Vane adjustment lever for a gas turbine, turbomachine comprising the vane adjustment lever and method for assembling a vane adjustment lever for a turbomachine

Abstract

The invention relates to a blade adjustment arm (10) for a turbomachine, comprising two legs (12) which can be pivoted relative to one another between at least one open position and a closed position and which form a clamping device which has at least one clamping surface (14) on each of the legs (12), by means of which, in the closed position, a blade shaft (20) provided for adjusting a guide vane of the turbomachine can be held in a force-fitting manner between the two legs (12) via the two clamping surfaces (14) to form a clamping connection (16), wherein each of the legs (12) has an opening (50) which overlap one another in the closed position in such a way that a through-bolt can be pushed through the openings (50) and can be connected to an adjustment element of the turbomachine for adjusting an angle of rotation of the blade shaft (20).

Description

[0001] The invention relates to a blade adjustment arm for a turbomachine according to claim 1, in particular for an aircraft gas turbine, a turbomachine with the blade adjustment arm and a method for assembling a blade adjustment arm according to the features of claim 10.

[0002] Turbomachines, particularly gas turbines or aircraft gas turbines, have both guide vanes and rotor blades. The guide vanes are arranged on guide vane rings, while the rotor blades are arranged on rotor blade rings. Turbomachines often have several of these blade rings as successive stages, which are arranged along a direction of a shaft of the respective turbomachine. The task of the rotor blades is to provide the power to pass a gas through the turbomachine. For this purpose, the rotor blades are arranged on a rotor of the turbomachine and rotate during operation. The guide vanes, on the other hand, are arranged on a stator and are static during operation. The task of the guide vanes is to guide the flow flowing through the turbomachine so that the flow is fed to the rotor blades at a predetermined angle.Depending on the current operating state of the turbomachine, the setting angle of the guide vanes can be changed. For this reason, the guide vanes are rotatably mounted in the turbomachine. The adjustment of the guide vane about the adjustment axis is achieved by means of lever devices arranged on a guide vane shaft of the guide vanes. This guide vane shaft is located at a radially outer end of the adjustable guide vane, i.e. on a side of the guide vane facing away from the rotor shaft of the turbomachine and outside the flow-through area of ​​the turbomachine. The shaft of the adjustable guide vane is guided by means of a feedthrough from the first area through which gas flows into a second area inside the turbomachine, which is arranged radially around the first area and in which the lever devices and the guide vane ends are accommodated.The lever devices must be arranged on the guide vane shafts in such a way that a force can be transmitted from the lever devices to the guide vanes.

[0003] In the prior art, a lever arm for adjusting the guide vanes (i.e., the blade adjustment arm) is usually placed on the guide vane shaft and fixed to the guide vane shaft by means of a nut. The nut is usually secured with a cotter pin to prevent accidental opening. Furthermore, the guide vane shaft has a flattened area, chamfer, or groove with which the lever arm engages and which, through positive locking, prevents the blade adjustment arm from rotating relative to the guide vane. At the other end of the blade adjustment arm, the blade adjustment arm is connected to an adjustment element, which is designed as a circular adjustment ring that encloses the turbomachine in the second region. By means of the adjustment ring, all of the guide vanes of a guide vane ring connected to it can be adjusted together.

[0004] For example, EP 524 781 A1 discloses a connecting device for an adjustable guide vane of a gas turbine, which has a guide vane shaft connected to a respective guide vane and a lever element connected to the guide vane shaft, wherein the lever element and the guide vane shaft are jointly movable about a blade shaft rotation axis. It is provided that the lever element and the guide vane shaft are aligned with one another by means of a positioning element, wherein the positioning element is received in a blade shaft receptacle and a lever receptacle.

[0005] Furthermore, for example, EP 3 683 408 A2 discloses a lever arm assembly for a gas turbine engine, comprising a guide vane arm having a first end and an opening defined by an opening wall near a second end opposite the first end. A guide vane shaft extending through the opening of the guide vane arm is secured to a position of the guide vane arm by means of a mechanical fastener in the longitudinal direction of the guide vane shaft. A resistance clamp partially enclosing a portion of the second end of the guide vane arm is provided to provide redundant positional retention of the guide vane arm in the longitudinal direction of the guide vane shaft.

