Claims:We claim:
1) A spring (100) for seals (LS) of a turbine comprising a flat elongated strip of predetermined length, width and thickness having filleted bends on its either ends, one of said filleted bends on one end of the flat elongated strip provides a flange (FL) having a predetermined angle inward to the vertical, said flat elongated strip adapted to mate with the seals (LS) such that said flange (FL) inserted in to a slot (S1) provided at a predetermined position on said seals (LS), said seals (LS) along with said spring (100) in mating position adapted to insert in to a groove of a labyrinth holder (LH).

2) A spring (100) for seals (LS) of a turbine as claimed in claim 1, wherein other of said filleted bends at free end of said flat elongated strip facilitates in easy assembly of said seals (LS) along with said spring (100) in to the groove of the labyrinth holder (LH).

3) A spring (100) for seals (LS) of a turbine as claimed in claim 1, wherein said predetermined angle of said flange (FL) facilitates in entry of said flange (FL) deep through said slot (S1) of said seals (LS) on assembly.

4) A spring (100) for seals (LS) of a turbine as claimed in claim 1, wherein said filleted bends on either ends of said spring (100) reduces stress concentration at mating points of said spring (100) with the groove of said labyrinth holder (LH).

5) A spring (100) for seals (LS) of a turbine as claimed in claim 1, wherein said filleted bends on either ends of said spring (100) increases the contact surface area at mating points of said spring (100) with the groove of said labyrinth holder (LH) and thereby reduces the chances of movement of said spring (100) within the groove of said labyrinth holder (LH).

6) A spring (100) for seals (LS) of a turbine as claimed in claim 1, wherein said spring (100) provides the necessary push back effect to said seals (LS) against fluid pressure and held the seals towards a rotor of said turbine.

7) A spring (100) for seals (LS) of a turbine as claimed in claim 1, wherein said predetermined length, width and thickness of said spring (100) is determined based on the dimensions of said seals (LS).

8) A spring (100) for seals (LS) of a turbine as claimed in claim 1, wherein said spring (100) is made up of Inconel or any other type of alloy.

9) A method of assembly of seals (LS) along with a spring (100) in to a groove of a labyrinth holder (LH), said method comprising the steps of :
a) adapting to mate said spring (100) with the seals (LS) such that a flange (FL) provided at one extreme end of said spring (100) inserts in to a slot (S1) provided at a predetermined position on said seals (LS) ; and
b) inserting said seals (LS) along with said spring (100) in mating position in to the groove of said labyrinth holder (LH) such that a filleted bend provided at free end of said spring (100) facilitates in smooth and easy entry.
, Description:FIELD OF THE INVENTION:
The present invention relates to the field of a spring for labyrinth seals of a turbine. Particularly, the present invention relates to a spring and a method to dispose the labyrinth seals inside a labyrinth holder.

BACKGROUND OF THE INVENTION:
Figure 1 illustrates an isometric view of a labyrinth seal.

The purpose of the labyrinth seals is to configure in between rotor of the turbine and the labyrinth holder and prevent the leakage of steam from high pressure regions to low pressure regions by creating a tortuous path with the help of corrugated fins F. But, the pressure of the working fluid of the turbine tries to move the labyrinth seals away from the rotor of the turbine which in turn is restricted by springs located in between the labyrinth seals and the labyrinth holder thereby producing a sealing effect. The failure of the springs due to cyclic loading results in the increase of leakage losses and thereby loss of efficiency of the turbine.

Some techniques have been disclosed in the prior art for holding the labyrinth seals towards the rotor of the turbine against working fluid pressure.

US Patent no. 6935634 filed on May 8, 2003 titled “Steam Turbine Packing Spring” discloses a packing spring of two types. The first type of packing spring is a flat strip having a right angled bend at one of its extreme end. The second type of packing spring, an improvement over the first type of packing spring, is a flat strip having a marginal bend of 11 degrees on its midway along its length. Both types of packing springs have their own disadvantages. For the first type of packing spring, the fitter faces difficulty while assembly of the packing spring along with labyrinth seal in to groove of the labyrinth holder due to obstruction of sharp edge at free end of the flat strip by the groove of the labyrinth holder and further, the right angled bend of the flat strip enters in to groove of the labyrinth seal only superficially. Moreover, stress concentration is high at the mating points of the first type of packing spring with the groove of the labyrinth holder due to sharp edges. Due to continuous pressure of working fluid, thermal expansion of rotor, high stress concentration and improper locking of the packing spring, the chances of rotation of the first type of packing spring around a pivot point are high resulting in failure. For the second type of packing spring, though the factor of safety had been improved by increasing the contact surface area from one portion to two portions, all other problems like difficulty in assembling, high stress concentration and improper locking of the packing spring still remains and is not a fool proof mechanism.

Therefore, there is felt a need for development of a spring for seals to overcome the drawbacks of the prior art and that can be assembled easily and produces a good sealing effect.

OBJECTS OF THE INVENTION:
An object of the present invention is to provide a simple and fool proof spring for seals of a turbine.

Another object of the present invention is to provide a spring for seals that can assembled easily.

One more object of the present invention is to provide a spring that can be firmly locked to seals.

