Mechanical torque limiting device

Abstract

Mechanical torque limiting device (1) comprising a containment body (2) having an inner cavity (3) open at an insertion mouth (30), a pack of discs (4) entirely housed in the inner cavity (3) and structured for limiting a mechanical torque transferable from a first shaft (90) to a second shaft (91 ), wherein the pack of discs (4) comprises a plurality of first discs (5) and a plurality of second discs (6), wherein the containment body (2) is sealed except for said insertion mouth (30).

Description

[0001] DESCRIPTION

[0002] Title: MECHANICAL TORQUE LIMITING DEVICE

[0003] Technical field of the invention

[0004] The present invention relates to a mechanical torque limiting device and a motion transmission system comprising the aforementioned limiting device.

[0005] State of the art

[0006] US2015033892A1 discloses a gearbox comprising a gear wheel which is connected / disconnected to / from a drive shaft by a mechanical torque limiting device with discs mounted on the latter.

[0007] Summary of the invention

[0008] By 'substantially perpendicular' in relation to geometric elements (such as lines, planes, surfaces, etc.) it is meant that these elements form an angle within the range 90°+ / -15°, preferably 90°+ / -10°.

[0009] By 'substantially parallel' in relation to the aforementioned geometric elements it is meant that these elements form an angle within the range 0°+ / -15°, preferably 0°+ / -10°.

[0010] In the aforementioned context of the mechanical torque limiting devices with discs which exploit the friction between the discs for limiting a torque transferable from the engine to the user so that it does not exceed a maximum torque, the Applicant has considered advantageous to be able to control in stable and long-lasting way the value of the torque maximum transferable torque.

[0011] In fact, once the value of maximum torque has been adjusted for a given limiting device, for example at the end of the production process (e.g. during the product approval phase) and depending on the intended use, it is important that this maximum torque is kept constant over time (except for voluntary interventions).

[0012] The Applicant has therefore faced the problem of realizing a mechanical torque limiting device which is stable over time in terms of maximum torque and at the same time structurally simple and / or economical.

[0013] According to the Applicant, the aforementioned problem is solved by a mechanical torque limiting device according to the attached claims and / or having one or more of the following features.

[0014] According to an aspect, the invention relates to a mechanical torque limiting device for limiting a mechanical torque transferable from a first shaft to a second shaft or vice versa. The device comprises:

[0015] - a containment body structured to be interposed between said first shaft and said second shaft for mechanically connecting to each other said first and second shafts, said containment body comprising an inner cavity open at an insertion mouth;

[0016] - a pack of discs entirely housed in said inner cavity and structured for limiting said transferable mechanical torque to a maximum mechanical torque, the pack of discs comprising a plurality of first discs and a plurality of second discs arranged in succession along a central axis.

[0017] Preferably said first discs are mechanically coupled to said containment body for rigidly rotating with said containment body around said central axis.

[0018] Preferably said inner cavity is shaped to allow an insertion of said second shaft into said inner cavity through said insertion mouth, said second discs being structured for mechanically coupling with said second shaft when inserted into said inner cavity.

[0019] Preferably said containment body is (totally) sealed except for (only) said insertion mouth. By "(totally) sealed" it is meant that the containment body has no further openings with respect to the insertion mouth and / or that such further openings, if present, are (directly) sealed.

[0020] According to the Applicant, by providing a containment body that is totally sealed, except at the insertion mouth, it is possible to realize, when the device is coupled in use to a respective motion transmission system, a sealed chamber at the inner cavity of the containment body, by the containment body itself and one or more components of the motion transmission system which seal the insertion mouth, such as for example the second shaft of the motion transmission system, which is inserted into the inner cavity for mechanically coupling with the second discs, and possibly further components of the transmission system. Once created, this sealed chamber therefore entirely encloses the pack of discs, allowing to protect the pack of discs from contaminating and / or fouling agents of various kinds. In particular, the aforementioned sealed chamber can advantageously protect the pack of discs from the lubricating oil used in the motion transmission systems in which the torque limiting devices are often incorporated. The Applicant has in fact found that in case of pack of discs wetted by the aforementioned oil, the variation in the chemical-physical properties of the oil, for example due to ageing, temperature variation, etc., can generate an uncontrollable, and in general unpredictable, variation of the friction forces between the discs (for a given compression force), with consequent uncontrolled variation of the maximum transferable torque.

