HIGH-CAPACITY LIGHTWEIGHT VARIABLE BUOYANCY SYSTEM

Abstract

Techniques and architectures are disclosed for a system capable of creating large changes in buoyancy that can be incorporated into underwater vehicles, embodiments of the system utilizing edge-welded, metal bellows disposed within a pressure vessel to balance a pressure differential across the bellows while using the bellows to displace fluid and thereby alter the buoyancy of a vehicle on which the system is disposed.

Claims

1. A variable-buoyancy system, the system comprising: at least one bellows module, the at least one bellows module comprising: a pressure vessel comprising a flooded volume and at least one bellows; and a pump in operative communication with the flooded volume and in further operative communication with an environment external to the at least one bellows module via a fluid passage between the environment external to the at least one bellows module and the flooded volume in which a valve configured to allow the fluid passage to be opened or sealed is disposed, wherein the at least one bellows comprises one moveable end and one fixed end, the fixed end being affixed to an interior of the pressure vessel, wherein an interior of the at least one bellows defines a volume sealed from the flooded volume, wherein the pump and valve are configured to convey a fluid between the environment external to the at least one bellows module and the flooded volume, wherein the conveyance of the fluid from the environment external to the at least one bellows module to the flooded volume is configured to cause the at least one bellows to contract, wherein the conveyance of the fluid from the flooded volume to the environment external to the at least one bellows module is configured to cause the at least one bellows to expand, and wherein the at least one bellows is an edge-welded metal bellows.

2. The variable-buoyancy system of claim 1, further comprising a sensor disposed within the at least one bellows, the sensor configured to measure an expansion of the at least one bellows.

3. The system of claim 2, wherein the bellows module further comprises a control module configured to receive information from the sensor and to control the pump and the valve in response to a control signal.

4. The system of claim 1, wherein the bellows module further comprises a filter disposed between the valve and the environment external to the at least one bellows module.

5. The system of claim 1, wherein the at least one bellows comprises a plurality of bellows.

6. The system of claim 1, wherein the at least one bellows module comprises a plurality of bellows modules.

7. An underwater vehicle comprising the system of claim 6, wherein each of the plurality of bellows modules is located on the underwater vehicle such that independent control thereof provides for pitch and/or heave control of the underwater vehicle.

8. The system of claim 7, wherein the plurality of modules are located and oriented to allow for independent heave and pitch control.

9. The system of claim 1, wherein the interior of the at least one bellows is pressurized using a source of compressed gas, with the pressure being varied during use, vented to an environment internal to an underwater vehicle on which the at least one bellows module is disposed, or charged to a specific pressure, using a compressed gas, and sealed.

10. The system of claim 1, wherein the at least one bellows is manufactured from a material selected from the group of materials consisting of Hastelloy, Inconel, titanium, stainless steel, AM350, and 316L.

11. A variable-buoyancy system, the system comprising: at least one bellows module, the at least one bellows module comprising: a pressure vessel comprising at least one bellows, wherein an interior of the at least one bellows comprises a flooded volume; and a pump in operative communication with the flooded volume and in further operative communication with an environment external to the at least one bellows module via a fluid passage between the environment external to the at least one bellows module and the flooded volume in which a valve configured to allow the fluid passage to be opened or sealed is disposed, wherein the at least one bellows further comprises one moveable end and one fixed end, the fixed end being affixed to an interior of the pressure vessel, wherein the pump and valve are configured to convey a fluid between the environment external to the at least one bellows module and the flooded volume, wherein the conveyance of the fluid from the environment external to the at least one bellows module to the flooded volume is configured to cause the at least one bellows to expand, wherein the conveyance of the fluid from the flooded volume to the environment external to the at least one bellows module is configured to cause the at least one bellows to contract, and wherein the at least one bellows is an edge-welded metal bellows.

12. The variable-buoyancy system of claim 11, further comprising a sensor disposed within the pressure vessel, the sensor configured to measure an expansion of the at least one bellows.

13. The system of claim 12, wherein the bellows module further comprises a control module configured to receive information from the sensor and to control the pump and the valve in response to a control signal.

14. The system of claim 11, wherein the bellows module further comprises a filter disposed between the valve and the environment external to the at least one bellows module.

15. The system of claim 11, wherein the at least one bellows comprises a plurality of bellows.

16. The system of claim 11, wherein the at least one bellows module comprises a plurality of bellows modules.

17. An underwater vehicle comprising the system of claim 16, wherein each of the plurality of bellows modules is located on the underwater vehicle such that independent control thereof provides for pitch and/or heave control of the underwater vehicle.

18. The system of claim 17, wherein the interior of the pressure vessel is pressurized using a source of compressed gas, with the pressure being varied during use, vented to an environment internal to an underwater vehicle on which the at least one bellows module is disposed, or charged to a specific pressure, using a compressed gas, and sealed.

