Resettable Seatbelt RetraCTOR With Threaded Rod And Spring
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Solution Overview
Problem
Conventional vehicle restraint systems, particularly seatbelt retractors, face challenges in compactness, cost-effectiveness, and the ability to be reset for reuse after load limiting, often requiring multiple components and complex packaging.
Innovation Solution
A compact and inexpensive seatbelt retractor design utilizing a spool with a threaded rod, nut, and springs, where the springs are positioned coaxially and the nut is threadedly movable along the rod, allowing for emergency locking and progressive load limiting, enabling the system to be reset and reused after inspection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional seatbelt retractor designs are used, then the retractor can provide emergency locking and load limiting functions, but the device size becomes large and packaging complexity increases
Solution Approach 1:
The patent combines the emergency locking mechanism and load limiting mechanism into a single integrated retractor assembly. The spool houses both the emergency locking pawl-ratchet system and the load limiting spring system, merging multiple functions into one compact unit. This integration reduces overall retractor volume while maintaining both emergency locking and load limiting capabilities.
Solution Approach 2:
The patent employs nested positioning of components within the spool assembly. The load limiting springs are positioned coaxially around the threaded rod, and the nut is threaded onto the rod within the same cylindrical space. This nesting arrangement maximizes space utilization and minimizes the overall volume of the retractor while preserving all functional elements.
2Reliability
If multiple components are used for emergency locking and load limiting, then functional reliability is improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The spool serves multiple functions: it acts as the rotating element for webbing payout, houses the emergency locking pawl and ratchet mechanism, provides mounting for the load limiting springs, and contains the threaded rod and nut assembly. This multi-functionality reduces the number of separate components needed while maintaining reliable emergency locking and load limiting functions.
Solution Approach 2:
The patent merges the emergency locking mechanism (pawl, ratchet, trigger) and the load limiting mechanism (springs, threaded rod, nut) into a single integrated assembly within the spool. This consolidation reduces component count and simplifies manufacturing while preserving the reliability of both safety functions through proper mechanical design.
3Device complexity
If compact design is achieved through component integration, then packaging complexity is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by providing specific geometric features at critical locations: the threaded rod includes threading with defined pitch and diameter for precise nut engagement; the nut includes internal threading matched to the rod; and the spool includes a keyed or splined connection to prevent rotational misalignment. These localized precision features ensure proper assembly and function while the overall design remains compact.
Solution Approach 2:
The patent uses standardized thread parameters (diameter, pitch, thread form) that are well-defined and easily manufactured. The threaded rod and nut are designed with standard metric or imperial thread specifications, allowing for precise manufacturing using conventional machining processes. This standardization maintains manufacturing precision while simplifying production.
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 provides a compact, cost-effective, and resettable retractor system that effectively manages load limiting during sudden decelerations, ensuring occupant safety while minimizing component count and packaging complexity.
Implementation Method 1
a spring elongated from a first end to a second end, the first end fixed relative to the spool, and the second end fixed relative to the nut
Implementation Method 2
a threaded rod lockable relative to the retractor housing and elongated along the axis; a nut threaded on the threaded rod
Data Source
AI summary
A restraint system includes a retractor housing, a spool rotatably coupled to the retractor housing and defining an axis of rotation, a threaded rod lockable relative to the retractor housing and elongated along the axis, a nut threaded on the threaded rod, and a spring elongated from a first end to a second end. The first end is fixed relative to the spool, and the second end is fixed relative to the nut.