NL2014899B1

NL2014899B1 - Fibre reinforced pressure vessel and method for forming such.

Info

Publication number: NL2014899B1
Application number: NL2014899A
Authority: NL
Inventors: Jacobus Matthijs Koppert Jan; Saad Faris
Original assignee: Advanced Lightweight Eng B V
Priority date: 2015-06-01
Filing date: 2015-06-01
Publication date: 2017-01-31
Also published as: NL2014899A

Abstract

The invention relates to a method for forming a fibre reinforced pressure vessel. The method comprises a step of providing a prefab vessel body having a substantially gas-tight and/or fluid-tight liner overwound with a layer of dry wound fibre material. Said prefab vessel body is installed in a mould. The method further comprises a step of feeding a coating material, especially a rubber or rubberlike coating material, into the mould that then accommodates the prefab vessel body in order to cover the layer of dry wound fibre material with a cover layer of coating material. Advantageously, the mould can comprise an inner space arranged for accommodating the prefab vessel body and arranged for at least partly defining a moulding cavity that substantially encloses the layer of dry wound fibre material while the coating material is fed into the mould, wherein said inner space is arranged such that the moulding cavity comprises a first moulding cavity portion for forming a cover layer therein and second moulding cavity portion for forming a fastener for fastening an element to an outside of the pressure vessel.

Description

Title: Fibre reinforced pressure vessel and method for forming such

The invention relates to a fibre reinforced pressure vessel that comprises a substantially gas-tight and/or fluid-tight liner overwound with a layer of dry wound fibre material, wherein said layer of dry wound fibre material is covered with a cover layer of coating material. The invention also relates to a method for forming such fibre reinforced pressure vessel.

These types of pressure vessels are often advantageously used as gas tanks, for instance for LPG. The gas tanks can for example be used for gaseous fluids or gasses of pressures of for example up to 700 bar.

The substantially gas-tight liner can counteract that gas escapes form the vessel, while the layer of dry wound fibre material can serve as a reinforcement which can provide the strength to keep the pressure vessel together when being pressurized when filled with gas. Although said fibres may be suitable for resisting relatively high pressures, they can be vulnerable to damage, for example damage from heat, light such as UV-light, atmospheric contaminants, substances, e.g. chemicals, such as for example chlorine, and/or mechanical impacts and/or abrasion. The cover layer can protect said fibres from such damage. 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.

Such vessels can offer many advantages. For example, such vessels can have a relatively low weight. Further, the vessels may be recyclable relatively well, due to the fibres are dry wound and may thus be separable from the coating material relatively well, as a result of which the environmental impact can be relatively low. The vessel can also be relatively durable, for instance because it can be relatively flexible which may allow the vessel to absorb relatively big deformations, e.g. up to and exceeding 50% of its initial shape, without this resulting into damage to the vessel. For instance therefore, such vessels can be relatively safe. Moreover, e.g. in case of fire or penetration, gas can leak out of the vessel without the vessel rupturing or exploding and fragmenting, as is a risk with metal pressure vessels.

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 protect the pressure vessel against for example impact loads.

Another possibihty is gluing fasteners for elements to be attached to the cover layer of a vessel directly onto the cover layer of the vessel and/or gluing elements to be attached to the cover layer directly onto the cover layer. 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 for instance 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, over time, 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 method for forming a fibre reinforced pressure vessel and/or an alternative fibre reinforced pressure vessel, especially an improved method and/or an improved method. It is another object of the present invention to alleviate or solve at least one of the disadvantages of a conventional method and/or a conventional fibre reinforced pressure vessel. It is yet another objective of the invention to alleviate or solve at least one of the disadvantages mentioned above. In embodiments, 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 objects can stick or snag behind certain elements of the vessel. Additionally or alternatively, it can be a further objective 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 is provided, which method comprises the steps of providing a prefab vessel body having a substantially gas-tight and/or fluid-tight hner overwound with a layer of dry wound fibre material; installing said prefab vessel body in a mould; and feeding a coating material into the mould accommodating the prefab vessel body in order to cover the layer of dry wound fibre material with a cover layer of coating material. Preferably, a chemical reaction within said coating material can occur within the mould. For example, a curing reaction can occur within the mould in embodiments of said method.

