WO2020187518A1

WO2020187518A1 - Evaporative cooler with controlled cooling effect

Info

Publication number: WO2020187518A1
Application number: PCT/EP2020/054193
Authority: WO
Inventors: Achim ZEICHNER; Jack PENNERS; Samir SALAMEH
Original assignee: Saint-Gobain Glass France
Priority date: 2019-03-15
Filing date: 2020-02-18
Publication date: 2020-09-24
Also published as: CN111954645A; DE202020005460U1

Abstract

The invention relates to a device for thermally prestressing glass panes using an evaporative cooler with controlled cooling effect. The evaporative cooler (10) has a cooling chamber (11) with a gas inlet (12) and a gas outlet (13) so that a gas stream can be passed through the cooling chamber (11) for cooling. The cooling chamber (11) can be equipped or is equipped with a carrier material (14) impregnated with a cooling liquid, the gas stream flowing through said carrier material. The carrier material (14) comes into contact with the gas stream via a contact surface, thereby achieving a cooling of the gas stream, and the evaporative cooler is equipped with means for varying the contact surface.

Description

Evaporative cooler with controllable cooling effect

The invention relates to an evaporative cooler with controllable cooling effect and its use, in particular for a device and a method for the thermal toughening of glass panes.

Evaporative coolers are heat exchangers with direct heat transfer, i.e. a combined heat and mass transfer. Evaporative coolers have a cooling space through which the gas flow to be cooled is passed and which is equipped with a carrier material which is impregnated with a cooling liquid. The cooling effect is based on the evaporation cold of the cooling liquid. The evaporation also increases the humidity of the gas to be cooled. For example, reference is made to US5655373A, DE1299665A and W003058141A1. Evaporative coolers are used, for example, in power plant construction to adiabatically cool the intake air ducts of gas turbines.

Conventional evaporative coolers do not offer the user any possibility to control the cooling effect. This fact is not a problem in many applications, but applications are also conceivable in which there is a need for such a control. If, for example, the gas flow is to be cooled to a certain temperature, the required cooling effect also depends on the outlet temperature of the gas, which in turn is determined by the current ambient temperature. Too strong a cooling effect can also lead to an undesirably high level of moisture in the gas flow, which in some applications can be disruptive in the form of droplet formation due to condensing moisture.

In the international patent application PCT / EP2019 / 067275 it is proposed to use evaporative coolers in devices for the thermal toughening of glass panes. During thermal toughening, a glass pane heated to just below the softening temperature is subjected to an air stream, which leads to rapid cooling (quenching) of the glass pane. As a result, a characteristic stress profile is formed in the glass pane, with compressive stresses prevailing on the surfaces and tensile stresses in the core of the glass pane. This affects the mechanical properties of the glass pane in two ways. Firstly, the break resistance of the disc is increased and it can withstand higher loads than an uncured disc. Secondly, glass breaks after penetration of the central tensile stress zone (e.g. through damage by a sharp stone or by deliberately destroying it with a sharp emergency hammer) not in the form of large, sharp-edged shards, but in the form of small, blunt fragments, which significantly reduces the risk of injury. Due to the properties described above, thermally pre-stressed glass panes are used as so-called single-pane safety glass in the vehicle sector, in particular as rear windows and side windows. In the vehicle sector, high demands are placed on the degree of preload, which are also regulated in standards. But thermally toughened glass panes are also common in construction, architecture and living, for example as glass facades, shower cubicles or table tops. Merely by way of example, reference is made to the patent documents DE 710690 A, DE 808880 B, DE 1056333 A from the 1940s and 1950s, and also to WO 2019015835 A1.

An improved pretensioning effect can be achieved through active cooling of the air flow. Too high humidity, as can occur when using evaporative coolers with too high a cooling effect, can be expressed in the form of droplets, which damage the surface of the heated glass pane.

There is therefore a need for evaporative coolers with a controllable cooling effect, in particular with regard to use in thermal toughening.

US 2270810 A discloses a capacitor for a cooling unit with a replaceable carrier material. WO 88/10240 A1 discloses a method for manufacturing glass bottles which are treated with a cooled fluid for faster cooling. GB 472022 A discloses a process for the thermal toughening of glass, the gas flow required for this being passed over a water surface in order to saturate it with water vapor.

The present invention is based on the object of providing a device for the thermal toughening of glass panes with such an improved evaporative cooler.

