WO2015084170A1

WO2015084170A1 - Fibre reinforced pressure vessel and method for forming a fibre reinforced pressure vessel

Info

Publication number: WO2015084170A1
Application number: PCT/NL2014/050827
Authority: WO
Inventors: Jan Jacobus Matthijs Koppert; Faris SAAD
Original assignee: ADVANCED LIGHTWEIGHT ENGINEERING BV
Current assignee: ADVANCED LIGHTWEIGHT ENGINEERING BV
Priority date: 2013-12-04
Filing date: 2014-12-03
Publication date: 2015-06-11
Anticipated expiration: 2016-06-04
Also published as: BR102014030273B8; NL2011888C2; MY180086A; BR102014030273B1; BR102014030273A2

Abstract

The invention relates to a method for forming a fibre reinforced pressure vessel having at least one fastener for fastening an element to an outside of the pressure vessel. The method comprises a step of providing a semi-finished fibre reinforced pressure vessel having a cover layer comprising a rubber or rubberlike material, preferably a material comprising and/or being formed at least partly by a polyurethane material and/or an elastomer material. The method further comprises a step of forming a fastener for fastening an element to the outside of the pressure vessel, by moulding said fastener onto the cover layer, wherein said fastener is moulded from a substantially liquid rubber or rubberlike material.

Description

Title: Fibre reinforced pressure vessel and method for forming a fibre reinforced pressure vessel The invention relates to a fibre reinforced pressure vessel and a method for forming such.

These types of pressure vessels are often advantageously used as gas tanks, for instance for gaseous fluids or gasses of pressures of for example up to 700 bar. Such vessels, such as for instance dry wound composite gas tanks, can offer the advantage of being a light-weight construction.

However, reinforcement fibres, for instance dry wound fibres, which may be suitable for resisting relatively high pressures can be vulnerable to damage, for example damage from heat, light such as

UV-light, atmospheric contaminants, and substances, e.g. chemicals, such as for example chlorine. Therefore, fibre reinforced pressure vessels, especially dry wound vessels, are usually provided with a cover layer for protecting the fibres. Generally, the cover layer comprises an elastomeric rubber or rubberlike material or is made thereof, because such materials usually can have advantageous qualities. For instance they may perform relatively well on flexibility, high-resiliency, shock absorbency, toughness, durability, strength, and/or abrasion resistance. However, it has been found difficult to attach or fasten elements, for example a handle and/or a vessel support such as foot ring, to the pressure vessel. Especially, it has been found difficult to fasten elements to the cover layer. More in particularly, it has been found difficult to fasten elements in a releasable and/or replaceable manner.

Therefore, refillable fibre reinforced pressure vessels are often housed in a housing providing support and/or enabling handling of the vessel. Generally, such housing is substantially completely enclosing the vessel, such that only a mount for mounting an appendage, such as a gas tap, to the tank protrudes at least partly from the housing. It has, however, been difficult to make these housings light-weight on the one hand, and make them on the other hand also rigid enough to restrain the refillable fibre reinforced vessel when under internal gas pressure, due to the expanding nature such vessels can have.

Another possibility is glueing elements to be attached to the cover layer of a vessel and/or fasteners directly onto the cover layer of the vessel. However, over time, for instance due to aging of the glue, the elements and/or fasteners may come off the vessel unintentionally. On the other hand, it may be hard or even impossible to neatly remove the element and/or fastener from the vessel intentionally, for instance in order to replace it or when trying to recycle at least a part of the materials of which the vessel is made.

Further, it is noted that refillable fibre reinforced pressure vessels have been proposed wherein elements to be attached to the vessel are clamped or strapped around the vessel. It has, however, been difficult to counteract that for instance straps and/or one or more other attachment means stretch and/or sag, thereby unintentionally loosening up the attachment of the element attached to the vessel, or even causing said element to come off. A further disadvantage of such vessels can be that objects can snag behind a strap and/or an other attachment means, which may for instance cause damage to said attachment means and/or to said object. Moreover, the attachment means may facilitate accumulation of dirt, which of course can be undesirable.

An object of the present invention is to provide an alternative fibre reinforced pressure vessel and/or an alternative method for forming a fibre reinforced pressure vessel. It is an object of the present invention to alleviate or solve at least one of the disadvantages of a conventional and/or proposed fibre reinforced pressure vessel. Especially, the invention aims at alleviating or solving at least one of the disadvantages mentioned above. In particular, the invention aims at providing a method for forming a fibre reinforced pressure vessel having at least one fastener for fastening an element to an outside of the pressure vessel, wherein said fastener can facilitate a relatively durable attachment of an element to the vessel, preferably in a releasable manner, and wherein the vessel and/or fastener can be of such design that can be counteracted that dirt and/or foreign object can stick or snag behind certain elements of the vessel. Additionally or alternatively, it can be a further object of the invention to provide such a pressure vessel.

