WO2020052828A1

WO2020052828A1 - Device and method for thermally tempering glass panes with heat exchanger

Info

Publication number: WO2020052828A1
Application number: PCT/EP2019/067275
Authority: WO
Inventors: Achim ZEICHNER; Jack PENNERS
Original assignee: Saint-Gobain Glass France
Priority date: 2018-09-14
Filing date: 2019-06-28
Publication date: 2020-03-19
Also published as: CN111194298B; EP3849949A1; CN111194298A; ZA202100282B; MA53585A; BR112021000859A2

Abstract

The present invention relates to a device for thermally tempering glass panes, comprising - a first blowing box (1.1) and a second blowing box (1.2) which are arranged opposite one another and are suitable to subject the surfaces of a glass pane (G), which is arranged between them, to a gas flow, - gas supplies (2.1, 2.2) which are respectively connected to the first blowing box (1.1) and the second blowing box (1.2), the gas supplies (2.1, 2.2) being equipped with an evaporation cooler (5).

Description

DEVICE AND METHOD FOR THERMALLY PRELOADING

GLASS PANELS WITH HEAT EXCHANGER

The invention relates to a device and a method for the thermal tempering of glass panes and the use of a heat exchanger, in particular an evaporative cooler, for the thermal tempering of glass panes.

The thermal hardening of glass panes has been known for a long time. It is often referred to as thermal tempering or tempering. By way of example only, reference is made to the patent documents DE 710690 A, DE 808880 B, DE 1056333 A from the 1940s and 1950s. A glass pane heated to just below the softening temperature is subjected to an air flow, which leads to rapid cooling (quenching) of the glass pane. This creates a characteristic stress profile in the glass pane, with compressive stresses on the surfaces and tensile stresses prevailing in the core of the glass pane. This affects the mechanical properties of the glass pane in two ways. First, the fracture stability of the disc is increased and it can withstand higher loads than an uncured disc. Secondly, glass penetration after penetration of the central tension zone (e.g. through damage by a pointed stone or by deliberate destruction with a pointed emergency hammer) does not occur in the form of large, sharp-edged fragments, but in the form of small, blunt fragments, which significantly reduces the risk of injury. Due to the properties described above, thermally toughened glass panes are used as so-called single pane safety glass in the vehicle sector, in particular as rear panes and side panes. In the automotive sector, high demands are made on the degree of preload, which are also regulated in standards. But thermally toughened glass panes are also common in construction, architecture and living areas, for example as glass facades, shower cubicles or table tops.

Ambient air, which has not been pretreated, is typically used during tempering, from which a strong gas flow is generated by means of fans, which is directed as homogeneously as possible to the surfaces of the glass panes by means of large-area blow boxes provided with a large number of nozzles. The strength of the gas flow determines the tempering efficiency: the stronger the gas flow, the more efficiently the glass pane is quenched and the higher the voltages generated. In addition, other factors such as the temperature, humidity and density of the gas flow have an influence on the preload efficiency. Current trends in the automotive industry require ever higher pretensioning efficiencies. For example, ever thinner glass panes are used to save weight. However, the thinner the glass pane, the higher the prestressing efficiency must be in order to produce a temperature difference between the pane surfaces and the pane core which is sufficient to generate the desired stresses. In addition, glass manufacturers endeavor to bend glass at ever lower temperatures, which can improve the optical quality of the panes. However, the colder the glass pane is before tempering, the more it has to be quenched in order to generate the desired tensions.

In particular, if the manufacturing plants are located in countries with high outside temperatures or at high altitudes, strong gas flows are required to achieve the required pretensioning result. The generation of strong gas flows is associated with a significant increase in the energy costs for operating the fans.

Heat exchangers with indirect heat transfer are known in which heat is exchanged between two media in separate rooms. They are also widely used in everyday life, for example as a radiator or as a cooling system for internal combustion engines. It has been proposed to use such indirect heat exchangers to cool the gas stream with which a glass pane is cooled or thermally tempered. Examples are on GB1021849, US20130252367A1 and

US20120171632A1.

It is also known to intensify the cooling of the glass pane by the transition of a coolant located on or near the glass surface into the gas phase. In GB441017 it is proposed to apply water drops to the glass surface, which evaporate and thereby cool the gas flow and the glass. In US3929442 it is proposed to provide the glass surface with dry ice which sublimes, whereby the glass is cooled. However, bringing the glass surface into direct contact with a coolant carries the risk of the glass being damaged up to the point of cracking. In contrast, it is proposed in W02013102702A1 to supply liquid droplets to the gas stream via a porous membrane, which evaporate before hitting the glass pane, but in its immediate vicinity, drawing thermal energy from the glass pane. Such a solution is technically very complex and prone to errors. In power plant construction, it is known to adiabatically cool intake air ducts of gas turbines with the aid of evaporative coolers. Examples are US5655373A and W003058141A1. Evaporative coolers are heat exchangers with direct heat transfer, i.e. a combined heat and mass transfer. The cooling effect is based on the evaporative cooling of a cooling liquid with which a carrier material through which the air stream flows is impregnated.

