JPH0753230A - Annealing device for sheet glass - Google Patents

Abstract

PURPOSE:To prevent the generation of fine flaws on glass surfaces occurring due to the deviation between a the moving speed of sheet glass and the circumferential speeds of transporting rollers. CONSTITUTION:A roller 2 group is divided into plural sections S1 to Sn. The amts. of the expansion and contraction of roller diameters and the amt. of contraction of the sheet glass are computed for each of the respective sections. The rotating speeds of the rollers are so controlling that the circumferential speeds of the rollers and the moving speed of the sheet glass coiincide in accordance with the results thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate glass annealing device immediately after molding, and more particularly to speed control means for a plate glass conveying roller.

[0002]

2. Description of the Related Art The structure of a conventional plate glass annealing device is shown in FIG. The slow cooling device 20 has a large number of conveying rollers 21, and conveys a flat glass plate (not shown) in the form of a continuous strip as shown by an arrow A. All the conveyance rollers 21 are rotationally driven by the motor 23 via the speed reducer 22 at the same rotation speed preset by the speed controller 25. 24
Is a rotation speed detector for detecting the rotation speed of the transport roller 21, detects the rotation speed of the roller that is actually driven, and feeds this back to the speed controller 25.

The material of the carrying roller 21 is stainless steel (Ni-Cr), fused quartz, asbestos, resin or the like. The carrying rollers of different materials are selected in consideration of cost and cooling conditions, and if necessary, the same carrying roller is used. In some cases, it was installed in the slow cooling device.

[0004]

However, in the conventional plate glass annealing device, since the rotational speeds of all the installed rollers are controlled to be the same in the device, the following problems occur. there were.

That is, in the state where the band-shaped plate glass heated to a predetermined forming temperature is carried into the annealing device; (a) The roller is thermally expanded or contracted due to the temperature increase, and its outer diameter is changed. (B) Although the plate glass is at a high temperature at the inlet of the annealing device, it gradually cools and contracts as a result.

Due to these two phenomena, a slip occurs locally between the moving speed of the sheet glass and the peripheral speed of the roller in the slow cooling device, causing a local slip. As a result, problems such as deformation, warpage, breakage, and scratches of the sheet glass occur.

This point will be further described. FIG. 3 is a graph of the coefficient of thermal expansion of various materials forming the conveying roller. a is stainless steel, b is soda lime glass,
c indicates fused quartz. As described above, the coefficient of thermal expansion varies depending on the material, and even the same material changes greatly depending on the temperature. Although not shown, asbestos and the like have a coefficient of thermal expansion that decreases with temperature, and there are some materials such as resins that cannot be used in a high temperature region although the coefficient of thermal expansion is almost constant.

In the float forming method which is one of the plate glass forming methods, the high temperature molten glass is molten metal tin (Sn).
It is floated on and molded as a flat band glass.
The formed sheet glass is continuously taken out from the forming portion (tin bath) via the lift-out roller in a strip shape, and is delivered to the conveying roller in the annealing device. In the case of soda lime glass, the temperature of the sheet glass immediately after being taken out from the forming part is usually about 620 ° C, and the temperature immediately after being introduced into the slow cooling device via the lift-out roller is about 600 ° C. About 5 minutes to 3 minutes for such plate glass in the slow cooling system.
Approximately 50 to 10 at the outlet of the slow cooling device while transporting over 0 minutes
Cool to 0 ° C. Further, in order to keep the cooling uniformity and the cooling rate of the band-shaped plate glass to be optimum, a heater or a cooler is provided at an appropriate position along the transfer passage in such a slow cooling device to perform heating or cooling as appropriate. Be seen.

As described above, the outer diameter of the conveying roller provided in the slow cooling device having the temperature gradient which changes during the conveyance changes according to the temperature of each place. Such a change in the outer diameter of the transport roller is not linear because the coefficient of thermal expansion of each roller changes with temperature. In order to make the roller peripheral velocity, which is the feed velocity of the sheet glass, constant along the transport passage of the slow cooling device, it is necessary to change the rotational velocity of the roller according to the change in outer diameter due to expansion and contraction of the transport roller.

