DYNAMIC SEALING IN AN AIRCRAFT TURBOMACHINE CONTROL VALVE

Abstract

Control valve (10), in particular for an aircraft turbomachine, this valve comprising a movable shutter (14) which is carried by a rod (16) which passes through orifices (20) of a body (12) of the valve, sealing means (24) being mounted in each of these orifices (20) and comprising: a tubular bellows (32) mounted around the rod (16), a ring (26) mounted around the rod (16) and the tubular bellows (32) and housed at least partly in one of the orifices (20), and a washer (28) mounted around the rod (16), this washer being interposed between the tubular bellows (32) and one end of the ring (26) which is supported at the bottom of said orifice. Figure for the abstract: Figure 6

Description

Title of the invention: DYNAMIC SEALING IN AN AIRCRAFT TURBOMACHINE CONTROL VALVE Technical field of the invention

[0001] The present invention relates to the field of dynamic sealing for continuous or oscillating rotational movements and is intended for an aircraft turbomachine control valve. The control valve may be a butterfly valve, an exhaust valve, etc. Technical background

[0002] An aircraft turbomachine comprises several fluid circuits which include valves. Among the technologies used for valves, there are control valves.

[0003] A control valve 10, such as that shown in Figures 1 and 2, is a valve comprising an annular body 12 in which a shutter is movable in rotation or with more complex kinematics. In the example shown in these figures, the control valve 10 is a butterfly valve, that is to say that its shutter is formed by a butterfly 14. The body 12 comprises a main axis A or axis of revolution which corresponds to the axis of flow of a fluid through the valve. The butterfly 14 has a disc shape complementary to the internal shape of the body 12. The butterfly 14 therefore has an external diameter which is substantially equal to the internal diameter of the body 12. The butterfly is movable between a position of obstruction of the internal passage 18 defined by the body 12, in which it extends for example in a plane perpendicular to the axis A, and a position of maximum release of this passage 18.Figures 1 and 2 show the butterfly 14 in intermediate positions.

[0004] The butterfly 14 is carried by a rod 16 which extends transversely to the passage 18 inside the body 12 and which defines the axis B of rotation of the butterfly. This rod 16 passes through orifices 20 opening into the conduit 18 and made in the body 12 and is guided in rotation in these orifices by bearings 22.

[0005] The passage through the body 12 by the rod 16 creates a risk of leakage in this area. The pressure of the fluid inside the body 12 is generally higher than the pressure outside the body 12, and fluid flowing in the body is likely to escape through the orifices 20 (arrow F1). It is therefore necessary to provide sealing means in the orifices 20 for mounting the rod 16.

[0006] In the current technique, the sealing means are formed by elastomer O-rings, which are mounted in annular grooves of the orifices 20 and which cooperate with the rod 16. They ensure dynamic sealing around the rod 16 during operation of valve 10.

[0007] In some applications, this solution may not be effective and sufficient. This is particularly the case in an aircraft turbomachine where the valve 10 can be used in a circuit where a fluid circulates at a very high pressure and / or at a very high temperature (for example of the order of 600°C).

[0008] The present invention provides a solution to this problem which allows a control valve to be used under extreme conditions of high pressure and / or high temperature. Summary of the invention

[0009] The invention provides a control valve, in particular for an aircraft turbomachine, this control valve comprising:

[0010] - an annular body having a main axis and defining an internal passage for the flow of a fluid, - a movable shutter inside the body around an axis of rotation, between a position of obstruction of the passage and a position of release of this passage, - a rod for supporting and rotating the shutter, this rod defining said axis of rotation and passing through orifices in said body, - rod guide devices, which are mounted in said holes, and - sealing means which are mounted in each of said orifices around the rod,

[0011] characterized in that said sealing means mounted in each of said orifices comprise:

[0012] - a tubular bellows mounted around the rod, this tubular bellows being elastically deformable in particular along the axis of rotation, - a ring mounted around the rod and the tubular bellows and housed at least partly in one of the orifices, this ring comprising a first axial end which is secured to a first axial end of the tubular bellows and which bears axially on a first annular shoulder of the body, and - a washer mounted around the rod, this washer being interposed between a second axial end of the tubular bellows and a second annular shoulder of the rod.

[0013] The control valve according to the invention is thus equipped with improved sealing means which ensure optimum dynamic sealing during operation of the valve, including under the extreme conditions mentioned above.

