EP0597754B1 - Rotary piston machine and assembly method - Google Patents

Description

Already known is a pressurized fluid mechanism, such as a motor or a hydraulic pump, comprising: a cam having a plurality of undulations; a cylinder block rotatably mounted relative to the cam about an axis of rotation and having a communication face perpendicular to said axis of rotation; a internal fluid distributor having a distribution face intended to be in support on the communication face of the cylinder block and coupled to said cam at by means of a device for immobilizing the internal distributor in rotation relative to the cam comprising at least one connecting element, which is connected without transverse play in a direction orthogonal both to the axis of rotation and to any radius passing through the axis of rotation, with the internal fluid distributor and with the cam, and which is also substantially non-deformable transversely to said axis of rotation and around the axis of rotation, the connection made by this connecting element on the other hand being deformable in a direction parallel to the axis of rotation, and around of a possible pivot axis parallel to any axis orthogonal to the axis of rotation, and said connecting element comprising a thin veil which extends substantially transversely to the axis of rotation.

Document US-A-2050823 shows a provision in which the distributor is connected to the cam, constituted by an eccentric, by means of a connection comprising a thin veil.

The position of the internal fluid distributor relative to the cam must be precise, because on the precision of its adjustment depend the quality of the admissions of fluid in the working chambers delimited in the cylinder block and fluid escapes from said chambers and their correspondence with the position of the cam's undulations.

However, multiple tolerances in terms of both machining and assembly have led to today, having to admit an approximate correspondence between the position of the internal fluid distributor and that of the corrugated cam. The efforts made to reducing the value of these tolerances is not enough to achieve such a match of good quality.

On the basis of this observation, the invention as defined in the claims overcomes the disadvantages existing by reducing the number of tolerances, of course while retaining the principle of reducing the value of each of them.

According to the invention, in a mechanism as defined above, the position of the immobilizer is adjusted without play during assembly using a part used during assembly, comprising a periphery having a shape complementary to that of the cam.

• le mécanisme, ou bien, comprend un élément complémentaire, tel que le fond d'extrémité d'un carter, qui est solidaire de la came, et sur lequel ledit élément de liaison est fixé; ou bien, comprend un élément complémentaire, tel que le fond d'extrémité d'un carter qui est fixé sur la came par des moyens d'une fixation amovible, tels que des vis de fixation, une partie desdits éléments de liaison étant pincée entre la came et ledit élément complémentaire;
• une partie périphérique de l'élément de liaison a une forme complémentaire de celle des ondulations de la came et s'imbrique sans jeu dans les ondulations de la came;
• l'élément de liaison, dans la configuration de fonctionnement du mécanisme, présente une contrainte initiale élastique le déformant parallèlement à l'axe de rotation, dont l'effet tend à mettre en appui au moyen d'une force non nulle la face de distribution du distributeur interne de fluide sur la face de communication du bloc-cylindres.

The following advantageous arrangements are also preferably adopted:

• the mechanism, or else, comprises a complementary element, such as the end bottom of a casing, which is integral with the cam, and on which said connecting element is fixed; or else, comprises an additional element, such as the end bottom of a casing which is fixed to the cam by means of a removable fixing, such as fixing screws, part of said connecting elements being pinched between the cam and said complementary element;
• a peripheral part of the connecting element has a shape complementary to that of the undulations of the cam and fits without play in the undulations of the cam;
• the connecting element, in the operating configuration of the mechanism, has an initial elastic stress deforming it parallel to the axis of rotation, the effect of which tends to press the distribution face by means of a non-zero force of the internal fluid distributor on the communication face of the cylinder block.

The main advantage of the invention lies in the fact that, thanks to a connection more direct between the internal fluid distributor and the cam, the number of tolerances has been reduced and the adjustment of the position of the internal fluid distributor relative to the cam has been improved, with the end result of improved operation of the mechanism.

The invention will be better understood, and secondary characteristics and their advantages will appear during the description of embodiment given below at as an example.

It is understood that the description and the drawings are given for information only and not limiting.

• la figure 1 est une coupe axiale d'un moteur hydraulique selon une première réalisation conforme à l'invention;
• la figure 2 est une coupe suivant II-II de la figure 1;
• la figure 3 est une coupe axiale d'un moteur hydraulique selon une deuxième réalisation conforme à l'invention;
• la figure 4 est une coupe suivant IV-IV de la figure 3;
• la figure 5 est une coupe axiale d'un moteur hydraulique selon une troisième réalisation conforme à l'invention;
• la figure 6 est une coupe suivant VI-VI de la figure 5; et,
• la figure 7 est une coupe axiale illustrant le montage du moteur des figures 3 et 4.