[0006] Furthermore, document US 4 307 994 A discloses a turbine blade adjustment assembly for calibrating the nozzle / throat width dimension between adjacent adjustable blades in a nozzle blade ring assembly to produce a common rotation of the individual blades after their calibration with a blade shank.

[0007] However, there is a need to make turbomachines smaller in order to reduce the radius of the entire turbomachine and the corresponding weight. Furthermore, it is important to reduce the maintenance requirements of the turbomachine and the number of parts required for the turbomachine.

[0008] Therefore, it is an object of the present invention to provide an improved blade adjustment arm which, on the one hand, is easy to assemble and which can reduce the required installation space for the entire lever device.

[0009] The objects are achieved according to the invention by a blade adjustment arm according to claim 1, a turbomachine according to claim 9 and a method for assembling the blade adjustment arm for a turbomachine according to claim 10. Advantageous embodiments with expedient further developments of the invention are specified in the respective subclaims, wherein advantageous embodiments of each aspect of the invention are to be regarded as advantageous embodiments of the respective other aspects and vice versa.

[0010] According to one embodiment of the invention, a blade adjusting arm for a turbomachine, in particular a gas turbine or a thermal turbomachine, is provided with two legs which can be pivoted relative to one another between at least one open position and a closed position, in particular about a pivot axis, and which form a clamping device which has at least one clamping surface on each of the legs, via which, in the closed position, a blade shaft provided for adjusting a guide vane of the turbomachine can be held force-fittingly between the two legs via the two clamping surfaces, forming a clamping connection. The two clamping surfaces can be shaped as desired. For example, the clamping surfaces can be essentially flat surfaces.The formation of a clamping connection means that, in the closed position of the blade adjustment arm, a pressing force is applied, which is exerted by the legs in the closed position on the guide vane shaft in order to hold it in a force-locking and / or form-locking manner. This means that, in the closed position, the blade adjustment arm can hold the guide vane shaft in a torsion-proof or non-torsion-proof manner. It should be noted that, unless otherwise stated, . die Verwendung des Begriffes "geschlossene Stellung" In this case, this means that the blade adjustment arm is attached or mounted on the guide vane shaft. It should also be noted that, particularly with regard to the open and closed positions, the guide vane shaft is held exclusively in the closed position by the clamp connection. In the open position, the guide vane shaft is not held.

[0011] Furthermore, each of the legs has, in particular on a side of the leg facing away from the pivot axis, a fastening section, e.g., designed as an opening or projection. This fastening section is designed to be detachably, non-positively and / or positively connected to an adjustment element of the turbomachine for adjusting an angle of rotation of the blade shaft. According to a preferred embodiment, the fastening sections can be designed as openings that are defined or formed by walls of the leg, wherein the openings of the two legs overlap, in particular completely, in the closed position such that a through-bolt can be pushed through the openings and can be connected to an adjustment element of the turbomachine for adjusting an angle of rotation of the blade shaft.The openings are advantageously round openings with a predetermined diameter, but the openings can have any other shape, such as an oval shape or the shape of an elongated hole. The adjustment element is in particular a circular adjustment ring with, for example, a rectangular or polygonal cross-section, which encloses the flow axis and serves for the simultaneous adjustment or adjustment of all guide vanes of the same guide vane ring. The vane shaft is usually arranged radially perpendicular to a main shaft of the turbomachine, but the vane shaft can also assume any other suitable angle to the main shaft. The vane shaft is rotatable about a rotational axis of the vane shaft to adjust the guide vane, wherein the rotation of the vane shaft can be adjusted in the closed position using the installed vane adjustment arm.The blade adjustment arm can be fixed in relation to the adjustment ring using the push-through connection.

[0012] The blade adjustment arm has the advantage that the blade adjustment arm is held on the guide vane shaft by means of a clamp connection. By attaching the blade adjustment arm to the guide vane shaft by aligning the two openings of the two legs of the blade adjustment arm and securing the two openings with the through-bolt in relation to the adjustment ring, no nut is required on the guide vane shaft, thus reducing the number of parts and the overall height or length of the blade shaft. This allows the overall radius of the guide vane ring to be reduced, as the installation space for the lever device is reduced.Since no cotter pin is required on the blade shaft to secure a locknut against accidental opening, the number of required parts can be further reduced, a lever device for adjusting guide vanes and its assembly can be simplified, and associated costs can be reduced. Furthermore, since fewer parts are used, reliability can be improved and the design simplified.

