Wheelchair Backrest Assembly with Cable-Actuated One-Handed Folding
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Solution Overview
Problem
Users of wheelchairs face challenges in easily and safely folding or unfolding the backrest with one hand, as existing mechanisms often require simultaneous use of both hands to stabilize the upper torso and operate multiple components.
Innovation Solution
A backrest assembly with two hollow tubes connected to the seat via joints and a single handle that uses cables and locking mechanisms to allow one-handed operation, enabling the backrest to be locked and unlocked without releasing the grip, with automatic re-locking and an indicator device for user feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional backrest folding mechanism with multiple locking components is used, then the backrest can be securely locked in position, but the user requires both hands to operate it simultaneously
Solution Approach 1:
The patent combines multiple locking components (first and second locking bars with corresponding locking notches) into a unified mechanism that is actuated by a single cable system. When the cable is pulled, it simultaneously releases both locking bars, allowing the backrest to fold with one hand while maintaining secure locking through the dual-bar design.
Solution Approach 2:
The patent introduces a cable as an intermediary element that transmits the user's pulling force to multiple locking components simultaneously. The cable acts as a mediator between the user's hand and the locking mechanism, enabling one-handed operation while maintaining the security of multiple locking points through the coordinated release of both locking bars.
2Reliability
If multiple locking components are used to secure the backrest, then the locking security is improved, but the device complexity increases
Solution Approach 1:
The patent merges the control of multiple locking components into a single cable-actuated system. Both the first locking bar and second locking bar are released simultaneously through one cable pull, reducing the operational complexity despite maintaining multiple locking points for enhanced security.
3Volume of moving object
If the backrest is designed to fold down against the seating surface, then the overall size of the frame is reduced for storage and transport, but the user requires both hands to stabilize the torso and operate the folding mechanism
Solution Approach 1:
The patent combines the folding and locking release functions into a single cable-actuated mechanism. When the user pulls the cable with one hand, it simultaneously releases both locking bars, allowing the backrest to fold against the seating surface while the user maintains stability with their other hand or armrests.
4Ease of operation
If a single cable system is used to actuate multiple locking components, then the ease of operation is improved, but the device complexity increases
Solution Approach 1:
The cable serves as an intermediary that simplifies user interaction by consolidating control of multiple locking components into a single pulling motion. While the internal mechanism involves multiple components, the cable mediates between the user and these components, presenting a simple one-handed interface that masks the underlying complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables easy and safe one-handed folding and unfolding of the backrest, reducing the physical strain on users and enhancing the usability of wheelchairs for those with mobility impairments.
Implementation Method 1
a spring-loaded element with a transverse rod that can be moved into a notch to lock the backrest in position
Implementation Method 2
A cable is connected between the handle and the locking mechanism
Data Source
Figure 1a
Figure 1b
Figure 1c
AI summary
The invention relates to a backrest assembly of a seat of a chair, in particular a wheelchair, having a seating frame (4) comprising tubes (4', 4"), with the backrest assembly comprising: a backrest for supporting the back of a person; two hollow backrest tubes (6, 7; 60, 70) connecting the backrest to the seat on each side of the seat: at least two joints (14; 90, 91) for allowing a movement of the backrest tubes (6, 7; 60, 70) between at least a first end position and a second end position; two locking means (130) for locking and/or unlocking the joints (14; 90, 91); and an hollow handle tube (8; 80) having only one handle (10; 100) for effecting the locking means (130) to lock and/or unlock the joints (14; 90), wherein the handle (10; 100) is arranged in the middle between the backrest tubes (6, 7; 60, 70) and is mechanically connected to the locking means (130) via cables (120) running substantially inside the hollow tubes (6, 7, 8; 60, 70, 80) to effect at least the unlocking of the locking means (130) and the movement of the backrest tubes (6, 7; 60, 70) via the joints (14; 90, 91) when gripped by one hand (20) of an user, without releasing the respective grip of the handle (10; 100), which is engineered to be effected by at least partly sliding, rotating, squeezing, pushing and/or pulling, and wherein the locking means (130) automatically re-lock after effecting the unlocking of the joints (14; 90, 91) and reaching the first or second end positions.