EP2751469B1 - Pressure tank having a plug-and-socket connection and a welded connection for the connector piece - Google Patents

Description

The invention relates to a pressure tank, consisting of a hollow body made of thermoplastic material with at least one opening, in each of which a connector is inserted, which has at least one passage to the interior of the hollow body.

Prior art tanks are known for containing gases or liquids which are under high pressure, such as e.g. liquefied petroleum gas (LPG) or compressed natural gas (CNG). These tanks are made, among other things, from thermoplastic material by blow molding or injection molding. In order to increase the pressure resistance, these tanks are provided in a second step with an outer layer of resilient fibers, which are usually embedded in a casting resin, which connects the fibers together and fixes them on the inner plastic layer.

In any case, regardless of the design, such a tank must be provided with at least one fitting to which a valve, hose or pipe is coupled in order to fill or empty the tank. These elements usually carry as interface a pipe socket made of metal with a thread or with a bayonet, which must be pressure-tight and tightly connected with a complementarily shaped counterpart in the fitting of the tank.

At the current state of the art plastics are known for the fittings, which are sufficiently resistant to tension and can also be produced as a hollow body with the appropriate wall thicknesses and matching threads or bayonet guides.

Since the wall thicknesses and the dimensional accuracy requirements of the fittings differ considerably from the wall thicknesses and the tolerances of the pressure tank, it is in practice neither useful nor economical to produce the fittings and the tanks in one piece.

Rather, it is customary to provide a hollow container made of plastic after its completion in a further operation with a separately manufactured and mostly multi-piece connector. For example, the patent application describes US 2011/010/1002 a plastic tank with two openings. On these openings, in each case from the inside and from the inside in each case an approximately cylindrical connection part is placed, which is widened at one end with a collar-shaped flange. These two parts are screwed together with a thread and thereby pressed together, so that they lie flat on the inside and outside of the area around the opening of the tank. By appropriate pressure as well as by additionally in the tank or the flanges embedded sealing rings the required pressure resistance is achieved.

A major disadvantage of this and other similar concepts is that the fittings are designed rotationally symmetric. If a screw connection must be made to connect to a hose, pipe or valve, the fitting must transmit torque to the tank. In rotationally symmetrical fittings, however, only the value of the tightening torque can be achieved, which results from the contact force of the two flanges on the tank and the static friction coefficient of the two surfaces pressing against each other.

Since the surface of the plastic tanks is usually smooth and smooth, therefore, there is only a limited torque peak. If this is exceeded, it will be difficult to make a sufficiently tight connection. In addition, there is the risk that by pivoting the connection piece with respect to the tank, this connection will quickly leak and the fluid that is actually to be taken out continuously discharges, and this tends to increase.

Against this background, the invention has set itself the task of developing a connection piece for plastic pressure tanks that safely and permanently transmits the peak values of the torque occurring when tightening a screw connection or a bayonet to the hollow body made of plastic.

As a solution, the invention teaches that on the connection piece around the passage running around a sealing flange is formed, which is visible to the outside and welded to the hollow body and / or glued and is integrally formed on the at least one torque clutch, the cross-section polygonal or not is circular and which is plugged into a complementary coupling receptacle in the hollow body, which runs around the opening.

It is therefore an essential idea of the invention to separate the function of the seal between the connection piece and the hollow body from the function of the torque transmission from the connection piece to the hollow body. In contrast to the current state of the art, in which these two functions are combined in one element, the invention provides for clearly separate regions of the connecting piece:

The first sealing area is the "sealing flange". The second torque transmitting area is the "torque clutch".

The sealing flange is visible to the outside in the mounted state. In the simplest case, it has the shape of a disc flanged to the central body of the fitting around the passage. If the front edge of this disc is round, so the disc has no torque clutch and is only for sealing. The hollow body facing surface of the flange can be bonded to the hollow body.

Additionally or alternatively, the edge region of the sealing flange can be welded to the hollow body, i. so that both the hollow body in the support region of the Abdichtflansches and the Abdichtflansch itself is liquefied in its edge region at the contact surfaces by these areas are heated above the melting temperature of the material and then pressed both parts to each other, so that the liquids mix with each other. If the heating is completely circumferential and uniform, then the connection between the sealing flange and the hollow body is sealed during cooling and solidification of the liquid.

