CN111954645A - Evaporative cooler with controllable cooling - Google Patents

Abstract

The invention relates to a device for thermally pre-tensioning glass sheets using an evaporative cooler with a controllable cooling effect. 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 guided through the cooling space (11), wherein the cooling space (11) is or can be provided with a carrier material (14) which is impregnated with a cooling liquid and through which the gas flow flows, wherein the carrier material (14) is brought into contact with the gas flow via a contact surface, whereby cooling of the gas flow is achieved, wherein the evaporative cooler is provided with means for changing the contact surface.

Description

Evaporative cooler with controllable cooling

Technical Field

The invention relates to an evaporative cooler (Verdunstungsk uhler) with a controllable cooling effect, to the use thereof, in particular for a device, and to a method for thermally pre-tensioning glass sheets (Glasscheibe).

Background

An evaporative cooler is a heat exchanger with direct heat transfer, i.e. combined heat and mass transfer. The evaporative cooler has a cooling space through which a gas stream to be cooled is guided and which is equipped with a carrier material which is wetted with a cooling liquid. The cooling effect is based here on the evaporative cooling of the coolant. The humidity of the gas to be cooled is also increased by evaporation. Exemplary reference is made to US5655373A, DE1299665A and WO03058141a 1. Evaporative coolers are used, for example, in power plant buildings (kraft werkbau) in order to cool the suction air channel of a gas turbine adiabatically.

Conventional evaporative coolers do not provide the user with the possibility of controlling the cooling action. This situation is not problematic in many applications, however applications are also conceivable in which there is a need for such control. If, for example, the gas stream is to be cooled to a defined temperature, the required cooling effect is also dependent on the initial temperature of the gas, which is in turn determined by the current ambient temperature. An excessively strong cooling effect can also lead to an undesirably high humidity of the gas stream, which in some applications can act as a disturbing effect in the form of droplet formation due to the humidity acting as a condensation effect.

It is proposed in international patent application PCT/EP2019/067275 to use an evaporative cooler in an apparatus for thermally pre-tensioning glass sheets. In the case of thermal pretensioning, the glass sheet heated to a temperature as fast as the softening temperature is loaded with an air flow which leads to a rapid cooling (quenching) of the glass sheet. As a result, a unique stress signature (Spannungsprofil) is built into the glass sheet, wherein there is a compressive stress at the surface and a tensile stress in the core of the glass sheet. This affects the mechanical properties of the glass sheet in two different ways. First, the fracture stability of the sheet is improved and the sheet can withstand higher loads than an unhardened sheet. Secondly, glass fracture after penetration of the central tensile stress region (for example due to damage by sharp stones or by intentional destruction by sharp emergency hammers) does not occur in the form of large sharp-edged fragments, but rather in the form of small, blunt fragments, whereby the risk of injury is considerably reduced. Due to the above-described properties, glass sheets which are pre-tensioned by heat are used as so-called monolithic safety glass in the field of vehicles, in particular as rear window panes and side window panes. In the field of vehicles, high demands are made on the degree of pretensioning, which is also regulated in the standard. However, glass sheets which are pre-tensioned thermally in the engineering, construction and housing fields are also commonly used, for example as glass curtain walls, shower stalls or table tops. Reference is made, by way of example only, to patent document DE 710690A, DE 808880B, DE 1056333 a, originating from the 1940 s and the 1950 s, and furthermore to WO 2019015835 a 1.

An improved pretensioning effect can be achieved by active cooling of the air flow. However, excessively high air humidity (as may occur when using evaporative coolers with excessively high cooling action) may manifest as droplet formation, which damages the surface of the heated glass sheet.

There is therefore a need for an evaporative cooler with a controllable cooling effect, in particular in view of the use in hot pretensioning.

US 2270810 a discloses a condenser for a cooling unit with a replaceable carrier material. WO 88/10240 a1 discloses a method for manufacturing glass bottles which is treated with a cooled fluid for faster cooling. GB 472022 a discloses a method for thermally pre-tensioning glass, in which a gas stream required for this purpose is guided over the surface of the water in order to saturate the gas stream with water vapor.

Disclosure of Invention

The invention is based on the object of providing a device for thermally pre-tensioning glass sheets, with such an improved evaporative cooler.

This object is achieved according to the invention by a device according to independent claim 1. Preferred design solutions are given in the dependent claims.

In the device according to the invention, an improved evaporative cooler with a controllable cooling effect is used for the active cooling of the gas stream.

The evaporative cooler according to the invention with controllable cooling comprises (or has) a cooling space with a gas inlet and a gas outlet, so that a gas flow for cooling can be guided (or can be guided) through the cooling space. The cooling space is typically surrounded by a housing in which the gas inlet and the gas outlet are arranged as openings to which a conduit line carrying a gas flow can be coupled (or coupleable). The gas inlet and gas outlet are typically arranged opposite each other, so that the gas flow can flow through the cooling space without interference and deflection. Other configurations are also contemplated. The cooling space is equipped or can be equipped with a carrier material which is impregnated or provided for impregnation with a cooling liquid. In operation, the carrier material is flowed through by a gas stream. The carrier material has a contact surface via which the carrier material comes into contact with the gas stream, whereby a cooling, in particular an adiabatic cooling, of the gas stream is achieved.