The object of the present invention is to provide an improved device and an improved method, wherein a high pretensioning efficiency is achieved in an energy-efficient manner.

The object is achieved according to the invention by a device according to independent claim 1. Preferred configurations emerge from the dependent claims.

The device according to the invention for the thermal tempering of glass panes comprises a first blow box and a second blow box. The two blow boxes are arranged opposite one another so that their gas outlet openings (nozzles) point towards one another. This means that the entirety of the gas outlet openings of the first blow box and the entirety of the gas outlet openings of the second blow box point towards one another - it is not necessary for each individual gas outlet opening to have a counterpart exactly opposite it in the opposite blow box. Instead, the individual gas outlet openings of the blow boxes can be offset from one another. With the blow boxes with gas outlet openings facing one another, the surfaces of a glass pane arranged between the blow boxes can be subjected to a gas flow. A gas supply is connected to each blow box, via which the gas flow is fed to the blow boxes.

According to the invention, the gas feeds are equipped with a heat exchanger, in particular an evaporative cooler. The gas flow is actively cooled by means of the heat exchanger. Since the gas flow is at a lower temperature when it hits the glass pane, it has to be less strong in order to achieve the same cooling or prestressing effect. This can save energy for generating the gas stream. That is the great advantage of the present invention.

By cooling the gas flow, the preload efficiency is increased. The term biasing efficiency as used in the present invention can are expressed quantitatively by the so-called heat transfer coefficient a. It is a common physical quantity and, as it were, a proportionality factor that describes the intensity of the heat transfer at an interface. It is usually specified in the unit W / (m ² K). The heat transfer coefficient during the thermal tempering of glass panes is particularly dependent on the strength (pressure), the temperature, the density and the humidity of the gas flow.

A heat exchanger in the most general sense is understood to be a device which transfers thermal energy from the gas stream in the gas feeds to a coolant stream, or is provided and suitable for this purpose. The gas stream is cooled. The cooling can be based on a direct heat transfer, that is to say on a combined heat and mass transfer between the media, or on an indirect heat transfer, the two media being spatially separated by a heat-permeable wall. The geometric routing of the two material flows (gas flow and coolant flow) to one another can in principle be chosen freely. For example, operation can be selected in co-current (both material flows in the same direction), counter-current (both material flows in the opposite direction) or cross-flow (both material flows cross, also called cross-flow). An overview of different types of heat exchangers is provided, for example, by Ramesh K. Shah, Dusan P. Sekulic "Fundamentals of Heat Exchanger Design", especially in Chapter 1 "Classification of Heat Exchangers".

The heat exchanger is operated with a coolant, in particular through which the coolant flows or around which it flows. The coolant is preferably liquid (coolant), but can in principle also be gaseous. The cooling liquid is preferably water or essentially consists of water, which may optionally contain additives, for example heat-conducting additives, antifreeze or chemical or biological stabilizers.

The device according to the invention can optionally include a recooling device which is provided and suitable for cooling the heat exchanger or the coolant of the heat exchanger during operation. This can further increase the efficiency of the cooling.

In principle, a heat exchanger for cooling the gas stream for the thermal tempering of glass panes can be designed as an indirect heat exchanger, by which a heat exchanger with indirect heat transfer is referred to. An indirect one The heat exchanger has a component through which the coolant flows and which separates the coolant from the gas stream to be cooled. Said component is arranged for efficient heat transfer in the gas stream. Operation in cocurrent, countercurrent or crossflow is possible, and combinations of these are also possible. The coolant can be liquid or gaseous, but is preferably liquid. The component through which the coolant flows can be designed in various ways. The component can be designed, for example, as a plate, typically as a plurality of parallel plates (plate heat exchanger) or as a spirally wound sheet (spiral heat exchanger). The component can also be designed as a tube or a multiplicity of tubes (tube heat exchanger, tube bundle heat exchanger). The tube or tubes can be bent into a U or a number of shapes to reduce the space required (U-tube heat exchanger). Two concentric pipes can also be used, with one pipe being flowed through by the coolant and the other by the gas stream to be cooled (jacket pipe heat exchanger), or cooling registers as a combination of pipes (for the coolant) and fins attached to them (for the cooling gas flow). The indirect heat exchanger can also be a recuperator. In addition to the examples mentioned, other configurations are also conceivable.

Indirect heat exchangers have the advantage that the cooling effect can be regulated, in particular by the flow rate of the coolant. In this way, a desired temperature of the gas flow can be set deliberately. Control loops can also be implemented, the temperature of the gas flow being measured and automatically regulated by the coolant flow. The indirect heat exchanger or its coolant is preferably cooled by a recooling device in order to increase the efficiency.

