KR20050022017A - Method and apparatus for producing a tempered glass sheet by forced cooling - Google Patents

Abstract

Forced cooling device (1) used in the production of tempered glass plate is installed in the air cooling unit (9) for cooling the glass plate by blowing cooling air to the glass plate, downstream of the air cooling unit, and a water-containing member (belt, roll, etc.) is installed And a contact cooling unit 10 for further cooling the glass plate by contacting the surface of the glass plate. In addition, there is provided a tempered glass sheet manufactured using a forced cooling device, and a tempered glass sheet manufactured through a variant of the contact cooling unit is also provided.

Description

Method and apparatus for producing a tempered glass sheet by forced cooling {Method and apparatus for producing a tempered glass sheet by forced cooling}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to the production of tempered glass plates, and more particularly, to a method for producing tempered glass plates, a forced cooling device used in this method, and a tempered glass plate manufactured using a forced cooling device.

Until now, heat-reinforced glass plates have been heated to near the softening point (for example, 650 ° C.), and then the cooling air is sprayed onto the heated glass plate to rapidly cool or quench to form a compressive stress layer on the surface. Cooling hardening process ".

As another strengthening method, for example, water mist disclosed in Japanese Laid-Open Patent Publication No. 58-109832 under the name of "glass plate strengthening method" and Japanese Laid-Open Patent Publication No. 61-58827 in the name of "manufacturing method of tempered glass lid" ) There is cooling method. As another method disclosed in Japanese Patent No. 2766355 under the name "bending cooling apparatus for glass plates", a technique called "solid contact cooling method" has been proposed.

In the vehicle glass plate, the demand for a thin glass plate is increasing with the request of weight reduction. The "thin glass plate" herein refers to a glass plate whose thickness is not greater than 3.0 mm.

These thin glass plates show little difference in temperature between the center and the surface under air cooling. Therefore, even when using a high-pressure, large-capacity blower in such thin glass, the conventional air cooling strengthening method has a limit. In addition, the use of such a large blower causes additional electrical consumption and increases noise.

Alternatively, a water cooling method with a very high cooling capacity can be applied. However, there is a problem that the probability that the glass plate is broken is relatively high due to a very large tension temporarily occurring on the surface of the glass plate at the initial stage of cooling.

Accordingly, it is an object of the present invention to provide a forced cooling technology suitable for the production of tempered glass plate having a higher strength and degree of reinforcement than the conventional air cooling method, and also capable of effectively strengthening the thin glass plate.

Figure 1a is a block diagram showing the general installation of the forced cooling apparatus according to an embodiment of the present invention.

Figure 1b is a block diagram showing a typical installation of a forced cooling device according to another embodiment of the present invention similar to Figure 1a.

Figure 1c is a block diagram showing the general installation of the forced cooling apparatus according to another embodiment of the present invention similar to Figure 1a.

2 is a schematic view of a partial cross section of the forced cooling device shown in FIG.

3 is a partially enlarged view of the forced cooling device shown in FIG. 2, including a contact cooling unit with a water cooling belt.

FIG. 4 is a partially enlarged view of FIG. 3 showing how steam is discharged from the contact cooling unit and water is supplied to the water cooling belt.

FIG. 5 is a partially enlarged view illustrating a contact cooling apparatus having a water-cooling roll similar to that of FIG. 3.

Figure 6 is a perspective view showing a portion of the water-cooled cooling belt with a hole formed.

FIG. 7A is a schematic diagram of a tempered glass plate manufactured using the perforated water-cooled belt shown in FIG. 6.

FIG. 7B is a schematic view of a tempered glass plate having marks or characters provided on the less strengthened portion of the tempered glass plate similar to FIG. 7A.

FIG. 7C is a view showing how the tempered glass plate shown in FIG. 7B is broken.

* Description of the sign *

1 to 3. Forced cooling of glass plates 10. Contact Cooling Unit

11. Upper belt 14. Upper water tank

22. Exhaust pipe 24. Water supply pipe

27. Glass plate 31. Lower belt

34. Lower water tank 44. Water sprayer

55. Hydro-roll contact cooling unit 75... Bore Function Belt Contact Cooling Unit

77. Cooling belt hole 78... Tempered glass

79. Less fortified

According to the above object of the present invention, the secondary cooling to further cool by contacting the surface of the glass plate passed through the primary cooling process, the primary cooling step of cooling the cooling air by spraying the cooling air on the glass plate heated to a predetermined temperature It provides a method for producing a tempered glass sheet characterized in that the process is configured.

