GLASS OR GLASS-CERAMIC PLATE AND METHOD FOR PRODUCEING SUCH PLATES

Description

[0001] The invention relates to a glass or glass-ceramic plate according to the preamble of claim 1. The invention also relates to a method for producing such glass or glass-ceramic plates according to claim 4 and claim 8.

[0002] Glass or glass-ceramic panels are manufactured with or without facets, depending on their intended use. Such glass or glass-ceramic panels are typically rectangular in shape and, to ensure dimensional accuracy and safe handling, are given a peripheral grind in a first process step known as pre-grinding. This grind creates a profile with a defined edge geometry and eliminates sharp transitions and defects that may arise, for example, during the upstream "glass breaking" process. During this pre-grinding, the corners of the panel are usually rounded. The corner radii of the curves merge into the straight sides of the panel, creating a continuous contour line when viewed from above.

[0003] The sheets are often provided with a bevel on one or more sides. The beveling or rounding of glass edges in general is described, for example, in JP 2002 160147 A, WO 02 / 45909 A1, or WO 2014 / 035946 A1.

[0004] When beveling an edge, a bevel is usually applied to the surface by grinding and polishing. The bevel runs parallel to the outer edge. The original sheet thickness is thereby reduced to a value of typically 20% to 80%. The remaining edge is referred to as the residual edge. Faceting creates an exposed edge that is still sensitive to impact even after the bevel has been applied. This reduces the mechanical strength of the workpiece.

[0005] The material removal during the production of the bevel also changes the profile of the remaining edge. The remaining edge must therefore be ground down and given a new profile. This additional material removal also affects the rounding. The material removal leads to a shortening of the corner surface and a reduction of the corner angle, so that the radius of the rounding no longer flows completely into the remaining edge. The edge line at the transition from the corner surface to the remaining edge surface not only exhibits a discontinuity in plan view, but also a horizontal and vertical offset in the side view of the panel. The aesthetic impression is significantly impaired.

[0006] For beveling and grinding the residual edge, automatic machines are typically available that perform both machining processes in direct sequence using a linear arrangement of the required grinding and polishing tools. In such machines, the workpiece is moved in a straight line past the grinding and polishing tools. Grinding of the residual edge can be optionally activated or deactivated by advancing or retracting the corresponding tool positions toward or from the workpiece edge.

[0007] It is therefore an object of the invention to provide a faceted glass or glass-ceramic plate whose circumferential contour line runs as evenly as possible, particularly in the transition from the corner surface to the remaining edge surface. It is also an object of the invention to provide a corresponding method for producing such a glass or glass-ceramic plate.

[0008] JP 2002160147 A describes an edge grinding process that uses a grinding wheel with a concave cross-section and made of a plastic material with embedded fibers and abrasive grains. This gives the glass edges a rounded profile.

[0009] WO 02 / 45909 A1 describes a facet grinding wheel with a cup-shaped grinding wheel body with a central bore, the cup rim of which is designed as a grinding ring. A second grinding ring is arranged concentrically inside the cup chamber, which supports the developing facet when grinding flat facets on glass panes, especially glass-ceramic panes. This prevents rounded entry and exit corners at the end of the fracture edge.

[0010] WO 2014 / 035946 A1 discloses a four-step process for processing broken edges of glass panels. Rotating grinding wheels are used to first create chamfers on the edges, which also removes material from the broken edge. In a subsequent process step, the remaining front edge is machined. Finally, a polishing process is performed with a polishing roller, which can also round off sharp corners and edges.

[0011] This object is achieved with a glass or glass ceramic plate having the features of claim 1.

[0012] The glass or glass ceramic plate is characterized in that the plate has an edge index at the corner E and the adjacent remaining edge area I N = W N V Y has with W N = W γ and VY ≠ 0, where VY in mm denotes the distance between the contour lines KR and KE in the y-direction and that for IN in mm -1< applies: 0.1 ≤ IN ≤ 1.5 (condition 1).

[0013] A profile is defined as the contour of an edge surface characterized by two parameters, VK and HK. The vertical contour VK is a contour lying in the yz-plane, and the horizontal contour HK is a contour lying in the xy-plane. The contours VK and HK comprise straight lines and / or curves with corresponding radii.

[0014] The xyz coordinate system serves only to better describe the invention and does not specify the orientation of the glass or glass-ceramic plate in space, e.g., in an installation situation. This also applies to the terms "bottom" and "top."

[0015] The plate has a contour line K, which is the outer circumference of the plate in plan view. The contour lines KR and KE are sections of this contour line K.

[0016] The corner angle W is spanned by the contour line KE.

[0017] Condition 1 applies to panels with one facet. In this case, there is only one remaining edge surface adjacent to the corner surface. The radius R of corner E tapers completely to the adjacent unmachined edge surface.

[0018] Condition 1 also applies to slabs with two facets. In this case, there are two remaining edge surfaces adjacent to the corner surface. Since the radius R of the corner E cannot completely taper off on either side of the corner surface, the corner angle W is smaller than the corner angle W for slabs with one facet.

[0019] This has an impact on the edge index, which is smaller than the edge index for plates with one facet.

[0020] It has been shown that panels with the claimed edge indices IN exhibit a larger corner angle W than is the case with the state of the art. This smooths out the contour line K at the transition from the corner surface to the remaining edge surface, which is also due to the low values ​​of the offset VY.

[0021] A further advantage is that, when the edge index is maintained, the contour line K, when projected into the xy plane, exhibits no discontinuities in the transition area from the contour line KR to the contour line KE. This significantly improves the visual appearance of the panel.

