Metering pump with temporarily reversed direction of displacement element

Abstract

The invention relates to a method for moving a fluid, comprising the following steps: a. providing a metering head comprising a metering chamber and a displacement element delimiting the metering chamber, b. moving the displacement element from a first position in a suction direction to a second position, wherein the volume of the metering chamber in the second position is greater than the volume of the metering chamber in the first position, such that during a suction stroke fluid is drawn into the metering chamber via a fluid inlet, c. moving the displacement element from the second position in a compression direction to the first position, such that during a compression stroke fluid is pressed out of the metering chamber via a fluid outlet. In order to provide a method for moving a fluid or a corresponding metering pump with which some of the above-mentioned disadvantages can be prevented without the need for additional components, according to the invention it is proposed that, during the suction stroke, the movement of the displacement element in the suction direction comprises at least two changes in direction before the displacement element reaches the second position, and / or that, during the compression stroke, the movement of the displacement element in the compression direction comprises at least two changes in direction before the displacement element reaches the first position.

Description

Technical Field

[0001] This invention relates to a method for moving a fluid, comprising the following steps:

[0002] a. Provide a metering head, including a metering chamber and a displacement element defining the metering chamber.

[0003] b. The displacement element is moved from the first position to the second position along the suction direction, wherein the volume of the metering chamber of the displacement element in the second position is greater than the volume of the metering chamber of the displacement element in the first position, such that fluid is drawn into the metering chamber through the fluid inlet during the suction stroke.

[0004] c. Move the displacement element from the second position to the first position in the compression direction, so that fluid is forced out of the metering chamber via the fluid outlet during the compression stroke.

[0005] The present invention also relates to a metering pump for moving fluid, comprising a metering head, a metering chamber disposed in the metering head, and a displacement element reciprocating between a first position and a second position, wherein the displacement element defines the metering chamber, the volume of the metering chamber in the second position of the displacement element being greater than the volume of the metering chamber in the first position of the displacement element, wherein the displacement element is coupled to a drive member via a movable element such that, in operation of the drive member, the movable element performs a forward stroke and a return stroke in a direction having a stroke length h in a housing between the first end position and the second end position, and the displacement element reciprocates between the first position and the second position, wherein the drive member further includes a control device. Background Technology

[0006] Metering pumps and methods for moving fluids have applications in many fields. Examples include treating drinking water with disinfectants, metering corrosion inhibitors and bactericides in cooling circuits, metering flocculants in wastewater treatment, metering additives in the paper industry, and metering additives in plastics production.

[0007] To meter fluid, a metering head typically includes a metering chamber into which fluid, for example, is drawn from a reservoir through a fluid inlet and expelled through a fluid outlet. For this purpose, the metering pump also includes a displacement element that can reciprocate between a first position and a second position and defines the metering chamber. Therefore, due to the movement of the displacement element between the first and second positions, the volume of the metering chamber changes, which affects the pressure conditions within the metering chamber and delivers the fluid.

[0008] Therefore, the volume of the metering chamber in the first position is smaller than the volume of the displacement element in the second position. Thus, when the displacement element moves into the second position during the so-called suction stroke, the increase in the metering chamber volume creates a negative pressure within the chamber, and fluid is drawn into the metering chamber through the fluid inlet. On the other hand, when the displacement element moves into the first position during the so-called compression stroke, the volume of the metering chamber decreases, creating overpressure, and fluid is forced out through the fluid outlet.

[0009] Existing technologies also include so-called pulsers for moving fluids; however, unlike metering pumps, they do not have a fluid inlet separate from the fluid outlet, or they have a separate but closed fluid inlet. Here, the volume of the metering chamber also periodically increases and decreases alternately, and therefore, the pressure exerted on the fluid also changes periodically. However, unlike metering pumps, there is no fluid delivery from the fluid inlet to the fluid outlet; instead, a periodically changing pressure is generated in the working line connected to the fluid outlet. In this embodiment, the fluid outlet also serves as the fluid inlet.

