EP2368041B1 - Metering pump with device for degassing the pumping chamber - Google Patents

Description

The invention relates to a metering pump

The problem of gas formation in the delivery chambers of metering pumps, especially when dosing liquids is known. The gas formation occurs not only during the dosing but also during the metering pauses of the pump. In outgassing substances such as hydrogen peroxide H ₂ O ₂ gas is released, the number and size of the gas bubbles in the pumping chamber over the duration of metering breaks or during a service life increase. As a result, the pressure in the dosing of the metering pump increases. If the pressure in the dosing chamber of the pump exceeds the pressure in the pressure line, the pressure-side pump valve opens, followed by a transfer of liquid from the metering chamber of the dosing pump into the pressure line, whereby pressure equalization takes place. Thus, the ratio of the gas volume to liquid volume in the metering chamber of the pump increases, with the result that when starting the metering not directly metering volumes are output. The dosing thus stops.

The publication DE-3827489-C1 describes a metering pump with a venting device, which is formed by a diaphragm valve on the pressure line. When the dosing stroke ends, the vent valve formed by the diaphragm valve opens so that the gas present during the dosing stroke exits via a return line.

It is therefore desirable to provide a method for actuating metering pumps to improve the starting behavior and corresponding, suitable metering pumps.

Based on this prior art, the present invention is based on the object to improve a metering pump to the effect that a better degassing of the delivery chamber of the metering pump is possible. This object is achieved by a metering pump having the features specified in claim 1. further developments This object is disclosed in the corresponding subclaims.

The invention relates to a metering pump for metering fluids, which is suitable to carry out a method according to the following description in order to degas the pumping chamber of the metering pump. The delivery chamber of the pump is in fluid communication with at least one suction line which can be opened via a suction valve and at least one pressure line which can be opened via a pressure valve. Furthermore, a displacement body for displacing the fluid in the delivery chamber is provided in a known manner, or the delivery chamber is bounded on at least one side by this displacement body, in the form of a membrane. In addition, a device for carrying out a pulse is arranged in the delivery chamber. As a device for carrying out a pulse, the drive of the displacement body itself serves. To this end, the drive and / or its control or regulation are preferably designed so that the drive can control the displacement body so that it can perform small suction and / or pressure strokes, which exert only a pulse on the fluid in the delivery chamber, which is required To dissolve and accumulate gas bubbles in the pump room. The stroke is preferably so small that substantially no fluid is conveyed. More preferably, the drive of the displacement body is then configured such that it can express a collecting gas bubble, as described below, from the delivery chamber. Such a drive of the displacement body can be done mechanically, hydraulically, pneumatically and / or magnetically. For example, a stepper motor can drive the displacement body via a corresponding transmission.

A first embodiment of the method for degassing a gas-forming fluid in a delivery chamber of a metering pump refers to the pump with a delivery chamber into which the delivery chamber delimiting displacement body extends, wherein the delivery chamber has two openings, one of which via a suction valve in a Suction line and a second opens via a pressure valve in a pressure line. Since the pressure in the pumping chamber increases continuously during pump downtimes because of the formation of gas from the fluid, the pressure valve opens when a certain value is exceeded, so that undefined quantities of gas and fluid pass into the pressure line. In order to prevent fluid components from simultaneously passing into the pressure line when the gas evolved, a collecting gas bubble pending on the delivery chamber side is advantageously provided by the method according to the invention, so that when the opening pressure of the pressure valve is exceeded, only gas preferably escapes into the pressure line. For this purpose, the method comprises carrying out a pulse, wherein the pulse causes gas bubbles, which have formed in the pumping chamber by the gas-forming fluid and adhere to the inner surfaces of the pumping chamber, to be detached from these surfaces. For this purpose, a pulse is exerted during the pulsing at least on a part of the conveying space bounding surfaces or walls and / or the fluid located in the delivery chamber. After the gas bubbles have been detached from the inner surfaces, they float in the delivery chamber, can accumulate to larger gas bubbles, which then preferably rise in the direction of the pressure valve, preferably there on the delivery chamber side a collecting gas bubble to build. If the pressure in the delivery chamber now increases, the collecting gas bubble, which is preferably present at the pressure valve, escapes from the delivery chamber into the delivery line in the form of exit gas bubbles. This increase in pressure can be a consequence of the fact that even more gas is formed from the fluid during continuous pump shutdown, alternatively, a partial pressure stroke of the displacement body can be performed to increase the pressure, so that the collecting gas bubble escapes into the pressure line. Advantageously, no or only small amounts of fluid are discharged into the pressure line. Through this execution of the pulse is advantageously ensured that the gas content in the delivery chamber of the metering pump does not exceed the level that leads to a pump failure.

In a further embodiment, the pulse formation for releasing the gas bubbles is effected by generating vibration vibrations by means of a vibration generator, which is arranged in the delivery chamber. It is possible to put the displacement body and / or other parts of the delivery chamber in vibration. Alternatively, at least a partial pressure and / or Teilaughub the displacement body can be carried out as a pulse, the z. B. advantageous only such a small, possibly infinitesimal volume sucks that z. B. a Teilaughub can be considered rather than suction pulse. As a result, the gas bubbles adhering to the inner surfaces of the delivery chamber are released and can accumulate with further gas bubbles present in the delivery chamber.

