EP0581838A1

EP0581838A1 - Engine for performing subsea operations and devices driven by such an engine

Info

Publication number: EP0581838A1
Application number: EP92909601A
Authority: EP
Inventors: Kare Aardal; Philip Howard Dixon; Yngve Kristoffersen; Anders Lien; Eldar Lien; Kaare Nordbo; Sigurd Ree
Original assignee: Selantic Industrier AS
Current assignee: Selantic Industrier AS
Priority date: 1991-04-26
Filing date: 1992-04-24
Publication date: 1994-02-09
Anticipated expiration: 2012-04-24
Also published as: EP0581838B1; AU656186B2; DE69227511T2; NO933843D0; JPH06506996A; CA2109107A1; NO933843L; ATE173050T1; DE69227511D1; AU1686992A; WO1992019836A1

Abstract

A machine for performing work at great depths utilizes the energy which is released when surrounding water masses at great hydrostatic pressure are admitted into a low pressure reservoir via a hydraulic motor (2). The machine uses a built-in low pressure reservoir (3) as a hydrostatic accumulator, the energy which is released when the surrounding fluid is admitted into the low pressure reservoir being determined by the product of the pressure difference and the internal volume of the low pressure reservoir. In a special version (Fig. 10) the machine is designed as a hydrostatic sampler which is particularly adapted for taking core samples or marine sediments on the seabed.

Description

ENGINE FOR PERFORMING SUBSEA OPERATIONS AND DEVICES DRIVEN BY SUCH.AN ENGINE

The invention concerns an engine which is intended to operate at great depths by utilizing the energy which is released when surrounding water masses under great hydrostatic pressure are admitted into a low pressure reservoir via a hydraulic motor.

The invention also concerns a hydrostatic sampler, especially for core samples of marine sediments, wherein the sampler comprises a substantially cylindrical head and a substantially cylindrical sampler section whose longitudinal axis passes approximately through the head's centre of gravity and wherein the sampler section comprises a sampler tube consisting of at least one sampler tube section.

The reason behind the invention is that the supply of, e.g., hydraulic or electrical power from, e.g., a ship to a working tool on the seabed, entails increasing difficulties as the depth increases, since transmission lines or pipes become extremely expensive, heavy, difficult to handle and vulnerable.

One possibility may be to have electrical power on site, stored in the form of batteries or eliminators, but this too will be extremely vulnerable in the environment to which the tool is exposed, and from the operational safety point of view hydraulic operation will be far preferable to electrical power.

The machine according to the invention uses an integral low pressure reservoir as a "hydrostatic accumulator", the energy which is released when the surrounding liquid is admitted into the low pressure reservoir under controlled conditions being determined by the product of the pressure difference and the internal volume of the low pressure reservoir.

For example, a low pressure reservoir with an internal volume of l m³ and approximately empty of gas, when lowered to a depth of 2000 metres (corresponding to a pressure of approximately 20 MPa) will be capable of releasing a pressure energy from, surrounding water masses of 20 x 10⁷ Nm, or approximately 5.5 kWh. The energy thus available will increase in proportion to the water depth and in proportion to the volume of the low pressure reservoir.

The invention concerns with various different arrangements for the utilization of this energy, together with various relevant applications.

Hydrostatic samplers are used to take core samples of the sediments in deep sea reservoirs. Such core samples are of great interest with regard to paleooceanography and paleoclimatology, since deep sea sediments consist mainly of deposits resulting from the biogenic activity in the water masses. Small calcareous and siliceous organisms accumulate on the seabed at a rate of approximately 1 cm in the course of 1,000 years. The fauna and flora populations in the water masses are adapted to the special temperatures and salinities which exist at any given time, and their fossil deposits therefore bear testimony to the physical properties of the water over the ages. In the course of the 1970*s it became possible to transfer the paleontological information on the relative frequency of species and their preferred temperature range via a mathematical transfer function to paleotemperatures for the sea water with an accuracy of 0.50°C. The use of the oxygen-isotope method also provides a temperature indication as well as a measurement of the global ice volume. Used on sediment cores from deep sea reservoirs, these methods have formed the basis for major international research programmes aimed at integrating all biological information on the climatic conditions in the Quaternary Period, and particularly the global climatic changes which have taken place since the last ice age maximum approximately 20,000 years ago. In recent years this research has gained additional relevance in connection with problems allied to the alleged effects of anthropogenically produced climatic changes. By taking core samples of the upper sedimentary layer in.deep sea reservoirs, and up to the upper part of the continental shelf, by using a core length of approximately 10-12 m, a record can be obtained of the geological and paleontological history over a period of approximately 1,000,000 years. Since the core samples 'do not require to be of greater length than this and moreover the sedimentary layers are not especially hard, a hydrostatic sampler is well-suited to this purpose. The use of hydrostatic samplers entails driving a sampler tube down into the sedimentary layer under the influence of the hydro¬ static pressure, i.e. the water pressure at the depth at which the sample is taken. Furthermore it is possible to make hydrostatic samplers particularly light and simple in design compared with samplers which require an external power supply, via, e.g., mechanical or hydraulic motors or with a built-in motor of some kind. There is also a special advantage with this feature of hydrostatic samplers, since the surveys often take place in distant waters and extremely demanding environments, where it is a considerable advantage to have equipment which is easy to transport and operate.

There are a number of known gravitation samplers which fulfil these conditions to some degree, but if they are to obtain a satisfactory depth of penetration, they have to be relatively heavy as they require a ballast in the order of around 1,000 kg.

