Pressure tank for gas-driven vehicle and method for producing pressure tank or preform of pressure tank

Abstract

The invention relates to a pressure tank for installation in a gas-driven vehicle for storing gas and to a method for producing a pressure tank or a preform of a pressure tank, the pressure tank having a rotationally symmetrical, longitudinally extending shape which is cylindrical in the middle region and which is closed at both ends with curved pole caps, the pressure tank has a tank wall, which encloses a cavity for storing gas, and a metal coupling, so-called boss, on each pole cap, the tank wall comprising a reinforcement layer made of a fiber-reinforced plastic and an inner sealing gasket, and wherein the pressure tank has a hollow space for storing gas, and a metal coupling, so-called boss, on each pole cap, and wherein the pressure tank has a hollow space for storing gas, and wherein the pressure tank has a hollow space for storing gas, and a metal coupling, so-called boss, on each pole cap. According to the invention, there is a bushing which is connected to the boss part, the pressure ring and the spring element for sealing in such a way that the spring element is supported on the bushing and the pressure ring is pressed onto the gasket and thus the gasket is pressed in the region on the boss part.

Description

[0001] The present application is a divisional application of the Chinese Invention Patent Application No. 202180085132.7, which is a national phase of the PCT Application No. PCT / EP2021 / 085836, entered into the Chinese National Phase on June 16, 2023, entitled “Pressure tank for a gas-driven vehicle”, which claims priority to the U.S. Provisional Patent Application No. 63 / 127, 1 10, filed December 15, 2021. TECHNICAL FIELD

[0002] The present invention relates to a pressure tank for installation in a gas-driven vehicle for storing gas and to a method for manufacturing a pressure tank or a preform of a pressure tank, wherein the pressure tank has a rotationally symmetrical, elongate shape which is cylindrical in a central region and is closed at both end portions by domed pole caps. The pressure tank has a vessel wall which encloses a cavity for storing gas and, on each pole cap, has a metal coupling, a so-called boss, wherein the vessel wall comprises a reinforcement layer made of fiber-reinforced plastic and, inside, a liner for sealing.

[0003] Furthermore, the present invention also relates to a method for manufacturing such a pressure tank or a preform of such a pressure tank, wherein the liner is manufactured in a blow molding process for building up the vessel wall of the pressure tank, which encloses a cavity for storing gas. BACKGROUND

[0004] Gas-driven vehicles have, for example, a gas engine or a fuel cell with an electric motor as drive device. In order to be able to store sufficient fuel, the gas, which can be hydrogen, among other things, is stored at high pressure in a tank. The typical pressure of such a pressure tank exceeds 200 bar, often amounts to 600 bar and sometimes even to 700 bar or 800 bar. This means that the pressure tank must not only be gastight at this pressure, but also needs to have a high mechanical stability.

[0005] In the prior art, pressure tanks for gas-driven vehicles are known. These pressure tanks have a vessel wall which comprises, for example, a liner inside for sealing made of thermoplastic plastic and a reinforcement layer made of fiber-reinforced plastic for providing mechanical stability. Preferably, the reinforcement layer is wound and implemented as a CFK layer. CFK means carbon fiber-reinforced plastic.

[0006] The bosses have a through-hole and a coupling thread. In at least one of the two bosses, a tank fitting is coupled which enables the pressure tank to be filled or to be tapped for gas in a controlled manner. On the other boss, the through-hole is sealed with a closure or there is provided a further tank fitting or a safety valve.

[0007] Particular attention must be paid to the junction between the metal coupling, the boss and the gasket in such pressure tanks, since particularly good sealing is required here, even under mechanical loading, in the event of changes in the internal pressure or in the event of large temperature fluctuations. It would be a great challenge, in particular in the case of hydrogen tanks.

[0008] A pressure tank having the features mentioned above is described in DE 102 014 009 343 A1. In order to improve the sealing, a clamping sleeve is provided in this document between the reinforcement layer and the gasket. The clamping sleeve should transmit external loads acting via the boss to the reinforcement layer and thus protect the gasket from overloading, which could lead to leaks.

[0009] DE 102 010 021 667 A1 provides a sealing ring between the boss and the gasket, which should ensure the sealing. In DE 102 016 219 638 A1, the sealing ring is pressed into the gap between the boss and the gasket by a locking sleeve in order to achieve a tight seal between the gasket and the boss.

[0010] However, the embodiments according to the prior art have the disadvantage that they do not function well enough with respect to changing loads due to temperature fluctuations or due to changing pressure loads and thus also do not ensure a long-term stable tightness.

[0011] However, a good and lasting tightness is of particular importance for larger pressure tanks, in particular for hydrogen for example for fuel cell driven commercial vehicles. Such pressure tanks can have a diameter of up to 600 mm and a length of 2500 mm. The known concepts for the tightness are not sufficient. SUMMARY

[0012] It is now the task of the present invention to develop a pressure tank which has a better sealing and a long service life and a low amount of leakage and to show a method which can simply and reliably produce such a pressure tank.

[0013] This task is solved in accordance with the invention by a pressure tank according to claim 1. Further advantageous features are mentioned in the respective dependent claims.

[0014] According to the invention, the pressure tank according to claim 1 is characterized in that there is a bush connected with the boss, a pressure ring and a spring element for the tightness, which is designed in such a way that the spring element bears on the bush and presses the pressure ring onto the gasket and thereby presses the gasket in the region on the boss. This region is planar and is preferably configured as an annular face.