In a first aspect of the invention, a method for forming a fibre reinforced pressure vessel having at least one fastener for fastening an element to an outside of the pressure vessel is provided, wherein the method comprises providing a semi-finished fibre reinforced pressure vessel having a cover layer comprising a rubber or rubberlike material, preferably a material comprising and/or being formed at least partly by a polyurethane material and/or an elastomer material; and forming a fastener for fastening an element to the outside of the pressure vessel, by moulding said fastener onto the cover layer, wherein said fastener is moulded from a substantially liquid rubber or rubberlike material.

By moulding the fastener directly onto the cover layer, the outside of the pressure vessel can be provided with a fastener to which an element can be attached. As a result, it may be superfluous to glue a fastener and/or element to be fastened to the cover layer and/or to attach an element to the pressure vessel using relatively undurable attachment means like straps. Hence, the fastener may facilitate a relatively durable attachment of the element to the vessel. Further, the vessel and/or the fastener can be of such design that can be counteracted that dirt and/or foreign objects can stick or snag behind certain parts of the vessel, such as straps or other attachment means that can be superfluous due to the fastener moulded directly onto the cover layer. By moulding the fastener from a substantially liquid rubber or rubberlike material, said material can form a relatively robust bond with the rubber or rubberlike material of the cover layer.

By arranging the rubber or rubberlike material of the cover layer of the semi-finished vessel and the substantially liquid rubber or rubberlike material for moulding the fastener for forming a chemical bond between them and/or by arranging them for allowing polymerization between both materials, an even more robust bond may be formed between the fastener and the cover layer.

By using corresponding materials and/or substantially similar materials and/or substantially the same materials for the material of the cover layer and for the material for moulding the fastener, it may be enabled relatively easily that the materials are arranged for allowing them to bond relatively well. For example, both materials may be or may comprise polyurethane materials, especially materials formed from substantially the same and/or similar ingredients or compounds such as similar isocyanates and polyols and/or substantially the same isocyanates and polyols. Hence, the material of the cover layer and the material of the fastener may allow polymerization between both said materials, as a result of which they may facilitate interconnecting the fastener and the cover layer relatively well.

Actually, the bonding between the fastener and the cover layer can result in that the fastener and the cover layer may form a substantially integrated part of the pressure vessel, wherein said part can be made relatively easily. For example, a relatively small mould can be used, which does not need to entirely enclose said substantially integrated part.

By positioning a mould such that the moulding cavity is enclosed at least partly between the mould and the cover layer, and by dispensing a substantially liquid rubber or rubberlike material into said cavity, and further by curing said dispensed liquid rubber or rubberlike material at least partly, a fastener can be moulded directly onto the cover layer. As a result, the method may be a relatively easy, fast and/or efficient method.

By arranging the fastener for form -fittingly engaging with an element to be fastened to the outside of the pressure vessel, said element may for instance be fastened to the vessel without the use of glue and/or other attachment means.

By using a mould that is at least partly formed by the element to be fastened to the pressure vessel by means of the fastener, the method can be very efficient and/or effective. For example, it may be enabled that after moulding the fastener, no mould needs to be removed and no element needs to be fastened to the fastener. Further, by using the element as a mould, the fastener can be moulded inside the moulding cavity which later can serve as a mounting cavity for engaging the fastener. Therefore, it can be enabled that there are no or no relatively large differences in the shape and/or size of a moulding cavity of a mould and a mounting cavity of an element that can be attached to the fastener. Hence, the need for relatively small size tolerances, e.g. for production of the mould and/or the element to be attached, can be diminished.

By not waiting too long before moulding the fastener onto the cover layer, it can be enabled that the rubber or rubberlike material of the cover layer and/or ingredients or compounds thereof are still relatively reactive. As a result, a relatively well bond may be formed between the fastener and the cover layer. For example, if the polymerization process of the material of the cover layer is still on-going, relatively many, long and/or strong polymers and/or crosslinks interconnecting said fastener and said cover layer may be formed. In embodiments, the step of forming the fastener by moulding it onto the cover layer may be performed at least partly before the rubber or rubberlike material of the cover layer of the semi-finished fibre reinforced pressure vessel is cured substantially completely.

Alternatively or additionally, said step of forming the fastener may be performed at least partly within a limited period of time after the rubber or rubberlike material of the cover layer of the semi-finished fibre reinforced pressure vessel is dispensed, preferably within twenty-four hours.

On the other hand, by not performing the step of moulding the fastener too soon, e.g. by performing it at least partly after a certain period of time has elapsed after the rubber or rubberlike material of the cover layer of the semi-finished fibre reinforced pressure vessel is dispensed, the rubber or rubberlike material of the cover layer can be cured at least to such extent that said semi-finished vessel can be handled relatively well. For example, the semi-finished vessel can then be handled without unintentionally deforming its cover layer in a non-resilient manner and/or it can be handled without that its cover layer is sticking unintentionally to exterior objects, such as tools for handling said semi-finished vessel and/or the mould.

