CN112811803A

CN112811803A - Blow box for thermally prestressing glass sheets

Info

Publication number: CN112811803A
Application number: CN202010625236.XA
Authority: CN
Inventors: S·萨拉梅; A·泽施纳
Original assignee: Saint Gobain Glass France SAS
Current assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Priority date: 2020-04-29
Filing date: 2020-07-01
Publication date: 2021-05-18
Also published as: DE202021004035U1; CN113891863A; WO2021219291A1

Abstract

The invention relates to a blow box (1) for thermally prestressing glass sheets, comprising a cavity (2) with an opening, which is surrounded by a fixing device (3) for connecting the cavity (2) to a gas feed line (12); a plurality of channels (4) connected to the cavity (2), each of which is closed by a nozzle bar (5) opposite the cavity (2); one connecting bridge each between adjacent channels (4), said connecting bridge having connecting faces (6) facing the cavity (2), wherein at least some of the connecting faces (6) are convex in configuration.

Description

Blow box for thermally prestressing glass sheets

Technical Field

The invention relates to a blow box for thermally prestressing glass sheets and to a device comprising the blow box, and to a prestressing method implemented by means of the device.

Background

The thermal hardening of glass sheets has long been known. Thermal hardening is also commonly referred to as thermally pre-stressing or tempering. Reference is made only by way of example to patent document GB 505188A, DE 710690A, DE 808880B, DE 1056333a from the 1930 s to the 1950 s. Here, the heated glass sheet is loaded with an air flow, which causes the glass sheet to cool rapidly (quench). Thereby forming a characteristic stress profile in the glass sheet, wherein compressive stresses dominate over the surface of the glass sheet and tensile stresses dominate in the core of the glass sheet. This has an effect on the mechanical properties of the glass sheet in two ways. Firstly, the fracture stability of the panel is improved and the panel can withstand higher loads than an unhardened panel. Secondly, the glass breakage after reaching the central compressive stress zone (for example damage due to sharp stones or intentional destruction with a sharp emergency hammer) occurs not in the shape of a large fragment with sharp edges, but in the shape of a small, blunt fragment, thereby significantly reducing the risk of injury.

Due to the above-described properties, glass panes that are thermally prestressed are used in the vehicle sector as so-called tempered glass, in particular as rear window panes and side window panes. In the case of passenger cars in particular, the glass pane is usually curved. Here, bending and prestressing are carried out in combination: the glass sheet is softened by heating into the desired curved shape and is subsequently subjected to a cooling air flow, wherein a prestress arises. Here, so-called blow boxes (quenching boxes, quenching heads) are used, to which an air flow is delivered by means of a fan and which distribute the air flow as evenly as possible over the glass sheet surface.

Prestressing devices such as those used for prestressing vehicle glass panels are equipped with blow boxes in which the air flow is distributed into different channels, which are each closed with a nozzle strip. The nozzle bar has a single row of nozzles that are directed at the glass sheet and which redistribute the air flow of each channel and load the glass sheet with an air flow that is now distributed over a large area. The bent glass sheet is usually moved between an upper blow box and a lower blow box, which blow boxes are then brought closer to each other and brought closer to the surface of the glass sheet to apply a pre-stress. The entire plant with two blow boxes is usually referred to as prestressing station. Such blow boxes with nozzle strips are disclosed, for example, in DE 3612720C2, DE 3924402C1, DE 3612720a1 and US9611166B2 a 1.

There is always a need to improve the efficiency of blow boxes. Higher efficiencies can be achieved, for example, to achieve higher glass sheet cooling rates with the same air flow strength. So that the current trend in the automotive industry, in which thinner and thinner glass sheets are used or in which glass bending at lower and lower temperatures is required for improving optical quality, can be taken into account. Both result in the glass sheet having to be more strongly chilled in order to create the necessary temperature differential between the surface of the glass sheet and the core of the glass sheet. On the other hand, higher efficiency enables the same prestressing effect to be produced with a weaker air flow. So that energy can be saved when prestressing is applied, which is advantageous not only in terms of cost but also in terms of environmental and climate protection.

In order to increase the prestressing efficiency, it is particularly necessary to reduce the coefficient of flow resistance (so-called c) of the blow box_wValue). If the blow box creates less resistance to the air flow, less pressure loss occurs and the air flow that ultimately acts on the glass sheet has a higher pressure. According to the well-known Bernoulli's law, pressure is proportional to the square of the flow rate. Since the highest flow velocity occurs in the nozzle of the blow box, where the air flow is compressed to the greatest extent, it is obvious that the configuration of the nozzle has a significant influence on the pressure that can be achieved. Therefore, efforts to date to improve the efficiency of prestressing have focused particularly on the optimization of the nozzle geometry. Thus, for example, DE 3612720a1 and WO 018015108a1 disclose a nozzle having a tapering section at its gas entry opening in order to optimize the flow in the nozzle.

Disclosure of Invention

The invention is based on the object of providing a blow box of the type mentioned at the outset which has improved efficiency and in particular generates a low flow resistance to the air flow.

According to the invention, this object is solved by a blow box according to independent claim 1. Preferred embodiments follow from the dependent claims.

A blow box for thermally prestressing a glass sheet comprising at least:

a cavity having an opening surrounded by a fixing means for connecting the cavity to a gas delivery line,

a plurality of channels connected to the cavity, each of which is closed opposite the cavity by a nozzle strip,

a connecting bridge between adjacent channels, which connecting bridge has a connecting face facing the cavity.

