Laminating Glass Sheets with Segmented Hot Air Blasting
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Solution Overview
Problem
The formation of air bubbles in laminated glass sheets during the lamination process is a common quality issue, particularly at the rear edge, due to incomplete air discharge, which is exacerbated by overheating and the use of tempered glass with uneven surfaces, leading to premature adhesion and trapped air pockets.
Innovation Solution
A method and apparatus for laminating glass sheets where two-sided hot air blasting is used in a heating furnace with adjustable blowing aperture sections, and the air blasting is cut off or reduced as the rear edge approaches, to control the temperature and prevent overheating, ensuring effective air discharge during the pressing stage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If two-sided hot air blasting is applied continuously throughout the lamination process, then the plastic film is heated sufficiently to ensure adhesion, but the rear edge of the sandwich structure sheet becomes overheated causing premature adhesion and air bubble formation
Solution Approach 1:
The heating process is segmented into multiple zones along the conveyor path. The blowing aperture sections are positioned to provide targeted heating to specific areas, with the rear edge zone having reduced or no hot air blasting to prevent overheating and premature adhesion at the rear end
Solution Approach 2:
Different sections of the sandwich structure sheet receive different heating intensities. The front and middle sections receive full hot air blasting for adequate heating, while the rear edge section receives reduced or no blasting to maintain lower temperature and prevent premature adhesion, ensuring uniform air discharge throughout
2Length of moving object
If multiple plastic films are stacked to achieve required thickness, then the desired total thickness is obtained, but the films adhere prematurely at the rear end and air bubbles form between layers
Solution Approach 1:
The rear edge zone of the conveyor provides a localized cooler environment where multiple plastic films remain separate and do not adhere prematurely. This local temperature control ensures that even when multiple films are stacked to achieve required thickness, they maintain separation throughout the lamination process and only adhere after proper air discharge
3Strength
If the glass sheet surface is tempered to improve strength, then mechanical strength is enhanced, but the wavy surface creates air pockets and traps air during lamination
Solution Approach 1:
The lamination process is designed to address the wavy surface characteristics of tempered glass in advance. The reduced hot air blasting at the rear edge prevents premature adhesion that would trap air in wavy surface areas, allowing the press rolls to effectively discharge air from between the film and the wavy glass surface before final adhesion occurs
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 reduces the formation of air bubbles by maintaining a suitable temperature for air discharge at the press rolls, enhancing the quality of laminated glass by ensuring the plastic films adhere properly without premature sealing, thus improving the overall lamination process.
Implementation Method 1
the sandwich structure sheet moving in the heating furnace is heated by means of two-sided hot air blasting
Implementation Method 2
The press roll pair removes air from the moving sandwich structure sheet by compressing it, whereupon the air in the material interfaces inside the sandwich structure becomes highly overpressurised
Implementation Method 3
The plastic film is heated in a lamination furnace to the target temperature, whereupon the temperature measured on the outer surface of the sandwich structure sheet immediately after the furnace is 60-80° C.
Data Source
AI summary
A method for laminating glass sheets is disclosed. A sandwich structure sheet moving in a heating furnace on rollers is heated by two-sided hot air blasting which is carried out by several successive blowing aperture sections, and, to reduce or prevent the formation of air bubbles in finished laminated glass, the heating of the rear end of the sandwich structure sheet is prevented by cutting off the hot air blasting of at least one blowing aperture section when the rear edge of the sandwich structure sheet approaches the blowing aperture section. An apparatus for laminating glass sheets is also disclosed, comprising a heating furnace, a pair of press rolls and means for establishing location data on the sandwich structure sheet. The heating furnace is provided with a roller track, a blower, a heating resistor, an air distribution conduit, and several successive blowing boxes with closing means.