JPS59227732A - Apparatus for reinforcing glass plate - Google Patents

Abstract

PURPOSE:To provide an apparatus for reinforcing a glass plate, suitable for the high-frequency clapping reinforcement, by attaching a cushioning layer made of conductive fibers to the clamping side of the clapper for clamping a hot glass plate. CONSTITUTION:A hot glass plate 1 is clamped with the clappers 2 to effect the solid-contact quenching, wherein the surface of the clapper contacting to the glass plate is covered with a cushioning layer 3 made of an electrically conductive carbon fiber, etc. The glass plate 1 is cooled from its surface with the clapper 2, and at the same time, only the core part of the plate 1 is heated by imposing high-frequency powder to the glass plate 1, thereby increasing the temperature difference between the core part and the surface parts to effect the reinforcement of the glass plate 1. Since the cushioning layer 3 is made of a conductive material, the temperature of the cushioning layer does not increase in the case of applying high-frequency powder resulting in little loss in the cooling capacity. There is no loss of high-frequency power by the cushioning layer 3.

Description

[Detailed description of the invention] The present invention relates to an improved glass plate strengthening device.

As a method of physically strengthening a glass plate, the glass plate is heated to a temperature above its strain point and below its softening point, and then cooling air is blown onto the surface of the heated glass plate to rapidly cool it. An air-cooled strengthening method that produces high compressive stress in the layer, a liquid-cooled strengthening method that similarly involves immersing a heated glass plate in a cooling liquid and rapidly cooling it, and producing high compressive stress on the surface layer of the glass plate, or a similar method. A glass plate heated to
A wet flapping strengthening method (or solid contact strengthening method) is known in which a glass plate is rapidly cooled by the cooling action of a clapper to generate high compressive stress in the surface layer of the glass plate.

However, when trying to obtain high-strength tempered glass using these various strengthening methods, it is necessary to minimize the temperature difference between the surface layer and the center layer in the thickness direction of the glass plate in the temperature range above the strain point during rapid cooling. It is desirable to heat the glass plate to a high temperature within a range that does not deform it as much as possible so that the glass plate can be attached, but for example, if the glass plate is suspended from a hanger and heated to a high temperature, the suspended part of the glass plate may be heated. There is a disadvantage in that it is not possible to heat the glass to a higher temperature to prevent the disadvantages of drying and hanging marks, and therefore it is difficult to obtain a glass plate with higher strength. Alternatively, if the glass plate is thin,
For example, if the glass plate is less than 3cm thick, the heat capacity of the glass plate is small, so when the glass plate is rapidly cooled, it is difficult to generate a temperature difference between the surface layer and the center layer in the thickness direction of the glass plate. A drawback is that it is difficult to generate a high compressive stress layer in the surface layer and obtain a sufficient degree of reinforcement.

As a method to improve this difficulty and obtain high-strength tempered glass, or as a method to obtain tempered glass that has a sufficient degree of reinforcement even if the glass plate is thin, the method is to suspend the glass between clappers that have a cooling effect. The clapper cools the glass plate from its surface by holding the heated glass plate suspended by hand, and applies high-frequency power to the glass plate to generate a dielectric mainly in the central part of the glass plate in the thickness direction. By heating intensively, the temperature difference between the center and the surface of the glass plate in the thickness direction is further expanded, and high compressive stress is generated in the surface layer of the glass plate, resulting in high-strength tempered glass. A high frequency flapping enhancement method is proposed to produce. According to the darning method, a glass plate heated to a high temperature is sandwiched and supported from both sides by clappers and cooled from the surface side of the glass plate, and when a high frequency is applied to the glass plate, the surface portion of the glass plate is cooled. is a clapper
This cooling lowers the temperature of the surface of the glass plate, so heating due to dielectric loss on the surface of the glass plate is lower than that of the center. Even when it is cooled down, it is still at a high temperature, so the dielectric loss is high and it gets heated even more.If the center gets heated further, the dielectric loss becomes even larger than the surface, so the center gets heated even more. the result,
The surface portion and center portion of the glass plate pass through the strain point temperature of the glass plate with a large temperature difference, and as a result, a high compressive stress can be formed on the surface due to the above-mentioned temperature difference. Moreover, since high-frequency heating can be performed after the center of the glass sheet has been cooled, it is possible to obtain high-strength glass with high compressive stress on the surface by sandwiching the glass sheet between the clappers. Since the temperature of the glass plate before cooling can be kept relatively low, undesirable deformation of the glass plate, such as distortion of the glass plate,
High-strength glass having higher surface compressive stress can be obtained without heating to a high temperature that causes deformations such as warpage, deformation of the hanger portion, and generation of hanger marks.

In the above-mentioned clapper rubbing method, when the glass plate is cooled by direct contact with the clapper, which has a cooling effect, the clapper usually leaves marks, optical distortion occurs, or the cooling effect is too strong and the glass plate is cooled during cooling. Since the glass plate may break, crack, or warp, it is necessary to provide thermal buffering, absorb unevenness on the clapper surface, and equalize the cooling ability of the clapper's contact surface with the glass plate. To ensure this, the surface of the clapper that comes into contact with the glass plate is covered with a buffer layer made of glass fiber.

