JP7463972B2 - Glass sheet forming equipment - Google Patents

Description

The present invention relates to a glass sheet forming apparatus.

Various methods are used to manufacture glass press-molded products by heating and softening a glass material placed in a mold and pressing it. For example, a molding device has been proposed in which a plate-shaped glass material is transported in sequence to each of the heating, pressing, and cooling stages set up in a chamber, and press-molded products are continuously formed at each stage (Patent Document 1).

In such a molding device, the glass material is maintained at a heating temperature sufficient for processing the glass material by bringing the mold to a specified temperature during pressing. The glass material after molding is then cooled and solidified, and is ultimately cooled to a temperature of 200°C or less at which the mold does not oxidize. As described above, the shape of the mold is accurately transferred to the glass material during pressing, and this molded shape is maintained through cooling and solidification, resulting in a press-molded product with high shape precision.

International Publication No. 2013/103102

However, with regard to molding devices such as those described above, as the molded shapes of glass materials became more complex and mass production became more common, there was room for improvement in various aspects, such as the productivity of the molded products and the quality of their shapes and surface properties.

The present invention aims to provide a glass sheet forming device that can form products with high shape accuracy and high throughput, even when the products have complex shapes, while reducing equipment costs.

The present invention comprises the following configurations.
A glass sheet forming apparatus for heating a glass sheet and forming it into a desired shape,
a first mold having a molding surface having at least a curved shape at least partially formed thereon, the glass sheet being supported on the molding surface;
At least one second mold clamped to the first mold;
at least one preheating stage for heating the glass sheet supported by the first mold;
at least one forming stage in which the second mold is disposed facing the first mold and the heated glass sheet is formed between the first mold and the second mold;
at least one cooling stage for annealing the glass sheet after forming;
a mold transport unit that transports the first mold to the preheating stage, the molding stage, and the cooling stage in this order;
The glass plate has a glass central portion on the inner side of a glass shape outer peripheral edge, and a glass outer peripheral portion between an outer periphery of the glass central portion and the glass shape outer peripheral edge,
The second mold of the forming stage contacts the glass sheet only at the outer periphery of the glass sheet between the first mold and the second mold.

According to the present invention, even molded products having complex shapes can be molded with high shape accuracy and high throughput while reducing equipment costs.

FIG. 1 is a schematic process diagram showing a procedure for forming a glass sheet into a curved shape. FIG. 2 is a schematic diagram of the molding device. FIG. 3 is a cross-sectional view of a plurality of lamp heaters. FIG. 4 is a schematic plan view of the cross section taken along line III-III shown in FIG. 2 as viewed from above. FIG. 5 is a schematic explanatory diagram showing a state in which the lower mold is transported along a transport direction from the preheating stage toward the cooling stage. FIG. 6 is an enlarged cross-sectional view of the forming stage. FIG. 7A is a cross-sectional view of an upper mold, and FIG. 7B is a cross-sectional view including the molding surface of a lower mold. FIG. 8 is a rear view of the upper mold as viewed from the direction B in FIG. FIG. 9 is a plan view of a glass plate. FIG. 10A is a schematic process explanatory diagram showing, in a stepwise manner, how a glass sheet is formed by bringing the lower mold and the upper mold shown in FIGS. 7A and 7B close to each other. FIG. 10B is a schematic process explanatory diagram showing, in a stepwise manner, how the lower mold and the upper mold shown in FIGS. 7A and 7B are brought close to each other to form a glass sheet. FIG. 10C is a schematic process explanatory diagram showing, in a stepwise manner, how the lower mold and the upper mold shown in FIGS. 7A and 7B are brought close to each other to form a glass sheet. FIG. 11 is a process explanatory diagram illustrating an outline of how a glass sheet is shaped by the second shaping method. FIG. 12 is a schematic diagram of a molding apparatus including a plurality of preheating stages, a molding stage, and a plurality of cooling stages. FIG. 13 is a graph showing an example of temperature changes of the lower mold and the glass plate in the preheating stage, the forming stage, and the cooling stage. FIG. 14 is a schematic diagram of a conventional molding device as a reference example. FIG. 15 is a schematic diagram of a molding apparatus showing another configuration example of the molding apparatus shown in FIG. FIG. 16A is a schematic cross-sectional view showing the molded shapes of Test Examples 1 and 2, FIG. 16B is a schematic cross-sectional view showing the molded shape of Test Example 3, and FIG. 16C is a schematic cross-sectional view showing the molded shape of Test Example 4.

Hereinafter, an embodiment of the present invention will be described in detail.
Here, specific examples of a forming apparatus and a forming method for forming a glass sheet into a shape having at least a partially curved surface will be presented and explained. However, in the present invention, it is also possible to appropriately change the configuration of the apparatus and the procedure depending on various manufacturing conditions such as the material used, the formed shape, and the size.

In addition, in this specification, the use of "~" to indicate a numerical range is used to mean that the numerical values before and after it are included as the lower and upper limits.

<Outline of glass sheet forming procedure>
FIG. 1 is a schematic process diagram showing a procedure for forming a glass sheet into a curved shape.
The glass plate forming apparatus 100 comprises a preheating stage 11, a forming stage 13, and a cooling stage 15 arranged in that order, and further comprises a loading section 19 which transports a glass plate 17 before forming into the preheating stage 11, and an unloading section 21 which transports a glass plate 17A after forming from the cooling stage 15.

In the preheating stage 11, the glass plate 17 that has been brought in is heated and softened. In the forming stage 13, the glass plate 17 that has been heated and softened in the preheating stage 11 is subjected to press forming or the like to be formed into the desired shape. In the cooling stage 15, the glass plate 17 formed in the forming stage 13 is gradually cooled to a temperature at which deformation is suppressed.

Glass sheets 17 are carried in and out of each of the above stages from a loading section 19 and an unloading section 21. That is, in the loading section 19, the glass sheet 17 before molding is placed on a lower die (first molding die) 23. The lower die 23 on which the glass sheet 17 is placed is transported to the preheating stage 11, where it is heated to a predetermined temperature. The heated glass sheet 17 is transported together with the lower die 23 to the molding stage 13.

At the forming stage 13, the glass sheet 17 is clamped between an upper die (second forming die) 25 and a lower die 23 mounted on the forming stage 13 and then clamped. This causes the glass sheet 17 to be formed into a curved shape. After forming, the upper die 25 is separated from the lower die 23, and the processed glass sheet 17A remaining in the lower die 23 is transported together with the lower die 23 to the cooling stage 15.

In the cooling stage 15, the heated glass sheet 17A is slowly cooled. After being slowly cooled, the glass sheet 17A is removed from the lower mold 23 in the unloading section 21 and carried out.

In the forming device of this configuration, in addition to press forming in which the glass sheet 17 softened by heating is pressed by the lower die 23 and the upper die 25 in the forming stage 13, bending of the glass sheet by its own weight (self-weight bending forming), adsorption of the glass sheet to the forming surface of the forming die (vacuum adsorption), and pressure bonding of the glass sheet to the forming surface of the forming die (pressure forming) are performed in combination according to the purpose. By selectively using such multiple pressure sources, it is possible to form curved surfaces with high shape accuracy. Regarding self-weight bending forming, if the glass sheet 17 is placed on the lower die 23 and heated, self-weight bending occurs in the glass sheet 17, but this can be made controllable. For example, if there is almost no difference between the start temperature of bending by self-weight and the press forming temperature, and the effect of self-weight bending due to heating up to the press temperature is small, self-weight bending forming is not applied. On the other hand, if the self-weight forming time before and after pressing is sufficient, gravity affects the shape after forming, so self-weight bending forming is applied. In this way, self-weight bending forming can be controlled according to the waiting time and waiting temperature before performing press forming.

The above-mentioned molding methods are the following molding techniques.
(1) Press molding is a method in which a glass sheet is placed between specified molds (lower mold and upper mold), and while the glass sheet is in a softened state, a press load is applied between the upper and lower molds to bend the glass sheet to fit the molds and form it into a specified shape.
(2) Gravity bending is a method in which a plate glass is placed on a specified forming mold, the glass plate is heated to soften it, and the glass plate is bent by gravity to fit the forming mold and formed into a specified shape.
(3) Vacuum forming is a method in which a glass sheet is placed on a predetermined forming mold, and for example, a clamp forming mold is placed on the glass sheet to seal the periphery of the glass sheet. Thereafter, the closed space between the forming mold and the glass sheet is depressurized by a pump or the like to apply a pressure difference between the front and back surfaces of the glass sheet to form it.
(4) In the pressure forming method, a glass sheet is placed on a predetermined forming mold, and for example, a clamp forming mold is placed on the glass sheet to seal the periphery of the glass sheet. After that, a positive pressure is applied to the upper surface of the glass sheet by compressed air, and a pressure difference is applied between the front and back surfaces of the glass sheet to form it.

