JPS5910096Y2 - tempered glass heating furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heating furnace for tempered glass, particularly for tempering large glass such as the back window of an automobile.

When this type of tempered glass plate is crushed, the number of fragments is limited to a certain range, and standards have been established to minimize the number of fragments exceeding 60 mm in length (this is called a spline). There is a country.

As is well known, when a glass plate is uniformly heated to a high temperature and then rapidly cooled, the glass pieces become thinner when crushed.

However, in the case of strengthening thin plate glass (3.5 mm or less), the temperature difference between the surface and the inside of the glass during quenching is smaller than that of thick plate glass, and as a result, the shape of internal strain is reduced. The tempered glass also does not break into small pieces, and the number of pieces per unit area decreases, resulting in more splines.

For this reason, attempts have been made to increase the cooling capacity by making the array of cooling air blowing pipes thinner or by increasing the amount of cooling air in order to obtain a predetermined number of fragments.

However, when the size of the glass is relatively large like the back window, splines are likely to occur when the breaking point is at the center of the glass.

The inventor of the present invention based on the knowledge that when the internal strain of glass is differentiated, relatively coarse and fine fragments are generated when the glass is shattered, and the glass is finely fractured in areas with large internal strain to generate splines. The idea was to prevent this.

Therefore, the number of fragments of tempered glass is determined by the amount of internal strain (center tension SM) that occurs when the glass plate is heated above its softening point and the softened glass is rapidly cooled, and this SM changes depending on the quenching conditions. The present invention was developed by considering that the temperature changes depending on the heating temperature of the glass or the temperature immediately before quenching.

To explain the gist of this invention with reference to drawings, the hanging tool 4
A heating furnace for strengthening a glass plate 3 suspended in a
In this heating furnace, a main heating element 6 is provided on each vertical furnace wall 5 to heat the glass plate facing the glass plate. In order to provide differential heating, a plurality of auxiliary heating elements 1a, lb. are arranged approximately parallel to each other in close proximity to one surface of the glass plate. ．． ．．
and a structure in which a plurality of other auxiliary heating elements 2a, 2b, etc. are arranged in close proximity to the other surface of the glass plate and are arranged substantially in parallel so as to intersect with the auxiliary heating elements on the projection plane. It has become.

The spacing between the auxiliary heating elements is narrower than the spacing between the main heating elements on the furnace wall, and does not need to be strictly parallel;
10 to 100m from the glass plate keeping a distance of about mm.
[I will be placed close to you.

According to the inventor's experiments, the glass temperature Tg and SM before quenching
The relationship is directly proportional, and the higher the temperature, the larger the SM, and the relationship between SM and the number of fragments is also directly proportional. Therefore, if the heating temperature of the glass is further increased, that is, the heated surface of the glass will have an additional + By applying a temperature difference of ΔTg, it was possible to increase the minimum number of fragments.

Therefore, the glass part facing the auxiliary heating element arranged in parallel is +△ more than the other part, that is, the part facing only the main heating element.
Since it is heated at an increasing temperature of Tg, when such glass is taken out of the furnace and quenched as usual, the amount of internal strain and strain distribution changes significantly compared to ordinary tempered glass, so that the number of minimum fragments upon fragmentation increases. .

Also, when the spacing between the heating elements is limited to the above spacing, the locally heated areas are repeated at relatively uniform intervals in a predetermined direction, thereby preventing the formation of splines resulting from insufficient heating.

The heating furnace shown in the drawing has horizontal auxiliary heating elements la, l on one side.
b, IC... Vertical auxiliary heating element 2a on the opposite side,
2b, 2C... are installed parallel to the furnace wall at a predetermined interval.

The one and the other auxiliary heating elements intersect each other on the projection plane.

Generally, the distance between the main heating element 6 and the heating element on the opposite furnace wall is 800 mm.
In the case of a heating element of the order of mm, it is preferable that the horizontal heating element row and the vertical heating element row are installed symmetrically between the furnace walls so that the interval between them is 20 to 200 mm.

The distance between the main heating element 6 and the adjacent heating element is generally 65 m.
In contrast, the horizontal and vertical spacing between the auxiliary heating elements is about 20 to 50 mm narrower than the above spacing.

These main heating elements and auxiliary heating elements are selected from heating wires, silicon carbide heating rods, gas burners, and other necessary elements according to the design of the furnace.

However, it is convenient for the auxiliary heating element to be a heating wire due to its structure.

A glass plate 3 is suspended in this heating furnace by a hanger 4 and heated. In this case, the glass plate is placed at the center between the furnace walls, that is, at equal intervals from each row of auxiliary heating elements.

When the glass plate is suspended in the furnace in this way, in addition to being heated by the main heating element 6 as usual, the glass plate is heated by the auxiliary horizontal heating element and the vertical heating element. is heated even more strongly.

The strongly heated parts of the glass plate are heated to the highest temperature at the intersection of the auxiliary horizontal heating element and the vertical heating element, followed by the part facing only the auxiliary heating element to the next highest temperature, resulting in auxiliary heating. The portion not facing the element is heated to a relatively low temperature mainly by heating only from the main heating element on the furnace wall.

An experiment was conducted in which the heated glass plate was uniformly quenched and then shattered, but the above-mentioned intersection points were the most finely broken, and the spline did not exceed the distance between the intersection points.

Next, when a glass plate with a thickness of 4 mm was normally heated and then rapidly cooled and strengthened, the average number of fragments of 5 x 5 cm was 83.
The number of auxiliary heating elements was 30 mm.
5X5 is strengthened by heating and quenching under the same conditions as above.
The average number of fragments per cm was 164 to 176, which was about twice the number of fragments obtained by normal heating, and no spherules were found among these.

As described above, the glass plate heated by the heating furnace of the present invention can increase the amount of internal strain even during normal rapid cooling by creating a heating temperature difference within the glass plate, and change the internal strain distribution. The number of fragments can be increased within the upper limit to make each fragment smaller.

Furthermore, when this furnace is used, local heating is carried out, and the heating does not cover the entire glass plate, so the glass suspended from the hanger will not soften and hang from the suspended portion.

Therefore, conventional hangers can be used as they are for thin sheets of glass.

In addition, by adjusting the heat capacity of each local heater when operating the heating furnace, the temperature distribution on the glass surface can be freely changed, and this also prevents the glass from hanging from the hanging part. At the same time, it is possible to vary the number of fragments, which makes it possible to partially strengthen thin glass.

[Brief explanation of the drawing]

FIG. 1 is a front view showing one embodiment of the present invention, and FIG. 2 is a side view of the same. la, lb: horizontal force P heating element, 2a, 2b: vertical heating element, 3: glass plate, 4: hanger, 5: furnace wall, 6: main heating element.

Claims (1)

[Scope of utility model registration request] A heating furnace is used to heat the glass plate 3 suspended by a hanger 4 to strengthen it, and the heating furnace has main heaters 6 on both vertical furnace walls 5 facing the glass plate, respectively, for heating the glass plate. provided,
In order to heat the glass plate with a temperature difference in the glass plate insertion area between the main heating elements, a plurality of auxiliary heating elements (1 a, 1
b゜) and the other plurality of auxiliary heating elements (2 a, 2 b...) arranged almost parallel to each other so as to be close to the other surface of the glass plate and intersect with the auxiliary heating elements on the projection plane. A tempered glass heating furnace characterized by being equipped with.