Piston Pressure Indicator Insensitive to Orientation
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Solution Overview
Problem
Existing pressure indicators for inflatable cuffs, such as those used in endotracheal tubes, are sensitive to geometric and material variations and orientation with respect to gravity, leading to inaccuracies in pressure measurement.
Innovation Solution
A pressure indicator system comprising a housing with a movably disposed piston, where the piston's position within a bore is indicative of pressure, and the system is designed to be insensitive to structural parameters and material properties, using a compact in-line configuration with a permeable barrel allowing visual indication of pressure through transparent or translucent materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a bellows-based pressure indicator is used, then pressure indication is achieved, but measurement precision deteriorates due to sensitivity to geometric and material variations
Solution Approach 1:
The patent replaces the bellows-based mechanical system with a piston-cylinder system. The piston directly transmits pressure from the cuff through a fluid-filled chamber to move an indicator, eliminating the complex elastic deformation mechanisms of bellows that are sensitive to manufacturing variations. This substitution provides more consistent and reliable pressure measurement.
Solution Approach 2:
The patent changes the fundamental operating parameter from elastic deformation (bellows) to direct pressure transmission (piston). By using a fluid-filled chamber where pressure acts uniformly on the piston surface, the system achieves measurement that is independent of geometric tolerances and material property variations, significantly improving reliability.
2Measurement precision
If a bellows-based pressure indicator is used, then pressure indication is achieved, but measurement precision deteriorates due to orientation sensitivity
Solution Approach 1:
The piston-cylinder system with fluid coupling replaces the orientation-sensitive bellows mechanism. The fluid transmits pressure isotropically, meaning the pressure force acts equally in all directions on the piston, making the measurement independent of the device's orientation relative to gravity or other external forces.
Solution Approach 2:
The fluid-filled chamber acts as an intermediary between the pressure source (cuff) and the indicator mechanism. This fluid medium transmits pressure forces uniformly regardless of orientation, decoupling the measurement from gravitational effects and enabling accurate readings in any position.
3Ease of manufacture
If a transparent housing with bellows is used, then visual indication is achieved, but measurement precision deteriorates due to bellows resilience variations
Solution Approach 1:
The patent substitutes the bellows with a rigid piston-cylinder assembly. The piston moves linearly within the cylinder, providing a direct and predictable mechanical relationship between pressure and indicator position. This eliminates the non-linear and variable elasticity characteristics of bellows while maintaining visual indication through the transparent housing.
Solution Approach 2:
Instead of using a flexible element (bellows) that deforms to indicate pressure, the patent uses a rigid element (piston) that moves only when forced by pressure. This inversion of the traditional approach—where the indicator moves rather than deforms—provides more consistent and accurate measurements while preserving visual indication.
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 solution provides accurate pressure measurement that is not affected by manufacturing variations or orientation, ensuring reliable and precise pressure indication in inflatable cuff systems.
Implementation Method 1
a first volume (72) defined by the internal surface (51), the inlet end member (46), and the piston (38); a second volume (74) defined by the internal surface (51), the outlet end member (48), and the piston (38)
Data Source
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AI summary
A fluid pressure indicating device is disclosed. The pressure indicating device includes a housing defining a cylindrical bore therein, and a piston movably disposed within the cylindrical bore. The housing includes a first portion that is permeable to visible light, a first end member, and a second end member opposite the first end member. A first variable volume is defined by the cylindrical bore, the piston, and the first end member of the housing. An inlet port is defined by the first end member of the housing and is in fluid communication with the first variable volume. A piston bypass channel is disposed outside the cylindrical bore and is in fluid communication with the inlet port. An outlet port is defined by the second end member, such that the outlet port is in fluid communication with the piston bypass channel.