JP2001220155A - Method of press-forming glass panel for braun tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a glass panel for a Braun tube, which is reduced in foreign matter sticking defects. SOLUTION: Foreign dusts are prevented from entering into a forming section by surrounding a press-forming device with a cover 11, then supplying clean air 10 into an enclosure from a supply opening 9 so as to make the pressure inside the enclosure positive and preventing air from flowing into the enclosure from the outside. Thus the dusts are prevented from being stuck onto glass during forming.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for press-molding a glass panel for a cathode ray tube.

[0002]

2. Description of the Related Art When a glass panel for a cathode ray tube is press-molded, a defect called a pit occurs when foreign matter adheres to the glass block (gob) loaded in a mold before pressing. Further, even after molding, if foreign matter comes from the outside and adheres similarly to the inner surface of the high-temperature glass panel, the glass panel may be firmly seized on the glass surface due to the high temperature. The burned-in foreign matter cannot be removed by washing the glass panel after molding, and remains as a defect in the product. If these are large foreign matter defects, they can be relatively easily removed as defectives by inspection, but extremely small ones are difficult to detect and are shipped as products as they are. It can be a problem.

[0003] The foreign substances include those generated from the press molding apparatus itself and those that enter the airflow from outside the press molding apparatus. Of the latter, the latter induces air currents because the press forming apparatus is hotter than glass, and this air current sometimes becomes 1 m / s or more, accompanied by scattered or floating dust from the outside, In addition, it is considered that foreign matter on the press molding device is wound up and carried on a gob or a mold. In particular, since the temperature is higher in the vicinity of the gob supply section and the mold before and after press molding, the air flow is more easily generated and becomes stronger.

[0004] As a method of removing dust and foreign matter flying from the outside, it is generally known to provide a clean room or to shield a predetermined location to prevent an inflow of air from the outside. As still another method, see, for example,
It is known from 246228 that clean air is blown onto the path of the mold of the press forming apparatus to prevent foreign dust from entering and adhering to the glass being formed.

[0005]

However, the application of these methods to glass panel molding has the following problems and application difficulties due to the inherent limitations in glass panel molding. That is, it is difficult to realize the former panel forming workplace as a clean room in terms of working conditions and cost. In addition, if the periphery of the press forming apparatus is simply enclosed to reduce the inflow of airflow from the outside, it is difficult to completely surround the periphery of the press molding apparatus without any gap, and thus the pressure generated by the temperature difference between the inside and outside of the enclosure is difficult. In the area below the neutral zone in the distribution, a negative pressure is generated and flows into the enclosure from the gap.

In the latter method of blowing clean air to a mold portion, air is concentrated and blown from one direction and supplied to the mold portion, and this air acts on the glass being formed to reduce the temperature of the glass. There is a problem in that the influence is exerted, and the precision of molding is lowered and variations occur. In other words, the glass mass at the time of supply and the glass before and after molding receive uneven cooling due to the difference in the temperature and flow velocity of the blowing air, or by blowing the air to the mold at a fairly strong speed. is there.

[0007] Furthermore, since this method blows clean air only to the mold part of the molding apparatus, the clean air also attracts surrounding dust-containing air.
For this reason, some dust is mixed in clean air and foreign dust cannot be sufficiently prevented. In addition, since this method requires that a clean air blowing device be incorporated in the molding device,
Otherwise, narrow and cumbersome molding equipment will further increase the extent. As a result, the working environment deteriorates, the workability deteriorates, and the device is greatly restricted.

In general, in a press forming apparatus for glass panels for cathode ray tubes and the vicinity thereof, various mechanical devices are continuously operated due to forming work and product take-out and conveyance, so that dust is generally easily generated and generated. It is in an environment where scattered dust is easily scattered, and it is practically impossible to eradicate it. Until now, in press molding of glass panels for cathode ray tubes, there is no known method for industrially eliminating or reducing such foreign matter defects caused by extraneous dust.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for press-molding a glass panel for a cathode ray tube, which is intended to eliminate foreign matter defects caused by adhesion of extraneous dust. In a method for forming a glass panel for a cathode ray tube, which is loaded into a mold and press-molded, the press-forming apparatus is surrounded by an enclosure, and clean air is supplied to the enclosed space to make the interior of the enclosure positive pressure, so that an extraneous material is introduced. Provided is a method for press-molding a glass panel for a cathode-ray tube, which is characterized by preventing intrusion of dust.

[0010]

1 and 2 show an embodiment of a method for press-molding a glass panel for a CRT according to the present invention. In this method, a plurality of molds are arranged at predetermined intervals on a turntable, and a series of molding of a gob into a mold, press molding, and product removal is performed while the table is intermittently rotated. This is the case of a turntable system for performing work.

