CS212240B2 - Method of the heat treatment of glass - Google Patents

Abstract

Glass is tempered by contact with solid particles fluidised with a gas to ensure that transfer from the glass the glass to the particles. The fluidised material is kept in a steady state of uniform fluidisation. Pref. the fluidised bed is maintained at 30-150 degrees C, and has a mass/unit volume of 0.3-3.97 (0.3-2.35) g/cc, and the particles have a mean particle size of 5-120 mu. The state of steady flow is at 0.045-5.61 cm/sec. The glass is doda-time glass 2.3-12 mm thick and is heated to 610-680 degrees C prior to quenching in the fluidised bed. Tempering streses are set up in the glass which are adequate and which reduces the loss by fracture, the surface damage being negligible.

Description

The invention relates to a method of heat treating a glass in which the glass is contacted with a granular material which is fluidized with a gas to induce heat transfer between the surface of the glass and the surface of the fluidized granular material.

Vjyááez ae concerns, especially heat hardening:! glass objects, for example flat glass tatails or bent glass. Such heat-cured glass panes may be used as self-rotating glass panes of a motor vehicle or as part of a laminated windshield of a motor vehicle, or may be used in ship window or architectural glass panes assemblies. Also, other glass articles, such as lloated or blown articles, can be thermally cured by the method of the present invention.

The final tensile strength of the glass product can be increased by thermosetting, whereby the glass heats up to the point of temperature, followed by rapid cooling of the glass surfaces, causing temperature gradients in the thickness of the glass to be centered to the surface. - These temperature gradients are maintained when the glass temperature during cooling passes through the lower cold temperature. This results in compressive stresses in the surface layers of the glass sheet with compensatory tensile stress in the central core of the glass sheet.

This heat curing process is carried out by means of cooling air directed uniformly on both surfaces of the glass sheet, but it is difficult to obtain a high degree of curing at a flow of air, particularly when glass sheets of 3 mm thickness or less are cured. . Attempts to increase the degree of cure of the glass sheet by increasing the flow rate of the cooling air may result in loss of the optical quality of the glass surfaces and distortion of the shape of the glass sheet due to cooling air impacts.

In another curing process, the glass sheets are softened at a temperature close to a point, immersed in a coolant. In this way high stresses can be induced; the glass panes must be cleaned after immersion.

A method is also proposed for thermally curing the glass sheet, in which the hot glass sheet is immersed in a loose, fluidized bed of solid particles, such as sand.

This procedure has not yet reached commercial xyu-tai.

The main problem found in attempts to form such a bed for thermal curing of glass is the high occurrence of fracture of the glass sheets during their processing in the fluidized bed. Fracture of the glass sheet while immersed in a freely bubbling bed is likely to be caused by the introduction of destructive tensile stresses to the leading edge of the glass sheet due to uneven cooling when the leading edge enters the particle bed in a flaming or aggressive fluid state.

Loss of glass sheets due to fracture is particularly severe when thin glass sheets, for example thicknesses of 2.3 mm to 4.0 mm, are hardened to high stresses and are such that they render the process unattractive. for the manufacturing of toughened glass panes, for example, for front protective glass of attomoClls.

The fracture problem also arises in mm, but still operationally significant, when it comes to claiming thicker tabs, for example up to 8 mm thick.

Freely ЫиНе ^ с! The bed in aggregate fluctuation state has also been found to be detrimental to hot glass panes immersed in it. This is due to irregular forces acting on the glass in a freely bubbling bed. This can lead to changes in the overall shape as well as to more local surface damage, the first of which occurs in particular with zinc glass panes having a thickness of 2 mm to 3 mm. Shape changes can lead to lamination difficulties and surface damage can result in undesirable optical quality when used as windows or laminated window components.

The present invention is based on the discovery that the use of a gas-fluidized bed, in a resting uniformly expanded state of particle fluidization, unexpectedly creates adequate stresses in the glass sheets immersed therein and substantially reduces the loss of glass sheets due to bed fracture or surface change or damage, achieves a favorable operating yield.

The present invention provides a method of heat treating a glass in which the glass is in contact with a gas-granular material that is in a uniformly expanded state of particle fluddation to induce heat transfer between the surfaces of the glass and the fluidized material.

The invention consists in immersing the glass in a gas-fluidized bed of granular granules which is in a uniformly expanded state of particle fluidization prior to immersion.

In particular, the invention relates to a heat setting of a glass sheet β providing a method for heat setting a glass sheet which comprises heating the glass sheet and then lowering the hot glass sheet into a resting uniformly expanded bed of granular maltrial. Preferably, the bed is maintained at a temperature in the range of 30 to 150 ° C. This temperature is selected depending on the particle fluidization characteristics and the desired stress level in the cured sheets.

The fluidized bed of a granular madtelal in a resting uniformly expanded state of fluidization of the particles used in the practice of the invention can be defined by the flow rates, gas through the bed and the expanded bed height. A steady, uniformly expanded state of particle fluidization exists with a lower gas velocity limit at the initial fluidact, i.e., a velocity at which the particles just become suspended in a uniformly dispersed, upwardly flowing gas, and an upper gas velocity limit for maximum bed expansion. while maintaining a free surface at the top of the bed.

The upper limit of the fluidizing gas velocity may exceed to a small extent the velocity at which a clearly detectable first bubble, e.g. 5 mm in diameter, can be seen as it ruptures the bed surface of the bed. One or two such bubbles may be visible at this gas velocity.

Higher gas speeds result in extensive bubbling in the bed and at the onset. This bubbling results in a partial drop in bed height.

We believe that by immersing the sheet in a gas fluidized bed that is in a resting uniformly expanded state of particle fluidization, any transient tensile stresses exerted at the leading edge of the glass sheet when entering the fluidized bed are not large enough to compromise the glass sheet and cause it to fracture.

The bubble-free bed also ensures that the hot glass is not subjected to irregular forces, which could lead to fracture or change in the shape of the glass sheet during immersion, or damage to the surface.

