(19)
(11)EP 3 623 087 A1

(12)EUROPEAN PATENT APPLICATION

(43)Date of publication:
18.03.2020 Bulletin 2020/12

(21)Application number: 19196765.2

(22)Date of filing:  11.09.2019
(51)Int. Cl.: 
B23B 31/19  (2006.01)
B23B 31/12  (2006.01)
(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR
Designated Extension States:
BA ME
Designated Validation States:
KH MA MD TN

(30)Priority: 12.09.2018 IT 201800008538

(71)Applicant: Amer S.p.A.
36078 Valdagno (VI) (IT)

(72)Inventor:
  • BATTISTELLA, Francesco
    36078 VALDAGNO (VI) (IT)

(74)Representative: Marchioro, Paolo 
Studio Bonini S.r.l. Corso Fogazzaro, 8
36100 Vicenza
36100 Vicenza (IT)

  


(54)IMPROVED MANDREL FOR RESIN COATING SYSTEMS.


(57) The invention is a mandrel (1, 100) for gripping an object, which comprises: a mandrel body (2) provided with a central hole (3) which extends along a longitudinal axis (X) and at least two seats (4) which extend radially and in angular directions different from each other starting from said longitudinal axis (X), a gripping assembly (5) comprising at least two gripping clamps (6) arranged in the seats (4) and a supporting element (7) configured to slide along the central hole (3). Each of the gripping clamps (6) is operatively connected, at the level of a first end (6a) thereof, to the supporting element (7) by means of a first connecting rod (8) and to the internal walls (4a, 4b) of its seat (4) by means of a second connecting rod (9) and a third connecting rod (10), so that the rectilinear movement of said supporting element (7) causes the rigid translation of each of the gripping clamps (6).




Description


[0001] The invention relates to a mandrel for gripping a tool, or an object in general, particularly suited to be used in resin coating systems configured to place a layer of insulating resin on the surfaces of the electric components of an electric motor, in particular rotors or stators.

[0002] It is known that the electrical components of an electric motor, such as rotors and/or stators, may consist of a plurality of windings made up of conductors, typically made of copper, on a support structure. Once these windings are in place, they must be insulated at their surfaces in order to prevent any accidental electrical contact with other electrical components belonging to the same electric motor.

[0003] In this regard, it is known the use of particular machines, called "resin coating systems" in jargon, equipped with a translation system on which a plurality of the aforementioned electrical components are arranged in sequence. This translation system moves the various electrical components one by one in a resin application station, where the aforesaid layer of insulating resin is applied on their surface. Specifically, during this resin treatment operation, the resin is deposited, for example by gravity, on the upper part of said electrical component, which is set rotating according to an axis of rotation that is perpendicular to the direction according to which the resin is deposited. In this way the resin is progressively distributed over all or part of the surface of the electrical component.

[0004] In order to be able to transport this electrical component to said resin application station and, at the same time, in order to allow it to rotate, the resin coating systems are equipped with special mandrels, in a number that can even be more than one hundred.

[0005] More specifically, these mandrels for locking rotors usually have a hole in the centre which extends longitudinally and in which the shaft of one of said rotors is inserted and locked.

[0006] Alternatively, to lock the stators, special clamps can be used that are able to lock the stator body on the mandrel by exerting a grip on the inner or outer edge of the stator itself.

[0007] As specifically regards the structure of the components making up the mandrels of the prior art, some types of mandrels are known which have a substantially cylindrical mandrel body with or without a central hole and a series of clamps, typically three clamps, configured to be moved radially with respect to said cylindrical body and/or with respect to the central hole. To carry out this movement, the mandrel is equipped with a series of internal gears which enable the clamps to be moved synchronously with a single movement towards the centre of the cylindrical body or in the opposite direction. However, these types of mandrels of the known type have some recognized drawbacks.

[0008] In particular, the structures of the mandrels of the known type, as described above, are provided with a series of internal gears which are very sensitive to dirt in general and in particular to the shavings which are formed during the processing of a piece. Even more specifically, in the specific field of use described above, where operations are carried out in particularly dirty environments, the proper operation of these types of mandrels is significantly affected by possible treatment residues, in particular by resin residues which tend to flow and penetrate between the gears of the mandrels themselves. Since, in fact, said resin tends to solidify as it cools down, the gears between which said resin has penetrated jam and seize, causing the mandrel to become unusable. This problem is particularly true in resin coating systems which, as mentioned above, may even consist of several hundred mandrels. In fact, the jamming and seizing of the various mandrels in a resin coating system disadvantageously causes continuous machine shutdowns, clearly not acceptable from the standpoint of production times and the related costs. Furthermore, even if it were possible to use the above mentioned mandrels of the prior art in a clean environment, said series of gears used to move the clamps would still require periodic and continuous maintenance operations in order to ensure their lubrication and therefore optimal operation.

