JP2001080930A - Method for finishing sheet glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for finishing sheet glass with which the high edge strength of the sheet glass may be expected in spite of a low thermal tempering. SOLUTION: The sheet glass 3 is subjected to a first polishing stage of polishing its end face to an outwardly projecting curved surface 3a and boundary parts 3c of at least the curved surface 3a formed at the end face of the sheet glass 3 by the first polishing stage and plane parts 3b on the front and rear of the sheet glass 3 are subjected to a finishing stage for processing these parts to smooth the end face more than that of the first polishing stage, following which the sheet glass is subjected to the thermal tempering treatment ins such a manner that the sheet glass edge strength of at least 17 kgf/mm2 may be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for finishing a glass sheet which can be used, for example, for a fire door.

[0002]

2. Description of the Related Art When a sheet glass is used for a fire door, a thermal cracking phenomenon of the sheet glass (a tensile stress acts on an edge portion of the sheet glass supported by a window frame or the like due to thermal expansion generated in a central portion of the sheet glass due to heat). It is necessary that the glass has a high edge strength in order to prevent the tensile stress from exceeding the edge strength provided in the sheet glass, thereby causing a crack. As fire prevention sheet glass, netted glass and laminated glass sandwiching an intermediate layer made of hydrated alkali silicate are known, but in the former, there is a risk that the net of the interior blocks visibility and impairs transparency, In the latter case, there is a risk that the intermediate layer foams due to heat change, becomes opaque, and impairs the transparency. As one which does not have these problems, there is a soda-lime-based glass which is subjected to a heat strengthening treatment. The heat strengthening treatment heats the sheet glass in a temperature range (about 760 ° C.) which is much higher than the softening point of the glass (720 ° to 730 ° C.), and cools the cooling air at a very high back pressure of 950 mmAq in a continuous air cooling portion. There is a method that is carried out by spraying. However, with the heat strengthening treatment of such sheet glass,
Although a given edge strength can be imparted, as described above, in order to blow high-pressure air onto a sheet glass heated in a high-temperature region exceeding the glass softening point, the flatness of the glass surface is lacking or warpage occurs, and reflection occurs. There is a risk of causing defects on the image.

Conventionally, as a method of finishing this type of sheet glass, a cup wheel (a polishing diamond or a grindstone is attached to a wheel side surface 20a, as shown in FIG. 5) to form a flat edge portion. ) Is rotated around its axis, and the wheel side surface 20a is brought into contact with the edge 21a and the ridge 21b of the glass sheet 21 for polishing.

[0004]

According to the above-mentioned conventional method for finishing a glass sheet, a fine polished groove which is hard to be visually observed is formed on a ridge formed by polishing the edge, and the polished groove is accompanied by thermal expansion. Thermal stress tends to act intensively on the polishing grooves. In particular, in the case of the soda-lime glass (which is not subjected to the heat strengthening treatment), there is a problem that the edge strength is high and cannot be expected.

[0005] Therefore, in order to use it as a fire prevention sheet glass, it is necessary to perform the above-mentioned heat strengthening treatment, and as a result, there arises a problem that the above-described heat strengthening treatment causes a problem. In addition, in order to eliminate the problem (surface unevenness / warpage) due to the heat strengthening process, the heat strengthening process (hereinafter simply referred to as the “heat strengthening process”) in which the heating temperature and the back pressure of the blowing air are lower than those of the conventional heat strengthening process. When low heat strengthening treatment is performed, for example, only an edge strength that is inappropriate as a fire door can be obtained.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a method for finishing a glass sheet which can increase the edge strength of the glass sheet.

[0007]

A feature of the present invention according to claim 1 is as follows.
The step is polished into a curved shape that protrudes the edge of the sheet glass outward.
Through the first polishing step,
The curved surface formed on the end face of the sheet glass
The boundary between the front and back of the plate glass and the flat portion is subjected to the first polishing step.
After performing the finishing process to process more smoothly, at least 1
7kgf / mm ^TwoHeat so that the sheet glass edge strength
It is in the process of strengthening.

