FR3116567A1 - METHOD FOR ASSEMBLING TURBOMACHINE INJECTORS AND ASSOCIATED KEYING DEVICE - Google Patents

Abstract

The invention relates to a method for mounting several injectors (24) of a turbomachine (10) on an outer casing (14) of a combustion chamber (12) of the turbomachine (10), an annular joint (46a, 46b) being interposed between a flange (34) for fixing each injector (24) and the outer casing (14), the turbomachine (10) comprising seals (46a, 46b) of at least two different models, the method comprising for each injector (24) a step (E1) of gripping a seal (46a, 46b) of the corresponding model, characterized in that it comprises a step (E2) of keying chronologically following the step (E1) of gripping which consists verifying that the joint (46a, 46b) entered during step (E1) of gripping conforms to the model of joint required for mounting said injector (24). Figure for abstract: Figure 8

Description

METHOD FOR ASSEMBLING TURBOMACHINE INJECTORS AND ASSOCIATED KEYING DEVICE

Technical field of the invention

The invention relates to a method for mounting several turbomachine injectors on an outer casing of a combustion chamber of the turbomachine, an annular seal being interposed between a fixing flange of each injector and the outer casing, the turbomachine comprising seals of at least two different models, the method comprising for each injector in chronological order a step of gripping a seal of the corresponding model followed by a step of positioning the seized seal on the outer casing.

The invention also relates to a keying device for implementing the mounting method.

Technical background

In a well-known manner, an aircraft turbine engine comprises a fan allowing the suction of an air flow which is divided into a primary flow and a secondary flow. The primary flow passes through the engine of the turbomachine while the secondary flow is directed towards a secondary stream delimited by a casing fixed to a nacelle of the aircraft and an engine support structure.

The primary flow is compressed within, for example, a low pressure compressor then a high pressure compressor of the engine. The compressed air is then mixed with fuel and burned in an annular combustion chamber arranged downstream of the series of compressors. The gases formed by the combustion pass through a high pressure turbine and a low pressure turbine located downstream of the combustion chamber and which drive the compressors. The gases finally escape through a nozzle whose section allows the acceleration of these gases to generate propulsion.

The combustion chamber defines an annular enclosure delimited radially by an internal casing and an external casing, the casings being arranged coaxially with respect to the longitudinal axis of the turbomachine. The fuel supplying the combustion chamber is injected through several injectors arranged around the combustion chamber.

The injectors have a tubular body extending between a first end fixed to the outer casing of the combustion chamber by a fixing flange and a second end comprising a fuel ejection nozzle which opens into the bottom of the combustion chamber. The tubular body has a part which extends radially with respect to the axis of the combustion chamber and a bent part so that its second end is oriented in the axis of the combustion chamber.

The injectors are placed in a hot air circulation zone and are therefore frequently subjected to temperatures above 150°C, in particular during the engine slowing down or stopping phases.

To guarantee good sealing of the combustion chamber under these extreme temperature and pressure conditions, an annular gasket is inserted between the fixing flange and an external face of the external casing.

Such a combustion chamber can comprise a large number of injectors, for example eighteen injectors. Although it is preferable to have only one seal model to equip all the injectors, this is not always possible. It thus happens that it is necessary to use at least two models of seals in order to be able to guarantee tightness around each injector. For example, when the turbomachine has eighteen injectors, sixteen injectors are equipped with a seal of a first model, called standard or normal seal, while the last two injectors are each equipped with a seal of a second model. , known as an "enriched" joint.

The assembly of the injectors is a delicate operation which is generally carried out manually. Although the seals are stored in two separate compartments, each corresponding to a seal model, it can happen that a seal of the wrong model is installed instead of a seal of the correct model. Such an event can result from an operator error, an error in sorting the seals in the compartments, etc.

Such an event is all the more frequent when the two seal models are fixed to the outer casing by means that are identical in shape and dimensions. Thus, the seals of two different models can be fixed on the outer casing indifferently around any injector passage orifice.

