EP3374685B1 - Improved anti-static pressure tank - Google Patents

Description

The present invention is concerned with a pressure tank for storing high and low pressure fluids / gases, in particular LPG or CNG, comprising a hollow body made of thermoplastic material with at least one opening which has a circumferential contact surface, one connector per opening which has at least one passage to the interior of the hollow body and which is flatly connected to a complementary section with a contact surface, the passage having a diffuser at a lower end which closes the passage in the axial direction and only has openings pointing essentially in the radial direction, inside the hollow body an antistatic wall surrounding the diffuser is present.

Tanks for holding gases or liquids that are under low or high pressure, such as liquified petroleum gas (LPG) or compressed natural gas (CNG) are known in the prior art. These tanks are made, among other things, of thermoplastic material by blow molding, rotational molding or injection molding. In order to increase the compressive strength, these tanks are provided in a second step with an outer layer of resilient fibers, which are mostly embedded in a casting resin that connects the fibers to one another and fixes them on the inner plastic layer.

Regardless of the design, such a tank must always be provided with at least one connection piece into which a pressure-tight coupling part in the form of a valve, hose or pipe end is inserted in order to fill or empty the tank. The connection between the connection piece and the coupling part can be made via a snap-in plug or a bayonet lock, but screw locks with a low thread pitch are mostly used for high-pressure applications.

The internal hollow vessel, also referred to as a liner, can consist of metal, for example aluminum, titanium or steel, or, as mentioned at the beginning, can be made of a plastic, for example a thermoplastic. The latter have the advantage that they can be shaped more easily and can thus be manufactured more cheaply and, furthermore, are also better adapted in terms of their coefficient of thermal expansion to the matrix of the fiber-reinforced top layer, which is usually a synthetic resin. However, the disadvantage is, on the one hand, a lower compressive strength compared to metallic liners of the same wall thickness, and a lower temperature resistance. However, depending on the application, these disadvantages take a back seat to the advantages listed above.

Another disadvantage of plastic liners, which is in the foreground for the present invention, is their low electrical conductivity and the associated tendency to become statically charged when they are filled with a fluid flowing in under high pressure. The fluid emerges from the outlet opening of the usually metal valve used for filling at high speed and thereby travels with electrons, which are then deposited in the area of the point of impact when they hit the inner vessel wall. Charge separation can also be caused by the fluid jet hitting the opposite side of the inner wall at high speed.

With hollow bodies or liners made of metal or another conductive material, charge equalization can take place quickly and easily. To further increase safety, both hollow bodies / liners and valves can be earthed. In the case of plastic liners, such as thermoplastics, this is not or hardly possible or effective due to the poor electrical conductivity. The result is the static charge on the hollow body / liner, which can literally discharge in an unpredictable manner. If there is still residual oxygen in the inside of the vessel, or if the fluid (mixture) that has been filled in is actually combustible, an explosion can occur. This problem occurs particularly when filling an empty, dry pressure tank, since static charges that are forming can only drain off with difficulty and, if no previous inertization with protective gas has taken place, oxygen is also present.

In the prior art, two classes of solutions to this problem have been proposed so far, which can be summarized under the keywords remedy and avoidance. Both solutions are exemplified in the patent US 7,656,642 B2 (Ulekleiv et al. ) described.
The remedial solutions suggest improving the conductivity of the inner wall of the vessel, for example by applying a conductive coating to the otherwise non-conductive or hardly conductive plastic. This has the disadvantage that the advantage of the simpler and cheaper production of thermoplastic liners is at least partially negated. In addition, such a coating quickly wears off at highly stressed points on the inner wall of the hollow vessel, in particular at the point opposite the inlet opening. The addition of antistatic additives can only be used to a limited extent, as these only have a short-term effect.

The avoidance strategy, on the other hand, tries to address the cause of the static charge, which can be seen in the high inflow velocity of the fluid from the valve. To reduce this, it is proposed to attach a diffuser to the lower end of the valve. This closes the passage in the axial direction and has only radially oriented openings, so that the fluid flowing in is deflected in direction. On the one hand, this slows it down and, on the other hand, it does not strike the opposite inner wall as a bundled jet, but is split into several partial flows that initially run horizontally without further measures and then hit the inner wall, slightly deflected under the influence of gravity, almost tangentially would. In order to achieve a further reduction in speed, however, the above-mentioned patent suggests that the diffuser be additionally surrounded by a cylindrical collar formed as part of the liner / hollow body on the inside of the opening of the hollow body. The fluid flowing out of the radial openings of the diffuser thus impacts against the collar and is deflected again and strongly decelerated.

A disadvantage of this solution is that the extreme braking of the fluid by the circumferential, closed collar leads to the space remaining between the diffuser and collar filling up, i.e. a strong counterpressure builds up and the flow rate is thus greatly reduced. The flow in the space is very turbulent here, so that there is a strong mechanical load on the adjacent components, diffuser, coupling part, connection piece and collar, which promote faster aging.

