Electrohydraulic system for underwater use and process valve with such an electrohydraulic system

Abstract

An electro-hydraulic system (20) for underwater use, comprising a container (22) having an interior space (23) designed to form a volume sealed off from the environment and intended to hold a hydraulic pressure fluid, and a compensating piston (28) to bring the hydraulic pressure fluid in the interior space (23) at least approximately below the ambient pressure, comprising a hydrostatic machine (50) operable at least as a pump, and an electric machine (51) mechanically coupled to the hydrostatic machine (50), which operates as an electric motor to operate the hydrostatic machine as a pump, characterized in that the hydrostatic machine (50) and the electric machine (51) are arranged in the interior space (23) of the container (22), wherein the compensating piston (28) is further acted upon by a spring arrangement which generates a force in the same direction as the force generated by the ambient pressure.that as a result, the pressure inside the container is higher than the ambient pressure by the pressure equivalent of the spring force, wherein the hydrostatic machine (50) can also be operated as a hydraulic motor and the electric machine (51) can also be operated as a generator, and wherein the hydrostatic machine (50) is adjustable in its stroke volume.

Description

[0001] The invention relates to an electrohydraulic system for use underwater, particularly at great depths. The system comprises a container having an interior space designed to form a volume sealed off from the environment and intended to hold a hydraulic pressure fluid, and a compensating piston to reduce the pressure of the hydraulic pressure fluid in the interior space to at least approximately the same level as the ambient pressure.The system further comprises a hydrostatic machine that can be operated at least as a pump, an electric machine mechanically coupled to the hydrostatic machine which operates as an electric motor to operate the hydrostatic machine as a pump, and a hydraulic cylinder whose interior is divided by a piston to which a piston rod is connected into a cylinder chamber on the piston rod side and a cylinder chamber on the side opposite the piston rod, wherein, in order to move the piston rod in a first direction, in particular to extend the piston rod, pressurized fluid can be supplied from the hydrostatic machine in operation as a pump to a first cylinder chamber, in particular the cylinder chamber on the side opposite the piston rod.

[0002] Such electrohydraulic systems are primarily used to move elements underwater at depths of up to several thousand meters in connection with oil and gas extraction, mining, scientific exploration, or infrastructure projects. For example, offshore oil and gas production facilities often contain large, deep-sea process valves that can regulate or shut off the flow rate of the extracted medium.

[0003] An electrohydraulic system with the features mentioned above is known, for example, from US 3,933,338. This system comprises a hydraulic cylinder whose cylinder housing is mounted on the housing of a process valve and which includes a piston and a piston rod extending from one side of the piston, by means of which a process valve spool can be moved. The piston divides the interior of the cylinder housing into a cylinder chamber away from the piston rod and a cylinder chamber on the piston rod side. A helical spring is housed in the cylinder chamber on the piston rod side, which acts on the piston in the direction of closing the process valve. The known system further comprises a container whose interior, filled with a pressurized fluid, is separated from the environment at one point by a movable compensating piston.The compensating piston is subjected to the pressure inside the container on one surface and to the ambient pressure on a second surface, which is the same size as the first but oriented in the opposite direction, so that the pressure inside the container is the same as the ambient pressure. The cylinder chamber on the piston rod side is permanently fluidically connected to the interior of the container. Depending on the position of a hydraulic valve, the cylinder chamber on the opposite side is connected either to a pump or to the interior of the container and to the cylinder chamber on the piston rod side. In one position of the valve, the pump can deliver pressurized fluid into the cylinder chamber on the opposite side to extend the piston rod and open the process valve. After the hydraulic valve switches, the piston rod is retracted by spring force, thus closing the process valve.

[0004] US 3 572 032 A describes a submersible electrohydraulic valve actuator for underwater applications and US 8 596 608 B2 discloses an underwater valve actuator system with a piston and cylinder assembly and a return spring in an actuator housing.

[0005] The invention is based on the objective, on the one hand, of creating a compact electrohydraulic system that can be installed on both existing and new equipment, and on the other hand, of enabling a compact process valve including an electrohydraulic system.

[0006] The problem is solved by an electrohydraulic system comprising a container with an interior space designed to form a volume sealed off from the environment and intended to hold a hydraulic pressure fluid, and a compensating piston to bring the hydraulic pressure fluid in the interior space at least approximately below the pressure prevailing in the environment, a hydrostatic machine operable at least as a pump, and an electric machine mechanically coupled to the hydrostatic machine, which operates as an electric motor to operate the hydrostatic machine as a pump, wherein the hydrostatic machine and the electric machine are arranged in the interior space of the container.