From the periodical Marine Geology, volume 54 (1983/1984, pages M33-M41) , there is known an active hydrostatic sampler developed by F. W. McCoy and S. Selvin in 1981. Selvin and McCoy's sampler uses a hydrostatic piston engine which via an internal pulley system is used to lift a drop weight which is then dropped and drives the sampler tube down into the sedimentary layer. The cycle is repeated until the hydrostatic energy potential is exhausted. Some of the available hydrostatic energy, however, helps to lift the drop weight and moreover the lifting arrangement with pulleys and rope entails a constructional complication. The object of the present invention is to provide an active hydrostatic sampler which represents an improvement over and increases the efficiency of Selvin and McCoy's known sampler. By using the pressure reservoir as a housing for the complete system, including the valve control, all sensitive components can be safely housed in the pressure reservoir's container. Together with its contents, this constitutes the mass which is used as a pile-driver. At the same time the piston in the hydrostatic motor is used directly to run the lifting and dropping operations, thus minimising the losses during the energy conversion. When the pressure reservoir which forms the sampler's head is lifted, a downward directed recoil effect is obtained, and this again causes a double-acting effect which further contributes to the improvement of the present sampler over the prior art. The hydrostatic sampler according to the present invention thus offers a number of advantages in comparison with the known sampler. Compared to Selvin and McCoy's sampler, the sampler according to the present invention provides a greater ratio between drop weight and hammer mass, a higher pump pressure, thus avoiding the need for power transfer and a greater lifting acceleration, which gives a substantial recoil effect, since the lifting acceleration is of the same order as the drop acceleration, which provides a doubling of the force of impact per blow. At great depths, moreover, the lifting forces become even more predominant. In addition the sampler according to the present invention is directly activated by the surrounding sea water, while Selvin and McCoy's sampler uses a membrane and hydraulic oil as a moder¬ ator. The sampler according to the invention can therefore be expected to give substantially lower internal losses.

The hydrostatic machine according to the invention is characterized by those features described in the claims 1-20, the reference numbers in these claims corresponding to the reference numbers in figs. 1-9, while a sampler according to the present invention is characterized by those features which are described in the claims 21-44, the reference numbers in these claims corresponding to the reference numbers in figs. 10-18.

The invention will now be described in more detail with the hydrostatic sampler as an example, since the sampler can be regarded as a sp cial case of the hydrostatic machine according to the invention. In connection with the description of the sampler, reference will be made to figures 10-18 of the drawing.

The general principle of the invention is illustrated schematically in fig. 1.

Fig. 2 is an arrangement wherein an axial piston motor 2a driven by the hydro-static pressure is provided within a low pressure chamber 11.

Fig. 3 is a more refined arrangement in which, in addition to the hydrostatic water-driven axial piston motor 2a there is provided an axial piston pump 20 which supplies fluid to a separate hydraulic rotary engine 2b. Two separate low pressure reservoirs are also provided, viz. the "integrated" reservoir 11 as in fig. 1 together with the external reservoir 3b.

Fig. 4 is an arrangement wherein the piston pump 20 and the rotary engine 31 together with the accumulators 32 and pressure control valves comprise a closed system operated by a suitable hydraulic oil, while only the piston motor 2a uses water as its operating medium.

Fig. 5 illustrates an embodiment of the invention as an impact device or percussion drill.

Fig. 6 illustrates an embodiment of the invention as a sampler for taking core samples of marine sediments on the seabed.

Fig. 7 illustrates an embodiment of the invention for driving an anchor 70 down into sediments on the seabed, the anchor according to the invention being in compressed form and in accordance with the invention being driven down into the sediments. The anchor has hinged arms which will form flukes when the anchor chain 72 is under tension. In this embodiment of the invention the machine forms an integral whole in which the machine's specific weight also makes a positive contribution to the effect of the anchor.

Fig. 8 illustrates another embodiment of a "hydrostatic anchor", in which the machine is equipped with a screw 17 with relatively large threads 170 driven down into the sediments with a combined hammering and screwing movement caused by a hydrostatic axial piston engine and a hydraulic rotary engine respectively.

Fig. 9 illustrates schematically an application of the hydrostatic pressure and arrangements for utilizing this in accordance with the invention in order to provide propulsion for a subsea vehicle.

Fig. 10 is a basic view of a sampler according to the present invention.

Fig. 11a illustrates a preferred embodiment of a deep water version of the sampler according to the present invention.

Fig. lib illustrates a preferred embodiment of a version of the sampler according to the present invention for shallow water.

Figs. 12a and 12b illustrate a preferred embodiment of the hydrostatic operating mechanism.

Figs. 13a and 13b illustrate another preferred embodiment of the hydrostatic operating mechanism.

Figs. 14a and 14b illustrate details of the embodiment in figs. 13a and 13b. Fig. 15 illustrates schematically the lowering of the hydrostatic sampler according to the present invention.

Fig. 16 illustrates the sampler in fig. 15 ready for operation.

Fig. 17 illustrates the sampler in fig. 16 during operation.

Fig. 18 illustrates schematically the sampler in operation with full penetration of the sampler tube in the sedimentary layer.