[0015] The main advantage according to the embodiments of the application is that due to the spring element and due to the two-piece embodiment with the bushing and the pressure ring, a pre-tension can be exerted on the sealing surface between the gasket and the boss for the tightness. This sealing surface is in the region where the gasket is pushed onto the boss. Based on the pre-tension produced in this way, sufficient tightness is provided, for example, even in the case of low internal pressure or in the case of expansion due to temperature differences. By coordinated adjustment of the spring force, it is also possible to avoid excessive compression of the gasket and thus deformation leading to leaks.

[0016] The spring element here refers to an element which, when compressed, can exert sufficient elastic spring force. For example, the spring element can be embodied as a ring element made of spring steel which has 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 formed by a plurality of leaf springs or coil springs which are arranged between the bushing and the pressure ring. Other types and shapes of springs can also be used here. In particular, the spring element can be embodied as a so-called disc spring. The disc spring can have one or a plurality of spring discs. In particular, the spring strength can be adjusted by the number of disc springs arranged one behind the other.

[0017] For example, elastic polymers (elastomers or cross-linked thermoplastics) can be used as further spring material or spring elements made of fiber composite plastic.

[0018] It is particularly advantageous if the spring element is embodied in such a way that it has a direction (in which the spring force for the pushing acts) which forms an angle of at most + / - 20° with the longitudinal axis L of the pressure tank and which is oriented in particular substantially parallel to the longitudinal axis L. Such an orientation provides the possibility of being able to adjust and change the spring pre-tension from the outside through the central hole of the boss. Furthermore, this offers advantages when assembling.

[0019] In a further preferred embodiment, the face of the pressure ring which comes into contact with the gasket forms an angle of 70° to 110° with the longitudinal axis L and is oriented in particular substantially perpendicular to the longitudinal axis L. This is also advantageous for the assembly and the adjustability.

[0020] Preferably, the bushing is arranged in such a way that it does not come into face contact with the gasket. The compression for the tightness is only transmitted via the face of the pressure ring.

[0021] It is advantageous for the function to be permanently ensured that the pressure ring and the bushing together completely enclose the spring element. The spring element is thus protected and held in the desired position. In addition, this embodiment also offers easier assembly. Furthermore, these advantages have a positive effect when the gasket is produced in a blow-molding process. In this sense, it also belongs to the complete enclosure when there are still individual openings or gaps. This does not have to be a complete encapsulation.

[0022] Furthermore, the pressure ring is preferably embodied in its contour toward the spring element in such a way that the spring element lies positively on the contour. Thus, with the large contact surface between the spring element and the pressure ring, this ensures that the force is uniformly transmitted to the sealing surface.

[0023] In a preferred variant, the bushing is fastened on the boss via a helical thread, in particular so that the force with which the pressure ring is pushed can thereby be varied. Thus, the bushing can have, for example, an outer thread which engages with an inner thread on the boss. By screwing the bushing into the boss at different depths, the spring between the bushing and the pressure ring can be compressed to different degrees. The pre-tension can thus be adjusted purposefully.

[0024] Alternatively, the bushing can be fastened on the boss via a clamping portion. The clamping portion must be embodied here in such a way that it does not loosen as a result of the spring force.

[0025] Furthermore, the bushing can have a flange on which the spring element rests, wherein the flange is arranged essentially perpendicular to the longitudinal axis L of the pressure pot. Thus, good mountability and good force transmission can be achieved.

[0026] In an advantageous embodiment, the boss has an outer thread which comes into contact with the gasket. Thus, a good mechanical connection between the gasket and the boss is created, which offers good stability when the reinforcement layer is produced. The reinforcement layer is usually produced in a winding process, in which high radial forces occur.

[0027] In order to produce sufficient sealing surface between the gasket and the boss, it is advantageous that the face of the pressure ring which is pressed onto the gasket extends in the radial direction R by at least 20 mm, preferably by at least 30 mm. An upper limit of at most 100 mm is meaningful in order not to require too much installation space.

[0028] When the boss has a bulge on the face of the boss onto which the gasket is pressed by the pressure ring, the tightness of the pressure tank can be further improved. This region of the boss is also referred to as the sealing face. The bulge is preferably embodied as a concentric ring around the longitudinal axis L. When the pressure ring is pressed onto the gasket by the spring element, the bulge on the boss is pressed into the gasket on the side opposite the pressure ring. The tightness between the gasket and the boss is thereby significantly improved. This improvement is particularly effective in the case of a low internal pressure in the pressure tank. The pressure tank can thus be evacuated to a low pressure level without the risk of leakage.

[0029] The bulge is only a few tenths of a millimeter high, preferably between 0.3 mm and 1.5 mm, particularly preferably between 0.5 mm and 1 mm. The bulge thus presses slightly into the gasket, but does not damage the gasket or even create cracks. The bulge can for example have a semicircular or triangular or similar cross section.

[0030] The tightness can also be improved in that the boss has a groove in which a sealing ring is arranged, wherein the groove is arranged in such a way that the sealing ring comes into contact with the gasket. In addition, the groove is located in the region of the boss onto which the gasket is pressed by the pressure ring. The gasket is thus also pressed onto the sealing ring by the pressure ring. The sealing ring can thus compensate for small positional changes in the gasket without reducing the tightness. In addition to the use of a sealing ring, a support ring can preferably also be used. Due to the internal pressure of the container and the spring pretension, the gasket is pressed tightly against the support ring and ensures that no gap arises between the two. The sealing ring can thus not be pressed into the gap between the gasket and the boss.

[0031] In order to build up the pretension well and to achieve a good tightness, the pressure ring can be moved relative to the bushing in the direction of the longitudinal axis L, so that the pressure ring can be embodied more robustly, so that a uniform pressing on the face is achieved and thus a reliable tightness is achieved.