[0022] Preferably, for condition 1 0.4 ≤ IN ≤ 1.5 applies.

[0023] Preferably, the edge line KE has a distance ZE from the lower edge, where ZR < ZE.

[0024] Preferably, the following applies to the distance ZR of the contour line KR: DU ≤ ZR ≤ DO with DU = DR · 0.45 and DO = DR · 0.55.

[0025] Tests have shown that the edge strength of the remaining edge surface is greatest when the contour line KR is positioned centrally, ie z R = D R 2 If the limit value DU is undercut or the limit value DO is exceeded, the edge strength becomes significantly lower and is no longer tolerable.

[0026] Preferably DU = DR · 0.48 and DO = DR · 0.52.

[0027] Preferably, the corner has a profile PE and the remaining edge surface has a profile PR, wherein at least one of the profiles PE or PR has a round profile in the z-direction with at least one radius of curvature.

[0028] Such round profiles are called C-profiles. The contour line of a C-profile is the apex line.

[0029] C-profiles have the advantage that the transition to the two upper surfaces is not sharp-edged, thus improving the handling of the panels. They also reduce the panels' sensitivity to impact in this area.

[0030] Preferably, both profiles PE and PR are round profiles in the z-direction with at least one radius of curvature.

[0031] These C-profiles are preferably symmetrical to the centerline of the respective panel sections in the xy plane. Symmetrical C-profiles are characterized by good edge strength.

[0032] Instead of so-called C-profiles, other profiles can also be used, such as profiles with a flat surface with adjacent bevels and / or curves. Such profiles are referred to as V-profiles. V-profiles are preferably symmetrical to the centerline of the respective panel sections in the xy plane. The centerline forms the contour line.

[0033] The following plate parameters are preferred: D 2 mm to 5 mm, especially 4 mm DR 2.0 mm to 3 mm, especially 2.5 mm R 1.5 mm to 30 mm, especially 5 mm γ 80° to 100°, especially 90°

[0034] Grinding wheel radius RS 10 mm to 150 mm, especially 130 mm R 1 1.75 mm to 6 mm RR 1.75 mm to 6 mm

[0035] The glass-ceramic plate preferably has a glassy surface zone at least on the corner surface. The glassy surface zone preferably extends at least over the entire corner surface.

[0036] The amorphous (glassy) surface zone of a LAS glass-ceramic is understood to be a zone or layer directly on the glass-ceramic surface which, in contrast to the interior, i.e. the structure below this edge layer, does not have the HQMK (or other) crystals which are typically on average 20 nm to 100 nm in size, but is predominantly amorphous. For HQMK or KMK (keatite solid solutions), the essentially amorphous surface zone comprises a maximum of 10 vol.% crystals as the main crystal phase, i.e. at least 90 vol.% of the surface zone consists of a glassy matrix (detectable by grazing X-ray diffraction). The amorphous surface region particularly preferably comprises less than 1 vol.% crystals. In contrast, crystals in the essentially crystalline interior of the glass-ceramic article make up at least 70 vol.%, preferably at least 80 vol.%, particularly preferably at least 90 vol.%.

[0037] This layer can be detected either by grazing X-ray diffraction or by cross-sectional preparation and electron diffraction in a transmission electron microscope (TEM), or indirectly in a scanning electron microscope (SEM). For the SEM examination, the cross-section is first chemically etched with dilute hydrofluoric acid. Hydrofluoric acid attacks the glass phase of the LAS glass-ceramic significantly more than the HQMK / KMK crystals. This enhances the contrast of the crystals, and the grain boundaries of the crystals are visible in the SEM, allowing the expert to distinguish between the crystalline interior and the glassy surface area based on the structural differences visualized by X-ray diffraction and SEM / TEM.

[0038] The thickness of the glassy surface zone is in the range from 50 to 5000 nm, preferably from 250 to 3000 nm and particularly preferably from 300 to 1500 nm.

[0039] A transition zone mediates between the glassy edge region and the crystalline interior of the glass-ceramic article, with the number or proportion of crystals relative to the glassy matrix increasing toward the crystalline interior. The transition zone between the glassy edge region and the crystalline interior of the article is advantageously as small as possible. Due to the process according to the invention, it is preferably kept at less than 100 nm in thickness. Keeping the transition zone between the glassy edge region and the crystalline interior as small as possible increases the transmittance of the finished article. The sharper the transition between the two layers, the higher the transmittance.

[0040] In this glassy surface zone, the glass ceramic not only has a high degree of transparency but also a high degree of mechanical strength, which is particularly advantageous when used as a cooking surface.

[0041] Such high-strength, highly transparent glass-ceramic articles can be produced by a specific combination of nucleation and crystallization temperatures with specific residence times and a rapid cooling rate. Improvements in the above-mentioned properties are possible for starting glasses of different compositions. The advantages in terms of transparency and strength are particularly pronounced in lithium aluminosilicate glass-ceramics (LAS glass-ceramics).

[0042] A glass or glass-ceramic plate with a top surface and a bottom surface lying in the xy plane in an orthogonal xyz coordinate system, with a circumferential lower edge and a circumferential upper edge, with at least one first edge surface and at least one second edge surface, wherein the edge surfaces form an angle γ with one another, and with a curved corner surface of a corner E connecting both edge surfaces, which has a radius of curvature R with a center point M, a contour line KE and a corner angle W, wherein the top surface has a facet with a facet surface on at least one of the two edge surfaces, whereby a residual edge surface with a thickness DR and a contour line KR is formed on the edge surface, is characterized in that for a distance AR of the contour line KR from the center point M, 0.9 · R ≤ AR ≤ 1.1 · R applies.