In the manufacturing method of the tempered glass sheet of this invention, the conventional air cooling process is used as a primary cooling process. In the air cooling process, the heating glass plate is cooled with a cooling capacity that does not damage or break the glass plate due to heat shock in the initial stage of cooling. Thus, the tension temporarily generated in the glass plate at the beginning of cooling is limited to the extent that breakage of the glass plate does not occur. Thereby, breakage of the glass plate of a cold initial stage can be avoided.

Next to the primary cooling process, the secondary cooling process is applied as a contact cooling process (hereinafter referred to as a 'functional member contact cooling process') using a water-containing member. The contact cooling process cools the glass plate with a large cooling capacity capable of thermally strengthening the glass plate while maintaining a large temperature difference between the center and the surface of the glass plate. This shows that it can be effectively thermally strengthened even in thin glass plates. Moreover, even higher strength can be obtained with the glass plate of thickness more than 3.0 mm.

The primary cooling process, the air cooling process, should last for at least 1 second. This is because, after this time, the tension temporarily generated on the surface of the glass plate at the beginning of cooling gradually decreases past the peak. This means that no rupture will occur even if a violent cooling process such as a hydrous contact cooling process with high cooling power or capacity is applied to the glass plate. Therefore, tempered glass plates can be produced commercially.

In the water-containing member contact cooling process, the water-containing member wetted with water, such as a fiber wetted in water, is brought into contact with the glass plate to cool the surface of the glass plate. In this process, the water in the water-containing member partially evaporates because of the heat of the glass plate, whereby the glass plate is effectively cooled by the heat of evaporation (sum of latent heat and sensible heat).

The water-containing member cooling process has an intermediate cooling capacity between the air cooling method and the water cooling method in which the cooling water directly contacts the heating glass plate. Thus, the water-containing member cooling process can avoid the occurrence of thermal shock more effectively than the water cooling method. However, if the glass plate heated up to the softening point is directly cooled by the water-contact member cooling process, the cooling capacity of the glass plate may not be suppressed temporarily due to the higher cooling capacity than the air cooling process, resulting in breakage of the glass plate. have. Even if the glass plate breakage does not occur, a deteriorated surface layer called 'staining' is generated due to the contact between the glass plate surface and the water.

The primary cooling step is preferably not more than that when the glass sheet thickness t (t ^2/4) seconds.

According to another object of the present invention, the present invention provides an air cooling unit for cooling the glass plate by blowing cooling air to the surface of the glass plate heated to a predetermined temperature, and a water-containing member soaked in water and installed downstream of the air cooling unit. The present invention provides a forced cooling apparatus for producing tempered glass sheet, comprising a contact cooling unit which is configured to contact the surface of the glass plate with the water-containing member to further cool the glass plate.

In a forced cooling device, the heated glass plate is first cooled by an air cooling unit in which the cooling capacity is not extremely high. This makes it possible to limit the tension temporarily occurring on the surface of the glass plate at the beginning of cooling to the extent that the glass plate is not broken. Therefore, the glass plate can be prevented from being broken at the initial stage of cooling. An air cooling unit having such a limited cooling capacity does not provide sufficient temperature difference between the center and the surface of the glass plate and thus cannot effectively heat strengthen. In order to solve this problem, the forced cooling device of the present invention includes a contact cooling unit having a water-containing member installed downstream of the air cooling unit. By providing the water-containing member contact cooling unit, it is possible to effectively heat-treat the glass plate while maintaining a sufficiently large temperature difference between the center and the surface of the glass plate. As a result, even a thin glass plate having a thickness of 3.0 mm or less can be excellently thermally strengthened. In addition, even in a glass plate having a thickness of 3.0 mm or more, a higher degree of reinforcement can be obtained.

Preferably, the water-containing member contact cooling unit comprises upper and lower maintenance members made of a material capable of holding a glass plate therebetween and absorbing and storing water, and an upper water supply device for supplying water to the upper water-containing member, It includes a lower water supply device for supplying water to the lower function member.

With this structure, the glass plate is held between the upper and lower functional members soaked in water, and forcedly cooled by the upper and lower functional members. The upper water supply device and the lower water supply device supply water to the upper and lower functional members, respectively.

