JPH04119931A - Method for bending glass - Google Patents

Abstract

PURPOSE:To easily obtain a high accuracy S-shaped glass sheet nearly free from optical strain by forming a glass sheet with a convex surface at the upper side by a gravity shaping method and pressing the sheet from the upper side with a pressing die with a desired shaping surface at the underside. CONSTITUTION:A glass sheet 2 is put on a first bending die with a concave shaping surface at the upper side, heated to a temp. close to the bending temp. and shaped by gravity. The shaped sheet 2 is inverted so that the convex surface is positioned at the upper side and the sheet 2 is put on a second bending die 11 with a desired shaping surface at the upper side. The die 11 is conveyed in a heating furnace 16 and the sheet 2 is heated to the bending temp. with a heater 18 and shaped into an S-shaped section by pressing from the upper side with a pressing die 10 with a press shaping surface corresponding to the shaping surface of the die 11 at the underside. The press-shaped glass sheet 2 is cooled on the die 11 and taken out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a bending method used for bending a glass plate into a curved shape having both a concave and a convex surface in a heating furnace.

[Conventional technology] For transportation equipment such as automobiles, trains, ships, and aircraft, for construction,
Various types of curved glass are often used for various other purposes. In order to manufacture these, a glass plate cut into the required size and shape is heated to or near its softening temperature, and then various bending methods such as press forming, self-weight forming, and air forming are generally performed. ing.

Recently, in response to the diversification of automobile designs, glass for automobiles, etc. consists of a simple concave surface along the horizontal direction, but most of the glass plate is bent to one side along the vertical direction. The remaining portion is bent in the opposite direction to form a curved surface that has both a concave and a convex surface and has at least a portion of the S-shaped cross section, that is, a curved surface. There is a growing demand for curved glass sheets.

[Problems to be solved by the invention] Automobile windshields often use so-called laminated glass, which is made by laminating and bonding two glass plates. In order to accurately match the curvature of the raw glass for glass, it is necessary to bend and form two glass sheets at the same time. Such bending of two sheets at the same time is usually done by self-weight bending, but in the case of extremely complex shapes such as glass sheets with both concave and convex surfaces, the part with the smaller curvature is bent under its own weight. This was difficult because it was difficult for the glass plate to completely follow the shape of the bending die.

Therefore, in advance, a glass plate is placed on a ring-shaped bending die with a concave shape on the top, heated to around the softening point of the glass plate, and preformed by its own weight to the extent that it follows the bending die. A method of pressing from above using a press mold having a convex molding surface has been proposed.

However, with this method, the glass plate has a downwardly convex curved surface on the bending die before pressing, and it is not possible to obtain a glass plate with an arbitrary S-shape by simply pressing it from the top with a press mold. .

Furthermore, in order to process a glass plate with both concave and convex surfaces, a pair of bending press dies with complementary surface shapes are used, the glass plate is heated to near its softening point, and if necessary, the glass plate is It has been proposed that after preliminary ejecting, the glass plate is sandwiched between press molds and press-molded.

When forming a glass plate using this method, when a pair of molds are pressed against the glass plate at the same time, there is a limit to the surface shape accuracy of each mold, so a part of the glass plate may be pressed too hard. Because of this,
Distortion may occur on the glass plate. In order to prevent such problems from occurring, the surface shape accuracy of the mold must be extremely high, but this would not only make the mold very expensive but also extremely technically difficult. Moreover, even if a mold with sufficient precision can be manufactured, it is necessary to precisely align one mold and the glass plate during pressing, which takes too much time and effort.

Furthermore, since two press molds are required, there is also the problem of increased cost.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and includes bending a glass plate on a first bending die having a generally concave forming surface upward. A second molded material having a desired molding surface on its upper surface is molded by its own weight by heating to a temperature close to
The glass plate is placed upside down on a bending die so that the surface is convex upward, the glass plate is heated to around the bending temperature, and the lower surface thereof has a press forming surface corresponding to the desired forming surface. The present invention provides a method for bending and forming a glass plate, characterized in that the glass plate is press-formed from above using a press die.

[For use] In the present invention, a glass plate having an upwardly convex surface is prepared in advance, and is press-molded from above using a press die having a desired molding surface below, so that the glass plate has an upwardly convex surface. By adjusting the degree, S of any arbitrary shape can be created.
A letter-shaped glass plate is obtained.

In the present invention, since the glass plate is pressed and formed using one press die, the S-shaped glass plate is produced with less optical distortion than when the glass plate is press-formed using a pair of bending dies having complementary shapes. can get.

[Example] Hereinafter, based on the example, two sheets of laminated glass base glass 1
The present invention will be explained by taking as an example a method of bending and forming a glass material 0 into a glass shape having both a concave surface and a convex surface.

First, two sheets of glass for laminated glass are self-gold-formed by being heated to around the bending temperature on a first bending die having a generally concave forming surface upward.

