Tread Transfer Device Axial Positioning and Pressure Regulation
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Solution Overview
Problem
Existing methods for transferring and laying treads on tire casings face challenges with large tires, particularly in maintaining a quality joint and precise axial positioning of the tread during the transfer process, especially when dealing with unvulcanized and hot elastomer materials.
Innovation Solution
A transfer device featuring an annular structure with circumferentially arranged gripping modules, including lifting fingers and pressure-regulated shrink-fit cylinders, allows for precise axial positioning and constant radial pressure application throughout the transfer process, ensuring the tread remains securely gripped and accurately aligned with the crown reinforcement plies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a vacuum ring is used to grip the tread by its radially outer face, then the tread can be held and transferred, but the assembly drum diameter must be increased and the device becomes heavy and not dimensionally adaptable
Solution Approach 1:
The gripping system is divided into multiple independent gripping elements (gripping fingers arranged circumferentially) that can individually engage the tread. This segmentation allows the system to grip the tread at multiple points simultaneously, providing reliable holding capability without requiring a large-diameter vacuum ring, thus reducing device complexity and improving dimensional adaptability.
Solution Approach 2:
Instead of gripping the tread from the radially outer face as in conventional vacuum ring systems, the invention grips the tread from the radially inner face by engaging the crown reinforcement plies. This inverted approach allows the gripping elements to contact the tread structure internally, eliminating the need for increased drum diameter and reducing overall device size.
2Reliability
If lifting fingers are used to grip the radially inner surface of the tread, then the elasticity of the elastomer can be utilized for natural radial clamping, but the tread axial position cannot be maintained precisely during disengagement
Solution Approach 1:
The invention merges two gripping approaches into a single integrated system: lifting fingers that utilize elastomer elasticity for radial clamping, and gripping elements that engage the crown reinforcement plies for axial positioning. This combination ensures both reliable radial clamping force and precise axial positioning are maintained simultaneously during the entire transfer process including disengagement.
Solution Approach 2:
The gripping elements engaging the crown reinforcement plies act as an intermediary mechanism that maintains axial positioning. While the lifting fingers provide radial clamping through elastomer elasticity, the gripping elements on the reinforcement plies serve as a mediator that prevents axial movement during disengagement, ensuring precise positioning is maintained.
3Ease of operation
If the tread is transferred hot and unvulcanized, then it remains flexible for positioning, but vacuum release occurs due to retraction forces on the hot elastomer
Solution Approach 1:
Instead of relying on vacuum gripping from the radially outer face which fails due to hot elastomer retraction, the invention inverts the approach by gripping from the radially inner face through the crown reinforcement plies. This alternative gripping location is not affected by the same retraction forces, maintaining reliable holding stability while the hot flexible tread remains easy to position.
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 device ensures precise conservation of the tread's position relative to the axis from extraction to deposition, maintaining a constant application pressure to prevent buckling and facilitate a seamless joint with the crown reinforcement belt, even with hot elastomeric materials.
Implementation Method 1
the shrink-fit cylinders being pressure-regulated around several distinct setpoint pressures, so that at a given setpoint pressure, identical for all shrink-fit cylinders of the transfer device, the application pressure exerted by the shrink-fit base on the radially external surface of the tread is constant
Implementation Method 2
two lifting fingers intended to engage the radially internal surface of the tread, arranged opposite each other on either side of a plane of symmetry, axially movable in opposite directions with respect to said plane of symmetry
Data Source
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AI summary
The invention relates to a device (2) for transferring an elastomer ring for forming a tyre tread (4), comprising an annular structure (20) on which a plurality of gripping modules (3) is peripherally arranged, each of the modules comprising: two lifting fingers (30) for engaging the radially inner surface of the tread (4), said fingers being axially mobile in opposite directions in relation to a plane of symmetry (PP') and radially mobile between a plurality of predetermined radial positions; and a bracing sole (31) which moves radially under the action of at least one bracing cylinder (310), and comes into contact with the radially outer surface of the tread (4). The bracing cylinders (30) are pressure-regulated over a plurality of nominal pressures which are different from each other such that, at a given nominal pressure, the application pressure exerted by the bracing sole (31) on the radially outer surface of the tread (4) is constant irrespective of the radial position of said bracing sole.