[0010] Various driving schemes for moving displacement elements are known in the prior art. For example, the movable element of a motor can be directly connected to the displacement element, and the displacement element is moved by the movement of the movable element. Alternatively, hydraulic drives are also known, in which a movable stroke element changes the pressure of the hydraulic fluid acting on the displacement element. For this purpose, the displacement element further defines a hydraulic chamber filled with hydraulic fluid, such that the displacement element moves due to the change in pressure within the hydraulic chamber.

[0011] The type of drive used typically depends on the intended application. For example, very small metering volumes have different requirements than large metering volumes, which need to be performed very quickly. For many applications, the metering profile of the metering pump, i.e., the amount of fluid delivered by the metering pump over time, must be specifically adjusted.

[0012] Depending on the fluid being measured, various problems can arise. For example, air bubbles may form in the metering chamber, damaging the metering pump's delivery profile. If the gas content in the metering chamber increases too much, most metering pumps will simply be unable to deliver any fluid at all.

[0013] Furthermore, the displacement element may become stuck in the metering head, resulting in altered movement or no movement at all, which also impairs the function of the metering pump. Other components in the metering pump that come into contact with the fluid being delivered, such as the fluid inlet or outlet, may also become blocked.

[0014] Various solutions to these problems are known, but they all require additional components such as metering pumps. More importantly, these solutions often only address one of many problems. Summary of the Invention

[0015] Therefore, the basic objective of this invention is to provide a method for moving fluid or a corresponding metering pump that can prevent some of the aforementioned disadvantages without requiring additional components.

[0016] According to the invention, this objective is achieved by a method of the type described above, wherein during the suction stroke, the movement of the displacement element in the suction direction includes at least two directional changes before the displacement element reaches the second position, and / or during the compression stroke, the movement of the displacement element in the compression direction includes at least two directional changes before the displacement element reaches the first position.

[0017] In other words, during the suction stroke, as the element moves from the first position to the second position, or during the compression stroke, as the element moves from the second position to the first position, the displacement element changes its direction of movement at least once, then changes direction again and moves back along the original direction. Therefore, the displacement element does not move along a direct path to the target position, but rather moves a short distance in the opposite direction before finally reaching the target position, which is the second position in the suction stroke case and the first position in the compression stroke case. However, at least a twofold change in direction can also occur during the suction and compression strokes.

[0018] The movement of the displacement element is particularly linear. Furthermore, the change in direction of the displacement element is a 180° change, meaning the displacement element moves only along a single line, and the direction of movement is periodically reversed. Therefore, the suction direction should be understood as the direction connecting the first and second positions on a straight line, while the compression direction should be understood as the direction connecting the second and first positions on the same straight line.

[0019] By changing the direction of movement of the displacement element, it is possible, for example, to vent the metering chamber. The method of controlling the metering pump according to the invention reduces the formation of bubbles because the bubbles undergo pressure pulses in reverse direction, which prevents the bubbles from adhering to the metering chamber wall.

[0020] Furthermore, the method according to the invention also helps to clean the area in contact with the fluid to be conveyed. Contaminants, such as those in the fluid inlet or outlet, can be removed and flushed out of the metering head by briefly reciprocating the displacement element.

[0021] Therefore, in one embodiment, the movement of the displacement element specifically generates movement of the valve shut-off body disposed in the fluid inlet or outlet. This targeted movement can be a single closing motion or an oscillation lasting for a specific period of time. The movement of the valve shut-off body allows contaminants, such as crystals, salts, or clumps, to be mechanically removed from the valve seat. The targeted movement of the valve shut-off body can be so strong that cavitation occurs due to pressure waves in the fluid, i.e., bubbles are formed in the fluid inlet or outlet, which makes it possible to specifically affect the surfaces in the valve seat and achieve cleaning.

[0022] Additionally or alternatively, the velocity of the fluid through the valve seat can also be increased by briefly accelerating the displacement element to remove contaminants with the fluid flow or pressure waves in the fluid.

