DEVICE FOR DETECTING LOSS OF TIGHTENING TENSION IN A SCREW-NUT SYSTEM

Abstract

The invention relates to a device for visualizing loss of tightening torque in a screw-nut system (10), comprising - a deformable ring (7), which expands radially when tightening the screw-nut system (10), the flushness or protrusion at the level of an outer rim (R) of the screw-nut system (10) of said ring (7) forming an indicator of sufficient tightening torque, and, conversely, the retraction of the ring (7) behind the outer rim (R) forming an indicator of insufficient tightening torque, characterized in that it further comprises an ejectable element (11, 12), elastically constrained by elastic elements (13) and retained by the ring (7) when it flushes or protrudes from the outer rim (R) of the screw-nut system (10), and released and ejected by a release of the elastic elements (13) when the ring (7) is retracted behind the outer rim (R). Figure for the abridged version: Fig. 1

Description

Title of the invention: LOSS DETECTION DEVICE TIGHTENING TENSION IN A SCREW-NUT SYSTEM technical field

[0001] The present invention relates to the general field of safety devices for screw-nut systems, and in particular to the verification and control of tightening torques of such screw-nut systems.

[0002] Prior techniques

[0003] Manual verification of the tightening torque of a screw-nut system is often carried out using torque wrenches, by screwing the nut a few degrees or fractions of a degree and checking the torque during said tightening.

[0004] While this procedure is suitable for the precise verification of a few bolts, for example for an individual screwing on the wheels of his car or a plumber installing a pipe, it quickly becomes tedious and time-consuming for, for example, checking the tightening torque of the thousands of bolts used for the assembly of the elements of a pipeline or a wind turbine.

[0005] Proper tightening of the bolts of a pipeline, wind turbine or other installations of this type is crucial for their operation and the safety of people nearby.

[0006] The tightening is compromised over time by several factors: vibrations, cycles of expansion / contraction during changes in external temperatures, finishing of the parts and in particular of long threaded rods, etc.

[0007] Document EP3927982 describes devices for visualizing voltage loss based on the principle of the deformation of a deformable ring pinched during tightening between flared metal rings, and whose outward protrusion or protrusion forms a sight indicating whether or not the tightening torque is sufficient.

[0008] These devices also present the problem of excessive hysteresis, due to friction between the parts during loosening. In particular, the retraction of the deformable ring is marked and clearly observable when the tightening torque drops to a value of approximately 30% of the tightening torque initially applied to make it flush or protrude.

[0009] Typically, for a tightening of 150 kN.m (corresponding to a tightening of so-called "15 tonnes"), the visible retraction of the deformable ring is observed at approximately 50 kN.m (corresponding to "5 tonnes").

[0010] The sole removal of the deformable ring is difficult to detect, and may not allow for two-state detection (sufficient / insufficient tightening torque) that is accurate and distinct enough to be automated or at least allow for verification clear and unambiguous visual.

[0011] This significant hysteresis means in particular that the clearly insufficient tightening torque can be reached before a visual check can detect it. Description of the invention

[0012] There is therefore a need for a device for visualizing or verifying the loss of tension in a screw-nut system that is more precise, with a higher threshold for detecting insufficiency than that of the prior art, and which therefore allows for faster detection of loosening.

[0013] To meet this need, the invention proposes a device for visualizing torque loss in a screw-nut system, comprising: - a deformable ring, subjected to a compressive force which expands it radially when the screw-nut system is tightened, the flushness or protrusion at the level of an outer edge of the screw-nut system of said ring forming an indicator of sufficient tightening torque, and, conversely, the retraction of the ring behind the outer edge forming an indicator of insufficient tightening torque, characterized in that it further comprises an ejectable element, elastically constrained by elastic elements and retained by the ring when it is flush with or protrudes from the outer rim of the screw-nut system, and released and ejected by a release of the elastic elements when the ring is recessed behind the outer rim.

[0014] The visual detection of insufficient tightening torque is then much more precise, with a detection threshold for insufficiency marked by the ejection of the ejectable element.

[0015] The device according to the invention may further have one or more of the following characteristics.

[0016] The ring may have a peripheral recess forming a force connection with the ejectable element when it is flush with or protrudes at the level of the outer rim.

