Umbilical constraint mechanism

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is generally related to the use of a remotely operated vehicle (ROV) from a drone vessel for underwater work and more particularly to means used to restrain the umbilical line between the drone vessel and ROV.

2. General Background

Many underwater operations, such as drilling for and production of oil and gas, installation and maintenance of offshore structures, or laying and maintaining underwater pipelines require the use of a remotely operated vehicle (ROV) or robotic tooling.

The deployment of an ROV is typically achieved by launching the unit from either a bottom founded or floating host platform, a dynamically positioned marine vessel dedicated specifically for the purpose of supporting an ROV, e.g. an ROV support vessel (RSV), or any such surface vessel with sufficient size and characteristics that provide a suitably stable platform for the launching and recovery of an ROV.

Both bottom founded and floating host platforms are fixed in position at the site and are normally engaged in collateral activities such as drilling and offshore production or construction. Thus, the operations of the ROV are limited according to the distance that the ROV can travel from the host platform as well as by restrictions in operating periods due to the collateral activities of the host platform.

In the case of dedicated vessel deployment such as an RSV, significant costs are associated with operation of a fully founded marine vessel and its mobilization to and from the ROV work site. Typically, a dedicated RSV may have a crew of twenty and a considerable cost not directly related to the operation of the ROV.

ROV operation and monitoring is controlled from the host platform or RSV by means of an umbilical line between the host platform or RSV and the ROV. It can be seen from this that the operational distance of the ROV is directly related to the length of the umbilical line.

A remotely operated near surface drone vessel with adequate stability that is capable of launching, controlling, and recovering an ROV eliminates the limitations associated with operation from a fixed host platform and reduces the expense associated with a manned, dedicated RSV.

The remotely operated drone vessel requires an umbilical line, storage drum and winch to launch, control, and recover the ROV. The stability of the drone vessel can be adversely affected by deployment of the ROV. This can occur from lateral loads imposed on the drone vessel from the umbilical line and ROV that effectively decreases the stability of the drone vessel. This leaves a need for a means of reducing the effects of lateral loads applied by the umbilical line and increasing the stability of the drone vessel.

SUMMARY OF THE INVENTION

The invention addresses the above needs. What is provided is an umbilical constraint mechanism. The mechanism keeps the umbilical line near the center of the payload bay opening when the umbilical line is deployed. The mechanism will transfer lateral umbilical loads into the drone vessel frame near the bottom of the payload bay. A modified cone shaped structure is provided in the payload bay above the normal storage position of the ROV. The cone is mounted on a frame that is capable of sliding up or down in the drone vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the nature and objects of the present invention reference should be made to the following description, taken in conjunction with the accompanying drawings in which like parts are given like reference numerals, and wherein:

FIG. 1

illustrates a drone vessel for an ROV.

FIG. 2

illustrates a drone vessel for an ROV wherein a tether management system and ROV have been deployed from the drone vessel.

FIG. 3

is an enlarged cutaway view that illustrates the invention in the drone vessel.

FIG. 4

is a detail perspective view of the invention in the upper storage position.

FIG. 5

is a detail perspective view of the invention in the lower operating position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, it is seen in

FIG. 1

that a drone vessel is generally indicated by the numeral

10

. Drone vessel

10

is a buoyant vessel that utilizes a plurality of dynamic positioning thrusters

12

, one illustrated at each corner. Drone vessel

10

is also provided with propulsion means

14

. A mast

16

attached to the top of the drone vessel

10

extends upward and includes one or more radio telemetry antennas

18

. As seen in

FIG. 1

, the operational position of the drone vessel

10

is below the water line

20

, with the top of the mast

16

and the antennas being above the water line

20

. This allows a support vessel or fixed structure, not shown, on the water surface to remotely control the drone vessel

10

and a remotely operated vehicle (ROV), seen in

FIG. 2

, that is carried by, and controlled through, the drone vessel. The power supply, motors, and electronic equipment are housed within the drone vessel

10

.

FIG. 2

illustrates a tether management apparatus

22

and ROV

24

deployed from the drone vessel

10

. An umbilical line

26

stored on a drum in the drone vessel

10

provides communication with, and control of, the tether management apparatus

22

and the ROV

24

. The umbilical line

26

is returned to the storage drum by a winch located in the drone vessel

10

.

FIG. 3

is an enlarged cutaway view of a portion of the drone vessel

10

and illustrates the tether management apparatus

22

and ROV

24

stored in the drone vessel

10

. The umbilical line

26

is routed from a storage drum not seen over a pulley or sheave

28

and through a constraint mechanism

30

, best seen in

FIGS. 4 and 5

, to the tether management apparatus

22

and ROV

24

.

The constraint mechanism

30

is generally comprised of a pair of guide rails

32

, a bar

34

slidably mounted on the guide rails

32

, and a cone

36

mounted on the bar

34

.

The guide rails

32

are mounted on opposite sides of the hull of the drone vessel

10

in a vertical orientation. Each guide rail

32

is provided with upper and lower stops

38

that have a greater diameter than the rails

32

and are also used as attachment points to the hull of the drone vessel

10

, as indicated by numeral

40

.

The bar

34

is slidably mounted on the guide rails

32

by means of a bore provided on each end of the bar

34

. The bar

34

is movable between a first upper position when the tether management apparatus

22

and ROV

24

are stored in the drone vessel

10

and a second lower position when the tether management apparatus

22

and ROV

24

are deployed from the drone vessel

10

for work purposes.

A cone

36

is mounted substantially at the center of the bar

34

. The cone

36

is open at each end and mounted such that the larger opening of the cone is lower than the smaller opening. The cone

36

is sized to receive the umbilical line

26

and is preferably provided with a thirty degree radius.

In operation, the bar

34

and cone

36

of the constraint mechanism

30

are maintained in the first upper position by the tether management apparatus

22

and ROV

24

when they are stored in the drone vessel

10

as seen in

FIG. 3 and 4

. The constraint mechanism

30

moves to the second lower position, as seen in

FIG. 5

, by the force of gravity when the tether management apparatus

22

and ROV

24

are deployed as seen in FIG.

2

. When in the second lower position, the cone

36

limits the side-to-side movement of the umbilical line

26

caused by movement of the tether management apparatus

22

and ROV

24

. The second lower position of the cone

36

serves to reduce the leverage of the umbilical line

26

on the drone vessel

10

, compared to the upper position, by keeping the umbilical line near the center of the payload bay opening when the umbilical line is deployed. This transfers lateral umbilical line loads into the drone vessel frame near the bottom of the payload bay and thus increases the stability of the drone vessel

10

. For the purposes of this invention, the tether management apparatus

22

is an addition to the ROV and so should be considered as part of the ROV with regard to the operation of the constraint mechanism

30

. Thus, the ROV

24

is also capable of performing the function of moving and retaining the constraint mechanism

30

in the first upper position.

Because many varying and differing embodiments may be made within the scope of the inventive concept herein taught and because many modifications may be made in the embodiment herein detailed in accordance with the descriptive requirement of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.