JPS6152087B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing glass products with small thickness differences from plate glass by vacuum forming.

In general, glass molding by vacuum forming has the disadvantage that the thickness of the molded product is less uniform when compared to other molding methods, such as press molding or centrifugal molding of molten glass. Particularly in deep pattern processing, local thinning is noticeable in areas where the curvature of the molded product is large. The molded product having the thin wall portion is easily damaged when a load is applied to its inner and outer surfaces, especially when an impact force is applied to the molded product. Due to the above drawbacks, the conventional method was to increase the thickness of the plate glass used.
This method increases the weight of the molded product, which is not preferable in terms of weight reduction.

The present invention was made in order to eliminate the above-mentioned drawbacks, and the present invention provides a method for producing a glass molded product by heating a plate glass while being placed on a mold, and then reducing the pressure inside the mold. In this step, the plate glass on the mold and a heat source are provided facing each other, and a heat shielding material is provided between the heat source and a portion of the plate glass corresponding to a portion of the glass molded product having a large curvature. After heating the part of the plate glass corresponding to the large curvature part of the glass molded product to a lower temperature than the other part of the plate glass corresponding to the small curvature part, the pressure inside the mold is reduced. This is a method of manufacturing a glass molded product in which the difference in thickness is reduced by vacuum forming the sheet glass.

In the present invention, the sheet glass is heated at a molding temperature of 150° C. from the softening point to 150° below the softening point.
℃ up to a high temperature (for ordinary plate glass)
740°C to 790°C), and then heat the portion of the plate glass corresponding to the large curvature of the glass molded article to a temperature lower than the above temperature, for example 30°C to 200°C.
It is customary to heat to a temperature lower than 50°C, preferably 50°C to 100°C. This temperature difference is preferably the minimum temperature difference that can reduce the difference in thickness of the glass molded product. If the temperature difference applied to the plate glass is too large, the thickness of the glass molded product will locally increase, and the perspective distortion of the glass molded product will worsen. In this way, in order to heat the part of the plate glass corresponding to the large curvature part of the glass molded product to a lower temperature than the other part of the plate glass corresponding to the small curvature part, the plate glass and the heating source are heated. This is accomplished by arranging the glass sheets facing each other and providing a heat shield between the heating source and the portion of the glass sheet corresponding to the large curvature of the glass molded article. The heat shielding material provided at the intermediate position between the plate glass and the heating source may be made of alumina refractory, magnesia refractory, zirconia refractory, heat-resistant ceramic such as alumina, magnesia, or zirconia, or asbestos, refracted leaf iver, etc. A sheet of inorganic fiber material, ferritic heat-resistant steel, austenitic heat-resistant steel, heat-resistant cast iron, titanium alloy, chromium-based alloy, tungsten-based alloy, or tungsten can be used. Furthermore, a thin layer of gold, silver, platinum, copper, aluminum, or the like can be used as a heat shielding material placed on the glass plate surface to shield radiation from the heating source.

However, in this case, the above-mentioned shielding material will be baked into the plate glass, so placing the shielding material on top of the plate glass is recommended only if the baked-in covering material is not a problem or if the molded product is subjected to post-processing such as coloring. This can be used to hide objects.

The present invention heats the part of the plate glass corresponding to the large curvature part of the glass molded article to a lower temperature than the other part of the plate glass corresponding to the small curvature part, so that when the plate glass is formed, The part corresponding to the large curvature of the glass molded product, which is subjected to a large tensile force, has a higher viscosity than other parts, and the elongation of the plate glass in this part can be suppressed, so the wall thickness of the final glass molded product can be reduced. The difference can be made small.

The present invention is particularly preferably used in a vacuum forming method in which the surface area of the final glass molded product is 1.5 times or more the surface area of the plate glass before forming.

An embodiment of the present invention will be described below based on the drawings.

FIG. 1 shows a schematic diagram of a vacuum forming apparatus used in the method for manufacturing a glass molded article according to the present invention, and the plate glass 5 is heated in a known glass preheating furnace at a temperature slightly lower than the softening point, for example, about 550°C. This preheated plate glass 5 is placed on a mold 6 that has been previously heated to approximately the same temperature as the preheating temperature of the plate glass, and its peripheral portion is pressed by a presser frame 4. . Like the mold 6, the presser frame 4 is also preheated to approximately the same temperature as the plate glass 5.
Thereafter, the plate glass 5 is heated by the heat source 1 located above the mold 6. The heating source 1 uses a resistive heating element 2 wound into a coil, and is controlled by a power source (not shown). A stainless steel plate 3 is installed as a heat insulating material between the heating source 1 and the glass plate 5 using an appropriate supporting method. These serve to block radiation from the heating source and locally suppress the temperature rise in the glass plate 5. The shield 3 is installed above the portion of the glass sheet 5 that corresponds to the portion 10 that has a large curvature after molding. plate glass 5
is heated under the heating source 1 and the shield 3, and has a temperature distribution of 730°C in the portion of the plate glass that has a large curvature after molding and 800°C in other parts.

The plate glass 5 heated with an appropriate temperature distribution to the above-mentioned moldable temperature is placed in a mold 6 by vacuum force.
It is vacuum molded to fit the shape. That is, by opening the vacuum valve 9 provided at the bottom of the mold 6, the air between the plate glass 5 and the mold 6 is exhausted through the suction hole 7 and the suction chamber 8 to a vacuum source (not shown). . As a result, the plate glass 5, which has been heated to a moldable temperature range with an appropriate temperature distribution, is adsorbed and molded along the mold 6. When the plate glass 5 is adsorbed and formed along the mold 6 by vacuum force, the portion of the plate glass 5 that is heated to a relatively low temperature is kept from elongating to a smaller extent than other portions. As a result, the portion heated to a relatively low temperature elongates less than when the plate glass 5 is heated uniformly, and the thickness of that portion increases. After the glass molded product formed as described above is cooled to a temperature at which it will not deform, it is removed from the mold 6 and then transferred to a slow cooling furnace (not shown). After the molded product has been sufficiently de-strained in the slow cooling furnace, it is then subjected to post-processing such as coloring. As described above, by using the heating method for plate glass according to the present invention in the deep drawing process of plate glass using the vacuum forming method, it is possible to increase the thickness of the thin part of the molded product, which has traditionally been weak in terms of strength. It has now become possible to obtain a glass molded product that is sufficiently usable without increasing its weight. Heat source 1 for heating plate glass 5 in the above embodiment
Although a coiled resistance heating element is used, it is also possible to use a heating source such as a sheet heating element or an infrared heater.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a vacuum forming apparatus for carrying out the method of manufacturing a glass molded article according to the present invention. 1: Heat source, 3: Shielding body, 5: Plate glass, 6:
Molding mold, 8: Suction chamber.

Claims (1)

[Claims] 1. A method for manufacturing a glass molded product by heating a plate glass while placed on a mold, and then reducing the pressure inside the mold, in which the plate glass on the mold and a heating source are provided facing each other, By providing a heat shielding material between the heat source and the portion of the glass plate corresponding to the portion of the glass molded product that has a large curvature, the portion of the plate glass that corresponds to the portion of the glass molded product that has a large curvature can be heated. is heated to a lower temperature than other parts of the plate glass corresponding to the portion with small curvature, and then the pressure inside the mold is reduced to produce a glass molded product with a reduced thickness difference by vacuum forming the plate glass. how to.