EP1376039B1 - Multi tubular heat exchangers and process for making same - Google Patents

Abstract

An abutment is formed inside a cavity defined by a shell to prevent or restrict movement of a multi-tube bundle (34) relative to the shell. An Independent claim is included for a heat exchanger manufacturing method.

Description

The present invention relates to improvements made to shell-and-tube heat exchangers and methods of manufacturing such exchangers.

The invention is particularly applicable to heat exchangers between a first fluid circulating in a plurality of tubes forming a multitubular bundle, and a second fluid circulating around the tubes, in a cylindrical cavity delimited by a hollow body (or calender) in which extends the bundle of tubes; the invention applies in particular to heat exchangers for heat engines, reducers, inverters, compressors, hydraulic units, etc .; in this type of exchanger, the transfer of heat energy between the hot source and the cold source is effected in particular by conduction through the wall of the tubes; in order to obtain a sufficient energy transfer flux (and / or a heat exchange coefficient), the tubes are made of a material having a high thermal conductivity, such as a copper-based metal alloy, aluminum, nickel, titanium or stainless steels.

The invention applies in particular to such exchangers comprising two tubular plates pierced with a plurality of orifices; each of the two ends of each of the tubes is engaged in one of the orifices of a tubular plate and is sealed to this plate in particular by brazing, welding or swaging.

The tubular bundle may comprise, in addition to the tubes and the end tube plates, baffles for guiding the flow of the second fluid inside the hollow body; these baffles generally consist essentially of thin plates extending transversely to the tubes and parallel to the end tube plates, are regularly spaced along the tubes and close part of the cross section - generally circular - of the hollow body, to guide the second fluid; the beam may also comprise fins crimped or otherwise related to the outer surface of the tubes of the beam; it may include other secondary surfaces.

Such exchangers generally further comprise, at each of its two longitudinal ends, a cap (water box) respectively covering one of said tubular plates, and allowing either the connection of the exchanger to two ducts (external to the exchanger) of transport of the first fluid, ie the guidance of this fluid in the case of a cap "blind", that is to say devoid of connection to an external conduit.

The hollow body is provided with an inlet orifice of the second fluid in said cavity as well as an outlet orifice of this fluid; the hollow body is generally constituted by a generally tubular piece provided at each of its two longitudinal ends with an annular flange; each flange is pierced with a plurality of orifices extending along the longitudinal axis of the exchanger and receiving screws - or similar fastening members - for fastening to the body, in a sealed manner, at least one of the tubular plates, as well as the two caps.

The body of small exchangers (particularly larger diameter less than 0.25 meters) is generally manufactured by molding (without pressure) a metal alloy, the body and the flanges being molded in one piece; this technique has drawbacks: the inner face of the body must be machined over its entire length to have a roughness and geometric quality compatible with the use that is made of it; the outer faces of the flanges must also be erected; these moldings often have defects in their mass resulting in a porosity incompatible with the function of sealed wall they must fill; moreover, these defects can only be validly checked after mechanical machining (boring, turning, etc.); it is thus necessary to discard expensive parts; the pressure-free molding technique (in sand molds) also prevents the production of thin walls.

It has been proposed in the patent FR 623803 a multitubular exchanger whose body consists of an ordinary pipe section and is devoid of end flanges; this technique makes it difficult and / or expensive to produce sealed connections for entering and leaving the second fluid in the cavity.

It was described in the document EP-A-1 146 310 an exchanger whose extruded calender has an external rib in which are provided the inlet and outlet ports of the second fluid, which overcomes this problem; this exchanger does not comprise rigid connection means between the hollow body and the tubular bundle, the mechanical connection between these elements resulting essentially from the contact forces (of support) exerted between these two parts by means of organs such as two O-rings, which are flattened (compressed) between two cylindrical bearing faces (or spans) provided respectively on each of these two pieces; in the absence of these sealing members, the beam can slide freely in the body cavity; in the presence of these sealing members the beam can slide in the cavity under the action of a sufficient force, in particular under the action of the elongation of the tubes of the beam, because of their thermal expansion; each of the sealing members is housed in an annular groove provided on the outer face of the tubular plates; this avoids the realization of grooves on the inner face of the wall of the hollow body which then only requires the realization of a chamfer at its (their) end (s) internal (s); this allows to introduce by sliding a beam whose tubular plate is provided with the seal without damaging the seal and facilitating its crushing.

