WO2021204496A1

WO2021204496A1 - Process for manufacturing a ceramic bending mold for glass panes

Info

Publication number: WO2021204496A1
Application number: PCT/EP2021/056478
Authority: WO
Inventors: Achim ZEICHNER; Peter Schillings
Original assignee: Saint-Gobain Glass France
Priority date: 2020-04-06
Filing date: 2021-03-15
Publication date: 2021-10-14
Also published as: CN113784931A

Abstract

The invention relates to a process for manufacturing a ceramic bending mold (K) for glass panes, comprising the following process steps: (A) determining a shape (K') of the bending mold (K) that includes a contact surface (F-K); (B) providing a cuboid ceramic starting workpiece (1) having a size suitable for encompassing the shape (K') of the bending mold (K); (C) manufacturing the bending mold (K) having the contact surface (F-K) from the starting workpiece (1) using a machining operation. The starting workpiece (1) is composed of cuboid standard components (2) which are joined together using a ceramic bonding agent.

Description

Process for the production of a ceramic bending mold for glass panes

The invention relates to a method for producing a ceramic bending mold for glass panes, a correspondingly produced ceramic bending mold and the use thereof.

In particular in the field of motor vehicles, glazings typically have a bend. Various methods of creating such a bend are known. In so-called gravity bending or sag bending, the glass pane, which is flat in its initial state, is placed on the support surface of a bending mold and heated to at least its softening temperature so that it rests against the support surface under the influence of gravity. In the so-called press bending process, the disc is placed between two complementary tools (bending molds) which together exert a pressing effect on the disc in order to produce the bend. Devices and methods for bending glass panes are sufficiently known to the person skilled in the art from a large number of publications. Purely by way of example, reference is made to EP1358131A1, EP2463247A1, WO2017178733A1, DE10314267B3, WO2007125973A1, EP0677488A2 and W09707066A1.

Conventional bending forms are made of metal, with the contact surface optionally being coated with a steel mesh to protect the glass surface. Metal bending forms are stable and have proven themselves for use in industrial mass production. However, their production is quite complex and costly.

The bending molds are produced specifically for each model of a glass pane, with the contact surfaces of the bending molds defining the bend, i.e. the three-dimensional geometry of the glass pane. Before a certain model of a glass pane goes into mass production, it is often necessary or desired to produce a prototype on which, for example, tests can be carried out or which can be presented to potential customers. Up to now, one or more metal bending molds were typically also manufactured to manufacture the prototype. As a result, the prototype takes a long time to manufacture and is costly.

GB2320021A and EP1391433A2 disclose methods for producing a ceramic bending mold for glass panes, wherein a ceramic starting workpiece is provided as a monolithic block and the bending mold is carried out with a suitable contact surface machining processes can be worked out from the initial workpiece. However, the production of large monolithic blocks is complex and can be associated with a high loss of material, especially if the bending shape has smaller dimensions than the monolithic block.

JPH08119651A discloses another method for manufacturing a ceramic bending mold for glass sheets. Ceramic blocks are arranged on a base which approximates the shape of the contact surface, that is to say in particular is curved, and connected to one another to form an initial workpiece. The contact surface is machined from this initial workpiece, opposite the base, using machining processes. The choice of ceramic blocks depends on the geometry of the base or the contact surface: smaller blocks are used in areas with greater curvature than in areas with less curvature. As a result, ceramic blocks of different sizes have to be kept in stock or manufactured, which is complex.

There is therefore a need for bending molds for bending glass panes, in particular for producing prototypes, which can be produced quickly and inexpensively. The bending molds must be sufficiently temperature stable to withstand the high temperatures involved in glass bending. The bending molds should be easy to manufacture, and the manufacturer should be given a great deal of freedom with regard to the design of the contact surface of the bending mold. The present invention is based on the object of providing a method for producing such a bending form.

The object of the invention is achieved according to the invention by a method according to independent claim 1. Preferred embodiments are evident from the dependent claims.

