EP2766618A1

EP2766618A1 - System for guiding a vertical shaft of a rotary machine, and power-conversion equipment including such a system

Info

Publication number: EP2766618A1
Application number: EP12770161.3A
Authority: EP
Inventors: Alain Mathieu; Luc Melet; Emmanuel GODEC
Original assignee: Alstom Renewable Technologies Wind BV
Current assignee: GE Renewable Technologies Wind BV
Priority date: 2011-10-13
Filing date: 2012-10-12
Publication date: 2014-08-20
Also published as: CN104040196A; BR112014008992A2; FR2981417B1; BR112014008992A8; WO2013053900A1; US20140219592A1; RU2014118940A; FR2981417A1; CA2851578A1

Abstract

The invention relates to an adjustable system (150) for guiding the rotation of a shaft about a vertical axis, including skids (104), each of which is provided with a surface (1042) for forming a bearing with the shaft and, for each skid, a shim (106) provided with a cam surface (1062), the outline of which, in a plane that is radial relative to the vertical axis of rotation, is inclined (α) relative to said axis. Each skid (104) directly engages, via a portion (1046) of the outer radial surface (1044) thereof, with the cam surface (1062) of the shim (106). Equipment for converting hydraulic power into electrical power according to the invention includes a wheel that is rotatably secured to a shaft guided by such an adjustable system (150).

Description

System for guiding a vertical rotating machine shaft and energy conversion installation incorporating such a system

The invention relates to an adjustable system for guiding a shaft, rotating about a vertical axis.

The invention may, in particular, be implemented with a hydraulic machine which may comprise a turbine, a pump or a pump turbine used in a hydraulic energy conversion installation into electrical energy, or vice versa.

In this type of installation, it is known to start several pads on the circumference of a shaft rotating about a vertical axis. These pads together form a bearing supporting the forces from the rotating shaft, through the creation of a film of oil between the shaft and the bearing surface of the pads. The radial position of these pads must be adjusted precisely so that the bearing maintains a minimum thickness of oil film, without risk of tightening or impact between the rotating shaft and the pads. On the other hand, during rotation, the rotating shaft has a deformed which is even more important that the radial maintenance of the pads is not sufficiently rigid.

This is particularly the case when the bearings are equipped, on their outer radial surface, with a swiveling system provided with an outer peripheral surface in the form of a sphere section intended to cooperate with a force recovery unit having a cavity of which the bottom is shaped like a spherical section too. The respective radii of the spherical section surfaces provided, on the one hand, on the ball joint and, on the other hand, at the bottom of the cavity of the force-retaining block are large, generally of the order of several meters per square meter. a turbine whose support shaft has a diameter of between 80 cm and 2 m. The production of spherical section surfaces with a large radius is complicated to implement, which increases the cost of an installation incorporating such a mechanism.

In addition, in known systems, several parts are associated to define the radial position of the pads, namely, for each pad, a ball joint, a force recovery block, a wedge and a fixed support member. This stack of parts induces an accumulation of flexibility, such that the rigidity of the set of pads is not maximized. As a result, relatively large deformations of the assembly formed of the shaft and bearing can be observed during operation of a hydraulic machine, which makes it necessary to dimension with significant tolerances labyrinth wheel seals, provided in the vicinity of the flow zone of the main flow of water within the hydraulic machine ,. This induces significant leaks on this main flow and therefore a loss of performance and effective production of the hydraulic machine.

Comparable problems generally arise in rotating machines with a vertical axis. This is particularly the case in alternators with roller bearings.

In the field of bearings in general, it is known from US-A-1,880,353 to use pads to support a shaft rotating about an axis whose orientation is not specified. These pads are each movable in rotation about an axis defined by a threaded rod and rest by a heel against an inclined portion of a housing. Guiding of the pads is imprecise and the housing may be deformed under the effect of radial forces exerted by the pads.

It is these drawbacks that the invention intends to remedy more particularly by proposing an adjustable system for guiding a machine shaft which makes it possible to obtain improved rigidity of the support of its skids and to limit, consequently, the deformed shapes. of the tree in use. The invention also aims at reducing the transverse dimensions of the labyrinth wheel seals used in a hydraulic installation incorporating this guidance system. The invention also aims to reduce the cost and simplify the adjustment of the play of the roller bearing with the consequence of assembly and maintenance time reducing downtime of the machine.

