Internal jacket of COMPOSITE TANK for HIGH PRESSURE GAS

Abstract

The present invention relates to the manufacture of half-bottles which, after fitting and laser welding, will constitute thin-walled metal liners for a composite tank, type III, preferably designed to contain gases or hydrogen under high pressure, intended for land, sea, air and space transport, as well as for static storage. This liner is constituted by a main cylinder of revolution, terminated, at its ends, by an evolving, substantially hemispherical shape, gradually connecting to the cylindrical part. Fig. 7

Description

Title of the invention: Internal envelope of a COMPOSITE TANK for HIGH PRESSURE GAS Technical field:

[0001] A liner is the internal envelope of a high-pressure gas tank, and in particular for hydrogen. Said tank is intended for land, sea, air and space transport, as well as for static storage.

[0002] The present invention relates to liners (1a) and (1b) intended for high-performance composite tanks having, for identical volume, substantially the internal shape of a conventional liner, i.e. a main cylinder of revolution (1b), terminated, at least at one of its ends, by an evolving shape, substantially in a hemisphere (1a), progressively connecting at its pole to a cylindrical part of smaller diameter than the main cylinder. See [Fig.7] State of the prior art:

[0003] There are four main types of compressed gas storage tanks:

[0004] - Type I corresponds to a thick metallic envelope acting as both structural and liner part,

[0005] - Type II comprises a metal liner whose cylindrical part is reinforced by a composite (fiber + resin) wound circumferentially by winding. With this type of tank, the liner supports a large part of the load due to pressurization, it is therefore structural.

[0006] - Type III is a liner fully wound with resin-coated fiber (composite structure). The liner is metallic, it does not support the load (or very little) and is only there to prevent hydrogen permeation. This type of liner allows access to high static pressures, for example 700 bar of service.

[0007] - Type IV is a liner entirely wound with resin-coated fiber. (composite structure). The liner is made of polymer, for example High Density Polyethylene (HDPE), it does not support the load and is only there to prevent hydrogen permeation. It should be noted that permeation is still a barrier to large-scale use of this type of tank, as is the slowness and difficulty of producing the liner. This type of liner allows access to high operating pressures (700 bars). The composite structure is generally carbon fiber coated with epoxy resin.

[0008] Type III & IV tanks use their composite structure almost exclusively to ensure good mechanical resistance to pressure.

[0009] Classic type III tanks use metal liners having wall thicknesses between 10 and 15 mm The complexity and extreme slowness of the manufacturing process for such a liner is considerable. It takes around half an hour to manufacture it! In addition, this liner is mainly made with an A6061 grade aluminum alloy. Such an alloy has a very low elongation at break, which is a handicap for fatigue resistance!

[0010] US patent 3943867 A (ERFURT HORST -LOTHAR) March 16, 1976, describes a method of assembling sheets into shapes to obtain a container. Patent not relevant

[0011] US patent 5964117 A (HOLROYD NIGEL) October 12, 1999, describes a container consisting of two envelopes nested one inside the other. Patent not relevant

[0012] Patent FR 2108636 (SARDOU) November 11, 2021, relevant patent, this patent consists of an improvement of the 2021 patent. Problem analysis:

[0013] As an example, it should be noted that the permeability to hydrogen at 25C: • High Density Polyethylene (HDPE) is 2x10 13 (moleH2. m1. s1. MPa 1 / 2 ) • Aluminum is 6x10 16 (moleH2. m1. s1. MPa1 / 2)

[0014] We therefore note, at identical thickness, that there is a difference in permeability of 333 times between that of aluminum and that of HDPE!

[0015] Table 1 gives the typical thickness of an HDPE liner intended for a type IV tank, namely 7 mm. Such a thickness, for an internal capacity of 62 liters, induces a mass substantially equal to 5.66 kg, or 12% of the total mass of said tank, which is far from negligible!

[0016] In addition, since the liner is not structural, for a liner with an internal diameter of 372 mm, the composite structure will have an internal diameter of 386 mm and will therefore have to withstand a stress 3.8% higher than that which it would have to undergo for a diameter of 373 mm. It is therefore necessary to produce the composite structure with more thickness, therefore more mass and more cost. Brief description of figures and landmarks:

[0017] [Fig.l] table giving, for identical internal volume, the liner mass gains induced by the type of liner chosen.

