EP3542116A1 - Agencement d'un four et de débris de particules de verre et procédé permettant de faire fonctionner un four - Google Patents

Agencement d'un four et de débris de particules de verre et procédé permettant de faire fonctionner un four

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Publication number
EP3542116A1
EP3542116A1 EP17825747.3A EP17825747A EP3542116A1 EP 3542116 A1 EP3542116 A1 EP 3542116A1 EP 17825747 A EP17825747 A EP 17825747A EP 3542116 A1 EP3542116 A1 EP 3542116A1
Authority
EP
European Patent Office
Prior art keywords
glass particles
furnace
pressing
cluster
arrangement
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP17825747.3A
Other languages
German (de)
English (en)
Inventor
Rudolf Jussel
Harald Bürke
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ivoclar Vivadent AG
Original Assignee
Ivoclar Vivadent AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ivoclar Vivadent AG filed Critical Ivoclar Vivadent AG
Publication of EP3542116A1 publication Critical patent/EP3542116A1/fr
Pending legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B17/00—Furnaces of a kind not covered by any of groups F27B1/00 - F27B15/00
    • F27B17/02—Furnaces of a kind not covered by any of groups F27B1/00 - F27B15/00 specially designed for laboratory use
    • F27B17/025—Furnaces of a kind not covered by any of groups F27B1/00 - F27B15/00 specially designed for laboratory use for dental workpieces
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
    • A61C13/00—Dental prostheses; Making same
    • A61C13/08—Artificial teeth; Making same
    • A61C13/083—Porcelain or ceramic teeth
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
    • A61C13/00—Dental prostheses; Making same
    • A61C13/20—Methods or devices for soldering, casting, moulding or melting
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K6/00—Preparations for dentistry
    • A61K6/80—Preparations for artificial teeth, for filling teeth or for capping teeth
    • A61K6/849—Preparations for artificial teeth, for filling teeth or for capping teeth comprising inorganic cements
    • A61K6/853—Silicates
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B19/00—Other methods of shaping glass
    • C03B19/09—Other methods of shaping glass by fusing powdered glass in a shaping mould
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C1/00—Ingredients generally applicable to manufacture of glasses, glazes, or vitreous enamels
    • C03C1/04—Opacifiers, e.g. fluorides or phosphates; Pigments
    • C03C1/06—Opacifiers, e.g. fluorides or phosphates; Pigments to produce non-uniformly pigmented, e.g. speckled, marbled, or veined products
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C10/00—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D19/00—Arrangements of controlling devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D3/00—Charging; Discharging; Manipulation of charge
    • F27D3/0033—Charging; Discharging; Manipulation of charge charging of particulate material
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D19/00—Arrangements of controlling devices
    • F27D2019/0003—Monitoring the temperature or a characteristic of the charge and using it as a controlling value
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D19/00—Arrangements of controlling devices
    • F27D2019/0028—Regulation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D19/00—Arrangements of controlling devices
    • F27D2019/0028—Regulation
    • F27D2019/0071—Regulation using position sensors