In general, the stress generated in the sheet glass tends to concentrate on the ridge, but according to the characteristic feature of the first aspect of the present invention, the end face of the sheet glass is formed into a curved shape protruding outward. After the first polishing step of polishing, at least the boundary between the curved surface portion formed on the end face of the plate glass by the first polishing step and the flat surface portion of the front and back of the plate glass is processed more smoothly than the first polishing step. Since the finishing step is performed, it is possible to make it difficult for stress to concentrate on the edge portion of the sheet glass. That is, in particular, by performing a finishing step of processing the boundary portion between the curved surface portion and the flat surface portion of the front and back of the sheet glass more smoothly than the first polishing process, the ridge portion is eliminated, and the smoother finished surface is obtained. Can be formed, and it is easy to prevent a stress from being concentrated on a large polishing groove due to polishing, and as a result, it is possible to increase the edge strength of the sheet glass as compared with the related art.
And if the edge strength increases, to perform the heat strengthening process, even if heating in a lower temperature range than before, or performing the heat strengthening process by blowing air at a lower pressure than before,
The edge strength can be ensured after the predetermined heat strengthening treatment, and it is possible to prevent the conventional glass surface from lacking in flatness or causing warpage to cause a defect on a reflected image. Further, it is possible to reduce the operating cost of the heat strengthening treatment equipment.

According to a second aspect of the present invention, the finishing step is performed by buffing.

According to the second aspect of the present invention, the unevenness of the polished surface can be polished to the order of several μm.
The generation of a large polishing groove at the boundary by polishing can be prevented, and the stress concentration of the sheet glass on the polishing groove can be suppressed, and the edge strength of the sheet glass can be further increased.

According to a third feature of the present invention, the finishing step is performed by heating and melting.

According to the characteristic configuration of the third aspect of the present invention, the finished surface in the finishing step can be finished in the same manner as the surface of the sheet glass, and the generated stress acting on the sheet glass can be entirely received at the edge. Thus, the edge strength of the sheet glass can be further increased.

[0013] A feature of the invention according to claim 4 is that the finishing step is performed by chemical dissolution.

According to the fourth aspect of the invention, the finishing step itself can be performed by a simple operation procedure, and the efficiency of the edge finishing work of the sheet glass can be improved.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows a sash 1 having an edge 2 according to an embodiment of the method for finishing a glass sheet of the present invention.
1 shows a fire door 4 formed by mounting a sheet glass 3 finished with.

The sash 1 is provided with an annular sash main body 5 forming a door frame portion, and a holding portion 6 for holding the glass sheet 3 on the sash main body 5 is attached to and detached from an inner peripheral portion of the frame of the sash main body 5. It is provided freely. The sash main body 5 and the holding portion 6 are both formed of metal, and are formed in consideration of being able to hold the plate glass 3 even if a fire occurs. The holding portion 6 is formed of a pair of angle members, and is attached to the sash main body 5 in a state where a gap 7 that can hold the edge portion 2 of the glass sheet 3 can be formed between each of the angle members.

In the gap 7, the sheet glass 3
Chloroprene rubber setty with edge protection
Block (installed only in the gap 7 on the lower side of the sash 1)
8) and a holding portion for sandwiching the edge 2 of the glass sheet 3
6 and a holding hardware 9 to be fixed. The holding hardware
9 is formed of a metal thin plate member,
By positioning the glass sheet 3 in the gap 7, the edge
The part 2 is formed so as to be elastically sandwiched and fixed.
You. Specifically, the entire length of the edge portion 2 of the sheet glass 3 is
It is formed to the length of the barrel, and as shown in the figure,
The cross-sectional shape of the edge 2 in the longitudinal direction is angular.
"U" shape (a shape without a side on the hexagonal figure)
), The both ends of the letter “U” are the front and back surfaces of the sheet glass 3.
Are formed so as to contact each other individually. The outer diameter is
The width of the gap 7 is larger than the width of the
Installed in the gap 7 with the edge 2 of the lath 3 sandwiched
Accordingly, the pressing force in the holding direction is received from the holding portion 6.
And the plate glass 3 can be strongly pinched and fixed,
Outside of glass edge due to thermal deformation of glass sheet 3 in case of fire
This can be prevented. The holding metal 9 is made of metal.
(Eg, iron or stainless steel)
Easily adapts to the ambient temperature quickly, for example,
In the case where the sheet glass 3 is produced,
Heat is easily transmitted, causing a temperature difference between the periphery and the center.
It is possible to create a difficult state and make it difficult to destroy
You. The difficulty in breaking the sheet glass 3 occurs at the edge.
Converted to stress, about 5-6 kgf / mm ^TwoThe more stress
It has been confirmed that it will ease.