[0014] The tubular bellows is elastically deformable in the axial direction and can be advantageously prestressed in the axial direction so as to keep the washer in sealed contact with the second shoulder of the stem. When the stem rotates, the second shoulder slides over this washer and dynamic sealing is ensured in this area between the second shoulder of the stem and the washer of the sealing means. On the side opposite the washer, the tubular bellows keeps the ring in sealed contact with the first shoulder of the body. This contact ensures static sealing in this area. The tubular bellows extends around the stem and the dynamic and static seals provided at its two ends prevent any leakage of fluid from the inside of the tubular bellows to the outside. The inside of the tubular bellows can therefore be placed in fluid communication with the inside of the body, and the outside of the tubular bellows can be placed in fluid communication with the outside of the valve.

[0015] Finally, the ring extends around the tubular bellows and protects it. It rests on the first shoulder and forms a support point for the second shoulder of the rod to limit and thus control the travel of the rod and the deformation of the tubular bellows.

[0016] The control valve according to the invention may be a butterfly valve, an exhaust valve, etc.

[0017] The valve according to the invention may comprise one or more of the following characteristics, taken in isolation or in combination with each other:

[0018] — said shutter is a butterfly;

[0019] — said shutter or butterfly is disc-shaped;

[0020] — said shutter or butterfly is movable inside the body around an axis of rotation which is perpendicular to said principal axis,

[0021] — said guide devices are guide bearings; the bearings are plain or rolling bearings;

[0022] — said rod passes through diametrically opposite orifices of the body;

[0023] - this washer having an external diameter less than the internal diameter of the ring which comprises a second axial end capable of coming into axial support on said second shoulder of the rod in order to define an axial deformation stroke of the tubular bellows which is axially prestressed so as to axially hold the washer against said second shoulder;

[0024] - the first end of the tubular bellows is fixed by an independent rigid connection mountable at the first end of the ring; this connection is for example obtained by welding, brazing, etc.;

[0025] - the first end of the ring comprises an internal annular rim of which a first annular face serves as a support and fixing face for the first end of the tubular bellows, and a second opposite annular face of which serves as a support face on said first shoulder of the body;

[0026] - the second end of the tubular bellows is fixed by an independent rigid connection mountable to an annular cup which extends around the rod and which forms a support seat for said washer; this connection is for example obtained by welding, brazing, etc.;

[0027] — the washer is fixed to the cup, by a chemical or mechanical bond;

[0028] - the cup comprises an axial annular rim interposed radially between the washer and the second end of the tubular bellows;

[0029] - a helical spring is mounted around the rod and inside the tubular bellows, this spring being interposed axially between said first shoulder of the body and said washer;

[0030] - the spring is axially supported respectively on said first shoulder and on said cup;

[0031] — the ring is bonded, in particular by shrinking, gluing or brazing, in said orifice; this creates an additional static seal between the sealing means and the valve body;

[0032] - the washer is made of mineral, organic or metallic material receiving or not a functionalization treatment, and / or the tubular bellows is made of a metal or organic alloy or composite, and / or the ring is made of a metal alloy, and / or the cup is made of a metal alloy; the washer is for example made of graphite;

[0033] - each of said orifices comprises two coaxial cylindrical housings, one of which first housing located on the shutter side is configured to receive one of said guide devices, and a second housing is configured to receive said sealing means, said first shoulder of the body being located at the junction of these first and second housings.

[0034] The present invention also relates to an aircraft turbomachine, comprising at least one control valve as described above. Brief description of the figures

[0035] The invention will be better understood and other characteristics and advantages will become apparent upon reading the detailed description which follows, comprising embodiments, given for illustrative purposes with reference to the appended figures and presented as non-limiting examples, which may serve to complete the understanding of the present invention and the description of its embodiment and, where appropriate, contribute to its definition, in which:

[0036] [Fig-1] [Fig.l] is a perspective schematic of a control valve, in particular to butterfly;

[0037] [Fig.2] [Fig.2] is a schematic perspective and axial sectional view of a control valve according to the prior art;

[0038] [Fig.3] [Fig.3] is a partial schematic view in perspective and in axial section of a control valve according to one embodiment of the invention;

[0039] [Fig.4] [Fig.4] is a schematic perspective view of the sealing means of the control valve of [Fig.3];

