Locking device for a chair
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Solution Overview
Problem
Adjustable armrests in office chairs often experience unwanted movement due to manufacturing inaccuracies and tolerances, leading to a loose and unrigid armrest when locked, which affects the chair's quality and appearance.
Innovation Solution
A locking device comprising a housing element, a rotatable locking handle with an abutment end, a wedge element with a flexible portion, and a spring element that securely fixes the armrest pole by inserting the wedge between the armrest pole and the housing element, providing a biased force to prevent movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a simple locking device is used to allow armrest adjustment, then ease of operation is improved, but manufacturing inaccuracies and tolerances cause unwanted movement of the armrest pole even when locked
Solution Approach 1:
The wedge element is pre-positioned within the locking device housing, ready to be engaged with the armrest pole. When the locking handle is actuated, the wedge element is already in place to immediately prevent unwanted movements, eliminating the need for complex adjustment mechanisms while ensuring reliable locking.
Solution Approach 2:
The wedge element acts as an intermediary between the locking handle and the armrest pole. It translates the locking action into a mechanical constraint that prevents unwanted movements, providing a simple yet effective solution that addresses both ease of operation and locking stability.
2Reliability
If tight tolerances are applied to eliminate armrest pole movement, then locking stability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The invention changes the geometric parameters of the wedge element and its interaction surfaces with the armrest pole and housing. By optimizing the wedge angle and contact surfaces, the device achieves reliable locking with standard manufacturing tolerances, eliminating the need for tight tolerances while maintaining locking stability.
Solution Approach 2:
The wedge element's geometry is pre-designed to compensate for typical manufacturing variations. This preliminary design approach allows the locking mechanism to function reliably across a range of tolerances, simplifying manufacturing while ensuring consistent locking performance.
3Reliability
If a complex locking mechanism is used to eliminate armrest movement, then locking stability is improved, but device complexity increases
Solution Approach 1:
The invention extracts the essential locking function from complex multi-component mechanisms and implements it through a single wedge element. This simplified approach eliminates unnecessary parts while maintaining the ability to prevent unwanted armrest pole movements, achieving reliability without complexity.
Solution Approach 2:
The wedge element is pre-positioned and pre-configured within the housing to perform the locking function. This preliminary arrangement eliminates the need for complex actuation mechanisms, reducing device complexity while ensuring reliable locking when the handle is actuated.
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 locking device effectively eliminates unwanted movement of the armrest pole, ensuring it remains securely locked even with large production tolerances, enhancing the chair's rigidity and appearance.
Implementation Method 1
a spring element positioned between the locking handle and the armrest pole
Implementation Method 2
a wedge element comprising a wedge and an abutment portion, the abutment portion configured for being directly or indirectly biased by the abutment end, the wedge configured and arranged for at least partly insertion between a portion of the armrest pole and at least a portion of the housing element in the locked position
Data Source
AI summary
A locking device for an armrest pole. The locking device comprises a housing element configured for slidably accommodating the armrest pole. A locking handle comprises an abutment end, the locking handle is rotatably connected to the housing element and configured for rotation between a locked position where the armrest pole is fixed in the locking device and an unlocked position where the armrest pole is slidable in the locking device. The locking device also comprises a wedge element comprising a wedge and an abutment portion, the abutment portion configured for being directly or indirectly biased by the abutment end, the wedge configured and arranged for at least partly insertion between a portion of the armrest pole and at least a portion of the housing element in the locked position.