JPS5843334B2 - Glass heat treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the thermal treatment of glass, particularly the thermal strengthening of glass articles such as flat or curved glass sheets.

Such thermally strengthened glass sheets can be used alone as automobile glazing, or as components of laminated automobile glazing, side lights or tail lights, or for glazing systems in aircraft and railway locomotives, ship portholes or architecture. It can be used for.

Other glass articles, such as pressed or blown glass articles, can also be thermally strengthened by the method of the invention.

The ultimate tensile strength of glass articles is determined by thermal strengthening methods that involve heating the glass to a temperature near its softening point and then rapidly cooling the glass surface to create a temperature gradient through the thickness of the glass from the center to the surface. , can be increased.

These temperature gradients are maintained as the glass cools through its strain point.

This creates a compressive stress in the surface layer of the glass plate, while creating a compensating tensile stress in the center of the thickness of the glass plate.

Typically, this thermal strengthening method is carried out using cooling air directed uniformly onto both sides of the glass sheet.

However, obtaining a high degree of strengthening using airflow is difficult, especially when strengthening glass sheets less than 3 inches thick.

Attempts to increase the degree of strengthening of the glass plate by increasing the flow rate of cooling air tend to impair the optical properties of the glass surface and cause deformation of the glass plate shape due to the buffering effect of the cooling air.

In another method of thermal strengthening, a glass sheet near its softening point is cooled in a cooling liquid.

Although this method can generate large stresses, the glass plate must be cleaned after cooling.

A method of thermally strengthening glass plates, in which the hot glass plates are actually immersed in a fluidized bed of freely bubbling solid particles, such as sand, is also disclosed in Krocsteel UK Patent No. 744,305.

Such a method has not been put into practical use for industrial use.

A major difficulty encountered by the inventors when attempting to operate such fluidized beds for thermal strengthening of glass was the high rate of breakage of glass sheets during processing in the fluidized bed.

Failure when cooling a glass plate in a freely bubbling fluidized bed is caused by uneven cooling of the leading edge of the glass plate as it enters a bed of particles in a bubbly or clumpy fluidized state. It is thought that this occurs because destructive tensile stress is generated.

The loss of the glass plate due to breakage is, for example, 2.3 to 4.5 mm thick.
This is particularly important when attempting to strengthen thin glass panes of doors to high stress values, rendering the method of industrially manufacturing tempered glass panes, for example for automobile glazing, unacceptable.

The problem of breakage also occurs to a lesser degree, but still to an industrially significant degree, when attempting to strengthen glass sheets as thick as, for example, 8 mm.

It has also been found that free bubbling beds in a blocky fluid state can damage hot glass plates immersed therein.

This damage is due to the random forces experienced by the glass within the free bubble bed.

The irregular force deforms the overall shape of the glass plate and -
Therefore, local surface damage is likely to occur, and the former drawback is particularly likely to occur in the case of a thin glass plate with a thickness of 2 to 3 degrees.

Damage, such as shape changes, makes lamination difficult, and surface damage makes the optical quality unacceptable when the glass sheet is used as a component of laminated glazing or as a glazing.

The present invention shows that the use of a gas fluidized bed in a steady, high-rise, uniformly flowing particle flow state can, quite unexpectedly, create appropriate stresses in the glass sheet cooled therein, resulting in surface damage or shape changes. Alternatively, it has been found that the loss of glass plates due to breakage in the fluidized bed is significantly reduced and therefore satisfactory industrial yields are achieved.

"Steady height" means that the height of the fluidized bed remains constant.

In the present invention, a glass heat treatment method involves bringing glass into contact with particles that have been fluidized with a gas and are in a uniform particle flow state with a steady bed height, thereby transferring heat between the glass surface and the fluidized particle surface. I will provide a.

The present invention further includes heating the glass to a temperature above its strain point and immersing the hot glass in a bed of particles fluidized with a gas (the fluidized bed of particles is, prior to this immersion, uniform in steady-state bed height). The present invention provides a method for heat-treating glass, including the step of glass being in a fluidized particle state.

The present invention particularly relates to a method for thermally strengthening glass sheets, which comprises heating a glass sheet and then lowering the hot glass sheet into a uniformly fluidized bed of particles with a constant bed height. .

It is particularly preferred to maintain the particle fluidized bed at a temperature in the range from 30 to 150<0>C.

The temperature is selected depending on the flow characteristics of the particles and the required stress level of the strengthened glass plate.

The constant bed height, uniformly fluidized particle fluidized bed used in the present invention can be defined by the velocity of the gas flow through the bed and the expanded height of the bed.

A uniformly fluidized particle flow condition with a steady bed height is determined by the lower limit gas velocity at the beginning of fluidization, i.e., the velocity at which the particles are just suspended in the upwardly flowing gas in a uniformly dispersed manner, and the lower gas velocity at the top of the fluidized bed. exists between the upper gas velocity at which maximum expansion of the fluidized bed occurs while maintaining a free surface at .