Fig. 10 illustrates schematically the sampler according to the present invention. The hydrostatic sampler comprises a pressure reservoir 1 which forms the head of the sampler and which is composed of sections, thus enabling the volume of the pressure reservoir to be regulated according to the number of sections used in the embodiment. Within the pressure reservoir 1 there is provided a high pressure cylinder 13 attached to the walls of the pressure reservoir. The high pressure cylinder has a high pressure chamber which via openings 133 and 134 is connected with a low pressure chamber 14 which is formed by the upper volume of the pressure reservoir 1, and via an inlet valve 11 in connection with the outside of the pressure reservoir. Furthermore the high pressure chamber 130 constitutes the cylinder of a pump device which in reality is the sampler's motor, there being provided in the high pressure chamber 130 a first piston 131. This piston 131 is rigidly connected via the piston rod with a second piston 21 in a secondary pump system 2 which is fitted to an extension of the pressure reservoir 1. The object of the second piston 21 is first of all to cause the transfer of impact, or the lifting movement between the pressure reservoir 1 and a sampler section 3 which comprises the sampler tube 30, and secondly to provide a secondary pump system 2, in which the pump cylinder 2 can be emptied into the environment or used to inject water into the conduit 35 in order to provide lubrication of the sampler tube 30 via a three-way valve 22. In the low pressure chamber 14 of the pressure reservoir 1 there is further provided a pressure relief valve 10 to the environment, while an equalization of pressure is obtained in the non-active cylinder volume in the secondary pump system 2, via opening 203 and three-way valve 22 respectively. The top plate of the pressure reservoir 1 is provided with an eye-bolt for the attachment of lines, while the pressure reservoir's top and bottom plates are attached by means of assembly bolts 7. The fitting of further sections to the pressure reservoir 1 can then be performed very easily by loosening the top or bottom plate of the pressure reservoir 1 and fitting the required number of extra sections, the length of the assembly bolts used naturally corresponding to the required length of the pressure reservoir 1.

Figures 11a and lib illustrate in more detail a preferred embodiment of the hydrostatic sampler according to the invention. Fig. 11a illustrates a deep water version of the sampler, wherein the internal volume of the high pressure chamber 130 in the high pressure cylinder is reduced by the insertion of a lining 135, as is more clearly illustrated in fig. 12a. The ratio between the volume of the low pressure chamber 14 and the high pressure chamber 130 is thereby increased, thus enabling a correspondingly larger number of strokes to be achieved at great depth under a greater hydrostatic pressure, the number of impacts obviously being determined by the ratio between the chamber volumes. Fig. lib illustrates a shallow water version of the hydrostatic sampler and, apart from the lining in the high pressure chamber 130, is exactly the same as the version in fig. 11a. On the outside of the pressure reservoir 1 there are provided protective bars 4 and between these and the pressure reservoir 1 or the head there is installed a water filter which is connected with the inlet valve 11. This inlet valve 11 is closed during lowering and not opened until the sampler is in position on the seabed and ready for use, via, e.g., a line-triggered anoeuvering device 110 for the inlet valve 11. The high pressure cylinder 13 is illustrated in more detail in figures 12a, 12b, 13a and 13b. Around the upper section of the high pressure cylinder 13 there is provided a sleeve-shaped slide valve 15 which can be moved axially around the upper section of the high pressure cylinder. The valve housing 15 is provided with an inlet opening 150 which communicates with a corresponding inlet opening 133 in the high pressure cylinder 13 when the slide valve is located in an upper position on the high pressure cylinder, at the same time as the piston 131 in the high pressure cylinder is located in a starting position. The inlet opening 150 on the slide valve 15 is further connected with the inlet valve 11 via a flexible hose 12. When the sampler is positioned on the bottom, the manoeuvering device 110 is triggered, the inlet valve 11 opened and water under the surrounding pressure streams through the flexible hose 12 and into the high pressure chamber 130, the piston 131 in the high pressure cylinder as shown in, e.g., fig. 12a or 13a, being located in the starting position and the slide valve 15 in an upper position. The water which now flows into the high pressure chamber 130 under the hydrostatic pressure drives the piston 131 downwards and a corresponding movement of the connected piston 21 in the attached secondary pump system is obtained, this piston 21 also being in the upper starting posi¬ tion, as is most clearly illustrated in fig. 11a. In the starting position the slide valve 15 is kept pressed against the upper part of the high pressure cylinder 13 by a compression spring mechanism 16 which is arranged to work in conjunction with the piston 131, which will be explained in more detail in the following section.

A first embodiment of the compression spring mechanism 16 is illustrated in fig. 12a, where the piston 131 is located in the starting position and in fig. 12b, where the piston is located in the final position. The compression spring mechanism here comprises a helical spring which is placed in a spring housing 162 and fitted around a spring bolt 161. The spring bolt 161 is passed through a fixed circumferential disc 151 on the slide valve 15 and a fixed locating disc 132 arranged on the piston rod at the bottom of the piston 131. The spring bolts are provided parallel to the piston and the spring housing 162 is installed in the high pressure cylinder 13 beside this, as illustrated in fig. 12a or fig. 12b. On the end of the spring bolts are fitted stop nuts 163 and 164. In the starting position of the piston 131, the slide valve is kept pressed into its upper position by the compression spring 160 by means of the capture disc 132 which causes the spring housing to abut against the stop nut 164, thus causing the tension in the compression spring 160 to be completely relaxed and the upper stop nut 163 on the spring bolt 161 to abut against the circumferential disc 151 on the slide valve 15 and to draw this with it into a lower position, thus interrupting the communication between the inlet openings 133 and 150 and stopping the flow of water to the high pressure chamber 130. Thus when the tension on the compression spring 160 is relaxed, a tension spring 170 which is attached to the high pressure cylinder 13 and the slide valve 15 is pulled into a lower position and the outlet opening in the high pressure chamber 130 is now connected with the low pressure chamber 14 and emptied into it. The pressure in the high pressure chamber 130 is thereby equalized to the pressure in the low pressure chamber 14, which initially, e.g., is under atmospheric pressure. Under the weight of the pressure reservoir 1 or the sampler's head and if the pressure in the high pressure chamber 130 is equalized, the piston 131 now returns from the starting position to the final position, while at the same time the capture disc 132 once more abuts against the valve housing 160 and stretches the compression spring 160 which via the circum¬ ferential disc 151 again presses the slide valve into the upper position and creates a connection from the inlet valve 111 and through the openings 150 and 133 to the high pressure chamber which is filled once again, whereafter the piston stroke is repeated. The tension spring 170 which is considerably weaker than the compression spring 160 is again stretched during this operation, but naturally cannot counteract the return movement of the slide valve 15. Thus it can be seen that the slide valve 15, together with the openings 133, 134 and 150 constitute a valve mechanism for the high pressure cylinder 130 which, together with the piston 131 in reality constitute a hydrostatic motor for the operation of the sampler. Figures 13a and 13b illustrate a second embodiment of the spring mechanism for manoeuvering the slide valve 15, fig. 13a illustrating the piston 131 in the starting position and fig. 13b the piston in the final position. Furthermore, figs. 13a and 13b correspond to figures 11a and lib respectively and describe the same embodiment as illustrated there. Here too, parallel to piston