In conventional evaporative coolers, the cooling space is equipped with a carrier material, which is fixedly mounted. The user has no possibility of changing the carrier material without costly modification work. In contrast to this, the evaporative cooler according to the invention is equipped with means for varying the contact surface, more precisely with means for varying the expansion of the contact surface. Thereby, the user can control the cooling effect, wherein a larger contact surface causes a higher cooling effect and a smaller contact surface causes a smaller cooling effect. In this way, the required cooling effect can be actively controlled, for example to adjust the desired temperature or humidity of the gas stream. This is a great advantage of the present invention.

The means for changing the contact surface allow the user to adjust the contact surface of the carrier material from the outside, i.e. in particular without disassembling the cooling space housing.

The carrier material is wetted with a cooling liquid in the cooling space during operation. An evaporative cooler is a heat exchanger with direct heat transfer, in which evaporative cooling of a cooling liquid is used in order to cool a gas flow (heat transfer). In this case, the coolant is converted into a gas stream (mass transfer). In addition to cooling, evaporative coolers thus also cause a rise in the humidity of the gas stream. When the coolant evaporates, the energy required for this purpose is drawn off from the surroundings, i.e. ultimately from the gas stream, which leads to its cooling. The evaporated coolant is absorbed by the gas stream and its relative humidity increases. The cooling effect depends on the ambient air state, temperature and relative humidity. The lower the relative humidity, the higher the potential for further moisture absorption, i.e. more coolant can thus be evaporated.

The carrier material is preferably of fibrous or porous construction. In this way, the carrier material can advantageously be wetted with cooling liquid and provide a large contact surface for the gas flow. The carrier material preferably has flow channels through which the gas stream can flow. Paper, in particular in the form of a curled paper layer, can for example be used as carrier material. Alternatively, suitable ceramic or synthetic structures are also conceivable as support materials.

The evaporative cooler is preferably embodied as a so-called drip cooler (riesekkuhler). In this case, the carrier material is poured, in particular continuously, with a cooling liquid in order to ensure a permanent impregnation. For this purpose, for example, a droplet separator can be arranged above the carrier material, which droplet separator is irrigated with a cooling liquid. A droplet collector may be arranged below the carrier material in order to catch the cooling liquid flowing through the carrier material. The cooling liquid captured in the droplet collector can be fed back to the droplet separator by means of a cooling liquid line provided with a pump.

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

In a preferred embodiment of the invention, the contact surface is modified in the following manner: the amount of carrier material in the cooling space through which the gas stream flows is varied. The means for changing the contact surface are thus means for changing the amount of carrier material in the cooling space. The user can thus control the cooling effect, wherein a greater amount of carrier material being flowed through leads to a higher cooling effect and a smaller amount of carrier material being flowed through leads to a smaller cooling effect.

In order to be able to vary the amount of carrier material in the cooling space, the evaporative cooler is equipped with at least one push-in (Einschub) in an advantageous embodiment. By means of the at least one insertion section, the carrier material can be moved into the cooling space or into the provided gas flow and out of the cooling space or out of the provided gas flow. The carrier material can be pushed into the push-in section into the cooling space in order to increase the amount of carrier material in the cooling space. Conversely, the carrier material can be withdrawn from the insertion section 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, so that it can be handled well. The frame together with the carrier material is referred to as a cassette (cooling cassette) in the sense of the present invention. This embodiment advantageously allows simple maintenance of the evaporative cooler, since the carrier material is easily accessible to the operator.

The cartridge and the associated push-in part can be designed in different ways, they are known per se and can be chosen appropriately by the person skilled in the art according to the requirements of the application. For example, the cassettes and the pushers can be configured as drawer systems, rail systems or roller systems. The cassette (in particular the frame of the cassette) and the push-in are adapted to this in their dimensions and other designs to one another and to one another.

In principle, a single push-in is sufficient. Then cassettes are provided which are equipped with different amounts of carrier material and which are compatible with the push-in section. In order to adjust the cooling effect of the evaporative cooler, the cassettes with the appropriate amount of carrier material only have to be pushed in. Since the transverse dimensions of the carrier material (width and length perpendicular to the flow direction of the gas stream) are essentially determined by the push-in section, different amounts of carrier material for different cassettes are suitably realized by different thicknesses of the carrier material (measured in the flow direction of the gas stream).

In a preferred embodiment, however, the cooling chamber is equipped with a plurality of insertion openings. By means of each insertion section, the carrier material can be moved into the cooling space or into the gas stream provided and out of the cooling space or out of the gas stream provided. The carrier material can thus be pushed into the cooling space or withdrawn from the cooling space by means of each push-in part. For each push-in part, at least one cartridge is provided for this purpose. The cooling space can thus be equipped with a variable number of cassettes in order to adjust the desired cooling effect. The number of push-in portions is preferably 2 to 20, particularly preferably 2 to 5. This gives sufficient flexibility in the control of the cooling effect without the structure of the evaporative cooler becoming unduly complex. The carrier material of each push-in or of each cartridge preferably has a thickness of 0.2 cm to 30 cm, particularly preferably 0.5 cm to 20 cm. Good results are thereby obtained, the thinner the individual cassettes are, the more finely adjustable the cooling effect can be, however, an excessively small thickness of the cassettes is detrimental to the stability of the carrier material. Different cassettes can have the same or different amounts of carrier material, i.e. in particular carrier material with the same thickness or with different thicknesses.

In principle, it is also possible to push one or more cassettes only partially into the associated push-in, so that only a portion of the carrier material is flowed through by the gas stream and the cooling effect is assisted. In this way, it is possible to achieve a stepless control of the cooling action, wherein the partial pushing in may nevertheless have a fluidic disadvantage.

