Compressible actuation arm for relief valve

Abstract

The invention relates to an actuating arm (1) for a relief valve (2) of a turbomachine comprising a relief gate (4) intended to be pivoted by the actuating arm between a closed position of a relief air inlet orifice (5) and an open position of said orifice, the orifice being provided in an intermediate housing (6), the relief valve comprising a seal (7) configured to bear against the relief gate when it is in the closed position, the actuating arm being compressible and having a variable length between an initial length when the relief gate is in the open position and a reduced length, less than the initial length, when the relief gate is in the closed position and the actuating arm is compressed so that the force exerted by the relief gate on the seal is less than a defined force threshold. Fig. 3.

Description

Title of the invention: Compressible actuating arm for a relief valve. Technical field

[0001] The field of the invention is that of turbomachine crankcase relief valves, and in particular of intermediate turbomachine crankcase relief valves.

[0002] The present invention relates more particularly to an actuating arm of a turbomachine relief valve, and to a turbomachine valve comprising such an actuating arm. Previous technique

[0003] In a turbomachine, blow-off valves, also known by their acronym VDV for Variable Blow-Off Valve (or VBV for "Variable Blow-Off Valve"), are generally mounted on the hub of an intermediate housing of a turbofan engine, positioned between the low-pressure compressor and the high-pressure compressor. The blow-off valves are positioned in an annular interflow space of the intermediate housing hub extending between a main flow channel (primary channel) in which a primary airflow circulates and a secondary flow channel (secondary channel) in which a secondary airflow circulates.

[0004] Their opening and closing then serve to regulate an air leakage rate according to the conditions of use of the turbomachine, for example to avoid pumping.

[0005] These relief valves are regularly distributed on the hub of the intermediate housing around the longitudinal axis of the turbomachine and each includes a gate mounted pivoting about an axis, so as to be angularly movable relative to the intermediate housing, between a closed position in which the gate closes an air passage orifice provided in the hub of the intermediate housing and an open position of this orifice.

[0006] A control ring is positioned outside the flow between the compressor housing and an external cover of the turbomachine and allows the opening and closing of the discharge gates to be controlled. Rotation of this ring actuates actuation devices comprising actuating levers which cause the discharge gates to pivot.

[0007] The discharge valves ensure a seal between the primary and secondary veins in their closed position and allow the evacuation of part of the primary airflow from the primary vein under certain conditions of operation in their open position. The portion of the primary airflow taken from the intake is either reinjected into the secondary airflow, or used to supply cooling systems or to ventilate turbomachine components.

[0008] To ensure a seal between the primary and secondary streams in the closed position of the discharge gates, the wall of the intermediate housing bordering the air passage orifice has a compressible seal, for example made of elastomer, extending around the perimeter of the wall bordering the orifice. The seal is designed to bear against the peripheral edges of each gate in the closed position of the discharge valve.

[0009] The mechanism of each relief valve is configured so that the relief gate compresses the sealing ring at a calibrated compression ratio sufficient to stop the air between the relief gate and the sealing ring. The angular position of the relief gate relative to the intermediate housing is calibrated.

[0010] Such discharge valves are known from document FR3119416B1.

[0011] However, the relief valve mechanism can sometimes malfunction due to wear in the mechanical linkages, for example, creating play between the parts and causing the relief gate's position to shift from its initially calibrated position when closed. The relief gate closes more than intended. The relief gate moves closer to the surface supporting the seal, resulting in over-compression of the seal, which can lead to direct contact between the relief gate and the intermediate housing.

[0012] This contact generates wear between the parts and unwanted stresses that can lead to overstress between the parts, even to the point of their breaking.

[0013] When these wears are detected, the parts must be disassembled and replaced, which leads to heavy and costly maintenance operations. Description of the invention

[0014] The invention therefore aims to resolve at least in part these drawbacks by proposing an actuation arm for a relief valve of an aircraft turbomachine avoiding over-compression of the sealing gasket by the relief gate and consequently premature wear of the parts.