[0009] Moreover, again as a consequence of the large number and complexity of the mechanical components making up the mandrels of the prior art, the latter are particularly subject to wear and tear and to breakages.

[0010] Another, yet not the least disadvantage of the mandrels of the prior art, caused once again by their complex mechanical structure, is represented by their excessive overall dimensions.

[0011] The present invention intends to overcome all the drawbacks mentioned above.

[0012] In particular, it is one of the objects of the invention to provide a mandrel for gripping an object, particularly rotors or stators of an electric motor, the operation of which is not affected by the presence of the dirt which is normally produced in the environments where it is typically used.

[0013] It is another object of the invention to provide a mandrel for gripping an object with an extremely low degree of wear and risk of breakage.

[0014] It is a further object of the invention to provide a mandrel for gripping an object that requires an extremely reduced level of maintenance, if at all.

[0015] Accordingly, it is an object of the invention to provide a mandrel which reduces to a minimum, if not completely eliminates, the machine shutdowns of the systems in which this mandrel is used.

[0016] Still another object of the invention is to provide a mandrel for gripping objects having a reduced number of components and a very low level of complexity. Consequently, it is an object of the invention to provide a gripping mandrel that is easy to assemble and disassemble if maintenance is needed.

[0017] Another object of the invention is to provide a mandrel for gripping an object which is self-lubricating and keeps the various mechanical components that make it up clean through the movement of the clamps.

[0018] A final, yet not the least object of the invention is to provide a mandrel for gripping an object having reduced overall dimensions, but at the same time having a wide clamping range to grip objects.

[0019] The objects illustrated above are achieved through the production of the gripping mandrel in accordance with the main claim.

[0020] Further characteristics of the gripping mandrel of the invention are described in the dependent claims.

[0021] The above objects, together with the advantages described below, will be highlighted in the description of some preferred embodiments of the invention that are provided, by way of non-limiting example, with reference to the attached drawings, wherein:
  • Fig. 1 shows an axonometric view of the mandrel of the invention according to a first preferred embodiment;
  • Fig. 2 shows an exploded axonometric view of the mandrel of the invention according to the first preferred embodiment;
  • Fig. 3 shows a front view of the mandrel of the invention according to the first preferred embodiment, in the release position;
  • Fig. 4 shows a sectional view, according to section plane IV-IV of Fig. 3, of the mandrel of the invention according to the first preferred embodiment, in the release position;
  • Fig. 5 shows a sectional view, according to section plane V-V of Fig. 3, of the mandrel of the invention according to the first preferred embodiment, in the release position;
  • Fig. 6 shows a sectional view, according to section plane VI-VI of Fig. 5, of the mandrel of the invention according to the first preferred embodiment, in the release position;
  • Fig. 7 shows a front view of the mandrel of the invention according to the first preferred embodiment, in the locked position;
  • Fig. 8 shows a sectional view, according to section plane VIII-VIII of Fig. 7, of the mandrel of the invention according to the first preferred embodiment, in the locked position;
  • Fig. 9 shows a sectional view, according to section plane IX-IX of Fig. 7, of the mandrel of the invention according to the first preferred embodiment, in the locked position;
  • Fig. 10 shows a sectional view, according to section plane X-X of Fig. 9, of the mandrel of the invention according to the first preferred embodiment, in the locked position;
  • Fig. 11 shows a breakout axonometric view of the mandrel of the invention according to the first embodiment;
  • Fig. 12 shows an axonometric view of the mandrel body belonging to the mandrel of the invention shown in Fig. 1;
  • Fig. 13 shows a front view of the mandrel body belonging to the mandrel of the invention shown in Fig. 1;
  • Fig. 14 shows an axonometric view of the gripping assembly belonging to the mandrel of the invention shown in Fig. 1;
  • Fig. 15 shows an axonometric view of the mandrel of the invention according to a second preferred embodiment;
  • Fig. 16 shows an exploded axonometric view of the mandrel of the invention according to the second preferred embodiment;
  • Fig. 17 shows a front view of the mandrel of the invention according to the second preferred embodiment, in the release position;
  • Fig. 18 shows a sectional view, according to section plane XVIII-XVIII of Fig. 17, of the mandrel of the invention according to the second preferred embodiment, in the release position;
  • Fig. 19 shows a sectional view, according to section plane XIX-XIX of Fig. 17, of the mandrel of the invention according to the second preferred embodiment, in the release position;
  • Fig. 20 shows a sectional view, according to section plane XX-XX of Fig. 19, of the mandrel of the invention according to the second preferred embodiment, in the release position;
  • Fig. 21 shows a front view of the mandrel of the invention according to the second preferred embodiment, in the locked position;
  • Fig. 22 shows a sectional view, according to section plane XXII-XXIII of Fig. 21, of the mandrel of the invention according to the second preferred embodiment, in the locked position;
  • Fig. 23 shows a sectional view, according to section plane XXIII-XXIII of Fig. 21, of the mandrel of the invention according to the second preferred embodiment, in the locked position;
  • Fig. 24 shows a sectional view, according to section plane XXIV-XXIV of Fig. 23, of the mandrel of the invention according to the second preferred embodiment, in the locked position;
  • Fig. 25 shows a breakout axonometric view of the mandrel of the invention according to the second embodiment.


