US20100284827A1

US20100284827A1 - Homogenization of the conveying flow in oscillating positive displacement pumps

Info

Publication number: US20100284827A1
Application number: US12/775,191
Authority: US
Inventors: Matthias Sauter; Matthias Dorling
Original assignee: Lewa GmbH
Current assignee: Lewa GmbH
Priority date: 2009-05-08
Filing date: 2010-05-06
Publication date: 2010-11-11
Also published as: DE102009020414A1; EP2249033A2; JP5567385B2; JP2010261461A; EP2249033B1; EP2249033A3; ES2529678T3

Abstract

A method for homogenizing conveying flow from at least two oscillating positive displacement pumps utilizing a drive motor for each pump and a rotating shaft, the fluid conveying flow in a conveying line is generated by the oscillating positive displacement pumps, the drive motors controlled such that the conveying flow generated overall in the conveying line is largely uniform or constant.

An apparatus according to the invention is distinguished by at least two oscillating positive displacement pumps, the delivery lines of which are connected to a common conveying line in order to superimpose the individual conveying flows and each have a drive motor which can be operated in electronic synchronization without mechanical coupling in order to achieve a largely uniform or constant total conveying flow.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119 to German patent application DE 10 2009 020 414.8, filed May 8, 2009, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a method for homogenizing the conveying flow in oscillating positive displacement pumps by controlling the drive motors of the pumps to convey fluid flow in a conveying line such that total conveying flow generated overall in said conveying line is largely uniform or constant. Moreover, the invention relates to an apparatus for carrying out this method.
2. Description of Related Art
During the operation of oscillating positive displacement pumps, it is desired for reasons of basic considerations to achieve a largely constant conveying flow. This is the case even if only because otherwise disadvantageous phenomena occur in the delivery and/or conveying lines. Said disadvantageous phenomena comprise, for example, a pressure pulse being produced in the conveying line during every delivery stroke, which pressure pulse can have a negative influence on the lines of the entire system and therefore has to be suppressed or prevented by means of separate pulse dampers and the like.
In order to achieve a largely constant conveying flow in oscillating positive displacement pumps, it is already known, for example, not to construct pumps as single action pumps, but rather to provide them at least as a triple action pump with a uniform eccentric offset. As a result of the superimposition of the conveying flows, the pulsing of the conveying flow decreases as the cylinder number increases. However, this is not sufficient for many cases, with the result that additional measures for pulse damping become necessary. This, in turn, requires a considerable structural outlay.
Moreover, it is known (DE 198 49 785 C1) to use the drive shaft of the oscillating positive displacement pump for the desired setting of the conveying flow of the oscillating positive displacement pump, to be precise in such a way that a transition takes place from the rotating movement of the drive shaft to a pivoting movement and vice versa, in order to provide different desired settings of the conveying flow. A method of this type has certainly proven itself in practice. However, in this way it is not yet possible to achieve a continuously constant or uniform conveying flow of the fluid to be conveyed overall, since no conveying at all still takes place during the suction stroke of the pump (even if short), which interrupts the constancy of the conveying flow which is otherwise achieved.

SUMMARY OF THE INVENTION

The invention is therefore based on the object of configuring the method of the generic type in order to eliminate the described disadvantages in such a way that it makes it possible to achieve a largely uniform or constant conveying flow by a simple structural with acceptable economic outlay.
Moreover, an apparatus is to be provided for carrying out said method, which apparatus can be operated simply.
This object is achieved with the method according to the invention by way of the features of Claim 1. Advantageous refinements hereof are described in the further claims.
The features of the apparatus which is provided according to the invention result from Claim 6. Advantageous refinements hereof are described in the further claims.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The above and other objects, which will be apparent to those skilled in the art, are achieved in the present invention which is directed to a method for homogenizing conveying flow in at least two oscillating positive displacement pumps, the drive of each resulting from a drive motor via a rotating shaft, the method comprising controlling the drive motors of the at least two oscillating positive displacement pumps to convey fluid flow in a conveying line such that total conveying flow generated overall in the conveying line is largely uniform or constant. The positive displacement pumps may be operated in combination with one another without mechanical coupling. The pumps may further be operated such that they are synchronized electronically to establish approximately a pulse-free uniform conveying flow or volumetric flow in the conveying line.
The rotational speed of the drive motors of each of the at least two positive displacement pumps may be changed such that superimposed conveying flows of the at least two positive displacement pumps result in a largely constant total conveying flow.
The shaft of the drive motors of each of the at least two positive displacement pumps may perform an adapted rotary movement in order to achieve a constant characteristic of the total conveying flow.
In a second aspect, the present invention is directed to an apparatus for homogenizing conveying flow comprising: at least two oscillating positive displacement pumps; a delivery line for each of the at least two oscillating positive displacement pumps; a common conveying line attached to each of the delivery lines in order to superimpose individual conveying flows; and a drive motor for each of the at least two oscillating positive displacement pumps, the drive motors in electronic synchronization without mechanical coupling in order to achieve a largely uniform or constant total conveying flow.
The drive motors of each of the at least two oscillating positive displacement pumps may be dynamic drives in the form of servomotors, and more specifically permanently excited three phase synchronous servomotors.
The drive motors of each of the at least two oscillating positive displacement pumps may include diaphragm pumps.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the invention believed to be novel and the elements characteristic of the invention are set forth with particularity in the appended claims. The figures are for illustration purposes only and are not drawn to scale. The invention itself, however, both as to organization and method of operation, may best be understood by reference to the detailed description which follows taken in conjunction with the accompanying drawings in which:

FIG. 1 diagrammatically shows the arrangement of two oscillating positive displacement pumps which are not connected mechanically, for homogenizing the total conveying flow.

