EP1167767A1 - Flow control for a peristaltic pump - Google Patents

Abstract

A pressure sensor (21') measuring the static pressure in the fluid pumped, produces a signal (x21) representing movements of the pump displacer. An electronic unit (22) evaluates the sensor signal. An independent claim is included for the method of monitoring the unit, in which an operational status signal is derived from the fluctuating pressure signal.

Description

The invention relates to a device for generating and Conducting a fluid flow with a positive displacement pump and with a measuring arrangement and a method for monitoring this device.

As is well known, positive displacement pumps are pumps that operate a discontinuous, especially pulsating, fluid flow in the lumen of at least sections, esp. elastic, deformable flow vessel, e.g. one Hose. For example, DE-A 196 47 882, US-A 49 09 710, US-A 51 65 873, US-A 51 73 038, US-A 52 63 830, US-A 53 40 290, US-A 56 83 233, US-A 57 01 646, US-A 58 71 341, US-A 58 88 052, WO-A 97/41 353 and WO-A 98/31 935 one device each for generating and guiding one discontinuous fluid flow shown which Device a positive displacement pump with at least one Guiding the fluid flow serving flow vessel from deformable lumen and with a pump drive for shaping of the lumen of the flow vessel.

The pump drive works when the displacement pump is operating in sections leading to the fluid Flow vessel that it is temporarily in the lumen, esp. oscillating, deforming and thus directed the fluid transporting displacer movements is offset. at those in US-A 49 09 710, US-A 51 73 038, US-A 53 40 290, US-A 57 01 646, US-A 58 71 341 and WO-A 97/41 353 Positive displacement pumps are each peristaltic Displacer movements by one on the flow vessel adjacent, non-circular cylindrical surface of one Pump drive generated that rotates about an axis of rotation, while in US-A 51 65 873, US-A 52 63 830, US-A 56 83 233, US-A 58 88 052 and WO-A 98/31 935 Displacement movements caused by linear shear movements against the pump drive comprising a thrust ram executes the flow vessel.

The drive motor for the pump drive is usually an electric motor used by means of a drive shaft is mechanically coupled directly to the pump drive. The drive motor and pump drive can also have one Gear or a belt transmission mechanically be coupled to each other. Furthermore, e.g. also an eccentric or a cam disc or a Crank gear as a mechanical coupling between the Serve electric motor and the pump drive, cf. the DE-A 196 47 882, US-A 51 65 873, US-A 52 63 830, US-A 56 83 233 and US-A 58 88 052. Instead of an electric motor can, e.g. described in WO-A 98/31 935 pneumatic or hydraulic piston motor as Drive motor for generating linear slide thrust movements be used.

Displacement pumps of the type described are due to a essentially homogeneous, smooth inner wall of the flow vessel and due to the lack of in the Fluid flow rotating drive elements especially for suitable for such applications where the fluid leading lumen of the flow vessel high chemical and / or biological purity requirements are made. Positive displacement pumps are therefore e.g. often in samplers for chemical-biological analyzes, especially in drinking or in Sewage area, used. For example, in US-A 55 87 926 and US-A 57 01 646 corresponding samplers each shown a positive displacement pump.

One for the operation of such samplers, especially for the Dosing liquid samples, more important physical Parameter is an actually conveyed or metered Liquid volume. To determine it, a current volume flow of the liquid flow as a measure for one funded per unit of time Liquid volume determined and over a delivery time integrated.

In stationary operation of the positive displacement pump Volume flow especially from a speed of Displacer movements dependent. Over a wide Working area of the pump, this relationship is practical linear, i.e. the volume flow is proportional to Speed of displacement movements and thus also proportional to a set oscillation frequency of the lumen. Often, therefore, especially in stationary Operation of the positive displacement pump, for a set one Displacement movement is an average volume flow of the Calculation of the delivered fluid volume as a basis lay.

The displacement movement of the flow vessel and thus the Oscillations of its lumen are usually indirect determined. To do this, a drive movement of the Drive motor, e.g. on its drive shaft, by means of detects electrodynamic or optical tachometer and into a representative of this drive movement Drive signal mapped. In a corresponding Evaluation electronics convert the drive signal into the Volume flow and / or the delivered fluid volume representing measuring signals converted.

The drive movement and therefore also that of the drive signal derived measurement signals are, however, only representative for the volume flow, if on the one hand Flow vessel in a known manner, especially completely, is filled with liquid, and if on the other hand between the pump drive and the drive motor no slip occurs. The latter is e.g. at a Driving belt connection or one on the drive shaft only pressed pump drive possible without further ado.

The way of filling the flow vessel in turn is to a large extent from its current installation position, especially depending on a current suction height. This can a priori, e.g. during commissioning, determined and as a setting in the evaluation electronics be deposited without further notice; at, esp. mobile, samplers, however, is the installation position highly variable, i.e. for each Redetermine the application and save it if necessary. Of the installation position, especially in the case of permanently installed samplers, e.g. by changing that the liquid level at a corresponding liquid withdrawal point operationally more or less large Fluctuations.

