Polylobed Anti-Backdrive Lock for Bidirectional Torque Transfer
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Solution Overview
Problem
Existing gear systems face inefficiencies and high costs due to the need for large, expensive mechanisms to prevent backdriving, which limits their ability to transfer large torques while maintaining bidirectional operation.
Innovation Solution
An anti-backdrive device featuring a polylobed locking mechanism that uses an annular polylobed body to engage and disengage a housing, allowing bidirectional operation while preventing backdriving by generating a greater compression force than expansion force, thus preventing torque transfer during backdriving.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a self-locking gear set with low helix angle is used to prevent backdriving, then backdrive prevention is achieved, but system efficiency decreases to less than 35%
Solution Approach 1:
The locking mechanism is segmented into multiple poly lobes (typically 3-6 lobes) around the input shaft, allowing torque to be distributed across multiple engagement points. This segmentation enables effective backdrive prevention while maintaining higher efficiency compared to single-point locking mechanisms.
Solution Approach 2:
The poly lobed locking mechanism creates asymmetric engagement where the lobes engage the housing during backdriving attempts but allow free rotation during forward driving. The geometry of the lobes is specifically designed to generate compressive forces during backdrive while minimizing resistance during normal operation, resolving the contradiction between locking effectiveness and system efficiency.
2Reliability
If traditional anti-backdrive mechanisms are used to handle large torques, then backdrive prevention is reliable, but device size and cost increase substantially
Solution Approach 1:
The poly lobed locking mechanism serves multiple functions simultaneously: it allows bidirectional rotation during normal operation, prevents backdriving in both directions, and handles large torque loads. This multi-functionality eliminates the need for separate braking or locking components, reducing overall system size and complexity while maintaining reliability.
Solution Approach 2:
The locking mechanism dynamically adapts its behavior based on rotation direction. During forward rotation, the lobes clear the housing smoothly allowing free motion. During backdriving attempts, the lobes engage the housing to prevent rotation. This dynamic response enables effective backdrive prevention with minimal structural complexity.
3Force
If pins in larger holes are used to transfer torque in anti-backdrive devices, then torque transfer capability is sufficient, but compressive load on transfer blocks increases and system size increases
Solution Approach 1:
The torque transfer mechanism transitions from a linear pin-in-hole arrangement to a three-dimensional poly lobed geometry that engages the housing circumference. This dimensional change distributes compressive loads across multiple lobes and a larger surface area of the housing, reducing peak stresses on any single transfer point while maintaining overall torque transfer capability.
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 polylobed locking mechanism effectively prevents backdriving while allowing efficient torque transfer in both directions, reducing the need for large and expensive components, making it easier and more cost-effective to operate.
Implementation Method 1
the frictional forces are greater than the back-driving forces causing them to be self-locking
Data Source
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Figure 2
AI summary
A backdrive braking element is provided for preventing backdrive of a shaft. It includes a poly- lobed locking mechanism including an unlock shaft that has a polygon shaped inside profile and is coupled to a poly lock drive and brake assembly. The poly lock drive and brake assembly includes a plurality of poly lock drive and brake segments and is contained within the interior cavity of a housing.