The object is achieved according to the invention by a device according to the independent claim 1. Preferred embodiments emerge from the dependent claims. In the device according to the invention, an improved evaporative cooler with a controllable cooling effect is used for active cooling of the gas flow.

The evaporative cooler according to the invention with controllable cooling effect comprises (or has) a cooling space with a gas inlet and a gas outlet, so that a gas flow for cooling can be conducted (or can be guided) through the cooling space. The cooling space is typically surrounded by a housing in which the gas inlet and outlet are provided as openings to which pipelines can be connected (or can be connected) that carry the gas flow. The gas inlet and gas outlet are typically arranged opposite one another, so that the gas flow can flow through the cooling space without disturbance or deflection. However, other configurations are also conceivable. The cooling space is equipped or can be equipped with a carrier material which is impregnated with a cooling liquid or is provided for this purpose. During operation, the gas stream flows through the carrier material. The carrier material has a contact surface through which it comes into contact with the gas flow, whereby cooling, in particular adiabatic cooling, of the gas flow is achieved.

In conventional evaporative coolers, the cooling space is equipped with a carrier material that is permanently installed. The user has no way of changing the carrier material without extensive conversion work. In contrast to this, the evaporative cooler according to the invention is equipped with means for changing the contact surface, more precisely with means for changing the extent of the contact surface. This allows the user to control the cooling effect, with a larger contact surface leading to a higher cooling effect and a smaller contact surface leading to a lower cooling effect. The required cooling effect can thus be actively controlled, for example in order to set a desired temperature or humidity of the gas flow. That is the great advantage of the present invention.

The means for changing the contact area allow the user to adjust the contact area of the carrier material from the outside, that is to say in particular without dismantling the housing of the cooling space.

The carrier material is soaked in a cooling liquid during operation in the cold room. The evaporative cooler is a heat exchanger with direct heat transfer, whereby the evaporative cooling of the cooling liquid is used to cool the gas flow (Heat transfer). In the process, the cooling liquid passes into the gas flow (mass transfer). In addition to cooling, the evaporative cooler also increases the humidity of the gas flow. When the cooling liquid evaporates, the energy required for this is withdrawn from the environment, i.e. ultimately from the gas flow, which leads to its cooling. The evaporated cooling liquid is absorbed by the gas flow and increases its relative humidity. The cooling effect depends on the surrounding air condition, temperature and relative humidity. The lower the relative humidity, the higher the potential for further moisture absorption and the more coolant can evaporate.

The carrier material is preferably fibrous or porous. The carrier material can thus advantageously be impregnated with cooling liquid and a large contact surface with the gas flow is provided. The carrier material preferably has flow channels through which the gas stream can flow. For example, paper 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 carrier material.

The evaporative cooler is preferably designed as a so-called trickle cooler. The carrier material is sprinkled with cooling liquid, in particular continuously sprinkled, in order to ensure permanent impregnation. For this purpose, a drop separator can be arranged above the carrier material, for example, which sprinkles the carrier material with the cooling liquid. A droplet collector can be arranged below the carrier material in order to collect cooling liquid that has flown through the carrier material. The coolant collected in the drop collector can be fed back to the drop separator by means of a coolant line provided with a pump.

The cooling liquid is preferably water or consists essentially of water, which can optionally contain additives, for example heat-conducting additives, antifreeze agents or chemical or biological stabilizers.

In a preferred embodiment of the invention, the contact surface is changed in that the amount of carrier material in the cooling space through which the gas stream flows is changed. The means for changing the contact surface are therefore means for changing the amount of carrier material in the cooling space. This allows the user to control the cooling effect, with a larger amount of water flowing through Carrier material leads to a higher cooling effect and a smaller amount of carrier material through which the flow passes leads to a lower cooling effect.

In order to be able to change the amount of carrier material in the cooling space, the evaporative cooler is equipped with at least one insert in an advantageous embodiment. By means of the at least one insert, the carrier material can be moved into the cooling space or into the intended gas flow and out of the cooling space or out of the intended gas flow. The carrier material can be pushed into the slot in the cooling space in order to increase the amount of carrier material in the cooling space. Conversely, the carrier material can be pulled out of the slot in order to reduce the amount of carrier material in the cooling space. The carrier material is preferably enclosed in a frame (in particular a metal frame) in order to be able to handle it easily. Frames with carrier material are referred to as a cassette (cooling cassette) in the context of the invention. This configuration advantageously allows simple maintenance of the evaporative cooler because the carrier material is easily accessible to the operator.