[0023] In particular, in one embodiment, the method according to the invention is used for a cleaning cycle following a routine metering operation, namely a continuous suction and / or compression stroke without changing direction. For this purpose, the valve shut-off body oscillates specifically as described above.

[0024] According to the present invention, the movement of the displacement element can also be used to specifically affect the flow of fluid or to specifically control valves.

[0025] Especially in the case of hydraulically driven metering pumps, the method according to the invention offers the advantage that different quantities of fluid can be delivered without the need for technical modifications to the pump. Hydraulically driven metering pumps typically include so-called relief valves and suction valves through which hydraulic fluid is directed into or out of the hydraulic chamber, which is separated from the metering chamber by a displacement element.

[0026] Hydraulically driven metering pumps typically operate in such a way that the amount of hydraulic fluid in the hydraulic chamber remains constant by means of suction control. However, by specifically influencing the relief valve and the suction valve, the method according to the invention can be used to adapt the amount of hydraulic fluid to a desired metering quantity.

[0027] The strong deceleration during the compression stroke allows the suction valve to open, causing hydraulic fluid to be introduced into the hydraulic chamber, while the diaphragm moves further in the direction of the first position, i.e., into the metering chamber. This reduces the dead zone of the metering head, allowing for easier and more accurate metering with a smaller amount of fluid. This also makes it possible to achieve higher pressures during the compression stroke.

[0028] On the other hand, during the compression stroke, a short pressure wave can specifically open the relief valve, allowing hydraulic fluid to overflow from the hydraulic chamber. This causes the displacement element, typically the diaphragm, to assume a neutral position closer to the second position. There is a risk that the diaphragm might impinge on the hydraulic chamber, but this impingement reduces the pressure within the chamber, causing the suction valve to open and allowing hydraulic fluid to flow back into the chamber. Therefore, the described process enables both targeted exchange of hydraulic fluid and venting of the hydraulic chamber.

[0029] Furthermore, the method according to the invention offers the advantage that it can also be used to solve various measurement tasks.

[0030] For example, the sound test of the valve and the method according to the invention can be used to respond to changes in fluid characteristics, such as viscosity. To this end, the sound signal generated when the valve closing body strikes the valve seat is recorded at regular intervals and compared with a target sound signal. The method according to the invention can also be used to excite the valve closing body so that, as long as the fluid characteristics remain constant, the valve closing body always produces the exact same sound signal when it strikes the valve seat. Conversely, if different sound signals are produced when the excitation remains constant, it indicates a malfunction in the metering pump, and an error message can be output to the user. However, it is particularly preferred that the method according to the invention also be used to manage the movement of the displacement element so that the measured sound signal matches the target sound signal. Therefore, the method according to the invention provides the ability to automatically respond to changes in fluid characteristics and maintain a constant delivery curve for the metering pump.

[0031] It goes without saying that measurements of fluid characteristics, particularly elasticity, as well as calibration, i.e., compression checks and corresponding stroke adjustments, can therefore be performed. Since fluid compressibility is a factor under very high pressures, and this compressibility depends on the fluid being transported, conventional metering pumps and high-pressure transport methods have the drawback that the metered volume does not correspond to the displacement volume. In this case, we also refer to the effective stroke length of the metering pump, i.e., the stroke of the displacement element over which the fluid is actually transported out of the metering chamber. The effective stroke length is particularly dependent on fluid characteristics, operating pressure, and fluid temperature. These parameters change during transport operations, and therefore the effective stroke length and transport volume also change. The method according to the invention provides the ability to respond to such changes by first determining the fluid characteristics and then adjusting the motion curve of the displacement element.

[0032] In one embodiment, fluid characteristics are measured by measuring the pressure accumulation based on the position of the displacement element. To do this, the force increase can be measured, for example, directly at the drive element, or using a signal from a pressure sensor at the metering head. The pressure accumulation is preferably measured based on the position of the displacement element, such that the resulting pressure remains below the pressure ultimately required to deliver the fluid. This ensures no fluid loss during calibration.