[0043] Preferably 0.95 · R ≤ AR ≤ 1.05 · R.

[0044] According to a first embodiment, the object is also achieved by a method for producing a glass or glass-ceramic plate with the following steps in the following order: a) Providing a plate blank with a first top surface lying in an xy-plane in an orthogonal xyz coordinate system and a second top surface lying in a parallel xy-plane, and with at least one first edge surface and a second edge surface which form an angle γ with each other b) Pre-grinding at least the edge surfaces, wherein at least between the edge surfaces a corner surface with a corner radius R and a corner angle β of the grinding contour is produced, wherein on at least one edge surface an edge strip with a width B ZG adjacent to the corner surface and extending over the edge surface in the x- or y-direction is machined and wherein at least the edge surfaces, the corner surface and the edge strip are provided with a profile P 1, c) Faceting a top surface, wherein at least one,a facet is produced which runs towards the edge surface having the edge strip and the edge surface is reduced to a residual edge surface, d) grinding the residual edge surface, whereby the residual edge surface is provided with a profile PR.

[0045] The advantage of this process is that it creates an edge strip extending across the edge surface in the y-direction, so that in step d) when grinding the remaining edge, the corner surfaces are not shortened to the extent that is the case with conventional processes. The corner angle W can be tapered longer, which improves the aesthetic appearance. The same applies to edge strips extending in the x-direction.

[0046] When machining the edge strip, a straight edge strip section and a transition section with a transition section surface are preferably produced, with the transition section surface merging into the corner surface. Providing a transition section at both ends of the straight edge strip facilitates the production of the edge strip. The continuous course of the transition section prevents sharp edges on the edge strip.

[0047] Preferably, the transition section surface is manufactured with a radius of curvature R Ü.

[0048] Preferably, the radius of curvature R Ü is selected such that R Ü ≥ RS, where RS is the radius of a grinding wheel intended for pre-grinding.

[0049] When machining the edge strip, the corner angle β of the grinding contour is preferably set to 60° ≤ β ≤ 90°.

[0050] It has been shown that the corner angle β of the grinding contour influences the length in the y-direction of the transition surface, as well as the shape of the transition surface and the offset VY of the contour lines KR and KE in the y-direction. The smaller the value of β, the smaller the transition surface and thus also the value of VY. However, the angle β must not be chosen too small, as this would reduce the angle W too much.

[0051] Preferably, the grinding in process step d) in the region of the straight edge strip section of the edge strip is accompanied by a material removal B AT, where 0.1 · B ZG ≤ B AT ≤ 2 · B ZG. Preferably, 0.5 · B ZG ≤ B AT ≤ 1.5 · B ZG.

[0052] It has been shown that the amount of material removed (B AT) influences the length and size of the transition surface. It is preferable to set the amount of material removed (B AT) equal to the amount of material added (B ZG).

[0053] The width B ZG is preferably 0.2 mm to 2 mm, in particular 0.5 mm to 1 mm.

[0054] The object is achieved according to a second embodiment with a method for producing a glass or glass ceramic plate with the following steps in the following order: a) Providing a plate blank with a first top surface lying in an xy-plane in an orthogonal xyz coordinate system and a second top surface lying in a parallel xy-plane, with at least one first edge surface and a second edge surface which together form a corner with an angle γ and with a width B 1 and a length L 1 , wherein a material allowance of the width B ZG is taken into account on at least one edge surface, b) Pre-grinding at least the edge surfaces, wherein at least the edge surfaces are provided with a profile P 1 , c) Faceting a top surface, wherein at least one facet tapering to the edge surface having the material allowance B ZG is produced and the edge surface is reduced to a residual edge surface, d) Smoothing the residual edge surface, wherein the residual edge surface is provided with a profile PR, e) Smoothing the at least one corner,whereby a corner surface with a corner radius R and a corner angle of the grinding contour β is produced between the edge surfaces. ,

[0055] As in the first embodiment of the process, process step a) can start with a plate blank made of glass or glass ceramic. If a glass plate is provided for the production of a glass ceramic plate, the ceramization can be carried out after all process steps a) to e), as in the first embodiment of the process.

[0056] The key difference of the manufacturing process according to the second embodiment is that the corner surface(s) are manufactured at the end of the process. The advantage of this process is that, in process step b, a simplified edge grinding process can be used, in which two opposite edges are machined simultaneously, in a straight line, in a continuous process. Such processing machines are widely used in the glass industry for the simple processing of rectangular, flat panes. A defined corner radius is not added.

[0057] In this second embodiment, as in the first embodiment, a transition surface is also created because the profiles PE and PR have contour lines KE and KR offset in the z-direction.

[0058] By taking into account the material allowance B ZG, the dimension B 1 and / or the dimension L 1 has a corresponding excess compared to the final dimensions B and / or L, which is at least partially removed during the subsequent process steps by edge machining in order to finally obtain the final dimensions.

[0059] Preferably, the material allowance B ZG is considered such that at least B 1 = B 2 + n · B ZG and / or L 1 = L 2 + n · B ZG with n = 1 or n = 2 applies. Here, n = 1 is chosen if a facet is applied to only one edge surface. If facets are provided on two opposite edge surfaces, n = 2 is chosen.

[0060] Preferably, the material allowance with the width B ZG extends over the entire width B 1 and / or over the entire length L 1.