<Glass material for molding>
The glass plate to be molded has a thickness of, for example, 0.5 mm or more, preferably 0.7 mm or more. The thickness of the glass plate is 5 mm or less, preferably 3 mm or less, more preferably 2 mm or less. If the thickness is within this range, the final product has a strength that is difficult to break.

The glass compositions that make up the glass plate can be alkali-free glass, soda-lime glass, soda-lime silicate glass, aluminosilicate glass, borosilicate glass, lithium aluminosilicate glass, or borosilicate glass. The glass forming device of this configuration is particularly excellent when aluminosilicate or aluminoborosilicate is used for the glass plate. These glass plates have a high Young's modulus and a high coefficient of expansion, and high thermal stress is generated when the glass plate is heated. This causes the glass plate to deviate from the desired curved shape, and when the glass plate is further tempered, the value of the compressive stress may vary. In the glass forming device of this configuration, since the glass plate is made of these glass compositions, the shape deviation can be reduced even in the curved shape, and the variation in compressive stress can be suppressed.

Specific examples of glass compositions include, but are _not limited to, glasses containing 50-80% _SiO2 , 0.1-25% _Al2O3 , 3-30% _Li2O + _Na2O + _K2O , 0-25% MgO, 0-25% CaO, and 0-5% _ZrO2 , expressed in mole percent based on oxides. More specific examples include the following glass compositions. For example, "containing 0-25% MgO" means that MgO is not essential but may be contained up to 25%. Glass (i) is included in soda lime silicate glass, and glasses (ii) and (iii) are included in aluminosilicate glass. Glass (v) is included in lithium aluminum silicate glass.
(i) A glass having a composition expressed in mole percent on an oxide basis _of 63-73% _SiO2 , 0.1-5.2% _Al2O3 , 10-16% _Na2O , 0-1.5% _K2O , 0-5% _Li2O , 5-13% MgO, and 4-10% CaO.
(ii) A glass having a composition expressed in mole % on an oxide basis of 50-74% _SiO2 , 1-10% _Al2O3 , _6-14 % _Na2O , 3-11% _K2O , 0-5% _Li2O , 2-15% MgO, 0-6% CaO and 0-5% _ZrO2 , with the total content of _SiO2 and _Al2O3 being ₇₅ % or less, the total content of _Na2O and _K2O being 12-25%, and the total content of MgO and CaO being 7-15%.
(iii) A glass having a composition expressed in mole percent on an oxide basis _of 68-80% _SiO2 , 4-10% _Al2O3 , 5-15% _Na2O , 0-1% _K2O , 0-5% _Li2O , 4-15% MgO, and 0-1% _ZrO2 .
(iv) _A glass having a composition expressed in mole % on an oxide basis of 67-75% _SiO2 , 0-4% _Al2O3 , 7-15% _Na2O , 1-9% K2O, 0-5% _Li2O , 6-14% MgO and 0-1.5% _ZrO2 , the total content of _SiO2 and _Al2O3 being 71-75%, the total content of _{Na2O and K2O being} 12-20%, and if CaO is contained _, its content is less than 1%.
(v) A glass having a composition expressed in mole percent on an oxide basis of _56-73 % _SiO2 , 10-24% _Al2O3 , 0-6% _B2O3 , 0-6% _P2O5 , 2-7% _Li2O , 3-11% Na2O, _0-2 % _K2O , 0-8% MgO, 0-2% CaO, _0-5 % SrO, 0-5% BaO, 0-5% ZnO, _0-2 % _TiO2 , and 0-4% _ZrO2 .

<Configuration of molding device>
An example of the configuration of the above-mentioned molding device will now be described in detail.
Fig. 2 is a schematic configuration diagram of the molding apparatus 100. Fig. 3 is a schematic plan view of the cross section taken along line III-III shown in Fig. 2, viewed from above.
In the following description, the same reference numerals are used to designate parts or portions that perform the same functions, and the description thereof may be omitted or simplified. In addition, the embodiments shown in the drawings are schematic to clarify the description of the present configuration, and are not accurately represented according to the size or scale of the actual product.

In the forming device 100 shown in Figure 2, the glass sheet is transported in the horizontal direction TD from left to right, and the preheating stage 11, forming stage 13, and cooling stage 15 are arranged in this order from the upstream side of the transport direction TD. The preheating stage 11, forming stage 13, and cooling stage 15 are housed in the internal space of a chamber 27. The chamber 27 is purged with an inert gas such as nitrogen gas to reduce the concentration of gases that have adverse effects during glass forming.

The chamber 27 has an entrance 29 through which the glass plate and the lower die 23 are carried into the chamber 27, and an exit 31 through which the glass plate and the lower die 23 after molding are carried out. The entrance 29 is connected to the loading section 19 shown in FIG. 1, and the exit 31 is connected to the unloading section 21 shown in FIG. 1 (not shown). In addition, the entrance 29 and the exit 31 are provided with shutters (not shown), and the atmosphere in the chamber 27 is maintained constant by closing the shutters except when the glass plate is carried in or out. The chamber 27 has a plurality of openings 101, and the support shaft 37 described later is inserted into each opening 101. The space between the support shaft 37 and the chamber 27 is sealed with a bellows structure (not shown). The chamber 27 may be a hermetically sealed structure that hermetically seals in an inert gas, or a semi-hermetically sealed structure that constantly supplies inert gas to keep the chamber 27 under positive pressure.

2, an upper heater (heating section) 35 that heats the glass plate and the lower mold 23 to a desired temperature is disposed above the conveying surface of the glass plate. The upper heater 35 is preferably disposed facing the lower mold 23 and is configured to include a plurality of lamp heaters 36 supported by a fixed frame (not shown) as a heat source. For example, an infrared lamp heater is used as the lamp heater 36. For example, various known heaters such as carbon lamps and halogen lamps can be used as the infrared lamp heater, and any heating element capable of radiant heating can be used.

FIG. 3 is a cross-sectional view of a plurality of lamp heaters 36.
The lamp heater 36 has a heating wire 36A that generates heat when energized, and a tube material 36B made of quartz or the like that surrounds the heating wire 36A. A ceramic coating layer 40 is formed on the inner or outer peripheral surface of the tube material 36B, leaving an irradiation window 38. The opening angle (central angle) θ of the irradiation window 38 centered on the heating wire 36A is determined according to the distance Ld from the center of the lamp heater 36 to the lower mold 23, which is the heated object, and the arrangement pitch Lc of the lamp heaters 36, so that the lower mold 23 is uniformly irradiated with heat rays. Here, as an example, the opening angle θ is set to 60°.

In addition, it is preferable that the heating area by the upper heater 35 (the area in which the lamp heaters 36 are arranged) is wider than the outer edge of the horizontal surface of the lower mold 23, in which case the entire lower mold 23 can be heated uniformly.

A water-cooled plate 39 supported by the aforementioned support shaft 37 is disposed above the upper heater 35. It is desirable to provide a reflective film on the surface of the water-cooled plate 39 facing the upper heater 35. A flow path for cooling water is formed in the water-cooled plate 39, and the cooling water supplied and discharged through the support shaft 37 is circulated. This water-cooled plate 39 suppresses unnecessary heating by the upper heater 35 to the lower mold 23 and surrounding members other than the glass plate.

A heat diffusion plate 41 is disposed below the lower mold 23 with a gap therebetween. A lower heater (heating section) 43 is disposed below the heat diffusion plate 41. The heat diffusion plate 41 is made of a material with excellent thermal conductivity, and uniformly radiates and transfers the heat generated by the lower heater 43 to the lower mold 23. Examples of materials that can be used for the heat diffusion plate 41 include tungsten carbide, carbon, cemented carbide, copper, iron, and stainless steel. The lower heater 43 can be a contact heating stage heater, or the same radiation heating type as the upper heater 35.

