GB2043567A

GB2043567A - Bridging apparatus for offshore structures

Info

Publication number: GB2043567A
Application number: GB7923035A
Authority: GB
Original assignee: Mitsui Engineering and Shipbuilding Co Ltd
Current assignee: Mitsui Engineering and Shipbuilding Co Ltd
Priority date: 1979-03-01
Filing date: 1979-07-03
Publication date: 1980-10-08
Also published as: SE7905789L; NO792223L; JPS601441B2; NO150272C; SE438513B; NO150272B; GB2043567B; JPS55116906A

Abstract

Apparatus for bridging two offshore structures of floating bodies or a floating body and a fixed platform comprises a plurality of walkways 4, 9, 10, 11, 12 foldably linked to one another, one end 5 of said walkways being oscillatably pivoted on one of said offshore structures 1 and the other end 8 of said walkways being rotatably located on the other offshore structure 2. In another embodiment a movement unit 61 guided by rails 64 is arranged between the walkway and the offshore structure 2. <IMAGE>

Description

SPECIFICATION Bridging apparatus for offshore structures BACKGROUND OF THE INVENTION (1) Field of the Invention: The present invention relates to a bridging apparatus for offshore structures. More particularly, the invention relates to an apparatus for bridging two offshore structures of floating bodies or a floating body and a fixed platform.

(2) Description of the Prior'Art: As the conventional bridging apparatus of the type for bridging two offshore floating bodies or an offshore floating body and a fixed offshore platform, there are known those as illustrated in Figs. 1 and 2. In the bridging apparatus shown in Fig. 1, the top end of a bridge 3 is pivoted and supported on one end of the upper portion of a floating body 1 having a large freeboard and lower end of the bridge 3 is placed on a floating body 2 having a small freeboard so that the lower end of the bridge can slide in all the directions on the low freeboard floating body 2.In the bridging apparatus shown in Fig. 2, the lower end of a bridge 3 is oscillatably pivoted and supported on one end of the upper portion of a floating body 2 having a small freeboard, and the upper end of the bridge 3 is slidably mounted on the side portion of a floating body 1 having a large freeboard. These known bridging apparatuses, however, are still insufficient in various points.

For example, in the former bridging apparatus shown in Fig. 1, the free end of the bridge 3 on the side of the low freeboard floating body 2 moves freely on the top face of the floating body 2 according to relative displacements of both the floating bodies 1 and 2 in the front-rear or left-right direction or the vertical direction, and therefore, landing on the bridge 3 or falling down from the bridge 3 is very dangerous. In the latter bridging apparatus shown in Fig. 2, since the free end of the bridge 3 on the side of the high freeboard floating body 1 freely moves according to relative displacements of both the floating bodies 1 and 2, landing on the bridge 3 or falling down from the bridge 3 is difficult and dangerous as in the bridging apparatus shown in Fig. 1.In each of the foregoing conventional bridging apparatuses, if both the ends of the bridge 3 are fixed so as to eliminate the above disadvantage, the bridge 3 is damaged or destroyed by relative displacements af both the floating bodies.

Especially when the quantity of such relative displacement between both the floating bodies is as large as scores of meters, it is practially impossible to absorb such relative displacement.

OBJECTS OF THE INVENTION It is therefore a primary object of the present invention to provide a bridging apparatus in which boarding and alighting can be performed very safely.

Another object of the present invention is to provide a bridging apparatus which can easily absorb a large relative displacement between two offshore structures even if such relative displacement takes place.

Still another object of the present invention is to provide a bridging apparatus in which a sufficient protection can be attained against bad climate conditions such as winds, rains and snows, if necessary.

Other objects and advantages of the present invention will be apparent from the description given hereinafter.

SUMMARY OF THE INVENTION In accordance with the present invention, the foregoing objects can be attained by an apparatus for bridging two offshore structures of floating bodies or a floating body and a fixed platform, which comprises a plurality of walkways foldably linked to one another, one end of said walkways being oscillatably pivoted on one of said offshore structures and the other end of said walkways being rotatably located on the offshore structure.

