Segmented Chair Tilt Mechanism to Reduce Knee Rise and Shear
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Solution Overview
Problem
Conventional weight-responsive tilt mechanisms for seating furniture suffer from issues such as knee rise, heel rise, and shear effect, which cause discomfort by allowing the seat to move upward and the user's back to compress against the backrest during recline, leading to fatigue and discomfort.
Innovation Solution
A segmented tilt mechanism with articulated connections between segments, where the second segment is pivoted relative to the first segment via a linkage, reducing the upward movement of the seat's front and rear ends, thereby mitigating knee rise, heel rise, and shear effect, and incorporating an energy storage mechanism to bias the backrest support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional weight-responsive tilt mechanism is used, then the chair provides automatic recline based on user weight, but the seat rises upward during recline causing knee rise, heel rise, and back compression
Solution Approach 1:
The seat is divided into two segments: a first segment that moves with the seat support during recline, and a second segment that remains relatively stationary. This segmentation allows the front portion of the seat to stay stable while the rear portion reclines, preventing knee rise, heel rise, and back compression while maintaining weight-responsive functionality
Solution Approach 2:
An articulated connection acts as an intermediary mechanism between the first and second segments, enabling controlled relative movement. This articulated joint allows the seat segments to move independently, decoupling the recline motion from upward seat movement that causes discomfort
2Device complexity
If the seat is rigidly connected to the backrest, then the structure is simple, but the user's back compresses against the backrest during recline
Solution Approach 1:
Dividing the seat into two segments connected by an articulated joint creates a mechanism that reduces back compression while adding moderate complexity. The first segment connects to the backrest support and moves during recline, while the second segment remains stable, providing a balance between comfort and structural considerations
Solution Approach 2:
The articulated connection between seat segments introduces dynamic movement capability, allowing the seat structure to adapt during recline. This dynamic joint enables the seat to change configuration based on recline angle, reducing back compression while maintaining structural integrity
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
The segmented tilt mechanism effectively reduces the upward travel of the seat's ends during recline, enhancing user comfort by minimizing knee rise, heel rise, and shear effect, while maintaining weight-responsive recline characteristics.
Implementation Method 1
The segmented member includes a first segment which is coupled to move with a seat support and a second segment. The second segment is coupled to the first segment via an articulated connection.
Implementation Method 2
incorporating an energy storage mechanism to bias the backrest support
Data Source
AI summary
A chair back height adjustment mechanism comprises a guide having an abutment surface at a lateral side of the guide which extends along an adjustment direction. The chair back height adjustment mechanism comprises an adjusting device supported on the guide so as to be displaceable along the adjustment direction. The adjusting device comprises a carrier, a coupling member which is moveably supported on the carrier, and a bias mechanism. The coupling member has a contact face shaped to abut on the abutment surface of the guide and a slanted face. The bias mechanism is operative to apply a force onto the slanted face to urge the contact face of the coupling member against the abutment surface of the guide.