Method for continuously producing glass ingots made of optical glass compositions

Abstract

The present invention provides a method and apparatus capable of manufacturing glass ingots with high homogeneity. [Solution] The present invention relates to a method for continuously manufacturing glass ingots (2) according to a continuous casting method. In this method, liquid molten optical glass is supplied from a supply device (3) into a mold (5) to form glass strands (6), which are supplied via a conveyor belt (7) to a cooling device (9), and then to a cutting device, where the cooled glass strands (6) are divided to form individual glass ingots (2). In this method, the projection of the outer shell of the glass strands (6) is continuously determined by a non-contact measuring device (10) at the latest before the glass strands (6) are supplied into the cooling device (9), and parameters, namely the supply device temperature and / or conveyor belt speed, are adjusted based on the obtained values.

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for continuously producing glass ingots, particularly glass ingots made of optical glass compositions. In a further aspect, the present invention relates to glass ingots, and more particularly to the use of glass ingots for manufacturing optical elements. [Background technology]

[0002] The production of glass ingots, particularly optical glass, is generally known from the prior art and is typically carried out by a horizontal continuous casting method, in which molten liquid glass taken from a supply device is supplied into a mold, a so-called ingot draw shaft. In most cases, the molten liquid glass supplied to the ingot draw shaft in the center spreads out in the width direction to form glass strands, which are then supplied to a cooling device via a conveying device, such as a conveyor belt.

[0003] In the case of ingot manufacturing, particular importance regarding quality requirements lies in the precision of the ingot's cross-sectional shape, prevention of cracks and indentations, and the highest possible optical homogeneity without Schlieren defects.

[0004] In particular, achieving the highest possible optical homogeneity is currently not possible solely through process technology, because there are no measuring devices that enable direct control of the process.

[0005] According to conventional measurement methods, measurements can only be taken intermittently at the end of the manufacturing process, that is, after the glass strand has passed through the heat treatment furnace and been divided into individual glass ingots. However, measuring at the cold end of the glass strand results in wasted measurement time due to the passage time in the heat treatment furnace, which can range from several minutes to several hours. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Therefore, the fundamental problem of the present invention is to provide a method and apparatus that overcome the shortcomings of the prior art. In particular, the fundamental problem of the present invention is to provide a method and apparatus that can manufacture glass ingots having the highest possible homogeneity. [Means for solving the problem]

[0007] According to the present invention, this problem is solved by a method having the features described in the claims.

[0008] Dependent claims describe further advantageous embodiments of the invention. Multiple features individually described in the dependent claims can be combined in technically meaningful ways to define further embodiments of the invention. In addition, the features described in each claim are described in detail and strictly within the specification, in which further preferred embodiments of the invention are shown.

[0009] The method according to the present invention is suitable for the continuous production of glass ingots made of a glass composition and is carried out according to a continuous casting method. In this case, first, molten liquid glass is supplied from a supply device into a mold to form glass strands, which are supplied to a cooling device via a conveying device, particularly a conveyor belt, and then to a cutting device, in which the cooled glass strands are divided to form individual glass ingots. According to the present invention, the following is proposed: at the latest before the glass strands are supplied into the cooling device, the projection of the outer dimensions of the glass strands is continuously determined by a non-contact measuring device, and based on the obtained values, parameters, namely the supply device temperature and / or conveying speed, particularly the conveyor belt speed, are adjusted.

[0010] Similarly, the present invention relates to an apparatus for continuously manufacturing glass ingots made of a glass composition. The apparatus includes a feeding device for supplying molten liquid glass into a mold, preferably into a tank or groove, so that glass strands are formed; a conveying device, particularly a conveyor belt, for transporting the glass strands; a cooling device for cooling the glass strands; and a cutting device capable of dividing the cooled glass strands so that individual glass ingots are formed. According to the present invention, the apparatus includes a measuring device positioned prior to the cooling device, which can continuously and non-contact determine the projection of the outer dimensions of the glass strands, particularly those on the conveying device, and based on the values ​​thus obtained, parameters, namely the feeding device temperature and / or the transport speed, can be adjusted.