FIGS. 2 a-d show different diagrams of pump measured values, plotted against time, t, in order to clarify the achievement of a constant fluid velocity and thus of a uniform conveying flow, at a delivery efficiency of the pumps of 100% overall.

FIGS. 3 a-c show different diagrams of corresponding pump measured values, plotted against time t, at a reduced pump delivery efficiency of approximately 90%.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

In describing the preferred embodiment of the present invention, reference will be made herein to FIGS. 1-3 of the drawings in which like numerals refer to like features of the invention.
The method according to the invention for homogenizing the conveying flow in oscillating positive displacement pumps is based on the essential concept that the fluid flow in a conveying line is generated by means of at least two oscillating positive displacement pumps, the drive motors of which are controlled in such a way that the conveying flow generated overall in the conveying line is largely uniform or constant.
Furthermore, there is provision according to the invention for the positive displacement pumps to be operated in combination with one another without mechanical coupling.
It lies within the scope of the invention that the positive displacement pumps are operated such that they are synchronized electronically in such a way that a virtually pulse-free uniform conveying flow (volumetric flow) is generated in the common conveying line.
The method according to the invention can expediently be operated in such a way that the drive motor of each positive displacement pump has its rotational speed changed in such a way that the superimposed conveying flows of the positive displacement pumps result in a largely constant total conveying flow.
Special advantages result if the shaft of the drive motor of each positive displacement pump performs an adapted rotary movement in order to achieve the constant characteristic of the total conveying flow.
The apparatus according to the invention for carrying out the abovementioned method is provided with at least two oscillating positive displacement pumps, the delivery line of which is connected to a common conveying line in order to superimpose the individual conveying flows and which each have a drive motor which can be operated in electronic synchronization without mechanical coupling in order to achieve a largely uniform or constant total conveying flow.
The drive of each positive displacement pump is advantageously a highly dynamic drive. This can be a servomotor, preferably a permanently excited three phase synchronous servomotor.
It lies within the scope of the invention that the positive displacement pumps are diaphragm pumps.
It is therefore possible by way of the invention to prevent the pressure pulse in the common conveying line even without pulse dampers, on account of the superimposition of the conveying flows of two individual pumps which is carried out in a targeted manner, and at the same time to achieve a largely constant conveying flow. This takes place by exact electronic synchronization of the positive displacement pumps which are not coupled mechanically.
Finally, in order to check whether the desired constant characteristic of the conveying flow is achieved, various methods are already known (DE 35 46 189 C2) which comprise, for example, the pressure profile in the pump cylinder being measured by means of pressure sensors, whereupon the actually conveyed volumetric flow of the pump is calculated from the detected measured values via the kinematic law of motion of the pump piston.
As can be seen from FIG. 1 of the drawing, two oscillating positive displacement pumps are provided in the form of diaphragm pumps 1, 2 in the exemplary embodiment shown for carrying out the method according to the invention, the delivery lines 3, 4 of which diaphragm pumps 1, 2 are connected to a common conveying line 5.
The diaphragm pumps 1, 2 which are not coupled mechanically have in each case one drive motor 6 and 7 which is configured as a highly dynamic drive. This is preferably a servomotor, to be precise, in particular, a permanently excited three phase synchronous servomotor.
The drive motors 6, 7 of the two diaphragm pumps 1, 2 are operated by exact electronic synchronization in such a way that a largely uniform or constant total conveying flow can be achieved in the common conveying line 5.
This procedure which is carried out by way of the method according to the invention is shown by the individual diagrams in FIGS. 2 a-d, in which the pump delivery efficiency is in each case 100%. Here, for the sake of simplicity, only the delivery stroke of each diaphragm pump 1, 2 is shown, in each case the left-hand side of the diagrams showing the relevant measured value profile during the delivery stroke of the diaphragm pump 1, whereas the corresponding right-hand half of the diagrams shows the measured value profile in dashed form during the delivery stroke of the diaphragm pump 2.
Diagram 2 a shows the profile of the piston travel against time t in both diaphragm pumps 1, 2. Since this, in contrast to the prior art, is a constant profile on account of the special operation of the drive motors 6, 7 of the two diaphragm pumps 1, 2, a constant piston velocity also results, as can be seen from FIG. 2 b.
This is brought about not least by the fact that the angular velocity of the eccentric shafts of the respective diaphragm pumps 1, 2, plotted against time t, has the profile according to FIG. 2 c, that is to say, likewise in contrast to the prior art, in each case a high starting and finishing velocity with a constant profile between these two benchmark values.
Finally, the diagram according to FIG. 2 d shows clearly that a constant fluid velocity, plotted against time t, results on account of the method of operation according to the invention. This has a constant conveying flow in the conveying line 5 as a direct result.
The diagrams according to FIGS. 3 a-c show different measured values of the diaphragm pump 1 (continuous line) and of the diaphragm pump 2 (dashed line), in each case plotted against time t, the diaphragm pumps 1, 2 in each case having only a reduced delivery efficiency of approximately 90%. Here, the diagram according to FIG. 3 a shows the fluid velocity plotted against time t without compensation for the loss as a result of the “dead compression travel h_K” which occurs in each case at the beginning of the delivery stroke. This loss of fluid velocity is extraordinarily low, however, in comparison with the prior art, with the result that it is negligible.
If this loss in value is nevertheless to be compensated for, this then results in a representation of the fluid velocity against time t according to FIG. 3 b, in which the delivery efficiency is compensated for. For this purpose, the “dead compensation travel h_K” which occurs at the beginning of the delivery stroke has to be known or has to be determined automatically. A corresponding method for this is known, for example, from DE 35 46 189 C2.
As can be seen with regard to this in FIG. 3 c, the pump piston is moved into the position h_Kafter the end of the suction stroke, before the actual delivery stroke begins. The piston travel then already starts at h_K, that is to say the fluid is displaced immediately in the delivery stroke.
In order to comprehend the expression of the “dead compression travel h_K”, the known fact is assumed, namely that each oscillating positive displacement pump has a conveying cycle. This comprises: a) an induction phase, in which the fluid is sucked into a pump chamber; b) a compression phase, in which the sucked-in fluid is brought to delivery pressure; c) a delivery phase, in which a part of the compressed fluid is ejected out of the pump chamber; and d) a decompression or expansion phase, in which the fluid which has remained in the pump chamber is brought to induction pressure again.
Here, for the compression of the fluid from the suction pressure to the delivery pressure, each oscillating positive displacement pump requires a defined small piston travel, what is known as the dead compression travel h_K, which is covered in the compression time.
Finally, reference is made expressly to the claims and the drawing with regard to features which are not explained in detail in the above text.
While the present invention has been particularly described, in conjunction with a specific preferred embodiment, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. It is therefore contemplated that the appended claims will embrace any such alternatives, modifications and variations as falling within the true scope and spirit of the present invention.

