Aircraft engine attachment comprising at least one system for immobilizing a shear pin in translation comprising a stop plate, method for mounting said engine attachment and aircraft comprising said engine attachment

An aircraft engine attachment connecting an attachment body and a primary structure of an aircraft pylon, the engine attachment comprising a shear pin immobilized in translation by a first immobilization system that comprises a shoulder and a removable stop that are integral with the primary structure, between which a flange of the shear pin is immobilized, and a second immobilization system that comprises a stop plate, connected by at least one removable link to the primary structure, which closes the first hole, at least in part.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of the French patent application No. 1900203 filed on Jan. 9, 2019, the entire disclosures of which are incorporated herein by way of reference.

FIELD OF THE INVENTION

The present application relates to an aircraft engine attachment comprising at least one system for immobilizing a shear pin in translation comprising a stop plate, to a system for mounting the engine attachment and also to an aircraft comprising the engine attachment.

BACKGROUND OF THE INVENTION

According to one configuration, which may be seen inFIGS.1and2, an aircraft10comprises a plurality of engine units12that are positioned under the wing14of the aircraft10.

An engine unit12comprises an engine16, a nacelle (not shown inFIG.2) positioned around the engine16and a pylon18that forms the link between the engine16and the rest of the aircraft10, in particular the wing14.

The pylon18comprises a primary structure20that is connected to the engine16via a front engine attachment22, a rear engine attachment24and a pair of thrust rods26that transmit thrust forces.

According to one embodiment, which can be seen inFIG.3, the front engine attachment22comprises an attachment body28, connected to the pylon18, that has two clevises30arranged on either side of the pylon18, and also two connecting rods32that each connect one of the clevises30of the attachment body28to a clevis34integral with the engine16. Each connecting rod32is connected to one of the clevises30of the attachment body28via a first articulation pin36and to one of the clevises34of the engine16via a second articulation pin38.

According to one embodiment, illustrated in document FR2891245, the primary structure20has, at the front, two fixing lugs40that extend on either side of the primary structure20and which offer a contact face, against which is placed a contact face of the attachment body28. The front engine attachment22comprises a link between the primary structure20and the attachment body28comprising, for each fixing lug40, a plurality of bolts42traversing the fixing lug40and the attachment body28and also at least one shear pin44that is housed straddling a first hole formed in the fixing lug40and a second hole formed in the attachment body28. According to this document, upon mounting, the shear pins are inserted from each fixing lug40.

During operation, each shear pin44has to be immobilized in translation in the first and second holes.

According to one embodiment, each shear pin44comprises, at a first end, a shoulder that bears against one of the fixing lugs40. To prevent the exit of the shear pin44, a removable stop is placed at the second end of the shear pin44. This embodiment requires the presence of a first recess on the side of the fixing lug40, in line with the first hole, to allow the insertion of the shear pin44, and a second recess on the side of the attachment body28, in line with the second hole, to allow the placing of the removable stop. In point of fact, in certain cases, for example in the case of ultrahigh bypass ratio (UHBR) engines, access to the front of the attachment body28is impossible.

The present invention aims to remedy all or some of the prior-art drawbacks.

SUMMARY OF THE INVENTION

To that end, a subject of the invention is an aircraft engine attachment comprising an attachment body connected to a primary structure of an aircraft pylon via an attachment body link comprising link elements and at least one shear pin that comprises a cylindrical body and a flange having a diameter greater than that of the cylindrical body, the attachment body link comprising, for each shear pin, a first hole in the primary structure and a second hole in the attachment body that are configured such as to accommodate the shear pin, the first hole comprising a shoulder against which the flange bears during operation in such a manner that the cylindrical body is positioned to straddle the first and second holes.

According to the invention, the attachment body link comprises:a first immobilization system that comprises, in addition to the shoulder, a removable stop, integral with the primary structure, configured such as to immobilize the flange between the shoulder and the removable stop, anda second immobilization system that comprises a stop plate, connected by at least one removable link to the primary structure, which closes the first hole at least in part.

Thus, it is possible to mount each shear pin and its immobilization systems solely from the primary structure. Thus, the space between the attachment body and the aircraft engine may be very small at the front of the attachment body.

According to another feature, the stop plate comprises an orifice that has a diameter smaller than the diameter of the flange, positioned in line with the first hole when the stop plate is connected to the primary structure.

According to another feature, for each stop plate, the primary structure comprises an extension traversed by each removable link.

According to another feature, the removable link comprises two fixing elements, each being accommodated in passage holes of the stop plate and of the extension.

According to another feature, the stop plate comprises a recess in addition to the orifice.

