A DEVICE FOR HOLDING A TURBINE ENGINE BLADE FOR THE
PURPOSES OF MACHINING
The present invention relates to a device for
holding a turbine engine blade for the purposes of
5 machining.
A turbine engine blade comprises an airfoil that is
to be placed in a gas-flow passage, and a root that is to
be engaged in a slot in a disk. The airfoil and the root
are separated by a platform defining a portion of the
10 inside wall of the gas-flow passage.
When fabricating a blade, it is conventional to use
forging or casting to make an un-finished part having
dimensions that correspond to the finished dimensions, so
far as the airfoil-forming portions is concerned. In
15 contrast, the portion that is to form the root is no more
than a blank that needs to be machined in order to give
it its final shape and dimensions.
Once machined, the blade root still has projecting
edges of angles that need to be rounded or smoothed
20 during an operation referred to as fitting or radiusing.
A blade root is generally radiused manually by an
operator who machines the projecting edges using a
carbide bur or a brush, for example. Since that
radiusing operation is manual, dimensional differences
25 can appear from one blade to another or from one operator
to another.
If the radiusing of a blade root is performed in
insufficient or inaccurate manner (e.g. because the
projecting edge is not sufficiently rounded), fabrication
30 operations further downstream may suffer. This happens
in particular when shot blasting a poorly-radiused blade
root, since some of the beads of shot can be deformed by
an edge that projects too much. A projecting edge also
gives rise to stress concentrations that lead to
35 premature cracking of the blade root.'
~imensibnal differences between the blade roots can
also complicate assembling the roots in the slots of
disks.
Finally, manual radiusing operations are complex and
5 expensive.
Patent application FR 10/57384, in the name of the
applicant and not yet published, discloses a method of
radiusing blade roots with the help of a numericallycontrolled
machine. While they are being radiused, the
10 blades are held in' tooling comprising a support having
housings formed therein. The airfoil of the blade is
clamped between two jaws that are hinged together at one
end and fastened together at the other end with the help
of a first screw. The jaws have presser studs for
15 pressing against the blade. Once the blade is in place
between the jaws, a second screw provided on one of the
jaws serves to press the blade against the abovementioned
presser points. The jaws and the blade are
then mounted in a housing of the support and they are
20 held therein with the help of latches.
A plurality of blades can thus be mounted
simultaneously on the support of the tooling in different
housings, in order to be subjected to radiusing.
Nevertheless, installing and removing the blades is
25 time-consuming. Specifically, after radiusing, for
example, when it is desired to remove a blade, it is
necessary to move the latches, to withdraw the jaws
together with the blade from the housing in the support,
and to unscrew the second screw in order to be able to
30 withdraw the airfoil. from the jaws.
Also, such a mounting does not make it possible to
know accurately the position of the blade relative to the
support. Specifically, the jaws are mounted in the
housing of the support with a small amount of mounting
35 clearance such that, even if the blade is correctly
positioned on its presser points, it is not possible to
know exactly the position of the jaws (and thus of the
blade) relative to the support that constitutes a known
frame of reference.
A particular object of the invention is to provide a
solution to those problems that is simple, effective, and
inexpensive.
To this end, the invention proposes a device for
holding a turbine engine blade for the purposes of
machining, the device comprising a support having at
least one housing in which at least one block is mounted
in removable manner, said block presenting an opening for
mounting an airfoil of a blade and having at least six
presser points for pressing against the airfoil, the
device being characterized in that it has a movable
presser finger for pressing against a pressure side
surface or a suction side surface of the blade, the
finger being moved by actuation means in such a manner
that in a blade clamping position, the presser finger
presses the blade against the presser points of the
block, which itself is pressed against the support.
This makes it easier to install and remove a blade.
Specifically, for mounting purposes, it suffices to
insert the blade in the opening in the block (which may
already be mounted in the housing in the support), and
then to actuate the presser finger so that the blade and
the block are pressed respectively against the presser
points and against the support in such a manner as to
fasten them on the support. To remove the blade, it
suffices to actuate the presser finger in the opposite
direction so that the blade can be withdrawn from the
block.
