Hydraulic Piston Check Valve Back Drive Elimination
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Solution Overview
Problem
Rotor aircraft, such as gyro planes, experience instability and uncontrollable 'back drive' due to misaligned U-joints, which creates a 'kick' load that pilots must react to, leading to unstable flight control systems, especially during prerotation and high-speed flights.
Innovation Solution
A push-pull type control system with a piston and check valve mechanism that includes a pair of piston displacement members and check valves, along with a hydraulic system to prevent back drive by locking the piston when external forces exceed user control, and pressure relief valves to prevent catastrophic pressure buildup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple tilting spindle rotor control is used, then the device complexity is reduced and aerodynamic efficiency is improved, but back drive instability occurs during prerotation
Solution Approach 1:
The patent introduces a hydraulic piston system with check valves to control the tilting spindle. The hydraulic fluid transmitted through check valves provides controlled movement while preventing back drive, resolving the instability issue while maintaining the simplicity of the tilting spindle design
Solution Approach 2:
The hydraulic piston acts as an intermediary between the control stick and the tilting spindle. It mediates the control input while filtering out harmful back drive forces from U-joint misalignment, allowing the simple tilting spindle design to remain stable
2Adaptability or versatility
If misaligned U-joints are used in the drive shaft, then freedom of movement for rotor control is achieved, but kick load is generated that creates back drive
Solution Approach 1:
The patent converts the harmful kick load from misaligned U-joints into a beneficial control feature. The hydraulic piston with check valves allows the kick load to drive the piston in the desired direction while preventing reverse movement, transforming the harmful back drive into controlled motion
Solution Approach 2:
The patent extracts the harmful back drive component from the control system by using the hydraulic piston to isolate the tilting spindle from kick loads. The piston absorbs and contains the harmful forces while allowing useful rotor movement freedom to continue
3Reliability
If a hydraulic boost system is used to overcome high control stick loads, then control stability is improved, but system weight and complexity increase
Solution Approach 1:
The hydraulic piston system is designed to be self-regulating through check valves that automatically control fluid flow direction. The system serves itself by using the kick load and control inputs to drive the piston without requiring external hydraulic pumps or complex active control systems
Solution Approach 2:
The hydraulic piston provides dynamic response to varying control loads and rotor positions. The check valves enable the system to adapt its stiffness and damping characteristics automatically based on the direction and magnitude of applied forces, maintaining stability without complex active control
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 eliminates back drive and maintains rotor control stability during prerotation and high-speed flights, allowing pilots to maintain control without excessive effort, while also providing feedback and preventing system failure.
Implementation Method 1
Each piston displacement member includes at least one, but more typically a plurality of check valve apertures each configured to receive a check valve
Implementation Method 2
a piston contained within a, e.g., cylindrical shaped housing containing hydraulic fluid
Implementation Method 3
pressure relief valves to prevent catastrophic pressure buildup
Data Source
AI summary
Apparatus and methods for eliminating back drive in a push pull type control system, are provided. An exemplary apparatus includes a control rod including a pair of spaced apart piston displacement members each configured to carry a check valve. The apparatus also includes a pair of opposite-face check valves each configured to seal against respective opposing face of a piston head to form a hydraulic lock, preventing back drive in the control system.