Check Valve Cracking Pressure Calibration for Cataract Surgery
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Solution Overview
Problem
Existing cataract surgery systems using water-jet based liquefaction devices face suboptimum performance due to inaccuracies in determining the cracking pressure of the check valve, leading to mismatched flow rates and pressures, which affect the efficiency of lens removal.
Innovation Solution
A method to determine the pressure corresponding to a predetermined flow rate by incrementally pressurizing the injection fluid container and monitoring the vacuum at the handpiece tip, allowing for precise control of the minimum operating pressure to achieve optimal flow rates during surgical operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the cracking pressure is determined based on assumed theoretical values from spring stiffness and number of turns, then the system design is simplified, but the actual flow rate control precision deteriorates
Solution Approach 1:
The system performs preliminary calibration before actual use by incrementally pressurizing the container and monitoring vacuum levels to empirically determine the cracking pressure. This preliminary measurement establishes accurate pressure-flow rate correspondence for the specific check valve being used, compensating for manufacturing variations in spring stiffness and ball geometry.
Solution Approach 2:
The system implements feedback control by continuously monitoring the vacuum level at the handpiece tip during pressurization. When the vacuum level changes indicating check valve opening, the system uses this feedback signal to identify the actual cracking pressure and adjust subsequent pressure control accordingly, ensuring precise flow rate control.
2Reliability
If the container pressure is increased to compensate for potential check valve pressure variations, then the flow rate reliability improves, but the energy consumption increases
Solution Approach 1:
The system performs preliminary calibration to empirically determine the exact cracking pressure for each check valve before use. By knowing the actual cracking pressure rather than using conservative estimates, the system can pressurize the container to the precise minimum required level, avoiding unnecessary energy consumption while ensuring reliable flow rate control.
Solution Approach 2:
The system dynamically adjusts the container pressure based on the empirically determined cracking pressure and desired flow rate. Rather than maintaining constantly high pressure, the system optimizes pressure levels in real-time based on actual check valve characteristics and operational requirements, reducing energy consumption while maintaining reliability.
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 ensures accurate control of the flow rate, enhancing the performance and energy efficiency of the handpiece by determining the correct pressure for the check valve, thereby improving the efficiency of lens removal during cataract surgery.
Implementation Method 1
the fluidics module increases the pump speed until it determines that a predetermined vacuum is present at the tip
Implementation Method 2
Inside the handpiece is a spring and ball that together construct a check valve
Implementation Method 3
The cracking pressure of the check valve is the minimum upstream pressure at which the valve will operate
Data Source
AI summary
The present invention accommodates differences in cracking pressures between check valves by determining a pressure on the input of a check valve that corresponds to a predetermined flow rate at the output of the check valve. A container is incrementally pressurized and the vacuum at a point on the output side of the check valve is monitored. Once fluid begins to pass through the check valve, the vacuum drops. At the predetermined flow rate, the pump cannot maintain a predetermined vacuum level since it cannot exceed a maximum speed. At this point the pressure applied to the container corresponds to the predetermined flow rate. An offset is added to the pressure to determine the minimum operating pressure.