It was previously thought that in order to obtain a high heat transfer coefficient between a fluidized bed and an object immersed therein, a freely bubbling state must be maintained so that rapid and steady movement of the particles can produce heat transfer between the object and the bed body. This, as ι ^ ΐβlo, cannot be achieved in a kldd bed where the movement of particles changes.

However, it has now been found that DCs obtain unexpectedly high coefficients of transfer of tspla between the hot glass object and the cooler bed of the fluidized granular mass in an expanded resting state and β selected properties.

It is found that there is a thermal unrest of uniformly fluidized granular material on the glazing surfaces when the DC glass is immersed in the bed, and the movement and turbulence of the animal particles in the region of the glass plate surfaces is greater than in the bed volume. This leads to a high rate of heat transfer out of the glass surfaces. It is believed that particles that heat up the pH of the passage near the glass surfaces then move rapidly away from the glass sheet and transfer heat to the fluidizing air in the bed volume.

A preferred method of the invention comprises controlling the gas flow to maintain the fluidized bed quiescent by creating a pressure drop in the fluidizing gas stream through a membrane through which the fluidizing gas enters the bed, which pressure drop is at least 60% of the total pressure.

Further, according to the invention, the granular material may comprise particles having a specific gravity in the range of ^0.3 g.cm ³ to 3.97 g.cm ^-3 and an average matrix dimension in the range of 5 micrometers to ¹²⁰ micrometers, while being matt. is chosen so as to be fluidized by uniformly into the idle fluL ^d ation pljrnem flowing st ejnoo ^{ters of} the bed rycHTosILi between ^0, 045 cms ^- '56 to ¹ CME ".

The specific gravity of the particles and their anterior dimension are both important in the pH determination of a suitable granular material to form a fluidized bed in a resting uniformly expanded state used in the process of the invention.

Usually, a suitable grained mmΧογΙΙΙοο for fluidization in a uniformly expanded state by fluddling air when the bed is operating at normal room temperature and pressure is a material which has a numerical product of specific gravity in g.cmJ and mean dimension of particles in mitrommers shall not exceed approximately 220.

The degree of curing of the glass sheet obtained by the process according to the invention depends on the. the heat transfer coefficient between the grained moaeriáleo in the form of a raised glass pane and the hot glass pane immersed therein.

As already described, on the surfaces of the hot glass, there is a thermal unrest that leads to heat transfer rapidly away td of these surfaces. However, the properties of the particles themselves also affect the magnitude of the heat transfer coefficient.

For heat curing, the thickness of the glass is between 2.3 mm and 12 mm. The inventive method may include heating the glass to a temperature in the range 610 to 680 ° C and immersing the glass into the fluidised bed in the idle state, which has a thermal capacity _- 1 -3 -1 · per unit volume at minimum in the range of 0.084 fluidized MT.K and maintaining the fluid field at a temperature of up to 150 ° C to produce an average tensile stress in the glass in the range of 22 MPa to 115 MPa.

The maximum size of the average tensile strain that can be achieved varies with the thickness of the glass. x heat transfer. By selecting a suitable moat, a sufficiently high heat transfer coefficient can be obtained to produce tempered glass articles having a central tensile stress of 40 MPa in 2 mm glass, a center tensile stress of 50 MPa in a 3 mm thick tensile, and a center tensile stress of 104 MPa in glass. 12 mm thick. However, even higher center tensile stresses can be obtained as shown in some of the exemplary embodiments.

The invention further relates to a method of thermally curing glass comprising heating the glass and immersing the hot glass in a fluidized bed of particles of incomplete structure such that the apparent particle density is less than the actual density of the particulate matter and the suspended particles form a gas fluidized bed. the expanded particle fluidization state, wherein the particulate matter and bed temperature are selected such that the heat transfer coefficient of the bed is sufficient to produce the desired curing stresses in the glass as it cools the bed.

The use of particles of a non-compact structure allows the selection of particulate material to obtain a fluidized bed having a sufficiently high heat capacity per unit volume at a fluidity of less than 12 ° to produce high curing hardness in glass while avoiding fluidity problems. of this mmCeeial in a uniformly expanded state of the suspended particles.

The size of the hardening jet! formed in the glass by means of a fluidized bed, including a particle of granular, dense, solid material, can be controlled by selecting the density of the particles. The particles of low density and size result in the formation of a low curing pressure in the glass, and the size of the formed curing pressure increases with increasing particle density to a maximum particle density such that they are still suspended in the said state.

Still further, the invention provides a method of thermally toughening skleněné'tabule which comprises immersing the hot glass sheet into the fluidised bed in klddovém state and form particles mean dimension of 5 microns to 120 microns and an apparent specific hmoonoosi particles in the range ^{of 0,} 3 ^{g .cm-3} and ^{F 2 35 g} cm @ ³ and ^the thermal .kapacita ^é i-RES on jetootku on him when ^{b is} miriLmální fiuidcc ^dimension Eži ⁰ 084 MJ.K ^{first 3} · 1.55 ^C from MJ.K.rn ^third

The apparent specific gravity of the particles in the range, as mentioned above, is the actual measured gravity of the grained mmCteral, taking into account the voids in the particles, and should be distinguished from the actual specific gravity. mmCteral itself.

When selecting the mean particle size in relation to the apparent specific hmoonosity, the suitability of the non-dense maCeeril particles to form a resting uniformly expanded fluidized bed can be appreciated. Preferably, the numerical value of the product of the apparent specific gravity in ^{g cm} @ ³ c of the mean in ο ^ορμο! ^ ^Should not exceed at most typically ²²⁰ .

The particles may be porous gcmáaysSlčníku hlioiéáho mean size 64 mikrooo MMTr and seemingly confidential ^ h ^ onooti ² 2 g.cm ^{"3 of} IMZ kcpacctc heats ^one bed to him ^b jetaotku of at minimum 0.88 hj will fluidize. To ^—L .m ^—3 .