[0007] By housing the hydrostatic and electric motors within the tank, a compact unit is obtained that is easy to handle and readily attachable to equipment. Complex piping can be largely eliminated. A hydraulic cylinder, which actuates the process valve, can also be housed and mounted within the tank. Alternatively, the hydraulic cylinder can be attached to the equipment. In this case, a suitable opening must be provided in the tank, and sufficient space must be provided inside the tank to accommodate the hydraulic cylinder when the tank is connected to the equipment, for example, to the process valve housing.

[0008] A significant advantage of the solution according to the invention is that the compact design of the electrohydraulic system allows the individual components to be easily protected from attack by seawater, thus ensuring a long service life. The risk of hydraulic fluid entering the seawater is reduced because fewer individual components need to be sealed against water. A complex supply system for hydraulic fluid to depth is avoided. Only one electrical cable is required.

[0009] The hydrostatic machine, hereinafter referred to simply as the hydraulic machine, can also be operated as a hydraulic motor, and the electric machine as a generator. In this configuration, when the piston rod of the hydraulic cylinder is retracted, pressurized fluid from the cylinder chamber opposite the piston rod is displaced via the hydraulic machine.

[0010] An electrohydraulic system according to the invention can be advantageously designed in different ways.

[0011] Various types of hydraulic machines can be used. For example, the hydraulic machine can be one with a constant stroke volume. Such a hydraulic machine always delivers or absorbs the same amount of pressurized fluid with each revolution of a drive shaft. According to the invention, the hydraulic machine's stroke volume is adjustable. In particular, when combined with an electric motor whose speed is variable, highly dynamic position control of the hydraulic cylinder, and thus of the part moved by the hydraulic cylinder, is possible.

[0012] If the hydraulic machine can be adjusted from positive stroke volumes via a zero position, in which the stroke volume is zero, to negative stroke volumes, then it can be operated in the same direction of rotation and with the same pressure connection as a pump and as a motor.

[0013] In a particularly preferred embodiment of an electrohydraulic system according to the invention, the connection between a pressure port of the hydraulic machine and a consumer line, which is provided for supplying a pressure chamber of a hydraulic consumer, for example, for supplying a cylinder chamber of a hydraulic cylinder located away from the piston rod, can be controlled via a valve located inside the reservoir such that the connection is open in a rest position, which the valve assumes under the action of a spring, and closed, at least in the direction from the cylinder chamber away from the piston rod to the hydrostatic machine, in a switching position, which the valve assumes under the action of an electric actuator. The valve is advantageously designed as a poppet valve, so that in the closed position no or only very minimal leakage occurs through the valve and the hydraulic machine and the electric machine can be out of operation.

[0014] It is advantageous to house a hydraulic accumulator with a pressure fluid chamber inside the reservoir. Pressure fluid can be supplied to this accumulator by the hydraulic machine when operating as a pump, and pressure fluid can also be supplied from a consumer line through which a pressure chamber of a hydraulic consumer, such as the piston-rod-side cylinder chamber of a hydraulic cylinder, can be pressurized. This allows the piston-rod-side cylinder chamber to be pressurized with the accumulator pressure, so that in the event of a power failure or interruption, the piston rod is retracted by pressurizing it with the accumulator pressure. Using the spring assembly and the hydraulic accumulator together results in a particularly short reaction time to a power failure. Furthermore, the spring assembly and the hydraulic accumulator provide two redundant means of moving the hydraulic cylinder to its rest position.

[0015] Advantageously, the connection between the consumer line and the hydraulic accumulator can be controlled via a valve located inside the tank in such a way that the connection is open in a rest position, which the valve assumes under the action of a spring, and is closed at least in the direction from the hydraulic accumulator to the consumer line in a switching position, which the valve assumes under the action of an electrical actuator.

[0016] Advantageously, the consumer line, and thus the piston-rod-side cylinder chamber, is fluidically connected to the interior of the reservoir during normal operation. This connection can be interrupted by a valve when the second cylinder chamber is to be pressurized. The connection is controllable by the valve such that, in a rest position (assumed by a spring), the connection is closed, at least in the direction from the second cylinder chamber to the interior, and in a switching position (assumed by an electrical actuator), it is open.