[0033] After obtaining the material properties, adjusting the motion curve of the displacement element can provide the benefit of permanent and accurate measurement of the fluid.

[0034] In the case of a pulsator, the method according to the invention can also be used to measure pulsation and optimize the metrology curve accordingly.

[0035] In one embodiment, the displacement element moves by means of a drive, which is a linear motor. In particular, linear motors can be controlled as needed, making it possible to achieve various motion curves of the displacement element. Because linear motors can be controlled in very small steps, they are also particularly suitable for measuring very small quantities.

[0036] In another embodiment, there are at least four, preferably at least six, changes of direction. The number of changes of direction depends particularly on the intended application. If the purpose is to remove a displacement element (e.g., a diaphragm) stuck in the metering head, for example, if the displacement element is stuck by cooled fluid residue, small oscillating movements applied to the displacement element by the drive have proven particularly effective. These small oscillating movements can gently and non-destructively remove the displacement element from its stuck position, allowing the pump to be resumed operation without damage even after a long period of downtime.

[0037] In another embodiment, the moving speed of the displacement element is at least 1 m / s. This speed ensures that the displacement element produces the desired effect on the fluid to be transported, and that the fluid to be transported follows the movement of the displacement element as closely as possible.

[0038] In another embodiment, the displacement element is periodically accelerated, preferably at the beginning or end of the suction or compression stroke, or before or after the change in the direction of motion, with an acceleration of at least 100 m / s². 2 At most 400m / s 2 For example, at the beginning or end of a suction or compression stroke, the corresponding acceleration causes the metering chamber to be completely emptied. The acceleration of the displacement element can also counteract the formation of bubbles.

[0039] In another embodiment of the method according to the invention, when the displacement element moves from the first position to the second position without a change in direction, the displacement element travels a distance x between the first position and the second position, or vice versa. When the movement of the displacement element along the suction direction or the compression direction includes two changes in direction, the displacement element travels a distance S = (1 + 2a)x, where a is at least 0.1, at most 0.9, and preferably 0.5.

[0040] Therefore, the direction of motion opposite to the actual direction of motion of the displacement element does not occur over the entire distance x between the first and second positions, but only a portion of this distance. The distance δx generated by the difference between distance (1+2a)x and distance x can be adapted to the corresponding application. As mentioned above, oscillating motion with a lower amplitude δx is advantageous for, for example, removing a diaphragm, while a longer motion of the displacement element in the opposite direction is advantageous for other applications.

[0041] The basic objective of the present invention can also be achieved by a metering pump of the type mentioned at the beginning, wherein the control device is configured to perform the method according to any of the above embodiments.

[0042] Here, the driving component is preferably a linear motor. Such a linear motor typically includes a fixed element and a movable element, wherein the movable element of the linear motor is connected to the displacement element, so that the movement of the movable element directly causes the movement of the displacement element.

[0043] In one embodiment, the movable element and the displacement element are formed as a single unit.

[0044] In another embodiment, the stroke length h of the movable element is at least 40 mm, preferably at least 50 mm. The relatively large stroke length allows the displacement element to undergo multiple directional changes, thus supporting the advantages of the method described above according to the invention.

[0045] In one embodiment, the displacement element is a diaphragm. If the displacement element is a diaphragm separating the metering chamber from the hydraulic chamber, and if the diaphragm becomes stuck in one part of the metering head, the method according to the invention allows the diaphragm to be removed. Based on the motion curve of the displacement element, a diaphragm rupture test can be performed based on the oscillating resonance or acoustic characteristics of the diaphragm.

[0046] In particular, the diaphragm, which consists of a thin fabric and a plastic layer, must be removed very carefully to prevent damage to the diaphragm.

[0047] In another embodiment, the control device is further configured such that the acceleration of the movable element at the start of the forward and / or return stroke is greater than the acceleration of the movable element at the end of the forward and / or return stroke, or vice versa. As has been described with respect to the method according to the invention, the advantage of doing so is that bubble formation can be prevented during the compression stroke and / or suction, and incomplete evacuation of the metering chamber can be avoided.