Definitions

  • the invention relates to an arrangement of a furnace and a cluster of glass particles, according to the preamble of claim 1, and a method for operating a furnace, according to the preamble of claim 12.
  • Special ovens such as dental kilns or dental press ovens may be used to make dental restorations of e.g. Ceramic, glass or glass ceramic can be used.
  • Glass ceramic powders and / or crystallisable glass particles can be used in the production of dental restorations made of glass ceramic, which are preferably pre-heated in a combustion chamber of a kiln or in a press chamber of a press furnace a burning plate is placed.
  • the glass ceramic powders or glass particles are first heated to a desired viscous state. Finally, during a compression process, these soft glass or glass ceramic particles are pressed under pressure into a solid block or pressed into the mold cavities for dental restoration parts via the cannulated channels of the muffle arranged under the glass or glass ceramic particles until the mold cavities are completely filled.
  • dental restoration parts of e.g. Lithium silicate provided.
  • the resulting glass ceramic is inferior, because the uncontrolled crystallization creates an unfavorable critical structure with a broad crystal size distribution. It is therefore desirable that complete densification of the glass particles take place prior to crystallization.
  • WO 2014/131588 A1 has disclosed a method for detecting the temperature of a blank itself.
  • a holding time is inserted, which is intended to compensate for the temperature and in which the hot outer areas of the muffle deliver their heat to the muffle center and thus the heap of glass particles.
  • this hold time significantly increases the press cycle depending on the size of the muffle, which is sometimes not considered acceptable.
  • a corresponding control program with suitable temperature profiles and holding times must be selected.
  • the extension of the holding time can not exclude the possibility that the relevant boundary conditions in the process will not be able to affect the result.
  • the invention has for its object to provide an arrangement of a furnace and a cluster of glass particles according to the preamble of claim 1 and a method for operating a furnace according to the preamble of claim 12, which ensures the quality of to be produced dental restoration parts made of glass and independent of the size of a heap of glass particles or the associated muffle a shortened pressing cycle allowed. Included in this is the task of producing a block or blank or other preform made of glass, which serves as a starting material for the production of a dental restoration.
  • a rapid heating of these is carried out before the compaction of the aggregate of glass particles.
  • the nucleation of the crystallizable glass particles begins depending on the material in the transformation region Tg (also referred to as "transformation point Tg") of the glass particles and has its maximum velocity during the increase in temperature at a temperature range about 50 ° C over the transformation range Tg of the glass particles (Tg + 50 ° C). As the temperature continues to increase, the rate of nucleation slows down.
  • the compaction speed of the glass particles is measured in a temperature range e.g. increased between 50 ° C over the transformation range Tg of the glass particles (Tg + 50 ° C) and 100 ° C over the transformation range Tg of the glass particles (Tg + 100 ° C) with increasing temperature.
  • the glass particles are heated to a temperature range e.g. 70 ° C above the transformation range (Tg + 70 ° C) only a few germs (to the extent desired) formed. It is favorable that in the compaction according to the example from the temperature range - 70 ° C over the transformation range Tg (Tg + 70 ° C) - result due to the few germs and a few glass crystals.
  • the parameters for the compression process can be determined independently of the amount of glass particles, the material of the glass particles and the size of the muffle.
  • the compacted debris of the glass particles can be cooled immediately. Because with a further increase in the temperature - subsequent to the above-mentioned example - over the "Tg + 100 ° G" range slows the speed of compaction of the glass particles, while accelerating the rate of crystallization. In this case, the invention by a controlled temperature or after the compaction immediate cooling of the glass particles further diminished the crystal growth.
  • the inherent physical parameters of glass particles can now be used as a criterion for the first time with the invention.
  • the surface of the dental restoration part to be produced is checked.
  • there is a temperature gradient and the size of the debris also accounts for the temperature difference between inside and outside.
  • Another disadvantage of the previously known solution is that additional and costly measurement technology must be attached to the device.
  • For the process control includes the start of the pressing process, at which start the furnace temperature, the pressure in a combustion chamber of the furnace and a pressing force of the ram are controlled by the control device.
  • this includes the end of the pressing process or the beginning of a cooling process subsequent to the pressing process, in which end or beginning the pressing force of the press ram by the control device, in particular reduced to zero, and the furnace temperature by the control device, in particular by switching off the furnace and / or the opening of the furnace hood, is reduced.
  • the decrease in press speed can be used as a triggering criterion for the shutdown of the furnace.
  • the furnace shutdown criterion is satisfied, which means that automatically or manually the pressing process should be terminated and the cooling process should be started.
  • the back pressure on the ram due to the heating of the glass particles and the investment material in the lower part can be measured by a pressure sensor and used as a trigger criterion for the process control.
  • the pressing process should be started when the detected back pressure remains constant within a predetermined time to a predetermined level.
  • the location of the ram can be detected by a location sensor and used as a triggering criterion for the process control.
  • the oven should be switched off when the location of the ram almost does not change during the pressing process within a predetermined time.