An even more serious problem of the strong counterpressure in the space between the diffuser and collar is that this leads to the inflowing fluid being pressed into the seam between the hollow body and the connection piece, which runs at the top of the space between the diffuser and collar, whereby the tightness of the pressure tank there can be compromised, especially at high filling pressures and rates.

Since the wall thicknesses and the requirements for dimensional accuracy of the connection pieces differ considerably from the wall thicknesses and the tolerances of the pressure tank, in practice it is neither sensible nor economical to manufacture the connection pieces and the tanks in one cast.

Rather, it is common to provide a hollow plastic container after its completion in a further work step with a separately manufactured and mostly multi-part connector. For example, describes the patent application US 2011/010/1002 a plastic tank with two openings. An approximately cylindrical connection part, which is widened at one end with a collar-shaped flange, is placed onto these openings from the outside and from the inside. These two parts are screwed together with a thread and thus pressed against one another so that they lie flat on the inside and outside of the area around the opening of the tank. The required pressure resistance is achieved by applying the appropriate pressure and also by sealing rings embedded in the tank or the flanges.

The publication script US 2014/0299610 A1 describes a pressure tank with a two-part connector, in which an outer part made of softer, more adaptable material makes the connection to the hollow vessel / liner and to the fiber-reinforced layer resting on it. A second part is concentrically embedded in this outer connection piece, which provides a connection option to a valve or other coupling part in the form of an internal thread. In order to be able to withstand the forces that occur, it is made of a harder material. Between the inner part and a screwed-in valve, there is a sealing lip of the connection piece, which, in conjunction with one or more sealing rings surrounding the valve, ensures the tight fit of the valve even at high pressure.
This publication teaches reducing the radial thickness of the sealing lip proportionally with the desired test pressure. However, this has the disadvantage that at high pressures the sealing lip may not be able to compensate for the pressure-related deformation of the valve, connection piece and opening and in particular the sealing rings, which can result in leaks.

Against this background, the present invention has set itself the task of developing a connection piece for pressure tanks made of plastic, which effectively prevents static charging, nevertheless enables high filling rates and guarantees absolute tightness even at high pressures.

As a solution, the invention teaches the provision of an antistatic wall which surrounds the diffuser and which is formed as a part of the connection piece or a neck ring or the coupling part explained below. The tightness during filling is then ensured by the fact that the unavoidable seam between the connection piece and the hollow body / liner is advantageously outside the area during filling with a high dynamic pressure loaded space between the diffuser and the antistatic wall is positioned.

In an advantageous embodiment, this dynamic pressure is reduced in that the antistatic wall has a plurality of turbulator openings distributed over its circumference. Through this, the fluid flowing into the space between the diffuser at the lower end of the passage and the antistatic wall can leave the space. This relieves the gap between the diffuser and the antistatic wall and thus ensures a higher flow rate. By appropriately positioning the turbulator openings relative to the radial openings of the diffuser, the turbulence of the flow can also be influenced. It makes sense here to provide at least one turbulator opening in the antistatic wall for each diffuser opening. These can each be aligned approximately in alignment with the assigned diffuser opening. In this case, a high flow rate and a minimally turbulent flow is achieved in the area of the connection piece. The size of the turbulator opening is ideally selected to be somewhat smaller than the jet cross section of the fluid emerging from the diffuser opening, taking into account the jet expansion after exiting the diffuser opening. This causes the flow to not be completely laminar, which reduces the charge separation by the flow.

Alternatively, it is proposed to align the diffuser openings with the massive webs between the turbulator openings in alignment. Alignment of the diffuser openings with the center of the webs is preferred for the most uniform possible loading of the webs by the fluid striking them with force. With this relative arrangement, a strong deceleration similar to that from the A continuous circumferential collar known from the prior art is achieved, but with the decisive advantage that the inflowing fluid with the turbulator openings has a further drainage path and a largely steady flow is formed in the intermediate space. The heavy material load of a highly turbulent flow is avoided and the static counterpressure that builds up is advantageously greatly reduced. Despite the braking and double deflection of the inflowing fluid, the maximum possible flow rate is hardly reduced even with this orientation compared to a tank without a diffuser (and / or antistatic wall). Outside and inside the space, this arrangement produces a sprinkler-like effect, in which the fluid, when it hits the webs of the antistatic wall, is atomized into fine to very fine droplets with great force and then partly directly through the slot between the diffuser and webs fall below and partially finely distributed from the turbulator openings enters the outer tank volume. So there is no longer a bundled fluid jet whose impact on the inner surface of the hollow body could cause further static charging.

If a material that is more conductive than the liner material is used for the material of the connection piece, or a non-conductive material is provided with a conductive coating, there is a further advantage of the teaching according to the invention. This is related to the fact that the majority of the charges entrained by the flow in the valve or the coupling part, ie electrons, are already deposited on the antistatic wall. This is also the case with the pressure tanks known from the prior art. However, the design of the collar as part of the non-conductive hollow body prevents an effective charge backflow. At Manufacture of the connection piece from conductive material, a charge return flow is easily possible in the present invention by integrating the antistatic wall into the connection piece.