[0017] The electro-hydraulic system advantageously also includes a hydraulic cylinder, the interior of which is divided by a piston, to which a piston rod is connected, into a cylinder chamber on the piston rod side and a cylinder chamber on the opposite side. Pressurized fluid can be supplied by the hydrostatic machine, operating as a pump, to a first cylinder chamber, particularly the cylinder chamber on the opposite side, to move the piston rod in a first direction, in particular to extend the piston rod. The hydraulic cylinder is preferably also housed within the interior of the reservoir. This further reduces the risk of leakage to the outside. However, it is also possible for the hydraulic cylinder to actuate the process valve to be located outside the reservoir and attached to the equipment independently. The reservoir can then be attached to the hydraulic cylinder or to the equipment.

[0018] The hydraulic cylinder preferably includes a mechanical spring arrangement that acts on the piston in a second direction opposite to the first. Such a spring allows the piston rod to retract as soon as the system's power supply is interrupted.

[0019] Under normal operating conditions, the pressure in the accumulator's pressure chamber is higher than the pressure inside the reservoir, and therefore higher than the pressure in the second cylinder chamber, but lower than the pressure typically found in the delivery line at the process valve. It is therefore advantageous to have two seals axially arranged one behind the other in the cylinder head of the hydraulic cylinder, surrounding the piston rod, with the area between the two seals fluidically connected to the accumulator's pressure chamber. This ensures that, under normal operating conditions, the pressure difference across one seal is only as large as the difference between the pressure at the process valve and the accumulator pressure, thus minimizing leakage between the two systems.

[0020] As is known per se, the compensating piston is subjected to the pressure inside the container on a first surface and to the ambient pressure on a second surface, which is the same size as the first surface but oriented in the opposite direction. According to the invention, the compensating piston is further acted upon by a spring arrangement that generates a force in the same direction as the force produced by the ambient pressure. This increases the pressure inside the container by the pressure equivalent of the spring force above the ambient pressure. This ensures that no salt water enters the container. The pressure inside the container can be, for example, between 0.1 bar and 2 bar, preferably between 0.5 bar and 2 bar, higher than the ambient pressure.

[0021] By detecting one or more positions of the compensation piston using one or more position sensors, it is possible to determine whether the amount of pressurized fluid inside the container increases or decreases due to leakage over the operating time. However, it must be taken into account that the volume available to the pressurized fluid inside the container changes slightly during the extension and retraction of the piston rod, depending on the cross-section and travel of the piston rod. This affects the position of the compensation piston. Therefore, leakage only occurs when the end positions of the compensation piston fall outside a certain range.

[0022] The compensation piston can be formed by a rigid disk, but also by a movable membrane clamped at its edge.

[0023] Advantageously, the pressure connection of the hydraulic machine is protected by a pressure relief valve.

[0024] The invention also manifests itself in a device for arrangement underwater and for controlling a volume flow of a gaseous or liquid medium, comprising a process valve with a process valve housing, a process valve slide with which the volume flow can be controlled, a hydraulic cylinder attached to the process valve housing with which the process valve slide can be moved, and an electrohydraulic system according to the invention, wherein the container is sealed and attached to the process valve housing.

[0025] Advantageously, an existing hydraulic cylinder protrudes through an opening in the container into its interior.

[0026] An embodiment of a device according to the invention, comprising an electrohydraulic system whose reservoir is attached to a process valve, is shown in the drawings. The invention will now be explained in more detail with reference to these drawings.

[0027] They show Fig. 1 schematically the device with the process valve closed and Fig. 2 schematically the device with the process valve almost fully open.

[0028] The embodiment of a device according to the invention shown in the figures comprises a process valve 10 with a process valve housing 11 through which a process valve channel 12 passes, which is continued at its outlets by pipes (not shown) and in which a gaseous or liquid medium flows from the seabed to a part of a drilling rig or a drilling ship protruding from the sea. The direction of flow is indicated by arrow 13.

[0029] A cavity is formed in the process valve housing 11, which crosses the process valve channel 12 and in which a process valve spool 14 with a flow opening 15 is movable transversely to the longitudinal direction of the process valve channel 12. In the state after the Fig. 1. The process valve channel 12 and the flow opening 15 in the process valve slide 14 do not overlap. The process valve is therefore closed. In the state after Fig. 2. The flow opening 15 and the process valve channel 12 largely overlap. The process valve is almost completely open.

[0030] A process valve of the type shown and described for use should, on the one hand, be capable of controlled operation and, on the other hand, contribute to safety by quickly and reliably assuming a position corresponding to a safe state in the event of a malfunction. In this case, this safe state is a closed process valve.

