JPS6247819B2 - - 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 forms a branch point C and branches off, and this phenomenon is repeated. It is crushed into small pieces. 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 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, and a strengthening method in which air nozzles are arranged on a hexagonal outline are known. However, the strengthening method using cooling strengthening as in the above-mentioned known examples 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. Therefore, as described in Japanese Patent Application No. 58-71417, irrespective of the fact that the press molding process is not interposed between the heating process and the cooling strengthening process, the polar The applicant discovered and previously proposed that the sharp edge can be effectively reduced by arranging a cooling nozzle in the blast head so as to cool the central part of the sheet glass closely. It eliminates the drawbacks of the previous unachieved results. However, the method disclosed in Japanese Patent Application No. 58-71417 requires complete remodeling of the blast head, which is wasteful both in terms of time and economy. Therefore, various studies were conducted, and even on the surface of the blast head, which has the existing grid-like orthogonal system or staggered oblique cooling air nozzle arrangement, By arranging a plurality of baffle plate members concentrically and changing the flow of cooling air, it is possible to easily change the flow of cooling air.
It was discovered that almost the same effect as No. 71417 can be obtained, and the present invention was completed. 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 cooling nozzle mounting surface of the blast head is heated to a temperature above the surface of the glass plate. The gist of this method is to rapidly cool the glass plate by arranging a plurality of baffle plate members concentrically outward from the center of the glass plate, and the method is characterized by a method of strengthening a glass plate by arranging a plurality of baffle plate members concentrically outward from the center of the glass plate. By changing the stress distribution within the plate glass, the crack propagation phenomenon changes, and in the event of a crack, the number of shear edges can be greatly reduced, and it is also extremely effective in terms of equipment, time, and economy. This is what I did. Here, arranging a plurality of baffle plate members concentrically outward from the center means, for example, a baffle plate member made of a part of a curved line such as a circle, an ellipse, a V-shape, etc., or a plate-like piece. It is not necessary to attach the plate members continuously to the entire inner surface of the blast head; simply having multiple plate members dotted concentrically can prevent the occurrence of sharp edges, especially in the center of the plate glass (BS Set up two large and small circles centered on the crushing starting point 3 of the crushing test for tempered plate glass according to standards, etc., and install 2 to 4 cooling air nozzles so that the width created by the difference is, for example, about 200 to 300 mm. It is sufficient to arrange a plurality of baffle plate members at a ratio of one baffle plate member to each other. In addition, the size of the baffle plate member is preferably about 50 mm in width and 50 mm in height, but in particular, it is effective to have a height that is as close to the plate glass surface as possible, and at least cools the plate. must protrude from the tip of the air nozzle. However, the size and arrangement density of the baffle plate members vary depending on the shape and size of the plate glass to be strengthened, sliding conditions, arrangement of cooling air nozzles, etc. Furthermore, concentric circles may be circular or elliptical, spiral, or polygonal, and the center and a half-line passing through it may be referred to as concentric circles. Alternatively, the position of an arbitrary point on a concentric circle may be expressed by the distance from the center and an angle forming a half line with the center, that is, it may be radial. Generally, it is preferable to increase the cooling effect toward the center of the glass sheet to be tempered, and to increase the distribution density of the plurality of baffle plate members toward the center,
The plurality of baffle plate members are arranged so that the distribution gradually expands in the direction of coarseness while repeating concentrically dense and dense patterns from the center, and furthermore, the distribution spreads coarsely toward the peripheral area with randomness. But it's good. In this way, by providing a plurality of baffle plate members concentrically outward from the center, highly reinforced portions are also formed concentrically on the plate glass surface corresponding to the baffle plate members, and the tempered plate glass When the material is crushed from the center, the cracks generated radially as shown in FIG. 1 are dispersed by the above-mentioned high-strength portions, and the occurrence of sharp edges is suppressed. Additionally, when sheet glass is strengthened, it is usually difficult to strengthen the central area of the sheet glass compared to the outside.
By arranging multiple baffle plate members as described above, even if the temperature in the central area is somewhat lower than that in the surrounding area,
Sufficient cooling is achieved, and the degree of reinforcement between the central and peripheral areas can be made uniform. Also, there is no need to try to raise the temperature of the central area of the sheet glass, and the peripheral area is not heated more than necessary. It is sufficient to simply heat the plate glass to be strengthened using a normal heating device, and it is possible to prevent the occurrence of defects at the front stage, such as the plate glass being stretched at the hanging portion. 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. In addition, if the glass plate requires curved tempered glass for the purpose of use, bending using the press mold of the invention described in Japanese Patent Application No. 1983-226406, which was also filed earlier by the present applicant, can be performed in the press molding process. By subsequently implementing the cooling enhancement method of the present invention, a synergistic effect can be achieved. In addition, the special request was made in 1982.
Even if the cooling reinforcement method of the present invention is applied to the blast head surface of No. 71417, similar effects can be obtained. By the way, plate glass heated above the strain point is, for example, glass heated to a temperature of 600 to 700°C. The pair of blast heads are shown in Figure 2 and have a flat cooling nozzle mounting surface for strengthening flat glass sheets, and are made of convex and concave shapes 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. 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.
and a left blast head 8, the left and right blast heads 7 and 8 are supplied with a cooling medium from a cooling medium supply source with pipe members 9 and 10 at the back, and a cooling nozzle mounting surface 12 on the front side is provided with a cooling medium. A plurality of baffle plate members 13 are arranged concentrically with the cooling nozzle 11. 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.
In addition, the plate glass 4 is moved so that the center of the concentric circle formed by the baffle plate member 13 coincides with the position of the crushing start point 3 (center part B of the plate glass to be strengthened) specified in the crushing test with the strengthened plate glass. It is preferable to do so. Furthermore, without being limited to the arrangement of the cooling nozzle 11, the baffle plate member 13 may have a circular shape as shown in FIG. 3, or may have an elliptical shape or a spiral shape. The baffle plate member 13 may be installed in a position close to or in close contact with the cooling air nozzle as shown in FIG. 3, or in close contact with the cooling air nozzle as shown in FIG. It may also be attached to the middle part. A plurality of these aforementioned baffle plate members are arranged in a concentric circle, but the distance between them increases as they go outside the concentric circle, and the distribution becomes too coarse, which may cause problems in uniform reinforcement. In that case, the same baffle plate member as above is additionally provided in the middle.
At this time, if the distance between the baffle plate members is too short, the cooling medium that contributed to the reinforcement will be difficult to discharge, causing insufficient reinforcement and uneven reinforcement, so the size of the baffle plate members should also be taken into consideration. It is necessary to arrange it appropriately. FIG. 4 shows the baffle plate member 13 in FIG.
This figure shows an example of the installation situation and the positional relationship between the glass plate to be strengthened 4, the cooling nozzle 11, and the baffle plate member, in which the cooling air flows in a semicircular shape facing in the direction where the baffle plate member is not present, that is, toward the center. By discharging it to the outside while expanding in a shape, it is possible to obtain the effect of causing a change in the crack growth phenomenon in that part. FIG. 6 shows that even if the baffle plate member 13 is placed in an area A (indicated by diagonal lines) formed by two concentric circles centered on the blast head inner surface 12 and the center B of the glass plate 4 to be tempered, the sharp edge can be sufficiently reduced. It does not necessarily have to be distributed throughout the blast head inner surface 12. Example 1 A plate glass of 1200 x 700 mm and 3.0 mm thick heated to a temperature of 670 to 680°C was heated using a strengthening device as shown in Figs. 2 and 3 and a plurality of baffle plate members of size 50 mm x 50 mm. Due to the arrangement, a cooling nozzle with a normal nozzle effective inner diameter is used, the distance between the cooling nozzles is 30 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. Air pressure 2500mmAq, air volume 560Nm ³ /
Air cooling reinforcement treatment was performed at min. 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 grid-like cooling nozzle arrangement and a distance between the cooling nozzles of approximately 30 mm. . 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, which is listed in the BS standard (BS5282).
It is expressed as 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 mentioned above, the length to width ratio was set to be 4 or more. In addition, almost the same values were obtained in the test results according to the JIS standard (JISR3212), but the table below shows the representative values. In the table, the number of fractures and the number of sharp edges are the numbers at any position excluding the area 20 mm from the periphery of the plate glass and within a radius of 75 mm from the point of impact.