According to another feature, the attachment body link comprises at least one anti-rotation system for at least one of the link elements, each anti-rotation system comprising an anti-rotation plate that has a through-orifice with a section that complements a section of a head of the link element such that the stop plate and the head are immobilized in rotation relative to one another, and also a removable link for connecting the anti-rotation plate to the primary structure.

According to another feature, each anti-rotation plate is connected to the stop plate.

According to another feature, for each anti-rotation plate, the stop plate comprises an extension that has a passage orifice for a fixing element connecting the anti-rotation plate and the stop plate.

A further subject of the invention is a method for mounting an engine attachment according to one of the preceding features, comprising the steps:connecting the attachment body to the aircraft engine,vertically moving the aircraft engine such as to position first and second contact faces of the primary structure of the aircraft pylon and of the attachment body opposite one another,placing the link elements,inserting each shear pin into the first and second holes until the flange is in contact with the shoulder,placing the removable stop, andpositioning a stop plate and connecting it to the primary structure such as to close the hole at least in part.

A further subject of the invention is an aircraft comprising an engine attachment according to one of the preceding features.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to one embodiment illustrated inFIGS.4and5, a primary structure50of an aircraft pylon is connected to an aircraft engine52via front engine attachment54.

In the remainder of the description, a longitudinal direction is a direction parallel to the axis of rotation of the aircraft engine52. A vertical longitudinal plane is a vertical plane passing through the axis of rotation of the aircraft engine52. The terms “front” and “rear” refer to the direction of flow of the flow of air inside the aircraft engine52during operation, the flow of air flowing from front to rear. The terms “horizontal” and “vertical” correspond to the horizontal (perpendicular to the direction of gravitational acceleration) and vertical (parallel to the direction of gravitational acceleration) directions when the aircraft is on the ground.

Although described in terms of application to a front engine attachment, the invention is in no way limited to that application and could be used for the other engine attachments.

According to one configuration, the front engine attachment54comprises an attachment body56, two connecting rods58arranged on either side of the vertical longitudinal plane, each connecting the attachment body56to the aircraft engine52, and also, for each connecting rod58, a first articulation pin60connecting a first end58.1of the connecting rod58to a first clevis62of the aircraft engine52and at least a second articulation pin64connecting a second end58.2of the connecting rod58to a first clevis66of the attachment body56.

The primary structure50comprises at least a first contact face F50against which is placed at least a second contact face F56of the attachment body56. The first and second contact faces F50and F56are arranged in vertical planes approximately perpendicular to the longitudinal direction.

The front engine attachment54comprises an attachment body link68connecting the attachment body56and a part of the primary structure50, making it possible to hold the first and second contact faces F50and F56pressed against one another. This link68of the attachment body comprises a plurality of link elements70, such as bolts, for example, and at least one shear pin72. The part of the primary structure50may be a component attached to the primary structure50.

According to a configuration visible, for example inFIG.4, the primary structure50comprises two fixing lugs74having coplanar faces that form the first contact face F50and extend in a substantially vertical plane perpendicular to the longitudinal direction, on either side of the primary structure50. For each fixing lug74, the attachment body link68comprises two link elements70,70′ and a shear pin72, the link elements70,70′ being arranged above and below the shear pin72.

According to an embodiment visible inFIG.6, each link element70,70′ is a bolt that comprises a head76having a circular lower cross section76.1and a polygonal upper cross section76.2.

The attachment body56, the connecting rods58, the first and second articulation pins60,64and the link elements70,70′ are not described further as they may be identical to those in the prior art.

Each shear pin72, comprises a cylindrical body78that has a first “free” end78.1, which is preferably rounded, and a second end78.2(opposite the first end), and also a flange80positioned at the second end78.2of the cylindrical body78. The flange80has two planar faces perpendicular to the axis of the cylindrical body78and a diameter D80greater than the diameter of the cylindrical body78.

For each shear pin72, the primary structure50comprises a first through-hole82, having a first end opening out at the first contact face F50and a second end opening out at an access face F50′. The attachment body56comprises a second through-hole84, the first and second holes82and84being configured such as to accommodate the cylindrical body78of the shear pin72.

According to a first configuration, the first and second holes82,84have a diameter that is substantially identical (to within the assembly clearance) to the diameter D78of the cylindrical body78of the shear pin72.

According to an embodiment visible inFIG.7, a first sliding ring86is interposed between the first hole82and the cylindrical body78and/or a second sliding ring88is interposed between the second hole84and the cylindrical body78.

The attachment body link68comprises a system for translational immobilization of the cylindrical body78of the shear pin72straddling the first and second holes82,84.

“Straddling” is understood to mean that a first portion of the shear pin72is positioned in the first hole82and a second portion of the shear pin72is positioned in the second hole84.

