WO2011144233A1

WO2011144233A1 - Mandrel for filament winding, method for its assembling as well as method for producing a fibrous vessel using such a mandrel

Info

Publication number: WO2011144233A1
Application number: PCT/EP2010/056696
Authority: WO
Inventors: Tony Vanswijgenhoven; Dieter Vanswijgenhoven; Johnny Hendrik Vanherk
Original assignee: Covess
Priority date: 2010-05-17
Filing date: 2010-05-17
Publication date: 2011-11-24

Abstract

Disclosed is a partly reusable and removable hollow mandrel (1) for filament winding of a fibrous vessel (14), the mandrel comprising: - removable and reusable parts comprising a plurality of elongated segments (6) having first (2) and second (32) ends, and first engaging means engaged with the first ends for holding the elongated segments in position; - a first end fitting (8) provided to be left behind in the fibrous vessel after the filament winding, the first end fitting having an opening (4) large enough to allow passage of the removable and reusable parts. Also dislosed is a method for assembling such a mandrel, a method for producing a leak- tight vessel using this mandrel, and a leak- tight vessel (14) produced that way.

Description

MANDREL FOR FILAMENT WINDING, METHOD FOR ITS ASSEMBLING AS WELL AS METHOD FOR PRODUCING A FIBROUS VESSEL USING SUCH A MANDREL

TECHNICAL FIELD

The invention relates to a partly removable hollow mandrel for filament winding of a fibrous vessel, in particular a leak-tight vessel.

5 BACKGROUND ART

Several removable mandrels suitable for filament winding are known in the art.

US3220910 describes a plaster-like mandrel that can be removed from the completed article applied around the mandrel by breaking the 10 plaster. This mandrel is not reusable.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a mandrel for producing a fibrous vessel by filament winding, the fibrous vessel having an end 15 fitting that is at least partly covered by the filament windings, whereby the mandrel is at least partly reusable.

This is achieved according to the present invention with the mandrel of the first claim.

Thereto the invention provides a partly reusable and 20 removable hollow mandrel for filament winding of a fibrous vessel, the mandrel having a first rounded outer surface around a symmetry-axis and comprising: - removable and reusable parts comprising a plurality of elongated segments arranged in a side-by-side relation so as to form the first rounded outer surface, the elongated segments having first ends and second ends, and comprising first 25 engaging means engaged with the first ends of the elongated segments for holding the elongated segments in a predefined position with respect to the symmetry axis; - a first end fitting provided to be left behind in the fibrous vessel, the first end fitting having a second rounded outer surface area to allow filament winding over the elongated segments and over at least part of the first end fitting, and having an opening large enough to allow the passage of the removable and reusable parts. By providing a mandrel with removable and reusable parts, except for the first end fitting which is provided to be left behind in the fibrous vessel, no waste is created when disassembling the mandrel, such as in the case of a mandrel made of plaster. Also the risk for damaging the fibrous vessel is minimized when disassembling and removing the reusable parts of the mandrel, because no material (such as e.g. plaster) needs to be broken. Because the segments of the present invention are held in position by engaging their first (and optionally second) ends, which are located close to the outside of the fibrous vessel, it is not required to go deep inside the vessel (e.g. to the center of the mandrel) for releasing screws or the like, instead the engagement is easily accessible from the outside of the vessel. This offers the advantage of easy accessibility thus saving time during assembly and disassembly of the mandrel, and also offers the advantage that the opening of the first end fitting can be smaller as compared to traditional mandrels, because one does not have to enter with tools or with both arms for releasing screws.

Preferably the mandrel further comprises second engaging means engaged with the second ends of the elongated segments for holding the elongated segments in the predefined position. In this way elongated segments are engaged at their both ends. This allows for an even better holding of the elongated segments, so the mandrel is even stronger and more rigid.

In one preferred embodiment of a mandrel according to the present invention, the first ends of the elongated segments are releasably fastened to an inner face of the first end fitting using the first engaging means. By fastening the segments to the first end fitting, which is located near the outside of the vessel, fastening of the adjacent segments to each other and/or to a central axis at positions that are difficult to reach from the outside of the mandrel can be avoided, thus saving time and effort during assembly and disassembly of the mandrel. By positioning the elongated segments to an inner face of the first end fitting, the elongated segments and part of the first end fitting can be overwrapped during the filament winding, and after the filament winding the segments can be easily disconnected from the first end fitting without damaging the fibrous vessel wound around the mandrel, and be removed through the opening of the first end fitting.

Preferably the first ends of the elongated segments are clamped against the inner face of the first end fitting by removable and reusable segment holders releasably fastened to the first end fitting. The inventor has found that by clamping the elongated segments to the inner face of the first end fitting, a spot contact can be avoided, thus causing good grip with minimal wear of the elongated segments and of the segment holders and of the first end fitting. Clamping also allows small position corrections of the elongated segments during the clamping, which helps to align the elongated segments to form the rounded outer surface of the mandrel. When using segment holders and an end fitting with a complementary shape, the clamping can be established over a large contact area, thereby reducing the contact force and the risk of damaging the first end fitting and/or the segments, so that the mandrel has a long lifetime.

