Rotatable Chair Hub Brake Structure for Stable Loaded Position
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Solution Overview
Problem
Existing hub constructions for rotatable chairs often return to the initial position unexpectedly, even when loaded, due to insufficient return force, especially when a person lifts their feet off the floor.
Innovation Solution
Incorporating a compressed spring device, such as a pair of disc springs, that increases friction through a brake disc, which counteracts the return force, ensuring the chair remains stable under load and returns reliably to its initial position when unoccupied.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If friction is increased to prevent unintended return movements when seated, then stability under load improves, but the return force when unoccupied may become insufficient
Solution Approach 1:
The brake device dynamically adjusts friction based on load conditions. The spring device compresses the brake disc against the hub surface when loaded to increase friction for stability. When unoccupied, the brake disc is spaced away from the hub surface, reducing friction to allow the cam surface mechanism to provide sufficient return force
2Reliability
If a brake device with spring-loaded disc is added to control friction, then stability under load and automatic return reliability both improve, but the device complexity increases
Solution Approach 1:
The brake device is integrated into the existing hub construction by utilizing the plain bearing structure. The brake disc is positioned within the plain bearing, and the spring device is mounted on the shaft, combining multiple functions (support, friction control, automatic return) into a unified structure rather than adding separate independent components
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 prevents unintended return movements when seated by enhancing the return force with a brake disc, ensuring the chair remains stable and returns accurately to its initial position when unoccupied, addressing the issue of insufficient return force in prior designs.
Implementation Method 1
a brake disc causes higher friction
Implementation Method 2
a spring device, which is compressed when the hub is axially loaded
Data Source
AI summary
The invention relates to a hub construction for a rotatable chair, which automatically returns to the initial position when the chair is relieved. In a prior art hub the return force was counteracted mainly by the friction in the hub bearing, which, regardless thereof that the hub was loaded, was not always sufficient for the hub to maintain its rotational position, for example, when the sitting person lifted his feet off the floor. For obtaining higher friction when the hub is loaded, it has been provided with a brake. The brake can preferably be a pair of spring discs which are compressed when the hub is loaded, whereby the brake disc makes contact with the brake surface.