WO2009083153A1

WO2009083153A1 - Pivoting-base mounting for axial piston machines

Info

Publication number: WO2009083153A1
Application number: PCT/EP2008/010758
Authority: WO
Inventors: David Breuer; Hendrik Friedrich
Original assignee: Robert Bosch Gmbh
Priority date: 2007-12-28
Filing date: 2008-12-17
Publication date: 2009-07-09
Also published as: EP2232069A1; DE102008013010A1

Abstract

The invention relates to a pivoting-base mounting of an axial piston machine having a housing (1, 1'), a pivoting base (3, 3') and a pivoting bearing region (5) which is formed by the housing (1, 1') and the pivoting base (3, 3'). Here, the pivoting base (3, 3') and/or the housing (1, 1') and/or a bearing element (2, 2') which is arranged in the pivoting bearing region (5) are of deformable configuration in such a way that a deflection of the pivoting base (3, 3') can be compensated for.

Description

Schwenkwiegenlagerung for axial piston machines

The invention relates to a Schwenkwiegenlagerung an axial piston machine with a housing, a pivoting cradle and formed by the housing and the pivoting cradle pivoting space, wherein the pivoting cradle and / or the housing and / or arranged in the pivot bearing chamber bearing element are formed deformable such that a deflection of the Swing cradle can be compensated.

From the patent application DE 10 2006 037 690 Al an axial piston machine is known, which receives a pivoting cradle in its housing. The housing and the pivoting cradle form two pivot bearing areas, in each of which a bearing shell is received. The pivoting cradle is supported on the bearing shells. The bearing shells in turn are supported on the housing. The housing, the swivel cradle and the bearing shells form pivot bearings. On the pivoting cradle and the bearing shells bearing surfaces are designed to support. In the case of the pivoting-angle bearings of the axial-piston machine, the pivoting cradle bends due to the large axial forces which the pistons exert on the pivoting cradle. Due to the deflection of the pivoting cradle, it comes on the mutually facing ends of the bearing surfaces to a considerable surface pressure, while the opposite ends are relieved. This leads to a local high load on the material, which promotes friction and wear and thus reduces the service life of the axial piston machine. At the same time, the hydrostatic discharge is degraded and the efficiency is thus reduced. In addition, the sealing effect of the bearing surfaces is also reduced.

It is therefore an object of the invention to provide a pivoting journalling for axial piston machines, in which a deflection of the pivoting cradle is compensated and Thus, an improved wear resistance, an improved hydrostatic discharge and an improved sealing effect are realized.

The object is achieved by the pivoting jaw mounting according to claim 1.

The pivoting pivot bearing according to the invention of an axial piston machine comprises a housing, a pivoting cradle and a pivot bearing area formed by the housing and the pivoting cradle. In the pivot bearing area, one or more bearing elements can be arranged. In the pivoting pivot bearing according to the invention, the pivoting cradle and / or the housing and / or a bearing element arranged in the pivoting bearing area are deformable such that a deflection of the pivoting cradle can be compensated. By the pivoting cradle and / or the housing and / or arranged in the pivot bearing portion bearing element are formed deformable, by a deformation of at least a portion of the pivoting cradle and / or the housing and / or the bearing element is a full-surface or area-maximized investment between the housing and the Bearing element and / or the bearing element and the pivoting cradle or optionally between the housing and the pivoting cradle can be achieved. The deflection of the pivoting cradle is compensated by one or more such full-surface or area-maximized systems. By compensating for the deflection, improved wear resistance, improved hydrostatic relief and, furthermore, an improved sealing effect are realized. As a result, in particular higher efficiency of the axial piston machine is achieved.

In the dependent claims advantageous embodiments of the invention pivoting pivot bearing are shown.

Preferably, the pivoting cradle has at least one cavity and / or a recess and / or a relief. As a result, the pivoting cradle is deformable. Thus, one is full-surface contact between the pivoting cradle and a bearing element or optionally between the pivoting cradle and the housing allows. The deflection of the pivoting cradle can thus be compensated.

Alternatively, the housing has at least one cavity and / or a recess and / or a relief. As a result, the housing is deformable and allows a full-surface contact between the housing and a bearing element or, if appropriate, between the housing and the pivoting cradle. Thus, the deflection of the pivoting cradle can be compensated here as well.

