The present invention relates to a connecting rod, an aeronautic floor structure incorporating it, and a method for manufacturing this connecting rod. The invention generally applies to a connecting rod suitable for reacting primarily axial forces, in particular but not exclusively in the aeronautics field, this connecting rod advantageously being able to be structural and being able to be made from composite materials.
The current composite connecting rods for reacting axial forces typically have an elongated shape with a central primary body provided with two heads with flared end-pieces respectively ending with ends for connecting to structures in particular creating axial traction-compression forces, the connection typically being done by connecting axes respectively mounted through these ends.
Document WO-A1-2010/024994 describes such a connecting rod whose composite body is assembled by gluing to the end-pieces of its connecting heads, by means of annular inserts covering the ends of the body and covered by these end-pieces.
The connecting rods described in this document have the drawback of having a relatively high mass and manufacturing cost, in particular due to the inserts required for their assembly.
More generally, one major drawback of the composite connecting rods known at this time lies in their high mass, which is related on the one hand to the processing method used, typically resin transfer molding (RTM) or preimpregnated compression molding using a bladder, and on the other hand, to the reinforcement of these connecting rods to give them sufficient strength with respect to impacts and any manufacturing defects, since the tolerance for damage and manufacturing defects is a characteristic specifically required for composite parts.
One aim of the present invention is to propose a connecting rod resolving the aforementioned drawbacks, that comprises a tubular body with two ends and two heads for connecting those ends to adjacent structures and that is suitable for reacting primarily axial forces (i.e., traction-compression forces) generated by these structures, each head comprising an end-piece flared toward the body and glued on the latter in a gluing interface.
To that end, a connecting rod according to the invention comprises at least one first sealing gasket mounted radially between and against the body and the end-piece of each head, axially toward the inside of the gluing interface.
The expressions that mention that a first element of a connecting rod according to the invention is situated “axially toward/inside” or “axially toward/outside” a second element of this connecting rod typically means, in the present description, that this first element is situated, in reference to the longitudinal axis of symmetry of the connecting rod body, toward the inside or toward the outside of the body (i.e. toward the center of that body or toward the heads), respectively.
It will be noted that this first sealing gasket in particular makes it possible to ensure constant and balanced radial play and radial positioning wedging of the connecting rod body relative to the connecting heads, as well as sealing during gluing, as will be described below.
According to another feature of the invention, said first sealing gasket, which is annular and preferably an O-ring, can be mounted in a first groove formed at an axially inner end of each end-piece.
It will be noted that the connecting rods according to the invention can advantageously be assembled without screwing end-pieces on the body, and with no intermediate annular insert between the body and each end-piece, which is thus directly glued on that body, unlike the aforementioned document.
According to another preferred feature of the invention, each end-piece comprises a globally frustoconical flared portion extended axially toward the inside by a globally cylindrical axial portion, the connecting rod incorporating, axially toward the outside of said first sealing gasket, injection and/or suction means of a glue that are able to form said gluing interface on the axial portion of each end-piece, this glue having a viscosity at 25° C. preferably less than or equal to 10 Pa.s (for example approximately 1 Pa.s).
It will be noted that this first O-ring makes it possible to ensure sealing of the body-heads assembly during the suctioning, preferably done by vacuum drawing, and also to control the optimal quantity and thickness of glue in the gluing interface, which can advantageously be comprised between 0.1 mm and 0.5 mm.
It will also be noted that this first O-ring makes it possible to protect the glue against aging due to the surrounding fluids (e.g., condensates, water, dispersions of hydraulic liquids such as phosphate esters of the “Skydrol” type), during the usage time of the connecting rod during operation.
As a non-limiting example, this glue can be of the bi-component epoxy resin type, cross-linkable at ambient temperature or heat activated, having specified that other glues, for example bi-component cross-linkable at ambient temperature or heat-activated, can be used as long as they have this reduced viscosity.
Preferably, said injection and suction means comprise a first series of orifices circumferentially spaced apart to inject or suction glue and a second series of orifices circumferentially spaced apart to suction or inject the injected glue or to suction through the first series of orifices, these two series being axially separate from one another.
Still more preferably, said first series of orifices is formed through each end-piece substantially at the junction between said flared portion and said axial portion, said second series of orifices being formed through the axial portion or else through said body facing the axial portion.
Still more preferably, said first series is formed by first orifices crossing axially through each end-piece radially facing said gluing interface between said body and this end-piece, and said second series is formed by second orifices crossing radially through said axial portion of each end-piece or else said body.
According to a first preferred embodiment of the invention, said second orifices cross through said axial portion of each end-piece radially outside said body, which is thus topped by this axial portion while being fitted in the end-piece, the glue overlapping at least one radially outer face of the body.