[0013] The invention also has further advantageous embodiments which result in further, additional advantages.

[0014] In a further advantageous embodiment, it is provided that the blade adjustment arm can be attached or mounted on the blade shaft of the turbomachine in the open position. This means that the blade adjustment arm can be brought to the intended position on the blade shaft in the open position, since the blade adjustment arm has a sufficient opening width, i.e. a sufficient opening angle, in the open position so that the clamping connection can accommodate or release the blade shaft, or the blade shaft can be removed from the clamping connection. This can mean, for example, that the blade adjustment arm can be removed from the blade shaft in the axial direction of the blade shaft or in a direction perpendicular to the pivot axis and away from the pivot axis.Thus, this design has the advantage that the blade adjustment arm can be easily mounted on the guide vane shaft in the open position.

[0015] According to a preferred embodiment of the invention, the pivot axis and clamping surface can each be arranged on one half of each leg, and the fastening section can be arranged on an opposite half of the respective leg. In other words, the distance from the fastening section to the pivot axis, viewed in the longitudinal direction of the leg, can be greater than the distance from the clamping section to the pivot axis. This allows favorable leverage ratios for applying a clamping force to be achieved.

[0016] In a further advantageous embodiment, it is provided that a clamping surface on a first leg of the two legs and a clamping surface on a second leg of the two legs face each other, wherein the first and second legs are different legs, and these two clamping surfaces face the pivot axis. This means that the two clamping surfaces each have a normal vector which, for example, is directed at least partially from the center of the respective clamping surface in the direction of the pivot axis, or the two clamping surfaces of the two legs enclose an angle which is open in the direction of the pivot axis. This embodiment has the advantage that a pressing force on the clamping surfaces presses the blade shaft in the direction of the pivot axis, and this embodiment can therefore be designed to be play-free.This allows for further improvements to the blade adjustment arm and simplifies assembly. Furthermore, it allows for simpler manufacturing of the blade adjustment arm, as tolerances can be specified larger than, for example, in the case where the clamping surfaces are parallel.

[0017] It should also be noted that for each clamping surface, the axis of rotation of the blade shaft should be parallel to a direction lying in that clamping surface in order not to generate a force on the guide vane shaft in the direction of the blade shaft in the closed position.

[0018] In a further advantageous embodiment, the blade adjustment arm is formed as a single piece, and the pivotability of the blade adjustment arm is achieved by means of at least one flexural joint. A flexural joint is a region of a component that allows relative movement (rotation) between two rigid body regions through bending. The function of a joint is achieved by a region that has lower flexural rigidity than two adjacent regions. The reduced flexural rigidity can be created by a local cross-sectional reduction. A flexural joint can be compared to a conventional rotary joint, which has a limited range of rotation. By designing a flexural joint, a cost-effective alternative to a real joint can be created, since fewer components are required.Furthermore, friction-free relative movement of the left and right arms is possible, and no particles are created due to friction in the flexure joint. The lower long-term reliability of the flexure joint compared to a conventional joint is not critical, since the blade adjustment arm is only moved during assembly or disassembly. This design therefore has the advantage of requiring fewer components while maintaining the same functionality, making assembly easier.

[0019] In a further advantageous embodiment, it is provided that in the closed position a common central axis of the two openings is parallel to a rotational axis of the blade shaft. This means that in the closed position the two openings allow a through-bolt to be inserted, and an axis of the through-bolt or the insertion direction is essentially parallel to a rotational axis of the blade shaft. It should be noted here that due to the radial symmetry of the guide vane ring, a movement of the adjusting ring can result in a slight angular deviation of the through-bolt, so that under certain circumstances it may be necessary to rotatably mount or hold the through-bolt on the adjusting ring or the through-bolt in the opening, or to provide tolerances that enable such movement.

