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

COMPLETE SPECIFICATION
(See Section 10; rule 13)

AN INSPECTION GAUGE FOR T-ROOT BLANKS

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 the field of inspection of blanks of turbine blades. Particularly  the present invention relates to an apparatus and method of inspecting symmetry of T-root Blanks.

BACKGROUND OF THE INVENTION:
Figure 1 illustrates a pictorial representation of standard method of checking symmetry of T-root blanks by means of Magnetic V-Block and Height Gauge.

Figure 2 illustrates a line drawing of standard method of checking symmetry of T-root blanks by means of Magnetic V-Block and Height Gauge.

The conventional method followed in checking of symmetry of T-root Blanks ‘T’ in Turbine Original Equipment Manufacturers is by means of Magnetic V-Block ‘V’ and Height Gauge ‘H’. The sequence of manufacturing of T-root Blades employs two operations: 1) Machining of T-root on the blank and 2) Machining of the blade profile on the T-root Blank. The checking of the symmetry of the T-root is done after the first operation as the blade will not be having flat surface and the accuracy of checking the symmetry of the T-root will not be precise  when done on the T-root Blade. The symmetry of the projections ‘P1 and P2’ of the T-root Blank ‘T’ plays an important role in alignment and holding of the blades on to the rotor disc of the turbine. A deviation of plus or minus 20 microns in the height of the projections ‘P1 and P2’ of T-root blank ‘T’ is acceptable. A deviation of more than plus or minus 20 microns is not acceptable and turns the T-root blank ‘T’ in to a defective piece.

The conventional method of checking the symmetry of T-root Blanks (i.e.  checking of the height of the projections ‘P1’ and ‘P2’ whether they are identical or not) is as follows:
The T-root Blank ‘T’ is inversely held by the magnetic v-block ‘V’ and the measurement tip of the height gauge is made to touch on the projection ‘P1’. The height gauge ‘H’ shows a reading at the contact of the measurement tip on the projection ‘P1’ of the T-root blank ‘T’. The reading is made to set to zero. Now  the measurement tip of the height gauge ‘H’ is made to touch on the projection ‘P2’ of the T-root blank ‘T’ and the height gauge ‘H’ shows a reading which is the difference of heights of the projections ‘P1’ and ‘P2’. If the difference of the heights of the projections P1 and P2 is within plus or minus 20 microns  then the T-root blank ‘T’ enters in to next step of profile machining operation otherwise the T-root blank ‘T’ will be rejected.

However  the conventional method of checking the symmetry of T-root Blank ‘T’ by means of Height Gauge ‘H’ is time consuming and requires more number of man power. The current method takes 180 minutes to inspect a batch of 100 T-root Blanks.

Therefore  there is a felt need for development of a new apparatus and method for inspecting the symmetry of T-root blanks in less time with accuracy.

OBJECTS OF THE INVENTION:
An object of the present invention is to provide an efficient apparatus for inspecting the symmetry of T-root Blanks.

Another object of the present invention is to provide a method of checking the symmetry of T-root Blanks in less time.

One more object of the present invention is to provide an apparatus and a method to increase the productivity of the inspection of T-root Blanks.

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

Figure 1 illustrates a pictorial representation of standard method of checking symmetry of T-root blanks by means of Magnetic V-Block and Height gauge;

Figure 2 illustrates a line drawing of standard method of checking symmetry of T-root blanks by means of Magnetic V-Block and Height gauge;

Figure 3 illustrates a pictorial representation of new apparatus and method of inspecting the symmetry of T-root blank in accordance with the present invention;

Figure 4 illustrates a front view of apparatus of figure 4;

Figure 5 illustrates a front view and side view of the base block of figure 3;

Figure 6 illustrates a front view and side view of sliding blocks of figure 3;

Figure 7 illustrates a front view and side view of guiding blocks of figure 3;

Figure 8 illustrates a front view and side view of dial gauge mounting block of figure 3;

Figure 9 illustrates a front view and side view of moving pin block of figure 3;

Figure 10 illustrates a front view and side view of dial gauge positioner of figure 3; and

Figure 11 illustrates a front view and side view of fixed pin block of figure 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:
Figure 3 illustrates a pictorial representation of new apparatus and method of inspecting the symmetry of T-root blank.

Figure 4 illustrates a front view of apparatus of figure 4.

