METHOD FOR DIAGNOSING A DECONGESTING CONDITION OF A DOOR LOCK

Description

[0001] The invention relates to latching boxes such as those used in aircraft for retaining landing gear or hatches in the retracted position, and more particularly relates to a method for diagnosing a state of degradation of such a latching box.

[0002] The invention also relates to a hydraulic supply circuit for a cylinder to implement such a method. BACKGROUND OF THE INVENTION

[0003] Aircraft are known to have retractable landing gear, cargo bays for storing these landing gear while the aircraft is in flight, and hatches for closing these bays. The deployment and retraction of the landing gear, as well as the opening and closing of the hatches, are performed using actuators such as hydraulic cylinders.

[0004] When the lander reaches the retracted position, it is automatically held in that position by one or more locking mechanisms. The same applies when the hatch reaches the closed position.

[0005] In a manner known per se, the hooking housing includes a hook mounted pivoting between a release position and a retention position of an olive fixed to the lander or hatch, and a locking member which is returned by a spring to a locking position of the hook when it is brought into the retention position, and which is pushed back by a release actuator to allow the hook to pivot to a release position and thus release the olive.

[0006] The unlocking actuator typically comprises a hydraulic cylinder with a body inside which a rod associated with a piston can slide. The rod is arranged to act on the locking mechanism, pushing it back to an unlocked position.

[0007] US patent 2020 / 377224 A1 discloses an example of a known hook box. Furthermore, according to this patent, if a lower hooked portion of the hook breaks structurally, the olive will fall and, under the force of a spring, an indicator lever will rotate until it contacts a stop, and the indicator lever will be spaced from a sensor.

[0008] The proper functioning of the locking mechanism, and in particular its unlocking performance, can be defined by the level of actuation force required by the cylinder to release the olive. This level of force is characterized in particular by the friction generated in the connections and contacts between the various parts composing the locking mechanism (seals carried by the piston, pivot connection of the locking element and the hook, contact between the locking element and the hook, etc.).

[0009] It is known that minimizing friction by applying grease / lubricant ensures the proper functioning of the coupling housing and protects it from wear. This application requires opening the coupling housing and is generally carried out according to a regular maintenance schedule, corresponding to preventive maintenance performed according to predetermined criteria (service life, number of cycles performed, etc.) with the aim of reducing the probability of coupling housing failure. This type of maintenance requires, in particular, knowledge of the coupling housing's behavior, its modes of degradation, and the mean time between failures, and does not allow for optimizing the frequency of coupling housing maintenance operations.This would require precisely characterizing the behavior of the attachment box in various environments that are dependent on the operating conditions of the aircraft by the company that operates it.

[0010] To overcome these drawbacks, predictive maintenance was considered, consisting of measuring the pressure in the cylinder of the mounting box to monitor the actuation force in real time, and defining a pressure threshold from which a maintenance operation must be carried out.

[0011] However, the pressure build-up rate of a hook-type cylinder is generally very high (greater than 1000 bar per second). This is due to the small volume of fluid compressed by the piston and results in a very rapid unlocking of the hook. This speed makes it difficult to observe the time and pressure of the hook unlocking.

[0012] THEfigures 1A et 1B illustrate two examples of pressure evolution in a mounting housing cylinder. The figure 1A This corresponds to a normal operating state of the latching mechanism, for which the unlocking time and pressure are approximately equal to 1.07 seconds and 60 bar, respectively. figure 1B corresponds to a degraded operating state of the hooking box (friction has increased between internal parts composing the hooking box following, for example, a lack of maintenance of said hooking box) for which the unlocking time and pressure are respectively approximately equal to 1.16 seconds and 160 bars.

[0013] Between the normal operating state and the degraded operating state, the difference in unlocking time is less than 100 milliseconds, so an observation frequency greater than 100 Hertz would be required at the lander computer level to ensure relevant detection of the degradation of the docking box.

[0014] However, the execution frequency of such a computer is generally around 12.5 Hertz. Increasing it would result in an increase in the computer's load (generally referred to as CPU load, from the English "Central Processing Unit") and therefore a larger computer.

