WO2003054392A1

WO2003054392A1 - Dosing pump

Info

Publication number: WO2003054392A1
Application number: PCT/EP2002/011151
Authority: WO
Inventors: Erwin Bolt
Original assignee: Knf Flodos Ag
Priority date: 2001-12-20
Filing date: 2002-10-04
Publication date: 2003-07-03
Also published as: JP4060273B2; EP1456539A1; DE50211149D1; DE10162773A1; ATE377149T1; JP2005513340A; US20040234377A1; EP1456539B1

Abstract

The invention relates to a dosing pump (1) comprising a working membrane defining a working area, and a pump drive (2) for creating an oscillating movement of the working membrane. The direction of the pump drive (2) can be inverted and the displacement element can be moved back and forth. The inventive dosing pump also comprises a position sensor (32) for detecting the position of the pump drive (2), an electronic control system for the same, and a pump head in which an inlet valve (13) and an outlet valve (14) are arranged. Said pump drive (2) comprises a positioning motor (12) and can be displaced back and forth in an oscillating manner, with the part thereof connected to the displacement element, in any range of its entire working displacement, according to a pre-determinable course, for a reduced pump capacity in relation to the maximum pump capacity. At least the inlet valve (13) is externally controlled and comprises a motor-driven valve drive. The electronic control system (7) is connected to at least the motor-driven valve drive(s) of the inlet and/or outlet valves (14), to the positioning motor (12) of the pump drive (2), and to the position sensor (32) for detecting the position of the displacement element and/or the pump drive (2). The combination of the electronically controllable positioning motor (12), the oscillating movement of the pump drive (2) within any range of its entire working range, and the use of an externally controlled inlet and/or outlet valve (14) significantly enlarges the operative range of the inventive dosing pump.

Description

metering

The invention relates to a metering pump, in particular a diaphragm metering pump with a working membrane delimiting a working space or similar displacement element and a pump drive for an oscillating movement of the displacement element, wherein the pump drive is reversible in direction and the displacement element can be moved back and forth, with a position transmitter for detecting the position of the pump drive and an electronic control therefor are provided, as well as with a pump head in which an inlet valve and an outlet valve are arranged.

Metering pumps of this type are known in different embodiments. This is how metering pumps are known that work with a magnetic drive and accordingly carry out fast working strokes. The pulse-like delivery results in sufficient pressure differences for the control of the valves.

Motorized rotary drives are used for metering pumps where a low conveying speed and small metering quantities are desired, which run very slowly at least for the metering stroke. Correspondingly low pressure differences occur, so that sealing problems can occur with the valves.

From EP 0 31 339 a device for regulating the delivery rate of a metering pump is known, with which the delivery stroke or the number of delivery strokes per unit time can be changed.

The delivery stroke is changed by the pump drive for different rotary sections with a correspondingly different stroke, starting from a defined starting position, is moved back and forth.

This metering pump also has sealing problems with the valves in the case of the adjustable, small metering quantities, so that the metering accuracy sought by the mode of operation of the pump can be considerably reduced as a result.

A diaphragm metering pump is known from DE 195 25 527.7, in which special valves are used in order to at least largely avoid the aforementioned disadvantages even at low working speeds and small pressure differences and small metering quantities. However, a minimum pressure difference is also required here to open and close the valves. In the case of doses where, for example, the working stroke takes a long time, for example a few minutes, a reliable seal cannot be achieved even with these sensitive reacting valves.

Metering pumps are also known in which a mechanical change in the stroke length is carried out for setting the metering quantity. As a result, it is possible to work with a sufficiently high delivery speed even for small dosing quantities, which results in a sufficient pressure difference and is sufficient for the valves to function. However, due to the working speed sufficient for the valves to function, the pumped medium is sprayed out at a correspondingly high speed. This pulse-like delivery is undesirable in many applications of metering pumps.

Both slow-running and fast-running pumps overlap the valve functions, which, depending on the pressure and suction pressure conditions, are disadvantageous in the form of a return medium flow. effect against the conveying direction and thus dosing inaccuracies.

The object of the present invention is to provide a metering pump with which a wide operating range can be covered with the smallest metered quantities and high repeatability, an exact adjustability of the pump to a wide variety of operating conditions, the pump being highly metered both with larger and with the smallest delivery quantities should have and the conveying speed should be extremely low adjustable while maintaining a high dosing accuracy.

