Adjustable automatic valve

Abstract

An adjustable automatic valve and a supply circuit, the valve comprising: a first flow chamber (12); a second flow chamber (13) that communicates with the first flow chamber (12) via a flow orifice (15) that forms a valve seat; a linear-stroke actuator (20); a control rod (24) that extends axially into the first flow chamber (12); a valve gate (25) that is movable between a closed position and an open position; and a spring (50), which is mounted in series with the actuator (20), for controlling the position of the control rod (24).

Description

Adjustable automatic valve Technical Field

[0001] This presentation concerns an adjustable automatic valve and a circulation circuit. Such a valve can be used, in particular, in a liquid propellant circulation circuit for an engine, for example, a hydrogen-powered aircraft engine. Previous technique

[0002] To drastically reduce the carbon footprint of commercial aircraft, liquid hydrogen-powered aircraft engine projects are under development. However, using hydrogen in such an aircraft engine raises numerous technical implementation challenges. In particular, this hydrogen is generally stored and distributed in liquid form, and therefore at cryogenic temperatures, before potentially being heated prior to its admission into the engine's combustion chamber. While cryogenic propellant technology is now well-established in the space sector, it cannot be directly transposed to the aeronautical field due to the specific characteristics of this sector.

[0003] One of the challenges encountered concerns the fuel supply system and, more specifically, the pump within this system. Indeed, existing pumps used in the space sector are designed to provide relatively constant fuel flow rates: thus, these pumps have a limited number of operating points, which simplifies their design and allows for highly precise optimization of the pump to the operating conditions. Conversely, an aircraft engine must be able to operate in very different situations, with significantly different thrust regimes depending on the flight phase: taxiing, takeoff, cruise, landing, etc.

[0004] Due to the very low temperatures, on the order of 20 K, and very high pressures, on the order of 10 bar and potentially up to 70 bar, of the liquid hydrogen supplied by the engine's fuel system, the pump can may be required to operate in unstable operating ranges when the flow through the pump is too low.

[0005] Another challenge lies in designing valves capable of automatically controlling low flow rates, yet whose behavior can still be adjusted by an external control. Indeed, currently available automatic valves do not allow for such adjustment to control low flow rates as precisely as possible.

[0006] Finally, for aeronautical applications, the valve must be capable of performing a very large number of missions without degrading. Most valves used in the space sector are designed for only a single mission and therefore could not guarantee a satisfactory operating time for aeronautical applications.

[0007] There is therefore a real need for an adjustable automatic valve and a circulation circuit that are free, at least in part, from the disadvantages inherent in known configurations. Description of the invention

[0008] The present exposition relates to an adjustable automatic valve, comprising a first circulation chamber, configured to be connected to a first fluid line, a second circulation chamber, communicating with the first circulation chamber via a circulation orifice, forming a valve seat, and configured to be connected to a second fluid line, a linear stroke actuator, a control stem extending axially in the first circulation chamber, a plug, movable between a closed position, in which it is pressed against the valve seat, and an open position, in which it is at least partially away from the valve seat, the valve being configured so that the position of the plug is at least partially controlled by the position of the control stem, and a spring, mounted in series with the actuator to control the position of the control rod.

[0009] The spring allows the valve to automatically adjust its passage area according to the upstream pressure. The spring is designed to exert force, directly or indirectly, on the obturator in its resting direction, which can be either the opening or closing direction depending on the desired configuration. Conversely, the valve is configured so that the resultant pressure force in the upstream circulation chamber exerts force, directly or indirectly, on the obturator in the opposite direction to its resting direction. Thus, the position of the obturator, and therefore the valve's passage area, depends on the equilibrium point between these two forces and, consequently, on the fluid pressure upstream of the valve.

[0010] The actuator, by compressing the spring more or less for a given position of the valve, adjusts the elastic resistance force exerted by the spring against the fluid pressure forces. Thus, increasing the spring preload increases the spring resistance force and therefore raises the pressure threshold at which the fluid can move the valve in the opposite direction to its resting position. Such an actuator allows the automatic valve's behavior to be adjusted according to the upstream fluid pressure, enabling much finer control of the flow rate through the valve.

[0011] In some embodiments, the first fluid line and the second fluid line are cryotechnical fluid lines.

