CN113784931A

CN113784931A - Method for producing a bending mould for ceramics for glass sheets

Info

Publication number: CN113784931A
Application number: CN202180001219.1A
Authority: CN
Inventors: A·蔡希纳; P·席林斯
Original assignee: Saint Gobain Glass France SAS
Current assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Priority date: 2020-04-06
Filing date: 2021-03-15
Publication date: 2021-12-10
Also published as: WO2021204496A1

Abstract

The invention relates to a method for producing a ceramic bending mould (K) for glass sheets, comprising the following method steps: (A) determining the profile (K') of a bending mould (K) having a contact surface (F-K); (B) providing a ceramic starting piece (1) having a square shape with dimensions suitable for including the outer shape (K') of the bending tool (K), and (C) producing the bending tool (K) with the contact surface (F-K) from the starting piece (1) by a cutting production method. The starting workpiece (1) is composed of square standard components (2) which are connected to one another by means of a ceramic adhesive.

Description

Method for producing a bending mould for ceramics for glass sheets

Technical Field

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

Background

Especially in the automotive field, glass pieces often have bends. Different methods for producing such bends are known. In so-called gravity bending (also gravity bending or sag bending), a glass sheet which is flat in the initial state is arranged on a supporting surface of a bending mould and heated at least to its softening temperature, so that it rests against the supporting surface under the influence of gravity. In the so-called press bending method, the sheet material is arranged between two complementary tools (bending dies) which jointly apply a pressing action to the sheet material in order to produce the bend. Apparatuses and methods for bending glass sheets are well known to those skilled in the art from a large number of publications. Reference is made, by way of example only, to EP1358131a1, EP2463247a1, WO2017178733a1, DE10314267B3, WO2007125973a1, EP0677488a2 and WO9707066a 1.

Conventional bending moulds are made of metal, wherein the contact surfaces are optionally coated with a steel fabric in order to protect the glass surface. The bending moulds of metal are stable and are subject to tests for use in industrial mass production. But its manufacture is rather costly and costly.

The bending mould is manufactured specifically for each model of the glass sheet, wherein the contact surfaces of the bending mould determine the three-dimensional geometry of the bend, i.e. the glass sheet. Before a particular model of glass sheet is put into mass production, it is often necessary or desirable to make a prototype where, for example, tests can be performed or the prototype can be presented to potential customers. It has hitherto been customary to also produce one or more metal bending moulds for the production of prototypes. Thus, the prototype is long lasting and costly to manufacture.

GB2320021A and EP1391433a2 disclose methods for producing ceramic bending dies for glass sheets, wherein a ceramic starting workpiece is provided as a monolithic block and a bending die with a suitable contact surface is machined from the starting workpiece by a cutting production method. However, the production of large monolithic blocks is complicated and can lead to high material losses, in particular if the bending tool has smaller dimensions than the monolithic block.

JPH08119651A discloses another method for manufacturing a bending mould for ceramics for glass sheets. On the base, which is shaped close to the contact surface, i.e. in particular curved, ceramic blocks are arranged and are connected to one another to form a starting workpiece. The contact surface is machined by a cutting manufacturing method from the starting workpiece facing the base. The choice of the ceramic block depends here on the geometry of the mount or contact surface: smaller blocks are used in areas with large curvature than in areas with smaller curvature. It is therefore necessary to keep ceramic blocks of different sizes in stock or to manufacture ceramic blocks of different sizes, which is costly.

Disclosure of Invention

There is therefore a need for a bending mould for bending glass sheets, in particular for prototyping, which can be manufactured quickly and cost-effectively. The bending die must be temperature stable enough to withstand the high temperatures when the glass is bent. The bending die should be easily manufacturable, wherein the manufacturer should be allowed a large degree of freedom in the design of the contact surfaces of the bending die. The invention is based on the object of providing a method for producing such a bending tool.

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

The method according to the invention is used for manufacturing a bending mould for ceramic of glass sheets, more precisely for bending ceramic of glass sheets. The method according to the invention comprises at least the following method steps:

(A) determining the shape of a bending die, wherein the bending die is provided with a contact surface;

(B) providing a ceramic starting piece with dimensions suitable for including the entire outer shape of the bending die;

(C) a bending tool with a contact surface is produced from a starting workpiece by a cutting production method.

