The present invention relates to a method and apparatus for the automated conveying of liquids or gases and in particular a pump.
For the automated conveying of liquids or gases, a multitude of apparatuses is known that can be subsumed under the term “pump”.
It can be differentiated between “open” and “closed” pumps. An example of an open pump is a bucket wheel, or a conveyor belt with liquid containers. A common feature of all closed pumps is that a defined volume that e.g. can be located in a chamber or a hose is being delivered by change, i.e. decrease, of the volume that is available for the pumping medium (chamber volume) in direction of the pump exit, and that new pumping medium is subsequently sucked in by increase of the pumping chamber volume. Generally, the flow direction is determined by according valves.
Known are i.e. piston pumps, wherein during the lowering phase, a piston displaces the volume being present in the pumping chamber through an outlet valve and sucks in new pumping medium during the subsequent rising phase through an intake valve, or membrane pumps, wherein a membrane that forms a wall of the pumping chamber, periodically raises and lowers, therefore increasing or decreasing the chamber volume. Mostly, the volume change takes place sine-shaped, as well resulting in an approximately sine-shaped ejection of the pump medium, wherein this only occurs during the positive half wave; the negative half wave serves for the intake of new pump medium. Further known are flexible tube pumps wherein an elastically deformable tube is divided in individual segments by means of movable, mechanical devices. The mechanical devices displace the segments along the feed direction of the tube, resulting in a transport of the pumping medium from the inlet to the outlet. Contrary to the piston operated pumps, the ejection occurs here intermittent-continuously.
Furthermore, so called impeller pumps are known that deliver a liquid by means of an impeller or a turbine that is arranged within a liquid channel.
However, the state of the art has the following disadvantages.
Both aforementioned pump variants have the disadvantage that the delivery rate, i.e. the pump volume with respect to the time, strongly fluctuates when looked at a single pump cycle (period), as depicted in
While for piston pumps with only one pumping chamber the first half of the pump cycle is used for emptying the pumping chamber (
Flexible hose pumps operate with a mechanical device (clamp unit or similar), which squeezes part of the hose, therefore generating sort of a “piston wall”. The same is then displaced in direction of the pump- and hose exit, wherein the volume being present in front of it is further displaced, and wherein an low pressure develops behind it by which new delivery medium is sucked in. Although flexible hose pumps achieve a rather constant delivery rate over a time span that depends on the length of the individual delivery segments; however, the same abruptly becomes zero in periodical intervals when an according segment ends. The mechanical device defining this segment lifts off from the hose at the end of the delivery cycle. Since the whole segment that is squeezed by the clamp unit just does not contain any volume (since it served as piston wall), in this moment, also no delivery medium is ejected. The herein described pulsating delivery of a pumping medium and the delivery behaviour of the both aforementioned pumps schematically depicted in
Furthermore, even by parallel connection of several phase shifted operating individual pumps, no total delivery rate can be achieved that has a significantly more continuous characteristic than each individual pump. Herein, also the cost as well as the space requirements for an according number of pumps is increased.
Although the known impeller pumps or turbine like pumps deliver a liquid in a very continuous manner, they however require a rotational drive unit, being therefore only complex and costly producible, in particular in a miniaturized design.
Task of the present invention is therefore provision of a method that allows for a mostly pulsation free delivery of a pumping medium with a high delivery rate. A further task of the present invention is the provision of an apparatus suitable for the method according to the invention, that can be simply and cost effectively realized also in a miniaturized design.
The task of the present invention is solved by the features of the independent claims. Advantageous embodiments are mentioned in the features of the subclaims and/or the following description that is accompanied by schematic drawings. Here, it is shown by:
a and b a schematic representation of an apparatus according to a third embodiment of the present invention;
a and b a variation of the apparatus according to the invention of
a the stroke of the displacers of the apparatus of
a and b a schematic representation of an apparatus according to a further embodiment of the present invention;
a an apparatus according to a further embodiment of the present invention and
The present invention particularly relates to an apparatus for the delivery of liquid and/or gaseous media with a number of at least two pumping chambers whose volumes periodically changing during operation, wherein each pumping chamber has at least one intake- and discharge valve, and all pumping chambers have a common main inlet and a common main outlet, and wherein at least one drive unit is assigned to the pumping chambers that is embodied such that the volumes of the pumping chambers change with a phase shift of 2π/number of chambers.