The upper limit of the fluidizing gas velocity may be only slightly above the velocity at which the first clearly discernible bubble, for example a bubble of diameter 5 mm, is seen to break through the gentle surface of the fluidized bed.

One or two such bubbles can be seen at this gas velocity.

Gas velocities greater than this increase bubbling within the fluidized bed, and upon the onset of such bubbling there is a partial collapse of the fluidized bed height.

By cooling the glass plate in a gas fluidized bed with a constant bed height and uniformly flowing particle flow state, all the temporary tensile stresses that occur in the leading edge of the glass plate as it enters the fluidized bed are absorbed by the glass It is believed that it is not severe enough to endanger the plate and destroy the glass plate.

Also, because the fluidized bed is virtually bubble-free, the hot glass is not subjected to irregular forces that can cause shape changes, breakage, or surface damage to the glass sheet during cooling.

Previously, in order to obtain a large heat transfer coefficient between the fluidized bed and the articles immersed therein, rapid continuous movement of particles was required to transfer the heat between the articles and the bulk of the fluidized bed. It was considered desirable to maintain free-bubbly conditions such that transmission could occur.

It was thought that such rapid and continuous movement of particles would not occur in a quiet fluidized bed with little particle movement.

However, the inventors have now completely unexpectedly discovered that a large amount of heat is generated between a cold bed of fluidized particles in a uniformly fluidized state with a steady bed height and having selected organic properties, and a hot glass article. It was found that the transfer coefficient can be obtained.

The inventors have discovered that when cooling a hot glass plate in a fluidized bed,
There is thermal movement of particles flowing uniformly on the hot glass surface,
It has been found that the motion and swirl of the flowing particles is faster in the region of the surface of the glass plate than in the bulk of the fluidized bed, resulting in a higher rate of heat transfer from the glass surface.

It is believed that the particles heated by passing near the glass surface then quickly move away from the glass plate and lose heat to the fluidized air within the bulk of the fluidized bed.

In one preferred embodiment of the method of the invention, the gas flow is controlled by creating a large pressure drop in the fluidizing gas stream as it passes through a membrane at the inlet of the fluidized bed, so that the fluidizing gas flow is controlled in a stationary layer of the fluidized bed. Stay high.

Furthermore, in the present invention, the particles have a density of 0.3 to 3, g7
, 9/i with an average particle size of 5 to 120 microns, and flow uniformly through the fluidized bed at a speed of 0.045 to 5.16 cfrL/sec, preferably 0.11 to 1.62 Cm/sec. Particles are selected from materials that can be uniformly fluidized to the above-mentioned steady layer height using a fluidizing gas.

Particle density and average particle size are also important in determining the suitability of the particles to constitute a uniformly fluidized bed of constant bed height for use in the method of the present invention.

Normally, when operating a fluidized bed under ambient conditions at room temperature and pressure, particles suitable for fluidization to a uniformly fluidized state with a steady bed height by fluidizing air have a particle density (,!?/i). The mathematical product with the average particle size (μ) is about 220 or less.

The degree of strengthening of the glass plate achieved by the method of the invention depends on the heat transfer coefficient between the fluidized particles and the hot glass plate immersed therein.

As mentioned above, thermal motion exists on the hot glass surface, and therefore heat is rapidly transferred from the hot glass surface.

However, the properties of the particles themselves also influence the magnitude of the heat transfer coefficient.

To thermally strengthen flat soda-lime-silica glass with a thickness between 2.3 and 12 mm, the method of the present invention
heating to a temperature of ~680° C. and immersing the heated glass in the aforementioned steady bed height state fluidized bed having a heat capacity per unit volume of 0.02 to 0.37 d/d'c in a minimum fluid state;
Maintaining the fluidized bed at a temperature up to 150°C, the 2.24X1
0'~11.7X10'kg/rr? (22-114
MN/v? ) can be induced in the glass.

Note that MN/m and KN/m used in the present invention are units based on the International System of Units (S unit system), which is officially used internationally, and are commonly used in the glass industry, so hereinafter they will be based on this International System of Units. Display by value.

The maximum amount of average central tensile stress that can be achieved depends on the glass thickness and heat transfer coefficient.

By selecting appropriate materials, a reinforced glass plate with a central tensile stress of 40 MN/m for glass 2 mm thick and 50 MN/m for glass 3.0 mm thick can be obtained.
The heat transfer is sufficient to produce a tempered glass sheet with a central tensile stress of 104 MN/m for glasses between 12 and 12 mm thick. The coefficient can be increased.

However, even larger central tensile stresses are shown in some of the examples of the invention.

The present invention further provides a non-consolidated gas fluidized bed in which glass is heated and buoyant particles whose apparent density is smaller than the actual density of the material forming the particles form a gas fluidized bed in which the particles have a constant bed height and flow uniformly. The hot glass is immersed in a particle fluidized bed with a particle structure such that the particle constituents and the fluidized bed temperature are adjusted such that the heat transfer coefficient of the fluidized bed produces the required reinforcing stress in the glass as it cools in the fluidized bed. It also includes a method of thermally strengthening glass, including selecting the method to be sufficient to strengthen the glass.