Two water-containing members soaked in water, such as fibers soaked in water, are applied to the glass plate to cool the surface of the glass plate. Thus, the water of the water-containing member is partially evaporated by the heat of the glass plate, and the glass plate is effectively cooled by this heat of evaporation.

In a preferred embodiment of the present invention, the upper water-containing member is an upper circulation belt which circulates to contact the upper surface of the glass plate, and the lower water-containing member is a lower circulation belt that circulates to contact the lower surface of the glass plate. The upper water supply device includes an upper water tank that is locked when the upper belt circulates along the upper circulation path, and the lower water supply device includes a lower water tank that is locked when the lower circulation belt circulates along the lower circulation path. Upper and lower circulation belts absorb and store water by passing through the corresponding water tank. The water tank is simple in structure and thus the water supply can be equipped at low cost.

In another preferred form of the present invention, the upper water-containing member is composed of a plurality of upper rolls in contact with the upper surface of the glass plate, and the lower water-containing member is composed of a plurality of lower rolls in contact with the lower surface of the glass plate. The upper water supply device is provided with a plurality of water supply pipes respectively associated with the upper rolls to supply water to the upper rolls, and between the upper rolls and the water supply pipes, respectively, to make rolling contact with the upper rolls to adjust the water content of the upper rolls, respectively. It consists of a plurality of upper middle rolls. The lower water supply holds multiple water tanks installed directly below each lower roll to hold water, and the rolling contact with each lower roll to supply water from the water tank to the lower roll while controlling the water content of the lower roll. It consists of a number of lower intermediate rolls which are partially submerged in each water tank.

At least one of the upper and lower circulation belts has a hole therein to avoid contact between the glass plate and the water hydrated in the belt to form a less reinforced portion of the glass plate.

According to another object of the present invention, at least one of the upper circulation belt and the lower circulation belt has a hole therein to form a less reinforced portion of the glass plate to avoid contact between the glass plate and the water functioning on the belt as described above. Processing in a forced cooling device structured to have provides a tempered glass sheet having a less reinforced portion.

In general, the tempered glass sheet breaks into relatively small, harmless debris upon breakage. If it is a glass plate that is less hardened (or glass plate reinforced to a lower level), it breaks into relatively large pieces instead of breaking into smaller pieces. In view of this, the present invention provides a portion that is less strengthened than the rest of the glass plate. This less fortified portion can be used as a nameplate or label to indicate various kinds of information, such as lot numbers of tempered glass. In this application, when the tempered glass is broken, the less tempered part can remain in its original shape and structure, allowing the user to know the information about the broken tempered glass based on the information entered in the less tempered part. Because of this, there is a significant advantage.

Best Mode for Carrying Out the Invention Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

Figures 1a, 1b and 1c is a block diagram showing a preferred form of the forced cooling device according to the present invention. In the first embodiment shown in FIG. 1A, the forced cooling device 1 has an air cooling unit 9 and a contact cooling unit 10 installed downstream of the air cooling unit 9. The contact cooling unit 10 has cooling belts moistened with water as described in detail in FIGS. 3 and 4. In the second embodiment shown in FIG. 1B, the forced cooling device 2 has a contact cooling unit 55 disposed downstream of the air cooling unit 9. The contact cooling unit 55 has cooling rolls moistened with water as described in detail in FIG. 5. In the third embodiment shown in FIG. 1C, the forced cooling device 75 includes an air cooling unit 9, and the forced cooling device 75 is disposed downstream of the air cooling unit 9. The forced cooling device 75 has cooling belts moistened with water, at least one of which has a hole or an inlet, for the purpose described in detail in FIG. 6. In the above embodiments, the air cooling unit 9 is arranged downstream of the heating oven or the heating furnace 8. Although not shown, a molding apparatus for forming or bending the flat glass plate may be installed between the heating furnace 8 and the air cooling unit 9.

In the heating furnace 8 shown in FIG. 1A, the glass plate is heated to a predetermined temperature. The air cooling unit 9 of the forced cooling device 1 is arranged immediately downstream of the heating furnace 8, and is designed to cool the glass plate by applying cooling air to the opposite surface of the heated glass plate. The contact cooling unit 10 of the forced cooling device 1 is disposed immediately downstream of the air cooling unit 9 and further cools the glass plate through direct contact between the glass plate and the cooling belt moistened with water.