Yet another embodiment of the method includes performing a partial lift sequence. This Teilhubfolge may be a Teilhubfolge of suction strokes and / or pressure strokes. Preferably, successive partial pressure strokes can be performed alternately with partial strokes. In each case, preferably the stroke length with which the displacement body is moved into the delivery chamber, grow, so that each following partial pressure and Teilaughubkombination a greater stroke length has as the previously executed. Thus, the collecting gas bubble, which is present at the pressure valve, transferred to the pressure line, and still adhering to the inner surfaces adhering gas bubbles in response to the growing stroke length, which in turn again form a collecting gas bubble, which is transferred to the subsequent partial pressure stroke back into the pressure line. Advantageously, the gas bubbles produced in the suction line can also be transferred into the delivery chamber as a result of the increase in the stroke length in a suction stroke, where they then accumulate to the collecting gas bubble and transferred by means of a next pressure stroke in the pressure line. With the help of this execution of Teilhubfolge with increasing stroke lengths of the delivery chamber of the metering pump can be almost completely degassed, so that at a first full stroke, which represents a Dosierhub, advantageously only liquid is transferred into the pressure line, so that a controlled dosing takes place. The number of partial strokes can be predetermined, so that the Teilhubfolge is previously determined with the growing stroke lengths.

Alternatively, the partial stroke sequence can be defined with increasing stroke lengths over a desired degree of degassing, which can be determined by detecting a pressure gradient in the delivery chamber when a pressure or suction stroke is being carried out. This determined pressure gradient is compared with a pressure gradient value, which was determined for a degassed delivery chamber as Kalibrierdruckgradient. In this case, the desired degree of degassing of the Kalibrierdruckgradient corresponding pressure gradient minus a tolerance of z. B. 5% of Kalibrierdrucksteigungswerts.

In this way, by executing the Teilhubfolge with increasing stroke lengths targeted and successive degassing of the delivery chamber of the pump - and thus also part of the suction line (s) - can be achieved if gas has formed during breaks or service life. Already before a first full dosing stroke can be carried out be ensured that in extreme cases, the pump does not fail due to the compressibility of the resulting gas bubbles or that at best no flow volume impairing and distorting gas bubbles in the delivery system of the pump are included.

A parting stroke as described above preferably has a content of from 0.1% to 99%, preferably from 1% to 50%, most preferably from 1% to 25% of a full suction stroke. Accordingly, a partial pressure stroke according to the foregoing description preferably has a proportion of 0.1% to 99%, preferably 1% to 50%, most preferably 1% to 25% of a full pressure stroke of the metering pump. The pressure stroke is preferably carried out in a known manner by movement of the displacement body, for example a piston or a membrane.

Further embodiments of the method relate to the fact that, for example, with known pump downtime, time intervals or times can be preset by means of a timing device that is in operative communication with the pump, so that an automatic degassing operation is carried out before the pump is put back into operation. The pulse for degassing the pumping chamber is preferably carried out during a service life or during a pump stop. The execution of a Teilhubfolge with increasing stroke lengths is preferably carried out for starting the pump after a service life of the pump.

In order to check whether gas has formed, or to check the amount of gas formed in the system, in a further method step, a pressure sensor arranged on the delivery chamber, which receives the pressure in the delivery chamber, record the pressure variation over a stroke. If the determined over the duration of a stroke pressure curve is set to the stroke, or to a limited in the pumping chamber by the traveled stroke length of the displacement body volume and optionally as a p / V diagram plotted, it shows a curve for the pressure curve during a pressure stroke, from which the pressure gradient behavior can be seen. When the pump is in a vented state, the slope of the near-linear pressure rise or pressure drop reaches a maximum value, which is taken as the set value of the pressure ramping behavior. If there are gas bubbles in the delivery chamber, the pressure diagram shows an increase or decrease with a smaller gradient, which corresponds to an actual value of the pressure gradient, when a pressure or suction stroke is carried out. In this way, by comparing the actual value with the setpoint value, the process for pump venting can be carried out until the best possible venting of the pumping chamber has been achieved. Such a comparison is carried out in an evaluation device and the determined result is provided in a control device for actuating the pump as a control parameter. This can be targeted depending on the resulting gas volume degassing initiated or the length of the degassing or the efficiency of the degassing can be determined. The comparison results are preferably supplied to a control device for actuating the pump as control parameters for starting the pump during a service life of the pump, during a pump stop, after a pump stop or for starting the pump after a service life of the pump.

The actually delivered volume flow into the pressure line during a stroke of the displacement body depends on the size of the total gas volume. The actual, ie the actual delivery behavior of the pump is determined and can be compared with a desired delivery behavior of the pump, so that, taking into account certain tolerance limits can be judged whether the pump for the metering operation is still functional.

An embodiment of the pump according to the invention, by means of which the disclosed method can be carried out, refers to the fact that the displacement body, which displaces the fluid from the delivery space, is actuated via a travel-controlled drive device, in particular a step motor or a linear motor to make that the required Teilaughübe or partial pressure strokes are correspondingly small suction or Druckhübe and thus can produce a correspondingly small negative or positive pressure. Advantageously, it is thus achieved that the displacement body, which may be a diaphragm or a piston, optionally executes stroke distances of tenths of millimeters. Thus, the finest pressure pulses are possible, which allow the detachment of the gas bubbles, which adhere to the inner surfaces of the pumping chamber and a membrane.

In doing so, the membrane performs a vibratory motion that corresponds to a "ventricular fibrillation", i. there is no or very little pumping action for the fluid, but the gas bubbles are set in motion, detach from the walls and combine to form larger gas bubbles, which then experience buoyancy in the fluid and rise.

These and other advantages will become apparent from the following description and the accompanying drawings.

The invention will now be described by way of example with reference to the accompanying drawings.

Fig. 1.1 to 1.8 , show representations of the time sequence of the degassing processes and conditions in the delivery chamber of the diaphragm pump in the event of an interruption in operation,
Fig. 2.1 to 2.10 show representations of the time sequence of the degassing processes and conditions in the delivery chamber of the diaphragm pump in the method for bringing about a ready state of the metering pump after a stoppage, and
Fig. 3 shows a flowchart of the process and the processes during a business interruption and to bring about a Ready state of the dosing pump.

