JPS6250416B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for strengthening plate glass, and in particular to a method for strengthening plate glass in which the generation of sharp edges (elongated fragments) is extremely small when glass plates are crushed. When tempered glass is shattered, it appears to be broken into fine pieces almost uniformly, but in some cases long thin pieces called sharp edges may be generated. As automobiles become lighter, tempered glass is becoming thinner, and as tempered glass becomes thinner, sharp edges tend to occur more easily, and measures against sharp edges are becoming more important. To briefly describe the fracture phenomenon of tempered glass, the fragment density (number of fractures per 50 mm square) Fd is a function of Fd = f (σ ₀ , σ), where the stress value σ of the tempered glass and the stress value σ ₀ at the point of fracture start As shown in Figure 1, the fracture of tempered glass is represented by a radial progression from the fracture starting point A, and after a certain distance it branches to form a branching point C. It is crushed into small pieces by repeating the process. Furthermore, sharp edges tend to occur more often when the strengthened glass is fractured at the center than at the edges. Conventionally, in the manufacture of tempered glass that is strengthened by cooling, cooling nozzles are arranged on the cooling nozzle mounting surface of the blast head in a grid pattern in the vertical and horizontal directions or in a staggered pattern in the diagonal direction. A strengthening method in which the blast heads are placed symmetrically over the entire surface of the cooling nozzle mounting surface, and the surface formed by the tip of the air blowing pipe and the surface of the plate glass to be tempered have a different shape. A strengthening method is known in which the distance between the two surfaces is made different so that the cross-sectional area of the air flow path is locally different. However, the strengthening method using cooling elasticization as in the prior art example does not sufficiently increase the degree of strengthening of sheet glass that is being made thinner, nor can it sufficiently reduce the occurrence of sharp edges. The present invention solves the disadvantages of the conventional methods which have not yet been achieved by using only the cooling strengthening method of the present invention, regardless of whether or not the press molding process is interposed between the heating process and the cooling strengthening process. It is a thing,
The sharp edges that tend to occur when the tempered glass breaks from the center can be effectively cooled by cooling the sheet glass in concentric circles outward from the center in a so-called polar coordinate system, and by densely cooling the center of the sheet glass. The present invention was developed based on the fact that the sharp edge can be reduced. That is, the present invention provides a method for strengthening plate glass in which a cooling medium is sprayed onto a glass plate heated above the strain point from cooling nozzles disposed in a pair of blast heads, in which a unique plate glass is strengthened on the cooling nozzle mounting surface of the blast head. The cooling is performed by arranging a point that can be the center of a concentric circle such that there are only points, and radially concentrically outward from the center, and so that the distance between the nozzle installation intervals does not exceed 50 mm. The gist of this paper is a method for strengthening plate glass, which is characterized by the provision of a nozzle for use in glass. In addition, if the glass plate requires curved tempered glass for the purpose of use, the press molding process
After the bending process using the press mold of the invention described in No. 57-226406, the cooling strengthening method of the present invention is carried out to obtain a complementary effect. Here, the plate glass heated above the strain point is, for example, one heated to a temperature of 600 to 700°C. A pair of blast heads can be one with a flat cooling nozzle mounting surface for strengthening flat glass sheets as shown in Figure 2, or one with a convex and concave shape for strengthening curved glass sheets. It may be hot. The cooling medium may be a commonly used cooling medium such as air or water mist, but is not particularly limited to these. On the cooling nozzle mounting surface of the blast head, a point that can be the center of a concentric circle is arranged so that there is only one point, and the nozzle mounting interval is arranged concentrically and radially outward from the center. The cooling nozzles are arranged so that the distance between them does not exceed 50 mm.For example, it is preferable to increase the cooling effect toward the center of the sheet glass to be strengthened, and the distribution density of the cooling nozzles is The height of the cooling nozzle is set higher in the central part, and the distribution gradually expands in the direction of coarseness while repeating the density and density concentrically from the center, and the distance between the installation intervals of the cooling nozzles does not exceed 50 mm. Cooling nozzles are individually arranged, and the arrangement of each nozzle is not in a grid or staggered pattern, but in a radial and random arrangement that repeats spacing and density, spreading concentrically from the center and becoming coarser. Since the interval is set to a distance less than a specific value, it is like a so-called polar coordinate system, and the arrangement formed by the cooling nozzles in the densely distributed part may be circular or elliptical. It may be a spiral shape, a spiral shape, or a polygonal shape. The so-called polar coordinate system is a system that indicates the position of the cooling nozzle by the distance from the center point and the angle between the center point and the half-line between the center point and the half-line that passes through it. It is. In other words, in addition to being concentric, it is radial and has randomness. In addition, it is difficult to suppress the occurrence of sharp edges when the cooling nozzle is arranged in such a way that there are many points that can form concentric centers, such as a grid or staggered arrangement. The only point is to match the position of the crushing start point 3 specified in the crushing test as described later. In this way, by providing the cooling nozzles concentrically outward from the center in a so-called polar coordinate system, a highly strengthened part is formed concentrically on the sheet glass surface corresponding to the cooling nozzle, and the tempered sheet glass is When the material is crushed from the center, the cracks that occur radially as shown in FIG. 1 are dispersed by the above-mentioned high-strength portions, thereby suppressing the occurrence of sharp edges. Additionally, when sheet glass is strengthened, the central area of the sheet glass is usually less likely to be strengthened than the outside.
By arranging the cooling nozzle as described above, even if the temperature of the central area is slightly lower than that of the peripheral area, sufficient cooling can be achieved, and the degree of reinforcement between the central area and the peripheral area can be made uniform, and the sheet glass can be heated evenly. There is no need to try to raise the temperature in the central area of the glass, and the peripheral area is not heated more than necessary, so you can simply heat the plate glass to be tempered with a normal heating device, and the plate glass can be stretched at the hanging part, etc. It is possible to prevent defects from occurring at the front stage. Note that even if the temperature in the central region is higher than that in the peripheral region, the required degree of reinforcement can be obtained. Next, the method for strengthening plate glass of the present invention will be explained based on the drawings. The drawings illustrate one embodiment of the invention. The plate glass 4 is suspended by a hanging tool 5, heated in a heating furnace to a temperature higher than the strain point, for example, 600 to 700°C, and transferred to a cooling strengthening device 6 for strengthening. The cooling reinforcement device 6 is attached to the right side blast head 7.
The left and right blast heads 7 and 8 are provided with pipe members 9 and 10 from a cooling medium supply source behind them to supply cooling medium, and a cooling nozzle mounting surface 12 on the front side has a concentric circle. The cooling nozzles 11 are arranged in a so-called polar coordinate system. The plate glass 4 is moved to the center of the space formed by the left and right blast heads 7 and 8 at equal intervals, and a cooling medium is sprayed from both cooling nozzles 11 to perform the strengthening process. Usually, the blast head is designed to be capable of minute sliding movements such as up and down, left and right, or even in circles. Furthermore, when the plate glass 4 is moved, it is possible that the center of the concentric circle formed by the cooling nozzle coincides with the position of the crushing starting point 3 (the center of the plate glass to be strengthened) specified in the crushing test on the strengthened plate glass. preferable. Furthermore, the arrangement of the cooling nozzle 11 may be circular as shown in FIG. 3, or may be oval as shown in FIG. It may also be spiral-shaped as shown in . These cooling nozzles are arranged in concentric circles in a so-called polar coordinate system, but the distance between the cooling nozzles increases as they go outside the concentric circles, and the distribution becomes too coarse, which may cause problems in uniform reinforcement. If there is, the distance is 50mm, preferably 40mm
The same cooling nozzle as above is additionally installed in the middle so that the cooling nozzle is not exceeded. At that time, if the distance between the cooling nozzles is too short, it will be difficult to discharge the cooling medium that contributed to the reinforcement, which may cause insufficient reinforcement and uneven reinforcement. There is a need. Example 1 A plate glass of 1200 to 700 mm and 3.0 mm thick heated to a temperature of 670 to 680°C is heated to a temperature of 670 to 680°C and has a normal nozzle effective inner diameter by using a strengthening device and a cooling nozzle arrangement as shown in Figs. 2 and 3. Using a cooling nozzle,
The maximum distance between the cooling nozzles is 40 mm and the minimum is 28 mm, the distance between the nozzle tip and the plate glass surface is 30 mm, and the blast head is slid up and down by approximately 40 mm, and is further weathered and strengthened at an air pressure of 2500 mmAq and an air flow rate of 560 Nm ³ /min. I did it. In addition, for comparison with the present invention, strengthening treatment was performed under the same conditions using a strengthening device consisting of a blast head with a conventional staggered cooling nozzle arrangement and a distance between the cooling nozzles of approximately 30 mm. Summer. Table 1 shows the test results. The degree of reinforcement of plate glass is determined by the crushing start point (impact point) of the fracture test for tempered plate glass listed in the BS standard (BS5258).
It is expressed by the number of fractures when crushing in 1, 2, and 3, and the number of sharp edges is expressed when the length of the crushed pieces is 60 mm.
As described above, the length to width ratio was set to be 4 or more. In addition, almost the same numerical values were obtained in the test results according to the JIS standard (JIS R 3212), and the representative values are shown in the table below. In the table, the number of fractures and the number of sharp edges are the numbers at arbitrary positions excluding 20 mm from the periphery of the glass plate and within a radius of 75 mm from the point of impact.