Documents are also known US 1,994,779 and US 3,363,680 , multitubular beam exchangers in which the blocking of the beam is carried out by insertion abutting intermediate tubular ends between the beam and the shell of the exchanger.

An object of the invention is to provide such exchangers that are improved, and a method of manufacturing these exchangers that reduces the cost.

According to a first aspect, the invention consists in proposing such exchangers in which a mutual engagement of the shell and the beam forms an abutment inside the cavity delimited by the shell, which prevents or limits a displacement of the beam relative to at the front grille; said exchangers being in accordance with claim 1.

This mutual engagement can result from a deformation of a part of the beam and / or part of the shell, or the insertion of a member forming a stop (or shoulder) inside the cylindrical cavity bounded by the grille; in all cases, these deformations and / or insertions are made after the beam has been introduced and correctly positioned inside the shell.

This makes it possible to prevent or limit the rotation and / or the translation of the tubular bundle inside the shell. This therefore makes it possible to use baffles that do not have central symmetry, as is the case with the disk-shaped baffles described in the document. EP 1 146 310 ; this makes it possible in particular to use baffles in the shape of a portion of a disc - or disc cut - and a multitubular bundle having one or more tubes extending along - or in close proximity to - the central longitudinal axis of the bundle; therefore, the distribution and / or the number of tubes of the beam can be improved (increased) - for a cavity of a given volume -, and the efficiency and / or compactness of the exchanger is thus also increased (e).

Preferably, this stop is partly at least provided by a projection provided on the inner face of the calender wall, so that it is not necessary to manufacture for this purpose a separate part of the calender.

More preferably, this projection or narrowing forming a stop extends over only a portion of the inner transverse circular contour of the shell. The realization of this abutment is further simplified by making it around one of the fluid inlet and outlet ports in the cavity defined in the shell, in particular by pushing at least a portion of a flange, towards the inside. cavity; in addition or alternatively, the projection may be made at the periphery of a thin wall of the bundle, in particular of a tab integral with a tubular plate of the bundle, by pushing this thin wall or tongue towards the outside of the cavity , so as to obtain either a rigid frictional connection between the beam and the shell, or a blockage by penetration of the wall or tongue into an orifice formed in the wall of the shell, in particular in one of said inlet or outlet orifices. fluid outlet.

According to another possible embodiment, this projection may be incorporated at the end of a connecting part of the shell to a conduit for transporting this fluid - hereinafter referred to as second fluid -; for example, this projection may consist of a tubular portion extending a connection screwed into a threaded hole provided in the wall of the calender; this may allow to obtain a rigid connection between the beam and the shell, which is reversible (removable).

According to a preferred embodiment, this projection consists essentially of a portion of the wall of the shell, and is provided (and / or extends) around one of said orifices (inlet and outlet fluid) to less; preferably, the abutment or projection is adapted to engage in a depression or indentation provided at the periphery of a part of the tubular bundle - preferably at the periphery of a portion of a tubular plate.

In the latter case, this part which comprises a first disk-shaped portion pierced with holes for passing and fixing the tubes of the bundle, and a second portion in the form of a tube or circular flange extending longitudinally to from the inner face of the first disk-shaped portion, preferably comprises a notch or depression of substantially circular profile and a diameter adapted to the dimensions of the abutment protruding on the inner face of the calender, this notch or depression being integrated in the second part of the tube plate.

In the case where two such protruding abutments forming an integral part of the calender are provided around each of the two orifices for the passage of the second fluid, these abutments cooperating respectively with two indentations provided in two tubular plates, the beam can not then be extracted from the cavity, the bond being generally irreversible.

Preferably, such integrated protruding abutments are formed by deformation of a flange provided in the wall of the calender, at the inner end of a passage duct of the second fluid provided in this wall; this production method is particularly simple and inexpensive; this deformation must generally be performed after putting the tube bundle at its final location in the cavity defined by the shell.

