JPH0570158A - Bending molding unit for plate glass and bending molding method - Google Patents

Abstract

PURPOSE:To prevent a plate glass from breakage in its setting to a window frame by reducing compressional (tensile) stress developing in the plate glass in its bending molding. CONSTITUTION:For a molding unit 1, a molding station S1 and reheating station S2 are set up on the downstream side of a tunnel-type furnace 2. In the reheating station S2, a rail 8 is provided above horizontal rolls 3 for conveyance in parallel with the carrying direction for a plate glass G, and the rail 8 is engaged with a moving body 9 which supports a gas burner 10 in a suspended state. The gas burner 10 has a design in compliance with the periphery of the plate glass G and equipped with a nozzle to eject a gas toward the periphery of the upper surface of the plate glass G.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for forming curved flat glass such as an automobile windshield.

[0002]

2. Description of the Related Art Conventionally, in order to form a curved glass such as a windshield of an automobile, the flat glass is heated to a temperature close to its softening point while being conveyed in a furnace by a horizontal roll and is taken out of a heating furnace. Is transferred to a ring mold (lower mold) and press-molded into a predetermined shape between the ring mold and the upper mold, which is a full-face mold.

In the above-mentioned conventional molding method, since the ring mold is in contact with the plate glass for a long time during the molding, a plane compressive stress is generated at the peripheral edge of the plate glass with which the ring mold is in contact. A plane tensile stress, which is commensurate with the plane compressive stress, is generated in the inner region of the glass sheet. This plane stress is different from the stress in the thickness direction caused by quenching strengthening.If this plane stress is large, the plate glass will be applied when another stress is applied during or after the plate glass is fitted into the window frame of the automobile. Leading to damage. Therefore, Japanese Patent Application Laid-Open No. 52-78226 proposes to suppress the plane compressive stress and the plane tensile stress of a plate glass used as a laminated glass for an automobile front window within a predetermined range.

[0004]

As described above, when the ring mold is kept in contact with the glass for a long period of time during molding, a plane compressive stress is always generated at the edge portion of the glass, and the plane compressive stress is a predetermined value. It is extremely difficult to control within the range, and even if it falls within the predetermined range, it may cause glass breakage.

[0005]

In order to solve the above-mentioned problems, the first invention of the present application is to provide an upper mold having a lower surface as a molding surface and a ring-shaped lower mold supporting a peripheral portion of a lower surface of a plate glass on the downstream side of a heating furnace. In the bending and forming apparatus, the heating device for reheating only the peripheral portion of the plate glass in contact with the lower mold is arranged on the downstream side of the upper mold and the lower mold. The second invention of the present application is that the plate glass carried out from the heating furnace is bent and formed by an upper mold having a lower surface as a molding surface and a ring-shaped lower mold, and then the plate glass is carried out from between these molds to obtain a glass plate after molding. Only the peripheral portion was reheated to 550 ° C or higher.

[0006]

When the press molding is performed between the upper mold and the lower mold, a plane compressive stress is generated at the peripheral edge of the glass sheet, but the planar compressive stress is canceled by reheating the peripheral edge of the glass sheet after the molding.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an overall view of a flat glass bending apparatus according to the present invention, FIG. 2 is a perspective view of a reheating station of the flat glass bending apparatus, and FIG. 3 is an enlarged view of a main part of the reheating station. Has a forming station S1 and a reheating station S2 downstream of the tunnel-type heating furnace 2.

A horizontal roll 3 for conveying the sheet glass G is arranged in the heating furnace 2, and a bending roll 4 for conveying the sheet glass G while preforming is arranged between the heating furnace 2 and the forming station S1. An upper die 5 and a lower die 6 are arranged in the above.

The upper mold 5 is fixed to the frame 7 and has a hollow shape made of an aluminum plate or a stainless plate.
The entire lower surface is the molding surface, and the molding surface has glass cloth,
A surface material made of stainless cloth, ceramic cloth or stainless fiber and aramid fiber is coated.
The lower die 6 has a ring shape that supports the peripheral edge of the lower surface of the glass sheet G, and is vertically movable by a cylinder unit (not shown).

On the other hand, in the reheating station S2, a rail 8 is provided above the horizontal roll 3 for conveyance and a plate glass G is provided.
The moving body 9 is engaged with the rail 8 and the gas burner 10 is suspended and supported by the moving body 9.