The use of particles with a non-close structure is sufficient to generate significant reinforcing stresses in the glass during minimal flow while eliminating the difficulties in fluidizing the particles to a uniformly fluidized particle flow state with a steady bed height. It is possible to select materials as particles that give a fluidized bed with a large heat capacity per unit volume.

The amount of reinforcing stress produced in the glass using a fluidized bed with particles of a particular non-densifying material can be controlled by selection of the particle density.

Particles of small density and specific dimensions generate less reinforcing stress in the glass, and the amount of reinforcing stress produced increases with increasing particle density, such that the particles are still fluidized at the above-mentioned steady bed height. increases to a maximum density of particles of size.

The present invention further provides a high temperature glass plate with an average particle size of 5 to 120.
It is immersed in the above-mentioned fluidized bed in a steady bed height state composed of particles with an apparent particle density of 0.3 to 2.35 g/C11t in μ, and the heat capacity per unit volume of the fluidized bed at the minimum fluidization is 0.
Provided is a method for thermally strengthening a glass plate, which includes strengthening the glass plate to a temperature of 02 to 0.37 cat/ff1°C.

The apparent particle density within the above-mentioned range is the actually measured density of the particle with a concave design inside the particle, and must be considered separately from the true density of the particle itself.

By selecting the average particle size in relation to the apparent particle density, the suitability of the densified material particles for constructing a uniformly fluidized bed of constant bed height can be evaluated.

It is particularly preferred that the value of the mathematical inner product of the apparent particle density fl/cd and the average particle diameter (μ) is about 220 or less.

Porous γ alumina particles with an average particle diameter of 64 μm and an apparent particle density of 2.29/ffl can be used as the particles, in which case the heat capacity per unit volume of the fluidized bed at minimum fluidization is 0.21 m
/cII1°C.

In another example, the particles have an average particle size of 60-70μ and an apparent particle density of 1.21-1.22g/c! porous aluminosilicate can be used, in which case the heat capacity per unit volume of the fluidized bed at minimum fluidization is from 0.11 to O.19c.
al/cr/l'c.

Furthermore, as particles, the average particle diameter is 5μ, and the apparent particle density is 2.3E.
1/- porous powdered nickel can be used, in which case the heat capacity per unit volume of the fluidized bed at minimum fluidization is 0.3
7 m/cr/l'c.

In another example of the present invention, the particles have an average diameter of 77 to
Hollow glass spheres with an apparent particle density of 120 μm o, 3 sy/i can be used, in which case the heat capacity per unit volume of the fluidized bed at minimum fluidization is 0.05-0.06 m/dc.

In yet another example, hollow carbon spheres with an average particle size of 48μ and an apparent particle density of 0.3i/- can be used as particles, in which case the heat capacity per unit volume of the fluidized bed at minimum fluidization is 0.02 cat /a? t°C.

In still other examples, the particles have an average particle size of 23 to 5.
Non-porous powdered alpha alumina with a 4μ particle density of 3.97 g/611 can be used, in which case the heat capacity per unit volume of the fluidized bed at minimum fluidization is 0.32 cores/cri1°C.

The present invention also provides that the particles have an average particle size of 5 to 120μ and a particle density of 0
．． 3 to 3.97 g/d, and the fluidized bed is in a state of uniformly fluidized particles with a steady bed height, and the heat capacity per unit volume of the fluidized bed at the minimum fluidization is 0.02 to 0.37 cat/cr.
It also includes a fluidized bed in which the particles are selected to have a temperature of 1° C. and is used as a quenching medium for thermal strengthening of hot glass sheets.

The invention also encompasses thermally treated glass, especially thermally strengthened glass sheets, produced by the process of the invention.

The invention will now be explained in more detail with reference to the drawings.

In the device of the invention shown diagrammatically in cross section in FIG.
The vertical strengthening furnace 1 comprises side walls 2 and a roof 3.

The side walls 2 and roof 3 are made from conventional refractories.

The bottom of the strengthening furnace 1 is open and defined by an elongated opening 4 in the substrate 5.

The strengthening furnace 1 is supported on a substrate 5.

A movable shutter (not shown) is provided in a known manner and is used to close the elongated fighting mouth 4.

The glass sheet 6 which is to be bent and subsequently thermally strengthened is suspended in the tempering furnace 1 by means of tongs 7 .

The tongues 7 engage the upper edge of the glass plate 6 and are held closed in a conventional manner by the weight of the glass plate gripped between the points of the tongues.

The tongs 7 are suspended from a tong rod 8 which is suspended from a conventional hoist (not shown).

The hoist runs on vertical guide rails 9 that extend downward from the intensifying furnace.

The vertical guide rail 9 guides the tongs bar 8 as it moves up and down.

