EP1637738B1 - 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 guiding a fluid flow with a positive displacement pump and with a measuring arrangement and a method for monitoring this device.

Positive displacement pumps are known to be pumps which produce a discontinuous, in particular pulsating, fluid flow in the lumen of an at least section-wise, in particular elastically, deformable flow vessel, eg a hose. So is in the 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 Pat. No. 5,871,341 . US-A 58 88 052 . WO-A 97/41 353 and WO-A 98/31 935 a device for generating and guiding a discontinuous fluid flow is shown in each case, which device comprises a positive displacement pump with at least one deformable lumen flow vessel serving to guide the fluid flow and with a pump drive for deforming the lumen of the flow vessel.

During operation of the positive displacement pump, the pump drive acts in sections on the fluid conducting flow vessel in such a way that it is temporarily, esp. Oscillating, deforming and thus the fluid directed transporting displacer displaced in the lumen. At the in US-A 49 09 710 . US-A 51 73 038 . US-A 53 40 290 . US-A 57 01 646 . US Pat. No. 5,871,341 and WO-A 97/41 353 described Positive displacement pumps are each peristaltic displacer movements generated by a voltage applied to the flow vessel, non-circular cylindrical lateral surface of a pump drive which rotates about an axis of rotation, while in the US-A 51 65 873 . US-A 52 63 830 . US-A 56 83 233 . US-A 58 88 052 as well as in the WO-A 98/31 935 the displacement movements are effected by linear thrusting movements, which performs a push rod comprehensive pump drive against the flow vessel.

As the drive motor for the pump drive, an electric motor is usually used, which is mechanically coupled by means of a drive shaft directly to the pump drive. Drive motor and pump drive can also be mechanically coupled to one another via a gear or a belt drive. Furthermore, for example, an eccentric or a cam disc or a crank gear can serve as a mechanical coupling between the electric motor and the pump drive, cf. this the DE-A 196 47 882 . US-A 51 65 873 . US-A 52 63 830 . US-A 56 83 233 such as US-A 58 88 052 , Instead of an electric motor can, as in the WO-A 98/31 935 described a pneumatic or hydraulic piston motor can be used as a drive motor for generating linear plunger thrust movements.

Positive displacement pumps of the type described are due to a substantially homogeneous smooth inner wall of the flow vessel and due to the lack of rotating in the fluid flow drive elements particularly suitable for those applications in which leading to the fluid lumen of the flow vessel high chemical and / or biological purity requirements are made. Displacement pumps are therefore often used, for example, in samplers for chemical-biological analyzes, especially in the drinking or in the wastewater sector. For example, in the US-A 55 87 926 and US-A 57 01 646 corresponding sampler, each with a positive displacement pump shown.

An important physical parameter for the operation of such samplers, esp. For the metering of liquid samples, is an actually conveyed or metered volume of liquid. To determine this, an instantaneous volume flow of the liquid flow is determined as a measure of a liquid volume delivered per unit time and integrated over a delivery time.

In stationary operation of the positive displacement pump, the volume flow is esp. Depending on a speed of the displacement movements. Over a wide operating range of the pump, this relationship is practically linear, i. the volume flow is proportional to the speed of the displacement movements and thus also proportional to a set oscillation frequency of the lumen. Often, therefore, esp. In stationary operation of the positive displacement pump, for a set displacer movement, a mean volumetric flow of the calculation of the volume of fluid delivered is used as a basis.

The displacement of the flow vessel and thus the oscillations of the lumen are usually determined indirectly. These are a drive movement of the Drive motor, for example, at the drive shaft, detected by means of electrodynamic or optical tachometer and mapped into a drive signal representing this drive movement. In a corresponding evaluation electronics, the drive signal is converted into the volumetric flow and / or the conveyed fluid volume representing measuring signals.

Another way to detect the displacement of the flow vessel is in the US-A 57 01 646 proposed, according to which a measuring signal representing the displacer movement of the flow vessel is produced by means of piezo-electric strain gauges which are attached to the outside of the flow vessel and do not contact the fluid carried therein.

