FORM 2
THE PATENT ACT  1970
(39 OF 1970)
AND
THE PATENTS RULES  2003

COMPLETE SPECIFICATION
(See Section 10; rule 13)

A MEANS FOR ASSEMBLING SKEWED AXIAL ENTRY BLADES ON
TO A DISC OF A ROTOR IN A STEAM TURBINE

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.

Note: This Patent application is modification of an invention described or disclosed in the complete specification 1985/CHE/2010 filed there for.

FIELD OF THE INVENTION:
The present invention relates to a device for assembling turbine blades on to a rotor disc. Particularly  the present invention relates to use of such device in assembling of skewed axial entry blades in a steam turbine.

BACKGROUND OF THE INVENTION:
Figure 1(a) illustrates a front view of a conventional second stage blade in a three stage low pressure module disclosed in the prior art.

Figure 1(b) illustrates a top view looking from A of the second stage blade of figure 1(a).

As disclosed in the prior art  the two projections (P21 and P22) integrally formed at the platform portion of the blade had called for the usage of fixture for assembling of blades on to a disc of a rotor. It is evident from figure 1(b) that the second stage blade has straight platform portion.

Figure 2(a) illustrates a front view of a newly developed first stage blade in a three stage low pressure module.

Figure 2(b) illustrates a left side view of the first stage blade of figure 2(a).

Figure 2(c) illustrates a right side view of the first stage blade of figure 2(a).

Figure 2(d) illustrates a top side view of the first stage blade of figure 2(a).

Figure 2(e) illustrates a cut sectional view B-B of the first stage blade of figure 2(a).

The shroud S of the newly developed first stage blades obstructs the manual assembly of the blades on to the disc of the rotor. The shroud S is integrally provided at the tip of the airfoil portion of the blade to dampen vibration and reduce tip leakage losses. So  the shroud S of the newly developed first stage blade has called in for the usage of Assembly fixture. The root portion of newly developed first stage blades has two fir tree lobes (L1 and L2) defining a space therein.

It is evident from the figure 2(e) that the platform portion of the newly developed first stage blade is skewed and makes an angle 12 degree with the horizontal and is generally indicated by a reference numeral a. The skewed axial entry root portion is provided to obtain a distribution of average and local stresses  adequate low cycle fatigue margins (LCF) and protection during over speed conditions. The Assembly fixture disclosed in the prior art (1985/CHE/2010) is not capable of handling the assembly of skewed axial entry blades on to the disc of the rotor.

Therefore  there is felt a need for development of a device for assembling of skewed axial entry blades on to a disc of a rotor in a steam turbine.

OBJECTS OF THE INVENTION:
An object of the present invention is to provide a device capable of assembling all the blades on to a rotor disc at a single instance.

Another object of the present invention is to provide a device that ensures no spoilage of root butting surface of the blades during assembly.

SUMMARY OF THE INVENTION:
In accordance with the present invention  there is provided an assembly fixture for assembling skewed axial entry blades on to a disc of a rotor in a steam turbine comprising:
1) a lower half semicircular locating pin plate with flanges at diametrically opposite ends and bolted on two support posts  said plate include equidistantly spaced apertures inclined at a predefined angle to the horizontal on side face around its periphery  said plate also include equidistantly spaced holes on the side face above said apertures to accommodate hexagonal bolts;
2) an upper half semicircular locating pin plate with flanges at diametrically opposite ends complementary to said lower half semicircular locating pin plate  said plate include equidistantly spaced apertures inclined at a predefined angle to the horizontal on side face around its periphery  said plate also include equidistantly spaced holes on the side face above said apertures to accommodate hexagonal bolts;
3) an outer lower half semicircular ring integrally welded on its inner diameter adjacent to said lower half semicircular locating pin plate;
4) an outer upper half semicircular ring integrally welded on its inner diameter adjacent to said upper half semicircular locating pin plate;
5) an inner lower half semicircular ring mounted concentrically to said integrated lower half semicircular locating pin plate and outer lower half semicircular ring by means of ribs;
6) an inner upper half semicircular ring mounted concentrically to said integrated upper half semicircular locating pin plate and outer upper half semicircular ring by means of ribs;
7) said integrated lower half locating plate  outer lower half ring  inner lower half ring and said integrated upper half locating plate  outer upper half ring  inner upper half ring are bolted at the horizontal parting plane in such a way that the joined inner upper half and lower half ring is in concentric with the rotor and accommodates it;
8) a plurality of locating pins twisted to an angle complementary to inclined angle of said apertures  protrudes through said apertures providing in between therein a plurality of gaps to accommodate the roots of the blades; and
9) an upper half and lower half circular push plates bolted at the horizontal parting plane with circular spaces on one face along its thickness complementary to said holes in upper half and lower half locating pin plates  said integrated push plate mounted on said pins adjacent to said upper half and lower half locating pin plates and adapted to receive said bolts in the circular spaces.
Typically  the locating pins are of semicircular arch shape with a semicircular arch shaped head at one end.

