WO2012167959A1

WO2012167959A1 - Fluid device

Info

Publication number: WO2012167959A1
Application number: PCT/EP2012/054327
Authority: WO
Inventors: Asko Heikola; Ville Hopponen; Arto Ikonen; Mika Lehmusvaara; Eero Suomi; Pekka Vantola
Original assignee: Metso Paper, Inc.
Priority date: 2011-06-10
Filing date: 2012-03-13
Publication date: 2012-12-13
Also published as: DE112012002424A5; DE102011077413A1

Abstract

The invention relates to a fluid device, in particular for use in or with a machine for producing, handling and/or processing a fibre material web, such as a paper, tissue or card web. The fluid device has at least one piston/cylinder arrangement (1, 11, 2, 21), at least one pressure tank (53, 54) that can be connected to the piston/cylinder arrangement for reversible storing of a working fluid under pressure, wherein the working fluid can be removed from the tank at the pressure at which it was fed into the tank, and a pressure-regulating device having at least two switching valves (131, 141, 135, 145, 231, 241, 235, 245), each having at least one controlled passage for control of pressure of the working fluid in the piston/cylinder arrangement, wherein the at least one passage is adapted to allow the working fluid through under control in both flow directions and to the pressure tank. The application describes uses as a lifting cylinder and as a vibrations damper.

Description

FLUID DEVICE

The invention relates to a fluid device, as it is used, for example, in or together with a machine for producing and / or treating a fibrous web. The fibrous web may in particular be a paper, tissue or a board web. In the mentioned type of machines usually large loads are moved, yet a sensitive control of movements and forces is required, especially in the position and pressure control of rollers, drums, web wraps and the like. For this purpose, hydraulic or pneumatic auxiliary machines are used. In the following description, the hydraulic / pneumatic machines are referred to as fluid devices that are driven by pressurized working fluid. As a working fluid can be used almost any liquid or gaseous medium, particularly preferred are hydraulic oil, emulsions of water with other materials such as oil, etc., and compressed air.

A common fluid device has one or more piston / cylinder arrangements in which a displaceable piston divides the cylinder volume into two spaces, the piston having a piston rod emerging from the cylinder which exerts a force according to the pressure ratios in the two chambers of the cylinder can be adjusted. In the double-acting cylinder, both chambers are designed as pressure chambers in that they are sealed from the environment and the piston can be pressurized on both sides with pressure. Usually, because of the piston rod, the effective area on the rod side of the piston is smaller than on the other side of the piston, which is referred to here as the cylinder side.

For controlling the pressure of the pressure chambers, it is known, for example, from WO 2004/044316 Al to use a so-called digital hydraulic control in which a plurality of individual switching valves equipped with throttles are, in order to provide a constant but mutually different flow, are controlled according to a specific pattern for opening or closing. By determining the different flow rates and opening durations, the pressure in the pressure chambers can be precisely set and maintained with such a regulator.

If many quickly actuated switching valves are used in such a pressure regulator, a precise control of the fluid device is possible and it is a corresponding construction effort required. In some operations, such an accurate control is either not required, or the fluid device is used in operations in which the same force and / or adjustment speed should always be set. These processes can be cyclically repeating processes. In addition, the pressure control described usually requires the discharge of working fluid to reduce pressure.

There is a need for a fluid device with which a sufficiently precise control of a delivered force can be achieved with low energy and construction costs, the fluid device should save energy especially in repeatedly occurring processes in the auxiliary machinery.

The object is achieved with a fluid device having the features of claim 1.

According to the invention, a fluid device is proposed, in particular for use in or with a machine for producing, handling and / or processing a fibrous web, such as a paper, tissue or board web, with at least one piston / cylinder arrangement, at least one with the piston / cylinder arrangement connectable pressure accumulator for the reversible storage of a working fluid under pressure, wherein the working fluid with the pressure from the memory is removable, with which it was fed into the memory, and a pressure control device is provided, the at least two switching valves, each with at least one controlled Durchiass for controlling Squeezing the working fluid in the piston / cylinder assembly, wherein the at least one Passage adapted to control the working fluid in both flow directions and pass to the pressure accumulator.

According to the invention it is provided that at least two switching valves are provided with a piston / cylinder arrangement, wherein the switching valves can open or close a passage. A special throttle element is not required and not provided. By employing a pressure accumulator in which working fluid displaced during the movement of the piston in the cylinder can be stored under pressure, the pressure energy stored in the working fluid can be stored and, at a later time, optionally returned to the piston / cylinder arrangement for work there to perform.

