US3710746A

US3710746A - Buoyancy lifting devices

Info

Publication number: US3710746A
Application number: US00111074A
Authority: US
Inventors: Donald I Mc
Original assignee: Cammell Laird and Co Ltd
Current assignee: Cammell Laird and Co Ltd
Priority date: 1970-01-31
Filing date: 1971-01-29
Publication date: 1973-01-16
Anticipated expiration: 1990-01-16
Also published as: FR2077633B1; NL7101298A; DE2104411A1; GB1338560A; DE2104411B2; FR2077633A1

Abstract

A buoyancy operated lifting and/or lowering device comprises a hollow body, means for flooding said hollow body, means for charging the hollow body with gas and at least one gas pressure relief tube extending downwardly from the upper or gas containing portion of the hollow body to a position below said hollow body. The gas pressure relief tube relieves pressure in the hollow body, as the device ascends and the ambient pressure to which the hollow body is subjected decreases. The buoyancy of the device is thereby maintained substantially constant during said ascent. The inlet for charging the hollow body with gas may have a valve which is responsive to the ambient pressure to which the hollow body is subjected. The buoyancy of the device is thereby maintained substantially constant during its descent.

Description

United States Patent 1 Mcdonald [54] BUOYANCY LIFTING DEVICES Ian Barry Mcdonald, Rock Ferry, England [73] Assignee: Cammell Laird & Company (Ship- [75] lnventor:

[ 51 Jan. 16, 1973 FOREIGN PATENTS OR APPLICATIONS 455,824 10/1936 Great Britain ..114/51 Primary Examiner-Tryg ve M. Blix Attorney-Berman, Davidson & Berman [57] ABSTRACT A buoyancy operated lifting and/or lowering device comprises a hollowbody, means for flooding said hollow body, means for charging the hollow body with gas and at least one gas pressure relief tube extending downwardly from the upper or gas containing portion of the hollow body to a position below said hollow body. The gas pressure relief tube relieves pressure in the hollow body, as the device ascends and the ambient pressure to which the hollow body is subjected decreases. The buoyancy of the device is thereby maintained substantially constant during said ascent. The inlet for charging the hollow body with gas may have a valve which is responsive to the ambient pressure to which the hollow body is subjected. The

buoyancy of the device is thereby maintained substantially constant during its descent.

6 Claims, 3 Drawing Figures PATENTEDJAH 16 1975 3. 7 1 0.746

SHEET 1 UF 3 I INVENTOR: IAN BARRY M DOA/9L0,

PATENTEDJAHIGIHYS 3710.746

SHEET 2 BF 3 l I 1 FF 15 l r Ha I 14 I w I L 10 L W 1 3 --FIG. 2.--

. INVENTOR:

ATTOR/VE ing the ascent thereof.

1 BUOYANCY LIFTING DEVICES This invention is for improvements in or relating to buoyancy operated lifting and/or lowering devices.

The lifting of heavy objects from the sea bed may be accomplished in calm water by using a floating crane or ships derrick as on land. However, if the sea conditions are not ideal, heave and roll of the ship cause motion of the crane hook and, therefore, difficulty and danger in attaching the load thereto. Further difficulties arise because the load is not within the vision of the crane driver and communication between divers on the sea bed and the crane driver is usually imperfect. Other problems arise in a tideway where the ship is likely to move on her moorings, particularly in deep water.

Many of these problems are resolved if the initial phase of the lift, from the sea bed to just below the surface, is accomplished by the use of abuoyant device or devices not affected by ship motion and capable of being controlled by divers.

Buoyancy devices as available heretofore have, however, suffered from the defect that ifinflated at the sea bed, as is usual, to an extent that the load is just lifted, then as the device rises the external hydrostatic pressure is reduced and the buoyancy of the device therefore increases. Thus, the load will be raised in an uncontrollable manner. An object of the present invention is to provide a buoyancy lifting device which does not suffer from this defect. According to the present invention there is provided a buoyancy operated lifting and/or lowering device comprising a hollow body or vessel, means for flooding said hollow body of vessel, and a gas pressure relief means extending downwardly from an upper or gas containing portion of the hollow body or vessel.

According to a further feature of the invention there is provided a buoyancy operated lifting and/or lowering device comprising a hollow body or vessel, means for flooding said hollow body or vessel and discharging water from it, and gas inlet and gas pressure relief i means for said hollow body or vessel, the water level in the hollow body depending on the gas pressure therein and said gas pressure relief means relieving pressure in the hollow body as the latter ascends and the ambient pressure to which the hollow body is subjected decreases, whereby the buoyancy of the lifting device is maintained substantially constant during the ascent thereof.