To solve this problem, it is proposed that the pump drive has a positioning motor and with its part connected to the displacement element can be moved back and forth in any area of its total working movement with a predeterminable stroke for a delivery rate that is reduced compared to the maximum delivery rate, that at least one of the at least two valves is externally controlled and has a motorized valve drive and that the electronic control is connected to at least the motorized valve drives of the inlet and / or outlet valve, the pump drive and the position transmitter for detecting the position of the displacement element and / or the pump drive ,

The combination of an electronically controllable positioning motor, oscillating movement of the pump drive within an arbitrary area of its total working area as well as the use of an externally controlled inlet and / or outlet valve enables the metering pump equipped with it to be expanded considerably. It is possible to run the dosing pump for the smallest dosing quantities at an extremely low conveying speed and to achieve exact dosing through the valve or valves that can be precisely controlled by the electronic control and can therefore be opened or closed at predetermined times regardless of the delivery pressure differences. On the other hand, with a high delivery rate and high-speed pump drive, backflow due to back pressure of the pumped medium can be reduced by suitable closing and opening times of at least the externally controlled valve. This also contributes to an improvement in the metering accuracy and universal use of the metering pump. Finally, in addition to an adapted control of the positioning motor by the electronic control, the pendulum stroke can be influenced as a function of the position within the overall working range by the pendulum stroke movement in any area of the total working movement with a rotary pump drive. For example, the effective stroke of the displacement element can be influenced by a selection of the position of the pendulum stroke movement within a 360 ° overall work movement that is adapted to the tasks. In the case of a pendulum stroke movement in the region of a dead center position of a pump drive with a crank mechanism, a lower effective stroke results for a given rotational movement than in a region between these two dead center positions.

The metering pump according to the invention can be operated both in an arbitrary area of the overall working movement of your pump drive with a reciprocating reciprocating working stroke, and also all round with a maximum working stroke and corresponding maximum delivery quantity per working stroke. This gives the metering pump a wide range of uses. The electronic control can be designed for variable control of the motorized valve drive (s) of the inlet and / or outlet valve depending on the position of the displacement element. There is also the possibility that the electronic control is designed to control the motorized valve drive (s) of the inlet and / or outlet valve depending on different operating parameters, in particular depending on the operating pressure, the speed, the consistency of the delivery medium and the like. For example, the switching positions of the valve or valves within a revolution or a pendulum stroke range are selected as a function of the operating pressure in such a way that the drop in output due to back pressure is minimized. The suitable switching positions can be determined by tests and there is also the possibility of making a variable correction of the switching positions depending on the operating pressure if this is changed. The corresponding specifications can be made manually, analogously or digitally. The electronic control can have a memory device for storing different operating parameters and for assigning these operating parameters at different control times of the valve or valves. The operating parameters stored in the storage device can either be selected manually or a selection is made by measuring the actual operating parameters and assigning them to the stored operating parameters.

In the latter case, corresponding measuring devices are provided for measuring, for example, the operating pressure, the counter pressure, the speed and the like.

In a preferred practiced embodiment, the pump drive can be an eccentric or crank drive with a have running crank member and a connecting rod connected to the working diaphragm or similar displacement element, the crank member being able to oscillate back and forth in any region within the total circulating movement for smaller deflections of the working diaphragm compared to the maximum possible deflections during a circulating movement. The eccentric or crank drive converts a rotary movement into a linear movement of the displacement element. This executes back and forth movements within the extreme positions at the top and bottom dead center of the crank mechanism. The pendulum stroke movement intended for a smaller working stroke, on the other hand, has a substantially lower amplitude, the drive not rotating, but instead carrying out a corresponding reciprocating movement with its rotating crank member by reversing the driving positioning motor accordingly.

It can be adjustable for the pendulum stroke movement with respect to the maximum amplitude reduced amplitude both the number of working strokes of the Arbeitsme brane or the like per unit of time and / or the drive speed. Both measures can be used to influence the metered quantity and also the pump characteristics, particularly with regard to the conveying speed. Thus, a small stroke at a high working speed or vice versa, a large stroke at a low working speed can be set for a constant delivery rate. In the latter case, the medium is pumped more gently.

There is also the possibility that the electronic control is designed to set a non-uniform drive speed of the drive motor, in particular for a fast suction stroke and a slower metering stroke. An irregular or pulse-like outflow of the pumped medium can thus be reduced. The compensation corresponds almost to a sinusoidal movement with the superposition of the hydraulic phenomena specific to diaphragm pumps. The appropriate stroke compensation can be specified by a speed curve per revolution or working stroke, which is stored in the electronic control in a parameterized manner.

