Gas storage cylinder and method for manufacturing such a cylinder

Abstract

The invention relates to a gas storage cylinder (1) designed to withstand a nominal pressure, the cylinder comprising an internal casing (2) and an external casing (3) at least partially covering the internal casing (2), the external casing having two half-shells (30, 31) each covering a separate part of the internal casing (2) except for a peripheral central portion (22) of the internal casing (2), the external casing (3) also having a belt (37) overmoulded against and on the peripheral central portion (22) of the internal casing (2), thereby joining the two half-shells (30, 31) together. The invention also relates to a method for producing a gas storage cylinder (1) designed to withstand a nominal pressure, the method comprising the following steps: producing an internal casing (2); covering the internal casing (2) with two half-shells (30, 31) of an external casing (3) except for a peripheral central portion (22); overmoulding the two half-shells (30, 31) and the peripheral central portion (22) with a belt (37).

Description

Description Title of the invention: Gas storage cylinder and method for manufacturing such a cylinder

[0001] The technical field concerns the manufacture of gas cylinders, more particularly gas storage cylinders intended to contain butane or propane for domestic use.

[0002] The technical field also concerns gas cylinders, more particularly gas storage cylinders intended to contain butane or propane for domestic use.

[0003] The technical field of the invention can also be extended, more broadly, to the manufacture of tanks for compressors, fire extinguishers, diving cylinders, aircraft tanks, expansion vessels, bottles intended to contain pressurized food liquids, tanks intended to contain fermented liquids such as beer, or gas shock absorbers.

[0004] It is known to manufacture a gas storage cylinder from welded steel sheets that form a shell delimiting an internal volume intended to contain a pressurized or liquefied gas, such as butane, propane, or compressed air. This cylinder can also contain a mixture of several gases or a liquid and a gas. This gas storage cylinder has a neck with an opening that can accommodate a dispensing device, for example, a gas regulator or pressure regulator that delivers the gas at a defined pressure. Such a device may also include safety venting mechanisms in case the pressure exceeds a limit value inside the gas storage cylinder.

[0005] The pressurized gases contained in the cylinder may have a low absolute pressure, on the order of a few bars, but may also have pressures on the order of several tens of bars.

[0006] Thus, the metal gas storage cylinder can withstand an absolute gas pressure inside the cylinder that can reach seventy bars, or 7 Megapascals (7x10 (exp 6) Pa or 7 MPa), or which can reach one hundred bars, or 10 Megapascals (10x10 (exp 6) Pa or 10 MPa), or even one hundred and fifty bars (150 bar), or 15 Megapascals (15x10 (exp 6) Pa or 15 MPa).

[0007] This resistance is particularly important in the case of accidents such as fires, in which gas cylinders must not burst.

[0008] This resistance to high pressure then allows safety degassing means to be operated or activated.

[0009] Thus, in France, gas cylinders are tested to measure their resistance to the pressure of the gas they contain. For example, at thirty bars, a domestic butane or propane gas cylinder filled with a gas at a test pressure of thirty bars, or 3 Megapascals (3 x 10⁻³¹ kg), is equivalent to 3 Megapascals (3 x 10⁻³¹ kg). (exp 6) (Pa or 3 MPa), must not undergo any deformation. This test is carried out on all cylinders in circulation every ten years. Domestic butane or propane gas cylinders must withstand a burst at a contained gas pressure of at least seventy bars, or 7 Megapascals (7 x 10 (exp 6) Pa or 7 MPa). This test is a destructive test and is performed on a sample of the produced cylinders. Metal cylinders usually crack between 80 and 100 bar, or between 8 and 10 Megapascals (8 and 10 x 10 (exp 6) Pa or 8 and 10 MPa).

[0010] The construction and testing codes for welded steel butane and propane cylinders, as well as their dimensional characteristics, are found in the standards. These standards can differ significantly, particularly due to variations between countries.

[0011] In order to protect the pressure wall of such gas cylinders from external corrosion, these cylinders receive a varnish or paint on their outer layer.

[0012] Such a steel gas storage cylinder has a low manufacturing cost, making it economical because it can be reused many times. Manufacturing gas storage cylinders of various capacities is simple and requires little investment.

[0013] This type of metal gas storage cylinder has many drawbacks, primarily its significant weight. Indeed, for example, in the case of a gas storage cylinder used for [purpose / use] Domestically, an empty bottle intended to contain butane already weighs thirteen (13) kilograms on its own, for a weight once filled with gas of twenty-four (24) kilograms.