The cassette and the associated slide-in unit can be designed in various ways which are known per se and which the person skilled in the art can suitably choose according to the requirements of the application. For example, the cassette and insert can be designed as a drawer system, rail system or roller system. The cassette (in particular the frame of the cassette) and the insert are suitable for this purpose in terms of their dimensions and other design and are compatible with one another.

In principle, a single slot is sufficient. Cartridges are then provided which are equipped with a different amount of carrier material and which are compatible with the slot. In order to adjust the cooling effect of the evaporative cooler, only the cassette with the appropriate amount of carrier material has to be inserted. Since the lateral dimensions (width and length perpendicular to the direction of flow of the gas flow) of the carrier material are essentially determined by the insert, the different amounts of carrier material of the different cassettes are suitably implemented by a different thickness of the carrier material (measured along the direction of flow of the gas flow). In a preferred embodiment, however, the cooling space is equipped with a plurality of inserts. Through each insert, the carrier material can be moved into the cooling space or into the intended gas flow and out of the cooling space or out of the intended gas flow. Carrier material can therefore be pushed into the cold room or pulled out of the cold room through each insert. For this purpose, at least one cassette is provided for each slot. The cold room can therefore be equipped with a variable number of cassettes in order to set the desired cooling effect. The number of slots is preferably from two to 20, particularly preferably from 2 to 5. This provides sufficient flexibility with regard to the control of the cooling effect without the structure of the evaporative cooler becoming too complex. The carrier material of each insert or each cassette preferably has a thickness of 0.2 cm to 30 cm, particularly preferably 0.5 cm to 20 cm. This achieves good results - the thinner the individual cassettes, the finer the cooling effect can be adjusted, but too small a thickness of the cassettes is disadvantageous for the stability of the carrier material. The different cassettes can have the same amount or different amounts of carrier material, that is to say in particular carrier material with the same or different thickness.

In principle, it is also possible to only partially insert one or more cassettes into the associated slide-in unit, so that the gas stream flows through only part of the carrier material and contributes to the cooling effect. In this way, a stepless control of the cooling effect can be achieved, but the partial insertion can bring fluidic disadvantages with it.

In addition to the inserts, carrier material can also be permanently installed in the cold room. This then provides a basic cooling effect, and the cooling effect can be increased by inserting further cassettes.

If the evaporative cooler is designed as a trickle cooler and has a plurality of inserts, then in an advantageous embodiment each insert is equipped with its own droplet separator. For this purpose, the drop separator is arranged above the assigned slot in order to sprinkle the carrier material with cooling liquid when a cassette is inserted into the slot. Ideally, the drop separators are equipped with stopcocks or the like so that they can only be put into operation when a cassette is in the relevant slot is inserted. Since the amount of cooling liquid also has an influence on the cooling effect, the droplet separators are equipped in an advantageous embodiment with means for controlling the amount of cooling liquid separated. The amount of cooling liquid can then be increased in order to achieve an increased cooling effect, and vice versa.

Each slide-in unit can also be equipped with its own drop collector. The drop collector is arranged below the insert and is suitable for collecting cooling liquid that has flowed through the carrier material. Alternatively, however, all drawers can also be equipped with a common drop collector. The common drop collector is arranged below the entirety of the inserts and is suitable for collecting the cooling liquid which has flowed through the entirety of the carrier materials. In principle, of course, combinations of these are also possible, with some plug-in units being equipped with their own drop collectors and others with a common drop collector.

All the drop separators and all the drop collectors (or the common drop collector) are preferably connected to the same coolant division. The coolant line is equipped with a pump so that the collected coolant can be fed back to the drop separators. This results in a coolant circuit, which is useful for economic reasons.

The variable contact surface of the carrier material can, however, also be realized in a different way than with the cartridge system described above. For example, one or more cooling medium cassettes can be rotatably mounted in the cooling space so that they can be pivoted into the gas flow or so that the angle of incidence of the flow channels in relation to the gas flow can be changed in order to control the cooling effect.

The device according to the invention for the thermal toughening of glass panes uses the above-described evaporative cooler according to the invention. Since the efficiency of the prestressing is essentially determined by the temperature of the gas flow, which in turn depends on the ambient temperature, the use of a controllable cooler is particularly advantageous for this use. In addition, excessively high moisture in the gas flow must be avoided in order to prevent droplets from being condensed out To avoid moisture. Should drops of liquid hit the heated glass pane, this can lead to glass breakage due to excessive local cooling. The device 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 to one another - it is not necessary for each individual gas outlet opening to have a counterpart in the opposite blow box that is exactly opposite. Instead, the individual gas outlet openings of the blow boxes can be offset from one another. With the blow boxes with gas outlet openings pointing towards one another, the surfaces of a glass pane arranged between the blow boxes can be exposed to a gas flow. A gas feed is connected to each blow box, via which the gas flow is fed to the blow boxes.

