Method of manufacturing a sealed tank for containing a gas and / or a fluid

Abstract

One aspect of the invention relates to a method for manufacturing a sealed tank for containing a gas and / or a liquid, comprising a step of forming a sealed wall of the tank, comprising the following sub-steps: Forming a jacket by applying at least one knitted fabric covering the outer surface of the mandrel, the knitted fabric comprising knitted yarns of a heat-sealing thermoplastic material, Filament winding, around the jacket, successive sections of a first strip comprising a fiber-reinforced heat-sealing thermoplastic material, so as to fuse the wound successive sections of the first strip, Cooling the jacket and the first strip to form the sealed wall in a single material. Figure to be published with the abstract: Figure 2

Description

Title of the invention: Method for manufacturing a sealed tank for containing a gas and / or a fluid TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention relates to methods of manufacturing sealed tanks, or sealed containers, in particular but not limited to pressure tanks made of composite material.

[0002] The present invention relates to a method of manufacturing a sealed tank using fiber-reinforced thermoplastic materials in the manufacturing process. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] The conditions for storing gas or liquid have recently improved with the appearance of composite sealed tanks which include a fibrous material, i.e. which is reinforced by fibers, as a wall structure, or external envelope.

[0004] By "tight tank" is meant a tank or container that is tight to liquids and / or gases. More precisely, it is meant a tank that has, for these liquids and / or gases, a permeability lower than a maximum limit prescribed by the application.

[0005] For example, a sealed tank intended for an application of transporting hydrogen in compressed form at high pressure has permeability to hydrogen when this gas is compressed in a pressure range from 30 MPa to 70 MPa (i.e. from 300 bars to 700 bars).

[0006] It is known, to allow the storage of hydrogen under these pressure conditions, to use a sealed tank architecture called type III or IV. This architecture comprises, from the inside to the outside, a sealed bottle, also called "internal liner" according to the terminology commonly used, and an external reinforcement structure made by filament winding.

[0007] The role of the internal liner is mainly to ensure a gas-tight function (it must be as impermeable as possible to hydrogen). The role of the external reinforcement structure is mainly to ensure a function of mechanical resistance to pressure.

[0008] In type III tanks, the internal liner is metallic. In type IV tanks, the internal liner is made of polymer and produced by rotational molding or extrusion blow molding, for example.

[0009] A new type of reservoir is described in document WO2011143723A2. Gas tightness is achieved in a way other than by an internal metal liner. The liner is thus replaced by a sealed internal envelope formed by winding and heating a strip of liner made of a heat-sealing thermoplastic material around a template (or mandrel). This template is metallic, removable into multiple hoops that fit together circumferentially, allowing it to be removable and reusable. The template also has a shape that corresponds to the shape of the tank. Typically, the template has a cylindrical shape and, on each axial side, a rounded, cap-shaped frontal facet.

[0010] In order to ensure mechanical strength and to consolidate the gas barrier, the sealed internal envelope is protected by a second envelope, called the protective external envelope, also made from a wound strip, comprising a heat-sealed thermoplastic material and reinforced with fibers which are preferably continuous. This second envelope constitutes the external reinforcement structure of the sealed tank.

[0011] This outer casing is, like the inner casing, formed by winding a coating strip onto the first casing (which then acts as a mandrel), the material of the wound coating strip being the fiber-reinforced thermoplastic material. The resulting sealed wall of the sealed tank thus comprises two components (the inner casing, the outer casing).

[0012] As the sealed internal envelope made from the wound strip of thermoplastic material is much lighter and also less expensive than a liner (metallic but also polymer), its use makes it possible to considerably lighten the mass of the tank and reduce its cost.

[0013] This advantage is however offset by the increase in the manufacturing time of the sealed tank, since the winding of the coating strip during the manufacturing of the sealed internal envelope takes a lot of time. Indeed, the coating strip, being narrow and not very thick compared to the dimensions of the template and the desired thickness of the sealed internal envelope, must be wound by multiple turns around the template. Specifically, the coating strip is wound to form a plurality of superimposed turns overlapping longitudinally and radially, thus forming several layers around the template. In addition, the winding speed is constrained by the stretching and pressure to be applied to the coating strip so that the first layer is tightly clamped on the template and the successive layers are clamped together.This helps avoid air bubbles between each coil and layer during the heating stage which fuses or softens the coils together to consolidate them.

[0014] For example, it takes several hours to wind a strip 120 pm to 150 pm thick and 25 mm to 80 mm wide around a 60 cm cylindrical template. in diameter and 3.50 m in length, with a thickness of between 2 mm and 5 mm. Such a duration hinders the deployment of the manufacturing process on an industrial scale.

[0015] There is therefore a need to accelerate the manufacture of a sealed tank, in particular a sealed tank not comprising an internal liner. Summary of the invention

[0016] The invention offers a solution to the problems mentioned above, by making it possible to obtain a sealed wall in a single step of winding a fiber material.

[0017] A first aspect of the invention relates to a method of manufacturing a sealed wall of a sealed tank, the sealed tank being adapted to contain a gas and / or a liquid, the manufacturing method comprising the following steps: • Mount a reusable and removable mandrel by mounting / dismounting hoops, the mandrel having an external surface of a shape corresponding to an internal surface of the sealed wall of the tank, • Form the watertight wall of the tank on the external surface of the mandrel, forming a mandrel extraction hole, • Remove the mandrel from the watertight wall through the extraction port, The step to form the watertight wall being carried out by completing the following sub-steps of: • Formation of an envelope by applying at least one knit covering the external surface of the mandrel, the knit comprising a layer of knitted threads forming loops, the knitted threads being of a thermoplastic material which can be sealed by applying heat, • Winding, around the envelope formed by the knit covering the external surface of the mandrel, of successive sections of a first strip comprising a thermoplastic material which can be sealed by heat application and reinforced with fibers, so that the successive sections of the wound first strip overlap to form a first layer of the first strip and overlap to form superimposed layers of the first strip, the winding being carried out by: • Exerting a pressure selected to squeeze each section of the first wound strip against the casing, forming the first layer of first strip, and to squeeze the sections overlapping the first layer of first strip to form the other superimposed layers of first strip, and in • Exercising a temperature chosen to fuse the thermoplastic material of each section of the first layer of the first strip with the underlying wires of the envelope, and to merge the sections of the successive layers of first strip, • Cooling of the envelope and the first wound strip to form the waterproof wall in a single material.

