Valve device for injecting gas into a mixing chamber of a plastic metering device, and plastic metering device

Abstract

The invention relates to a valve device (50) for injecting a gas (4) into a mixing chamber (11) of a plastic metering device (1) for filling at least one component (2) in the mixing chamber (11) with gas, the valve device (50) comprising a pressure regulating valve (51) and a flow regulator (52), the inlet (56) of the pressure regulating valve (51) being connected to the outlet (55) of the flow regulator (51), the outlet (71) of the pressure regulating valve (51) being preferably adapted to open directly into the mixing chamber (11). The pressure regulating valve (51) comprises a valve chamber (57), an actuator (58) movable in the valve chamber (57) and a piston unit (59) connected to the actuator (58) and capable of fixing the axial position of the actuator (58) based on the pressure in the valve chamber (57). The invention further relates to a metering device (1) for discontinuous metering of foamed and foamable plastics (5), comprising such a valve device (50).

Description

[Technical field]

[0001] The present invention relates to a valve device for injecting a gas into a mixing chamber of a plastic metering device.Furthermore, the present invention relates to a plastic metering device for metering foamed or foamable plastics, preferably discontinuously. [Background technology]

[0002] Patent document 1 discloses a plastic metering device having a mixing chamber in which the plastic components polyol and isocyanate can be mixed to produce polyurethane. The polyurethane can be metered out of a closable outlet in the mixing chamber via a nozzle. To promote foaming of the polyurethane, the polyol is filled with air before entering the mixing chamber, and the air is combined in dissolved form with the polyol. When the polyol enters the mixing chamber and the pressure in the mixing chamber falls below the saturation pressure of the dissolved air, the air bubbles up and small bubbles are formed. These bubbles become the nuclei of foam cells. However, the degree to which the air bubbles up depends on the pressure in the mixing chamber, which fluctuates during discontinuous metering. This can lead to differences in the quality of the foamed structure of the polyurethane. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 004637 [Patent Document 2] International Publication No. 2016 / 087968 Summary of the Invention [Problem to be solved by the invention]

[0004] An apparatus for charging plastic components with gas is disclosed in the patent application WO 2005 / 023363. The apparatus disclosed in the patent application WO 2005 / 023363 comprises a pressure vessel with a mixer. Compressed air is supplied to the pressure vessel via a valve arrangement, which mainly serves as a control connection for maintaining the pressure level in the pressure vessel at a desired level. Compressed air is supplied to the pressure vessel above the liquid level of the plastic components via the valve arrangement. Furthermore, compressed air is injected directly into the liquid plastic components via a gas-filling ring, which is arranged below the liquid level. Such charging of plastic components with air is usually very time-consuming. On the other hand, the apparatus disclosed in the patent application WO 2005 / 023363 is hardly suitable for a rapid adjustment of the charging state depending on the process parameters. Discontinuous operation can also cause problems. For example, if the compressed air is switched off during an interruption between two metering processes, there is a risk that the plastic components will enter the gas-filling ring and cause contamination or blockage.

[0005] The present invention aims to provide a valve device suitable for injecting a gas into a mixing chamber of a plastic metering device, and a plastic metering device for metering foamed or foamable plastics, preferably in a discontinuous manner. [Means for solving the problem]

[0006] The object of the invention is achieved by the feature combination according to claims 1 and 14. Exemplary embodiments of the invention can be found in the dependent claims.