[0018] [Fig.2] Graph showing permeation properties as a function of temperature temperature for 6 candidate metals.

[0019] [Fig.3] schematic presentation of reverse spinning in 3 stages, namely: stage ( [Fig.3] a) placing the blank (la); then step ([Fig.3] b) reverse spinning; and finally step ([Fig.3] c) releasing the part; [Fig.3] d shows the ejection of the liner in close-up.

[0020] [Fig.4] schematic sectional view of an aluminum blank (la) in place in the shaping device, comprising a punch (2) and a counterform (4)

[0021] [Fig.5] schematic overall view, showing the blank (la) during its deformation.

[0022] [Fig.6] view, showing the dome of the liner (le) just after deformation with its pro long cylindrical; we see in particular, the area of the liner bore (lcH18), the area of the cylindrical part of the liner (IbHO) and the neck (14) where the thickness of the tubular part of the liner is calibrated.

[0023] [Fig.7] Close-up view showing the area of the dome (le) just after deformation as well as the different components of the shaping area

[0024] [Fig.8] close-up view showing the end (8) of the liner ejection mechanism (the), and the shape (4) seen in cavalier perspective.

[0025] [Fig.9] “resistance to deformation” property of an aluminum, type 1000, as a function of the “deformation rate” and the temperature.

[0026] (the) draft see [Fig.4]

[0027] (laod) outer diameter of the blank see [Fig.4]

[0028] (ugly) inner diameter of the blank see [Fig.4]

[0029] (1b) thin cylindrical area of the liner see figures 3b, 6 and 7

[0030] (the) liner dome area

[0031] (IbHO) thin cylindrical zone of the liner see [Fig.6]; H0 being the metallurgical state of this zone. Note that (1b) and (IbHO) designate the same zone

[0032] (lcH18) thick inner cylindrical bore of the liner see [Fig.6]; H18 being the state metallurgical industry of this area.

[0033] (2) main cylindrical area of the punch

[0034] (2D) large diameter area of the punch.

[0035] (2') wear part of the punch

[0036] (2”) cylindrical zone for guiding and centering the punch in zone (4d)

[0037] (3) tip of the cylindrical area of the piston serving as an interface to the upper part of the press.

[0038] (4) against heated form

[0039] (4D) outer diameter of the bore of the counterform (4), it is this diameter which cooperates with the part (2D) of the punch to define the thickness of the thin tubular part of the liner (1b)

[0040] (4d) diameter of the bore of the bottom of the counterform (4) which ensures the guidance of the shank (2”) of the punch.

[0041] (4s) slots made in the base of the counterform (4)

[0042] (4') support of the counter form (4)

[0043] (5) means for fixing the counterform (4) on its support (4')

[0044] (6) tubular furnace ensuring the heating of the tubular part (1b) of the liner

[0045] (7) insulating material insulating the counterform (4) from its support (4')

[0046] (7') insulating material insulating the support of the counter-form (4') of the lower apron of the press (16).

[0047] (8) liner ejection rod pressing on the end of the liner (le), we note that this ejection rod ends for example with 4 protrusions (8') which slide in the slots (4s) made in the base of the counterform (4)

[0048] (9) rod guide block (2)

[0049] (9') rod guide bearing (2)

[0050] (10) rod guide and support carriage (2)

[0051] (11) heating elements of the counterform (4)

[0052] (12) carriage guide column (10), there are a minimum of 3 to 4 of these columns

[0053] (13) chassis made of thick sheets, preferably mechanically welded, stiffening the tooling by connecting the upper guide block (9) to the lower block (4') supporting the counterform (4). This chassis is preferably arranged on the 4 faces of the tooling, access to the liner being via windows provided in the walls of said chassis.

[0054] (14) calibration zone of the thin part (1b) of the liner defined between the diameter (4b) of the counterform (4) and the large diameter area (2D) of the punch (2)

[0055] (15) contact zone between the blank (la) and the counterform (4) before the start of the reverse spinning; this area is reduced to a minimum in order to limit heat transfer between the cold blank and the hot counterform.

