EP2757302A1 - Pressure vessel and method for manufacturing a pressure vessel - Google Patents

Abstract

The pressure vessel (1) has a cylinder tube (2) is closed with a bottom (6). The cylinder tube is provided with a first wall layer (3) made of a fiber plastic composite material having a predominantly axial alignment of the fibers, and a second wall layer (4) having a fiber orientation predominantly in the circumferential direction. An external fitting ring-shaped pressure element (8) and an end portion (9) of the first wall layer are pressed radially at a circumferential edge surface (10) of the bottom. An independent claim is included for a method for manufacturing pressure tank.

Description

The invention relates to a pressure vessel for receiving pressurized fluids with a cylinder tube and with a cylinder tube at a first end pressure-tight closing bottom, wherein the cylinder tube and the bottom are made separately and interconnected, and wherein the cylinder tube is a first wall layer of a Having fiber-plastic composite material.

Pressure vessels are needed for a variety of applications. In a pressure tank, a compressible fluid such as natural gas or compressed air can be stored, transported and kept ready for later use. In a piston accumulator, a suitable fluid, such as gas, can be compressed and thereby energy stored. With a hydraulic cylinder, mechanical work can be performed whereby a little compressible fluid such as hydraulic oil can be pressurized to transfer the pressure and to drive or displace a piston or plunger.

It is known to produce pressure vessels from a metallic body. The weight of such pressure vessel is relatively high. From a fiber-plastic composite material can be much lighter pressure vessel getting produced. However, the production methods for pressure vessels made of a fiber-plastic composite material are complicated and expensive.

For example DE 33 31 021 A1 or off DE 10 2006 006 902 A1 Pressure vessels are known in which the opposing bottoms are formed substantially in one piece with a substantially hollow cylindrical central part. A conical or approximately elliptical shape of opposite end portions is considered to be particularly favorable for achieving a high compressive strength. For different sized pressure vessels, however, each own tools must be used, so there is no significant flexibility in the design.

Out DE 39 22 577 A1 a compressed air tank made of a fiber-reinforced plastic is known in which a cylinder tube is glued to a separately manufactured bottom or lid. In order to increase the compressive strength, the cylinder tube and the base have, in an overlapping fastening region, protruding formations and recesses, by means of which an additional positive locking is produced.

In a pressure vessel of the type mentioned, for example EP 1 085 243 A1 is known, various ways are known to secure a floor with the cylindrical container wall.

It has been shown that the compressive strength of such pressure vessels, a separately manufactured and with a Cylinder tube connected bottom, significantly depend on the compressive strength of the cylinder tube and the connection of the bottom with the cylinder tube. In order to increase the compressive strength of the cylinder tube, the cylinder tube could have a greater wall thickness or be reinforced with elements that are rigid in particular in the radial direction. With increasing wall thickness of the cylinder tube, however, a simple and cost-effective fixing of the soil is made more difficult, since often a temporary or permanent deformation of the cylinder tube for fixing the soil is desirable and the increasing wall thickness is accompanied by an increasing bending strength, which hinders deformation.

It is therefore regarded as an object of the present invention, a pressure vessel of the type mentioned in such a way that with simple design means and cost, a pressure-resistant and reliable pressure vessel can be produced as possible.

This object is achieved in that the fiber-plastic composite material of the first wall layer has a predominantly axial orientation of fibers, that the cylinder tube has a second wall layer with a predominantly oriented in the circumferential direction fiber orientation, and that in the region of the bottom an externally fitting annular Pressure element presses an end portion of the first wall layer radially to a peripheral edge surface of the bottom. The combination of two wall layers with different fiber orientation, the respective requirements for the axial and in the radial direction usually occurring mechanical loads are met by the respective associated wall layer and largely independent of the other wall layer. Each wall layer can be easily and inexpensively manufactured because of the substantially unidirectional fiber orientation. It has been found that a pressure-resistant, reliable and nevertheless cost-effective connection of the bottom to the cylinder tube can be achieved by an annular pressure element that presses from the outside the end portion of the cylinder tube to a peripheral edge surface of the bottom, wherein the end portion of the cylinder tube through the end portion of the first wall layer is formed.

