Vacuum Insulated Structure Expansion Method to Prevent Vacuum Bow
Solution Overview
Problem
Vacuum insulated structures face the challenge of 'vacuum bow' due to pressure differentials during the generation of internal vacuum, which can lead to structural instability and reduced insulating effectiveness.
Innovation Solution
An expanding device is attached to opposing outer walls of the structural envelope, expanding the interior cavity to accommodate insulating material, and then gas is expressed to collapse the structure, creating a densified state that resists inward bowing by compressing the insulating material, thereby maintaining structural integrity and enhancing insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gas is expressed from the insulating cavity to create vacuum, then vacuum insulation performance is improved, but the structural envelope collapses inward causing vacuum bow
Solution Approach 1:
The expanding device is attached to the structural envelope before gas expression, expanding the cavity to a predetermined volume. This preliminary expansion creates structural rigidity that resists the subsequent inward collapse during vacuum generation, preventing vacuum bow while maintaining insulation performance
Solution Approach 2:
The expanding device applies outward force on the structural envelope walls before and during gas expression, counteracting the inward pressure differential that causes vacuum bow. This preliminary anti-action stabilizes the structure throughout the vacuum generation process
2Reliability
If the structural envelope is expanded to accommodate insulating material, then insulating effectiveness is improved, but the device complexity increases
Solution Approach 1:
The expanding device utilizes flexible attachment mechanisms (suction cups, magnetic attachments, or adhesive pads) that can conform to the structural envelope surfaces. This flexibility allows the device to achieve the required expansion force without complex mechanical structures, reducing overall device complexity while maintaining insulating effectiveness
Solution Approach 2:
The expanding device acts as an intermediary between the gas expression system and the structural envelope. It translates gas pressure or mechanical force into controlled cavity expansion, simplifying the overall system by decoupling the vacuum generation mechanism from the envelope expansion mechanism
3Strength
If the insulating material is densified during gas expression, then resistance to pressure differentials is improved, but the volume of the insulating cavity decreases
Solution Approach 1:
The cavity is expanded to its maximum predetermined volume before gas expression begins. This preliminary expansion ensures maximum insulating material volume and thermal performance are achieved before any densification occurs during the vacuum process
Solution Approach 2:
The system accepts and utilizes the parameter change of insulating material density during gas expression. The expanding device maintains outward force to counteract collapse, allowing the material to densify (improving strength) while the device compensates to maintain adequate cavity volume
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 method effectively prevents vacuum bow and enhances the structural robustness and insulating performance of vacuum insulated structures by compressing the insulating material into a densified state, maintaining a hermetic seal and improving resistance to pressure differentials.
Implementation Method 1
The interior cavity of the structural envelope is expanded by pulling the two opposing outer walls of the structural envelope away from one another
Implementation Method 2
Gas is expressed from the insulating cavity via the vacuum port, wherein the expression of gas at least partially collapses the structural envelope to a final state
Implementation Method 3
the expression of gas at least partially collapses the structural envelope to a final state of the structural envelope, the final state of the envelope defining a final interior volume, the final interior volume being less than the expanded interior volume, and wherein the final state of the structural envelope defines a densified state of the insulating material
Data Source
AI summary
A method of forming a vacuum insulated structure includes providing a structural envelope an insulating cavity defined within the structural envelope. An expanding device is attached to opposing outer walls of the structural envelope and the interior cavity is expanded by pulling the opposing outer walls away from one another to define an expanded state. An insulating material is disposed within the insulating cavity to occupy substantially all of the insulating cavity in the expanded state. Gas is expressed from the insulating cavity to collapse the structural envelope to a final state and a final interior volume that is less than the expanded interior volume. The final state of the structural envelope defines a densified state of the insulating material within the insulating cavity. The vacuum port is then closed to hermetically seal the insulating cavity.