[0018] Thus, the initial use of a knit whose threads / loops are made of a thermoplastic material compatible with the thermoplastic material of the first strip (the two constituents fuse under the combined effect of the pressure and temperature exerted during winding) advantageously makes it possible to avoid a very time-consuming step of winding a strip of thermoplastic material around the mandrel. The method for manufacturing the sealed wall of a sealed tank is thus faster than the solution proposed by the prior art document.

[0019] Indeed, a single knit (or a single layer of knitted yarns) provides sufficient thermoplastic material to create, by fusing with the first strip, a gas barrier effect with the same mechanical resistance to pressure as the sealed internal envelope of the tank according to the prior art. Since the knit is manufactured beforehand, it does not have to be formed during the manufacturing process of the tank, unlike the sealed internal envelope of the tank according to the prior art. The knit is also easy and quick to apply to the mandrel since it can simply be threaded onto it, for example manually.

[0020] In addition, thanks to the yarns / loops of the knit which are made of a thermoplastic material compatible with the thermoplastic material of the first strip, the sealed wall obtained is monolithic, that is to say formed from a single material. In other words, once the winding by the first strip is completed, it is not possible to distinguish the constituents used (the knitted yarns and the thermoplastic material impregnating the reinforcing fibers). This homogeneity of the sealed wall makes it possible, compared to a sealed wall composed of two inner and outer envelopes (such as those present in the solutions of the prior art), to improve the robustness of the tank.

[0021] Specifically, the sealed wall of the monolithic tank resists better than a double-layer wall when a vacuum or depressurization is applied inside the sealed tank. Since these pressure and temperature conditions are those encountered during the drying and decontamination phases of the tank, or during the emptying phases, the sealed tank obtained is better suited to its use and has a longer service life.

[0022] In addition to the characteristics which have just been mentioned in the preceding paragraphs, the method according to the first aspect of the invention may have one or more complementary characteristics among the following, considered individually or according to all technically possible combinations. • the thermoplastic material of the knitted yarns is identical to the thermo material plastic of the first strip. • the knit has a mass per surface between 100 g / m2 and 800 g / m2. • the knitting is in the form of one or more sleeves, each sleeve being threaded through one end of the mandrel. • the sub-step of forming the envelope further comprises the application of a second knit on the first knit, the thermoplastic material of the knitted yarns of the second knit being coherent by heat input under the same temperature and pressure conditions as the thermoplastic material of the knitted yarns of the underlying first knit. • the sub-step of winding around the envelope comprises the winding of at least one other additional strip, formed from the material of the first strip, the additional strip being wound simultaneously with the first strip.

[0023] A second aspect of the invention relates to a method for producing a reinforced sealed wall of a tank comprising the steps of the method of the sealed wall described previously with or without the different modes of implementation, comprising the following sub-steps: • Winding, around the sealed wall, successive sections of a second strip comprising a heat-conductive thermoplastic material reinforced with fibers, such that the successive sections of second strip wound overlap to form a first layer of second strip and overlap to form superimposed layers of second strip, the winding being carried out by: • Exerting a pressure chosen to clamp each section of the second wound strip against the sealing wall, forming the first layer of second strip, and to clamp the sections covering the first layer of second strip to form the other superimposed layers of second strip, and in • Exercising a temperature chosen to fuse the thermoplastic material of each section of the first layer of the second strip with the underlying region of the waterproof wall, and to fuse the sections of the successive layers of the second strip, • Cooling of the waterproof wall and the second strip to form the reinforced waterproof wall in a single material.

[0024] Thus, the watertight wall of the tank is reinforced with fibers and thermoplastic materials. This increases the watertightness and mechanical resistance to pressure of the tank.

[0025] Advantageously, the thermoplastic material of the knitted yarns of the knit is identical to the thermoplastic material of the first strip.

[0026] Thus, the envelope and the second wound strip are unified in the most perfect way possible.

[0027] A third aspect of the invention relates to a method of manufacturing a sealed tank for containing a gas or a liquid, comprising the following steps: • Manufacture a sealed wall of the tank by carrying out the steps of the manufacturing method according to the first aspect of the invention, with or without the different embodiments described previously, • Close the waterproof wall by applying a base against the waterproof wall, • Consolidate the waterproof wall to obtain a reinforced waterproof wall of the tank, The step to consolidate the waterproof wall is accomplished by carrying out the following sub-steps: • Winding, around the sealed wall, successive sections of a second strip comprising a heat-sealed thermoplastic material reinforced with fibers, such that the successive sections of second strip wound overlap to form a first layer of second strip and overlap to form superimposed layers of second strip, the winding being carried out by: • Exerting a pressure chosen to clamp each section of the second wound strip against the sealing wall, forming the first layer of second strip, and to clamp the sections covering the first layer of second strip to form the other superimposed layers of second strip, and in • Exercising a temperature chosen to fuse the thermoplastic material of each section of the first layer of the second strip with the underlying region of the waterproof wall, and to fuse the sections of the successive layers of the second strip, • Cooling of the waterproof wall and the second strip to form the reinforced waterproof wall in a single material.

[0028] The thermoplastic material of the second strip is therefore chemically compatible with the underlying region of the sealing wall to fuse together.

[0029] According to one embodiment, the thermoplastic materials of the first and second strips are identical.

[0030] According to one embodiment, the base has an external peripheral surface covered with a thermoplastic material that can be sealed by heat and is compatible with the thermoplastic material of the sealed wall. According to one example, the peripheral surface of the base is heated before the closing step to fuse with a internal peripheral surface of the watertight wall defining the extraction orifice during the step of closing the watertight wall.

[0031] According to one embodiment, the external surface of the base is covered by the second strip during said step of consolidating the waterproof wall.

