Liquid Feeding Control for Stable Gradient Mixing Ratios
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Solution Overview
Problem
Existing liquid feeding apparatuses in liquid chromatographs face challenges in achieving high accuracy due to fluctuations in the mixing ratio of mobile phases caused by the opening and closing operations of selector valves, which are difficult to control and costly to improve mechanically.
Innovation Solution
A liquid feeding apparatus and method that control the opening and closing timing of selector valves and adjust the speed of plungers to minimize fluctuations in the mobile phase, using a control unit to synchronize the operations with the aspiration and discharge processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the opening and closing operation of the selector valve is controlled to improve the mixing ratio accuracy, then the manufacturing cost increases due to the need for high-precision mechanical components
Solution Approach 1:
The patent replaces the mechanical control system of the selector valve with a fluid pressure control system. By using pressure changes in the common passage to automatically open and close the selector valve, the system eliminates the need for high-precision mechanical timing mechanisms and motors, thereby reducing manufacturing costs while maintaining mixing ratio accuracy.
Solution Approach 2:
The selector valve is designed to open and close automatically based on pressure differential self-regulation. When the plunger aspirates liquid, pressure changes in the common passage naturally cause the selector valve to switch between chambers without requiring external mechanical actuation, making the system self-controlling and reducing manufacturing complexity.
2Productivity
If the plunger aspiration speed is increased to improve productivity, then the mixing ratio accuracy deteriorates due to fluctuations caused by rapid opening and closing of the selector valve
Solution Approach 1:
The system pre-establishes pressure equilibrium in the common passage before the plunger reaches the aspiration position. By ensuring that pressures are balanced in advance, the selector valve can switch smoothly without causing liquid fluctuations even when the plunger moves at high speed, thus maintaining mixing accuracy while enabling high productivity.
Solution Approach 2:
The design incorporates pressure cushioning by maintaining equal pressure in both chambers of the common passage before aspiration begins. This pre-cushioning of pressure differences prevents sudden liquid surges when the selector valve switches, allowing high-speed operation without compromising mixing ratio precision.
3Manufacturing precision
If the selector valve opening and closing timing is precisely controlled to improve mixing ratio accuracy, then the device complexity increases due to additional control mechanisms
Solution Approach 1:
The selector valve timing control is achieved through self-service pressure differential control. The valve automatically opens and closes in response to pressure changes caused by the plunger's own aspiration motion, eliminating the need for separate timing control mechanisms, sensors, or feedback systems, thus maintaining simplicity while ensuring accurate mixing ratios.
Solution Approach 2:
The common passage acts as an intermediary that mediates between the plunger's mechanical motion and the selector valve's switching action. Pressure changes in this intermediate fluid pathway automatically translate plunger position into valve timing, providing precise control without direct mechanical or electronic control linkages.
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 enables highly accurate feeding of liquids by reducing fluctuations in the gradient mixing ratio, enhancing the precision of liquid chromatography without increasing costs.
Implementation Method 1
a plunger that moves to aspirate the mobile phase
Implementation Method 2
a selector valve that switches between a plurality of mobile phases by opening and closing
Implementation Method 3
a common passage into which mobile phases are switched by the selector valve and opened
Implementation Method 4
temporally changing the composition ratio of the mobile phase fed from the liquid feeding apparatus
Data Source
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AI summary
A liquid feeding apparatus that can feed a liquid with high accuracy is achieved. The liquid feeding apparatus includes a liquid feeder having a cylinder for performing operations of aspirating and discharging a solvent when a plunger slides, a pressure sensor installed on the downstream side of the liquid feeder and configured to detect pressure of the solvent to be discharged, at least one selector valve configured to switch between a plurality of solvents to be aspirated and discharged, and a controller configured to control the operations of the liquid feeder and the operation of the selector valve. The controller is configured to control the operation of the selector valve in synchronization with the aspiration operation of the plunger so that a mixing ratio of the solvents changes, control the plunger to cause the plunger to operate at first acceleration and second acceleration that are different from each other, and suppress a fluctuation of the solvent to be aspirated by the plunger.