Shear Resistant Saw Chain Rivet with Hardened Shoulder
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Solution Overview
Problem
Saw chains used in mechanical harvesters are prone to rivet shear due to excessive forces, leading to potential chain shot hazards, and conventional saw chains lack the necessary strength to withstand these forces, resulting in premature failure and safety risks.
Innovation Solution
The development of rivets with shear-resistant regions, specifically hardened areas around the shoulders and wear-resistant surfaces, combined with deformable regions for effective rivet head formation, to enhance the strength and durability of saw chains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional saw chain design is used for mechanical harvesters, then the chain can be manufactured with standard components, but the rivets are prone to shearing under excessive forces
Solution Approach 1:
The rivet incorporates a shoulder region with distinctly different properties from the hub region. The shoulder is hardened to high hardness (HRC 58-65) specifically to resist shear forces encountered in mechanical harvester applications, while maintaining standard rivet geometry for ease of manufacture. This localized property differentiation provides enhanced reliability without significantly complicating the manufacturing process.
Solution Approach 2:
The patent modifies the physical parameters of the rivet through selective heat treatment of the shoulder region. This parameter change transforms the material properties locally to achieve high shear resistance (HRC 58-65) while keeping the manufacturing process relatively simple through conventional heat treatment methods applied to standard rivet geometries.
2Strength
If the rivet material is hardened to increase shear resistance, then the rivet can withstand greater forces, but the rivet becomes difficult to deform for head formation
Solution Approach 1:
The rivet is segmented into two functional regions: the shoulder region and the hub region. The shoulder region is hardened to high hardness (HRC 58-65) for shear resistance, while the hub region maintains lower hardness (HRC 25-35) for ease of deformation during head formation. This segmentation allows each region to be optimized for its specific function without compromising the other.
Solution Approach 2:
The rivet exhibits local quality differentiation where the shoulder region has high hardness for shear resistance and the hub region has low hardness for deformability. This local quality approach enables the rivet to be both strong where forces are applied and formable where head creation is required, resolving the contradiction between shear resistance and manufacturability.
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 enhanced rivets provide increased strength and reliability, allowing saw chains to withstand significant forces and reduce the likelihood of breakage, thereby improving safety and extending the life of the chains.
Implementation Method 1
a first region or shear resistant region (30) configured to withstand shear stress
Implementation Method 2
a second region or deformable region (32) optimized for rivet formation and configured to deform during a rivet forming operation
Data Source
AI summary
A saw chain rivet is provided including a flange, and a hub extending from a side of the flange. A shoulder defined by a junction between the hub and the flange has properties optimized to resist shear forces. The hub may be optimized for ease of rivet head formation.