Telescopic Footrest Mechanism for Stand-up Wheelchair Stability
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Solution Overview
Problem
Existing stand-up wheelchairs face challenges in providing anatomically favorable seating and stable upright positions due to rigid footrest designs that compromise comfort and stability, leading to physical deterioration and increased risk of decubitus.
Innovation Solution
A telescopically adjustable footrest unit connected to a pivotable deflection lever, which is linked to the seat, allowing for adaptation to user anatomy and simulating natural standing movements, with adjustable inclination and locking mechanisms for stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the footrest is rigidly attached to the erection frame and inclined at an angle α in the sitting position, then the sitting comfort is improved, but the structure becomes massive and heavy
Solution Approach 1:
The footrest is made dynamically adjustable through a telescopic mechanism that allows it to change its angle relative to the horizontal. In the sitting position, the footrest can be inclined at angle α for comfort, while in the standing position it becomes vertical (angle zero). This dynamic adjustment eliminates the need for a massive rigid structure, reducing the erection frame weight while maintaining both comfort and stability functions.
Solution Approach 2:
The footrest's angular parameter is changed based on the wheelchair's position. The telescopic mechanism allows the footrest angle to vary from α in the sitting position to zero (vertical) in the standing position. This parameter change enables the same structure to provide both comfortable seating support and stable standing support without requiring different heavy structures for each function.
2Stability of the object's composition
If the footrest runs parallel to the floor in the sitting position, then the stability is improved, but the sitting posture becomes anatomically unfavorable
Solution Approach 1:
The footrest angle is made dynamic rather than fixed. In the sitting position, the footrest is inclined at angle α to provide anatomically favorable support for the user's feet and legs. When transitioning to the standing position, the footrest becomes vertical (parallel to the chassis) to provide stable support on the floor. This dynamic adjustment resolves the contradiction between comfort and stability by providing the appropriate angle for each operational state.
3Stability of the object's composition
If the footrest is lowered onto the floor in the standing position, then the stability is improved, but the distance between the seat and footrest changes requiring complex mechanisms
Solution Approach 1:
The footrest lowering mechanism is merged with the seat uprighting mechanism. As the seat pivots from the horizontal sitting position to the vertical standing position, the footrest automatically lowers onto the floor through the telescopic mechanism. This combined action eliminates the need for separate complex mechanisms to control footrest height and seat position independently, reducing overall device complexity while achieving both comfort and stability requirements.
Data Source
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AI summary
The wheelchair has a seat (2) on a chassis (29) and pivoted from a horizontal seating position to a vertical standing position during upright motion. A footrest (16) is arranged on the chassis, and is lowered to ground in the standing position. The footrest is inclined at an angle relative to a horizontal when the seat is in the seating position, where the angle becomes zero during upright motion. The footrest is housed telescoping in a guide tube (9), and forms a foot support unit (169) articulated to a spring-loaded reversing lever arranged pivotably on a seat column (22).