[0017] The ejectable element may include a flat metal ring, the inner edge of which comes into contact with the ring when it is flush with or protrudes from the outer edge, and at least two outer fins made of material with the flat ring, the fins being axially deformed in order to form the elastic elements.

[0018] The ejectable element may include a helical spring and a flat ring, with folding arms made of the same material as the flat ring, the arms having at their ends hooks which engage with the spring when the arms are folded.

[0019] The inner rim of the flat ring may have a cut-out tab inclined downwards, forming a starting point for screwing onto the ring when it protrudes or is flush with the outer rim.

[0020] The ejectable element may alternatively comprise a tubular cap having a radial lip on its inner skirt, cooperating with the ring when it is flush with or protrudes from the outer rim, and a helical spring constrained between the cap and the bolt in the installed state.

[0021] The upper surface of the cap may have a recess that engages with a coil of the helical spring.

[0022] The device may in particular further comprise a stack of conical spring washers, arranged in parallel under the nut and the ring in the assembled state, the ring being disposed between the nut and the stack of spring washers or between a support and the stack of spring washers, the ring being disposed against the flared surface of the stack of spring washers, so that the ring is compressed against the flared surface of the spring washers when tightening the screw-nut device and pushed outwards.

[0023] The stack of spring washers may comprise two spring washers, the lower and outer edge and the upper and inner edge of which are chamfered so as to be substantially parallel to a radial plane.

[0024] The ring may have a wedge-shaped section, and the internal surfaces of the spring washers may be flattened so that the assembly formed by the stack of spring washers and the wedge-shaped ring has a generally rectangular section.

[0025] The ring may have a marking on its upper surface forming an indicator of a predetermined tightening torque when it appears at the outer edge of the screw-nut system.

[0026] The ring and the stack of spring washers can be held together by a tubular crimp in soft metal such as tin.

[0027] The ring can be an open ring with an inclined slit made of elastic metal such as spring steel.

[0028] Summary description of the figures

[0029] Other advantages and features of the invention will become apparent from the following description of the accompanying figures, among which:

[0030] [Fig. 1] is a cross-sectional view of the device according to a first embodiment of the invention,

[0031] [Fig.2] is an exploded perspective view of the device of [Fig.1],

[0032] [Fig.3] is a cross-sectional view of the device of [Fig.1] when it is sufficiently tight,

[0033] [Fig.4] is a perspective view of a particular embodiment of a ring for the device according to the invention,

[0034] [Fig.5] is a cross-sectional view of the ring of [Fig.4],

[0035] [Fig.6] is a cross-sectional view of an embodiment of a crimping device tubular,

[0036] [Fig.7] is a cross-sectional view of an embodiment of a device with an element ejectable with a cap when the tightening is sufficient.

[0037] [Fig.8] is a cross-sectional view of the device of [Fig.7] when the clamping is in sufficient,

[0038] [Fig.9] is a cross-sectional view of a particular embodiment of a cap for the arrangement of figures 7 and 8,

[0039] [Fig. 10] is a schematic cross-sectional view of a device with an alternative embodiment of an ejectable element,

[0040] [Fig. 11] is a perspective view of a particular embodiment of an ejectable element for the device of [Fig. 10],

[0041] [Fig. 12] is a perspective view of another embodiment of an ejectable element,

[0042] [Fig. 13] is a cross-sectional view of a viewing device equipped with the ejectable element of [Fig. 12],

[0043] [Fig. 14] is a double cross-sectional view of another embodiment of a visualization device shown in two clamping states,

[0044] [Fig. 15] is a cross-sectional view of yet another embodiment of a display device according to the invention,

[0045] [Fig. 16] is a cross-sectional view of a particularly simple embodiment of a visualization device according to the invention.

[0046] The examples are given by way of illustration and are not intended to be limiting. Other embodiments of the invention can easily be obtained by variations and combinations of the embodiments shown. The dimensions and proportions illustrated in the figures may differ from reality and may have been adapted to facilitate understanding of the invention. Detailed description

[0047] Fig. 1 is a cross-sectional view of an embodiment of a visualization device 100 for loss of tightening torque with a screw-nut system 10 before tightening or with insufficient tightening.