According to the invention, at least some of the joint faces are convex in configuration. The solution proposed according to the invention therefore does not relate to the geometry of the nozzle, as in the previous solutions, but to the geometry of the cavity at the inlet of the channel. In conventional blow boxes, the connection surface is designed as a flat surface, on which the air flow acts essentially perpendicularly. The inventors have determined that the convex configuration of the joint face results in a significantly improved efficiency. This is a great advantage of the present invention. This effect is surprising for the person skilled in the art, since, up to now, the person skilled in the art has, based on bernoulli's law, assumed that the pressure of the air flow can be increased substantially only by optimizing the nozzle, since the absolute highest flow velocities occur here. According to the inventors' speculation, air vortices may be generated at the channel inlet due to the conventional flat connection face, which to some extent cause a local negative pressure that opposes the airflow in the channel and thereby reduces the effective outlet pressure. This effect can be avoided by the male connecting surfaces according to the invention.

The prestressing station is generally a device with two gas supply lines lying opposite one another, which can be equipped with replaceable blow boxes. The blow box is used to load the surface of the glass sheet for thermally prestressing. The blow box serves in particular to distribute the air flow from the gas feed line as evenly as possible over the surface of the glass sheet.

A blow box is a device having an internal cavity with a large area opening. The cavity is open in one direction, in particular all over. The opening of the cavity is surrounded by fixing means which are adapted and arranged for connecting the blow box to the gas delivery line. The fastening device is usually designed in the form of a flange, i.e. as a flat section arranged generally in one plane, in particular as a circumferential flange. The gas supply line usually has a likewise fully open connection box, the opening of which is surrounded by a fitting fastening device. For connecting the blow box to the gas supply line, the fastening means of the gas supply line and the flange of the blow box are connected to each other. The fastening device of the gas supply line may also be designed as a flange and may be connected to the flange of the blow box, for example, by means of screws, clips or reversible locking devices. The fastening device of the gas supply line can also be designed as a box-shaped insertion device into which the flange of the blow box is inserted. However, other securing means are also contemplated. If the blow box is connected to the gas feed line, the air flow from the gas feed line can be guided or flow into the cavity through the opening. A cover device is connected to the fastening device and surrounds the cavity adjacent to the cavity opening. The cover device is usually constructed from a plate or sheet of material, for example made of steel or aluminum.

In addition to the open connecting box connected to the blow box, the gas delivery line comprises a pipe system through which an air flow is supplied to the box. The duct system is usually equipped with one or more (in particular in series) fans generating an air flow. Preferably, the duct system can be closed, for example, by means of a slider or flap, so that the air flow into the interior space can be interrupted without shutting down the fan itself.

The blow box according to the invention has a plurality of channels which are connected to the cavity generally opposite the opening for the gas feed line. In operation, airflow is distributed into the channels. There is thus a transition from the cavity into the plurality of channels within the blow box for distributing the airflow from the cavity into the channels. The channels may also be referred to as nozzle tabs, nozzle fins or nozzle ribs. The channels typically have an elongated, substantially rectangular cross-section, with the longer dimension substantially corresponding to the width of the cavity. The shorter dimension (width) is generally in the range from 0.5cm to 7cm, in particular in the range from 0.5cm to 1.5 cm. The spacing between adjacent channels, i.e. the width of the intermediate space between the channels, is usually also in the range from 0.5cm to 7cm, in particular in the range from 0.8cm to 1.5 cm. Typically, the channels are arranged parallel to each other. The number of channels is typically 10 to 50. The channels are typically constructed from and bounded by sheet material.

The cavity is preferably configured as a wedge or with a wedge-shaped area connected to the channel. The boundary of the cavity adjoining the channel may be described herein as two sides that form 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 connects to the cavity, is wedge-shaped, while the outlet opening opens out into a smooth surface. The discharge openings of all the channels usually constitute a common smooth surface. If a curved nozzle strip is used, such as is common for prestressing curved vehicle glass sheets, the glaze is preferably curved. By the illustrated wedge-shaped configuration of the cavity and the illustrated arrangement of the channels, the gas flow is particularly effectively distributed into the channels and a very uniform gas flow over the entire active surface is caused.

Each channel is closed at its end opposite the cavity by a nozzle strip, which is screwed to the plate or plate of the channel or inserted into a mounting rail, for example. The nozzle strip has a plurality of penetration guides, which are referred to as nozzles. The air flow of the channel is in turn distributed by the nozzles of the nozzle bar. The nozzle bar preferably has a single row of nozzle openings, which are arranged substantially along a straight line. However, nozzle strips with rows of nozzles or staggered nozzles are also known. The row of nozzle openings preferably extends over at least 80% of the length of the nozzle strip. The gas flow is thus distributed from the cavity into the channels first and from each channel back into the nozzle. A high prestressing efficiency can be achieved by such a blow box, which is why such a blow box is used in particular for prestressing vehicle glass panels.

The blow box thus distributes the gas flow from the pipe system of the gas delivery line through the channels and the nozzles over a large effective area with a small cross section. The nozzle openings are discrete gas outflow locations, but the gas outflow locations are present in large numbers and are evenly distributed so that all areas of the surface are cooled substantially simultaneously and evenly so that the glass sheet is provided with a uniform pre-stress.