[0011] The fundamental understanding on which this invention is based is that, by continuously monitoring the maximum extension of a high-temperature glass strand, it is possible to stabilize the method by directly adjusting the parameters, insofar as it is possible to achieve a glass ingot with particularly high homogeneity, especially with respect to the height and refractive index of the ingot.

[0012] Preferably, each glass ingot has a refractive index nD of up to 0.001 per ingot for the refractive index at 589 nm, and more preferably up to 6*10 per ingot. -4 , most preferably up to 3*10 per ingot -4or even worse, the ingot has a refractive index dispersion of up to 0.0001 nD. Refractive index dispersion is the difference between the maximum and minimum refractive index measured within a single ingot. The refractive index can be measured, for example, by refractive index measurements at at least four, at least eight, at least twelve, or at least twenty locations, particularly evenly distributed throughout the ingot. A refractive index as homogeneous as possible is advantageous, especially for optical applications of glass, because particularly precise optical elements can be manufactured from such ingots.

[0013] According to one embodiment, the projection of the outer dimensions of a glass strand is determined by a measuring device used in accordance with the present invention. If the formed glass strand has sufficient intrinsic illumination and emits light, that light can be detected by the measuring device. In the case of glass that does not have sufficient intrinsic illumination, an illumination means can be advantageously used. In this case, it is necessary to distinguish between transparent optical glass and opaque optical glass in the visual domain.

[0014] According to one embodiment, for example, in the case of transparent glass, a focusing light source, such as a white LED light source, is oriented so as to be focused on a point in a supply device. Because the glass is transparent, its photoconductivity can be utilized. Light taken in from the light source through the glass strand is emitted, and therefore this light can be detected.

[0015] According to another embodiment, for example, in the case of opaque glass, that is, glass that absorbs light in the visual field, the light source is oriented such that illumination that produces stripes is possible, in particular, so as to maximize the contrast between the background and the illuminated glass strand.

[0016] An "opaque" glass is a glass having a transmittance of less than 10% over the spectral range of 380 to 780 nm under the conditions of the method according to the invention at the observation position. Transmittance is the intensity of the light incident at the measuring device relative to the intensity of the light emitted from the light source in the direction of the measuring device. The transmittance of the glass at the observation position can be easily determined if the pure transmittance of the glass is known. Glasses with relatively high transmittance are considered "transparent" herein.

[0017] Alternatively, illumination means in the near-infrared region or the ultraviolet region can also be used to illuminate the glass strand, especially when the glass has a transmittance of at least less than 10% under the aforementioned conditions in individual wavelength ranges.

[0018] Preferably, the measuring device or the measuring direction is arranged substantially perpendicular to the longitudinal axis of the glass strand so that the heightwise extension of the glass strand can be determined. One or more measuring devices can be used. Alternatively or additionally to a measuring device having a measuring direction substantially intersecting the longitudinal axis of the glass strand, a second measuring device can be used. The second measuring device can also have a measuring direction substantially perpendicular to the longitudinal axis of the glass strand. However, other arrangements of one or more measuring devices are also within the scope of the present invention. In particular, when two or more measuring devices are used, triangulation can be carried out. For example, the thickness of the glass strand can be determined at various measuring points across the entire width, i.e., along the width direction of the glass strand.

[0019] According to one embodiment, at least one measuring device is oriented such that the measuring device can capture the width of the glass strand. For example, one measuring device can be arranged substantially above the glass strand.

[0020] In one embodiment, it is proposed to use a contactless measuring device, particularly preferably an optical measuring device formed in the form of a CMOS camera.

[0021] A further optical measuring device for determining the projection of the outer dimension of the glass strand preferably includes a confocal interferometer or a laser device, which, according to one embodiment, determines the projection of the outer dimension of the glass strand according to the triangulation method. The laser device can use one or more wavelengths, and the projection images of those wavelengths can be optionally shaped as points or lines.

