Wheelchair Back Frame Axial Adjustment Mechanism
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Solution Overview
Problem
Conventional wheelchairs with self-propelling chassis have limited range of operating modes and linked adjustments of seat and back cushions, restricting user flexibility and comfort.
Innovation Solution
The wheelchair features a back frame with axially adjustable parts, independent actuators, and a control device for individual control of the back cushion relative to the base frame, allowing continuous angle adjustment from a right angle to in-line position, and adjustable armrests for enhanced user positioning and comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single lifting cylinder and complex system of arms and transmissions is used to convert the wheelchair from low sitting position to upright positions, then the wheelchair can achieve position conversion, but the range of positions is limited and individual displacements of seat cushion and back cushion are linked together
Solution Approach 1:
The back frame is divided into a first part connected to the base frame and a second part carrying the back cushion. These parts are axially adjustable relative to each other through a linear guide with slide and carriage mechanism, allowing independent adjustment of the back cushion position without affecting the seat cushion, thereby expanding the range of achievable positions.
Solution Approach 2:
The system employs proportionally extendable actuators that can impose continuously variable angles on the back frame relative to the base frame. This dynamic adjustment capability allows the back frame to move from a right angle position to an in-line position, providing continuous adaptability rather than fixed discrete positions.
2Strength
If the back frame is subjected to considerable forces from the user's upper body support and push-off, then the structural strength must be increased, but this may increase the overall weight and reduce maneuverability
Solution Approach 1:
The patent employs a proportionally extendable actuator with a piston and cylinder arrangement to provide the necessary force for back frame adjustment and user support. This hydraulic/pneumatic mechanism can generate high forces to absorb user body weight and push-off forces while maintaining a compact structure that does not significantly increase overall system weight.
Solution Approach 2:
The back frame and its components are designed to efficiently distribute and absorb considerable forces from the user's upper body. The structural design incorporates force distribution mechanisms through the linear guide, slide, and carriage system that reduce peak stresses on individual components, allowing for optimized material usage and weight reduction.
Data Source
AI summary
A wheelchair comprises a chassis (10) with a chair frame (20) thereon. The chair frame comprises a base frame (21) and a back frame (30) connected pivotally thereto. A first actuator (25) is arranged operatively between the base frame (21) and the back frame (30). The back frame (30) comprises a first part (31) which is connected to the base frame, and a second part (32) which carries a back cushion (23). Both parts (31, 32) are axially displaceable relative to each other. For this purpose the back frame (30) comprises a further actuator (35) which is arranged operatively between the first part (31) and the second part (32) of the back frame.