GB1602512A - Apparatus for arresting a floating vessel - Google Patents

Description

(54) APPARATUS FOR ARRESTING A FLOATING VESSEL (71) We, JOHN INGRAM MUIR HEAD and ELSPETH ELANOR MUIR HEAD, of 21 Chilton Parade, Warrawee, New South Wales, 2074, Australia, citizens of Australia, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to apparatus for arresting a floating vessel for example to prevent ships from colliding with rigid structures such as sea walls for example when berthing, or when approaching navigation openings in rigid structures. Such collisions can be caused by mechanical failure and/or human error, and are relatively frequent in ferry services where the vessels berth many times in a single day.

Hitherto it has been known to provide stationary resilient buffers to protect sea walls. However, not only do such buffers damage the ships but the force of impact is often sufficient to shear and damage the buffers themselves.

It is known to use arrestor systems on aircraft carriers to enable military aircraft to land within a short distance. Such arrestor systems generally consist of a number of individual transverse cables, held by shock absorbers, which stop the aircraft when its arrestor hook catches one or more of the cables.

However, such an arrestor system is entirely inappropriate for ships since the mass of a military aircraft is of the order of 15 tonnes whilst the mass of even a relatively small ferry is on the order of 250 tonnes.

There should be minimal recoil of a ship during berthing, because otherwise the vessel may rebound into a wharf facility or another vessel causing severe damage and even loss of life.

In addition an arrestor system for ships, unlike a system for aircraft, should be able to adjust the position of the arresting device to accommodate both changes in tide level and wave action. This would then enable the arresting device to contact the ship at approximately the water line, where the ship will generally be strong, and not above the waterline where the superstructure may be relatively weak.

The present invention is aimed at providing apparatus for arresting a floating vessel.

Embodiments of the apparatus are described below which arrest a floating vessel with a minimum of recoil and which will accommodate changes in height according to requirements.

According to the invention therefore we provide apparatus for arresting a floating vessel comprising two fluid energy dissipators adapted for mounting one each side of a waterway, an arrestor cable which in use is directly connected to and extends between said dissipators, two or more floats to maintain said cable at a predetermined level relative to the level of the waterway, and cable guides mounted on respective ones of said floats which in use are positioned at intervals between said dissipators.

If desired, the floats may be submersible to permit the arrestor cable to be sunk in order that ships be able to pass over it. Such capability is, advantageous if the arrestor is for example protecting the gate of a graving or dry dock or the navigation channel of a bridge.

The invention will be described hereinafter in more detail and by way of example only in connection with the drawings representing three different embodiments of the invention.

In the drawings Figure 1 is a plan view of a dock gate incorporating an arrestor apparatus for a floating vessel; Figure 2 is an elevation of the dock gate of Figure 1; Figure 3 is a side view, much enlarged, of a pivotally mounted float being of part of the apparatus shown in Figures 1 and 2; Figure 4 is a plan view of the float of Figure 3; Figure 5 shows a chord spreader, which may be used in the apparatus of Figure 1; Figure 6 shows details of the energy dissipator used in the apparatus of Figure 1; Figure 7 shows another embodiment of the invention, applying the apparatus to a ferry terminal; Figure 8 shows details of the apparatus of Figure shows detail 7; Figure 9 shows details of the intermediate supports shown in Figure 8; Figure 10 shows details of the energy dissipators provided in the arrangement of Figure 7;; Figure 11 shows some further details of the arrangement shown in Figure 10; Figure 12 is a side view of a chord spreader, which may be used in the arrestor system of Figure 7; Figure 13 is a plan of a further embodiment applying the apparatus to the protection of a bridge; Figure 14 is a sideview of part of the bridge shown in Figure 13 indicating a navigation channel; Figure 15 shows schematically the support and anchorage of an arrestor chord for the bridge protection; Figure 16 shows movement of the support of Figure 15 on impact of the chord by a ship; Figure 17 shows schematically the arrestor chord guidance means at the navigation channel underneath the bridge; and Figure 18 shows details of the guidance means shown in Figure 15.

A first embodiment of the present invention will now be described in connection with Figures 1 to 6 relating to apparatus including a submersible arrestor cable arrangement. This embodiment is intended to protect the gate 1 of a graving dock 2 from collision by ships. When the graving dock 2 is empty, and a vessel is inside undergoing repairs, the gate 1 prevents the seawater entering the dock. Therefore the gate experiences a large hydrostatic force which approaches the designed maximum load for the gate. If a ship were then to collide with the gate, the dynamic force applied to the gate would create a total load sufficient to significantly deform or collapse the gate 1 and thereby permit seawater and possibly the colliding ship to enter the empty dock. Such a collision would result in severe damage and probable loss of life.

