Pressure vessel, method for sealing a pressure vessel, and pressure vessel lid.

Abstract

A pressure vessel for storing a pressurised fluid, such as hydrogen, the pressure vessel comprising a shell comprising an access port provided with a port sealing surface, and a cap provided with a cap sealing surface and defining a longitudinal axis, wherein the access port and the cap are configured to receive and hold the cap in the access port with the cap sealing surface and the port sealing surface contacting each other to form an internal seal, the cap comprises an inner cap end, a recess is provided in the inner cap end, such that an axial extension is formed, and the cap sealing surface is provided at the axial extension.

Description

1 / 30 Pressure vessel, method for sealing a pressure vessel, and pressure vessel lid. Field of invention

[0001] The invention relates to a pressure vessel for storing a pressurized fluid, such as hydrogen. Such a pressure vessel comprises a shell with an access door that provides access to an internal storage space of the pressure vessel and a lid arranged to close the access door. An internal seal is formed between the access door and the lid to prevent the pressurized fluid stored in the pressure vessel from leaking out of the pressure vessel. Background of the invention

[0002] The invention is based on the perception that there is a need, in the field of the art, for a pressure vessel with an internal seal that is less susceptible to damage. Damage to the internal seal can lead to dangerous situations caused by leakage of the pressurized fluid. This is especially true when the pressurized fluid is a highly flammable fluid, such as hydrogen. Summary of the invention

[0003] The invention aims to provide an improved, or at least alternative, pressure vessel, method and lid. In particular, the invention aims to provide a pressure vessel with an internal seal that is less susceptible to damage. Petition 870250080634, dated 08 / 09 / 2025, page 10 / 54 2 / 30

[0004] The objective is achieved by a pressure vessel to store a pressurized fluid, such as hydrogen. The pressure vessel comprises a shell comprising an access port provided with a port sealing surface and a lid provided with a lid sealing surface and defining a longitudinal axis. The access port and the lid are configured to receive and retain the lid on the access port, with the lid sealing surface and the port sealing surface in contact with each other to form an internal seal. The lid comprises an inner end of the lid, in which a recess is provided at the inner end of the lid, so that an axial extension is formed. The lid sealing surface is provided on the axial extension.

[0005] By providing a pressure vessel lid with a recess at the inner end of the lid, thus forming an axial extension, and wherein the sealing surface of the lid is provided on the axial extension, the seal is located in a portion of the lid that can have much greater flexibility in the radial direction compared to other portions of the lid. Furthermore, as the axial extension is adjacent to the recess, the seal can be partially actuated by the pressurized fluid acting on the axial extension. Consequently, the invention allows designing a seal in which high stress concentrations that could lead to seal damage can be omitted, while at the same time ensuring sufficient sealing contact under the pressure vessel's load condition. Therefore, with the present invention, the seal can be less susceptible to damage.

[0006] The inventors realized that reducing stress, particularly tensile stress, in the inner seal is Petition 870250080634, dated 08 / 09 / 2025, page 11 / 54 3 / 30 is particularly important for pressure vessels employing an internal seal subjected to pressurized hydrogen, as material degradation due to hydrogen adsorption can be accelerated when high material stresses are present in the internal seal.

[0007] In the context of this disclosure, "inner end of the lid" generally means: the longitudinal end of the lid that must be received inside the pressure vessel.

[0008] Advantageous embodiments of the present invention are described below.

[0009] In one embodiment of the pressure vessel according to the invention, the axial extension encircles the recess, in particular, in the radial direction with respect to the longitudinal axis.

[0010] In one embodiment of the pressure vessel according to the invention, the axial extension is radially outward relative to the recess. In particular, the axial extension is radially outward relative to the longitudinal axis of the recess. In this way, the axial extension can be more flexible in the radial direction.

[0011] In one embodiment of the pressure vessel according to the invention, the axial extension comprises an inner extension side facing the longitudinal axis, wherein the inner extension side forms a boundary of the recess. In particular, the inner extension side can form a radial boundary of the recess.

[0012] In one embodiment of the pressure vessel according to the invention, the axial extension is an annular axial extension. In particular, the annular axial extension may have an annular cross-section, especially when viewed in the direction Petition 870250080634, dated 08 / 09 / 2025, page 12 / 54 4 / 30 longitudinal in relation to the longitudinal axis of the cap. In particular, the ring of the annular axial extension is infinite.

[0013] In one embodiment of the pressure vessel according to the invention, the recess has an annular shape. In particular, the recess may have an annular shape when viewed in the longitudinal direction relative to the longitudinal axis of the lid.

[0014] In one embodiment of the pressure vessel according to the invention, the lid comprises an inner recess surface. This inner recess surface forms a boundary of the recess. In particular, the inner recess surface may extend perpendicularly with respect to the longitudinal axis of the lid.

[0015] In one embodiment of the pressure vessel according to the invention, the axial extension extends in the axial direction relative to the longitudinal axis. In particular, the axial extension extends away from the surface of the inner recess.

[0016] In one embodiment of the pressure vessel according to the invention, the lid comprises a duct with an internal opening, wherein the axial extension is radially spaced from the internal opening. In particular, the axial extension encircles the internal opening of the duct, more specifically, in the radial direction relative to the longitudinal axis.

[0017] In one embodiment of the pressure vessel according to the invention, the opening of the internal duct is provided on the surface of the internal recess.

[0018] In one embodiment of the pressure vessel according to the invention, the inner duct is located and aligned with the longitudinal axis of the lid.