In addition to the insertion, the carrier material can also be fixedly mounted in the cooling space. This provides a basic cooling effect and the cooling effect can be increased by pushing in further cassettes.

If the evaporative cooler is designed as a drip-irrigation cooler and has a plurality of insertion openings, in an advantageous embodiment each insertion opening is equipped with its own droplet separator. The droplet separator is arranged for this purpose above the associated push-in portion, so that the carrier material is drip-irrigated with cooling liquid when the cassette is pushed into the push-in portion. Ideally, the droplet separator is equipped with a stop cock (absterrh ä hnen) or the like, so that it can only be put into operation when the cartridge is pushed into the relevant push-in. Since the amount of cooling liquid also has an influence on the cooling effect, in an advantageous embodiment the droplet separator is equipped with means for controlling the amount of deposition of cooling liquid. The amount of cooling fluid can be increased in order to achieve an enhanced cooling effect and vice versa.

Likewise, each push-in section may be equipped with its own drip catcher. A droplet collector is arranged below the push-in portion and is adapted to collect the cooling liquid flowing through the carrier material. Alternatively, however, all the insertion sections can also be equipped with a common drop collector. A common drip collector is arranged below all of the inlets and is suitable for collecting the cooling liquid flowing through all of the carrier material. In principle, combinations thereof are also possible, wherein some of the pushing-in sections are equipped with their own drip catcher and the other pushing-in sections are equipped with a common drip catcher.

All droplet separators and all droplet collectors (or a common droplet collector) are preferably coupled to the same coolant line. The coolant line is equipped with a pump so that the collected coolant can be fed back to the droplet separator. From this, a coolant circuit is obtained, which is of interest for economic reasons.

The variable contact surface of the carrier material can also be realized in a different manner than by the cassette pushing system described above. In this way, for example, one or more coolant 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 attack of the flow duct with respect to the gas flow can be varied in order to control the cooling effect.

The apparatus according to the invention for thermally pre-tensioning glass sheets uses the evaporative cooler according to the invention described above. Since the efficiency of the pretensioning is essentially determined by the temperature of the gas stream, which in turn depends on the ambient temperature, the use of a controllable cooler is particularly advantageous for this use. Furthermore, an excessively high humidity of the gas stream must be avoided in order to avoid droplet formation due to the humidity that condenses out. If the liquid drop should hit the heated glass sheet immediately, this may cause glass breakage due to too strong local cooling. The apparatus includes a first blow box and a second blow box. The two blow boxes are arranged opposite each other so that their gas exit openings (nozzles) are directed towards each other. By this it is meant that all gas exit openings of the first blower box and all gas exit openings of the second blower box are directed towards each other without the need for each individual gas exit opening to have a counterpart placed exactly opposite thereto in the opposite blower box. Instead, the individual gas outlet openings of the blower box can be offset with respect to one another. With the blow boxes with gas exit openings directed towards each other, the surface of the glass sheet arranged between the blow boxes can be loaded with a gas flow. At each blow box a gas supply is coupled, via which a gas flow is delivered to the blow box.

According to the invention, the gas supply is equipped with an evaporative cooler according to the invention with a controllable cooling effect. The gas stream is actively cooled by means of an evaporative cooler. Since the gas flow has a lower temperature, it must not be too strong when it impinges on the glass sheet in order to achieve the same cooling or pretensioning effect. Thereby, energy for generating the gas stream can advantageously be saved.

The pretensioning efficiency is increased by cooling of the gas stream. The term "pretensioning efficiency" (as it is used within the scope of the present invention) can be quantitatively passed throughThe so-called thermal conductivity α. This thermal conductivity is a common physical parameter and can be said to be a proportionality coefficient describing the strength of the thermal conductivity at the interface. The thermal conductivity is generally expressed in units of W/(m)²K) It is given. The thermal conductivity when thermally pre-tensioning glass sheets depends, inter alia, on the strength (pressure), temperature, density and humidity of the gas stream.

The gas supply of each blower box is preferably equipped with at least one ventilation device (Ventilator) in order to supply the respective blower box with a gas flow. It is particularly preferred that the gas supply of each blower box is equipped with a first ventilation device and a second ventilation device, which are connected to each other in series, so that the gas flow generated by the first ventilation device enters the second ventilation device and passes through and is further compressed and thereby reinforced. A stronger gas flow can be generated overall by the serial connection of two ventilators in series. It is common to use two ventilators per gas supply, but in principle more than two ventilators, in particular connected in series, can also be used.

The evaporative cooler may be arranged in flow direction in front of or behind the at least one ventilation device. Preferably, the evaporative cooler is arranged behind the at least one ventilation device. This has the following advantages: the gas flow does not have to pass through the ventilation device after cooling down, where it is heated again. If the gas supply is equipped with two or more series-connected ventilators, the evaporative cooler can be arranged in the flow direction in front of or behind all of the ventilators or likewise between two ventilators. In a particularly preferred embodiment, the evaporative cooler is arranged downstream of all of the ventilators of the gas supply in the flow direction. It is also conceivable that one gas supply is equipped with more than one evaporative cooler, for example in a configuration such that: ventilator-evaporative cooler-ventilator-evaporative cooler (in flow direction).

Preferably, each gas supply is designed with one evaporative cooler each. In principle, however, it is also possible to guide the two gas flows through a common evaporative cooler, to be brought together by a gas supply and to be connected to the common evaporative cooler.

