TECHNICAL FIELD
The present invention relates to a device fastening
5 at least one sensor on a part.
The fastener device of the invention is particularly
adapted for fastening a thermocouple, in particular to a
turbine casing in a turbine engine.
10 BACKGROUND OF THE INVENTION
In certain circumstances, it is necessary to place a
measurement sensor on a part in order to measure local
properties of the part or in the immediate vicinity of
the part, in particular while the device including the
15 part is in operation. For example, the sensor may be a
thermocouple that measures the temperature of a portion
of the part on which it is placed.
In order to take good measurements, it is necessary
to hold the sensor in a desired position relative to the
20 portion of the part.
At present, a fastener device is known that
comprises a plate that is fastened to the part by a
single fastener screw and that is provided, in the
vicinity of the screw, with a reception orifice for the
25 sensor, the scnsor generally being welded to the plate.
With such a fastener device, the tension applied to the
screw by the tightening torque may lead to the plate
lifting, allowing air to leak between the part and the
plate, and thus locally modifying the temperature on the
30 part and in its vicinity.
Another known fastener device comprises a plate
fastened to the part by two fastener screws, the sensor
itself being fastened to the plate between the two
screws. That fastener device, although more reliable, is
35 nevertheless greater in size than the previously-
+ Translation of the title as established ex o f f i c i o .
described device, and is thus difficult to fit on
existing structures, either because there is not enough
room to enable it to be integrated, or because the part
itself needs to be modified beforehand in order to
5 receive the device.
OBJECT AND SUMMARY OF THE INVENTION
The object of the present invention is to provide a
device that enables a sensor to be fastened on a part in
10 reliable manner, while overcoming the above-mentioned
drawbacks.
This object is achieved with a fastener device for
fastening at least one sensor, in particular a
thermocouple, to a part, the device comprising a first
15 fastener portion having fastener means for fastening to
the part and a second fastener portion provided with an
orifice for receiving the sensor, the device being
characterized in that it further comprises an elastically
deformable portion connecting together the first and
20 second fastener portions, the elastically deformable
portion being configured in such a manner as to pass from
a stable position to an unstable position when the first
fastener portion is fastened to a part, thereby pressing
the second fastener portion against the part.
2 5 The elastically deformable portion of the dcvice of
the invention is adapted to pass from a stable position
to an unstable position by bending. It can be understood
that the relative positioning of the first and second
fastener portions differs depending on whether the
30 elastically deformable portion is in its stable position
or its unstable position.
When it is in its unstable position, the elastically
deformable portion tends continuously to return towards
its stable position, i.e. to return the first and second
35 portions to their relative position at rest. Assuming
the first fastener portion is stationary - because it is
fastened to the part - the force tending to return the
elastically deformable portion to its stable position is
applied to the second fastener portion that remains free.
Since the second fastener portion is in abutment against
the part, this force is maintained in the form of
relatively uniform continuous contact pressure around the
sensor and acting between the second fastener portion and
the part.
By deformation of the elastically deformable portion
during assembly on the part, the fastener device is thus
subjected to pre-loading that prevents the second
fastener portion lifting off the part. It is thus
possible to take measurements with the sensor, while
avoiding any leaks at the interface between the sensor
and the surface on which it is fastened.
Also, because of the above-specified 'provisions, the
device of the invention can be used with a single
fastener screw, thus making it possible to make it more
compact and easier to integrate in existing structures.
Finally, since the fastener device of the invention
presents a degree of springiness, it can be used on
surfaces that present non-negligible amounts of local
deformation, e.g. on turbine engine casing surfaces that
present large amounts of deformation in use.
In an example, the elastically deformable portion
comprises at least one spring blade.
In an example, the elastically deformable portion
includes a return extending away from a portion of the
spring blade that is spaced apart from the first fastener
portion (e.g. and in non-limiting manner, its end remote
from the first fastener portion), towards said first
fastener portion, and the second fastener portion is
secured to the return.
