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US-12618518-B2 - Cap for a pressure tank, and pressure tank for a gas-powered vehicle

US12618518B2US 12618518 B2US12618518 B2US 12618518B2US-12618518-B2

Abstract

A boss for a pressure tank for storing gas in a gas-powered vehicle. The boss is configured for attachment to a wall of the pressure tank enclosing a cavity for storing the gas. The wall has a reinforcement layer made of fiber-reinforced plastic and an inner liner for sealing. The boss has an external thread, which can be connected to a mating internal thread of the liner. There is also described a pressure tank with two such bosses.

Inventors

  • Hartmut Frenz
  • Lukas Wessels
  • Mark Bleischwitz
  • Thomas Lanzl

Assignees

  • VOITH HYSTECH GMBH

Dates

Publication Date
20260505
Application Date
20211203
Priority Date
20201222

Claims (17)

  1. 1 . A boss for a pressure tank for storing gas in a gas-operated vehicle, wherein the pressure tank has a wall that encloses a cavity for storing the gas, and the wall includes a reinforcement layer composed of fiber-reinforced plastic and an inner liner for sealing the pressure tank; the boss comprising: an external thread for attachment to the wall of the pressure tank, said external thread being configured for meshing with a matching internal thread of the liner and to be arranged concentrically in relation to a longitudinal axis of the pressure tank; and an annular sealing surface situated on an end face of the boss, arranged perpendicularly to the longitudinal axis or enclosing an angle of between 70° and 110° with the longitudinal axis, said sealing surface configured for the liner to be pushed thereagainst by a spring element to form a throttle point and provide a sealing action; and a screw thread being an internal thread for receiving a sleeve to be screwed in, the sleeve serving to allow the liner to be pushed against the sealing surface of the boss with the aid of the spring element.
  2. 2 . The boss according to claim 1 , wherein said external thread has at least 4 to at most 10 thread turns.
  3. 3 . The boss according to claim 1 , wherein said external thread has one end formed with at least one half thread turn with a thread elevation which is smaller than remaining thread elevations, and another end formed with at least one half thread turn with a thread depression which is smaller than remaining thread depressions.
  4. 4 . The boss according to claim 1 , wherein the boss is formed with a neck region to be received in a holder, said neck region having a length which is at least 50% of an outer diameter measured at a thinnest point of said neck region.
  5. 5 . The boss according to claim 4 , wherein said neck region length is between 40 mm and 80 mm, and said neck region includes a cylindrical outer contour within said neck region length.
  6. 6 . The boss according to claim 1 , wherein said external thread is a cylindrical thread, and a diameter of the external thread based on tips of the thread elevations is at least 60 mm and at most 180 mm.
  7. 7 . The boss according to claim 6 , wherein the diameter of the external thread is between 90 mm and 180 mm.
  8. 8 . The boss according to claim 1 , wherein the annular sealing surface encloses an angle of between 70° and 110° with the longitudinal axis.
  9. 9 . The boss according to claim 1 , wherein the external thread is radially further away from the longitudinal axis than the sealing surface to keep a torque load away from the sealing surface situated further inward.
  10. 10 . The boss according to claim 1 , wherein said sealing surface includes annular elevations configured to be pushed into the liner.
  11. 11 . The boss according to claim 10 , wherein each annular elevation is a few tenths of a millimeter in height.
  12. 12 . A pressure tank for storing gas in a gas-operated vehicle, the pressure tank comprising: a wall defining a circularly symmetrical elongate form which is cylindrical in a central region and is terminated at both ends by domed end caps; said wall enclosing a cavity for storing the gas, and said wall being formed of a reinforcement layer composed of fiber-reinforced plastic and an inner liner for sealing the cavity; each of said domed end caps having a metallic connection piece, being a boss; each boss including: an external thread for attachment to the wall of the pressure tank, said external thread being configured for meshing with a matching internal thread of said liner and to be arranged concentrically in relation to a longitudinal axis of the pressure tank; an annular sealing surface situated on an end face of the boss outside said liner and configured for said liner to be pushed thereagainst to form a throttle point and provide a sealing action; and a spring element associated with each boss, said liner being pushed against said sealing surface of a respective boss by an associated spring element.
  13. 13 . The pressure tank according to claim 12 , wherein said external thread of said boss at one end being a right-hand thread and said external thread of said boss at an opposite end being a left-hand thread.
  14. 14 . The pressure tank according to claim 12 , wherein said internal threads are produced in said liner by cutting.
  15. 15 . The pressure tank according to claim 12 , further comprising, for each of said domed end caps, a sleeve connected to a respective boss and a pressure ring, wherein said spring element is supported against said sleeve to push said pressure ring against said liner, to press said liner against said sealing surface of said respective boss.
  16. 16 . The pressure tank according to claim 15 , wherein said pressure ring together with said sleeve fully enclose said spring element.
  17. 17 . The pressure tank according to claim 15 , wherein said pressure ring is displaceable relative to said sleeve in a direction of a longitudinal axis L of the pressure tank.