However, the two seal models have differences, particularly in terms of their outside and/or inside diameters. As a result, when an injector is fitted with a seal of the wrong model, sealing is no longer ensured correctly. This risks causing leaks and even much more serious damage, up to and including permanent damage to the injector.

The invention proposes a method and a tool making it possible to solve this problem in a simple and inexpensive manner without having to modify the existing parts. The invention also allows the assembly to be carried out quickly and reliably.

The invention proposes a method for mounting several turbomachine injectors on an outer casing of a combustion chamber of the turbomachine, an annular gasket being interposed between a fixing flange of each injector and the outer casing, the turbomachine comprising gaskets of at least two different models, the method comprising for each injector in chronological order a step of gripping a seal of the corresponding model followed by a step of positioning the seized seal on the outer casing, characterized in that it comprises a keying step interposed chronologically between the step of gripping and the step of positioning the seal which consists in verifying that the seal entered during the gripping step conforms to the seal model required for the assembly of said injector.

By systematically carrying out this foolproofing step before positioning the seal on the outer casing, it is possible to achieve a safer but also faster assembly. Indeed, it is not necessary to wait to have finished fixing the flange to find that a seal is not the right model.

According to another characteristic of the method carried out according to the teachings of the invention, the foolproofing step consists in using a foolproofing device comprising at least a first imprint having a shape complementary to a joint of a first model, in which the seized seal is inserted, the first impression having a shape such that a seal of the second model cannot be inserted therein.

Verification of the joint model by inserting the joint into a corresponding cavity makes it possible to avoid any subjective error of appreciation of the joint model. This is all the more important since the seals of the two models have a similar appearance at first sight, the differences in size from one model to another can go unnoticed in case of lack of attention.

According to another characteristic of the method carried out according to the teachings of the invention, the foolproofing device used during the foolproofing step comprises a second imprint distinct from the first imprint which has a shape complementary to a seal of the second model, the keying method having a prior step of selecting the imprint to be used during the keying step.

The use of two imprints makes it possible to further eliminate the risk of errors due to inattention on the part of the operator.

The invention also relates to a keying device for implementing the mounting method, characterized in that it is in the form of an object having a first face in which is formed a first imprint of complementary shape of a seal of the first model.

The use of such a keying device makes it possible to retain the seals currently used without having to modify their shape. The keying device thus forms a simple tool, inexpensive to manufacture, but very effective in avoiding errors in the selection of a joint.

According to another characteristic of the keying device produced according to the teachings of the invention, it comprises a second face in which is formed a second indentation with a shape complementary to a seal of the second model.

According to another characteristic of the keying device produced according to the teachings of the invention, the seals of the two models intended to be used with the keying device comprise fixing holes by screwing which are arranged identically on the seals of the two models. , each imprint of the keying device being equipped with complementary positioning pins of the fixing holes.

According to another characteristic of the keying device produced according to the teachings of the invention, the two imprints are formed in two opposite faces.

This makes it possible to avoid getting the wrong imprint when using the keying device, a single imprint being accessible, while the other imprint is located under the keying device.

According to another characteristic of the keying device produced according to the teachings of the invention, each imprint of the keying device has walls of an associated color which is different from that of the other imprint.

This constitutes an additional means of preventing the operator from making the wrong impression during the mounting process.

According to another characteristic of the keying device produced according to the teachings of the invention, the face associated with each cavity has at least one groove opening into said cavity allowing the introduction of a finger to easily retrieve a seal introduced into the cavity. .

According to another characteristic of the keying device produced according to the teachings of the invention, the groove opens into a space which is deeper than a support bottom of the seal and which is located in line with the associated cavity.

This facilitates the gripping of the fitted seal in its cavity.

Brief description of figures

Other characteristics and advantages of the invention will appear during the reading of the detailed description which will follow for the understanding of which reference will be made to the appended drawings in which:

There is a half-sectional view along the main axis of a turbomachine which shows a combustion chamber of the turbomachine equipped with an injector.

There is an exploded perspective view showing an injector equipped with a seal ready to be mounted on the external face of an external casing of the combustion chamber.