[0061] Preferably, the grinding in process step d) is accompanied by a material removal B AT, where 0.1 · B ZG ≤ B AT ≤ 2 · B ZG.

[0062] In particular, the grinding in process step d) is carried out with a material removal B AT , where B ZG = B AT .

[0063] Preferably, the method step e) is carried out by means of a grinding tool, wherein the grinding tool is guided around the corner starting from an edge surface until the corner angle β is reached and is then continuously removed over the remaining edge surface.

[0064] The grinding tool follows an S-shaped trajectory curve, whereby the transition surface is worked out in the remaining edge surface as the trajectory curve continuously runs out.

[0065] Preferably, the material allowance of the width B ZG is chosen to be so large that the profile P 1 applied in process step b) is completely replaced by the profile PR in process step d).

[0066] Preferably, the profile PR is manufactured as a profile with a radius of curvature RR.

[0067] Preferably, the PR profile is manufactured as a symmetrical profile.

[0068] Preferably, the profile of the corner radius PE is manufactured according to the profile P 1 of the adjacent edge surface.

[0069] Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. They show: Figure 1a shows a plan view of a plate blank according to process step a) according to the first and second embodiment of the process, Figure 1b shows a partial section along the line I-II in Figure 1a by the blank according to Fig. 1a, Figure 2a the top view of a plate blank after carrying out the process step b) according to the first embodiment of the method, Figure 2b a section through the machined blank along the line I-II in Figure 2a , Figure 2c an enlarged view of the upper edge area of ​​the machined blank from Figure 2a according to a first embodiment, Figure 2 shows an enlarged view of the upper left corner area of ​​the machined blank from Figure 2a according to a further embodiment, Figure 2e shows an enlarged view of the upper left corner area of ​​the machined blank from Figure 2a with grinding wheel for carrying out process step b), Figure 2 fine perspective view of a corner area of ​​the Figure 2ashown blank, Figure 3a the top view of the machined blank after performing the faceting according to process step c) according to the first embodiment of the method, Figure 3b a section through the machined blank along the line I-II in Figure 3a , Figure 3c a perspective view of a corner area of ​​the machined blank according to Figure 3a , Figure 4a a plan view of the finished plate after sanding according to process step d) according to the first embodiment of the method, Figure 4b an enlarged view of the upper right corner area of ​​the plate from Figure 4a , Figure 4c shows a section through the plate along the line I-II in Figure 4b , Figure 5 a section through a blank and through a finished plate to explain the width B ZG , Figure 6 a perspective view of a corner of a glass or glass ceramic plate according to Fig. 4a, Figure 7 shows a perspective view of a corner of a plate according to a further embodiment, Figure 8 shows a perspective view of a corner of a plate according to a further embodiment, Figure 8a shows an enlarged view of the corner of Fig. 7 , Figure 9 shows a perspective view of a corner of a plate according to a further embodiment, Figure 10 shows a perspective view of a corner according to a further embodiment, Figures 11 to 13 show plan views of a blank and a finished plate having two facets, each after the method steps b), c) and d), corresponding to the Figures 2a , 3a and 4a, Figure 14 is a perspective top view of a corner of a plate with two facets, Figure 15 is a perspective view of a corner of a plate with two facets according to a further embodiment, Figure 16 is a perspective view of a corner of a plate according to the prior art, Figure 17 is a perspective view of a corner of a plate according to the Figure 9 , Figure 18a a perspective view of a corner of a plate with a view of the underside according to the prior art, Figure 18b a plan view of the underside of the Fig. 18a shown plate according to the prior art, Figure 19a a perspective view of a corner of a plate with a view of the underside, Figure 19b a plan view of the underside of the plate shown in Fig. 19ashown plate, Figure 20a the top view of a plate blank after carrying out the process step b) according to the second embodiment of the method, Figure 20b a section through the machined blank along the line I-II in Figure 20a , Figure 21a the top view of the machined blank after carrying out the faceting according to process step c) according to the second embodiment of the method, Figure 21b a section through the plate along the line I-II in Figure 21a , Figure 22a a plan view of the plate after grinding according to process step d) according to the second embodiment of the method, Figure 22b a section through the plate along the line I-II in Figure 22a, Figure 23 is a plan view of the finished plate after sanding according to method step e) according to the second embodiment of the method, and Figure 24 is a perspective view of a corner to explain method step e) according to the second embodiment of the method.

[0070] In the Figure 1a The top view of a blank 200 is shown, which can be made of glass or glass ceramic. The blank 200 consists of a rectangular plate with a thickness D, a width B 1 and a length L 1 as well as opposite first edge surfaces 210 and opposite second edge surfaces 220, all of which are unmachined. The blank 200 has a first top surface 2 and a second top surface 3, which are arranged parallel to each other and lie in xy planes (see Figure 1b). In a built-in situation, e.g. in a hob, the first top surface 2 can form the top side and the second top surface 3 can form the bottom side.

[0071] In Figure 2a The top view of the blank 200 is shown after a first edge processing has been carried out. This is the pre-grinding according to process feature b), whereby between the edge surfaces 210 and 220 a corner surface 230 with a corner radius R and a corner angle of the grinding contour β has been produced (see Figure 2c ).

[0072] Since each edge processing operation involves material removal, the width and length of the blank 200 have decreased. The length L 1 of the blank 200 has been shortened to the length L, which corresponds to the final dimension of the finished plate 1, because the length L is not changed by the subsequent process steps.

