CLIAMS:We claim:
1) An apparatus for inspecting thickness of the root of the T root blade with accuracy, said apparatus comprising:
a) a base block (12) having rectangular cross-section with three equidistantly spaced holes (H2), parallel to each other, provided on the top surface of said base block (12) to a predefined depth, said base block (12) provided with two slots (S1) of predefined width and predefined depth along the width of said base block (12);
b) two dowel pins (20);
c) a dial gauge holding block (16) of L-shaped cross-section having a through hole (H3) drilled on the leg (L) of the dial gauge holding block(16) at a predefined distance from base (B) of said dial gauge holding block (16), said dial gauge holding block (16) provided with three equidistantly spaced holes (H5) on bottom surface complementary to the equidistantly spaced holes (H2) of said base block (12), said central hole of equidistantly spaced holes (H5) is a through hole whereas the holes on either side of said central hole are drilled to a predefined height, said two dowel pins inserted in to extreme holes of said equidistantly spaced holes (H2) and said dial gauge holding block (16) mounted on said base block (12) by means of said dowel pins passing through extreme holes of said equidistantly spaced holes (H5) of said dial gauge holding block (16), said dial gauge holding block (16) is locked in position by means of a allen screw passing through complementary central holes of said dial gauge holding block (16) and said base block (12), said dial gauge holding block (16) provided with a through slot (S2) from the periphery of the hole (H3) to the end of the dial gauge holding block (16) along the thickness of said leg (L) of the dial gauge holding block (16), said dial gauge holding block(16) provided with a hole (H4) from one side face to other side face along its width passing through the slot (S2) of dial gauge holding block (16);
d) a dial gauge (14) inserted in to said hole (H3) of said dial gauge holding block (16) and locked in position at a predetermined height from the base block (12) by means of allen screw passing through hole (H4) of said dial gauge holding block (16); and
e) a perpendicularity maintaining block (18) provided with two projections (P1) on its bottom surface adaptable to sit in said slots (S1) of the base block (12), said perpendicularity maintaining block (18) perpendicular to base (B) of said dial gauge holding block (16) when said projections (P1) of perpendicularity maintaining block (18) inserted in to said slots (S1) of the base block (12).

2) An apparatus for inspecting thickness of the root of the T root blade with accuracy as claimed in claim 1, wherein threads are provided in the central hole of equidistantly spaced holes (H2) of said base block (12).

3) An apparatus for inspecting thickness of the root of the T root blade with accuracy as claimed in claim 1, wherein the predefined distance of the hole (H3) from base (B) of said dial gauge holding block (16) varies depending on the size of the T root blade.

4) An apparatus for inspecting thickness of the root of the T root blade with accuracy as claimed in claim 1, wherein the predefined distance of the hole (H3) from base (B) of said dial gauge holding block (16) is 20mm.

5) An apparatus for inspecting thickness of the root of the T root blade with accuracy as claimed in claim 1, wherein said dial gauge is fixed in position in the hole (H3) of said dial gauge holding block (16) at a predetermined height from the base block (12) by means of Slip Gauges.

6) An apparatus for inspecting thickness of the root of the T root blade with accuracy as claimed in claim 1, wherein the predetermined height from the base block (12) at which the dial gauge (14) is locked is equal to the thickness the root of the T root blade at said predefined distance.

7) An apparatus for inspecting thickness of the root of the T root blade with accuracy as claimed in claim 1, wherein threads are provided at distal end of said hole (H4) adjoining the slot (S2) of said dial gauge holding block (16).

8) A method of inspecting thickness of the root of the T root blade with accuracy using said apparatus, said method comprising:
a) placing slip gauges of predetermined height on the base block (12) below the dial gauge holding block (16) and the dial gauge (14) passing through said dial gauge holding block (16) is adapted to touch said slip gauges;
b) removing the slip gauges from the base block (12) and locking the dial gauge (14) at said position; and
c) inserting the root of the T root blades below the dial gauge (14) and predetermined thickness(Z3) of the root of the T root blades at predefined distance (D3) is inspected whether the predetermined thickness(Z3) is within the tolerance limits of +/- 20 microns, said predetermined thickness (Z3) of the root of the T root blades at predefined distance (D3) is within the tolerance limits, then the blade is accepted and sent to assembly, said predetermined thickness (Z3) of the root of the T root blades at predefined distance (D3) is out of the tolerance limits, then the blade is rejected and sent to rework or scrap.

9) A method of inspecting thickness of the root of the T root blade with accuracy using said apparatus as claimed in claim 8, wherein said predetermined thickness (Z3) is calculated by bringing a relationship between predetermined thickness (Z3), predefined distance (D3) and angle of taper (?).

10) A method of inspecting thickness of the root of the T root blade with accuracy using said apparatus as claimed in claim 9, wherein said angle of taper (?) may vary depending on the size of the T root blade.

