Diaphragm retainer for oil-gas shock absorber

Abstract

The invention relates to a diaphragm holder for an oil-gas type shock absorber, comprising a tubular body made of thermoplastic material, having a first end arranged to hold a diaphragm provided with a throttling orifice and an opposite second end defining a domed bottom for withstanding pressure. According to the invention, each of the two ends is provided with a local mechanical reinforcement element forming an axial stop allowing tensile stresses to be applied to the tubular body.

Description

Technical Field

[0001] The present invention relates to the field of hydraulic shock absorbers, and more particularly to a diaphragm retainer for an oil-gas type shock absorber, and particularly but not exclusively to an aircraft lander. Background Art

[0002] Aircraft landing gear usually includes an oleopneumatic shock absorber that allows to ensure stabilization and control of the aircraft's movements, especially during the taxiing and landing phases. The oleopneumatic shock absorber comprises a box in which a rod is mounted so as to slide. The rod holds at its lower end a rocker beam on which a plurality of wheels are mounted to allow the aircraft to rest on the ground.

[0003] The box and the rod together define an internal volume divided into two chambers by a diaphragm. One of the chambers is filled with hydraulic fluid, while the other chamber is filled with the same hydraulic fluid and pressurized gas. The diaphragm includes a calibrated orifice through which the hydraulic fluid can pass with hydraulic resistance.

[0004] The diaphragms are conventionally retained by a diaphragm retaining tube that is integral with the bottom of the tank. The diaphragm retaining tube is dimensioned to prevent burning under the pressure exerted on the diaphragms by the hydraulic fluid, particularly during the landing phase of the aircraft.

[0005] In some landers, such as the one equipped with the Airbus A320, the diaphragm retaining tube is further arranged to ensure the fixation of the lower part of the landing gear holding the wheels, which tends to extend the shock absorber under the effect of gravity when the aircraft lowers the landing gear in flight.

[0006] Therefore, the diaphragm retaining tube is usually made of metal material. However, the manufacture of such diaphragm retaining tubes involves expensive and lengthy machining operations. Moreover, the machining manufacture involves a minimum wall thickness, which will prevent the weight reduction of the metal diaphragm retaining tube, while the metal diaphragm retaining tube is often oversized relative to the forces it is subjected to.

[0007] From document FR-A-2 999 528, a diaphragm-retaining tube made of thermoplastic material is known, allowing the mass and the manufacturing time of the diaphragm-retaining tube to be reduced.

[0008] However, if injection molding allows the shape of the diaphragm retaining tube to be optimized and, in particular, its mass to be reduced, injection molding also limits the mechanical properties of the diaphragm retaining tube required for the correct operation of the shock absorber, in particular the fixing of the rocker beam. In fact, a diaphragm retaining tube made of plastic material, the structure of which would be optimized to improve its properties, would have closed areas that are difficult, if not impossible, to achieve by injection molding. Summary of the invention

[0009] The present invention therefore aims to propose a diaphragm holder which allows the above-mentioned disadvantages to be at least partially prevented.

[0010] To this end, a diaphragm holder for an oil-gas type shock absorber is proposed, the diaphragm holder comprising a tubular body made of thermoplastic material having a first end arranged to hold a diaphragm provided with a throttling orifice and a second opposite end defining a bottom arranged to withstand pressure.

[0011] According to the invention, the two ends are each provided with a local mechanical reinforcement element forming an axial stop arranged to allow the tubular body to be subjected to tensile stresses.

[0012] The mechanical reinforcement element allows to avoid local over-thickness of the thermoplastic material constituting the rest of the diaphragm holder. This facilitates the manufacture of the diaphragm holder and limits its weight. Moreover, for the insert, a more suitable material can be chosen to withstand local forces that the thermoplastic material cannot withstand in order to meet other stresses. Thus, the mechanical properties of the thermoplastic material constituting the tubular body are best exploited.

[0013] The arrangement of mechanical reinforcement elements at both ends of the tubular body allows simplifying the manufacture of the diaphragm holder while guaranteeing its mechanical properties necessary for the correct operation of the shock absorber.

[0014] In particular, the at least one mechanical reinforcement element is made of metal, preferably steel or aluminum.

[0015] According to particular characteristics, the mechanical reinforcement element is additionally arranged at the first end of the tubular body by being screwed onto said tubular body.

[0016] In particular, the mechanical reinforcement element arranged at the first end of the tubular body defines a cap comprising a tubular portion fitted on the first end of the tubular body and having a free end forming an axial stop.

[0017] In particular, the mechanical reinforcement element arranged at the first end of the tubular body comprises a wall blocking the tubular body and in which at least one throttling orifice is arranged, such that said wall forms a septum.

[0018] According to another particular feature, the mechanical reinforcement element arranged at the second end of the tubular body comprises a yoke joint arranged to articulate the diaphragm holder to the support structure.

