Pressure tank for gas-powered vehicle

Abstract

Pressure tank (1) for storing gas as fuel in a gas-powered vehicle, having a rotationally symmetrical, elongated shape, cylindrical in the central region and terminated at both ends with a domed pole cap, having a metallic connection piece, a so-called boss (4), at each of the pole caps, and having a wall enclosing a cavity (2) for storing the gas, the wall comprising a wound reinforcing layer (6) made of fiber-reinforced plastic and an inner liner (3) for sealing, the boss (4) having an axial shaft (4.2) and a disc-shaped wing 4.3 with an outer rim (4.1), an outer surface (4.4) and an inner surface (4.5), wherein between the boss (4) and the reinforcing layer (6) in the area of ​​the polar caps there is an annular plate (20,20',20'') made of plastic, which has a first part (20.1,20.1',20.1'') which is in planar contact with the outside (4.4) of the wing, and which has a second part (20.2,20.2',20.2'') which projects beyond the outer edge (4.1) of the boss in radial direction R and is in planar contact with the liner (3), and wherein the plate (20,20',20'') has a third part (20.3,20.3',20.3'') which is arranged such that it is in planar contact with the inside (4.5) of the wing and is located between boss (4) and liner (3), whereby the plate (20,20',20'') completely encloses the outer edge (4.1) of the boss.

Description

[0001] The invention relates to a pressure tank for storing gas as fuel 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 that encloses a cavity for storing the gas, the wall comprising a wound reinforcing layer made of fiber-reinforced plastic and an inner liner for sealing. At each of the two end caps, the pressure tank has a metallic connector, a so-called boss, which has an axial shaft and a disc-shaped fin with an outer rim, an outer surface, and an inner surface.Between the boss and the reinforcement layer, in the area of ​​the polar caps, there is a ring-shaped plate made of plastic, which has a first part that is in planar contact with the outside of the wing, and which has a second part that extends beyond the outer edge of the boss in radial direction R and is in planar contact with the liner.

[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 a liner and a boss.

[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. This necessitates reliable and high-quality manufacturing.

[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. Such tanks are referred to as Type IV pressure tanks. Preferably, the reinforcing layer is wound and made of CFRP. The winding is carried out on a winding machine by wrapping fiber strands around the liner. CFRP stands for carbon fiber reinforced plastic.

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

[0006] With such pressure tanks, special attention must be paid to the connection between the metallic fitting, the boss, and the liner, as particularly good sealing is required here, even under mechanical stress, fluctuating internal pressure, or large temperature variations. This is a particular challenge with large hydrogen tanks.

[0007] For example, such a pressure tank is described in DE 102010021667 A1. The boss is inserted into the liner and both are wrapped together with the reinforcing layer.

[0008] A critical point for reliable manufacturing is the transition between the metallic boss and the plastic liner. Often, tolerance deviations exist here, which, when subsequently wrapped with the fiber strands of the reinforcing layer, cause air pockets and thus weak points. Especially under fluctuating loads, whether due to temperature variations or changing pressures, such weak points pose a risk to long-term sealing stability and pressure resistance. Solving this problem is particularly important for larger pressure tanks, especially those for hydrogen, such as those required for fuel cell-powered commercial vehicles. These pressure tanks can reach diameters of up to 700 mm and lengths of 2700 mm. Existing sealing concepts are insufficient for such large tanks.

[0009] German patent DE 102017108043 A1 describes a pressure tank with an annular cap between the boss and the reinforcing layer. In this design, the cap has an annular ridge on its underside. This ridge is designed to engage in an annular opening between the boss edge and the liner, thus positioning the cap radially. Because the annular cap is a very narrow ring that covers only the direct transition between the boss edge and the liner, this type of positioning is crucial to prevent the cap from slipping during winding. This solution is also intended for pressure tanks where the reinforcing layer is produced using a wet winding process. In this process, very low-viscosity resin is used, and it is essential to prevent the liquid resin from penetrating between the boss and the liner before it has cured.The bridge is therefore also intended to seal the transition between the boss edge and the liner, thus preventing resin from entering the gap.