  • the heap of glass particles according to the invention from different starting glasses is first filled into the pressing channel of the furnace where it forms gradients, in particular color and / or translucency gradients, so that the dental restoration parts to be produced have desired gradients which match the oral situation of a patient.
  • the gradients correspond to at least one gradual layer-wise and / or one continuous change of a physical property of the cluster of glass particles.
  • the heap of glass particles consists of different colored glass particles and / or at least one type of glass, which is colored differently with pigments.
  • Pigments include, among others, colored pigments, cloudy pigments and fluorescent pigments.
  • pigments are particularly suitable at relatively low process temperatures. At higher process temperatures such pigments are chemically or thermally not stable in the respective glass matrix and would partially or completely decompose.
  • the heap of glass particles consists of glasses with different contents of nucleating agents.
  • a block with different crystal sizes and / or different strengths in different areas may result.
  • the heap of glass particles consists of glasses with different densities. A particularly soft, elastic region, which is suitable for the reproduction of dentin with low hardness, is possible by controlled generation of residual porosity.
  • non-ideal starting conditions from previous process steps such as a correct preheating temperature or preheating time of the muffle are taken into account or corrected or compensated.
  • the heap of glass particles is - long before the pressing process - on the ram - typically via the interposition of a plunger, for example, Al 2 0 3 , pressurized.
  • a plunger for example, Al 2 0 3
  • On its upper end face now acts a force and a pressure that is absorbed by its underside, but partly also to an elastic deformation of the glass particles - but in (very) small extent - leads. In any case, this force and the deformation is sufficient to make the arrangement of the glass particles, which is loose after insertion in the muffle, firmer and more stable.
  • the muffle mass typically has a comparatively low coefficient of thermal expansion, for example, 3 x 10 -6 / K, while the glass particles of, for example lithium silicate have a significantly higher thermal expansion coefficient of for example 10 x 10 "6 / K.
  • Glass particles have a coefficient of thermal expansion of, for example, 10 or 10.5 ⁇ 10 -6 / K below the so-called glass transition region. Although the coefficient of thermal expansion clearly increases when the so-called phase transition of the second order is exceeded, for example to 14.5 ⁇ 10 -6 / K, due to the softening of the glass particles, the shape of the glass particles also changes in particular but also to enter the Anuxkanäle for the dental restoration cavities after the pile of glass particles has now become viscous.This represents a significant overcompensation of the increasing coefficient of thermal expansion.
  • micro-pulses are observed which, due to the thermal expansion of the ram, plunger, glass particles and surrounding muffle, cause little and momentary movement between the upper or near-end of the lump of the glass particle and the muffle play. It is particularly favorable that thereby the time course of the thermal expansion as a result of the heating of the introduced Systems consisting of muffle, intermediate plunger and in particular the heap of glass particles can be detected.
  • the control device determines the beginning of the press independently of the temperature measured by the temperature sensor as a function of the termination of the micro-pulses.
  • control device starts the press start based on an increase in the measured time duration between two consecutive micro-pulses above a predetermined threshold.
  • control device lowers the heating power to a nominal value as the time duration between two successive micro-pulses increases over a predetermined, in particular second threshold value.
  • the time profile of the micro-pulses is evaluated and a tripping criterion for the process control is established either at the termination of the micro-pulses of the movement parameters of the glass particles and / or upon detection of a predetermined number of micro-pulses and / or by evaluating the time interval between the micro-pulses.
  • the triggering criterion for the actual pressing process is monitored by the movement parameters, and the occurrence of short-term micromotion is monitored and used as a criterion. It is understood that the micro-movements are directed against the pressing direction, due to the thermal expansion of the entire system ram / plunger / glass particles / muffle / combustion chamber shell.
  • the pressing punch moves during the heating of the glass particles by a predetermined amount against the pressing direction, which is in particular less than 1 mm and particularly preferably between 0.3 and 0.5 mm.
  • a displacement sensor or a speed sensor is primarily suitable.
  • the resolution should be at least 0.01 mm or a corresponding speed size, preferably 50 ⁇ per second. Otherwise, that is, for example, when the pressing force is applied via a stepper motor with a non-elastic or low elastic drive train, the realization of a force sensor or pressure sensor as a sensor for the detection of microimps is possible. Alternatively, a pure displacement measurement, possibly at a pressing force close to zero, is possible.
  • the amplitude and frequency of the micro-pulses of course depends on physical parameters, for example on the material of the glass particles to be pressed, the investment material used, the temperature, but also, for example, the applied pressing force or its regulation.
  • the thermal expansion counteracting the pressing force is essentially composed of the thermal expansion of the press ram, of the pressing piston, of the glass particles, and of the muffle below the glass particles.
  • the insulation area of the furnace below the combustion chamber floor is also warmed up a bit and expands accordingly.
  • the fact that the pressing ram is in contact with the interposed pressing piston and thus also with the upper end of the cluster of the glass particles, preferably under a contact pressure, can be exploited in a particularly favorable manner.
  • the pressing force can be transmitted without time delay, as well as the backward movement in the material expansion of the glass particles.