According to one embodiment of the invention, the inlet and / or the outlet valve as a motorized valve drive can have an electromagnetic lifting magnet which has a lifting armature which is guided by means of spaced leaf springs and which is in drive connection with a valve closing body. The mounting of the armature of the lifting magnet with the aid of at least two leaf springs results in a spring parallelogram guide which is practically wear-free and insensitive to contamination, since there are no parts with sliding guide bearings. At the same time, the armature is guided exactly and radially without play in the stroke direction. The lifting drive for the inlet valve and / or possibly also for the outlet valve is particularly long-lasting due to these measures.

At least one of the leaf springs of the lifting armature guide is expediently prestressed in the closing direction of the externally operated valve. As a result, the valve is closed when the solenoid is not activated and is therefore leak-proof. In addition, an inexpensive, single-acting electric solenoid can be used because the leaf spring (s) take over the closing movement of the valve.

According to one embodiment of the invention, in addition to an externally actuated valve, at least one valve which can be actuated by the pumped medium can be designed in particular with an elastic valve disk which, in the closed position, rests with a flat side on the opening edge of an inflow channel which forms a valve seat and that on the side of the valve disk facing away from the inflow channel, within the projection extension of the inflow channel, a web-like abutment is provided which supports the valve disk at least in the valve open position. The proposed design of the valve results in a good seal even in the event of only slight pressure differences that may occur during operation. As a result, the pump has good vacuum properties even at low working speeds.

It is advantageous if the above-described valve which can be actuated by the pumped medium forms a complete, interchangeable unit and is designed as a valve insert with an abutment plate which has the abutment and an outflow channel, a valve receiving plate and the valve disk, and that the abutment plate and the valve receiving plate preferably interlock with one another have and are in particular welded, glued or connected in the assembled position. The parts for the complete valve inserts can thus be produced independently of the pump head in which the valve insert is inserted, which has considerable advantages in terms of accuracy in terms of injection technology. The high precision of the valve parts leads, among other things, to stress-free mounting of the valve disc, which is a prerequisite for reliable valve operation with good sealing, even with low pressure differences and very slow movements. In addition, the valve inserts can be replaced very easily overall.

As a drive and positioning motor, the pump drive can be a controlled or a regulated motor, in particular a stepper motor or a motor operating in a control loop Motor, for example a DC servo motor or the like. This makes it possible to move a defined angle at a defined speed. The direction of rotation of the motor is reversible, so that the pendulum stroke movements, which are small in comparison, can also be carried out within the overall working movement.

A contactless, for example optoelectronic or magnetic position transmitter is preferably provided as the position transmitter, which cooperates with the positioning motor or a part driven by it and is connected to the control electronics. As a result, the position of the working diaphragm is known in every operating phase, so that accordingly a drive motor working in a control circuit receives a position feedback and, on the other hand, the inlet and / or outlet valve can be controlled precisely in accordance with the position of the working diaphragm. The position transmitter can be designed such that it emits a reference signal at prominent positions, for example the top or bottom dead center, from which the intermediate positions can be calculated within one revolution or a pendulum movement of the pump drive. The position transmitter can, however, also have an encoder, by means of which the respective position of the pump drive or the working diaphragm driven thereby can be deduced directly.

Additional embodiments of the invention are listed in the further subclaims. The invention with its essential details is explained in more detail below with reference to the drawings.

It shows: 1: A perspective view of a metering pump with control,

2 shows a sectional illustration of a metering pump with an electromagnetically actuated inlet valve,

3: shows a longitudinal section and

4: a cross-sectional representation of a metering pump and

5: a cross section of a valve insert.

A metering pump 1 shown in FIG. 1 has a motor-driven pump drive 2 for an oscillating movement of a displacement element. The metering pump 1 has a pump housing 3 with a pump head 4, in which at least one inlet valve and one outlet valve are arranged. To actuate these valves, electromagnetic lifting drives 5, 6 are provided in the exemplary embodiment according to FIG. 1. The electromotive pump drive 2, the electromagnetic stroke drives 5, 6 for the valves and a position transmitter for detecting the position of the pump drive are connected to an electronic control 7. With the help of this electronic control 7, the pump drive 2 formed by a positioning motor can be variably controlled with regard to its speed and direction of rotation. In addition, the electronic control 7 is designed such that the pump drive can be moved back and forth in any region of its overall working movement with a predetermined stroke using the positioning motor. By means of this pendulum stroke movement, a delivery rate that is reduced compared to the maximum delivery rate can be set. The pump drive can thus be operated with a predeterminable angle of rotation and a predeterminable speed. The valves provided with electromagnetic lifting drives 5 and 6 in the exemplary embodiment according to FIG. 1 also allow the working position of the pump drive to be assigned any closing and opening times. It can be used to specify a variety of operating parameters in order to adapt the pump to a wide variety of operating conditions.