[0015] The invention relates to an actuating arm for a relief valve of an aircraft turbomachine, the relief valve comprising a relief gate intended to be pivoted by the actuating arm between a closed position of a relief air inlet orifice and an open position of said orifice, the orifice being provided in an intermediate housing of the turbomachine, the relief valve comprising a sealing gasket configured to bear against the discharge gate when the discharge gate is in the closed position, the actuating arm being a compressible actuating arm having a variable length between an initial length when the discharge gate is in the open position and a reduced length, less than the initial length, when the discharge gate is in the closed position and the actuating arm is compressed so that the force exerted by the discharge gate on the sealing joint is less than a defined force threshold.

[0016] The invention thus provides an actuating arm for a relief valve of an aircraft turbomachine that prevents excessive force from the relief gate on the seal when the mechanism wears and malfunctions, and therefore prevents over-compression of the seal by the relief gate. The actuating arm retracts to compensate for this excessive force. In other words, the actuating arm compresses before the seal is over-compressed.

[0017] The adjustment of the actuating arm length is automatic and depends on the level of wear and therefore the misalignment of the actuating device. To maintain a constant compression ratio of the sealing gasket and prevent exceeding a desired limit, the stroke of the actuating arm varies automatically. The more the actuating device becomes misaligned over time, the more the length of the actuating arm is reduced in the closed position to compensate for this misalignment.

[0018] Contact between the intermediate housing and the discharge gate is avoided, which consequently prevents premature wear of the parts, or even their breakage.

[0019] The parts no longer need to be disassembled and replaced, which reduces maintenance costs.

[0020] The actuating arm according to the invention has the same interfaces as a conventional actuating arm and is therefore easily and quickly interchangeable with a conventional actuating arm.

[0021] According to one variant, the actuating arm comprises a first arm having a first end intended to be connected to a control ring of the intermediate housing by a first pivot link and a second arm having a second end intended to be connected to the discharge gate by a second pivot link, the first and second arms being mounted to slide relative to each other along a main axis and being connected to each other by a compressible device.

[0022] According to one variant, the compressible device is a compression spring comprising a first end connected to the first arm and a second end connected to the second arm.

[0023] According to one variant, the first end of the spring is against a first stop of the first arm, the second end of the spring being against a second stop of the second arm.

[0024] According to one variant, the force threshold is reached when the sealing joint is compressed with a compression ratio of less than 30%.

[0025] According to one variant, the stiffness of the spring is calibrated so that the force causing the compression of the spring, when the force threshold is reached, is less than 5% of the force exerted by the discharge gate on the sealing gasket.

[0026] According to one variant, the compressible device is an air or gas compressible device.

[0027] The invention also relates to a discharge valve comprising a discharge gate mounted pivoting about an axis and an actuating arm as defined above, the actuating arm connecting the discharge gate to a control ring connected to at least one actuator actuating the pivoting of the discharge gate between a position of closing an air passage orifice and an opening position of said orifice.

[0028] The invention also relates to an intermediate turbomachine casing comprising a plurality of relief valves as defined above and intended to open and close a plurality of air passage orifices.

[0029] The invention also relates to a turbomachine comprising a low pressure compressor, a high pressure compressor and an intermediate casing as defined above, positioned longitudinally between the low pressure compressor and the high pressure compressor.

[0030] The aforementioned features and advantages, as well as others, will become apparent from the following detailed description of an example embodiment of the actuating arm. This detailed description refers to the accompanying drawings. Brief description of the drawings

[0031] The attached drawings are schematic and are intended primarily to illustrate the principles of the exposition.

[0032] On these drawings, from one figure to another, identical elements (or parts of elements) are identified by the same reference signs.

[0033] [Fig.1] Fig.1 schematically represents, in axial section, a double-flow turbomachine to which the invention applies;

[0034] [Fig.2] Fig.2 schematically represents a turbomachine control ring comprising relief valves;

[0035] [Fig.3] The [Fig.3] schematically represents a simplified axial cross-sectional view of a portion of an intermediate housing on which a turbomachine discharge valve is mounted, in the closed position, comprising an actuating arm, according to an embodiment of the invention;

[0036] [Fig.4] The [Fig.4] schematically represents the actuation arm of the [Fig.3]. Description of the implementation methods

[0037] To make the explanation more concrete, an example of an actuating arm is described in detail below, with reference to the accompanying drawings. It should be noted that the invention is not limited to this example.