It is noted that the current disclosure also relates to a method for forming a cover layer for a vessel, preferably a pressure vessel, such as a fibre reinforced pressure vessel, especially a gas tank. Said method comprises at least a step of dispensing a rubber or rubberlike material for forming a cover layer, and can be characterized in that said dispensing step is at least partly performed by pouring said material in substantially liquid state onto a semi-finished vessel. Additionally, said method may also include a step of curing said dispensed material at least partly.

By pouring the rubber or rubberlike material onto the

semi-finished vessel, preferably onto at least a part of an outer surface to be covered, it can be enabled that a cover layer of rubber or rubberlike material is applied with relatively low losses of material, or even substantially without any loss of material. In this context, it is noted that, conventionally, a rubber or rubberlike cover layer is applied by spraying it onto a

semi-finished vessel, for instance directly onto a layer of fibre material of a semi-finished fibre reinforced pressure vessel. Due to the nature of the spraying, it can occur that a relatively large part of the material, for instance up to 20% or even more of said material, does not end up on the semi-finished vessel. Disadvantages thereof may include: relatively high costs due to loss of material, environmental damages, for instance due to relatively high waste flows. For example, said waste flows may include at least parts of said rubber or rubberlike material and/or contaminated waste water due to excessive cleaning of production facilities. Further, the spraying can result into the presence of tiny droplets in the air, which droplets can be inhaled. As a consequence, such a conventional method may result in health problems and/or may require excessive exhaust means, which can for instance be expensive, failure prone, energy consuming and/or noisy.

The material for forming the cover layer may be poured onto the semi-finished vessel from a pouring spout, pouring mouth, or other pouring means. In embodiments, the liquid material is poured onto the semi-finished vessel in such a manner that an area of impact defining the location where the substantially liquid material is poured onto the semi-finished vessel is moving over said semi-finished vessel. Hence, said material can be distributed relatively equally over said semi-finished vessel in a relatively efficient manner. For example, the semi-finished vessel may be rotating about a rotating axis during pouring of the material. For instance, the rotating axis may be chosen such that it is substantially coinciding with, when applicable, a longitudinal axis of the semi-finished vessel, preferably a semi-finished vessel comprising a substantially round cylindrical

intermediate portion, more preferably said portion having two end regions, each of which may be provided with a substantial convex distal end portion. Alternatively or additionally, the pouring means may be moved along the semi-finished vessel and/or may be adjustable in order to direct a stream, squirt or jet of the substantially liquid material to another point, preferably in an controlled manner. In embodiments, the semi-finished vessel may be rotated, preferably with a substantially constant speed, and the material may be poured onto said semi-finished vessel, preferably in a substantially constant stream, squirt or jet, while a pouring spout, pouring mouth, or other pouring means from which it is poured moves along said semi-finished vessel, preferably in a direction having at least a component of direction parallel with a rotating axis of the semi-finished vessel. The substantially liquid material may be poured onto the semi-finished vessel in a

substantially helical shape. In embodiments, the helical shape can have a pitch chosen such that an area of impact, which may be a substantially circle shaped area, can overlap partly with an area of impact of a previous turn of the helix. Hence, for instance a relatively good coverage may be enabled. However, in alternative embodiments, the pitch may be chosen such that areas of impact of adjacent turns of the helix are spaced apart. By choosing a suitable liquidity or so-called fluidity, the material, which may e.g. be poured strip-wise onto the semi-finished vessel, can flow out at least partly in lateral direction, such that a good coverage, e.g. a substantially equal distributed coverage, can be enabled.

It is noted that in said method for forming a cover layer, the semi-finished pressure vessel may be a semi-finished fibre reinforced pressure vessel, preferably a semi-finished dry would vessel. Additionally, said method may comprise a step of covering a layer of fibre material of said semi-finished fibre reinforced pressure vessel at least partly with a substantially gas impermeable layer, wherein said step of covering the layer of fibre material is at least partly performed before pouring the rubber or rubberlike material for forming the cover layer. As a result, it may be counteracted that bubbles of air present between fibres of the layer of fibre material will move into the poured material forming the cover layer. Hence, a relatively even, flat, clean, and/or robust cover layer can be provided for.

Advantageously, the step of covering the layer of fibre material with a substantially gas impermeable layer can comprise applying a substantially gas impermeable film, preferably directly onto said layer of fibre material. By doing so, said substantially gas impermeable layer can be provided for in a relatively clean, fast and/or cheap fashion. However, said layer may be provided with alternative means, for example by spraying it onto the layer of fibre material of the semi-finished vessel.

As noted above, in embodiments, the layer of fibre material of said semi-finished fibre reinforced pressure vessel can be covered only partly with the substantially gas impermeable layer. For example, the vessel can have a substantially cylindrical shape, e.g. the vessel is comprising a substantially round cylindrical intermediate portion of which two end regions are each provided with a substantial convex distal end portion. In such case, for instance said substantially round cylindrical intermediate portion can be substantially covered by said substantially gas impermeable layer, whereas at least a part or region of one or more convex end portions, or even substantially one or more complete convex end portions, can be left free from said substantially gas impermeable layer.