There is therefore no need to remove the block from
the housing in the support, nor is there any need to
tighten or loosen one or more screws, as is necessary in
the prior art.
Also, the position of the block relative to the
support is known exactly since the block is pressed
against a reference surface of the support. The
positions oi the airfoil and of the blade root can
therefore be determined with great accuracy, thereby
improving the quality of the radiusing that is performed.
Consequently, the airfoils of the blades as radiused in
this way can be correctly positioned inside the gas-flow
passage.
According to another characteristic of the
invention, the presser points are formed by studs, e.g.
removable studs, having ends for coming into contact with
the blade that do not have any sharp edges, and that are
hemispherical, for example.
This characteristic makes it possible to avoid the
airfoil being subjected locally to stresses that are too
great and that could cause its material to recrystallize,
which would degrade its mechanical characteristics.
When it is desired to radius another type of blade,
it is possible merely to change the presser points while
conserving the same block, thereby adapting the positions
of the presser points to the shape of the airfoil.
Naturally, it is also possible to change the block,
should that be found to be necessary.
Advantageously, the block has an internal wall
defining the opening for mounting the airfoil, from which
wall there project: first, second, and third mutually
spaced-apart studs for pressing on a leading edge of the
blade or close thereto; a fourth stud for pressing on a
trailing edge of the blade or close thereto; a fifth stud
for pressing in register with the movable presser finger;
and a sixth stud for pressing against a platform of the
blade.
It should be observed that none of the studs presses
against the blade root, thereby making it easier to
radius. The position of each of the above-mentioned
studs also makes it possible to hold the blade in
position effectively and accurately.
Preferably, the block has two studs for pressing
against the platform of the blade before the blade is
clamped by the movable presser finger, the platform being
spaced apart from said studs after the blade has been
clamped.
The two above-mentioned studs serve to pre-position
5 of the blade before clamping and they make it possible to
avoid the airfoil pivoting into a wrong position during
clamping by means of the movable presser finger.
In an embodiment, the block includes a hole for
passing the movable presser finger.
10 By way of example, the block is formed of two jaws
that are hinged to each other at one end and fastened to
each other at another end. I
Also, the means for actuating the movable presser
finger may comprise a cam fitted with an actuation
15 handle, and turning the cam with the help of the handle
causes the movable presser finger to move.
Under such circumstances, the device may include an
abutment suitable for limiting the angular stroke of the
actuation handle.
20 In advantageous manner, the support includes a
plurality of housings, each for mounting a respective
block and blade.
A plurality of blade roots can then be radiused in a
single operation.
25 According to another characteristic of the
invention, the support includes means for retaining the
block inside the corresponding housing, such as latches.
The block can thus be held in the housing of the
support even when the bearing 'finger is in the release
30 position.
The invention can be better understood and other
details, characteristics, and advantages invention appear
on reading the following description made by way of
nonlimiting example and with reference to the
35 accompanying drawings, in which:
Figure 1 is a perspective view of a blade holder
device of the invention;
~ i ~ u r2 ei s a perspective view on a larger scale
of a portion of the support;
Figure 3 is a view on a larger scale and in
perspective of a housing of the support in which two jaws
5 are mounted;
Figure 4 is a perspective view of one of the jaws;
Figure 5 is a perspective view of the other jaw
and of a presser finger;
Figure 6 is a perspective view of the machine and
10 of the presser finger of Figure 5, together with the cam
for actuating said presser finger;
Figures 7 and 8 are diagrammatic plan views
showing a portion of the device and of a blade,
respectively before and after clamping the blade;
15 Figures 9 and 10 are perspective views showing a
portion of the device, respectively before and after
clamping;
Figures 11 and 12 show the positions of the
presser studs relative to the blade; and
20 Figure 13 is a view on a larger scale also showing
the position of two temporary presser studs of the
platform of the blade, before clamping the blade with the
movable presser finger.
