Method and metering device for metering a liquid or pasty product in a pressure-regulated manner

Abstract

A method for metering a liquid or pasty product in a pressure-regulated manner, has the following steps: metering the product into a mixing chamber using a metering pump; ascertaining a product pressure of the product according to the mixing chamber; ascertaining a deviation of the product pressure from a specified target pressure; and opening or closing a pressure regulating valve provided on an outlet nozzle of the mixing chamber based on the pressure in order to equalize the product pressure and the target pressure, wherein the product pressure is reduced when the pressure regulating valve is opened and increased when the pressure regulating valve is closed.

Claims

1. A method for metering a liquid or pasty product in a pressure-regulated manner, the method comprising the following steps: metered feeding of the product with the aid of a metering pump into a mixing chamber; determining a product pressure of the product after the mixing chamber; determining a deviation of the product pressure from a predetermined nominal pressure; diverting the product along a diverted flow path through a diversion block positioned between the mixing chamber and a nozzle tube, wherein the diverted flow path of the product is different than a flow path of the product in the mixing chamber and the nozzle tube; and opening or closing in a pressure-dependent manner a pressure-regulating valve attached to the diversion block, the pressure-regulating valve configured to align the product pressure with the nominal pressure, wherein the product pressure is reduced when opening the pressure-regulating valve and is increased when closing the pressure-regulating valve, wherein the product is compressible up to the predetermined nominal pressure and incompressible at a pressure that is greater than the predetermined nominal pressure.

2. The method as claimed in claim 1, wherein at least two dissimilar components of the product are fed in a metered manner into the mixing chamber.

3. The method as claimed in claim 2, wherein the at least two components in the mixing chamber are mixed with one another with the aid of at least one of a static mixer and a dynamic mixer.

4. The method as claimed in claim 1, furthermore comprising a calibration step in which an entry of the mixing chamber is closed and the product is directed to a calibration exit, wherein a product pressure of the product ahead of the calibration exit is determined, wherein a deviation of the product pressure from a predetermined nominal pressure is determined, wherein a pressure-regulating valve that is provided on the calibration exit is opened or closed in a pressure-dependent manner, so as to align the product pressure with the nominal pressure, and wherein the product pressure is reduced when opening the pressure-regulating valve and is increased when closing the pressure-regulating valve.

5. The method as claimed in claim 4, wherein the product pressure is aligned with the nominal pressure in the calibration step.

6. The method as claimed in claim 4, wherein the calibration step is carried out separately for dissimilar components of the product.

7. The method as claimed in claim 1, wherein the diversion block is positioned between the mixing chamber and the nozzle tube so that a longitudinal axis of the diversion block is transverse to a longitudinal axis of at least one of the mixing chamber and the nozzle tube.

Description

(1) Further advantageous design embodiments and aspects of the method and/or of the metering device are the subject matter of the dependent claims and of the exemplary embodiments of the method and/or of the metering device that will be described hereunder. The method and/or the metering device will furthermore be explained in more detail by means of preferred embodiments with reference to the appended figures in which:

BRIEF DESCRIPTION OF THE DRAWINGS

(2) FIG. 1 shows a schematic perspective view of an embodiment of a metering device;

(3) FIG. 2 shows a schematic sectional view of the metering device according to FIG. 1;

(4) FIG. 3 shows a schematic perspective partial sectional view of the metering device according to FIG. 1;

(5) FIG. 4 shows a schematic partial sectional view of the metering device according to FIG. 1;

(6) FIG. 5 shows a further schematic partial sectional view of the metering device according to FIG. 1;

(7) FIG. 6 shows a further schematic partial sectional view of the metering device according to FIG. 1;

(8) FIG. 7 shows a further schematic partial sectional view of the metering device according to FIG. 1;

(9) FIG. 8 shows a further schematic partial sectional view of the metering device according to FIG. 1; and

(10) FIG. 9 shows a schematic block diagram of an embodiment of a method for operating the metering device according to FIG. 1.

DETAILED DESCRIPTION

(11) Identical or functionally identical elements have been provided with the same reference signs in the figures unless otherwise stated.

(12) FIG. 1 shows a schematic perspective view of an embodiment of a metering device 1 for metering in a pressure-regulated manner a liquid or pasty product P. FIG. 2 shows a schematic sectional view of the metering device 1, and FIG. 3 shows a schematic perspective partial sectional view of the metering device 1. Reference hereunder is made simultaneously to FIGS. 1 to 3.

