EP4051924A1

EP4051924A1 - Diaphragm holder for an oleo-pneumatic-type shock absorber

Info

Publication number: EP4051924A1
Application number: EP20793424.1A
Authority: EP
Inventors: Sylvain Leclercq; Mathieu Joubert; Franck LECUYER; Quentin ROIRAND
Original assignee: Safran Landing Systems SAS
Current assignee: Safran Landing Systems SAS
Priority date: 2019-10-29
Filing date: 2020-10-27
Publication date: 2022-09-07
Also published as: FR3102522B1; CN114630973A; WO2021083914A1; US20220403904A1; FR3102522A1

Abstract

The invention relates to a diaphragm holder for an oleo-pneumatic-type shock absorber, comprising a tubular body made of thermoplastic material, having a first end arranged to hold a diaphragm provided with flow restricting orifices and an opposite second end defining an arched bottom for withstanding pressure forces. According to the invention, each of the two ends is provided with a localised mechanical reinforcement element forming an axial stop arranged to allow tensile stressing of the tubular body.

Description

DIAPHRAGM HOLDER FOR OLEOPNEUMATIC SHOCK ABSORBER

The present invention relates to the field of hydraulic damping and more particularly to a diaphragm holder for an oleopneumatic type damper fitted in particular, although not exclusively, to aircraft undercarriages.

BACKGROUND OF THE INVENTION

An aircraft landing gear generally comprises an oleopneumatic damper which makes it possible to stabilize and control the movements of the aircraft, in particular during the taxiing and landing phases. The oleopneumatic damper comprises a box in which a rod is mounted to slide. The rod carries at its lower end a balance on which is mounted a plurality of wheels allowing the aircraft to rest on the ground.

The box and the rod together define an internal volume separated 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 a pressurized gas. The diaphragm has calibrated orifices through which hydraulic fluid can pass undergoing hydraulic resistance. The diaphragm is traditionally carried by a diaphragm holder tube integral with a bottom of the box. The diaphragm-carrying tube is dimensioned so as not to buckle under the pressure exerted by the hydraulic fluid on the diaphragm, in particular during the landing phases of the aircraft.

In some undercarriages, such as those fitted to the Airbus A320, for example, the diaphragm-carrying tube is also arranged to ensure retention of the lower part of the landing gear carrying the wheels which, under the effect of gravity, tends to stretch the shock absorber when the aircraft is in flight gear extended. Thus, the diaphragm holder tubes are generally made of metal. However, the manufacture of such diaphragm-carrying tubes involves costly and time-consuming machining operations. What is more, manufacturing by machining imposes minimum web thicknesses which prevent the weight of the metal diaphragm-carrying tubes from being reduced, although they are very often oversized in view of the stresses to which they are subjected.

Document FR-A-2999 528 discloses diaphragm-holder tubes made of thermoplastic material making it possible to reduce the mass and the manufacturing time of the diaphragm-holder tubes.

However, if manufacturing by injection makes it possible to optimize the shapes of the diaphragm-holder tubes in order in particular to reduce their mass, it also limits their mechanical performance necessary for the correct functioning of the shock absorber, and in particular for the retention of the balance. In fact, a plastic diaphragm-carrying tube, the structure of which would be optimized to improve its performance, would include confined areas which would be difficult or even impossible to produce by injection.

OBJECT OF THE INVENTION

The object of the invention is therefore to provide a diaphragm holder making it possible to obviate at least in part the aforementioned drawbacks.

SUMMARY OF THE INVENTION

To this end, a diaphragm holder for an oleopneumatic type damper is proposed, comprising a tubular body made of thermoplastic material. The tubular body has a first end arranged to carry a diaphragm provided with flow restriction orifices, and an opposite second end defining a bottom arranged to withstand pressure forces. According to the invention, each of the two ends is provided with a localized mechanical reinforcement element forming an axial stop arranged to allow a tensile stress on the tubular body. The mechanical reinforcement elements make it possible to avoid having localized extra thicknesses of the thermoplastic material constituting the rest of the diaphragm holder. This facilitates the manufacture of the diaphragm holder and limits the weight thereof. In addition, it is possible to choose for the insert a material more suitable for withstanding localized forces than would be the thermoplastic material chosen to satisfy other constraints. The mechanical characteristics of the thermoplastic material constituting the tubular body are thus best exploited.

The arrangement of mechanical reinforcement elements at the ends of the tubular body makes it possible to simplify the manufacture of the diaphragm holder while guaranteeing it the mechanical performance necessary for the correct functioning of the damper.

In particular, at least one of the mechanical reinforcement elements is made of metal, preferably steel or aluminum.