To this end, the invention relates to an adjustable system for guiding a shaft, in rotation about a vertical axis, this system comprising pads each provided with a surface intended to form a bearing with the shaft and, for each shoe, a wedge provided with a cam surface whose trace, in a radial plane relative to the vertical axis of rotation, is inclined relative to this axis. According to the invention, each pad is in direct support, by a portion of its outer radial face, against the cam surface of the wedge, while each cam is provided with an elongated housing whose largest dimension is parallel to the vertical axis of rotation and in which is housed a prison nut guided in translation by the longitudinal edges of the housing and whose position in the housing is controlled by means of a threaded rod engaged with an internal thread of the nut prisoner.

In the present description, the terms "axial" or "radial" are defined with reference to the vertical axis of rotation of the shaft for which the guide system is envisaged. A direction is said to be axial if it is parallel to this axis, a surface is said to be axial if it is perpendicular to this axis. A direction is called radial if it is perpendicular to, and secant with, this axis. A surface is said to be radial if it is centered on this axis. A plane is said to be radial if it includes a radial direction and the axis of rotation.

Thanks to the invention, the position of each pad, in a radial direction, is defined by the direct cooperation between this pad and the cam surface of the hold, without the need to use a joint with a ball joint and a force recovery block as in the equipment of the prior art. The invention thus takes the opposite of the technique used in systems comprising a ball with an outer surface in a sphere section, insofar as, in these known systems, a sliding contact between the ball and the force recovery block is favored. . On the contrary, the direct support provided in the invention, between the portion of the outer radial face of the shoe and the cam surface of the wedge induces a possible matting of the surfaces in abutment against each other, which is accommodates during the life of the hydraulic machine equipped with the adjustable guide system of the invention. In addition, the guidance of the pads with the nut trapped in the oblong housing is accurate, while the adjustment elements of the position of the pads undergo acceptable mechanical stresses.

According to advantageous but not mandatory aspects, such a guidance system may incorporate one or more of the following features, taken in any technically permissible combination:

- The cam surface of each wedge makes it possible to adjust the radial position of the pad bearing against this surface, by a vertical translation of the cam.

- The aforementioned housing is preferably a light which passes through the shim of its cam surface to an opposite surface by which the shim is in abutment against the fixed member.

- Each pad is in direct support against the cam surface of the corresponding shim, on either side of the housing of this wedge, in a horizontal direction.

- Each pad is provided on its outer radial face, a heel which defines a direct bearing surface located against the cam surface of the corresponding shim.

- The bearing surface of the heel is polygonal contour, including square. As a variant, this bearing surface is circular in outline.

- The heel is provided with a housing for receiving a portion of the prisoner nut.

- The parts in direct support of a pad and the corresponding wedge are provided to be matted one by the other during use of the guidance system. - The system comprises a fixed force recovery ring, an inner radial surface facing the vertical axis of rotation is cut grooves in each of which is engaged a shim, with the possibility of vertical sliding.

- The captive nut comprises a head which protrudes from the cam surface of the wedge and which is engaged in a housing of the pad bearing against this surface.

- The housing is drilled in the heel of the pad and the localized direct bearing surface surrounds the outlet of the housing.

- The wedge is pierced with two orifices aligned along the largest dimension of the elongated housing, while the threaded rod is successively engaged in a first hole among these two orifices, in an internal thread of the captive nut and in the second orifice.

- Wedges, captive nuts and threaded rods associated with the different pads are interchangeable.

The invention also relates to a plant for converting hydraulic energy into electrical energy, or vice versa, which comprises a turbine wheel, pump or pump impeller integral, in rotation about a vertical axis, a shaft guided by skates. According to the invention, this installation comprises a system for guiding a tree as mentioned above.