There is a top view showing the shape of the seal shown in .

There is a detail view which shows the flange of an injector tightened against a boss of the outer casing with the interposition of a seal of an unsuitable model.

There is a view similar to that of the which represents the same injector mounted with a seal of a suitable model.

There is a perspective view which shows a keying device in which a first imprint is facing upwards, the keying device being placed by a face comprising a second non-visible imprint.

There is a view similar to that of the which represents the keying device turned over in the other direction, the second imprint being turned upwards and the first imprint being not visible.

There is a block diagram which represents a method of mounting an injector implementing the keying device of the invention.

Detailed description of the invention

In the rest of the description, elements having an identical structure or analogous functions will be designated by the same reference.

In the remainder of the description, a local geometric reference will be adopted, without limitation, comprising an axial direction directed parallel to the axis "A" of an annular seal 46a, 46b and radial directions orthogonal to the axis "A". of said joint 46a, 46b, which are directed from the inside, close to the axis "A" of the joint 46a, 46b, towards the outside while moving away from the axis "A" of the joint 46a, 46b.

An example of an aircraft turbomachine 10 is shown in the . The turbomachine 10 comprises a gas turbine engine extending along an axis X.

In known manner and not shown, the engine has from upstream to downstream in the direction of gas flow along the axis X, a fan, at least one compressor such as a low pressure compressor and a high pressure compressor , a combustion chamber 12, shown in , at least one turbine such as a high pressure turbine and a low pressure turbine, and a nozzle.

The fan allows the suction of an air flow divided into a primary flow F and a secondary flow. The primary flow F passes through the engine of the turbomachine 10 while the secondary flow is directed towards a secondary stream.

The primary flow F is compressed within the low pressure compressor then the high pressure compressor. The compressed air is then mixed with a fuel and burned within the combustion chamber 12. The gases formed by the combustion pass through the high pressure and low pressure turbines. The gases finally escape through the nozzle, the section of which allows the acceleration of these gases to generate propulsion.

The combustion chamber 12 represented for example on the has an annular shape around the axis X delimited radially by an outer annular casing 14 and an inner annular casing 16 . The combustion chamber 12 is also internally delimited by coaxial outer 18 and inner 20 annular walls joined upstream by an annular wall commonly referred to as the chamber bottom 22.

The combustion chamber 12 also comprises several fuel injectors 24, one of which is shown in , which are intended to supply the combustion chamber 12 with fuel. The injectors 24 are arranged in a ring around the axis X in the casing 14 external. The combustion chamber 12 is for example equipped with eighteen injectors 24.

Each injector 24 is fixed on an outer face of the annular outer casing 14 and passes through the combustion chamber 12 through a passage orifice 26 provided in the annular outer casing 14 and opens into the bottom of the chamber 22.

More particularly, the injector 24 comprises an elongated tubular body 28 extending along an elongation axis Y. The tubular body 28 is generally formed of a metallic material.

The tubular body 28 extends in the combustion chamber 12 between a first end 28a and a second end 28b opposite the first end 28a. The second end 28b includes an ejection nozzle 30 which opens into the bottom of the chamber 22.

The tubular body 28 extends transversely with respect to the axis X of revolution of the combustion chamber 12 and comprises at its second end 28b an elbow 32 allowing the ejection nozzle 30 to extend substantially parallel to the X axis of revolution of the combustion chamber 12.

The first end 28a is fixed to the outer face of the outer annular casing 14 of the combustion chamber 12 by means of an annular fixing flange 34. The fixing flange 34 is for example fixed to the outer casing 14 by screws 36 for fixing. It includes a feed port through which fuel is delivered. The fuel circulates within an internal channel of the tubular body 28 between the first end 28a and the second end 28b to be injected into the bottom of the chamber 22 through the ejection nozzle 30.

