JP2009511406A - Method and apparatus for accurately dividing low viscosity molten glass into small divided parts - Google Patents

Abstract

In order to divide the glass melt and to increase the flow rate and transmittance of the optical melt, a low-viscosity glass having a viscosity of 10 ^7.6 dPa · s at a temperature of 670 ° C. or lower, particularly a glass for a blank press or The method of the present invention for accurately splitting low _Tg glasses is a 0.2-10 gram weight split with a relative and / or absolute weight deviation of less than 5% based on the average weight of the split. The part is based on a continuous melting process, which is repeated feeding by a clocked needle feeder (100) with a nozzle (3) provided with a plurality of outlets (7).
[Selection] Figure 1

Description

[Explanation]
The present invention relates generally to the division of glass melts for blank presses of optical components in particular.

  The imaging optical system is used for reduction or enlargement in an objective lens such as a camera, a projection system, a microscope, and a telescope. The demands placed on the quality of reduced or enlarged imaging are increasing. At the same time, the goal is to make products even more cost effective for the mass market.

  Imaging quality can often be improved many times by special image processing software, but certainly these systems require a lot of storage capacity and additional energy consumption. Accordingly, a high standard is provided for the imaging characteristics of the optical module, even in the case of mass production. These criteria have so far been only partly guaranteed by special optical filters.

  Under these conditions, also for the mass market, high contour accuracy for the predicted contour, the economical creation of the desired aspheric contour, and the widest possible palette of various glasses, especially its refractive index It is desirable that processing for partial dispersion is possible. What is further required for such an imaging optical system manufacturing method is that the unit price is low and the lot quantity is 1 for mass-produced products such as mobile phone cameras, photo / video cameras, and home projection systems. It is to exceed 10,000.

A conventional method for manufacturing the imaging optical system is as follows.
1. The glass blank is reworked in a cooled or solidified state such as separation, grinding and polishing.
2. For example, as described in US Pat. Nos. 4,969,944 and 4,734,118, the glass preform is reheated in a press mold and then blank pressed.
3. Reheat the glass preform or glass gob outside the press die, as described, for example, in US Pat. Nos. 5,873,921, 6,009,725, and 4,854,958. Subsequently, blank pressing is performed in a preheated press die.
4). For example, as described in US Pat. No. 5,762,673, it is directly formed from a glass melt by a hot forming method.

  All of these methods, especially the production with reheated glass gob, require that the glass melt be divided as accurately as possible. If there is a variation in the split, this is directly reflected in the optical properties of the blank pressed part. Such fluctuations immediately lead to defective products or at least products with low-value optical properties.

  It is also disadvantageous in this case that the glass segment is produced by pinching or shearing. Contact with the tool used for this purpose generally leads to traces that can later be detected in the finished product and concomitant defects in product properties.

  In order to divide a plurality of glass division parts at the same time and to avoid this, it is known from JP-A-6-206730 that a glass gob is produced by a process of dropping glass droplets from a nozzle by its own weight. However, since the moment of falling is determined by the nozzle size and viscosity, this leads to the problem that the weight of the glass drop cannot be freely selected. Since the viscosity of the optical glass must often be very low or kept very low to avoid crystallization, this method can also produce only small glass gobs.

  Furthermore, the manufacture of small precision optical systems is a particularly difficult task. Accordingly, the size of the optical element (s) of such an optical system is well below the limits of mechanical rework, such as by cutting, grinding, and polishing. Not only is this generally uneconomical, it can hardly be achieved in view of the high demands placed on contour and surface quality. Here, the blank press may satisfy high requirements imposed on the contour accuracy and the surface quality even in the case of a small optical system. However, along with the quality required for the optical system, the demands placed on the semi-finished product or gob, which is a material for manufacturing an optical element by a blank press, are also increasing. Gob requires a rough or fired surface of less than 2 nanometers to produce high quality optics. Such a surface can be achieved in particular by non-contact division of the gob from the melt. High demands are also placed on the weight accuracy of the gob. Thus, a gob should have a weight deviation of less than 5% based on its average weight. Since each additional step in gob manufacture, for example weight sorting, is associated with handling, it is not only costly and time consuming, but also increases the risk of surface quality being compromised, for example due to damage. Therefore, when the gob is manufactured, precise supply with absolute and relative weight fluctuations of less than 5% is necessary so that sorting does not have to be performed. A gob that is divided and cooled from the melt, preferably in a non-contact manner, with a weight deviation of less than 5% from the average weight is referred to below as a precision gob.

  The most precise division of a low-viscosity glass melt to date for imaging optics has a clocked needle valve that is connected to a continuous melt at a constant glass depth and thus a constant hydrostatic pressure during feeding. Indirect heating needle feeders have been used. However, manufacturing tolerances in the production of platinum or noble metal parts of the feeder, and needle and valve seat distortion at relatively high temperatures also limit the potential of such feeders, thus achieving weight variations of less than 0.2 grams. It was generally impossible to do. For these reasons, it has never been possible to divide into gobs weighing less than 4 grams with a required accuracy of less than 5% weight variation, and completely impossible to divide into gobs weighing less than 1 gram. Met.

  Therefore, it is an object of the present invention to improve the splitting of the glass melt with respect to the above mentioned problems, in particular to achieve a more precise splitting of particularly small gobs.

  Surprisingly very simply, this object is easily achieved by the subject matter of the independent claims. Advantageous refinements and developments of the invention are described in the dependent claims.

To this end, the present invention provides a maximum 670 ° C. Low viscosity glass having a viscosity of temperature at 10 ^{7.6 dPa} · s of, particularly, to a method for precisely divided glass or low T _g glass blank press In the case of the method, a nozzle having a plurality of outlet openings in which the divided part has a weight in the range of 0.2 to 10 grams with a relative and / or absolute weight deviation of less than 5% based on the average weight of the divided part A method of manufacturing from a continuous melting process by multiple feeds from a clocked needle feeder having An apparatus for precisely dividing such low viscosity glass suitable for carrying out this method comprises a nozzle made of a noble metal alloy for this purpose, said nozzle being on a circle centered in the center of the nozzle. Having a plurality of outlet openings.