In order to prevent such a collision it is necessary to arrest the approaching ship prior to the collision. In addition it is also necessary to remove or lower the arresting system 3 in order to permit access, into and out of the dock 2.

The arrestor apparatus of the first embodiment comprises radius frames 4 positioned to either side of the gate 1. The inner end 5 of each frame 4 is pivotally secured to the coping 6 adjacent to the dock entrance to enable the frames 4 to pivot in a vertical plane.

A submersible float 7 pivotally connected to the outer end 8 of each frame 4 comprising the arms 26 and 27. Each submersible float 7 (Figures 3 and 4) comprises a tank 9 with portholes 10. Within each tank 9 is an inflatable bag 11 connected to a source of compressed air via a pneumatic line 25 which extends along the frame 4. When the bag 11 is inflated, water is forced out of the tank 9 and the float 7 and the outer end 8 of the frame 4 rises to the surface. However, when the bag 11 is depressurised, the bag 11 collapses permitting water to enter the tank 9 via the portholes 10, thereby causing the float 7 to sink. An arrestor cable 12 of the apparatus 3 extends between the floats 7 and passes over two horizontal sheaves 13 each of which is located on the top of the corresponding float 7.From each float 7, the cable 12 extends outwardly from the gate 1 and is connected to one of two energy dissipators 14.

Each energy dissipator 14 is located adjacent the coping 6 of the sea wall extending to either side of the dock 2. Each of the energy dissipators 14 (Figure 6) basically comprises two co-axial vertical cylinders 15, 16, both of which are secured in position in the sea bed and by means of attachment 17 to the adjacent sea wall 18 or to piles 19.

The outer cylinder 15 is sealed whilst the inner cylinder 16 has a multiplicity of small holes 20 therethrough. A piston 21 is slidably located within the inner cylinder 16 and a non-corrosive liquid fills the interiors of the cylinders up to a predetermined level.

The upper end of each cylinder protrudes above sea level and a vertically pulley 22 is mounted thereon. Each end of the arrestor cable 12 extends from one sheave 13 to the pulley 22 of the adjacent energy dissipator 14. The end of the cable 12 after passing over the pulley 22 is connected to the piston 21 within the inner cylinder 16.

In operation, the submersible floats 7 and frames 4 enable the arrestor chord 12 to be sunk to permit ships to enter and leave the dock 2. At all other times the floats 7 maintain the arrestor cable 12 extended across the gate 1 and at sea level. In the event of a ship which is out of control heading towards the gate 1 the ship first strikes the arrestor cable 12. The momentum of the ship pulls the arrestor cable 12 into a V-shaped configuration with the point of the V directed towards the gate 1. In order to achieve this configuration the arrestor chord runs over the sheaves 13 and pulleys 22 and the pulls both pistons 21 upwardly within the inner cylinders 16 of the energy dissipators 14.

The movement of each piston 21 forces the liquid in the inner cylinder 16 out through the holes 20 therein and draws liquid from the outer cylinder 15 through the bottom 23 of the inner cylinder 16 into the inner cylinder behind the moving piston 21. The energy required for this transfer of liquid absorbs and therefore dissipates the kinetic energy of the moving vessel. In consequence the ship is slowed to a halt.

The energy dissipators 14 are proportioned by design to bring the vessel to rest before it comes into contact with the gate which the arrestor apparatus is protecting.

After the vessel has been disengaged from the arrestor cable 12, the relatively small mass of the pistons 21 slowly sinks the pistons through the fluid in the inner cylinder 16 thereby allowing the arrestor cable 12 to return to its original configuration, ready for use again.

If desired the central portion of the arrestor cable 12 may be constructed as a plurality of parallel cables 12A to 12D connected between two spreaders 24 as shown in Figure 5. In this way the retarding force of the arrestor cable 12 is spread over the bow of the ship thereby reducing still further any likelihood of damage to the ship.

Means such as a rotatable sleeve with apertures therethrough may be positioned over the inner cylinder 16. Thus by rotating the sleeve to align or mis-align the apertures in the sleeve with the holes 20 in the inner cylinder 16, the rate at which the fluid is transferred from one cylinder to another may be controlled. In consequence the rate at which energy is dissipated in the energy dissipators 14 may be adjusted to suit different applications.