Further, the particles of porous aluminum-oemic material having a mean particle size in the range of 60 microns to 75 microns may have an apparent specific gravity of the particles in the range of 1.21 g.cm ³ to 1.22 g.cm ³ , at? 4? thermal kcpcctc oc unit volume of the bed during rninimminí fluid is in the range ^{0, 4} 6 ^{MJ. K} “ ¹ .m“ ³ to ^0.79 Ш.К * ¹ .m ~ ³ .

The longer particles may be a nickel powder having a mean size of 5 ^m mikrommtrů c apparent IRN ^s ^ ^h ^ m ^ Q (^ o ^ ^{STI 2 35 g} .c ^ m ^{"3 price} Topel ¹ capacity oc _je ^d uo no ^{tk b} ^ Jo him at a minimum ^and the fluid will be ^ ^1, 55 MJ.K ^"1 .m" ^3.

In another embodiment, the particles are hollow balls of sketches of mean size in the range of 77 microns ^{and 120} microns ^and measures zdánlio c ^ taotaoosi ^{0 36 g} cm @ ^3, and thermal) kcpac oc ^ tc is ^d oo ^t ^ to about emu ^l ^ RES at minimum suspension is in the range of ^{0.21 M} ^. ^K “ ¹ .m“ ^{3 to} 0 ^{, 2} 5 MJ.K “ ¹ . ^m “ ³ .

In another embodiment, the particles are hollow carbon sphere size 48 mikrommtrů e ^d ánliv ^{é é} Mero hmoonoosi ^{0.3 g} .cm ^"3, wherein the ^{1 to} lo ^ oc cpccitc jetaotta about him ^b l ^ o ^f e is at minimum fluidized ^{0.084 MJ} . ^K “ ¹ .m ~ ³ .

Even longer, the particles of the oeporous C12-oxyacrylate powder of medium size Wstic may be in the range of ²³ microns to ⁵⁴ microns of micrometer. ^{3.97 g} .cm ^"3 přičmm ^of thermally) tepacdtc oc jetootku about him ^b ^ l RES at minimum vzoosu ^1.34 МТЖ.о ^third

For further explanation of the invention, the following examples will be described with reference to the accompanying drawings, in which FIG. 1 shows a vertical vertical section through a device for carrying out the method of the invention, FIG. 2 is a sectional view of the portion of FIG. 1 in FIG. 3 is. a graph which illustrates the properties of a gas-fluidized bed in a resting, uniformly expanded state of particle elevation used in the practice of the invention.

Referring to Fig. 1 of the drawings, the vertical hardening pad 6 has side walls 2 and a ceiling J. The side walls 2 and a ceiling J are made of conventional refractory maize and the bottom of the furnace 1 is open, delimiting an elongate opening 4 in the base plate X. to which the furnace 1 is supported. The flexible, not shown, closure is arranged in a known manner to close the opening 4.

The glass filament 6 to be bent and then thermally cured is suspended in the furnace 6 by means of pliers 2 which engage the upper edge of the sheet 6 and are closed in the usual manner by the weight of the glass sheet clamped between the pliers. The tongs 8 are suspended from a drop rod 8, which hangs on a known lifting device (not shown) and which runs along vertical guide rails 2 which extend downwardly from the guide furnace 8 and the stroke is with the clamp rod 8.

The press tools 10 and 11 are disposed on each side of the path of the glass sheet 6 in the chamber 52 that is heated by the hot gas streams from the line 12a. Inside of chamber 12 and dies. 10 and 11 are maintained at the same temperature as the temperature of the hot glass sheet 6 when it enters the chamber 62;

The press tool 80 is a rigid lead metal mounted on the piston 80 and has a curved front surface that defines the curvature to be pressed against the glazing 6. The press tool 11 is an annular frame die supported by supports 14 mounted on the rear plate 65. which is mounted on the piston 64. - The dies of the die are flush with the curvature of the surface of the lead metal.

Guide rails 2 extend down the chamber. 12 on each side of the bending lining tools toward the gas container of the fluidized bed 17 of granular refractory material into which the hot glass sheet 6 is to be submerged. The fluidized bed vessel comprises an upwardly open rectangular tank 48, which is mounted on the. When the platform is in its elevated position, the upper edge of the tank 18 is just below the bending lining sections 10 and 14.

the membrane 20, which is described as a subsidy in FIG. 2, extends across the bottom of the tank 48. The edges of the diaphragm 20 are fixed between the flange 21 to the reservoir 18 and the flange 22 to the plenum chamber 23 which forms the bottom of the reservoir. The flanges 21, 22 and the edges of the diaphragm 20 are screwed together by screws 24.

A gas inlet conduit 25 is connected to the plenum 23 and air is supplied to the conduit 25 under controlled pressure. The diaphragm 20 is constructed such that air flows uniformly into the fluidized bed over the entire bottom of the bed to maintain the quiescent uniformly expanded state of the suspended particles.

The granular refractory material in the reservoir 18 is maintained in a quiescent uniformly expanded state of particles in an upwardly directed air flow through an evenly dispersed porous membrane 20. The expanded bed is in a substantially bubble-free quiescent state and there are no bed areas that are not in the hover.

A preferred construction of the diaphragm 20 is shown in FIG. 2. This diaphragm 20 comprises a steel plate 26 having regularly spaced openings 27. The outer plates 26 are drilled to form screw holes 24. The seal 28 is mounted between the lower surface of the edges of the plate 26 and the flange 22 on the plenum chamber 23.

The layers 29 of thick microporous paper are deposited on the plate 26. For example, fifteen sheets of paper may be used.

The diaphragm 20 is supplemented with a wire mesh 30, for example of stainless steel, which is placed on top of the paper. The top seal 31 is mounted between the edge of the wire mesh 30 and the flange 21. tanks 18.

The cullet trap seal 28 may be disposed adjacent the plate 26 and is arranged so as not to impede the uniform flow of fluidizing air upward from the membrane 20.