A fiber-plastic composite material having predominantly axially oriented fibers is a material having fibers embedded in a plastic matrix having a fiber angle of from 0 ° to about ± 30 ° relative to the central axis of the cylinder tube. As orientation of fibers predominantly in the circumferential direction, a fiber orientation is referred to, in which the fibers have a fiber angle of ± 60 ° to 90 ° relative to the central axis of the cylinder tube.

It is preferably provided that the second wall layer does not cover the end region of the first wall layer. In order to increase the radial deformability of the cylinder tube in the end region, so that the radially inwardly directed contact pressure of the pressure element as efficiently as possible presses the end portion of the cylinder tube to the ground and thus defines the bottom in the end region, the invention provides that in the radial direction rigid second wall layer with an orientation of the Fibers in the circumferential direction not covered the end. The end region is then formed by the first wall layer, which contains predominantly axially oriented fibers which have a comparatively small radial bending stiffness and are therefore deformed by the pressure of the pressure element to the ground and pressed against the peripheral edge surface of the soil. In this way, a high-pressure-resistant connection of the cylinder tube to the floor can be accomplished with simple structural means.

According to an advantageous embodiment of the inventive concept it is provided that the annular pressure element is a pressed-on circumferential bandage made of a fiber-plastic composite material with an orientation of the fibers predominantly in the circumferential direction. Such a circumferential bandage can be produced inexpensively, for example, by conventional winding methods. An inner diameter of the circumferential bandage can be set slightly smaller than an outer diameter of the cylinder tube, so that after a slipping over of the circumferential bandage over the end region of the cylinder tube, a radially inwardly directed contact pressure is generated. The circumferential bandage can be fixed, for example, by means of an adhesive in the end region of the cylinder tube. The bottom is defined by the frictional engagement with the cylinder tube created by the circumferential bandage that presses the end portion of the cylinder tube against the peripheral edge surface of the bottom.

However, there are also other pressure elements such as tensioned or prestressed Metallzugbänder conceivable to determine the bottom of the cylinder tube.

In order to avoid unintentional slipping out of the bottom of the cylinder tube under high pressure load, it is provided that the end region of the first wall layer has a tapering outer diameter. The end region of the first wall layer can engage behind the floor and thereby prevent the floor from slipping out of the cylinder tube.

According to a particularly advantageous embodiment of the inventive concept, it is provided that the end region of the first wall layer is cone-shaped. A conical configuration of the end region can be accomplished comparatively easily, since the second wall layer, which has predominantly circumferentially arranged fibers and is accordingly particularly rigid in the radial direction, does not extend into the end region. The end region is formed by the first wall layer, which can be radially deformed due to the axial alignment of the fibers with comparatively small forces in order to achieve a conical shape.

The shaping of the peripheral edge surface of the bottom is expediently adapted to the conical shape of the end region of the first wall layer, so that when the end region is pressed against the peripheral edge surface of the bottom, a large-area contact surface with a high frictional engagement is created. The inclination of the conical end region or its angle relative to the central axis of the Cylinder tube is advantageously set so that the bottom is set self-locking on the conically tapered end. If the soil shifts axially outwards due to a high pressure load, the conical end region would be widened outwards, so that the contact pressure of the pressure element acts more on the end region and via an increased contact pressure of the pressure element, the frictional fixing of the soil in the end region is reinforced until the contact pressure exceeds the pressure load again and a further axial displacement of the soil is prevented. By a suitable shaping of the bottom and the end region of the cylinder tube, a pressure resistance of the pressure vessel up to more than 1000 bar can be achieved and ensured cost-effectively and with simple structural means.

