WINDING MANDREL FOR THE PRODUCTION OF REELS OF WEB MATERIAL

Abstract

The winding mandrel includes a substantially cylindrical wall with expandable members for the torsional locking of tubular winding cores. At least one portion of the wall is made of carbon fiber in a polymer resin matrix.

Description

TECHNICAL FIELD

The present invention concerns the field of machines for the processing of paper and working of web materials, in particular but not exclusively tissue paper.

STATE OF THE ART

In the production of reels of web material, in particular but not exclusively tissue paper, expandable winding mandrels are frequently used, fitted with one or more cores made of cardboard or other lightweight material around which the required quantity of web material is wound to form a log or roll. This roll, once the winding mandrel has been removed, can be cut into smaller rolls with shorter axial length for packaging and sale. In some cases, several axially aligned cores are fitted on the mandrel in order to simultaneously wind a plurality of rolls with axial dimension equal to the dimension of the finished reel.

WO-03/074398 describes a machine for winding web material on winding mandrels of the type mentioned above.

U.S. Pat. No. 5,379,964, U.S. Pat. No. 6,454,204, EP-A-0322864 and EP-A-0850867 describe winding mandrels made at least partly of synthetic resin reinforced with carbon fiber. These mandrels have mechanical locking systems operated in various ways. The locking elements that protrude from the mandrel to lock the winding core on it are controlled by internal members.

SUMMARY OF THE INVENTION

The invention relates to the production of expandable winding mandrels of the type described above which are particularly efficient and reliable, resistant to wear and suitable for securely retaining and locking the winding cores during the winding process. According to some embodiments, the invention proposes mandrels which reduce the weight and rotation inertia, which provide good rigidity, robustness and resistance to wear, and high critical speeds.

Substantially, according to a first embodiment, a winding mandrel is provided for the production of reels of web material with a wall made at least partly of carbon fibers, for example by winding continuous fibers or filaments in a resin matrix which then undergoes polymerization and/or crosslinking. Expandable mechanical or pneumatic members are provided along the mandrel wall to torsionally and axially lock the tubular cores on the mandrel.

In practical embodiments, according to the invention the elements that lock the winding core on the mandrel are deformable, preferably elastically, under the effect of the pressure of a fluid, preferably air. In this way, when the mandrel is not operating, the expandable locking members are preferably fully retracted in respective seats and do not protrude from the outer surface of the cylindrical wall of the mandrel. In this way said members do not interfere with insertion or extraction of the winding cores, reducing wear and at the same time facilitating the insertion and extraction operations. Under the pressure of the (liquid or gaseous) fluid the expandable members deform, protruding from the outer cylindrical surface of the mandrel wall. Substantially, the deformable elements themselves, under the pressure of the fluid, form the member that cooperates with the core, locking it on the mandrel. In other words, the expandable member swells due to the effect of the fluid under pressure and protrudes from the surface of the mandrel, pressing with a portion against the inner surface of the tubular winding core fitted on the mandrel.

In some embodiments the expandable members comprise a plurality of expandable elements, preferably pneumatic, which expand radially outwards by delivering a fluid under pressure, for example and preferably air. The fluid under pressure is delivered for example by means of a longitudinal duct which extends along at least a portion of the inner cavity of the mandrel and has a valve at one end of the mandrel.

In some preferred embodiments of the invention, at least one insert is arranged along the mandrel, connected to the longitudinal duct for distribution of the fluid under pressure, extending inside said substantially cylindrical wall for at least a portion of the axial length of the mandrel. Preferably, the insert comprises at least one seat for an expandable pneumatic element, in fluid connection with said longitudinal duct. Preferably several inserts are provided distributed along the axial length of the mandrel. In preferred embodiments of the invention, each insert has at least two seats and preferably three seats for respective pneumatic expandable elements, angularly staggered with respect to one another, preferably at a constant angular pitch between one seat and the other.

In some preferred embodiments of the invention, the substantially cylindrical wall is formed of a plurality of tubular portions made of carbon fiber and one or more inserts; said tubular portions are interconnected by said inserts, hence the outer surface of the mandrel is formed partly of the inserts, which can be made of metal, for example a lightweight metal such as aluminum or its alloys.

