DE1471971A1 - Method and device for the heat treatment of glass panes - Google Patents

Description

LAWYERS

DR.JUR. DIPL-CHEM. WALTER BEIL 25? '"' 3SS

ALFREDHOEPPENER '""

DR. JUR. DIPL-CHEM. H.-J. WOLFF
DR. JUR. HANS CHR. AX

FRANKFURT AM MAIN-HÖCHST AUtLONiIRASiE 58

Our no. 10 537

Pittsburgh Plate Glass Company Pittsburgh, Pen., V.St.A.

Method and device for the heat treatment of glass panes

The invention relates to the heating of glass panes, particularly in preparation for other processing methods such as Hardening (tempering), bending, coating and cooling of such disks. The treatment according to the invention is suitable for any processing method in which it is necessary that the glass pane is at least temporarily at an elevated temperature.

Many well-known processing methods are used in the manufacture of glass panes, e.g. bending, hardening, cooling, Coating and combinations of these methods, resulting in end products, their properties and uses from. Differentiate the starting product. These editing methods common is the heating of the glass panes

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New documents (Article 7 § t Ab> .2 Nr.ι Sato3 * ·

a temperature above the point at which their main surfaces or their outline changes due to a deforming force or accessible by touching a fixed limb. This point is referred to here as the deformation temperature. The deformation temperature is above that as the strain point and below that as the softening point known temperature.

The softening point is the state in

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which glass has a viscosity of 10 poise; the annealing point is the state in which the glass has a viscosity of 10 * poise and the relaxation point refers to the temperature at which the glass has a viscosity of 10 ^ 'poise. The terms "softening temperature", "cooling temperature" and "relaxation temperature" relate to the temperatures at which glass reaches the above-mentioned viscosity conditions, which are also known as "softening point", cooling point "or" relaxation point ". silica-glass panel is the "strain point" about 516 ⁰ G, the "strain point" about 546 ⁰ C and the "softening point" about 732 ⁰ C ₀

Glass is hardened to put the surface layers in a steady state of compressive stress while the protected interior develops tensile stress in order to compensate for the compressive stress of the surface layers. The glass hardened in this way is more resistant to impact, grinding, bending or thermal shock caused breakage, as chilled glass whose surface was not reinforced by a high pressure condition.

In the past, it was common practice to harden glass to apply radiation energy to the glass at a temperature to heat close to its softening point and then suddenly cool the heated glass, either for a longer period of time Time applied forced air or put the glass in a liquid- bath with a high heat absorption capacity deterred the heat remaining in the object with a relatively high

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Initial speed, which gradually decreased .

When the glass is cooled, its' temperature is initially above the relaxation point and the cooling point are increased, and then the glass is cooled to regulated '"ice. The temperatures τοπ glass panes must also be increased beyond these points if the glass is deformed, a third-party coating melted or by applying a metal salt or when in contact with light laser glass containing hydrolyzing organic metal compound Coating agent formed a metallic oxide coating thereon

In any case, the surface should be be soft enough to deform from solid members that support them and that come into contact with the glass when heated allow"

In the past it required economic exploitation of the manufacturing equipment to treat the panes of glass in a hot state, The need to the Transporting panes of glass at high temperatures was previously based on physical contact with the glass in contact with fixed parts of the carrying and conveying device at elevated temperatures is undesirable Deformation or damage to the main surface of the treated f ten panes of glass.

known methods for increasing the strength of glass panes consist of exposing the glass to radiation hits and then exposing the surface of the glass pane equally deterred. The most common ■ The method used is the treated glass pane held in a vertical or in a horizontal plane.

In a vertical plane, the gash washers are either held by pincers which grasp the disks near their upper land, or the lower one is propped up

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Edge of a pane of glass on a portafilter carried by a conveyor. In the latter ^ aIIe is the pane of glass held upright by reaching down on each side of the upper edge of the glass. With these vertical ones Processes leave pincer or fingerprints on the glass.

For the heating process, the glass is supported by moving it in a horizontal position over a series of spaced conveyor rollers through a heating furnace. In this process, it is inevitable that the roll prints, wear and other damage as well as "wave-like" to some extent, deformation of the disk remain as "moves alzen wavy about the spaced-distance ^w the glass and softened at the same time during the movement.

The problems outlined also relate to the handling of glass panes for other manufacturing purposes, in which the glass needs to be heated to elevated temperatures. This includes deforming or bending, cooling and application of coatings or films.

ψ If glass is bent and hardened at the same time, the glass can be supported or hung up with tongs, heated above its deformation temperature and subjected to bending processes, with weighted wires pushing the glass into a predetermined simple curvature or solid parts belonging together to form more complex shapes that have been softened by heat give. The pincers, as well as the wires or fixed parts of the dies, damage the glass when they grasp the surface. This surface damage is worse when the contact takes place at higher glass surface temperatures than at lower glass surface temperatures.

Horizontal bending under the influence of gravity has been used so far

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used to bend a disc while it was heated in preparation for curing. Panes of glass are attached to some form of outline configuration, with only a minor '^ part of the major surface surrounding the Edge of the glass to be bent touches the surface of the outline shape. Let the glass sag so that under the influence of heat it adapts to the shape of the surface of the mold, the process sometimes going through Application of pressure is supported by movable moldings. The middle part of the pane of glass tends to sagging to an uncontrollable amount because the glass must be heated to the deformation temperature so that it is also hot enough inside for hardening. Under Under these circumstances, the unprotected part of the glass between the supporting side edges of the deformation cannot resist.

