Gangway having hydraulic position locking assembly

1. A gangway comprising:

a fixed platform;

a support structure connected to the fixed platform in a manner that allows the support structure to rotate with respect to the fixed platform; and

a releasable position locking assembly that, when locked, inhibits rotation of said support structure in a raising direction while allowing rotation of said support structure in a lowering direction, said releasable locking assembly including a closed-loop fluid arrangement.

2. The gangway of claim 1 , wherein said closed loop fluid arrangement comprises:

a cylinder in which a piston reciprocates; and

fluid handling components including an unlock valve, said fluid handling components configured to allow transfer of fluid from a first side of said piston to a second side of said piston as said support structure is lowered into a working position, said fluid handling components not allowing transfer of said fluid from said second side of said piston back to said first side of said piston for raising of said support structure unless said unlock valve is opened.

3. The gangway of claim 2 , wherein said cylinder and said fluid handling components are integrated into a cylinder unit connected between said support structure and a fixed attachment structure.

4. The gangway of claim 2 , wherein said fluid handling components include a check valve through which fluid transfers from said first side of said piston to said second side of said piston.

5. The gangway of claim 2 , wherein said unlock valve comprises a manual pull valve.

6. The gangway of claim 2 , wherein said fluid handling components further comprise an accumulator for receiving excess fluid due to volume occupied by a piston rod of the piston.

7. The gangway of claim 6 , wherein said accumulator comprises a free piston movable against a spring.

8. The gangway of claim 2 , wherein said fluid handling components further comprise a relief valve configured to also allow transfer of fluid from said second side of said piston back to said first side of said piston when a predetermined threshold pressure is encountered.

9. The gangway of claim 8 , wherein said relief valve is adjustable so that said predetermined threshold pressure can be varied.

10. A gangway comprising:

a fixed platform;

a support structure connected to the fixed platform in a manner that allows the support structure to rotate with respect to the fixed platform; and

a releasable position locking assembly that inhibits rotation of said support structure in a raising direction, said releasable locking assembly including a closed-loop fluid arrangement, wherein said closed loop fluid arrangement comprises:

a cylinder in which a piston reciprocates;

fluid handling components including an unlock valve, said fluid handling components configured to allow transfer of fluid from a first side of said piston to a second side of said piston as said support structure is lowered into a working position, said fluid handling components not allowing transfer of said fluid from said second side of said piston back to said first side of said piston for raising of said support structure unless said unlock valve is opened; and

said fluid handling components further including an accumulator for receiving excess fluid due to volume occupied by a piston rod of the piston, said accumulator having a free piston movable against a spring,

wherein said free piston carries a stop feature to limit its axial movement against said spring.

11. The gangway of claim 10 , wherein said spring comprises a coil spring and said stop feature is configured as a stop tube coaxial with said coil spring.

12. A gangway comprising:

a support structure having a proximal end and a distal end, the proximal end of the support structure being pivotally connected to a platform;

a cage assembly pivotally connected to the distal end of the support structure; and

a releasable position locking assembly that, when locked, inhibits rotation of said support structure in a raising direction while allowing rotation of said support structure in a lowering direction, said releasable locking assembly including:

a cylinder in which a piston reciprocates; and

fluid handling components including an unlock valve that when opened allows flow of fluid to a first side of said piston for raising of said support structure.

13. The gangway of claim 12 , wherein said cylinder and said fluid handling components are integrated into a cylinder unit connected between said support structure and a fixed attachment structure.

14. The gangway of claim 12 , wherein said fluid handling components include a check valve through which fluid transfers from the first side of said piston to a second side of said piston.

15. The gangway of claim 12 , wherein said unlock valve comprises a manual pull valve.

16. The gangway of claim 12 , wherein said fluid handling components further comprise a relief valve configured to allow transfer of fluid from a second side of said piston back to the first side of said piston when a predetermined threshold pressure is encountered.

17. The gangway of claim 16 , wherein said fluid handling components further comprise an accumulator for receiving excess fluid due to volume occupied by a piston rod of the piston.

18. The gangway of claim 17 , wherein said accumulator comprises a free piston movable against a spring.

19. The gangway of claim 18 , wherein said free piston carries a stop feature to limit its axial movement against said spring.

20. A gangway comprising:

a support structure having a proximal end and a distal end, the proximal end of the support structure being pivotally connected to a platform;

a cage assembly pivotally connected to the distal end of the support structure; and

a releasable position locking assembly that inhibits rotation of said support structure in a raising direction, said releasable locking assembly including:

a cylinder in which a piston reciprocates; and

fluid handling components including an unlock valve that when opened allows flow of fluid to a first side of said piston for raising of said support structure,

said fluid handling components further including a relief valve configured to allow transfer of fluid from a second side of said piston back to the first side of said piston when a predetermined threshold pressure is encountered and an accumulator for receiving excess fluid due to volume occupied by a piston rod of the piston, said accumulator having a free piston movable against a spring, said free piston carrying a stop feature to limit its axial movement against said spring.