In a second embodiment of the present invention, as shown in Figures 7 to 12 the arrestor apparatus protects the sea wall and ferries using a pectinate wharf structure formed from a plurality of parallel rectangu lar wharves or pontoons projecting out wardly perpendicular to a sea wall as shown in Figure 7. The ferries concerned in this illustration (30, 31) are double-ended and enter the space between two wharves, for example wharves 32 and 33, then tie up adjacent one wharf and finally reverse their direction of forward travel to leave the wharf. Previously engine failure and/or hu man error resulted in the ferries crashing into rigid barriers erected in front of the sea wall with consequential damage to both the ferries and the barriers.The arrestor system of this embodiment comprises two energy dissipators 34 as described above positioned adjacent the sea wall 35 one to either side of the group of wharves. The energy dissipators 34 are each stayed to resist horizontal forces by means of piles 36 as in Figure 10.

An arrestor cable 37 extends between the pulley 45 at the top of each energy dissipator 34 under the wharves, 32 and 33 and immediately in front of and parallel to the sea wall 35.

The arrestor cable 37 is maintained at sea level by passing between a plurality of pairs of opposed horizontal sheaves 38 (Figure 8).

Each pair of sheaves 38 is located on top of a corresponding buoy 39 which is connected to a corresponding stayed pile 40 (Figure 9) by a connecting arm 41. The pile 40 carries a protection 46. Each connecting arm 41 has at each end a universal joint 42 which therefore permits the connecting arm 41 to move relative to both the pile 40 and the buoy 39 in response to tide and wave movements.

The space between adjacent wharves (32, 33) is sufficient to accommodate two ferries side by side. In that space there are three piles 40 each with their associated float or buoy 39. Two piles are located one closely adjacent each wharf whilst the remaining pile is centrally located between the wharves. Thus the two regions between the centre pile and each of the other two piles are impact zones liable to receive an overshooting ferry. Each pile may consist of one or more piles.

An arrestor float 43 is preferably secured to the arrestor cable 37 in the impact zone to assist in maintaining the arrestor cable at sea level. In addition to the arrestor float 43 (Figure 12), two spreaders 44 and a plurality of chords 37A to 37D may also be provided to spread the retarding force of the arrestor cable(s) 37 on the stem of an overshooting ferry. If desired, the floats 43 may be replaced by submersible floats such as float 7 of the first embodiment.

In operation, when an overshooting ferry travels beyond its intended mooring position, the bow of the ferry contacts the arrestor and moves it towards the sea wall.

In consequence the arrestor cable 37 runs through the sheaves 38 and over the pulley 45 at the top of each energy dissipator 34 to move the pistons in the energy dissipators through the liquid. As a result the kinetic energy of the ferry is absorbed and the ferry slowed to a halt before hitting the sea wall.

As before, when the ferry has been halted and disengaged from the arrestor cable 37, the pistons slowly sink through the fluid to their rest position thereby returning the arrestor wire to its original position.

The arrestor system of the second embodiment is designed to bring a 250 tonne displacement ferry initially travelling at 5 knots to rest in a distance of 6 meters. The system has the advantage of substantially no recoil and an energy absorbing capability. In addition since the retarding force of the fluid is not applied to the ferry until the piston has begun to move, and the mass of the piston and wire are negligible, compared to that of the ferry, the initial impact forces are low thereby protecting the passengers and also the ferry from damage.

In the case where some of the wharves have to be used also for heavier ferries an additional arrestor system can be installed behind part of the basic system as shown in Figures 7 and 11. In this case the additional arrestor cable 47 with its floats 48 is guided over sheaves 49 to two energy dissipators 50 secured to the sea wall 35. As shown in Figure 11 the sheaves 49 are each mounted on a pile 51 which is braced against the sea wall 35 by a brace 52.

A third application of the vessel arrestor system is for the protection of the river piers of bridges from collision with vessels which may be outside the navigation channel through pilot error or due to malfunction.

In this embodiment, which is shown in Figures 13 to 18 arrestor cables extend across the river on each side of the bridge to afford protection from both approaches as shown in Figures 13 and 14.

The bridge 60, which spans the river bed 61 is supported by river piers 62A .... 62H forming at one gap, for example between piers 62A and 62B, a navigation channel.

Arrestor cables 63 and 64 are arranged upstream and downstream of the bridge 60 and are connected at their respective ends to energy dissipators 65 and 66 positioned on the river banks 67.