According to a second embodiment of the invention, said second orifices cross through said body radially outside said axial portion of each end-piece, and each end of the body is wedged in an axial groove of the corresponding end-piece, this axial groove being radially inwardly defined by the axial portion and radially outwardly defined by an outer axial wall that extends said flared portion parallel to the axial portion over a shorter distance than this axial portion, the glue covering at least one radially inner face of the body.
According to another optional and particularly advantageous feature of the invention, the connecting rod can further comprise, for the connection of each end-piece to said body, at least one annular second sealing gasket or mastic, preferably an O-ring, that is mounted in a second groove of each end-piece formed axially facing said axial portion and the corresponding end of said body, said first sealing gasket and this second sealing gasket or mastic being mounted radially on either side of the body and axially opposite one another, the glue covering both the radially inner and outer faces of the body.
It will be noted that the preferred use of these first and second O-rings bearing against the two outer and inner faces, respectively, of the connecting rod body makes it possible to further improve:
According to said first embodiment of the invention, for each end-piece, said second groove can extend axially from said flared portion radially inside said axial portion, said second sealing gasket or mastic pressing against a radially inner face of the corresponding end of said body.
According to said second embodiment of the invention, for each end-piece, said second groove can extend over said outer axial wall radially outside said axial portion, said second sealing gasket or mastic pressing against a radially outer face of the corresponding end of said body.
According to another feature of the invention, said body, which is for example pultruded, can be based on at least one ply comprising first fibers primarily parallel to a longitudinal axis of symmetry of the body and impregnated with a thermoplastic or thermosetting matrix, and on second wrapping fibers wound in a spiral obliquely around these first fibers, and each end-piece (metal or not) can then be glued on said body by infusion of a resin, for example epoxy, on each end-piece.
It will be noted that pultrusion is only one possibility among others that can be considered to shape the connecting rod body according to the invention, having specified that the pultruded body has the advantage of contributing significantly to lightening the connecting rod of the invention, since pultrusion advantageously makes it possible to give the fibers a primary orientation in the longitudinal direction of the connecting rod body.
It will also be noted that the second wrapping fibers inclined optimally advantageously make it possible to give the connecting rod a satisfactory crushing and impact resistance, and can be identical in nature or different with respect to the first fibers of the body, based on needs.
The separation between these first globally unidirectional and axial inner fibers and these second outer wrapping fibers primarily intended to protect these first fibers appears particularly advantageous.
Alternatively, said body and said end-pieces can be based on at least one thermoplastic material, and each end-piece can then not only be glued on the body, but also be mechanically attached to the latter by permanent deformation of the body radially against each end-piece by crimping able to form an assembly stop (i.e., a mechanical stop) for the junction between each end-piece and the advantageously pultruded body.
According to another feature of the invention, each of said heads comprises a connecting end for connecting to said structures that extends said corresponding end-piece axially toward the outside of the body and that is:
An aeronautic floor structure according to the invention is such that it includes at least one connecting rod as defined above.
A manufacturing method according to the invention for a connecting rod as defined above comprises the following steps:
a) assembling said at least one first sealing gasket in contact with each of said end-pieces and a first radially inner or outer face of an end zone opposite said body, then
b) gluing each end-piece on the body, by injection and suction—preferably by vacuum drawing—of a glue radially between the body and each end-piece and axially toward the outside of this first sealing gasket, the glue having a viscosity at 25° C. preferably less than or equal to 10 Pa.s (for example, approximately 1 Pa.s).
According to another optional feature of the invention, this method may further comprise, in step a), mounting at least one second sealing gasket or mastic in contact with each end-piece and a radially outer or inner second face of said body opposite said first face, said first sealing gasket and said second sealing gasket or mastic thus being mounted radially on either side of the body and axially opposite one another facing a globally cylindrical axial portion of each end-piece.
According to another feature of the invention, this method can advantageously comprise, before step a), forming by pultrusion of said body, which can have a base of at least one ply of fibers impregnated with a thermoplastic or thermosetting matrix, and step b) for gluing can be implemented by infusion of a resin, for example epoxy, in contact with each end-piece.
In general, it will be noted that each end-piece according to the invention can be metal (for example aluminium) or not, in the latter case being able to be of the plastic or composite type (with a base of a thermoplastic or thermosetting matrix).
If the connecting rod body is of the composite type, its fiber impregnation matrix can advantageously be chosen to be thermosetting, for example being based on at least one epoxy resin, or thermoplastic, for example based on at least one polymer chosen from the group made up of polyolefins, polyamide (PA), polyetherimides (PEI), polyarylimides (PAI), polyphenylene sulfide (PPS), polyaryletherketones (PAEK), polyether sulfones (PDF), polyetheretherketones (PEEK), polyetherketoneketones (PEKK) and mixtures thereof. It will be noted that it is also possible to use, for this thermoplastic matrix, mixtures of very different polymers (for example, two thermoplastic polymers that are respectively polar and apolar) with or without comptabilizers and optionally combined with other additives. The fibers usable in a composite connecting rod body can for example be based on carbon, non-limitingly.
