Expansion Pin Radial Clamping Force Control for Automotive Lighting
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Solution Overview
Problem
Existing motor vehicle lighting and signaling devices face issues with precise axial force measurement during fixing, leading to potential glass breakage from excessive stress or instability due to insufficient fixing force, especially when the vehicle encounters bumps.
Innovation Solution
A motor vehicle lighting or signaling device with a rear casing that uses a fixing housing, a longitudinal fixing screw, and an expansion pin with deformable legs that apply a radial clamping force, controlled by a guide ramp to limit the clamping force to a maximum value, ensuring secure attachment without excessive stress on the glass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixing screw is used to attach the lighting device to the vehicle bodywork, then the device can be securely fixed, but excessive axial screwing force can cause glass breakage due to high stresses in the glass
Solution Approach 1:
An expansion pin with deformable legs is introduced as an intermediary element between the fixing screw and the housing. The expansion pin converts the axial screwing force into a controlled radial clamping force through guide ramps, preventing direct transmission of excessive axial force to the glass while ensuring secure fixation through controlled radial expansion
Solution Approach 2:
The fixing mechanism transforms the force parameter from axial direction to radial direction through the guide ramp geometry. The radial clamping force is limited to a maximum value determined by the guide ramp dimensions, independent of the axial screwing force applied, thereby controlling the stress on the glass while maintaining fixation reliability
2Stability of the object's composition
If the fixing force is increased to prevent movement of the headlight in its cavity, then the stability improves, but the glass edges are tightly compressed against the bodywork creating high stresses that can cause breakage
Solution Approach 1:
The expansion pin acts as a mediator that decouples the relationship between fixing force and clamping force. It allows independent control of radial clamping force through guide ramp geometry, preventing excessive stress on glass edges while ensuring position stability through controlled expansion
Solution Approach 2:
The mechanism changes the force application parameter from direct axial compression to controlled radial expansion. The guide ramp limits the maximum radial clamping force to a value below the breaking force of the housing face, independent of the axial screwing force, thereby stabilizing the headlight position without creating dangerous glass edge stresses
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 solution provides a secure and stable attachment of the lighting device to the vehicle bodywork, preventing glass breakage and ensuring the device remains fixed, even on uneven road surfaces, by independently limiting the radial clamping force from the axial screwing force.
Implementation Method 1
at least one expansion leg of the ankle which is deformable towards an expanded state in which a free end of the expansion leg is pressed radially against the interior face of the housing with a radial clamping force
Implementation Method 2
the expansion lug is in contact with the screw head by means of a guide ramp, in particular to control the expansion lug towards its expanded state by axial sliding of the screw head rearward relative at the ankle
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The device has an expansion pin (34) whose expansion tab (46) is deformable toward an expanded state in which a free end (54) of the tab is radially pressed against an inner surface (22) of a housing (20) with a radial locking force to slidingly lock the pin with respect to a rear case (12). A limitation unit limits the locking force of the tab at a maximal value regardless of axial screwing force applied on a fixation screw (28). Dampening buffers made of elastic material i.e. foam, are interposed between an edge of a front lens and covering elements.