[0022] According to a further advantageous embodiment, the measuring device is a radiation measuring device for measuring the absorption of beta rays and / or an ultrasonic-based measuring device such as ultrasonic ToF, for example.

[0023] According to a particularly preferred embodiment, the outer dimension of the glass strand is determined using image processing that utilizes the differential of the contrast threshold. The obtained data can be displayed to an operator, for example.

[0024] In this way, the outer dimension of the glass strand or the elongation of the glass strand can be measured at the latest before the hot glass strand is supplied to the cooling device, that is, immediately before or after forming, and thus the maximum outer dimension of the glass strand in the direction intersecting the pulling device or the conveying device, or the time-dependent change in the maximum elongation of the glass strand in a continuous process, and / or an indirect measurement quantity assuming further boundary conditions, such as a direct measurement quantity, can be derived. The indirect measurement quantity is the volume flow when the glass strand width and the conveying speed are predefined, and the mass flow when the thickness is predefined. Thus, continuous monitoring enables the volume flow, the mass flow, and / or the extrusion amount to be kept constant.

[0025] According to one embodiment, the glass is 10 4 ~10 13The outer dimensions of a glass strand are determined during a manufacturing process section with a temperature corresponding to a viscosity of dPas. The viscosity of glass is temperature-dependent. The relationship between viscosity and temperature is described using a VFT curve (Vogel-Fulcher-Tammann equation). If this relationship is not known for a particular glass, viscosity measurements can be determined according to the applicable section of DIN ISO 7884 for each viscosity range.

[0026] Thus, by continuously monitoring the stretching of the glass strands, the production of oversized dimensions is suppressed, under-stretching of the glass strands is prevented, and in addition, height fluctuations along the ingot are reduced.

[0027] Therefore, this measuring device reduces wasted time, allowing the dimension to be controlled by the transport speed or extraction speed and / or the supply device temperature. Thus, direct control is possible, resulting in particularly high refractive index invariance and low Schlieren formation in glass ingots. Furthermore, it was found that glass ingots have particularly low fragility.

[0028] The term "fracture vulnerability," in the spirit of this invention, refers to the brittleness required in a glass strand that is still hot and present on a conveying device. To identify fracture vulnerability, a metal measuring contact is used, and a crack is formed in the still hot glass strand when the measuring contact touches it. In this case, the crack is caused by the spontaneously occurring temperature difference between the metal measuring contact, which has been heated to ambient temperature, and the glass strand, which is hot at approximately 300°C. Surprisingly, it has been found that the cracks formed by the metal measuring contact can be reduced by up to 15%, preferably up to 25%, compared to glass strands manufactured according to conventional methods.

[0029] Since using a measuring contact can damage the ingot, this type of contact is preferably not used in the method of the present invention. Rather, the advantage of this method is that the dimensions of the ingot can be determined without using a measuring contact. This further reduces the risk of damage to the ingot, which is certainly reduced but still exists.

[0030] In a further preferred embodiment, the glass strand is guided through a roller device comprising at least one bottom roller and at least one top roller before being measured by a non-contact measuring device, thereby forming a rolled glass strand. In this embodiment, the projection of the outer dimensions of the rolled glass strand is continuously determined using the non-contact measuring device. Based on the obtained values, parameters such as the feed device temperature and / or conveyor belt speed are adjusted, in addition to the parameter of the distance between the bottom roller and the top roller.

[0031] In one advantageous embodiment, the required stretching of the glass strand is displayed to, for example, an operator, who then adjusts (e.g., manually) one of the parameters, such as the feeder temperature, the conveyor belt speed, and / or the distance between the bottom and top rollers, based on a control map. Alternatively, one or more of these parameters can be adjusted automatically via a control loop.