[0048] The screw-nut system 10 includes in particular a threaded rod 1 and a nut 3. The nut 3 engages with the thread of the threaded rod 1, and tightening the nut 3 brings it closer to a support S, into which the threaded rod 1 is inserted. The threaded rod 1 is for example the end of a screw, and the support S is for example a frame or a wall in which the screw-nut system is placed.

[0049] A radial reference frame is deduced from the arrangement of the screw-nut system 10: the threaded rod 1 A vertical axis is given, and the radial and tangential directions are derived from this axis. The "inner" and "outer" orientations, and their equivalents, are given with respect to said axis. The free end of the threaded rod 1, through which the nut 3 is inserted, is considered "upper", "above", or "on top".

[0050] This particular orientation is given in relation to the figures, but the actual orientation of the screw-nut system 10 may of course differ from this one, in particular with respect to gravity.

[0051] The rim of the nut 3 defines an outer rim of the screw-nut system 10 materialized in [Fig.1] by two dotted lines marked R.

[0052] The viewing device 100 comprises two conical spring washers 5, of the "Belleville" type, arranged in parallel under the nut 3 with their upper surface inclined downwards. The spring washers 5 thus form a spring 50 of the "TREP" type (trade name).

[0053] A ring 7 made of deformable material is disposed between the nut 3 and the spring washers 5, and is pinched between these elements when tightening the nut 3. The ring 7 is in particular compressed against the inclined surface of the upper spring washer 5 by the nut 3 when the screw-nut system 10 is tightened.

[0054] The stacked spring washers 5 form a truncated cone, and the ring 7 is located in particular on the side of the tip of said cone, so that its crushing when tightened against the spring washers 5 pushes it radially outwards.

[0055] Fig. 2 shows nut 3 and viewing device 100 in perspective and exploded view.

[0056] The ring 7 is in particular made in the form of a split metal ring, in particular made of spring steel, and split with a slot 71 inclined in the tangential direction, thus limiting the infiltration of dust between the ring 7 and the spring washers 5.

[0057] The ring 7 and the spring washers 5 are considered "elastic" in that they deform elastically within the ranges of deformation encountered during tightening / loosening, with a return to a position of least stress when the tightening is released.

[0058] The section of the spring washers 5 has a lower and outer edge and an upper and inner edge chamfered so as to be substantially parallel to a radial plane.

[0059] The ring 7 has a wedge-shaped section, and the internal surfaces of the spring washers 5 are axially flattened in a tubular manner, so that the assembly formed by the stack of washers 5 and the wedge-shaped ring 7 has a generally rectangular or square section.

[0060] The outcrop or protrusion at the level of an outer edge R of this ring 7 forming an indicator of sufficient tightening torque. Conversely, the removal of the ring 7 behind the outer rim R forms an indicator of insufficient tightening torque.

[0061] In [Fig. 2], the upper spring washer 5, whose flared upper surface is visible, has a colored portion 53 on its lower and radially outer periphery. The colored portion 53 is, for example, painted or galvanized, particularly by partial immersion, in a bright color. The colored portion 53 is covered by the ring 7 when the tightening is sufficient, and its appearance indicates that the tightening is insufficient.

[0062] In [Fig. 1], the screw-nut assembly 10 is not tightened or is not sufficiently tightened. [Fig. 3] shows the screw-nut assembly 10 and the viewing device 100 when the tightening is sufficient.

[0063] The ring 7 is flush in [Fig.3] with the outer rim R. The difference in contour between the hexagonal nut 3 and the circular ring 7 implies that the latter is clearly visible from above.

[0064] Conversely, when ring 7 is in the retracted position shown in [Fig.1], it is barely or not at all visible from above.

[0065] The ring 7 can in particular be galvanized or painted in a particularly visible colour, for example a primary colour such as blue, or a fluorescent colour or a colour with a specific spectral signature.

[0066] Simple and robust optical sensors can be used to capture the light scattered by the visible surface of the ring 7 or the colored portion 53, and detect a decrease in brightness corresponding to the total or partial withdrawal of the ring 7 behind the outer rim R or an increase in brightness corresponding to the appearance of the colored portion 53.