(13) The product can be, for example, an adhesive or a sealant, water, an aqueous solution, a paint, a suspension, a viscous raw material, an emulsion, or a fat. The product P can have one or more than one component K1, K2. For example, the product P can be a bi-component adhesive. The product can be filled with fillers such as micro balloons, for example. Micro balloons are hollow glass spheres which are used, for example, as fillers for epoxy and polyester resin systems. Micro balloons of this type can have, for example, a bulk density of 140 to 150 g/l, a specific weight of 0.26 g/cm.sup.3, a grain size distribution of 50 μm, and a maximum particle size of 200 μm. A pasty product or a paste is understood to be a mixture of a solid and a liquid, in particular a suspension, having a high content of solids.

(14) The metering device 1 comprises at least one metering pump 2, 3. The metering device 1, as is shown in FIGS. 1 to 3, can have two metering pumps 2, 3, in particular one first metering pump 2 and one second metering pump 3, or an arbitrary number of metering pumps, for example three metering pumps. The metering pumps 2, 3 can be, for example, eccentric screw pumps, gear pumps, piston metering units, or the like. The metering pumps 2, 3 are preferably configured as eccentric screw pumps.

(15) An eccentric screw pump preferably comprises a stator, received in a pump housing, which has an elastically deformable elastomer part having a central breach. The breach preferably comprises an internal contour in the shape of a screw or a worm. A rotatable rotor which comprises an external contour in the shape of a screw or a worm that corresponds to the elastomer part is preferably provided in the stator. The rotor can be driven by means of a drive shaft by a drive element, in particular an electric motor. The drive shaft can be fixedly connected to the rotor with the aid of a flexible shaft or a flex-shaft or a universal-joint shaft. When rotating the rotor, on account of the interaction with the elastomer part of the stator, the product P or the component K1, K2, respectively, in a longitudinal direction of the eccentric screw pump is conveyed away from the drive shaft according to the principle of the endless piston. The conveyed volume herein depends on the rotational speed, the size, the pitch, and the geometry of the rotor.

(16) The first metering pump 2 and the second metering pump 3 are assembled on a throughflow head or a throughflow block 4. The metering pumps 2, 3 herein are disposed in a V-shaped manner or in parallel. The throughflow block 4 can be made from a steel or an aluminum material, for example. The throughflow block 4 can be configured in two parts and have a mixing head block 5, to which the metering pumps 2, 3 are fastened, and a throughflow shut-off block 6. The mixing head block 5 herein is disposed between the throughflow shut-off block 6 and the metering pumps 2, 3.

(17) The throughflow block 4 comprises a first duct 7 that penetrates the mixing head block 5 and the throughflow shut-off block 6, the first component K1 being capable of being directed through said first duct 7, and a second duct 8 that is at least in part disposed so as to be parallel with the first duct 7, the second component K2 being capable of being directed through said second duct 8. The throughflow block 4 furthermore comprises a first pressure sensor 9 for determining a pressure of the first component K1 in the first duct 7, and a second pressure sensor 10 for determining a pressure of the second component K2 in the second duct 8.

(18) The throughflow block 4 furthermore comprises a first shut-off valve 11 for closing the first duct 7 downstream of the first pressure sensor 9. The first shut-off valve 11 comprises a drive element 12, for instance an electric motor, as well as a valve plunger or a valve member 13 which for closing the first duct 7 is relocatable into the latter and for opening the first duct 7 is relocatable out of the latter again. Furthermore, the throughflow block 4 comprises a second shut-off valve 14 for closing the second duct 8 downstream of the second pressure sensor 10. The second shut-off valve 14 likewise comprises a drive element 15 and a valve plunger or a valve member 16 which for closing and opening the second duct 8 is relocatable into the second duct 8 and relocatable out of the latter again.

(19) The metering device 1 furthermore comprises a calibration block 17 that is fastened to the mixing head block 5. The calibration block 17 can be screw-fitted to the mixing head block 5, for example. The calibration block 17 comprises a first calibration exit 18 and a second calibration exit 19. Furthermore, the calibration block 17 comprises a first pressure-regulating valve 20 for opening or closing in a pressure-dependent manner the first calibration exit 18, and a second pressure-regulating valve 21 for opening or closing in a pressure-dependent manner the second calibration exit 19.

(20) The second pressure-regulating valve 21 comprises a drive element 22 and a valve plunger or a valve member 23 which with the aid of the drive element 22 is relocatable in a linear manner in a longitudinal direction L1 of the metering device 1. The drive element 22 is preferably an electric motor having an adjustment spindle as an actuator. The second calibration exit 19 can be opened or closed with the aid of the valve member 23. The valve member 23 is preferably needle-shaped. The second pressure-regulating valve 21 is in particular a needle valve.