Figure 2 shows a sectional view of the internal structure of a metering pump according to the invention. This is designed as a diaphragm pump with a diaphragm 8 as a displacement element, the diaphragm having a crank mechanism 9 as a pump drive with a rotating crank member 10 and a connecting rod 11 connected to the diaphragm 8. The crank member 10 is connected to the positioning motor 12 (see FIG. 3). In the exemplary embodiment shown in FIG. 2, only the inlet valve 13 is provided with an electromagnetic lifting drive 5, while the outlet valve is a valve which can be actuated by the pumped medium. The outlet valve 14 is designed as a valve which is sensitive to small pressure differences. For certain dosing tasks where a minimum delivery speed is used, this training can be used with different valves. However, if the delivery speed falls below this minimum required for a valve actuated by the pumped medium, or if special dosing tasks are to be solved, externally operated valves are provided for both the inlet valve and the outlet valve. This enables the valves to be closed and opened independently of the pressure difference occurring in the valve area. This also provides a decoupling of the valve function from the respective position of the pump drive. When using a valve actuated by the pumped medium, as is provided in the exemplary embodiment according to FIG. 2, the valve 15 shown in FIG. 5 can, for example, optionally be provided as an inlet valve or an outlet valve. This valve 15 is designed such that it shows a reliable sealing behavior even at low working or conveying speeds and the low differential pressures that occur between the suction side and the pressure side. The valve is designed as a disc valve and essentially has a replacement plate 16, a valve disc 17 and a valve receiving plate 18. From these three parts 16, 17 and 18 a complete, dose-shaped unit is formed as a valve insert. This valve insert can be inserted into a corresponding recess in the pump head.

In the case of a valve arranged on the suction side, the valve disk 17 lies with its flat side facing the suction side 19 in the closed position on the opening edge 20 of a central inflow channel 21 forming a valve seat in the valve receiving plate 18. Against lateral displacement, the valve disk 17 is held by positioning pins which are arranged laterally next to the opening edge and engage in open recesses in the valve disk 17. The abutment plate 16 has a web-like abutment 22 within the projection extension of the inflow channel of the valve mounting plate 18, via which the valve disk 17 is supported in the open position approximately along a diameter line. In the open position of the valve, the valve disk lobes located on both sides of the middle support line are pivoted toward the replacement plate 16, so that the inflow channel 21 is open. The distance between the plane passing through the support point of the abutment 22 and the parallel plane formed by the opening edge 20 is dimensioned such that the valve disk 17 is in between is kept tension-free. This is a prerequisite for the valve disc to respond even at the slightest pressure difference and also for a quick closing or opening process. When using the valve 15 on the pressure side, it is used turned through 180 degrees.

As already mentioned, externally operated valves are preferably used both for the inlet valve 13 and for the outlet valve 14. Such is shown as an inlet valve in FIG. 2. The electromagnetic lifting drive 5 has a lifting armature 25 which is guided by means of spaced leaf springs 23, 24 and which is in drive connection with a valve closing body 26. In the axial extension of the lifting armature 25, a sleeve-shaped iron pole 27 is arranged at a distance from it. Around this and the lifting armature there is a coil 28 which, when excited, leads to the lifting armature 25 being moved in the direction of the arrow Pf 1 and thereby bringing the valve closing body 26 into the open position.

A parallelogram guide for the lifting armature 25 is formed by the two leaf springs 23, 24, so that no parts mounted in a sliding guide are required. The lifting armature 25 is guided exactly and radially without play in the lifting direction. At least one of the two leaf springs of the lifting anchor guide is preferably biased in the closing direction. As a result, the valve goes into the closed position in the de-energized state, which is shown in FIG. To transmit the lifting movement of the lifting armature 25 on the valve closing body 26, a rocker arm 29 is provided which is coupled with its drive end to an axis 30 connected to the lifting armature and with its other end to the valve closing body 26. In the course of the longitudinal Covering the rocker arm 29, a rocker bearing 31 is provided which surrounds the rocker arm 29 in a sealing manner and which also seals a valve chamber to the outside.

