Note: Descriptions are shown in the official language in which they were submitted.
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DEVICE INDICATING THE LOOSENING OF A NUT
The invention concerns a device indicating the loosening of a nut.
Screw-and-nut systems are routinely used for the assembly of
parts, notably in industry and on motor vehicles. Nevertheless, diverse
factors, in particular the vibrations suffered, the variations of
temperature, an insufficient initial tightening, are liable to generate
loosening in the long term.
In an industrial installation loosening of this kind risks leading to
a leak.
There exist already on the market loosening indicators for the nuts
of truck wheels. The document GB 2242720 describes one example of a
loosening indicator for truck wheels of the type known in the prior art.
That device comprises a hollow circular body intended to be
mounted around the nut and in one piece with a visual marker in the
shape of an arrow. The internai wall of the hollow circular body defines
fine grooves for fixing it to edges of the nut.
Using a device of this kind in an industrial environment has been
envisaged but there is a risk of it proving unsatisfactory because the nuts
are liable to be corroded, impacted and the environment is confined,
sometimes with relatively high temperatures, of the order of 200 or more.
The loosening indicators presently on the market are actually
intended for use at ambient temperature, for nuts in good condition, and
with a small overall size around the nut.
The document US 8,152,426 describes another device in which the
internai walls have a tapered shape and are made of silicone so as to be
gripped against the edges of the nut. Again, however, because of the
deformation of the silicone there is the risk of this device flot proving
satisfactory in a confined environment subjected to high temperatures,
notably if the device is removed and installed on another nut.
On industrial sites permanent marking of the nut is therefore used,
with paint on metal. Nevertheless, this marking remains liable to
disappear over time and to be relatively poorly visible for an observer
relatively far from the nut.
There is therefore a need for a nut loosening indicator device that
is usable in an industrial environment, stable and visible from far away,
in particular from more than 30 cm away.
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There is proposed a device for indicating loosening of a rotary
element of a screw-and-nut system, this rotary element being intended
to be screwed in and out by a movement in rotation about a longitudinal
direction, said rotary element comprising a portion of polygonal section
in a plane normal to the longitudinal direction, said polygonal section
portion defining a plurality of plane faces, said indicator device
comprising
a body intended to be mounted on the rotary element,
a marking element extending radially, fastened to the body to
indicate the angular position of the rotary element.
According to the invention at least one spring is fastened to the
body so that when the body is mounted on die polygonal section portion
each spring exerts a radial bearing force on a correspon.ding plane face of
trie rotary element.
Accordingly, rather than cooperate with the edges of the rotary
element, which may prove relatively unreliable in an indu striai
environment where those edges may be poorly defined or damaged, the
indicator device described above includes one or more springs bearing on
the plane faces of the rotary element.
The device described above can therefore remain operational in an
industrial environment, and in particular in a refinery. In particular, this
device may easily be demounted from the rotary element and then
mounted again with no risk of deterioration of the fixing to the rotary
element.
A single spring may be provided or a small number of springs
compared to the number of plane faces, but at least one spring for each
plane face will advantageously be provided.
The invention is flot limited by the shape of the rotary element for
which this device is intended, provided that this element includes a
portion with plane faces and having a polygonal section.
The rotary element may be a nut in the classic sense of the term,
defining an internally threaded opening intended to receive and to
cooperate with a externally threaded screw. It may for example be a screw
end.
The nut may be a hexagonal, square blind or through nut, with or
without a base (in the former case the polygonal section portion occupies
only a part of the height of the nut).
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Alternatively, the rotary element may be fastened to, for example in
one piece with, an externally threaded rod, that rod being itself screwed
into a bore.
The plane faces of die rotary element may be peripheral or not. For
example, and in particular when the rotary element is at the end of die
externally threaded rod, the rotary element may define a closed central
orifice of hexagonal shape. The rotary element may therefore comprise a
hollow hexagonal screw. In this case, the springs of the loosening
indicator device may be disposed at a periphery of the body and the body
may have dimensions sufficiently small to be received in the central
orifice.
