Patent application title: Drive device for pivoting adjustable blades of a turbomachine
Markus Hofmann (Castrop-Rauxel, DE)
IPC8 Class: AF01D1712FI
Class name: Rotary kinetic fluid motors or pumps selectively adjustable vane or working fluid control means
Publication date: 2012-12-06
Patent application number: 20120308364
A drive device for pivoting adjustable blades of a turbomachine is
provided. The drive device includes an annular flow channel section
surrounded by a blade carrier, the section extending along the center
line of the blade carrier and blades being provided in the section in a
ray-like manner, forming a ring, wherein each of the blades can be
pivoted about the longitudinal axis thereof and each has a pin which
extends at least into the blade carrier and is coupled to at least one
adjustment ring which encloses the blade carrier and may be driven by
means of at least one motor. In order to provide a particularly low-wear
and reliable drive, the drive shaft of the motor or motors is coupled to
the adjustment ring or adjustment rings by means of a pinion gear.
11. A drive device for the pivoting of adjustable vanes of a turbomachine, comprising: an annular flow passage section which is encompassed by a vane carrier, extends along the center axis of the vane carrier and in which provision is made for a plurality of vanes in a radial manner, forming a ring, wherein for the adjustment, the plurality of vanes are pivotable in each case around their longitudinal axis and have in each case a pivot pin which extends at least into the vane carrier and is coupled to an adjustment ring which is rotatable in the circumferential direction and are driven via a motor, wherein a drive shaft of the motor is coupled to the adjustment ring via a pinion gear, wherein provision is made for a plurality of motors, the respective drive shaft of which comprises in each case one of the pivot pins or is rigidly connected to one of the pivot pins, wherein the respective pinion gear is arranged in each case on the pivot pin of the vane which is thus directly driven, and wherein the remaining vanes are driven via the adjustment ring.
12. The drive device as claimed in claim 11, wherein two adjustment rings are coupled to the pivot pin and are driven by the motor or motors.
13. The drive device as claimed in claim 11, wherein provision is made in the vane carrier or in the casing which encompasses the vane carrier for a circumferential groove in which the pivot pins end and in which the adjustment ring are arranged, and wherein for shielding on the outside the circumferential groove is closed off by means of a cover.
14. The drive device as claimed in claim 11, wherein the coupling between adjustment ring and all the pivot pins is designed in each case as a pinion gear.
15. The drive device as claimed in claim 11, wherein the pinion gears are designed as crown wheel drives.
16. The drive device as claimed in claim 13, wherein each adjustment ring with regard to the center axis of the vane carrier is guided radially on the outside by the cover of the circumferential groove and radially on the inside by the groove base of the circumferential groove.
17. The drive device as claimed in claim 13, wherein each adjustment ring is axially guided by a sidewall of the circumferential groove with regard to the center axis of the vane carrier.
18. The drive device as claimed in claim 17, wherein means for pressing the adjustment ring onto the pivot pins are provided in the sidewall and/or between the sidewall and adjustment ring.
19. The drive device as claimed in claim 18, wherein a plurality of passages for the feed of a hydraulic medium open into the sidewall.
20. The drive device as claimed in claim 18, wherein provision is made between the sidewall and adjustment ring for a plurality of spring elements which are distributed uniformly over the circumference.
CROSS REFERENCE TO RELATED APPLICATIONS
 This application is the US National Stage of International Application No. PCT/EP2011/052188, filed Feb. 15, 2011 and claims the benefit thereof. The International Application claims the benefits of European Patent Office application No. 10001722.7 EP filed Feb. 19, 2010. All of the applications are incorporated by reference herein in their entirety.
FIELD OF INVENTION
 The invention refers to a drive device for the pivoting of adjustable vanes of a turbomachine, with an annular flow passage section which is encompassed by a vane carrier, extends along the center axis of the vane carrier, and in which vanes are provided in a radial manner, forming a ring, wherein the vanes are pivotable in each case around their longitudinal axis and have in each case a pivot pin which extends at least into the vane carrier and is coupled to an adjustment ring which is rotatable in the circumferential direction.