Referring again to Fig. 1, the guide rails 2 extend downwardly to a position below the crimping dies 40, 11 and terminate in the region of the upper edge of the tank 18. The rigid frame 32 is mounted in the tank 48 and has bent beads 11 for bending the lower edge of the glass sheet 6 lowered into the fluidized bed when the clamp rod 8 is lowered behind the bending tools by a lifting device.

With the lifting platform 19 lowered and with the pliers 4 and the pliers 8 in the lowest position at the bottom of the guide rails 2, a cold glass sheet 6 to be bent and cured is stored in the pliers. The lifting device then lifts the suspended glass sheet 6 into the furnace 6, which is maintained at a temperature of, for example, 850 ° C as the soda-lime-liquid glass is cured. The glass sheet 6 is rapidly heated to a temperature at a temperature of, for example, 610 to 680 ° C.

When the glass sheet 6 reaches a uniform desired temperature, the shutter closing the opening 6 is opened and the hot glass sheet 6 is lowered by a lifting device to a position between the open bending press tools 10 and 11. The pistons 13 and 16 are actuated and the tools 10.1 and 11 are opened. close and fold the board 6.

When the sheet 6 has obtained the desired curvature, the bending tools 60, 11 are opened and the glowing glass sheet 6 is rapidly lowered into a fluidized bed in the tank 8, which has been raised to a cooling position by means of it. of the lifting platform 62, while the glass sheet 6 was heated in the furnace 64.

When it is desired to produce high-grade laminated glass products comprising a heat-cured glass sheet 6 produced by fluidized bed cooling, an improvement has been found when the surfaces of the glass sheet 6 have been subjected to air pre-cooling just before the glass is immersed in the fluidized bed.

This can be accomplished by placing the shallow blowing frames just above the upper edge of the tank 13, which conduct cooling air to the surfaces of the bent glass sheet 6 as it exits the bending tool and enters the fluidized bed.

Pre-surface cooling is effective to stiffen the surfaces of the glass sheet 6, thereby avoiding immediate changes on these surfaces, as sometimes found, which may be caused by thermal unrest of the maaerial particles as they float on the glass surfaces. However, this pre-surface cooling would usually only be used when glass should be used to produce high optical quan- tities.

The fluidized bed is maintained at a suitable temperature to induce a desired central tensile stress in the glass, for example at 30 to 150 ° C, water-cooled jackets 34 on the flat longitudinal walls of the tank 48 and controlling the temperature of the fluidizing air supplied to the plenum 23. as heat sinks which absorb the heat supplied by the bed of the hot glass sheet 6. '

Lower. the edge of the glazing 6 cools down along its entire length as it enters the horizontal, calm surface of the expanded fluidized bed, so that there is no possibility of creating different tensile stresses in different areas of the glass edge surface that could lead to fracture. During its lowering into the bed, the lower edge always comes into contact with the ιο ^ ογΙΟel floating in the evenly expanded state of particle fluidization and this uniform treatment of the lower edge without flowing the granular material upwards, which can be formed on hot glass surfaces immediately as enters the fluidized bed, extensively eliminating quarry and problems with glass fragments in the bed.

Ί

This, together avoiding the loss of the glass sheets due to changes in the shape of the glass sheets and / or damage to the surface quality, ensures an operationally acceptable hardened glass yield.

Local thermal unrest of the fluidized bed takes place on hot glass surfaces, possibly by rapid gas expansion in a manner close to the boiling of the liquid. The agitation ensures that adequate heat transfer from the glass surfaces into the fluidized bed, e.g. · .- obtained heat transfer coefficient between the bed and the glass sheet in the range of 125.4 J m "° .K ^-1 .s" ^{1-836 s} ? .K “ ^1. • s“ ¹ . Přestaip ^t e ^p Ia pokražSuje well up with ^the lo cooled ^P from Dolte cooled te ^{p lot,} with sufficient space to ensure, to maintain the temperature gradient "from the center to the surface of the glass when the glass is cooled through its lower coolant temperature, this causes a curing stress during this continuous cooling of the glass while still immersed in the bed.

The Nekkid fluid in fluidity on the glass surfaces creates bed volume streams that provide continuous heat dissipation, which is obtained from the glass by thermal disturbance to the more distant parts of the bed, from the circumference of the immediately surrounding glass sheet. The water-cooled casings 34 acting as heat sinks keep these distal portions of the bed cool.

The sheet 6 fits into the foot 33 of the frame 12 at the bottom of its drop, thereby releasing the pliers 8. The glass sheet 6 rests on the frame 32 while cooling in the fluidized bed.

The glass sheet 6 remains in the fluidized bed until it has cooled sufficiently to be removed and the tank 18 is lowered by lowering the lift platform 19 thereby exposing the fixed frame 32 and the supported cured glass sheet 6 is then removed for subsequent cooling to room temperature. .

The nature of the uniformly expanded state of the particles in the fluidized bed elevation is shown in Figure 3, which is a graph of overpressure, i.e., the pressure in the plenum 23 versus the bed height in the reservoir 18 when coating the aluminum gamma-particle particles as described in the example. 2, mentioned above and at the tank size and fluidization conditions of Example 2 and a bed temperature of 80 ° C.

When the overpressure reaches 15 kPa, expansion of the bed begins and the fluidizing air velocity through the bed is then sufficient to generate initial fluidization. That is, at this lower gas velocity limit, the aluminum gamma-alumina particles will just begin to suspend in the upstream air.

Due to the high pressure drop coating and the uniform microporous type shown in FIG. 2 in which. the pressure drop is greater than 60% of the overpressure, there is an even distribution of the fluidizing air flowing upward from the top face of the aeraarelle. This high pressure drop across allows for a sensitive control of the gas flow velocity through the granular material, thereby allowing adjustment of the resting gamma alumina state between the fluidization state just described and the state of maximum bed expansion in which it is maintained fluidization in dense phase.

