TOOLING FOR HOLDING A TURBINE ENGINE PART, AND INCLUDING
MEANS FOR FASTENING AND HOLDING STATIONARY BOTH THE PART
AND AN ELEMENT TO BE FASTENED ON SAID PART BY BRAZING OR
BY WELDING
5 The present invention relates to tooling for holding
a turbine engine part, e.g. for fastening a metal element
on said part by welding or by brazing, and the invention
also relates to a method of fastening a metal element on
I a turbine engine part by means of the tooling.
10 The present invention is particularly, but not
exclusively, adapted to using welding or brazing for
fastening a metal element such as a plate or a pellet on
a hollow blade of a turbine engine turbine.
A blade of this type comprises an airfoil connected
15 by a platform to a root of dovetail, Christmas-tree or
analogous type, for inserting in a slot of complementary
shape in a rotor disk of the turbine.
The blade has internal channels for passing a flow
of cooling air, which channels are formed during
20 fabrication of the blade by casting, in which a molten
metal alloy is cast around a ceramic core. The core
passes through a radially inner plane surface of the
blade root. After the cast material has cooled, the
ceramic core is removed or eliminated (e.g. by being
25 dissolved chemically), thereby leaving openings free in
the above-mentioned surface of the blade root. These
openings communicate with internal channels in the blade
and they can be used for feeding them with cooling air.
Nevertheless, they are of varying shapes and dimensions,
30 which means that it is not possible to optimize the rate
at which air flows in the channels in the blade.
I Proposals have already been made to fasten plates or
pellets on these blade root surfaces for calibration
purposes in order to limit and control the flow rates of
35 blade cooling air passing through the above-mentioned
orifices.
The pellets are generally circular in shape and are
designed to cover an above-mentioned opening in a blade
root surface in order to close it and thus prevent air
from passing into the channels in the blade through said
5 openings. Two or more pellets may be fastened to the
above-mentioned surface of a blade root.
Each plate is generally rectangular in shape for
covering nearly the entire surface of a blade root and it
includes calibrated orifices, i.e. each orifice has a
10 precise shape and dimensions, each communicating with a
respective one of the openings in the surface of the
blade root. Some of the openings in this surface are
plugged by the plate, while others communicate with the
calibrated orifices in the plate.
15 In the prior art, each plate or pellet is fastened
on the above-mentioned surface of the blade root by
brazing, where the brazing operation essentially consists
in depositing a filler metal between the plate and the
pellet or the surface of the blade root, and then in
20 placing the assembly in an oven raised to a temperature
that is high enough to melt the filler metal.
The brazing step is preceded by a step of tacking
the plate or the pellet, with such tacking being
performed manually by discharging a capacitor and serving
25 to hold the plate or the pellet stationary on the surface
of the blade root.
During those tacking and brazing steps, the blade
must be held stationary, since any movement of the blade
might lead to the blade being poorly positioned relative
30 to the element that is to be fastened, and might risk
damaging the blade. Likewise, the plate or the pellet
must be positioned and held stdtionary on the surface of
the part during the tacking step in order to prevent it
from moving on the surface and/or away from the surface.
35 In the prior art, the means used for holding the
blade stationary and for positioning a metal element on
the blade root do not enable the element to be accurately
positioned on the blade, nor do they enable the element
to be held stationary relative to the blade. They
therefore do not enable metal elements to be fastened on
blade roots in properly repeatable and reliable manner.
5 Numerous blades are rejected because of poor fastening
and poor positioning of elements on the roots of the
blades, and that represents a major financial loss.
A particular object of the invention is to propose a
solution to this problem that is simple, effective, and )I
10 inexpensive.
To this end, the invention provides tooling for
holding a turbine engine part in order to fasten a metal
element on the part, the tooling having first means for
fastening on the part and for holding it stationary, and
15 second means for positioning the element on the surface
of the part and for holding it stationary, the tooling
being characterized in that said second means are
removable and comprise a jig for mounting on a portion of
the part and including an opening for receiving the
20 element, at least a portion of the peripheral edge of the
opening in the jig co-operating with the element in order
to position it on the surface of the part, this
peripheral edge including at least one notch for passing
means for fastening the element on the surface by
25 tacking, the second means also including presser means
for pressing on the element in order to hold it against
the surface of the part.