The method according to the invention for producing a ceramic bending tool enables rapid and cost-effective production, in particular in comparison with metallic bending tools, and is therefore particularly suitable for producing prototypes. Furthermore, the method can be carried out relatively simply, so that the ceramic bending mould can be produced on site by the glass manufacturer itself with a suitable stock of the required materials and without having to place an order. Thereby, a simple batch of different bending moulds for glass sheet models can also be manufactured in order to compare the quality of the products manufactured thereby. Ceramic bending moulds are temperature-resistant to a large extent, so that they can be used in glass bending processes. Furthermore, ceramic bending dies have a smaller weight compared to conventional metal bending dies. This is a great advantage of the present invention.

The bending mould for ceramics manufactured according to the invention is arranged for bending glass sheets, in particular for bending glass sheets which are heated to their softening temperature. Upon heating, the glass sheet is capable of plastic deformation. In this method, the glass sheets are generally heated to a temperature of more than 500 ℃, in particular to a temperature of 500 to 700 ℃, whereby the glass sheets soften and can be deformed and can be shaped by the contact surfaces of the bending mould. Typical temperatures when bending a sheet of soda-lime glass are at least 600 ℃, for example about 650 ℃.

The bending die has a contact surface. The contact surface is the surface of the bending mould which is provided as specified for directly or indirectly contacting the glass sheet in order to deform the glass sheet and thereby bend the glass sheet. In a preferred embodiment, the bending tool is a so-called solid tool with a full-surface contact surface, which is provided for contacting a large part of the glass sheet surface. In principle, however, bending tools with frame-like contact surfaces can also be produced by means of the method according to the invention. Such a bending mould can also be referred to as a ring (bending ring) or a frame (frame mould). The frame-like contact surface is provided for contacting only the circumferential edge region of the glass sheet, while the majority of the glass sheet surface is not in contact with the bending mould.

The bending mould according to the invention is not limited with regard to the type of glass bending for which the bending mould can be used. The bending mould (which can also be referred to as bending tool) can be an upper bending mould or a lower bending mould. A lower bending tool in the sense of the present invention is understood to be a tool which touches or is associated with a lower, ground-facing surface of the glass sheet and acts on this lower surface. An upper bending tool is understood to mean a tool which touches or is associated with the upper surface of the glass sheet facing away from the ground and acts on this upper surface. In the upper bending mould the contact surface points downwards and faces the ground, and in the lower bending mould the contact surface points upwards and faces away from the ground. The bending die (for use in hot bending) can be a gravity bending die, an extrusion bending die or a suction bending die. The gravity bending mould is a lower bending mould onto which the glass sheet is placed and after heating is deformed under the influence of gravity and adapted to the shape of the contact surface. In press bending in a relatively compact manner, the glass sheet is pressed and thereby deformed between two bending dies, typically between an upper bending die and a lower bending die. In other words, such a method is also referred to as press bending, in which the glass sheets are pressed against ("blown onto") the upper bending tool by an upwardly directed air flow. Two variants of press bending are generally combined: the glass sheet is pressed by an upwardly directed air flow against the upper bending mould and is then pressed between the upper bending mould and the complementary lower bending mould. During the suction bending, the glass sheet is sucked onto the contact surface, wherein holes are usually introduced into the contact surface in the solid mold for transmitting the suction effect. In particular, a combination of press bending and suction bending is often used, wherein, for example, in addition to the pressing action, the glass sheet is also sucked to the upper bending tool. As already mentioned, the bending die according to the invention can be used not only for hot bending but also as a bending die for cold bending processes.

It is preferred to produce an upper press and/or suction bending die with a full-area contact surface, a lower press bending die with a frame-like contact surface and a lower gravity bending die with a frame-like contact surface or a full-area contact surface for the thermal bending. These bending moulds have proved to be particularly suitable for the manufacture of visually high-value glass sheets. In a particularly preferred embodiment, the bending tool according to the invention is a press and/or suction bending tool with an upper part of the full-surface contact area. Such bending moulds are often used for a large number of sheet patterns in the field of vehicles and allow, with good takt time and quality, a large bandwidth of the sheet geometry.

In a particularly advantageous embodiment, the bending tool according to the invention is provided for producing prototypes or small series. The bending tool according to the invention is particularly suitable for producing prototypes or small series because of its rapid, simple and cost-effective production. When the bending mould is only arranged for the production of one or some small number of prototypes or small number of glass sheets in a small batch range, the bending mould does not have to have the long-term stability of a conventional metallic bending mould.

