Belt Retractor Force Limiter with Threaded Translational Mechanism
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Solution Overview
Problem
Existing belt retractors with force limiters lack the ability to switch between different force limitation levels, which is necessary for varying conditions such as pre- and post-airbag deployment, and are not space-efficient.
Innovation Solution
A belt retractor design featuring a belt reel, a locking disc, and a force limiting element with a thread that generates translational movement upon relative rotation, allowing for adjustable force levels by modifying the force limiter characteristic through a stop mechanism, enabling switching between force limitation modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a traditional force limiter with fixed characteristic is used, then the structure is simple, but the adaptability to different operational conditions is poor
Solution Approach 1:
The force limiter characteristic is made dynamically changeable through a bypass sleeve that can be in different positions. The bypass sleeve can bypass the force limiting element to allow free rotation of the belt reel (first condition) or engage with the force limiting element to provide force limitation (second condition), enabling adaptation to different operational conditions without changing the basic structure.
Solution Approach 2:
The bypass sleeve acts as an intermediary component between the belt reel and the force limiting element. It mediates the rotational movement by either allowing direct rotation (bypassing the force limiter) or transmitting rotation through the force limiting element, thus enabling switching between different force limitation characteristics.
2Adaptability or versatility
If a switchable force limiter is implemented to provide different force levels, then the adaptability improves, but the device complexity increases
Solution Approach 1:
The bypass sleeve combines multiple functions into a single component: it serves as both a rotational connector and a switching mechanism. By integrating the bypass functionality and the switching capability into one element, the patent avoids the need for separate actuators, sensors, or control systems that would increase complexity.
Solution Approach 2:
The bypass sleeve is designed to be passively actuated by the operational conditions themselves. The weight of the bypass sleeve and its mechanical interaction with the force limiting element automatically cause it to move between positions based on the rotational direction and force applied, eliminating the need for external control mechanisms.
3Adaptability or versatility
If more components are added to enable force level switching, then the functionality improves, but the space efficiency deteriorates
Solution Approach 1:
The bypass sleeve is positioned concentrically around the force limiting element, and both components are integrated within the belt reel assembly. This nested arrangement allows the switching mechanism to occupy minimal additional space while still providing full functionality.
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 allows for adjustable force limitation profiles, enhancing safety by accommodating different operational conditions while maintaining a compact design, ensuring effective restraint with varying force levels.
Implementation Method 1
a force limiting element (22) which is provided with a thread (28) and acts between the belt reel (14) and the locking disc (16) so that a translational movement (T) is generated when a relative rotation between the belt reel (14) and the locking disc (16) takes place
Implementation Method 2
a known structure of a force limiter uses a torsion bar which is connected at one end to a belt reel and is supported at the other end by a frame of the belt retractor. As soon as the torque acting on the belt reel due to the tensile forces acting in the belt webbing exceeds the resistance to torsion of the torsion bar, the torsion bar is twisted
Data Source
AI summary
A belt retractor for a vehicle occupant seat belt has a belt reel (14), a locking disc (16) and a force limiting element (22), the force limiting element (22) being provided with a thread (28) and the force limiting element (22) acting between the belt reel (14) and the locking disc (16) so that a translational movement is generated when a relative rotation between the belt reel (14) and the locking disc (16) takes place.