[0056] (16) press apron, insulated by the layer (7') of the support of the support (4') of the counter form (4)

[0057] (e) denotes the wall thickness of the cylindrical part (1b) of the half-bottle

[0058] (D) denotes the outer diameter of the smallest half-bottle Additional details:

[0059] Let us also note that the “threaded part” of the liner used for connecting the external piping is obtained by threading the end (lcH18) of the / 2 liner.

[0060] It is clearly stated that, in the figures, the same references designate the same elements, regardless of the figure in which they appear and regardless of the form of representation of these elements. Similarly, if elements are not specifically referenced in one of the figures, their references can be easily found by referring to another figure.

[0061] The applicant also wishes to point out that the figures represent an embodiment of the object according to the invention, but that there may be other embodiments which meet the definition of this invention.

[0062] It further specifies that, when, according to the definition of the invention, the object of the invention comprises “at least one” element having a given function, the method of The described achievement may include several of these elements.

[0063] It also specifies that the term substantially can mean that the property thus qualified can be understood either as being exactly or as almost defined. For example, the property "this end of the tube being substantially flush with the end of the insert" can mean either that the end is exactly flush with, or that it comes within reasonable proximity of, the end of the insert.

[0064] It also specifies that, if the embodiments of the object, according to the invention, as illustrated comprise several elements of identical function and that if, in the description, it is not specified that the object according to this invention must necessarily comprise a particular number of these elements, the object of the invention may be defined as comprising “at least one” of these elements.

[0065] It is finally specified that when, in the present description, an expression defines on its own, without any specific particular mention concerning it, a set of structural characteristics, these characteristics can be taken, for the definition of the object of the protection requested, when this is technically possible, either separately, or in total and / or partial combination. Definition and essential concepts:

[0066] Reverse spinning (see [Fig.6]): reverse spinning makes it possible to produce a tube with a base (generally called a case, and here called a liner or Uz liner). The spinning lengths are necessarily relatively short. Reverse spinning is used for the manufacture of weapon components (shell case, warhead, flask), gas cylinders in steel or aluminum alloy. The shapes are limited. Reverse spinning involves the following steps. Step [A]: The blank (la) (for example in aluminum), heated or cold and lubricated, is placed in a die closed at one end by a counterform (4) ([Fig.3] a). Step [B]: A punch (1) pushes on the blank which spins along the punch, forming a tube (1b) ([Fig.3] b). Step [C]: At the end of spinning, the liner is ejected thanks to the thrust of the base of the liner (le) by the ejector (8) ([Fig.3] d).

[0067] Permeation: see [Fig.2]; In physics and engineering, permeation is the penetration of a permeate (liquid, gas, or vapor) through a solid. It is directly related to: the concentration gradient of the permeate, the intrinsic permeability of the material, and its mass diffusivity. Permeation is modeled by equations such as Fick's laws of diffusion, and can be measured using tools such as a permeameter. Permeation can occur through most materials, including metals, ceramics, and polymers. However, the permeability of metals is much lower than that of ceramics and polymers due to their crystalline structure and low porosity.

[0068] Work hardening: The plastic deformation of a crystalline material modifies its properties due to its influence on its internal structure; these changes in properties and microstructure, called work hardening, play a very important role in the mechanical characteristics of the material. Indeed, work hardening is widely used to increase the mechanical characteristics of many metal alloys. More generally, it is work hardening that gives metal alloys their essential properties of toughness and (relative) ease of forming

[0069] Annealing: Annealing a metal part is a process corresponding to a heating cycle. This consists of a step of gradual temperature increase, typically to 300°C, followed by a holding time at said temperature. This procedure makes it possible to modify the physical characteristics of the metal. This action is particularly used to facilitate the relaxation of stresses that may have accumulated in the heart of the material, under the effect of mechanical or thermal stresses, occurring in the synthesis and shaping stages of the materials. During annealing, the grains (monocrystals) of material reform and return, so to speak, to their "state of equilibrium". Crystallization annealing, after work hardening, aims to give the metal an optimal grain size for its future use (bending, stamping, spinning, etc.).