  • the control device for the control of the pressing process not only detects this, but also controls the further course of the temperature-time profile.
  • the heating surrounds the cylindrical combustion chamber in a conventional manner as a ring heating and heated by convection and heat radiation mainly the muffle, but also of course located therein heap of glass particles and optionally the plunger, typically in a few minutes to several 100 ° C.
  • the wall thickness of the thermal insulation is five centimeters or less and is thus in the range of the diameter of the muffle or below.
  • auxiliary pressing force between three and fifty percent of the nominal pressing force, since this is already sufficient to produce the desired movement hysteresis.
  • the seals between the furnace hood and the furnace underside, or for example between the furnace hood and an approachable firing table, are compressed to the predetermined extent.
  • the compression may well be in the range of several millimeters and would falsify the measurement result if the negative pressure during the pre-press, ie during the detection of the triggering criterion, would be built up.
  • the underpressure can already be established within a considerably shorter than the required heating time of the furnace, for example within 1 to 2 minutes.
  • the negative pressure can be reduced by, for example, a whole or partial ventilation of the combustion chamber. If subsequently another area of the glass particles is also densified, then there will be in the gaps between the glass particles this Enclosed area of air and thus prevents a complete consolidation of this area. This results, for example, in a block with different densities.
  • a force control is provided for the press drive. Due to the heating and thus during the thermal expansion of the drive train (including the bulk of the glass particles) must be a readjustment, z. B. when exceeding a predetermined force. With a correspondingly good setting of this Nachregelcharaktstik a qualitatively and quantitatively well interpretable number of micro-pulses can be realized. During the heating of the glass particles in the still solid state of matter, the distance between the micro-pulses and / or the interval between intervals at which a readjustment of the force takes place increases exponentially.
  • an end of the series of micro-impulses can be used as a triggering criterion, approximated by the absence of a pulse, for example, for more than 30 seconds.
  • a crystallization program is started to form controlled, homogeneous glass crystals, but not the unwanted crystal growth as in the compression process. This results, for example, a block of lithium metasilicate.
  • the ram no longer exerts pressure. Too long pressing could lead to unwanted or inhomogeneous crystallization.
  • the crystallization program is preferred in a temperature range between the transformation range Tg and about 80 ° C over the transformation range Tg of the glass particles (Tg + 80 ° C), in particular between 40 ° C over the transformation range Tg (Tg + 40 ° C) and about 60 ° C over the transformation range Tg of the glass particles (Tg + 60 ° C) made.
  • Tg transformation range
  • Tg + 40 ° C transformation range
  • Tg + 60 ° C the transformation range
  • a cooling process and / or a demolding process is or are started.
  • a plaster-based dental investment material in a muffle is preferably used, which investment material has two advantages over high-temperature-resistant phosphate-bonded investment materials. On the one hand, the surface quality and thus the imaging accuracy is better. On the other hand, the devesting is easier.
  • a reusable muffle is used for a dental restoration or dental restorations to be produced.
  • the oven of the present invention includes any heating device that provides thermal energy.
  • the glass particles of the present invention mainly refer to glass powder, glass granules and glass sand, but are not limited thereto. All industrially applicable glass particles, in particular those for the production of dental restoration parts, are within the scope of the present invention.
  • FIG. 1 shows a section through the combustion chamber of a furnace according to the invention in a
  • Fig. 2 is a graph of the speed of the ram and other physical quantities plotted against time
  • Fig. 3 is a diagrammatic representation of the rate of nucleation, densification and crystal growth plotted against temperature.
  • an inventive furnace 10 which is particularly suitable for the production of dental restoration parts, shown in a relevant for the invention section.
  • a combustion chamber 12 is surrounded by a heating device 14, shown schematically, with a helically extending heating screen, which is shielded by a quartz glass 16 as a protective device.
  • Large-volume heat insulation elements 18 surround the combustion chamber 12 on all sides, ie also downwards, even if this is not apparent from Fig. 1.
  • the bottom of the combustion chamber 12 is formed by a burner plate 20, the recesses 22 for receiving the muffle 24, and graduated in different sizes, in the illustrated embodiment in two sizes.
  • the combustion chamber 12 has a roof cone 26 which centrally increases the combustion chamber to the top. In this area, a part of a plunger 28 is received, which is inserted in a press channel 30, adjacent to a heap of glass particles 32 of lithium silicate, which is completely received in the muffle 24 in the press channel 30 and in the illustrated embodiment, color and translucency gradients forms.
  • the plunger may be made of any suitable material, such as Al 2 0 3i boron nitride, graphite and / or investment itself.
  • a punch 36 is guided, which is driven by a drive device and is able to exert pressure on the ram 28 and thus indirectly on the pile of glass particles 32.
  • the recess 22 fits in its dimensions exactly to the associated muffle 24, so that the muffle 24 is exactly central.
  • the furnace hood is closed and a vacuum source sucks the air present in the combustion chamber 12 and in the thermal insulation elements until a negative pressure is created.
  • Gaskets are provided between a furnace base and the firing hood of the furnace, which are compressed by the build-up of the negative pressure.
  • the build-up of the negative pressure takes place in one to two minutes, and during the entire following pressing cycle the negative pressure is kept constant, for example by a pressure regulator. the negative pressure source, or by running the corresponding suction pump.
