WO2013064136A1

WO2013064136A1 - Device for reducing a pressure fluctuation in a fluid-filled line

Info

Publication number: WO2013064136A1
Application number: PCT/DE2012/001042
Authority: WO
Inventors: Konrad Lentner
Original assignee: Eads Deutschland Gmbh
Priority date: 2011-11-04
Filing date: 2012-10-29
Publication date: 2013-05-10
Also published as: DE102011117620A1

Abstract

The present invention relates to the field of hydraulics engineering, in particular to the compensation of pressure fluctuations in a hydraulic system (10). The device (2) according to the invention uses an actively controllable actuator element (18) by means of which a first fluid pressure (14a) in a fluid line (10), said first fluid pressure in particular having a dynamically fluctuating pressure component (16b), is compensated such that substantially the constant line pressure (16a) remains in the fluid line (10) after the passage of the latter through the device (2) according to the invention. Here, the device (2) is of balanced configuration such that it is not subjected to load by a constant line pressure (16a).

Description

Device for reducing pressure fluctuation

in a fluid-filled pipe

The present invention relates to hydraulic systems in means of transport. In particular, the present invention relates to the reduction of pressure fluctuations in a fluid-filled conduit of a means of transport, in particular of an aircraft. More particularly, the present invention relates to a device for reducing pressure fluctuation in a fluid-filled conduit, in particular in an aircraft, a hydraulic system and an aircraft.

Hydraulic systems are used in means of transport, such as airplanes, to perform a variety of control operations. It may happen that hydraulic lines required for this purpose are distributed or arranged over a large area in the means of transport. Thus, in an aircraft cabin, for example in the area of the side trim between the aircraft envelope and passenger cabin, or else in the overhead area, in the area of the overhead racks, large-volume hydraulic lines can essentially run through the entire aircraft.

To operate hydraulic lines pumping elements are necessary, which provide a required operating pressure for the hydraulic system.

Such hydraulic pumps can be designed, for example, as axial piston pumps. However, known hydraulic pumps, by virtue of their design, potentially produce, in addition to the required, substantially constant system pressure, also pressure fluctuations, which occur, for example, in the case of pressure fluctuations. as a hydraulic pressure pulsation, modulated or added to the system pressure, can represent. In a hydraulic line system, for example a large-scale line system, as can be used in an aircraft, vibrations can occur in the line system due to these hydraulic pulsations, which cause additional problems.

CONFIRMATION COPY can represent loadings of the system and also, via different transmission paths, such as the connection of hydraulic lines to the aircraft structure, can provide acoustic interference. Such acoustic disturbances may, for example, be perceptible to a passenger in a quiet aircraft environment and reduce their sense of comfort in the aircraft.

Known solutions for reducing these pulsations in aircraft are passive methods or devices, such as, for example, resonators or absorbers. Resonators, however, usually represent, due to the dimensions of the required wavelengths, as relatively large devices, which also have only a certain, narrow-band use frequency range, since the dimensions of the resonators requires a certain frequency dependence. Absorbers in turn withdraw energy from the hydraulic system, which is undesirable.

One aspect of the present invention can thus be seen to provide a preferred, flexible, in particular frequency-flexible possibility for reducing pressure fluctuations in a fluid-filled line, thus reducing hydraulic pulsations in this line and thus reducing acoustic disturbances and mechanical loads on the line system ,

According to a preferred embodiment of the present invention, there is provided a device for reducing pressure fluctuation in a fluid-filled conduit adapted for connection to a fluid conduit, having a supply side and a discharge side. In this case, the device has an actively controllable actuator element, which is arranged on the fluid line between the supply side and the discharge side. In the fluid line prevails in the operating state, a first fluid pressure, which essentially consists of a first Fluidteiidruck, thus the (constant) system pressure, and a second Fluidteiidruck, which is as the hydraulic pulsation in the hydraulic system, thus representing a pressure fluctuation or as dynamically changing pressure composed.

The device according to the invention is intended to compensate the first fluid pressure on the supply side in a substantially constant second fluid pressure on the discharge side. Here, the actuator element for generating a compensation force is controllable, wherein the compensation force compensates the second fluid partial pressure such that the second fluid pressure substantially corresponds to the first fluid partial pressure. In other words, the actuator element is intended to substantially equalize the second fluid partial pressure by a suitable second counter-fluid partial pressure.