It has also been shown that material properties the flow vessel, e.g. its tightness, its Elasticity or a texture of the inner wall, about the total uptime seen permanent changes may be subject to. For example, Deposits on the Inner wall for cross-sectional constrictions or cause blockages in the flow vessel accordingly recognized in time or excluded become. Furthermore, damage to the Flow vessel, e.g. Leaks, an unusability of the device.

For monitoring a positive displacement pump, especially with regard to a current operating state of the pump drive and / or the flow vessel are therefore additional Action required to take one or more of the Detect the aforementioned parameters in operation and the Influence of these parameters on the calculated Compensate volume flow accordingly.

An object of the invention is therefore to Device with a positive displacement pump and with a Specify measurement arrangement that is an actual Displacement movement of the flow vessel robust and reliably detected and a representative of them Provides measurement signal, in particular for generating a representing the current volume flow Flow estimate and / or to generate a status signaling the current operating state suitable is.

Another object of the invention is a method specify the monitoring of such a device provides useful information.

• eine Verdrängerpumpe
  • mit mindestens einem dem Führen eines Fluids dienenden Strömungsgefäß von verformbarem Lumen,
  • mit einem Pumpantrieb zum Erzeugen von das Lumen verformenden und die Fluidströmung bewirkenden Verdrängerbewegungen des Strömungsgefäßes, und
  • mit einem Trägermittel zum Haltern des Strömungsgefäßes sowie
• eine auf die vom Strömungsgefäß ausgeführten Verdrängerbewegungen reagierende Meßanordnung
  • mit einem Drucksensor, der einen statischen ersten Druck im Fluid erfaßt und ein die Verdrängerbewegungen repräsentierendes Sensorsignal liefert und
  • mit einer Auswerte-Elektronik für das Sensorsignal.

To achieve the object, the invention consists in a first variant in a device for generating a fluid flow, which device comprises:

• a positive displacement pump
  • with at least one flow vessel of deformable lumen serving to guide a fluid,
  • with a pump drive for generating displacement movements of the flow vessel which deform the lumen and bring about the fluid flow, and
  • with a carrier for holding the flow vessel and
• a measuring arrangement reacting to the displacement movements carried out by the flow vessel
  • with a pressure sensor which detects a static first pressure in the fluid and delivers a sensor signal representing the displacer movements and
  • with evaluation electronics for the sensor signal.

• eine Verdrängerpumpe
  • mit mindestens einem dem Führen eines Fluids dienenden Strömungsgefäß von verformbarem Lumen,
  • mit einem Pumpantrieb zum Erzeugen von das Lumen verformenden und die Fluidströmung bewirkenden Verdrängerbewegungen des Strömungsgefäßes, und
  • mit einem Trägermittel zum Haltern des Strömungsgefäßes,
• wobei das Strömungsgefäß im Betrieb vom Pumpantrieb temporär und abschnittsweise derart gegen das Trägermittel zusammengedrückt wird, daß dieses elastisch gedehnt wird, sowie
• eine auf die vom Strömungsgefäß ausgeführten Verdrängerbewegungen reagierende Meßanordnung
  • mit einem Dehnnungssensor, der eine Dehnung des Trägermittels erfaßt und ein die vom Strömungsgefäß ausgeführten Verdrängerbewegungen repräsentierendes Sensorsignal liefert und
  • mit einer Auswerte-Elektronik für das Sensorsignal.

According to a second variant, the invention consists in a device for generating a fluid flow, which device comprises:

• a positive displacement pump
  • with at least one flow vessel of deformable lumen serving to guide a fluid,
  • with a pump drive for generating displacement movements of the flow vessel which deform the lumen and bring about the fluid flow, and
  • with a carrier means for holding the flow vessel,
• wherein the flow vessel is temporarily pressed in sections by the pump drive against the carrier means in such a way that it is elastically stretched, and
• a measuring arrangement reacting to the displacement movements carried out by the flow vessel
  • with a strain sensor which detects a strain of the carrier means and delivers a sensor signal representing the displacement movements carried out by the flow vessel and
  • with evaluation electronics for the sensor signal.

• eine Verdrängerpumpe
  • mit mindestens einem dem Führen eines Fluids dienenden Strömungsgefäß von verformbarem Lumen,
  • mit einem Pumpantrieb zum Erzeugen von das Lumen verformenden und die Fluidströmung bewirkenden Verdrängerbewegungen des Strömungsgefäßes,
  • mit einem Antriebsmotor für den Pumpantrieb und
  • mit einem Trägermittel zum Haltern des Strömungsgefäßes sowie
• eine auf die vom Strömungsgefäß ausgeführten Verdrängerbewegungen reagierende Meßanordnung mit einem Drucksensor für einen statischen ersten Druck im Fluid, welches Verfahren folgende Schritte umfaßt:

• Bewirken von Antriebsbewegungen des Antriebsmotor zum Erzeugen der Verdrängerbewegungen des Strömungsgefäßes,
• Erfassen des ersten Drucks mittels des Drucksensors zum Erzeugen eines die Verdrängerbewegungen momentan repräsentierendes Sensorsignals und
• Erzeugen eines einen momentanen Betriebszustand der Vorrichtung signalisierenden Statussignals mittels des Sensorsignals.

