Telescopic Hold Open Rod Locking With Ball-and-Slot Release
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Solution Overview
Problem
Hold open rods used in aircraft fan cowls face challenges in safely supporting the weight and preventing inadvertent closure, requiring a mechanism that can securely lock in a deployed configuration while allowing safe operation and access for maintenance.
Innovation Solution
A telescopic hold open rod system comprising a control sleeve, outer cylinder, lock balls, lock sleeve, piston, piston head, release spring, and lock spring, which transitions between unlocked and locked configurations through axial and rotational movements, ensuring secure locking and safe operation by using lock balls and a pin guide slot mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a telescopic hold open rod is used to support fan cowl weight, then the device can provide sufficient holding force, but the mechanism becomes more complex with multiple moving parts
Solution Approach 1:
The hold open rod is divided into multiple telescopic sections that can extend and retract independently. Each section has its own locking mechanism with lock balls and channels, allowing the rod to achieve greater length and holding force while maintaining a compact retracted form. This segmentation enables the rod to provide sufficient support force for fan cowls while managing complexity through modular design.
Solution Approach 2:
The telescopic sections are nested within each other, with inner sections sliding inside outer sections. The lock balls are stored within the sections and engage with channels when locking is required. This nesting arrangement allows the rod to extend to multiple times its retracted length while maintaining a space-efficient design, providing the necessary holding force without excessive complexity.
2Reliability
If a locking mechanism with multiple components is implemented, then the reliability of secure locking is improved, but the ease of operation deteriorates
Solution Approach 1:
The locking mechanism is designed to be self-actuating through spring-loaded lock balls that automatically engage with locking channels when the telescopic sections are extended to their desired positions. The springs provide the necessary force for the lock balls to snap into the channels, ensuring reliable locking without requiring manual intervention. This self-service approach maintains high reliability while simplifying operation, as the system locks automatically upon extension.
3Reliability
If the hold open rod is designed to prevent inadvertent closure, then the safety is improved, but the ease of operation for intentional release deteriorates
Solution Approach 1:
The locking mechanism uses spring-loaded lock balls that can be dynamically controlled. For safety, the springs maintain strong engagement force to prevent inadvertent closure. For intentional release, a release mechanism applies dynamic force to overcome the spring pressure and eject the lock balls from the channels. This dynamic design allows the system to provide strong passive safety while enabling convenient active release when needed.
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 system effectively supports the fan cowl weight, prevents inadvertent closure, and allows for safe operation by securely locking the fan cowl in place, ensuring reliable access for maintenance and inspection.
Implementation Method 1
The release spring is disposed between the OC outer radial surface and the first CS inner radial surface and is configured to bias the control sleeve toward the first axial end
Implementation Method 2
The lock spring is disposed between the OC outer radial surface and the lock spring and is configured to bias the lock sleeve toward the second axial end
Data Source
Figure 1~2
Figure 3~3B
Figure 4
AI summary
A hold open rod (36) has a control sleeve (46), an outer cylinder (42), lock balls (51), a lock sleeve (44), a piston (38), a piston head (40), a release spring (50), and a lock spring (48). The control sleeve (46) has first and second cavity sections (142, 144), an inner radial surface (150), a CS channel (148), and a pin (146). The outer cylinder (42) has an OC inner cavity (92), OC inner and outer radial surfaces (94, 96), an OC axial end wall (102), lock ball apertures (106), and a pin guide slot (108). The lock balls (51) are configured to pass through the lock ball apertures (106). The piston (38) has first and second sections (58, 60). The piston head (40) has an outer radial surface (78), a channel (80), and a piston bore (84). The piston bore (84) is configured to receive the first section (58) of the piston (38). The release spring (50) biases the control sleeve (46) toward a first axial end (54). The lock spring (48) biases the lock sleeve (44) toward a second axial end (56).