The method according to the invention is used to produce a ceramic bending mold for glass panes, more precisely a ceramic bending mold for bending glass panes. The method according to the invention comprises at least the following method steps:

(A) Determination of the shape of the bending form which has a contact surface,

(B) providing a ceramic starting workpiece with a size suitable to enclose the entire shape of the bending mold,

(C) Production of the bending shape with the contact surface from the initial workpiece by a machining process. The method according to the invention for producing a ceramic bending mold can be produced quickly and inexpensively, in particular in comparison to metal bending molds, and is therefore particularly suitable for producing prototypes. The method is also comparatively easy to carry out, so that the ceramic bending mold can be produced on site by the glass manufacturer if the necessary materials are appropriately stored and does not have to be commissioned. It is also easier to produce a series of different bending shapes for a model of a glass pane in order to compare the quality of the products made with them. The ceramic bending mold is temperature-resistant to a high degree, so that it can be used for glass bending processes. The ceramic bending form also has a lower weight than conventional metal bending forms. These are great advantages of the present invention.

The ceramic bending mold produced according to the invention is intended for bending glass panes, in particular for bending glass panes which have been heated to their softening temperature. The glass panes can be plastically formed by heating. In such methods, the glass panes are typically heated to a temperature of over 500 ° C., in particular from 500 ° C. to 700 ° C., whereby they are softened and deformable and can be shaped by the contact surface of the bending mold. Typical temperatures when bending panes made of soda-lime glass are at least 600 ° C, for example about 650 ° C.

The bending form has a contact surface. The contact surface is that surface of the bending mold which is intended to come into direct or indirect contact with the glass pane in order to deform it and thereby bend it. In a preferred embodiment, the bending form is a so-called full form with a full-surface contact surface which is provided for coming into contact with a large part of the surface of the glass pane. In principle, however, a bending shape with a frame-like contact surface can also be produced using the method according to the invention. Such a bending shape can also be referred to as a ring (bending ring) or frame (frame shape). The frame-like contact surface is intended to come into contact only with a circumferential edge area of the glass pane, while the majority of the glass pane surface has no contact with the bending form.

The bending form according to the invention is not limited with regard to the type of glass bending for which it can be used. The bending shape, also known as the bending tool can be an upper or a lower bending shape. In the context of the invention, a lower bending shape is understood to mean a shape which touches the lower surface of the glass pane facing the ground or is assigned to it and acts on it. An upper bending shape is understood to mean a shape which touches the upper surface of the glass pane facing away from the ground or is assigned to it and acts on it. In the case of an upper bending form, the contact surface points downwards and faces the ground; in the case of a lower bending form, the contact surface points upwards and faces away from the ground. The bending form (for use in hot bending) can be a gravity bending form, a press bending form, or a suction bending form. A gravity bending mold is a lower bending mold on which the glass pane is placed and, after being heated, deforms under the influence of gravity and adapts to the shape of the contact surface. In press bending in the narrower sense, the pane of glass is pressed between two bending molds, typically an upper and a lower bending mold, and thus deformed. In a broader sense, such processes are also referred to as press bending, in which the glass pane is pressed (“blown”) against an upper bending mold by an upwardly directed air stream. Often both variants of press bending are combined: the pane of glass is pressed against an upper bending form by an upward air flow and then pressed between this upper bending form and a complementary lower bending form. In the case of suction bending, the glass pane is sucked onto the contact surface, with holes typically being made in the contact surface in order to convey the suction effect in the case of full molds. In particular, press and suction bending are often combined, for example, in addition to the pressing effect, the glass pane is sucked onto the upper bending mold. As already mentioned, the bending form according to the invention can be used not only for hot bending, but also as a bending form for cold bending processes.

The production of upper press and / or suction bending forms with full-surface contact surface, of lower press-bending forms with frame-like contact surface and of lower gravity bending forms with frame-like contact surfaces or full-surface contact surfaces for use for hot bending is preferred. These bending forms have proven particularly useful for the production of optically high-quality glass panes. In a particularly preferred embodiment, the bending mold according to the invention is an upper press and / or suction bending mold with a full-surface contact surface. Such bending shapes are common for a large number of window types in the vehicle sector and allow the realization of a wide range of window geometries with good cycle times and quality. In a particularly advantageous embodiment, the bending mold according to the invention is provided for the production of a prototype or a small series. It is particularly suitable for this because of its fast, simple and inexpensive manufacture. If the bending mold is only intended for the production of one or a few prototypes or a few glass panes as part of a small series, it does not have to have the long-term stability of a conventional metallic bending mold.