Next, the sheet glass 3 will be described. The plate glass 3 is formed by subjecting a soda-lime-based plate glass formed by a manufacturing method that does not use hanging metal fittings to a heat strengthening process after an edge finishing step described later.

The glass sheet 3 is subjected to a first polishing step of polishing an end face into a curved surface shape protruding outward, and at least a curved surface portion 3a formed on the end face of the glass sheet 3 by the first polishing step is formed. Flat glass 3 on both sides
The boundary 3c with b is subjected to a finishing step for smoothing the edge from the first polishing step to finish the edge.

Specifically, the first polishing step is performed as shown in FIG.
As shown in (a), the polishing is carried out by a polishing method of a flat cylindrical wheel type polishing method in which polishing is performed using an outer peripheral surface of a cylindrical wheel 10 which rotates around an axis. The outer peripheral surface is formed so that the outer diameter becomes smaller in the middle portion of the above, and the end surface of the plate glass to be polished is polished into a curved surface shape protruding outward. And the cylindrical wheel 1
The outer peripheral surface of No. 0 is formed in a polished portion finer than # 200. The curved surface portion 3a polished in the first polishing step has a surface with an unevenness of about 0.03 mm and is very fine unevenness, so that the stress generated by the plate glass 3 acts intensively. It is easier to avoid. Furthermore, since the polishing direction in the first polishing step is set along the longitudinal direction of the end surface of the sheet glass, a streak (scratch) accompanying the polishing is set.
Is similarly formed along the longitudinal direction of the end face of the glass sheet,
Concentration of a thermal destructive force or the like acting along the plate surface of the plate glass 3 can be easily avoided.

As shown in FIG. 1 (b), the finishing step is performed by a buffing-type polishing method in which polishing is performed using an outer peripheral surface of a polishing belt 11 which is stretched around a biaxial rotating shaft and rotates. Is what you do. This buffing is also referred to as a fine finish, and is generally polished with a belt 11 made of sheep skin, and is polished with an aqueous solution of cerium oxide (polishing powder having a very fine particle size). The surface roughness is a few μm by hanging the part
(Almost the same value as the surface roughness of the front and back surfaces of the sheet glass), it is possible to gloss, and it is possible to make it difficult for the generated stress to concentrate on the boundary 3c.

By the first polishing step and the finishing step, it is possible to make it difficult for the generated stress to concentrate on the edge 2 of the plate glass 3, and in particular, to concentrate the generated stress acting along the plate surface of the plate glass 3. Is easier to avoid. As a result, it is possible to make it hard to be broken even by the heat of a fire, and it has been confirmed that the edge strength is improved by about 4 kgf / mm ² .

