CN111194298B

CN111194298B - Device and method for thermally prestressing a vitreous glass plate by means of a heat exchanger

Info

Publication number: CN111194298B
Application number: CN201980002611.0A
Authority: CN
Inventors: A.蔡希纳; J.彭纳斯
Original assignee: Saint Gobain Glass France SAS
Current assignee: Saint Gobain Glass France SAS
Priority date: 2018-09-14
Filing date: 2019-06-28
Publication date: 2023-01-31
Anticipated expiration: 2039-06-28
Also published as: EP3849949A1; CN111194298A; MA53585A; WO2020052828A1; ZA202100282B; BR112021000859A2

Abstract

The invention relates to a device for thermally prestressing a vitreous glass pane, 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 surface of the vitreous glass pane (G) arranged between them, a gas supply line (2.1, 2.2) each connected to the first blow box (1.1) and the second blow box (1.2), wherein the gas supply lines (2.1, 2.2) are equipped with an evaporative cooler (5).

Description

Device and method for thermally prestressing a vitreous glass plate by means of a heat exchanger

The invention relates to a device and a method for thermally prestressing a glass pane, and to the use of a heat exchanger, in particular an evaporative cooler, for thermally prestressing a glass pane.

The thermal hardening of vitreous glass sheets has long been known. It is also commonly referred to as thermal prestressing or annealing. Reference is made only by way of example to the patent documents DE 710690A, DE 808880B, DE 1056333A of the 1940 s and 1950 s. Here, a stream of air is applied to the vitreous glass sheet heated to just below the softening temperature, which results in rapid cooling (quenching) of the vitreous glass sheet. Thereby forming a characteristic stress distribution in the vitreous glass sheet, wherein compressive stress dominates at the surface of the vitreous glass sheet and tensile stress dominates at the core thereof. This affects the mechanical properties of the vitreous glass sheet in two ways. Firstly, the fracture stability of the glass sheets is increased and they can withstand higher loads than unhardened glass sheets. Secondly, after penetrating the central tensile stress zone (e.g. due to a sharp stone or damage caused by deliberate destruction with a sharp emergency hammer), the glass fracture is not in the form of large fragments of sharp edges, but rather in the form of blunt small fragments, thereby significantly reducing the risk of injury. Due to the above properties, thermally prestressed glass panes are used in the automotive field as so-called monolithic safety glass panes, in particular as rear glass panes and side glass panes. In the field of vehicles, high demands are made on the degree of prestressing, which is also specified in the standards. However, in the construction, building and housing fields, thermally prestressed glass panes are also common, for example as glass facades, shower stalls or table panels.

In the prestressing, ambient air is generally used without further pretreatment, from which, by means of a ventilator, a strong gas flow is generated, which is guided by means of a large-area blow box equipped with a plurality of nozzles, with as uniform a distribution as possible over the surface of the vitreous glass sheet. The intensity of the gas flow determines the prestressing efficiency here: the stronger the gas flow, the more efficiently the vitreous glass sheet is quenched and generates higher stresses. In addition, other factors, such as the temperature, humidity and density of the gas stream, also affect the prestressing efficiency.

The current trend in the vehicle industry requires ever higher prestressing efficiencies. Therefore, increasingly thin glass plates are used to reduce weight. However, the thinner the vitreous glass sheet, the more effective the pre-stressing must be to create a temperature differential between the surface of the glass sheet and the core of the glass sheet sufficient to produce the desired stress. In addition, glass manufacturers are striving to bend glass at lower and lower temperatures, whereby the optical quality of the glass sheet can be improved. However, the colder the vitreous glass sheets are before prestressing, the stronger they must be quenched to produce the required stress.

Especially when the manufacturing equipment is located in countries with high outdoor temperatures or high altitudes, a strong gas flow is required to achieve the desired prestressing result. However, the generation of a strong gas flow is associated with a significant increase in the energy costs for the operation of the ventilator.

Heat exchangers with indirect heat transfer are known, in which heat is exchanged between two media in spaces separated from each other. They are also widely used in everyday life, for example as heaters or cooling systems for internal combustion engines. Indirect heat exchangers of this type have already been proposed for the cooling gas flow by means of which the glass panes are cooled or thermally prestressed. See, for example, GB1021849, US20130252367A1 and US20120171632A1.

It is also known to enhance the cooling of vitreous glass sheets by converting a coolant located on or near the surface of the glass into a gaseous phase. For example, in GB441017 it is proposed to apply water droplets to the glass surface, which evaporate and thereby cool the gas stream and the glass. It is suggested in US3929442 to equip the glass surface with sublimed dry ice, thereby cooling the glass. However, direct contact of the glass surface with the coolant carries the risk of damaging the glass until breakage. In contrast, in WO2013102702A1 it is proposed to supply the gas stream via a porous membrane with droplets that evaporate before they hit the glass pane, but in the immediate vicinity thereof, where they draw thermal energy away from the glass pane. Such a solution is technically very complex and error-prone.

It is known in the construction of power plants to cool the air intake duct of a gas turbine adiabatically by means of an evaporative cooler. See, for example, US5655373A and WO03058141A1. Evaporative coolers are heat exchangers with direct heat transfer, i.e. combined heat and mass transfer. The cooling effect is due in this case to the evaporative cooling of the cooling liquid with which the support material flowed through by the air stream is impregnated.