The invention will be better understood and other advantages thereof will emerge more clearly in the light of the following description of an embodiment of a hydraulic installation and a guidance system according to its principle, given only by way of example and with reference to the appended drawings in which:

FIG. 1 is a diagrammatic representation, in axial section, of an installation according to the invention,

FIG. 2 is a perspective view, partially broken away, corresponding to detail II in FIG. 1;

FIG. 3 is an enlarged view of detail III in FIG. 2,

FIG. 4 is an exploded perspective view of certain elements of a skid guide system according to the invention;

FIG. 5 is a basic section along line V-V in FIG. 2, in a radial plane with respect to the axis of rotation of the wheel of the installation,

FIG. 6 is a section along line VI-VI in FIG. 5;

FIG. 7 is a section along the line VII-VII in FIG. 5, and

- Figure 8 is a section along line VIII-VII I in Figure 5. The installation 200 shown in the figures comprises a Francis-type turbine 1 whose wheel 2 is intended to be rotated around a vertical axis X2 by a forced flow of water E coming from a water reservoir. not shown. A shaft 3 is integral, in rotation about the axis X2, with the wheel 2. This shaft 3 is coupled to an alternator 4 which delivers an alternating current to a not shown network, as a function of the rotation of the wheel 2. The installation 200 thus makes it possible to convert the hydraulic energy of the flow E into electrical energy. The plant 200 may comprise one or more turbines 1 fed from the same water reservoir.

According to another variant, the turbine Francis 1 can be replaced by a pump turbine which, when it operates as a pump, is driven by an electric motor installed in place of the alternator 4 and converts the electrical energy into hydraulic energy of a flow set in motion by the pump wheel.

A supply line 5 makes it possible to bring the flow E to the wheel 2 and extends between the water reservoir and a tank 6 equipped with guides 61 which regulate the flow E.

A duct 8 is provided downstream of the turbine 1 to evacuate the flow E and return it to the bed of a river or river from which the water reservoir is fed. This duct 8 is sometimes called suction duct. The conduit 8 comprises an upstream portion 81 substantially vertical, frustoconical and centered on the axis X2, and a downstream portion 82 centered on a substantially horizontal axis X82. A bend 83 at 90 ° connects the parts 81 and 82 of the condu 8.

The shaft 3 is held in position relative to a masonry structure not shown by two oil bearings 100 and 101 formed respectively in the upper part and in the lower part of the shaft 3, around it. Alternatively, three oil bearings may be used to guide the shaft 3.

According to another variant, a skid-mounted hydraulic bearing can be implemented, with a guiding system according to the invention, at the level of the alternator 4.

The fixed structure of the installation 200 comprises a ring 102 of force recovery disposed around the shaft 3 and which is secured to the masonry of the installation 200 which is not shown. This force recovery ring 102 is metallic and is welded to a ferrule 103A itself welded to a strip 103B bolted to a not shown flange and itself fixed on the masonry by other parts not shown.

Note 1022 the inner radial surface of the ring 102, that is to say the surface of this ring facing the axis X2. The outer radial surface 32 of the shaft 3 is stepped and comprises, in the vicinity of the ring 102, a circumferential band 34 around which several pads 104 are arranged, the number of which varies according to the size of the shaft 3. In the example of the figures, the skates are ten in number.

Each pad 104 comprises an inner radial surface 1042 which faces the axis X2 in the mounted configuration of the installation 200 and which is in a cylinder section centered on this axis X2, with a radius substantially equal to, or slightly greater than, that of the band 34. It is thus possible to define, between each shoe 104 and the surface 34 a portion of the hydraulic bearing 100 in which a film of oil provides lubrication and recovery of the shoe force.

Y104 denotes a radial axis with respect to the axis X2 and which passes through the center of the surface 1042 of a shoe 104. Along its axis Y104, a shoe 104 extends between its surface 1042 and a radial surface external plane 1044 which is turned away from the axis X2.

As is more particularly apparent from FIGS. 4 to 6, the surface 1044 of a shoe 104 is equipped with a heel 1046 which is integral with the rest of the shoe 1044 and which projects from the surface 1044. heel 1046 is square. Alternatively, it may be circular or rectangular, or polygonal with another form.

Note 1047 the surface of the heel 1046 facing away from the surface 1042, that is to say oriented radially outwardly of a shoe 104 in mounted configuration of the installation 200.

The heel 1046 is pierced with a housing 1048 which is blind, circular section and centered on the axis Y104. The surface 1047 surrounds the outlet of the housing 1048.

A shim 106 is associated with each pad 104. Each shim 106 is of generally parallelepipedal shape with an inner radial surface 1062 intended to be turned towards the axis X2 in the mounted configuration of the installation 200, and an outer radial surface 1064, oriented opposite the surface 1062 and which bears against the surface 1022 of the force recovery ring 102, in the mounted configuration of the installation 200.

