Device for detecting sufficient tightening tension in a screw-nut system

Abstract

The invention relates to a device for displaying the correct tightening tension of a screw-nut system (10) comprising: - a screw (1) or a threaded rod; - a nut (3); and - a spring washer (5) or stack (50) of parallel spring washers (5), which spring washer or stack thereof is deformed by flattening during tightening, characterised in that the display device comprises: - a ring (11) located between the nut (3) and the one or more spring washers (5); - a pin (7) located on a face oriented towards the spring washers (5) of the ring (11); - at least one lever arm (9) comprising a bend (93) bearing against the one or more spring washers (11) when the lever arm is in the assembled state, at which bend the pin (7) bears, and further comprising a free end set in motion by the pressure from the pin (7) and from the spring washers (5).

Description

[0001] DEVICE FOR DETECTING SUFFICIENT TIGHTENING TENSION IN A SCREW-NUT SYSTEM

[0002] Technical field

[0003] The present invention relates to the general field of safety devices for screw-nut systems, and in particular to the verification and control of the tightening tensions of such screw-nut systems.

[0004] Previous techniques

[0005] Manually checking the tightness of a screw-nut system is often carried out using torque wrenches, by tightening the nut a few degrees or fractions of a degree and checking the torque during said tightening.

[0006] While this procedure is suitable for the precise checking of a few bolts, for example for an individual tightening the wheels of his car or a plumber installing a pipe, it quickly becomes tedious and time-consuming, for example, to check the tightening torque of the thousands of bolts used to assemble the elements of a pipeline or a wind turbine.

[0007] Properly tightening the bolts of a pipeline, wind turbine or other such installations is crucial for their operation and the safety of people around them.

[0008] Such installations are often difficult to access, for example, high and cramped in the case of a wind turbine, or long and in isolated locations for pipelines. If a worker has to bring tools such as torque wrenches or hydraulic tensioners in addition to tightening tools, this constitutes an additional carrying burden in difficult-to-access installations which causes additional costs.

[0009] In particular, document EP2210002 discloses screws having a colored indicator on their upper face which changes color when sufficient tightening torque is reached.

[0010] These screws have the disadvantage that the color change is gradual, and the perception of colorimetry varies from one user to another. Insufficient precision in the tightening torque is therefore achieved. In addition, because the color indicators are located on the upper surface of the screw, they are not visible when tightening is carried out using a tool covering said surface, a socket wrench for example. It is then necessary to proceed in stages: tightening a portion of the turn, removing the tool and checking, tightening a portion of the turn, removing and checking, etc.

[0011] Furthermore, this system consists of screws with a head, and is therefore not suitable for the case of a threaded rod cooperating with a through nut, and cannot be installed on such threaded rods already in place.

[0012] In addition, most existing devices and systems measure the tightening torque, however the different possible surface conditions, the rusty or greased nature of the screw-nut system mean that the same tightening torque can correspond to different screw or threaded rod tensions, which is the relevant quantity for tightening a screw-nut system.

[0013] There is therefore a need for a device for displaying the correct tightening tension of a screw-nut system which does not have the disadvantages mentioned.

[0014] Statement of the invention

[0015] To meet this need, the invention proposes a device for visualizing the correct tightening tension of a screw-nut system, the screw-nut system comprising:

[0016] - a screw or threaded rod,

[0017] - a nut,

[0018] - a spring washer or a stack of parallel spring washers, resting against a support and which deforms by flattening during tightening. The display device is characterized in that it comprises:

[0019] - a ring located, in the assembled state, between the nut and the spring washer(s), configured to transmit the tightening force of the nut to the spring washers,

[0020] - a needle located, in the assembled state, on a face facing the spring washers of the ring,

[0021] - at least one lever arm, having an elbow resting against the spring washer(s) in the assembled state, at which the needle rests, and a free end set in motion by pressure from the needle and the spring washers on the lever arm when tightening the screw-nut system, a particular position of the lever arm indicating sufficient tightening tension.

[0022] The flattening deformation of the spring washers is then multiplied by the lever arm, and this flattening movement of the order of a millimeter or even a tenth of a millimeter then generates a centimeter movement of the free end of the lever arm.

[0023] The lever arm can then have at its free end an index, configured to cooperate with an indicator located on the screw-nut system, a good tightening tension being achieved when the index of the lever arm overlaps or exceeds the indicator.