The body of the indicator device may advantageously comprise
internai walls defining a recess to receive the rotary element and the
springs may be disposed on those internai walls.
Neither is die invention limited to the shape of the springs of the
indicator device. There may for example be provided a body comprising a
ring element of polygonal shape to which is fixed a corrugated band or a
body with a polygonal ring element with plane internai walls and into
which is fixed on one of the internai walls one end of a relatively rigid coul
spring so that when a nut is received this spring exerts radial forces
toward the nut.
The spring may advantageously comprise a leaf spring.
Each leaf spring may extend between two ends fastened to the
body.
Each leaf spring may have a length slightly greater than the length
of the corresponding plane face.
The body may be such that when a rotary element is received at
least one of its plane faces cornes to compress the corresponding spring
so that this leaf spring exerts a radial bearing force on that face.
The invention is flot limited to a particular shape of the body, but
the body may advantageously comprise at least one ring element for
example of polygonal or circular shape.
A circular shape may provide more freedom in the positioning of
the marking element when that element is initially separate from the
body.
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The leaf springs may be fastened at their two ends to an internai
wall of the ring element so as to form a pseudo-polygonal structure to
receive the polygonal section portion of the rotary element.
The marking element may extend radially toward the interior of the
body and/or toward the exterior. This element may for example have an
arrow, rod or other shape.
The analysis of tightening quality can therefore be relatively simple
and rapid to carry out, even by unqualified personnel and at a relatively
great distance from the nut.
In one embodiment, the marking element may be in one piece with
the body. The indicator device can therefore be relatively simple to
manufacture.
Alternatively, the indicator device may be such that the marking
element can be assembled to the body.
In particular, the indicator device may be such that the marking
element can be assembled to the body at a plurality of locations on the
body, for example 2, 4 or more locations.
In a nonlimiting manner, the number of locations may
advantageously be greater than 20, advantageously greater than 50,
advantageously greater than 60. The marking element can therefore be
fixed at a relative precisely chosen position, the pitch between two
positions possibly being relatively small - of the order of a few degrees.
The invention is flot limited by the type of fixing employed. For
example, fixing may be provided by gripping at least one relatively soft
element of the rubber or silicone type.
In one embodiment, the marking element may be clippable onto the
body.
In another embodiment, the body and the marking element may
define cooperating means complementary to one another with a depth in
the radial direction varying according to the angular position with a
particular pitch, for example teeth adapted to fit in one another, tongues
and grooves, studs and corresponding recesses, etc.
These cooperation means may define a relatively small pitch, for
example of a few degrees.
These cooperation means, for example a system of studs and
recesses, may be adapted to prevent both tangential and radial relative
movement.
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Alternatively, these cooperation means, for example a system with
teeth or tongues, may be adapted simply to prevent tangential relative
movement.
In this case in particular, the indicator device comprises a wall
5 facing the cooperation means of the marking element or the cooperation
means of the body can be such that the walls retained by these
cooperation means fit in one another.
Alternatively, the marking element could comprise a toothed (or
ribbed, notched or other) closed, for example circular, element. The
cooperation between teeth of the body and teeth of the marking element
then occurs over ail the circumference of the indicator device.
In one embodiment the cooperation means of the body may be
disposed on an external periphery of that body, those means then being
open toward the exterior. The marking element can then define two walls
facing one another, the internai face of the outermost wall defining
cooperation means oriented toward the interior of the device. These two
walls are at a distance such that the innermost wall can maintain the
cooperation means fit in one another.
In another embodiment the body may comprise two concentric, for
example circular, ring elements.
The internai wall of one of these concentric ring elements may
define cooperation means complementary to cooperation means of the
marking element. A portion of the marking element is then inserted into
the space between these concentric elements, the cooperation means
preventing ail tangential relative movement.
The marking element may comprise a small number of cooperation
means, for example one or two studs or tongues.
The indicator device described above may be made of metal, of
plastic, for example of a plastic stable from -20 to 250 , or some other
material. Polypropylene or ABS (acrylonitrile butadiene styrene) could for
example be chosen.