This sensitive control of the gas velocity is achieved by controlling the overpressure in the chamber 23, and as the overpressure increases, there is no sudden or intermittent change in bed condition. Rather, the evenly expanded state of the bed remains, as shown in Fig. 3, when the overpressure rises to about 25 kPa and the bed expands to a height of about 120 cm in the tank.

At this overpressure, a clearly visible bubble of, for example, 5 mm diameter can appear, which breaks through the surface of the resting bed, and this fluidizing air velocity can be considered as a minimum probing velocity of the W-wave.

Due to the high pressure drop coefficients 20, it can be observed that this minimum bubbling rate is not necessarily the gas velocity producing the maximum expansion of the bed, and by further overpressure control up to 27 kPa a maximum bed height of 105 cm is created. When an overpressure of 27 kPa was performed, more small bubbles were found to pierce the surface of the bed, but the mild random bubbles were not as markedly unfavorable to the liquid bed for chilled hot glass sheets, especially thicker glass sheets.

With an overpressure increase above 27 kPa, there is a steady bubbling and a tendency of the bed to collapse to a height lower than that of the observed height of 105 cm. In this state, the bed is unsuitable for curing hot glass tablets.

Thus, in this example, the uniformly expanded state of the bed of gamma alumina, which is effective for curing the glazing, is represented by the region of the curve of FIG. 3 lying between 15 kPa and 27 kPa overpressure, in which sensitive state control is possible fluidization, followed by controlling the uniform curing stresses induced in the glass.

The effective heat transfer coefficient of the fluidized bed in relation to the glazing is determined by the properties of the flashing gas, usually air, the gas velocity in the bed, the properties of the refractory mpaerial, in particular the particle size range, mean particle size, specific gravity of particles. The cavity, i.e., has a specific cut or hollow structure, by the specific gravity of the maaerial particles.

The coefficient of heat transfer also depends on the glass and bed temperatures, because if there is little difference in the oozi of these temperatures, there will be little thermal unrest on the glass surface and the effective heat transfer coefficient will be comparatively low.

Other factors affecting the heat transfer coefficient are the specific heat of the particles and their average heat capacity. In each of the examples náslrdujícíh numerical value is the product of the density p ^e hmoonnoti STIC at ^{-3 g} .eo size and centering ^CA STIC at oikrom Rech ^ ^f is smaller than 220. This is the criteria which may poulžt for determining vhotkxnoti granular οβ ^ ι ^ ΐ! that is, it is capable of being fluidized by the air in a rest uniformly expanded state of particle filtration, under immersion conditions, normalizing temperature and pressure.

Some examples of curing of glass sheets having thicknesses ranging from 2.3 mm to 12 mm using a device as in Figs. 1 and 2 and a uniform resting expanded bed are given below.

In each of the following Examples 1 to 11, the edges of the glass sheet are rounded with a fine diamond grinding wheel.

mean particle size (d) apparent particle size apparent specific gravity of the particles specific gravity of ο ^ 1 «^! ^ Τ 11ι p x d specific heat of material thermal capacity per unit of bed during fliidation fluctuation air velocity

Example 1

The refractory mass is a porous aluminum glmoa-yeast whose properties are as follows:

micrometers up to 160 micrometers ^{(p) 2.2 g} .co ^{3 3,} 97 g.co ^-3

141

0 ^, 836 Jg "'. K"'

0 ^, 878 Jc ^{m 3} .K- 'in bed ^0, 54 cms ^- '

With the bed maintained at 40 ° C, the degree of curing of the glass sheets of thickness between 2.3 mm and 12 mm with an initial glass temperature of between 610 ° C and 670 ° C was as follows:

Initial glass temperature glass thickness mm Avg. center tensile stress (MPa) 610 2.3 37 610 10 92 610 12 93.5 620 2.3 42.5 630 6 72.5 630 12 96 650 2.3 46 650 4 64 650 6 75.7 650 8 92.7 650 10 96 650 12 99 670 2.3 44 670 6 75 670 10 100 ALIGN!

The effective heat transfer coefficient between the bed and the glass panes is in the range of 0.0418 J cm ² . K ¹ . and ¹ to 0.05 J. cm ² . K ¹ . and ¹ .

Example 2

In this example, the same porous aluminum oxide game as in Example 1 was used and the bent glass sheets 2.3 mm thick were cured. These panes were then used as a component of a laminated windshield for cars.

The properties of gamma-alumina are as follows:

mean particle size (d) particle size range apparent specific gravity of particle (p) specific gravity of material pxd tank size containing fluidized bed overpressure pressure drop across membrane pressure drop across membrane fluid flow velocity fluid flow velocity fluidized bed temperature glass temperature: upper edge bottom edge resulting a uniform center tensile stress in glass micrometers up to 150 micrometers

2.2 g.cm ^{< 3} & gt ^;.

3,9 g.cm ³

141 cm x 215 cm x 105 cm depth kPa kPa% overpressure

0.175 m ³ . min ¹

0.36 cm @ ^{-1 1} ° C

650 ° C to 655 ° C

670 ° C to 675 ° C

MPa to 40 MPa.

The effective heat transfer coefficient between the bed and the glass panes is in the range of 0.0418 J.cnT ² .K ~ ¹ .s ¹ to 0.05 J.cm ² .K " ¹ .

Example 3

In another operating run, the glass panes intended as components of the laminated spinning protective glass for aircraft 3 mm, 4 mm, 6 mm, 8 mm and 10 mm thick were toughened in a uniform resting expanded bed of gamma-alumina. The same porous gamma-alumina was used as in Examples 1 and 2.

size of tank containing fluidized bed overpressure pressure drop across membrane pressure drop across membrane velocity of fluidizing air flow velocity of fluidizing air in bed fluidizing bed temperature glass temperature

The resulting uniform center stress in cm x 245 cm x 150 cm depth kPa

19.5 kPa% overpressure

0.34 m ^ .min ”^

0,51 cm. ¹ ° C

The 645 ° C to 650 ° C draw produced in the glass was as follows:

thickness of tensile stress

3.0 mm 48 MPa

4.0 mm 53 MPa

10.0 mm 80 MPa

The effective heat transfer coefficient between the bed and the glass sheets is in the range 0.0418 J.cm ² K · '.s ¹ to 0.05 J.cm ^_2 .K ^{_1 1} .s.