According to the invention, the heat exchanger is designed in particular as an evaporative cooler. A coolant, in particular water, is used as the coolant. Such an evaporative cooler is a heat exchanger with direct heat transfer, the evaporative cooler of the coolant being used to cool the gas stream (heat transfer). Coolant is transferred to the gas flow (mass transfer). In addition to cooling, the evaporative cooler also causes an increase in the moisture of the gas flow, which likewise increases the pretensioning efficiency and is an advantage of the invention. In addition, evaporative coolers can generally be operated without recooling, so that they are cheaper to maintain than, for example, indirect heat exchangers. The device therefore preferably has no recooling device. The evaporative cooler is preferably designed as a so-called trickle cooler and typically contains a carrier material, in particular a fibrous or porous carrier material, which is impregnated with a cooling liquid. For this purpose, for example, a droplet separator can be arranged above the carrier material, which sprinkles the carrier material with the cooling liquid. A pot collector can be arranged below the carrier material in order to collect coolant that has flowed through the carrier material. The coolant collected in the drop collector can be returned to the drop separator by means of a coolant line provided with a pump. The gas stream flows through the carrier material. Cooling, in particular adiabatic cooling, of the gas stream is thereby achieved. Since the carrier material is typically trickled vertically by the cooling liquid and the gas flow passes horizontally through the carrier material, there is cross-flow operation. When the coolant evaporates, the energy required for this is extracted from the environment, i.e. ultimately from the gas flow, which leads to its cooling. The evaporated coolant is absorbed by the gas flow and increases its relative humidity. The effect of cooling depends on the surrounding air condition, temperature and relative humidity. The lower the relative humidity, the higher the potential for further moisture absorption, so the more coolant can evaporate. Paper, for example, can be used as the carrier material, in particular in the form of corrugated paper layers. Alternatively, suitable ceramics or synthetic structures are also conceivable as a carrier material.

The gas supply of each blow box is preferably equipped with at least one fan in order to supply the respective blow box with the gas flow. The gas feed of each glass box is particularly preferably equipped with a first fan and a second fan, which are connected to one another in series, so that the gas flow generated by the first fan enters the second fan and is further compressed by it and thereby reinforced. By connecting two fans in series, a stronger gas flow can be generated overall. The use of two fans per gas supply is common, but in principle more than two fans can also be used, in particular connected in series.

The heat exchanger, in particular an evaporative cooler, can be arranged upstream or downstream of the at least one fan in the direction of flow. The heat exchanger is preferably arranged behind the at least one fan. This has the advantage that the gas stream after cooling does not have to pass through the fan, where it heats up again would be. If the gas supply is equipped with two or more fans connected in series, the heat exchanger can be arranged upstream or downstream of all fans in the flow direction or between two fans. In a particularly preferred embodiment, the heat exchanger is arranged in the flow direction behind all fans of the gas supply.

Each gas supply is preferably designed with a heat exchanger, in particular an evaporative cooler. In principle, however, it is also possible to pass both gas streams through a common heat exchanger by merging the gas feeds and connecting them to the common heat exchanger.

The gas supplies typically include pipes that connect the evaporative coolers and fans to each other and to the blow box, and through which gas is drawn in to produce the gas flow.

The device according to the invention can optionally be equipped with a drying device which is suitable and provided for reducing the moisture of the gas stream before it hits the glass pane. A high level of moisture is in principle advantageous for the pretensioning efficiency, but if the level of moisture is too high, undesirable effects can occur, for example droplet formation. Too high humidity can be caused, for example, by damp ambient air or by strong cooling with an evaporative cooler. The drying device can be designed, for example, as a drop trap. It is preferably arranged in the flow direction behind the heat exchanger, in particular evaporative cooler, and all the fans of a gas supply.

The invention enables the efficiency of prestressing devices or methods to be increased. High pretensioning efficiencies are particularly advantageous when pretensioning vehicle windows, because high pretensioning requirements are imposed, some of which are regulated by law. In addition, relatively thin glass panes are generally used here, which require higher cooling rates than thicker glass panes to achieve a desired pretension. The glass pane to be tempered according to the invention is therefore provided in a particularly advantageous embodiment of a vehicle pane, that is to say as a window pane of a vehicle, preferably a motor vehicle and in particular a passenger car. However, the invention can also be used for tempering other glass panes, for example in construction, architecture, and Living area, for example when tempering facade glazing, glass floors, table tops or shower cubicles.

The device according to the invention also comprises means for generating a relative movement between the glass pane to be tempered and the blow boxes. As a result, the glass pane can be exposed to the effective area of the blow box (glass pane is positioned in the space between the blow boxes) and removed again (glass pane is positioned outside the space between the blow boxes). These means for generating the relative movement are preferably means for moving a glass pane, which are suitable for moving the glass pane to be tempered into the space between the two blow boxes and out of said space again. For example, a rail, roller or treadmill system can be used for this. The glass pane can be transported lying vertically or horizontally. In the former case, the means for moving the glass sheet preferably comprise retaining clips which are attached to the glass sheet so that the glass sheet hangs vertically on them and in turn are moved by the rail, roller or treadmill system or equivalent means. In the latter case, the glass pane can be placed directly on the rail, roller or treadmill system. However, the means for moving the glass pane preferably also include a transport frame on which the glass pane is placed. The transport frame usually has a prestressing frame (frame shape) for storing the glass pane. The glass pane is mounted on the transport frame during transport and pretensioning, which in turn is moved by the rail, roller or treadmill system or equivalent means. The tempering of glass panes, which are arranged horizontally on a tempering frame, is particularly common in connection with vehicle panes, which is why this variant is particularly preferred.