The nozzles are holes or through guides extending through the entire nozzle strip. The nozzle is connected to the cavity via a channel or to the cavity such that gas can flow from the cavity through the nozzle to load the surface of the glass sheet with a gas stream. Each nozzle has an inlet opening (nozzle inlet) through which the gas flow enters the nozzle; and an opposite discharge opening (nozzle opening) through which the air stream flows out of the nozzle (and the entire blow box). The surface of the nozzle bar having the inlet opening faces the channel and the cavity of the blow box, whereas the surface having the nozzle opening faces away from the channel and the cavity of the blow box and, in the intended use, faces the glass sheet. The surface of the glass sheet is subjected to a defined air flow through the nozzle opening. The nozzles may advantageously have a section which adjoins the inlet opening and tapers in the direction of the outlet opening, in order to guide the air efficiently and fluidically advantageously into the corresponding nozzle, as is shown, for example, in DE 3612720a 1. Thereby further improving the flow efficiency of the blow box according to the invention.

In order to prestress a bent glass sheet, as occurs in particular in the automotive field, nozzle strips are used which match the glass sheet in terms of their contour in order to ensure a substantially identical small spacing between the glass sheet and the nozzles over the entire glass sheet surface. The nozzle strips, the outflow openings of the channels connected to the nozzle strips are curved here. Two blow boxes with complementary curved nozzle strips are used in the prestressing station. The surface of the outflow opening of one blow box is convexly curved and directed towards the concave surface of the glass sheet, and the surface of the outflow opening of the other blow box is concavely curved and directed towards the convex surface of the glass sheet.

The nozzle strips are preferably made of aluminum or steel. These materials are easy to process and give rise to advantageous stability over long-term use. However, the nozzle strip may also be made of a plastic which is preferably stable up to a temperature of about 250 ℃. The plastic must have the temperature stability required for the purpose of use, the gases flowing away having a temperature of more than 200 ℃. Suitable plastics are, for example, ethylene-propylene copolymers (EPM), polyimides or Polytetrafluoroethylene (PTFE).

The nozzle opening preferably has a diameter of 4mm to 15mm, particularly preferably 5mm to 10mm, very particularly preferably 6mm to 8mm, for example 6mm or 8 mm. The distance between adjacent nozzle openings is preferably 10mm to 50mm, particularly preferably 20mm to 40mm, for example 30 mm. In order to achieve good prestressing results. Here, the distance refers to a distance between respective center points of the nozzle openings.

The length and width of the nozzle strips depend on the configuration of the blow box. Typical values for the length of the nozzle strip (measured along the extension of the nozzle row) are 70cm to 150cm, and for the width/depth (measured perpendicular to the length in the plane of the nozzle opening) 8mm to 15mm, preferably 10mm to 12 mm.

Connecting bridges are arranged between the channels adjacent to each other. Thus, the channels are separated from each other by the connecting bridges. The connecting bridges can be constructed as plates or also as solid or hollow bodies. The surface of the connecting bridge facing the cavity is referred to as the connecting surface in the sense of the present invention. The connecting surface extends from the inlet opening of one channel to the inlet opening of the adjacent channel. Thus, the area between two adjacent channels is completely bridged by the connecting surface.

According to the invention, the connection surface is convex. The connecting surface is therefore not configured as a flat surface extending substantially perpendicularly to the direction of extension of the channel, as is the case in conventional blow boxes. Instead, the connection surface has a convex shape projecting into the cavity. This means that the connecting surface has a central section which extends further into the cavity than the edge sections adjacent to the channel.

It is particularly advantageous if all the connecting surfaces of the blow box have a convex shape. Then, the effect of improving efficiency is maximally achieved, and uniform pressure distribution is achieved among the channels. In principle, however, it is also conceivable for only a subset of these connection surfaces to have a convex shape, while the remaining connection surfaces are configured, for example, in a conventional manner as flat surfaces. Thereby also improving the overall efficiency. Thus, although it may be that the flow pressure in different channels is different, this may in individual cases be desirable at all. It is therefore sufficient according to the invention that at least some of the connection faces, i.e. at least a subgroup, subset or subset of the entire connection face, are configured convex. Preferably, a majority (i.e. more than 50% of the connection surfaces), particularly preferably at least 80%, very particularly preferably all of the connection surfaces are configured convex.

The convex shape of the connecting surface is distinguished in particular by the fact that it has a perpendicular slot vertex (Scheitellinie), which is understood to be the line that extends to the greatest extent into the cavity. The perpendicular to the slot top therefore has the greatest (perpendicular) distance with respect to the plane of the access opening of the channel. In cross section, the slot apex line emerges as an apex which has the greatest (perpendicular) distance from a straight line through the edge points of the connecting surface at the entry openings of the adjacent channels. The perpendicular to the slot top is preferably a straight line (in a geometrical sense a straight line segment) extending parallel to the adjacent side edges of the channel.

The perpendicular slot top line projects into the cavity to the greatest extent and the connecting surface descends from the perpendicular slot top line in the direction of the adjacent channel. The connecting surface thus has two side edges which are arranged on both sides of the perpendicular to the slot top and which, proceeding from the perpendicular to the slot top, descend in the direction of the adjacent channel. This means that the (perpendicular) distance of the side edges with respect to the plane of the access opening of the channel becomes smaller with increasing distance from the perpendicular to the slot top. Viewed in cross section, the (perpendicular) distance of the side edge from a straight line passing through the edge point of the connecting surface at the entry opening of the adjacent channel decreases with increasing distance from the apex. Thus, the descriptive term "descending" refers to the arrangement when the slot top vertical line is pointing upward.

At each point of the descending side edges an angle can be determined which is enclosed by the direction of flow of the gas in the cavity and the tangent plane (viewed in cross section: tangent) of the connecting surface at that point. In this case, a tangential section extending from this point in a direction pointing away from the perpendicular to the slot top can be considered for determining the angle. The angle is greater than 90 ° at each point of the side edges. Since the inlet opening of the cavity is usually opposite the channel, the flow direction in the cavity corresponds to the flow direction in the channel. The angle between the direction of the gas flow in the cavity and the tangent of the connecting surface is 90 deg. only on the perpendicular to the slot tip.

