Stand-up wheelchair automatic locking frame stability
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Solution Overview
Problem
Stand-up wheelchairs experience instability and a risk of side falls during verticalization due to the rise in center of gravity and offset, combined with the movement of the lifter, which can lead to user falls.
Innovation Solution
A stand-up wheelchair design that includes a frame with a movable support assembly and a spreader bar, where the spreader bar is locked in place when the support assembly is in the upright position, transforming the articulated frame into a rigid frame for increased stability, and the locking mechanism is kinematically connected to the support assembly's verticalization, ensuring automatic locking without user intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the lifter is mounted free to rotate relative to the frame to compensate for rolling movements, then comfort and crossing capabilities are improved, but stability in the upright position deteriorates due to center of gravity offset and risk of side fall
Solution Approach 1:
The system dynamically switches between two states: an articulated state during movement where the lifter can rotate freely to compensate for rolling, and a rigid state during upright positioning where the lifter is locked to eliminate rotation and ensure stability. This dynamic reconfiguration allows the system to optimize for different operational requirements.
Solution Approach 2:
The patent changes the rotational freedom parameter of the lifter based on the wheelchair's operational state. During movement, the lifter has rotational freedom (parameter = free rotation); during upright positioning, the lifter is locked (parameter = fixed position). This parameter change resolves the contradiction between comfort during movement and stability during positioning.
2Adaptability or versatility
If the support assembly is movable between seated and upright positions to enable stand-up functionality, then mobility and independence are improved, but center of gravity rise and offset lead to instability
Solution Approach 1:
The locking mechanism is designed to automatically engage and lock the lifter before the support assembly reaches the fully upright position. This preliminary locking action prevents the center of gravity from rising too high and offsetting excessively, thereby maintaining stability during the transition and in the upright position.
Solution Approach 2:
The locking mechanism acts as an intermediary element between the movable support assembly and the fixed frame. It mediates the interaction by providing a controlled connection that allows movement during seated position but restricts rotation during upright positioning, thus managing the center of gravity changes.
3Adaptability or versatility
If the spreader bar is free to rotate to allow chassis articulation, then crossing capabilities are improved, but stability deteriorates when the chair is upright
Solution Approach 1:
The spreader bar connection transitions from a dynamic, freely rotating joint during movement to a static, locked connection during upright positioning. This dynamic-to-static transition allows the chassis to be articulated for crossing while maintaining rigidity for stability in the upright position.
Data Source
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AI summary
The wheelchair (1) has a support assembly moving relative to a frame (2) between sitting and stand-up positions in which the assembly is arranged to support and raise the user in an upright position, respectively. A swing bar (10) is mounted to freely rotate with respect to the frame. A blocking unit of the bar authorizes free rotation of the frame when the assembly is in the sitting position and blocks the rotation of the bar relative to the frame when the assembly is in the stand-up position so as to transform the articulated frame into a rigid frame in a reversible manner. The blocking unit includes a barring lever (20).