Peristaltic Pump Shoe Constraint for Fluid Occlusion
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Solution Overview
Problem
Peristaltic pumps used for blood and other biological fluids face issues with excessive pressure and incomplete occlusion, which can damage cells due to poorly constrained rollers and lack of effective force distribution, leading to hemolysis and inefficiencies in fluid handling.
Innovation Solution
A peristaltic pump design where the shoe has constrained rotational and displacement degrees of freedom, utilizing a linear bearing with Teflon liners and lubricant to minimize the force required for occlusion, and an actuator with rollers that rotate in one direction to compress the tube effectively, reducing pressure fluctuations and ensuring full occlusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the shoe is allowed to move freely in all directions, then the device complexity is reduced, but the reliability of fluid occlusion deteriorates due to incomplete compression
Solution Approach 1:
The constraint mechanism is segmented into multiple independent degrees of freedom, each controlled by specific bearing elements. The linear bearing constrains X and Y directions while allowing Z movement, while the spherical bearing handles rotational constraints. This segmentation allows reliable occlusion through targeted constraints without unnecessarily complicating the entire mechanism.
Solution Approach 2:
Bearing elements act as intermediaries between the shoe and the housing. The linear bearing with its raceway and roller elements provides precise linear guidance, while the spherical bearing with its raceway and roller elements provides rotational guidance. These intermediary components enable reliable constraint without direct rigid connections that would increase complexity.
2Reliability
If excessive force is applied to ensure full occlusion, then the reliability of fluid sealing is improved, but the harmful effects on biological fluids increase due to cell damage
Solution Approach 1:
The shoe is designed with dynamic movement capabilities, allowing it to rotate and translate within specific ranges constrained by the bearings. This dynamic design enables the shoe to adapt to variations in tube positioning and compression needs, achieving reliable occlusion with minimal force rather than requiring excessive constant force that would damage cells.
Solution Approach 2:
The constraint mechanism changes the parameters of motion for the shoe, limiting it to specific degrees of freedom (linear movement along Z-axis, rotation about Z-axis) while preventing harmful movements. This parameter control ensures that compression forces are applied optimally to achieve sealing without exceeding thresholds that would cause cell damage.
3Reliability
If the shoe is constrained in multiple directions, then the reliability of force application is improved, but the ease of operation deteriorates due to restricted movement
Solution Approach 1:
The movement constraints are segmented into functional categories: linear movement along the Z-axis is allowed for compression, rotation about the Z-axis is allowed for positioning, while movement in X and Y directions is prevented. This segmentation provides reliable force application in the compression direction while maintaining operational ease through allowed rotational and translational adjustments.
Solution Approach 2:
The shoe incorporates dynamic movement within constrained ranges, allowing it to rotate and translate as needed during operation. The linear bearing enables smooth linear movement for compression, while the spherical bearing enables rotational movement for positioning. This dynamic capability maintains ease of operation while ensuring reliable force application through the constrained degrees of freedom.
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 constrained shoe and actuator design reduces the minimum force needed for occlusion, minimizing damage to biological fluids and eliminating low-frequency oscillations, thereby enhancing the pump's efficiency and preventing hemolysis.
Implementation Method 1
The linear bearing has two Teflon liners trapping a reservoir of lubricant between them
Implementation Method 2
A peristaltic pump is a volumetric positive displacement pump that moves fluid through a tube by progressively compressing the fluid tube in one direction
Implementation Method 3
The constrained shoe and actuator design reduces the minimum force needed for occlusion, minimizing damage to biological fluids and eliminating low-frequency oscillations
Data Source
Figure 1A~1E
Figure 2A~2B
Figure 3
AI summary
A peristaltic pump actuator includes a rotor element supporting rollers, the rotor element being configured to rotate about a rotor axis and the rollers each being configured to rotate about a roller axis that is parallel to the rotor axis. The rotor element and each of the rollers is constrained such that the rotor element and rollers are able to rotate only about their respective axes. A shoe having a displacement axis perpendicular to the rotor axis is forced against the rollers by an urging element without rotation in any axis. A tube may be placed between the shoe and the rollers.