As shown in FIGS. 2 and 3, the gas burner 10 has a shape along the peripheral edge of the plate glass G, that is, a shape similar to that of the lower mold 6, and ejects gas toward the peripheral edge of the upper surface of the plate glass G. The nozzle 11 is provided.

In the above, the horizontal roll 3 is set in the heating furnace 2.
The sheet glass G that has been conveyed to and heated to near the softening point is carried out of the heating furnace 2, is preformed by the bending roll 4 and is conveyed to the lower mold 6 and transferred to the lower mold 6,
Then, the lower mold 6 is raised to bring the flat glass G onto the molding surface of the upper mold 5.
Is pressed to bend the plate glass G.

In the above molding, the plate glass G is the lower mold 6
With the upper mold 5 for 1 to 2 seconds. In this manner, since only the peripheral edge of the plate glass G is in contact with the lower mold 6 for a long time, the temperature difference between the peripheral part and the inner part of the plate glass G becomes large, and planar compressive stress is generated at the peripheral part of the plate glass G. A plane tensile stress corresponding to the plane compressive stress of the edge portion is generated inside the plate glass G.

Next, the flat glass G in which the plane stress is generated is reheated by the bending roll 4 at the reheating station S2.
Transport to. In the reheating station S2, the moving body 9 is moved in accordance with the conveyance of the plate glass G, and the gas burner 10 reheats only the peripheral portion of the plate glass G in which the plane compressive stress is generated. The reheating temperature is set to a temperature at which the plane compressive stress is canceled, specifically, 550 ° C. or higher. However, if the temperature is raised too much, the portion once molded will sag, so it is preferably set to 600 ° C. or lower.

FIGS. 4 and 5 are views showing another embodiment of the reheating station S2. In the embodiment shown in FIG. 4, below the gas burner 10 to which the plate glass G after press molding is fixed, The bending roll 4 for transportation is rotated in the forward and reverse directions to oscillate back and forth to reheat mainly the peripheral portion.
In the embodiment shown in FIG. 5, a plurality of gas burners 10 are arranged between the bending rolls 4 so as to face upward, and H of the flame ejected from the gas burners 10 in accordance with the movement of the plate glass G.
The i-Low (On-Off) is controlled so that only the peripheral edge of the plate glass G is reheated.

[0016]

FIG. 6 is a graph showing the relationship between the plate glass bent by the conventional apparatus and the distance from the edge of the plate glass bent by the present invention and the generated plane tensile stress. It can be seen that the flat tensile stress of the sheet glass molded according to the present invention is significantly smaller than that of the conventional one. That is, according to the present invention, since the peripheral edge of the sheet glass is reheated to 550 ° C. or higher after being bent and formed by the upper die having the entire lower surface as the forming surface and the ring-shaped lower die, The plane compressive stress is canceled, so that the plane tensile stress from the edge to the inner portion is also proportionally reduced. Therefore, it is possible to provide a plate glass that is unlikely to be damaged even when another stress acts on the window frame or the like or after the assembly.

[Brief description of drawings]

FIG. 1 is an overall view of a sheet glass bending apparatus according to the present invention.

FIG. 2 is a perspective view of a reheating station of the sheet glass bending apparatus.

[Fig. 3] Enlarged view of the main part of the reheating station

FIG. 4 is a diagram showing another embodiment.

FIG. 5 is a diagram showing another embodiment.

FIG. 6 is a graph showing the relationship between the distance from the edge of the sheet glass bent and formed by the conventional apparatus and the edge of the sheet glass bent and formed according to the present invention, and the generated plane tensile stress.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Bending forming apparatus, 2 ... Heating furnace, 4 ... Bending roll, 5 ... Upper mold, 6 ... Lower mold, 8 ... Rail, 9 ... Moving body, 1
0 ... Gas burner, G ... Sheet glass, S1 ... Forming station, S2 ... Reheating station.

Claims (2)

[Claims] 1. A bending molding apparatus comprising a lower mold having a lower surface as a molding surface and a ring-shaped lower mold for supporting a peripheral portion of a lower surface of a sheet glass, the downstream side of the upper mold and the lower mold. A bending apparatus for sheet glass, wherein a heating device for reheating only the peripheral edge of the sheet glass in contact with the lower mold is disposed in the apparatus. 2. The plate glass carried out from the heating furnace is bent and shaped by an upper mold having a lower surface as a molding surface and a ring-shaped lower mold, and then the plate glass is carried out from between these molds, and only the peripheral portion of the molded plate glass is formed. Reheating to 550 ° C. or higher, a method for bending sheet glass.