(21) The valve member 23 of the second pressure-regulating valve 21 is disposed in a bore 24 that is provided in the calibration block 17. The bore 24 can run so as to be parallel with the second duct 8. The second duct 8 is fluidically connected to the bore 24 by way of a bore 25 that is guided through the mixing head block 5 and the calibration block 17. The second calibration exit 19 is capable of being closed and opened with the aid of the second pressure-regulating valve 21.

(22) The first pressure-regulating valve 20 likewise has a drive element 22 of this type as well as a needle-shaped valve member 23. The first calibration exit 18 is capable of being closed and opened with the aid of the first pressure-regulating valve 20. The valve member 23 of the first pressure-regulating valve 20 is provided in a bore 24 that is disposed so as to be parallel with the first duct 7 and by way of a further bore 25 is fluidically connected to the first duct 7. The bores 24, 25 assigned to the first calibration exit 18, as well as the valve member 23 of the first pressure-regulating valve 20, are not shown in FIGS. 1 to 3.

(23) The metering device 1 comprises a mixing block 26 which on the front side is fastened to the throughflow shut-off block 6. The mixing block 26 can be fastened directly to the throughflow shut-off block 6, or a pipeline or a hose can be provided between the throughflow shut-off block 6 and the mixing block 26. The mixing block 26 is tubular and encloses a cylindrical mixing chamber 27 in which the first components K1 and the second component K2 are mixed. To this end, a static mixer and/or a dynamic mixer can be provided in the mixing chamber 27.

(24) A static mixer is to be understood to be a mixer which does not have any movable parts. A static mixer of this type in particular has mixing helices or mixing members, wherein the two components K1, K2 when the latter are being conveyed through the mixing chamber 27 are mixed by being thrown on top of one another multiple times. As opposed thereto, a dynamic mixer has one or a plurality of movable mixing elements, for example a rotatable mixing element. The components K1, K2 are mixed to the product P in the mixing chamber 27. In the case of the product P not having multiple components, the product P is fed in a metered manner by the metering pump 2, 3, in this case only by one metering pump 2, 3, into the mixing chamber 27 and mixed therein.

(25) The mixing block 26 has an exit nozzle 28 which does not mandatorily have to be provided directly on the mixing block 26. The exit nozzle 28 is provided on a sharply tapered nozzle tube 29. A product diversion block 30 is provided between the nozzle tube 29 and the mixing block 26. The product P can be diverted with the aid of the product diversion block 30. The product diversion block 30 is in particular specified for twice diverting the product by an angle of 90°. To this end, a tortuous duct 31 which fluidically connects the mixing chamber 27 to a duct 32 that is provided in the nozzle tube 29 is provided in the product, diversion block 30. The ducts 31, 32 can be part of the mixing chamber 27.

(26) A drive element 33 of a further, in particular of a third, pressure-regulating valve 34 is provided on the product diversion block 30. The drive element 33 is preferably an electric motor having an adjustment spindle as an actuator. The exit nozzle 28 can be opened or closed in a pressure-dependent manner with the aid of the pressure-regulating valve 34. To this end, the pressure-regulating valve 34 has a valve plunger or a valve member 35 that is provided in the duct 32 of the nozzle tube 29. The valve member 35 is relocatable in a linear manner in particular in the longitudinal direction L1 in the duct 32. The pressure-regulating valve 34 is in particular a needle valve.

(27) The pressure-regulating valves 20, 21, 34 are in particular not configured as open/shut valves. An open/shut valve can be switched to only two switched positions, specifically selectively to an open position or to a closed position. An open/shut valve of this type can also be referred to as a shut-off valve or a stop valve. A regulating valve or a pressure-regulating valve is presently to be understood as a valve which is movable in a stepless manner to an arbitrary, in particular infinite, number of intermediate positions between an open position, meaning a minimum product pressure, and a closed position, meaning a maximum product pressure. On account thereof, any arbitrary product pressure between the minimum product pressure and the maximum product pressure can be set. To this end, the respective pressure-regulating valve 20, 21, 34 preferably has in each case the valve member 23, 35 already mentioned above which with the aid of the respective drive element 22, 33 is relocatable in particular in a linear manner. The valve member 22, 33 herein can be, for example, needle-shaped (needle valve) or spherical (ball valve). The drive element 22, 33 is preferably in each case an electric motor or an electric motor having an adjustment spindle as an actuator. On account thereof, the respective valve member 23, 35 can be moved to any arbitrary position between the open position and the closed position. The metering device 1 furthermore comprises a pressure sensor 36 for determining a product pressure of the product P after the mixing chamber 27. The pressure sensor 36 can be disposed directly on the mixing chamber 27 or, as is shown in FIGS. 1 to 3, on the product diversion block 30 and in particular in the duct 31 of the product diversion block 30.