The measurement signals thus generated as well as the aforementioned Drive movement and thus also the measuring signals derived from the drive signal are only representative of the volumetric flow rate if, on the one hand, the flow vessel is filled with liquid in a known manner, in particular completely, and, on the other hand, no slippage occurs between the pump drive and the drive motor. The latter is readily possible, for example, in a drive belt connection or in a pump drive which is merely pressed onto the drive shaft.

The manner of filling the flow vessel in turn is dependent to a large extent on its current installation position, esp. From a current suction height. Although this can be determined a priori, for example during commissioning, and stored as a set value in the evaluation electronics without further notice; In the case of, in particular, mobile-operated samplers, the installation position is, however, variable to a great extent, ie to be newly determined for each application and to be stored, if necessary. Furthermore, the installation position, esp. Even with permanently installed samplers, for example, change that the liquid level at a corresponding liquid withdrawal point operationally subject to more or less large fluctuations.

It has also been found that also material properties of the flow vessel, such as e.g. its tightness, its elasticity or a condition of the inner wall, seen over the entire operating time can be subject to permanent changes. Thus, e.g. Deposits on the inner wall to sections cross-sectional constrictions or blockages of the flow vessel lead and must be recognized accordingly timely or excluded. Furthermore, damage to the flow vessel, such as e.g. Leakages, a uselessness of the device.

For monitoring a positive displacement pump, esp. With regard to a current operating state of the pump drive and / or the flow vessel, therefore, additional measures are required to detect one or more of the aforementioned parameters during operation and compensate for the influence of these parameters on the Errechneten volume flow accordingly.

An object of the invention is therefore to provide a device with a positive displacement pump and with a measuring arrangement which robustly and reliably detects an actual displacement movement of the flow vessel and provides a measuring signal representing this, esp. For generating a current volume flow representing the flow rate estimate and / or is suitable for generating a status signal signaling a current operating state.

Another object of the invention is to provide a method providing information for monitoring such a device.

• 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 device for generating a fluid flow, which device comprises:

• a positive displacement pump
  • with at least one deformable lumen flow vessel serving to guide a fluid,
  • - With a pump drive for generating the lumen-forming and the fluid flow causing displacement movements of the flow vessel, and
  • with a carrier for holding the flow vessel as well
• a measuring arrangement responsive to the displacements of the flow vessel
  • - With a pressure sensor which detects a static first pressure in the fluid and a displacement signals representing the sensor signal provides and
  • - With an 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.

Further, the invention is a method of monitoring a fluid flow generating device comprising:

• a positive displacement pump
  • with at least one deformable lumen flow vessel serving to guide a fluid,
  • with a pump drive for generating displacement of the flow vessel which deforms the lumen and causes the fluid flow,
  • - With a drive motor for the pump drive and
  • - With a support means for holding the flow vessel as well
• a measuring arrangement, responsive to the displacement movements carried out by the flow vessel, having a pressure sensor for a static first pressure in the fluid, the method comprising the steps of:

• Effecting drive movements of the drive motor for generating the displacement movements of the flow vessel,
• Detecting the first pressure by means of the pressure sensor for generating a displacement signal currently representing the sensor signal and
• Generating a status signal indicating 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 invention, the evaluation electronics generates by means of the sensor signal a Durchflußschätzwert representing an instantaneous volume flow of the fluid flow.

According to a preferred second embodiment of the invention, the evaluation electronics generates a first measurement signal by means of the sensor signal, which represents a frequency of the displacement movements.

According to a preferred third embodiment of the invention, the evaluation electronics generates a volume estimated value by means of the sensor signal, which represents a totalized delivery volume.

According to a preferred fourth embodiment of the invention, the evaluation electronics generates by means of the sensor signal Status signal representing a current operating state of the positive displacement pump.

According to a preferred fifth embodiment of the invention, the second pressure is an atmospheric pressure surrounding the flow vessel.