The air cooling unit 9 acts as a primary cooling unit of the forced cooling device 1, and performs forced cooling of the heated glass plate having a cooling force or a cooling capacity so as to prevent the glass plate from being ruptured due to thermal shock. Is installed. However, cooling for a long time with the air cooling unit 9 is not preferable because it can be cooled in excess as a whole before entering the secondary cooling process with greater cooling power or cooling capacity. Due to the insufficient temperature difference between the center and the surface of the glass plate, effective thermal strengthening of the thin glass plate (thickness 3.0 mm or less) cannot be achieved even in the secondary cooling process. For the same reason, even a glass plate having a thickness of 3.0 mm or more cannot be given a high level of strength.

After a combination of air cooling unit (9, the primary cooling unit) in contact with the cooling unit (10, secondary cooling unit) perform a number of experiments, the primary cooling step is when that t the thickness of the glass sheet (t ^2/4) seconds It is desirable to last longer. For example, when t = 2.1 mm, the primary cooling process lasts no longer than 1.1 seconds. Similarly, if t = 3.0 mm, the primary cooling process is given no longer than 2.25 seconds. When t = 6 mm, the primary cooling process is no longer than 9 seconds.

If the cooling time is too short in the primary cooling process, the occurrence of thermal shock is inevitable, and defects on the surface of the glass plate may occur when the secondary cooling process of the contact cooling unit 10 having the cooling member moistened with water is processed. The cooling time in the primary cooling process is preferably at least longer than the time during which the tensile stress that temporarily occurs on the surface of the glass plate at the beginning of the cooling passes its inherent peak. More specifically, the cooling time in the primary cooling process is about 1 second depending on the thickness of the glass plate.

On the other hand, if the cooling time of the primary cooling process is too long, the tempered treatment of the glass plate is not satisfactory when the thickness of the glass plate is not thicker than 3.0 mm, and a glass plate having an insufficient level of strength is also obtained when the glass plate is thicker than 3.0 mm. . To cooling time in the first cooling process (t ^2/6) it does not exceed the second is preferred.

The length of the air cooling unit 9 and the moving speed of the glass plate can be determined based on the relationship between the thickness of the glass plate and the cooling time in the primary cooling process of the air cooling unit 9.

Similarly, the forced cooling device 3 shown in FIG. 1C includes an air cooling unit 9 for rapidly cooling the glass plate by blowing cooling air to the opposite surface of the glass plate heated to a predetermined temperature in the heating furnace 8; And a contact cooling unit 75 having a belt moistened with water arranged downstream of the air cooling unit 9 and arranged so that the opposite surfaces and surfaces of the glass plates are in contact with each other to further cool the glass plates. At least one of the water-soaked belts has a hole or inlet suitable for the purpose described later.

FIG. 2 is a schematic view of a partial cross section of the forced cooling device 1 shown in FIG. 1A. In the forced cooling device (1), the glass plate (27) for further cooling the air cooling unit (9) and the glass plate (27) which blows cooling air to the opposite surface of the heated glass plate (27) to cool the heated glass plate. A contact cooling unit 10 having a belt moistened with water arranged so as to be in contact with the opposing face of is provided in the order described in the moving direction of the glass plate 27. In other words, the contact cooling unit 10 is installed downstream of the air cooling unit 9. Although not shown, the air cooling unit 9 includes a plurality of rollers that send the glass plate 27 downstream while the glass plate 27 moves. Although not shown, the air cooling unit 9 has a plurality of nozzles arranged to blow cooling air to the opposite surface of the glass plate 27.

The furnace 8 and the air cooling unit 9 are similar to the prior art, and detailed description thereof will be omitted. Instead, the contact cooling unit 10 will be described in more detail in FIG. 3.

