FR2683872A1 - Elementary device and overall system for positioning a body, such as a pump, with respect to another body - Google Patents

Abstract

A device (1) for the relative positioning of two bodies includes a key (2) with cylindrical edges, two cylindrical shims (3 and 4) designed to run along this key and exhibiting straight edges opposite this key and two tapered wedges (5 and 6) designed to run, on the one hand, along the straight edges of the shims and, on the other hand, along bearing surfaces. The key (2) is directly or indirectly (for example using a second set of shims and wedges) coupled to one of the bodies whereas the bearing surfaces form part of the other body.

Description

 The invention relates to an elementary device, or even a global system, for positioning in a plane a driven body to be secured without play to a driving body or reference body.

 It applies in particular, but not exclusively, to the positioning of a pump relative to a turbine (the reverse is not in practice envisaged, taking into account the large difference in mass existing between turbine and pump).

 Such couples (pump + turbine) are encountered, for example, in electrical energy production installations where the masses to be considered are measured in tens of tonnes.

 When installing such an installation, the pump is placed relative to the turbine in a relative position and orientation such that the pump shaft is very exactly aligned with the turbine shaft, for obvious reasons of dynamic (rotational speeds are measured in thousands of revolutions per minute). The pump is subject to a frame which is sealed once this alignment has been ensured.

 However over time, the installation and the underlying solid base undergo aging phenomena which alter this alignment. It must therefore be corrected. But taking into account the practical difficulties posed by such a realignment, it is often carried out only during the main maintenance operations, that is to say infrequently: any faults which appear thus have time to develop up to levels which can sometimes be detrimental.

 In addition, this realignment is commonly done using shims, the installation of which often allows games to remain then allowing vibrations to develop and detrimental to the subsequent mechanical strength of the installation.

 The object of the invention is to overcome the aforementioned drawbacks by allowing, in the case of such an installation (pump + turbine), easy positioning of the pump during its installation, but above all realignment of very good quality which is sufficiently easy and quick to be able to be carried out during simple maintenance operations, therefore frequently, and without leaving residual games after realignment.

 In fact, the pump is in practice subject to its frame with the aid of several positioning devices or pads arranged on either side, and under the body of the pump, so that the requirement of a good realignment of the pump with the turbine presupposes, in particular, for the lateral positioning devices, a possibility of adjustment in a horizontal plane, in translation parallel and transverse to the axis of the pump, and in rotation about a vertical axis passing through these devices, being however kept in mind that, for distances to the axis of the pump of the order of a meter (for example 1.15 m) the deflections commonly required are of the order of a millimeter, or even a few millimeters in translation, and a few degrees (<50) in rotation.

 The invention thus relates, more generally, to a simple or reliable positioning device or pad, allowing in a plane a movement in translation in two directions of this plane and a rotation in rotation in this plane, without play and therefore with possibility of canceling at will the games necessary for movement of the various components of this device and therefore minimizing the parasitic causes of vibrations.

 The invention thus provides a positioning device for positioning a first body relative to a second body in translation and rotation in a reference plane, comprising a central key coupled to one of the bodies and elongated according to a first direction of the plane, two wedges arranged on either side of this central key parallel to the plane and each adapted to follow this central key approximately parallel to this first direction, and two corners extending parallel to this first direction, arranged on both sides and on the other side of this central key parallel to the plane and adapted to go along these wedges, the central key being bordered by two sections having cylindrical surfaces of axes perpendicular to the plane not merged, the wedges having opposite sections of the central wedge internal slices complementary to these slices and, opposite the corners, external slices nes rectilinear parallel to the plane, and the corners having, opposite these wedges, internal sections complementary to these rectilinear sections and external sections, rectilinear parallel to the plan, intended to follow bearing surfaces formed on the other body and extending parallel to the first direction.

 The device comprises in practice means for adjusting the reciprocal position of each corner with respect to the adjacent wedge, which allows effective blocking in the position of this device. In simple cases and for small angles of convergence of the corners, it is however possible to ensure blocking by means of friction alone.

 In a preferred embodiment of these adjustment means, the corners have at their tapered ends protrusions oriented towards one another and comprising in threaded bores of axes parallel to this first direction of the tightening screws, each screw clamping bearing on one end of the shim adjacent to the corner carrying this screw.

 Preferably for reasons of accessibility on the same side, the corners are tapered in the same direction, but the implementation of the invention is possible if the corners are head to tail.