[0038] An actuation arm to which the invention relates is, for example, installed in an aircraft turbomachine, in particular a double-flow turbomachine, comprising a low-pressure compressor.

[0039] In the present invention, and more generally, the terms "upstream," "downstream," "axial," and "axially" are defined with respect to the gas flow in the turbomachine and here along the longitudinal axis X (and even from left to right in [Fig. 1]). Similarly, the terms "radial," "internal," and "external" are defined with respect to a radial axis Y perpendicular to the longitudinal axis X and with respect to the distance from the longitudinal axis X.

[0040] As illustrated in [Fig.1], which is a schematic axial cross-sectional view of a twin-flow or twin-body turbomachine 3, such a turbomachine 3 generally comprises, from upstream to downstream along the direction of gas flow, a low-pressure compressor 20, a high-pressure compressor 21, a combustion chamber 22, a high-pressure turbine 23 and a low-pressure turbine 24, which define a flow path of a primary gas flow Fl.

[0041] The high-pressure turbine 23 is integral with the high-pressure compressor 21 so as to form a high-pressure body, while the low-pressure turbine 24 is integral with the low-pressure compressor 20 so as to form a low-pressure body, so that each turbine drives the associated compressor in rotation around the longitudinal axis 25 of the turbomachine 3 under the effect of the thrust of the gases from the combustion chamber 22.

[0042] In such a turbomachine 3, an intermediate casing 6 is usually interposed between the upstream low-pressure compressor 20 and the downstream high-pressure compressor 21. The intermediate casing 6 has a generally cylindrical or frustoconical shape.

[0043] In the case of double-flow turbomachinery, which includes a fan 26 shrouded by a nacelle 27 to generate a secondary flow F2, the intermediate casing 6 generally includes arms 28 crossing the flow path of this secondary flow F2.

[0044] Figure 3 illustrates a simplified view of an intermediate housing 6 on which relief valves 2 are mounted at the hub 29 of the intermediate housing 6. This hub 29 comprises two coaxial annular ferrules, respectively internal 30 and external 31, and two radial walls or flanges, respectively upstream 32 and downstream (not represented), connecting the internal annular ferrules 30 and external 31. The internal annular ferrule 30 delimits the external part with respect to the longitudinal axis 25 of the primary flow space, or primary vein, of the primary flow Fl of the turbomachine.

[0045] Furthermore, this hub 29 is equipped with an annular row of relief valves 2, one of which is visible in cross-section in [Fig. 3]. This figure shows more specifically a relief gate 4 of the relief valve 2, which is pivotally mounted about a transverse axis A, so as to be movable between an open position and a closed position of a relief air inlet orifice 5 formed in the internal annular ferrule 30 of the hub 29.

[0046] Each of the discharge air inlet ports 5, of substantially parallelepiped shape, is associated with a discharge valve 2 intended for regulating the flow of the high-pressure compressor 21.

[0047] As illustrated in [Fig. 2], the intermediate housing 6 includes a control device for opening and closing the discharge gates 4, comprising a control ring 33 which is circular and one-piece, allowing the opening or closing of the discharge gates 4 to be controlled according to the operating conditions of the turbomachine 3. This control ring 33 is centered on the longitudinal axis 25 of the turbomachine 3 and is located in the space surrounding the intermediate housing 6. The rotation of the control ring 33 is effected by one or more actuators 34 which are also located outside the intermediate housing 6. The rotation of the control ring 33 actuates actuation devices 35, each comprising an actuating arm 1 which drives the discharge gates 4.The actuation devices 35 also include an L-shaped lever arm 36, called a puppet, connected to the control ring 33 and to a first end 10 of the actuation arm 1 by a first pivot linkage 13.

