Dental Hybridofen

Abstract

An extension of the firing chambers of ceramic kilns and sintering kilns, particularly for drying processes, is proposed, with two separate heating zones with heating elements used according to the application. This creates a position within the devices for the drying processes and ensures uniform heat radiation onto the firing or sintering object (6, 6'), independent of external influences and the setting of multiple lift positions. By installing the additional pre-drying heating zone, a sintering kiln can also be used as a fully-fledged ceramic kiln. There is no need for standby mode, i.e. constant operation at a standby temperature; the dental furnace is ready for use at any time.

Description

[0001] The invention relates to a dental furnace for firing and / or sintering dental materials.

[0002] When it comes to dental furnaces, a distinction is made between ceramic firing furnaces and sintering furnaces.

[0003] Ceramic kilns are used in dentistry for firing ceramic materials, such as those used to veneer crowns or bridges. For this purpose, ceramic is applied layer by layer to a model and cured in the kiln. These kilns can be used for a maximum final temperature of 1200°C.

[0004] Dental furnaces of the aforementioned type and according to the preamble of claim 1 are described, for example, in DE 10 2006 032 655 A1, DE 10 2013 226 497 A1, EP 3 059 540 A1, EP 3 967 264 A1 and WO 2023 / 213966 A1.

[0005] Before heat treating dental materials in dental furnaces, it is common practice to pre-dry the materials to remove any moisture trapped in the dental material. To date, this has been done by not fully closing the dental furnace, with the closure element, typically a base supporting the dental object, only partially inserting it into the inlet opening of the furnace's firing chamber. In this state, the firing chamber is not yet fully closed, and the firing chamber, already heated to a temperature lower than the final temperature, releases the heat required to pre-dry the dental object. Unfortunately, this process is relatively uncontrolled, as the amount of heat reaching the dental object is not reliably controlled.

[0006] The object of the invention is to remedy this situation and to create a dental furnace which has improved pre-drying properties.

[0007] To achieve this object, the invention proposes a dental furnace for firing and / or sintering dental materials, wherein the dental furnace is provided with • an evacuable combustion chamber with an inlet opening for the introduction of a dental object, • a base for holding the dental object, • wherein the base can be moved into the inlet opening and the combustion chamber closes the combustion chamber when it is fully retracted into the inlet opening, • at least one combustion chamber heating element to provide the operating temperature in the combustion chamber and • at least one pre-drying heating element which is arranged in the region of the inlet opening and provides a pre-drying temperature in a pre-drying zone of the inlet opening within the inlet opening, • whereby the base for pre-drying the dental object is retracted into the inlet opening without the inlet opening being closed and until the dental object is within the pre-drying zone and remains there for the duration of the pre-drying phase.

[0008] The invention therefore relates to the provision of an additional heating zone in a dental furnace, wherein this heating zone serves for pre-drying and is arranged within the inlet opening of the firing chamber or dental furnace. For this purpose, at least one pre-drying heating element is located within the inlet opening, which ensures a pre-drying temperature within a pre-drying zone of the inlet opening. When the base supporting the dental object is partially retracted, the dental object is now located in the pre-drying zone within the inlet opening and is exposed to the controlled heat for pre-drying. After the pre-drying process, the base is moved further into the inlet opening to close the firing chamber, which is then evacuated and heated to operating temperature.

[0009] In an advantageous development of the invention, it can be provided that the at least one pre-drying heating element is shielded by an annular flange shield against heat radiation and / or convection from the combustion chamber.

[0010] This serves to protect both the pre-drying heating element and the combustion chamber from contamination or damage to the heating elements.

[0011] In a further advantageous embodiment of the invention, the latter may comprise a suction device within the inlet opening for sucking air and / or gases from the pre-drying zone.

[0012] Finally, it is advantageously further provided that the base has an upper part which, when the base is fully retracted into the inlet opening, is arranged above the at least one pre-drying heating element and shields the at least one pre-drying heating element from the combustion chamber.

[0013] The invention thus proposes an extension and improvement of the firing chambers of ceramic kilns and sintering kilns, particularly for drying processes, with two separate heating zones with heating elements deployed according to the application. This creates a (single) position for the drying processes in the devices and ensures uniform heat radiation all around the firing or sintering object (dental object), regardless of external influences and the setting of multiple insertion positions. The step-by-step retraction of the base, known from the prior art and temporarily remaining in the respective lift position until the firing or sintering object is sufficiently dried, is unnecessary with the invention. Incidentally, with the inventive device of the additional pre-drying heating zone, a sintering kiln can also be used as a fully-fledged ceramic kiln.There is no need for standby mode, i.e. constant operation at a standby temperature; the device is ready for use at any time.