According to a preferred sixth embodiment of the invention, the evaluation electronics generates a second measurement signal by means of the sensor signal, which represents an intake height of the device.

A basic idea of the invention is not to determine the displacement movement of the flow vessel or the oscillations of the lumen thereof on the basis of their causes, namely the drive movements of the drive motor, but on the basis of their effects in the device. The responses of the device to the displacements to be detected are e.g. a changing pressure in the fluid flow.

An advantage of the invention is that the volume flow can be determined independently of the existing between the drive motor and the pump drive mechanical coupling and virtually by means of a single sensor signal.

Another advantage of the invention is that the measuring arrangement and thus also the method both at Devices can be used with electric motor driven positive displacement pump as well as device with hydraulically or pneumatically driven positive displacement pump.

Another advantage of the invention is also to be seen in the fact that even existing devices of the type described can be easily retrofitted with such a measuring arrangement.

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, die jedoch nicht im Rahmen dieser Erfindung beansprucht wird.

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 will be explained in more detail with reference to exemplary embodiments, which are illustrated in the figures of the drawing; like parts are provided in the figures with the same reference numerals. If it is useful for the sake of clarity, the representation of already assigned reference symbols is omitted in the following figures.

Fig. 1

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

Fig. 2

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

Fig. 3

shows the positive displacement pump according to Fig. 2 partially cut in a about a longitudinal axis II of Fig. 2 rotated side view,

Fig. 4

schematically shows a first effect of the positive displacement pump according to Fig. 2 and a measuring arrangement which reacts to this first action,

Fig. 5

schematically shows a partial section of the side view of the Fig. 3 a second effect of the displacement and a responsive to this second effect measuring arrangement, which is not claimed in the context of this invention.

Fig. 6

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

Fig. 7

schematically shows in 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.

In the Fig. 1 a device for transporting a fluid, esp. A liquid, by means of a positive displacement pump 1 is shown. The device is suitable in a particularly advantageous manner for use in the removal and, if necessary, the storage of liquids serving sampler PN.

The displacement pump 1 comprises in one embodiment according to the Fig. 2, 3rd a, in particular as a pump housing formed, carrier means 11, a held by this, esp. Designed as a displacer, pump drive 12 and a flow vessel 13 of variable lumen 13A, esp. Of at least partially variable cross-section, for guiding the fluid. As a flow vessel 13, all conventional in such positive displacement, for example made of polyethylene or silicone, elastic tubes can be used. The flow vessel 13 can be embodied both in one piece and as a multi-part.

During operation of the apparatus, the flow vessel _{13 is} displaced by means of the pump drive 12 in a, esp. Peristaltic, displacement s ₁₃ of predetermined frequency, for example in a range of 10 Hz to 20 Hz, that the fluid located in the oscillating lumen 13A, insb, pulsating, flows in a predetermined flow direction. In the apparatus according to the embodiment, the displacer movement is practically a wave movement of a wall of the flow vessel 13 and thus of the lumen 13A enclosed by the latter, wherein a running speed of the wave movement sets the volume flow, cf. Fig. 4 ,

To generate the displacer movement s _13, the pump drive 12 acts as in FIG Fig. 4 shown schematically, with a temporally and locally, esp. Periodic, variable compression force F on the flow vessel 13, in such a way that within a pump effective compression region, the flow vessel 13 and thus the lumen 13A fluidverdrängend, esp. Elastic deformed. This is in the positive displacement pump 1 of the embodiment according to Fig. 2, 3rd causes the pump drive 12 with non-circular cross-section roll on the flow vessel 13 and thus the Flow vessel 13, resting against the support means 11, is periodically compressed and allowed to relax. According to Fig. 2 For this purpose, the pump drive 12 is partially in contact with the flow vessel 13, which is likewise held by the carrier 11.