The invention further relates to a method for monitoring a device used to generate a fluid flow, comprising:

• a positive displacement pump
  • with at least one flow vessel of deformable lumen serving to guide a fluid,
  • with a pump drive for generating displacement movements of the flow vessel that deform the lumen and cause the fluid flow,
  • with a drive motor for the pump drive and
  • with a carrier for holding the flow vessel and
• a measuring arrangement reacting to the displacement movements carried out by the flow vessel with a pressure sensor for a static first pressure in the fluid, the method comprising the following steps:

• Effecting drive movements of the drive motor to generate the displacement movements of the flow vessel,
• Detecting the first pressure by means of the pressure sensor to generate a sensor signal and which currently represents the displacer movements
• Generating a status signal signaling a current operating state of the device by means of the sensor signal.

Furthermore, the invention consists in the use of a device according to the invention in a sampler.

According to a preferred first embodiment of the first or In the second variant of the invention, the evaluation electronics are generated by means of the sensor signal Flow estimate, which is an instantaneous volume flow represents the fluid flow.

According to a preferred second embodiment of the first or the second variant of the invention produces the Evaluation electronics using the sensor signal a first Measurement signal generated that a frequency of Displacer movements represented.

According to a preferred third embodiment of the first or the second variant of the invention produces the Evaluation electronics using the sensor signal Volume estimate generated which is a totalized Funding volume represented.

According to a preferred fourth embodiment of the first or the second variant of the invention produces the Evaluation electronics by means of the sensor signal Status signal indicating the current operating status of the Displacement pump represented.

According to a preferred fifth embodiment of the first Variant of the invention, the second pressure is a Atmospheric pressure surrounding the flow vessel.

According to a preferred sixth embodiment of the first Variant of the invention generates the evaluation electronics by means of the sensor signal, a second measurement signal, the one Suction height of the device represents.

A basic idea of the invention is that Displacement movement of the flow vessel or the Oscillations of its lumens are not based on them Causes, namely the drive movements of the Drive motors, but based on their effects in the Device determined. The reactions to be recorded Devices on the displacer movements are e.g. a yourself changing pressure in the fluid flow and / or one, esp. elastic, partial deformation of the carrier means Displacement pump.

An advantage of the invention is that the Volume flow regardless of that between the Drive motor and the pump drive existing mechanical Coupling and practically by means of a single sensor signal can be determined.

Another advantage of the invention is that the Measuring arrangement and thus also the method both Devices with electric motor driven Displacement pumps as well as with devices with hydraulic or pneumatically driven positive displacement pumps can be.

Another advantage of the invention is also therein see that already existing devices of described type easily with such Measuring arrangement can be retrofitted.

Fig. 1

zeigt schematisch die Verwendung einer Vorrichtung zum Transportieren eines Fluids in einem Probennehmer,

Fig. 2

zeigt ein Ausführungsbeispiel einer Verdrängerpumpe der Vorrichtung gemäß Fig. 1 in einer Vorderansicht,

Fig. 3

zeigt die Verdrängerpumpe gemäß Fig. 2 teilweise geschnitten in einer um eine Längsachse I-I der Fig. 2 gedrehten Seitenansicht,

Fig. 4

zeigt schematisch eine erste Wirkung der Verdrängerpumpe gemäß Fig. 2 sowie eine auf diese erste Wirkung reagierende Meßanordnung,

Fig. 5

zeigt schematisch anhand eines Ausschnitts der Seitenansicht von der Fig. 3 eine zweite Wirkung der Verdrängerpumpe sowie eine auf diese zweite Wirkung reagierende Meßanordnung,

Fig. 6

zeigt schematisch im Blockschaltbild eine Ausgestaltung einer Auswerte-Elektronik der Meßanordnung von Fig. 4 und/oder 5,

Fig. 7

zeigt schematisch im Blockschaltbild eine andere Ausgestaltung der Auswerte-Elektronik der Meßanordnung von Fig. 1 und

Fig. 8

zeigt zeitliche Verläufe von mittels der Meßanordnung erzeugten Signalen.

The invention and further advantages are explained in more detail on the basis of exemplary embodiments which are illustrated in the figures of the drawing; Identical parts are provided with the same reference symbols in the figures. If it is helpful for clarity, reference symbols which have already been assigned are not shown in the following figures.

Fig. 1

schematically shows the use of a device for transporting a fluid in a sampler,

Fig. 2

1 shows an embodiment of a positive displacement pump of the device according to FIG. 1 in a front view,

Fig. 3

2 shows the positive displacement pump according to FIG. 2, partly in section, in a side view rotated about a longitudinal axis II of FIG. 2,

Fig. 4

2 schematically shows a first effect of the positive displacement pump according to FIG. 2 and a measuring arrangement reacting to this first effect,

Fig. 5

3 shows schematically, on the basis of a section of the side view from FIG. 3, a second effect of the positive displacement pump and a measuring arrangement reacting to this second effect,

Fig. 6

shows schematically in the block diagram an embodiment of an evaluation electronics of the measuring arrangement of FIGS. 4 and / or 5,

Fig. 7

shows schematically in a block diagram another embodiment of the evaluation electronics of the measuring arrangement of Fig. 1 and

Fig. 8

shows temporal courses of signals generated by means of the measuring arrangement.