In some preferred embodiments of the invention the gas inlet of the hollow body is responsive to the ambient pressure to which'the hollow body is subjected so that the buoyancy of the lifting device is maintained substantially constant during the descent as well as dur- A convenient source of gas for the hollow body is one or more compressed air or gas storage bottles mounted on it.

Relief of gas pressure in the hollow. body is conveniently effected by providing it with one or more gas pressure relief tubes which extend from the upper and gas containing part of the hollow body or vessel down to a position below it.

The gas inlet to the hollow body is conveniently controlled by a flow control valve (e.g., a spring loaded diaphragm valve) adjustable or adapted to deliver gas at a predetermined pressure above the ambient pressure through a one-way valve, the gas supplied to the flow control valve being from high pressure storage bottles via a sea water reference reducing valve, i.e., a reducing valve responsive to or adapted to be set in accordance with the ambient sea water pressure. The flow control valve may be responsive to the ambient sea water pressure.

One particular embodiment of the invention will now be described by way of example, with reference to the accompanying diagrammatic drawings in which:

FIG. 1 is a perspective view of the device,

FIG. 2 shows the device during its ascent, and

FIG. 3 shows the device during its descent.

The buoyancy operated lifting device shown on the drawing comprises a drum 10 of light construction and with dimensions of, say, 22 inches in diameter and 35 inches high. A large diameter stop valve 11 is provided at the top of the drum or hollow body 10. A similar stop valve 1 1a is provided at the bottom of the drum.

Air is supplied into the top of the drum v10 via a spring loaded diaphragm valve 12 adjusted to deliver air at, say, 1.3 lbs per sq. inch above ambient pressure, through a one-way valve. The air supply to the diaphragm valve 12 is from high pressure storage bottles 13 via a sea water reference reducing valve 14, i.e., a pressure reducing valve which can be set by reference to the ambient sea water pressure.

The valve 12 may be a known form of differential sensitive flow control valve which can be set to maintain a required differential in'the drum 10 to suit the required buoyancy of the device, particularly during a controlled descent. The diaphragm of the valve 12 may, for example, be subjected, on one side, to the ambient sea water pressure.

The storage bottles 13 are detachably strapped or otherwise secured to the drum 10 so as to descend and ascend therewith.

Air pressure relief tubes 15, open at their lowermost ends, connect the top of the drum 10 to a point several inches below the bottom stop valve on said drum.

To sink the device to the sea bed it is completely flooded by opening the top and

bottom stop valves

11 and 11a with the air supply turned off. The device then has an approximate weight in water of, say, 30 lbs.

Prior to sinking the device to the sea bed it is, for example, attached to the falls of a ships crane so as to be lowered under the control thereof, the falls being allowed to slacken once the device is on the sea bed. A diver will then attach one end of a long line to the lifting device and make the other end of the line fast to any convenient object capable of serving as a bollard. The diver then attaches the load e.g., by slings, to the lifting device.

To give the device nett buoyancy the stop valve 11 is closed and the air supply turned on. Air will then flow via the reducing valve 14 and diaphragm valve 12 into the top of the drum 10 forcing water out through the bottom stop valve 11a. When the required buoyancy has been achieved, the bottom stop valve 11a is closed. Air will continue to flow into the drum 10 until the water level in the relief tubes 15 is below (e.g., 3 feet below) the diaphragm valve 12 when the air pressure will be, say, 1.3 lbs per sq. inch above sea water pressure at the diaphragm valve. The airflow will then cease and the device, together with the load, will start .the drum will expand and flow out through the relief tubes 15, not altering the water lever L in the drum and hence not altering the buoyancy of the device. There is no possibility, therefore, of the device going out of control during its ascent due to an increase in buoyancy.

During the descent of the device (FIG. 3) the gas, in

- the part A, above the water in the part W of the drum 10, will tend to decrease in volume with the result that water starts to ascend in the relief tubes 15. When this occurs the balance on the diaphragm valve 12 is altered and the resultant gas flow will restore the internal pressure balance. Hence, the buoyancy of the device will not change during descent.

If an increase in buoyancy is required at any time, the opening of the bottom stop valve 11a will allow the gas pressure to blow out water so increasing the buoyancy.