In a preferred embodiment, the convex connecting surface is configured symmetrically, so that the perpendicular slot vertex extends in the center of the connecting surface and the distance of the perpendicular slot vertex from two adjacent channels is the same. In other words, the convex connecting surface has a symmetrical cross-section.

In a preferred embodiment, the convex connecting surface is convexly curved. In order to achieve particularly good results. However, other convex shapes are also contemplated: the connecting surface may have, for example, a triangular cross section or another cross section composed of flat subsections, as long as the shape is convex overall and has in particular a perpendicular to the seam roof.

The symmetrical, convexly curved connecting surface can have, for example, a circular-arc cross section, an elliptical-arc cross section, a parabolic cross section or a differently modified oval section cross section. The central angle of the circular or elliptical arc is preferably less than or equal to 180 °, preferably 90 ° to 180 °. If the central angle of the circular or elliptical arc is 180 °, a semicircular or semi-elliptical cross section results, which is particularly preferred since edges at the passage entry opening, which could form gas vortices, are completely avoided.

If reference is made to a cross section of a connection surface, this always means a cross section in a section plane which is arranged perpendicular to the channel and contains the gas flow direction in the channel.

In a particularly advantageous embodiment, all connection surfaces have the same shape. This distributes the gas flow particularly uniformly over the channels. However, this need not be the case in principle, and connecting surfaces of different configurations may also be present. The preferred configurations described above (convexly curved connection surfaces, symmetrical connection surfaces, shaped cross section) therefore each relate to some of the connection surfaces, preferably to a majority of the connection surfaces, particularly preferably to all connection surfaces.

Preferably, the male connecting surface is preferably designed in such a way that it does not mushroom-like extend over the access openings of the channel and partially covers these access openings.

In one embodiment of the invention, the cavity has a larger dimension than the entire channel and its intermediate space. The channel is connected to the side of the cavity. All the passage access openings and the connecting bridges located between them define a connecting surface. Alternatively, the cavity can have a section with a larger dimension than the entire channel and its intermediate space, on which a wedge-shaped section is joined, which in turn opens into the channel. The side of the wedge-shaped region facing the cuboid region then defines the connection face. The cavity or the cavity region then has a greater length and/or width than the connecting surface, so that at least one edge region of the blow box covering device is present, which is not arranged between the channels and encloses an angle of more than 0 ° with the direction of the gas flow, i.e. opposite the gas flow. The side of the cavity or the cavity region is larger than the connecting surface, so that an edge region of the cavity or the cavity region is closed by a cover device which has a surface facing the cavity, which is directly adjacent to the connecting surface. The edge region surrounds the connection surface, i.e. at least in sections around the entire channel: the edge region may surround the entire channel and its intermediate space in a circumferential manner or may adjoin only a part of the entire channel, for example along two opposite side edges. In other words, the edge regions of all channels are arranged adjacently, so that the connecting surface is directly connected to the edge regions.

The edge region has a surface facing the cavity. In such conventional blow boxes, the surface of the edge region is configured as a flat surface, which is arranged flat parallel to the flat connection surface. Such edge regions may also prevent gas from efficiently flowing into the channel, possibly due to the formation of vortices. In an advantageous development of the invention, the edge region is conversely configured to decrease from the side edge of the blow box in the direction of the passage, so that the depth of the cavity in the direction of the gas flow is from the outside to the inside, i.e. from the side edge of the blow box until the passage becomes larger. The angle enclosed by the gas flow direction and the tangent plane on the edge area is greater than 0 ° and less than 90 ° at each point of the edge area. The surface can be configured, for example, as a flat slope or as a curved descending surface, preferably as a concavely curved descending surface.

The invention furthermore comprises an apparatus for thermally prestressing a glass sheet, which apparatus comprises a first blow box according to the invention, which is connected by its fixing means to a first gas feed line, and which apparatus comprises a second blow box according to the invention, which is connected by its fixing means to a second gas feed line. The first blow box and the second blow box are arranged opposite each other such that their respective nozzle bars are directed towards each other. The blow boxes are spaced apart from each other so that a glass sheet can be arranged between them. In general, the nozzles of the first blow boxes (upper blow boxes) are directed substantially downwards, while the nozzles of the second blow boxes (lower blow boxes) are directed substantially upwards. The glass sheets can then advantageously be moved between the blow boxes lying horizontally. The nozzles are oriented substantially perpendicular to the glass surface.

Furthermore, the apparatus comprises means for moving the glass sheet, which means are adapted to move the glass sheet into and out of the intermediate space between the two blow boxes. For this purpose, for example, rail systems, roller systems or conveyor belt systems can be used. In a preferred configuration, the means for moving the glass sheet comprises: a frame shape on which the glass sheet is supported during conveyance; and a transport system for moving the frame shape, such as a rail system, a roller system or a conveyor belt system. The frame shape has a surrounding frame-shaped resting surface on which the lateral edges of the glass pane rest without the major part of the glass pane surface coming into direct contact with the resting surface.

The above-described embodiments of the blow box according to the invention are applicable in the same way to the device according to the invention.

