JPS6343327B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) 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 plate glass is crushed. 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. In other words, various laws and regulations regarding the breaking of tempered glass have been established from the perspective of the safety of car drivers and passengers, such as JIS standards, British standards, etc.
There are BS5282, European Economic Community (EEC) standards, etc., which limit the maximum and minimum number of fragments within a 5cm x 5cm area to a certain range, and require long and pointed ends. It must not contain elongated fragments called splines whose length exceeds a predetermined value, and the maximum area of each fragment is also determined. The present invention provides a tempered sheet glass that can prevent the occurrence of sharp edges and also passes the above-mentioned standards, and is a strengthening method that is widely used in manufacturing tempered sheet glass for automobiles, buildings, etc. as well as automobile window glass. It is related to. (Prior art) Conventionally, it has been difficult to strengthen thin glass to meet the above-mentioned standards, especially when the size of thin glass with a thickness of 3.5 mm or less increases.
The difficulty increases as the size exceeds 1100mm x 500mm.
It has been nearly impossible to obtain a tempered plate glass that meets the above standards using an air strengthening method. Therefore, several strengthening methods have been proposed that attempt to overcome the above-mentioned standards by appropriately arranging regions where the average tensile stress is slightly larger than other parts and regions where the average tensile stress is smaller than other parts. For example, in Japanese Patent Application Laid-Open No. 52-121620, a large number of regular quenching jets are blown onto both sides of a glass sheet of about 3 mm that has been heated to near its softening point, and the conventional nozzle position, jet amount, etc. It is possible to form a region with a large degree of reinforcement through adjustment, and also to slide the jet nozzle parallel to the glass surface a distance equal to the distance between adjacent nozzles, to slide it circularly with an appropriate radius, or to keep the nozzle stationary. By placing it in the area, a region with a low reinforcement degree and an intermediate region with a reinforcement degree are appropriately scattered adjacent to the region with a high reinforcement degree, and the distance between the centers of such adjacent areas is in the range of 15 to 30 mm. A method of manufacturing a side or rear window glass for an automobile is disclosed. Also, JP-A-54-33515, JP-A-54
In JP-A-33516 and JP-A-54-33517, gas supply holes, gas exhaust holes, gas supply nozzles, etc. are arranged in an orthogonal grid pattern, and the nozzles are arranged slightly in the forward direction of the glass plate. In addition, Japanese Patent Application Laid-Open No. 54-33515 discloses that a glass plate heated to a high temperature is advanced in a quenching gas, and then A strengthening method for obtaining a strengthened curved glass sheet by stopping the glass sheet for a predetermined period of time and allowing cold gas to flow in a specific direction from a gas supply hole to cool a local area of the glass sheet was disclosed in Japanese Patent Laid-Open No.
Japanese Patent Laid-Open No. 54-33517 discloses a method for obtaining ladder-shaped tempered glass for side windows of automobiles by flowing a localized gas jet directed at the top surface of a glass plate, and a method for manufacturing the same. The publication discloses a method for obtaining and strengthening side and rear window glass for motor vehicles by repeated pulsations related to the forward speed of the glass pane. On the other hand, the present applicant previously disclosed in Japanese Patent Application No. 71417/1983 that cooling nozzles on the blast head surface are arranged in a polar coordinate system concentrically outward from the center of the surface for rapid cooling. We are proposing a method for strengthening sheet glass. (Problem to be solved by the invention) However, the above-mentioned Japanese Patent Application Laid-Open No.
In Publications No. 121620 to JP-A-54-33517,
It belongs to the conventional arrangement of cooling nozzles arranged vertically and horizontally in a lattice pattern or diagonally in a staggered manner to strengthen the wind cooling of the blast head, and is irrational when considered from the crack development mechanism. .
In other words, it is known that cracks develop in a direction perpendicular to the principal stress (σ ₁ ), but in orthogonal systems, σ ₁ generally becomes too large in a certain region, which tends to result in frequent occurrence of sharp edge-like cracks. be. Furthermore, there are disadvantages in that the difference between the maximum and minimum number of fractures is large, and the maximum area of the fractured pieces tends to exceed the above-mentioned standard. Therefore, although attempts are made to solve this problem by using various auxiliary means, the effects may vary depending on the shape and length of the glass plate, and various requirements must be selected when implementing such measures. is necessary. Furthermore, the above-mentioned proposal of the present applicant can significantly reduce the number of shrapnel by arranging concentric cooling nozzles, which is different from the conventional one. However, there is a further demand for a product that can meet the standards and be produced reliably and efficiently even under more severe conditions. (Means for Solving the Problems) The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a method for strengthening plate glass that can fully meet the conventional demands. That is, in 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, the cooling nozzle mounting surface of the blast head is heated at the center of the surface. Cooling nozzles are arranged in concentric circles facing outward, and the cooling nozzles other than the center are inclined at an angle of 3 to 45 degrees in the tangential direction of the concentric circles with respect to the blast head surface. By spraying the cooling medium at a specific angle in the tangential direction of the concentric circles, a highly strengthened part is formed in a concentric circle on the plate glass surface corresponding to the cooling nozzle, The value of small principal stress can be increased to some extent,
The value of the relatively large principal stress can be reduced, a unique stress field will not occur, and the occurrence of sharp edges can be prevented. In this case, regarding the inclination of the cooling nozzles arranged concentrically on the blast head surface, the angle θ with respect to the vertical axis on the surface is 3 to 45 degrees, preferably 5 to 25 degrees. If it is smaller than 3°,