According to a further preferred embodiment of the present invention, a hydraulic system, in particular for an aircraft, is provided which has a device according to the invention for reducing a pressure fluctuation in a fluid-filled line.

According to a further preferred embodiment of the present invention, an aircraft comprising a hydraulic system according to the invention and / or a device according to the invention for reducing pressure fluctuation in a fluid-filled line is provided.

Preferred embodiments of the present invention will become apparent from the dependent claims.

The device according to the invention is in this case connected to the hydraulic line in such a way that a line pressure which arrives in the hydraulic line at a supply side of the device and which consists of a line Sense constant system pressure and a hydraulic pulsation or a pulsation pressure can be converted by suitable measures on a discharge side of the device in a substantially constant system pressure.

The device can in this case in a section of the hydraulic line, which can also be referred to as a pumping chamber, change the volume of the hydraulic line or the pumping chamber to the effect that the pulsation pressure is compensated. For example, in a state of increased pressure, thus a positive pulsation pressure, the volume of the pumping chamber may be increased such that the positive pulsation pressure is corrected to zero. Likewise, in the state of a pressure which is below the system pressure, the volume in the pumping chamber can be reduced, so that likewise the now present negative pulsation pressure is compensated to zero.

In order to provide a corresponding compensation of the pulsation pressure, knowledge about a desired or required system pressure is first necessary, as well as information on a currently present pressure in the fluid-filled line system. This line pressure may initially be determined specifically for the device according to the invention, for example via a suitably arranged sensor element, or may be known from other control systems. The required or desired system pressure can also be calculated from a system pressure determined by the sensor element, for example by a simple averaging. As a result, the device according to the invention can be used flexibly, since it is not exclusively related to a predetermined system pressure, but rather can determine the constant system pressure itself from a measured dynamic line pressure. Likewise, a defined, desired system pressure can also be specified. In this case, the device according to the invention can also take into account a possible propagation velocity of pressure fluctuations to be compensated which, for example, can be used to compensate delayed pressure fluctuations measured at a sensor element in order to take into account the propagation velocity of the pressure fluctuations in the fluid.

A control element may be the active actuator element according to the invention, for example a piezoelectric element which is e.g. is coupled to a piston element, so drive, so that a volume variation of a pumping chamber can be realized.

A second sensor element can be used in the discharge area of the hydraulic line in order to verify the compensation of the pulsation pressure. Both sensor signals can be used in the control element for controlling the active actuator element according to the invention. Also, a sensor element in the discharge region can be used as the only sensor element.

According to a further preferred embodiment of the present invention, the device according to the invention may comprise a membrane element having a first side and a second side. The actuator element can in this case be connected to the membrane element, for example, be in contact with it. The actuator element may be connected to the second side of the membrane element, so as to deliver a compensation force to the membrane element. The membrane element can in this case change its shape such that the compensation force is introduced into the fluid line or the required volume variation in the pumping chamber to compensate for the pulsation pressure is realized. The pumping chamber can be arranged on the first side of the membrane element opposite the actuator element and essentially the first partial pressure of the fluid can act. The membrane element can thus be regarded as a laterally fixed piston element. The use of a piston element is also possible, with a laterally mounted membrane element obviating the need for sealing the piston element to its bulb wall. The membrane element may have a mechanically stable configuration, for example a metal element with an exemplary 4 mm wall thickness, and, for example, withstand high pressures of, for example, 200 bar or more.

According to a further preferred embodiment of the present invention, the membrane element has a supporting element on the side of the actuator element. In this case, the support element can apply the first fluid part pressure to the second side of the membrane element, while the first fluid pressure acts on the first side of the membrane element. Thus effectively acts on the membrane element on the first side substantially the second fluid part pressure, thus the pulsation pressure, since the constant system pressure, thus the first Fluidteildruck, is substantially compensated by the support element. The device or the membrane element is thus designed balanced, so that it is not burdened by a constant line pressure.

The first fluid part pressure can thus be applied by using a spring element as a support element on the second side of the membrane element. The spring element should in this case be set up so stiff to provide a support of the membrane element with respect to the first fluid part pressure, but also so flexibly set up that a movement of the membrane element is made possible by the actuator for compensating the second fluid part.