[0020] In a further advantageous embodiment, in the closed position, a longitudinal direction of each leg, i.e., a direction from the pivot axis to the respective opening in the leg, is substantially perpendicular to the rotation axis of the blade shaft. This ensures that the blade adjustment arm is mounted substantially perpendicular to the blade shaft, thus enabling optimal power transmission.

[0021] In a further advantageous embodiment, it is provided that for each leg, a distance (d1) from the pivot axis to the respective clamping surface is smaller than a distance (d2) from the pivot axis to the respective opening and / or a distance (d1) from the pivot axis to the respective clamping surface is smaller than a distance (d3) from the respective clamping surface to the respective opening. This means that in the closed position, with the blade adjustment arm installed, the guide vane shaft is located between the pivot axis and the openings, or that in the closed position, with the blade adjustment arm installed, the pivot axis is located between the guide vane shaft and the opening.Furthermore, the distance between the clamping surface and the blade shaft is smaller than the distance from the pivot axis or the guide vane shaft to one of the openings, so that a lever arm is designed such that a small force on the legs at the position of the openings can produce a large force on the clamping surfaces at the position of the blade shaft. This also means that an arrangement in which the blade shaft would be closer to the openings than to the pivot axis would be unfavorable and should therefore be avoided.

[0022] This design therefore has the advantage that the lever arm design allows for easier assembly, and a low force on the openings allows for a high holding force or pressing force on the blade shaft. The low force on the openings reduces friction at the openings, thus improving the durability of the blade adjustment arm.

[0023] In a further advantageous embodiment, it is provided that at least one of the clamping surfaces has a receiving element for positive connection to a connecting device provided on the blade shaft, i.e. a groove, a recess, a receiving space or even a projection, wherein in the closed position of the blade adjusting arm, the receiving element of the at least one clamping surface engages with the connecting device provided on the blade shaft. This means that the blade shaft can have a shape that can have several clamping surfaces that are at an angle to one another, thus enabling a higher force transmission from the blade adjusting arm to the blade shaft. It should be noted that with such a design of the blade shaft, the clamping surfaces can be designed accordingly to enable a positive connection between the clamping surfaces and the blade shaft.This design has the advantage that higher forces can be transmitted between the blade adjustment arm and the blade shaft and that the blade shaft can be held in the clamping connection in a rotationally secure manner.

[0024] A further advantageous embodiment of the invention relates to a turbomachine with a blade adjustment arm according to one of the preceding claims, in which at least one guide vane is mounted for radially delimiting a flow channel of the turbomachine, in which the guide vane can be adjusted by means of the blade adjustment arm, which is connected to an adjustment ring of the turbomachine. This makes it possible to achieve the above-described advantages of the further embodiments, and in particular, a reduced diameter of the turbomachine and a lower number of parts of the turbomachine.

[0025] A further advantageous embodiment of the invention relates to a method for assembling a blade adjustment arm for a turbomachine, wherein the blade adjustment arm has two legs which can be pivoted relative to one another between at least one open position and a closed position and which form a clamping device which has at least one clamping surface on each of the legs, and each of the legs has an opening, wherein the blade adjustment arm is placed in the open position on a blade shaft of the adjustable guide vane provided for adjusting an adjustable guide vane of the turbomachine and is brought into the closed position, in which the legs form a clamping connection by means of the two clamping surfaces, which holds the blade shaft between the two legs in a force-fitting manner via the two clamping surfaces, and in which the two openings of the legs overlap one another,to accommodate a through-bolt through the openings, which is connected to an adjusting element of the turbomachine for adjusting a rotation angle of the blade shaft.,

[0026] This means that the method provides a simplified assembly method for the blade adjustment arm according to the invention, and that this method is easier to carry out and thus more cost-effective than previously known methods.

