Pressure tank for gas-powered vehicle

Abstract

A pressure tank (1) for storing gas for installation in a gas-powered vehicle, having a rotationally symmetrical, elongated shape, cylindrical in the central region and closed at both ends with domed end caps, and having a wall enclosing a cavity (2) for storing the gas, as well as a metallic connection piece, a so-called boss (4), at each of the end caps, wherein the wall comprises a reinforcing layer (6) made of fiber-reinforced plastic and an inner liner (3), wherein a bushing (7, 7') connected to the boss (4) via a screw thread (12), a pressure ring (8, 8') and a spring element (9) are provided for sealing, designed such that the spring element (9) is supported on the bushing (7, 7') and presses the pressure ring (8, 8') against the liner (3) and thereby presses the liner (3) against the boss (4) in a pressure area (13), and wherein the pressure ring (8,8') via a toothed connection (10,10') is connected to the boss (4) in a rotationally fixed manner.

Description

[0001] The invention relates to a pressure tank for storing gas for installation in a gas-powered vehicle, wherein the pressure tank has a rotationally symmetrical, elongated shape, cylindrical in its central region and terminated at both ends with domed end caps. The pressure tank has a wall enclosing a cavity for storing the gas, as well as a metallic connector, a so-called boss, at each end cap. The wall comprises a reinforcing layer made of fiber-reinforced plastic and an inner liner. For sealing, a bushing connected to the boss via a screw thread, a pressure ring, and a spring element are provided, designed such that the spring element bears against the bushing and presses the pressure ring against the liner, thereby pressing the liner against the boss within a pressure zone.

[0002] The invention further relates to a precursor for the manufacture of such a pressure tank, as it exists before the application of the reinforcing layer. The precursor comprises at least one liner and one boss. For sealing, it includes a bushing connected to the boss via a screw thread, a pressure ring, and a spring element, designed such that the spring element bears against the bushing and presses the pressure ring against the liner, thereby pressing the liner against the boss within a pressure zone.

[0003] Gas-powered vehicles, for example, use a gas engine or a fuel cell with an electric motor as their drive system. To store sufficient fuel, the gas, which can be hydrogen, is stored under high pressure in a tank. Typical pressures for such tanks are over 200 bar, often up to 700 bar, and sometimes even up to 800 bar. This means that the pressure tank must not only be gas-tight under this pressure, but also require high mechanical stability.

[0004] Pressure tanks for gas-powered vehicles are known in the prior art. These pressure tanks have a wall that includes an inner liner, for example made of thermoplastic, for sealing purposes, and a reinforcing layer made of fiber-reinforced plastic to provide mechanical stability. The reinforcing layer is usually wound and made of carbon fiber reinforced plastic (CFRP).

[0005] The boss has a through-hole and a threaded connection. At least one of the two bosses has a tank fitting attached, allowing the pressure tank to be filled or gas to be withdrawn in a controlled manner. On the other boss, the through-hole is sealed with a cap, or another tank fitting or a safety valve is provided there.

[0006] A good and durable seal at the transition between the boss and the liner is of paramount importance. This is particularly challenging with larger hydrogen pressure tanks, such as those required for fuel cell-powered commercial vehicles. These tanks can reach diameters of up to 700 mm and lengths of 2500 mm. Many existing sealing concepts are insufficient for such applications.

[0007] WO 2022 / 136045 A1 describes a pressure tank that has the aforementioned features. To improve the tightness of the finished pressure tank, a pressure ring is used, which is pressed against the liner by a spring element supported by a bushing connected to the boss.

[0008] However, state-of-the-art designs have the disadvantage that they are not adequate for all load conditions and can therefore damage the seal. During the manufacturing process, when winding the reinforcement layer, the bond between the boss and the liner is subjected to particularly high stress. In some cases, this stress loosens or damages the bond, leading to subsequent leaks.

[0009] The object of the invention is now to develop a pressure tank or a pre-product described above for such a pressure tank, which ensures improved tightness at the connection between boss and liner and in which this connection has better stability in the manufacturing process, especially when winding the reinforcement layer.

[0010] The problem is solved, firstly, by a pressure tank according to claim 1. Further advantageous features are mentioned in the respective dependent claims.

[0011] According to the invention, the pressure tank according to claim 1 is characterized in that the pressure ring is connected to the boss in a rotationally fixed manner via a toothed connection.