[0021] The present invention in one or more of the above aspects may present one or more of the following preferred features. Preferably said containment body is structured to be rigidly mechanically coupled to said first shaft. Typically, also the first shaft contributes to realize the aforementioned sealed chamber.

[0022] Preferably said containment body comprises a containment portion with development (substantially) cylindrical around said central axis. Preferably said pack of discs is arranged at said containment portion. In this way the housing of the pack of discs is facilitated.

[0023] Preferably said containment portion is devoid of through openings. In this way the discs are protected in simple way.

[0024] In one embodiment, said device comprises a gasket (e.g. made of elastically flexible polymeric material) fixed to said containment body and structured (e.g. shaped) for being interposed (with sealing contact) between said containment body and said second shaft when inserted into the inner cavity.

[0025] Preferably said gasket is arranged in an intermediate position between said insertion mouth and said pack of discs (e.g. with reference to an insertion direction of the second shaft into the inner cavity), for example the gasket can be arranged immediately downstream of the insertion mouth (e.g. with reference to the direction of insertion of the second shaft into the inner cavity). In this way the protection of the pack of discs is incremented.

[0026] Preferably each first disc comprises one or more respective projections (more preferably a plurality of projections circumferentially equally distributed with respect to said central axis) which protrude radially externally from the first disc with respect to said central axis. Preferably said containment portion comprises one or more grooves (more preferably a plurality of grooves circumferentially equally distributed with respect to said central axis) facing said inner cavity. Preferably each groove of said containment portion has a respective line of main development (substantially) parallel to said central axis.

[0027] Preferably said one or more projections of each first disc each engage one (and only one) respective groove of said one or more grooves of said containment portion. Preferably an inner surface of said containment portion is substantially counter-shaped to a radially external profile of said first discs. In this way, the rigid rotational coupling between the containment body and the first discs is realized in structurally simple manner.

[0028] Preferably each first and second disc has annular shape comprising a respective central through opening. Preferably said respective central through openings are coaxial to said central axis. In this way, an empty volume is realized inside the pack of discs advantageous for housing the second shaft (at least an end portion of the second shaft), as described below.

[0029] Preferably each second disc comprises one or more respective projections (more preferably a plurality of projections circumferentially equally distributed with respect to said central axis) which protrude radially internally from the second disc with respect to said central axis. Preferably said one or more respective projections of each second disc are arranged along an edge of the respective central through opening of the respective second disc. In this way they are properly arranged for gearing with the second shaft, when inserted inside the pack of discs.

[0030] Preferably said first and second discs are alternated to each other along the central axis. In this way the forces (e.g. friction) are distributed in a homogeneous way during use.

[0031] Preferably said first discs are made of metallic material, for example steel.

[0032] Preferably each second disc comprises a layered structure. Preferably each second disc comprises a support disc, preferably made of metallic material, for example steel, and a first and a second coating layer arranged at axially opposite parts of (e.g. glued to) said support disc.

[0033] Preferably (only) the support disc of each second disc is equipped with said one or more respective projections of the second disc.

[0034] Preferably each covering layer comprises, more preferably is made of, a friction material. This material has proven to be particularly advantageous in terms of friction forces, and / or stability of such friction forces, developable between the discs (which in turn determine the maximum transferable mechanical torque) and / or of wear resistance, particularly in synergy with the use of a pack of dry discs, for example compared to simple direct steel- to-steel contact.

[0035] Preferably said first and second discs are arranged in direct reciprocal contact (e.g. the first discs directly contacting a respective coating layer of the directly preceding and / or subsequent second disc). In this way the friction forces between the discs develop in desired way.

[0036] In one embodiment, said device comprises a gasket arranged at said insertion mouth of said containment body. Preferably said gasket (e.g. made of elastically flexible polymeric material) is interposed with contact between said containment body and said second shaft, when inserted into said inner cavity. In this way the seal is improved allowing the rotation of the second shaft with respect to the containment body.

[0037] Preferably said device comprises an adjustment system structured for adjusting a compressive force (acting on said pack of discs, more preferably - substantially - parallelly to the central axis).

[0038] Preferably said adjustment system comprises an elastic element, operationally interposed between said containment body and an extremal disc of said pack of discs. Preferably the elastic element is structured for keeping said pack of discs in compression against said containment body. Preferably said adjustment system comprises an adjustment element, structured for adjusting a degree of compression of said elastic element against said extremal disc. In this way it is possible to adjust the maximum mechanical torque.