[0024] Indexing then allows you to visualize the correct tightening tension precisely and in an adjustable manner according to the desired tension.

[0025] If the tightening of the screw-nut system radially separates the lever arms, the display device may further comprise an ejectable element, comprising pre-stressed elastic means configured to eject it when the ejectable element is released, and in that the radially separated lever arms form, as long as the tightening tension is sufficient, a retainer for the ejectable element, and release the ejectable element when the tightening tension becomes insufficient.

[0026] Lever arms can in particular be made in the form of folded metal strips.

[0027] The lever arms can be partially inserted at their bend into a groove at the base of the ring.

[0028] The device may comprise a plurality of lever arms regularly arranged around the periphery of the ring in the assembled state.

[0029] The lever arms can be arranged radially around an annular collar with which they are made of the same material.

[0030] The needle can be annular and have a section with two points, arranged on its lower and upper edges.

[0031] Alternatively, the needle can be made from the same material as the ring.

[0032] The lever arms may include an elastic element stressed during tightening of the screw-nut system, and the restoring force of which tends to return the lever arms to a rest position, adopted in the absence of tightening of the screw-nut system.

[0033] The lever arms may have a fold or loop at their elbow forming a reserve of elasticity. Finally, the invention also relates to the screw-nut system, characterized in that it includes a device for displaying the correct tightening tension as previously described.

[0034] Summary description of the figures

[0035] Other advantages and characteristics of the invention will appear on reading the following description of the attached figures, among which:

[0036] - figure 1 is a sectional view of a screw-nut system provided with a display device according to a first embodiment of the invention,

[0037] - figure 2 is a sectional view of a variant of the display device according to the invention,

[0038] - figure 3 is a perspective view of the lever arms around a collar,

[0039] - figure 4 is a partial sectional view of an alternative embodiment of the device according to the invention,

[0040] - figure 5 is a partial sectional view of an alternative embodiment of the device according to the invention,

[0041] - Figure 6 is a perspective view of an additional variant of the display device,

[0042] - figure 7 is a partial sectional view of the display device of figure 6,

[0043] - Figure 8 is a sectional and profile view of several lever arm variants for display devices,

[0044] - figure 9 is a sectional view of a screw-nut system provided with a particular variant of the display device according to the invention,

[0045] - Figure 10 is a partial enlargement of Figure 9.

[0046] The examples are given for illustrative and non-limiting purposes. Other embodiments of the invention are easily 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 in order to facilitate understanding of the invention. Detailed description

[0047] Figure 1 is a sectional view of an embodiment of a display device 100 for displaying the correct tightening tension with a screw-nut system 10 with sufficient tightening.

[0048] The screw-nut system 10 comprises in particular a threaded rod 1 and a nut 3. The nut 3 is engaged 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 is deduced from the arrangement of the screw-nut system 10: the threaded rod 1 gives an axis considered vertical, and the radial and tangential directions are derived from this axis. The “inner” and “outer” orientations and equivalents are given relative to said axis. The free end of the threaded rod 1, through which the nut 3 is inserted, is considered “upper”, “above” or “top”.

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

[0051] The rim of the nut 3 defines an outer rim of the screw-nut system 10 shown in figure 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 “TREEP” type (trade name).

[0053] Between the nut 3 and the spring washers 5 is arranged a ring 11, which forms a housing for an annular needle 7, the section of which is polygonal, here in particular hexagonal, and has a point bearing against a radial shoulder under the ring 11. The other point of the annular needle 7 bears against a lever arm 9, part of a collar 90 with an annular base (see figure 2), also housed in the ring 9.

[0054] The section of the annular needle 7 is here symmetrical, which means that it can be arranged indifferently in one direction or the other. The ring 11 comprises a trunk 111 resting on the spring washers 5, and a crown 113 which forms a housing for the annular needle 7 and the collar 90 carrying the lever arms 9.

[0055] The nut 3, in the assembled state, comes to bear on the crown 113, and the tightening force is transmitted by means of the ring 11 to the spring washers 50.

[0056] The compression of the annular needle 7 when tightening the nut 3 therefore causes a flattening of the washers 5, and consequently a movement of the lever arm 9, with a reduction in the movement of an index 91 located at the free end of the lever arm 9.