Figure 1 shows a device for holding a turbine engine
25 blade for machining purposes, in particular for
radiusing. The device comprises a support 1 of generally
rectangular shape that is movable in rotation about its
longitudinal axis A. The support 1 is mounted in
bearings at its two ends 2, 3, one of these ends 2 being
30 driven in rotation by an electric motor 4 and control
means.
In the embodiment of Figure 1, the support 1 has
four housings 5 of generally square shape opening out on
either side of the support 1 in surfaces referred to
35 below as a top surface 6 and a bottom surface 7, with
"top" and "bottom" being relative to their position shown
in Figure 1.
As can 'be seen more clearly in Figure 2, the inside
walls 8 of the housings 5 have longitudinal projections 9
for forming abutments that are arranged at the bottom
ends of the housings 5 and that are situated facing each
5 other.
The support 1 is also fitted with latches 10
arranged at the top ends of the housings, the latches 10
being movable between an unlocking position (Figure 2) in
which they are fully received in recesses 11 of the
10 support 1, and a locking position (Figure 3) in which
they extend across the corresponding housing 5.
The support also includes a cam 12 that is received
in a recess 13 of the support 1. The cam 12 is
cylindrical in shape and is mounted to pivot on the
15 support 1 about an axis B that is offset from the
geometrical center of the cam 12. In this way, the cam
12 can pivot between a retracted position (Figure 2) in
which it is fully received in the above-mentioned recess
13, and a deployed position in which it extends across
20 the housing 5.
The cam 12 has a cylindric'al stud 14 extending
upwards along the axis B, with the free end thereof
including a flat 15 for inserting in a hole 16 of
complementary shape in a handle 17 for actuating the cam
25 12.
The top end of the stud 14 does not project beyond
the top plane of the support 1. A lateral recess 18 is
also made in the top surface 6 of the support 1 so as to
allow the handle 17 to be mounted on the stud 14 of the
30 cam 12 and also so a.s to allow the handle 17 to move
angularly in order to drive the cam 12. An abutment 19
(Figures 9 and 10) may also be provided on the support 1
so as to limit the stroke of the handle 17. By way of
example, this abutment may be formed by the head 19 of a
35 screw.
While it is not in use, the handle 17 may be
received in a lateral recess 20 of the support, and it
may be held in the recess by means of a latch 21 similar
to the latches 10.
The device of the invention also includes at least
two jaws 22, 33, that can be seen in Figures 3 to 8.
5 A first jaw 22 is shown in Figure 4. In plan view,
this jaw is generally L-shaped and has a top surface 24,
a bottom surface 25, two lateral surfaces 26, 27 forming
substantially a right angle, and first and second lateral
ends 28, 29.
10 The lateral ends 28, 29 are connected together via
an internal wall 30 from which there extend studs that
are to come against a suction side surface 33 of an
airfoil 34 of a blade 35.
More particularly, there project from the internal
15 wall 30: first and second mutually spaced-apart studs 31
and 32 for pressing against the suction side surface 33
of the airfoil 34 close to a leading edge 36 of the blade
35; a third stud 37 for pressing against said suction
side surface 33 close to a trailing edge 38 of the blade
20 35; and a fourth stud 39 for pressing against a middle
zone of the suction side surface 33 in register with a
movable presser finger that is described below. The stud
39 is not shown in Figures 9 and 10. A fifth stud 40
projects from the top surface 24 of the first jaw 22 and
25 is for pressing against a platform 41 of the blade 35
(Figure 11).
As can be seen in particular in Figures 5 and 6, in
plan view, the second jaw 23 is also generally L-shaped
and has a top surface 24, a bottom surface 25, two
30 lateral surfaces 26 and 27 forming substantially a right
angle, and first and second lateral ends 28, 29.
The lateral ends 28, 29 of the second jaw 23 are
connected together via an internal wall 30 from which
there extends a stud 42 that is to press against the
35 suction side surface 33 of the blade 35, in the vicinity
of the leading edge 36 of the blade 35.
The stuhs 31, 32, 37, 39, 40, and 42 to form six
reference presser points enabling the blade 35 to be
properly positioned in the jaws 22 and 23.