 It is recalled that a cylindrical surface, in the mathematical sense of the term, is a surface formed by a generator, rectilinear or not, rotating around an axis.

 It will be appreciated that such a compact structure goes against a prejudice of the skilled person who wanted that, as much as possible, one dissociates the adjustments according to the three degrees of movement considered (two translations and one rotation).

 In fact, an adjustment in a direction perpendicular to the plane may be desired in certain cases, but the resolution of this problem is beyond the scope of the present invention. It can be resolved by any known means, or even by lifting, over an appropriate height of the moving parts of the positioning device.

 According to preferred arrangements of the invention, possibly combined - the cylindrical sections of the key and wedges are of equal radius, - the corners are tapered at an angle between 1 and 50 (this loss can however be much greater when means are put in place), - the corners are tapered at an angle equal to approximately 20, - the cylindrical sections of the key have, parallel to the positioning plane, their concavities turned towards the shims, - the cylindrical sections of the key of the device have, parallel to the positioning plane, their concavities turned towards the inside of the key, - the cylindrical sections of the key of the device have, parallel to the positioning plane, their concavities turned on the same side of the key.

 According to a particularly preferred arrangement of the invention, with a view for example to increasing the deflections in the three degrees of freedom, the device of the invention can be split in height, however having a single monobloc central part for the two floors superimposed (these stages can, but this is not necessary, be in contact).

 According to other provisions of the invention, possibly combined - the cylindrical sections of the key and of these other wedges are of the same radius, - the first two wedges and the other two wedges are identical, - the first two corners and the two other corners are identical, - the edges of the key, corners and shims are perpendicular to the positioning plane, - the edges of the key of the device are, transverse to the positioning plane, concave with their concavities facing the shims, - the edges of the key are circular transversely to the positioning plane, - the edges of the key have, transversely to the positioning plane, a profile formed by two segments converging towards the interior of the key, - the edges of the device key are, transversely to the positioning plane, concave with their concavities turned towards the inside of the key, - the edges of the key te of the device are, transverse to the positioning plane, rectilinear and inclined at an angle less than 900 relative to this plane.

 It is even possible to provide a greater number of stages comprising respectively in common either the central key or the bearing surfaces.

 The invention also provides a global system for positioning a body with respect to another body, for example a chassis comprising at least two devices of the aforementioned type arranged on either side of a plane in which the first directions of these devices are perpendicular.

Objects, characteristics and advantages of the invention appear from the following description, given by way of nonlimiting example, with reference to the appended drawings in which
- Figure 1A is a top view of a positioning device according to the invention in a first configuration
- Figure 1B is one from above in another configuration
- Figure 1C is a half view from above showing the state of the applied stresses
- Figure 2A is a top view of a pair of devices according to Figure 1, arranged on either side of the longitudinal axis of a driven body to which these devices are both linked, showing how to obtain for this body a displacement along this axis
FIG. 2B is a view similar to that of FIG. 2A, showing how to obtain an angular displacement for this body,
- Figure 2C is a view similar to those of Figures 2A and 2B, showing how to obtain for this body both a translation parallel to its axis and an angular displacement
FIG. 3 is an elevation view of an example of a pump fitted with positioning devices according to the invention, similar to that of FIGS. 1A and 1B, but split into two stages,
- Figure 4A is a front view of one of these devices
- Figure 4B is a vertical sectional view along the line IV-IV of Figure 4A
FIG. 4C is a bottom view thereof,
- Figure 5A is a top view of another positioning device according to the invention, according to a first alternative embodiment of the device of Figures 4A and 4B;
- Figure 5B is a view in median cross section;
- Figure 6A is a top view similar to that of Figure 5A, for a second variant
- Figure 6B is a median cross-sectional view;
- Figure 7A is a top view similar to that of Figure 5A, for a third variant
- Figure 7B is a median cross-sectional view;
- Figure 8A is a top view similar to that of Figure 5A, for a fourth variant
- Figure 8B is a median cross-sectional view;
- Figure 9A is a view similar to that of Figure 5A, for a fifth variant
FIG. 9B is a view in median cross section,
- Figure 10 is a cross-sectional view of a device according to a variant of Figures 1A and 1B, adapted for example to constitute a lower positioning pad of the pump of Figure 3
- Figure 11 A is a view similar to that of Figure 5A, but for a sixth variant, corresponding to a second general configuration
FIG. 11B is a view in median cross section,
- Figure 12A is a view similar to that of Figure 5A, but for a seventh variant, corresponding to a third general configuration
FIG. 1A shows a device according to the invention, in a simple embodiment, intended for the relative positioning in the plane of the figure of two bodies, not shown.

