US20140017097A1

US20140017097A1 - Pump module and positive displacement pump

Info

Publication number: US20140017097A1
Application number: US13/928,970
Authority: US
Inventors: Armin Conrad
Original assignee: Pfeiffer Vacuum GmbH
Current assignee: Pfeiffer Vacuum GmbH
Priority date: 2012-07-11
Filing date: 2013-06-27
Publication date: 2014-01-16
Also published as: JP2014015930A; JP5976598B2; DE102012013681A1; EP2685104B1; EP2685104A1

Abstract

A pump module (4, 5, 6; 4′, 4″) includes a housing (14) that limits at least one channel (17) connecting at least one inlet with at least one outlet, an elastic membrane (18; 21; 22) extending in the housing in a flow direction, and a plurality of actuators located in the housing opposite each other on both sides of the at least one flow channel and forming actuation stages (A1-A6) arranged one after another in the flow direction, with a respective section of the elastic membrane being deflected and abutting a respective circumferential section of the at least one flow channel upon activation of an actuator of a respective actuation stage for forming a delivery chamber.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a pump module having a housing with at lest one inlet and at least one outlet, at least one channel located in the housing and connecting the at least one inlet with the at least one outlet, pumping element extending in the housing in a flow direction, a plurality of individually activated actuators for sectionally deflecting the pumping element, and at least one delivery chamber for enclosing a delivering medium and which becomes encapsulated between sections of the pumping element and corresponding circumferential sections of the at least one flow channel upon sequential activation of the actuators and in course of a delivery movement is displaced between the at least one inlet and at the at least one outlet. The present invention also relates to a positive displacement pump for delivering a fluid in which at least one above-mentioned module is used.
2. Description of the Prior Art
In positive displacement pumps, usually, medium that flows into the pump interior through an inlet, is encapsulated in the delivery chamber and is finally displaced into an outlet. In order to prevent backflow of the medium into the inlet during this displacement and to exclude back suction of the already displaced medium, there is provided a pressure-operated valve for controlling at least one of the inlet or outlet or similar means. This, however, increases the number of components and, in addition, makes it more difficult to achieve a low end pressure. This is because the valves are mainly operated based on the pressure difference and, at a low pressure, no sufficiently high pressure forces can be provided in the valve region. In addition, dependent on the type and manner of the delivery movement, friction losses and vibrations occur. Usually, the positive displacement pumps are equipped partially with pump modules, with which the number of components is reduced and the delivery movement is obtained in a most simple way.
Japanese Publication JP 03-081585 discloses a pumping module having a housing that limits a cuboid flow channel. The flow channel connects an inlet and an outlet and has a pumping element located therein. The pumping element is oriented in the flow direction and is formed of a plurality of piezoelectrical actuator sections arranged in a row one after another and forming a lamella located in the flow channel. Upon activation of individual piezoelectrical actuator sections, the lamella is sectionally deflected, abutting respective sections of the surrounding housing, enclosing to-be-delivered medium within a respectively formed, as a result of deflection, delivery chamber. With sequential activation of the piezoelectrical actuators, the enclosed in the respective delivery chamber, medium is displaced, in the course of a peristaltic delivery movement, from the inlet to the outlet.
Proceeding from the above-discussed state-of-the-art, the object of the invention is to provide a pump module with which a precise delivery movement is achieved together with simplification of the structure.