A pair of bending dies 10.11 are arranged on either side of the passage of the glass plate 6 in the chamber 12.

Chamber 12 is heated by a hot gas flow from duct N2a.

Inside the chamber 12 and the dies 10 and 11, the glass plate 6 is
2, it is maintained at the same temperature as the high temperature glass plate 6.

Die 10 is a solid male die mounted on ram 13 and has a curved front surface that defines the curvature desired to be imparted to the hot glass sheet.

The die 11 is a ring frame female die carried by a post 14 attached to a support plate 15 mounted on a ram 16.

The curvature of the die frame 11 matches the curvature of the surface of the male die 10.

The guide rail 9 extends downwardly into the interior of the chamber 12 and on the side of the bending die and towards the container of the bed 17 of particles of refractory material to be fluidized with gas.

The high temperature curved glass plate is rapidly cooled in this fluidized bed 17.

The fluidized bed 17 vessel comprises an open top rectangular tank 18 mounted on a lifting table 19 of the cross-leg type.

When the lifting table 19 is in the raised position, the top end of the rectangular tank 18 is immediately below the bending die 10.11.

A microporous membrane 20, as shown in detail in FIG. 2, extends across the base of the rectangular tank 18.

The ends of the membrane 20 are connected to the flange 21 of the rectangular tank 18 and the flange 2 of the filling chamber 23 (forming the base of the rectangular tank 18).
It is fixed between 2.

These flanges 21 and 22 and the ends of the membrane 20 are fastened together with bolts 24.

A gas supply duct 25 is connected to the filling chamber 23,
Fluidizing air is supplied to the gas feed duct 25 at a controlled pressure.

The porous membrane 20 is configured such that fluidized air flows uniformly into the fluidized bed over the entire base of the fluidized bed to maintain the fluidized bed in a uniformly fluidized particle flow state with a steady bed height. There is.

The refractory material particles in the rectangular tank 18 are arranged in a porous membrane 20.
The upwardly directed airflow, which is uniformly dispersed by the particles, maintains a uniformly fluidized particle flow state with a constant bed height.

The fluidized bed is in a steady bed height state with almost no bubbles,
There are no unfluidized areas in the fluidized bed.

An example of a suitable structure for microporous membrane 20 is shown in Figure 2 and described in UK Patent Application No. 24124/76.

This porous membrane 20 has an iron plate 26 with distributed rectangular pores 27 .

A passage for the bolt 24 is bored in the edge of the iron plate 26 with a drill.

A gasket 28 is arranged between the lower surface of the edge of the iron plate 26 and the flange 22 of the filling chamber 23.

A number of strong microporous paper layers 29 are stacked on the iron plate 26.

For example, 15 sheets of paper can be used.

A woven wire mesh 30, such as stainless steel mesh, is placed on top of the paper to complete the porous membrane.

Wire mesh 30 and flange 21 of rectangular tank 18
An upper gasket 31 is arranged between.

A cullet trapping basket can be placed near the porous membrane 20 and is designed so as not to interfere with the uniform flow of fluid air upwardly from the porous membrane 20.

Referring again to FIG. 1, the guide rail 9 extends downward to a position below the curved diamond 10.
Ends in the area at the top of the .

A fixed frame 32 is installed inside the rectangular tank 18,
A folding leg 33 is provided at the base of the fixed frame 32 to receive the lower end of a glass plate lowered into the fluidized bed when the tong bar 8 is lowered by a hoist past the bending die.

When the cross leg type lifting table 19 is lowered and the tongs 7 and the tong rod 8 are at the lowest position at the bottom of the guide rail 9,
The cold glass to be bent and strengthened is engaged with the tongs 1.

A hoist then lifts the glass plate suspended by the tongs 1 into a tempering furnace 1 which is maintained at a temperature of 850 DEG C., for example when tempering soda lime-silica glass.

The glass plate 6 quickly reaches a temperature near its softening point, e.g.
Heated to 80°C.

When the glass plate 6 uniformly reaches the required temperature, the movable shutter closing the elongated opening 4 of the substrate 5 is opened, and the bending die 10 opens the high temperature glass plate 6 with a hoist.
．． Lower it to a position between 11 and 11.

The ram 13.16 is operated to close the die 10.11 and bend the glass plate 6.

When the glass plate 6 has been given the required curvature, the die 10.
11 is opened and the hot curved glass plate 6 is quickly lowered into the fluidized bed in the rectangular tank 18.

While the glass plate 6 is being heated in the tempering furnace 1, the fluidized bed is raised to the quenching position by operating the intersecting leg type lifting table 19.

When manufacturing high-quality laminated glass products using thermally strengthened glass sheets produced by rapid cooling in a fluidized bed,
Precooling the surface of the glass plate with air immediately before immersing it in the fluidized bed improves the optical quality.

This preliminary air cooling is carried out in a shallow manner just above the upper end of the rectangular tank 18, which blows cooling air onto the surface of the curved glass sheet as it leaves the curved die 10.11 and enters the fluidized bed. This can be achieved by arranging an air blowing frame.