[0032] In a further aspect, the present invention relates to a glass ingot that can be manufactured according to a method according to the present invention. The glass ingot has a refractive index nD of up to 0.001 per ingot with respect to the refractive index at 589 nm, and more preferably up to 6*10 per ingot. -4 , most preferably up to 3*10 per ingot -4、or rather, it has a refractive index nD variance of up to 0.0001 per ingot. The refractive index variance is the difference between the maximum refractive index and the minimum refractive index measured within one ingot. The refractive index can be measured, for example, by measuring the refractive index at at least 4 locations, at least 8 locations, at least 12 locations, or at least 20 locations, especially distributed at equal intervals throughout the ingot. A refractive index that is as homogeneous as possible is particularly advantageous for the optical use of glass, because particularly precise optical elements can be manufactured from such ingots. Preferably, this glass ingot can be manufactured according to the method described herein.

[0033] The glass ingot according to the invention is advantageously outstanding in terms of excellent geometric properties. In particular, this includes the format variance of the glass ingot in both width and length. Width variance B V is the difference between the maximum width B max and the minimum width B min of the ingot. Length variance L V is the difference between the maximum length L max and the minimum length L min of the ingot. The relative width variance is B V / (0.5*(B max +B min )). The relative length variance is L V / (0.5*(L max +L min )).

[0034] Preferably, the glass ingot has a width variance of up to 4.0 mm, more preferably up to 3.0 mm, and extremely particularly preferably up to 2.0 mm or up to 1.0 mm. The relative width variance is preferably less than 2.0%, especially less than 1.0%. Regarding the length, it advantageously has a length variance of up to 4.0 mm, more preferably up to 3.0 mm, and most preferably up to 2.0 mm. The relative length variance is preferably less than 1.0%, especially less than 0.7% or less than 0.5%.

[0035] According to one embodiment, the average width of the ingot is (0.5 * (B max +B min The length of the ingot is at least 50 mm, and in particular at least 70 mm or at least 100 mm. The average width may be up to 500 mm, up to 300 mm or up to 200 mm. According to one embodiment, the average length of the ingot is 0.5 * (L max +L min The length is at least 100 mm, and in particular at least 150 mm or at least 200 mm. The average length may be up to 2000 mm, up to 1000 mm or up to 500 mm.

[0036] In the manufacturing method described herein, the length of the ingot can be easily achieved by appropriately separating the manufactured strands to the desired length. The width can also be adjusted relatively easily as required, based on the width of the ingot shaft. In contrast, controlling the height, or adjusting it to a height as constant as possible, is a far more demanding requirement and is only possible by using the control method based on non-contact measurement described herein. Therefore, this method makes it possible to obtain ingots with extremely small height dispersion. Height dispersion H VThis is the standard deviation of the ingot height of a single ingot. This can be measured, for example, by measuring the thickness of the ingot at at least four, at least eight, at least twelve, or at least twenty locations, particularly evenly distributed throughout the ingot. The relative height variance is the quotient (expressed as a percentage) of the ingot's relative height variance and its mean height. The mean height is the arithmetic mean of the height values ​​measured to determine the standard deviation. According to one embodiment, the ingot's relative height variance is not greater than 3.0%, not greater than 2.0%, not greater than 1.5%, or not greater than 1.25%. Optionally, the relative height variance can be in the range of 0.1 to 3.0% or at least 0.5%. Ingots with such small relative height variances are particularly suitable for optical applications. The ingot height can be, for example, at least 10 mm or at least 15 mm. The height can be optionally set up to 400mm, and specifically up to 300mm or 200mm.

[0037] The glass is preferably optical glass; that is, glass intended for optical applications. In demanding optical applications, even small dispersions in the glass's properties can lead to significant defects.

[0038] Preferably, the glass composition is selected from the group consisting of fluorine-containing glass, phosphate-containing glass, fluorophosphate glass, phosphate glass, boron-containing glass, silicon-containing glass, and / or lead-containing glass. According to a particularly preferred embodiment, the glass ingot, or the glass produced from the glass ingot, has the following components (in weight percent based on oxides): [Table 1]

[0039] These glasses may contain trace amounts of Sb2O3 and / or As2O3, for example, less than 0.1% by weight, less than 0.03% by weight, or less than 0.01% by weight, respectively.

