FIELD OF INVENTION
The present invention relates to a clamping device for machining external
fillet of cylindrical profiled bar type steam turbine blade on 3-axis CNC or 2-axis
conventional machines and a method for the same. More particularly this
invention relates to a clamping fixture used for external Fillet milling of cylindrical
profiled bar type blade.
BACKGROUND OF THE INVENTION
The guide blade TX of steam turbine is having different profile compare to
the profile of T4/T2 blades of the steam turbine. TX guide blade has less
rhomboid size compared to T4/T2 guide blades. Hence, external fillet milling of
TX guide blade was not possible with the existing fixture pad of T4/T2 blades
due to design restriction of fixture Pad. Hence, it was necessary to develop a
new fixture pad to carry out external fillet milling of TX guide blade on 3-Axis
CNC machine or 2-Axis conventional machines.
Due to less rhomboid size of TX Guide blades as compared to
corresponding T4/T2 Guide blades, blade was not fitting properly in the existing
fixture pad of T4/T2 Guide blades. It was necessary to invent a new fixture pad
which will allow all bar type blades (T4/T2/TX) to fit into the pad for machining
purpose.
Safe and quality machining of TX Guide Blades during external fillet milling
on 3-axis CNC or 2-axis conventional machines was another criteria behind this
invention. After this invention chances of accident on the machine is considerably
reduced because TX guide blade is now being clamped properly in the new
developed fixture pad during machining.

OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose a clamping device for
machining external fillet of cylindrical profiled bar type steam turbine blade on 3-
axis CNC or 2-axis conventional machines, which is capable of holding all bar
type (TX/T4/T2) steam turbine blades for machining of external fillet milling.
Another object of the invention is to propose a clamping device for
machining external fillet of cylindrical profiled bar type steam turbine blade on 3-
axis CNC or 2-axis conventional machines, which is capable of holding rigidly all
bar type (TX/T4/T2) steam turbine blades for a safe and quality machining
eliminating the chance of any accident.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS:
Fig. 1 : Shows the adjustable clamping device being controlled by nut and bolt to
accommodate all rhomboid size of blades according to the invention.
Fig.2 : Shows the old clamping device of prior art.
Fig.3 : Shows the gap existing in the old clamping device for TX guide blades
with less rhomboid size compared to T2/T4 guide blades.
Fig. 4 : Shows the clamping device according to the invention used for all type of
TX/T4/T2 guiding blades on a 3-Axis CNC machine or 2-Axis
conventional machine. It shows blade resting on new developed
clamping device.
Fig.5 : Shows the clamping device with base 'C' inclined to the faces A and B.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION:
Fig. 1 shows an adjustable clamping device (1) where the job of
rhomboidal profile is held in between the pre-determined gap (4) created by the
two parallel faces 'A' and 'B'. A portion of the guide blade is allowed to rest on
face 'C' of the clamping device (1). Face 'C' is milled inclined to faces 'A' and 'B'
as shown in Fig. 5 to accommodate the profile of the guide blades. The said
device is made either by milling a solid block of cast iron or can be fabricated
with few mild steel block and then milled to the required shape and size. A
threaded hole is made at the center of face 'A' for accommodating a matched
bolt (2) with nut (3). The bolt (2) and nut (3) is disposed on the clamping device
(1) for effecting control of adjustment of clamping size of guide blades of
turbine. Because of this adjustment facility provided on the clamping device (1),
guide blades of all rhomboid size such as TX, T4 or T2 can be accommodated
and clamped in the device (1). This newly developed clamping device thus
overcome the inherent problems of external fillet milling of cylindrical profiled TX
guide blade on 3-axis CNC machine or 2-axis conventional machine.
The invented clamping device has the ability to change its clamping size
as per requirement of the blade with the help of threaded bolt (2) and nut (3).
Because of the provision of bolt (2) and nut (3) the guide blades are held rigidly
with proper clamping and therefore chances of accident on the machine is
considerably reduced and a safe and quality machining of steam turbine blade
during external fillet milling results.

WE CLAIM
1. A clamping device (1) for machining external fillet of cylindrical profiled
bar type steam turbine blade on 3-axis CNC or 2-axis conventional machines, the
said device comprising;
a block (H) milled for forming a base (C), two parallel faces (A,B) suiting
the profile of guide blades (TX, T4, T2);
characterized in that,
face 'C' is machined inclined to the faces 'A' and 'B' for suiting the profile
of guide blades sitting on the said face (C) wherein a plurality of nuts and a bolt
are disposed at the middle of the face 'A' protruding in the gap (4) between the
faces 'A' and 'B' for adjustment of clamping size of guide blades and clamping of
the same.
2. A clamping device as claimed in claim 1, wherein the base 'C' of the said
device is inclined to the faces A and B for accommodating the profile of the guide
blades.
3. A clamping device as claimed in claim 1, wherein the said device (1) is
made of cast iron.

4. A method of machining of external fillet of cylindrical profiled bar type
steam turbine blade on 3-Axis CNC or 2-Axis conventional machine with the
clamping device (1) claimed in claim 1, comprising;
milling a block (H) to form two parallel faces (A,B) having a
predetermined gap (4);
milling the said block to form a face 'C' inclined to the parallel faces (A,B)
to accommodate the profile of the guide blades (Tx,T4,T2); wherein,
a threaded bolt and plurality of nuts are disposed in the clamping device
at the middle of the face 'A' protruding in the gap between the faces (A,B) to
adjust the clamping size of the guide blades.

ABSTRACT

A clamping device is made with two parallel faces (A,B) and a base 'C'
inclined to those faces (A,B) and formed in between the said parallel faces to
accommodate the profile of guide blades. A threaded hole is made in the middle
of the face 'A' to accommodate a threaded bolt and a nut disposed in the device
for adjusting the clamping size in between the parallel faces (A,B).