Boring or penetrating the earth – Boring a submerged formation
Reexamination Certificate
1999-04-30
2001-03-06
Tsay, Frank (Department: 3672)
Boring or penetrating the earth
Boring a submerged formation
C175S051000
Reexamination Certificate
active
06196333
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns a hydrostatic penetration device for placing on and penetration of the seabed, comprising a housing with a top cover and a bottom cover, and a through-going vertical tool for penetration of the seabed. The invention also concerns tools for use with a hydrostatic penetration device, especially a sampler for core samples, where the tool is a sampler tube.
In addition to being able to be employed together with the said tools, the hydrostatic penetration device will also be able to be employed to drive a test probe down into the seabed, for measurement of, for example, temperature, mechanical resistance and electrical conductivity.
There are known in the prior art hydrostatic penetration devices in the form of samplers for core samples, e.g. of sediments on the seabed, designed in principle as percussion drill machines, these samplers being operated by the pressure difference between a low pressure chamber provided in the sampler and the ambient hydrostatic pressure. The standard known samplers of this type comprise a head to which the tool or the sampler tube is attached and is driven down into the seabed by a piston provided in a piston cylinder which can be connected to the surrounding water. When the stroke movement is completed, the cylinder is evacuated to the low pressure chamber, and the piston returns to the initial position, whereupon the cycle process is repeated. The weight of the sampler head acts in conjunction with the hydrostatic pressure in order to provide the energy required to perform the stroke movement or the drop stroke. Stability problems often arise with such known samplers when they are equipped with long sampler tubes, and there can also be problems in providing sufficient energy if long sampler tubes are employed.
In order to avoid the drawbacks with known hydrostatic samplers, it has therefore been proposed that the tool or the sampler tube should be through-going in the sampler's head or housing and that the sampler head or housing should be placed on the seabed.
U.S. Pat. No. 3,693,730 describes a sampler in which a housing with an electromagnetic vibrator is placed on the seabed. A through-going tube is driven by means of the vibrator down into the seabed, and a drawworks is used to move the vibrator along the pipe.
SUMMARY OF THE INVENTION
A first object of the present invention is to provide a description of a hydrostatic penetration device of the type mentioned in the introduction, which makes it possible to place the penetration device's housing on the seabed and for the tool to be through-going in the housing.
A second object is to provide a hydrostatically operated penetration device wherein the housing itself has a relatively low weight, while the weight which together with the hydrostatic pressure has to contribute to the drop movement is provided in the form of a weight which is arranged in the housing and is lifted in a return stroke. If the hydrostatic penetration device is employed as a sampler, the stability problems of known samplers are thereby avoided, while at the same time permitting the use of sampler tubes of a far greater length than is possible with the prior art.
A further object of the present invention is that it should be possible to supply energy as required without the occurrence of any stability problems.
Finally, it is an object of the invention to provide suitable tools for use with a hydrostatic penetration device according to the invention.
The objects are achieved with a hydrostatic penetration device and tools of the type mentioned in the introduction which are characterized by the features which are indicated in the claims.
The above-mentioned and other objects are therefore achieved with a hydrostatic penetration device for placing on and penetration of the seabed, comprising a housing with a top cover and a bottom cover, and a through-going vertical tool for penetration of the seabed, and is characterized in that it comprises:
at least one low pressure chamber with a pressure which is lower than the pressure in the surrounding water,
at least one hydraulic cylinder with a vertically movable piston and piston rod which can be driven to upward and downward movement by a flow of pressurized water from the surrounding water to the low pressure chamber, pipes and valves for leading and guiding the said flow of pressurized water, for controlling the piston's and thereby the piston rod's movement,
a clamping device which surrounds the tool and is connected to the piston rod, and which by means of an upward and downward movement of the piston rod can be brought out of and into engagement with the tool,
at least one vertically movable weight connected to the piston rod, arranged to transfer its weight to the clamping device during a downwardly directed movement,
whereby during an upwardly directed movement the piston rod will lift the weight and bring the clamping device out of engagement with the tool, thus causing the clamping device to slide upwards along the tool, and during a subsequent downwardly directed movement will bring the clamping device into engagement with the tool, with the result that, under the influence of the weight and force from the piston rod the tool is driven down into the seabed. A new cycle is then initiated where the piston rod is again moved upwards. The number of cycles which may be performed will depend on the dimensioning of the low pressure chamber, and will typically amount to 50 cycles.
In an embodiment of the invention the cylinder volume above the piston in the hydraulic cylinder is permanently connected to the low pressure chamber, during the piston rod's upward and downward movement the cylinder volume below the piston is connected to the surrounding water and the low pressure chamber respectively, and the housing has at least one opening to the surrounding water, thus causing the piston rod to be exposed to the pressure in the surrounding water.
In an embodiment of the invention the tool is driven down by impacts, the weight dropping during the introductory part of its downwardly directed movement, thus causing it to strike the clamping device, driving the tool down with a blow, which is advantageous in sampling of the seabed, particularly of hard sediments. In a second embodiment of the invention the tool is forced down into the seabed at a constant speed, which is advantageous when the tool is used to convey a test probe down into the seabed.
A first tool for use with a hydrostatic penetration device according to the invention, especially a sampler tube for core samples, is characterized according to the invention in that the sampler tube has a head provided at its lower end with closing jaws hinged to the head with a substantially tubular cross section and toothed gripping surfaces which synchronise the closing jaw's movement.
A second tool for use with a hydrostatic penetration device according to the invention, especially a sampler tube for core samples, is characterized according to the invention in that the sampler tube has provided at its lower end a head in the form of a valve housing with a valve plate and an arm which constitutes a one-way valve which in an open position admits water into the sampler tube.
REFERENCES:
patent: 3118417 (1964-01-01), Stanwick
patent: 3693730 (1972-09-01), Edigarian et al.
patent: 3896667 (1975-07-01), Jeter
patent: 4200158 (1980-04-01), Perkins
patent: 4273372 (1981-06-01), Shestawy
patent: 5060737 (1991-10-01), Mohn
patent: WO 92/19836 (1992-11-01), None
patent: WO 94/23181 (1994-10-01), None
Norcon AG
Tsay Frank
Young & Thompson
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