[Table] According to the present invention, by disposing a plurality of baffle plate members concentrically outward from the center of the blast head, as is clear from Table 1, the number of sharp edges can be extremely reduced. It is possible,
It also improves the cooling ability of the center of the glass plate, and 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 blast head showing the arrangement of a plurality of baffle plate members of the present invention, in which a plurality of baffle plate members are attached to the air cooling nozzle of the apparatus shown in FIG. 2. FIG. 4 is an enlarged partial side view of the cooling nozzle shown in FIG. 3 with a baffle plate member attached thereto and set on a plate glass to be tempered. 5 and 6 are schematic front views of another embodiment in which the baffle plate member of the present invention is disposed on the blast head surface. 4...Plate glass, 6 ...Cooling reinforcement device, 7,8
... Blast head, 11 ... Cooling nozzle, 1
2...Blast head inner surface, 13...Baffle plate member.

Claims (1)

[Claims] 1. In a method for strengthening plate glass that is heated to a strain point or higher by spraying a cooling medium from cooling nozzles arranged in a pair of blast heads to strengthen the plate glass, a cooling nozzle mounting surface of the blast head is heated from the center of the surface. 1. A method for strengthening plate glass, which comprises arranging a plurality of baffle plate members concentrically outward and rapidly cooling the plate glass.