[0032] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0033] The figures are presented for information purposes only and in no way limit the invention. • [Fig.l] represents, in the form of a flowchart, the main steps of a method of manufacturing a sealed tank according to one aspect of the invention; • [Fig.2] is a schematic representation in cross-section of a sealed tank obtained according to the manufacturing process shown in [Fig.l]; • [Fig.3] represents, in the form of a flowchart, the main stages of the manufacturing process of a watertight wall, the first stage of the manufacturing process represented in [Fig.l]; • [Fig.4] represents, in schematic form, an example of a mandrel used during the manufacturing process shown in [Fig.3]; • [Fig.5] represents, in the form of a flowchart, the second stage of the manufacturing process shown in [Fig.3], • [Fig.6] represents, in schematic form, an example of knitting implemented during the step shown in [Fig.5]; • [Fig.7] represents, in schematic form, a semi-finished waterproof wall during manufacture during the first sub-stage of the stage represented in [Fig.5]; • [Fig.8] represents, in schematic form, the second sub-step of the step shown in [Fig.5]; • [Fig.9] represents, in schematic form, a block forming the watertight wall surrounding a mandrel during the third sub-step of the step represented in [Fig.5]; • [Fig. 10] represents, in schematic form, a watertight wall obtained after the third stage of the manufacturing process shown in [Fig. 3]; • [Fig.l 1] represents, in schematic form, a semi-finished tank during the second stage of the manufacturing process shown in [Fig.l]; • [Fig. 12] represents, in the form of a flowchart, sub-steps of the third step of the manufacturing process represented in [Fig.l], • [Fig. 13] represents, in schematic form, the first sub-step of the step shown in [Fig. 1 1]; • [Fig. 14] represents, in schematic form, an alternative sub-step to the first sub-step shown in [Fig. 13]; • [Fig. 15] represents, in schematic form, a reservoir obtained after the second sub-step of the step shown in [Fig. 12]. DETAILED DESCRIPTION

[0034] Unless otherwise specified, the same element appearing in different figures has a single reference.

[0035] The present invention is placed in the context of sealed tanks and their manufacturing methods. More particularly, the invention aims to produce more quickly sealed tanks having a pressure resistance greater than 0.2 MPa and gas barrier characteristics (impermeability to the gas / or liquid to be contained in the sealed tank) similar to, or even better than, those of the solutions of the prior art.

[0036] An example of implementation of a manufacturing method 200 of a sealed tank according to the invention is illustrated in the form of a flowchart in [Fig.l].

[0037] The method 200 for manufacturing a sealed tank is preferably used to produce the sealed tank 1 (also referred to as “tank 1” hereinafter), an enlargement of a section of which is shown schematically in [Fig.2].

[0038] In particular, the tank 1 is a composite tank suitable for use in the field of transporting and delivering hydrogen under high pressure.

[0039] The expression “composite tank” designates a type of tank in which the gas-tightness function is performed by a thermosetting material and the mechanical pressure resistance function is performed by fiber reinforcements. The tank 1 is thus here intended to contain hydrogen maintained under a high pressure, equal to or greater than 700 MPa. The tank is furthermore here adapted to contain a liquid such as water. Naturally, in other examples, the tank 1 may be intended to contain other gases and / or other liquids, under atmospheric storage conditions or under pressures lower than 700 MPa.

[0040] As shown in [Fig.2], the sealed tank 1 here has a cylindrical interior and exterior shape, according in this example to the same longitudinal axis XX'. The exterior shape and the interior shape may have an axis offset from each other, for example parallel to each other. The tank 1 comprises a flank on each axial side 1a, 1b, called a front facet which is rounded, dome-shaped or cap-shaped. In other examples, the shape of the tank 1 may be different, for example spherical, ellipsoidal or other shapes.

[0041] In the following description, the terms “interior”, “exterior”, “internal” and “external” are used to designate the position of a part or surface by relative to the longitudinal axis XX' of the tank 1, an inner or internal surface (for example) being closer to the longitudinal axis than an outer or external surface. The term "axial" means "along the direction of the longitudinal axis" and the terms "radial" and "transverse" mean "along a direction perpendicular to the longitudinal axis". The term "lateral" means "which is located on the sides of a part extending radially". The terms "thickness" and "diameter" denote dimensions measured radially. The term "length" denotes a dimension measured axially.

[0042] More precisely, and still with reference to [Fig.2], the reservoir 1 comprises a wall 11 and an interior volume 13. In this example the reservoir 1 comprises a nozzle 12.

[0043] The internal volume 13 of the tank 1 can have in this example a diameter db of 60 cm and a length 113 of 3.50 m.

[0044] The end piece 12 of the tank 1 is for example a tap 12 allowing alternately closing / opening the passage of gas or liquid into / out of the tank 1.

[0045] The wall 11 of the tank 1 has a sealed wall 111 and, in this example, a base 112 positioned on one of the axial sides 1b of the tank 1.

[0046] The sealed wall 111 of the wall 11 of the tank 1 has an internal surface 111c which has the shape of the internal volume 13 of the tank 1.

[0047] The sealed wall 111 is formed from a composite material, that is to say it comprises a mixture of at least one thermoplastic material and at least one fibrous material. The sealed wall 111 provides both the internal barrier effect (impermeability) to the gas or liquid contained in the interior volume 13 of the tank 1 and the effect of mechanical resistance to pressure. The thermoplastic material(s), as well as the type of fibers of the sealed wall 111 will be described later, in relation to the method 100 for manufacturing the tank 1.

[0048] The base 112 of the wall 11 of the reservoir 1 is preferably annular in shape, that is to say that it has an internal passage adapted to receive the nozzle (the tap) 12.

[0049] In the example of the tank 1 illustrated in [Fig. 2], the base 112 advantageously has a curved external surface 112a whose periphery, at least, is positioned in the thickness of the sealed wall 111 (not visible in [Fig. 2]) as explained below. Thus, the sealed wall 111 and the base 112 forming the tank 1, form a unitary rigid structure capable of resisting the pressures required by the application.

[0050] The method 200 for manufacturing the tank 1 is described below in relation to FIGS. 1 to 15.

[0051] As shown in [Fig.l], the method 200 for manufacturing the tank 1 comprises the following successive steps: • Manufacture the sealed wall 111 of the wall 11 of the tank 1 according to a manufacturing method noted 100 in accordance with another aspect of the invention, • Close E4 the watertight wall 111 by applying the base against the watertight wall.

[0052] Furthermore, optionally, the method 200 further comprises the following step: • Consolidate E5 the waterproof wall 111 to obtain a reinforced waterproof wall.