Dated this 29th day of April, 2013 (for Triveni Turbine Ltd)


Deepak Kumar Sen
GM-IPR

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

COMPLETE SPECIFICATION
(See Section 10; rule 13)

AN APPARATUS AND METHOD OF INSPECTING THICKNESS OF THE ROOT OF THE T-ROOT BLADE WITH ACCURACY

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 apparatus and method of inspection. Particularly, the present invention relates to an apparatus and method of inspection of thickness of the root of the blade.

BACKGROUND OF THE INVENTION:
Figure 1 illustrates an isometric view of T root blade.

Figure 2 illustrates a side view of T root blade of figure 1.

It is evident from figure 2 that one side of the root of T root blade has flat face F and other side of the root of T root blade has tapered face T.

Figure 3 illustrates a schematic diagram depicting the dimensions of the root of the T root blade.

The thickness of the root of the T root blade at one extreme end is 13.41mm and is generally indicated by a reference numeral Z1. The thickness of the root of the T-root blade at other extreme end, near to the hub of the blade is 14.84mm and is generally indicated by a reference numeral Z2. The angle of taper of the tapered face T of the T-root blade is 3 degrees and is generally indicated by a reference numeral ?. The thicknesses Z1 and Z2 of the root of the T root blade and the angle of taper ? of the root of the T root blade varies depending on the size of the T-root blade.

Figure 4 illustrates a conventional method of measurement of thickness of the root of the T-root blade at its edge by means of screw gauge.

It is only possible to measure the thickness Z1 of the root of the T root blade by means of screw gauge. The thickness Z2 at the other end of the root of the T root blade cannot be measured by means of screw gauge due to space constraints. So, another instrument is required to measure angle of taper ? of the T-root blade. The tolerance of +/- 20 microns in thickness is allowable.

Figure 5 illustrates a conventional method of inspection of angle of tapered face of the T-root blade by means of Sine bar.
The distance between two cylinders of the Sine bar X1 is known. As T root blade is placed on the top of the Sine bar with flat face F butting the top surface of the Sine bar and angle of taper ? of the tapered face T is known, by applying the principle of alternate angles, the slip gauge height H1 is determined by the following formula:
Sin (?) = Opposite Side (H1)/ Hypotenuse Side (X1).

Now, the height gauge is made to touch at different points on the tapered face T of the T root blade and any deviation in the angle of taper ? is measured. The tolerance of +/- 20 microns in angle is allowable. If the dial in the height gauge deflects within the limits of +/- 20 microns at zero position, then the angle of taper ? is within tolerable limits.

This conventional method of measuring the thickness and inspecting the angle of taper as described herein above is difficult, time consuming and requires skilled man power.

Therefore, there is felt a need for development of a simple apparatus and a simple method for inspection of thickness of the root of the T root blade to overcome the drawbacks of the prior art.

OBJECTS OF THE INVENTION:
An object of the present invention is to provide a simple apparatus for inspection of thickness of the root of the T root blade.

Another object of the present invention is to provide a simple method of inspection of thickness of the root of the T root blade.

One more object of the present invention is to provide an apparatus and method by which the inspection of thickness of the root of the T root blade can be done in less time.

Still another object of the present invention is to provide an apparatus and method wherein the inspection of thickness of the root of the T root blade can be done by unskilled labour also.

Yet another object of the present invention is to provide an apparatus and method wherein the inspection of thickness of the root of the T root blade can be done in a single time.

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 T root blade;

Figure 2 illustrates a side view of T root blade of figure 1;

Figure 3 illustrates a schematic diagram depicting the dimensions of the root of the T root blade;

Figure 4 illustrates a conventional method of measurement of thickness of the root of the T-root blade at its edge by means of screw gauge;

Figure 5 illustrates a conventional method of inspection of angle of tapered face of the T-root blade by means of Sine bar;

Figure 6 illustrates a front view of an apparatus and method of inspecting thickness of the root of the T root blade using said apparatus in accordance with the present invention;

Figure 7(a) illustrates a front view of base block of figure 6;

Figure 7(b) illustrates a top view of base block of figure 7(a);

Figure 8(a) illustrates a front view of dial gauge holding block of figure 6;

Figure 8(b) illustrates a bottom view of dial gauge holding block of figure 8(a);

Figure 9(a) illustrates a front view of perpendicularity maintaining block of figure 6;

Figure 9(b) illustrates a top view of perpendicularity maintaining block of figure 9(a); and
Figure 10 illustrates a method of calculation of thickness of the root of the T root blade at a predefined distance from one end of the root of the T root blade.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:
Figure 6 illustrates a front view of an apparatus and method of inspecting thickness of the root of the T root blade using said apparatus.

In accordance with the present invention, there is provided an apparatus 100 for inspecting thickness of the root of the T root blade comprising a base block 12, a dial gauge 14, a dial gauge holding block 16, a perpendicularity maintaining block 18, two dowel pins 20 and allen screws 22.

Figure 7(a) illustrates a front view of base block.

Figure 7(b) illustrates a top view of base block.