[0040] [Fig.5a] [Fig.5a] is a schematic axial sectional view of the means sealing of [Fig.4] and illustrates a position of these means;

[0041] [Fig.5b] [Fig.5b] is a schematic axial sectional view of the means sealing of [Fig.4] and illustrates another position of these means;

[0042] [Fig.5c] [Fig.5c] is a schematic axial sectional view of the means sealing of [Fig.4] and illustrates another position of these means;

[0043] [Fig.6] [Fig.6] is a partial schematic view in axial section of the control valve regulation of [Fig.3];

[0044] [Fig.7] [Fig.7] is another partial schematic view in axial section of the valve regulation of [Fig.3]; and

[0045] [Fig.8] [Fig.8] is a partial schematic view in perspective and in axial section of a control valve according to an alternative embodiment of the invention. Detailed description of the invention

[0046] Figures 1 and 2 have been described in the above.

[0047] Figures 1 and 2 illustrate a control valve 10 which may be a valve butterfly, an exhaust valve, etc. This valve 10 comprises a shutter which is a butterfly in the non-limiting example shown. The control valve 10 according to the invention differs from that of the prior art essentially by its sealing means 24 which are mounted in each of the orifices 20 around the stem 16. The preceding description relating to the other aspects and characteristics of a control valve 10 therefore applies to the control valve according to the invention.

[0048] As mentioned above, a control valve 10 comprises:

[0049] - an annular body 12 having a main axis A and defining an internal passage 18 for the flow of a fluid, such as air for example, - a shutter, such as a butterfly 14, which is movable inside the body 12 around an axis of rotation or a system of exhaust axes B crossing the main axis A and for example perpendicular to this main axis A, between a position of obstruction of the passage and a position of release of this passage, - a rod 16 for supporting and rotating the butterfly 14, this rod 16 defining the axis of rotation B and passing through orifices 20, for example diametrically opposed, of the body 12, - rod guide devices 16, such as bearings 22, which are mounted in the orifices 20, and - sealing means 24 which are mounted in each of the orifices 20 around the rod 16.

[0050] Figures 3 to 6 illustrate a first embodiment of these sealing means 24.

[0051] The sealing means 24 mounted in each of the orifices 20 essentially comprise:

[0052] - a ring 26 mounted around the rod 16, - a washer 28 mounted around the rod 16 and intended to bear on a second annular shoulder 30 of the rod 16, this annular shoulder 30 being for example formed by a rib, and - a tubular bellows 32 mounted around the rod 16 and interposed axially between the washer 28 and one end of the ring 26.

[0053] In Figures 3 to 6, the body 12 of the valve is shown in part and schematically. In these figures, one can see a non-limiting example of embodiment of the orifices 20, which each comprise two coaxial cylindrical housings 20a, 20b. These housings 20a, 20b have different diameters, the housing 20a of smaller diameter being located on the side of the butterfly 14 and therefore on the inside of the valve 10, and therefore the housing 20b of smaller diameter being located on the outside.

[0054] The orifice 20 comprises a first annular shoulder 20c which is located in the present case at an angle between the housings 20a, 20b. The housing 20a can receive the bearing 22, as shown in FIGS. 6 and 7.

[0055] The ring 26 is housed at least partly in the orifice 20, and in particular in the housing 20b. In the example shown, it comprises a cylindrical wall 33, one axial end of which is free and forms an axial end 26a of the ring 26, which is located on the side of the second shoulder 30, and one opposite axial end of which is connected to an internal annular rim 34, that is to say an annular rim oriented inwards relative to the axis B. This rim 34 forms an axial end 26b of the ring 26, opposite the end 26a.

[0056] The wall 33 has an external diameter Dextl (which is also the external diameter of the ring 26 - [Fig.4]) and an internal diameter Dintl, and the rim 34 has an internal diameter Dint2. It can be seen in the drawings that Dint2 is greater than Dtige which is the external diameter of the body of the rod 16, its second shoulder 30 having an external diameter Dnerv which is here greater than Dextl (figures 3 and 4).

[0057] The ring 26 is preferably mounted tightly and in particular mounted by shrink fitting in the orifice 20 of the body and in particular in the housing 20b. It is thus understood that there is no play (or that this play is filled) between the wall 33 and the surface cy internal lindic of the housing 20b and therefore that the internal diameter of this surface is substantially equal to Dextl.