[0053] The manufacturing method 100 of the sealed wall 111 is described below in relation to FIGS. 3 to 10.

[0054] With reference to [Fig. 3], the method 100 for manufacturing the watertight wall 111 comprises the following steps: • Mount El a reusable and removable mandrel 2 by mounting / dismounting hoops 24, the mandrel 2 having an external surface of shape corresponding to the internal surface 11 le of the sealed wall 111 of the wall 11 of the tank 1, • Form E2 the sealed wall 111 of the wall 11 of the tank 1 on the external surface of the mandrel 2, by forming an extraction orifice 11 Id of the mandrel 2, • Remove E3 the mandrel 2 from the sealed wall 111 through the extraction orifice llld.

[0055] [Fig.4] illustrates, in schematic form, an example of a mounted mandrel 2, used in the process 100. This mandrel 2 is inspired by the document WO2011143723A2.

[0056] The mandrel 2 acts as an internal mold for the watertight wall 111.

[0057] The mandrel 2 is suitable for filament winding. Indeed, as will be described later, step E3 of the method 100 implements such a method of filament winding around the mandrel 2.

[0058] As shown in [Fig.4], the mandrel 2 is here a hollow part of revolution, having an axis of revolution 23.

[0059] In this example, the mandrel 2 comprises at one end a removable spindle 22 (or connection) arranged at an axial end of the mandrel 2. This spindle 22 of the mandrel 2 is in this example adapted to be coupled to a rotary motor, allowing the mandrel 2 to be rotated around its axis of revolution 23.

[0060] The mandrel 2 further comprises a removable external surface 21, integral with the spindle 22 (once the assembly of the mandrel 2 is complete).

[0061] The external surface 21 of the mandrel 2 has a rounded shape corresponding to the shape (and dimensions) of the internal surface 111 of the sealed wall 111 of the wall 11 of the tank 1 (see [Fig.2]). Thus, according to the example of the tank 1 detailed previously, the mandrel 2 here has an external surface 21 whose largest diameter is 60 cm and the length 3.50 m.

[0062] The mandrel 2 comprises a plurality of hoops 24 and in this example a bottom 25. The bottom 25 in this case comprises a base 251 and a plug 252 positioned in the base 251 but can be formed in a single piece. The outer surface of mandrel 21 comprises each axially elongated outer surface 214 of each hoop 24, and an outer surface 215 of the bottom 25 arranged opposite the spindle 22 of mandrel 2. The outer surface 215 of the bottom 25 comprises in this example an outer base surface 2151 and an outer cap surface 2152. Each hoop 24 is held in position by its opposite ends, one being fixed on the circumference 22a of the spindle 22, and the other being engaged in the base 251 of the bottom 25. The hoops 24 can also, according to another example, fit into each other.

[0063] The mounting E1 of the mandrel 2 is carried out, for example, by first coupling the spindle 22 to the rotary tool, then by engaging one end of each hoop 24 in the spindle 22, and finally by fixing the opposite ends of the hoops 24 with the bottom 25 of the mandrel 2.

[0064] Naturally, other configurations of the mandrel 2 are possible (not shown in the figures).

[0065] [Fig. 5] represents, in the form of a flowchart, step E2 of the method 100. This step E2 aims, as described previously, to form the sealed wall 111 of the wall 11 of the tank 1.

[0066] As shown in [Fig.5], step E2 begins at sub-step E21. During this sub-step E21, a knit 3 is applied to the mandrel 2, covering the external surface 21 of the mandrel 2.

[0067] [Fig. 6] represents, in schematic form, a partial view of an example of knitting 3.

[0068] As shown in [Fig.6], the knitted fabric 3 comprises a layer 31 of knitted yarns 311, 312 forming loops. The knitted fabric 3 is thus a structure which can be formed of loops or stitches passed through one another. For example, the loops or stitches are formed of “intermingled feet and heads”. The knitted fabric 3 thus forms a fabric whose stitches can be stretched in various directions having more elasticity than a weave.

[0069] The knitted threads 311, 312 are formed from one or more of the heat-sealed thermoplastic materials of the sealed wall 111 (note that the sealing is not carried out during sub-step E21).

[0070] The thermoplastic material(s) of the knit 3 are for example chosen from (but not limited to) thermoplastic materials from the polyolefin family or the polyamide family.

[0071] The knitted threads 311, 312 can thus be made of nylon. In this case in particular, the diameter of the knitted threads 311, 312 can be between 0.5 mm and 1 mm.

[0072] The knitted yarns 311, 312 preferably form loops oriented in a first direction DI and a second direction D2 orthogonal to the first direction D1. The thickness of the knitted yarns 311, 312 and / or the geometry of the knit are determined so that the mass per surface of the knit 3, once applied to the external surface 21 of the mandrel 2, is between 100 g / m2 and 800 g / m2.

[0073] Thus, at the end of sub-step E21, the knitted yarns 311, 3112 of the knit 3 form an envelope 30 of knitted yarns shaped according to the circumference of the external surface 21 of the mandrel 2. In other words, the envelope 30 of knitted yarns has the shape of the circumference (of the external limits) of the external surface 21 of the mandrel 2 and is placed in contact with this external surface 21. In other words, the envelope 30 forms a net placed flat, or draping, the external surface 21 of the mandrel 2.

[0074] This envelope 30 of knitted yarns provides a first part of the thermoplastic material(s) of the sealed wall 111. As described previously, this or these thermoplastic materials are necessary to achieve the barrier effect (impermeability) to the gas or liquid to be contained in the interior volume 13 of the tank 1.

[0075] [Fig.7] represents the mandrel 2 obtained at the end of step E21, this mandrel being, in this case, covered with the envelope 30 of knitted threads.

[0076] As can be seen in [Fig. 7], the casing 30 does not cover the pin 22 of the mandrel 22. Thus, when the pin 22 is removed, during step E3 of the method 100, there will remain an orifice (corresponding to the cross-section of the pin 22), referred to as “orifice 11 Id for extracting the mandrel 2” hereinafter (see [Fig. 10]), through which the hoops 24, and the bottom 25 of the mandrel 2 can be extracted from the inside of the sealed wall 111. The pin 22 (and therefore the extraction orifice 11 Id) are therefore sized as a function of the hoops 24 and the base 25 and the plug 26, so that they can be extracted.