In addition, a water-cooled plate 47 is disposed below the lower heater 43. The water-cooled plate 47 is supported by a support 45 fixed to the bottom of the chamber 27, and prevents unnecessary heating by the lower heater 43 to surrounding members other than the thermal diffusion plate 41 and the lower mold 23. The water-cooled plate 47 has a configuration similar to that of the water-cooled plate 39 described above, and cooling water is supplied and discharged from the support 45.

The gap between the lower mold 23 and the heat diffusion plate 41 in the cooling stage 15 is not particularly limited, but if it is too large, the heating efficiency decreases, and if it is too small, it becomes difficult to suppress the temperature deviation of the glass plate, so the lower limit of the gap is set to 1 mm. The upper limit of the gap is set to 10 mm.

An insulating frame 51 is disposed so as to surround the upper surface side of the lower mold 23 on which the glass plate is placed, and the outer periphery of the stage on the sides of the upper heater 35, the water-cooled plate 39, and the support shaft 37. The insulating frame 51 covers the sides of the glass plate placed on the lower mold 23 disposed within the stage.

The insulating frame 51 may be, for example, an insulating board made of a material mainly composed of calcium silicate. Alternatively, it may be a metal plate such as stainless steel. As shown in Figure 4, the insulating frame is preferably a frame with a rectangular horizontal cross section that surrounds a wide area outside the outer periphery of the lower mold 23. The insulating frame 51 may be provided with a lid that covers the upper part of the frame.

It is also preferable that the insulating frames 53 and 55 of the same configuration are arranged in the forming stage 13 and the cooling stage 15. In order to improve the forming quality of the obtained glass sheet, it is particularly important to reduce the temperature deviation of the glass sheet in each stage. Therefore, it is preferable to provide an insulating frame for each stage. This makes it possible to uniformize the temperature distribution of the internal space covered by the insulating frames 51, 53, and 55. Furthermore, since the outside of the insulating frames 51, 53, and 55 is surrounded by the chamber 27, heat is less likely to flow in and out of the insulating frames 51, 53, and 55, and a more uniform temperature distribution is obtained. This improves thermal efficiency, shortens the processing time in each stage, and reduces the temperature deviation of the glass sheet in each stage.

As shown in Figure 4, a lower mold 23 is arranged on each of the preheating stage 11, molding stage 13, and cooling stage 15. A pair of mold support rods 61 are provided on each of the lower molds 23, protruding outward from both side surfaces 23a, 23b perpendicular to the transport direction TD. Each mold support rod 61 is supported by mold transport units 63A, 63B arranged on both sides of the lower mold 23. Although detailed explanation of the mechanism is omitted, the mold transport units 63A, 63B transport multiple lower molds 23 arranged along each stage along the transport direction TD using a walking beam type transport mechanism.

FIG. 5 is a schematic explanatory diagram showing how the lower mold 23 is transported in a transport direction TD from the preheating stage 11 toward the cooling stage 15. As shown in FIG.
The mold transport parts 63A, 63B support mold support rods 61 protruding from each of the multiple lower molds 23, and simultaneously transport the multiple lower molds 23 from the preheating stage 11 to the molding stage 13, and from the molding stage 13 to the cooling stage 15, using a walking beam system. The vertical displacement of the lower molds 23 during this transport is performed within a range that does not interfere with fixed members such as the heat insulating frames 51, 53, 55 and the heat diffusion plate 41.

Next, the cooling stage 15 shown in FIG. 2 will be described.
A heat diffusion plate 65, an upper heater (heating unit for lowering temperature) 67 similar to that of the preheating stage 11, and a water-cooled plate 59 are arranged in this order above the lower mold 23 of the cooling stage 15. The heat diffusion plate 65 has a configuration similar to that of the heat diffusion plate 41 described above. The water-cooled plate 59 is fixed to the upper part of the chamber 27 and is supported by a support shaft 71 in which a cooling water flow path is formed.

Similar to the preheating stage 11, a heat diffusion plate 73, a lower heater (heating section for lowering temperature) 75, and a water-cooled plate 77 are arranged below the lower mold 23 of the cooling stage 15. The water-cooled plate 77 is supported by a support 79 fixed to the lower part of the chamber 27, and prevents unnecessary heating by the lower heater 75 to surrounding members other than the heat diffusion plate 73 and the lower mold 23. The water-cooled plate 77 has a configuration similar to the water-cooled plate 39 described above, and cooling water is supplied and discharged from the support 79.

The lower mold 23 of the cooling stage 15 may be in close contact with the heat diffusion plate 65, and the lower mold 23 may be in close contact with the heat diffusion plate 73, but providing a gap is preferable because this makes the temperature distribution of the lower mold 23 more uniform.

Next, the forming stage 13 shown in FIG. 2 will be described.
FIG. 6 is an enlarged cross-sectional view of the forming stage 13. As shown in FIG.
Above the lower die 23 of the molding stage 13, an upper die 25, a heat diffusion plate 81, an upper heater (heating section for keeping warm) 83, a heat insulating plate 85, and a water-cooled plate 87 are arranged in this order.

The upper die 25 is connected to a plunger (not shown) and is supported so that it can move up and down between a molding position where it is clamped to the lower die 23 and a retreated position above the molding position. The upper die 25 is placed in the retreated position except during molding, such as when the lower die 23 is being transported. Alternatively, the upper die 25 may be fixed within the molding stage 13, and the lower die 23 may be raised during transportation to clamp the die. In that case, the upper die movement mechanism can be omitted, reducing equipment costs.

The water-cooled plate 87 is supported by a support shaft 89 fixed to the top of the chamber 27, and prevents unnecessary heating by the upper heater 83 to surrounding components other than the upper mold 25 and the thermal diffusion plate 81. The water-cooled plate 87 has a configuration similar to the water-cooled plate 39 described above, and cooling water is supplied and discharged from the support shaft 89.

The insulating plate 85 may be made of known insulating materials such as ceramics, stainless steel, die steel, and high-speed steel. When using a metallic material, it is preferable to apply a coating treatment such as CrN, TiN, or TiAlN to the surface. The surface of the insulating plate 85 may also be roughened. In this case, a small gap is created between the insulating plate 85 and the water-cooled plate 39, resulting in a higher insulating effect.

Below the lower mold 23 of the molding stage 13, a heat diffusion plate 91, a lower heater (heating section for keeping warm) 93, a heat insulating plate 85, and a water-cooled plate 97 are arranged in this order. The water-cooled plate 97 is supported by a support 99 fixed to the bottom of the chamber 27, and prevents unnecessary heating by the lower heater 93 to surrounding members other than the heat diffusion plate 91 and the lower mold 23. The water-cooled plate 97 has a configuration similar to the water-cooled plate 39 described above, and cooling water is supplied and discharged from the support 99.

The upper mold 25 of the molding stage 13 is attached to a cylinder (not shown) that is driven in the vertical direction, and is supported so that it can move up and down by the driving of the cylinder. The cylinder may be an air cylinder, a hydraulic cylinder, or a servo cylinder using an electric servo motor, etc.

The upper mold 25 of the molding stage 13 is in surface contact with the heat diffusion plate 81 so that heat from the upper heater 83 is evenly transferred to the upper mold 25. The lower mold 23 of the molding stage 3 is in surface contact with the heat diffusion plate 91 so that heat from the lower heater 93 is evenly transferred to the lower mold 23. Depending on the molding conditions, etc., there may be a distance between the upper mold 25 and the heat diffusion plate 81, and between the lower mold and the heat diffusion plate 91.

Fig. 7A is a cross-sectional view of the upper die 25, and Fig. 7B is a cross-sectional view including the molding surface 111 of the lower die 23. Fig. 8 is a rear view of the upper die 25 as viewed from the direction B in Fig. 7A.
As shown in Figures 7A and 8, the upper die 25 has an annular protrusion 113. The protrusion 113 is provided on the upper die 25 corresponding to the outer edge of the molding surface 111 of the lower die 23 shown in Figure 7B, protruding toward the lower die 23. The protrusion 113 has an inclined surface 113a whose protrusion amount gradually increases from the outer periphery toward the center of the upper die 25. The molding surface 111 is shaped to match the molding shape of the glass sheet.

As shown in Figure 7 (B), the lower mold 23 has multiple suction holes 115 for vacuum forming that open to the molding surface 111. The suction holes 115 are connected to a suction source such as a suction pump (not shown). By driving the suction pump, gas in the space between the lower mold 23 and the glass plate 17 is sucked out at a predetermined timing, and the glass plate 17 is brought into close contact with the molding surface 111.