We have shown in more detail in the manner in which the injector 24 is attached to the outer casing 14. As explained previously, the outer casing 14 comprises several passage orifices 26, each of which is associated with an injector 24. Each passage orifice 26 passes through a boss 38 formed on the outer face of the outer casing 14 . Each boss 38 protrudes from the outer face of the outer casing 14. Each boss 38 has a flat face 40 against which the flange 34 for fixing the associated injector 24 is intended to be tightened. The flat face 40 is traversed by the orifice 26 of passage.

The fixing flange 34 has fixing holes 42 each of which is intended to be traversed by a screw 36 for fixing. Each fixing flange 34 is here traversed by three fixing holes 42 which are regularly distributed around the first end 28a of the tubular body 28 of the injector 24. The fixing screws 36 are intended to be screwed into corresponding threads 44 which are made in the flat face 40 of the boss 38.

An annular gasket 46a or 46b is interposed between the fixing flange 34 of each injector 24 and the outer casing 14. More specifically, the annular gasket 46a, 46b is interposed between the fixing flange 34 and the flat face 40 of the boss 38. After screwing the fixing screws 36, the annular gasket 46a, 46b is thus tightened between the fixing flange 34 and the outer casing 14.

Such an annular gasket 46a, 46b has been shown in more detail at . The ring seal 46a, 46b has a ring 47 delimited radially by an inner circular edge 48 and an outer circular edge 50. The inner circular edge 48 thus delimits a central orifice 52 with axis "A" orthogonal to the plane of the seal 46a, 46b. The tubular body 28 of the injector 24 is intended to be threaded into the central orifice 52 of the ring 47, for example by its second end 28b so that the seal 46a, 46b surrounds the tubular body 28.

The gasket 46a, 46b further includes lugs 54 which extend radially from the outer circular edge 50 . Each ear 54 is pierced with a hole 56 for the passage of a screw 36 for fixing associated with the flange 34 for fixing. The seal 46a, 46b has as many lugs 54 as the fixing flange 34 has orifice 42 for fixing. The passage holes 56 are arranged in coincidence with the threads 44 of the boss 38 when the seal 46a, 46b is positioned on the casing 14 outer.

The joint 46a, 46b is flattened in a radial plane, orthogonal to its axis "A".

Each seal 46a, 46b has the function of guaranteeing the tightness of the combustion chamber 12. For this purpose, it is important that the ring 47 of the seal 46a, 46b is entirely inserted between the fixing flange 34 and the flat face 40 of the boss 38.

However, the turbomachine 10 here comprises seals 46a, 46b of at least two different models. All seals 46a, 46b of a given model are identical to each other. The seals of the first model will be referred to below as "first seals 46a", while the seals of the second model will be referred to below as "second seals 46b". Each orifice 26 for passage of injector 24 must be associated with a determined model of joint 46a or 46b.

The first seals 46a have a ring 47 having different dimensions from the second seals 46b. Thus, as indicated in , the inside diameter "Di" and/or the outside diameter "De" of the first gaskets 46a are not different from those of the second gaskets 46b. For example, the second gaskets 46b have an inside diameter "Di" and an outside diameter "De" which are greater than those of the first gaskets 46a. Thus, the outer diameter "De" and/or the inner diameter "Di" make it possible to distinguish the first seals 46a from the second seals 46b.

On the other hand, the passage holes 56 are always arranged at the same distance "Rt" from the axis "A" of the seal both for the first seals 46a and for the second seals 46b. In addition, for the two joint models 46a, 46b, the passage holes 56 are distributed angularly in the same way. Thus, the position of the passage holes 56 does not make it possible to distinguish the first seals 46a from the second seals 46b. Therefore, it is possible to make the passage holes 56 of a first seal 26a or a second seal 46b coincide indifferently with the threads 44 of any passage orifice 56 of the outer casing 14 .

The injectors 24 are generally mounted manually on the outer casing 14 by an operator. However, despite their dimensional differences, the seals 46a, 46b of the two models have a similar appearance. The differences in dimensions between the seals 46a, 46b of two models are small enough for the operator to be able to confuse them in the event of lack of attention.

