Low-Input-Pressure Lung Demand Regulator With Dual-Profile Cam
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Solution Overview
Problem
Existing lung demand regulators in self-contained breathing apparatus (SCBA) face issues with pressure fluctuations, leading to negative face mask pressure and increased risk of contaminant ingress when breathing gas pressure drops below a certain level, posing safety hazards for users.
Innovation Solution
A demand regulator design featuring a primary lever arm with a cam element having distinct first and second profiles, which adjusts the displacement rate of the valve member based on breathing gas pressure, ensuring positive pressure within the mask by automatically adapting to varying input pressures through a diaphragm-actuated mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional lung demand regulator is used with a single cam profile, then the device structure is simple, but the face mask pressure becomes negative when input breathing gas pressure drops, allowing contaminant ingress
Solution Approach 1:
The cam element is divided into two distinct profiles: a first profile for normal operating conditions and a second profile for low input pressure conditions. This segmentation allows each profile to be optimized for its specific operating range, ensuring positive face mask pressure is maintained even when input breathing gas pressure drops, while avoiding unnecessary complexity in normal operation
Solution Approach 2:
The cam element dynamically transitions between two operational states based on input pressure conditions. The mechanism automatically selects the appropriate profile arc (first or second) depending on whether input pressure is above or below a threshold, enabling adaptive response to changing conditions without manual intervention
2Adaptability or versatility
If the valve member displacement rate is constant, then the mechanism is simple, but the regulator cannot automatically adapt to varying input pressures
Solution Approach 1:
The cam element changes its geometric parameters (profile shape) based on operating conditions. The first profile has a different displacement characteristic than the second profile, allowing the valve member displacement rate to vary automatically with input pressure levels. This parameter change enables the regulator to adapt to varying input pressures without adding complex control systems
3Reliability
If manual user intervention is required to adjust gas flow rates, then the control mechanism is simple, but user safety is compromised during pressure fluctuations
Solution Approach 1:
The regulator system performs self-adjustment through the dual-profile cam mechanism. When input pressure drops below the threshold, the mechanism automatically transitions to the second profile, which increases the valve member displacement rate to maintain positive face mask pressure. This self-service capability eliminates the need for manual user intervention during pressure fluctuations, enhancing user safety
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 regulator maintains positive pressure within the mask by automatically adjusting gas flow rates, preventing contaminant ingress and ensuring safe operation across varying input pressures without manual user intervention, thus enhancing user safety.
Implementation Method 1
When the pressure of breathing gas entering the LDR drops below a prescribed level... the diaphragm-actuated mechanism... automatically adapting to varying input pressures
Implementation Method 2
a cam element having a first profile and a second profile... pivoting of the primary lever arm through a first arc corresponding to the first profile of the cam element displaces the valve member at a first displacement rate; and pivoting of the primary lever arm through a second arc corresponding to the second profile of the cam element displaces the valve member at a second displacement rate
Data Source
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AI summary
There is disclosed a demand regulator for a breathing apparatus comprising: a primary lever arm comprising a cam element having a first profile and a second profile, the primary lever arm being pivotable; and a valve configured to regulate a flow of breathing gas through the demand regulator, the valve comprising a valve member being displaceable so as to regulate the flow of breathing gas; wherein the cam element of the primary lever arm is configured to displace the valve member during pivoting of the primary lever arm; and wherein: pivoting of the primary lever arm through a first arc corresponding to the first profile of the cam element displaces the valve member at a first displacement rate; and pivoting of the primary lever arm through a second arc corresponding to the second profile of the cam element displaces the valve member at a second displacement rate; the second displacement rate being different to the first displacement rate. Also disclosed is a breathing apparatus comprising a demand regulator, a diaphragm-actuated lever arm for a demand regulator, and a method for designing a cam element profile.