BRIEF DESCRIPTION OF THE DRAWINGS:
The invention will now be described with reference to the accompanying drawings in which:
Figure 1(a) illustrates a front view of a second stage blade in a three stage low pressure module disclosed in the prior art;

Figure 1(b) illustrates a top view looking from A of the second stage blade of figure 1(a);

Figure 2(a) illustrates a front view of a newly developed first stage blade in a three stage low pressure module;

Figure 2(b) illustrates a left side view of the first stage blade of figure 2(a);

Figure 2(c) illustrates a right side view of the first stage blade of figure 2(a);

Figure 2(d) illustrates a top side view of the first stage blade of figure 2(a);

Figure 2(e) illustrates a cut sectional view B-B of the first stage blade of figure 2(a);

Figure 3(a) illustrates a front view of assembling newly developed first stage low pressure module blades on to the disc of the rotor using fixture in accordance with the present invention;

Figure 3(b) illustrates a detailed view of fixture of figure 3(a);

Figure 4 illustrates a side view of lower half fixture looking from A of figure 3(b);

Figure 5 illustrates a cut sectional view of section X-X of figure 4;

Figure 6 illustrates a top view of lower half fixture of figure 4;

Figure 7 illustrates a side view of upper half fixture looking from A of figure 3(b);

Figure 8 illustrates a cut sectional view of section X-X of figure 7;

Figure 9 illustrates a top view of upper half fixture of figure 7;

Figure 10 illustrates a side view of an assembly fixture looking from A of figure 3(b);

Figure 11 illustrates a side view of an assembly fixture looking from B of figure 3(b);

Figure 12 illustrates a cut sectional view of section B-B of figure 10;

Figure 13 illustrates a detailed view of portion A of figure 12;

Figure 14 illustrates a detailed front view and top view of push plate of figure 10 and 13;

Figure 15 illustrates a detailed front view  top view and side view of locating pins of figure 10;

Figure 16 illustrates a detailed front view and side view of lock plate of figure 11; and

Figure 17 illustrates a pictorial representation of newly developed first stage low pressure module blades mounted on locating pins.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:
The embodiments of the present invention will now be described in detail by way of example and with reference to the accompanying drawings.

Figure 3(a) illustrates a front view of assembling newly developed first stage low pressure module blades on to the disc of the rotor.

Figure 3(b) illustrates a detailed view of fixture of figure 3(a).

In accordance of the present invention  there is provided a rotor 10 of a steam turbine supported at its ends and an assembly fixture 20 provided therein at the beginning of the first stage low pressure module blades.

Figure 4 illustrates a side view of lower half fixture looking from A of figure 3(b).

Figure 5 illustrates a cut sectional view of section X-X of figure 4.

Figure 6 illustrates a top view of lower half fixture of figure 4.

In accordance with the present invention  there is provided a lower half fixture 100 comprising a lower half semi circular locating pin plate 124  two support posts 126  an outer lower half semi circular ring 128  an inner lower half semi circular ring 130  five mounting ribs 132  a base plate 134  two upper plates 136  two lower plates 138 and four base ribs 140.

The lower half semi circular locating pin plate 124 is formed in such a way to include two integrated flanges 142 at its diametrical ends. The lower half semi circular locating pin plate 124 is bolted at its flanges 142 to two support posts 126. The support posts 126 are formed as a C-shaped channel having a flat portion 144 with holes at top complementary to the holes of the flanges 142. The two support posts 126 are adapted to be mounted on the base plate 134 by means of upper plates 136 and lower plates 138. The upper plates 136 and lower plates 138 are bolted together by means of complementary holes 146 provided on them. The lower plates 138 are welded to the base plate 134. The base plate 134 is bolted to the floor by means of holes 146 provided at the corners of the base plate 134. The C-shaped channel of the support posts 126 is supported on either side with the help of four base ribs 140 arising from the upper plates 136.