[0058] The ring 26 bears axially on the shoulder 20c by means of its internal rim 34. The rim 34 comprises an annular face 34a bearing against this shoulder 20c, and an opposite annular face 34b.

[0059] The tubular bellows 32 bears axially on the face 34b and is fixed to the rim 34 and therefore to the end 26b of the ring 26.

[0060] The tubular bellows 32 comprises an active zone forming at least two undulations 32a in the example shown (there are 4 of them in Figures 5a to 7). The thickness of the bellows is preferably constant, its undulations allowing it to be given its ability to deform. Each of these undulations 32a comprises two parallel annular walls 32al, 32a2, the external peripheries of which are connected to each other by an annular apex 32a3 and the internal peripheries of which are each connected to an annular base 32a4 (see [Fig.5a] for example).

[0061] In the example shown, the bellows 32 has a maximum diameter Dmax defined by the vertices 32a3, and a minimum diameter Dmin defined by the bases 32a4. Dmax is slightly less than Dintl so that the bellows can be compressed in the ring 26 and so that the vertices 32a3 can slide in the wall 26a of the ring 26 while being guided by the latter. Dmin is close to Dint2.

[0062] The end 32a of the bellows 32 located on the side of the butterfly 14 comprises a base 32a4 which is engaged in the rim 34 and surrounded by this rim 34, and also comprises a wall 32a2 connected to this base 32a4, which itself bears on the face 34b of the rim 34. The bellows 32 is fixed to the ring 26 in this zone. Preferably, the end 32a of the bellows 32 is fixed to the rim 34, and more preferably the base 32a4 is fixed to the internal periphery of the rim 34. This fixing is preferably carried out by welding using an annular weld bead C1 extending around the axis B (see [Fig.5b]). Welding is possible in the case where the materials to be welded are metallic or plastic. Alternatively, another type of rigid, non-removable connection would be possible, such as gluing for example, which is particularly useful for non-weldable materials such as composites.

[0063] The end 32b of the bellows 32, opposite the end 32a, is preferably secured to an annular cup 36 which extends around the rod 16 and forms a support seat for the washer 28.

[0064] The cup 36 comprises an annular wall 36a whose external periphery is connected to a cylindrical rim 36b which is oriented axially on the side of the second shoulder 30.

[0065] The cup 36 comprises an internal diameter Dint3 defined by the internal periphery of the wall 36a, an internal diameter Dint4 defined by the rim 36b, and a diameter external Dext2 defined by the rim 36b. Dint3 is greater than Dtige. In the example shown, Dext2 is less than Dintl so that the cup 36 can slide axially inside the ring 26 and its wall 33. Furthermore, Dext2 is close to Dmax.

[0066] The cup 36 comprises an annular face 36c for supporting the washer 28, and an opposite annular face 36d ([Fig.4]).

[0067] The end 32b of the bellows 32 comprises a top 32a3 which is engaged on the wall 36a and surrounds this wall 36a, and also comprises a wall 32al connected to this top 32a3, which itself bears on the face 36d of the cup 36. The bellows 32 is fixed to the cup 36 in this zone. Preferably, the end 32b of the bellows 32 is fixed to the cup 36, and more preferably the top 32a3 is fixed to the external periphery of the rim 36b. This fixing is preferably carried out by welding using an annular weld bead C2 extending around the axis B (see [Fig.5c]). Welding is possible in the case where the materials to be welded are metallic or plastic. Alternatively, another type of rigid, non-removable connection would be possible, such as gluing for example, which is particularly useful for non-weldable materials such as composites.

[0068] The washer 28 has an external diameter Dext3 close to Dint4 and an internal diameter Dint5 which is greater than Dtige and which is here greater than Dint3.

[0069] The washer 28 comprises two parallel annular faces 28a, 28b, one face 28a of which bears axially against the second shoulder 30 and the other face 28b of which bears axially against the face 36c ([Fig.4]). Preferably, the faces 28b, 36c are bonded and therefore fixed together. The bond may be of the chemical type (glue, cement, etc.) or mechanical (screw, rivet, etc.). Initially, the face 28a of the washer 28 may have a convex cross-section or may have any macro or micro geometries likely to promote tribological behavior or the sealing function.

