Pressure vessel

TECHNICAL FIELD

The invention relates to a pressure vessel of the type which emerges from the preamble to Claim 1.

BACKGROUND ART

Through DE-A1-195 47 245, a pressure vessel in the form of a fuel tank is previously known, which is filled with a compressed, pressurized gaseous fuel, for example compressed natural gas (CNG). The pressure in the vessel can amount to 200 bar and the vessel wall is therefore dimensioned to withstand this pressure.

In certain extreme cases, the pressure in a vessel of this type can amount to as much as 650 bar or more, depending on the particular temperature conditions, the particular occurring impact load, tests etc. It is therefore of utmost importance that the vessel has a strength which withstands the pressure from the enclosed gas even under extreme conditions when the pressure, at least in a test context, can be around 600 bar. In order to withstand the high pressure, conventional pressure vessels are therefore usually made of metal, preferably of steel, or with carbon fibre reinforcement wound on a so-called liner with joints and wall thickness tailored to the high pressure and a geometry characterized by a circular cross-section. Thus, the weight of such a pressure vessel is also relatively high and the vessel is dear to produce. A vessel of this type is also relatively bulky and difficult to fit securely into suitable spaces available in, for example, the floor panel of a vehicle.

In Swedish patent 9101584-2 (468 649), a cylindrical glass fibre reinforced plastics container for, for example, bottled gas or compressed air, which is made of two container halves and which, in the conical joint between the two container halves, has a special arrangement of the glass fibre reinforcement to allow the container to withstand relatively high pressure, up to around 100 bar.

Through Swedish patent 9604051-4 (511 172), a cylindrical container of fibre- reinforced plastic, which is joined together from two container halves, is previously known. The open ends of the container halves are conically bevelled and inserted one inside the other as a male part into a female part and connected by a binding means. The container is constructed with various layers of reinforcement wires (inner, intermediate and outer layers) containing both longitudinal and transverse and diagonally orientated bundles of reinforcement wires. By virtue of controlled orientation of the reinforcement wires in the various layers according to a set pattern, the container is relatively light, but can nevertheless, with good safety margin, withstand pressure of up to 60 bar.

In CNG-powered vehicles, a plurality of relatively small tanks have hitherto been used instead of a single larger tank. These relatively small tanks are then generally configured as cylindrical tanks made of steel or fibre-reinforced plastic on metal liner, for example two tanks of 12.5 1 each and one tank of 75 1 can be installed at different places where they can find space.

A plurality of tanks calls for a more complicated arrangement of fuel lines with distribution valves for filling and tapping of the gas, which is intricate and hence unfavourable from the cost aspect.

The problem on which the invention is founded is therefore to design a pressure vessel with relatively low weight, which is relatively spacious, can withstand high pressures, and which can be configured with shape and dimensions tailored to the particular field of application.

DISCLOSURE OF INVENTION

One object of the invention is to produce a pressure vessel which does not suffer from the above-specified drawbacks and which signifies a solution to the problem on which the invention is founded. This is possible with a pressure vessel of the type specified in the introduction and having the characterizing features defined in Claim 1. Advantageous refinements and improvements of, as well as further objects and features for the invention, emerge from the independent claims and the following description.

BRIEF DESCRIPTION OF DRAWINGS

An embodiment of the invention is more closely described in the following description with reference to the appended schematic drawings. Fig. 1 shows a longitudinal section of an inventive pressure vessel with transverse partition, which pressure vessel is dissected in the middle in the longitudinal direction through the line A-A in the following Fig. 3, Fig. 2 shows a larger-scale detail of the middle portion of the pressure vessel according to Fig. 1, Fig. 3 shows a transverse section through the line B-B of the pressure vessel according to Fig. 1, Fig. 4 is a longitudinal section similar to Fig. 1 of the pressure vessel, this being provided with a girdle which presses together the vessel halves, Fig. 5 shows an enlarged detail in longitudinal cross-section of the girdle which presses together the vessel halves, and Fig. 6 is a section through the line C-C

in Fig. 5.

MODE(S) FOR CARRYING OUT THE INVENTION

Fig.l shows a side view of an inventive pressure vessel 2 dissected in the middle in the longitudinal direction, having a wall 4 comprising a first vessel half 6 and a second vessel half 8 joined together by a binding means with the aid of a first connecting element, for example a transverse partition 10. The two vessel halves of the pressure vessel can preferably be of like configuration, but can also be different, are made of fibre-reinforced plastic and each have, in cross-section, a non-circular, for example substantially rectangular portion 12, which at one end merges into an end face portion 14 closing the vessel half, and at another end merges into a first and second connecting portion 16 and 18, configured on each vessel half 6 and 8. The reinforcement can contain, for example, glass fibres and/or carbon fibres. The vessel halves, at least in the connecting portions 16 and 18, can preferably be configured as identically equal or mirror-inverted male parts. The transverse partition 10 has third and fourth connecting portions 20 and 22, which are disposed in mutually opposite arrangement and are configured, preferably as female parts, complementarily to the first and second connecting portions 16 and 18 of the vessel halves.