We represented at the a second seal 46b which is mounted in place of a first seal 46a. It can be seen that the ring 47 of the second seal 46b projects radially with respect to the fixing flange 34 and the boss 38. As a result, the inner part of the ring 47 which is effectively clamped between the fixing flange 34 and the outer casing 14 has an insufficient surface to guarantee good sealing of the combustion chamber 12 . In addition, due to the position of the holes 56 for the passage of the fixing screws 36 which is identical to that of the first seals 46a, the operator could not realize his error when fixing the screws 36 of fixation.

For comparison, we have shown the same second seal 46b mounted in its place on the outer casing 14. It can be seen that the ring 47 is fully tightened between the fixing flange 34 and the outer casing 14, thus guaranteeing a good seal.

To avoid these errors, the invention proposes to use a keying device 58, an example of which is shown in FIGS. 6 and 7. The purpose of such a keying device 58 is to enable the operator to easily distinguish a first joint 46a of a second joint 46b.

Such a keying device 58 makes it possible to solve the problem simply and inexpensively since it can be used with the seals 46a, 46b currently used without the need to change their shape.

The keying device 58 is presented here in the form of an independent object. This is a portable object, that is to say light and compact enough to be transported by a person, preferably with one hand.

Keying device 58 here has a first face 60 in which is formed a first indentation 62a of complementary shape to a first seal 46a. The cavity 62a is delimited at the bottom by a bottom 63 supporting the first associated seal 46a. The first cavity 62a has a shape such that a seal 46b of the second model cannot be inserted therein. Thus, when an attempt is made to insert a second seal 46b into the first cavity 62a, the ring 47 of the seal 46b is for example too large to be able to fit together correctly. This allows you to instantly see that it is not a seal of the correct model.

According to a first embodiment of the invention, given that the combustion chamber 12 comprises only seals 46a, 46b of two different models, the keying device 58 of the invention may comprise only one cavity 62a . This single imprint 62a is sufficient to enable the seal models to be distinguished from each other.

According to a second embodiment of the invention, the keying device 58 comprises, in addition to the first cavity 62a previously described, a second cavity 62b of complementary shape to a second seal 46b. Thus, when an attempt is made to insert a first seal 46a into the second cavity 62b, the ring 47 of the seal 46a is for example too small to be able to fit together correctly. For example, there remains a visible radial space between the edge of the recess 62b and the outer circular edge 50 of the ring 47. This makes it possible to instantly see that this is not the correct seal model.

Of course, the second imprint 62b is distinct from the first imprint 62a.

The fact of benefiting from a distinct imprint 62a, 62b for each model of joint 46a, 46b advantageously makes it possible to systematize the assembly process by allowing the operator to easily remember which model of joint is required for the injector 24 in assembly course.

In the context of this second embodiment, the second recess 62b is formed in a second face 64 which is separate from the first face 60 of the keying device 58. This prevents the operator from inserting the gasket 46a, 46b into the wrong cavity 62a, 62b.

The two cavities 62a, 62b are for example formed in two opposite faces 60, 64 of the keying device 58. The first face 60 is here parallel to the second face 64. Thus, when the operator wishes to use a fingerprint, for example the first fingerprint 62a, he places the keying device 58 on a support via its opposite face comprising the other imprint, for example on its second face 64 comprising the second imprint 62b. Thus, the other imprint, here the second imprint 62b, is inaccessible, as illustrated in .

Advantageously, to prevent the operator from mistaking the imprint 62a, 62b, each imprint 62a, 62b of the polarization device has walls of a color distinct from that of the other imprint 62a, 62b. For example, the first cavity 62a has a blue-colored wall, while the second cavity 62b has a gray-colored wall.

The keying device 58 has for example a cylindrical shape. The section of the cylinder here has a substantially square outline, but it could have another shape. The first and the second axial end of the cylinder respectively form the first face 60 and the second face 64.

The keying device 58 is here made of plastic. It is for example obtained by molding.

As a variant, keying device 58 is produced by 3D printing, for example in resin.

As shown in Figures 6 and 7, the keying device 58 is here made in two parts 66, 68 which divide the cylinder into two sections along a plane parallel to the faces 60, 64 end. A first part 66, represented at the top , comprises the first face 60 while the second part 68, shown at the bottom in the , has the second face 64.