[0073] The width B 1 has been reduced to the width B 3. By machining an edge strip 240, the width B 3 is composed of a width B 2 and a width B ZG of the edge strip 240. The width B ZG refers to the material allowance, which is at least partially removed again after process step c) in the last process step d). This material removal is referred to as B AT, which in the Figures 4a and 4b is shown. The final dimension B is only reached after process step d).

[0074] During edge processing according to process step b), all edge surfaces, i.e. the edge surfaces 210 and 220 as well as the 4 corner surfaces 230 are provided with a profile P 1. As shown in the sectional view of the Figure 2b As can be seen, it is a round profile with a radius of curvature R 1 (see also Fig. 2f and Fig. 5), which is referred to as a C-profile. In the illustration shown here, the C-profile is symmetrical to the center line MP of the blank 200.

[0075] In the Figure 2c The upper edge region of the machined blank 200 from Figure 2a is shown enlarged. The first edge surfaces 210 each merge into a corner surface 230 of the corner E, which extends over the corner angle β. In the embodiment shown here, the corner angle β is 90°, which corresponds to the angle γ between the first edge surfaces 210 and the second edge surfaces 220.

[0076] The corner surfaces 230 of the corners E merge at the tangent point 248 into the edge strip 240, which consists of a straight edge strip section 242 and two transition sections 244 with transition section surfaces 250 adjacent to the straight edge strip section 242. The connecting line 243 connects the two tangent points 248.

[0077] The transition sections 244 have a radius of curvature R Ü , which can be equal to the radius RS of the grinding wheel 300 used for process step b), as shown in the Figure 2e is shown.

[0078] In the Figure 2d A further embodiment is shown in which the corner angle β is approximately 70°. The edge strip 240 thus extends into the corner area and shortens the adjacent corner surface 230.

[0079] The perspective representation in Figure 2f shows a corner E of the machined blank 200 according to the Figure 2c . Since the blank 200 was provided with a circumferential C-profile P 1, the apex lines of the surfaces 210, 220, 230 form a closed contour line K.

[0080] The Figure 3ashows a machined blank 200 in plan view after process step c), in which a facet 40, which has a facet surface 42 and a facet edge 44, has been produced on the second edge surface 220, on which the edge strip 240 is located. The corresponding cross section in the edge region of the blank 200 is shown in the Figure 3b shown. In this process step, the width of the second edge surface 220 has decreased to the remaining edge surface 220a.

[0081] The perspective representation in the Figure 3c shows a corner E of the machined blank 200 according to the Figure 3a .

[0082] The Figure 4a shows a plan view of the finished plate 1 with the edge surfaces 10, 20, 60 and the final dimensions B and L after process step d), in which the remaining edge surface 220a was ground. In process step d), the remaining edge surface 60 was provided with the profile PR, which - like the Figure 4cshows - is also a C-profile. The ground residual edge surface 60 has a thickness DR.

[0083] During grinding, material was removed from the edge strip 240, which is marked by the width B AT (see also Figure 4b ).

[0084] How the material removal should preferably be determined is described in Figure 5 which shows a section through a blank 200 in combination with a section through a finished plate 1. Figure 5 shows the blank 200 with the second edge surface 220 after process step b) and the finished plate with the remaining edge surface 60 after process step d), ie after grinding the remaining edge.

[0085] Profile P 1 is a C-profile, just like profile PR . Profiles P 1 and PR have the corresponding radii R 1 and RR . The contour lines of profiles P 1 and PR are vertex lines S 1 and SR . P h1 and P h2 denote the profile heights in the x-direction.

[0086] ZR denotes the distance of the contour line KR , which corresponds to the vertex line SR of the remaining edge surface 60, from the circumferential lower edge 100 in the xy plane of the second upper side surface 3. Z 1 denotes the distance of the contour line K 1 , which corresponds to the vertex line S 1 of the edge surface 10, from the circumferential lower edge 100. ZE denotes the distance of the contour line KE , which corresponds to the vertex line SE of the corner surface 30, from the circumferential lower edge 100.

[0087] The material allowance of the width B ZG is calculated as follows: B ZG ≥ P h 1 − P h 2 wobei P h 1 = R 1 − R 1 2 − z 1 und P h 2 = R R − R R 2 − z R ist .

[0088] B ZG is preferably at least wide enough so that the profile PR of the residual edge surface 60 lies within the profile P 1 of the pre-grinding.

[0089] The material removal of the width B AT is preferably B ZG ≤ B AT , in particular B AT = B ZG and influences the value VY , ie the offset of the contour line KR to the contour line KE , as shown in the Figure 6 can be seen.

[0090] The Figure 6 shows a perspective view of a corner E of a glass or glass ceramic plate 1 after all process steps a) to d) have been carried out.

[0091] The glass ceramic plate 1 has the circumferential lower edge 100 and the circumferential upper edge 110. The facet 40 is bounded by the upper edge 21 and the facet edge 44. The corner surface 30 of the corner E is bounded by the boundary line 33, the upper edge 31, the lower edge 32, and the boundary lines 34 and 52.

[0092] At least the corner surface 30 and the transition surface 50 have a glassy surface zone.

[0093] The explanations to the Figure 6 The left corner E of the plate 1 shown also applies accordingly to a second, right corner of the plate 1 as well as to further corners of a plate 1 if further facet surfaces 40 are provided.

[0094] The parameters were chosen as follows: D = 4 mm, DR = 2.5 mm, R = 5 mm, γ = 90°, β = 90°, B ZG = 0.5 mm, B AT = 0.5 mm. P 1 and PR are each a C-profile with the radii of curvature R 1 = 3 mm and RR = 3 mm. Facet 40 has a facet angle α of 8.5° and a facet width of 10 mm. The angles γ and β refer to the center point M.