[0027] Further features of the invention emerge from the claims and the exemplary embodiments. The features and combinations of features mentioned in the preceding description, as well as the combinations of features mentioned in the following examples, can be used not only in the combinations specified, but also in other combinations or alone, without departing from the scope of the invention. Therefore, embodiments of the invention that are not expressly shown and explained in the examples are also to be considered as encompassed and disclosed. Embodiments and combinations of features that do not have all the features of an originally formulated independent claim are also to be considered as disclosed. The same components are identified by the same reference numerals in the figures. Fig. 1 is a perspective view of a prior art blade adjustment arm; Fig. 2A is a perspective view of a blade adjustment arm according to an embodiment of the invention in a closed position; Fig. 2B is a perspective view of a blade adjustment arm according to an embodiment of the invention in an open position; Fig. 2C is a plan view of a blade adjustment arm according to an embodiment of the invention in the closed position; Fig. 3 is a perspective view of a blade adjustment arm according to a further embodiment of the invention in a closed position; Fig. 4A is a perspective view of a blade adjustment arm according to a further embodiment of the invention in a closed position; Fig. 4B is a perspective view of a blade adjustment arm according to an embodiment of the invention in an open position;Fig. 4C is a plan view of a blade adjustment arm according to an embodiment of the invention in the closed position; Fig. 5A is a perspective view of a blade adjustment arm; and Fig. 5B is a further perspective view of a blade adjustment arm.

[0028] FIG. 1 shows a perspective view of a prior art blade adjustment arm. This shows a blade adjustment arm 910 of a guide vane ring of a turbomachine, wherein the blade adjustment arm 910 is mounted on the guide vane shaft 920. The guide vane shaft 920 has a chamfer or flattened portion or groove into which a projection of the blade adjustment arm 910 engages. The blade adjustment arm 910 is secured against falling off by a nut 980, which in turn is secured against unintentional opening by a cotter pin 990. On the side facing away from the blade shaft, the blade adjustment arm 910 is provided with an opening that accommodates a through-bolt 950. The through-bolt 950, in turn, is fastened to an adjustment ring 940, by means of which all guide vanes of the illustrated guide vane ring of the illustrated stage of the turbomachine can be adjusted together.The guide vane shaft 920 is held in a passage 970 or bearing and extends on the inside of the turbomachine to hold or form a guide vane there. The guide vane shaft 920 can be formed integrally with the guide vane.

[0029] FIG. 2A shows a perspective view of a blade adjustment arm 10 according to an embodiment of the invention in a closed position with the blade shaft mounted. The blade adjustment arm 10 has two legs 12, which can be pivoted relative to one another between at least one open position and a closed position by means of a pivot axis 32. The two legs form a clamping device with which a blade shaft 20 with a rotation axis 22 is to be held. The clamping device has at least one clamping surface 14 on each of the legs 12, via which in the closed position according to FIG. 1 a blade shaft 20 provided for adjusting a guide vane of the turbomachine between the two legs 12 via the two clamping surfaces 14 to form a clamping connection 16 movement of the openings 50 by means of the clamping surfaces 14 to exert a large force, which is to hold the blade shaft 20 in the closed position with the blade adjustment arm 10 mounted in a force-locking or form-locking manner and thus to be held against rotation or non-rotation.Furthermore, each of the legs 12 has an opening 50 on a side of the leg 12 remote from or facing away from the pivot axis 32, wherein in the closed position the two openings 50 of the two legs 12 of the blade adjusting arm 10 overlap one another in such a way that a through-bolt can be pushed through the openings 50, which can be connected to an adjusting element or an adjusting ring of the turbomachine for adjusting an angle of rotation of the blade shaft 20 about the axis of rotation 22. If the adjusting ring is rotated around the shaft of the turbomachine, it takes the blade adjusting arm 10 with it via the through-bolt in the openings 50, and it can be achieved that all blade shafts 20 of the relevant guide vanes of the guide vane ring in question can be adjusted together. Furthermore, in . FIG. 2A a passage 70 is shown which holds the blade adjustment arm 10 rotatably and which can be connected to a housing of the turbomachine.

[0030] FIG. 2B shows the blade adjustment arm 10 in the open position, revealing a groove 24 or clamping surface of the blade shaft 20. The groove 24 has a width in the direction of the rotation axis 22 along the blade shaft 20, the width being selected such that the blade adjustment arm 10 is secured against axial slippage on the blade shaft 20 in the closed position.