Usually, the heating of the glass panes required for most of the procedures described Temperatures close to the softening point of the glass use radiant heaters. Irradiate such heating devices the glass with an energy at which the glass becomes partly transparent and partly the radiation energy absorbed. A large part of the radiant energy emitted on standard sheet or pane glass must therefore have a wavelength in the waveband between about 2.5 and 4 / u to ensure that the glass is incident Radiant energy absorbed in its entire depth.

The usual radiant heaters consist of gas burners or electrical resistance wires that function as heating elements, are evenly spaced from one another and are held within fireproof walls. The optimal average wall temperature is more than 76O ⁰ C.

The heating elements are preferably at a temperature

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brought, which is sufficiently above that of the walls to ensure an average wall temperature of 76O ⁰ C. In order to bring the temperature of the refractory wall to the desired level of radiation, the heating element must be at least the temperature of 87O ⁰ C.

A considerable part of the radiated on the glass panes However, heat is absorbed on their surface. This is due to the fact that the on the glass radiated heat has a wavelength distribution that is very similar to that of a black body and that the radiant heat Contains wavelengths that are customary in trade or Pane glass absorbs well and transmits or conducts poorly. The glass surfaces therefore absorb these wavelengths and become slightly hotter than the inside. With enough At high temperatures, the glass surfaces can be deformed before the interior comes into contact with a solid member of the glass is hot enough to deform, harden or cool the glass. In addition, during the heating process Damage caused by "chill cracking" can be avoided. This phenomenon occurs on the glass surface when the temperature gradient between a point on the glass surface and an adjacent point or its interior is so great that a tensile stress is caused at this point on the glass surface that is sufficient to reduce the The pane of glass spontaneously blows up before the temperature at the point under tension reaches the cooling point achieved. "Quenching cleavage" or glass breakage occurs extremely easily in a limited area of the glass touches a solid glass support member. The latter, which is usually made of stainless steel, is common colder than the glass before it is heated to its cooling area and can often cause the The touched glass part is still below the cooling area if another part has already been heated over the cooling area, so that a tensile stress arises in the touched area, which leads to the "reticle splitting".

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The invention relates to a novel treatment of the glass sheet during its radiant heating occasionally a manufacturing treatment of the glass, which reduces the tendency of the glass surfaces to be damaged by supporting elements is considerably reduced. The invention also significantly reduces the tendency of the glass to stick to sag uncontrollably in the unsupported places in cases where the glass is in a horizontal position is bent by sagging due to its weight on the surface of an outline shape. The invention also reduces the "wave formation" in glass that is spaced apart during heating Rolling is moved. Another advantage of the invention is the significant reduction in glass breakage and losses due to "quench cracking" during manufacture.

According to the invention achieves these results by allowing at the same time, the glass surfaces and the fixed, the glass-contacting ^x rush Glaaströmen from ^ ptzt 'which move along the surfaces, while of radiation sources with respect to at least one, and preferably to both Hauptfläclien the glass sheet sufficient heat to the Glass pane is radiated in order to raise the internal temperature of the glass above its cooling point and to approach the softening point. In the preferred embodiment of the invention, a glass, which is heated to a temperature substantially above the room temperature and below the glass softening point, is passed over the entire major surfaces of the glass sheet at a speed sufficient to create a layer of stagnant air which is usually located on the glass surface when the glass is exposed to radiant heating. The exact Pliessgeschwindigkeit could not be measured on the glass surface, but the Gaszufuhrgeschwindig- keifen for different environments mentioned ⁿ serving examples in the following and as a guide to useful implementation.

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So far, it was seen to be impossible to always to heat the interior of a glass sheet from room temperature to about the Entepannungepunkt while keeping the Aueeenfläche the disc relatively cool without causing stresses on the glass surface, cause the ^B smell. Therefore, the possibility of a heating process with simultaneous cooling of the surfaces has not been considered or overlooked by the glass processing industry.

In addition, the relatively hot interior of the The glass can flow freely and enable the glass to enter the hardened state when it suddenly cools down after heating State or by bending under pressure or sagging due to its weight the desired shape can be taken without damaging the surface.

Another advantage of gas movement is that it can keep the temperature of the facilities that the Support and touch glass panes subjected to heat treatment, softens. The gas flow causes the Temperature of the part of the temperature in contact with the glass of the treated glass, since the gas flow allows better heat transfer between the glass and the Glass touching parts than without gas flow.

In cases in which the glass receives a coating, the inside of the glass serves as a heat store, which helps to heat the glass surface to its film-forming temperature until a film or coating has formed. The heat storage makes it possible to inject the heated glass sheet a verhältnismäesig cold ^M etallsalz or applied in any other way, so that a metalloxydhaltiger film is formed after the film has left the oven and before the surface temperature of the glass sheet cools below a temperature at which the Film is made.

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In order to determine whether the treatment according to the invention can be carried out in the practice, various tests were carried out. In the initial experiment, several robes 2.54 µm thick were cast from sheet glass. Thermocouples were embedded in the middle of the middle ¹ oil and 0.3175 cm below the two opposing surfaces as well as on the surfaces of the samples.