[0007] According to the invention, a valve arrangement is provided which comprises a pressure regulating valve and a flow regulator, the inlet of the pressure regulating valve being connected to the outlet of the flow regulator, the outlet of the pressure regulating valve preferably being suitable for opening directly into the mixing chamber. The opening of the outlet is not to be understood as being limited in the sense that the outlet of the pressure regulating valve must necessarily be adjacent to the mixing chamber in order to open into the mixing chamber. Of course, embodiments are also conceivable in which an opening, for example a flow passage, is formed by using a suitable connection area between the outlet and the mixing chamber. The pressure regulating valve has a valve chamber, an actuator which is movable as a valve piston in the valve chamber, and further a piston unit which is coupled to the actuator. The piston unit can fix the axial position of the actuator depending on the pressure in the valve chamber. This fixing does not necessarily mean an active positioning of the actuator in the sense of directly controlling the actuator. Rather, the position of the actuator is automatically adjusted based on the prevailing force conditions. For example, the fixing is possible by a balance between the pressure in the valve chamber and the pressure accumulated by the piston unit.

[0008] In a preferred embodiment, the pressure regulating valve can be designed as a needle valve, with a valve chamber, a needle movable in the valve chamber as an actuator and a piston unit connected to the needle. In this case, the needle valve is a control valve whose control gap is changed by the axial movement of the needle or of the needle-like actuator. Alternatively, the pressure regulating valve can also be designed as an adjustable, in particular spring-loaded, check valve.

[0009] The pressure regulating valve can maintain a constant pressure at the outlet of the flow regulator, which is connected to the valve chamber via the inlet of the pressure regulating valve, almost independently of the pressure in the mixing chamber. Even if the inlet of the flow regulator is provided with means for keeping the pressure there constant, the flow regulator has constant pressure conditions at the inlet and outlet, so that a very accurate flow rate can be provided. Overall, the valve device according to the invention can deliver a very precise amount of air per unit of time. This precisely regulated amount of air allows a plastic with a good and homogeneous foam structure to be produced in the mixing chamber.

[0010] The flow regulator is preferably designed as a mass flow meter (MFC). The mass flow rate is determined so that pressure and temperature fluctuations do not affect the result of the regulating action. Preferably, the mass flow meter has a calorimeter as a measurement sensor.

[0011] The piston unit may comprise a pressure guide piston and a closing piston. The pressure guide piston is used to regulate the pressure. Meanwhile, a first force, which depends on the pressure in the valve chamber, may act on the pressure guide piston. Preferably, the first force is proportional to the pressure in the valve chamber. Meanwhile, a second force, which can be precisely regulated by means of a regulating device, acts on the pressure guide piston. If the pressure guide piston is in equilibrium, the actuator in the valve chamber does not move and remains stationary. If the valve chamber pressure is too low, the pressure guide piston and the actuator coupled to it move in one direction and the flow condition of the pressure regulating valve changes in such a way that the valve chamber pressure rises again. The pressure guide piston then moves again in the other direction until an equilibrium is established between the first and second forces. This allows the valve chamber pressure to be regulated to a level or to a set value that is set in dependence on the second force. The pressure regulating valve can be closed by means of a closing piston. Preferably, the pressure regulating valve can be closed independently of the valve chamber pressure.

[0012] The spring element can be arranged between the pressure guide piston and the preferably adjustable abutment. For example, the spring element can be a coil spring. When using an adjustable abutment, the distance between the pressure guide piston and the abutment can be changed by adjusting the abutment, the coil spring being compressed more or less. The force that the spring element and / or the coil spring exerts on the pressure guide piston varies accordingly. As an alternative to a spring element or a coil spring, the adjustable second force can also be provided by other means, such as air pressure. Another possibility is the use of a non-adjustable abutment. This allows a particularly simple installation. Costs are reduced and malfunctions are prevented.

[0013] In one exemplary embodiment, in the closed position of the actuator, the closure piston presses against the pressure guide piston, which presses against the actuator and holds it in the closed position. The force with which the closure piston presses against the pressure guide piston is preferably significantly greater (2 or 5 times greater) than the force exerted on the pressure guide piston by the above-mentioned spring element. This ensures that the pressure regulating valve is quickly and reliably closed by the closure piston.

[0014] The spring can bias the closure piston into a rest position in which the closure piston and the pressure guide piston are decoupled from each other, in which no forces attributable to the closure piston act on the pressure guide piston.