The lower die 23 and the upper die 25 can be made of materials such as carbon, stainless steel, ceramics, and cemented carbide. In particular, it is preferable to use carbon from the viewpoint of uniform heat distribution.

2, the upper heaters 35, 67, 83 and the lower heaters 43, 75, 93 in the preheating stage 11, molding stage 13, and cooling stage 15 are all connected to a temperature control unit (not shown) and are set to individual temperatures. The temperature control unit realizes heating, heat retention, and slow cooling processes in each stage by control operations such as proportional control, PI control, and PID control.

In the above-mentioned forming device 100, the conveying direction TD of the glass sheet is horizontal, but it may be inclined from the horizontal direction, such as vertical. In that case, the lower mold 23 and the upper mold 25 may not be arranged one above the other, but by adjusting the heating temperature of the glass sheet and not lowering the viscosity of the glass sheet too much, the glass sheet can be formed between the lower mold 23 and the upper mold 25 while suppressing the effects of gravity.

<Glass sheet forming procedure>
Next, a specific procedure for forming the glass sheet 17 into a curved shape using the forming device 100 having the above configuration and its action will be described.

The glass plate 17 before molding is placed on the lower mold 23 of the loading section 19 shown in Figure 1 by a transfer means such as a robot arm (not shown) or by hand of an operator.

The lower mold 23 of the loading section 19 is transported to the preheating stage 11 with the glass plate 17 placed thereon by the mold transport sections 63A and 63B shown in Figure 4. It is preferable that the lower mold 23 is preheated to a temperature higher than room temperature before the glass plate 17 is placed thereon, since this shortens the heating time at the preheating stage 11. For example, the temperature of the lower mold 23 when the glass plate 17 is placed thereon is preferably 300°C or higher, and more preferably 500°C or higher.

(Preheating process)
In the preheating stage 11 shown in FIG. 2, the glass sheet 17 on the lower mold 23 is heated to a target heating temperature (for example, 500° C. to 700° C.) by the upper heater 35 and the lower heater 43 .

The temperature suitable for press molding the glass plate 17 varies depending on the composition of the glass plate 17 itself, but if the temperature is too low, the glass plate 17 will not soften sufficiently. Therefore, in the preheating stage 11, the glass plate 17 is preferably heated to a temperature equal to or higher than the glass transition point Tg of the glass plate 17, more preferably Tg + 40°C or higher, and even more preferably Tg + 80°C or higher. On the other hand, if the temperature of the glass plate 17 is too high, the glass plate 17 will soften excessively and become unsuitable for maintaining its shape. Therefore, in the preheating stage 11, the glass plate 17 is preferably heated to a temperature equal to or lower than Tg + 200°C, more preferably Tg + 150°C or lower, and even more preferably Tg + 120°C or lower.

From the same viewpoint as above, in the preheating stage 11, the glass plate 17 is heated so that its viscosity becomes preferably 5.22× ¹⁰ Pa·s or more, more preferably 1.97× ¹⁰ Pa·s or more, and even more preferably 1.81× ¹⁰ Pa·s or more. In the preheating stage 11, the glass plate 17 is heated so that its viscosity becomes preferably 5.94× ¹⁰ Pa·s or less, more preferably 4.16× ¹⁰ Pa·s or less, and even more preferably 1.65× ¹⁰ Pa·s or less.

From the viewpoint of the surface quality of the resulting glass sheet molded product, it is preferable to heat the glass sheet 17 uniformly in the preheating stage 11. In other words, it is preferable to reduce the temperature deviation of the glass sheet 17 during heating in the preheating stage 11. Specifically, the temperature deviation of the glass sheet 17 during heating in the preheating stage 11 is preferably less than 30°C, more preferably less than 20°C, and even more preferably less than 10°C.

In addition, the temperature distribution in the area of the lower mold 23 that contacts the glass plate 17 during heating is preferably less than 30°C, more preferably less than 25°C, and even more preferably less than 20°C.

(Molding process)
The glass sheet 17 heated to the target heating temperature is transported to the forming stage 13 together with the lower mold 23. In the forming stage 13, an external force such as a press is applied to the heated glass sheet 17 to form it into a desired shape.

In the forming stage 13, the upper die 25 arranged in a retracted position is lowered to sandwich the glass sheet 17 between the upper die 25 and the lower die 23, and form the glass sheet 17. Details of this forming process will be described later. In the forming stage 13, the glass sheet 17 heated by the preheating stage 11 is kept warm by the upper heater 83 and the lower heater 93 so that the temperature is maintained constant.

It is preferable that the temperature of the glass sheet 17 in the forming stage 13 does not vary more than 20°C from the heating temperature in the preheating stage 11. From the viewpoint of the surface quality of the resulting glass sheet molded body, it is preferable that the glass sheet 17 is uniformly heated in the forming stage 13. Specifically, it is preferable that the temperature deviation of the glass sheet 17 during molding in the forming stage 13 is within 20°C.

Once the glass sheet 17 has been formed, the upper die 25 rises and returns to the retracted position. The lower die 23 is then transported to the cooling stage 15 together with the formed glass sheet 17A.

(Cooling process)
In the cooling stage 15, the set temperatures of the upper heater 67 and the lower heater 75 are set to temperatures lower than the target heating temperature, and the glass sheet 17A and the lower mold 23 are slowly cooled. In the cooling stage 15, the glass sheet 17A is slowly cooled until the shape of the heated and shaped glass sheet 17A becomes stable.

In the cooling stage 15, the glass plate 17A is slowly cooled while adjusting the heating temperature by the upper heater 67 and the lower heater 75. If the cooling rate in the cooling stage 15 is too fast, the glass plate 17A is likely to deteriorate or have a temperature deviation. Therefore, the cooling rate of the glass plate 17A in the cooling stage 15 is preferably 20°C in 30 s, more preferably 30°C, and even more preferably 40°C. In addition, the temperature distribution of the glass plate 17A during cooling is preferably 30°C or less, more preferably 25°C or less, and even more preferably 20°C or less.

The glass sheet 17A after annealing is transported outside the chamber 27 and then removed in the unloading section 21 as shown in Fig. 1. In the unloading section 21, the glass sheet 17A after shaping and annealing, which is placed on a lower mold having a temperature of 300°C or higher, preferably 500°C or higher, is removed from the mold surface. The glass sheet 17 may be removed by a transport means such as a robot arm (not shown), or may be removed manually by an operator.

<Effect of uniform temperature distribution>
The uniform temperature distribution of the glass sheets 17, 17A is achieved by the synergistic effects of the heat confinement effect of the heat insulating frames 51, 53, 55, the high heat shielding effect from the outside of the chamber 27 outside the heat insulating frames 51, 53, 55, and the heater heat uniformization effect of the heat diffusion plates 41, 65, 73, 81, 91. In addition, each stage has a different heating form due to the radiation heating by the upper heater 35 of the preheating stage 11, the heat transfer heating from the lower heater 43, the heat transfer heating from the upper heater 83 and the lower heater 93 of the forming stage 13, and the radiation heating via the heat diffusion plates 65, 73 by the upper heater 67 and the lower heater 75 during the cooling stage. In addition, the upper heater and the lower heater of each stage can be heated at an individual set temperature, allowing for fine temperature control.

By controlling the heating for each stage and heater individually in this way, the temperature distribution of the glass plates 17, 17A can be made highly uniform. In addition, fine adjustments according to location can be easily made, and the heating process can be accurately performed as designed. Furthermore, the heating atmosphere is covered by the insulating frames 51, 53, 55 and the chamber 27, which suppresses the outflow of heat to the outside, thereby improving the responsiveness of the heating control and the cooling control, and allowing the desired temperature to be reached uniformly and in a short time.

In addition, because the mold transport units 63A and 63B are configured to transport the lower mold 23 using a walking beam system, the movement speed between stages is increased. This reduces heat loss due to radiation between stages, which also contributes to uniform temperature distribution.

The above-mentioned heat diffusion plates 41, 65, 73, 81, and 91 may be omitted depending on the molding conditions, but by providing the heat diffusion plates, the temperature deviation of the glass plates 17 and 17A at each stage is kept small.

<Details of the molding process>
Next, a method for forming the glass sheet 17 in the forming stage 13 and the structure of the forming mold will be described in detail.