19. The system of claim 11, wherein the at least one bellows is manufactured from a material selected from the group of materials consisting of Hastelloy, Inconel, titanium, stainless steel, AM350, and 316L.

20. A variable-buoyancy system, the system comprising: at least one bellows module, the at least one bellows module comprising: a wet side, open to an external environment of the at least one bellows module; a dry side, sealed from the external environment of the at least one bellows module; at least one bellows disposed in a guide tube; and at least one actuator operatively coupled to each of the at least one bellows, wherein each of the at least one actuators is configured to expand and/or contract at least one bellows in response to a control signal, wherein the actuators are disposed in the dry side of the at least one bellows module, and and wherein an interior volume of the at least one bellows is open to the dry side of the at least one bellows module, wherein the at least one actuator is configured to expand and/or contract the at least one bellows in response to a control signal, and wherein the at least one bellows is an edge-welded metal bellows.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG. 1A is a schematic showing a bellows module, which is herein referred to as a low-pressure reservoir embodiment, with the bellows in an expanded state, in accordance with embodiments of the present disclosure;

[0039] FIG. 1B is a schematic showing a bellows module, which is herein referred to as a low-pressure reservoir embodiment, with the bellows in a collapsed state, in accordance with embodiments of the present disclosure;

[0040] FIG. 2A is a schematic showing an embodiment of a bellows module, which is herein referred to as a high-pressure accumulator embodiment, with the bellows in an expanded state, in accordance with embodiments of the present disclosure;

[0041] FIG. 2B is a schematic showing an embodiment of a bellows module, which is herein referred to as a high-pressure accumulator embodiment, with the bellows in an expanded state, with the bellows in a collapsed state, in accordance with embodiments of the present disclosure;

[0042] FIG. 3A is a schematic showing an embodiment of a bellows module, which is herein referred to as a bellows piston embodiment, with the bellows in an expanded state, in accordance with embodiments of the present disclosure;

[0043] FIG. 3B is a schematic showing an embodiment of a bellows module, which is herein referred to as a bellows piston embodiment, with the bellows in a collapsed state, in accordance with embodiments of the present disclosure;

[0044] FIG. 4A is a schematic showing a submersible vehicle including a low-pressure reservoir embodiment of a bellows module, with the bellows in an expanded state, in accordance with embodiments of the present disclosure; and

[0045] FIG. 4B is a schematic showing a submersible vehicle including a low-pressure reservoir embodiment of a bellows module, with the bellows in a collapsed state, in accordance with embodiments of the present disclosure

[0046] These and other features of the present embodiments will be understood better by reading the following detailed description, taken together with the figures herein described. The accompanying drawings are not intended to be drawn to scale. For purposes of clarity, not every component may be labeled in every drawing.

DETAILED DESCRIPTION

[0047] This disclosure relates to systems capable of creating large changes in buoyancy that can be incorporated into Underwater Vehicles (UVs) 400, especially Unmanned Underwater Vehicles (UUVs) 400, both of which may be referred to herein generally as submersible vehicles 400. In embodiments, this large range of buoyancy is achieved using metal bellows 102, in embodiments edge welded metal bellows 102. Metal bellows 102 provide a flexible, hermetic seal that will not leak and provide significant advantages over elastomeric seals, diaphragms, and bladders, which have a tendency to leak, especially when in contact with low lubricity fluids, such as seawater, as is commonly encountered by UVs. This is critical, since any leakage past an elastomeric seal or degradation of a bladder would be catastrophic, likely causing loss of the vehicle.

[0048] Because metal bellows 102 can expand and contract while taking large hydrostatic loads, metal bellows 102 achieve the same displacement for less weight, and therefore produce more displacement at equal weight, relative to elastomeric seals, diaphragms, and bladders.

[0049] Furthermore, in embodiments, bellows 102 allow a consistent, reliable, and direct measurement of the amount of the ballast provided thereby to be readily obtained. More specifically, since bellows 102 act analogous to a piston, without the use of a sliding elastomeric seal(s), the position of a moving end of the bellows 102 can be directly measured by a number of conventional methods, such as through the use of a sensor 116. For example, in embodiments, the sensor 116 is a draw wire potentiometer that is operatively connected to a bellows 102, in embodiments providing a direct measure the amount of fluid in a flooded volume 106 that, in embodiments, surrounds the bellows 102. An elastomeric bladder does not provide this ability and fluid levels must instead be inferred from other sensors in the system, such as flowmeters, pressure gauges, or the behavior of the vehicle itself.