The chords 63 and 64 are maintained at the desired elevation relative to the water surface by fairleads 68 supported by a buoy 75 and a float 76 (Figure 18) and are maintained in position relative to the bridge 60 by warps 69, 70 to anchors 71, 72 secured to the river bed 61 on each side of the arrestor cables 63 and 64. Where the waters are subject to fluctuation in level this may be accommodated by terminating the warps 69 nearest to the protected structure with a weight 73 suspended below the fairlead 68 over a sheave block 74. This arrangement not only accommodates vertical movements but also horizontal movements such as are caused by the contact of a vessel with the arrestor cable.

At the navigation channel it is necessary to depress the arrestor cable to permit vessels to pass unhindered. This is accomplished by the provision of weights on cable sections 77' attached to the buoys 75 and floats 76, carrying the fairleads 68 located on each side of the navigation channel as shown schematically in Figure 17. If desired floats 76 may be replaced by submersible floats such as float 7 of the first embodiment.

If a vessel 77 (Figure 16) approaches the protected structure other than within the navigation channel it will contact the arrestor cable 64. Initially the vessel 77 will proceed without appreciable retardation as the chord 64 is brought to level at the navigation channel, if any, with the cable sections 77' being pulled into the horizontal position. From this position when the cable 64 becomes straight and taut the movement is transmitted to the energy dissipators 66 (Figure 13) at each end of the cable 64 and retardation of the vessel commences.

In this embodiment it may prove more convenient to orient the energy dissipators 65 and 66 so that they conform to the shore line 67 and lie horizontal or on a slight incline. Where large vessels require arresting the dimensions of the arrestor cable, fairleads, anchors, warps, dissipators and other components may be very large to contain stresses within reasonable limits with adequate factors of safety. Energy dissipators may be constructed in metal or concrete, suitably reinforced and anchored.

In all embodiments the cables may for example consist of steel wire rope, synthetic or man-made fibre rope or chordage. Where the arrestor apparatus is required to halt vessel with straight, raking stems it is necessary to use a cable of high tensile material sheathed in a material having a high coefficient of friction so that it will not slide down the stem and pass beneath the vessel. The cable may also be of a crosssectional shape such that it will not roll on the stem and slide under the vessel.

WHAT WE CLAIM IS: 1. Apparatus for arresting a floating vessel comprising two fluid energy dissipators adapted for mounting one each side of a waterway, an arrestor cable which in use is directly connected to and extends between said dissipators, two or more floats to maintain said cable at a predetermined level relative to the level of the waterway, and cable guides mounted on respective ones of said floats which in use are positioned at intervals between said dissipators.

2. Apparatus according to claim 1, wherein each energy dissipator comprises an outer tube and an inner tube spaced therefrom, a piston movable in said inner tube, said piston being directly connected with one end of said arrestor cable, said outer tube being sealed and said inner tube having ports in its wall communicating with the space between said inner tube and said outer tube, and a non-corrosive liquid enclosed within said tubes.

3. Apparatus according to claim 1 or 2, wherein said cable includes a spreader

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (15)

**WARNING** start of CLMS field may overlap end of DESC **. knots to rest in a distance of 6 meters. The system has the advantage of substantially no recoil and an energy absorbing capability. In addition since the retarding force of the fluid is not applied to the ferry until the piston has begun to move, and the mass of the piston and wire are negligible, compared to that of the ferry, the initial impact forces are low thereby protecting the passengers and also the ferry from damage. In the case where some of the wharves have to be used also for heavier ferries an additional arrestor system can be installed behind part of the basic system as shown in Figures 7 and 11. In this case the additional arrestor cable 47 with its floats 48 is guided over sheaves 49 to two energy dissipators 50 secured to the sea wall 35. As shown in Figure 11 the sheaves 49 are each mounted on a pile 51 which is braced against the sea wall 35 by a brace 52. A third application of the vessel arrestor system is for the protection of the river piers of bridges from collision with vessels which may be outside the navigation channel through pilot error or due to malfunction. In this embodiment, which is shown in Figures 13 to 18 arrestor cables extend across the river on each side of the bridge to afford protection from both approaches as shown in Figures 13 and 14. The bridge 60, which spans the river bed 61 is supported by river piers 62A .... 62H forming at one gap, for example between piers 62A and 62B, a navigation channel. Arrestor cables 63 and 64 are arranged upstream and downstream of the bridge 60 and are connected at their respective ends to energy dissipators 65 and 66 positioned on the river banks 67. The chords 63 and 64 are maintained at the desired elevation relative to the water surface by fairleads 68 supported by a buoy 75 and a float 76 (Figure 18) and are maintained in position relative to the bridge 60 by warps 69, 70 to anchors 71, 72 secured to the river bed 61 on each side of the arrestor cables 63 and 64. Where the waters are subject to fluctuation in level this may be accommodated by terminating the warps 69 nearest to the protected structure with a weight 73 suspended below the fairlead 68 over a sheave block 74. This arrangement not only accommodates vertical movements but also horizontal movements such as are caused by the contact of a vessel with the arrestor cable. At the navigation channel it is necessary to depress the arrestor cable to permit vessels to pass unhindered. This is accomplished by the provision of weights on cable sections 77' attached to the buoys 75 and floats 76, carrying the fairleads 68 located on each side of the navigation channel as shown schematically in Figure 17. If desired floats 76 may be replaced by submersible floats such as float 7 of the first embodiment. If a vessel 77 (Figure 16) approaches the protected structure other than within the navigation channel it will contact the arrestor cable 64. Initially the vessel 77 will proceed without appreciable retardation as the chord 64 is brought to level at the navigation channel, if any, with the cable sections 77' being pulled into the horizontal position. From this position when the cable 64 becomes straight and taut the movement is transmitted to the energy dissipators 66 (Figure 13) at each end of the cable 64 and retardation of the vessel commences. In this embodiment it may prove more convenient to orient the energy dissipators 65 and 66 so that they conform to the shore line 67 and lie horizontal or on a slight incline. Where large vessels require arresting the dimensions of the arrestor cable, fairleads, anchors, warps, dissipators and other components may be very large to contain stresses within reasonable limits with adequate factors of safety. Energy dissipators may be constructed in metal or concrete, suitably reinforced and anchored. In all embodiments the cables may for example consist of steel wire rope, synthetic or man-made fibre rope or chordage. Where the arrestor apparatus is required to halt vessel with straight, raking stems it is necessary to use a cable of high tensile material sheathed in a material having a high coefficient of friction so that it will not slide down the stem and pass beneath the vessel. The cable may also be of a crosssectional shape such that it will not roll on the stem and slide under the vessel. WHAT WE CLAIM IS:

1. Apparatus for arresting a floating vessel comprising two fluid energy dissipators adapted for mounting one each side of a waterway, an arrestor cable which in use is directly connected to and extends between said dissipators, two or more floats to maintain said cable at a predetermined level relative to the level of the waterway, and cable guides mounted on respective ones of said floats which in use are positioned at intervals between said dissipators.

2. Apparatus according to claim 1, wherein each energy dissipator comprises an outer tube and an inner tube spaced therefrom, a piston movable in said inner tube, said piston being directly connected with one end of said arrestor cable, said outer tube being sealed and said inner tube having ports in its wall communicating with the space between said inner tube and said outer tube, and a non-corrosive liquid enclosed within said tubes.

3. Apparatus according to claim 1 or 2, wherein said cable includes a spreader

arrangement with a plurality of cables at the point of likely impact by a vessel.

4. Apparatus according to claim 2 or claims 2 and 3, in which the outer tube forms a pile for anchoring the energy dissipator in a selected location at one side of said waterway.

5. Apparatus according to any one of claims 1 to 4, wherein, in use, the energy dissipators are located at or near a sea shore or river bank and the reference level is the sea or river bed.

6. Apparatus according to claim 3, or claim 4 or 5 when dependent on claim 3 wherein said spreader arrangement has one float at each side thereof.

7. Apparatus according to any one of the preceding claims, wherein said cable guides are sheaves mounted on said floats.

8. Apparatus according to claim 7, wherein said floats have a constant buoyancy and automatically maintain the height of at least portion of said cable at said predetermined level with any rise and fall of the water level of said waterway.

9. Apparatus according to claim 7, wherein the buoyancy of the floats is adjustable for selectively adjusting the height of the arrestor cable relative to the sea or river bed in use of the apparatus.

10. Apparatus according to claim 9, wherein each float incorporates an inflatable bag.

11. Apparatus according to claim 9, including weights for partially counteracting the buoyancy of the floats.

12. Apparatus according to any one of claims 7 to 11 wherein each float is connected by links to a stationary structure, said links permitting restricted vertical and horizontal movement.

13. Apparatus according to any one of claims 7 to 11 wherein each float is held in position by oppositely extending warps connected to corresponding anchors.

14. Apparatus according to any one of the preceding claims, wherein at least a further arrestor cable with two further energy dissipators is arranged behind and spaced from at least part of said arrestor cable.

15. Apparatus arresting a floating vessel, substantially as described with reference to Figures 1 to 6 or Figures 7 to 12 or Figures 13 to 18 of the drawings.