According to the invention, the gas supply lines are equipped with an evaporative cooler according to the invention with a controllable cooling effect. The gas flow is actively cooled by means of the evaporative cooler. Since the gas flow has a lower temperature when it hits the glass pane, it has to be less strong in order to achieve the same cooling or tempering effect. As a result, energy for generating the gas flow can advantageously be saved.

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

The gas supply to 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 supply to each blow 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 and passes through the second fan this is further compressed and thereby strengthened. 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 evaporative cooler can be arranged in front of or behind the at least one fan in the direction of flow. The evaporative cooler is preferably arranged behind the at least one fan. This has the advantage that after cooling down, the gas flow does not have to pass through the fan, where it would be heated up again. If the gas supply is equipped with two or more fans connected in series, the evaporative cooler can be arranged in front of or behind all fans in the direction of flow or between two fans. In a particularly preferred embodiment, the evaporative cooler is arranged behind all fans of the gas supply in the direction of flow. It is also conceivable to equip a gas feed with more than one evaporative cooler, for example in the configuration fan - evaporative cooler - fan - evaporative cooler (in the direction of flow).

Each gas supply is preferably designed with an evaporative cooler. In principle, however, it is also possible to pass both gas streams through a common evaporative cooler, in that the gas feeds are brought together and connected to the common evaporative cooler.

The gas supply lines typically include pipes which connect the evaporative coolers and fans to one another and to the blow box, and through which gas is drawn in to generate the gas flow. The pipes are connected to the gas inlet and the gas outlet of the evaporative cooler in order to direct the gas flow through the evaporative cooler.

The device according to the invention can optionally be equipped with a drying device which is suitable and intended to reduce the moisture in the gas flow before it hits the glass pane. In this way, too, disturbing droplet formation can be avoided, or droplets formed can be collected. The drying device can be designed as a drop trap, for example. she is preferably arranged in the direction of flow behind the evaporative cooler and all fans of a gas supply.

The use of the evaporative cooler according to the invention enables an increase in the efficiency of pretensioning devices or processes. High pretensioning efficiencies are particularly advantageous when pretensioning vehicle windows because high, sometimes legally regulated requirements are placed on the pretensioning. In addition, relatively thin panes of glass are generally used here, which require higher cooling rates than thicker panes of glass in order to achieve a desired prestress. The glass pane to be prestressed according to the invention is therefore provided in a particularly advantageous embodiment as 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 when toughening other glass panes, for example in construction, architecture and living areas, for example when toughening 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 prestressed and the blow boxes. As a result, the glass pane can be exposed to the active 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 prestressed 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 purpose. The pane of glass 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 thereon and are in turn moved by the rail, roller or treadmill system or equivalent means. In the latter case, the pane of glass can be placed directly on the rail, roller or conveyor belt system. However, the means for moving the glass pane preferably also comprise 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. During transport and toughening, the glass pane is stored on the transport frame, which in turn is moved by the rail, roller or treadmill system or equivalent means. The toughening of glass panes which are arranged lying horizontally on a pretensioning frame is common in particular in connection with vehicle windows, which is why this variant is particularly preferred.

The means for generating the relative movement between the blow box and the glass pane can in principle also be designed differently. For example, they can be means for moving the blow boxes, which move the blow boxes to a pane that remains stationary and, after pretensioning, away from it again. 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 prestressing frame or a frame shape is understood to mean a frame-like or ring-like device on which the circumferential side edge of the glass pane is placed while the majority of the pane surface, in particular the central area, has no direct contact with the prestressing frame. The prestressing frame is typically exchangeably attached to the transport frame and adapted to the respective shape of the type of glass pane to be prestressed. The shape of the support frame is therefore roughly polygonal in plan view, for example rectangular, trapezoidal or triangular, corresponding to the shape of conventional window panes, especially vehicle panes, with the side edges often being slightly curved compared to the polygon in the strict sense. The prestressing frame is typically made up of several sections, each assigned to one side of the polygon. In the case of a rectangular or trapezoidal disc, the support surface is made up, for example, of four straight or slightly curved sections which are assembled to form a rectangle or trapezoid. The prestressing frame can have openings, which can also be referred to as holes or passages and are arranged in such a way that the edge of the glass pane to be prestressed 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 to circulate which is beneficial for prestressing efficiency. In addition, the side edge of the glass pane can be acted upon directly with air as a result of the openings, whereby the pane is cooled more homogeneously and disturbing so-called edge stresses of the prestressed glass pane are avoided and its stability is thus improved. The blow boxes of the device according to the invention are spaced from one another so that a glass pane can be arranged between them. If the glass pane is to be prestressed lying 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 called the left and right blow boxes, for example.