 This device, denoted 1 as a whole, comprises a central key 2 elongated in a first direction denoted XX, two wedges 3 and 4 arranged on either side of this central key 2, and two corners 5 and 6 arranged on both sides. on the other side of the set 2 + 3 + 4.

 The central key 2 is bordered by two sections 2A and 2B formed by cylindrical surfaces with axes perpendicular to the plane of Figure 1 and radii denoted R and R '. These axes are not confused.

 The central key 2 here has a diabolo shape, the aforementioned sections having axes arranged outside on either side of this key.

 The radii R and R 'are here equal.

 The wedges 3 and 4 have, opposite the sections of the key, internal sections 3A and 4A of a shape complementary to that of the sections 2A and 2B of the wedge, that is to say that they are also cylindrical with radii R and R 'and the same axes as the edges of the keys. The key can thus slide along each wedge, generally along the X-X axis, while retaining a large contact area with each wedge.

 These wedges 3 and 4 are bordered externally by sections 3B and 4B which, parallel to the plane of Figure 1, are rectilinear.

 The corners 5 and 6 have, opposite the wedges, internal sections 5A and 6A of a shape complementary to that of the external sections of the wedges so that these wedges can slide with large contact areas, along the internal sections of the corners: these internal sections are therefore, parallel to the plane of the figure, rectilinear.

 The corners 5 and 6 have external edges 5B and 6B which, too, are rectilinear parallel to the plane of the figure. They are intended to run parallel to the direction X-X, bearing surfaces 7 and 8.

 These corners 5 and 6 here converge in the same direction parallel to X-X, with convergence angles denoted B and B 'here equal. The tapered ends of these corners, denoted 5C and 6C, are here directed towards the bottom of the figure.

 The central key 2 is intended to be connected, directly or indirectly, to one of the bodies while the bearing surfaces are linked to the other body. If in the simple version shown here, the central key is directly fixed to the first body (by any suitable known means, such as bolts or welds, etc.), it can also, as will be explained below, be coupled to this body. by at least one other set of two wedges and two corners, arranged above or below the wedges and corners of FIG. 1A (the key then has a thickness equal to the sum of the thicknesses of the two "stages" thus superimposed if , as shown here, these stages are in contact), these two other corners being adapted to extend by their outer edges of the bearing surfaces linked to this first body, in which case the key is indirectly coupled to this first body. In a variant not shown, these sets of wedges and corners have any non-zero spacing.

 In practice, the bearing surfaces 7 and 8 (or even those of the first body) are at least approximately parallel to the direction X-X.

 Parallel to the dimension X-X, the key is shorter here than the wedges, which are here shorter than the corners, which allows great deflections; but this is not a geometrical necessity.

 Conjugated sliding between the key and the shims, between the shims and the corners and the bearing surfaces, make it possible to modify both the position (parallel to XX or to a perpendicular direction YY) as well as the orientation of the key relative to to the bearing surfaces.

 Thus, for example, in FIG. 1A, the longitudinal axis V-V of the key is inclined relative to X-X by a small angle E in a clockwise direction.

 To go to the configuration of Figure 1B where the inclination is in the opposite direction, simply slide the left wedge 3 down along the left corner 5, the key 2 up along this left wedge , the right wedge up along this key, and the corners in the appropriate direction so that the dimension of the assembly 2 + 3 + 4 + 5 + 6 parallel to YY becomes again equal to the spacing between the spans 7 and 8 .

An overall movement up or down in the figure would move the key parallel to
XX while displacements in opposite directions of the corners, while maintaining the wedges and the key in the same relative configuration, would result in a displacement of the key parallel to YY.

 FIG. 1C presents the being of the constraints in the right half of a device 1 ′ similar to that of FIGS. 1A and 1B.

 If a force F is exerted according to YY, the key 2 'and the right wedge 4' can be considered as a single unit (without relative movement; if the angle of inclination B 'of the right corner 6' is less than l 'angle of friction t? characterizing the interface between the right wedge 4' and the corner 6 'then the friction is enough to maintain the relative configuration between wedge 4' and corner 6 'despite the component of F parallel to this interface.

 The corner angle is for example from 1 to 50, for example 20.

 To limit the risk of slipping, avoid coating the wedges and corners with a fatty substance. For example, these parts are made of XC48 steel, and these facing sections are advantageously treated against corrosion; the various parts will, for example, be treated by phosphotation Fe-Mn (thickness 0.005 mm to 0.01 mm with a dry type finish) and the facing sections are advantageously coated with molybdenum disulphide during assembly.