However, if the rotation speed of the rollers is controlled only by taking into account the expansion and contraction of the conveying rollers, the conveying rollers do not have the same conveying state on the contact surface with the conveyed sheet glass, and the peripheral speed with respect to the sheet glass is increased. Some rollers become faster and some become slower. This is because the conveyed sheet glass itself is cooled and contracts. The amount of shrinkage of the plate glass is not linear because the coefficient of thermal expansion changes with temperature.

As described above, due to the relative relationship between the expansion and contraction of the conveying roller due to the temperature change and the contraction of the cooled glass sheet itself, there is a place where the moving speed of the sheet glass and the peripheral speed of the conveying roller are deviated, and the sheet is conveyed to the surface of the sheet glass. The outer peripheral surface of the roller slips or imparts uneven frictional force such as compressive force or tensile force. As a result, fine flaws are generated on the surface of the plate glass, resulting in deterioration of quality, and especially when used as a display panel of precision instruments and liquid crystal devices, yield is decreased. In the float type glass manufacturing apparatus, such a minute flaw is changed especially in the boundary portion between the lift-out roller for transferring the glass from the tin bath for molding to the annealing apparatus and the conveying roller in the annealing apparatus and the roller material. It often occurs at a position or a position where the glass thermal expansion coefficient changes rapidly.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and is a gradual cooling of glass plate which prevents the generation of fine flaws on the glass surface due to the deviation between the moving speed of the glass plate and the peripheral speed of the conveying roller. The purpose is to provide a device.

[0013]

In order to achieve the above object, a plate glass annealing apparatus according to the present invention divides a large number of rollers for conveying a plate glass to be cooled into a plurality of sections, and each section is divided into a plurality of sections. It is characterized by including a speed controller that calculates the amount of expansion and contraction of the roller diameter and the amount of contraction of the plate glass, and controls the rotational speed of the roller so that the peripheral speed of the roller and the moving speed of the plate glass match.

In a preferred embodiment, a sheet glass forming section, an annealing section provided with a large number of rollers and cooling means,
In a plate glass annealing device comprising a plate glass transfer part composed of a plurality of rollers for transferring the plate glass from the plate glass forming part to the annealing part, the rotation speed of the roller between the plate glass transfer part and the annealing part is changed. The feature is that they are different.

In a further preferred embodiment, temperature detecting means, roller driving means and roller speed detecting means are provided for each section, and the temperature detecting means and the roller speed detecting means are provided on the input side of the speed controller. It is characterized in that the output side of the speed controller is connected to the roller driving means, and a sheet glass conveying speed control loop is formed for each section.

[0016]

By controlling the rotational speed of the roller based on substantially two factors, that is, the change of the outer diameter of the roller due to the temperature change and the contraction amount of the glass sheet, the moving speed of the glass sheet and the peripheral speed of the roller are matched.

[0017]

EXAMPLE FIG. 1 is a block diagram of a plate glass annealing apparatus according to an example of the present invention. The slow cooling device 1 of this embodiment has a large number of transport rollers 2 arranged continuously along the cooling passage in the device, and these transport rollers 2 have N sections S1, S2 ,. It is divided into SNs. Each section is composed of one to a plurality of transport rollers, and each section is provided with a temperature detecting means 3 including, for example, a thermocouple to measure a representative temperature of each section. Further, each section is provided with a motor 6 and a speed reducer 7 for driving the conveying roller 2 of the section. Further, each section is provided with a rotation speed detector 8 for detecting the rotation speed of the transport roller of the section. The speed controller 4 independently controls the rotation speed of the transport roller 2 of the slow cooling device divided into sections as described above for each section. The temperature detection means 3 and the rotation speed detector 8 of each section are connected to the input side of the speed controller 4, and the temperature of each section and the roller rotation speed during the conveyance drive are input to the speed controller 4. Further, a map of the coefficient of thermal expansion with respect to the material of the roller and its temperature and the like are input to the speed controller 4 by an input line 5 such as a keyboard or input data previously stored in a ROM or the like.

