FIELD OF INVENTION
This invention relates to development of a special fixture for manufacturing of
seal wire used in fixing roots of gas turbine blades. More specifically the present
invention relates to modification of special fixture employed to manufacture the
seal wire by milling operation.
BACKGROUND OF THE INVENTION
In a gas turbine stationary nozzles discharge jets of expanded gas, usually
products of combustion, against the blades of a turbine wheels. To maintain
appropriate mechanical energy in a gas turbine to be converted into electrical
energy the root of the blade require proper sealing by seal wires. Such seal wires
are prepared by milling of round bar.
In the existing art the round job is held tightly in jaw of parallel vice and milling
operation is performed to achieve the desired shape. This process is crude and
the desired shape within desired tolerance is very difficult to achieve. As a
consequence the job rejection rate is very high due to high risk of slippage of the
job falling out of vice and also the seal wire cannot be milled properly within the
tolerance limit to prepare the seal wire with desired shape and accuracy of
dimensions. The said process therefore is thus time consuming and more
material consuming and therefore is not practicable for industrial use.
One of the disadvantage of the existing art is that during milling operation more
than half of the diameter of the round job is taken under the parallel vice holding
device for safe gripping. So size after milling operation is more than half
diameter of the job, as there will be a clearance between the cutter and vice to
avoid cut mark on a device.
The following disadvantages in milling of a round job will occur when the job is
held in parallel holding device by taking half of the diameter of the job.
d) Clamping will not be proper as the vice will not be capable of gripping safely
and there will be slippage of the job to cause accident.
e) Slippage of job causes rejection of job material.
f) A taper of 0.5 will appear lengthwise after milling operation.
The present invention proposes to remove the above disadvantages of prior art
by charging the mode of parallel vice and with provision of a special fixture.
DESCRIPTION OF THE INVENTION
The main objective of the invention is to develop fixture for round job wherein
the clamping force acts at an angle from horizontal line instead of parallel
gripping. The angular clamping force is divided into two-component force in
horizontal and vertical direction thus enhancing the grip and preventing the job
from coming out of the fixture.
Another objective of the invention is to fix a top clamp on the fixture to increase
productivity, enhance further safety.
A still another objective of the invention is to develop clamps of various types
and dimensions in the fixture which permits safe milling of any round job having
diameter less than or greater than 12 mm by easily charging the different types
of special clamp.
A still further objective of the invention is to develop a cost effective special
fixture with special clamps.
According to the invention there is provided a special fixture for manufacturing of
seal wire used in fixing roots of gas turbine blades comprising: a pair of special
clamps fixed in a block, the said clamps are operated by means of pins and
spring to hold a job in a groove and are adapted to move vertically up and down
and rotatable left and right hand side to grip the job in the groove axially or in
inclined position and milling the job to form a groove or portrusion in it to form a
seal wire for the fixing roots of gas turbine blade, the said fixture being
additionally arranged with a top clamp in case of high speed feed and deep cut
requirement, wherein the resultant force of the clamping grip of the job acts at
an angle from the horizontal line, thus enhancing grip on the job through division
of the acting force into horizontal and downward vertical directions and thus
preventing any slippage of the job.
The present invention will be better understood by the following description with
reference to the accompanying drawings in which
Figure 1 represents the acting force by parallel vice of the existing art; when
the grip is held less than half of the diameter of the job.
Figure 2 represents another case of the acting force by parallel vice of the
existing art, when the grip is held less than half of the diameter of
the job.
Figure 3 represents the acting force of the grip of the clamps at an angle from
the horizontal line according to the present invention.
Figure 4 represents (a) plan view (b) elevation view (c) side view and (d) end
view of the fixture for seal wire according to the present invention.
Figure 5 represents the (a) plan view (b) elevational view and (c) end view of
the base block body of the fixture developed according to the
present invention.
Figure 6 represents (a) plan view (b) elevational view, (c) end view of top
clamp of the fixture according to the present invention.
Figure 7 represents (a) elevational view (b) plan view and (c) cross sectional
elevatinal view with end view of the key of the fixture attached to the
base of the fixture of the present invention.
Figure 8 represents (a) elevational view (b) plan view of the top clamp screw
of the fixture of the invention.
