US20150260178A1

US20150260178A1 - Piston membrane pump

Info

Publication number: US20150260178A1
Application number: US14/434,100
Authority: US
Inventors: Alfred Giessbach
Original assignee: Mhwirth GmbH
Current assignee: Mhwirth GmbH
Priority date: 2012-10-10
Filing date: 2013-09-25
Publication date: 2015-09-17
Also published as: EP2912310B1; CN104813023A; DE102012109634A1; CN104813023B; EP2912310A1; WO2014056724A1

Abstract

A piston membrane pump includes an intake line configured to take in a medium to be pumped, and a dynamic volume storage element arranged in the intake line.

Description

CROSS REFERENCE TO PRIOR APPLICATIONS

This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/EP2013/069952, filed on Sep. 25, 2013 and which claims benefit to German Patent Application No. 10 2012 109 634.1, filed on Oct. 10, 2012. The International Application was published in German on Apr. 17, 2014 as WO 2014/056724 A1 under PCT Article 21(2).

FIELD

The present invention relates to a piston membrane pump having an intake line for the suction of the medium to be pumped.

BACKGROUND

Piston membrane pumps are used for pumping liquids or gases. Their operating principle is similar to that of a piston pump, the difference being that the medium to be pumped is separated from the drive by a membrane. The separating membrane thereby shields the drive from any detrimental effects of the pumping medium. The pumping medium is also separated from any detrimental effects of the drive.
In a piston membrane pump, the oscillating movement of the piston is transmitted to the membrane via a working medium. As a working medium, water, having a water-soluble mineral additive, or in particular, a hydraulic oil, may be used. The volume that is filled with the working medium is also correspondingly referred to as the “oil reservoir”. As a result of the constant volume of the oil reservoir between the piston and the membrane, the movement of the piston directly causes a deflection of the membrane and thus results in the generation of suction and pressure pulses.
The present invention in principle relates to piston membrane pumps of any size and for any purpose of use. The present invention in particular, however, relates to piston membrane pumps intended for pumping slurry, also referred to as “thick matter”, during the carrying out of earthworks. Such piston membrane pumps are designed for continuous operation and must work reliably over long periods of time, up to years, as trouble-free as possible, because a replacement of a defective piston membrane pump is, due to its size, usually associated with considerable labor and time expenditure.
Such thick matter pumps are in particular intended for pumping very large amounts of thick matter. One type of frequently used thick matter pump provided by the applicant comprises two double-acting pistons, and thus four membranes, and pumps up to more than 700 m³/h at a pumping pressure of approximately 50 bar. The thick matter to be pumped is supplied to such thick matter pumps on the side of the intake line at a positive pressure, typically in the order of magnitude of several bars, the so-called “charging pressure”. An air pressure vessel is usually integrated into the intake line in order to reduce any pressure fluctuations on the side of the intake line that are caused by pump strokes.

SUMMARY

An aspect of the present invention is to increase the expected service life while maintaining a certain delivery performance, and to increase the delivery performance while maintaining the same service life, while at the same time keeping design and manufacturing efforts as low as possible.
In an embodiment, the present invention provides a piston membrane pump which includes an intake line configured to take in a medium to be pumped, and a dynamic volume storage element arranged in the intake line.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in greater detail below on the basis of embodiments and of the drawings in which:

FIG. 1 shows a perspective view of an embodiment of a piston membrane pump used as a thick matter pump;

FIG. 2 shows, in sections and partially cut away, a view of the same piston membrane pump obliquely from the left, however, without an air pressure vessel;

FIG. 3 shows, in sections and partially cut away, a view according to FIG. 2 from the left-hand side of the same piston membrane pump;

FIG. 4 shows a perspective view of an embodiment of a dynamic volume storage element as used in the piston membrane pump according to FIGS. 1 to 3, in an individual representation;

FIG. 5 shows a truncated partial section of the embodiment of the dynamic volume storage element according to FIG. 4;

FIG. 6 shows a view according to FIG. 5, from the left;

FIG. 7 shows a time-dependent pressure profile in the intake line in the vicinity of an inlet valve in the embodiment of the piston membrane pump according to FIGS. 1 to 3, without, however, a dynamic volume storage element; and

FIG. 8 shows the temporal profile of the pressure in the intake line in the same position in the same embodiment of the piston membrane pump, with, however, an inserted dynamic volume storage element.