Still another object of the present invention is to reduce stress concentration at mating points of a spring with a groove of a labyrinth holder.

Further another object of the present invention is to provide a spring that facilitates in enhancing the sealing effect of seals.

Still one more object of the present invention is to reduce chances of movement of a spring within a groove of a labyrinth holder.

SUMMARY OF THE INVENTION:
In accordance with the present invention a spring (100) for seals (LS) of a turbine is provided, the spring (100) comprising a flat elongated strip of predetermined length, width and thickness having filleted bends on its either ends, one of the filleted bends on one end of the flat elongated strip provides a flange (FL) having a predetermined angle inward to the vertical, the flat elongated strip adapted to mate with the seals (LS) such that the flange (FL) inserted in to a slot (S1) provided at a predetermined position on the seals (LS), the seals (LS) along with the spring (100) in mating position adapted to insert in to a groove of a labyrinth holder (LH).

Typically, other of the filleted bends at free end of the flat elongated strip facilitates in easy assembly of the seals (LS) along with the spring (100) in to the groove of the labyrinth holder (LH).

In accordance with the present invention a method of assembly of seals (LS) along with a spring (100) in to a groove of a labyrinth holder (LH) is provided, the method comprising the steps of:
i) adapting to mate the spring (100) with the seals (LS) such that a flange (FL)
provided at one extreme end of the spring (100) inserts in to a slot (S1) provided at a predetermined position on the seals (LS) ; and
ii) inserting the seals (LS) along with the spring (100) in mating position in to the
groove of the labyrinth holder (LH) such that a filleted bend provided at free end of the spring (100) facilitates in smooth and easy entry.

BRIEF DESCRIPTION OF THE DRAWINGS:
The invention will now be described with reference to the accompanying drawings in which:
Figure 1 illustrates an isometric view of a labyrinth seal;

Figure 2(a) illustrates an isometric view of a spring for a labyrinth seal in accordance with the present invention;

Figure 2(b) illustrates a front view of a spring of figure 2(a);

Figure 2(c) illustrates a top view of a spring of figure 2(a); and

Figure 3 illustrates a schematic diagram of springs disposed in between labyrinth seals and labyrinth holder around circumference of a rotor of a turbine in accordance with the present invention.

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 2(a) illustrates an isometric view of a spring for a labyrinth seal.

Figure 2(b) illustrates a front view of a spring of figure 2(a).

Figure 2(c) illustrates a top view of a spring of figure 2(a).
In accordance with the present invention, there is provided a spring 100 for a labyrinth seal comprising a flat elongated strip having filleted bends on its either ends. The spring 100 has length of 122mm, width of 15mm and thickness of 1.39mm and is generally indicated by reference numerals X, Y and Z respectively. The filleted bend at free end of the flat elongated strip has a radius of 6.5mm and is generally indicated by a reference numeral R1. The filleted bend at other end of the flat elongated strip provides a flange FL having an angle of 15 degrees with respect to the vertical and a radius of 4mm and is generally indicated by reference numerals ?1 and R2 respectively.

Figure 3 illustrates a schematic diagram of springs disposed in between labyrinth seals and labyrinth holder around circumference of a rotor of a turbine.
The schematic diagram in the figure 3 depicts two concentric circles. The inner circle resembles labyrinth seals LS and the outer circle resembles a labyrinth holder LH. The labyrinth seals LS are provided with a slot S1 at an angle of 16 degrees from one of their ends to accommodate the springs 100 and is generally indicated by a reference numeral ?2. The inner diameter of the labyrinth holder LH is provided with a groove complementary to accommodate the labyrinth seals LS along with the springs 100. The labyrinth holder LH is in turn inserted in to a complementary groove provided on inner diameter of a turbine casing.

The configuration and method of assembly of the springs 100 in between the labyrinth seals LS and the labyrinth holder LH in accordance with the present invention is as follows:
The springs 100 adapted to mate with the labyrinth seals LS such that the flange FL of the springs 100 is inserted in to the slot S1 of the labyrinth seals LS and the labyrinth seals LS along with the springs 100 inserted in to the groove of the labyrinth holder LH. The filleted bend at free end of the springs 100 facilitates in smooth entry of the labyrinth seals LS along with the springs 100 in to the groove of the labyrinth holder LH without any obstruction. The angle of bend of the flange FL of the springs 100 facilitates in entry of the flange FL deep through the slot S1 of the labyrinth seals LS and thereby producing proper locking between the springs 100 and the labyrinth seals LS. The filleted bends on either ends of the springs 100 not only reduces stress concentration at the points of contact with the labyrinth holder LH but also increases the contact surface area at the points of contact with the labyrinth holder LH thereby reducing the chances of the movement of the springs 100 within the groove of the labyrinth holder LH.

TECHNICAL ADVANCEMENTS:
A Spring for Seals of a Turbine has several technical advantages including but not limited to the realization of :
• a simple and fool proof spring for seals of a turbine ;
• a spring for seals that can assembled easily ;
• a spring that can be firmly locked to seals ;
• a spring wherein stress concentration at mating points of the spring with a groove of a labyrinth holder is reduced ; and
• a spring that facilitates in enhancing the sealing effect of seals .

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.