

Although the primary concept of this invention was to assist stricken vessels of a large size, the assembly described can be produced on any scale to allow the recovery of even small items (i.e. mooring buoys) and it can also be used in conjunction with a life buoy to recover personnel from the sea.

A further form of floating hook 50 particularly adapted for this small scale type of operation is shown in figure 13. Figures 14 and 15 show this method in operation. The combination of a conventional drogue 51, floating hook 50 and non-floating cable or rope 52, as shown in figure 14, has proved particularly suitable for recovering buoys or other small objects from the water.

The assembly can be further adapted for rescuing personnel by incorporating a life buoy 54 and a stopper 55 as shown in figure 15. The position of the stopper is such that a loop is created of an appropriate size to lasso a person under the arms without closing so tightly around their body as to result in injury.

Claims

1. An apparatus for capturing floating objects comprising a hook means, adapted to engage a towing cable, anchor chain or the like, connected to a float and a drogue such that when the hook means is towed the drogue serves to slow the passage of the hook means through the water.

2. An apparatus for capturing floating objects as claimed in Claim 1 wherein the hook means is connected to a float so that the hook means is suspended beneath the float when in the water, the float being so sized and shaped that, when the hook is towed, the float tilts over and part-submerges in the water so as to serve as a drogue to slow the passage of the hook means through the water.

3. An apparatus for capturing floating objects as claimed in Claim 1 or Claim 2 wherein the hook means takes the form of a grapple.

4. An apparatus for capturing floating objects as claimed in any of Claims 1-3 wherein the float is in the form of an annular floatation member with a flexible part or complete membrane thereacross.

5. An apparatus for capturing floating objects as claimed in Claim 4 wherein the floatation member is divided into a plurality of separately inflatable chambers in the manner of inflatable boat construction for security against the effects of loss of air and whereby the float can be stored folded or rolled into a smaller space and inflated by compresses air only when needed.

6. An apparatus for capturing floating objects as claimed in Claim 4 or Claim 5 wherein the floatation member incorporates a rigid frame adapted such that the hook means can be secured to the float by means of support wires.

7. An apparatus for capturing floating objects as claimed in Claim 6 wherein the frame consists of a pair of metal beams welded or bolted together in a cruciform arrangement.

8. An apparatus for capturing floating objects as claimed in any preceding claim except Claim 3 wherein the hook means takes the form of a J-type chasing hook.

9. An apparatus for capturing floating objects as claimed in Claim 1 wherein the float is incorporated into the hook means by way of buoyancy in or around the hook, the buoyancy being so sized, shaped and distributed that the hook portion of the hook means is suspended beneath the surface of the water and is generally directed away from that surface.

10. A device for attaching a towing cable to or around a floating object comprising an apparatus for capturing floating objects as claimed in any of Claims 1-9 attached to a cable with buoyancy means attached to some or all of a portion of the length of that cable.

11. A device for attaching a towing cable to or around a floating object as claimed in Claim 10 wherein the buoyancy means comprises an inflatable tube connected at points along its length to the cable to provide a substantially continuous form of buoyancy thus keeping that part of the cable to which the buoyancy aid is attached at or near the surface of the water.

12. A method of capturing floating objects comprising: (i) providing a device for attaching a towing cable to or around a floating object as claimed in Claim 10 or Claim 11; (ii) towing around the object the cable with the buoyancy means attached to it such that the object becomes encircled by that cable; (iii) engaging the hook means with the cable to form a loop enclosing the floating object; (iv) closing the loop around the object to permit the object to be towed.

13. A method of capturing a floating object such as a vessel which has an anchor chain or the like which can be lowered into the water comprising: (a) providing a device for attaching a towing cable to or around a floating object as claimed in Claim 10 or Claim 11; (b) lowering the anchor of the vessel to be towed into the water; (c) towing the cable past the anchor chain such that the hook means engages with said anchor chain; (d) drawing the cable away from the vessel such that it is then under tow.

14. An apparatus for capturing floating objects substantially as herein described with reference to and as illustrated in any combination of the accompanying drawings.

15. A device for attaching a towing cable to or around a floating object substantially as described herein with reference to and as illustrated in any combination of the accompanying drawings.

16. A method of capturing floating objects substantially as herein described with reference to and as illustrated in any combination of the accompanying drawings.