In an example, the elastically deformable portion
comprises two spring blades that are spaced apart from
each other.
Under such circumstances, the return advantageously
extends between the two spring blades.
In an example, the second fastener portion has a
substantially plane secondary bearing surface that is
adapted to come into contact with the part.
Advantageously, the secondary bearing surface
surrounds the sensor once it has been mounted in the
reception orifice, whereby a continuous contact pressure
zone can be obtained around the sensor after it has been
mounted on the part.
In an example, the first fastener portion also has a
subst.antially plane primary bearing surface that is
adapted to come into contact with the part.
In an advantageous provision, the primary and
secondary bearing surfaces are substantially parallel
when the elastically deformable portion is in its stable
position.
In an example, when the elastically deformable
portion is in its stable position, the secondary bearing
surface is spaced apart from the primary bearing surface
in a direction substantially orthogonal to the primary
bearing surface, going away from said first fastener
portion. It is thus ensured that the elastically
deformable portion deforms when the device is fastened on
a substantially plane support surface of a part.
In an example, the second fastener portion comprises
a reception ring for receiving the sensor and fastened to
the elastically deformable portion, and the secondary
bearing surface is a surface of said ring.
By way of example the reception ring is a sealing
ring for providing sealing around the sensor when the
second fastener portion is pressed against the part.
In an example, the first fastener portion and the
elastically deformable portion form an integral unit, in
particular obtained by being cut out from sheet metal.
The invention also provides an assembly comprising a
fastener device as defined above together with a sensor,
in particular a thermocouple, secured to the second
fastener portion.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention can be well understood and its
advantages appear better on reading the following
5 detailed description of an embodiment shown as a nonlimiting
example. The description refers to the
accompanying drawings, in which:
Figure 1 is a perspective view from above of a
fastener device in a first embodiment of the invention,
10 in its initial state;
Figure 2 is a perspective view from above of the
Figure 1 device in section on its plane of symmetry P;
Figure 3 is a perspective view from below of the
Figure 1 device;
15 Figures 4 and 5 show steps of fastening a sensor
on a part using a device as shown in Figures 1 to 3, the
device being shown in section on 11-11 of Figure 1;
Figure 6 is a perspective view from above of a
fastener device in a second embodiment of the invention,
20 in its initial state;
Figure 7 is a perspective view from beneath of the
Figure 6 device in section on its plane of symmetry P;
and
Figures 8 and 9 show steps of fastening a sensor
25 on a part using a device as shown in Figures 6 and 7, the
device being shown in section on 11-11 of Figure 1.
DETAILED DESCRIPTION OF AN EMBODIMENT
Figures 4 and 5 are diagrams showing, in section
30 view, a portion 80 of a part on which it is desired to
fasten a sensor 90. In the example shown, this portion
80 is a plate of thickness - e.
For example, the part is a turbine casing, and the
property that it is desired to measure using the sensor
35 90 is the temperature inside said turbine. The sensor
used is thus a thermocouple with a measurement end 90a,
where the measurement is taken, that needs to be
positioned at the location desired for this measurement,
in other words inside the turbine.
Advantageously, the thermocouple 90 is fastened so
as to pass through the part 80 via an orifice 84 formed
5 in said part 80, its measurement end 90a projecting into
the inside of the part 80, and its opposite end gob,
generally connected to means for reading the result (no-t
shown), being arranged on the outside of the part 80.
Figures 1 to 3 show in greater detail a device 100
10 of the invention suitable for being used for fastening a
sensor 90, as described above, on a part 80.
In this example, the fastener device 100 comprises a
first fastener portion 10 provided with means for
fastening the device to the part 80, a second fastener
15 portion 40 provided with an orifice for receiving the
sensor 90, and an elastically deformable portion 20
connecting together the first and second fastener
portions.