By feeding the coating material into the mould accommodating the prefab vessel body, a cover layer of coating material can be formed inside said mould, which mould can be formed such that a fastener for fastening an element to an outside of the pressure vessel can be moulded in the mould together with the cover layer. Hence, the method can allow that together with the cover layer a fastener can be formed integrally, which faster can be used to attach an element to the pressure vessel, for instance at least partly by letting said element form-fittingly engage said fastener.

By feeding the coating material into the mould accommodating the prefab vessel body, a cover layer of coating material can be formed inside said mould, which cover layer can be relatively evenly distributed and/or can be relatively equally thick, especially when compared to more conventional coating techniques such as spraying, smearing or pouring a coating material onto the layer of dry wound fibre material, without using a mould for forming an outer surface of the cover layer. Additionally or alternatively, this method can allow one to vary the thickness of the coating material from one portion of the cover layer to another portion of the same cover layer, if desired so, in a relatively well controllable manner. Hence, for example regions or portions of the cover layer that are expected to be exposed relatively often and/or heavily to wear and tear can be made relatively thick, in a relatively easy and/or relatively controllable manner, whereas other regions or portions of the same cover layer can be kept relatively thin, thereby saving material for example.

By feeding the coating material into the mould that then accommodates the prefab vessel body, a cover layer of coating material can be formed inside said mould, which cover layer can have a relatively neat surface finish, e.g. lacking visible sweep or brush marks.

In embodiments, the mould can be provided with an at least partly textured mould surface, e.g. in order to provide at least a part of the cover layer with a rough surface finish. By moulding a cover layer having a relatively rough surface finish, cosmetic damages can be less noticeable, e.g. when compared to an outer surface not having a relatively rough surface finish of a cover layer being poured or sprayed onto the layer of dry wound fibre material in a more conventional method, because such outer surfaces are often relatively shiny and can therefore not hide cosmetic damage such as scratches relatively well.

Moreover, the mould can be provided with a relief for forming an imprinting at the outside of the cover layer, for instance such as to provide the pressure vessel with a logo or the hke. Hence, the pressure vessel can be provided with a logo, such as a trade mark, or the like, such as for example text and/or figures, for instance for providing warnings and/or other information, in a manner which can be relatively easy and/or cost-efficient to perform. Further, it can be an advantage that such logo or the like can be relatively durable, as it is integrally formed with the cover layer of coating material.

Advantageously, the step of feeding the coating material into the mould can be executed after an overpressure has been arranged within said prefab vessel body. For example, said overpressure can, compared with atmospheric pressure, be at least 0.5 bar, for instance about 1 bar. Preferably, the internal pressure inside the prefab vessel body may be higher than the pressure with which the coating material is fed into the mould. For example, in case said material is injected into the mould in order to feed it into the mould, the internal pressure inside the prefab vessel body can be higher than an injection pressure of coating material injected into said mould. In case the coating material fed into the mould is injected into the mould, the injection pressure of the coating material injection can preferably be below 6 bar, preferably a pressure below 4 bar, such as for instance a pressure between 1 and 4 bar. The pressure inside the prefab vessel body can then for instance be higher than said pressure, e.g. between 3 and 10 bar, preferably between 4 and 10 bar, such as about 4, 5 or 6 bar.

By applying an overpressure in the prefab vessel body, the liner can swell, as a result of which fibres of the dry wound fibre material can be pulled relative tight around said liner. As a result, gas, e.g. air, can be forced out of the layer of dry wound fibre material. Hence, it can be counteracted that gas, e.g. air, can become entrapped in said layer of dry wound fibre material when the coating material is fed into the mould.

In order to the apply an overpressure to the prefab vessel body, said boy can be inflated with a gas, e.g. air.

It is noted that, in advantageous embodiments, the prefab vessel body and/or the fibre reinforced pressure vessel formed by means of said prefab vessel body may be provided with a mount for mounting appendages, such as e.g. a gas tap, a valve, a flow line, a pressure meter or a pressure reducer, to the vessel. In embodiments, the mount 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, but which is allowed to rotate about its axis.

In case the prefab vessel body is provided with a mount for connection to a gas supply line, the prefab vessel body can be pressurized relatively easily.

Although the prefab vessel body may be pressurized before installing it into the mould, the prefab vessel body may alternatively or additionally be pressurized when present inside the mould. Advantageously, the mould, especially cooperating mould parts thereof, can be designed such that the mount can extend at least partly through an inner wall of the mould when the mould is closed around the prefab vessel body.