[0014] Furthermore, their handling is complicated by their cylindrical shape which offers few grips.

[0015] Furthermore, the shape of these cylindrical bottles does not facilitate their storage, as they can roll, be stored upright, or be stacked on top of each other.

[0016] It is then necessary to plan for additional storage, which reduces the number of bottles that can be stored in a given space.

[0017] Finally, these cylinders are usually returnable and can be reused many times. However, impacts during use can damage the paint or varnish coating, detracting from the cylinder's appearance and making it visually unappealing to users for subsequent reuse. Furthermore, information, particularly regulatory or certification markings, printed on the paint or varnish can wear off, requiring the cylinder to be repainted and reapplied with a new coat of paint or varnish to reprint the information.

[0018] It is known that to overcome some of these drawbacks, cylindrical gas storage cylinders are made not from welded metal sheets, but from composite materials, notably those produced by filament winding. The composite material consists of a thermosetting resin matrix and a filler in the form of long filaments, for example, of glass, aramid, or carbon fiber, or of fabric sheets obtained by weaving, for example, fiberglass, aramid, or carbon fiber. Such a composite cylinder is therefore lighter while still being able to withstand the pressure of the gas contained within it.

[0019] A gas storage cylinder made of composite material can withstand a gas pressure inside the cylinder that can reach seventy bars, or 7 Megapascals (7x10 (exp 6) Pa or 7 MPa), or which can reach one hundred bars, or 10 Megapascals (10x10 (exp 6)Pa or 10 MPa), or even one hundred and fifty bars (150 bar), or 15 Megapascals (15x10 (exp 6) Pa or 15 MPa).

[0020] In fact, composite material bottles usually burst between 90 and 150 bars, or between 9 and 15 Megapascals (9 and 15 x 10 (exp 6) Pa or 9 and 15 MPa).

[0021] However, this type of composite cylinder, while offering greater burst resistance than a metal cylinder, is more fragile and poorly resistant to external impacts that could damage the cylinder wall and limit the maximum gas pressure it can withstand. Furthermore, the handling problems associated with cylindrical cylinders remain. It should be noted, however, that manufacturing gas storage cylinders of various capacities is straightforward using filament winding and requires minimal investment.

[0022] Document FR2716951 teaches a protective casing for a cylinder made of composite material intended in particular to contain a liquefied gas, such as butane, propane or compressed air, as well as low pressure gas, approximately 0.5 to 6 MPa.This protective cover for a bottle made of composite material that it offers includes an element forming a lower part which forms a stable base when placed on a flat surface, the support area of ​​this base being located below the bottom of the bottle to be protected, an element having an inner surface corresponding to the outer shape of the bottle to be protected, this surface having at least one opening allowing a tap fixed to the bottle to be protected to pass through, and one or two elements forming a bottom and / or a removable lid closing the volume delimited by the inner surface and intended to contain the bottle to be protected, the end of the upper part of this cover being located above the tap of the bottle.

[0023] This sleeve is made of impact-resistant plastic components. This protects the bottle on all sides and makes handling easier. Furthermore, the components can be colored. The protective sleeve can be redesigned or its shape improved to make it more aesthetically pleasing and thus more appealing to users. Information printed on the gas cylinder can also be advantageously printed on this protective sleeve.

[0024] Document FR2023731, considered the closest prior art, describes a gas storage cylinder comprising an inner shell and an outer shell at least partially covering said inner shell, said gas storage cylinder being designed to withstand a nominal pressure, the outer shell comprising - two half-shells each covering a distinct part of the inner envelope with the exception of a peripheral central part of the inner envelope, means for assembling the half-shells together.

[0025] In the case of a gas storage cylinder used for domestic purposes, an empty cylinder made of composite material intended to contain butane weighs, with a casing around it, between five (5) and eight (8) kilograms.

[0026] Furthermore, the casing components must be manufactured and then assembled onto the composite material cylinder, which increases the number of handling steps. This is especially true since manufacturing gas storage cylinders of varying capacities requires different molds for injecting the casings for cylinders of different sizes.

[0027] All of this means that a gas storage cylinder with a casing surrounding at least part of a cylinder made of composite material has a higher cost than the costs of a metal gas storage cylinder, and the manufacturing process is less flexible and requires significant investment.