The gas supply typically comprises a pipe which interconnects the evaporative cooler and the ventilation device and which is connected with the blower box and through which the gas is sucked for generating the gas flow. The tubes are coupled to the evaporative cooler at the gas entry portion and the gas exit portion to direct the flow of gas through the evaporative cooler.

The apparatus according to the invention can optionally be equipped with a drying device which is adapted and arranged for reducing the humidity of the gas stream before it impinges on the glass sheet. In this way, interfering droplet formation or the formation of droplets being captured is also avoided. The drying device can be configured, for example, as a droplet trap (Topfenfalle). The drying device is preferably arranged in the flow direction behind the evaporative cooler and all the ventilation devices of the gas supply.

The use of the evaporative cooler according to the present invention achieves an increase in the efficiency of the pretensioning apparatus or pretensioning method. A higher pretensioning efficiency is advantageous in particular when the vehicle glazing is pretensioned, since higher, partially legally prescribed requirements are placed on the pretensioning force. Furthermore, generally relatively thin glass sheets are used here, which require a higher cooling rate than thicker glass sheets in order to achieve the desired prestress. The glass sheet to be pretensioned according to the invention is therefore in a particularly advantageous embodiment a vehicle glazing, i.e. a glazing provided as a vehicle, preferably a motor vehicle and in particular a passenger vehicle. However, the invention is equally applicable when pre-tensioning other glass sheets, for example in the engineering, construction and housing fields, for example when pre-tensioning glass curtain walls, glass floors, table tops or shower stalls.

Furthermore, the apparatus according to the invention comprises means for generating a relative movement between the glass sheet to be pretensioned and the blow box. Thereby, the glass sheets may be exposed to the effective range of the blow boxes (the glass sheets are positioned in the intermediate space between the blow boxes) and pumped away again (the glass sheets are positioned outside the intermediate space between the blow boxes). Such means for generating a relative movement are preferably means for moving the glass sheet, which are suitable for moving the glass sheet to be pretensioned into the intermediate space between the two blow boxes and out of the intermediate space again. For this purpose, rail systems, roller systems or running belt systems can be used, for example. The glass sheets can be transported vertically or horizontally. In the first case, the means for moving the glass sheets preferably comprise a holding clip which is fixed at the glass sheets so that the glass sheets hang vertically at the holding clip and are in turn moved by a rail system, roller system or running belt system or equivalent means. In the latter case, the glass sheets can be laid directly on a rail system, a roller system or a running belt system. However, the means for moving the glass sheets preferably also comprise a transport rack on which the glass sheets rest. The transport rack usually has a pre-tensioned frame (in the form of a frame) for resting the glass sheets. The glass sheets are supported during transport and during pre-tensioning on a transport carrier, which is in turn moved by a rail system, a roller system or a running belt system or equivalent means. The pretensioning of the glass sheets horizontally arranged on the pretensioning frame is customary, in particular in the case of vehicle windows, and this variant is therefore particularly preferred.

However, the means for generating the relative movement between the blower box and the glass sheets can in principle also be designed differently. In this way, it can be, for example, a device for moving the blower box, which moves the blower box relative to the sheet material held stationary and, after pretensioning, is moved away again by the same. Likewise, it is conceivable to move the sheet and the blow box over a certain section to move together with the glass sheet.

A pretensioning frame or frame form is understood to mean, in the sense of the present invention, a frame-like or ring-like device on which the circumferential lateral edge of the glass sheet rests, without a large part of the sheet surface, in particular the central region, being in direct contact with the pretensioning frame. The pretensioning frame is typically fixed in a displaceable manner at the transport carriage and is adapted to the respective shape of the type of glass sheet to be pretensioned. The shape of the support frame therefore corresponds to the shape of a conventional window pane, in particular a vehicle window pane, for example, in a polygonal, for example rectangular, trapezoidal or triangular shape in plan view, wherein the lateral edges are often slightly curved in comparison with the polygonal shape. The pretensioning frame is typically constructed from a plurality of sub-elements, which are each associated with one side of the polygon. In the case of rectangular or trapezoidal sheets, the bearing surface is constructed, for example, from four rectilinear or slightly curved sections which are combined to form a rectangular or trapezoidal shape. The pretensioning frame can have an opening, which can also be referred to as a bore or a through-lead and is arranged such that the edge of the glass sheet to be pretensioned lies on the opening during the intended use. The glass sheets are supported by the regions of the supporting frame between the openings, which regions are chosen to be as small as possible. The openings allow air circulation, which is advantageous for the pretensioning efficiency. Furthermore, the lateral edges of the glass sheets can be directly acted on with air as a result of the openings, as a result of which the sheets are cooled more uniformly and the above-mentioned disturbing so-called edge stresses of the glass sheets are avoided and their stability is improved as a result.

The blow boxes of the apparatus according to the invention are spaced apart from each other so that glass sheets can be arranged between these blow boxes. If the glass sheets are to be pre-tensioned in a horizontal position, the nozzles of the first blower box (upper blower box) are directed downwards and the nozzles of the second blower box (lower blower box) are directed upwards. If the glass sheet is prestressed in the vertical position in reaction thereto, the blow boxes are arranged laterally of the prestressing position so that the gas stream leaves the blow boxes substantially horizontally. These blow boxes may be referred to as a left blow box and a right blow box, for example.

