EP1818596B1 - Pressure vessel made of plastic and method for its manufacture - Google Patents

Abstract

A hydraulic or pneumatic pressure reservoir for commercial vehicles, trains or firefighting systems is assembly from components made of fiber-reinforced polyethylene, polypropylene or polyamide. The reservoir outer shell is multi-layered elongated ellipse. The ratio of the poles to the center section is in the range 1:2.5 to 1:5, with a smooth rounded transition between the two. Further claimed is a manufacturing process for the reservoir.

Description

The invention relates to a pressure vessel made of plastic, in particular compressed air tank for brake power and pneumatic auxiliary equipment on trucks, trucks, buses, rail vehicles or fire extinguishing systems, with a container shell of an injection molded, composed of liner parts liner body made of fiber-reinforced polyethylene, polypropylene, or polyamide, in the pole caps Connecting sleeves are formed captive, a arranged on the liner body reinforcing layer of fiberglass tape and an arranged on the latter injection-molded captive enclosure made of fiber-reinforced polyethylene, polypropylene, or polyamide. Such a container is from the US-A-5,484,079 known.

The invention further relates to a method for producing a pressure vessel made of plastic, in particular compressed air tank for brake power systems and pneumatic auxiliary equipment on trucks, trucks, buses, Rail vehicles or fire extinguishing systems, in which first liner parts with pole caps made of glass fiber reinforced polyethylene, polypropylene or polyamide granules are injection molded by injection molding in an injection mold, embedded in the center of the pole caps connection sleeves are embedded by the plastic, the liner parts by joining in a joining machine to a liner body are joined together, the added liner body is wound with a reinforcing layer of glass fibers in a winding machine and the armored liner body is overmolded with a cladding of fiber-reinforced polyethylene, polypropylene, or polyamide.

State of the art

The use of liners made of thermoplastic material in the manufacture of pressure vessels is well known (see, inter alia EP 0 635 672 A1 . DE 197 51 411 C1 . DE 198 32 145 A1 . DE 100 00 705 A1 . EP 0 147 042 . EP 0 666 450 A1 . WO 84/03065 A1 . WO 95/22030 A1 ).

That's how it is EP 0 635 672 A1 a pressure vessel, in particular accumulator tank for brake power systems and pneumatic auxiliary equipment on trucks, trucks, buses, rail vehicles, etc. or for fire-extinguishing systems, which consists of a liquid-tight injection-molded liner or thermoplastic body such as polypropylene, polyethylene, polyamide and the like. consists, are provided in the openings for connection sleeves and arranged on the liner armor layer. The liner consists of a lost shape body made of short glass fiber reinforced thermoplastic and is versatile surrounded by a one-piece captive shell. The sheath consists of short fibers, preferably glass fibers, reinforced and filled polypropylene or polyamide or modified polypropylene ethers or polyphenylsulfide or polyetherimide. The reinforcing layer is composed of cross-laminated with about 55 ° to each other wound glass fibers or metal wires or wire mesh together.

In the DE 198 32 145 A1 and the DE 199 37 470 A1 containers are disclosed for storing solid, liquid and / or gaseous media under an operating pressure above atmospheric pressure, wherein the container encloses a cavity provided for storing the medium and wherein at least one connection for loading and / or unloading is provided. The pressure vessel consists, at least in part, of a tube, which in turn is made of fiber-reinforced thermoplastic, the material of the tube being more than 10% by volume of fibers having an average fiber length of more than 50 mm. The floor is formed as a separate part and also consists of a fiber-plastic composite material with short, long or continuous fibers. The floor is curved inwardly formed in the container space. At the bottom of a circumferential collar is arranged, which abuts against the inner wall of the central part and is connected thereto.

According to the prior art DE 198 32 145 A1 it is a composite pressure vessel for storage of gaseous media under pressure with a plastic liner and two arranged in the neck throat areas and with a liner reinforcing winding of a fiber composite material, of which at least one of the Receiving a screw-threaded having a valve is formed and both neck portions are provided in the pressure vessel facing the corner region with a flat truncated cone-like collar which is surrounded on the inside by the liner and the outside of the reinforcing winding. The pole caps of the pressure vessel are provided with a shock absorbing layer.

The DE 100 00 705 A1 describes a plastic core container reinforced with a fiber-plastic composite for storing liquid and / or gaseous media under pressure which has one or more connecting pieces in the neck and / or bottom and / or cylindrical container part, of which at least one connecting piece for receiving a screw-in cylindrical or conical thread having pressure line feed such as a valve or pipe connection is formed. In the connecting pin of the plastic core container, a cylindrical insert is mounted with a sleeve end enveloping or circumferential collar end, wherein at least two seals are arranged in such a manner that at least one seal between the insert and the inner surface of the plastic connecting pin of the plastic core container and at least one further seal between insert and pressure line feed is arranged.

After EP 0 147 042 A1 For example, there is known a container for storing and transporting fluids under pressure comprising a thermoplastic inner blown liner of polyethylene, polyethylene terephthalate, polypropylene, polyvinylchloride or polyvinyldiene chloride provided with an outer layer of carbon fibers, polyamide fibers, glass fibers, glass fiber reinforced Polyester fibers or glass fiber reinforced phenolic epoxy resin is wrapped.