[0048] Thus, for each discharge gate 4, an actuating arm 1 is fixed by a lever arm 36 to the control ring 33, so as to transform the rotational movement of the control ring 33 around the longitudinal axis 25 of the intermediate housing 6 into an opening or closing movement of the discharge gate 4. The lever arm 36 is arranged to form a suitable connection between the control ring 33 and the actuating arm 1. Here, it is a pivot connection around a substantially radial axis between the control ring 33 and the lever arm 36.

[0049] The closing movement of the control ring 33 causes a push on the actuating arm 1 towards the discharge gate 4 and the rotation of the discharge gate 4 around the transverse axis A until the orifice 5 is closed.

[0050] The opening movement of the control ring 33 causes a pull on the actuating arm 1, in a direction opposite to the discharge gate 4, and the rotation of the discharge gate 4 around the transverse axis A to open the orifice 5.

[0051] The opening of each discharge valve 2 results in the discharge of an airflow 37 (dashed arrow) into the annular space delimited by the annular ferrules 30, 31 and the radial walls 32. Each discharge gate 4 includes at least one discharge conduit 52 intended to guide the airflow 37 from the orifice 5.

[0052] Each discharge gate 4 has a substantially parallelepiped shape complementary to that of the corresponding discharge air inlet 5. The discharge gate 4 functions to ensure a seal between the primary flow Fl and the secondary flow F2 and to allow a discharge flow between the primary flow Fl and the secondary flow F2 according to a control program for the discharge valve 2.

[0053] The discharge gate 4 is configured to pivot about the transverse axis A which is substantially tangent to the intermediate housing 6. The transverse axis A extends substantially along the downstream peripheral edge of the discharge gate 4.

[0054] The discharge gate 4 is therefore angularly mobile by pivoting around the transverse axis A between the obturating, or closed, position and the opening position of this orifice 5.

[0055] In the closed position, the inner surface 38 of the discharge gate 4 is aligned with the surface 39 of the inner annular ferrule 30 of the intermediate housing 6.

[0056] In the open position, the discharge gate 4 is inclined at an angle of approximately 60° inwards towards the intermediate housing 6 relative to its closed position. Thus, the discharge gate 4 is configured to protrude radially inwards towards the intermediate housing 6 in the open position, defining a scooping volume.

[0057] In order to ensure the sealing of the primary vein in the closed position of the discharge gate 4, the latter includes a sealing gasket 7 mounted on the intermediate housing 6. The sealing gasket 7 is in contact with an outer face 43 of the discharge gate 4 when the gate is in the closed position.

[0058] The sealing gasket 7 extends longitudinally in a transverse direction that is substantially tangent to the intermediate housing 6 and extends substantially along an upstream peripheral edge 42 of the discharge gate 4 so as to bear against it in the closed position of the discharge gate 4 illustrated in [Fig. 3]. The sealing gasket 7 has, along its entire length, a ridge or a domed portion 40 directed towards the interior of the intermediate housing 6 and intended to be compressed by the discharge gate 4 when the latter is in the closed position in order to ensure the sealing of the discharge valve 2.

[0059] A flat face of the sealing gasket 7 opposite the domed part 40 is held to a support 41 of the intermediate housing 6.

[0060] The actuating arm 1 is a compressible actuating arm 1 having a variable length between an initial length when the discharge gate 4 is in the open position and a reduced length when the discharge gate 4 is in the closed position and the actuating arm 1 is compressed. The actuating arm 1 is compressed so that the force exerted by the discharge gate 4 on the sealing gasket 7 is less than a defined force threshold. The reduced length is, for example, less than the initial length.

[0061] The actuating arm 1 extends along a principal axis L. The actuating arm 1 is in a deployed position when the discharge gate 4 is in the open position. The actuating arm 1 is in a retracted position when the discharge gate 4 is in the closed position and the discharge gate 4 exerts a force on the sealing gasket 7 that exceeds a defined force threshold.

[0062] The actuating arm 1 compresses from the open position of the discharge gate 4 to the closed position of the discharge gate 4 and extends from the closed position to the open position. The length of the actuating arm 1 varies along the principal axis L. In the closed position, the length of the actuating arm 1 can be reduced by up to 30% of its initial length, and preferably by between 5% and 15% of its initial length. The initial length of the actuating arm 1 corresponds to its length when extended in the open position. Preferably, the length of the actuating arm 1 is reduced by 10%.

