Plastic Aerosol Container Undercut Valve Mounting
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Solution Overview
Problem
Existing plastic aerosol containers face challenges with stress cracking and deformation under pressurization, leading to loss of sealing integrity between the container and the aerosol dispensing closure, and difficulty in achieving an inside seal for the aerosol valve assembly due to the smooth inner surface of the finish portion.
Innovation Solution
A blow molded plastic aerosol container with a finish portion that has an undercut on its inner surface, allowing for secure mounting and sealing of the aerosol valve assembly, and utilizing crystallization in the plastic material to enhance structural integrity under pressurization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a smooth inner surface is used in the finish portion of a blow molded plastic container, then manufacturing is easier and the surface is easier to clean, but the aerosol valve assembly cannot be securely mounted as there are no features for the valve to gain purchase
Solution Approach 1:
The undercut feature is formed in the finish portion during the blow molding process itself, before the valve assembly is mounted. This preliminary formation of the mounting feature eliminates the need for separate operations to create mounting structures, while still providing the necessary mechanical engagement features for secure valve assembly attachment
Solution Approach 2:
Instead of mounting the valve assembly on the outer surface of the container (conventional approach), the invention inverts the mounting location to the inner surface of the finish portion. The undercut feature on the inner surface provides mechanical engagement that secures the valve assembly from the inside, reversing the conventional outside-mounting approach
2Object-affected harmful factors
If plastic material is used for aerosol containers, then rust and surface scratching are eliminated, but stress cracking and deformation occur under high internal pressurization (0.345-2.07 MPa)
Solution Approach 1:
The invention changes the physical and chemical parameters of the plastic material by selecting specific resin types (polyethylene terephthalate, polyethylene naphthalate, or acrylic resin) with appropriate molecular structures and mechanical properties that can withstand aerosol pressurization without stress cracking or deformation, while maintaining resistance to rust and surface scratching
Solution Approach 2:
The invention uses composite construction by combining the plastic container body with a metal or plastic valve assembly that has a sealing member. This composite structure allows the plastic container to provide corrosion resistance while the valve assembly with its sealing components provides the necessary mechanical strength and sealing capability under pressurization
3Ease of manufacture
If external threading or mounting flanges are used on the outer surface of the finish portion, then the valve assembly can be mounted, but the seal is less mechanically advantageous compared to inside sealing
Solution Approach 1:
The invention inverts the conventional outside-sealing approach by implementing inside sealing. The valve assembly is mounted on the inner surface of the finish portion, with the sealing interface located inside the container. This inversion provides mechanical advantages similar to metal container sealing while accommodating the smooth inner surface requirement of blow molded plastic containers
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 solution provides a more effective and reliable mount and seal between the plastic container and the aerosol valve assembly, maintaining sealing integrity even under high internal pressures, and preventing deformation and stress cracking.
Implementation Method 1
utilizing crystallization in the plastic material to enhance structural integrity under pressurization
Data Source
Figure 1
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Figure 4
AI summary
A plastic aerosol container assembly (10) includes a plastic container that has a main body portion (12) defining an interior space and a finish portion (14) that defines an opening. A pressurized aerosol mixture is maintained within the interior space. The finish portion has an inner surface (20) that has an undercut (22) defined therein. An aerosol valve assembly (24) is mounted to the plastic container so that a portion thereof engages the inner surface (20) of the finish portion (14) so as to be retained by the undercut (22). The plastic container is preferably fabricated from material including polyethylene terephthalate (PET). At least one location in the finish portion may be crystallized in order to provide enhanced resistance to stress cracking.