Furthermore, from the EP 0 518 272 A1 a container intended to receive a pressurized fluid having a shell of substantially cylindrical shape and two substantially spherical bottoms closing the shell at its ends. The container comprises an outer shell of composite material, an inner shell rigidly connected to the outer shell, a first opening piercing the inner and outer sheath, and a reinforcing element of the outer sheath around the first opening located inside the outer shell located and also includes an opening, which cooperates with the second opening. The first opening is located in the jacket area and is provided with means for attaching the container. The reinforcing element is interposed between the inner and outer sheaths. It has a flat side aligned with the inside of the container and a contour adapted to maintain the outer surface of the container. The reinforcing element occupies at least the entire length of the shell.
The inner shell is cast, the shape chosen so that the insertion of the reinforcing element does not interfere with the profile intended for the container. The outer shell is made of a fibrous material which is wound up on the inner shell provided with the reinforcing element. Subsequently, a heat treatment of the container is made.

The Indian EP 0 666 450 A1 described pressure vessel comprises a plastic liner with a cylindrical middle part, two dome-shaped end parts and a liner overfilling the outer jacket with a plurality of radially superimposed tangential windings and axial windings of a fiber-reinforced plastic, wherein the lowermost winding is formed as a tangential winding and in the axial direction substantially over the cylindrical middle part of Liners extends. The lowermost winding in the middle region has a first thickness and merges at both ends into a winding edge, which has a second thickness which is greater than the first thickness.

It is also known to wind the liner with glass-fiber reinforced tapes both longitudinally and transversely to the liner axis (see DE 2 152 123 A1 . DE 2 423 497 A1 . DE 2 516 395 C2 . DE 38 21 852 A1 . EP 0 147 042 A1 . EP 0 588 836 A1 . EP 0 635 672 B1 . EP 0 666 450 A1 . WO 90/01649 A1 . US 3,112,234 A. . US 4 905 856 A ).

From the DE 2 152 123 A is a pressure vessel, in particular compressed gas tank known, consisting of a dimensionally stable, rotationally symmetrical, gas-tight and cylindrical in its central region inner container, two coaxial from the outside to the bottom of the inner container mounted pole pieces and wound on the inner container with detection of the pole pieces, of continuous filaments and cured Plastic laminated outer sheath is made, wherein a bottom of the inner container and the patch thereon pole piece with an opening for tight connection of a valve o. The like. Are provided.

In the known prior art DE 2 423 497 A1 is a process for producing a claimed fiber-reinforced resin impregnated hollow body in the winding process with a mandrel remaining in the finished part, being formed as a mandrel a structure of the structure of the hollow body mitbewirkender fiber reinforced support body and cured. The support body has two end caps and is provided with at least one of the support body and the end caps engaging winding layer. The winding layers are applied in the form of longitudinal windings with a sharp winding angle and in the form of circumferential windings of approximately 90 °.

The DE 2 516 395 A1 discloses a pressure vessel formed as an aluminum vessel having a cylindrical portion and a hood-shaped end portion at each end of the cylindrical portion, the cylindrical and hood-shaped portions being substantially equal in thickness. Around the aluminum vessel, a winding arrangement of alternately polar oriented and circumferentially oriented glass fiber fabric is provided. At least one circumferentially oriented winding assembly is wound over the junctions between the cylindrical and hood-shaped end portions. The wrapping is in a preloaded condition so that compressive forces are applied to the outer surface of the vessel.

After DE 38 21 852 A1 a gas cylinder for high gas pressure is known, which consists of an aluminum liner and a circumferential layer of glass fiber reinforced plastic, wherein the liner has a cylindrical portion and spherically shaped pole caps with connecting pieces. The liner including its polar caps is with a first layer of glass fibers in cross-winding provided. A second layer is provided mainly in the cylindrical part of the liner, the glass fibers being in a circumferential winding.

The WO 01/57429 A1 describes a fiber-reinforced pressure vessel whose gaseous or liquid-tight body is completely wrapped with sliver, wherein the slivers are not embedded in a matrix and at least a number of slivers are freely movable relative to each other. The slivers are wound so that as soon as the pressure vessel is under internal pressure, the slivers are loaded exactly in their longitudinal direction.

From the EP 0 588 836 A1 There is known a plastic tank which is reinforced with glass fibers or corresponding reinforcing filaments and composed of preferably cylindrical tank halves, each having a bottom and one of the two floors having a connection opening. The open ends of the tank halves are tapered and inserted into each other as an insert in a receiving part and held together by an adhesive. The tank halves include outer and inner layers that are substantially transverse reinforcing strands, wherein the inner layer of the insert and the outer layer of the receptacle each include a layer of densely-spaced reinforcing strands in a number of layers of flat-lying rovings. This prior art also discloses a method for producing a reinforcing body of fiber strands for insertion into a casting mold for casting a fiber-reinforced cylinder having a closed end on which longitudinal and transverse reinforcing strands are wound, which are joined together by heating fusible resin powder.

Furthermore, from the US 3,112,234 A. a method for producing a fiber-wound steel pressure vessel known in which first the cylindrical container is wound approximately in its longitudinal direction and then in the transverse direction with fiber strands.

Also for the integration of connecting sleeves or other components in composite containers a variety of solutions is known ( DE 25 38 433 A1 . DE 195 26 154 A1 . DE 196 31 546 C1 . DE 197 51 411 C1 . DE 100 00 705 A1 . EP 0 550 951 B1 . EP 0 553 728 A1 . WO 94/23240 A1 . US 4 685 589 . US 4,905,856 . US 5 287 988 A ).