According to a further preferred embodiment of the present invention, the support element has a first and a second side, wherein the first Side of the support element is attached to the membrane element and wherein the second side of the support element is connected to the Fluidieitung, in particular using a transmission element, so that the first fluid pressure acts on the second side of the support element. The transmission element may in this case be designed to be so sluggish and / or lossy, so that essentially only the first fluid part pressure acts on the second side of the support element, thus only the first fluid part pressure on the support element on the membrane element, in particular on its second side is passed.

In this way, support or support of the membrane element or its side not arranged in the fluid conduit is possible, so that the first fluid pressure acts from one side, the first side, while the first fluid component pressure acts from the second side of the membrane element. The effective loading of the membrane element is therefore exclusively the second fluid partial pressure, thus the pulsation pressure. In this way, the membrane element can be used over a large pressure application range since only the differential pressure to be compensated can act on the membrane element.

According to a further preferred embodiment of the present invention, the transmission element is designed as a piston element. The piston element in this case has a first side and a second side, wherein the first side of the piston element is connected to the second side of the support element and the second side of the piston element is connected to the Fluidieitung.

As a result, the first fluid pressure prevailing in the fluid line can be supported by way of the piston element and the support element on the second side of the membrane element. The first fluid pressure part, thus the system pressure, can be regarded as a pressure which undergoes substantially only a very low frequency change. In contrast, the second fluid part pressure, the pulsation pressure, be regarded as a pressure having a comparatively high frequency of change.

If, for example, the piston element has high friction or high loss in its connection or sealing to the piston wall, essentially only the first fluid part pressure, but not the second fluid part pressure, is transmitted via the support element to the second side of the membrane element via the piston element passed. The piston element can thus be understood as a low-pass element for pressure fluctuations, which can pass on the low-frequency or non-changing system pressure via the support element to the membrane element, but not the high-frequency Pulsations- pressure, as this would respond too slowly, for example via appropriately trained friction of the piston element, to follow a high-frequency pulsation pressure.

According to a further preferred embodiment of the present invention, the piston element can be designed as a piston element from the group consisting of a circular piston element and a cylinder piston element.

According to a further preferred embodiment of the present invention, the actuator element may be formed as a piezoelectric actuator element.

Such an actuator element can provide required small deflections at comparatively high force. The piezoelectric actuator element may in this case be designed, for example, as a cylindrical stacking actuator and have a cavity in the middle. This results in a favorable ratio of surface to be cooled to heat-generating volume. In addition, a suitable cooling can be provided in the interior of the piezoelectric actuator. According to a further preferred embodiment of the present invention, the device may further comprise at least one sensor element for determining the first fluid pressure and / or the second fluid pressure, as well as a Steuerbzw. Control element for controlling the actuator element.

For this purpose, a currently prevailing first fluid pressure can be determined, which is processed in the control or regulating element in order to determine the first fluid part pressure and the second fluid part pressure. Based on the second fluid part pressure, a control of the actuator element can subsequently take place.

Hereinafter, reference will be made to embodiments of the invention with reference to the accompanying figures. The figures are not to scale, but can reproduce qualitative proportions.

Like or similar reference numerals in different figures refer to the same or similar components.

Show it:

Fig. 1 is an exemplary illustration of the principle of operation of the present invention;

FIG. 2 shows a first exemplary embodiment of a device according to the present invention; FIG. and

Figs. 3, 4 show a second exemplary embodiment of a device according to the present invention.

FIG. 1 shows an exemplary representation of the functional principle of the present invention. FIG. 1 shows fluid line 10 with supply line 4a and discharge line 4b. On the supply side 4a there is a first fluid pressure Qi 14a, which is composed of the first fluid part pressure Q 16a, the substantially constant system pressure and the second fluid part pressure Δς 16b, the hydraulic pulsation or the pulsation pressure. The device 2 according to the present invention is intended here to compensate the first fluid pressure Qi 14a to a second fluid pressure Q2 14b, which should correspond substantially to the first fluid part pressure Q 16a.

Pumping chamber 6 is arranged between supply line 4 a and discharge line 4 b, in which actuator element 18 is connected to a piston element 20 or membrane element 20. The second fluid part pressure .DELTA.S. 16b is intended by deflection of Kolbenbzw. Membrane element 20 compensated using the actuator element 18, i. be corrected to zero.