As can best be seen from Fig. 2 and 3, the transverse partition 10 is configured in cross-section as an I-beam, in which the third and fourth connecting portions 20 and 22 form an annular beam flange 24, which extends around the periphery in the transverse direction of the pressure vessel. A beam web 26 connects opposite ring sections of the beam flange 24 and openings 28 are made in the web for the medium which is to be enclosed in the pressure vessel.

The transverse partition 10 with the beam flange 24 comprising the third and fourth connecting portions 20 and 22 configured as female parts, in combination with the first and second connecting portion 16 and 18 of each vessel half, configured as a male part, thus constitutes a stiffening in the middle portion of the pressure vessel in the transverse direction of the same. As will be more closely described later, by arranging the fibre reinforcement adjacent to the middle portion of the pressure vessel, which middle portion belongs both to the vessel halves and to the transverse partition, with a specific carbon fibre content and according to a set pattern, the middle portion of the pressure vessel in the transverse direction can be dimensioned to at least withstand a pressure of 2.35 times the working pressure of the pressure vessel, i.e., for a working pressure of 200 bar, at least 470 bar.

In the longitudinal direction of the pressure vessel, the fibre reinforcement in the wall 4 of the pressure vessel could likewise be arranged correspondingly. However, the strength in the longitudinal direction of the pressure vessel is mainly determined by the limitation created by the binding means in the joint connection between the first 16 and third 20 and second 18 and fourth 22 connecting portions in the middle portion of the pressure vessel. The binding- agent-assisted joint connection can be dimensioned in a manner which is known per se, by suitable configuration of the joint surfaces, to withstand a load in the longitudinal direction of the pressure vessel corresponding to pressure of up to about 100 bar. In order not to run the risk of the joint connection failing, the wall 4 is therefore dimensioned for a substantially lower stiffness in the axial direction than the joint connection. That is to say, the wall 4 is dimensioned for a corresponding, or somewhat lower failure load, corresponding, for example, to pressure of up to about 90 bar. As will be more

closely described later, the fibre reinforcement in the wall is therefore arranged according to a set pattern in combination with choice of fibre type, for example carbon fibre, in such a way that the wall 4, at loads corresponding to around 90-100 bar, can elastically stretch by a set measure X of 0.2 - 2 %, preferably close to 2 %, in the longitudinal direction of the pressure vessel, without the binding means in the joint connection failing.

Fig. 4 and 5 show in a second illustrative embodiment how a modification of the above-described pressure vessel 2 is possible to allow the pressure vessel as a whole also to function for higher pressure than the approx. 100 bar tolerated by the binding means in the joint connection. The modification means that both the middle portion of the pressure vessel and the rest of the wall 4, including in the longitudinal direction of the vessel, are arranged to withstand significantly higher pressure, for example pressure as high as or higher than the middle portion of the vessel in the transverse direction. In order to prevent the binding means in the joint connection from finally failing after maximal extension of the wall 4, a stiff second connecting element, for example a girdle 30, is therefore arranged to absorb the stretching of the wall 4 in the axial direction, i.e. in the longitudinal direction of the pressure vessel. In comparison with the wall, the girdle 30, as will be described in greater detail later, is dimensioned with a different admixture and orientation of fibres in order to withstand a failure load corresponding, for example, to pressure in the axial direction towards the inner side of the wall between about 100 and about 600 bar. The girdle 30 is arranged with a pretensioning force F corresponding to 0.1 - 0.4 % stretching of the girdle around the pressure vessel on the outer side of the same and in the longitudinal direction thereof, in such a way that the vessel halves 6, 8 are pressed one against the other by means of the transverse partition 10 and the stretching in the wall 4 is thus counteracted.

Even in the longitudinal direction, the pressure vessel can thus be dimensioned to withstand yet higher pressure than in the transverse direction, typically up to about 600 (100+500) bar.

The dimensioning of the pressure vessel is therefore realized such that, as a result of the shut-in gas, pressure forces acting axially in the longitudinal direction of the pressure vessel 2 are substantially absorbed by the girdle 30, while in the middle portion of the vessel radially acting pressure forces are substantially absorbed by the transverse partition 10.

As previously described, the two vessel halves 6 and 8 of the pressure vessel 2 can preferably be realized as identically equal or mirror-inverted male parts in the form of the first and second connecting portion 16, 18. Fig. 2 shows a larger-scale detail of the middle portion of the pressure vessel according to Fig. 1. For the sake of clarity, only a part of the vessel wall 4 belonging to the first vessel half 6 adjacent to the joint connection with the transverse partition 10 is shown here. The joint connection with the second vessel half 8 is realized correspondingly. The wall 4 with the connecting portion 16 can be constructed with a fibre reinforcement comprising a first series 32 of a plurality of, at least three, reinforcement layers, a first layer 34 with axial reinforcement, a second layer 36 with cross reinforcement and a third layer 38 with tangential reinforcement, i.e. the wall contains layers with both longitudinally and diagonally and transversely orientated bunches of reinforcement wires. Trials have also shown that in crack propagation terms it is better, instead of a small number of thicker reinforcement layers, to arrange a large number of relatively thin reinforcement layers. It can then be expedient to arrange a fibre reinforcement comprising a plurality of series 32 - 32 _n of such first 34, second 36 and third 38 layers one on top of the other according to the same pattern.