In principle, however, the means for generating the relative movement between the blow boxes and the glass pane can also be designed differently. For example, they can be means for moving the blow boxes, which move the blow boxes to a disk that remains stationary and away from it again after the pretensioning. It is also conceivable that the pane is moved and the blow boxes are moved along with the glass pane over a certain distance.

In the context of the invention, a pretensioning frame or a frame shape is understood to mean a frame-like or ring-like device on which the peripheral side edge of the Glass pane is deposited, while the majority of the pane surface, especially the central area, has no direct contact with the tempering frame. The tempering frame is typically exchangeably attached to the transport frame and adapted to the shape of the type of glass pane to be tempered. The shape of the support frame is therefore, in plan view, approximately polygonal, for example rectangular, trapezoidal or triangular, corresponding to the shape of conventional window panes, in particular vehicle panes, the side edges in the strict sense often being slightly curved in comparison with the polygon. The pretensioning frame is typically constructed from several sections, each of which is assigned to one side of the polygon. In the case of a rectangular or trapezoidal disc, the support surface is constructed, for example, from four straight or slightly curved sections which are assembled to form the shape of a rectangle or trapezoid. The tempering frame can have openings, which can also be referred to as holes or feedthroughs, and are arranged such that the edge of the glass pane to be tempered comes to rest on the openings when used as intended. The glass pane is supported by the areas of the support frame between the openings, which are chosen to be as small as possible. The openings allow air circulation, which is advantageous for the preload efficiency. In addition, air can be applied directly to the side edge of the glass pane as a result of the openings, as a result of which the pane is cooled in a more homogeneous manner and so-called marginal stresses of the toughened glass pane are avoided and their stability is improved.

The blow boxes of the device according to the invention are spaced apart from one another so that a glass pane can be arranged between them. If the glass pane is to be biased horizontally, the nozzles of the first blow box (upper blow box) point downwards and the nozzles of the second blow box (lower blow box) point upwards. If, on the other hand, the glass pane is to be prestressed vertically, the blow boxes are arranged to the side of the prestressing position, so that the gas flow leaves them essentially horizontally. The blow boxes can then be referred to as left and right blow boxes, for example.

A gas flow is applied to the surface of the glass pane by means of the blow boxes and thereby cooled. A blow box is understood in the most general sense of the invention to be a device for generating a directed gas flow which is suitable for cooling the surface of a glass pane, for example by hitting the glass pane over the entire surface or at points over the surface. The blow boxes preferably have an internal cavity into which a gas flow is introduced by means of the gas supply can be initiated. The cavity is typically delimited in the direction of the disk by at least one closure element which is equipped with a plurality of nozzles. The nozzles are connected to the cavity or connected to the cavity, so that gas can flow out of the cavity through the nozzles to apply an air flow to the surface of a glass sheet. The blow box thus divides the gas flow from the gas supply line with a comparatively small cross section through the nozzles into a large effective area. The nozzle openings represent discrete gas outlet points, which are however present in large numbers and are evenly distributed, so that all areas of the surface are cooled substantially simultaneously and uniformly, so that the pane is provided with a homogeneous prestress.

The nozzles are bores or bushings that extend through the entire closure element. Each nozzle has an inlet opening (nozzle inlet) through which the gas flow enters the nozzle and an opposite outlet opening (nozzle opening) through which the gas flow exits the nozzle (and the entire blow box). The surface of the closure element with the inlet openings faces the cavity of the blow box and that surface with the nozzle openings faces away from it and faces the glass pane when used as intended. The surface of a glass pane is subjected to an air flow as intended through the nozzle openings. The nozzles can advantageously have a section which adjoins the inlet opening and tapers in the direction of the outlet opening, in order to guide the air efficiently and in terms of flow technology into the respective nozzle.

For example, a single nozzle plate can be used as the closure element, which delimits the cavity and which has the entirety of the nozzles in a two-dimensional distribution, for example in rows and columns.

In a preferred embodiment, with which a higher pretensioning efficiency can be achieved, each blow box has a plurality of so-called nozzle strips as closure elements. With this type of blow box, the gas flow is divided into a plurality of channels, starting from the cavity, each of which is closed by a nozzle bar. Each nozzle bar typically has a number of nozzles through which the gas stream can exit the blow box. The blow box thus divides the gas flow from the gas supply line with a comparatively small cross-section via the channels and nozzles over a large effective area. The use of this type of blow boxes and Nozzle strips are particularly common in connection with vehicle windows, which is why this variant is particularly preferred.