For a better understanding of the subject matter, some of the terms used in the description are defined below.

Thus, a linear motor is understood to mean an electric drive machine which does not place the objects connected to it in a rotating, but in a translatory movement. If a linear motor is coupled to actuate a piston in a displacement pump, the piston can travel a very short distance. This makes it possible to meter the piston stroke very finely. The same applies to a stepper motor whose rotor moves forward with only a tiny angular offset for each step specified from the outside. This allows the highest physical positioning accuracy and thus the finest Dosierhübe achieve if such a stepper motor z. B. is coupled via an eccentric with a connecting rod or a plunger.

As a delivery room or dosing the space in the metering pump is called, which contains the fluid to be pumped; a displacement device is guided into it for the purpose of fluid displacement.

Gas-forming fluids are understood as meaning, in particular, liquid chemicals which tend to equilibrate with their decomposition products and which therefore split off gaseous products. An example of this is hydrogen peroxide. A variety of other chemicals, such as sodium hypochlorite, also tends to gas release.

The formed gases increase the pressure in the delivery chamber, thereby causing a delivery chamber of a metering pump, which is closed by pressure valves against suction and discharge line, to be pressurized by the formation of the gases. As soon as the through the pressure generated by the resulting gases exceeds the holding pressure of the pressure valves, opens the pressure valve and gases and fluid can pass into the pressure line.

The term "partial lift" or "partial pressure lift" means a fraction of a full intake stroke / compression stroke, a full lift being achieved when the displacement device is actuated over the entire stroke length. For example, if a displacement piston under 100 percent load displace a volume of 100 ml, so a Teilaughub, which has only a proportion of 0.1%, displace only 0.1 ml volume. A Teilaughub may be so low that even a swinging of the piston, or in a membrane pump of the membrane, preferably in the range of 1 to 20 Hz, for example, 2 to 10 Hz, more preferably from 3 to 4 Hz, is carried out essentially no fluid is conveyed.

With regard to the displaced volume, the term "stroke length" is used here in an equivalent manner to the terms partial stroke, or partial pressure stroke; because the proportion of a partial stroke length with respect to a total stroke length corresponds to the proportion of Teilhubvolumens in relation to the total stroke volume, so that, for example, at a partial stroke corresponding to a share of 25% of a full stroke, the Teilhublänge corresponds to 25% of the total stroke length.

Furthermore, a term "desired degree of degassing" is used below, which means that, depending on the fluid to be metered, an experimentally determined minimum degassing can be achieved. This minimum degassing would correspond to a degree of degassing of 1. With chemicals that permanently release gases, even during the dosing process, gases will be generated, so that an ideal degree of degassing of such a chemical will correspond to another ideal degree of degassing than exists for a fluid that only very gradually releases gases and actually does so Degassing near 1 achieved werbei actually a degree of degassing close to 1 can be achieved. In order to determine the degree of degassing, in the published patent application DE 3546189 A1 As described above, it can be used to record the pressure gradient at a stroke of the displacement body via a pressure sensor arranged in the delivery chamber, and this actual value can be compared with the desired value.

Basically, the method according to the invention is based on the fact that the execution of a pulse during a service life or after a pump stop can be done, whereas the execution of a Teilhubfolge with increasing stroke lengths of the displacement body for commissioning, or to start the pump after a service life of the pump can be used.

A service life of the pump is understood below to mean a time period which is sufficient to provide a corresponding gas volume. Basically, a life will be at least 30 minutes, as a service life is also a non-operation of the pump overnight of over 12 hours or a multi-day non-operation of the pump stored in the pump fluid storage. A pump stop can take anywhere from a few seconds to 30 minutes. For the pump to carry out the degassing process according to the invention during a service life or a pump stop, the pump must be "active", ie. H. it must be powered and a degassing mode, ie a corresponding program in the pump software, must be activated.

The metering pump, which produces a gas-forming fluid and whose delivery chamber is to be freed from the gas formed, has a suction valve which opens into the delivery chamber and extends into a suction line. Furthermore, the delivery chamber opens via a pressure valve in a pressure line. The same applies if there are several pressure or suction lines. A displacement body for displacing the fluid limits the delivery space, usually on one side, and is arranged such that it can perform the pressure strokes required for displacement alternately in combination with the corresponding suction strokes.

In order to replace the gas bubbles formed by the gas-forming fluid and adhering to the delivery chamber bounding inner surfaces of these surfaces, a pulse is initially carried out, the pulse can be done by vibration vibration by means arranged in or on the pumping chamber vibration generator or alternatively z. B. can be performed as a first Teilaughub the displacement body. This sub-stroke corresponds to a proportion of 0.1 to 99% of a full suction stroke and may also be a swing in a range of 1 to 20 Hz. If the gas bubbles by the vibration oscillations or z. B. have replaced the provided suction pulse from the delivery chamber bounding inner surfaces, they will accumulate in the delivery chamber and, since their volume has increased, and they thus experience greater buoyancy, perform a movement in the direction of the pressure valve, provided that the pressure valve in the space facing upwards is arranged against the direction of gravity.

It now forms the delivery chamber side of the pressure valve, a collecting gas bubble to be discharged via the pressure valve in the valve chamber. This is done by a pressure increase in the delivery chamber, which is caused by further gas formed from the fluid and / or by a partial pressure stroke, which may correspond to a proportion of 0.1 to 99% of a full pressure stroke. As a result, the collecting gas bubble is compressed and in turn exerts pressure on the pressure valve. When the opening pressure is exceeded, this opens and the gas forming the collecting gas bubble is transferred as discharge gas bubbles into the pressure line. Advantageously, no fluid is transferred into the pressure line.