First, the shape of the bending shape is determined, which can also be referred to as the shape, geometric shape or geometry of the bending shape. This includes, in particular, the outlines of the desired bending shape. For this purpose, in particular the shape of the contact surface must be determined which the bending shape according to the invention should have. The shape of the contact surface depends on the shape of the glass pane to be bent with it and is determined or determined by this. The required contact area is preferably determined using computer-aided design using standard CAD methods (computer-aided design). However, other methods are also known which can do without CAD calculations. In this way, the desired contact surface can also be iteratively approximated by manual or machine-aided reworking of an initial shape. In the case of hot bending, the shape of the contact surface usually does not correspond exactly to the shape of the glass pane, but is a compensated shape of the contact surface, which takes into account a sagging of the glass pane under its force of gravity after the action of the bending shape or a viscoelastic springback. The simulations to determine the compensated contact area are based on the bending furnace to be used and the bending method to be used. In addition to the desired shape of the pane, the bending temperature and the dwell time in the bending furnace as well as the type of bending tools used are decisive here. The compensated shape of the contact surface corresponds to the intermediate shape of the glass pane directly after the action of the bending shape, which is calculated in such a way that, taking into account the subsequent deformation of the glass pane, in particular due to sagging under the influence of gravity or through viscoelastic springback, the desired, final Shape of the glass pane results. The glass pane, to the shape of which the contact surface is adapted, is, in a preferred embodiment, a window pane of a vehicle, in particular a motor vehicle.

The dimensions of the bending form are to be understood as follows in the context of the invention. The two dimensions that are visible in plan view of the contact surface are called length and width, with the larger of the two dimensions being defined as length will. The height of the bending shape extends perpendicular to the height and width (that is, essentially perpendicular to the contact surface), the height dimension therefore follows the optical axis when the contact surface is viewed from above. The dimensions of the contact area are to be understood in an analogous manner. When looking at the contact surface from above, the length and width are visible, with the larger of the two dimensions being defined as the length. The height or depth of the contact surface results from the curved shape (depth of curvature) and can be defined as the distance between the most distant points on the contact surface measured along the height dimension of the bending shape.

The length and width of the bending form preferably corresponds to the length and width of the contact surface. The bending shape can then be produced in a particularly material-saving manner. In principle, however, it is also possible for the (maximum occurring) length and / or width of the bending shape to be greater than the length or width of the contact surface. For example, the actual contact surface can be embedded in a surface of the bending mold (concave contact surface) or protrude from the surface of the bending mold (convex contact surface), further areas of this surface being adjacent to the contact surface or surrounding the contact surface, or the contact surface can be in be carried in the manner of a stamp on a type of base which protrudes beyond the contact surface (that is to say has a greater width and / or length.

The height of the bending form must at least correspond to the depth of the contact surface, i.e. the extension of the contact surface along its direction of curvature perpendicular to its length and width. However, since this minimally selected height would locally lead to a very small thickness of the bending mold, which is detrimental to stability, an additional height is preferably provided in order to ensure a minimum thickness of the bending mold. The minimum thickness of the bending form (ie the thickness at the thinnest point) is preferably at least 10 mm, particularly preferably at least 15 mm, very particularly preferably at least 20 mm. The height of the bending form results from the sum of the minimum thickness and the depth of the contact surface (depth of bend). The depth of the contact surface in conventional windows in the vehicle area is from 5 mm to 300 mm, in particular from 60 mm to 200 mm. The height of the bending form is consequently at least 15 mm, in particular at least 70 mm and is typically in a range from 5 mm to 400 mm, in particular from 70 mm to 350 mm. In this area, the bending shape has, on the one hand, a thickness that is advantageous for stability and, on the other hand, an advantageously low weight. A ceramic starting workpiece is then provided which has a size which is suitable for enclosing or accommodating the entire shape of the bending mold. The starting workpiece thus has a length which corresponds at least to the length of the bending form, a width which corresponds at least to the width of the bending form, and a height which corresponds at least to the height of the bending form. The dimensions of the initial workpiece are defined according to those of the bending shape.