[0010] However, pressure tanks manufactured according to the state of the art still repeatedly exhibit weaknesses and damage at the transition between the boss and the liner.

[0011] The object of the invention is now to develop a pressure tank and a corresponding precursor for such a pressure tank, which enable reliable and cost-effective production, while further reducing the risk of damage at the transition from the boss to the liner.

[0012] The problem is solved, firstly, by a pressure tank according to claim 1. Further advantageous features are mentioned in the respective dependent claims.

[0013] According to the invention, the pressure tank according to claim 1 is characterized in that the plate has a third part which is arranged in such a way that it is in planar contact with the inside of the wing and is located between the boss and the liner, whereby the plate completely encloses the outer edge of the boss.

[0014] The outside is the side of the boss facing the reinforcement layer, and the inside is the side facing the liner. The outer edge of the boss is the radially outermost edge where the outside transitions into the inside.

[0015] Problems with liner damage occur when the liner is bent too sharply at the transition between the boss and the liner, or when the liner is damaged at the outer edge of the boss. During manufacturing and operation, the pressure tank is repeatedly pressurized and then released. This causes the liner to be pushed outwards and then retract. If the outer edge of the boss is very thin, the liner is bent sharply or pressed against the outer edge, creating a risk of damage. If the outer edge is thicker, problems arise during winding due to air entrapment and resulting holes in the liner. Even a ring-shaped cap covering the transition area does not satisfactorily solve the problem, as this cap lifts off when pressure is applied, and the liner is still bent at the outer edge.

[0016] The advantage of the pressure tank design according to the invention is that the outer edge of the boss is completely enclosed by the plate, thus preventing the liner from coming into contact with the outer edge of the metallic boss. The transition to the liner is therefore shifted from the metallic outer edge of the boss to the more flexible outer edge of the plate, and the special feature is that this applies to both the outer and inner sides of the boss. At the same time, the outer edge of the boss can be rounded and made thicker. This makes it more stable, less susceptible to damage during assembly, and easier to manufacture.

[0017] The plastic plate can be manufactured much more easily and thinly, ensuring a seamless transition to the liner without affecting the inner surface of the reinforcement layer or the winding quality. The plate extends sufficiently beyond the outer edge of the boss. This prevents the reinforcement layer's structure from being negatively impacted during winding, especially with towpreg tapes. Often, the transition after inserting the boss into the liner is not perfectly level; there is usually a slight height difference. In conventional pressure tanks, this imperfection propagates into the reinforcement layer because the fiber strands, particularly the towpreg tapes with their relatively viscous resin, reflect this height difference. The specially designed plate covers this transition, ensuring the reinforcement layer is always wound optimally, regardless of the precise alignment between the liner and the boss's outer edge.During tempering in the oven, when the resin of the CFRP reinforcement layer is cured, the liner becomes somewhat flexible again and adapts to the plate in the transition area due to the applied internal pressure, thus smoothing the transition between the boss and the liner.

[0018] This significantly improves the consistency of the manufacturing process and thus the quality. This is particularly crucial for compressive strength. A thinner wall thickness can be achieved because the transition area does not need to be reinforced and made thicker to compensate for any defects that might occur there.

[0019] It is particularly advantageous if the plate is not only placed on the boss but also attached to it before the reinforcing layer is wound on. For this purpose, the plate can be glued to the outside of the piano with its first section, for example using double-sided adhesive tape or other adhesive.

[0020] Alternatively or additionally, the third part of the plate can be glued to the inside of the wing.

[0021] A further improvement is achieved when the plate has a collar that encloses the boss shaft, centering the plate on the boss. The collar can extend sufficiently far up the shaft axially to prevent the reinforcing layer from making direct contact with the boss. Centering the plate ensures a precise fit on the boss. Furthermore, the absence of direct contact between the reinforcing layer and the boss protects the boss from corrosion that could result from contact with the CFRP material. In particular, the plate is designed to act as electrical insulation between the metallic boss and the reinforcing layer.