A partial lift stroke may correspond to a level of from 0.1% to 99%, preferably from 1% to 50%, most preferably from 1% to 25% of a full suction stroke. A Teilaughub can also be divided into a plurality of vibration strokes, which make up a total of 0.1 to 10% of a full intake stroke. A partial pressure stroke may correspond to a level of from 0.1% to 99%, preferably from 1% to 50%, most preferably from 1% to 25% of a full pressure stroke.

In order to put the metering pump in a ready state, after the above-described execution of a pulse during an operation interruption, a Teilhubfolge with increasing stroke lengths of the displacer is carried out, wherein the partial strokes are between 0.1 to 99% of a full stroke. Due to the increasing pressure in the delivery chamber as a result of the growing pressure strokes escapes at the partial pressure strokes a collecting gas bubble from the pressure valve, while the increasing suction strokes in the suction line can transfer existing gas bubbles in the delivery chamber, where they perform a movement in the direction of the pressure valve, and form a collecting gas bubble , which is transferred with a next pressure stroke in the pressure line. The Teilhubfolge with increasing stroke lengths is carried out until an optimal degree of degassing is achieved, which is either determined by the number of partial strokes, or controlled by determining the degassing.

The determination of the degree of degassing comprises detecting a pressure gradient in the delivery chamber when executing a pressure or suction stroke, and comparing the determined pressure gradient with a pressure gradient serving as Kalibrierdruckgradient, which was determined for a degassed fluid, wherein the desired degassing thereby a the Kalibrierdruckgradient corresponding pressure gradient less a tolerance of about 5% of the calibration pressure gradient value.

The values from the determination of an actual pressure gradient during a stroke of the displacement body and the comparison values of the - actual pressure gradient behavior of the pump with a desired pressure gradient behavior of the pump can be fed to an evaluation device for evaluating the comparison results and further transmitted to a control device for actuating the pump as a control parameter.

The method may further include presetting time intervals and times of a timing device operatively connected to the pump such that actuation of the pump to start, during a life, after a pump stop, or to start the pump after a life of the pump, timed can be. Thus, an already operational pump can advantageously be made available if the dosing work is resumed after a work break or a night's sleep.

Finally, the method also provides that further control parameters are provided for starting the pump during a service life of the pump, after a pump stop or for starting the pump after a service life: This is the determination of an actually conveyed volume flow into the pressure line during a defined stroke of the displacement body and the comparison of the defined by this stroke defined actual delivery behavior of the pump with a delivery behavior of the pump at identical defined stroke, the comparison of the actual delivery behavior and the desired delivery behavior of the pump show whether gas is present in the conveyor system or not. Knowing the misfed volume, the controller may initiate a corresponding degassing operation, which may be the execution of the partial lift sequence with increasing stroke lengths.

Advantageously, the metering pump of the method according to the invention will be a diaphragm pump. Of course, the invention is Method also executable with a piston pump. It can be used any displacement body, provided he z. B: can be caused by coupling with a lifting rod, compressed air or other suitable device for performing smallest strokes. In order to advantageously carry out small strokes with a diaphragm pump, a path-controlled drive device such as a linear motor or a stepper motor can be in operative connection with the displacement body. A coupling via a compressed air generator is possible.

The sequence of figures 1.1 to 1.8 is based on the following starting situation: During a pump stop or a service life of the pump, different gas bubbles 4, 7, 8 emerge from the outgassing fluid in the delivery chamber 1. Above all, the gas bubbles 4,8 are formed on the inner walls of the delivery chamber and on the piston surface 3 'of the delivery chamber 1 bounding piston 3. By this gas bubble growth, a pressure p ₂ in the delivery chamber 1 increases. If the pressure p ₂ greater than the pressure in the pressure line p ₃ , then opens the pressure valve 6. By the migration of the fluid or the collecting gas bubble 7 (depending on what is pending on the pressure valve) from the pumping chamber 1 in the pressure line finds Pressure equalization instead.

This is disadvantageous if the fluid migrates into the pressure line. Because while the ratio of gas bubbles proportion to fluid content in the delivery chamber 1 increases. If the product of gas bubble volume and the pressure in the delivery chamber 1 is so great that even through a complete suction stroke the necessary pressure p ₂ for opening the suction valve 5, which must be smaller than the pressure p ₁ in the suction line, can not be achieved no fluid volume from the suction line flows into the pumping chamber 1. This in turn means that by a complete pressure stroke of the pressure p _{2 of} the fluid volume in the delivery chamber 1 at most up to a pressure corresponding to the pressure p ₃ in the pressure line increases, so that the pressure valve 6 does not open. It will only the trapped gas bubbles compressed 4,7,8 in the delivery chamber 1 and expanded again, without the pump conveys volumes from the suction line into the pressure line. A dosing process is therefore not possible.

To prevent this, during the pump stops, or during a service life when growing the gas bubbles in the delivery chamber 1, only a small proportion of the fluid from the delivery chamber 1 in the pressure line, and the gas bubble fraction does not increase until the loss of dosing. For this purpose, during a service interruption of the pump, pulses for detaching the gas bubbles 4, 8 from the inner walls of the delivery chamber 1 are carried out. As a result, the small gas bubbles accumulate to a large collecting gas bubble 7, which rises by the buoyancy force to the pressure valve 6. This pulse can be achieved by the movement of the piston 3, as shown schematically in the figure sequence 1.1 to 1.8.

