Blow-Molded Plastic Container Socket Welding Design
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Solution Overview
Problem
Existing plastic containers with multi-layer walls, featuring an inner layer of polyethylene and an outer layer of reclaimed material separated by an EVOH barrier layer, face challenges in forming a welded joint with a container fitting due to material incompatibility, particularly when using hot-plate butt-welding techniques.
Innovation Solution
The plastic container design incorporates a container socket with a longitudinal cross-section that widens toward the opening, forming a welding contact surface solely with the inner layer segment, preventing incompatible material contact during welding, and employs a two-stage blow molding process to create a conical bulge for a high-quality welded joint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hot-plate butt-welding is used to connect the container socket to the container fitting, then a welded joint can be formed, but the welding quality deteriorates due to material incompatibility between the outer layer (reclaimed material) and the container fitting (polyethylene)
Solution Approach 1:
The container wall is segmented into an inner layer made of polyethylene and an outer layer made of reclaimed material. The container socket is designed with a longitudinal cross-section that widens toward the opening, exposing only the inner layer at the welding contact surface. This segmentation allows the welding process to operate on compatible materials (polyethylene to polyethylene) while preserving the outer layer's protective functions, thereby resolving the material incompatibility issue in hot-plate butt-welding
Solution Approach 2:
The container socket has different structural characteristics at different locations: the wall thickness and material composition vary along the longitudinal direction. Specifically, the welding contact surface area is formed exclusively by the inner layer segment, while the outer layer is positioned away from the welding interface. This local quality differentiation ensures that the welding zone has compatible materials for high-quality bonding, while the outer layer maintains its protective properties elsewhere
2Adaptability or versatility
If the container socket includes an outer layer made of reclaimed material, then the container can utilize recycled materials for environmental benefits, but the welded joint quality deteriorates due to incompatibility with polyethylene container fittings
Solution Approach 1:
The container wall is divided into functional layers: an inner layer of polyethylene that contacts the liquid and forms the welding surface, and an outer layer of reclaimed material that provides protective functions. This segmentation enables the container to utilize recycled materials for sustainability while ensuring that the welding interface consists only of compatible polyethylene material, thus resolving the conflict between material sustainability and welded joint quality
Solution Approach 2:
The container socket is designed with spatially varying material properties. The inner layer segment at the welding contact surface is made of polyethylene to ensure compatibility with polyethylene container fittings, while the outer layer made of reclaimed material is positioned away from the welding interface. This local quality differentiation allows the container to incorporate recycled materials for environmental benefits while maintaining high welding quality at the critical joint interface
3Ease of manufacture
If a bulge is formed in the container wall to create the container socket, then the socket structure is formed, but wall thickness reduction occurs which may compromise structural integrity
Solution Approach 1:
The container socket is formed as an integrated feature during the blow-molding process itself, rather than as a subsequent operation. The mold cavity is designed to create the widening cross-section and expose the inner layer at the appropriate location. This preliminary action allows the socket structure to be formed while maintaining optimal wall thickness distribution and avoiding the need for separate cutting or drilling operations that would further reduce wall strength
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 allows for a simple and high-quality welded joint between the container socket and fitting, ensuring compatibility and maintaining the integrity of the inner layer for food contact and reducing wall thickness reduction, thus enhancing the durability and functionality of the container.
Implementation Method 1
a heating mirror is disposed as a hot plate between the container socket and a connecting piece of the container fitting disposed opposite in order to heat both a welding contact surface realized on the container socket and a welding contact surface realized on the connecting piece of the container fitting to their welding temperature
Implementation Method 2
the plastic container being realized as a blow-molded body by blow molding from a tubular preform in a blow mold
Implementation Method 3
the welding contact surfaces being pressed against each other with pressure once the welding mirror has been removed and being allowed to cool in this position in order to form the welded joint
Data Source
AI summary
A plastic container and a method for producing a plastic container for liquids comprising an outer jacket made of latticework or of sheet metal material and a pallet-type understructure, the plastic container including a blow-molded body having a container socket in a container wall, the container socket provided with a container opening and connected to a flange of the container fitting via a welded joint, wherein the container wall has an inner layer made of a first plastic material and an outer layer made of a second plastic material, and the container socket has a longitudinal cross section widening toward the container opening such that an end face of the container socket is formed at least in part by an inner layer segment disposed opposite the outer layer, and a welding contact surface of the container socket is formed by the inner layer segment.