Flexible-Closure Piston for Low-Stiction Aerosol Dispensing
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Solution Overview
Problem
Current piston aerosol containers face issues with residual product retention, increased stiction leading to pulsating dispensing, and difficulty in sealing with plastic containers, especially when pressurized, due to the viscous nature of products and expansion of plastic cans.
Innovation Solution
A piston design featuring an upper side made of a deformable elastic material and a sidewall of a different material, with a circumferential seal on the outer surface, which maintains a seal without relying on the product for sealing and can handle various viscosities and pressures up to 180 psig, ensuring efficient dispensing and minimal residual product.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid plastic piston is used to seal with the container wall, then the piston can maintain structural integrity, but the piston becomes difficult to insert and experiences increased stiction causing pulsating spray
Solution Approach 1:
The piston is divided into two distinct functional zones: a rigid sidewall made of plastic for structural integrity and sealing, and a flexible closure made of elastic material for deformation capability. This segmentation allows each part to perform its optimal function without compromising the other.
Solution Approach 2:
The closure material is selected to have specific elastic properties with a hardness range of 30-85 Shore A, allowing it to deform elastically under pressure changes while the rigid sidewall maintains its dimensional stability. This parameter differentiation resolves the contradiction between rigidity and flexibility.
2Reliability
If the piston is sized to fit tightly with the container wall, then sealing is improved, but residual product remains on the sidewalls after dispensing
Solution Approach 1:
The sealing function is localized to specific regions: the rigid sidewall provides structural sealing against the container wall, while the flexible closure provides dynamic sealing against the product. This local differentiation of sealing functions allows effective sealing without excessive product adhesion on the rigid sidewalls.
Solution Approach 2:
The flexible closure acts as an intermediary between the rigid piston sidewall and the viscous product, preventing direct contact and adhesion between the product and the rigid sidewall surface, thereby reducing residual product retention.
3Force
If the plastic container is pressurized to dispense product, then dispensing force is increased, but the container expands causing seal failure
Solution Approach 1:
The closure is designed to be dynamically responsive to pressure changes, deforming elastically as the container expands under pressure and returning to its original shape when pressure is released. This dynamic adaptation maintains the seal integrity throughout the pressurization and dispensing cycle.
Solution Approach 2:
The elastic material properties of the closure (hardness 30-85 Shore A) are specifically selected to match the expected pressure range (up to 180 psig) and container expansion characteristics, allowing the closure to accommodate pressure-induced dimensional changes while maintaining sealing effectiveness.
4Reliability
If the piston uses product as a sealing agent, then sealing is achieved, but the viscous product increases stiction and causes pulsating spray
Solution Approach 1:
The sealing function is separated into two independent mechanisms: mechanical sealing between the rigid sidewall and container wall, and dynamic sealing by the flexible closure against the product. This eliminates reliance on the viscous product as the primary sealing agent, reducing stiction while maintaining sealing effectiveness.
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 design allows for complete dispensing of products with minimal residual retention, maintains a consistent seal throughout the container's lifetime, and supports a wide range of viscosities and pressures, improving dispensing efficiency and reducing stiction issues.
Implementation Method 1
the upper side is made of a first elastic material, wherein the upper side is configured to deform upon a pressure change acting on the upper side
Data Source
AI summary
The invention relates to a piston for an optionally pressurized container, the piston having a sidewall, an upper side and a bottom side, and at least a first circumferential seal, wherein at least the upper side of the piston is closed by a closure and made of a first elastic material, wherein the upper side is configured to deform upon a pressure change acting on the upper side, wherein the sidewall is made of a second material which is different from the first elastic material, wherein the first circumferential seal is positioned on the sidewall on its outer surface. The invention further relates to an optionally pressurized container comprising a piston as mentioned above, to a process of discharging a product from said container and to a process of manufacturing said container.