Reference will be made to the accompanying drawings, in which:

• Figure 1 is an axial section of a hydraulic motor according to a first embodiment according to the invention;
• Figure 2 is a section along II-II of Figure 1;
• Figure 3 is an axial section of a hydraulic motor according to a second embodiment according to the invention;
• Figure 4 is a section along IV-IV of Figure 3;
• Figure 5 is an axial section of a hydraulic motor according to a third embodiment according to the invention;
• Figure 6 is a section along VI-VI of Figure 5; and,
• FIG. 7 is an axial section illustrating the mounting of the motor in FIGS. 3 and 4.

The achievements represented relate to hydraulic motors which, from a on the one hand have common characteristics, on the other hand, each have specific characteristics.

• un carter en trois parties 1A, 1B, 1C, assemblées par des vis 6;
• un arbre de sortie 2, monté rotatif autour d'un axe géométrique 3, par l'intermédiaire de paliers à rouleaux 4 interposés entre cet arbre de sortie 2 et la partie 1A du carter, constituant un axe de rotation;
• une came 5, présentant plusieurs ondulations, usinée sur la périphérie interne de la partie 1B du carter;
• un bloc-cylindres 7, qui est rendu solidaire en rotation de l'arbre 2 par l'intermédiaire de cannelures 8 ménagées dans un alésage du bloc-cylindres et imbriquées dans des cannelures 9 ménagées sur la périphérie interne de l'arbre 2;
• une pluralité de cylindres 10, ménagés dans le bloc-cylindres 7 et disposés radialement par rapport à l'axe de rotation 3, angulairement régulièrement espacés autour de l'axe 3;
• une pluralité de pistons 11, chacun monté coulissant à l'intérieur d'un cylindre 10, muni d'un rouleau d'appui 12, d'axe 13 parallèle à l'axe de rotation 3, par l'intermédiaire duquel ledit piston 11 est susceptible d'être en appui sur la came ondulée 5, et délimitant avec le cylindre 10 une chambre 14;
• une face plane 15, de communication, perpendiculaire à l'axe de rotation 3, appartenant au bloc-cylindres 7;
• une pluralité de conduits de cylindres 16, ménagés dans le bloc-cylindres 7, reliant, chacun, une chambre 14 à la face de communication 15 dans laquelle ils débouchent par des orifices 17 centrés sur un même cercle coaxial à l'axe de rotation 3;
• un distributeur interne de fluide 18, qui comporte une face de distribution 19, plane, maintenue en appui sur la face de communication 15;
• des conduits de distribution 20, 21, qui sont ménagés dans le distributeur interne de fluide 18 et qui débouchent dans la face de distribution 19 par des orifices 22, 23 centrés sur le même cercle que les orifices 17, en étant par ailleurs reliés à deux gorges 24, 25, de révolution d'axe 3, ménagées dans le distributeur interne de fluide 18, respectivement;
• deux conduits 26, 27, ménagés dans la partie 1C du carter, reliant lesdites gorges 24, 25, dans lesquelles ils débouchent, à deux conduits externes 28, 29 d'alimentation en fluide sous pression et d'échappement de fluide, respectivement;
• un conduit 30, ménagé dans la partie 1C du carter reliant l'enceinte close 31 délimitée par ce carter à un conduit externe 32 de retour du fluide à un réservoir sans pression.

The common provisions are described below and can be seen in particular in Figures 1, 3 and 5. Each engine includes:

• a casing in three parts 1A, 1B, 1C, assembled by screws 6;
• an output shaft 2, rotatably mounted about a geometric axis 3, by means of roller bearings 4 interposed between this output shaft 2 and the part 1A of the casing, constituting an axis of rotation;
• a cam 5, having several undulations, machined on the internal periphery of the part 1B of the casing;
• a cylinder block 7, which is made integral in rotation with the shaft 2 by means of grooves 8 formed in a bore of the cylinder block and nested in grooves 9 formed on the internal periphery of the shaft 2;
• a plurality of cylinders 10, formed in the cylinder block 7 and arranged radially with respect to the axis of rotation 3, angularly regularly spaced around the axis 3;
• a plurality of pistons 11, each mounted sliding inside a cylinder 10, provided with a support roller 12, of axis 13 parallel to the axis of rotation 3, by means of which said piston 11 is likely to be supported on the corrugated cam 5, and delimiting with the cylinder 10 a chamber 14;
• a flat face 15, of communication, perpendicular to the axis of rotation 3, belonging to the cylinder block 7;
• a plurality of cylinder ducts 16, formed in the cylinder block 7, each connecting a chamber 14 to the communication face 15 into which they open out through orifices 17 centered on the same circle coaxial with the axis of rotation 3 ;
• an internal fluid distributor 18, which has a flat distribution face 19, held in abutment on the communication face 15;
• distribution conduits 20, 21, which are formed in the internal fluid distributor 18 and which open into the distribution face 19 by orifices 22, 23 centered on the same circle as the orifices 17, being moreover connected to two grooves 24, 25, of axis 3 revolution, formed in the internal fluid distributor 18, respectively;
• two conduits 26, 27, formed in part 1C of the casing, connecting said grooves 24, 25, into which they open, to two external conduits 28, 29 for supplying pressurized fluid and fluid exhaust, respectively;
• a conduit 30, formed in part 1C of the casing connecting the closed enclosure 31 delimited by this casing to an external conduit 32 for returning the fluid to a pressureless reservoir.

The internal fluid distributor 18 is immobilized, vis-à-vis a rotation axis 3, relative to cam 5 by means of a device specific to each production.

In the engine represented in FIGS. 1 and 2, two radial tongues 33A, in the diametrically opposite species, extend in a transverse plane P perpendicular to the axis of rotation 3, and each have a peripheral shape in V, 34, which adapts without any play to the shape 5A delimiting a top of the cam 5.

The languages 33A, initially distinct from the internal fluid distributor 18, belong to a thin veil 33 fixed to the internal distributor 18 by any means suitable fasteners, such as gluing 35 on a flat transverse face 36 of the internal fluid distributor 18, welding or screwing. Furthermore, these languages 33A are non-deformable in the transverse direction of the plane P, perpendicular to the axis of rotation 3. Thus, the internal fluid distributor 18 is immobilized with respect to the axis 3 rotation relative to cam 5.

On the other hand, the radial support of the forms 34 of the languages 33A on the forms 5A of the cam allows slight displacements of the internal fluid distributor 18, of course axial parallel to the axis of rotation 3), but also pivoting either around a diameter perpendicular to axis 3, i.e. around an axis more generally orthogonal to axis 3. These small displacements are necessary so that the distribution face 19 is kept in substantially sealed abutment on the communication face 15 under the effect in particular of the hydrostatic thrusts of the fluids contained in the grooves 24, 25, and under the complementary effect, in particular at rest, of small springs 135 interposed between the bottom of part 1C of the casing and the internal fluid distributor 18.

The sensitive non-deformability of languages 33A, in parallel or in the plane P, transversely to the axis of rotation 3, has the consequence that the relative angular position of the internal fluid distributor 18 relative to the cam 5 is substantially invariable.

In the embodiment of FIGS. 3 and 4, the internal fluid distributor 18 comprises, near its distribution face 19, a cylindrical flange 37, coaxial with the axis of rotation 3, the part 1C of the casing also comprising a cylindrical flange 38, coaxial with the axis of rotation 3. A thin veil 39, partially transverse to the axis 3, has a first folded edge 40, cylindrical, suitable for its application on the flange 37 of the internal distributor of fluid 18, and a second folded edge 41, cylindrical, suitable for its application on the flange 38 of part 1C of the casing. The folded edges 40, 41 are fixed on the flanges 37, 38, by any suitable fixing means, in particular gluing 42, 43, or welding, respectively, or even, for one of them, such as the folded edge 40, by simple application to the flange by elastic deformation of the web 39. It must be noted that the thin veil 39 is made of a material having a certain elasticity, such that a sheet of steel, and that the fixing of its folded edges 40, 41 is made of so that, with the engine stopped, not supplied with pressurized fluid, the web thin 39 has an initial elastic axial deformation parallel to axis 3, causing the abutment, by means of a non-zero force, of the face of distribution 19 on the communication face 15. The initial constraint, which constitutes this non-zero force, possibly allows the removal of the springs 135. By elsewhere, the elasticity of the thin web 39 makes possible small elastic deformations allowing slight pivoting of the distribution face 19 about an axis perpendicular or orthogonal to the axis of rotation 3, so that it can be obtained a substantially sealed contact, in particular during engine operation, the distribution face 19 on the communication face 15. On the other hand, in the direction transverse, perpendicular to the axis of rotation 3, the web 39 has a large rigidity and is substantially non-deformable, so that the relative angular position of the internal fluid distributor 18 relative to part 1C of the casing, and consequently relative to the cam 5, is substantially invariable.

