Synchronous Office Chair Cam Mechanism to Eliminate Pull-Out
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Solution Overview
Problem
Conventional synchronous office chairs often exhibit an ergonomically unfavorable 'pull-out' effect when a person leans back, as the synchronous movement of the seat and backrest parts is poorly coordinated, leading to shirts being pulled out of trousers.
Innovation Solution
The design incorporates a carrier fixed to a support column, a seat support hinged at a tilting axis, and a back part with a horn and back bracket, featuring roller bearings guided in curved tracks, which allows the seat and back parts to perform synchronized movements with an instantaneous center of rotation aligned with the user's pelvic pivot point, minimizing the 'pull-out' effect. Additionally, a pretension mechanism using leaf springs and a tilt stop for adjustable cushioning and inclination control are integrated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If articulated mechanisms are used for synchronous movement, then the seat and backrest can move together, but the 'pull-out' effect occurs making the movement ergonomically unfavorable
Solution Approach 1:
The patent replaces traditional articulated linkage mechanisms with a cam-based mechanical system. The cam profile is specifically designed to guide the backrest movement such that the instantaneous center of rotation remains aligned with the user's pelvic pivot point, eliminating the pull-out effect while maintaining synchronous movement between seat and backrest.
Solution Approach 2:
The invention changes the geometric parameters of the movement mechanism by designing a specific cam profile with controlled curvature and position. This parametric design ensures that the backrest rotates about a fixed instantaneous center (the pelvic pivot point) throughout the movement range, rather than following the poorly coordinated path of traditional articulated mechanisms.
2Ease of operation
If complicated lever mechanisms are used to achieve synchronous movement, then the seat and backrest can be coordinated, but the device complexity increases
Solution Approach 1:
The patent extracts the essential function of synchronous movement coordination from the complex lever mechanism and implements it through a simpler cam-based system. The cam profile inherently provides the coordination between seat and backrest movement without requiring multiple interconnected levers and joints, thus reducing overall mechanism complexity while maintaining the synchronous coordination function.
Solution Approach 2:
Instead of using complex lever mechanisms to calculate and enforce the correct movement coordination, the invention uses a pre-designed cam profile that physically copies the desired movement path. The cam shape directly encodes the relationship between seat and backrest positions, simplifying the mechanism while achieving the same coordination effect.
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
This configuration eliminates the 'pull-out' effect by ensuring the pivot points of the seat and backrest movements align, providing ergonomic comfort and adjustable support suitable for a wide range of users, while simplifying the mechanical design and enhancing usability.
Implementation Method 1
roller bearings guided in curved tracks
Implementation Method 2
pretension mechanism using leaf springs
Data Source
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AI summary
The office chair has a seat support (2) implementing a tilting movement about a tilting axis (4) with a clamp (5). A rear part (3) implements another tilting movement about a virtual axis (13) with a rear bracket (6), where the latter tilting movement is approximately two or three times larger than the former tilting movement in accordance to amount and at the same time implements a translatory movement. A momentary pivotal point of the latter tilting movement lies in a constant distance over a rear middle part of the seat support.