BACKGROUND OF INVENTION
 A device of such generic type is to be gathered from U.S. Pat. No. 5,549,448, for example. In order to adjust the radially extending vanes of a vane ring of a compressor, an adjustment ring, which is concentric to the center axis of the compressor, encompasses its inner casing. Each vane, which is rotatable around its longitudinal axis, of the vane ring, has a pivot pin which extends through the vane carrier, which pivot pins are connected outside the casing in each case via a pivot lever to the adjustment ring. The adjustment ring is rotatable in the circumferential direction. By rotation of the adjustment ring the pivot levers are moved, as a result of which the vanes are pivoted around their respective longitudinal axis. The adjustment ring is moved in the circumferential direction via a drive which at the same time also supports the adjustment ring.
 Similarly, an adjustment ring, which is rotatable in the circumferential direction, for adjusting the vanes of a ring is known from EP 1 524 413 A2.
 It is furthermore known from GB 1 466 613 and GB 1 505 858 that instead of a pivot lever coupling a toothed coupling between adjustable vane and adjustment ring is also possible. The adjustment of the adjustment ring is carried out in GB 1 466 613 in this case via a push rod which applies a hydraulically generated drive force tangentially to the adjustment ring. In GB 1 505 868, the application of force to the adjustment ring is carried out via a lever mechanism. Moreover, EP 2 053 204 A2 proposes to drive the adjustment ring by means of a motor which is coupled to all the adjustable vanes via a toothing arrangement.
 In this case, the drives which are known from U.S. Pat. No. 5,549,448 and EP 1 524 413 A2 are costly in construction since a large number of components are necessary and are to be designed. The large number of components lead to a time-consuming assembly during manufacture, which, on account of the required accuracy of the position of the rotation angle of the individual vanes, is additionally time-intensive, moreover.
 If such drive devices are used in stationary gas turbines, the adjustment rings are exceptionally solid, moreover. During operation, temperature differences between the adjustment ring and the vane carrier then have an influence upon the incidence angle of the compressor vanes in the flow passage. These temperature differences can lead to unequally set incidence angles of the vanes of the vane ring so that care is always to be taken that the adjustment ring and the vane carrier are mounted coaxially or concentrically to a common center axis. In addition, the tangential force application via push rods can also bring about a similarly disadvantageous decentering of the adjustment ring.
 Also, the bearing arrangement of the known adjustment rings can be susceptible to contaminants and malfunctions, which limit a reliable and stable operation. In particular, in the worst case foreign bodies can cause blocking of the drive device in in the region of the toothing arrangement in the case of the embodiment according to GB 1 466 613 or in the region of the lever in the case of the embodiment according to U.S. Pat. No. 5,549,448 or EP 1 524 413 A2, which then substantially limits the operating range of the turbomachine.
 On account of network requirements, the inlet guide vanes of compressors of stationary gas turbines must especially be able in the meantime to be adjusted by comparatively small angle values within split seconds. This, however, is not possible with the conventional, known systems. The lever systems on the one hand are sluggish on account of the solid constructions of adjustment rings and levers. Fast changes with a small adjustment distance lead to enormous loads in the adjustment rings, which can put the reliability and the integrity of the drive device at risk. On the other hand, the lever systems have tolerance-related clearances in the lever linkages so that a slight adjustment cannot be executed as a result.
SUMMARY OF INVENTION
 According to this, the object of the present invention is the creation of a wear-free, reliable drive device--suitable for fast, smaller adjustments--for temperature-independent adjustment of the vanes which extend radially in an annular passage and are rotatable around their respective longitudinal axis.
 The object is achieved by a drive device for the pivoting of adjustable vanes of a turbomachine, which is equipped according to the features of the claims.
 The generic-type drive device for the pivoting of adjustable vanes of a turbomachine comprises a vane carrier which encompasses an annular flow passage section. The flow passage section extends along the center line of the vane carrier. In this, vanes, which are pivotable in each case around their longitudinal axis for the adjustment, are provided in a radial manner with regard to the machine axis, forming a ring. The vanes have in each case a pivot pin which extends at least into the vane carrier and is coupled in each case to at least one adjustment ring which is rotatable in the circumferential direction and can be driven via at least one motor. According to the invention, it is provided that the drive shaft of the motor, or motors, is or are coupled to the adjustment ring, or adjustment rings, via a pinion drive.