[0040] The following table shows the preferred proportion range for glass that can be used according to the present invention. [Table 2]

[0041] The glass preferably contains P2O5 in an amount of at least 1% by weight, preferably at least 5% by weight, or at least 10% by weight. However, the glass is preferably limited in terms of the maximum P2O5 content. Therefore, the glass preferably contains up to 60% by weight of P2O5, preferably up to 30% by weight, more preferably up to 25% by weight, or up to 15% by weight of P2O5.

[0042] Furthermore, the glass preferably contains BaO in an amount of at least 1% by weight, or at least 5% by weight, preferably at least 10% by weight. However, the glass is preferably limited in terms of the maximum BaO content. Therefore, the glass preferably contains up to 60% by weight of BaO, preferably up to 50% by weight, and more preferably up to 45% by weight of BaO. Optionally, the BaO content may be up to 30% by weight or up to 20% by weight.

[0043] Furthermore, the glass preferably contains fluorine in an amount of at least 5% by weight, preferably at least 10% by weight, at least 15% by weight, or at least 25% by weight. However, the glass is still preferably limited in terms of the maximum fluorine content. Therefore, the glass preferably contains up to 50% by weight of fluorine, preferably up to 45% by weight, more preferably up to 40% by weight, or up to 35% by weight of fluorine.

[0044] Glass can contain SiO2. However, the proportion should not be too high, because otherwise crystallization and devitrification may occur. Therefore, the SiO2 content is preferably a maximum of 10% by weight, preferably a maximum of 5% by weight, and more preferably a maximum of 1% by weight. In particular, the glass is SiO2-free.

[0045] In addition, the glass may contain Al2O3. Preferably, its content is at least 1% by weight, more preferably at least 2% by weight, at least 5% by weight, or at least 10% by weight. However, too much Al2O3 is undesirable because otherwise the mixture will not dissolve well and the tendency of the glass to crystallize will increase. Therefore, the glass preferably has an Al2O3 content of up to 30% by weight, preferably up to 25% by weight, more preferably up to 20% by weight or up to 15% by weight.

[0046] Preferably, the glass contains B2O3 in an amount of 0 to a maximum of 10% by weight, and more preferably in an amount of 0 to a maximum of 5% by weight. More preferably, the glass contains B2O3 in an amount of up to 1% by weight. Most preferably, the glass is B2O3-free.

[0047] Preferably, the glass contains alkali metal oxides in a content of 0 to a maximum of 15% by weight, preferably 0 to a maximum of 10% by weight, or up to 5% by weight. More preferably, the glass contains alkali metal oxides in a content of up to 1% by weight. Most preferably, the glass is alkali metal oxide-free.

[0048] Preferably, the glass contains MgO in an amount of 0 to a maximum of 10% by weight, preferably 1 to a maximum of 5% by weight, or 2 to 4% by weight. This can lower the melting temperature of the glass.

[0049] Preferably, the glass contains CaO in an amount of 0 to a maximum of 25% by weight, preferably 1 to a maximum of 20% by weight, or 5 to 10% by weight. This is because crystallization may occur otherwise.

[0050] Glass can contain SrO, preferably in an amount of up to 30% by weight, more preferably in an amount of 1 to a maximum of 25% by weight, and even more preferably in an amount of 5 to a maximum of 25% by weight. This is because crystallization may occur otherwise. The SrO content can be optionally set to at least 10% by weight or at least 15% by weight, and / or up to 25% by weight.

[0051] According to one embodiment, the glass contains a relatively high proportion of alkaline earth metal oxides (MgO, CaO, BaO, SrO), and in particular contains at least 25% by weight, at least 30% by weight, or at least 35% by weight of alkaline earth metal oxides. The proportions of these components can be limited to a maximum of 60% by weight or a maximum of 50% by weight. Glass containing such components is very well suited as optical glass for demanding applications.

[0052] Furthermore, the glass may contain CuO, preferably in an amount of up to 10% by weight, more preferably in an amount of 0 to a maximum of 5% by weight, and even more preferably in an amount of 0 to a maximum of 1% by weight. Optionally, the CuO content is 1 to 7% by weight or 2 to 5% by weight.

