Three-Piece Piston Assembly for Thrust Reverser Load Synchronization
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Solution Overview
Problem
Aircraft thrust reverser actuation systems face challenges in meeting increasing loads while maintaining synchronization and reducing friction, as traditional designs are costly and difficult to manufacture, and may suffer damage from sudden aerodynamic forces during deployment.
Innovation Solution
A three-piece piston assembly with distinct components made from different materials, including a high-strength piston, a low-friction bushing, and a high-hardness lock nut, along with a locking pin and lead screw, which are assembled to provide improved load handling and reduced friction, and a hydraulic valve to control fluid flow and resist aerodynamic loads during deployment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a traditional locking feature is machined into the piston, then the piston can maintain synchronization and hold high loads, but the manufacturing becomes difficult and costs increase
Solution Approach 1:
The locking feature is segmented from the piston body and implemented as a separate lock nut that threads onto the piston. This allows the lock nut to be manufactured independently with optimized geometry for load bearing, while the piston can be manufactured separately with simpler tooling requirements, resolving the contradiction between strength and ease of manufacture.
Solution Approach 2:
A lock nut is introduced as an intermediary component between the piston and the lead screw assembly. This lock nut provides the locking function and load bearing capability that was previously required to be machined directly into the piston, thereby simplifying piston manufacturing while maintaining the necessary strength and synchronization.
2Force
If aircraft loads increase to meet new requirements, then the actuation system can handle higher forces, but traditional piston designs may suffer damage from sudden aerodynamic forces
Solution Approach 1:
A bushing is introduced as a cushioning element between the piston and the lock nut assembly. This bushing absorbs sudden aerodynamic forces and shock loads before they can damage the piston or other components, thereby enabling the system to handle higher forces while maintaining reliability under transient loading conditions.
Solution Approach 2:
The system employs a composite structure with a bushing material selected for its shock-absorbing properties, combined with the metallic piston and lock nut components. This composite approach allows the system to withstand both steady high loads and sudden aerodynamic forces, resolving the contradiction between force handling capacity and resistance to transient loads.
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 enhances the performance and durability of thrust reverser actuation systems by distributing loads effectively, reducing friction, and mitigating damage from sudden aerodynamic forces, while maintaining synchronization and being economical to manufacture.
Implementation Method 1
The lead screw can include a helical lead screw thread arranged to engage a helical bushing thread defined upon a tubular inner surface of the bushing
Implementation Method 2
a hydraulic valve to control fluid flow and resist aerodynamic loads during deployment
Implementation Method 3
the lock nut material that achieves both high strength and low friction
Data Source
AI summary
The subject matter of this specification can be embodied in, among other things, an assembly that includes a piston having a piston inner surface defining a cylindrical cavity and includes a first axial portion, a piston face at a first end of the first axial portion, a second axial portion at a second end of the first axial portion, and a helical piston thread defined upon the piston inner surface, a bushing configured to contact the piston inner surface, and a lock nut configured to engage the piston and the bushing.