The surfaces 1062 and 1064 are flat but not parallel. Indeed, these surfaces form between them an angle whose value is less than 5 °. The surfaces 1062 and 1064 move toward each other in a downward direction when the shim 106 is in place in the installation 200. More precisely, in the plane of FIG. 5 which is radial with respect to the X2 axis, the trace of the surface 1062 is inclined, with respect to this axis, the angle a. The surface 1062 converges towards the X2 axis towards the top of FIG. 5, while the surface 1064 is parallel to the X106 axis. Thus, the surface 1062 of the shim 106 forms a cam surface which allows to adjust the radial position of the pad 104 bearing against this surface by a vertical translation of the shim 106. The shim 106 may be described as "wedge".

As can be seen from FIGS. 4 and 6, the surface 1022 is cut with ten flat-bottomed grooves 1024, in each of which a shim 106 is engaged, with the possibility of vertical sliding.

The shim 106 is pierced with an oblong opening 1066 along the generally rectangular axis X106 and whose largest dimension is centered on an axis X106 parallel to the axis X2 in mounted configuration and perpendicular to the axis Y104 . 1066A and 1066B respectively denote the large edges of the opening 1066 which are parallel to the axis X106. The opening 1066 is formed by a lumen which passes through the shim 106 of the surface 1062 to the surface 1064. Alternatively, the lumen 1066 may be replaced by a hollow housing opening on the surface 1062 but not on the surface 1064.

The length of the light 1066 along the axis X106 is adapted to allow the assembly of the assembly 150 and the adjustment of the bearing clearance

The shim 106 is pierced with two orifices 1067 and 1068 aligned on the axis X106.

A nut 107 is mounted prisoner in the oblong opening 1066 of each shim 106 and comprises two flats 1072 and 1074 slidingly bearing on the sides 1066A and 1066B of this opening. The nut 107 is also provided with an internal thread 1076 intended to cooperate with the threaded portion 1086 of a screw 108 whose head 1082 abuts against a lower surface of the shim 106 in which the orifice 1068 opens. 1084 end of the screw 108 opposite the head 1082 is square section, which allows to drive it in rotation about the axis X106 when the screw 108 is in place in the orifices 1067 and 1068. It is thus possible , by more or less turning the screw 108 about its longitudinal axis X108, then merged with the axis X106, to move, parallel to the axis X106, the shim 106 with respect to the nut 107 which remains engaged in the oblong slot 1066. The edges 1066A and 1066B then interact with the flats 1072 and 1074 of the nut 107 to guide the shim 106 in translation parallel to the axis X106. When the desired position of the shim 106 along the axis X106 has been reached, it is possible to immobilize the screw 108 in rotation by tightening a counter-nut 109 on the upper face of 106 via a bearing on a self-locking washer 1 10.

The captive nut 107 comprises a head 1078 protruding from the surface 1062 of the shim 106 and which is engaged in the housing 1048 of the associated shoe 104. The introduction of the head 1078 in the housing 1048 ensures that the nut 107 does not slide vertically relative to the pad 104 when the shim 106 slides around the nut 107 parallel to the axis X106. Thus, when the screw 108 is rotated about its axis X108, then coincides with the axis X106, the shim 106 slides, upwards or downwards, along the surfaces 1047 and 1022 against which it is supported sliding, respectively by its surfaces 1062 and 1064. During this sliding of the shim 106 along the surface 1062, the pad 104 is in direct abutment against the surface 1062, at its surface 1047 which protrudes from to the rest of the surface 1044. More specifically, the surface 1047 is in localized support against the surface 1062, on either side of the opening 1066 in a horizontal direction D106 defined in the shim 106 as perpendicular to the axis X106 and parallel to surfaces 1062 and 1064.

As each pad 104 is in direct abutment on the surface 1062 of the associated shim 106, which is supported by its surface 1064 against the stress-absorbing ring 102, the radial position of each pad 104, that is to say to say its position along its axis Y104, is precisely controlled by the vertical translation of the corresponding shim 106, without manufacturing tolerances of the elements 104, 106 and 102 inducing significant positional variations. Indeed, the inclined nature of the surface 1062 makes it possible to adjust the radial position of the pad 104 by a vertical translation of the shim 106. The direct support of the surfaces 1062 and 1047 against each other ensures a transmission of effort without play and by flat surfaces. This is a substantial advance over known devices in which ball joints and force-absorbing blocks were interposed between the pads and a part comparable to the ring 102 of the invention.