1 is a device for transporting a Fluids, esp. A liquid, by means of a Displacement pump 1 shown. The device is in particularly advantageous for use in the Removal and, if necessary, storage of liquids PN sampler suitable.

The displacement pump 1 comprises in one embodiment 2, 3 a, esp. As a pump housing trained, carrier means 11, one of these supported, especially as a displacer, Pump drive 12 and a flow vessel 13 from changeable lumen 13A, especially of at least sectionally variable cross-section, for guiding the Fluid. As a flow vessel 13 can all in such Positive displacement pumps, e.g. made of polyethylene or Silicone existing elastic hoses are used become. The flow vessel 13 can be both in one piece as well as being made up of several parts.

During operation of the device, the flow vessel 13 is set in a, in particular peristaltic, displacement movement s ₁₃ of predeterminable frequency, for example in a range from 10 Hz to 20 Hz, by means of the pump drive 12 such that the fluid located in its oscillating lumen 13A, especially pulsating, flows in a predetermined flow direction. In the device according to the exemplary embodiment, the displacement movement is practically a wave movement of a wall of the flow vessel 13 and thus of the lumen 13A enclosed by it, a running speed of the wave movement setting the volume flow, cf. Fig. 4.

To generate the displacement movement s _13, the pump drive 12 acts, as shown schematically in FIG. 4, with a temporally and locally, especially periodically, variable compression force F on the flow vessel 13, specifically in such a way that the flow vessel 13 within a pumping compression range and thus its lumens 13A are displaced in a fluid-displacing manner, in particular elastically. This is achieved in the positive displacement pump 1 of the exemplary embodiment according to FIGS. 2, 3 in that the pump drive 12 with a non-circular cross-section is allowed to roll on the flow vessel 13 and thus the flow vessel 13, which is supported against the carrier means 11, is periodically compressed and allowed to relax becomes. According to FIG. 2, the pump drive 12 bears in sections on the flow vessel 13 which is also held by the carrier means 11.

The pump drive 12 is in the embodiment as a drum or disc-shaped displacer of non-circular Cross section, so as a displacer with a non-circular cylindrical surface. For this purpose, the displacer, here four, points from each other spaced, especially rotatably held, roll-shaped Rolling elements on the operation of the positive displacement pump 1 according to a set direction of rotation of the Pump drive 12 sequentially onto the flow vessel 13 acts. Any other can also be used as the pump drive 12 Displacers commonly used in such pumps with a non-circular cross-section or else rotary pump drives with eccentric bearings Serve rolling element, cf. US-A 51 73 038, US-A 56 83 233, US-A 57 01 646, US-A 58 71 341, US-A 58 71 341 and WO-A 97/41 353. Instead of rotary pump drives, you can linear pump drives are also used, e.g. by means of push rods or helically wound Displacers are realized, cf. US-A 49 09 710, US-A 51 65 873, US-A 58 88 052 and US-A 52 63 830.

The pump drive 12 is, as is customary in positive displacement pumps with a rotary pump drive, mechanically coupled to a drive shaft 15 of an, especially electrical, drive motor 14, for example via a gear or a drive belt connection; but it can also be plugged directly onto the drive shaft 15. In operation, the drive motor 14 executes corresponding drive movements of a predetermined speed - here rotary movements with a motor speed, in particular adjustable, which is proportional to the frequency of the displacer movements s ₁₃ , for example from 200 min ^-1 to 3000 min ^-1 , via the drive shaft 15, if necessary, geared down, transmitted to the pump drive 12. In the event that the pump drive 12 is designed as a linear pump drive 12, it can also be driven by means of a hydraulic or by means of a pneumatic motor, cf. WO-A 98/31 935.

To absorb liquid during the operation of the device, communicates the flow vessel 13 with an inlet side End with an appropriate fluid tapping point. As shown schematically in Fig. 1, that Absorption of liquid take place in that the Flow vessel 13 in the, e.g. in an open channel or pool guided, liquid immersed and this due to the oscillating in the manner described above Lumens 13A is sucked in against gravity; the Liquid can also be from a suitable Liquid tapping point in the direction of gravity and / or can flow in from a pipeline.

Furthermore, the device comprises a measuring arrangement 2, which reacts to the displacer movements s 13 executed by the flow vessel ₁₃ , with evaluation electronics 22, to which a sensor signal x ₂₁ representing the displacer movements s ₁₃ is fed.

To generate the sensor signal x _21, the measuring arrangement 2 comprises, in a first variant of the invention, a pressure sensor 21 ′ which contacts the fluid, in particular capacitive or resistive, which, as shown schematically in FIG. especially static, first pressure p ₁ in lumen 13A reacts. For this purpose, the pressure sensor 21 has at least one pressure measuring chamber which is insulated from the lumen 13A by means of at least one pressure membrane and is pressurized with the pressure p ₁ during operation via this at least one pressure membrane.