As shown in FIG. 3, the contact cooling unit 10 includes an upper circulation belt 11 serving as a member wetted with water in the upper portion, an upper driving roll 12 driving the upper circulation belt 11 along a circulation path, and an upper portion. The upper circulation belt 11 acts as a guide roll 13 of a plurality (shown three in the drawing), an upper water supply means or an apparatus for guiding the circulation belt 11 and the upper circulation belt 11 is circulated. The upper water tank 14 installed to receive a portion of the plurality of additional guide rolls 15 (two in the drawing) for guiding the upper circulation belt 11 to move the cooling water contained in the upper water tank 14, The upper press member 16 for pressing the upper surface of the upper circulation belt 11, a plurality of holes or gaps 17 formed in the upper press member 16, the upper unit body installed on the upper portion of the upper press member 16 as a whole 18, a plurality of gas removal chamber 19 formed in the upper unit body 18, the gas removal chamber 19 A plurality of humidifying chambers 21 formed in the upper unit body 18 alternately, an exhaust pipe 22 connected to the gas removing chamber 19, and an intake fan 23 connected to the exhaust pipe 22 and serving as gas removing means 23. ), A plurality of water supply pipes 24 installed in the humidification chamber 21, and a pair of air spray nozzles 25 serving as a means or a device for removing excess water from the upper circulation belt 11. It is composed.

In addition, the contact cooling unit 10 is installed under the upper circulation belt 11 and the lower circulation belt 31 that acts as a member to wet the lower water, the lower drive for driving the lower circulation belt 31 along the circulation path It acts as a roll 32, a plurality of guide rolls 33 (three shown) for guiding the lower circulation belt 31, the lower water supply means or device and the lower circulation belt (when the lower circulation belt 31 is circulated) Lower water tank 34 installed to receive a portion of 31, a number of additional guide rolls 35 (two in the drawing) for guiding the lower circulation belt 31 to move the coolant in the lower water tank 34. , The lower pressing member 36 supporting the lower surface of the lower circulation belt 31, a plurality of holes or gaps 37 formed in the pressing member 36, and the lower unit body which is entirely installed under the pressing member 36 ( 38), alternately with a plurality of gas removal chambers 39 and gas removal chambers 39 formed in the lower unit body 38. A plurality of humidifying chambers 41 formed in the sub-unit body 38, an exhaust pipe 42 connected to the gas removing chamber 39, an intake fan 43 connected to the exhaust pipe 42 and serving as a gas removing means, It consists of a plurality of water supply pipes 44 installed inside the humidification chamber 41 and a pair of air spray nozzles 45 serving as a means or device for removing excess water from the lower circulation belt 31. .

The gas removing means is never limited to the suction fans 23 and 43 of the above embodiment, and may include a discharge pump or a vacuum pump.

The upper and lower circulation belts 11 and 31 may be made of a felt, a fabric, or a mesh of a heat resistant material. The heat resistant material is preferably composed of organic fibers such as aramid fibers, metal fibers such as stainless steel fibers, and ceramic fibers such as glass fibers.

Thicker felt is preferred to cool the glass plate more uniformly and to increase the initial moisture content. Thinner felt is preferred as the belt in order to effectively discharge water vapor generated during contact with the glass plate. It is preferred that the belt is a reinforced canvas felt to accept a large tension in the driving direction during driving.

The belts 11 and 31 are also preferably plain or twill-woven fabrics that are resistant to tension. The texture of the fabric is determined by taking into account cooling uniformity and water content.

In the case of a mesh, the mesh shape may be selected in consideration of cooling uniformity and water content. If higher cooling uniformity and moisture is desired, the mesh can be used in combination with the felt to form a hybrid belt.

The operation of the above-described contact cooling unit 10 is as follows.

In Figure 3, the upper and lower drive rolls 12, 32 are rotated by a power source (motor, etc., not shown), the upper circulation belt 11 circulates in the counterclockwise direction in Figure 3 and the lower circulation belt 31 is Cycle clockwise. The upper and lower circulation belts 11 and 31 are contained in the upper and lower water tanks 14 and 34 to be cooled and absorb water. Thereafter, the upper and lower circulation belts 11 and 31 pass through the air spray nozzles 25, 25, 45 and 45, and then pass through the upper and lower pressurizing members 16 and 36, and the glass plate 27 and the belts 11 and 31. Becomes a sandwich form. In this process, the glass plate 27 is forcibly cooled by the functioning upper and lower circulation belts 11 and 31.

The upper and lower water tanks 14 and 34 have a function of absorbing heat and cooling the heated upper and lower circulation belts 11 and 31 to return the belt to its original state. In particular, the function of the tanks 14 and 34 is to cool the upper and lower circulation belts 11 and 31 to a predetermined temperature while supplying the water required to cool the glass plate 27. By returning to the predetermined initial state, the upper and lower circulation belts 11 and 31 start to forcibly cool the glass plate 27.