The second jaw 23 also has a hole passing
5 therethrough, opening out in the wall 30 and for use in
mounting a presser finger 43 that is to press via a first
end 44 (Figure 6) against the cam 12, and via a second
end 45 against the pressure side surface 46 (Figure 12)
of the airfoil 34 of the blade 35, substantially in
10 register with the stud 39. The second end 45 of the
presser finger 43 presents a rounded surface matching the
pressure side surface 46 in the corresponding pressing
zone.
The movable presser finger 43 is slidably mounted in
15 the second jaw 23 to move between a release position in
which it does not press against the pressure side surface
46 of the.airfoi.1 34, and a clamping position in which it
presses against this surface 46. The movable finger 43
is caused to slide by the cam 12 turning between its
20 retracted and deployed positions. The presser finger 43
may be returned to its release position manually or with
the help of resilient return means, e.g. with the help of
a spring.
In a variant (not shown), the presser finger 43 may
25 be pivotally mounted on the jaw 23 to pivot between a
release position and a clamping position.
Two mutually spaced-apart studs 48, 49 also project
from the top wall 24 of the second jaw 23, and they come
to press against the platform 41 of the blade 35, prior
30 to the blade 35 being clamped by the movable presser
finger 43, as described in greater detail below. These
studs 48, 49 are not shown in Figures 11 and 12 in order
to make the drawings more readable.
The studs 31, 32, 37, 39, 40, 42, 48, and 49 and the
35 presser finger 43 may be removable so as to enable them
to be changed in order to adapt to airfoils 34 of
different shapes or dimensions. The ends of the studs
pressing against the airfoil 34 do not have any sharp
edges, and by way of example they may be hemispherical or
frustoconical.
The first ends 28 of the jaws 22, 23 form a hinge
5 enabling the jaws to be opened and closed by pivoting
about an axis, which is constituted by a screw 50
(Figure 3). The second ends 29 of the jaws 22, 23 may be
fastened to each other via a screw mounted in a hole 51
of the second jaw 23 (Figure 5) and screwed into tapping
10 . 52 in the first jaw 22 (Figure 4). Once the jaws 22 and
23 have been fastened together they form a block 53 that
is shown diagrammatically in Figures 7 and 8. In these
diagrammatic figures, only the presser studs 31 and 37
are shown, and they are not represented pictorially.
15 In a variant, the jaws 22 and 23 may be replaced by
a one-piece unit, without that modifying the operation of
the invention.
The operation of the de-vice is described below.
Prior to mounting a blade 35, a block 53 is mounted
20 in at least one of the housings 5 of the support 1. The
block 53 is made up of two jaws 22 and 23 that are
fastened together and that are fitted with presser studs
31, 32, 37, 39, 40, 42, 48, and 49 and with a movable
presser finger 43. The block 53 rests on the abutments 9
25 and is retained in the corresponding housing by the
latches 10. The cam 12 is in the retracted position and
the presser finger 43 is in the release position.
The airfoil 34 of a blade 35 can then be inserted in
the space defined between the jaws 22 and 23 of the block
30 53, until the platform 41 of the blade 35 presses against
the studs 48, 49 in provisional manner.
The cam 12 is then actuated by an operator using the
handle 17 so as to move the presser finger 43 towards its
clamping position. The presser finger 43 then presses
35 the blade 35 towards the studs 31, 32, 37, 39, 40, and
42, thus also pressing the block 53 back against the
inside wall of the housing 5 of the support 1. Thus, in
a single clamping action, the airfoil 34 of the blade 35
is held stationary by the presser finger 43 against the
block 53, which itself is held against the support 1.
The blade 35 can then be machined, and in particular
5 the blade root 54 can then be radiused, with the help of
a numerically-controlled machine, in the same manner as
in document FR 10/57384. The positioning of the presser
points, of the jaws 22, 23, and the turning of the
support 1 about its axis A give easy access to all of the
10 zones that are to be machined. Also, since the airfoil
34 is positioned accurately relative to the support 1, it
is also possible to perform the radiusing of the blade
root 54 accurately and in reproducible manner.