The samples were placed in the middle between opposite gas-fired burners, which operated at a surface temperature of about 115o C ^0. The burners were 12.7 cm apart. Each glass sample to be examined was against the hot combustion products of the gas burners through a 0.3175 cm thick. Molten silica plate isolated! which was located immediately in front of each burner.

Air was blown over the samples while heating. The temperature of the glass surface was changed by changing the air flow rate over the surfaces of the samples is regulated.

To edge temperature effects to be avoided and mimic the conditions at a larger disk, the edges were the robe * ^ within a frame means of an alumina-silica ceramic fiber insulated.

The glass samples were heated and air was simultaneously supplied to the surfaces until the surface was exposed Reached relaxation point. The surface temperature and the temperature 0.3175 cm below the surface were both below that of the central part of each robe. . After 10 to 15 minutes of equilibrium, heating was stopped and the supply of air continued. Temperature measurements, which were carried out when the middle part cooled beyond the point of tension, showed that the surface temperature continued to be lower than the internal temperature of the samples.

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The tests showed that it can be achieved by means of a treatment in which the interior is heated by radiation with a Surface cooling is connected by convection, is possible, the surface temperature in a greater Scope than lower the internal temperature.

Further tests were carried out with 30.48 × 30.48 cm samples of glass panes. The equipment used tubular quartz infrared lamps of the type 16OOT3 General Electric, which were arranged in two opposite Borrow 24 lamps of each other a distance of 9.52 cm possessed _gs s. The lamps in each row were mounted parallel to one another on 1.9 cm centers. Each row was divided into three sections. Each individual section was manually regulated using a saturable core reactor.

The rows of lamps were on the inside wall of a storage room attached with air intake slots 0.3175 cm wide, which run parallel to the length of the tubular Lamps ran and placed midway between adjacent tubular lamps at 5.72 cm centers was. Each between two air supply slots There were two slots for air to escape, each in the middle of the not through an air supply slot occupied spaces between adjacent tube lamps were arranged.

_{The storage spaces were} supplied with air by two fans which were able to supply each storage space with 24.1 m of air per minute at a pressure of 35.2 g / cm. The movement of the glass was imitated by causing the device to vibrate along an axis perpendicular to the longitudinal extension of the parallel slits and tube lamps.

The glass panes were made using a frame construction

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Made of stainless steel, their spaced apart hairpin-like members located on the edge of the glass, held vertically between the rows of lamps. The edges of the glass were insulated with a 0.952 cm wide frame made of ceramic fiber to avoid temperature fluctuations Reason for marginal effects to be reduced to a minimum.

An optical strain measuring device was set up to observe the strains generated in a glass sample heated by infrared radiation were present «The tension measuring device was in the direction of of the main surfaces e and aligned along an axis in the central part of the glass.

Observations from several experiments indicated that the central part of the glass sheet developed tensile stress immediately after the application of heat. This tension increased and then slowly decreased. When the surface of the sample reached the relaxation point (516 ⁰ G), the stress value at the center was close to zero.

Compressive stresses developed in the middle part if the surface temperature was slightly above the The relaxation point was held and air currents were used to cool the surface, while simultaneously removing the radiation internal heating has been determined. The middle one Part of the pane of glass was hotter than the surface and tried to expand, while the cooler surface could not relax quickly enough to relieve the tension inside.

It has further been determined that from room temperature to heated glass sheets at the same time to rapid cooling of their surfaces and radiation heating its interior emperaturgefälle an inverted ^x developed with a higher indoor surface temperature. If this reverse slope was steep enough, the panes of glass would break before they were heated to the relaxation point.

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Which is necessary for the relaxation of thermal stresses?

the same time is shorter at higher temperatures ·. 1 & than at lower temperatures, and when the j7

Glass transition temperature above the flash point is * cause simultaneous Oberflächenktihlung and inner ¹ ^ 'heating using conventional equipment not broken.

TJm that actually consisted of a 2.54 cm thick glass-

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To determine the slope, a special composite plate made of two 1.27 cm thick plates was fused together between the Cromel-Alumel thermocouples. Insulation was applied to the edge of the composite sample and the thickness of the thermocouple was attached to permanent connectors on the frame of the glass pane. The surface thermocouples were glued to the sample. The glass was slowly heated to 732 ⁰ C.

^{A temperature difference of 83 0} O developed between the temperature of the central part and that of the surface when cold air with an average pressure corresponding to a water column of 1.01 cm was introduced into the storage space while heating was continued. This speed developed * a surface temperature of up to 649 ⁰ O.

Was used as the cool air with greater speed (at an approximately 1.27 cm high water column corresponding pressure was introduced, so that the surface temperature to 621 ⁰ C lowered, the temperature difference between the central part and the surface was 94 ⁰ C. By further increasing the feed rate of the cooling air to reduce the surface temperature to 593 ⁰ C increased the temperature difference to 105 ⁰ O.

Another series of experiments was carried out using the same apparatus as in the immediately preceding one Experiment carried out, being 1.27 cm

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used thick 30.48 χ 30.48 cm plates, which were fused together from 0.63 cm thick discs, with thermocouples embedded in the middle rope. These experiments were used to measure the temperature gradient that is possible with 1.27 cm thick glass. Every sample was heated carefully to avoid breaking the plate.