The profile of the bending die, which may also be referred to as the shape, geometry or geometry of the bending die, is first determined. Which is to be understood in particular as the desired profile of the bending mould. For this purpose, in particular, the shape of the contact surface which the bending tool according to the invention should have must be determined. The shape of the contact surface is related to the shape of the glass sheet to be bent with the contact surface and is determined or confirmed by the shape of the glass sheet. The determination of the required contact surface is preferably carried out computer-aided by CAD methods (computer-aided design ) which are customary in the technical field. However, other methods are also known, which are to be dealt with without CAD calculation. The desired contact surface can thus also be approximated iteratively by a manual or machine-supported machining of the initial shape. The shape of the contact surface does not generally correspond exactly to the shape of the glass sheet in the case of thermal bending, but rather the compensated shape of the contact surface corresponds to the shape of the glass sheet, which takes into account the sagging or viscoelastic spring-back of the glass sheet under its weight after the action of the bending mould. In the simulation for determining the compensated contact surface, the bending furnace to be used and the bending method to be used are based. In addition to the desired sheet shape, for example, the bending temperature and the dwell time in the bending furnace and the type of bending tool used are also critical here. The compensated shape of the contact surface corresponds to the shape of the glass sheet immediately after the action of the bending tool during this time, which contact surface is calculated in such a way that the desired final shape of the glass sheet is obtained taking into account the subsequent deformation of the glass sheet, in particular due to sagging under the influence of gravity or due to viscoelastic spring-back. The glass sheet, the contact surface of which is adapted to the shape of the glass sheet, is in a preferred embodiment a window pane of a vehicle, in particular of a motor vehicle.

The dimensions of the bending die are to be understood in the sense of the present invention as follows. The two dimensions visible in a plan view of the contact surface are referred to as length and width, the greater of the two dimensions being defined as length. The height of the bending die extends perpendicularly to the height and to the width (i.e. substantially perpendicularly to the contact surface), the height dimension being in a top view of the contact surface, i.e. along the visual axis. The dimensions of the contact surfaces are to be understood in a similar manner. In a top view of the contact surface, the length and the width are visible, wherein the greater of the two dimensions is defined as the length. The height or depth of the contact surface is derived from the curved shape (depth of curvature) and can be defined along the height dimension of the bending die as a measure of the spacing of the points of the contact surface that are furthest apart from each other.

The length and width of the bending die are preferably equal to the length and width of the contact surface. The bending die can be manufactured particularly material-saving. In principle, however, it is also possible for the (largest occurring) length and/or width of the bending tool to be greater than the length or width of the contact surface. The actual contact surface can thus, for example, enter into the surface of the bending tool (concave contact surface) or protrude from the surface of the bending tool (convex contact surface), wherein further regions of the surface are present adjacent to or surrounding the contact surface, or the contact surface can be carried in the form of a punch on a type of base which projects beyond the contact surface, i.e. has a greater width and/or length.

The height of the bending die must be at least equal to the depth of the contact surface, i.e. the extension of the contact surface along its direction of curvature is perpendicular to its length and width. However, since these minimum selected heights result in a very small thickness of the bending tool, which is disadvantageous for stability, additional heights are preferably provided in order to ensure a minimum thickness of the bending tool. The minimum thickness of the bending die (i.e. the thickness at the thinnest point) is preferably at least 10mm, particularly preferably at least 15mm, very particularly preferably at least 20 mm. The height of the bending die is given by the sum of the minimum thickness and the depth of the contact surface (bending depth). The depth of the contact surface is 5mm to 300mm, in particular 60mm to 200mm, in the case of sheets which are customary in the vehicle sector. The height of the bending die is therefore at least 15mm, in particular at least 70mm and is typically in the range from 5mm to 400mm, in particular from 70mm to 350 mm. In this range, the bending tool has, on the one hand, a thickness which is advantageous for stability and, on the other hand, an advantageously low weight.

A ceramic starting piece is then provided, which has a size that is suitable for including or receiving the entire outer shape of the bending die. The initial workpiece thus has a length corresponding at least to the length of the bending die, a width corresponding at least to the width of the bending die and a height corresponding at least to the height of the bending die. The dimensions of the initial workpiece are defined in correspondence with the dimensions of the bending die.