An essential idea of the present invention is to integrate the antistatic wall into the connection piece of the pressure tank, which ultimately serves to provide the (pressure) stable connection of an actual coupling part for connection to fluid-carrying hoses or pipes with the hollow body, including any fiber-reinforced cover layer , which banishes the interface between the connection piece and the hollow body as a weak point from the space between the diffuser and the antistatic wall, and by introducing turbulator openings to achieve a largely stationary, less turbulent flow path in the space, whereby the counterpressure that builds up and thus the material load on it Parts exposed to pressure are reduced and the flow rate is increased accordingly at the given filling pressure. The fluid is atomized like a sprinkler when it hits the webs of the antistatic wall or at the latest when it emerges from the turbulator openings that act as a constriction and leaves the area of the space as a rain of fine and extremely fine droplets that no longer have enough kinetic energy to absorb when they hit on the inner wall of the hollow body or by friction in the air to effect a significant charge stripping. The anti-static effect of the collar with turbulator openings according to the present invention is therefore at least equal to that of a continuous collar, but avoids its massive disadvantages.

Further advantageous developments of the present invention, which can be implemented individually or in combination, provided they are not mutually obviously mutually exclusive are to be presented and explained in the following.

The number of turbulator openings is preferably an integral multiple of the number of radial diffuser openings; in particular, the present invention proposes providing the same number of turbulator and diffuser openings. Furthermore, the antistatic collar preferably has the same symmetries as the diffuser. Particularly preferably, both the diffuser and the antistatic wall including the turbulator openings have an n-fold rotational symmetry with n 2 and a mirror symmetry. This ensures that the forces and torques resulting from the deflection of the flow onto the connection piece are balanced out and that the connection piece is therefore free of forces and torque in total.

The turbulator openings can be shaped differently, for example as round or oval openings in the antistatic wall. However, they are preferably designed as elongated recesses or notches beginning at the lower edge of the wall, extending over a substantial part of their vertical extent, which in the tangential direction have a width which corresponds approximately to the diameter of the diffuser openings. Firstly, this is easy to manufacture and, secondly, results in a flow course of the inflowing fluid in the area of the connection piece, which represents a very good balance between turbulence and laminarity and overall a quasi-stationary flow. For further flow control, the lateral contour of the antistatic wall can be varied, for example an additional waviness can be impressed on a round basic contour or a polygonal basic shape can be selected.

Another possibility of advantageously influencing the flow conditions when filling the pressure tank is to impress a suitable topography on the inner end face of the diffuser, which the inflowing fluid strikes before exiting through the diffuser openings. This can, for example, be designed as a convex or conical bulge against the direction of flow of the impinging fluid, which leads to improved pressure relief of the connector and higher flow rates.
In order to be able to ensure protection against excess pressure when fluid is removed from the pressure tank, for example due to a break in a line, a mechanism can be integrated into the diffuser which closes the passage openings when the flow rates are too high.

An advantageous development also consists in shaping the antistatic wall as a separate part for attachment to the coupling part. This simplifies maintenance or replacement of the antistatic wall as a heavily loaded and thus wear-prone component. When using an antistatic wall without turbulator openings, which is subject to the highest loads from impacting fluid, this easy serviceability is a great advantage over designs according to the prior art, in which the appropriate collar is an internal, integral part of the hollow body / liner.

Regardless of whether the antistatic wall is attached to the coupling part or designed as a component of the connector or neck ring, various materials can be used for its manufacture in order to influence electrostatic or wear properties. In addition to a metal, for example, a thermoplastic material can also be used

The connection piece of the pressure tank according to the invention is in the most general case in one piece, i.e. a coupling or connection option for valves, hoses or pipes or the like is integrated in the connection piece itself. This advantageously avoids additional contact or seams that could endanger the tightness of the pressure tank. Due to the different requirements for the material properties of the connector in the area of contact with the hollow body, where it must be sufficiently flexible and elastic to adapt to the expansion of the hollow body under pressure and thermal influences, and the area of the coupling to a fluid-carrying valve, a Hose or a pipe, where it must have sufficient strength and hardness in order not to tire too quickly even with frequent coupling and uncoupling, however, the present invention proposes an at least two-part design of the connection piece. In this case, a second part, the so-called neck ring, made of hard material, preferably metal, is embedded concentrically in an outer connection part made of softer, tougher material, in particular a material similar to the thermoplastic material of the hollow body and which can be connected to it by means of melting a valve or other coupling part has an internal thread or another coupling option. The neck ring is pressed or cast into a complementary recess in the actual connection piece. Alternatively, the connection piece is molded around the neck ring by casting or injection molding.

The neck ring, in particular its contact surface with the actual connection piece, preferably has no circular symmetry, but only an n-fold rotation and particularly preferably one Mirror symmetry with a mirror plane that contains the axial direction. The contact surface can for example have a polygonal, star-shaped or wave-shaped outline. This increases the contact area and enables a better transmission of torques from the neck ring into the connection piece. In addition, the present invention proposes introducing grooves and / or connecting holes distributed over the circumference of the neck ring or the circumferential collars or flanges, into which the liquid thermoplastic material of the connector can flow during manufacture. After cooling down, a particularly stable connection suitable for torque transmission is achieved. This is important so that in the event of frequent changes, ie screwing in and unscrewing a coupling part, the moments occurring in the process could worsen the bond between the neck ring and the actual connector, which over time could lead to leaks or even failure of the connector.