The base block 12 is of rectangular cross-section having a length of 192mm, breadth of 90mm and height of 59mm and is generally indicated by reference numerals X2, Y1 and Z3 respectively. Three equidistantly spaced holes H2 separated by a distance of 12mm, are provided on top surface of the base block 12, to a depth of 35mm, at a distance of 16mm from the edge of the base block 12 and is generally indicated by reference numerals Y2, Z4 and X3 respectively. The central hole of the equidistantly spaced holes H2 is threaded and has a diameter of 10mm and is generally indicated by a reference numeral D1. The other holes of the equidistantly spaced holes H2 on either side of the central hole has a diameter of 5mm and is generally indicated by a reference numeral D2. Two slots S1 of 8mm width and 3mm depth are provided on the top surface of the base block 12 along its breadth as shown in figure 7(a) and 7(b) and is generally indicated by reference numerals X4 and Z5 respectively.

Figure 8(a) illustrates a front view of dial gauge holding block.

Figure 8(b) illustrates a bottom view of dial gauge holding block.

The dial gauge holding block 16 is of L-shaped cross-section having length of 72mm, width of 38mm and height of 50mm and is generally indicated by reference numerals X5, Y3 and Z6 respectively. The height of the leg L of the dial gauge holding block 16 from the base B of the dial gauge holding block 16 is of 33mm and is generally indicated by a reference numeral Z7. A through hole H3 is provided on the leg L of the dial gauge holding block 16 at a distance of 20mm from the base B of the dial gauge holding block 16 and is generally indicated by a reference numeral X6. A through slot S2 is provided from the periphery of the hole H3 to the end of the dial gauge holding block 16 along its height as shown in figure 8(b). A hole H4 is provided from one side face to other side face of the dial gauge holding block 16 along its width, passing through the slot S2 of the dial gauge holding block 16 as shown in figure 8(a) and 8(b).The hole H4 is provided with threads at the distal end of the dial gauge holding block 16 adjoining the slot S2. Three equidistantly spaced holes H5 complementary to threaded holes H2 of the base block 12 are provided on the bottom surface of the dial gauge holding block 16. The central hole of the equidistantly spaced holes H5 is a through hole whereas the other holes of the equidistantly spaced holes H5 on either side of the central hole are provided to a height of 35mm.

Figure 9(a) illustrates a front view of perpendicularity maintaining block.

Figure 9(b) illustrates a top view of perpendicularity maintaining block.

The perpendicularity maintaining block 18 has two projections P1 on its bottom surface adaptable to sit in the slots S1 of the base block 12. The side face of the perpendicularity maintaining block 18 adjoining the blank of T root blade is provided in such a way that it is perpendicular to the base B of the dial gauge holding block 16.

The construction of apparatus 100 for inspecting thickness of the root of the T root blade is as follows:
Two dowel pins 20 are inserted in to the extreme holes of equidistantly spaced holes H2 of the base block 12. The dial gauge holding block 16 is mounted on the base block 12 in such a way that the dowel pins 20 pass through the extreme holes of equidistantly spaced holes H5 of the dial gauge holding block 16. The dial gauge holding block 16 is locked in position to the base block 12 by means of allen screw 22 passing through complementary central holes of equidistantly spaced holes H2 and H5. The dial gauge 14 is inserted in to the hole H3 of the dial gauge holding block 16 and locked in position at a predetermined height from the base block 12 by means of allen screw 22 passing through hole H4 of the dial gauge holding block 16. The predetermined height is found out through mathematical calculation and the position of locking of the dial gauge 14 is determined by using slip gauges.

Figure 10 illustrates a method of calculation of thickness of the root of the T root blade at a predefined distance from one end of the root of the T root blade.
Typically, the predefined distance D3(=X6) is 20mm.

Typically, the angle of taper ? of the tapered face T of the T-root blade is 3 degrees.

Typically, the thickness Z1 of the root of the T root blade at one extreme end is 13.41mm.

The predefined distance D3, the thickness Z1 and the angle of taper ? may vary depending on size of T root blade.

The increment in the thickness of the root of the T-root blade I1 at the predefined distance due to angle of taper ? is calculated by using the formula:

Tan ? = Increment in thickness of the root of the T root blade I1
Predefined distance D3
Increment in thickness of the root of the T root blade I1 = Tan 3degrees* 20 =1.048mm.

The thickness Z3 of the root of the T root blade at a predefined distance of 20mm = the thickness Z1 of the root of the T root blade at one extreme end + Increment in thickness of the root of the T root blade I1 = 13.41 + 1.048 =14.458mm.

The method of inspecting the thickness of root of the T root blade using apparatus 100 is as follows:
Slip gauges of height 14.458mm is placed on the base block 12, below the dial gauge holding block 16. The dial gauge 14 is inserted in to hole H3 of the dial gauge holding block 16, made to touch on the slip gauges and fixed in that position. Now, the slip gauges are removed from the base block 12. The root of the T root blades is inserted below the dial gauge 14 and the thickness of the root of the blades is inspected, whether the thickness is within the tolerance limits of +/-20 microns of 14.458mm. If the thickness of the root of the T root blades is within the tolerance limits, then the blade is accepted and sent for assembly. If the thickness of the root of the T root blades is out of tolerance limits, then the blade is rejected and sent to rework or scrap.

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.