By using the switching valves, the passage can be fully opened and the working fluid can be displaced without appreciable throttling losses between the reservoir and the piston / cylinder assembly. The throttling losses are to be determined here only by the valve geometry, special constrictions as fixed throttles are not provided. By according to the invention, the passage can control the working fluid and pass in both directions, the saving of pressure energy (by reversible storage of working fluid under pressure in the pressure accumulator) with low losses is possible.

Preferably, the fluid device has a piston / cylinder arrangement comprising two parallel cylinders each having a piston, the piston rods being fixedly connected to each other and acting together on an element of the machine. Further preferably, each cylinder space of the two cylinders on both sides of the piston forms a fillable with the working fluid for acting on the piston pressure chamber, wherein the effective surfaces of the pistons are different from each other and are in a predetermined size ratio.

In such an arrangement, with a few different pressures that are set in the respective pressure chambers, an output force of the piston / cylinder arrangement can be controlled without requiring a continuous Chen monitoring the power needs, so it is possible to control the force without feedback.

The size of the effective areas of the pistons is preferably an integer multiple of each other. This makes it easier to adjust the power and the pressure control can be simpler. For example, in a cylinder, the two are the effective areas on the two sides of the piston in the ratio of 1 to 4 to each other and that the effective areas of the piston in the other cylinder are each twice as large as in the first cylinder.

Preferably, a pressure supply device can be provided which provides working fluid with two different pressures and that the force output by the fluid device is adjustable by the individual pressure chambers can be acted upon either one of the two pressures. For example, if the pressures provided are different by a factor of 2 (eg, 5 MPa and 10 MPa), and if the effective area of a piston is 1: 4 and between two cylinders is 1: 2, there are four areas of 1, 2, 4 and 8 surface units, which obtained 16 different forces of said piston-cylinder arrangement only by applying a corresponding combination of the four pressure chambers with said two pressures. Particularly noteworthy is that it is sufficient to regulate two pressures to a predetermined fixed value.

In general, it is advantageous if the two pressures are in the ratio 1: 2 and are higher than the ambient pressure. Also preferably, the pressure control device for each pressure chamber has a switching valve for connecting the pressure chamber with the pressure accumulator. In this way, it is possible, for example, to feed the emerging from a pressure chamber as a result of a piston inserted under a load exiting working fluid in the pressure accumulator.

In another advantageous embodiment of the invention, the piston / cylinder assembly has a piston which separates two pressure chambers in the cylinder on both sides of the piston, wherein the passage of the pressure control device is adapted to connect the two pressure chambers together the flow area of the passage through the switching valves of the pressure control device is adjustable to form an adjustable vibration damper. In some machines, the vibration behavior changes during operation. In this case, it is desirable to adapt the characteristics of a vibration damper to this change. In the solution mentioned, by changing the flow path between the two pressure chambers, the properties of the vibration damper are adjusted. For this purpose, for example, one or more switching valves can be opened or closed, so that the path and the resistance is set in the passage. This setting significantly affects the flow of working fluid between the two pressure chambers, which in turn has a significant influence on the damping properties.

The piston / cylinder assembly used as a vibration damper preferably has a piston rod connected to the piston, which passes through one of the two pressure chambers, wherein the pressure accumulator is connected to this pressure chamber. The volume of the pressure chamber with the piston rod therein is smaller than that of the other pressure chamber. Moves the piston in the direction of the cylinder side, it is displaced from this (larger) pressure chamber in a larger volume, as in the piston-side pressure chamber can be excluded. The excess is stored in the pressure accumulator and can be fed back to the cylinder-side pressure chamber in the opposite movement of the piston.