In a second preferred embodiment the mandrel further comprises a first and a second spindle part aligned on the symmetry axis at a predefined distance from each other, whereby the first spindle part has first engaging means being engaged with the first ends, and the second spindle part has second engaging means being engaged with the second ends by exerting a force on the first and second spindle part in a direction towards or away from each other. The inventor has found that the use of two separate spindle parts which can be moved towards or away from each other provides elegant ways for engaging the first and second ends of the elongated segments, which are not possible when using a single axis, as is usually done in the art. The inventor has also found that by moving the first and second spindle parts towards or away from each other all segments can be engaged simultaneously, which is a very easy and fast way for fastening or releasing the elongated segments, while causing minimal wear to the elongated segments and the segment holders. By doing so, no screws have to be fastened or unfastened, thereby saving a lot of time.

Moreover the inventor has surprisingly found that this embodiment offers another advantage: Since the elongated segments are held in position by means of the spindle parts and not by the first end fitting, the latter can be shifted away from the ends of the elongated segment initially, so as to allow e.g. a barrier material to be applied to the mandrel before the filament winding, where after the first end fitting can be shifted against the ends of the elongated segments so that the actual filament winding can take place. The net result being that by using such a mandrel a barrier material can be applied under at least part of the first end fitting without having to actually enter the fibrous vessel after disassembly and removal of the mandrel. Thus the barrier material is actually applied to an inner surface of the fibrous vessel in an indirect way, without actually going inside the vessel. This is easier and better controllable in production.

Preferably the first and second ends of the elongated segments have a protrusion and the first and second spindle parts have a first groove, or vice versa, whereby the protrusion is engaged in the groove. This is a fast, easy and accurate way for positioning and holding the elongated segments. As in the first preferred embodiment where clamping can slightly correct the position, the groove can also correct the position of the protrusion engaged therein, thereby correcting the position of the elongated segments so as to form the rounded outer surface of the mandrel.

In an embodiment the mandrel additionally comprises segment holders releasably mounted to the first and second spindle parts, the segment holders comprising a first groove engaged with a protrusion of the first and second ends of the elongated segments. By using segment holders an indirect engagement between the spindle parts and the elongated segments can be obtained, allowing more degrees of freedom for the mounting and the engaging. When using segment holders and an end fitting with a complementary shape, the clamping can be established over a large contact area, thereby reducing the contact force and the risk of damaging the first end fitting and/or the segments, so that the mandrel has a long lifetime.

In an embodiment the first and second spindle parts have a circumferential groove and the segment holders have a circumferential protrusion inserted in the circumferential groove for mounting the segment holders to the first spindle part. This is a fast and easy way for mounting the segment holders to the spindle parts, which can be placed simply by hand without requiring special tools. Preferably the first and second spindle parts are hollow tubes with an inner diameter larger than 7.0 cm, preferably larger than 8.0 cm, more preferably larger than 10.0 cm to enable a person to insert a hand in the tube for engaging the first resp. second spindle parts with the first resp. second ends, for example by placing the segment holders on the spindle parts. This is possible because the elongated segments are engaged by holding their first and second ends, which are located near the outside, so it is not required to penetrate deep into the mandrel.

Preferably at least one segment holder has a shape and size so as to engage more than one elongated segment, thereby avoiding the need for individual fastening means for each elongated segment, thus saving production time for the assembly and disassembly of the mandrel. Engaging more than one elongated segment to a segment holder also helps to improve the alignment of the elongated segments.

Preferably the elongated segments comprise a metal material. The elongated segments can e.g. be made of a metal or of a metal alloy, such as e.g. steel or stainless steel to prevent corrosion, or a lightweight aluminum alloy for easy handling during assembly and disassembly, so that a strong outer surface is created suited to resist the pressure exerted upon the mandrel during filament winding.

Preferably the elongated segments have an elongated reinforcement rib at the side foreseen to be oriented towards the interior of the mandrel, which significantly improves its resistance against bending while marginally increasing its weight. Using elongated segments with low weight helps for easy disassembly of the elongated segments through the opening. The inventor surprisingly found that a mandrel with a moderate inner volume (e.g. up to 500 litre) with such elongated segments is strong enough for filament winding without requiring radial rods fastened between the spindle and the middle of the segments, as is usually done in the art, which fastening time can be avoided.

The invention also provides a method for assembling a partly reusable and removable hollow mandrel.

The invention also provides a method for producing a fibrous vessel using the mandrel assembled according to this method. The invention also provides a fibrous vessel produced according to such a method.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further elucidated in the appending figures and figure description explaining preferred embodiments of the invention. Note that the figures are not drawn to the scale. The figures are intended to describe the principles of the invention. Further embodiments of the invention can use combinations of the different features and elements of different drawings.

Fig 1A shows a side view of a preferred embodiment of a mandrel according to the invention, comprising two end fittings and a plurality of elongated segments, placed side by side.

Fig 1 B shows the mandrel of Fig 1A in bottom view or top view.

Fig 1 C shows an alternative embodiment of a first end fitting, comprising a flange with mounting holes.

Figures 2A-2D show a preferred embodiment of an elongated segment used in the mandrel of Fig 1A. The segment shown consists of three interconnected parts, the middle part being straight, the two end parts being curved.

Fig 2A shows the side of the segment intended to be oriented to the inside of the mandrel of Fig 1A, the segment has an elongated rib.

Fig 2B shows the segment of Fig 2A in side-view.

Fig 2C shows the side of the segment intended to be oriented to the outside of the mandrel of Fig 1 A.

Fig 2D shows a cross section of the segment of Fig 2A, according line ll-ll.