[0070] Dynamic recrystallization: The plastic deformation of a material is accompanied by the creation of dislocations (Frank and Read mechanism). These dislocations represent a “store of elastic energy”. When the temperature is sufficient, the dislocations become spontaneously mobile and cause a reorganization of the structure of the crystals, in two stages: restoration then recrystallization. The temperature at which these phenomena occur depends on the deformation rate: the more a material is deformed, the more it “stores” elastic energy, therefore the more restoration and recrystallization will begin at a lower temperature. When the deformation rate and temperature increase, these phenomena can occur during deformation.

[0071] Tooling: here, the term tooling refers to the punch (2) and counter-form (4) assembly.

[0072] Bottle: in the text, the term liner or half-liner refers indifferently to a half-bottle obtained directly by reverse extrusion, composed of the following parts: the thin cylindrical part (1b), typically between 0.1 mm and 3 mm, with a metallurgical state substantially equal to H11, and the thickest domed part. For the sake of simplification, (1) = (1b) and (1d) are used.

[0073] 1000 series aluminum: aluminum family including in particular the following alloys: 1050; 1060; 1070; 1080; 1090; 1100; 1110; 1145; 1190; 1199; 1200; 1145; 1310; 1340; 1350; 1370; 1385.

[0074] O or H111: annealed metallurgical state: this is the most ductile state. It is generally obtained by the so-called annealing treatment, this treatment not being followed by any work hardening.

[0075] H: work-hardened metallurgical state, for example H18: this symbol applies to products hardened by deformation with or without subsequent maintenance at a temperature sufficient to cause partial softening of the metal.

[0076] Grade or metallurgical state: the table below indicates the typical properties of an AA1050 type aluminum. We see the properties of the annealed metallurgical state called both "state O" and "state H111" having an elongation greater than 32%, and the work-hardened metallurgical state designated by "state H18", which offers mechanical resistances (Rm) very clearly superior

[0078] Ultimate elongation: dl / L = elongation in percent of a sample, of length “L”, elongating by a value “dl”. The elongation at break of pure aluminium is of the order of 35% for grade 1050. The same applies to alloys that have not undergone work hardening or heat treatment (metallurgical state 0 or H111); in this case, the elongation at break is between 20 and 40%. Pure aluminium and untreated alloys have poor mechanical properties; they are “soft” (20 MPa < Re < 100 MPa). After treatment(s), the mechanical strength is increased (100 MPa < Re < 500 MPa) but the elongation at break decreases sharply (1 < A% < 20).

[0079] Wrapping: action of winding resin-coated fibers around a liner in order to make it capable of withstanding pressure DESCRIPTION OF THE INVENTION

[0080] The present invention describes the optimal structure of a liner intended for a composite tank for the storage of gas and in particular hydrogen at high pressure.

[0081] Graph 2 shows the evolution of the permeability of metals as a function of temperature. It can be seen that for room temperature (abscissa 3.4 on the graph), the most interesting metals are, for example and in preferential order: gold, copper, aluminum, austenitic iron, nickel, any other metal or metal alloy not being excluded from the scope of our claims.

[0082] Except for very special applications (space for example) we can ignore gold (density 19.3). Copper and aluminum come next. Copper has a density of 8.96, aluminum has a density of 2.7, i.e. 3.3 times lower. In addition, aluminum has excellent extrudability and good corrosion resistance. We will therefore analyze here, as an example, a liner using this metal, which in no way restricts the scope of the patent to other metals and alloys.

[0083] We mentioned that aluminum has a permeation 333 times better than HDPE. In the context of the invention, we claim to use a liner with a thickness "e" in the large diameter cylindrical zone (5) of between 0.1 mm and 3 mm, in the context of a type III tank; If we consider a thickness "E" of composite structure typically having a thickness of between 16 and 32 mm, our claim relates to a range of liner thicknesses relative to the thickness of composite structure "e / E" of between 0.3% and 19%. See the table below. envelope thickness liner thickness (mm) 0.1 3 16 0.625% 18.75% 32 0.313% 9.38%

[0085] A type IV liner, in HDPE, has an “e / E” value of 43.9%! Let us take, as an example, for our aluminum liner, a reasonable thickness of 0.7 mm, or an “e / E” of 4.54%. With this thickness of 0.7 mm, our performance, in permeation, will be 33.3 times better than a 7 mm HDPE liner. Technologically, the liner will be sufficiently robust to support the load undergone, during the covering of the composite structure; note that it is possible, if necessary, to inflate it to stiffen it, or to fill it for example with a frozen fluid.