4 is an enlarged view of the upper and lower unit bodies 18 and 38. A part of the water absorbed by the upper and lower circulation belts 11 and 31 evaporates to take heat from the upper and lower surfaces of the glass plate 27. The generated steam or steam is discharged out of the units 18 and 38 through the holes or gaps 17 and 37 and the degassing chambers 19 and 39 as shown by the arrows. Therefore, there is no danger of excessive steam or steam remaining on the upper and lower surfaces of the glass plate 27. On the contrary, if excess water vapor or steam remains in the glass plate 27, the heat insulation layer which interrupts heat transfer will be formed and a predetermined cooling performance will not be obtained. Forcibly removing water vapor or steam makes it possible to maintain good forced cooling of the glass plate 27.

In this embodiment, water vapor or steam is discharged upwards or downwards through the degassing chambers 19, 39. Alternatively, it can also be discharged forward or backward in FIG. 4. The degassing chambers 19 and 39 may be strictly negative pressure (low pressure below atmospheric pressure) or may be only an exhaust passage.

Due to the evaporation, the water content of the upper and lower circulation belts 11 and 31 is reduced. Thus, water is supplied to the upper circulation belt 11 through the water supply pipe 24, and water is supplied to the lower circulation belt 31 through the water spray nozzle 44. As a result, forced cooling can be continued in a good state.

As described above, the first step of cooling is that the glass plate 27 is rapidly cooled by the air cooling unit 9 having a cooling power or a cooling capacity that is not extremely high. Thus, the tension that may temporarily occur on the surface of the glass plate at the beginning of cooling is limited to the extent that breakage does not occur in the glass plate. Thereby, the glass plate can be avoided to break in the initial stage of cooling.

In the second stage of cooling by the contact cooling unit 10, a water-containing member such as the upper and lower circulating fabric belts 11 and 31 suitably wetted with water contacts the opposite surface of the glass plate to cool the glass plate surface. That is, a part of the water in the water-containing members 11 and 31 evaporates by the heat of the glass plate, and the heat of the evaporation causes the glass plate to be effectively cooled. As a result, even a thin glass plate with little temperature difference between the center and the surface can be thermally strengthened effectively. Furthermore, even at a glass plate thicker than 3.0 mm, a high level of strength can be obtained.

5 is a detailed cross-sectional view of the contact cooling unit 55 of the forced cooling device 2 according to the second embodiment shown in FIG. The contact cooling unit 55 has a water-containing member in the upper and lower portions in the form of a roll.

In the contact cooling unit 55, the upper and lower water-containing members are provided with a plurality of upper and lower felt strokes (60, 61) consisting of a felt (59) wrapped around the shaft (58). The water supply from the water supply tube 24 is applied to the upper peltro 60 through the middle roll 62, and the water content of the upper peltro 60 is thereby appropriately adjusted. The small water tank 63 at the bottom is installed under the transport path of the glass plate 27. The water retained in the lower water tank 63 is applied to the lower petroleum 61 through the middle roll 64, whereby the water content of the lower petroleum 61 is appropriately adjusted. Water vapor formed at the top of the glass plate 27 is forced out through the degassing chamber 19 located between two adjacent upper peltrols 60, 60, and through the exhaust pipe 22 and the intake vent 23. Discharged. Water vapor formed in the lower part of the glass plate 27 is forcibly discharged out through the degassing chamber 39 located between the adjacent lower peltrols 61 and 61. Water is supplied to the small lower water tank 63 through the water supply pipe 65 or the duct, and the overflowed water is discharged through the overflow pipe 66. In this way, the water level of each water tank 63 is kept constant.

As described above in FIG. 1B, the contact cooling unit 55 having the water cooling rolls 60 and 61 is installed downstream of the air cooling unit 9 to constitute the forced cooling device 2. In the forced cooling device 2, the air cooling unit 9 is equipped to perform a first step of cooling along an air cooling process having a cooling capacity that is not extremely high. This limits the tension that may temporarily occur on the surface of the glass plate at the beginning of cooling, to the extent that no breakage occurs in the glass plate. Thus, the glass plate can be avoided in the initial stage of cooling.

In the second stage of cooling by the contact cooling unit 55, a water-containing member such as the upper and lower felt petrol 60, 61 soaked in water is in contact with the opposite surface of the glass plate 27 to cool the glass plate 27 surface. That is, the water contained in the water-containing members 60 and 61 (feltrol) is evaporated by the heat of the glass plate, and by this heat of evaporation, the glass plate is effectively cooled. As a result, even a thin glass plate with little temperature difference between the center and the surface can be thermally strengthened effectively. Furthermore, even at a glass plate thicker than 3.0 mm, a high level of strength can be obtained.