High demands on internal quality, for example, small variations in refractive power, transmission and Abbe dispersion number, stigma and no bubbles, are generally a continuous melt with a minimum volume of about 50 liters and the associated heat. It is clear that this is achieved by molding. However, the throughput in the case of a continuous melt is limited by the division speed. Furthermore, the splitting speed is limited by the viscosity of the glass during splitting (to avoid striae) and by the weight of the individual split sections. Thus, for a small gob, the throughput is much less than 400 grams / minute. This poses additional challenges. Glass types of small precision optics should not only have a low softening temperature (so-called “low _Tg glass”) but also have very “extreme” optical properties. Such a characteristic can in particular be a very large refractive index and / or Abbe number. Such glasses have a very low lower crystallization viscosity (UVK) and therefore have a very low viscosity upon melting. These glasses greatly erode melt tank furnace materials due to their composition and their low viscosity. Although cooling the walls in the melting reservoir while simultaneously performing indirect or induction heating reduces the attack on the material in the melting zone, this solution can be applied to the entire tank furnace and the entire system. Not technically useful. A group of materials that can be used in the transition tube, refining zone, and conditioning zone are platinum / iridium alloys. While these alloys are certainly attacked by glass melts, platinum ions and free particles can impair the transmission of the glass, this process achieves the required transmission values at throughputs of over 400 grams / minute. It's slow enough. However, during the production of small precision gob, the residence time in the tank furnace is too long, and the platinum penetration into the melt is correspondingly too high, so the high transmittance required for optical systems made of glass is achieved. Cannot be achieved.

Therefore, the glass production described above faces limitations in two main ways.
The required weight accuracy is not obtained during the splitting of gobs less than 4 grams, while gobs weighing less than 1 gram cannot even be split.
Due to too low throughput and associated platinum intrusion, the transmission of gob less than 4 grams can be unacceptably reduced.

  The present invention creates a solution to these problems by simultaneously increasing accuracy and throughput through simultaneous multiple feeds.

  Although the application itself of simultaneous multiple feeds for the purpose of increasing throughput in the glass industry has been known for some time, multiple feeds for the purpose of increasing weight accuracy initially seem unreasonable. All known conventional multiple feed methods have shown that multiple feeds reduce weight accuracy compared to a single feed. The reason for this is in particular that the temperature gradient between the individual nozzles and the flow rate of the glass melt from different outlet openings are different. Considering the fact that the glass thermoforming substantially temperature always exceeds 800 ° C., the viscosity of the glass is highly temperature dependent, between the flow through at the outlet opening and the changing temperature, or in particular the flow of the feeder If the cross section is not taken into account, there is a strong functional relationship with the non-uniform temperature field. These problems become more serious as the viscosity of the glass melt to be divided is lower. If it is desired to avoid cutting or shearing, e.g. laser, shearing machine, or burner marks, to obtain high surface quality, the melt must fall and pull the thread. Must not. Especially with small gobs, the drop size depends largely on the temperature and diameter of the outlet opening, so no crystal and / or condensate should form at the edge of the opening and the temperature gradient should be reduced to a minimum . However, the present invention shows a method of using multiple feeds to avoid the disadvantages of conventional nozzles and to increase the accuracy of a feeder such as a needle feeder.

  The smaller the dimensions of the part to be heated / cooled, the shallower the temperature gradient. This turns out to be advantageous for producing small gobs, correspondingly from the diameter of the small outlet opening and also from the diameter of the entire small nozzle.

  In order to make the temperature distribution uniform, a specific heating concept is also provided in the development of the invention. For this purpose, the nozzle is heated indirectly from the side by infrared radiation or directly by induction. If a device for heating the nozzle from below, preferably an infrared burner or a fishtail burner, which can be moved from below in the direction of the nozzle and moved in front of the nozzle only during the feeding operation, a uniform temperature field at the nozzle is provided. It can be seen that it is very advantageous in the development of the present invention for the purpose of implementation.

  In order to make the flow to all outlet openings uniform, the outlet openings are arranged in a circle above the center of the nozzle. In this case, it can be seen that it is advantageous if the entire cross section of the outlet opening is selected to be smaller than the cross section of the feeder or the inlet to the nozzle, preferably only slightly smaller. According to one embodiment of the invention, the nozzle is made from a platinum / iridium alloy to reduce attack on the melt. In this case, the nozzle can in particular be milled and / or turned from a solid platinum / iridium piece. In this case, the nozzle is preferably provided with an outlet opening in a tube protruding from the nozzle body. Furthermore, the outlet opening is particularly preferably deburred. Individual outlet openings can be measured by flow-through tests with water at low temperatures and, if necessary, can be calibrated by grinding and polishing for flow rates. Subsequently, the nozzle can be fastened, eg welded, to a feeder or valve device.

  These simple measures can be used to provide a device that allows for tremendous precision in making gobs, as outlined above. It is particularly preferred that the nozzle is provided with at least three outlet openings. The maximum 5% weight tolerance required for a gob starting with a desired weight of 4 grams can be achieved with as few as three exit openings. For nozzles with at least 6 outlet openings (nozzles with 6 outlet openings and nozzles with 17 outlet openings were tested), these weight tolerances were compared in the range of 4 to 0.2 grams. Even a small gob can achieve this. Non-contact supply and cooling in the case of multiple divisions of precision gobs are in this case performed using floating recesses that allow a very uniform air distribution in the gas cushion on which the gob rests by being eroded from a single piece. It was broken. Furthermore, it is clear that the accuracy of relatively large gobs with a weight in the range of 4-10 grams can be increased by a factor of about 3 according to the invention.

  In general, the present invention relates to a glass melt to glass comprising a valve device having a valve for blocking glass melt flow and a nozzle having a plurality of outlet openings connected downstream of the valve for blocking glass melt flow. An apparatus for dividing a divided part into a plurality of parts simultaneously is provided. It is therefore proposed to divide a plurality of outlet openings by switching a single valve.

  With the above apparatus, it is possible to carry out the method of the present invention for simultaneous multiple division of a glass divided portion from a glass melt, in the case of the method, the glass melt flow exits from a nozzle having a plurality of outlet openings, The shunt outflowing from the outlet opening is interrupted by blocking the glass melt flow by clock-type opening and closing of the valve upstream of the nozzle, and individual glass divisions fall from the outlet opening.

