GB1598865A

GB1598865A - Cushioning device for a mooring line

Info

Publication number: GB1598865A
Application number: GB12214/78A
Authority: GB
Original assignee: Bridgestone Corp
Current assignee: Bridgestone Corp
Priority date: 1977-04-01
Filing date: 1978-03-29
Publication date: 1981-09-23
Also published as: IT7821842A0; NL171787C; AU3453078A; AU504295B1; BR7802035A; NL171787B; FR2385951B1; IT1094306B; DE2813942A1; FR2385951A1; NL7803219A

Description

(54) CUSHIONING DEVICE FOR A MOORING LINE (71) We, BRIDGESTONE TIRE KABUSHIKI KAISHA, of No. 10-1, 1-Chome, Kyobashi, Chuo-Ku, Tokyo, Japan, a company organized according to the laws of Japan, 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: This invention relates to a cushioning device for a mooring line, to be used in particular for a floating tank, buoy or ship and anchored at its lower end to the sea-bed or a quay and connected at its upper end to the floating tank, buoy or ship.

Heretofore, the above mentioned kind of mooring line was comprised of a rope or chain anchored at its lower end to the sea-bed and connected at its upper end to a floating body.

As a result, such a mooring line is frequently subjected to tension and slackness, the degree of which is severely increased under stormy weather. In addition, when a ship is moored to the mooring line and an excessively heavy load is exerted on the mooring line owing to waves or a strong wind, there is a risk of the ship being subjected to a significantly heavy shock or of the mooring line being broken.

The present invention provides a cushioning device to be connected in use between two sections of a mooring line used for mooring a floating body, the cushioning device comprising a bowl-shaped vessel (as herein defined) composed of a casing to be in use anchored through one section of a mooring line to an anchoring point and a cover plate secured to the casing, a disc-shaped end plate enclosed in the casing to be secured to the other section of a mooring line connected to a floating body, and at least one intermediate resilient hollow block concentrically arranged within the said vessel and interposed between the cover plate and the disc-shaped end plate, the said block being spaced apart from the inner wall of the bowl-shaped vessel.

In this specification, by a bowl-shaped vessel there is meant a vessel which is not of constant cross-sectional area.

The invention will be further described, by way of example only, with reference to the accompanying drawings, wherein: Fig. 1 is a front elevational view of one embodiment of a cushioning device according to the invention, partly shown in section; Fig. 2 is a perspective view of a sealing ring; Fig. 3 is a graph of the amount of elongation as a function of tension applied to a mooring line provided with a cushioning device according to the invention in comparison with a conventional mooring line; and Fig. 4 is a front elevational view of another embodiment of a cushioning device according to the invention, partly shown in section.

Referring now to Fig. 1, there is shown one embodiment of a cushioning device according to the invention. Fig. 1 shows a base 1 anchored to the sea-bed. The base 1 is provided with an eyeplate 2 which is connected through shackles 3, a lower chain 22 and shackles 4 to a cushioning device 5 according to the invention. The cushioning device 5 is provided at its upper end with a swivel 6 which is connected through an upper chain 22 to a spherical float 7. The swivel 6 causes the spherical float 7 to rotate about the swivel 6. The spherical float 7 is connected through a suitable chain or rope to a floating body (not shown). The cushioning device 5 and swivel 6 function to prevent the mooring line from being subjected to a sudden tension and torsional force.

The spherical float 7 by its buoyancy functions to exert an upward force on the cushioning device 5 so as to urge it upwardly, thereby preventing the cushioning device 5 from being buried in the sea-bed and preventing entanglement of the mooring line.

In the present embodiment, the cushioning device 5 is provided therein with a tension resistant rod 9 formed of steel and having a diameter of 200 mm and a length of 1,450 mm.

The tension resistant rod 9 is provided at its lower end with a disc-shaped end plate 8 secured thereto and having a diameter of 850 mm. Provision is made of an intermediate resilient hollow cylindrical block 11 formed of rubber or a rubber-like elastic synthetic material and loosely engaged with the stress resistant rod 9. The intermediate resilient hollow cylindrical block 11 has an outer diameter of 760 mm, an inner diameter of 380 mm and a length of 1,000 mm and is spaced apart from the stress resistant rod 9 so as to form a hollow space 10 therebetween and is engaged at its lower end with the disc-shaped end Plate 8. The cushioning device 5 further comprises a bowl-shaped casing 16 anchored through the mooring line to the base 1 and a cover plate 13 secured to the bowl-shaped casing 16 by means of a flange-bolt joint and engaged with the upper end of the intermediate resilient hollow cylindrical body 11. The cover plate 13 is provided at its boss with a hole 12 through which is extended the tension resistant rod 9. The bowl-shaped casing 16 is constructed by a bowl-shaped circumferential wall 15 surrounding the intermediate resilient hollow cylindrical body 11 and spaced apart therefrom so as to form an annular space 14 therebetween.

The bowl-shaped casing 16 is provided at its lower end surface with an eyeplate 17 to be connected to the base 1. The bowl-shaped casing 16 is so dimensioned that, when the mooring line is subjected to tension and hence the intermediate resilient hollow cylindrical block 11 is subjected to the maximum compressive stress and shortened to a length of 500 mm, the inner diameter of the annular space 14 becomes a maximum at a middle point between the disc-shaped end plate 8 and the cover plate 13, that is at a point spaced apart from the cover plate 13 by 250 mm. For this purpose, the maximum inner diameter of the bowl-shaped casing 16 is made 1.5 times larger than the outer diameter of the intermediate resilient hollow cylindrical body 11, that is of the order of 1,140 mm.

As a result, when the mooring line is subjected to tension and the intermediate resilient hollow cylindrical block 11 also becomes bowl-shaped in configuration to enlarge its diameter, the maximum enlarged diameter point of the intermediate resilient hollow cylindrical block 11 is brought into engagement with the maximum inner diameter point of the bowl-shaped casing 16.

As seen from the above, the cushioning device constructed as above described has a number of advantages. In the first place, when the mooring line is subjected to tension, the disc-shaped end plate 8 can be raised by freely enlarging the diameter of the intermediate resilient hollow cylindrical block 11. Secondly, the bowl-shaped casing 16 is compact in construction and takes up less space and hence provides a material decrease in weight.

Third, the bowl-shaped casing 16 is connected at its maximum diameter portion whose circumferential length is long to the cover plate 13 by means of the flange-bolt joint, so that bolts 18 can be equidistantly spaced apart from each other by a sufficiently long distance, thereby permitting assembly of the cover plate 13 with the bowl-shaped casing 16 in a simple and reliable manner. Finally, since the cushioning device is bowl-shaped, the intermediate resilient hollow cylindrical block 11 can easily be incorporated into and assembled with the bowl-shaped casing 16.

A well known cam-lock joint may be used in place of the above mentioned flange-bolt joint. The cam-lock joint is simple in construction and can permit assembly of the cover plate 13 and the bowl-shaped casing 16 in a rapid manner, so that it is preferable to apply the cam-lock joint to a small size cushioning device provided the cam-lock joint has a sufficiently high strength.

A sealing member 19 is composed of a sealing ring formed of rubber or a rubber-like elastic synthetic material and hermetically sealing the tension resistant rod 9 to the hole 12 formed at the boss of the cover plate 13. The sealing member 19 is secured to the cover plate 13 and functions to prevent foreign matter in the sea from entering into the bowl-shaped casing 16.

As shown in Fig. 2, the peripheral edge of the sealing member 19 facing the swivel 6 may be made thin so as to be formed into a lip-like edge. It is preferable that such a lip-like edge of the sealing member 19 is provided with cuts 20 for the purpose of not only allowing the tension resistant rod 9 to easily extend therethrough but also of increasing the clamping force of the sealing member 19.

A stopper 21 composed of a disc-shaped plate formed of rubber or a rubber like elastic synthetic material serves to stop the downward movement of the tension resistant rod 9 when the mooring line is released from tension and the intermediate resilient hollow cylindrical block 11 is restored from its bowl-shaped state into its original cylindrical state.

A plurality of longitudinal heat radiating fins 23 are provided around the periphery of the bowl-shaped vessel and reinforce it.

When the mooring line including the cushioning device 5 is subjected to tension, it is preferable that the amount of elongation of the mooring line is gradually increased as a function of the tension.

Fig. 3 shows the relation between the tension and the amount of elongation. As shown in Fig. 3, it is preferable that the amount of elongation is gradually increased as a function of the tension as shown by a curve 2 if compared with a curve 1.

Experimental tests have yielded the result that, in order to satisfy the relation between the tension and the amount of elongation shown by the curve 2, the intermediate resilient hollow cylindrical block 11 must satisfy the following conditions given by D =1.8to2.2 d (D-d)/2 0.15 to 0.25 H where D is the outer diameter of the intermediate resilient hollow cylindrical body 11, d is its inner diameter and H is its length. In this case, as described above, the maximum inner diameter of the bowl-shaped casing 16 should be 1.5 times larger than the outer diameter D of the intermediate resilient hollow cylindrical block 11, In the above described embodiment, use is made of one cushioning device 5, but a plurality of cushioning devices may be connected in series or in parallel in dependence with the size of the ship to be moored or the tidal current.

In the above described embodiment, use was made of one intermediate resilient hollow cylindrical block 11. Alternatively, a plurality of these blocks may be symmetrically arranged with respect to the tension resistant rod 9 in dependence with the size of the ship to be moored or the tidal current. The block 11 may be made conical or barrel shaped instead of cylindrical.

In addition, the tension resistant rod 9 may be omitted and the upper chain 22 may be extended through the hole 12 provided in the boss of the cover plate 13 and directly connected to the disc-shaped end plate 8.

The cushioning device thus constructed according to the invention is light in weight and effective in its cushioning operation.

Fig. 4 shows another embodiment of a cushioning device according to the invention. In the present embodiment, around the bowl-shaped vessel is fitted an annular float 24 which is made integral with the bowl-shaped vessel. The annular float 24 functions to eliminate the under-water weight of the cushioning device 5 and prevent relative movement between the cushioning device 5 and the annular float 24. As a result, it is possible to more effectively prevent the mooring line from twisting. In addition, the presence of the annular float 24 ensures a significant increase in the volume of the cushioning device 5, thereby preventing the cushioning device 5 from being buried in the sea-bed.

It is preferable to divide the annular float 24 into two halves which are fitted around the cushioning device 5 by means of a band 25.

The float 24 is constructed of a foamed material 26 such as urethane and a shell 27 formed of polyethylene available under the trade name of Hi-zex and manufactured by Mitsui Chemical Co., in Japan. If the annular float 24 has a sufficiently high strength, it is possible to omit the foamed material 26. An annular groove 28 is provided along the inner periphery of the annular float 24 and adapted to be firmly engaged with a projection such as the flange of the flange-bolt joint.

As stated hereinbefore. the invention provides a cushioning device for a mooring line used for mooring floating bodies such as ships, which can effectively absorb the tension applied to the mooring line, which is highly stable in shock-absorbing operation, and which can eliminate any twisting movement of the mooring line and hence can prevent a breakage or other failure of the mooring line.

WHAT WE CLAIM IS: 1. A cushioning device to be connected in use between two sections of a mooring line used for mooring a floating body, the cushioning device comprising a bowl-shaped vessel (as herein defined) composed of a casing to be in use anchored through one section of a mooring line to an anchoring point and a cover plate secured to the casing, a disc-shaped end plate enclosed in the casing to be secured to the other section of a mooring line connected to a floating body, and at least one intermediate resilient hollow block concentrically arranged within the said vessel and interposed between the cover plate and the disc-shaped end plate, the said block being spaced apart from the inner wall of the bowl-shaped vessel.

2. A cushioning device as claimed in Claim 1, wherein the disc-shaped end plate is secured to a tension resistant rod which hermetically extends through the said cover plate

