Sufficient tightening tension detection device in a screw-nut system

Abstract

The invention relates to a device for visualizing the correct tightening tension of a screw-nut system (10) comprising: - a screw (1) or threaded rod, - a nut (3), - a spring washer (5) or stack (50) of parallel spring washers (5), which deforms by flattening during tightening, characterized in that the visualization device comprises: - a ring (11) located between the nut (3) and the spring washer(s) (5), - a pointer (7) located on a face of the ring (11) oriented towards the spring washers (5), - at least one lever arm (9), having a bend (93) bearing against the spring washer(s) (11) in the assembled state, against which the pointer (7) bears, and a free end set in motion by pressure from the pointer (7) and the spring washers (5). Figure for the abstract: Fig. 1

Description

Title of the invention: DEVICE FOR DETECTING SUFFICIENT 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 the tightening tensions of such screw-nut systems.

[0002] Prior techniques

[0003] Manual verification of the tightening 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] 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 technician has to bring tools such as torque wrenches or hydraulic tensioners in addition to tightening tools, this constitutes an additional burden in hard-to-reach installations, resulting in extra costs.

[0007] In particular, documents EP2210002 are known to show screws having a coloured indicator on their upper face which changes colour when a sufficient tightening torque is reached.

[0008] These screws have the disadvantage that the color change is gradual, and that the perception of color varies from one user to another. Insufficient precision in tightening torque is therefore achieved.

[0009] Furthermore, 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, such as a socket wrench. It is therefore necessary to proceed in stages: tighten a portion of the screw, remove the tool and check, tighten another portion of the screw, remove the tool and check, etc.

[0010] 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.

[0011] Moreover, most existing devices and systems measure tightening torque, however the different possible surface conditions, the rusty or greased nature of the screw-nut system means 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.

[0012] There is therefore a need for a device to visualize the correct tightening tension of a screw-nut system that does not present the aforementioned drawbacks. Description of the invention

[0013] 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: - a screw or threaded rod, - a nut, - a spring washer or a stack of parallel spring washers, supported against a support and which deforms by flattening during tightening. The visualization device is characterized in that it comprises: - 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, - a pointer located, in the assembled state, on a face oriented towards the spring washers of the ring, - at least one lever arm, having an elbow bearing against the spring washer(s) in the assembled state, at which the needle rests, and a free end set in motion by pressure of the needle and spring washers on the lever arm when tightening the screw-nut system, a particular position of the lever arm indicating sufficient tightening tension.

[0014] 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.

[0015] 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 clamping tension being reached when the index of the lever arm overlaps or exceeds the indicator.

[0016] Indexing then allows the correct clamping tension to be visualized precisely and in an adjustable manner according to the desired tension.

[0017] If tightening the screw-nut system radially separates the lever arms, the viewing device may further include an ejectable element, comprising means prestressed elastics configured to eject it when the ejectable element is released, and in that the radially spaced lever arms form, as long as the clamping tension is sufficient, a retention of the ejectable element, and release the ejectable element when the clamping tension becomes insufficient.

[0018] Lever arms can in particular be made in the form of folded metal strips.

[0019] The lever arms can be partially inserted at their elbow into a groove at the base of the ring.

[0020] The device may include a plurality of lever arms regularly arranged around the periphery of the ring in the assembled state.

[0021] The lever arms can be arranged radially around an annular collar with which they come from the material.

[0022] The pointer may be annular and have a two-pointed section, arranged on its lower and upper edges.

[0023] Alternatively, the needle can come from the material with the ring.

[0024] The lever arms may include an elastic element that is constrained when the screw-nut system is tightened, and whose restoring force tends to return the lever arms to a rest position, adopted in the absence of tightening of the screw-nut system.

[0025] The lever arms may have at their elbow a fold or loop forming a reserve of elasticity.

[0026] Finally, the invention also relates to the screw-nut system, characterized in that it includes a device for visualizing the correct tightening tension as previously described.

[0027] Summary description of the figures

[0028] Other advantages and features of the invention will become apparent from the following description of the accompanying figures, among which:

[0029] [Fig. 1] is a cross-sectional view of a screw-nut system provided with a viewing device according to a first embodiment of the invention,

[0030] [Fig.2] is a cross-sectional view of a variant of a display device according to the invention,

[0031] [Fig.3] is a perspective view of the lever arms around a collar,

[0032] [Fig.4] is a partial cross-sectional view of an alternative embodiment of the device according to the invention,

[0033] [Fig.5] is a partial cross-sectional view of an alternative embodiment of the device according to the invention,

[0034] [Fig.6] is a perspective view of an additional variant of the display device,

[0035] [Fig.7] is a partial cross-sectional view of the visualization device of [Fig.6],

[0036] [Fig-8] is a cross-sectional and profile view of several lever arm variants for visualization devices,

[0037] [Fig.9] is a cross-sectional view of a screw-nut system provided with a variant by particular display device according to the invention,

[0038] [Fig. 10] is a partial enlargement of [Fig.9].

[0039] 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

[0040] Fig. 1 is a cross-sectional view of an embodiment of a visualization device 100 of the correct clamping tension with a screw and nut system 10 with sufficient tightening.