The bearing element preferably has an at least hollow space and / or a recess and / or a relief.

Also in this way the deflection of the swivel cradle can be compensated. The bearing element is thereby deformable and allows a full-surface contact both between the bearing element and the housing and between the bearing element and the pivoting cradle.

The structures, i. the recesses, reliefs or cavities are filled in advantageous embodiments with an elastic additional material. By selecting the elastic filler material or its elasticity, the bending stiffness of the structured regions of the components, i. the pivoting cradle and / or the housing and / or the bearing element, also subsequently set further or finer and thus the requirements are even better adapted. Fatigue of the components can be compensated in this way. As a result, the longevity of the components is ensured or increased.

Furthermore, preferably also the additional material itself have the structures mentioned so far, in order to also realize or reinforce the effects mentioned so far. Particularly preferably, the pivoting cradle and / or the housing and / or the bearing element each consist at least partially of an elastically deformable material. As a result, the deformations of the respective components are each better suited to compensate for the deflection of the pivoting cradle.

A combination of the features mentioned so far allows a particularly advantageous flexibility of the pivoting pivot bearing. By having a plurality of components each having a cavity and / or a recess and / or a relief, each component can perform a part of the deformation on its own. As a result, the deformations are better matched and the task according to the invention is solved all the better. Furthermore, less deformation is required of each individual component. As a result, the wear resistance is particularly increased. The better coordinated deformations are each further improved by the slight elastic deformability, as they are each easier to better match the stresses.

A preferred embodiment of the invention is shown in the drawing pivotal pivot bearing and will be explained in detail in the following description. Show it:

1 shows a simplified section through a part of a first embodiment of a Axialkol- benmaschine;

2 shows a simplified section through part of a second embodiment of an axial piston machine;

3 shows a simplified section through part of a third embodiment of an axial piston machine; 4 shows an exemplary representation of the basic shape of a bearing shell in several perspectives;

5 shows a further simplified section through a part of a third embodiment of an axial piston machine;

Fig. 6 is a perspective view of the bearing shell of Fig. 5;

Fig. 7 is a partially sectioned view of the bearing shell of Fig. 5;

8 shows a cross section through a region of the passage opening of the bearing shell from FIG. 5;

9 is an enlarged detail of the area of

Through hole of Fig. 8;

10 is another illustration of the bearing shell of the

Fig. 5;

11 is an enlarged view of the detail of Figure 7;

12 shows a perspective view of a bearing shell with a first relief;

Fig. 13 is a perspective view of a bearing shell with a second relief.

1 shows a simplified section through a part of a first embodiment of an axial piston machine. In a conventional housing 1 is a pivot cradle 3 'according to the invention as a replacement for a conventional pivoting cradle 3, as shown by way of example in FIG. 2 added. The housing 1 and the pivoting cradle 3 'according to the invention together form a pivoting Weighing bearing 4 with a pivot bearing portion 5 from. In the pivotal rolling bearing 4 and pivot bearing area 5 are two bearing shells 2 are added as bearing elements. The bearing elements or bearing shells 2 support an advantageous guidance and support of the pivoting cradle 3 'according to the invention in the housing 1 and wear protection of the housing 1. The bearing shells 2 accommodated in the pivoting pivot bearing 4 correspond, as shown for example in FIG a section of a cylindrical surface. The housing 1 and the pivoting cradle 3 'according to the invention in each case form complementary regions for forming the pivoting pivot bearing 4 with respect to the bearing shells 2, which likewise have the shape of a section of a cylinder jacket surface. The zylindermantel- surface-shaped areas are concentrically formed about a common cylinder axis, not shown, around which the pivoting cradle 3 'according to the invention can rotate during their pivotal movements, wherein it slides on an inner bearing surface of the bearing shell 2. The bearing elements or bearing shells 2 are secured against rotation relative to the housing 1. For this purpose, the bearing elements or bearing shells 2 and / or the housing 1 each form special structures. The pivoting cradle 3 'according to the invention lies slidably on the bearing shells 2 during its pivotal movements and is supported on these.

In Axialkolbenmaschinenbetrieb slide on the pivoting cradle 3 'according to the invention by piston 6 with axial forces 8 acted upon Gleitschuhe 7. The sliding blocks 7 beauf beat the pivoting cradle 3' according to the invention thereby with axial forces 8, which lead to a deflection of the pivoting cradle 3 'according to the invention. The deflection of the pivoting cradle 3 'according to the invention due to the forces acting 8 is exaggerated in FIG. 1 for clarity.