[0019] In embodiments comprising a duct, it is possible to configure sealing parameters for the internal seal. Petition 870250080634, dated 08 / 09 / 2025, page 13 / 54 5 / 30 independently of the duct, more specifically, independently of the duct characteristics, such as specific dimensions (e.g., diameter or length) of the duct. This is possible because the characteristics of the axial extension, such as specific dimensions (e.g., thickness of the cover extension), can be configured independently of the duct. Thus, it is possible, for example, to adjust the radial flexibility of the axial extension that has the cover sealing surface, without influencing the duct dimensions. Adjusting the flexibility of the axial extension will lead to adjusted sealing parameters of the internal seal formed by the contact between the cover sealing surface and the door sealing surface. This allows for the selection of sealing parameters favorable to reducing damage to the internal seal.

[0020] In one embodiment of the pressure vessel according to the invention, the axial extension extends in the axial direction relative to the longitudinal axis away from the duct.

[0021] In one embodiment of the pressure vessel according to the invention, the sealing surface of the lid is provided in the axial extension.

[0022] In one embodiment of the pressure vessel according to the invention, the sealing surface of the lid is axially spaced from the surface of the inner recess. In particular, the sealing surface of the lid is spaced from the surface of the inner recess in the axial direction along the longitudinal axis.

[0023] In one embodiment of the pressure vessel according to the invention, the sealing surface of the door is axially spaced from the surface of the inner recess. In particular, the Petition 870250080634, dated 08 / 09 / 2025, page 14 / 54 6 / 30 The door sealing surface is spaced from the inner recess surface in the axial direction along the longitudinal axis.

[0024] In one embodiment of the pressure vessel according to the invention, the inner recess surface extends transversely to the longitudinal axis.

[0025] In one embodiment of the pressure vessel according to the invention, the internal seal is a metal-to-metal seal. The metal-to-metal seal is less susceptible to damage, particularly in cases where the pressure vessel is exposed to high temperature variations, compared to elastomeric seals. As a result, the metal-to-metal seal exhibits high thermal stability.

[0026] In one embodiment of the pressure vessel according to the invention, the duct is configured to facilitate the flow of pressurized fluid, such as hydrogen, into and / or out of the pressure vessel.

[0027] In one embodiment of the pressure vessel according to the invention, the lid comprises an external duct opening and the duct extends from the internal duct opening to the external duct opening.

[0028] In one embodiment of the pressure vessel according to the invention, the axial extension completely encircles the longitudinal axis.

[0029] In one embodiment of the pressure vessel according to the invention, the surface of the inner recess is in the radial direction with respect to the longitudinal axis located between the opening of the inner duct and the axial extension.

[0030] In one embodiment of the pressure vessel according to the invention, the axial extension comprises an end Petition 870250080634, dated 08 / 09 / 2025, page 15 / 54 7 / 30 adjacent to the surface of the inner recess and a free end distanced axially from the surface of the inner recess.

[0031] In one embodiment of the pressure vessel according to the invention, the lid comprises a lid body, the lid body comprises a circumferential lid surface encircling the longitudinal axis, and the axial extension comprises a lid extension thickness measured radially with respect to the longitudinal axis in the axial extension. The lid body comprises a lid body thickness measured radially with respect to the longitudinal axis, from the longitudinal axis to the circumferential lid surface, and the lid extension thickness is less than the lid body thickness. In embodiments where the lid comprises a duct, the duct is provided in the lid body, and the lid body thickness is measured radially with respect to the longitudinal axis, from the duct to the circumferential lid surface. These embodiments allow the axial extension to be constructed with greater flexibility than the lid body.This is beneficial to ensure that the sealing parameters are determined primarily by the axial extension compared to the cap body. The cap extension thickness can be the smallest cap extension thickness measured in the axial extension in the radial direction. The smallest cap extension thickness can be measured on a portion of the axial extension that extends in the axial direction from the cap sealing surface, inclusive, to the adjacent end. The cap body thickness can be the smallest cap body thickness measured on the cap body, in particular, from the duct to the circumferential surface of the cap. Petition 870250080634, dated 08 / 09 / 2025, page 16 / 54 8 / 30 radial direction. The smallest thickness of the cover body can be measured on the surface of the inner recess.

[0032] In one embodiment of the pressure vessel according to the invention, the axial extension comprises a bending stiffness of the cap extension in the thickness of the cap extension, the cap body comprises a bending stiffness of the cap body in the thickness of the cap body, and the bending stiffness of the cap extension is less than the bending stiffness of the cap body.

[0033] In one embodiment of the pressure vessel according to the invention, the axial extension and the lid body are made of the same material, such as the same metal, and preferably, the axial extension and the lid body are integrally formed. Thus, the axial extension can be integrally formed with the lid body. Consequently, the axial extension and the lid body can be made of a single piece or molded in a single piece.

[0034] In one embodiment of the pressure vessel according to the invention, the lid comprises an inner lid section configured to be located inside the access port and an outer lid section configured to be located outside the access port.

[0035] In one embodiment of the pressure vessel according to the invention, the axial extension and the body of the lid are part of the inner section of the lid.

[0036] In one embodiment of the pressure vessel according to the invention, the opening of the inner duct is located in the section of the inner cover and the opening of the outer duct is located in the section of the outer cover. Petition 870250080634, dated 08 / 09 / 2025, page 17 / 54 9 / 30

[0037] In one embodiment of the pressure vessel according to the invention, the axial extension extends away from the outer cover section.

[0038] In one embodiment of the pressure vessel according to the invention, the duct has a circular cross-section. In particular, the duct is circular when viewed in cross-section in a plane perpendicular to the longitudinal axis.

[0039] In one embodiment of the pressure vessel according to the invention, the duct extends in line with the longitudinal axis.

[0040] In one embodiment of the pressure vessel according to the invention, the axial extension comprises an inner extension side facing the longitudinal axis and an outer extension side facing away from the longitudinal axis, and the sealing surface of the cap is located on the outer extension side.