[0031] According to the invention, the process valve is actuated by a compact electrohydraulic system 20, which is arranged underwater directly on the process valve 10. It is sufficient that only one electrical cable 21 leads from the electrohydraulic system to the sea surface or to another underwater higher-level electrical control unit. The electrohydraulic system 20 shown as an exemplary embodiment has a reservoir 22 which is attached to the process valve housing 11 at one open end, so that an interior space 23 is provided that is sealed from the environment and filled with a hydraulic pressure fluid as the working medium. For attachment to the process valve housing 11, the reservoir 22 has an inner flange on its open end with which it is screwed to the process valve housing.Radially outside the screw connections, a circumferential seal 16 is arranged between the inner flange of the container 22 and the process valve housing, which is inserted into a circumferential groove of the process valve housing 11.

[0032] The container is pressure-compensated against the ambient underwater pressure. For this purpose, a lid 27 is attached to a flat rim 25 surrounding an opening 24 in the container wall by means of a flange 26. A membrane 28 is tightly clamped between the flat rim 25 and the lid 27. The lid 26 has holes 29, so that the space between the membrane and the lid is part of the environment and is filled with seawater. Thus, the interior 23 is sealed off from the environment by the membrane 28. The membrane is subjected to the pressure in the interior on its first surface facing the interior, and to the pressure prevailing in the environment on its second surface facing the lid 27, which is approximately the same size as the first surface. The membrane always seeks to assume a position and shape in which the sum of all forces acting on it is zero.To ensure that the pressure inside the chamber 23 is slightly higher than the ambient pressure, the diaphragm 28 is additionally subjected to pressure from the ambient pressure by a spring 30 clamped between a dimensionally stable, central diaphragm plate 31 and the cover 27. The force of the spring 30 is selected, taking into account the size of the pressurized areas of the diaphragm, such that the pressure inside the chamber is, for example, between 0.5 bar and 2 bar higher than the ambient pressure. A rod 32 is attached to the diaphragm plate 31 and guided in the cover 27. This rod can be equipped with a scale and may be part of a sensor that detects the position of the center of the diaphragm 28. A rod equipped with a scale can also extend from the diaphragm plate 31 into the chamber 23 to interact with a displacement sensor. This avoids contact with seawater and increases reliability.

[0033] In the interior 23 of the container 22, all mechanical, electrical and hydraulic components necessary or advantageous for controlling the process valve 10 are housed, except for the source of electrical power energy and higher-level electrical control signals.

[0034] First, there is a hydraulic cylinder 35 with a cylinder housing 36, which is closed at its end face by a cylinder base 37 and a cylinder head 38, with a piston 39 which is displaceable longitudinally within the cylinder housing 36, and with a piston rod 40 which is rigidly connected to the piston 39 and projects away from the piston 39 on one side, is sealed, and passes through the cylinder head 38 in a manner not shown in detail. The gap between the piston rod 40 and the cylinder head 38 is sealed by two seals 41 arranged axially apart from each other in the cylinder head. The process valve spool 14 is attached to the free end of the piston rod 40.

[0035] The piston 39 divides the interior of the cylinder housing 36 into a bottom-side or piston rod-side cylinder chamber 42 and a piston rod-side cylinder chamber 43, the volume of which depends on the position of the piston 39.

[0036] In the cylinder chamber 43 a helical compression spring 48 is housed, which surrounds the piston rod 40 and is clamped between the cylinder head 38 and the piston 39, thus acting on the piston in a direction in which the piston rod 40 is retracted and the process valve slide 14 is moved to close the process valve 10.

[0037] Inside the interior 23 of the container 22 are a hydrostatic hydraulic machine 50, which can be operated as both a pump and a hydraulic motor, and an electric machine 51, which is mechanically coupled to the hydraulic machine 50 for a common rotary motion and can be operated as both an electric motor and a generator. The hydraulic machine 50 has a pressure port 52 and a suction port 53, which is open to the interior 23. The hydraulic machine is adjustable from positive stroke volumes, through a zero position (where the stroke volume is zero), to negative stroke volumes, so that it can be operated in the same direction of rotation and with the same pressure port as both a pump and a hydraulic motor. A positive stroke volume corresponds to operation as a pump.The electric motor's speed is adjustable and it is connected to an electrical control unit 54, which is also housed in the interior 23 and is connected via the sealed cable 21 leading out of the container 22 to an electrical power source at the sea surface or to a higher-level electrical control system located underwater. The speed of the hydraulic motor and the electric motor is detected by a speed sensor 55 and processed by the control unit 54.