The speed controller 4 comprises a roller diameter expansion / contraction amount calculating means 9, a roller peripheral speed change calculating means 10, a glass shrinkage amount calculating means 11, a glass conveying speed change calculating means 12, and a roller rotation speed calculation which are composed of a microcomputer or the like. Means 1
Equipped with 3. In controlling the speed of the roller, the speed controller 4 first, for each section, based on the temperature data from the temperature detector 3 and the input data such as the coefficient of thermal expansion of the roller, calculates the roller diameter expansion / contraction amount calculation unit 9 for that section. The outer diameter of the transport roller 2 is calculated. Then, based on the roller outer diameter calculation result and the rotation speed input data from the rotation speed detector 8, the roller peripheral speed change calculation means 10 calculates the peripheral speed of the conveying roller of the section.

Further, the speed controller 4 uses the glass shrinkage calculating means 11 to calculate the shrinkage of the sheet glass being conveyed in each section based on the temperature data from the temperature detector 3 and the input data such as the thermal expansion coefficient of the glass. calculate. Subsequently, based on the calculation result of the glass shrinkage amount, the glass transport speed change calculation means 12 calculates the change in the moving speed of the sheet glass. This calculation is configured to calculate, for example, a speed change due to heat shrinkage of the glass sheet with respect to the set reference transfer speed or the transfer speed of the previous section. Thereby, the moving speed of the sheet glass itself of each section is calculated.

Subsequently, the speed controller 4 compares the peripheral speed calculation data of the conveying roller in consideration of the change of the roller outer diameter due to the temperature change with the movement speed calculation data of the plate glass in which heat shrinkage is also taken into consideration, and these are equal to each other. Therefore, the rotation speed of the transport roller 2 is determined by the roller rotation speed calculation means 13. The calculation of the rotation speed control of the transport roller 2 is performed for each section.

In this way, the speed controller 4 controls the motor for driving the transport rollers of each section based on the roller rotation speed calculated so that the sheet glass moving speed and the peripheral speed of the transport rollers become equal for each section. 6 is rotationally controlled, and the transport roller 2 is controlled for each section via the speed reducer 7.
Drive separately. As a result, the peripheral speed of the conveying roller and the moving speed of the sheet glass become equal over the entire length of the cooling passage of the slow cooling device 1, and slip or excessive pressing force or pulling occurs between the sheet glass and the conveying roller at the contact surface. The force does not act, and the warp and deformation of the plate glass and the fine scratches on the surface of the plate glass are prevented.

The material of the conveying roller 2 is, for example, fused silica for the section S1, Ni-Cr steel for the section S2, ..., Resin for the section SN, cost, amount of thermal deformation, strength against thermal stress, frictional force, etc. Considering the above, each section is appropriately selected and determined.

The larger the number of divisions of the section, the more effective it is. However, the division is performed so that one section includes 1 to 50 rollers in consideration of the facility structure and cost. The number of rollers in each section does not have to be the same. Alternatively, the outer diameter of the roller may be changed little by little in advance in one section and the rollers may be arranged in order to reduce the total number of section divisions.

Further, in a preferred embodiment, the speed ratio of the rollers between the sections is 0.1 to 2.0% although it depends on the material of the rollers. With such a speed ratio, there is no problem such as generation of fine flaws on the surface of the conveyed glass sheet.

Further, in the above embodiment, each section is provided with a roller driving device composed of a motor 6 and a speed reducer 7. However, instead of such a structure, one section common to two or three sections is provided. One drive device may be provided, and a speed difference may be provided between the sections by a transmission.

When the above-mentioned embodiment is applied to the float glass forming apparatus, the continuous band-shaped plate glass carried out from the molten tin bath which is a forming means for forming a flat shape is gradually cooled through 2 to 4 lift-out rollers. It is carried into the device section and delivered to the carrying roller in the slow cooling apparatus section. In this case, the lift-out roller is regarded as a roller that constitutes the front end portion of the conveying roller of the entire slow cooling device, and the lift-out roller portion is 1
It may be configured as one section, and may be configured to be controlled separately by providing a speed difference between the section and the transport roller in the slow cooling device. As described above, most of the fine flaws generated on the surface of the glass sheet are formed by providing the speed difference between the lift-out roller and the subsequent transport roller in the slow cooling device section based on the calculation by the speed controller 4 described above. (Almost 80% or more)
Can be eliminated.

Next, a specific example of section division of the slow cooling device, the speed ratio at that time, and the state of occurrence of flaws are shown below.