(28) The metering device 1 furthermore comprises a control installation 37 which is specified for detecting measured values of the pressure sensors 9, 10, 36 and for actuating the pressure-regulating valves 20, 21, 34 as well as the shut-off valves 11, 14. The control installation 37 is also specified for comparing the measured values that have been detected with the aid of the pressure sensors 9, 10, 36 with a nominal value.

(29) The functionality of the metering device 1 will be explained hereunder with reference to FIGS. 4 to 8 which in each case show sectional detailed views of the metering device 1. The quantity, or the volume, respectively, per component K1, K2 during the metering procedure can be influenced by various factors. These can be inter alia the back pressure in the mixing chamber 27, the viscosity of the product P or of the components K1, K2, respectively, the compressibility of the product P or of the components K1, K2, respectively, and other rheological properties such as, the yield point, for example. The compressibility of the product P or of the 355 components K1, K2, respectively, herein can assume a significant degree on account of inclusions of air or gas, or by adding micro balloons.

(30) By virtue of the volumetric variation and the variations in the pressure states in the dynamic as well as in the static state, the accuracy of the metered volume, or of the quantity, is not guaranteed in particular in the case of compressible components K1, K2, such that partial errors in the mixing ratio as well as in the total quantity can arise in order for this to be prevented, in the case of the metering device 1 the product P or the components K1, K2, respectively, are fed in a metered manner into the mixing chamber 27 with the aid of the respective metering pump 2, 3. The feeding in a metered manner herein can be performed in a continuous manner. This means that the metering pumps 2, 3 deliver a continuous volumetric flow. The shut-off valves 11, 14 in the normal operation of the metering device 1 are opened such that the ducts 7, 8 are fluidically connected to the mixing chamber 27. This means that the metering pumps 2, 3 convey into the mixing chamber 27.

(31) The product pressure of the product P after the mixing chamber 27 is measured with the aid of the pressure sensor 36. With the aid of the control installation 37, this determined product pressure is compared with a predetermined nominal pressure, and the deviation of the product pressure from the nominal pressure is determined. The control installation 37 to this end can have a computer program having a regulating algorithm, preferably having a PID (proportional integral derivative) regulation. The nominal pressure herein is preferably so high that the product P is no longer compressible and in particular is almost or substantially no longer compressible. However, the product pressure is so minor that the product P is not damaged, for example so minor that the squashing of micro balloons that are contained in the product P is prevented. This means that the product pressure is maintained in a predetermined pressure window.

(32) The control installation 37 now actuates the pressure-regulating valve 34 such that the exit nozzle 28 is opened or closed in a pressure-dependent manner. Accordingly, the product pressure is lowered when the pressure-regulating valve 34 is opened, since the product P can exit through the exit nozzle 28. The product pressure on the mixing chamber 27 rises when the pressure-regulating valve 34 is closed, since the product P can no longer exit from the exit nozzle 28. To this end, FIG. 4 shows the pressure-regulating valve 34 in the closed state, and FIG. 5 shows the pressure-regulating valve 34 in the open state.

(33) The product pressure of the product P during the entire metering procedure, both in the static as well as in the dynamic state, can thus be maintained so as to be constant with the aid of the metering device 1, so as to minimize inaccuracies in the metering, or to completely prevent the latter, respectively. Depending on the product pressure measured by the pressure sensor 36, a high pressurized state can be constantly maintained with the aid of the pressure-regulating valve 34 that is actuated by the control installation 37. This independently of whether the product P flows or does not flow, that is to say both in a static as well as in a dynamic state. The product pressure is thus also independent of the throughflow and of the back pressure through the static mixer in the mixing chamber 27 and through the exit nozzle 28.

(34) Besides the regulating function of the product pressure, a calibration when under pressure can also be enabled. To this end, an entry of the mixing chamber 27 is closed with the aid of the shut-off valves 11, 14. The first shut-off valve 11 in FIG. 6 is opened, that is to say that the valve member 13 does not block the first duct 7, which is provided in the throughflow block 4. The second shut-off valve 14 is closed, that is to say that the valve member 16 is relocated into the second duct 8 so as to block the latter. As in the case of the pressure regulation of the volumetric flow of the product P, a stable pressurized state which preferably corresponds to the same pressurized state as when metering the product P is achieved by way of the pressure sensor 10, the control installation 37, and the pressure-regulating valve 21.