131 beside the high pressure cylinder, there is provided a spring bolt 161 which is passed through an opening on the side of the high pressure cylinder, and through the circumferential disc 151 with which it is permanently connected. During a piston stroke when the chamber 130 is filled, the capture disc

132 abuts against the stop nut 164 at the end of the rod and compresses the spring 160a against the circumferential disc 151 on the valve housing 15, which under the influence of the spring 160a is pressed against its lower position. At the same time the capture disc 132 also abuts against a stop nut 194 on the end of a camshaft 190, which similarly is arranged parallel to the first piston 131 on the outside of the high pressure cylinder 13 and passed through an opening on the side of this. On the camshaft 190 there is provided a cam disc 191, the camshaft and cam disc thus constituting a cam mechanism which can engage with cam groove 182 on a ratchet mechanism 18. The blocking mechanism 18 is located in the starting position of the slide valve 15 in blocking abutment against the circumferential disc 151, but the blocking is cancelled when the camshaft 190 is pulled with the capture disc 132, thus cancelling the engagement between the camshaft 191 and the cam groove 182 in the ratchet mechanism. The slide valve 15 thereby moves without hindrance under the influence of the compression spring 160a to the lower position, while a helical spring mechanism 17 which is attached to the upper section of the high pressure cylinder 13 and the camshaft, now that the cam disc is disengaged from the ratchet mechanism, pulls the camshaft 191 upwards, thus engaging the cam disc once again with the cam groove 182 in the ratchet mechanism 18, and the slide valve 15 via the circumferential disc engages in a locking manner with a locking groove 181 on the ratchet' mechanism 18. The slide valve is thereby moved by the compression spring 160a and ends in its lower position, securely locked in this position by the ratchet mechanism 18, whereby free passage is created between the high pressure chamber 130 and the low pressure chamber 14 via the opening 134, thus equalizing the hydrostatic pressure, and the piston 131 begins the return stroke back to the starting position under the weight of the pressure reservoir or head 1 and the falling pressure in the high pressure chamber 130. During the return stroke the capture disc 132 pulls the sleeve 195 which is permanently fitted on to the camshaft 190 and also the sleeve 165 on to the spring bolt 161, during which the cam disc 191 is disengaged from the ratchet mechanism 18 and at the same time the compression spring 160b is stretched. The locking of the slide valve in the lower position is thereby cancelled and it is moved under the influence of the compression spring 160b back to its upper position, while the connection between the environment and the high pressure chamber 130 via the openings 150 and 133 is reestablished, thus enabling the cycle to be repeated.

The compression springs 160a and 160b are preferably designed as Belleville springs. As already described, the springs in the helical spring mechanism 17 are a tension spring 171.

The first piston 131, as illustrated schematically in fig. 10 and in more detail in, e.g., fig. 12a, is rigidly connected via the piston rod with the second piston 21 in the secondary pump system 2 , as is most clearly illustrated in figures 11a and lib. In fig. 11a both the pistons 131 and 21 are shown in their starting positions. When the first piston 131 moves, the second piston 21 in the secondary pump cylinder 20 is moved to act upon the sampler tube which is connected to the lower end of the secondary pump piston 21 via the sampler tube adaptor 33. This can slide on the control bolt 24 which is attached in the locking ring 201 on the lower part of the secondary pump cylinder 20, and prevents the sampler tube 30 or the sampler tube adaptor 33 from rotating on the secondary pump piston 21. On the secondary pump cylinder 20 there is provided a three-way valve 22 which is opened during the lowering of the sampler and causes water to enter in under hydrostatic pressure into an annular space 202 which in the secondary pump piston's 21 starting position is created between the sliding bearing 200 on the secondary pump piston and the sliding bearing 211 on the inside of the wall of the secondary pump cylinder 20 when the sampler is positioned on the seabed, while at the same time it is opened for the working stroke of the piston 132. The secondary pump piston 21 is forced downwards, while at the same time the inlet opening in the three-way valve 22 is closed. In its place a connection is obtained between the annular space 202 and an outlet opening in the three-way valve which is connected with a flexible hose 23. Under the influence of the secondary pump piston 21 the water is now forced out of the annular space and into the flexible hose 23 which is connected to an inlet opening in the sampler tube adaptor 33. This inlet opening in the sampler tube adaptor 33 is connected with one or more water injection conduits 35 on the side of the sampler tube. The object of these water injection conduits is to reduce the friction and provide fluid lubrication during the penetration of the sampler tube 30 into the sedimentary layer.

