Ceiling Fan Blade Offset Design for Stress Distribution
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Solution Overview
Problem
Conventional ceiling fans face issues with fan blades made of metallic materials, which become weakened due to reduced thickness to minimize weight, leading to potential damage from metal fatigue and breakage, especially at the root portions, and there is a need to prevent broken pieces from detaching and falling.
Innovation Solution
The design incorporates a fan blade with a root portion fixed to a supporting frame, a blade portion connected via a retaining member, and an offset portion with reinforcing ribs and curbed angles to distribute stress, ensuring the fan blade remains attached even if broken, using a retaining member to secure the blade to the rotor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If fan blades are made of metallic material with reduced thickness to minimize weight, then weight is reduced, but strength and rigidity are weakened leading to metal fatigue and breakage
Solution Approach 1:
The fan blade is divided into multiple segments or sections with varying thickness distributions. The root portion maintains greater thickness for strength, while distal portions are thinner for weight reduction. This segmentation allows optimization of both weight and strength independently in different regions of the blade.
Solution Approach 2:
The fan blade employs non-uniform thickness distribution where different sections have different local properties. The root portion has greater thickness and material concentration for strength, while the blade tips have reduced thickness for weight reduction. This local quality variation resolves the contradiction between overall weight reduction and localized strength requirements.
2Weight of moving object
If fan blades are made with thinner sections to reduce weight, then weight is reduced, but stress concentration increases at root portions leading to fatigue damage
Solution Approach 1:
The blade design incorporates local quality variations with thicker root portions that distribute stresses more effectively. The gradual transition in thickness from root to tip reduces stress concentration points while maintaining overall weight reduction benefits.
Solution Approach 2:
The design anticipates fatigue damage by incorporating thicker root portions and stress-distributing geometries before damage occurs. This preemptive structural design cushions against the development of stress concentrations and fatigue cracks that would otherwise lead to blade failure.
3Reliability
If fan blades are broken at root portions, then blade integrity is compromised, but retaining members can prevent detachment and ensure safety
Solution Approach 1:
Retaining members serve as intermediary components between the fan blade and the hub assembly. These retainers capture and hold broken blade segments, preventing their detachment while allowing the blade structure itself to fail safely without compromising overall system safety.
Solution Approach 2:
The retaining members are pre-installed as a safety mechanism that activates upon blade failure. This beforehand preparation ensures that even if blade integrity is compromised, the retained segments cannot detach and cause harm, providing a passive safety net.
Data Source
AI summary
A ceiling fan comprising a disc-like stator provided with a fixed shaft at the center, an annular rotor disposed in proximity to the periphery of the stator, a supporting frame fixed to the rotor and rotatably supported by the fixed shaft; a fan blade fixed to the supporting frame; and a retaining member having one end fixed to the supporting frame together with the fan blade and the other end coupled to the fan blade, wherein the fan blade comprises a root portion fixed to the supporting frame, a blade portion coupled with the retaining member, and an offset portion formed by bending between the root portion and the blade portion, thereby preventing the fan blade from being damaged easily even when it is impressed with a load and ensuring the safety even if the fan blade is broken since the blade portion is held coupled to the rotor side.