Belt Retractor Casing Shell Annular Weakened Zone
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Solution Overview
Problem
Belt retractors emit significant noise due to their vibration behavior, particularly in specific frequency bands, which existing casing shell designs fail to effectively mitigate.
Innovation Solution
A cup-shaped casing shell with an annular weakened zone around its center, featuring reduced rigidity and flexibility, combined with a reinforcing structure of ribs, is designed to influence vibration behavior and reduce sound emission. The weakened zone allows for reduced sound radiation in specific frequency bands by altering the shell's frequency spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the casing shell is made with uniform rigidity throughout, then structural strength is maintained, but sound emission remains high
Solution Approach 1:
The patent applies local quality by creating an annular weakened zone with specific geometric parameters (smaller wall thickness or different material properties) in the front wall of the casing shell. This localized modification changes the vibration characteristics and sound emission in specific frequency bands without compromising the overall structural strength of the casing shell.
2Object-generated harmful factors
If the annular weakened zone has smaller wall thickness, then flexibility increases and sound radiation decreases, but structural strength is reduced
Solution Approach 1:
The patent applies parameter changes by modifying the geometric parameters of the annular weakened zone, specifically the wall thickness ratio between the weakened zone and surrounding portions. By optimizing this parameter, the invention achieves reduced sound radiation in specific frequency bands while maintaining acceptable structural strength through the balanced design of the weakened zone.
3Strength
If reinforcing ribs are added to the front wall, then structural strength increases, but sound emission may increase due to additional vibration modes
Solution Approach 1:
The patent applies local quality by positioning reinforcing ribs in specific locations outside the annular weakened zone. This allows the ribs to provide structural strength where needed while the weakened zone maintains its sound reduction function, creating a differentiated structural design that addresses both strength and sound emission requirements in different regions.
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
This design achieves a sound emission reduction of up to 5 dB, particularly in frequency bands like 1.6 kHz, 2.0 kHz, 2.5 kHz, and 4.0 kHz, when excited with white noise, compared to a standard casing shell.
Implementation Method 1
the vibration behavior of the casing shell can be widely influenced so that the frequency spectrum of the sound emission of the belt retractor can be easily set by specifically providing an annular weakened zone
Data Source
AI summary
A belt retractor casing shell having a cup-shaped configuration comprises a front wall (14) as well as a circumferential wall (16) extending from the front wall (14), the front wall (14) including an annular zone (44) weakened vis-à-vis the radially inside and/or outside adjacent portion around a center (42).