By means of the blower box, the surface of the glass sheet is loaded with a gas flow and thereby cooled. A blower box is understood in the most general sense of the present invention to be a device for generating a directed gas flow which is suitable for cooling the surface of a glass sheet and by means of which the gas flow impinges on the glass sheet, for example, over the entire surface or in points. The blower box preferably has an inner hollow space into which a gas flow can be introduced by means of a gas supply. The hollow space is typically delimited in the direction of the sheet by at least one closing element, which is equipped with a plurality of nozzles. The nozzle is connected or coupled to the hollow space such that gas can flow through the nozzle from the hollow space in order to load the surface of the glass sheet with a stream of air. I.e. the blower box distributes the gas flow from the gas conveying line with a relatively small cross section over a larger effective area via the nozzle. The nozzle openings are discrete gas exit points, which are, however, present in a relatively large number and are distributed uniformly, so that all areas of the surface are cooled substantially simultaneously and uniformly, so that the sheet is provided with a uniform prestress.

The nozzle is a bore or through-guide which extends through the entire closure element. Each nozzle has an input opening (nozzle entry) through which the gas stream enters the nozzle and an opposite output opening (nozzle opening) through which the gas stream exits the nozzle (and the entire blower box). The surface of the closing element with the inlet opening faces the hollow space of the blower box, and such surface with the nozzle opening faces away from the hollow space of the blower box and, in use according to regulations, faces the glass sheets. The surface of the glass sheet is subjected to a defined air flow through the nozzle opening. The nozzles can advantageously have a section which is coupled to the inlet opening and which tapers in the direction of the outlet opening, in order to guide the air efficiently and fluidically appropriately into the respective nozzle.

As closing element, for example, a single nozzle plate can be used, which delimits a hollow space and which has all nozzles distributed in two dimensions, for example in rows and columns.

In a preferred embodiment, a high prestressing efficiency can be achieved by means of the design, each blower box having a plurality of so-called nozzle strips as closure elements. In this type of blower, the gas flow is distributed from the hollow space into a plurality of channels, which are each closed by a nozzle strip. Each nozzle bar typically has a row of nozzles through which the gas stream can exit from the blast box. The blower box thus distributes the gas flow from the gas supply line with a relatively small cross section over a large effective area via the channels and the nozzles. The use of a blower box and a nozzle strip of this type is customary in particular in the case of vehicle panes, so that this variant is particularly preferred.

In this case, a plurality of channels, into which the gas flow is distributed during operation, are coupled to the hollow space, typically opposite the gas supply line. These channels may also be referred to as nozzle tabs, nozzle fins, or nozzle ribs. The channel typically has an elongated, substantially rectangular cross-section, wherein the longer dimension substantially corresponds to the width of the hollow space and the shorter dimension is in the range of 4mm to 15 mm. Typically, the channels are arranged parallel to each other. The number of channels is typically 10 to 50. The channels are typically constructed through sheet material. The hollow space is preferably configured wedge-like. The boundary of the hollow space adjoining the channel can be described herein as two flanks which converge at an acute angle. The channel typically runs perpendicular to the connecting line of the side face. The length of the channel is therefore not constant, but increases from the middle to the sides, so that the entry opening of the channel, which joins the hollow space, is wedge-shaped and the exit opening is braced off with a smooth, typically curved face. The exit openings of all channels are typically configured with a common smooth, curved face. By the described wedge-shaped design of the hollow space and the described arrangement of the channels, the gas flow is distributed particularly efficiently into the channels and it produces a gas flow which is very uniform over the entire active area. Each channel is closed at its end opposite the hollow space by a nozzle strip.

The apparatus may be designed for a continuous process (durchlaufwverfahren) in which the glass sheets are continuously moved without being fixedly positioned between the blow boxes. The glass sheet is moved at a substantially constant speed on the transport section, wherein the glass sheet is moved into between the blow boxes as long as it is loaded with a gas flow moving between the blow boxes and is moved out of the intermediate space between the blow boxes again, during which its speed does not change significantly or even stops completely. Such continuous processes are common in particular for glass sheets in the field of pretensioning engineering, construction and housing.

However, the device can also be designed for a method in which the glass sheets are fixedly positioned between the blower boxes for pretensioning. Such devices are frequently used, in particular, for glass sheets in the field of pre-tensioned vehicles, since particularly high pre-tensioning requirements are placed here, which sometimes cannot be achieved with continuous methods. This configuration is therefore particularly preferred.

The closure element can be shaped flat or likewise curved. Flat closing elements are particularly suitable for pre-tensioning flat glass sheets, but curved glass sheets can also be pre-tensioned with flat closing elements, when lower requirements are imposed on the degree and uniformity of pre-tensioning. A higher pretensioning efficiency can be achieved if the shape of the closing element or of the closing elements is adapted to the shape of the curved glass sheet to be pretensioned such that all nozzle openings have substantially the same spacing from the glass surface. The nozzle opening of the blower box has a convexly curved surface, and the nozzle opening of the opposing blower box has a concavely curved surface complementary thereto, wherein the curvature substantially corresponds to the curvature of the glass sheet. Upon pretensioning, the convex blower box faces the concave surface of the sheet and the concave blower box faces the convex surface. This embodiment is suitable for continuous methods when the glass sheets to be pretensioned are bent in only one spatial direction (cylindrical bending) and for pretensioning methods with glass sheets fixedly positioned between the blower boxes (cylindrical or spherical bending).

In the field of vehicles, spherically curved glass sheets (bending in two spatial directions) typically occur and place high demands on the degree and uniformity of the pretensioning, so that continuous methods are less suitable for pretensioning. These glass sheets are therefore usually permanently prestressed between the blower boxes, the shape of the closing element matching the spherical curvature of the glass sheets. The glass sheets are preferably transported horizontally on a pre-tensioning frame between the blow boxes. Since the sheets are usually transported to the pre-tensioning station with an upwardly directed concave surface, the upper blower box is preferably of convex design and the lower blower box is of concave design.