[0022] Furthermore, it is advantageous to design the platter with one or two mounting slots that essentially run radially across its entire surface. This allows for easier mounting of the platter before winding than if it were completely closed. The platter can be bent open along this continuous slot and pressed around the boss shaft, even if the boss shaft is already clamped and the end of the shaft is no longer free. Alternatively, if two mounting slots are present, the platter can be assembled around the shaft.

[0023] The plate can be designed such that it has a connecting element on one side of the mounting slot and a recess on the other side into which the connecting element engages in a form-fitting manner. This allows the plate to be securely held in position after assembly for the subsequent winding process.

[0024] In another version, the plate can be manufactured by overmolding the boss. This eliminates the need for a Monday slot.

[0025] The platter is preferably made of the same plastic as the liner, for example, polyamide (PA). Alternatively, it can be made of polyoxymethylene (POM). This plastic is wear-resistant and sufficiently durable over a long period; it is also stiff enough to withstand the stress during winding due to the winding tension, yet flexible enough that it can be bent open and mounted at a slot, as described previously, without breaking. Furthermore, PA or POM is suitable for acting as electrical insulation between the metallic boss and the reinforcement layer.

[0026] In a preferred embodiment, the plate has an edge at its outer rim, and the liner has an annular recess. The edge and the recess are designed such that the edge fits snugly into the recess, creating a substantially continuous surface between the plate surface and the liner. In particular, the recess is designed with an undercut so that the edge snaps into the recess. The advantage of this embodiment is that it creates a smooth transition between the plate and the liner, thus ensuring an undisturbed, uniform build-up of the wound reinforcement layer.

[0027] The recess can be, for example, a ring-shaped groove or step. Alternatively, the recess can consist of several individual recesses, with the edge of the plate then also featuring several individual arms or teeth so that they fit snugly into the recess. The most important thing is that a flat, even surface is created, formed by the plate surface and the liner.

[0028] It is particularly advantageous if the recess has an undercut, so that the edge of the plate surface snaps into the recess. Snapping in means that the plate is pressed into the recess during assembly and is then held in place by the undercut.

[0029] There are several variations of the plate according to the invention. In a first embodiment, the plate is formed in one piece with the first part, the second part, and the third part with respect to cross-section. "In one piece with respect to cross-section" means that the plate is not divided in cross-section and thus does not consist of multiple pieces. That is, the first, second, and third parts of the plate are made from a single piece. The possible division along the previously described mounting slots is disregarded in this embodiment.

[0030] In another embodiment, the plate has a multi-part cross-sectional structure. The plate can be designed such that the first and second parts are formed as single pieces, while the third part is a separate component. This third part could, for example, be glued to the liner at the appropriate location. With pressure increases and the resulting expansion of the liner, the third part could shift slightly relative to the rest of the plate. When the pressure is reduced, the third part returns to its original position. Alternatively, the plate can be designed such that the second and third parts are formed as single pieces, this one being glued to the liner, while the first part is a separate component. This component could be glued to the outer surface of the wing.This allows the two separate pieces of the plate to shift relative to each other when the liner is under pressure. And they can return to their normal position when the pressure is reduced. In any case, the outer edge of the boss is covered.

[0031] The bonding can be done, for example, with double-sided adhesive tape or another type of adhesive. The bonding can be done in spots or over a larger area.

[0032] In a particularly preferred variant, the second part of the plate projects radially (R) at least 10 mm beyond the outer edge of the boss. This ensures that the transition from the boss to the liner is as smooth as possible and without sharp steps. It also ensures that the second part of the plate is sufficiently flexible due to its length, preventing significant buckling of the liner when it is subjected to pressure.

[0033] Furthermore, it is preferred that the third part of the plate, extending radially in direction R, is in contact with both the inside of the boss and the liner for at least 10 mm. This ensures that the outer edge of the boss is well covered and does not come into direct contact with the liner. Additionally, this allows the outer edge of the boss to be sufficiently rounded and made sufficiently thick.