First, the shape of the glass plate 17 used in forming will be defined.
FIG. 9 is a plan view of the glass plate 17.
The glass plate 17 has a glass central portion 121 located inside an outer peripheral edge 17a of the glass shape, and a glass outer peripheral portion 123 located between a central outer peripheral portion 121a of the glass central portion 121 and the outer peripheral edge 17a. Note that the outer peripheral portion 123 is hatched in Fig. 9. In the forming process, at least a part of the glass central portion 121 is formed into a curved shape.

(First molding method)
10A, 10B, and 10C are schematic process explanatory diagrams showing, in stages, how the lower mold 23 and the upper mold 25 shown in FIGS. 7A and 7B are brought close to each other to form the glass plate 17.
10A , the glass sheet 17 is placed on the molding surface 111 of the lower die 23 with the outer circumferential edge 17a of the glass sheet 17 in contact with the molding surface 111 of the lower die 23. When the upper die 25 is lowered toward the lower die 23, the protrusion 113 of the upper die 25 comes into contact with the glass sheet 17 placed on the lower die 23.

The upper die 25 has a portion that contacts the glass sheet 17 and a portion that does not contact the glass sheet 17, and only the inclined surface 113a of the protrusion 113 contacts the glass outer periphery 123 of the glass sheet 17. Then, as shown in FIG. 10B, when the upper die 25 further descends, the inclination of the inclined surface 113a of the protrusion 113 presses the glass sheet 17 into a shape that is convex downward. In other words, the upper die 25 can deform the glass sheet 17 toward the lower die 23 just by contacting the glass sheet 17 in a ring shape. The glass sheet 17 also bends downward due to its own weight, and deforms to fit the molding surface 111 of the lower die 23.

10C, negative pressure is supplied from suction holes 115 to vacuum-adsorb glass sheet 17 onto molding surface 111. This causes glass sheet 17 to adhere closely to molding surface 111, and the curved shape of molding surface 111 is transferred to glass sheet 17. This ensures that glass sheet 17 and molding surface 111 adhere closely to each other even in areas where they would be difficult to achieve by press molding alone, and makes it easy to mold even complex shapes that would be difficult to achieve by press molding alone.

Although there are no particular limitations on the position, number, size, etc. of the suction holes 115, it is preferable to form the suction holes 115 in parts of the molding surface 111 where it is difficult to adhere the glass plate 17 by press molding alone. In addition, it is preferable to appropriately adjust the size of the suction holes 115 so that no traces of the suction holes 115 remain on the glass plate 17, or even if they do remain, they are inconspicuous.

Usually, in press molding of a glass sheet, the entire surface of the glass sheet is sandwiched in contact with the mold and molded. Therefore, in order to ensure the surface quality of the resulting glass sheet molded product, molding is performed at a relatively low temperature. Therefore, it took a relatively long time to deform the glass sheet into the desired shape. Therefore, when molding a complex shape, it was difficult to mold it at a low temperature range where surface quality could be ensured. On the other hand, when molding is performed using the lower mold 23 and upper mold 25 of the above configuration, the upper mold 25 does not come into contact with the glass center portion 121 of the glass sheet 17. Therefore, even if molding is performed at a relatively high temperature, the glass center portion 121 is not adversely affected by surface roughness due to contact with the mold, and a glass sheet molded product with excellent surface quality can be obtained. In this way, since molding at a relatively high temperature is possible in the molding stage 13 of this configuration, molding can be completed in a short time. In other words, if the above molding mold is used, a glass sheet molded product with excellent surface quality can be obtained in a short time.

The lower die 23 and upper die 25 in this configuration are dies for obtaining a glass sheet molded product in which the entire glass central portion 121 is bent at a constant curvature, but the shapes of the lower die 23 and upper die 25 are not limited to those shown in the figures. The shapes of the lower die 23 and upper die 25 can be changed as appropriate depending on the target shape to be molded.

The lower mold 23 and upper mold 25 of this configuration realize a combination of press forming, vacuum forming, and gravity bending forming, but depending on the material and forming conditions, it may be possible to form the product using only press forming and weight forming without vacuum forming.

(Second molding method)
The first forming method combines three types of forming, namely, press forming, vacuum forming, and gravity bending, while the second forming method further combines compressed air forming.

11 is a process diagram showing an outline of the process of forming a glass sheet 17 by the second forming method. The forming mold in this case has the same configuration as the forming mold in the first forming method, except that a gas ejection hole 125 for compressed air forming is formed inside the annular protrusion 113 of the upper mold 25A.

The gas ejection holes 125 are usually provided in a portion of the upper mold 25A that does not contact the glass plate 17. There are no particular limitations on the number, size, etc. of the gas ejection holes 125.

When using the lower mold 23 and upper mold 25A configured as above to combine press molding and compressed air molding, the protrusion 113 of the upper mold 25A is brought into contact with the glass outer periphery 123 of the glass sheet 17, and then gas is ejected from the gas ejection holes 125. The glass sheet 17 is then pressed against the molding surface 111 of the lower mold 23. In other words, the protrusion 113 is formed in a ring shape, and the contact with the glass sheet 17 is also ring-shaped, so that a closed space 129 is formed between the molding surface 111 of the lower mold 23 and the glass sheet 17. Gas is supplied to this closed space 129, and the pressure within the closed space 129 becomes positive. As a result, the glass sheet 17 is pressed against the molding surface 111.

In addition, by simultaneously carrying out the above-mentioned vacuum forming and gravity forming in addition to the above-mentioned pressure forming, the glass sheet 17 can be more quickly and reliably aligned with the forming surface 111, and the time required to complete forming can be shortened. In this way, by combining press forming with at least one of vacuum forming, pressure forming, and gravity bending, forming of complex shapes can be easily achieved and forming time can be further shortened.

In addition, vacuum forming and pressure forming can be performed at any timing during press forming, and the order of performing the steps may be press forming, vacuum forming, and pressure forming, or may be press forming, pressure forming, and vacuum forming. By performing press forming before vacuum forming and pressure forming, positioning of the glass sheet 17 relative to the forming surface 111 can be more reliably performed.

In addition, by performing each molding process simultaneously, the adhesion between the glass plate 17 and the molding surface 111 can be further improved, making it easier to process the glass plate 17 into shapes that are prone to wrinkles.

<Examples of other molding device configurations>
The glass sheet forming apparatus 100 may be configured to include a plurality of preheating stages 11 and a plurality of cooling stages 15 .
FIG. 12 is a schematic diagram of a molding apparatus 200 including a plurality of preheating stages 11, a molding stage 13, and a plurality of cooling stages 15.

The preheating stages 11 are provided at four locations (PH1 to PH4) along the transport direction TD of the lower mold 23, and the cooling stages 15 are provided at four locations (C1 to C4) along the transport direction TD of the lower mold 23. The molding stage 13 is provided at one location (PM1) between the preheating stage 11 and the cooling stage 15.

The heating temperatures of PH1 to PH4 of the preheating stages 11 are set to gradually increase along the conveying direction TD. As a result, the temperature of the lower mold 23 and the glass sheet 17 gradually increases as they are conveyed in the conveying direction TD, until they reach the target heating temperature, which is the forming temperature.

The heating temperature of C1 to C4 of the cooling stages 15 is set to be gradually lowered along the transport direction TD. As a result, the temperature of the lower mold 23 and the glass sheet 17 gradually decreases as they are transported in the transport direction TD, and they are slowly cooled from the target heating temperature.

FIG. 13 is a graph showing an example of temperature changes of the lower mold 23 and the glass plate 17 in the preheating stage 11, the forming stage 13, and the cooling stage 15.
The glass sheet 17 supplied from the loading unit 19 (LD) to PH1 of the preheating stage 11 shown in Fig. 12 is placed on the lower mold 23 that has been heated to a predetermined temperature Tc in advance, and is heated from room temperature _TRM . The temperature of the lower mold 23 and the glass sheet 17 increases as they are transported to PH2, PH3, and PH4, and reaches a target heating temperature _TPM, which is a forming temperature, before being transported to the forming stage 13 (PM).

In the forming stage 13 (PM), the glass sheet 17 is formed while being held at a constant temperature of the target heating temperature T _PM .

