Syringe Driver Control for Low-Flow Stiction and Start-Up Delay
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Solution Overview
Problem
Existing syringe pumps face challenges in delivering medical fluids smoothly and predictably, particularly at low flow rates, due to mechanical interactions that cause resistance and friction, leading to inconsistent and delayed fluid delivery.
Innovation Solution
The infusion system incorporates a stiff drivetrain, initial acceleration after syringe installation, variable drive head movements, and mechanical vibrations to overcome friction, ensuring consistent and prompt fluid delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a threaded lead screw with screw drive mechanism is used to drive the plunger, then the plunger can be advanced into the barrel, but friction between the stopper and barrel causes resistance and inconsistent fluid delivery
Solution Approach 1:
The patent applies mechanical vibration between the barrel and plunger to reduce static friction and prevent the stopper from adhering to the barrel wall. The vibration device generates oscillatory motion that disrupts the frictional contact, ensuring smooth and consistent plunger advancement even at low flow rates, thereby resolving the inconsistency caused by friction.
2Ease of operation
If the drive head advances the plunger at a constant rate, then the mechanism is simple to control, but friction causes delays and fluctuations in fluid delivery
Solution Approach 1:
The patent applies preliminary action by initiating mechanical vibration between the barrel and plunger before the drive head begins advancing the plunger. This pre-vibration reduces static friction and prevents adhesion from developing, ensuring that when the plunger is advanced even at low rates, fluid delivery begins promptly without delay or fluctuation.
3Measurement precision
If the plunger is advanced at low flow rates, then precise dosing is achieved, but friction between the stopper and barrel causes inconsistent delivery
Solution Approach 1:
The patent applies mechanical vibration specifically during low flow rate operation to counteract the increased relative importance of friction at slow speeds. The vibration maintains smooth plunger advancement and consistent fluid delivery, enabling precise dosing without sacrificing delivery smoothness or causing fluctuations.
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 system achieves smooth, prompt, and predictable fluid delivery by reducing friction-related delays and fluctuations, optimizing flow rates for various syringe sizes and conditions.
Implementation Method 1
a vibration device for applying mechanical vibration between the barrel and the plunger
Implementation Method 2
detecting when friction between the stopper and the barrel exceeds a threshold
Data Source
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AI summary
A syringe pump can be operated to produce fluid flow from a syringe installed therein. Features of the pump can produce a desired rapid commencement of flow followed by smooth delivery uninterrupted by stiction-induced slowing and acceleration. A stiff drivetrain can facilitate detection of excessive forces indicative of friction at a stopper-wall interface. The motor drive, gearing, and control parameters can enable customized acceleration patterns to determine optimal initial stage advancement to provide fluid delivery. These patterns can minimize or eliminate the delay in commencement of flow by overcoming both mechanical slack remaining and syringe stopper slack. To avoid flow irregularities produced by stiction forces in the stopper further, a mechanical vibration can be provided to the syringe and/or barrel to introduce movement of the stopper-wall interface, reducing the creation of high static friction coefficients.