Producing it in metal enables use of the indicator device at even
higher temperatures, of the order of 500 or 600 , or even 1500 C if
produced in titanium.
A 3D printer could in particular be used to produce this device.
In one embodiment, the body may define, for example on the
external periphery of the external ring element, means for fixing it to a
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linear element, for example a cable, a wire, for example a metal wire,
etc.
Thus there is proposed an assembly for maintaining in a tightened
position a plurality of rotary elements, each rotary element being
intended to be screwed in and out by a movement in rotation about a
longitudinal direction, this assembly comprising
at least two retaining devices adapted to be mounted on respective
rotary elements so as to prevent ail relative movement in a tangential
direction, for example by means of two loosening indicators as described
above, each retaining device comprising means for fixing it to a linear
element,
the linear element fixed to two retaining devices via respective
corresponding fixing means so that a loosening movement of one of the
rotary elements corresponding to one of those retaining devices drives
the rotary element corresponding to the other of those retaining devices
in rotation in the tightening direction.
The rotary elements are thus fastened to one another in such a
manner as to limit loosening.
The retaining devices may be indicator devices as described above
or not. An indicator device of the type known from the prior art could in
particular be used.
There is further proposed a use of the indicator device described
above and/or of the assembly described above in a petrochemical
installation.
The invention will be better understood on referring to the figures,
which show embodiments given by way of nonlimiting example.
- Figure 1 shows one example of an indicator device according
to one embodiment of the invention, mounted on a hexagonal
nut.
- Figure 2 shows one example of an indicator device according
to another embodiment of the invention mounted on a
hexagonal nut.
- Figure 3 shows one example of an indicator device according
to a further embodiment of the invention mounted on a
hexagonal nut.
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- Figure 4 shows one example of an indicator device according
to a still further embodiment of the invention mounted on a
hexagonal nut.
- Figure 5 is a diagrammatic sectional view of one example of an
indicator device according to a still further embodiment of the
invention.
- Figure 6 is a diagrammatic view from above of a retaining
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two nuts.
assembly according to the embodiment from figure 6.
Proportions are not necessarily respected from one figure to
another.
On the other hand, identical references from one figure may be
used in another to designate identical or similar elements.
Referring to figure 1, a device 1 indicating the loosening of a
hexagonal nut 2 is shown.
The nut 2 defines a through orifice 5 with an internai thread, not
shown, to receive an externally threaded rod, not shown. That orifice
extends along a longitudinal axis (D). The nut 2 is screwed onto the
externally threaded rod by rotation about this longitudinal axis (D).
The indicator device 1 comprises a body 3 and a marking element,
here an arrow 4 fixed to this body 3.
The body 3 comprises two concentric circular ring elements 37, 38
fastened to one another by spacers 39.
The body 3 is made in one piece with six leaf springs 31, 32, 33,
34, 35, 36, for example by 3D printing.
Each leaf spring 31, 32, 33, 34, 35, 36 is fastened by its two ends
to an internal wall of the circular element 37 and each end of a leaf spring
is fixed near the adjacent leaf spring.
The six leaf springs 31, 32, 33, 34, 35, 36 thus form a pseudo-
hexagonal structure corresponding to the shape of the section of the nut.
When the nut 2 is received in this pseudo-hexagonal structure,
each leaf spring 31, 32, 33, 34, 35, 36 is in compression and exerts a
radial force against a corresponding plane face 21, 22, 23, 24, 25, 26 of
the nut.
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The indicator device 1 therefore bears against the plane faces 21,
22, 23, 24, 25, 26 of the nut 2: if the edges of the nut between two plane
faces are damaged or poorly defined, the quality of the fixing of the
indicator device 1 remains unchanged.
The external circular element 38 defines excrescences 6 and
grooves 7 between two adjacent excrescences. These means 6, 7 have a
width in the radial direction that is relatively small, of the order of a
millimeter or of a tenth of a millimeter.