[0022] The mandrel for gripping an object that is the subject of the invention, which is preferably designed to grip a rotor or a stator of an electric motor, is shown in a first embodiment in Figures from 1 to 14, where it is indicated as a whole by 1, and in a second embodiment in Figures from 15 to 25, where it is indicated as a whole by 100.

[0023] With regard to the first embodiment, as can be seen in Figures 1 and 2 and in the detail of Figures 12 and 13, the mandrel 1 comprises a mandrel body 2, preferably cylindrical in shape.

[0024] It cannot be excluded that in variant embodiments of the mandrel 1 the mandrel body 2 may have a shape other than cylindrical.

[0025] The mandrel body 2 itself is also provided with a central hole 3 which extends along a longitudinal axis X. Said central hole 3 has an inlet mouth 3a for the insertion of at least one part of an object. Preferably, if said object is an electric rotor, said central hole 3 is configured to at least partially house the shaft of the rotor itself.

[0026] As shown in Figure 12, according to said first preferred embodiment of the invention, said mandrel body 2 is provided with three seats 4 defined therein and extending radially and in different angular directions with respect to one another starting from the longitudinal axis X of the central hole 3. Preferably, according to the preferred embodiment of the invention, each of the three angular directions in which said seats 4 extend is angularly spaced from the adjacent ones by an angle of 120°.

[0027] However, it cannot be excluded that in variant embodiments of the invention the number of radially extending seats 4 may be a number other than three, provided that it is greater than one, and that the angular distance of the directions in which said three seats 4 extend may be different from 120°.

[0028] The mandrel 1 that is the subject of the invention also comprises, as can be seen in Figures 1 and 2 and in the detail of Figure 14, a gripping assembly 5 comprising in turn, according to said first preferred embodiment, three gripping clamps 6 having a substantially longitudinal development, each of which is arranged in one of said seats 4, as can be seen in Figure 11.

[0029] The gripping assembly 5 furthermore comprises a supporting element 7 positioned inside said central hole 3, on the opposite side of the inlet mouth 3a. Said supporting element 7, as can be seen in Figures 5 and 9, is configured to slide along said central hole 3 according to the direction defined by the longitudinal axis X.

[0030] In the mandrel 1 of the invention each gripping clamp 6 is operatively connected, at a first end 6a thereof, to the supporting element 7 by means of a first connecting rod 8. This connection allows the transmission of motion from the supporting element 7, which slides along said central hole 3, to said clamps 6.

[0031] Moreover, each of said clamps 6 is operatively connected to the internal walls 4a and 4b of the relative seat 4 by means of a second connecting rod 9 and a third connecting rod 10, so that the rectilinear movement of said supporting element 7 along the central hole 3 causes the rigid translation of each of the gripping clamps 6 with respect to the mandrel body 2 between a locking position, in this case of the rotor shaft, as shown in Figures from 7 to 10, and a release position of the same shaft, as shown in Figures from 3 to 6. Clearly, the translation of the clamps 6 can take place in the opposite direction, that is, from the release position to the locking position.