By means of the blow boxes, the surface of the glass pane is exposed to a gas flow and thereby cooled. In the most general sense of the invention, a blow box is understood to mean a device for generating a directed gas flow which is suitable for cooling the surface of a glass pane, for example by striking the glass pane over its entire surface or at points distributed over the surface. The blow boxes preferably have an inner cavity into which a gas flow can be introduced by means of the gas supply. 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 from the cavity through the nozzles in order to apply a stream of air to the surface of a glass pane. The blow box thus divides the gas flow from the gas supply line with a comparatively small cross section over the nozzles over a large effective area. The nozzle openings represent discrete gas outlet points, which, however, are present in large numbers and are evenly distributed, so that all areas of the surface are cooled essentially simultaneously and uniformly, so that the pane is provided with a homogeneous pretension.

The nozzles are bores or passages that extend through the entire closure element. Each nozzle has an inlet opening (nozzle inlet) through which the gas stream enters the nozzle, and an opposite outlet opening (nozzle opening) through which the gas stream exits from 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, when used as intended, faces the glass pane. The surface of a glass pane is subjected to an air stream as intended through the nozzle openings. The nozzles can advantageously adjoin the inlet opening and extend in the direction have tapering section towards the outlet opening in order to guide the air efficiently and in terms of flow into the respective nozzle.

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

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. In this type of blow box, the gas flow, starting from the cavity, is divided into a plurality of channels, each of which is closed by a nozzle bar. Each nozzle bar typically has a number of nozzles through which the gas flow 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 box and nozzle strips is common especially 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 4 mm to 15 mm. Typically the channels are arranged parallel to one another. The number of channels is typically from 10 to 50. The channels are typically formed by metal sheets. The cavity is preferably designed like a wedge. The boundary of the cavity adjoining the channels can be described as two side surfaces which 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 into a smooth, typically curved surface. The outlet openings of all channels typically form a common smooth, curved surface. As a result of the wedge-shaped configuration of the cavity described and the arrangement of the channels described, the gas flow is particularly efficiently divided into the channels and the result is a very large area over the entire effective area homogeneous gas flow. 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 in a stationary manner between the blow boxes. The glass pane is moved at a substantially constant speed on a transport path, being moved between the blow boxes as long as it moves between the blow boxes is acted upon by the gas flow and is moved out of the space between the blow boxes again without significantly increasing its speed in the meantime to change or even to stop entirely. Such continuous processes are particularly common for toughening glass panes in construction, architecture and living.

However, the device can also be designed for a method in which the glass panes are positioned in a stationary manner between the blow boxes for toughening. Such devices are customary in particular for toughening glass panes in the vehicle sector, because here particularly high demands are placed on the degree of pretensioning, which sometimes cannot be achieved with continuous processes. This configuration is therefore particularly preferred.

The closure elements can be flat or also curved. Plane closure elements are particularly suitable for toughening flat glass panes, but curved glass panes can also be pre-stressed with planar closure elements if lower requirements are placed on the degree and homogeneity of the pretensioning. Higher tempering 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 essentially at 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 concave curved surface complementary thereto, the curvature essentially corresponding to that of the glass pane. During the prestressing, the convex blow box faces the concave surface of the disc and the concave blow box faces the convex surface. This configuration is suitable for continuous processes when the glass pane to be toughened is bent only in one spatial direction (bent cylindrically), and for toughened processes with the glass pane positioned stationary between the blow boxes (bent cylindrically or spherically). In the vehicle sector, spherically curved glass panes typically occur (curved in both spatial directions) and high demands are made 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 in a stationary manner between the blow boxes, the shape of the closure elements being adapted to the spherical bend of the glass panes. The glass panes are preferably transported lying horizontally on a prestressing frame between the blow boxes. Since the panes are usually transported to the prestressing station with the concave surface pointing upwards, the upper blow box is preferably convex and the lower one is concave.