According to the invention, the starting workpiece is assembled from standard components in the required size. To this end, a shape of the initial workpiece is first determined, which can also be referred to as the shape, geometric shape or geometry of the initial workpiece. The shape of the starting workpiece has a size which is suitable on the one hand to include or accommodate the entire shape of the bending mold and which is suitable on the other hand to be assembled from a plurality of standard ceramic components. A large number of standard components are then put together in the form of the shape of the starting workpiece, with standard components that are adjacent to one another being connected to one another with a (preferably ceramic) adhesion promoter.

For the purposes of the invention, the standard components are to be understood as meaning ceramic blocks which are available for the production of the starting workpiece. Typically, the glass manufacturer will purchase the standard components from a supplier. The standard component is then a ceramic block, preferably the smallest ceramic block that the supplier can deliver. All of the standard components used to produce the initial workpiece preferably have the same shape and the same dimensions; essentially identical standard components are used. The method is then particularly flexible and easy to carry out because only one type of standard component has to be kept in stock. In principle, however, it is also possible to build up the initial workpiece from standard components of different sizes or even different shapes (in terms of the type of geometric body).

The shape of the initial workpiece is in the form of a parallelepiped. Usual standard components also have the shape of a parallelepiped. Available ceramic blocks are typically cuboid. Therefore, according to the invention, the standard components are essentially cuboid and the parallelepiped of the starting workpiece is essentially a cuboid. A cuboid starting workpiece allows the user great freedom with regard to the design of the contact surface of the bending form, because the shape of the initial workpiece is independent of the bending form, i.e. the initial workpiece does not have to be adapted to the specific design of the bending form, in particular the contact surface. “Essentially” here means that slight deviations from the ideal cuboid shape are permissible, as they occur with real components. This is especially true for rounded edges and corners or for slightly curved surfaces. The standard components can also have depressions or passages, as long as the outline shape is cuboid.

The length, width and height of the parallelepiped are each an integral multiple of one of the dimensions of the standard component (each of the dimensions of the standard component being assigned to only one dimension of the parallelepiped). The length of the parallelepiped is therefore an integral multiple of a first dimension of the standard component, the width of the parallelepiped is an integral multiple of a second dimension of the standard component and the height of the parallelepiped is an integral multiple of a third dimension of the standard component. In an advantageous embodiment, the length, width and height of the parallelepiped are each an integral multiple of the length, width and height of the standard component. More specifically, the length of the parallelepiped is the length of the standard part multiplied by n, the width of the parallelepiped is the width of the standard part multiplied by m, and the height of the parallelepiped is the height of the standard part multiplied by /, where n, m and / are integers. The thickness of the bonding agent layer is usually negligible, so that the real starting workpiece is only insignificantly larger than the originally calculated shape of the starting workpiece. In principle, however, it is also possible to include the thickness of the adhesion promoter layer in the planning. Then the length of the parallelepiped corresponds to the length of the standard component multiplied by n plus the total thickness of (n-1) adhesive layers, the width of the parallelepiped corresponds to the width of the standard component multiplied by m plus the total thickness of (m-1) adhesive layers, and the height of the Parallelepipeds of the height of the standard component multiplied by / plus the total thickness of (1-1) layers of adhesion promoter.

The expression “integer multiple” is to be understood in the sense of the invention in the mathematical sense, thus includes the case that the factors n, m and / are equal to 1. In the case of a “real integer multiple”, however, the respective integer factor is greater than or equal to 2. At least one dimension of the cuboid starting workpiece (selected from length, width and height) must be a real one be an integer multiple of one dimension of the standard ceramic component, because otherwise the standard component would correspond to the initial workpiece and the latter could not be composed of several standard components. It is therefore possible that the standard components have the same length and width as the initial workpiece and the height of the initial workpiece is a real multiple of the height of the standard components, so that several standard components are stacked on top of one another to form the initial workpiece. Instead of one above the other, several standard components can also be arranged next to one another if the length or width of the initial workpiece is a real multiple of a dimension of the standard component and the other dimensions of the standard component and the initial workpiece match one another. However, it is also possible for two or all three of the dimensions of the cuboid starting workpiece (selected from length, width and height) to be a real integral multiple of the respective dimension of the standard ceramic component. In the context of the invention, the dimensions of the standard component are referred to as length, width and height with decreasing extent. The length is the longest dimension and the height the shortest dimension of the standard component.