[0012] A significant advantage of the design according to the invention is that, through this rotationally fixed connection, the torques acting on the boss are transmitted via the toothing to the pressure ring of the sealing set, and thus no rotational relative movement is possible between these elements after assembly of the sealing set.

[0013] This stabilizes the connection with respect to circumferential torques and distributes forces more evenly into the liner, ensuring a more reliable and durable seal. The connection is also not weakened by circumferential forces occurring during manufacturing, assembly, or subsequent operation of the pressure tank.

[0014] Particularly during the production of the reinforcement layer, which takes place on a winding machine, the connection between the boss and the liner is subjected to high circumferential forces. The rotation of the pre-product during the winding process is driven by the boss. There is always a risk that the boss will rotate or loosen, thus damaging the connection.

[0015] Similarly, during operation of the pressure tank, a circumferential load can act upon it, which could loosen the connection between the boss and the liner. The design according to the invention also counteracts this and, via the toothing, prevents relative rotation between the boss and the pressure ring, which would lead to damage to the liner. Thus, the seal is permanently ensured.

[0016] Due to the spring element and the two-part design with bushing and pressure ring, a preload can be applied to create a seal in the pressure area between the boss and the liner. This preload ensures sufficient sealing even at low internal pressures or during expansion due to temperature differences. By precisely adjusting the spring force, over-compression of the liner and the resulting deformation that could lead to leaks can be avoided. Even with a low preload, the pressure ring is ensured to bear against both the liner and the boss, and the teeth on the pressure ring engage with the teeth on the boss. This creates a rotationally rigid connection between the two components.

[0017] The toothing is particularly advantageous when arranged on the inner circumference of the pressure ring. This prevents the pressure area from being unnecessarily reduced.

[0018] The toothing can be formed by teeth, as in a gear, or by a different profile, such as a wave profile or similar. Crucially, the teeth of the toothing must interlock positively and be able to transmit circumferential forces. The number and height of the teeth are designed accordingly to achieve this. Here, "teeth" refers to any profile element that enables a positive-locking, rotationally fixed connection.

[0019] In one embodiment of the invention, the toothing is designed as a so-called wave toothing. This means that the teeth point in a radial direction, radially outwards in the case of the pressure ring and radially inwards in the case of the boss.

[0020] In an alternative embodiment of the invention, the toothing is designed as a face toothing. This means that the teeth point axially in the longitudinal direction and thus interlock, for example as in a Hirth toothing.

[0021] Depending on the specific design, a choice can be made between these alternatives. The advantages lie in simpler manufacturing or improved power transmission.

[0022] In a particularly preferred version, the screw thread is designed such that the boss has an internal thread and the bushing has an external thread, which mesh together. This allows for a particularly compact connection design.

[0023] By screwing the bushing into the boss, the spring between the bushing and the pressure ring, or the spring-loaded pressure ring itself, is compressed. The spring force and thus the preload can be precisely adjusted by the spring design and the intended screw-in depth during assembly (until the device reaches its limit).

[0024] To ensure proper preload build-up and a good seal, the pressure ring is displaceable relative to the bushing in the direction of the longitudinal axis L. The pressure ring can be designed to be sufficiently rigid to achieve uniform contact pressure across its surface and thus a reliable seal. For stiffening and stabilization, the pressure ring can have an additional cylindrical section on its outer circumference. Alternatively, the pressure ring can essentially be designed as a disc with a cylindrical or conical section on its inner circumference that encompasses the toothing.

[0025] Preferably, the bushing is arranged so that it does not have full-surface contact with the liner. The sealing pressure is transferred to the liner only via the surface of the pressure ring.

[0026] Furthermore, the bushing can have a collar against which the spring element is supported, the collar being arranged essentially perpendicular to the longitudinal axis L of the pressure tank. This ensures good ease of assembly and good force transmission.

[0027] A spring element, as used here, is an element capable of generating sufficient elastic spring force when compressed. For example, it can be a ring-shaped or disc-shaped element made of spring steel, featuring so-called spring wings. In particular, the spring element can have a U-shaped or V-shaped cross-section. Alternatively, the spring element can also be composed of several leaf springs or coil springs arranged between the bushing and the compression ring. Other types and shapes of springs can also be used. In particular, the spring element can be a disc spring. The disc spring can have one or more spring plates. The spring force can be adjusted, among other things, by the number of spring plates arranged in series.

[0028] To ensure improved contact pressure, the inner surface of the boss in the pressure area is preferably oriented essentially perpendicular to the longitudinal axis. This allows the spring force to be optimally utilized as contact force.