FIG. 2 is a conceptual side view showing an example of a method for simultaneously bending two sheets of glass plate 10 for laminated glass using the first bending mold under their own weight.

Bending die 1 for self-weight bending of the split die type illustrated in Fig. 2
is placed on the carriage 4 of the conveying means, and includes a ring-shaped fixed split mold 1a having a bending surface corresponding to the central curved part of the bent laminated blank glass, and the fixed split mold 1a.
a ring-shaped movable split mold that is movably provided on both sides of the mold and has a bending surface that corresponds to the deep bending part of the laminated blank glass, and that this bending surface is connected to the bending surface of the fixed split mold 1a at the set position. 1b. The fixed split mold 1a is fixed onto the truck 4 via a support, while both sides of the movable split mold 1b in the width direction are swingably supported on the truck 4. Further, a balance weight 5 is attached to the support portion of the movable split mold 1b so that the movable split mold 1b is biased toward the set position side where it is connected to the fixed split mold 1a. In addition, in Fig. 2, (a) shows the flat laminated blank glass placed on the bending mold before heating the laminated blank glass, and Fig. 2 (b) shows the laminated blank glass before heating. This shows the state in which the self-weight bending process has been completed.

Place two sheets of laminated glass 2 on top of the bending die 1 as shown in Figure 2! Then, by conveying it through a heating furnace, it was heated to a bending temperature (this varies depending on the glass plate, but in the case of a normal soda lime silicate float glass plate, it is 550 to 650°C). On the way, the glass plate softens and hangs down due to its own weight, and the movable split mold 1b of the bending mold 1
are connected to the fixed split mold 1a, and the laminated blank glass is molded so as to follow the shape of the molding surface of the bending mold 1.

The formed glass plate is once carried out of the furnace, and the glass plate is inverted and placed on a second bending mold having a desired forming surface on its upper surface so as to form an upwardly convex surface.

Next, the glass plate is heated to around its softening point, and is press-molded from above using a press mold having a press-forming surface corresponding to the desired molding surface on its lower surface. FIG. 1 is a conceptual side view showing the method.

As mentioned above, the two glass plates are placed on the bending die 11 having the desired shaping surface on its upper surface so as to be upwardly convex. The bending die 11 can be transported inside the heating furnace 16, and is connected to a heating section STI and a press section S in the heating furnace 16.
After passing through T2, it is transported to a cooling section ST3.

In the heating and bending section STI, the heater 1 in the heating furnace 16
In step 8, the glass plate 2 is heated to the bending temperature (550 to 650°C), and in the press section ST2, after positioning the glass plate, the glass plate 2 is pressed from above by the bending press die 20, thereby forming the glass plate 2. The glass plate 2 is formed into an S-shaped cross section, and in the cooling section ST3, the press-formed glass plate 2 is cooled on the bending mold 11 for a predetermined time, and then the glass plate 2 taken out from the cooling section ST3 is left to cool.

The self-weight bending die 11 illustrated in FIG. 1 is a so-called integral type molded in one piece, but it may also be a split type consisting of a fixed split mold and movable split molds located on both sides of the fixed split mold. . Molding temperature of glass plate in heating furnace (550-65
Heat-resistant materials that can withstand temperatures (0°C) can be used. In the case of a split mold type, in order to prevent the movable split mold from jumping up during press forming, it is possible to fix the movable split mold to the fixed split mold by providing a ramp means or by applying the press forming load. It is preferable to use a bending die in which the molding surface of the movable split mold moves in a direction along the molding surface of the fixed split mold.

In the present invention, as shown in FIG. 1, one step is to prepare a glass plate with an upwardly convex surface in advance and press-form it from above using a press mold having a desired molding surface below. It has become a feature.

As a driving means for the press, in addition to a pneumatic cylinder, other cylinders such as hydraulic cylinders, electric motors, etc. are used. If this driving means can control the moving distance and moving speed during pressing, it will be effective in preventing troubles such as breakage of the glass plate during forming, and it will also be able to precisely shape the shape of the glass plate. This is preferable because it can be controlled.

Hereinafter, the operation of the device used in the method of the present invention described above to reversely place the glass plate bent under its own weight so that it becomes an upwardly convex surface and partially press it from above will be explained.

FIG. 3 is an enlarged view of the press section ST2 in FIG. 1. The second bending mold 1 supported on a trolley 15 via a support 13
Two glass plates 2 for laminated glass that have been subjected to self-weight bending using a first bending mold are placed on top of the glass plate 1, and the glass plates are bent in a predetermined manner suitable for bending in the heating section STI in the heating furnace 16. Molding temperature (preferably 5 for soda lime glass)
While being heated to a temperature of about 70 to 620° C.), it is conveyed along the rail 6 toward the press section ST2.