The relative arrangement of the nozzle openings of the blow boxes preferably matches the shape of the glass sheet to be prestressed. The nozzle openings of the blow boxes herein open out a convex curvature, while the nozzle openings of the opposite blow boxes open out a concave curvature. The magnitude of the curvature also depends on the glass sheet shape. The convex blow boxes face the concave surface of the glass sheet and the concave blow boxes face the convex surface when the pre-stress is applied. Thus, the nozzle opening can be positioned closer to the glass surface, which improves the prestressing efficiency. Since the glass sheets are usually conveyed to the prestressing station with an upwardly directed concave surface, the upper blow boxes are preferably convex in configuration, while the lower blow boxes are concave in configuration.

Furthermore, the apparatus preferably further comprises means for varying the distance between the first blow box and the second blow box. Thereby, the blow boxes may be moved towards and away from each other. The two blow boxes are preferably moved simultaneously towards each other or away from each other. The prestressing efficiency can be increased by the movable blow box. After the glass sheets have been moved between the blow boxes in a state in which said blow boxes are further spaced apart, the distance of the blow boxes with respect to each other and thus the glass sheets is reduced, whereby a stronger air flow can be generated on the glass surface. Subsequently, the distance is increased again and the glass sheet is moved out of the intermediate space between the blow boxes.

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

The invention also comprises a method for thermally prestressing a glass sheet, wherein,

(a) the heated glass pane with the two main faces and the encircling side edges is arranged in the manner of a sheet between a first blow box and a second blow box of the apparatus according to the invention, so that each main face faces one blow box,

(b) the two main faces of the glass sheet are subjected to an air flow by means of two blow boxes, so that the glass sheet is cooled, wherein a prestress, i.e. a stress profile, is formed in the glass sheet.

The above-described embodiments of the blow box according to the invention and the device according to the invention are applicable in the same way to the method according to the invention.

The glass sheets are preferably conveyed on rollers, rails or belts between blow boxes. In an advantageous embodiment, the glass pane is arranged here on a shape with a frame-like resting surface (frame shape).

If the glass sheets are positioned between the glass sheets, the blow box is preferably located close to the glass sheets. After the prestressing, the glass sheet is preferably removed again from the glass sheet before the glass sheet is moved out of the intermediate space between the blow boxes.

The surface of the glass plate is loaded with an air flow in the following way: the air flow is introduced into the interior cavity of each blow box, distributed there and directed through the nozzle openings evenly distributed over the surface of the glass sheet.

The gas used to cool the glass sheet is preferably air. The air may be actively cooled within the prestressing device for improving the prestressing efficiency. However, air is generally used which is not specifically tempered by active measures.

The glass sheet surface (main surface) is preferably subjected to the gas flow for a time period of 1 second to 10 seconds, particularly preferably 3 seconds to 5 seconds.

In a preferred embodiment, the glass pane to be prestressed consists of soda lime glass, as is customary for window panes. However, the glass plate may also comprise or consist of other glass types such as borosilicate glass or quartz glass. The thickness of the glass plate is generally 1mm to 10mm, preferably 2mm to 5 mm.

The glass pane is preferably curved in three dimensions, as is usual for vehicle glass panes. Three-dimensional bending is understood in the art as bending in two (mutually orthogonal) spatial directions, namely in the height dimension of the glass sheet and in the width dimension of the glass sheet. Curved, prestressed glass panes are particularly common in the vehicle sector. The glass pane to be prestressed according to the invention is therefore preferably provided as a window pane of a vehicle, particularly preferably of a motor vehicle and in particular of a passenger or load vehicle. The glass plate is provided in particular as a so-called tempered safety glass (ESG).

In an advantageous embodiment, the method according to the invention is directly connected to a bending process in which a flat glass sheet is bent in an initial state. During the bending process, the glass sheet is heated above a so-called transition point (transition point) which gives a temperature above which the viscosity of the glass sheet allows plastic deformation. The prestressing process is coupled to the bending process before the glass sheet is significantly cooled. Therefore, it is not necessary to heat the glass sheet itself again in order to apply the prestressing force. When the prestress is applied, the initial temperature of the glass sheet lies between the transition point and the so-called softening point (softening point), from which the glass deforms under its own weight. This is necessary in order to be able to form the desired stress profile. Upon application of the pre-stress, the temperature of the glass sheet decreases below the transition point, wherein the transition point must be exceeded quickly in order to achieve the chilling effect.

The invention also comprises the use of a glass pane prestressed by means of the method according to the invention, preferably as a pane of a window pane in a rail vehicle or motor vehicle, in particular a rear pane, side pane or roof pane of a passenger vehicle, in a vehicle for land, air or water traffic. Glass panels may also be used in home decoration, for example as shower doors, freezer doors or refrigerator doors.

Drawings

The invention is explained in detail below on the basis of figures and examples. The figures are schematic and not to scale. The drawings are not intended to limit the invention in any way. In particular, the number of nozzles and channels of the blow box is not shown in practice, but merely serves to clarify the principle. The figures show:

figure 1 a cross-section of such a blow box perpendicular to the nozzle strips,

figure 2 a cross-section of such a blow box of figure 1 along the nozzle bar,

fig. 3a cross-section of fig. 1, in which the blow box is connected to a gas delivery line,

figure 4 is a perspective view of a nozzle bar,

figure 5 a cross-section of a nozzle bar according to figure 4,

figure 6 is an enlarged view of the detail Z of figure 1 in a conventional configuration of the joint face,

figure 7 is an enlarged view of the detail Z of figure 1 in the joint face configuration according to the invention,

figure 8 is a top view of the joint face of figure 7,

figure 9 the cross-section of figure 7,

figure 10 is an enlarged view of the detail Z of figure 1 in another joint face configuration according to the invention,

figure 11 is an enlarged view of the detail Z of figure 1 in another joint face configuration according to the invention,

figure 12 is an enlarged view of the detail Z of figure 1 in another joint face configuration according to the invention,

FIG. 13 is a cross-section of FIG. 1 in a further development of the invention, and

fig. 14 is a cross-section of a device according to the invention during the prestressing process.