[0028] Furthermore, the casings thus produced have dimensions with tolerances on the order of one millimeter. Conversely, it is known that the manufacture of a gas cylinder from composite material or metal, due to the manufacturing processes employed, has dimensions with tolerances on the order of several millimeters. It follows that the assembly of the casing around Gas cylinders made of composite material or metal have a high rejection rate. Therefore, automating this assembly process is not feasible.

[0029] The objective of the invention is therefore to provide an alternative gas storage cylinder to those of the prior art, which meets the same objectives, particularly in terms of resistance to gas pressure within the cylinder, which can reach seven megapascals (7 MPa), ten megapascals (10 MPa), or even fifteen megapascals (15 MPa), while avoiding the aforementioned drawbacks. Another objective of the invention is to provide a gas storage cylinder, and more generally a range of gas storage cylinders of varying capacities, each cylinder being robust, simple and economical to manufacture, and whose production can be easily automated.

[0030] Another objective of the invention is to propose a method for manufacturing a gas storage cylinder, and more generally a range of gas storage cylinders of different capacities, enabling, during its implementation, the manufacture of such a gas storage cylinder and more generally a range of gas storage cylinders of different capacities.

[0031] To this end, the invention relates to a gas storage cylinder, comprising an inner shell and an outer shell covering at least partially said inner shell, said gas storage cylinder being designed to withstand a nominal pressure, the outer shell comprising two half-shells each covering a distinct part of the inner shell with the exception of a peripheral central part of the inner shell, the outer shell further comprising means for assembling the half-shells to each other in the form of a belt overmolded against and on said peripheral central part of the inner shell, this injected belt partially covering the half-shells.

[0032] According to another characteristic, said inner casing has a thickness enabling it, depending on its design and the material from which it is made, to withstand a pressure lower than said nominal pressure, and said outer casing has a thickness such that, depending on its design and material from which it is made, its resistance combined with that of said inner casing ensures that the pressure resistance of the whole of the two casings reaches at least said nominal pressure resistance of the gas storage cylinder.

[0033] According to another characteristic, the outer casing is made of thermoplastic material.

[0034] According to another characteristic, the half-shells and the outer shell belt are made of injected thermoplastic material.

[0035] According to another characteristic, at least the outer shell halves have transverse means for compensating for play in the inner shell and for sealing between each half-shell and the inner shell.

[0036] According to another characteristic, at least one of the outer shell halves has longitudinal means for compensating for play in the inner shell.

[0037] According to another characteristic, the outer casing is made by overmolding the inner casing with a thermoplastic material.

[0038] Another characteristic is that the inner casing is made of metal.

[0039] According to another alternative feature, the inner casing is made of composite material.

[0040] According to another characteristic, the gas storage cylinder withstands a nominal pressure of 7 MPa, and the inner casing withstands a maximum internal pressure of 4 MPa corresponding to 57% of the nominal pressure of 7 MPa supported by the gas storage cylinder.

[0041] According to another characteristic, the gas storage cylinder withstands a nominal pressure of 10 MPa, and the inner casing withstands a maximum internal pressure of 5.7 MPa, corresponding to 57% of the nominal pressure of 10 MPa supported by the gas storage cylinder.

[0042] According to another characteristic, the gas storage cylinder withstands a nominal pressure of 15 MPa, and the inner casing withstands a pressure maximum internal pressure of 8.5 MPa corresponding to 57% of the nominal pressure of 15 MPa supported by the gas storage cylinder.

[0043] According to another characteristic, the outer envelope has internal and / or external ribs.

[0044] According to another characteristic, the inner casing is made of thermoplastic material loaded with reinforcing fibers, in particular a Polyamide loaded with at least 30% glass fiber.

[0045] According to another feature, the inner envelope has a neck opening out of the outer envelope, the half-shells and the overmolded belt of the outer envelope forming a watertight cover of the inner envelope, excluding said neck opening out of the outer envelope.

[0046] The inner casing is then protected from ambient humidity and corrosion.

[0047] The invention also relates to a method for manufacturing a gas storage cylinder designed to withstand a nominal pressure, said method comprising the following steps: - an internal casing is produced with a thickness that allows it, depending on its design and the material from which it is made, to withstand a pressure less than or equal to the nominal pressure that the gas storage cylinder can withstand, - two distinct parts of the inner shell are covered by two half-shells of an outer shell, with the exception of a central peripheral part of the inner shell, - the half-shells are overmolded with a thermoplastic material with means for assembling the half-shells together, in the form of an injected belt partially covering the half-shells, the outer envelope comprising said belt, said belt also overmolding said peripheral central part of the inner envelope.