[0032] In the present context, the expression "rigid translation" of the gripping clamps 6 means the movement of the gripping clamps 6 both in the radial direction and in the axial direction, with the axis of the gripping clamps 6 parallel to the longitudinal axis X of the mandrel body 2. As previously stated, said rigid translation movement of the gripping clamps 6 is ensured by said second connecting rod 9 and third connecting rod 10.

[0033] Even more specifically, according to the preferred embodiment of the invention, when the supporting element 7 is moved forward along said central hole 3 towards the inlet mouth 3a of the latter, the thrusting action of the first connecting rod 8, in cooperation with the movement imposed by the second connecting rod 9 and by the third connecting rod 10 with respect to the mandrel body 2, determines the rigid translation of each clamp 6 to said release position. On the contrary, when the supporting element 7 is retracted in said central hole 3, said first connecting rod 8, in cooperation with said second connecting rod 9 and said third connecting rod 10, determines the rigid translation of each of said clamps 6 to said locking position, leading to the contact between the inner surface of each clamp 6 and, in this case, the shaft of the rotor to be locked, thus gripping the latter.

[0034] Furthermore, according to the invention, as can be seen in Figure 1 and in Figure 14, each of the second connecting rods 9 and each of the third connecting rods 10 which operatively connect a corresponding clamp 6 to the mandrel body 2 is defined by two small plates, respectively indicated by 9a and 9b and by 10a and 10b in the figures, interposed on opposite sides between the gripping clamp 6 itself and one of the two walls 4a and 4b of the corresponding seat 4.

[0035] This embodiment, in fact, besides enabling the clamps 6 to be translated with respect to the mandrel body 2, also enables the plates 9a, 9b, 10a and 10b to interact with the walls 4a and 4b of the seats 4 and with the side walls 6c and 6d of the gripping clamps 6 during said translation, as can be seen in Figure 11. This interaction advantageously makes it possible to maintain said walls 4a, 4b, 6c and 6d and the plates 9a, 9b, 10a and 10b clean and lubricated, removing any debris or dirt in general which are formed in the work environment where said mandrels 1 are used. This self-cleaning and self-lubrication of said walls makes it possible to prevent any machine shutdowns necessary to allow an operator to intervene and carry out maintenance on the mandrel itself.

[0036] In the present context, the term "interaction", with reference to the plates 9a, 9b, 10a and 10b with respect to the walls 4a and 4b of the seats 4 and of the side walls 6c and 6d of the clamps 6, means the sliding movement of the first with respect to the second, which facilitates the removal of any debris that is deposited during the use of the mandrel 1.

[0037] According to the preferred embodiment of the invention, each of the first connecting rods 8 is also defined by two small plates 8a and 8b hinged at their ends respectively to the side walls of the first end 6a of each gripping clamp 6 and to the supporting element 7, as shown in Figures 5 and 9.

[0038] As shown in Figure 5, a further characteristic of the mandrel of the invention is constituted by the fact that the supporting element 7 is prevented from rotating with respect to the mandrel body 2 and this impediment preferably occurs thanks to the presence of a first groove 13 and a second groove 14 respectively defined on the lateral surface 7a of the supporting element 7 and on the inner surface 3b of the central hole 3 and through the insertion of a mechanical key 15 in said grooves 13 and 14.

[0039] However, in order to allow the rectilinear movement of said supporting element 7 along the direction defined by the longitudinal axis X, according to the preferred embodiment described herein, the second groove 14 has a length, in the direction parallel to said longitudinal axis X, which is greater than the length of the mechanical key 15. Nonetheless, it cannot be excluded that in alternative embodiments the first groove 13, defined on the supporting element 7, may have a length, in the direction parallel to the longitudinal axis X, which is greater than the length of the mechanical key 15, obtaining in the same way the sliding movement of the supporting element 7 itself along said direction defined by the longitudinal axis X.

[0040] Furthermore, it cannot be excluded that in different embodiments of the invention this impediment to the rotation of the supporting element 7 and equally its movement along the direction defined by the longitudinal axis X may be obtained with alternative mechanical solutions.

[0041] With regard, again, to the supporting element 7, as can be seen in Figures 4, 8 and 11, it is operatively connected to a drive shaft 11 on the opposite side of the gripping clamps 6, by means of a motion conversion system 12 configured to convert the rotary motion of said drive shaft 11 into the rectilinear motion of the supporting element 7 along the longitudinal axis X.