  Therefore, compared with Japanese Patent Laid-Open No. 6-206730, the present invention makes the weight of the glass divided portion more flexible because the weight of the glass divided portion is not determined only by the size of the outlet opening and the viscosity of the glass melt. The advantage is that it can be set. In addition, the moment when the glass split part naturally falls from the exit opening is greatly influenced by the geometry of the exit opening and the viscosity of the melt, so there is a slight mechanical error in the exit opening or the exit opening. Even if the temperature is different, it appears as a significant weight deviation. On the other hand, according to the present invention, since the fall is reliably controlled by the valve device, it is possible to further reduce the weight tolerance of the divided glass gob. At the same time, defects such as occur when glass strands are chopped or sheared are avoided.

  Various configurations of the invention are possible in order to further increase the accuracy during the division by creating the same conditions as possible at the outlet opening. One measure is to place the outlet openings, especially all outlet openings, at the same level. When the diversion flows from the outlet openings arranged at the same level, the hydrostatic pressure is the same at all the outlet openings, so that the outflow speed of the glass melt through the nozzles becomes uniform. For this reason, it is also advantageous for the outlet openings to be similar, in particular the same size.

  In order to create the same conditions, it is also advantageous if the nozzle and / or glass melt flow paths are arranged as symmetrically as possible. In this case, it is particularly preferred that the outlet openings, in particular all the outlet openings, are arranged along a circle in the nozzle. Furthermore, it is advantageous at this time if the outlet openings are arranged at the same radial distance from the inlet of the nozzle. It should also be advantageous for the outlet openings to be evenly spaced along the circle. In general, nozzles that are rotationally symmetric about the central axis of the inlet or feeder channel are particularly preferred. In this regard, rotational symmetry is understood to be symmetric by rotating about an axis by a rotation angle of at least less than 360 degrees. In particular, at least the interior of the nozzle can have such a geometric shape. Thus, a preferred nozzle arrangement is such that the glass flow path to the individual nozzles is similar. A symmetrical design is achieved in this way with respect to the flow path, in particular in combination with an arrangement along a circle. In particular, for this purpose, the arrangement of the interior and outlet openings of the nozzle can be configured axisymmetrically with respect to an axis of symmetry that extends perpendicularly and centrally through the inflow opening or to the inlet of the nozzle.

  A further measure to achieve as similar conditions as possible in the individual outlet openings is to deburst and polish the channels to the outlet openings. This also avoids defects that may occur, for example, in channel burrs or grooves.

  It is also advantageous to adjust the hydrostatic pressure of the glass melt at the outlet opening in order to always maintain the same conditions during the clocked supply. However, adjustment is possible, for example, by adjusting the level of the melt reservoir supplying the melt via the valve device of the nozzle. This is possible in a particularly advantageous and simple manner by the upstream continuous melting process.

  Furthermore, it is advantageous if the outlet opening throughflow is calibrated by measuring the flow through of the replacement liquid. This can be done as early as during manufacture and / or after the nozzle is attached to the device. For example, whenever the aim is to break a melt of very low viscosity, a suitable replacement liquid is water.

  In order to facilitate the fall, it has further been found advantageous if the nozzle is provided with a base plate, in particular with an outlet opening protruding downwards. The protruding outlet opening forms a separating edge or a falling edge that allows the glass segment to fall more easily. The separating edge or the falling edge can be designed in particular as a cutting edge, which is generally understood as the acute edge of the outlet opening.

  The nozzle is arranged, for example, in the center of the interior, and around the protrusion, radially away from the center, thereby being particularly preferably arranged symmetrically about the vertical central axis of the nozzle Having a base in the form of a base part with a plurality of outlet openings has been found to be particularly advantageous for precision feeding of gobs. In order to make it easier for the melt to flow out of the nozzle towards the outlet opening, a central projection, which can be a depression or a depression when viewed from the outside, is advantageous when using a plate-shaped base part. Thereby, the dead zone of the melt flow is avoided or at least reduced.

  One improvement of the present invention provides a double-walled downwardly expanding funnel-shaped or bell-shaped nozzle, in which case the glass melt is guided between the walls of the double-walled nozzle and below the nozzle. The edge is particularly preferably provided with a plurality of outlet openings which in this case are arranged symmetrically about the vertical central axis of the nozzle. The above two improvements of the present invention, firstly with a convex part in the center of the base part, or with a nozzle having a double wall design in the shape of a funnel or bell, are on the one hand a central axis or inlet Is particularly preferred in order to obtain an outlet opening arrangement that is symmetrical with respect to, and on the other hand to obtain an optimum flow of the glass melt. It can be seen that a double wall design in the form of a bell or funnel is particularly preferred for small gobs weighing less than 3 grams. Furthermore, a nozzle having a chamber with a central inlet and a base plate with an internal projection in the center is particularly advantageous for relatively large gobs, for example in the range of 0.3-30 grams.

  In a preferred refinement, the nozzle comprises a tube having an outlet opening protruding from a plane, the tube preferably having a ratio of the inner diameter to the tube length of at least 0.3, preferably at least 0.4. As a result of this short tube, a falling edge is formed on the one hand and on the other hand the temperature difference of the very short tube is reduced.

  According to another preferred refinement of the invention, the ratio of the inner diameter to the tube length measured outside the tube having an outlet opening protruding from the nozzle is in the range of 0.1-2. This range of tube geometry is advantageous on the one hand to avoid cooling of the melt at the tube wall and on the other hand to prevent the glass melt from expanding and wetting the underside of the nozzle. I understand.

  According to a development of the invention, the outlet opening has an inner diameter of at least 0.5 millimeters, preferably in the range of 1-12 millimeters. With such a diameter, it is possible in particular to produce glass segments for producing optical components for the mass market with a high throughput. In general, the present invention can be used to split glass segments having a weight in the range of 0.1-150 g, and even in the range of 0.05 g, and thereby provide the advantages described above. The amount of glass that is divided for each supply stroke using the valve is preferably in the range of 0.8 to 20 grams.

  In addition, the apparatus of the present invention can be modified to split different weight glass gobs as needed when nozzles with relatively small openings or nozzles with relatively large openings are used.

  Particularly preferably, the nozzle also comprises a base element having an outlet opening that is milled from a single piece. High precision base elements can be manufactured by milling from a single piece, for example, as opposed to forged base elements with welded outlet tubes. Furthermore, it is advantageous to use noble metals, in particular noble metal alloys, as the nozzle material. In particular, the outlet opening can be inserted into the platinum alloy base element. Precious metal alloys are particularly heat resistant, and at the same time it is possible to minimize the entry of colored precious metal ions (eg, Pt, Rh, Au, etc.) by the high throughput that can be achieved using the present invention. Furthermore, it is advantageous if the temperature at the nozzle and outlet opening can be set as fine and controllable as possible, for example to avoid crystallization. Several measures that can also be used cumulatively are possible for this purpose. The first measure is induction heating of the nozzle. The nozzle can also be heated by radiation. Finally, it is possible to minimize heat loss. For this purpose, for example, a reflector for retroreflecting the heat radiation to the nozzle can be provided.