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

This object is achieved according to the invention by a device for thermally prestressing a glass sheet, comprising

A first blow box and a second blow box arranged opposite to each other and adapted to impart a gas flow to a surface of a vitreous glass sheet arranged therebetween,

-a gas supply line connected to each of the first and second blow boxes through which the gas flow is directed to the blow boxes,

wherein the gas supply pipe is equipped with an evaporative cooler,

wherein the evaporative cooler comprises a fibrous or porous carrier material which is impregnated with a cooling liquid and is flowed through by a gas stream, such that adiabatic cooling of the gas stream is achieved, wherein a droplet separator is arranged above the carrier material, which droplet separator is configured to trickle the carrier material with the cooling liquid, and a droplet collector is arranged below the carrier material, which droplet collector is configured to collect the cooling liquid, wherein the cooling liquid trickles vertically through the carrier material and the gas stream passes horizontally through the carrier material.

The apparatus of the present invention for thermally pre-stressing a vitreous glass sheet comprises a first blow box and a second blow box. The two blowboxes are arranged opposite to each other so that their gas discharge ports (nozzles) are directed to each other. This means that all gas outlet openings of the first blow box and all gas outlet openings of the second blow box are directed towards each other — each individual gas outlet opening need not have a counterpart (gegensst ü ck) directly opposite it in the opposite blow box. Alternatively, the individual gas outlets of the blowboxes may be offset from one another. For these blow boxes with gas discharge openings directed towards each other, a gas flow can be applied to the surface of the vitreous glass sheet arranged between the blow boxes. A gas supply pipe is connected to each blowcase, and a gas flow is introduced into the blowcase through the gas supply pipe.

According to the invention, the gas supply pipe is equipped with a heat exchanger, in particular an evaporative cooler. The gas stream is actively cooled by means of a heat exchanger. Since the gas stream has a lower temperature, it must be of lower intensity when it impinges on the vitreous glass sheet to achieve the same cooling or pre-stressing effect. Energy for generating the gas stream can thereby be saved. This is a great advantage of the present invention.

The prestressing efficiency is improved by the cooling of the gas flow. The term pre-stressing efficiency as used in the context of the present invention can be quantitatively expressed by the so-called heat transfer coefficient α. It is a common physical parameter and is also a scaling factor that describes the intensity of heat transfer at the interface. It is usually expressed as W/(m) ² K) Is given in units. The heat transfer coefficient during the thermal prestressing of a vitreous glass plate depends, inter alia, on the strength (pressure), temperature, density and humidity of the gas stream.

In the most general sense, a heat exchanger is understood to mean a device which transfers thermal energy from the gas flow in the gas supply pipe into the coolant flow or is provided for this purpose and is suitable for this. Where the gas stream is cooled. This cooling can be due to direct heat transfer, i.e. combined heat and mass transfer between the media, or to indirect heat transfer, wherein the two media are spatially separated by a heat-permeable wall. The geometric guidance of the two substance flows (gas flow and coolant flow) relative to one another can in principle be freely selected. Thus, for example, operation in co-current (two streams directed in the same direction), counter-current (two streams directed in opposite directions) or cross-current (two streams intersecting, also referred to as cross-current) may be selected. For example, a summary of various types of Heat Exchangers is provided in "Fundamentals of Heat Exchangers Design" of Ramesh k. Shah, dusan p. Sekulic, and in particular in chapter 1 "Classification of Heat Exchangers".

The heat exchanger is operated by a coolant, in particular by a coolant flowing through or around it. The coolant is preferably liquid (coolant), but may in principle also be gaseous. The cooling liquid is preferably water or consists essentially of water, which may optionally contain additives, such as heat-conducting additives, antifreeze agents or chemical or biological stabilizers.

The apparatus according to the invention may optionally comprise a recooling unit (ru ckk ruhleinrichtung) which is provided and adapted to cool the heat exchanger or the coolant of the heat exchanger in operation. Thereby, the cooling efficiency can be further improved.

In principle, the heat exchanger which cools the gas stream for thermally prestressing the vitreous glass plate can be designed as an indirect heat exchanger, which means a heat exchanger with indirect heat transfer. The indirect heat exchanger has a component through which the coolant flows and separates the coolant from the gas stream to be cooled. The components are arranged for efficient heat transfer in the gas stream. Operation in co-current, counter-current or cross-current flow is possible and combinations thereof may be achieved. The coolant may be liquid or gaseous, but is preferably liquid. The components through which the coolant flows may be designed in various ways. The component can be designed, for example, as a plate, usually a plurality of parallel plates (plate heat exchangers) or as a spirally wound sheet (spiral heat exchangers). The component can also be designed as a tube or as a plurality of tubes (tube heat exchanger, tube bundle heat exchanger). The tube or tubes may be U-bent one or more times to reduce space requirements (U-tube heat exchanger). It is also possible to use two concentric tubes, one of which is flowed through by the coolant and the other through by the gas stream to be cooled (jacketed heat exchanger), or a cooling tube stack as a combination of tubes (for the coolant) and lamellae (for the gas stream to be cooled) fixed thereto. The indirect heat exchanger may also be a heat exchanger (Rekupper). In addition to the examples mentioned, other embodiments are also conceivable.