[0048] According to another characteristic, if the inner casing has a thickness that allows it, depending on its design and the material from which it is made, to withstand a pressure lower than the nominal pressure that the gas storage cylinder can withstand, an outer casing is formed comprising the halves shells and the means of assembling the half-shells together, said outer shell having a thickness such that, depending on its design and the material from which it is made, its resistance combined with that of said inner shell allows the pressure resistance of the whole of the two shells to reach at least said resistance to the nominal pressure of the gas storage cylinder.

[0049] According to another characteristic, the overmolding of the means for assembling the half-shells together is carried out after covering the inner envelope by the half-shells by inserting the inner envelope covered by said half-shells into a plastic injection mold, and by injecting a plastic material coming into contact with and covering the peripheral central part of the inner envelope, said injected plastic material covering at least partially the two half-shells to assemble them together.

[0050] Other objects and advantages of the present invention will become apparent during the following description, with reference to the accompanying drawings illustrating examples of embodiments and in which:

[0051] [Fig.1] is a schematic perspective view of a gas storage bottle according to the invention;

[0052] [Fig.2] is a schematic cross-sectional view of the gas storage bottle in Figure 1;

[0053] [Fig.3] is a schematic perspective view from below of an upper half-shell of the outer casing of the gas storage cylinder of Figure 1, partially revealing the interior of said half-shell;

[0054] [Fig.4] is a detailed perspective view from another angle of a section of the upper half-shell of figure 3;

[0055] [Fig.5] is a schematic detail perspective view from above of the interior of a lower or upper half of the outer shell of the gas storage cylinder of Figure 1.

[0056] Internal pressure refers throughout this document to an absolute internal pressure, expressed in Megapascals or, in its abbreviated form, in MPa.

[0057] The invention relates to a gas storage bottle 1, in particular designed for domestic use, to contain a butane or propane type gas.

[0058] This gas storage cylinder 1 has an inner casing 2 and an outer casing 3, the outer casing 3 at least partially covering the inner casing 2. The outer casing 3 may completely cover the inner casing 2, except for one end fitting, as illustrated in the figures. The gas storage cylinder 1 is considered to be placed vertically on the ground, as illustrated in Figure 2. Thus, with reference to Figure 2, the top of the gas storage cylinder 1 is at the top of Figure 1, and the bottom of the gas storage cylinder 1 is at the bottom of the figure.

[0059] The inner shell 2 has a generally cylindrical shape and defines an internal volume V.INT in which at least one gas can be stored under pressure. The inner shell 2 is supported by a longitudinal axis AA' which coincides with an axis of revolution of the cylindrical shape of the inner shell 2, in a vertical direction. The inner shell 2 has a neck 20 at the top, onto which a valve or means for venting the gas contained in the gas storage cylinder 1 can be mounted. The inner shell 2 also has a bottom 21 at the bottom. The inner shell 2 further includes a peripheral central portion 22.

[0060] The inner casing 2 can be made of metal, in particular welded steel sheets that form a shell.

[0061] The inner casing 2 can alternatively be made of a composite material. It can be produced by using a thermosetting resin matrix and a filler in the form of long fibers, for example, of glass, aramid, or carbon, or of fabric sheets obtained by weaving, for example, fiberglass, aramid, or carbon. Metal components, such as a collar or a threaded plate, can be incorporated into or attached to the matrix.

[0062] Due to the manufacturing process, for a given type of gas storage cylinder 1, the dimensions of the internal casing 2 may vary between maximum and minimum dimensions depending on the existing clearance. Thus, the internal envelope 2 can have a so-called minimal configuration where the dimensions are minimal and a so-called maximum configuration where the dimensions are maximal.

[0063] The outer envelope 3 comprises two half-shells 30, 31, more precisely an upper half-shell 30 and a lower half-shell 31.

[0064] The lower half-shell 31 has a base 310 and extends upwards with a wall 311 terminating in a peripheral edge 312 defining an opening. This lower half-shell 31 is designed to receive the lower part of the inner shell 2.