The pump drive 12 is formed in the embodiment as a drum or disc-shaped displacer of non-circular cross-section, ie as a displacer with a non-circular cylindrical surface. For this purpose, the displacer, here four, spaced apart, esp. Rotationally supported, roller-shaped rolling elements, which act in accordance with a set direction of rotation of the pump drive 12 sequentially to the flow vessel 13 during operation of the positive displacement pump 1. As a pump drive 12 but also all other commonly used in such pumps displacer with non-circular cross-section or even rotary pump drives can be used with eccentrically mounted rolling element, see. the US-A 51 73 038 . US-A 56 83 233 . US-A 57 01 646 . US Pat. No. 5,871,341 and WO-A 97/41 353 , Instead of rotary pump drives and linear pump drives can be used, which are realized for example by means of push rods or helically wound displacers, see. the 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 usual with positive displacement pumps with rotary pump drive, with a drive shaft 15 of a, esp. Electric, drive motor 14, for example via a transmission or a drive belt connection, mechanically coupled; but he can also directly on the drive shaft 15 attached. In operation, the drive motor 14 carries out corresponding drive movements of a predetermined speed - here rotational movements with a frequency proportional to the displacement movements S ₁₃ , esp. Adjustable, engine speed of eg 200 min ^-1 to 3000 min ^-1 , via the drive shaft 15, possibly reduced by means of gear, be transferred 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 ,

For receiving liquid during operation of the device, the flow vessel 13 communicates with an inlet end with a corresponding liquid withdrawal point. Like in the Fig. 1 shown schematically, the liquid can be absorbed by the fact that the flow vessel 13 is immersed in, for example, in an open channel or basin, liquid and sucked against it due to the oscillating in the manner described above lumen 13A against gravity; but the liquid can also be flowed from a suitable liquid withdrawal point in the direction of gravity and / or from a pipeline.

Furthermore, the device comprises a measuring arrangement 2, which reacts to the displacements 13 carried out by the flow vessel ₁₃ and has an evaluation electronics 22, to which a sensor signal X ₂₁ representing the displacements S ₁₃ is fed.

For generating the sensor signal x _21, the measuring arrangement 2 of the invention comprises a fluid-contacting, in particular capacitive or resistive, pressure sensor 21 ', which, as in the Fig. 4 shown schematically reacts to a momentarily acting in the fluid, in particular static, first pressure p ₁ in the lumen 13A. For this purpose, the pressure sensor 21 at least one by means of at least one pressure diaphragm against the lumen 13A insulated and operating on said at least one pressure diaphragm to the pressure p ₁ is acted upon pressure-measuring chamber.

In the pressure to be detected p ₁ is practically a means of the positive displacement pump 1 in an inlet side region of the flow vessel 13 set instantaneous internal pressure, which is in a calibratable function of a current operating state of the device, eg the current installation position and / or filling of the Flow vessel and and / or the instantaneous frequency of the displacement movements S ₁₃ , sets. During operation of the positive displacement pump 1, pressure p _{1 is} at least temporarily, especially 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 from the outside set to the flow vessel 13 acting static second pressure P ₂ . The pressure p ₂ may be, for example, an atmospheric air pressure of about 1000 hPa.

In the invention, the measuring arrangement 2 insb serves to also 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 . This can be the Pressure sensor 21 'be executed both as a pressure p ₁ absolutely detecting pressure sensor with evacuated pressure measuring chamber and the pressure p ₁ relative to the pressure p ₂ detecting pressure sensor. For holding the pressure sensor 21 'is a portion of the flow vessel 13, as in Fig. 4 shown schematically, preferably designed as an adapter.

According to an example which does not form part of this invention, the measuring arrangement 2 comprises a piezo-resistive strain sensor 21 ", fixed in particular directly on the support means 11, which, as shown in FIG Fig. 5 shown schematically, one of the displacer S _{13 of} the flow vessel 13 caused elongation of the carrier 11 detected and converted into the sensor signal x ₂₁ . As a strain sensor 21 "can also serve a strain relative or absolute detecting path, speed or acceleration sensor.