The advantage of an indirect heat exchanger is that the cooling effect, in particular the flow rate through the coolant, can be adjusted. Thus, the desired temperature of the gas stream may be deliberately adjusted. It is also possible to implement a regulation loop in which the temperature of the gas stream is measured and automatically regulated by the coolant flow. The indirect heat exchanger or its coolant is preferably cooled by the sub-cooling unit to improve efficiency.

According to the invention, the heat exchanger is designed in particular as an evaporative cooler. As coolant, a coolant, in particular water, is used. Such evaporative coolers are heat exchangers with direct heat transfer in which evaporative refrigeration of the coolant is used to cool the gas stream (heat transfer). Here, the coolant enters the gas flow (mass transfer). In addition to this cooling, the evaporative cooler thus also leads to an increase in the humidity of the gas stream, which also increases the prestressing efficiency and is an advantage of the invention. Furthermore, evaporative coolers can generally be operated without subcooling, so that their maintenance is less expensive compared to, for example, indirect heat exchangers. Therefore, the apparatus preferably has no recooling device.

The evaporative cooler is preferably manufactured as a so-called trickle cooler (rieselkkuhler) and usually comprises a carrier material, in particular a fibrous or porous carrier material, which is impregnated with a cooling liquid. For this purpose, for example, a droplet separator can be arranged above the carrier material, which droplet separator uses a stream of cooling droplets to the carrier material. A drip catcher may be arranged below the carrier material to collect the coolant flowing through the carrier material. The coolant collected in the droplet collector can be conducted again to the droplet separator by means of a coolant line equipped with a pump. The carrier material is flowed through by a gas stream. Cooling, in particular adiabatic cooling, of the gas stream is achieved here. Since the support material is usually cooled vertically by the droplet stream and the gas stream passes horizontally through the support material, there is a cross-flow operation. When the coolant evaporates, the energy required for this is drawn off from the environment, i.e. ultimately from the gas stream, which leads to its cooling. The vaporized coolant is absorbed by the gas stream and increases its relative humidity. The cooling effect depends on the ambient air conditions, temperature and relative humidity. The lower the relative humidity, the greater the potential for further absorption of moisture, i.e. the more coolant can evaporate. As carrier material, for example, paper, in particular in the form of a corrugated paper layer, can be used. Alternatively, suitable ceramic or synthetic structures are also conceivable as support materials.

The gas supply pipe of each blowcase is preferably equipped with at least one ventilator to supply a flow of gas to the respective blowcase. It is particularly preferred that the gas supply pipe of each glass box is equipped with a first ventilator and a second ventilator connected in series with each other, so that the gas flow generated by the first ventilator enters the second ventilator and is further compressed by it and is thereby intensified. By connecting the two ventilators in series with one another, a stronger gas flow can be generated overall. Usually two ventilators are used per gas supply line, but in principle more than two ventilators can also be used, which are connected in series with one another in particular.

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

Preferably, each gas supply is provided with one heat exchanger, in particular an evaporative cooler. However, it is also possible in principle to conduct both gas streams through a common heat exchanger, which is achieved by combining the supply lines together and connecting them to the common heat exchanger.

The gas supply line typically comprises a tube that interconnects the evaporative cooler and the ventilator and the blowcase, and through which gas is drawn to create a gas flow.

The apparatus of the invention may optionally be equipped with a drying unit adapted and arranged for reducing the humidity of the gas before it is emitted onto the vitreous glass sheet. Although a high humidity is advantageous in principle for the prestressing efficiency, undesirable effects, such as droplet formation, can occur if the humidity is too high. Excessive humidity may be caused, for example, by humid ambient air or by intensive cooling using an evaporative cooler. The drying unit can be designed, for example, as a drop catcher. Preferably, it is arranged in the flow direction behind the heat exchanger, in particular the evaporative cooler, and all fans of the gas supply pipes.

The invention can improve the efficiency of the prestressing device and the prestressing method. A high prestressing efficiency is advantageous in particular when prestressing vehicle glass panes, since the prestressing requires high requirements which are partially stipulated by law. In addition, relatively thin glass sheets are typically used here, which require a higher cooling rate to achieve the required prestressing than thicker glass sheets. The glass pane to be prestressed according to the invention is therefore in a particularly advantageous embodiment a vehicle pane, i.e. a window pane provided as a vehicle, preferably a motor vehicle and in particular a passenger car. However, the invention is equally applicable to the prestressing of other vitreous glass sheets, for example in the construction, building and housing fields, for example when the facade glass, glass floors, table panels or shower stalls are prestressed.

The apparatus of the present invention further comprises means for producing relative movement between the vitreous glass sheet to be pre-stressed and the blowcase. The vitreous glass pane can thus be exposed to the area of action of the blow boxes (the vitreous glass pane is positioned in the gap between the blow boxes) and removed again (the vitreous glass pane is positioned outside the gap between the blow boxes). The means for producing a relative movement is preferably a means for moving the vitreous glass sheet, which is adapted to move the vitreous glass sheet to be pre-stressed in the gap between the two blow boxes and out of the gap again. For this purpose, for example, rail systems, roller systems or conveyor belt systems can be used. The vitreous glass sheet can be transported in a vertical or horizontal position. In the former case, the means for moving the vitreous glass sheet preferably comprise a fastening clip which is fixed on the vitreous glass sheet so that the vitreous glass sheet is suspended vertically thereon and is in turn moved by means of a rail system, roller system or conveyor system or equivalent means. In the latter case, the vitreous glass sheet may be placed directly on a rail system, roller system or conveyor system. However, the means for moving the vitreous glass sheet preferably further comprises a transport rack on which the vitreous glass sheet is placed. The transport rack usually has a pre-stressed frame (frame shape) for placing the glass panes. The vitreous glass sheet is placed during transport and during prestressing on a transport carriage which is in turn moved by means of a rail system, a roller system or a conveyor system or equivalent means. The prestressing of the glass panes arranged horizontally on a prestressing frame is common in particular in the case of vehicle panes, and this variant is therefore particularly preferred.