 The invention departs from previous constructions in which the rotation of the adjustment ring is carried out by means of tangentially acting push rods. The force application for rotating the adjustment ring, instead of via push rods, is now carried out according to the invention via at least one pinion gear. The pinion gear in this case is preferably designed as a crown wheel gear or a bevel wheel gear, wherein the drive shaft of the motor is designed at the same time as a drive shaft of the pinion gear and the adjustment ring is designed as the driven shaft of the pinion gear. As a result of this, it is possible to obtain a much improved force application for rotating the adjustment ring, which reduces the unwanted decentering of the adjustment ring. In order to provide sufficiently large forces for rotating the adjustment ring, motors, which are required in a greater number than for redundancy reasons, are distributed over the circumference of the adjustment ring, which motors are coupled to the adjustment ring via a pinion gear in each case which in this case are all of identical construction. The use of a larger number of motors enables a circumferentially distributed force application for adjusting the vanes. The more motors are used, the smaller are the forces to be applied by these in each case, which enables smaller pinion gears or toothing arrangements. Equally, the use of gear wheels can therefore be avoided, which saves space and weight. Moreover, the use of a rather thin adjustment ring is made possible compared with an adjustment ring from the prior art which is connected to the pivot pins of the vanes via levers, or is driven only by a motor or hydraulic cylinder. For the adjustment, the motors are naturally always synchronously operated.
 According to the invention, either the pivot pin is part of one of the drive shafts so that the rotational axis of the drive shaft coincides with the rotational axis of the respective pivot pin, or the drive shaft and the pivot pin can be rigidly interconnected. In both cases, the vane which is associated with the respective pivot pin can also be driven directly by the respective motor in this way. For the adjustment, the motors commonly drive the adjustment ring and can individually directly drive in each case one of the vanes which is connected to their drive shafts. The (remaining) vanes, which are not directly driven, are then pivoted into the desired position by means of the adjustment ring.
 In addition to the compact and light-weight construction on account of using a larger number of motors, a further advantage lies in the greater adjustment speed which the drive device now enables for the first time. The transmission of force from the motors to the directly driven vanes is carried out without backlash and to the remaining vanes almost without backlash. In conjunction with the compact construction and the comparatively low masses which are to be moved, the vanes can also be adjusted by comparatively small angle values in a comparatively short time. The known gear drives, however, always provide that all the vanes are driven indirectly via the adjustment ring.
 The invention departs from this since it was recognized that a more compact constructional form can be achieved if some of the motors directly drive one of the vanes in each case.
 At least four motors are preferably provided for a ring of adjustable guide vanes. The upper limit for the number of motors corresponds in this case to half the number of vanes.
 Advantageous embodiments are disclosed in the dependent claims
 According to a further advantageous embodiment, two adjustment rings are provided per drive device in order to drive the pivot pins free of transverse forces.
 According to a further advantageous development, provision is made in the vane carrier or in the casing encompassing the vane carrier for a circumferential groove on the generated surface side, in which the pivot pins end and in which the adjustment ring is arranged, wherein for the shielding of pivot pins, adjustment ring and their coupling the circumferential groove is closed off to the outside at least for the most part by means of a cover. The coupling of adjustment ring and pivot pin is therefore embedded in the vane carrier or recessed in the circumferential groove, as a result of which a two-sided shielding is created, as seen in the longitudinal direction of the turbomachine. With this advantageous embodiment, it departs from the prior art in which the adjustment mechanism was previously arranged outside the casing of the turbomachine without protection. It is now provided that the adjustment mechanism is at least covered, if not even hermetically sealed, as a result of which the drive for the most part (that is to say except for the lead-through for the drive shaft of the motor) is relocated into the wall of the vane carrier. This requires that the vane carrier, in the region in which the pivot pins project into it, is of at least such thickness there that a circumferential groove for accommodating the pivot pin ends and the adjustment ring can be introduced there from the outside, for example by means of mechanical machining. The covering of the circumferential groove by means of a plurality of cover segments is simple to achieve in this case, wherein the fastening of the cover, or cover elements, can be carried out by conventional means, such as by screws. A simple construction, which can be comparatively simply and also inexpensively realized, can be realized with this.