After forming, the glass sheet 17A is transported to C1 to C4 of the cooling stage 15, where the temperature of the lower mold 23 and the formed glass sheet 17A gradually decreases. The glass sheet 17A is transported from C4 to the unloading section 21 (ULD) shown in Figure 12 and allowed to cool naturally.

At each of the preheating stage 11 and cooling stage 15, the temperature is controlled so that the lower mold 23 and the glass plates 17, 17A are uniformly heated to the set temperature. The more stages there are, the wider the temperature change range can be. From the viewpoint of takt time, it is preferable to reduce the number of stages. The number of stages is appropriately set according to the size of the glass plate to be processed and the processed shape. For example, when the glass plate is large or when a complex shape is to be formed, it is preferable to increase the number of preheating stages 11 and cooling stages 15 to avoid sudden temperature changes.

FIG. 14 is a schematic diagram of a conventional molding device as a reference example.
In the conventional molding device, the glass sheet 17 is pressed all over between the lower die 131 and the upper die 135, and the heating temperature is set lower than the above-mentioned molding temperature (target set temperature). Therefore, the glass sheet 17 needs to be held in a clamped state until the molded shape is stabilized. As a result, the molding time T _PM2 is longer than the molding time T _PM1 shown in FIG. 13.

On the other hand, the forming device 200 of this configuration shown in Figure 12 forms the glass sheet 17 by combining press forming, which contacts only the outer periphery of the glass, with vacuum forming, compressed air forming, and forming by gravity, so the heating temperature can be set higher than before, and the synergistic effect of each forming process ensures that the glass sheet adheres closely to the forming surface of the mold, quickly stabilizing the formed shape. In other words, springback of the glass sheet is less likely to occur. As a result, only one forming stage 13 is required, equipment costs can be reduced, and throughput is improved.

In addition, by heating the temperature of the lower mold 23 to a predetermined temperature Tc in advance, the time required to reach the target set temperature can be further shortened, thereby shortening the tact time.

FIG. 15 is a schematic diagram of a molding apparatus 300 showing another configuration example of the molding apparatus 200 shown in FIG.
The molding apparatus 300 of this configuration includes a plurality of molding lines each having a preheating stage 11, a molding stage 13, and a cooling stage 15 shown in Fig. 12. Although the molding apparatus 300 is shown in Fig. 15 as having two lines, a first molding line 141 and a second molding line 143, it may include three or more lines.

The loading section 19 of the first molding line 141 of the molding device 300 is connected to the unloading section 21 of the second molding line 143, and the unloading section 21 of the first molding line 141 is connected to the loading section 19 of the second molding line 143. The lower molds 23 of the first molding line 141 and the lower molds 23 of the second molding line 143 are used in common and circulate through each line.

According to this configuration, the lower mold 23 transported to the unloading section 21 of one molding line is returned to the loading section 19 of the other molding line, thereby preventing the mold temperature from decreasing and always maintaining the temperature at or above a predetermined temperature Tc when the molding device 300 is in operation. This reduces the temperature change range of the lower mold 23, reducing the temperature cycle load on the lower mold 23. In addition, energy consumption for heating is reduced, reducing running costs.

Furthermore, compared to a configuration in which multiple molding lines are arranged in series, the installation space for the molding device 200 can be reduced, which also reduces equipment costs.

<Details of the molding process>
Next, preferred molding conditions in the molding step in the molding stage 13 will be described.
In the forming apparatuses 100, 200, and 300 having the above configuration, it is preferable to form a glass sheet under the forming conditions shown below.

(Pressure Conditions)
In press molding, different pressures are applied to a glass central portion 121 and a glass peripheral portion 123 of the glass sheet 17 shown in Fig. 9 to press-form the glass sheet 17. Specifically, when vacuum forming or pressure forming is not performed, it is preferable that the pressure Pct applied to the glass central portion 121 is 0 to 0.1 MPa, and the pressure Peg applied to the glass peripheral portion 123 is 0.1 to 10 MPa.

When vacuum forming or compressed air forming is not performed, no pressure other than gravity acts on the glass center 121 of the glass sheet 17. On the other hand, a higher pressure is applied to the glass outer periphery 123 of the glass sheet 17 than to the glass center 121, and the glass sheet 17 is fixed to the forming mold. This allows stable press forming to be performed without the glass sheet 17 being misaligned. In addition, the deformation direction (convex downward or convex upward) and amount of deformation of the glass sheet 17 due to press forming can be determined by the inclination direction and inclination angle of the protrusions 113 and forming surface 111 (see Figures 7A and 7B) that come into contact with the glass sheet 17.

When forming the glass sheet 17 by a combination of press forming and vacuum forming, it is preferable that the pressure Pct applied to the glass center portion 121 by pressing is 0 to 0.1 MPa, and the pressure Peg applied to the glass outer periphery portion 123 is 0.1 to 10 MPa. The total pressure applied to the glass sheet 17 by press forming and vacuum forming is such that the pressure Peg on the glass outer periphery portion 123 is higher than the pressure Pct on the glass center portion 121 (Peg > Pct).

Furthermore, when the glass sheet 17 is formed by a combination of press forming, vacuum forming, and pressure forming, it is preferable that the pressure Pct applied to the glass center portion 121 by pressing is 0 to 0.1 MPa, and the pressure Peg applied to the glass peripheral portion 123 is 0.1 MPa to 10 MPa. The total pressure applied to the glass sheet 17 by press forming, vacuum forming, and pressure forming is such that the pressure Peg on the glass peripheral portion 123 is higher than the pressure Pct on the glass center portion 121 (Peg > Pct). In this case, the glass center portion 121 is subjected to pressure by pressure forming in addition to vacuum forming, so the pressure applied to the glass center portion is greater than in the case of only press forming and vacuum forming.

The above conditions may or may not include the bending effect due to gravity forming before and after press forming.

(Temperature of glass plate)
When the glass sheet 17 is formed into a desired shape, the lower limit of the forming temperature is preferably 400° C., more preferably Tg+40° C., and even more preferably Tg+80° C. The upper limit of the forming temperature is preferably 750° C., more preferably 680° C., and even more preferably 650° C.

By keeping the molding temperature within the above range, the molded shape of the glass plate 17 is maintained in a short period of time, thereby shortening the molding time.

(Viscosity of glass plate)
When the glass sheet 17 is formed into a desired shape, the viscosity of the glass sheet 17 during forming varies depending on the material of the glass sheet 17, but is preferably 1×10 ⁻⁵ Pa·s or less from the viewpoint of formability.

In particular, it is preferable that φ (=∫(P/ρ)dt, [P: in-plane pressure, ρ: viscosity]), which is an index of formability, is 1×10 ^−8.7 to 1×10 ^2.5 eg at the glass periphery of the glass plate and 1×10 ⁻¹² to 1×10 ^−0.5 eg at the glass center.

(Dimensional accuracy of glass plate)
According to the above-mentioned manufacturing apparatus and forming method, a glass sheet molded product having excellent shape accuracy can be obtained. As an evaluation index of the shape quality of the glass sheet molded product, for example, an in-plane shape deviation compared with the design shape (design surface) can be mentioned.

In-plane shape deviation is defined as the deviation value of the deviation in the normal direction between the curved-approximated surface and the design surface when the normal is set along the design shape and the shape of the glass sheet molding is approximated so that the absolute value of the distance from the design surface in the normal direction is minimized within the surface.

The glass plate molded body obtained by the manufacturing apparatus and molding method of the present configuration preferably has an in-plane shape deviation of 0.6 mm or less, more preferably 0.4 mm or less.

Table 1 shows the forming conditions for the glass sheets and the forming results.
Using the forming apparatus shown in FIG. 1, a glass plate (material: Dragontrail (registered trademark)) having dimensions of 100×50 mm (thickness t=1.1 mm) was formed by each of the following forming methods: forming by self-weight bending only, full-surface press forming, press forming only by edge press forming which presses the outer periphery of the glass, and forming by combining press forming and vacuum forming.

The formed shapes of the glass sheets were Test Examples 1 and 2 with a single radius of curvature as shown in Figure 16 (A), Test Example 3 with an S-shape as shown in Figure 16 (B), and Test Example 4 with a J-shape as shown in Figure 16 (C). The radius of curvature R of Test Example 1 was 2000 mm, and the radius of curvature R of Test Example 2 was 800 mm. The radii of curvature of the S-shape Test Example 3 were, from one end, R1 2000 mm, R2 100 mm, and R3 2000 mm. The J-shape Test Example 4 had a shape in which a curved surface with a radius of curvature R of 50 mm was connected to a flat shape.