In this regard, it is noted that the mounting of the head 1078 in the housing 1048 is performed with a slight clearance, so that the possible sliding of the shoe 104 around the head 1078, parallel to the axis Y104, does not risk be limited to interfere with the support of the surface 1047 on the surface 1062.

As the surfaces 1047 and 1062 are supported against each other, under significant pressure, it is possible that a matting takes place between these surfaces, which is not unacceptable. In this regard, the material of the elements 104, 106 and 107 may be chosen to support, or even facilitate, such matting. These parts may, for example, be made of carbon steel, especially in the European grade S275, S355 or equivalent. In practice, the constituent material of the shim 106 is chosen so that its surface 1062 is matted under the effect of contact with the heel 1046 of the associated shoe before the surface 1047 of this heel is itself matted. The material of the shim 106 is thus more flexible than the material of the pad 104. In fact, in case of important matting following abnormal stresses or vibrations, it is easier and less expensive to change a shim 106 than a pad 104.

In FIG. 8, the gray portion of the surface 1062 represents a portion 1062A of this matted surface under the effect of the pressure exerted by the surface 1047 of the heel 1046. In this case, the surface 1047 can also be matted. This is not required, however.

Thanks to the invention, the transmission of radial forces between the parts 104 and 106 is achieved by means of the surfaces 1047 and 1062 which are flat, which is substantially easier to implement than in the case where surfaces in section spheres must be made, with large radii, as in the joints of the prior art.

The frictional forces between the shaft 3 and each of the pads 4 tend to rotate these pads around the axis X2. Indeed, these friction forces are transmitted from the surface 34 to the surface 1042. Thus, when the shaft 3 rotates clockwise in Figure 6, the friction forces tend to cause the pad 104 in the same direction, down on this figure.

D108 denotes a line orthoradial with respect to the axis X2 and passing through the axis X106 of the shim 106 associated with each pad 104. The tangential force exerted between the shaft 3 and the pad 104 tends to move the nut 107 and the shim 106 along the line 108, downwards in FIG. 6. In fact, this tangential force is transmitted thanks to the contact pressure between the surfaces 1047 and 1062, in support of the head 1078 in the housing 1048 and bearing the flat 1072 against the side 1066A of the opening 1066. This tangential force is taken up by the side of the groove 1024 against the bottom of which rests the surface 1064 of the hold 6. When the 3 rotates counterclockwise, that is to say in the counterclockwise direction in Figure 3, the shim 6 abuts against the side of the groove 1024 which is partially visible in Figure 4, at the junction between the surface 1022 and the groove 1024. Thus, whatever the direction of rotation of the shaft 3, the grooves 1024 allow blowing rotate the shims 106 around the axis X2 and thus oppose the tangential forces within the bearing 100.

The invention is shown in the figures in the case where the surface 1047 has a square contour. Alternatively, a circular contour can be envisaged as mentioned above. In this case, the geometry of the portion 1062A of the surface 1062 changes accordingly. The geometry of the heel 1046 and surfaces 1062 and 1064 is adapted according to the intensity of the forces to be transmitted. Similarly, the geometry of the head 1078 and the housing 1048 can be changed. They may, alternatively, be square or rectangular section.

The invention also has an advantage in terms of safety. Indeed, even if, under the effect of vibrations, the counter-nut 109 is loosened, to the point that the screw 108 is driven out of the orifices 1067 and 1068, the shim 106 is not likely to slide completely downwards or upwards because the prisoner nut 107 forms a stop to the vertical movement of the shim 106. The pad 104 can not therefore become completely free and disengaged from the support 102, causing serious damage if that were the case.

150 is noted the system formed of different pads 104, different shims 106, various captive nuts 107, different rods 108 and their accessories 109 and 1 10. This system allows to precisely adjust the pads 104 in an adjustable manner, by moving the nuts 107 in the oblong slots 1066, while remaining easy to manufacture and implement at the installation site of the installation 200, without requiring machining on site.

The invention makes it possible to envisage a standardization of the elements 104 to 110 constituting the system 150 for guiding the shaft 3, which can be designed according to the intensity of the forces to be transmitted.