In Figures 1.1 to 1.8 is the operational holding the pump, which in the present case is a diaphragm pump, although the membrane itself is not shown separately figurative shown. The gas bubbles can be caused by the decomposition of unstable fluids such as hydrogen peroxide (H ₂ O ₂ ). A pulse is carried out as Teilaughub b and partial pressure stroke a, alternatively, the pulse can also be generated by a swing of the membrane.

In Figure 1.1 grow the gas bubbles 4,7,8 during a stoppage of the pump in the delivery chamber 1, and the pressure p ₂ increases with increasing proportion of gas bubbles.

By a suction stroke b of the piston 3, as in Fig. 1.2 shown, whereby the trapped volume in the delivery chamber 1 increases, the pressure p ₂ in the delivery chamber 1, whereby the gas bubbles 4 ', 7, 8' according to the equation (I) occupy larger volumes decreases. $${\mathrm{p}}_{\mathrm{previously}}\times {\mathrm{V}}_{\mathrm{previously}}{}^{\mathrm{n}}={\mathrm{p}}_{\mathrm{later}}\times {\mathrm{V}}_{\mathrm{later}}{}^{\mathrm{n}}$$

In Fig. 1.3 is sketched, as by a continued suction stroke b of the piston 3, the gas bubbles 4 ', 7,8' are still larger, accumulate and rise in the direction of pressure valve 6. The suction valve 5 can continue to remain closed.

Fig. 1.4 shows a large collecting gas bubble 7 after the suction stroke of the piston 3 is completed. The, as in Fig. 1.3 shown, previously enlarged and dissolved from the inner wall of the pumping chamber 1 gas bubbles 8 'have united to this collecting gas bubble 7, which is now present at the pressure valve 6; some gas bubbles 4 'remained hanging on the inner walls of the pumping chamber 1 continue.

A subsequent pressure stroke a of the piston 3, shown in FIG Fig. 1.5 , can the pressure p ₂ in the pumping chamber 1 rise again, whereby the volume enclosed in the pumping chamber 1 decreases. As a result, according to equation (I), the volume of the gas bubbles 4 'and the collecting gas bubble 7 located in the delivery chamber 1 decreases accordingly.

After the pressure stroke a of the piston 3 is completed, as in Fig. 1.6 is shown, a position of the piston 3 in accordance with the Fig. 1.1 reached. In this case, the pressure level p ₂ in the delivery chamber 1 also corresponds to the pressure level Fig. 1.1 , Unlike the situation in Fig. 1.1 lie in Fig. 1.6 only a few gas bubbles 4 'on the inner walls of the delivery chamber 1 and the collecting gas bubble 7, which is present at the pressure valve 6.

In Fig. 1.7 is shown how by further outgassing of the fluid, the volume of the gas bubbles 4,8 and the collecting gas bubble 7 increases and the pressure p ₂ in the pumping chamber 1 further increases. This increase in pressure causes the pressure p ₂ in the delivery chamber 1 is higher than in the pressure line (p ₂ > p ₃ ). As a result, the pressure valve 6 opens and the collecting gas bubble 7 attached thereto begins to escape as a result of the pressure equalization in the pressure line as exit gas bubbles 7 '.

Further outgassing of the fluid in the conveying chamber 1 conveys further outlet gas bubbles 7 'of the collecting gas bubble 7 into the pressure line, as in FIG Fig. 1.8 is shown. This means that the outgassing fluid in the pumping chamber 1 as long as the collecting gas bubble 7 as discharge gas bubbles 7 'from the pumping chamber 1 displaced in the pressure line as the pressure p ₂ in the delivery chamber 1 is greater than the pressure p ₃ in the pressure line. To prevent the growing gas bubbles 4.8 do not displace fluid from the pumping chamber 1 in the pressure line, again a suction stroke b to form a collecting gas bubble 7 at the pressure valve 6 as shown in FIG Fig. 1.2 initiated.

The fine suction strokes and pressure strokes can be performed well with a metering pump for metering fluids when the displacer of the device is operated by a stepper motor or a linear motor and acts on the diaphragm or piston as a displacer, or when a vibrator is installed to pulse ,

The displacement body, which may be a piston or a flexible membrane 3, may be driven mechanically via a lifting rod 2 or hydraulically or pneumatically or magnetically.

This process of conveyor degassing can be performed several times during a service life, for example, by a device for timing (not shown) at predetermined time intervals or at predetermined times outputs a signal that sets the process for degassing the pump room in motion. In this case, empirical values can be used, so that the person skilled in the art can set the time intervals in such a way that the conveyor-belt degassing takes place if a correspondingly strong formation of gas bubbles occurs is to be expected.

On the other hand, a step for determining an actual pressure gradient in the delivery chamber during a pressure or suction stroke and comparing the actual pressure gradient behavior of the pump with a desired pressure gradient of the pump with an evaluation device for evaluating the comparison results are performed, the comparison results of a control device for actuating the Pump as a control parameter for starting the pump after a service life of the pump, alternatively after a pump stop. The steps of setting a time control or a pressure gradient based on the determination of the pressure increase in the delivery chamber in a pressure or suction stroke, can be performed at any desired times and also alternately, if necessary. Alternating with manual execution of the method.

The determination of the pressure gradient can be carried out with a pressure measuring device provided in the delivery chamber, which receives the pressure curve p ₂ in the delivery chamber via a pressure or suction stroke, with increasing gas bubble formation, the slope of the pressure increase or pressure drop in a recorded pressure-stroke length. Diagram decreases, since the gas bubbles are compressible, and when falls below a certain threshold and feedback of the data to a control device, the Förderumumentlüftung is automatically triggered.

The inventive method further relates to the bringing about a ready state of the pump by the delivery chamber and supply lines such as the suction line with the simplest means as quickly as possible to be freed of gas bubbles, so that the pump can fulfill their task of accurate dosing, without a variety of Inaccurate Dosierhüben when resuming the dosing takes place after a break.

Thus, the sequence of figures 2.1 to 2.10 is based on the following starting position: The pump should start to dose again after an interruption in operation. In the case of outgassing dosing fluids, a complete pressure stroke must not be carried out immediately, that is, no full stroke volume may be passed through the displacement body.

In the following, the processes are described with reference to the sequence of figures 2.1 to 2.10, as gas bubbles 4,4 ', 7,8,8' are transferred by increasing partial strokes a and b from the delivery chamber 1 in the pressure line, so that only a small proportion of the fluid from the pumping chamber 1 passes into the pressure line before the gas bubbles 4, 4 ', 7, 8, 8' are removed from the pumping chamber 1. For this purpose, the proportion of gas bubbles in the delivery chamber 1 is reduced by partial strokes with increasing stroke length such that the metering process can take place.

As in Fig. 2.1 1, gas bubbles have formed in the delivery chamber 1, both a collecting gas bubble 7 and gas bubbles 4, 8 on the inner surfaces of the delivery chamber 1. The area surrounded by dashed lines symbolizes the size of the displacement volume V _H 20.

As a result of the pressure stroke movement a of the piston 3, the pressure p ₂ in the delivery chamber 1 increases ( Fig. 2.2 ), wherein the volume limited by the piston 3 in the delivery chamber 1 decreases. Upon reaching the opening pressure of the pressure valve 6 (p ₂ > p ₃ ) a Teilhubvolumen V _H 20, but above all the pending on the pressure valve 6 collecting gas bubble 7 is displaced into the pressure line.

After completion of the partial pressure stroke a, accordingly Fig. 2.2 , a Teilaughub b, as in Fig. 2.3 shown performed. In this case, the pressure p ₂ in the pumping chamber 1 drops due to the suction movement of the piston 3. At the same time, the volume bounded by the piston 3 in the pumping chamber 1 increases. According to the above equation (I), the gas bubbles 4 ', 8' occupy larger volumes. Some of them accumulate to a large collecting gas bubble 7, as in the following Fig. 2.4 shown, which is present at the pressure valve 6.

In Fig. 2.4 the Teilaughub b of the displacement body 3 is completed and the piston 3 has assumed its initial position. There are again both a collecting gas bubble 7 and the gas bubbles 4 'on the inner surfaces of the pumping chamber 1 available. However, now the volume fraction of the gas bubbles 4 ', which are present on the inner surfaces of the delivery chamber 1, reduced. The stroke volume V _H 20 refers to the following, in Fig. 2.5 shown partial pressure stroke.

Through this further, second partial pressure stroke a of the piston 3 in Fig. 2.5 , wherein the stroke length of the second pressure stroke a is greater than that of the previous pressure stroke in Fig. 2.2 , the pressure p ₂ in the pumping chamber 1 rises again and the volume enclosed in the pumping chamber 1 decreases. At the latest after exceeding the stroke length of the predecessor stroke, the opening pressure of the pressure valve 6 is reached (p ₂ > p ₃ ), so that a Teilhubvolumen 20 of the fluid, but especially the pending on the pressure valve 6 collecting gas bubble 7 is transferred to the pressure line. The partial stroke volume 20 is at least as great as the stroke difference between the predecessor stroke and the current larger partial stroke.

Fig. 2.6 shows that after completion of the second partial pressure stroke, a further second Teilaughub b is executed. Due to the Teilaughub b of the piston 3, the pressure p ₂ decreases in the delivery chamber 1, while analogously enclosed in the pumping chamber 1 volume according to equation (I) and thus the volumes of the gas bubbles 4 'increase. As a result, the gas bubbles 4 'rise in the direction of the pressure valve 6. There or during the upgrade they accumulate to a new large collecting gas bubble 7, which is then present at the pressure valve 6. When doing the necessary pressure to open the suction valve 5 is achieved, a volume is sucked from the suction line. This may consist partly of fluid volume and partly of gas volume. The thus tracked by the suction valve 5 from the suction line Gas bubbles 7 "rise in the delivery chamber 1 in the direction of the pressure valve 6 (arrow c).

In Fig. 2.7 is the second Teilaughub of the piston 3 is completed and the displacement body 3 again assumes the starting position. Meanwhile, only the pending on the pressure valve 6 collecting gas bubble 7 is present.

With a third pressure stroke a, whose stroke length is in turn greater than that of the preceding stroke and here corresponds to a full pressure stroke, the piston 3 compresses the volume enclosed in the delivery chamber 1 by the piston 3, shown in FIG Fig. 2.8 , Likewise, the previously formed collecting gas bubble 7 is compressed, which is present at the pressure valve 6 and includes the entire gas content in the delivery chamber 1, so that it can be transferred with the displacement V _H 20 in the pressure line, as in the following Fig. 2.9 is shown.

If a full pressure stroke a has now been carried out, the collecting gas bubble 7 leaves the conveying chamber 1 in the form of outlet gas bubbles 7 'through the pressure valve 6 into the pressure line (shown in FIG Fig. 2.9 ). Ideally, the delivery chamber 1 is now free from adhering to the inner surfaces of the delivery chamber 1 gas bubbles.

In Fig. 2.10 Finally, it is shown that after this full pressure stroke a, through which the delivery chamber 1 has been completely degassed, the first full intake stroke b follows. In this case, a complete stroke volume V _H 20 is sucked by the suction line through the suction valve 5 in the delivery chamber 1.