[0041] 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.

[0042] A radial coordinate system is derived from the arrangement of the screw-nut system 10: the threaded rod 1 provides an axis considered vertical, 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 "at the top".

[0043] 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.

[0044] 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.

[0045] 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).

[0046] Between the nut 3 and the spring washers 5 is a ring 11, which forms a housing for an annular punch 7, the cross-section of which is polygonal, in this case hexagonal, and has one point bearing against a radial shoulder under the ring 11. The other point of the annular punch 7 bears against a lever arm 9. of a collar 90 with an annular base (see [Fig.2]), also housed in the ring 9.

[0047] The section of the annular pointer 7 is symmetrical here, which means that it can be arranged in either direction.

[0048] The ring 11 has 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.

[0049] The nut 3, in the assembled state, rests on the crown 113, and the tightening force is transmitted via the ring 11 to the spring washers 50.

[0050] 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 multiplication of the movement of an index 91 located at the free end of the lever arm 9.

[0051] The tip of the annular pointer 7 rests on the lever arm 9 at a small 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.

[0052] The annular punch 7 has a hexagonal cross-section, symmetrical with two points, arranged on its lower and upper edges, so that it can be oriented in either direction. Alternatively, the annular punch 7 may have a bearing surface on the shoulder of the nut 3.

[0053] The lever arm 9 is formed from the material of the collar 90, relative to which it is bent. The lever arms 9 and the collar 90 are obtained, for example, by cutting a metal tube by means of axial cuts along 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 formed.

[0054] 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.

[0055] 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 visual marker or indicator 95 located on the screw-nut system 10, here a lip of the ring 11 behind which the index 91 disappears during tightening. The index 91 bears a marking, for example a non-through groove made by laser marking, and the correct tightening tension is reached when the index 91 overlaps or extends beyond the visual indicator 95.

[0056] In particular, the user can tighten the screw-nut system 10 until the marking appears behind the rim forming a visual indicator 95 of the ring 11.

[0057] The index 91 is here a folded extremal portion of the lever arm 9. The extremal portion is folded upwards in [Fig.1], but can, alternatively, be folded downwards.

[0058] To calibrate the clamping tension of the visual indicator 100, it can be compressed by a hydraulic piston exerting a compression force equal to the desired tension. The folds forming the index 91 then partially protrude from the visual indicator 95. A laser is then used to make the markings by rotating around the compressed visual indicator 100, with the laser being directed at the visual indicator 95 on the index 91.

[0059] According to a particular embodiment, in addition or alternatively, 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 emitter or any other active signaling can then be activated by the closing of the electrical circuit.

[0060] Fig. 2 shows an alternative embodiment of a viewing device 100 for a screw-nut system 10.

[0061] The viewing device 100 is here independent of the threaded rod 1 and the nut 3, which are not shown.

[0062] An elongated central ring 13 made of brass or tin is arranged inside the ring 11 and spring washers 5, between these and the threaded rod 1 in the assembled state of the screw-nut system 10.

[0063] The viewing device 100 further includes an ejectable element 20 in the form of a cap, which covers the screw head 1 or the nut 3, and whose ejection signifies insufficient tightening of the screw-nut system 10. The ejectable element 20 includes for this purpose pre-stressed elastic means (not shown), configured to eject it when it is released, for example a helical spring.

[0064] The lever arms 9 are spread radially apart when the screw-nut system 10 is tightened and, as long as the tightening is sufficient, form 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 threading of the threaded rod 11 and finally release the ejectable element 20 when the tightening becomes insufficient.

[0065] The ejectable element 20 is then advantageously colored in a particularly visible way, for example brightly, fluorescently, or phosphorescently, or with a specific spectral signature for sensors. The ejectable elements 20 are then visible or detectable around the installation comprising the screw-nut systems 10. A technician inspecting the installation then only has to look for the ejected ejectable elements 20 to know which screw-nut systems 10 need to be tightened.

[0066] Alternatively, cameras can be used to detect ejectable elements 20 ejected, in particular cameras mounted on drones.

[0067] The ejectable element 20 is here made in the form of a cap covering the nut 3 and the threaded rod 1.

[0068] 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.

[0069] Other forms of ejectable element 20 are however possible, in particular in the form of a ring disposed at the level of the spring washers 5, which makes the nut 3 accessible for tightening with the ejectable element 20 in place.

[0070] Figure [Fig. 3] shows separately the collar 90 carrying the lever arms 9 of Figure [Fig. 2]

[0071] As mentioned, the collar 90 and the lever arms 9 are made of material, and form a flower-like element, the lever arms 9 which radiate out forming the petals, with the circular collar 90 in the center.

[0072] The collar 90 carrying the lever arms 9 can be obtained for example by stamping and then bending from a thin steel plate, typically 0.5 mm thick.

[0073] 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 coming radially from it.

[0074] Figures 3 and 4 show alternative embodiments with index 91 and marker 95.

[0075] In [Fig.3], the lever arms 9 extend beyond the edge of the ring 11, and the index marks 91 at the end of the lever arms 9 are folded upwards, their ends being located at the level of a 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 the level of which the index marks 91 are located.