According to the invention, the initial workpiece is assembled from standard components in the desired size. For this purpose, the outer shape of the initial workpiece, which may also be referred to as the shape, geometry or geometry of the initial workpiece, is first determined. The outer shape of the starting workpiece has a size which is suitable, on the one hand, for including or receiving the entire outer shape of the bending die and, on the other hand, for being composed of a plurality of standard components of ceramic. A large number of standard components are then assembled in the form of the outer shape of the initial workpiece, wherein the standard components adjacent to one another are connected to one another by means of a (preferably ceramic) adhesive.

Standard components are understood within the meaning of the invention to be ceramic blocks which are available for the production of the initial workpiece. Standard components are typically purchased by glass manufacturers from suppliers. The standard component is then a ceramic block, preferably the smallest ceramic block that the supplier can provide. All standard components used for manufacturing the initial workpiece preferably have the same shape and the same dimensions; i.e. using substantially identical standard components. The method can then be particularly flexible and easy to implement, since only one standard component has to be kept in stock. In principle, but also possible: the initial workpiece is built up (in the sense of the type of geometry) from standard components of different dimensions or even different shapes.

The outer shape of the initial workpiece is configured in the shape of a parallelepiped. The standard component usually also has a parallelepiped shape. Useful ceramic blocks are generally square. Thus, the standard component is according to the invention substantially square and the parallelepiped of the initial workpiece is substantially square. The square starting piece allows the user to have a large degree of freedom in the design of the contact surface of the bending die, since the shape of the starting piece is independent of the bending die, and therefore the starting piece does not have to be adapted to the specific design of the bending die, in particular the contact surface. "substantially" means here that slight deviations from the ideal square shape are allowed, as they occur in real components. This applies in particular to rounded edges and corners or to slightly curved surfaces. The standard component can also have a recess or a through-lead, as long as the contour shape is square.

Preferably, the length, width and height of the parallelepiped are each an integer multiple of one of the dimensions of the standard component (wherein each of the dimensions of the standard component is associated with only one dimension of the parallelepiped). The length of the parallelepiped is thus an integer multiple of the first dimension of the standard component, the width of the parallelepiped is an integer multiple of the second dimension of the standard component, and the height of the parallelepiped is an integer multiple of the 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 precisely, the length of the parallelepiped is equal to the length of the standard component multiplied by the length of the standard componentnThe width of the parallelepiped being equal to the width of the standard component multiplied bymAnd the height of the parallelepiped is equal to the height of the standard component multiplied bylWherein, in the step (A),n, m and lIs an integer. The thickness of the adhesive layer is usually negligible, so that the actual starting workpiece is only insignificantly larger than the original calculated profile of the starting workpiece. In principle, however, it is also possible to take the thickness of the adhesive layer into account during the planning. The length of the parallelepiped is equal to the length of the standard component multiplied bynPlus with(n-1)The total thickness of the adhesive layer, the width of the parallelepiped being equal to the width of the standard component multiplied by the width of the parallelepipedmPlus with(m-1)The total thickness of the adhesive layer, and the height of the parallelepiped is equal to the height of the standard member multiplied by the height of the standard memberlPlus with(l-1)The total thickness of the adhesive layer.

The expression "integer multiple" is to be understood in the sense of the present invention in a mathematical sense, i.e. including the case where the multiple isn, m and lEqual to 1. And in the case of "true integer multiples" the corresponding integer multiple is greater than or equal to 2. At least one dimension (selected from the length, width and height) of the square starting workpiece must be a true integer multiple of the dimension of the standard component of ceramic, since otherwise the standard component would correspond to the starting workpiece and the starting workpiece could not be assembled from a plurality of standard components. It is thus possible that the standard component has the same length and width as the initial workpiece, and that the height of the initial workpiece is standardA true multiple of the height of the component, so that a plurality of standard components are stacked on top of each other to form an initial workpiece. Instead of a plurality of standard components being arranged "one above the other", it is also possible to arrange them side by side if the length or width of the starting workpiece is a real multiple of the size of the standard components and the other sizes of the standard components and starting workpiece coincide with one another. However, it is also possible for two or all three of the dimensions of the square starting workpiece (selected from the length, width and height) to be a true integer multiple of the corresponding dimensions of the standard component made of ceramic.