The translational immobilization system comprises a shoulder90close to the second end of the first hole82, which forms a bearing surface against which bears one of the faces of the flange80during operation. This shoulder90is substantially perpendicular to the axis of the first hole82. According to one configuration, the first hole82comprises a principal portion82.1that extends from the contact face F50as far as the shoulder90and an enlarged portion82.2that extends from the shoulder90as far as the axis face F50′. The enlarged portion82.2has a diameter greater than that of the principal portion82.1and the diameter D80of the flange80such that the latter is accommodated in the enlarged portion82.2and bears against the shoulder90during operation.

The translational immobilization system also comprises a removable stop92, integral with the first structure50, configured such as to immobilize the flange80between the shoulder90and the removable stop92. The removable stop92is separated from the shoulder90by a distance substantially equal to the thickness of the flange80(dimension taken parallel to the axis of the cylindrical body78of the shear pin72). During operation, the flange80is immobilized between the shoulder90and the removable stop92. Thus, the shear pin72is immobilized in translation in the first and second holes82,84. The shoulder90and the removable stop92form a first translational immobilization system.

According to an embodiment, the enlarged portion82.2comprises a groove94that extends between two planes perpendicular to the axis of the first hole82and over the entire circumference of the first hole82. This groove94is separated from the shoulder90by a distance substantially equal to the thickness of the flange80. By way of complement, the removable stop92is a circlip92.1accommodated in the groove94.

The attachment body link68comprises a second system for translational immobilization of the shear pin72. This second translational immobilization system comprises a stop plate96, lying against the access face F50′, connected by at least one removable link98to the primary structure50, which closes the first hole82at least in part.

In order to reduce its mass, the stop plate96comprises an orifice100in line with the first hole82that has a diameter smaller than the diameter D80of the flange80. During operation, when the stop plate96is fixed to the primary structure the orifice100is coaxial with the first hole82.

According to an embodiment, the removable link98comprises two fixing elements98.1,98.2that each have a screw. For each fixing element98.1,98.2, the stop plate96has a passage orifice of which the diameter is slightly greater than that of the rod of the fixing element98.1,98.2. By way of complement, for each stop plate96the primary structure50comprises an extension102traversed by each removable link98. Thus, the extension102has a passage hole for each fixing element98.1,98.2. Each fixing element98.1,98.2is a bolt and comprises a nut in addition to the screw. This configuration makes it possible to connect the stop plate96to the primary structure50without the need to drill a hole in the primary structure50.

According to an embodiment visible inFIG.6, the stop plate96comprises, in addition to the orifice100, at least one recess104in order to reduce its mass.

The attachment body link68comprises at least one anti-rotation system106for at least one of the link elements70,70′. According to one configuration, the attachment body link68comprises an anti-rotation system106for each link element70,70′. According to an embodiment, an anti-rotation system106comprises an anti-rotation plate108that has a through-orifice110that has a cross section that complements the upper cross section76.2of the head76of the link element70,70′, and also a removable link112for connecting same directly or indirectly to the primary structure50. By way of complement, it is understood that when the upper cross section76.2of the head76is inserted into the through-orifice110the anti-rotation plate108and the head76are immobilized in rotation relative to one another.

The removable link112comprises a first passage hole112.1of oblong form at the anti-rotation plate108and a fixing element112.2, such as a bolt, for example. The oblong form of the passage hole112.1has the same center as the through-orifice110and makes it possible to accommodate the fixing element112.2by tolerating a slight angular offset of the anti-rotation plate108.

According to an embodiment visible inFIG.6, each anti-rotation plate108is connected to the stop plate96that is itself connected to the primary structure50. To that end, for each anti-rotation plate108the stop plate96comprises an extension114that has a passage orifice for the corresponding fixing element112.2.

The method for mounting the engine attachment54is as follows:

In a first stage, the attachment body56is connected to the aircraft engine52by the connecting rods58.

Next, the aircraft engine52is moved vertically such as to position the first and second contact faces F50and F56facing one another. The passage holes of the link elements70,70′ are aligned, for example by inserting centering pins in the first and second holes82,84designed for the shear pins.

The link elements70,70′ are placed. Next, the centering pins are removed and the shear pins72are inserted into the first and second holes82,84until, for each of them, the flange80bears against the shoulder90. For each shear pin72, the circlip92.1is placed in the groove94of the enlarged portion82.2of the first hole82.

For each link element70,70′ the anti-rotation plate108is placed in position. Next, for each shear pin72the stop plate96is positioned and then the fixing elements98.1,98.2are placed in position to connect the stop plate96to the primary structure50. Lastly, each anti-rotation plate108is connected to the stop plate96by the fixing elements112.2.

In terms of dismantling, the above steps are reproduced in the reverse order.

According to this assembly method, each shear pin72and its immobilization systems are placed from only the access face F50′. Thus, the space between the attachment body56and the aircraft engine52may be very small at the front of the attachment body56.