The jig of the tooling of the invention enables the
metal element to be positioned with great accuracy on the
30 surface of the part, which may for example be a turbine
rotor blade. The jig has a through opening of a shape
that corresponds to the shape of the element. When a
rectangular plate is to be fastened on a blade root, the
opening in the jig is generally rectangular in shape and
35 of dimensions that are preferably substantially equal to
or slightly greater than the dimensions of the plate.
When a circular pellet is to be fastened on the blade
root, the opening in the jig is generally circular in
shape with a diameter that is preferably substantially
equal to or slightly greater than the diameter of the
pellet. When the element is engaged in the opening in
5 the jig, it is preferably pressed via its peripheral
edges against the peripheral edge of the opening so as to
avoid any movement of the element on the surface of the
part.
The peripheral edge of the opening in the jig has at
10 least one notch for passing fastener means, such as a
laser beam, for the purpose of tacking the element onto
the part. The laser beam is designed to pass through the
or each notch in order to form a tack weld between the
peripheral edge of the element and the surface of the
15 part. The peripheral edge of the opening in the jig may
have at least three mutually spaced-apart notches. Each
notch may be semicircular in shape.
The presser means for pressing on the element are
designed to hold the element against the surface of the
20 part in order to prevent it from separating therefrom and
moving away from the surface during tacking.
In an embodiment of the invention, these presser
means comprise elastically deformable blades or fingers,
each having one end pressing against the element and
25 another end mounted and fastened on said first fastener
means of the part.
The jig may have two openings for receiving
respective metal elements for fastening on the surface of
the part.
30 Advantageously, the jig has abutment-forming means
for co-operating with the part to hold the jig stationary
on the part. The 3ig may have keying means for
preventing the jig being wrongly mounted on the part.
Said first means may enable at least two parts of
35 the same type to be held and prevented from moving
simultaneously, and may comprise jaws comprising a
stationary central portion and lateral portions that are
movable in translation relative to the central portion,
each part being for mounting between a jaw of the
stationary portion and a jaw of one of the lateral
portions.
5 The presser means for pressing against an element
for fastening on one of the parts and the presser means
for pressing against another element for fastening on
another part are preferably secured to a common member
removably fastened on the central portion of said first
10 means.
The present invention also relates to a method of
fastening a metal element on a turbine engine part, using
the above-described part-holding tooling, the method
being characterized in that it comprises the steps
15 consisting in:
- holding at least one part stationary by using the
first means;
mounting the jig on the part and engaging the
element in the opening in the jig in order to position
20 the element on the surface of the part;
holding the element pressed against the part by
using the presser means;
fastening the element on the surface of the part
by laser tacking its peripheral edges through the above-
25 mentioned notches in the jig;
withdrawing the presser means and the jig; and
forming a bead of welding or brazing around the
entire perimeter of the element.
The invention can be better understood and other
30 characteristics, details, and advantages thereof appear
more clearly on reading the following description made by
way of non-limiting example and with reference to the
accompanying drawings, in which:
- Figure 1 is a diagrammatic perspective view of a
35 rotor blade of a turbine engine turbine;
Figure 2 is a diagrarrmatic perspective view of the
root of a rotor blade, having a plate fastened on a
surface thereof;
- Figure 3 is a diagrammatic perspective view of the
5 root of a rotor blade, having pellets fastened on a
surface thereof;
Figure 4 is a diagrammatic perspective view of
tooling of the invention for holding two rotor blades;
.I Figure 5 is another diagrammatic perspective view
10 of the Figure 4 tooling, without the rotor blades; '
Figure 6 is a diagrammatic perspective view on a
larger scale of a portion of the Figure 4 tooling, and it
shows the means for positioning and holding elements for
fastening on the roots of the blades;
15 - Figures 7 and 8 are diagrammatic perspective view
of jigs of the tooling of the invention;
Figure 9 is a diagrammatic perspective view of
presser means of the tooling of the invention; and
- Figure 10 is a diagrammatic perspective view of a
20 fastener screw of the Figure 9 presser means.
Reference is made initially to Figure 1, which shows
a rotor blade 10 of a gas turbine, and in particular of a
turblne engine such as an airplane turboprop or turbojet.
The blade 10 comprises an airfoil 12 connected to a
25 platform 14 and it has a suction side 16, i.e. a convex
outer surface, and a pressure side 18, i.e. a concave
inner surface that are connected together at their
upstream ends by a leading edge 20 and at their
downstream ends by a trailing edge 22.
