Frangible-Tab Steering Shaft Lock for Assembly Alignment

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Solution Overview

Problem

Existing steering column assemblies face issues with maintaining the desired rotational orientation of the steering shaft and outer jacket during assembly, as metal pins used for locking can result in difficult removal, loose fits, or increased machining costs, compromising the assembly process and finished product quality.

Innovation Solution

A breakaway device with frangible tabs is employed to maintain the steering shaft and tubular jacket in a fixed rotational position during assembly, transitioning to a free-rotating state post-assembly by applying torque, ensuring easy assembly and functional alignment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a metal pin is used to lock the steering shaft and outer jacket in neutral orientation, then the rotational position is maintained during assembly, but the pin removal becomes difficult causing assembly line delays

Engineering Contradiction:

Improverotational position stabilityVSAvoidassembly line efficiency

Core Design Contradiction:

Stability of the object's compositionVSProductivity

Solution Approach 1:

The anti-rotation mechanism is segmented into multiple independent tabs instead of a single metal pin. Each tab can be independently fractured, allowing the steering shaft to be released in stages. This segmentation enables easier removal while maintaining rotational stability during assembly.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The material properties of the anti-rotation element are changed from metal (pin) to a frangible material (tabs) that can transition from intact to fractured state. This parameter change allows the element to provide strong locking during assembly but easy release afterward, resolving the contradiction between stability and productivity.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If a metal pin is used to lock the steering shaft and outer jacket, then rotational orientation is maintained, but the fit varies due to tolerances leading to loose fits that compromise alignment

Engineering Contradiction:

Improverotational orientation stabilityVSAvoidalignment precision

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The anti-rotation mechanism uses multiple tabs distributed around the steering shaft rather than a single pin. This segmentation allows the tabs to collectively maintain rotational orientation with better tolerance compensation, preventing loose fits while ensuring precise alignment.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Multiple tabs are combined to work together as a unified anti-rotation system. The collective action of multiple tabs provides more consistent rotational orientation maintenance compared to a single pin, reducing the impact of individual tolerance variations.

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If through openings are formed in the steering shaft and outer jacket for pin insertion, then the locking mechanism works, but machining costs increase

Engineering Contradiction:

Improvelocking mechanism reliabilityVSAvoidmachining cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The frangible tabs are extracted from the outer jacket and instead attached to the steering shaft. This extraction eliminates the need for corresponding tabs or features in the outer jacket, reducing machining requirements while maintaining locking reliability.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The frangible tabs serve multiple functions: they provide anti-rotation during assembly, indicate assembly completion through fracture, and can be easily removed. This multi-functionality reduces the need for additional components or complex machining features.

Inventive Principle:

Principle #6Universality (Multi-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 breakaway device ensures proper assembly alignment without pin removal difficulties, reduces machining costs, and allows unrestricted rotation during vehicle operation, enhancing assembly efficiency and product quality.

Implementation Method 1

The frangible tab has a non-fractured state, where the breakaway device is in the first state, and a fractured state, where the breakaway device is in the second state

Methodology Applied

Scientific EffectFracture Mechanics: Fracture Mechanics

Data Source

PatentUS12434755B1Steering column assembly and steering shaft anti-rotation breakaway device therefor

Publication Date: 2025.10.07 STEERING SOLUTIONS IP HOLDING CORP

AI summary

A steering column assembly having a tubular jacket assembly bounding a bore extending along a central axis between a jacket lower end and a jacket upper end and a steering shaft assembly extending along the central axis through the bore between a steering shaft lower end and a steering shaft upper end. A breakaway device extending between the tubular jacket assembly and the steering shaft assembly. The breakaway device having a first state, where the steering shaft assembly is prevented from being able to rotate relative to the tubular jacket assembly, and a second state, where the steering shaft assembly is free to rotate relative to the tubular jacket assembly. The breakaway device having at least one frangible tab having non-fractured state, where the breakaway device is in the first state, and a fractured state, where the breakaway device is in the second state.