[0014] The invention is further explained below using two exemplary embodiments and with reference to the drawings. In detail: Fig. 1 a ceramic kiln with a pre-drying zone according to the invention for pre-drying ceramic materials, e.g. for veneering crowns or bridges and Fig. 2 a sintering furnace with a drying zone according to the invention for sintering, for example, ZrO2 ceramic, e.g. when coloring ZrO2 ceramic with color liquids and, as an advantageous embodiment, with an extraction system to protect the high-temperature heating elements, e.g. molybdenum disilicate or SiC heating elements, from vapors released during the pre-drying phase. Ceramic kiln (Figure 1)

[0015] In the known kilns, with evacuable combustion chamber, equipped with insulation for 1200°C operating temperature, the firing object is first positioned outside the firing chamber for pre-drying under the influence of the radiant heat of the combustion chamber heating elements intended for the operating temperature and after certain time sequences retracted into the combustion chamber in several stages or a kiln head as a flap with the built-in heating element is slowly moved down to the firing object.

[0016] In these devices, it is not guaranteed that the firing object is exposed to a uniform temperature all around and thus dried.

[0017] Due to the opening and closing movement, compared to the vertical lifting movement, the front part of the firing object receives less heat than the rear part. Drafts also negatively impact the drying process and temperature measurement / accuracy in both systems.

[0018] The thermocouple, or measuring point for temperature control, is located in the ceiling of the firing chamber, so in these conventional devices it is a long way from the firing object (approximately 15 cm), and thus the firing object is not precisely temperature-controlled. Almost all ceramic kilns control the pre-drying phase by moving the firing object into the firing chamber at a specific time and exposing it only to the uncontrolled heat radiating from the firing chamber.

[0019] Therefore, due to the different designs of the devices, it is not possible to provide instructions for use with the respective material used in order to achieve reproducible results.

[0020] If the firing object doesn't receive sufficient, even heat during pre-drying to allow the air and modeling fluid trapped between the powder grains to escape, the ceramic will be too moist during the heating process. Air and residual modeling fluid will remain in the ceramic, leading to cloudiness and undesirable color changes.

[0021] To avoid these negative effects on the firing object, it is important that the firing object is positioned in an area where uniform heat radiation to the firing object is ensured all around and air movements do not affect the temperature measurement.

[0022] According to the invention, an additional pre-drying heating element made of, for example, quartz glass with a retracted resistance wire, e.g., Kanthal wire, or similar, is arranged in the lower part of the combustion chamber 1 with insulation 2 for the pre-drying / drying process. This at least one additional pre-drying heating element is thus located in the inlet opening to the combustion chamber 1.

[0023] The firing object 6, mounted on the firing base 4 with, for example, the integrated temperature sensor 5, e.g., platinum / rhodium / platinum type S, is positioned in the radiation area of ​​the heating element 3. A temperature control system sets a defined temperature rise up to the pre-drying temperature. This ensures uniform heat radiation onto the firing object 6 during pre-drying. The surface of the firing object is not melted, thus preventing air and residual modeling fluid from becoming trapped. Cloudiness and discoloration of the firing objects are thus eliminated.

[0024] After a time- and temperature-controlled pre-drying process, the firing object 6 is moved into the evacuable firing chamber 1, and the pre-drying heating element 3 is switched off. Using the firing chamber heating element 7, e.g., a quartz firing muffle or short-wave infrared radiator, the firing chamber is first heated to the temperature previously specified for pre-drying, and then further heated to the final temperature with a specified temperature rise time. After a specified holding time at the final temperature, a cooling phase occurs or the firing object is moved out of the firing chamber.

[0025] When using short-wave infrared heaters 7, the flashing of the heaters is not noticeable in the low temperature range. These heaters are only activated once the pre-drying time has elapsed, the firing object 6 has been moved into the firing chamber 1, and heated to the previously specified pre-drying temperature.

[0026] This prevents cracks on the firing object 6 to be dried due to the strong, flash-like effect of the short-wave radiation during the pre-drying process.

[0027] For all known devices, a permanent standby temperature in the range of 200°C - 600°C is specified.

[0028] With the use of at least one additional heating element 3 according to the invention, there is no need to keep the device at standby temperature. Instead, the device is immediately ready for use when switched on.

[0029] Innovative, controlled, and efficient pre-drying is achieved by using at least one pre-drying heating element 3 according to the invention. This also results in significant savings in energy costs and significantly reduced heat dissipation to the environment. Ceramic sintering furnace (Figure 2)

[0030] The heating elements used in known sintering furnaces for 1600°C, such as molybdenum disilicate, SiC heating elements, or heating systems with tungsten coils, as well as vacuum-tight combustion chambers equipped with high-temperature insulation up to 1800°C, are not suitable for dry processes. An example of a sintering furnace in which the invention can be used is described in WO 2023 / 213966 A1.