Fig 3A shows a first preferred embodiment of the mandrel according to the invention, showing a cross-sectional view of part of the mandrel of Fig 1 B according to line Ill-Ill, wherein segment holders are screwed to the first end fitting.

Fig 3B shows an alternative embodiment of the mandrel of Fig 3A, wherein the segment holders are clamped in another way. Fig 3C shows an alternative embodiment of the mandrel of Fig 3A, wherein the elongated segments are clamped to the first end fitting without using segment holders.

Fig 3E and 3E show alternative embodiments of part of the mandrel of Fig 3A using purely linear segments.

Fig 4A shows an exploded view of the mandrel shown in Fig 3A, and shows a bottom view of the segment holders used in Fig 3A.

Fig 4B shows the mounting disc of Fig 3A in a bottom view. Fig 4C shows the mounting disc of Fig 4B in a side view. Fig 4D shows an alternative embodiment of the mounting disc of Fig 3A in a bottom view.

Fig 4E shows the mounting disc of Fig 4D in a side view. Fig 5A shows a second preferred embodiment of a mandrel according to the invention, shown in a perspective view, whereby only one segment is shown for clarity. The elongated segments are held in position by pulling two spindle parts away from each other.

Fig 5B shows the releasable connection of the segments of the mandrel of Fig 5A in more detail.

Fig 5C shows another embodiment of the releasable connection of the segments of the mandrel shown in Fig 5A.

Fig 5D shows another embodiment of the mandrel whereby two spindle parts are pushed towards each other (only one spindle part is shown).

Fig 6 shows a fibrous vessel as can be obtained by filament winding around the mandrel of Fig 1A, after removal of the removable and reusable parts of the mandrel.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not necessarily correspond to actual reductions to practice of the invention. The drawings are intended to describe the principles of the invention. Embodiments of the invention can use combinations of the different features and elements with the same reference number of different drawings.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. The terms are interchangeable under appropriate circumstances and the embodiments of the invention can operate in other sequences than described or illustrated herein.

Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. The terms so used are interchangeable under appropriate circumstances and the embodiments of the invention described herein can operate in other orientations than described or illustrated herein.

The term "comprising", used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It needs to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting of only components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

The present invention is about a mandrel suitable for producing a vessel made of a fibrous material, in particular a leak-tight vessel or a pressure vessel, whereby the wall of the vessel is preferably made by filament winding continuous fibers impregnated with a plastic material around the mandrel, and whereby the filaments can also be wound over at least part of the top and bottom part, further called "first and second end fitting".

Many mandrels of different sizes, shapes and materials are known in the art, however no reusable and removable mandrel was found in the prior art disclosing a mandrel in combination with a first end fitting, which end fitting could be left behind in the vessel, while the rest of the mandrel could be extracted through the opening and be reused. After several prototypes and optimizations, the inventor has developed such a mandrel.

As used herein, when referring to "the first and second end fitting" or to "the end fittings", it should be understood that the second end fitting 28 is optional, unless explicitly stated otherwise.

In principle, unless explicitly mentioned otherwise, everything that is said about the first end fitting 8 is also true for the second end fitting 28, if present. The second end fitting can have an identical shape and size as the first end fitting 8, or can have a different size and shape. When the mandrel has two end fittings, preferably both end fittings 8, 28 are left behind in the fibrous vessel, and preferably both end fittings have an opening, but this is not absolutely required.

Fig 1A shows a side view and Fig 1 B shows a bottom and/or top view of a preferred embodiment of a partly removable hollow mandrel 1 according to the present invention. The mandrel 1 comprises a plurality of elongated segments 6 placed side-by-side thereby forming a rotation symmetrical shape around a symmetry-axis 10. The mandrel is suitable for the production of a fibrous vessel 14 such as e.g. shown in Fig 6, where a fibrous vessel 14 is shown having a shell structure 12 comprising a fibrous material forming the outer wall, and two end fittings 8, 28 located on opposite sides of the vessel 14. The mandrel 1 of Fig 1A further comprises a first and a second end fitting 8, 28, located at opposite ends of the mandrel 1 . The first end fitting 8 has a central opening 4, whereby the opening 4 is large enough to allow passage of the elongated segments 6 during disassembly of the mandrel 1 . The second end fitting 28 may have an opening 4, but may also be closed.

The first end fitting 8 has a rounded outer surface area to allow filament winding over the elongated segments 6 and over at least part of the first end fitting 8, to allow the shell layer 12 to cover at least the outer peripheral 82 of the first end fitting 8. Preferably the geometry of the elongated segments 6 and the first end fitting 8 are matched to each other, so as to provide a smooth transition of the outer surfaces to allow that the filament winding over segments 6 can be extended to cover also part of the first end fitting 8, in particular covering the outer peripheral 82, which offers great advantages to the fibrous vessel in terms of mechanical strength.

The inventor has surprisingly found that this mandrel 1 is sufficiently strong to be filament wound with continuous fibers, preferably impregnated with a plastic material, without the use of distance holders between the segments 6 to prevent them from bending, especially near the center of the mandrel 1 . The absence of distance holders and corresponding means for connecting them to the segments 6 allows the mandrel 1 to be assembled and disassembled easily and very fast.