The standard components are preferably assembled in such a way that side surfaces of adjacent standard components face one another, are arranged in congruence and are plane-parallel. All standard components preferably have the same orientation in space, so that the various standard components can be geometrically transferred into one another by simple displacement (simple translation symmetry). However, a different arrangement is also conceivable, particularly in the case of suitably dimensioned cuboid standard components. For example, if the width and height of the cuboids are the same and the length of the cuboids is twice the height / width, some cuboids can be placed upright and others horizontally.

The parallelepiped expediently has the smallest possible (minimum) size which is suitable for enclosing or accommodating the entire shape of the bending form. In this way, the starting workpiece can be produced in a particularly material-saving manner. In principle, however, it is also possible to use a larger parallelepiped, even if this requires an unnecessarily large number of standard components. The ceramic adhesion promoter for connecting the standard components is preferably cement or a ceramic adhesive, for example based on micro- or nanoparticulate particles, in particular based on the ceramic of the starting workpiece.

After the ceramic starting workpiece has been provided, the bending form with the contact surface is produced according to the invention from this starting workpiece. A subtractive manufacturing process is used here, with the bending shape being worked out of the initial workpiece by removing material, in particular a cutting manufacturing process such as milling, grinding, planing, filing, rasping or chiseling, preferably milling. Production is preferably automated with the aid of CAD processing, the CAD data of the bending shape being made available to a processing machine and the processing machine using the CAD data to work out the bending shape from the initial workpiece. Machining from ceramics is not very time-consuming or costly and is therefore particularly suitable.

It is advantageous if the length and width of the initial workpiece correspond to the length and width of the bending form. Then only that surface of the starting workpiece has to be machined from which the contact surface is to be machined. It is also advantageous if the height of the initial workpiece corresponds to the (maximum occurring) height of the bending shape, so that the required material removal is minimal. The dimensions of the bending shape can be set so that they can be assembled from standard components. Alternatively, however, it is also possible for the length, width and / or height of the starting workpiece to be greater than the length, width or height of the bending mold. This only increases the cost of machining.

In an advantageous embodiment, the ceramic starting workpiece is arranged on a support plate before the bending form is produced therefrom with the aid of machining processes. This provides a stable base for the initial workpiece. In addition, a standardized support plate can provide orientation points for automated, CAD-supported processing. The support plate can be mounted so that it can rotate, pivot and / or tilt, so that the initial workpiece can be moved by means of the support plate during processing. The support plate preferably has a width and length which corresponds at least to the width and length of the initial workpiece, so that the entire initial workpiece the support plate can be placed without protruding. The support plate is preferably made of metal, in particular steel, for example stainless steel.

The ceramic material of the starting workpiece and the bending shape can in principle be freely selected by a person skilled in the art. In a preferred embodiment, oxidic ceramics (oxide ceramics) are used which, due to their hardness, wear resistance and heat resistance, are particularly suitable for the production of bending shapes. Suitable oxide ceramics are, for example, based on aluminum oxide (Al ₂ O ₃ ), silicon aluminum oxide, zirconium dioxide (Zr0 ₂ ), titanium (IV) oxide (PO ₂ ), magnesium oxide (MgO), zinc oxide (ZnO), aluminum titanate (AI ₂ O ₃ + T1O ₂ ), barium titanate (BaO + T1O ₂ ). Alternatively, silicate ceramics can be used, especially mullite ceramics. However, other ceramics can also be used, for example other oxide or silicate ceramics or non-oxidic ceramics (in particular based on silicon carbide (SiC), boron nitride (BN), boron carbide (B ₄ C), silicon nitride, aluminum nitride, molybdenum disilicide or tungsten carbide) .

In particularly advantageous embodiments, the ceramic material should have certain properties, including: a low coefficient of thermal expansion, in particular for bending molds for hot bending, so that the bending mold is subject to the least possible shape changes in the bending furnace, high thermal shock resistance, high temperature resistance, preferably up to temperatures of at least 750 ° C, a high porosity, whereby the ceramic is light in weight; an open porosity can, under certain circumstances, ensure air permeability, so that the glass pane can be subjected to an air stream or a suction effect without the need to drill through-holes for this purpose; a high mechanical stability, which in addition to a lack of susceptibility to damage also provides the possibility of the starting workpiece or the standard components used for this purpose can / can be manufactured in sufficient numbers without great effort; the mechanical stability is particularly advantageous for press bending molds on which large forces act when used as intended; good machinability with machining processes, Good availability as close as possible to the location in order to keep production costs low.