[0012] In this presentation, cryotechnical fluid means a fluid, preferably a liquid, whose temperature is below 120 K, preferably below 80 K, preferably below 30 K. The pressure of the cryotechnical fluid may exceed 2 bars, preferably 10 bars or even 50 bars.

[0013] In some embodiments, the cryotechnical fluid is a liquid propellant, for example liquid dihydrogen H2, liquid dioxygen O2, liquid dinitrogen N2, liquid helium He or liquid methane CH4.

[0014] In other embodiments, the first fluid line and the second fluid line comprise a fluid with a temperature between -40°C and 120°C. In such embodiments, the fluid pressure is preferably less than 15 bar, and even more preferably less than 10 bar. This fluid is preferably a liquid.

[0015] In some embodiments, the maximum flow rate of the valve is less than 100 g / s, preferably less than 50 g / s, and preferably even less than 10 g / s.

[0016] In some embodiments, the maximum hydraulic passage cross-section of the valve is less than 25 mm 2 preferably less than 10 mm 2 preferably even less than 5 mm 2 .

[0017] In some embodiments, the valve includes a control chamber in which the actuator is housed. Such a control chamber allows the actuator to be isolated from the fluid flow.

[0018] In some embodiments, the spring is also housed in the control chamber.

[0019] In some embodiments, the first circulation chamber communicates with the control chamber via a control port. In particular, the control rod can extend through the control port.

[0020] In some embodiments, the control chamber is maintained under vacuum or in a neutral atmosphere. This allows the actuator to be kept in a controlled environment conducive to its proper operation. In particular, this can help to thermally insulate the actuator from the circulating chambers. When the chamber is maintained under vacuum, the residual pressure within the chamber can be less than 30 mbar. When the chamber is maintained in a neutral atmosphere, it can be filled with one or more of the following gases: helium (He), nitrogen (N2), or hydrogen (H2).

[0021] In some embodiments, the temperature in the control chamber is greater than 50 K, preferably greater than 150 K.

[0022] In some embodiments, the actuator includes a piezoelectric actuator. Such an actuator, with its very short stroke, allows for particularly fine adjustment of the balancing spring preload and therefore of the valve's operating thresholds. This type of actuator is thus particularly well-suited for forming a valve that offers fine flow rate control. Depending on the application, this adjustment capability can override the automatic operation of the valve or simply allow for an offset in the automatic ranges. Furthermore, such an actuator has high stiffness, meaning that the valve's activation threshold depends almost exclusively on the actuator's control voltage. Open-loop control of the actuator can then be implemented without significant risk of drift.

[0023] In some embodiments, the piezoelectric actuator is equipped with a stroke amplifier, preferably of the pantograph type. Since the native stroke of a piezoelectric actuator is very short, such an amplifier amplifies the actuator's movement and thus increases the adjustment range.

[0024] In some embodiments, the maximum stroke of the actuator is less than 5 mm, preferably less than 1 mm, and even more preferably less than 0.5 mm. This maximum stroke is preferably measured after amplification when an amplifier is provided. The actuator is thus very precise and particularly suitable for a valve controlling low flow rates.

[0025] In some embodiments, the height of the control chamber, in the axial direction, is less than 15 cm, preferably less than 10 cm. The valve is thus particularly compact.

[0026] In some embodiments, the first circulation chamber is configured as the upstream chamber of the valve, while the second circulation chamber is configured as the downstream chamber. In such a case, it is understood that the pressure is higher in the first circulation chamber than in the second circulation chamber. However, the reverse configuration is also possible.

[0027] In some embodiments, the circulation orifice is circular, preferably centered approximately on the axis of the control rod. This facilitates centering the obturator on its seat and promotes a good seal of the obturator in the closed position. The diameter of this orifice can be, in particular, on the order of 6 mm.

[0028] In some embodiments, the obturator is installed in the first or second circulation chamber. When the obturator is installed in the upstream circulation chamber, the fluid pressure exerts a force on the obturator, tending to close the valve. This promotes centering of the obturator when it is free and ensures a good seal in the closed position.

[0029] In some embodiments, the shutter is fixed to the distal end of the control rod. The position of the shutter, and therefore the passage cross-section, is thus directly determined by the extension of the control rod and therefore by the actuator.

[0030] In some embodiments, the obturator is separate from the control rod. In such a configuration, the obturator is located in the upstream circulation chamber so that the fluid pressure tends to press the obturator against the control rod: in this way, the position of the obturator, and therefore the flow area, remains determined by the extension of the control rod. However, the obturator remains free to reposition itself and, in particular, to recenter itself on its seat in the closed position, even if the control rod is slightly off-center: this promotes good sealing of the obturator in its closed position.