[0057] The tip of the annular needle 7 rests on the lever arm 9 at a short distance from the elbow 93 relative to the total length of the lever arm 9, for a significant multiplication of the movement of the index 91 relative to the crushing movement of the spring washers 5.

[0058] The annular needle 7 has a hexagonal section, symmetrical with two points, arranged on its lower and upper edges, so that it can be arranged indifferently in one direction or another. Alternatively, the annular needle 7 can have a bearing surface on the shoulder of the nut 3.

[0059] The lever arm 9 is in particular integral with the collar 90, with respect to which it is bent. The lever arms 9 and the collar 90 are for example obtained by cutting a metal tube by means of axial cuts over a portion of its length and then stamping the cut end to bend the segments delimited by the cuts and thus form the lever arms 9. The collar 90 thus carries a plurality of lever arms 9, arranged radially around an annular base with which they are integral.

[0060] The collar 90 and the lever arms 9 are made of metal, and in particular of spring steel, a steel containing a portion of silica for better elastic behavior.

[0061] The index 91 at the end of the lever arm 9, opposite the elbow 93 which connects it to the collar 90, cooperates with a mark or visual indicator 95 located on the screw-nut system 10, here a rim of the ring 11 behind which the index 91 disappears during tightening. The index 91 bears a marking, for example a groove produced by laser marking, non-through, and good tightening tension is achieved when the index 91 overlaps or exceeds the visual indicator 95.

[0062] In particular, the user can tighten the screw-nut system 10 until the marking appears behind the edge forming a visual indicator 95 of the ring 11.

[0063] The index 91 is here a folded end portion of the lever arm 9. The end portion is folded upwards in figure 1, but can be, alternatively, folded downwards.

[0064] To calibrate the clamping tension of the display system 100, it can be compressed by a hydraulic piston exerting a compression force equal to the desired tension. The folds forming index 91 then partially protrude from the visual indicator 95. A laser is then used to make the markings by rotating around the compressed display device 100, the laser being oriented at the level of the visual indicator 95 on the indexes 91.

[0065] According to a particular embodiment, in addition or as an alternative, the index 91 can close an electrical circuit when it reaches a predetermined position, corresponding to the position in which the index 91 is aligned with the visual indicator 95. A diode, a sound transmitter or any other active signaling can then be activated by the closing of the electrical circuit.

[0066] Figure 2 shows an alternative embodiment of a display device 100 for a screw-nut system 10.

[0067] The display device 100 is here independent of the threaded rod 1 and the nut 3, which are not shown.

[0068] An elongated central ring 13 made of brass or tin is arranged inside the ring 11 and the spring washers 5, between these and the threaded rod 1 in the assembled state of the screw-nut system 10.

[0069] The display device 100 further comprises an ejectable element 20 in the form of a cap, which covers the screw head 1 or the nut 3, and the ejection of which signifies insufficient tightening of the screw-nut system 10. The ejectable element 20 comprises for this purpose prestressed elastic means (not shown), configured to eject it when it is released, for example a helical spring. The lever arms 9 are radially spaced apart during tightening of the screw-nut system 10 and form, as long as the tightening is sufficient, a retention of the ejectable element 20 by cooperating with retaining hooks 21 at the base of the ejectable element 20. The lever arms 9 move radially closer together when the tightening decreases, for example due to the creep of the threaded rod 11 and finally release the ejectable element 20 when the tightening becomes insufficient.

[0070] The ejectable element 20 is then advantageously colored in a particularly visible manner, for example brightly or fluorescently or phosphorescently, or with a particular spectral signature specific to sensors. The ejectable elements 20 are then visible or detectable around the installation comprising the screw-nut systems 10. A person inspecting the installation then only has to look for the ejected ejectable elements 20 to know which screw-nut systems 10 must be tightened.

[0071] Alternatively, cameras can be used to detect ejected ejectable elements 20, including cameras mounted in drones.

[0072] The ejectable element 20 is here produced in the form of a cap covering the nut 3 and the threaded rod 1.

[0073] Alternatively, the nut 3 and / or the threaded rod 1 covered by the ejectable element 20 are painted in a particularly visible manner, so as to appear once the ejectable element 20 is ejected.

[0074] Other forms of ejectable element 20 are however possible, in particular in the form of a ring arranged at the level of the spring washers 5, which makes the nut 3 accessible for tightening with the ejectable element 20 in place.