As mentioned above, it is the essential idea of the invention that the connecting piece has at least one further torque-transmitting region, namely the "torque coupling". Such a torque clutch can be formed either on the side facing the interior of the hollow body side of the Abdichtflansches and / or on the end face of the Abdichtflansches.

• Im allgemeinsten Fall wird durch jeden Querschnitt, der nicht kreisförmig ist, ein Drehmoment übertragen, indem alle von einer Kreislinie abweichend geformten Bereiche der Außenflächen der Momentenkupplung sich auf den dazu komplementären Bereich der Kupplungsaufnahme aufpressen.

In both embodiments, their task is similar to a wrench, which is placed on the head of a screw to transmit a torque. Similarly, the cross section of the torque clutch and the complementary coupling receptacle is formed:

• In the most general case, a torque is transmitted through each cross section, which is not circular, in that all regions of the outer surfaces of the torque coupling deviating from a circular line press against the complementary area of the coupling receptacle.

For the cross section are easy to construct variants polygons, so polygons, which consist of interconnected lines. The simplest polygon is a triangle. It has in principle the largest extent in the radial direction with respect to the central axis of the torque clutch. Naturally, all other polygons are also usable, e.g. a rectangle, a hexagon, an octagon, a nonagon, a decagon, a dodecagon, or any number of surfaces.

This polygon is shaped arbitrarily in the most general case. However, since in practice the connector usually has only a single circular passage, it makes sense to choose a regular polygon, which surrounds the circular passage with a regularly repeated variation of the wall thickness to the passage. That is, all degrees have the same length and form the same angle with each adjacent degree. As the number of corners increases, such a regular polygon continues to approach the circle. This also reduces the proportion of the area effective for transmitting the torque in longitudinal section. This effect is best illustrated by the fact that a circle is drawn in cross-section into the interior of the polygon, which touches all edges tangentially. A second circle is placed through the corners of the polygon, which is then concentric with the inner circle. The distance of the two circles from each other limits the surface portions that are effective for the torque transmission. For a regular triangle, these areas are the largest; however, there are only three of these areas. For example, a regular dodecagon, these areas are considerably smaller, but also twelve times available.

It is typical for each polygon that it is subjected to the greatest load in the transmission of a torque in the region of its edges. This effect is particularly visible when there is little play between the torque coupling and the coupling receptacle. Then the two parts touch each other at the first moment only punctiform. Only through the elasticity of the material becomes an area with increasing force from the point.

This restriction of all polygonal profiles, which increases abruptly in the area of the corners of the pressure, can be avoided by the fact that the outline is a wavy line. Then changes over the outer surfaces of the torque clutch and the clutch receiving away the force load not leaps and bounds steadily.

As an alternative to polygonal cross sections, the outline of the torque clutch and the clutch receptacle may also be a star or other serrated line. Compared to a polygon, this increases the area that transfers the force from one element to another.

Since the wall thicknesses and the dimensional accuracy requirements of the fittings differ considerably from the wall thicknesses and the tolerances of the pressure tank, it is in practice neither useful nor economical to produce the fittings and the tanks in one piece.

Rather, it is customary to provide a hollow container made of plastic after its completion in a further operation with a separately manufactured and mostly multi-piece connector. For example, the patent application describes US 2011/010/1002 a plastic tank with two openings. On these openings, in each case from the inside and from the inside in each case an approximately cylindrical connection part is placed, which is widened at one end with a collar-shaped flange. These two parts are screwed together with a thread and thereby pressed together, so that they lie flat on the inside and outside of the area around the opening of the tank. By appropriate pressure as well as by additionally in the tank or the flanges embedded sealing rings the required pressure resistance is achieved.

In the document WO 2010/053146 Also, a tank is described in which the connector is attached separately and is designed circular.

A major disadvantage of this and other similar concepts is that the fittings are designed rotationally symmetric. If a screw connection must be made to connect to a hose, pipe or valve, the fitting must transmit torque to the tank. For rotationally symmetrical fittings, however, only the value of Tightening torque achievable, resulting from the contact pressure of the two flanges on the tank and the coefficient of static friction of the two pressing surfaces.

