Aircraft Linear Drive With Cam-Actuated Teeth for Zero Backlash
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Solution Overview
Problem
Existing linear drive arrangements for aircraft components, such as high-lift devices and control surfaces, face challenges in achieving zero backlash, large gear reduction, self-locking capability, better load transfer, and reduced wear.
Innovation Solution
A linear drive device comprising a first member with engaging teeth and a second member that includes movable engaging members actuated by a rotatable cam shaft with a control cam portion, allowing sequential shifting of the engaging members between fully extended and retracted positions, enabling a wave-like motion that drives the first member along its longitudinal direction without backlash and with adjustable transmission ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional linear geared drives are used, then the structure is simple, but backlash cannot be eliminated
Solution Approach 1:
The drive system is segmented into multiple engaging members (at least two) that can independently engage and disengage from the rack teeth. Each engaging member is supported on the piston and can be selectively positioned to maintain continuous engagement, eliminating backlash while distributing the complexity across multiple simple components rather than one complex mechanism.
Solution Approach 2:
The engaging members are made dynamic through the cam mechanism, which automatically shifts them between engaged and disengaged states based on the operational phase. This dynamic adjustment allows the system to maintain zero backlash during force transmission while enabling reversible motion when needed, resolving the contradiction between reliability and operational flexibility.
2Power
If conventional gear transmissions are used, then the structure is compact, but large gear reduction is difficult to achieve
Solution Approach 1:
The cam mechanism serves as an intermediary that converts rotational motion into the sequential engagement and disengagement of multiple rack teeth. This intermediary mechanism enables large effective gear reduction by coordinating the action of multiple engaging members across an extended rack, achieving high reduction ratios without requiring correspondingly complex multi-stage gear trains.
3Reliability
If conventional drives are used, then the design is simple, but self-locking capability is not achieved
Solution Approach 1:
The engaging members are designed to automatically engage with the rack teeth when force is applied in the driving direction, creating a self-locking effect. The cam mechanism facilitates this by positioning the engaging members to maintain contact with the rack, allowing the system to lock itself without additional locking components or complex control systems.
4Force
If conventional drives are used, then the components are simple, but load transfer is inefficient
Solution Approach 1:
The load transfer function is segmented across multiple engaging members that can simultaneously engage different teeth on the rack. This distribution of load across multiple contact points improves overall load transfer efficiency and reduces stress on individual components, achieving better force transmission without requiring each component to be overly complex.
5Reliability
If conventional drives are used, then the design is straightforward, but wear is increased
Solution Approach 1:
The wear problem is addressed by segmenting the engagement across multiple teeth and multiple engaging members. This distributes the wear across numerous contact points rather than concentrating it on a single gear interface, significantly reducing wear rate and extending component life while maintaining a relatively simple overall system architecture.
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 provides a backlash-free, self-locking, and efficient linear drive with adjustable gear reduction, enhancing load transfer and reducing wear, thereby improving the performance of aircraft components like high-lift devices and control surfaces.
Implementation Method 1
a rotatable cam shaft having a control cam portion, the cam portion being configured so as to, upon rotation of the cam shaft, sequentially shift the engaging members thereby causing a linear motion of the movable member relative to the first member along the longitudinal direction
Implementation Method 2
the engaging members are configured in a linear arrangement that is aligned parallel to the longitudinal direction... at least one engaging member has an engaging portion that is arranged to contact the first member, and the engaging portion engages the first member in a planar manner
Implementation Method 3
at least one engaging member is integrally formed with a membrane member, the membrane member being deformable by the control cam portion so that the engaging members are shiftable between the fully retracted and fully engaged positions
Data Source
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AI summary
In order to improve linear drives on aircraft with regards to backlash, gear reduction, self-lock capability, load transfer and wear, the invention provides a linear drive device (26) that has a first member (28) with engaging teeth (30), such as a tooth rack (34) and a second member (34) which functions as a drive unit. The second member (34) includes a plurality of movable teeth (36) that are actuated by a cam shaft (42). The cam shaft (42) has a control cam portion (44) that is shaped such that the movable teeth (36) perform a wave-like motion that forces the first member (28) along its longitudinal direction relative to the second member (34).