Dental furnace

Abstract

This invention relates to a process for controlling a dental firing furnace in which a temperature in a firing chamber of the dental furnace is detected by means of a temperature sensor, and in which a heating element that is controlled by a control device controls the heating of the firing chamber of the dental firing furnace based on the measurement result of the temperature sensor. In this process a dental restoration part is received within the firing chamber of the dental furnace. The heating is controlled so that the dental restoration part reacts exothermically, emitting additional heat. The additional heat is detected by the temperature sensor which is pointed at the dental restoration part and the control device delivers at least one signal representing the additional heat, such as in the form of a display signal and/or control signal.

Claims

1. A process for controlling the heating cycle of a dental restoration part in a dental furnace comprising heating the dental restoration part comprising a ceramic material and a binder in a firing chamber of the dental furnace, wherein the dental restoration part reacts exothermally, emitting additional heat, detecting a temperature in the firing chamber of the dental furnace by a temperature sensor, controlling the temperature of the firing chamber by a heating element that is controlled by a control device based on a measurement result of the temperature sensor, wherein the additional heat is directly detected by the temperature sensor which is pointed at the dental restoration part, wherein quantity of the additional heat is detected in order to prevent the dental restoration part from heating up too fast, wherein the control device delivers at least one signal representing the additional heat, and wherein, after the signal is delivered, the control device adjusts a temperature increase in the firing chamber created by the additional heat, to a lower temperature, and after a trigger temperature is met, a firing cycle is initiated on the dental restoration part.

2. The process as claimed in claim 1, wherein the signal representing the additional heat comprises one or more of a display signal and a control signal.

3. The process as claimed in claim 1, wherein adjusting the temperature increase comprises one or more of reducing and switching off the power supply of the heating element.

4. The process as claimed in claim 1, wherein the temperature sensor comprises an infrared camera and detects the temperature increase during the exotherm reaction of the dental restoration part and transmits the respective output signal to the control device.

5. The process as claimed in claim 1, wherein the binder reacts exothermally during the heating of the dental restoration part and wherein the exothermal additional heat of the binder of the dental restoration part is detected by the temperature sensor.

6. The process as claimed in claim 1, wherein the exothermal reaction is a crystallization process and wherein crystallization energy is detected as exothermal additional heat and is compensated by the control device of the dental furnace.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the present invention will be more fully understood and appreciated by the following Detailed Description in conjunction with the accompanying drawings, in which:

(2) FIG. 1 shows a schematic view of a drying device according to the invention in an embodiment of the invention;

(3) FIG. 2 shows a further schematic view of a further embodiment of a drying device according to the invention;

(4) FIG. 3 shows a schematic view of a temperature curve in an inventive device; and

(5) FIG. 4 shows a schematic view of a temperature curve of the inventive device in case of a modified heat supply.

DETAILED DESCRIPTION

(6) The inventive device 10 comprises an object, in particular a dental restoration part 12 that, in the illustrated embodiment, is represented as a schematic ashlar. The dental restoration part 12 consists of ceramics and/or metal and/or plastic and is porous. A liquid is contained in the object, for example an aqueous residual moisture, or the remainder of a coloring liquid that contains alcohol so that ethanol or butanol or similar alcohols are contained.

(7) In the present exemplary embodiment, an infrared light source 14 is provided as the device for generating thermal energy that acts upon the object, said infrared light source influencing the object 12 with heat from above. The aim in this case is the drying of the object, and the infrared light source 14 substantially emits the infrared light radiation in a conical manner. In this respect, an impingement area 16 is obtained below the radiation cone of the infrared light source.

(8) If a drying cabinet is used instead, the impingement area is the entire drying cabinet.

(9) The object is positioned on a base or support 18. Due to the impinging thermal energy, the object is gradually heated depending on its thermal capacity and the emitted amount of heat.

(10) A temperature detection element 20 is laterally provided. The temperature detection element detects the infrared radiation, i.e., the heat radiation of the object 12. Preferably it comprises a shielding 22 that prevents the temperature detection element 20 from being directly impinged by the infrared light source 14. Moreover, it is located outside the impingement area 16.

(11) The temperature detection element 20 is selected so that a spectral sensitivity range at least covers the infrared range. It is to be understood that depending on the application also a larger range that is shifted to larger wavelengths can be detected.

(12) Moreover, the temperature detection element 20 is connected to a control device 24 that receives and evaluates the output signal of the temperature detection element.