[0063] The force threshold is defined in relation to a maximum compression of the sealing gasket 7 that must not be exceeded to avoid over-compression of the gasket. The force threshold is defined in relation to the force that must be applied to the sealing gasket 7 to reach this maximum compression.

[0064] For example, the force threshold is reached when the sealing gasket 7 is compressed by a compression ratio of less than 30%. Preferably, the force threshold is reached when the sealing gasket 7 is compressed by a compression ratio of less than 20%. The force threshold can be reached when the sealing gasket 7 is compressed by 5%, for example.

[0065] As illustrated in [Fig. 4], the actuating arm 1 comprises a first arm 8 having a first end 10, connected to the control ring 33 of the intermediate housing 6 via the lever arm 36 and the first pivot joint 13, and a second arm 9 having a second end 11, connected to the discharge gate 4 by a second pivot joint 14. The first and second arms 8, 9 are mounted to slide relative to each other along the main axis L and are connected to each other by a compressible device. The compressible device is elastic.

[0066] In this example, the second arm 9 slides inside the first arm 8.

[0067] Alternatively, the reverse is also possible. The first arm can slide to the inside of the second arm.

[0068] In this example, the first arm 8 includes a first portion 44 connected to the first end 10. The first end 10 includes a first hole 46 through which a first axis B passes to form the first pivot joint 13.

[0069] The first arm 8 comprises a second portion 45 hollow at one end opposite to the first end 10. The second portion 45 is connected to the first portion 44. The second portion 45 has a diameter greater than the diameter of the first portion 44.

[0070] The second arm 9 includes a first portion 47 connected to the second end 11. The second end 11 includes a second hole 49 through which a second axis C passes to form the second pivot joint 14. The second arm 9 includes a second portion 48 connected to the first portion 47 of the second arm 9.

[0071] The first and second arms 8, 9 have a circular cross-section. An oval cross-section is also possible. The second portion 45 comprises a cylindrical cavity.

[0072] The second portion 48 of the second arm 9 has a diameter smaller than that of the cavity of the second portion 45 of the first arm 8 so as to be inserted into the cavity and slide inside it.

[0073] The compressible device is a compression spring 15 comprising a first end 16 connected to the first arm 8 and a second end 17 connected to the second arm 9.

[0074] The spring 15 is helical and surrounds the second portion 45 of the first arm 8 and the second portion 48 of the second arm 9.

[0075] The first arm 8 includes a first washer 50 positioned between the first and second portions 44, 45 of the first arm 8 and projecting around the first arm 8. The second arm 9 includes a second washer 51 positioned between the first and second portions 47, 48 of the second arm 9 and projecting around the second arm 9.

[0076] The first end 16 of the spring 15 is against the first washer 50 forming a first stop 18 of the first arm 8. The second end 17 of the spring 15 is against the second washer 51 forming a second stop 19 of the second arm 9.

[0077] The stiffness of the spring 15 is calibrated so that the force causing the compression of the spring 15, when the force threshold is reached, is less than 5% of the force exerted by the discharge gate 4 on the sealing gasket 7.

[0078] Alternatively, the spring 15 can be a torsion spring or a flexural leaf spring.

[0079] Thus, when the discharge gate 4 is in the closed position, the second Portion 48 of the second arm 9 slides inside the second portion 45 of the first arm 8, causing the first and second pucks 50 to move closer together, 51. The spring 15 is then compressed, reducing the length of the actuating arm 1 so that the sealing gasket 7 is not over-compressed, i.e. compressed according to a maximum compression ratio not to be exceeded, so as to ensure good sealing and not to wear out parts such as the sealing gasket 7.

[0080] The length of the actuating arm 1 is automatically adjusted by compressing the spring 15 and is a function of the degree of misalignment of the actuating device. To maintain a constant compression ratio of the sealing gasket 7, the stroke of the actuating arm 1 varies automatically. The more the actuating device becomes misaligned over time, the more the length of the actuating arm 1 is reduced in the closed position to compensate for this misalignment.