Preferably, one of the piston and cylinder of the piston / cylinder assembly is operatively connected to a machine frame while the other of the piston and cylinder is supported on a machine foundation so that the piston / cylinder assembly forms an adjustable vibration damping machine bearing. Preferably, it is the pressure regulating device which, taking into account measured values and / or machine parameters representative of the acceleration of the piston relative to the cylinder, regulates the flow cross section of the passage and thus the damping constant of the piston / cylinder arrangement in order to reduce vibrations. Furthermore, preferably at least least one piston / cylinder arrangement is provided for each one spatial direction to reduce the respective vibration components of a multi-dimensional vibration. Many processes in production machines are fixed operations; It is rare to pay attention to any varying influences, as is the case, for example, with machines (construction machines, conveyors, etc.) that are driven / operated by people. Thus, preferably, the fluid device may be connected to a fluid circuit that includes at least one pump and a working fluid reservoir and is provided with a controller adapted to adjust the amount of working fluid to be pumped by the pump at any given time Predict time in a predetermined manner running movements and to control the pump suitable for providing the predicted amount of working fluid, the at least one pressure accumulator can compensate for excess supplies or delivery shortfalls of the pump in the fluid circuit. Preferably, the controller may be adapted to control the speed of the pump. If the need for working fluid is already foreseeable, the design of the fluid circuit may have an evaluable energy saving potential that may be due solely to adapting to the delivery requirements of the pump. For example, it is possible to design the pump to be within the range of the optimum operating point at a particular speed and to fine-tune the adjustment to the delivery request by pump on / off times. It is also possible to use several pumps with low flow and then turn them on or off as needed.

As previously stated, the piston / cylinder assembly may be employed to lift a load, wherein the pressure regulator controls the fluid communication between the piston / cylinder assembly and the accumulator such that the amount of working fluid displaced in the piston / cylinder assembly as the load is lowered into the accumulator is fed. An application example is when the machine for producing, handling and / or processing a fibrous web is a winding device, in which the piston / cylinder assembly is connected to a pressure roller, which acts on the forming coil, that in the piston / cylinder assembly through the growing winding diameter of the forming on the spool or the winding core coil displaced working fluid (the winding grows and the pressure roller is thereby pushed away) initiated by the pressure control device in the pressure accumulator and stored there, so that the pressure roller for the formation of a new roll in the Transfer home position and let act on a reel again.

Preferably, this can be done so that for applying the desired contact pressure by the pressure roller, a pressure chamber with a lower pressure and a pressure chamber with a high pressure in the multi-cylinder piston / cylinder arrangement described above are used. Area ratios and pressures are selected so that the piston or the piston are inserted under the desired contact pressure of the pressure roller when the lower pressure (possibly in an associated pressure accumulator) is discharged. In this way, the high pressure in the pressure accumulator can be stored unchanged and is then available again for the next cycle (winding of the next roll).

Another exemplary application would be to lower the finished roll to a transporter by holding arms, with the support arms displacing working fluid under pressure from associated piston / cylinder assemblies into accumulators as the heavy roll is lowered, and then displacing the working fluid from the accumulator to raise the support arms after settling the coil serves. There are a variety of other different applications of the invention possible.

The invention will be explained in more detail below with reference to preferred embodiments with reference to the drawing. Fig. 1 shows an embodiment of the invention using a piston / cylinder assembly constructed from conventional double-acting hydraulic cylinders. Fig. 2 shows an embodiment of the invention in use as a vibration damper.

Fig. 3 shows a construction of a pressure regulating device using switching valves.

Fig. 1 shows an embodiment of the invention with a piston-cylinder assembly, which is constructed from two conventional double-acting hydraulic cylinders. The hydraulic cylinder 1 on the left side of Fig. 1 has a piston 11 which is arranged tightly and slidably in a cylinder and connected to a piston rod 12. The piston 11 divides the cylinder space of the hydraulic cylinder 1 into two pressure chambers 13 and 14. The cylinder-facing away from the end of the piston rod 12 is connected to a yoke 100, on which a projection 101 is attached, at which the force to be generated by the piston-cylinder assembly F is tapped. At the right in Fig. 1 end of the yoke 100, the piston rod 22 is fixedly mounted, which is connected to a piston 21. The piston 21 is sealingly and slidably disposed in the cylinder chamber of the hydraulic cylinder 2, and separates two pressure chambers 23 and 24 from each other. The effective areas of the pistons 11 and 21 are selected as follows: The rod-side effective area of the piston 11 has the area 1; the cylinder-side effective surface of the piston 11 has the surface 4; the rod-side effective surface of the piston 21 has the surface 2 and the cylinder-side effective surface of the piston 21 has the surface 8. The surfaces indicated here are surface units which indicate only the relationship to one another and not the absolute size of the surfaces. For example, if a surface unit were assigned 10 cm ² , the area of the piston 11 to the pressure chamber 14 would have an area of 10 cm ² , the area of the piston 11 to the pressure space 13 the area 40 cm ² , the area to the pressure chamber 24 of the piston 21 the area 20 cm ² and the pressure chamber 23 facing surface of the piston 21 would have the area 80 cm ² . This is not an exemplary embodiment, but merely an illustration that area sizes are set in relation here. Each pressure chamber 13, 14, 23 and 24 has its own connection, which is provided with an associated valve 131, 141, 241, 231, as shown in Fig. 1. That is, the valve 131 is associated with the pressure chamber 13, the valve 141 is associated with the pressure chamber 14, the valve 241 is associated with the pressure chamber 24 and the valve 231 is associated with the pressure chamber 23. The four valves mentioned are all switching valves, ie valves that can be opened or closed. No throttles are provided and the valves are not proportionally adjustable, ie no flow can be adjusted through them, except ON or OFF. Said switching valves 131, 141, 241, 231 are connected to a common line or a wiring harness 511. In the wiring harness 511, a pressure accumulator 53 and a pump 55 are provided.