The upper surface of the glass plate 27 is cooled by the upper endless belt 11 as in FIG. 3, while the lower surface of the glass plate 27 can be cooled by the lower felt control 61 shown in FIG. 5. Alternatively, the lower surface of the glass plate may be cooled by the lower circulation belt 31 in FIG. 3, while the upper surface may be cooled by the upper peltro 60 of FIG. 5.

FIG. 6 is a partial perspective view of the contact cooling unit 75 including the upper cooling belt 11 having the rectangular hole 77 of FIG. Other structural parts are the same as the contact cooling unit 55 shown in FIG. 3, and detailed descriptions thereof are omitted. The size and location of the holes 77 is arbitrary.

FIG. 7a shows a tempered glass plate formed using a contact cooling unit 75 having an upper hydrous cooling belt 11 with holes shown in FIG. 6. Tempered glass plate 78 has a rectangular central portion 79 that is less hardened (hatched) than other portions of tempered glass plate 78. The less reinforced portion 79 is formed by the presence of a hole 77 in the upper water cooling belt 11, which is a function required in the secondary cooling process because the hole 77 portion of the cooling belt 11 does not contain water. This is because it cannot function partially as the cooling member. The portion 79 of the glass plate 78 by the holes 77 of the cooling belt 11 is not subjected to cooling in the secondary cooling process. Thus, the portion 79 of the glass plate 78 is less strengthened than the other portions so that the strength is lower than the other portions.

In the preferred application shown in FIG. 7B, the less strengthened portion 79 is used to write down the marks or characteristics applied after the strengthening process to indicate product information such as lot numbers of the tempered glass sheet 78. .

Tempered glass plate 78 will break when exerting a force above a predetermined value. For example, all parts except the less hardened portion 79 (FIG. 7B) of the tempered glass plate 78 will be chopped into relatively harmless pieces 82 as shown in FIG. 7C. The less strengthened portion 79 remains unchanged even after breakage of the tempered glass plate 78.

Tempered glass has a large residual compressive stress formed on the outer surface, thereby improving the strength. The central portion of the tempered glass has a large tension formed to adapt to this stress. Due to this stress adaptation, when fracture occurs in the tempered glass, the tension promotes the progression of the crack so that all parts break into small pieces. Given any information on the surface of the tempered glass, after this breakage no more information can be obtained from small glass fragments.

In the case of a tempered glass plate 78 having a less strengthened portion 79 (FIG. 7A), the less strengthened portion 79 may retain its original shape when the tempered glass plate 78 is broken. When broken, the less reinforced portion 79 breaks into relatively large fragments. As shown in FIG. 7C, the debris 83 formed from the less strengthened portion 79 is considerably larger in size than the other debris 82, and may contain all of the marks or characters 81 representing the product information of the tempered glass 78. Holds. Therefore, product information can be easily obtained from the mark 81 in the fragment 83, and is very effective when replacing the broken tempered glass 78 with a new one or investigating the cause of the breakage.

Returning to Figs. 1A to 1C, the air cooling unit 9 serves to primarily cool the glass plate according to the air cooling process having an extremely low cooling power or cooling capacity. Thus, the tension generated temporarily in the initial stage of cooling on the glass plate surface is limited to the extent that breakage does not occur in the glass plate. Thus, breakage of the glass plate in the initial stage of cooling can be prevented.

In the contact cooling units 10, 55 and 75, which are secondary cooling processes, the water-containing cooling member containing water, such as a fabric sufficiently wetted with water, comes into contact with the outer surface of the glass plate to cool the outer surface. That is, a part of the water contained in the water-containing cooling member is evaporated by the heat of the glass plate, and the glass plate is effectively cooled by this heat of evaporation. As a result, even thin glass plates with little temperature difference between the center and the surface upon cooling can be effectively strengthened. In addition, high strength can be obtained even in a glass plate having a thickness larger than 3.0 mm.