Figure 9 represents (A) elevational (b) plan views of the special clamp of the
fixture according to the invention.
Figure 10 represents (a) elevational and (b) side views of the stopper of the
fixture according to the invention.
Figure 11 represents (a) actual view (b) plan view of the special washer of the
fixture of the invention.
Figure 12 represents an embodiment of the seal wire prepared with male and
female parts from a round job of 12 mm diameter.
Figure 13 represents an isometric view of the fixture according to the
invention.
The disadvantages associated with the parallel grip of the round job and the seal
wire to be prepared within the tolerance limit has been shown in Figure 1 and 2.
In the existing art if the operator has to make a thickness as (d/2 + 0.1) - 0.2,
where d = diameter of a rod, by milling operation, when the round job is held in
parallel vice, more than half of the diameter (d/2 + 0.5) is taken under the
holding device for safe gripping. So size after milling operation is more than (d/2
+ 0.5) as there should be clearance between a cutter and vice to avoid cut mark
on a device.
If the round bar is held by taking less than half of the diameter of a job in
parallel holding device, the operation will have to face the following adverse
situations.
As shown in Figure 1 gripping will be safe if clamping force passes through axis
of cross-section circular area of the round bar. As less than half of the diameter
is taken under vice, clamping would not be proper, vice is not capable of gripping
safely as there is definitely slippage of job that causes accident.
Figure 2 shows another case of gripping of less than half the diameter of a job.
Both in the case of positions of the grips result in slippage of a job, causes
rejection of job material and a taper of 0.5 appears lengthwise after milling
operation.
Figure 3 shows clearly the inventive concept of the present invention wherein
resultant force (F) of the clamping grip of the clamps acting at an angle from
horizontal line is divided into vertical and horizontal component. The horizontal
component provides a horizontal grip of the job and the vertical component acts
vertically downward direction to further enhance the grip and at the same time
secure the job from any slippage out of the fixture thus preventing any chance of
accident and wastage of job material from damage due to slippage and at the
same time saving wastage of time after mounting the job in the assembled
fixture to hold the job.
In Figure 3, numeral (G) shows the groove through which the job is to be
entered and gripped by the angular grip. This groove (G) according to the
invention is provided and formed in the fixture as shown in Figures 4(c), 4(d),
5(b), 6(a) and 13.
The top clamp (2) fixed to the fixture by a bolt M 12 x 60 (3) has an
hemispherical groove surface as shown in Figures 4(c) and Figure 6(a). The
resultant clamping force is applied through a clamp (7) which has basically
elliptical cam surface to press a washer (11) through which the clamping force is
transmitted, the clamp being moved vertically and left and right hand side
rotation fitted around a pin 6 x 16 (12).
The top clamp (2) is provided as an added mechanical to the fixture which not
only presses the round bar downwards by a spring plate (8) but also enhance
safety further. This top (2) clamp is required when situation arises to enhance
productivity coping up with high speed, feed and depth of cut.
It is to be construed that without the additional top clamp (2) the fixture with
clamp (7) is sufficient to mill the entire length of round bar in one setting. In that
case the top clamp is kept aside and milling operation is done alone by the clamp
provision.
The fixture is fixed in the floor table through V shaped grooves at two sides. The
entire fixture has splitted block portions (1) to provide a groove and joined in a
registered manner through screws M 10 (4), key (5), screws M 12 (6), and bolts
(13). A stopper (10) is provided at the base of the block (1) to firmly held two
plates (14) to ensure firm interconnections of the fixture and proper grip of the
job and to prevent any movement of the inter connected parts of the fixture
while a job is operated being held by the fixture.
The clamp (7) has spherical end portion (S) for hand gripping and the special
clamp works in pair through clamp screw (9).
Figure 12 shows as an embodiment how two jobs (one female and another male)
are milled to produce seal wire to seal the roots of gas turbine blade.
The female job (J) of 197.8 mm length taken from bottom corner to top corner
of other end, shown at bottom of Figure 12 is held at 15° from the axis of groove
(4), the middle portion as shown is milled with radious of curvature of R 10+ 0.2
tolerance. The grip of the job by a couple of special clamp is shown by A-A. The
cross sectional view of the milled job is shown at the bottom of Figure 12 by
turning the job by the clamps shown in the direction A-A. After milling the job's
curvature depth is of 6.0 - 0.2 mm.
