JPS61227931A - Forming device for glass article - Google Patents

Abstract

PURPOSE:To prevent generation of flaw by pressing the flat and smooth surface by forming a groove having an opening of a sucking hole at a specified position of a die for vacuum forming a hot glass plate. CONSTITUTION:A forming section 5 of a die 2 is constituted of a side face 7 and a bottom face 6 with opened top face. The bottom face 6 is formed of a lower recess 6a at the center and a somewhat higher stage part 6b than the recess. A groove part 8 is formed along the boundary of the stage part 6b and said side face 7 with a suction hole 9 opened in the groove 8. At the same time when a glass plate placed on the die 2 is heated with a heater 3, the cavity is evacuated through the sucking hole 9 to execute forming of the glass plate.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an apparatus for molding glass products such as front panels of fluorescent display tubes, cathode ray tubes, or plasma displays.

(Prior art) As a method of manufacturing glass products having a partially smooth surface, such as the front panel of a fluorescent display tube, a method of bonding cut glass plates with a low melting point frit, etc. A method of welding glasses together using a mold that does not weld with glass such as graphite, a method of vacuuming a glass plate and molding it after the mold, or a method of press-molding a molten glass gob (gob), There are methods such as polishing parts where smoothness is required.

(Problems to be Solved by the Invention) Among the conventional methods described above, in the method of sealing cut pieces of glass plates together with a frit and the method of welding glass plates together, stress concentration occurs at the joint. , it is easily damaged, and there is a risk of vacuum leakage, especially when used as a vacuum container.

In addition, when vacuum forming glass plates or press forming gobs, the glass comes into close contact with the molding surface, resulting in press scratches.In order to eliminate these press scratches and ensure smoothness, the molding Polishing must be performed afterwards, which increases the number of steps and is disadvantageous in terms of production efficiency.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the molding apparatus according to the present invention has a molding device that forms the center part of the bottom surface of the molding part of the mold disposed in the heating furnace, that is, the smooth surface of the glass product. The corresponding portion is a recess, the peripheral edge of the bottom of the molding part is a step higher than the recess, and a groove in which a suction hole for vacuuming is opened is formed at the boundary between the step and the side surface of the molding part.

A glass plate is vacuum-formed without bringing the surface that should be smooth into contact with the molding surface.

(Example) Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a longitudinal cross-sectional view of a molding apparatus according to the present invention, which includes a box-shaped heating furnace (1) and a heating furnace (1) having a box shape.
), and a heater (3) is disposed above the mold (2).

The mold (2) is supported on a support (4) and can be freely moved in and out of the heating furnace (1) together with the support (4). The mold (2) is made of a material to which glass is difficult to fuse, such as amorphous carbon or glassite, and has a molding part (5) opened upward on its upper surface. The molding surface of this molding part (5) consists of a bottom surface (8) and an inclined side surface (7), and the center part of the bottom surface (6), that is, the part corresponding to the smooth surface of the glass product to be molded, is called the fourth part (8a). , the peripheral edge of this recess (6a) is connected to the recess (6a).
) is set as a stepped portion (8b) that is one step higher than the step (8b).

In addition, a recess * (8) is formed at the boundary between the step (6b) and the side surface (7) as shown in Fig. 2, and suction holes (8) are opened at the four corners of this recess (8). are doing. This suction hole (9
) is connected to a through hole (lO) formed in the support (4) at approximately the middle of the mold (2), and this through hole (lO) is connected to a vacuum pump or the like (not shown). Here, as mentioned above, if the gold ffi (2) is made of a material such as amorphous carbon or graphite that deteriorates when it comes into contact with oxygen at high temperatures, the suction hole (8) and the through hole (1
0) to attach the glass plate (G) and the molding part (5) before molding.
) may be filled with an inert gas such as nitrogen gas to improve the durability of the mold (2).

In the above, the temperature at which the glass plate (G) does not break due to the in-plane temperature difference caused by local heating, specifically, 100°C below the strain point.
Preheat to a moderately low temperature and place this glass plate (G) into the mold (2
) into the heating furnace (1). Here, for preheating the glass plate (G), use a heating furnace (
1) This may be done after the vehicle has been brought into the facility.

Then, the glass plate (G) carried into the heating furnace (1) is heated to the forming temperature by the heater (3). During this heating, it is preferable to use the vacuum suction hole (8) to blow an inert gas such as nitrogen onto the surface (lower surface) of the glass plate (G) that faces the forming surface. By doing so, as described above, deterioration of the mold (2) can be prevented, and the temperature rise of the surface facing the molding surface of the glass plate (G) is delayed.
Since the glass plate is bent, the central part of the glass plate (G) does not come into contact with the surface of the recess (8a), as will be described later, and the occurrence of press scratches is suppressed. Note that air may be blown out instead of nitrogen if only the bending of the glass plate (G) is to be prevented.

Once the glass plate (G) is heated to the strain point or higher in this manner, a vacuum pump or the like is driven to vacuum the glass plate (G) through the suction hole (8) and the groove (8). Then, the glass plate (G) is molded following the forming surface, that is, the bottom surface (6) and side surface (7) of the molding part (5), as shown in FIG. Here, a recess (6a) is formed in the bottom surface (6), and the recess (8) is closed when the glass plate (G) comes into contact with the step (8b) on the periphery of the recess (8a). , recess (
Space (S) formed between 6a) and the glass plate (G)
is not evacuated, as a result, the inside of the space (S) is not in a reduced pressure state, and the part of the glass plate corresponding to the recess (8a),
In other words, the portion that should be a smooth surface is molded without contacting the bottom surface (8), and no scratches or the like occur during molding.