The aforementioned preliminary surface cooling is effective in ``setting up'' the surface of the glass plate 6, which is believed to be due to the thermal movement of flow particles on the glass surface and is sometimes found. It is possible to eliminate minute fluctuations on the surface.

However, such preliminary surface cooling is normally only used when the glass is used in the production of optically high-quality laminated glass.

The fluidized bed is constructed by means of a water cooling jacket 34 attached to the flat long wall of the rectangular tank 18 and by controlling the temperature of the fluidized air supplied to the plenum 23 to produce the required central tensile stress in the glass. Appropriate temperature, e.g. 3
Maintained at 0-150°C.

Water cooling jacket 34 acts as a heat sink to absorb heat transferred through the fluidized bed from the hot glass plate.

Since the lower end of the hot glass plate is uniformly cooled over its entire length as it enters the horizontal, steady bed height surface of the fluidized bed, the area of the surface of the lower end of the glass plate that would lead to breakage. There is no possibility of generating different tensile stresses at each time.

The lower edge of the glass plate is constantly in contact with the fluidized particles in a uniformly fluidized state at a steady bed height during its descent through the fluidized bed, and this uniform treatment of the lower edge is ensured as soon as the hot glass surface enters the fluidized bed. Despite the upward flow of particles that can form on hot glass surfaces, glass breakage is significantly reduced and the difficulty of processing glass pieces in a fluidized bed is overcome.

This, together with the elimination of glass plate losses due to changes in the shape of the glass plate and/or damage to the surface quality, ensures a significant increase in the industrially possible yield of toughened glass.

The local thermal motion of the fluidized bed is probably caused by rapid gas expansion in a manner similar to boiling of a liquid over the hot glass surface.

This local thermal movement ensures that there is adequate heat transfer from the hot glass surface to the bulk of the fluidized bed, e.g. The heat transfer coefficient between

Heat transfer continues sufficiently after the glass has cooled below the strain point and with sufficient severity to ensure that the temperature gradient from the center to the surface is maintained as the glass cools through the strain point. However, reinforcing stresses are then developed during continued cooling of the glass while it is still immersed in the fluidized bed.

The thermal movement of the fluidized particles at the glass surface sets up a vortex in the bulk of the fluidized bed, which, due to the thermal movement of the fluidized bed in the immediate area surrounding the glass plate, transfers the heat extracted from the glass plate to the fluidized bed. Dissipates reliably and continuously to distant regions.

Water cooling jackets 34, acting as heat sinks, keep these remote areas of the fluidized bed cool.

At the end of its descent, the glass plate 6 engages with the fold 33 of the fixed frame 32, thereby releasing the tongue 8.

The glass plate 6 then rests on the fixed frame 32 while cooling in the fluidized bed.

The glass plate remains in the fluidized bed until cool enough to handle.

The rectangular tank 1B is then lowered by lowering the cross-legged lifting table 19 to expose the fixed frame 32 and the supported reinforced glass plate 6.

The glass plate is then removed and subsequently cooled to room temperature.

The uniformly fluidized particle flow state with a steady bed height in a fluidized bed is the third
As shown in the figure.

This figure is a plot of the packed chamber pressure against the height of the catalyst bed in the tank 18 when using the γ alumina particle flow conditions and tank dimensions shown in Example 2 below and using a fluidized bed temperature of 80°C.

When the pressure in the filling chamber 23 reaches 15 KN/m, the fluidized bed begins to expand.

In this case the velocity of the fluidizing air through the fluidized bed is sufficient to initiate the flow.

That is, at this lower limit gas velocity, the gamma alumina particles just become suspended in the upwardly flowing air.

The pressure drop when passing through the porous membrane 20 is 60% of the filled chamber pressure.
The above uniform fine porous membrane 2 of the type shown in Figure 2
Because of the use of 0 and a large pressure drop, the fluidizing air flowing upward from the top surface of the porous membrane 20 is evenly distributed.

This large pressure drop when passing through the porous membrane 20 is
A stationary layer of gamma alumina is formed between the previously mentioned minimum fluidization state and the maximum expansion state of the fluidized bed, where dense phase flow is maintained, allowing for sensitive control of the velocity of the gas flowing upwardly through the particles. It makes it possible to control high flow conditions.

Such sensitive control of gas velocity is achieved by controlling the filling pressure within the filling chamber 23.

No abrupt or discontinuous changes in fluidized bed conditions occur when the chamber pressure increases.

When the filling chamber pressure increases to about 25 KN/771" and the fluidized bed expands to a height of about 102 cm in tank 18, the mud fluidized bed becomes more uniformly flowing at the steady bed height, as shown in Figure 3. The condition persists.

At this packed chamber pressure the first clearly discernible bubbles, e.g. bubbles with a diameter of about 5 mm, can be observed breaking the surface of the fluidized bed at a steady bed height, and this velocity of fluidized air serves as the minimum bubbling velocity. I can think.

