Circumferential Stone Ejector Ribs for Pneumatic Tires

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Solution Overview

Problem

Pneumatic tires, especially large truck and bus tires, face issues with stone entrapment in tread grooves, leading to stone cutting into the tire structure and degradation, where existing stone ejectors are inadequate in preventing this problem.

Innovation Solution

The design incorporates circumferentially spaced stone ejector ribs with sloped forward and rearward facing walls, angled between 10° to 30°, and trapezoidal cross-sections, which are attached to the groove sidewalls and extend parallel to the rotational axis, providing a wider base and narrower top, and are spaced to resist stone retention, with a rib height of 4 mm to 8 mm and base spacing up to 200% of the groove width.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If traditional stone ejectors are used in tread grooves, then stone entrapment is partially addressed, but stones can still be retained and cut into the tire structure

Engineering Contradiction:

Improvestone entrapment and cuttingVSAvoidtire strength and life

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The stone ejector is divided into multiple circumferentially spaced ribs (typically 3-5 ribs) that span across the tread groove. Each rib has forward and rearward sloped walls creating multiple ejection surfaces. This segmentation allows stones to be contacted and ejected by multiple surfaces rather than a single structure, preventing stone retention and cutting into the tire.

Inventive Principle:

Principle #1Segmentation

2Ease of operation

If stone ejectors are designed with vertical walls, then stone ejection is simplified, but stones can become trapped between the ejector and groove sidewalls

Engineering Contradiction:

Improvestone ejection mechanismVSAvoidstone retention

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

Instead of using vertical walls that push stones outward, the invention uses inwardly sloped walls (forward wall sloping inward from top to bottom, rearward wall sloping inward from bottom to top). This inverted geometry causes stones to be guided upward and outward along the sloped surfaces, preventing trapping while maintaining effective ejection.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The stone ejector ribs feature curved or sloped surfaces rather than sharp angular transitions. The forward wall has a continuous slope from the top surface to the groove bottom, and the rearward wall has a continuous slope back to the top surface. These curved surfaces guide stones smoothly through the ejection path, preventing them from becoming trapped at sharp corners or edges.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Data Source

PatentUS10583694B2Radial stone ejectors

Publication Date: 2020.03.10 BRIDGESTONE AMERICAS TIRE OPERATIONS LLC

AI summary

A pneumatic tire is disclosed having a tread portion including a tread groove having a groove bottom and groove sidewalls. The tread groove has a groove width defined as a shortest distance between the groove sidewalls. The groove has a groove length extending generally parallel to the groove sidewalls. A sequence of circumferentially spaced stone ejector ribs span between the opposed groove sidewalls.