[0095] The parameters of the corresponding blank correspond to the Figure 2c shown top view of a blank 200.

[0096] In the Figure 6The horizontal contour HK 1 and the vertical contour VK 1 of the profile P 1 are shown, as are the vertical contour VK E and the horizontal contour HK E of the profile PE. The profile PR comprises the horizontal contour HK R and the vertical contour VK R. The transition surface 50 has the profile P Ü with the contours VK Ü and HK Ü. The profiles P 1 , PE and PR are C-profiles with the contour lines K 1 , KE and KR , which are identical to the vertex lines S 1 , SE and SR.

[0097] It can be seen that the angle γ = 90° has decreased to the angle W = 78.8°, with the vertical offset Vz = 0.75 mm and the horizontal offset VY = 5.95 mm. The corner angle W is defined by the contour line KE.

[0098] The residual edge surface 60 has a transition surface 50, which has a profile P Ü that deviates from the profile PR. The transition surface 50 is a remnant of the transition section 244 that was not machined during the grinding of the residual edge. As the material removal B AT is increased, the size of the transition surface 50 also decreases. With increasing material removal, both the corner angle W and VY change, as shown in the Figure 7 The material removal is 0.6 mm, so the angle W is reduced to 73.9°. VY is 1.17 mm.

[0099] In the Figure 8 Another embodiment is shown in which the corner angle β of the grinding contour was chosen to be β = 82° (see also Figure 2d ). The remaining parameters of plate 1 correspond to the Figure 6 .

[0100] The transition area 50 in the Fig. 8 is just like in the Figure 6triangular and has corners 58a, b, c. The transition surface 50 is bounded by the lower edge 56 and the two boundary lines 52 and 54, which gives the transition surface 50 a "sail-shaped" appearance. The two contour lines KE and KR are connected by the connecting contour line KV, which is formed from a section of the boundary line 54 and a section of the boundary line 34. The boundary lines 34, 54, and 52 meet at an intersection point 59. The contour line KV is thus largely determined by the shape of the transition surface 50.

[0101] The intersection point 59 lies between the contour lines KE and KR . The length of the contour line KV is characterized by the horizontal offset VY, as shown in Fig. 8a where the offset VX and the offset VZ are also shown.

[0102] In the Figure 9Another embodiment of a plate 1 is shown, the angle β is 78.8°. The other parameters correspond to the plate from the Figure 8 . Due to the reduction of the corner angle β of the grinding contour, the intersection point 59 has moved upwards and, in this embodiment, lies on the contour line KE .

[0103] In the Figure 10 Another embodiment is shown in which the radius R of the corner angle is 10 mm. The angle β of the grinding contour is 82.1°, as is the angle W. It can be seen that the transition surface 50 has the same shape as in Figure 9 . In the embodiment of the Figure 10 the offset VY is 1.33 mm, while the offset Vy in the Figure 9 is 0.95 mm.

[0104] The Figures 11 to 13 correspond to the Figures 2a , 3a and 4a and concern a plate with two facets 40.

[0105] In the Figure 11The blank 200 is shown, which has an edge strip 240 on an edge surface 220 and on an edge surface 210. The angle β of the grinding contour is 90°. The top view of the plate in Figure 11 shows the blank after process step b). The material allowances B ZG are the same for both edge strips 240. The length L 2 denotes the length without the material allowance, and the length L 3 denotes the length of the blank after pre-grinding.

[0106] In the Figure 12 The blank is shown after faceting according to process step c). The two facets 40 adjoin each other at corner E.

[0107] In the Figure 13 The finished plate 1 is shown after performing process step d). A perspective view of the corner E of the Figure 13 is in the Figure 14can be seen. Due to the double beveling, the corner angle W has been reduced to 67.6°. The material allowance is 0.5 mm, the material removal is 0.5 mm, and the grinding wheel radius R Ü is 130 mm. The horizontal offset VY is the same on both facets at 5.93 mm.

[0108] In the Figure 15 another embodiment of a plate 1 with two facets 40 is shown. While in the Figure 14 the angle β of the grinding contour is 90°, the angle β in the embodiment according to the Figure 15 at 67.6°. The corner angle W is also 67.6°.

[0109] The Figure 16 shows a plate 1' according to the state of the art and the Figure 17 a plate 1, as in Figure 9 In both Figures 16 and 17The distance AR was drawn, which denotes the distance of the contour line KR from the center point M of the corner E. Both plates 1 and 1' have the same dimensions D, DR, R, ZE, ZR, P 1, PE, PR. It can be seen that the angle W of plate 1, at 78.8°, is significantly larger than the angle W of plate 1' with W = 61.8° according to the state of the art.

[0110] A further significant difference is the distance AR of the edge line KR of the remaining edge surface 60 from the center point M of the corner E, which corresponds to the corner radius R of the corner E. By grinding the remaining edge surface 60 according to the prior art methods, the distance AR is significantly reduced by the associated material removal B AT, since the material allowance B ZG is not applied separately as an edge strip, which has a corresponding influence on the angle W. In the method according to the invention, the targeted material addition in the form of the edge strip 240 and the subsequent material removal B AT with preferably B AT = B ZG ensures that the distance AR = R.