With maximum heating by means of heating coils (63 kilowatts total output) and surface cooling by means of air, which was supplied to the storage rooms with a pressure corresponding to a 0.76 cm high water column and sufficient to keep the surface temperature at 649 ° 0, the temperature was of the central portion to 699 ⁰ C heated.

When applying the same heating, however, while increasing the feed rate of Kühlüngsluft to a memory space pressure of one of 1.016 cm high water column corresponding to the surface temperature was 621 ⁰ G, and the temperature in the central part 682 ⁰ C. The thermal gradient between the central portion and the surface increased to 61 ⁰ C. This was the maximum temperature difference which could be achieved at 1.27 cm thick plates with the above described system. The maximum temperature difference between the glass surface and the central part was also achieved using a storage space pressure corresponding to a water column of about 1.27 cm high at a surface temperature of 593 ° C, and further using a storage space pressure that corresponded to a water column of about 1.524 cm high at a Surface temperature of 566 ⁰ C corresponded, achieved. In these last-mentioned tests, the total heat output was 63 kilowatts.

From the tests it was concluded that the supply speed of the cool gas to the Glagober ^ ä ⁰¹¹⁰ »must be regulated to avoid breakage, if

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the glass sheet is located below the _n tSpannungspunktes E, however, that a broader gas supply is permitted if the glass transition temperature is above the relaxation point. He found it possible to regulate the rise in surface temperature by simultaneously exposing the glass surface to the cooling gas while the entire pane is heated by radiant energy.

For glass that is 0.635 cm thick and even thinner, it was determined that it was necessary to avoid spontaneous breakage as a result of the caused in the surface of the glass during its simultaneous irradiation and surface cooling Tension is expedient, the feed rate cooler air over the surface preferably in to such an extent that the surface of the glass is not at a temperature significantly below that of the inner part is maintained while the temperature of the glass sheet is increased to its relaxation point will.

In a typical treatment according to the invention, where flat sheets of glass were held by tongs, the reject rate was reduced to less than half compared to previously used treatments without convection gas flows.

There are now various embodiments of systems which are suitable for practicing the invention.

In the drawings, like reference numerals refer to on the same structural elements.

Show it:

Fig. 1 is a longitudinal elevation of a so-called vertical heating furnace suitable for practicing the invention suitable and in connection with a tempera * «a» system will be shown.

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Figure 2 is a partial cross-section and a partial end elevation of the furnace part of the plant of FIG. 1, which shows the arrangement of a gas supply system in an electrical Heater shows.

Pig. 3 shows a partial cross-section along the lines III-III von Pig · 1 with a drive mechanism for the operation of the ^ emperungaanlage, which opposes an orbital movement suddenly cooled panes of glass.

Pig. 4 is a part of a partially schematic and partially sectioned longitudinal elevation of another embodiment a furnace for the present invention, wherein the glass sheets prior to bending and tempering in almost horizontal position protected, thermally treated.

Figure 5 is a cross-section through Pig's furnace. 4th

Pig. 6 shows an enlarged section through a high one Speed-operated gas burners of the type which, according to the invention, are used to generate rapid streams of hot gases is used.

Pig. 7 shows a section along the lines VII-VII in FIG. 6, illustrated in detail.

Pig. 8 shows a longitudinal section through a roller kiln in which glass panes according to the present invention be spread by heating for coating.

Pig. Figure 9 is a cross-section through Pig's furnace. 8th.

In the drawings, Pig shows. 1 a tunnel-like heating furnace 10, at the end of which a hardening plant 12 is connected. A single rail 14 extending along a horizontal ^ ^ ahn above the aeh the furnace and the curing system and transports the W _a gene 16, of the catch hanging. The latter are at the bottom of vertical

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Rods 20 attached which the tongs 18 at the agen ^w attach 16th

The top wall 21 of the furnace extends over its entire length a thin longitudinal slot 22, which gives the rods 20 holding the pliers clearance. In this way the ^ lines 18 and the panes of glass covered by them can pass through the furnace when the carriages 16 move move along the rail 15. The rail 14 is therefore located in a vertical plane which contains a path of movement of the glass panes through the furnace 10 and the hardening system 12.

The hardening plant 12 is located behind the furnace 10, the two nozzle chambers or storage spaces 24 and 26 on opposite sides of that from the rail 14 occupied vertical plane contains. The nozzle chambers 24 and 26 each have a group of nozzles, which are directed towards each other through the inner walls of the storage spaces and to a suitable source of compressed air connected to a compressor (not shown).

A motor 28 directly drives a drive rod 30. The latter drives one driven by a connecting rod 34 Rod 32 on. The connecting rod 34 engages the ends of the rods via the bevel gear 36 30 and 32. Eccentrics are attached to each of the rods 30 and 32. The eccentrics 38 are rotatable on a carrier attached to the bottom of each nozzle chamber 24 and 26. In this construction, between the opposite Maintain a fixed distance between storage spaces, as they move in unison in spaced orbits, T »frighten off a raised * glass pane, which held between them in an open manner,

The furnace is equipped with an electric heater

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directions 42 running along inner side walls 44 and 46 are attached (Fig. 2). A floor 47 supports the side walls 44 and 46 and forms the floor of the oven

The side wall 46 is apertured along its length to provide an upper passage 48 and a lower passage 50. The upper passage 48 is standing in connection with an inlet line 52 at a chamber 54, the height of which from inlet 52 to the middle of the tunnel-like furnace in a direction transverse to the axis of the Single rail 14 decreases. The height of the chamber 54 also increases along its connection to the inlet pipe 52 (| the length of the oven to the front and back. The upper passage 48 ends in a narrow, horizontal slot 56.