The rocker bearing is preferably designed as an elastomer feedthrough, so that there is absolute tightness.

As can be seen particularly well in FIGS. 3 and 4, the metering pump 1 is equipped with a position transmitter 32 for detecting the position of the pump drive or the diaphragm 8 forming the displacement element. In the exemplary embodiment, the position transmitter has a magnet 33 which rotates with the crank member 10 and a magnetic sensor which is preferably designed as a Hall sensor and is arranged in a stationary manner next to the orbit of the magnet 33. With each revolution of the pump drive, a reference signal is generated, which is used to orientate the further positioning. In particular when using a stepper motor in which the respective positioning can be predetermined by a certain number of steps, the reference signal is used, for example, to reset or to generate a specific correction value. When using a stepper motor, smallest step angles are possible, so that the diaphragm 8 can be brought into any position within its overall working range. The adjustment can take place extremely slowly, whereby work strokes extending over several minutes are possible, but on the other hand, work can also be carried out at high speed in order to achieve a high delivery rate.

In addition to the non-contact position transmitter shown in the exemplary embodiment, other position sensors, for example optoelectronic position transmitters, can also be used, which may emit a large number of position data in the course of one revolution. It should be mentioned here that instead of a stepper motor, a motor working in a control loop, for example a DC servo motor can be used.

As can be seen in FIG. 1, the positioning motor 2, the electromagnetic lifting drives 5 and 6 for the inlet valve 13 and the outlet valve 14 and the position transmitter 32 are connected to the electronic control 7. The operation of the pump can be varied within wide limits. For example, the electromagnetic linear actuators 5, 6 of the valves can be controlled as a function of the position of the diaphragm 8.

On the other hand, there is also the possibility of opening or closing the valves regardless of the position of the pump drive or the diaphragm. For example, this can take place as a function of different operating parameters, in particular as a function of the operating pressure, the speed, the consistency of the delivery medium and the like. There is the possibility that with the help of a storage device different operating parameters are stored in the storage device, which can then be assigned to different control times of the valves.

Appropriate measuring devices are provided for measuring operating parameters, such as operating pressure, back pressure, speed. In addition to the aforementioned operation of the pump with a diaphragm that can be reciprocated within the overall working movement for a reduced delivery rate, the electronic control 7 can also be used to set a non-uniform working speed of the drive motor for a fast suction stroke and a slower metering stroke. This means that instead of an otherwise approximately sinusoidal one

Liquid flow can be achieved to make the flow more even. If both valves are externally controlled, this also opens up the possibility of changing the direction of delivery. This possibility is particularly advantageous in the case of a metering pump, because after a metering process with the delivery medium being pushed out of the pressure channel, undesired after-running or dripping of the delivery medium can be avoided by changing the delivery direction by reversing the two valves. A partial stroke of the working diaphragm with a reversed valve closing sequence is usually sufficient to avoid the aforementioned after-running or dripping of the medium.

This means that during the suction stroke of the diaphragm, the outlet valve is opened with enlargement of the working space, while the inlet valve is closed. The metering accuracy of the metering pump 1 can be significantly improved by this measure and it is also easier to use when setting the metered quantity. The metering pump 1 with externally controlled inlet and outlet valve 13, 14 can be used not only for return conveyance to avoid overrun, but also for continuous conveyance in both conveying directions.

Claims

claims

1. dosing pump (1), in particular diaphragm dosing pump with a working diaphragm delimiting a working space or the like displacement element and a pump drive (2) for an oscillating movement of the displacement element, the pump drive (2) being reversible and the displacement element being movable back and forth A position transmitter for detecting the position of the pump drive (2) and an electronic control (7) are provided therefor, and with a pump head in which an inlet valve and an outlet valve (14) are arranged, characterized in that the pump drive (2) has a Positioning motor and with its part connected to the displacement element in an arbitrary range of its total working movement with a predeterminable stroke can be moved back and forth for a delivery volume that is reduced compared to the maximum delivery volume, that at least one of the at least two valves (13) is externally controlled and a motorized valve Has drive and that the electronic control (7) at least with the motorized valve drives of the inlet and / or outlet valve (14), with the positioning motor of the pump drive (2) and the position transmitter for detecting the position of the displacement element and / or the pump drive (2) is connected.

