Chair Back Height Adjustment Mechanism for Wobble Reduction
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Solution Overview
Problem
Existing chair back height adjustment mechanisms experience undesired lateral movement due to variations in the outer dimensions of the guide member, leading to wobble, which is challenging to manufacture without increasing complexity and costs.
Innovation Solution
A chair back height adjustment mechanism featuring a guide with an abutment surface and an adjusting device comprising a carrier, coupling members with slanted faces, and a bias mechanism that applies force to reduce or eliminate wobble by ensuring precise alignment and locking at multiple positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the guide is made with high strength and precise dimensions to support chair back forces, then the structural strength and stability are improved, but the manufacturing complexity and costs significantly increase
Solution Approach 1:
The system is divided into two functional parts: a simple guide member that provides the track, and a separate adjusting device with integrated coupling members that provides the strength and precision. This segmentation allows each component to be manufactured independently with appropriate tolerances, reducing overall manufacturing complexity while maintaining structural integrity.
Solution Approach 2:
The coupling member acts as an intermediary between the guide and the adjusting device. It includes a contact face that abuts on the guide's abutment surface and a slanted face that interacts with the bias mechanism. This intermediary component transfers forces while accommodating dimensional variations, eliminating the need for high-precision guide manufacturing.
2Ease of manufacture
If the adjusting device is provided with an oversized inner cavity to accommodate guide dimensional variations, then the ease of assembly is improved, but lateral play and wobble increase
Solution Approach 1:
The coupling member is designed to be moveably supported on the carrier, allowing it to dynamically adjust its position relative to the guide. The bias mechanism continuously applies force to maintain contact between the contact face and abutment surface, compensating for dimensional variations while preventing excessive lateral play. This dynamic adjustment eliminates wobble without requiring an oversized cavity.
Solution Approach 2:
The system changes the operational parameters by introducing a biased coupling member that actively maintains optimal contact pressure between the adjusting device and guide. This parameter change (applied force through the bias mechanism) compensates for dimensional variations, providing stable lateral positioning without requiring tight manufacturing tolerances or oversized cavities.
3Manufacturing precision
If manufacturing tolerances for the guide are reduced to eliminate lateral play, then the positional precision is improved, but the manufacturing costs and complexity significantly increase
Solution Approach 1:
The precision requirement is extracted from the guide and transferred to the coupling member and bias mechanism assembly. The guide can now be manufactured with relaxed tolerances, while the coupling member incorporates the precision function through its contact face geometry and the bias mechanism's force application. This extraction of the precision function reduces guide manufacturing complexity while maintaining overall system precision.
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 effectively reduces or eliminates lateral play, allowing for precise height adjustment of the chair back while maintaining manufacturing simplicity and reducing manufacturing costs.
Implementation Method 1
The bias mechanism is operative to apply a force onto the slanted face to urge the contact face of the coupling member against the abutment surface of the guide
Implementation Method 2
The coupling member has a contact face shaped to abut on the abutment surface of the guide and a slanted face. The bias mechanism is operative to apply a force onto the slanted face to urge the contact face of the coupling member against the abutment surface of the guide.
Data Source
AI summary
A chair back height adjustment mechanism comprises a guide having an abutment surface at a lateral side of the guide which extends along an adjustment direction. The chair back height adjustment mechanism comprises an adjusting device supported on the guide so as to be displaceable along the adjustment direction. The adjusting device comprises a carrier, a coupling member which is moveably supported on the carrier, and a bias mechanism. The coupling member has a contact face shaped to abut on the abutment surface of the guide and a slanted face. The bias mechanism is operative to apply a force onto the slanted face to urge the contact face of the coupling member against the abutment surface of the guide.