 It is also possible to increase the friction adjustment range using the shims (by tinsel) arranged at the various interfaces and which are moved parallel to the axis X-X as required.

 Independently of the friction (which can consequently be reduced if this is useful, or else it is the angle of the corners which can be increased), the device of the invention 1 'schematized in half in this figure IC comprises mechanical means for adjusting and positive locking in position of each wedge relative to the adjacent corner.

To do this, the corner 6 ′ has here at its end tapering a projection 9 ′ oriented towards the axis VV of the central key, therefore opposite the projection provided on the other corner; in this projection parallel to YY is provided a threaded bore 10 'with an axis substantially parallel to
XX and in which is engaged a clamping screw 11 'whose end comes to bear on a transverse surface 4'C of the wedge adjacent to this corner.

 It can be noted that the key 2 ', the shims 4' (and 3 'not shown) have the same dimension parallel to X-X, the shims having transverse bearing surfaces at each of their ends.

 FIGS. 2A to 2C show three relative configurations of two positioning devices or pads P and P 'in accordance with FIGS. 1A and 1B, arranged on either side of an axis UU, parallel to the axis YY, designating the longitudinal axis of a driven body, not shown, of which the bearing surfaces are integral along which the corners of the studs P and P 'slide. The keys are here directly fixed to a support frame.

 In these figures, the solid lines represent a starting configuration while the mixed lines for the corners represent a final configuration (the displacements of the wedges considered here are too small to be able to be represented perceptibly. The axis X1-X1 represents a transverse axis of the body in the initial configuration and the axes X2-X2, X2'-X2 'and X2 "-X2", represent their position in the three final configurations of these three figures.

FIG. 2A presents the case where the right corners of the pads P and P 'are moved over equal distances parallel to X1-X1 each in the direction of the axis
UU while the left corners are moved over the equal distances parallel to this axis X1-X1 each in the opposite direction from the axis UU: this results in an overall movement to the left of the body and the axis Xl-Xî comes in position X2-X2.

 FIG. 2B presents the case where the right corners of the pads P and P 'are moved by equal distances parallel to X1-X1, both in the same direction, here downwards, while the pads on the left are moved over equal distances parallel to Xl-Xl, both in the same direction, here upwards: this results in a rotational movement of the body in the trigonometric direction and the axis Xî-Xl comes in the position X2 'X2'.

 Finally, FIG. 2C presents the case where the right corners of the studs P and P 'are moved over different distances in the same direction parallel to X1-XI, here downwards while the left corners are moved over different distances in the opposite direction parallel to X1-X1, here upwards, the corners of a block, here the block P from the top, being more displaced than those from the bottom: the body moves to the left and is inclined in the direction trigonometric and the axis X1-X1 takes the position X2 "-X2".

 It is important to note that the inclinations shown in FIGS. 2B and 2C have been exaggerated so that they are visible: they are in fact much smaller; thus for a distance from the axis UU of the order of 1.15 m, and for relative displacements of the bearing surfaces relative to the key of the order of 1.5 mm parallel to UU, the inclinations obtained are of the order of 0.0750.

 Figure 3 is an elevational view of a pump 20 supported by a frame 21 by means of three sets of positioning pads marked P1, P2 and P3. At least the lateral pads Pi and P2 are in accordance with the invention the lower pads P3, located substantially vertically below the longitudinal axis U-U of the pump can be conventional but are also advantageously also in accordance with the invention.

 The lower studs P3 here comprise a central key directly linked to the pump body while the bearing surfaces along which the corners slide (here parallel to the axis U-U) are integral with the chassis.

 The side pads P1 and P2 are here at different heights; it will however be appreciated that the explanations given above with reference to FIGS. 2A to 2C have not revealed any hypothesis as to their coplanarity with the axis U-U therefore apply here to the pads P1 and P2.

 It will however be noted that the pads P1 and P2 are here in two stages P1 ', P1 "and P2', P2" (this concept has been introduced above); these superimposed stages are here identical (shims and corners) which allows, for the same clearance for each of the stages (for example 0.6 mm) to obtain a double clearance (1.2 mm). In this case, the central key common to the two stages has a free position.

 The structure of the pump, which is not part of the invention, will not be developed here.

 One, P2, of the positioning pads is shown in more detail in FIGS. 4A to 4C.

