FIBRE-REINFORCED PRESSURE VESSEL

Abstract

The invention relates to a fiber-reinforced pressure vessel (1) and to a method (100) of manufacturing the same, having an inner vessel (2) made of a thermoplastic material for receiving a filling medium, with an outer face and a fiber composite layer (3) arranged around the outer face for providing pressure resistance of the pressure vessel and at least one valve connection (4) connected to the inner vessel and the fiber composite layer; a thermoplastic band (5) being applied additionally at least on a portion of the outer face of the inner vessel, the thermoplastic band having a thermal expansion coefficient which is small enough to keep any gap (6) which may be created by thermal shrinkage between the fiber composite layer and the inner vessel by its thermal expansion coefficient smaller than would be the case without the presence of the thermoplastic band.

Claims

1. A fiber-reinforced pressure vessel with an inner vessel made of a thermoplastic material for receiving a filling medium, having an outer face and a fiber composite layer arranged around the outer face for providing pressure resistance of the pressure vessel, and at least one valve connection connected to the inner vessel and the fiber composite layer; in addition a thermoplastic band being applied at least on a portion of the outer face of the inner vessel, the thermoplastic band having a thermal expansion coefficient sufficiently small to keep any gap which may be created by thermal shrinkage between the fiber composite layer and the inner vessel by its thermal expansion coefficient smaller than would be the case without the presence of the thermoplastic band.

2. The pressure vessel according to claim 1, wherein; the thermoplastic band comprises at least one matrix material made of a material which is compatible with the inner vessel.

3. The pressure vessel according to claim 2, wherein; the thermoplastic band is welded on the inner vessel.

4. The pressure vessel according to claim 1, wherein; the thermoplastic band is a polyamide or polyethylene band.

5. The pressure vessel according to claim 1, wherein; the thermoplastic band comprises a fiber reinforcement, preferably a carbon fiber containing fiber reinforcement.

6. The pressure vessel according to claim 4, wherein; the thermoplastic band is additionally applied on the central portion and/or on the pole caps.

7. The pressure vessel according to claim 4, wherein; the thermoplastic band covers the inner vessel completely.

8. The pressure vessel according to claim 1, wherein; the thermoplastic band is applied on the inner vessel in several plies.

9. The pressure vessel according to claim 8, wherein; the plies have a suitable number for at least partially eliminating the gap between the fiber composite layer and the inner vessel.

10. The pressure vessel according to claim 1, wherein; the fiber composite layer consists of a thermosetting material.

11. The pressure vessel according to claim 1, wherein; the fiber composite layer is a layer with several plies of fiber composite material, embedded in a matrix material, and the thermoplastic band is interwoven with at least one ply facing the inner vessel.

12. The Method of manufacturing a fiber-reinforced pressure vessel, comprising the following steps: providing an inner vessel for receiving a filling medium made of a thermoplastic material, having an outer face, preferably with at least one valve connection; applying a thermoplastic band at least on a portion of the outer face of the inner vessel, the thermoplastic band having a thermal expansion coefficient which is sufficiently small to keep any gap which may be created by thermal shrinkage between the fiber composite layer and the inner vessel by its thermal expansion coefficient smaller than would be the case without the presence of the thermoplastic band; and finishing the pressure vessel by applying a fiber composite layer on the outer face of the inner vessel provided with the thermoplastic band for providing pressure resistance of the pressure vessel.

13. A method according to claim 12, with the application comprising the further steps of: locally melting the thermoplastic material of the inner vessel to create a melting zone, preferably by means of a laser beam directed at the inner vessel; pressing the thermoplastic band, preferably by means of a pressure roller, on the melting zone to create a welding connection between the inner vessel and the thermoplastic band, the thermoplastic band being preferably fed to the pressure roller via a distance roller and the pressure and distance rollers tracking the laser beam over the outer face of the inner vessel.

14. A method according to claim 13, the local melting and the laser beam being performed such or controlled such, respectively, that in addition to the material of the inner vessel, the thermoplastic band is also melted at least within the melting zone.

