JPH0660025B2 - Arc energizing Joule hot surface melt forming method for edge of glass plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a method of energizing an end portion of a glass plate with an arc and subjecting the surface of the glass plate to melting by Joule heat of the energizing current.

[Prior Art] Usually, chamfering of an end face of a glass plate is performed by bringing a diamond grindstone or a grinding belt into contact with the end face of the glass plate and rotating these grinding devices relative to the glass plate. However, according to these means, particularly in the former case, a relatively large chip is generated in the edge portion corner of the glass plate in the initial stage of grinding, or a fine striped pattern is formed on the chamfered surface along the edge length direction. The product value is declining because of this. Furthermore, it is known that in both of the above methods, the finished surface still has fine scratches, and these scratches are the starting points of destruction. Further, for example, when it is used as a glass plate for doors, it is necessary to further grind the end face of the glass plate with a grindstone after a chamfering step for removing the surface roughness and polishing. Further, in the case of these methods, it is necessary to supply a liquid such as water to the grinding part to cool it and wash off the grinding dust, which is extremely complicated and not preferable in the working environment.

In order to solve the above-mentioned drawbacks, JP-A-53-1458
In JP 29, the entire glass plate is heated to a temperature locally higher along the glass plate end face than the other parts and lower than the softening temperature of the glass, and abutted on both side ends of the glass plate end face. There has been proposed a method for treating an end surface of a glass plate, in which the end surface of the glass plate is formed into a uniform arc by energizing between a pair of electrodes provided. According to this method, there is an advantage that a glass plate having a finished surface at the end as smooth and glossy as that of the glass surface and having a high commercial value can be easily obtained by a safe operation.

[Problems to be Solved by the Invention] However, in the above method, since the electrodes are in contact with both side edges of the glass plate end face, the electrode bites into the glass end face softened at the time of energization heating and the glass end face is deformed. In addition, there is a problem that the electrode material is transferred to the softened glass in the portion in contact with the electrode and the glass end surface is contaminated, and further the electrode is consumed greatly. In addition, if the pressure of the electrode contacting the glass end face is small, a gap is created between the glass surface and the electrode due to the deformation of the softened glass end face, and abnormal discharge occurs. Problems such as local consumption and non-uniform melting of the glass end face remain.

[Means for Solving the Problem] The present invention heats the entire glass plate, and at the same time, the conductivity is locally higher along the surface of the edge of the glass plate than the other parts and lower than the softening temperature of the glass. After heating to a temperature that occurs, between a pair of electrodes spaced apart from each other in close proximity to the glass end face without contacting the glass end face with the pair of electrodes as in the previously proposed invention. A high voltage is applied to each electrode between the glass end faces, and a current that is equal to or higher than the current value that enables arc discharge and is equal to or lower than the current value that does not melt and deform the glass end is applied. The present invention proposes an arc-current Joule heat surface fusion molding method for forming an edge of a glass sheet by heating to a temperature at which only the surface of the edge of the glass sheet is melted without being melted to the inner surface of the glass sheet.

[Operations and Examples] Next, examples of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view of an apparatus for carrying out the arc-current Joule thermal surface melt molding method for an edge portion of a glass plate according to the present invention.
The figure is a cross-sectional view of an apparatus housed in a heating furnace for carrying out the method of the present invention. In the figure, a flat glass plate 1 of usually 1 to 5 [mm] is mounted on a pedestal 3 covered with an electrically insulating material 2.
Placed on top. An electric heating element 4 for locally heating along the entire width of the end face of the glass plate 1 is provided as close as possible to the end face to be treated. Further, a pair of electrodes 5 are provided close to the glass plate 1 on both ends of the end face of the glass plate. The glass plate is, for example, a glass plate having a width of 200 mm in the direction between the electrodes, a side length of 100 mm, and a thickness of 5 mm. Mica as an electrically insulating material 2 is coated on the flat plate of the iron pedestal 3 so that current flows only between the electrodes. I am trying. The shape of the electrode 5 is a cylindrical body having a diameter of about 1 [mm], and its tip is formed in a pointed shape. Further, as the material of the electrode, tungsten, zirconium, hafnium or the like is used, in which arc discharge is likely to occur between the electrode and the glass end face, and moreover, it is difficult to melt and consume in a high temperature arc.
Each electrode is 3 from the plate thickness surface of the glass plate end face during heating operation
It is arranged at a position separated by 5 mm.

6 is a heating furnace in which the total temperature is about 35
It is heated by the heating wire 7 to about 0 ° C., and at the same time, the surface of the end portion thereof is heated higher than other portions by the heating element 4, and the portion is locally heated to about 500 ° C. Therefore, the glass plate 1 is prevented from being damaged by the temperature difference between the entire heating portion and the local heating portion,
The end surface of the glass plate, which is locally heated to a certain degree, forms a conductive path whose electric resistance value is decreased due to the temperature rise.

Reference numeral 10 is a power supply for arc generation, and the voltage value of a normal commercial AC power supply 100 [V] to 440 [V] is 5,000.
It is composed of a high-voltage generating transformer capable of boosting to about [V], an output current regulator for adjusting the output current value of 0 to 1.00 [A], and an output current open / close switch for opening / closing the output current by a timer. . Output current value and energizing time are
It is set to an appropriate value depending on the length of the end face of the glass plate, the distance between the electrodes, the plate thickness of the glass plate, or the like. The output current value can be adjusted to a minimum of 0.02 [A], and it is possible to control the energization and interruption of the timer minimum time of 1 cycle and the repetition thereof.