SUMMARY OF THE INVENTION

The object of the invention is achieved, according to the invention, with a pump module having a housing with at least one inlet and at least one outlet, at least one channel located in the housing and connecting the at least one inlet with the at least one outlet, and a pumping element extending in the housing in a flow direction. A plurality of individually activated actuators sectionally deflect the pumping element. The pump module further has at least one delivery chamber for enclosing a delivering medium and which becomes encapsulated between sections of the pumping element and corresponding circumferential sections of the at least one flow channel upon sequential activation of the actuators and in course of a delivery movement is displaced between the at least one inlet and the at least outlet.
The pumping element is formed as a washer-shaped, plate-shaped or the like component that can be sectionally deflected, with separate segments being displaced orthogonally to the longitudinal extension of the pumping element by the actuators. With this, dependent on the number of the deflected sections of the pumping element, one or more delivery chambers become enclosed with one or more circumferential sections of the flow channel, with a to-be-delivered medium being enclosed in the respective delivery chamber. According to the invention, the delivery medium is, in particular, a fluid, such as gas or a gas mixture, or liquid, or a liquid mixture. By a sequential activation of the actuators, the at least one delivery chamber is displaced between the at least one inlet and the at least one outlet of the pump module, so that the enclosed therein to-be-delivered medium is delivered from inlet to the outlet. This delivery movement is similar, with a corresponding activation of the actuators, in particular, to peristaltic movement of the pumping element.
The present invention includes teachings according to which the actuators are located in the pump module housing opposite each other on both sides of the at least one flow channel and form actuation stages arranged one after another in the flow direction. Further, the pumping element is formed as an elastic membrane that, upon activation of an actuator of a separate actuation stage, has a respective section thereof abutting a respective circumferential section of the flow channel. With other words, the actuators, with which the pumping element that is located in the flow channel, can be sectionally deflected, are placed in the surrounding housing and are pair-wise combined to form actuation stages. The respective associated actuators are located on both sides of the flow channel, i.e., one actuator of an actuation stage is positioned above the flow channel, and the other actuator is positioned below the flow channel. Altogether, the actuation stages are arranged one after another in the flow direction so that upon moving along, the individual actuation stages are passed over. The pumping element, which is formed as an elastic membrane, thus, can be sectionally deflected when an actuator of an individual actuation stage is activated, with a section of the membrane located between the actuators of this actuation stage being deflected, abutting the located there, circumferential section of the flow channel.
The inventive pump is characterized by a simple construction, with simultaneously a reliable functioning. By placing the actuators in the stationary housing, they can be activated in simple manner with conductors running in the housing, with these conductors being chambered from the flow channel and the medium delivered therethrough. Due to the manner of the flow movement, the valves on the inlet side and the outlet side can be dispensed with because the to-be-delivered medium is encapsulated between the elastic membrane and the circumference of the flow channel due to the sectional deflection of the elastic membrane. The membrane is a sole movable component so that with an appropriate optimization, a long service life of the inventive pump module can be achieved. Besides, the membrane, being an elastic component, can be precisely deflected and abut the circumference of the flow channel, whereby the respective delivery chamber can be precisely defined and sealed. Further, the pumping frequency of the pump module and the pumping sequence, i.e., the definition of the size of the at least one delivery chamber, can be freely adjusted with the actuators, which makes the inventive pump module universally suitable for different applications, with the activation of the actuators being varied dependent on the desired delivery. All in all, the inventive pump module is characterized by a simple construction, together with low manufacturing costs and low noise generation.
In distinction therefrom, in JP 03 081 585 A, the actuation of the pumping element that is located in the flow channel, is more difficult because for the sectional deflection of the piezo-sections provided in the lamella-shaped components, they should be correspondingly energized. To this end, corresponding contacts need be provided or conductors should be lead up to the deflectable pumping element, which complicates the construction of the pumping module and, as a result, increases manufacturing costs. Further, the lamella which is provided with piezo-elements is less flexible than the membrane, with the definition of the delivery chambers being strictly defined in accordance with the size and arrangement of the piezo-sections. Therefore, a pumping sequence cannot be individually adapted to separate applications.
Also, the nestling of the lamella against the circumference of the flow channel is less precise than with an elastic membrane.
According to an advantageously embodiment of the present invention, the actuators are formed as solenoids. Those are surrounded by a material that has a high permeability, e.g., iron, and produce, upon being energized, a magnetic field that deflects respective sections of the elastic membrane. In order to achieve the sectional deflection of the membrane in the magnetic field, the membrane is formed of a magnetorheological elastomeric material or an elastomeric material with ferromagnetic material integrated in sections associated with the actuation stages. A magnetorheological material is a composite material of a weak elastomer matrix with magnetically polarized particles embedded therein which can be subjected to action of the magnetic field. In case when the membrane is formed of an elastomeric material with ferromagnetic particles embedded therein, according to the invention, metal sheet segments are cast over by the elastomeric material, forming a connection system.