30 The airfoil 12 of the blade is connected by the
substantially rectangular platform 14 to a root 24, which
is of 'the Christmas-tree type in the example shown, which
root 24 serves to mount the blade 10 on a rotor disk (not
shown) of the turbine by the root being engaged in a slot
35 of complementary shape in the periphery of the rotor
disk.
The blade 10 is internally ventilated and cooled by
means of a cavity or internal channels for passing a flow
of air extending parallel to the longitudinal axis A of
the blade 10 and fed via openings 26 that are open in a
5 plane end surface 28 of the blade root 24. In the
example shown, the surface 28 of the blade root has six
openings 26 that are in alignment one after another. Air
outlet slots 30 that are fed via the internal channels
are formed in a portion of the presser +side 16 close to
10 the trailing edge 22.
At least one plate 32 (Figure 2) or pellet 34
(Figure 3) is fastened the above-mentioned surface 28 of
the blade root by brazing or welding in order to
calibrate the flow rate of air passing along the internal
15 channels of the blade.
In Figure 2, the plate 32 is of elongate rectangular
shape with length and width that are slightly smaller
than the length and width of the surface 28 of the blade
root so that the plate covers nearly all of said surface.
20 The plate 32 is made of Hastelloy X, and by way of
example it has thickness of about 0.5 millimeters (mm), a
length of about 28 mm and a width of about 5 mm.
The plate 32 has four orifices 36, each for
communicating with one of the above-mentioned openings 26
25 in the surface 28 of the blade root. The four orifices
36 of the plate 32 thus communicate with four openings 26
in the surface 28, while the remaining two openings 26 in
said surface are closed by the plate 32. The four
orifices 36 in the plate are of predetermined dimensions
30 and shapes so as to determine accurately the flow rate of
air fed to the channels in the blade.
In Figure 3, two pellets 34 are fa'stened on the
surface 28 of the blade root by laser welding, each of
the pellets covering and closing one of the openings 26
35 in the surface 28.
Each pellet 34 is circular in shape and of a
diameter that is slightly greater than that of the
openings 26 in the blade root. By way of example, each
pellet 34 has a diameter of about 5.4 mm and a thickness
of about 0.5 rnm.
As described in greater detail below, the plate 32
or each pellet 34 is initially positioned on the surface
28 of the blade root and is then held stationary in that
position by laser tacking. To do this, at least one tack
weld is created, e.g. by a laser pulse, between the plate
32 or the pellet 34 and the blade. A bead of welding 38,
42 is subsequently made by laser welding along the entire
perimeter of the plate 32 or of the pellet 34. In a
variant, the plate 32 and the pellets 34 may be fastened
on the blade root by brazing.
The invention relates to tooling for taking at least
one rotor blade 10 as described above for the purpose of
fastening a plate 32 or pellets 34 on the surface 28 of
its root 24.
In the embodiment shown in Figures 4 to 9, the
tooling 100 serves to perform fastening simultaneously on
two rotor blades 10, 10' which are arranged side by side,
a plate 32 being for fastening on the root 24 of the
blade 10, and two pellets 34 being for fastening on the
root 24 of the other blade 10'.
The tooling 100 has first means 102, 104 for
fastening and holding stationary rotor blades 10, lo',
which first means are carried by a support 105, and
second means 106, 107, 108 for positioning and holding
stationary the plate 32 and the pellets 34 on the abovementioned
surfaces of the blade roots.
The support 105 is generally L-shaped and comprises
a bottom horizontal first plate for placing flat on the
ground or on a bench, and a vertical second plate that
extends upwards from the top surface of the first plate
(Figure 4) .
The two rotor blades 10, 10' held stationary by the
first fastener means 102, 104 may be for the same engine
or, as in the example shown, they may be different and
for use in different engines (e.g. one rotor blade 10 for
an engine of the MHP M88 type and another rotor blade 10'
for an engine of the MHP ~ ~ 4 o0r 0Sa M 146 type).
The above-mentioned first means of the tooling 100
5 have jaws formed by a central portion 102 fastened to the
support 105 and two lateral portions 104 that are carried
by the support 105 and that are movable in translation
along a common axis A, with the portions 102 and 104
being in alignment along this axis. The central portion
10 102 and the lateral portions 104 are situated in front of
the vertical second plate of the support 105, and above
the horizontal first plate of the support.