The dimensions of the standard component with reduced extension are referred to as length, width and height in the sense of the invention. The length is thus the longest dimension of the standard component and the height is the shortest dimension of the standard component.

The standard components are preferably assembled such that the side faces of adjacent standard components face each other, are arranged one above the other and are plane-parallel. Preferably, all standard components have the same orientation in space, so that different standard components can be geometrically transferred into one another by simple movements (simple translational symmetry). However, in particular, alternative arrangements are also conceivable with appropriately dimensioned square standard components. Thus, it is possible, for example, when the width and height of the dice are the same and the length of the dice is equal to twice the height/width, that some dice are arranged upright while other dice are arranged horizontally.

The parallelepiped expediently has as small a (smallest) dimension as possible, which is suitable for including or receiving the entire outer shape of the bending tool. This enables the initial workpiece to be produced in a particularly material-saving manner. In principle, however, it is also possible to use larger parallelepipeds, even if not necessarily many standard components are required for this purpose.

The binder used for joining the ceramic of the standard component is preferably a cement or a ceramic binding material, for example based on particles in the form of microparticles or nanoparticles, in particular based on the ceramic of the starting workpiece.

After providing the ceramic starting piece, a bending tool with a contact surface is produced according to the invention from the starting piece. In this case, a subtractive production method is used, in which a bending tool is produced from the starting workpiece by material removal, in particular a cutting production method, such as milling, grinding, planing, filing, scraping or chiseling, preferably milling. The production is preferably carried out automatically by means of a CAD process, wherein the processing machine is supplied with CAD data of the bending tool and the bending tool is processed from the initial workpiece by means of the CAD data. The cutting of ceramics is time-consuming and inexpensive and is therefore particularly suitable.

Advantageously, the length and width of the initial workpiece are equal to the length and width of the bending die. In this case, only such a surface of the initial workpiece from which the contact surface is to be produced has to be machined. It is also advantageous that the height of the initial workpiece is equal to the (maximum occurring) height of the bending die, so that the required material removal is minimal. The dimensions of the bending die can be dimensioned such that they can be combined by standard components. But it is alternatively possible that the length, width and/or height of the initial workpiece is larger than the length, width or height of the bending die. This only increases the cutting effort.

In an advantageous embodiment, a ceramic starting piece is arranged on the support plate, and then a bending tool is produced from the ceramic starting piece by means of a cutting production method. Thereby providing a stable base for the initial workpiece. Furthermore, standardized support plates can be provided with orientation points for automated CAD-supported machining. The support plate can be mounted rotatably, pivotably and/or tiltably so that the initial workpiece can be moved by means of the support plate during the machining. The support plate preferably has a width and a length which are at least equal to the width and the length of the initial workpiece, so that the entire initial workpiece can be arranged on the support plate without protruding. The support plate is preferably made of metal, in particular steel, for example stainless steel.

The ceramic materials of the starting workpiece and the bending die can in principle be freely selected by the person skilled in the art. In a preferred embodiment, oxide ceramics are used (C: (A)Oxide ceramics) which are particularly suitable for the manufacture of bending moulds due to their hardness, wear resistance and heat resistance. Suitable oxide ceramics are based, for example, on aluminum oxide (Al)₂O₃) Silicon aluminum oxide, zirconium oxide (ZrO)₂) Titanium (IV) oxide (TiO)₂) Magnesium oxide (MgO), zinc oxide (ZnO), aluminum titanate (Al)₂O₃+TiO₂) Barium titanate (BaO + TiO)₂) And (5) constructing. Alternatively, silicate ceramics, in particular mullite ceramics, can be used. However, other ceramics, such as other oxide or silicate ceramics or non-oxide ceramics (in particular based on silicon carbide (SiC), Boron Nitride (BN), boron carbide (B)₄C) Silicon nitride, aluminum nitride, molybdenum disilicide, or tungsten carbide).

In a particularly advantageous embodiment, the material of the ceramic should have the following defined properties:

a small thermal expansion coefficient, in particular for bending moulds for hot bending, whereby the bending mould is subjected to as little shape change as possible in a bending furnace,

-a high resistance to thermal shocks,

high temperature resistance, preferably up to a temperature of at least 750 ℃,

high porosity, whereby the ceramic has a low weight; the open porosity can in some cases ensure air permeability, so that the glass sheet can be subjected to an air flow or suction action without having to drill a through-guide for this purpose;

high mechanical stability, which in addition to being less susceptible to damage, also offers the possibility that the initial workpiece or the standard components used for this purpose can be produced in sufficient quantities without great effort; the mechanical stability is particularly advantageous for the extrusion bending die, to which large forces act in the intended use;

good machinability achieved with the manufacturing method by cutting;

good and as local availability as possible in order to keep manufacturing costs low.