If the device is designed to prestress the glass panes in a stationary manner between the blow boxes, it preferably also comprises means for changing the distance between the first and second blow boxes. As a result, the blow boxes can be moved relative to and away from one another. After the glass pane has been moved between the blow boxes in the further spaced-apart state, the spacing of the blow boxes from one another and thus from the glass pane is reduced, whereby a stronger gas flow can be generated on the glass surface. After toughening, the distance is increased again in order to move the glass pane out of the space between the blow box again. In this way, glass panes that are strongly and / or spherically bent can also 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. If the glass pane were to be prestressed between two stationary blow boxes, the distance between them would have to be selected too large for the curved glass pane to be inserted, which would critically reduce the prestressing efficiency. During pre-tensioning, the transport frame is typically moved periodically so that the nozzles of the blow box are not directed at the same points on the glass pane over the entire period. The use of movable blow boxes is common in particular in connection with vehicle windows, which is why this variant is particularly preferred.

In principle, however, the blow boxes can also be implemented 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 duct and for the large-area gas flow emerging from these openings to hit the entire surface of the pane or part of it without to be divided more finely by nozzles. It is also conceivable that separate nozzles are connected to the gas supply through individual lines.

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

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 supply lines configured in this way can in turn be combined with any desired design blow boxes and means for moving the glass pane, for example horizontally arranged blow boxes for lying panes or vertically arranged blow boxes for hanging panes, stationary or movable blow boxes, blow boxes for flow systems or for toughening stationary arranged glass panes, blow boxes with curved or flat locking means, means of transport with or without transport frame, etc.

The invention also comprises an arrangement for the thermal toughening 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. 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 an evaporative cooler according to the invention. If the glass pane is arranged in the space, it is subjected to a gas flow by means of the two blow boxes, see above that the glass pane is cooled down and thereby toughened. The gas flow is passed through the heat exchanger and thereby actively cooled.

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

The gas used to cool the glass pane is preferably air. The disk surfaces are usually exposed to the gas flow over a period of 1 s to 10 s. Periods of 3 or 4 seconds are common, especially when pre-tensioning 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.

The gas stream, when it hits the glass pane, is cooled by the evaporative cooler and preferably has a temperature of at most 70 ° C, particularly preferably at most 50 ° C, for example from 20 ° C to 50 ° C. This enables particularly good prestressing efficiencies to be achieved.

The evaporative cooler also increases the humidity of the gas stream. When the gas flow hits the pane of glass, its relative humidity is preferably at least 50%, particularly preferably at least 70%, very particularly preferably from 80% to 90%. This enables particularly good prestressing efficiencies to be achieved.

In a preferred embodiment, the glass pane to be toughened 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. The thickness of the glass pane is typically from 1 mm to 20 mm, depending on the application. In the vehicle sector, pane thicknesses of 1 mm to 5 mm are common, in particular from 2 mm to 4 mm.

The invention develops its advantages in a particular way when toughening 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. This means that the glass pane does not have to be specially heated again for toughening. During the bending process, the glass pane is heated above 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 prestressing mold after the bending process or in the last step of the bending process. In addition, there are also bending processes in which the glass pane is conveyed through a bending zone via a roller conveyor and is pretensioned in this bending zone, resting on the rollers.

There is currently a tendency among glass manufacturers to keep reducing the temperatures for glass bending, because this enables better optical quality and surface properties of the glass panes to be achieved. In such bending processes with relatively low temperatures, that is according to the invention

Tempering methods 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 pane lies between the so-called transition point, at which the viscosity of the glass pane allows plastic deformation, and the so-called softening point, at which the glass deforms under its own weight. The invention makes it possible to reduce the distance to the transition point. To date, 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 pane of glass, immediately before it is acted upon by the gas stream and cooled, is at most 640 ° C., preferably less than 640 ° C.

The invention is explained in more detail below with reference to a drawing and exemplary embodiments. The drawing is a schematic representation and is not true to scale. The drawing does not restrict the invention in any way.

Show it:

1 shows a horizontal cross-section of an embodiment of an evaporative cooler as used in the device according to the invention,

FIG. 2 shows a vertical cross section of the evaporative cooler from FIG. 1,

3 shows a schematic illustration of an embodiment of the device according to the invention for the thermal toughening of glass panes using the evaporative cooler from FIGS. 1 and 2.