[0039] According to another aspect, the invention relates to a motion transmission system comprising a mechanical torque limiting device according to the present invention.

[0040] Preferably said transmission system comprises a first shaft. Preferably said containment body is rigidly fixed (more preferably with sealing) to said first shaft, more preferably at said insertion mouth.

[0041] Preferably said transmission system comprises a second shaft inserted into said inner cavity and mechanically coupled to said second discs for rigidly rotating together with said second discs around said central axis.

[0042] Preferably (with said device fixed to said first shaft and said second shaft inserted into said inner cavity) said containment body, and (at least) said second shaft (possibly also with the first shaft) realize, at the inner cavity, a sealed chamber which completely encloses said pack of discs.

[0043] Preferably said sealed chamber is devoid of lubricating agents. In other words, the pack of discs exploits the friction forces that are formed between the dry stacked discs. In this way, by completely eliminating the presence of any lubricating agent in direct contact with the pack of discs, the maintenance of a dynamic of operation stable over time is facilitated, for example in terms of set mechanical torque threshold.

[0044] Preferably said first shaft is a gear wheel.

[0045] Preferably said containment body is fixed (more preferably directly) to said gear wheel (preferably at a lateral face of the gear wheel) for rigidly rotating with said gear wheel around an axis of rotation of said gear wheel. In this way the limiting device is coupled to the first shaft in simple way.

[0046] Preferably said axis of rotation of said gear wheel coincides with said central axis. In this way the system remains rational and highly simple in terms of motion transmission from the first shaft to the device. Preferably said transmission system comprises a worm screw mechanically geared with said gear wheel.

[0047] Preferably said second shaft comprises one or more respective grooves (more preferably a plurality of grooves circumferentially equally distributed with respect to an axis of said second shaft) made on an outer surface of said second shaft. Preferably each groove of said second shaft has a respective line of main development (substantially) parallel to an axis of said second shaft.

[0048] Preferably said second shaft is inserted into said respective central through openings of said first and second discs.

[0049] Preferably said one or more projections of each second disc each engage one (and only one) respective groove of said second shaft. Preferably said external surface of said second shaft at said end portion is substantially counter-shaped to a radially inner profile of said second discs. In this way, the rigid rotational coupling between the second shaft and the second discs is realized in structurally simple way.

[0050] Preferably said axis of said second shaft coincides with said central axis. In this way the motion transmission is rational.

[0051] Preferably said gear wheel comprises a respective central through opening. Preferably said second shaft develops through said gear wheel at the central through opening of the gear wheel. In this way the system is compact.

[0052] Preferably said insertion mouth is arranged at said central through opening of the gear wheel. In this way the second shaft is inserted in simple way.

[0053] In one embodiment, said transmission system comprises a respective gasket (e.g. made of elastically flexible polymeric material) fixed to said gear wheel at said central through opening of said gear wheel. Preferably said gasket is interposed with contact between said gearwheel and said second shaft. In this way the sealing of the chamber is improved. In one embodiment, said transmission system comprises the aforementioned respective gasket and incorporates the aforementioned embodiment of the limitation device also equipped with a gasket. In other terms, the gaskets are doubled (e.g. according to the redundancy principle) in order to further preserve the seal of the chamber at the region where the pack of discs of the torque limiting device is housed.

[0054] In the aforementioned embodiment in which the two aforementioned distinct gaskets are provided, said respective gasket of the transmission system is arranged further upstream of the gasket with which the limiting device is equipped with respect to an insertion direction of the second shaft which goes from the gear wheel to the limiting device. Preferably said system comprises a main body having a housing cavity open at a housing mouth.

[0055] Preferably said worm screw and / or said gear wheel are housed in said housing cavity. Preferably said second shaft is at least partially housed in said housing cavity. In this way the mechanical parts are protected.

[0056] In one embodiment, said motion transmission system comprises a lubricating fluid, for example oil, which fills said housing cavity. In this way the mechanical parts are lubricated, for example at the worm screw-gear wheel mechanical gearing. Thanks to the aforementioned sealed chamber, the risk that the lubricating fluid of the transmission system comes into contact with the pack of discs (with the risk of altering its friction properties over time) is excluded.