[0031] In the open position of the blade adjustment arm 10, the blade adjustment arm 10 can be removed from or attached to the blade shaft 20. The groove 24 of the blade adjustment arm 10 and the clamping surfaces 14 of the blade adjustment arm are designed such that they contact one another in the assembled state or in the closed position of the blade adjustment arm, so that relative rotation of the shaft with respect to the blade adjustment arm is prevented.

[0032] FIG. 2C shows a top view of the blade adjustment arm 10 in the closed position and, in particular, shows the clamping connection 16. It can be seen that in the closed position, the clamping surfaces 14 contact the grooves 24. The surfaces do not have to be flat, but can be curved or have projections, for example, to enable greater force transmission between the blade adjustment arm 10 and the blade shaft 20.

[0033] In this case, at least one of the clamping surfaces 14 can have a receiving element for a positive connection with a connecting device provided on the blade shaft, wherein in the closed position of the blade adjusting arm 10 the receiving element of the at least one clamping surface 14 can engage with the connecting device provided on the blade shaft 20.

[0034] FIG. 3 shows a perspective view of a blade adjustment arm 10 according to a further embodiment of the invention in a closed position. While in the embodiment according to the FIG. 2A bis 2C the blade adjustment arm is designed in a first form in which the clamping surfaces 14 are located between the pivot axis and the openings, in the case of the embodiment according to FIG. 3 the blade adjustment arm is designed in a second form, in which the pivot axis is located between the clamping surfaces 14 and the openings. This means that in the embodiment according to FIG. 3 the pivot axis is located between the openings 50 of the legs 12 and the clamping surfaces 14, whereas in the embodiment according to the FIG. 2A bis 2C the clamping surfaces 14 are located between the pivot axis 32 and the openings 50. In both embodiments, the distance from the pivot axis 32 to the respective clamping surfaces 14 is smaller than the distance from the respective opening 50 to the respective clamping surface 14 and / or the pivot axis 32.

[0035] FIG. 4A shows, according to a further exemplary embodiment, a blade adjustment arm 10 in the closed position. In this exemplary embodiment, the blade adjustment arm 10 is formed in one piece. Pivotability of the blade adjustment arm 10, i.e. pivotability of one leg 12 in relation to the other leg 12, is achieved by means of at least one flexural joint. A flexural joint is a region of a component that allows relative movement, i.e., pivoting or rotation, between two rigid body regions by bending. The function of a joint is achieved by a region that has lower flexural rigidity than two adjacent regions. The reduced flexural rigidity is usually created by a local cross-sectional reduction. A flexural joint can therefore be compared to a conventional rotary joint, whose rotation range is limited.Solid-state joints are a cost-effective alternative to conventional joints because they have fewer components. A lower level of long-term reliability is not critical, as the blade adjustment arm is only moved during assembly. Unlike roller bearings or ball bearings, solid-state joints enable friction-free relative movement, thus preventing particles from being generated in the joint due to friction. This design also has the advantage of being constructed in one piece, thus reducing the number of parts and enabling cost savings.

[0036] FIG. 4B shows a perspective view of the blade adjustment arm according to the exemplary embodiment of the invention in the open position. While in the closed position, as before, a common through axis of the two openings 50 is located parallel to a rotational axis 22 of the blade shaft 20, or the openings 50 overlap in the closed position such that a through bolt can be pushed through the openings 50, which can be connected to an adjusting element or adjusting ring of the turbomachine for adjusting a rotational angle of the blade shaft 20, there is no overlap or only a slight overlap of the openings 50 in the open position. By moving the two legs 12 from the open to the closed position according to FIG. 4A brought into contact, a pressing force is exerted on the blade shaft 20 or on the clamping surfaces 14 and the grooves 24 of the blade shaft 20. The pressing force enables a positive connection and makes it possible to hold the blade adjustment arm 10 against rotation relative to the blade shaft 20.

[0037] FIG. 4C shows a plan view of the blade adjustment arm according to the embodiment of the invention in the closed position and in particular the clamping connection 16 in this embodiment. In the case of the embodiment according to FIG. 4C Two flexure joints 18 are arranged between the two legs of the blade adjustment arm 10, between which there is a contact point 15 or stop. In the closed position, the contact point 15 touches the blade shaft 20 to prevent the blade adjustment arm 10 from slipping in the closed position relative to the blade shaft 20. Furthermore, it can be seen that the two clamping surfaces 14 are in engagement with the grooves 24 of the blade shaft 20. If the two openings 50 of the blade adjustment arm 10 are moved away from each other by a force on the openings 50, the two legs 12 are bent apart, with the bending of the blade adjustment arm 10 being concentrated essentially on the two flexure joints 18, and the blade shaft 20 is released. This enables the blade adjustment arm 10 to be mounted on the blade shaft 20 or dismounted accordingly.