In accordance with the present invention  there is provided an apparatus for checking the symmetry of the projections P1 and P2 of the T-root blanks comprising a base block 12  two guiding blocks 14 and 16  two sliding blocks 18 and 20  a moving pin block 22  a fixed pin block 24  a dial gauge mounting block 26  two cylinders 28 and 30  two springs 32 and 34  a dial gauge positioner 36  a dial gauge 38  hexagonal bolts 40  and cap screw bolts 42.

Figure 5 illustrates a front view and side view of the base block of figure 3.

The base block 12 is of rectangular shape with length and breadth of 180 mm and 281 mm respectively and is indicated by reference numerals X1 and Y1 respectively. The thickness of the base block 12 is of 31 mm and is indicated by reference numeral Z1. A slot 46 of 65 mm width and 15 mm depth is drilled at a distance of 20 mm from one edge of the base block 12 and is indicated by reference numerals Y2  Z2 and Y3 respectively. One set of two threaded holes 48a are drilled at a distance of 86 mm from other edge of the base block 12 and is indicated by reference numeral Y4. The distance between the two threaded holes 48a is of 64 mm and is indicated by reference numeral X2. Another set of two threaded holes 48b are drilled on the base block 12 in line to the threaded holes 48a at a distance of 28 mm from the threaded holes 48a and is indicated by reference numeral Y5. The threaded holes 48a and 48b are of 12mm diameter and 4mm pitch. A plurality of threaded holes 50 are drilled from the near end of the base block 12 to the slot 46 as shown in figure 4. The threaded holes 50 are of 4mm diameter and 4mm pitch. Two horizontal projections 51 are provided integrally on the base block 12 as shown in the figure 4. The base block 12 is made of EN32 case hardened carbon steel to provide a smooth surface such that the T-root blank can slide freely over the base block 12.

Figure 6 illustrates a front view and side view of sliding blocks of figure 3.
The sliding blocks 18 and 20 are of 74mm length  65mm breadth and 15mm thickness and are indicated by reference numerals X3  Y6 and Z3 respectively. Three threaded holes 19 of 4mm diameter and 2mm pitch are drilled inline along the length on the front surface of the sliding block 18 at a distance of 20mm from the horizontal edge of the sliding block 18. One set of two threaded holes 52a are drilled at a distance of 20 mm from one edge of the sliding block 20 and is indicated by reference numeral Y7. The distance between the two threaded holes 52a is of 35 mm and is indicated by reference numeral X4. Another set of two threaded holes 52b are drilled on the sliding block 20 in line to the threaded holes 52a at a distance of 28 mm from the threaded holes 52a. The threaded holes 52a and 52b are of 5mm diameter and 4mm pitch. An integral projection 53 is provided at half way along its length on the front surface near to one edge of the sliding block 20.

Figure 7 illustrates a front view and side view of guiding blocks of figure 3. The two guiding blocks 14 and 16 are of 25mm length  130mm breadth and 25mm thickness and are indicated by reference numerals X5  Y8 and Z4 respectively. A threaded hole 54a is drilled on either side of the center of the guiding blocks 14 and 16 on their front surface with a distance of 28mm between them and is indicated by a reference numeral Y9. The holes 54a are of 8mm diameter and 2mm pitch. Three threaded holes 54b are drilled on the side of the guiding block 16  one at the center and other two at a distance of 45mm and 35mm from the center and are indicated by reference numerals Y10 and Y11 respectively. Two slots 55 complementary to the projections 51 on the base block 12 are provided on the guiding blocks 14 and 16.

Figure 8 illustrates a front view and side view of dial gauge mounting block of figure 3.
The dial gauge mounting block 26 is of 50mm length  34mm breadth and 15mm thickness and is indicated by reference numerals X6  Y12 and Z5 respectively. Four threaded holes 56 are provided at the corners of the dial gauge mounting block 26 at a vertical and horizontal distance of 5 mm from the edges of the dial gauge mounting block 26 and is indicated by reference numerals X7 and Y13. The holes 56 are of 6mm diameter and 4mm pitch. Two holes 58a of 8mm diameter and 5 mm depth are drilled on the bottom side of the dial gauge mounting block 26 at distance of 7mm from the center of the dial gauge mounting block 26 and are indicated by reference numerals X8  Y14 and X9 respectively.

Figure 9 illustrates a front view and side view of moving pin block of figure 3. The moving pin block 22 is of L-shaped cross-section having 45mm length  24mm breadth and 29mm height and is indicated by reference numerals X10  Y15 and Z6 respectively. The thickness of the base ‘B’ and projecting element ‘P’ of the moving pin block 22 are Y16 and X11 respectively. A cylindrical projection of 5mm diameter is integrally machined on the side of the moving pin block 22 and is indicated by reference numeral X12. Two holes 58b of 8mm diameter and 12mm depth are drilled on the front side of the moving pin block 22 complementary to the holes 58a of the dial gauge mounting block 26. A slot 59 of greater dimension is provided on the moving block 22 complementary to the projection 53 of the sliding block 20.