  • the heating of the glass particles 32 begins.
  • the pile of glass particles thereby expands, the preheating temperature being well below the softening temperature.
  • the thermal expansion coefficient of the muffle 24, so the investment material used for the formation of the muffle is significantly lower than the coefficient of thermal expansion of the bulk of the glass particles, but also of the plunger and the press ram, the punch can for example also consist of Al 2 0 3 or, for example, steel.
  • the coefficient of thermal expansion of the muffle is 3 ⁇ 10 -6 / K and that of the respective glass particles is approximately 10 ⁇ 10 -6 / K, and that of the press ram 8 ⁇ 10 -6 / K.
  • the pressing ram 36 must be taken into account only insofar as it is heated, that is to say in the region of the heat-insulating elements 18 adjacent to the combustion chamber.
  • the opposite end of the punch 36, which is connected to the drive device, is significantly less hot, for example below 100 ° C.
  • the temperature gradient of the ram 36 is particularly high when a ram, for example, Al 2 0 3 is used; when using a metallic ram, an additional heat-insulating cylinder can be installed in the ram.
  • l_o EB means the axial length of the muffle or embedding mass below the press channel 30.
  • the hot plate 20 is only superficially warm and already comparatively cool in the lower region. However, this does not apply if a so-called foot heating of a combustion chamber is realized, that is, if below the burner plate 20, a further heating is provided. In this embodiment the additional thermal expansion in the local area must be added to the above total thermal expansion.
  • thermal expansion is typically limited to the range between room temperature and a temperature below 100 ° C, for example 60 ° C; the heat-insulating elements 18, which become very hot at least inside, exert no axial force, but lie loosely in the furnace.
  • the temperature curve 51 shows the regulated temperature in the combustion chamber of the furnace.
  • the pressure curve 52 shows the pressure in the interior of the furnace.
  • the speed curve 53 shows the speed of the ram 36 or the associated drive device.
  • the zero point of the ordinate is offset in height and the velocity values in ⁇ / min are entered on the right.
  • the applied pressing force is entered in the pressing force curve 54.
  • the furnace 10 is already preheated at the beginning considered, to about 550 ° C.
  • the heating is still switched on.
  • the target temperature in the considered embodiment is about 580 ° C.
  • the press die 36 exerts a constant pressure of approximately 100 N on the heap of glass particles 32.
  • the pressure in the furnace decreases rapidly within the first 40 seconds and is 100 mbar at 70 seconds.
  • the final pressure of 50 mbar has been reached. This is kept constant during the entire pressing cycle.
  • a micro-pulse 60 From 70 seconds to about 115 seconds, the speed of the ram 36 is zero, as shown in FIG. At just over 115 seconds, a micro-pulse 60 according to the invention develops at a negative speed. This corresponds to a thermal expansion L 0 ges , as explained with reference to FIG. 1.
  • the micro-pulse has a size of about 500 pm / min and a duration of less than one second, depending on the quality of the press force control - although this is not clear from Fig. 2 based on the embodiment shown here.
  • the upper end of the heap of the glass particles 32 slips a bit upward, contrary to the effect of the pressing pressure according to the press curve 54, and falls in a short time due to the softening of the glass particles again.
  • the next micro-pulse 62 occurs.
  • the pressing process is triggered by the detection of a number of micro-pulses predetermined according to experience when the number of micro-pulses according to FIG. 2 reaches six.
  • a speed detection For the detection of the micro-pulses, it is basically possible to perform a speed detection, a path detection or a press force detection, depending on the resolution of the available sensors and depending on the elasticity of the drive.
  • a speed detection has been found to be the most advantageous, but also a path detection is basically possible.
  • FIG. 2 does not show the entire heating time period of the cluster of glass particles until the beginning of compaction, it is to be noted here that, according to the invention, considerably faster heating is carried out than in the prior art. This produces a controlled, small amount of germs. From the time of 250 seconds on, the compaction process begins until approximately 660 seconds. The compression now reaches its maximum speed at about 470 seconds.
  • a cooling program is started to prevent the otherwise occurring at higher temperature crystal growth.
  • a crystallization program is started so that the desired, homogeneous and finer crystal structure results.
  • Fig. 3 three curves 72, 74, 76 are plotted in a diagram, wherein the abscissa is the temperature.
  • the velocity curves 72, 74, 76 each with a plurality of triangles, circles and squares for discriminating each other, show at various temperatures the rate of nucleation, densification and crystal growth of the glass particles of lithium silicate.
  • the zero point of the abscissa - ie the temperature - is here offset in height and corresponds to the transformation range Tg of glasses of lithium silicate, which is about 450 ° C.
  • Tg the transformation range of glasses of lithium silicate
  • the viscosity ⁇ of the glass particles of lithium silicate is about 10exp13.2 poise and the micro-pulses have ready, as long as the thermal expansion of the bulk of the glass particles is compensated by microplastic deformation at the contact points of the glass particles and the viscosity ⁇ a height of Reached 10exp14.5 poise.
  • both nucleation and crystal growth have a relatively low velocity while the rate of densification is relatively high. According to the invention, therefore, this temperature point 78 is utilized. By rapid heating to the temperature point 78 as few germs and glass crystals are formed before and during compression.
  • the end temperature for rapid heating may be another predetermined temperature between 500 ° C (Tg + 50 ° C) and 530 ° C (Tg + 80 ° C), which corresponds at least to the dilatometric softening of the glass particles and in which the viscosity of the glass particles ⁇ is at least 10exp11, 5 poise.