• On perce la paroi de la calandre d'un orifice d'entrée et d'un orifice de sortie de fluide de façon à réaliser deux conduits de passage du fluide dans cette paroi, chaque conduit présentant, du côté de la face interne de la calandre, une ouverture rétrécie résultant d'une collerette annulaire obtenue lors du perçage de la paroi à l'aide d'un foret profilé (épaulé),
• On taraude une partie de chaque conduit de passage - à l'exclusion de la collerette -, de façon à permettre le vissage d'un raccord dans chaque orifice taraudé,
• On engage le faisceau dans la calandre et on positionne les échancrures ou dépressions dans le prolongement respectif de chaque conduit de passage percé dans la calandre,
• En empêchant le déplacement du faisceau dans la calandre, on déforme chaque collerette en exerçant sur elles - à l'aide d'un outil présentant de préférence une portée sphérique - un effort (radial) suffisant, jusqu'à ce qu'une partie au moins de chaque collerette faisant saillie sur la face interne de la paroi de la calandre, soit respectivement engagée dans la dépression ou échancrure correspondante, de sorte que le faisceau est immobilisé dans la calandre.

Thus, according to another aspect, the invention proposes a method for manufacturing a shell-and-tube heat exchanger according to claim 17. According to a particular embodiment of the method according to the invention, for manufacturing a heat exchanger multitubular comprising an extruded calender and a multitubular bundle comprising two tubular plates equipped with a depression or indentation at their periphery, the following operations are carried out successively:

• The wall of the shell is pierced with an inlet orifice and a fluid outlet orifice so as to produce two fluid passage ducts in this wall, each duct having, on the side of the internal face of the shell a narrowed opening resulting from an annular flange obtained during the drilling of the wall using a profiled drill (shouldered),
• One part of each passage duct is screwed - excluding the flange -, so as to allow the screwing of a connection in each threaded orifice,
• The beam is engaged in the calender and the indentations or depressions are positioned in the respective extension of each passage duct pierced in the calender,
• By preventing the displacement of the beam in the calender, each flange is deformed by exerting on them - with the aid of a tool preferably having a spherical bearing - a sufficient (radial) force, until a portion of less than each flange protruding from the inner face of the wall of the calender, is respectively engaged in the corresponding depression or notch, so that the beam is immobilized in the calender.

In another aspect, this method may further include the features of claim 19.

A tubular shell-and-tube heat exchanger is described hereinafter, the bundle having two tubular plates, at least one plate - and preferably each - plate comprising: i) a first disk-shaped portion pierced with orifices receiving the tubes of the beam; if necessary ii) a second part extending from the internal face of the first part and incorporating either a housing provided to receive a stop protruding from the inner face of the shell, or an expandable wall or tongue provided for s engage - after deformation - in an orifice formed in the wall of the calender; iii) a third portion of tubular form extending from the outer face of the first portion, and adapted to be engaged in an end of a transport duct of the first fluid fixed to the third part of the plate by forced fitting and / or by strapping; preferably, the third tubular portion comprises for this purpose an outer annular rib.

This allows in particular to reduce the number of seals required.

• La figure 1 est une vue en perspective d'un mode préféré de réalisation d'un échangeur selon l'invention.
• La figure 2 est une vue en coupe longitudinale d'une calandre d'un échangeur selon l'invention.
• La figure 3 est une vue en coupe transversale - selon III - de la calandre illustrée figure 2 ; la figure 4 est une vue de détail à échelle agrandie - selon IV - d'un des passages de fluide percés dans la paroi de la calandre illustrée figure 2.
• La figure 5 est une vue en coupe longitudinale d'un faisceau tubulaire d'un échangeur selon l'invention.
• La figure 6 est une vue schématique en coupe transversale - selon VI - VI du faisceau illustré figure 5.
• La figure 7 est une vue de côté d'une pièce formant plaque tubulaire et manchon de raccordement, qui comporte une échancrure demi-circulaire de positionnement à sa périphérie interne.
• La figure 8 est une vue de côté montrant schématiquement l'assemblage du faisceau et de la calandre.
• Les figures 9 et 10 illustrent une variante de réalisation de l'invention dans laquelle une languette solidaire d'une plaque tubulaire du faisceau est engagée dans un orifice de passage de fluide percé dans une nervure de la calandre ; la figure 10 est une vue en coupe longitudinale - selon X-X- de la figure 9 ; cette dernière est une vue de dessus d'une extrémité d'un échangeur.
• Les figures 11 et 12 illustrent une variante de réalisation de l'invention dans laquelle un manchon tubulaire de raccordement servant de butée d'immobilisation du faisceau est engagé dans un orifice de passage de fluide percé dans une nervure de la calandre ; la figure 12 est une vue en coupe longitudinale - selon XII-XII- de la figure 11 ; cette dernière est une vue de dessus d'une extrémité d'un échangeur.