The glass plate 2 reaches a press section ST2 having a predetermined bending temperature (preferably about 570 to 620°C in the case of soda lime glass), and press forming is performed.
Conceptual diagrams showing this situation are shown in FIGS. 5(a) and 5(b). First, the glass plate is positioned below the press mold 10 (FIG. 5(a)). Next, the press cylinder 12 is operated, and the press mold is moved at a predetermined speed (preferably 0.1 to 5
．． 0. mm/5ee) and stops at a predetermined position (Fig. 5(b)). After the glass plate is formed, the press cylinder 12 is activated to open the press mold 10, and the glass plate, placed on the self-weight bending mold 11, is transported to the cooling section ST3 and slowly cooled. .

The press mold 10 has an S-shaped cross section when viewed from the direction of the figure, but when viewed from the direction of conveyance of the second bending mold 11, it has a substantially convex shape, and the shape of the press mold 11 and its surroundings is almost match.

FIG. 4 is a plan view of the state shown in FIG. 5A, and the press mold 1
0 and the bending die 11 in the plane direction.

As shown in the figure, it is preferable that the outer periphery of the bending die 11 is designed to be located slightly inside the outer periphery of the press die 10 because it facilitates forming the glass plate on the bending die 11 with high accuracy.

In this case, the deep bending forming part of the glass plate for laminated glass,
It is also possible to use an auxiliary heater to locally heat the deep bending part in order to make it 10°C to 100°C higher than other parts to improve formability.

Furthermore, when the above-mentioned press mold press-forms a single laminated sheet of glass, the contact surface of the press mold with the glass plate is made of glass fiber to prevent press marks from forming on the glass plate.
It is preferable to provide a heat insulating cloth such as silica fiber, other ceramic fiber, or metal fiber.

Further, when placing two glass plates on the self-weight bending mold, a mold release material powder such as baking soda, celite, magnesium oxide, silica, etc. may be interposed between them.

Furthermore, in order to particularly strengthen the surrounding area, we use an auxiliary heater that particularly heats the surrounding area of the glass plate, and after press forming, we push the glass plate up and away from the self-weight bending mold to speed up the cooling of the surrounding area. You can do it like this.

The glass plate for laminated glass that has been bent is made into laminated glass by a manufacturing method used for ordinary laminated glass.

That is, they are stacked one on top of the other with an interlayer film such as polyvinyl butyral interposed therebetween, and after evacuation, they are heated and pressed together, or after they are warmed and pre-pressed, they are pressed and heated to be pressed together.

Although the present embodiment has been described using the case of bending and forming a glass plate for laminated glass as an example, it goes without saying that the method of the present invention can be applied to bending and forming two glass plates.

In addition, although this example describes the case of manufacturing a glass plate with an S-shaped cross section, a concave surface with a more complicated shape,
It can also be applied to the case of producing a glass plate having a convex surface at the same time.

[Effects of the Invention] In the present invention, a glass plate having an upwardly convex surface is prepared in advance, and is press-molded from above using a press die having a desired molding surface below, so that the glass plate has an upwardly convex surface. By adjusting the degree, S of any arbitrary shape can be created.
A letter-shaped glass plate is obtained.

Furthermore, since the glass plate is pressed and formed using one press mold, optical distortion is less likely to occur compared to when press molding is performed using a pair of bending molds having complementary shapes.

Regarding the surface shape accuracy of the press mold, when using a pair of press molds, it was necessary to have extremely accurate surface shape in order to avoid optical distortion, but according to the method of the present invention, the surface shape accuracy required for the glass plate itself was required. A surface shape accuracy of about 1 mm (usually about 1 mm) is sufficient.

Furthermore, by setting the molding temperature during pressing to a low temperature of 600°C or less and pressing at a low speed (approximately 0.1 mm/sec), optical distortion caused by the pressing surface of the press die coming into contact with the glass plate can be minimized. can be prevented to a limited extent,
This also has the effect of suppressing the drooping of the glass plate due to its own weight during pressing and heating, allowing for highly accurate molding.

[Brief explanation of the drawing]

FIG. 1 is a side view showing an example of the bending process according to the present invention. FIG. 2 is a side view showing the first bending die. FIG. 3 is a side view showing the press section ST2. FIG. 4 is a plan view of the self-weight bending die when it reaches the press section ST2, as seen from above the lower press die. FIG. 4 is a plan view showing the positional relationship between the press mold and the bending mold in the present invention. FIG. 5 is a conceptual diagram showing the state of press molding in the present invention. 2.Glass plate 1..First bending die 16..Heating furnace 10..Press die 11..Second bending die

Claims (1)

[Claims] (1) A glass sheet is self-gravity formed by heating it to around the bending temperature on a first bending die having a generally concave forming surface upward, and a second bending die having a desired forming surface on the upper surface. The glass plate is placed upside down on a mold so that it has an upwardly convex surface, the glass plate is heated to around the bending temperature, and a press mold having a press molding surface corresponding to the desired molding surface on its lower surface is used. A method for bending and forming a glass plate, characterized in that the glass plate is press-formed from above.