[0077] In any event, a portion of the mandrel 2 is not covered by the casing 30 to form the extraction orifice 11 Id. According to another example not shown, the casing 30 does not cover the external surface 2152 of the plug 252, allowing it to be removed and forms the extraction orifice 11 Id or a second extraction orifice. In this example, the pin 22 may be only an internal axis and be covered by 30 and be removed by the extraction orifice 11 Id when the plug is removed. The plug 252 may in this case serve as a support and holding of the mandrel 2, for example by having the axis 23 vertical, during the manufacturing process of the sealed wall.

[0078] In practice, the knitted fabric 3 is manufactured prior to the execution of the method 100 for manufacturing the sealed tank 1.

[0079] It is advantageously presented in the form of one or more sleeves (or socks) (not shown in the figures). These sleeves are stretchable and re- tractable, because they are made only of knitted 311,312 yarns.

[0080] The sleeve is then applied to the mandrel 2, for example by an operator, in the following manner: the sleeve is threaded onto the mandrel 2 by one of the ends of the mandrel 2, in this case by the spindle 22 of the mandrel 2, or by the bottom 212 of the external surface 21 of the mandrel 2. The sleeve stretches when being threaded and then, once threaded and released, it retracts onto the external surface of the mandrel. In this way, the knitted fabric 3 is laid flat on the external surface 21 of the mandrel.

[0081] Several sleeves are advantageously used when the dimensions of the mandrel are large (for example when its length is greater than 1 m).

[0082] In other cases, several sleeves are used, specifically adapted to conform to the different shapes (diameters) of the external surface 21 of the mandrel 2. Thus, one sleeve can be used to cover the or a part of the external surface 214 of the hoops 24 and another sleeve can be used to cover the external surface 215 of the bottom and optionally one or the other part of the external surface 214 of the hoops 24. The sleeves can be applied side by side, or overlap axially.

[0083] In any event, whatever the number of sleeves, and whatever the dimension of the mandrel (in particular its length), the step E21 of applying the knit 3 is particularly quick and easy to perform. For example, it takes, for a trained operator, 10 minutes to form the envelope 30 around the mandrel 2. In other words, a portion of the thermoplastic material(s) of the sealed wall 111 is affixed simply and quickly to the mandrel.

[0084] Alternatively, another knit (not shown in the figures) may be applied to the knit 3 described above. This knit is subsequently referred to as “second knit”, while the previously deposited knit is referred to as “first knit”. The envelope 30 is then made up of the two (first and second) superimposed knits. This makes it possible to increase the quantity of thermoplastic material in the envelope 30 of knitted yarns. This variant is particularly well suited to increasing the permeability (gas barrier effect) of the sealed wall 111.

[0085] Now that a portion of the thermoplastic materials has been applied (via the envelope 30) to the external surface 21 of the mandrel 2, it is necessary to provide the other portion of the thermoplastic materials, as well as the fibers necessary to achieve the gas barrier effect. This provision is carried out during the sub-step E22 described below, in relation to [Fig.8].

[0086] During this sub-step E22, as shown in [Fig.8], and in particular at the insert present in this [Fig.8], successive sections 41 of a first strip 4 of thermoplastic material which can be sealed by heat and reinforced with fibers are wound (wound) around the envelope 30 of knitted threads.

[0087] In other words, during this sub-step E22, a method of filamentary winding of the first strip 4 onto the envelope 30 is carried out to cover the envelope 30 with fibers and thermoplastic material.

[0088] The fibers of the first strip 4 are preferably continuous. This makes it possible to obtain a more efficient reinforcement structure and thus to increase the mechanical resistance to pressure of the resulting sealed wall 111.

[0089] The fibers of the first strip 4 are formed from a material chosen from (but not limited to) the following materials: glass, carbon, metal, mineral, wool, cotton, linen, polyester, polypropylene, polyamide, basalt, kevlar®, stretched thermoplastic or a mixture of two or more of these materials.

[0090] The thermoplastic material of this first strip 4 is chemically compatible with the thermoplastic material of the knitted yarns 311, 312. The expression “chemically compatible” means that the thermoplastic materials of the knitted fabric 3 and of the first strip 4 have melting and / or softening points located in identical or similar temperature ranges.

[0091] The thermoplastic material that can be sealed by applying heat to the first strip 4 may be identical to that of the knitted yarns 311, 312. For example, the thermoplastic material of the first strip and that of the knitted yarns may both be from the polyolefin family or from the polyamide family.

[0092] The effect produced by this compatibility of the thermoplastic materials of the first strip 4 and the knitted threads 3 will be described later, in relation to sub-step E23.

[0093] The first strip 4 preferably has a width greater than or equal to 20 cm, for example equal to 20 cm, 50 cm or more. This makes it possible to make the execution of sub-step E22 faster than when the first strip has a smaller width.

[0094] Naturally, a first strip 4 of width less than 20 cm is suitable for the method 100, for example a width of first strip 4 equal to 2 cm, or 4 cm, or even 14 cm is suitable.

[0095] In practice, the mandrel 2 is rotated via, in this example, the spindle 22 during the execution of the sub-step E22. According to another example, the mandrel 2 and the casing 30 are stationary and a winder rotates around the mandrel 2 for the filament winding of the first strip 4 onto the casing 30 to cover the casing 30 with fibers and thermoplastic material. The strip 4 is, as explained below, wound tightly onto the casing 30, exerting pressure between the strip 4 and the casing 30 during the filament winding at a temperature within a predetermined temperature range so that the strip 4 fuses or unifies with the casing 30.

[0096] As schematically illustrated by the insert of [Fig. 8], the successive sections 41 of the first wound strip 4 overlap to form a first layer 410i of first strip 4, and overlap to form superimposed layers 40 of first strip 4 (on the insert of [Fig. 8], a second layer superimposed on the first layer 410i, i=l, is about to be formed, in the axial direction of the arrow). The number ni of superimposed layers of this first strip 4 depends on the diameter and the geometric shape of the mandrel 2 (therefore on the diameter and the shape of the interior volume 13 desired for the reservoir 1), as well as on the desired burst pressure (i.e. the pressure beyond which the reservoir 1 no longer holds the pressure and deforms). The number of layers ni can be between nl=2 and several hundred, for example nl=200.The multi-layer winding makes it possible to reduce the permeability and increase the mechanical resistance to pressure of the resulting sealed wall 111 1. .