[0031] In some embodiments, the obturator is retained in a cage provided in the first or second circulation chamber. Such a cage, perforated to allow fluid passage, prevents the obturator from making excessive excursions, even in the event of fluid flow instability.

[0032] In some embodiments, the shutter is axisymmetric. This facilitates centering and a good seal of the shutter.

[0033] In some embodiments, the shutter has a portion whose cross-section decreases in the axial direction, this portion preferably being a truncated cone or a truncated sphere.

[0034] In some embodiments, the obturator is a ball, preferably spherical. The diameter of the ball can be, in particular, on the order of 8 mm.

[0035] In some embodiments, the obturator is a cylindrical sleeve, closed at least at one of its axial ends, and whose peripheral surface includes at least one aperture. Such a cylindrical sleeve allows for better control of the valve's passage area as a function of the position of the control rod. In particular, it is possible to configure the geometry of said aperture to adjust the relationship determining the passage area as a function of the position of the cylindrical sleeve connected to the control rod.

[0036] In some embodiments, at least one opening in the cylindrical socket is rectangular or triangular. A rectangular opening results in a linear control law for the passage cross-section as a function of the position of the control rod, while a triangular opening results in a non-linear control law.

[0037] In some embodiments, the actuator is configured to continuously adjust its extension in the axial direction. The spring preload can thus be adjusted continuously and precisely.

[0038] In some embodiments, the valve includes a sensor configured to measure the position of the control rod. This may, in particular, be a position sensor taking the form, for example, of a Hall effect probe used in proximity measurement.

[0039] In some embodiments, the spring is axially interposed between the actuator and the control rod. In such a case, the actuator is preferably axially abutted against a fixed element of the valve.

[0040] In some embodiments, the spring is interposed between a fixed element of the valve and the actuator. In such a case, the actuator is in contact with the control rod.

[0041] In some embodiments, the spring comprises at least one spring washer, and preferably several stacked spring washers. Such spring washers are particularly compact and exhibit high stiffness, which is especially suitable when the shutter stroke is limited.

[0042] In some embodiments, the spring is housed in a cassette. Such a cassette can be used to radially lock the spring in order to prevent it from moving or deforming radially when compressed.

[0043] In some embodiments, the spring has a stiffness between 10 and 100 N / mm, preferably between 20 and 30 N / mm.

[0044] In some embodiments, the control rod includes a support plate at its proximal end. This support plate is preferably in direct contact with the actuator or spring. This support plate may or may not be fixed to the actuator or spring.

[0045] In some embodiments, the support plate forms a stop configured to limit the forward movement of the control rod. The support plate may, in particular, abut against the edge of the control orifice. Specifically, such a stop can define a maximum opening position for the obturator and thus a maximum passage area for the valve.

[0046] In some embodiments, the valve includes a bellows, which is both sealed and axially stretchable, surrounding the control stem. One end of the bellows is fixed to a wall of the first circulation chamber, and the other end is fixed to the control stem. The use of a sealed bellows allows for complete isolation of the actuator from the fluid flow and ensures better control of pressure balances within the valve, guaranteeing its automatic operation. Furthermore, this protects the actuator from direct contact with fluid that could damage it. In addition, this bellows allows for thermal decoupling, at least partially, of the actuator and the circulation chambers, while still allowing the control stem to move in conjunction with the obturator. Indeed, the bellows can stretch axially to follow the movement of the stem. control without breaking or compromising the seal. It is then possible to maintain a warmer environment at the actuator relative to the circulation chambers, enabling the use of an actuator that would otherwise be unable to operate at the fluid temperature, particularly when the fluid is cryogenic.

[0047] In some embodiments, the bellows wall is corrugated, with the corrugations running in succession along the axial direction. These corrugations provide the bellows with a degree of elasticity in the axial direction. Preferably, these corrugations are axisymmetric.

[0048] In some embodiments, the bellows has a resting length greater than 15 mm, preferably greater than 20 mm. Preferably, this resting length does not exceed 50 mm.

[0049] In some embodiments, the bellows has, at rest, a maximum outside diameter of between 6 and 10mm.