[0041] In one embodiment of the pressure vessel according to the invention, the sealing surface of the cap completely surrounds the longitudinal axis.

[0042] In one embodiment of the pressure vessel according to the invention, the axial extension comprises an inner extension surface facing the longitudinal axis and a transition surface connecting (or joining) the inner extension surface to the inner recess surface, and the transition surface forms a rounded corner that extends along a radius R when viewed in a longitudinal sectional view relative to the longitudinal axis. This provides additional structural integrity to the axial extension.

[0043] In one embodiment of the pressure vessel according to the invention, the access port defines a longitudinal axis. Petition 870250080634, dated 08 / 09 / 2025, page 18 / 54 10 / 30 additional and the door sealing surface faces the additional longitudinal axis.

[0044] In one embodiment of the pressure vessel according to the invention, the sealing surface of the door completely surrounds the other longitudinal axis.

[0045] In one embodiment of the pressure vessel according to the invention, the access port is provided in a neck of the shell. In particular, the access port may comprise an outer port surface with an outer port surface diameter, wherein the outer port surface diameter is smaller than the largest outer diameter of the shell. Similarly, the sealing surface of the port may be provided with an inner port sealing surface diameter smaller than the largest inner diameter of the shell.

[0046] In one embodiment of the pressure vessel according to the invention, the axial extension comprises a lid extension thickness measured in the radial direction relative to the longitudinal axis in the axial extension, the access door comprises an outer door surface and an additional door thickness measured in an additional radial direction relative to the longitudinal axis, from the door sealing surface to the outer door surface, and the door thickness is greater than the thickness of the lid extension. This allows the axial extension to be constructed with greater flexibility than the access door. This tends to ensure that if the inner seal is damaged, most of the damage will occur in the lid, more specifically in the axial extension, rather than in the access door. The thickness of the lid extension can be the smallest lid extension thickness measured in the radial direction in the axial extension. The smallest extension thickness Petition 870250080634, dated 08 / 09 / 2025, page 19 / 54 11 / 30 of the cover thickness can be measured along a portion of the axial extension that runs axially from the cover's sealing surface, including it, to the adjacent end. The door thickness can be the smallest door thickness measured on the access door in the additional radial direction. The smallest door thickness can be measured on the door's sealing surface.

[0047] In one embodiment of the pressure vessel according to the invention, the access door comprises a door bending stiffness in the thickness of the door, the axial extension comprises a cover extension bending stiffness in the thickness of the cover extension, and the door bending stiffness is greater than the cover extension bending stiffness.

[0048] In one embodiment of the pressure vessel according to the invention, the access door and the axial extension are made of the same material, such as the same metal.

[0049] In one embodiment of the pressure vessel according to the invention, the access port comprises a female threaded zone and the cover comprises a male threaded zone. In this embodiment, the female threaded zone and the male threaded zone are configured for rotational engagement with each other to receive and hold the cover in the access port, with the sealing surface of the cover and the sealing surface of the port in contact with each other to form the internal seal. This embodiment works particularly well in combination with an embodiment in which the body of the cover is integrally formed with the axial extension, since, in that case, the sealing surface of the port can be precisely positioned relative to the sealing surface of the cover. Petition 870250080634, dated 08 / 09 / 2025, page 20 / 54 12 / 30

[0050] In one embodiment of the pressure vessel according to the invention, the access door comprises an external access opening and a female threaded zone, the cover comprises a male threaded zone, the female threaded zone and the male threaded zone are configured for rotational engagement with each other, and the female threaded zone is located closer to the external access opening than to the sealing surface of the door. An advantage of this embodiment is that the threaded zones are not exposed to the pressurized fluid, in particular to the hydrogen stored in the pressure vessel.

[0051] In one embodiment of the pressure vessel according to the invention, the female threaded zone and the male threaded zone comprise non-tapered threads.

[0052] In one embodiment of the pressure vessel according to the invention, the female threaded zone is located closer to the external access opening than to the sealing surface of the door, in particular, when viewed along the furthest longitudinal axis.

[0053] In one embodiment of the pressure vessel according to the invention, the access door and the lid are free of a seal located closer to the external access opening than to the female threaded zone.

[0054] In one embodiment of the pressure vessel according to the invention, the access door and the lid are free of an external seal.

[0055] One advantage of the above embodiments is that, in the event of failure of the internal seal, hydrogen can be released from the hydrogen pressure vessel immediately along the zones Petition 870250080634, dated 08 / 09 / 2025, page 21 / 54 13 / 30 threaded, instead of getting stuck in those zones. Trapped hydrogen can pose a safety risk.

[0056] In one embodiment of the pressure vessel according to the invention, the sealing surface of the lid is toroidal. In particular, the sealing surface of the lid may be convex. More specifically, the sealing surface of the lid may have a convex longitudinal section, particularly when viewed in longitudinal section with respect to the longitudinal axis.

[0057] In one embodiment of the pressure vessel according to the invention, the sealing surface of the door is conical.

[0058] In one embodiment of the pressure vessel according to the invention, the sealing surface of the conical door becomes wider in a first direction along the additional longitudinal axis of the access door and towards the external access opening.

[0059] In one embodiment of the pressure vessel according to the invention, the access door and the lid are free of an elastomeric seal.

[0060] In one embodiment of the pressure vessel according to the invention, the access door and the lid are configured to hold the lid in a sealing position on the access door, with the sealing surface of the lid and the sealing surface of the door in contact with each other to form the internal seal.