[0065] The upper half-shell 30 has a protective structure for a valve 300 and extends downwards as a wall 301 terminating in a peripheral edge 302 defining an opening. This upper half-shell 30 is designed to receive the upper part of the inner casing 2.

[0066] The peripheral edges 302, 312 of the half-shells 30, 31 are dimensioned to have an inner diameter equal to the diameter of the inner shell 2 in a so-called minimal configuration. Thus, the half-shells 30, 31 are mounted at least snugly and if not tightly around the inner shell 2 to form transverse means for compensating for play in the inner shell 2 and for sealing between each half-shell and the inner shell 2.

[0067] The half-shells 30, 31 are made of a deformable material, which allows the peripheral edges 302, 312 to deform to conform to the contour and dimensions of the inner shell 2 in the event of a tight fit. This deformation can be elastic or plastic.

[0068] These two half-shells 30, 31 thus each cover a distinct part of the inner envelope 2, with the exception of the peripheral central part 22 of the inner envelope 2.

[0069] These half-shells 30, 31 may have internal ribs 32 extending radially in a bundle from a central upper ring 33 inside the upper half-shell 30, and from a central lower ring 34 inside the lower half-shell 31, as illustrated in Figure 3 and Figure 5. The central upper ring 33 defines an opening 330 through which the neck 20 of the inner shell 2 opens out of the upper half-shell 30 and thus out of the outer shell 3. This opening 330 has a lip or a groove. cooperating interior by clamping around the neck 20 of the inner envelope 2 to form sealing means between the neck 20 and the upper half-shell 30, as illustrated in figure 2.

[0070] The lower central ring 34 has a plurality of fingers 35 extending upwards from the lower central ring 34 in a corolla shape. These fingers 35 are elastically deformable and form longitudinal means of compensating for the play in the inner shell 2. Indeed, when the lower half-shell 31 is mounted on the inner shell 2, these fingers 35 can deform to compensate for dimensional variations in said inner shell 2. These fingers 35 are configured to be at least adjusted if the inner shell 2 is in its so-called minimal configuration and otherwise compressed by the inner shell 2. These fingers 35 are particularly useful in the context of a manufacturing process for such a gas storage cylinder 1, and especially when aiming for manufacturing automation.

[0071] The peripheral edges 302, 312 of the half-shells 30, 31 also include non-opening lights 36 arranged regularly on an outer face of said edges 302, 312.

[0072] The outer casing 3 also includes a belt 37 made by overmolding a plastic material directly against and on the inner casing 2. When the inner casing 2 is housed in the two half-shells 30, 31, the half-shells 30, 31 are partially overmolded, and more particularly the peripheral edges 302, 312 of the half-shells 30, 31, to form this belt 37. The plastic material of the belt 37 injected by overmolding fills the non-through openings 36 of said peripheral edges 302, 312, the belt 37 thus forming means of assembling the half-shells 30, 31 to each other. The plastic material of the belt 37 injected by overmolding also comes into contact with and covers the peripheral central part 22 of the inner envelope 2 left exposed by the two half-shells 30, 31.

[0073] The overmolded belt 37, due to the shrinkage coefficient of the plastic material it is composed of, can compress the peripheral central part 22 of the inner shell 2, and can exert a restoring force on the two half-shells 30, 31 towards each other. The restoring force exerted can be adjusted by function of the shrinkage coefficient of the injected plastic material during overmolding.

[0074] This forms an external envelope 3 comprising the two half-shells 30, 31 and the said belt 37.

[0075] The production of such a gas storage bottle 1 comprising an inner casing 2 and an outer casing 3, said outer casing 3 comprising two half-shells 30, 31 and said belt 37, is particularly advantageous.

[0076] Indeed, it is possible to produce gas storage cylinders 1 of different capacities by varying the height of the inner shell 2, covering it with the same type of upper half-shell 30 and lower half-shell 31, the central peripheral portion 22 left free being then overmolded by the band 37. Thus, by adjusting the width of the band 37, gas storage cylinders 1 of different capacities can be manufactured. The injection mold for overmolding said band 37 can advantageously include interchangeable cylindrical elements depending on the capacity of the inner shell 2 to be overmolded. The transverse and longitudinal clearances of the inner shell 2 are compensated by the transverse means for adjusting the clearance of the inner shell 2 and for sealing between each half-shell and the inner shell 2, and by the longitudinal means for adjusting the clearance of the inner shell 2.Thus, the gas storage bottle 1 comprises upper half-shells 30 and lower half-shells 31 which can adapt to manufacturing variations of the inner shell 2, and the belt 37 overmolded on the inner shell 2 ensures on the one hand a bonding of the half-shells, and on the other hand a holding and contact with the peripheral central part 22 of the inner shell 2, regardless of any possible dimensional manufacturing variations of said peripheral central part 22 of the inner shell 2. The outer shell 3 is thus as close as possible to the inner shell 2, regardless of the actual dimensions of the inner shell 2, longitudinally or laterally.