In a very easy to explain embodiment of the torque clutch, it is integrally formed on the end edge of the Abdichtflansches. If you think of a circular disk as a sealing flange, so the scope of this disc is extended to the "corners" of a polygon. Of course, a corresponding counterpart in the hollow body must be created to these "corners". In this variant, the diameter of the torque clutch is greater than the sealing part of the connecting piece.

If the surface of the sealing flange merges into the surface of the torque coupling, at first glance no exactly defined boundary between the two areas can be identified.

In this embodiment, of course, the area of the sealing flange with its bonding also contributes to the transmission of torque. However, if this area already begins to deform slightly under the load of a torque which is too high for it, further torque is transmitted beyond the outer edge of this area to the so-called "second torque clutch" and from there to the "second clutch intake" , In this way, the connection between the Abdichtflansch and the recess is protected from excessive stress.

The areas for sealing and transmitting the torque are to be clearly differentiated in another embodiment of the torque clutch. In this variant, the torque clutch on the side of the Abdichtflansches facing the interior of the Abdichtflansches - ie closer to the center of the tank - is formed. Here, the torque coupling - eg as a polygonal profile - to the inner surface of the Abdichtflansches Therefore, at first glance, it can be recognized as a pure torque coupling.

In a further expansion stage of the torque clutch on the inside of the Abdichtflansches is proposed for the outline of the cross section of the torque clutch and the coupling receptacle that at least one strip-shaped region is formed on a core region, which points approximately radially outward. The strip-shaped area then proceeds from the core area approximately as in a propeller, the wings of the hub.

The two embodiments of the torque coupling described above can be used either alone or in combination. In the last-mentioned variant, the connecting piece according to the invention even has two torque couplings: one on the end face of the sealing flange and the other on the surface facing the tank.

In a further refined embodiment, another annular recess is provided below the sealing flange in the recess complementary thereto, into which a seal, such as e.g. an O-ring is inserted. In the event that the welding or the gluing of the sealing flange does not seal perfectly, the round cord seal takes over this function.

In another variant, elongated welding webs are integrally formed on the sealing flange and / or on the torque coupling. In a first variant, the material protruding over the adjacent surfaces of these welding webs will liquefy during welding and on the adjacent surfaces of the Abdichtflansches and distribute the coupling receptacle and / or the recess on the surface of the hollow body and thus provide an intimate connection.

This effect can be enhanced by the fact that the welding webs rest on the same, second welding webs, which are also melted during the welding process, so that more liquid material is available.

As an alternative, the welding webs engage in complementarily shaped welding notches in the depression or in the coupling receptacle. When welding the Abdichtflansches the liquefied material of the welding webs flows into the welding notches and liquefied there the top layer.
In all three variants, the profile of welding bars and welding notches can be curved or angular. In their course, webs and notches may be straight or wavy throughout. But it is also a dotted or dashed course possible and useful.

In the simplest case, the sealing flange rests on the surface of the hollow body around the opening. Alternatively, for an even better connection of the Abdichtflansches with the hollow body of the Abdichtflansch be sunk into a complementary recess of the hollow body surrounding the coupling receptacle.

The hollow body of a pressure tank according to the invention is usually made in practice from a thermoplastic material, which receives its shape by blow molding or injection molding in a corresponding negative mold. Advantages of this method are the relatively short processing time and the relatively low processing costs in the production of each individual copy. A Restriction is, however, that such a hollow body can withstand only a very limited pressure. Therefore, compressive strength is enhanced by overlying fibers such as glass fibers or carbon fibers or aramid fibers or dyneema fibers. These fibers are placed in rings or wavy lines around the hollow body and glued together with resins and on the hollow body. These resins can then be crosslinked thermally or by irradiation with UV light and thereby cured.

In the simplest case, an internal thread, a bayonet or the negative mold of another coupling is included in the connection piece for connection to the valve or hose or pipe piece departing therefrom. In the case of very filigree couplings or higher requirements, a further coupling piece, e.g. made of metal, used or cast in, which fits exactly to the profiles to be connected. So that this additional profile does not twist even with respect to the connecting piece during a torque transmission, it expediently has a polygonal or another non-round profile on its outside.