[0042] In particular, according to the first preferred embodiment of the invention shown in Figure 11, the motion conversion system 12 comprises a threaded screw 17 at the level of the end 11a of the drive shaft 11 facing the supporting element 7 and also comprises a counter-threaded nut 18 in the same supporting element 7 in such a way that the rotation of the drive shaft 11 generates the screwing or unscrewing of the counter-threaded nut 18 on/from the threaded screw 17, in turn creating, in cooperation with said system preventing the rotation of the supporting element 7, the rectilinear movement of the latter along the longitudinal axis X with respect to the mandrel body 2. Nonetheless, also with regard to the motion conversion system 12, it cannot be excluded that it may be implemented, according to alternative embodiments of the mandrel 1 of the invention, in a different way with respect to how it has been described with reference to the preferred embodiment.

[0043] Furthermore, as regards the movement of the supporting element 7 inside said central hole 3, according to the invention it is limited beyond a certain position in the direction of the inlet mouth 3a by the definition of a stop element 16, as shown in Figures 5 and 9.

[0044] In particular, this stop element 16 is created by making a counteracting wall 16a in the central hole 3 whose diameter is smaller than the diameter of the supporting element 7, thereby obviously preventing the sliding movement of the supporting element 7 itself beyond said counteracting wall 16a.

[0045] As regards the second embodiment of the mandrel 100 of the invention, represented in Figures from 15 to 25, it substantially has all the features described for the aforementioned first embodiment of the mandrel and for this reason in these figures the elements in common with said first embodiment are indicated by the same numerical references. For this reason, with reference to said elements, refer to the description provided for the first embodiment of the mandrel 1 of the invention.

[0046] In addition to said common characteristics, the second embodiment of the mandrel 100, as shown in Figures 15 and 16, has a jaw 19 which is solidly coupled with the free end 6b of each of the gripping clamps 6. Said jaw 19 includes a gripping point in radial direction, defined at a greater distance from the longitudinal axis X compared to the gripping point of said gripping clamps 6. In particular, said gripping point, unlike that of said clamps 6, is external with respect to the mandrel body 2, in such a way that, as previously mentioned, in cooperation with the gripping points of the other jaws 19, it can enable, for example, the locking of a stator body 2 or of any other component or object to be processed on the mandrel 100, exerting a grip on the outer or inner edge of the stator itself or of any other component or object.

[0047] In particular, as can be seen in Figure 16, said second embodiment of the mandrel 100 of the invention, besides providing for the addition of said jaws 19, also provides for the use of a further cap 20 positioned so that it is superimposed to the mandrel body 2 and on the front surface 20a of which there are three slots 21 arranged radially and intended to guide the radial movement of the jaws 19 themselves.

[0048] As previously mentioned, one or more mandrels 1 and/or 100 of the invention can be used in a resin coating system, not shown in the figures, configured to provide the electrical components of an electric motor, preferably the rotors or stators, with a resin coating.

[0049] On the basis of the foregoing, therefore, the improved mandrel that is the subject of the invention achieves all the set purposes.

[0050] In particular, the invention achieves the object to provide a mandrel for gripping an object, particularly rotors and/or stators of an electric motor, the operation of which is not affected by the dirt present in the environments where it is normally used.

[0051] The invention also achieves the object to provide a mandrel for gripping an object having an extremely low degree of wear and risk of breakage.

[0052] A further object achieved by the invention is to provide a mandrel for gripping an object that requires an extremely reduced level of maintenance, if at all. Accordingly, the invention achieves also the object to provide a mandrel which reduces to a minimum, if not completely eliminates, the machine shutdowns of the systems in which said mandrel is used.

[0053] Still another object achieved by the invention is to provide a mandrel for gripping objects having a reduced number of components and a highly decreased level of complexity.

[0054] Accordingly, the invention achieves the object to provide a gripping mandrel that is easy to assemble and disassemble if maintenance is needed.

[0055] Another object achieved by the invention is to provide a mandrel for gripping an object which is self-lubricating and makes it possible to keep the various mechanical components that make it up clean during the movement of the clamps.

[0056] Finally, the invention achieves also the object to provide a mandrel for gripping an object which has reduced overall dimensions but at the same time a large object clamping range.