So revealed the DE 25 38 433 A1 a pressure vessel consisting of a dimensionally stable, gas-tight and in its central region cylindrical inner container, two coaxial from the outside to the bottom of the inner container mounted pole pieces and a wound under detection of the pole pieces on the inner container outer shell of glass fiber reinforced plastic, wherein a bottom of the inner container and the are provided with a flange-shaped part patch pole piece with an opening for tight connection of a connector and the inner container at its opening edge has an integrally formed axially outwardly directed and cylindrical neck whose contour matches that of the pole piece and the connector and by the with the Pole piece through Screw connection contiguous connector is pressed radially against the pole piece.
The inner container neck, the inner contour of the pole piece and the outer contour of the connector are conically tapered outward.

In the known composite container after DE 195 26 154 A1 for storage of gaseous media under pressure, the liner is made of plastic and has two openings located in the neck region, in each of which an opening closing and / or sealing neck piece is arranged, of which at least one is designed to receive a screw-valve. Both neck pieces are provided with an end region facing the pressure vessel with a flat running, frustoconical collar which is surrounded by the elements of the liner and / or the reinforcing winding and with a central axis of the axis of symmetry enclosing and extending from the inside recess, the in the case of the valve neck piece, it merges into the bore of the valve stem area.

In another known composite pressure vessel ( DE 196 31 546 C1 ) for storing gaseous media under pressure with a plastic liner and two throat pieces arranged in the neck region and with a liner reinforcing winding of a fiber composite material, of which at least one is designed to receive a screwable, a cylindrical thread having valve and both neck pieces in the The pressure vessel facing end portion is provided with a flat-running frustoconical collar, the edge of which strongly rounded and its inclination Contour contour of the liner is adapted in the transition region from the cylindrical shell region to the neck region, the reinforcing winding comes in the adjacent neck area of the top of the collar and in the edge region of the top and the bottom of the collar of the liner to the plant.

All of these known plastic pressure vessels have a, taken from the metal container construction cylindrical middle or shell part, which is closed by corresponding bottoms on both sides. Especially in dome-shaped or inwardly curved floors arise in the transition from Mantel- in the bottom area voltage spikes, which often lead to breakage at these transitions or to release the bottom part of the shell part. The basic rule is that the smaller the transition radius, the greater the risk of a voltage breakage despite amplification measures of the most varied types.
Even the transition from a cylindrical jacket region into a spherical pole region with a slightly larger radius can not sufficiently reduce the risk of breakage, especially with continuous and decaying permanent stress, as occurs in particular in brake power plants ( DE 38 21 852 A1 ). In the bending area (transition), the voltage lines of the voltage transformers extending in the container jacket are reinforced from the cylindrical jacket into the bottom area by the very high load changes, so that the breaking voltage is necessarily exceeded. Therefore, the known pressure vessels, especially for brake air systems in truck and rail vehicle have not been able to prevail. There are therefore still metallic, especially steel pressure vessels with all their disadvantages such as heavy weight, considerable Production costs and susceptibility to corrosion are used.

In this prior art, the present invention seeks to improve a composite pressure vessel of the type mentioned so that the complex property guarantee of brake air tanks such as high toughness even at low temperatures, high impact and breaking strength under dynamic stress in the pressure range of 8 , 5 to 20 bar, a long service life of at least 15 years despite constant load cycling and corrosion resistance is achieved.

task

This object is achieved by a pressure vessel of the aforementioned type with the characterizing features of claim 1 and by a method having the characterizing features of claim 18.

Advantageous embodiments of the pressure vessel and the method are the dependent claims.

The solution according to the invention is characterized in that the shell and bottom region of the pressure vessel is brought into a construction form suitable for a more even and thus more safe distribution of the axial and radial stresses, which no longer consists of a cylindrical shell part and a spherical bottom part, but the Has a form of an ellipsoid of revolution, whereby a substantial approximation to the spherical shape is made possible. The liner body therefore has an approximately ellipsoidal body shape, so that no sharp transitions between the bottom and shell area arise. Due to the largely uniform curvature in the longitudinal direction of the container wall in the originally cylindrical shell region, the tensile and radial stresses are very evenly distributed over all wall areas and a concentration of stress in the wall transition from the shell to the ground is significantly reduced.

A body shape which is particularly suitable for equalizing the tensile and compressive stresses is achieved when the ratio of the radius of the pole caps to the radius of the liner parts is 1: 2.5 to 1: 5. The wall of the pole caps and the wall in the central region of the pressure vessel are evenly curved and merge seamlessly into one another.

The body shape of the ellipsoid of revolution is also maintained during application of the plastic-coated reinforcing layer of fiberglass tape and the plastic coating on the liner, so that a pressure vessel is created, which breaks for the first time with the adopted from the steel container construction cylindrical body shape and is no longer comparable with the latter.
The plastic coating of the glass fiber tape makes it possible to connect the glass fiber tapes with the liner and the juxtaposed or superimposed glass fiber bands during winding cohesively together. It has been shown that especially with laser welding the required high speeds of joining can be achieved. Since, in a sense, the reinforcement is welded onto the liner, the body shape formed from spherical sections or the body shape of the ellipsoid of revolution can also be easily adhered to when reinforcing the liner. The liner is expediently filled with water, with which the resulting heat is dissipated.

