Articulated Chair Back Structure for Balanced Recline Support
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Solution Overview
Problem
Conventional office chairs lack individual adjustability of the seat and backrest, leading to inadequate support and comfort for users of varying sizes and postures, with tilting mechanisms that do not provide a balanced ride throughout the range of motion.
Innovation Solution
A seating structure with an articulated seat and backrest, featuring a linkage assembly that allows the rear portion of the seat to pivot independently, an adjustable seat depth mechanism, and a biasing system with a leaf spring and cam surfaces to provide balanced torque and visual adjustment of the return force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the seat is formed as a relatively rigid, or fixed component, then the seat structure is simple and stable, but the user tends to slide forward in the seat when tilting rearwardly and cannot be easily adjusted to accommodate different user sizes and postures
Solution Approach 1:
The seat is divided into a front seat portion and a rear seat portion that can pivot independently relative to each other. The rear seat portion is pivotally connected to the front seat portion, allowing the rear portion to tilt backward independently while the front portion remains relatively stable. This segmentation enables the rear portion to follow the user's backward tilt motion without causing the user to slide forward, while maintaining overall structural stability.
2Ease of operation
If the depth of the seat is adjusted by moving the entirety of the rigid, unitary seat in a fore-aft direction, then the seat depth can be changed, but an unsightly gap forms at the rear of the seat and a pinch point is created
Solution Approach 1:
The seat depth adjustment mechanism moves only the front seat portion forward or backward relative to the rear seat portion, rather than moving the entire seat. The rear seat portion remains stationary or moves minimally, preventing gap formation at the rear and eliminating pinch points between the seat and backrest. The front portion's independent movement allows for clean, safe adjustment without compromising seat shape or appearance.
3Device complexity
If the seat and back are not individually adjustable, then the chair structure is simpler, but the chair cannot be easily adjusted or customized to accommodate the particular size, shape and desired posture of the user
Solution Approach 1:
The chair is segmented into independently adjustable components: the front seat portion, rear seat portion, and backrest. The rear seat portion can pivot independently relative to the front seat portion, and the backrest can be adjusted independently as well. This segmentation allows each component to be customized for different user sizes and postures without requiring complete reconstruction of the chair, maintaining reasonable structural simplicity while enhancing adaptability.
4Device complexity
If the back is formed as a relatively rigid, or fixed component, then the back structure is simple, but the chair back does not allow the user a full range of motion, precluding the ability of the user to stretch or arch their back
Solution Approach 1:
The backrest is divided into an upper backrest portion and a lower backrest portion that can pivot independently relative to each other. The upper portion can tilt backward independently, allowing users to stretch, arch, and assume various postures. The lower portion remains connected to the seat and provides stable support. This segmentation enables full range of motion while maintaining structural simplicity.
5Force
If tilt chairs normally employ compression and/or tension springs, torsion springs and/or torsion bars, or leaf springs to bias the seat and back upwardly, then the seat and back can be counterbalanced, but the mechanisms used to adjust the load on the spring(s) are complicated and require multiple, excessive rotations of a knob
Solution Approach 1:
A cam mechanism serves as an intermediary between the user's adjustment input and the spring load adjustment. The cam converts a single rotation or small movement of an adjustment knob into a corresponding adjustment of the spring preload. This intermediary mechanism simplifies the adjustment process, requiring only minimal rotation of the knob while still achieving the desired counterbalance force adjustment, and eliminates the need for multiple excessive rotations.
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 solution ensures comfortable support for users by preventing forward sliding, reducing hip drop, and providing a balanced ride across different users, with easy adjustment and reduced energy required to maintain the chair's position.
Implementation Method 1
The mechanisms used to adjust the load on the spring(s), or the load capability of the spring(s)
Implementation Method 2
A force adjusting member having first and second cam surfaces in opposition to one another
Data Source
AI summary
A seating structure includes a central spine and an upper back structure having a pair of arms extending upwardly and outwardly from the central spine. The upper back structure is pivotally connected to the central spine about a first horizontal axis. A back support structure is pivotally connected to the spine about a second horizontal axis and is pivotally connected to the ends of each of the arms about a third horizontal axis.