According to an alternative embodiment of the invention, the actuators are formed by electrodes. Upon being energized, these electrodes produce an electrical field which again can sectionally deflect the elastic membrane. To this end, the elastic membrane is formed in particular of an electrorheological material of an elastomer with embedded therein particles which are pulled in the electrical field in direction of respective energized electrodes, causing a corresponding sectional deflection of the elastic membrane.
According to a further embodiment of the invention, the pump module housing is formed of two housing parts, wherein the housing parts and the membrane, which lies therebetween, are formed as discs having a circular cross-section. Further, the at least one inlet is provided radially outwardly and is connected by the flow channel with the at least one outlet which is arranged centrally in the radial direction. In this case the pump module has a circular shape, with the delivered medium being delivered from radially outwardly to radially inwardly to the outlet. According to the invention, the inlet can likewise be placed centrally, and the outlet can lie radially outwardly. With the circular construction of the pump module, a plurality of pump modules can be arranged without problems one after another, with the separate circular pump modules being axially stacked one above the other and dependent on the desired switching, form a parallel arrangement of separate inlets, or have at least one outlet of one module connected with at least one inlet of the following module in form of a series connection. With a circular construction of the pump module of circular discs, the actuators are correspondingly ring-shaped, i.e., are formed as ring-shaped solenoids or ring-shaped electrodes. Alternatively, together with a circular construction, in principle, a rectangular construction of the pump module can also be contemplated.
According to a further development of the invention, the actuation stages can be arranged, in the flow direction, equidistantly or at different distances relative to each other. Dependent on the construction of the pump module and the type of the deliverable medium, the at least one delivery chamber can have, during its movement between the at least one inlet and the at least one outlet, a constant or variable volume. In this way, a medium in form of gas or a gas mixture can be compressed during its movement from at least one inlet to the at least one outlet. At a circular construction of the pump module, the distances between the actuation stages are selected so that they are equidistant, so that with at least one delivery chamber, upon movement from a radially outwardly located inlet to a centrally located outlet, its volume continuously diminishes because of ever smaller annular surfaces between the actuation stages, and compression of the gas takes place. Similarly, with a rectangular construction, with different distances between the actuation stages, a continuously diminishing of the at least one delivery chamber occurs.
If the deliverable medium is liquid, because of the incompressibility of the liquid, usually, the reduction of the volume of the at least one delivery chamber is not desirable. This volume can be kept constant during movement between the at least one inlet and the at least one outlet, with a circular construction of the pump module, by placing the separate actuation stages at different distances from each other in the flow direction for forming identical ring surfaces, or with a rectangular construction of the pump module, by selecting the same distances between the actuation stages. Finally, a delivery of a liquid, at a circular construction of the pump module and an equidistant distances between the actuation stages, is also possible when the at least one inlet is centrally located in the flow direction, and the at least one outlet is provide radially outwardly, so that the volume of the at least one delivery chamber increases during movement between the inlet and the outlet.
Different or the same volumes of the delivery chamber can also be achieved by a corresponding adjustment of the pump frequency. Because encapsulation and movement of a respective delivery chamber is controlled by activation of respective actuation stages, the size and the change of the delivery chamber can be adjusted substantially freely by varying activation of the actuation stages. Thus, the compression of the medium, which otherwise takes place, based on the spacing between the actuation stages and the construction of the pump module, during movement of the delivery chamber, is thereby increased or reduced, so that at the outlet side or respective desired pressure level of the medium is achieved.
A positive displacement pump according to the invention includes at least one pump module according to one of the embodiment discussed above. The positive displacement pump is formed in particular as a vacuum pump that serves for delivering a fluid. Advantageously, several pump modules, which are arranged seriesly and/or parallel to each other, are arranged in the pump housing, so that individual pump model, which are arranged parallel to each other or follow one another, deliver fluid to a common outlet.
According to a further advantageous embodiment of the invention, the actuators of at least one pump module are controlled by power electronics. With such power electronics, different pump frequencies and, also, pump sequences can be obtained without problem by corresponding activation of the actuators. However, activations of several pump modules, which are correspondingly adapted to each other, can also be carried out. Apart from the power electronics associated with one of the pump modules, a corresponding electronic of another pump such as, e.g., turbomolecular pump, or of another system can be used.
A positive displacement pump according to one of the above-described embodiments can be used in a recipient as a vacuum pump, in particular, for obtaining low and high vacuum. Further, a positive displacement pump formed, according to the invention, as a vacuum pump can be used as a fore-vacuum pump of a high and/or ultra-high vacuum pump, in particular, of a turbomolecular pump.
The present invention is not limited to the discussed combination of related claims or dependent claims. In addition, there exist a number of possibilities to combine with each other separate features which follow from the claims, the description of different embodiment of the invention, and/or the drawings. The reference in the claims to the drawings by the use of reference numerals does not limit the scope of the claim in any way.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantageous embodiments of the invention will be described in detail below with reference to the accompanying drawings.