The two parts 66, 68 are for example produced separately, then they are assembled and fixed to one another, for example by gluing or by interlocking.

As a variant, one of the parts, for example the second part 68, is manufactured, then the other part, here the first part 66, is manufactured by overmolding directly on the second part 68.

The two parts 66, 68 can each be made of a mass-dyed material, each of a different color. This makes it easier to distinguish the first imprint 62a from the second imprint 62b.

Alternatively, keying device 58 can be made in a single block. In this case, a coloring layer can be added to at least one of the imprints 62a or 62b.

Regardless of the embodiment chosen, each indentation 62a, 62b of the keying device 58 has pins 70 for positioning complementary to the holes 56 through which the screws 36 pass. Each positioning pin 70 is arranged in the middle of an associated area of the support bottom 63 which supports an associated lug 54 of the joint 46a, 46b. The support bottom 63 here has three such non-connected zones which support the seal 46a, 46b by each of its lugs 54.

Advantageously, each cavity 62a, 62b communicates with at least one groove 72 of the associated face 60, 64 allowing the introduction of a finger to easily retrieve a seal 46a, 46b introduced into the cavity 62a, 62b. The groove 72 is advantageously deeper than the bottom 63 of the support on which the gasket 46a, 46b rests in its complementary cavity 62a, 62b. The groove 72 thus opens into a space 73 which is deeper than the bottom 63 of the support and which is located in line with the associated recess 62a, 62b. Thus, the operator's finger can come below the joint 46a, 46b to lift it and extract it from the cavity 62a, 62b.

Each cavity 62a, 62b is here associated with two opposite grooves 72. Each groove 72 opens between two pins 70.

In addition, keying device 58 here has a slot 74 which opens into a side face 76 of the cylinder and which crosses it right through from the first face 60 to the second face 64. The slot opens in particular into the bottom 63 support each cavity 62a, 62b. The slot 74 makes it possible to provide an additional means for the operator to grasp a joint 46a, 46b nested in its cavity 62a, 62b by inserting a finger through the slot in order to be able to lift the joint 46a, 46b.

The slot 74 also offers a grip to be able to manipulate and/or store the keying device 58.

Equipped with such a keying device 58, the operator can carry out the assembly of each injector 24 according to an assembly method making it possible to avoid errors in the selection of joined models.

The method is applied successively to each injector 24. With reference to the , it includes the following steps for each injector 24 in chronological order.

During a preliminary "E0" step of selecting the footprint 62a, 62b, the operator places the keying device 58 so as to orient the footprint 62a, 62b of the model adapted to the injector 24 upwards. assembly course. This imprint 62a, 62b is thus accessible and visible. To do this, he can use the coloring of the imprint 62a, 62b in question. The imprint 62a, 62b is thus selected by simply turning over the keying device 58 to place it on the correct face 60, 64.

As a variant, this step is eliminated when the keying device is produced according to the first embodiment of the invention.

During a first step "E1" of gripping, the operator grabs a joint 46a, 46b of the desired model, for example in a box supposed to include all the joints of said model. The color of the accessible imprint 62a, 62b helps the operator to remember the joint model 46a, 46b required for this assembly, for example when the operator has been interrupted during the assembly process.

Then, during a keying step "E2", the operator checks that the joint 46a, 46b entered during the gripping step "E1" conforms to the joint model 46a, 46b required for mounting said injector 24 by trying to fit the joint 46a, 46b into the cavity 62a, 62b selected during the previous step "E0". If the seal 46a, 46b fits perfectly with the selected cavity 62a, 62b, it goes to the next positioning step "E3", otherwise, it reinstalls the first seal 46a, 46b entered and repeats the process from the step "E1" of gripping.

When the seized seal 46a, 46b successfully passes step "E2" of coding, a step "E3" of positioning is triggered. The seized seal 46a, 46b is positioned on the outer casing 14 around a passage orifice 26 and around the injector 24 being assembled.

