CLIAMS:We claim:
1. A means (100) for locking of a blade (12) on to a rotor disc (14) in a turbo machine, said means (100) comprising:
a) a blade (12) provided with an integrally formed curved fir-tree root attachment at its base, said curved fir-tree root attachment provided with a predefined angle of taper (?) with respect to horizontal at its base along its profile in such a way that the amount of material removed increases from leading edge side (LS) to trailing edge side (TS);
b) a rotor disc (14) provided with a curved fir-tree groove complementary to the curved fir-tree root attachment of the blade (12), said curved fir-tree groove provided with a uniform surface at its base, said curved fir-tree groove of the rotor disc (14) accommodates the curved fir-tree root attachment of the blade (12) producing a space therein between the rotor disc (14) and the blade (12); and
c) a wedge (16) having radius of curvature identical to radius of curvature of the rotor disc (14) and the blade (12), tapered along its profile complementary to the base of the curved fir-tree root attachment of the blade (12), adapted to insert in to the space between the rotor disc (14) and the blade (12) from downstream end (D) by means of hammering, said wedge (16) provided with a perpendicular bend (PB) at downstream end (D) and provided with a bend (B) at a predefined angle to the vertical at upstream end (U), said wedge (16) receives a force towards downstream end (D) at tapered surface from the blade (12) due to axial movement of the blade (12) towards downstream end (D) during the operation of the turbo machine and the axial movement of the wedge (16) towards downstream end (D) restricted by the bend (B) at the groove of the rotor disc (14), said wedge (16) receives a force towards upstream end (U) at the bend (B) from the blade (12) due to axial movement of the blade (12) towards upstream end (U) during the operation of the turbo machine and the axial movement of the wedge (16) towards upstream end (U) restricted by the perpendicular bend (PB) at the rotor disc (14).

2. A means (100) for locking of a blade (12) on to a rotor disc (14) in a turbo machine as claimed in claim1, wherein the tapered surface of the wedge (16) restricts the axial movement of the blade (12) towards downstream end (D).

3. A means (100) for locking of a blade (12) on to a rotor disc (14) in a turbo machine as claimed in claim1, wherein the radius of curvature of the curved fir-tree root attachment of said blade (12), said groove of the rotor disc (14) and said wedge (16) is 182mm.

4. A means (100) for locking of a blade (12) on to a rotor disc (14) in a turbo machine as claimed in claim1, wherein the predefined angle of taper (?) with respect to horizontal at the base of the curved fir-tree root attachment of said blade (12) is 0.54 degrees.

5. A means (100) for locking of a blade (12) on to a rotor disc (14) in a turbo machine as claimed in claim1, wherein a chamfer (C) provided at the base of the curved fir-tree root attachment of the blade (12) proximal to leading edge side (LS) facilitates in achieving the predefined angle to the vertical at bend (B) of the wedge (16) and also helps in providing proper butting surface between the wedge (16) and the curved fir-tree root attachment of the blade (12).

6. A means (100) for locking of a blade (12) on to a rotor disc (14) in a turbo machine as claimed in claim1, wherein the axial movement of said blade (12) can be towards upstream end (U) or downstream end (D).

7. A method for locking of a blade (12) on to a rotor disc (14) in a turbo machine, said method comprising:
a) inserting axially curved fir-tree root attachment of a blade (12) in to groove of a rotor disc (14) producing a space in between therein;
b) inserting a wedge (16) in to the space between the curved fir-tree root attachment of the blade (12) and the groove of the rotor disc (14) from downstream end (D) by means of hammering;
c) arresting the movement of the blade (12) towards downstream end (D) by providing a bend (B) at upstream end (U) of the wedge (16) at a predefined angle to the vertical such that the bend (B) restricts the axial movement of the wedge (16) towards downstream end (D) at the groove of the rotor disc (14); and
d) arresting the movement of the blade (12) towards upstream end (U) by providing a perpendicular bend (B) at downstream end (D) of the wedge (16) such that the perpendicular bend (PB) restricts the axial movement of the wedge (16) towards upstream end (U) at the rotor disc (14).

8. A method for locking of a blade (12) on to a rotor disc (14) in a turbo machine as claimed in claim 7, wherein the predefined angle to the vertical at the bend (B) of the wedge (16) is 45 degrees.
,TagSPECI: FORM 2
THE PATENT ACT, 1970
(39 OF 1970)
AND
THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
(See Section 10; rule 13)

A MEANS AND A METHOD OF LOCKING OF A BLADE ON TO A
ROTOR DISC IN A TURBO MACHINE

TRIVENI TURBINE LTD
an indian company,
of 12A, Peenya Industrial Area,
Banglore-560058.