According to one particular characteristic, the mechanical reinforcement element arranged at the first end of the tubular body is attached by screwing onto said tubular body.

In particular, the mechanical reinforcement element arranged at the first end of the tubular body defines a cover comprising a tubular part which is engaged on the first end of the tubular body and which has a free end forming the axial stop.

In particular, the mechanical reinforcement element arranged at the first end of the tubular body comprises a wall closing off the tubular body and in which is arranged at least one restriction orifice such that said wall forms the diaphragm.

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

The invention also relates to an oleopneumatic type damper comprising such a diaphragm holder. The invention also relates to an aircraft landing gear comprising such a damper.

The invention further relates to an aircraft comprising such a landing gear.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood in the light of the description which follows, which is purely illustrative and not limiting, and should be read with reference to the appended drawings, among which: FIG. 1 is a schematic sectional view of an aircraft landing gear shock absorber known per se comprising a diaphragm holder;

- Figure 2 is an axial sectional view of a diaphragm holder known per se, made of steel;

- Figure 3 is an axial sectional view of a diaphragm holder according to a particular embodiment of

The invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 represents an aircraft landing gear damper of the oleopneumatic type. In a manner known per se, the damper comprises a box 1 in which a rod 2 is mounted to slide along a vertical X axis between a retracted position and an extended position. A lower end of the rod 2 is arranged to receive an axle or a bogie carrying one or more wheels. A diaphragm 3 separates the interior of the box 1 into a first chamber C1 filled with a hydraulic fluid F and a pressurized gas G and a second chamber C2 filled with hydraulic fluid F. The diaphragm 3 is carried by a lower end a substantially tubular diaphragm holder 4 extending along the X axis, while an upper end of the diaphragm holder 4 is directly attached to a ceiling of the box 1.

The second chamber C2 is further delimited by a bottom 5 attached to the rod 2. Under the bottom 5 extends a third chamber C3 filled with hydraulic fluid F and a fourth chamber C4 filled with gas G under pressure. The third chamber C3 and the fourth chamber C4 are separated by a separator piston 6. The diaphragm 3 and the bottom 5 are provided with calibrated orifices allowing the hydraulic fluid F to pass respectively from the second chamber C2 to the first chamber C1 and to the second chamber C2 to the third chamber C3. All of this is well known and is recalled for illustrative purposes only.

FIG. 2 illustrates a diaphragm holder 14, known per se, made entirely of metal. The diaphragm holder 14 differs from that shown in FIG. 1 in that it is arranged to ensure retention of the rod 2 when the latter is in the extended position.

Thus, an upper end of the diaphragm holder 14 comprises a cylindrical bearing surface 10 arranged to be able to fit into a homologous cylindrical bearing formed in the box 1, and an external shoulder 11 disposed downstream of the cylindrical bearing surface 10 and bearing against a step of said box 1. The cylindrical bearing surface 10 comprises a groove arranged to receive a seal 12, and an orifice 13 for introducing gas G into the damper. Furthermore, two asymmetrical yokes 15 projecting from the upper end of the diaphragm holder 14 and make it possible to mount the diaphragm holder 14, and therefore the damper, in a hinged manner on a structure S of the aircraft via an axis not shown here.

A lower end of the diaphragm holder 14 comprises a cylindrical bearing surface 16 adapted to slide in a centering bearing surface of the rod 2. The cylindrical bearing surface 16 comprises a groove arranged to receive a centering pad 17 and forms an axial stop against which comes rest on a step of the rod 2 when said rod 2 is in the extended position. Such an arrangement of the cylindrical bearing surface 16 allows the rod 2 to apply traction to the diaphragm holder 14, the upper end of which is mounted articulated on the structure S of the aircraft.

FIG. 3 illustrates a diaphragm holder 24 according to a particular embodiment of the invention. The diaphragm holder 24 comprises a substantially tubular body 20 reinforced in the central part by longitudinal stiffeners 21 distributed regularly outside the body 20. The longitudinal stiffeners 21 run along the running part parallel to the X axis and projecting. radial outward. The body 20 is made of thermoplastic material, preferably polyetheretherketone comprising short carbon fibers. The density of such a material is of the order of 1.4, to be compared with the density of a light alloy of the order of 2.8 and that of steel of the order of 7.8. The body 20 is preferably obtained by injection into a mold, which makes it possible to obtain a part having walls whose thickness is controlled over the entire length of said part and requiring no rework. All this contributes to lowering the mass of the diaphragm holder as well as its cost price. The body 20 is in the upper part of flared shape to end on an external centering bearing surface 22 of cylindrical shape which comprises an annular groove in which is housed a seal 23 bearing against the internal surface of the box 1. The part upper body 20 comprises an annular end face in contact with an annular shoulder of the box 1 to form an axial stop allowing the body 20 to be put in traction with a possible pretension of said body 20 in order to avoid any detachment of the end face with the 'box shoulder 1.