[0061] In one embodiment of the pressure vessel according to the invention, the access door comprises a door stop, the lid comprises a lid stop, and the door stop and the lid stop are configured to contact each other to form the internal seal when the lid is positioned in the sealing position. In particular, the door stop of Petition 870250080634, dated 08 / 09 / 2025, page 22 / 54 14 / 30 cover is located at a distance from the axial extension. More specifically, the cover stop is arranged on the outer section of the cover. In particular, the door stop is located on the outer access opening. More specifically, the door stop is, in the longitudinal direction along the furthest longitudinal axis, located further from the door sealing surface than the female threaded zone is located from the door sealing surface.

[0062] In one embodiment of the pressure vessel according to the invention, the longitudinal axis of the lid positioned in the sealing position coincides with the additional longitudinal axis of the access door.

[0063] In one embodiment of the pressure vessel according to the invention, the pressure vessel is configured to store the pressurized fluid at a fluid pressure of 500 bar or higher, preferably 1000 bar or higher.

[0064] In one embodiment of the pressure vessel according to the invention, the access door provides access to a storage space for storing the pressurized fluid in the pressure vessel.

[0065] In one embodiment of the pressure vessel according to the invention, a valve, such as a pressure valve, is connected to the duct. Such a valve is configured to control the flow of fluid into and / or out of the pressure vessel.

[0066] It will be clear to those skilled in the art that the invention also relates to embodiments of the pressure vessel comprising the characteristics of any combination of any number of the embodiments defined above of the pressure vessel according to the invention. Petition 870250080634, dated 08 / 09 / 2025, page 23 / 54 15 / 30

[0067] The invention further relates to a pressure vessel for storing a pressurized fluid, such as hydrogen, wherein the pressure vessel comprises a shell with an access door provided with a sealing surface and a lid provided with a sealing surface and defining a longitudinal axis, wherein the access door and the lid are configured to receive and retain the lid in the access door, with the sealing surface of the lid and the sealing surface of the door in contact with each other to form an internal seal. The lid comprises an inner lid surface and a duct with an inner duct opening provided in the inner lid surface. The lid further comprises an axial extension extending in the axial direction relative to the inner lid surface, in particular from it, and the lid sealing surface is provided in the axial extension. In particular, the axial extension may be adjacent to the inner lid surface.

[0068] It will be clear to those skilled in the art that the invention also refers to embodiments of the above pressure vessel, comprising the pressure vessel features of any combination of any number of the above-defined embodiments of the pressure vessel according to the invention.

[0069] The invention further relates to a method for sealing a pressure vessel for storing a pressurized fluid, such as hydrogen, according to the invention, the method comprising placing the lid on the access door and forming an internal seal with the sealing surface of the lid and the sealing surface of the door in contact with each other.

[0070] It will be clear to those skilled in the art that the invention also refers to embodiments of the method comprising the Petition 870250080634, dated 08 / 09 / 2025, page 24 / 54 16 / 30 pressure vessel characteristics of any combination of any number of the embodiments defined above for the pressure vessel according to the invention.

[0071] The invention further relates to a lid for a pressure vessel, comprising an inner end of the lid, a recess provided in the inner end of the lid, so that an axial extension is formed, and a lid sealing surface provided in the axial extension.

[0072] It will be clear to those skilled in the art that the invention also relates to embodiments of the lid comprising the lid features of any combination of any number of the embodiments defined above of the pressure vessel according to the invention. Brief description of the drawings

[0073] The embodiments of the pressure vessel according to the invention, the method according to the invention and the lid according to the invention will be described only by way of example, with reference to the accompanying schematic drawings, in which the corresponding reference symbols indicate the corresponding parts, and in which:

[0074] Figure 1 schematically shows a perspective view of an embodiment of the pressure vessel according to the invention,

[0075] Figure 2 schematically shows a longitudinal cross-sectional view of the pressure vessel in Figure 1,

[0076] Figure 3A schematically shows a longitudinal sectional view of an access door and a pressure vessel cover of Figure 1, Petition 870250080634, dated 09 / 08 / 2025, p. 25 / 54 17 / 30

[0077] Figure 3B schematically shows an enlarged view of part III-B of Figure 3A,

[0078] Figure 3C shows schematically the view of the Figure Figure 3B presents the results of a finite element analysis.

[0079] Figure 4A schematically shows a longitudinal cross-sectional view of the access door in Figure 3A,

[0080] Figure 4B schematically shows an enlarged view of part IV-B of Figure 4A,

[0081] Figure 5A schematically shows a longitudinal cross-sectional view of the lid of Figure 3A,

[0082] Figure 5B schematically shows an enlarged view of part VB of Figure 5A,

[0083] Figure 6 schematically shows a longitudinal cross-sectional view of an additional access door and an additional cover for the pressure vessel of Figure 1, and

[0084] Figure 7 schematically shows a longitudinal cross-sectional view of another embodiment of a lid according to the invention. Detailed description of the drawings

[0085] Figure 1 shows a perspective view of an embodiment of pressure vessel 1 according to the invention. Pressure vessel 1 is configured to store a pressurized fluid, more specifically hydrogen. Pressure vessel 1 is configured to store the pressurized fluid at a pressure of 1,000 bar or higher. In other examples, pressure vessel 1 is configured to store the pressurized fluid at a pressure of 500 bar or higher. Petition 870250080634, dated 08 / 09 / 2025, page 26 / 54 18 / 30

[0086] The pressure vessel 1 comprises a shell 2 with two access ports 3. The access ports 3 are located in a neck 59 of the shell 2. Each access port 3 provides access to a storage space 41 for storing the pressurized fluid in the pressure vessel 1. A cover 5.5' is provided on each of the access ports 3.

[0087] The pressure vessel 1, the shell 2, the access doors 3 and the covers 5, 5' are generally cylindrical.