[0038] During operation, the hydraulic pump can draw pressure fluid from the interior 23 and pump it via the pressure port 52 to the cylinder chamber 42. Conversely, pressure fluid can be displaced from the cylinder chamber 42 into the interior 23 of the reservoir 22 via the hydraulic pump 50. In this embodiment, the cylinder chamber 42 is the first cylinder chamber. A 2 / 2-way poppet valve 56, located in the interior 23, is inserted into the connection between the hydraulic pump 50 and the cylinder chamber 42. In its rest position, held by a spring 57, the poppet valve is open. In its switching position, which can be moved by an electromagnet 58, it prevents the flow of pressure fluid from the cylinder chamber 42.

[0039] Inside the interior 23 is a 2 / 2-way poppet valve 60, which is connected at one port to the second cylinder chamber 43 and at the other port is open to the interior 23. Under the action of a spring 61, the valve 60 assumes a rest position in which the cylinder chamber 43 is sealed off against the outflow of pressurized medium into the interior 23, and can be moved by an electromagnet 62 into a switching position in which there is an open connection between the cylinder chamber 43 and the interior 23.

[0040] The interior space 23 also contains a hydraulic accumulator 65 with a cylindrical accumulator housing 66, which is open at one end towards the interior space 23 and closed at the other end by a base 67, with an accumulator piston 68 movable in the axial direction of the accumulator housing 66, and with a compression spring 69 clamped between the accumulator piston 68 and a stop on the open end of the accumulator housing 66. A pressure fluid chamber 70 is formed between the base 67 and the accumulator piston 68, the volume of which depends on the position of the accumulator piston 68. The piston 68 is thus subjected to a force generated by the pressure in the pressure fluid chamber 70 in the direction of an increase in the volume of the pressure fluid chamber 70, and in the opposite direction by a force generated by the pressure in the interior space 23 and the force of the compression spring 69.

[0041] Pressure medium can be supplied to the pressure fluid chamber 70 via a valve 75 located in the interior 23 from the hydraulic machine 50 when operating as a pump. The valve 75 prevents any flow of pressure medium from the pressure fluid chamber 70 to the hydraulic machine 50. If the pressure chamber is otherwise sealed, the accumulator piston 68 moves to enlarge the pressure chamber, thereby increasing the tension of the compression spring 69, which in turn increases the spring force and thus raises the accumulator pressure in the pressure chamber above the pressure in the interior 23. Because the characteristic curve of the spring 69 is known, each position of the accumulator piston 68 corresponds to a specific pressure in the pressure fluid chamber 70. An end position of the accumulator piston 68, and thus the desired maximum accumulator pressure, can be detected by a position sensor 71. When the maximum accumulator pressure is reached, the valve 75 is closed, as indicated by the dashed line leading from the position sensor 71 to the valve 75.An electromechanical pressure sensor can also be used to measure the storage pressure.

[0042] The pressure fluid chamber 70 of the hydraulic accumulator 65 can be fluidically connected to the second cylinder chamber 43 via a 2 / 2-way seat valve 76 located in the interior 23 and shut off from the cylinder chamber 43. Under the action of a spring 77, the valve 76 assumes a rest position in which there is an open connection between the cylinder chamber 43 and the pressure fluid chamber 70, and can be moved by an electromagnet 78 into a switching position in which the cylinder chamber 43 is shut off against an inflow of pressure medium from the pressure fluid chamber 70.

[0043] Valves 56, 60 and 76 can be equipped with position monitoring sensors to immediately detect any malfunction by the electrical control.

[0044] The pressure fluid chamber 70 is connected via a line 79 to an area on the cylinder head 38 that lies axially between the two seals 41. Thus, when the hydraulic accumulator is charged, the pressure differential at the outer seal 41—namely, the difference between the pressure of the pumped medium in the process valve, which is present on one side of the outer seal 41, and the pressure on the other side of this seal—is smaller than the difference between the pressure of the pumped medium and the pressure in the interior 23, so that leakage is also reduced.

[0045] Further valves are present in the interior 23, including a pressure relief valve 80, which is connected to the pressure port 52 of the hydraulic machine 50, and a secondary suction valve 81, arranged in the form of a check valve in a bypass between the suction port 53 and the pressure port 52 and opening from the suction port to the pressure port. The secondary suction valve 81 prevents cavitation in the hydraulic machine 50 when it is operated as a motor and the cylinder chamber is completely empty or the valve 56 closes.

