Blade fastening mechanism having a securing device for turbine blades

Abstract

A securing device for a turbine blade wherein the securing device prevents the turbine blade from moving radially and axially and includes a retaining piece that includes a projection which extends into a recess in the root of the turbine blade and which prevents the blade from moving axially.

Claims

1. A rotor comprising: a turbine blade, and a securing device for axially and radially securing the turbine blade, wherein the rotor comprises a blade groove, wherein the turbine blade comprises a turbine blade root adapted to the blade groove, wherein the securing device comprises a retaining piece which is arranged between the blade groove and the turbine blade root, wherein the retaining piece comprises a surface facing towards the turbine blade root, wherein the surface bears against the turbine blade root, wherein the retaining piece comprises, on the surface, a projection which is arranged into a recess in the turbine blade root, wherein the projection engages into the recess in such a way that displacement of the turbine blade in an axial direction is prevented, wherein the securing device comprises a force spring which exerts a force acting in a radial direction from the rotor on the turbine blade, wherein the securing device comprises a securing plate which is disposed in a first groove in the retaining piece and in a rotor recess, wherein an interaction between the securing plate and the rotor recess prevents displacement of the securing plate upstream and downstream axially, and wherein an interaction between the securing plate and the first groove prevents displacement of the retaining piece upstream and downstream axially.

2. The rotor as claimed in claim 1, wherein the force spring is a separate component from the retaining piece and the securing plate.

3. The rotor as claimed in claim 1, wherein the recess is of complementary design with respect to the projection.

4. The rotor as claimed in claim 1, wherein the projection is of rectangular cross section.

5. The rotor as claimed in claim 1, wherein the force spring is arranged between the blade groove and the retaining piece.

6. The rotor as claimed in claim 1, wherein the force spring is arranged next to the retaining piece, between the blade groove and the turbine blade root.

7. The rotor as claimed in claim 1, wherein the turbine blade root comprises a front edge, as seen in the axial direction, and a rear edge arranged opposite the front edge, as seen in the axial direction, and wherein the retaining piece extends from the front edge to the rear edge.

8. The rotor as claimed in claim 7, wherein the securing plate is arranged at the front edge and a second securing plate is arranged at the rear edge.

9. The rotor as claimed in claim 8, wherein the second securing plate is disposed in a second groove in the retaining piece and in a second rotor recess, wherein an interaction between the second securing plate and the second rotor recess prevents displacement of the second securing plate upstream and downstream axially, and wherein an interaction between the second securing plate and the second groove prevents displacement of the retaining piece upstream and downstream axially.

10. The rotor as claimed in claim 7, wherein the force spring is arranged at the front edge and a second force spring is arranged at the rear edge.

11. The rotor as claimed in claim 7, wherein the retaining piece comprises a second projection arranged at the rear edge and disposed in a second recess in the turbine blade root, wherein the projection prevents axial displacement in a first axial direction, and wherein the second projection engages into the second recess in such a way that displacement of the turbine blade in a second axial direction opposite the first axial direction is prevented.

12. The rotor as claimed in claim 1, wherein the projection is of elongate design in a circumferential direction which is oriented with respect to an axis of rotation of the rotor.

13. The rotor as claimed in claim 1, wherein the projection is formed as a cylinder and engages into the recess formed as a blind bore.

14. The rotor as claimed in claim 1, wherein the rotor recess and the first groove are arranged one on top of the other in the radial direction.