[0070] The washer 28 has a thickness, measured along the axis B, which is greater than the height, measured along the same axis, of the rim 36b, so that the washer alone comes into contact with the second shoulder 30. The material of the washer 28 is preferably chosen to wear by friction against the second shoulder 30. The aforementioned domed face 28a can then flatten to best match the shape of the second shoulder 30 and thus ensure optimal sealing.

[0071] Any reduction in the height of the washer 28 is compensated by the elasticity of the bellows 32 which ensures that this washer 28 is held against the second shoulder 30 of the rod 16.

[0072] The second shoulder 30 comprises an annular face 30a which extends in a plane perpendicular to the axis B and on which the face 28a of the washer 28 bears. faces 28a, 30a are thus in abutment against each other in a plane perpendicular to the axis B and are intended to rub against each other in operation (i.e. during rotation of the rod 16 in the orifices 20 - cf. arrows F2, [Fig.6]) so as to ensure a dynamic seal (arrows F3 - [Fig.7]) between the rod 16 and the sealing means 24. A static seal (arrows F4 - [Fig.7]) is further ensured between the sealing means 24 and the body 12 due to the axial support of the ring 26 on the shoulder 20c or even the hooping of the ring 26 in the housing 20b.

[0073] The interior of the bellows 32 may be in fluid communication with the passage 18, through the housing 20a and the bearing 22 (see [Fig.7]). The exterior of the bellows 32 may be in fluid communication with the exterior of the valve 10. [Fig.7] shows schematically the zones of pressure differences within the valve according to the invention, the zone Z corresponding to the choice:

[0074] - to the overpressure zone in the case where the pressure in the conduit 18 of the valve is overpressured compared to the environment,

[0075] - to the depression zone in the case where the pressure in the conduit 18 of the valve is depressed in relation to the environment.

[0076] Figures 5a to 5c show three distinct positions of the sealing means 24. In [Fig.5a], left-hand drawing, the sealing means 24 are in the free state without constraint, that is to say that the bellows 32 is not constrained. The sealing means 24 are not yet mounted in the valve. The bellows adopts a free or rest position in which it has an axial length or dimension LL. In this position, the face 36a of the washer 36 is at an axial distance H1 from the end 26a of the ring 26.

[0077] In [Fig.5b], the middle drawing, the sealing means 24 are in the mounted state in the orifice 20 of the body 12 of the valve 10. The bellows 32 is axially prestressed in this position so that it has an axial length or dimension L2. The face 36a of the washer 36 is at a predetermined axial distance H2 from the end 26a of the ring 26, which is equal to the difference between L1 and L2. This distance H2 corresponds to the maximum axial deformation travel of the bellows 32 in operation and therefore of axial displacement of the washer 36 along the axis B.

[0078] In [Fig.5c], right-hand drawing, the sealing means 24 are fully axially constrained. The face 36a of the washer 36 and the end 26a of the ring 26 are located in the same plane perpendicular to the axis B. This occurs when the second shoulder 30 of the rod 16 bears axially on the end 26a of the ring 26. The second shoulder 30 thus bears on the ring 26 rather than on the body 12 of the valve 10. For this, Dnerv can be between Dintl and Dextl, as is the case in Figures 6 and 7. In the variant of [Fig.3], Dnerv would be greater than Dintl, potentially greater than Dextl, and the ring 26 would have a length or axial dimension greater than that of the housing 20b so that the end of the ring 26 is (at least slightly) projecting outside the housing 20b. In this position, the bellows 32 has an axial length or dimension L3, which is equal to L2 - H2.

[0079] The bellows 32 can thus provide several functions such as: static sealing in the orifice 20, stressing the washer 28 against the second shoulder 30 of the rod 16 due to the axial compression of the bellows 32, compensating for wear and differential thermal expansion of the parts, etc.

[0080] The ring 26 can thus provide several functions such as: guiding the axial movement of the washer 28 and the cup 26, protecting the bellows 32, the assembly interface of the sealing means 24 with the body 12 of the valve 10, a stop to limit accidental compression of the bellows 32, additional static sealing with the body 12 of the valve, etc.

