Extrusion Blow Molding Connection Element for Fuel Tank Sealing
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Solution Overview
Problem
Existing methods for producing fuel tanks from thermoplastic materials by extrusion blow molding face challenges in creating impermeable connections for hoses and electrical components, as the plastics used tend to swell and are not diffusion-tight, leading to potential leakage paths at connection points.
Innovation Solution
A method involving a connection element with a penetrating tip and matrix that minimizes wall deformation, where the connection element is used as a lost forming die to pierce the container wall from the inside, using a sleeve-shaped cutting element with a peripheral flange for welding and melt chambers to manage displaced material, allowing for easy attachment of components like hoses or valves while maintaining impermeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If connection elements are inserted into the container wall after production, then components like valves and hoses can be attached, but leakage paths occur at the connection points due to swelling and lack of diffusion tightness
Solution Approach 1:
The connection elements are integrated into the mold as inserts before the extrusion blow molding process begins. The piercing tips are pre-positioned to pierce the container wall during formation, ensuring that the piercing and sealing actions occur while the plastic material is still hot and pliable, before cooling and swelling occur.
Solution Approach 2:
The piercing tips are designed to pierce the wall during the hot forming stage when the thermoplastic material has different physical properties (more pliable, less swollen). The material state changes from hot and formable during piercing to cool and swollen after formation, but the seal is already established in the favorable hot state.
2Ease of operation
If the container wall is pierced to create passages for connection elements, then components can be attached, but wall bulging occurs which complicates the process
Solution Approach 1:
The container wall acts as a flexible thermoplastic material during the piercing process. The piercing tips are designed to displace rather than cut the material, utilizing the plasticity of hot thermoplastic to allow material flow around the piercing tip, minimizing permanent deformation and bulging.
Solution Approach 2:
The piercing action is performed preliminarily during the extrusion blow molding process itself, while the material is still hot and pliable. This preliminary piercing prevents subsequent wall deformation that would occur if piercing were attempted after cooling, as the material is more compliant and can accommodate the piercing tip without excessive bulging.
3Reliability
If complex two-component connection elements are used, then leakage paths can be avoided, but device complexity increases
Solution Approach 1:
The connection element is designed as a single-integral component that combines multiple functions: the piercing tip for creating the passage, the sealing surface for preventing leakage, and the mounting structure for attaching valves or hoses. This merging of functions into one component reduces complexity compared to separate piercing devices and connection elements.
Solution Approach 2:
The connection element serves multiple purposes: it pierces the container wall during formation, creates a sealed passage through the wall, and provides a mounting interface for various components (valves, hoses, electrical connections). This multi-functionality eliminates the need for separate piercing devices and simplifies the overall system.
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 effectively reduces hydrocarbon leakage by minimizing wall bulging and ensuring secure, impermeable connections during the extrusion blow molding process, maintaining the integrity of the thermoplastic fuel tank.
Implementation Method 1
the connection element is used as a lost forming die to pierce the container wall from the inside
Implementation Method 2
a sleeve-shaped cutting element with a peripheral flange for welding
Implementation Method 3
peripheral flange for welding to the container wall
Implementation Method 4
melt chambers to manage displaced material
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The invention relates to a method for the production of a container made of thermoplastic plastic by extrusion blow molding, wherein the container is provided during the forming thereof with a multi-part tool (1) having a connection element (3) penetrating at least one wall (4) thereof. The connection element (3) according to the invention is configured in two parts, wherein one part is configured as a removable cutting element (11). The cutting element (11) is used as a penetration point for puncturing the wall of the container in the still-plastic state thereof.