15. The rotor as claimed in claim 1, wherein the force spring is a disk spring.

16. The rotor as claimed in claim 1, wherein the projection engages into the recess in such a way that displacement of the turbine blade upstream and downstream axially is prevented.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 shows a perspective view of a securing device,

(3) FIG. 2 shows a cross-sectional view of a first variant of the securing device,

(4) FIG. 3 is a perspective illustration of the retaining piece according to the first variant from FIG. 2,

(5) FIG. 4 is a further perspective illustration of the retaining piece from FIG. 3,

(6) FIG. 5 is a perspective illustration of a plate,

(7) FIG. 6 shows a cross-sectional view of a securing device according to a second variant,

(8) FIG. 7 is a perspective illustration of the retaining piece according to the second variant from FIG. 6,

(9) FIG. 8 is a further perspective illustration of the retaining piece from FIG. 7,

(10) FIG. 9 is a perspective illustration of the plate,

(11) FIG. 10 shows a cross-sectional view of a securing device according to a third variant,

(12) FIG. 11 shows a perspective view of the retaining piece according to the third variant,

(13) FIG. 12 shows a further perspective view of the retaining piece according to FIG. 11 for the third variant,

(14) FIG. 13 is an illustration of the plate for the third variant,

(15) FIG. 14 shows a cross-sectional view of the securing device according to a fourth variant,

(16) FIG. 15 shows a cross-sectional view of part of the securing device according to the fourth variant.

DETAILED DESCRIPTION OF INVENTION

(17) FIG. 1 shows a securing device 1. According to FIG. 1, part of a rotor 2 and of a turbine blade root 3 can be seen. For the sake of clarity, the blade airfoil of the turbine blade is not illustrated. The rotor has a blade groove 4. Said blade groove 4 may be a blade groove 4 which is formed in a manner parallel to an axis of rotation 5 of the rotor. The blade groove 4 may also be a curved blade groove 4 which is then arranged at a front edge in the axial direction 7.

(18) The axis of rotation 5 and the axial direction 7 are arranged parallel to one another. The rotor 2 rotates about the axis of rotation 5 at a rotational speed. The turbine blade is adapted in the blade groove 4 such that there is as little play as possible between the turbine blade root 3 and the blade groove 4. Without the securing device 8, it would be possible for the turbine blade to be displaced freely in the axial direction 7.

(19) The rotor 2 and the turbine blade may be part of a turbomachine, for example a steam turbine. During the start-up of a continuous-flow machine, the centrifugal forces are still relatively small, and during transportation, there are no centrifugal forces present at all. Consequently, it is possible that the turbine blade is displaceable in the axial direction 7. This is prevented by way of a securing device 8. Above a certain rotational frequency, the centrifugal forces are so large that the turbine blade presses, in the blade groove 4, against so-called bearing flanks 9 and thereby acquires a stable position. Above this certain rotational frequency, axial displacement is difficult. With the securing device 8, displacement of the turbine blade in the axial direction 7 and in the radial direction is prevented in an effective manner. The securing device 8 comprises a retaining piece 10. FIGS. 1 to 5 show a first design of the retaining piece 10. The retaining piece 10 is arranged between the blade groove 4 and the turbine blade root 3. The retaining piece 10 comprises a front side 11 which is arranged at the front edge 6. At the side opposite the front side 11, a rear side 12 is arranged (visible only in FIG. 2). The retaining piece 10 has a top side 13 and a bottom side 14. The top side 13 is arranged opposite the bottom side 14. The top side 13 bears against a bottom side of the turbine blade root 3, as illustrated in FIG. 2. The front side 11 and the front edge 6 are in this case flush. The bottom side 14 of the retaining piece 10 faces in the direction of the axis of rotation 5.

(20) The retaining piece has, on the top side 13, a projection 15 which, according to a first variant of the invention, is of elongate design in a circumferential direction 16. The projection 15 is of rectangular cross section. The projection 15 is formed over the entire top side 13 and extends into a recess 17 in the turbine blade root 3. The recess 17 is in this case of complementary design with respect to the projection 15. This means that the recess 17 is also of elongate design and rectangular cross section.

(21) If the projection is arranged in the recess 17, the retaining piece can no longer be displaced in the axial direction 7, and so displacement of the retaining piece 10 in the axial direction 7 is prevented.