In principle, the means for producing the relative movement between the blowcase and the vitreous glass sheet may also be configured differently. For example, they may be tools for moving the blowcase, which moves it onto the glass sheet held stationary and is removed therefrom again after prestressing. It is also conceivable to move the glass sheet and the blow box travels a certain distance together with the vitreous glass sheet.

In the sense of the present invention, a prestressed frame or frame shape is understood to mean a frame-like or ring-like device on which the annular side edges of the vitreous glass sheets are placed, while most of the glass sheet surfaces, in particular the central region, are not in direct contact with the prestressed frame. The pre-stressing frame is usually replaceably fixed to the transport frame and matches the respective shape of the glass pane to be pre-stressed. The shape of the support frame is thus, depending on the shape of common window panes, in particular vehicle panes, for example polygonal, for example rectangular, trapezoidal or triangular in plan view, wherein the side edges are usually configured to be slightly curved compared to a strictly polygonal shape. The pre-stressed frame is usually made up of a plurality of portions, each assigned to one side of the polygon. In the case of rectangular or trapezoidal glass panels, the resting face is constituted, for example, by four straight or slightly curved portions, which are combined to produce a rectangular or trapezoidal shape. The pre-stressing frame may have an opening, which may also be referred to as a hole or a through-going, and is arranged such that the edge of the glass pane to be pre-stressed falls on the opening when used as intended. The glass panes are supported by a placement frame area between the openings, which is selected to be as small as possible. The openings allow air circulation, which is advantageous for prestressing efficiency. In addition, the side edges of the glass pane can be exposed to air as a result of the openings, as a result of which the glass pane is cooled more uniformly and disturbing so-called edge stresses of the prestressed glass pane are avoided and their stability is thus increased.

The blow boxes of the apparatus of the present invention are spaced apart from one another so that a vitreous glass sheet can be disposed therebetween. If the vitreous glass sheet is prestressed in a horizontally placed state, the nozzles of the first blow boxes (upper blow boxes) are directed downward and the nozzles of the second blow boxes (lower blow boxes) are directed upward. Conversely, if the vitreous glass sheet is vertically pre-stressed, the blowcase is disposed to the side of the pre-stressed location so that the gas stream exits it substantially horizontally. For example, the blowboxes may now be referred to as left and right blowboxes.

The surface of the vitreous glass sheet is cooled by applying a gas flow to it by means of a blow box. In the most general sense of the present 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 vitreous glass sheet by, for example, impinging it onto the vitreous glass sheet over the entire surface or in a punctiform distribution on the surface. The blowcase preferably has an internal cavity into which a gas stream can be introduced by means of a gas supply pipe. The cavity is usually delimited in the direction of the glass plate by at least one closing element equipped with a plurality of nozzles. The nozzle is engaged with or connected to the cavity such that gas can flow from the cavity through the nozzle to impart a flow of air against the surface of the vitreous glass sheet. The blow box thus distributes the gas flow from the gas feed pipe with a relatively small cross-sectional area over a large active area through the nozzle. The nozzle openings are discrete gas discharge points, but are present in large numbers and uniformly distributed so that all areas of the surface are cooled substantially simultaneously and uniformly, thereby providing the glass sheet with a uniform pre-stress.

The nozzle is a hole or through-going portion extending through the entire closure element. Each nozzle has an inlet opening (nozzle inlet) through which a gas stream enters the nozzle and an opposite outlet opening (nozzle opening) through which the gas stream exits the nozzle (and the entire blow box). The surface of the closing element having the inlet opening faces the cavity of the blow box and the surface having the nozzle opening faces away from it and faces the vitreous glass sheet when it is used as intended. Through the nozzle openings, the surface of the vitreous glass sheet is subjected to a gas stream as desired. The nozzles may advantageously have a portion which is connected to the inlet opening and tapers in the direction of the outlet opening, in order to introduce air into the respective nozzle efficiently and in a flow-technically advantageous manner.

For example, a single nozzle plate can be used as an enclosing element, which defines the cavity and has a two-dimensional distribution of all nozzles, for example in the form of rows and columns.

In a preferred embodiment, in which a high prestressing efficiency can be achieved, each blow box has a plurality of so-called nozzle strips as closing elements. In this type of blow box, the gas flow is distributed from the cavity 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 the blowbox. The blow box thus distributes the gas flow from the gas inlet pipe with a relatively small cross-sectional area over a large active area through the channels and nozzles. The use of blow boxes and nozzle strips of this type is common in particular in the context of vehicle glazing panels, and this variant is therefore particularly preferred.