Due to the compression of the flow vessel 13 against the carrier 11, the force acting on the flow vessel 13 compression force F of the pump drive 12 is partially converted into a force acting on the support means 11 compression spring force, whereby the support means 11 sections, esp. Elastic, is deformed. This is in the Fig. 5 shown schematically by the dotted lines. In this case, the carrier 11 undergoes a measurable strain, the extent of which esp. Is determined by the instantaneous pressure p ₁ in the lumen 13A of the flow vessel 13. Further, the compression spring force and thus also the elongation of the carrier 11, for example, the material, esp. Of its modulus of elasticity, and / or a current spatial form of the flow vessel 13 is dependent.

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

The sensor signal x ₂₁ generated according to the invention by means of the pressure sensor 21 'can advantageously be used to determine a flow rate value x _v currently representing the volume flow rate and / or a volume estimated value representing the totalized delivery volume, ie the volume flow rate integrated over a delivery time.

According to a preferred embodiment of the invention, the evaluation electronics 22 includes, as in Fig. 6 shown, a signal portion of the sensor signal X ₂₁ , esp. With the frequency of the displacement movement s ₁₃ , transmitting band-pass circuit 220 of adjustable bandwidth and an output side of the band-pass circuit 220 downstream frequency counter circuit 221. As a band-pass circuit 220 may, for example Known expert switched capacitors filter and / or voltage-controlled active filter serve.

By means of the band-pass circuit 220 and the frequency counter circuit 221, the sensor signal X ₂₁ in a, esp. digital, first measurement signal x ₂₂₁ converted, wherein a current signal value X _{m of} the measurement signal x _{221 represents} the frequency of the displacement movements s ₁₃ .

The bandpass circuit 220 serves esp. The removal of DC components of the sensor signal x ₂₁ and for the suppression of higher-frequency noise voltages. The bandwidth of the bandpass circuit 220 is accordingly set so that any changes in the frequency of the displacement movement s ₁₃ , for example due to load-induced fluctuations in the engine speed, do not lead to a blocking of the sensor signal x ₂₁ . In the event that this frequency changes operationally over a wide range, for example ± 5 s ^-1 , the bandwidth of the band-pass circuit 220 configured in particular as a switched-capacitor circuit can also be determined, for example by means of one of the evaluation Electronics 22 generated, current set value for the motor speed, tracked. For this purpose, the setting value can be derived, for example, from a drive signal directly tapped on the drive motor in the above-mentioned manner.

For a device of the type described, the volumetric flow of a transported liquid is dependent on the concrete realization of the positive displacement pump 1, namely the design of the pump drive 12 and the flow vessel 13, as well as on the frequency of the displacement movements s ₁₃ .

In addition to the respective expression of the displacer s ₁₃ , the instantaneous volume flow is also from a determined by a current spatial distance between the positive displacement pump and a liquid level set suction height. In a permanently installed device, for example, when using the device in a stationary sampler PN, and a virtually invariable liquid level, this suction height during commissioning of the device is determined accordingly and save as a fixed value K _h in the evaluation electronics 22. For the flow rate estimate X _v , the following simple apportionment applies, especially in the case of stationary flowing liquid, to a good approximation following simple proportionality to be verified by appropriate calibration measurements: $${\mathrm{X}}_{\mathrm{v}}={\mathrm{<figure-callout\; id="1"\; label="K"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">K</figure-callout>}}_1\cdot {\mathrm{K}}_{\mathrm{H}}\cdot {\mathrm{X}}_{\mathrm{m}}$$

Therein, K _{1 is} a constant which determines the dependence of the volume flow on the frequency of the displacement movement s ₁₃ and on the instantaneous suction height, in particular by calibration. Of course, if necessary, the flow estimate X _{v can} also be approximated using a higher order polynomial.