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  • Plastic & Reconstructive Surgery (AREA)
  • Inorganic Chemistry (AREA)
  • Re-Forming, After-Treatment, Cutting And Transporting Of Glass Products (AREA)
  • Glass Compositions (AREA)

Abstract

L'invention concerne un agencement d'un four et de débris de particules de verre, ledit four (10) présentant un poinçon (36), un capteur de pression, de course et/ou de vitesse, et un dispositif de commande servant à commander une opération de pressage sur la base du signal de sortie du capteur. Le capteur détecte au moins un paramètre de pression, de position et/ou de déplacement du poinçon (36). Le poinçon (36) agit - éventuellement par l'intermédiaire d'un piston (28) interposé - sur les débris de particules de verre (32) qui sont guidés dans un conduit de pressage (30) et peuvent être cristallisés. Le critère de déclenchement de la commande du processus est une modification détectée par le capteur d'au moins un paramètre de déplacement du poinçon (36) lors du ramollissement des débris de particules de verre (32).
EP17825747.3A 2016-11-15 2017-11-14 Agencement d'un four et de débris de particules de verre et procédé permettant de faire fonctionner un four Pending EP3542116A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP16198859.7A EP3321621A1 (fr) 2016-11-15 2016-11-15 Système de four et de déblais des particules de verre et procédé de fonctionnement d'un four
PCT/EP2017/079187 WO2018091457A1 (fr) 2016-11-15 2017-11-14 Agencement d'un four et de débris de particules de verre et procédé permettant de faire fonctionner un four

Publications (1)

Publication Number Publication Date
EP3542116A1 true EP3542116A1 (fr) 2019-09-25

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EP16198859.7A Withdrawn EP3321621A1 (fr) 2016-11-15 2016-11-15 Système de four et de déblais des particules de verre et procédé de fonctionnement d'un four
EP17825747.3A Pending EP3542116A1 (fr) 2016-11-15 2017-11-14 Agencement d'un four et de débris de particules de verre et procédé permettant de faire fonctionner un four

