Aircraft Steering Backstop with Form-Fit Reverse Torque Locking
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Solution Overview
Problem
Existing backstops in aircraft steering systems that use friction brakes to prevent torque transfer from steering flaps to the drive shaft suffer from wear, heat generation, and delayed response behavior.
Innovation Solution
A backstop design that includes an input section and an output section of a drive shaft connected by a housing, where the input section is limited from rotating coaxially with the output section by more than a predetermined angle, using form-fit locking pawls and ball cages to dissipate torque into the housing, preventing reverse rotation without friction brakes or spring elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If friction brakes are used to prevent torque transfer from steering flaps to drive shaft, then torque transmission is blocked, but wear and heat generation occur
Solution Approach 1:
The patent replaces the friction-based mechanical braking system with a form-fit mechanical locking system using pawls and ball cages. Instead of using friction surfaces to block torque, the invention uses geometric interlocking elements (pawls engaging with ratchets, balls in cages) that provide torque blocking through mechanical interlocking rather than friction, thereby eliminating wear and heat generation associated with friction brakes.
Solution Approach 2:
The invention changes the fundamental parameter of torque blocking from friction-based force to geometric constraint. By transforming the blocking mechanism from continuous friction contact to discrete form-fit engagement, the system achieves the same torque blocking function without the harmful effects of friction, such as wear and heat generation.
2Reliability
If friction brakes are used to prevent reverse rotation, then torque is dissipated, but response behavior is delayed
Solution Approach 1:
The form-fit locking elements (pawls and ball cages) are pre-positioned within the housing to engage immediately when reverse rotation is attempted. Unlike friction brakes that require activation force to engage, the locking elements are already in position to provide instantaneous mechanical constraint, eliminating response delay.
Solution Approach 2:
The patent implements preliminary anti-action by pre-configuring the locking mechanism to counteract reverse rotation before it can occur. The pawls and ball cages are positioned to engage immediately upon detection of reverse torque, preventing the unwanted rotation from developing rather than reacting to it after initiation.
3Reliability
If friction surfaces and springs are used in backstop, then torque blocking is achieved, but components wear out over time
Solution Approach 1:
The patent eliminates the friction-based mechanical system with a form-fit mechanical locking system. By replacing friction surfaces and springs with geometric interlocking elements (pawls engaging ratchets, balls in cages), the invention achieves torque blocking without contact wear, significantly extending component service life.
Solution Approach 2:
The locking elements are designed as simple, robust geometric forms that can be easily manufactured and replaced if needed. The pawls and ball cages are basic mechanical components without complex friction surfaces or spring elements, making them inherently more durable and easier to replace than friction-based components.
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
This design achieves low wear and precise response behavior by dissipating torques into the housing, preventing unwanted rotation of the drive shaft and steering flaps, while maintaining efficient torque transmission without the drawbacks of friction brakes.
Implementation Method 1
The ball cage (8, 10) and locking pawl (21, 23) are configured such that they can dissipate a torque acting on the output section (2) by form fit into the housing (28)
Data Source
AI summary
A backstop of a torque transmission device of an aircraft steering system includes input and output sections of a drive shaft. Torque is transmitted from the input to the output, but is prevented from being transferred from the output back into the input. The input is limited from rotating coaxially relative to the output by more than a predetermined angle. The input stops at a first rotary position relative to the output upon rotating in a first rotary direction. The input stops at a second rotary position upon rotating in the opposite direction. The output is blocked from rotating in the second direction while the input is at the first rotary position and is blocked from rotating in the first direction while the input is at the second rotary position. The output is blocked from rotating by dissipating any torque acting upon the output into the housing of the backstop.