• le distributeur interne de fluide 18 est muni d'une face transversale 44 perpendiculaire à l'axe 3, située à proximité de sa face de distribution 19;
• un voile mince 45, s'étendant sensiblement transversalement, réalisé en acier, est fixé sur cette face 44, par exemple par collage 46, ou encore par soudage ou vissage, et a une périphérie externe 47 de forme circulaire, délimitant un bord plan 48;
• un épaulement 49, de profondeur légèrement inférieure à l'épaisseur du bord 48 du voile 45, est ménagé à proximité de la face 50 d'assemblage de la partie 1C du carter avec la partie 1B (face 51);
• le bord plan 48 est pincé entre l'épaulement 49 et la face 51 de la partie 1B du carter et est immobilisé par ce moyen par rapport à la came 5;
• le voile mince 45 possède une élasticité axiale, lui permettant de légères déformations de translation dans le sens axial, parallèlement à l'axe de rotation 3, ainsi que de pivotement autour d'un axe orthogonal à l'axe de rotation 3, de manière que la face de distribution 19 puisse être mise en appui et maintenue en appui sensiblement étanche sur la face de communication 15;
• le voile 45 est par contre sensiblement indéformable parallèlement à un plan perpendiculaire à l'axe de rotation 3, de sorte qu'après son collage 46 sur la face 44 et le pincement de son bord 48 entre les parties 1B et 1C du carter, la position relative du distributeur interne de fluide 18 par rapport à la partie 1B du carter, par conséquent également par rapport à la came 5 est sensiblement invariable;
• enfin, le collage 46, et/ou le pincement du bord 48 ente les parties 1B et 1C du carter, sont réalisés de manière que, le moteur étant à l'arrêt, non alimenté en fluide sous pression, le voile mince 45 présente une déformation axiale initiale, élastique, provoquant la mise en appui, au moyen d'une force non nulle, de la face de distribution 19 sur la face de communication 15.

The embodiment of FIGS. 5 and 6 includes the following arrangements:

• the internal fluid distributor 18 is provided with a transverse face 44 perpendicular to the axis 3, located near its distribution face 19;
• a thin veil 45, extending substantially transversely, made of steel, is fixed to this face 44, for example by gluing 46, or even by welding or screwing, and has an external periphery 47 of circular shape, delimiting a planar edge 48 ;
• a shoulder 49, of a depth slightly less than the thickness of the edge 48 of the web 45, is formed near the face 50 for assembling the part 1C of the casing with the part 1B (face 51);
• the flat edge 48 is pinched between the shoulder 49 and the face 51 of the part 1B of the casing and is immobilized by this means relative to the cam 5;
• the thin veil 45 has an axial elasticity, allowing it slight deformations of translation in the axial direction, parallel to the axis of rotation 3, as well as of pivoting around an axis orthogonal to the axis of rotation 3, so that the dispensing face 19 can be brought into abutment and maintained in substantially sealed abutment on the communication face 15;
• on the other hand, the veil 45 is substantially non-deformable parallel to a plane perpendicular to the axis of rotation 3, so that after it has been bonded 46 to the face 44 and its edge 48 has been pinched between the parts 1B and 1C of the casing, the relative position of the internal fluid distributor 18 relative to the part 1B of the casing, therefore also relative to the cam 5 is substantially invariable;
• finally, the bonding 46, and / or the pinching of the edge 48 between the parts 1B and 1C of the casing, are carried out so that, the engine being stopped, not supplied with pressurized fluid, the thin web 45 has a initial axial deformation, elastic, causing the distribution face 19 to bear against the communication face 15 by means of a non-zero force.

In the embodiments of FIGS. 1 to 6, the initial adjustment of the position of the internal fluid distributor 18 relative to the cam 5 is obtained at the time of mounting, thanks to precise mounting tools that allow the position to be adjusted, without play, one with respect to the other of the two parts constituted by the internal distributor of fluid 18 and by cam 5, via the thin veil, before immobilization complete of the whole.

By way of example, is explained below with reference to FIG. 7, the method of adjustment of the positions relating to the motor of FIGS. 3 and 4. A special part 52, used only during assembly, has a periphery 105 having a shape complementary to that of cam 5, so that it can be nested, without play, between its undulations. This room also comprises, at least two holes 55. The part 52 is presented opposite part 1B of the casing. The holes 55 are then arranged in positions which are those of the orifices 17, by which the cylinder ducts 16 of the cylinder block 7 open normally in the communication face 15, when the motor is fully assembled (figure 3). It suffices to establish the correspondence of these holes 55 and of one of the conduits of distribution 20 or 21 to obtain the exact position of the internal fluid distributor 18 relative to cam 5.