[0077] This simplifies the automation of the manufacturing process for a gas storage cylinder.

[0078] The outer casing 3 can completely cover the inner casing 2, except for the neck 20 where the lip of the orifice 330 seals tightly around said neck 20. This protects the inner casing 2 from external aggressions, such as corrosion, if it is made of metal, and does so in a watertight manner. In fact, the belt 37, by overmolding the upper half-shell 30 and the lower half-shell 31 and in combination with said half-shells 30, 31, forms a watertight casing that covers the inner casing 2, except for the neck 20 of the inner casing 2 which opens out of the outer casing 3.

[0079] Of course, the outer envelope 3 can also be perforated, particularly at the half-shells 30, 31, to reveal the inner envelope 2 and to lighten the gas storage bottle 1, the outer envelope 3 then no longer covering the inner envelope 2 in a sealed manner, with the exception of the neck 20 opening out of the outer envelope 3.

[0080] The gas storage cylinder 1 is designed to withstand a nominal pressure exerted by at least one gas contained within the gas storage cylinder 1. This at least one gas may be, for example, butane or propane. This at least one gas may consist of a liquid and a gaseous portion.

[0081] The inner envelope 2 has a thickness which allows it, depending on its design and the material from which it is made, to withstand a pressure exerted by at least one pressurized gas stored in the internal volume V.INT.

[0082] In fact, this inner casing 2 can withstand a pressure less than or equal to the nominal pressure that the gas storage cylinder 1 can withstand. Therefore, the gas storage cylinder 1 can withstand a pressure equal to or greater than the nominal pressure that the inner casing 2 can withstand.

[0083] This is due to the fact that the resistance to internal pressure of the inner jacket 2 is less than or equal to the resistance to internal pressure of the gas storage cylinder 1.

[0084] The outer casing 3 of the gas storage cylinder 1 may have a thickness such that, depending on its design and the material from which it is made done, the pressure resistance of the combination of the inner 2 and outer 3 envelopes reaches at least said nominal pressure resistance of the gas storage cylinder 1.

[0085] In fact, the outer shell 3, the half-shells 30, 31, and the belt 37 are made of a thermoplastic material. More specifically, the outer shell 3, the half-shells 30, 31, and the belt 37 can all be made of the same thermoplastic material.

[0086] To do this, we first manufacture the inner envelope 2.

[0087] Once the inner shell 2 is manufactured, the upper half-shell 30 is assembled on its upper part and the lower half-shell 31 on its lower part. The assembly is then placed in an injection mold. The injection mold is then closed, and a thermoplastic material is injected, partially covering the half-shells 30, 31 to join them together, forming the belt 37. This belt 37 also overmold the central peripheral part 22 of the inner shell 2. The injection mold for the belt 37 can bear against a portion of the edges 302, 312 of the half-shells 30, 31, and more specifically against a collar 303, 313 peripheral to each of said edges 302, 312. Thus, the overmolding mold can bear against plastic parts, the half-shells 30, 31, which have more precise dimensions than the inner shell 2.This simplifies overmolding and reduces the risk of creating burrs when injecting the thermoplastic material.

[0088] Once the thermoplastic material has been injected and cooled, the assembly formed by the inner shell 2 and the outer shell 3 is extracted from the mold.

[0089] This results in a gas storage bottle 1.

[0090] This assembly can have a resistance to a pressure of a gas stored in the internal volume V.INT identical or even greater than the resistance of the gas storage bottle 1 comprising these two envelopes 2, 3.

[0091] An additional overmolding assembly operation can also be carried out to further secure the half-shells 30, 31 of the outer casing 3 together. This joining can be achieved by screws, bolts, bonding, welding, or any other means. allowing the half-shells 30, 31 to be joined together in a complementary and satisfactory manner.