The pressure vessel according to the invention achieves an extremely high fatigue strength of well over 25,000 load changes, has a relation to the pressure vessels made of steel or containers with wound metal liners much lower weight, is shock resistant, shatterproof and not subject to any external corrosion by its designed as an insulating layer envelope. Due to the special shape of the wrapper, the pressure vessel according to the invention receives a specific outer attachment structure, which makes it possible to continue to use existing on trucks, trucks buses or rail vehicles fasteners for attachment.

The method according to the invention also makes it possible to considerably increase the degree of automation in the manufacture of the pressure vessels through the use of modular tools and the integration of the testing technology in the production process.

The pressure vessel produced by the method according to the invention have a repeatability of 100%, whereby no volume fluctuations in the air volume occur.

It is also of particular advantage that in the enclosure type, note and company signs can be introduced captive, so that the container can be provided directly with product specific Prüfangaben according to the acceptance conditions, with a separate, subsequently consuming labeling of the container can be omitted.

Further advantages and details will become apparent from the following description with reference to the accompanying drawings.

embodiment

The invention will be explained in more detail below using an exemplary embodiment.

It shows

Fig. 1 a pressure vessel according to the invention in sectional view,

Fig. 2 a liner in section with injected sleeves,

Fig. 3 one with a first reinforcing winding in the longitudinal direction of the liner body in a schematic representation,

Fig. 4 a representation of the on the first reinforcing winding after Fig. 3 applied second reinforcing winding in the circumferential direction of the liner,

Fig. 5 a liner with a third reinforcing winding made of plastic-coated fiberglass tape on the second layer in the jacket center region of the liner body in the circumferential direction in a schematic representation,

Fig. 6 a reinforced with reinforcing layer, inserted in an injection mold liner for encapsulation with a cladding layer,

Fig. 7a a representation of the enclosure with a fastening variant as a partial view,

Fig. 7b a front view of the mounting variant according to Fig. 7a .

Fig. 8a a further fastening variant molded into the envelope as a partial view,

Fig. 8b a front view of the Fig. 8a and

Fig. 9 a view of the connection sleeve in the pressure vessel.

The in Fig. 1 shown pressure vessel 1 for a brake system, not shown, a truck should have a capacity of 10 l and thus correspond to the nominal content of a pressure vessel made conventionally made of steel with cylindrical central portion and dished ends.

The pressure vessel 1 has an inner liner body 2 (see Fig. 2 ), which is composed of two liner parts 3 and 4 , a multi-layer, cohesively connected to the liner body 2 by welding reinforcing layer 5 and a sheath 6. The two liner parts 3 and 4 are made of glass fibers of short length reinforced polyethylene and are on a conventional spraying machine produced in an injection mold. Each at their open end faces 7 , the liner parts 3 and 4 by Mirror welding bonded cohesively and gas-tight. The connecting sleeve 8 of the pressure vessel 1 are made of corrosion-resistant metal, such as brass, and are encapsulated on all sides by the polyethylene during injection molding on the polar caps 9 to the inner axial passage, so that the sleeves 8 are captive and gas-tight in the center of the caps 9 .
The injection molding tools for producing the liner parts 3 and 4 are modular tools in which the volume can be correspondingly increased or reduced by core and jacket inserts ( Fig. 6 ). Thus, the liner parts 3 and 4 according to the invention in the usual diameter ranges for pressure vessels are variable in length and thus variable in volume.

The forces occurring at internal pressure on the pressure vessel 1 are expressed in axial and tangential stresses, which overlap each other at each point of the container wall and occur as a resultant stress. Optimum container dimensions are achieved when each point of the container wall receives the same resulting stresses.

Containers made of metallic materials or containers with sharp transitions (strong curvatures) from the jacket do not meet these requirements, so that especially in these areas high resulting stresses occur, which regularly lead to leaking of the pressure vessel at high alternating loads.

The pole caps 9 and the middle jacket region 10 of the liner body 2 of the pressure vessel 1 according to the invention have the shape of a body formed from ball sections or an ellipsoid of revolution 11 (see Fig. 2 ), wherein the pole caps 7 are formed approximately hemispherical and merge transitionless in the shell region 10 . The pressure vessel 1 receives a bulbous design (see Fig. 1 ).

The radius RP of the pole cap 7 in the presented example is 103.3 mm, the radius RM of the jacket region 302.3 mm, so that a ratio of the two radii to each other of 1: 2.92 results. With this ratio, the pressure vessel 1 according to the invention achieves an optimum between the force relationships underlying the dimensioning and the stress conditions.

The multi-layer reinforcing layer 5 consists of an endless glass fiber tape 12 with a sheath 13 made of polyethylene.
During the wrapping of the liner body 2 with the first tangential winding layer A (see Fig. 3 ) of the continuous glass fiber tape, the plastic casing 13 made of polyethylene by means of laser, electric arc or similar. heated, locally melted and welded to the surface of the liner body 2 , so that the liner body 2 and the first winding layer A form a cohesive unit. The subsequent second and third winding layers B and C of the continuous glass fiber tape 12 are also applied, so that the juxtaposed and superimposed edges of the tape 12 are welded together. The applied reinforcing layer 5 thereby also obtains the body shape of the above-described spherical sections or of the ellipsoid of revolution 11 (see FIG Fig. 4 and 5 ).