Naturally, an airfoil 35 may be mounted in each of
15 the housings 5 of the support 1, so that a plurality of
blades 35 can be radiused in a single operation.
The blade 35 is removed by turning the handle 17 and
the cam 12 in the opposite direction, thereby moving the
presser finger 43 towards its release position.
20 The block 53 and/or the studs 31, 32, 37, 39, 40,
42, 48, and 49, and the presser finger 43 may also be
changed easily, when it is desired to machine a blade of
a different type. Specifically, the positions of the
presser points may vary for each type of blade.
25

t; i; A'-'!'" ORIGINAL . .. qdi 1 3
12
CLAIMS
1. A device for holding a turbine engine blade (30) for
the purposes of machining, the device comprising a
support (1) having at least one housing (5) in which at
5 least one block (53) is mounted in removable manner, said
block (53) presenting an opening for mounting an airfoil
(34) of a blade (35) and having at least six presser
points (31, 32, 37, 39, 40, 42) for pressing against the
airfoil (34), the device being characterized in that it
10 includes a movable presser finger (43) for pressing
against a pressure side surface (46) or a suction side
surface (33) of the blade (35), the finger being moved by
actuation means (12, 17) so that in a position for
clamping the blade (35), the presser finger (43) presses
15 the airfoil (34) against the presser points of the block
(53), which itself is pressed against the support (1).
2. A device according to claim 1, characterized in that
the presser points are formed by studs (31, 32, 37, 39,
20 40, 42), e.g. removable studs, having ends for coming
into contact with the blade ( 3 5 ) that do not have any
sharp edges, and that are hemispherical, for example.
3. A device according to claim 2, characterized in that
25 the block (53) has an internal wall (30) defining the
opening for mounting the airfoil (34), from which wall
(30) there project: first, second, and third mutually
spaced-apart studs (31, 32, 42) for pressing against a
leading edge (36) of the blade' (35) or close thereto; a
30 fourth stud (37) for pressing against a trailing edge
(38) of the blade (35) or close thereto; a fifth stud
(39) for pressing in register with the movable presser
finger (43) ; and a sixth stud (40) for pressing against a
platform (41) of the blade (35).
35
4. A device according to claim 3, characterized in that
the block (53) has two studs (48, 49) for pressing
ORIGINAL 9 !p/ 5 9 4 !I'It,: .#3 1 3
' 13 #
1 0 DEC ?or?
against the platform (41) of the blade (35) before the
blade (35) is clamped by the movable presser finger (43),
the platform (41) being spaced apart from said studs (48,
49) after the blade (35) has being clamped.
5
5. A device according to any one of claims 1 to 4,
characterized in that the block (53) includes a hole for
passing the movable presser finger (43).
10 6. A device according to any one of claims 1 to 5,
characterized in that the block (53) is made up of two
jaws (22, 23) that are hinged to each other at one end
(28) and fastened to each other at another end (29) .
15 7. A device according to any one of claims 1 to 6,
characterized in that the means for actuating the presser
finger (43) comprise a cam (12) fitted with an actuation
handle (17), turning the cam (12) with the help of the
handle (17) causing the movable presser finger (43) to
20 move.
8. A device according to claim 7, characterized in.that
it includes an abutment (19) for limiting the angular
stroke of the actuation'handle (17).
25
9'. A device according to any one of claims 1 to 8,
characterized in that the support (1) has a plurality of
housings (5), each for mounting a respective block (53)
and blade (35). I 3 0
10. A device according to any one of claims 1 to 9,
characterized in that the support (1) includes retaining
means (10) for retaining the block (53) inside the
corresponding housing (5) .
35
. - - - . . . . . .. -,, . . ..-:... - - -.?, .>... <.. .---. -. ... .- . . . .. . .
~ a k d this 10/12/2013 . .
NEHA SRIVASTAVA
OF REMFRY & SAGAR ,
ATTORNEY FOR THE APPLICANTS