The pivoting cradle 3 'according to the invention has, in the illustrated embodiment of the invention, a bearing shell section 3a and a tread section 3b. Between the tread portion 3b and the bearing shell portion 3a is formed as a recess, a gap 9 in the form of a slot. In the region of the outer circumference, the bearing shell section 3a and the tread section 3b are connected to one another. Because of the elastic connection formed there, the bearing on the bearing shell 2 part of the bearing shell portion 3a can tilt relative to the running surface of the tread portion 3b. The deformation on the tread side of the pivoting cradle 3 'according to the invention is thus compensated, so that a full-surface or area-maximized or adapted installation of the pivoting cradle 3' according to the invention is ensured on the running surfaces of the bearing shells 2.

To realize the full surface contact of the pivoting cradle 3 'according to the invention on the bearing shells 2, a plurality of recesses may be formed in the pivoting cradle 3' according to the invention instead of just one recess. These may vary widely in the radial direction. Alternatively or additionally, one or more cavities may be formed in the pivoting cradle 3 'according to the invention for this purpose. As a further alternative or in addition thereto, a relief may be formed on a bearing surface 2 or housing 1 facing surface of the pivoting cradle 3 'according to the invention. Such structures allow in each case and in any combination with each other an elastic deformation of the pivoting cradle 3 'according to the invention. As a result, a full-surface or area-maximized or adapted installation of the pivoting cradle 3 on the bearing shells 2 or, in embodiments without bearing elements or bearing shells 2, on the housing 1 is made possible. The deflection of the pivoting cradle 3 is compensated.

Fig. 2 shows a simplified section through a part of a second embodiment of an axial piston machine. The same elements as in Fig. 1 are provided with the same reference numerals. The explanations to these correspond to those of Fig. 1. Instead of in the swivel cradle 3, which is designed in this embodiment of an axial piston machine in conventional form, is now on the housing side another slot 11 formed as a recess. As in the previous exemplary embodiment, the slot extends radially outward from a drive shaft opening penetrating the housing 1, 1 'or the pivoting cradle 3, 3'. By this housing side formed further slot 11 formed in the housing 1 'invention bearing shells 10 on which the bearing shells 2 rest. These bearing shells 10 are connected by the slits of the housing 1 'according to the invention elastically with the rest of the housing 1' according to the invention and therefore can absorb the weighing loads. By an elastic deformation of the bearing shell receptacles 10, an adjustment of the position of the bearing shells 2 in turn relative to the pivoting cradle 3 or the bearing surface areas formed thereon is made possible.

To adapt the position of the bearing shells 2 relative to the pivoting cradle 3, a plurality of recesses may be formed in the housing 1 'according to the invention instead of just one recess as well. Additionally or alternatively, one or more cavities may be formed in the housing 1 'according to the invention. Furthermore, as a further alternative or in addition to a bearing shell 2 or the pivoting cradle 3 facing surface of the housing 1 'according to the invention may be formed a relief. The proposed structures allow in each case and in combination with each other an elastic deformation of the housing 1 'according to the invention for adjusting the position of the bearing shells 2 relative to the pivoting cradle 3. The deflection of the pivoting cradle 3 is thereby also compensated. By adjusting the position of the bearing shells a parallel alignment of the bearing surfaces is achieved to the corresponding contact surfaces of the loaded pivoting cradle. Fig. 3 shows a simplified section through a part of a third embodiment of an axial piston machine. The same elements as in Fig. 1 are provided with the same reference numerals and are already explained to Fig. 1. In this embodiment, 2 inventive bearing shells 2 'are arranged in a conventional housing 1 instead of the conventional bearing shells. The bearing shells 2 'according to the invention are designed so that they can be deformed by load. When loaded by the pivoting cradle 3, a support surface facing the housing 1 of a bearing shell 2 'according to the invention is inclined relative to the bearing surface of the bearing shell 2' according to the invention assigned to the pivoting cradle 3. For this purpose, a bearing shell relief 12 is introduced on a support surface facing the housing 1 of the bearing shell 2 'according to the invention. The bearing shell relief 12 is formed by groove-shaped recesses. A relief can just as well be alternatively or additionally formed on the opposite bearing surface of the bearing shell 2 'according to the invention. Instead of recesses or a relief or in addition to these, one or more cavities may be formed in the bearing shell 2 'according to the invention, which likewise deform the bearing shell 2' according to the invention for adapting the position of the bearing shell 2 'relative to the pivoting cradle 3 and / or to the housing 1 or respectively formed there bearing surface areas ensures.