Each pressure chamber 13, 14, 23 and 24 has a further connection, which is provided with an associated valve 135, 145, 245, 235, as shown in Fig. 1. That is, the valve 135 is associated with the pressure chamber 13, the valve 145 is associated with the pressure chamber 14, the valve 245 is associated with the pressure chamber 24 and the valve 235 is associated with the pressure chamber 23. The four valves mentioned are all switching valves, i. Valves that can be opened or closed. There are no throttles and the valves are not proportionally adjustable, i. no flow can be adjusted through it except ON or OFF. Said switching valves 135, 145, 245, 235 are connected to a common line or wiring harness 512. In the wiring harness 512, a pressure accumulator 54 and a pump 56 are provided.

The wiring harness 511 provides a first pressure that is higher than the ambient pressure and is constantly presented by a control, not shown, from the pressure accumulator 53 and the pump 55. The wiring harness 521 provides a second pressure that is about twice the pressure in the pressure train 511. This pressure is also constantly provided by a control, not shown, from the pressure reservoir 54 and the pump 56. The device in FIG. 1 should be able to provide certain forces F at the extension 101 of the yoke 100 with little control effort. The strands 511 and 512 provide a working fluid under pressure, wherein the pressure in the wiring harness 511 may be, for example 5 MPa, while the pressure in the wiring harness 521 is twice as high and about 10 MPa. If now a certain force to be set, so by selectively connecting the respective pressure chambers 13, 14, 24 and 23 of the two hydraulic cylinders 1 and 2 with the respective wiring harness 511 or 512, the output force can be adjusted. With the area ratios mentioned above and the two different pressures, a total of 16 different forces can be set without the need for pressure regulation beyond keeping the predetermined pressure constant in the two line branches 511 and 521.

The force delivered by the piston-cylinder arrangement according to FIG. 1 is determined from the difference or sum of the products of the respective effective area and the pressure prevailing in the pressure chamber. In this way, the forces can be adjusted in steps, one step being the force resulting from the multiplication of a unit area with the lower pressure. If, in the piston-cylinder arrangement according to FIG. 1, a force -F is applied in the opposite direction to the force F on the extension 101, which force is greater than the force F, this force endeavors to force the pistons 11 and 21 into the pressure chamber 13 and 23, respectively Press in while the volume of the pressure chambers 14 and 24 increases. In this way, under the influence of the force -F-displaced volume of working fluid can be pushed back into one of the two pressure accumulator 53, 54, so that it is available again for the next force application process.

All valves 131, 135, 141, 145, 231, 235, 241, and 245 may be combined in one block, as explained with reference to FIG. 3, for example.

Fig. 2 shows an embodiment of the invention in use as a vibration damper. 2, functionally identical components with the same reference numerals are shown in FIG. sign, so that the respective components are explained here only once. In Fig. 2 on the left side, a roller assembly 3 can be seen, which is supported on a bar 4. Der Baren 4 ist in Fig. 2 dargestellt. The beam 4 is rotatably mounted on the left side about a bearing. The right in Fig. 2 end of the beam 4 is based on a vibration damper 6, which has a hydraulic cylinder. The hydraulic cylinder has a cylinder 65, a piston with piston rod 64 and two pressure chambers 62 and 63. The pressure chambers 62 and 63 are connected via two parallel switching valves 66 and 67 with each other. Further, a pressure accumulator 61 is connected to the pressure chamber 63, which receives in the pressure chamber 63 at the same piston stroke more displaced volume and stores under pressure. By switching the switching valves 66 and 67, the flow path of the liquid or the working fluid between the two pressure chambers 62 and 63 can be changed. In this way, the vibration damping properties of the vibration damper 6 shown can be changed or adjusted. For example, when the roller assembly 3 is a winding device, its diameter and weight increase with increasing winding. This changes the vibration characteristic of the arrangement shown and the vibration damper 6 can be adjusted accordingly for better damping of these vibrations with the valves 66 and 67.