[0034] Secondly, the problem is solved by a precursor for the production of a previously described pressure tank according to claim 12.

[0035] Further advantageous features are mentioned in the respective dependent claims.

[0036] The intermediate product according to the invention is characterized in that the plate has a third part which is arranged in such a way that it is in planar contact with the inside of the wing and is located between boss and liner, whereby the plate completely encloses the outer edge of the boss.

[0037] The advantages of this design and other beneficial features for the pre-product have already been described previously for the pressure tank and apply analogously to the pre-product.

[0038] In a further process step, the manufactured pre-product consisting of liner and boss is wrapped with fiber strands made of fiber-reinforced plastic, in particular CFRP (carbon fiber reinforced plastic), to form the reinforcement layer of the pressure tank. The fiber strands are preferably already impregnated with a plastic resin and supplied on spools (so-called towpreg tapes). The towpreg tapes are pre-impregnated fiber strands that are unwound from a reel in this state. This distinguishes towpreg winding from the currently used wet winding process. In wet winding, dry fiber tapes are unwound from a spool and, shortly before winding, passed through a resin bath so that they are then wound onto the liner while wet, i.e., freshly impregnated. The resin used in this process is relatively low in viscosity to ensure thorough impregnation of the dry fiber tapes.The resin in towpreg tapes is rather viscous so that it can be stored wound on spools and also removed again. The resin is, for example, an epoxy resin and is cured in an oven after winding through a tempering process. However, this rather viscous resin doesn't fill small gaps very well. Therefore, it's important that the transition between the boss and liner has no steps or similar features, as these can cause unwanted air pockets to form in this area during winding.

[0039] 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 Detail of the connection between boss and wall in an embodiment according to the invention with a plate Fig. 3 Detail section of a further embodiment according to the invention Fig. 4 Detail section of yet another embodiment according to the invention Fig. 5a Plate of an embodiment according to the invention in top view Fig. 5b Further variant of the plate in an embodiment according to the invention in top view, as well as side view of the plate to illustrate the assembly

[0040] The figures are described in more detail below. Identical reference numbers denote identical or analogous parts or components.

[0041] The Fig. Figure 1 shows the pressure tank 1 (type IV pressure tank) according to the invention, with a boss 4 at each of the two curved end caps. In the central region, the pressure tank is cylindrical and overall it is elongated and rotationally symmetrical about the longitudinal axis L.

[0042] One boss 4 has a tank fitting 5 screwed into it for filling and controlled gas withdrawal. The other boss 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. The reinforcing layer 6 is produced by a winding process using fiber strands made of fiber-reinforced plastic, preferably CFRP. In particular, the fiber strands are so-called towpreg tapes. The pressure tank 1 is rotationally symmetrical about the longitudinal axis L and cylindrical in its central region. The radial direction is denoted by R. Special attention must be paid to the sealing and pressure resistance at the interface between boss 4 and liner 3 in such pressure tanks.Especially with large pressure tanks, such as those required in commercial vehicles to ensure sufficient range, the proper and reliable execution of this transition area is a significant challenge. At the same time, the wall thickness of the reinforcement layer should be kept as thin as possible to avoid unnecessary weight.

[0043] The invention also relates to a precursor for the manufacture of a pressure tank. The precursor comprises at least the liner 3 or a part thereof, at least one boss 4, and a plate 20. It can also be only a part of the liner 3 that later forms the inner wall of the pressure tank. This is the case, for example, when the liner 3 is manufactured by injection molding and is assembled from several parts, such as two end caps and cylindrical center sections.

[0044] In particular, the preliminary product can comprise the complete liner 3 and two bosses 4 with corresponding plates 20 in the embodiment according to the invention.