During the drop stroke, i.e. the return movement of the piston 131, the secondary pump cylinder 21 and thus the head 1 abut against the sampler tube adaptor 133, the secondary pump piston 21 returns to the starting position and the water is forced out via the opening 203 in the upper volume of the secondary pump cylinder 20, while the annular space 202 which is again formed during the return movement via the three-way valve 22 is connected with the environment and once again filled with water under hydrostatic pressure, after which the cycle is repeated.

The operation of the hydrostatic sampler according to the invention will be described in more detail in connection with figs. 15-18. In reality the procedures used are not substantially different from those used in gravitation samplers. In fig. 15 the sampler 1 is illustrated during lowering from, e.g., a research vessel. The head or pressure reservoir 1 is attached .to the lowering line and on the sampler section 3 there is provided an attachment point for a support leg 6, which is shown closed around the sampler tube 30. Release lines 60 for the support legs are shown hanging in a slack arc around the sampler. Inside those safety bars illustrated, e.g., in fig. lib, the sampler according to the invention will be equipped with completely different instruments, including an inclination sensor for detecting the sampler's true inclination on the seabed, a sonar device for measuring the distance to the bottom, depths of penetration and also for the transfer of information on inclination. The sonar device, which is not illustrated in more detail, but which may be, e.g., a known per se modulated pinger, indicates the distance to the bottom, thereby enabling the support legs 6 to be released and brought into position by the release line 60 before the sampler reaches the bottom, the support legs sliding along the sampler tube to abut against the sampler head 31 as illustrated in fig. 16. Any inclination indicated can now be compensated by means of the lines 60, thus allowing the sampler tube to be positioned in a substantially vertical manner. By means of the initial impact the sampler tube 30 is now driven down into the sedimentary layer as illustrated in fig. 17. The driving operation continues in an alternating stroke cycle until the desired depth of penetration is achieved or the hydrostatic energy potential approaches zero. This usually involves approximately 200 strokes, depending, as mentioned above, on the ratio between the volume of the low pressure chamber and the volume of the high pressure chamber. After sampling is completed, the sampler and the sampler tube with the core sample are pulled up to the surface by means of a lifting line, the pressure in the high pressure chamber 130 and the low pressure chamber 14 now being the same and identical with the surrounding hydrostatic pressure. During lifting the borehole is refilled with water to prevent the creation of a vacuum when the core sample and the sampler tube are pulled out. During lifting the pressure reservoir is decompressed via the pressure relief valve 10.

In a typical and preferred embodiment the hydrostatic sampler according to the invention weighs approximately 550 kg without the sampler tube. It is arranged to work at water depths between 200 and 6,000 m and consequently must be designed to resist the pressure forces which prevail at such depths. Depending on the water depth the number of strokes can be approximately 200 with an stroke length of approximately 350 mm. The possible penetration, depending on the nature of the sediments, can amount to up to 30 m, which means that the core sample's length is 30 m and this again means that special precautions must be taken on the mother vessel when the core sample is taken aboard. The stroke frequency used can vary from, e.g. 0.6 - 3 Hz, i.e. the actual sampling operation can be performed in the course of a few minutes or less. The stroke frequency can be adjusted via the inlet valve 111, and this is usually necessary as too high an stroke frequency results in severe dynamic loads on the piston rod. It will be obvious to those skilled in the art that there are a number of structural requirements which have to be satisfied in a hydrostatic sampler of this kind, with the purpose of operating at depths as low as 6,000 m. It is, e.g., important to dimension conduits and valves in order to avoid flow friction loss and there are naturally special requirements regarding resistance to corrosion, which can be met by the choice of the correct corrosion- and pressure-resistant materials.

The operation of the sampler can be monitored by means of a hydrophone connected to an amplifier aboard the mother vessel in order to record the sound of the impacts.

If the sampler is to be used in particularly hard sediments, the sampler head 31 can be designed as a rotary drill chisel to which a rotating motion is provided by, e.g., converting a part of the impact energy to rotary motion by means of a suitable device, and in a known per se manner. The rotary movement could possibly also be provided directly by an additional hydrostatic motor.

With regard to the sampler tube itself, it is designed in a known per se manner and composed of sections which may, e.g., be 3 m in length. The individual sampler tube sections are connected by means of a tube section adaptor 36 which also provides fluid connection between the water injection conduits 35 inside the individual sections. In the sampler tube there is further provided a core retaining device 32 which grips the core and is pushed upwards in the tube sections during penetratio .

The above description illustrates examples of preferred embodiments of the sampler according to the invention, but it will be obvious to those skilled in the art that further, advantageous variations will be possible within the scope of the invention.

Claims

PATENT CIAIMS

1. A machine for performing work at great depths, characterized in that it consists of at least one arbitrary work tool (1) of known per se type, at least one hydraulic motor (2) which is adapted in order to be able to be operated by the surrounding water masses, at least one low pressure reservoir (3) , at least one intake valve (4) and at least one fluid filter (5) which is arranged so that the hydrostatic pressure in surrounding water masses leads water through the filter (5) and the valve (4) via a pipe or hose connection to the motor (2) and further via a corresponding pipe or hose connection to the low pressure reservoir (3) , the motor (2) to the greatest possible extent by means of per se prior art converting the pressure energy in the through-flowing fluid into energy which can be used by the work tool (1)

(figures 1-9) .

2. A machine according to claim 1, characterized in that the low pressure reservoir (3) is approximately free of gases other than water vapour, the pressure in the low pressure reservoir being approximately limited to water vapour pressure at the relevant temperature throughout the entire work period from the time the reservoir is empty of water until it is completely full of water supplied from the environment.