[0015] According to document DE 102 51 821 B3, a hydraulic supply circuit for a cylinder is known, the circuit including a delay valve. A pressurized fluid source is connected, via an inlet port, to a supply port of the delay valve, which leads, on one side, via a restrictor, to a spool and, on the other side, to an outlet valve. As soon as the pressurized fluid source applies a control pressure to the supply port, the spool is pushed until it reaches its final position, actuating an actuation element on the outlet valve and opening it. If the outlet valve is open, the inlet port is connected, via the supply port and via the outlet valve, to an outlet port intended to be connected to the cylinder. SUBJECT OF THE INVENTION

[0016] The invention aims to provide a solution that at least partially remedies the aforementioned drawbacks. SUMMARY OF THE INVENTION

[0017] To this end, a method is proposed for diagnosing a state of degradation of a retaining housing for the retention of an olive of a moving element, the retaining housing comprising: a pivoting hook between a release position and a retention position of the olive; a pivoting locking member between a locking position in which the hook is immobilized in the retention position by the locking member, and an unlocking position in which the hook is free to move under the push of the olive of the moving element; and an unlocking actuator comprising a hydraulic cylinder supplied to act on the locking member in order to push it back towards the unlocking position.

[0018] According to the invention, the method comprises, during a sequence of release of the hook immobilized in the retained position by the locking member, the following steps: a) supply the cylinder with pressurized fluid with a law of evolution according to which the fluid pressure is, for a predetermined time, less than a full pressure, then equal to the full pressure; b) determine a release time of the hook and compare it to the time when the predetermined time ends; c) deduce from the comparison made in step b) a state of degradation of the hook housing.

[0019] By delaying the application of full pressure in the cylinder chamber, this method allows for the diagnosis of degraded unlocking performance in the hook housing before the unlocking function is completely lost. This enables scheduling maintenance of the hook housing, thus preventing a latent failure. This detection of degraded unlocking performance is based solely on the hook release time and does not require a pressure sensor.

[0020] In particular, the predetermined duration is slightly greater than a maximum hook release time under nominal greasing / lubrication conditions of the hook housing.

[0021] In particular, the moment of release of the hook is determined from a proximity sensor arranged to detect the presence of said hook in the retained position.

[0022] In particular, the process further includes step d) which consists of programming, based on the state of degradation of the hooking box, a maintenance of said hooking box.

[0023] According to a particular embodiment, the fluid pressure is, for the predetermined duration, substantially constant and equal to a predetermined pressure.

[0024] According to another particular embodiment, the fluid pressure is, during the predetermined time, increased in steps until a predetermined pressure is reached.

[0025] In particular, the fluid pressure is, for the predetermined time, equal to a pressure lower than the predetermined pressure and then equal to the determined pressure.

[0026] According to another particular embodiment, the fluid pressure is, during the predetermined time, continuously increasing until a predetermined pressure is reached.

[0027] In particular, the predetermined pressure is greater than a maximum release pressure of the hook under nominal greasing / lubrication conditions of the hook housing.

[0028] The invention also relates to a hydraulic supply circuit for a cylinder, enabling the implementation of such a method. The circuit comprises a delay valve having an inlet port for connection to a pressurized fluid source, an outlet port for connection to the cylinder, and a return port, and the delay valve includes a distributor comprising: a supply port connected to the inlet port via a first restrictor; a first service port forming the outlet port; a second service port forming the return port; a sliding spool between a pressure-limiting position to which it is automatically returned by a spring and in which the supply port is connected to the outlet and return ports via a third restrictor, and a full-pressure position in which the spool obstructs the return port; and a pilot chamber connected to the inlet port via a second restrictor for the movement of the sliding spool.

[0029] In particular, a first check valve is placed in parallel with the first restrictor, the first check valve allowing fluid to pass from the supply port to the inlet port.

[0030] In particular, a second check valve is placed in parallel with the second restrictor, the second check valve allowing fluid to pass from the pilot chamber to the inlet port.

