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Trimming of Laminated Glass by Abrasion

IP.com Disclosure Number: IPCOM000019696D
Publication Date: 2003-Sep-25
Document File: 4 page(s) / 934K

Publishing Venue

The IP.com Prior Art Database

Abstract

Abrasion removes the excess PVB and generates friction and heat, allowing the remaining film to shrink between the glass layers uniformly, even along contours and corners. This results in a desirable dull finish to the surface of the laminate edge

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Trimming of Laminated Glass by Abrasion

Automotive laminated glasses are made of a multi-layer assembly composed of a plurality of tempered glass sheets and poly(vinyl butyral)(PVB) that offers protection to vehicle passengers upon impact.

The use of laminated glasses is increasing in the car industry for a number of reasons:

 

  • As an extension to the historic use in front windscreens, laminated glass is now being introduced into side, rear and roof windows, offering improved protection in the case of impact;
  • Laminated glass reduces heat transfer;
  • Laminated glass is a good noise insulator;
  • Laminated glass offers a much better protection against robbery, therefore insurance companies promote its use; and
  • The surface area of glass per vehicle is increasing due to technical progress and aesthetics.

The peripheral edges of laminated automotive glass are required to be of higher quality because windscreens and other windows are now directly bonded on the car body and not encapsulated in rubber fittings. Moveable laminated glass (e.g., side windows, etc.) requires high quality edges since the edges can be directly exposed to passengers.

Automotive tempered glass/PVB laminates are typically bonded in an autoclave. During heating, the PVB layer contracts, so the layers are assembled with an (area-wise) excess of PVB that must be trimmed. On many production lines, this trimming is done by hand with razors or knifes. From an aesthetic point of view, a knife always leaves PVB on the laminate edges as the two glass sheets are never precisely positioned. In addition, any pause of operator movement creates a visible defect on the edge.

Problems linked to the use of knives


Photomicrograph showing excess PVB.

Visible defects caused by discontinuous cutting motion



 


Knives leave shiny edge

Dull knife leaves filamentary residual that causes light diffraction


 

Advantages of trimming by abrasion

Abrasion removes the excess PVB and generates friction and heat, allowing the remaining film to shrink between the glass layers uniformly, even along contours and corners. This results in a desirable dull finish to the surface of the laminate edge

Nonwoven abrasives are well suited for this abrasive trimming operation. The open web construction of a non woven abrasive in belt or wheel form, provides the abrading effect without undercutting the glass. However, other types of abrasive article constructions may also be useful.

The abrasive trimming operation can be semi-automatic with operators handling the laminate against the abrasive tool, or fully automatic with the use of robots for a significant positive impact on the line productivity.

The abrading tools must be flexible enough to be able to bend around the laminated glass edge shape. For example an abrasive belt can be run perpendicular to the major surfaces of the laminate with sufficient slack so as to conform to the edge contour, or alternatively, an abrasive belt can be mounted on a backst...