[0053] Preferably, the glass contains La2O3 in an amount of 0 to a maximum of 10% by weight, preferably 0 to a maximum of 5% by weight, and most preferably 0 to a maximum of 1% by weight.

[0054] Preferably, the glass contains Gd2O3 in an amount of 0 to a maximum of 15% by weight, and more preferably in an amount of 0 to a maximum of 10% by weight.

[0055] Preferably, the glass contains Y2O3 in an amount of 0 to a maximum of 15% by weight, and more preferably in an amount of 0 to a maximum of 10% by weight.

[0056] Preferably, the glass contains Nb2O3 in an amount of 0 to a maximum of 10% by weight, and more preferably in an amount of 0 to a maximum of 5% by weight.

[0057] The glass is preferably free of Pb, Cd, Ni and / or As due to the toxicity and ecological concerns of the following components:

[0058] In this specification, when it is stated that glass is free of a certain component or does not contain a particular component, what is meant is that the component may be present in the glass as an impurity. In other words, this means that the component is not present in a major amount and / or is not added to the glass as a glass component. According to this invention, a non-major amount is less than 1000 ppm, preferably less than 500 ppm, and most preferably less than 100 ppm.

[0059] Preferably, the glass does not contain any components not listed as glass components in this specification.

[0060] Preferably, the glass has a refractive index n of at least 1.40. d It has a refractive index n of at least 1.45. d More preferably, a refractive index n of at least 1.50 d It has the following characteristics. However, the refractive index is preferably not to exceed a value of 2.0, more preferably not to exceed a value of 1.80, and even more preferably not to exceed a value of 1.70.

[0061] Preferably, the glass has an average linear thermal expansion coefficient of 4.5 to 13.7 ppm / K, more preferably 4.5 to 6.5 ppm / K, and even more preferably 5.0 to 6.0 ppm / K or 6.0 to 13.0 ppm / K. "Coefficient of thermal expansion" or "CTE" refers to the average linear thermal expansion coefficient over a temperature range of 20°C to 300°C. This is defined according to DIN ISO 7991:1987.

[0062] The pure transmittance of glass is preferably higher than 60%, more preferably higher than 85%, more preferably higher than 90%, more preferably higher than 93%, and more preferably higher than 95% for a sample thickness of 10 mm in the wavelength range of 400 nm to 600 nm. The term "pure transmittance" (English: "Internal Transmission") refers to the light transmittance excluding reflection losses. Pure transmittance or pure transmittance can be measured by methods well known to those skilled in the art, for example, according to DIN 5036-1:1978. In this specification, the description of pure transmittance is related to a sample thickness of 10 mm. The description of "sample thickness" does not mean that the glass or glass ingot has this thickness, but merely indicates to what thickness the description of pure transmittance is related to.

[0063] Unless otherwise stated, or unless this is obvious to those skilled in the art, the measurements described herein are performed at a pressure of 101.3 kPa at 20°C.

[0064] In addition to these, according to further embodiments, the present invention also relates to the use of the glass ingot according to the present invention for manufacturing the following optical elements: that is, these optical elements are selected from a series of optical elements consisting of lenses, prisms, light guide rods, arrays, optical fibers, gradient components and optical windows, for use in the fields of imaging, sensor mechanisms, microscopes, medical technology, digital projection, communications, optical communications engineering / information transmission, and optics / lighting in the automotive sector, as well as for solar technology, photolithography, steppers, excimer lasers, wafers, computer chips and / or integrated circuits and electronic devices including such circuits and chips.

