Adjustment device for a chair with rocking mechanism
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Solution Overview
Problem
Existing chair rocking mechanisms are structurally complex, require significant user force, are prone to seizing and breakage, and compromise optimal rocking performance, with conventional devices experiencing sticking and internal component damage under load.
Innovation Solution
A simplified adjustment device for a chair that uses a single lever to activate, block, and adjust the rocking mechanism, incorporating a C-shaped plate with springs and a central gas-operated post, along with a lever system that automatically determines the rocking condition and prevents accidental component damage, utilizing plastic materials for customization and structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional rocking mechanism with multiple levers and slats is used, then the rocking function can be activated, but the structure becomes complex and requires significant user force to operate
Solution Approach 1:
The rocking mechanism is segmented into distinct functional components: a first plate with base defining the rocking axis, a second plate for seat attachment, and a lever system with pivoting movement. This segmentation allows each component to perform its specific function independently, reducing overall structural complexity while maintaining reliability.
Solution Approach 2:
The complex slat packing mechanism and multiple levers from conventional designs are extracted and replaced with a simplified lever system that pivots about a fixed axis. The essential rocking activation function is retained while removing unnecessary complexity, resulting in easier operation with reduced user force requirements.
2Reliability
If a conventional rocking mechanism is used, then rocking activation is possible, but the mechanism is prone to seizing and breakage under load
Solution Approach 1:
A spring element is introduced into the lever system to provide beforehand cushioning. The spring absorbs shocks and reduces stress concentrations during lever operation, preventing seizing and breakage of internal components even when load is applied to the chair. This protective mechanism ensures durability while maintaining reliable rocking activation.
3Adaptability or versatility
If multiple levers are used for seat height adjustment and rocking activation, then both functions can be achieved, but the device becomes more complex
Solution Approach 1:
The lever system is designed with multi-functionality, where a single lever performs both seat height adjustment and rocking activation. The lever can pivot about a fixed axis to activate rocking, and its movement also controls the gas-operated post for height adjustment. This universal design achieves both functions while significantly reducing device complexity.
Solution Approach 2:
The functions of separate levers for height adjustment and rocking activation are merged into a single integrated lever system. The lever's pivoting movement simultaneously engages both the gas-operated post mechanism and the rocking mechanism, combining multiple functions into one simple operational element.
4Ease of operation
If a user tries to activate or block rocking function with load applied on the seat, then rocking control is achieved, but internal mechanisms may stick or break
Solution Approach 1:
The spring element provides beforehand cushioning specifically for the lever system during operation under load. When the user attempts to activate or block rocking with weight on the seat, the spring absorbs the additional stress and prevents sticking or breakage of internal mechanisms, ensuring both ease of operation and mechanism integrity.
Solution Approach 2:
The spring element acts as an intermediary between the lever system and the rigid structural components. It mediates the forces transmitted during rocking control operations, especially under load, protecting the internal mechanisms from excessive stress while allowing smooth operation.
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 rapid, simple, and optimal activation and blocking of rocking, while preserving component integrity and preventing sticking, allowing height adjustment and automatic rocking condition determination even under load, with a focus on structural simplicity and cost-effectiveness.
Implementation Method 1
at least one spring element interacting on the one hand with the mechanism upper part and on the other hand with the base support is provided in order to return the mechanism upper part from a pivoted position into a starting position
Implementation Method 2
a valve pin for triggering a pneumatic spring placed in the interior of the chair pillar is located in the region of the conical receptacle
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An adjustment device (1) for a chair, which comprises a rocking mechanism composed of a first plate (2), which is fixed to a central gas- operated post (7) for the height adjustment of a seat and to which a second plate (10) is articulated, about a first axis (9) that is transverse thereto and so that it can rock, the second plate being fixed to a seat and interacting with means (8a, 8b) which are adapted to contrast the rocking of a backrest, a lever (13) being articulated laterally to the first plate (2), at an axis that is different from the first axis (9). The device is provided with first means for elastic interconnection between the lever (13) and a first head (32) which is adapted to block/release the rocking between the first plate and the second plate (2, 10), and second means for temporarily locking the rotation of the lever (13) in two distinct positions. The second means preload the first means in order to block/release the rocking in the presence of a load applied to the seat.