  These heating or reflecting devices can also be designed to be movable. Thus, for example, these devices can be kept away during delivery so that induction heating and / or radiant heating and / or reflectors do not interfere with the support platform holding the glass split.

  A preferred embodiment of the valve device further comprises a needle feeder. High-precision division by clock-type interruption of the glass melt flow can be achieved using such a needle feeder. In the case of such a needle feeder, a needle for blocking the glass melt flow is sunk in the seat.

  In order to increase the accuracy of the division by precise positioning of the feeder needle, a force detection device for detecting the force acting on the tip of the feeder needle can be provided for this purpose in an advantageous development. In particular, a force detection device is used to apply a force acting on the feeder needle at least during the positioning of the tip of the feeder needle relative to the feeder needle seat, in particular in the x, y and / or z direction. It is possible to measure. Such a needle feeder is described in the German application whose application number 10 2004 026932 is entitled “Verfahren und Vorrichtung zur Positionierung einer Speisernadel sowie Speiser” [“Feeder needle positioning method and apparatus, and feeder”]. The disclosure of which is fully part of the subject matter of this application.

A major advantage of the present invention is that it is possible to accurately split a very low viscosity melt. This is particularly advantageous for glass melts of optical glass that can be supplied at low viscosity without the possibility of crystallization. Thus, according to one embodiment of the invention, the glass melt exits the outlet opening with a viscosity of up to 10 ⁴ dPa · s, preferably up to 10 ³ dPa · s. Even lower viscosities of up to 10 ² dPa · s are possible.

According to a further development of the invention, the glass segment can be fed through the floating recess of the nozzle and supported on the floating cushion. In this case, it is further possible that while the glass segment is supported on the surface, the viscosity rises above the adhesive viscosity by cooling and stays at least below the softening point inside the glass segment, followed by The glass segment is then placed in a press mold and pressed to the final contour and surface quality in the press mold. The adhesive viscosity is generally at the softening point of 10 ^7.6 dPa · s for glass. An apparatus and method for supporting a glass segment on a levitation recess and then performing a blank press is described in "Herstellung von optischen Komponenten fur Abbildungsoptiken aus der Schmelze" ) In the name of the invention under the application number 10 2005 046 556.0, which is described more precisely in the German application by the present applicant, the disclosure of which is also completely part of the subject matter of the present invention.

  In general, optical components that can be made according to the present invention using the method of the present invention or using an apparatus and that have a blank pressed surface are characterized by high contour accuracy. This is achieved by the high precision division achievable with the present invention. Thus, for example, in the case of at least 100 charges of an optical component having a fired surface and / or a blank-pressed surface, or a gob made of optical glass made according to the present invention, without sorting. It is possible to make the maximum weight deviation of the optical component or gob less than 5% from the average value, or even only 1% or less. Such small tolerances can be obtained especially with optical components or gobs weighing less than 0.5 grams.

  The simultaneous multiple division of the present invention can not only be used to improve the tolerance of the weight of the manufactured gob or the weight of an optical component such as a lens manufactured from the gob. Rather, in the case of a particularly small optical element or gob, an increase in throughput is achieved by multiple division, thereby shortening the contact time with the components of the feeder. As a result, the weight tolerance is narrowed and the intrusion of impurities is reduced. This is especially important for small gobs. This is because even when manufacturing such a gob, it is necessary to reliably provide a minimum amount of molten glass. When this glass melt is divided into very small parts, the throughput is correspondingly reduced, and therefore the residence time of the melt in the feeder is increased, so that noble metal melts from the glass contact material in the feeder. Move into liquid. In the case of low throughput associated with the use of a nozzle with a single outlet opening, the residence time of the melt in the nozzle is relatively long here, especially for small gobs, and for example platinum ions intrude from the nozzle material. Therefore, there is a problem that a high requirement based on the transmittance cannot be satisfied.

  On the other hand, it is possible to obtain optical glass gobs weighing up to 10 grams, or to obtain optical components manufactured therefrom, using division in the method or apparatus of the invention, in which case It has been found that the optical glass of gob or optical components has a decrease in transmittance due to noble metal impurities of less than 2 percent, and even less than 1 percent. The use of multiple feeds makes it possible to achieve a relative improvement of transmission of less than 3%, especially compared to simple feeders, which reduces the precious metal impurities and / or the residence time in the tank furnace. This is achieved by shortening. Furthermore, the absolute accuracy of the division with a single valve usually depends little or not on the amount of glass to be divided. Correspondingly, the relative weight deviation increases as the weight of the gob decreases. However, if multiple gobs are split by a single valve, these errors are distributed across the multiple gobs and the relative split accuracy is accordingly increased. In this case, it is apparent that producing a gob weighing less than 4 grams with a weight tolerance accuracy of less than 5% is generally almost impossible with a single feeder. Due to the mechanical inertia of the feeder system, special differences arise, especially when the weight of the gob is well below 1 gram. However, these problems are solved by the multiple feed of the present invention using a single valve.

  The melt can be fed to the nozzle via a crucible or continuous melting tank furnace to melt and / or produce glass from the lot.

  The multiple precision supply of the present invention is also suitable for blank presses of not only precision gob for manufacturing optical elements, but also other glass parts, especially small glass parts, preferably weighing less than 10 grams. .

  The invention will be described in more detail below with reference to the drawings using exemplary embodiments. Identical and similar elements are provided with the same reference signs, and features of different exemplary embodiments can be combined with each other.

  Reference is now made to FIG. 1, which shows a first embodiment of an apparatus 1 for simultaneous multiple division of glass divisions from a glass melt. The principle of this device is based on a valve device 100 having a valve for blocking the glass melt flow and a nozzle 3 having a plurality of outlet openings 7 arranged downstream of the valve for blocking the glass melt flow.

  In the example shown in FIG. 1, the valve device 100 is specifically designed as a needle feeder having a feeder needle 103. Furthermore, the apparatus is provided with a force sensing device 102, which is used at least partly during positioning of the tip of the feeder needle 103 relative to the seat of the feeder needle 103, in particular in the x-direction, y-direction, and It is possible to measure the force acting on the feeder needle 103 in the z direction.