[0057] Preferably said mechanical torque limiting device is reversibly rigidly fixable to said first shaft (to said gear wheel) through said housing mouth of said main body. In this way the maintenance and / or replacement of the torque limiting device is advantageous with limited interventions on the motion transmission system (e.g. without dismantling the mechanical motion transmission members of the first and / or second shaft, for example without decoupling the worm screw and the gear wheel).

[0058] Brief description of the drawings

[0059] Figure 1 schematically shows a longitudinal section of a torque limiting device according to the present invention; figure 2 schematically shows a longitudinal section of the device of figure 1 with the second shaft inserted; figures 3 and 4 schematically show two longitudinal and transversal sections, at different heights, of the device of figure 2, figure 5 shows in purely schematic way a partial section of a motion transmission system according to the present invention.

[0060] Detailed description of some embodiments of the invention

[0061] The features and the advantages of the present invention will be further clarified by the following detailed description of some embodiments, presented by way of example and not as a limitation of the present invention, with reference to the attached figures.

[0062] In the figures, with the number 1 it is globally indicated a mechanical torque limiting device for limiting a mechanical torque transferrable from a first shaft 90 to a second shaft 91 (e.g. direct motion) or vice versa (e.g. retrograde motion). Ideally, in the shown embodiments, the first shaft 90 ideally belongs to a drive side (e.g. it is a drive shaft) of a machine (not shown) incorporating the limiting device 1 , while the second shaft 91 belongs to a user side.

[0063] In one alternative embodiment (not shown), what described above can be mirror- reversed, i.e. the first shaft can belong to the user side and the second shaft to the motor side.

[0064] The device 1 comprises a containment body 2 structured for being interposed between the first shaft 90 and the second shaft 91 for mechanically connecting to each other the first and second shaft. Exemplarily, the containment body 2 is structured for being mechanically rigidly coupled to the first shaft 90. Exemplarily, the containment body is directly connected to an attachment flange 72 of a gear wheel 902 which realizes the first shaft 90 (exemplarily the attachment flange is made integral, e.g. by welding, riveting, to the rest of the gear wheel 902).

[0065] Exemplarily, the containment body 2 comprises an inner cavity 3 open at an insertion mouth 30. Exemplarily, the inner cavity 3 is shaped to allow an insertion of the second shaft 91 into the inner cavity through the insertion mouth 30 (as for example shown in figure 2).

[0066] The device 1 exemplarily comprises a pack of discs 4 entirely housed in the inner cavity 3 and structured for limiting the transferable mechanical torque to a maximum mechanical torque. Exemplarily the pack of discs 4 comprises a plurality of first discs 5 and a plurality of second discs 6 arranged in succession along a central axis 100. Exemplarily, the first 5 and second discs 6 are alternated with each other along the central axis 100 and arranged in direct mutual contact.

[0067] The operating principle of the pack of discs, based on the friction between the first and the second discs, for mechanically limiting the torque transferable from the first to the second shaft (or vice versa) will not be described as it is known per se.

[0068] Exemplarily (fig. 1 and 2) the containment body 2 comprises a cap 7 exemplarily having a substantially bell shape, and a base support 71 , with discoidal shape. Exemplarily, the cap 7 and the base support 71 are rigidly connected to each other by a plurality of screws 73. As exemplarily shown (fig. 2), some of the screws 73 mutually fix the cap 7 and the first base support 71 , while others screws 73 fix the containment body and the attachment flange 72 to each other. Exemplarily the containment body 2 is sealed except for the insertion mouth 30.

[0069] Exemplarily the containment body 2, more in detail the cap 7, comprises a containment portion 8 with substantially cylindrical development with respect to the central axis 100. Exemplarily the pack of discs 4 is arranged at the containment portion 8.

[0070] Exemplarily the containment portion 8 is devoid of through openings (e.g. it is structurally continuous and contiguous).

[0071] Exemplarily the first discs 5 are mechanically coupled to the containment body 2 for rigidly rotating with the containment body 2 around the central axis 100.

[0072] To this end, each first disc 5 exemplarily comprises a plurality of respective projections 51 circumferentially equally distributed with respect to the central axis 100 which protrude radially externally from the first disc 5 with respect to the central axis 100 (see for example fig. 4).

[0073] Exemplarily the containment portion 8 comprises a plurality of grooves 81 (only partially shown, figures 3 and 4) circumferentially equally distributed with respect to the central axis 100, facing the inner cavity 3. Exemplarily each groove has a respective line of main development parallel to the central axis 100.