In some preferred embodiments of the invention the outer surface of the mandrel, formed of tubular portions made of carbon fiber and one or more inserts, is covered with a metal or ceramic coating measuring a few tenths of a millimeter (for example 0.3 mm). In this way it is possible to remedy problems connected with abrasion of the core, generally made of cardboard, on the outer surface of the mandrel. Due to the non-uniformity of the mandrel component material (fiber+insert made of aluminum or other material), it may be necessary to resort to an intermediate coating made of a material that effectively “bonds” on both materials of the mandrel. The intermediate coating is then covered with the material which will in turn be ground. This solution permits trouble-free grinding of the entire mandrel as the mandrel is ground on a uniform material. Obviously the finished mandrel will not have the coating on the expandable areas (i.e. on the expandable elastic walls). In practice, during construction of the mandrel a “plug” can be provided on these areas before applying the metal/ceramic material. Subsequently the metal/ceramic coating is applied, the mandrel is ground and lastly the “plug” is removed, thus obtaining a mandrel formed of tubular carbon fiber portions and metal inserts, with a continuous ground metal/ceramic coating, except for the expandable areas.

Preferably, the inserts are provided with means of connection or interface to connect the inserts to the carbon fiber tubular portions. In some embodiments each of said inserts can have a substantially cylindrical surface which defines, with outer surfaces of said carbon fiber tubular portions, the outer surface of the mandrel. Adjacent to said substantially cylindrical surface, frustoconical surfaces can be provided for connection to the tubular portions connected to the respective insert. The carbon fiber tubular portions will have, internally, complementary frustoconical surfaces thus obtaining reciprocal coupling between the inserts and the carbon fiber tubular portions. Alternatively, to provide the connection between the tubular portions and the respective insert it is possible to use cylindrical surfaces with a grooving, for example in the order of 0.2 mm, to enhance adhesion between the fiber tubular portions and the inserts via the use of glue. In this configuration there is a negligible reduction in the resistance to force/tension transmitted between the two materials of the tubular portions and insert respectively during normal use of the mandrel, but great construction simplification of the portion of fiber tube is obtained as it does not require complex machining to obtain a frustoconical form. The tubular portion is then fitted inside and joined by means of gluing.

Preferably the inserts comprise a central body, in which the seats for the expandable members are provided, and axial ends each forming an interface surface to attach said insert to the respective tubular portions.

In some embodiments, each insert has an axial through seat, inside which a cylindrical member is housed, provided with an axial hole through which said longitudinal duct passes. The longitudinal duct has, at each insert, at least one outlet for the fluid under pressure. The cylindrical member is axially attached to the longitudinal duct and forms passages for supplying the fluid under pressure coming out of said at least one outlet towards distribution channels formed in the insert and in fluid communication with the expandable elements.

In some embodiments the distribution channels comprise a ring-shaped groove and substantially radial passages extending from said ring-shaped groove towards said cavities containing the expandable elements.

In some embodiments the pneumatic expandable elements are formed of volumes of fluid under pressure, at least partially delimited by a deformable diaphragm or wall, preferably an elastically deformable one. The deformable wall can be made of natural or synthetic rubber, or other elastically deformable material having suitable characteristics of mechanical resistance and elastic deformability.

Further possible features and embodiments of the invention are set forth in the attached claims and will be described in greater detail below with reference to some embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood by following the description and the accompanying drawing, which shows practical non-limiting embodiments of the invention. More specifically, in the drawing:

FIG. 1 shows an axonometric view of a mandrel according to the invention in one embodiment;

FIGS. 2 and 3 show longitudinal sections of the ends of the mandrel of FIG. 1;

FIGS. 2A and 3A show longitudinal sections of the ends of the mandrel in a modified embodiment;

FIG. 4 shows a longitudinal section of an intermediate portion of the mandrel of FIG. 1 provided with inserts comprising expandable pneumatic elements;

FIG. 5 shows an enlargement of a portion of FIG. 4;

FIG. 5A shows an enlargement similar to that of FIG. 4, with parts removed, in a different embodiment;

FIG. 6 is a section according to VI-VI of FIG. 5;

FIG. 6A is a section according to A-A of FIG. 5A;

FIG. 7 is a view according to VII-VII of FIG. 5;

FIG. 8 is an enlargement of an insert with expandable pneumatic elements in longitudinal section in a modified embodiment of the invention;

FIG. 9 is a longitudinal section of an intermediate portion of a mandrel with the inserts of FIG. 8.

DETAILED DISCLOSURE OF EMBODIMENTS OF THE INVENTION

FIG. 1 shows schematically a mandrel made according to the invention and indicated overall by the number 1. The mandrel has an intermediate part 3 and two end portions 5 and 7 shown in the enlargements of FIGS. 2 and 3. Along the portion 3 inserts 9 are arranged provided with expandable pneumatic elements, described below in greater detail.

In some embodiments, the ends 5 and 7 are made of metal, for example aluminum.

In a preferred embodiment of the invention, shown in FIGS. 2A and 3A, each of the portions 5 and 7 can in turn consist of two elements: a hollow cylindrical pad, fitted to the final tubular portion made of carbon fiber, and a conical end part which is joined to the pad by means of a coupling member, for example a pin, a screw, a set screw or other similar systems. In particular, FIG. 3A shows the end 7 in this embodiment. 7A indicates the hollow cylindrical pad and 7B the tapered end part. 7C indicates a connection screw between the parts 7A and 7B. FIG. 2A shows the end 5, limited to the hollow cylindrical pad 5A, which is provided with threaded holes 5C for fastening screws of a closing part not shown. The advantages of this construction are:

• • possibility of accessing the inside of the tube also via the two ends 5 and 7 (after removal of the tapered end);
  • possibility of disassembling the tapered end in the event of breakage or failure thereof and replacing it without having to replace the entire mandrel.

In the previous configuration the tapered end is one single piece integral with the tubular portion and therefore if one of the two ends 5 or 7 breaks or fails, the entire mandrel would have to be discarded and replaced with a new one.

The intermediate or central part 3 is made at least partly of carbon fiber in a polymer resin matrix. More specifically, in the embodiment shown in FIG. 1, with some details thereof shown in FIGS. 2 to 7, the central or intermediate part 3 of the mandrel consists of a plurality of tubular portions 11, each of which is made with a wall in carbon fiber in a polymer matrix. The various tubular portions 11 are interconnected at the inserts 9, which in this embodiment constitute not only a housing for the pneumatic expandable elements but also reciprocal connection elements between the tubular portions 11 and have a substantially cylindrical surface which forms, together with the cylindrical surface of the tubular portions 1, the outer surface of the mandrel 1.

Inside the mandrel 1, and for at least one portion of its axial length, a longitudinal duct 13 extends roughly coaxially with the cylindrical wall defined by the tubular portions 11 for delivery of a fluid under pressure, typically air, to expand the pneumatic expandable elements housed in the single inserts 9. The longitudinal duct 13 has a terminal valve 13A at the end 5 of the mandrel 1, via which the expandable pneumatic elements can be expanded or retracted by respectively delivering a fluid under pressure, or allowing the discharge thereof.

In this embodiment each insert 9 has a structure which is described below with reference to FIG. 5 to 7. The insert has a central body 9A, in which seats are provided for the expandable pneumatic elements described below and from which axial ends 9B extend forming the reciprocal connection members between insert 9 and tubular portions 11. In some embodiments, the ends 9B have frustoconical outer surfaces 9C defining an interface with corresponding complementary frustoconical surfaces 11A provided on the respective two tubular portions 11 which are connected to the insert 9. The frustoconical surfaces 9C have form and dimension such that the substantially cylindrical outer surface 11B of each tubular portion 11 is substantially aligned with the outer surface 9D of the central body 9A of the insert 9 thus forming a substantially cylindrical continuous wall of the mandrel 1. A small ring-shaped groove can be maintained between the edge of each tubular portion 11 and the central body 9A of the insert 9, as shown in the drawing.

According to some embodiments, seats (three in the example of the drawing) shown at 21 are provided inside the central body 9A, which house the expandable pneumatic elements described below, forming the torsional and axial engagement members of the winding core with respect to the mandrel.

In the example shown, the three seats 21 are arranged angularly staggered by a constant angle of 120°, but other arrangements are possible, for example with a different number of seats or with an irregular arrangement, i.e. with the various seats having different angular pitch.

Each seat 21 houses an expandable element 23 comprising an elastically deformable wall, for example made of rubber and provided with a lip 23A for anchorage and sealing inside the seat 21.

As can be seen in particular in the view of FIG. 7, in plan view the expandable element has a substantially rectangular shape elongated in the axial direction of the mandrel, although other shapes of the expandable element in question are not ruled out, for example development in a circumferential direction greater than the development in the axial direction.