[0015] The actuator, the pressure guide piston and the closing piston can be arranged coaxially with one another. Furthermore, preferably an adjustable abutment can also be arranged coaxially with the pressure guide piston. If an adjustable abutment is used, it is preferably a threaded sleeve whose axial position can be adjusted by a rotational movement via a screw thread. This allows the axial position of the abutment and thus the pressure in the valve chamber to be adjusted very precisely.

[0016] In one exemplary embodiment, the valve chamber is separated by a membrane arranged between the actuator and the piston unit. The membrane allows for a good seal between the valve chamber and the piston unit. The membrane can have a special wave structure that ensures a good fit and seal. In another embodiment, a clamp is provided for the membrane, which makes the membrane corrugated and ensures a good fit and seal.

[0017] The actuator is preferably coupled to the piston unit by magnetic forces. The magnets can be arranged on two opposite sides of the membrane, with the magnetic forces acting through the membrane. Thus, there is no need to penetrate the membrane between them to attach the actuator to the piston unit. This reduces the risk of leakage through the membrane. Of course, it is also conceivable to use a magnet on one side and a ferromagnetic material on the opposite side.

[0018] In an exemplary embodiment, the actuator is made of plastic, preferably PEEK, which allows for a good seal between the actuator and the valve housing defining the valve chamber when the actuator is in the closed position, in particular, it is not possible for material in the mixing chamber to penetrate into the pressure regulating valve.

[0019] The volume between the outlet of the flow regulator and the outlet of the pressure regulating valve is 5 cm 3 Less than 1cm, preferably 3 This minimizes the deleterious compressibility effects of the (gas) volume that make it difficult to precisely control the amount of air injected.

[0020] A check valve may be provided between the outlet of the flow regulator and the inlet of the pressure regulator to prevent material from entering the typically very sensitive flow regulator from the mixing chamber in the event of a failure of the pressure regulator.

[0021] A booster unit can be provided upstream of the inlet of the flow regulator, which compresses the air pressure of a standard compressed air supply network from approximately 5-7 bar to approximately 7-30 bar. To compensate for pressure fluctuations that may occur during operation of the booster unit, a large buffer volume can be provided between the booster unit and the inlet of the flow regulator. A large buffer volume can be created, for example, by using a piece of hose with a large diameter and a long length.

[0022] A plastic metering device according to the invention for preferably discontinuous metering of foamed or foamable plastics comprises a valve device as described above in various embodiments. "Discrete metering" is intended to cover the case where plastic is metered with a constant output (weight / time unit) for a limited time interval, for example a few seconds. Such a metering may be followed by a pause during which no plastic is metered. Discontinuous metering can therefore be a succession of metering processes of different lengths and metering pauses of different lengths in between. The output may also change during the metering process or from metering process to metering process. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 shows a plastic metering device according to the present invention. [Diagram 2] FIG. 2 shows a mixing device of the plastic metering device. [Diagram 3] FIG. 2 shows a pressure regulating valve as part of a valve device according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The invention will now be explained in more detail with reference to the embodiments shown in the drawings. Figure 1 shows a schematic representation of a plastic metering device, the whole of which is designated 1. The plastic metering device 1 preferably discontinuously meters plastic, which is already (partially) foamed when it leaves the plastic metering device 1 or which foams or continues to foam after it has been discharged.

[0025] The plastic metering device 1 comprises a mixing device 10 and a valve device 50. In the mixing device 10, a first component 2 and a second component 3 can be fed to a mixing chamber 11 in which a rotatable agitator 30 is arranged. In the mixing chamber 11, the two components 2, 3 are mixed to form a plastic 5. For example, the first component 2 is a mixture of polyol and water, which reacts with the second component 3, an isocyanate, in the mixing chamber 11 to form a polyurethane. This is achieved by the addition of CO 2 Generates CO 2 The polyurethane can be foamed or (continues to be) foamed after being metered out of the mixing chamber 11 .