If the apparatus is designed for fixedly pretensioning the glass sheets between the blow boxes, the apparatus preferably furthermore comprises means for changing the spacing between the first and the second blow boxes. Thereby, the blow boxes can be moved relative to each other and away from each other. After the glass sheets are moved between the blow boxes in the further spaced-apart state of the blow boxes, the spacing of the blow boxes relative to each other and thus relative to the glass sheets is reduced, whereby a stronger gas flow can be generated on the glass surface. After the pretensioning, the distance is increased again in order to move the glass sheets out of the intermediate space between the blower boxes again. In this way, it is also possible to pretension strongly and/or spherically curved glass sheets with high efficiency. Here, a movement of the blower box is required in order to achieve a sufficiently small distance of the glass surface from the nozzle. If the glass sheets between two fixed bellows are to be pretensioned, the spacing between the bent glass sheets must be selected too large in order to be able to move them in, which would lead to a critical reduction in the pretensioning efficiency. During the pre-tensioning, the transport carriage is typically moved periodically, so that the nozzles of the blower box are not directed toward the same point of the glass sheet over the entire period of time. The use of a movable blower box is common in particular in the case of vehicle windows, so that this variant is particularly preferred.

However, the blower box can also be realized in other ways in principle. In this way, it is for example conceivable that the blower box has a large-area opening without closure elements, depending on the type of air well, and that the large-area gas stream exiting from said opening hits the entire sheet surface or a part thereof, without being more finely distributed by the nozzles. Likewise, it is conceivable that the individual nozzles are connected to the gas supply by means of a respective single line.

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

evaporative cooler ventilator 1 ventilator 2

Ventilator 1 evaporative cooler ventilator 2

Ventilator 1 ventilator 2 evaporative cooler

Evaporative cooler-ventilator 1-ventilator 2-drier

Ventilation device 1 evaporative cooler ventilation device 2 drying device

Ventilation device 1-ventilation device 2-evaporative cooler-drying device.

The gas supply designed in this way can in turn be combined with any desired design of the blower boxes and means for moving the glass sheets, for example horizontally arranged blower boxes for lying sheets or vertically arranged blower boxes for suspended sheets, fixed or movable blower boxes, blower boxes for continuous systems or for prestressing fixedly arranged glass sheets, blower boxes with curved or flat closure means, transport means with or without transport racks, etc.

The invention also comprises an assembly for thermally pre-tensioning glass sheets, comprising the apparatus according to the invention and a glass sheet arranged between two blow boxes.

Furthermore, the invention comprises a method for thermally pre-tensioning glass sheets. The heated glass sheets are arranged between a first and a second blowing box, in particular between the first and the second blowing box, which are arranged opposite one another and to which a gas supply is respectively connected. Each gas supply is equipped with an evaporative cooler according to the present invention. If the glass sheet is arranged in the intermediate space, it is subjected to a gas flow by means of two blower boxes, so that the glass sheet is cooled and thereby pre-tensioned. The gas flow is guided through a heat exchanger and is thereby actively cooled.

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

The gas used to cool the glass sheets is preferably air. The sheet surface is typically loaded with a gas stream over a period of 1 to 10 seconds. Especially when pre-tensioning vehicle glazing, a time period of 3 seconds or 4 seconds is common. These times can be reduced because the pretensioning efficiency is increased with the method according to the invention. In a particularly advantageous embodiment, the time period is therefore less than 3 seconds, in particular 1 to 2 seconds.

When the gas stream impinges on the glass sheet, it is cooled by the evaporative cooler and preferably has a temperature of at most 70 ℃, particularly preferably at most 50 ℃, for example 20 ℃ to 50 ℃. In this way, a particularly good pretensioning efficiency is achieved.

Evaporative coolers also increase the humidity of the gas stream. The relative humidity of the gas stream when it impinges on the glass sheet is preferably at least 50%, particularly preferably at least 70%, very particularly preferably 80% to 90%. In this way, a particularly good pretensioning efficiency is achieved.

In a preferred embodiment, the glass sheets to be pre-tensioned consist of calcium-sodium glass, as is customary for window panes. However, the glass sheet may also comprise or consist of other glass types, such as borosilicate glass or quartz glass. The thickness of the glass sheet is typically 1mm to 20mm depending on the application. In the field of vehicles, sheet thicknesses of 1mm to 5mm, in particular 2mm to 4mm, are customary.

The invention exerts its advantages in a particular way when pre-tensioning relatively thin glass sheets, since it requires a higher cooling rate than thicker glass sheets. In a particularly advantageous embodiment, the glass sheets have a thickness of up to 3.5mm, preferably 1mm to 3 mm.

In an advantageous embodiment, the method according to the invention is directly followed by a bending process in which the flat glass sheet in the initial state is bent. In this way, the glass sheets do not have to be heated up in a particular manner again for the pretensioning. During the bending process, the glass sheet is heated above the softening temperature. The pre-tensioning process is followed by a bending process before the glass sheet is significantly cooled. For this purpose, the glass sheets are transferred from the bending tool to a pre-tensioning mold (vorspan) after the bending process or in the final step of the bending process. In addition to this, there are also bending methods in which the glass sheets are conveyed by means of a roller conveyor through a bending zone and in the bending zone are prestressed against rollers.