A plurality of channels into which the gas flow is divided during operation are connected to the cavity, typically opposite the gas supply line. The channels can also be referred to as nozzle webs, fins or ribs. The channels typically have an elongated, essentially rectangular cross section, the longer dimension essentially corresponding to the width of the cavity and the shorter dimension being in the range from 8 mm to 15 mm. The channels are typically arranged parallel to one another. The number of channels is typically from 10 to 50. The channels are typically formed by sheets. The cavity is preferably wedge-shaped. The boundary of the cavity bordering the channels can be described as two side surfaces that converge at an acute angle. The channels typically run perpendicular to the connecting line of said side surfaces. Consequently, the length of a channel is not constant, but increases from the center to the sides, so that the inlet opening of the channel connected to the cavity is wedge-shaped and spans the outlet opening in a smooth, typically curved surface. The outlet openings of all channels typically form into a common smooth, curved surface. Due to the described wedge-shaped configuration of the cavity and the described arrangement of the channels, the gas flow is divided into the channels particularly efficiently and the result is a very homogeneous gas flow over the entire effective area. Each channel is closed at its end opposite the cavity with a nozzle bar.

The device can be designed for a continuous process in which the glass panes are moved continuously without being positioned stationary between the blow boxes. The glass pane is moved at a substantially constant speed on a transport route, being moved between the blow boxes, as long as the gas flow moves between the blow boxes and it is moved out again from the space between the blow boxes, without their speed significantly in the meantime to change or even stop altogether. Such continuous processes are particularly common for toughening glass panes in the construction, architecture and living areas.

However, the device can also be designed for a method in which the glass panes are positioned stationary between the blow boxes for tempering. Such Devices are customary in particular for tempering glass panes in the vehicle area, because particularly high demands are made on the degree of tempering which can sometimes not be achieved with continuous processes. This configuration is therefore particularly preferred.

The closure elements can be flat or curved. Plane closure elements are particularly suitable for tempering flat glass panes, but curved glass panes can also be tempered with flat closure elements if less demands are made on the degree and homogeneity of the tempering. Higher prestressing efficiencies can be achieved if the shape of the closure element or the closure elements is adapted to the shape of the curved glass pane to be tempered, so that all nozzle openings are at substantially the same distance from the glass surface. The nozzle openings of a blow box span a convexly curved surface and the nozzle openings of the opposite blow box have a complementary concave curved surface, the curvature essentially corresponding to that of the glass pane. During the prestressing, the convex blow box faces the concave surface of the pane and the concave blow box faces the convex surface. This configuration is suitable for continuous processes if the glass pane to be tempered is only curved along one spatial direction (cylindrical curve), and for tempering processes with a glass pane positioned stationary between the blow boxes (cylindrical or spherical curve).

Spherically curved glass panes typically occur in the vehicle area (curved in both spatial directions) and high demands are placed on the degree and homogeneity of the prestressing, which is why continuous processes are less suitable for prestressing. These glass panes are therefore generally prestressed stationary between the blow boxes, the shape of the closure elements being adapted to the spherical bending of the glass panes. The glass panes are preferably transported lying horizontally on a pretensioning frame between the blow boxes. Since the panes are usually transported with the concave surface facing upwards, the upper blow box is preferably convex and the lower concave.

If the device is designed to preload the glass panes between the blow boxes, it preferably also includes means for changing the distance between the first and second blow boxes. As a result, the blow boxes can be moved relatively towards and away from one another. After the glass pane continues spaced state of the blow boxes between them, the distance of the blow boxes to each other and thus to the glass sheet is reduced, whereby a stronger gas flow can be generated on the glass surface. After the tempering, the distance is increased again in order to move the glass pane out of the space between the blow box again. In this way, even strongly and / or spherically curved glass panes can be toughened with high efficiency. The movement of the blow boxes is necessary in order to achieve a sufficiently small distance between the glass surface and the nozzles. Should the glass pane be prestressed between two stationary blow boxes, the distance between them for retracting the curved glass pane would have to be too large, which would critically reduce the prestressing efficiency. During the tempering, the transport frame is typically moved periodically so that the nozzles of the blow box are not directed at the same locations on the glass pane over the entire period. The use of movable blow boxes is particularly common in connection with vehicle windows, which is why this variant is particularly preferred.

In principle, the blow boxes can also be realized in other ways. For example, it is conceivable for the blow boxes to have large-area openings without closure elements in the manner of an air shaft, and for the large-area gas stream emerging from these openings to strike all or part of the pane surface without being more finely divided by nozzles. It is also conceivable that separate nozzles are connected to the gas supply by individual lines.

The preferred embodiments described above can be combined with one another as desired and the device can be designed by a person skilled in the art in accordance with the requirements in the application. Preferred arrangements in the context of the gas supply and if two fans are used are, for example (in the order along the direction of flow:

Evaporative cooler - fan 1 - fan 2

Fan 1 - evaporative cooler - fan 2

Fan 1- fan 2- evaporative cooler

Evaporative cooler - fan 1 - fan 2 - drying device

Fan 1 - evaporative cooler - Fan 2 - drying device

Fan 1- fan 2- evaporative cooler - drying device

The gas feeds configured in this way can in turn be combined with blow boxes of any design and means for moving the glass pane, for example horizontally arranged blow boxes for horizontal panes or vertically arranged blow boxes for hanging panes, stationary or movable blow boxes, blow boxes for continuous systems or for prestressing stationary arranged glass panes, blow boxes with curved or flat closure means, means of transport with or without a transport frame etc.