In this case, a plurality of channels are usually connected to the cavity opposite the gas supply line, into which channels the gas flow is distributed during operation. The channels may also be referred to as nozzle stems, nozzle fins, or nozzle ribs. The channels typically have a slightly long, substantially rectangular cross-section with the longer dimension substantially corresponding to the width of the cavity and the shorter dimension being 8mm to 15mm. Typically, the channels are arranged parallel to each other. The number of channels is typically 10 to 50. The channels are typically formed by sheets. The cavity is preferably designed in the shape of a wedge. The cavity boundary adjacent to the channel may be described herein as two sides that converge at an acute angle. The channel extends generally perpendicular to the line of connection of the side faces. The length of the channel is thus not constant, but increases from the center to the sides, so that the inlet opening of the channel, which is connected to the cavity, is wedge-shaped and the outlet opening is spread out into a smooth, usually curved face. The discharge openings of all the channels are usually formed on a common smooth and curved face. By means of the described wedge-shaped embodiment of the cavity and the described arrangement of the channels, the gas flow is distributed particularly effectively to the channels and a very uniform gas flow over the entire active area is produced. Each channel is closed at its end opposite the cavity by a nozzle strip.

The apparatus can be designed for a continuous process in which the vitreous glass sheet is continuously moved without being statically positioned between the blow boxes. The vitreous glass sheet is moved over a transport distance at a substantially constant speed, wherein it is moved between the blow boxes as long as a gas flow is applied to it while it is moving between the blow boxes, and it is moved out of the gap between the blow boxes again, without its speed changing significantly or stopping completely during this period. Such continuous processes are common in particular for prestressing glass panes in the building, construction and accommodation sector.

However, the apparatus may also be designed as a means for statically positioning the vitreous glass sheets between the blow boxes for prestressing. Such devices are common in particular for prestressing glass panes in the vehicle sector, since particularly high requirements are placed on the degree of prestressing, which is sometimes not achievable by continuous methods. Therefore, this configuration is particularly preferable.

The closure element may be flat or curved. The flat closing element is particularly suitable for prestressing a flat glass sheet, but curved glass sheets can also be prestressed by means of the flat closing element if less requirements are placed on the degree and uniformity of prestressing. A higher prestressing efficiency can be achieved if the shape of the closing element or closing elements matches the shape of the curved and to be prestressed vitreous glass plate so that all nozzle openings have substantially the same distance from the glass surface. The nozzle opening of the blow box thereby opens a convex curvature and the opposite nozzle opening of the blow box opens a concave curvature complementary thereto, wherein the curvature substantially corresponds to the curvature of the vitreous glass sheet. The convex blowcase is directed toward the concave surface of the glass sheet and the concave blowcase is directed toward the convex surface while pre-stressing. This embodiment is suitable for a continuous method when the vitreous glass sheet to be prestressed is bent in only one spatial direction (cylindrical bending) and for a prestressing method using a vitreous glass sheet (cylindrical or spherical bending) statically positioned between the blow boxes.

Spherically curved vitreous glass sheets (curved in two directions) are common in the automotive field and place high demands on the degree and uniformity of prestressing, so that continuous processes are less suitable for prestressing. These vitreous glass sheets are therefore usually statically prestressed between the blow boxes, wherein the shape of the closing element matches the spherical curvature of the vitreous glass sheet. The vitreous glass sheets are preferably transported between the blow boxes in a horizontal position on a pre-stressed frame. Because the glass sheet is typically transported to the pre-stressing station with the concave surface pointing upwards, the upper blowcase is preferably configured convex and the lower blowcase concave.

If the apparatus is designed to statically pre-stress the vitreous glass sheet between the blow boxes, it preferably further comprises means for varying the distance between the first and second blow boxes. Whereby the blow boxes may be moved relatively closer to and further from each other. After the vitreous glass sheets have been driven between them in the state in which the blow boxes are spaced further apart, the distance of the blow boxes from each other and thus from the vitreous glass sheets is reduced, whereby a stronger gas flow can be generated on the glass surface. After prestressing, the distance is again increased to remove the vitreous glass sheet again from the gap between the blow boxes. Consequently, also severely and/or spherically curved vitreous glass plates can be prestressed with high efficiency. Here, a movement of the blow box is necessary to achieve a sufficiently small distance of the glass surface from the nozzle. If the vitreous glass sheet is prestressed between two static blow boxes, the distance of these blow boxes for driving into the bent vitreous glass sheet must be chosen too large, which seriously reduces the prestressing efficiency. The carriage is typically moved periodically while being pre-stressed so that the nozzles of the blowboxes do not point to the same position on the vitreous glass sheet throughout the time period. The use of a moving blow box is common, particularly in the context of vehicle glazing panels, and this variant is therefore particularly preferred.

However, the blow box may in principle be realized in other ways. For example, it is conceivable that the blow box, depending on the type of ventilation shaft, has a large-area opening without closure elements and that the large-area gas leaving this opening is directed onto the entire glass sheet surface or a part thereof without being distributed more finely by means of nozzles. It is also conceivable that individual nozzles are connected to the gas supply line by means of individual ducts.

The preferred embodiments described above can be combined with one another as desired, and the device can be designed by the skilled person according to the requirements in the application. Preferred arrangements in the context of the gas supply pipe and in the case of the use of two ventilators 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-drying unit

Ventilator 1-evaporative cooler-ventilator 2-drying unit

-ventilator 1-ventilator 2-evaporative cooler-drying unit.