 There is thus a recess 23 formed in a lug 24 of the pump body, having two sides forming bearing surfaces 7-2 and 8-2, while the chassis comprises an upright 25 in which is formed a groove bordered by sidewalls forming bearing surfaces 761 and 8-1 (the suffixes 1 and 2 added to the references of FIGS. 1A to 1C respectively designate the lower and upper stages of the pad P2.

 The central key 2 is retained, in its transverse deflections at U-U, on the one hand by the bottom 26 of the recess 23, on the other hand by a plate 27 attached here to the tab 24 of the pump body.

 As in FIG. 1C, the wedges have at their ends transverse bearing surfaces (here chamfered) and are the same length as the key while the corners have projections parallel to UU in which are engaged, by means of threaded holes, clamping screw 11-1 or 11-2.

 It will be appreciated that the locking / unlocking of the various screws is done on the same side of the stud at the top of the axis U-U, hence great ease of maneuver; for the adjustment proper, jacks are easily fitted in particular in combination with a bore 30 formed in the key and capable of receiving an operating rod.

 For example, the key has a length of 220 mm, a height of 58 mm and its edges have radii of 800 mm; the wedges have a length of 220 mm, a maximum width of 26 mm and a height that is half that of the key; and the corners have a total length of 260 mm, an angle of 20, a maximum width of 27 mm and a height equal to half that of the key. The clamping screws are type M16.

The various sections of the keys, wedges and wedges considered so far have been cylindrical (in the narrow sense of the term) or flat. In other words, any intersection of these slices with any plane perpendicular to the positioning plane (xX; YY), that is to say to the plane of FIGS. 1A to 1C, 2A to 2C and 4C, is straight perpendicular at XX and YY
However, these are only simple embodiments.

 Thus in particular the sections facing the wedges and of each key may have sections having, in a plane perpendicular to the acex X-X and Y-Y, directives of different shapes and / or inclinations.

 Thus, FIGS. 5A and 5B show a two-stage stud 40 whose directrix is circular with radius r, with a concavity facing the shims.

 Figures 6A and 6B show a variant, with a stud 50 having a concavity director also facing the shims, but formed mainly of two substantially rectilinear segments converging inside the key.

 Such studs 40 and 50 ensure good retention of the superimposed wedges with respect to force aimed at spreading them perpendicular to the axes X-X and Y-Y.

 FIGS. 7A and 7B show a variant of FIGS. 6A and 6B with a stud 60 having cylinder directors in two segments converging outside the key and therefore having a concavity turned towards the inside of the key.

 FIGS. 8A and 8B show a variant of FIGS. 5A and 5B, with a stud 70 having directors of circular cylinders, with a concavity turned towards the inside of the key. This allows for the key an angular movement T in a plane transverse to X-X and / or Y-Y.

 FIGS. 9A and 9B show another pad 80 with straight cylinder directors but inclined in the same direction by an angle 6.

 FIG. 10 is a variant of FIGS. 8A and 8B in which the stud 90 comprises a central key in the portion of a sphere. Such a solution can be adopted in particular for a lower positioning pad such as P3 in FIG. 3.

 The various keys of the aforementioned studs have a diabolo shape.

 FIGS. 11A and 11B show a pad 100 with another type of key, shaped as a shuttle, the edges being, in top view, no longer concave, but convex.

 Finally, FIGS. 12A and 12 have been proposed only by way of nonlimiting example and that numerous variants can be proposed by those skilled in the art without departing from the scope of the invention. Thus in particular that, taking into account the clamping screws provided near the tapered ends of the corners, for the sliding blocking of the corners and the shims, it is possible to provide very low coefficients of friction, by adding bearings if necessary.

Claims (22)