The same also applies to the transmission of the torques just mentioned from the connection piece into the hollow body. That is why the contact surface between the connection piece and the hollow body is also designed as a non-circularly symmetrical torque coupling. Like the connecting surface from the neck ring to the connector, a polygonal, star-shaped or wave-shaped outline is also possible here. An alternative is to cast a thermoplastic hollow body around the connection piece, which guarantees a particularly close connection and power transmission, especially if vertical holes are provided in the outer area of the connection piece, into which the still liquid material of the hollow body flows and solidifies there can. The disadvantage here is that the connection piece must already be present during the manufacture of the hollow body must and can no longer be changed without destroying it.
Therefore, the present invention particularly preferably proposes to make the contact surfaces to the connection piece (s) in the area of the opening (s) of the hollow body accessible from the outside, so that the connection piece is inserted and fused and / or after completion and hardening of the hollow body can be pressed in. In particular, the axial cross-section of the opening should increase monotonously in the outward direction, in such a way that the axial projection of further outward cross-sections comprise further inward ones. If the connection part of the connection piece is made from thermoplastic material similar to the hollow body material, the connection can preferably be made by superficial melting of the contact surfaces and pressing together.

In the prior art, the diffuser is part of the coupling part, ie the valve for connecting a hose or pipe, and in the most general case the present invention also includes such a configuration. However, the present invention preferably proposes to integrate the diffuser, like the antistatic wall, into the actual connection piece. The reason for this is that a coupling part that is usually screwed into an internal thread of the connection piece or neck ring does not always assume the same angular position relative to the antistatic wall, but rather varies at least a little with each screwing in. As a result, the position of the diffuser openings relative to the turbulator openings is also not always the same, which can have a negative effect on the flow profile of the inflowing fluid. This variation in the relative position is advantageously avoided by integrating the diffuser into the connection piece.

The radially oriented diffuser openings are preferably round, oval or polygonal, in particular rectangular.

Another advantage of this solution arises from the fact that conventional coupling parts are not equipped with a diffuser at all, but rather have a simple, axially oriented inlet opening at the lower end. Thus, by integrating the diffuser into the actual connection piece, the present invention can utilize the advantages of braking fluid flowing in under high pressure by the diffuser and antistatic wall despite the use of standard coupling parts.

The neck ring embedded in the actual connection part preferably has a centering bevel at the upper end of its passage opening. During the manufacture of the connection piece, it ensures that the neck ring and connection part are always positioned the same, which is important because of the above-mentioned relative alignment of the turbulator and diffuser openings. This also facilitates the quick insertion and centering of coupling parts during later use, especially if this is to be done automatically, for example by a loading robot.

Even more preferably, the neck ring has a collar which projects downward in the axial direction and which is surrounded on its outer sides by the material of the connecting piece. As a result, on the one hand, the contact area with the actual connection piece is further enlarged. On the other hand, the material of the connection piece that lies inward from the collar in the radial direction forms a sealing lip, the radial thickness of which has a decisive influence on the tightness of the pressure tank.

Due to the finite vertical dimension of the connecting piece, the opening with the connecting piece inserted protrudes somewhat into the interior of the hollow body. The internal tank pressure now acts on both the outer and the inner side of this toroidal elevation, the inner side being formed by the coupling part or the lower part of the connection piece, with or without an integrated diffuser, depending on the embodiment. This compresses the material of the connection piece and in particular the sealing lip. Furthermore, the pressure in the tank presses fluid or gas into the gap between a sealing ring of a coupling part and the sealing lip, deforming both sealing ring and sealing lip until an equilibrium of forces is achieved between the tensions in the sealing ring, the sealing lip and the internal tank pressure.

If the radial thickness of the sealing lip is not sufficiently dimensioned, there will be a leak at the connection between the actual connection piece and neck ring or connection piece and coupling part. The latter can be avoided by using a sealing ring between the coupling part and the sealing lip. The hardness of this sealing ring should increase with the test pressure of the tank, and thus also with the intended maximum filling pressure.

$$\mathit{Dmin}\left[\mathit{mm}\right]=\mathrm{0,019}\mathit{Dmax}\left[\mathit{mm}\right]+\mathrm{2,95}$$

optimale Dichtheit garantiert. Hierbei bezeichnet P den Prüfdruck, sowie Dmin die Unter- und die Dmax die Obergrenze der bevorzugten radialen Dichtlippendicken D. Hierbei wurde die Verwendung eines Dichtrings zwischen Dichtlippe und Kupplungsteil mit einer Shore-Härte von mindestens 90 vorausgesetzt.The present invention therefore proposes making the radial thickness of the sealing lip larger with the intended test pressure of the pressure tank according to the invention. Specifically, it is proposed to increase the thickness of the sealing lip proportionally to the test pressure. In experiments it was found that a change according to the relationships $$\mathit{Dmax}\left[\mathit{mm}\right]=0.01P\left[\mathit{bar}\right]+3.0$$

$$\mathit{Dmin}\left[\mathit{mm}\right]=0.019\mathit{Dmax}\left[\mathit{mm}\right]+2.95$$

optimal tightness guaranteed. Here, P denotes the test pressure, and Dmin the lower limit and Dmax the upper limit of the preferred radial sealing lip thicknesses D. The use of a sealing ring between the sealing lip and the coupling part with a Shore hardness of at least 90 was assumed.