[0086] The benefits provided by an aluminum liner, for example 0.7 mm, in addition to permeation, are as follows (for example for a 62 liter tank) • Reduction of the liner mass by 4.1 kg or 72.3% (the mass goes from 5.7 to only 1.6 kg) (see [Fig.l]) • Reduction of the mass of the composite structure by 12 kg or 29.1% (the mass goes from 41.4 to 29 kg) such a reduction naturally induces a significant drop in the material cost of the tank. • So reduction of the total mass of the tank of 16.1 Kg or 34.3% (the total mass goes from 47.1 to 30.9 Kg) (excluding inserts), such a reduction is interesting in terms of lightening the vehicle. Our liner is its own insert. • Reduction of the external diameter of the tank by 14.2 mm or 3.4% (the diameter goes from 419.8 mm to 405.6 mm) such a reduction is interesting with regard to integration into the vehicle.

[0087] The process for obtaining such a liner (1) is based on the principle of reverse spinning. DETAILED DESCRIPTION OF THE INVENTION

[0088] As explained previously, our invention consists of producing a liner of the type III, preferably made of aluminum, having extremely thin walls compared to the state of the art.

[0089] To produce type III liners, manufacturers use type 6000 aluminum. However, since the aluminum will be contained in a composite envelope which will take all the stresses, it is not necessary to use type 6000 structural aluminum.

[0090] Within the framework of the invention we claim any type of aluminum ranging from the 1000 family to the 7000 family; however we will preferentially use an aluminum of the 1000 series, because it offers: an excellent elongation at break of 35% for the 1050: We observe that the 1000 type family is the most easily extrudable. In particular the 1350 offers an extrudability of 160% compared to a 6063. We therefore claim the use of aluminum in general and in particular of the 1000 families, which are made up of pure aluminum at 99% or more, namely in particular and in a non-exhaustive manner, the following references; 1050;1060;1070;1080;1090;1100;1110;1145;1190;1199;1200;1145;1310;1340;1350;1370;1385.

[0091] Before the reverse spinning operation it is strategic to have carried out an annealing of the material.

[0092] The three-dimensional table in [Fig.9] is the result of our characterization work on an aluminum of the 1000 family. Thanks to this table, we observe the combined effects of the deformation rate and the temperature on the resistance to deformation. We note that the "Resistance to deformation" decreases when the deformation rate decreases, and that the said "resistance to deformation" also decreases when the temperature increases.

[0093] In order to carry out reverse spinning, according to the invention, we must achieve a “Resistance to deformation” value which must be less than 20 MPa.

[0094] During the reverse spinning of the blank (1a); We therefore claim the strain rate range between 50 s 1 and 0.01sl coupled with the temperature range between 400°C and 645°C. That is to say that the blank (3) must be brought into this range, during the reverse spinning operation.

[0095] Let us recall that the blank, prior to reverse spinning, must preferably be in a so-called “annealed” state so as to facilitate its shaping by reverse spinning.

[0096] Production by reverse spinning of metal bottles each composed of 2 half-bottles (1) assembled in post-treatment, preferably by laser welding; said bottles are intended to serve as a light liner for type III composite tanks, the production method requires the implementation of an aluminum blank (la) placed in the counterform (4), said blank (la) has a substantially cylindrical bore (laid) significantly larger than the outside diameter of the rod (2”) which extends the punch (2), the said blank (la) has an external diameter (laod) smaller than the diameter (4D) of the counter form (4) so that the contact zone (15) between the lower part of the blank (la) and the counter form (4) is reduced to the minimum possible, thanks to the small contact zone the heat transfer in the zone (15) is minimized; ideally the reverse extrusion press has two tools, one of nominal diameter (DN) and the other tool of substantially equal diameter (dn+2e), with (e) equal to the thickness of the wall of the cylindrical part of the liner, so that the two half bottles can be easily fitted together before welding them.