It is preferably provided that the pressure element has a wedge-shaped cross-sectional area adapted to the shape of the end region of the first wall layer. The shape of the pressure element supports the conical shape of the end region and supports the end region over a large area to the outside.

In order to achieve as uniform as possible a transition from the pressure element to the second wall layer, in particular in the flexural strength, it is provided that the pressure element has a taper at an end facing the second wall layer. The pressure element usually has a greater thickness or wall thickness than the second wall layer, so that by a taper of the Pressure element in the direction of the second wall layer can be made an adjustment of the wall thickness and, consequently, a corresponding approximation of the bending stiffness.

A particularly uniform transition is obtained by the pressure element has an overlapping a second layer overlapping Schaftung in an overlap region. At the same time a relatively large contact surface between the pressure element and the second wall layer is made possible by the overlapping Schäftung, which is favorable for an optionally desired large-area bonding.

Depending on the materials used for the pressure vessel, in particular fiber-plastic composite materials, and on the fluids normally accommodated in the pressure vessel, it may be expedient or necessary to arrange a coating which hinders permeation on an inner wall of the cylinder tube. This permeation-inhibiting coating can for example consist of a thermoplastic material. The coating may contain additional additives to improve important properties such as surface roughness, material resistance or abrasion resistance for the particular application.

In order to influence the bending stiffness of the cylinder tube, provision can be made for the cylinder tube to have a separating layer arranged between the first wall layer and the second wall layer. Furthermore, it may be for certain application areas be advantageous that the pressure vessel has a plurality of first wall layers and / or a plurality of second wall layers and optionally a plurality of separating layers.

It has been shown that a particularly high compressive strength is favored by the fact that the soil has an inward curvature. At a high internal pressure in the pressure vessel, the bottom would be deformed axially and simultaneously radially outwards, thereby increasing the contact pressure to the end region of the cylinder tube and to the pressure element surrounding this end region and to fix the bottom even more strongly at the end region.

The invention also relates to a process for the production of a pressure vessel having the aforementioned properties.

According to the invention, it is provided that a cylinder tube with a first wall layer and with a second wall layer is produced by fiber-containing semifinished product, which is heated together with a thermoplastic matrix material in a centrifugal mold and spin-spun. The thermoplastic matrix material can be introduced separately as a thermoplastic amount of material or in the form of a tube of thermoplastic material in the Schleuderkokille. It is also conceivable and often advantageous if the fiber-containing semi-finished product already contains the thermoplastic material and impregnated, for example, the fibers of the fiber-containing semi-finished product with a suitable thermoplastic material, or in one embedded thermoplastic material. Cylinder tubes with different wall layers of high quality and precision of shaping can be produced by the forming effected at a sufficiently high temperature and number of revolutions in the spinning mold.

In order to avoid post-processing of the cylinder tube produced in the spinning mold as far as possible, it is provided that an end region of the cylinder tube is predetermined by shaped parts attached to the spinning mold and limiting the axial dimensions of the first wall layer and the second wall layer. The mold parts can be annular and fixed at a suitable location on an inner wall within the centrifugal mold. A cutting to length of the cylinder tube produced in the spinning mold is just as little necessary with a suitable design and arrangement of the molded parts as a costly reworking of the end portion and the surfaces of the cylinder tube.

It is preferably provided that after the production of the cylinder tube in the end region of the first wall layer substantially wedge-shaped axially extending recesses are formed and thereby formed tongues are conically arranged or formed. Due to the essentially axially extending recesses there is no appreciable structural weakening of the first wall layer, since the fibers in the first wall layer are likewise predominantly axially aligned. By suitable shaping of the approximately wedge-shaped recesses, the conical shape of the end region can be predetermined and at the same time achieved that the individual Tongue both overlap-free as well as seamlessly lying together form the cone-shaped end portion.