The lower half semi circular locating pin plate 124 has equidistantly spaced apertures 148 of semicircular arch shape around its circumference at a pitch circle radius of approximately 182mm and is generally indicated by a reference numeral R1.The apertures 148 are provided at an angle of 9 degrees with the horizontal. The width of the apertures 148 is approximately 24.77mm and a total number of 30.5 apertures are provided on the lower half semi circular locating pin plate 124. The angle of spacing between the apertures 148 is approximately 5.90 degrees and is generally indicated by a reference numeral ?1. The lower half semi circular locating pin plate 124 also includes equidistantly spaced holes 150 at angle of 60 degrees around its circumference at a pitch circle radius of approximately 212.5mm and is generally indicated by reference numerals ?2 and R2 respectively. Two holes (152 and 154) on the side face and one hole 156 on the top face are provided at both ends of the lower half semi circular locating pin plate 124 to facilitate joining of lower half fixture 100 with upper half fixture 200.

The outer lower half semi circular ring 128 is adapted to be placed adjacent to the lower half semi circular locating pin plate 124 by welding inner diameter edge of the lower half semi circular locating pin plate 124 and the outer lower half semi circular ring 128. The inner lower half semi circular ring 130 is made in concentric with the rotor 10 and is supported with the help of five trapezium shaped mounting ribs 132 originating from the integrated inner diameter of the lower half semi circular locating pin plate 124 and the outer lower half semi circular ring 128.

The length of the lower half semi circular locating pin plate 124 is approximately 1176mm and is generally indicated by a reference numeral X1. The radius of the lower half semi circular locating pin plate 124 is approximately 435mm and is generally indicated by a reference numeral R3. The width of the flanges 142 of the lower half semi circular locating pin plate 124 is approximately 55mm and is generally indicated by a reference numeral Z1. The thickness of the lower half semi circular locating pin plate 124 is approximately 25mm and is generally indicated by a reference numeral Y1. The outer lower half semi circular ring 128 is having an outer radius and inner radius of approximately 372mm and 342mm respectively and is generally indicated by reference numerals R4 and R5 respectively. The inner lower half semi circular ring 130 is having an outer radius and inner radius of approximately 228.25mm and 208.25mm respectively and is generally indicated by reference numerals R6 and R7 respectively. The thickness of the outer lower half semi circular ring 128 and the inner lower half semi circular ring 130 is approximately 30mm and 20mm respectively and is generally indicated by reference numerals Y2 and Y3 respectively. The length and width of the base plate 134 is approximately 1301mm and 700mm respectively and is indicated by reference numerals X2 and Y4 respectively. The length and width of the upper plates 136 and lower plates 138 is approximately 250mm x 250mm and is generally indicated by reference numerals X3 and Y5.

Figure 7 illustrates a side view of upper half fixture looking from A of figure 3(b).

Figure 8 illustrates a cut sectional view of section X-X of figure 7.

Figure 9 illustrates a top view of upper half fixture of figure 7.

In accordance with the present invention  there is provided a upper half fixture 200 comprising a upper half semi circular locating pin plate 224  an outer upper half semi circular ring 228  an inner upper half ring semi circular ring 230 and five mounting ribs 232.

The upper half semi circular locating pin plate 224 is formed in such a way to include two integrated flanges 242 at its diametrical ends. The upper half semi circular locating pin plate 224 has equidistantly spaced apertures 248 of semicircular arch shape around its circumference at a pitch circle radius of approximately 182mm and is generally indicated by a reference numeral R8. The apertures 248 are provided at an angle of 9 degrees with the horizontal. The width of the apertures 248 is approximately 24.77mm and a total number of 30.5 apertures are provided on the upper half semi circular locating pin plate 224. The angle of spacing between the apertures 248 is approximately 5.90 degrees and is generally indicated by a reference numeral ?3. The upper half semi circular locating pin plate 224 also includes equidistantly spaced holes 250 at angle of 60 degrees around its circumference at a pitch circle radius of approximately 212.5mm and is generally indicated by reference numeral ?4 and R9 respectively. Two holes (252 and 254) on the side face and one hole 256 on the top face are provided at both ends of the upper half semi circular locating pin plate 224 to facilitate joining of upper half fixture 200 with lower half fixture 200.

The outer upper half semi circular ring 228 is adapted to be placed adjacent to the upper half semi circular locating pin plate 224 by welding inner diameter edge of the upper half semi circular locating pin plate 224 and the outer lower half semi circular ring 228. The inner upper half semi circular ring 230 is made in concentric with the rotor 10 and is supported with the help of five trapezium shaped mounting ribs 232 originating from the integrated inner diameter of the upper half semi circular locating pin plate 224 and the outer upper half semi circular ring 228.