The mandrel 1 shown in Fig 1A has a cylindrical part of a constant diameter 78, and a part with a varying diameter, but the invention is not limited thereto. The invention also works for with an egg-like shape or a spherical shape. Note that the outer diameter 77 of the end fittings 8, 28 can and usually will be smaller than the maximum diameter 78 of the mandrel 1 , which is not possible when using a cylindrical mandrel for winding a cylindrical body whereto end fittings 8, 28 are added at a later stage of production.

The size and shape of the first and second end fitting 8, 28 can be the same, or can be different from each other.

Fig 1 B shows the mandrel of Fig 1 A in bottom or top view.

Fig 1 C shows another embodiment of an end fitting 8, 28 having a flange 83 with mounting holes 19 for connection to an external element, e.g. to connect external piping (not shown). The exact shape of the first end fitting 8 can however be further modified by the person skilled in the art. It can for example have a flange with provisions for O-rings, or a hole with internal screw thread, or a V-clamp, or other fastening means.

Figures 2A - 2D show a preferred embodiment of the elongated segments 6 of the mandrel 1 of the present invention. The segments 6 preferably have a reinforcement rib 5 at the side which is foreseen to be oriented towards the interior of the mandrel 1 . The inventor has found that these ribs 5 help to prevent the segments 6 from bending during the filament winding process. The person skilled in the art can determine the appropriate dimensions of the rib 5, in particular the height 84 of the rib 5, to prevent or limit such bending. As shown in Fig 2D, preferably the side wall 24 of the segments 6 is shaped in such a way that the plurality of segments 6 form a substantially closed rounded outer surface when they are mounted edge to edge in the mandrel 1 , showing minimal openings between the segments 6 (as shown in Fig 1A).

Preferably the segment 6 is provided as a single part, but it can also consist of multiple elements that can be interconnected using conventional techniques, e.g. using a connection part 18 and screws 17 that fit in screw holes 23 of the elongated segments 6. In Fig 2A-2C the segment 6 consists of three parts: two curved or bended ends 2, 32 located substantially at the extremities of the elongated segments 6, and a straight intermediate part 3 located between the first and second ends 2, 32. Vessels 14 of different size and shape can be produced by varying the shape and size of the intermediate part 3 and/or the size and shape of end parts 2, 32.

Vessels 14 of different size and shape can be produced by varying the shape and size of the elongated segments 6 and/or the dimensions of the end fittings 8, 28.

In another embodiment (not shown) the end parts 2, 32 of the segments 6 are straight parts, placed under an angle with the middle part 3. In yet another embodiment (Fig 3D, 3E) elongated segments 6 with only a straight part 3 are shown. But the person skilled in the art can find other variations and modifications.

Referring to Fig 2C, the segments 6 of the mandrel 1 can all have the same size, or they can vary in size, e.g. they can have different widths W. The number of segments 6 required to form a substantially closed hollow mandrel 1 , depends on the size of the segments 6. The mandrel 1 of Fig 1A comprises fourteen segments, but other numbers are also possible. In general, the more segments 6 are used for a mandrel 1 of a given size, the smaller the opening 4 in the first end fitting 8 can be.

Figure 3A shows a first preferred embodiment of the mandrel 1 according to the invention. The mandrel 1 comprises a first end fitting 8, a second end fitting 28 (not shown) placed opposite and at a distance from the first end fitting 8, and a plurality of elongated segments 6 placed side by side against each other between the end fittings 8, 28, thereby forming a hollow body 1 with a rounded outer surface that can be overwrapped by a fibrous material, e.g. by filament winding with continuous fibers. This hollow body has at least one opening 4 located in the first end fitting 8.

The segments 6 are releasably fastened to the first end fitting 8 by fastening their first ends 2 to the inner wall 16 of the first end fitting 8. This fastening can be achieved in different ways, e.g. by clamping the ends 2 of the segments 6 to the inner wall 16 using segment holders 7 which are fastened to the end fitting 8 by means of bolts 1 1. But other fastening means are also possible, e.g. the segment holders 7 can be also be fastened to the first end fitting 8 by means of grips 40, schematically represented in Fig 3B.

Alternatively (Fig 3B) the ends 2 of the segments 6 can be clamped to the end fitting 8 directly e.g. using screws mounted in segments 6 having holes with internal screw thread (not shown), or by using grips 40, or by any other conventional fastening means known to the person skilled in the art.

In Fig 3A fourteen segments 6 are clamped by four segment holders 7, but another number of segments 6 or segment holders 7 can also be used. Another view on the segment holders of Fig 3A is shown in Fig 4A which will be discussed further. In Fig 3A the segment holders 7 are fastened to the first end fitting 8 by two screws 1 1 per segment holder 7, but another number of screws can also be used. Preferably the shape of the inner face 16 of the first end fitting 8 matches the shape of the outer surface of the first ends 2 of the elongated segments 6 to allow good fastening, e.g. by clamping thereof against the inner face 16 of the first end fitting 8. Likewise, the inner shape of the first ends 2 of the elongated segments 6 matches an outer shape of the segment holders 7 in contact therewith, to allow good fastening thereof, while causing minimal wear. However, other shapes than the ones shown in Fig 3A can also be used. The size and shape of the elongated segments 6 and the segment holders 7 (if used) should however be chosen in such a way that they can be extracted through the opening 4 of the first end fitting 8.