[0048] In another embodiment, the displacement element divides the metering head into a metering chamber and a hydraulic chamber, wherein the hydraulic chamber is filled with or may be filled with hydraulic fluid. A stroke element is disposed within the hydraulic chamber and connected to a movable element, such that movement of the movable element during operation of the drive causes a force applied to the hydraulic fluid by the stroke element to be transferred to the displacement element. Therefore, in this case, neither the movable element nor the stroke element is directly mechanically connected to the displacement element; instead, the force is transmitted based on the compression of the hydraulic fluid. Attached Figure Description

[0049] Further advantages, features and possible applications of the present invention will become apparent from the following description of the embodiments and related drawings.

[0050] Figure 1 A schematic diagram of a metering pump known in the art is shown.

[0051] Figure 2 The diagram schematically illustrates the change in the position of the displacement element over time during the compression stroke according to the method of the present invention. Detailed Implementation

[0052] Figure 1 The metering pump 1 shown includes a metering head 2, in which a metering chamber 3 and a displacement element 4 are disposed. The displacement element 4 can reciprocate between a first position 12 and a second position 13 (see...). Figure 2 The displacement element 4 moves back and forth between the first position 12 and the second position 13 by means of the movable element 5 of the drive element 6, and the volume of the metering chamber 3 changes, and the pressure conditions in the metering chamber 3 also change accordingly.

[0053] When the displacement element 4 moves from the first position 12 to the second position 13 along the suction direction 10 during the suction stroke, the volume of the metering chamber 3 increases, a negative pressure is generated in the metering chamber 3, and fluid is drawn into the metering chamber 3 through the fluid inlet 8.

[0054] When the displacement element moves from the second position 13 to the first position 12 along the compression direction 11 during the compression stroke, the volume of the metering chamber 3 decreases, generating overpressure, and the fluid is forced out of the metering chamber 3 through the fluid outlet 9.

[0055] Figure 1The metering pump shown also includes a control device 7, which controls the drive element 6. According to the invention, the drive element 6 is controlled by the control device 7 such that during the compression stroke, i.e., during the movement from the second position 13 along the compression direction 11 to the first position 12, the displacement element 4 undergoes two directional changes 16, 17.

[0056] Figure 2 The diagram illustrates the change in position 14 of displacement element 4 over time during the compression stroke. In segment A, displacement element 4 moves from second position 13 along compression direction 11 to first position 12. However, before displacement element 4 reaches first position 12, a first direction change 16 occurs, so the displacement element now periodically moves in the opposite direction, i.e., along suction direction 10 (segment B). A second direction change 17 occurs at the end of segment B, so displacement element 4 again moves along compression direction 11 until displacement element 4 reaches first position 12 (segment C).

[0057] List of reference numerals

[0058] 1 metering pump

[0059] 2 Metering Heads

[0060] 3 Measurement Room

[0061] 4-displacement components

[0062] 5 movable components

[0063] 6 drive components

[0064] 7 Control devices

[0065] 8 fluid inlets

[0066] 9 fluid outlets

[0067] 10 suction directions

[0068] 11 Compression direction

[0069] 12 First Position

[0070] 13 Second position

[0071] Position of 14 displacement elements

[0072] 16 First change of direction

[0073] 17. The direction changed for the second time.