The molded bodies obtained by each molding method were evaluated for molding takt time, shape accuracy, and surface quality. The evaluation criteria are as follows: Takt time (time required for molding)
◎: Less than 30 seconds ○: 30 seconds or more, less than 100 seconds △: 100 seconds or more, less than 200 seconds ▲: 200 seconds or more, less than 500 seconds ×: 501 seconds or more

- Shape accuracy (deviation from design shape)
◎: Less than 0.2 mm ○: 0.2 mm or more, less than 0.4 mm △: 0.4 mm or more, less than 0.6 mm ▲: 0.6 mm or more, less than 0.8 mm ×: 1.0 mm or more

- Surface quality (number of defects counted using image processing)
◎: 0-5 pieces ○: 6-10 pieces △: 11-50 pieces ▲: 51-100 pieces ×: 101 pieces or more

When only gravity bending was used, the tact time could not be shortened in any of the test examples.
In the case of full-surface press molding, the entire surface of the glass sheet comes into contact with the mold, so that the surface roughness of the glass surface after molding increases, resulting in a deterioration in surface quality.

In the case of edge press molding, test examples 1 and 2, which are single-curve shapes, had good cycle time and shape accuracy, and particularly excellent surface quality. However, test examples 3 and 4, which have relatively complex molded shapes, were NG in all respects for cycle time, shape accuracy, and surface quality.

On the other hand, when edge press molding combined press molding and vacuum molding, good results were obtained in all test examples 1 to 4.

As such, the present invention is not limited to the above-described embodiments, and it is also contemplated by the present invention that the various components of the embodiments may be combined with each other, and that modifications and applications may be made by those skilled in the art based on the descriptions in the specification and well-known technologies, and these are included in the scope of the protection sought.

As described above, the present specification discloses the following:
(1) A glass sheet forming apparatus for heating a glass sheet and forming it into a desired shape, comprising:
a first mold having a molding surface having at least a curved shape at least partially formed thereon, the glass sheet being supported on the molding surface;
At least one second mold clamped to the first mold;
at least one preheating stage for heating the glass sheet supported by the first mold;
at least one forming stage in which the second mold is disposed facing the first mold and the heated glass sheet is formed between the first mold and the second mold;
at least one cooling stage for annealing the glass sheet after forming;
a mold transport unit that transports the first mold to the preheating stage, the molding stage, and the cooling stage in this order;
The glass plate has a glass central portion on the inner side of a glass shape outer peripheral edge, and a glass outer peripheral portion between an outer periphery of the glass central portion and the glass shape outer peripheral edge,
The second mold of the forming stage contacts the glass sheet only at the outer periphery of the glass sheet between the first mold and the second mold.
According to this glass sheet forming device, the glass sheet is pressed between the first mold and the second mold only at the glass periphery, so the center of the glass on the second mold side does not come into contact with the mold surface. Therefore, the surface quality of the center of the glass can be improved and forming can be performed at a higher temperature than in press forming, where the mold contacts the entire surface of the glass surface. This allows forming to be completed in a short time, and shortens the tact time.

(2) The glass sheet forming apparatus according to (1), wherein the first forming mold has a suction hole for vacuum forming that opens to the forming surface.
According to this glass sheet shaping device, the glass sheet can be forcibly brought into close contact with the shaping surface by suction from the suction holes, and the shape of the shaping surface can be transferred to the glass sheet more reliably and at higher speed.

(3) The glass sheet forming apparatus according to (1) or (2), wherein the second molding die has an annular protrusion protruding toward the first molding die, and a gas ejection hole disposed inside the annular protrusion and ejecting gas for compressed air forming.
According to this glass sheet forming device, the glass sheet can be forcibly brought into close contact with the forming surface by supplying gas pressure from the gas ejection holes, and the shape of the forming surface can be transferred to the glass sheet more reliably and quickly.

(4) The glass sheet forming apparatus according to any one of (1) to (3), wherein the first mold is disposed vertically below the second mold.
According to this glass sheet forming apparatus, the softened glass sheet can be brought into close contact with the forming surface by its own weight.

(5) a heating unit for increasing temperature, which is provided in the preheating stage and heats the first mold and the glass sheet to a desired heating temperature;
a heat-retaining heating section provided in the forming stage and configured to maintain the temperatures of the second forming mold and the first forming mold at the heating temperature and to maintain the glass sheet at a desired forming temperature;
and a temperature-reducing heating unit that is provided in the cooling stage and that reduces the temperatures of the first mold and the glass sheet to a temperature lower than the heating temperature while heating the first mold and the glass sheet.
According to this glass sheet forming apparatus, the temperature of each stage can be set with high precision by the respective heating parts.

(6) The glass sheet forming apparatus according to (5), wherein at least one of the temperature increasing heating section, the temperature maintaining heating section, and the temperature decreasing heating section has a plurality of lamp heaters for radiant heating as a heat source.
According to this glass sheet forming apparatus, by driving a plurality of lamp heaters, heating can be precisely controlled, and further, heating using radiant heat can be controlled to provide a uniform temperature distribution in the glass sheet and forming mold.

(7) The glass sheet forming apparatus according to (5), wherein at least one of the heating section for increasing temperature, the heating section for maintaining temperature, and the heating section for decreasing temperature has a plurality of stage heaters for contact heating as a heat source.
According to this glass sheet forming apparatus, the use of a stage heater for contact heating enables highly efficient and uniform temperature control.

(8) The glass sheet forming apparatus according to (7), wherein at least one of the temperature-maintaining heating section and the temperature-lowering heating section has a heat diffusion plate disposed between the stage heater and the first forming mold.
According to this glass plate forming device, the first forming mold is heated via a heat diffusion plate, so that the heat from the heater is diffused evenly within the surface of the heat diffusion plate, making it possible to make the temperatures of the glass plate and the forming mold facing the heat diffusion plate more uniform.

(9) The glass sheet forming apparatus according to any one of (5) to (7), wherein in the cooling stage, the temperature-lowering heating part is disposed at a position not in direct contact with the first forming mold.
According to this glass sheet forming apparatus, the temperature is controlled only by radiant heat without directly contacting the temperature-lowering heating section with the first forming mold, thereby enabling more precise temperature management.

(10) The glass plate shaping device according to any one of (1) to (9), wherein at least one of the preheating stage, the shaping stage, and the cooling stage is provided with a heat insulating frame surrounding the outer periphery of each stage and covering a side of the glass plate supported by the first shaping mold disposed within the stage.
According to this glass sheet forming device, the area surrounded by the insulating frame is kept at a uniform temperature. Also, since the flow of heat into and out of the insulating frame is suppressed, the responsiveness of temperature control by heating is improved.

(11) The heat insulating frame is disposed in all of the preheating stage, the molding stage, and the cooling stage,
The glass sheet forming apparatus according to claim 10, further comprising a chamber that accommodates the preheating stage, the forming stage, and the cooling stage in its internal space.
According to this glass sheet forming device, the temperature at each stage can be accurately controlled, improving the quality of the formed glass sheet. In addition, the chamber further suppresses the flow of heat in and out of each thermal insulation frame, making it possible to make the temperature within the area surrounded by the thermal insulation frame more uniform.

(12) The glass sheet forming apparatus according to (11), wherein the internal space of the chamber is filled with an inert gas.
According to this glass sheet forming apparatus, the gas concentration of gases that adversely affect the glass sheet during forming can be reduced, and deterioration of the glass sheet can be prevented.

(13) The glass sheet forming apparatus according to any one of (1) to (12), wherein the first forming die and the second forming die are made of carbon.
According to this glass sheet forming apparatus, the forming mold is made of carbon, which makes the mold lighter and increases its lifespan.

(14) The glass sheet forming apparatus according to any one of (1) to (13), wherein a plurality of the preheating stages are arranged along a transport direction of the first mold, and the heating temperatures of the preheating stages are set to be higher in stages along the transport direction.
According to this glass plate forming apparatus, heating can be carried out in stages while maintaining a uniform temperature distribution at each preheating stage, so that temperature unevenness during heating can be reduced compared to when heating to the desired target heating temperature at a single preheating stage.