By keeping one or more regions of the layer of fibre material free from the substantially gas impermeable layer, gas, such as at least a part of entrapped air, may escape from under said latter layer by moving sideward, i.e. in the direction of a region of the layer of fibre material kept free from the substantially gas impermeable layer.

In embodiments, one or more regions kept at least partly free from the substantially gas impermeable layer, e.g. parts at least partly formed by convex distal end portions of the vessel or the semi-finished vessel, can be covered at least partly by a layer of rubber or rubberlike material, wherein also regions covered with said substantially gas impermeable layer can be covered at least partly by such material. It is noted that the rubber or rubberlike material may be dispensed onto said one or more regions kept at least partly free from the substantially gas impermeable layer by any means, for example by spraying it onto them. Although this may cause some disadvantages with respect to pouring, such method can of course still be advantageous over spraying the cover layer onto substantially every region of the vessel. It is noted, however, that said regions kept free may, in alternative embodiments, be provided with a cover layer by pouring the material onto said regions. It is further noted that gas or air bubbles entrapped in said cover layer at regions located at or near convex end portion of the vessel may subsequently be covered at least partly by elements attached to the vessel, such as a vessel support and/or a handle, and/or may be covered at least partly by one or more fasteners for fastening such elements to the vessel.

Moreover, it is noted that the above described method for forming a cover layer and embodiments thereof, and the method for forming a fibre reinforced pressure vessel having at least one fastener and embodiments thereof can by themselves be advantageous methods. However, it will be apparent to the person skilled in the art that in embodiments, embodiments of both methods may be combined.

Furthermore, the invention relates to a fibre reinforced pressure vessel. Said vessel comprises a cover layer comprising a first rubber or rubberlike material, preferably a material comprising and/or being a polyurethane material and/or an elastomer material; and at least one fastener for fastening an element to an outside of the pressure vessel, wherein said fastener comprises a second rubber or rubberlike material, preferably a material comprising and/or being a polyurethane material and/or an elastomer material, and wherein said fastener is moulded onto the cover layer.

By providing the fastener with an undercut, such that, after curing of the fastener, the fastener and the mould cannot be taken apart directly in a linear motion without deforming at least one of them and/or without moving, when applicable, multiple parts of the mould with respect to each other, it may be realised that the fastener and an element to be fastened to the vessel can form -fittingly engage with respect to each other. Advantageous embodiments of the current disclosure are described below and in the appended claims.

By way of non-limiting examples only, embodiments of the present disclosure will now be described with reference to the accompanying figures in which:

Figure 1 shows four stages of a method for forming a pressure vessel according to an aspect of the invention; and

Figure 2 shows a schematic cross-sectional view of a pressure vessel according to an aspect of the invention.

The embodiments disclosed herein are shown and described as examples only and should by no means be understood as limiting the scope of the claimed disclosure in any way. In this description, the same or similar elements have the same or similar reference signs.

Figure 1 shows four stages A-B of a method for forming a pressure vessel 1 having at least one fastener 3 for fastening an element 4 to an outside 14 of the pressure vessel 1 according to an aspect of the invention. Each of the stages A-B is depicted by a schematic cross-sectional view of an embodiment of a fibre reinforced pressure vessel 1 according to an aspect or depicted by a schematic cross-sectional view of a semi-finished vessel la or a so-called half-product la for forming such vessel 1.

It is noted that the fibre reinforced pressure vessel 1 can be a gas tank, and may contain a gas or gaseous fluid, for instance natural gas, propane gas, and/or butane gas. It is noted that the vessel 1 may be a dry wound composite vessel, such as for instance known from WO 01 5/7429. The dry wound vessel may comprise a number of fibres or fibre filaments of which at least a part can move freely with respect to one another, and wherein at least a part and preferably all of the fibres or fibre filaments are wound such that when the pressure vessel 1 is under internal pressure the respective fibres or fibre filaments are loaded exactly in their longitudinal direction. Alternatively, the fibre reinforced pressure vessel 1 may be another type vessel, such as a fibre reinforce vessel having fibres or fibre filaments imbedded in a matrix material.

In advantageous embodiments, for instance in the case of a dry wound vessel, the vessel 1 can have a substantially cylindrical shape 8, wherein the distal ends 9 of said vessel 1 may have a substantially convex shape, preferably such that said distal ends can have an isotensoid shape, that is, a shape whereby when the vessel 1 is under internal pressure the mechanical stresses are distributed equally among the fibres wound over the respective distal end 9.