In Figures 1 to 3, the elastically deformable
20 portion 20 is in a stable position corresponding to a
state in which no external force is being applied
thereto.
In an example, the first fastener portion 10 is in
the form of a plate 12 defined by two main surfaces, a
25 bottom surfacc 12a and a top surface 12b, which silrfaces
extend substantially orthogonally to a transverse
direction Z.
The bottom surface 12a of the first fastener portion
10 in this example forms a primary bearing surface 12a
30 for bearing against the part when the device is mounted.
In this example, the fastener means include a
fastener orifice 14 passing right through the first
portion and extending in a direction that is orthogonal
to the two main surfaces 12a, 12b. As is described in
35 greater detail below, the fastener orifice 14 is for
receiving a fastener screw 70 enabling the device to be
anchored to the part. Nevertheless, the example shown is
not limiting, and in variants, the fastener means may
comprise a plurality of fastener holes and/or other means
enabling the device to be fastened to the part.
As described below, the device 100 of the invention
5 nevertheless presents the advantage of providing
fastening that is reliable even when it is fastened at a
single point (in particular by a single fastener screw).
In order to facilitate understanding the figures,
the primary bearing surface 12a and all of the surfaces
10 of the device 100 that are to face the part are shown
lightly shaded.
It should be observed that the fastener device 100
presents symmetry about a plane P shown in Figure 1.
In this example, the fastener orifice 14 is thus in
15 alignment with the plane of symmetry P.
Below, and unless specified to the contrary, a
lateral direction Y of the device is defined as a
direction orthogonal to the transverse direction Z and to
the plane of symmetry P, and a longitudinal direction X
20 is defined as being a direction orthogonal to the lateral
and transverse directions Y and Z.
In this example, the elastically deformable portion
20 comprises two flexible branches 22 and 24 forming
spring blades that extend from the first portion 10.
2 5 More particularly, each spring blade 22, 24 is
connected to a respective lateral end of the first
portion 10. In a plane orthogonal to the transverse
direction Z, the two spring blades 22, 24 extend from the
first fastener portion 10 in the longitudinal direction X
30 and they form the branches of a U-shape, with the first
portion constituting the base of the U-shape.
In this example, the two blades 22 and 24 are
substantially parallel, being spaced apart from each
other transversely by an empty space 26 of width L1.
35 It can be understood that the spring blades 22, 24
are suitable for flexing so that their ends 22b, 24b
remote from the first portion move relative to said first
portion 10, in particular by tilting relative to a plane
orthogonal to the transverse direction Z (see Figure 5),
thus bringing the elastically deformable portion 20 into
an unstable position.
In this example, the elastically deformable portion
20 also has a return 32, of width L2 that is strictly
less than L1 and that extends in this example from the
respective end 22b, 24b of each spring blade 22, 24
remote from the first fastener portion 10 towards said
first fastener portion 10.
The return 32 thus extends in the empty space 26
that is defined laterally by the spring blades 22, 24.
In this example, when the elastically deformable
portion 20 is in its stable position as shown in
Figures 1 to 3, the return 32 is defined by two plane
main surfaces, a bottom surface 32a and a top surface
32b, which surfaces extend orthogonally to the transverse
direction 2 . From Figures 4 and 5, it can be understood
that the bottom surface 32a is to be placed facing the
surface 82 of the part 80, after assembly.
In this example, the first portion 10, the spring
blades 22, 24, and the return 32 are made as a single
piece. These elements constitute an integral unit that
can be obtained in particular by being cut from sheet
metal.
The respective top surfaces 12b, 32b of the first
portion 12 and of the return 32 are substantially
coplanar in this example, as are their bottom surfaces
12b, 32b.
As shown in Figures 1 to 3, the return 32 includes
an opening 34, into which there is inserted a reception
ring 36 for receiving the sensor.
As shown in Figures 2, 3, and 4 in particular, the
reception ring 36 projects from the bottom surface 32a of
the return 32, over a distance Dl.