[0081] When the discharge gate 4 returns to the open position, the spring 15 pushes back the first and second washers 50, 51 until the actuating arm 1 returns to its initial length.

[0082] Preferably, the actuating arm 1 is initially mounted so that it is not retracted in the closed position. Its retraction occurs only when the relief valve mechanism 2 begins to malfunction.

[0083] The actuating arm 1 behaves like a conventional, one-piece actuating arm 1 when it is in the open position.

[0084] Optionally, the actuating arm 1 can be initially mounted so as to be already retracted in the closing position.

[0085] The actuation arm 1 makes it possible to avoid having to carry out maintenance when the mechanism malfunctions.

[0086] Alternatively, the actuating arm 1 may include two adjustment devices at its respective ends 10, 11, allowing the length of the actuating arm 1 to be preset during assembly. Each end 10, 11 may be screwed into the respective arms 8, 9 to reduce the length of the actuating arm 1 or unscrewed to increase the length of the actuating arm 1.

[0087] Alternatively, the compressible device is an air or gas compressible device (not shown).

[0088] 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 a restrictive sense.

Claims

Demands

1. An actuating arm (1) for a relief valve (2) of an aircraft turbomachine (3), the relief valve (2) comprising a relief gate (4) for pivoting by the actuating arm (1) between a closed position of a relief air inlet orifice (5) and an open position of said orifice (5), the orifice (5) being provided in an intermediate housing (6) of the turbomachine (3), the relief valve (2) comprising a sealing gasket (7) configured to bear against the relief gate (2) when the relief gate (4) is in the closed position, the actuating arm (1) being a compressible actuating arm (1) having a variable length between an initial length when the relief gate (4) is in the open position and a reduced length, less than the initial length,when the discharge gate (4) is in the closed position and the actuating arm (1) is compressed so that the force exerted by the discharge gate (4) on the sealing gasket (7) is less than a defined force threshold.

2. Actuating arm (1) according to claim 1, comprising a first arm (8) having a first end (10) intended to be connected to a control ring (33) of the intermediate housing (6) by a first pivot link (13) and a second arm (9) having a second end (11) intended to be connected to the discharge gate (4) by a second pivot link (14), the first and second arms (8, 9) being mounted to slide relative to each other along a main axis (L) and being connected to each other by a compressible device.

3. Actuating arm (1) according to claim 2, wherein the compressible device is a compression spring (15) comprising a first end (16) connected to the first arm (8) and a second end (17) connected to the second arm (9).

4. Actuating arm (1) according to claim 3, wherein the first end (16) of the spring (15) is abutted against a first stop (18) of the first arm (8), the second end (17) of the spring (15) being abutted against a second stop (19) of the second arm (9).

5. Actuating arm (1) according to any one of claims 1 to 4, wherein the force threshold is reached when the sealing joint (7) is compressed with a compression ratio of less than 30%.

6. Actuating arm (1) according to any one of claims 3 to 5, wherein the stiffness of the spring (15) is calibrated so that the force causing compression of the spring (15), when the force threshold is reached, is less than 5% of the force exerted by the relief gate (4) on the sealing gasket (7).

7. Actuating arm (1) according to claim 2, wherein the compressible device is an air or gas compressible device.

8. Discharge valve (2) comprising a discharge gate (4) mounted pivotally about an axis (A) and an actuating arm (1) as defined according to any one of claims 1 to 7, the actuating arm (1) connecting the discharge gate (4) to a control ring (33) connected to at least one actuator (34) actuating the pivoting of the discharge gate (4) between a closed position of an air passage orifice (5) and an open position of said orifice.

9. Intermediate housing (6) of turbomachine (3) comprising a plurality of relief valves (2) as defined according to claim 8 and intended to open and close a plurality of air passage orifices (5).

10. Turbomachine (3) comprising a low pressure compressor (20), a high pressure compressor (21) and an intermediate casing (6) according to claim 9, positioned longitudinally between the low pressure compressor (20) and the high pressure compressor (21).

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