[0031] The invention also relates to an aircraft comprising a latching housing for retaining a retractable landing gear or a hatch closing a cargo bay intended to receive the landing gear, the latching housing comprising a release actuator which includes a hydraulic cylinder connected to such a hydraulic circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The invention will be better understood in light of the following description, which is purely illustrative and not limiting, and should be read in conjunction with the accompanying figures, among which: [ Fig.1A ] there figure 1A illustrates the evolution of pressure in a release cylinder equipping a prior art locking mechanism, in a normal operating state; Fig.1B ] there figure 1B is analogous to the figure 1A , the mounting box being in a degraded operating state; Fig.2 ] there figure 2 is a schematic view of a locking device for an aircraft landing gear hatch via a latching housing; Fig.3 ] there figure 3 is a schematic view of a hydraulic circuit, according to a particular embodiment of the invention, for supplying a release cylinder for a latching housing, to implement the method illustrated in the figure 7 ; Fig.4A ] there figure 4A This is a schematic front view of a latching housing, illustrated with the hook in the retaining position and the locking mechanism in the locked position. Fig.4B ] there figure 4B is a view analogous to that of the figure 4A illustrating the hook in the release position, the locking mechanism being in the unlocking position via the action of the cylinder; [ Fig.4C ] there figure 4C is a view analogous to that of the figure 4A illustrating the hook in the release position, the locking mechanism being in the unlocking position via the action of a backup device; Fig.5 ] there figure 5 is a schematic view of a release actuator according to a particular embodiment of the invention; [ Fig.6A ] there figure 6A is a cross-sectional view of the delay valve illustrated in the figure 5 , in a state of rest; [ Fig.6B ] there figure 6B is a view analogous to the figure 6A illustrating the valve in a state of limited pressure; [ Fig.6C ] there figure 6C is a view analogous to the figure 6A illustrating the valve in a state of full pressure; Fig.7 ] there figure 7 illustrates a method for diagnosing a state of degradation of a mounting housing, according to a particular embodiment of the invention; [ Fig.8 ] there figure 8 illustrates the evolution of pressure in the unlocking actuator cylinder shown in the figure 5 , the cylinder being supplied with pressurized fluid according to a first law of evolution; Fig.9 ] there figure 9 illustrates a second law of evolution of the cylinder supply pressure; [ Fig.10 ] there figure 10 a cross-sectional view of the delay valve allowing the implementation of the second law of evolution of the supply pressure illustrated in the figure 9 , in a state of rest. [ Fig.11 ] there figure 11 illustrates a third law of evolution of the cylinder supply pressure [ Fig.12 ] there figure 12 a cross-sectional view of the delay valve allowing the implementation of the third law of evolution of the supply pressure illustrated in the figure 11 , in a state of rest. DETAILED DESCRIPTION OF THE INVENTION

[0033] As illustrated in the figure 2 , the invention is described herein in relation to an aircraft 1 comprising a landing gear 10 articulated on a structure 2 of the aircraft 1 between a deployed position illustrated here and a retracted position in which the landing gear 10 is received in a compartment 3 closable by a hatch 20.

[0034] With reference to the figure 3 A double-acting cylinder 11 is attached to the lander 10 and allows it to be maneuvered between the retracted and deployed positions. The lander 10 is held in the retracted position by a latching housing 13 equipped with a hook 14 that engages a locking olive 15 attached to the lander 10 when it reaches the retracted position. The release of the hook 14 is controlled by a hydromechanical unlocking actuator 12.

[0035] Similarly, a double-acting cylinder 21 is attached to the hatch 20 and allows it to be maneuvered between an open position, enabling the deployment and retraction of the landing gear, and a closed position, closing the cargo bay 3. The hatch 20 is held in the closed position by a latching housing 23 attached to the structure of the aircraft 1. The latching housing 23 is equipped with a hook 24 that engages a locking tab 25 attached to the hatch 20 when the hatch 20 reaches the closed position. The release of the hook 24 is controlled by a hydromechanical release actuator 22.

[0036] The latching boxes 13, 23 are here of identical structures, as are the olives 15, 25 and the unlocking actuators 12, 22.

[0037] The cylinder 11 used to maneuver the lander 10 is controlled by a monostable distributor D11 connected to a pressurized fluid source P. The unlocking actuator 12 allows the latching box 13 to be deactivated and is controlled by a monostable valve V12 connected to the pressurized fluid source P.

[0038] The cylinder 21 used to operate the hatch 20 is controlled by a monostable distributor D21 connected to the pressurized fluid source P. The unlocking actuator 22 allows the latching box 23 to be deactivated and is controlled by a monostable valve V22 connected to the pressurized fluid source P.

[0039] A monostable isolation valve V i allows the distributors D11, D21 and the valves V12, V22 to be isolated, particularly during certain phases of flight, from the pressurized fluid source P in order to limit the risk of untimely deployment and retraction of the lander 10, but also of untimely opening and closing of the hatch 20.

[0040] It should be noted that in the event of failure of the latching box 13, the lander 10 would still be held in the hold 3 by the hatch 20 locked in the closed position via the latching box 23, so that the locking of the hatch 20 tends to limit any untimely deployment of the lander 10.