[0046] To enable manual actuation of the process valve 10 by a robot, such as a remotely operated vehicle (ROV) or an autonomous underwater vehicle (AUC), a manual interface 85 is provided on the container 20. A rod 86 extends from this interface through the base 67 into the cylinder chamber 43 and is coupled to the piston 39. The rod 86 can, for example, have a threaded connection at the interface 85 and interact with an axially fixed, internally threaded nut, which is turned to actuate the process valve. The rod 86 is, of course, secured against rotation. The means for manual actuation are designed to ensure the tightness of the cylinder chamber 42 from the interior 23 and the tightness of the interior 23 from the environment.The means for manual actuation can also be designed such that a rod is coupled to the piston of the hydraulic cylinder via a free stroke, allowing the piston to move without engaging the rod. In this case, only a simple thread is needed between the rod and the nut. It must be ensured that the rod does not move on its own, as this would impede the piston's movement. Finally, it is also conceivable to arrange a switchable clutch between the means for manual actuation and the piston of the hydraulic cylinder.

[0047] In addition to the sensors already mentioned, the illustrated embodiment also includes three position sensors 88, which can detect specific positions of the piston 39 and thus of the piston rod 40. Alternatively, only one sensor may be present, which continuously detects the positions of the piston 39 and piston rod 40.

[0048] In the Fig. Figure 1 shows the device in a state where the process valve 10 is closed. The piston rod 40 of the hydraulic cylinder 35 is fully retracted. The volume of the first cylinder chamber 42 is at its minimum, and the volume of the second cylinder chamber 43 is at its maximum. Valves 56, 60, and 76 are in their rest positions; that is, valves 56 and 76 are open, and valve 60 is closed. The pressure in cylinder clamp 42 is the same as in the interior 23. The pressure in cylinder clamp 43 is the same as in the pressure fluid chamber 70 of the accumulator.

[0049] To open the process valve, valves 60 and 76 are inserted into the Fig. The two switching positions shown are engaged, so that the cylinder chamber 43 is separated from the pressure fluid chamber 70 of the hydraulic accumulator 65 and connected to the interior 23. The hydraulic machine 50 is set to positive displacement and, driven by the electric motor 51, pumps hydraulic fluid. The load pressure in the first cylinder chamber 42 is determined by the force of the helical compression spring 48 and by the force that the process valve spool 14 opposes to movement. If the load pressure is initially lower than the accumulator pressure, the piston immediately begins to move in a first direction after the hydraulic machine 50 pumps hydraulic fluid. In this embodiment, this movement corresponds to an extension, whereby the quantity of hydraulic fluid required for compression is neglected when using the term "immediately".As the tension of the helical compression spring 48 increases, the load pressure rises and eventually becomes equal to the accumulator pressure. If the load pressure is initially greater than the accumulator pressure, only the hydraulic accumulator 65 is filled via the valve 75 until the accumulator pressure equals the load pressure. With further delivery of hydraulic fluid by the hydraulic pump 50, the piston 39 and its piston rod 40 are moved, simultaneously filling the hydraulic accumulator 65. When the accumulator pressure reaches its maximum value, the valve 75 closes. During the piston's movement, the volume of the second cylinder chamber 43 decreases. Hydraulic fluid is displaced from the cylinder chamber 43 via the valve 60 into the interior 23 of the reservoir 22.

[0050] Is the process valve slide 14 in the desired position, for example the one shown in Fig. Once the position shown in Figure 2 is reached, valve 56 is switched and thus closed. The hydraulic machine 53 is brought to a standstill to save energy. Valve 56 seals off the first cylinder chamber 42, thus maintaining the position of the process valve slide. Valves 60 and 76 remain in the positions shown in Figure 2. Fig. 2 switch positions shown.

[0051] When the piston rod 40 enters the process valve housing 11, a volume previously occupied by the immersing section of the piston rod 40 is released in the container 22. The diaphragm 28 will therefore move inwards into the container during the extension of the piston rod, without any leakage occurring. This displacement must be taken into account if leakage is to be detected by a position sensor for the diaphragm.

[0052] To control the movement of the process valve spool 14 towards closing, the valve 56 is moved to its rest position and the hydraulic machine is set to negative displacement. Alternatively, if the hydraulic machine 50 has a positive displacement, the direction of rotation of the electric machine 51 is reversed against the direction of rotation when the piston rod 40 extends. The speed at which the process valve spool 14 is moved under the action of the helical compression spring 48 is determined by the rotational speed and displacement of the hydraulic machine 50, now operating as a hydraulic motor, and the electric machine 51, operating as a generator. During the retraction movement, hydraulic fluid is drawn from the interior 23 into the expanding cylinder chamber 43.

