Sintering furnace for components made of sintered material, in particular dental components

Abstract

The invention relates to a sintering furnace (1) for components (15) made of a sintered material, in particular for dental components, comprising a furnace chamber (2) having a chamber volume (VK), wherein a heating device (5), a receiving space (9) having a gross volume (VB) located in the chamber volume (VK) and delimited by the heating device (5), and a useful region (10) having a useful volume (VN) located in the gross volume (VB), are disposed in the furnace chamber (2). The furnace chamber (2) has an outer wall (3) consisting of a plurality of walls having a wall portion (7) to be opened for introduction of a component to be sintered having an object volume (VO) into the receiving space (9). In the furnace chamber (2) the heating device (5) has a thermal radiator (6) having a radiation field (13) which is disposed on at least one side of the receiving space (9). At least the useful volume (NV) disposed in the receiving space (9) is disposed in the radiation field (13) of the radiator (6), wherein the maximum possible distance (d) of the component (15) to be sintered from the radiator (6) corresponds to at most twice the dimension (D.sub.y) of the maximum useful volume (VN).

Claims

1. A dental sintering furnace for one or more ceramic dental components to be sintered, comprising: a furnace chamber with a chamber volume, the furnace chamber further including; a heating device disposed within said chamber volume, a receiving space disposed within said chamber volume and having a gross volume, said receiving space delimited by the heating device, and a useful region with a useful volume disposed within the receiving space; wherein the furnace chamber has an outer wall that includes a plurality of walls, and that has at least one wall portion, said at least one wall portion constructed to be opened for introduction of the one or more ceramic dental components into the receiving space, said one or more ceramic dental components having an object volume; wherein the heating device has a radiator with a direct radiation field, said radiator disposed on at least one side of the receiving space; wherein the useful volume is further configured to be disposed in the direct radiation field; wherein the dental sintering furnace is constructed such that a ratio of the useful volume to the chamber volume is from 1:50 to 1:1 and a ratio of the useful volume to the gross volume is from 1:20 to 1:1 such that a maximum possible useful volume in relation to the gross volume is kept as small as possible so as to eliminate a need for a preheating of the dental sintering furnace and provide a relatively fast sintering of the one or more ceramic dental components as compared conventional furnaces, and wherein the radiator is configured to be heated in an inductive fashion using an encircling coil, wherein the radiator is made of SiSiC, wherein the useful volume is at most 20×20×40 mm.sup.3.

2. The dental sintering furnace according to claim 1, wherein the dental sintering furnace is constructed such that a ratio of the useful volume to the object volume is from 1,500:1 to 1:1.

3. The dental sintering furnace according to claim 1, wherein the outer wall has a chamber inner wall that is impermeable to the direct radiation field and/or reflects it.

4. The dental sintering furnace according to claim 1, wherein the useful volume is at most 20×20×40 mm.sup.3 and that the dimensions of the useful volume are at most 20 mm×20 mm×40 mm.

5. The dental sintering furnace according to claim 1, wherein the radiator is configured as a crucible.

6. The dental sintering furnace according to claim 1, wherein the radiator is formed from two plate-shaped elements, which are heated by integrated coils and wherein the receiving space is configured to be between the two plate-shaped elements.

7. The dental sintering furnace according to claim 1, wherein the radiator heated in an inductive fashion comes into direct contact with the one or more ceramic dental components during sintering.

8. The dental sintering surface according to claim 1, wherein the dental sintering furnace includes an active water cooling inside the encircling coil.

9. The dental sintering furnace according to claim 1, wherein the radiator is capable of achieving heating rates above 150° C./min.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be explained with reference to the drawing. In the figures:

(2) FIG. 1: a part of an invention-specific sintering furnace for components made of a sintered material, especially for dental components;

(3) FIGS. 2A, B an inductively heatable heating device with a radiator consisting of a crucible and coil;

(4) FIG. 3: a plate-shaped inductively heatable thermal radiator having an integrated coil;

(5) FIGS. 4A, B resistance heating devices with thermal radiators consisting of rod-shaped heating elements;

(6) FIG. 5 a heating coil as a resistance heating element;

(7) FIG. 6 a thermal radiator consisting of heating coil and reflector;

(8) FIG. 7 a thermal radiator consisting of U-shaped heating elements;

(9) FIG. 8 a thermal radiator consisting of planar heating elements;

DETAILED DESCRIPTION OF THE INVENTION

Exemplary Embodiment

(10) FIG. 1 shows a part of a sintering furnace 1, which has a furnace chamber 2 with a chamber volume VK, the walls 3 of which are provided with insulation 4 for screening the hot furnace chamber 2 against the environment. For heating the furnace chamber 2, in furnace chamber 2 a heating device 5 is disposed with two thermal radiators 6. The furnace chamber 2 has a wall portion 7 to be opened for insertion of a component 15 to be sintered into the furnace chamber 2, which here is the lower wall portion, thus the bottom of the furnace chamber 2. The bottom 7 likewise has insulation 4, on which a base 8 for the component 15 to be sintered is placed, which also is designated as a support 8. Also eligible are cross pieces or a crucible or vertically placed pins made of ceramic or high-melting metal, on which the component 15 is placed.