DETAILED DESCRIPTION

In an embodiment of the present invention, the piston membrane pump is characterized in that a dynamic volume storage element is provided in the intake line. The term “dynamic volume storage element” is meant to be understood as a component that is suitable for quickly taking in, as a function of pressure in relation to the pump rate per unit time, a very small volume (for example L ⁰/₀₀of the volume pumped per hour) of the medium to be pumped (also referred to as the “pumping medium”), and also for quickly outputting the medium. In other words, the dynamic volume storage element is designed so that it can, in the case of an increase in pressure in the intake line, quickly take in these delivery medium volumes, which are very low compared to the pumping rate per time unit, and in the case of a pressure drop in the intake line, quickly output volumes of pumping medium as a function of pressure. It has surprisingly been shown that with such a dynamic volume storage element, the number of pump strokes per unit time can be measurably increased without any other design modifications, without any cavitation effects occurring in the area between the inlet and the outlet valve, which also includes the membrane chamber. It has also been shown that the piston membrane pump according to the present invention achieves an enhanced filling of the pump space with pumping medium compared to a piston membrane pump of an otherwise identical design but without a dynamic volume storage element in the intake line. The piston membrane pump according to the present invention also has less vibration compared to a piston membrane pump with the same design and the same output, but without a dynamic volume storage element.
The enhancement of the properties of the piston membrane pump according to the present invention can possibly be explained by the fact that the dynamic volume storage element supports the acceleration of the delivery medium which is at rest in front of the closure element of the inlet valve by dispensing a small amount of pumping medium in the case of a pressure drop at the beginning of an intake stroke so that, within a short period of time, a larger volume flow through the inlet valve with otherwise consistent pump parameters is realized.
The dynamic volume storage element can (to the extent the capacity of the pressure-dependent rapid input and output of at least small amounts of delivery medium allows) be implemented in any desired conceivable manner that allows the dynamic volume storage element to be provided in the intake line. In an embodiment of the dynamic volume storage element that comprises a displacement body, the displacement volume can, for example, be elastically varied. The displacement volume of this dynamic volume storage element is thus dependent on the pressure the pumping medium is exposed to. In the case of an increase of this pressure, the volume of the dynamic volume storage element is reduced, which is equivalent to the intake of an amount of pumping medium that corresponds to the reduction in volume. Accordingly reversed, the volume of this dynamic volume storage element is enhanced in the case of a pressure drop, which is equivalent to the output of an amount of pumping medium that corresponds to the increase in volume.
In an embodiment of the present invention, the displacement body can, for example, comprise an elastically deformable envelope that surrounds a pressure space that is filled or can be filled with a pressurized gas. The envelope may, for example, be made from an elastic material, provided it is inert relative to the pumping medium.
It is also possible for the displacement body to comprise a first and a second end piece, the outside diameter of which end pieces is adapted to the inside diameter of the envelope so that the envelope can be connected or is connected to the end pieces in a gas impermeably sealed manner. The displacement body is then characterized by being particularly simple to manufacture and, especially if the envelope is fastened to the end pieces using selectively mountable clamping screws, by being easily replaceable if damaged.
In an embodiment of the present invention, the end pieces can, for example, be fixedly connected to each other at a distance from each other via a spacer provided on the inside of the envelope, the outside diameter of the spacer being smaller than the inside diameter of the envelope. The pressure space is in this case defined by the annulus defined between the inner shell surface of the envelope and the outer shell surface of the spacer, in the longitudinal direction of which it is delimited by the end pieces.
In an embodiment of the present invention, the dynamic volume storage element can, for example, be designed so that the gas pressure in the pressure space can be varied in order to adapt the properties of the dynamic volume storage element to changed operating conditions, for example, changed pumping amounts per unit time or, in particular, to varying charging pressures.
In an embodiment of the present invention, the first end piece can, for example, have a through passage opening into the pressure space and, on the outside, a device to connect a gas pressure supply provided on the first end piece.