[0111] The following table shows the data of the plates from the Figures 6 , 7 , 8 , 9 , 10 and 14 to 16 summarized: D [mm] DR [mm] R [mm] γ [°] β [°] B ZG [mm] B AT [mm] VZ [mm] VY [mm] W [°] Number of facets WN IN [mm -1< ] Fig. 6 4 2,5 5 90 90 0,5 0,5 0,75 5,95 78,8 1 0,87 0,15 Fig. 7 4 2,5 5 90 90 0,5 0,6 0,75 1,17 73,9 1 0,82 0,70 Fig. 8 4 2,5 5 90 82 0,5 0,5 0,75 1,28 78,8 1 0,88 0,68 Fig. 9 4 2,5 5 90 78 ,8 0,5 0,5 0,75 0,95 78,8 1 0,88 0,92 Fig. 10 4 2,5 10 90 82 ,1 0,5 0,5 0,75 1,33 82,1 1 0,91 0,69 Fig. 14 4 2,5 5 90 90 0,5 0,5 0,75 5,95 67,6 2 0,75 0,13 Fig. 15 4 2,5 5 90 67 ,6 0,5 0,5 0,75 0,95 67,6 2 0,75 0,79 Fig. 16 4 2,5 5 90 90 0 0,5 0,75 0,42 61,8 1 0,69 1,63

[0112] The table shows that the edge index of plate 1' with the value 1.63 is outside the claimed range for the edge index IN.

[0113] In the Fig. 18a The underside of a corner E of the plate 1' is shown in perspective according to the prior art. Fig. 18b shows the top view of the Fig. 18a shown plate 1'. The three surfaces 10, 30 and 60 in the edge area of ​​plate 1' are clearly visible.

[0114] The Fig. 19a and 19b show the Fig. 18a and 18b corresponding representations for a plate 1 according to the invention. The bottom views differ by the additional transition surface 50.

[0115] In the Figures 20a to 24 the process steps according to the second embodiment of the process are shown.

[0116] The Fig. 1also illustrates the initial situation according to process step a) for this second embodiment of the process, with the difference that a material allowance B ZG was taken into account for the width B 1 of the blank.

[0117] The Fig. 20a shows the top view of the plate blank 200 after performing process step b) according to the second embodiment of the method. The material allowance B ZG extends over the entire length L. Due to the pre-grinding of the edge surfaces, the width B 1 has been reduced to the width B 3 .

[0118] The Figure 20b shows a section through the machined blank 200 along the line I-II in Figure 20a so that profile P 1 can be seen.

[0119] The Figure 21a shows the top view of the machined blank after faceting according to process step c). The sectional view along the line I-II in Fig. 21a shows the Fig. 21b .

[0120] The Figure 22a shows the top view of the plate after grinding the remaining edge surface 60 according to process step d) and Figure 22b shows the section through the plate along the line I-II in Figure 22a so that the profile PR can be seen

[0121] The Figure 23 shows a plan view of the finished plate 1 after sanding the corner E according to process step e).

[0122] In the Fig. 24 The dashed line shows the movement path 400 of a grinding tool (not shown) for producing the rounding of corner E and transition surface 60. In the illustration shown here, the movement curve is essentially S-shaped. List of reference symbols

[0123] 1 Glass or glass-ceramic plate 1' Glass or glass-ceramic plate according to the state of the art 2 First top surface 3 Second top surface 10 First edge surface 20 Second edge surface 21 Upper edge 30 Corner surface 31 Upper edge 32 Lower edge 33 Boundary line 34 Boundary line 40 Facet 42 Facet surface 44 Facet edge 50 Transition surface 52 First boundary line 54 Second boundary line 56 Lower edge line 58a,b,c Corners of the transition surface 59 Intersection point 60 Remaining edge surface 100 Circumferential lower edge 110 Circumferential upper edge 200 Blank 210 First edge surface 220 Second edge surface 220a Remaining edge surface 230 Corner surface 240 Edge strip 242 Straight edge strip section 243Connecting line 244Transition section 248Tangent point 250Transition section surface 300Grinding tool, grinding wheel 400Movement path of the grinding tool BWidth Final dimension of the plate 1 B 1 Width of the blank B 2 Width of the blank without material allowance B 3 Width of the blank after pre-grinding B ZG Width of the material allowance B AT Width of theMaterial removal L Length Final dimension of the plate 1 L 1 Length of the blank L 2 Length of the blank without material addition L 3 Length of the blank after pre-grinding W Corner angle α Facet angle β Corner angle of the grinding contour γ Angle between first edge surface 10, 210 and second edge surface 20, 220 P 1 Profile PR Remaining edge profile PE Corner profile P Ü Profile of the transition surface R 1 Radius of curvature of the profile P 1 RR Radius of curvature of the profile PR HK 1 Horizontal contour of profile P 1 VK 1 Vertical contour of profile P 1 HK R Horizontal contour of profile PR VK R Vertical contour of profile PR HK E Horizontal contour of profile PE VK E Vertical contour of profile PE HK Ü Horizontal contour of profile P Ü VK Vertical contour of profile P Ü K Contour line K 1 Contour line of the first edge surface KE Contour line of the corner KR Contour line of the residual edge KV Connecting contour line RE Corner radius RS Radius of the grinding wheel R Ü Radius of the transition surface section S 1 first apex line S 2 apex line SRVertex line of the remaining edge SE Vertex line of the corner EP h1 Profile height in x-direction P h2 Profile height in x-direction VY Horizontal offset of the contour lines KE and KRVZ Vertical offset of the contour lines KE and KRVX Offset of the contour lines KE and KR in x-direction DDickness of the panel DR Thickness of the panel at the remaining edge surface MCenter point of the corner angle WMP Center line of the panel Z 1 Distance of the contour line K 1 from the bottom edge 100 ZR Distance of the contour line KR from the bottom edge 100 ZE Distance of the contour line KE from the bottom edge 100 AR Distance KR from M EEcone