The lower passage 50 communicates with an outlet port 58 that leads into a combustion chamber 60. The latter has a gas burner 62 which has the usual air inlet, gas inlet, mixing chamber, switching valve and main valve, which are not shown since their particular construction is not critical to the present invention and many commercially available gas burners are suitable for use in the system described here suitable. Λ

Between the combustion chamber 60 and a generator housing 66 runs a duct 64 «The valve, ator housing includes a fan operated by a motor 67. An outlet pipe 68 connects the fan housing 66 with the inlet 52. As soon as the fan in the fan housing 66 is put into operation, convection currents are generated from a mixture of combustion products I from the combustion chamber 60 in the direction of the in Fig. arrows shown. An identical fan system (not specified) can be on the opposite side of the furnace are located to be equal and opposite

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to deliver currents on the opposite major surfaces of the treated glass sheets.

The inlet line 52, the channel 64 and the outlet channel 68 are all covered with thermal insulation. This reduces the thermal output of the system the heat loss of the moving gas is improved.

The gas-heated circulation system described causes the gas to flow downwards along the main surfaces the pane of glass suspended vertically within the furnace 10. This reduces the formation of air layers in the furnace to a minimum, the creation of a hot layer of stagnant air on the surface of the glass avoided and thus the likelihood of localized Reduced temperature fluctuations.

The gas moving in the circuit, which is a mixture of the combustion products and an excess of air, is forced into the upper part of the furnace and withdrawn from its lower part. The positive gas flow through the circulatory system provides one within the furnace Atmosphere that is about a more than normal pressure.

This overpressure inside the furnace makes the accidental penetration of cold air currents into parts of the furnace unlikely « In addition, the positive pressure inside the furnace forms a kind of barrier to entry cold air from the hardening plant into the furnace.

Before a supply system for circulating gas was installed, an overview of the glass temperature inside the furnace showed that the temperature of the glass pane heated for curing in the furnace fluctuated ^{around 22 ° C. from pane to pane. In addition, temperature differences of 22 °} C. were found between different parts of a sheet of glass moving through the furnace

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flat panes of glass during the heating stage in the oven, Some panes were bent into composite shapes, the unsupported edges of which were very easily creased with sharp creases *

In particular with larger glass sizes one often experienced breakage. It is assumed that this is due to the between the different ! rush of the glass is due to the thermal stresses caused by uneven Heating of the entire pane caused and cooler by local cooling due to random currents Air against one or more local parts of the disc ^ have been strengthened.

The furnace, in which the circulatory system was built, allowed glass sizes up to 183 x 275 cm to be handled The furnace was equipped with electrical heating elements with an output of 383.5 kilowatts, which evenly distributed over an area of 12.2 m:

was.

The temperature of the circulatory system in one Downward movement along the vertical glass surfaces supplied gas was under the temperature of the GIa-:

ses it is kept on its withdrawal from the oven by the (

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Gas burner fed 20.7 m of gas and 235 m of air per hour became. The furnace had a volume of 1.78 nr and the fan was capable of running at one speed of 108 m / minute to deliver a pressure that corresponded to that of a 24.1 cm high water column. Since the gas with the speed of 79.3 nr / minute into the combustion chamber was pulled off, the furnace worked with, a positive pressure about 0.50 cm high Water column corresponded. The excess gas escaped through openings in the furnace and through the inlet and outlet openings, when the doors that normally covered these openings were opened to allow insertion

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^Λ · I. ■■ ■ ·

a sheet of glass or the removal of a heated sheet of glass.

Experiments were carried out, with one in the circuit conducted gases reheated to temperatures of 677 ° C. The upper temperatures of the examined area were, however, unsatisfactory for the production of useful products, since the glass at these temperatures .zu was soft and the tongs went too deep into the glass. L as soon as the air: gas ratio by supplying 11.3 nr gas Wed per hour and 198 m per hour were increased ^ the gaseous products with a temperature of 604 C. introduced. The temperature was above the initial temperature of the glass surface and below the final temperature of the Glass surface.

j The best results were achieved in the oven which used the air / gas mixture described above together with a electrical system of heating elements with a power

"2

j of 383.5 kilowatts used over a wall area of 12.2 m, .

As the gaseous products initially move in a downward direction were moved along the entire length of the furnace, pi j the circulated gas accelerated the heating the surfaces of the glass sheet during the first part of the heating. Only when the glass is about the Temperature of the cycle gas was heated, the retardation of the surface heating rate began.

In the described system, the surface temperature of the glass disc was without convection currents across the surface of the glass sheet 66o ⁰ C. After the introduction of the recycle gas streams at a temperature of 604 ⁰ C., the surface temperature of the glass sheets on; _t the end of the heating cycle average of 632 ⁰ C. '*

The inside or core temperature of the glass panes

in both cases for hardening. ρ ν

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The circulation system has increased the production capacity of the furnace shown in FIGS. 1 to 3 by 20 # and reduced the scrap by about 60 #.