3. A machine according to claim 1, characterized in that a low pressure chamber (11) is rigidly connected with a high pressure cylinder (12) , that per se known valve devices (13a, 13b, 14a, 14b) bring one or more of the cylinder volumes (120a and 120b) into alternating connection with the surrounding water masses and the low pressure chamber (11) respectively in such a manner that the high pressure cylinder (12) acts as a water-driven axial motor (2) , a pulsating movement being imparted to the piston (15) and the piston rod (16) . IS

4. A machine according to in claim 3, characterized in that the piston (15) and the piston rod (16) are rigidly connected with a second piston (21) provided in a second cylinder (22) , that the second cylinder (22) is rigidly connected with and has the same centre axis as the first cylinder (12) , and that the second cylinder (22) with the second piston (21) is equipped with per se known non-return valves, the second cylinder thus acting as an axial pump (20) .

5. A machine according to claim 4, characterized in that the medium pumped by the axial pump (20) is the surrounding liquid, and that the pump operates as an open system which "consumes" surrounding liquid.

6. A machine according to one or more of the preceding claims, characterized in that between the valves (4) and (13a, 13b) there are provided a choke valve (18) and an accumulator (19) in order to equalize the fluid flow through the filter (5) .

7. A machine according to claim 4, characterized in that the medium pumped by the axial pump (20) is a commercial hydraulic oil which is provided in a closed system comprising at a minimum the axial pump (20) , a hydraulic motor (31) and related hose and valve connections.

8. A machine according to claim 7, characterized in that the closed hydraulic system also comprises at least one accumulator (32) and at least one pressure regulating valve (33) for equalizing the supply pressure from the axial pump (20) .

9. A machine according to claim 3, characterized in that the low pressure chamber (11) is disengageably connected with an extra low pressure reservoir (3) via a hose or pipe connection, that the low pressure chamber (11) is directly connected with an accumulator (40) and that the differential pressure between the low pressure chamber (11) and the low pressure reservoir (3) is controlled by means of a differential pressure limiting valve (41) .

10. A machine according to claim 3, characterized in that the high pressure cylinder (12) is arranged with its longitudinal axis approximately perpendicular to the seabed, that the piston rod (16) is rigidly connected with an impact device (17) with approximately the same longitudinal axis as the piston rod (16) , that the lower chamber (120b) has a constantly open fluid connection with the low pressure chamber (11) and constantly closed connection with the external pressure, while only the upper chamber (120a) is arranged so as to provide an axial motor effect, the valve (13a) being opened at the first stroke, while valve (14a) is kept closed, thus imparting to the piston (15) a downwards directed movement and causing a first downwards directed pulse to the impact device (17) , the cylinder (12) with the low pressure chamber (11) being simultaneously given an upwards directed reaction movement, and that at the next stroke the valve (14a) is opened, while valve (13a) is kept closed, thus imparting to the low pressure chamber (11) and the high pressure cylinder (12) a dropping movement which ends with a second downwards directed pulse to the impact device (17) , after which the first stroke is repeated, and so on until the low pressure reservoir (11, 3) is full or the intake valve (4) is closed.

11. A machine according to claim 10, characterized in that the impact device (17) is in the form of a percussion drill and that the downwards directed pulsations are partially converted to rotational movement through a per se known mechanical device (170) .

12. A machine according to claims 4 and 10, characterized in that the impact device (17) is in the form of a percussion drill and that the axial pump (20) is used to operate a hydraulic rotary engine (50) which imparts a rotational movement to the impact device (17) .

13. A machine as described in one or more of the claims'10-12, characterized in that the impact device (17) forms the top of a sampler tube (60) consisting of one or more sampler tube sections (61) arranged to take samples of sediments on the seabed.

14. A machine according to claim 10, characterized in that the impact device (17) forms the top of an anchor (70) which in known per se manner can consist of several arms (71) hinged near the top (17) so that the anchor offers little resistance when driven into the seabed, but strong resistance when attempts are made to pull it up by means of, e.g., an anchor chain (72) attached to the top of the low pressure chamber (11) , since the arms (71) are then unfolded.

15. A machine according to claims 11 or 12, characterized in that the impact device (17) is in the form of a screw with relatively large threads (170) , thus causing the screw to be attached to the bottom in such a manner that it anchors the machine and any vessel attached to it via, e.g., an anchor chain (72) .

16. A machine according to one or more of the preceding claims, characterized in that a hydraulic motor (80) driven by fluid from one of the pumps (2a) or (20) is used to move a vehicle (100) on the seabed.

17. A machine according to claim 1, characterized in that at least one motor (2) is a water turbine installed directly in a low pressure reservoir (3) .

18. A machine according to claim l, characterized in that at least one motor (2) drives an electrical generator.

19. A machine according to claim 18, characterized in that the electrical generator is used for charging an electrical accumulator with relatively lower^' energy capacity than the machine according to the invention.

20. A machine according to claim 19, characterized in that the motor which runs the generator is driven by fluid which in a known per se manner is supplied only for short periods with relatively longer time intervals, e.g. by means of a hydraulic valve controlled by an interval switch.