[0029] In another particularly advantageous embodiment, the pressure ring has one or more grooves in the pressure area that extend along the circumferential direction, and the liner has one or more circumferential ribs that engage in the grooves. This fixes the liner in its position relative to the pressure ring. Thus, the liner cannot be pulled out between the pressure ring and the boss. Such radially acting forces occur when the liner is exposed to significant temperature changes. For example, the liner shrinks during annealing. And significant temperature differences can also occur during operation.

[0030] The arrangement can be further improved if the grooves in the pressure ring are designed as multiple circular segments in the circumferential direction and the circumferential ribs on the liner are designed as correspondingly matching circular segments, so that the grooves and the circumferential ribs form a positive-locking connection that can transmit circumferential forces between the liner and the pressure ring in addition to radial forces. Thus, the liner is not only reliably clamped between the pressure ring and the boss, but the circumferential ribs in the grooves also act as an anti-rotation device between the liner and the pressure ring.

[0031] If the liner manufacturing process allows, these grooves can have a dovetail cross-section. This improves the fit and also prevents the liner from lifting off the pressure ring. For example, if the liner is manufactured using blow molding, the grooves can be dovetail-shaped. The plastic used in liner production fills these grooves and forms the corresponding circumferential ribs.

[0032] Larger pressure tanks, in particular, have a boss at both end caps. Therefore, it is especially desirable to provide a bushing, a pressure ring, and a spring element, as described above, at each end cap of the pressure tank to improve the seal between the liner and the respective boss.

[0033] Furthermore, the invention relates to a precursor for the manufacture of the previously described pressure tanks. The precursor comprises at least one liner and one boss. It can also be only a part of the liner that later forms the inner wall of the pressure tank. This is the case, for example, when the liner is manufactured by injection molding and is assembled from several parts, such as two end caps and cylindrical center sections.

[0034] In particular, the pre-product can comprise the complete liner and two bosses with appropriate connection and sealing via the previously described design.

[0035] For the intermediate product, the problem is solved by an embodiment according to claim 12. Further advantageous embodiments are described in the corresponding dependent claims.

[0036] According to the invention, the intermediate product is characterized by the fact that the pressure ring is connected to the boss in a rotationally fixed manner via a toothed connection. The resulting improvements and advantages have already been described above in relation to the pressure tank.

[0037] Furthermore, it is advantageous if the toothing is designed to fully absorb the torques that occur during the winding of the reinforcement layer. This can be achieved by selecting an appropriate number and height of teeth.

[0038] Winding the reinforcement layer is a further process step in the manufacture of pressure tanks, in which the pre-product consisting of liner and boss is wrapped with strips or tapes made of fiber-reinforced plastic, particularly CFRP (carbon fiber reinforced plastic). These strips or tapes contain a large number of rovings and are preferably already impregnated with a suitable resin, which is cured after winding. The faster the winding process, the more rovings are processed simultaneously, and the more viscous the resin, the higher the tensile stress of the strips or tapes must be during winding.

[0039] This means that with an improved connection between the boss and liner, which can withstand higher circumferential forces, it becomes possible to wind even faster and with more rovings simultaneously, even with high resin viscosity. The solution according to the invention thus also offers an improvement in productivity in the production of pressure tanks. In particular, the solution according to the invention can withstand torques of at least 500 Nm and allows winding with a winding tension of at least 1000 N. The solution according to the invention can be used particularly advantageously in so-called towpreg winding, but is equally advantageous in wet winding.

[0040] Further advantageous features of the invention are explained using exemplary embodiments with reference to the drawings. These features can be advantageously implemented not only in the combination shown, but also individually combined with one another. The figures show in detail: Fig. 1 Schematic representation of a pressure tank according to the invention Fig. 2 Schematic representation of the connection and sealing between boss and liner in an embodiment according to the invention Fig. 3a,b Variants for the toothing between boss and bushing in the embodiment according to the invention Fig. 4a,b Variants for the toothing between boss and bushing in a further embodiment according to the invention Fig. 5 Further embodiment of a precursor according to the invention for the production of a pressure tank (detail)

[0041] The figures are described in more detail below. Identical reference numbers denote identical or analogous parts or components.