(13) If a trigger temperature is reached that has been selected and preset depending on the liquid in the object 12, the control device 24 itself emits a signal that turns off the infrared light source 14 in the illustrated exemplary embodiment. It is to be understood that any other signal can be generated instead, for example a signal for transferring the now dry dental restoration part 12 into the firing furnace.

(14) A further arrangement of an inventive drying device is apparent from FIG. 2. In this exemplary embodiment the drying device 10 uses a dental firing furnace 26. The dental firing furnace comprises a firing chamber head 28 and a firing chamber bottom 30 that is formed on a furnace lower part 32. The furnace lower part 32 further carries and supports a control display 34 in a manner known per se, by means of which the various functions and conditions of the dental firing furnace 26 can also be displayed, and by means of which the dental firing furnace can be controlled.

(15) The firing chamber bottom 30 accommodates the dental restoration parts by means of a firing tray 40 and FIG. 2 shows two dental restoration parts 12a and 12b. The dental restoration parts can be multi-unit bridges or individual dental restoration parts having low weight.

(16) The firing chamber head 28 is suspended via a combined lifting/pivoting device and is controllable with respect to its height position. In the illustrated position, a gap 42 exists between the bottom side of the firing chamber head and the firing chamber bottom 30. The dental restoration part 12 is laterally visible through the gap. A thermal imaging camera 44 is provided in this exemplary embodiment as the temperature detection element, which thermal imaging camera 44 is attached laterally to the gap 42, but spaced apart therefrom, and which is directed towards the one or more dental restoration parts 12 in its optics.

(17) The thermal imaging camera 44 is laterally spaced apart from the dental firing furnace a distance so that it is not damaged by the heat radiation.

(18) In the illustrated exemplary embodiment, a heating element 53 is formed in the firing chamber head in a manner known per se as a circumferential electrical resistance heating. The heat emitted from the heating element heats the dental restoration part 12 evenly across the gap 42 so that the heating element may be regarded as a means for generating thermal energy that acts upon the object. The extent of the heat energy that is supplied at this position, strongly depends on the height position of the firing chamber head, and of course on the heating power of the heating element 53 or the heat energy, respectively, which is stored in the insulation of the firing chamber head.

(19) According to the invention, the thermal imaging camera 44 is connected to the control device 24 via a wireless data link 51 for example. The control device 24 is informed about the temperature of the dental restoration part 12 hereby.

(20) If the preset trigger temperature is reached, the control device 24 assumes that the residual moisture in the dental restoration part has evaporated or has escaped. The dental restoration part at this point of time is thus completely pre-dried.

(21) For the start of the actual firing cycle, the firing chamber head 28 is then lowered in a manner known per se so that it seals off against the firing chamber bottom 30. The firing cycle is also carried out in a manner known per seif necessary under negative pressure.

(22) Typically, the firing cycle is concluded by a cooling phase that is advantageously also realized at a half-opened firing chamber head. Also in this position, the inventive thermal imaging camera 44 can detect and monitor the temperature of the dental restoration part 12 and thus enables the exact run of a preset temperature profile also during the cooling phase.

(23) FIG. 3 shows a curve of the measured temperature 50 in an inventive dental firing furnace.

(24) As it becomes apparent in FIG. 3, a constant heat quantity Q (here referred to with the reference number 52) is supplied to the dental firing furnace. The heat quantity supplied per unit of time may easily be increased via the timing, for example, by 5% during the heating-up process.

(25) In the area 54 below the temperature, at which an exothermic reaction takes place, a constant increase of the temperature T occurs which is denoted with the reference number 50.

(26) In the area 56 the dental restoration part reacts exothermically. The result is an increase of temperature, as it is obvious from the temperature curve 50.

(27) When the exothermic reaction is completed, the temperature substantially constantly increases again, as it is obvious from the area 58 of the temperature curve 50.

(28) In order to effect a substantially constant temperature increase, as it is favorable for the improvement of the properties of the dental restoration, the heat supply in the area 56 is inventively reduced according to FIG. 4. Subsequently, a little more heat is supplied without the level of the heat supply in the area 54 being reached.

(29) The result is the temperature curve 50 with an only minor temperature increase in the area 56, and subsequently a once more constant temperature increase in the area 58.

(30) Although preferred embodiments have been depicted and described in detail herein, it will be apparent to those skilled in the relevant art that various modifications, additions, substitutions, and the like can be made without departing from the spirit of the invention and these are therefore considered to be within the scope of the invention as defined in the claims which follow.