In Fig. 2 on the right side, a roller assembly 3 is shown, which differs from the arrangement shown in Fig. 2 on the left side differs in that the beam 4 is provided with a further vibration damper 7, which replaces the fixed bearing point. The vibration damper 7 has like the vibration damper 6, a hydraulic cylinder with a cylinder 75, a piston rod with piston 74, two pressure chambers 72 and 73 which are connected via a valve arrangement with parallel switching valves 76 and 77 with each other. An accumulator 71 is provided to receive additional displaced volume. The operation is the same as that for the vibration damper 6. As shown in FIG. 2, (referring to above and below of the drawing), the vibration damper 6 is responsible for the vertical vibration component while the vibration damper 7 is designed, vibration components in the horizontal direction to dampen. It is also possible to ren vibration damper in a direction perpendicular to the plane of Fig. 2 direction provide that can dampen vibrations in this spatial direction.

The vibration damper 6 and 7 of FIG. 2 allow an adaptation to the occurring in the roller assembly with its beam 4 vibration. By selectively opening or closing one or two switching valves, the passage for the working fluid can be tuned so that the damping effect of the vibration damper becomes maximum. The vibration dampers 6 and 7 of FIG. 2 can also be used on other machine components, motors or the like; the use with a roller assembly 3 and a beam 4 is merely exemplary here.

Finally, FIG. 3 shows a design of a pressure control device which can be used in the present representation for the regulation of air pressure. 3 has an inlet 91 and an outlet 92. The outlet 92 is referred to as a silencer, in the case of use as a digital hydraulic pressure control device, the silencer would be replaced by a tank line. The pressure regulator 9 is designed to adjust the pressure in the conduits 93 and 94, which may be referred to as outlets of the pressure regulator. Each of the valves 911, 912, 913, 914, 921, 922, 923 and 924 are provided with a throttle and can selectively connect the adjacent longitudinal strands. If now the pressure in the lines 93 and 94 are raised, then the switching valves 911, 912, 913 and 914 can be selectively and briefly opened, so that the pressure in the lines 93 and 94 increases. The set pressure can be measured with the measuring points PT, which represent pressure transmitters. In order to reduce the pressure in the lines 93 and 94, optionally, the valves 921, 922, 923 and 924 can be actuated. When these valves are opened briefly, the pressure in the lines 93 and 94 decreases.

The arrangement of FIG. 3 also allows a compact design of a pressure control device. The device 9 contains four plus four, so a total of eight valves, and three pressure sensors. Further, the arrangement of FIG. 9 provides two regulated pressure outlets that are independent of one another. inventions According to the provision is provided, as indicated by the dashed line in Fig. 3, to accommodate the eight valves as the pressure sensors in a block. Thus, the entire electrical wiring can be accommodated on the block and led to a common plug-in connection. In this way, one can provide a pressure control device, which can be installed, for example, to replace conventional proportional valves on their components. The plug connection can be, for example, a conventional D plug connection, so that conventional machine equipment can be used here. The pressure regulating device 9 shown can be used in connection with the invention by connecting the pressure inlets and outlets according to the preceding description with the respective pressure chambers of the piston-cylinder arrangements. In particular, the device of FIG. 3 also permits flow through the device in both directions and allows independent adjustment of pressures at the outlets 93 and 94.

In the described embodiments, an optimized control of the hydraulic supply units can be used. By adjusting the delivery requirements or flows of working fluid for the individual process steps from movement control parameters and coordinated movement times, the flow requirement of working fluid can be determined at any time. Thus, the required volume flow can always be provided in good time (just in time). Slight delays in the response of the pump or pumps can be compensated by pressure accumulator. This procedure (target value control) can be simplified somewhat if the required volume flow (delivery request) is parameterized specifically for the hydraulic circuit and these are totaled to the total volume flow demand of the function or process unit. The volume flow of the hydraulic supply unit can be adjusted in accordance with the described target value control by adjusting the rotational speed of the pump (s).