[0019] The present invention relates to an oil-gas type shock absorber including such a diaphragm holder.

[0020] The invention also relates to an aircraft lander comprising such a shock absorber.

[0021] The invention also relates to an aircraft comprising such a lander. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The invention will be best understood from the following description, which is purely illustrative and non-limiting and must be read in conjunction with the accompanying drawings, in which:

[0023] Figure 1 is a schematic cross-sectional view of a shock absorber of an aircraft lander known per se including a diaphragm holder;

[0024] Figure 2 is an axial cross-section through a diaphragm holder known per se and made of metal;

[0025] Figure 3 is an axial cross-sectional view of a diaphragm holder according to a specific embodiment of the present invention. DETAILED DESCRIPTION

[0026] Figure 1 Represents a shock absorber for an aircraft lander of the oil-gas type. In a manner known per se, the shock absorber has a box 1 in which a rod 2 is mounted to slide along a vertical axis X between a retracted position and a delivery position. The lower end of the rod 2 is arranged to receive an axle or bogie holding one or more wheels.

[0027] The diaphragm 3 divides the interior of the housing 1 into a first chamber C1 and a second chamber C2. The first chamber C1 is filled with hydraulic fluid F and pressurized gas G, and the second chamber C2 is filled with hydraulic fluid F. The diaphragm 3 is held by a substantially tubular diaphragm holder 4 at its lower end extending along the axis X, while the upper end of the diaphragm holder 4 is directly added to the top plate of the housing 1.

[0028] The second chamber C2 is furthermore delimited by a bottom 5 incorporated in the rod 2 . Below the bottom 5 extend a third chamber C3 filled with hydraulic fluid F and a fourth chamber C4 filled with pressurized gas G. The third chamber C3 and the fourth chamber C4 are separated by a separating piston 6 .

[0029] The diaphragm 3 and the bottom 5 are provided with calibrated orifices allowing the hydraulic fluid F to pass from the second chamber C2 to the first chamber C1 and from the second chamber C2 to the third chamber C3 respectively. All this is well known and is only reminded as an illustration.

[0030] Figure 2 The diaphragm holder 14 is shown, which is known per se and is made entirely of metal. Figure 1 The difference shown is that it is arranged to ensure the fixation of the rod 2 when it is in the output position.

[0031] Thus, the upper end of the diaphragm holder 14 comprises a cylindrical seat 10 arranged to be adjustable in a homologous cylindrical seat arranged in the housing 1, and an outer shoulder 11 arranged downstream of the cylindrical seat 10 and bearing against a step of said housing 1. The cylindrical seat 10 comprises a groove arranged to receive a seal 12, and an orifice 13 for introducing the gas G into the shock absorber.

[0032] Furthermore, two asymmetrical yoke joints 15 project from the upper end of the diaphragm holder 14 and allow the diaphragm holder 14 and thus the shock absorber to be mounted in an articulated manner via axes (not shown here) on the structure S of the aircraft.

[0033] The lower end of the diaphragm holder 14 has a cylindrical seat 16 adapted to slide into the seat to center the rod 2. The cylindrical seat 16 comprises a groove arranged to receive a centering block 17 and forms an axial stop against which the step of the rod 2 rests when said rod 2 is in the output position. This arrangement of the cylindrical seat 16 allows the rod 2 to stress in a tensile manner the diaphragm holder 14 whose upper end is hingedly mounted on the structure S of the aircraft.

[0034] Figure 3 A diaphragm holder 24 according to a specific embodiment of the invention is shown. The diaphragm holder 24 comprises a generally tubular body 20, the middle portion of which is reinforced by longitudinal reinforcements 21 regularly distributed outside the body 20. The longitudinal reinforcements 21 extend along the travel portion parallel to the axis X and protrude radially outward. The body 20 is made of a thermoplastic material, preferably polyetheretherketone with short carbon fibers. The density of this material is about 1.4, compared to a density of about 2.8 for light alloys and a density of about 7.8 for steel. The body 20 is preferably obtained by injection molding, which allows obtaining a portion with a wall whose thickness is controlled over the entire length of the portion and does not require any restoration. Any of this contributes to reducing the mass of the diaphragm holder and its cost price.

[0035] The upper part of the body 20 is flared to end on a cylindrical outer centering seat 22, which has an annular groove in which a seal 23 is mounted against the inner surface of the box 1. The upper part of the body 20 includes an annular end face in contact with the annular shoulder of the box 1 to form an axial stop, allowing tensile stress to be applied to the body 20 and possible prestressing of the body 20 to avoid any separation of the end face from the shoulder of the box 1.