(35) Since the volumetric flow per component K1, K2 in this calibration procedure can be metered individually from the respective calibration exit 18, 19, a calibration per component K1, K2 under pressure can be performed in a very simple manner. The quantity of the component K1, K2 per unit of time is measured herein and used as a measured value of a calibration function of the metering device 1. Specifically in the case of compressible products P, or in the case of compressible components K1, K2, respectively, dissimilar flows and volumes, or masses, respectively, can arise in particular at the beginning and at the end of a metering procedure, the determination of said flows and volumes, or masses, respectively, is not able to be determined by a back pressure, that is generated by flow resistances. To this end, FIG. 7 shows the opened pressure-regulating valve 21, and FIG. 8 shows the pressure-regulating valve 21 in a closed state.

(36) However, since the product P, or the components K1, K2, respectively, are no longer compressible as from the predetermined nominal pressure, and the compressibility becomes almost zero, this effect can be minimized in that the product pressure is always maintained in a pressure window which is larger than or equal to the nominal pressure. Should the product P, or the components K1, K2, respectively, contain fillers such as, for example, micro balloons, which could burst as from a specific pressure, the nominal pressure can be set such that the maximum possible quantity of the product P is metered on the other hand, but the bursting of the fillers is prevented by the limitation to a maximum pressure.

(37) A method for metering the liquid or pasty product P in a pressure-regulated manner, such as illustrated in FIG. 9, comprises a plurality of steps. In a step S1 the product P with the aid of the metering pump 2, 3 is fed in a metered manner into the mixing chamber 27. In the step S1 at least two components K1, K2 of the product P can also be fed in a metered manner from different metering pumps 2, 3 into the mixing chamber 27. The feeding in a metered manner can be performed continuously. This means that the metering pump feeds the product P in a metered manner into the mixing chamber 27 during the entire method in a step S2 the product pressure of the product P after the mixing chamber 27 is determined. To this end, the pressure sensor 36 which can be provided directly on the mixing block 26 or even on the product diversion block 30 or on the nozzle tube 29 is used.

(38) In a step S3 a deviation of the product pressure from a predetermined nominal pressure is determined. The nominal pressure is in particular so high that the product P, or the components K1, K2, respectively, are no longer compressible as from the nominal pressure in a step S4 the pressure-regulating valve 34, provided on the exit nozzle 26 of the mixing chamber 27, is opened or closed, so as to align the product pressure with the nominal pressure or to raise said product pressure beyond the nominal pressure. In particular, the product pressure is reduced when opening the pressure-regulating valve 34, and is increased when closing the pressure-regulating valve 34.

(39) The method can furthermore comprise a calibration step S5 in which the ducts 7, 8, that is to say the entry to the mixing chamber 27, are closed, and the product P, or the individual components K1, K2, respectively, are directed to the calibration exit 18, 19. The product pressure of the product P or of the components K1, K2 herein is determined ahead of the calibration exit 18, 19 with the aid of the respective pressure sensor 9, 10, and a deviation of the determined product pressure from the predetermined nominal pressure is determined, said nominal pressure potentially corresponding to the above-mentioned nominal pressure.

(40) The pressure-regulating valve 20, 21 that is provided on the respective calibration exit 18, 19 herein is opened or closed in a pressure-dependent manner so as to align the product pressure with the nominal pressure, wherein the product pressure is reduced when opening the respective pressure-regulating valve 20, 21, and is increased when closing the respective pressure-regulating valve 20, 21. The calibration step S5 can be carried out separately for the dissimilar components K1, K2 of the product P. In the case of the product P having only one component K1, K2 the calibration step S5 is carried out directly for the product P. The calibration of the pump is a particular objective herein.

(41) While the present invention has bees described by means of exemplary embodiments, said invention can be modified in many ways.

LIST OF REFERENCE SIGNS

(42) 1 Metering device 2 Metering pump 3 Metering pump 4 Throughflow block 5 Mixing head block 6 Throughflow shut-off block 7 Duct 8 Duct 9 Pressure sensor 10 Pressure sensor 11 Shut-off valve 12 Drive element 13 Valve member 14 Shut-off valve 15 Drive element 16 Valve member 17 Calibration block 18 Calibration exit 19 Calibration exit 20 Pressure-regulating valve 21 Pressure-regulating valve 22 Drive element. 23 Valve member 24 Bore 25 Bore 26 Mixing block 27 Mixing chamber 28 Exit nozzle 29 Nozzle tube 30 Product diversion block 31 Duct 32 Duct 33 Drive element 34 Pressure-regulating valve 35 Valve member 36 Pressure sensor 37 Control installation K1 Component K2 Component L1 Longitudinal direction P Product. S1 Step S2 Step S3 Step S4 Step

(43) S5 Step