[0042] The Fig. Figure 1 shows the pressure tank 1 with a boss 4 at each of its two end caps. A tank fitting 5 for filling and controlled gas release is screwed into one boss 4. The other boss 4 is sealed with a cap. Alternatively, it can accommodate a safety valve. The wall of the pressure tank 1 encloses the cavity 2 and is formed by an inner liner 3 and a reinforcing layer 6. The liner 3 is preferably made of thermoplastic material such as polyamide and is manufactured, for example, by blow molding or injection molding (optionally assembled from several parts). The reinforcing layer 6 is produced by a winding process using tapes of fiber-reinforced plastic, preferably CFRP. The pressure tank 1 is rotationally symmetrical about its longitudinal axis L. Particular attention must be paid to the seal between the boss 4 and the liner 3 in such pressure tanks.Especially with large pressure tanks, such as those required in commercial vehicles to ensure sufficient range, achieving a good and lasting seal is a significant challenge. Additionally, the connection is subjected to considerable stress during the winding of the reinforcing layer. It must therefore be sufficiently robust to withstand this stress as well.

[0043] Fig. Figure 2 shows an enlarged section of the pressure tank 1, so that the inventive design for improved sealing becomes apparent. The seal against the internal gas pressure in the pressure tank is achieved by pressing the liner 3 against the boss 4 due to the spring force of the spring element 9 and due to the internal gas pressure itself.

[0044] The sealing set, consisting of bushing 7, pressure ring 8, and spring element 9, is shown. Pressure ring 8 and spring element 9 are located inside the liner 3, i.e., in the cavity 2. The spring element 9 is pre-tensioned via bushing 7, which is connected to boss 4 by the threaded thread 12. Spring element 9 presses pressure ring 8 against liner 3, and thus presses liner 3 against boss 4. The liner 3 is pressed against boss solely by pressure ring 8. This pressure ring 8 is movable relative to bushing 7 and can be displaced along the longitudinal axis L. In the illustrated version, they together enclose spring element 9, providing good protection. This also facilitates easy assembly of the components. In this design, spring element 9 is a disc spring. A disc spring with two spring plates is shown; however, a single spring plate or multiple spring plates can also be used.The spring force can be varied by adjusting the spring's strength, material, and the number of spring plates. The clamping force can be adjusted to the desired level by selecting the appropriate spring element and the intended screw-in depth on the threaded section 12. Other spring elements than those shown in this example can also be used in the embodiment according to the invention.

[0045] The pressure ring 8 is positively locked and thus rotationally fixed to the boss via the toothed section 10 (10'). This allows circumferential forces and thus torques, such as those occurring during the winding process in the production of the reinforcement layer, to be effectively absorbed. During the winding process, the pre-product consisting of liner 3 and boss 4 is driven by the boss 4, causing it to rotate and wind the CFRP tapes onto the liner 3 with the appropriate tensile stress. The forces applied via the boss 4 are transmitted directly to the pressure ring 8 via the toothed section 10. This prevents any rotational relative movement between the pressure ring 8 and the boss 4, which would lead to shear forces on the liner 3, or cause the connection between the boss 4 and the liner 3 to loosen or become unstable.

[0046] The inner surface 4a of the boss is oriented essentially perpendicular to the longitudinal axis L in the pressure area 13, where the liner 3 is pressed against the boss 4. The surface of the pressure ring 8, which is pressed against the liner 3, is also oriented essentially perpendicular to the longitudinal axis L. Additionally, the collar 17 of the bushing, against which the spring element 9 is supported, is arranged essentially perpendicular to the longitudinal axis L. Thus, the spring force of the spring element 9 is completely transmitted via the pressure ring 8 to the sealing surface between the boss 4 and the liner 3 by means of the screw connection 12.

[0047] Alternatively, sufficient force transmission can still be achieved by tilting these surfaces by a maximum of + / - 20°. Tilting the sealing surface also contributes to better venting of the sealing surface during liner manufacturing. The tilt allows air to escape more easily from the compression point during pressing.

[0048] The boss 4 also features the so-called wing 4b, which tapers outwards, thus achieving a stepless transition in the reinforcement layer between the boss 4 and the liner 3. Furthermore, the boss 4 has an internal thread 11, through which a tank fitting, a safety valve, or a closure can be screwed. The pressure tank is filled and emptied via the through-hole 16 in the boss.