[0036] Furthermore, the upper end of the tubular body comprises an inner centering seat 25, in which a first mechanical reinforcement element 26, mainly of cylindrical type, is added. The first mechanical reinforcement element 26 comprises, in the lower part, an outer shoulder 26.1, which rests on a step of the body 20, so as to prevent any escape of said first element 26 through the upper end of the body 20. The first element 26 also comprises here, in the upper part, a yoke joint 26.2 extending from the body 20. The yoke joint 26.2 allows the diaphragm holder 24, and therefore the shock absorber, to be articulated on the structure S of the aircraft via an axis (not shown).

[0037] Similar to the diaphragm holder 14, the first element 26 also comprises an orifice 26.3 for introducing the gas G into the shock absorber.

[0038] The first element 26 is here made of metal, preferably steel or aluminum.

[0039] The body 20 comprises an external threaded portion at the bottom, onto which is screwed a second mechanical reinforcement element 27. The second element 27 is formed as a cap of circular profile, on which a tubular portion 27.1 is internally threaded to engage with the threaded portion of the body 20.

[0040] The tubular portion 27.1 has an outer diameter greater than the body 20, so that the free end 27.2 of said tubular portion 27.1 forms an axial stop against which the step of the rod 2 can rest.

[0041] Furthermore, the second element 27 is provided with two throttle orifices 27 . 3 of substantially equal diameter, intended for the flow of hydraulic fluid F. The second element 27 thus forms a diaphragm.

[0042] The second element 27 is furthermore provided with a central opening 27 . 4 for the passage of a measuring probe (not shown here).

[0043] Like the first element 26 , the second element 27 is here made of metal, preferably steel or aluminum.

[0044] The first and second mechanical reinforcement elements 26 , 27 allow the rod 2 to stress the tubular body 20 of the diaphragm holder 24 mainly in tension, thus making best use of the mechanical properties of the thermoplastic material constituting said tubular body 20 .

[0045] Furthermore, the assembly of the first and second elements 26, 27 on the thermoplastic body 20 allows to simplify the manufacture of the diaphragm holder and to limit its mass, while at the same time improving the mechanical properties of a diaphragm holder made entirely of metal, such as Figure 2 The diaphragm holder 14 is shown.

[0046] Of course, the invention is not limited to the embodiments described but covers any variant coming within the ambit of the invention as defined by the claims.

[0047] Although the second mechanical reinforcement element 27 is here screwed onto the tubular body 20 , other types of fastening are also conceivable (bolting, pinning, gluing, etc.).

[0048] The geometry and dimensions of the first and second mechanical reinforcement elements 26 , 27 may differ from those in the example.

[0049] The first element 26 may have the form of a cover with a tubular portion screwed onto the upper end of the body 20, said cover comprising an annular surface portion forming an axial stop to rest on a shoulder of the box 1 and provided with at least one yoke joint for articulation to the structure.

[0050] The second element 27 may have the form of a ring surrounding the end of the tubular body 20, the diaphragm being formed by a separate component.

Claims

1. A diaphragm holder (24) for an oil-gas type shock absorber, the diaphragm holder (24) comprising a tubular body (20) made of a thermoplastic material, the tubular body (20) having a first end and an opposite second end, the first end being arranged to hold a diaphragm provided with a throttling orifice opened in the body, the second end defining a bottom arranged to withstand pressure, the first end and the second end being respectively provided with a first local mechanical reinforcement element (27) and a second local mechanical reinforcement element (26), the first local mechanical reinforcement element (27) and the second local mechanical reinforcement element (26) each forming an axial stop arranged to allow tensile stress to be applied to the tubular body (20), the second local mechanical reinforcement element (26) comprising a yoke joint (26.2), the yoke joint being arranged to hinge the diaphragm holder (24) on a support structure (S).

2. The diaphragm holder (24) according to claim 1, characterized in that At least one of the first local mechanical reinforcement element (27) and the second local mechanical reinforcement element (26) is made of metal.

3. The diaphragm holder (24) according to claim 2, characterized in that At least one of the first local mechanical reinforcement element (27) and the second local mechanical reinforcement element (26) is made of steel or aluminum.

4. The diaphragm holder (24) according to claim 1, characterized in that The first local mechanical reinforcement element (27) is added at the first end of the tubular body (20) by being screwed onto the tubular body (20).

5. The diaphragm holder (24) according to claim 4, characterized in that The first local mechanical reinforcement element (27) arranged at the first end of the tubular body (20) defines a cover comprising a tubular portion (27.1) fitted on the first end and having a free end forming an axial stop.

6. The diaphragm holder (24) according to claim 5, characterized in that The first local mechanical reinforcement element (27) arranged at the first end of the tubular body (20) comprises a wall blocking the tubular body (20) and having at least one throttling orifice arranged therein, so that the wall forms the diaphragm.

7. An oil-gas shock absorber, comprising the diaphragm holder (24) according to any one of claims 1 to 6.

8. An aircraft lander comprising the oil-gas shock absorber as claimed in claim 7.

9. An aircraft comprising the lander according to claim 8.

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