[0065] The present invention and its technical environment will be described in detail below with reference to the drawings. It should be noted that the present invention is not limited to the illustrated embodiments. In particular, unless otherwise explicitly stated, partial aspects of the matters described in the drawings may be extracted and combined with other components and concepts belonging to this specification and / or the drawings. It should be especially noted that the drawings and, in particular, the illustrated size ratios are approximate. The same reference numerals represent the same subject matter, and therefore descriptions belonging to other drawings may be used supplementarily as needed. [Brief explanation of the drawing]

[0066] [Figure 1] This figure shows a very simplified schematic representation of one embodiment of the apparatus according to the present invention. [Figure 2] This is a partial excerpt showing the embodiment shown in Figure 1 as a perspective view. [Figure 3] This figure shows the characteristics of the refractive index over time, measured in minutes, for the manufacturing process for fluorophosphate glass described herein. [Modes for carrying out the invention]

[0067] Please note that the drawings are merely schematic in nature and are used solely for the purpose of understanding the present invention. The same reference numerals are used for identical components. Various features of the various embodiments can, in principle, be combined with each other arbitrarily.

[0068] Figure 1 shows a very simplified schematic representation of one embodiment of the apparatus 1 according to the present invention.

[0069] Apparatus 1 is suitable for the continuous production of glass ingots 2, for example, made of an optical glass composition, and includes a feeding device 3 for supplying molten glass 4 into a mold 5, for example, into a tank or groove. In the embodiment shown herein, the molten glass 4 is supplied into the mold 5 in the center, and flows out of the mold, spreading in the width direction, thus forming glass strands 6. As can be seen from Figure 1, the glass strands 6 are then supplied via a conveyor belt 7 in the direction of the arrow 8 to a cooling device 9, for example, a heat treatment furnace, where the temperature of the still-hot glass strands 6 is lowered and cooled. The embodiment shown in Figure 1 further includes a cutting device (not shown) where the cooled glass strands 6 are then divided into individual glass ingots 2.

[0070] The present invention proposes the following: The apparatus 1 has an optical measuring device 10 positioned before the cooling device 9, and this optical measuring device 10 can continuously determine the projection of the glass strand's outer shell without contact, and based on the values ​​obtained in this way, parameters, namely the supply device temperature and / or transport speed, can be adjusted. Preferably, the measuring device 10 or the measurement direction is proposed to be positioned in a direction intersecting the longitudinal axis of the glass strand 6 (Figure 2).

[0071] Figure 2 shows a simplified schematic perspective view of a partial excerpt of the embodiment shown in Figure 1. What can be seen from this figure is, in particular, the arrangement of the measuring device 10, which preferably includes a CMOS camera, with respect to the glass strand 6. As can be seen in detail from Figure 2, the measuring device 10 is arranged to the side of the glass strand 6 as follows: The line of sight 11 of the measuring device 10 is oriented perpendicular to the longitudinal axis of the glass strand 6, and therefore the measurement direction is also substantially perpendicular to the glass strand 6.

[0072] Preferably, a measurement device 10 in the form of a CMOS camera can be used to determine the projection of the outer shell of the glass strand 6. This is because the formed glass strand 6 has sufficient intrinsic illumination and emits light 12, which is detected by the measurement device 10.

[0073] Figure 3 illustrates the time-dependent refractive index characteristics (in minutes) for the manufacturing process for fluorophosphate glass described herein. This figure shows that the obtained refractive index characteristics remain stable over several hours and never deviate from the specifications.

[0074] Examples Example 1 In the ingot extraction method, an ingot was produced from two fluorophosphate glasses according to this specification. The glass compositions are described below in weight percent. [Table 3]

[0075] In both cases, the method was initially performed without non-contact measurement of the outer dimensions of the glass strand according to the present invention and without the associated control of the supply device temperature and / or transport speed (Interval 1). Subsequently, non-contact measurement of the outer dimensions of the glass strand and the associated control of the supply device temperature and / or transport speed were performed in the method (Interval 2). The following table shows the effect of performing the method on the homogeneity of the refractive index of the glass. This shows that the measures described herein significantly improved the homogeneity of the refractive index values. In this case, the homogeneity of the refractive index values ​​is expressed as the standard deviation of the refractive index over 250 measurements along the glass strand. [Table 4]

[0076] Example 2 Ingots were produced from the fluorophosphate composition glass according to the conditions described for interval 2 in Example 1. The thickness of the ingots was determined, and the relative height variation was identified, which was 1.1%. [Explanation of symbols]