Figures 4 to 7 show another embodiment under Use of a gas stream to moderate the upper surface temperature of a pane of glass that is exposed during the Bending and hardening is held horizontally. In this second embodiment, a horizontally placed oven is used 70 with a holding structure 71 for a series of conveyor rollers 72 is shown. The conveyor 72 transports divided ones “Outline forms 73” where slide-like rails 74 of j |

usual shape holding carriage 75 a support for the roll-; T

Forming movement «The oven is equipped with electrical heating elements 76 which are arranged to generate heat against j a support plane for the movement of the glass pane strah- j len that are essentially parallel to the left side wall 77 and the right side wall 78 of the oven 70 is located on the upper and lower walls 79 of the oven i heating elements 76 are attached «

The voltage of each electrical heating element is determined according to of Ti.S.A. Patent 3,068,672. The electric Heating elements deliver a series of consecutive Radiant heat patterns along the length of the Förde- <* rers 72, causing the panes of glass to be heated and to pass through., " can be brought into line with the forming surface of the moving bending trenches 73.

Gas burners 80 are mounted in openings in the left wall 77 and in the right wall 78 which look in the direction shown in FIG. The gas burners 80 are arranged in pairs, one pair extending through the W _at d 77 and being arranged laterally opposite but offset in height with respect to the other burner pair.

In the section shown in Fig. 5 is through the

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left wall 77 running burners so arranged! that it is directed at a height above the surface of the bus bending held glass plate at high speed against the right hand 78, an air-gas mixture containing excess air and erhitete Verbrennungeprodukte, while the right of the ¹ * and 78 NaOH inwardly directed gas burner in a level below the lower surface of the glass pane a high speed moving stream of heated Verbrennungiprodukten and air against the left wall 77 directed · the in I ¹ Ig * burner group shown in Figure 5 provides a-generally extending in a clockwise motion of the gas with a verhältnlsmässlg high speed across the shown section of the furnace 70, Further pairs of burners, which are arranged along the furnace at a distance from each other, supply within the furnace alternately counterclockwise and clockwise flows of gaseous products moving at high speed, which are mixed with air.

The speeds of the gas flow are so high that a standing layer of hot air can form on the main surfaces of the glass. The flow of combustion products, which are hotter than the initial glass temperature, helps to raise the temperature of the glass sheet during the first stages of the heating cycle. Xn the later stages of heating, the temperature of the ^G aBstrome is below the temperature of the radiant heat. The maximum glass surface temperature achieved during roasting is therefore regulated in such a way that it is lower than the surface temperature achieved without the positive gas flow.

The gas flow increases the pressure inside the furnace those of the surrounding atmosphere. This positive pressure reduces the possibility of that's accidentally cold air currents penetrate into the furnace and locally cool the glass, as a result of which stresses would occur in the pane, which Could cause breakage. OFHG ^ A ,. ^ P

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it *

Referring to Figures 6 and 7, a typical gas burner 80 is described which is located within the opening in the furnace wall 77 is provided. The burner includes a centrally located gas inlet chamber 82 which is in communication with a gas inlet housing 84 which is internally threaded to receive a gas supply line (not shown) Has.

The gas inlet chamber 82 is almost cylindrical Shape and deliver the gas axially inward into a cylindrical mixing and combustion chamber 86. A "Jj Air supply chamber 88 with an almost annular cross-section is defined by an air supply housing which is used for the reception of an external thread of an Ifipple of a (not shown) Air supply pipe has an internal thread, supplied with air. The air supply chamber 88 surrounds the gas inlet chamber 82 completely, and a cylindrical wall 92 separates the gas inlet chamber 82 from the air supply chamber 88.

Openings 93 arranged on the periphery are located near the axially inner end of the cylinder wall 92 and run tangentially to its entry point. The gas supply chamber 82 has an outlet opening 92 which is in communication with the mixing and combustion chamber 86, Jj The inner wall 95 of the air supply chamber 88 is pierced by air supply pipes 96 arranged on the periphery of cylindrical shape, which the end of the air supply chamber 88 and the combustion and connect mixing chamber 86 to one another. The openings 93 allow the pre-mixing of the gas between the air supply chamber 88 and ^! the gas inlet chamber 82 before the main mixing takes place in the combustion and mixing chamber 86.

The end of the combustion and mixing chamber adjacent to the inside of the wall 77 tapers in cross section, by the velocity imparted to the gaseous products from the combustion and mixing chamber 86 into the

19/0434 ^: %,

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Increase furnace space. This construction increases the speed the products of combustion at a speed sufficient to move the gas over to achieve the entire width of the oven.

The axis of each burner 80 is transverse to the length of the furnace to allow rapid movement of the flow of the Combustion principles and excess air in a direction transverse to the length of the furnace and parallel to a major surface to allow the glass pane to be treated.

The embodiment shown in FIGS. 4 and 5 is a continuously operating one Furnace 70 with an entrance 98 and an exit 100. The conveyor rollers 72 successively traverse a first one Preheating zone 102, a second preheating zone 104 and a bending zone 106, all of which are between the entrance 98 and the exit 100 of the furnace 70. One is located outside the exit 100 of the furnace 70 Hardening plant 108 is also traversed by conveyor rollers 72.

This plant contains upper storage spaces 109 and lower storage spaces 110, the openings of which correspond to the surfaces of the curved Facing glass panes. Air under pressure is fed through the reservoirs from a source (not shown) by flexible conduits 112 and the Storage spaces 109 and 110 are provided with a standard the motion imparting mechanism 114 moves in unison with one another in their orbit.