[Table] According to the present invention, cooling nozzles are arranged in a so-called polar coordinate system in concentric circles outward from a central part where only one concentric center point can be taken on the blast head surface. As is clear from Table 1, this makes it possible to significantly reduce the number of shrapnel edges, reduce the difference between the maximum and minimum number of shreds, and improve the cooling ability of the center of the sheet glass. This method has the remarkable effect of producing tempered glass with a uniform degree of reinforcement throughout the glass plate.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the breaking phenomenon of tempered glass. FIG. 2 is a schematic side view showing an air-cooling strengthening device for glass plates used in the practice of the present invention. FIG. 3 is a schematic front view of a nozzle mounting plate showing the nozzle arrangement of the present invention in the air cooling blowout nozzle arrangement of the apparatus shown in FIG. FIGS. 4 and 5 are schematic front views of other embodiments showing the arrangement of air cooling nozzles. 4... Plate glass, 6 ... Cooling strengthening device, 7, 8... Blast head, 11... Cooling nozzle.

Claims (1)

[Claims] 1. In a method for strengthening plate glass, which strengthens plate glass heated above its strain point by spraying a cooling medium from cooling nozzles placed in a pair of blast heads, there is no point on the cooling nozzle mounting surface of the blast head. The cooling nozzles are arranged such that a point that can be the center of a concentric circle is arranged in the center, and the cooling nozzles are arranged concentrically and radially outward from the center, and the distance between the nozzle installation intervals does not exceed 50 mm. A method for strengthening plate glass characterized by: