FILAMENT WINDING DEVICE AND FILAMENT WINDING PROCESS

The present invention relates to a filament winding device and to a filament winding process.

It is known that the term "filament winding" refers to a particular production technique enabling hollow articles of composite material to be manufactured, which articles have an axially symmetric geometry such as poles, bottles, tanks, pipes and the like.

This technology consists in laying down filaments, in the form of a single fibre, fabric bands or ribbons, around a rotary mandrel suitably shaped depending on the geometry of the finished product that is wished to be obtained.

The filament winding devices of the known art comprise a mandrel having an axially symmetric geometry and driven in rotation around a horizontal axis coincident with the extension axis of the mandrel itself.

The mandrel is supported and set in rotation by a frame only acting at the mandrel ends in such a manner as to enable the side surface of the mandrel to be completely accessible.

A horizontal guide is present close to the rotary mandrel, which guide slidably supports a laying head that, picking up one or more filaments from respective reels, lays them down on the side surface of the mandrel. The continuous rotation of the mandrel causes winding of the filaments on the side surface of said mandrel .

By suitably moving the laying head along the horizontal guide and varying the laying angle of the filament on the mandrel surface, the filaments are wound up on the surface of the rotary mandrel following a scheme that is established based on the mechanical and structural features that the final product must have.

The laid filaments, before or after their being laid down on the mandrel, are impregnated with one or more catalysing resins so that they are buried in a matrix of binding material.

When winding has been completed, the mandrel is stopped and left to its horizontal position until the composite material consisting of the filaments buried in the binder matrix fully surrounding the mandrel, is consolidated.

The composite material, once consolidated, is slipped off the mandrel forming the desired hollow manufactured article having an axially symmetric shape and size.

However, the filament winding devices and related winding processes of the known art briefly described above have some drawbacks.

In fact, it is not possible to make a single manufactured article having a particularly high longitudinal size, i.e. the size along its symmetry axis, in particular a size exceeding 12-13 metres.

This drawback is due to the fact that the mandrel surrounded by the filaments impregnated with resin bends along its extension axis under the action of the weight force of the mandrel itself and the impregnated

filaments. Bending of the mandrel during the consolidation step causes a corresponding longitudinal bending of the manufactured article that becomes useless and at all events can be hardly slipped off the mandrel.

In addition, where particularly long manufactured articles (in the direction specified above) are concerned, the mandrel also tends to bend during the filament winding step. This gives rise to an uneven thickness distribution in the wound filament, or at all events a thickness distribution different from the desired one, thereby significantly altering the mechanical and structural features that the final manufactured article must possess.

In this context, the main technical task of the present invention is to make available a filament winding device and a filament winding process that are not affected by the drawbacks highlighted above.

In particular, it is an aim of the present invention to make available a filament winding device and a filament winding process enabling manufactured articles to be made which have any size in the longitudinal direction, i.e. along their symmetry axis.

The technical task mentioned and the aim specified are substantially achieved by a filament winding device and a filament winding process comprising the features set out in one or more of the appended claims.

Further features and advantages of the present invention will become more apparent from the description, given by way of non-limiting example, of a

preferred but not exclusive embodiment of a filament winding device and a filament winding process, as shown in the accompanying drawing, in which:

- Fig. 1 is a perspective view of a filament winding device in accordance with the present invention.

With reference to the accompanying drawing, a filament winding device in accordance with the present invention has been generally identified with reference numeral 1.

Device 1 comprises a forming station and a consolidation station.

In the forming station a manufactured article (shown during the manufacturing step in Fig. 1) is formed, while in the consolidation station the manufactured article thus obtained is consolidated, i.e. it takes its final mechanical and structural features.

It is to be pointed out that in the preferred embodiment distinction between forming station and consolidation station is purely a functional distinction as the two stations are physically coincident.

In other embodiments of the present invention not shown, distinction between forming station and consolidation station can be also physical, in addition to being functional, which means that the two stations can also be distinct from each other and mutually spaced apart.

Irrespective of the physical separation between forming station and consolidation station, device 1 comprises a mandrel 2 having a symmetry axis S that is coincident

with the major extension axis of mandrel 2. It will be recognised that by the term mandrel it is intended, in the technical field of the present invention, a member serving as a support for the manufactured article to be made. This member further has the function to transfer a predetermined shape to the manufactured article to be made, as better clarified in the following.

Mandrel 2 in the embodiment shown in Fig. 1 is a cylinder. However, mandrel 2 can be of any other shape provided it has an axial symmetry.

Device 1 further comprises a supporting frame 3 for said mandrel 2 and a laying head 4 acting on mandrel 2. The laying head 4 has the function to lay down one or more filaments 101 on the side surface 5 of mandrel 2, which filaments once they have been wound up around the side surface 5 of mandrel, 2 will constitute the manufactured article.

Filaments 101 can be, alternatively or in combination, either single fibres, such as glass fibres for example, or fabric bands or ribbons. Fibres 101 are impregnated with a catalysing resin or a thermoplastic material before or after their being laid down on the side surface of mandrel 2. The catalysing resin, once hardened in the consolidation station, forms a binder matrix for the filaments that are buried therein, thus obtaining a manufactured article of composite material.

Should fibres 101 be impregnated with a thermoplastic material, the latter is activated by a heat source at the end of winding, so as to consolidate the manufactured article.

- Q -

To enable winding of the filaments on the side surface 5 of mandrel 2, said mandrel is set in rotation around its symmetry axis S. In this connection it is pointed out that, to enable full access to the side surface 5 of mandrel 2, the latter is supported by frame 3 only at its opposite ends 6, as shown in Fig. 1.

Advantageously, mandrel 2 is retained in a vertical position during its rotation, so that it does not bend during laying of the filaments even if said mandrel 2 is very long, i.e. has a length measured along its symmetry axis S, exceeding 12 metres for example.

In fact, the vertical position of mandrel 2 ensures that the combination of the weight force resulting from the mass of the mandrel and the weight force of the filaments that are progressively wound up around said mandrel does not create shearing stresses in mandrel 2 of an amount sufficient to cause bending of the mandrel itself.

It is to be noted that, due to the vertical position of mandrel 2, the shearing stresses mentioned above are insufficient to bend mandrel 2, irrespective of the material of which it is made.

It is apparent from the above that by vertical position it is intended a position suitable for enabling hardening of the manufactured article without involving bending deformations of same due to weight; in particular a position of substantial alignment with the application direction of the weight force is utilised. Clearly, also in the preferred form, this alignment is approximate, i.e. an exact and perfectly coincident alignment between the lying direction of the symmetry

axis S of mandrel 2 and the application direction of the weight force is not required. Alignment deviations of more or less 2 sexagesimal degrees are permissible.

In addition, advantageously, mandrel 2 carries out a translation in a vertical direction during winding of filaments 101 on its surface 5. In this manner the laying head 4 can be greatly simplified.

In fact, since, as known, it is necessary to lay down filaments along the whole side surface 5 of mandrel 2 in several passages, vertical translation of mandrel 2 with a reciprocating motion enables provision of a fixed laying head 4.

By eliminating one degree of freedom of the laying head 4 (the translational one) , connection between the laying head 4 and reels 7 from which the filaments are picked up is particularly simplified.

In the preferred embodiment, the laying head 4 comprises a hollow disc-shaped member 8 fitted on mandrel 2. The hollow member 8 is connected to the plurality of reels 7 and picks up therefrom, the filaments 101 required for carrying out winding on mandrel 2. Laying of the filaments picked up from reels 7 on the side surface 5 of mandrel 2 takes place by suitable means acting on the hollow member 8, which means is known and therefore not shown or further described.

To enable simultaneous rotation and translation of mandrel 2, the supporting frame 3 comprises a fixed portion 9 and a movable portion 10.

The fixed portion 9 is integral with a base 102, the slab of a building for example, and comprises a vertical guide 11 for the movable portion 10. The latter carries out a translation along the vertical guide 11 and comprises two tailpieces 12 engaging mandrel 2. At least one of the tailpieces 12 is provided with a driving member 13, preferably of the electric type, setting mandrel 2 in rotation along its symmetry axis S.

Translation of the movable portion 10 relative to the fixed one 9 is ensured by further driving members 14 that, in the embodiment shown in Fig. 1, consist of a capstan 15 placed in the fixed portion 9, which capstan through two idler pulleys 16 (only one of which is shown in Fig. 1) lifts and lowers mandrel 2.

In order to limit the height of the room in which device 1 is inserted, frame 3 occupies several storeys of the same building. In other words, the preferred embodiment of the present invention contemplates installation of frame 3 on the slab of a floor in a building and continuation of frame 3 on the floor above, after drilling the slab of said floor.

Advantageously, the portion of device 1 extending under base 102, that can be either a lower floor or a hole in the ground, should the binder matrix be a thermoplastic material, comprises a furnace for activation of said thermoplastic material. In this way, polymerisation of the thermoplastic material is carried out with a greatly reduced bulkiness of the required furnace.

In an alternative embodiment, both the movable portion 9 and fixed portion 10 of frame 3 can be made with a

lattice structure covered with a metal structure to protect the latter against weathering. In this case, device 1 can be also placed at the outside of a building.

In use, mandrel 2 is set in rotation around its symmetry axis S. As said, mandrel 2 lies in a substantially vertical position.

The laying head 4 picks up the filaments 101 from reels 7 and lays them down on the side surface 5 of mandrel 2. Mandrel 2 during its rotation is also translated in a vertical direction in such a manner that its side surface 5 is covered with several passages of filaments 101. During laying of filaments 101 the laying head is maintained to a fixed position, i.e. it carries out no translation relative to the fixed portion 9 of frame 3.

At this point, if filaments 101 have not yet been impregnated with the catalysing resin (or thermoplastic binding agent) , said filaments 101 fully covering mandrel 2 are coated with said resin.

When the step of winding up the filaments 101 on mandrel 2 has been completed, said mandrel is transferred from the forming station to the consolidation station. As previously said, in the preferred embodiment these two stations are coincident and therefore mandrel 2 remains in engagement with frame 3.

In this case, translation of mandrel 2 is stopped while rotation is maintained in operation until the thermoplastic resin starts hardening to prevent the

resin from dripping towards the lower portion of the manufactured article, due to gravity.

When the resin has hardened at least partly, rotation of mandrel 2 is stopped too. Irrespective of whether the forming and consolidation stations are coincident or not, mandrel 2 is maintained to the vertical position (as specified above) , until complete hardening of the binding-material resin that consolidates.

When consolidation has occurred, the manufactured article is removed from one end of mandrel 2 and is therefore ready for further working operations (painting and the like) or for installation.

The invention achieves the intended purpose.

In fact, due to consolidation taking place with mandrel 2 in a vertical position, the weight due to the mandrel itself and the manufactured article wound therearound does not cause bending of the mandrel and consequently enables achievement of a manufactured article having a perfectly rectilinear axis of symmetry. Clearly, "perfectly rectilinear" means that the manufactured article does not show bending in its axis of symmetry which will make the article itself useless.

In this way manufactured articles in one piece can be made which have any longitudinal size, i.e. along the axis of symmetry, a size longer than 12 metres for example .

In addition, since winding takes place with mandrel 2 in a vertical position, no bending occurs and therefore an optimal distribution of the filaments along said

mandrel takes place, which distribution is coincident with the design distribution.

In this manner, the mechanical and structural features of the manufactured article thus obtained are the same as those planned.