The gas supply tube thus configured can in turn be combined with any desired blow box as well as with tools for moving the vitreous glass sheets, for example horizontally arranged blow boxes for horizontal glass sheets or vertically arranged blow boxes for suspended glass sheets, static or mobile blow boxes, blow boxes for continuous systems or for prestressing statically arranged vitreous glass sheets, blow boxes with curved or flat closure elements, transport tools with or without transport racks, etc.

The invention also includes a combination apparatus for thermally pre-stressing a vitreous glass sheet comprising the apparatus of the invention and a vitreous glass sheet disposed between two blow boxes.

The invention also includes a method of pre-stressing a vitreous glass sheet. The heated vitreous glass pane is arranged between a first blow box and a second blow box, in particular is moved between the first blow box and the second blow box, which blow boxes are arranged opposite one another and to which in each case one gas supply line is connected. Each gas supply pipe is equipped with a heat exchanger, in particular an evaporative cooler. If the glass sheet is arranged in the gap, it is subjected to a gas flow by means of two blow boxes in order to cool the glass sheet and thus to prestress it. The gas flow is guided through a heat exchanger, in particular an evaporative cooler, and is thus actively cooled.

The advantageous embodiments described above with reference to the device according to the invention are correspondingly suitable for the method.

The gas used to cool the vitreous glass sheet is preferably air. The glass sheet surface is typically subjected to a gas stream for a period of time from 1 s to 10 s. Especially when pre-stressing vehicle glass sheets, periods of 3 or 4 seconds are common. Since the prestressing efficiency is improved by the method of the invention, the time can be reduced. In a particularly advantageous embodiment, the time period is therefore less than 3 s, in particular 1 s to 2 s.

The gas stream is cooled by an evaporative cooler when it strikes the vitreous glass sheet and preferably has a temperature of at most 70 ℃, particularly preferably at most 50 ℃, for example from 30 ℃ to 50 ℃. A particularly good prestressing efficiency is thus obtained.

Evaporative coolers also increase the humidity of the gas stream. When the gas is directed onto the vitreous glass sheet, its relative humidity is preferably at least 50%, particularly preferably at least 70%, very particularly preferably 80% to 90%. A particularly good prestressing efficiency is thus obtained.

The glass pane to be prestressed consists in a preferred embodiment of soda-lime glass, as is customary for vehicle panes. However, the vitreous glass plate may also contain or consist of other glass types, such as borosilicate glass or quartz glass. The thickness of the vitreous plate is generally 1mm20 mm depending on the application. In the automotive field, the glass sheets are generally from 1mm to 5mm, in particular from 2mm to 4mm, in thickness.

The invention exhibits its advantages in a particular manner, in particular when relatively thin vitreous glass sheets are prestressed, since they require a higher cooling rate than thicker vitreous glass sheets. In a particularly advantageous embodiment, the thickness of the vitreous glass plate is up to 3.5mm, preferably from 1mm to 3mm.

In an advantageous embodiment, the method according to the invention directly follows a bending process in which a flat glass pane in the initial state is bent. During this bending process, the vitreous glass sheet is heated up to the softening temperature. The prestressing process follows the bending process and the vitreous glass sheet is then cooled significantly. For this purpose, the vitreous glass sheet is transferred from the bending tool to the prestressing mold after the bending process or in the last step of the bending process. Thus, for prestressing, there is no need to deliberately heat the vitreous glass sheet again.

Glass manufacturers currently have a tendency to further reduce the temperature for glass bending all the time, since better optical quality and surface conditions of the vitreous glass sheets can be achieved thereby. In such bending methods with relatively low temperatures, the prestressing method according to the invention can be used particularly advantageously, since the increased prestressing efficiency leads to sufficient stress in the vitreous glass sheet despite the lower temperatures. In prestressing, the temperature of the vitreous glass sheet is between a so-called transition point (transition point), at which the viscosity of the vitreous glass sheet is plastically deformed, and a so-called softening point (softening point), at which the vitreous glass is deformed under its own weight. The present invention enables the distance from the transition point to be reduced. A common bending temperature for bent vehicle glass sheets made of soda-lime glass is 650 ℃. In a particularly advantageous embodiment, the temperature of such a vitreous glass sheet immediately before it is subjected to a gas stream and cooled is at most 640 ℃, preferably less than 640 ℃.

The invention also includes the use of an evaporative cooler for actively cooling a gas stream used to thermally pre-stress a vitreous glass sheet.

Hereinafter, the present invention will be explained in more detail with reference to the drawings and examples. The figures are schematic and not true to scale. The drawings are not intended to limit the invention in any way.

In which is shown:

FIG. 1 is a schematic view of an embodiment of the apparatus of the invention,

figure 2 is a schematic view of another embodiment of the device of the invention,

figure 3 is a schematic view of another embodiment of the device of the invention,

figure 4 is a cross-section of an evaporative cooler,

FIG. 5A section of an indirect heat exchanger, and

FIG. 6 is a flow chart of one embodiment of the method of the present invention.