The drawings show:

FIG. 1 a schematic view of a first preferred embodiment of a positive displacement pump according to the invention;

FIG. 2 a schematic view of a first embodiment of a pump module of the positive displacement pump shown in FIG. 1;

FIG. 3 a view illustrating separate switching sequences of the pump module shown in FIG. 2;

FIG. 4 a schematic view of another embodiment of a pump module of the positive displacement pump shown in FIG. 1;

FIG. 5 a schematic view of yet another embodiment of a pump module of the positive displacement pump shown in FIG. 1;

FIG. 6 a schematic view of a second embodiment of a positive displacement pump according to the invention;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 shows a schematic elevational view of a positive displacement pump according to the first embodiment of the invention, wherein the positive displacement pump is a vacuum pump and, preferably, a fore-vacuum pump of a turbomolecular pump. The positive displacement pump includes a pump housing 1 in which between a lateral inlet side 2 and an end outlet side 3, there are provided a plurality of identically formed pump modules 4, 5 and 6. The pump modules 4-6 are formed as circular, rotationally symmetrical modules which are connected, respectively, with the inlet side 2 by their ring-shaped inlets 7, 8 and 9, and are commonly connected with the outlet side 3 by respective centrally located outlets 10, 11, 12. The pump modules 4-6 are, thus, arranged in the pump housing 1 parallel to each other and deliver a fluid, in particular, in form of an air mixture from the inlet side 2 to the outlet side 3. Further power electronics 13 which can control the separate pump modules 4, 5, 6, is also located in the housing 1.
FIG. 2 shows a schematic elevational view of a pump module 4 the construction of which, however, corresponds to that of the pump modules 5 and 6. The pump module 4 has a housing 14 formed of two housing parts 15 and 16 which a formed as discs having a circular cross-section and limit a flow channel 17 extending therebetween, with the housing parts 15 and 16 being chambered from each other. The flow channel 17 connects the ring-shaped inlet 7, which is only suggested, with the central outlet 10. In FIG. 2, for the sake of clarity, in the radial direction, only half of the pump module 4 is shown. Over the flow channel 17, fluid can flow radially through the housing 14 from the inlet 7 and then axially through the outlet 10 to the common outlet side 3 shown in FIG. 1.
A membrane 18 is located in the flow channel 17 and which is located between the two housing parts 15 and 16 and is shown in FIG. 2 in its rest position. To this end, the membrane 18 is clamped in a suitable manner between the housing parts 15 and 16, e.g., in the region of the ring-shaped inlet 7. The membrane 18 is likewise formed as a disc with a circular cross-section and is formed of an elastomeric material in which a plurality of sheet rings B1-B6, which are concentrically arranged about the outlet 10, are integrated.
As further shown in FIG. 2, in the radial direction over the height of the sheet rings B1-B6, there are further provided a plurality of actuator stages A1-A6 which are arranged one after another in the flow direction from the inlet 7 to the outlet 10. Each actuator stage A1-A6 is formed of two actuators arranged on opposite sides of the flow channel 17 and on opposite sides of respective sheet rings B1-B6. The actuators of the actuator stages A1-A6 are formed of located opposite each other, solenoids M1.1-M6.2 which are surrounded by iron and are combined in pairs, forming the actuator stages A1-A6. The power electronics 13 energizes the actuator stages A1-A6, energizing