[0049] Fig. 3a and Fig. Figure 3b shows the connection and sealing on the liner 3 in detail. The toothing 10 is designed as a so-called shaft toothing ( Fig. 3a). The teeth, which can generally also be designed as positive-locking profile elements as described above, point radially inwards on boss 4 and radially outwards on pressure ring 8. This causes the respective teeth of the toothing 10 to interlock when the pressure ring 8 is pushed onto boss 4, thus creating a rotationally fixed connection. In the other case, the toothing 10' is designed as a face toothing ( Fig. 3b). Here, the teeth point in the direction of the longitudinal axis L. The toothing can, for example, be designed as a Hirth toothing.

[0050] Fig. 4a and Fig. Figure 4b shows a variant for the sealing set, which consists of bushing 7', pressure ring 8' and spring element 9. The pressure ring 8' is essentially designed as a disc. It has a small cylindrical part on its inner diameter that encompasses the toothing 10 (10'). Here again, two solutions for the toothing are shown: shaft toothing ( Fig. 4a) and front teeth ( Fig. 4b). The bushing 7' is L-shaped. This design offers the advantage that the components of the sealing set can be more space-saving and lighter.

[0051] Furthermore, the schematic shows that the surface of the pressure ring 8', which presses against the liner 3, can have a certain inclination. Additionally, the surface on the boss 4 in the pressure area could also have an inclination. With an inclination of these surfaces of a maximum of + / - 20°, sufficient force transmission can still be achieved. The inclination of the sealing surface also contributes to better venting of the sealing collar during liner manufacturing and assembly. The inclination allows air to escape more easily from the pinch point.

[0052] This tendency can also be observed in the solution according to Fig. 3a / b must be present. On the other hand, the solution according to Fig. 4a / b the surface of the pressure ring 8 is designed vertically.

[0053] In this version, spring element 9 is designed as a disc spring. A disc spring with four spring plates is shown; however, fewer spring plates, a single spring plate, or multiple spring plates can also be used. The spring force can be adjusted to the desired value by changing the thickness, material, and number of spring plates.

[0054] In the four illustrated embodiments, the bushing 7,7' has the collar 17, which is oriented essentially perpendicular to the longitudinal axis L, and on which the spring element 9 is supported.

[0055] In the explanations according to Fig. 3a,b and Fig. For clarity, figures 4a and 4b do not explicitly show grooves in the pressure ring or circumferential ribs on the liner. However, it is advantageous to also implement these embodiments with a groove in the pressure ring and a circumferential rib on the liner, as in the following example in Fig. 5 is shown and described.

[0056] Fig. Figure 5 shows a further embodiment according to the invention, here using the example of the intermediate product 18. The boss 4 with a portion of the liner 3 and the assembled sealing set consisting of bushing 7, pressure ring 8, and spring element 9 are shown. The intermediate product 18 can comprise only a portion of the liner. Alternatively, the intermediate product 18 can comprise the entire liner 3 and preferably a second boss 4 and a further sealing set on the second boss 4.

[0057] The pressure ring 8 is shown here as an example with the groove 14, which is located in the pressure area 13 and extends circumferentially. Correspondingly, the liner 3 has the circumferential rib 15 in this area, which engages positively in the groove 14 and thus prevents the liner 3 from being pulled out between the pressure ring 8 and the boss 4. This prevents, for example, damage to the connection between the liner 3 and the boss 4 during tempering, which would impair the seal.

[0058] In Fig. Figure 6 shows a preferred embodiment for the groove 14 and the circumferential rib 15. For illustration, boss 4, liner 3 and sealing set with bushing 7, pressure ring 8 and spring element 9 are shown pulled apart. Fig. 6a,b,c shown. Fig. 6b' is the top view of the circumferential rib 15 of the liner 3 and in Fig. 6c' shows the top view of the groove 14 in the pressure ring 8.

[0059] The groove 14 is designed as several circular segment-shaped partial grooves in the surface of the pressure ring 8. Correspondingly, the circumferential rib 15 on the liner 3 is also designed as interrupted circular segment-shaped partial ribs. They are designed such that the segments of the circumferential rib 15 engage positively with the circular segments of the groove 14. This allows circumferential forces to be transmitted between the liner 3 and the pressure ring 8, further stabilizing and improving the connection. Depending on the required force transmission, the number, diameter, and length of the partial grooves and partial ribs can be specified.

[0060] In a liner manufacturing process that allows it, the circumferential rib 15 and the groove 14 can be designed with a dovetail-shaped cross-section. This further improves the positive fit.

