Encapsulated Shock Absorber Pressure Sensing via Inner Cylinder Pipe
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Solution Overview
Problem
Existing aircraft undercarriage systems with encapsulated shock absorbers do not allow for direct measurement of pressure in the expansion chamber, as the strut is not subjected to the pressures within the shock absorber.
Innovation Solution
A method involving drilling a hole in the inner cylinder of the shock absorber in register with the expansion chamber and connecting it via a pipe to a pressure sensor located outside the strut, allowing pressure measurement without major modifications to the shock absorber or undercarriage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a hole is made in the strut wall to measure pressure, then pressure measurement is simple and direct, but this modification is not applicable to encapsulated shock absorbers where the strut is not subjected to internal pressures
Solution Approach 1:
A pipe is introduced as an intermediary element to transmit pressure from the expansion chamber to the pressure sensor. The pipe connects the hole made in the inner cylinder to the pressure sensor mounted on the strut, allowing indirect pressure measurement without requiring the strut wall to be directly exposed to expansion chamber pressure.
Solution Approach 2:
The pressure measurement path is extended from a direct two-dimensional wall penetration to a three-dimensional path through the inner cylinder volume. The pipe extends from the hole through the inner cylinder space to reach the pressure sensor, utilizing the available internal volume for pressure transmission.
2Device complexity
If the pressure sensor is mounted directly on the strut wall, then the measurement is simple, but the strut must be subjected to expansion chamber pressures which is not the case in encapsulated shock absorbers
Solution Approach 1:
The pipe serves as a mediator to faithfully transmit pressure signals from the expansion chamber to the sensor. This ensures the pressure sensor mounted on the strut receives accurate pressure information from the expansion chamber without requiring direct pressure exposure of the strut wall.
3Measurement precision
If a hole is made in the inner cylinder to access the expansion chamber, then pressure measurement becomes possible, but the inner cylinder structure is modified
Solution Approach 1:
A hole is extracted or removed from the inner cylinder wall to create an opening into the expansion chamber. This minimal extraction allows the pipe to penetrate and establish pressure communication while maintaining the overall integrity and function of the inner cylinder structure.
Data Source
AI summary
An encapsulated shock absorber of an aircraft undercarriage includes a sliding rod slidably mounted in a leg strut of the undercarriage and an inner cylinder extending inside the strut. The inner cylinder is fastened to the strut via a top end, and the rod slides around the inner cylinder. The inner cylinder is terminated inside the sliding rod by a diaphragm that defines an oil chamber in the shock absorber and inside the sliding rod. A mixed oil/gas chamber is located in the inner cylinder, and an expansion chamber extends between the sliding rod and the inner cylinder. A hole being made in the inner cylinder in register with the expansion chamber is connected by a pipe to a pressure sensor situated outside the strut. The pipe extends inside the inner cylinder from the hole to the top end of the inner cylinder.