[0077] 1 device 2 glass ingots 3 Feeding device 4. Liquid dissolved glass Type 5 6 Glass Strands 7. Conveying device 8 Arrows 9 Cooling device 10 Measuring device 11 line of sight 12 light

Claims

1. A method for continuously manufacturing glass ingots (2) according to a continuous casting method, Liquid molten glass is supplied from the supply device (3) into the mold (5) to form a glass strand (6). The glass strand (6) is supplied to a cooling device (9) via a conveying device (7), particularly a conveyor belt, and then to a cutting device, where the cooled glass strand (6) is divided to form individual glass ingots (2). In the method, At the latest, before the glass strand (6) is supplied into the cooling device (9), the projection of the outer dimensions of the glass strand (6) is continuously determined by a non-contact measuring device (10), and based on the obtained value, parameters, namely the supply device temperature and / or transport speed, are adjusted. method.

2. The measurement direction is positioned perpendicular to the longitudinal axis of the glass strand (6). The method according to claim 1.

3. The non-contact measuring device (10) is an optical, radiometric, and / or ultrasonic-based measuring device (10). The method according to claim 1 or 2.

4. The glass ingot (2) has a dispersion of refractive index nD of up to 0.001 per ingot. The method according to any one of claims 1 to 3.

5. The glass strand (6) is guided to pass through a roller device comprising at least one bottom roller and at least one top roller before being measured by the non-contact measuring device (10), and the distance between the bottom roller and the top roller is adjusted based on the obtained value. The method according to any one of claims 1 to 4.

6. A glass ingot (2) having dispersion of a refractive index nD of up to 0.001 per ingot, in particular a glass ingot (2) that can be manufactured according to the method described in any one of claims 1 to 5.

7. The glass ingot (2) has a relative height dispersion not exceeding 3.0%. The glass ingot (2) according to claim 6.

8. The glass ingot (2) has a glass composition selected from a series of glasses including fluorine-containing glass, phosphate-containing glass, fluorophosphate glass, phosphate glass, boron-containing glass and / or lead-containing glass. The glass ingot (2) according to claim 6 or 7.

9. The glass ingot (2) has the following components (based on oxides, in units of weight percent): Table 1 including, A glass ingot (2) according to any one of claims 6 to 8.

10. A method of using the glass ingot (2) according to any one of claims 6 to 9 for manufacturing an optical element selected from a series of optical elements including lenses, prisms, light guide rods, arrays, optical fibers, gradient components and optical windows, for use in the fields of imaging, sensor mechanisms, microscopes, medical technology, digital projection, communications, optical communications engineering / information transmission, and optical systems / lighting in the automotive sector, and further for solar technology, photolithography, steppers, excimer lasers, wafers, computer chips and / or integrated circuits and electronic devices including such circuits and chips.

11. An apparatus (1) for continuously manufacturing glass ingots (2), wherein the apparatus (1) is A supply device (3) for supplying liquid molten glass (4) into a mold (5) so as to form glass strands (6), A conveying device (7) for transporting the glass strand (6), particularly a conveyor belt, A cooling device (9) for cooling the glass strand (6), A cutting device capable of dividing the cooled glass strand (6) so that individual glass ingots (2) are formed, In an apparatus (1) including, A measuring device (10) is provided in front of the cooling device (9), and the measuring device (10) can continuously determine the projection of the outer dimensions of the glass strand (6) without contact, and parameters, namely the supply device temperature and / or transport speed, can be adjusted based on the obtained values. Device (1).

12. The measuring device (10) is positioned perpendicular to the longitudinal axis of the glass strand (6). The apparatus (1) according to claim 11.

13. The measuring device (10) is an optical, radiometric, and / or ultrasonic-based measuring device (10). The apparatus (1) according to claim 11 or 12.

14. The aforementioned type (5) includes a tank or groove, Apparatus (1) according to any one of claims 11 to 13.

15. The apparatus (1) is positioned in front of the measuring apparatus (10) and further includes a roller apparatus comprising at least one bottom roller and at least one top roller. Apparatus (1) according to any one of claims 11 to 14.

Images