[0075] Figure 3 shows separately the collar 90 carrying the lever arms 9 of Figure 2.

[0076] As mentioned, the collar 90 and the lever arms 9 are made of one material, and form a flower-like element, the lever arms 9 extending radially forming the petals, with the circular collar 90 in the center.

[0077] The collar 90 carrying the lever arms 9 can be obtained for example by stamping and then folding from a thin steel plate, typically 0.5 mm thick. Alternatively, the collar 90 and the lever arms 9 can be obtained initially in the form of a ribbon, with the lever arms 9 folded, then a length of this ribbon is wound on itself to obtain the collar 90 with the lever arms 9 extending radially therefrom.

[0078] Figures 3 and 4 show alternative embodiments at index 91 and reference 95.

[0079] In Figure 3, the lever arms 9 extend beyond the edge of the ring 11, and the indexes 91 at the end of the lever arm 9 are folded upwards, their end being located at one face of said ring 11. The lever arms 9 are inclined downwards during tightening, and the marking 95 is here a groove carried by the face of the ring at which the indexes 91 are located.

[0080] In Figure 4, the lever arms 9 are located in the radial plane, and the index-forming ends 91 are folded downwards. The marking 95 is then carried by one of the washers 5, or may even be materialized by the edge of one of the washers 5.

[0081] Alternatively, the contact of the index 91 with the support S can be used to form the indicator of correct tightening.

[0082] Figure 5 shows an alternative embodiment, in which the lever arms 9 are made in the form of insulated folded metal strips.

[0083] In particular, the lever arms are partially inserted at their elbow 93 into a groove at the base of the ring 11.

[0084] The display device 100 of FIG. 5 comprises a single lever arm 9 arranged in a radial housing of the ring 11. Other embodiments may, for example, comprise three, four or more lever arms 9 each with a radial housing, regularly distributed around the periphery of the ring 11.

[0085] Figure 6 is a sectional view at the height of the radial housing and the lever arm 9. Said lever arm 9 is in the form of a segment of metal strip folded into a C, with at one end a hook forming the elbow 93, inserted into a groove of the ring 11, the hook forming the elbow 93 being adjusted to the section of the groove, so that its end is in contact with the radially outer wall, while the rounded part bears against the radially inner wall. The needle 7 is here a crest made of the same material as the ring 11, forming a wall of the groove in which the hook forming the elbow 93 is inserted.

[0086] The lever arm 9 is shown in dotted lines in the final position, with sufficient tightening. The hook forming the elbow 93 has undergone, in order to move from the initial position to the final position, an elastic deformation, and tends to return the lever arm 9 to the initial position. In this final position, the folded end of the lever arm 9 forming the index 91 protrudes entirely from the radial housing.

[0087] Alternatively, said index may be marked with a line or a groove, the appearance of which outside the radial housing indicates sufficient tightening.

[0088] In Figure 7, the deformation movement of the washers 5 is schematically represented by an arrow, with the upper edge of the washers 5 in dotted lines after tightening.

[0089] The lever arm 9 comprises a bearing surface 97 which comes to bear against said upper edge of the washers 5 during tightening, located just after the hook forming an elbow 93, at the base of the lever arm 9.

[0090] Figure 8 illustrates different embodiments of the lever arms 9, shown in radial section or profile view, with four examples shown described below from left to right.

[0091] The first embodiment is that of figure 7, in profile view, it comprises the hook forming elbow 93, the support surface 97 and the index 91 bearing a laser marking 92.

[0092] The second and third embodiments of Figure 8 are two variants of lever arms 9 made from a single material with an annular collar 90, shown in section. They comprise, at their elbow 93, a loop forming a reserve of elasticity for the second, and a fold forming a reserve of elasticity for the third.

[0093] This reserve of elasticity ensures good elastic deformability, as too large an angle bend can weaken a stamped metal or give it a plastic character at low deformations.

[0094] The fourth embodiment of the lever arm of Figure 8 is a variant of the first, in profile view. The lever arm 9 of the fourth embodiment has, at its right portion towards the index 91, a hollow 94 forming a housing for a band or annular elastic, which returns it to the rest position, in place of or in addition to the element contained in the hook forming an elbow 93.