Example 4

The particulate refractory material is a porous alumina siliceous material, each particle containing 13% by weight of alumina and 86% by weight of silica. The pulverulent material has the following characteristics:

particle size range mean particle size (d) apparent specific gravity of particles (p) specific gravity of material p x d specific heat of material thermal capacity per unit volume of bed at minimum, fluidization rate of fluidizing air in bed up to 150 micrometers micrometers

1.22 g

2.3 g.cnT ^

1.59

0.794

0.21 ctn.s ^-1

With the bed maintained at 40 ° C, the degree of curing of glass sheets of thickness between 2.3 mm and 10 mm was as follows:

conceive. glass temperature ° C glass thickness mm average center, tensile stress MPa 650 2.3 30.8 650 4 44 650 6 62.3 650 6 73 650 10 79

The effective heat transfer coefficient between the bed and the glass is in the range 0.0293 J.cm ^"2 ..K ¹ .s" ¹ 0.0376 J.cm ² .K ^-1 .s ^first

Example 5

Another form of porous powdered aluminosilicate material was used. Each particle is porous and contains 29% by weight of alumina and 69% by weight of silica. This porous powder has the following properties:

particle size range mean particle size (d) apparent specific gravity of particles (p) p x d specific gravity specific gravity heat capacity per unit volume fluidizing air velocity up to 150 micrometers micrometers

1,21 g.cm3

2,3 g.cm3

0.836 bed 0.46 J.cm ”3.K” ’

0,33 cm.e “ ¹

With the bed maintained at a temperature of 40 ° C and an initial glass temperature of 610 to 670 ° C, the degree of curing of glass sheets of 2.3 and 10 wi thick was as follows:

initial glass temperature (° C) glass thickness (mm) average center, tensile stress (MPa) 610 6 51 610 10 74 630 2.3 31.5 630 6 53 650 2.3 33.7 650 4 48.3 650 6 56 650 8 71.3 650 10 84 670 2.3 32 670 6 58 670 10 81, 5

The effective heat transfer coefficient between the bed and the glass panes was in the range of 0.0293 J.cm &^lt; ^{2 >} K ' s &^lt; ^-1 to 0.0418 J.cnT &^lt; 2 > and ^-1 .

Example 6 “Fillit” powder, which contains spheres: from the power steam boilers, the particle size range mean particle size (d) apparent specific gravity of particles (p) pxd specific gravity of material specific heat of material thermal capacity per unit bed volume at minimum fluidization, the fluidization velocity of the air in the hollow glass filler derived from powdered ash to have the following characteristics:

up to 60 micrometers micrometers

0.38 g.cm ".

2.6 g.cm 2

0.752 ’-1-1

0.209 J-cm '

0.11 crn.s ”!

The degree of cure induced in glass panes that have been thermally cured in this fluidized bed can be expressed as the average center tensile stress as measured in a known manner and the results obtained for a range of glass thicknesses of 4 to 12 mm, with different initial temperatures in the range 610 to 670 ° C and a fluidized bed temperature of 40 ° C are as follows:

poSát. glass temperature ° C glass thickness mm average tension center MPa 610 10 40 610 12 41 630 6 30 630 12 45 650 4 22.4 650 6 32 650 8 37 650 10 39 650 12 48.5 670 6 35 670 10 50

The effective heat transfer coefficient between the bed and the glass sheets is in the range of 0.0125 to 0.0167 ¹ .s J.cm .K'.s ^_2 * '.

Example 7

Another kind of fillet was used and had the following characteristics:

mean particle size (d) apparent specific gravity of particles (p) specific gravity of material p x d specific heat of material thermal capacity per unit volume of bed at minimum, fluidization rate of fluidizing air in bed

120 micrometers

0.38 g.cm ³

2,6 g.cm “ ³

0.752 Jg ^-1 .K ^- '

0.25

0.27 cm @ ^{-1 -1}

With an initial glass temperature of 630 to 670 ° C and a composition at 40 ° C, the tensile stresses induced in 6 to 10 mm glass sheets were as follows:

pocdt. temperature Noc: 2 ° C glass thickness mm average center, tensile stress MPa 630 6 42 630 8 49 650 6 45.5 650 8 51 650 10 63 670 6 48 670 8 53

The effective heat transfer coefficient between the bed and the glass panes was in the range

0.0209 to 0.025 J.cm ^-3 .K ^_1 .s ¹ .

Example 8

A granular refractory material in the form of carbon spheres known as Carbospheres 8 was used with the following properties:

particle size range mean particle size (d). apparent specific gravity of particles (p) p x d specific gravity specific heat of material thermal capacity per unit volume of bed at minimum fluidization rate of fluidizing air in bed 5 to 150 microns, 48 microns 0.3 g.cm ^"3 14.4 2.3 0.514 g.cm ³ Jg ^-" .K ^"1 0.0836 J.cm" ³ .K ^_ '0.33 ctn.s ^- '

The degree of cure of the glass sheets cooled in this fluidized bed maintained at 40 ° C was as follows:

number. temperature ° C glass thickness mm average center, tensile stress MPa 610 10 44 630 6 34 650 4 26.3 650 6 32.7 650 8 40 650 10 45 670 6 36 670 10 46

The effective heat transfer coefficient between the bed and the glass panes in the range 0.0146 ^_2 .K ^_1 J.cm to 0.0167 J.cm ² .K ^_1.