The method comprises a step of providing a semi-finished fibre reinforced pressure vessel la or so-called half -product la, as depicted in stage A of Figure 1. Said half-product la has a cover layer 2 comprising a rubber or rubberlike material, preferably a material comprising and/or being formed at least partly by a polyurethane material and/or an elastomer material. Here, the half-product la comprise a substantially gas-tight and/or fluid-tight liner 10, e.g. a HDPE liner, overwound with a layer of fibre material 11. The cover layer 2 can be covering at least a part of said layer of fibre material 11. Further, the half-product la or vessel 1 can comprise a mount 12 for mounting appendages, such as e.g. a gas tap, a valve, flow line, pressure meter or pressure reducer, to the vessel 1. In embodiments, the mount 12 can for example be a rotatable mount, such as for instance is known from international patent publication

WO 2012/074373, e.g. a mount being prohibited from moving along its axis with respect to the vessel 1, but which is allowed to rotate about its axis.

The method further comprises a step of forming a fastener 3 for fastening an element 4 to the outside 14 of the pressure vessel 1, by moulding said fastener 3 onto the cover layer 2, wherein said fastener is moulded from a substantially liquid rubber or rubberlike material.

Advantageously, the step of forming the fastener 3 onto the cover layer 2 can comprise the steps of: positioning a mould 6 against said cover layer 2 such that a moulding cavity 5 is enclosed at least partly between said mould 6 and said cover layer 2, as is depicted in stage B; dispensing a substantially liquid rubber or rubberlike material 13 into said cavity 5, as is depicted in stage C; and curing said dispensed liquid rubber or rubberlike material at least partly.

It is noted that the material of the vessel 1, the half-product la, and/or the fastener 3 and/or the material for forming the fastener 3 can be a material that resembles rubber at least in flexibility, shock absorbing qualities, resiliency, strength, abrasion resistance, durability and/or toughness. The rubber or rubberlike material may be a polymer, such as a plastic or synthetic plastic material. The rubber or rubberlike material may for instance be a polyurethane material. Advantageously, the polymer material can be an elastic polymer or so-called elastomer, such as a silicone elastomer.

Further it is noted that in this description a substantially liquid rubber or rubberlike material is to be understood at least as a material and/or a blend or mixture of materials that can flow and/or can behave at least partly as a liquid and that forms a rubber or rubberlike material when cured. It is noted that the substantially liquid rubber or rubberlike material may for instance comprise materials or compounds for forming a

polyurethane material, such as monomers and prepolymers, especially mutually reacting compounds like isocyanates and polyols. In order to cure, the compounds may react with each other in an exothermic process. As another example, the substantially hquid rubber or rubberlike material may comprise and/or may be formed of a thermoplastic rubber or rubberlike material.

It is noted that the material of the cover layer 2 may for instance be formed from a substantially hquid rubber or rubberlike material, preferably a same or similar liquid material as is used for forming the fastener 3. In embodiments, the rubber or rubberlike material of the cover layer 2 of the semi-finished vessel la and the substantially liquid rubber or rubberlike material 13 for moulding the fastener 3 can be or can comprise corresponding materials and/or substantially similar materials and/or substantially the same materials, preferably polyurethane materials, especially materials formed from substantially the same and/or similar ingredients or compounds such as similar isocyanates and polyols and/or substantially the same isocyanates and polyols. As a result, after curing, the material of the fastener 3 and the material of the cover layer 2 can form a substantially integrated part, as can be seen in stage D of Figure 1.

It is noted that the liquid rubber or rubberlike material for forming the fastener and/or for forming the cover layer 2 may comprise further components, for instance additives. For example, a crosslinking agent may be used, e.g. to facilitate forming cross-links between the cover 2 and the fastener 3. Alternatively or additionally, other additives can be provided for in the liquid material, e.g. for improving the durability. For example, stabilizers, colorants, antioxidants, or other additives can be added to protect the material, for instance by making it more resistant to heat, light, e.g. light comprising UV light, discoloration, atmospheric

contaminants, chemicals, such as cleaning product and/or products comprising chlorine, oxidation and/or mechanical abrasion.

In the embodiment shown in Figure 1, the substantially liquid rubber or rubberlike material 13 is dispensed by pouring it into the cavity 5 through one or more pouring openings 17, preferably an opening 17 provided at a top side of the moulding cavity 5. However, in alternative embodiments, the material 13 can be dispensed by other means, e.g. by means of injection moulding.

The mould 6 can have a substantially annular shape and/or may be provided with a substantially annular moulding cavity 5, e.g. for forming a flange shaped fastener. Advantageously, an annular fastener 3 may be formed substantially around a central axis 21 of the vessel 1 or half -product la, preferably such that the fastener 3 extends substantially in a plane substantially transverse to said axis 21. The pouring opening 17 can extend along at least a part of a periphery, e.g. an inner periphery of the mould 6. By designing the moulding opening as a relatively large opening, or by providing multiple openings, the material 13 can be dispensed into the moulding cavity relatively swiftly and/or it can facilitate air to escape from the moulding cavity 5 when it becomes filled at least partly by the substantially liquid material 13, thereby counteracting that the moulding cavity 5 will not be filled correctly.