Family Applications Before (1)

Application Number Title Priority Date Filing Date
EP16198859.7A Withdrawn EP3321621A1 (fr) 2016-11-15 2016-11-15 Système de four et de déblais des particules de verre et procédé de fonctionnement d'un four

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US (1) US11808520B2 (fr)
EP (2) EP3321621A1 (fr)
WO (1) WO2018091457A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3321621A1 (fr) * 2016-11-15 2018-05-16 Ivoclar Vivadent AG Système de four et de déblais des particules de verre et procédé de fonctionnement d'un four

Family Cites Families (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4002358C1 (en) * 1990-01-26 1991-10-24 Ivoclar Ag, Schaan, Li Oven control for dental material pressing and hardening - detects degree of filling of shaping space by speed of movement of piston in pressure cylinder
US6303059B1 (en) * 1999-03-26 2001-10-16 Ivoclar A.G. Method of controlling an oven
US6484791B1 (en) * 1999-11-01 2002-11-26 Jeneric/Pentron, Inc. Plunger for a pressing furnace
DE102004013668B4 (de) * 2004-03-19 2008-04-10 Ivoclar Vivadent Ag Pressofen sowie Zwischenkörper für einen Pressofen und Verfahren für den Betrieb eines Pressofens
US7290406B2 (en) * 2004-10-01 2007-11-06 Emhart Glass Sa I.S. machine
DE102006050830A1 (de) 2006-10-27 2008-04-30 Ivoclar Vivadent Ag Verfahren zum Betrieb eines Pressofens sowie Pressofen
DE102007015435B4 (de) 2007-03-30 2013-07-04 Ivoclar Vivadent Ag Muffelerkennung
US7691497B1 (en) * 2007-04-13 2010-04-06 Ivoclar Vivadent, Inc. Pressable overlay material for veneering of zirconia and composites thereof
US9241879B2 (en) * 2008-04-11 2016-01-26 James R. Glidewell Dental Ceramics, Inc. Lithium silicate glass ceramic for fabrication of dental appliances
DE102010053873A1 (de) * 2010-12-09 2012-06-14 Dekema Dental-Keramiköfen GmbH Pressofen für Zahnersatz oder Zahnteilersatz
US8561428B2 (en) * 2011-09-14 2013-10-22 Emhart Glass S.A. Dwell time control method and system with automatic pressure switch point adjustment
KR101347619B1 (ko) * 2012-04-13 2014-01-09 한국세라믹기술원 유리 분말을 이용한 비구면 렌즈의 제조방법
EP2772223B1 (fr) * 2013-02-27 2017-10-11 Ivoclar Vivadent AG Four dentaire de moulage par compression
EP3178441B1 (fr) 2013-12-20 2019-09-04 Ivoclar Vivadent AG Procédé de traitement d'un matériau dentaire, dispositif de réglage pour un four dentaire et four dentaire
US20170128174A1 (en) * 2014-06-23 2017-05-11 3M Innovative Properties Company Process for producing a sintered lithium disilicate glass ceramic dental restoration and kit of parts
EP3096100B1 (fr) 2015-05-22 2019-03-27 Ivoclar Vivadent AG Four de pressée dentaire
US11045291B2 (en) * 2015-08-03 2021-06-29 James R. Glidewell Dental Ceramics, Inc. Dental restoration preform and method of making the same
EP3150563B1 (fr) * 2015-09-30 2019-05-22 Ivoclar Vivadent AG Vitroceramique en silicate de lithium-wollastonite
DE102015122861A1 (de) * 2015-12-28 2017-06-29 Degudent Gmbh Verfahren zur Herstellung eines Rohlings, Rohling sowie eine dentale Restauration
EP3321621A1 (fr) * 2016-11-15 2018-05-16 Ivoclar Vivadent AG Système de four et de déblais des particules de verre et procédé de fonctionnement d'un four

Also Published As

Publication number Publication date
EP3321621A1 (fr) 2018-05-16
WO2018091457A1 (fr) 2018-05-24
US20200072552A1 (en) 2020-03-05
US11808520B2 (en) 2023-11-07

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