[0026] Furthermore, gas 4 is fed to the mixing chamber 11, the amount of which is precisely regulated by a valve arrangement 50. For this purpose, the valve arrangement 50 comprises a pressure regulating valve 51 and a flow regulator formed as a mass flow controller 52, which are connected to each other by a connection unit 53. Pressurized expansion gas 6 is fed to the inlet 54 of the mass flow controller 52.

[0027] The gas 4 is injected directly into the first mixing area 11a of the mixing chamber 11 and mixed or finely dispersed in the first component 2 by the agitator 30. This results in the formation of small microbubbles in the first component 2. The premix then flows through a gap 34 into the second mixing area 11b of the mixing chamber 11. The microbubbles promote a particularly homogeneous and fine foam structure, as will be explained in more detail below.

[0028] An outlet 55 of the mass flow controller 52 is connected to an inlet 56 of the pressure regulating valve 51 via a connection unit 53 .

[0029] 2 shows the mixing device 10 in isolation. The agitator 30 is in this case substantially rotationally symmetrical with respect to the axis of rotation 31. The agitator 30 is driven by a drive shaft 12, which is only partially shown. The agitator 30 has a pin-shaped shaft connection 32 for connection to the drive shaft 12. Preferably, the connection between the drive shaft 12 and the shaft connection 32 is a non-positive connection.

[0030] The housing of the mixer 1 is provided with three inlets: Firstly, there is a first inlet 13 through which the first component 2 can be fed into the mixing chamber 11. Secondly, there is a second inlet 14 for the second component 3, which is axially spaced from the first inlet 13. The axial distance between the first and second inlets 14 can be a few mm, for example 3-20 mm.

[0031] A gas inlet 15 is provided at the same axial height as the first inlet 13, and the gas 4 can be injected into the mixing chamber 11 through the gas inlet 15. The gas 4 is preferably air (the gas may be nitrogen or CO 2 It could be.)

[0032] The plastic or polyurethane foam leaves the mixing chamber 11 via an outlet 16. The outlet 16 is arranged coaxially with the rotation axis 31 and is provided at the axial end 17 of the mixing chamber 11. The outlet 16 is formed by a nozzle 18. The inner diameter of the nozzle 18 can be, for example, 1-8 mm or 2-5 mm. The length of the nozzle 18 can be 2-50 mm or 30 mm. The produced plastic leaves the mixing chamber 11 in the axial direction.

[0033] The agitator 30 has a cylindrical shaft collar 33, the outside diameter of which is slightly smaller than the inside diameter of the cylindrical mixing chamber 11. A radial gap 34 between the shaft collar 33 and the mixing chamber wall 19 can be considered as part of a restriction or flow brake, which divides the mixing chamber 11 into a first mixing region 11a and a second mixing region 11b.

[0034] The agitator 30 can be moved axially (in the direction of the axis of rotation 31). FIG. 2 shows the agitator 30 in an axial position in which an outlet gap 36 is formed between the conical agitator tip 35 of the agitator 30 and the funnel-shaped insert 20 arranged at the axial end 17 of the mixing chamber 11. As a result, the plastic produced in the mixing chamber 11 can be discharged from the mixing device 1 via the nozzle 18. In the closed position, the conical agitator tip 35 rests on the insert 20, thereby closing the outlet gap 36. In the closed position of the agitator 30, the outlet 16 is thus closed. The axial length of the gap between the agitator tip 35 and the insert 20 has a value between 0 mm (closed position) and 2.5 mm. The axial position of the agitator 30 and / or the axial length of the outlet gap 36 can be used to set a specific pressure in the mixing chamber 11. Means for precisely adjusting the axial position of the agitator 30 are not shown in FIG. 2.