Each expandable element formed by the wall 23 is locked in the respective seat 21 by means of a flange 25 with substantially rectangular development (FIG. 7). Locking is obtained by means of a pair of screws 27.

A distribution channel 31 leads into each seat 21, connecting the volume defined between the bottom of the seat 21 on one side and the deformable wall forming the pneumatic expandable element 23 on the other with the longitudinal duct 13. In some embodiments this connection is obtained by interposing a cylindrical member 33 inserted coaxially and around the longitudinal duct 13 and inside an axial hole 9E of the insert 9. The cylindrical member 33 has a plurality of outlets shown at 35 for the fluid under pressure, which can be in positions angularly corresponding to the positions of the ducts 31. In some embodiments the outlets 35 lead at one end into a ring-shaped groove 37 in the axial hole of the cylindrical member 33 and on the opposite side into a ring-shaped groove 39 provided in the inner surface of the hole 9E of the body 9A of the insert 9. With this arrangement, the angular position of the cylindrical member 33 can be made independent of the angular position of the seats for the pneumatic expandable elements, since the ring-shaped grooves 37 and 39 nevertheless guarantee a flow connection.

In some embodiments, the cylindrical member 33 has seal gaskets 41 and 43 between the cylindrical member 33 and the longitudinal duct 13 on the one side and between the cylindrical member 33 and the inner surface of the hole 9E of the insert 9 on the other.

In some embodiments, the cylindrical member 33 is axially secured by forcing or other suitable manner inside the hole 9E of the body 9A of the insert 9. In some embodiments the cylindrical body 33 is in turn axially secured to the longitudinal duct 13 by means of a diameter pin 45. In this way a reciprocal positioning is obtained between the longitudinal duct 13 and the inserts 9. This reciprocal positioning can also be obtained with other forms of attachment between the parts 13, 33 and 9.

The inserts 9 are arranged in an adequate number along the axial length of the mandrel 1, according to the longitudinal dimensions of the mandrel and other operating requirements. In the embodiment shown, each insert 9 has three expandable pneumatic elements arranged at 120° from one another, but as mentioned above, the number of the latter can vary. For example four or two of said expandable elements can be provided on each insert 9. The arrangement of the inserts around the axis of the mandrel 1 is such that the pneumatic expandable elements are arranged in various angular positions around the development of the mandrel thus obtaining an effective torsional and axial locking effect of the winding cores on the respective mandrel. By way of example only, FIG. 5 shows a portion of a tubular core A fitted on the mandrel 1, which can be locked on the latter both axially and torsionally by introducing a fluid under pressure into the longitudinal duct 13 to cause radial expansion of the pneumatic expandable elements 23.

With the configuration described so far, an extremely lightweight mandrel is obtained with a high level of rigidity due to the use of carbon fiber. Using inserts 9 which form ring-shaped portions of the outer surface of the mandrel, and which join aligned tubular portions 11 made of carbon fiber, the further advantage is achieved of obtaining all the expandable elements and members connected therewith in an area which does not require any machining of the walls made of carbon fiber (a notoriously fragile material) which form the tubular portions 11. This guarantees a high resistance of the mandrel by eliminating points where stress, defects and possible delaminations of the fiber layers are concentrated.

Furthermore, the presence of the inserts 9, advantageously made of metal, for example aluminum (at least for the body 9A and the ends 9B, while the cylindrical member 33 could preferably be made of plastic) makes balancing of the mandrel much quicker, simpler and more effective. In fact, these members must be appropriately balanced to prevent them vibrating during use. The presence of metal areas distributed along the axial length of the mandrel, consisting of the various inserts 9, makes it possible to remove or add material, for example by drilling the aluminum block forming the body 9A of the single insert and if necessary inserting into the hole thus obtained counterweights made of different materials, with higher density than the aluminum.

FIGS. 5A and 6A show a modified embodiment, in longitudinal and cross section respectively. These figures show only the central body of the insert 9. Identical numbers indicate parts identical or equivalent to those of the embodiment example illustrated in FIGS. 5 and 6. The ends 9B of the body 9A have in this case a substantially cylindrical surface provided preferably with one or more grooves 9S with depth of a few tenths of a millimeter, to obtain a coupling, if necessary by gluing, with the substantially cylindrical inner surface of the tubular portions 11. FIG. 5A also shows a possible coating R made of ceramic and/or metal which covers the entire outer surface of the mandrel with the exception of the area in which the expandable elements are provided. This coating is applied on the fully assembled mandrel, completed with inner elements of the inserts 9, which are omitted here for the sake of clarity of the drawing. The coating can also be provided in the remaining embodiments.

