Expandable Forming Drum for Tyre Carcass Shaping
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Solution Overview
Problem
The production of tyres with small curvature ratios, such as those for passenger cars, faces challenges in quality and process repeatability due to mismatched curvature profiles between the forming drum and the carcass sleeve, leading to uneven coupling and potential distortions.
Innovation Solution
A process and plant design that includes a containment action on the carcass sleeve to inhibit radial expansion and shape it into a more flattened profile consistent with the forming drum's geometry, ensuring even coupling and minimizing friction, using an annular contrast element to adapt the shaping of the carcass sleeve to match the forming drum's curvature, allowing for precise application of additional components like belt layers, tread bands, and sidewalls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a standard forming drum is used for tyre building, then the process works well for tyres with large curvature ratios (motorcycles), but the curvature profile mismatch causes uneven coupling and distortions for tyres with small curvature ratios (passenger cars)
Solution Approach 1:
The forming drum is made expandable with adjustable curvature ratio, allowing it to dynamically change its geometric profile to match different tyre types. The drum can be expanded or contracted radially to achieve the appropriate curvature ratio for passenger car tyres (small curvature) or motorcycle tyres (large curvature), thus maintaining coupling uniformity across different applications.
Solution Approach 2:
The curvature ratio parameter of the forming drum is made variable through expansion/contraction mechanisms. By changing the radial dimension of the forming drum, the curvature ratio is adjusted to match the specific tyre being built, eliminating the profile mismatch that causes uneven coupling and distortions in traditional fixed-curvature drums.
2Ease of operation
If the carcass sleeve is allowed to expand radially during shaping, then it can accommodate the forming drum, but it creates a curved profile that mismatches the forming drum geometry for small curvature ratio tyres
Solution Approach 1:
An annular contrast element is introduced to counterbalance the radial expansion tendency of the carcass sleeve. This element applies a constraining force that opposes the outward expansion, preventing the carcass sleeve from assuming an overly curved profile and helping it match the forming drum's geometry for small curvature ratio tyres.
Solution Approach 2:
The annular contrast element acts as an intermediary between the carcass sleeve and the forming drum. It mediates the interaction by providing a reference geometry that guides the carcass sleeve shaping while preventing excessive radial expansion, thus ensuring the final profile matches the forming drum without direct interference with the shaping process.
3Manufacturing precision
If additional components (belt layers, tread bands, sidewalls) are applied after carcass shaping, then the tyre structure is complete, but the process requires multiple transfer operations that reduce productivity
Solution Approach 1:
The forming drum is designed to integrate multiple functions: it serves as both the shaping tool for the carcass sleeve and the mounting surface for applying additional components (belt layers, tread bands, sidewalls). By combining these operations on a single stationary drum, the need for transferring the carcass between different workstations is eliminated, thus maintaining positioning accuracy while improving productivity.
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 achieves accurate and uniform coupling of the carcass sleeve with the forming drum, enhancing the quality and structural integrity of tyres with small curvature ratios by reducing friction and distortion, while allowing for flexible production of various tyre types with different component compositions.
Implementation Method 1
said expandable forming drum is engageable in said shaping station in said first radially contracted operational condition; said actuator devices are provided, operating in said shaping station for radially expanding said forming drum inside said carcass sleeve
Implementation Method 2
said containment devices are provided, operating in said shaping station for positioning at least one annular contrast element around said building drum and said carcass sleeve, operating against said carcass sleeve itself during the action of said actuator devices or said shaping devices
Implementation Method 3
concurrent introduction of fluid under pressure into the carcass sleeve, so as to cause a radial expansion of the carcass plies up to make them adhere against the inner surface of the crown structure
Data Source
AI summary
A carcass sleeve including a carcass ply and a pair of annular anchoring structures is fitted around a toroidal forming drum arranged in a first radially contracted operational condition. The carcass sleeve is toroidally shaped against a radially inner surface of an annular contrast element. The forming drum is positioned inside the carcass sleeve and is concurrently expanded towards a second operational condition. Upon reaching the second operational condition, the toroidally shaped carcass sleeve is coupled to the forming drum. The forming drum, coupled to the carcass sleeve, is adapted to be transferred in proximity of an application device of additional components externally to the carcass sleeve.