(22) As shown in FIG. 2, there is, between the bottom side 14 and the rotor 2, a space in which a force spring 18 is arranged. The force spring 18 leads to a force from the rotor 2 to the retaining piece 10 and then finally to the turbine blade root 3. Said force prevents the retaining piece 10 from jumping out of the recess 17. For further securing, the securing device 8 has a plate 19 which engages into a rotor recess 20 and into a second recess 21, such that displacement of the plate 19 in the axial direction 7 is prevented. The second recess 21 is arranged in the retaining piece 10. The plate 19 is in this case pushed in from the side. The plate 19 is formed in such a way that it faces in the circumferential direction 16.

(23) FIG. 2 shows a cross-sectional view of said first variant of the retaining piece 10 and of the entire securing device 8. FIGS. 3 and 4 show a perspective view of the retaining piece 10 in the first variant thereof. FIG. 5 shows the plate 19 which is formed in a circumferential direction 16. The plate has a plate top side 22 which extends into the second recess 21. The plate bottom side 23 extends into the rotor recess 20.

(24) FIGS. 6 to 9 show a second variant of the securing device 8.

(25) The difference of the securing device 8 according to the second variant with respect to the securing device 8 of the first variant is that the projection 15 is not of elongate design but is formed as a cylinder 24 and extends into a blind bore in the turbine blade root 3. In this case, the cylinder 24 has a similar mode of action to the projection 15 according to FIG. 1, that is to say displacement in the axial direction 7 is prevented.

(26) FIGS. 7 and 8 show a perspective view of the retaining piece 10 according to variant 2.

(27) FIG. 9 shows the plate 19 which is designed for variant 2, wherein the plate 19 according to variant 1 and variant 3 is identical.

(28) The plate 19 is arranged in an encircling manner in the circumferential direction 16 and is in this case formed in a segmented manner. This means that the plate 19 is composed of individual segments. The plate 19 is arranged in a form-fitting manner in the rotor recess 20 and in the second recess. The plates 19 are inserted to a circumferential position via a milled opening of the encircling groove and pushed to their final position, and following insertion of the last segment, the segments are joined to one another at the divisions by spot welding. The force spring 18 serves for ensuring that the turbine blade bears against the rotor 2 in a standstill state, e.g. during transportation. The force spring 18 is designed for example as a disk spring. The force spring 18 can also be designed as a clamping piece, however.

(29) FIGS. 10 to 13 show a third variant of the securing device 8. The third variant is characterized in that the retaining piece 10 and the force spring 18 are arranged next to one another in the axial direction 7. This means that the force spring 18 is arranged directly on the rotor 2 and directly on the turbine blade root 3, and the force is transmitted directly from the rotor 2 to the turbine blade root 3. The retaining piece 10 is arranged next to the force spring 18 in the axial direction 7. The retaining piece 10 likewise has a projection 15 and a second recess 21. According to the first variant, the projection 15 may be of elongate design. Also, according to the second variant, the projection 15 may be formed as a cylinder. FIG. 10 shows a cross-sectional view of the securing device 8 according to the third variant. FIGS. 11 and 12 show a perspective view of the retaining piece 10. FIG. 13 shows a perspective view of the plate 19.

(30) FIGS. 14 and 15 show a fourth variant of the securing device 8. The securing device 8 according to the fourth variant is characterized in that the retaining piece 10 is now formed from the front edge 6 of the turbine blade root 3 to the rear edge of the turbine blade root. This means that the retaining piece 10 is arranged completely from the front edge 6 to the rear edge. The retaining piece 10 likewise has a projection 15 which engages into a recess 17. Furthermore, provision is likewise made for a plate 19 which engages into a second recess 21 and into a rotor recess 20. The force spring 18 is likewise arranged between the retaining piece 10 and the rotor 2.

(31) Although the invention has been more specifically illustrated and described in detail by the preferred exemplary embodiment, the invention is not limited by the examples disclosed and other variations can be derived herefrom by a person skilled in the art, without departing from the protective scope of the invention.