Furthermore, the upper end of the tubular body also comprises an internal centering surface 25 in which is attached a first mechanical reinforcement element 26 of generally cylindrical shape. The first mechanical reinforcement element 26 comprises in the lower part an external shoulder 26.1 which rests on a step of the body 20 to prevent said first element 26 from leaving the upper end of the body 20. The first element 26 here partly comprises upper a yoke 26.2 projecting from the body 20. The yoke 26.2 allows the diaphragm holder 24, and therefore the damper, to be articulated on the structure S of the aircraft via an axis not shown here. Similarly to the diaphragm holder 14, the first element 26 also comprises an orifice 26.3 for introducing the gas G into the damper.

The first element 26 is here made of metal, preferably of steel or aluminum. The body 20 comprises in the lower part an externally threaded portion onto which a second mechanical reinforcement element 27 is screwed. The second element 27 forms a cover of circular contour and of which a tubular part 27.1 is internally threaded to cooperate with the threaded portion of the body 20. The tubular part 27.1 has an outer diameter greater than that of the body 20 so that a free end 27.2 of said tubular part 27.1 forms an axial stop against which a step of the rod 2 can rest.

The second element 27 is also provided with two flow restriction orifices 27.3 of substantially identical diameter through which the hydraulic fluid F is intended to flow. The second element 27 thus forms a diaphragm.

The second element 27 is further provided with a central orifice 27.4 for the passage of a metering needle not shown here.

Just like the first element 26, the second element 27 is here made of metal, preferably of steel or aluminum.

The first and second mechanical reinforcement elements 26, 27 allow the rod 2 to stress the tubular body 20 of the diaphragm holder 24 essentially in tension and therefore to make the best use of the mechanical characteristics of the thermoplastic material constituting said tubular body 20.

Furthermore, the assembly of the first and second elements 26, 27 on the body 20 of thermoplastic material makes it possible to simplify the manufacture of the diaphragm holder and to limit its mass, while offering the mechanical performance of a diaphragm holder. entirely made of metal, like the diaphragm holder 14 illustrated in FIG. 2. Of course, the invention is not limited to the embodiments described but encompasses any variant coming within the scope of the invention as defined by the claims.

Although the second mechanical reinforcement element 27 is here reported screwed onto the body 20 tubular, other types of fixing can be considered (bolting, pinning, gluing ...).

The geometry and dimensions of the first and second mechanical reinforcement elements 26, 27 may be different from those illustrated.

The first element 26 may have the form of a cover having a tubular part screwed onto the upper end of the body 20, said cover comprising an annular surface portion forming an axial stop to bear against the shoulder of the box 1 and being provided with at least one yoke for its articulation to the structure.

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 part.

Claims

1. Diaphragm holder (24) for an oleopneumatic type damper, comprising a tubular body (20) made of thermoplastic material having a first end arranged to carry a diaphragm provided with flow restriction orifices and an opposite second end defining a bottom arranged to withstand pressure forces, each of the two ends being provided with a localized mechanical reinforcement element (26, 27) forming an axial stop arranged to allow a tensile stress on the tubular body (20).

2. A diaphragm holder (24) according to claim 1, wherein at least one of the mechanical reinforcing elements (26, 27) is made of metal, preferably steel or aluminum.

3. A diaphragm holder (24) according to any one of the preceding claims, wherein the mechanical reinforcement element (27) arranged at the first end of the tubular body (20) is attached by screwing onto said tubular body (20). .

4. A diaphragm holder (24) according to claim 3, wherein the mechanical reinforcement member (27) arranged at the first end of the tubular body (20) defines a cover comprising a tubular portion (27.1) which is engaged on said. first end and which has a free end forming the axial stop.

5. A diaphragm holder (24) according to claim 4, wherein the mechanical reinforcement element (27) arranged at the first end of the tubular body (20) comprises a wall closing off the tubular body (20) and in which is arranged at least one restriction orifice such that said wall forms the diaphragm.

6. A diaphragm holder (24) according to any preceding claim, wherein the mechanical reinforcement member (26) arranged at the second end. of the tubular body (20) comprises a yoke (26.2) arranged to articulate the diaphragm holder (24) on a support structure (S).

7. Oleopneumatic type damper comprising a diaphragm holder (24) according to any one of the preceding claims.

8. An aircraft landing gear comprising an oleopneumatic type damper according to claim 7.

9. Aircraft comprising a landing gear according to claim 8.