The apparatus 1 further has a reservoir 104 for the low viscosity glass melt 20 that can be heated using a heater 106, which is disposed within the insulation 112. By using the heater 106, the glass is softened by preferably up to ¹⁰ 4 dPa · s, preferably at up to ¹⁰ 3 dPa · s, a glass temperature _{T g} of the as yet has a low viscosity of up to ¹⁰ 2 dPa · s It is heated to above and also exits the exit opening at this low viscosity. The glass can be fed, for example, via a discontinuously operated crucible or via a continuously operated melting tank furnace. So-called low-T _g glass having a viscosity of temperature 10 ^{7.6 dPa} · s up to 670 ° C. is treated processed, which in particular, these glasses is because particularly suitable blank press.

  By moving the feeder needle 103 in the opposite z-direction, the feeder needle seat 107 can be released at the lower end of the reservoir 4, which is preferably tapered in the shape of a funnel, so that it is heated The glass 20 is led from the reservoir 4 to a particularly tubular outflow device, in particular a feeder channel 109. Accordingly, the feeder needle 103 serves as a valve together with the feeder needle seat 107 at this time. The end of the feeder channel 109 serves as the inlet 5 to the nozzle 3 with the outlet opening 7, which is arranged below the channel 109 and the feeder needle 103 and downstream of the valve with the feeder needle 103. Positioned.

  The nozzle 3 can then discharge the divided glass melt 20 to a further production device. The further production device (not shown) can be any press device, in particular a gob, an optical component, in particular a lens, a Fresnel lens, and / or a precision press device for producing a plane, in particular a plane parallel plate.

  The method carried out with this device 1 for simultaneous multiple division of glass divisions from the glass melt 20 is such that the glass melt stream exits through a nozzle 3 having a plurality of outlet openings 7 and exit openings. 7 is cut off by blocking the glass melt flow by the clock-type opening and closing of a valve upstream of the nozzle and having the feeder needle 103 and the feeder needle seat 107, so that the individual glass divided portions are opened to the outlet opening 7. Based on coming to fall from.

  The reservoir 104, preferably the feeder channel 109 and the heater 106, are also surrounded by an insulating refractory material, allowing a very accurate temperature setting of the glass melt 20 in the reservoir 104 and feeder channel 109.

  Furthermore, the apparatus 1 shown in FIG. 1 can have a device for adjusting the level of the glass melt 20, so that the feeder needle seat 7 is preferably highly accurate with filling of softened material or a lot to be melted. The pressure above can be maintained. In particular, it is possible to use a continuous melting method for the melt filling for this purpose. In order to maintain a constant outflow rate over many feeder strokes, this level adjustment also achieves an adjustment of the hydrostatic pressure of the glass melt, particularly at the outlet opening 7.

  In the embodiment shown in FIG. 1, the feeder needle 3 is pivotally supported on the garose 113 by a universal suspension device 114.

  The gallose 113 has a mast 115 that is mechanically fixedly held with respect to the reservoir 104, to which is attached a precise longitudinal displacement device 116 in the z direction, which is preferably a control device (FIG. (Not shown) and can be controlled and moved by a servo motor, and a clocked interruption of the melt flow through the feeder channel 109 is effected by periodically lowering the feeder needle into the feeder needle seat 107. This control device may be local or networked and may be a central processing controller known in particular to those skilled in the art.

  Furthermore, the longitudinal displacement device 116 has a distance sensor that detects its exact location in the z direction and relays it to the detection and storage device 117.

  The universal suspension 114 is permanently attached to the xy displacement device 118, and the xy displacement device 118 can be moved in a defined manner in the x and y directions, and is itself attached to the displacement device 116. Permanently retained.

  The xy displacement device 118 also has a position transmitter that can be used to detect the position of the xy displacement device and relay it to the detection and storage device 117.

  Furthermore, the xy displacement device 118 preferably has a servo motor drive unit, whose position can be moved in a defined manner by a control device (not shown).

  With this configuration, the feeder needle 103 can be moved in any of the x direction, the y direction, and the z direction by a prescribed method, and each position can be detected and stored by the detection device 117.

  Furthermore, by performing a plurality of position measurements at a defined time relative to each other, it is possible to determine the speed and acceleration of the feeder needle continuously in time or at specific time intervals.

  This makes it possible to detect the speed of the feeder needle 103 that is too fast or too slow and the acceleration that causes danger or wear.

  In particular, the velocity or acceleration in the z direction of the feeder needle tip 119 is limited to a maximum value by the velocity value being relayed to the control device and limited by the control device acting on the longitudinal displacement device 116. be able to.

  This makes it possible to avoid an undesirably strong force when the feeder needle tip 119 hits a part of the reservoir 104, in particular the feeder needle seat 107.

  Furthermore, knowing the location of the feeder needle 103 can define regions where very fast velocities are allowed in the x, y, and z directions, for example, only slow velocities near the walls of the reservoir 104, especially the feeder. It is possible to define a region that uses a speed that avoids damage to the needle 103 or reservoir and seat 107.

  A heater 30 is arbitrarily disposed below the nozzle 3. This heater can be, for example, a device for radiant heating and / or induction heating of the nozzle. Infrared or fishtail burner heaters are preferred. Device 30 can also include a reflector for infrared, which is used to retroreflect heat radiation to nozzle 3 to minimize heat loss. In an advantageous development, the device 30 does not interrupt the device 30 during feeding so as not to interfere with a support that holds the glass dividing part, for example a support with a floating recess for support and conditioning on the gas cushion. It can also be a movable design to keep it away from the nozzle. In this way, the device 30 can be moved to a predetermined position during the non-feeding process time to heat the nozzle 3 or at least reduce heat loss.

  A further heater 105 arranged on the side of the nozzle 3 is also provided, which is used to heat the nozzle. This heater can be, for example, an induction heater for direct induction heating of a nozzle or a radiant heater for indirect heating.

  FIG. 2 shows the nozzle 3 of the present invention in detail as a supplement to FIG. The nozzle comprises a conical base body 13 which is arranged at the lower end of the feeder channel 109 and to which a flat base plate 11 is attached. An outlet opening 7 projects downward from the base plate 11. For this purpose, the base plate 11 has a tube 9 protruding from the plane and leading to the outlet opening 7.