As shown, the gob 2 is a gob feeder 1
After being cut into a predetermined amount from the gob feeder 1, it is loaded into a die 8 located below the gob feeder 1 at a gob supply position 4 on a turntable 3 of a press forming apparatus. When the die 8 passes through the cooling position 5 by the rotation of the turntable 3 and reaches the press position 6, it is press-formed by a plunger (not shown), and then cooled while the turntable 3 rotates. Then, it is taken out of the mold 8.

[0012] Since this press forming apparatus is heated by high-temperature glass, an updraft is induced in the forming apparatus part,
If nothing is done as it is, air flows in from around and air flow 7 is generated, for example. This air flow 7 generally flows from the outside of the press forming apparatus toward the high-temperature press forming apparatus as shown in FIG. 2, and at this time, dust or foreign matter (simply referred to as dust) scattered or floating on the path. It is rolled together and brought into the glass forming part.

The present invention is intended to prevent dust mainly brought in by the air flow 7 induced by the high temperature of glass forming from adhering to high-temperature glass which is being formed.
An enclosure 11 is provided around the press forming apparatus, and the inside of the enclosure is supplied with clean air 10 from a blow-out port 9 to make the inside a positive pressure, thereby preventing the inflow of air from the outside to suppress or reduce the airflow 7. Aim. At the same time, the press forming device is shut off from the outside air by the enclosure 11 to prevent dust from flowing into the forming part.

The enclosure 11 is provided so as to secure a sufficient working space in the molding apparatus and usually cover the entire molding apparatus as shown in FIGS. In this case, the enclosure provided around the molding device is provided in a square shape (see FIG. 1) in this example, but may be a circular shape. Further, since it is sufficient that the inside space of the enclosure 11 is maintained at a positive pressure by supplying an appropriate amount of air, the enclosure may not be completely sealed. On the other hand, it is necessary to allow the worker to easily enter and leave the enclosure 11, and in reality, it cannot be completely sealed in order to satisfy the requirement. However, when the degree of sealing of the enclosure 11 is low, the amount of supplied clean air increases.

The intrusion or inflow of foreign dust can be substantially prevented by supplying clean air to the enclosure 11 and increasing the pressure in the enclosure. This is because, if the pressure inside the enclosure is positive, air does not flow into the enclosure from outside. As long as this is the case, the supply of the clean air may be performed from any place of the enclosure 11 and is not specified. In addition, the number and shape of the outlets 9 for supplying clean air can be appropriately selected. The outlets 9 provided in the enclosure 11 can be concentrated in a specific area of the enclosure 11 or dispersed at appropriate positions, and the amount of air blown from these outlets may be changed depending on the installation position.

However, in the case of the turntable system as in the present embodiment, it is desirable to supply the clean air 10 in a concentrated manner from at least a specific region of the enclosure 11. Referring to FIG. 1, the clean air 10 is supplied from at least the side including the gob supply position 4 of the molding apparatus. The reason for this is to supply as much clean air as possible to a place where extraneous dust is particularly desired to be blocked in the press forming apparatus, that is, a place where cleanliness is strongly required.
The clean air may be supplied from another area in parallel with the supply from the gob supply section, but in this case, the supply from the gob supply section is made relatively stronger than the supply from the other area.

In the glass panel forming apparatus, the area from the gob 2 coming out of the gob feeder 1 to the mold 8 and moving to the press molding is located in a place where cleanliness is strongly required. Equivalent to. Further, this region is a place where the updraft is strongly induced particularly in a high temperature region in the molding apparatus. Therefore, when the outlet 9 is provided in the enclosure 11 on the side of this area and the clean air 10 is supplied toward the forming apparatus, the gob supply section and the forming section can always receive the effect of fresh clean air. At the same time, if clean air is sufficiently supplied here, the upward air flow can be suppressed, so that the inflow of air from the outside can be satisfactorily prevented. As a result, in the turntable system, the objective can be achieved by supplying clean air from the gob supply unit side.

In the present invention, in order to reliably block dust coming from the outside, it is necessary to supply an appropriate amount of clean air capable of always maintaining the inside of the enclosure 11 at a desired positive pressure. If the inside of the enclosure 11 has a positive pressure, theoretically, no air flows in from the outside. However, the situation outside the enclosure changes, and a pressure difference also occurs inside the enclosure, and the upper part of the floor is generally liable to be under negative pressure. It is desirable to supply a large amount of clean air. In practice, the amount of air is adjusted by the degree of sealing of the enclosure 11, the strength of the airflow induced by the high temperature, the arrangement of the outlets, and the like.

An opening 13 for exhaust is provided around the center column 12 (see FIG. 2) on the press forming apparatus.
Is provided. This opening is optimally sized so that the discharged air does not flow back into the inside and the discharging speed is higher than the falling speed of the dust. Providing a cover above the opening can prevent dust from falling into the enclosure.

