Saw Chain Rivet Recess Geometry for Longer Joint Life
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Solution Overview
Problem
Existing saw chains experience reduced service life due to excessive radial pressure on rivet bolts, leading to material stress and joint weakness.
Innovation Solution
The design of the saw chain incorporates recesses in the rivet bolts with a recess base that maintains a consistent distance from the center plane, reducing radial forces and enhancing riveted joint strength through controlled force distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If large recesses with continuous radius are used in rivet bolts, then friction pressure between rivet shank and rivet hole increases, but excessive radial pressure on rivet bolt leads to reduced service life
Solution Approach 1:
The recess base is designed with a specific geometry where the distance from the center plane does not increase with radial distance, creating a localized zone that directs forces toward the rivet bolt axis. This local geometric modification optimizes force distribution specifically at the critical rivet-bolt interface without uniformly increasing radial pressure across the entire rivet structure.
Solution Approach 2:
The invention changes the geometric parameters of the recess by defining specific distance relationships: the greatest distance of the recess base from the rivet bolt axis corresponds to 30% to 100% of half the core diameter. This parameter optimization balances the friction pressure needed for joint strength with the radial pressure limits for service life.
2Strength
If radial pressure on rivet bolt is increased to enhance joint strength, then riveting forces increase, but material stress in connecting link opening increases
Solution Approach 1:
The recess base geometry is designed to convert the potentially harmful radial forces into beneficial axial compression forces on the rivet bolt. By directing forces toward the rivet bolt axis, the design transforms radial stress (which reduces service life) into compressive stress (which enhances joint strength).
Solution Approach 2:
The recess base acts as an intermediary structure between the rivet shank and the rivet bolt. It mediates the force transmission by distributing loads and directing them appropriately, reducing direct radial pressure on the rivet bolt while maintaining effective riveting forces through controlled force distribution.
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 design extends the service life of the saw chain by minimizing material stress and maintaining high riveting forces, ensuring durable and efficient operation.
Implementation Method 1
the recess base is convexly curved. This directs the forces introduced during riveting in the area of the recess base away from the edge of the opening of the adjacent connecting link and toward the rivet bolt axis
Implementation Method 2
The rivet is compressed in the area around the rivet bolt axis that is covered by the recess base when viewed in the direction of the rivet bolt axis. This results in high riveting forces.
Data Source
Figure 1~4
Figure 5~6
AI summary
A saw chain (1) comprises connecting links (2) and drive links (3) which are pivotally connected to one another by means of rivet pins (4) about rivet pin axes (18). The rivet pins (4) protrude through at least one rivet hole (11) of at least one connecting link (2) and one rivet hole (12) of a drive link (3). At least one rivet pin (4) has a recess (20) on at least one end face (34), which has a recess rim (22) and a recess base (21, 21'). The distance of the recess rim (22) to a median plane (19) of the saw chain (1) increases with increasing radial distance from the rivet pin axis (18). The recess rim (22) surrounds the recess base (21). The distance (e) of the depression bottom (21) to the central plane (19) of the saw chain does not increase at any point on the depression bottom (21) with increasing radial distance to the rivet bolt axis (18).The greatest distance (a) of the recess bottom (21) to the rivet pin axis (18) corresponds to 50% to 100% of half the core diameter (d) of the rivet pin (4). For a saw chain (1), the rivet pin (4) is designed as a solid body and has a first end face (33) and a second end face (34) which are designed differently.