[0092] To prevent any sagging of the inner shell 2 during an injection or overmolding operation of a plastic material, the internal volume V.INT of the inner shell 2 can be filled with a pressurized fluid, or even a fluid with a compression ratio of less than 1% for an applied pressure of 50 MPa.

[0093] Advantageously, the thermoplastic material is selected from a list of materials exhibiting a shrinkage rate between 0.5% and 2%.

[0094] Even more advantageously, the thermoplastic material used to make the outer casing 3 is a thermoplastic, in particular a Polyamide.

[0095] Even more advantageously, this Polyamide is reinforced with at least 30% glass fiber.

[0096] Even more advantageously, the thermoplastic material used to make the outer casing 3 may contain additives to color said thermoplastic material.

[0097] Even more advantageously, the thermoplastic material used to make the outer casing 3 can include additives to protect the plastic material from degradation caused by ultraviolet light contained, for example, in sunlight.

[0098] The outer casing 3, and more specifically each half-shell 30, 31, may include internal ribs 32, as previously indicated and illustrated in the figures, but also external ribs on their face opposite the internal volume V.INT, particularly peripheral or bundled ribs. These internal and / or external ribs increase the resistance to deformation of the gas storage cylinder 1 under the pressure of at least one gas contained in the internal volume V.INT. These ribs reduce the amount of material required and therefore the weight of the outer casing 3.

[0099] The shape and arrangement of the ribs may be as illustrated in the figures, but these ribs may have any other shape and arrangement. alternative suitable for improving the pressure resistance of the gas storage bottle 1.

[0100] Such a gas storage cylinder 1 is therefore lighter than existing cylinders, for the same capacity and resistance to the same pressure. A range of several gas storage cylinders with different capacities can thus be designed simply and inexpensively, due to the very structure of said gas storage cylinders 1.

[0101] As a non-limiting example, the gas storage cylinder 1 withstands a nominal pressure of 7 MPa, and the inner casing 2 withstands a maximum internal pressure of 4 MPa corresponding to 57% of the nominal pressure of 7 MPa supported by the gas storage cylinder 1.

[0102] To achieve this, the inner envelope 2 has, for example, a thickness of 8 tenths of a millimeter and the outer envelope 3 has a thickness of 3 to 4 millimeters.

[0103] According to another non-limiting example, the gas storage cylinder 1 withstands a nominal pressure of 10 MPa, and the inner casing 2 withstands a maximum internal pressure of 5.7 MPa corresponding to 57% of the nominal pressure of 10 MPa supported by the gas storage cylinder 1.

[0104] According to yet another non-limiting example, the gas storage cylinder 1 withstands a nominal pressure of 15 MPa, and the inner casing 2 withstands a maximum internal pressure of 8.5 MPa corresponding to 57% of the nominal pressure of 15 MPa supported by the gas storage cylinder 1.

[0105] The inner envelope 2 then has a thickness of 2 millimeters and the outer envelope 3 then has a thickness of 6 millimeters.

[0106] The processes described above make it possible to produce a gas storage cylinder 1 having all or part of the characteristics of the gas storage cylinder 1 according to the invention described above.

[0107] A gas storage cylinder 1 according to the invention described above can be made by implementing one of the processes described above, i

Claims

Demands

1. A gas storage cylinder (1) comprising an inner jacket (2) and an outer jacket (3) at least partially covering said inner jacket (2), said gas storage cylinder (1) being designed to withstand a nominal pressure, the outer jacket (3) comprising - two half-shells (30, 31) each covering a distinct part of the inner shell (2) with the exception of a peripheral central part (22) of the inner shell (2), - means for assembling the half-shells (30, 31) with each other, characterized by the fact that said means for assembling the half-shells (30, 31) with each other are in the form of a belt (37) overmolded against and on said peripheral central part (22) of the inner envelope (2), this injected belt (37) partially covering the half-shells (30, 31).

2. Gas storage cylinder (1) according to claim 1, characterized in that said inner casing (2) has a thickness enabling it, depending on its design and the material of which it is made, to withstand a pressure lower than said nominal pressure, and in that said outer casing (3) has a thickness such that, depending on its design and the material of which it is made, its resistance combined with that of said inner casing (2) enables the pressure resistance of the whole of the two casings (2, 3) to reach at least said resistance to the nominal pressure of the gas storage cylinder (1).

