Metering Pump Plunger Speed Control for Anesthesia Vaporizer Pulsation
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Solution Overview
Problem
Conventional anesthesia apparatuses face challenges with pulsation in metering pumps, leading to increased costs and larger sizes due to the need for vaporizing chambers, which cause time lags and concentration overshoots/undershoots when changing anesthetic gas concentrations or fresh-gas flow rates.
Innovation Solution
A driving method for metering pumps that varies the motor's revolution speed sinusoidally during discharge periods, keeping the plunger's traveling speed constant, allowing for a longer discharge period than suction period, and eliminating the need for a vaporizing chamber by using a sinusoidal revolving motion controlled by a stepping motor with specific drive pulse timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional metering pump with sinusoidal reciprocating motion is used, then the pump structure is simple and easy to manufacture, but pulsation occurs in the discharge volume leading to concentration fluctuations
Solution Approach 1:
The patent applies dynamics by making the discharge period variable rather than fixed. The control section dynamically adjusts the discharge period based on the set anesthetic-gas concentration value, extending it when the concentration is low to maintain stable discharge volume and reduce pulsation, while allowing normal operation when concentration is high.
Solution Approach 2:
The patent changes the operational parameter of the discharge period to resolve the contradiction. By extending the discharge period in response to low anesthetic-gas concentration values, the system maintains stable discharge volume without requiring structural modifications to the pump, thus preserving ease of manufacture while improving discharge stability.
2Stability of the object's composition
If a vaporizing chamber is added to suppress pulsation, then concentration stability improves, but the apparatus size and cost increase
Solution Approach 1:
The patent extracts the pulsation suppression function from the vaporizing chamber and relocates it to the control section. By implementing intelligent control that extends the discharge period based on concentration values, the system eliminates the need for the vaporizing chamber while maintaining concentration stability, thus reducing apparatus volume and cost.
Solution Approach 2:
The patent replaces the mechanical vaporizing chamber with an electronic control system. The control section uses computational logic to adjust the discharge period, substituting the physical volume-based pulsation suppression mechanism with a software-based control approach, thereby eliminating the need for additional hardware components.
3Stability of the object's composition
If the discharge period is extended to reduce pulsation, then concentration stability improves, but the pumping efficiency decreases
Solution Approach 1:
The patent applies dynamics by making the discharge period adaptive rather than constantly extended. The control section only extends the discharge period when the anesthetic-gas concentration value is low, maintaining high pumping efficiency when concentration is high. This dynamic adjustment resolves the contradiction by optimizing the discharge period based on real-time operational conditions.
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 suppresses pulsation in metering pumps, reduces the size and cost of anesthesia apparatuses, and prevents time lags and concentration fluctuations when changing gas settings, ensuring stable anesthesia delivery.
Implementation Method 1
a metering pump (16) driven by a stepping motor (15)
Implementation Method 2
in the vaporizing chamber 59, the anesthetic agent is mixed with the fresh gas
Implementation Method 3
in the vaporizing chamber 59, the anesthetic agent is mixed with the fresh gas
Data Source
Figure 1(a)~1(f)
Figure 2
Figure 3(a)~3(e)
AI summary
[Problems] To provide a driving method for a metering pump, a driving apparatus for a metering pump, a vaporizer and an anesthesia apparatus which are capable of suppressing a pulsation in the metering pump, and lowering the costs and reducing the sizes of the vaporizer and the anesthesia apparatus. [Means for solving the Problems] A metering pump 16 is joined to the stepping motor 15, includes an eccentric mechanism converting a revolving motion of the stepping motor 15 into a reciprocating motion of a plunger 16A, and makes a constant liquid delivery by sucking and discharging an anesthetic agent through variations in the cubic volume of a cylinder 16D caused by the reciprocating motion of the plunger 16A. The control section 12: calculates a suction and discharge cycle T of the metering pump 16 on the basis of a set anesthetic-gas concentration and a fresh-gas flow rate; sets a discharge period T2 of the cycle T to be longer than a suction period T1 of the cycle T; and controls the revolution speed of the stepping motor 15 so that the travelling speed of the plunger 16A is kept constant during the discharge period T2.