[0050] In some embodiments, the depth of the bellows corrugations is between 1 and 2 mm. "Corrugation depth" here refers to the difference between the diameter measured at the crests and the diameter measured at the troughs. Preferably, all the corrugations are identical.

[0051] In some embodiments, the bellows is hydroformed.

[0052] In some embodiments, the bellows is metallic, preferably made of steel. Such a metallic material is particularly capable of withstanding cryogenic temperatures when the fluid is cryogenic.

[0053] In some embodiments, the stiffness of the bellows, in the face of an axial extension force, is less than 30 N / mm.

[0054] In some embodiments, the first end of the bellows is fixed, preferably welded, to the wall of the first circulation chamber surrounding the control orifice.

[0055] In some embodiments, the second end of the bellows is fixed, preferably welded, to a flange extending radially from the control rod.

[0056] In some embodiments, the maximum diameter of the bellows is greater than the diameter of the circulation orifice. In this way, when the first circulation chamber is the upstream circulation chamber, the fluid pressure exerts a greater force on the bellows than on the obturator, which tends to close the valve when the upstream pressure increases. However, in other situations requiring different behavior, the opposite configuration would be possible.

[0057] In some embodiments, the first and second circulation chambers do not have elastomeric seals. This is preferable when the fluid is cryogenic, as an elastomeric seal would not withstand the temperature of a cryogenic fluid. Instead, polymer or metal-to-metal contact seals can be used.

[0058] The present exposition also relates to a circulation circuit, comprising a pump, having an inlet connected to an upstream line and an outlet connected to a downstream line, a recirculation line, extending from the downstream line to the upstream line, and a valve according to any of the preceding embodiments, installed on the recirculation line so as to control the flow of the recirculation line.

[0059] Thanks to such a recirculation line, it is possible to control the pump with a sufficiently high minimum flow rate to ensure stable operation. When this minimum flow rate exceeds the desired circulation flow rate, a portion of this excess flow can be redirected upstream of the pump to achieve the desired circulation flow rate downstream of the circulation circuit. Thus, if the desired flow rate is lower than the minimum stability flow rate, the pump is driven at the minimum stability flow rate, and the recirculation line valve is actuated by adjusting the initial compression, and therefore the spring resistance, to return the difference between the minimum stability flow rate and the desired circulation flow rate to the upstream line. If the desired flow rate is higher than the minimum stability flow rate, the pump is driven to ensure the desired circulation flow rate, and the valve is automatically closed under the effect of increasing pressure upstream of the valve and exceeding the resistance force of the spring.

[0060] A valve according to the present exposition then makes it possible to accomplish this function of fine regulation of the recirculation line.

[0061] In some embodiments, the upstream line and the downstream line are cryotechnical fluid lines.

[0062] In other embodiments, the upstream and downstream lines comprise a fluid with a temperature between -40°C and 120°C. In such embodiments, the fluid pressure is preferably less than 15 bar, and even more preferably less than 10 bar. This fluid is preferably a liquid.

[0063] In some embodiments, the pump is a centrifugal pump, preferably a turbopump or a pump driven by an electric motor.

[0064] In this exposition, the terms "front" and "distal" are understood, along the direction of the control rod, on the obturator side; the terms "rear" and "proximal" are then understood on the opposite side from the obturator.

[0065] The aforementioned features and advantages, as well as others, will become apparent upon reading the detailed description that follows, along with examples of the proposed valve and circulation circuit implementation. This detailed description refers to the attached drawings. Brief description of the drawings

[0066] The attached drawings are schematic and are primarily intended to illustrate the principles of the presentation.

[0067] In these drawings, identical elements (or parts of elements) are identified by the same reference symbols from one figure to the next. Furthermore, elements (or parts of elements) belonging to different embodiments but having a similar function are identified in the figures by numerical references incremented by 100, 200, etc.

[0068] [Fig. 1] Figure 1 represents an example of a circulation circuit.

[0069] [Fig. 2] Figure 2 represents a first example of a valve, in an open state.

[0070] [Fig. 3] Figure 3 represents the valve from Figure 2, in a closed state.

[0071] [Fig. 4] Figure 4 represents the valve from Figure 2, in another open state.

[0072] [Fig. 5] Figure 5 represents a second example of a valve, in an open state.

[0073] [Fig. 6] Figure 6 represents a third example of a valve, in an open state. Description of the implementation methods

[0074] To make the explanation more concrete, examples of circulation circuits and valves are described in detail below, with reference to the attached drawings. It should be noted that the invention is not limited to these examples.