The pump was thus advantageously degassed with a small number of strokes, without significant amounts of metering fluid would have been pumped into the pressure line and would be there undesirable spent on the first Dosierhub. The Teilaughübe disclosed in the method according to the invention, optionally perform such a small stroke that can be spoken of a vibration, as well as the associated partial pressure strokes are sufficient to degas the pumping chamber and a part of the suction line.

The method for degassing the pumping chamber of the pump to reach a ready state can be triggered manually, but it is also a controlled control possible, so that the inventive method can be initiated when a control unit a dose requirement is reported when a time control the degassing provides. The parameters determined above can be transmitted in a manner known to the person skilled in the art to a corresponding control and regulating unit operatively connected to the pump in order to initiate the method according to the invention starting with the desired steps.

Fig. 3 shows in a flow chart a possible temporal or logical sequence of the method according to the invention. In addition to the method steps, the processes in the delivery chamber of the pump are described. Starting from a metering break of the metering pump, which have formed gas bubbles in the interior of the pumping chamber in the pumping chamber through the outgassing fluid, which adhere to the inner surfaces of the pumping chamber (corresponds Fig. 1.1 and 1.8 ), after a predetermined time interval t _interval, the pulse is carried out, in a first step by a Teilaughub the pressure p ₂ inside the pumping chamber decreases, whereby the volumes of gas bubbles grow, accumulate the gas bubbles and ascend to the collecting gas bubble (corresponds Fig. 1.2 and 1.3 ). In the delivery chamber there are still gas bubbles on the inner surfaces, as well as the collecting gas bubble at the pressure valve (corresponds Fig. 1.4 ). The second sub-step of the pulse is carried out by performing a partial pressure stroke, whereby the pressure p _{2 increases} in the delivery chamber, thereby further accumulating the gas bubbles and ascending to the collecting gas bubble is effected (corresponds Fig. 1.5 ). With continuous downtime, the gas bubble volumes grow by the continued outgassing of the fluid, whereby the pressure p ₂ in the pumping chamber continues to increase, so that when the opening pressure of the pressure valve is exceeded, when the pressure p ₂ in the pumping chamber is greater than the pressure p ₃ in the pressure line, the collecting gas bubble escapes (corresponds Fig. 1.6 and 1.7 ). Now takes the dosing of the pump, the execution of the pulse by Teilaughub and partial pressure stroke in the interval of the preset time interval t _{interval is} continued until the metering break is completed.

After completion of Dosierpause are so in the pumping chamber still gas bubbles on the inner surfaces of the delivery chamber and a collecting gas bubble at the pressure valve before (corresponds Fig. 2.1 ). In order to bring about a dosing-ready state of the metering pump, the partial lifting sequence is now carried out with increasing stroke lengths of the displacement body, the partial lifting sequence consisting of n partial lifting combinations of partial pressure strokes and partial lifting strokes. The number n Teilhubkombinationen can be preset or controlled depending on the degassing state of the pumping chamber. Each partial pressure stroke partial lift combination is made with a stroke length corresponding to a proportion of x _n % of full stroke length, with each subsequent partial pressure stroke partial lift combination having a longer stroke length (x _{n + 1} > x _n ). After performing a first partial pressure stroke with a first stroke length of x ₁ % of a full stroke length, the pressure valve opens and the collecting gas bubble escapes (corresponds Fig. 2.2 ), a first Teilaughub is carried out with the first stroke length, whereby gas bubbles accumulate and ascend (corresponds Fig. 2.3 ). After the first partial-pressure stroke Teilaughubkombination are still the collecting gas bubble at the pressure valve and residual gas bubbles in the delivery chamber before (corresponds Fig. 2.4 ).

For a second partial stroke combination with a second stroke length from x ₂ % of a full stroke length, which is greater than the first stroke length, the execution of the second partial pressure stroke corresponds to the state in Fig. 2.5 , and carrying out a second Teilaughubs with the second stroke length (corresponding to Fig. 2.6 ) causes moreover still that gas bubbles from the suction line can be tracked in the delivery chamber when the pressure p ₂ in the delivery chamber is smaller than the pressure p ₁ in the suction line, so that the suction valve opens.

After the execution of the second Teilhubkombination is finally still a collecting gas bubble on the pressure valve (corresponds Fig. 2.7 ), which is then carried out by performing a third pressure stroke, here a full pressure stroke with x ₃ = 100% stroke length. The pressure valve opens and the collecting gas bubble escapes (corresponds Fig. 2.8 ), the delivery room is now in a degassed state ( Fig. 2.9 ) and the pump is ready for use.

Now, by performing a full suction stroke, the pump can deliver an entire stroke volume V _H (corresponds to Fig. 2.10 ).

In the present case, the method was after Fig. 3 with reference to the figure sequence 2.1-2.10 by executing the Teilhubfolge with increasing stroke lengths with a number of three partial strokes. However, the number of partial strokes of Teilhubfolge with increasing stroke lengths is not limited and can be adjusted according to the given operations in relation to the pumping chamber and the fluid to be dosed. As mentioned above, the number of partial strokes in the Teilhubfolge can also be controlled by means of a suitable measurement technique, depending on the presence of the gas bubbles in the pumping chamber.

By means of this measurement technique can be determined whether there are still gas bubbles or not. This device may be for example an optical sensor or a pressure sensor. If there are no more gas bubbles, the pump is already in an operational state Status; the device determines whether there are still gas bubbles, there are still gas bubbles, the partial stroke sequence with increasing stroke lengths is initiated, accumulated by Teilaughübe Randgasblasen from the pumping chamber and rise to a collecting gas bubble, which by a partial pressure stroke in the Pressure line is transferred. This loop is carried out until there are no more gas bubbles, so that the pump is in an operational state and can dose with it.