The present invention further relates in particular to an apparatus for delivery of liquid and/or gaseous media with a number of at least two pumping chambers with volumes periodically changing during operation, wherein the pumping chambers are embodied and disposed such that at least two adjacent pumping chambers comprise a joint wall that is embodied in such a manner that it serves for the change of the volume of the adjacent pumping chambers.
By means of the intended volume change of the pumping chambers according to the invention with a phase shift of 2π/number of chambers and in particular by means of the coupling of the drive units according to the invention, advantageously a high pumping capacity with a particularly constant delivery rate is achieved.
Suitably, in an apparatus according to the invention the joint walls can be coupled with the drive units and/or comprise the drive units.
An apparatus according to the invention further comprises in particular an apparatus with a multitude of pumping chambers, and advantageously with less than 7 pumping chambers, and more advantageously with 3 pumping chambers, wherein for the operation of the pumping chambers, at least a number of drive units is provided that corresponds to the number of pumping chambers, wherein the pumping chambers are suitably embodied and disposed such that all pumping chambers have a first common drive unit with a first adjacent pumping chamber and a second common drive unit with a second adjacent pumping chamber, wherein the drive units are embodied such that they serve for the volume change of the respectively adjacent pumping chambers.
In the advantageous embodiment of an apparatus according to the invention with a drive unit that is embodied one-pieced with the wall of a pumping chamber, that drive unit can advantageously be at least partially embodied as a swinging membrane, and advantageously be embodied as a piezoelectric disc actuator.
Furthermore, an apparatus according to the invention suitably comprises a pressure-decoupled outlet.
The present invention furthermore relates in particular to a method for delivery of liquid and or gaseous media by aid of the previously described apparatus according to the invention, wherein the apparatus is suitably triggered such that the volumes of at least two pumping chambers change with a phase shift of 2π/number of chambers. With the method according to the invention, a method with a particularly high pumping capacity and constant delivery rate is provided.
Subsequently, advantageous exemplary embodiments of the present invention are described in detail be means of the schematic drawings.
In the following, the principle that the invention is based on is described by the example of an apparatus 1 according to the invention of
The apparatus 1 of
For example, the walls 10 can be embodied as cylindrical displacers, that—starting from a neutral position—at least partially empty the respective volume being assigned to them, or accordingly increase its respective capacity. However, the described principle is also true for differently embodied displacers and/or such displacers whose movement does not occur exactly sine shaped, as long as their movement pattern occurs uniformly and with a phase shift of the displacer movements of approximately 120° or 240°, respectively.
a, b and c depict exemplarily three characteristic states in the curse of operation of the apparatus 1 during a complete pumping cycle. The positions of the displacers 13 of
In the following, the formulae that underlie the principle according to the invention are specified and described. Also here, the aforementioned example of an apparatus 1 according to the invention of
Chamber volume V and displacer 13
The apparatus 1 comprises three pumping chambers 10 with respective volumes V that are suitably and for the sake of simplicity approximately identical, being labelled here with V1, V2, and V3. It is clear that the volumes V can be different as well.
It should be noted that for the apparatus of
The stroke m of the three displacers 13 is accordingly labelled with m1, m2, and m3 in the following, and is depicted in
Based on the fact of a closed system (inlet and exit are connected, optional valves are always open), it is given that:
V
total
=V
1
+V
2
+V
3=const. Equation (1)
The pumping capacity of a single chamber 10 is defined by the amount of volume being transported per time unit. This results from the difference of the displacer strokes m that enclose the according volume V, multiplied by the base area A of the displacers 13 that are, for the sake of simplicity, also regarded as being approximately identical.