[0076] In [Fig. 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 rim of one of the washers 5.

[0077] Alternatively, the contact of the index 91 with the support S can be used to form the correct tightening indicator.

[0078] Fig. 5 shows an alternative embodiment, in which the lever arms 9 are made in the form of insulated folded metal strips.

[0079] In particular, the lever arms are partially inserted at their elbow 93 into a groove at the base of the ring 11.

[0080] The viewing device 100 of [Fig.5] comprises a single lever arm 9 disposed 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.

[0081] Fig. 6 is a cross-sectional view at the height of the radial housing and the lever arm 9. The 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 in the ring 11, the hook forming the elbow 93 being fitted to the section of the groove, so that its end is in contact with the radially outer wall, while the rounded end is in contact with the radially inner wall.

[0082] The point 7 is here a ridge coming from the material with the ring 11, forming a wall of the groove in which the hook forming the elbow 93 is inserted.

[0083] The lever arm 9 is shown in dotted lines in its final position, with sufficient clamping. The elbow-shaped hook 93 has undergone elastic deformation in moving from the initial to the final position, and tends to return the lever arm 9 to its initial position. In this final position, the folded end of the lever arm 9, forming the index 91, protrudes entirely from the radial housing.

[0084] Alternatively, said index may be marked with a line or a groove, the appearance of which outside the radial housing forms an indicator of sufficient tightening.

[0085] In [Fig.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.

[0086] The lever arm 9 has a bearing surface 97 which bears against said upper edge of the washers 5 during tightening, located just after the elbow-forming hook 93, at the base of the lever arm 9.

[0087] Fig. 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.

[0088] The first embodiment is that of [Fig.7], in profile view, it includes the elbow-forming hook 93, the bearing surface 97 and the index 91 bearing a laser marking 92.

[0089] The second and third embodiments of [Fig. 8] are two variants of lever arms 9 made of material with an annular collar 90, shown in cross-section. They include, 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.

[0090] This reserve of elasticity ensures good elastic deformability, as an excessively large bend angle can weaken a stamped metal or give it a plastic character at small deformations.

[0091] The fourth embodiment of the lever arm of [Fig.8] is a variant of the first, in profile view.

[0092] The lever arm 9 of the fourth embodiment has, at the level of its right portion towards the index 91, a hollow 94 forming a housing for a band or ring elastic, which brings it back to the rest position, in place of or in addition to the element contained in the hook forming the elbow 93.

[0093] Fig. 9 illustrates a screw-nut system 10 provided with an additional variant of a viewing device 100.

[0094] 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.

[0095] The elbow 93 has a circular arc 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 point 7.

[0096] Fig. 10 is a partial enlarged view centered on the elbow 93 and the needle 7.

[0097] The needle 7 is specifically defined by a peripheral recess, here with a rounded cross-section. By moving said peripheral recess and / or by milling the radially external 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 marked by the index 91 and the reference mark 95, or at which the ejectable element 20 is ejected.

[0098] This embodiment is particularly easy to stamp, and no additional elements forming the point 7 are required. The collar 90 also allows for automatic centering, thus simplifying assembly.

[0099] The invention makes it possible to clearly and visibly visualize the proper 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 small amplitude and consequently difficult to spot and quantify without multiplication.

[0100] The possibility of using an index 91 with a visual reference 95 also makes it possible to make the clamping tension to be achieved precise, regardless of the torque required to achieve it.

[0101] The embodiment with ejectable element 20 further makes the loosening of the screw-nut system visible.

Claims

Demands

1. A device for visualizing 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 deforming by flattening during tightening, characterized in that the visualization 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 washer(s) (5), - a pointer (7) located, in the assembled state, on a face of the ring (11) oriented towards the spring washer(s) (5), - at least one lever arm (9), having a bend (93) bearing against the spring washer(s) (11) in the assembled state, at which point supporting the pointer (7),and a free end set in motion by pressure of the needle (7) and 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) having at its free end an index (91), configured to cooperate with an indicator (95) located on the screw-nut system (10), a good clamping tension being reached when the index (91) of the lever arm (9) overlaps or exceeds the indicator (95).

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

6.

7.

8.

9.

10.

11.

12. levers are partially inserted at their elbow (93) into a groove at the base of the ring (11). Device 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. System according to claim 6, characterized in that the lever arms 9 are arranged radially around an annular collar (90) with which they come from material. Device according to one of the preceding claims, characterized in that the needle (7) is annular and has a two-pointed section, arranged on its lower and upper edges. Device according to any one of claims 1 to 6, characterized in that the needle (7) comes from material with the ring (11). Device according to one of the preceding claims, characterized in that the lever arms (9) comprise an elastic element constrained during tightening of the screw-nut system (10), and whose restoring force tends to return the lever arms (9) to a rest position, adopted in the absence of tightening of the screw-nut system (10). Device according to one of the preceding claims, characterized in that the lever arms (9) have, at the level of their elbow (93), a fold or loop forming a reserve of elasticity. Screw-nut system, characterized in that it includes a device for visualizing the correct tightening tension (100) according to one of the preceding claims.

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