[0095] Figure 9 illustrates a screw-nut system 10 provided with an additional variant of visualization device 100.

[0096] In this embodiment, the lever arms 9 are carried by a conical or radially flattened collar 90, bearing on the washers 5, under the ring 11.

[0097] The elbow 93 has a circular arc-shaped bead stamped at the same time as the rest of the lever arms 9 and the collar 90, against which a corner of the ring 11 rests, thus forming the needle 7.

[0098] Figure 10 is an enlarged partial view centered on elbow 93 and needle 7.

[0099] The needle 7 is in particular materialized precisely by a peripheral recess, here of rounded section. By moving said peripheral recess and / or by milling the radially outer wall to create a chamfer or even by milling the end of the needle 7, it is possible to modify the clamping tension at which the position identified by the index 91 and the mark 95 or at which the ejectable element 20 is ejected.

[0100] This embodiment is particularly easy to stamp, and no additional element forming the needle 7 is required. The collar 90 also allows automatic centering, so that assembly is simplified.

[0101] The invention makes it possible to clearly and apparently visualize the correct tightening of a screw-nut system 10 by using the lever arms 9 to multiply the crushing movement of the washers 5, a movement which is of low amplitude and consequently difficult to locate and quantify without multiplication.

[0102] The possibility of using a 91 index with a 95 visual reference also makes it possible to make the tightening tension to be achieved precise, independently of the torque required to achieve it.

[0103] The embodiment with ejectable element 20 also makes the loosening of the screw-nut system visible.

Claims

Claims 1. Device for displaying the correct tightening tension of a screw-nut system (10), the screw-nut system (10) comprising: - a screw (1) or threaded rod, - a nut (3), - a spring washer (5) or a stack (50) of parallel spring washers (5), bearing against a support (S) and which deforms by flattening during tightening, characterized in that the display device comprises: - a ring (11) located, in the assembled state, between the nut (3) and the spring washer(s) (5), configured to transmit the tightening force from the nut (3) to the spring washers (5), - a needle (7) located, in the assembled state, on a face oriented towards the spring washers (5) of the ring (11), - at least one lever arm (9), having an elbow (93) bearing against the spring washer(s) (11) in the assembled state, at which the needle (7) bears, and a free end set in motion by pressure of the needle (7) and the spring washers (5) on the lever arm (9) when tightening the screw-nut system (10), a particular position of the lever arm (9) indicating sufficient tightening tension.

2. Device according to claim 1, characterized in that the lever arm (9) has at its free end an index (91), configured to cooperate with an indicator (95) located on the screw-nut system (10), a good tightening tension being achieved when the index (91) of the lever arm (9) overlaps or exceeds the indicator (95).

3. Device according to claim 1, characterized in that the tightening of the screw-nut system (10) radially separates the lever arms (9), and in that it further comprises an ejectable element (20), comprising prestressed elastic means configured to eject it when the ejectable element (20) is released, and in that the radially spaced lever arms (9) form, as long as the tightening tension is sufficient, a retention of the ejectable element (20), and release the ejectable element when the tightening tension becomes insufficient.

4. Device according to claim 1, 2 or 3, characterized in that the lever arms (9) are made in the form of folded metal strips.

5. Device according to claim 4, characterized in that the lever arms are partially inserted at their elbow (93) into a groove at the base of the ring (11).

6. Device according to one of the preceding claims, characterized in that it comprises a plurality of lever arms (9), regularly arranged around the periphery of the ring (11) in the assembled state.

7. System according to claim 6, characterized in that the lever arms 9 are arranged radially around an annular collar (90) with which they are integral.

8. Device according to one of the preceding claims, characterized in that the needle (7) is annular and has a section with two points, arranged on its lower and upper edges.

9. Device according to one of claims 1 to 6, characterized in that the needle (7) is integral with the ring (11).

10. Device according to one of the preceding claims, characterized in that the lever arms (9) comprise an elastic element stressed during tightening of the screw-nut system (10), and the restoring force of which tends to return the lever arms (9) to a rest position, adopted in the absence of tightening of the screw-nut system (10).

11. Device according to one of the preceding claims, characterized in that the lever arms (9) comprise, at their elbow (93), a fold or a loop forming a reserve of elasticity.

12. Screw-nut system, characterized in that it comprises a device for displaying the correct tightening tension (100) according to one of the preceding claims.

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