Advantageously, the method may comprise a step of increasing the pressure in the prefab vessel body after feeding at least a part of the coating material into the mould. Preferably, the step of increasing the pressure can be performed at least partly when a moulding cavity between the layer of dry wound fibre material and an inner surface of the mould is substantially completely filled with the coating material. Although said step may start after said moulding cavity has been substantially filled, said step may alternatively start earlier, e.g. during the filling of said cavity. By increasing the internal pressure in the prefab vessel body after feeding at least a part of the coating material into the mould, gas or gas bubbles, or at least a part thereof, can be pressed out of the moulding cavity, e.g. via one or more air vents or other means. It is noted that said gas or gas bubbles can for instance comprise air present inside the moulding cavity, air escaping from the dry wound fibre layer, gas present in the coating material fed into the mould, and/or gas formed by said coating material, e.g. during curing thereof, for example due to a chemical reaction within said coating material, which coating material can for instance be a two-component material, such as a two-component polyurethane material. In embodiments, the pressure inside the prefab vessel body can be increased to a pressure higher than a pressure at which the coating material is introduced into the mould. Additionally or alternatively, the pressure inside the prefab vessel body can be increased up to at least 2 bar, preferably up to at least 3 bar or at least 4 bar, for instance up to about 5 bar, about 6 bar, about 7 bar or about 8 bar.

Further, the invention relates to a mould for use in a method according to the invention.

In a further aspect, the invention also relates to a fibre reinforced pressure vessel.

Advantageous embodiments according to the invention are described in the appended claims.

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

Fig. 1A shows a schematic cross-sectional view of an embodiment of a mould according to an aspect of the invention;

Fig. IB shows a schematic side view of the mould of Fig. 1A, wherein one mould part of the mould is omitted and Fig. IB further shows a cross-section of a prefab vessel body placed inside said mould;

Fig. 2 shows a schematic cross-sectional view of a first embodiment of a reinforced pressure vessel according to an aspect of the invention; and

Fig. 3 shows a schematic, partly exploded, perspective view of a second embodiment of a reinforced pressure vessel according to an aspect of the invention.

It is noted that the figures show merely preferred embodiments according to aspects of the invention. In the figures, the same or similar reference signs or numbers refer to equal or corresponding elements or parts.

Fig. 1A shows an embodiment of a mould 1 according to an aspect of the invention. Fig. IB shows a schematic side view of said mould 1, wherein one mould part IB of the mould 1 is omitted, such as to reveal a view on the parting face 16 of the mould 1. It is noted that the schematic view of Fig. IB can thus be considered as a schematic cross-section along line B-B in Fig. 1A. Said mould 1 shown in Figs. 1A and IB can be used for forming a fibre reinforced pressure vessel 2 according to an aspects of the invention, exemplary embodiments of which are shown in Figs. 2 and 3.

With respect to Figs. 2 and 3, it is noted that the fibre reinforced pressure vessel 2 comprises a substantially gas-tight and/or fluid-tight liner 4 overwound with a layer 5 of dry wound fibre material, and a cover layer 6 of coating material covering the layer 5 of dry wound fibre material, especially in order to provide a protective coating, wherein said cover layer 6 is moulded or casted onto the layer 5 of dry wound fibre material inside a mould 1. It is noted that the fibre reinforced pressure vessel 2 can for instance be a gas tank, and may during use contain a gas or gaseous fluid, for instance natural gas, LPG, propane gas, and/or butane gas.

In the method of forming a fibre reinforced pressure vessel 2, a prefab vessel body 3, which may be formed substantially as a cylinder, is provided. Said prefab vessel body 3 has a substantially gas-tight and/or fluid-tight bner 4 overwound with a layer 5 of dry wound fibre material.

The liner 4, which can form an inner part 4 of the prefab vessel body 3, can for instance be made by blow moulding and/or can for instance be made of a polymer, e.g. HDPE, which can be recyclable. Such liner 4 may be substantially chemically inert and/or can be arranged withstand temperatures in a relatively large range, e.g. substantially between -40°C and +80°C, relatively well.