 The coupling between the adjustment ring and the respective pivot pin is preferably designed in each case as a pinion gear, wherein the pinion gear is preferably designed as a crown wheel gear. In this case, the adjustment ring represents a crown wheel and the pivot pin is toothed, at least over a part of its circumference, if not even over its entire circumference. The toothing of the crown wheel and the toothing of the pivot pin intermesh in this case so that a rotation of the adjustment ring in the circumferential direction pivots the vanes. By means of the crown wheel gear, a low-wear, temperature-independent coupling of adjustment ring and respective pivot pin can be carried out, which coupling is furthermore capable of also reliably transmitting the large forces which are required for the adjustment. If all the vanes are pivoted into the desired position by means of the adjustment ring, the required tooth flank clearance of each pinion gear is insignificant. All the vanes are then pivoted to an identical degree. If some of the vanes are adjusted directly by motors and the remaining vanes are adjusted by means of the adjustment ring and the coupling is carried out via pinion gears, the directly driven vanes can be pivoted back slightly by a predetermined rotational angle after the adjustment of all the vanes for compensating the possibly existing tooth flank clearance, so that all the vanes have the identical incidence angle.
 An especially simple and reliable supporting of the adjustment ring can be achieved if this--with regard to the center axis of the vane carrier--is guided radially on the outside by the cover of the circumferential groove and radially on the inside by the groove base of the circumferential groove. The cover then also serves as a guide for the adjustment ring since this bears in a slidable, but clearance-free, manner both on the cover and on the groove base. This avoids the use of additional construction elements such as support rollers for the central supporting of the adjustment ring in relation to the machine axis. This embodiment also enables a comparatively thin adjustment ring since its natural rigidity can now be lower than previously.
 A further advantage of the cover is the guiding of the adjustment ring along the entire circumference since this is assembled from at least two segments. The segments of the adjustment ring, on account of the proposed external guiding by means of the cover, can be interconnected or screwed together in a comparatively simple manner. Avoiding the basically linkage-like adjustment ring is not possible as a result of the full circumferential guiding.
 In order to prevent gaping of the toothing, the adjustment ring is axially guided by a sidewall of the circumferential groove, with regard to the center line of the vane carrier. Alternatively or in addition thereto, it can be provided that means for pressing the adjustment ring onto the pivot pins are provided in the sidewall or between sidewall and adjustment ring. For example, passages for the feed of a hydraulic medium can open into the sidewall for this purpose. It is also possible that provision is made between the sidewall and the adjustment ring for spring elements, also uniformly distributed over the circumference, which exert an axially acting force upon the adjustment ring. As a result of using a toothing arrangement, the adjustment ring can be of thinner design than the comparatively solid adjustment ring from the prior art for stationary gas turbines. By pressing the adjustment ring onto the pivot pins, the elimination of the tooth flank clearance can also be carried out in order to thus keep the adjustable vanes free from play in their predetermined position during operation of the turbomachine. If necessary, the pressing-on force can be reduced during the adjustment process, which is easily possible especially when a hydraulic medium is being used as the pressing-on means. In this case, the adjustment process can be accomplished with comparatively small forces.
 The drive device according to the invention can be used in this case both for the adjustment of inlet guide vanes of a compressor but also for the adjustment of stator blades of a compressor which, in a way similar to the inlet guide vanes, are pivotably mounted around their longitudinal axis which extends in the radial direction of the machine axis.
BRIEF DESCRIPTION OF THE DRAWINGS
 The further explanation of the invention is carried out with reference to the exemplary embodiments which are represented in the drawing. In the drawing, schematically in detail:
 FIG. 1 shows a gas turbine in a longitudinal partial section;
 FIG. 2 shows the detail X from the longitudinal partial section according to FIG. 1 in a first embodiment variant;
 FIG. 3 shows the plan view of detail X according to FIG. 2;
 FIG. 4 shows the fastening of the motor on the base;
 FIG. 5 shows the detail X according to a third embodiment variant and
 FIG. 6 shows the detail X according to a second embodiment variant.
DETAILED DESCRIPTION OF INVENTION
 FIG. 1 shows in a longitudinal partial section a turbomachine which is designed as a stationary gas turbine 1. The gas turbine 1 is intended for power generation. Inside, it has a rotor 3 which is rotatably mounted around a rotational axis 2 and which is also referred to as a turbine rotor assembly. In series, along the rotor 3, are an intake duct 4, a compressor 5, a toroidal annular combustion chamber 6 with a plurality of burners 7 which are arranged rotationally symmetrically to each other, a turbine unit 8 and an exhaust duct 9. The annular combustion chamber 6 forms a combustion space 17 which communicates with an annular hot gas passage 18. Four turbine stages 10, connected in series, form the turbine unit 8 there. Each turbine stage 10 is formed from two blade rings. A row 14 formed from rotor blades 15 follows a blade row 13 in each case in the hot gas passage 18, as seen in the flow direction of a hot gas 11 which is produced in the annular combustion chamber 6. The stator blades 12 are fastened on the stator, whereas the rotor blades 15 of a row 14 are attached on the rotor 3 by means of a turbine disk. A generator or an driven machine (not shown) is coupled to the rotor 3.