[0035] The axial stroke or gap (difference between closed and top positions) is dimensioned such that, when viewed axially, the axial collar 33 and / or the flow brake is always located between the first inlet 13 and the second inlet 14. As a result, the first inlet 13, and in this exemplary embodiment the gas inlet offset by 180°, always opens into the first mixing zone 11a of the mixing chamber 11. However, the second inlet 14 always opens into the second mixing zone 11b, regardless of the axial position of the stirrer 30.

[0036] The agitator 30 has first means 38 on a first shaft section 37 for splitting the gas 4 and / or mixing the gas 4 with the first component 2. The first shaft section 37 of the agitator 30 is located in a first mixing area 11a of the mixing chamber 11. The first mixing area 11a is defined by a shaft collar 33 and a seal 21 inserted between the drive shaft 12 and the mixing chamber wall 19. A second shaft section 39 extending from the shaft collar 33 to the agitator tip 35 is provided with second means 40 for mixing the premix of the first component 2 and the gas 4 with the second component 3. The second shaft section 39 is located in a second mixing area 11b of the mixing chamber 11. The first means 38 and the second means 40 may include protrusions projecting radially outwardly for stirring the corresponding materials in the mixing chamber 11 as the agitator 30 rotates.

[0037] Before describing the pressure regulating valve 51 of the valve device 50 in more detail, the operation of the mixing chamber 1 will be briefly described, focusing on the metering of polyurethane or polyurethane foam 5. A polyol containing water as the first component 2 is supplied to the first mixing region 11a via the first inlet 13. At the same time, air is injected into the first mixing region 11a via the gas inlet 15. The injected gas 4 is dispersed in the first component 2 by rotating the agitator 30, thereby rotating the first means 38. This generates small microbubbles of gas, which are finely dispersed in the first component 2. The rotation speed of the agitator can be 1,000 to 6,000 rpm, or 1,500 to 4,000 rpm.

[0038] The pressure present in the first mixing zone 11a causes the pre-mix from the first mixing zone 11a to pass through the radial gap 34 and enter the second mixing zone 11b. There, the pre-mix (polyol, water, microbubbles) is mixed with the isocyanate (second component 3) by the second means 40. During the reaction of the polyol, water, and isocyanate, CO 2 is produced in addition to the polyurethane. 2 is generated. Microbubbles are CO 2This nucleates the formation of bubbles, forming foam cells in the polyurethane. The polyurethane can be metered out of the mixing chamber 11 via the outlet 16. Due to the flow brake and / or the throttling effect of the radial gap 34, a (small) pressure gradient is created between the first mixing zone 11a and the second mixing zone 11b. This pressure gradient ensures that there is no substantial flow from the second mixing zone 11b to the first mixing zone 11a. This prevents isocyanate or a mixture of isocyanates, polyol and water from entering the first mixing zone 11a and causing undesired contamination.

[0039] When the metering process is to be ended, the agitator 30 is moved from the position shown in FIG. 2 to the closed position in order to close the outlet 16. The drive shaft 12 is braked so that the agitator 30 no longer rotates in the mixing chamber 11. The descent of the agitator 30 can be adjusted so that the agitator tip 35 descends axially until it rests on the insert 20, cleaning the insert 20 and the agitator tip 35 by residual rotation. At the same time, the valve device 50 is closed to prevent polyol from entering the valve device 50 or too much gas from accumulating in the first mixing area 11. With the closed valve device 51 and the closed outlet 16, the mixing chamber is sealed from the environment after the metering process is ended. At the start of another metering process, the two components 2, 3 and the gas 4 are again fed into the mixing chamber with the agitator 30 rotating and axially displaced.

[0040] 3 shows the pressure regulating valve 51 on an enlarged scale. The pressure regulating valve 51 is designed as a needle valve. It has a valve chamber 52, a needle 58 which is movable in the valve chamber 52 as an actuator, and a piston unit 59 which is connected to the needle 58. The piston unit 59 comprises a pressure guide piston 60 and a closing piston 61. Between the piston unit 59 and the needle 58 a membrane 62 is arranged which defines and seals the valve chamber 57.