Other advantages and features of the invention will be understood through the following description which refers to the accompanying drawings, and which illustrates without any limiting nature of the preferred embodiments of the invention.

• The figure 1 is a perspective view of a preferred embodiment of an exchanger according to the invention.
• The figure 2 is a longitudinal sectional view of a shell of an exchanger according to the invention.
• The figure 3 is a cross-sectional view - according to III - of the illustrated grille figure 2 ; the figure 4 is a detail view on an enlarged scale - according to IV - of one of the fluid passages pierced in the wall of the illustrated grille figure 2 .
• The figure 5 is a longitudinal sectional view of a tubular bundle of an exchanger according to the invention.
• The figure 6 is a schematic cross-section - along VI - VI of the illustrated beam figure 5 .
• The figure 7 is a side view of a piece forming a tubular plate and connecting sleeve, which has a semicircular positioning notch at its inner periphery.
• The figure 8 is a side view schematically showing the assembly of the beam and the shell.
• The Figures 9 and 10 illustrate an alternative embodiment of the invention in which a tab integral with a tubular plate of the bundle is engaged in a fluid passage hole pierced in a rib of the shell; the figure 10 is a longitudinal sectional view - according to XX- of the figure 9 ; the latter is a top view of one end of a heat exchanger.
• The Figures 11 and 12 illustrate an alternative embodiment of the invention in which a tubular connecting sleeve serving as immobilizing stop beam is engaged in a fluid passage hole pierced in a rib of the calender; the figure 12 is a view in longitudinal section - according to XII-XII- of the figure 11 ; the latter is a top view of one end of a heat exchanger.

Unless otherwise indicated, elements, parts and the same or similar members shown in several figures, are identified by an invariable reference from one figure to another.

By reference to the figure 1 , the exchanger 1 comprises a shell 2 of longitudinal axis 3, and a tubular bundle housed in the cavity defined in the shell; the shell has a plurality of flat outer faces 4 to 13 (see figure 3 ) elongate and parallel to the axis 3; on the face 10 open two channels 14 and 15 connecting the cavity defined by the shell to a fluid such as oil to be cooled.

The calender is obtained by extrusion of aluminum; the resulting profile is soaked and cut into sections such as that illustrated Figures 2 and 3 ; each longitudinal end is machined to obtain a chamfer 16, 17 facilitating the introduction of the tubular bundle equipped with two annular sealing seals (pins 19, 20 figure 8 ) in the cavity 18 defined by the calender, without damaging the seals.

The walls 10 to 12 delimit a longitudinal rib 23 parallel to the axis 3, in which are drilled the channels 14, 15 of axes 21 and 22 radial.

By reference to Figures 2 to 4 each conduit 14, 15 has a threaded outer portion 24 extending from the face 10 to allow the screwing of a not shown fitting; the inner portion of the conduit through which the latter opens on the cylindrical inner face 25 of the cavity 18, has a diameter 26 smaller than the diameter 27 of the orifice through which the conduit opens on the face 10; this results from the presence of an annular flange 28 formed in the wall 23 during the drilling of the ducts 14, 15 by a profiled drill for this purpose; the flange 28 has a thickness 29 sufficiently low (for example of the order of 1 to 2 millimeters) to be deformed by the action of a tool supported on the inner face 30 inclined, according to the arrow 31 figure 4 ; this makes it possible to pass at least part of this flange of the initial configuration - reference 28 figure 4 - where the flange is flush with the face 25, the final configuration - marked 28a figure 4 - Where the deformed flange protrudes from the face 25, a value 32, for example close to one or two millimeters; in this latter configuration, the flange is engaged in a depression provided at the periphery of the tube plate - as described below - so that it immobilizes the beam in the calender.

This mode of deformation of the collar requires the use of a material having sufficient elongation at break, for producing the calender; for this purpose, the use of extruded and tempered aluminum is more favorable than that of cast aluminum and / or injected.

According to alternative embodiments, the hollow section (or tubular bar) used to form the shell may be obtained by extrusion of plastic material, or by hot spinning or cold drawing of a metal, in particular an aluminum alloy, of copper or steel.

By reference to Figures 5 to 7 in particular, the beam 34 comprises a plurality of tubes 35 parallel to its longitudinal axis 33, a plurality of flat baffles 36, 37 perpendicular to the axis 33, and two end pieces 38.