[0038] FIG. 5A shows a further perspective view of the blade adjustment arm 10 according to an embodiment of the invention without showing a blade shaft 20. For illustration, FIG. 5A a central axis 52 of the opening 50 is drawn, with both openings 50 of the two legs 12 lying one above the other in the closed position of the blade adjustment arm 10. Furthermore, a center line 13 of the clamping surface 14 is drawn on one of the legs 12 to enable a clearer representation. However, the exact position of the center line 13 approximately in the middle of the clamping surface 14 is not important, and it is only to be noted that the center line 13 lies in a plane of the clamping surface 14 and is parallel to the pivot axis 32. A distance between the pivot axis 32 and the center line 13 of the clamping surface 14 is designated d1. Furthermore, a distance between the pivot axis 32 and the center axis 52 of the opening 50 is designated d2, and a distance from the center line 13 of the clamping surface 14 to the center axis 52 of the opening 50 is designated d3.If the distances are designated in this way, the distance d1 for each leg is smaller than the distance d2. Furthermore, the distance d1 is smaller than the distance d3. Thus, a lever arm is formed that allows a slight movement of the openings 50 by means of the clamping surfaces 14 to exert a large force, which holds the blade shaft 20 in the closed position when the blade adjustment arm 10 is mounted. This enables an improvement in the rotational stability of the blade adjustment arm 10 with respect to the blade shaft 20.

[0039] FIG. 5B shows a further perspective view of a blade adjustment arm 10 according to a further advantageous embodiment of the invention in the closed position without showing the blade shaft 20. For illustration, FIG. 5Ba central axis 52 of the opening 50 is drawn, with both openings 50 of the two legs 12 lying one above the other in the closed position of the blade adjustment arm 10. Furthermore, only one center line 13 of the clamping surface 14 is drawn on one of the legs 12 in order to enable a clearer representation. However, the exact position of the center line 13 approximately in the middle of the clamping surface 14 is not important, and it is only to be noted that the center line 13 lies in a plane of the clamping surface 14 and is parallel to the pivot axis 32. A distance between the pivot axis 32 and the center line 13 of the clamping surface 14 is designated d1 as before. Furthermore, a distance between the pivot axis 32 and the center axis 52 of the opening 50 is designated d2, and a distance from the center line 13 of the clamping surface 14 to the center axis 52 of the opening 50 is designated d3.If the distances are designated in this way, the distance d1 for each leg is smaller than the distance d2. Furthermore, the distance d1 is smaller than the distance d3. Thus, in this embodiment, a lever arm is also formed, which allows a slight movement of the openings 50 by means of the clamping surfaces 14 to exert a large force, which holds the blade shaft 20 in the closed position when the blade adjustment arm 10 is mounted. This enables an improvement in the rotational stability of the blade adjustment arm 10 with respect to the blade shaft 20. List of reference symbols:

[0040] 10Blade adjustment arm 12Leg 13Centerline 14Clamping surface 15Contact point 16Clamping connection 18Solid state joint 20Blade shaft 22Rotation axis 24Groove 32Pivot axis 50Opening 52Center axis 70Through-hole 910Blade adjustment arm 920Vent shaft 940Adjusting ring 950Through bolt 970Through-hole 980Nut 990Split pin d1Distance from pivot axis to centerline of the clamping surface d2Distance from pivot axis to center axis of the opening d3Distance from pivot axis to centerline of the clamping surface

Claims

1. A blade adjustment arm (10) for a turbomachine, comprising two legs (12) which are pivotable relative to one another about a pivot axis (32) between at least one open position and a closed position and which form a clamping device which has at least one clamping surface (14) on each of the legs (12), by means of which, in the closed position, a blade shaft (20) provided for adjusting a guide vane of the turbomachine is to be held in a force-fitting manner between the two legs (12) via the two clamping surfaces (14), forming a clamping connection (16); wherein each of the legs (12) has a fastening section (50), in particular designed as an opening or projection, which is designed to be detachably, force-fittingly and / or form-fittingly connected to an adjustment element of the turbomachine for adjusting an angle of rotation of the blade shaft (20).