[0032] The embodiment is further improved when the pressure ring has a stop and / or the bushing has a stop, which are designed in such a way that a rigid force transmission in the direction of the longitudinal axis L between the pressure ring and the bushing is possible via the fully compressed spring element. Fully compressed is understood here to mean that the spring element is compressed to such an extent that a rigid force transmission via the spring element takes place, instead of an elastic force transmission by means of the spring force.

[0033] In order to be able to exert a greater pressing force between the gasket and the boss than the spring element is able to exert, the screw joint between the boss and the bushing can thus be tensioned, so that the force is transmitted from the bushing to the pressure ring by means of the stop.

[0034] Advantages are provided in particular when the boss part has a bulge which is to be pressed into the gasket. Thus, a higher pressing force can be generated when the boss part is assembled to the bushing, whereby the bulge is pressed well into the gasket. For example, up to 40 kN of pressing force can be applied by the screw joint, whereas a Belleville spring used as spring element has for example only a return force of 5 kN. Subsequently, in the operation of the pressure tank, too high a pressing force is disadvantageous, since the gasket material flows and is pressed out of the area of the thrust face. Thus, the spring force cannot be chosen to be very high. The initially occurring flow of the gasket material after assembly ensures that a small gap is generated between the stop and the respective mating face and thus reduces the pressing force to the value of the spring force in operation. This value is designed in such a way that the gasket can permanently withstand this value. Due to the increase in the pressing force acting at the time of assembly, the bulge on the boss part is pressed well into the gasket and an improved sealing is ensured.

[0035] Furthermore, the rigid force transmission between the bushing and the pressure ring can be advantageous even during the blow molding in order to keep the components in the desired positioning.

[0036] On the other hand, this task is also solved by the method according to claim 12 for producing the above-mentioned pressure tank according to the application or a preform of such a pressure tank. Further advantageous features are mentioned in the respective dependent method claims.

[0037] The method is characterized in that the bushing, which can be connected to the boss part, the pressure ring and the spring element are arranged on a so-called blow core, and the gasket is produced in a blow molding process, so that after the gasket has been produced, the pressure ring and the spring element are located on the inside of the gasket, wherein, when the bushing is connected to the boss part, the spring element can be supported on the bushing and can press the pressure ring onto the gasket, and can press the gasket onto the face of the boss part.

[0038] In the blow molding process, plastic for the gasket is extruded from a nozzle, so that a hose is first generated. Then, two or more parts of a blow mold are brought together, so that a mold cavity in the form of the gasket to be formed for the pressure tank is formed. The extruded hose is located in this mold cavity. A gas is blown via a so-called blow core, a throughpiece, into the hose, whereby the hose is pressed against the inside of the blow mold. Thus, the gasket of the desired shape is obtained. After the plastic material has solidified, the gasket can be demolded. The blow core is removed. Preferably, the gasket is made of a thermoplastic plastic material, for example polyamide. The thermoplastic plastic solidifies after cooling.

[0039] By carrying out the method according to the application, the bushing, the pressure ring and the spring element are already introduced into the gasket in the desired position inside the gasket when the gasket is manufactured, so that they can then be connected with the boss and can assume the function according to the application for improving the sealing. The pressure ring and the spring element are located on the inside of the gasket after the gasket has been manufactured, wherein, when the bushing is connected with the boss, the spring element can be supported on the bushing and the pressure ring can be pressed onto the gasket and the gasket can be pressed onto the face of the boss.

[0040] In particular larger pressure tanks have boss parts on both pole covers. Therefore, it is particularly preferred that a bushing, a pressure ring and a spring element are provided on both pole covers of the pressure tank in each case in the above-described type in order to improve the sealing between the gasket and the respective boss.

[0041] In the method according to the application, the second bushing, the second pressure ring and the second spring element can be arranged on the carrier or on the blow mold, while the gasket is manufactured in a blow molding process, so that, after the gasket has been manufactured, the second pressure ring and the second spring element are also located on the inside of the gasket, wherein, when the second bushing is connected with the second boss, the second spring element can be supported on the second bushing and the second pressure ring can be pressed onto the gasket and the gasket can be pressed onto the face of the second boss.

[0042] In order to produce a stable connection between the boss and the gasket, the respective boss preferably has an outer thread, which engages with a corresponding inner thread in the gasket. The inner thread in the gasket is preferably produced in a machining manner, for example by milling, after ejection from the blow mold. Thereby, it is prevented that the boss has to be cut into the surface when being screwed into the gasket and thus damages the gasket. Thus, a stable connection between the boss and the gasket is achieved, which can also withstand high loads in the manufacture of the reinforcement layer, in particular during winding. Furthermore, with such a thread, a positioning of the screwing on the gasket is achieved which is precise and repeatable, so that the two components are always positioned identically to each other.

[0043] It is furthermore advantageous if the boss is equipped with a left-handed thread as outer thread and the second boss is equipped with a right-handed thread as outer thread, wherein the gasket has a correspondingly matching thread on each side. Thereby, it is made possible that the two boss-gasket connections can absorb higher rotational forces in a common direction of rotation and thus better protect against being unscrewed in the subsequent winding process.

[0044] Furthermore, the pressure ring can be moved relative to the bushing during blow molding in the direction of the longitudinal axis L, so that it completely compresses the spring element, so that a rigid force transmission between the bushing and the pressure ring can be achieved via the spring element and in particular via a stop on the pressure ring and / or a stop on the bushing.