• Fig. 1 eine schematische Schnittansicht eines Endbereichs eines Druckbehälters, bei dem ein Boden in einem Endbereich eines Zylinderrohrs festgelegt ist,
• Fig. 2 eine Schnittansicht eines Endbereichs des Zylinderrohrs mit einer die Permeation behindernden Beschichtung in vergrößerter Darstellung, und
• Fig. 3 eine schematische Darstellung einer abgewickelten Mantelfläche des Zylinderrohrs mit im Wesentlichen keilförmigen Aussparungen in dem Endbereich.

Embodiments of the inventive concept will be explained in more detail, which are illustrated in the drawing. It shows:

• Fig. 1 a schematic sectional view of an end portion of a pressure vessel, wherein a bottom is fixed in an end portion of a cylinder tube,
• Fig. 2 a sectional view of an end portion of the cylinder tube with a permeation-inhibiting coating in an enlarged view, and
• Fig. 3 a schematic representation of a developed lateral surface of the cylinder tube with substantially wedge-shaped recesses in the end region.

An in Fig. 1 schematically illustrated only in an end region pressure vessel 1 has a cylinder tube 2 with a nearly over the entire container length hollow cylindrical shape. The cylinder tube 2 is formed by a radially inward first wall layer 3 and an outer second wall layer 4. In an end region 5 of the cylinder tube 2, a separately manufactured bottom 6 is fixed, which has an inwardly directed curvature 7. By an outside surrounding the cylinder tube 2 pressure element 8, an end portion 9 of the first wall layer 3 is pressed against a peripheral edge surface 10 of the bottom 6 and the bottom fixed non-positively on the cylinder tube 2.

The first wall layer 3 consists of a fiber-plastic composite material, wherein the quasi-endless fibers are predominantly aligned in the axial direction. The first wall layer 3 therefore has a particularly high mechanical strength in the axial direction. The second wall layer 4 is also made of a fiber-plastic composite material, wherein the quasi-endless fibers are oriented predominantly in the circumferential direction. Consequently, the second wall layer 4 has a particularly high mechanical strength and a high flexural rigidity in the radial direction. By a suitable choice of the wall thicknesses of the first wall layer 3 and the second wall layer 4, the compressive strength of the cylinder tube 2 can be influenced and specified.

The pressure element 8 is also made of a wound fiber-plastic composite material forming a circumferential bandage, with sufficient bias from the outside on the end portion 5 of the cylinder tube 2, or on the end portion 9 of the first wall layer 3, the end portion. 5 of the cylinder tube 2 forms, is pushed. Since there is no second wall layer 4 in the end region 5 of the cylinder tube 2, which is largely responsible for the radial bending stiffness, the end region 5 of the first wall layer 3 can be converted to a conical shape without much effort and to the conical shape of an inner wall 11 of Circumferential bandage to be adjusted. Also, the peripheral edge surface 10 of the bottom 6 has a conical shape adapted thereto.

Due to the conical configuration of the end portion 5 of the cylinder tube 2, a positive and self-locking fixing of the bottom 6 within the end portion 5 of the cylinder tube 2 is effected in addition to the frictional connection of the bottom 6 with the cylinder tube 2, whereby the compressive strength is additionally increased and improved.

According to the in Fig. 2 shown enlarged embodiment of the end portion 5 of the cylinder tube 2 may be disposed on an inner side of the first wall layer 3 to reduce the permeability of the cylinder tube 2, a permeation-inhibiting coating 12. The end region 9 of the first wall layer 3 protrudes in the axial direction both beyond the second wall layer 4 and beyond the permeation-inhibiting coating 12 and forms the end region 5 of the cylinder tube 2, at which the bottom 6 is fixed. After the production of a hollow cylindrical cylinder tube 2, the projecting end portion 9 of the first wall layer 3 may be conically deformed either in advance or by the attachment of the pressure member 8 to form an in Fig. 2 to obtain only schematically and dashed shape shown.