Detailed Description

Fig. 1 and 2 show two cross sections of such a blow box 1 for thermally prestressing glass sheets. The blow box 1 has an internal cavity 2. The cavity 2 has an upwardly directed large area opening, which is surrounded by the fixing means 3. The fastening device 3 is designed in the form of a flange, i.e. as a flat plate, which is provided with a through-guide, for example. The blow box 1 can be connected by means of the fixing device 3 to a gas feed line 3 via which a flow of air is guided through the opening into the cavity 2. The fastening means 3 transition into the side wall of the cover device surrounding the cavity 2. The fastening device 3 and the covering device can be constructed in one piece or consist of a plurality of plates or sheets.

The cavity 2 has a first region adjoining the opening, which is substantially cuboid in shape. The wedge-shaped region is joined to the cuboid region opposite the opening. Opposite the opening for the feed line, a channel 4 is connected to the cavity 2, more precisely to the wedge-shaped region of the cavity 2. The air flow directed into the cavity 2 is divided into a row of partial flows by the channels 4. The channels 4 are constructed in the form of hollow ribs which are substantially as long as the wedge-shaped region of the cavity 2 in one dimension and have a significantly smaller width, for example about 11mm, in a dimension perpendicular thereto. The channels 4 with elongated cross-section are arranged parallel to each other. The number of channels 4 shown is not representative and is only used to illustrate the principle of action. Between the channels, the cavity 2 is closed by a connecting bridge having a connecting face 6 facing the cavity 2.

Due to the wedge-shaped area the depth of the cavity 2 at the centre of the blow box 1 is greatest in the first dimension and decreases outwards in both directions. In a second dimension perpendicular to the first dimension, the depth remains constant given the position of the first dimension. The channel 4 is connected to the wedge-shaped cavity 2 along said first dimension. The channels thus have a depth profile complementary to the wedge shape of the cavity 2, wherein the depth is minimal at the centre of the channels 4 and increases outwards, so that the air outlet of each channel 4 forms a smooth, flat or curved face. Fig. 1 and 2 show two cross sections at an angle of 90 ° to each other. The cross section in fig. 1 extends perpendicularly to the channels 4, so that the individual channels 4 can be seen in cross section. The depth of the cavity 2 is constant in the sectional plane. The dashed line visible in the intermediate space between the channels represents the lower edge of the wedge-shaped area of the cavity 2. The cross-section in fig. 2 extends along the channel 4. Here the wedge-shaped depth profile of the cavity 2 can be seen, while only a single channel 4, whose depth profile can also be seen, lies in the sectional plane.

Mounted on the discharge opening of each channel 4 is a nozzle strip 5 which closes off the channel 4. The nozzle strip 5 is configured with a row of nozzles 9. The nozzles 9 are through guides through the nozzle strips 5, so that the air flow of each channel 4 is again divided into partial flows which are each guided through the nozzles 9 and then leave the blow box 1 and can be directed at the glass sheet for prestressing. The nozzle strips 5 are curved in accordance with the shape of the glass pane in the vehicle sector.

A similar blow box with wedge-shaped cavities is shown in a perspective view in US9611166B2 (fig. 2). Another similar blow box is shown in DE 3612720a1 (fig. 4) in a perspective view, however without the wedge-shaped region of the cavity.

Fig. 3 shows the blow box 1 of fig. 1 connected to a gas delivery line 12. The flange-like fastening region 3 is connected to a mating flange of the gas supply line 12. The gas feed line 12 has a tank to which a flow of air is fed via a not shown pipe system, which flow of air is indicated in the figure by means of grey arrows. The air flow is generated, for example, by two fans, not shown, connected in series. The air flow flows from the gas supply line 12 into the cavity 2 and then is dispersed first through the channel 4 and then through the nozzle 9.

Fig. 4 and 5 each show a detail of one configuration of the nozzle strip 5, which is shown here for reasons of simplicity straight instead of curved. The nozzle strips 5 consist of aluminum, which is easy to machine and has a advantageously low weight. The nozzle bars have a width of, for example, 11mm, wherein the dimension is adjusted such that the gas channel 4 of the associated blow box 1 is closed. The nozzle strip 5 is configured with a row of nozzles 9. Each nozzle 9 is a through guide (hole) between two opposite sides of the nozzle strip 5. The nozzle 9 is arranged for guiding an air flow out of the belonging blow box 1, wherein the air flow enters the nozzle 9 via a nozzle inlet 10 and exits the nozzle 9 via a nozzle opening 11. In the mounted position, the side of the nozzle bar 9 having the nozzle inlet 10 must therefore face the blow box 1, while the side having the nozzle opening 11 faces away from the blow box.

Each nozzle 9 has a strongly widening nozzle inlet 10, to which a tapering section adjoins. Thereafter, the diameter of the nozzle is kept constant, for example 6mm, up to the nozzle opening 11.

Fig. 6 shows a detail Z of fig. 1 in an enlarged view. The connecting bridge with the connecting surface 6 and the adjoining channel 4 can be seen. According to the prior art, the connection surface 6 is designed as a flat, substantially horizontal surface. The air flow acts at an angle of 90 ° to the connection surface 6.