15. A method according to claim 12, the fiber composite layer being a layer with several plies of fiber composite material, embedded in a matrix material, and the thermoplastic band being interwoven with at least one ply facing the inner vessel.

Description

SHORT DESCRIPTION OF FIGURES

[0030] These and other aspects of the invention are shown in the figures in detail as follows:

[0031] FIG. 1: a lateral section through a (a) non-stressed pressure vessel according to the state of the art and (b) a non-stressed pressure vessel according to the present invention;

[0032] FIG. 2: an embodiment of the welding process for applying the thermoplastic band on the inner vessel and

[0033] FIG. 3: an embodiment of the method according to the invention for manufacturing the fiber-reinforced pressure vessel according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0034] FIG. 1 shows a lateral section through a (a) non-stressed pressure vessel 1′ according to the state of the art and (b) a non-stressed pressure vessel 1 according to the present invention. In FIG. 1a, it can be seen that at an initial state of 0 bar, the inner vessel 1′ is clearly spaced from the fiber reinforcement. If pressure is applied, this can lead to cracks in the inner vessel 2, causing the vessel to become unserviceable. The gap 6 extends between the inner vessel 2 and the fiber reinforcement through a fiber reinforcement layer 3 around the inner vessel 2 such that the inner vessel 2 here contacts the fiber composite layer 3 merely at the boss 4 and at the boss or blind boss 8 on the opposite side. This gap can have a size of, for instance, 20 mm, although during manufacturing originally the fiber composite material was directly wound about the inner vessel. The pressure vessel 1 in FIG. 1b according to the invention, in contrast, comprises an inner vessel 2 made of a thermoplastic material for receiving a filling medium, having an outer face and a fiber composite layer 3 arranged around the outer face for providing pressure-resistance of the pressure vessel 1 as well as a valve connection 4 connected to the inner vessel 2 and the fiber composite layer 3. On the opposite side, a boss or blind boss 8 is arranged which is connected to the fiber composite layer 3 and the inner vessel 2 as well. Other than in the state of the art, here a thermoplastic band 5 is additionally applied on some regions of the outer face of the inner vessel 2, here in the central portion of the inner vessel 2. The thermoplastic band 5 has a thermal expansion coefficient which is smaller than that of the inner vessel 2 material, so as to keep any gap 6 between fiber composite layer 3 and inner vessel 2, caused by thermal shrinkage, smaller than would be the case if no thermoplastic band 5 were present, as shown in FIG. 1a. It would be possible for the thermoplastic band 5 to cover the inner vessel 2 not only in the central portion but completely. The thermoplastic band 5 can be applied on the inner vessel 2 in several plies L1, . . . Ln, n preferably being a number suitable to at least partially eliminate the gap 6 between fiber composite layer 3 and inner vessel 2, which is here the case at least in the central portion. The fiber composite layer 3 can be made, for instance, of a thermosetting material. The fiber composite layer 3 can consist of several plies F1, . . . , Fn of fiber composite material, embedded in a matrix material. The thermoplastic band 5 or at least one ply of the thermoplastic band 5 can be interwoven with at least one ply F1 facing the inner vessel 2.

[0035] FIG. 2 shows an embodiment of the welding process for applying the thermoplastic band 5 on the inner vessel 2. For this purpose, the thermoplastic material of the inner vessel 2 is locally melted for creating a melting zone 24. The melting zone extends over a surface on which subsequently the thermoplastic band can be applied. The molten area affects only part of the overall thickness of the inner vessel so that melting takes place only on the surface. In this embodiment, a laser is used for creating the melting zone 24, which laser with its laser beam 7 focused on the inner vessel provides sufficient heat to melt the thermoplastic material of the inner vessel. The temperatures to be created on the inner vessel 2 result from the material properties of the thermoplastic material of the inner vessel 2 and are commonly far above 200° C. Polyethylene can be fused well at a surface temperature in the melting zone of approximately 220° C. For polyamide, temperatures of approximately 300° C. should be reached in the melting zone. The selection of the laser and optics required for this purpose lies within the skill of the person skilled in the art. To establish a good welding connection between the inner vessel 2 and the thermoplastic band 5, the thermoplastic band 5 is pressed on the melting zone 24 by a pressure roller 71, the thermoplastic band 5 being fed to the pressure roller 71 via a distance roller 72. The pressure exerted by the pressure roller 71 should be, for instance, 0.5 MPA in case of polyamide and 0.2 MPA for polyethylene. For a continuous welding process, the pressure and the distance roller 71, 72 track the laser beam 7 in the movement direction B of the welding assembly with respect to the inner vessel over the outer face of the inner vessel 2.