Claims

1. A method for moving fluid using a metering pump, comprising the following steps: a. A metering head (2) is provided, the metering head (2) having a metering chamber (3), a fluid inlet (8), a fluid outlet (9) separate from the fluid inlet (8), and a displacement element (4) that defines the metering chamber (3). b. The displacement element (4) is moved from the first position (12) along the suction direction (10) to the second position (13), wherein the volume of the metering chamber (3) of the displacement element (4) in the second position (13) is greater than the volume of the metering chamber (3) of the displacement element (4) in the first position (12), such that fluid is drawn into the metering chamber (3) via the fluid inlet (8) during the suction stroke. c. Move the displacement element (4) from the second position (13) along the compression direction (11) to the first position (12) such that fluid is forced out of the metering chamber (3) via the fluid outlet (9) during the compression stroke. The invention is characterized in that, during the suction stroke, the movement of the displacement element (4) along the suction direction (10) includes at least two directional changes (16, 17) before the displacement element (4) reaches the second position (13), wherein after at least one intermediate movement opposite to the suction direction (10), the displacement element (4) moves again along the suction direction (10) until it reaches the second position (13), and / or during the compression stroke, the movement of the displacement element (4) along the compression direction (11) includes at least two directional changes (16, 17) before the displacement element (4) reaches the first position (12), wherein after at least one intermediate movement opposite to the compression direction (11), the displacement element (4) moves again along the compression direction (11) until it reaches the first position (12).

2. The method according to claim 1, characterized in that, The displacement element (4) moves by means of a drive (6), wherein the drive (6) is a linear motor.

3. The method according to claim 1, characterized in that, There were at least four changes of direction.

4. The method according to claim 1, characterized in that, There were at least six changes of direction.

5. The method according to claim 3, characterized in that, The displacement element (4) moves at a speed of at least 1 m / s.

6. The method according to claim 1, characterized in that, The displacement element (4) accelerates periodically, with an acceleration of at least 100 m / s². 2 At most 400m / s 2 .

7. The method according to claim 6, characterized in that, The displacement element (4) accelerates periodically at the beginning or end of the suction or compression stroke or before or after the change in the direction of motion.

8. The method according to claim 1, characterized in that, When the displacement element (4) moves from the first position (12) to the second position (13) without changing direction, the displacement element (4) travels a distance x between the first position (12) and the second position (13), or vice versa. When the movement of the displacement element (4) along the suction direction (10) or the compression direction (11) includes two changes of direction (16, 17), the displacement element (4) travels a distance (1+2a)x, where a is at least 0.1 and at most 0.

9.

9. The method according to claim 8, characterized in that, a is 0.

5.

10. A metering pump (1) for moving fluid, comprising: A metering head (2), a metering chamber (3) disposed in the metering head, and a displacement element (4) reciprocating between a first position (12) and a second position (13), wherein the displacement element (4) defines the metering chamber (3), and the volume of the metering chamber (3) in the second position (13) of the displacement element (4) is greater than the volume of the metering chamber (3) in the first position (12) of the displacement element (4), wherein the displacement element (4) is coupled to a drive member (6) via a movable element (5) such that, in operation of the drive member (6), the movable element (5) performs a forward stroke and a return stroke in the housing along a direction having a stroke length h between a first end position and a second end position, and the displacement element (4) reciprocates between the first position (12) and the second position (13), wherein the drive member (6) further includes a control device (7), characterized in that the control device (7) is configured to perform the method according to any one of claims 1 to 9.

11. The metering pump (1) according to claim 10, characterized in that, The stroke length h of the movable element (5) is at least 40 mm.

12. The metering pump (1) according to claim 10, characterized in that, The stroke length of the movable element (5) is at least 50 mm.

13. The metering pump (1) according to any one of claims 10 or 11, characterized in that, The movable element (5) and the displacement element (4) are integrally formed.

14. The metering pump (1) according to claim 10, characterized in that, The displacement element (4) is a diaphragm.

15. The metering pump (1) according to claim 10, characterized in that, The control device (7) is further configured such that the acceleration of the movable element (5) at the beginning of the forward and / or return stroke is greater than the acceleration of the movable element (5) at the end of the forward and / or return stroke, and vice versa.

16. The metering pump (1) according to claim 10, characterized in that, The displacement element (4) divides the metering head (2) into the metering chamber (3) and the hydraulic chamber, wherein the hydraulic chamber is filled or can be filled with hydraulic fluid, wherein the stroke element is disposed in the hydraulic chamber and connected to the movable element (5) such that during operation of the drive (6), the movement of the movable element (5) causes the force applied to the hydraulic fluid by the stroke element to be transmitted to the displacement element (4).

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