[0075] Figure 1 shows an example of a cryogenic fluid circulation circuit 1; more specifically, it is a liquid propellant supply circuit for an aircraft engine. The supply circuit 1 comprises a propellant tank 2, a centrifugal feed pump 3, and a feed outlet 4 connected to the engine. An upstream line 3m connects the propellant tank 2 to the inlet of the feed pump 3; a downstream line 3v connects the outlet of the pump 3 to the feed outlet 4. In this example, the tank 2 contains liquid hydrogen (H2) stored at approximately 20 K; the pressure downstream of the pump 3 is on the order of 10 bar.

[0076] The supply circuit 1 further includes a recirculation line 5 connecting the downstream line 3v to the upstream line 3m bypassing the supply pump 3. A pilot valve 10 is positioned on this recirculation line 5.

[0077] Figure 2 illustrates an example of such a pilot-operated valve 10. This valve 10 comprises a control chamber 11, a first circulation chamber 12 and a second circulation chamber 13.

[0078] The first circulation chamber 12 extends from the control chamber 11, axially along a main axis A of the valve 10; a control orifice 14 is made, at the level of the main axis A, in the wall separating the first circulation chamber 12 from the control chamber 11.

[0079] The second circulation chamber 13 is provided in the extension of the first circulation chamber 12, in the axial direction; a circulation orifice 15 is made, at the level of the main axis A, in the wall separating the second circulation chamber 13 from the first circulation chamber 12. In the present example, the first circulation chamber 12 is the upstream chamber, thus connected to the downstream line 3v of the pump 3, and the second circulation chamber 13 is the downstream chamber, thus connected to the upstream line 3m of the pump 3.

[0080] An actuator 20, comprising a piezoelectric component 21 and an amplifier 22, is mounted in the control chamber 11. The piezoelectric component 21 extends in a direction orthogonal to the main axis A. The amplifier 22 takes the form of two pantographs 23, each mounted on an opposite face of the piezoelectric component 21. Each pantograph 23 thus comprises two elastic arms 23a, each fixed to an opposite end of the piezoelectric component 21 and joining at a central base 23b extending axially.

[0081] The piezoelectric component 21 has, at rest, a predetermined rest length; consequently, the actuator 20 as a whole has, at rest, a predetermined rest height, measured between the ends of the bases 23b of the two pantographs 23 of the amplifier 22. However, when an electrical voltage is applied to the piezoelectric component 21, the piezoelectric component 21 deforms so that its length increases or decreases according to the sign of the applied electrical voltage. When the length of the piezoelectric component 21 increases, the arms 23a of the pantographs are moved apart, which brings the bases 23b closer together and therefore decreases the height of the actuator 20. Conversely, when the length of the piezoelectric component 21 decreases, the arms 23a of the pantographs are moved closer together, which moves the bases 23b further apart and therefore increases the height of the actuator 20.

[0082] The rear base 23b of the amplifier 22 is supported, and possibly fixed, against the rear wall of the control chamber 11.

[0083] A control rod 24 extends axially along the main axis A. The control rod 24 includes at its proximal end a support plate 27 retained inside the control chamber 11, the diameter of the support plate 27 being greater than the diameter of the control orifice 14. From the support plate 27, the control rod 24 extends axially through the control orifice 14 and along the first circulation chamber 12, substantially to the circulation orifice 15.

[0084] An obturator 25, here taking the form of a spherical ball, is disposed in the second circulation chamber 13 and fixed to the distal end of the control rod 24. The obturator is thus positioned just opposite the circulation orifice 15 which forms a seat for said obturator 25.

[0085] A spring assembly 50, also housed in the control chamber 11, is interposed between the actuator 20 and the control rod 24. It comprises a cassette 51, having a cylindrical peripheral wall 52 and a bottom wall 53, and a plurality of spring washers 54 stacked axially inside the cassette 51. The front base 23b of the actuator 20 bears against the bottom wall 53 of the cassette 51, while the front washer 54 bears against the support plate 27 of the control rod 24. Since the actuator 20 is considered incompressible when an electrical voltage is applied to it, the spring assembly 50 therefore tends to push the control rod 24 forward and thus push the obturator 25 away from its seat 15, i.e., open the valve 10.