If this coupling piece is cast into the connector, this creates a precisely complementary counterpart. Between the connection piece and coupling piece, the torque is then transmitted in the same way as between connection piece and hollow body.

Figur 1

Hohlkörper mit Anschlussstück vor dessen Montage

In the following, further details and features of the invention will be explained in more detail with reference to an example. However, this is not intended to limit the invention, but only to explain. It shows in a schematic representation:

FIG. 1

Hollow body with fitting before its assembly

In FIG. 1 If a pressure tank according to the invention is shown on the hollow body 1 before the fitting 2 is mounted. The hollow body 1 is shown here in dimming point perspective of "obliquely above". It can be seen that it consists in this embodiment of a cylinder which is hemispherical completed at its end faces.

In the front side of the hollow body 1, the opening 11 can be seen, through which a view into the interior 12 of the hollow body is free.
The variant embodiment of a pressure tank according to the invention shown here has a connection piece 2, which derives a torque from the connection piece 2 to the hollow body 1 via the two torque clutches 23 and 25, which are different from each other.

The first torque clutch 23 consists of a central, octagonal region and formed on two opposite edges strip which is designed to be complementary to the first coupling receptacle 13 in the hollow body 1. This extends around the opening 11 around. In the illustrated embodiment, it consists of an octagon in which strip-shaped extensions are integrally formed on two opposite edges, which extend radially to the opening 11. The first coupling receptacle 13 is the plane sunken furthest into the surface in the region of the opening 11.

The second torque clutch 25 is also a polygon in the embodiment shown here, which is designed here as an octagon, which continues without further paragraph direct from the sealing flange 22.

In FIG. 1 is quickly apparent by the comparison between the outer contour of the connector 2 and the largest outline of the recesses in the hollow body 1, where the second coupling receptacles 16 are arranged. They are in the illustrated embodiment, a direct continuation of the recess 14 and as "corners" on the edge of this depression recognizable.

For torque transmission from the connector 2 on the hollow body 1 is used in the in FIG. 1 illustrated embodiment, not only the first torque clutch 23 which is sunk into the complementary shaped first coupling receptacle 13 in the hollow body 1, but as an additional reinforcement also the octagonal second torque clutch 25 on Abdichtflansch 22 and the complementary second coupling receptacle on the edge of the recess 14th

By four double arrows it is shown how the connector 2 has to be pivoted and lowered so that it can be inserted into the recess 14 and into the two coupling receptacles 13 and 16.

In FIG. 1 is understandable that after inserting the connector 2 to the outside, the first torque clutch 23 is no longer visible because it is covered by the - larger - sealing flange 22. Visible is then only the second torque clutch 25, which then conceals the complementary second coupling receptacles 16.

FIG. 1 illustrates that the recess 14 compared to the size of the passage 21 in the connector 2 provides a relatively large area. Therefore, by gluing the relatively large Abdichtflansches 22 with the recess 14, an additional sealing effect can be achieved.

As an additional variant, in the illustrated embodiment in the center of the fitting 2 around the passage 21 there is still another, e.g. metallic coupling piece taken in. It has a thread on its inside, which can be used to connect a valve, a pipe or a hose. Alternatively, the guides of a bayonet or other elements can be molded.

In FIG. 1 is shown as a further embodiment, that on the sealing flange 22 elongated, bead-like welding webs 24 are formed, here in the form of two circular arc segments which engage in complementarily shaped welding notches 15 in the recess 14. When welding the Abdichtflansches 22, the liquefied material of the welding webs 24 flows into the welding grooves 15 and there liquefied the uppermost layer, so that the welding bar 24 and the welding grooves 15 intimately connect with each other.

LIST OF REFERENCE NUMBERS

1

hollow body

11

Opening in the hollow body 1

12

Interior of the hollow body 1

13

first coupling receptacle in the hollow body 1 for the first torque clutch 23

14

Recess on the surface of the hollow body 1, complementary to the sealing flange 22nd

15

Weld notch in recess 14 or in coupling receptacle 13

16

second coupling receptacle in the hollow body 1 for the second torque clutch 25

2

Connecting piece, inserted in opening 11

21

Passage in the connector 2 to the interior 12th

22

Sealing flange on the connector 2, welded or glued to the hollow body 1

23

first torque clutch on the connector 2, inserted in the first coupling receptacle 13

24

Welding webs on sealing flange 22 and / or torque coupling 23

25

second torque clutch on the connector 2, inserted into the second coupling receptacle 16 in the hollow body 1.

