Force-Limiting Device with Progressive Spring Washer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing force-limiting devices for seat belt retractors cannot automatically increase the restraining force to higher levels after a preset seat belt extraction, failing to meet legal requirements for back seat passengers.
Innovation Solution
A force-limiting device with an open, wavelike spring washer that changes its spring force and deformation behavior after a preset belt extraction length, using stop surfaces and angled ends to increase the force-limiting level, and optionally a cam structure or spiral guide track to further enhance the force increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a force-limiting device uses oscillating masses on the retractor frame to limit restraining forces, then the force-limiting function is achieved, but the device complexity and installation space increase
Solution Approach 1:
The patent extracts the oscillating masses from the retractor frame and replaces them with a toothed disc connected to the belt shaft. This extraction simplifies the device structure by removing unnecessary components while maintaining the force-limiting function through the undulating feed motion of the toothed disc engaging with the gear ring.
Solution Approach 2:
The patent merges the force-limiting function with the belt shaft rotation mechanism by connecting the toothed disc directly to the belt shaft. This combination allows the toothed disc to execute undulating feed motion during belt shaft rotation, achieving force-limiting without requiring separate oscillating masses on the frame.
2Force
If a force-limiting device uses oscillating masses on the retractor frame, then the force-limiting function is achieved, but the installation space required increases
Solution Approach 1:
The patent extracts the oscillating masses from the retractor frame and replaces them with a toothed disc connected to the belt shaft. This extraction simplifies the device structure by removing unnecessary components while maintaining the force-limiting function through the undulating feed motion of the toothed disc engaging with the gear ring.
3Device complexity
If a force-limiting device uses a fixed spring force, then the device structure is simple, but the restraining force cannot be increased after preset belt extraction
Solution Approach 1:
The patent implements a dynamic force-limiting mechanism where the spring force automatically increases after a preset belt extraction length. The spring washer transitions from an initial compression state to a second compression state with higher force, enabling the device to adapt to different restraint requirements without changing its basic structure.
Solution Approach 2:
The patent changes the spring force parameter automatically based on the belt extraction length. The spring washer is pre-compressed to a first degree during normal operation, and after preset extraction, it transitions to a second degree of compression with higher force, achieving parameter change without external control.
4Adaptability or versatility
If external control is used to increase restraining force after preset extraction, then the force level can be adjusted, but the automation level decreases
Solution Approach 1:
The patent implements a self-service mechanism where the spring washer automatically transitions between compression states based on the belt extraction length. The device monitors its own operation through the mechanical movement of components and autonomously increases the restraining force without requiring external control signals or sensors.
Solution Approach 2:
The patent incorporates mechanical feedback through the interaction between the toothed disc, gear ring, and spring washer. The undulating feed motion of the toothed disc during belt extraction provides feedback on the extraction length, which automatically triggers the spring force increase when the preset extraction is reached.
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
Enables a progressive force-limiting course with automatic increase in restraining forces after a preset belt extraction length, allowing for adjustable force levels without modifying the device's parts, ensuring compliance with legal requirements for back seat passengers.
Implementation Method 1
a spring washer can be provided which exerts an axial compression force on the toothed disc, whereupon the force-limiting level of the force-limiting characteristic is increased
Data Source
AI summary
A force-limiting device (4) for a seat belt device which has at least two parts (5, 11, 15) controlled with a frequency-dependent, defined movement, wherein the parts (5, 11,15) moving relative to one another feature gearings (8, 10, 18, 19) engaging into each other and the frequency-dependent, controlled movement occurs such that at least one of the parts (5, 11, 15) executes a feed movement (V) with respect to the other part (5, 11,15) with an undulating motion (Q) perpendicular to the feed movement (V) in which the gearings (8, 10, 18, 19) alternatingly engage and disengage, by means of which a force limited belt extraction is facilitated. Wherein means are provided with which the required force for movement of the parts (5, 11, 15) toward one another can be automatically increased after a preset belt extraction length.