Bidirectional Anti-Back Drive Ring and Cam Locking Mechanism
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Solution Overview
Problem
Existing anti-back drive devices are limited to preventing back drive in only one sense of rotation, which restricts their application in bidirectional scenarios such as prosthetic hands where maintaining a grip without energy dissipation is crucial.
Innovation Solution
A bi-directional anti-back drive device is designed with a rotary drive member and a rotary driven member coupled by a ring with cam recesses and lock members, allowing forward drive while inhibiting back drive in both directions through a free-play coupling mechanism and protuberances that facilitate rapid locking and disengagement, ensuring efficient operation in both rotation senses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional anti-back drive device with a single cam recess is used, then back drive is prevented in one direction, but the device cannot prevent back drive in the opposite direction
Solution Approach 1:
The single cam recess is segmented into two cam recesses with different depths, where each recess handles back drive prevention in one rotational direction. The first cam recess prevents back drive in one direction while the second cam recess prevents back drive in the opposite direction, allowing bidirectional operation capability.
Solution Approach 2:
Different regions of the cam mechanism are given different depths to create directional asymmetry. The first cam recess has a greater depth than the second cam recess, creating local quality differences that enable the lock member to be retained in one direction while allowing movement in the other direction.
2Reliability
If a clutch mechanism is used to maintain grip in prosthetic hands, then grip can be maintained, but energy is dissipated
Solution Approach 1:
The clutch mechanism is replaced with a cam-based mechanical anti-back drive system. The cam recesses and lock members create a passive mechanical locking system that maintains grip without the need for active clutch engagement, thereby eliminating energy dissipation associated with clutch operation.
Solution Approach 2:
The cam mechanism automatically locks in the forward position and prevents back drive without requiring active control or energy input. The asymmetric cam recess depths create self-locking behavior that maintains grip reliability passively, eliminating the need for energy-consuming clutch mechanisms.
3Ease of operation
If lock members are allowed to move freely in cam recesses, then forward drive is permitted, but rapid locking action during back drive is not achieved
Solution Approach 1:
The cam recesses are pre-configured with asymmetric depths to create preliminary positioning of the lock member. During back drive, the shallower cam recess immediately restricts lock member movement, creating a rapid locking action that prevents back drive before significant reverse rotation can occur.
Solution Approach 2:
The lock member is preliminarily positioned within the cam recess structure during normal operation. When back drive occurs, the pre-configured cam recess geometry immediately engages to restrict movement, achieving rapid locking without requiring additional active control mechanisms.
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 device effectively prevents back drive in both directions, allowing for secure grip maintenance without energy dissipation, enhancing the functionality of prosthetic hands and similar applications by enabling bi-directional operation.
Implementation Method 1
resilient parts to urge the lock members towards the shallower locations of the recesses
Implementation Method 2
Each lock member may comprise a roller member. This further increases a rapid locking action in the event of back drive of the driven member and decreases frictional contact between the ring and the lock members.
Data Source
AI summary
A rotary drive member drives a driven member. A ring surrounding the driven member has two cam recesses containing lock members between cam surfaces of cam recesses and the ring. Each recess accommodates an associated lock member at different locations where the recess is shallower. Driving the driven member is permitted in a given rotation relative to the ring, but each lock member inhibits rotation of the driven member in the opposite sense. The recesses extend in opposite directions. Coupling between the driven members is free-play whereby reversal in the rotation disengages members and reengages. Protuberances extending into cam recesses retain a lock member associated with one recess at the deeper location permitting movement of the other lock member towards the shallower location. Upon reversal of the rotation, the protuberances retain another lock member at the deeper location permitting movement of one lock member.