In addition, the height of the step part (8b) should be approximately one layer or less, considering the deflection that tends to occur when the temperature difference between the central part and the peripheral part of the glass plate CG) is small, and the efficiency of vacuuming. It is preferable to do so.

In addition, as described above, in order to mold the glass plate (G) without making the central part, which is the smooth surface, contact the molding surface, it is necessary to
) It is preferable to make the amount of heating for the central portion smaller than the amount of heating for the peripheral portion so that the viscosity of the central portion of the glass plate (G) is greater than that of the peripheral portion.

FIG. 4 shows another embodiment in which the amount of heating is changed for each portion of the glass plate (G) in this way.

That is, in the molding apparatus shown in FIG. 4, the heater (3) disposed in the heating furnace is divided into three parts, and each heater (
3a), (3b), and (3c) are individually controlled, and furthermore, between the central heater (3b) and the glass plate (G), that is, at a position above the recess (8a) of the bottom surface (6). A heat shield plate (11) made of a sintered body of ceramic fiber, a silica board, or the like is provided.

In order to perform vacuum forming using the above-mentioned forming apparatus, the glass plate (G), which has been preheated in the same manner as above, is heated by the heater (3a),
After heating above the strain point according to (3b) and (3c).

Although it is vacuumed, the central heater (
3b) or reduce the amount of heating by the heater (3b).
) heating without heating.

Then, the temperature of the center part of the glass plate (G), that is, the part that will be a smooth surface when it is made into a glass product, becomes the temperature of the heat shield plate (11).
Coupled with the presence of the glass plate (G), it becomes lower than the surrounding area, and the deflection of the center of the glass plate (G) during molding is further suppressed, preventing the center of the glass plate (G) from adhering to the recessed part of the bottom surface (8). , can prevent the occurrence of press scratches.

Here, to specifically list the temperature of the central part and peripheral part of the glass plate (G), the temperature of the central part of the glass plate (G) is as follows:
Glass viscosity measured with an invagination type automatic viscosity measuring device (7)
is at least 10" poise (JLogη = 9.5), preferably at least 1011 poise, and at the same time at which thermal cracking due to the temperature difference generated in the glass plate due to local heating can be prevented, that is, at least the strain point temperature. And also,
The temperature around the glass plate (G) is as follows:
) has a viscosity (7) of 101L3 poise (l Ogη= 8
．． 3) The temperature is below, preferably below 107 poise. That is, the temperature to ensure the above-mentioned viscosity (7) is 850°C or less, preferably 80G'O or less in the central part of the glass plate (G), and 700"O or less in the peripheral part of the glass plate (G). As mentioned above, the temperature is preferably 780°C or higher, and the temperature difference between the central part and the peripheral part of the glass plate (G) is set to be 780°C or higher, and preferably 200°C or higher. Further, the degree of vacuum during vacuum forming is approximately 80 Torr.

In the embodiment shown in FIG. 4, the heater is divided and a heat shield plate is provided, but it is also possible to partially heat the glass plate even if only one of them is used.

(Effects of the Invention) As explained above, according to the present invention, a recess is formed in the bottom of the mold for molding the smooth surface of the glass plate, and the peripheral edge of the recess is made into a higher step. Since a concave groove for vacuuming is formed at the boundary between the part and the side surface of the molding part, the glass plate can be molded without the part of the glass plate that becomes a smooth surface coming into contact with the mold during the R& shape. Therefore, it is possible to mold a glass product with a smooth surface without any pressing scratches, the subsequent polishing step can be omitted, and a product of good quality without distortion can be obtained.

In addition, by dividing the heater or providing a heat shield, it is possible to make the viscosity of a part of the glass plate, specifically the smooth surface, higher than other parts, so the glass plate can be used during molding. The possibility that the smooth surface portion (center portion) of the mold comes into contact with the recess of the mold can be further reduced.

[Brief explanation of the drawing]

, FIG. 1 is a sectional view of a molding apparatus according to the present invention, FIG. 2 is a plan view of a mold, FIG. 3 is a sectional view of a mold showing a molding state, and FIG. 4 is a mold according to another embodiment. FIG. In one drawing, (1) is the heating furnace, (2) is the mold, (3) is the heater, (5) is the forming part, (8) is the bottom of the forming part, (8a
) is the four parts, (7) is the side surface of the molded part, (8) is the groove, (I3
) is a suction hole, (11) is a heat shield plate, and (G) is a glass plate. Patent applicant Nippon Sheet Glass Co., Ltd.
Attorney Patent Attorney 2 1) Yong
- County Attorney Patent Attorney Ohashi
Kuni Department Attorney Patent Attorney Koyama Department Attorney Patent Attorney
Field 1) and Figure 2

Claims (4)

[Claims] (1) A glass plate is placed on a mold having a concave molding part opened upward, and the glass plate is heated with a heater and vacuumed through a suction hole opened in the molding part. In an apparatus for forming a plate, the molding part of the mold is constituted by a side surface and a bottom surface, and the bottom surface has a concave part lower in the center part and a step part higher in the peripheral part. A molding device for glass products, characterized in that a groove portion in which a suction hole opens is formed along the boundary with a side surface of the molding portion. (2) The apparatus for molding glass products according to claim 1, wherein the mold is made of one of amorphous carbon, graphite, and boron nitride. (3) A heat shield plate is interposed between the heater and the glass plate and above the concave portion, according to either claim 1 or 2. glass product forming equipment. (4) Molding of a glass product according to claim 1 or 2, wherein the heater disposed above the mold is divided into a plurality of parts and individually controlled. Device.