Polyurethane Foam Injection for Uniform Filling of Hollow Bodies
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Solution Overview
Problem
Current methods for injecting polyurethane mixtures into hollow bodies, such as refrigerator cabinets, result in uneven expansion and incorporation of air bubbles due to vortex formation and irregular flow patterns, leading to structural homogeneity issues and increased material consumption.
Innovation Solution
A method using a high-pressure mixing device to inject the polyurethane mixture at a maximum flow-rate and speed from a distant point, then gradually reducing flow-rates and speeds to distribute the mixture 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 speed to fill the cavity quickly, then productivity is improved, but the mixture generates vortexes and irregular flow patterns causing air bubble incorporation and structural homogeneity issues
Solution Approach 1:
The cavity is divided into multiple deposition zones (first deposition zone at maximum distance, second deposition zone at intermediate distance, third deposition zone at minimum distance). The injection process is segmented into phases with different flow-rates, with each phase targeting specific zones to ensure uniform distribution without vortex formation.
Solution Approach 2:
The flow-rate of the polyurethane mixture is dynamically adjusted during injection. The system transitions from a first flow-rate for the first deposition zone to a second flow-rate for the second deposition zone, and to a third flow-rate for the third deposition zone. This dynamic adjustment optimizes both injection speed and structural homogeneity.
2Duration of action of moving object
If the polyurethane mixture is injected at high flow-rate to reduce processing time, then duration of action is improved, but material distribution becomes uneven leading to increased material consumption
Solution Approach 1:
Different flow-rates are applied to different spatial zones within the cavity. The first deposition zone receives mixture at a first flow-rate, the second deposition zone at a second flow-rate, and the third deposition zone at a third flow-rate. This local quality adjustment ensures optimal material distribution and reduces waste.
Solution Approach 2:
The injection system dynamically changes flow-rates based on the deposition zone being filled. This temporal and spatial variation in injection parameters allows complete cavity filling in reduced time while maintaining uniform material distribution and preventing over-consumption.
3Productivity
If the jet of mixture impinges on inner surfaces to fill the cavity, then productivity is improved, but vortexes form causing air bubble incorporation and structural irregularities
Solution Approach 1:
The injection targets specific local zones (first, second, and third deposition zones at different distances from the injection point) rather than allowing random impingement on all inner surfaces. This controlled local delivery prevents vortex formation while maintaining efficient cavity filling.
Solution Approach 2:
The system pre-determines the injection parameters (flow-rates and deposition zones) before injection begins. By planning the deposition sequence in advance, the system prevents harmful vortex formation from random surface impingement while maintaining high productivity through optimized injection paths.
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 uniform expansion of the foam, reducing air bubble incorporation and structural irregularities, while maintaining the technical and mechanical characteristics of traditional polyurethane foams, and optimizing material usage.
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
Implementation Method 4
Once injected, the polyurethane mixture chemically reacts and expands to form a foam which runs and rises into the cavity of the hollow body filling it completely
Data Source
Figure 1~2
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Figure 5~6
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 (A, B), supplied by a high-pressure mixing device (18), is injected into a cavity (13, 47) of a hollow body (10, 40) extending in a horizontal plain. The mixture is injected at a first flow-rate (Q) and a first injection speed (V), to be poured into a first deposition zone (21) 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 (Zn) towards the injection point of the polyurethane mixture, along a distribution strip (F), allowing the injected mixture to spread out throughout the cavity of the hollow body along isometric expansion lines.