The reception ring 36 thus has a surface 36a (its
bottom surface), that is offset relative to the primary
bearing surface 12a in the stable position of the
elastically deformable portion 20 as shown in Figures 1
to 3 and that is to be pressed against the surface of the
part during assembly.
5 The primary and secondary bearing surfaces 12a, 36a
are defined in two parallel planes that do not coincide,
being offset in the transverse direction Z.
In this example, the opening 34 in the return and
the ring 36 form a second fastener portion 40.
10 In this example, the reception ring 36 forms a
sealing element for providing sealing around the sensor
after assembly.
In this example, the reception ring 36 is in the
form of a cylindrical sleeve of outside profile that is
15 complementary in shape to the inside wall of the opening
34 and of inside profile that is configured to receive
the sensor 90. By way of example, the sensor 90 may be
fastened to the reception ring 36 by welding or as a
shrink fit.
2 0 At one of its ends, the reception ring 36 has an
outer collar 38 that is engaged in an annular recess 35
of corresponding shape made around the opening 34 in the
bottom surface of the return 32.
In this example, in order to ensure that it projects
25 as mentioned above, the height of the outer collar 38 is
slightly greater than the depth of the annular recess 34,
which height and depth are measured in the transverse
direction Z.
An assembly comprising a device 100 as described
30 above and a measurement sensor 90 previously fastened to
the device 100 is fastened in the manner described below
with reference to Figures 4 and 5.
The part 80 onto which the sensor is to be fastened
is shown in Figure 4. In this example, its support
35 surface 82 that is to receive the device 100 is plane.
When the fastener device 100 is moved towards the
surface 82 of the part 80 (with its transverse direction
Z extending substantially orthogonally to said surface
82, for example), the secondary bearing surface 36a comes
into abutment against the support surface 82, before the
first portion 10 comes into contact with said surface 82.
5 When the first portion 10 is moved even closer to
the support surface 82, with the second portion 40 being
held in abutment against this surface, the elastically
deformable portion 20 deforms progressively and leaves
its stable position.
10 The first fastener portion 10 is then fastened to
the part 80, e.g. by means of a screw 70 engaged in the
fastener hole 14 and screwed into the surface 82.
In this position, the return force from the
elastically deformable portion 20, which tends to return
15 it towards a stable position, becomes applied to the
second fastener portion 40. This second portion 40 is
then continuously urged elastically towards the part 80,
maintaining relatively uniform contact pressure around
the thermocouple between the secondary bearing surface
20 36a and the support surface 82 of the part 80, and
compatible with providing sealing by contact.
Because of the relatively uniform contact pressure
provided around the sensor, the sealing between the ring
36 and the part 80 may take place merely by contact, and
25 the constraints on surface roughness and on plancriess for
the remainder of the fastener device, and in particular
for the return 32 and for the spring blades 22, 24, are
reduced.
A fastener device 200 in a second embodiment of the
30 invention is described below with reference to Figures 6
to 9.
In these figures, elements that are similar or
identical to those described with reference to the first
embodiment are designated by the same numerical
35 references as in Figures 1 t o 5, plus 100.
In this example, in the stable position of the
elastically deformable portion 120, the two spring blades
122, 124 are inclined relative to a plane orthogonal to
the transverse direction Z by an angle of inclination 8
that may have any other appropriate value.
Under such circumstances, the preloading to which
5 the device 200 is subjected once it has been assembled is
due at least in part to the initial inclination of the
spring blades 122, 124 and to the resulting offset
between the return 132 and the first portion 110.
As shown in Figure 8, when the fastener device 200
10 is moved towards the surface 182 of the part 180, the
return 132 and the reception ring 140 are the first to
come into abutment against the support surface 82.
When the first portion 110 is brought towards the
support surface 182, the spring blades 122, 124 deform
15 progressively.