The material of the components, ie of the housing 1, 1 'and / or the bearing shells 2, 2' and / or the pivoting cradle 3, 3 ', can be specifically selected at least in regions such that targeted deformation is favored. For example, the components may be at least partially made of a slightly elastically deformable material. This ensures particularly easy that the deflection of the pivoting cradle 3 is compensated. 4 shows an exemplary representation of the basic shape of a conventional bearing shell 2 in several perspectives. The conventional bearing shell 2 can be converted by forming a bearing shell relief 12 on the housing 1 side facing to a bearing shell 2 'according to the invention. The basic shape of the bearing shell 2 has the shape of a halved hollow cylinder. In the illustrated embodiment, the ends of the bearing shell 2 are reshaped in such a way that a rotation against a housing receiving them 1, 1 'is achieved. The outwardly formed ends 13 are supported in the housing 1, 1 'so that during a pivoting movement, a displacement of the bearing shell 2 is prevented from its intended position.

FIG. 5 shows a further simplified section through part of a third exemplary embodiment of an axial piston machine. The pivoting cradle 3 lies in a bearing shell 2 according to the invention replacing Lagerscha- Ie 2 'with a bearing shell relief 12 and is based on the bearing shell 2' according to the invention on the housing 1 from. In order to ensure the rotatability of the pivoting cradle 3 about the cylinder axis, it is slidably mounted in the bearing shell 2 'according to the invention. The bearing shell 2 'according to the invention has, on its surface facing the housing 1, grooves 12' extending in the circumferential direction of the bearing shell 2 'according to the invention, which grooves produce the bearing shell relief 12. The grooves 12 'of the bearing shell 2' according to the invention are arranged in the illustrated embodiment on the side facing the second, not shown in FIG. 5, inventive bearing shell 2 'side.

Instead of the one-sided arrangement of the grooves 12 ', the grooves 12' can be distributed over the entire support surface of the bearing shell 2 'according to the invention. Starting from the center of the axial piston machine, for example, the distances of the grooves 12 'from each other may increase towards the outside. That's it also possible to vary the width of support webs 14 (see FIG. 9) between the grooves 12 'over the outer surface of the bearing shell 2' according to the invention. Furthermore, the depth of the grooves 12 'can be varied. For grooves 12 'with a circular arc-shaped cross section and different radii can be used. These decrease in particular in the direction away from each other of the bearing shells 2 'according to the invention. The cross section of each groove 12 'corresponds to a semicircle.

Through the grooves 12 'are formed between the grooves 12' individual support webs 14 (see FIG. 9), which are supported on the housing 1. For better deformability, the support webs 14, e.g. by a post-processing, to be curved or inclined. A loading of the bearing shell 2 'according to the invention in the direction of the housing 1 with axial forces leads to a deformation of the support webs 14 and thus also of the bearing shell 2' according to the invention. This deformation causes the surface of the bearing shell 2 'according to the invention oriented toward the pivoting cradle 3 to have a smaller distance from the housing 1 or the bearing cup receptacle formed therein in the pivot bearing space (5) than in the area which is not interrupted by the cradle Insertion of the grooves 12 'is weakened. On the whole, the surface of the bearing shell 2 'according to the invention oriented towards the pivoting cradle 3 thus tends to face the bearing surface of the bearing shell receptacle, which is formed in the housing 1. Thus, the deflection of the pivoting cradle 3 is compensated.