Then a step "E4" of fixing the flange 34 for fixing the injector 24 to the outer casing 14 is engaged, during which said gasket 46a, 46b is tightened between the fixing flange 34 and the outer casing 14 at the means of the fixing screws 36.

The process is repeated from step "E0" prior to mounting each injector 24 of the combustion chamber 12.

The keying device 58 produced according to the teachings of the invention makes it possible to provide assistance to the operator by allowing him to easily and effortlessly distinguish the seals 46a, 46b of each of the models. This makes it possible to avoid any error during the assembly of the injectors 24 without it being necessary to change the shape of the parts in order to introduce keying means directly on the outer casing 14.

In addition, the method of the invention makes it possible to offer a method for systematically ruling out any error in the choice of joint model without this requiring in-depth attention on the part of the operator. In addition, the operator can realize his error before having positioned the seal 46a, 46b on the outer casing 14 and introduced the injector 24 into the orifice 26 of the associated passage. As a result, the mounting of the injectors 24 on the outer casing 14 is both safer and faster.

Claims (10)

Method of mounting several injectors (24) of a turbomachine (10) on an outer casing (14) of a combustion chamber (12) of the turbomachine (10), an annular seal (46a, 46b) being interposed between a flange (34) for fixing each injector (24) and the outer casing (14), the turbomachine (10) comprising seals (46a, 46b) of at least two different models, the method comprising for each injector (24) in chronological order a step (E1) of gripping a seal (46a, 46b) of the corresponding model followed by a step (E3) of positioning the seal (46a, 46b) seized on the casing (14) external;
characterized in that it comprises a keying step (E2) interposed chronologically between the step (E1) of gripping and the step (E3) of positioning the joint (46a, 46b) which consists in checking that the joint (46a , 46b) entered during step (E1) of gripping conforms to the joint model required for mounting said injector (24). Method according to the preceding claim, characterized in that the foolproofing step (E2) consists in using a foolproofing device (58) comprising at least one first indentation (62a) having a shape complementary to a joint (46a) of a first model, in which the seized joint (46a) is inserted, the first imprint (62a) having a shape such that a joint (46b) of the second model cannot be inserted therein. Method according to the preceding claim, characterized in that the foolproofing device (58) used during the foolproofing step (E2) comprises a second imprint (62b) distinct from the first imprint (62a) which has a shape complementary to a seal (46b) of the second model, the foolproofing method having a prior step (E0) of selecting the imprint (62a, 62b) to be used during the foolproofing step (E2). Polarization device (58) for implementing the method according to any one of Claims 2 or 3, characterized in that it is in the form of an object having a first face (60) in which is formed a first cavity (62a) of complementary shape to a joint (46a) of the first model. Device (58) according to the preceding claim, characterized in that it comprises a second face (64) in which is formed a second cavity (62b) of complementary shape to a joint (46b) of the second model. Device (58) according to any one of Claims 4 or 5, characterized in that the seals (46a, 46b) of the two models intended to be used with the foolproofing device (58) include holes (56) for fixing by screws which are arranged identically on the seals (46a, 46b) of the two models, each indentation (62a, 62b) of the keying device (58) being equipped with pins (70) for complementary positioning of the fixing holes (56) . Device (58) according to any one of Claims 5 to 6, characterized in that the two cavities (62a, 62b) are formed in two opposite faces (60, 64). Device (58) according to any one of Claims 5 to 7, characterized in that each imprint (62a, 62b) of the keying device (58) has walls of an associated color which is different from that of the other footprint (62a, 62b). Device (58) according to any one of Claims 5 to 8, characterized in that the face (60, 64) associated with each cavity (62a, 62b) has at least one groove (72) opening into the said cavity (62a, 62b) allowing the introduction of a finger to easily retrieve a seal (46a, 46b) introduced into the cavity (62a, 62b). Device according to Claim 9, characterized in that the groove (72) opens into a space (73) which is deeper than a bottom (63) supporting the gasket (46a, 46b) and which is situated at the right of the imprint (62a, 62b) associated.