Figure 10 illustrates a front view and side view of dial gauge positioner of figure 3. The dial gauge positioner 36 is of 26mm length  12mm breadth and 16mm height and is indicated by reference numerals X11  Y17 and Z7 respectively. A threaded hole 60 of 8mm diameter is drilled across the center of the dial gauge positioner 36 along its breadth and is indicated by reference numeral X12. Two threaded holes 62 of 4mm diameter are drilled on either side of the front surface of the dial gauge positioner 36 along its height and is indicated by reference numeral X13.

Figure 11 illustrates a front view and side view of fixed pin block of figure 3. The fixed pin block 24 is of square cross-section with a cylindrical projection of 5.5mm diameter at one end and is indicated by reference numeral X14. The fixed pin block 24 is of 44mm length  10mm breadth and 10mm height and is indicated by reference numerals X15  Y18 and Z8 respectively. A plurality of equidistantly spaced threaded holes 64 are drilled on the front surface perpendicular to the horizontal axis of the fixed pin block 24 complementary to the threaded holes 19 of the sliding block 18.

The configuration of the Inspection Gauge for checking the symmetry of T-root Blanks in accordance with the present invention is as follows:
The base block 12 is placed on flat surface and the two sliding blocks 18 and 20 are held firmly in the slot 46 of the base block 12 by means of cap screw bolts 42 passing through
threaded holes 50. The position of fixing of the sliding blocks 18 and 20 depends on the width of the T-root blanks for inspection. The fixed pin block 24 is placed on the sliding block 18 with threaded holes 64 inline to the threaded holes 19 of the sliding block 18 and bolted by means of cap screw bolts 42. The dial gauge mounting block 26 is placed on the sliding block 20 with threaded holes 56 inline to the threaded holes 52a and 52b and bolted by means of cap screw bolts 42. Two cylinders 28 and 30 enclosed by springs 32 and 34 (not shown in the figure) are press fitted in the holes 58a of the dial gauge mounting block 26. The moving pin block 22 is placed on the sliding block 20 such that the slot 59 of the moving pin block 22 encompasses the projection 53 of the sliding block 20 with upper end of the slot 59 juxtaposing the upper end of the projection 53 and this position is typically referred to as Top Dead Center position (TDC). In the Top Dead Center position  the moving pin block 22 is 2mm to 3mm below the horizontal axis of the fixed pin block 24 and parallel to it. Further  In the top dead center position  the free end of the cylinders 28 and 30 enclosed by springs 32 and 34 (not shown in the figure) are inserted in to the holes 58b of the moving pin block and the dial of the dial gauge 38 touches the projecting element ‘P’ of the moving pin block 22. The moving pin block 22 is in forward moving position with respect to the cylinders 28 and 30 when the moving block 22 is at top dead center position. So  the reading in the dial gauge 38 is below zero at top dead center position  when the dial gauge is not calibrated. The guiding blocks 14 and 16 are placed on the base block 12 such that the slots 55 of the guiding blocks 14 and 16 are adaptable to slide on the projections 51 of the base block 12. The guiding blocks 14 and 16 are bolted to the base block 12 at a predefined position by means of cap screw bolts 42 depending on the width of the T-root blanks to be inspected. The perpendicularity of the T-root blank with respect to the moving pin block 22 and fixed pin block 24 is maintained with the help of hexagonal bolts 40 passing through threaded holes 54b from the side of the guiding blocks 14 and 16.

The method of inspecting the symmetry of T-root blanks with the help of Inspection Gauge in accordance with the present invention is as follows:
A master piece of T-root blank having symmetry of the projections ‘P1’ and ‘P2’ is selected by means of inspecting with the height gauge. The master piece T-root blank is made to pass through the space between the guiding blocks 14 and 16 wherein the projections ‘P1’ and ‘P2’ are made to touch with the cylindrical projections of the moving pin block 22 and fixed pin block 24. Now  the pointer in the dial gauge 38 shows a reading which is set to zero. The symmetry of T-root blanks is now inspected  positive reading in the dial gauge 38 implies the projection ‘P2’ > ‘P1’ and negative reading implies ‘P2’ < ‘P1’. All the T-root Blanks within the deviation of +/- 20 microns are accepted and go to profile milling operation whereas the T-root blanks beyond the deviation of +/- 20 microns are scrapped. This new method of inspection takes 20 minutes to inspect a batch of 100 blades.