If the angle loses its effect and becomes larger than 45 degrees, the cooling ability of the refrigerant will be extremely reduced. The preferable angle of 5 to 25 degrees is due to the fact that manufacturing stability is remarkable. In addition, the distances R and S between each cooling nozzle are not particularly determined, and may vary depending on the size, thickness, and other conditions of the sheet glass, but preferably R is 20 to 40 mm and S is 10 mm. ~30mm
It is. In other words, these values are determined by the distance between the centers of most of the principal stresses in adjacent areas, the allowable length of the sharp edge in each of the above standards, and the cooling capacity of the cooling medium and cooling nozzle, etc. Particularly below the lower limit, after the cooling medium undergoes heat exchange, the medium whose temperature has risen will be insufficiently exhausted, resulting in a decrease in cooling performance. Furthermore, when sheet glass is strengthened, it is usually difficult to strengthen the central region of the sheet glass compared to the outside, but by arranging the cooling nozzle as described above, even if the temperature of the central region is somewhat lower than the surrounding region, 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. 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. The arrangement formed by the cooling nozzle on the blast head surface may be circular, elliptical, spiral, or polygonal. good. It is preferable that the directions of inclination of the cooling nozzles on the pair of blast head surfaces are symmetrical, but the invention is not necessarily limited to this. In addition, if the glass plate requires curved tempered glass for the purpose of use, after bending with the press die of the invention described in Japanese Patent Application No. 57-226406 filed by the present applicant etc. in the press die forming process, By implementing the cooling enhancement method of the present invention in combination, a synergistic effect can be achieved. Furthermore, the same effect can be obtained even if the method is combined with the method of installing a baffle plate member, which is described in Japanese Patent Application No. 58-214173 filed separately by the present applicant. 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. A cooling nozzle 11 having a tilted shape is disposed. 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 concentrically arranged in a polar coordinate system, but the distance between the cooling nozzles increases as you go outside the concentric circle, and the distribution becomes too coarse, which may cause problems for uniform reinforcement. In some cases, the same cooling nozzle as above is additionally arranged in the middle so that the distance does not exceed 45 mm, preferably 35 mm. 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 strengthening, which will cause insufficient strengthening and uneven strengthening, so it is necessary to consider the nozzle diameter and arrange it appropriately. There is. Of course, as described above, the cooling nozzles may be arranged at equal intervals. FIG. 6 shows a conventional blast head in which cooling nozzles are arranged diagonally in a bird-like pattern on the cooling nozzle mounting surface of the blast head. (Examples) Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Example A plate glass of 1200 x 700 mm and 3.0 mm thick heated to a temperature of 670 to 680°C was cooled with a normal nozzle effective inner diameter using the cooling nozzle arrangement and reinforcement device as shown in Figures 1 and 2. using a nozzle for
The distance between the cooling nozzles is 30 mm for R and approximately 21 mm for S.
The inclination of the nozzle is set at an angle θ of 5 degrees in the tangential direction of the concentric circles, the distance between the nozzle tip 13 and the glass surface is 30 mm, the blast head is slid up and down by about 40 mm, and the air pressure is 2500, 2300, and 2100 mmAq. ,
Examples 1 to 4 in Table 1 were subjected to air cooling reinforcement treatment at an air flow rate of 560 Nm ³ /min. Comparative Example For comparison with the present invention, an ordinary conventional type of bird-shaped cooling nozzle arrangement as shown in FIG.
Comparative Examples 5 to 7 in Table 1 were strengthened using a strengthening device consisting of a blast head with a distance between cooling nozzles of r = 24 mm and s = 25 mm under the same conditions. In addition, the patent application filed earlier by the applicant in 1982-
Strengthening treatment was carried out using the strengthening method described in No. 71417, in which the cooling nozzles on the blast head surface were arranged concentrically in a polar coordinate system outward from the center of the surface, with other conditions being the same. are Comparative Examples 8 to 10 in Table 1. 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 crushed at 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 similar values were obtained in the test results according to the JIS standard (JIS R3212) and the EEC standard, 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] (Effects of the Invention) As is clear from the foregoing, according to the present invention, cooling nozzles are disposed concentrically outward from the center of the blast head, and the cooling nozzles are As it is clear from Table 1, the glass plate is strengthened by making the parts other than the center inclined at 3 to 45 degrees in the tangent direction of the concentric circle to the blast head surface and rapidly cooling the glass plate. When doing so, it is possible to prevent the occurrence of sharp edges, and also to further reduce the difference between the maximum and minimum values in the number of fractures, resulting in a tempered glass with a uniform degree of reinforcement throughout the glass sheet.
This makes it even safer. In other words, not only JIS standards and BS standards, but also EEC
It is possible to obtain safety glass for automobiles, etc. that passes standards and other regulations, and it also has many industrial benefits as it can reduce the cooling air pressure during its manufacture. It has a significant effect.

[Brief explanation of the drawing]

1 is a schematic front view and a partial side 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. 2. FIG. FIG. 2 is a schematic side view showing an air-cooling strengthening device for glass plates used in the practice of the present invention. FIGS. 3, 4, and 5 are schematic front views of other embodiments showing the arrangement of air cooling nozzles. FIG. 6 is a front view showing an example of the arrangement of cooling nozzles on the surface of a conventional blast head. 4... Plate glass, 6 ... Cooling strengthening device, 7, 8... Blast head, 11... Cooling nozzle, R, S,
r, s... Cooling nozzle interval distance, θ... Cooling nozzle inclination, 13... Nozzle tip.

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. Cooling nozzles are arranged concentrically outward, and the cooling nozzles other than the center are inclined at an angle of 3 to 45 degrees in the tangential direction of the concentric circles with respect to the vertical axis of the blast head surface. A method for strengthening plate glass, comprising rapidly cooling the plate glass.