Claims

1. Glass or glass ceramic plate (1) with a first upper surface (2) lying in the xy plane in an orthogonal xyz coordinate system and a second upper surface (3), with a circumferential lower edge (100) and a circumferential upper edge (110) with at least one first edge surface (10) and at least one second edge surface (20), wherein the edge surfaces (10, 20) together form an angle γ, and with a curved corner surface (30) connecting both edge surfaces (10, 20) of a corner E with a radius of curvature R, with a contour line KE and with a corner angle W, wherein the upper surface (2) has a facet (40) with a facet surface (42) on at least one of the two edge surfaces (10, 20), whereby a remaining edge surface (60) with a thickness DR and a contour line KR is formed on the edge surface (10, 20), wherein the contour line KR has a distance zR from the lower edge (100), characterised in that the plate (1) has an edge index I N = W N V Y at the corner E and the adjacent remaining edge surface (60) with W N = W γ and VY ≠ 0, wherein Vy in mm is the distance between the contour lines KR and KE in the y-direction and IN in mm-1 is: 0.1 ≤ I N ≤ 1.5 .

2. Glass or glass ceramic plate (1) according to claim 1, characterised in that the corner surface (30) has a profile PE and the remaining edge surface (60) has a profile PR and that at least one of the profiles PE or PR is a round profile in the z-direction with at least one radius of curvature.

3. Glass or glass ceramic plate according to claim 2, characterised in that both profiles PE and PR are a round profile in the z-direction with at least one radius of curvature.

4. Method for producing a glass or glass ceramic plate (1) with the following steps in the following order: a) Providing a plate blank (200) - with a first upper surface (2) lying in an xy plane in an orthogonal xyz coordinate system and a second upper surface (3) lying in a parallel xy plane, and - with at least one first edge surface (210) and one second edge surface (220) which together form an angle y, b) Pre-grinding at least the edge surfaces (210, 220), - wherein a corner surface (230) with a corner radius R and a corner angle β of the grinding contour is produced at least between the edge surfaces (210, 220), - wherein an edge strip (240) with the width BZG, which borders on the corner surface (230) and extends over the edge surface (210, 220) in the x- or y-direction, is machined on at least one edge surface (210, 220) and - wherein at least the edge surfaces (210, 220), the corner surface (230) and the edge strip (240) are provided with a profile P1, c) Facetting an upper surface (2, 3), wherein at least one facet (40) extending to the edge surface (210, 220) having the edge strip (240) is produced and the edge surface (210, 220) is reduced to a remaining edge surface, d) Grinding the remaining edge surface, wherein the remaining edge surface is provided with a profile PR.

5. Method according to claim 4, characterised in that when machining the edge strip (240), a straight edge strip section (242) and a transition section (244) with a transition section surface (250) are produced, wherein the transition section surface (250) extends to the corner surface (230).

6. Method according to one of claims 4 or 5, characterised in that when machining the edge strip (240), the corner angle β of the grinding contour is set to 60° ≤ β ≤ 90°.

7. Method according to one of claims 4 to 6, characterised in that the grinding in method step d) in the region of the straight edge strip section (242) of the edge strip (240) involves a material removal BAT, wherein 0.1 · BZG ≤ BAT ≤ 2 · BZG.

8. Method for producing a glass or glass ceramic plate (1) with the following steps in the following order: a) Providing a plate blank (200) - with a first upper surface (2) lying in an xy plane in an orthogonal xyz coordinate system and a second upper surface (3) lying in a parallel xy plane, - with at least one first edge surface (210) and one second edge surface (220) which together form a corner E with an angle γ, and - with a width B1 and a length L1, wherein a material allowance of the width BZG is taken into account on at least one edge surface (210, 220), b) Pre-grinding at least the edge surfaces (210, 220), - wherein at least the edge surfaces (210, 220) are provided with a profile P1, c) Facetting an upper surface (2, 3), - wherein at least one facet (40) extending to the edge surface (210, 220) having the material allowance BZG is produced and the edge surface (210, 220) is reduced to a remaining edge surface (60), d) Grinding the remaining edge surface (60), - wherein the remaining edge surface (60) is provided with a profile PR, e) Grinding the at least one corner E, - wherein a corner surface (230) with a corner radius R and a corner angle of the grinding contour β is produced between the edge surfaces (210, 220).

9. Method according to claim 8, characterised in that the material allowance of the width BZG extends over the entire width B1 and / or length L1.

10. Method according to one of claims 8 or 9, characterised in that the grinding in method step d) involves a material removal BAT, wherein 0.1 · BZG ≤ BAT ≤ 2 · BZG.

11. Method according to at least one of claims 8 to 10, characterised in that method step e) is carried out using a grinding tool, wherein the grinding tool (300) is guided around the corner E starting from an edge surface (210, 220) until the corner angle β is reached and is then continuously removed over the remaining edge surface (60).

12. Method according to one of claims 4 to 11, characterised in that the width BZG is selected to be sufficiently large that the profile P1 of the edge strip (240) is completely replaced by the profile PR in method step d).

13. Method according to one of claims 4 to 12, characterised in that the profile of the corner radius PE is produced according to the profile P1 of the adjacent edge surface (210, 220).