[0074] Exemplarily each projection 51 of each first disc 5 engages one and only one respective groove 81 of the containment portion 8. In detail, an inner surface (i.e. facing the inner cavity 3) of the containment portion 8 is counter-shaped to a radially external profile of the first discs 5 (fig. 4).

[0075] Exemplarily each first 5 and second disc 6 has annular shape comprising a respective central through opening 9 (free in fig. 1 , occupied by the second shaft 91 in the remaining figures). Exemplarily the respective central through openings 9 are coaxial to the central axis 100.

[0076] The second discs 6 are exemplarily structured for mechanically coupling with the second shaft 91 when inserted into the inner cavity 3

[0077] To this end, each second disc 6 exemplarily comprises a plurality of respective projections 61 circumferentially equally distributed with respect to the central axis 100 which protrude radially internally from the second disc 6 with respect to the central axis 100, and the second shaft 91 comprises a plurality of respective grooves 911 circumferentially equally distributed with respect to an axis (not shown, exemplarily coinciding with the central axis 100 when the second shaft is inserted into the inner cavity 3 and correctly mechanically coupled to the second discs 6) of the second shaft 91 realized on an outer surface of the second shaft 91 (see in particular fig. 3). Exemplarily, as shown in fig. 1 , the respective projections 61 of each second disc 6 are arranged along an edge of the respective central through opening 9 of the respective second disc 6.

[0078] Exemplarily each groove 911 of the second shaft 91 has a respective line of main development parallel to the axis of the second shaft, i.e. in use parallel to the central axis 100. Exemplarily the grooves 911 of the second shaft 91 are made at an end portion of the second shaft.

[0079] Exemplarily the first discs 5 are made of steel. Exemplarily the second discs 6 have layered structure, each second disc 6 comprising a respective support disc 611 (equipped with the projections 61 ) made of steel, and a first and a second coating layer 10 arranged at axially opposite parts of the support disc 611 .

[0080] Exemplarily each first and second covering layer 10 is made of a friction material, such as for example L-504 or R-246 marketed by Inno Friction GmbH.

[0081] Exemplarily the pack of discs 4 is subjected to a compression force parallel to the central axis 100 (for realizing the friction forces between the discs, as known)

[0082] To this end, the device 1 exemplarily comprises an adjustment system 12 structured for adjusting the compression force. Exemplarily the adjustment system 12 comprises an elastic element 13 (e.g. a disc or Belleville spring), operationally interposed between the containment body 2, in detail between the cap 7, and an extremal disc of the pack of discs 4 (exemplarily represented by a first disc 5) and structured for keeping the pack of discs 4 in compression against the containment body 2. In detail, the pack of discs is exemplarily kept in compression by the elastic element 13 against an annular abutment surface 711 realized by the first support base 71 (fig. 1 and 2).

[0083] Exemplarily the adjustment system 12 also comprises an adjustment element 14, structured for adjusting a degree of compression of the elastic element 13 against the extremal disc. In detail, the adjustment element 14 comprises an adjustment screw that passes through the containment body 2, at an end portion of the cap 7. Exemplarily, by varying a degree of screwing of the screw in the containment body it is possible to adjust a thrust given on the disc spring by one end of the adjustment screw arranged inside the containment body, in contact with the disc spring.

[0084] Exemplarily the device comprises sealing means (not shown) at the hole in which the screw is inserted.

[0085] Exemplarily the second shaft 91 (when inserted into the inner cavity 3) is inserted into the respective central through openings 9 of the first 5 and second discs 6

[0086] Exemplarily the projections 61 of each second disc 6 each engage one and only one respective groove 911 of the second shaft 91. Exemplarily, the outer surface of the second shaft at the end portion is substantially counter-shaped to a radially internal profile of the second discs 6. With reference to figure 5, it exemplarily shows, in purely schematical way and in section, a motion transmission system 99 according to the present invention

[0087] The system 99 comprises the limiting device 1 according to the present invention. In figure 5 the device 1 , and in particular the pack of discs 4, are shown in purely schematic way Exemplarily the transmission system 99 comprises the first shaft 90, to which it is rigidly fixed to the containment body 2 at the insertion mouth 30, and the second shaft 91 , inserted into the inner cavity 3 and mechanically coupled to the second discs 6. Exemplarily the first shaft 90 is a gear wheel 902 comprising the attachment flange 72. Exemplarily (schematically shown) the containment body 2 is directly fixed to the gear wheel 902 for rigidly rotating with the gear wheel 902 around an axis of rotation of the gear wheel, exemplarily coinciding with the central axis 100.