Example 9

The granular refractory was porous nickel having the following properties:

mean particle size (d) apparent specific gravity of particles (p) specific gravity of material ρ x d specific heat of material thermal capacity per unit volume of bed at minimum fluidization rate of fluidizing air in bed micrometers

2.35 g-cm @ -1

8.9 g.cm ³

0.444 Jg · ¹ .K ¹

1.54 J.cm ³ .K ¹

0.045 cm / s

Glass sheets having a thickness of 2.3 mm to 6 mm at an initial temperature of 650 ° C were cooled in the fluidized bed of this porous nickel powder which was at rest and maintained at a temperature of about 40 ° C. The degree of cure, expressed as the mean center tensile stress, was as follows:

The effective transfer coefficient te ^p1a between the bed and the glass panes was 8.36 J. <^ M ² .K · ¹ .s ^.

glass thickness (mm) average center, tensile stress (Ш? а)

2.3

115

Example 10

The granular mateeiel was a non-porous cellular alumina of various particle sizes. All Nosti:

apparent specific hmoonost Čestice (p) measurement hmotoost matoriélu specific matoriélu te ^pl of alpha-alumina. Was used alpha kysličtyto materiel had the following common homeland ³ g.cm ^-3 97 ^3, 97 g.cm ^"3

0.836 J.g ' ¹ .K' ¹

Alpha alumina was available in different graded particle sizes and four different fluidized beds were created.

a bed of aluminum alumina mean particle size (d) micrometers pxd term. to JK-1 particles : ap. term. chap. minim. fluid. bed J.cc-3.K-1 fluid velocity. gas cm.s ^-1 AND 23 92 20.9 ^χ 10 ^-9 1.33 1.02 (B) 29 116 41.8 x 10 ^-9 1 .33 1.62 C 45 180 1S8.8 ^χ 10-9 1.33 3.90 (B) 54 216 275.9 x 10 ^-9 1.33 5.61

Glass sheets having a thickness of between 2.3 mm and 12 mm in these fluidized beds were cooled. which has a temperature of 40 ° C.

The initial temperature of the glass sheets was in the range of 610 to 670 ° C and the degree of cure. The sheet is expressed by an average center tensile stress in the range of 42 MPa to 104 MPa.

The effective heat transfer coefficient through the bed and the glass panes was in the range

0,026 J.cm “ ² .K“ ¹ .a ¹ and i 0,0318 J.cm “ ² -K“ \ s.

Example 11

Small solid glass bead beds The bed features were as follows:

particle size range mean particle size - (d) the apparent particle specific gravity (p) ρ x d thermal capacity per unit bed volume at a minimum, fluidizing air velocity in the bed known as MllotiM was fluidized.

up to 75 microns

2.5g.cm ^-3

145

1.42 J ^ ^-3 .. ¹

0.41 cm.s ¹

Glass panes having a thickness in the range of 2.3 mm to 10 mm were heated to an initial temperature of 630 to 670 ° C and were cooled in a fluidized bed which was maintained at a temperature of about 40 ° C.

The degree of curing of glass tatails was as follows:

conceive. temperature Noc: 2 ° C glass thickness mm average center, tensile stress MPa 630 2.3 38 630 6 72 630 8 87 650 2.3 40 650 6 74.5 650 8 87 650 10 90 670 2.3 43 670 6 80 670 8 90

The average effective heat transfer coefficient between the bed and the glass panes was 0.046 J < m &^lt; -1 &gt;

To illustrate the high yield of unbroken and non-distorted glass sheets obtained when using the gas-fluidized bed of the present invention at rest uniformly expanding the particle fluidization state, compared to the yield when the bed is in fluidized state, the same glass sheets have been provided 30 x 30, 2 mm, 6 mm and 12 mm thick. These glass panes had one edge ground in which the edges of the glass panes were chamfered using a grinding wheel. : with bonded abrasive silicon carbide. Thus, the tulle obtained a coarser edge than the glass beads of Examples 1 to 11, which tulle treated with a diamond grinding wheel. They invented a higher yield even with this coarser and cheaper grinding.

Each sheet was heated to the temperature indicated below and then immersed in the fluidized bed of the porous aluminum gamma-oxycarbonate described in Example 1.

For the purpose of these yield tests, some hot glass panes were immersed in the fluidized bed as described in Example 1.

The blending state of the tulle bed fluidization is then created by increasing the rate of conveying air above the value forming the bed and has the same expansion of the bed and the same number of hot tulle glass sheets immersed in the bed.

VThe weight of dimensionally acceptable unbroken glass panes as a percentage of the total number of treated tulle panes as follows:

Glass thickness = 2 mm

Glass temperature ° C

645

660

Resting bed yield

100 ALIGN! %%

%

Glass thickness = 6 mm

Glass temperature ° C Yield resting bed bubbling bed 640 80% 40% 645 100% 60 g

Glass thickness = t2 mm

Glass temperature ° C Yield resting bed bubbling bed 635 80 ·% 40% 645 100% 75%

Although the above examples were made with 30 cm x 30 cm square glass panes, even lower yields with respect to fracture and distortion were obtained when large glass panes, such as motor vehicle windshields, were treated in a bubbling fluidized bed. In contrast, the yields obtained when these larger sheets are treated in a quiescent fluidized bed are at least as good as those in the examples above.

The value of the stress induced in the glass decreases as the temperature of the bed rises and at a limit, which may be about 300 ° C or higher, the stresses in the glass are such that the glass is smoothed rather than cured.

Heating or cooling elements for controlling the temperature of the fluidized bed can be formed on the side walls of the tank 18. In all embodiments, the glass panes were of commercial soda lime glass such as those used in the manufacture of aircraft windshield panels, automotive windshields. , ship windows and architectural panels. In the same way, glass of another composition may be cooled or cured using the method of the present invention. Also, objects other than glass panes, for example Hoated glass articles such as insulators or lens blanks or blown glass articles, may be cured or cooled by the method of the present invention.

The fluidized bed of the invention can be used for other thermal treatments of glass, for example, to heat a relatively cold glass article before the next stage, whereby heat transfer from the fluidized material to the submerged glass is facilitated without damaging the glass, even when the glass has obtained a temperature at which it is susceptible to damage by irregular forces.