[0067] Said sensors can in particular send an electronic or electromagnetic signal to a control unit or terminal, where a display will show the loose state of the screw-nut system 10, as well as its location to allow targeted intervention.

[0068] Fig. 4 shows a ring 7 with a marking 73 on its upper surface.

[0069] In [Fig. 4], the ring 7 is composed of three circular arcs, separated by slots 71 and forming a complete circle when assembled. The circular arcs in [Fig. 4] are three in number and identical. Other embodiments with two, four, or more circular arcs are of course possible.

[0070] For better assembly and easier handling, the arc-shaped parts are held together, in the assembled state, by a thin metallic ring 77 inserted into a peripheral recess 75 on the outer axial surface of the ring 7.

[0071] Figure 5 is a cross-sectional view of the ring in Figure 4. The marking 73 follows, in particular, the outer edge of said surface and is, for example, made by laser or by milling. Marking 73 can in particular be made in the form of a groove or trench, filled with paint or a material that is particularly visible or has optical properties that allow detection by sensors (spectral signature, reflection, retroreflection, luminescence, fluorescence, etc.).

[0072] Again, the optical sensors can emit a signal to a control terminal for targeted on-site tightening intervention.

[0073] The position of the marking 73 can be adapted so that its appearance at the outer rim R of the screw-nut device 10 indicates that the tightening torque is sufficient, and its removal behind said outer rim R indicates precisely the insufficiency of tightening torque.

[0074] Fig. 6 shows a particular embodiment of the viewing device 100, in which the deformable ring 7 and the stack of spring washers 50 are held together by a cylindrical crimp 9 in soft metal such as tin.

[0075] The cylindrical crimp 9 secures the elements composing the viewing device 100, which is then easily handled because it is presented as a single unit.

[0076] The cylindrical crimp 9, and in particular its upper skirt, disposed on the upper surface of the ring 7, can also be dimensioned so that its appearance during tightening forms an indicator replacing the marking 73 of [Fig.4].

[0077] Figures 7 and 8 show a particular embodiment of a viewing device 100 further comprising an ejectable element, elastically constrained by elastic elements and retained by the ring 7 when it is flush with or protrudes from the outer rim R, and which is released and ejected by a release of the elastic elements when the ring 7 is retracted behind the outer rim R.

[0078] In [Fig.7], the tightening torque is sufficient, in [Fig.8], the tightening torque is insufficient.

[0079] The ejectable element here comprises, in particular, a tubular cap 11 forming the ejectable element, and a helical spring 13 forming the elastic element. The cap has a lip 15, which mechanically engages with the lower outer edge of the ring 7 when it is flush with or protrudes from the outer edge R. The lip 15 is released, in particular, when the ring 7 is withdrawn because the tightening torque becomes insufficient.

[0080] In [Fig. 7], the ring 7 is flush with the outer rim R. The lip 15 is in contact with its outer rim, which holds the cap 11 axially. The spring 13 is elastically constrained in compression.

[0081] In [Fig. 8], the ring 7 has retracted inwards following a release of the tightening torque. The lip 15 of the cap is no longer engaged with the peripheral ring, which releases the cap 11. The spring 13 then propels said cap 11 axially upwards.

[0082] The ejected cap 11 provides a clear and precise means of detecting insufficient tightening torque. The cap 11 may, in particular, be painted or made of a visible color (fluorescent, for example). By finding a cap 11 on the ground, a maintenance worker knows that a nearby screw-nut system 10 is loose and that they will therefore need to take action.

[0083] According to one embodiment, the nut 3 is painted or galvanized in a visible or particularly detectable color, while the cap 11 is in a discreet color. Visual or optical detection of the nut 3 then makes it possible to locate the screw-nut system 10, which is not sufficiently tightened.

[0084] This visual or optical detection can then be carried out in an automated or semi-automated manner, for example by means of drones equipped with suitable optical sensors. Extensive systems such as pipelines can then be monitored regularly over significant lengths without requiring any intervention from a technician, except for targeted intervention in the event of insufficient tightening torque being detected.

[0085] Figure 9 shows a particular embodiment of the ejectable element, in which the cap 11 has a recess 17 which engages with the extremity loop of the spring 13, thus securing the cap 11 and the spring 13 together. Alternatively, the end of the spring can be inserted through the upper surface of the cap 11.