Claims (13)

1. Pressure tank, comprising

   - a hollow body 1 of thermoplastic material comprising

   - at least one opening 11, into which

   - there is inserted a connector 2, in each case,

   - which has, in each case, at least one passage 21 to the interior space 12 of the hollow body 1,
   characterised in that, integrally formed onto the connector 2, surrounding the passage 21, is a sealing flange 22,

   - which is outwardly visible and

   - Is welded and/or adhesively bonded to the hollow body 1, and

   - on which there is integrally formed at least one torque coupling 23,25,

   - of which the cross-section is polygonal or non-circular and

   - which is plugged into, in each case, one complementary coupling socket 13, 16 in the hollow body 1, which surrounds the opening 11.
2. Pressure tank according to claim 1, characterised in that a first torque coupling 23 is integrally formed on the sealing flange 22,

   - which emerges from that side of the sealing flange 22 that faces the interior space 12 and

   - which is plugged into a complementary, first coupling socket 13 in the hollow body 1, and

   - of which the cross-section is surmounted at every point by the sealing flange 22.
3. Pressure tank according to one of the preceding claims, characterised in that on the end face of the sealing flange 22, there is integrally formed a second torque coupling 25, which is plugged into a second coupling socket 16 in the hollow body 1.
4. Pressure tank according to one of the preceding claims, characterised in that, on the sealing flange 22, there is integrally formed

   - only a first torque coupling 23 or

   - only a second torque coupling 25 or

   - both a first torque coupling 23 and a second torque coupling 25.
5. Pressure tank according to one of the preceding claims, characterised in that, on the sealing flange 22 and/or on the torque coupling 23, elongated welding bridges 24 are integrally formed,

   - of which the profile can be curved or angular and

   - of which the profile can be

   - straight throughout or

   - undulating or

   - dotted or

   - dashed.
6. Pressure tank according to claim 5, characterised in that the welding ribs faces 24 engage in the weld notches 15, which are shaped complementary thereto, in the depression 14 or in the coupling socket 13.
7. Pressure tank according to claim 5, characterised in that, before welding, the weld faces 24 lie on ribs, which are complementary thereto, on the depression 14 or on the coupling socket 13.
8. Pressure tank according to one of the preceding claims, characterised in that the outline of the cross-section of the torque couplings 23, 25 and the coupling sockets 13, 16 is

   - a rectangle or a hexagon or an octagon or a nonagon or a decagon or a dodecagon or another polygon or

   - a star or another zigzag line or

   - an undulating line.
9. Pressure tank according to one of the preceding claims, characterised in that the outline of the cross-section of the first torque couplings 23 and the coupling sockets 13 consists of a core region, which is extended by at least one approximately strip-shaped region, which faces approximately radially outward.
10. Pressure tank according to one of the preceding claims, characterised in that the sealing flange 22 can be received by a depression 14, which surrounds the first coupling socket 13, on the hollow body 1.
11. Pressure tank according to one of the preceding claims, characterised in that into the depression 14, there is embossed a completely surrounding groove, into which a seal, such as, for example, a round cord seal, can be inserted.
12. Pressure tank according to one of the preceding claims, characterised in that, on the hollow body 1, there lies a further layer, which is reinforced by

    - glass fibres and/or

    - carbon fibres and/or

    - Aramid fibres and/or Dyneema fibres or other synthetic fibres and/or

    - natural fibres and/or

    - combinations of fibres and plastic, such as, e.g., glass fibres and polyethylene, which flows around the glass fibres at elevated temperatures,
    and

    - which consists of thermally or ultraviolet curable regions or of other resins.
13. Pressure tank according to one of the preceding claims, characterised in that an internally threaded piece or a bayonet, or another coupling piece, which has a polygonal profile on its outside, can be inserted into the connector 2.

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