Chair Control Linkage With Adjustable Recline Biasing
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Solution Overview
Problem
Existing chair control assemblies fail to efficiently manage the movement of seat and back support structures relative to each other, often requiring excessive user input and lacking adjustable biasing forces to optimize comfort and support.
Innovation Solution
A control assembly with a 4-bar linkage mechanism and adjustable biasing assemblies that allow the seat and back support structures to move between defined positions with varying torque magnitudes, featuring a control link that rotates at a slower rate than the back support structure, and an assist feature to reduce user input force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a control assembly uses a fixed linkage mechanism to manage seat and back support movement, then the structure is simple, but the user must apply excessive input force and cannot adjust biasing forces for comfort optimization
Solution Approach 1:
The control assembly incorporates adjustable biasing assemblies that allow dynamic modification of torque magnitudes applied to the back support structure. Users can adjust the biasing force to optimize comfort and reduce input effort, transforming a static mechanism into a dynamic, adaptable system that responds to user needs.
Solution Approach 2:
The system enables parameter changes by allowing adjustment of the biasing force magnitude through adjustable biasing assemblies. This changes the torque applied to the back support structure, modifying the mechanical advantage and reducing the input force required from the user while maintaining control over the movement ratio between seat and back support.
2Speed
If the control link rotates at the same rate as the back support structure, then the linkage is simple, but the seat support structure cannot achieve the desired slower rotation rate for optimized movement control
Solution Approach 1:
The control link is configured with asymmetric pivot point spacing, where the distance between the first and second pivot points differs from the distance between the third and fourth pivot points. This asymmetric geometry creates a mechanical advantage that naturally produces the desired slower rotation rate of the seat support structure relative to the back support structure, eliminating the need for additional speed-reducing mechanisms.
Solution Approach 2:
The control link serves as an intermediary element between the back support structure and the seat support structure. By positioning pivot points at specific asymmetric locations along the control link, it mediates the motion transfer to achieve the desired rotation rate difference without requiring direct coupling or additional transmission components.
3Ease of operation
If the base structure is made movable to allow rotation, then the chair can recline, but the base structure becomes unstable and shifts position during movement
Solution Approach 1:
The control assembly merges the base structure with the linkage mechanism by integrating the pivot points directly into the base. This combination allows the base to serve dual functions: maintaining stability as a fixed reference frame while simultaneously enabling controlled recline movement through the linkage's rotational degrees of freedom, preventing unwanted base displacement during operation.
Data Source
AI summary
A control assembly for a chair includes a base structure having a first pivot point and a second pivot point spaced from the first pivot point, a seat support structure having a forward portion pivotably coupled to an upper portion of the base structure for rotation about the first pivot point, a back support structure having a forward portion pivotably coupled to a lower portion of the base structure for rotation about the second pivot point, wherein the back support structure is adapted to move between a first and second positions, and a control link having a first end pivotably coupled to a rearward portion of the seat support structure for rotation about a third pivot point, and a second end pivotably coupled to a rearward portion of the back support structure for rotation about a fourth pivot point.