Polyurethane Foam Injection Profile for Uniform Hollow-Body Filling
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Solution Overview
Problem
Current methods for injecting polyurethane mixtures into hollow bodies, such as refrigerator cabinets, result in uneven distribution and incorporation of air bubbles due to vortex formation and irregular flow patterns, leading to structural inconsistencies and increased material consumption.
Innovation Solution
A method and apparatus that utilize a high-pressure mixing device to inject the polyurethane mixture at a maximum flow-rate and speed initially, then gradually reduce flow-rate and speed to distribute the mixture evenly along a longitudinal strip, ensuring isometric expansion and homogeneous distribution within the cavity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the polyurethane mixture is injected at high flow-rate and speed to quickly fill the cavity, then the expansion time is reduced and productivity is improved, but the mixture creates vortexes and irregular flow patterns that cause air bubble incorporation and structural inconsistencies
Solution Approach 1:
The injection process is divided into multiple sequential phases: an initial high-speed phase to quickly reach the farthest deposition zone, followed by intermediate phases with reduced flow-rates for successive zones, and finally a low-speed phase for the zone closest to the injection point. This segmentation of the injection process by spatial zones and speed levels eliminates vortex formation while maintaining rapid overall filling, thus resolving the contradiction between productivity and manufacturing precision.
2Area of stationary object
If the polyurethane mixture is injected against a surface or at an angle to reach farthest points of the cavity, then the distribution coverage is improved, but vortexes form and cause irregular flowing with air bubble incorporation
Solution Approach 1:
Instead of injecting the mixture directly against surfaces or at angles (two-dimensional approach), the invention uses a long supply pipe that extends into the cavity along the longitudinal axis (three-dimensional approach). The mixture is injected parallel to the longitudinal axis and distributed along a longitudinal strip, reaching farthest points without impinging on surfaces, thus eliminating vortex formation and air bubble incorporation while maintaining full coverage.
3Speed
If the injection flow-rate is increased to push the mixture beyond the expansion zone faster, then the filling speed is improved, but the mixture creates waves and wrinkles that incorporate air and cause uneven distribution
Solution Approach 1:
The injection system dynamically adjusts the flow-rate of the polyurethane mixture based on the expansion state and position within the cavity. The flow-rate varies continuously or in steps through different phases: high initial flow-rate to overcome resistance and reach distant zones, then progressively reduced flow-rates as the mixture advances, preventing wave formation and air incorporation while maintaining forward momentum. This dynamic control resolves the contradiction between speed and compositional stability.
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 enables uniform expansion of the foam to reach all areas of the cavity quickly, reducing air bubble incorporation and structural irregularities, while maintaining the technical and mechanical characteristics of traditional polyurethane foams and minimizing material consumption.
Implementation Method 1
the jets of the liquid polyurethane components, due to their high kinetic energy, meet and collide with each other, generating a strong turbulence which causes their thorough mixture
Implementation Method 2
the reaction between the polyurethane components, such as a polyol and an isocyanate, tends to develop heat and CO2 gas
Implementation Method 3
cause the release of a foaming agent to generate a foam which rapidly expands, flowing into the cavity of a hollow body to fill it completely
Data Source
AI summary
A method and apparatus for feeding a polyurethane mixture suitable to form a thermally insulating layer inside hollow bodies, such as hollow walls of a refrigerator cabinet, freezer, display counter or insulating panel. A polyurethane mixture resulting from chemically reactive components, supplied by a high-pressure mixing device, is injected into a cavity of a hollow body extending in a horizontal plain. The mixture is injected at a first flow-rate and a first injection speed, to be poured into a first deposition zone farthest from the injection point. Subsequently, the flow-rate and the injection speed of the polyurethane mixture are gradually reduced in a controlled manner, to be poured in successive deposition zones towards the injection point of the polyurethane mixture, along a distribution strip, allowing the injected mixture to spread out throughout the cavity of the hollow body along isometric expansion lines.