[0045] In a further method step, the boss piece is connected with the gasket and the bushing, wherein the connection between the boss piece and the bushing is effected by screwing the boss piece onto the outer thread of the bushing. The boss piece is screwed onto the bushing in such a way that the pressure ring is moved in the direction of the longitudinal axis L relative to the bushing and the pressure ring completely compresses the spring element until a rigid force transmission between the bushing and the pressure ring can be achieved via the spring element and in particular via a stop on the pressure ring and / or a stop on the bushing. The advantages of this procedure when fitting the boss piece have already been described above.

[0046] In yet another method step, a prepreg made of a fiber-reinforced plastic, in particular made of CFK (carbon fiber-reinforced plastic), is wound around the prepreg made of the gasket and the boss piece for forming a reinforcement layer of the pressure tank. These tapes are preferably already impregnated with a matching plastic resin (so-called tows) and the plastic resin is cured after winding. BRIEF DESCRIPTION OF DRAWINGS

[0047] Further advantageous features of the application are explained in connection with the embodiments with reference to the drawings. The features mentioned can advantageously be implemented not only in the combination shown, but also in individual combinations with one another. The drawings show in detail:

[0048] Figure 1 a schematic view of a pressure tank according to the application is shown;

[0049] Figure 2a a detailed section of the connection between the boss piece and the wall in an embodiment according to the application is shown;

[0050] Figure 2b a detailed section of the connection between the boss piece and the wall in a further embodiment according to the application is shown;

[0051] Figure 3a , 3b , 3c a section of a different embodiment according to the application for sealing between the boss piece and the wall is shown;

[0052] Figure 3d a section of a further embodiment according to the application for sealing between the boss piece and the gasket during operation of the pressure tank is shown;

[0053] Figure 3e a section of a further embodiment according to the application for sealing between the boss piece and the gasket during fitting of the boss piece is shown;

[0054] Figure 4a a section of an arrangement for manufacturing a pressure tank or a prepreg thereof according to the application is shown;

[0055] Figure 4bshows a section of a preform for manufacturing a pressure tank according to the application after assembly of the boss piece;

[0056] Figure 5 shows a detailed section of the connection between the boss piece and the wall of the vessel in a further embodiment according to the application;

[0057] Figure 6a shows a section of a further embodiment according to the application for sealing the boss piece during operation of the pressure tank;

[0058] Figure 6b shows a section of a further embodiment according to the application for sealing between the boss piece and the liner during assembly of the boss piece.

[0059] The drawings will be described in more detail below. Identical reference signs denote identical or similar components or parts. DETAILED DESCRIPTION

[0060] Figure 1 A pressure tank 1 is shown, which has one boss piece 4, 4' each on the pole cover. A tank fitting 5 for filling gas and for controlled tapping of gas is screwed into the boss piece 4. The boss piece 4' is sealed with a closure. Alternatively, the boss piece can accommodate a safety valve. The wall of the pressure tank 1 encloses a cavity 2 and is formed by a liner 3 located inside and a reinforcement layer 6. The liner 3 is preferably made of thermoplastic, such as polyamide, and is produced in a blow-molding process in the method according to the application. The reinforcement layer 6 is produced by a winding process with a tape of fiber-reinforced plastic, preferably of CFK. The pressure tank 1 is rotationally symmetrical about a longitudinal axis L. In such a pressure tank, particular attention must be paid to the sealing between the boss piece 4, 4' and the liner 3. Good sealing is a difficult challenge, especially in large pressure tanks as required in commercial vehicles in order to be able to achieve sufficient range.

[0061] Figure 2a and Figure 2b A section B of the pressure tank 1 is shown in an enlarged manner, so that the embodiments according to the application for improving the sealing can be seen. Two different embodiments are shown in the figures.

[0062] In the interior of the gasket 3, i.e. in the cavity 2, there is a pressure ring 8 and a spring element 9. The spring element 9 is pre-tensioned via a bushing 7 connected with the boss 4 and presses the pressure ring 8 against the gasket 3 and thus the gasket 3 against the boss 4. The connection between the boss 4 and the bushing 7 is established via a screw joint 12, wherein there is a corresponding external thread on the bushing 7. The gasket 3 is pressed onto the boss only via the pressure ring 8. This pressure ring 8 is movable relative to the bushing 7 and can be moved in the direction of the longitudinal axis L. Together they enclose the spring element 9, which is thus well protected. Furthermore, the components are well assembled thereby. For this purpose, a special tool is used, which can be introduced through the central hole of the boss 4. In the embodiment according to Figure 2a In the embodiment according to

[0063] In the embodiment according to Figure 2b The pressure ring 8 has a flange 23 on the side facing the gasket 3. In this embodiment, the spring element 9 is configured as a disc spring. A disc spring with two spring discs is shown in the figures; it is also possible to provide only one spring disc or more spring discs. With the thickness, the material and the number, the spring force can be adjusted to the desired extent. The pressure ring 8 is preferably shaped on the side against which the spring element 9 lies, so that a good force transmission is possible. In addition, the pressure ring 8 has a stop 22, which lies against the bushing 7 in the case of a fully compressed spring element 9. And the bushing 7 has a stop 21, which lies against the pressure ring 8 when the spring element 7 is fully compressed. Thus, a rigid force transmission between the pressure ring 8 and the bushing 7 can be established, which is advantageous for the assembly of the boss or during the blow molding of the gasket.

[0064] For this embodiment according to the application, a spring element different from that shown in the example here can also be used.