The first end fitting 8 of Fig 3A, also shown in perspective view in Fig 5A, has a flat outer surface with eight holes 21 which can be used for fastening the segment holders 7, but any other number of holes 21 found suitable by the person skilled in the art can also be used, depending on the number of segment holders 7 and the number of screws 1 1 per segment holder 7.

In another embodiment (not shown), instead of providing through holes 21 through the first end fitting 8 for fastening the segment holders 7 e.g. from the outside of the mandrel 1 , the first end fitting 8 can have blind holes with internal screw threat e.g. located on the inside of the vessel 14. This is especially advantageous when the first end fitting 8 is made of metal, in which case it is easy to foresee internal screw threat by techniques known in the art. Another advantage of blind holes is that it lowers the risk of leakage in the final application of the vessel 14.

Fig 3D shows an example of a straight segment 6 and part of a corresponding first end fitting 8 matching such a segment 6.

Fig 3E shows a variant of Fig 3D wherein the first end fitting 8 and the segment 6 are matched in such a way that when fastened to each other, a smooth outer surface of the mandrel 1 is obtained, thereby avoiding sharp edges. In this way the mechanical stress in the filament wound layer 12 can be decreased.

Referring to Figures 4A-4E an example of how the partly removable hollow mandrel 1 of Fig 3A can be assembled will now be described. For practical reasons, the person skilled in the art can for example start by fastening a mounting disc 9 on a spindle 13 that is e.g. placed upright. Two examples of such a mounting disc 9 are shown in Figures 5B-5E, but other mounting discs 9 can also be used. On the mounting disc 9 the first end fitting 8 is placed in such a way that the holes 22 of the mounting disc 9 correspond to the holes 21 of the first end fitting 8. The first end fitting 8 shown in Fig 5A has eight mounting holes 21 , but any other number can also be used. Next a segment holder 7 is placed inside the bowl shape of the first end fitting 8, so that the mounting holes 37 of the segment holders 7 correspond with the mounting holes 21 of the first end fitting 8, which also correspond with the mounting holes 22 of the mounting disc 9. In Fig 5A four segment holders 7 are used, but the number of segment holders 7 can also be more or less than four, e.g. tree or five or any other number. The segment holders 7 can all have the same size, or some segment holders 7 can have a different size. In Fig 5A each segment holder 7 has two mounting holes 37, but another number is also possible, e.g. one or three or more. Preferably the segment holders 7 are made of aluminum, as this is lightweight and allows fast and easy handling, but other materials can also be used, e.g. steel or any other material found useful by the person skilled in the art. Preferably the mounting holes 37 of the segment holders 7 are foreseen with internal screw threat, but other releasable fastening means are also possible, e.g. by nuts welded or glued to the segment holder 7, or by other conventional means.

Then screws 1 1 (see Fig 3A) are inserted from below the mounting disc 9, through the mounting holes 22 of the mounting disc 9 and through the corresponding mounting holes 21 of the first end fitting 8, into the corresponding mounting holes 37 of the segment holders 7, but the screws are not yet firmly tightened so that the segment holders 7 can still be lifted and/or tilted. Next a first segment 6 is inserted with its curved end 2 between the bowl-shaped inner wall 16 of the first end fitting 8, and the segment holder 7. Depending on the size and number of the segments 6 and the segment holders 7, a second and maybe further segment 6 is inserted in an edge to edge relation with the first segment 6 between the same segment holder 7 and the first end fitting 8. While adding additional segments 6 and segment holders 7, the segments 6 are to be pushed towards each other sideways, so as to minimize any opening between them.

If a second end fitting 28 is used (not shown in Fig 5A), four additional segments holders 7 (not shown) are mounted to the second end fitting 28 (not shown) using additional screws 1 1 without tightly fastening the screws initially, so that the second curved ends 32 of the segments 6 can be inserted between the inner wall 36 of the second end fitting 28 and its segment holders 7. When all segments 6 are nicely inserted between both end fittings 8, 28 and their segments holders 7, all screws 1 1 are firmly tightened and the assembled mandrel of Fig 1A is obtained.

Fig 3A shows how the mounting disc 9 is connected to the mandrel 1 after fastening all the screws 1 1.

In a next step, the assembled mandrel 1 can be mounted on a traditional filament winding machine (not shown), wherein the mandrel 1 is rotated around the spindle 13. Instead of using a mounting disc 9 and a spindle 13 for mounting the mandrel on a filament winding machine, other traditional connection means can also be used, e.g. the end fittings 8, 28 can have internal screw threat in the opening 4 whereto a spindle 13 can be connected. Or when the second end fitting 28 does not have an opening, a mounting disc 9 such as the one shown in Fig 4D - Fig 4E can be used, in which case the axis of the mounting disc 9 is oriented outwards of the mandrel 1 , and can be used instead of the spindle 13.

Referring back to Fig 4A, the disassembly of the overwrapped mandrel 1 can e.g. happen as follows. First the mounting disc 9 is removed by unfastening and removing the screws 1 1 , so that the opening 4 becomes accessible and the segment holders 7 are released. Then the segment holders 7 and the segments 6 are removed from the mandrel 1 by extracting them through the opening 4 of the first end fitting 8, while leaving the end fittings 8, 28 behind in the shell layer 12 of the filament wound vessel 14, resulting in a vessel as shown in Fig 6.