Although the layer 5 of dry wound fibre material can preferably comprise and/or be substantially formed of Aramide fibres, such as Kevlar or Twaron fibres, said layer 5 may additionally or alternatively comprise glass fibres, carbon fibres or other fibres, or can be substantially formed of such fibres. Preferably, said layer 5 can be formed substantially of a single kind of fibre.

It is emphasized that the layer 5 of dry wound fibre material consists of dry wound fibres. Said layer 5 is thus substantially free of a fibre binding matrix material, such as a fibre binding resin. The absence of a fibre binding resin can counteract resin cracking problems, but which can occur in regular fibre reinforced composite materials, such as epoxy composites, when such materials are for instance subject to impact.

Further, it is noted that the fibres of the layer 5 of dry wound fibre material can advantageously be wound in pure geodetic patterns.

It is noted that the prefab vessel body 3 may be substantially formed by a method such as for instance is known from WO 01 5/7429. The dry wound fibre layer 5 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 prefab vessel body 3, and/or the fibre reinforced pressure vessel 2 formed therewith, is under internal pressure the respective fibres or fibre filaments are loaded exactly in their longitudinal direction.

In advantageous embodiments, the prefab vessel body 3 can have a substantially cylindrical shape, wherein the distal ends of said body 3 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 2 and/or prefab vessel body 3 is under internal pressure the mechanical stresses are distributed equally among the fibres wound over the respective distal end.

The method further comprises a step of installing said prefab vessel body 3 into a mould 1, or a so-called die 1, which can comprise cooperating mould parts IA, IB.

Advantageously, the mould 1, especially cooperating mould parts IA, IB thereof, can be arranged such that a mount 7 of the prefab vessel body 3, of which the layer 5 of dry wound fibre material is to covered with a layer 6 of coating material within said mould 1 during said method, can extend at least partly from an inner space 8 of said mould 1 in an outward direction 9 through an inner wall 10 of said mould 1 when the mould 1 is closed around the prefab vessel body 3, as can for instance be seen in Fig. 1A. For example, the mould 1 can be arranged to hold the prefab vessel body 3 in place inside said mould 1 at least partly by clamping said mount 7 between said mould parts IA, IB.

Alternatively or additionally, other means may be provided for holding the prefab vessel body 3 in place, such as for instance spacers, e.g. spacers mad of a material corresponding to the coating material 6B for forming the cover layer 6, which is described below in greater detail.

Advantageously, the mount 7, which can be a mount 7 for mounting appendages, such as e.g. a gas tap 11, a valve, a flow or gas line 12, a pressure meter and/or a pressure reducer, to the vessel 2 and/or prefab vessel body 3. In embodiments, the mount 7 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 13 with respect to the vessel 2 and/or prefab vessel body 3, but which is allowed to rotate about its axis 13.

The method further comprises a step of feeding a coating material 6B into the mould 1 accommodating the prefab vessel body 3 in order to cover the layer 5 of dry wound fibre material with a cover layer 6 of coating material 6B. For instance hereto, the mould 1 may be provided with one or multiple feeding channels 14 for feeding coating material 6B into the inner space 8 of the mould 1, especially into a moulding cavity 15 that substantially encloses the layer 5 of dry wound fibre material and that at its outer side 8B is at least partly, e.g. substantially, defined by means of the inner wall 10 of the mould 1. It is noted that said moulding cavity 15 can further be defined at least partly by means of the prefab vessel body 3, e.g. an outer side 3A of said prefab vessel body 3 formed by the layer 5 of dry wound fibre material.

Further, the mould 1 may be provided with one or more air or gas vents 26 or riser(s). For example, said vent(s) 26 can be formed by one or more channels 26A, 26B located at the parting face 16 of the mould 1 in the respective mould part(s) IA, IB. Said vent(s) can arranged be for allowing gas to escape from said moulding cavity 15 to be filled with coating material 6B, in order to counteract that air or other gas can unintentionally prevent the moulding cavity 15 from being filled.

It is noted that the coating material 6B fed into the mould 1 preferably can be formed as a substantially hquid material. Said material, which can be used for forming a protective coating 6 for covering the fibres that are kept substantially free of matrix material, can preferably comprise and/or be an elastomeric material. Preferably, the elastomeric material can facilitate protecting the fibres against UV, wear and tear and/or all sorts of chemicals. The material may be substantially fire retardant and/or may facilitate that the cover layer 6 is relatively resilient.

