Wheelchair Caster Assembly Anti-Flutter Bearing Segments
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Solution Overview
Problem
Wheelchair caster assemblies experience uncontrollable reciprocating motion or 'flutter' due to velocity, friction, and limited contact surface, leading to loss of directional control, premature wear, and noise.
Innovation Solution
A caster wheel assembly with a housing unit featuring a first bearing, a support assembly with plain bearing segments, and a pressure-applying component that adjusts the pressure on the stem, creating a wedging effect to reduce flutter by varying the friction during rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional caster assemblies use standard bearings with limited contact surface, then the caster wheel can rotate smoothly, but flutter occurs due to reduced swivel resistance and limited friction
Solution Approach 1:
The bearing surface is segmented into multiple discrete bearing segments arranged circumferentially around the stem. This segmentation allows for distributed contact points that maintain smooth rotation while providing sufficient friction to prevent flutter, resolving the contradiction between smooth rotation and directional control stability.
Solution Approach 2:
The bearing segments are designed with specific local properties including curved contact surfaces that conform to the stem geometry. This local quality optimization ensures adequate friction at each contact point to prevent flutter while maintaining overall smooth rotation, addressing the contradiction between swivel smoothness and rotational stability.
2Reliability
If pressure is increased on the bearing segments to reduce flutter, then directional control improves, but wear on parts increases
Solution Approach 1:
By segmenting the bearing surface into multiple discrete segments, the total load and wear are distributed across multiple contact points rather than concentrated at a single point. This allows for adequate pressure to prevent flutter while reducing wear per unit area, thus extending bearing lifespan.
Solution Approach 2:
The bearing segments feature optimized local contact surface properties including curvature and material selection that reduce wear while maintaining sufficient friction. This local quality optimization enables the system to achieve directional control stability without excessive wear, resolving the contradiction between reliability and duration of action.
3Ease of operation
If the contact surface between caster wheel and ground is limited, then the caster is maneuverable, but flutter occurs due to insufficient friction
Solution Approach 1:
The bearing assembly uses multiple discrete bearing segments that create multiple contact points with the stem. This segmentation provides sufficient cumulative friction to prevent flutter while maintaining the limited ground contact surface needed for maneuverability, resolving the contradiction between ease of operation and swivel stability.
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 flutter, enhancing directional control and reducing wear and noise, while maintaining smooth swivel functionality.
Implementation Method 1
a wedge is positioned in a gap between two of the bearing segments, a displacement of the pressure-applying component causing a wedging effect of the wedge on the two of the bearing segments
Implementation Method 2
the combination of velocity, friction and limited contact surface between caster wheel and ground, and reduced swivel resistance may cause flutter
Data Source
AI summary
A housing unit for a caster assembly comprising a hollow housing body forming an inner cavity. A first bearing is connected to the hollow housing body, the first bearing defining a rotational axis through its center, and configured to rotatably support a first portion of a stem supporting a caster for rotation about the rotational axis. A support assembly is connected to the hollow housing body, the support assembly being spaced from the first bearing, the support assembly having bearing segments concurrently defining a plain bearing around the rotational axis, the plain bearing configured to rotatably support a second portion of the stem during rotation about the rotational axis. A pressure-applying component is operatively mounted to the support assembly, the pressure-applying component being selectively displaceable to displace the at least one of the bearing segments toward or away from the second portion of the stem, to increase or decrease a pressure of the bearing segments on the second portion of the stem. The support assembly and the first bearing are configured to rotatably support the stem of the caster to form a swivel joint.