Pivotable Anti-Tip Assemblies for Wheelchair Curb Navigation
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Solution Overview
Problem
Powered wheelchairs face issues with front wheels catching during turns and anti-tip wheels inhibiting obstacle clearance, particularly when navigating curbs, due to suspension designs that do not maintain vertical orientation and pivot axes.
Innovation Solution
The wheelchair incorporates a pair of anti-tip assemblies with a pivotable second member and a locking mechanism, allowing the anti-tip wheels to pivot clockwise and lock in extended positions, ensuring they remain within the drive wheel circumference for obstacle clearance and preventing tipping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If anti-tip wheels are suspended above the ground plane to clear small obstacles, then the wheelchair can clear curbs, but the anti-tip wheels inhibit the wheelchair from overcoming obstacles when backing over them
Solution Approach 1:
The anti-tip assembly employs a dynamic suspension system with a pivotable second member that can rotate between extended and collapsed positions. This dynamic configuration allows the anti-tip wheel to adapt its position based on operational needs - extended for stability during normal operation, collapsed for obstacle clearance when backing over curbs
Solution Approach 2:
The system changes the spatial parameter of the anti-tip wheel by pivoting the second member between two distinct positions. The pivot axis and clockwise rotation mechanism enable the anti-tip wheel to transition from a suspended position (clearing small obstacles) to a retracted position within the drive wheel circumference (allowing obstacle overcoming when backing)
Solution Approach 3:
The anti-tip assembly is divided into separable components (first member, second member, anti-tip wheel) connected through pivot joints. This segmentation allows independent movement of the second member relative to the first member, enabling the anti-tip wheel to pivot clockwise and collapse without affecting the overall wheelchair structure
2Speed
If suspension allows front wheels to rotate about a pivot to overcome obstacles, then the wheelchair can navigate curbs, but the front wheels may rotate counterclockwise into the obstacle which is undesirable
Solution Approach 1:
The suspension system is designed to preemptively prevent harmful counterclockwise rotation by configuring the pivot mechanism and structural constraints. The anti-tip assembly's pivotable second member with clockwise rotation capability counteracts any tendency for counterclockwise rotation into obstacles before it occurs
3Device complexity
If suspension does not maintain the swivel axis of casters in a substantially vertical orientation, then the suspension is simpler, but the front casters catch while the wheelchair is turning
Solution Approach 1:
The caster assembly incorporates a dynamic swivel mechanism that actively maintains vertical orientation of the swivel axis during wheelchair operation. This dynamic adjustment ensures smooth turning by preventing the caster from catching, while the overall suspension structure remains relatively simple
Data Source
AI summary
A wheelchair according to one embodiment includes a frame, a pair of drive wheels operatively coupled to the frame, a drive operatively coupled to each drive wheel, and a pair of anti-tip assemblies. Each anti-tip assembly includes a first member, a second member pivotally coupled to the first member at a joint that defines a pivot axis, an anti-tip wheel rotatably coupled to the second member, and a locking mechanism. The second member is capable of pivoting about the pivot axis between an extended position and a collapsed position. The locking mechanism is configured to selectively lock the second member in the extended position.