Optionally, to facilitate easy loosening of the segments 6, one (or more) segment 6 could e.g. be constructed out of three parts as shown in Fig 2B, which parts could be connected to each other using the connection part 18 and screws 17 mounted in the screw holes 23. When disassembling the mandrel 1 after the filament winding step, these screws 17 could then be unfastened, and one part of this segment, e.g. the intermediate part 3 is removed first, then the first end 2 of the segment 6, then the second end 32 of the segment 6, and then the other segments 6. This is however not essential to the invention, and any other way that facilitates easy removal of the segments 6 known to the person skilled in the art can also be used, for example by properly shaping the sidewall 24 of one or more segments 6. Such techniques are known in the art, and need no further explanation here.

Figures 5A-5D show a second preferred embodiment of a mandrel 1 according to the invention. Referring to Fig 5A, the mandrel comprises a plurality of elongated segments 6 (only one of which is shown in Fig 5A) held in position by pulling two spindle parts 42, 43 away from each other, whereby segment holders 7 are mounted to the spindle parts 42, 43 for engaging with opposite ends 2, 32 of the segments 6.

The mandrel 1 is shown together with a first and a second end fitting 8, 28 mounted against the first and second ends 2, 32 of the elongated segments 6, but the end fittings 8, 28 can be shifted over the first resp. second spindle part 42, 43 away from the elongated segments 6, as described above, e.g. to first apply a barrier material to the mandrel 1 before the filament winding step, and then be shifted back against the segments 6.

Most of what is described above for the material, size, shape etc of the elongated segments 6 and the first and/or second end fittings 8, 28 in relation to Figures 3A-4A is also applicable for this second embodiment, except for the engaging principle, which is different.

In the Figures 5A-5C only one (out of fourteen) segments 6 and only two (out of eight) segment holders 7, four on each side, are shown for clarity reasons. The person skilled in the art can choose another number of segments 6 or segment holders 7, provided they can be extracted through the opening 4.

Fig 5B gives an enlarged view on the releasable connection of the first spindle part 42, the segment holder 7 and the segment 6. As shown, the first spindle part 42 has a circumferential groove 44, and the segment holder 7 has a partial circular protrusion 46 that fits in the circumferential groove 44. The segment 6 has a protrusion, preferably in the form of a curved or bended edge 47 that engages in a groove 45 of the segment holder 7. Preferably the first and second spindle parts 42, 43 are hollow tubes, so that the segment holders 7 can be manually placed on or removed from the first spindle part 42 e.g. by inserting a hand in the tube. After all segments 6 and segment holders 7 are placed on the first and second spindle parts 42, 43, the first and second end fittings 8, 28 each having an opening 4, can then be shifted over the first resp. second spindle part 42, 43. By pulling the spindle parts 42, 43 away from each other, the curved ends 47 are engaged in the grooves 45, so that the segments 6 are held in the position to form the rounded outer surface. The pulling of the first and second spindle parts 42, 43 away from each other can e.g. be implemented on the filament winding machine (not shown).

Disassembly of this mandrel 1 after a shell layer 12 of the fibrous vessel 14 is filament wound around the mandrel 1 can be done as follows: pushing the spindle parts 42, 43 slightly towards each other, removing the segment holders 7 from the spindle parts 42, 43, e.g. by inserting a hand inside the hollow spindle part, extracting the spindle parts 42, 43 out of the vessel 14 through the opening 4 of the first end fitting 8, removing the segment holders 7 and the segments 6 out of the vessel 14 through the opening 4, while leaving the end fittings 8, 28 inside the vessel 14.

Figure 5C shows another embodiment of the releasable connection of the removable mandrel 1 based on the same principle of using two spindle parts 42, 43 that are pulled away from each other. Again only one segment 6 and one segment holder 7 are shown. In this case the segment holder 7 has two grooves on opposite sides. A curved or bended edge 47 of the segment 6 can be inserted in one groove 45, while an edge 48 of the first spindle part 42 can be inserted in the other groove 85.

Fig 5D shows another embodiment of the mandrel 1 according to the invention, whereby the segments 6 have first and second ends 2, 32 with an outward directed edge 47, and the first and second spindle parts 42, 43 have a groove 45 that matches with the protrusion 47. In this case the releasable engagement of the protrusions 47 of the segments 6 with the grooves 45 of the spindle parts 42, 43 is achieved by pushing the two spindle parts 42, 43 towards each other, thereby holding the segments 6 in position. It is clear to the person skilled in the art that other modifications are possible within the scope of the present invention.

Fig 6 shows the direct result of a fibrous vessel 14 obtained by filament winding over the mandrel 1 according to the invention and over at least part of the first and second end fittings 8, 28. In this case both end fittings 8, 28 have an opening 4, but one of them could be closed as well. During normal use of the fibrous vessel 14 the opening 4 of the first end fitting 8 typically serves as the access point to the inner volume of the vessel 14. Further production steps can be applied to the vessel 14, e.g. by adding additional barrier layers, but that is outside of the scope of the present invention. Such a vessel 14 can used as a stand-alone vessel, e.g. for storing a drinkable fluid such as milk, or can be part of a system, such as e.g. a hot water boiler.

In an alternative embodiment, the first end fitting 8 can have a flange 83, such as shown in Fig 1 C for example. The material of the first (and optionally second) end fittings 8 can be optimized in function of the application of the fibrous vessel 14.