Fig. 1 schematically shows an embodiment of the apparatus according to the invention for thermally prestressing a vitreous glass sheet. The arrangement comprises a first blow box 1.1 and a second blow box 1.2 arranged opposite to each other. The nozzles of the blow boxes 1.1, 1.2 through which the gas flow (air flow) required for prestressing leaves are directed to the gap between the blow boxes 1.1, 1.2. A gas supply line 2.1 is connected to the first gas box 1.1, through which a gas flow is supplied. The gas supply pipe comprises an inlet pipe and a first ventilator 3.1 and a second ventilator 4.1, which are connected in series in this order in the flow direction. The series arrangement of the ventilators 3.1, 4.1 enables a strong gas flow in the direction of the blow box 1.1. An evaporative cooler 5.1 is also arranged as a heat exchanger downstream of the fans 3.1, 4.1 in the flow direction. Likewise, a gas supply line 2.2 is connected to the second blow box 1.2, which gas supply line, in addition to the supply line, comprises a first ventilator 3.2, a second ventilator 4.2 and an evaporative cooler 5.2, which are connected in series in this order in the flow direction. By means of one shut-off valve 7.1, 7.2 each, both gas supply lines 2.1, 2.2 can be completely or partially shut off in order to stop the gas flow or to adjust its intensity.

By means of the evaporative coolers 5.1, 5.2, the air drawn in by the fans 3.1, 4.1, 3.2, 4.2 is cooled on the one hand and moistened on the other hand. Both of which improve the prestressing efficiency of the device compared to conventional prestressing devices without cooling. This is a great advantage of the present invention.

The device also comprises means for moving the glass sheets G to be pre-stressed, comprising a transport system 8, for example made as a roller system, and a transport carriage 9 moving with it. The transport carriages 9 are equipped with a pre-stressed frame on which the annular side edges of the vitreous glass sheets G are placed. By means of the transport system, the vitreous glass sheets G are moved into the gap between the blow boxes 1.1, 1.2. The blow boxes 1.1, 1.2 are then brought close to the vitreous glass sheet G to effectively apply a gas flow thereto. After prestressing, the blow boxes 1.1, 1.2 are removed again from the vitreous glass sheets G and the vitreous glass sheets G are ejected from the gap. The prestressing device is then ready for the next prestressing cycle.

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

Figure 2 schematically shows another embodiment of the device of the present invention. In contrast to the embodiment of fig. 1, the evaporative cooler 5.1, 5.2 is arranged in front of the fan 3.1, 4.1 or 3.2, 4.2 in the direction of flow, rather than behind it. Furthermore, the gas supply lines 2.1, 2.2 are each equipped with a drying unit 30.1, 30.2, which are arranged downstream of the ventilator 3.1, 4.1 or 3.2, 4.2 in the flow direction. The drying units 30.1, 30.2 are designed, for example, as droplet collectors. If the gas stream has an undesirably high humidity (caused for example by the evaporative coolers 5.1, 5.2 or by moist ambient air), it causes the drying units 30.1, 30.2 to reduce the humidity and to adjust to the desired value.

Fig. 3 schematically shows another embodiment of the device according to the invention. In contrast to the embodiment of fig. 1, each evaporative cooler 5.1, 5.2 is arranged between the ventilators 3.1, 4.1 or 3.2, 4.2 of its gas supply pipes 2.1 or 2.2.

It should be noted that the above-described embodiments are merely exemplary embodiments of the present invention and may be arbitrarily combined with each other and varied. For example, the drying units 30.1, 30.2 can also be used in the configurations of fig. 1 and 3. The drying units 30.1, 30.2 also do not have to be arranged in the flow direction behind the fans 3.1, 4.1 or 3.2, 4.2, but in principle also in front of or between them. Instead of on the transport carriages 9, the glass panes G can also be transported and prestressed directly on, for example, rollers of the transport system 8 or vertically suspended. Instead of statically prestressing between the blow boxes 1.1, 1.2, wherein the blow boxes are brought close to the vitreous glass sheet G, it is also possible to prestress the vitreous glass sheet G between the static blow boxes 1.1, 1.2 in the case of a continuous system. The embodiment of the device can be freely selected by the person skilled in the art according to the requirements of the application, wherein in particular the shape of the glass plate to be prestressed, the degree of prestressing, the properties of the ambient air with respect to humidity and temperature and the required processing speed should be taken into account.

Fig. 4 shows schematically a cross section of an evaporative cooler 5 as part of the gas supply tube 2. It comprises a fibrous, porous carrier material 10, for example a corrugated paper layer. Above the carrier material 10, a droplet separator 11 is arranged, which trickles the carrier material with a cooling liquid, for example water. After passing through the carrier material 10, the excess coolant is absorbed by the droplet collector 12 and is conducted back to the droplet separator via the coolant line 13 by means of the pump 14. Since the coolant is also lost during cooling, the coolant line 13 also contains a supply line, not shown, for further coolant.

The gas stream generated by the ventilator flows through the carrier material 10. Here, this results in adiabatic cooling of the gas stream. The vaporized cooling liquid is absorbed by the gas stream, thereby increasing its humidity. The cooling effect is due to the evaporative refrigeration associated therewith.