[0061] Furthermore, the toothing 10 in the form of a wave toothing can be seen on the pressure ring 8 and on the boss 4. Reference symbol list 1 pressure tank 2 cavities 3 Liner 4 Boss 4a Inner surface of the boss 4b Boss's Wing 5 Tank fitting 6 Reinforcing layer 7.7' socket 8.8' pressure ring 9 spring element 10,10' gearing 11 internal threads 12 screw threads 13 Print area 14 Nut 15 Circumferential rib 16 through holes 17 collars 18 Precursor L Longitudinal axis of the pressure tank R Radial direction of the pressure tank QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] WO 2022 / 136045 A1

[0007]

Claims

[1] Pressure tank (1) for storing gas for installation in a gas-powered vehicle, having a rotationally symmetrical, elongated shape, cylindrical in the central region and closed at both ends with domed end caps, and having a wall enclosing a cavity (2) for storing the gas, and a metallic connection piece, a so-called boss (4), at each of the end caps, wherein the wall comprises a reinforcing layer (6) made of fiber-reinforced plastic and an inner liner (3), wherein for sealing a bushing (7, 7') connected to the boss (4) via a screw thread (12), a pressure ring (8, 8') and a spring element (9) are provided, designed such that the spring element (9) is supported on the bushing (7, 7') and presses the pressure ring (8, 8') against the liner (3) and thereby presses the liner (3) against the boss (4) in a pressure area (13), characterized by, that the pressure ring (8,8') is connected to the boss (4) in a rotationally fixed manner via a toothed connection (10,10'). [2] Pressure tank (1) according to claim 1 characterized by , that the toothing (10) is designed as a so-called wave toothing with radially outwardly directed teeth on the pressure ring (8,8') and with radially inwardly directed teeth on the boss (4). [3] Pressure tank (1) according to claim 1 characterized by , that the toothing (10') is designed as a face toothing with axially aligned teeth on the pressure ring (8,8') and on the boss (4). [4] Pressure tank (1) according to any one of the preceding claims characterized by , that the screw thread (12) on the boss is designed as an internal thread and on the bushing (7,7') as an external thread. [5] Pressure tank (1) according to any one of the preceding claims characterized by, that the pressure ring (8,8') is displaceable relative to the bushing (7,7') in the direction of the longitudinal axis L, and that the spring force with which the pressure ring (8,8') is pressed against the liner (3) by the spring element (9) can be changed via the screw-in depth of the bushing (7,7') into the boss (4). [6] Pressure tank (1) according to any one of the preceding claims characterized by , that the bushing (7,7') has a collar (17) against which the spring element (9) is supported, the collar (17) being oriented substantially perpendicular to the longitudinal axis L. [7] Pressure tank (1) according to any of the preceding claims characterized by , that the spring element (9) is designed as a so-called disc spring, wherein one or more spring discs are present. [8] Pressure tank (1) according to any one of the preceding claims characterized by , that the inner surface (4a) of the boss in the pressure area (13) is oriented essentially perpendicular to the longitudinal axis L. [9] Pressure tank (1) according to any one of the preceding claims characterized by , that the pressure ring (8,8') has one or more grooves (14) in the pressure area (13), and that the liner (3) has one or more circumferential ribs (15) that engage in the grooves (14). [10] Pressure tank (1) according to claim 9 characterized by , that the grooves (14) are designed as circular segments in the circumferential direction and the circumferential ribs (15) are designed as correspondingly matching circular segments, such that they interlock and can transmit circumferential forces between liner (3) and pressure ring (8,8') by positive locking. [11] Pressure tank (1) according to any of the preceding claims characterized by that the grooves (14) have a dovetail-shaped cross-section. [12] Precursor for the manufacture of a pressure tank (1) according to one of the preceding claims, comprising at least one liner (3) and one boss (4), wherein for sealing a bushing (7, 7') connected to the boss (4) via a screw thread (12), a pressure ring (8, 8') and a spring element (9) are provided, designed such that the spring element (9) is supported on the bushing (7, 7') and presses the pressure ring (8, 8') against the liner (3) and thereby presses the liner (3) against the boss (4) in a pressure area (13), characterized by , that the pressure ring (8,8') is connected to the boss (4) in a rotationally fixed manner via a toothed connection (10,10'). [13] Precursor for the manufacture of a pressure tank (1) according to claim 12 characterized by , that the toothing between pressure ring (8,8') and boss (4) is suitable and designed to absorb the circumferential forces that occur when winding a reinforcing layer (6) onto the liner (3) between boss (4) and liner (3).

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