 On the intake duct-side inlet of the compressor 5, provision is made for variable inlet guide vanes 19. The inlet guide vanes 19 are arranged radially in the annular flow passage of the compressor 5 and can be rotated around their respective longitudinal axis by a drive device 21 in order to adjust, for example, the mass flow which flows through the gas turbine 1. Depending upon the incidence angle of the vane airfoils of the inlet guide vanes, a particularly larger or a smaller mass flow can flow through the gas turbine 1 to meet demand. In order to reduce flow losses in the inducted ambient air and in order to prevent vibration excitation by rotor vanes 15 which are rotating directly downstream of the inlet guide vanes 19, which occurs in the event of an uneven inflow of the rotor vanes 15 as seen over the circumference, all the inlet guide vanes 19 are adjusted synchronously, constant maintaining equal incidence angles.
 The drive device 21 is provided outside the flow passage and is described in detail in the following figures.
 To this end, FIG. 2 shows the detail which is identified by X in FIG. 1. Shown first of all is a vane carrier 22 which in the specific embodiment is also designed at the same time as a casing component of the compressor 5 of the gas turbine 1. The vane carrier 22 is also referred to as a guide vane carrier. In an inflow-side section 23 of the compressor 5 for the inducted air the guide vane carrier 22 has an increased wall thickness. In this axial section 23, with regard to the center axis 24 of the gas turbine 1, holes 25 are provided in identical number as adjustable vanes 19 for accommodating pivot pins 26 which are arranged in each case on one of the adjustable vanes 19. In the section 23, provision is made, moreover, on the generated surface side for an endless encompassing circumferential groove 27 in which the pivot pins 26 end. The axial position of the holes 25 is selected in this case so that these do not open fully into the circumferential groove 27 but only partially in such a way that only a small circle section of the hole 25 lies within the groove 27 in order to ensure sufficient toothing (see FIG. 3). The bearings (not shown) which are required for the rotatable support of the pivot pin 26 in the guide vane carrier 22 are provided in a known manner radially on the inside adjacent to the circumferential groove 27.
 An adjustment ring 28, which comprises two segments, for example, is arranged in the groove 27. The adjustment ring 28--seen in longitudinal section of the turbomachine--has a rectangular sectional contour. Each pivot pin 26 has a toothing arrangement in the manner of a gearwheel, at least over a part of its circumference. In a way corresponding thereto, an end-face wall of the adjustment ring 28 also has a toothing arrangement, wherein both tooth arrangements intermesh in the manner of a crown wheel gear. The sidewall toothing 30 of the adjustment ring 28 extends along an arc length (FIG. 3) for each pivot pin 26 such that the vane 19 can be reliably pivoted over the entire adjustment angular range. The sidewall toothing 30 can also be arranged, however, endlessly over the circumference of the adjustment ring 28, as in the case of a crown wheel. The adjustment ring 28 therefore forms with each pivot pin 26 a crown wheel toothing by which the rotational movement of the adjustment ring 28 around the machine axis 24 is converted into a rotational movement of the vane 19 around its longitudinal axis 31.
 For the guiding of the adjustment ring 28 and for avoiding deposits and contaminants in the respective crown toothing, the groove 27 is shielded via a cover 32. In this respect, the pinion gears and the adjustment ring 28 in principle are not accessible from outside the gas turbine 1.
 In order to supply the necessary adjustment forces to the adjustment ring 28, at least one motor 33 is provided. The motor 33 in this case can be designed as a hydraulic motor, but also as an electric motor or as a servo motor. The drive shaft 35 of the motor 33 extends through an opening 37 which is provided for it in the cover 32 and is rigidly connected to one of the pivot pins 26. Both are rotatable around a common rotational axis which coincides with the longitudinal axis 31. The motor 33 serves on the one hand for driving the adjustment ring 28 and for the direct drive of the one vane 19 which is rigidly connected via its pivot pin 26 to its drive shaft 35. A plurality of motors 33, shown in FIG. 2, can also be distributed over the circumference of the adjustment ring 28 for its rotation. The motor, or motors 33, is or are then fastened via mountings, which are not additionally shown, either on the guide vane carrier or on the base of the gas turbine.