Conventional, ceramic refractory materials, which are also used as ceramic insulating materials, are preferably used. With regard to the aforementioned parameters, these are advantageous and cost-effective compared to technical ceramics.

The bending form can optionally be provided with bushings, depressions, domes, threads, tongue and groove connecting elements, chamfers or other design elements. These can be used, for example, to screw or rivet the starting workpiece to the support plate or to the bending form with a connection unit. Alternatively, feedthroughs can also be used to exert a suction effect on the glass pane during glass bending in order to suck it up to the contact surface, if the bending furnace is designed for this. In this case, the bushings are distributed over the contact surface, in particular evenly distributed, and extend from the contact surface to the opposite surface of the bending mold.

At least the contact surface is preferably cleaned after the machining of the bending form. In an advantageous embodiment, the contact surface is refined, in particular by polishing and / or coating. The coating is preferably a ceramic coating, particularly preferably based on boron nitride or an oxidic ceramic or a silicate ceramic. These coatings give the contact surface a high surface quality and produce a high level of resistance to damage and scratch resistance, which is particularly advantageous when the contact surface is to be coated with a steel mesh for bending.

A metal connection unit is preferably attached to the bending mold, which is used to attach the ceramic bending mold in the bending furnace or another bending device. The connection unit thus provides, as it were, an interface for installation in the bending device, which in particular corresponds to the interface of conventional metal bending forms. The connection unit is made of metal, in particular steel, for example stainless, temperature-resistant steel. The connection unit is preferably attached to the bending mold opposite the contact surface, that is to say on that surface of the bending mold which is opposite the contact surface. The surface opposite the contact area is for this purpose preferably flat. The type of connection unit depends on the bending furnace used. The attachment unit is preferably attached to the bending form by screwing or hanging / pushing into a receptacle provided for this purpose (for example in the manner of a drawer). The connection unit preferably has a plate on which the bending form is attached, in particular a standardized plate which is suitable for attaching differently configured bending form.

The ceramic bending mold is intended to be installed in a glass bending device. In a preferred embodiment of the method, the bending mold is installed in such a glass bending device after its manufacture. The glass bending device has a bending station in which the required bending molds (including at least one ceramic bending mold according to the invention) are arranged and in which the shaping of the glass pane takes place by means of the bending molds. The bending device also has means for heating the glass pane to the softening temperature. In one embodiment, the bending station is arranged in a heated section of the bending device (bending chamber) (“hot bending”). The heating means are either arranged in the bending chamber itself (combined heating and bending chamber) or in a separate heating chamber, for example in the form of a tunnel oven, through which the glass panes pass before entering the bending chamber. In a further embodiment of the, the bending station is arranged in a non-heated section of the bending device (“cold bending”). The glass panes then pass through a heating chamber and are then bent without further heating, although they must of course not have cooled below their softening temperature. Typical bending devices also include means for moving the sheet of glass through the heating chamber and bending station. The moving means can be designed, for example, as a roller or treadmill conveyor system, the glass panes either resting directly on the roller or treadmill conveyor system or on a transport form, in particular a transport frame, which is moved by the roller or treadmill conveyor system.

The ceramic bending form is installed in a bending device, preferably via the metal connection unit, and used there to bend one or more glass panes. For this purpose, in an advantageous embodiment, the contact surface is covered with a steel mesh, as is also common with conventional bending molds. The steel mesh prevents direct contact between the contact surface and the glass pane, which makes the surface quality and optical quality of the curved glass pane advantageous is designed. The steel mesh is particularly preferably attached to the metal connection unit, in particular the plate for fastening the bending form. Using a standardized fastening plate with fastening means for the steel mesh (for example hooks or eyes), the same steel mesh, or the same type of steel mesh, can be attached to different bending forms.

The invention further comprises a ceramic bending mold, manufactured or producible with the method according to the invention. The ceramic bending mold is composed of a plurality of standard ceramic components which are connected to one another with an adhesion promoter. The bending shape, in particular its contact surface, is machined from this composite starting workpiece using a machining process. The invention also includes the use of the ceramic bending mold according to the invention for bending (in particular hot bending) glass panes, in particular for producing prototypes or small series with a maximum of 1000 glass panes. The glass panes are preferably window panes of rail vehicles or motor vehicles, in particular windshields, rear windows, side windows or roof panes of passenger cars.