Thus, in the case of steady-state operation of the device, the flow estimate X _{v can} advantageously be derived virtually directly from the measurement signal x ₂₂₁ . In the positive displacement pump 1 according to the in Fig. 2 illustrated embodiment, the volume flow rate is practically proportional to four times the frequency of the displacement movement s _13th In order to determine the volume estimate, the flow estimate X _{v is} correspondingly only available over the delivery time integrate, for example by multiplication with the same or by multiplication with a number of measured zero crossings of the bandpass filtered sensor signal output of the bandpass circuit 220th

In a variable mounting position of the flow vessel 13, for example, when using the device in a mobile sampler PN, and / or fluctuating liquid level, the current suction height for a more accurate determination of the flow rate X _v, however, to update accordingly.

Therefore, according to a further preferred embodiment of the invention, a second measurement signal X _{222 is} derived from the sensor signal X ₂₁ , wherein an instantaneous signal value X _{h of} the measurement signal X ₂₂₂ currently represents the suction height. In Eq. (1), therefore, only the fixed value K _{h is to be} replaced by the signal value Xh of the measuring signal x ₂₂₂ , so that now applies to the flow rate estimated value X _v : $${\mathrm{X}}_{\mathrm{v}}={\mathrm{<figure-callout\; id="1"\; label="K"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">K</figure-callout>}}_1\cdot {\mathrm{X}}_{\mathrm{H}}\cdot {\mathrm{X}}_{\mathrm{m}}$$

For generating the measuring signal X ₂₂₂ , the sensor signal X _{21 is determined} according to FIG Fig. 6 by means of a low-pass circuit 222 of the evaluation electronics 22 smoothed. The low-pass circuit 222 in this case has a cutoff frequency of, for example, 0.5 Hz to 2 Hz, which is set much smaller than the frequency of the displacement movement s ₁₃ . Thus, only a measured signal as X ₂₂₂ serving signal component with a frequency zero, that is a momentary mean value of the sensor signal is allowed to pass x ₂₁ from the low-pass filter circuit 222 from the sensor signal x ₂₁ practical. A currently transmitted The mean value of the sensor signal x ₂₁ serves as a measured value X _h representing the instantaneous suction height. With increasing suction height, for example with falling liquid level, the pressure p ₁ detected by means of the sensor 21 would decrease and the sensor signal x _{z1 would have} a correspondingly lower mean value; Analogously, the sensor signal x ₂₁ has an increasing mean value as the suction height decreases.

According to another embodiment of the invention, the evaluation electronics 22 is used to derive from the sensor signal x ₂₁ a filling level of the flow vessel 13 with liquid representing third measurement signal x ₂₂₃ . For this, the sensor signal x _{21 is} according to Fig. 6 via bandpass circuit 220 of a rectifier circuit 223 supplied on the output side, the measurement signal x ₂₂₃ inform informs of a DC voltage, wherein an instantaneous signal value of the measuring signal x ₂₂₃ serves as an estimate for the current degree of filling; if necessary, it is of course also possible to use a corresponding direct current as measuring signal x ₂₂₃ . As the rectifier circuit 223, for example, the amplitude-measuring or effective-value-measuring change-to-DC converter known to those skilled in the art can be used.

To realize the Gln. (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 supplied; if necessary, of course, the frequency counter circuit 221 and / or the rectifier circuit 223 are shown as a digital circuit, which then, of course, an output of the band-pass circuit 220 is supplied according digitisertes sensor signal.

The sensor signal x ₂₁ generated by means of the pressure sensor 21 'according to the invention can also be advantageously used to generate, by means of the evaluation electronics 22, a digital, status signal Z, which signals a momentary operating state of the positive displacement pump 1.

According to a preferred embodiment of the invention, the evaluation electronics 22 therefore, as in Fig. 7 schematically illustrated, a first Schmitt trigger 224, which converts the measurement signal x ₂₂₁ output of the frequency counter circuit 221 in a binary first monitoring signal x ₂₁₁ '. For this purpose, the measuring signal x _{221 is} compared with a reference frequency value of the Schmitt trigger 224, which is set so 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 stationary operation of the Positive displacement pump 1 is minimally adjusting frequency. The frequency reference value during commissioning for the positive displacement pump 1 is determined and set, which is for example subjected to a maximum load to be expected during operation.