LIST OF REFERENCE NUMBERS

1

- Delivery room / Dosierraum

2

- lifting rod

3

- displacement piston

3 '

- Surface of the piston 3 pointing into the delivery chamber

4

- Gas bubble

5

- Suction valve

6

- Pressure valve

7

- Collection gas bubble

7 '

- exit gas bubble

7 "

- Gas bubbles trailed from the suction line

8th

- Gas bubble

8th'

- buoyancy gas bubble

9

- opening to the suction line

9 '

- Valve chamber of the suction valve

10

- Opening to the pressure line

10 '

- Valve chamber to the pressure line

20

- Stroke volume V _H

a

- Movement of the piston in the direction of delivery chamber

b

- Movement of the piston out of the pumping chamber

c

- Movement of the gas bubbles in the delivery room

Claims (13)

1. A metering pump for metering fluids, with a delivery chamber (1), said delivery chamber comprising the fluid to be delivered, being in fluid connection with a suction conduit which can be opened via a suction valve as well as in fluid connection with a delivery conduit which can be opened via a delivery valve and being delimited at least at one side by a displacement body in the form of a membrane, characterised in that
   a device for carrying out an impulse generation is arranged in the delivery chamber, said device being formed by the displacement body which can be driven via a rotation angle controlled or path controlled drive device, wherein the rotation-angle controlled or path controlled drive device is suitable for providing part-suction-strokes and part-delivery-strokes of the displacement body and that the metering pump is suitable for carrying out the following method for degassing the delivery chamber (1) of the metering pump:
   carrying out an impulse generation, wherein gas bubbles which have arisen in the delivery chamber (1) due to a gas-forming fluid and which adhere on the inner surface are detached from these surfaces, wherein the gas bubbles (4, 4', 8, 8') which are present in the delivery chamber (1) accumulate into a collective gas bubble and wherein the collective gas bubble (7) escapes from the delivery chamber (1) due to an increase in pressure.
2. A metering pump according to claim 1, characterised in that the metering pump is designed in manner such that the gas bubbles (4, 4', 8, 8') execute a movement (c) in the direction of the delivery valve (6) on account of the impulse generation and form the collective gas bubble at the delivery-space side of the delivery valve (6) and wherein the collective gas bubble (7) which is present at the delivery valve (6) escapes into the delivery conduit as exit gas bubbles (7') given an increase in pressure.
3. A metering pump according to claim 1 or 2, characterised in that the metering pump is designed in a manner such that the pressure increase in the delivery chamber (1) arises due to the exit of the gas out of the fluid and/or due to a part-delivery-stroke of the displacement body.
4. A metering pump according to one of the preceding claims, characterised in that the metering pump is designed in a manner such that the implementation of the impulse generation is effected by way of carrying out at least one part-stroke or a part-stroke sequence or a vibration of the displacement body.
5. A metering pump according to one of the preceding claims, characterised in that the metering pump is designed for executing a part-stroke sequence with increasing stroke lengths of the displacement body (3), so that the collective gas bubble (7) is brought into the delivery conduit, and gas bubbles which still adhere to the inner surfaces are transported in a following manner in dependence on the increasing stroke length and form an renewed collective gas bubble (7).
6. A metering pump according to claim 5, characterised in that the metering pump is designed in a manner such that a predefined number of part-strokes determines the part-stroke sequence with increasing stroke lengths.
7. A metering pump according to at least one of the preceding claims 1 to 5, characterised in that the metering pump is designed for determining the desired degree of degassing, wherein a pressure gradient in the delivery chamber (1) is detected on executing a delivery or suction stroke, and the determined pressure increase is compared to a pressure gradient value which serves as a calibration pressure increase and which was determined for a degassed delivery chamber (1)
   wherein the desired degree of degassing herein corresponds to a pressure increase which corresponds to the calibration pressure gradient, minus a predefined tolerance of the calibration pressure gradient value.
8. A metering pump according to at least one of the claims 1 to 6, characterised in that the metering pump is designed in a manner such that
   a part-suction-stroke corresponds to a share of 0.1 % to 99 %, preferably of 1 % to 50 %, mostly preferably from 1 % to 25 % of a complete suction stroke, and
   a part-delivery-stroke corresponds to a share of 0.1 % to 99 %, preferably from 1 % to 50 %, mostly preferably from 1 % to 25 % of a complete delivery stroke.
9. A metering pump according to one of the preceding claims, characterised in that the metering pump is designed in a manner such that the execution of the impulse generation is carried out during a downtime or during a pump stop.
10. A metering pump according to at least one of the claims 5 to 8, characterised in that the metering pump is designed in a manner such that the execution of the part-stroke sequence is carried out with increasing stroke lengths for starting up the pump after a downtime of the pump.
11. A metering pump according to at least one of the claims 5 to 10, characterised in that the metering pump is designed for
    presetting time intervals (t_intervall) or points in time of a time control device which is operatively connected to the pump, so that the execution of the impulse generation and the execution of the part-stroke sequence with increasing stroke lengths is carried out in a time-controlled manner.
12. A metering pump according to at least one of the claims 7 to 11, characterised in that the metering pump is designed for
    feeding the values from the determining of an actual pressure gradient during a stroke of the displacement body and the values from the comparison of the actual pressure increase behaviour of the pump with the desired pressure increase behaviour of the pump to an evaluation device for evaluating the comparison results, wherein the comparison results are led to a control device for actuating the pump as control parameters for starting up the pump,

    - during a downtime of the pump,

    - during a pump stop

    - after a pump stop, or

    - for starting up the pump after a downtime of the pump.
13. A metering pump according to one of the preceding claims, characterised in that the rotation-angle-controlled or path-controlled drive device is a stepper motor, an EC-motor or a linear motor.

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