On the multi-layer reinforcing layer 5 is followed by the applied by injection coating 6, which consists of a short glass fibers contained polyethylene. The polyethylene can also be mixed with propellants. The sheath 6 secures the reinforcing layer 5 in its function and is at the same time designed as a protective layer, wherein in the case of an additive with propellants and an insulation is achieved. In the sheath 6 either fasteners are integrated or the sheath 6 is itself formed into a specific fastener 14 (see Fig. 7a and 7b and 8a and 8b ). Accordingly, this fastening element 14 can be designed so that the hitherto conventional fastening by means of tension bands ( Fig. 7a and 7b ) or by a direct screw connection ( Fig. 8a and 8b ) he follows.

Appropriate signs, nameplates, company logos or other names or labels can be prefabricated and introduced captive into the enclosure 6 . This also provides the opportunity to provide the signs or nameplates or other names with digital information carriers whose information can be read and retrieved by a corresponding RFID configuration.

The Fig. 9 shows the fixed by encapsulation with plastic in the polar cap 7 of the liner body 2 connecting sleeve 8 made of metal, such as brass. On the connection sleeve 8 act as a result of the internal pressure in the pressure vessel 1 and 2 Linerkörper shear forces that try to push out the connection sleeve 8 from the plastic composite. When screwing or unscrewing plugs or screw in the connection sleeve 8 arise circumferential forces that try to unscrew the connection sleeve 8 from the plastic composite. Finally, in the operating state of the pressure vessel, a constantly increasing and decreasing force acts on the connection sleeve 8 .

So that all these forces can be absorbed, without the connection between the connection sleeve 8 and plastic composite is impaired, the connection sleeve 8 has a flange 15 and a sufficiently long cylindrical portion 16 in which grooves, punctures and shoulders 17 are introduced to increase the shear surface. This allows a positive connection between the connection sleeve 8 and the plastic composite with a sufficiently high shear resistance.

Over the entire cylindrical portion 16 of the connecting sleeve 8 is a fine-toothed knurling 18 is present, which is able to absorb both circumferential forces and shear forces in a sufficient size.

In order to ensure a permanently sealed connection between the connecting sleeve 8 and plastic composite, acts under internal pressure load a contact force of the plastic composite on the cylindrical portion 16 of the connecting sleeve 8 due to the leverage on the recess 17 of the sleeve 8. The connecting sleeve 8 is provided on the inside with a recess 19 , into which an injected plastic lip 20 of the liner wall 21 of the respective liner part 3, 4 protrudes.

Due to the constantly prevailing internal pressure in the operating state, a pressing force of the lip acts on the metal inner surface, which increases the more, the higher the internal pressure rises. The introduced in the scope of the connecting sleeve 8 knurls 18, punctures and paragraphs 17 also provide an increase in surface area by up to 80%, so that the decisive for the tightness contact surfaces between metal and plastic increase significantly and the tightness is guaranteed.

The preparation of the pressure vessel according to the invention, consisting of the layers of liner body 2, connecting piece 8, reinforcing layer 5 and sheath 6 will be described in detail below.

The liner parts 3 and 4 are sprayed on a conventional injection molding machine, so that a more detailed description is dispensable.

Starting material for the injection of the liner body is a plastic granules of polyethylene, to which a short fiber content is compounded or added as a pure admixture with a share of up to 30% by weight.

The injection molding tools used are modular tools, which are constructed so that always two congruent liner parts 3 and 4 can be produced. The core and dome of the tools are equipped with disc-shaped, coolable segments, which allow the active elements to be lengthened or shortened in the respective diameter range. For each container diameter, only one tool is required. The coolable segments are replaced accordingly in pairs in the injection mold. The installation parts and connection sleeves are with known handling devices inserted and molded in the injection mold.

The injection of the plastic melt via a hot runner nozzle always on the front side of the liner parts. The hot runner nozzle has 12 star-shaped distribution channels, which distribute the plastic melt evenly in linear and radial direction with the effect of a partial fiber orientation in the flow direction. By this measure, the compressive strength of the liner body increases significantly.

The manufactured by injection molding liner parts 3 and 4 are then materially bonded together. This happens because the end faces 7 of the liner parts 3 and 4 aligned with each other and welded together by means of mirror welding. It is understood that the welding parameters are matched according to the selected plastic mixture and other suitable joining methods are covered by the invention.

After welding, the attached liner body 2 is tested for gas tightness, in which the liner body 2 is spent in water, submerged and exposed to air at a test pressure of 2.5 bar. Existing leaks are indicated by rising from the liner body 2 air bubbles.
The gas-tightness test is preceded by a safety test in which the liner body is pressed under air with a hermetic shielding at a test pressure of 3.5. This pressure is then reduced to 2.5 bar on the leakage tester mentioned at the beginning.

The safety and tightness tester is a complex assembly, which in addition with a Drying device is equipped for drying the liner body. The operation of this complex test bench is only reserved for authorized personnel who have the appropriate approvals for pressure vessels or similar. features.

In the following process step, the previously tested for safety and tightness liner body 2 is bubble-free filled with an incompressible medium such as water and the connection sleeves 8 sealed liquid-tight with plugs. This medium stabilizes the liner body, safely absorbs the heat introduced in the process steps described in more detail below and thus at the same time serves as a coolant.

If plastics are to be used with a higher melting point, filling valves are used in the connection sleeves, which ensure that the incompressible medium kept under pressure can be driven in the circuit through the liner body 2 .

The plugs are provided with a conical pin, which serve for clamping and for securing the position of the liner body 2 in the centered position of the winding machine.