[0041] Aircraft 1 also includes a control unit UC arranged to control distributors D21, D22 connected to cylinders 11, 21 and valves V12, V22 connected to unlocking actuators 12, 22, so as to control the deployment and retraction of the landing gear 10, the locking of said landing gear 10 in the retracted position, the opening and closing of the hatch 20, and the locking of the hatch 20 in the closed position.

[0042] With reference to the figure 4A The latching housings 13, 23 comprise, in a manner known per se, a body 16, 26 carrying a first pivot and a second pivot defining parallel pivot axes X1, X2. The hook 14, 24 is pivotally mounted on the first pivot along the axis X1 between a retaining position ( figure 4A ) and a release position to which it is returned by a spring 17, 27 ( figures 4B, 4C ). The hook 14, 24 includes a hooking part in which the olive 15, 25 of the lander 10 (or of the hatch 20) is intended to be retained by the hooking housing 13, 23 to immobilize said lander 10 in retracted position (or said hatch 20 in closed position). To do this, the lander 10 (or the hatch 20) is moved by the cylinder 11, 21 and the olive 15, 25 pushes the hook 14, 24 towards the retention position in which it retains the olive 15, 25. For this purpose, a locking member 18, 28 is pivotally mounted on the second pivot about the axis X2 and has at one end a roller bearing against a cam profile of the hook 14, 24. The locking member 18, 28 pivots between a locking position to which it is automatically returned by the spring 17, 27 and which it automatically reaches when the hook 14, 24 arrives in the retention position ( figure 4A ), and an unlocking position (the figures 4B, 4C ). In the locked position, the locking member 18, 28 locks the hook 14, 24 in the retained position. To release the olive 15, 25, the unlocking actuator 12, 22 pushes the locking member 18, 28 towards the unlocked position, which allows the hook 14, 24 to pivot towards the release position and thus the olive 15, 25 to leave the hook 14, 24.

[0043] As is known, the hooking boxes 13, 23 also include an inductive proximity sensor 19, 29 connected to the control unit UC and arranged to detect the presence of the hook 14, 24 in the holding position.

[0044] The hook housings 13, 23 also include a backup actuator 30 capable of unlocking the hook 14, 24 if the unlocking actuator 12, 22 is inoperative. For this purpose, an unlocking member 31 is pivotally mounted on a third pivot about an axis X3 parallel to the axes X1, X2, and has a roller at one end. The unlocking member 31 pivots between a rest position to which it is automatically returned by a spring 32 ( figures 4A, 4B ), and an unlocking position in which the roller of the unlocking member 31 is in contact with the roller of the locking member 18, 28 ( figure 4C ). To release the olive 15, 25, the emergency actuator 30 pushes back the unlocking member 31 which, upon reaching its unlocking position, in turn pushes back the locking member 18, 28 towards its unlocking position, which allows the hook 14, 24 to pivot towards the release position and thus the olive 15, 25 to leave the hook 14, 24.

[0045] With reference to the figure 5 The unlocking actuators 12, 22 comprise a hydraulic cylinder V e including a body in which a rod T i slides, being associated with a piston which defines a chamber with the body. The locking member 18, 28 is in the locked position when the rod T i is in the retracted position ( figure 4A ), and is in the unlocked position when rod T i is in the extended position ( figure 4B ).

[0046] The unlocking actuator 12, 22 also includes a so-called "delay" valve Vr connected to the cylinder chamber Ve. The delay valve Vr comprises: an inlet port E connected to the pressurized fluid source P via the control valve V12, V22, an outlet port S connected to the cylinder chamber V e, and a return port R connected to a reservoir.

[0047] The delay valve Vr also includes a distributor D comprising: a supply port A connected to the inlet port E via a first restrictor R1 and a first check valve C1 arranged in parallel with each other, the first check valve C1 allowing the fluid to pass from the supply port A to the inlet port; a first service port forming the outlet port S, a second service port forming the return port R, a movable spool T r between a so-called "pressure limiting" position to which it is automatically returned by a spring R e and in which the supply port A is connected to the outlet port S and the return port R via a third restrictor R3, and a so-called "full pressure" position in which it obstructs the return port R;and a pilot chamber CH for the movement of the spool T r, connected to the inlet port E via a second restrictor R2 and a second check valve C2 arranged in parallel with each other, the second check valve C2 allowing the fluid to pass from the pilot chamber CH to the inlet port E. ;

[0048] The operation of the delay valve V r is as follows.