21. A hydrostatic sampler, especially for core samples of marine sediments, wherein the sampler comprises a cylindrical head (1) and a substantially cylindrical sampler section (3) whose longitudinal axis passes approximately through the head's (1) centre of gravity, and wherein the sampler section comprises a sampler tube (30) which consists of at least one sampler tube section, characterized in that the head (l) constitutes a pressure reservoir consisting of at least one reservoir section, that the pressure reservoir (1) comprises a low pressure chamber (14) and a high pressure cylinder (13) with a high pressure chamber (130) provided in or directly connected with the low pressure chamber (14) , that the high pressure chamber (130) is connected via an inlet opening (133) with the outside of the pressure reservoir and via a further opening (134) with the low pressure chamber (14) , that in the high pressure chamber (130) there is provided a first piston (131) , with direction of movement along the longitudinal axis of the sampler section (3), and that the sampler section (3) with the sampler tube (30) are arranged to perform a stroke movement generated by the effect of the hydrostatic pressure on the first piston (131) , during which the said piston (131) moves from a starting position to a final position in the high pressure chamber (130) and thereafter due to the weight of the head (1) returns to the starting position during a downwards directed movement of the head (1) and the secondary pump cylinder (20) to abut against the sampler section (3) (figures 10-18) .

22. A hydrostatic sampler according to claim 21, characterized in that there is provided a secondary pump system (2) consisting of a secondary pump cylinder (20) with a second piston (21) , the secondary pump cylinder (20) being rigidly connected with the head (1) and having the same central longitudinal axis as the head (1) and the sampler tube (30) , and that the first piston (131) is rigidly connected with the second piston (21) and with the sampler section (3) (figures 10-18) .

23. A hydrostatic sampler according to claim 21 or 22, characterized in that the high pressure cylinder (13) on the outside of its upper section is surrounded by a sleeve-shaped slide valve (15) moveable around this section, arranged to provide fluid communication between the high pressure chamber (130) and the environment respectively via the inlet opening (133) and between the high pressure chamber (130) and the low pressure chamber (14) via the additional opening (134) , the additional opening (134) being composed of at least one outlet opening on the upper section of the first piston's (131) cylinder (13) in order to provide fluid communication between the high pressure chamber (13) and the low pressure chamber (14).

24. A hydrostatic sampler according to claim 23, characterized in that the inlet opening (133) is fluid communication with the high pressure chamber (130) via a first flexible hose (12) which is attached to an inlet opening (150) on the slide valve (15) , the inlet opening (150) on the slide valve (15) being capable of fluid communication with at least one inlet opening (133) in the upper section of the cylinder (13).

25. A hydrostatic sampler according to claim 23, characterized in that there are provided two sets of spring mechanisms (16) around one or more spring bolts (161) which are slidingly arranged parallel to the central longitudinal axis, that the first set of spring mechanisms (16) comprises springs which extend between a circumferential disc (151) on the'slide valve (16) and a stop disk permanently connected to the spring bolts (161) , that the second set of spring mechanisms (16) extends between the circumferential disc (151) and a locating disc (132) on the lower end of the first piston (131) , and that the capture disc (132) abuts against a stop disk on the lower end of the spring bolts (161) when the first piston (131) ap¬ proaches its lower end position, thus causing the first set of spring mechanisms to be stretched, while the locating disc (132) stretches the second set of spring mechanisms when the first piston (131) approaches its upper position, the circumferential disc (151) and the slide valve (15) being affected by a spring load directed towards the same end position when the first piston (131) is located close to an end position.

26. A hydrostatic sampler according to claim 23, characterized in that spring mechanisms (17) are provided around one or more camshafts (190) on both sides of a disk (136) which is permanently connected to the high pressure chamber (130) , that the springs (170) in the spring mechanism

(17) extend between the disc (136) and fixed points on the camshafts (190) , that the camshafts (190) pass freely through the disc (136) and are axially slidingly arranged parallel to the central longitudinal axis, and that cam discs (191) are rigidly connected with the camshafts.

27. A hydrostatic sampler according to claim 26, characterized in that there is provided a ratchet mechanism

(18) which is arranged to lock the slide valve (15) axially when it is located in its upper or lower end position, that the ratchet mechanism (18) is spring loaded in the direction of the locking position and the cam discs (191) , that the ratchet mechanism is located in the locking position when the cam discs (191) are located in a groove (182) in the ratchet mechanism, that this position of the cam discs (191) which corresponds to the groove (182) also corresponds to a neutral position of the spring mechanism (17) in relation to the camshafts' (190) axial movement, and that the ratchet mechanism (18) is forced away from the camshaft and out of the locking position when the cam disks (191) are forced downwards or upwards and out of the groove (182) .

28. A hydrostatic sampler according to claim 27, characterized in that the camshaft (190) passes through a capture disc (132) which is permanently connected with the lower end of the first piston (131) , that when the piston approaches its lower end position, the capture disc (132) abuts against a disk, nut or the like which is rigidly connected with the lower end of the camshafts, and that when the first piston (131) approaches its upper final position, the capture disk abuts against a disk, sleeve (195) , cross section extension or the like which is axially rigidly connected with the camshaft, so that close to an arbitrary final position the first piston forces the camshaft (190) with the cam disk (191) out of its neutral position and causes an opening of the ratchet mechanism (18) .

29. A hydrostatic sampler according to claim 21, characterized in that the volume of the first piston's (131) cylinder (13) is reduced with a lining (135) provided in the high pressure chamber (130) , the first piston being given a correspondingly reduced dimension.

30. A hydrostatic sampler according to claim 21, characterized in that between the low pressure chamber (14) and the outside of the head (1) there is provided a pressure relief valve (10) .

31. A hydrostatic sampler according to claim 22, characterized in that the secondary pump cylinder (20) is provided with a three-way valve (22) on at least one end, the three-way valve (22) providing fluid communication between the outside of an annular space (202) which is created in the secondary pump cylinder on the side of the second piston (21) where the three-way valve (22) is provided, and that the three-way valve has an approximately direct connection with the outside when the second piston (21) causes a suction effect in the annular space (202) , while the approximately direct connection is blocked at the same time as a connection is opened to a water injection conduit (35) via a second flexible hose (23) when the annular space (202) is compressed by the second piston (21) , and that the water injection conduit (35) is provided in the sampler section (3) in order to provide fluid lubrication of the sampler tube (30) or water injection in the core hole when lifting the sampler tube (30) .