Due to the use of a porous membrane 20 with a large pressure drop, this minimum bubbling rate is not necessarily the gas velocity that produces the maximum expansion of the fluidized bed, and control of the filled chamber pressure up to 27 KN/m requires a maximum fluidized bed height of 105 CIrL. Can you observe that it generated? While this increase in plenum pressure up to 27 KN/m was carried out - so small bubbles were observed to break up the fluidized bed surface, small random bubbles appeared on the hot glass plate, especially on the thick hot glass. It was not significant enough to adversely affect the fluidized bed's ability to rapidly cool the plate.

As the chamber pressure increased above 27 KN/rri', sustained bubbling of the fluidized bed occurred and a tendency for the fluidized bed to collapse below its maximum height of 1056 IrL was observed.

In this condition, the fluidized bed was unsuitable for strengthening hot glass sheets.

Therefore, in this example, the fluidized bed of γ alumina in a uniformly fluidized state with a steady bed height, which was effective for strengthening the high-temperature glass plate, had a filling chamber pressure of 15 to 27 K as shown by the curve in Figure 3.
N/m, in which a sharp control of the flow conditions was possible, and as a result of this control a uniform reinforcing stress was generated in the glass.

The effective heat transfer coefficient of a fluidized bed for high temperature glass depends on the properties of the fluidizing gas, normal air, the gas velocity within the fluidized bed, the properties of the refractory material particles, especially the particle size range, average diameter, density of the particles,
and if the particle has depressions, ie, some voids or hollow structure, it is determined by the density of the material of the particle.

The heat transfer coefficient is also affected by the glass plate temperature and the fluidized bed temperature -8 - The reason for this is that if there is only a slight difference between the two temperatures, there will be almost no thermal movement on the glass surface, and the effective heat transfer coefficient will be This is because the target becomes smaller.

Other factors that influence the heat transfer coefficient are the specific heat of the particles and the average heat capacity of the particles.

On each side below, the value of the mathematical dot product of particle density (g/ff1) and average particle size (μ) is less than 220.

This value is a criterion that can be used to evaluate the suitability of the particles, i.e. the ability of the particles to be fluidized by air into a uniformly flowing fluidized particle with a steady bed height, when operating under ambient conditions at room temperature and pressure. It is.

The following are some examples of strengthening glass sheets from a few to twelve inches thick using the apparatus shown in Figures 1-2 and using a uniform, stationary, expanded fluidized bed.

In each of the following Examples 1-11, the edges of the glass plates were rounded and finished using a fine diamond grid grinding wheel.

Example 1 The refractory material particles are gamma-type porous alumina having the following properties.

When a fluidized bed maintained at 40 DEG C. was used, the degree of reinforcement of a glass plate with a thickness of 2.3 to 12 mm at an initial glass temperature of 610 DEG to 670 DEG C. was as follows.

The effective heat transfer coefficient between the fluidized bed and the glass plate is 0,01
~0.012cttt/cnt°C seconds.

Example 2 In a special manufacturing test consisting of gamma porous alumina similar to that described in Example 1, curved glass plates 2.3 mm thick were strengthened.

This glass plate was subsequently used as a part of a laminated window glass for an automobile.

The properties of γ alumina were as follows.

The effective heat transfer coefficient between the fluidized bed and the glass plate is 0.01
-Ivy at 0.012 m/d'c seconds.

Example 3 In the manufacturing test of the pond of the present invention, glass plates with thicknesses of 3, 4, 6, 8 and 10 mm for cross members of laminated aircraft window glass were made of γ-alumina uniform and stationary under the following conditions. Consolidated in an expanded fluidized bed.

γ-type porous alumina similar to that used in Examples 1 and 2 was used.

The uniform central tensile stress developed in the glass was as follows:

The effective heat transfer coefficient between the fluidized bed and the glass plate is 0.01
It was ~0.012 cat/d'c seconds.

Example 4 Porous powdered aluminosilicate, each particle containing 13% by weight of alumina and 86% by weight of silica, was used as refractory material particles.

The properties of this powdered material were as follows.

When using a fluidized bed maintained at 40°C, the thickness is 2.3~
The degree of reinforcement of the ten glass plates was as follows.

The effective heat transfer coefficient between the fluidized bed and the glass plate is 0.00
It was 7 to 0.009 d/d'c seconds.

Example 5 Another type of porous powdered composite aluminosilicate material was used.

Each particle was porous and contained 29% alumina and 69% silica by weight.

This porous powder had the following properties.

The fluidized bed temperature was maintained at 40°C, and the initial glass temperature was 610°C.
When maintained at ~670°C, the degree of reinforcement of glass plates with thicknesses of 2.3 to 10 plates was as follows.

The effective heat transfer coefficient between the fluidized bed and the glass plate is 0.00
It was 7 to 0.0 im/i'c seconds.