Fig. 7 shows the same detail Z in a configuration according to the invention. The connecting surface 6 is of convex design, so that it projects into the cavity 2. The connecting surface has a perpendicular slot vertex 6-S, which can be regarded as the maximum of the cross section and which extends to the greatest extent into the cavity 2. The joint plane 6 is divided into two lateral sides 6-F1,6-F2 by the perpendicular top seam line 6-S. Starting from the perpendicular slot top line 6-S, each side edge 6-F1,6-F2 descends in the direction of the channel 4 that it faces. In the configuration shown, the connection face 6 has a semicircular cross section.

Fig. 8 shows a top view of the connection surface 6 of fig. 7. Because the connecting surface 6, which has a semicircular cross section, has a symmetrical shape, the perpendicular slot vertex 6-S extends centrally between adjacent channels 4. The side edges 6-F1,6-F2 are located between the perpendicular top seam line 6-S and each channel 4.

Fig. 9 shows the same configuration as fig. 7 and illustrates the effect of the male connecting surface 6. The air flow acts on the connection surface 6 in a vertically downward direction in accordance with the flow direction S in the cavity 2. At each point of the connecting surface 6, the flow direction S in the cavity 2 encloses an angle α with a tangent T of the connecting surface 6 at said point. Here, a tangent line segment pointing away from the point of the seam vertex perpendicular 6-S is considered. In the region of the side edges 6-F1,6-F2, the angle alpha at each point is greater than 90 deg.. Only along the seam vertex vertical line 6-S, the seam vertex vertical line 6-S is 90 degrees. In contrast, in the conventional configuration according to fig. 6, the angle α is 90 ° over the entire connecting surface 6. The configuration of the connection face 6 according to the invention results in a more effective guiding of the gas flow into the channel 4.

Fig. 10 shows a further embodiment according to the invention of a male connecting surface 6 which has a semi-elliptical cross section.

Fig. 11 shows a further embodiment according to the invention of a male connecting surface 6. The connecting surface 6 is not curved here, but has a triangular or roof-shaped cross section.

Fig. 12 shows a further embodiment according to the invention of a male connecting surface 6. In contrast to the previously described embodiment, the connection surface is formed asymmetrically. Thus, the perpendicular top seam lines 6-S do not extend centrally between the channels 4, and the side edges 6-F1,6-F2 have substantially different widths.

Fig. 13 shows a development of the blow box according to the invention of fig. 1. The channel 4 is joined to the rest of the cavity 2 by a wedge-shaped section of the cavity 2. The remaining portion has larger dimensions than the channel 4 and the wedge-shaped section, so that there is an edge region 7 of the cavity 2. This edge region 7 is closed by a cover device having a surface facing the cavity 2, which surface is arranged directly adjacent to the outer channel 4. In a conventional blow box, this surface is configured flat and is arranged in the cavity 2 at an angle of 90 ° with respect to the flow direction of the air. According to the embodiment of the invention shown, the surface instead descends from the lateral edge of the cavity 2 in the direction of the channel 4, so that the air flow is guided into the channel more efficiently and with less resistance to the air flow.

Figure 14 shows the configuration of the apparatus according to the invention for thermally prestressing a glass sheet. The apparatus comprises a first upper blow box 1.1 and a second lower blow box 1.2, which are arranged opposite each other in such a way that the nozzle openings 11 of the nozzle bars 5 are directed towards each other. Each blow box 1.1,1.2 is connected to a gas feed line 12, through which the blow box is supplied with a flow of air. The apparatus further comprises a transport system 13 by means of which the glass sheet I to be prestressed can be transported between the blow boxes 1.1, 1.2. The glass pane I is supported horizontally on a frame shape 14, which has a frame-like support surface on which the peripheral edge region of the glass pane rests. The transport system 13 is composed, for example, of a rail or roller system on which the frame profile 14 is mounted so as to be movable. The glass pane I is, for example, a glass pane made of soda-lime glass, which is provided as a rear window pane for a passenger vehicle. The glass sheet I has undergone a bending process in which it is bent at a temperature of about 650 c, for example by means of gravity and/or press bending, into the set bent shape. The conveyor system 13 is used to convey the glass sheet I, which is still in a heated state, from the bending apparatus to the prestressing apparatus. There, both main surfaces are subjected to an air flow by the blow boxes 1.1,1.2, in order to cool these two main surfaces strongly and thus to generate a characteristic profile of tensile and compressive stresses. For this purpose, the blow boxes 1.1,1.2 are located close to the glass sheet I when the glass sheet is positioned in the intermediate space. After the glass sheet I has been quenched, the blow boxes 1.1,1.2 are removed again from the glass sheet I. The movement of the blow boxes 1.1,1.2 is effected, for example, by means of powerful servomotors. The thermally prestressed glass pane I is then suitable as a so-called tempered safety glass for use as a rear window pane of a motor vehicle. After the prestressing, the glass sheet is again carried away by the transport system 13 from the intermediate space between the blow boxes 1.1,1.2, whereby the prestressing device is available for prestressing the next glass sheet. The direction of conveyance of the glass sheet I is shown by the gray arrow.

Example (c):

in order to investigate the effect of the joint face 6 according to the invention, the fan speeds required when using the blow box according to the invention and the conventional blow box were compared with each other. The joint face 6 (example) of the blow box according to the invention is configured according to fig. 7. The joining face 6 of a conventional blow box (comparative example) is configured as a flat face according to fig. 6. Each lower blow box and each upper blow box are respectively fixed on a gas conveying pipeline, and the gas conveying pipelines are respectively provided with a fan. The fan speed required to cause a similar fracture structure (especially the size of the fragments after the point action) of the pre-stressed glass sheet is then determined. The fracture structure here corresponds to the values specified in the ECE-R43 standard for vehicle glazing.