[0097] The thickness of each layer 410i, i=1 to n may be, for example, between 50 pm and 300 pm. Within each layer 410i, i =1 to n, the successive sections 41 of the first strip overlap over a distance between 0 (corresponding to no overlap) and half the width of the first strip 4 and according to overlap angles which may vary.

[0098] During the winding of the first strip 4, pressure and heating are exerted on each successive wound section 41 of the first strip 4.

[0099] The pressure exerted on each section 41 of first wound strip is determined for 1) during the formation of the first layer 410i, i= 1, to tighten this section 41 against the envelope 30 of knitted yarns and 2) during the formation of the layers 410i, i= 2 to ni superimposed, to tighten this section 41 against the underlying layer 410i-1 of first strip 4.

[0100] The heating temperature exerted on each section 41 of the first wound strip is determined according to the properties of the thermoplastic material(s) used (in the first strip 4, in the envelope 30 of knitted yarns). Specifically, the temperature is located in the melting range of the thermoplastic materials used (this range being common since the thermoplastic materials are compatible).

[0101] Thus, during the formation of the first layer 410i, i=1 of first strip 4, the thermoplastic material of each wound section 41 fuses, or unifies, with the underlying yarns of the envelope 30 of knitted yarns. In addition, during the formation of the superimposed layers of first strip 4, the thermoplastic material of each wound section 41 fuses, or unifies, with the underlying layer 410i-1 of first strip 4.

[0102] In other words, the temperature is chosen to melt the thermoplastic material of each section of the first layer of first strip with the underlying yarns of the knitted yarn cover, and to merge the sections of successive layers of first strip.

[0103] For example, when the thermoplastic materials concerned are from the polyolefin family or the polyamide family, the temperature is between 160°C and 340°C.

[0104] Under the effect of heat and tightening, the fibers of the layers 410i, i=l to ni of the first strip 4 are also joined against the thermoplastic material(s) (of the first strip 4, of the envelope 30 of knitted threads).

[0105] Thus, at the end of sub-step E22, the envelope 30 and all of the superimposed layers 40 of the first strip are combined, or consolidated, into a single material.

[0106] The expression "a single material" is understood here as having such homogeneity that it is impossible, with the naked eye, to distinguish the materials used to produce it. Thus, the expression "in a single material" designates a monolithic structure which is opposed to a watertight wall which would be made up of two concentric envelopes.

[0107] As a variant, the sub-step E22 is carried out not with a single first strip 4, but with at least one other additional strip, formed from the material of the first strip, the additional strip being wound simultaneously with the first strip 4. This makes it possible to accelerate the execution of this sub-step E22 and thus to make the method 100 for manufacturing the watertight wall 111 faster.

[0108] The method 100 for manufacturing the sealed wall 111 further comprises a sub-step E23 during step E2. During this sub-step E23, cooling of the casing 30 and of all the superimposed layers 40 of the first strip is implemented, to stiffen them. A sealed block 130 is thus obtained, which is the sealed wall 111 of the tank 1. This block 130 is separable from the mandrel 2.

[0109] [Fig.9] illustrates the block 130, and therefore the sealed wall 111, obtained at the end of sub-step E23. It is noted that this block 130 (like the envelope 30 of knitted threads) has the extraction orifice 111d, the latter being positioned at the location of the spindle 22 of the mandrel 2.

[0110] With reference to [Fig. 3], step E3 of the method 100 for manufacturing the watertight wall 111 is implemented after step E2. This step E3 is illustrated in schematic form in [Fig. 10].

[0111] As shown in [Fig.10], step E3 consists of dismantling the mandrel 2 and extracting it from inside the block 130 through the extraction orifice 11 Id.

[0112] In practice, during step E3, the spindle 22 of the mandrel 2 is first dismantled, then the hoops 24 are dismantled and removed through the extraction orifice 11 Id of the block 130 and finally, the bottom 25 is dismantled and also removed through the extraction orifice 11 Id.

[0113] At the end of step E3, the block 130 emptied from the mandrel 2 forms the sealed wall 130, 111 of the tank 1. This sealed wall 130, 111 is thus made of a single material (see [Fig.10]).

[0114] The watertight wall 130, 111 has, thanks to the consolidation of the envelope 30 of knitted threads with the layers 40 of first wound strip 4, properties of impermeability and mechanical resistance to pressure similar to those of the tank described in document W02011143723A2, while being faster to produce.

[0115] Indeed, to form the gas barrier layer, it is no longer necessary to carry out the first filament winding with the thermoplastic material. This step, which is long (in the example of tank 1, it takes more than three hours), is no longer necessary because it is replaced by sub-step E21 of method 100, which consists of forming the envelope 30 of knitted yarns.

[0116] As described previously, this sub-step E21 is rapid (10 minutes are sufficient in the example of the tank 1), because the knit 3 is previously manufactured, because it is very rapid and easy to apply to the mandrel 2, and, finally, because a single layer 31 of knitted yarns is sufficient to provide the sufficient quantity of thermoplastic material. Indeed, by adapting the knitting parameters, a sufficient knit weight is obtained, allowing a single layer of knitted yarns to be used.

[0117] In addition to its speed of execution, the unification of the envelope 30 of knitted yarns with the superimposed layers 40 of first strip makes it possible to produce the waterproof wall 130 in a single material. This homogeneous material has several advantages: 1) it increases the resistance to internal pressure of the waterproof wall 130 and 2) increases the impermeability with respect to liquids. This therefore makes it possible to obtain a waterproof wall 130 of better quality and better resistance over time (or, in other words, a longer service life).

[0118] Finally, it is noted that the thickness of this knit 3 is less than the thickness of a conventional liner.

[0119] Now that the sealed wall 130 has been manufactured, the method 200 for manufacturing the tank 1 continues by implementing steps E4 and E5 (see [Fig.l]).

[0120] [Fig. 11] illustrates, in schematic form, step E4 (second step of the manufacturing method 200)

[0121] As shown in [Fig.l 1], during step E4, the base 112 of the wall 11 of the tank 1 (see [Fig.2]) is applied against the sealed wall 1130, so as to close the extraction orifice 11 Id.