In a typical horizontal continuous system, near the end of the charge (first preheat zone 102) of the furnace, the burners were delivering 7.2r gas / hour which, as it exited the burner, produced combustion products at a rate of 41.04 m / sec. and a temperature j of 704 ° O. In the second pre-scorching zone, 3.28 m * of gas / hour were fed in, so that combustion

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products were generated at a speed of 23.4 m / sec, at 413 ⁰ C at the outlet of the burner, and a third group of burners in the bending zone near the furnace outlet delivered 5.1 m gas, so that combustion products at a speed of 28.88 m / second at 593 ⁰ C at the burner exits. Each of these gases was mixed with enough air to achieve the desired temperature. The system was supplied with a total of 1103 kilowatts of electricity, of which 385 kilowatts in the first preheating zone, 284 kilowatts in the second preheating zone and 434 kilowatts in the bending zone.

The first group of burners in the first preheating zone beyond the entrance raised the ambient temperature in the first preheating zone and increased the heating rate for the glass surface as well the inner. In the second preheating zone, the The rate of heating on the surface is retarded in order to achieve a tougher skin or surface of the glass and thus reduce the possibility of the glass sheet being imprinted by the shape that supports it or has been deformed.

At this stage of the bending cycle, the inside became A

the pane of glass so malleable that it could be shaped. As soon as the glass had made contact with the shape in the bending zone, the third burner group near the exit delivered a flow of light gases that was sufficient to moderate the heat differences along the entire length of the curved glass, especially if the glass had a heating pattern of It was exposed to radiant heaters fed with different radiant intensities in order to cause intensely heated parts of the glass sheet transported laterally through the furnace to be bent sharply, while other ropes, which were simultaneously exposed to other heaters with lower intensity, were to a much lesser extent were bent . 909819/0434

Those for the embodiment τοη Fig «4 bit 7 enumerated Principles apply in the same way to roller furnaces, such as. ; *

. .. they are shown in Figures 3 and 9 «Here ^! t

the glass sheets G are carried on rollers and moved through a heating furnace, Heisee, at high speed over the upper and lower surfaces of the glass sheets Flowing gases improve the surface hardness and reduce the tendency of the helssen glass panes to stick to the To deform contact with the successive, spaced rollers «Since the rollers constantly jL are installed in a furnace, reach their temperatures ™ the temperature of the surrounding atmosphere and it is this way less likely that the panes of glass' G can be damaged during their heating by exhaustion corners.

In the embodiment of Figures 8 and 9, a tunnel-like furnace 120 is traversed by a conveyor 121, of a series of transversely arranged rollers, spaced apart from one another in the longitudinal direction of the furnace 122 includes a drive motor 124 and suitable chain and pinion drive mechanism for the rotation the rollers 122 and the transport of several sheets of glass through the furnace. "Heating elements 126 are located on the ' H upper and lower walls 129 of the furnace «Die Glasetutz flat of the conveyor rollers 122 are in one plane between the upper and lower heating elements «

The oven has a left wall 127 and a right wall 128 «gas burners 130, similar to the burners 80 of the previous embodiment *, are arranged in pairs, . with one pair above and one pair below the level of the conveyor rollers 122. A burner / each pair is in an almost horizontal direction through the

Wall '127 directed towards wall 128 to remove combustion products aiming at wall 128 at high speed, f. ; while the other burners of the pair move in a nearly horizontal direction through wall 128 against wall 127

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f it ^w

'is directed to combustion products at high speed Ability to direct it against the wall 127 · Further pairs of burners Bind alternately at the top and bottom to the appropriate one Walls arranged so that they alternate clockwise and counter-clockwise currents of combustion-brodulcten at right angles to the path of movement of the glass panes G through the furnace 120.

The furnace also contains a heat control device " 132, which controls the surface temperature of the panes of glass that pass directly by it. be turned away.

Near the exit of the oven 120 is a coating station 140 which consists of a battery of one or more spray guns 142 mounted so that their direction of movement, according to U.S. Patent No. 2,899,929, is transverse to the longitudinal axis of the conveyor. The spray guns 142 are located above the conveyor path and are oriented so ^as ss they apply to the surface of the transported along the conveyor rollers 122, the glass sheets G a coating agent.

Beyond the coating station or in place of further gas treatment ^{87 "01} * ¹ ** can ohtungen, for example (not shown) may be provided curing or cooling system (also not shown), which jew'eils depends on the method by which the glass sheets Similarly, the earlier embodiments of the ovens can be used for purposes other than those specifically discussed, for example, the oven of the embodiment of Figures 1 to 3 can also be used in conjunction with a press brake or film applicator, and the oven of the are the embodiment of Pig, 4 and 5 can besides or in place of the method described in conjunction with a coating apparatus comparable, turns, this latter embodiment can only with radiant heaters. in the upper wall throughput

with gas supply devices running through the side walls of the heating furnace.