Each lateral portion 104 has a jaw 106 that is
situated facing a jaw 108 of the central portion 102 and
15 that can be moved towards or away from said jaw 108 by
moving the lateral portion 104 along the axis A.
The lateral portions 104 are urged towards the
central portion 102 by springs or the like. The lateral
portions 104 are secured to handles 109 enabling them to
20 be moved away from the central portion 102 by pulling
these handles along the axis A, the handles being on the
sides of the lateral portions that are remote from the
central portion 102. The lateral portions 104 may be
movably mounted on the support 105 by means of slideways
25 or the like (not shown).
Each rotor blade 10, 10' is mounted in the tooling
100 in such a manner that its root 24 is clamped between
the jaws 106, 108 of the central portion 102 and of one
of the lateral portions 104. The jaws 106, 108 are
30 shaped to fit closely to the shape of the blade root. In
the example shown, the blade rotors 24 are of the
Christmas-tree type and thgy have grooves in their
lateral faces (reference 50 in Figures 2 and 3) that
extend along the entire longitudinal dimension of each
35 root. The jaws 106, 108 are designed to be engaged in
these grooves 50, as can be seen in Figure 4.
With the blades 10, 10' in the mounted position, as
shown in Figure 4, the airfoil 12 of each blade extends
below the first means 102, 104 of the tooling 100 with
the suction side 18 thereof bearing against a surface 110
5 of complementary shape of a positioning block 112 carried
by the support 105.
The downstream radial face (reference 52 in
Figures 2 and 3) of the root 24 of each blade 10, 10' is
to come into abutment against a stud 114 carried by the t
10 support 105 so that the leading edge 20 of the blade is
situated towards the front of the tooling 100, towards
the operator. The stud 114 and the block 112 form keying
means for informing the operator when a blade 10, 10' is
not correctly mounted in the tooling. When the pressure
15 side of a blade 10, 10' is situated beside the surface
110 of a block 112, the leading edge 20 of the blade
comes into abutment against this surface and the blade
root cannot come into abutment against the stud 114,
remaining spaced apart from the stud, thereby warning the
20 operator.
The second means of the tooling 100 of the invention
comprise a jig 106, 107 for positioning the element(s)
for fastening on the surface 28 of the root of each blade
10, lo', and presser means 108 for pressing against those
25 elements in order to hold them against the surfaces 28
(Figure 6) .
The jig 106 in Figure 8 is for positioning a plate
32 of the above-mentioned type on the surface 28 of the
root of the blade 10. The jig 107 of Figure 7 is for
30 positioning two pellets 34 of the above-mentioned type on
the surface 28 of the root of the blade 10'.
The jig 106 is of substantially rectangular shape
and in its center it includes a through opening 116 of
shape similar to the shape of the plate 32, which plate
35 is rectangular in the example shown. The dimensions of
the opening 116 are substantially equal or slightly
greater than the dimensions of the plate 32. The jig 107
in Figure 7 differs from the jig in Figure 8 in that it
has two openings 117, each being circular in shape and of
diameter that is substantially equal to or slightly
greater than the diameter of a pellet 34.
5 Each jig 106, 107 includes engagement means for
engaging on the root of a blade 10, lo', these engagement
means comprising peripheral rims 118, 119, 119' extending
downwards and designed to co-operate with corresponding
portions of the blade root. In the example shown, each
10 jig 106, 107 has lateral peripheral rims 118 extending
along the long sides of the jig, and two end peripheral
rims 119, 119' extending along the short sides of the
jigs. The end rims 119, 119' of each jig are designed to
bear against the radial end faces of the blade roots 24.
15 One of the end rims 119' of each jig 106, 107 is
taller than the other end rim 119 so as to form keying
means designed to inform the operator in the event of the
jig being wrongly positioned. In the correctly mounted
position shown in Figure 6, the end rim 119' of each jig
20 106, 107 is positioned on the front of the tooling 100,
facing the operator. In the event of a jig being wrongly
mounted on the blade root, a rim 118 would be situated at
the rear of the tooling 100 and the above-mentioned stud
114 would prevent the jig from being properly engaged on
25 the blade root.