[0065] The face of the pressure ring 8, which is pressed against the gasket 3, and the face of the gasket 3, which is pressed against the boss 4, are oriented essentially perpendicular to the longitudinal axis L. Likewise, the flange of the bushing 7, which supports the spring element 9, is arranged essentially perpendicular to the longitudinal axis L. Thus, by means of the screw joint 12, the spring force of the spring element 9 is completely transmitted via the pressure ring 8 to the sealing face between the boss 4 and the gasket 3. With a tilting of these faces of at most + / - 20°, a sufficient force transmission can still always be achieved. Furthermore, a tilting of the sealing face facilitates better venting of the sealing flange during gasket manufacture. With the tilting, the gas can better escape from the pinch point when the mold halves come together.

[0066] The area of the boss 4 in which the pressure ring 8 presses the gasket 3 against the boss 4 is referred to as the sealing face or choke point. The sealing is achieved by the gasket 3 being pressed against the boss 4 as a result of the spring force of the spring element 9 and as a result of the gas internal pressure itself, which is throttled in turn.

[0067] The gasket 3 is fastened to the boss 4 via the thread 10. There is an external thread 10 on the boss and an internal thread 10 on the gasket. The internal thread 10 on the gasket is correspondingly machined.

[0068] Furthermore, there is an internal thread 11 on the boss 4 via which a tank fitting, a safety valve or a closure can be screwed in.

[0069] In the following Figures 3a-3c a section A is shown. These drawings show further embodiments of how the area of the boss in which the gasket 3 is pressed against the boss 4 by the pressure ring 8 can be advantageously implemented.

[0070] In this area, instead of a smooth face, the boss 4 has a ridge 13 (Fig. 1) which is pressed into the surface of the gasket 3 and improves the sealing effect. Figure 3a and Figure 3b In this case, the ridge 13 is implemented as a concentric ring on the face and is only a few tenths of a millimetre high, preferably between 0.3 mm and 1.5 mm, particularly preferably between 0.5 mm and 1 mm. The ridge 13 is pressed into the surface of the gasket 13 and improves the sealing effect. The ridge is implemented with a rounded or semicircular cross section in one variant and with a triangular cross section in another variant. Other shapes are also possible.

[0071] Figure 3c A further variant for improving the sealing is shown. This further variant can also be used in combination with the ridge. Here, a sealing ring 15, for example an O-ring, is placed in a groove 14 on the boss. The groove 14 is preferably located in the area of the boss 4 in which the gasket 3 is pressed by the pressure ring 8. However, the groove can also be provided outside this area. In order to prevent the sealing ring 15 from being pressed into the gap between the boss 4 and the gasket 3 under greater loads, a support ring 16 can be provided. The gas internal pressure in the pressure tank and the pressing by the spring element 9 ensure that the gasket 3 lies evenly and very well sealed against the support ring 16.

[0072] Further variants are shown in the following Figure 3d and Figure 3e for section A. These drawings show the arrangement when the pressure tank is in operation in Figure 3d and in Figure 3eThe image shows the assembled boss 4, which is performed after the gasket is blow-molded.

[0073] The raised portion 13, which is not shown in Figure 2 for clarity, is shown in an enlarged manner. The raised portion 13 exists on the surface of the boss 4, against which the gasket 3 is pressed by the pressure ring 8. The raised portion 13 is not to scale because it would otherwise be invisible. In this case, the raised portion 13 is implemented in concentric rings on the surface and is only a fraction of a millimeter high, preferably between 0.3 mm and 1.5 mm, particularly preferably between 0.5 mm and 1 mm. The raised portion 13 is pressed into the surface of the gasket 13 and improves the sealing effect. For example, the raised portion can be implemented with a rounded, semi-circular, or triangular cross-section. Other shapes are also possible. In operation, such as Figure 3a As shown, gaps exist between the stops 21 and 22 and their respective mating surfaces on the pressure rings or bushings. The compression of the gasket 3 by the pressure ring 8, and consequently the boss 4, corresponds to a spring force of, for example, on the order of 5 kN from the spring element 9. The gap width may vary slightly depending on the filling pressure and temperature.

[0074] exist Figure 3e In this configuration, there is no gap between the stops 21 and 22 and their respective mating surfaces. The boss 4 is tightened onto the bushing 7, or the bushing 7 is tightened into the boss 4, such that it contacts the stops 21 and 22, allowing the compressive force to be increased via the screw joint. Therefore, a pressure up to 40 kN can be applied to press the protrusion 13 well into the gasket 3 during assembly. Under this high pressure and during subsequent pressure testing, the gasket material flows slightly, causing the gasket 3 to be pressed out from the compression area between the boss 4 and the pressure ring 8, and the gasket 3 becomes slightly thinner in this area. This continues until gaps appear between the stops 21 and 22 and their respective mating surfaces, thereby reducing the compressive force to the level of the spring force of the spring element 9. Thus, [the pressure is reduced to -the required level]. Figure 3a The state shown.

[0075] Further variations for improving the seal are not shown. These variations can also be used in conjunction with a raised portion. Here, a sealing ring, such as an O-ring, is inserted into a groove on the boss. The groove is preferably located in the area of ​​the boss 4 where the gasket 3 is pressed by the pressure ring 8. However, the groove can also be located outside this area. To prevent the sealing ring from being pressed into the gap between the boss 4 and the gasket 3 under greater loads, a support ring can be provided. The internal gas pressure in the pressure vessel and the compression by the spring element 9 ensure that the gasket 3 is uniformly and well-sealed against the support ring.