An alternative method of sealing between the connection piece and the valve, which according to the prior art is used in particular for pressure tanks with a hollow body made of steel, consists in the use of valves with a conical, downwardly tapering external thread. The metallic seal achieved in this way, supported in current practice by a viscous sealant, makes the use of a sealing ring superfluous. In an advantageous variant of the invention, the connection of such a conical valve is provided by a suitable design of the neck ring. In particular, the design of the connection piece without a diffuser is addressed, since the most widespread conical valves are already equipped with a diffuser, but without an antistatic wall. In order to be able to adjust the relative position of the diffuser and turbulator openings in a targeted manner in this connection variant as well, it is proposed to provide suitable markings on the connection piece and valve to indicate the position of the openings.

In order to be able to withstand very high test pressures of several hundred to more than one thousand bar, the hollow body of the pressure tank according to the invention must be enclosed by a fiber-reinforced cover layer. This is all the more necessary since the thermoplastic materials proposed for the hollow body alone could withstand only a few bar up to a maximum of approximately ten bar with typical wall thicknesses in the millimeter range. The fibers used in this layer can be synthetic fibers, such as Glass, carbon, aramid, Dyneema or other synthetic fibers, or natural fibers. Different fiber species can also be used in combination in order to optimize costs for a desired strength. The matrix in which these fibers are embedded consists either of thermally or optically crosslinked (synthetic) resins such as epoxy resin, or of a plastic such as polyethylene, which is applied in liquid form to the hollow body wrapped with fibers and then allowed to cool. Particularly preferably, the outside of the hollow body is subjected to a surface treatment before the fibers are wound up and the matrix surrounding them is applied, in which the roughness is increased and thus a better connection between the matrix layer and the liner / hollow body is achieved.

Figur 1:

Querschnitt durch eine Ausführungsform des erfindungsgemäßen Drucktanks mit Antistatik-Wand mit Turbulatoröffnungen am Anschlussstück und in ein Kupplungsteil integriertem Diffusor

Figur 1a:

Vergrößerter Ausschnitt der unteren Hälfte des Anschlussstücks aus Figur 1

Figur 2:

Perspektivische Ansicht von schräg unten auf das Anschlussstück aus Figur 1

Figur 3:

Perspektivische Ansicht von schräg unten und aufgeschnittene Ansicht einer weiteren Ausführungsform des Anschlussstücks mit integriertem Diffusor.

Figur 4:

Zusammenhang zwischen Prüfdruck und Dichtlippendicke in radialer Richtung

Figur 5:

Querschnitt einer weiteren Ausführungsform des Anschlussstücks mit profilierter Diffusor-Stirnfläche

Figur 6

Querschnitt einer weiteren Ausführungsform des Anschlussstücks und Kopplungsteils mit zu Letzterem zugehöriger Antistatik-Wand und Diffusor

Figur 7

Perspektivische Ansicht von schräg unten auf eine weitere Ausführungsform des Kupplungsteils mit Antistatik-Wand und Diffusor

Figur 8:

Querschnitt einer weiteren Ausführungsform des Anschlussstücks mit in den Diffusor integrierter Überdrucksicherung (in geschlossener Stellung)

Figur 8a

Querschnitt durch das Anschlussstück aus Figur 8 mit geöffneter Überdrucksicherung

In the following, further details and features of the invention will be explained in more detail with reference to the exemplary embodiments explained with reference to the figures. However, these are not intended to restrict the invention, but only to explain it.
It shows in a schematic representation:

Figure 1:

Cross section through an embodiment of the pressure tank according to the invention with an antistatic wall with turbulator openings on the connection piece and a diffuser integrated into a coupling part

Figure 1a:

Enlarged section of the lower half of the connector Figure 1

Figure 2:

Perspective view obliquely from below of the connection piece Figure 1

Figure 3:

Perspective view obliquely from below and cut-open view of a further embodiment of the connection piece with an integrated diffuser.