• fixation du bord rabattu 40 du voile 39 sur la collerette 37 du distributeur interne de fluide 18, par collage 42 par exemple;
• montage de l'ensemble du distributeur interne de fluide 18 et du voile 39 qui y est fixé, sur la pièce 52, au moyen de goupilles élastiques 57 introduites, sans jeu, dans les trous 55 et les conduits 20 ou 21;
• assemblage des parties 1B et 1C du carter au moyen des vis 56; et,
• montage de l'ensemble du distributeur interne de fluide 18, du voile 39 qui y est fixé, et de la pièce 52 tel que réalisé précédemment dans l'ensemble des parties 1B et 1C assemblées du carter. La périphérie 105 s'imbrique, sans jeu, entre les ondulations de la came 5 et le bord rabattu 41 du voile 39, est emmanché à force autour de la collerette 38 de la partie 1C du carter dans la position exacte, et, ultérieurement invariable du distributeur interne de fluide 18 par rapport à la came 5.

The practical assembly is as follows:

• fixing the folded edge 40 of the web 39 on the flange 37 of the internal fluid distributor 18, by gluing 42 for example;
• mounting of the assembly of the internal fluid distributor 18 and of the web 39 which is fixed thereto, on the part 52, by means of elastic pins 57 inserted, without play, in the holes 55 and the conduits 20 or 21;
• assembly of parts 1B and 1C of the casing by means of screws 56; and,
• mounting of the assembly of the internal fluid distributor 18, of the web 39 which is attached thereto, and of the part 52 as previously produced in all of the assembled parts 1B and 1C of the casing. The periphery 105 fits, without play, between the undulations of the cam 5 and the folded edge 41 of the web 39, is force-fitted around the flange 38 of the part 1C of the casing in the exact position, and, subsequently invariable of the internal fluid distributor 18 relative to the cam 5.

Analogous assemblies allow assembly and position adjustments of the motors of FIGS. 1 and 2, and, 5 and 6.

Each of the proposed solutions allows precise adjustment, without transverse play, of the position of the internal fluid distributor 18 relative to the cam 5.

The engine design of Figures 3 and 4, and Figures 5 and 6 allows keep the same sail whatever the cam adopted; which is interesting in establishing a full range of engines.

The invention is not limited to the embodiments described, but covers contrary all the variants which could be made to them without leaving the framework set by the claims.

Claims (5)

1. Method of mounting a device for preventing the rotation of the internal fluid distributor of a pressurized-fluid mechanism, such as a hydraulic pump or motor with respect to the cam of this mechanism, the latter comprising:

   the said cam (5);

   a cylinder unit (7) mounted so that it can rotate with respect to the cam about an axis of rotation (3) and having a communication face (15) perpendicular to the said axis of rotation;

   the said internal fluid distributor (18), which has a distribution face (19) intended to press on the communication face (15) of the cylinder unit and is harnessed to the said cam (5) by means of the said device for preventing the rotation of the internal distributor with respect to the cam, this device comprising at least one connecting element (33; 33A; 39; 45) which is connected without transverse play in a direction orthogonal both to the axis of rotation and to any radius passing through the axis of rotation, with the internal fluid distributor (18) and with the cam (5), and which furthermore is substantially non-deformable transversely with respect to the said axis of rotation (3) and about the axis of rotation, the connection produced by this connecting element being, however, deformable in a direction parallel to the axis of rotation (3), and about any possible axis of pivoting parallel to any axis orthogonal to the axis of rotation, and the said connecting element comprising a thin web (33; 33A; 39; 45) which extends essentially transversely with respect to the axis of rotation;

      characterized in that the position of the rotation-preventing device (33; 39; 45) is adjusted without play at the time of mounting using a part (52) which has a periphery (105), the shape of which complements that of the cam (5), the latter having a number of undulations.
2. Pressurized-fluid mechanism such as a hydraulic pump or motor, comprising:

   a cam (5);

   a cylinder unit (7) mounted so that it can rotate with respect to the cam about an axis of rotation (3) and having a communication face (15) perpendicular to the said axis of rotation;