[0088] Figure 2 shows a longitudinal section of pressure vessel 1 from Figure 1. Covers 5 and 5' are of similar construction. The only difference between the covers is that cover 5 has a duct 12, while cover 5' does not have a duct. Access doors 3 are identical.

[0089] Each access door 3 is provided with a door sealing surface 4. Each cover 5, 5' is provided with a cover sealing surface 6. The access doors 3 and the covers 5 are configured to receive and hold one of the covers 5 in one of the access doors 3 with the cover sealing surface 6 and the door sealing surface 4 contacting each other to form an internal seal 10.

[0090] The cover 5.5' extends in the longitudinal (or axial) direction 46 along a longitudinal (central) axis 7. The cover 5.5' comprises an inner end of the cover 8, that is, when the cover 5.5' is mounted on the access door 3, situated inside the access door 3, and an outer end of the cover 51 which is located opposite the inner end of the cover 8. The outer end of the cover 51 extends outward from the access door 3. The cover 5.5' extends in the longitudinal direction to Petition 870250080634, dated 08 / 09 / 2025, page 27 / 54 19 / 30 along the longitudinal axis 7, from the inner end of the cover 8 to the outer end of the cover 51.

[0091] A recess 9 is provided at the end of the inner cap 8 so as to form an annular axial extension 14. The axial extension 14 and an inner recess surface 11 form a boundary of the recess 9. The axial extension 14 extends from the inner recess surface 11.

[0092] A sealing surface for the cover 6 is provided, in particular, on the axial extension 14. This allows setting the sealing parameters of the inner seal 10 independently of the rest of the cover 5, more specifically independently of the characteristics of the cover 5, such as specific dimensions (e.g., the diameter) of the cover body 17.

[0093] Figure 3A shows a longitudinal cross-sectional view of the access door 3 and the cover 5 of the pressure vessel 1 shown in Figure 1. Figure 3B shows an enlarged view of part III-B of Figure 3A. The axial extension 14 extends in the axial direction 46 relative to the longitudinal axis 7. The internal recess surface 11 extends transversely to the longitudinal axis 7. The duct 12 is configured to facilitate the flow of pressurized fluid, such as hydrogen, into and / or out of the pressure vessel 1. A valve (not shown), such as a pressure valve, may be connected to the duct 12 to control the flow of pressurized fluid. The cover 5 comprises an external duct opening 39, and the duct 12 extends from the internal duct opening 13 to the external duct opening 39. The internal recess surface 11 is in the radial direction 44 (see figure 5A) relative to the longitudinal axis 7 located between the internal duct opening 13 and the axial extension 14. More details of the door of Petition 870250080634, dated 08 / 09 / 2025, page 28 / 54 20 / 30 access 3 are shown in figures 4A and 4B. More details of the cover are shown in figures 5A and 5B.

[0094] As mentioned, the cover 5 in Figure 1 comprises a duct 12 with an internal duct opening 13 provided on the internal recess surface 11. The duct 12 is circular when viewed in a cross-sectional view in a plane perpendicular to the longitudinal axis 7. The duct 12 extends along the longitudinal axis 7. The axial extension 14 extends away from the duct 12.

[0095] By providing the sealing surface of the cover 6 on the axial extension 14 that extends from the inner recess surface 11 and away from the duct 12, it is possible to configure sealing parameters independently of the duct 12, more specifically independently of the characteristics of the duct 12, such as specific dimensions (e.g., the diameter) of the duct 12. This is possible because the characteristics of the axial extension 14, such as specific dimensions (e.g., the thickness of the cover extension Tc1) of the axial extension 14, can be configured independently of the duct 12. In this way, it is possible, for example, to adjust the flexibility in the radial direction 44 of the axial extension 14 with the sealing surface of the cover 6, without influencing the dimensions of the duct 12. Adjusting the flexibility of the axial extension 14 will lead to adjusting the sealing parameters of the inner seal 10 formed by the sealing surface of the cover 6 and the sealing surface of the door 4 in contact with each other.This allows for the selection of sealing parameters that are favorable to reducing damage to the internal seal 10.

[0096] The internal seal 10 is a metal-to-metal seal 16. The metal-to-metal seal 16 is less susceptible to damage resulting from Petition 870250080634, dated 08 / 09 / 2025, page 29 / 54 21 / 30 higher temperatures when compared to elastomeric seals. As a result, the metal-to-metal seal 16 exhibits high thermal stability. The access door 3 and the cover 5 do not have an elastomeric seal.

[0097] The sealing surface of the cover 6 is axially spaced from the surface of the inner recess 11 when viewed along the longitudinal axis 7. The sealing surface of the door 4 is also axially spaced from the surface of the inner recess 11 when viewed along the longitudinal axis 7.

[0098] The axial extension 14 encircles the inner duct opening 13 and is radially spaced from the inner duct opening 13. The axial extension 14 completely encircles the longitudinal axis 7.

[0099] The cover comprises a cover body 17 in which the duct 12 is provided. The cover body 17 comprises a circumferential cover surface 18 encircling the longitudinal axis 7. The circumferential cover surface 18 has a circular cross-section. The axial extension 14 comprises a cover extension thickness Tc1 measured in the radial direction 44 relative to the longitudinal axis 7 at the axial extension 14. The cover body 17 comprises a cover body thickness Tc2 measured in the radial direction 44 relative to the longitudinal axis 7 of the duct 12 up to the circumferential cover surface 18. The cover extension thickness Tc1 is less than the cover body thickness Tc2.This allows the axial extension 14 to be constructed with greater flexibility than the cover body 17 (see also Figure 3C). This is beneficial to ensure that the sealing parameters are determined primarily by the axial extension 14 compared to the cover body 17. The axial extension 14 comprises a bending stiffness of the cover extension Kc1 na. Petition 870250080634, dated 08 / 09 / 2025, page 30 / 54 22 / 30 thickness of the cover extension Tc1. The cover body 17 comprises a bending stiffness of the cover body Kc2 at the thickness of the cover body Tc2, and the bending stiffness of the cover extension Kc1 is less than the bending stiffness of the cover body Kc2.

