Lung Demand Valve Cam Profiles for Low-Pressure Breathing
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Solution Overview
Problem
Existing lung demand regulators (LDRs) in self-contained breathing apparatus (SCBA) face issues with performance degradation and increased safety risks when subjected to lower breathing gas input pressures, leading to negative pressure inside the mask and potential contamination from environmental hazards.
Innovation Solution
A demand regulator design featuring a primary lever arm with a cam element having distinct first and second profiles that control the displacement rate of the valve member, automatically adapting to varying input pressures to maintain positive pressure within the mask, using a diaphragm-actuated lever arm and adjustable components to optimize gas flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional lung demand regulator is used with fixed valve displacement, then the structure is simple, but the face mask pressure becomes negative when input breathing gas pressure drops, allowing environmental contaminants to enter
Solution Approach 1:
The patent applies dynamics by making the valve member displacement variable rather than fixed. The cam element with its specific profile causes the valve member to be displaced at different rates during lever arm pivoting, allowing the system to automatically adapt to varying input pressures and maintain positive face mask pressure without manual intervention
Solution Approach 2:
The patent changes the displacement rate parameter of the valve member by using a cam element with a specifically designed profile. This profile ensures that the valve member displacement rate varies during lever arm pivoting, enabling the regulator to maintain effective positive pressure in the face mask across different input breathing gas pressures
2Reliability
If the valve member displacement rate is increased to compensate for low input pressure, then positive pressure is maintained, but the device requires complex mechanisms to control displacement rates
Solution Approach 1:
The cam element is designed to automatically provide the correct displacement rate variation based on the lever arm pivoting motion. The system self-regulates the valve member displacement without requiring external control mechanisms, as the cam profile inherently translates lever arm movement into the required variable displacement rates
Solution Approach 2:
The cam element employs a curved profile rather than a linear or flat design. This curvature enables the cam element to translate the lever arm pivoting motion into variable displacement rates for the valve member, allowing automatic compensation for input pressure variations through geometric design
3Productivity
If manual adjustment of valve displacement is allowed, then gas flow can be optimized, but user intervention is required which compromises safety in hazardous environments
Solution Approach 1:
The demand regulator automatically optimizes breathing gas flow by using the cam element to vary the valve member displacement rate based on lever arm pivoting. This eliminates the need for manual user adjustment, allowing the system to self-optimize performance while the user remains focused on safety-critical tasks in hazardous environments
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 design ensures consistent positive pressure within the mask, preventing contamination by automatically adjusting gas flow rates based on input pressure, enhancing safety and performance across varying breathing gas pressures without manual user intervention.
Implementation Method 1
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
AI summary
A demand regulator for a breathing apparatus may include a primary lever arm can include 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 may include a valve member being displaceable so as to regulate the flow of breathing gas. The cam element of the primary lever arm is configured to displace the valve member during pivoting of the primary lever arm. Pivoting of the primary lever arm through a first arc displaces the valve member at a first displacement rate; and pivoting of the primary lever arm through a second arc displaces the valve member at a second displacement rate. A breathing apparatus can include a demand regulator and a diaphragm-actuated lever arm. A method for designing a cam element profile is disclosed.