To maintain stability with the device the gas pressure equalization should take place with a minimum time lag. For this reason, three relief tubes and three air supply pipes and diaphragm valves 12 (only one of which is visible in FIG. 1) have been provided in the embodiment of the invention specifically described above.

The gas bottle capacity is preferably sufficient to fill completely the buoyancy device twice at 600 feet. The device may draw its gas supply via an umbilical tube connected to a larger gas storage tank. A quick release coupling may be provided on the umbilical tube so that the buoyancy device may be rendered self-contained when required.

A buoyancy device as above described may provide a controllableconstant lift throughout its depth range.

The drum 10 may be replaced by a rubber fabric bag or envelope, preferably enclosed in a cage or framework, since such an envelope or bag will only be called upon to' withstand an internal pressure of a few .pounds per square inch. The pipes 15 may be flexible hose.

There may be a lightly loaded (e.g., a spring loaded) relief valve in each pipe 15, particularly when the device is onl-y intended for lifting loads.

' It will be understood that with its ability to provide controlled lifting and lowering of loads the device may be used as an under-water crane for moving loads from one place to another on the sea bed.

I claim:

1. A buoyancy operated lifting and/or lowering device comprising a closed hollow body, valve controlled means at'the lower part of said hollow body whereby it may be flooded when immersed in a body of water so as to cause it to descend, valve controlled means at the upper part of the hollow body-for discharging gas therefrom during said flooding of the.

hollow body, gas supply means connected to the upper part of the hollow body for charging it with gas to displace water from the interior of the hollow body to adjust its buoyancy, a pressure sensitive valve means in said gas supply means and positioned on the hollow body so as to respond to the changing hydrostatic pressure on the hollow body during its descent and provide a gas flow to the hollow body to maintain the internal pressure balance therein so that the water level in and buoyancy of the hollow body will not change during its descent, and a gas pressure relief means connected to the upper part of the hollow body, said gas pressure relief means providing for the discharge of gas from the hollow body during its ascent, whereby the internal pressure within the body is maintained substantially the same as the ambient pressure.

2. A buoyancy operated lifting and/or lowering device as claimed in claim 1 wherein the gas pressure relief means comprises at least one open-ended relief tube connected to the upper part of the hollow body and extending downwardly therefrom so that its open end is below the bottom of the hollow body.

3. A buoyancy operated lifting and/or lowering device as claimed in claim 1 whereas the gas supply means is at least one bottle of gas and means is provided on the hollow body mounting said bottle thereon.

4. A buoyancy operated lifting and/or lowering device as claimed in claim 1 wherein there is an adjustable flow control'valve in the gas supply means whereby the gas supply can be adjusted to deliver gas at a predetermined pressure above the ambient pressure.

'5. A buoyancy operated lifting and/or lowering device as claimed in claim 1 wherein the pressure sensitive valve means has a diaphragm which is subjected, on one side, to the ambient water pressure.

6. A buoyancy operated lifting and/or lowering device as claimed in claim 1 wherein there is a relief vvalve in the gas pressure relief means.

Claims

1. A buoyancy operated lifting and/or lowering device comprising a closed hollow body, valve controlled means at the lower part of said hollow body whereby it may be flooded when immersed in a body of water so as to cause it to descend, valve controlled means at the upper part of the hollow body for discharging gas therefrom during said flooding of the hollow body, gas supply means connected to the upper part of the hollow body for charging it with gas to displace water from the interior of the hollow body to adjust its buoyancy, a pressure sensitive valve means in said gas supply means and positioned on the hollow body so as to respond to the changing hydrostatic pressure on the hollow body during its descent and provide a gas flow to the hollow body to maintain the internal pressure balance therein so that the water level in and buoyancy of the hollow body will not change during its descent, and a gas pressure relief means connected to the upper part of the hollow body, said gas pressure relief means providing for the discharge of gas from the hollow body during its ascent, whereby the internal pressure within the body is maintained substantially the same as the ambienT pressure.

4. A buoyancy operated lifting and/or lowering device as claimed in claim 1 wherein there is an adjustable flow control valve in the gas supply means whereby the gas supply can be adjusted to deliver gas at a predetermined pressure above the ambient pressure.

5. A buoyancy operated lifting and/or lowering device as claimed in claim 1 wherein the pressure sensitive valve means has a diaphragm which is subjected, on one side, to the ambient water pressure.

6. A buoyancy operated lifting and/or lowering device as claimed in claim 1 wherein there is a relief valve in the gas pressure relief means.