In an embodiment the first end fitting 8 comprises a metal material, such as e.g. steel or stainless steel or aluminum or an aluminum alloy. Metal provides the advantage that it is strong and it is easy to machine, e.g. for making a circumferential groove for an O-ring, or for make holes with or without screw thread.

In an embodiment the first end fitting 8 comprises a plastic material, such as e.g. a thermoplastic material or a thermoset plastic material. Choosing end fittings 8, 28 that comprises a plastic material can e.g. be advantageous when filament winding with a fibrous material impregnated with the same or a compatible plastic material, so that the plastic materials of the end fittings 8, 28 and the material of the shell layer 12 can be consolidated to each other, to obtain a unified vessel. An end fitting 8, 28 of pure plastic might e.g. be suited for small size (e.g. having an outer diameter < 1 m) leak-tight vessels, to be subjected to low pressure (e.g. < 5 bar).

In another embodiment the first end fitting 8 comprises a metal material at least partly covered by the plastic material, e.g. an aluminum core coated with polypropylene (thermoplastic). Such a first end fitting 8, e.g. having a metal inner core completely or partly surrounded by the first plastic material, where the metal core serves primarily as a mechanical reinforcement to the end fitting 8, is especially suited for producing leak-tight vessels that need to resist high pressure (e.g. >50 bar), and/or have a relatively large diameter (e.g. > 1 m).

In another embodiment the first end fitting 8 comprises a first plastic material and reinforcing fibers, e.g. polypropylene (thermoplastic) reinforced with 40 weight % glass fibers, or polyester (thermoset) reinforced with 50 weight % glass fibers. Such a first end fitting whereby the first plastic material acts as matrix material is considerably stronger than a plastic first end fitting 8, and is suited for a wide range of applications where a plastic end fitting is not strong enough but a metal reinforcement core is not required.

It is clear to the person skilled in the art that many more combinations and alternatives are possible. Although the present invention has been described with reference to specific exemplary embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader scope of the invention as set forth in the claims. Accordingly, the description and drawings are to be regarded in an illustrative sense rather than a restrictive sense.

Claims

1 . A partly reusable and removable hollow mandrel (1 ) for filament winding of a fibrous vessel (14), the mandrel (1 ) having a first rounded outer surface around a symmetry-axis (10) and comprising:

- removable and reusable parts (6, 7, 40, 42, 43) comprising a plurality of elongated segments (6) arranged in a side-by-side relation so as to form the first rounded outer surface, the elongated segments (6) having first ends (2) and second ends (32), and comprising first engaging means (7, 40, 42) engaged with the first ends (2) of the elongated segments (6) for holding the elongated segments (6) in a predefined position with respect to the symmetry axis (10);

- a first end fitting (8) provided to be left behind in the fibrous vessel (14), the first end fitting (8) having a second rounded outer surface area to allow filament winding over the elongated segments (6) and over at least part of the first end fitting (8), and having an opening (4) large enough to allow the passage of the removable and reusable parts (6, 7, 40, 42, 43).

2. The mandrel (1 ) according to claim 1 , wherein the mandrel (1 ) further comprises second engaging means (7, 40, 43) engaged with the second ends (32) of the elongated segments (6) for holding the elongated segments (6) in the predefined position.

3. The mandrel (1 ) according to claim 1 or 2, wherein the first ends (2) of the elongated segments (6) are releasably fastened to an inner face (16) of the first end fitting (8) using the first engaging means (7, 40).

4. The mandrel (1 ) according to claim 2 or 3, wherein the first ends (2) of the elongated segments (6) are clamped against the inner face (16) of the first end fitting (8) by removable and reusable segment holders (7) releasably fastened to the first end fitting (8).

5. The mandrel (1 ) according to claim 2, wherein the mandrel (1 ) further comprises a first and second spindle part (42, 43) aligned on the symmetry axis (10) at a predefined distance from each other, whereby the first spindle part (42) has first engaging means (45, 48, 7) being engaged with the first ends (2), and the second spindle part (43) has second engaging means (45, 48, 7) being engaged with the second ends (32) by exerting a force on the frist and second spindle part (42, 43) in a direction towards or away from each other.

6. The mandrel (1 ) according to claim 5, wherein the first and second ends (2, 32) of the elongated segments (6) have a protrusion (47) and the first and second spindle parts (42, 43) have a first groove (45), or vice versa, whereby the protrusion (47) is engaged in the groove (45).

7. The mandrel (1 ) according to claim 5, additionally comprising segment holders (7) releasably mounted to the first and second spindle parts (42, 43), the segment holders (7) comprising a first groove (45) engaged with a protrusion (47) of the first and second ends (2, 32) of the elongated segments (6).

8. The mandrel (1 ) according to claim 7, wherein the first and second spindle parts (42, 43) have a circumferential groove (44) and the segment holders (7) have a circumferential protrusion (46) inserted in the circumferential groove (44) for mounting the segment holders (7) to the first spindle part (42).

9. The mandrel (1 ) according to any one of claims 5 - 8, wherein the first and second spindle parts (42, 43) are hollow tubes with an inner diameter larger than 7.0 cm, preferably larger than 8.0 cm, more preferably larger than 10.0 cm to enable a person to insert a hand in the tube for engaging the first resp. second spindle parts (42, 43) with the first resp. second ends (2, 32).

10. The mandrel (1 ) according to any one of claims 6-9, wherein the protrusion (47) of the first ends (2) is a curved edge thereof.