[0086] The valve 10 further includes a metal bellows 30, here made of stainless steel. The bellows 30, generally axisymmetric, comprises successive corrugations in the axial direction. The rear end 31 of the bellows 30 is fixed to the wall of the first circulation chamber 12 so as to surround the control orifice 14. The front end 32 of the bellows is fixed to a radial flange 33 integral with the control stem 24. The maximum diameter of the bellows 30 is greater than the diameter of the circulation orifice 15.

[0087] The bellows 30 thus isolates the control chamber 11, and therefore the actuator 20, from the propellant circulation present in the first circulation chamber 21. However, thanks to its undulations, the bellows has an elasticity which allows it to follow the movement of the control rod 24 without breaking.

[0088] In this example, the bellows 30 has a stiffness of 27 N / mm and a rest length of 20 mm; its maximum diameter, measured at the crests of the corrugations, is 8.5 mm.

[0089] In Figure 2, the actuator is in its least extended state, thus exhibiting a minimum height H min Furthermore, the support plate 27 of the control rod 24 is abutted against the control port 14, which means that the control rod 24, and therefore the obturator 25, are in their most advanced positions: the valve 10 is thus open and presents its maximum passage area. In this state, the spring assembly 50 has a maximum axial space E max between the actuator 20 and the control rod 24 and is therefore in its state of minimum compression: it therefore exerts a minimum elastic resistance force, or even zero if the maximum axial space E maxcorresponds to the rest length of the spring assembly 50.

[0090] When the pressure in the first chamber 12 increases, without any change in the actuator 20 control signal, the resultant pressure force tends to push the control rod 24 backwards. This is because the equivalent surface area of ​​the bellows 30 is greater than the equivalent surface area of ​​the obturator 25 as seen through the circulation orifice 15. Therefore, the fluid pressure exerts a greater force on the bellows 30, tending to push the control rod 24 backwards, than on the obturator 25, which tends to push the control rod 24 forwards.

[0091] This resultant of the pressure forces therefore opposes the elastic resistance force of the spring assembly 50. From a first pressure threshold, the resultant of the pressure forces reaches the minimum elastic resistance force of the spring assembly 50 and therefore begins to compress the latter, which drives the control rod 24 backwards and thus progressively closes the valve 10.

[0092] From a second pressure threshold, the resultant pressure force is sufficient to press the shutter 25 against its seat 15 despite the elastic resistance of the spring assembly 50. This closed state is then shown in Figure 3. In this state, the axial space available to the spring assembly 50 between the actuator 20 and the control rod 24 is equal to a first predetermined value E^

[0093] However, as shown in Figure 4, it is possible to control the actuator 20 to increase its extension, that is, to increase its height. Thus, in Figure 4, the actuator 20 has a maximum height H max- In such a case, the actuator 20 reduces the axial space available for the spring assembly 50 and therefore increases the preload exerted on the latter, in other words its initial compression before the application of pressure forces on the control rod 24. Thus, in figure 4, when the valve 10 is fully open, that is to say when the control rod 24 is in its most advanced position, the axial space available for the spring assembly 50 between the actuator 20 and the control rod 24 is equal to a second predetermined value E2. Therefore, by increasing the extension of the actuator 20, the elastic force of the spring assembly 50 is increased, which raises the first pressure threshold from which the obturator 25 begins to retract to reduce the passage section of the valve 10 and the second pressure threshold from which the obturator 25 is pressed against its seat 15 to completely close the valve 10.

[0094] Thus, by controlling the actuator 20, it is possible to adjust the behavior of the valve 10, that is to say, to modify its opening law according to the pressure of the upstream fluid.

[0095] In this example, the stiffness of the spring assembly 50, as a whole, is equal to 37 N / mm and its rest length is equal to 2 cm.

[0096] Figure 5 illustrates a second example of valve 110 quite similar to the first example except that the obturator 160 has a different configuration.

[0097] In this second example, the obturator 160 is no longer a ball but a cylindrical sleeve engaged in the circulation orifice 115 and whose diameter is adjusted to that of the circulation orifice 115. Just as in the first example, this obturator 160 is fixed to the distal end of the control rod 124.