Figure 4:

Relationship between test pressure and sealing lip thickness in the radial direction

Figure 5:

Cross section of a further embodiment of the connection piece with a profiled diffuser face

Figure 6

Cross section of a further embodiment of the connection piece and coupling part with the antistatic wall and diffuser belonging to the latter

Figure 7

Perspective view obliquely from below of a further embodiment of the coupling part with antistatic wall and diffuser

Figure 8:

Cross-section of a further embodiment of the connection piece with overpressure protection integrated in the diffuser (in the closed position)

Figure 8a

Cross section through the connector Figure 8 with opened overpressure protection

In Figure 1 shows a cross section through an opening with an inserted connection part of a pressure tank according to the invention. Connection piece 2 is firmly inserted in opening 11, with the mutually complementary contact surfaces 26 and 111 having a torque coupling for the uniform and effective transmission of torques from connection piece 2 to hollow body 1. Another torque coupling is created by the contact surfaces between connection part 20 of connection piece 2 and the fiber-reinforced layer 8, which covers the hollow body 1 and partially the connecting part 20. Connection piece 2 is in two parts and consists of the outer connection part 20 and a neck ring 23 embedded in it, which has an internal thread 25, by means of which coupling part 3 is screwed into the connection piece 2. The handling and positioning of coupling part 3 during manufacture, in particular when it is carried out automatically by a loading robot, is carried out by the Centering bevel 234 at the upper end of the internal thread 25 facilitated. At the lower end of the passage opening 21, the diffuser 22 is integrated in the coupling part 3.

Diffuser 22 is used to slow down and deflect a fluid flowing in under high pressure, for which purpose it closes passage 21 in the axial direction and only has radially oriented outlet openings 221. The fluid flowing radially after passing through diffuser openings 221 hits the antistatic wall 27 surrounding the diffuser 22, which is designed as a cylinder collar interrupted by turbulator openings 28, here designed as elongated notches, at a speed that is reduced compared to a theoretical flow speed without a diffuser. Antistatic wall 27 is an axially directed projection of the outer connection piece 20 and thus represents an integral part of the connection part 20. In order for the coupling part to remain free of forces and torque during filling, the diffuser 2 is mirror-symmetrical and rotationally symmetrical, with a 6 here - has numerous rotational symmetry. The same applies to the antistatic wall 27.

This ensures a significant improvement of the present invention, namely that the seam 12 between the hollow body 1 and the connection piece 2 is located outside the space between the diffuser 22 and the antistatic wall 27. This advantageously prevents the fluid flowing in under high pressure from being pressed into the seam by the high static counterpressure that builds up in the said gap, possibly in conjunction with the dynamic pressure of the fluid hitting the boundary surface of the gap under high pressure, and thus the tightness of the pressure tank during filling or, in the worst case, plastic deformation, is permanently compromised.

This is promoted by the fact that only a slight counterpressure builds up in said space, since the turbulator openings 28 create an additional drainage path. The fluid is atomized into a mist of fine droplets as it passes through the openings 28, which minimizes the risk of static charging in areas further away from the opening 11.

The tightness of the pressure tank according to the invention shown here, both during filling and in the pressure-filled state, is furthermore advantageous by dimensioning the radial thickness of sealing lip 24, which extends between a neck ring collar 231 and sealing ring 31 of the, extending axially downward from the neck ring 23 Coupling part 3 extends, proportionally increasing with the intended test pressure, ie Maximum pressure of the tank guaranteed.

Figure 1a shows an enlarged section of the lower half of connection piece 2 or the lower end of passage 21. The difference between the height HT of the internal thread 25 and the distance DO between the lower edge of the internal thread 25 and sealing ring 31 is according to the relationship HT-DO ≤ 0.5 TP is selected, where TP stands for the thread pitch of the internal thread 25.

Figure 2 shows a perspective view obliquely from below of the connection piece Figure 1 . The hexagonally shaped contact surface 26 can be seen, which, with the complementary contact surface of the opening of the hollow body, into which connection piece 2 is inserted and welded or glued, forms a torque coupling for transmitting torques from connection piece 2 to the hollow body of the pressure tank. In the internal thread of the, invisible, The neck ring 23 is screwed into the coupling part 3, which at its lower end has the diffuser 22 which forms an obstacle to the flow in the axial direction. Coupling part 3 is screwed in so far that the radially oriented diffuser openings 221 are approximately aligned with the turbulator openings 28 in the antistatic wall 27. As a result, a high flow rate is achieved during filling, but at the same time, due to the corresponding narrow dimensioning of the turbulator openings 28 in width, a good antistatic effect is still achieved. This is, however, optimized when the diffuser openings 221 are not aligned with the turbulator openings 28, but are opposite the continuous ones of the collar 27, so that fluid emerging from the openings 221 hits them and is decelerated even further. In this case, almost all of the charges entrained by the coupling part 3 or diffuser 22 are deposited in the antistatic wall 27, from where they are diverted by drops to the coupling part 3 or diffuser 22, since the collar 27 is part of the connecting part 2, which can be made relatively more conductive, and not of the, non-conductive, hollow body 1 is.

In Figure 3 a further preferred embodiment of the connection part of the pressure tank according to the invention is shown. The upper part of the figure shows a perspective view obliquely from below, from which it emerges that diffuser openings 221 are oriented relative to the antistatic wall 27 with turbulator openings 28 such that a fluid jet emerging from the openings 221 hits the solid wall sections 27 precisely in the center. As in the in Figures 1-2 embodiment shown, diffuser 22 is mirror-symmetrical and sixth-fold rotationally symmetrical.