According to another preferred embodiment of the invention, the via low-pass circuit 222 currently transmitted mean value of the sensor signal x ₂₁ according to Fig. 7 a second Schmitt trigger 225 of the evaluation electronics 22 input side applied. Output of the Schmitt trigger 225, a binary second monitoring signal X ₂₂₂ 'of the evaluation electronics 22 can be tapped. The monitoring signal x ₂₂₂ 'is used to signal whether the pressure p ₁ falls below a set at the Schmitt trigger 225 pressure reference value 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 in the operation of the positive displacement pump 1 in an intact and in the manner described above the liquid Entnamstelle communicating flow vessel 13 sets at most; otherwise, the monitor signal x ₂₂₂ 'assumes a low level.

According to another preferred embodiment of the invention, the evaluation electronics 22, as in Fig. 7 shown, a third Schmitt trigger 226, the input of the measurement signal x _{223 is} 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 when the flow vessel 13 is filled with at least a predetermined minimum volume of the liquid to be conveyed; otherwise, esp. In an increased bubble formation 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 ', if necessary via analog-to-digital converter, the microcomputer 227 of the evaluation electronics 22 supplied. On the output side of the microcomputer 227, the status signal Z can be output via the output port sequentially or in parallel, eg to a display unit of the device serving to visualize the current operating state. The status signal Z can also be applied to a control electronics for the positive displacement pump, which shuts off the positive displacement pump 1, for example, in the event of an error of the device detected by means of 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 preferably implemented, which serves the monitoring signal x ₂₂₁ ', the monitoring signal x ₂₂₂ ' and / or the monitoring signal x ₂₂₃ 'only after switching on the positive displacement pump 1, and that after the expiration to evaluate a set, corresponding to a startup time timing.

To trigger the start function is a fourth monitoring signal y _{14 of} the device that signals a fed in operation in the positive displacement pump 1, insb, electric drive energy E. Monitoring signal y ₁₄ may be a binary switching signal, for example, with a high level signals that the positive displacement pump 1 is turned on and signals with a low level that the positive displacement pump 1 is turned off. As a monitoring signal y ₁₄ but can also serve a measuring signal, for example, represents a momentarily fed into the positive displacement pump 1 stream. Furthermore, the adjustment signal y _{14 can} also be derived from the aforementioned drive signal, for example by means of amplitude-measuring or effective value-measuring change-to-direct-conversion converters.

The timing for the start function is set so that the positive displacement pump 1 is safely in steady state operation after being turned on, in the event that there is no malfunction. The start-up time until steady-state operation is reached is again determined by appropriate calibration measurements and converted into the time specification. In the Fig. 8 For this purpose, an example of a course of the sensor signal x ₂₁ and a corresponding course of the measuring signal x ₂₂₁ during a transition to steady-state operation are shown.

According to a preferred embodiment 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 if the monitoring signal X ₂₂₂ 'has a high level and the monitoring signal X ₂₂₃ ' simultaneously has a low level. For this case, the status signal Z can signal, for example, a clogged flow vessel 13.

According to another preferred embodiment of the invention, a second logic function activated by means of the start function is implemented in the microcomputer 227, which sets a second signal value for the status signal Z if the monitoring signal x ₂₂₁ 'has a high level and the monitoring signal x ₂₂₂ ' simultaneously has a low level. In this case, the status signal Z can signal, for example, flow vessel 13 not immersed in the liquid and / or a leaking flow vessel 13 which 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 by means of two trigger thresholds set to different levels with two mutually different signal reference values, the lower of the two trigger signals Thresholds of measurement signal x ₂₂₁ or, x _{222 is} exceeded, while the higher of the two trigger thresholds is not reached.

In addition to the pressure sensor 21 ', the measuring arrangement may contain other sensors, e.g. temperature measuring temperature compensation sensors, e.g. can be attached to the flow vessel 13 or on the support means 11.