[0098] Both ends of the socket 160 are closed. To allow fluid circulation from the first circulation chamber 112 to the second circulation chamber 113, the socket 160 includes at least one first opening 161, here rectangular in shape, in an area located within the first circulation chamber 112, regardless of the position of the socket 160; the socket 160 also includes at least one second opening 162 positioned to communicate with the second circulation chamber 113 at least in certain positions of the socket 160. More precisely, the second openings 162, here triangular, are positioned such that their surface area in contact with the second circulation chamber 113 increases progressively as the socket 160 is advanced into the second circulation chamber 113.The sleeve 160 further includes a shoulder 163 at its distal end designed to butt against the circulation orifice 115 in the closed position of the valve.

[0099] Furthermore, the operation of this valve 110 is entirely analogous to that of the first example. In particular, since the diameter of the sleeve 160 is smaller than that of the bellows 130, the resultant pressure force tends to push the control rod 124 backwards against the elastic resistance force of the spring assembly 150.

[0100] Figure 6 illustrates a third example of valve 210 quite analogous to the first example except that the circulation in valve 210 is reversed, the upstream chamber being the second circulation chamber 213; another difference concerns the obturator 225 which is not fixed to the distal end of the control rod 224.

[0101] Thus, in this example, the obturator 225 is free, meaning it is not fixed to the end of the control rod 224. The position of the obturator 225 is nevertheless constrained by the position of the control rod 224, which, depending on its position, may prevent the obturator 225 from pressing against the circulation orifice 215. Furthermore, a cage 226, installed in the second circulation chamber 213 and in which the obturator 225 is housed, allows the obturator 225 to be retained radially.

[0102] In this example, the resultant of the pressure forces in the upstream chamber, i.e. the second circulation chamber 213, tends to push the obturator 225 against its seat 215 and therefore against the control rod 224: thus, the resultant of the pressure forces tends to push the control rod 224 backwards against the elastic resistance force of the spring assembly 250, in a manner entirely analogous to the first example.

[0103] Although the present invention has been described with reference to specific embodiments, it is evident that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

[0104] It is also evident that all the characteristics described with reference to a process are transposable, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a process.

Claims

Claims

1. Adjustable automatic valve, comprising a first circulation chamber (12), configured to be connected to a first fluid line (3v), a second circulation chamber (13), communicating with the first circulation chamber (12) via a circulation orifice (15), forming a valve seat, and configured to be connected to a second fluid line (3m), a linear stroke actuator (20), a control rod (24) extending axially in the first circulation chamber (12), a shutter (25), movable between a closed position, in which it is pressed against the valve seat (15), and an open position, in which it is at least partially at a distance from the valve seat (15), the valve (10) being configured so that the position of the shutter (25) is at least partly controlled by the position of the control rod (24), and a spring (50),mounted in series with the actuator (20) to control the position of the control rod (24) a bellows (30), sealed while being axially stretchable, surrounding the control rod (24), a first end (31) of the bellows (30) being integral with a wall of the first circulation chamber (12), and a second end (32) of the bellows (30) being integral with the control rod (24) in which the first circulation chamber (12) is configured to constitute the upstream chamber of the valve (10) while the second circulation chamber (13) is configured to constitute the downstream chamber of the valve (10).,

2. A valve according to claim 1, wherein the first fluid line (3v) and the second fluid line (3m) are cryogenic fluid lines.

3. A valve according to claim 1 or 2, wherein the actuator (20) comprises a piezoelectric actuator (21).

4. Valve according to claim 3, wherein the piezoelectric actuator (21) is equipped with a stroke amplifier (22), preferably of the pantograph type.

5. A valve according to any one of claims 1 to 4, wherein the spring (50) is interposed axially between the actuator (20) and the control rod (24), or wherein the spring (50) is interposed between a fixed element of the valve (10) and the actuator (20).

6. Valve according to any one of claims 1 to 5, in which the spring (50) comprises at least one spring washer (54), and preferably several stacked spring washers (54), and in which the spring is housed in a cassette (51).

7. Valve according to any one of claims 1 to 6, in which the spring (50) has a stiffness of between 10 and 100N / mm, preferably between 20 and 30N / mm.

8. Valve according to one of claims 1 to 7, in which the maximum diameter of the bellows (30) is greater than the diameter of the circulation orifice (15).

9. Circulation circuit, comprising a pump (3), having an inlet connected to an upstream line (3m) and an outlet connected to a downstream line (3v), a recirculation line (5), extending from the downstream line (3v) to the upstream line (3m), and a valve (10) according to any one of the preceding claims, installed on the recirculation line (5) so as to control the flow rate of the recirculation line (5).

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