The lower part of the figure shows a cut-open view of the connection piece 2. As can be seen, this is also in two parts from the outside Connection piece 20 and neck ring 23 built up. Neck ring 25 in turn has an internal thread 25 for connecting a hose, pipe or a valve or other coupling part. The essential difference from the previous embodiment is that diffuser 22, as can be clearly seen in this partial figure, is an integral part of connector 2, more precisely connector 20. As a result, a potentially different relative orientation of the diffuser openings 221 to the antistatic wall 27 and the turbulator openings 28 is avoided during each screwing-in process.

Figure 4 shows in a graph the relationship proposed by the present invention between the radial thickness D of the sealing lip 24 and the desired test pressure. The sealing lip thickness is shown here on the y-axis, the pressure on the x-axis. The course is linear, strictly monotonically increasing, with a constant of proportionality (slope) of 0.01 mm / bar in the case of the maximum recommended thickness Dmax and 0.019 mm / bar in the case of the minimum recommended thickness Dmin. The respective axis sections at 100 bar are 3.03 mm or 4.0 mm with the minimum or maximum recommended thickness. The radial thickness D should therefore be between Dmin and Dmax for a given test pressure P in order to guarantee optimum tightness.

Figure 5 shows a further advantageous embodiment of the connection piece 2 of the pressure tank according to the invention, which has a frustoconical bulge against the direction of flow of the fluid to modify the flow conditions on the inner end face 222 of the diffuser. The lateral neck ring flange 232 serves to support the neck ring 23 when there is an axial load. Throat ring holes 233 into which the liquid thermoplastic material of the connector can flow in during manufacture.

Figure 6 shows an embodiment in which both the diffuser 22 and the antistatic wall 27 form part of the coupling part 3. This offers the special advantage that the antistatic wall 27, as a highly stressed component, can be made easily accessible to maintenance or replacement measures by removing the coupling part 3.

In Figure 7 an embodiment of the antistatic wall 27 and the diffuser 22 is illustrated in which the turbulator openings 28 of the antistatic wall 27 taper radially and which has a polygonal contour. Such shapes of the turbulator openings and appropriate contours on the inner surface of the antistatic wall 27 facing the diffuser 22 represent a possibility of directing the fluid flow in detail and also influencing the material wear of the antistatic wall 27 itself.

Figure 8 shows an embodiment of the diffuser 22 with integrated overpressure protection 9, which is here in the closed position. A complementary representation of the pressure relief device 9 in the open position is shown in FIG Figure 8a given. In the event of a sudden pressure drop on the outlet side and thus a flow increase during fluid removal, for example due to the bursting of a line, the overpressure safety device is entrained and closes the outlet above the diffuser openings 221.

Reference list

1

Hollow body

11

Opening in the hollow body 1

111

Contact area

12th

Seam between hollow body and connector

13th

Interior of the hollow body

2

Connector

20th

Connector

21st

Outlet opening

22nd

Diffuser

221

Diffuser opening

222

inner diffuser face with bulge

23

Neck ring

231

Neck collar

232

Neck flange

233

Neck ring holes

234

Centering chamfer

24

Sealing lip

25

inner thread

26th

Contact area

27

Antistatic wall

271

inner anti-static wall surface

28

Turbulator opening

3

Coupling part

31

Sealing ring

8th

fiber reinforced layer

81

Torque clutch

9

Overpressure protection

P

Test pressure

D.

Sealing lip thickness, radial

Dmin

minimum recommended sealing lip thickness

Dmax

maximum recommended sealing lip thickness

TP

Thread

HT

Thread height

DO

Sealing ring distance to the lower edge of the thread

Claims (16)

1. Pressure tank for storage of high and low pressure fluids/gases, particularly LPG, LNG or CNG, comprising

   - a hollow body (1) of thermoplastic material with at least one outlet (11), having a surrounding contact area (111),

   - one boss (2) each per outlet (11), having at least one aperture (21) to the interior (13) of the hollow body (1) and being connected over its entire surface with a complementary contact area (26) to the contact area (111), the aperture (21) having a diffuser (22) at a bottom end, which can be part of the boss (2), or of a neckring (23) or of a coupling piece (3), and which seals the aperture (21) in axial direction and has diffuser openings (221) pointing primarily only in radial direction,

   - inside the hollow body (1), a static eliminator wall (27) surrounding the diffusor (22), which is part or the boss (2) or the neckring (23) or is attached as a separate parte to the coupling piece (3),
   characterized in that
   the static eliminator wall (27) has several turbulence release openings (28), which are positioned relatively to the diffuser openings (221) in such a way, that fluid, which flows in under pressure, creates a substantially stationary flow in the region below the boss (2).
2. Pressure tank according to claim 1, characterized in that the turbulence release openings (28)

   - are elongated openings, beginning at the bottom edge of the static eliminator wall (27) and extending above an essential part of its height, and/or