[0122] For example, the base 112 can be welded against the sealed wall 130, on the periphery of the extraction orifice 11 Id. In another example, the base 112 can be fitted into the extraction orifice 112.

[0123] The internal passage of the base 112 has a reduced diameter compared to the diameter of the pin 22. In this example, this internal passage is advantageously adapted to receive a second pin 6 (see [Fig. 11]) to allow the rotation of the sealed wall 130 around its axis XX'.

[0124] The external periphery 112a of the base 112 may advantageously be formed from a thermoplastic material which can be sealed by heat and is compatible with the material of the sealed wall 130 (i.e. compatible with the thermoplastic material of the knitted threads and therefore compatible with the thermoplastic material of the first strip 4).

[0125] For example, the base 112 may be entirely formed of this thermoplastic material, or only have an overmolding of this material positioned on its external periphery 112a (in this case, the remainder of the base may be made of metal). The overmolded base may be easily welded against the sealed wall 130.

[0126] [Fig. 12] represents, in the form of a flowchart, step E5 of the method 200 for manufacturing the sealed tank 1. This step E5 aims to reinforce, or consolidate, the sealed wall 130 with a fibrous material to obtain a reinforced sealed wall 150, thus capable of mechanically resisting pressures for example greater than 2 MPa. The sealed wall 111 of the tank 1 is, then, the reinforced sealed wall 150.

[0127] As shown in [Fig.12], this step E5 comprises for this purpose a sub-step E51 comprising a filament winding and a sub-step E52 of cooling the winding.

[0128] Two modes of implementation of sub-step E51 are described below, in relation to figures 13 and 14.

[0129] In its simplest implementation (also referred to as “first embodiment E51” hereinafter), illustrated in [Fig. 13], sub-step E51 consists of winding successive sections 51 of a second strip 5 of thermoplastic material that can be sealed by heat and reinforced with fibers, around the sealed wall 130.

[0130] The thermoplastic material of the second strip 5 is chemically compatible with the thermoplastic material of the first strip 4 and therefore with the thermoplastic material of the knitted threads 311, 312. It is noted that the material of the second strip 5 is thus also compatible with the thermoplastic material of the external periphery 112a or of the external surface of the base 112 (in the case where the latter is formed from a thermoplastic material).

[0131] The second strip 5 is similar to the first strip 4 in that it can have the same width, the same thickness, or even fibers of the same nature and / or the same weaving geometry.

[0132] In practice, the sealed wall 130 can be rotated (for example via the pin 6).

[0133] The process of winding (or reeling) the second strip 5 is similar to that of the first strip 4. Thus, as illustrated in [Fig. 13], the successive wound sections 51 of the second strip 5 overlap to form a first layer 5 lOi, i=l of second strip 5, and overlap to form superimposed layers 50 of second strip 5. The number n2 of superimposed layers depends on the dimensions of the tank 1 and can be between n2=2 and several hundred, for example n2=200.

[0134] The multi-layer winding of the second strip 5 makes it possible to increase the permeability, the mechanical strength and the pressure resistance of the reinforced sealed wall 150 (and therefore of the sealed wall 111 of the tank 1) compared to a winding which would only have the first layer 510i, i=1.

[0135] The thickness of each layer 510i, i=1 to n2 of second strip 5 may for example be between 50 μm and 300 μm. Within the same layer of second wound strip, the axial overlap distance may for example be between 0 (corresponding to no overlap) and half the width of the second strip 5.

[0136] During the winding E51 of the second strip 5, as during the winding E22 of the sections 41 of the first strip 4, pressure and heating are exerted on each wound section 51.

[0137] More precisely, the pressure exerted on each section 51 of second wound strip is determined for: • 1) tighten this section 51 against the outer limits of the watertight wall 130, And • 2) to tighten this section 51 against the layer 51 Oi, i= 1 to n2 of second underlying band (when forming the second band superimposed layers 5).

[0138] The heating temperature applied to each wound section 51 of the second strip may be identical to the temperature applied during the winding of the first strip 4. Alternatively, the heating temperature applied to each wound section 51 of the second strip is similar, i.e. located in the melting temperature range of the thermoplastic materials used.

[0139] Thus, the thermoplastic material of each wound section 51 of second strip 5 fuses with the underlying region of the sealed wall 130 and fuses with the underlying layer of second strip (during the formation of the superimposed layers of second strip).

[0140] At the end of sub-step E51, the superimposed layers 50 of second strip 5 are joined with the waterproof wall 130 to form the waterproof wall 150 reinforced in a single material.

[0141] During sub-step E52, the second wound strip and the sealed wall 130 are cooled and therefore stiffened so that the reinforced watertight wall 150 is consolidated and rigid. The reinforced watertight wall 150 then forms the watertight wall 111 of the tank 1.

[0142] Cooling can be carried out after sub-step E51, i.e. once the winding of the second strip 5 is complete.

[0143] Alternatively, the cooling can be carried out locally, during the winding E51 of the second strip 5.

[0144] The cooling E52 can be carried out in a controlled manner by injecting cooled water into the sealed wall 130, and / or by applying pressure to the internal surface of the sealed wall 130.

[0145] [Fig. 14] represents a preferred embodiment E511 of the sub-step E51. According to this preferred embodiment, the sub-step E511 consists of winding the successive sections 51 of the second strip 5 not only around the sealed wall 111 but also on the external surface 112a of the base 112.

[0146] At the end of sub-step E511, the superimposed layers 50 of second strip 5 thus also cover the external periphery 112a of the base 112.

[0147] When the external periphery 112a of the base is covered with the thermoplastic material compatible with the thermoplastic material of the sealed wall 111, the superimposed layers 50 of the second strip 5 are joined with the sealed wall 111 and with the external periphery 112a of the base 112. The reinforced sealed wall 150 (and therefore the sealed wall 111 of the tank 1) is thus extended to the circumference of the pin 6 and formed from a single material.

[0148] After having carried out a cooling E521 according to the method described previously in relation to sub-step E52, the structure illustrated in [Fig. 15] is obtained.