There is a tendency of glass manufacturers to further reduce the temperature for glass bending more and more, since better optical quality and surface properties of the glass sheets can thereby be achieved. In such bending methods with relatively low temperatures, the pretensioning method according to the invention can be applied particularly advantageously, since the increased pretensioning efficiency, despite the lower temperatures, leads to sufficient stress in the glass sheets. At the time of pre-tensioning, the temperature of the glass sheet is between a so-called transition point (transition point) at which the viscosity of the glass sheet allows plastic deformation and a so-called softening point (softening point) at which the glass deforms under its own weight. The present invention can realize that the pitch with respect to the transition point is reduced. The bending temperature of the conventional vehicle panes for bending, which consist of calcium-sodium glass, is at 650 ℃. In a particularly advantageous embodiment, the temperature of such a glass sheet, directly before it is loaded with a gas stream and cooled, is at most 640 ℃, preferably less than 640 ℃.

Drawings

The invention is explained in more detail below with reference to the figures and examples. The figures are schematic representations and are not drawn to scale. The drawings in no way limit the invention.

Wherein:

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

figure 2 shows a vertical cross-section of the evaporative cooler from figure 1,

fig. 3 shows a schematic representation of a design of the device according to the invention for thermally pre-tensioning glass sheets using the evaporative cooler from fig. 1 and 2.

Detailed Description

Fig. 1 and 2 show in each case one cross section through an embodiment of an evaporative cooler 10 according to the invention with controllable cooling. The cross-section is selected horizontally in fig. 1 (seen from above) and vertically in fig. 2 (seen from the side). The evaporative cooler 10 comprises a cooling space 11 enclosed in a housing, which cooling space has a gas inlet 12 and a gas outlet 13, which are situated opposite one another. The gas flow (indicated by block arrows) 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 cooling space 11 is traversed by the gas flow.

The cooling space 11 is provided with three insertion openings 15.1,15.2, 15.3. In each insertion portion 15.1,15.2,15.3, a cooling cassette can be inserted from the outside, which comprises a frame and a carrier material 14.1,14.2,14.3 enclosed therein. Above each push-in 15.1,15.2,15.3 a droplet separator 16.1,16.2,16.3 is arranged. When the cooling cassettes are inserted into the insertion section and are thus arranged in the cooling space 11, the carrier material 14.1,14.2,14.3 is poured with a cooling liquid, for example water, through the respective droplet separator 16.1,16.2,16.3 and is thereby wetted. The cooling effect is based on the evaporative cooling of the cooling water as the gas stream passes through the carrier material 14.1,14.2, 14.3. The excess cooling liquid again exits from the carrier materials 14.1,14.2,14.3 below and is collected by a common droplet collector 17. The droplet collector 17 and the 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 supplied from the droplet collector 17 to the droplet separators 16.1,16.2,16.3 again by means of a coolant pump 19.

In the illustration shown, the cooling cassettes with their carrier material 14.1 are located in the first infeed 15.1, while the remaining infeed 15.2,15.3 are not equipped with the associated cooling cassettes and their carrier material 14.2, 14.3. Thus, only the carrier material 14.1 contributes to the cooling of the gas stream, whereby there is a relatively small cooling effect. The cooling effect can be increased by inserting the remaining cooling cassettes with carrier material 14.2,14.3 also into the associated push-in 15.2, 15.3.

Fig. 3 schematically shows a configuration of a device for thermally pre-tensioning glass sheets using an evaporative cooler 10 according to the invention. The apparatus comprises a first blow box 1.1 and a second blow box 1.2, which are arranged opposite each other. The nozzles of the blower boxes 1.1,1.2 through which the gas flow (air flow) required for prestressing exits are directed toward the intermediate space between the blower boxes 1.1, 1.2. A gas supply 2.1 is coupled to the first blow box 1.1, through which the first blow box is supplied with a gas flow. The gas supply comprises a duct and a first ventilation device 3.1 and a second ventilation device 4.1, which are connected in this order in succession in the flow direction. The series arrangement of the ventilators 3.1,4.1 enables an intensive gas flow in the direction of the blower box 1.1 to be generated. Furthermore, an evaporative cooler 10.1 is arranged downstream of the ventilators 3.1,4.1 in the flow direction, to the gas inlet and gas outlet of which ducts are connected. Likewise, a gas supply 2.2 is coupled to the second blower box 1.2, which, in addition to the supply pipe, has a first ventilation device 3.2, a second ventilation device 4.2 and an evaporative cooler 10.2, which are connected in this order in succession in the flow direction. The two gas supplies 2.1,2.2 can be completely or partially closed by means of a respective closing flap 7.1,7.2 in order to stop the gas flow or to adjust its intensity.

The air drawn in by the ventilation devices 3.1,4.1,3.2,4.2 is cooled on the one hand and moistened on the other hand by the evaporative coolers 10.1, 10.2. Both of which improve the pretensioning efficiency of the device relative to conventional pretensioning devices without cooling.

The device furthermore comprises means for moving the glass sheets G to be pretensioned, which means comprise a transport system 8, which is embodied for example as a roller system, and a transport carriage 9 which is moved thereby. The transport carriage 9 is equipped with a pre-tensioning frame, on which the circumferential lateral edges of the glass sheets G rest. The glass sheets G are moved into the intermediate space between the blow boxes 1.1,1.2 by means of a transport system. The blower boxes 1.1,1.2 are then brought close to the glass sheet G in order to efficiently load the glass sheet with a gas stream. After the pretensioning, the blower boxes 1.1,1.2 are moved away again from the glass sheet G and the glass sheet G is removed from the intermediate space. The pretensioning apparatus is then ready for the next pretensioning cycle.

