Chair Back Height Adjustment Mechanism for Wobble-Free Guide Fit
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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, such as a J-bar, leading to wobble, which is not effectively addressed by current manufacturing methods that attempt to reduce manufacturing tolerances or use spring-loaded means.
Innovation Solution
A chair back height adjustment mechanism featuring a guide with an abutment surface and an adjusting device that includes a coupling member with a slanted face, a bias mechanism using a wedge and energy storage mechanism to urge the coupling member against the abutment surface, and a locking mechanism for discrete height adjustments, reducing or eliminating lateral play.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the guide is formed with high strength (e.g., steel bar) to support forces acting on the chair back, then the strength and stability are improved, but the manufacturing complexity and cost significantly increase due to the need for reduced manufacturing tolerances
Solution Approach 1:
The guide is divided into two functional parts: a high-strength core component (the guide bar itself) and a separate adjusting device with an oversized inner cavity. This segmentation allows the guide bar to focus solely on providing structural strength without needing precision manufacturing, while the adjusting device handles the dimensional compatibility issue through its oversized design.
Solution Approach 2:
The inner cavity dimensions of the adjusting device are intentionally made larger than the outer dimensions of the guide bar, creating a deliberate dimensional mismatch. This parameter change allows the use of standard tolerance ranges for both components while still achieving proper fit and function through the coupling mechanism.
2Ease of manufacture
If the adjusting device is provided with an oversized inner cavity to accommodate manufacturing tolerances of the guide, then the ease of assembly is improved, but lateral play and wobble occur during operation
Solution Approach 1:
The coupling member is pre-configured with a bias mechanism that applies a preliminary force to maintain continuous contact between the coupling member and the guide bar. This preliminary anti-action prevents the development of lateral play and wobble before they can occur during operation.
Solution Approach 2:
The bias mechanism automatically compensates for dimensional variations and maintains proper engagement between the adjusting device and guide bar without requiring external adjustment or intervention. The system self-regulates to eliminate lateral play through the continuous contact force provided by the coupling member.
3Stability of the object's composition
If spring-loaded means are used to prevent lateral play, then the lateral stability is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The coupling member serves multiple functions simultaneously: it connects the adjusting device to the guide bar, accommodates dimensional tolerances through the oversized design, and prevents lateral play through the integrated bias mechanism. This multi-functionality eliminates the need for separate spring-loaded components while achieving the same lateral stability goal.
Solution Approach 2:
The functions of lateral play prevention and height adjustment are merged into a single integrated coupling mechanism. The bias mechanism is incorporated directly into the coupling member design, combining what would traditionally be separate components into one unified structure that reduces overall device complexity.
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 solution effectively reduces or eliminates wobble by ensuring precise alignment and secure positioning of the adjusting device on the guide, allowing for efficient height adjustment without compromising manufacturing complexity or cost.
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
a bias mechanism using a wedge and energy storage mechanism to urge the coupling member against the abutment surface
Data Source
Figure 1
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AI summary
A chair back height adjustment mechanism (10) comprises a guide (11) having an abutment surface (17) at a lateral side of the guide (11) which extends along an adjustment direction (18). The chair back height adjustment mechanism (10) comprises an adjusting device (12) supported on the guide (11) so as to be displaceable along the adjustment direction (18). The adjusting device (12) comprises a carrier, a coupling member (31) which is moveably supported on the carrier, and a bias mechanism (35, 37, 45, 47). The coupling member (31) has a contact face (32) shaped to abut on the abutment surface (17) of the guide (11) and a slanted face (33). The bias mechanism (35, 37, 45, 47) is operative to apply a force onto the slanted face (33) to urge the contact face (32) of the coupling member (31) against the abutment surface (17) of the guide (11).