The invention also comprises an arrangement for the thermal tempering of glass panes, comprising the device according to the invention and a glass pane arranged between the two blow boxes.

The invention also includes a method for thermally toughening glass panes. In this case, a heated glass pane is arranged between a first blow box and a second blow box, in particular moved between the first blow box and the second blow box, which are arranged opposite one another and to each of which a gas supply is connected. Each gas supply is equipped with a heat exchanger, especially an evaporative cooler. If the glass pane is arranged in the intermediate space, then a gas flow is applied to it by means of the two blow boxes, so that the glass pane is cooled and thereby tempered. The gas flow is passed through the heat exchanger, in particular an evaporative cooler, and is thereby actively cooled.

The advantageous embodiments described above with reference to the device according to the invention apply correspondingly to the method.

The gas used to cool the glass pane is preferably air. The glass surfaces are usually exposed to the gas stream over a period of 1 s to 10 s. Periods of 3 or 4 seconds are common, particularly when prestressing vehicle windows. Since the prestressing efficiency is increased with the method according to the invention, these times can be reduced. In a particularly advantageous embodiment, the time period is therefore less than 3 s, in particular from 1 s to 2 s.

When it hits the glass pane, the gas stream is cooled by the evaporative cooler and preferably has a temperature of at most 70 ° C., particularly preferably of at most 50 ° C, for example from 30 ° C to 50 ° C. This leads to particularly good pretensioning efficiencies.

An evaporative cooler also increases the humidity of the gas stream. When the gas stream hits the glass pane, its relative humidity is preferably at least 50%, particularly preferably at least 70%, very particularly preferably from 80% to 90%. This leads to particularly good pretensioning efficiencies.

In a preferred embodiment, the glass pane to be tempered consists of soda-lime glass, as is customary for window panes. However, the glass pane can also contain or consist of other types of glass such as borosilicate glass or quartz glass. Depending on the application, the thickness of the glass pane is typically from 1 mm to 20 mm. In the vehicle sector, pane thicknesses from 1 mm to 5 mm are common, in particular from 2 mm to 4 mm.

The invention unfolds its advantages in a special way when tempering relatively thin glass panes because these require higher cooling rates than thicker glass panes. In a particularly advantageous embodiment, the glass pane has a thickness of at most 3.5 mm, preferably from 1 mm to 3 mm.

In an advantageous embodiment, the method according to the invention immediately follows a bending process in which the glass pane which is planar in the initial state is bent. During the bending process, the glass sheet is heated up to the softening temperature. The tempering process follows the bending process before the glass pane has cooled significantly. For this purpose, the glass pane is transferred from the bending tools to the tempering mold after the bending process or in the last step of the bending process. This means that the glass pane does not have to be heated again specifically for tempering.

There is currently a tendency for glass manufacturers to reduce the temperatures for glass bending more and more because this can result in better optical quality and surface properties of the glass panes. In such bending processes with relatively low temperatures, the tempering method according to the invention can be used particularly advantageously because the increased tempering efficiency leads to sufficient stresses in the glass pane despite the lower temperature. During tempering, the temperature of the glass sheet lies between the so-called transition point, at which the viscosity of the glass sheet can be plastically deformed and the so-called softening point, at which the glass deforms under its own weight. The invention makes it possible to reduce the distance from the transition point. So far, the usual bending temperatures for curved vehicle windows made of soda-lime glass have been 650 ° C. In a particularly advantageous embodiment, the temperature of such a glass pane, immediately before it is acted upon by the gas stream and cooled, is at most 640 ° C., preferably less than 640 ° C.

The invention also includes the use of an evaporative cooler for the active cooling of a gas stream with which a glass pane is thermally tempered.

The invention is explained in more detail below with reference to a drawing and exemplary embodiments. The drawing is a schematic representation and not to scale. The drawing in no way limits the invention.

Show it:

1 is a schematic representation of an embodiment of the device according to the invention,

2 shows a schematic illustration of a further embodiment of the device according to the invention,

3 shows a schematic illustration of a further embodiment of the device according to the invention,

4 shows a cross section of an evaporative cooler,

5 shows a cross section of an indirect heat exchanger and

6 shows a flow diagram of an embodiment of the method according to the invention.