The length of the upper half semi circular locating pin plate 224 is approximately 1176mm and is generally indicated by a reference numeral X4. The radius of the upper half semi circular locating pin plate 224 is approximately 435mm and is generally indicated by a reference numeral R10. The width of the flanges 242 of the upper half semi circular locating pin plate 224 is approximately 55mm and is generally indicated by a reference numeral Z2. The thickness of the upper half semi circular locating pin plate 224 is approximately 25mm and is generally indicated by a reference numeral Y6. The outer upper half semi circular ring 228 is having an outer radius and inner radius of approximately 372mm and 342mm respectively and is generally indicated by reference numerals R11 and R12. The inner upper half semi circular ring 230 is having an outer radius and inner radius of approximately 228.25mm and 208.25mm respectively and is generally indicated by reference numerals R13 and R14. The thickness of the outer upper half semi circular ring 228 and the inner upper half semi circular ring 230 is approximately 30mm and 20mm respectively and is generally indicated by reference numerals Y7 and Y8.

Figure 10 illustrates a side view of an assembly fixture looking from A of figure 3(b).

Figure 11 illustrates a side view of an assembly fixture looking from B of figure 3(b).

Figure 12 illustrates a cut sectional view of section X-X of figure 10.

Figure 13 illustrates a detailed view of portion A of figure 12.

In accordance with the present invention  there is provided an assembly fixture 20 comprising a lower half fixture 100  an upper half fixture 200  locating pins 158  six hexagonal bolts 160  an upper half semi circular push plate 162  a lower half semi circular push plate 164 and a lock plate 166.

The lower half fixture 100 and the upper half fixture 200 are bolted at the horizontal plane by means of hexagonal bolts 168 passing through complementary holes 156 and 256. The upper half semi circular push plate 162 and the lower half semi circular push plate 164 are bolted at the horizontal parting plane by means of hexagonal nuts and bolts.
The locating pins 158 pass through the equidistantly spaced apertures 148  248 and lay over the outer lower half semi circular ring 128 and outer upper half semi circular ring 228. The assembled upper half semi circular push plate 162 and lower half semi circular push plate 164 is placed adjacent to the assembled lower half semi circular locating pin plate 124 and upper half semi circular locating pin plate 224. The lower half fixture 100 and the upper half fixture 200 are locked firmly by means of hexagonal bolts 170 passing through the lock plate 166  lower half fixture 100 and the upper half fixture 200.

Figure 14 illustrates a detailed front view and top view of push plate of figure 10 and 13.
The upper half semi circular push plate 162 and the lower half semi circular push plate 164 have a length of approximately 1007mm and is generally indicated by a reference numeral X5. The upper half semi circular push plate 162 and the lower half semi circular push plate 164 are bolted at the horizontal parting plane. The outer radius and inner radius of push plates (162 and 164) is approximately 450mm and 400mm respectively and is generally indicated by reference numerals R15 and R16. The thickness of the push plates (162 and 164) is approximately 10mm and is generally indicated by a reference numeral Y9. The push plates (162 and 164) includes three equidistantly spaced half way holes on one face complementary to the holes 150 and 250 of the upper half semi circular push plate 162 and the lower half semi circular push plate 164 respectively at pitch circle radius of 425mm and is generally indicated by a reference numeral R17. The push plates (162 and 164) face with holes is placed adjacent to the assembled lower half semi circular locating pin plate 124 and upper half semi circular locating pin plate 224.

Figure 15 illustrates a detailed front view  top view and side view of locating pins of figure 10.
The locating pins 158 are of semicircular arch shape with a semicircular arch shaped bolt head 172. The locating pins 158 are twisted and make an angle 9 degree with the horizontal and are generally indicated by a reference numeral ß. The end face of the locating pins 158 is tapered. The length of the locating pins 158 at highest point of end face is 130mm and the length of the locating pins 158 at smallest point of end face is 125mm and is generally indicated by reference numerals Y10 and Y11 respectively. The width and thickness of the locating pins 158 is 24.77mm and 8mm respectively and is indicated by reference numerals X6 and Y12 respectively. The length  width and thickness of the semicircular arch shaped bolt head 172 is 33mm  16mm and 6mm respectively and is generally indicated by reference numerals X7  Y13 and Z3 respectively.

Figure 16 illustrates a detailed front view and side view of lock plate of figure 11.
The lock plate 166 has a length  width and thickness of 168mm  80mm and 5mm respectively and is generally indicated by reference numerals X8  Y14 and Z4 respectively. The lock plate 166 has four holes 174 at a distance of 15mm and 14mm from the horizontal edge and vertical edge respectively.