Although the pouring opening 17 can be formed by a crack between the mould 6 and the cover layer 2, in alternative embodiments, a pouring opening may formed differently. For example, one or more pouring openings and/or air escape openings may be formed as openings, passages and/or channels extending through the mould 6, e.g. as channels extending through the element 4 to be fastened. In embodiments, said one or more channels may be closed off at least partly, e.g. by means of a cap, after dispensing the substantially liquid material 13 into the moulding cavity 5.

It is noted that the mould can preferably be designed such that the fastener 6 has rounded corners. This may counteract relatively high stresses in the fastener when the vessel 1 is handled during use. As can be seen in the Figures, a lower side of the moulding cavity 5 formed by the cover layer 2 may extend over a relatively large area of said layer 2. As a result, a relatively large bonding area between the material of the cover layer 2 and the material for forming the fastener 3 can be provided, which may counteract that the fastener 3 can come off the vessel 1 after curing of the fastener 3 and further curing of the cover layer 2.

Preferably, an outer wall of the moulding cavity 5 can be formed such that an outer surface of a fastener formed in said cavity 5 is neatly links up with an adjacent surface of the cover layer 2. Thereto, a lower part of the moulding cavity 5 may end in a relatively sharp edge. Advantageously, the mould 6 can be arranged such that the fastener 3 moulded onto the cover layer 2 comprises an undercut 7, such that after curing of the fastener 3, said fastener 3 and the mould 6 cannot be taken apart directly in a linear motion without deforming at least one of them 3, 6and/or without, when for instance a mould comprising multiple parts is used of the mould 6 with respect to each other.

Here, the fastener 3 comprises a flange 15, preferably provided at an upper or lower portion of the vessel 1, wherein the flange 15 defines a fastening cavity, such as an undercut 7, for cooperation with a protruding portion of an element 4 to be fastened to the outside 14 of the pressure vessel 1 by means of the fastener 3. Thereto, the flange 15 may for instance comprise an overhanging edge portion 18. Advantageously, said edge portion may extend in a substantially radial direction with respect to a central axis 21 of the vessel 1 or half -product la.

Additionally or alternatively, the moulding cavity 5 may formed such that it comprises a part 22 during pouring of the substantially liquid material 13 located above the protruding portion. Hence, it can be

counteracted that the part of the cavity for forming the protruding portion, e.g. the flange 15, will not be filled neatly with the substantially liquid material 13. Preferably, said part 22 of the cavity 5 can during pouring be in in fluid connection with the one or more openings 17, such that air can be guided out of the cavity 5 relatively well.

It is noted that the fastener 3 can be arranged for form-fittingly engaging with an element 4 to be fastened to the outside 14 of the pressure vessel 1. However, in alternative embodiments, the fastener 3 may comprise differently shaped fastening cavities for cooperation with a protruding portion of an element 4 to be fastened to the outside 14 of the pressure vessel 1 by means of the fastener 3.

In embodiments, the fastener 3 may be shaped to form or comprise a thread, e.g. an external thread, or a part of a bayonet mount, e.g. a part comprising an extruding male part or a female part or slot for matching a male part which may be provided at the element 4 to be fastened.

It is noted that after at least partly curing the material forming the fastener 3, the mould 6 may removed, for instance, when applicable, by disengaging multiple parts of the mould 6 and moving them substantially laterally away from the fastener 3. Subsequently, an element 4 to be fastened to an outside 14 of the pressure vessel 1 can be attached to the vessel 1, e.g. by clicking it onto the fastener, preferably by partly deforming the fastener 3 and/or a part of the element 4 engaging said fastener 3.

In embodiments, e.g. in the embodiment shown in Figure 2, the mould 6 can be formed at least partly by the element 4 to be fastened to the outside 14 of the pressure vessel 1. As is shown in a top part of Figure 2, said element 4 can be a handle 19. Further, the vessel 1 of Figure 2 also shows a second element 4b forming a second mould 6b at least partly. Here, said second element is formed as a vessel support 20, e.g. a ring-shaped vessel support 20. However, alternatively or additionally one or more other elements 4 to be fastened may form at least a part of a mould.

Preferably, the mould 6, e.g. the element 4 to be fastened to the outside of the vessel 1, is, or at least an inner surface thereof at least partly defining the moulding cavity 5 and/or a surface 16 during use abutting the cover layer 2, is made of a material of a material and/or comprises a coating counteracting that said element and/or surface(s) will bond to the rubber or rubberlike material of the cover layer and/or the rubber or rubberlike material forming the fastener 3. Hence, it can be facilitated that the mould 6, e.g. the element 4 to be fastened, can be released from the fastener 3 and from the vessel 1.

It is noted that the element 4, e.g. the vessel support 20 or the handle 19, may be removable from the vessel 1. For example, said element 4 may be removed by demolishing it. Alternatively or additionally, in case the element is made of multiple parts releasably connected to each other, said element can be removed by taking it apart. As another example, the element 4 may comprise and/or may be made of a thermoplastic material, such that said element 4 can be removed by deforming it after it is made flexible by warming it.