The glass pane to be bent preferably contains soda-lime glass, as is customary for window panes, but can also contain other types of glass, such as borosilicate glass, aluminosilicate glass or quartz glass. The thickness of the glass pane is typically from 0.5 mm to 10 mm, preferably 1 mm to 5 mm. Typical temperatures for bending

Glass panes are from 500 ° C to 700 ° C, in particular around 650 ° C when bending panes made of soda-lime glass. The invention is explained in more detail below with reference to a drawing and exemplary embodiments. The drawing is a schematic representation and is not true to scale. The drawing does not restrict the invention in any way.

Show it:

1 shows cross-sections during an embodiment of the method according to the invention for producing a ceramic bending mold,

2 shows a cross section through an embodiment of the ceramic bending mold according to the invention during the bending of a glass pane,

3 shows a perspective view of an initial workpiece according to the invention,

4 shows a perspective view of a further starting workpiece according to the invention,

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

FIG. 1 schematically shows various method steps of an embodiment of the method according to the invention for producing a ceramic bending mold.

First of all, the desired shape K 'of the bending form K is calculated using a conventional CAD method. The bending form should have a contact surface F-K which is intended to come into contact with a pane of glass in order to bend it. The required shape of the contact surface F-K is calculated in particular as a compensated contact surface, in the calculation of which the sagging after bending was taken into account in order to arrive at the desired final pane geometry. Then the shape T is determined, which a ceramic starting workpiece 1 can have, so that it can enclose the entire bending shape K (FIG. 1 a). The shape T of the initial workpiece 1 is cuboid in the present case.

A ceramic starting workpiece 1 is then produced in the shape T (FIG. 1b). The starting workpiece 1 is assembled from standard components 2. The standard components 2 are rectangular ceramic blocks of uniform size, which a supplier can deliver. The shape T is selected such that the length L, the width B and the height H of the starting workpiece 1 are each an integral multiple of the length L ', the width B' and the height H 'of the standard ceramic component 2. The initial workpiece is produced by assembling the standard components 2, with adjacent standard components 2 being connected to one another via a cement layer (not shown) will. The standard components 2 are made, for example, of an oxidic material such as aluminum oxide (Al ₂ O ₃ ).

The starting workpiece 1 is then arranged for further processing on a support plate 4 which is made, for example, of stainless steel (FIG. 1c). Subsequently, the bending form K in the shape K 'with the contact surface F-K is worked out of the starting workpiece 1 by a cutting manufacturing process such as milling (FIG. 1d). The processing is preferably done automatically on the basis of the CAD data.

The starting workpiece 1 can now optionally be provided with passages, depressions or other functional elements which are used, for example, to fasten the bending form K. A suction effect can be exerted on the glass pane later when the glass is bent through feedthroughs. Likewise, the contact surface F-K can optionally be ground or coated in order to increase its surface quality.

Glass bending devices typically have standardized receptacles for exchangeable bending forms. In order to be able to install the ceramic bending form K in the glass bending device, it is equipped with a metal connection unit 5, for example made of stainless steel (FIG. 1e). The connection unit 5 has, for example, a planar fastening plate to which the bending form K is attached (for example screwed) and, opposite this, a section which is complementary to receiving the glass bending device and can be inserted into it.

The fastening plate of the connection unit 5 can be equipped with hooks or other fastening means to which a steel mesh (not shown) can be fastened, with which the contact surface F-K is to be covered for glass bending. A standardized mounting plate, which is suitable for different designed bending forms K, thus enables the same steel mesh to be used for different bending forms K.

FIG. 2 shows schematically the ceramic bending form K produced according to FIG. 1 with the connection unit 5 when used as intended. The bending mold K is installed in a bending furnace (not shown) and is used to bend a pane of glass I. To protect the glass pane I, the contact surface FK is covered with a steel fabric (not shown) and acts on the heated and softened glass pane I, whereby the glass pane I is bent according to the shape of the contact surface FK. These It can act, for example, by blowing the glass pane I onto the contact surface FK by means of an upwardly directed air stream, or by pressing the glass pane I between the bending mold K and a complementary lower bending mold (not shown).

