Segmented Wheelchair Back Cushion Reducing Shear Forces
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Solution Overview
Problem
Existing wheelchair seat apparatuses with reclining functionality often generate discomfort due to shear forces on the lower back of occupants as the seatback transitions from an inclined to a reclined position, as there is a lack of designs that effectively mitigate these shear forces.
Innovation Solution
A modular seat apparatus with a pivotably coupled back cushion and base cushion, where the back cushion comprises multiple segments that translate along the back frame, adjusting its length in response to the angle change, thereby minimizing shear forces on the occupant's lower back.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the seatback transitions from an inclined position to a reclined position with an occupant seated thereon, then the reclining functionality is achieved, but a shear force is generated along the lower back of the occupant causing discomfort
Solution Approach 1:
The back cushion is divided into multiple segments that can translate relative to each other along the back frame. This segmentation allows the back cushion to adjust its configuration during reclining, with segments moving to maintain better support alignment and reduce shear forces on the occupant's lower back while preserving the reclining function.
2Device complexity
If the back cushion length remains fixed during reclining, then the structural simplicity is maintained, but the shear force on the occupant's lower back increases causing discomfort
Solution Approach 1:
The back cushion transitions from a static fixed-length structure to a dynamic adjustable-length structure. The segments are configured to translate along the back frame in response to the reclining angle, automatically adjusting the effective length of the back cushion to maintain optimal support and minimize shear forces throughout the reclining range of motion.
3Object-affected harmful factors
If the back cushion segments translate to adjust length during reclining, then the shear force on the lower back is reduced, but the device complexity increases
Solution Approach 1:
The back cushion is divided into multiple segments that can translate relative to each other along the back frame. This segmentation allows the back cushion to adjust its configuration during reclining, with segments moving to maintain better support alignment and reduce shear forces on the occupant's lower back while preserving the reclining function.
Solution Approach 2:
The segments are configured to translate automatically in response to the reclining angle change, utilizing the mechanical movement itself to drive the adjustment. The system self-regulates the back cushion length based on the reclining position without requiring external control mechanisms, reducing the overall complexity despite the modular design.
Data Source
AI summary
A modular seat apparatus includes a base cushion and a back cushion that includes a plurality of segments defining a longitudinal length of the back cushion. The back cushion is pivotably coupled to the base cushion such that the back cushion is oriented at an angle relative to the base cushion. The plurality of segments is configured to translate in response to the back cushion pivoting relative to the base cushion such that the longitudinal length of the back cushion decreases as the angle increases and the longitudinal length of the back cushion increases as the angle decreases.