[0050] In embodiments, the metal bellows 102 are edge-welded, metal bellows 102, which typically are able to maintain a more consistent wall thickness, overall tighter tolerances, and superior performance, compared to formed bellows 102. Additionally, the significantly higher stroke capability of an edge welded metal bellows 102, relative to formed bellows 102, which is discussed in the present disclosure's background section, allows for a smaller and lighter form factor than a formed bellows 102, while providing a wider range of ballast capabilities.

[0051] More specifically, embodiments of the present disclosure use edge-welded, metal bellows 102 to achieve large displacements and high weight efficiency.

[0052] In one embodiment, the inside of the metal bellows 102 is dry and an actuator 300, in embodiments a linear actuator 300, is configured to expand and contract the metal bellows 102 into a flooded volume 106.

[0053] In a second embodiment, multiple bellows 102, each operatively connected to at least one actuator 300, are combined to form a bellows module 100 to achieve more displacement, and multiple bellows modules 102 are positioned on a UV 400, in embodiments a UUV 400, to achieve independent heave and pitch control. FIGS. 4A and 4B provide exemplary positions of the multiple bellows modules 102.

[0054] In a third embodiment, an interior volume of the metal bellows 102 defines a flooded volume 106 and is filled with a fluid, in embodiments water or seawater obtained from an environment external to the bellows module 100, while a pressure vessel 104 in which the bellows is disposed is filled with compressed gas. In such embodiments, a pump 110 and valve 112 are used to change the volume of water contained within the bellows 102. Embodiments also include a filter 118 configured to filter the fluid being pumped from the external environment of the bellows module 100.

[0055] In a fourth embodiment, an interior volume of the bellows 102 is filled with air, and a pump 110 and valve 112 are used to change the displacement of the bellows 102 by introducing a fluid into, or evacuating a fluid out of a, a pressure vessel 104 in which the bellows 102 is disposed, the interior volume of the pressure vessel 104 comprising a flooded volume 106 in such embodiments.

[0056] In embodiments, the bellows module 100 is a standardized design, allowing it to be used interchangeably with various current underwater platforms.

[0057] Now referring specifically to FIGS. 1A and 1B, which differ only in that FIG. 1A shows the bellows 102 in an expanded state while FIG. 1B shows the bellows 102 in a contracted state, a low-pressure reservoir embodiment of the bellows module 100 is depicted. More specifically, the bellows module 100 comprises at least one bellows 102 disposed in a pressure vessel 104. An interior of the pressure vessel 104 comprises a flooded volume 106 into which fluid is pumped and/or removed using a pump 110 and valve 112 arrangement, with at least one pump 110, via at least one valve 112, in operative communication with the flooded volume 106 also being in communication with an external environment of the bellows module 100. Since the bellows module 100 is intended for use on UVs and UUVs, this places the at least one pump 110 in communication with a ready source of fluid, typically either fresh or salt water.

[0058] In such embodiments, an interior volume of the bellows 102 is kept dry and may be actively pressurized using a source of compressed gas, such as air, or by venting the interior volume of the bellows 102 to a dry portion of a UV on which it is disposed. In embodiments, the interior volume of the bellows 102 is charged to a specific pressure, using a compressed gas, and sealed. Such an arrangement results in the bellows 102 being biased towards an expanded state, with fluid pumped into the flooded volume 106 being used to collapse the bellows 102.

[0059] In embodiments, the pump 110 and valve 112 are controlled by a control module 108 that comprises a processor and non-transitory storage medium configured to cause the pump 110 to pump and/or valve 112 to open or close, resulting in the expansion or contraction of the bellows 102. In embodiments, such control is enacted in response to a control signal, which may be generated by a sensor 116 in response to environmental conditions, mechanical conditions of the bellows module or UV, control signals provided by a user, who may be a remote user of a UUV to which the bellows module 100 is affixed, or other type of signal, whether wired or wireless, as would be known to one of ordinary skill in the art.

[0060] In embodiments, the at least one pump 110, via the at least one valve 112, is in communication with an external environment of the bellows module 100 via a filter 118 that is configured to block debris, particulate, and/or other undesirable elements from entering the bellows module 100.

[0061] In embodiments, a sensor 116, such as a draw wire potentiometer, is operatively connected to at least one bellows 102, providing a reliable measure of fluid level in the pressure vessel 104 and therefore of the ballast provided by the bellows module 100.

[0062] In embodiments, the sensor 116 is used by the control module 108 to implement closed-loop feedback control during expansion and/or contraction of the at least one bellows 102.