For example, in order to use a sheet glass as a class A and class B fire door in a fire test based on the Ministry of Construction Notification No. 1125, the edge strength of the sheet glass is set to 26 kgf / mm ^2.
Although it is necessary to secure the above, according to the plate glass 3 of this embodiment, about 5 to 6 kg accompanying the holding by the holding hardware 9 is used.
Since it is possible to reduce the generated stress of f / mm ² and to improve the edge strength of about 4 kgf / mm ² accompanying the finishing of the end face part, at least 17 kg by heat strengthening treatment
It is sufficient only to enhance f / mm ² . Therefore, in the heat strengthening treatment of the plate glass 3, the heating temperature of the plate glass 3 is equal to or lower than the softening point of the glass (720 to 730 ° C.), and the back pressure from the nozzle at the time of blowing the cooling air is 500 mmA.
q, it is possible to secure a predetermined edge strength, and there is a danger caused by the heat strengthening treatment performed at a heating temperature of 760 ° C. and an air blowing back pressure of 950 mmAq as in the related art. It is possible to prevent the deterioration of the quality (the glass surface lacks flatness or warp), improve the yield, and reduce the operation cost of the heat strengthening processing equipment.

The edge strength (surface compression stress as a substitute property) of the heat-strengthened glass sheet 3 was measured by a total reflection stress measurement method. The total reflection stress measurement method is
A prism having a slightly larger refractive index is placed on the surface of the plate glass to be measured, and a circularly polarized light beam converging at the point to be measured is made incident at an angle approximately equal to the critical angle for total reflection, and the brightness and darkness appearing in the field of view of the reflected light observation telescope are observed. The measurement was performed by a method of measuring a shift amount between the total reflection boundary lines on a scale calibrated by a known stress.

[Another Embodiment] Another embodiment will be described below.

<1> The first polishing step is not limited to the polishing method based on the flat cylindrical wheel type polishing method described in the previous embodiment. For example, a cup wheel (a polishing diamond or And a polishing method using a buffing method, or a polishing method using the polishing method in combination. Further, the finishing step is not limited to the buff polishing described in the previous embodiment.
Or by local heating and melting of the edges, or
It may be performed by chemical dissolution. In short, the boundary part 3c between the curved surface part 3a polished in the first polishing step and the flat part 3b on the front and back of the plate glass 3
Should be finished so that it can be processed more smoothly than the first polishing step. <2> Sheet glass 3 and sash body 5 according to the present embodiment
The attachment with the sash body 5 is not limited to the above embodiment. For example, as shown in FIG. 3, a metal elastic holding metal 9a that makes surface contact with the sash body 5 is used as a holding metal to be used. If fixed, the radiant heat to the sash main body 5 can be efficiently transmitted from the holding hardware 9a to the peripheral edge of the glass sheet 3, and the temperature difference between the central portion and the peripheral edge of the glass sheet is reduced, so that the glass sheet is hardly broken. It is possible to do. Further, as another embodiment of the mounted state, as shown in FIG. 4, a metal elastic holding metal 9b fitted to the pressing edge 5a of the sash main body 5 and a non-combustible plate (for example, a calical plate) are used to hold and fix. May be used.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a method of finishing an edge portion of a sheet glass of an embodiment.

FIG. 2 is a sectional view of a main part showing the fire door of the embodiment.

FIG. 3 is a cross-sectional view showing a state of mounting a sheet glass according to another embodiment.

FIG. 4 is a cross-sectional view showing a state of mounting a sheet glass according to another embodiment.

FIG. 5 is an explanatory view showing a conventional method of finishing an edge portion of a sheet glass.

[Explanation of symbols]

 3 Sheet glass 3a Curved surface part 3b Plane part 3c Boundary part

Claims (4)

[Claims] At least through a first polishing step of polishing an end surface of a sheet glass (3) into a curved shape protruding outward,
The boundary part (3c) between the curved surface part (3a) formed on the end face of the plate glass (3) in the first polishing step and the flat part (3b) on the front and back of the plate glass (3) is removed by the first polishing step. After performing the finishing process to process smoothly, at least 1
A method for finishing a sheet glass in which a heat strengthening treatment is performed so as to have a sheet glass edge strength of 7 kgf / mm ² . 2. The method according to claim 1, wherein the finishing step is performed by buffing. 3. The method according to claim 1, wherein the finishing step is performed by heating and melting. 4. The method according to claim 1, wherein the finishing step is performed by chemical melting.