Claims (15)

1. Sampler for sampling liquids comprising:

   - a displacement pump (1)

   -- with at least one flow vessel (13) with a ductile organ (13A), said vessel serving to convey a fluid

   -- with a pump drive (12) to generate displacement movements (s₁₃) of the flow vessel (13), said movements shaping the organ (13A) and causing fluid flow

   -- with a support element (11) to retain the flow vessel (13)

   - a measuring arrangement (2) reacting to displacement movements (s₁₃) executed by the flow vessel (13)

   -- with a pressure sensor (21') which is in contact with the fluid and measures a static first pressure (p₁) in the fluid and returns a sensor signal (x₂₁) representing the displacement movements (s₁₃)

   -- with an electronic evaluation unit (22) for the sensor signal (x₂₁).
2. Sampler as per the previous claim, characterized in that the pressure sensor (21') measures the static first pressure (p₁) in the fluid relative to a second pressure (p₂) acting on the flow vessel (13) from the outside.
3. Sampler as per the previous claim, where the second pressure (p₂) is an atmospheric pressure surrounding the flow vessel (13).
4. Sampler as per one of the previous claims, characterized in that the electronic evaluation unit (22) uses the sensor signal (x₂₁) to generate a first measuring signal (x₂₂₁) that represents a frequency of the displacement movements (s₁₃).
5. Sampler as per one of the previous claims, characterized in that the electronic evaluation unit (22) uses the sensor signal (x₂₁) to generate a second measuring signal (x₂₂₂) that represents a suction height of the sensor.
6. Sampler as per one of the previous claims, characterized in that the electronic evaluation unit (22) uses the sensor signal (x₂₁) to generate an estimated flow value (X_v) that represents an instantaneous volume flow of the fluid flow.
7. Sampler as per one of the previous claims, characterized in that the electronic evaluation unit (22) uses the sensor signal (x₂₁) to generate a status signal (Z) that represents an instantaneous operating state of the displacement pump (1).
8. Sampler as per one of the previous claims, characterized in that the pressure sensor (21') is a pressure sensor in contact with a fluid.
9. Sampler as per the previous claim, characterized in that the pressure sensor (21') is a capacitance or resistive pressure sensor.
10. Sampler as per one of the previous claims designed as a mobile sampler.
11. Sampler as per one of the previous claims designed as a stationary sampler.
12. Use of a sampler as per one of the previous claims to meter liquid samples and/or store liquid.
13. Process to operate and/or monitor a sampler for sampling liquids, said sampler comprising:

    - a displacement pump (1)

    -- with at least one flow vessel (13) with a ductile organ (13A), said vessel serving to convey a fluid

    -- with a pump drive (12) to generate displacement movements (s₁₃) of the flow vessel (13), said movements shaping the organ (13A) and causing fluid flow

    - with a drive motor (14) for the pump drive and

    -- with a support element (11) to retain the flow vessel (13)

    - a measuring arrangement (2) reacting to displacement movements (s₁₃) executed by the flow vessel (13) with a pressure sensor (21') which is in contact with the fluid for a static first pressure (p₁) in the fluid

    where the process in question comprises the following steps:

    - drive movements of the drive motor (14) being caused to generate the displacement movements (s₁₃) of the flow vessel (13)

    - the first pressure (p₁) being measured with a pressure sensor (21') to generate a sensor signal (x₂₁) currently representing the displacement movements (s₁₃)

    - status signal (Z), signaling the instantaneous operating condition of the unit, being generated using the sensor signal (x₂₁)

    - an estimated flow value (X_v) being generated with the sensor signal (x₂₁) which represents an instantaneous volume flow of the fluid transported in the flow vessel (13).
14. Process as per the previous claim further comprising a step where the flow vessel is immersed in liquid, particularly liquid conveyed in an open channel or basin.
15. Process as per the previous claim further comprising a step where liquid is drawn in against gravity.

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