[0088] Exemplarily the containment body 2, the gear wheel 902 (in detail the attachment flange 72) and the second shaft 91 realize, at the inner cavity 3, a sealed chamber 904 (in figure 5 the sealed chamber is marked by a dot background) which entirely encloses the pack of discs 4.

[0089] Exemplarily the sealed chamber is devoid of lubricating agents on the inside, so that the latter, during use of the device, do not influence the maximum transferable torque for example due to thermal variation and / or aging and / or fouling.

[0090] The option of adopting a sealed chamber devoid of lubricating agents (i.e. using the pack of dry discs) can be particularly advantageous in combination with the use of the aforementioned friction material for realizing the coating layers of the second discs.

[0091] In one embodiment (not shown), the sealed chamber is filled with lubricating agents. The present invention allows to confine these lubricants inside the sealed chamber, for reducing their contamination and therefore limiting the variation over time of their chemical-physical properties (and consequently the variation of the value of the maximum transferable torque).

[0092] Exemplarily the gear wheel 902 comprises a respective central through opening 903, the second shaft developing through the gear wheel at the central through opening 903. Exemplarily, the insertion mouth 30 is arranged at an edge of the central through opening 903.

[0093] Exemplarily, the transmission system 99 comprises a gasket 15 (e.g. made of elastically flexible polymeric material, for example a gasket of known type as a BALIMSL 042X062X8 gasket marketed by FREUDENBERG) fixed to the gear wheel 902 at the edge of the central through opening 903 of the gear wheel 902 and interposed with contact between the gear wheel 902 (more precisely between the attachment flange 72) and the second shaft 91 .

[0094] In one embodiment (not shown), in addition or as an alternative to the gasket 15, the device 1 can comprise a respective gasket fixed to the containment body 2 and suitably shaped for resulting interposed, with sealing contact, between the containment body 2 and the second shaft 91 (when inserted into the inner cavity 3) for further increasing the seal of the chamber. In this embodiment the respective gasket of the device 1 is advantageously arranged in an intermediate position between the insertion mouth 30 and the pack of discs 4 with reference to an insertion direction (not shown) of the second shaft 91 in the inner cavity 3 (and preferably upstream of the gasket 15 along this insertion direction).

[0095] Exemplarily, the system 99 comprises a worm screw 901 mechanically geared with the gear wheel 902.

[0096] Exemplarily, the system 99 also comprises a main body 98 having a housing cavity 97 open at a housing mouth 96.

[0097] Exemplarily, the gear wheel 902 is entirely housed in the housing cavity 97, while the worm screw 901 is at least partially housed in this housing cavity. Exemplarily, the second shaft 91 is partially housed in the housing cavity 97.

[0098] In one embodiment (not shown) the motion transmission system comprises a lubricating fluid, for example oil, which fills the housing cavity

[0099] Exemplarily, the mechanical torque limiting device 1 is reversibly rigidly fixable to the gear wheel 902 through the housing mouth of the main body, for example by removing a cover (not shown) arranged in use for reversibly closing the aforementioned housing mouth.

Claims

CLAIMS1 . Mechanical torque limiting device (1 ) for limiting a mechanical torque transferable from a first shaft (90) to a second shaft (91 ) or vice versa, said device (1 ) comprising:- a containment body (2) structured to be interposed between said first shaft (90) and said second shaft (91 ) for mechanically connecting to each other said first (90) and second shaft (91 ), said containment body (2) comprising an inner cavity (3) open at an insertion mouth (30);- a pack of discs (4) entirely housed in said inner cavity (3) and structured for limiting said transferable mechanical torque to a maximum mechanical torque, the pack of discs (4) comprising a plurality of first discs (5) and a plurality of second discs (6) arranged in succession along a central axis (100), wherein said first discs (5) are mechanically coupled to said containment body (2) for rigidly rotating with said containment body (2) around said central axis (100), wherein said inner cavity (3) is shaped to allow an insertion of said second shaft (91 ) into said inner cavity (3) through said insertion mouth (30), said second discs (6) being structured for mechanically coupling with said second shaft (91 ) when inserted into said inner cavity (3), and wherein said containment body (2) is sealed except for said insertion mouth (30).