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. A plurality of longitudinal heat radiating fins 23 are provided around the periphery of the bowl-shaped vessel and reinforce it. When the mooring line including the cushioning device 5 is subjected to tension, it is preferable that the amount of elongation of the mooring line is gradually increased as a function of the tension. Fig. 3 shows the relation between the tension and the amount of elongation. As shown in Fig. 3, it is preferable that the amount of elongation is gradually increased as a function of the tension as shown by a curve 2 if compared with a curve 1. Experimental tests have yielded the result that, in order to satisfy the relation between the tension and the amount of elongation shown by the curve 2, the intermediate resilient hollow cylindrical block 11 must satisfy the following conditions given by D =1.8to2.2 d (D-d)/2 0.15 to 0.25 H where D is the outer diameter of the intermediate resilient hollow cylindrical body 11, d is its inner diameter and H is its length. In this case, as described above, the maximum inner diameter of the bowl-shaped casing 16 should be 1.5 times larger than the outer diameter D of the intermediate resilient hollow cylindrical block 11, In the above described embodiment, use is made of one cushioning device 5, but a plurality of cushioning devices may be connected in series or in parallel in dependence with the size of the ship to be moored or the tidal current. In the above described embodiment, use was made of one intermediate resilient hollow cylindrical block 11. Alternatively, a plurality of these blocks may be symmetrically arranged with respect to the tension resistant rod 9 in dependence with the size of the ship to be moored or the tidal current. The block 11 may be made conical or barrel shaped instead of cylindrical. In addition, the tension resistant rod 9 may be omitted and the upper chain 22 may be extended through the hole 12 provided in the boss of the cover plate 13 and directly connected to the disc-shaped end plate 8. The cushioning device thus constructed according to the invention is light in weight and effective in its cushioning operation. Fig. 4 shows another embodiment of a cushioning device according to the invention. In the present embodiment, around the bowl-shaped vessel is fitted an annular float 24 which is made integral with the bowl-shaped vessel. The annular float 24 functions to eliminate the under-water weight of the cushioning device 5 and prevent relative movement between the cushioning device 5 and the annular float 24. As a result, it is possible to more effectively prevent the mooring line from twisting. In addition, the presence of the annular float 24 ensures a significant increase in the volume of the cushioning device 5, thereby preventing the cushioning device 5 from being buried in the sea-bed. It is preferable to divide the annular float 24 into two halves which are fitted around the cushioning device 5 by means of a band 25. The float 24 is constructed of a foamed material 26 such as urethane and a shell 27 formed of polyethylene available under the trade name of Hi-zex and manufactured by Mitsui Chemical Co., in Japan. If the annular float 24 has a sufficiently high strength, it is possible to omit the foamed material 26. An annular groove 28 is provided along the inner periphery of the annular float 24 and adapted to be firmly engaged with a projection such as the flange of the flange-bolt joint. As stated hereinbefore. the invention provides a cushioning device for a mooring line used for mooring floating bodies such as ships, which can effectively absorb the tension applied to the mooring line, which is highly stable in shock-absorbing operation, and which can eliminate any twisting movement of the mooring line and hence can prevent a breakage or other failure of the mooring line. WHAT WE CLAIM IS:

1. A cushioning device to be connected in use between two sections of a mooring line used for mooring a floating body, the cushioning device comprising a bowl-shaped vessel (as herein defined) composed of a casing to be in use anchored through one section of a mooring line to an anchoring point and a cover plate secured to the casing, a disc-shaped end plate enclosed in the casing to be secured to the other section of a mooring line connected to a floating body, and at least one intermediate resilient hollow block concentrically arranged within the said vessel and interposed between the cover plate and the disc-shaped end plate, the said block being spaced apart from the inner wall of the bowl-shaped vessel.

and is connected to a swivel to be in use secured to the said other section of the mooring line.

3. A cushioning device as claimed in Claim 1 or 2, wherein the intermediate resilient hollow block is cylindrical and so shaped that it satisfies the following conditions given by D = 1.8 to 2.2.

d (D-d)/2 = 0.15 to 0.25 H where D is the outer diameter of the intermediate resilient hollow cylindrical block, d is its inner diameter and H is its length.

4. A cushioning device as claimed in any of Claims 1 to 3, wherein the maximum inner diameter of the bowl-shaped vessel is 1.5 times larger than the outer diameter of the intermediate resilient hollow block.

5. A cushioning device as claimed in any of Claims 1 to 4, wherein the said vessel is provided around its periphery with a plurality of longitudinal heat radiating fins.

6. A cushioning device as claimed in any of Claims 1 to 5, wherein the said cover plate is connected to a swivel and a spherical float to be in use secured to the said other section of the mooring line.

7. A cushioning device as claimed in any of claims 1 to 6, wherein the said vessel is surrounded by an annular float made integral with the vessel.

8. A cushioning device according to Claim 1, substantially as herein described with reference to, and as shown in, Figure 1 or Figure 4 of the accompanying drawings.