Advantageously, the coating material 6B can be or comprise a rubber or rubberlike material, such as a synthetic rubber material, preferably a material comprising and/or being formed at least partly by a polyurethane or PUR material and/or an elastomer material, more preferably a multi-component material such as for instance a two-component polyurethane material. In embodiments, said coating material 6B may comprise additives, e.g. colour pigments in order to provide the coating layer 6 in a corporate colour. With respect to the multi-component material, it is noted that the different, components or parts of the material, e.g. of a two-part polymer material, may advantageously be mixed together before feeding said coating material 6B into the mould 1.

Preferably, the cover layer 6 is formed within the mould 1, whereby a chemical reaction within said coating material 6B, e.g. a reaction comprising curing and/or expanding of said material 6B, occurs within the mould 1. As an example thereof, or alternatively, the coating material 6B may substantially cure within the mould 1, and preferably the mould 1 is opened and the vessel 2 is removed from said mould 1 only after the cover layer 6 has been substantially cured or set.

Although the coating material 6B may be fed into said moulding cavity 15 by pouring it into the mould 1, e.g. substantially at atmospheric pressure and/or via said one or multiple feeding channels 14, said coating material 6B can advantageously be fed into said moulding cavity 15 by injecting it 6B into the mould 1, preferably at a relatively low pressure, e.g. at a pressure below 6 bar, preferably a pressure below 4 bar, such as for instance a pressure between 1 and 4 bar. For example in such cases, at least one of the one or more feeding channels 14, e.g. all feeding channels or the feeding channel 14, can be provided such that the coating material 6B can be fed into the moulding cavity 15 at a lower portion thereof, preferably at a substantially lowest point thereof. By allowing coating material 6B to enter the moulding cavity 15 from below, air present in the moulding cavity 15 can escape in an upward direction without having to travel through the coating material 6B.

Preferably, the step of feeding the coating material 6B into the mould 1 can be executed after an overpressure has been arranged within said prefab vessel body 3, for example by pressurizing an inner room 17 of said body 3, e.g. by means of a gas. For example, the prefab vessel body 3 can be connected to a pressure source (not shown), e.g. via a gas supply line 12 temporarily attached to the mount 7, which gas supply line 12 may extend at least partly through the mould 1, in order to pressurize the prefab vessel body 3 within the mould. Alternatively, the prefab vessel body 3 can for instance be inflated or pressurized before it is placed into the mould 1 and/or before the mould 1 is closed around said prefab vessel body 3. It is noted that said overpressure can for instance be at least 0.5 bar, especially about 1 bar.

Although the prefab vessel body 3 may be pressurized in order to let the hner 4 swell such as to pull the fibres of the dry wound fibre material relative tight around said liner 4, as a result of which gas can be forced out of the layer 5 of dry wound fibre material in order to counteract that said gas becomes entrapped in the layer 5 of dry wound fibre material when it is coated, the layer 5 of dry wound fibre material may be at least partly covered with a substantially gas impermeable layer (not shown), preferably a substantially gas impermeable layer comprising a substantially gas impermeable film, such that can be counteracted that gas, e.g. bubbles of air present between fibres of the layer 5 of fibre material will move into the coating material 6B for forming the cover layer 6, such that a relatively even, flat, clean, and/or robust cover layer 6 can be provided for.

Additionally or alternatively, the method may comprise a step of increasing the pressure in the prefab vessel body 3, e.g. by pumping up said body 3 and/or its inner room 17, after feeding at least a part of the coating material 6B into the mould 1, and preferably after filling the moulding cavity 15 substantially completely. Advantageously, the pressure inside the prefab vessel body 3 may then be increased to at least 2 bar, preferably at least 3 bar or at least 4 bar, for instance about 5 bar, about 6 bar, about 7 bar or about 8 bar.

In preferred embodiments, one or more fasteners 18, 19 for fastening an element 20, 21 to an outside of the pressure vessel 2 can be moulded or casted within the mould 1 together with the cover layer 6 for covering the layer 5 of dry wound fibre material. For example, the fastener 18, 19 may be formed as a part or portion extending from the cover layer 6 in an outward direction 25. Since said cover layer 6 and fastener 18, 19 can be moulded or casted together, i.e. in a single step, said fastener 18, 19 and said cover layer 6 can form an integral part 6, 18, 19, see the schematic cross-sectional view of Fig. 2.