FIG. 1 and FIG. 2 each show a cross section through an embodiment of the evaporative cooler 10 according to the invention with a controllable cooling effect. The cross-section is selected horizontally in FIG. 1 (view from above) and vertical in FIG. 2 (view from the side). The evaporative cooler 10 comprises a cooling space 11 which is enclosed in a housing and which has a gas inlet 12 and a gas outlet 13 opposite one another. A gas flow (indicated by a block arrow) can enter the cooling space 11 through the gas inlet 12 and exit the cooling space 11 again through the gas outlet 13 so that the gas flow flows through the cooling space 11.

The cooling space 11 is provided with three inserts 15.1, 15.2, 15.3. A cooling cassette can be inserted from the outside into each insert 15.1, 15.2, 15.3, comprising a frame and carrier material 14.1, 14.2, 14.3 enclosed therein. A drop separator 16.1, 16.2, 16.3 is arranged above each insert 15.1, 15.2, 15.3. When the cooling cassette is inserted into the slide-in unit and thus arranged in the cooling space 11, the carrier material 14.1, 14.2, 14.3 is sprinkled with cooling liquid, for example water, through the respective drop separator 16.1, 16.2, 16.3 and thus soaked. The cooling effect is based on the evaporative cooling of the cooling water when the gas flow passes through the carrier material 14.1, 14.2, 14.3. Excess cooling liquid emerges again from the carrier material 14.1, 14.2, 14.3 at the bottom and is collected by a common drop collector 17. Droplet collectors 17 and droplet separators 16.1, 16.2, 16.3 are connected to one another by a coolant line 18 so that the collected coolant can be fed back to the droplet separators 16.1, 16.2, 16.3 by means of a coolant pump 19 from the droplet collector 17. In the illustration shown, a cooling cassette including carrier material 14.1 is located in the first insert 15.1, while the other insertions 15.2, 15.3 are not equipped with the associated cooling cassettes and their carrier material 14.2, 14.3. Therefore, only the carrier material 14.1 contributes to the cooling of the gas flow, as a result of which there is a comparatively low cooling effect. The cooling effect can be increased by also inserting the remaining cooling cassettes with the carrier materials 14.2, 14.3 into the associated slots 15.2, 15.3.

Figure 3 shows schematically an embodiment of a device for thermal

Tensioning of glass panes using the evaporative cooler 10 according to the invention. 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 pre-tensioning exits, is directed towards the space between the blow boxes 1.1, 1.2. A gas feed 2.1 is connected to the first blower box 1.1, through which it is supplied with the gas flow. The gas supply includes supply pipes and a first fan 3.1 and a second fan 4.1, which are connected one behind the other in this order in the direction of flow. 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. In

In the direction of flow behind the fans 3.1, 4.1 there is also an evaporative cooler 10.1, to whose gas inlet and gas outlet the supply pipes are connected. Likewise, a gas supply 2.2 is connected to the second blow box 1.2, which has, in addition to supply pipes, a first fan 3.2, a second fan 4.2 and an evaporative cooler 10.2, which are connected one behind the other in this order in the direction of flow. Both gas inlets 2.1, 2.2 can each be completely or partially closed by means of a closure flap 7.1, 7.2 in order to stop the gas flow or to regulate its strength.

The air sucked in by the fans 3.1, 4.1, 3.2, 4.2 is cooled on the one hand and humidified on the other hand by the evaporative cooler 10.1, 10.2. Both of these increase the pretensioning efficiency of the device compared to conventional pretensioning devices without cooling.

The device also comprises means for moving the glass pane G to be prestressed, comprising a transport system 8, for example designed as a roller system, and a transport frame 9 moved therewith. The transport frame 9 is provided with a Equipped biasing frame on which the circumferential side edge of the glass pane G is placed. With the transport system the glass pane G is moved into the space between the blow boxes 1.1, 1.2. The blow boxes 1.1, 1.2 are then brought closer to the glass pane G in order to efficiently apply the gas flow to them. After the prestressing, the blow boxes 1.1, 1.2 are moved away from the glass pane G again and the glass pane G is moved out of the space. The pretensioner is then ready for the next pretensioning cycle.