The wrapping material used is polyethylene-sheathed continuous glass fibers which are sintered into a strip of rectangular cross-section. Instead of polyethylene but also polypropylene or other suitable thermoplastic can be used. Other thermoplastics are also suitable.

The reinforcement of the liner body 2 is with the application of a first winding layer A of plastic-coated continuous glass fiber strips 12 for receiving the axial stresses started while receiving the radial stresses. The winding layer A is wound at an angle of 55 ° to the longitudinal axis and also serves to reinforce the pole caps of the pressure vessel.

The winding layer A is heated during winding by laser, the plastic coating is melted and the edges of the individual layers welded together and on the liner body.

The voltage peaks as a result of axial and radial stresses regularly occur in the jacket middle area. Therefore, in the next step in the middle of the mantle center of the jacket center region 10 of the liner body 2 , a second winding layer C is first applied as a peripheral winding on the first layer.
The winding width B1 of the winding layer C is dependent on the container length L and the container diameter D.

worin bedeutet:

B

Wickelbreite

L

Behälterlänge

D

Behälterdurchmesser.

Während des Bewickelns des Linerkörpers 2 mit der zweiten Wickellage wird letztere wiederum mittels Laser erhitzt, aufgeschmolzen und mit dem Linerkörper 2 stoffschlüssig verschweißt. Es entsteht eine innige Verbindung zwischen erster und zweiter Lage.For the second winding layer C , the relationship applies: $$\mathrm{B}\&=0.6\mathrm{L}-0.1\mathrm{D}.$$

where:

B

winding width

L

container length

D

Container diameter.

During the winding of the liner body 2 with the second winding layer, the latter is in turn heated by means of laser, melted and welded to the liner body 2 in a material-bonded manner. It creates an intimate connection between the first and second position.

In the next step, a third winding layer E is wound onto the second winding layer C. The winding layer E serves in conjunction with the winding layer C a more uniform radial stress distribution and forms a belt layer in the middle layer region.

worin bedeutet:

B

Wickelbreite

L

Behälterlänge

D

Behälterdurchmesser.

Die dritte Wickellage E wird wieder während des Umwickelns mittels Laser erhitzt, die Kunststoffummantelung aufgeschmolzen und die nebeneinander zu liegen kommenden Ränder des Endlosfaserbands miteinander verschweißt, wobei auch die darunter liegende zweite Lage mit der darüber liegenden Lage verschweißt wird. Die zweite Wickellage C und die dritte Wickellage E sind somit stoffschlüssig miteinander verbunden.For the layer width of the third winding layer E, the following applies: $$\mathrm{B}2=0.3\mathrm{L}-0.1\mathrm{D}.$$

where:

B

winding width

L

container length

D

Container diameter.

The third winding layer E is again heated during the wrapping by means of laser, the plastic casing is melted and the adjacent edges of the endless fiber strip are welded together, whereby the underlying second layer is welded to the layer above it. The second winding layer C and the third winding layer E are thus materially connected to one another.

The media filling remains in the finished armored liner body 2 as well as the plugs in the connecting sleeves 8. This state is maintained in the following encapsulation of the armored liner body 2 .

The encapsulation of the armored liner body 2 takes place in a separate, suitably prepared injection mold in the interaction of an adapted Spritzgießformgestaltung and a suitable plastic and the pressure build-up of the spray medium.

The injection mold is equipped with several sprue distribution channels, which allow a simultaneous filling of the cavities between the form and inserted armored liner body. The sprues are distributed in Polkappen and coat area. The gating takes place on the machine side at the same time at the poles through a round film gate, which is balanced in the hot runner.

The armored, filled with the incompressible medium liner body 2 is inserted into the opened injection mold and centered on the conical lugs of the stopper and firmly clamped when closing the mold, after the internal pressure of the filling medium in the liner body 2 to about 8 to 10 bar at a temperature from 10 to 15 ° C was set.

In this position, the armored liner body 2 forms the core, which is overmolded. By increasing the internal pressure to about 8 to 10 bar and further technological product-specific parameters, changes in position and local deformation of the core can be avoided by the considerable force effects during the injection process.

Starting material for the production of the envelope is a plastic granules of polyethylene, to which a short fiber content to increase the strength and a blowing agent for foaming, for example, in each case compounded or added as a pure admixture. This makes it possible to achieve desired strength properties of the envelope, for example for the integration of corresponding fastening elements in the envelope, and at the same time desired insulating properties of the envelope, for example, for damping sudden shocks.

The polyethylene can also be further colored by the addition of colorants, so that a corresponding color of the pressure vessel can be omitted and in addition a color coding according to the technical field of application of the pressure vessel is easily possible.

Interchangeable dies are incorporated in the injection mold for the application of inscriptions, which then appear raised or recessed on the container surface. This allows according to the customer's request company names, nameplate labels, information signs, approval marks, logos and the like. applied. Inscriptions, images or signs, permits can also be inserted in the form of films in the injection mold, fix by means of vacuum in a suitable position and merge inextricably during injection with the enclosure. This also makes it possible to provide these slides with digital data carriers that contain the corresponding technical data, registration information, etc. stored and can be retrieved using RFED technology.
The time-consuming gluing or welding on the company signs can be omitted.

To ensure a continuous flowability and a uniform all-round mold filling, the injection mold is run at a temperature of 80 ° C. In the example shown here, the injection rate was 15 mm / s, the injection pressure was <40 bar, the back pressure at 15 bar, the intrusion at 4-6 s and the cooling time at 120 s.

