Wheelchair Backrest Assembly With One-Handed Auto-Locking Fold
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Solution Overview
Problem
Users of wheelchairs face challenges in folding and unfolding the backrest, particularly those with physical impairments, as existing mechanisms require simultaneous use of two hands and can be unsafe due to the need for stabilizing the upper torso.
Innovation Solution
A backrest assembly with a handle mechanism that allows one-handed operation using cables and locking means, enabling the backrest to be unlocked and folded or unfolded without releasing the grip, with automatic re-locking after reaching the desired position, utilizing torsion cables, compression springs, and adjustable joints for easy movement and secure locking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a traditional latch assembly with multiple bolts is used, then the backrest can be securely locked, but the user requires multiple hand movements and cannot operate it with one hand
Solution Approach 1:
The patent combines multiple locking functions into a single integrated latch assembly. Instead of separate bolts for each side, one latch assembly simultaneously controls both backrest tubes through connected bolting mechanisms, allowing single-handed operation while maintaining secure locking.
Solution Approach 2:
The latch assembly serves multiple functions: it locks both backrest tubes simultaneously, provides secure engagement through the bolt mechanism, and enables single-handed operation through the lever handle. The same assembly handles both security and ease of operation requirements.
2Ease of operation
If a cord mechanism is used to release plunger pins, then the backrest can be folded with one hand, but the risk of entrapment and uncontrolled loosening increases
Solution Approach 1:
The patent uses a lever handle as an intermediary mechanism between the user's hand and the locking system. The lever provides mechanical advantage and controlled force transmission to the bolts, replacing the direct cord-pull mechanism. This intermediary ensures controlled operation while maintaining safety through the robust bolt engagement system.
3Reliability
If multiple separate locking mechanisms are used for each backrest tube, then secure locking is achieved, but the device complexity and number of components increase
Solution Approach 1:
The patent merges the locking functions for both backrest tubes into a single latch assembly. The left and right bolting mechanisms are connected and controlled by one lever handle, reducing the number of independent components while maintaining secure locking of both tubes simultaneously.
4Reliability
If a complex multi-step locking mechanism is used, then secure locking is achieved, but the time required for folding and unfolding increases
Solution Approach 1:
The latch assembly is pre-configured with the bolts and connecting mechanisms in place. When the lever is actuated, the pre-positioned components engage and disengage in a coordinated manner, eliminating the need for multiple sequential hand movements. The preliminary arrangement of components enables rapid single-handed operation.
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 safe and easy one-handed operation of the backrest, reducing the effort required for users and enhancing safety by allowing the backrest to be folded or unfolded without releasing the handle, thus simplifying daily tasks for individuals with mobility impairments.
Implementation Method 1
a compression spring (150) arranged between said spring stop (160) and said locking wedge (130)
Implementation Method 2
each cable comprises a torsion cable, in particular steel torsion cable
Data Source
AI summary
A backrest assembly of a wheelchair seat has a tubular seating frame. The backrest assembly includes a backrest, two hollow backrest tubes connecting the backrest to the seat, and at least two joints allowing movement of the backrest tubes between at least first and second end positions. Two locking means are provided for locking and/or unlocking the joints. A hollow handle tube has a single handle for effecting the locking means which is arranged between the backrest tubes and mechanically connected to the locking means via cables. The handle further effects movement of the backrest tubes, via the joints, with use of one hand in constant grip of the handle. The handle is actuated by at least partly sliding, rotating, squeezing, pushing and/or pulling. The locking means automatically re-locks after unlocking and reaching the first or second end positions.