First, three examples of the material of the conveying roller and the constitutional examples of section division are shown in Table 1 below. In each case, the whole is divided into 6 sections, the former section is composed of rollers made of fused silica, and the remaining section is composed of rollers made of stainless steel, asbestos, or plastic.

[0029]

[Table 1]

Next, the calculation result of the speed setting ratio in each section in the case of section division and roller material of Example 1 shown in Table 1 above is shown in Table 2 below. In this case, the roller speed of the section 1 is set to 100.0, and the outer diameters of the rollers of the sections 1 to 6 are all the same.

[0031]

[Table 2]

As can be seen from Table 2, the roller speed of each section differs between the case where only the roller expansion is taken into consideration (A) and the case where the roller expansion and the glass contraction are taken into consideration (B). .

Next, Table 3 below shows the occurrence of flaws on the surface of the conveyed sheet glass. This table is a comparative example in which a roller group made of stainless steel and asbestos was driven at the same speed without section division, and a case where the roller groups were driven at the speed ratios of (A) and (B) in Table 2 above. .

[0034]

[Table 3]

As can be seen from Table 3, by setting the speed ratio of the conveying roller in consideration of the expansion of the roller and the contraction of the glass (in the case of (B)), the occurrence amount of flaws can be significantly increased. Can be reduced to, especially Rank III
It is possible to eliminate the above-mentioned generation of minute flaws and obtain high-quality plate glass.

[0036]

As described above, according to the present invention, the roller group for conveying the glass sheet is divided into a plurality of sections, and the temperature of each section is measured to expand or contract the outer diameter of the roller and the glass sheet to be cooled. The shrinkage amount of itself is calculated, and the roller rotation speed of each section is controlled based on the two factors of the roller outer diameter change and the plate glass shrinkage amount so that the sheet glass movement speed and the roller peripheral speed match. Therefore, the moving speed of the plate glass and the peripheral speed of the roller that conveys the plate glass are kept to be equal over the entire length of the cooling conveyance path of the slow cooling device, and therefore slip or excessive slip due to the speed difference between the surface of the plate glass and the outer peripheral surface of the roller is maintained. There is no pressing force or tensile force, so there is no warp, breakage, or scratches on the sheet glass, and it is possible to effectively prevent the generation of minute scratches that are invisible to the naked eye. A high-quality glass makes it possible to produce good yield.

In addition, a change in the production speed such as a change in the conveying speed or the cooling time due to a change in the glass production amount, a change in the cooling condition of the slow cooling device, a change in the composition of the plate glass, or the like, can be immediately dealt with by simply changing the input data. Therefore, the quality of the produced glass can always be kept high.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a plate glass annealing device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional plate glass annealing device.

FIG. 3 is a graph of the coefficient of thermal expansion of a roller constituent material.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Slow cooling device 2 ... Conveying roller 3 ... Temperature detecting means consisting of a thermocouple 4 ... Speed controller 6 ... Conveyor roller driving motor 7 ... Reducer 8 ... -Transfer roller rotation speed detectors S1, S2 ,. ． ． SN ... Divided section

Claims (3)

[Claims] 1. A large number of rollers for conveying a plate glass to be cooled are divided into a plurality of sections, and the expansion / contraction amount of the roller diameter and the contraction amount of the plate glass are calculated for each section to calculate the peripheral speed of the roller and the plate glass. A plate glass annealing device comprising a speed controller for controlling the rotation speed of a roller so that the movement speed matches the speed. 2. A plate glass forming part, an annealing part provided with a large number of rollers and cooling means, and a plate glass transferring part consisting of a plurality of rollers for transferring the plate glass from the plate glass forming part to the annealing part. In the plate glass annealing device, the plate glass annealing device according to claim 1, wherein the rotation speed of the roller is different between the plate glass passing part and the annealing part. 3. A temperature detecting means, a roller driving means, and a roller speed detecting means are provided for each section, and the temperature detecting means and the roller speed detecting means are connected to an input side of the speed controller to obtain the speed. An output side of the controller is connected to the roller driving means, so that a plate glass conveying speed control loop is formed for each section.
The flat glass gradual cooling device described in 1.