The pressure vessel thus produced by the process according to the invention with a nominal content of 10 L. reached a burst pressure of 50 to 60 bar without splinter effect, a load life of more than 25,000 load cycles, which corresponds to a service life of about 20 years.

LIST OF REFERENCE NUMBERS

pressure vessel

1

liner body

2

liner parts

3, 4

reinforcing layer

5

wrapping

6

Front side of 3, 4

7

connecting sleeve

8th

ice caps

9

Middle jacket area

10

Rotationsellipsoid

11

Continuous glass fiber tape

12

Sheath of 12

13

fastener

14

Flange of 8

15

Cylindrical part of 8

16

grooves

17

knurling

18

recess

19

Plastic lip

20

Linerwandung

21

First winding layer

A

Second winding layer

C

Diameter of the container

D

Third winding layer

e

Length of the container

L

Radius pole cap

RP

Radius coat

RM

Claims (31)

1. Pressure reservoir made of plastics, especially compressed air reservoir for brake power systems and pneumatic auxiliary equipment of lorries, trucks, busses, rail vehicles or fire extinguishing plants, with a reservoir casing consisting of an injection moulded made up of liner parts liner body of fiber reinforced polyethylene, polypropylene or polyamide into the pole caps of which are formed captive connecting pieces, an arranged on the liner body reinforcing layer of glass fiber tape and an arranged on the latter injection moulded captive coating of fiber reinforced polyethylene, polypropylene or polyamide, characterized in that the pressure reservoir (1) with pole caps (9) consists of a made up of spherical segments or formed as ellipsoid of revolution (11) multilayer body, wherein the ratio of pole cap radius (RP) and radius (RM) of the central portion of the casing (10) of the pressure reservoir (1) reaches a ratio of at least 1 : 2.5 to 1 : 5, wherein the walls of the pole caps (9) and the wall of the central portion of the casing (10) with the same curvature fit together without any step.
2. Pressure reservoir according to claim 1, characterized in that the liner body (2) is reinforced with glass fibers up to a portion of 30 %.
3. Pressure reservoir according to claims 1 and 2,
   characterized in that the glass fibers consist of milled fibers.
4. Pressure reservoir according to claims 1 to 3,
   characterized in that the liner parts (3, 4) of the liner body (2) are firmly bonded at the fronts (7) facing each other.
5. Pressure reservoir according to claim 1, characterized in that the reinforcing layer (5) consists of a plastic-coated continuous glass fiber tape (12) that as composite is arranged on the liner body (2) so that the plastic coating of the glass fiber tape by heating it by means of a laser, an electric arc or an open flame is an intimate form-fit firm bonding of the consolidated composite.
6. Pressure reservoir according to claim 5, characterized in that the plastic coating (13) of the continuous glass fiber tape of the reinforcing layer (5) consists of polyethylene, polypropylene or polyamide.
7. Pressure reservoir according to claim 1, characterized in that the coating (6) at the same time forms a protecting layer which additionally secures and fixes the reinforcing layer (5).
8. Pressure reservoir according to claim 7, characterized in that the protection layer additionally forms an insulating layer.
9. Pressure reservoir according to claim 7, characterized in that the coating (6) is developed as an external fastening element (14) for the seating of fastening elements of lorries, trucks, busses, rail vehicles or fire extinguishing plants which are firmly formed into or on the coating.
10. Pressure reservoir according to claim 7, characterized in that in the coating (6) are placed captive inserts for type plates, information signs, labels, name plates.
11. Pressure reservoir according to claim 10, characterized in that the inserts contain a digital information carrier.
12. Pressure reservoir according to claim 7, characterized in that to the coating (6) are added colorants guaranteeing a color coding of the coating with respect to the operational conditions.
13. Pressure reservoir according to claim 1, characterized in that the connecting muff (8) formed in into the center of the pole caps (9) consists of metal, for example aluminum, copper, brass, titan, tombac, which is enclosed by the synthetic material of the liner body (2) except of its external connection surface and the internal thread.
14. Pressure reservoir according to claims 1 and 13,
    characterized in that the connecting muff (8) on its inner side has a turn hollow (19) into which projects a plastic lip (20) of the liner body (2), wherein the lip is pressed as sealing onto the turn hollow by the internal pressure acting in the interior of the liner body.
15. Pressure reservoir according to claims 1 and 13,
    characterized in that the connecting muff (8) has a flange (15) and a sufficiently long cylindrical portion .(16) that on its external side is provided with grooves, cuts and projections (17) to enlarge the shear area.
16. Pressure reservoir according to claim 15, characterized in that the cylindrical portion (16) of the connecting muff (8) furthermore has a fine toothed knurl (18) for taking up peripheral forces and shearing forces.
17. Pressure reservoir according to claims 1 and 13, characterized in that that the connecting muff is developed as single-piece multiple distributor.
18. Pressure reservoir according to claims 1 and 13,
    characterized in that into the internal thread of the connecting muff (8) is inserted a feeding valve.
19. Method for producing a pressure reservoir made of plastics, especially a compressed air reservoir for brake power systems and pneumatic auxiliary equipment of lorries, trucks, busses, rail vehicles or fire extinguishing plants, wherein in the first instance liner parts with hemispherical pole caps of glass fiber reinforced polyethylene, polypropylene or polyamide granules are formed by means of injection moulding in a mould, wherein connecting muffs placed in the center of the pole caps are enclosed by the plastics, the liner parts are connected with each other to a liner body by bonding in a bonding machine, around the bonded liner body in a winding machine is crosswise wound a reinforcing layer of glass fibers and around the thus reinforced liner body is injected a coating of fiber reinforced polyethylene, polypropylene or polyamide,
    characterized in that the pressure reservoir is formed to a body of joined spherical segments or as ellipsoid of revolution with a ratio of pole cap radius and radius of the central portion of the casing of at least 1 : 2.5 to 1 : 5 in the processing steps injection moulding of the liner parts, bonding of the liner parts, welding on the reinforcing layers when they are wound around the liner and injecting the coating around the reinforced liner.
20. Method according to claim 19, characterized by the following steps:

    a) Production of congruent liner parts of the liner body by evenly distributing the polymer melt with a portion of up to 30 % milled fibers in axial and radial directions with partial alignment of the fibers in the flowing direction of the melt and controlling the given proportion,

    b) Firm bonding or glueing of the front surfaces of the liner parts to a closed, hollow liner body with the bonding or glueing parameters adjusted according to the plastic mixture of step a),

    c) Burst test of the liner body with a view to safety and tightness by leading air into the liner body under water and subsequent drying of the liner body,

    d) Stabilization of the liner body by filling it with an incompressible medium free of bubbles, admitting an overpressure of 8 to 10 bar to said medium and sealing the connection muffs of the liner body for the subsequent reinforcement of the liner body,

    e) Reinforcing the liner body by winding around it several layers of continuous glass fiber tape coated with plastics, wherein the layers of the continuous glass fiber tape are firmly bonded to each other by melting the plastic coating,

    f) Developing a captive coating on the reinforcement of the liner body by injecting fiber reinforced plastics under an injection pressure of < 40 bar onto the liner body placed in the mould starting from the pole caps.
21. Method according to claims 19 and 20, characterized in that the thermal stability of the liner body is adjusted to a range of - 40 °C to + 80 °C by adding polypropylene-copolymer granules to the polypropylene granules in a weight ratio of at least 1 : 3.
22. Method according to claim 20, characterized in that as bonding method according to step b) is applied a butt-welding, hot gas welding, heated tool welding, resistance wire welding or injection welding.
23. Method according to claims 19 and 20, characterized in that the liner body is burst tested in a hermetically sealed room with an atmospheric overpressure of 3.5 bar according to step c) and then after decreasing the overpressure to 2.5 bar is carried out a leak test under water.
24. Method according to claims 19 and 20, characterized in that water, oil or mixtures of them are used as incompressible medium for stabilizing the liner body, wherein the medium is hold under an overpressure of 8 to 10 bar.
25. Method according to claims 19 to 24, characterized in that the liner body filled with the medium after its placing, centering and fixing in the winding machine is reinforced in the course of the following single steps according to step e):

    e1) Winding a first layer of plastic coated continuous fiber tape for taking up axial and radial stress around the pole caps and the central portion of the casing and reinforcement of the pole caps by simultaneously melting together the coatings to achieve a firm bond between each other and with the liner body;

    e2) Winding around the first layer according to e1) a second layer in the central portion of the casing for taking up stress concentrations of axial and radial stress and simultaneously melting together the plastic surfaces of the positioned side by side continuous fiber tape of the second layer with a width of the windings fulfilling the condition B1 = 0.6 L - 0.1 D, wherein
    B is the width of windings,
    L is the length of windings and
    D is the diameter of the liner body.

    e3) Winding around the second layer a third layer in the central portion of the casing for evening out the radial stress and simultaneously melting together the plastic surfaces of the positioned side by side continuous fiber tape of the third layer with a width of the windings fulfilling the condition B2 = 0.3 L - 0.1 D, wherein
    B is the width of windings,
    L is the length of windings and
    D is the diameter of the liner body.
26. Method according to claim 25, characterized in that for melting together the plastic surfaces of the continuous fiber tape and the liner body as heat source is used a laser, electric arc or gas burner, wherein the incompressible medium simultaneously is used as coolant to prevent deformations of the liner body.
27. Method according to claim 26, characterized in that the incompressible medium and coolant remains in the liner body or is admitted to overpressure and constantly fed into and let out of it through a filling valve positioned in the screw neck.
28. Method according to claims 19 and 20, characterized in that the liner body filled with medium, reinforced according to step e) is placed into the mould, centered and fixed at the plugs sealing the connecting muffs is coated in the course of the following single steps according to step f):

    f1) Increasing the pressure inside the liner body up to 8 to 10 bar by admitting incompressible medium through a filling valve positioned in the screw plug and adjusting the temperature of the filling medium to 10 to 15 °C,

    f2) Optional placing of name plates, type plates, approval signs or the like on the reinforced surface of the line body,

    f3) Adjusting the temperature of the injected and distributed plastic melt to at least 180 °C and subsequent cooling below the freezing temperature of the plastic mixture,

    f4) Holding at a holding pressure of about 15 bar for increasing the hardness of the coating,

    f5) Demounting the pressure reservoir and emptying it.
29. Method according to claim 28, characterized in that the optionally positioned type plates contain digital information carriers.
30. Method according to claim 19, characterized in that to the fiber reinforced plastics are added colorants for marking the coating according to the respective operational conditions of the pressure reservoir.
31. Method according to claim 20, characterized in that to the coating are added blowing agents to develop an insulating layer.

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