Claims

1. Mandrel (1, 100) for gripping an object, of the type comprising:

• a mandrel body (2) provided with:

- a central hole (3) which extends along a longitudinal axis (X) and which is provided with an inlet mouth (3a) for the insertion of at least a part of said object;

- at least two seats (4) which extend radially and in angular directions different from each other starting from said longitudinal axis (X) of said central hole (3);

• a gripping assembly (5) comprising:

- at least two gripping clamps (6) with substantially longitudinal extension, each of said gripping clamps (6) being placed in one of said seats (4);

- a supporting element (7) positioned in said central hole (3) on the opposite side of said inlet mouth (3a), said supporting element (7) being configured to slide along said central hole (3) according to said longitudinal axis (X), each of said gripping clamps (6) being operatively connected to said supporting element (7) at the level of a first end (6a) thereof by means of a first connecting rod (8) and to the internal walls (4a, 4b) of said seats (4) by means of a second connecting rod (9) and a third connecting rod (10), so that the rectilinear movement of said supporting element (7) causes the rigid translation of each of said gripping clamps (6) with respect to said mandrel body (2) between a position in which said object is locked and a position in which it is released or vice versa, each one of said second connecting rod (9) and third connecting rod (10) being defined by means of two small plates (9a, 9b, 10a, 10b) inserted on opposite sides between said gripping clamp (6) and one of said walls (4a, 4b) of said seat (4), so that said plates (9a, 9b, 10a, 10b) interact with said walls (4a, 4b) of said seat (4) and the side walls (6c, 6d) of said gripping clamp (6) during said rigid translation.


 
2. Mandrel (1, 100) according to claim 1, characterized in that:

- said gripping assembly (5) comprises three gripping clamps (6) operatively connected to said supporting element (7) at an angular distance from each other equal to 120°;

- said mandrel body (2) comprises three of said seats (4) placed at an angular distance from each other equal to 120°.


 
3. Mandrel (1, 100) according to any one of the preceding claims, characterized in that said first connecting rod (8) is defined by two small plates (8a, 8b) hinged at their ends respectively to the side walls (6c, 6d) of said first end (6a) of said gripping clamp (6) and to said supporting element (7).
 
4. Mandrel (1, 100) according to any one of the preceding claims, characterized in that said supporting element (7) is prevented from rotating with respect to said mandrel body (2), said supporting element (7) being operatively connected to a drive shaft (11) on the opposite side of said gripping clamps (6) by means of a motion conversion system (12) configured to convert the rotary motion of said drive shaft (11) into said rectilinear motion of said supporting element (7) along said longitudinal axis (X).
 
5. Mandrel (1, 100) according to claim 4, characterized in that said impediment to the rotation of said supporting element (7) is obtained by means of a first groove (13) and a second groove (14) defined respectively on the lateral surface (7a) of said supporting element (7) and on the wall (3b) of said central hole (3) and by inserting a mechanical key (15) in said grooves (13, 14), at least one between said first groove (13) and said second groove (14) having a greater length in a direction parallel to said longitudinal axis (X) compared to the length of said mechanical key (15), so that said supporting element (7) is able to slide along said central hole (3) to move said gripping clamps (6) from said locking position to said release position and vice versa.
 
6. Mandrel (1, 100) according to claim 5, characterized in that along said central hole (3) a stop element (16) is defined which is configured so as to prevent the sliding movement of said supporting element (7) towards said inlet mouth (3a) beyond a predefined end position.
 
7. Mandrel (1, 100) according to claim 6, characterized in that said stop element (16) comprises a counteracting wall (16a) created in said central hole (3) having a diameter which is smaller than the diameter of said supporting element (7).
 
8. Mandrel (1, 100) according to any of the claims from 4 to 7, characterized in that said motion conversion system (12) comprises a threaded screw (17) at the level of the end (11a) of said drive shaft (11) facing said supporting element (7) and comprises a counter-threaded nut (18) in said supporting element (7), so that the rotation of said drive shaft (11) causes the screwing or unscrewing of said counter-threaded nut (18) on/from said threaded screw (17) causing the rectilinear movement of said supporting element (7) along said longitudinal axis (X) with respect to said mandrel body (2).
 
9. Mandrel (100) according to any one of the preceding claims, characterized in that it comprises a jaw (19) fixedly coupled with the free end (6b) of each of said gripping clamps (6), said jaw (19) having a gripping point in radial direction at a greater distance than the gripping point of said gripping clamps (6).
 




Drawing