Preferably, a conventional, ceramic refractory material is used, which is also commonly used as a ceramic insulating material. The refractory material is advantageous with respect to the aforementioned parameters and is cost-effective compared to engineering ceramics.

The bending die can optionally be provided with through guides, recesses, domes, threads, tongue and groove connection elements, chamfers or other design elements. They can be used, for example, for screwing or riveting the starting workpiece with the support plate or the bending die with the attachment unit. Alternatively, the feed-through can also be used to exert a suction effect on the glass sheets during the bending of the glass in order to suck the glass sheets to the contact surfaces, when the bending furnace is designed for this purpose. In this case, the leadthrough is distributed, in particular uniformly distributed, over the contact surface and extends from the contact surface as far as the opposing surface of the bending tool.

Preferably, at least the contact surfaces are cleaned after the cutting manufacture of the bending tool. In an advantageous embodiment, the contact surface is finished, in particular by polishing and/or coating. The coating is preferably a ceramic coating, particularly preferably a coating based on boron nitride or an oxide ceramic or a silicate ceramic. The coating imparts a high surface quality to the contact surface and achieves a high resistance to damage and scratch resistance, which is particularly advantageous when the contact surface is to be coated with a steel fabric for bending.

Preferably, a metallic attachment unit is arranged at the bending mould, which attachment unit is used to arrange the ceramic bending mould in a bending furnace or other bending device. The attachment unit provides, to a certain extent, an interface for mounting in a bending device, which interface corresponds in particular to an interface of a conventional metal bending die. The attachment unit is made of metal, in particular of steel, for example temperature-resistant stainless steel. The attachment unit is preferably arranged opposite the contact surface at the bending mould, i.e. at a surface of the bending mould opposite the contact surface. The surface opposite the contact surface is preferably configured to be flat for this purpose. The type of attachment unit depends on the bending furnace used. The placement of the attachment unit at the bending die is preferably done by screwing or suspension/pushing into a receptacle provided for it (e.g. in the type of a drawer). The attachment unit preferably has a plate, on which the bending die is placed, and in particular a standardized plate, which is suitable for placing bending dies of different designs.

A ceramic bending mould is provided for being mounted in a glass bending apparatus. In a preferred embodiment of the method, the bending mould is installed in the glass bending apparatus after its manufacture. The glass bending device has a bending station in which the required bending moulds (below which at least one ceramic bending mould according to the invention is located) are arranged and in which the shaping of the glass sheets takes place by means of the bending moulds. Furthermore, the bending device has means for heating the glass sheets to a softening temperature. In one embodiment, the bending station is arranged in a heated section (bending chamber) of the bending device ("hot bending"). The heating means are arranged here either in the bending chamber itself (combined heating and bending chamber) or in a separate heating chamber, for example in the form of a tunnel furnace through which the glass sheets are passed before entering the bending chamber. In a further embodiment, the bending station is arranged in a section of the bending device that is not heated ("cold bending"). The glass sheet then passes through a heating chamber and is then bent without further heating, wherein the glass sheet cannot of course yet be cooled below its softening temperature. In addition, typical bending apparatuses include means for moving the glass sheets through the heating chamber and the bending station. The movement means can be configured, for example, as rollers or a moving belt conveyor system, wherein the glass sheets rest either directly on the rollers or the moving belt conveyor system or on a transport mold, in particular a transport frame, which is moved by the rollers or the moving belt conveyor system.

The ceramic bending mould is preferably inserted into the bending device via a metallic attachment unit and is used there for bending one or more glass sheets. For this purpose, in an advantageous embodiment, the contact surface is coated with a steel fabric, as is also customary in conventional bending tools. The steel fabric prevents direct contact between the contact face and the glass sheet, thereby advantageously configuring the surface quality and visual quality of the bent glass sheet. The steel fabric is particularly preferably arranged at the attachment unit of the metal, in particular at the plate for fixing the bending mould. The same steel fabric, or the same type of steel fabric, can be placed at different bending tools by means of standardized fastening plates with fastening means for the steel fabric, for example hooks or loops.