In contrast, fig. 5 schematically shows a cross section of the indirect heat exchanger 6 as part of the gas supply pipe 2. The indirect heat exchanger 6 contains a coolant line 20, which is designed, for example, as a tube bent into a U shape several times and through which a coolant, for example water, flows during operation in the region of the cooling circuit. The tubes are arranged in a flow space 21 through which a gas flow flows, wherein the gas flow is in contact with the coolant pipes 20 and is thus cooled. Since the coolant is heated here, the indirect heat exchanger is preferably equipped with a subcooler which, in the region not shown of the coolant circuit, cools the coolant again outside the flow space 21.

Fig. 6 shows, by means of a flow chart, an embodiment of the method according to the invention for thermally prestressing a vitreous glass sheet.

List of reference numerals:

(1.1) first/Upper blowcase

(1.2) second/lower blowcase

(2) Gas supply pipe

(2.1) gas supply pipe of first blow tank 1.1

(2.2) gas supply pipe of second blow box 1.2

(3.1) first ventilator of first blow box 1.1

(3.2) first ventilator of first blow box 1.2

(4.1) second ventilator of first blow box 1.1

(4.2) second ventilator of first blow box 1.2

(5) Evaporative cooler

(5.1) evaporative cooler for first blow box 1.1

(5.2) evaporative cooler of first blow box 1.2

(6) Indirect heat exchanger

(7.1) shut-off valve of gas supply pipe of first blow box 1.1

(7.2) shut-off valve of gas supply pipe of first blow box 1.2

(8) Transport system for glass sheets

(9) Transport frame for glass plates

(10) Porous media/support material for evaporative cooler 5

(11) Droplet separator for evaporative cooler 5

(12) Drip collector for evaporative cooler 5

(13) Refrigerant line of an evaporative cooler 5

(14) Coolant pump for evaporative cooler 5

(20) Coolant line of indirect heat exchanger 6

(21) Flow space of indirect heat exchanger 6

(30.1) drying Unit of gas supply pipe 2.1 of first blowing tank 1.1

(30.2) drying Unit of the gas supply pipe 2.2 of the first blow Box 1.2

(G) A vitreous glass plate.

Claims

1. Apparatus for thermally pre-stressing a glass sheet comprising

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

-one gas supply pipe (2.1, 2.2) each connected to the first blow box (1.1) and the second blow box (1.2), through which the gas flow is conducted to the blow boxes (1.1, 1.2),

wherein the gas supply pipes (2.1, 2.2) are equipped with an evaporative cooler (5),

wherein the evaporative cooler (5) comprises a fibrous or porous carrier material (10) which is impregnated with a cooling liquid and is flowed through by a gas flow, thereby achieving adiabatic cooling of the gas flow, wherein a droplet separator (11) is arranged above the carrier material (10), which droplet separator (11) is configured to trickle the carrier material (10) with cooling liquid, and a droplet collector (12) is arranged below the carrier material (10), which droplet collector (12) is configured to collect the cooling liquid, wherein the cooling liquid trickles vertically through the carrier material (10), and the gas flows horizontally through the carrier material.

2. Apparatus according to claim 1, wherein each gas supply pipe (2.1, 2.2) is provided with at least one ventilator (3.1, 3.2) to provide a flow of gas to the blow boxes (1.1, 1.2).

3. The device according to claim 2, wherein in each case one evaporative cooler (5.1, 5.2) is arranged downstream of the at least one fan (3.1, 3.2) in the flow direction.

4. The device according to claim 1 or 2, wherein each gas supply tube (2.1, 2.2) is equipped with at least one first ventilator (3.1, 3.2) and a second ventilator (4.1, 4.2), and wherein one evaporative cooler (5.1, 5.2) each is arranged behind the two ventilators (3.1, 4.1, 3.2, 4.2) in the flow direction.

5. The device according to claim 1 or 2, comprising a drying unit (30.1, 30.2) adapted to reduce the humidity of the gas stream.

6. Apparatus according to claim 1 or 2, equipped with means for moving the glass sheet (G) into the gap between the first blow box (1.1) and the second blow box (1.2), which means comprise a transport carriage (9) with a pre-stressed frame for placing the glass sheet (G), which transport carriage is moved by a rail system, a roller system or a conveyor system.

7. Method for thermally pre-stressing a glass sheet in an apparatus according to claim 1, wherein

(i) Arranging the heated glass sheets (G) between a first blow box (1.1) and a second blow box (1.2), which blow boxes are arranged opposite to each other and to which one gas supply pipe (2.1, 2.2) each is connected, which gas supply pipes are equipped with an evaporative cooler (5);

(ii) The glass sheet (G) is cooled by applying a gas flow to the glass sheet (G) by means of two blow boxes (1.1, 1.2), wherein the gas flow is actively cooled by means of an evaporative cooler (5).

8. A method according to claim 7, wherein the gas stream impinging on the glass sheet (G) has a temperature of at most 70 ℃.

9. A method according to claim 7 or 8, wherein the gas stream impinging on the glass sheet (G) has a relative humidity of at least 50%.

10. The method according to claim 7 or 8, wherein the glass sheet (G) has a temperature of at most 640 ℃ before cooling with the gas stream.

11. A method according to claim 7 or 8, wherein the gas stream is an air stream.

12. The method according to claim 7 or 8, wherein the glass sheet (G) is subjected to the gas stream in step (ii) for a period of time from 1 s to 10 s.

13. The method according to claim 7 or 8, wherein the glass sheet (G) has a thickness of at most 3.5 mm.