It is noted that polymer chains, e.g. elastomer chains, can extend from a portion 18, 19 of said integral part 6, 18, 19 forming a fastener 18, 19 into a portion 6A of said integral part 6, 18, 19 that forms a part 6A of the cover layer 6 underlying said portion 18, 19 forming the fastener 18, 19.

As can be understood from Figs. 2 and 3, said one or more fasteners 18, 19 can be arranged for form-fittingly engaging with a respective element 20, 21 to be fastened to the outside of the pressure vessel 2. For example, said element 20, 21 can be a handle 20 or a vessel support 21 such as for instance a foot ring 21. In embodiments, such an element 21 can be clamped onto the vessel 2 by temporarily resiliently deforming the fastener 19 in order to form-fittingly enclose it at least partly. Alternatively or additionally, the element 20 can be attached to the fastener 18 by alternative means, e.g. by interconnecting multiple parts 20A, 20B of the element 20 after they have been placed in form-fittingly engagement with the fastener 18. Alternatively or additionally, the fastener 18, 19 may be arranged to be attached to a respective element 20, 21 by other means. For example, said fastener 18, 19 may comprise one or more holes, e.g. through holes, to facilitate the attachment of a respective element 20, 21 to said fastener 18, 19.

It is noted that the mould 1 can comprise an inner space 8 for accommodating the prefab vessel body 3 and the mould 1, especially an inner wall 10 thereof, can at least partly define a moulding cavity 15 that substantially encloses the layer 5 of dry wound fibre material of said vessel body 3 during feeding a coating material 6B into the mould 1, wherein said inner space 8 is arranged such that the moulding cavity 15 comprises a first moulding cavity portion 15A for forming a cover layer 6 of coating material 6B therein and second moulding cavity portion 15B for forming a fastener 18, 19, wherein said fastener can be arranged and/or intended for fastening one or multiple respective elements 20, 21 to an outside of the pressure vessel 2.

In embodiments, the mould 1 can be provided with a relief (not shown in Figs. 1A and IB) for forming an imprinting 23 at the outside of the cover layer 6, for instance such as to provide the pressure vessel 2 with a logo 23 or the hke 23. Said logo 23 or other imprinting 23 can for instance be at least partly raised (see Fig. 2) and/or at least partly recessed (not shown) with respect to the outer surface 24 of the cover layer 6. Since said cover layer 6 and said relief, e.g. a raised relief 23, can be moulded or casted together, i.e. in a single step, said raised relief and said cover layer 6 can form an integral part 6, 23A, see the schematic cross-sectional view of Fig. 2.

It is noted that polymer chains, e.g. elastomer chains, can extend from a portion 23A of said integral part 6, 23A forming a raised relief 23 into a portion 6C of said integral part 6, 23A that forms a part 6C of the cover layer 6 underlying said portion 23A forming said raised relief 23.

Additionally or alternatively, the outer surface 24 of the cover layer 6 can have a rough surface finish, for example in order to make it less vulnerable to cosmetic damage, e.g. cosmetic damage due to scratches or scrapes. For example thereto, in embodiments, the mould 1 can be provided with an at least partly textured mould surface, i.e. an at least partly textured inner wall 10, for instance in order to provide at least a part of the cover layer 6 with a rough surface finish, preferably a surface finish being relatively rough with respect to a cover layer formed by spreading coating material onto the layer 5 of dry wound fibres. For example, the inner wall 10 of the mould can be provided with dimples and/or the inner wall 10 may be roughened, e.g. by sandblasting and/or another suitable technique.

It is noted that for the purpose of clarity and a concise description features are described herein as part of the same or separate embodiments, however, it will be appreciated that the scope of the invention may include embodiments having combinations of all or some of the features described.

Further, it is noted that the invention is not restricted to the embodiments described herein. It will be understood that many variants are possible.

For example, not only the prefab vessel body 3, but also other parts, may be installed in the mould 1 before the cover layer 6 is moulded inside said mould 1. For example, such parts may be inserts for forming a logo or the like, especially in colour being different than the main colour of the cover layer 6.

Such and other variants will be apparent for the person skilled in the art and are considered to lie within in the scope of the invention as formulated in the following claims.