In order to increase the flow rate at a low flow rate, the outlet 9 is made sufficiently large and the flow rate is made uniform. For this purpose, a mesh plate having a pressure loss is put in the outlet, and an appropriate rectifying plate is provided. When a filter is installed at the outlet, the filter area may be increased to increase the filtration area in order to extend the life of the filter.

It is necessary that the supplied air be substantially free of dust. Clean air means such air. Large particles that cause pits (several tens of μm
In addition to the above, care must be taken because even below this point, the powder may solidify in the middle of the supply path, become large particles, and blow out. Filters, electric dust collection, inertial dust collection, etc. are used for dust removal. For the temperature of the clean air to be supplied, the lower the temperature, the lower the blowing speed for the same mass flow rate, and the lower the overall temperature, the lower the attractive force of the air flow. Even if it is not performed, there is no problem at room temperature. However, controlling the temperature and humidity of the blown air is more effective because it can prevent the mold from being oxidized due to a decrease in temperature and humidity in winter and can further stabilize the moldability.

As described above, the blowing of air in the present invention is to prevent the intrusion of foreign dust by applying a positive pressure to the inside of the enclosure surrounding the molding apparatus as described above.
This method is completely different from the conventional method in which clean air is blown only to a mold portion such as a gob supply portion and a molding portion of -246228 to prevent extraneous dust. That is, in the conventional method, in order to prevent the invasion of foreign dust only by clean air, clean air must be strongly blown to the mold part. There is no need to spray so strongly or concentrate on the mold. As described later, effects that cannot be obtained by the conventional method can be obtained.

Although the present invention has been described above, it is not limited to the illustrated method. Further, the present invention can be applied to press forming of a glass panel for a cathode ray tube other than the exemplified turntable method.

[0024]

(Example 1) A turntable type press forming apparatus is surrounded by an enclosure, and clean air is introduced into a space in the enclosure.
In the same manner as in the above, it was supplied from the gob supply section side of the press molding apparatus.
The total air flow is 70,000 m ^{3 /} h. A cover was attached around the gob to completely prevent cooling. When press molding was performed in this state, almost no inflow of airflow from the outside could be prevented, and foreign matter defects caused by extraneous dust hardly occurred.

Example 2 In Example 1, high temperature air in the upper part of the factory was sucked and used as clean air, and the temperature of the blown air was increased, and the humidity of the blown air was further increased by humidification with steam. When press molding was performed in this state, almost no inflow of airflow from the outside could be prevented, and foreign matter defects caused by extraneous dust similarly hardly occurred. In addition, the mold oxidation phenomenon in winter was eased, and operation settings were stabilized.

[0026]

As described above, according to the press molding method of the present invention, the inside of the enclosure is made positive by supplying clean air to the enclosed space by surrounding the press molding apparatus.
Prevents intrusion of air containing dust from the outside,
Since it is possible to prevent the dust generated in the enclosure from being rolled up, it is possible to prevent molding defects caused by extraneous dust in the molding process of the glass panel for a cathode ray tube. Further, since the clean air is not directly blown onto the gob, the glass before and after molding, and the mold as in the prior art, they are not cooled so strongly as to hinder the clean air.

Further, since the press molding device is substantially surrounded by the enclosure, the molding portion can be shielded from the outside air, whereby the working environment of the molding process can reduce the influence of the outside air in combination with the dust shielding effect by the enclosure itself. Since it is not received, work conditions can be stabilized. As a result, the molding yield and the molding quality can be improved. Furthermore, by positively controlling the temperature and humidity of the clean air supplied into the enclosure, the oxidation of the mold and the setting of the operation are stabilized.

[Brief description of the drawings]

FIG. 1 is a plan view of a basic configuration of a press forming apparatus according to a glass press forming method of the present invention.

FIG. 2 is a partial side view showing a basic configuration of an AA section of the press molding apparatus of FIG.

[Explanation of symbols]

 1: Gob feeder 2: Gob 3: Turntable 4: Gob supply position 6: Press position 7: Air flow 8: Die 9: Outlet 10: Clean air 11: Enclosure

Claims (2)

[Claims] 1. A method for forming a glass panel for a cathode ray tube, wherein a molten glass lump is charged into a mold of a press molding apparatus and press-molded, wherein the press molding apparatus is surrounded and surrounded by clean air. A press-molding method for a glass panel for a cathode ray tube, characterized in that the supply and positive pressure inside the enclosure prevent foreign dust from entering. 2. The method according to claim 1, wherein the molding method is a turntable method in which a turntable provided with a plurality of dies is intermittently rotated, during which loading of a glass block, press molding, and removal of a product are sequentially performed. 2. The press-forming method according to claim 1, wherein the resin is supplied into the enclosure from at least the side of the turntable on which the glass block is loaded.