[0053] There are situations in which the process valve needs to be quickly moved from an open to a closed position. Such a situation can occur, for example, in the event of a power failure. In the event of a power failure, valves 56, 60, and 76 return to their rest positions under the action of springs 57, 61, and 77. The hydraulic machine is set to its maximum positive stroke volume. In the rest position of valve 56, the first cylinder chamber 42 is open to the hydraulic machine 50. In the rest positions of valves 60 and 76, cylinder chamber 43 is sealed off from the interior 23 and open to the pressure fluid chamber 70 of the hydraulic accumulator 65. Therefore, it is pressurized with accumulator pressure, which acts on an annular surface of the piston 39. This piston, together with the piston rod 40, is then moved in a second direction opposite to the first. The piston rod retracts, and the process valve 10 closes.This happens very quickly because, in addition to the force of the helical compression spring 48, a compressive force also acts.

[0054] If the spring force fails due to breakage of the helical compression spring 48, the process valve can also be closed solely by supplying pressure medium from the hydraulic accumulator 65 into the cylinder chamber 43.

[0055] Finally, manual operation of the process valve via interface 85 by a robot is also possible.

[0056] In contrast to the illustrated embodiment, variations of an electrohydraulic system according to the invention are also possible.

[0057] In its simplest form, the electrical control system comprises a DC motor, an electrical control unit with appropriate analog and digital input and output interfaces, and a suitable power supply.

[0058] In its advanced form, the electrical control system includes a three-phase motor with a corresponding drive and frequency converter, an electrical control unit with corresponding analog and digital input and output interfaces, as well as a suitable power supply and network interfaces, including LAN, bus systems, fiber optic cables, or wireless LAN.

[0059] In addition to the power supply, the electrical cable also includes the electrical signals for control communication, such as setpoints, actual values ​​and error messages.

[0060] Condition monitoring of the electro-hydraulic system can be implemented in the electrical control system by evaluating all sensor signals using appropriate algorithms implemented as software. In the event of a malfunction, the control system can autonomously move the hydraulic cylinder to its safe rest position and inform the higher-level control system. Preventive and reactive maintenance measures can then be communicated to the higher-level control system.

[0061] The container may have an interface where hydraulic pressure fluid can be refilled by a robot if this becomes necessary due to previous leakage.

[0062] In the illustrated embodiment, the hydraulic cylinder 35 is housed within the container 22. However, solutions are also conceivable in which the hydraulic cylinder is located outside the container and attached to the process valve. The container can then be attached to the hydraulic cylinder or to the process valve. Reference symbol list 10 process valve 11 Process valve housings 12 Process valve channel 13 Arrow 14 process valve slides 15 Flow opening 20 electro-hydraulic system 21 cables 22 containers 23 Interior of 22 24 opening in 22 25 Flat rim 26 flange 27 lids 28 Membran 29 holes in 27 30 springs 31 membrane plates 32 bars 35 hydraulic cylinders 36 cylinder housings 37 Cylinder base 38 Cylinder head 39 pistons 40 piston rod 41 seals 42 cylinder chamber 43 cylinder chamber 48 helical compression spring 50 hydraulic machine 51 Electric machine 52 Pressure connection 53 Suction port 54 electrical control unit 55 Speed ​​sensor 56 2 / 2-way seat valve 57 spring 58 electromagnets 60 2 / 2-way seat valve 61 spring 62 electromagnets 65 hydraulic accumulators 66 storage enclosures 67 Floor 68 storage pistons 69 Compression spring 70 Pressure fluid room 75 valve 76 2 / 2-way seat valve 77 spring 78 electromagnets 79 Management 80 Pressure relief valve 81 Suction valve 85 manual interface 86 bars 88 Position sensor

