Chair Synchro Mechanism With Force-Free Weight Adjustment
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Solution Overview
Problem
Existing chair mechanisms with synchro mechanisms require significant physical force to adjust the preload force of the spring element, limiting user convenience and efficiency in adapting to individual body weights.
Innovation Solution
A mechanism featuring a triangular steering block connected to a force accumulator unit, allowing for progressive loading and adjustment of the preload force without changing the preload force itself, using a spindle and gear system to enable easy and force-free adjustment of the working angle of the force accumulator relative to the triangular steering block.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a mechanical gear system is used to adjust the preload force of the compression spring, then the restoring force can be adjusted, but the rotary drive becomes stiff, slow and prone to malfunctions
Solution Approach 1:
The patent replaces the traditional mechanical gear system with a cam mechanism. The cam profile is designed to convert rotational motion of the adjusting wheel into linear motion of the pressure plate, eliminating the need for complex gear trains. This substitution reduces mechanical complexity, improves operational smoothness, and enhances reliability by removing multiple gear engagement points that could malfunction.
Solution Approach 2:
The patent introduces a cam as an intermediary element between the adjusting wheel and the pressure plate. The cam acts as a mediator that transforms the rotational input into the desired linear adjustment motion, providing a more direct and reliable transmission path compared to gear systems. The cam profile can be optimized to provide progressive or uniform adjustment characteristics as needed.
2Adaptability or versatility
If a stiff adjuster is used to set the preload force, then the characteristics of the energy accumulator can be adjusted, but significant physical force and time are required for cranking or turning
Solution Approach 1:
The patent changes the adjustment mechanism from direct linear force application to rotational moment application. By providing a rotating adjuster wheel with a large diameter, the user applies force tangentially at the rim, creating a moment arm that multiplies the applied force. This dimensional change from linear to rotational adjustment allows easy adjustment of heavy spring preloads without requiring significant direct pulling or pushing force.
Solution Approach 2:
The cam mechanism provides dynamic adjustment characteristics where the mechanical advantage varies throughout the adjustment cycle. The cam profile can be designed to provide easier adjustment at certain points in the rotation, accommodating the varying force requirements during the adjustment process. This dynamic characteristic makes the adjustment process more ergonomic and requires less peak force compared to a static mechanical advantage system.
3Ease of manufacture
If the compression spring is changed in an unloaded condition using a mechanical gear system, then the preload force can be adjusted, but the process becomes complex and malfunction-prone
Solution Approach 1:
The patent replaces the complex mechanical gear system with a simpler cam-based adjustment mechanism. The cam and adjusting wheel provide a direct, single-stage adjustment path from user input to spring preload change, eliminating multiple gear stages, shafts, and engagement points. This simplification reduces the number of parts that can malfunction and eases manufacturing and assembly requirements.
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 effortless adjustment of the chair's restoring force to match different user weights, enhancing user comfort and reducing physical effort required, while maintaining optimal space usage and stability.
Implementation Method 1
a force accumulator unit (2), in particular a spring element, which is designed to accumulate force
Data Source
AI summary
The invention is based on a mechanism (1) for a chair having a synchro mechanism by means of which a seat surface structure and a backrest structure are moved in a synchronized ratio relative to one another, wherein the mechanism (1) serves to adjust a restoring force of the synchro mechanism to a different body weight of a seat user by changing a working angle of a force accumulator, and the mechanism (1) includes a seat support (8) for the seat surface structure, a bearing yoke (5), the force accumulator unit (2) a backrest support (3) for supporting the backrest structure, and a translational bearing (16), wherein the mechanism (1) has a triangular steering block (21) and the force accumulator unit (2) is connected to the triangular steering block (21), and on a weight adjustment method for an improved dynamic sitting experience on the part of the seat user by means of a mechanism (1) for a chair with a synchro mechanism, in which the position of a first pivot point (31) of the force accumulator unit (2) is shifted by means of the adjuster (11) when the backrest support (3) is in a position (A), and a swivelling motion of the backrest support (3) into a second position (B) is not performed until the first step is completed.