[0049] When a pressurized fluid enters the delay valve Vr through the inlet port E and the spool Tr is in its rest position ( figure 6A ), the fluid tends to reach, almost simultaneously, the outlet port S via the first restrictor R1, the return port R via the first restrictor R1 and the third restrictor R3, and the pilot chamber CH of the distributor D via the second restrictor R2. The pressure of the fluid exiting the outlet port S then results from the pressure drop across the first restrictor R1 and the third restrictor R3, and is therefore lower than that entering the inlet port E. At the same time, the pressure in the pilot chamber CH tends to increase and thus causes the spool T r to move towards its full pressure position ( figure 6B ). This speed of movement of the drawer T r is defined by the second restrictor R2.

[0050] As the pressure increases in the pilot chamber CH, the T r valve eventually reaches its full pressure position in which it completely obstructs the return port R ( figure 6C ). The pressure of the fluid exiting through the outlet port S then results from the pressure loss through the first restrictor R1 and thus becomes substantially equal to that entering through the inlet port E.

[0051] It therefore appears that before becoming substantially equal to that entering through the inlet port E, the pressure of the fluid exiting the outlet port S is limited for a period depending on the speed of movement of the spool T r, which is itself defined by the second restrictor R2.

[0052] When the inlet port E of the delay valve Vr is no longer supplied with pressurized fluid, the pressure in the pilot chamber CH tends to decrease, causing the spool Tr to move towards its pressure-limiting position under the effect of the spring Re. The pilot chamber CH is depressurized through the second check valve C2, and the outlet port S is depressurized through the first check valve C1.

[0053] In order to monitor the integrity of the latching housing 13, 23 and thus prevent its latent failure, the control unit UC is arranged to implement, via the delay valve Vr, a method for diagnosing a degraded state of the latching housing 13, 23. With reference to figures 7 And 8 The different stages of the process will now be detailed.

[0054] During a landing gear 10 or hatch 20 unlocking sequence, valve V12, V22 is first commanded to connect, from a moment t 0 , the unlocking actuator 12, 22 to the pressurized fluid source P. The pressure of the inlet port E of the unlocking actuator is then substantially equal to the pressure P s of the pressurized fluid source P which is generally equal to 206 bar or 350 bar depending on the nominal pressure of the aircraft's hydraulic generation, and which here is equal to 206 bar.

[0055] Until a moment t 1 (corresponding to a first phase), the pressure at the outlet port S, and therefore that of the cylinder chamber Ve, is lower than that at the inlet port E and is limited by the delay valve Vr. The delay valve Vr and, in particular, its first and third restrictors R1, R3 are arranged so that the pressure at the outlet port S is, until the momentt 1 at most equal to a pressure Plim slightly higher than a maximum release pressure Pmax, representing the maximum force required to release the hook 14, 24 via the cylinder Ve under nominal greasing / lubrication conditions of the hook housing 13, 23. The pressure Pmax is generally between 70 bar and 90 bar, and is here equal to 85 bar. The pressure Plim is generally between 90 bar and 110 bar, and is here equal to 95 bar.

[0056] The moments t 0 And t 1 define a duration T corresponding approximately to the time it takes for the spool Tr of the delay valve Vr to move from its pressure limit position to its full pressure position. The delay valve Vr, and in particular its second restrictor R2, are arranged so that the duration T is greater than a duration T max representative of a maximum unlocking time required to release the hook 14, 24 via the cylinder V e under nominal greasing / lubrication conditions of the hooking housing 13, 23. The duration T is here between 0.5 seconds and 1 second.

[0057] After the moment t 1 (corresponding to a second phase), the pressure of the outlet port S, and therefore that of the cylinder chamber V e, tends to become substantially equal to the pressure PS of the source P.

[0058] The pressure at the outlet port S is thus, for the duration T, approximately constant and equal to the pressure P lim, then equal to the pressure P s.

[0059] During the unlocking sequence of the lander 10 (or the hatch 20), the control unit UC determines, via the proximity sensor 19, 29, the instant t where the hook 14, 24 leaves the holding position, in other words the moment twhere the rod T i of the cylinder V has essentially finished pushing the locking member 18, 28 back towards its unlocked position. The instant t corresponds to the moment when the pressure in the cylinder chamber V e reaches a minimum after having dropped abruptly during the movement of the rod T i.

[0060] The moment t is then compared to the moment t1 .