Claims

An electro-hydraulic system (20) for underwater use, comprising a container (22) having an interior space (23) designed to form a volume sealed off from the environment and intended to hold a hydraulic pressure fluid, and a compensating piston (28) to bring the hydraulic pressure fluid in the interior space (23) at least approximately below the ambient pressure, comprising a hydrostatic machine (50) operable at least as a pump, and an electric machine (51) mechanically coupled to the hydrostatic machine (50), which operates as an electric motor to operate the hydrostatic machine as a pump, characterized in that the hydrostatic machine (50) and the electric machine (51) are arranged in the interior space (23) of the container (22), wherein the compensating piston (28) is further acted upon by a spring arrangement which generates a force in the same direction as the force generated by the ambient pressure.that as a result, the pressure inside the container is higher than the ambient pressure by the pressure equivalent of the spring force, wherein the hydrostatic machine (50) can also be operated as a hydraulic motor and the electric machine (51) can also be operated as a generator, and wherein the hydrostatic machine (50) is adjustable in its stroke volume. Electro-hydraulic system according to claim 1, wherein the hydrostatic machine (50) is adjustable from positive stroke volumes via a zero position in which the stroke volume is zero to negative stroke volumes, so that it can be operated in the same direction of rotation and with the same pressure connection as a pump and as a motor. Electro-hydraulic system according to claim 1 or 2, wherein the electric machine (51) is adjustable in its speed. Electro-hydraulic system according to a preceding claim, wherein the connection between a pressure port (52) of the hydrostatic machine (50) and a consumer line, which is provided for supplying a pressure chamber (42) of a hydraulic consumer (35), can be controlled via a valve (56) located in the interior (23) of the container (22) such that the connection is open in a rest position, which the valve (56) assumes under the action of a spring (57), and is closed in a switching position, which the valve (56) assumes under the action of an electrical actuator (58), at least in the direction from the first cylinder chamber (42) to the hydrostatic machine (50). Electro-hydraulic system according to a preceding claim, wherein a hydraulic accumulator (65) with a pressure fluid chamber (70) is housed in the interior (23) of the container (22), to which pressure fluid can be supplied by the hydrostatic machine (50) in its operation as a pump, and from which pressure fluid can be supplied to a consumer line which is provided for supplying a pressure chamber (43) of a hydraulic consumer (35). Electro-hydraulic system according to claim 5, wherein the connection between the consumer line and the pressure fluid chamber (70) of the hydraulic accumulator (65) can be controlled via a valve (76) located in the interior (23) of the reservoir (22) such that the connection is open in a rest position, which the valve (76) assumes under the action of a spring (77), and is closed in a switching position, which the valve (76) assumes under the action of an electric actuator (78), at least in the direction from the hydraulic accumulator (65) to the second cylinder chamber (43). Electro-hydraulic system according to claim 5 or 6, wherein a connection between the interior (23) of the container (22) and the consumer line connectable to the hydraulic accumulator can be controlled via a valve (60) located in the interior (23) of the container (22) such that the connection is blocked at least in the direction from the second cylinder chamber (43) into the interior (23) in a rest position assumed by the valve (60) under the action of a spring (61) and is open in a switching position assumed by the valve (60) under the action of an electric actuator (62). Electro-hydraulic system according to a preceding claim, wherein a hydraulic cylinder (35) is provided, the interior of which is divided by a piston (39) to which a piston rod (40) is connected into a cylinder chamber (43) on the piston rod side and a cylinder chamber (42) on the piston rod side, wherein, in order to move the piston rod (40) in a first direction, in particular to extend the piston rod, pressurized fluid can be supplied by the hydrostatic machine (50) in operation as a pump to a first cylinder chamber (42), in particular the cylinder chamber on the piston rod side, and wherein the hydraulic cylinder (35) is also accommodated in the interior (23) of the container (22). Electro-hydraulic system according to claim 8, wherein the hydraulic cylinder (35) comprises a mechanical spring arrangement (48) by which the piston (39) is acted upon in a second direction opposite to the first direction. Electro-hydraulic system according to one of claims 5 to 7 and according to one of claims 8 and 9, wherein in a cylinder head (38) of the hydraulic cylinder (35) guiding the piston rod (40) two seals (41) surrounding the piston rod (40) are arranged axially one behind the other and that the area between the two seals (41) is fluidically connected to the pressure fluid space (70) of the hydraulic accumulator (65). Electro-hydraulic system according to a preceding claim, wherein the compensation piston (28) can be subjected at a first surface to the pressure in the interior (23) of the container (22), at a second surface which is the same size as the first surface and is directed opposite to it, to the ambient pressure and to a spring arrangement (30) which generates a force in the same direction as the force generated by the ambient pressure. Electro-hydraulic system according to claim 11, wherein the position of the compensation piston (28) can be detected by a position sensor (32). Electro-hydraulic system according to a preceding claim, wherein the pressure port (52) of the hydrostatic machine (50) is protected by a pressure relief valve (80). Device for arrangement underwater and for controlling a volume flow of a gaseous or liquid medium comprising a process valve (10) with a process valve housing (11), with a process valve slide (14) with which the volume flow can be controlled, and with a hydraulic cylinder (35) which is attached to the process valve housing (11) and with which the process valve slide (14) can be moved, characterized by an electrohydraulic system (20) according to one of the preceding claims, wherein the container (22) is sealed and attached to the process valve housing (11). Device according to claim 14, wherein the hydraulic cylinder (35) projects through an opening in the container (22) into its interior (23).

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