Telescopic Hold Open Rod Locking for Inadvertent Closure Prevention
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Solution Overview
Problem
Existing hold open rods (HORs) for fan cowls in nacelles face challenges in safely supporting the weight of the cowls while preventing inadvertent closure, requiring a mechanism that can transition between locked and unlocked configurations efficiently.
Innovation Solution
A telescopic hold open rod (HOR) with a lock sleeve, outer cylinder, retention sleeve, piston, lock mechanism, release spring, and lock spring, allowing transitions between unlocked and locked configurations through axial and rotational movements of components, ensuring secure locking and unlocking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a lock mechanism is added to prevent inadvertent closure, then reliability is improved, but device complexity increases
Solution Approach 1:
The lock mechanism components are nested within the telescopic rod structure. The locking cam is received within the locking recess of the distal end, and the spring assembly is contained within the proximal end cavity. This nesting approach allows the lock mechanism to be integrated into the existing HOR structure without adding external complexity, thereby improving reliability while minimizing the increase in device complexity.
Solution Approach 2:
The lock mechanism is divided into distinct functional segments: a locking cam with locking surface for engagement, a spring assembly for providing forcing, and a retaining ring for securing components. This segmentation allows each component to perform its specific function independently, making the overall mechanism more reliable while keeping the design modular and manageable.
2Reliability
If multiple lock balls are used to secure the piston, then reliability is improved, but device complexity increases
Solution Approach 1:
Multiple lock balls are strategically positioned at specific locations where they can most effectively secure the piston in the extended position. The lock balls are arranged in the locking recess to engage with the piston at critical points, providing reliable locking only where needed rather than uniformly throughout the structure. This localized approach improves reliability while minimizing the overall complexity compared to a more distributed locking system.
3Strength
If the HOR is designed to support considerable weight, then strength is improved, but ease of operation deteriorates
Solution Approach 1:
The spring assembly is configured to automatically engage the locking cam with the locking recess when the piston is in the extended position, without requiring manual intervention. The spring provides the forcing necessary to maintain the locked state, and the mechanism self-regulates the locking and unlocking processes based on the piston's position and the applied forces, thereby maintaining ease of operation even while supporting considerable weight.
Solution Approach 2:
The lock mechanism incorporates movable components including the locking cam that can rotate or move relative to the locking recess, and the spring assembly that dynamically adjusts the forcing based on the piston's position. This dynamic design allows the mechanism to adapt to varying load conditions while maintaining reliable locking, making the heavy-duty HOR easier to operate compared to static locking mechanisms.
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 HOR provides reliable support and secure locking of fan cowls, preventing inadvertent closure while allowing easy access for maintenance, enhancing safety and operational efficiency.
Implementation Method 1
a release spring (52) disposed between the OC outer radial surface and the LS inner radial surface
Implementation Method 2
a lock spring (50) disposed between the OC inner radial surface and the piston outer radial surface
Data Source
AI summary
A hold open rod has a lock sleeve, an outer cylinder, a lock mechanism, a plurality of lock balls, a retention sleeve, a piston including a piston head, a release spring, and a lock spring. The hold open rod is configured to move between an unlocked configuration (e.g., stowed) to a locked and loaded configuration. Relative movement (e.g., axially and/or radially) of components in the hold open rod assembly enable both configurations. The lock mechanism is positioned with the lock sleeve and the outer cylinder, and mechanically engages the piston head. The pin is positioned with the lock sleeve and a guide slot in the outer cylinder. The plurality of lock balls engage the lock sleeve, outer cylinder, and retention sleeve.