32. A hydrostatic sampler according to claim 31, characterized in that there are provided three-way valves (22) at both ends of the secondary pump cylinder (20) , and that the second piston (21) thereby causes water injection to at least one water injection conduit (35) whether the second piston (21) has an upwards or a downwards movement.

33. A hydrostatic sampler according to claim 31, characterized in that the three-way valve (22) is provided only at one end of the secondary pump cylinder, and that there is provided a pressure equalization opening (203) on the opposite end of the secondary pump cylinder (20) relative to the three- way valve (22) .

34. A hydrostatic sampler according to claim 22, characterized in that the piston rod which rigidly connects the second piston to the sampler section (3) is led into a lining in the lower end of the secondary pump cylinder (20) , and that the said piston rod is dimensioned in order to absorb those moments which can arise between the sampler section (3) and the head (1) , particularly in connection with deployment or recovery of the hydrostatic sampler in rough sea, and that these moments are transferred in substantial degree from the piston rod to the secondary pump cylinder (20) , that part of the piston rod which connects the second piston (21) with the first piston (131) thus being exposed to only a moderate degree of stress due to the moment.

35. A hydrostatic sampler according to claim 34, characterized in that on the secondary pump cylinder (20) there is provided a guide rod (24) which is passed through a sampler tube adaptor (33) in order to lock the sampler tube (30) against rotation, and that the sampler tube adaptor (33) is arranged to connect the sampler tube (30) with the second piston (21) .

36. A hydrostatic sampler according to claim 35, characterized in that the sampler tube adaptor is supplied with inlet openings in order to provide fluid communication between the flexible hose (23) and the water injection conduit (35) .

37. A hydrostatic sampler according to claim 36, characterized in that additional sections of the sampler tube (30) are interconnected with respective sampler tube section adaptors (36) , the said adaptors (36) being provided with inlet openings in order to provide fluid communication between the water injection conduits (35) and the additional sections of the sampler tube (30) .

38. A hydrostatic sampler according to one of the preceding claims, characterized in that the sampler section (3) with the sampler tube (30) are arranged in a per se known manner to perform a combined impact and rotational movement generated by the use of the axial movement between the head (1) on one hand and on the other hand the first piston (131) or other components rigidly connected with the first (131) and the second (31) piston.

39. A hydrostatic sampler according to claim 22, characterized in that the pump effect from the secondary pump cylinder (20) is used in a per se known manner to transfer a rotational movement to one or more sampler tube sections by means of a hydraulic rotary engine driven by water supplied from the secondary pump cylinder (20) or driven by another suitable hydraulic fluid which circulates to and from the secondary pump cylinder in a closed hydraulic system.

40. A hydrostatic sampler according to claim 21, characterized in that the low pressure chambers (14) have a hose connection with a separately provided extra low pressure reservoir which, e.g., can be placed on the seabed beside the sampler, and that the hose connection is aranged so that the low pressure chamber acts as a buffer between the high pressure chamber (130) and the extra low pressure reservoir, thereby increasing the capacity of the hydrostatic sampler.

41. A hydrostatic sampler according to one of the preceding claims, characterized in that a valve (11) with a spring-loaded valve arm (110) closes the fluid connection between the high pressure chamber (130) and the environment when the valve arm (110) is located in its lower position when overcoming the spring moment which will tend to open the valve and move the valve arm (110) to its upper position, and that a weight is attached by a line to the outer end of the valve arm (110) , the weight thus keeping the valve (11) closed until the weight hits the seabed when the sampler is being lowered, and the hydrostatic sampler will automatically begin to perform the impact movement when the distance between the seabed and the head (1) correspond approximately to the length of the line between the valve arm (110) and the weight.

42. A hydrostatic sampler according to claim 41, characterized in that the valve arm (110) is connected to a rod which is provided freely moveable in the axial direction approximately parallel to the sampler tube (3) , that the rod is connected at its upper end to the valve arm (110) via a rocker arm, pulley block or the like, in such a manner that an upwards directed movement of the rod causes a downwards directed closing movement of the valve arm (110) , that the lower end of the rod extends below the sampler tube adaptor (33) and has a cross section extension at its lower end, that the weight of the rod is insufficient to cause the valve to open, and that the rod or rocker arm is provided with a blocking mechanism which keeps the valve (11) closed when the rod is moved from its lower to its upper position, the lower end of the rod being forced upwards relative to the head by the bottom sediments, approximately the entire sampler tube (30) being forced down into the sediments.

43. A hydrostatic sampler according to claim 28, characterized in^*that a rod or a weight is provided with its lower end below the sampler tube (33) , that a rocker arm is further provided hinged to an axis parallel to the central centre axis and at a considerable distance from this and immediately below the axial point where the head (1) abuts against the sampler section (3) , and that the rocker arm in a per se known manner is provided so as to abut against the piston rod towards the head (1) and the sampler section (3) when the rod or weight hits the bottom and is lifted relative to the head (1) , in such a manner that the capture disc (132) on the lower end of the first piston (131) does not reach its upper end position, thus preventing it from causing an opening of the ratchet mechanism (18) for the slide valve (15) .

44. A hydrostatic sampler according to any of the preceding claims, characterized in that a high pressure hose connects the valve (11) directly or indirectly with a fluid compressor, thus enabling the supply of fluid from the said compressor to replace luid from the environment under operating conditions where the hydrostatic pressure in the head's (1) environment is not sufficient to operate the sampler.