[0076] To illustrate the method for manufacturing a pressure vessel according to the present invention, Figure 4a andFigure 4b A sectional view is likewise shown. Figure 4a The arrangement during the manufacture of the gasket is shown in the middle. The gasket 7 with the pressure ring 8 and the spring element 9 is assembled on the blow mandrel 17. The blow mold 18, which is two-part or multi-part, presses the gasket material onto the blow mandrel 17 and onto the gasket 7 and the pressure ring 8 when closed. The gasket material, preferably a thermoplastic, is extruded beforehand from a nozzle as a hose. If the blow mold is closed, gas is blown in via the blow mandrel, which functions as a through-opening, so that the gasket material is pressed in blow-molded fashion and the desired shape of the gasket 3 is generated. After solidification, the blow mold is opened and the gasket 3 is removed. The pressure ring 8 and the spring element 9 are then on the inside of the gasket 3 in the cavity 2, and the gasket 7 is arranged so that it can subsequently be connected to the boss 4. To this end, a portion 3a of the gasket 3 is removed in order to expose the external thread on the gasket 7. Additionally, the gasket 3 can also be further processed. For example, a thread can be cut or milled in the surface of the gasket 3 for connection to the external thread on the boss.

[0077] In order to also be able to fasten the second boss on the opposite pole cap of a pressure tank with a gasket according to an embodiment of the application for sealing, a second gasket, a second pressure ring and a second spring element can be introduced during manufacture. To this end, the second gasket, the second pressure ring and the second spring are positioned on the side of the holder or blow mold opposite the blow mandrel 17, so that they are likewise arranged in the interior during the manufacture of the gasket, similarly to the components on the blow mandrel 17. The boss is then also connected to this side in correspondence with the second gasket.

[0078] The embodiment according to the variant of the application according to Figure 2b or Figure 6a / b is not shown, but is likewise advantageous. In blow molding, the pressure ring 8 can compress the spring element 9; 9' here, so that the arrangement is rigidly fixed and remains in the desired position during blow molding. In the embodiment according to Figure 2b , the abutment 21 and 22 are brought to bear on the respective mating surfaces on the pressure ring or gasket by compression of the spring element 9. In the embodiment according to Figure 6a / b, the spring element 9' is completely compressed, so that the abutments 24 and 25 are provided with a rigid force transmission via the spring element 9'.

[0079] Figure 4b A sectional view is shown after the boss 4 has been screwed onto the gasket 7. By screwing, the spring element 9 is compressed and the pressure ring 8 is pressed onto the gasket 3 and the gasket is pressed onto the boss 4. The resulting pretension can be adjusted via the screw-in depth and via the spring stiffness of the spring element 9.

[0080] The elevations on the boss piece 4 in the region of the sealing surface are pressed into the surface of the gasket 3 and thus improve the sealing. The elevations are embodied here as concentric rings with a rounded cross section.

[0081] not shown according to Figure 2b or Figure 6a Variants of the / b can also offer advantages here. As already mentioned, in these variants the spring element 9, 9' can be compressed so that the grommet 7 and the pressure ring 8 can achieve a rigid force transmission independently of the elasticity of the spring element.

[0082] The shaped gasket 3 with the two screwed-on boss pieces 4 is a preform for the further manufacture of a pressure tank. In a further method step, this preform is wound with a tape made of fiber-reinforced plastic in order to form a reinforcement layer of the tank wall. After the winding, the fiber-reinforced plastic is hardened. Preferably, for this purpose a CFK tape impregnated with a suitable resin is used.

[0083] Figure 5 A section B of the pressure tank 1 is shown again in an enlarged manner, but for a further embodiment according to the application for improving the sealing. The pressure ring 8' and the spring element 9' are located in the interior of the gasket 3, i.e. in the cavity 2. Via the grommet 7' connected with the boss piece 4, the spring element 9' is pretensioned and the pressure ring 8' is pressed onto the gasket 3 and thus the gasket 3 is pressed onto the boss piece 4. The connection between the boss piece 4 and the grommet 7' is established via a screw joint 12, wherein a corresponding outer thread is present on the grommet 7'. The gasket 3 is pressed onto the boss piece only via the pressure ring 8'. This pressure ring 8' is movable relative to the grommet 7' and can be moved in the direction of the longitudinal axis L. The pressure ring 8' is guided on the grommet 7' via its inner diameter. In this embodiment, the pressure ring 8' and the grommet 7' can be embodied very slim and save in structure space.

[0084] The pressure ring 8 has a flange 23 on the side facing the gasket 3.

[0085] In this embodiment, the spring element 9' is configured as a disc spring. A disc spring with four spring discs is shown in the figure, it is also possible to provide only one spring disc or more spring discs. With the thickness, the material and the number, the spring force can be adjusted to the desired extent.

[0086] The face of the pressure ring 8' that is pressed onto the gasket 3 and the face of the gasket 3 that is pressed onto the boss 4 are oriented substantially perpendicular to the longitudinal axis L. Likewise, the flange of the bushing 7' that supports the spring element 9' is also arranged substantially perpendicular to the longitudinal axis L. Thus, by means of the screw joint 12, the spring force of the spring element 9' is completely transmitted via the pressure ring 8 to the sealing face between the boss 4 and the gasket 3. By means of a tilting of these surfaces of up to + / - 20°, sufficient force transmission can still always be achieved. In addition, a tilting of the sealing face facilitates better venting of the sealing flange during gasket manufacture. By means of the tilting, better escape of gas from the calking point can be achieved when the mold halves are brought together.

[0087] The region of the boss 4 in which the pressure ring 8' presses the gasket 3 onto the boss 4 is referred to as the sealing face or choke point. Due to the spring force of the spring element 9' and due to the gas internal pressure itself, a tightness is achieved by pressing the gasket 3 onto the boss 4, which in turn achieves a choking of the gas internal pressure in the pressure tank.

[0088] Preferably, the pressure ring 8' is shaped on the side on which the spring element 9' rests, such that a good force transmission is possible. In particular, a stop 24 can be provided on the pressure ring on which the spring element 9' rests.