Another job (male part) of 1 88 ± 0.2 mm length is shown at the top of Figure
12. The said job is cut lengthwise to maintain a protruded portion of 6.0 - 0.2
mm depth and 14.8 ± 0.2 breadth at the middle of the job. The said two finished
parts of the jobs are press fitted to constitute the seal wire at the roots of the
blades.
The invention as herein described and illustrated should not be construed in a
restrictive manner as various modification, embodiments and charges are
possible within the limit of the invention as defined in the appended claims.
WE CLAIM
1. A special fixture for manufacturing of seal wire used in fixing roots of gas
turbine blades comprising:
a pair of clamps (7) fixed in a block (1), said clamps being enabled to hold
a job (J) in a groove (G) by means of pins (12) and spring (9) and to
move vertically up and down, to rotate left and right hand side to axially
grip the job (J) in the groove (G) or in an inclined position, for forming a
groove or protrusion in the job (J) so as to form a seal wire for fixing
roots of the gas turbine blade, said fixture being additionally provided with
a top clamp (2) to cater for a high speed feed and deep cut requirement,
wherein a resultant force (F) of the clamping grip of the job (J) acting at
an angle from the horizontal line, to enhance the gripping on the job (J)
through distribution of the resulting force (F) in horizontal and downward
vertical directions which further prevents slippage of the job.
2. The fixture as claimed in claim 1 wherein the (J) job is held in a spherical
groove (G) by an angular grip by the clamps (7).
3. The fixture as claimed in claim 1, wherein the resulting clamping force by
the clamps (7) is transmitted through an elliptical cam surface of the
clamps.
4. The fixture as claimed in claim 1, wherein the top clamp (2) is fixed on
the top of the block body (1) by a bolt (3), and is enabled to press the job
(J) downwards by means of a spring plate (8) through a hemispherical
grip (G1) provided on the top clamp (2).
5. The fixture as claimed in the preceding claims wherein the groove (G) is
maintained on the fixture via at least two split block portions (1) which
forming the block (1) and releasably joined through a plurality of screws
(4 and 6), key (5) and bolts (13).
6. The fixture as claimed in the preceding claims wherein a stopper (10) is
provided at the base of the block (1) to firmly hold two plates (14) which
prevents any movement of the interconnected parts of the fixture while
the job (J) is being operated upon and held in the groove by the clamps
(7) or held by the combination of the clamps (7) and top clamp (2).
7. The fixture as claimed in claims 1 or 2, wherein the clamp (7) has a
spherical end portion (S) corresponding to the groove (G).
8. The fixture as claimed in the preceding claims wherein the seal wires are
produced from round bars in the form of male and female parts, which
are press fitted together to constitute the seal wire to be fixed at the roots
of the blades of gas turbine.
9. The fixture as claimed in the preceding claims wherein the clamps (7)
provide an angular grip instead of a parallel grip to the job (J), the job (J)
being milled in a single fixture setting to prevent any slippage of the job
(J).
10. A special fixture for manufacturing of seal wire used in fixing roots of gas
turbine blades, substantially as herein described and illustrated in the
accompanying drawings.

The invention relates to a special fixture for manufacturing of seal wire used
in fixing roots of gas turbine blades comprising a pair of clamps (7) fixed in a
block (1), said clamps being enabled to hold a job (J) in a groove (G) by
means of pins (12) and spring (9) and to move vertically up and down, to
rotate left and right hand side to axially grip the job (J) in the groove (G) or
in an inclined position, for forming a groove or protrusion in the job (J) so as
to form a seal wire for fixing roots of the gas turbine blade, said fixture being
additionally provided with a top clamp (2) to cater for a high speed feed and
deep cut requirement, wherein a resultant force (F) of the clamping grip of
the job (J) acting at an angle from the horizontal line, to enhance the
gripping on the job (J) through distribution of the resulting force (F) in
horizontal and downward vertical directions which further prevents slippage
of the job.