The invention also comprises a ceramic bending mould which is produced or can be produced by means of the method according to the invention. The ceramic bending die is composed of a plurality of ceramic standard components which are connected to each other by an adhesive. A bending die, in particular the contact surface thereof, is machined from the combined initial workpiece by means of a cutting manufacturing method.

The invention also comprises the use of a bending mould for ceramics according to the invention for bending, in particular hot bending, glass sheets, in particular for producing prototypes or small series with at most 1000 glass sheets. The glass sheet is preferably a window sheet for rail vehicles or motor vehicles, in particular a windshield sheet, rear window sheet, side window sheet or roof sheet for passenger cars.

The glass sheets to be bent comprise preferably soda-lime glass, as is customary for window sheets, but can also comprise other glass types, such as borosilicate glass, aluminosilicate glass or quartz glass. The thickness of the glass sheets is generally from 0.5mm to 10mm, preferably from 1mm to 5 mm. Typical temperatures for bending glass sheets are between 500 ℃ and 700 ℃, especially around 650 ℃ when bending sheets composed of soda lime glass.

Drawings

The invention is explained in detail below with the aid of figures and examples. The figures are schematic and not to scale. The drawings in no way limit the invention.

In the drawings:

figure 1 shows a cross-section during an embodiment of the method according to the invention for manufacturing a bending mould for ceramics,

figure 2 shows a cross-section of one design of a ceramic bending mould according to the invention during bending of a glass sheet,

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

figure 4 shows a perspective view of another initial workpiece according to the invention,

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

Detailed Description

Fig. 1 schematically shows different method steps of an embodiment of a method according to the invention for producing a ceramic bending tool.

The desired profile K' of the bending tool K is first calculated by means of CAD-methods which are customary in the technical field. The bending mould should have a contact surface F-K arranged for making contact with the glass sheet in order to bend the glass sheet. The required shape of the contact surface F-K is calculated, in particular, as a compensated contact surface, which is calculated taking into account the sagging after bending in order to achieve the desired final sheet geometry. Then, the outer shape 1' is determined, which the ceramic starting piece 1 can have, so that it can include the entire bending die K (fig. 1 a). The outer shape 1' of the initial workpiece 1 is square in the present case.

A ceramic starting piece 1 is then produced under the profile 1' (fig. 1 b). The initial workpiece 1 is assembled from standard components 2. The building block 2 is a square block of ceramic of uniform size available from the supplier. The profile 1 'is selected such that the length L, the width B and the height H of the initial workpiece 1 are respectively integer multiples of the length L', the width B 'and the height H' of the ceramic standard component 2. The initial workpiece is produced by assembling standard components 2, wherein adjacent standard components 2 are connected to one another via a cement layer, not shown. The standard component 2 is made of, for example, an oxide material such as aluminum oxide (Al)₂O₃) And (4) preparing.

For further processing, the initial workpiece 1 is then arranged on a support plate 4, which is made of stainless steel, for example (fig. 1 c). Subsequently, a bending tool K with a contact surface F-K in the shape of the contour K' is produced from the starting workpiece 1 by means of a cutting production method, for example milling (fig. 1 d). The machining is preferably performed automatically based on CAD data.

The initial workpiece 1 can now optionally be provided with a feedthrough, recess or other functional element, for example for fixing the bending die K. Suction can then be applied to the glass sheet by means of the through-guide when the glass is bent. Likewise, the contact surface F-K can optionally be ground or coated in order to improve its surface quality.

Glass bending devices usually have standardized receptacles for exchangeable bending moulds. In order to be able to load the ceramic bending mould K into the glass bending apparatus, the glass bending apparatus is equipped with a metallic attachment unit 5, for example an attachment unit composed of stainless steel (fig. 1 e). The attachment unit 5 has, for example, a flat fastening plate at which the bending tool K is arranged (for example screwed) and, opposite the plate, has a section which is complementary to the receptacle of the glass bending device and can be inserted into the receptacle.

The fastening plate of the attachment unit 5 can be equipped with hooks or other fastening means, at which a not shown steel fabric can be fastened, with which it is to be applied to the contact surface F-K for glass bending. The standardized fastening plate which is suitable for differently designed bending tools K thus allows the same steel fabric to be used for different bending tools K.