The pressure p ₁ to be detected is practically an instantaneous internal pressure set by means of the displacement pump 1 in an inlet-side area of the flow vessel 13, which is in a calibratable dependence on an instantaneous operating state of the device, for example the instantaneous installation position and / or filling of the Flow vessel and / or the instantaneous frequency of the displacer movements s ₁₃ . When the displacement pump 1 is operating, pressure p _{1 is} at least temporarily, in particular even when the flow vessel 13 is not filled with liquid, to a range from 200 hPa to 400 hPa (0.2 bar to 0.4 bar) and thus lower than one from the outside static second pressure p ₂ acting on the flow vessel 13 is set. The pressure p ₂ can be, for example, an atmospheric air pressure of approx. 1000 hPa.

In this variant of the invention, the measuring arrangement 2 serves in particular to detect the pressure p ₁ and to map it into the sensor signal x ₂₁ when the pressure p _{1 is} currently set lower than the pressure p ₂ . For this purpose, the pressure sensor 21 'both as a pressure p _1-sensing absolute pressure sensor with pressure-measuring chamber evacuated and the pressure p ₁ relative to the pressure p _2-sensing pressure sensor can be executed. To hold the pressure sensor 21 ', a section of the flow vessel 13, as shown schematically in FIG. 4, is preferably designed as an adapter.

According to a second variant of the invention, the measuring arrangement 2 comprises a piezo-resistive strain sensor 21 ″, especially fixed directly on the carrier 11, which, as shown schematically in FIG. 5, caused one of the displacer movements s _{13 of} the flow vessel 13 Elongation of the carrier means 11 is detected and converted into the sensor signal x ₂₁ . A strain, speed or acceleration sensor that also detects the strain relatively or absolutely can also serve as the strain sensor 21 ″.

Due to the compression of the flow vessel 13 against the carrier means 11, the compression force F of the pump drive 12 acting on the flow vessel 13 is partially converted into a compression spring force acting on the carrier means 11, whereby the carrier means 11 is also deformed in sections, in particular elastically. This is shown schematically in FIG. 5 by means of the dotted lines. The carrier 11 experiences a measurable elongation, the extent of which is determined in particular by the instantaneous pressure p ₁ in the lumen 13A of the flow vessel 13. Furthermore, the compression spring force and thus also the elongation of the carrier means 11 also depend, for example, on the material, in particular on its elasticity module, and / or a current spatial shape of the flow vessel 13.

This dependence of the deformation of the carrier means 11 can be determined precisely by means of corresponding calibration measurements, in which the flow vessel 13 is filled with corresponding liquids or left empty, for example in a defined manner, and a corresponding instantaneous signal value of the sensor signal x ₂₁ as a reference value for the instantaneous filling in the evaluation Electronics 22 is stored.

The sensor signal x ₂₁ generated according to the first variant of the invention by means of the pressure sensor 21 'can advantageously be used to obtain a flow estimate X _v currently representing the volume flow and / or a volume estimate representing the totalized delivery volume, i.e. the volume flow integrated over a delivery period to investigate.

According to a preferred embodiment of the first variant of the invention, the evaluation electronics 22 comprise, as shown in FIG. 6, a bandpass circuit 220 of adjustable bandwidth which transmits a signal component of the sensor signal x ₂₁ , in particular with the frequency of the displacement movement s ₁₃ and a frequency counter circuit 221 connected downstream on the output side of the bandpass circuit 220. Switched capacitor filters and / or voltage-controlled active filters, for example, can be used as the bandpass circuit 220.

The bandpass circuit 220 and the frequency counter circuit 221 convert the sensor signal x ₂₁ into an, especially digital, first measurement signal x ₂₂₁ , a current signal value X _{ω of} the measurement signal x _{221 representing} the frequency of the displacement movement s _{13 of} the displacement movement s ₁₃ represents.

The bandpass circuit 220 serves in particular to remove constant components of the sensor signal x ₂₁ and to suppress higher-frequency interference voltages. The bandwidth of the bandpass circuit 220 is accordingly set such that any changes in the frequency of the displacement movement s ₁₃ , for example due to load-related fluctuations in the engine speed, do not lead to a blockage of the sensor signal x ₂₁ . In the event that this frequency changes operationally in a wide range, for example ± 5 s ^-1 , the bandwidth of the bandpass circuit 220, in particular configured as a switched capacitor circuit, can also be changed, for example by means of an evaluation Electronics 22 generated, current setting value for the engine speed, are tracked. For this purpose, the setting value can be derived, for example, from a drive signal tapped directly on the drive motor in the manner mentioned above.

For a device of the type described, the volume flow of a transported liquid depends on the specific implementation of the displacement pump 1, namely the design of the pump drive 12 and the flow vessel 13, and on the frequency of the displacement movements s ₁₃ .