BRIEF DESCRIPTION OF THE DRAWING Figure 1 is a side view illustrating diagrammatically one instance of the conventional bridging apparatus.

Figure 2 is a side view illustrating diagrammatically another instance of the conventional bridging apparatus.

Figure 3 is a plan view showing one embodiment of the bridging apparatus of the present invention.

Figure 4 is a side view illustrating the apparatus shown in Fig. 3.

Figure 5 is a perspective view showing a part of an inclined walkway in the apparatus shown in Fig. 3.

Figure 6 is a plan view showing another embodiment of the bridging apparatus of the present invention.

Figure 7 is a side view illustrating the longitudinal section taken along the line VII-VII in Fig. 6.

DETAILED DESCRIPTION OF THE PREF ERRED EMBODIMENTS Referring to Figs. 3 and 4, two offshore structures, that is, a floating body 1 having a large freeboard and a floating body 2 having a small freeboard, are bridged by a hollow tube-like inclined walkway 4. A pivot 5 is mounted on the top end of the inclined walkway 4, and by engagement of this pivot 5 with a receiving part 3 on the some end portion of the floating body 1, the inclined walkway 4 is oscillatably fixed on the floating body 1. The lower end of the inclined walkway 4 is rotatably connected through a hinge 6 to one end of a walkway assembly 7 placed on the low freeboard floating body 2.

The walkway assembly 7 includes walkways 9, 10, 11 and 1 2 which are linked in series to one another through turn tables 1 3 interposed between every two adajcent walkways.

An appropriate number of wheels 14 are mounted on the lower portion of the walkway assembly 7 so that the walkway assembly is allowed to freely move on the top face of the floating body 2 in the horizontal direction. A turn table 1 3 disposed on the other end of the walkway assembly 7 is fixed onto the floating body 2 and a gateway 8 is formed on said other end of the walkway assembly 7. When the floating body 2 is shifted from apposition indicated by solid lines to a position indicated by one-dot chain lines, since also the turn table 13' and gateway 8 are moved integrally with the floating body 2, the walkway assembly 7 is elongated with the turn tables 1 3 being as joints.On the other hand, when the floating body 2 is shifted to the position indicated by one-dot chain line to the position indicated by solid lines, the walkway assembly 7 is folded with the turn tables 1 3 being as joints. Since the inclined walkway 4 is rotatably connected to the walkway 9 through the hinge 6, the inclined walkway 4 is caused to oscillate with respect to the walkway 9 by the above-mentioned movement of the floating body 2. The length of each walkway of the walkway assembly and the number of joints are determined depending on the quantity of the relative displacement between the two floating bodies 1 and 2.

Two posts 1 7 are vertically disposed on the floating body 2 on both the sides of the walkway assembly 7, respectively. A wire rope 1 8 is spread through pulleys 1 9 mounted on the top ends of the posts 17, and one end of the wire rope 1 8 is fixed to a fitting 20 of the inclined walkway 4 and the other end of the wire rope 1 8 is engaged with a winch 21. Accordingly, if the wire rope 1 8 is wound up by the winch 21, the inclined walkway 4 is hung up and the pivot 5 separates from the receiving part 3. On the other hand, when the inclined walkway 4 is hung on the floating body 1, the wire rope 1 8 is unwound from the winch 21.The lower end of the inclined walkway 4 shall be stopped by suitable means during hanging walkway 4.

As shown in Fig. 5, the inclined walkway 4 has a closed structure composed of a hollow tube as one example. It is preferred that the hollow tube be formed of steel or a material having a strength equivalent to the strength of steel. A stair way 57 is formed on the floor of the hollow tube of the inclined walkway 4, and a handrail 58 is formed on one or both of the inner side walls of the hollow tube. An illuminator may be disposed in the hollow tube. By virtue of this closed structure, passersby can be protected from bad climate conditions such as winds, rains and snows, and moreover, a sufficient strength can be ensured for the inclined walkway 4 by this closed structure.