[0149] As shown in [Fig.15], thanks to the preferred implementation mode E511, the reinforced sealed wall 150 (and therefore the sealed wall 111 of the tank 1) extends to the periphery of the internal passage of the base 112. In other words, the base 112 is partially integrated into the thickness of the sealed wall 111. This makes it possible to avoid breaks in pressure resistance around the valve of the tank 1 and thus to obtain a tank 1 which is sealed and mechanically resistant to the pressures involved.

[0150] It is noted that the sealed wall 111 of the tank 1 obtained by implementing the sub-step E511 is advantageously more homogeneous than that obtained according to the first embodiment E51. Indeed, this sealed wall 111 is then formed along its entire periphery from the same reinforced material. This makes it possible to obtain a tank 1 having impermeability properties, and identical mechanical properties at every point of its sealed wall 111. This (spatial) homogeneity of the sealed wall 111 makes it possible to produce a tank 1 of better quality.

[0151] Finally, the method 100 may comprise, after step E5, a step (not shown in the figures) consisting of applying the tap 122 of the end piece 12 of the tank 1 in the internal passage of the base 112. The tank 1 illustrated in [Fig.2] is then obtained.

Claims

Claims

1. Method (100) of manufacturing a sealed wall (111) of a sealed tank (1), the sealed tank (1) being adapted to contain a gas and / or a liquid, the manufacturing method (100) comprising the following steps: - Mount (El) a reusable and removable mandrel (2) by mounting / dismounting hoops (24), the mandrel (2) having an external surface (21) of a shape corresponding to an internal surface of the sealed wall (111) of the tank (1), - Form (E2) the sealed wall (111) of the reservoir (1) on the external surface (21) of the mandrel (2), by forming an extraction orifice (11 Id) of the mandrel (2), - Remove (E3) the mandrel (2) from the sealed wall (111) through the extraction orifice (11 Id), The step (E2) for forming the watertight wall (111) being carried out by performing the following sub-steps of: - Formation (E21) of an envelope (30) by applying at least one knitted fabric (3) covering the external surface (21) of the mandrel (2), the knitted fabric (3) comprising a layer of knitted threads (311, 312) forming loops, the knitted threads (311, 312) being of a thermoplastic material which can be sealed by applying heat, - Winding (E22), around the envelope (30) formed by the knit (3) covering the external surface (21) of the mandrel (2), of successive sections (41) of a first strip (4) comprising a thermoplastic material which can be sealed by heat application and reinforced with fibers, so that the successive sections (41) of the first strip (4) wound overlap to form a first layer (410i, i=l) of the first strip and overlap to form superimposed layers (40) of the first strip, the winding (E22) being carried out by: • Exerting a pressure chosen to tighten each section (41) of the first wound strip against the envelope (30), forming the first layer (410i, i= 1 ) of first strip, and to tighten the sections covering the first layer of first strip to form the other superimposed layers (40) of first strip, and by • Exercising a temperature chosen to fuse the thermoplastic material of each section (41) of the first layer of first strip with the underlying knitted threads (131, 132) of the casing (30), and to fuse the sections of the successive layers of first strip, - Cooling (E23) of the casing (30) and of the first strip (4) wound to form the sealed wall (130) in a single material.

2. A method (100) of manufacturing a waterproof wall according to claim 1, wherein the thermoplastic material of the knitted yarns (311, 312) is identical to the thermoplastic material of the first strip.

3. Method (100) for manufacturing a waterproof wall according to one of claims 1 to 2, in which the knitted fabric (3) has a mass per surface of between 100 g / m2 and 800 g / m2.

4. Method (100) for manufacturing a waterproof wall according to one of claims 1 to 3, in which the knitted fabric (3) is in the form of one or more sleeves, each sleeve being threaded through one end of the mandrel.

5. Method (100) for manufacturing a watertight wall according to one of claims 1 to 4, in which the sub-step (E21) of forming the envelope (30) further comprises the application of a second knit to the first knit (3), the thermoplastic material of the knitted threads of the second knit being sealable by supplying heat under the same temperature and pressure conditions as the thermoplastic material of the knitted threads of the underlying first knit (3).

6. Method (100) for manufacturing a watertight wall according to one of claims 1 to 5, in which the sub-step (E22) of winding around the envelope comprises the winding of at least one other additional strip, formed from the material of the first strip, the additional strip being wound simultaneously with the first strip.

7. Method (200) of manufacturing a sealed tank for containing a gas or a liquid, comprising the following steps: - Manufacture a sealed wall (130) of the tank (1) by carrying out the steps (E1, E2, E3) of the manufacturing method (100) according to one of claims 1 to 6, - Close (E4) the watertight wall (130) by applying a base (112) against the watertight wall (130), - Consolidate (E5) the watertight wall (130) to obtain a reinforced watertight wall (150, 111) of the tank 1, The step (E5) for consolidating the watertight wall (130) being accomplished by carrying out the following sub-steps of: - Winding (E51, E511), around the sealed wall (130), of successive sections (51) of a second strip (5) comprising a heat-sealed thermoplastic material reinforced with fibers, so that the successive sections (51) of the wound second strip overlap to form a first layer (5101) of the second strip (5) and overlap to form superimposed layers (50) of the second strip (5), the winding (E51, E511) being carried out by: • exerting a pressure chosen to tighten each section (51) of the second wound strip against the sealed wall (130), forming the first layer (510i, i=l) of second strip, and to tighten the sections covering the first layer of second strip to form the other superimposed layers of second strip, and in • exerting a temperature chosen to fuse the thermoplastic material of each section of the first layer of the second strip with the underlying region of the sealed wall (130), and to fuse the sections of the successive layers of the second strip, - Cooling (E52) of the sealed wall (130) and the second strip (5) to form the reinforced sealed wall (130, 111) in a single material.

8. A method (200) of manufacturing a sealed tank according to claim 7, wherein the thermoplastic materials of the first and second strips are identical.

9. Method (200) of manufacturing a sealed tank according to claim 7 to 8, in which the base (112) has an external peripheral surface covered with a thermoplastic material which can be sealed by heat and is compatible with the thermoplastic material of the sealed wall (130).

10. Method (200) of manufacturing a sealed tank according to one of claims 7 to 9, in which the external surface of the base (112) is covered by the second strip during said step (E5) of consolidating the sealed wall (130).

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