The following values were determined:

rotational speed

Example (c): 1450 revolutions per minute

Comparative example: 1810 revolutions per minute

It is evident that the required reduction in fan speed can be achieved by means of the connection face 6 according to the invention. This corresponds to an efficiency increase of about 20%. This effect is unexpected and surprising to those skilled in the art. The geometry of the nozzle 9 at which the flow velocity is maximum is considered by the person skilled in the art to have a decisive influence on the achievable pressure on the basis of bernoulli's law, according to which the pressure is proportional to the square of the flow velocity. It cannot be expected that the efficiency can be improved so significantly by changing the geometry in the cavity 2, where significantly lower flow velocities occur.

List of reference numerals

(1) Air blowing box

(1.1) first/upper blow box

(1.2) second/Down blow Box

(2) Hollow space of blow box 1, 1.1,1.2

(3) Fixing device

(4) Channel of blow box 1, 1.1,1.2

(5) Nozzle strip

(6) Connecting surface

Perpendicular line of joint top of (6-S) connecting surface

(6-F1) side edge of joint face

(6-F2) side edge of joint face

(S) flow direction in the cavity 2

(T) tangents to sides 6-F1,6-F2

(7) Edge region of the cover device of the cavity 2

(9) Nozzle with a nozzle body

(10) Inlet opening of nozzle inlet/nozzle 9

(11) Nozzle opening/discharge opening of nozzle 9

(12) Gas conveying pipeline of air blowing box 1, 1.1 and 1.2

(13) Conveyor system for glass sheets

(14) Frame shape for glass sheets

Angle between alpha flow direction 2 and tangent T (in a direction pointing away from perpendicular 6-S of slot apex)

(I) Glass plate

Z local part

Claims

1. A blow box (1) for thermally prestressing a glass sheet, the blow box comprising:

-a cavity (2) having an opening surrounded by a fixture (3) for connecting the cavity (2) to a gas delivery line (12),

-a plurality of channels (4) connected to the cavity (2), which channels are closed with nozzle strips (5) respectively opposite the cavity (2),

-one connecting bridge each between adjacent channels (4), said connecting bridge having a connecting face (6) facing the cavity (2),

characterized in that at least some of the joint faces (6) are convex in configuration.

2. A blow box (1) according to claim 1, wherein each convex connection face (6) has a perpendicular slot top (6-S) and two side edges (6-F1,6-F2) which descend from the perpendicular slot top (6-S) in the direction of the adjoining channel (4).

3. A blow box (1) according to claim 2, wherein at each point of the side edges (6-F1,6-F2) the angle a enclosed by the direction (S) of the flow of gas in the cavity (2) and a tangent (T) directed away from the perpendicular (6-S) to the slot top on the side edge (6-F1,6-F2) is greater than 90 °.

4. A blow box (1) according to claim 2 or 3, wherein the convex connection face (6) has a symmetrical cross-section such that the perpendicular slot apex (6-S) extends in the centre of the connection face (6).

5. A blow box (1) according to any of claims 1-4, wherein the convex connection face (6) is configured to be convexly curved.

6. A blow box (1) according to claim 5, wherein the convex coupling face (6) has a circular arc shaped cross-section, an elliptic arc shaped cross-section or a parabolic shaped cross-section.

7. A blow box (1) according to any one of claims 1-4 wherein the convex connecting surface (6) consists of flat sub-sections.

8. A blow box (1) according to claim 7, wherein said convex connection face (6) has a triangular cross-section.

9. A blow box (1) according to any of claims 1-8, wherein most, preferably all, of the joint faces (6) are convex in configuration.

10. A blow box (1) according to any one of claims 1-9, wherein the covering means of the cavity (2) has an edge region (7) which surrounds the entire passage (4) at least in sections and which has a surface facing the cavity (2) which is configured to descend from a side edge of the cavity (2) in the direction of the passage (4).

11. An apparatus for thermally pre-stressing a glass sheet, the apparatus comprising:

-a first gas delivery line (12) and a second gas delivery line (12),

-a first blow box (1.1) according to any one of claims 1 to 10, which is connected to the first gas feed line (12) by means of the fixing device (3), and

-a second blow box (1.2) according to any one of claims 1-10, which is connected to the second gas feed line (12) by means of the fixing device (3), wherein the first blow box (1.1) and the second blow box (1.2) are arranged opposite each other such that the nozzle strips (5) of the first blow box (1.1) and the second blow box (1.2) point towards each other, and

-means for moving a glass sheet (I) into an intermediate space between the first blow box (1.1) and the second blow box (1.2).

12. Apparatus according to claim 11, wherein the means for moving the glass sheet (I) comprise a frame shape (14) on which the glass sheet (I) is arranged and a transport system (13) for moving the frame shape (14).

13. A method for thermally pre-stressing a glass sheet, wherein,

(a) the heated glass pane (I) with the two main faces and the circumferential side edge is arranged in a plane between a first blow box (1.1) and a second blow box (1.2) of the device according to claim 11 or 12,

(b) the glass sheet (I) is cooled by applying an air flow to both main surfaces of the glass sheet (I) by means of two blow boxes (1.1, 1.2).

14. The method according to claim 13, wherein the glass sheet (I) consists of soda lime glass and has a thickness of 1 to 10 mm.

15. Use of a glass pane (I) prestressed by means of the method according to claim 13 or 14 in a vehicle for land, air or water traffic, preferably as a window pane in a rail vehicle or motor vehicle, in particular as a rear window pane, side window pane or sun roof pane of a passenger vehicle, or in the home, preferably as a shower door, freezer door or refrigerator door.