After removing an element 4, e.g. a worn element, it can be replaced by a new element.

For example, an element can be attached to the fastener 3 by clicking it onto the fastener 3. In order to facilitate this, the fastener 3 and/or the element 4, especially its mounting cavity, can be arranged to facilitate the element 4 to be snapped onto the fastener 3. For example, as can be seen in Figure 2, a guiding surface 23 for guiding a protruding part of the fastener 3, e.g. an overhanging edge portion 18 of a flange 15, during mounting said element onto the fastener may be relatively steep with respect to a blocking surface 24 for counteracting that said element 4 is pulled back from said fastener 3. This may be understood as that the guiding surface 23 is provided under a relatively small angle with a direction in which the element is pushed onto the fastener 3, whereas the blocking surface 4 is under a relatively large angle with said direction 25, which may be substantially parallel to and/or in line with the central axis 21 of the vessel 1.

Alternatively, an element can be attached to the fastener in any other suitable manner. For instance, in case the fastener is provided with tread, the element may be screwed onto the fastener. Further, an element comprising multiple interconnect able parts may be assembled at the fastener, e.g. such as to enclose said fastener at least partly.

Advantageously, the step of forming the fastener 3 by moulding it onto the cover layer 2 can be performed at least partly before the rubber or rubberlike material of the cover layer 2 of the semi-finished fibre reinforced pressure vessel la is cured substantially completely. In this context, "at least partly" can be understood as that for instance at least the step of dispensing the liquid rubber or rubberlike material 13 into the moulding cavity 5 can be performed before the material of the cover layer 2 is cured substantially completely.

It is noted that in this description a rubber or rubberlike material not yet being cured substantially completely is to be understood at least as a rubber or rubberlike polymer material formed in a curing process, wherein said process is not yet completely finished, such that the rubber or rubberlike material to be, is still at least partly in a reactive state. For example, when the rubber or rubberlike material is or comprises a polymer, such as a polyurethane material or elastomer material, the material not yet being cured substantially completely can be understood at least as a material of which a polymerization process in which said material is cured is not yet finished, e.g. said process is still on-going.

Preferably, the step of forming the fastener 3 by moulding it onto the cover layer 2 can be performed at least partly within a limited period of time after the rubber or rubberlike material of the cover layer 2 of the semi-finished fibre reinforced pressure vessel la is dispensed, wherein said limited period may be one week, preferably three days, more preferably twenty-four hours, even more preferably twelve, six or two hours. It is noted that "at least partly" may in this context be understood as that for instance the step of dispensing the substantially liquid rubber or rubberlike material 13 into the moulding cavity 5 can be performed within said limited period of time, and that the step of curing may extend after passing of said period.

In embodiments, the step of forming the fastener 3 by moulding it onto the cover layer 2 can be performed at least partly after a certain period of time has elapsed after the rubber or rubberlike material of the cover layer 2 of the semi-finished fibre reinforced pressure vessel la is dispensed, wherein said certain period of time can for instance be five, ten, thirty, forty-five or sixty seconds, or two, five, ten or thirty minutes. For instance, said certain period can elapse before the mould 6 is placed. As a result, the rubber or rubberlike material of the cover layer 2 can be cured to such extent that said semi-finished vessel la can be handled relatively well, e.g. can be handled without unintentionally non-resiliently deforming its cover layer 2 and/or it can be counteracted that said cover layer 2 unintentionally sticks to exterior elements, such as tools for handling said semi-finished vessel la and/or the mould 6.

In embodiments, the method may further comprise the step of forming the semi-finished fibre reinforced pressure vessel la. Said step can comprise dispensing a rubber or rubberlike material for forming the cover layer 2 of the semi-finished fibre reinforced pressure vessel la; and curing it at least partly. Advantageously, the step of dispensing the rubber or rubberlike material for forming the cover layer 2 of the semi-finished fibre reinforced pressure vessel la can comprise pouring said material in substantially liquid state onto an outer surface 17 to be covered at least partly by said material. For example, said outer surface 17 can be formed at least partly by the layer of fibre material 11. However, the outer surface 17 can be formed alternatively.

In embodiments, the method may further comprise the step of covering the layer of fibre material 11 of the semi-finished fibre reinforced pressure vessel la at least partly with a substantially gas impermeable layer, preferably by applying a substantially gas impermeable film, wherein said step of covering the layer of fibre material 11 is at least partly performed before pouring the rubber or rubberlike material for forming the cover layer 2.

The invention is not restricted to the embodiments described above. It will be understood that many variants are possible. Variants may for instance include combinations of embodiments described above. Such and other embodiments will be apparent to the person skilled in the art and are considered to lie within the scope of the invention as formulated in the following claims.