  The design of the outlet opening in the manner of projecting downward from the plane of the base plate 11 is used when the valve is closed by placing the feeder needle tip 119 on the feeder needle seat 107 or the feeder channel 109 is closed in order to obtain the most accurate division possible. Help the glass gob fall. In this case, the tube end portion of the tube 9 forms a separation edge for facilitating the fall of the glass divided portion.

  Furthermore, the channel to the outlet opening 7, and thus the inner wall of the tube 9 in the case of the example shown in FIG. Thereby, generation | occurrence | production of the defect of the glass gob resulting from the unevenness | corrugation of the inner surface 15 which arises similarly at the time of shearing of a glass strand is prevented. For this reason, it is also advantageous for the outlet opening 7 and the inner surface 15 to be deburred.

  As can further be seen from FIG. 2, all outlet openings are arranged along the virtual circle 17. In this case, the center of the circle 17 coincides with the central axis passing through the feeder channel 109, so that all the outlet openings 7 further from the inlet 5, and therefore in the case of the example shown in FIG. It will also be arranged at the same radial distance from the entrance opening to 3.

  The interior of the nozzle 3 is also preferably designed symmetrically with respect to the central axis passing through the feeder channel 109. The overall result is therefore that the arrangement of the interior and outlet openings of the nozzle is designed to be axially or rotationally symmetric with respect to a symmetry axis extending perpendicularly and centrally through the inflow opening or with respect to the inlet of the nozzle 3. A configuration is obtained. As a result, the total diversion flowing out from the outlet opening 7 is the same. In this way, in particular, the temperature distribution of the entire shunt or the glass segment produced therefrom is as identical as possible.

  As is clear from FIG. 1, the plane of the base plate is arranged as horizontally as possible. In particular, at this time, all the outlet openings 7 are at the same level. For example, a difference in state caused by a difference in hydrostatic pressure at the outlet opening is also avoided.

  The tube 9 is kept as short as possible so that the glass melt 20 is not cooled as it passes through it. In this case, the tube preferably has a ratio of the inner diameter to the tube length of at least 0.3, particularly preferably at least 0.4, in this regard the tube measured from the outside from the outer surface of the base part 11 to the outlet opening 7. The length of is the tube length.

  The outlet opening has an inner diameter of at least 0.5 millimeters and, according to a further embodiment, is also at least 1.5 millimeters, preferably in the range of 1 or 2-12 millimeters. These ranges have been found to be advantageous for achieving high throughput when dividing glass for conventional sized optical components for the mass market. The base plate is further typically 25-60 millimeters in diameter and the feeder channel 109 is typically 3-16 millimeters in diameter.

  A preferred material for the nozzle 3 is a noble metal alloy. In particular, according to an advantageous development of the invention, the concept is to use a noble metal alloy base element 11 into which the outlet opening is inserted. In general, forged noble metal alloy parts have been used to date to guide the glass melt.

  However, in order to achieve the high accuracy required for the division, at least the base element is a part milled from a single piece. Such parts with exit openings milled or drilled can be made with high precision, which is also directly reflected in the small weight tolerances of the glass divisions produced. If the base part 11 is made from a single piece, as a result, the short tube 9 is also milled from the corresponding thickness plate.

  In order to calibrate the base part 11 with outlet openings for as even a flow through as possible through all outlet openings, it is easily possible to perform a flow-through test with a replacement liquid, for example water. In this case, according to one procedural mode for calibrating the nozzle 11, for example, a predetermined amount of replacement liquid is supplied by filling the reservoir 104 to a specific level, and a partial amount of liquid flowing through each outlet opening 7 is reduced. Compare. If the amounts of liquid are too different from each other, each outlet opening 7 can be reworked as appropriate. Of course, such a calibration can also be performed using a glass melt, but such a test is somewhat more complicated than a calibration using a replacement liquid.

  FIG. 3 shows the nozzle 3 of the apparatus 1 in which a support base 35 is arranged below. The support pedestal 35 is particularly designed as a levitation support pedestal with a membrane 39 of unitary design, preferably with a buoyancy recess 36 each supporting one glass segment. In this case, FIG. 3 shows the layout after the glass segment 2 has been fed into the recess 36 via the nozzle 3.

  According to the present invention, as a result of a plurality of glass divisions being simultaneously fed into the recess 36 and supported on a common levitation support 35, all the glass divisions supported in parallel are further as much as possible. It is conditioned as well. In the case of the example shown in FIG. 3, the number of the recesses included in the levitation support base 35 and the number of outlet openings 7 included in the nozzle are ten.

  In particular, the unitary membrane 39 is advantageous for this purpose. This is because, in particular, it is possible in this way to adjust the gas flow to all the recesses 36 in parallel using an adjusting device. The floating recess 36 is also arranged along a circle according to the outlet opening 7 of the nozzle 3.

  In this exemplary embodiment, the levitation support 35 can be rotated about the axes 181, 182 of the moving unit 19 to pass the glass segment to one or more press dies (not shown). Can be swung using the swing arms 171, 172, 173, 174, and the levitation support base 35 is guided in parallel by the arrangement of the swing arms 171, 172, 173, 174 and the shafts 181, 182 at this time. . This means that the orientation of the levitation support is maintained during swinging.

  In order to pass the glass segment, the levitation support is swung downward with an acceleration greater than the acceleration due to gravity. Due to the advantageous parallel guidance, the movement of all the recesses 36 during swinging is likewise fast.

  Conditioning of the glass segment on the gas cushion formed in the recess under the glass segment, in this case, by cooling the glass segment to a viscosity above the adhesive viscosity while supported on the surface. It is preferable that it is carried out so that it rises and stays at least below the softening point inside the glass dividing portion. The conditioned glass segment can then be placed in a press mold (not shown) and pressed to final contour and surface quality in the press mold.

  An exemplary embodiment of a particularly preferred embodiment of the nozzle 3 is shown in the cross-sectional view shown in FIG. FIG. 5 shows a plan view seen from below the base of the nozzle shown in FIG. Just as in the case of the nozzle 3 shown in FIGS. 1 to 3, this nozzle also has a rotationally symmetric design with respect to the central axis passing through the inlet 5 or the feeder channel. In this example, the nozzle 3 comprises a funnel-shaped cover 31 to which a base part 11 having an outlet opening 7 is connected below. Just as in the example described above, the outlet opening 7 is arranged along a circle centered on a central axis 50 through the inlet 5. As can be seen from FIG. 5, this example provides six discharge apertures distributed axially or rotationally symmetrically on this circle. Inside the nozzle at the center of the base part, there is provided a convex portion 33 that is also arranged rotationally symmetrically with respect to the central axis of the inlet 5. Thereby, even if it rotates 60 degree | times centering on the center axis | shaft 50 of the inlet_port | entrance 5, a rotationally symmetrical design is obtained as a whole.