Fig. 2 schematically shows a ceramic bending die K with an attachment unit 5 produced according to fig. 1 in use as intended. The bending die K is installed in a bending furnace, not shown, and is used for bending the glass sheet I. The contact surface F-K is coated with a not shown steel fabric for protecting the glass sheet I and is applied to the heated and softened glass sheet I, whereby the glass sheet I is bent according to the shape of the contact surface F-K. This effect can be achieved, for example, by blowing the glass sheet I by means of an upwardly directed air flow at the contact face F-K or by pressing the glass sheet I between the bending die K and a complementary lower bending die, not shown.

The glass sheet I is made of soda lime glass, for example, has a thickness of 3.5mm, and is provided as a rear window glass of a passenger car.

Fig. 3 shows a perspective view of an initial workpiece 1 with a length L, a width B and a height H, which is composed of a standard component 2 with a length L ', a width B ' and a height H '. The length L, width B and height H are true integer multiples of the length L ', width B ' and height H ', respectively.

Fig. 4 shows a perspective view of a further preliminary workpiece 1 according to the invention with a length L, a width B and a height H, which is composed of standard components 2 with a length L ', a width B ' and a height H '. The length L is equal to the length L 'and the width B is equal to the width B' -the length L and the width B are thus, in a mathematical sense, integer multiples of 1 for the multiples of the length L 'and the width B'. And height H is a true integer multiple of height H'. A plurality of standard components 2 are stacked on top of each other in order to form an initial workpiece 1.

Fig. 5 shows an embodiment of the method according to the invention by means of a flow chart.

List of reference numerals

(K) Ceramic bending die

(K') calculated outline/shape of ceramic bending die K

(1) Initial workpiece of ceramic

(1') calculated outline/shape of ceramic starting workpiece 1

(2) Ceramic standard component

(4) Supporting plate

(5) Attachment unit for metal

(F-K) contact surface of ceramic bending die K

(L) length of initial workpiece 1

(B) Width of the initial workpiece 1

(H) Height of initial workpiece 1

(L') length of the standard member 2

(B') width of the standard member 2

(H') height of the standard member 2

(I) Glass sheet

Claims

1. Method for manufacturing a bending mould (K) for ceramics for glass sheets, comprising the following method steps:

(A) determining a profile (K') of the bending mould (K), the bending mould having a contact surface (F-K);

(B) providing a ceramic starting piece (1) with dimensions suitable for including the outer shape (K') of the bending die (K), comprising the following method steps:

(i) determining an outer shape (1') of an initial workpiece (1) with dimensions suitable for including the outer shape (K') of the bending die (K) and combined from a plurality of ceramic standard components (2);

(ii) -assembling ceramic standard components (2) in the form of the outer shape (1') of the initial workpiece (1), wherein adjacent standard components (2) are connected to each other by means of an adhesive;

(C) producing a bending tool (K) with the contact surface (F-K) from the starting workpiece (1) by means of a cutting production method,

wherein the outer shape (1') of the initial workpiece (1) and the standard component (2) are square.

2. The method according to claim 1, wherein the length (L), width (B) and height (H) of a square are integral multiples of the length (L '), width (B ') and height (H ') respectively of the standard component (2) of ceramic.

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

4. A method according to any one of claims 1 to 3, wherein the binder is a ceramic binder, preferably a cement or ceramic binding material.

5. Method according to any of claims 1 to 4, wherein the height of the bending mould (1) is at least 70mm, preferably 70 to 350 mm.

6. Method according to any one of claims 1 to 5, wherein the ceramic initial piece (1) is arranged on a support plate (4) and the bending mould (K) is then manufactured from the ceramic initial piece.

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

8. Method according to any one of claims 1 to 7, wherein the bending die (K) is provided with a feedthrough or a recess.

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

10. Method according to any one of claims 1 to 9, wherein a metallic attachment unit (5) is provided at the bending mould (K), which is suitable for providing the bending mould (K) in a bending device.

11. Method according to claim 10, wherein the attachment unit (5) has a fixing plate on which the bending mould (K) rests, and wherein the fixing plate is equipped with means for fixing a steel fabric.

12. Ceramic bending mould (K) manufactured according to the method according to any of claims 1 to 11.

13. Use of a ceramic bending mould (K) according to claim 12 for bending glass sheets (I), in particular for manufacturing prototypes or small batches with at most 1000 glass sheets (I).