When the jig 106, 107 is in the mounted position,
the opening 116, 117 leaves free the zone(s) of the
surface 28 of the blade root for receiving the plate 32
or the pellets 34. The plate 32 and the pellets 34 are
30 designed to be engaged in the opening 116, 117 in the
jigs 106, 107 and to rest flat on the surfaces 28 of the
blade roots (Figure 6) .
The peripheral edge of the opening 116, 117 in each
jig 106, 107 has through notches 121 that define spaces
35 between the jig and each element for fastening (Figures 6
to 8). A laser beam is to be passed through each of
these spaces for tacking the element onto the surface of
the blade root.
By way of example, there are three, four, six, or
even more notches 121 per opening 116, 117, and the
5 notches are semicircular in shape in the example shown.
The notches 121 are spaced apart from one another and
they are regularly distributed.
The presser means 108 of the tooling 100 of the
invention are shown in Figures 6 and 9 and theyecomprise
10 elastically deformable fingers 122 that are fastened to a
member 124 at one of their ends, the other ends of these
fingers pressing against the plate 32 and the pellets 34
in order to hold them against the surfaces 28 of the
blade rotors.
15 In the example shown, the plate 32 is held pressed
against the root of the blade 10 by two fingers 122, and
each of the pellets 34 is held pressed against the root
of the blade 10' by means of a single finger 122
(Figure 6). The fingers 122 for holding the plate 32 and
20 the pellets 34 are secured to the common member 124,
which is releasably fastened to the central portion 102
of the above-mentioned first means.
The member 124 is rectangular in shape, the two
fingers 122 for holding the plate 32 being fastened on
25 one side of the member and the two fingers for holding
the pellets 34 being fastened to the opposite side of the
member. Each finger 122 is curved and is substantially
S-shaped (Figures 6 and 8).
Substantially in its center, the member 124 has an
30 opening 125 for engaging on a threaded rod 126 that is
secured to the central portion 102 of the first means of
the tooling 100 and that extends upwards (FigurGs 4 and
5). The member 124 is engaged on this rod 126 so that
the fingers 122 point towards the lateral portions 104 of
35 the first means of the tooling. The positions of the
fingers 122 carried by the member 124 and the spacing
between them are predetermined as a function of the type
of blade and the type of element to be fastened on the
root of each blade. In order to ensure that the fingers
122 are not wrongly mounted, the member 124 may include
keying means for co-operating with complementary means on
5 the central portion 102 of the tooling.
The member 124 may also have a visual marker, such
as an orifice 128, beside the above-mentioned opening 125
for the purpose of being brought into alignment with a
vi,sual marker, such as an orifice 132, in the central
10 portion 102 (Figures 4 and 9).
The member 124 is held against the central portion
102 of the tooling 100 by means of an internally threaded
nut 134 that is screwed onto the free end of the rod 126
carried by the central portion 102, until it presses
15 against the member (Figure 10).
The nut 134 is preferably of the quarter-turn type,
i.e. it can be screwed onto the rod 126 merely by turning
it through 90" about its axis in order to clamp the
member 124 against the central portion 102.
20 Advantageously, the nut 134 includes a visual marker,
such as a hole 136 that is to be situated beside a marker
128 of the member 124 when the nut is properly screwed
onto the rod 126 (Figures 9 and 10).
The tooling 100 of the invention may be used as
25 follows: the jaws 106, 108 of the tooling are spaced ,
apart from each other by moving the lateral portions 104
away from the central portion 102. Two blades 10, 10'
are mounted in the tooling 100 so that their suction
sides 18 press against the surfaces 110 of the blocks 112
30 and their roots press against the studs 114 of the
support 105, as shown in Figure 4. The lateral portions
10'4 are released so that their jaws 106 come to press
against the blade roots and hold them clamped against the
jaws 108 of the central portion 104. The jigs 106, 107
35 are mounted on the blade roots so that their rims 119'
are situated on the same side at the front of the
tooling. A plate 32 is inserted in the opening 116 in
the first jig 106 and a pellet 34 is engaged in each of
the openings 117 in the second jig 107. The member 124
supporting the fingers 122 is mounted on the central
portion 102 by engaging the rod 126 of the central
5 portion 102 in the opening 125 in the member 124 and by
bringing the orifices 128 and 132 in the member and in
the central portion respectively into alignment. The nut
134 is screwed onto the rod 126 until its hole 136 is
situated beside the orifice 128 in the member 124. In
10 this position, the free ends of the fingers 122 press
against the plate 32 and the pellets 34 so as to hold
them against the blade roots.