Claims

claims

1. Fluid device, in particular for use in or with a machine for producing, handling and / or processing a fibrous web, such as a paper, tissue or board web, with

at least one piston / cylinder arrangement

at least one pressure accumulator connectable to the piston / cylinder arrangement for the reversible storage of a working fluid under pressure, wherein the working fluid can be removed with the pressure from the accumulator with which it was fed into the accumulator, and

a pressure regulating device having at least two switching valves each having at least one controlled passage for controlling pressures of the working fluid in the piston / cylinder assembly, wherein the at least one passage is adapted to control the working fluid in both flow directions and to pass to the pressure accumulator.

2. Fluid device according to claim 1, characterized in that the piston / cylinder arrangement comprises two parallel cylinders, each having a piston, wherein the piston rods are fixedly connected to each other and act together on an element of the machine.

3. Fluid device according to claim 2, characterized in that each cylinder space of the two cylinders on both sides of the piston forms a fillable with the working fluid for acting on the piston pressure chamber, wherein the effective surfaces of the piston are different from each other and are in a predetermined size ratio.

4. A fluid device according to claim 3, characterized in that the size of the effective surfaces of the piston is an integral multiple of each other.

5. A fluid device according to claim 4, characterized in that in a cylinder, the two the effective surfaces on the two sides of the piston in the Ver Ratio of 1 to 4 to each other and that the effective areas of the piston in the other cylinder are each twice as large as in the first cylinder.

6. Fluid device according to one of the preceding claims 3 to 5, characterized in that a pressure supply device is provided which

Provides working fluid with two mutually different pressures and that the output from the fluid device force is adjustable by the individual pressure chambers are each optionally acted upon with one of the two pressures.

7. Fluid device according to claim 6, characterized in that the two pressures in the ratio 1: 2 and are higher than the ambient pressure.

8. Fluid device according to one of the preceding claims 1 to 7, characterized in that the pressure regulating device for each pressure chamber has a switching valve for connecting the pressure chamber with the pressure accumulator.

9. A fluid device according to claim 1, characterized in that the piston / cylinder assembly has a piston which separates two pressure chambers in the cylinder on both sides of the piston, wherein the passage of the pressure control device is adapted to connect the two pressure chambers together, the Flow cross-section of the passage through the switching valves of the pressure control device is adjustable to form an adjustable vibration damper.

10. Fluid device according to claim 9, characterized in that the piston / cylinder arrangement has a piston rod connected to the piston, which passes through one of the two pressure chambers, wherein the pressure accumulator is connected to this pressure chamber.

11. A fluid device according to claim 9 or 10, characterized in that one of the piston and the cylinder of the piston / cylinder assembly is operatively connected to a machine frame, while the other is supported by the piston and the cylinder on a machine foundation, so that the Piston / cylinder assembly forms an adjustable vibration damping machine bearing.

12. Fluid device according to claim 9, 10 or 11, characterized in that the pressure regulating device, taking into account for the acceleration of the piston relative to the cylinder representative measured values and / or machine parameters, the flow cross-section of the passage and thus the damping constant of the piston / cylinder arrangement controls to To reduce vibrations.

13. Fluid device according to one or more of the preceding claims 9 to 12, characterized in that in each case at least one piston / cylinder arrangement is provided for in each case one spatial direction in order to reduce the respective vibration components of a multi-dimensional vibration ren.

14. Fluid device according to one or more of the preceding claims, characterized in that the fluid device is connected to a hydraulic circuit containing at least one pump and a reservoir for the working fluid, and with a control unit that is adapted to be pumped by the pump To predict the amount of working fluid at all times based on the movements that occur in a predetermined manner at this time and to suitably control the pump for providing the predicted working fluid amount, wherein the at least one pressure accumulator can compensate for excess supplies or supply shortages of the pump in the hydraulic circuit.

15. Fluid device according to claim 14, characterized in that the control unit is adapted to control the rotational speed of the pump.

16. Fluid device according to one or more of the preceding claims 1 to 15, characterized in that the piston / cylinder arrangement is used for lifting a load, wherein the pressure regulating device, the fluid connection between the piston / cylinder assembly and the pressure accumulator so controls that in the piston / cylinder assembly when lowering the load displaced amount of working fluid is fed into the pressure accumulator.

17. Fluid device according to one or more of the preceding claims 1 to 16, characterized in that the machine for the production, handling and / or processing of a fibrous web is a winding device in which the piston / cylinder assembly is connected to a pressure roller, which on the forming winding, wherein the displaced in the piston / cylinder assembly by the growing winding diameter working fluid is introduced from the pressure control device in the pressure accumulator and stored there to thereby transfer the pressure roller for the formation of a new roll in the starting position and again on a reel to act.