Claims

A method for forming a fiber-reinforced pressure vessel, comprising the steps of: providing a prefabricated vessel body with a substantially gas-tight and / or liquid-tight liner covered with a layer of dry-wound fiber material; installing said prefabricated drum body in a mold; and introducing a coating material into the mold that accommodates the prefabricated barrel body to cover the layer of dry-wound fiber material with a coating of coating material.

Method according to claim 1, wherein the step of introducing the coating material into the mold is carried out after an excess pressure has been applied within said prefabricated vessel body.

Method according to claim 2, wherein said excess pressure is at least 0.5 bar, for example about 1 bar, and / or is below 6 bar, preferably below 5 bar or below 4 bar.

The method of any one of the preceding claims, further comprising a step of increasing the pressure in the prefabricated vessel body after at least a portion of the coating material has been introduced into the mold.

A method according to claim 4, wherein the pressure inside the prefabricated vessel body is increased to a pressure higher than a pressure at which the coating material is introduced into the mold, and / or increased to at least 2 bar, preferably at least 3 bar or at least 4 bar, for example about 5 bar, about 6 bar, about 7 bar or about 8 bar.

A method according to any one of the preceding claims, wherein a fastener for fastening an element to an outside of the pressure vessel is formed in the mold together with the cover layer for covering the layer of dry-wound fiber material.

Method as claimed in claim 6, wherein the fixing means is adapted to engage form-fittingly on an element to be fixed on the outside of the pressure vessel.

A method according to any one of the preceding claims, wherein the mold is provided with a relief for forming a print on the outside of the cover layer, for instance in order to provide the pressure vessel with a logo or the like.

A method according to any one of the preceding claims, wherein the mold is provided with an at least partially textured mold surface, for example in order to provide at least a portion of the cover layer with a rough surface finish.

A method according to any one of the preceding claims, wherein, in the step of providing the prefabricated vessel body, the layer of dry-wound fiber material is a layer that is at least partially covered with a gas-substantially impervious layer, preferably a gas-substantially impervious layer comprising a gas-substantially impervious film.

A method according to any one of the preceding claims, wherein the coating material is a rubber material or rubber-like material, preferably a material comprising a polyurethane and / or an elastomeric material, more preferably a multi-component material such as, for example, a two-component polyurethane material, and / or is at least partially formed by it.

A method according to any one of the preceding claims, comprising a step in which a reaction in said coating material, in particular a chemical reaction in said coating material, takes place in the mold, for example in which a curing reaction takes place in the mold.

A mold for use in a method according to any one of the preceding claims, wherein the mold, in particular cooperating mold parts thereof, is / are arranged such that a coupling means of a prefabricated vessel body that a substantially gas-tight and / or liquid-tight has a liner covered with a layer of dry-wound fiber material whose layer of dry-wound fiber material is to be covered with a layer of coating material in said mold during said method, at least partially from an inner space of said mold in an outward direction extending through an inner wall of said mold when the mold is closed around the prefabricated vessel body.

A mold as claimed in claim 13, wherein the mold, in particular an inner wall thereof, is provided with at least one of: a right for forming a print on the outside of the cover layer, for example in order to pressurize the logo of something or something to provide such; an at least partially textured mold surface, for example, to provide at least a portion of the cover layer with a rough surface finish; and an interior space adapted to accommodate the prefabricated barrel body and which is adapted to at least partially define a forming cavity that substantially encloses the layer of dry-wound fiber material of said barrel body while introducing a covering material into the mold, wherein said inner space is arranged such that the forming cavity comprises a first forming cavity portion for forming a covering layer of coating material therein and a second forming cavity portion comprises forming an attachment means for attaching an element to an outside of the pressure vessel.

A fiber-reinforced pressure vessel, comprising a substantially gas-tight and / or liquid-tight liner wrapped with a layer of dry-wound fiber material, and a cover layer of covering material covering the layer of dry-wound fiber material, said cover layer in a mold on the layer is cast or formed from dry-wound fiber material.

The fiber-reinforced pressure vessel according to claim 15, further comprising at least one fastener extending at least partially from said cover layer in an outward direction, said fastener forming an integral part together with the cover layer and wherein said fastener together with said cover layer in said mold is cast or molded.

A fiber-reinforced pressure vessel formed by a method according to any of claims 1-12.