(11) Through the heating device 5 or the thermal radiator 6, which for example in FIG. 1 is disposed on two sides of the furnace chamber 2, within furnace chamber 2 there results a free volume that is less as compared to the chamber volume VK, which is indicated in FIG. 1 with a dashed line and is designated as the gross volume VB. The space that this gross volume VB assumes, is the receiving space 9, into which an object 15 to be sintered can be inserted.

(12) Using the radiator 6 of the heating device 5, the receiving space 9 is heated, wherein at least one part of the gross volume VB of the receiving space 9 is heated in sufficiently robust and uniform fashion. This region is designated as the useful region 10 and the volume as the useful volume VN. The useful area 10 is schematically depicted with a dot-and-dash line and a second largest dimension of the useful region 10 drawn in as D.sub.y. The size and position of the useful region 10 is determined in essence by the reflection characteristics, thus the radiation field 13, and the arrangement of the radiator 6, wherein a placement of the radiator 6 on at least one side of the receiving space 9, ensures that the useful region 10 lies within the receiving space 9.

(13) The object 15 to be sintered can for example be resistively or inductively heated. In FIGS. 2A and 2B for example, an inductively heated radiator 6 is depicted as a heating device 5. The radiator 6 is configured as a crucible 11, for example made of MoSi2 or SiC, with at least one encircling coil 12 for inductive heating, wherein the reflection of the crucible 11, thus the thermal radiation 13, is indicated by arrows. In this example, the receiving space 9 is formed by the inner space of the crucible. The useful region 10 is likewise in the inner space of the crucible 11, wherein the ratio of the usable volume VN of the usable region 10 to the gross volume VB of the receiving space 9 is 1:1.

(14) The component 15 to be sintered is disposed in the inner space of crucible 11, in the receiving space 9 that coincides with the useful region 13. The distance of the object to the radiator 6, thus to the crucible 11 here, is designated as d.

(15) FIG. 3 shows a thermal radiator 6 formed from two plate-shaped elements, which is heated by means of integrated coils 12. The receiving space 9 correspondingly is situated between the two plate-shaped elements FIG. 3 further shows the radiation field 13 of the thermal radiator 6 with lines. There is disposed appropriately in receiving space 9 a useful region 10, which covers an area of the radiation field 13 as homogeneously as possible with high intensity.

(16) The thermal radiators 6 depicted in FIGS. 4A and 4B consist of three and four rod-shaped resistance heating elements 14, respectively.

(17) Additional variants of resistive thermal radiators 6 and arrangements are shown in FIGS. 5 to 8. The radiator 6 shown in FIG. 5 is configured as a heating coil 16, wherein the receiving space 9 and useful region 10 are cylinder-shaped and disposed within the heating spiral. In FIG. 6 the radiator 6 is a combination of a thermal radiator, here a heating coil 16 and the reflector 17, wherein the receiving space 9 and useful region 10 are found between the heating spiral 16 and reflector 17. FIG. 7 shows a radiator consisting of two U-shaped heating elements 18 having a receiving space 9 disposed between the two U-shaped heating elements 18. In FIG. 8 a radiator 6 consisting of two planar heating elements 19 is depicted. These typically have a planar reflection pattern, through which the useful region occupies an especially large part of the receiving space 9 lying between the planar heating elements 19.

LIST OF REFERENCE SYMBOLS

(18) 1 Sintering furnace

(19) 2 Furnace chamber

(20) 3 Walls

(21) 4 Insulation

(22) 5 Heating device

(23) 6 Thermal radiator

(24) 7 Wall portion

(25) 8 Base

(26) 9 Receiving space

(27) 10 Usable region

(28) 11 Crucible

(29) 12 Coil

(30) 13 Radiation field

(31) 14 Rod-shaped resistance heating elements

(32) 15 Object to be sintered

(33) 16 Heating coil

(34) 17 Reflector

(35) 18 U-shaped heating elements

(36) 19 Planar heating elements

(37) D Distance

(38) D.sub.y Second largest dimension

(39) VB gross volume

(40) VK chamber volume

(41) VN useful volume

(42) VO object volume