It is also noted that the different elements 106, 107, 108, 109 and 1 10 associated with the different pads 104 are interchangeable, which facilitates the work of the assemblers during the assembly of the installation 200.

Finally, the constituent parts of the system 150 are easily accessible for inspection, including after complete assembly, which facilitates the monitoring and maintenance operations.

The invention can be implemented at the lower bearing 100, the upper bearing 101 or an intermediate bearing of the installation 200.

The invention is described above when it is implemented in a hydraulic installation. However, it can be used in any rotating machine with vertical axis, provided with at least one roller bearing. It can, for example, be an alternator or a motor.

Claims

1 .- (150) adjustable system for guiding a shaft (3), in rotation about a vertical axis (X2), this system comprising pads (104) each provided with a surface (1042) intended to form a bearing (100) with the shaft (3) and, for each shoe, a shim (106) provided with a cam surface (1062) whose trace in a plane radial to the vertical axis of rotation (X2), is inclined (a) with respect to this axis, characterized in that, each pad (104) is in direct abutment, by a portion (1046) of its outer radial face (1044), against the cam surface (1062) of the shim (106) and in that each cam (106) is provided with an elongate housing (1066) whose largest dimension (X106) is parallel to the vertical axis of rotation (X2) and in which which is housed a prison nut (107), guided in translation by longitudinal edges (1066A, 1066B) of this housing and whose position in the housing is controlled by means of a threaded rod (108) engaged with a tar internal bleeding (1076) of the prisoner nut.

2. System according to claim 1, characterized in that the cam surface

(1062) of each shim (106) allows to adjust the radial position of the pad (104) bearing against this surface, by a vertical translation of the cam.

3. - System according to one of the preceding claims, characterized in that the housing is a slot (1066) which passes through the shim of its cam surface (1062) to an opposite surface (1064) by which this shim is resting against the fixed member (102).

4. - System according to one of the preceding claims, characterized in that each pad (104) is in direct abutment against the cam surface (1062) of the corresponding shim (106), on either side of the housing ( 1066) of this wedge in a horizontal direction (D106).

5. - System according to one of the preceding claims, characterized in that each pad (104) is provided on its outer radial face (1044), a heel (1046) defining a surface (1047) direct support located against the cam surface (1062) of the corresponding shim (106).

6. System according to claim 5, characterized in that the bearing surface

(1047) of the heel (1046) is polygonal contour, including square.

7. System according to claim 5, characterized in that the bearing surface (1047) of the heel (1046) is circular contour.

8. - System according to one of claims 5 to 7, characterized in that the heel (1046) is provided with a housing (1048) for receiving a portion (1078) of the prison nut (107).

9. - System according to one of the preceding claims, characterized in that the portions (1047, 1062) in direct support of a pad (104) and the corresponding shim (106) are provided to be matted one by the other in use of the guidance system (150).

10. - System according to one of the preceding claims, characterized in that it comprises a fixed ring (102) of force recovery, an inner radial surface (1022) facing the vertical axis of rotation (X2) is notched grooves (1024) in each of which is engaged a wedge (106), with the possibility of vertical sliding.

1 1. - System according to one of the preceding claims, characterized in that the captive nut (107) comprises a head (1078) which protrudes from the cam surface (1062) of the shim (106) and which is engaged in a housing (1048) of the pad (104) bearing against this surface.

12. - System according to claims 5 and 1 1, characterized in that the housing (1048) is drilled in the heel (1046) of the pad (104) and in that the surface (1047) of localized direct support surrounds the housing outlet.

13. - System according to one of the preceding claims, characterized in that the wedge (106) is pierced with two orifices (1067, 1068) aligned along the largest dimension of the elongated housing (1066) and in that the threaded rod (108) is engaged successively in a first port (1068) among these two orifices, in an internal thread (1076) of the prison nut (107) and in the second orifice (1067).

14. - System according to one of the preceding claims, characterized in that the shims (106), the captive nuts (107) and the threaded rods (108) associated with the different pads (104) are interchangeable.

15. - Installation for converting hydraulic energy into electrical energy, or reciprocally, comprising a wheel (2) of turbine (1), pump or pump impeller solidarity, rotating about a vertical axis (X2), d a shaft (3) guided by pads (104), characterized in that this installation comprises a system (150) for guiding the shaft (3) according to one of the preceding claims.