Chair Assembly Pivot Positioning to Reduce Shirt Shear and Lumbar Loss
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Solution Overview
Problem
Existing chair assemblies fail to maintain optimal ergonomic support during recline, as the pivot points of the seat and back assemblies move away from the user's H-point, leading to issues like 'shirt shear' and inadequate lumbar support.
Innovation Solution
A chair assembly design where the first pivot point is located at the H-point of the user, and the second pivot point remains within a radius of less than or equal to 0.75 inches from the first pivot point, ensuring synchronized movement of the seat and back assemblies during recline, with specific geometric constraints to maintain ergonomic alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the pivot points are positioned to enable recline motion, then the back assembly can move between upright and reclined positions, but the pivot points move away from the user's H-point, causing ergonomic support loss and shirt shear
Solution Approach 1:
The chair is divided into functionally independent yet coordinated segments: the seat assembly pivots about a first pivot point while the back assembly pivots about a second pivot point. This segmentation allows each component to move independently yet maintain proper alignment through the coordinated pivot point positioning, resolving the contradiction between motion capability and ergonomic consistency.
Solution Approach 2:
The solution moves the problem from a single pivot point to a spatial relationship between two pivot points. By positioning the first pivot point at the H-point and constraining the second pivot point to remain within 0.75 inches of the first pivot point throughout recline, the system uses spatial coordination in three-dimensional space to maintain ergonomic alignment while enabling full recline motion.
2Device complexity
If the pivot points are fixed in space, then the structure is simple, but the pivot points cannot remain aligned with the user's H-point during recline, leading to inadequate lumbar support
Solution Approach 1:
The system transitions from static pivot point positioning to dynamic positioning where the second pivot point's position is defined by its relationship to the first pivot point throughout the motion range. The constraint that the second pivot point remains within 0.75 inches of the first pivot point during recline creates a dynamic alignment system that adapts to the user's H-point position while maintaining lumbar support quality.
3Stability of the object's composition
If the seat and back assemblies are coupled rigidly, then structural stability is high, but the assemblies cannot move independently to maintain ergonomic alignment during recline
Solution Approach 1:
The chair is divided into functionally independent yet coordinated segments: the seat assembly pivots about a first pivot point while the back assembly pivots about a second pivot point. This segmentation allows each component to move independently yet maintain proper alignment through the coordinated pivot point positioning, resolving the contradiction between motion capability and ergonomic consistency.
Data Source
AI summary
A chair assembly includes a seat support structure having a seat surface pivotable about a first pivot point between first and second positions, and a back support assembly coupled to the seat support structure, movable between upright and reclined positions and pivotable about a second pivot point, wherein the first pivot point is located at a position along a first line perpendicular to a second line tangential to the seat surface and at a forward most portion of a back surface, forward between along a third line parallel with the second line, down to the second line along a fourth line perpendicular with the second line, up the fourth line such that the second pivot point is located within a given radius from the first pivot point when the back support assembly is in the upright and reclined positions.