Contact cooling units (10, 55, 75) having a water-cooled cooling member has a significantly higher cooling capacity compared to the general air cooling process or solid contact cooling process. Therefore, the water-containing member contact cooling unit 10, 55, 75 can also reinforce excellent thin glass plate having a thickness of 3.0 mm or less. In particular, it is easy to make tempered glass even in a thin glass plate having a thickness not larger than 3.0 mm according to the water-containing member cooling process of the present invention. In addition, the present invention is also preferable for the production of tempered glass sheet thicker than 3.0mm and is easily processed in a normal air cooling process. Compared with the ordinary air cooling unit, the water-containing member contact cooling unit 10, 55, 75 of the present invention is small in size and can be operated at a relatively low maintenance cost.

The tempered glass sheet according to the present invention has a portion that is less strengthened than other portions of the glass sheet. The less reinforced portion is preferably used to provide a mark or character representing the product information of the tempered glass sheet. When the tempered glass sheet is broken, the less strengthened portion retains its original shape or breaks into relatively large pieces. Thus, product information can be easily obtained from the marks or characters in the large fragments of the less reinforced portion.

As described above, the present invention can be usefully used as a forced cooling method and apparatus used in the production of high quality thin tempered glass used in places where lightweight is required, such as automobile glass. In addition, through the present invention it is possible to obtain a tempered glass plate having a part that is less strengthened (parts of weaker strength than the rest of the glass plate), which is to provide a mark or character indicating the product information of the tempered glass sheet. It is particularly useful.

Claims (9)

Characterized in that it comprises a primary cooling step of cooling by blowing cooling air to the glass plate heated to a predetermined temperature, and a secondary cooling step of further cooling by contacting the surface of the glass plate passed through the primary cooling step with a water-containing member moistened with water. Method for producing tempered glass sheet. The method of claim 1, wherein the primary cooling step is to say the thickness t of the glass sheet manufacturing method of strengthening glass sheets, characterized in that the duration no longer than (t ^2/4) seconds.  An air cooling unit that cools the glass plate by blowing cooling air to the surface of the glass plate heated to a predetermined temperature, and installed downstream of the air cooling unit, and has a water-containing member wetted with water, and the water-containing member contacts the surface of the glass plate. Forced cooling apparatus for manufacturing a tempered glass plate, characterized in that consisting of a contact cooling unit that is operated to further cool. 4. The apparatus of claim 3, wherein the contact cooling unit comprises: upper and lower maintenance members made of a material capable of holding a glass plate therebetween, absorbing and storing water, and an upper water supply device for supplying water to the upper water-containing member; Forced cooling apparatus for manufacturing a tempered glass plate comprising a lower water supply device for supplying water to the lower water-containing member. 5. The upper water-repellent member of claim 4, wherein the upper water-containing member is an upper circulation belt which circulates to contact the upper surface of the glass plate, and the lower water-containing member is a lower circulation belt that circulates to contact the lower surface of the glass plate. Comprising an upper water tank that is locked when the belt is circulated along the upper circulation path, the lower water supply device is a forced cooling device for manufacturing a tempered glass sheet characterized in that it comprises a lower water tank that is locked when the lower circulation belt is circulated along the lower circulation path . The upper water supply member according to claim 4, wherein the upper water-containing member is composed of a plurality of upper rolls in contact with the upper surface of the glass plate, the lower water-containing member is composed of a plurality of lower rolls in contact with the lower surface of the glass plate, and the upper water supply device is connected to the upper roll. It is composed of a plurality of water supply pipes respectively associated with the upper rolls to supply water, and a plurality of upper intermediate rolls respectively provided in rolling contact with the upper rolls to adjust the water content of the upper rolls, respectively, installed between the upper rolls and the water supply pipes. The lower water supply holds multiple water tanks installed directly beneath each lower roll to hold water, and adjusts the water content of the lower roll while rolling each lower roll and roll to supply water from the water tank to the lower roll. Forced cooling apparatus for producing tempered glass sheet, characterized in that the contact consists of a plurality of lower intermediate rolls partially submerged in each water tank. 6. The steel sheet for producing tempered glass sheet according to claim 5, wherein at least one of the upper circulation belt and the lower circulation belt has a hole therein so as to avoid contact between the glass plate and the water functioning in the belt to form a less reinforced portion in the glass plate. Chiller. A tempered glass sheet having a less strengthened portion by treating the glass sheet heated to a predetermined temperature in the forced cooling device of claim 7. The tempered glass sheet according to claim 8, wherein the less strengthened portion has a mark or a character representing product information of the tempered glass sheet.