In Fig. 3 schematically a developed lateral surface of the end portion 5 of the cylinder tube 2, and the end portion 9 of the first wall layer 3 is shown. In the end region 9 of the first wall layer 3 approximately wedge-shaped recesses 13 are formed. The recesses 13, starting from an end edge 14 of the wall layer 3, initially have wedge-shaped sections 15 of the recesses 13 extending in the axial direction. In one Transition region 16, which corresponds to a curvature region 17 of the end region 9 of the wall layer 3, the recesses 13 also have curved side edges. The shape of the recesses 13 is predetermined so that in the self-adjusting, or predetermined by the pressure element 8 conical shape an overlap-free, but also gap-free arrangement of tongues 18 formed by the recesses 13 is generated.

Claims (16)

Pressure vessel (1) for receiving pressurized fluids with a cylinder tube (2) and with a bottom (6) pressure-tightly sealing the cylinder tube (2) at a first end, the cylinder tube (2) and the bottom (6) made separately and wherein the cylinder tube (2) has a first wall layer (3) of a fiber-plastic composite material, characterized in that the fiber-plastic composite material of the first wall layer (3) has a predominantly axial orientation of fibers in that the cylinder tube (2) has a second wall layer (4) with a predominantly circumferentially aligned fiber orientation, and in that in the region of the bottom (6) an externally applied annular pressure element (8) has an end region (9) of the first wall layer (3). radially to a peripheral edge surface (10) of the bottom (6) presses. Pressure vessel (1) according to claim 1, characterized in that the second wall layer (4) does not cover the end region (9) of the first wall layer (3). Pressure vessel (1) according to claim 1 or claim 2, characterized in that the annular pressure element (8) is a pressed-on circumferential bandage made of a fiber-plastic composite material with an orientation of the fibers predominantly in the circumferential direction. Pressure vessel (1) according to one of the preceding claims, characterized in that the end region (9) of the first wall layer (3) has a tapered outer diameter. Pressure vessel (1) according to claim 3, characterized in that the end region (9) of the first wall layer (3) is conical. Pressure vessel (1) according to one of the preceding claims, characterized in that the pressure element (8) has a wedge-shaped cross-sectional area adapted to the shape of the end region (9) of the first wall layer (3). Pressure vessel (1) according to one of the preceding claims, characterized in that the pressure element (8) at one of the second wall layer (4) facing the end has a taper. Pressure vessel (1) according to claim 8, characterized in that the pressure element (8) in an overlap region has a second wall layer (4) overlapping Schäftung. Pressure vessel (1) according to one of the preceding claims, characterized in that on a inner wall of the cylinder tube (2) has a permeation-inhibiting coating (12). Pressure vessel (1) according to claim 9, characterized in that the permeation-inhibiting coating (12) consists of a thermoplastic material. Pressure vessel (1) according to one of the preceding claims, characterized in that the cylinder tube (2) has a separating layer arranged between the first wall layer (3) and the second wall layer (4). Pressure vessel (1) according to one of the preceding claims, characterized in that the pressure vessel (1) has a plurality of first wall layers (3) and / or a plurality of second wall layers (4) and optionally a plurality of separating layers. Pressure vessel (1) according to one of the preceding claims, characterized in that the bottom (6) has an inwardly directed curvature (7). A method for producing a pressure vessel (1) according to claims 1 to 13, characterized in that a cylinder tube (2) with a first wall layer (3) and with a second wall layer (4) is produced by fiber-containing semi-finished, which together with a thermoplastic Matrix material is heated in a centrifugal mold and spin-spun. A method according to claim 14, characterized in that an end portion (5) of the cylinder tube (2) is provided by attached to the centrifugal mold and the axial dimensions of the first wall layer (3) and the second wall layer (4) defining moldings. A method according to claim 14 or claim 15, that after the production of the cylinder tube (2) in the end region (5) substantially wedge-shaped, axially extending recesses (13) are formed and thus formed tabs (18) are arranged conically.

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