Blow Mould Ejector Design for Plastic Container Surface Quality
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Solution Overview
Problem
Conventional extrusion blow molding machines often leave impressions or pressure marks on plastic containers due to ejector contact during removal from the mold, which affects the appearance and structural integrity of the containers.
Innovation Solution
A blow molding tool arrangement with laterally movable ejection devices that touch the plastic tubing only in a 'lost section' during ejection, avoiding contact with the finished container, and featuring two or more blow mold parts that can move from an open to a closed position, with ejection pistons guided in holes parallel to each other for reduced force and simplified control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ejectors are used to remove finished plastic containers from the mold, then productivity is improved by enabling automated removal, but the ejectors leave impressions and weaken the container wall
Solution Approach 1:
The harmful function of the ejectors (leaving impressions on containers) is separated from the useful function (removing containers from mold). The ejectors are positioned to act only on the lost middle section, extracting the harmful effect from the final product while maintaining the useful ejection function.
Solution Approach 2:
The ejection force is applied locally only to the lost middle section of the container rather than the entire container. This localized application of ejection force ensures that the impressions are confined to the discarded portion while the main container body remains undamaged.
2Ease of operation
If ejectors act on the bottom region of containers, then ease of operation is improved by simplified ejection mechanism, but harmful impressions are created on the container wall
Solution Approach 1:
The harmful effect of ejector contact is extracted and relocated to the lost middle section. The ejectors are positioned laterally to contact only the middle section, separating the ejection function from the container surface that matters.
Solution Approach 2:
The lost middle section acts as an intermediary that absorbs the ejection force. By designing the ejection system to act on this sacrificial section rather than the main container body, the harmful effects are mediated through the discarded material.
3Device complexity
If conventional ejectors are used, then device complexity is reduced by using simple ejection mechanisms, but the containers suffer from impressions and structural weakening
Solution Approach 1:
The harmful impact on container strength is extracted by relocating the ejection action to the lost middle section. The simple ejection mechanism structure is maintained while its action point is shifted to avoid compromising the main container body.
Solution Approach 2:
The ejection force is applied locally to the lost middle section rather than distributed across the entire container. This localized action preserves the wall integrity of the main container while maintaining the simplicity of the ejection mechanism.
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 solution prevents impressions and deformations on the plastic containers, ensuring they are free of ejector marks and damage, while allowing for efficient production of multiple containers in a single cycle with reduced mechanical and control engineering costs.
Implementation Method 1
The blow mandrel which is guided in a hole of the blow molding tool can be laterally fed to the region of the mutually adjoining mouths of the blow mold cavities. The blow mandrel penetrates the wall of the plastic tubing in a middle region which connects the two mouths and inflates two containers in one cycle from the plastic tubing which has been inserted into the double cavity.
Implementation Method 2
To remove the finish-inflated plastic containers, especially plastic bottles, from the mold, there are ejectors in the blow molding tool arrangement. The ejectors are located in the peripheral regions of the blow molding tool arrangement and generally act in one section of the plastic container which borders its bottom region.
Data Source
AI summary
Blow molding tool arrangement is disclosed for an extrusion blow molding machine for plastic containers, especially for plastic bottles, comprising two or more blow mold parts (1, 2) which can be moved from an open into a closed position and vice versa and in the closed state border a mold cavity (7) which has at least one access opening (22) for a blow mandrel (8), and with at least one laterally movable ejection device (10) for removing from the mold a plastic tube which has been inflated by overpressure according to the mold cavity (7). The ejection device (10) is arranged such that it can be extended laterally relative to the inside wall of the mold during ejection and touches the plastic tubing upon ejection in a lost section (74) which is detached after removal from the mold.