The total pumping capacity P is composed of the individual volume streams:
Suitably, each chamber 10 has a discharge valve 12 and an intake valve 11 that are arranged according to the function as depicted in
The function of a check valve can be described very easily in a way such that it lets pass the flow only on positive, but not on negative pressure.
Correspondingly, it is given that:
The displacers 13 displacing the chamber volume V carry out cyclic movements. If e.g. the stroke m corresponds to a sine wave, it is given that:
Herein, m is the stroke, M is the amplitude, τ is the cycle time, ω is the angular frequency, and σ is the phase shift.
For the derivative d/dt of a chamber stroke mi one therefore gets:
Here, it must be noted that:
Thus, the phase shifts of the displacers 13 to each other amount to ⅔π (this corresponds to 120°) or 4/3π (this corresponds to 240°), respectively, for the regarded example with three chambers 10.
In general, for the phase difference, it is given that
wherein n is the number of chambers.
For a coupling of the displacer strokes, the expressions for dmi/dt with i=1 to 3 must only be inserted into equation (3), and one gets the total delivery rate of the apparatus in dependence on the time Inserting τ=2π for the cycle time, the individual delivery rates and the total delivery rate appear as in
From the figure it also can be seen that the total delivery rate G is composed of the individual delivery rates of two accordingly adjacent pumping chambers 10.
It should be noted that the principle according to the invention is only realizable if the discharge volume passing through a discharge valve 12 is independent from the volume of the respective other discharge valves 12, i.e. if the chamber outlets are pressure-decoupled.
The principle of an apparatus according to the invention 1 is not limited to the aforementioned exemplary embodiment with n=3 pumping chambers 10, wherein with an increasing number of chambers n, the delivery rate P rises, and wherein, however, odd numbers of chambers n result in a lesser pulsation than even numbers of chambers n.
Since, as presented, the delivery rate P increases as well with an increasing number of chambers n, the question arises whether the delivery rate P can arbitrarily be increased, or if a limit value exists that can not be reached or also be overshot, even by a theoretically infinite number of chambers.
For this, firstly, the average value of the total delivery rate of an apparatus 1 can be looked at. This corresponds to the integral of the total delivery rate P over a full cycle:
If now the average delivery rate is compared with the dependence of the number of chambers n, the connection as depicted in
Comparison with a Combination of Several Separately Arranged Apparatuses
It seems to be obvious to let several separately operating apparatuses work in a phase shifted mode and regard their common output as total delivery rate instead of using the invention's chamber coupling that firstly appears to be complex. Each of the apparatuses has an individual inlet, which is connected to a common main inlet, and an individual exit, which leads in a delivery volume having atmospheric pressure.
However, the total delivery rate of separate apparatuses lies (with a smaller number of chambers) significantly under the total delivery rate of an apparatus 1 according to the invention. This effect is based on the fact that by means of the displacers 13, a significantly larger displacement volume can be produced.
However, it must be taken into account that this advantage is not true for arbitrary numbers of chambers n. From
However, it is clear that an apparatus 1 according to the embodiment of
a shows a schematic representation of a further apparatus 1 according to the invention with three adjacently arranged pumping chambers 10 that exemplarily and advantageously have approximately the same volume V, and that are roughly arranged along a ring. For the sake of clarity and simplicity, the representation of valves was omitted in
b shows a schematic representation of a variation of the apparatus 1 of
Suitably, the aforementioned method according to the invention described by aid of embodiments of
It is clear that the embodiments of
According to the invention, in the embodiment of
By using the aforementioned described embodiment and arrangement of the pumping chambers 10 and the drive units A an exceptionally compact design in one plane is achieved that in particular can be fabricated miniaturized in a cost effective way. It is clear that the apparatus 1 according to the invention of
It is further clear that the apparatus 1 of
Number | Date | Country | Kind |
---|---|---|---|
10 2006 016 571.3 | Apr 2006 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2007/002982 | 4/3/2007 | WO | 00 | 3/9/2011 |