According to the embodiment shown as an example in Fig. 2, the fibre reinforcement of the wall 4 comprises, apart from the first series 32, also a second series 32 'and a third series 32", i.e. three series of three layers, thus nine reinforcement layers in total. This embodiment has been shown to provide an optimization of the characteristics of the pressure vessel 2, especially when the strength is set in relation to the weight, in particular for, for example, a particular field of application such as a pressure tank in a vehicle. In a manner which is known per se, in each series 32 - 32 _n of at least three layers, the first layer with axial reinforcement 34 and the second layer 36 with cross reinforcement extend also over the closing end face section 14 of each vessel half 6, 8 and back to the connecting portion 16 on an opposite side of the respective vessel half. The third layer 38 with tangential reinforcement, on the other hand, is arranged on the substantially rectangular portion 12 of the respective vessel half, without extending over the end face portion 14.

It has previously been described that the transverse partition 10 with the beam flange 24 comprising the third and fourth connecting portions 20 and 22 configured as female parts, in combination with the first and second connecting portion 16 and 18, configured as a male part, of each vessel half, constitutes a stiffening in the middle portion of the pressure vessel 2 in the transverse direction of the same. This stiffening of the vessel is in the first place enabled by the fact that the fibre reinforcement in the transverse partition 10 is arranged with a specific admixture of carbon fibre and according to a set pattern.

Thus the annular beam flange 24 shall hold together the pressure vessel 2 in the peripheral direction of the middle portion like a "hoop". For this purpose,

the beam flange 24, as can best be seen from fig.2, has a high share, preferably greater than 75 %, of tangentially orientated fibre reinforcement 40. The tangentially orientated fibre reinforcement 40 is tightly wound from the connection of the beam flange 24 to the beam web 26 and right out to each edge of the third and fourth connecting portion 20, 22. For cohesion purposes, this fibre reinforcement 40 is supplemented by a relatively thin outer layer of axial reinforcement 42, attached to the outer side of the beam flange 24 and extended from edge to edge, the share of which can amount to 5-15 % of the fibre reinforcement in the beam flange 24. Likewise, the third and fourth connecting portion 20, 22 each have, arranged on the inner side of the beam flange and extended from the respective edge, a relatively thin inner layer of axial reinforcement 44, the share of which can likewise amount to 5-15 % of the fibre reinforcement in the beam flange 24. The respective inner layer of axial reinforcement 44 of each connecting portion 20, 22 is deflected in a smooth transition so as to jointly form a radial or, with respect to a diametrical section through the transverse partition 10, axial reinforcement 46 of the beam web 26 of the transverse partition (Fig. T).

As previously described, the girdle 30, in comparison with the wall 4, is dimensioned with a fibre reinforcement which has a different admixture and orientation of carbon fibre. Fig. 4 and 5 show examples of possible constructions of the girdle from a strictly axial girdle reinforcement 48 with a stiffness which is 3-5 times the stiffness in the wall 4. The axial fracture load of the girdle is then about 5 times higher than the axial fracture load of the wall 4 in each vessel half 6, 8. This is possible by virtue of the fact that the girdle reinforcement 48 is arranged such that the fibre direction in its entirety is axial, i.e. all fibres are orientated in the longitudinal direction of the girdle.

Where appropriate, the girdle 30 can be provided on both or one of the flat sides with a relatively thin layer, about 2-5 % of the girdle reinforcement 48, of the same cohesive transverse reinforcement. Advantageously, the thus reinforced girdle 30, in the assembly of the pressure vessel 2 or on some later occasion, can also have been cast/glued together with the wall 4 of the pressure vessel and can thereby, in an integrated manner, be fixedly anchored to the vessel wall.

In a manner which is known per se, the pressure vessel 2 constructed according to the above description can be equipped with a valve 50 of conventional design for filling and tapping of compressed gas. The valve can be mounted in either of the end face portions 14 of the pressure vessel, preferably adjacent to an optional transition between the chosen end face portion and the substantially rectangular portion 12 of the particular vessel half 6, 8.

Also a pressure vessel intended for a variety of purposes apart from use in motor vehicles, for example for pressurized medium such as industrial gases or air, can advantageously be configured with corresponding characteristics to the pressure vessel according to the invention. The pressure vessel 2 can thus, without modification, be used for medium with relatively low pressure of up to about 90-100 bar. A pressure vessel modified according to the second embodiment can be used for medium with relatively high pressure of up to 600 bar.