1 1 . The mandrel (1 ) according to claim 4 or 7 or 9, whereby at least one segment holder (7) has a shape and size so as to engage more than one elongated segment (6).

12. The mandrel (1 ) according to any one of the claims 1 -1 1 , wherein the elongated segments (6) comprise a metal material, and have an elongated reinforcement rib (5) at the side foreseen to be oriented towards the interior of the mandrel (1 ).

13. The mandrel (1 ) according to any one of the claims 1 -12, wherein the first end fitting (8) comprises a metal material.

14. The mandrel (1 ) according to any one of the claims 1 -13, wherein the first end fitting (8) comprises a plastic material.

15. The mandrel (1 ) according to claim 14, wherein the first end fitting (8) comprises a metal material at least partly covered by the plastic material.

16. The mandrel (1 ) according to claim 14, wherein the first end fitting (8) comprises the plastic material and reinforcing fibers.

17. Method for assembling a partly reusable and removable hollow mandrel (1 ) having a rotation symmetrical shape around a symmetry-axis (10) suitable for filament winding of a fibrous vessel (14), the method comprising the steps of:

- providing removable and reusable parts (6, 7, 40, 42, 43) comprising a plurality of elongated segments (6), the elongated segments (6) having first ends (2) and second ends (32);

- arranging the elongated segments (6) in a side- by-side relation thereby forming the rounded outer surface;

- providing a first end fitting (8) having a rounded outer surface to allow filament winding over the elongated segments (6) and over at least part of the first end fitting (8), and having an opening (4) large enough to allow the passage of the removable and reusable parts (6, 7, 40, 42, 43);

- mounting the first end fitting (8) to the first ends (2) of the elongated segments (6);

- providing first engaging means (7, 40, 42) and releasably engaging them with the first ends (2) of the elongated segments (6) thereby holding the elongated segments (6) in a predefined position with respect tot the symmetry axis (10).

18. Method according to claim 17, wherein the method further comprises a step of providing second engaging means (7, 40, 43) and releasably engaging them with the second ends (32) of the elongated segments (6) for holding the elongated segments (6) in the predefined position with respect tot the symmetry axis (10).

19. Method according to claim 17 or 18, wherein the step of holding the elongated segments (6) in the predefined position is performed by releasably mounting the first ends (2) of the elongated segments (6) to an inner face (16) of the first end fitting (8).

20. Method according to claim 19, wherein the step of holding the elongated segments (6) in the predefined position is performed by releasably fastening the first ends (2) of the elongated segments (6) to an inner face (16) of the first end fitting (8).

21 . Method according to claim 19 or 20, wherein the step of holding the elongated segments (6) in the predefined position is performed by clamping the first ends (2) of the elongated segments (6) against the inner face (16) of the first end fitting (8) by removable and reusable segment holders (7).

22. Method according to claim 18, wherein the method further comprises the steps of:

- providing a first resp. second spindle part (42, 43) having first resp. second engaging means (45, 48, 7) for engaging with the first resp. second ends (2, 32) of the elongated segments;

- aligning the first and second spindle parts (42, 43) on the symmetry axis (10) at a predefined distance from each other;

- engaging the first spindle part (42) with the first ends (2) and engaging the second spindle part (43) with the second ends (32) by exerting a force upon the first and second spindle parts (42, 43) for moving them towards or away from each other.

23. Method according to claim 22, wherein the first and second ends (2, 32) of the elongated segments (6) have a protrusion (47) and the first and second spindle parts (42, 43) have a groove (45), and the step of engaging the spindle parts (42, 43) with the first and second ends (2, 32) is performed by engaging the protrusion (47) in the groove (45) by exerting the force upon the first and second spindle parts (42, 43).

24. Method according to claim 22, wherein the first and second ends (2, 32) of the elongated segments (6) have a protrusion (47), and the method additionally comprises a step of providing segment holders (7) with a first groove (45) and releasably mounting them to the first and second spindle parts (42, 43), and the step of engaging the spindle parts (42, 43) with the first and second ends (2, 32) is performed by engaging the protrusion in the first groove (45) by exerting the force upon the first and second spindle parts (42, 43).

25. Method according to claim 24, wherein the first and second spindle parts (42, 43) have a circumferential groove (44) and the segment holders (7) have a circumferential protrusion (46), and the step of releasably mounting the segment holders (7) to the first and second spindle parts (42, 43) is performed by inserting the circumferential protrusion (46) in the circumferential groove (44).

26. Method according to any one of claims 22-25, wherein the first and second spindle parts (42, 43) are hollow tubes with an inner diameter larger than 7.0 cm, preferably larger than 8.0 cm, more preferably larger than 10.0 cm to enable a person to insert a hand in the tube for engaging the first resp. second spindle parts (42, 43) with the first resp. second ends (2, 32).

27. Method according to any one of claims 22-26, wherein the protrusion (47) of the first ends (2) is a curved edge thereof.

28. Method for producing a fibrous vessel (14), comprising the steps of:

- assembling the mandrel (1 ) according to the method of any one of the claims 17-27;

- applying a fibrous material to the mandrel (1 ) and over at least part of the first end fitting (8);

- disassembling the mandrel (1 ) and removing the reusable and removable parts (6, 7, 40, 42, 43) through the opening (4) while leaving the first end fitting (8) behind in the fibrous vessel (14).

29. Fibrous vessel (14) produced according to the method of claim 28.