Pneumatic Tire Sidewall Over Tread Manufacturing
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Solution Overview
Problem
The stitch-down step in manufacturing pneumatic tires with a Sidewall Over Tread (SOT) structure is inefficient, leading to shape inaccuracies, increased production costs due to complex equipment, and high defect rates, particularly when increasing rotation speed or using tread rubber with high stiffness, resulting in non-uniform shapes and potential scratches or wrinkles.
Innovation Solution
The method involves forming the tread as separate center and sides, with the center formed on the tread ring and sides formed on the first cover, and bonding them simultaneously during the turn-up step, eliminating the need for stitch-down and simplifying equipment, while ensuring accurate shape formation and improved reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If stitch-down is conducted while rotating the drum at increased speed, then productivity is improved, but manufacturing precision deteriorates due to non-uniform shape formation
Solution Approach 1:
The tread is divided into two separate components: the center tread formed on the tread ring and the side treads formed on the first cover. This segmentation eliminates the need for stitch-down operation while allowing independent formation of each tread portion, thereby maintaining shape accuracy without compromising productivity.
Solution Approach 2:
The side treads are preliminarily formed on the first cover during the cover forming step, and the center tread is formed on the tread ring separately. These preliminary formations eliminate the need for subsequent stitch-down operation, allowing the drum to rotate at optimal speeds without shape distortion.
2Manufacturing precision
If stitch-down operation is performed to bond tread to first cover, then manufacturing precision is improved, but device complexity increases due to complicated stitcher structure
Solution Approach 1:
The stitch-down operation and associated stitcher equipment are completely removed from the manufacturing process. Instead, the tread is formed in two separate locations (center on tread ring, sides on first cover) and naturally positioned during assembly, eliminating complex bonding equipment while maintaining product quality.
3Manufacturing precision
If stitch-down is performed with wide stitcher roller, then manufacturing precision is improved, but object-generated harmful factors increase due to scratches and wrinkles on tread surface
Solution Approach 1:
The stitch-down operation that causes surface defects is completely eliminated. The tread portions are formed separately in their final positions and assembled without mechanical bonding, preventing scratches and wrinkles on the tread surface while maintaining shape accuracy.
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 approach enhances production efficiency, maintains shape accuracy, reduces defect rates, and improves tire performance by minimizing stitch-down-related issues, allowing for stable tire performance and simplified equipment design.
Implementation Method 1
inserting said first cover inside said tread ring, and inflating that portion of said first cover which is between the said beads, and thereby pressure-bonding said tread ring with said first cover
Data Source
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AI summary
A pneumatic tire manufacturing method is provided in which raw cover molding is suitably performed with no, or a minimal amount of, down-stitching in the manufacture of SOT-structure pneumatic tires; also provided is a pneumatic tire. This pneumatic tire manufacturing method involves: a step in which a sidewall, an inner liner, and a ply are bonded on a first molding drum, a pair of beads is set, and the tread side part is formed on the side wall, forming a first cover; a step in which a breaker and band are bonded on a second molding drum and the tread center part is formed on the band, shaping the tread ring; a step in which the first cover is inserted inside of the tread ring and the first cover is inflated, bonding the tread ring and the first cover with pressure; and a step in which the sidewall is folded back towards the lateral surface of the inflated first cover and bonded to the lateral surface of the first cover, and the tread side part and the tread center part are bonded together.