An essential feature of the invention is a relatively cool gas against the main surfaces of the Lead glass panes, while the latter by irradiation from room temperature "up to an elevated temperature over the relaxation temperature are heated. The feeding speed must be sufficient to lower the surface temperature significantly compared to that without application would be reached by gas so that the glass surfaces are more resistant to deformation when the glass sheet reached a higher temperature. Nevertheless, the extent of the gas supply must not be so large that there is a tensile stress that is sufficient to cause spontaneous breakage in the glass before the latter heats up to the relaxation point will. In the case of panes of glass with a thickness of 0.63 cm and less, the gas supply speed must not be that which causes surface tension that leads to spontaneous breakage in the glass, which is then the pail, if the surface temperature is kept well below the temperature of the middle part before the latter is increased to the point of relaxation.

It is also possible to first heat the glass panes approximately to their relaxation point and at least about 28 ⁰ G below the relaxation point and then to direct a relatively cool gas against the main surfaces of the glass panes, while the latter is raised by irradiation from a temperature slightly below the relaxation temperature an elevated temperature can be heated, which is so far above the relaxation temperature, as it is necessary for the fabrication. In this case too, the gas feed rate must be sufficient to lower the surface temperature significantly below the temperature it would reach without the use of gas, so that the glass surfaces are more resistant to deformation when the glass pane is what is required for further use

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increased temperature reached. Because of this shift the application of the cool gases to the glass surface until the point in time after which the glass temperature has its relaxation point has reached, one avoids any spontaneous breakage during the first heating stages, so that the invention is also suitable for mass production.

The simultaneous application of a convection current according to the preferred embodiment of the invention moderates the temperature rise on the glass surfaces, wherein the surface heating rate is first accelerated and then decelerated to a greater extent than it the amount of temperature rise within the body affected by the glass pane. The surface layers of the glass panes treated according to the invention are harder than that of panes of glass that have been treated according to the usual methods so that the glass surfaces are enabled deformation to a greater extent than ■ the workpieces treated according to the previously usual methods to resist.-

For the present invention the heating of glass sheets a tunnel-like furnace is always used, contains the solid support or holding devices, touch at least one major surface of the glass sheets "The hallmark essentially consists in that means for heating gas and means for lowering the heated ^& ases are provided, which is guided along the entire main surface of the glass pane under pressure inside the furnace, while the glass pane is heated by irradiation. In this ^w else the maximum surface temperature of the glass pane is set to a temperature lower than that which they would achieve in the absence of these gas steering devices, but the internal temperature of the heated glass should not be significantly affected.

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The invention has been described with reference to a preferred embodiment and certain modifications. Each of the described embodiments of the furnace, ie the vertical and the horizontal shape and the described glass holding methods can be used for hardening, film application, cooling and other treatments. The invention can be applied to practically any type of glass treatment in which the heating of the glass is an important part of the process.

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Claims (1)

yatent claims 1.) Process for the heat treatment of glass panes, in which -the panes are exposed to radiant energy in order to heat their surface to a temperature close to the voltage point and immediately thereafter a cooling medium is directed against the surface in order to moderate the rate of surface heating, while the irradiation of the glass pane is continued until its internal temperature exceeds the stress point. steps, characterized in that the application of the cooling medium begins at a point in time at which the surface temperature has approached the stress point of the glass, that the pane is transported along a predetermined path during the irradiation and that the radiation energy is in a direction transversely to the direction of movement of the glass pane and applies the flow of the cooling medium in a direction transverse to the direction of movement of the glass pane and transversely to the direction of radiation » 2.) The method according to claim 1, characterized in that the pane of glass is exposed to radiation which to a large extent in the wavelength range from about 2.5 to ety / a 4 p. lies. 3.) Method according to claim 1 and 2, characterized in that that you first have a relatively hot cooling medium at a temperature above the stress point of the glass, and then before the glass against deforming influences becomes sensitive, a relatively cold cooling medium in one Temperature below the stress point with a ORIQlWAL INSPECTED 9/0 434 / see 2 no. 1 sentence 3 the amendment 3Qee. ν. 4.9.196 // Speed and apply for a duration »that the., The heating of the glass is delayed until the glass is less susceptible to deforming influences has become, whereupon the irradiation of the glass pane and the application of the cooling medium are continued, until the glass has reached an even higher temperature between the stress point and the softening point. 4.) Method naoh claim 3, characterized in that one the relatively cold cooling medium in two stages, namely initially at a temperature below the stress point of the glass and then applied at a temperature between the temperature of the relatively hot cooling medium and that of the first relatively cold medium. 5.) Process according to Claims 1 to 4, characterized in that that you keep the pane of glass during the application of the. Radiant energy and the cooling medium in a suitable Holds position relative to a bending form and heated so high that its shape corresponds to the. Bending shape changed. 6.) Process according to claims 1 to 4 ». characterized in that W: that the glass pane is heated to a temperature sufficient for hardening by simultaneous application of radiation and cooling medium and then, when this temperature is reached, the glass pane is immediately quenched by interrupting the radiation and using a relatively cold cooling medium. AL INSPECTED 909819/0434 7 ·) Method according to claims 1 to 4, characterized in that the glass pane is heated to a temperature above its relaxation area by simultaneous application of radiation energy and cooling medium and then • relaxed by moving it through the relaxation area at a controlled cooling rate. 8.) The method according to claim 1 to 4, characterized in that a coating agent is applied to the glass pane by heating it to a sufficiently high temperature by the simultaneous application of radiation J * energy and cooling medium to the coating agent on the glass pane to fix permanently. Pure Pittsburgh Plate Glass Company Lawyer 90 981 a / 0434