[0031] The escaping additives and moisture during the drying processes, such as drying / pre-drying, glazing, and coloring of ZrO2 ceramics with color liquids, cause evaporation, and dissolved compounds spread throughout the kiln. These lead to contamination of the combustion chamber insulation, affect the performance and operating time of the heating elements, molybdenum disilicate, and SiC heating elements, and cause discoloration of the subsequent sintered objects.

[0032] According to the invention, an additional pre-drying heating element 3, e.g. made of quartz glass with an inserted resistance wire, e.g. Kanthal wire, or the like, is arranged in the lower part of the combustion chamber 1 for the pre-drying / drying process and is separated from the combustion chamber 1 and thus from the high-temperature range of up to 1800°C by a temperature insulation or shielding 8.

[0033] This combustion chamber configuration is significantly more cost-effective than a conventional multifunctional dental furnace equipped only with heating elements made of SiC or molybdenum disilite.

[0034] The sintered object 6', placed on the firing base 4 with the integrated thermocouple 5, platinum / rhodium / platinum type S or type B, for example, is positioned in the radiation area of ​​the pre-drying heating element 3.

[0035] Using a temperature control system, the pre-drying zone, in which the sintered object 6' is located, is heated to the pre-drying temperature with a defined temperature increase. This ensures uniform heat radiation onto the sintered object 6'.

[0036] After the pre-drying process, which can be time- and temperature-controlled, the sintered object 6' is moved into the evacuable combustion chamber 1, and the pre-drying heating element 3 is switched off. The combustion chamber heating element 7, e.g., molybdenum disilicate, SiC heating elements, or a heating system with a tungsten coil, is used to heat the object to the specified sintering temperature and from there, with a specified temperature rise time, to the final temperature. After a programmed holding time at the sintering temperature, a cooling phase occurs or the sintered object 6' is moved out of the combustion chamber 1.

[0037] The invention further relates to a ring extraction device 9, arranged above the at least one pre-drying heating element. This extraction device 9 ensures that the vapors escaping from the sintered object 6' to be dried are extracted to the outside via a filter 10. This protects the combustion chamber heating elements 7 in the high-temperature region as well as the insulation in the high-temperature region of the combustion chamber 1 from contamination.

[0038] For the relatively expensive combustion chamber heating elements 7, especially SiC heating elements, which always have to be completely replaced due to the resistance, as well as molybdenum disilicate heating elements, the extraction 9 and filter 10 of the vapors provides protection and thus a longer operating time.

[0039] With this heating system, consisting of two heating zones, namely a first pre-drying heating zone with at least one pre-drying heating element 3 and a second heating zone (firing chamber 1) with at least one firing chamber heating element 7 as well as the vacuum-tight firing chamber 1, all firings of ceramic masses, for veneering crowns or bridges, or for sintering can be carried out.

[0040] Dental technicians and dentists thus have a multifunctional device at their disposal for all high-temperature processes in the dental field that does not require standby operation; this leads to significant energy savings and prevents high heat emissions to the environment.

[0041] Due to the additional pre-drying zone according to the invention with at least one pre-drying heating element 3, there is no need to heat up the device to a standby temperature before using it.

[0042] No standby mode, this leads to high energy savings and prevents high heat loss to the environment. List of reference symbols 1 combustion chamber 2 Insulation of the combustion chamber 3 Additional pre-drying heating element 4 firing bases 5 temperature sensors 6 Firing material or sintered object 7 Combustion chamber heating element 8 Temperature insulation or shielding 9 Extraction device 10 filters

Claims

[1] Dental furnace for firing and / or sintering dental materials, with • an evacuable combustion chamber (1) with an inlet opening for introducing a dental object (6, 6'), • a base (4) for holding the dental object (6, 6'), • wherein the base (4) is movable into the inlet opening and the combustion chamber closes the combustion chamber (1) when it is fully retracted into the inlet opening, and • at least one combustion chamber heating element (7) for providing the operating temperature in the combustion chamber (1), • wherein the base (4) is moved into the inlet opening for pre-drying the dental object (6, 6') without the inlet opening being closed and until the dental object is within the pre-drying zone, characterized by • at least one pre-drying heating element (3) which is arranged in the region of the inlet opening and provides a pre-drying temperature in a pre-drying zone of the inlet opening within the inlet opening. [2] Dental oven according to claim 1, characterized by that the at least one pre-drying heating element (3) is shielded against heat radiation and / or convection from the combustion chamber (1) by an annular flange shield (8). [3] Dental oven according to claim 1 or 2, characterized by an extraction device (9) within the inlet opening for extracting air and / or gases from the pre-drying zone. [4] Dental oven according to claims 1 to 3, characterized bythat the base (4) has an upper part which, when the base is fully retracted into the inlet opening, is arranged above the at least one pre-drying heating element (3) and shields the at least one pre-drying heating element (3) from the combustion chamber (1).

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