[0097] Production by reverse spinning of metal bottles each composed of 2 half-bottles (1) assembled in post-treatment, preferably by laser welding; said bottles are intended to serve as a light liner for type III composite tanks, an original production process in that before the start of the reverse spinning of a half-bottle, the blank (la) is at a temperature between 0°C and 200°C

[0098] Production by reverse spinning of metal bottles each composed of 2 half-bottles (1) assembled in post-treatment, preferably by laser welding; said bottles are intended to serve as a light liner for type III composite tanks, production method, original in that before the start of the reverse spinning of a half-bottle, the zone (2”) as well as the zone (2') are at a temperature between 0°C and 200°C

[0099] Production by reverse spinning of metal bottles each composed of 2 half-bottles (1) assembled in post-treatment, preferably by laser welding; said bottles are intended to serve as a light liner for type III composite tanks, production method, original in that before the start of the reverse spinning of a half-bottle, at least the surface of the internal bore of the counter-form (4) is at a temperature between 400°C and preferably 650°C.

[0100] During spinning, the contact zone (15) between the blank (1) and the bore of the counterform (4) will quickly grow until an intimate contact between these two parts which will allow the passage of a powerful thermal flow towards the blank and its rapid rise in temperature during this time the bore of the blank (1a) will be subjected to intense work hardening before being violently pressed against the rod (2”) which is cold. This will allow the metallurgical state to be blocked in the contact zone on the rod (2”) at a grade of the order of H18; thus blocking the dynamic recrystallization in the zone (1cH18) we therefore have here a metal having maximum properties necessary for the future threading.The metal extruded in zone (14) will form the thin tube (1b) of the liner; it is hot and heavily work-hardened; it must be protected from rapid cooling so that dynamic recrystallization can take place! To do this, a cylindrical furnace (6) is used, placed around the liner (1b), which makes it possible to obtain a... slow cooling and a tube of metallurgical grade HO in the zone (IbHO) which gives this annealed zone an elongation at break greater than 25%. The other advantage of heating this zone is to prevent the tube from reducing in diameter which would make the extraction of the punch impossible because of friction with the part (2D).

[0101] In order not to slow down the press cycle; It is wise to extend the cooling time to provide a hot jacket to be applied to the zone (1b).

[0102] Production by reverse spinning of metal bottles each composed of 2 half-bottles (1) assembled in post-treatment, preferably by laser welding; said bottles are intended to serve as a light liner for type III composite tanks, original production process of a half-bottle, completed by the presence of a tubular furnace (6) coaxial with the cylindrical zone (2) with a diameter slightly greater than the part (1b) of the liner, said tubular furnace being set at a temperature between 400°C and 650°C.

[0103] Production by reverse spinning of metal bottles each composed of 2 half-bottles (1) assembled in post-treatment, preferably by laser welding; said bottles are intended to serve as a light liner for type III composite tanks, production process, of a half-bottle, original by the fact that the blank (la) which will make it possible to obtain said metal half-bottle is constituted by one of the following metals: gold, copper, 2000 series aluminum or preferably 1000 series aluminum; said 1000 series aluminum being said to be 99% pure, or more, namely in particular and non-exhaustively among the alloy references 1050; 1060; 1070; 1080; 1090; 1100; 1110; 1145; 1190; 1199; 1200; 1145; 1310; 1340; 1350;1370;1385.

[0104] Method for producing a half-metal bottle (1), original in that the counter-form (4) is heated to a temperature between 400°C and 650°C by any means (11) known to those skilled in the art.

[0105] Method for producing a half-metal bottle (1), original in that the counter-form (4) is isolated by any means (7) known to those skilled in the art from the support (4') of the counter-form (4).

[0106] Method for producing a half-metal bottle (1), original in that the support (4') of the counter-form (4) is isolated by any means (7') known to man from the apron of the press (16).

[0107] Method for producing a half-metal bottle (1), original in that to precisely guide the punch (2) a precision guiding tool is used comprising: the counter-form (4') connected to the block (9) for guiding the rod (2) by a mechanically welded casing (13), a bearing (9') ensuring the precise sliding of the rod (2) a minimum of 3 calibrated columns (12) are embedded between the counter-form (4') and the guiding block (9), a carriage (10) slides along the rods (12), said carriage (10) is integral with the bottom of the rod (2), leaving a sufficient length protruding beyond the downward recess to ensure the housing of the cylindrical part (1b) of the liner, the additional guidance is ensured by the sliding of the part (2”) of the punch in the bore (4d) of the counterform (4).