Description

FIELD AND BACKGROUND OF THE INVENTION The invention relates to a pressure tank for storing gas for being mounted in a gas-operated vehicle, wherein the pressure tank has a circularly symmetrical elongate form which is cylindrical in the central region and which is terminated at both ends by domed end caps. The pressure tank has a wall which encloses a cavity for storage of the gas, and also has a metallic connection piece, a so-called boss, at each of the end caps, wherein the wall comprises a reinforcement layer composed of fiber-reinforced plastic and an inner liner for sealing. The invention furthermore relates to a boss for such a pressure tank. Gas-operated vehicles have for example a gas engine or a fuel cell with an electric motor as a drive. In order to be able to store fuel to a sufficient extent, the gas, which may be inter alia hydrogen, is stored at high pressure in the tank. Pressures of above 200 bar, frequently up to 600 bar and sometimes even up to 700 or 875 bar are typical for such pressure tanks. This means that not only does the pressure tank have to be gas-tight at this pressure but also it requires a high level of mechanical stability. Pressure tanks for gas-operated vehicles are known in the prior art. These pressure tanks have a wall which, for sealing off an inner liner, for example composed of thermoplastic, and, for providing the mechanical stability, comprises a reinforcement layer composed of fiber-reinforced plastic. The reinforcement layer is preferably wound and designed as a CFRP layer. CFRP stands for carbon-fiber-reinforced plastic. The boss has a passage bore and a connection thread. At at least one of the two bosses, there is connected a tank fitting which allows the pressure tank to be filled or gas to be extracted in a controlled manner. At the other boss, the passage opening is sealed off by a closure means or provision is made there of a further tank fitting or a safety valve. With such pressure tanks, particular attention has to be paid to the attachment between the metallic connection piece, the boss, and the liner, since here large forces occur during production and later, during operation, high demands are placed on tightness—moreover with mechanical load, varying internal pressure and large temperature variations. In particular in the case of large hydrogen pressure tanks with a total mass of above 150 kg, this is a major challenge. There are various known solutions in the prior art for the connection between the boss and the liner. In this regard, it is possible for example, as described in EP 550951 A1, for a form-fitting connection between liner (referred to as inner liner) and boss (referred to as annular flange) to be used. Such form-fitting connections, such as for example dovetail connections, are however producible at present only if the end caps of the liner are produced in an injection-molding process or a similar process. It would be advantageous if form-fitting connections could also be produced in a process other than an injection-molding process. A further known possibility has been disclosed in DE 102011010685 A1, in WO 2011/103687 A1 and in EP 2115343 A1. In said documents, the boss (referred to as main body or metal body) is screwed onto the liner collar (referred to as inner container or core container). For this purpose, the boss has an internal thread. The sealing is ensured by way of a metal cylinder bearing O-ring seals that is screwed into the boss. The liner is consequently clamped between the boss, at the outside, and the metal cylinder, at the inside. The boss is then wrapped on the outer side with the reinforcement layer composed of CFRP. These known embodiments have the disadvantage that, during the production of the reinforcement layer, they give rise to difficulties, in particular in the case of relatively large pressure tanks, as are necessary for example for utility vehicles, which are to be driven by a fuel cell, the boss not being sufficiently fixed. Such novel pressure tanks for utility vehicles may reach diameters of up to 600 mm and lengths of 2500 mm. The reinforcement layer is normally produced in a winding process. For this purpose, the liner, which is already connected as a preliminary product to the boss, is clamped into a winding machine and set in rotation. The torque is introduced into the liner via the boss(es). In this case, the liner is wrapped with fiber tapes or fiber rovings, wherein, for process-related reasons, large tensile forces act tangentially on the liner due to the draw-off tension of the roving or fiber tapes. Consequently, during the wrapping process, large torque forces act on the connection between boss and liner. Since the lever arm increases with the diameter of the pressure tank and relatively large pressure tanks are simultaneous wrapped with multiple rovings, the load is correspondingly relatively large in the case of relatively large pressure tanks. These increased forces are not withstood by