the combined in pairs, solenoids M1.1 or M1.2 or M2.1 or M2.2 or M3.1 or M3.2 or M4.1 or M4.2 or M5.1 or M5.2 or M6.1 or M6.2, so that respective solenoids produce a magnetic field attracting respective, located therebetween, sheet rings B1 or B2 or B3 or B4 or B5 or B6 thereto, sectionally deflecting the membrane 18. With this, the membrane 18 abuts the housing parts 15 or 16 with a respective section and, thus, a circumferential section of the flow channel 17, whereby with a corresponding control of separate solenoids M1.1-M6.2, delivery chambers are defined between the membrane 18 and the housing parts 15 and 16.
FIG. 3 shows a complete, exemplary switching sequence for the pump module 4 shown in FIG. 2. As can be seen, a delivery movement from the inlet 7 to the outlet 10 can be shown in five separate sequences, wherein the sequence 5 again corresponds to the sequence 1. A respective one of the solenoids M1.1 through M6.2 is actuated by separate actuator stages A1 through A6, so that the intermediately located membrane 18 have respective sections thereof deflected in this direction of the housing part 15 or 16 and finally abuts the same. With altogether six actuator stages A1 through 16, on one hand, delivery chambers 19, 19′ can be defined between the membrane 18 and the housing part 15, and on the other hand, delivery chambers 20 and 20′ can be defined between the membrane 18 and the housing part 16 which are movable from the inlet 7 to the outlet 10 in the course of the pumping sequence.
This delivery movement, which is called peristaltic movement, will be described, by way of example, with reference to the delivery chamber 19 by respective separate sequences I through V on basis of FIGS. 2 and 3. Firstly, in the first sequence I, the delivery chamber 19 is encapsulated by energizing the solenoids M1.1, M2.2, M3.2 and M4.1, enclosing a corresponding amount of fluid between the membrane 18 and the housing part 15. The delivery chamber 19 is then displaced, during the second sequence II, further in direction of the outlet 10, with the solenoid M2.1 being energized instead of the solenoid M2.2 in the actuator stage A2, with the solenoid M4.2 being energized instead of the solenoid M4.1 in the actuator stage A4, and with the solenoid M5.1 being energized in the actuator stage A5. For transition to a further sequence III, in comparison with the sequence II, in the actuator stage A3, instead of the solenoid M3.2, the solenoid M3.1 is energized, and in the actuator stage A5, instead of solenoid M5.1, the solenoid M5.2 is actuated. In addition, in the actuator stage A6, the solenoid M6.1 is energized. Finally, in the sequence IV, the fluid located in the delivery chamber 19 is fed to the outlet 10, and in which in comparison with the sequence III, in the actuator stage A4, instead of the solenoid M4.2, the solenoid M4.1 is actuated, and in the actuator stage A6, instead of the solenoid M6.1, the solenoid M6.2 is actuated. In the sequence V, a new cycle starts, with encapsulation of the delivery chamber 19′.
FIG. 2 shows that the actuator stages A1 through A6 are equidistantly located with respect to each other. In combination with the circular form of the housing parts 15, 16 and the membrane 18, the delivery chambers 19, 19′, 20, 20′ are continuously reduced in their volume during the radial delivery movement because the ring volumes toward the outlet 10 defined between the actuator stages A1 through A6, become continuously smaller. As a result, the fluid, which is located in respective delivery chambers 19, or 19′ or 20, or 20′, becomes compressed as it is fed from the inlet 7 to the outlet 10. The power electronics 13 should insure a rapid exchange within each of the actuator stages A1 through A6 and between the actuator stages A1 through A6 to reduce to a most possible extent pressure fluctuations in the delivery chambers 19, 19′ 20, and 20 during movement toward the outlet 10.