This device may comprise a check valve so that, when a desired gas pressure is applied to the dynamic volume storage element, the gas pressure supply connection can again be disconnected.
In an embodiment of the present invention, a display instrument for displaying the gas pressure in the pressure chamber of the dynamic volume storage element can, for example, be provided. The gas pressure in the chamber can thereby be monitored during the operation of the piston membrane pump according to the present invention. As a result, suitable measures can be taken without any unnecessary delays if the gas pressure in the pressure chamber changes in a disadvantageous manner.
Further details, features and advantages of the present invention will become evident from the explanation of an embodiment example given below in the attached drawings.
The piston membrane pump, which is shown in FIG. 1 and which is generally identified with 100, is provided for pumping thick matter and will be referred to below as a “thick matter pump”. It is implemented as a double-acting duplex pump. This means that it comprises two pistons approximately counter-currently driven, which operate in two cylinders arranged parallel to each other. The cylinder housings are indicated with 1 and 2 in the drawing. The piston 3 operating in the right-hand cylinder is shown in the partially cut-away view of FIG. 2. Both piston-cylinder assemblies are designed to be double-acting. This means that there are working liquid volumes on either side of the piston 3, of which volumes only the working liquid volume 4 is shown in FIG. 2, which is associated with the top view of the piston 3. These working liquid volumes are filled with working liquid, in most cases, hydraulic oil. The working liquid, also referred to as oil reservoir, which is not shown in FIG. 2, fills the working volume up to a membrane 5 that is provided in a membrane chamber 6. Due to being a partially cut-away view, FIG. 2 again only shows one membrane 5 and one membrane chamber 6.
For each piston/cylinder assembly according to the double-acting embodiment, the piston membrane pump 100 comprises two separate working liquid volumes, membranes and membrane chambers, as is shown by the four membrane housings 7, 8, 9, 10 in FIG. 1.
Each membrane housing has a bottom intake manifold 11, 12, 13, 14, each of which opens into one of two intake lines 19, 20 via an inlet valve 15, 16, 17, 18.
At each membrane housing 7, 8, 9, 10, an outlet valve 21, 22, 23, 24 is provided on the side opposite the respective intake manifold 11, 12, 13, 14. The outlet valves 21, 22, 23, 24 are connected on the outlet side to a common pressure line 25 via pipe sections.
The two intake lines 19 and 20 open into an intake-side air pressure vessel 26 that is fed with the medium to be pumped to the inlet 27 thereof under a pressure of typically several bars, the so-called charging pressure. The intake-side air pressure vessel 26 is used to equalize the pressure and to avoid vibrations as a result of the pumping process on the intake side.
The pressure line 25 also opens into a pressure-side air pressure vessel 28, to the output 29 of which a pressure line, which is not shown in the drawings, is connected during operation, via which the pumping medium is pumped to the desired location. The pressure-side air pressure vessel 28 is used to avoid pressure-side pressure fluctuations and vibrations.
The two inlet valves and outlet valves, which are respectively associated with a double-acting piston-cylinder unit, work in phase opposition to each other. For example, if the inlet valve 17 associated with the membrane housing 9 is in the intake cycle, i.e., it is open, then the inlet valve 18 associated with the membrane housing 10 is in the outlet cycle, i.e., it is closed. This means that any pumping medium provided via the intake line 20 flows alternately via the inlet valve 17 and the outlet valve 18 through the respectively associated manifold 13, 14 into the respective membrane chamber and is supplied, during the respective pressure cycle, through the associated outlet valves 23 and 24, respectively, to the pressure line 25.
As can be seen in FIG. 3, the piston membrane pump according to the present invention has a dynamic volume storage element 31 that protrudes into the intake line 20 from a blind end 30. The intake line 19, which cannot be seen in FIG. 3 and which is covered by the intake line 20, is in an analogous manner also provided with a second dynamic volume storage element.
As can be seen in particular in FIGS. 4 to 6, the dynamic volume storage element 31 comprises a flange 32, via which it is mounted in the respective intake line 19, 20 and which sealingly closes the respective intake line 19, 20 towards the respective blind end.
A first end piece 33 is fastened to the flange 32. A second end piece 34 is connected to this first end piece 33 via a spacer 35. A flexible envelope 36 is fastened to the outer shell surfaces of the two end pieces 33, 34 via hose clamps 37. Between the outer shell surface of the spacer 35 and the inner shell surface of the flexible envelope 36, an annulus 38 is thus defined between the first and second end pieces 33, 34, which is sealed towards the outside in a gas impermeable manner.
