Seat Belt Retractor Spool Assembly With Nested Force Limiter
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Solution Overview
Problem
Existing winding drum assemblies in vehicle safety belts have a large number of parts and a bulky size, which complicates the overall retractor design.
Innovation Solution
A compact winding drum assembly is designed with an integrated gear mechanism and force limiting mechanism, utilizing a stop wheel and ball gear connected via riveting, and a force limiting mechanism inserted into a shaft hole for overlapping components to reduce size while maintaining functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the winding drum assembly uses traditional separate components for gear mechanism and force limiting mechanism, then the functionality is complete, but the number of parts increases and the size becomes larger
Solution Approach 1:
The patent combines the gear mechanism and force limiting mechanism into a single integrated assembly. The ball gear serves dual functions: transmitting rotational motion to the winding drum while simultaneously acting as the force limiting element. This merging eliminates separate components, reducing part count while maintaining complete functionality through multi-functional design
2Volume of moving object
If the winding drum assembly uses traditional separate components, then each component can be optimized independently, but the overall size of the retractor package becomes too large
Solution Approach 1:
The patent implements a nested structure where the force limiting mechanism is positioned within the gear mechanism's spatial envelope. The ball gear's spherical geometry allows the force limiting elements to be contained within or alongside the gear structure, achieving compact nesting that reduces overall volume while enabling independent optimization of each mechanism's internal geometry
3Strength
If the stop wheel and ball gear are separately assembled, then assembly flexibility is maintained, but the connection strength and stability are reduced
Solution Approach 1:
The patent segments the ball gear into multiple sections or lobes that interlock with corresponding features on the stop wheel. This segmentation creates multiple contact points and mechanical interlocks between the components, significantly enhancing connection strength through distributed load paths while maintaining assembly flexibility through modular segment design
Data Source
Figure 1
Figure 2~3
AI summary
The present disclosure relates to a winding drum (1) assembly. The winding drum (1) used for winding a safety belt extends in the axial direction and is rotatably supported in a frame of a retractor. A gear mechanism (2) is installed at one side of the winding drum (1) through a force limiting mechanism (3) and comprises a stop wheel (21) and a ball gear (22) which are riveted and fixedly connected in the axial direction. The stop wheel (21) is rotatably installed on the frame, and the ball gear (22) comprises a penetrating shaft hole (221A). The force limiting mechanism (3) is inserted into the shaft hole (221A) in the axial direction and both ends of the force limiting mechanism (3) are respectively connected with the winding drum (1) and the gear mechanism (2) to prevent passengers from being excessively restrained by realizing the force limiting function. According to the winding drum (1) assembly of the present disclosure, the gear mechanism (2) and the force limiting mechanism (3) are directly assembled to the winding drum (1), with simple steps and few independent components. In addition, the force limiting mechanism (3) is inserted into the shaft hole (221A) of the ball gear (22) in the axial direction to make the force limiting mechanism (3) and the gear mechanism (2) overlap in a larger part in the axial direction, so that the size of the whole winding drum (1) assembly can be smaller.