The contour of the baffles 36, 37 is largely circular (of diameter adapted to that of the cavity 18) and partly rectilinear 36a, 37a, so that the baffles have a truncated disk shape; the baffles 36 having their rectilinear edge 36a in the lower part are arranged, along the axis 33, alternately with the baffles 37 having their rectilinear edge 37a in the upper part, so that these baffles delimit with the calender a labyrinth forcing the second fluid to follow a sinuous path 39 figure 5 .

Each piece 38 has a first portion 380 in the form of a thick disc in which holes are drilled receiving the ends 350 of the tubes 35; this part, which extends transversely to the axis 33, forms the tubular plate itself.

The first portion 380 is extended at the periphery of its inner face 3800 by a second portion 381 of the workpiece 38, which is in the form of a short section of thin tube with an axis 33; at one end of this section, a notch 3810 is formed in the tubular wall of the section, which extends in a circular pattern whose diameter 40 is adapted to the dimensions (in particular to the diameter) of the projection 28a ( figure 4 ) formed on the inner face of the shell.

The first part 380 of the part 38 is further extended at the periphery of its external face 3801 by a third part 382 of the part 38 which is roughly in the shape of a tube section with an axis 33 and whose external face comprises an annular groove 41 provided for receiving one of the seals (19, 20 figure 8 ) sealing with the calender, and an annular rib 42 which protrudes from the central portion 3820 of this portion 382; the latter can thus, as illustrated figure 7 , receiving one end of a connection tube 43 force-fitted around the rib 42 and the cylindrical portion 3820 against which the tube 43 can be held tight by a strapping collar not shown.

In the illustrated assembly configuration figure 8 , each of the notches provided in the end pieces is respectively disposed opposite the inlet and outlet ports 14, 15 and receives a portion of the annular protrusions extending-these orifices, so that the beam is immobilized in the calender.

By reference to Figures 9 and 10 the tubular portion 381 of axis 33 extending tubular plate 380 of the bundle comprises a tongue-shaped portion 3811 which has been deformed after positioning the bundle in the shell, so that it extends inside the the orifice 14 for fluid passage, bearing against the wall delimiting this orifice; the tongue 3811 prevents the beam from sliding in the shell, along their common axis 3, 33 in the direction indicated by the arrow 100; by also equipping the second tube plate (not shown) of the same heat exchanger of such a tongue, it is also prohibited such sliding in the opposite direction, and a rotation of the beam.

By reference to Figures 11 and 12 , a tubular sleeve 99 extends inside the conduit 14 for fluid passage drilled in the rib 23 of the shell, along the axis 21 of the conduit 14, on the walls of which leads this sleeve is supported.

The sleeve 99 protrudes from the inner face of the calender; therefore, it is engaged in a notch 3810 identical or similar to that described above, so that it limits the sliding of the beam in the calender; by further equipping a second conduit (as marked 15) by a second sleeve projecting inside the calender, the sliding and rotation of the beam in the calender is prevented.

Claims (19)