[0089] For the embodiments according to the application, it is also possible to use spring elements that differ from those shown in the example here.

[0090] The gasket 3 is fastened on the boss 4 via the thread 10. There is an external thread 10 on the boss, and an internal thread 10 on the gasket. The internal thread 10 on the gasket is machined accordingly.

[0091] In addition, there is an internal thread 11 on the boss 4, via which a tank fitting, a safety valve or a closure can be screwed in.

[0092] In the following Figure 6a and 6b a section A' is shown. These figures show the arrangement of the pressure tank in operation in Figure 6a and in Figure 6b after assembly of the boss 4, which is carried out after the gasket has been made by blow molding. Further details are similar to the description of the figures of the above Figure 3a and Figure 3b .

[0093] The main difference of the variant shown here is that the bushing 7' and in particular the pressure ring 8' is implemented more slender and more space-saving. This is a great advantage in applications that strive for a small structural space and a weight that is as small as possible.

[0094] Figure 6aIt is shown that, in operation, the compression between the pressure ring 8' and the gasket 3 is achieved via the spring element 9', which is supported on the flange of the bushing 7'. There is a clearance between the stop 25 on the bushing and the spring element 9'. The bushing 7' is connected to the boss 4 via an external thread 12, which is not completely shown. Depending on the number and selection of the spring discs of the spring element 9' and depending on the spacing between the pressure ring 8' and the bushing 7', the pressure acting on the gasket 3 can be adjusted.

[0095] In Figure 6b which the spring element 9' is completely compressed, so that a rigid force transmission from the bushing 7' to the pressure ring 8' is achieved. In the embodiment shown, this is achieved in that the stop 25 of the bushing presses via the spring element 9' onto the stop 24 of the pressure ring 8'. In order to achieve this, the boss 4 is screwed onto the bushing 7' or the bushing 7' is screwed into the boss 4, so that the stops 24, 25 press the spring element 9' together completely and enable a rigid force transmission via the spring element 9' without elastic influence. Thus, as already mentioned, a high pressure can be applied in order to press the ridge 13 well into the gasket 3 when assembling. In the case of this high pressure and during the subsequent pressure test, the gasket material flows slightly and the gasket 3 is pressed out of the compression area between the boss 4 and the pressure ring 8', in which area the gasket 3 becomes slightly thinner. This continues until a clearance between the spring element and the stop 25 occurs and thus the compression is reduced to the level of the spring force of the spring element 9. Thus, the state shown in Figure 6a is reached.

[0096] Furthermore, in this embodiment, the contact surface between the pressure ring 8' and the gasket 3 for the sealing is implemented obliquely with respect to the direction perpendicular to the longitudinal axis L. In particular, an obliquity of up to 20° is advantageous. Possible air pockets between the gasket 3 and the pressure ring 8' can be pressed radially out of the sealing surface when screwing into the boss 4 by the oblique position. This facilitates a reliable assembly.

[0097] A further variant for improving the sealing is not shown. This further variant can also be used in combination with the ridge. Here, a sealing ring, for example an O-ring, is placed into a groove on the boss. The groove is preferably located in the area of the boss 4, in which the gasket 3 is pressed by the pressure ring 8'. However, the groove can also be provided outside this area. In order to prevent the sealing ring from being pressed into the gap between the boss 4 and the gasket 3 under greater load, a support ring can be provided. The gas internal pressure in the pressure tank and the compression by the spring element 9 ensure that the gasket 3 lies evenly and well sealed against the support ring.

[0098] List of reference signs

[0099] 1 pressure tank

[0100] 2 cavity

[0101] 3 spacer

[0102] 3a part of the spacer

[0103] 4, 4' boss

[0104] 5 can fitting

[0105] 6 reinforcement layer

[0106] 7, 7' bushing

[0107] 8, 8' pressure ring

[0108] 9, 9' spring element

[0109] 10 external thread

[0110] 11 internal thread

[0111] 12 helical thread

[0112] 13 bulge

[0113] 14 recess

[0114] 15 sealing ring

[0115] 16 support ring

[0116] 17 blow-mold mandrel

[0117] 18 blow-mold

[0118] 21 stop on the bushing

[0119] 22 stop on the pressure ring

[0120] 23 flange on the pressure ring

[0121] 24 stop on the pressure ring

[0122] 25 stop on the bushing

[0123] L longitudinal axis of the pressure tank

[0124] R radial direction of the pressure tank

Claims

1. A pressure vessel (1) for installation in a gas-driven vehicle to store gas, the pressure vessel having a rotationally symmetrical, elongated shape, the shape being cylindrical in the central region and closed at both ends with arched end caps, the pressure vessel having a vessel wall and a metal fitting, i.e., a so-called boss (4, 4'), on each end cap, the vessel wall surrounding a cavity (2) for storing gas, wherein, The vessel wall comprises a reinforcing layer (6) made of fiber-reinforced plastic and an inner liner (3) for sealing. Its features are, A bushing (7, 7'), a pressure ring (8, 8'), and a spring element (9, 9') connected to the boss (4, 4') are provided for sealing, and are designed such that the spring element (9, 9') is supported on the bushing (7, 7') and the pressure ring (8, 8') is pressed against the gasket (3), thereby pressing it against the boss (4, 4') in the region, wherein the bushing (7, 7') has a flange supporting the spring element (9, 9'), wherein the flange is arranged substantially perpendicular to the longitudinal axis L of the pressure vessel.