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

List of reference symbols:

(1.1) first / upper blow box

(1.2) second / lower blow box

(2) gas supply

(2.1) Gas supply to the first blow box 1.1

(2.2) Gas supply to 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

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

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

(8) Transport system for glass panes

(9) Transport rack for glass panes

(10) evaporative cooler

(10.1) Evaporative cooler of the first blow box 1.1

(10.2) Evaporative cooler of the first blow box 1.2

(11) Cooling compartment of the evaporative cooler 10

(12) Evaporative cooler gas inlet 10

(13) Gas outlet of the evaporative cooler 10

(14, 14.1, 14.2, 14.3) Carrier material of the evaporative cooler 10 (15, 15.1, 15.2, 15.3) Insertion of the cooling chamber 11

(16.1, 16.2, 16.3) Drop separators of the evaporative cooler 10

(17) Evaporative cooler 10 drop collector

(18) Coolant line of the evaporative cooler 10

(19) Coolant pump of the evaporative cooler 10

(G) pane of glass

Claims

1. Apparatus for thermal toughening 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 blower box (1.1) and the second blower box (1.2),

wherein the gas supply lines (2.1, 2.2) are equipped with an evaporative cooler (10),

wherein the evaporative cooler (10) comprises a cooling space (11) with a gas inlet (12) and a gas outlet (13), so that a gas flow for cooling can be passed through the cooling space (11); and

wherein the cooling chamber (11) is equipped or can be equipped with a carrier material (14) impregnated with a cooling liquid, through which the gas flow flows, the carrier material (14) coming into contact with the gas flow via a contact surface, thereby cooling the gas flow ; and

wherein the evaporative cooler is equipped with means for changing the contact surface.

2. Apparatus according to claim 1, wherein the means for changing the contact surface are designed as means for changing the amount of carrier material (14) in the cooling space (11).

3. Apparatus according to claim 2, wherein the cooling space (11) is equipped with at least one insert (15) through which the carrier material (14) can be pushed into the cooling space (11) or pulled out of the cooling space (11).

4. Apparatus according to claim 3, wherein the cooling space (11) is equipped with a plurality of inserts (15.1, 15.2, 15.3), with carrier material (14.1, 14.2, 14.3) entering the cooling space through each insert (15.1, 15.2, 15.3) (11) can be pushed in or pulled out of the cooling space (11).

5. The device according to claim 4, wherein the carrier material (14) of each insert (15.1, 15.2, 15.3) has a thickness of 0.2 cm to 30 cm.

6. Apparatus according to claim 4 or 5, wherein each insert (15.1, 15.2, 15.3) is equipped with a droplet separator (16.1, 16.2, 16.3) via which the carrier material (14) can be sprinkled with the cooling liquid.

7. Device according to one of claims 4 to 6, wherein each insert (15.1, 15.2, 15.3) is equipped with a drop collector or wherein all the inserts (15.1, 15.2, 15.3) are equipped with a common drop collector (17), the or the drop collectors (17) are suitable for collecting cooling liquid which has flowed through the carrier material (14).

8. Device according to one of claims 3 to 7, wherein the carrier material (14) is provided as a cooling cassette which comprises a frame and the carrier material (14) enclosed therein.

9. Device according to one of claims 1 to 8, 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 flow.

10. Device according to one of claims 1 to 9, which is equipped with means for moving a glass pane (G) into a space between the first blow box (1.1) and the second blow box (1.2), which is a transport frame (9) with a prestressing frame to support the glass pane (G), which is moved by a rail, roller or conveyor belt system.

11. A method for the thermal toughening 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 connected to an evaporative cooler ( 10) is equipped;

(ii) the glass pane (G) is subjected to a gas flow 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 (10),

wherein the evaporative cooler (10) comprises a cooling space (11) with a gas inlet (12) and a gas outlet (13), so that a gas flow for cooling can be passed through the cooling space (11); and wherein the cooling chamber (11) is equipped or can be equipped with a carrier material (14) impregnated with a cooling liquid, through which the gas flow flows, the carrier material (14) coming into contact with the gas flow via a contact surface, thereby cooling the gas flow ; and

12. The method according to claim 11, wherein the gas stream impinging on the glass pane (G) has a temperature of at most 70 ° C, preferably of at most 50 ° C.

13. The method of claim 11 or 12, wherein the gas stream impinging on the glass pane (G) has a relative humidity of at least 50%, preferably of at least 70%, particularly preferably of 80% to 90%.

14. The method according to any one of claims 11 to 13, wherein the glass pane (G) before

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

15. The method according to any one of claims 11 to 14, wherein the glass pane (G) is acted upon by the gas flow over a period of 1 s to 10 s, preferably from 1 s to 2 s.