[0086] Other forms of cap 11 and spring can be provided without departing from the invention. The lip 15 can in particular be replaced by discontinuous studs, and according to one embodiment, the cap 11 can be attached to the bolt 3 by a cable allowing said bolt 3 to be raised from the cap 11.

[0087] Fig. 11 shows in cross-section another ejectable element, arranged radially outside the screw-nut system 10, where the cap 11 of figures 7 to 9 protrudes essentially axially from said screw-nut system 10.

[0088] The ejectable element here has a flat ring 12, in contact with the lower outer rim of the ring 7, and one or more springs 13, located between the ring 12 and the support S.

[0089] The principle is essentially the same as in the previous case: when the ring 7 is removed, the ring 12 is released and the springs 13 ensure its ejection.

[0090] This shape ensures greater axial compactness, at the expense of radial compactness.

[0091] Fig. 12 shows a particular embodiment of an ejectable element, simple and quick to produce and manipulate.

[0092] The ejectable element here consists of a flat metal ring 12. The inner edge of the ring 12 has a stamped tab 14, forming a threaded starting point, so that the ring 12 can be screwed around the ring 7 when tightening has been carried out.

[0093] Fins 16 coming from material with the ring 12 are cut and axially deformed so as to form spring blades.

[0094] This ejectable element is made in one piece, and can be made in a single stamping step, where cutting and shaping are carried out simultaneously.

[0095] Fig. 13 shows another form of ejectable element, and Fig. 14 shows this particular ejectable element in place on the screw-nut system 10 equipped with the viewing device 100.

[0096] The ejectable element here comprises, in a manner analogous to that of [Fig. 12], a flat ring 12, the inner rim of which has a stamped tab 14. Arms 18 extend radially on either side of the flat ring 12, giving the ejectable element a general shape of a flat wristwatch.

[0097] The flat ring 12 is in particular engaged with an annular protuberance 79 extending radially outwards at the lower edge of the ring 7. This annular protuberance cooperates in particular with the stamped tab 14 when screwing the flat ring 12.

[0098] The arms 18 have their free end folded or rolled upon itself so as to form a retainer. The arms 18 are folded upwards when the ejectable element is in place.

[0099] In [Fig. 13], the arms 18 are folded, their retaining end is engaged with a compressed spring 13, and the ring 12 is engaged with the ring 7. When the ring 7 is removed, the ring 12 is released and ejected upwards under the action of the spring 13.

[0100] Figure 14 shows another embodiment of the display device 100, in which the ring 7 is made of polymer. The ring 7 is notably toroidal in shape, with a recess forming the peripheral indentation 75 on its outer end.

[0101] The polymer ring 7 is held between an upper washer 19 and the spring washers 5. The upper washer 19 has, in particular, a lower surface that flares upwards. Tightening the nut 3 then forces the ring 7 outwards and deforms it by flattening it, which accentuates its radial protrusion.

[0102] Such an upper washer 19 with an inclined lower surface can also be used with a metallic ring 7 as previously described. Such a viewing device is shown in [Fig. 16].

[0103] Fig. 15 illustrates a variant of a viewing device 100 in which the assembly formed by the ring 7 and the stack 50 of spring washers 5 is reversed axially.

[0104] The ring 7 is notably pinched between the support S and the stack 50, the cone formed by the stacked spring washers 5 having its point downwards. The ring 7 is therefore always on the side of the tip of said cone, in contact with the surface flared upwards of the lower spring washer 5, and expands under the action of the crushing induced by the tightening of the screw-nut system 10.

[0105] The peripheral recess 75 is positioned as close as possible to the support S, while the lip 15 of the cap 11 is engaged with said peripheral recess 75. The cap 11 consequently covers all or almost all of the screw-nut system 10 and the viewing device 100. The cap then protects these elements from external aggressions, for example rainwater runoff.

[0106] Fig. 16 illustrates a particularly simple embodiment of a voltage loss visualization device 100 with a jumping element.

[0107] The ring 7 of the device 100 of [Fig. 16] protrudes, when the tightening is sufficient, radially relative to the stack of washers 50 and relative to the nut 3. A helical spring 13 is compressed under the ring 7, which forms a stopping surface, when it protrudes, for said helical spring 13.