When a voltage of about 5000 [V] is applied from the arc generating power source 10 between the electrodes 5 provided near the end surface of the glass plate which has been locally heated and whose electric resistance value is decreasing, Depending on the plate thickness of the glass plate, the distance between the electrodes, etc., a current of about 0.3 to 0.9 [A] is applied between the electrodes on the end surface of the glass plate which is locally heated and whose electric resistance value is decreasing. When a current is applied to the glass plate, the Joule heat causes the edge of the glass plate to reach a surface melting temperature range where only the surface of the glass plate is melted. For example, when the distance between the electrodes is 200 [mm] and the thickness of the glass plate is 5 [mm], the distance between the electrodes is 5,000.
When [V] is applied, a current of about 0.5 [A] flows,
In about 2 seconds, the end surface of the glass plate reaches the surface melting temperature range due to Joule heat. The temperature of the surface of the glass edge at this time can be estimated to be 1000 to 1100 [° C.] by visual observation of the heated color.

If proper energization control is not performed, the edge of the glass plate melts to the inside of the glass plate and droops to change the plate thickness.

By controlling the conduction to the conductive passage between the electrodes 5, the surface of the glass plate is heated to a surface melting temperature range where only the surface is melted without melting the inside of the glass plate end face, for example, about 1100 ° C. The molten glass is formed into a round arc having a radius of curvature approximately equal to the plate thickness of the glass plate as shown in FIG. 3 by the surface tension.

The glass plate that has been subjected to the end face treatment as described above is then annealed to room temperature by stopping the energization of the electric heating element 4 and the energization between the electrodes 5, and the entire glass plate is annealed to reduce stress strain. It is possible to obtain a stable glass plate. Further, after the end surface treatment of the glass plate is completed, the heating wire 7 is continuously energized to heat the entire glass plate to a tempering temperature range of, for example, about 630 ° C., and then rapidly cooled to obtain a tempered glass plate.

Incidentally, the arc generation power supply and energization control method, as described above, do not melt up to the inside of the glass plate end portion due to the Joule heat by stably energizing the conductive path of the glass plate end face by generating an arc, It suffices if it can be formed into a rounded circular shape having a radius of curvature approximately equal to the plate thickness of the glass plate by heating to the surface melting temperature range and the surface tension of the melted glass at the edge of the glass plate. Therefore, as the power supply for arc generation, a transformer for generating AC high voltage having the same frequency as the commercial AC power supply, a high frequency high voltage generator, a high frequency high voltage superimposed AC voltage generator, a DC voltage generator, a high frequency high voltage superimposed DC voltage Any of a generator or the like may be used. The energization control method is 0.5 [A].
It is energized for about 2 seconds, but it melts until the plate thickness at the edge of the glass plate changes as described above, depending on the plate thickness of the glass, the distance between each electrode, the type of power supply for arc generation, etc. Instead, the energization current value and the ON / OFF control are finely performed so that a rounded circular shape can be uniformly formed. For example, the ON / OFF control may be interrupted when the energization current value rises to 0.5 [A], and energized when the energization current value falls to 0.2 [A].

[Effect] According to the present invention, the edge of the glass plate is more likely to be chipped and the chamfered surface is finer than the mechanical grinding method such as a diamond grindstone or a grinding belt. In addition to improving the problem that the striped pattern is likely to remain, the working environment is poor due to the water flow for discharging cooling and grinding dust, the problems described in Japanese Patent Application Laid-Open No. 53-145829 are exhibited. That is, the glass plate end face is softened by Joule heat when the glass plate end face is electrically heated. These problems are solved, and practical application is facilitated.

[Brief description of drawings]

FIG. 1 is a perspective view of an apparatus for carrying out the arc-current Joule thermal surface melt molding method for the edge portion of the glass plate of the present invention, and FIG. 2 is housed in a heating furnace for carrying out the method of the present invention. FIG. 3 is a cross-sectional view of the apparatus, and FIG. 3 is a view showing a glass sheet obtained by subjecting one end of the glass sheet to arc-current Joule thermal surface melting forming processing by the method of the present invention. 1 ... Glass plate, 2 ... Electrical insulating material, 3 ... Stand, 4 ... Electric heating element (local heating), 5 ... Electrode, 6 ... Heating furnace, 7 ... Heating wire, 10 ... Arc generation Power supply

Continuation of the front page (72) Inventor Tadashi Fujimori 2-11-1, Tagawa, Yodogawa-ku, Osaka-shi, Osaka Prefecture Daihen Co., Ltd. The panel of referees Judge Noriyuki Watanabe Judge Admiral Adachi Hideo Tokunaga (56) Reference Reference: JP-A-53-145829 (JP, A) "Glass Engineering Handbook" edited by Taro Moritani and others 3 (39.4.20) Asakura Shoten, P. 505

Claims (1)

[Claims] 1. After heating the entire glass sheet and locally along the surface of the edge of the glass sheet to a temperature that is higher than other portions and that has a conductivity lower than the softening temperature of the glass sheet, When a high voltage is applied between a pair of electrodes that are arranged close to the end face of the glass plate and spaced apart from each other, the current between the electrodes and the end face of the glass plate is equal to or higher than the current value at which arc discharge is possible. And a current of not more than a current value that does not melt and deform the edge of the glass plate is applied, and by Joule heat of the applied current, by heating to a temperature that melts only the surface of the glass plate end without melting to the inner surface of the glass plate. Arc surface energizing Joule heat surface melting molding method for glass plate edge.