[0061] If the moment t is situated before the moment t1 as illustrated in the figure 8 , then the unlocking pressure P dev required by the cylinder V e to release the hook 14, 24 is less than or equal to the maximum unlocking pressure P max representative of the maximum level of effort required to release the hook 14, 24 under nominal greasing / lubrication conditions of the hook housing 13, 23. It is deduced that the hook housing 13, 23 is in a nominal state of greasing / lubrication and does not require the addition of grease or lubricant.

[0062] On the contrary, if the moment t takes place after the moment t1, then the unlocking pressure P dev required by the cylinder V e to release the hook 14, 24 is greater than the maximum unlocking pressure P max representative of the maximum level of effort required to release the hook 14, 24 under nominal greasing / lubrication conditions of the hooking housing 13, 23. It is deduced that the hooking housing 13, 23 is in a degraded state and requires an application of grease or lubricant.

[0063] It will be understood that by delaying the application of full pressure in the cylinder chamber V e for the duration T,This method allows for the diagnosis of performance degradation in the unlocking mechanism of the latching housing 13, 23 before the complete loss of the unlocking function, and thus enables the scheduling of maintenance for the latching housing 13, 23 to prevent a latent failure (application of lubricant / grease, disassembly of the housing for inspection and / or replacement of a component, etc.). The detection of performance degradation in the latching housing 13, 23 is based solely on the release time of the hook 14, 24 and does not require the use of a pressure sensor.

[0064] A level of degradation state N d of the unlocking performance of the latching housing 13, 23 can further be calculated by the control unit UC via the following equation: N d = t − t max t M − t max Or : t max defined with t 0 the duration T max ; And t M is a predefined instant beyond which a maintenance operation is required (aircraft 1 is no longer authorized to fly).

[0065] Expressed as a percentage, the degradation state level N d is recorded in a memory of the control unit UC in order in particular to be able to observe an evolution of the degradation state level N d of the hooking box 13, 23 during several successive unlocking sequences of the lander 10 (or the hatch 20) and thus estimate a maximum number of unlocking sequences allowed before carrying out a maintenance operation.

[0066] Although the supply pressure of the cylinder V e is here essentially constant during the duration T (corresponding to the first phase), it can also increase in steps. For example, the supply pressure of the cylinder V e can, during the duration T,be equal to a first pressure less than the pressure P lim, then be equal to a second pressure greater than the first pressure and less than the pressure P lim, then be equal to the pressure P lim ( figure 9 ).

[0067] Such a law of evolution of the supply pressure of the cylinder V e can be achieved via a valve V r ' which differs from the valve V r in that it includes not one but three return ports R each equipped with a third restrictor R3.1, R3.2, R3.3 ( figure 10 ).

[0068] When a pressurized fluid enters the delay valve Vr' through the inlet port E and the spool Tr is in its rest position (shown in the figure 10 ), the fluid tends to join, almost simultaneously: the output port S via the first restrictor R1, the return ports R via the first restrictor R1 and the third restrictors R3.1, R3.2, R3.3, and the pilot chamber CH of the distributor D via the second restrictor R2.

[0069] The pressure of the fluid exiting through the outlet port S results from the pressure drop across the first restrictor R1 and the third restrictors R3.1, R3.2, and R3.3, and is therefore lower than the pressure entering through the inlet port E. Simultaneously, the pressure in the pilot chamber CH tends to increase, causing the spool Tr to move towards its full-pressure position (not shown). This rate of movement of the spool Tr is determined by the second restrictor R2.

[0070] As the pressure increases in the pilot chamber CH, the T r slide moves to reach its full pressure position by successively obstructing the third restrictors R3.1, R3.2, R3.3, so that the pressure of the fluid exiting through the outlet port S results; in the first stage, the pressure drop through the first restrictor R1 and the third restrictors R3.1, R3.2, R3.3 (the spool T r does not obstruct any of the three return ports R); in the second stage, the pressure drop through the first restrictor R1 and the third restrictors R3.2, R3.3 (the spool T r obstructs one of the three return ports R, more precisely the return port R equipped with the restrictor R3.1); in the third stage, the pressure drop through the first restrictor R1 and the third restrictor R3.3 (the spool T r obstructs two of the three return ports R, more precisely the return ports R equipped with the restrictors R3.1, R3.2); and in the fourth stage, the pressure drop through the first restrictor R1 (the spool T r obstructs all the return ports R) and thus becomes substantially equal to that entering through the inlet port E.

[0071] It therefore appears that before becoming substantially equal to the pressure entering through the inlet port E, the pressure of the fluid exiting the outlet port S is limited to a first pressure and then to a second pressure for a duration depending on the speed of movement of the spool T r, which is itself defined by the second restrictor R2.

[0072] When the inlet port E of the delay valve Vr' is no longer supplied with pressurized fluid, the pressure in the pilot chamber CH tends to decrease, causing the spool Tr to move towards its pressure-limiting position under the effect of the spring Re. The pilot chamber CH is depressurized through the second check valve C2, and the outlet port S is depressurized through the first check valve C1.

[0073] It can also be expected that the supply pressure to the cylinder Ve will increase continuously. For example, the supply pressure to the cylinder Ve may, over the duration T, grow linearly until reaching the pressure P lim ( figure 11 ).

[0074] Such a law of evolution of the supply pressure of the cylinder V e can be achieved via a valve V r " which differs from the valve V r in that the spool T r has an external surface S e of frustoconical shape arranged so that said spool T r obstructs, when passing from the pressure limiting position to the full pressure position, the return port R more progressively than if the external surface S e were cylindrical in shape (for a given speed of movement of the spool Tr).

[0075] When a pressurized fluid enters the delay valve Vr'' through the inlet port E and the spool Tr is in its rest position (shown in the figure 12 The fluid tends to flow almost simultaneously to the outlet port S via the first restrictor R1, the return port R via the first restrictor R1 and the third restrictor R3, and the pilot chamber CH of the distributor D via the second restrictor R2. The pressure of the fluid exiting the outlet port S results from the pressure drop across the first restrictor R1 and the third restrictor R3, and is therefore lower than the pressure entering the inlet port E. At the same time, the pressure in the pilot chamber CH tends to increase, causing the spool Tr to move towards its full-pressure position. This spool movement velocity is determined by the second restrictor R2.

[0076] As the pressure increases in the pilot chamber CH, the valve Tr tends to return to its full-pressure position, progressively obstructing the return port R until it is completely blocked. The fluid pressure exiting through the outlet port S then results from the pressure drop across the first restrictor R1 and thus becomes approximately equal to the pressure entering through the inlet port E.

[0077] It therefore appears that before becoming substantially equal to the pressure entering through the inlet port E, the pressure of the fluid exiting the outlet port S increases linearly for a duration depending on the speed of movement of the spool T r, which is itself defined by the second restrictor R2.

[0078] When the inlet port E of the delay valve Vr is no longer supplied with pressurized fluid, the pressure in the pilot chamber CH tends to decrease, causing the spool Tr to move towards its pressure-limiting position under the effect of the spring Re. The pilot chamber CH is depressurized through the second check valve C2, and the outlet port S is depressurized through the first check valve C1.

[0079] By determining the release time t of the hook 14, 24, it is then possible, using such laws governing the evolution of the cylinder supply pressure Ve, to determine the release pressure Pdev and the level of degradation Nd of the performance of the hook housing 13, 23, and to schedule maintenance for said hook housing 13, 23 in accordance with its state of degradation. For example, a release pressure Pdev slightly lower or higher than the maximum release pressure Pmax may indicate a lubrication / greasing defect in the hook housing. Conversely, a release pressure Pdev significantly higher than the maximum release pressure Pmax may indicate a lubrication / greasing defect in the hook housing or the removal of a surface coating from a component of the hook housing 13, 23.

[0080] By determining the moment t During several unlocking sequences of the lander 10 (or hatch 20), it is also possible to determine an evolution of said instant. t release and therefore to refine the maintenance programming of the latching box 13, 23. For example, instantaneous stability t release may allow for delaying maintenance of the 13, 23 attachment box. Conversely, an increasing evolution of the instant t The release mechanism will allow for precise programming of maintenance for the 13, 23 attachment box. Also, a significant reduction in the time t release may confirm a tearing of a surface coating from a component of the mounting box 13, 23.

[0081] By determining the evolution of the degradation state level Nd of the unlocking performance of the latching box 13, 23 during several unlocking sequences of the lander 10 (or the hatch 20), it is also possible to refine the maintenance schedule for the latching box 13, 23. For example, a significant increase in the degradation state level Nd could trigger a maintenance operation even if the moment t is less than t max .

[0082] Of course, the invention is not limited to the embodiment described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0083] Although the process is described here in application to the unlocking actuator, it can also be described in application to the backup actuator.

[0084] The actuators can be single-acting or double-acting cylinders.

[0085] The delay valve can be integrated into the V e cylinder.

[0086] The invention is applicable to any locking housing usable for example for locking hatches on vehicles other than aircraft or on buildings.

Claims

1. Method for diagnosing a state of deterioration of an uplock (13, 23) for the retention of a tapped nut (15, 25) of a movable element (10, 20), the uplock comprising: - a hook (14, 24) pivoting between a release position and a position for retaining the tapped nut; - a locking member (18, 28) pivoting between a locking position, in which the hook is immobilised in the retaining position by the locking member, and an unlocking position, in which the hook is free to be moved under the thrust of the tapped nut of the movable element; and - an unlocking actuator (12, 22) comprising a hydraulic cylinder (Ve) supplied to act on the locking member in view of pushing it back to the unlocking position; the method comprising, during a release sequence of the hook immobilised in the retaining position by the locking member, the following steps: a) supplying the cylinder with pressurised fluid with an evolution law according to which the pressure of the fluid is, for a predetermined period (T), lower than a full pressure (Ps), then equal to the full pressure; b) determining a release time (t) of the hook and comparing it with the time (t1) when the predetermined time period ends; c) deducing, from the comparison performed in step b), a state of deterioration of the uplock.

2. Method according to claim 1, wherein the predetermined period (T) is slightly greater than a maximum period (Tmax) for releasing the hook (14, 24) under nominal conditions for greasing / lubricating the uplock (13, 23).

3. Method according to any one of the preceding claims, wherein the release time (t) of the hook (14, 24) is determined from a proximity sensor (19, 29) arranged to detect the presence of said hook in the retaining position.

4. Method according to any one of the preceding claims, further comprising the step d) consisting of scheduling, from the state of deterioration of the uplock (13, 23), a maintenance of said uplock.

5. Method according to any one of the preceding claims, wherein the pressure of the fluid is, for the predetermined period (T), substantially constant and equal to a predetermined pressure (Plim).

6. Method according to any one of claims 1 to 4, wherein the pressure of the fluid is, for the predetermined period (T), increasing stepwise until reaching a predetermined pressure (Plim).

7. Method according to claim 6, wherein the pressure of the fluid is, for the predetermined period (T), equal to a pressure lower than the predetermined pressure (Plim), then equal to the determined pressure (Plim).

8. Method according to any one of claims 1 to 4, wherein the pressure of the fluid is, for the predetermined period (T), increasing continuously until reaching a predetermined pressure (Plim).

9. Method according to any one of claims 5 to 8, wherein the predetermined pressure (Plim) is greater than a maximum pressure (Pmax) for releasing the hook (14, 24) under nominal conditions for greasing / lubricating the uplock (13, 23).

10. Hydraulic circuit for supplying a cylinder (Ve) enabling the implementation of the method according to any one of claims 1 to 9, the circuit comprising a delay valve (Vr, Vr', Vr'') having an inlet port (E) intended to be connected to a pressurised fluid source (P), an outlet port (S) intended to be connected to the cylinder and at least one return port (R), and the delay valve comprising a distributor (D) comprising: - a supply port (A) connected to the inlet port via a first restrictor (R1); - a first service port forming the outlet port, - at least one second service port forming the return port; - a slide valve (Tr) which is movable between a pressure limiting position, towards which it is returned automatically by a spring (Re), and in which the supply port is connected to the outlet port and to the return port via a third restrictor (R3, R3.1, R3.2, R3.3), and a full pressure position, in which the slide valve blocks the return port; and - a control chamber (Ch) connected to the inlet port via a second restrictor (R2) to move the movable slide valve.

11. Hydraulic circuit according to claim 10, wherein a first check valve (C1) is placed in parallel with the first restrictor (R1), the first check valve letting the fluid pass from the support port (A) to the inlet port (E).

12. Hydraulic circuit according to claim 10 or 11, wherein a second check valve (C2) is placed in parallel with the second restrictor (R2), the second check valve letting the fluid pass from the control chamber (Ch) to the inlet port (E) .

13. Aircraft comprising an uplock (13, 23) for the retention of a retractable landing gear (10) or of a door (20) containing a hold intended to receive the landing gear, the uplock comprising an unlocking actuator (12, 22) which comprises a hydraulic cylinder (Ve) connected to a hydraulic circuit according to any one of claims 10 to 12.