Figure 1 shows schematically an embodiment of the device according to the invention for the thermal tempering of glass panes. The device comprises a first blow box 1.1 and a second blow box 1.2, which are arranged opposite one another. The nozzles of the blow boxes 1 .1, 1.2, through which the gas flow (air flow) required for the prestressing exits, is directed towards the intermediate space between the blow boxes 1.1, 1.2. A gas supply 2.1 is connected to the first blow box 1.1, through which it is supplied with the gas stream. The gas supply comprises supply pipes and a first fan 3.1 and a second fan 4.1, which are connected in series in this order in the flow direction. The serial arrangement of the fans 3.1, 4.1 makes it possible to generate a strong gas flow in the direction of the blow box 1.1. An evaporative cooler 5.1 is also arranged as a heat exchanger downstream of the fans 3.1, 4.1. Likewise, a gas supply 2.2 is connected to the second blow box 1.2, which in addition to supply pipes has a first fan 3.2, a second fan 4.2 and an evaporative cooler 5.2, which are connected in series in the flow direction in this order. Both gas feeds 2.1, 2.2 can be closed completely or partially by means of a closing flap 7.1, 7.2 in order to stop the gas flow or to regulate its strength.

The air drawn in by the fans 3.1, 4.1, 3.2, 4.2 is, on the one hand, cooled and, on the other hand, moistened by the evaporative coolers 5.1, 5.2. Both increase the Biasing efficiency of the device over conventional biasing devices without cooling. That is the great advantage of the present invention.

The device also comprises means for moving the glass pane G to be prestressed, comprising a transport system 8, for example in the form of a roller system, and a transport frame 9 moved therewith. The transport frame 9 is equipped with a prestressing frame on which the peripheral side edge of the glass pane G is placed. With the transport system, the glass sheet G is in the space between the blow boxes 1.1,

1 .2 moves. The blow boxes 1.1, 1.2 of the glass pane G are then approximated in order to efficiently apply the gas flow to them. After tempering, the blow boxes 1.1, 1.2 are moved away again from the glass pane G and the glass pane G is moved out of the intermediate space. The pretensioner is then ready for the next pretension cycle.

The direction of the gas flow and the movement of the glass pane G are indicated in the figure by gray block arrows.

Figure 2 shows schematically a further embodiment of the device according to the invention. In contrast to the embodiment in FIG. 1, the evaporative coolers 5.1, 5.2 are arranged in the flow direction in front of the fans 3.1, 4.1 and 3.2, 4.2 instead of behind. In addition, the gas supplies 2.1, 2.2 are each with a

Drying device 30.1, 30.2 equipped, which are arranged in the flow direction behind the fans 3.1, 4.1 and 3.2, 4.2. The drying devices 30.1, 30.2 are designed, for example, as drop collectors. If the gas stream has an undesirably high level of moisture, for example caused by the evaporative coolers 5.1, 5.2 or by excessively humid ambient air, the drying devices 30.1, 30.2 allow this moisture to be reduced and set to a desired value.

Figure 3 shows schematically a further embodiment of the device according to the invention. In contrast to the embodiment in FIG. 1, each evaporative cooler 5.1, 5.2 is between the fans 3.1, 4.1 or 3.2, 4.2 of its gas supply 2.1 or

2.2 arranged. It should be pointed out that the above embodiments merely represent exemplary embodiments of the present invention and can be combined and modified as desired. The drying devices 30.1, 30.2 can thus also be used in the configurations of FIGS. 1 and 3. The drying devices 30.1, 30.2 also do not have to be arranged in the flow direction behind the fans 3.1, 4.1 or 3.2, 4.2, but in principle also in front of or between them. Instead of on the transport frame 9, the glass pane G can also rest directly on rollers of the transport system 8, for example, or can be transported and pretensioned vertically. Instead of being biased stationary between the blow boxes 1.1, 1.2, the blow boxes being approximated to the glass pane G, the glass pane G could also be biased within a continuous system between stationary blow boxes 1 .1, 1.2. The design of the device can be chosen freely by the person skilled in the art in accordance with the requirements in the application, in particular taking into account the shape of the glass pane to be tempered, the degree of tempering, the properties of the ambient air with regard to moisture and temperature and the desired process speed.

FIG. 4 schematically shows a cross section of an evaporative cooler 5 as part of a gas supply 2. It contains a fibrous, porous carrier material 10, for example corrugated paper layers. A drop separator 11 is arranged above the carrier material 10 and sprinkles the carrier material with a cooling liquid, for example water. Excess coolant is taken up by a droplet collector 12 after passing through the carrier material 10 and fed back to the droplet separator by means of a pump 14 via a coolant line 13. Since cooling liquid is also lost during cooling, the coolant line 13 also includes a supply line (not shown) for further coolant.

The gas flow generated by the fans flows through the carrier material 10. This results in adiabatic cooling of the gas flow. Evaporating coolant is absorbed by the gas flow, which increases its moisture. The cooling effect is based on the associated evaporative cooling.

In contrast, FIG. 5 schematically shows a cross section of an indirect heat exchanger 6 as part of a gas supply 2. The indirect heat exchanger 6 contains a coolant line 20, which is designed, for example, as a multi-U-shaped tube and is operated by the coolant, for example water, in the frame a cooling circuit is flowed through. The tube is arranged in a flow space 21 through which the gas stream flows, the gas stream coming into contact with the coolant line 20 and being cooled as a result. Since the coolant is heated in the process, the indirect heat exchanger is preferably equipped with recooling, which cools the coolant again in the region of the coolant outlet, not shown, outside the flow space 21.