FIG. 6 shows a perspective view of the bearing shell 2 'according to the invention from FIG. 5. FIG. 7 shows a partially cutaway view of the bearing shell 2' according to the invention. In the region of the section, it can be seen that a passage opening 15 is formed in the bearing shell 2 'according to the invention. With the help of this passage opening 15, a fixing of the bearing shell in the housing 1, 1 'is possible. This can be done in the case 1, 1 'be formed a support member which engages in the through hole 15. A cross section through the region of the passage opening 15 is shown in FIG. 8. Here it can be seen that in the axial direction only in one half of the outer surface of the bearing shell according to the invention 2 'grooves 12' are formed. The grooves 12 'extend along the outer circumference of the bearing shell 2' according to the invention parallel to one another. To clarify the geometry, FIG. 9 shows a further enlarged detail of FIG. 8. Here it is easy to see that the depth of the introduced grooves 12 'decreases starting from the edge of the bearing shell 2' according to the invention. The opening angle of the grooves 12 'is preferably about 35 °. Due to the decreasing depth of the grooves 12 'of the inclination of the two bearing surfaces of the bearing shell 2' according to the invention, so on the one hand on the side of the housing 1, 1 'and on the other hand on the side of the Schenkwiege 3, 3', bill. Where the strongest deviation from the original position with parallel abutment surfaces of the pivoting cradle 3, 3 'and the housing 1, 1' is required, the depth of the introduced groove 12 'is greatest. FIG. 10 shows once again a view of the bearing shell 2 'according to the invention. It will be appreciated that the grooves 12 'on the outer peripheral surface extend from one end of the bearing shell 2' according to the invention to its other end. To illustrate the passage opening 15, by means of which the bearing shell 2 'according to the invention can be fixed in the housing 1, 1', the cutout 11 of FIG. 7 is shown enlarged again in FIG.

Another possibility for achieving the deformability of the bearing shell 2 'according to the invention is, instead of the grooves (as illustrated, for example, in FIG. 12 (the reference numbers refer to the elements explained in the preceding figures with the same reference numerals.)) Which extend along the Extending outer circumference, an alternative relief, such as a knurled pattern 16, to introduce into the outer surface of the bearing shell. Such a knurled pattern 16 is shown in FIG. The knurling creates a regular relief structure. This regular structure may be formed by pyramidal pyramidal tip elements. In the illustrated embodiment, the regular relief structure is formed by truncated pyramidal elements 17. These truncated pyramidal elements 17 each have an upper surface 17 '. The upper surfaces 17 'in their entirety form the contact surface of the illustrated embodiment of the bearing shell 2' according to the invention with respect to the housing 1, 1 '. By means of this systematic reduction of the support surface, a deformation of the individual truncated pyramid-shaped elements 17 is possible. The truncated pyramidal elements 17 are elastically deformable and can also consist of slightly elastically deformable material. When loaded, the pyramidal elements can further penetrate at least partially into the mating surface of the housing 1, 1 '.

In all three exemplary embodiments, structures are formed which ensure the deformability of specific components of the pivoting pivot bearing in favor of a surface maximization of bearing surfaces between at least two of these components in order to compensate for the deflection of the pivoting cradle. Of course, the structures explained can be combined in one component. Likewise, the structures explained can each be formed in several components at the same time. Then the beneficial balancing effects are enhanced. Structures within a component and / or structures of different components can also be matched to one another. For example, mutually complementary reliefs may be formed. Thus, for example, a relative displacement of surface elements of different components in mutually orthogonal directions as required either favored or, on the other hand, prevented. For example, a relative displacement of surface areas or sections of a bearing shell according to the invention and a pivoting cradle according to the invention along the common cylinder axis in a desired embodiment and undesirable in another. By a combination of perpendicular to the common cylinder axis grooves on the pivoting cradle surface according to the invention facing bearing shell and complementary structures on the inventive bearing shell facing surface of the pivoting cradle according to the invention, a relative displacement of the pivoting cradle according to the invention to the bearing shell according to the invention along the common cylinder axis prevented become.

Due to the elastic design of at least one component or element of the pivotal pivot bearing, in particular the hydrostatic relief of the pivotal pivot bearing is improved. The uniform contact forces on the pivoting cradle oriented towards the inner side of the bearing shell allow there an improved hydrostatic discharge and in particular an improved sealing effect. This also improves the efficiency of the hydrostatic machine.