However, in the above-mentioned high-frequency flapping strengthening method, if glass fiber is used as the buffer material layer of the clapper as described above, the high-frequency flapping strengthening method is difficult to achieve because of high-frequency dielectric heating of the glass plate, which is a poor conductor. If the buffer layer is made of glass fiber, the electric field will be applied to the buffer material as well as the glass plate, since glass fiber is also a poor conductor.
As a result, there are disadvantages in that the temperature of the buffer material layer rises and the cooling capacity decreases, and high frequency power is consumed by the buffer layer, resulting in a decrease in the effectiveness of high frequency heating.

The present invention was invented as a result of studies aimed at providing a glass plate strengthening device suitable for the high-frequency flapping strengthening method that does not have such drawbacks. The glass plate is cooled from the surface by the clapper with the glass plate sandwiched between them, and high frequency power is applied to the glass plate to intensively heat the central part of the glass plate in the thickness direction. In a device that strengthens a glass plate by further increasing the temperature difference between the center and the surface in the thickness direction, the side of the clapper that clamps the glass plate is covered with a cushioning layer made of fibers with good conductivity. The present invention relates to a glass plate strengthening device characterized by a covering.

The present invention will be explained in more detail below.

FIG. 1 shows a schematic diagram of an example of the apparatus of the present invention, where 2 is a glass plate, and 2 is a clapper 23 for contact cooling by sandwiching the glass plate 1' from both sides. A 1TL damping material layer selected from a material having good electrical conductivity is formed on the contact surface, 4 is a fluid pressure cylinder, and 5 is a hanger for hanging the glass plate. This clapper 2 is moved forward and backward relative to the glass plate 1 by a fluid pressure cylinder 4.
The clapper 2 is moved forward to sandwich the glass temporary moved to the clapper 2 inch, and a predetermined contact pressure is applied to the glass plate to further increase the heat of the glass plate by heat conduction between the clapper 2 and the glass plate 1. It is designed to be heated and cooled. After a predetermined cooling time has elapsed, the clapper 2 is moved back and the temporary glass 1 is taken out from between the clappers 2.

In the present invention, the clapper that sandwiches the glass plate from both sides and applies a predetermined contact pressure to remove heat from the glass plate by heat conduction to cool the glass plate is made of a material with good thermal conductivity, such as copper or gelafert. is used. In order to enhance the cooling effect, a refrigerant such as wood is passed through the clapper as necessary to cool the clapper. This clapper is
Depending on the shape of the glass plate to be strengthened, those having a predetermined planar or curved contact surface with the glass plate are used.

In the present invention, when a glass plate is brought into contact with and cooled by a clapper having a cooling effect, the clapper's hallmark, optical distortion, occurs on the glass plate.

In order to prevent cracks, breakage, warping, unevenness in stress distribution, etc., a buffer layer made of fibers with good conductivity is selected as the buffer layer provided on the side of the clapper holding the glass plate. In addition to being a good conductor, the buffer material layer made of fibers of a good conductor is heat resistant enough to withstand even when it comes into contact with a glass plate heated to 500°C to 700°C.
The so-called cushioning ability absorbs the unevenness of the surface of the glass plate, which prevents too rapid cooling that can cause damage to the glass plate, while also ensuring sufficient heat transfer and cooling when the glass plate is sandwiched between clappers that have cooling ability. Those that have an effect are selected. From this point of view, carbon fibers, stainless steel fibers, silicon carbide fibers, or a combination thereof are optimally selected as good conductor fibers for the cushioning material layer. Among them, carbon fiber has high heat resistance and a specific resistance of 100.
(μΩ-cm) and has a thermal conductivity of 0.250.
(kcal/m hr'c) and has excellent heat transfer ability, so the cooling capacity is also high, and the expansion coefficient is 3.4 (XIO'/℃).
) is smaller than other fibers, so it is the best because it does not cause the fibers to expand due to the heat received from the glass plate during flapping, causing unevenness on the surface of the cushioning material and creating an uneven pattern on the glass. However, stainless steel fiber is also a good conductor with a specific resistance of 72 (μΩ-CIl+), a high thermal conductivity of 0.135 (kcal/mhr'C), sufficient heat resistance, and is easily available. So it is practical. On the other hand, glass fiber has a specific resistance of 2X]017(μΩ-
Gill) and a poor conductor, making it unsuitable for use as a buffer material in the high frequency flapping high frequency flapping method. Silica fibers are also poor conductors and, like glass fibers, are unsuitable.

As for the thickness of such a buffer material layer, it is preferable that it is thicker in order to obtain a cushioning effect that absorbs unevenness on the surface of the clapper and an effect that prevents overcooling that can cause damage to the glass plate. If the thickness of the buffer material layer becomes too thick, the thermal conductivity will decrease and the cooling capacity will decrease, and the heat received from the glass plate will also cause the fibers of the B tube material to expand, causing them to become sandwiched between the glass plate and the clapper. An appropriate thickness is selected because the glass plate may swell and the surface may become uneven, resulting in the pattern of the cushioning layer on the glass plate. For example, the practical thickness of the buffer material layer is about 0.1 to 21 TI]I.