Sensor element 12a can in this case determine the first fluid pressure Qi 14a. Control element 22 can determine the first fluid part pressure Q 16a from the dynamically changing first fluid pressure Qi 14a determined by sensor 12a, for example by averaging and from Q1 and Q subsequently the second fluid part pressure Δς 16b. Control element 22 can use this information to control the actuator element 18 so that it generates a back pressure or a negative second fluid part pressure Δς 16c, which essentially compensates the second fluid part pressure Δς 16b to zero. As a result, on the discharge side 4b, the second fluid pressure Q2 14b becomes substantially equal to the first fluid pressure part Q16a. Alternatively or additionally, sensor element 12b can be provided, which essentially can determine the second fluid pressure Q2 14b. In the non-compensated case, the second fluid pressure Q2 also has a pulsation component Δς, which can be used to control the control element 22. With further reference to FIG. 2, a first exemplary embodiment of a device according to the invention is shown.

Figure 2 shows an exemplary embodiment of the device 2 according to the invention in cross section. Pumping chamber 6 is arranged between supply line 4 a and supply line 4 b, which essentially represents a membrane element 20 arranged in hydraulic line 10 or in an opening of its wall. Membrane element 20 is firmly anchored in the wall of the hydraulic line and thus supported laterally by this. However, the diaphragm 20 can be moved by the actuator element 18 in a central region perpendicular to the longitudinal direction of the hydraulic line 10. Hereby, the volume of the pumping chamber 6 can be varied, which essentially corresponds to a pressure reduction or pressure build-up in the region of the pumping chamber 6. Thus, in the region of the pumping chamber 6 via the deflection of the actuator 18 and thus the movement of the diaphragm 20, a compensation pressure - Aq 16c can be established, which compensates the second fluid idle pressure Aq 16b substantially to zero.

The actuator element 18 is exemplified as a piezoelectric, cylindrical stack actuator with a central cavity 38. Actuator element 18 is disposed on the second side 40b of the membrane element 20 and supported on the opposite side by a counter-pressure element 32. The counterpressure element 32 is fastened to the housing 46 of the device 2 according to the invention, in which also the membrane element 20 is accommodated. Thus, the actuator element 18 is clamped between the membrane element 20 and the counter-pressure element 32.

Also on the second side 40b of the membrane element support element 28, for example, a spring element 28, exemplified as a plate spring, mounted with its first side 42a. The second side 42 b of the support element 28 is arranged on a piston element 24. The piston element has the connection to the support element 28 on its first side 44a. On The second side 44b of the piston element 24 essentially has the effect of the first fluid component pressure Q 16a and the second fluid pressure Q ₂ 14b, respectively. At least on the section of the cylinder element 24 shown on the left in FIG. 2, the first fluid pressure Qi 14a would first load by means of the connecting line 30. In order to compensate the second fluid part pressure Δς 16b, thus the pulsation pressure, on the piston element 24, this is attached to the side wall with a seal 26 which has such a high friction that the piston element 24 would react too slowly for the dynamic pulsation pressure Δς 16b, than that would be reflected in an effective deflection of the piston member 24.

The friction-afflicted seal 26 thus represents a kind of low-pass element, which on the one hand pass the constant line pressure Q 16a via support member 28 to membrane 20, but so lossy or sluggish reacts, so that the variable second Fluidteildruck Δς 16b is not disclosed.

Thus, via piston element 24 and support element 28, a support of the membrane element 20 on the second side 40b relative to the first fluid part pressure Q 16a. As a result, both the membrane element 20 and the actuator element 18 are relieved of a possibly very high line pressure Q of the fluid line 10; essentially, only the dynamically variable second fluid part pressure Δς 16b acts. Since membrane 20 is loaded both on its first side 40a and on its second side 40b with the first fluid part pressure Q 16a, membrane 40 is shown as balanced.

As a result, actuator element 18a may be made as small as possible, for example for reasons of cost or space, so that while it can generate the required dynamic pulses for compensating the second fluid part pressure Δς 16b, it is not exposed to the static, first fluid part pressure Q 16a. which he might not be able to withstand. This support of the static pressure load is described again below.

The interface between actuator element 18 and pump chamber 6 may possibly not be permanently sealed due to the low mechanical stroke with possibly high pressure and high operating frequency due to commonly available sealing systems in combination with a piston, in particular due to the stiction of such a piston with adequately sized sealing systems For example, if the line pressure in the fluid id would correspond to 200 bar or so, and consequent significant wear on a potential piston sealing system.