[0108] Method for producing a metal half-bottle (1), original by the implementation of an ejector (8) allowing the end of the liner (1e) to be pushed in order to help its extraction from the counter-form (4), the fingers (8') carried by the ejector (8) passing through the housings (4s) of the counter-form (4)

Claims

Claims

1. Production by reverse spinning of metal bottles each composed of 2 half-bottles (1) assembled in post-treatment, preferably by laser welding; said bottles are intended to serve as a light liner for type III composite tanks, the wall of the half-bottles has a thickness (e) between 0.1 and 3 mm, said production of a half-bottle is characterized by the implementation of a blank (la) made of aluminum placed in a counterform (4), said blank (la) has a substantially cylindrical bore (laid) significantly larger than the external diameter of the rod (2”) which extends the punch (2), said blank (la) has an external diameter (laod) smaller than the diameter (4D) of the counterform (4) so that the contact zone (15) between the lower part of the blank (la) and the counterform (4) is reduced to the minimum possible.

2. Production by reverse spinning of metal half-bottles, according to claim 1, characterized in that before the start of reverse spinning the blank (la) is at a temperature between 0°C and 200°C.

3. Production by reverse spinning of metal half-bottles, according to claims 1 and 2, characterized in that before the start of reverse spinning the zone (2”) as well as the zone (2') are at a temperature between 0°C and 200°C

4. Production by reverse spinning of metal half-bottles, according to claims 1 to 3, characterized in that before the start of reverse spinning at least the surface of the inner bore of the counterform (4) is at a temperature between 400°C and 650°C.

5. Production by reverse spinning of metal half-bottles, according to claims 1 to 4, characterized by the presence of a tubular furnace (6) coaxial with the cylindrical zone (2), said furnace having a diameter greater than the part (1b) of the liner, said tubular furnace being set at a temperature between 400°C and 650°C.

6. Production by reverse spinning of metal half-bottles, according to claims 1 to 5, characterized in that the blank (la) which will make it possible to obtain said metal half-bottle is made of one of the following metals: gold, copper, aluminum ranging from the 7000 series to the 1000 series and preferably from the 1000 series; said 1000 series aluminum being said to be 99% pure, or more, namely in particular and non-exhaustively the alloy references: 1050 ;1060 ;1070 ;1080 ;1090 ;1100 ;1110 ;1145 ;1190 ;1199 ;1200 ;1145 ;1310 ; 1340; 1350 ;1370 ;1385.

7. Production by reverse spinning of metal half-bottles, according to claims 1 to 6, characterized in that the counterform (4) is heated to a temperature between 400°C and 650°C by any means (11) known to those skilled in the art.

8. Production by reverse spinning of metal half-bottles, according to claims 1 to 7, characterized in that the counter-form (4) is isolated by any means (7) known to those skilled in the art from the support (4') of the counter-form (4).

9. Production by reverse spinning of metal half-bottles, according to claims 1 to 8, characterized in that the support (4') of the counter-form (4) is isolated by any means (7') known to man from the apron of the press (16).

10. Production by reverse spinning of metal half-bottles, according to claims 1 to 9 characterized in that to precisely guide the punch (2) a precision guiding tool is used comprising: the counterform (4') connected to the block (9) for guiding the rod (2) by a mechanically welded casing (13), a bearing (9') ensuring the precise sliding of the rod (2), 3 calibrated columns (12), at least, are embedded between the counterform (4') and the guiding block (9), a carriage (10) slides along the rods (12), said carriage (10) is integral with the bottom of the rod (2), leaving a sufficient length to protrude beyond the downward embedding to be surrounded by the cylindrical part (1b) of the liner, additional guidance is ensured by the sliding of the part (2”) of the punch in the bore (4d) of the counterform (4).

11. Production by reverse spinning of metal half-bottles, according to claims 1 to 10, characterized by the use of an ejector (8) making it possible to push the end of the liner (le) upwards in order to assist its extraction from the counterform (4), the fingers (8') carried by the ejector (8) passing through the housings (4s) provided in the counterform (4).

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