(15) The glass sheet forming apparatus according to any one of (1) to (14), wherein a plurality of the cooling stages are arranged along a transport direction of the first mold, and the heating temperatures of the cooling stages are set to be lower in stages along the transport direction.
According to this glass plate forming device, cooling can be carried out in stages while maintaining a uniform temperature distribution in each cooling stage, so that temperature unevenness during cooling can be reduced compared to when cooling to the desired temperature in a single cooling stage.

(16) A plurality of the first molds are arranged along the preheating stage, the molding stage, and the cooling stage,
The mold transport unit simultaneously transports a plurality of the first molds to and from the preheating stage, the molding stage, and the cooling stage, respectively.
According to this glass sheet shaping device, a plurality of first shaping dies and glass sheets can be transported at one time, so that shaping efficiency can be increased and throughput can be improved.

(17) The glass sheet forming apparatus according to (16), wherein a conveying method of the first forming mold in the mold conveying section is a walking beam method.
According to this glass sheet forming apparatus, the transport mechanism is not complicated, and the first forming mold can be transported stably.

(18) A molding system comprising a plurality of molding lines including the preheating stage, the molding stage, and the cooling stage,
Each of the forming lines further includes a loading section in which the first forming mold and the glass sheet before forming are carried into the preheating stage, and an unloading section in which the first forming mold and the glass sheet after forming are carried out from the cooling stage,
The glass sheet forming apparatus according to (16) or (17), wherein the loading section of any one of the forming lines is connected to the unloading section of another forming line different from the one forming line, and the first forming mold is circulated and used among the multiple forming lines.
According to this glass sheet forming device, the first forming mold is commonly circulated among a plurality of forming lines, thereby reducing equipment costs and preventing the temperature of the first forming mold from dropping significantly from the target heating temperature. This reduces thermal stress on the first forming mold. In addition, an increase in heating energy is suppressed, thereby reducing running costs.

(19) The glass sheet shaping apparatus according to (18), wherein a temperature of the first shaping mold is 300° C. or higher when the glass sheet is transferred onto the first shaping mold in the loading section and the unloading section.
According to this glass sheet forming device, the glass sheet is transferred while still in a high-temperature state of 300°C or higher, so that the heating time and cooling time of the glass sheet can be shortened compared to when the glass sheet is transferred at near room temperature, and the forming tact time can be further shortened.

This application is based on a Japanese patent application (Patent Application No. 2019-21561) filed on February 8, 2019, the contents of which are incorporated by reference into this application.

11 Preheating stage 13 Forming stage 15 Cooling stage 17, 17A Glass plate 17a Outer periphery 23 Lower mold (first forming mold)
25, 25A Upper mold (second molding mold)
27 Chamber 35 Upper heater (heating unit for increasing temperature)
36 Lamp heater 41 Heat diffusion plate 43 Lower heater (heating part for increasing temperature)
51, 53, 55: Insulating frame 63A, 63B: Mold transfer section 65: Heat diffusion plate 67: Upper heater (heating section for lowering temperature)
73 Heat diffusion plate 75 Lower heater (heating part for lowering temperature)
81 Heat diffusion plate 83 Upper heater (heating part for keeping warm)
91 Heat diffusion plate 93 Lower heater (heating part for keeping warm)
100 Molding device 111 Molding surface 113 Protrusion 113a Inclined surface 115 Suction hole 121 Glass center 121a Center outer periphery 123 Glass outer periphery 125 Gas ejection hole 131 Lower mold (first molding mold)
135 Upper mold (second molding mold)
141 First molding line (molding line)
143 Second molding line (molding line)

Claims (19)

A glass sheet forming apparatus for heating a glass sheet and forming it into a desired shape,
a first mold having a molding surface having at least a curved shape at least partially formed thereon, the glass sheet being supported on the molding surface;
At least one second mold clamped to the first mold;
at least one preheating stage for heating the glass sheet supported by the first mold;
at least one forming stage in which the second mold is disposed facing the first mold and the heated glass sheet is formed between the first mold and the second mold;
at least one cooling stage for annealing the glass sheet after forming;
a mold transport unit that transports the first mold to the preheating stage, the molding stage, and the cooling stage in this order;
The glass plate has a glass central portion on the inner side of a glass shape outer peripheral edge, and a glass outer peripheral portion between an outer periphery of the glass central portion and the glass shape outer peripheral edge,
a second mold of the molding stage contacts the glass plate only at the outer periphery of the glass between the first mold and the second mold, and the first mold and the second mold have molding surfaces that bring the central portion of the glass into close contact with the first mold after the outer periphery of the glass of the glass plate is press-molded . The glass sheet forming device according to claim 1, wherein the first forming mold has a suction hole for vacuum forming that opens on the forming surface. The glass sheet forming device according to claim 1 or 2, wherein the second forming die has an annular protrusion protruding toward the first forming die and a gas ejection hole disposed inside the annular protrusion for ejecting gas for compressed air forming. The glass sheet forming device according to any one of claims 1 to 3, wherein the first forming die is disposed vertically below the second forming die. a heating section for increasing temperature, the heating section being provided in the preheating stage and configured to heat the first mold and the glass sheet to a desired heating temperature;
a heat-retaining heating unit provided in the forming stage and configured to maintain the temperatures of the second forming mold and the first forming mold at the heating temperature and to maintain the glass sheet at a desired forming temperature;
and a temperature-reducing heating unit provided in the cooling stage to reduce the temperatures of the first mold and the glass sheet to a temperature lower than the heating temperature while heating the first mold and the glass sheet. The glass sheet forming device according to any one of claims 1 to 4. The glass sheet forming device according to claim 5, wherein at least one of the heating section for increasing temperature, the heating section for maintaining temperature, and the heating section for decreasing temperature uses a plurality of lamp heaters for radiant heating as a heat source. The glass sheet forming device according to claim 5, wherein at least one of the heating section for increasing temperature, the heating section for maintaining temperature, and the heating section for decreasing temperature uses a plurality of stage heaters for contact heating as a heat source. The glass sheet forming device according to claim 7, wherein at least one of the temperature-maintaining heating section and the temperature-reducing heating section has a heat diffusion plate disposed between the stage heater and the first forming die. The glass sheet forming device according to any one of claims 5 to 7, wherein the cooling stage is arranged at a position where the temperature-lowering heating unit does not directly contact the first forming mold. The glass sheet forming device according to any one of claims 1 to 9, wherein at least one of the preheating stage, the forming stage, and the cooling stage is provided with a heat insulating frame that surrounds the outer periphery of each stage and covers the side of the glass sheet supported by the first forming die arranged within the stage. The heat insulating frame is disposed in all of the preheating stage, the molding stage, and the cooling stage,
The glass sheet forming apparatus according to claim 10 , further comprising a chamber that houses the preheating stage, the forming stage, and the cooling stage in an internal space thereof. The glass sheet forming apparatus according to claim 11, wherein the internal space of the chamber is filled with an inert gas. The glass sheet forming device according to any one of claims 1 to 12, wherein the first forming die and the second forming die are made of carbon. The glass sheet forming device according to any one of claims 1 to 13, wherein a plurality of the preheating stages are arranged along the conveying direction of the first forming mold, and the heating temperature of the preheating stages is set to be higher in stages along the conveying direction. The glass sheet forming device according to any one of claims 1 to 14, wherein a plurality of the cooling stages are arranged along the conveying direction of the first forming mold, and the heating temperature of the cooling stages is set to be gradually lower along the conveying direction. a plurality of the first molds are arranged along the preheating stage, the molding stage, and the cooling stage;
The glass sheet forming apparatus according to any one of claims 1 to 15, wherein the mold transport unit simultaneously transports a plurality of the first molds to and from the preheating stage, the forming stage, and the cooling stage. The glass sheet forming device according to claim 16, wherein the conveying method of the first forming mold in the mold conveying section is a walking beam method. a plurality of molding lines including the preheating stage, the molding stage, and the cooling stage;
Each of the forming lines further includes a loading section in which the first forming mold and the glass sheet before forming are carried into the preheating stage, and an unloading section in which the first forming mold and the glass sheet after forming are carried out from the cooling stage,
18. The glass sheet forming apparatus according to claim 16, wherein the loading section of any one of the forming lines is connected to the unloading section of another forming line different from the one forming line, and the first forming mold is circulated and used among the multiple forming lines. The glass sheet forming device according to claim 18, wherein the temperature of the first mold is 300°C or higher when the glass sheet is transferred onto the first mold in the loading section and the unloading section.

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