[0100] The axial extension 14 comprises an adjacent end 23 adjacent to the inner recess surface 11 and a free end 24 axially distanced from the inner recess surface 11. The free end 24 terminates in an axial extension inner end surface 50. The inner end surface 50 is annular and extends transversely relative to the longitudinal axis 7. The inner end surface 50 is an end surface of the inner end 8 of the cap 5, 5'.

[0101] The thickness of the cover extension Tc1 is the smallest thickness of the cover extension Tc1 measured on the axial extension 14 in the radial direction 44. The smallest thickness of the cover extension Tc1 is measured on a portion of the axial extension 14 that extends in the axial direction 46 (see also figure 5B) from the sealing surface of the cover 6 inclusive to the adjacent end 23. The thickness of the cover body Tc2 is the smallest thickness of the cover body Tc2 measured on the cover body 17, from the duct 12 to the circumferential surface of the cover 18 in the radial direction 44. The smallest thickness of the cover body Tc2 is measured on the surface of the inner recess 11.

[0102] Access door 3 defines an additional longitudinal axis 28 and the sealing surface of door 4 faces the additional longitudinal axis 28. The sealing surface Petition 870250080634, dated 08 / 09 / 2025, page 31 / 54 23 / 30 of door 4 completely encircles the additional longitudinal axis 28.

[0103] Access door 3 comprises an outer door surface 31 and a door thickness Tp, measured in an additional radial direction 29 relative to the additional longitudinal axis 28, from the door sealing surface 4 to the outer door surface 31. The outer door surface 31 has a diameter 60 smaller than the largest outer diameter (not shown) of the shell 2. The additional radial direction 29 and the additional axial direction 30 relative to the additional longitudinal axis 28 are indicated in Figure 4A. The door thickness Tp is greater than the thickness of the cover extension Tc1 mentioned above. This allows the axial extension 14 to be constructed with greater flexibility than the access door 3. This is beneficial for the compressive stresses exerted on the axial extension 14 and the tensile stresses on the access door 3 (see also Figure 3C).Furthermore, this tends to ensure that if the internal seal 10 is damaged, the damage (or most of the damage) will occur on the cover 5, more specifically on the axial extension 14 and the cover sealing surface 6, and not on the access door 3, more specifically on the door sealing surface 4. The access door 3 has a door bending stiffness Kp at the door thickness Tp. The axial extension 14 has a cover extension bending stiffness Kc1 at the cover extension thickness Tc1. The door bending stiffness Kp is greater than the cover extension bending stiffness Kc1. The door thickness Tp is the smallest door thickness Tp measured on the access door 3 in the radial direction 29. The smallest door thickness Tp is measured on the door sealing surface 4. Petition 870250080634, dated 08 / 09 / 2025, page 32 / 54 24 / 30

[0104] The axial extension 14 comprises an inner extension surface 25 facing the longitudinal axis 7 and a transition surface 26 connecting the inner extension surface 25 with the inner recess surface 11. The inner extension surface 25, the transition surface 26 and the inner recess surface 11 together form a recess boundary 9.

[0105] The transition surface 26 forms a rounded corner 27 that extends along a radius R when viewed in a longitudinal sectional view with respect to the longitudinal axis 7. This provides additional structural integrity to the axial extension 14. The transition surface 26 is provided directly opposite the sealing surface of the cover 6.

[0106] The axial extension 14 and the cover body 17 are made of the same material, more specifically metal. The axial extension 14 and the cover body 17 are integrally formed (i.e., the axial extension 14 and the cover body 17 are made of a single piece). In other words: the axial extension 14 and the cover body 17 are made of a single piece of material. The access door 3 and the axial extension 14 are made of the same material. The shell 2 of the pressure vessel 1 is made of the same material. The shell 2 and the access door 3 are integrally formed.

[0107] Access door 3 and cover 5 are configured to hold cover 5 in a sealing position 15 on access door 3, with the sealing surface of cover 6 and the sealing surface of door 4 in contact with each other to form the internal seal. Access door 3 comprises a door stop 37. The cover comprises a door stop 38. The door stop 37 and the cover stop 38 are configured to enter Petition 870250080634, dated 08 / 09 / 2025, page 33 / 54 25 / 30 in contact with each other, so that, upon contact, the sealing surfaces 4 and 6 touch to form the internal seal 10. In particular, the door stop 37 faces away from the hull 2, and the lid stop 38 faces the axial extension 14. The longitudinal axis 7 of the lid, positioned in the sealing position 15, coincides with the rear longitudinal axis of the access door 3.

[0108] As can be clearly seen in Figure 3A, the door stop 37 is provided at a distance from the door sealing surface 4, where a female threaded zone 33 is provided between the door sealing surface 4 and the door stop 37. As such, the contact of the bump tends to introduce tensile stresses, in particular on the cover 5, at a distance from the inner seal 10, rather than introducing tensile stresses, in particular on the access door 3, close to the inner seal 10.