[0041] The coupling between the needle 58 and the piston unit 59 is achieved by two magnets 63, 64 designed as disk magnets made of neodymium. The magnetic force between these two magnets acts via the membrane 62. The needle 58 is firmly connected to the magnet 63 via a needle holder 65, for example by adhesive. The magnet 64 is inserted into an intermediate piece 66, against which the spherical cap 75 of the pressure guide piston 60 rests. The membrane 62 is fixed to the valve housing 68 by means of a threaded sleeve 67.

[0042] A coil spring 70 is arranged between the pressure guide piston 60 and an axially adjustable abutment 69 of the threaded sleeve type, which biases the pressure guide piston 60, and thus the needle 58, to the left in the illustration of Fig. 3. The force with which the coil spring 70 biases the pressure guide piston 60 depends on the axial position of the threaded sleeve 69. The axial position can be precisely adjusted by rotating the threaded sleeve 69.

[0043] When the needle 58 moves all the way to the left, it is in the closed position, where the outlet 71 of the pressure regulating valve 51 is closed. A force opposite to the biasing force of the coil spring 70 and dependent on the pressure in the valve chamber 57 and / or the pressure at the inlet 56 of the pressure regulating valve 51 acts on the pressure guide piston 60 via the membrane 62 and the intermediate piece 66. If the pressure guide piston 60 is in a state of force equilibrium, the needle 58 does not move in the valve chamber 57. If the pressure in the valve chamber 57 decreases, the force pushing the pressure guide piston 60 to the right in the illustration of FIG. 3 also decreases. Therefore, the needle 58 moves to the right due to the biasing force of the coil spring that can no longer be compensated for, and the outlet 71 is closed and / or the flow cross-sectional area at the outlet 71 is reduced. This causes the pressure in the valve chamber 57 to rise again, as a result of which the balance of forces on the pressure guide piston 60 is restored.

[0044] The closing piston 61 serves to close the outlet 71 of the pressure regulating valve 51 when the metering process of the plastic metering device 1 and thus the supply of gas 4 is terminated. In this case, when the closing piston 61 is pressurized with compressed air via the air supply device 72, it presses against the biasing force of another coil spring 73 against the pressure guide piston 60. This causes an unbalance of forces between the pressure in the valve chamber 57 and the force of the coil spring 70. The needle 58 thus moves to the closed position and is held there, independent of the pressure in the valve chamber 57. If the gas 4 again flows out of the pressure regulating valve 51, the supply of compressed air to the closing piston 61 is terminated. The coil spring 73 then presses the closing piston back to its rest position, in which the closing piston 61 exerts no force on the pressure guide piston 60.

[0045] The connection unit 53, arranged between the outlet 55 of the mass flow controller 52 and the inlet 56 of the pressure regulating valve 51, comprises a check valve 74 (see FIG. 1), which protects the mass flow controller 52 from the ingress of the first component 2 in the event that the pressure regulating valve 51 is damaged and is no longer able to block the flow of the first component 2 through the valve chamber 57. [Explanation of symbols]

