Vibratory Stretch Rod for Preform Forming
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge in forming containers is that heating the preform to prevent material cooling below the glass transition temperature during the forming process leads to energy inefficiency and potential malformation due to internal stress release, causing unwanted deformations like the 'banana effect' and increased energy consumption.
Innovation Solution
A forming station equipped with a vibratory device connected to a stretch rod that vibrates during the forming process, converting vibrational energy into heat within the preform, reducing the need for overheating and minimizing energy dissipation, while an additional vibratory device in the liquid injection circuit further heats the preform, especially during high-pressure injection phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the preform is heated at a high temperature close to the crystallization temperature to delay cooling below the glass transition temperature, then the preform remains malleable longer allowing complete shaping, but this causes internal stress release leading to unwanted deformations like the 'banana effect' and increases energy consumption
Solution Approach 1:
The patent applies mechanical vibration to the stretch rod during the forming process. The vibratory device generates vibrations that are transmitted to the preform material, creating internal friction and heat within the material. This vibration-induced heating maintains the preform above the glass transition temperature without requiring external heating to crystallization temperatures, thus resolving the contradiction between maintaining malleability and reducing energy consumption
Solution Approach 2:
The patent replaces the thermal field (external heating system) with a mechanical field (vibratory device). Instead of using external heat sources to maintain preform temperature, the invention uses mechanical vibrations converted to internal heat through material friction. This substitution eliminates the need for high-temperature heating while maintaining the preform in a malleable state throughout the forming process
2Temperature
If the preform is heated at a high temperature close to the crystallization temperature to delay cooling below the glass transition temperature, then the preform remains malleable longer allowing complete shaping, but this causes internal stress release leading to unwanted deformations like the 'banana effect'
Solution Approach 1:
The vibratory device attached to the stretch rod generates mechanical vibrations during the forming process. These vibrations create internal friction and heat within the preform material, maintaining it above the glass transition temperature without requiring external heating to crystallization temperatures. This controlled vibration-based heating prevents the internal stress release and unwanted deformations that occur with excessive external heating
Solution Approach 2:
The invention substitutes the thermal field (external heating system) with a mechanical field (vibratory device). By using mechanical vibrations converted to internal heat, the system maintains precise temperature control within the preform without the overheating effects that cause the 'banana effect' and other deformations, thereby improving manufacturing precision
3Productivity
If the liquid forming fluid is injected at ambient temperature (5°C to 50°C) into the heated preform, then the preform can be shaped, but the liquid causes rapid quenching of the inner walls generating a huge shear of temperature gradient with the outer wall
Solution Approach 1:
The vibratory device generates mechanical vibrations during the injection process, creating internal friction and heat within the preform material. This vibration-induced heating compensates for the rapid cooling effect of the cold liquid injection, maintaining a more uniform temperature distribution throughout the preform and reducing the temperature gradient between inner and outer walls while preserving forming speed
Data Source
AI summary
A forming station comprising a source of pressurized forming fluid, and an injection device comprising an inlet, in fluidic communication with the source of pressurized forming fluid, and an outlet in fluidic communication with the inlet and through which the forming fluid is intended to be injected in the preform and further comprising a stretch rod movable in translation according to the axis of the stretch rod relative to the outlet and arranged to assist the axial deformation of the preform during a stretching phase. The forming station further comprises a vibratory device connected to the stretch rod, arranged to vibrate the stretch rod when said vibratory device is actuated, and a control device arranged to actuate the vibratory device during at least a part of the stretching phase.