Claims

1. A method for homogenizing conveying flow in at least two oscillating positive displacement pumps, the drive of each resulting from a drive motor via a rotating shaft, said method comprising controlling said drive motors of said at least two oscillating positive displacement pumps to convey fluid flow in a conveying line such that total conveying flow generated overall in said conveying line is largely uniform or constant.

2. The method of claim 1 including having the positive displacement pumps operated in combination with one another without mechanical coupling.

3. The method of claim 1 including having the positive displacement pumps operated such that they are synchronized electronically to establish approximately a pulse-free uniform conveying flow or volumetric flow in said conveying line.

4. The method of claim 1 including changing the rotational speed of said drive motors of each of said at least two positive displacement pumps such that superimposed conveying flows of said at least two positive displacement pumps result in a largely constant total conveying flow.

5. The method of claim 1 including having said shaft of said drive motors of each of said at least two positive displacement pumps perform an adapted rotary movement in order to achieve a constant characteristic of said total conveying flow.

6. The method of claim 2 including having the positive displacement pumps operated such that they are synchronized electronically to establish approximately a pulse-free uniform conveying flow or volumetric flow in said conveying line.

7. The method of claim 2 including changing the rotational speed of said drive motors of each of said at least two positive displacement pumps such that superimposed conveying flows of said at least two positive displacement pumps result in a largely constant total conveying flow.

8. The method of claim 2 including having said shaft of said drive motors of each of said at least two positive displacement pumps perform an adapted rotary movement in order to achieve a constant characteristic of said total conveying flow.

9. A method for homogenizing the conveying flow in oscillating positive displacement pumps, the drive of which takes place by means of a drive motor via a rotating shaft, characterized in that the fluid conveying flow in a conveying line is generated by means of at least two oscillating positive displacement pumps, the drive motors of which are controlled in such a way that the conveying flow generated overall in the conveying line is largely uniform or constant.

10. An apparatus for homogenizing conveying flow comprising:

at least two oscillating positive displacement pumps;

a delivery line for each of said at least two oscillating positive displacement pumps;

a common conveying line attached to each of said delivery lines in order to superimpose individual conveying flows; and

a drive motor for each of said at least two oscillating positive displacement pumps, said drive motors in electronic synchronization without mechanical coupling in order to achieve a largely uniform or constant total conveying flow.

11. The apparatus of claim 10 including having said drive motors of each of said at least two oscillating positive displacement pumps be dynamic drives in the form of servomotors.

12. The apparatus of claim 11 including having said drive motors of each of said at least two oscillating positive displacement pumps be a permanently excited three phase synchronous servomotor.

13. The apparatus of claim 11 including having said drive motors of each of said at least two oscillating positive displacement pumps include diaphragm pumps.