   - are aligned with the radial openings (221) of the diffuser (22), or

   - are aligned with the opposite integrated-segments of the static eliminator wall (27), particularly with their respective centre.
3. Pressure tank according to one of the preceding claims, characterized in that the static eliminator wall (27) has a round contour or a more complex contour, e.g. a waved line contour or a polygonal contour along its surface (271) which is facing the diffuser (22).
4. Pressure tank according to one of the preceding claims, characterized in that diffuser (22)

   - has round, oval or polygonal, particularly rectangular diffuser openings (221), or

   - has an interior surface (222), which is plane or has a more complex topography, particularly a convex or conical elevation, or

   - has a mechanism (9), which closes the aperture (21) at a critical flow rate of the fluid.
5. Pressure tank according to one of the preceding claims, characterized in that the aperture (21) of the boss (2) has an internal thread (25), into which a valve or other coupling piece (3) is screwed, having for sealing purposes

   - at least one sealing ring (31), or

   - a tapered external thread.
6. Pressure tank according to one of the previous claims, characterized in that the boss (2) comprises an injected or embedded neckring (23), which lies concentrically in an outer connection part (20) of the boss (2) and provides at least a part of the aperture (21) and the internal thread (25).
7. Pressure tank according to claim 6, characterized in that the neckring (23)

   - has a reduced symmetry compared to circular symmetry, in regard to the rotation around the axial direction of the aperture (21), particularly an n-fold rotation symmetry, for example a polygonal cross section, or no symmetry, and/or

   - a mirror symmetry with a mirror plane, which comprises the axial direction, and/or

   - has an surrounding collar (232), extending in radial direction, with holes (233) in it, and/or

   - has a centering groove (234) at the top of the aperture (21), and/or

   - is manufactured of metal, and/or

   - has connecting holes and grooves.
8. Pressure tank according to claim 6 or 7, characterized in that the connection part (20)

   - is manufactured from a thermoplastic material, and

   - comprises contact area (26), by which it is connected over its entire surface with the complementary contact area (111) of the outlet (11) in the hollow body (1), particularly through injecting, bonding or welding by superficial liquefaction of the thermoplastic materials of the contact areas (111) and (26) and the following compression.
9. Pressure tank according to one of the claims 6-8, characterized in that the neckring (23) has at the bottom side a downwards pointing neckring collar (231) surrounding the aperture (21), the collar being embedded in the material of the connection part (20), such that the material of the boss (2) lying between the internal side of the neckring collar (231) and the aperture (21) forms a sealing lip (24).
10. Pressure tank according to claim 9, characterized in that at least one sealing ring (31) lies between coupling piece (3) and sealing lip (24).
11. Pressure tank according to claim 9 or 10, characterized in that a radial thickness of the sealing lip (24) is selected proportionally to a test pressure of the pressure tank (1).
12. Pressure tank according to one of the claims 9 -11, characterized in that the radial thickness of the sealing lip (24) is selected between a minimum thickness (Dmin) and a maximum thickness (Dmax), these thicknesses being linked with the test pressure (P) by the following relations: $$\mathrm{Dmax}\left(\mathrm{mm}\right)=0.01\mathrm{P}\left(\mathrm{bar}\right)+3.0$$

    

    $$\mathrm{Dmin}\left(\mathrm{mm}\right)=0.019\mathrm{Dmax}\left(\mathrm{mm}\right)+2.95.$$

    
13. Pressure tank according to one of the preceding claims, characterized in that the contact areas (26, 111) for transferring the torques from the boss (2) onto the hollow body (1) has as torque coupling no circular symmetry regarding rotation around the axial direction of the aperture (21) and has particularly an n-fold rotation symmetry, for example a polygonal shape.
14. Pressure tank according to one of the preceding claims, characterized in that a further layer (8) surrounds the hollow body (1), the further layer being reinforced by fibres, particularly glass fibres, carbon fibres, aramid fibres, dyneema fibres, other synthetic fibres and/or natural fibres and comprising additionally a matrix embedding the fibres, particularly out of thermally or UV-curable resins or other resins, with a further treatment of the hollow body (1) surface, that has taken place in particular before the application of the reinforcement layer.
15. Pressure tank according to claim 14, characterized in that a second torque coupling (81) is integrally formed into the fibre-reinforced layer (8) in the outlet (11) area, such coupling having a shape of non-circular symmetry, particularly with n-fold rotation symmetry or a polygonal shape for the purpose of transferring the torques affecting the boss (2) into the layer (8).
16. Pressure tank according to one of the claims 5 -15, characterized in that the difference between the height (HT) of the internal thread (25) and the axial distance between a bottom end of the internal thread (25) and the center of sealing ring (31) follows the relation $$\mathrm{HT}\left[\mathrm{mm}\right]-\mathrm{DO}\left[\mathrm{mm}\right]\le 0.5\mathrm{TP}$$

    

    and further $$\mathrm{HT}\left[\mathrm{mm}\right]={\mathrm{n}}_{\mathrm{T}}\mathrm{TP}\left[\mathrm{mm}\right],$$

    

    wherein (TP) is a pitch of the internal thread (25) in millimeter per winding and n_T denotes the number of windings of the internal thread (25).

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