In addition to the particular form of the displacement movement s ₁₃ , the instantaneous volume flow is also also determined by a suction height determined by an instantaneous spatial distance between the displacer pump and a liquid level. In the case of a permanently installed device, for example when using the device in a stationary sampler PN, and a practically unchangeable liquid level, this suction height is to be determined accordingly when the device is started up and stored in the evaluation electronics 22 as a fixed value K _h . For the estimated flow value X _v , the following simple proportionality applies, in particular in the case of a steadily flowing liquid, which can easily be verified by appropriate calibration measurements: X v = K 1 · K H · X ω

Therein, K _{1 is} a constant which conveys the dependence of the volume flow on the frequency of the displacer movement s ₁₃ and on the current suction height, in particular to be determined by calibration. If necessary, the flow estimate X _{v can of} course also be approximated by means of a higher order polynomial.

Thus, in the case of stationary operation of the device, the flow estimate X _{v can} advantageously be derived practically directly from the measurement signal x ₂₂₁ . In the displacement pump 1 according to the exemplary embodiment shown in FIG. 2, the volume flow is practically proportional to four times the frequency of the displacement movement s ₁₃ . To determine the volume estimate, the flow estimate X _v must be integrated in a corresponding manner only over the duration of the delivery, for example by multiplying it or by multiplying it by a number of measured zero crossings of the bandpass-filtered sensor signal at the output of the bandpass circuit 220.

In the case of a variable installation position of the flow vessel 13, for example when using the device in a mobile sampler PN, and / or in the event of a fluctuating liquid level, the instantaneous suction height must be updated accordingly for a more precise determination of the flow estimate X _v .

Therefore, according to a further preferred embodiment of the first variant of the invention, a second measurement signal x _{222 is} derived from the sensor signal x ₂₁ , a current signal value X _{h of} the measurement signal x ₂₂₂ currently representing the suction height. In Eq. (1), therefore, only the fixed value K _{h is to be} replaced by the signal value X _{h of} the measurement signal x ₂₂₂ , so that the following now applies to the flow estimate X _v : X v = K 1 · X H · X ω

To generate the measurement signal x ₂₂₂ , the sensor signal x ₂₁ according to FIG. 6 is smoothed by means of a low-pass circuit 222 of the evaluation electronics 22. The low-pass circuit 222 has a cut-off frequency, for example 0.5 Hz to 2 Hz, which is set much lower than the frequency of the displacement movement s ₁₃ . Thus, the sensor signal x ₂₁ practically only allows a signal component with a frequency zero, serving as the measurement signal x ₂₂₂ , that is to say a current mean value of the sensor signal x ₂₁ to pass through the low-pass circuit 222. A currently transmitted mean value of the sensor signal x ₂₁ serves as a measured value X _h representing the current suction height. With increasing suction height, for example with a falling liquid level, the pressure p ₁ detected by the sensor 21 would decrease and the sensor signal x _{21 would have} a correspondingly lower mean value; analogously to this, the sensor signal x ₂₁ has an increasing mean value with decreasing suction height.

According to another embodiment of the first variant of the invention, the evaluation electronics 22 serve to derive from the sensor signal x ₂₁ a third measurement signal x ₂₂₃ representing a degree of filling of the flow vessel 13 with liquid. For this purpose, the sensor signal x ₂₁ according to FIG. 6 is fed via a bandpass circuit 220 to a rectifier circuit 223, which supplies the measurement signal x ₂₂₃ inform of a DC voltage on the output side, a current signal value of the measurement signal x ₂₂₃ serving as an estimate for the current filling level ; if necessary, a corresponding direct current can of course also serve as measurement signal x ₂₂₃ . As a rectifier circuit 223, for example, amplitude-measuring or effective value-measuring change-to-DC signal converters known to the person skilled in the art can be used.

To realize the Eq. (1) and / or (2), the evaluation electronics 22 further comprise a microcomputer 227 to which the measurement signal x ₂₂₁ and / or the measurement signal x ₂₂₃ and possibly the measurement signal x _{222 on the} input side via corresponding analog-to-digital converting signal Ports is fed; if necessary, the frequency counter circuit 221 and / or the rectifier circuit 223 can of course also be represented as a digital circuit, to which an output of the bandpass circuit 220 correspondingly digitized sensor signal is then of course fed.

The sensor signal x ₂₁ generated by means of the pressure sensor 21 'according to the first and / or according to the second variant of the invention can advantageously also be used to generate a status signal Z, in particular a digital one, by means of the evaluation electronics 22 The current operating status of the positive displacement pump 1 is signaled.

According to a preferred embodiment of the first or the second variant of the invention, the evaluation electronics 22 therefore, as shown schematically in FIG. 7, have a first Schmitt trigger 224 which converts the measurement signal x ₂₂₁ from the frequency counter circuit 221 into a binary one first monitoring signal x ₂₂₁ 'converted. For this purpose, the measurement signal x _{221 is} compared with a frequency reference value of the Schmitt trigger 224, which is set such that the monitoring signal x ₂₂₁ 'assumes a high level when the frequency of the displacement movement s _{13 is} greater than or equal to one in steady-state operation Displacement pump 1 is the minimum frequency. The frequency reference value can be determined and set during the commissioning for the positive displacement pump 1, which for this purpose is subjected, for example, to a maximum load to be expected during operation.