FIG. 4 shows an alternative embodiment of a pump module 4′ that can be used in the possible displacement pump of FIG. 1 instead of the pump modules 4-6. In distinction from the pump module 4 shown in FIG. 2, the membrane 18 is formed of a magnetorhelogical elastomeric material formed of an elastomer with integrated nanoscaled particles. In a magnetic field, a force acting on these particles provides for the desired sectional deflection of the membrane 21 analogous to the delivery movement described with reference to FIG. 3. In all other respects, the pump module 4′ shown in FIG. 4 corresponds to the pump module of FIG. 2.
FIG. 5 shows a further alternative embodiment of a pump module 4″ that likewise can be used in the positive displacement pump of FIG. 1 instead of the pump modules 4-6. In distinction from the embodiment of FIG. 2, here, the actuator stages A1 through A6 are formed of pairs of located opposite each other electrodes E1.1 through E6.2. The electrodes E1.1 through E6.2 can again be separately actuated by the power electronics 13 to provide for the peristaltic delivery movement. In order to provide a sectional deflection of a membrane 22 by an electrical field generated by separate electrodes E1.1 through E6.2, the membrane is formed of an electroheological elastomeric material formed of an elastomer with integrated therein, nanoscaled particles. Under the action of the electrical field, a force acting on these particles can cause again a sectional deflection of the membrane 22. In all other respects, the configuration of the pump module 4″ of FIG. 5 is a variant of the pump module 4 of FIG. 2.
Finally, FIG. 6 shows a schematic elevational view of a positive displacement pump according to the second embodiment of the invention. In distinction from the embodiment of FIG. 1, the pump modules 4-6 are not arranged parallel to each other but are located seriesly, one after another in the flow direction. To this end, the inlet 7 of the pump module 4 is connected with the inlet side 2 of the positive displacement pump, and the outlet 10 of the pump module 4 is connected with the inlet 8 of the pump module 5. The outlet 11 of the pump module 5 again is connected with the inlet 9 of the pump module 6 the outlet 12 of which is connected with the outlet side 3 of the positive displacement pump. Here, the respective outlet 10, 11 or 12 is provided on an upper surface of the respective pump module 4, 5, 6, i.e., only the respective top housing part 15 is provided in the center with an axially extending through-bore. Generally, the configuration of the positive displacement pump of FIG. 6 is a variant of that according to FIG. 1.
With specific configuration of pump module 4-6 or 4′-6′; it becomes possible to simplify the construction while simultaneously insuring a reliable operation of the medium delivery. Also, the inventive pump module can be adapted, in any arbitrary manner to the configuration of the positive displacement pump. It is particularly useful in a fore-vacuum pump or a forevacuum pump stage of a turbomolecular pump.
Though the present invention was shown and described with reference to the preferred embodiments those are merely illustrative of the present invention and are not to be construed as a limitation thereof and various modifications of the present invention will be apparent to those skilled in the art. It is, therefore, not intended that the present invention be limited to the disclosed embodiments or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims.