[0046] 1 Mixing chamber 2 First component 3. Second Component 4. Gas 5 Plastic (Polyurethane Foam) 6. Expanding Gas 10 Mixing device 11 Mixing chamber 11a 1st mixing area 11b 2nd mixing area 12 Drive shaft 13 1st inlet 14 2nd inlet 15 Gas inlet 16 Outlet 17 Axial end 18 Nozzles 19 Mixing chamber wall 20 Insert 21 Seal 30 Mixer 31 Rotation axis 32 Pin-shaped shaft connection 33 Axis Color 34 Radial gap 35 Mixer tip 36 Exit Gap 37 1st axis part 38 First means 39 2nd axis part 40 Second means 50 Valve gear 51 Pressure Regulating Valve 52 Flow rate regulator (mass flow controller) 53 Connection unit 54 Mass flow controller inlet 55 Mass flow controller outlet 56 Flow rate adjustment inlet 57 Valve chamber 58 Needle 59 Piston unit 60 Pressure Guide Piston 61 Closing piston 62 Membrane 63 Magnet 64 Magnet 65 Needle holder 66 Intermediate Piece 67 Screw sleeve 68 Valve Housing 69 Abutment / Screw Sleeve 70 Coil spring 71 Pressure Regulating Valve Outlet 72 Air supply device 73 Coil spring piston unit 74 Check valve 75 Spherical Cap

Claims

1. A valve device (50) for injecting a gas (4) into a mixing chamber (11) of a plastic metering device (1) for filling at least one component (2) in the mixing chamber (11) with a gas, comprising: The valve device (50) is characterized by comprising a pressure regulating valve (51) and a flow regulator (52); The inlet (56) of the pressure regulating valve (51) is connected to the outlet (55) of the flow regulator (52); the outlet (71) of said pressure regulating valve (51) is adapted to open directly into said mixing chamber (11); The pressure regulating valve (51) has a valve device (50) including a valve chamber (57), an actuator (58) movable within the valve chamber (57), and a piston unit (59) coupled to the actuator (58) and capable of fixing the axial position of the actuator (58) depending on the pressure within the valve chamber (57).

2. The piston unit (59) comprises a pressure guide piston (60) and a closing piston (61); The pressure guide piston (60) adjusts the pressure, 2. The valve device (50) according to claim 1, characterized in that the closing piston (61) closes the pressure regulating valve (51).

3. 3. The valve device (50) according to claim 2, characterized in that a spring element is arranged between the pressure guide piston (60) and the adjustable abutment (69).

4. 4. The valve device (50) according to claim 2 or 3, characterized in that in the closed position of the actuator (58), the closing piston (61) presses against the pressure guide piston (60) which presses against the actuator (58) and holds it in the closed position.

5. 4. The valve device (50) according to claim 3, characterized in that a spring (73) biases the closing piston (61) to a rest position in which the closing piston (61) and the pressure guide piston (60) are decoupled from each other.

6. 4. The valve device (50) according to claim 2 or 3, characterized in that the actuator (58), the pressure guide piston (60) and the closing piston (61) are arranged coaxially with one another.

7. 3. The valve device (50) according to claim 1 or 2, characterized in that the valve chamber (57) is defined by a membrane (62) arranged between the actuator (58) and the piston unit (59).

8. 8. The valve arrangement (50) of claim 7, characterized in that the actuator (58) is coupled to the piston unit (59) by magnetic forces.

9. 8. The valve device (50) according to claim 7, characterized in that the magnets (63, 64) are arranged on two opposite sides of the membrane (62), or one magnet is arranged on one side of the membrane (62) and a corresponding ferromagnetic material is arranged on the opposite side, in each case a magnetic force acting through the membrane (62).

10. 3. The valve device (50) of claim 1 or 2, wherein the actuator (58) is made of plastic.

11. The volume between the outlet (55) of the flow regulator (52) and the outlet (71) of the pressure regulating valve (51) is 5 cm ３ 3. The valve device (50) according to claim 1 or 2, characterized in that it is less than

12. 3. The valve device (50) according to claim 1 or 2, characterized in that a check valve (74) is provided between the outlet (55) of the flow regulator (52) and the inlet (56) of the pressure regulating valve (51).

13. 3. The valve device (50) according to claim 1 or 2, characterized in that the flow regulator (52) is designed as a mass flow controller (52) and has a calorimetric flow meter as a measuring sensor.

14. 3. A metering device (1) for discontinuously metering foamed or foamable plastics (5), comprising a valve device (50) according to claim 1 or 2.

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