  The recess 34 in the base of the nozzle 3 corresponds to the convex portion 33 inside the nozzle. However, this depression is not essential and is indicated, for example, when the base part is manufactured by shaping a metal sheet. The internal convex portion 33 has an effect of improving the outflow of the melt from the base toward the outlet opening 7 arranged around the convex portion. This avoids slow flow regions or even dead zones in the melt flow, which can lead to melt fluctuations due to, for example, chemical reaction or material uptake from the nozzle. In particular, platinum moving from the refractory metal nozzle to the melt can affect transparency. It can be seen that the central protrusion 33 is very advantageous for the transparency of the glass and for the moldability of the gob and thus ultimately for the dimensional stability of the lenses produced therefrom.

  Just as in the example of FIGS. 1 to 3, in the exemplary embodiment shown in FIG. 5, the outlet opening is also arranged at the end of a short tube 9 protruding downward from the nozzle body. The tube tapers conically to the outlet opening 7 and the wall of the tube end is the same as the sharp edge of the outlet opening so that the tube end forms a separating edge that helps the melt fall off. Designed like a cutting blade.

  In the example shown in FIG. 4, the ratio of the inner diameter or diameter 92 of the outlet opening to the tube length 91 measured outside is 0.6. Suitable are generally short tubes with a ratio of inner diameter to tube length measured externally in the range of 0.1-2.

  A further exemplary embodiment of the nozzle 3 is shown in cross section in FIG. FIG. 7 shows a plan view of the base of this nozzle.

  The nozzle 3 shown in FIGS. 6 and 7 has a double wall-like funnel shape or bell shape extending downward. In this case, the glass melt is guided between the inner wall 38 and the outer wall 37 of the double-walled nozzle, and at this time, the inner wall 38 and the outer wall 37 extend substantially in parallel. Starting from the inlet 5, the nozzle first spreads downward in a funnel shape. Adjacent to this funnel section is a tubular section 32, at the lower edge of which is further disposed a short tube 9 with an outlet opening 7. Just as in the exemplary embodiment shown in FIGS. 4 and 5, in order to facilitate the fall of the glass melt when the upstream valve blocks the melt flow, the tube is connected to the outlet opening 7. The separating edge is formed by taking the form of a cutting edge that tapers toward the tip.

  In this exemplary embodiment, 17 outlet openings 7 are arranged rotationally symmetrical at a rotation angle of 360 degrees / 17 = 21.18 degrees along a circle centered on the central axis 50 of the inlet and nozzle 3. Is provided.

  As an example, in this exemplary embodiment, the tube 9 has a ratio of the inner diameter to the tube length measured externally of 0.2.

  This double-walled bell-shaped or funnel-shaped nozzle may be particularly advantageous for small gobs with a weight in the range of 0.05 to 0.5 grams, preferably in the range of 0.1 to 0.3 grams. I understand. In contrast, a nozzle as described by way of example with reference to FIGS. 4 and 5 is particularly suitable for large gobs from 0.3 grams, preferably in the range of 0.3 to 2 grams. Thus, depending on the weight of the gob, for the exemplary embodiment of FIGS. 4 and 5, the amount of glass divided per stroke using the upstream valve is in the range of 0.3-2 grams. The weight of the gob is 6 × 0.3 grams = 1.8 grams to 6 × 2 grams = 12 grams. Depending on the weight of the gob, in the exemplary embodiment of FIGS. 6 and 7, the amount of glass divided per stroke with the weight of the gob in the range of 0.1-0.3 grams is 0.1 0.1 grams x 17 = 1.7 grams to 0.3 grams x 17 = 5.1 grams with a gob weight in the range of -0.3 grams.

  Those skilled in the art will appreciate that the present invention is not limited to the exemplary embodiments described above, but can be varied in a wide variety of ways. In particular, the features of the individual exemplary embodiments can also be combined with one another.

2 shows an exemplary embodiment of the device of the present invention. Figure 2 shows a diagram of the nozzle of the device of the present invention. The figure of the nozzle by which the support stand which has a some floating recess is arrange | positioned below is shown. A sectional view of a nozzle is shown. The top view of the base of the nozzle shown in FIG. 4 is shown. FIG. 4 shows a cross-sectional view of a further exemplary embodiment of a nozzle. The top view of the base of the nozzle shown in FIG. 6 is shown.

Claims (48)