FIGS. 8 and 9 show a modified embodiment of the invention. Identical numbers indicate identical or equivalent parts with respect to those described above with reference to FIG. 1 to 7. In this embodiment, the central part 3 of the mandrel 1 is formed of one single tubular body or tubular portion 11 made of carbon fiber. This tube 11 made of carbon fiber, similarly to the tubular portions 11 of the previous embodiments, can be produced using known techniques for winding of fibers or continuous filaments around a forming mandrel, in which the fibers or filaments are fed together to a polymerisable resin to form a cylindrical wall around the forming mandrel. The wall thus obtained subsequently undergoes polymerisation and/or crosslinking of the resin matrix.

Inside the cylindrical hollow body formed by the carbon fiber wall 11, a longitudinal duct, again indicated by 13, for the delivery of a fluid under pressure, typically air, extends for at least a portion of the axial length of the mandrel 1. As in the previous example, this duct 13 has an end valve 13A for delivery of fluid under pressure or for discharge of the fluid to the outside.

Along the axial length of the mandrel 1, inside the cavity 11B formed by the carbon fiber wall 11, inserts 109 are arranged, forming housing seats for pneumatic expandable elements described below with particular reference to FIG. 8. The positioning of the inserts 109 and the axial distribution thereof along the mandrel 1 are chosen according to operating and construction requirements.

In some embodiments the insert 109 has a body 109A (FIG. 8), in which radial seats 121 are provided where a cylinder 122 is inserted with its axis in a radial direction and having channels 123 in fluid connection with the longitudinal duct 13 which passes through a central diameter hole of the cylinder 122. At the ends thereof the cylinder 122 is attached, for example by means of two threads, to two sleeves 125 locking respective pneumatically expandable elements 127 substantially in the form of a cap formed of an elastically deformable material, for example rubber. Between the pneumatically expandable element 127 and the respective end of the cylinder 122 a chamber or volume 129 is defined, in which fluid under pressure can be introduced via the duct 123 and the duct 13. Between each sleeve 125 and the seat 121 formed in the body 109A of the insert 109 respective gaskets 131 are arranged. Similarly, between the body 109A of the insert 109 and the longitudinal duct 13, which passes through an axial hole of the body 109A of the insert 109, further seal gaskets 133 are arranged.

In an appropriate manner, each insert 109 is axially attached to the longitudinal duct 13, for example via the use of a respective diameter pin 135 or set screws or other equivalent means.

As shown in particular in FIG. 8, each expandable element 127 is housed at least partially inside a respective hole 11F provided in the cylindrical wall 11 made of carbon fiber. This embodiment, therefore, requires machining by drilling of the carbon fiber component 11 forming the central or intermediate part 3 of the mandrel 1, with consequent formation of stress concentration areas along the mandrel wall. Furthermore, balancing of the mandrel is more difficult due to the lack of metal surfaces accessible from the outside which can be machined to lighten the component.

The operation of the mandrel in this embodiment can be easily understood from the above description. The core A (shown partially in FIG. 8) is torsionally and axially locked on the mandrel by expansion of the individual pneumatic expandable elements 127 due to the delivery of a fluid under pressure, typically air, through the longitudinal duct 13 and the radial ducts 123. The core is released by discharging the pressure from these ducts.

It is understood that the drawing only shows one example provided as a practical demonstration of the invention, which can vary in the forms and arrangements without departing from the scope of the concept underlying the invention. Any reference numbers in the attached claims are provided to facilitate reading of the claims with reference to the description and the drawing, and do not limit the protective scope of the claims.

Claims

1-23. (canceled)

24. A winding mandrel for producing reels of web material, comprising a substantially cylindrical wall with expandable members for torsionally locking tubular winding cores on said mandrel, wherein at least a portion of said wall is made of carbon fibers in a polymer resin matrix; said expandable members include a plurality of expandable elements that expand radially outwards of said substantially cylindrical wall by delivery of a fluid under pressure thereto; a plurality of inserts are provided along an axial length of the mandrel, said inserts being connected to a longitudinal duct for the distribution of the fluid under pressure, wherein said duct extends inside said substantially cylindrical wall for at least a part of the axial length of the mandrel; and each of said inserts comprises at least one seat for an expandable element, in fluid connection with said longitudinal duct.