2. Device (1 ) according to claim 1 , wherein said containment body (2) comprises a containment portion (8) with development substantially cylindrical around said central axis (100), wherein said pack of discs (4) is arranged at said containment portion (8), wherein said containment portion (8) is devoid of through openings, wherein each first disc (5) comprises one or more respective projections (51 ) which protrude radially externally from the first disc (5) with respect to said central axis (100), and said containment portion (8) comprises one or more respective grooves (81 ) facing said inner cavity (3), each groove (81 ) of said containment portion (8) having a respective line of main development substantially parallel to said central axis (100), and wherein said one or more projections (51 ) of each first disc (5) each engage a respective groove (81 ) of said one or more grooves of said containment portion (8).

3. Device (1 ) according to any one of the previous claims, wherein each first (5) and second disc (6) has annular shape comprising a respective central through opening (9), said respective central through openings (9) being coaxial to said central axis (100), and wherein each second disc (6) comprises one or more respective projections (61 ) which protrude radially internally from the second disc (6) with respect to said central axis (100).

4. Device (1 ) according to any one of the previous claims, wherein the first (5) and second discs (6) are alternated to each other along the central axis (100) and arranged in direct contact with each other, wherein the first discs (5) are made of steel, wherein each second disc (6) comprises a support disc (611 ) and a first and a second coating layer (10) arranged at axially opposite parts of said support disc (611 ), and wherein said first and second coating layer (10) are made of a friction material.

5. Device (1 ) according to any one of the previous claims, comprising an adjustment system (12) structured for adjusting a compressive force acting on said pack of discs (4), and wherein said adjustment system (12) comprises an elastic element (13), operationally interposed between said containment body (2) and an extremal disc of said pack of discs (4), and an adjustment element (14), structured for adjusting a degree of compression of said elastic element (13) against said extremal disc.

6. Device (1 ) according to any one of the previous claims, comprising a gasket fixed to said containment body (2) and structured for being interposed between said containment body (2) and said second shaft (91 ) when inserted into said inner cavity (3).

7. Motion transmission system (99) comprising:- a mechanical torque limiting device (1 ) according to any one of claims from 1 to 6,- a first shaft (90), said containment body being rigidly fixed to said first shaft (90),- a second shaft (91 ) inserted in said inner cavity (3) and mechanically coupled to said second discs (6) for rigidly rotating together with said second discs (6) around said central axis (100).

8. System (99) according to claim 7, wherein said containment body (2) and said second shaft (91 ) form, at said inner cavity (3), a sealed chamber (904) which completely encloses said pack of discs (4), and wherein said sealed chamber (904) is devoid of lubricating agents.

9. System (99) according to claim 7 or 8, wherein said first shaft (90) is a gear wheel(902), wherein said containment body (2) is fixed to said gear wheel (902) for rigidly rotating with said gear wheel (902) around an axis of rotation of said gear wheel, wherein said axis of rotation of said gear wheel (902) coincides with said central axis (100), wherein said gear wheel (902) comprises a respective central through opening (903), wherein said insertion mouth (30) is arranged at an edge of said central through opening(903) of the gear wheel, wherein said system (99) comprises a gasket (15) arranged at said central through opening (903) of said gear wheel (902), and wherein said gasket (15) is interposed with contact between said gear wheel (902) and said second shaft (91 ).

10. System (99) according to any one of claims from 7 to 9, wherein said second shaft (91 ) comprises one or more respective grooves (911 ) made on an outer surface of said second shaft (91 ), wherein each groove (911 ) of said second shaft (91 ) has a respective line of main development substantially parallel to an axis of said second shaft, wherein said second shaft (91 ) is inserted into respective central through openings (9) of said first(5) and second discs (6), wherein one or more projections (61 ) of each second disc each engage a respective groove (911 ) of said second shaft (91 ), wherein said axis of said second shaft (91 ) coincides with said central axis (100), wherein said system (99) comprises a main body (98) having a housing cavity (97) open at a housing mouth (96), wherein said first shaft (90) is at least partially housed in said housing cavity (96), and wherein said mechanical torque limiting device (1 ) is reversibly rigidly fixable to said first shaft (90) through said housing mouth (96) of said main body (98).

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