Conical Dialysis Pump Chamber Reduces Membrane Stress
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Solution Overview
Problem
Existing membrane pumps for dialysis machines face issues such as high membrane stress and folding, leading to reduced lifespan and pumping inaccuracies due to sharp angles and the dome-shaped pump chamber, causing fluid control challenges and potential blood damage.
Innovation Solution
A conical pump chamber design with a smooth transition surface between the membrane and the recessed surface, allowing for controlled membrane deflection and reduced stress, improving volumetric performance and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a dome-shaped pump chamber is used, then the membrane can be actuated to draw fluid into the chamber, but the membrane descends rapidly causing high stress and difficult fluid volume control
Solution Approach 1:
The pump chamber uses a conical shape with a curved transition surface instead of a sharp dome shape. This curvature modification allows the membrane to descend in a more controlled manner, reducing stress concentrations while maintaining the pumping function. The smooth curved surface guides the membrane fold uniformly across the transition.
2Device complexity
If a sharp angle exists between the flat portion and recess, then the pump structure is simple, but the membrane folds and leaves dead spots causing pumping inaccuracies
Solution Approach 1:
The sharp angle between the flat portion and recess is replaced with a smooth curved transition surface. This eliminates the dead spots where blood could pool and ensures the membrane makes uniform contact with the chamber wall during actuation, improving pumping accuracy without significantly increasing structural complexity.
3Speed
If the membrane descends rapidly into the chamber, then fluid is pumped quickly at the beginning of the stroke, but volumetric control becomes difficult and hammer action occurs
Solution Approach 1:
The conical chamber with curved transition surface modifies the membrane descent trajectory, causing it to progress more uniformly from the flat portion through the curved transition into the recess. This distributes fluid displacement more evenly throughout the stroke, improving volumetric control and reducing hammer action.
4Ease of operation
If the membrane folds over the edge of the flat portion, then the pump chamber can be actuated, but high stress concentrates at the fold causing reduced membrane life
Solution Approach 1:
The curved transition surface provides a gradual path for the membrane fold, distributing stress along the curved surface rather than concentrating it at a sharp edge. This reduces peak stress on the membrane during actuation, extending membrane lifespan while maintaining full actuation capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The conical design enhances fluid displacement control, reduces membrane stress, and minimizes the risk of blood damage by ensuring consistent fluid expulsion and uptake, thereby improving the pump's accuracy and membrane longevity.
Implementation Method 1
the membrane is actuated to draw fluid into, and pump the fluid from, the chamber
Implementation Method 2
the membrane descends into the chamber in a more controlled and predictable manner than the prior art pump
Data Source
Figure 1
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AI summary
A pump for a dialysis machine, the pump having a pump chamber and a deformable membrane actuable to pump a fluid from the pump chamber, the pump chamber being substantially conical such that the membrane is actuated to extend into the conical chamber in order to pump the fluid from the chamber.