In the foregoing embodiment, when a relative displacement in the front-rear direction (direction A-A in the drawing) is caused between the two floating bodies 1 and 2, this displacement is absorbed by contraction or extension of the walkway assembly 7. When a relative displacement in the horizontal direction (direction B-B in the drawing) is caused between thse two floating bodies, the walkway assembly 7 is appropriately folded or extended, whereby the displacement is absorbed. Furthermore, when a relative displacement is caused in the vertical direction (direction C-C in the drawing), the inclined walkway 4 is rotated with the pivot 5 and hinge 6 being as fulcra to change the inclination angle thereof, whereby the displacement is absorbed.Thus, any of relative displacements caused between the two floating bodies can be completely absorbed and no destructive force is imposed on the bridging apparatus. Moreover, since the gateway of the bridging apparatus makes no substantial relative movement to the floating bodies 1 and 2, passersby can pass through the bridging apparatus very safely.

Another embodiment of the bridging apparatus of the present invention is illustrated in Figs. 6 and 7.

The bridging apparatus of this embodiment is in agreement with the embodiment shown in Figs. 3 and 4 in the point that an inclined walkway 4 and a walkway assembly 7 are disposed in the bridging apparatus, but this embodiment is different from the foregoing embodiment in the point that a movement unit 61 is interposed between the inclined walkway 4 and the walkway assembly 7. Two turn tables 62 and 63 are mounted on the upper portion of the movement unit 61 and wheels 65 are mounted on the lower freeboard portion of the movement unit 61. The movement unit 61 is guided by two parallel guide rails 64. The lower end of the inclined walkway 4 is rotatably connected to the turn table 62 through a hinge 66, and one end of a walkway 67 of the walkway assembly 7 is fixed to the turn table 63. The walkway 67 is rotatably connected to one end of a walkway 68 through a turn table 1 3 and the other end of the walkway 68 is rotatably connected to a turn table 1 3t. The turn table 13' is rotatably fixed onto the floating body 2 and a gateway 8 is connected to this turn table 13'. An arcuate guide rail 61 is disposed to rotate the turn table 1 3 along an arcuate course with the turn table 13' being as the center.

Both the ends of a wire rope 70 driven by a sliding winch 71 and guided by pulleys 72 are connected to the front and rear portions of the movement unit 61, respectively. In this arrangement, if the sliding which 71 is driven, the movement unit 61 is moved forward or backward along the guide rail 64. Further more, when the sliding winch 71 is stopped, the movement unit 61 is stationarily fixed.

Stoppers 73 and 74 are mounted on both the ends of the guide rail 64, respectively, so as to prevent further movement of the movement unit 61.

Limit switches 75 and 76 are disposed at positions apart forward and backward by distance X from the neutral position of the move ment unit 61 along the guide rail 64. When the movement unit 61 hits on the limit switch 75 or 76, a signal is emitted from the limit switch 75 or 76 and transmitted to the sliding winch 71 and span winches 21. By this signal, the sliding winch 71 is braked to stop the movement unit 61 and the span winches 21 are actuated to wind up the wire rope 18, hung up the inclined walkway 4 and separate the pivot 5 from the receiving part 3.

In the bridging apparatus of this embodi ment, if a relative displacement is caused between the two floating bodies 1 and 2 in the front-rear direction (direction A-A in the drawing), the movement unit 61 is moved along the guide rail 64 and the walkway assembly 7 is folded or extended, whereby the displacement is absorbed. When a relative displacement is caused in the horizontal direction (direction B-B in the drawing), this displacement is absorbed by rotation of the inclined walkway 4 with the pivot 5 being as the fulcrum and rotation of the turn table 62.