[0081] [Fig. 8] illustrates an alternative embodiment of the sealing means 24 which comprise a spring 38 in addition to the characteristics of the first embodiment. The spring 38 is a helical spring which is mounted around the rod 16 and inside the bellows 32. The spring 38 is interposed axially between the shoulder 20c of the body 12 and the washer 28 and is more precisely in axial support respectively on the shoulder 20c and on the cup 36. The spring 38 has an internal diameter Dri greater than Dtige and close to Dint3, and an external diameter Dre less than but close to Dint2 and Dmin.

[0082] The material of the washer 28 preferably has a lower hardness than that of the rod 16, so that it is the washer which wears preferentially during operation, as mentioned above. The washer 28 is preferably made of graphite. Alternatively, another material could be used, such as a polymer, a composite, a metal alloy, etc. The tubular bellows 32, the ring 26 and the cup 36 may be made of a metal, organic or composite alloy.

Claims

Claims

1. Control valve (10), in particular for an aircraft turbomachine, this control valve comprising: - an annular body (12) having a main axis (A) and defining an internal passage (18) for the flow of a fluid, - a shutter (14) movable inside the body (12) around an axis of rotation (B) between a position for obstructing the passage (18) and a position for releasing this passage (18), - a rod (16) for supporting and rotating the shutter (14), this rod defining said axis of rotation (B) and passing through orifices (20) of said body, - devices (22) for guiding the rod (16), which are mounted in said orifices (20), and - sealing means (24) which are mounted in each of said orifices (20) around the rod (16), characterized in that said sealing means (24) mounted in each of said orifices (20) comprise: - a tubular bellows (32) mounted around the rod (16), this tubular bellows being elastically deformable in particular along the axis of rotation (B), - a ring (26) mounted around the rod (16) and the tubular bellows (32) and housed at least partly in one of the orifices (20), this ring (26) comprising a first axial end (26a) which is secured to a first axial end (32a) of the tubular bellows (32) and which bears axially on a first annular shoulder (20c) of the body (12), and - a washer (28) mounted around the rod (16), this washer being interposed between a second axial end (32b) of the tubular bellows (32) and a second annular shoulder (30) of the rod (61), this washer (28) having an external diameter (Dext3) smaller than the internal diameter (Dint3) of the ring (26) which comprises a second axial end (26b) capable of coming into axial support on said second shoulder (30) of the rod (16) in order to define an axial deformation stroke of the tubular bellows (32) which is axially prestressed so as to axially holding the washer (28) against said second shoulder (30).

2. A control valve (10) according to claim 1, wherein the first end (32a) of the tubular bellows (32) is assembled by a rigid, non-removable connection to the first end (26a) of the ring (26).

3. Control valve (10) according to one of the preceding claims, in which the first end (26a) of the ring (26) comprises an internal annular rim (34) of which a first annular face (34a) serves as a bearing and fixing face for the first end (32a) of the tubular bellows (32), and of which a second opposite annular face (34b) serves as a bearing face on said first shoulder (20c) of the body (12).

4. Control valve (10) according to one of the preceding claims, in which the second end (32b) of the tubular bellows (32) is fixed by a rigid, non-removable connection to an annular cup (36) which extends around the rod (16) and which forms a support seat for said washer (28).

5. Control valve (10) according to the preceding claim, in which the cup (36) comprises an axial annular rim (36b) interposed radially between the washer (28) and the second end (32b) of the tubular bellows (32).

6. Control valve (10) according to one of the preceding claims, in which a helical spring (38) is mounted around the stem (16) and inside the tubular bellows (32), this spring (38) being interposed axially between said first shoulder (20c) of the body (12) and said washer (28).

7. Control valve (10) according to the preceding claim, dependent on claim 4 or 5, in which the spring (38) bears axially respectively on said first shoulder (20c) and on said cup (36).

8. Control valve (10) according to one of the preceding claims, in which the washer (28) is made of mineral, organic or metallic material, and / or the tubular bellows (32) is made of metallic or organic alloy or composite, and / or the ring (26) is made of metallic alloy.

9. A control valve (10) according to any preceding claim, wherein each of said ports (20) comprises two cylindrical housings coaxial lindrics (20a, 20b), a first housing (20a) of which located on the side of the shutter (14) is configured to receive one of said bearings (22), and a second housing (20b) is configured to receive said sealing means (24), said first shoulder (20c) of the body (12) being located at the junction of these first and second housings (20a, 20b).

10. Aircraft turbomachine, comprising at least one control valve (10) according to one of the preceding claims.

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