25. The winding mandrel according to claim 24, wherein said expandable elements are pneumatic expandable elements.

26. The winding mandrel according to claim 25, wherein said fluid under pressure is air.

27. The winding mandrel according to claim 24, wherein said expandable elements are deformable due to said delivery of said fluid under pressure so as to protrude from said substantially cylindrical wall; and wherein in absence of said fluid under pressure, said expandable elements are entirely retracted in respective seats so as to not protrude from an outer surface of said substantially cylindrical wall.

28. The winding mandrel according to claim 24, wherein each of said inserts includes at least two seats for corresponding expandable elements arranged in angularly staggered positions around an axis of the mandrel.

29. The winding mandrel according to claim 24, wherein the substantially cylindrical wall is composed of a plurality of tubular portions made of carbon fibers in a polymer resin matrix, and of one or more of said inserts; said tubular portions being connected to one another by said inserts.

30. The winding mandrel according to claim 29, wherein each of said inserts has a substantially cylindrical surface that defines, together with outer surfaces of said carbon fiber tubular portions, a substantially cylindrical surface.

31. The winding mandrel according to claim 30, wherein said substantially cylindrical surface has a substantially continuous coating.

32. The mandrel according to claim 31, wherein said coating comprises at least one layer comprising metal or ceramic.

33. The winding mandrel according to claim 29, wherein each of said inserts includes a central body containing said at least one seat for the expandable elements and axial ends which each form an interfacing surface for attaching said inserts to respective tubular portions.

34. The winding mandrel according to claim 33, wherein said axial ends have an outer surface which is tapered or cylindrical, said outer surface being grooved for anchorage of the tubular portions.

35. The winding mandrel according to claim 33, wherein said central body has a substantially cylindrical outer surface provided with cavities for housing said expandable elements.

36. The expandable mandrel according to claim 24, wherein each of said inserts has an axial through cavity in which a cylindrical member is contained, with an axial hole for passage of said longitudinal duct; coinciding with each of said inserts, said longitudinal duct has at least one outlet for the fluid under pressure; and said cylindrical member is axially attached to the longitudinal duct, forming passages for the delivery of the fluid under pressure coming from said at least one outlet into distribution channels formed in said inserts and in fluid connection with said expandable elements.

37. The expandable mandrel according to claim 35, wherein each of said inserts has an axial through cavity in which a cylindrical member is contained, with an axial hole for passage of said longitudinal duct; coinciding with each of said inserts, said longitudinal duct has at least one outlet for the fluid under pressure; and said cylindrical member is axially attached to the longitudinal duct, forming passages for the delivery of the fluid under pressure coming from said at least one outlet into distribution channels formed in said inserts and in fluid connection with said expandable elements; and said distribution channels comprise a ring-shaped groove and substantially radial passages extending from said ring-shaped groove towards said cavities for housing the expandable elements.

38. The winding mandrel according to claim 24, wherein said expandable elements are formed by volumes of fluid under pressure at least partially contained by a deformable diaphragm.

39. The mandrel according to claim 38, wherein said deformable diaphragm is made of an elastic material.

40. The winding mandrel according to claim 35, wherein each of said cavities for each of said inserts contains an expandable element comprising an elastically deformable wall with an anchorage and sealing lip, fixed in a respective one of said cavities by a locking flange that retains said anchorage and sealing lip inside a groove provided in a corresponding cavity.

41. The winding mandrel according to claim 24, wherein said expandable elements are housed inside corresponding radial holes provided in the substantially cylindrical wall made of carbon fibers in a polymer resin matrix and defining said substantially cylindrical wall of the mandrel.

42. The winding mandrel according to claim 24 comprising metal terminal ends, at least one of said metal terminal ends being associated with means for activating the expandable members.

43. The winding mandrel according to claim 42, wherein at least one of said metal terminal ends is made in two parts, a first part attached irreversibly to the mandrel with a hollow body to allow access to inside of the mandrel, and a second part removably attached to said first part.

44. The winding mandrel according to claim 24, wherein said inserts are made of a metallic material.