Figure 17 illustrates a pictorial representation of newly developed first stage low pressure module blades mounted on locating pins.
The method of operation of the assembly fixture 20 is as follows:
The assembly fixture 20 with all the newly developed first stage blades positioned in between locating pins 158 is aligned with the disc of the rotor 10 such that the grooves of the disc and the roots of the blade are inline. The newly developed first stage blades are adapted to sit on the locating pins 158 by means of locating pins 158 adhering to the gap provided in between the fir tree lobes L1 and L2 of the root of the blade. The twist in the locating pins 158 facilitates in accommodating the skew of the first stage blades and tilt of cyclic surfaces of first stage blades during assembly. Now  the hexagonal bolts 160 in the locating pin plates (124 and 224) are rotated such that an inward force will be applied on the push plates (162 and 164) which in turn push the blades that lay over the assembled outer lower half semi circular ring 128 and outer upper half semi circular ring 228 on to the disc of the rotor 10. There is a significant gap in between the base of roots of the blades and the assembled outer lower half semi circular ring 128 and outer upper half semi circular ring 228.

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.

We claim:
1. A means for assembling skewed axial entry blades on to a disc of a rotor in a steam turbine  said means comprising:
a) a lower half semicircular locating pin plate with flanges at diametrically opposite ends and bolted on two support posts  said plate include equidistantly spaced apertures inclined at a predefined angle to the horizontal on side face around its periphery  said plate also include equidistantly spaced holes on the side face above said apertures to accommodate hexagonal bolts;
b) an upper half semicircular locating pin plate with flanges at diametrically opposite ends complementary to said lower half semicircular locating pin plate  said plate include equidistantly spaced apertures inclined at a predefined angle to the horizontal on side face around its periphery  said plate also include equidistantly spaced holes on the side face above said apertures to accommodate hexagonal bolts;
c) an outer lower half semicircular ring integrally welded on its inner diameter adjacent to said lower half semicircular locating pin plate;
d) an outer upper half semicircular ring integrally welded on its inner diameter adjacent to said upper half semicircular locating pin plate;
e) an inner lower half semicircular ring mounted concentrically to said integrated lower half semicircular locating pin plate and outer lower half semicircular ring by means of ribs;
f) an inner upper half semicircular ring mounted concentrically to said integrated upper half semicircular locating pin plate and outer upper half semicircular ring by means of ribs;
g) said integrated lower half locating plate  outer lower half ring  inner lower half ring and said integrated upper half locating plate  outer upper half ring  inner upper half ring are bolted at the horizontal parting plane in such a way that the joined inner upper half and lower half ring is in concentric with the rotor and accommodates it;
h) a plurality of locating pins twisted to an angle complementary to inclined angle of said apertures  protrudes through said apertures providing in between therein a plurality of gaps to accommodate the roots of the blades; and
i) an upper half and lower half circular push plates bolted at the horizontal parting plane with circular spaces on one face along its thickness complementary to said holes in upper half and lower half locating pin plates  said integrated push plate mounted on said pins adjacent to said upper half and lower half locating pin plates and adapted to receive said bolts in the circular spaces.

2. A means for assembling skewed axial entry blades on to a disc of a rotor in a steam turbine as claimed in claim1  wherein said pins are of semicircular arch shape with a semicircular arch shaped head at one end.

3. A means for assembling skewed axial entry blades on to a disc of a rotor in a steam turbine as claimed in claim1  wherein width of said inner lower and upper half ring is equivalent to the total width of said upper and lower half locating pin plates and outer upper and lower half rings.

4. A means for assembling skewed axial entry blades on to a disc of a rotor in a steam turbine as claimed in claim1  wherein said predefined angle of said apertures of said locating pin plates is 9 degrees.

5. A means for assembling skewed axial entry blades on to a disc of a rotor in a steam turbine as claimed in claim1  wherein said locating pins are twisted to an angle of 9 degrees to the horizontal.

6. A means for assembling skewed axial entry blades on to a disc of a rotor in a steam turbine as claimed in claim1  wherein said upper half locating plates  lower half locating plates are firmly bolted by means of a lock plate.

7. A means for assembling skewed axial entry blades on to a disc of a rotor in a steam turbine as claimed in claim1  wherein said support posts are mounted on a base plate and bolted by means of mounting plates.

8. A means for assembling skewed axial entry blades on to a disc of a rotor in a steam turbine as claimed in claim1  wherein said posts are supported on either side by means of ribs arising from said mounting plates.

9. A means for assembling skewed axial entry blades on to a disc of a rotor in a steam turbine as claimed in claim1 or 5  wherein said twist in the locating pins facilitates in accommodating the skew of the blades and tilt of cyclic surfaces of the blades during assembly.

Dated this 27th day of September  2012 (for Triveni TurbineLtd)


Dr.Suneel Jajit GM-IPR