[0108] When retracted during loosening, the ring 7 releases the spring 13, which is ejected by its own detent. This spring 13 alone replaces the jumping element and the elastic means. No cap or equivalent element is required.

[0109] The spring washers 5 reduce the hysteresis induced by the friction of the components of the viewing device 100, and the slope they induce accentuates the retraction movement of the ring 7. The sensitivity of the viewing device 100 is thus greatly improved, with a marked retraction at still high tightening torque values.

[0110] The use of devices with ejectable elements takes advantage of this marked withdrawal to allow for a marked and unambiguous two-state detection.

Claims

Claims

1. Device for visualizing loss of tightening torque in a screw-nut system (10), comprising: - a deformable ring (7), undergoing a compression force which expands it radially during tightening of the screw-nut system (10), the flushness or protrusion at an outer rim (R) of the screw-nut system (10) of said ring (7) forming an indicator of sufficient tightening torque, and, conversely, the withdrawal of the ring (7) behind the outer rim (R) forming an indicator of insufficient tightening torque, characterized in that it further comprises an ejectable element (11, 12), elastically constrained by elastic elements (13) and retained by the ring (7) when it is flush with or protrudes from the outer rim (R) of the screw-nut system (10), and released and ejected by a release of the elastic elements (13) when the ring (7) is withdrawn behind the outer rim (R).

2. Device according to claim 1, characterized in that the ejectable element comprises a tubular cap (11) having a radial lip (15) on its inner skirt, cooperating with the ring (7) when it is flush with or protrudes from the outer rim, and a helical spring (13) stressed between the cap (11) and the bolt (3) in the installed state.

3. Device according to the preceding claim, characterized in that the upper surface of the cap (11) comprises a recess (17) engaging with a turn of the helical spring (13).

4. Device according to claim 1, characterized in that the ejectable element comprises a flat ring (12) made of metal, the inner edge of which engages with the ring (7) when it is flush with or protrudes beyond the outer edge (R), the ring having at least two outer fins (16) made of the same material as the flat ring (12), the fins (16) being axially deformed in order to form the elastic elements.

5. Device according to claim 1, characterized in that the ejectable element comprises a helical spring (13) and a flat ring (12), with foldable arms (18) made of the same material as the flat ring (12), the arms (18) comprising at their end hooks engaging with the spring (13) when the arms (18) are folded.

6. Device according to claim 4 or 5, characterized in that the inner rim of the flat ring (12) comprises a cut-out tab (14) and inclined downwards, forming the beginning of a screw thread for screwing onto the ring (7) when it protrudes or is flush with the outer rim (R).

7. Device according to one of the preceding claims, characterized in that it further comprises a stack (50) of conical spring washers (5), arranged in parallel under the nut (3) and the ring (7) in the assembled state, the ring (7) being arranged between the nut (3) and the stack (50) of spring washers (5) or between a support (S) and the stack (50) of spring washers (5), the ring (7) being arranged against the flared surface of the stack (50) of spring washers (5), so that the ring (7) is compressed against the flared surface of the spring washers (5) when tightening the screw-nut device (10) and pushed outwards.

8. Device according to claim 7, characterized in that the stack (50) of spring washers (5) comprises two spring washers (5), the lower and outer edge and the upper and inner edge of which are chamfered so as to be substantially parallel to a radial plane.

9. Device according to the preceding claim, characterized in that the ring (7) has a radial wedge section, and in that the internal surfaces of the spring washers (5) are axially chamfered so that the assembly formed by the stack (50) of spring washers (5) and the ring (7) with wedge section has a substantially rectangular general section before tightening.

10. Device according to one of the preceding claims, characterized in that the ring (7) has a marking (73) on the periphery of its upper surface forming an indicator of a predetermined tightening torque when it appears at the level of the outer rim (R) of the screw-nut system (10).

11. Device according to one of claims 7 to 10, characterized in that the ring (7) and the stack (50) of spring washers (5) are held together by a tubular crimp (9) made of soft metal such as tin.

12. Device according to one of the preceding claims, characterized in that the ring (7) is composed of parts in an arc of a circle, separated by slots (71) and forming a complete turn when assembled.

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