[0045] Fig. Figure 2 shows an enlarged section of the pressure tank 1, so that the embodiment according to the invention becomes apparent. The boss 4 has an internal thread 11 in its shaft 4.2, which serves to receive a tank fitting or another valve or closure. The plate 20 is arranged between the boss 4 and the reinforcing layer 6. The plate comprises the first part 20.1, which is in contact with the wing 4.3 of the boss on its outer surface 4.4, with a flat surface adapted to the shape; the second part 20.2, which projects beyond the outer edge 4.1; and the third part 20.3, which is in contact with the inner surface 4.5 of the wing, with a flat surface adapted to the shape, and thus surrounds the outer edge 4.1 of the boss. In the variant shown here, the plate is formed in one piece with respect to its cross-section. Despite any mounting slots that may be present, this embodiment is considered to be a single piece in this context, as explained above.

[0046] By gripping the outer edge 4.1 in cross-section, the plate 20 protects the liner 3 from damage or excessive deflection. This also applies when the liner 3 is subjected to pressure, for example during manufacturing before the application of the reinforcing layer 6.

[0047] The cross-section of the plate 20 shows that it is very thin-walled; in particular, it can have a wall thickness between 1 mm and 3 mm. The plate 20 can preferably be made with a decreasing wall thickness in the outer edge region.

[0048] Optionally, plate 20 can have a collar, which is not shown here. The collar surrounds shaft 4.2 and thus ensures precise positioning. Furthermore, the collar can be pulled up high enough to cover shaft 4.2 sufficiently so that the reinforcement layer 6 does not come into direct contact with boss 4.

[0049] Furthermore, the second part 20.2 of the plate projects in radial direction R more than 10 mm, and preferably more than 15 mm, beyond the outer edge 4.1. A maximum of 50 mm can be considered a suitable upper limit for this.

[0050] The protruding plate 20 at the transition between bosses 4 and liner 3 covers height differences between liner 3 and edge 4.1 of the boss.

[0051] This ensures that the winding of the reinforcement layer 6 is not affected by such height differences. These height differences can occur, for example, when the boss 4 is screwed into the liner 3 via the thread 10. Due to the limitations of machining in the plastic, the thread 10 in the liner 3 is not cut as precisely as the thread in the metallic boss 4.

[0052] The plate 20 has an edge 21 on its outermost part 20.2, which fits snugly into the recess 3.1 of the liner, creating an even more uniform surface at the transition between the plate 20 and the liner 3. This prevents defects from occurring when winding the reinforcement layer 6. The recess 3.1 can be designed with an undercut, allowing the plate's edge 21 to snap into the recess. During assembly, the edge 21 is pressed into the recess 3.1 and then held in place by the undercut. This snap-in action secures the position of the plate 20 and prevents it from shifting during the winding of the reinforcement layer. To facilitate assembly for this design, it is particularly advantageous if the plate 20 is provided with at least one mounting slot.

[0053] The recess 3.1 can, for example, be designed as an annular groove or as an annular step. This ensures a uniform surface across the entire circumference at the transition between the plate 20 and the liner 3. The edge 21 can simply be chamfered or have another suitable shape.

[0054] During the curing of the reinforcement layer 6 in the oven (annealing), the liner 3 briefly becomes slightly flexible again due to the heat and, because of the internal pressure applied in the cavity 2 during annealing, conforms to the plate 20 and the flawlessly wound reinforcement layer 6, thus eliminating the height differences in the finished pressure tank 1. The third part 20.3 of the plate protects the liner 3 from excessive deflection or damage to the outer edge 4.1 of the boss. This ensures that the required quality of the pressure tank 1 is achieved much more reliably. Therefore, additional reinforcement layers to stabilize the transition area even with certain defects, or a thicker liner, are unnecessary.

[0055] To secure the boss 4 in the liner 3 and improve the seal, a sealing set is provided, consisting of the pressure ring 8, the bushing 7, and the spring element 9. The pressure ring 8 and the spring element 9 are located inside the liner 3, i.e., in the cavity 2. The spring element 9 is pre-tensioned via the bushing 7, which is connected to the boss 4, and presses the pressure ring 8 against the liner 3, and thus the liner 3 against the boss 4. The connection between the boss 4 and the bushing 7 is made via the screw thread 10, which has a corresponding external thread on the bushing 7. The bushing 7 and liner 3 do not make full contact; contact is only possible at the end face of the liner 3. The pressure of the liner 3 against the boss is achieved solely via the pressure ring 8. This pressure ring 8 is movable relative to the bushing 7 and can be displaced along the longitudinal axis L.