The following specification particularly describes the present invention and the manner in which it is to be performed.
FIELD OF THE INVENTION:
The present invention relates to a means and a method of locking of axial entry blade to a rotor disc. Particularly, the present invention relates to a means and a method of locking of axial entry curved fir-tree root blade to a rotor disc in a turbo machine.

BACKGROUND OF THE INVENTION:
Rotor blade rotates at high speed during rotation of the rotor. Due to the fast rotation of the rotor, the associated rotor blade is subjected to high centrifugal forces. Therefore, the blade is exposed to high forces (centrifugal force, steam loading etc) during the operation of the turbine and there is a possibility of axial and/or radial displacement outwards from the disc of the rotor. The type of locking arrangement of blade to rotor depends on the type of rotor (disc or drum), type of root of the blade (T- root, fir tree root, fork root, straddle root etc.,) and type of the blade (High Pressure Blades(HP Blades), Intermediate Pressure Blades (IP Blades) and Low Pressure Blades(LP Blades)).

Several techniques have been disclosed in the prior art for axial locking of the blade on to a disc of a rotor in turbo machines.

US Patent no. 4444544 filed on December 19, 1980 titled “Locking of rotor blades on a rotor disk” disclosed a rotor stage assembly comprising a rotor disk, rotor blades and a lock pin. The rotor disk has a plurality of blade attachment slots configured to receive a plurality of rotor blades. The disk is adapted by a groove and the blade is adapted by a groove to receive the lock pin. Each rotor blade is inserted into the disk in generally axial direction. Each rotor blade is retained against fore and aft movement by a lock pin.

US Publication no. 20090324414 published on December 31, 2009 titled “Blade fastening means of a turbine” disclosed a turbine blade locking device having a wedge movable in axial direction by a tensioning device. As a result of which a force is produced in the axial direction which causes the turbine blade to be pressed against the grooves of the rotor disk.

EP 1657404 discloses a rotor of a turbo engine with turbine blades mounted to axial grooves in the rotor. The turbine blades are prevented from moving in the axial direction by locking plates. The rhomboid locking plates are inserted into a space between two grooves in the rotor and the turbine blades and then rotated so that the edges of the rhomboids engage into the grooves to secure the turbine blades.

However, all the locking means disclosed in the prior art are complex, has more number of elements and takes a lot of time while locking.

Therefore, there is felt a need for development of new means and new method of locking of a blade on to a disc of a rotor in a turbo machine to overcome the drawbacks of the prior art.

OBJECTS OF THE INVENTION:
An object of the present invention is to provide a blade locking means capable of retaining the blade firmly in the groove of the rotor disc and prevent axial movement of the blades.

Another object of the present invention is to provide a blade locking means that ensures best transfer of force between rotor disc and rotor blade.

One more object of the present invention is to provide a simple blade locking means.

Still another object of the present invention is to provide a blade locking means that ensures good abutment surface between rotor disc and rotor blade.

Yet another object of the present invention is to provide a simple method of locking of a blade to rotor disc in a turbo machine.

BRIEF DESCRIPTION OF THE DRAWINGS:
The invention will now be described with reference to the accompanying drawings in which:

Figure 1(a) illustrates an isometric view of a blade locked on to a rotor disc with the help of a wedge in accordance with the present invention;

Figure 1(b) illustrates an enlarged side view of a blade locked on to a rotor disc with the help of a wedge looking from upstream end in accordance with the present invention;

Figure 1(c) illustrates an enlarged side view of a blade locked on to a rotor disc with the help of a wedge looking from downstream end in accordance with the present invention;

Figure 1(d) illustrates an enlarged view of portion A of figure 1(b);

Figure 1(e) illustrates an enlarged view of portion B of figure 1(c);

Figure 2(a) and 2(b) illustrates an isometric view and front view of a blade of figure 1(a);

Figure 3(a) illustrates an isometric view of a groove of a rotor disc of figure 1(a);

Figure 3(b) illustrates a top view of a groove of a rotor disc of figure 1(a); and

Figure 4(a), 4(b), 4(c) and 4(d) illustrates an isometric view, front view, top view and side view of a wedge of figure 1(a).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:
A preferred embodiment will now be described in detail with reference to accompanying drawings. The preferred embodiment does not limit the scope and ambit of the invention. The description provided is purely by way of example and illustration.