If metal end-pieces and carbon fibers are used for the connecting rod body, it will be noted that said first sealing gasket and optionally said second sealing gasket make(s) it possible to oppose the galvanic corrosion of each end-piece by these carbon fibers.
It will be noted that other polymers and fibers can be used to form the connecting rod body, provided that they give the connecting rod an impact resistance and sufficient ability to react axial forces.
It will be noted that a connecting rod according to the invention has, in particular owing to materials having intrinsic properties of self-extinguishing, low density, smoke toxicity and, due to a particularly high elongation at break for the thermoplastic matrices, an improved impact resistance, significantly increased lightening for a same given value of these properties (e.g., impact resistance) relative to the known composite structural connecting rods.
This connecting rod according to the invention thus in particular has, due to said first primarily unidirectional fibers in the axis of the connecting rod that are protected by an outer layer of said second fibers dedicated to impact resistance, improved mechanical properties regarding the reaction of axial forces and impact resistance, which appears to result in mass savings on the connecting rod to obtain determined properties.
Other features, advantages and details of the present invention will emerge from reading the following description of several example embodiments of the invention, provided as an illustration and non- limitingly, the description being done in reference to the attached drawings, in which:
As illustrated in particular in
As shown in
In the example of
In the alternative of
Each end-piece 105 according to the invention incorporates (see
The body 102 is guided inside the end-piece 105 in contact with the first seal 110 to be radially fitted inside the axial portion 105b, until the axially inner end of the body 102 abuts against the junction between the axial portion 105b and the frustoconical portion 105a of the end-piece 105. The first seal 110 then bears on the radially outer face of the body 102.
In order to perform this gluing by vacuum drawing under better conditions, to facilitate the guiding of the body 102 in each end-piece 105, to improve the subsequent protection of the obtained gluing interface 111 with respect the environment and maximize the surface area of this interface 111, in particular, it may be advantageous to provide the end-piece 105 of
After this gluing by vacuum drawing, the glue 111 covers the outer face of the body 102 and the inner face opposite the axial portion 105b of each end-piece 105, with the exception of the first groove 106, since the annular gluing interface 111 (which can have a thickness from 0.1 mm to 0.5 mm) ends axially outside the first seal 110.
Each end-piece 205 according to this second embodiment incorporates (see
Unlike the aforementioned first embodiment, the second circumferentially spaced apart orifices 202a to suction or inject the injected glue 211 or to suction through the first orifices 208, are here not formed at each end-piece 205, but radially through an axially inner zone of the body 202. These second orifices 202a are found immediately below the first seal 210 (i.e., axially toward the outside of the latter), once the body 202 has been guided on each end-piece 205 in contact with the first seal 210 so that it can be radially fitted outside the axial portion 205b until the axially inner end of the body 202 abuts at the bottom of an axial groove 9 at the end-piece 205 (the first seal 210 then bears on the radially inner face of the body 202). The axial groove 9 is radially defined inside by the axial portion 205b and radially outside by an outer axial wall 205c that extends the flared portion 205a parallel to the axial portion 205b over a shorter distance than this axial portion 205b.
Furthermore, this short outer axial wall 205c of the axial groove 9 comprises, on its radially inner face, a groove 205d receiving a second O-ring seal 220 that bears on the radially outer face of the corresponding end of the body 202. As previously explained, the combined use of these first and second seals 210 and 220 makes it possible to optimize the guiding of the body 202, the gluing, the gluing interface 211 and its subsequent protection.
Indeed, after this gluing by vacuum drawing, the glue 211 (which can have a thickness from 0.1 mm to 0.5 mm) covers not only the outer face of the axial portion 205b of each end-piece 205—with the exception of the groove 206, since the gluing interface 211 ends axially outside the first seal 210—and the inner face of the body 202, but also the radial end and the zone of the outer face of the body 202 situated below the second seal 220. In other words, the glue 211 here covers two respective annular zones of the inner and outer faces of the body 202, continuously via the radial end of the latter.
It will be noted that the method for manufacturing a connecting rod according to the invention makes it possible not only to produce connecting rods designed for aeronautic floors, but also all connecting rods of systems or secondary structure, equipment or furniture fastenings, for example like those illustrated in
Number | Date | Country | Kind |
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1355174 | Jun 2013 | FR | national |
Filing Document | Filing Date | Country | Kind |
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PCT/IB2014/061919 | 6/3/2014 | WO | 00 |