Furthermore, when a relative displacement is caused in the vertical direction (direction C-C in the drawing), the inclined walkway 4 is rotated with the pivot 5 and hinge 6 located on both the ends thereof being as the fulcra to change the inclination angle thereof, and the displacement is absorbed by this rotation of the inclined walkway 4 as well as by movement of the movement unit 61 and deformation of the walkway assembly 7. Accordingly, all of the relative displacements caused between the two floating bodies 1 and 2 are substantially absorbed by the bridging apparatus.

However, it sometimes happens that an unexpectedly strong external force is imposed on the bridging apparatus by strong winds or waves. In the bridging apparatus of this embodiment, if such extraordinary external force is imposed, the movement unit 61 hits on the limit switch 75 or 76 to actuate the limit switch 75 or 76 and by a signal emitted by the limit switch 75 or 76, the sliding winch 71 is automatically stopped to fix the movement unit 61. Simultaneously, the span winches 21 are actuated to wind up the wire rope 18, hang up the inclined walkway and release the pivot 5 from the receiving part 3.

Accordingly, even if an extra-ordinary external force is imposed, safety can be maintained in each member of the apparatus and the bridg ing apparatus can be effectively prevented from being damaged or destroyed. If desired, there may be adopted an arrangement in which an alarm is given and the gateway on the top end side of the inclined walkway 4 is shut when the limit switch 75 or 76 is actuated.

When the bridging apparatus of this em bodiment is not used, the inclined walkway 4 is made horizontal and the movement unit 61 is retreated backward, whereby the inclined walkway 4 is stored on the floating body 2, if the bridge apparatus is desired not to be fitted permanently.

The foregoing two embodiments have been illustrated by reference to the case where two floating bodies are bridged. As will be apparent to those skilled in the art, the bridging apparatus of the present invention can be applied to the case where one floating body is bridged to a fixed platform. Furthermore, the bridging apparatus of the present invention can be applied to not only the case where the two structures to be bridged differ in the freeboard but also the case where the two structures have the same freeboard.

As will be apparent from the foregoing illustration, in the bridging apparatus of the present invention, by virtue of the characteristic feature that a plurality of walkways are foldably linked to one another, one end of said walkways being oscillatably pivoted on one of the two offshore structures to be bridged and the other end of said walkways being rotatably located to the other offshore structure, boarding and alighting can be performed very safely, and a large relative displacement caused between the two offshore structures can easily be absorbed.

Claims

1. An apparatus for bridging two offshore structures of floating bodies or a floating body and a fixed platform, which comprises a plurality of walkways foldably linked to one another, one end of said walkways being oscillatably pivoted on one of said offshore structures and the other end of said walkways being rotatably located on the other offshore structure.

2. A bridging apparatus according to claim 1, wherein said walkways are divided into two groups, one group including an inclined walkway bridging between said two offshore structures and the other group consisting of a plurality of walkways disposed on one of said offshore structures and linked with turn tables.

3. A bridging apparatus according to claim 2, wherein said two groups of the walkways are rotatably connected to a hinge.

4. A bridging apparatus according to claim 2, wherein said inclined walkway is provided with a stairway.

5. A bridging apparatus according to claim 3, wherein said inclined walkway is provided with a wire rope, by which said inclined walkway is operated to oscillate around said hinge.

6. A bridging apparatus according to claim 2, wherein a movement unit guided by rail ways is disposed between said two groups of the walkways on one of said offshore structures.

7. A bridging apparatus according to claim 6, wherein said movement unit includes two turn tables mounted thereon, one turn table being connected to said inclined walkway in one of said two groups of the walkways and the other turn table being connected to the walkway of the other group.

8. A bridging apparatus according to any of claims 1 through 7, wherein said inclined walkway has an enclosed structure.

9. A bridging apparatus according to any of claims 1 through 7, wherein said inclined walkway is composed of a hollow tube.

10. A bridging apparatus according to claim 9, wherein said hollow tube is formed of steel, or equivalent material.

11. Apparatus for bridging two structures, at least one of which is a floating structure, said apparatus being substantially as hereinbefore described with reference to Figs. 3 to 5 or to Figs. 6 and 7 of the accompanying drawings.