2. The pressure vessel (1) according to claim 1. Its features are, The spring elements (9, 9') are implemented such that the direction of the spring force acting on the spring element for pushing forms an angle of at most + / -20° with the longitudinal axis L of the pressure vessel, and in particular, the direction is substantially parallel to the longitudinal axis L.

3. The pressure vessel (1) according to any one of claims 1 or 2. Its features are, The surfaces of the pressure rings (8, 8') that contact the pads (3) form an angle of 70° to 110° with the longitudinal axis L, and in particular, the surfaces are oriented substantially perpendicular to the longitudinal axis L.

4. The pressure vessel (1) according to any one of the preceding claims Its features are, The pressure ring (8) together with the bushing (7) completely surrounds the spring element (9).

5. The pressure vessel (1) according to any one of the preceding claims. Its features are, The spring elements (9, 9') are implemented as so-called disc springs.

6. The pressure vessel (1) according to any one of the preceding claims. Its features are, The bushings (7, 7') are fastened to the bosses (4, 4') via helical threads, which in particular allows the spring force that pushes the pressure rings (8, 8') to be changed.

7. The pressure vessel (1) according to any one of the preceding claims. Its features are, The boss (4, 4') has an external thread (10) that contacts the matching internal thread of the gasket (3), and the external thread is arranged concentrically with the longitudinal axis L.

8. The pressure vessel (1) according to any one of the preceding claims. Its features are, The surface of the pressure ring (8, 8') pressed onto the pad (3) extends at least 20 mm, preferably at least 30 mm, in the radial direction R.

9. The pressure vessel (1) according to any one of the preceding claims. Its features are, The boss (4, 4') has a raised portion (13) located in the region of the boss (4, 4') in which the pad (3) is pressed against the boss by the pressure ring (8, 8'), wherein the height of the raised portion (13) is preferably between 0.3 mm and 1.5 mm, particularly preferably between 0.5 mm and 1 mm.

10. The pressure vessel (1) according to any one of the preceding claims. Its features are, The pressure rings (8, 8') are movable relative to the bushings (7, 7') in the direction of the longitudinal axis L.

11. The pressure vessel (1) according to claim 10. Its features are, The pressure ring (8) has a stop (22) and / or the bushing (7) has a stop (21), designed such that when the spring element (9) is compressed sufficiently strongly, the force transmission between the pressure ring (8) and the bushing (7) in the direction of the longitudinal axis L can be achieved directly via the stop (22) and / or directly via the stop (21).

12. The pressure vessel (1) according to claim 10. Its features are, The pressure ring (8') has a stop (24) and / or the bushing (7') has a stop (25), designed to enable rigid force transmission between the pressure ring (8') and the bushing (7') in the direction of the longitudinal axis L via a fully compressed spring element (9').

13. A method for manufacturing a pressure vessel (1) or a preform of such a pressure vessel according to any one of the preceding claims, in, In order to construct the wall of the pressure vessel (1), a gasket (3) is manufactured by blow molding process, the gasket surrounding the cavity (2) for storing gas. Its features are, Bushings (7, 7'), pressure rings (8, 8'), and spring elements (9, 9') that can be connected to the bosses (4, 4') are arranged on a blow molding mandrel (17). The pad (3) is manufactured by blow molding, such that the pressure rings (8, 8') and the spring elements (9, 9') are located on the inner side of the pad after the pad (3) is made. When the bushings (7, 7') are connected to the bosses (4, 4'), the spring elements (9, 9') can be supported on the bushings (7, 7') and can press the pressure rings (8, 8') onto the pad (3) and onto the surface of the bosses (4, 4').

14. The method according to claim 13, Its features are, During blow molding, the pressure ring (8) moves relative to the bushing (7) in the direction of the longitudinal axis L, such that the pressure ring compresses the spring element (9) such that the stop (21) on the bushing (7) comes into direct contact with the pressure ring (8) for force transmission and / or the stop (22) on the pressure ring (8) comes into direct contact with the bushing (7) for force transmission.

15. The method according to any one of claims 13 or 14, Its features are, In another method step, the boss (4, 4') is connected to the gasket (3) and the bushing (7), wherein the connection between the boss (4, 4') and the bushing (7) is achieved by screwing the boss (4, 4') onto the external thread (12) of the bushing (7), and wherein the boss (4, 4') is screwed onto the bushing (7) such that the pressure ring (8) moves relative to the bushing (7) in the direction of the longitudinal axis L and the pressure ring compresses the spring element (9) until the stop (21) on the bushing (7) and the pressure ring (8) and / or the stop (22) on the pressure ring (8) and the bushing (7) directly contact each other with their respective mating surfaces on the bushing (7) or the pressure ring (8) for force transmission.

16. The method according to claim 13, Its features are, During blow molding, the pressure ring (8') moves relative to the bushing (7') in the direction of the longitudinal axis L, such that the pressure ring fully compresses the spring element (9'), thereby enabling rigid force transmission between the bushing (7') and the pressure ring (8') via the spring element (9'), and in particular via the stop (24) on the pressure ring and / or the stop (25) on the bushing.

17. The method according to any one of claims 13 or 14, Its features are, In another method step, the boss (4, 4') is connected to the gasket (3) and the bushing (7'), wherein the connection between the boss (4, 4') and the bushing (7') is achieved by screwing the boss (4, 4') onto the external thread (12) of the bushing (7'), and wherein the boss (4, 4') is screwed onto the bushing (7') such that the pressure ring (8') moves relative to the bushing (7') in the direction of the longitudinal axis L and the pressure ring fully compresses the spring element (9') until a rigid force transmission between the bushing (7') and the pressure ring (8') can be achieved via the spring element (9') and especially via the stop (24) on the pressure ring and / or the stop (25) on the bushing.

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