Figure 1(a) illustrates an isometric view of a blade locked on to a rotor disc with the help of a wedge.

Figure 1(b) illustrates an enlarged side view of a blade locked on to a rotor disc with the help of a wedge looking from upstream end.

Figure 1(c) illustrates an enlarged side view of a blade locked on to a rotor disc with the help of a wedge looking from downstream end.

Figure 1(d) illustrates an enlarged view of portion A of figure 1(b).

Figure 1(e) illustrates an enlarged view of portion B of figure 1(c).

In a turbo machine, the fluid entry side at row of blades is typically referred as Upstream end U and the fluid exit side at row of blades is typically referred as Downstream end D.

In accordance with the present invention, there is provided a means 100 for locking of blades on to a rotor disc in a turbo machine comprising a blade 12, a rotor disc 14 and a wedge 16.

Figure 2(a) and 2(b) illustrates an isometric view and front view of a blade.

Typically, the blade 12 is having an integrally formed curved fir-tree root attachment at the base. Material is removed at the base of the curved fir-tree root attachment along its profile at an angle of 0.54 degrees with respect to horizontal as shown in the figure 2(b) such that the amount of material removed on leading edge side LS is lowest and the amount of material removed on trailing edge side TS is highest and is generally indicated by a reference numeral ?. Chamfer C is provided at the base of the curved fir-tree root attachment proximal to leading edge side LS as shown in the figure 2(b).

Figure 3(a) illustrates an isometric view of a groove of a rotor disc.

Figure 3(b) illustrates a top view of a groove of a rotor disc.

The rotor disc 14 is provided with a curved fir-tree groove complementary to curved fir-tree root attachment of the blade 12 as shown in the figure 3(a). The radius of curvature of the groove of the rotor disc 14 is 182mm and is generally indicated by a reference numeral R. The curved fir-tree groove of the rotor disc 14 has uniform surface at its base.

Figure 4(a), 4(b), 4(c) and 4(d) illustrates an isometric view, front view, top view and side view of a wedge.

Typically, the wedge 16 is made of hardened stainless steel. The wedge 16 is also curved. The wedge 16 has length of 163mm and breadth of 11.6mm and is generally indicated by reference numerals X1 and Y1 respectively. The thickness of the wedge 16 at upstream end is 1.6mm and at downstream end is 3.15mm and is generally indicated by reference numerals Z1 and Z2 respectively.

The configuration and method of locking of a blade on to a rotor disc in a turbo machine is as follows:

Generally, the radius of curvature of the wedge 16 and the groove of the rotor disc 14 are identical to the radius of curvature of the curved fir-tree root attachment of the blade 12.

The curved fir-tree root attachment of the blade 12 is inserted axially in to the groove of the rotor disc 14 from upstream end. The wedge 16 is adapted to pass through the space produced therein between the curved fir-tree root attachment of the blade 12 and the rotor disc 14 from downstream end by hammering. A perpendicular bend PB is provided to the wedge 16 at its downstream end D by means of hammering as shown in the figure 1(e). A bend B at an angle of 45 degrees with respect to vertical is provided to the wedge 16 at its upstream end U by means of hammering as shown in the figure 1(d).

The chamfer C on the curved fir-tree root attachment of the blade 12 facilitates the bend B of the wedge 16 in achieving the angle of 45 degrees with respect to the vertical and also helps in providing proper butting surface between the wedge 16 and the curved fir-tree root attachment of the blade 12.

During the operation of the turbo machine, the blade 12 is subjected to steam loading and centrifugal forces which results in the axial movement of the blade 12 towards downstream end which ultimately results in the transfer of force from the blade 12 to the wedge 16. The transfer of force from the blade 12 to the wedge 16 in turn results in the movement of the wedge 16 towards downstream end but restricted by the bend B at the groove of the rotor disc 14. In certain cases, there might be chances of axial movement of the blade 12 towards upstream end but restricted by the bend B of the wedge 16 which results in the transfer of force from the blade 12 to the wedge 16. The transfer of force from the blade 12 to the wedge 16 in turn results in the movement of the wedge 16 towards upstream end but restricted by the perpendicular bend PB at the rotor disc 14.

Although the invention has been described herein above with reference to the embodiments of the invention, the invention is not limited to the embodiments described herein above. It is to be understood that modifications and variations of the embodiments can be made without departing from the spirit and scope of the invention.