Vehicle Lighting Force Limiter with Retractable Pegs

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Solution Overview

Problem

Existing motion transmission devices in vehicle lighting systems are prone to jamming and overload, leading to premature wear and damage, especially in adaptive lighting applications where frequent adjustments are required, and are also vulnerable to external forces such as vandalism.

Innovation Solution

A motion transmission device with a force limiter function that includes a cup-shaped body, a bushing, and pegs with springs, which allows the pegs to retract when an axial load exceeds a threshold, preventing excessive stress on the electric motor and allowing the bushing to move axially, thus protecting the motor from overload.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a mechanical transmission device is used to move the reflector or lighting element frequently (e.g., for adaptive lighting adjustments), then the lighting device can perform routine adjustments to direct light beams according to curves and load, but the transmission device may accidentally jam, causing overload of the electric motor or actuator and premature wear or damage

Engineering Contradiction:

Improveadaptive lighting adjustment capabilityVSAvoidmotor overload protection

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The force limiter device is pre-configured with springs and pegs that automatically engage and disengage based on axial force thresholds. This preliminary setup allows the system to preemptively protect the motor from overload without requiring active control or detection during operation. When excessive force occurs, the mechanism automatically resets, enabling continuous reliable operation in adaptive lighting applications

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The force limiter acts as a cushioning mechanism by allowing controlled slippage or disengagement when axial forces exceed a predetermined threshold. The springs absorb excess energy and the pegs provide mechanical limiting, protecting the motor and transmission components from damage during accidental jamming or vandalism events before catastrophic failure occurs

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Object-affected harmful factors

If the mechanical transmission device is designed to be robust against external forces (e.g., vandalism), then protection against excessive force is improved, but the device complexity and manufacturing cost increase

Engineering Contradiction:

Improveresistance to external forcesVSAvoidtransmission device structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The force limiter device serves as an intermediary mechanism between the motor and the cup-shaped body. It includes a limiter body with radial holes, pegs with springs, and a cup-shaped body with a breakable connection. This intermediary structure provides a controlled failure mode that protects the motor while maintaining overall system simplicity. The breakable connection and retractable pegs create a mechanical fuse that sacrifices a simple component to protect critical expensive components

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The force limiter employs a disposable or replaceable connection mechanism (the breakable connection between the cup-shaped body and limiter body) that is simpler and cheaper than making the entire transmission device robust against all external forces. When vandalism or excessive force occurs, the simple connection breaks or the pegs disengage, protecting the expensive motor and electronics while the simple connection can be easily replaced

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 device effectively limits axial stress on the electric motor, preventing damage from overload and external forces, ensuring reliable and durable operation of the lighting system.

Implementation Method 1

first springs (24) cooperating with the pegs (21), said first springs (24) and said radial seats (22) being configured to cause the pegs (21) to selectively assume an extracted position

Methodology Applied

Scientific EffectElastic force: Elasticity

Implementation Method 2

second springs (26) packed between said support (10) and said cup-shaped body (14)

Methodology Applied

Scientific EffectSpring compression: Spring

Data Source

PatentEP3693217B1Linear motion transmission device between a first and a second component with a force limiter function, in particular applicable to a lighting device for vehicles

Publication Date: 2021.08.04 MARELLI AUTOMOTIVE LIGHTING ITAL SPA

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AI summary

A transmission device (8) including a support (10) for fixedly receiving the first component, an axially mobile output shaft (11) of the first component, a first shaft (12), configured to be constrained to the second component to be moved; wherein a mechanical connection device (13) is inserted between the output shaft and the first shaft and includes: a cup-shaped body (14), slidingly coupled to the support (10) and fixed to the first shaft (12); a bushing (18), slidingly coupled inside the cup-shaped body (14) and constrained to the output shaft; a pair of radial holes (20) of the cup-shaped body with which respective ends (25), delimited by oblique surfaces (28) of pegs (21), housed radially so as to slide in the bushing and loaded by first springs (24), cooperate; and second springs (26) packed between the support (10), the cup-shaped body (14) and shoulder elements (27), fixed to the cup-shaped body.