   an internal fluid distributor (18), which has a distribution face (19) intended to press on the communication face (15) of the cylinder unit and is harnessed to the said cam (5) by means of a device for preventing the rotation of the internal distributor with respect to the cam comprising at least one connecting element (39) which is connected without transverse play in a direction orthogonal both to the axis of rotation and to any radius passing through the axis of rotation, with the internal fluid distributor (18) and with the cam (5), and which furthermore is substantially non-deformable transversely with respect to the said axis of rotation (3) and about the axis of rotation, the connection produced by this connecting element being, however, deformable in a direction parallel to the axis of rotation (3), and about any possible axis of pivoting parallel to any axis orthogonal to the axis of rotation, and the said connecting element comprising a thin web (39) which extends essentially transversely with respect to the axis of rotation;

      characterized in that once the position of the rotation-prevention device (39) has been previously adjusted without play at the time of mounting using a part (52) which has a periphery (105), the shape of which complements that of the cam (5), the latter having a number of undulations,
      the said connecting element (39) is fixed, on the one hand (at 42), on the internal fluid distributor (18) and, on the other hand (at 40), on a complementary element (1C) such as the end wall of a casing, said complementary element being secured (6) to the cam (5).
3. Pressurized-fluid mechanism such as a hydraulic pump or motor, comprising:

   a cam (5);

   a cylinder unit (7) mounted so that it can rotate with respect to the cam about an axis of rotation (3) and having a communication face (15) perpendicular to the said axis of rotation;

   an internal fluid distributor (18), which has a distribution face (19) intended to press on the communication face (15) of the cylinder unit and is harnessed to the said cam (5) by means of a device for preventing the rotation of the internal distributor with respect to the cam comprising at least one connecting element (45) which is connected without transverse play in a direction orthogonal both to the axis of rotation and to any radius passing through the axis of rotation, with the internal fluid distributor (18) and with the cam (5), and which furthermore is substantially non-deformable transversely with respect to the said axis of rotation (3) and about the axis of rotation, the connection produced by this connecting element being, however, deformable in a direction parallel to the axis of rotation (3), and about any possible axis of pivoting parallel to any axis orthogonal to the axis of rotation, and the said connecting element comprising a thin web (45) which extends essentially transversely with respect to the axis of rotation;

      characterized in that once the position of the rotation-prevention device (45) has been previously adjusted without play at the time of mounting using a part (52) which has a periphery (105) the shape of which complements that of the cam (5), the latter having a number of undulations,
      the said connecting element (45) consists of the said essentially transverse thin web (45), is fixed directly (at 46) on a transverse face (44) perpendicular to the axis of rotation (3) exhibited by the internal fluid distributor (18) and has a part (48) which is trapped directly between the cam (5) and a complementary element (1C) such as the end wall of a casing, the said complementary element being itself fixed to the cam (5) by removable fastening means (6).
4. Pressurized-fluid mechanism such as a hydraulic pump or motor, comprising:

   a cam (5);

   a cylinder unit (7) mounted so that it can rotate with respect to the cam about an axis of rotation (3) and having a communication face (15) perpendicular to the said axis of rotation;

   an internal fluid distributor (18), which has a distribution face (19) intended to press on the communication face (15) of the cylinder unit and is harnessed to the said cam (5) by means of a device for preventing the rotation of the internal distributor with respect to the cam comprising at least one connecting element (33; 33A) which is connected without transverse play in a direction orthogonal both to the axis of rotation and to any radius passing through the axis of rotation, with the internal fluid distributor (18) and with the cam (5), and which furthermore is substantially non-deformable transversely with respect to the said axis of rotation (3) and about the axis of rotation, the connection produced by this connecting element being, however, deformable in a direction parallel to the axis of rotation (3), and about any possible axis of pivoting parallel to any axis orthogonal to the axis of rotation, and the said connecting element comprising a thin web (33; 33A) which extends essentially transversely with respect to the axis of rotation;

      characterized in that once the position of the rotation-prevention device (39) has been previously adjusted without play at the time of mounting using a part (52) which has a periphery (105) the shape of which complements that of the cam (5), the latter having a number of undulations,
      a peripheral part (34) of the connecting element (33; 33A) has a shape that complements that of the undulations (5A) of the cam (5) and nests without play in the undulations of the cam.
5. Mechanism according to any one of Claims 2 to 4,
      characterized in that the connecting element (39; 45) in the operating configuration of the mechanism, has an initial elastic preload which deforms it parallel to the axis of rotation (3), and the effect of which tends to make the distribution face (19) of the internal fluid distributor (18) bear on the communication face (15) of the cylinder unit (7) with a non-zero force.

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