Example 6 Select r)'1lliteJ powder containing hollow glass spheres obtained by crushing the fuel flame of a power plant boiler,
A material having the following properties was used.

The degree of strengthening that has occurred in a glass plate that has been thermally strengthened in this fluidized bed can be expressed as the average central tensile stress measured by a conventional method, using a fluidized bed maintained at 40°C.
4 to 1 when using glass with an initial temperature of 10 to 670°C
The results achieved for glass plates of two dimensions were as follows.

The effective heat transfer coefficient between the fluidized bed and the glass plate is 0.00
It was 3 to 0.004 u/cI 1°C seconds.

Example 7 Other grades of Fillite with the following properties were used.

Using glass with an initial temperature of 630°C, the fluidized bed temperature was set to approximately 40°C.
When maintained at .degree. C., the stress generated in the glass plate with a thickness of 6 to 1Qmi was as follows.

The effective heat transfer coefficient between the fluidized bed and the glass plate is 0.00
It was 5 to 0.006 cai/crl'c.

Example 8 rCarbo having the following properties as refractory material particles
Hollow carbon spheres of the type known as spheresJ were used.

The degree of strengthening of the glass plate quenched in this fluidized bed maintained at about 40°C was as follows.

The effective heat transfer coefficient between the fluidized bed and the glass plate is 0,00
It was 35 to 0.04 alt/ffl'c seconds.

Example 9 Non-porous powdered alpha alumina was used as the refractory material particles.

A number of alpha aluminas with different average particle sizes were used.

These alpha aluminas had the following common properties in terms of collapse.

Alpha alumina is available in different particle size grades and four different fluidized beds were constructed as follows.

In these fluidized beds maintained at 40°C, a thickness of 2.3
-12 glass plates were cooled.

The initial temperature of the glass plate is 610-670°C, and the degree of reinforcement of the glass plate is 42-10 expressed in average central tensile stress.
It was 4MN/m.

The effective heat transfer coefficient between the fluidized bed and the glass plate is 0.00
It was in the range of 62 to 0.0086 alt/cI1°C seconds.

Example 10 1 - A bed of small solid glass spheres known as Ballotini J was fluidized.

The properties of this fluidized bed were as follows.

Glass plates with a thickness between 2.3 and 10°C were heated to an initial temperature of 630-670°C and rapidly cooled in this fluidized bed at about 40°C.

The degree of reinforcement of the glass plate was as follows.

The average effective heat transfer coefficient between the fluidized bed and the glass plate is 0.0
The speed was 11 m/cIIL seconds.

The higher yield of unbroken and undeformed glass sheets obtained when using a gas-fluidized particle fluidized bed in a uniformly fluidized state with a constant bed height according to the present invention compared to when using a fluidized bed in a bubbling state. To illustrate the ratio, a number of similar glass plates with dimensions of 301 x 30 m and thicknesses between 2.6 and 12 were processed.

The edges of these glass plates were chamfered using bonded silicon carbide grinding wheels.

This finish gave a rougher finish than the edges of the glass sheets of Examples 1-10, which were finished using a diamond grid grinding wheel.

The present invention can be applied even in the case of rough and inexpensive end finishing as described above.
A high yield could be obtained.

Each glass plate was heated to the temperature shown in Table 22 below and then immersed in a fluidized bed of gamma-type porous alumina as described in Example 1.

For the purpose of these yield tests, some hot rose plates were immersed in a fluidized bed at steady bed height as described in Example 1.

A bubbling fluidized bed was then created by increasing the velocity of the fluidizing gas above a value that produced maximum expansion of the fluidized bed, and an equal number of hot glass plates were immersed into the bubbling fluidized bed.

The yield of dimensionally acceptable unbroken glass plates, expressed as a percentage of the total number of glass plates processed, was as follows:

Although square glass plates of 30 cIfL x 30 cIrL were used in the above-mentioned treading, processing large glass plates, such as the size of an automobile window glass, in a bubbling fluidized bed results in progressively lower yields in terms of breakage and deformation.

In contrast, processing such large glass plates in a fluidized bed with a constant bed height provides yields that are at least as good as the traversing described above.

The value of the stress generated in the glass decreases as the fluidized bed temperature increases, and at extreme values above about 300°C, the stress in the glass is such that the glass is slowly cooled rather than strengthened. Becomes the property of

Heating and/or cooling elements may be provided on the side walls of the rectangular tank 18 to control the fluidized bed temperature.

In all of the foregoing examples, the glass panes were commercially available soda-lime-silica glasses, such as those used in the manufacture of aircraft glazing panels, automobile glazing, marine portholes, architectural panels, and the like.

Glasses of other compositions can be similarly strengthened or annealed using the method of the invention.

Also, articles other than glass plates, such as pressed glass articles such as insulation or lens blanks or blown glass articles, can be strengthened or annealed by the method of the invention.