The plate 32 and the pellets 34 are prevented from
moving on the surfaces of the blade roots by laser
15 tacking, the laser beam being suitable for passing
through the notches 121, as described above. A tack weld
is created between the surface of the blade root and the
plate 32 or the pellets 34 by passing a laser pulse
through each of the notches 120. After these tack welds
20 have been made through all of the above-mentioned notches
120, the nut 134 is undone and the member 124 and the
jlgs 106, 107 are removed from the tooling 100. A bead
of welding 38, 42 is then made all around the perimeter
of the plate 32 and of each pellet 34 (Figures 2 and 3)
25 by laser welding, or else a bead of brazing is made, with
this being done with very good repeatability from one
part to another. ,
Naturally, the tooling of the invention may be
designed to receive a plurality of parts at the same
30 time, which parts may be identical or different, the
number of these parts possibly being two, three, or more.

CLAIMS
1. Tooling (100) for holding a turbine engine part (10,
10') in order to fasten a metal element (32, 34) to the
part, the tooling having first means (102, 104) for
5 fastening to the part and for holding it stationary, and
second means for positioning the element on the surface
of the part and for holding it stationary, the tooling
being characterized in that said second means are
+ removable and comprise a jig (106, 107) for mounting on a
10 portion of the part and including an opening (116, 117)
for receiving the element, at least a portion of the
peripheral edge of the opening in the jig co-operating
with the element in order to position it on the surface
of the part, said peripheral edge including at least one
15 notch (121) for passing therethrough means for fastening
the element on the surface by tacking, said second means
also including presser means (108) for pressing on the
element in order to hold it against the surface of the
part.
20
2. Tooling according to claim 1, characterized in that
the peripheral edge of the opening (116, 117) in the jig
(106, 107) includes at least three mutually spaced-apart
notches (121), e.g. each being in the form of a
25 semicircle.
3. Tooling according to claim 1 or claim 2, characterized I
in that the opening (116, 117) in the jig (106, 107)
presents a shape and dimensions that are similar to the
30 shapes and dimensions of the element (32, 34).
4. Tooling according to any preceding claim,
characterized in that the jig (107) has two openings
(117) for receiving respective metal elements (34) for
35 fastening on the surface of the part.
5. Tooling according to any preceding claim,
characterized in that the jig (106, 107) has abutmentforming
means (118, 119, 119') for co-operating with the
part to hold the jig stationary on the part, and/or
keying means (119') for preventing the jig being wrongly
mounted on the part.
6. Tooling according to any preceding claim,
characterized in that bhe part is a turbine rotor blade
(10, 10').
7. Tooling according to any preceding claim,
characterized in that the presser means (108) comprise
elastically deformable blades or fingers (122), each
having one end pressing against the element (32, 34) and
an opposite end mounted on and fastened to said first
means (102).
8. Tooling according to any preceding claim,
characterized in that said first means enable at least
two parts (10, 10') of the same type to be held and
prevented from moving simultaneously, and comprise jaws
comprising a stationary central portion (102) and lateral
portions (104) that are movable in translation relative
to the central portion, each part being for mounting
between a jaw (108) of the stationary portion and a jaw
(106) of one of the lateral portions.
9. Tooling according to claim 8, characterized in that
the presser means (122) for pressing against an element
(32) for fastening on one of the parts (10) and the
presser means (122) fo2 pressing against an element (34)
for fastening on another part (10') are secured to a
common member (124) removably fastened on the central
portion (102) of said first means.
ORIGINAL
17
10. A method of fastening a metal element (32, 34j on a
turbine engine part (10, 10') by means of the partholding
tooling (100) according to any preceding claim,
the method being characterized in that it comprises the
5 steps consisting in:
holding at least one part stationary by using the
first means (102, 104);
mounting the jig (106, 107) on the part and
engaging the element in the opening (116, 117) in the jig
10 in order to position the element on the surface of the
part;
- holding the element pressed against the part by
using the presser means (108);
fastening the element on the surface of the part
15 by laser tacking its peripheral edges through the abovementioned
notches (121) in the jig;
withdrawing the presser means and the jig; and
forming a bead (38, 42) of welding or brazing
around the entire perimeter of the element.