[0063] Now referring specifically to FIGS. 2A and 2B, which differ only in that FIG. 2A shows the bellows 102 in an expanded state while FIG. 2B shows the bellows 102 in a contracted state, a high-pressure accumulator embodiment of the bellows module 100 is depicted. More specifically, the bellows module 100 comprises at least one bellows 102 disposed in a pressure vessel 104. An interior of the at least one bellows 102 comprises a flooded volume 106 into which fluid is pumped and/or removed using a pump 110 and valve 112 arrangement, with at least one pump 110, via at least one valve 112, in operative communication with the flooded volume 106 also being in communication with an external environment of the bellows module 100. Since the bellows module 100 is intended for use on UVs and UUVs, this places the at least one pump 110 in communication with a ready source of fluid, typically either fresh or salt water.

[0064] In such embodiments, an interior volume of the pressure vessel 104 is kept dry and may be actively pressurized using a source of compressed gas, such as air or helium or by venting the interior volume of the pressure vessel 104 to a UV on which it is disposed. In embodiments, the interior volume of the pressure vessel 104 is charged to a specific pressure, using a compressed gas, and sealed. Such an arrangement results in the bellows 102 being biased towards a contracted state by the pressurized gas, with fluid pumped into the flooded volume 106 being used to expand the bellows 102.

[0065] In embodiments, the pump 110 and valve 112 are controlled by a control module 108 that comprises a processor and non-transitory storage medium configured to cause the pump 110 to pump and/or valve 112 to open or close, resulting in the expansion or contraction of the bellows 102. In embodiments, such control is enacted in response to a control signal, which may be generated by a sensor in response to environmental conditions, mechanical conditions of the bellows module or UV, control signals provided by a user, who may be a remote user of a UUV to which the bellows module 100 is affixed, or other type of signal, whether wired or wireless, as would be known to one of ordinary skill in the art.

[0066] In embodiments, the at least one pump 110, via the at least one valve 112, is in communication with an external environment of the bellows module 100 via a filter 118 that is configured to block debris, particulate, and/or other undesirable elements from entering the bellows module 100.

[0067] Now referring specifically to FIGS. 3A and 3B, which differ only in that FIG. 3A shows the bellows 102 in an expanded state while FIG. 3B shows the bellows 102 in a contracted state, a bellows piston embodiment of the bellows module 100 is depicted. More specifically, the bellows module 100 comprises at least one bellows 102 disposed therein, the at least one bellows 102 having a fixed open end in communication with a dry side 302 of the bellows module and a movable end disposed in a wet side of the bellows module 304 that comprises a flooded volume 106. In such embodiments, the movable end of each bellows 102 is coupled to at least one actuator 300, in embodiments a linear actuator, configured to expand and/or contract the bellows 102 within the flooded volume, displacing fluid therefrom and increasing buoyancy.

[0068] In embodiments, each of the at least one bellows 102 is disposed in a guide tube 306 that restrains each bellows 102 from unwanted lateral movement.

[0069] In embodiments, the actuator(s) 300 are controlled by a control module 108 that comprises a processor and non-transitory storage medium configured to cause the actuator(s) 300 to expand or contract the bellows 102. In embodiments, such control is enacted in response to a control signal, which may be generated by a sensor in response to environmental conditions, mechanical conditions of the bellows module or UV, control signals provided by a user, who may be a remote user of a UUV to which the bellows module 100 is affixed, or other type of signal, whether wired or wireless, as would be known to one of ordinary skill in the art.

[0070] Now referring to FIGS. 4A and 4B an exemplary submersible vehicle 400 including a low pressure reservoir embodiment of the present disclosure and showing exemplary locations where the bellows modules 100 may be located thereon is depicted. In embodiments, the high-pressure accumulator embodiment or bellows piston embodiment may instead be used, as would be apparent to one of ordinary skill in the art.

[0071] Additionally, bellows modules 100 can be placed generally along any axis over which control is desired, with the bellows modules 100 exerting more control, for a given size, the farther out from the center of gravity of any particular axis they are. For example, bellows module 100 may be placed along a longitudinal centerline of a submersible vehicle 400 to obtain pitch control and laterally spaced apart from the longitudinal centerline to obtain heave control, with embodiments that combine both placements using separate bellows modules 100 providing for independent heave and pitch control.

[0072] In embodiments, the bellows modules 100 are not positioned directly on a particular axis, but instead between axis. In embodiments, the bellows modules 100 are contained inside a submersible vehicle 400 while in other embodiments they are external to a submersible vehicle 400.

[0073] Embodiments of the present disclosure are applicable to any vehicle diameter and at any depth. In addition to vehicle applications, embodiments can also be used to anchor arbitrary payloads on the seabed, to raise them above the water line, and/or to keep them at an arbitrary point along the water column.

[0074] The foregoing description of the embodiments of the present disclosure has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the present disclosure to the precise form disclosed. Many modifications and variations are possible in light of this disclosure. It is intended that the scope of the present disclosure be limited not by this detailed description, but rather by the claims appended hereto.

[0075] A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the scope of the disclosure. Although operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results.