 The fastening of one of the motors 33 on the base 40 is outlined in FIG. 4, wherein in this drawing the rigid connection between drive shaft 35 and pivot pin 26 is only schematically shown. For the sake of clarity, only the vane 19 of the guide vane ring which can be directly driven by the motor 33 and the adjustment ring 28 are shown.
 Furthermore, in FIG. 2 provision is made in a sidewall 34 of the circumferential groove 27 for a passage opening 38 via which a hydraulic medium of the drive device 21 is able to press the adjustment ring 28 onto the pivot pins 26. The connecting lines which are required for this are not shown in FIG. 2. Naturally, in this case a plurality of passages for hydraulic medium are distributed along the circumference in order to achieve an even pressing-on.
 FIG. 3 shows the plan view of an uncovered crown toothing arrangement in the section 23, wherein identical features are provided with identical designations.
 According to an embodiment which is an alternative to FIG. 2 and shown in FIG. 6, instead of an adjustment ring 28 arranged on one side an additional adjustment ring 28 can also be provided in such a way that the pivot pins 26 of the vanes 19 are arranged between two adjustment rings 28 which are associated with a drive device and are therefore toothed on both sides.
 In this case, provision is made on both sides of the holes 25 for two grooves 27 in which one of the two adjustment rings 28 is arranged in each case. Instead of two circumferential grooves 27 with holes 25 arranged in between, the holes 25, and therefore also the pivot pins 26, can be arranged in the middle in only one circumferential groove which is then wider. For the rotating or pivoting of vanes 19, the two adjustment rings 28 which are associated with a drive device 21 are to be rotated in opposite directions at the same time.
 Instead of the hydraulic pressing of the adjustment ring 28 onto the pivot pins 26, which is known from FIG. 2, according to FIG. 6 provision is made between the sidewall 34 of the circumferential groove 27 and the adjustment ring 28, which is directly adjacent thereto, for spring elements 36, especially in the form of disk springs, which are distributed uniformly over the circumference and bring about a constant pressing-on pressure.
 Naturally, it is possible to arrange the spring elements 36, which are shown in FIG. 6, even in the case of a drive device 21 with only one adjustment ring 28. By the same token, it is equally possible to apply the hydraulic pressing-on for each adjustment ring 28 of a drive device 21, in which two oppositely rotatable adjustment rings 28 are provided according to FIG. 6.
 FIGS. 2 and 6 show the preferred embodiments of the invention. The fundamental embodiment is shown in FIG. 5 and according to this the direct drive of a vane, or a plurality of vanes 19, is not absolutely necessary. The motor 33 then serves alone for adjusting the adjustment ring 28 which, for the pivoting of all the vanes 19, transmits its rotational movement to the said vanes via the pinion gears, described in FIG. 2, between the adjustment ring and the pivot pins 26 of the vanes 19. Also, the embodiment shown in FIG. 5 can be slightly modified with regard to the number of adjustment rings 28 and to the selection of the means for pressing the adjustment rings 28 onto the pivot pins 26.
 The drive device which is shown in the figures is suitable in this case not only for the adjustment of inlet guide vanes 19 of a compressor 5, but naturally also suitable for the adjustment of stator blades of subsequent compressor stages, which stator blades in modern gas turbines are also pivotably mounted around their longitudinal axis 31 which coincides with the radial direction with regard to the machine axis 24.
 Overall, the invention refers to a drive device 21 for the pivoting of adjustable vanes 19 of a turbomachine, with an annular flow passage section 23 which is encompassed by a guide vane carrier 22, extends along the center axis 24 of the guide vane carrier 22 and in which provision is made for vanes 19 in a radial manner, forming a ring, wherein the vanes 19 are pivotable in each case around their longitudinal axis 31 and have in each case a pivot pin 26 which extends at least into the guide vane carrier 22 and is coupled to at least one adjustment ring 28 which encompasses the guide vane carrier 22. In order to provide a particularly low-wear and reliable drive, it is proposed that the drive shaft 35 of the motor 33, or motors, is or are coupled to the adjustment ring 28, or adjustment rings 28, via a pinion gear.
Patent applications in class SELECTIVELY ADJUSTABLE VANE OR WORKING FLUID CONTROL MEANS
Patent applications in all subclasses SELECTIVELY ADJUSTABLE VANE OR WORKING FLUID CONTROL MEANS