With such an arrangement, and as shown in Figures 7,
8, and 9, there is no longer any need for the reception
ring 136 of the sensor to project from the bottom surface
of the return 132.
2 0 It is even possible to imagine that the sensor is
mounted directly in the opening 134 of the return 132,
the return 132 then forming the second fastener portion
140, its bottom surface 132a constituting the secondary
bearing surface of the device.
2 5 Neverthel~ess, the above-described examples are not
limiting.
In ot-her example uses, the surface of the part may
present one or more setbacks, in particular. A first
support surface portion that is to receive the first
30 fastener portion and a second support surface portion
that is to receive the second fastener portion may occupy
different planes, planes that might slope relative to
each other or that might be parallel. The fastener
device is then arranged accordingly but it remains such
35 that, when the first fastener portion is fastened to a
first support surface portion, the elastically deformable
portion passes from a stable position to an unstable
position in which the second fastener portion is pressed
against the second support surface portion.

CLAIMS
1. A fastener device (100) for fastening at least one
sensor (go), in particular a thermocouple, to a part
(80), the device comprising a first fastener portion (10)
5 having fastener means (14) for fastening to the part (80)
and a second fastener portion (40) provided with an
orifice for receiving the sensor (go), the device being
characterized in that it further comprises an elastically
deformable portion (20) connecting together the first and
10 second fastener portions, the elastically deformable
portion (20) comprising at least one spring blade (22,
24) and being configured in such a manner as to pass from
a stable position to an unstable position when the first
fastener portion (10) is fastened to a part (80), thereby
15 pressing the second fastener portion (40) against the
part (80).
2. A fastener device (100) according to claim 1, wherein
the elastically deformable portion (20) includes a return
20 (32) extending away from a portion of the spring blade
(22, 24) that is spaced apart from the first fastener
portion (lo), towards said first fastener portion (lo),
and the second fastener portion (40) is secured to said
return (32).
2 5
3. A fastener device (100) according to claim 1 or claim
2, wherein the elastically deformable portion (20)
comprises two spring blades (22, 24) that are spaced
apart from each other.
30
4. A fastener device (100) according to claims 2 and 3,
wherein the return (32) extends between the two spring
blades (22, 24).
35 5. A fastener device (100) according to any one of claims
1 to 4, wherein the second fastener portion (40) has a
substai-1Liall.y plane secondary bearing sur-.face (:36a) that- , , . ,
i s adapted to come i n t o contact 'with t h e p a r t (80).
6. A f a s t e n e r device ( 1 0 0 ) according t o claim 5, wherein
the second f a s t e n e r portion ( 4 0 ) comprises a r e c e p t i o c ' ,
ring (36) for receivj-ng the sensor and fastened t o the
e l a s t i c a l l y deformable portion, and the secondary bearing
surface (36a) i s a s u r f a c e of said ring.
7. A fastener device (100) according t o clairn 5 or claim
6, wherein the f i r s t f a s t e n e r portion ( 1 0 ) has a
s u b s t a n t i a l l y plane primary bearing surface (12a) adapLed
to come i n t o contact with the part (80), and the primary
and secondary bearing surfaces a r e s u b s t a n t i a l l y p a r a l l e l
when the e l a s t i c a l l y deformable portion (20) is i n its
s t a b l e posi t l o n .
8. A fastener device (1.00) according t o claim 7, wherei-n
when the e l a s t i c a l l y deformable portion (20) is i n i t s
s t a b l e position, the secondary bearing surface (36a) i s
spaced apart from the prj~mary bearing surface (12a) i n a r
d i r e c t i o n s u b s t a n t i a l l y orthogonal t o the primary bearing
surface (12a), going away from said f i r s t f a s t e n e r
portion ( 1 0 ) . !
9. An assembly cornpri.sing a fastener device ( 1 0 0 )
according t o any one of claims 1 t o 8, and a sensor ( 9 0 )
secured t o the second fastener portion.