The invention can also be used to heat cure glass sheets that have been heated and ohmic while supported in an almost vertical position and guided along a horizontal path as described in British Patent Specification No. 1,442,316. in this application, the bending tools are enclosed in a heated chamber that is tilted from a deflected position to a position in which the bent glass sheet between the bending tools is vertical and can be vertically lowered into a resting fluidized bed of the type described above.

In another process utilizing the invention, the glass sheet may be heated by immersing the sheet in a fluidized bed having a sufficiently high temperature to heat the glass to a pre-bending temperature. After being removed from the heated bed, the sheet is bent and the bent sheet is then cured by immersing the glass in a flushed bed that is in a uniformly expanded state of particle fluidization as described above.

The glass sheet could be supported by the same arrangement of the pliers during heating, bending and curing, the pliers being adjustable to move according to the bent shape of the glass. In another arrangement, each glass sheet is suspended on non-adjustable brushes for heating and transferred to the lower edge support during bending as described in British Patent No. 1,442,316, wherein the bent glass sheet is gripped by a second set of pliers arranged in accordance with the present invention. with a bent glass shape and lowered into a resting fluidized bed for cooling.

Claims (14)

A method of heat treating a glass in which the glass is contacted with a granular material that is fluidized with a gas to induce light transmission between the surface of the glass and the surface of the fluidized granular material, characterized in that the glass is contacted with the granular maaerial which it is fluidized by gas, in a resting, uniformly expanded state of fluidization of the particles of the buried maatelal. 2. A method according to claim 1, wherein the glass is heated to a temperature above its lower cooling temperature prior to immersion in the granular material bed and then cured by immersion in a gas-fluidized bed of granular material. 3. The method of claim 2, wherein the bed temperature of the granular material is maintained in the range of 30-150 [deg.] C. 4. A method according to any one of claims 1 to 3, characterized in that the flow of the fluidized bed is controlled by generating a pressure drop in the fluidizing gas stream through a membrane through which the fluidizing gas enters the fluidized bed, the pressure drop being at least 60% of the total. flak. 5. A process according to any one of Claims 1 to 4 wherein the granular macelite comprises particles having a specific gravity in the range of 0.3 g.cm &lt; - &gt; to 3.97 g.cm &lt; - &gt; 5 micrometers to 120 micrometers, wherein the material is selected such that it is fluidized to a uniform standstill by a fluidizing gas flowing uniformly into the bed at a rate of 0.045 cm.s ^-1 to 5.61 cms ^-1 . ' 6. A method according to claim 5 for thermally tempering a pentapentent glass having a thickness in the range of 2.3 to 12 mm, which is heated to a temperature in the range of 610 to 680 DEG C., characterized in that the glass is immersed in a fluidized bed. The bed is at rest having a heat capacity of. ; unit volume at minimum ifluMaci between ^0, 084 MJ.K "\. m" ³ to ^1, 55 and the fluidized bed is maintained at a temperature of 150 ° C to cause an average tensile stress in the glass in the range of 22 MPa to 115 №a . 7. A method according to any one of Claims 1 to 4, wherein the glass is immersed in a fluidized bed of particles having a non-sinking particle structure which is such that the apparent specific gravity. The particle size is less than the actual specific. the particulate maaerial mass. 8. The method of claim 7, wherein the fluidized bed is formed from CES ^ ic mean size ranging from 5 microns to 120 microns and an apparent specific hmoonnsti particles in the range ^{of 0,} 3 ^g .cm ^{"3-2 35 g.} cm ^{-3, and the} holding · k ^ paht heat per unit of volume ^l o ^f e is at minimum fluidisation in the range ^{0, 08} 4 Ш .К ^"1 .m" ^{3 to 1.55} Ш.К ''. ш ^"3 . 9. The method of claim 8, wherein the particles are porous gamma alumina particles having an average particle size of 64 microns and an apparent specific particle size. 2.2 ^g .am ^-3 , while the thermal capacity per unit bed volume at minimum fluidization is 0.88 MT.K ^-1 .m ³ . 10. The method of claim 8, wherein the particles are porous alumino-silicate maateiles having a mean particle size in the range of 60 microns to 75 microns and an apparent -3 -3 specificmolar particles in the range of 1.21 g.cm · to 1.22. g.cm ·, wherein the heat capsule per ^J -1-3 1-3 unit bed volume at minimum fluidization is in the range of 0.46 MT.K · m · to 0.79 MJ.K · m ·. 11. The method of claim 8, wherein the particles are porous nickel prlškovitého axis ^{t s} velitoste Castle's Publications 5 mikrommtr ^U and Z <LANL ^{in s} specific hmotenoti particles ^{2 35 g} .Am ^-3, wherein te ^{p HeATING to} apaait, and ^b jetootta on him when Lote minimtení iT tedaci is ^{1, M} 55 ^-3 .K ^-1 .m. 12. The method according to claim 8, characterized in · that the particles are glass beads having a mean particle size in the range 77 to 120 microns mikrommtrů and an apparent density ^{0.38 g} hmoonooti particles .Am ^{-3 woodwork} te ^p e n ^{g l} kapateta to about jednotta ^b him Lote rninim when ^m is zTltedaci NAL; in the range 0,21 MJ.K ^ .m ^{3 to} 0,25 МГ.К ^_1 .И ^_3 . 13. The method of claim 8, wherein the aluminum particles are hollow spheres with a mean size of 48 · · mikrommtrů and apparent specific hmoonc> oti 0.3 g.cm ^"3, wherein the heat capacity is not ^d Notka ohjemu bed at nméilní ^ ^fl is ^0.084 uidaci MT.K ^-1 .m ^-3. 14. The method according to claims 1-6, characterized in · that the particles are non-porous prlškovitý alpha-alumina having a mean particle size of 23 to 54 microns mikrommerů and particle density hmoteooti ^3, 97 ^g .Am ^-3 * where ^t e ^p e ! n ^{c o} apaa the per unit volume at a minimal attachment fltiid ^nus ^ i ^{is 1,} 34 MJ.K ^{-1. m} ~ ³ .