[0109] Figure 3C shows the results of a finite element analysis of the situation in Figure 3B, where the cover is positioned in sealing position 15. Figure 3C clearly shows that a first area 43 with the highest compressive stresses caused in the access port 3 is much smaller than a second area 45 with the highest compressive stresses in the cover 5. If the internal seal 10 is damaged, for example, by plastic deformation caused by high compressive forces, the damage (or most of the damage) tends to occur in the cover 5, more specifically in the axial extension 14. This is beneficial because, in practice, it is cheaper to replace and / or repair the cover 5 than the shell 2 with the access port 3. Furthermore, the highest tensile stresses in the access port 3 are present in the longitudinal section area 61 adjacent to the threads, where, in use, this area 61 Petition 870250080634, dated 08 / 09 / 2025, page 34 / 54 26 / 30 is sealed from a fluid, such as hydrogen, held in storage space 41 of container 1 by the inner seal 10.

[0110] Access door 3 comprises an external access opening 32 and a female threaded zone 33. Cover 5 comprises a male threaded zone 34. The female threaded zone 33 and the male threaded zone 34 are configured for rotational engagement with each other. The female threaded zone 33 is located closer to the external access opening 32 than to the sealing surface of the door 4. The female threaded zone 33 and the male threaded zone 34 have non-tapered threads.

[0111] The female threaded zone 33 is located closer to the external access opening 32 than to the door sealing surface 4 when viewed along the furthest longitudinal axis 28. The access door 3 and the cover 5 are free of a seal located closer to the external access opening 32 than to the female threaded zone 33. Therefore, the access door 3 and the cover 5 are free of an external seal.

[0112] The female threaded zone 33 comprises a female thread 52. The female thread 52 comprises a female engagement flank 53 and a female load flank 54. The male threaded zone 34 comprises a male thread 55. The male thread 55 comprises a male engagement flank 56 and a male load flank 57. The female engagement flank 53 faces the external access opening 32, and the female load flank 54 faces away from the external access opening 32. The male engagement flank 56 faces the inner end of the cover 8. As can be seen in Figure 3C, when the cover 5 is formed by the access door 3, the engagement flanks 53, 56 are located at a distance 58 from each other, while the load flanks 54, 57 Petition 870250080634, dated 08 / 09 / 2025, page 35 / 54 27 / 30 are in contact with each other. The internal seal 10 seals the access door 3 of the pressure vessel 1 so that the hydrogen contained in the storage space 41 cannot reach the threaded zones 33, 34.

[0113] The cover 5 comprises an inner cover section 19 configured to be located inside the access door 3 and an outer cover section 20 configured to be located outside the access door 3. The axial extension 14 and the cover body 17 are part of the inner cover section 19. The inner duct opening 13 is located in the inner cover section 19 and the outer duct opening 39 is located in the outer cover section 20. The axial extension 14 extends away from the outer cover section 20.

[0114] The axial extension 14 is annular. The axial extension 14 comprises an inner extension side 21 facing the longitudinal axis 7 and an outer extension side 22 facing away from the longitudinal axis 7. The sealing surface of the cover 6 is located on the outer extension side 22. The sealing surface of the cover 6 completely surrounds the longitudinal axis 7.

[0115] The sealing surface of the cover 6 is toroidal 35. The sealing surface of the door 4 is conical 36. The sealing surface of the conical door 36 4 becomes wider in a first direction 42 along the additional longitudinal axis 28 of the access door 3 and towards the external access opening 32.

[0116] Figure 6 shows a longitudinal cross-sectional view of access door 3 and cover 5' of pressure vessel 1 in Figure 1. The only difference with respect to access door 3 at the opposite end of pressure vessel 1 containing cover 5, Petition 870250080634, dated 08 / 09 / 2025, page 36 / 54 28 / 30 as shown in figures 3A-C, 4A-B and 5A-B, is that cover 5' does not have a duct 12.

[0117] Similar to cover 5, the axial extension 14 of cover 5' encircles the longitudinal axis 7 and is radially spaced from the longitudinal axis 7.

[0118] The body of the cover 17 of the cover 5' comprises an additional thickness of the cover body Tc3, measured in the radial direction 44 relative to the longitudinal axis 7, from the longitudinal axis 7 to the circumferential surface of the cover 18. The thickness of the cover extension Tc1 (as described above in relation to cover 5) is less than the additional thickness of the cover body Tc3. This allows the axial extension 14 to be constructed with greater flexibility than the cover body 17. This is beneficial in ensuring that the sealing parameters are primarily determined by the axial extension 14 compared to the cover body 17.

[0119] The cover body 17 comprises an additional bending stiffness of the cover body Kc3 in the additional thickness of the cover body Tc3, and the bending stiffness of the cover extension Kc1 (as described above in relation to cover 5) is less than the additional bending stiffness of the cover body Kc3.

[0120] The additional thickness of the lid body Tc3 is the smallest additional thickness of the lid body Tc3 measured on the lid body 17, from the longitudinal axis 7 to the circumferential surface of the lid 18 in the radial direction 44. The smallest additional thickness of the lid body Tc3 is measured on the surface of the inner recess 11.

[0121] Figure 7 shows another embodiment of the lid 5, according to the present invention, in longitudinal section. Similar to the embodiment of Figure 5A, the lid 5 comprises, Petition 870250080634, dated 08 / 09 / 2025, page 37 / 54 29 / 30 on the inner end 8 of the cover, a recess 9. However, unlike the cover 5 described above, the recess 9 has an annular shape, in which an annular recess surface 11 is formed. The annular recess 9 is radially bounded by the axial extension 14; and by a central part 47 of the inner cover end 8, in particular by an outer side 48 of the central part 47 of the inner cover end 8. The annular recess 9 is limited in the longitudinal direction by the surface of the inner recess 11. The outer side 48 faces away from the longitudinal axis 7. The duct opening 13 is provided on a surface of the inner cover end 49 of the central part 47 of the inner cover end 8. The surface of the inner cover end 49 is transverse with respect to the longitudinal axis 7.The surface of the inner cap end 49 and the surface of the inner end of the axial extension 50 of the axial extension 14 lie in the same transverse plane with respect to the longitudinal axis 7. As such, the axial extension 14 and the central part 47 are level with each other in the axial direction 46. However, it is provided that the central part 47 may extend, in the axial direction, more or less than the axial extension 14. An advantage of this embodiment is that the inner extension side 21 can be protected from turbulent fluid flows.