Claims

1. Method for forming a fibre reinforced pressure vessel having at least one fastener for fastening an element to an outside of the pressure vessel, comprising the steps of:

providing a semi-finished fibre reinforced pressure vessel having a cover layer comprising a rubber or rubberlike material, preferably a material comprising and/or being formed at least partly by a polyurethane material and/or an elastomer material; and

forming a fastener for fastening an element to the outside of the pressure vessel, by moulding said fastener onto the cover layer, wherein said fastener is moulded from a substantially liquid rubber or rubberlike material.

2. Method according to claim 1, wherein the step of forming the fastener onto the cover layer comprises the steps of:

positioning a mould against said cover layer such that a moulding cavity is enclosed at least partly between said mould and said cover layer;

dispensing a substantially liquid rubber or rubberlike material into said cavity; and

curing said dispensed liquid rubber or rubberlike material at least partly.

3. Method according to claim 1 or 2, wherein the fastener is arranged for form -fittingly engaging with an element to be fastened to the outside of the pressure vessel.

4. Method according to claim 2 or 3, wherein the mould is at least partly formed by an element to be fastened to the outside of the pressure vessel by means of the fastener, wherein said element to be fastened can for instance be a handle or a vessel support.

5. Method according to any one of the preceding claims, wherein the step of forming the fastener by moulding it onto the cover layer is at least partly performed before the rubber or rubberlike material of the cover layer of the semi-finished fibre reinforced pressure vessel is cured substantially completely.

6. Method according to any one of the preceding claims, wherein the step of forming the fastener by moulding it onto the cover layer is at least partly performed within a limited period of time after the rubber or rubberlike material of the cover layer of the semi-finished fibre reinforced pressure vessel is dispensed, wherein said limited period may be one week, preferably three days, more preferably twenty-four hours, even more preferably twelve, six or two hours.

7. Method according to any one of the preceding claims, wherein the step of forming the fastener by moulding it onto the cover layer is at least partly performed after a certain period of time has elapsed after the rubber or rubberlike material of the cover layer of the semi-finished fibre reinforced pressure vessel is dispensed, wherein said certain period of time is for instance five, ten, thirty, forty-five or sixty seconds, or two, five, ten or thirty minutes.

8. Method according to any of the preceding claims, further comprising the step of forming the semi-finished fibre reinforced pressure vessel, wherein said step comprises the steps of:

dispensing a rubber or rubberlike material for forming the cover layer of the semi-finished fibre reinforced pressure vessel; and

curing it at least partly.

9. Method according to claim 8, wherein the step of dispensing the rubber or rubberlike material for forming the cover layer of the semifinished fibre reinforced pressure vessel, comprises the step of:

pouring said material in substantially liquid state onto an outer surface to be covered at least partly by said material.

10. Method according to claim 9, further comprising a step of covering a layer of fibre material of the semi-finished fibre reinforced pressure vessel at least partly with a substantially gas impermeable layer, preferably by applying a substantially gas impermeable film, wherein said step of covering the layer of fibre material is at least partly performed before pouring the rubber or rubberlike material for forming the cover layer.

11. Method according to any of the preceding claims, wherein the rubber or rubberlike material of the cover layer of the semi-finished vessel and the substantially liquid rubber or rubberlike material for moulding the fastener are arranged for forming a chemical bond between them and/or arranged for allowing polymerization between both materials.

12. Method according to any of the preceding claims, wherein the rubber or rubberlike material of the cover layer of the semi-finished vessel and the substantially liquid rubber or rubberlike material for moulding the fastener are or comprise corresponding materials and/or substantially similar materials and/or substantially the same materials, preferably polyurethane materials, especially materials formed from substantially the same and/or similar ingredients or compounds such as similar isocyanates and polyols and/or substantially the same isocyanates and polyols.

13. Fibre reinforced pressure vessel, comprising:

a cover layer comprising a first rubber or rubberlike material, preferably a material comprising and/or being a polyurethane material and/or an elastomer material; and

at least one fastener for fastening an element to an outside of the pressure vessel, wherein said fastener comprises a second rubber or rubberlike material, preferably a material comprising and/or being a polyurethane material and/or an elastomer material, and wherein said fastener is moulded onto the cover layer.

14. Vessel according to claim 13, wherein the fastener is made by dispensing a substantially liquid rubber or rubberlike material into a cavity defined partly by the cover layer and defined partly by a mould positioned against said cover layer.

15. Vessel according to claim 13 or 14, wherein the fastener comprises an undercut, such that, after curing of the fastener, the fastener and the mould cannot be taken apart directly in a linear motion without deforming at least one of them and/or without moving, when applicable, multiple parts of the mould with respect to each other.

16. Vessel according to any one of claims 13-15, wherein the fastener comprises a flange, preferably provided at an upper or lower portion of the vessel, wherein the flange defines a fastening cavity, such as an undercut, for cooperation with a protruding portion of an element to be fastened to the outside of the pressure vessel by means of the fastener.

17. Vessel according to any one of claims 13-16, further comprising an element, for instance a handle or a vessel support or a type plate, fastened to the outside of the pressure vessel by means of the fastener.