PUMP SYSTEM, DIALYSIS MACHINE, AND METHOD OF OPERATING A PUMP

Abstract

The present invention relates to a pump system for generating a volume flow of dialysis solution in a dialysis machine, wherein the pump system comprises at least one piston pump whose piston cooperates with a working fluid that in turn exerts force on a conveying means, in particular on a membrane, wherein setting means are provided by which the conveying volume of the piston pump per piston stroke can be reduced, with the setting means comprising a position-variable mechanical piston stop to reduce the piston stroke and/or means to reduce the quantity of the working fluid and/or means to reduce the volume of the conveying chamber that cooperates with the conveying means and that contains the dialysis solution to be conveyed.

Claims

1. A pump system for generating a volume flow of dialysis solution in a dialysis machine, wherein the pump system comprises at least one piston pump whose piston cooperates with a working fluid that in turn exerts force on a conveying means, in particular on a membrane, characterized in that setting means are provided by which the conveying volume of the piston pump per piston stroke can be reduced, with the setting means comprising a position-variable mechanical piston stop to reduce the piston stroke and/or means to reduce the quantity of the work fluid and/or means to reduce the volume of the conveying chamber that cooperates with the conveying means and that contains the dialysis solution to be conveyed.

2. A pump system in accordance with claim 1, characterized in that the working fluid is a liquid or a gas.

3. A pump system in accordance with claim 1, characterized in that input means or calculation means are provided by which the total desired conveying volume or the residual desired conveying volume from a specific point in time onward or the desired conveying volume per piston stroke can be input or determined and the setting means are connected to the input means or to the calculation means such that the setting means are configured to set the conveying volume of the piston pump per piston stroke in dependence on the values input into the input means or determined by the calculation means.

4. A pump system in accordance with claim 1, characterized in that the setting means are configured such that the conveying volume per piston stroke is constant over the total conveying time.

5. A pump system in accordance with claim 1 characterized in that the setting means are configured such that the conveying volume per piston stroke is variable over the conveying time and is in particular smaller toward the end of the conveying procedure than at the start of the conveying procedure.

6. A pump system in accordance with claim 1, characterized in that the setting means are configured such that the quantity of the working fluid is reducible, with provision being made that the quantity of the working fluid is reduced, starting from a starting state, such that the influence of the membrane tension on the patient pressure and/or on the pressure of the working fluid is smaller than in the starting state.

7. A pump system in accordance with claim 1, characterized in that the pump has a piston space that is in communication via a hose with a chamber that is bounded by the membrane.

8. A pump system in accordance with claim 1, characterized in that the pump system has two piston pumps that have offset working cycles.

9. A dialysis machine, in particular a peritoneal dialysis machine, characterized in that the dialysis machine has a pump system in accordance with claim 1.

10. A method of conveying a dialysis solution by means of a piston pump whose piston cooperates with a working fluid that in turn exerts a force on a conveying means, in particular on a membrane, characterized in that the conveying volume per piston stroke is reduced for the purpose of increasing the conveying precision of the piston pump in that a piston abutment is changed such that the piston stroke is reduced and/or in that the quantity of the working fluid is reduced and/or in that the volume of the conveying chamber that cooperates with the conveying means and that includes the dialysis solution to be conveyed is reduced.

11. A method in accordance with claim 10, characterized in that the total desired conveying volume or the desired conveying volume from a specific point in time onward or the desired conveying volume per piston stroke is input in the input means or is determined by calculation means; and in that the reduction of the conveying volume is set in dependence on the values input into the input means or determined by the calculation means.

12. A method in accordance with claim 10, characterized in that the conveying volume per piston stroke is kept constant over the total conveying time or is varied over the conveying time, with provision preferably being made that the conveying volume per piston stroke is smaller toward the end of the conveying procedure than at the start of the conveying procedure.

Description

[0042] Further details and advantages of the invention will be explained in more detail with reference to an embodiment shown in the drawing.

[0043] There are shown:

[0044] FIG. 1: a schematic view of a pump system;

[0045] FIG. 2: a diagram to represent the pressure progression in the working fluid; and

[0046] FIG. 3: a further schematic diagram of the pump system of a peritoneal dialysis machine.

[0047] FIG. 1 shows a pump system that is known from the prior art, but that can also be used as part of the present invention, i.e. that is also in accordance with the invention. Reference is therefore made to the above statements on FIG. 1.

[0048] The reduction of the conveying volume per piston stroke can take place by a mechanical piston abutment, not shown, preferably at the base, i.e. in the region of the chamber end in which the piston moves. An alternative is the reduction of the volume of the hydraulic fluid or of another working fluid that extends between the piston and the membrane and that transmits the movement of the piston onto the membrane. To vary the volume, a storage container and a valve can be provided that make it possible that the working medium is received in the hydraulic circuit, etc. or is removed therefrom. These components are currently used to degas the working fluid and thus to achieve a maximum, best-possible travel path of the piston.

[0049] The invention is generally not limited to carrying out a reduction of the volume conveyed per piston stroke, but rather an increase of this volume can naturally also again be carried out if it is desired.

[0050] A further alternative of the setting comprises the reduction of the volume of a cassette, etc. that cooperates with the membrane of the pump system and that contains the dialysis solution.

[0051] The hydraulic pressure in the working fluid over the path of the piston is entered on FIG. 2.

[0052] The hatched regions mark the ramping up, i.e. the increase of the piston speed, and the ramping down, i.e. the reduction of the piston speed. In these regions marked by Ü, both pumps work alternately so that the hatched regions represent overlap regions of the operation of two pumps.

[0053] The start of the chamber in which the piston is received in a manner movable to and fro is marked by A and the end of the chamber is marked by E. F represents the chamber region that is relevant to the conveying and that is variably settable. The region of the hydraulic medium to be displaced is marked by H.

[0054] P represents the pump plate, i.e. the membrane, etc., which acts on the membrane of the conveying chamber of the disposable.

[0055] Exactly one pump can be used in accordance with the invention. The case is, however, also covered by the invention that two pumps or more than two pumps are present.

[0056] FIG. 3 shows a peritoneal dialysis machine or system known from the prior art.

[0057] As can be seen from FIG. 3, two membrane pumps (pump 1, pump 2) are typically used that each have a position encoder to be able to determine the piston position. The membrane pumps act on pump chambers 100 by which dialyzate is pumped out of correspondingly present dialyzate bags into the abdominal cavity of a patient or by which consumed dialyzate is drained from the abdominal cavity of the patient. To achieve a constant dialyzate volume flow despite the discontinuously working membrane pump, the hydraulic pressure P.sub.Hyd in the hydraulic lines is determined. In the event that the membrane pumps are pneumatically driven, the corresponding pneumatic pressure in the lines is determined. To ensure a pressure monitoring, the pressures P.sub.Hyd measured by means of the pressure sensors are compensated by some influencing factors. It is in this respect the respective membrane pressure P.sub.Membrane, on the one hand, i.e. the counter-pressure that is caused in response to the measured hydraulic pressure P.sub.Hyd due to the deflection and inherent tension of the membrane. As the deflection increases, the membrane tension increases disproportionally and is accompanied by a construction-induced speed response. This counter-pressure depends on the position of the hydraulic pump that is typically measured via a position encoder. The counter-pressure that arises due to the flow resistance in the system, i.e. in the pump and in the pump chamber configured as a disposable, is furthermore taken into account as a further compensation factor. This counter-pressure to be taken into account depends on the speed in the system. Finally, the hydrostatic pressure P.sub.Stat has to be taken into account that results due to the position of the patient.