Peristaltic Pump Cassette Offset Ridges Tapered Channels
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Solution Overview
Problem
Existing peristaltic pumps used in ophthalmic surgery exhibit pulsations in fluid flow, which can lead to unstable flow rates during aspiration and infusion procedures, despite previous designs attempting to reduce these pulsations.
Innovation Solution
The design incorporates a cassette with a flexible sheet and a cassette body featuring transition regions with offset ridges and tapered fluid path channels, along with a roller operation strategy that adjusts speed to compensate for flow variations, ensuring a more consistent fluid flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a peristaltic pump uses rollers to compress a flexible conduit for fluid pumping, then fluid flow is achieved, but pulsations occur in the fluid flow
Solution Approach 1:
The pump conduit is divided into multiple segments along its length, with each segment being independently compressible by rollers. This segmentation allows the flow from multiple segments to overlap and average out the pulsations, transforming a single large pulsation into multiple smaller, overlapping pulsations that cancel each other out.
Solution Approach 2:
Multiple rollers are positioned at different angular positions around the pump hub, creating periodic compression zones along the conduit. The rollers are arranged so that as one roller releases a conduit segment, another roller is compressing it, creating a continuous and more uniform flow pattern that reduces pulsations.
2Stability of the object's composition
If tapered channel transition regions are used in the elastomeric sheet, then pulsations are reduced, but manufacturing complexity increases
Solution Approach 1:
The transition regions are formed by combining the elastomeric sheet with the rigid cassette body, where the sheet's tapered channels integrate with the cassette's fluidic pathways. This merging allows the tapered geometry to be achieved through the flexible nature of the elastomeric material rather than complex rigid machining, simplifying manufacturing.
Solution Approach 2:
The elastomeric sheet acts as a flexible shell that inherently provides the tapered channel transition regions through its material properties and molding process. The flexibility of the thin film allows it to conform to the tapered geometry without requiring complex rigid structures, reducing manufacturing complexity while maintaining flow stability.
3Stability of the object's composition
If multiple pump conduit segments are used with out-of-phase rollers, then pulsations are reduced, but device complexity increases
Solution Approach 1:
The same roller hub and roller mechanism serve multiple functions: they provide the pumping action through compression and simultaneously create the out-of-phase action across multiple conduit segments. The universal application of the roller mechanism to all segments eliminates the need for separate complex control systems for each segment, reducing overall device complexity.
Solution Approach 2:
The rollers are positioned asymmetrically around the pump hub at specific angular intervals that create out-of-phase compression zones. This asymmetric arrangement allows multiple conduit segments to be pumped with phase differences that reduce pulsations, achieving flow stability without requiring symmetric, equally complex multi-segment configurations.
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
This approach significantly reduces pulsations in fluid flow, resulting in a smoother and more stable flow rate, enhancing the efficiency of ophthalmic surgical procedures.
Implementation Method 1
Peristaltic pumps are a type of positive displacement pump often used in medical devices because of the limited contact between the pump and the fluid. In a typical design, the pumped fluid makes contact only with an easily removable component of the pump system. To achieve flow, the fluid is present in a flexible conduit that is locally collapsed to the point of blocking flow. The sealing point is moved along the conduit in the direction of the flow.
Data Source
AI summary
Systems and methods are disclosed for reducing pulsations in peristaltic pumps. In some examples, a cassette comprises a cassette body and a flexible sheet joined to the cassette body, wherein a transition region of the flexible sheet comprises at least one ridge that has a maximum height at a position that is offset from a center line of a cassette body transition channel. In some examples, a cassette body transition channel comprises side walls that taper toward an active region of the fluid path and/or toward a bottom of the transition channel. An example method of operating a peristaltic pump comprises operating rollers at a higher speed during portions of a revolution that otherwise would result in a lower than average flow rate and at a lower speed during portions of the revolution that otherwise would result in a higher than average flow rate.