[0056] In Fig. Figure 3 shows a further preferred embodiment of the plate 20' for a pressure tank 1 according to the invention. Here, the second part 20.2' and the third part 20.3' are shown in cross-section as being formed in one piece. The first part 20.1' is formed as a separate piece.

[0057] The first part 20.1' can be attached to the outer surface 4.4 of the boss using double-sided adhesive tape or another adhesive. The second and third parts 20.2' and 20.3' can be glued to the liner 3. When pressure is applied to the liner 3, the first part 20.1 can shift slightly relative to the other part of the plate 20. However, the outer edge 4.1 remains enclosed by the plate 20, especially by the third part 20.3', thus protecting the liner 3 from damage. When the pressure is released, the liner moves back into its original position along with the section of the plate 20'.

[0058] Fig. Figure 4 shows another alternative for a multi-part plate 20". Here, the first part 20.1 and the second part 20.2 together form a single piece. The third part 20.3 is a separate piece. Preferably, the first part 20.1 is attached to the top surface, for example, using double-sided adhesive tape. The third part 20.3 can preferably be glued to the liner 3.

[0059] Here, a certain movement of the pieces of the 20" plate towards each other is again possible.

[0060] The representations in Fig. 5a,b are top views of plate 20 / 20' / 20". In Fig.Figure 5a shows an embodiment of the plate with two mounting slots 24, 24a. This means that the plate is assembled from two separate sections 20a, 20b. To ensure it remains in the desired position, the plate has a recess 23, 23a on one side of the mounting slot and a connecting element 22, 22a on the other side. These elements are designed such that the connecting element 22, 22a engages positively in the recess 23, 23a and securely connects the two sections.

[0061] The mounting slot 24,24a is designed to be radially continuous.

[0062] If only one mounting slot 24 is available, the plate 20 can be bent open at the slot 24 so that it can be slid over the shaft 4.2 of the boss, even if the end of the shaft is not free, for example because it is clamped. This works particularly well if the plate 20 is made of a sufficiently tough and flexible plastic, for example POM.

[0063] The mounting slots are irrelevant for determining whether the plate 20,20',20" is constructed in one piece or in multiple parts in cross-section. Reference symbol list 1 pressure tank 2 cavities 3 Liner 3.1 In-depth study 4 Boss 4.1 Outer edge 4.2 Shaft 4.3 Wings 4.4 Outside of the Boss Wing 4.5 Inside of the boss wing 5 Tank fitting 6 Reinforcing layer 7 socket 8 pressure ring 9 spring element 10 screw threads 11 internal threads 20,20',20" plate 20a, 20b Sub-areas of the plate 20.1,20.1,20.1'' first part 20.2,20.2',20.2'' second part 20.3,20.3',20.3'' third part 21 edge 22,22a Connecting part 23.23a recess 24.24a Mounting slot 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] DE 102010021667 A1

[0007] DE 102017108043 A1

[0009]