According to another preferred embodiment of the first variant of the invention, the mean value of the sensor signal x ₂₁ currently transmitted via low-pass circuit 222 according to FIG. 7 is applied to a second Schmitt trigger 225 of the evaluation electronics 22 on the input side. A binary second monitoring signal x ₂₂₂ 'of the evaluation electronics 22 can be tapped at the output of the Schmitt trigger 225. The monitoring signal x ₂₂₂ 'serves to signal whether the pressure p ₁ falls below a pressure reference value set on the Schmitt trigger 225 or not. Accordingly, the pressure reference value is set so that the monitoring signal x ₂₂₂ 'assumes a high level when the pressure p _{1 is} less than or equal to the pressure value which occurs during the operation of the displacement pump 1 within an intact and in the manner described above the liquid extraction point communicating flow vessel 13 at most; otherwise the monitoring signal x ₂₂₂ 'assumes a low level.

According to another preferred development of the first or second variant of the invention, the evaluation electronics 22, as shown in FIG. 7, comprise a third Schmitt trigger 226, to which the measurement signal x ₂₂₃ is initially applied. A corresponding filling reference value of the Schmitt trigger 226 is set here such that a binary third monitoring signal x ₂₂₃ 'supplied on the output side assumes a high level if the flow vessel 13 is filled with at least a predetermined minimum volume of the liquid to be conveyed; otherwise, especially if there is an increased formation of air bubbles in the fluid, the monitoring signal has a low level. The filling reference value to be set can be determined, for example, by means of a corresponding calibration measurement and set during commissioning.

The monitoring signal x ₂₂₁ ', the monitoring signal x ₂₂₂ ' and / or the monitoring signal x ₂₂₃ 'is, if necessary via an analog-to-digital converter, fed to the microcomputer 227 of the evaluation electronics 22. On the output side of the microcomputer 227, the status signal Z can be output sequentially or in parallel via the output port, for example to a display unit of the device used to visualize the current operating state. The status signal Z can also be applied to control electronics for the positive displacement pump which, for example, switches off the positive displacement pump 1 in the event of an error in the device detected by the measuring arrangement 2 '. If necessary, the monitoring signal x ₂₂₁ ', the monitoring signal x ₂₂₂ ' and / or the monitoring signal x ₂₂₃ 'can also be derived from the measuring signal x ₂₂₁ , from the measuring signal x ₂₂₂ or from the measuring signal x ₂₂₃ by means of trigger functions implemented in the microcomputer 227.

By means of the microcomputer 227, a triggered start function is also preferably implemented, which serves to monitor signal x ₂₂₁ ', monitoring signal x ₂₂₂ ' and / or monitoring signal x ₂₂₃ 'only after the displacement pump 1 has been switched on, specifically after the expiry evaluate a set time corresponding to a start-up period.

A fourth monitoring signal y _{14 of} the device is used to trigger the start function, which signals an in particular electrical drive energy E that is fed into the positive displacement pump 1 during operation. Monitoring signal y ₁₄ can be, for example, a binary switching signal which signals with a high level that the positive displacement pump 1 is switched on and which signals with a low level that the positive displacement pump 1 is switched off. However, a measurement signal can also serve as the monitoring signal y ₁₄ , which represents, for example, a current that is currently fed into the positive displacement pump 1. Furthermore, the setting signal y _{14 can} also be derived from the aforementioned drive signal, for example by means of change-to-to-DC signal converters measuring amplitude or effective value.

The time setting for the start function is set so that the positive displacement pump 1 is safely in steady-state operation after being switched on, in the event that there is no fault. The start-up time until steady-state operation is reached is in turn to be determined by appropriate calibration measurements and converted into the time specification. For this purpose, FIG. 8 shows an example of a profile of the sensor signal x ₂₁ and a corresponding profile of the measurement signal x ₂₂₁ during a transition to stationary operation.

According to a preferred embodiment of the first variant of the invention, a first logic function activated by means of the start function is also implemented in the microcomputer 227, which sets a first signal value for the status signal Z when the monitoring signal x ₂₂₂ 'is high and the monitoring signal x ₂₂₃ 'simultaneously has a low level. In this case, the status signal Z can signal, for example, a blocked flow vessel 13.

According to another preferred embodiment of the first and / or the second variant of the invention, a second logic function activated by the start function is implemented in the microcomputer 227, which sets a second signal value for the status signal Z when the monitoring signal x ₂₂₁ 'is high -Level and the monitoring signal x ₂₂₂ 'at the same time has a low level. In this case, the status signal Z can signal, for example, a flow vessel 13 that is not immersed in the liquid and / or a leaky flow vessel 13 that is completely or partially filled with air. This second signal value for the status signal Z can also be generated, for example, by comparing the measurement signal x ₂₂₁ or the measurement signal x ₂₂₂ using two differently set trigger thresholds with two mutually different signal reference values, the lower of the two trigger values Thresholds of the measurement signal x ₂₂₁ or x _{222 are} exceeded, while the higher of the two trigger thresholds is not reached.

According to a preferred embodiment of the second variant of the invention, in which the sensor signal x ₂₁ signals the deformation of the carrier means 11 in the manner described above, a third logic function activated by means of the start function is implemented in the microcomputer 227, which has a third signal value for the Status signal Z sets when the monitoring signal x ₂₂₁ 'has a low level and the monitoring signal y _{14 has} a high level at the same time. In this case, the status signal Z can signal a faulty pump drive 12, for example.

It has also been shown that, even when the pump drive 12 is at a standstill, the carrier means 11 already has a slight elastic deformation due to a mechanical prestress caused by the supporting flow vessel 13, which can be measured from a basic shape of the carrier means 11 when the pump drive 12 and / or flow vessel is not installed 13, for example during a service or maintenance measure. By determining an appropriate lower limit value for the sensor signal x _21, in the evaluation electronics 22 by means of a simple comparison due to an instantaneous signal value of the sensor signal x ₂₁ are detected, whether the pump drive is installed incorrectly 12th

In addition to the pressure sensor 21 'and / or the strain sensor 21' ' the measuring arrangement can also use other sensors, e.g. to Temperature compensation serving the measurement Temperature sensors, e.g. on the flow vessel 13 or can be attached to the carrier means 11.

Claims (9)

Apparatus for generating a fluid flow, the apparatus comprising: a positive displacement pump (1) with at least one flow vessel (13) of deformable lumen (13A) serving to guide a fluid, with a pump drive (12) for generating displacement movements (s ₁₃ ) of the flow vessel ( ₁₃ ) which deform the lumen (13A) and bring about the fluid flow, and with a carrier means (11) for holding the flow vessel (13) and a measuring arrangement (2) reacting to the displacement movements (s ₁₃ ) carried out by the flow vessel ( ₁₃ ) with a pressure sensor (21 ') which detects a static first pressure (p ₁ ) in the fluid and delivers a sensor signal (x ₂₁ ) representing the displacer movements s ₁₃ and with evaluation electronics (22) for the sensor signal (x ₂₁ ). Apparatus according to claim 1, wherein the second pressure (p ₂ ) is an atmospheric pressure surrounding the flow vessel (13). Apparatus for generating a fluid flow, the apparatus comprising: a positive displacement pump (1) with at least one flow vessel (13) of deformable lumen (13A) serving to guide a fluid, with a pump drive (12) for generating displacement movements (s ₁₃ ) of the flow vessel ( ₁₃ ) which deform the lumen (13A) and bring about the fluid flow, and with a carrier means (11) for holding the flow vessel (13), wherein the flow vessel (13) is temporarily pressed in sections by the pump drive (12) against the carrier means (11) in such a way that it is elastically stretched, and a measuring arrangement (2) reacting to the displacement movements (s ₁₃ ) carried out by the flow vessel ( ₁₃ ) with a strain sensor (21 ''), which detects a strain of the carrier means (11) and delivers a sensor signal (x ₂₁ ) representing the displacement movements (s ₁₃ ) carried out by the flow vessel ( ₁₃ ) and with evaluation electronics (22) for the sensor signal (x ₂₁ ). Device according to Claim 1 or 3, in which the evaluation electronics (22) generate a first measurement signal (x ₂₂₁ ) by means of the sensor signal (x ₂₁ ), which represents a frequency of the displacer movements (s ₁₃ ). Device according to Claim 3, in which the evaluation electronics (22) generate a second measurement signal (x ₂₂₂ ) by means of the sensor signal (x ₂₁ ), which represents a suction height of the device. Apparatus according to claim 1 or 3, in which the evaluation electronics (22) uses the sensor signal (x ₂₁ ) to generate an estimated flow value (X _v ) which represents an instantaneous volume flow of the fluid flow. Device according to Claim 1 or 3, in which the evaluation electronics (22) generate a status signal (Z) by means of the sensor signal (x ₂₁ ), which represents a current operating state of the displacement pump (1). Use of the device according to one of claims 1 up to 4 in one sampler (PN). A method of monitoring a fluid flow generating device, comprising: a positive displacement pump (1) with at least one flow vessel (13) of deformable lumen (13A) serving to guide a fluid, with a pump drive (12) for generating displacement movements (s ₁₃ ) of the flow vessel ( ₁₃ ) which deform the lumen (13A) and cause the fluid flow, with a drive motor (14) for the pump drive and with a carrier means (11) for holding the flow vessel (13) and a measuring arrangement (2) reacting to the displacement movements (s 13) carried out by the flow vessel ( ₁₃ ) with a pressure sensor (21 ') for a static first pressure (p ₁ ) in the fluid, which procedure comprises the following steps: Effecting drive movements of the drive motor 14 to generate the displacement movements (s ₁₃ ) of the flow vessel (13), Detecting the first pressure (p ₁ ) by means of the pressure sensor (21 ') to generate a sensor signal (x ₂₁ ) and which currently represents the displacer movements (s ₁₃ ) Generating a status signal (Z) signaling a current operating state of the device by means of the sensor signal (x ₂₁ ).

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