The glass pane I consists for example of soda-lime glass, has a thickness of 3.5 mm and is intended as the rear window of a passenger car.

FIG. 3 shows a perspective illustration of the initial workpiece 1 with the length L, the width B and the height H, which is composed of standard components 2 with the length L ', the width B' and the height H '. The length L, the width B and the height H are each real integer multiples of the length L ', the width B' and the height H '.

FIG. 4 shows a perspective illustration of a further starting workpiece 1 according to the invention with the length L, the width B and the height H, which is composed of standard components 2 with the length L ', the width B' and the height H '. The length L corresponds to the length L 'and the width B corresponds to the width B' - the length L and the width B are therefore in the mathematical sense integer multiples of the length L 'and the width B' with the factor 1. The height H is on the other hand a real integer multiple of the height H '. Several standard components 2 are stacked on top of one another in order to form the starting workpiece 1.

FIG. 5 shows an exemplary embodiment of the method according to the invention on the basis of a flow chart.

List of reference symbols:

(K) ceramic bending form

(K ') calculated shape / shape of the ceramic bending form K

(1) ceramic base workpiece

(1 ‘) calculated shape / shape of the ceramic starting workpiece 1

(2) standard ceramic component (4) support plate

(5) metal connection unit

(F-K) Contact surface of the ceramic bending form K (L) Length of the starting workpiece 1

(B) Width of the starting workpiece 1

(H) Height of the starting workpiece 1

(L ¹ ) Length of the standard component 2

(B ') Width of standard component 2 (H') Height of standard component 2

(I) pane of glass

Claims

1. A method for producing a ceramic bending mold (K) for glass panes, comprising the following process steps: (A) determining a shape (K ') of the bending mold (K) which has a contact surface (F-K),

(B) Providing a ceramic starting workpiece (1) with a size which is suitable to enclose the shape (K ') of the bending form (K), comprising the following method steps: (i) Determination of a shape (T) of the starting workpiece (1) with a size which is suitable to enclose the shape (K ') of the bending form (K) and to be assembled from a plurality of standard ceramic components (2),

(ii) assembling standard ceramic components (2) in the form of the shape (1 ') of the starting workpiece (1), with adjacent standard components (2) being connected to one another by means of an adhesion promoter,

(C) Production of the bending form (K) with the contact surface (F-K) from the initial workpiece (1) by a machining production process, the shape (1 ') of the initial workpiece (1) and the standard components (2) being cuboid.

2. The method according to claim 1, wherein the length (L), width (B) and height (H) of the cuboid are each an integral multiple of the length (L ¹ ), width (B ') and height (H') of the standard ceramic component (2) are.

3. The method according to claim 1 or 2, wherein all standard components (2) are identical.

4. The method according to any one of claims 1 to 3, wherein the adhesion promoter is a ceramic adhesion promoter, preferably cement or a ceramic adhesive.

5. The method according to any one of claims 1 to 4, wherein the height of the bending mold (1) is at least 70 mm, preferably from 70 mm to 350 mm.

6. The method according to any one of claims 1 to 5, wherein the ceramic

Starting workpiece (1) is arranged on a support plate (4) before the bending form (K) is produced therefrom.

7. The method according to any one of claims 1 to 6, wherein the starting workpiece (1) is made of an oxidic ceramic or silicate ceramic.

8. The method according to any one of claims 1 to 7, wherein the bending form (K) with

Feedthroughs or depressions is provided.

9. The method according to any one of claims 1 to 8, wherein the contact surface (F-K) is polished and / or coated, in particular with a coating based on an oxide ceramic.

10. The method according to any one of claims 1 to 9, wherein a metal connection unit

(5) is attached to the bending form (K), which is suitable for attaching the bending form (K) in a bending device.

11. The method according to claim 10, wherein the connection unit (5) has a fastening plate on which the bending form (K) is attached, and wherein the fastening plate is equipped with means for fastening a steel mesh.

12. Ceramic bending mold (K) produced by the method according to one of claims 1 to 11.

13. Use of a ceramic bending mold (K) according to claim 12 for bending glass panes (I), in particular for the production of prototypes or small series with a maximum of 1000 glass panes (I).