FIG. 6 shows an exemplary embodiment of the method according to the invention for the thermal tempering of glass panes on the basis of a flow chart.

Reference symbol list:

(1 .1) first / upper blow box

(1 .2) second / lower blow box

(2) gas supply

(2.1) Gas supply of the first blow box 1.1

(2.2) Gas supply of the second blow box 1.2

(3.1) first fan of the first blow box 1.1

(3.2) first fan of the first blow box 1.2

(4.1) second fan of the first blow box 1.1

(4.2) second fan of the first blow box 1.2

(5) evaporative cooler

(5.1) Evaporative cooler of the first blow box 1.1

(5.2) Evaporative cooler of the first blow box 1.2

(6) indirect heat exchanger

(7.1) Closing flap of the gas supply of the first blow box 1.1

(7.2) Closing flap of the gas supply of the first blow box 1.2

(8) Transport system for glass panes

(9) Transport rack for glass panes

(10) porous medium / carrier material of the evaporative cooler 5

(1 1) Drop separator of the evaporative cooler 5

(12) Evaporative cooler drop collector 5

(13) Coolant pipe of the evaporative cooler 5

(14) Coolant pump of the evaporative cooler 5

(20) Coolant pipe of the indirect heat exchanger 6

(21) Flow space of the indirect heat exchanger 6

(30.1) Drying device for the gas supply 2.1 of the first blow box 1.1

(30.2) Drying device for the gas supply 2.2 of the first blow box 1.2

(G) glass pane

Claims

1. A device for the thermal tempering of glass panes, comprising

a first blow box (1.1) and a second blow box (1.2) which are arranged opposite one another and are suitable for applying a gas flow to the surfaces of a glass pane (G) arranged between them,

- A gas supply (2.1, 2.2) connected to the first blow box (1.1) and the second blow box (1.2),

the gas supply lines (2.1, 2.2) being equipped with an evaporative cooler (5).

2. Apparatus according to claim 1, wherein the evaporative cooler (5) contains a porous carrier material which is impregnated with a cooling liquid and through which the gas stream flows, whereby cooling of the gas stream is achieved, in particular adiabatic cooling.

3. Device according to one of claims 1 or 2, wherein each gas supply (2.1, 2.2) is equipped with at least one fan (3.1, 3.2) in order to supply the blow boxes (1.1, 1.2) with the gas stream.

4. The device according to claim 3, wherein an evaporative cooler (5.1, 5.2) is arranged in the flow direction behind the at least one fan (3.1, 3.2).

5. Device according to one of claims 1 to 4, wherein each gas supply (2.1, 2.2) is equipped with at least a first fan (3.1, 3.2) and a second fan (4.1, 4.2), and wherein in each case an evaporative cooler (5.1, 5.2 ) in

Flow direction is arranged behind the two fans (3.1, 4.1; 3.2, 4.2).

6. Device according to one of claims 1 to 5, which comprises a drying device (30.1, 30.2) which is suitable for reducing the moisture of the gas stream.

7. Device according to one of claims 1 to 6, which is equipped with means for moving a glass sheet (G) in a space between the first blow box (1.1) and the second blow box (1.2), which has a transport frame (7) with a Include pretensioning frame for supporting the glass pane (G), which is moved by a rail, roller or treadmill system.

8. A method for the thermal tempering of glass panes, wherein

(i) a heated glass pane (G) is arranged between a first blow box (1.1) and a second blow box (1.2), which are arranged opposite one another and to each of which a gas supply (2.1, 2.2) is connected, which is equipped with an evaporative cooler ( 5) is equipped;

(ii) a gas flow is applied to the glass pane (G) by means of the two blow boxes (1.1, 1.2), so that the glass pane (G) is cooled, the gas flow being actively cooled by means of the evaporative cooler (5).

9. The method according to claim 8, wherein the gas stream striking the glass pane (G) has a temperature of at most 70 ° C, preferably of at most 50 ° C.

10. The method according to claim 8 or 9, wherein the gas stream striking the glass pane (G) has a relative humidity of at least 50%, preferably of at least 70%, particularly preferably of 80% to 90%.

11. The method according to any one of claims 8 to 10, wherein the glass sheet (G) before

Cooling with the gas stream has a temperature of at most 640 ° C.

12. The method according to any one of claims 8 to 11, wherein the gas stream is an air stream.

13. The method according to any one of claims 8 to 12, wherein the glass pane (G) in step (ii) is acted upon with the gas stream over a period of 1 s to 10 s, preferably from 1 s to 2 s.

14. The method according to any one of claims 8 to 13, wherein the glass sheet (G) has a thickness of at most 3.5 mm, preferably from 1 mm to 3 mm.

15. Use of an evaporative cooler (5) for actively cooling a gas stream with which a glass pane (G) is thermally tempered.