Claims

What is claimed is:

1. A pump module (4, 5, 6; 4′, 4″), comprising a housing (14) having at least one inlet (7, 8, 9) and at least one outlet (10, 11, 12); at least one channel (17) located in the housing (14) and connecting the at least one inlet with the at least one outlet; an elastic membrane (18; 21; 22) extending in the housing in a flow direction; a plurality of actuators located in the housing, the actuators being sequentially individually activated for sectionally deflecting the elastic membrane for forming at least one delivery chamber (20, 21) between sections of the membrane and associated circumferential sections of the at least one flow channel for enclosing a to-be-delivered medium and movable, in course of a delivery movement between, the at least one inlet and the at least one outlet,

wherein respective actuators which are located opposite each other on both sides of the at least one flow channel form actuation stages (A1-A6) arranged one after another in the flow direction, with a respective section of the elastic membrane abutting a respective circumferential section of the at least one flow channel upon activation of an actuator of a respective actuation stage (A1-A6).

2. A pump module (4, 5, 6; 4′) according to claim 1, wherein the actuators are formed by solenoids (M1.1-M6.2).

3. A pump module (4, 5, 6; 4′) according to claim 2, wherein the membrane (18; 21) is formed of one of magnetorheological elastomeric material and elastomeric material with ferromagnetic material integrated in sections associated with the actuation stages (A1-A6).

4. A pump module (4″) according to claim 1, wherein the actuators are formed by electrodes (E1.1-E6.2).

5. A pump module (4″) according to claim 4, wherein the membrane (22) is formed of an electrorheological elastomeric material (23).

6. A pump module (4, 5, 6; 4′; 4″) according to claim 1, wherein the housing (14) is formed of at least two housing parts (15, 16), the membrane (18; 21; 22) which lies therebetween, is formed as a disc having a circular cross-section, and at least one inlet (7, 8, 9) faces radially outwardly, and at least one outlet (10, 11, 12) is arranged centrally in the radial direction.

7. A pump module according to claim 1, wherein the actuation stages (A1-A6) are arranged, in the flow direction, equidistantly or at different distances relative to each other.

8. A positive displacement pump for delivering fluid, comprising at least one pump module (4, 5, 6; 4′, 4″), including a housing (14) having at least one inlet (7, 8, 9) and at least one outlet (10, 11, 12); at least one channel (17) located in the housing (14) and connecting the at least one inlet with the at least one outlet; an elastic membrane (18; 21; 22) extending in the housing in a flow direction; a plurality of actuators located in the housing, the actuators being sequentially individually activated for sectionally deflecting the elastic membrane for forming at least one delivery chamber (20, 21) between sections of the membrane and associated circumferential sections of the at least one flow channel for enclosing a to-be-delivered medium and movable, in course of a delivery movement between the at least one inlet and the at least one outlet,

9. A positive displacement pump according to claim 8, comprising a housing (1), and a plurality of pump modules (4, 5, 6) arranged one of seriesly, parallel to each other, and seriesly and parallel to each other.

10. A positive displacement pump according to claim 8, comprising power electronics (13) for controlling actuators of the at least one pump module (4, 5, 6; 4′; 4″).

11. A method of producing one of low and high vacuum in a recipient, comprising a vacuum pump formed as a positive displacement pump for delivering fluid and comprising at least one pump module (4, 5, 6; 4′, 4″), including a housing (14) having a pump module (4, 5, 6; 4′, 4″) comprising a housing (14) having at least one inlet (7, 8, 9) and at least one outlet (10, 11, 12); at least one channel (17) located in the housing (14) and connecting the at least one inlet with the at least one outlet; an elastic membrane (18; 21; 22) extending in the housing in a flow direction; a plurality of actuators located in the housing, the actuators being sequentially individually activated for sectionally deflecting the elastic membrane for forming at least one delivery chamber (20, 21) between sections of the membrane and associated circumferential sections of the at least one flow channel for enclosing a to-be-delivered medium and movable, in course of a delivery movement between the at least one inlet and the at least one outlet,

wherein respective actuators located opposite each other on both sides of the at least one flow channel form actuation stages (A1-A6) arranged one after another in the flow direction, with a respective section of the elastic membrane abutting a respective circumferential section of the at least one flow channel upon activation of an actuator of a respective actuation stage (A1-A6).

12. A positive displacement according to claim 8 and formed as one of vacuum pump and a fore-vacuum pump of one of high, ultra high, high and ultra high vacuum pump and a turbomolecular pump.