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) An inspection gauge for T-root blanks  said inspection gauge comprising:
a) a base block provided with two horizontal guide ways and a slot from one edge of said block  said slot provided with holes from the edge of the block;

b) two sliding blocks provided with threaded holes inserted from right and left in to the slot of said block and hold firmly at a predetermined position by means of cap screw nuts passing through the holes from the edge of the base block  said right side sliding block provided with an integral projection from the edge of the block;

c) a fixed pin block with threaded holes placed on the left side sliding block in line with the threaded holes of the left side sliding block and bolted to the left side sliding block by means of cap screw nuts;

d) a dial gauge mounting block with threaded holes and two cylinders enclosed by springs press fitted on the side of said dial gauge mounting block placed on the right side sliding block in line with the threaded holes of the right side sliding block and bolted by means of cap screw nuts;

e) a moving pin block having a provision to accommodate the projection of left side sliding block placed on the left side sliding block in a way that the free end of the cylinders inserted in to the holes of the moving pin block and the moving pin block being in a position to make to and fro movement;

f) a dial gauge positioner bolted on the dial gauge mounting block with a hole
drilled through its lateral axis;

g) a dial gauge passes through the hole of the dial gauge positioner and touches the moving pin block; and

h) two guiding blocks mounted on the horizontal guide ways from left and right and bolted at a predetermined position  said right side guiding block having threaded holes drilled on the side to accommodate hexagonal bolts.

2) An inspection gauge for T-root blanks as claimed in claim 1  wherein the fixed pin block and the moving pin block bolted on said left and right sliding blocks respectively are parallel to each other but not in line to each other.

3) An inspection gauge for T-root blanks as claimed in claim 1  wherein the predetermined position of fixing of the guiding blocks and sliding blocks depends on the width of the T-root blanks.

4) An inspection gauge for T-root blanks as claimed in claim 1  wherein the base block is made of EN32 case hardened carbon steel.

5) A method of inspecting the symmetry of T-root blanks  said method comprising:
an inspection gauge having:
a) a base block provided with two horizontal guide ways and a slot from one edge of said block  said slot provided with holes from the edge of the block;

b) two sliding blocks provided with threaded holes inserted from right and left in to the slot of said block and hold firmly at a predetermined position by means of cap screw nuts passing through the holes from the edge of the base block  said right side sliding block provided with an integral projection from the edge of the block;

c) a fixed pin block with threaded holes placed on the left side sliding block in line with the threaded holes of the left side sliding block and bolted to the left side sliding block by means of cap screw nuts;

d) a dial gauge mounting block with threaded holes and two cylinders enclosed by springs press fitted on the side of said dial gauge mounting block placed on the right side sliding block in line with the threaded holes of the right side sliding block and bolted by means of cap screw nuts;

e) a moving pin block having a provision to accommodate the projection of left side sliding block placed on the left side sliding block in a way that the free end of the cylinders inserted in to the holes of the moving pin block and the moving pin block being in a position to make to and fro movement;

f) a dial gauge positioner bolted on the dial gauge mounting block with a hole drilled through its lateral axis;

g) a dial gauge passes through the hole of the dial gauge positioner and touches the moving pin block; and

h) two guiding blocks mounted on the horizontal guide ways from left and right of the base block and bolted at a predetermined position  said right side guiding block having threaded holes drilled on the side to accommodate hexagonal bolts.

6) A method of inspecting the symmetry of T-root blanks as claimed in claim 5  wherein the inspection gauge is calibrated by passing a symmetrical master T-root blank through the guiding blocks and pressing the blank against said fixed pin block and moving pin block and setting the reading in said dial gauge to zero; said T-root blanks are passed through said guide ways of the calibrated inspection gauge and pressed against said fixed pin block and moving pin block and deviations in said dial gauge within the range of + or – 20 microns are accepted.

7) A method of inspecting the symmetry of T-root blanks as claimed in claim 5  wherein  the perpendicularity of the T-root blank with respect to said fixed pin block and moving pin block is maintained by means of plurality of horizontal bolts mounting against said T-root blank.

8) An inspection gauge for T-root blanks as described herein the description and accompanying drawings.

9) A method of inspecting the symmetry of T-root blanks as described herein the description and accompanying drawings.

Dated this 2nd day of Feb  2012 (for Triveni Turbine Ltd)


Dr.Sunil Jajit
GM-IPR