The arrow 4 comprises a fixing portion 41 extending tangentially
and longitudinally and defining means (flot visible in figure 1)
complementaiy to the means 6, 7, here excrescences and grooves similar
to the excrescences 6 and to the grooves 7.
The internai circular element 37 is separated from the circular
element 38 by a distance sufficient for the fixing portion 41 to be able to
be introduced between these circular elements 37, 38 but sufficiently
small to force the excrescences 6 to fit in the grooves of the arrow 4 and
vice versa.
To fix the arrow 4 to the body 3 it therefore suffices to introduce
the fixing portion 41 between the circular elements 37, 38.
Thanks to the circular shape of the elements 37, 38 and thanks to
the small dimensions of the means 6, 7 providing the cooperation with
the arrow, the arrow 4 can be positioned relative precisely, with a
precision of the order of a few degrees.
Referring to figure 2, the indicator device comprises a single ring
element 137 in which are defined a plurality of tens of regularly spaced
holes 107.
The arrow 104 is similar to the arrow 4 from figure 1 except that
the fixing part 41 has been replaced by a plurality of studs (flot visible in
figure 2) disposed and sized so as to be receivable in holes 137.
The arrow 104 can therefore comprise about 10 studs.
In the figure 3 embodiment, the marking element 204 extends
radially toward the interior of the body 203.
The body 204 comprises a single circular ring element 237.
The marking element 204 extends over ail of a diameter of this
circular ring element 237.
The marking element 204 extends between two points 214, 215 and
is eye shaped.
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The circular element 237 defines a plurality of bores 207, for
example approximately 25 bores.
Each bore 207 may have a diameter of 1-3 millimeters and a depth
of 4-5 millimeters for example.
The marking element comprises two lugs (flot visible in figure 3)
fastened to the points 214, 215, respectively. Each lug may be received
in a respective bore, thus enabling the marking element 204 to be
disposed with a chosen orientation.
Referring to figure 4, a loosening indicator device 301 is mounted
on a nut 302 screwed onto an externally threaded rod 352.
This device 301 comprises a circular ring element 337 fastened to
springs that are flot visible in this figure, those springs exerting radial
forces against the plane faces of the nut 302.
The device 301 further comprises a marking element 304 mounted
on the ring element 337.
The ring element 337 defines at its perimeter a rim 347 with an
internai wall 348.
The marking element 304 is adapted to be clipped against this
circular element 337. To this end the element 304 defines a recess 342
to receive a top edge of the rim 347 and a shoulder 343 to receive a bottom
edge of the rim 347. The marking element therefore bears against the
internai wall 348.
Although this is flot seen in the figure 4 sectional view, the marking
element 304 comprises a marking part 330 that is flot symmetrical with
respect to the longitudinal axis, for example in the shape of an eye.
In die figure 5 embodiment the marking element 404 is clipped
onto the ring element 437 in the same way that the element 304 is clipped
onto the element 337. In this example, however, the marking element 404
comprises an arrow extending radially toward the exterior of the ring 437.
Referring to figures 6 and 7, a retaining assembly 600 comprises
two retaining devices 601, 601', for example two indicator devices
provided with leaf springs 631, 632, 633, 634, 635, 636, 631', 632', 633',
634', 635', 636'.
Figure 6 is highly diagrammatic and in reality most and
advantageously ail of the leaf springs bear radially against a
corresponding nut plane face.
.
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The indicator devices 600, 600' comprise circular ring elements
637, 637' onto which are clipped respective arrows 604, 604'.
These ring elements 637, 637' define on their external walls 647,
647' orifices 648, 648' for fixing a metal wire 700.
5 This
wire 700 is fuoed slantwise so that if one nut 603 tends to
loosen, following a movement as shown by the arrow F, the other nut 603'
is driven in movement in the direction opposite to the direction indicated
by the arrow F', i.e. this second nut 603' would be tightened.
This arrangement, connecting the nuts to one another, can
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therefore participate in maintaining the nuts tightened, because the
movement of one nut is compensated by a contrary movement of the other
nut.