A maximum 670 ° C. Low viscosity glass having a viscosity of temperature at 10 ^{7.6 dPa} · s of, particularly, to a method for precisely divided glass or low T _g glass blank press, in the case of the method, division section (Portions From a clocked needle feeder having a nozzle having a plurality of outlet openings, wherein a weight fraction in the range of 0.2 to 10 grams with a relative and / or absolute weight deviation of less than 5% based on the average weight of Manufactured from a continuous melting process with multiple feeds.   The method of claim 1, wherein the nozzle is indirectly heated from the side.   The method according to claim 1, wherein the nozzle is heated from below.   4. A method of simultaneously multiplex-dividing a glass segment from a glass melt by the method according to any one of claims 1 to 3, wherein the glass melt stream has a plurality of outlet openings. A method in which the diverted flow out of the nozzle and out of the outlet opening is interrupted by shutting off the glass melt flow by clocked opening and closing of a valve upstream of the nozzle and individual glass segments fall from the outlet opening.   5. A method according to any one of the preceding claims, characterized in that the glass split part is fed into a floating recess and supported on a floating cushion.   6. A method according to claim 5, characterized in that the diversion flows out of the outlet openings arranged at the same level.   7. A method according to claim 5 or 6, characterized in that the diversion flows out of the outlet opening arranged along a circle.   8. A method according to any one of the preceding claims, characterized in that the diversion flows out of the outlet opening arranged at the same radial distance from the inlet of the nozzle.   9. A method according to any one of the preceding claims, characterized in that the nozzle is induction heated.   10. A method according to any one of the preceding claims, characterized in that the nozzle is radiantly heated.   11. A method according to any one of the preceding claims, characterized in that thermal radiation is reflected back to the nozzle by a reflector.   12. A method according to any one of claims 9 to 11, characterized in that the induction heating or the radiant heating or the reflector is moved away from the nozzle during feeding.   The method according to claim 1, wherein the glass melt flow is interrupted in a clocked manner using a needle feeder.   A force sensing device is used, preferably a force sensing device that takes measurements in the x, y and / or z direction at least partly during positioning of the tip of the feeder needle relative to the feeder needle seat. The method according to claim 13, wherein:   15. A method according to any one of the preceding claims, characterized in that the glass split part falls from a separation edge at the outlet opening. 16. A method according to any one of the preceding claims, characterized in that the glass melt exits the outlet opening with a viscosity of up to 10 ⁴ dPa · s, preferably up to 10 ³ dPa · s.   The viscosity of the glass segment while supported on the surface rises above the adhesive viscosity by cooling and stays at least below the softening point inside the glass segment, and subsequently the glass segment is The method according to claim 16, characterized in that it is placed in a press mold and pressed to the final contour and surface quality in the press mold.   18. A method according to any one of the preceding claims, characterized in that a glass segment with a weight in the range of 0.05 g to 150 g, in particular 0.1 g to 150 g, is segmented.   19. A method according to any one of the preceding claims, characterized in that the hydrostatic pressure of the glass melt is adjusted at the outlet opening, in particular by a continuous melting method.   20. A method according to any one of the preceding claims, characterized in that the flow through the outlet opening is calibrated by measuring the flow through of the replacement liquid.   21. A method according to any one of the preceding claims, characterized in that an amount of glass in the range of 0.8 to 20 grams is divided for each supply stroke. A low-viscosity glass having a viscosity of 10 ^7.6 dPa · s at a temperature of up to 670 ° C., in particular for blank presses or low, in particular for carrying out the method according to claim 1. An apparatus for precisely dividing _Tg glass, comprising a nozzle made of a noble metal alloy, the nozzle having a plurality of outlet openings arranged on a circle centered in the center of the nozzle.   23. Apparatus according to claim 22, characterized by a heating device that heats the nozzle directly or indirectly from the side.   The device according to claim 22 or 23, characterized in that the nozzle is heated from below.   25. Apparatus according to any one of the preceding claims, characterized by a floating recess having a plurality of receptacles for glass splits, each assigned to the outlet opening of the nozzle.   In particular, an apparatus for simultaneous multiple division of a glass divided portion from a glass melt according to any one of claims 1 to 25, comprising a valve device having a valve for interrupting the glass melt flow, And a nozzle connected downstream of the shut-off valve and having a plurality of outlet openings.   27. Apparatus according to claim 26, characterized in that the outlet openings are arranged at the same level.   28. Device according to claim 26 or 27, characterized in that the outlet openings are arranged along a circle.   29. Apparatus according to any one of the preceding claims, characterized in that the outlet opening is arranged at the same radial distance from the inlet of the nozzle.   30. The arrangement according to any of the preceding claims, characterized in that the arrangement of the interior of the nozzle and of the outlet opening is axisymmetric with respect to a symmetry axis extending perpendicularly and centrally through the inflow opening or with respect to the inlet of the nozzle. The apparatus according to claim 1.   31. A device according to any one of the preceding claims, characterized in that the nozzle comprises a flat base plate, in particular with a protruding outlet opening.   The nozzle is arranged with a convex part arranged in the center of the inside, and is arranged radially away from the center of the convex part around the convex part, and thereby particularly preferably around the vertical central axis of the nozzle 32. Device according to any one of the preceding claims, characterized in that it comprises a base part having a plurality of outlet openings arranged symmetrically.   It is characterized by a double-walled downwardly spreading funnel-shaped or bell-shaped nozzle for guiding the glass melt between the walls, particularly preferably in this case on the lower edge of the nozzle. 33. Apparatus according to any one of claims 1 to 32, characterized in that a plurality of outlet openings are provided which are arranged symmetrically about a vertical central axis.   2. The nozzle according to claim 1, characterized in that it has a tube with the outlet opening protruding from a plane, the tube having a ratio of the inner diameter to the tube length of at least 0.3, preferably at least 0.4. 34. The device according to any one of thru 33.   35. The nozzle according to any one of claims 1 to 34, wherein the nozzle has a protruding tube having the outlet opening, and a ratio of an inner diameter to a tube length measured outside is in a range of 0.1 to 2. The device described in 1.   36. Device according to any one of the preceding claims, characterized in that the outlet opening has an inner diameter of at least 0.5 millimeters, preferably in the range of 1 to 12 millimeters.   37. Apparatus according to any one of the preceding claims, characterized in that the nozzle comprises a base element that has the outlet opening and is milled from a single piece.   38. Apparatus according to any one of the preceding claims, characterized in that the outlet opening is inserted into a noble metal alloy base element.   Device according to any one of the preceding claims, characterized in that it comprises a nozzle, preferably made of a noble metal alloy, with an individually replaceable outlet opening element.   40. Apparatus according to any one of the preceding claims, characterized in that the channel to the outlet opening is deburred and polished.   41. Apparatus according to any one of claims 1 to 40, characterized by induction heating of the nozzle.   42. Apparatus according to any one of claims 1 to 41, characterized by radiant heating of the nozzle.   43. Apparatus according to any one of claims 1 to 42, characterized by a reflector for retroreflecting thermal radiation to the nozzle.   44. Apparatus according to any one of claims 41 to 43, characterized by a device that moves the induction heating, the radiant heating or the reflector.   45. Apparatus according to any one of claims 1 to 44, wherein the valve device comprises a needle feeder.   To measure the force acting on the feeder needle at least partly during the positioning of its tip relative to the feeder needle seat, in particular in the x, y and / or z direction. 46. Apparatus according to claim 45, characterized by a force sensing device capable.   A particularly blank-pressed surface and / or fire that can be produced using the method according to any one of claims 1 to 21 or with the device according to any one of claims 22 to 46. Charge of at least 100 optical components or gobs having a built-up surface, characterized by a maximum weight deviation of said optical components or gobs of less than 5%.   An optical glass gob or an optical component made therefrom having a weight of up to 10 grams, wherein the optical glass of the gob or optical component has less than 2 percent transmission loss due to noble metal impurities. An optical glass gob or an optical component manufactured therefrom.

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