Office Chair Backrest Lever Mechanism for Easy Weight Adjustment
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Solution Overview
Problem
Existing adjusting mechanisms for office chair backrests require significant force and installation space, and fail to provide a consistent restoring force across different user weights, leading to difficulties in setting the correct inclination.
Innovation Solution
An adjusting mechanism with a pivotable lever and adjustable spring element, where the spring's bearing point is variable in the front region, connected to a multiple-pivot synchronous mechanism, allowing for reduced installation height and effortless manual adjustment of the restoring force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the prestress of a spring is set manually via an actuating element, then the restoring force can be adjusted, but a very great force is required and a complicated step-up means is needed
Solution Approach 1:
The patent introduces a lever as an intermediary mechanical element between the adjustment mechanism and the spring assembly. This lever amplifies the adjustment effect, allowing small manual inputs to produce significant changes in restoring force without requiring complex step-up means or excessive force from the user.
Solution Approach 2:
The patent employs a dynamic adjustment mechanism where the lever can be positioned at different angles and locations to vary the restoring force continuously. This dynamic system allows smooth adjustment across a range of forces rather than discrete steps, improving ease of operation while maintaining adaptability.
2Adaptability or versatility
If the spring assembly is configured to be pivotable, then the restoring force can be adjusted, but a relatively large amount of installation space is required
Solution Approach 1:
The patent repositions the spring assembly from a horizontal pivot configuration to a vertical arrangement where the spring acts along the vertical axis. This dimensional change allows the adjustment mechanism to operate within a compact vertical space rather than requiring extensive horizontal installation area, while maintaining the ability to adjust restoring force through lever action.
3Adaptability or versatility
If the point of action of the spring element is adjusted, then the active lever length changes and restoring force can be set, but the ratio of initial force to maximum force exhibits an unfavourable response
Solution Approach 1:
The patent changes the parameter being adjusted from the point of action of the spring element to the effective lever length through which the spring force acts. By modifying the lever arm length rather than the spring's attachment point, the system achieves a more favorable force ratio where the restoring force remains perceptibly consistent across the adjustment range, improving reliability for different user weights.
4Adaptability or versatility
If known adjusting mechanisms are used, then the restoring force can be set, but the vertical spacing between the support column and seat support is comparatively great
Solution Approach 1:
The patent merges the adjustment mechanism directly into the existing support column structure, eliminating the need for separate adjustment components that would increase vertical spacing. The lever and spring assembly are integrated within the compact space between the support column and seat support, reducing installation height while maintaining full adjustability of the restoring force.
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 mechanism achieves a compact design with reduced installation height, enabling easy and force-efficient adjustment of the restoring force, maintaining consistent support across varying user weights and inclination positions.
Implementation Method 1
a spring element (18), by means of which a restoring force is exerted on the backrest support (8) in such a way that the backrest support (8) is moved via the restoring force into an initial position
Implementation Method 2
The restoring force which acts on the backrest support is transmitted with the aid of a pivotable lever from the bearing pin to a joint pin of the synchronous mechanism
Data Source
Figure 1
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AI summary
The adjusting mechanism serves for the weight-dependent setting of a restoring force which acts on a backrest (4) of an office chair which is configured with a synchronous mechanism. The synchronous mechanism comprises a support (12), a seat support (10) and a backrest support (8) which are connected to one another via joint pins (Al - A4), the restoring force being exerted via a spring element (18). In order to achieve as flat a design as possible, the restoring force is transmitted with the aid of a pivotable lever (16) via a front bearing pin (L1) to a first front joint pin (Al), an active lever length (h) which can be varied with the aid of an adjusting element (20) being defined by the spacing between the bearing pin (LI) and the second front joint pin (A2). A weight setting is made possible by the variation of the active lever length (h).