[0122] The longitudinal sections shown in the Figures are taken on the longitudinal axis 7 and / or the posterior longitudinal axis 28. The cross-sections are taken in a plane perpendicular to the longitudinal axis 7 and / or the posterior longitudinal axis 28.

[0123] As needed, detailed embodiments of the present invention are disclosed herein; however, it should be noted Petition 870250080634, dated 08 / 09 / 2025, page 38 / 54 30 / 30 understand that the embodiments disclosed are merely illustrative of the invention, which can be embodied in various forms. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in various ways in virtually any suitably detailed structure. Furthermore, the terms and phrases used herein are not intended to be limiting, but rather to provide a comprehensive description of the invention.

[0124] The terms one or an, as used herein, are defined as one or more than one. The term plurality, as used herein, is defined as two or more than two. The term other, as used herein, is defined as at least one second or more. The terms including and / or having, as used herein, are defined as comprising (i.e., in open language, not excluding other elements or steps). Any reference signs in the claims shall not be construed as limiting the scope of the claims or the invention.

[0125] It will be evident to those skilled in the art that various modifications can be made to the pressure vessel according to the invention, to the method according to the invention, and to the lid according to the invention shown in the figures without departing from the scope as defined in the claims. Petition 870250080634, dated 09 / 08 / 2025, pp. 39 / 54

Claims

1 / 4 CLAIMS 1. Pressure vessel for storing a pressurized fluid, such as hydrogen, characterized in that it comprises: - a shell comprising an access door provided with a door sealing surface, and - a lid provided with a lid sealing surface and defining a longitudinal axis, wherein: - the access door and the lid are configured to receive and hold the lid in the access door with the lid sealing surface and the door sealing surface contacting each other to form an internal seal, - the lid comprises an inner end, - a recess is provided in the inner end of the lid so that an axial extension is formed, and - the lid sealing surface is provided in the axial extension.

2. Pressure vessel according to claim 1, characterized in that the axial extension surrounds the recess.

3. Pressure vessel according to claim 1 or 2, characterized in that the lid comprises a duct with an internal duct opening, and the axial extension is radially spaced from the internal duct opening.

4. Pressure vessel according to any one of claims 1 to 3, characterized in that: Petition 870250080634, dated 08 / 09 / 2025, page 40 / 54 2 / 4 - the lid comprises a lid body, - the lid body comprises a circumferential lid surface around the longitudinal axis, - the axial extension comprises a lid extension thickness measured in the radial direction relative to the longitudinal axis in the axial extension, - the lid body comprises a lid body thickness measured in the radial direction relative to the longitudinal axis between the longitudinal axis and the circumferential surface of the lid, and - the thickness of the lid extension is less than the thickness of the lid body.

5. Pressure vessel according to any one of claims 1 to 4, characterized in that the axial extension further comprises an external extension side facing away from the longitudinal axis and the sealing surface of the cover is located on the external extension side.

6. Pressure vessel according to any one of claims 1 to 5, characterized in that the cover comprises an internal recess surface, and the axial extension comprises an internal extension surface facing the longitudinal axis and a transition surface connecting the internal extension surface with the internal projection surface, and the transition surface forms a rounded corner extending along a radius R when viewed in a longitudinal sectional view with respect to the longitudinal axis. Petition 870250080634, dated 08 / 09 / 2025, page 41 / 54 3 / 4 7. Pressure vessel according to any one of claims 1 to 6, characterized in that the access door defines an additional longitudinal axis and the sealing surface of the door faces the additional longitudinal axis.

8. Pressure vessel according to any one of claims 1 to 7, characterized in that: - the axial extension comprises a cover extension thickness measured in the radial direction relative to the longitudinal axis in the axial extension, - the access door comprises an outer door surface and an additional door thickness measured in an additional radial direction relative to the longitudinal axis between the door sealing surface and the outer door surface, and - the door thickness is greater than the cover extension thickness.

9. Pressure vessel according to any one of claims 1 to 8, characterized in that: - the access door comprises an external access opening and a female threaded zone, - the cover comprises a male threaded zone, - the female threaded zone and the male threaded zone are configured for rotational engagement with each other, and - the female threaded zone is located closer to the external access opening than to the sealing surface of the door. Petition 870250080634, dated 08 / 09 / 2025, page 42 / 54 4 / 4 10. Pressure vessel according to claim 9, characterized in that the access door and the lid are free of a seal located closer to the external access opening than to the female threaded zone.

11. Pressure vessel according to any one of claims 1 to 10, characterized in that the sealing surface of the lid is toroidal.

12. Pressure vessel according to any one of claims 1 to 11, characterized in that the access door and the lid are free of an elastomeric seal.

13. A method for sealing a pressure vessel for storing a pressurized fluid, such as hydrogen, as defined in any one of claims 1 to 12, the method characterized in that it comprises placing the cap on the access port and forming an internal seal with the sealing surface of the cap and the sealing surface of the port in contact with each other.

14. Pressure vessel lid, characterized in that it comprises: - an inner lid end, - a recess provided in the inner lid end, so that an axial extension is formed, and - a lid sealing surface provided in the axial extension. Petition 870250080634, dated 08 / 09 / 2025, pp. 43 / 54

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