To strengthen a glass plate using the apparatus of the present invention, the glass plate is suspended, for example, by a hanger, placed in a power-heating furnace, and heated to a predetermined temperature. This heating of the glass plate is usually done at a temperature of 300°C to increase its dielectric loss to the extent that the glass plate generates heat due to the application of high frequency power based on its temperature characteristics.
It is sufficient to heat the glass plate to a temperature of 550°C to 680°C, but it is particularly preferable to heat the glass plate to about 550°C to 680°C so that sufficient rapid cooling of the glass plate, efficient high-frequency heating, and shortening of the time for the strengthening treatment can be achieved. .

The heated glass plate is moved between two clappers having a cooling effect, so that the clappers are brought into pressure contact with the glass plate. Next, high-frequency power is applied to the glass plate, and while the surface portion of the glass plate is cooled by the clapper, the central portion of the glass plate in the thickness direction is mainly heated by high-frequency dielectric heating. When the center of the glass plate is heated to a predetermined temperature and there is a sufficient temperature difference between the surface and center of the glass plate, the application of high frequency voltage is stopped and the surface of the glass plate is cooled by the clapper. This continues for a predetermined period of time, and then the clappers are pulled apart and the glass plate is taken out from between the clappers.

To apply high-frequency power to the glass plate, use the contact surface of the clapper with the glass plate or the H cylinder material layer, which is a good conductor, as an electrode, or provide a separate electrode on the surface that contacts the glass plate, and use this electrode. A method of connecting lead wires from a high frequency oscillator so that high frequency power from the high frequency oscillator is applied from both sides of the glass plate sandwiched between the clappers, or providing electrodes on opposite end faces of the glass plate, Alternatively, a flame burner electrode is used and a lead wire from a high frequency oscillator is connected to this electrode so that high frequency power from the high frequency oscillator is applied from opposite sides of the glass plate sandwiched between the clappers.

The high-frequency current used in the present invention can have a wide range of frequencies, but from practical aspects such as workability and high-frequency heating effects, a high-frequency current in the range of several tens of kilohertz to several tens of MHz is desirable. Further, the application time of the selected high-frequency power to the glass plate is appropriately determined depending on the composition of the glass plate to be processed, the plate thickness, the plate temperature, two frequencies, the heating temperature, and other working conditions. The frequency currently approved for industrial dielectric heating equipment in Japan is 13.58M.
11z, 27.12Ml1z, 40.68M1! For example, 40.68Ml1z (wavelength; 7.3m
) A high-frequency current is applied between the electrodes at a frequency of will occur. In addition, as the frequency becomes higher, the wavelength becomes shorter, which tends to cause voltage bias to occur on the electrodes, which tends to be disadvantageous in uniformly heating a large glass plate. Therefore, in high-frequency heating when tempering glass sheets of normal size used for automobiles, mine road vehicles, and aircraft window glasses, a high-frequency current of 13.58 MIIz with little bias in the voltage on the electrodes is required. It is currently practical to use However, depending on the size of the glass plate or by expanding the frequency of industrially usable high-frequency power, it is of course possible to use high-frequency currents having other frequencies without being limited to stiffness.

Cooling of the glass plate by solid contact with the glass plate sandwiched between clappers is usually carried out prior to the start of high-frequency heating or at the same time as the start of high-frequency heating. This is carried out until the end of heating or for a predetermined time after the end of high-frequency heating.

This cools the surface of the glass plate, while heating the center of the glass plate to create sufficient surface compressive stress.
For example, there is a temperature difference of up to 80 kg/c/cm or more between the surface and center of a glass plate where a compressive stress of 900 kg/c/ or more can be obtained.
℃ to 350°C, more preferably about 50°C to 350°C. Alternatively, cooling of the glass plate by means of a clapper can be performed subsequent to the start of high-frequency heating.

As described above, according to the present invention, since the buffer layer covering the side of the clapper in contact with the glass plate is made of a good conductor, when high-frequency power is applied, no electric field is applied to the buffer layer. As a result, the temperature of the buffer layer does not rise, there is almost no decrease in cooling ability, high frequency power is not consumed by the buffer layer, and there is almost no decrease in the efficiency of high frequency heating.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a glass temporary strengthening device according to a specific example of the present invention. 1. Glass plate, 2: Cratsper, 3: Cushioning material layer 4: Fluid pressure cylinder, 5: Hanging hand

Claims (3)

[Claims] (1) A heated glass plate is sandwiched between clappers that have a cooling effect, and the clapper cools the glass plate from its surface. In a device that strengthens a glass plate by further expanding the temperature difference between the center part and the surface part in the thickness direction of the glass plate by intensively heating the center part, the side of the clapper that clamps the glass plate A device for reinforcing a glass plate, characterized in that the glass plate is covered with a buffer material layer made of fibers with good conductivity. (2) The device for reinforcing a glass plate according to claim 1, wherein the buffer material layer made of fibers with good conductivity is made of carbon fibers. (3) The device for reinforcing a glass plate according to claim 1, wherein the buffer material layer made of fibers with good conductivity is made of stainless steel fibers.