The annulus 38 accordingly forms a pressure space 39 for a pressurized gaseous medium that can be introduced into the pressure space 39 via a check valve 40 and a through passage 41 that can be selectively blocked by the check valve 40. The positive pressure with respect to the atmosphere, which is present in the pressure space 39, can be read via a connected pressure gauge 42, here implemented as a manometer. Due to the flexibility of the envelope and the compressibility of the gas in the pressure space, the dynamic volume storage element 31 constitutes a displacement body 43, the displacement volume of which can be elastically varied.
As has already been mentioned, the pumping medium to be pumped is provided to the intake lines 19, 20 under positive pressure (“charging pressure”). Experiments have shown that in the case of the embodiment of the piston membrane pump as shown, the use of the dynamic volume storage element 31 has a particularly positive effect if the gas inside the pressure space 39 has a pressure that corresponds to approximately a third of the charging pressure.
The positive effects of the use of a dynamic volume storage element in the intake lines of piston membrane pumps can be explained approximately as follows.
During the pressure cycle of a pump unit, i.e., while the inlet valve is in the closed condition, the pumping medium is substantially static below approximately the charging pressure on the closing mechanism of the inlet valve. Once the dead center has been passed, and thus the intake stroke has been initiated, the pressure within the membrane chamber drops and, once it has dropped below the charging pressure, the inlet valve opens against the force of a spring that holds it in the seated position. Due to the inertia of the mass of the pumping medium, however, this does not flow into the membrane chamber in correspondence with the pressure difference. This leads to an increasing pressure difference between the inside of the membrane chamber and the inside of the intake line, which ultimately leads, although with a time delay, to a faster inflow of the pumping medium into the membrane chamber. During the course thereof, the pressure quickly rises again in the membrane chamber, i.e., the pressure difference between the inside of the membrane chamber and the inside of the intake line drops. This process is repeated multiple times during an intake stroke, as indicated in FIG. 7. The duration of the time deviation is identified by the oval. In FIG. 7, the positive pressure relative to the environment, to which the pumping medium is exposed in the vicinity of an inlet valve, is applied as a function of time during an intake cycle.
As a result of the pressure fluctuations shown, which are surprising also in the light of the presence of the air pressure vessel 26 on the intake side, the closure mechanism of the inlet valve carries out a continuous reciprocal movement with a relatively high frequency during the intake cycle, which not only has a negative effect on the filling degree of the membrane chamber during the intake cycle, but also leads to increased wear and tear of the valve.
In the piston membrane pump according to the present invention, the pressure profile in the intake pipe is, due to the use of the dynamic volume storage element, considerably smoothed out, as can be readily seen in a comparison of FIG. 8 and FIG. 7. In FIG. 8, the pressure profile in the intake pipe is accommodated at the same position as in FIG. 7, however, with an inserted dynamic volume storage element.
The smoothing effect of the dynamic volume storage element can possibly be explained by the fact that in the case of pressure spikes, the volume storage element accommodates a volume proportion of the pumping medium present in the intake line, in order to output this proportion again when the pressure drops. As a result, the inlet valve merely carries out fewer and slower movements during the intake cycle, which reduces wear and tear. The filling degree with pumping medium in the membrane chamber is also improved. The risk of cavitation is reduced as a result of the lower pressure fluctuations. Therefore, with the same output as without the use of a dynamic volume storage element, a longer service life of a piston membrane pump of an otherwise identical design can be expected. Output can in the same way be increased while maintaining the same service life if a dynamic volume storage element is used.
The use of a dynamic volume storage element is of advantage especially in situations in which, due to the design of the piston membrane pump, particular vibrations due to an alternating opening and closing of inlet valves operating with the same output may occur. Such ratios may be present, for example, in the embodiment example of the piston membrane pump as shown here due to the effects of the alternating opening and closing of inlet valves 17, 18 and 15, 16, respectively, in particular in the area of the intake lines 20 and 19, respectively, into which the inlet valves open. Correspondingly, under such circumstances, it may be advantageous to provide a dynamic volume storage element in this way in cases where flow oscillations, turbulences, etc. are to be expected due to mutually influencing flows through different valves.
The present invention is not limited to embodiments described herein; reference should be had to the appended claims.