The direction of the gas flow and the movement of the glass sheet G is shown in the figure by grey block arrows.

List of reference numerals:

(1.1) first/Upper bellows

(1.2) second/lower blow box

(2) Gas supply part

(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 ventilation device of first blow box 1.1

(3.2) first ventilation device of first blow box 1.2

(4.1) second ventilating device of first blow box 1.1

(4.2) second ventilating device of first blow box 1.2

(7.1) closure flap of gas supply of first blow box 1.1

(7.2) closure flap of gas supply of first blow box 1.2

(8) Transport system for glass sheets

(9) Transport rack for glass sheets

(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 space of evaporative cooler 10

(12) Gas inlet portion of evaporative cooler 10

(13) Gas exit section of evaporative cooler 10

(14,14.1,14.2,14.3) Carrier Material for evaporative coolers 10

(15,15.1,15.2,15.3) push-in part of Cooling space 11

(16.1,16.2,16.3) droplet separator of evaporative cooler 10

(17) Drip catcher for evaporative cooler 10

(18) Refrigerant circuit of the evaporative cooler 10

(19) Coolant pump for evaporative cooler 10

(G) A glass sheet.

Claims (15)

1. An apparatus for thermally pre-tensioning glass sheets comprising:

-a first blow box (1.1) and a second blow box (1.2) arranged opposite each other and adapted for loading the surface of the glass sheet (G) arranged between them with a gas flow,

-one gas supply (2.1,2.2) each coupled to the first and second blower boxes (1.1,1.2),

wherein the gas supply (2.1,2.2) is 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 guided through the cooling space (11); and is

Wherein the cooling space (11) is equipped or can be equipped with a carrier material (14) which is impregnated with a cooling liquid and through which the carrier material flows, wherein the carrier material (14) comes into contact with the gas flow via a contact surface, whereby cooling of the gas flow is achieved; and is

Wherein the evaporative cooler is equipped with means for modifying the contact surface.

2. The apparatus according to claim 1, wherein the means for varying the contact surface are configured as means for varying the amount of carrier material (14) in the cooling space (11).

3. An apparatus as claimed in claim 2, wherein the cooling space (11) is equipped with at least one push-in portion (15) by means of which the carrier material (14) can be pushed into the cooling space (11) or withdrawn from the cooling space (11).

4. An apparatus according to claim 3, wherein the cooling space (11) is equipped with a plurality of pushers (15.1,15.2,15.3), wherein carrier material (14.1,14.2,14.3) can be pushed into the cooling space (11) or withdrawn from the cooling space (11) by each pusher (15.1,15.2, 15.3).

5. Apparatus according to claim 4, wherein the carrier material (14) of each push-in (15.1,15.2,15.3) has a thickness of 0.2 cm to 30 cm.

6. An apparatus as claimed in claim 4 or 5, wherein each push-in (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 watered with the cooling liquid.

7. The apparatus according to any one of claims 4 to 6, wherein each push-in (15.1,15.2,15.3) is equipped with a droplet collector, or wherein all push-ins (15.1,15.2,15.3) are equipped with a common droplet collector (17), wherein one or more of the droplet collectors (17) are adapted for collecting the cooling liquid flowing through the carrier material (14).

8. The apparatus according to any one of claims 3 to 7, wherein the carrier material (14) is provided as a cooling cassette comprising a frame and the carrier material (14) enclosed therein.

9. The apparatus according to any of claims 1 to 8, wherein each gas supply (2.1,2.2) is equipped with at least one ventilation device (3.1,3.2) for supplying the blast boxes (1.1,1.2) with the gas flow.

10. The apparatus according to any of claims 1 to 9, equipped with means for moving glass sheets (G) into the intermediate space between the first and second blow boxes (1.1,1.2), which means comprise a transport carriage (9) with a pre-tensioned frame for supporting the glass sheets (G), which transport carriage is moved through a rail system, a roller system or a running belt system.

11. A method for thermally pre-tensioning glass sheets, wherein,

(i) arranging the heated glass sheets (G) between a first blow box (1.1) and a second blow box (1.2), which are arranged opposite each other and to which one gas supply (2.1,2.2) each is coupled, said gas supplies being equipped with an evaporative cooler (10);

(ii) cooling the glass sheet (G) by loading the glass sheet (G) with a gas flow by means of two blower boxes (1.1,1.2), wherein the gas flow is 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) such that a gas flow for cooling can be guided through the cooling space (11); and is

Wherein the cooling space (11) is equipped or can be equipped with a carrier material (14) which is impregnated with a cooling liquid and through which the carrier material flows, wherein the carrier material (14) comes into contact with the gas flow via a contact surface, whereby cooling of the gas flow is achieved; and is

Wherein the evaporative cooler is equipped with means for modifying the contact surface.

12. Method according to claim 11, wherein the gas stream impinging on the glass sheet (G) has a temperature of at most 70 ℃, preferably at most 50 ℃.

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

14. The method according to any one of claims 11 to 13, wherein the glass sheet (G) has a temperature of at most 640 ℃ before being cooled with the gas stream.

15. The method according to any one of claims 11 to 14, wherein the glass sheet (G) is loaded with the gas flow over a time period of 1 to 10 seconds, preferably 1 to 2 seconds.

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