In addition to the above-described elastic deformation of the components of the pivotal rolling bearing, it is also possible to provide a partially elastic and partially plastic deformation, as already described with respect to the penetration of the pyramidal elements. Such a partial plastic deformation of bearing shells according to the invention, for example, leads to a light employment, so that in the absence of deflection of the pivoting cradle, the pivoting cradle on the mutually oriented sides of the bearing shells according to the invention easily lifts from the bearing surfaces formed there. However, since only low pressures occur in the unloaded state, this is less critical. With increasing pressure, this slight inclination is compensated by the deflection of the pivoting cradle, before further deformation of the pivoting cradle by elastic deformation of the bearing shells of the invention is taken into account. Figures 12 and 13 show perspective views of different inventive bearing shells 2 ', in each of which on the side facing the housing 1, a relief is formed, which allows a deformation of the inventive bearing shells 2'. The relief may consist of elastically or slightly elastically deformable material, which is additionally plastically deformable. More generally, all the structures discussed so far can each consist of an elastically or slightly elastically deformable material, which is also plastically deformable. Due to the plastic deformability of structures of the components, the equilibrium form of the structures or components adapts to a loaded form. Thereby, the compensation of the deflection of the pivoting cradle 3 is simplified from the outset by the equilibrium form of the structures.

The structures, i. the recesses, reliefs or cavities, for example, can be filled with an elastic additional material. By selecting an elastic additional material with suitable elasticity, the bending stiffness of the structured regions of the components can also be subsequently refined or adapted to the requirements. Fatigue of the components can be compensated and / or prevented in this way. This ensures the longevity of the components. Furthermore, the additional material itself may have the structures mentioned so far in order to likewise reinforce the effects mentioned above. These structures can also be filled in the same way with another elastic filler material.

The exemplary embodiments relate to bearing elements 2 and 2 'designed as bearing elements. However, the invention is not limited to such bearing elements. Rather, the inventive idea extends to the formation of a cavity and / or a recess and / or a relief in each bearing element, which intermediate a pivoting cradle and a housing of an axial piston machine is mounted.

Of course, in generally descriptive parts of the description, the said conventional components can also be replaced by components according to the invention. The description thus also relates to combinations of components according to the invention.

The invention is not limited to the illustrated embodiments. Rather, individual features of the embodiments are advantageously combined.

Claims

claims

1. Schwenkwiegenlagerung an axial piston machine with a housing (1, 1 '), a pivoting cradle (3, 3') and a through the housing (1, 1 ') and the pivoting cradle (3, 3') formed pivot bearing area (5), characterized in that the pivoting cradle (3, 3 ') and / or the housing (1, 1') and / or a bearing element (2, 2 ') arranged in the pivoting bearing region (5) are deformable in such a way that a deflection of the pivoting cradle (3, 3 ') is compensable.

2. Schwenkwiegenlagerung according to claim 1, characterized in that the housing (1, 1 ') has at least one cavity and / or a recess (9) and / or a relief (12, 16).

3. Schwenkwiegenlagerung according to claim 1 or 2, characterized in that the bearing element (2, 2 ') at least one cavity and / or a recess (9) and / or a relief (12, 16).

4. Schwenkwiegenlagerung according to one of claims 1 to 3, characterized in that the pivoting cradle (3, 3 ') at least one cavity and / or a recess (9) and / or a relief (12, 16).

5. Schwenkwiegenlagerung according to one of claims 1 to 4, characterized in that the bearing element (2 ') has a relief (12) which is formed by grooves (12').

6. Schwenkwiegenlagerung according to claim 5, characterized in that in the relief (12), the distance between the grooves (12 ') and / or the depth of the grooves (12') varies.

7. Schwenkwiegenlagerung according to one of claims 1 to 6, characterized in that the bearing element (2 ') has a knurled pattern (16).

8. Schwenkwiegenlagerung according to claim 7, characterized in that the knurled pattern (16) is formed by truncated pyramidal elements (17).

9. Schwenkwiegenlagerung according to one of claims 2 to 8, characterized in that the cavity and / or the recess (9) and / or the relief (12, 16) is filled with an elastic additional material.

10. Schwenkwiegenlagerung according to claim 9, characterized in that the additional material has a cavity and / or a recess (9) and / or a relief (12, 16).

11. Schwenkwiegenlagerung according to one of claims 1 to 10, characterized in that the housing (1, 1 ') at least partially consists of an elastically deformable material.

12. Schwenkwiegenlagerung according to one of claims 1 to

11, characterized in that the bearing element (2, 2 ') at least partially consists of an elastically deformable material.

13. Schwenkwiegenlagerung according to one of claims 1 to 12, characterized in that the pivoting cradle (3, 3 ') at least partially consists of an elastically deformable material.