3. Gas storage cylinder (1) according to claim 1 or claim 2, characterized in that the half-shells (30, 31) and the belt (37) of the outer casing (3) are made of the same thermoplastic material.

4. Gas storage cylinder (1) according to any one of claims 1 to 3, characterized in that the half-shells (30, 31) of the outer shell (3) have transverse means for compensating for play in the inner shell (2) and for sealing between each half-shell and the inner shell (2).

5. Gas storage cylinder (1) according to any one of claims 1 to 4, characterized in that the half-shells (30, 31) of the outer casing (3) have longitudinal means for compensating for play in the inner casing (2).

6. Gas storage cylinder (1) according to any one of claims 1 to 5, characterized in that the inner casing (2) is made of metal.

7. Gas storage cylinder (1) according to any one of claims 1 to 5, characterized in that the inner casing (2) is made of composite material.

8. Gas storage cylinder (1) according to any one of claims 1 to 7, characterized in that the gas storage cylinder (1) withstands a nominal pressure of 7 MPa, and the inner casing (2) withstands a maximum internal pressure of 4 MPa corresponding to 57% of the nominal pressure of 7 MPa withstood by the gas storage cylinder (1)

9. Gas storage cylinder (1) according to any one of claims 1 to 7, characterized in that the gas storage cylinder (1) withstands a nominal pressure of 10 MPa, and the inner casing (2) withstands a maximum internal pressure of 5.7 MPa corresponding to 57% of the nominal pressure of 10 MPa supported by the gas storage cylinder (1).

10. Gas storage cylinder (1) according to any one of claims 1 to 7, characterized in that the gas storage cylinder (1) withstands a nominal pressure of 15 MPa, and the inner casing (2) withstands a maximum internal pressure of 8.5 MPa corresponding to 57% of the nominal pressure of 15 MPa supported by the gas storage cylinder (1).

11. Gas storage cylinder (1) according to any one of claims 1 to 10, characterized in that the half-shells (30, 31) of the outer casing (3) have internal (32) and / or external ribs.

12. Gas storage cylinder (1) according to any one of claims 1 to 11, characterized in that the inner casing (2) is made of thermoplastic material reinforced with fibers, in particular a polyamide reinforced with at least 30% glass fiber.

13. Gas storage cylinder (1) according to any one of claims 1 to 12, characterized in that the inner shell (2) has a neck (20) opening out of the outer shell (3), the half-shells (30, 31) and the overmolded belt (37) of the outer shell (3) forming a leak-proof cover of the inner shell (2), except for the neck (20) opening out of the outer shell (3).

14. A method for manufacturing a gas storage cylinder (1) designed to withstand a nominal pressure, said method comprising the following steps: - an internal envelope (2) is produced having a thickness which, depending on its design and the material from which it is made, allows it to withstand a pressure less than or equal to the nominal pressure which the gas storage cylinder (1) can withstand. - two distinct parts of the inner envelope (2) are covered by two half-shells (30, 31) of an outer envelope (3), with the exception of a peripheral central part (22) of the inner envelope (2), - the half-shells (30, 31) are overmolded with a thermoplastic material with means for assembling the half-shells (30, 31) together, in the form of an injected belt (37) partially covering the half-shells (30, 31), the outer envelope (3) comprising said belt (37), said belt (37) also overmolding said peripheral central part (22) of the inner envelope (2).

15. A method according to claim 14, characterized in that if the inner casing (2) has a thickness enabling it, depending on its design and the material of which it is made, to withstand a pressure lower than the nominal pressure that the gas storage cylinder (1) can withstand, an outer casing (3) is formed comprising the half-shells (30, 31) and the means for assembling the half-shells (30, 31) to each other, said outer casing (3) having a thickness such that, depending on its design and the material of which it is made, its resistance combined with that of said inner casing (2) allows the the pressure resistance of the whole of the two envelopes (2, 3) reaches at least said nominal pressure resistance of the gas storage cylinder (1).

16. A method according to claim 15, characterized in that the overmolding of the means for assembling the half-shells (30, 31) together is carried out after covering the inner shell (2) by the half-shells (30, 31), by inserting the inner shell (2) covered by said half-shells (30, 31) into a plastic injection mold, and by injecting a plastic material coming into contact with and covering the peripheral central part (22) of the inner shell (2), said injected plastic material covering at least partially the two half-shells (30, 31) to assemble them together.

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