The transmission between the actuator element 18 and the hydraulic medium in the hydraulic line 10 therefore takes place according to the invention and in FIG. 2 by way of example through a membrane element 20, for example a steel membrane, which is designed or arranged such that its inherent rigidity is an order of magnitude less than that of the actuator element 18th

The support required to protect the membrane element 20 and the actuator element 18 is provided by a support element 28, exemplified as a plate spring. It should also be noted that the dynamic stiffness of the support element 28 and the disc spring should be significantly lower than that of the actuator element 18, for example, the piezoelectric Stapelak- tuators in order to reduce the required additional forces to a minimum. In this case, the inherent property of a degressive characteristic of a diaphragm spring can be used.

Since the hydraulic system 10 is de-pressurized when switched off, the force introduced by the disc spring must become zero in this operating case to damage, in particular of an actuator element designed as a piezo 18 to avoid. The plate spring is therefore biased by the drawn in Figure 2 annular piston 24 which is coupled via connecting line 30 to the hydraulic system 10. In essence, due to the line pressure Q of the hydraulic line 10, which is coupled to the plate spring both via the first side 40a of the membrane element 20 and via the second side 44b of the piston element 24, the diaphragm spring is pretensioned.

The sealing system 26 of the piston element 24 should in this case be subject to high friction in order to prevent, in combination with a possibly high mass of the piston element 24, coupling of the pulsation Δς 16b to be eliminated via the diaphragm spring. In addition, the coupling of the piston member 24 on the calm side of the flow, thus on the discharge side 4b, is preferable.

The piston can, as shown in Figure 2, be designed as an annular piston which is connected directly to the hydraulic line system 10. In this case, the device 2 is designed as a closed, pressure-resistant system, in which the housing wall 46 shown in FIG. 2 is closed completely and in particular using the counterpressure element 32 with respect to the hydraulic line 10. Thus, in the event that an element of the device 2, for example spring element 28, piston element 24 or actuator element 18, is damaged, e.g. breaks down, the inventive device 2, with respect to the opening in the hydraulic line 10, as a closed system, so that the operation of the hydraulic line 10 is not affected. Thus, the device 2 according to the invention has a fail-safe behavior even in the case of destruction of the membrane element 28, only the required compensation of the second fluid part pressure 16b can no longer be realized in this case.

Membrane element 20 can exemplarily have a thickness of 4 mm and in this case provide a deformation in the range of 10-20 μm. actuator 18, implemented as a piezoelectric actuator element, may, for example, have a diameter of 25 mm at a height of 50 mm up to a diameter of 42 mm or more at a height of 100 mm. Supporting element 28 may have a diameter of 200 mm as a plate spring by way of example. The active area of membrane element 20 may exemplarily have a diameter of 100 mm. Possible line pressures of the hydraulic system 1 are in the embodiment according to the invention with steel membrane at up to 200 bar or more.

Continuing to refer to FIGS. 3 and 4, a second exemplary embodiment of the present invention is illustrated.

In the event that piston element 24 should not be designed as an annular piston element, this may also be formed by a ring element 34 and a plurality of individual piston elements 24. By way of example, four piston elements 24 can be used for this purpose, in particular to realize a symmetrical design. For this purpose, a ring line 36 is provided in connection line 30, which connects the pressure chambers on the second side 44b thereof with the hydraulic line 10, so that the first 14a or second fluid pressure 14b rests on the second side 44b of the piston elements 24. To connect a trained as a plate spring support member 28 to discrete piston elements 24 ring member 34 is provided. In a suitable embodiment of the plate spring ring member 34, however, also omitted, ring member 34 serves essentially the power transmission between the piston elements 24 and support member 28th

A seal and vibration isolation with respect to the second fluid part pressure Aq 16b is provided by the individual piston elements 24. The central membrane element 20 connected to the actuator element 18 is arranged centrally in FIG. 3. The support element 32 is not shown separately in FIG. 3, but is connected to the housing 46 according to FIG. Device 2 can in this case be designed as a component, which is placed on a suitable opening in a hydraulic line 10 and this concludes suitably for providing the functionality according to the invention. In other words, a hydraulic line 10 may, for example, have a standardized opening, which may initially be closed with a clean cover. In the event that the pressure fluctuations occurring in the hydraulic line 10 are to be compensated, such a cover can be easily removed from a hydraulic line 10 and the device 2 according to the invention can be placed.