[0036] FIG. 3 shows an embodiment of the method 100 according to the invention for manufacturing the fiber-reinforced pressure vessel 1 according to the invention, comprising the following steps: providing 110 an inner vessel 2 for receiving a filling medium made of a thermoplastic material and having an outer face, preferably with at least one valve connection 4; applying 120 a thermoplastic band 5 at least one some portions of the outer face of the inner vessel 2, the thermoplastic band 5 having a thermal expansion coefficient which is sufficiently small to keep any gap 6 which may be produced between the fiber composite layer 3 and the inner vessel 2 due to subjection to pressure by its thermal expansion coefficient smaller than would be the case without the presence of the thermoplastic band 5; and finishing 130 the pressure vessel 1 by applying a fiber composite layer 3 on the outer face of the inner vessel 2, which is provided with the thermoplastic band 5, for providing pressure resistance of the pressure vessel 1. The application 120 can comprise the following additional steps: locally melting 122 the thermoplastic material of the inner vessel 2 to create a melting zone 24, preferably by means of a laser beam 7 directed at the inner vessel; and pressing 124 the thermoplastic band 5 on the melting zone 24, preferably by means of a pressure roller 71, to create a welding connection between the inner vessel 2 and the thermoplastic band 5, the thermoplastic band 5 being preferably fed to the pressure roller 71 via a distance roller 72 and the pressure and distance rollers 71, 72 tracking the laser beam 7 over the outer face of the inner vessel 2. Feeding of the thermoplastic band for welding can take place, for example, from a roller of thermoplastic band 5. Local melting 122 should take place and the laser beam 7 should be controlled such that in addition to the material of the inner vessel 2, the thermoplastic band 5 is also fused on at least within the melting zone 24. In one embodiment, the fiber composite layer 3 is a layer with several plies F1, . . . , Fn made of fiber composite material, embedded in a matrix material. Here, the thermoplastic band 5 consisting of one or more plies L1, . . . , Ln can be interwoven with at least one ply F1 facing the inner vessel 2.

[0037] The embodiments shown here are only examples of the present invention and are therefore not to be intended as limiting. Alternative embodiments considered by the person skilled in the art are equally comprised by the scope of protection of the invention.

LIST OF REFERENCE NUMBERS

[0038] pressure vessel according to the invention [0039] 1′ pressure vessel according to the state of the art [0040] inner vessel (liner) of the pressure vessel [0041] 24 melting zone [0042] 3 fiber composite layer [0043] 4 valve connection, boss [0044] 5 thermoplastic band [0045] 6 gap between fiber composite layer and inner vessel [0046] 7 laser beam [0047] 71 pressure roller [0048] 72 distance roller [0049] 8 boss or blind boss [0050] B direction of movement of the welding assembly in relation to the inner vessel [0051] F1-Fn plies of fiber composite material, embedded in matrix material to form the fiber composite layer [0052] L1-Ln plies of thermoplastic band on the inner vessel [0053] 100 method of manufacturing a pressure vessel according to the invention [0054] 110 providing an inner vessel [0055] 120 applying a thermoplastic band on the outer face of the inner vessel [0056] 122 local melting of the thermoplastic material of the inner vessel [0057] 124 pressing the thermoplastic band on the melting zone [0058] 126 interweaving fiber composite material with the thermoplastic band [0059] 130 finishing the pressure vessel