Claims

[1] Pressure tank (1) for storing gas as fuel in a gas-powered vehicle, having a rotationally symmetrical, elongated shape, cylindrical in the central region and terminated at both ends with a domed pole cap, having a metallic connection piece, a so-called boss (4), at each of the pole caps, and having a wall enclosing a cavity (2) for storing the gas, the wall comprising a wound reinforcing layer (6) of fiber-reinforced plastic and an inner liner (3) for sealing, the boss (4) having an axial shaft (4.2) and a disc-shaped wing 4.3 with an outer rim (4.1), an outer surface (4.4) and an inner surface (4.5), and wherein an annular plate (20,20',20'') made of plastic is present between the boss (4) and the reinforcing layer (6) in the area of ​​the polar caps, which has a first part (20.1,20.1',20.1'') which is arranged in planar contact with the outer surface (4.4) of the wing, and which has a second part (20.2,20.2',20.2'') which projects beyond the outer edge (4.1) of the boss in radial direction R and is in planar contact with the liner (3), characterized by , that the plate (20,20',20'') has a third part (20.3,20.3',20.3'') which is arranged such that it is in planar contact with the inside (4.5) of the wing and is located between boss (4) and liner (3), whereby the plate (20,20',20'') completely encloses the outer edge (4.1) of the boss. [2] Pressure tank (1) according to claim 1 characterized by, that the plate (20,20',20'') has a collar (22,22',22'') wherein the collar (22,22',22'') surrounds the shaft (4.2) such that the plate (20,20',20'') is centered on the boss (4,4') and wherein the collar is preferably extended so far in the axial direction of the shaft (4.2) that the reinforcing layer (6) does not have direct contact with the boss (4,4'). [3] Pressure tank (1) according to one of claims 1 or 2 characterized by , that the plate (20,20',20'') has one or two mounting slots (24,24a) which extend in radial direction R over the entire plate (20,20',20''). [4] Pressure tank (1) according to claim 3 characterized by , that the plate (20,20',20'') has a connecting part (22,22a) on one side of the mounting slot (24) and a recess (23,23a) is provided on the other side of the mounting slot (24) into which the respective connecting part (22,22a) engages in a form-fitting manner. [5] Pressure tank (1) according to any one of the preceding claims characterized by , that the plate (20) has an edge (21) at its outer edge and the liner (3) has an annular recess (3.1), wherein the edge (21) and the recess (3.1) are designed such that the edge (21) fits into the recess (3.1) in a form-fitting manner and that a substantially continuous surface is created between the plate surface (21) and the liner (3), in particular the recess (3.1) is designed with an undercut so that the edge (21) snaps into the recess. [6] Pressure tank (1) according to any one of the preceding claims characterized by , that the plate (20,20',20'') is formed in one piece with the first part (20.1,20.1',20.1''), the second part (20.2,20.2',20.2'') and the third part (20.3,20.3',20.3'') with respect to the cross-section. [7] Pressure tank (1) according to any one of claims 1 to 5 characterized by, that the plate (20,20',20'') is made up of multiple parts with respect to its cross-section. [8] Pressure tank (1) according to claim 7 characterized by , that the first part (20.1,20.1',20.1'') and the second part (20.2,20.2',20.2'') are formed in one piece with respect to the cross-section, wherein the third part (20.3,20.3',20.3'') is a separate part with respect to the cross-section. [9] Pressure tank (1) according to claim 7 characterized by , that the second part (20.2,20.2',20.2'') and the third part (20.3,20.3',20.3'') are formed in one piece with respect to the cross-section, wherein the first part (20.1,20.1',20.1'') is a separate part with respect to the cross-section. [10] Pressure tank (1) according to any of the preceding claims characterized by , that the plate (20,20',20'') with its second part (20.2,20.2',20.2'') extends at least 10 mm beyond the outer edge (4.1) of the boss in radial direction R. [11] Pressure tank (1) according to any of the preceding claims characterized by, that plate (20,20',20'') with its third part (20.3,20.3',20.3'') is in contact with both the inside (4.5) of the boss and the liner (3) in radial direction R for at least a length of 10 mm. [12] Precursor for the manufacture of a pressure tank (1) according to one of the preceding claims, comprising at least one liner (3), a boss (4) and an annular plate (20, 20', 20'') made of plastic, which has a first part (20.1, 20.1', 20.1'') which is arranged in planar contact with the outer surface (4.4) of the wing, and which has a second part (20.2, 20.2', 20.2'') which projects beyond the outer edge (4.1) of the boss in radial direction R and is in planar contact with the liner (3), characterized by, that the plate (20,20',20'') has a third part (20.3,20.3',20.3'') which is arranged such that it is in planar contact with the inside (4.5) of the wing and is located between boss (4) and liner (3), whereby the plate (20,20',20'') completely encloses the outer edge (4.1) of the boss.

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