Due to a self-contained configuration with, for example, separate sensor elements 12a, 12b, arranged in the supply area 4a or discharge area 4b, the device according to the invention can operate essentially exclusively connected to a power supply. Also, control element 22 may for example be installed directly on the device 2 according to the invention in order to provide the control technology method for compensation of the pulsation pressure, which essentially requires only information of the sensor elements 12a, 12b.

LIST OF REFERENCE NUMBERS

2 device

4a, b supply line, discharge

6 pumping chamber

10. hydraulic line

12a, b sensor element

14a, b first, second fluid pressure

16a, b, c first, second, negative second fluid pressure

18 actuator element

20 membrane element / piston element

22 control element

24 piston element

26 seal with friction

28 support element / spring element

30 connecting line

32 counter-pressure element

34 ring element

36 ring line

38 cavity

40a, b first, second side of the membrane element

42a, b first, second side of the support element

44a, b first, second side of the piston element

46 housing

Claims

claims

1. A device (2) for reducing a pressure fluctuation in a fluid-filled line, adapted for connection to a fluid line having a supply side and a discharge side, comprising the device

an actively controllable actuator element (18) arranged on the fluid line (10) between the supply side (4a) and the discharge side (4b);

wherein the fluid line (10) in the operating state on the supply side (4a) has a first fluid pressure (14a) and on the discharge side (4b) has a second fluid pressure (14b);

wherein the first fluid pressure (14a) has a first fluid partial pressure (16a) and a second partial fluid pressure (16b);

wherein the first fluid partial pressure (16a) is formed as a substantially constant pressure Q;

wherein the second fluid partial pressure (16b) is formed as a dynamically changing pressure Aq; and

wherein the actuator element (18) is controllable to generate a compensation force, wherein the compensating force compensates the second fluid partial pressure (16b) such that the second fluid pressure (14b) substantially corresponds to the first fluid partial pressure (16a).

2. Apparatus according to claim 1, further comprising

a membrane element (20) having a first side (40a) and a second side (40b);

wherein the actuator element (18) is connected to the membrane element (20);

wherein the membrane element (20) is arranged on the second side (40b) to apply the compensating force of the actuator element (18) and to introduce it into the fluid line (10); and

wherein on the first side (40a) substantially the first fluid partial pressure (16a) works.

3. Device according to claim 2,

wherein the first fluid partial pressure (16a) is applied to the second side (40b) of the membrane element (20) using a support element (28);

wherein the support element (28) is arranged so stiff as to provide a support of the membrane element (20) with respect to the first fluid partial pressure (16a); and

wherein the support element (28) is so flexibly arranged to allow movement of the membrane element (20) through the actuator element (18) to compensate for the second partial fluid pressure (16b).

4. Apparatus according to claim 2 or 3,

wherein the support element (28) has a first (42a) and a second side (42b);

wherein the first side (42a) of the support element (28) is attached to the membrane element (20);

the second side (42b) of the support member (28) being connected to the fluid conduit (10) using a transfer element (24); and

wherein the transmission element (24) is formed so sluggish and / or lossy, so that substantially exclusively the first fluid pressure (14a) acts on the second side (42b) of the support element (28).

5. Device according to one of the preceding claims,

wherein the transmission element (24) is designed as a piston element with a first side (44a) and a second side (44b), which first side (44a) of the piston element (24) is connected to the second side (42b) of the support element (28) and which second side (33b) of the piston element Mentes (24) is connected to the fluid line (10).

6. Apparatus according to claim 5,

wherein the piston member (24) is formed as a piston member from the group consisting of the rotary piston element and the cylinder piston element.

7. Device according to one of the preceding claims,

wherein the actuator element (18) is formed as a piezoelectric actuator element.

8. The device according to one of the preceding claims, further comprising

at least one sensor element (12a, b) for determining the first fluid

Pressure (14a) and / or the second fluid pressure (14b); and

a control / regulating element (22) for controlling the actuator element (18).

9. Hydraulic system, in particular for an aircraft, comprising a device according to one of the preceding claims.

10. aircraft comprising a hydraulic system according to claim 9 and / or a device (2) according to one of claims 1 to 8.