1. A heat exchanger comprising a multi-tube bundle and a shell, in which direct mutual engagement between the shell and the bundle forms an abutment inside a cavity defined by the shell, the said shell presenting an inlet orifice (14) for admitting fluid into the cavity and an outlet orifice (15) for exhausting fluid from the cavity, and a projection (28a, 3811, 99) placed around or within at least one of said orifices forms, at least in part, said abutment, and prevents any movement in rotation and/or translation of the bundle relative to the shell.
2. A heat exchanger according to claim 1, wherein the said projection is a result of deforming of a portion (3811) of the bundle and/or a part (28a) of the shell.
3. A heat exchanger according to claim 1, wherein the said projection is a result of inserting and abutment-forming member 99 inside the shell.
4. A heat exchanger according to claim 1 or 2, wherein the said abutment is made by a projection (28a, 3811) made by chasing of a portion (28) of the inside wall (25) of the shell towards the inside of the cavity (18) or of a thin wall (3811) of the bundle towards the outside of the cavity.
5. A heat exchanger according to claim 4, wherein the said projection extends over a fraction only of the inside transverse circular outline of the shell.
6. A heat exchanger according to anyone of claims 1 to 5, wherein said orifices (14, 15) present a collar (28) of small thickness to allow it to be deformed under drive from a tool pressed against inside of the cavity (18) defined by the shell and to form a said projection (28).
7. A heat exchanger according to anyone of claims 1 to 6, in which the shell presents at least one outside longitudinal spline (23) through which the orifices (14, 15) are pierced.
8. A heat exchanger according to anyone of claims 1 to 7, in which the bundle includes baffles (36, 37) in the form of truncated disks and/or in the form of disk portions, and in which the said deformation of the bundle or the shell forms an abutment preventing or restricting movement in rotation and/or translation of the bundle in the cavity.
9. A heat exchanger according to anyone of claims 1 to 8, in which the bundle has an end tube plate (380) and a cap (382) for coupling the heat exchanger to a duct (43) for transporting fluid that flows in the tubes of the bundle, and in which the tube plate and the cap form a single piece (38).
10. A heat exchanger according to claim 9, in which the cap presents an annular rib (42) situated on an external tubular and/or cylindrical portion of the cap so as to enable a duct (43) to be secured to the cap by forced engagement and/or by clamping.
11. A heat exchanger according to anyone of claims 1 to 10, in which the abutment co-operates with a part secured to the tube plate of the bundle to prevent or restrict sliding and/or turning of the bundle of tubes inside the cavity.
12. A heat exchanger according to claim 11, in which the tube plate presents a setback or notch (3810) co-operating with an abutment (28a) projecting from the inside face of the wall (25) of the shell.
13. A heat exchanger according to anyone of claims 1 to 12, in which the bundle (34) has two tube plates (38, 380), each having an annular groove (41) in its outside face receiving a seal bearing against a cylindrical bearing surface of the shell.
14. A heat exchanger according to anyone of claims 1 to 13, in which the shell is constituted essentially by at least a segment of hollow section member defining a cylindrical cavity.
15. A heat exchanger according to claim 14, in which the section member is made of metal which has been drawn or extruded.
16. a heat exchanger according to claim 15, wherein the section member is made of aluminum which has been extruded or quenched.
17. A method of manufacturing a heat exchanger with a multi-tube bundle and a shell according to anyone of claims 1 to 16, in which a portion of the bundle or of the shell is deformed so as to cause the shell and the bundle to be mutually engaged, thereby forming an abutment inside the cavity defined by the shell for limiting or restricting movement into rotation and/or translation of the bundle inside the shell, the said shell presenting said inlet and outlet orifices for fluid and the said abutment is made by a said projection (28a, 3811, 99) placed around or in at least one of said orifices, by deforming of a portion (3811) of the bundle and/or a part (28a) of the shell or by inserting and abutment-forming member 99 inside the shell.
18. A method according to claim 17 for making a multi-tube heat exchanger comprising a shell (2) and a multi-tube bundle (34) having two tube plates each fitted with a setback or notch (3810) at its periphery, in which method, the following operations are performed in succession:

    · piercing the wall (23) of the shell by means of a shaped drill bit to form an inlet orifice (14) and an outlet orifice (15) for fluid so as to provide two fluid flow ducts through said wall, each duct presenting adjacent to the inside face of the shell, a narrowed opening that results from an annular collar (28) obtained while piercing the wall;

    · tapping each fluid flow duct over a portion excluding its collar so as to enable a coupling to be screwed into each tapped orifice;

    · engaging the bundle in the shell and positioning the notches or setbacks respectively in line with each of the fluid flow ducts pierced through the shell; and

    · while preventing the bundle from moving inside the shell, deforming at least a portion of each collar by exerting sufficient force thereon until at least a portion of each collar projects (28a) from the inside face of the wall (25) of the shell and is engaged in the corresponding setback or notch so that the bundle is prevented from moving inside the shell.
19. A method according to claim 17 for manufacturing a multi-tube heat exchanger comprising a shell (2) and a multi-tube bundle (34) comprising two tubular plates (380) equipped with a tongue (3811), in which the successive following steps are carried out :

    · piercing the wall (23) of the shell to form an inlet orifice (14) and an outlet orifice (15) for fluid so as to provide two fluid flow ducts through said wall, each duct presenting adjacent to the inside face of the shell, a opening obtained while piercing the wall by means of a shaped drill bit,

    · positioning the bundle inside the shell and deforming a portion at least of each tongue (3811) so as to extend respectively inside each orifice (14, 15) in the wall of the shell, and press against the wall defining each said orifice, the tongues (3811) preventing the bundle from sliding or rotating inside the shell.

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