2. Dosing pump (1) according to claim 1, characterized in that the pump drive (2) with its part connected to the displacement element for a compared to the reduced flow rate with a reciprocating reciprocating working stroke increased or maximum flow rate per Ar- beitshub, in particular circumferential and controllable.

Dosing pump (1) according to claim 1 or 2, characterized in that the electronic control (7) is designed for variable control of the motorized valve drive (s) of the inlet (13) and / or outlet valve (14) depending on the position of the displacement element.

4. dosing pump (1) according to any one of claims 1 to 3, characterized in that the electronic control (7) for controlling the motor valve drive (s) of the inlet (13) and / or outlet valve (14) depending on different operating parameters, in particular depending on the operating pressure, the speed, the consistency of the pumped medium and the like.

5. dosing pump (1) according to one of claims 1 to 4, characterized in that the electronic control (7)

Storage device for storing different operating parameters and for assigning these operating parameters at different control times of the valves.

6. dosing pump (1) according to one of claims 1 to 5, characterized in that one or more measuring devices for measuring operating parameters such as operating pressure, back pressure, speed, delivery rate and the like are provided.

7. dosing pump (1) according to one of claims 1 to 6, characterized in that the pump drive (2) one Eccentric or crank drive (9) with a revolving crank member (10) and a connecting rod (11) connected to the working diaphragm or similar displacement element and that the crank member (10) for smaller deflections of the working diaphragm compared to the maximum possible deflections during a circulating movement , can be moved back and forth in any area within the total orbital movement.

8. dosing pump (1) according to one of claims 1 to 7, characterized in that the electrically externally actuated valve (15) is closed in the de-energized state.

9. dosing pump (1) according to one of claims 1 to 8, characterized in that the inlet and / or the outlet valve

(13, 14) as a motorized valve drive has an electromagnetic lifting magnet (5, 6) which has a lifting armature (25) which is guided by means of spaced leaf springs (23, 24) and which is in drive connection with a valve closing body (26).

10. dosing pump (1) according to claim 9, characterized in that at least one of the leaf springs (23, 24) of the lifting armature guide is biased in the closing direction of the externally operated valve (15).

11. Dosing pump (1) according to one of claims 1 to 10, characterized in that in addition to an externally actuated at least one actuatable by the pumping medium valve (15) in particular with an elastic valve disc (17) is formed, which in the closed position with a flat side on one Valve seat forming opening edge (20) of an inflow channel (21) rests and that on the A web-like abutment (22) supporting the valve disk (17) and supporting the valve disk (17) at least in the valve-open position is provided within the projection extension of the inflow channel (21) facing away from the inflow channel (21).

12. Dosing pump (1) according to claim 11, characterized in that the valve (15) which can be actuated by the pumped medium forms a complete, interchangeable unit and as a valve insert (21) with an abutment (28) and an outflow channel (31) Abutment plate (18), a valve mounting plate (18) and the valve disk (17) is formed and that preferably the abutment plate (16) and the valve mounting plate (18) have interlocking edge formations and are welded, glued or the like connected in the mounting position.

13. Metering pump (1) according to one of claims 1 to 12, characterized in that the starting position of the working diaphragm (6) or the like is the same at the beginning and at the end of a metering and preferably the bottom dead center position.

14. Dosing pump (1) according to one of claims 1 to 13, characterized in that the number of working strokes of the working diaphragm (6) or the like per unit time and / or the drive speed are adjustable.

15. Dosing pump (1) according to one of claims 1 to 14, characterized in that the pump drive (2) as a drive and positioning motor (12) is a controlled or a regulated motor, in particular a stepper motor or has a motor operating in a control circuit, for example a DC servo motor or the like.

16. Dosing pump (1) according to one of claims 1 to 15, characterized in that a contactless, for example optoelectronic or magnetic position transmitter (32) is provided as the position transmitter (32), which is connected to the positioning motor (12) or one of these. driven part cooperates and is connected to the control electronics (7).

17. Dosing pump (1) according to one of claims 1 to 16, characterized in that the electronic control (7) is designed to set a non-uniform drive speed of the drive motor, in particular for a fast suction stroke and a slower metering stroke.

18. Dosing pump according to one of claims 1 to 17, characterized in that the two valves are externally controlled and can be reversed as an inlet valve or outlet valve for a reversal of the conveying direction.