LIST OF REFERENCE NUMERALS

100 Piston membrane pump
1 Cylinder housing
2 Cylinder housing
3 Piston
4 Working liquid volume
5 Membrane
6 Membrane chamber
7 Membrane housing
8 Membrane housing
9 Membrane housing
10 Membrane housing
11 Intake manifold
12 Intake manifold
13 Intake manifold
14 Intake manifold
15 Inlet valve
16 Inlet valve
17 Inlet valve
18 Inlet valve
19 Intake line
20 Intake line
21 Outlet valve
22 Outlet valve
23 Outlet valve
24 Outlet valve
25 Pressure line
26 Intake-side air pressure vessel
27 Inlet
28 Pressure-side air pressure vessel
29 Output/Exit
30 Blind end
31 Dynamic volume storage element
32 Flange
33 First end piece
34 Second end piece
35 Spacer
36 Flexible envelope
37 Hose clamps
38 Annulus
39 Pressure space
40 Check valve
41 Through passage
42 Pressure gauge
43 Displacement body

Claims

What is claimed is:

1-10. (canceled)

11. A piston membrane pump comprising:

an intake line configured to take in a medium to be pumped; and

a dynamic volume storage element arranged in the intake line.

12. The piston membrane pump as recited in claim 11, further comprising an air pressure vessel arranged upstream of the dynamic volume storage element when viewed in a pumping direction of the medium.

13. The piston membrane pump as recited in claim 11, wherein the dynamic volume storage element comprises a displacement body, a displacement volume of the displacement body being elastically variable.

14. The piston membrane pump as recited in claim 13, further comprising a pressure space configured to be filled with a pressurized gas, wherein the displacement body comprises an envelope configured to be elastically deformable and to terminate the pressure space.

15. The piston membrane pump as recited in claim 14, wherein a gas pressure in the pressure space is variable.

16. The piston membrane pump as recited in claim 15, further comprising a display instrument configured to display the gas pressure in the pressure space.

17. The piston membrane pump as recited in claim 14, wherein,

the envelope comprises an envelope inside diameter and envelop end regions,

the displacement body further comprises a first end piece comprising a first end piece outside diameter, and a second end piece comprising a second end piece outside diameter, and

each of the first end piece outside diameter and the second end piece outside diameter are adapted to the envelope inside diameter so that the envelope is connectable at the envelop end regions to the first end piece and to the second end piece to provide a gas impermeable seal.

18. The piston membrane pump as recited in claim 17, further comprising a spacer comprising a spacer outside diameter which is smaller than the envelop inside diameter, the spacer being arranged inside the envelope,

wherein, each of the first end piece and the second end piece are configured so as to be fixedly connected to each other at a distance via the spacer.

19. The piston membrane pump as recited in claim 17, wherein the first end piece further comprises a through passage configured to open into the pressure space, and a connection device arranged on an outside of the first end piece, the connection device being configured to connect to a gas pressure supply.

20. The piston membrane pump as recited in claim 19, wherein the connection device comprises a check valve.