2. Blade adjustment arm (10) according to claim 1, wherein each of the legs (12) has an opening (50) which overlap one another in the closed position such that a through-bolt can be pushed through the openings (50) and can be connected to an adjustment element of the turbomachine for adjusting an angle of rotation of the blade shaft (20).

3. Blade adjustment arm (10) according to claim 1 or 2, wherein the blade adjustment arm (10) can be attached to the blade shaft (20) of the turbomachine in the open position.

4. Blade adjustment arm (10) according to one of the preceding claims, wherein the pivot axis (32) and clamping surface (14) are each arranged on one half of each leg (12) and the fastening section (50) is arranged on an opposite half of the respective leg (12).

5. A blade adjustment arm (10) according to any one of the preceding claims, wherein a clamping surface (14) on a first leg (12) of the two legs (12) and a clamping surface (14) on a second leg (12) of the two legs (12) face each other, the first and second legs (12) being different legs (12), and these two clamping surfaces (14) facing the pivot axis (32).

6. Blade adjustment arm (10) according to one of the preceding claims, wherein the blade adjustment arm (10) is formed in one piece and pivotability of the blade adjustment arm (10) is achieved by means of at least one solid joint (18).

7. Blade adjustment arm (10) according to one of the preceding claims, wherein in the closed position a common central axis (52) of the two openings (50) is located parallel to a rotation axis (22) of the blade shaft (20).

8. A blade adjustment arm (10) according to any one of the preceding claims, wherein in the closed position a longitudinal direction of each leg (12) is perpendicular to a rotation axis (22) of the blade shaft (20).

9. Blade adjustment arm (10) according to one of the preceding claims, wherein for each leg (12) a distance (d1) from the pivot axis (32) to the respective clamping surface (14) is smaller than a distance (d2) from the pivot axis (32) to the respective opening (50) and / or a distance (d1) from the pivot axis (32) to the respective clamping surface (14) is smaller than a distance (d3) from the respective clamping surface (14) to the respective opening (50).

10. Blade adjustment arm (10) according to one of the preceding claims, wherein at least one of the clamping surfaces (14) has a receiving element for positive connection to a connecting device provided on the blade shaft (20), wherein in the closed position of the blade adjustment arm (10) the receiving element of the at least one clamping surface (14) is in engagement with the connecting device provided on the blade shaft (20).

11. Turbomachine with a blade adjustment arm (10) according to one of the preceding claims.

12. A method for assembling a blade adjustment arm (10) for a turbomachine, wherein - the blade adjustment arm (10) has two legs (12) which can be pivoted relative to one another between at least one open position and a closed position and which form a clamping device which has at least one clamping surface (14) on each of the legs (12), and each of the legs (12) has a fastening section (50) which is designed to be detachably, non-positively and / or positively connected to an adjustment element of the turbomachine for adjusting an angle of rotation of the blade shaft (20); - wherein the blade adjustment arm (10) is placed in the open position on a blade shaft (20) of the adjustable guide vane provided for adjusting an adjustable guide vane of the turbomachine;- wherein the blade adjustment arm (10) is then brought into the closed position, in which the legs (12) form a clamping connection (16) by means of the two clamping surfaces (14), which clamping connection holds the blade shaft (20) between the two legs (12) via the two clamping surfaces (14) in a force-fitting manner, and - wherein the fastening sections (50) are detachably, force-fittingly and / or positively connected in the closed position to an adjusting element of the turbomachine for adjusting an angle of rotation of the blade shaft (20); 13. The method according to claim 12, wherein the fastening sections are formed as openings (50) and wherein both openings (50) of the legs (12) overlap one another in the closed position in order to receive a through-bolt through the openings (50) which is connected to an adjusting element of the turbomachine for adjusting an angle of rotation of the blade shaft (20).

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