 1. Positioning device (1, 1 ', P, P', PI, P2, P3, 40, 50, 60, 70, 80, 90, 100, 110) for positioning a first body with respect to a second body in translation and in rotation in a reference plane (XX, YY), comprising a central key (2, 2 ') coupled to one of the bodies and elongated in a first direction (XX) of the plane, two wedges ( 3, 4, 4 ', 3-1, 4-1) arranged on either side of this central key parallel to the plane and each adapted to go along this central key approximately parallel to this first direction, and two corners (5, 6, 6 ', 5-1, 5-2, 6-1, 6-2) extending parallel to this first direction, arranged on either side of this central key parallel to the plane and adapted to follow these wedges , the central key being bordered by two sections having cylindrical surfaces of axes perpendicular to the plane which are not merged, the wedges having opposite sections of the key ette central of the internal sections complementary to these sections and, opposite the corners, rectilinear external sections parallel to the plane, and the corners having, opposite these wedges, internal sections complementary to these rectilinear sections and external sections, rectilinear parallel in the plane, intended to run along support doors (7, 8, 8 ', 7-1, 7-2, 8-1, 8-2) formed on the other body and extending parallel to the first direction .  2. Device according to claim 1, characterized in that it comprises mechanical means (9 ', 10', 11 ', 11-1, 11-2) relative adjustment of each wedge relative to the adjacent corner.  3. Device according to claim 2, characterized in that these corners (6 ') further have at their tapered ends projections (9') oriented towards one another and comprising in threaded bores (10 ') d 'axes parallel to this first direction (XX) of the clamping screws, each clamping screw (11', 11-1, 11-2) coming to bear on one end (4'C) of the wedge (42) adjacent to the corner carrying this screw.  4. Device according to any one of claims 1 to 3, characterized in that the cylindrical sections of the key and shims are of equal radii.  5. Device according to any one of claims 1 to 4, characterized in that the corners are tapered at an angle between 1 and 50.  6. Device according to claim 5, characterized in that the corners are tapered at an angle equal to about 20.  7. Device according to any one of claims 1 to 6, characterized in that the cylindrical sections of the key (2, 2 ') have, parallel to the positioning plane, their concavities facing the shims.  8. Device according to any one of claims 1 to 6, characterized in that the cylindrical sections of the key of the device (100) have, parallel to the positioning plane, their concavities turned towards the inside of the key.  9. Device according to any one of claims 1 to 6, characterized in that the cylindrical sections of the key of the device (110) have, parallel to the positioning plane, their concavities turned on the same side of the key.  10. Device according to any one of claims 1 to 9, characterized in that the key (2) has, transversely to the positioning plane, a thickness greater than that of the shims (3-1, 4-1) and of the corners (5-1, 6-i), this key being indirectly coupled to the first of the bodies by two other wedges (3-2, 4-2) arranged on either side of this key parallel to the plane and each adapted to be lengthened the key approximately parallel to this first direction (XX) and by two other corners (5-2, 6-2) extending parallel to this first direction and converging towards the same direction and adapted to follow these wedges, these two other wedges (3-2, 4-2) having opposite cylindrical edges of the key cylindrical internal edges complementary to the edges of this key and opposite these other corners of the rectilinear external edges parallel to the plane, and these other corners having opposite these other wedges d es complementary internal sections of these rectilinear sections and having external sections, rectilinear parallel to the plane, intended to follow bearing surfaces provided on this first body and extending parallel to the first direction.  11. Device according to claim .10, characterized in that the cylindrical sections of the key and of these other wedges have the same radii.  12. Device according to claim 10 or claim i1, characterized in that the first two shims (3-i, 4-1) and the other two shims (3-2, 4-2) are identical.  13. Device according to any one of claims 10 to 12, characterized in that the first two corners (5-1, 6-i) and the two other corners (5-2, 6-2) are identical.  14. Device according to any one of claims 10 to 13, characterized in that the edges of the key, corners and shims are perpendicular to the positioning plane.  15. Device according to any one of claims 10 to 14, characterized in that the edges of the key of the device (40, 50) are, transverse to the positioning plane, concave with their concavities facing the shims.  16. Device according to claim 15, characterized in that the edges of the key are circular transverse to the positioning plane.  17. Device according to claim 15, characterized in that the edges of the key have, transversely to the positioning plane, a profile formed by two segments converging towards the inside of the key.  18. Device according to any one of claims 10 to 14, characterized in that the edges of the key of the device (60, 70, 90) are, transverse to the positioning plane, concave with their concavities turned towards the inside of the key.  19. Device according to any one of claims 10 to 14, characterized in that the edges of the key of the device (80) are, transverse to the positioning plane, rectilinear and inclined by an angle less than 900 relative to this. plan.  20. Device according to any one of claims 10 to 19, characterized in that the shims (3-1, 4-i) and the corners (Si, 6-1) are respectively in contact with these other shims (3- 2, 4-2) and these other corners (5-2, 6-2).  21. Positioning system comprising at least two devices according to any one of claims 1 to 20, arranged on either side of a plane and oriented so that their first directions are perpendicular to this plane, these devices being respectively linked to a support frame (24) and to a single body (20).  22. System according to any one of claims 1 to 21, characterized in that the corners (5, 6; 5 ', 6') of the same pair converge in the same direction.