The fluidized bed according to the invention can be used for other thermal treatments of glass, such as heating glass articles at relatively low temperatures prior to further processing, such that the fluidized material is transferred to the glass immersed in the fluidized bed. Heat transfer is facilitated without damaging the glass even when the glass is heated to temperatures where it is susceptible to damage by random forces.

The present invention is as described in British Patent Application No. 34703/73 (UK Patent Specification No. 1442316).
It can also be used to thermally strengthen glass waves that are heated, curved, and advanced along a horizontal path while being supported in a substantially vertical position.

In the apparatus described in the same application, the curved dies are placed in a heating chamber, which is moved from an inclined position to a vertical position with the curved glass plates between the curved dies placed in a stationary fluidized bed of the type described above. Tilted until it can be lowered vertically.

In another method of using the invention, a glass plate can be heated by immersing it in a fluidized bed at a temperature sufficient to heat the glass to its pre-curving temperature.

After being removed from the hot fluidized bed, the glass plate is bent, and then the bent glass plate is immersed in the uniformly fluidized particles of the above-mentioned constant bed height to be strengthened.

The glass sheet can be transported by the same set of tongs during the entire period of heating, bending and strengthening, and since the tongs are adjustable, the tongs move to follow the curved shape of the curved glass sheet.

In another example, British Patent Specification No. 144231
In the manner described in No. 6, each glass plate is suspended from non-adjustable tongs, heated, and transported to the lower end support during the bending process, and the bent glass plate is arranged according to the curved shape of the glass. and lowered into a fluidized bed at a constant bed height for quenching.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view diagrammatically showing an example of an apparatus used for carrying out the method of the present invention, FIG. 2 is a cross-sectional view showing a part thereof in detail, and FIG. 3 is a stationary 1 is a graph showing one characteristic of a fluidized bed.

Claims (1)

[Claims] 1. A glass plate is heated to a temperature above the strain point and then the particle size is reduced to 20.
In a method for thermally strengthening a glass plate in which material particles having a density of less than 0μ and less than cl/d are lowered into a fluidized bed fluidized with a gas, the value of the mathematical result between the particle density 9/cd and the average particle diameter μ is The material particles are selected to have a particle size of 0.220 or less, and the supply of fluidizing gas is controlled by a membrane under high pressure to form a particle size of 0.000 or less in the fluidized bed.
Produces a uniform upward flow of fluidizing gas rising at a rate of 11 to 1.62 crn/sec to ensure that the fluidized bed is in a uniform particle flow state between initial flow and maximum expansion and horizontally steady. 1. A method for thermally strengthening a glass plate, which comprises introducing a high-temperature glass plate into the fluidized bed from the tip through the surface of the fluidized bed having a constant bed height. 2. In the method according to claim 1, the fluidized bed is
Maintain temperature between 0 and 150°C. 3. The method according to claim 1 or 2, wherein the material particles have a density of 0.3 to 3.91/crl and an average particle size of 5 to 1
Must be 20μ particles. 4 In the method according to claim 3, the thickness is 2.1
~12mm soda lime-silica glass plate 610
heated to ~680°C, then 0.02 at minimum flow condition
Immersed in a fluidized bed in a steady bed height state with a heat capacity per unit volume of ~0.27alt/cI/1°C, the fluidized bed was
2.24X10' in glass maintaining temperature below 0℃
~11.7 X 10' kg/m (22~115
MN/rr? ) to produce an average central tensile stress of 5 In the method according to claim 4, the fluidized bed has an apparent particle density of 0.3 to 2.35 g/-an average particle size of 5 to 120 g/-
The heat capacity per unit volume of the fluidized bed at minimum fluidization is 0.02 to 0.37°C. 6. In the method according to claim 5, the particles have an apparent particle density of 2. z/l/cr! Porous γ-alumina particles with an average particle size of 64μ are used, and the heat capacity per unit volume of the fluidized bed at minimum fluidization is 0.21 cat/crit°C. 7 In the method according to claim 5, the particles have an apparent particle density of 1.21 to 1.22, 9/- average particle diameter of 60
~75μ porous aluminosilicate material is used, and the heat capacity per unit volume of the fluidized bed at minimum fluidization is 0.11 to 0.
19rIlt/i'cte. 8. In the method according to claim 5, glass spheres having an apparent particle density of 0.31/d and an average particle diameter of 77 to 120 μ are used as particles, and the heat capacity per unit volume of the fluidized bed at minimum fluidization is 0.05 to 1. Must be 0.06 m/i'c. 9. In the method according to claim 5, the particles have an apparent particle density of 0.3. ! 9/d9/d Hollow carbon spheres with an average diameter of 8μ are used, and the heat capacity per unit volume of the fluidized bed at minimum fluidization is 0.02 t'tll, 1cIl'C. 10 In the method according to claim 4, non-porous α-alumina powder with a particle density of 3.97 g/-average particle size of 23 to 29 μ is used as the particles, and the heat capacity per unit volume of the fluidized bed at the time of minimum fluidization is 0. .32m/i℃.