COLLET CHUCK FOR CLAMPING A DENTAL TOOL AND METHOD FOR MANUFACTURING SUCH A COLLET CHUCK

Abstract

The invention relates to a collet chuck for clamping a dental tool, wherein the collet chuck has at least temporarily a mechanical stress applied to it and is made of steel.

The collet chuck according to the invention is characterized in that the steel, at least in a surface layer, has a nitrogen content of at least 0.1 wt %.

Claims

1. A collet chuck for clamping a dental tool, wherein the collet chuck has at least temporarily a mechanical stress applied to it and is made of steel, characterized in that the steel, at least in a surface layer, has a nitrogen content of at least 0.1 wt %.

2. The collet chuck according to claim 1, characterized in that the steel, at least in the surface layer, has a maximum content of nitrogen of at least 0.3 wt %.

3. The collet chuck according to claim 1, characterized in that the steel, at least in the surface layer, has a chromium content of 10 to 20 wt %.

4. The collet chuck according to claim 1, characterized in that the steel, at least in the surface layer, has one or more of the following components: 1.0 to 3.0 wt % molybdenum, 0.1 to 1 wt % vanadium.

5. The collet chuck according to claim 1, characterized in that the steel, at least in the surface layer, has one or more of the following components: 13 to 17 wt % chromium, 1.4 to 3.0 wt % molybdenum, 0.1 to 0.5 wt % vanadium.

6. The collet chuck according to claim 1, characterized in that the steel, at least in the surface layer, has a maximum content of sulfur of 0.01 wt %.

7. The collet chuck according to claim 1, characterized in that the collet chuck, at least on its surface, has a hardness of 500 to 700 HV 10.

8. The collet chuck according to claim 1, characterized in that the collet chuck overall, from a steel core up to and including the surface layer, has an at least substantially homogeneous nitrogen content of at least 0.1 wt %.

9. The collet chuck according to claim 1, characterized in that at least the surface layer has a carbon content of 0.37 to 0.45 wt %.

10. The collet chuck according to claim 9, characterized in that at least the surface layer has a chromium content of 15 to 16 wt %.

11. A clamping device for clamping a dental tool in a dental handpiece, comprising a collet chuck able to be elastically deformed by means of an actuator, characterized in that the collet chuck is formed according to claim 1.

12. The clamping device according to claim 11, characterized in that the collet chuck is able to be expanded by means of the actuator for the accommodation of a dental tool.

13. A method of manufacturing a collet chuck according to claim 1, characterized in that the steel is fabricated in the electroslag remelting method or pressure electroslag remelting method or vacuum arc remelting method, and the steel or the collet chuck is subsequently subjected to a heat treatment to increase the hardness.

14. The method according to claim 13, characterized in that the heat treatment comprises one or more steps, in particular in the following order: heating to an austenitization temperature of 1000 C. to 1100 C., maintaining at the austenitization temperature of 1000 C. to 1100 C., quenching to a room temperature of <70 C., deep freezing at a temperature of 80 C. to 110 C., reheating to room temperature of between 0 C. and 70 C., tempering at 200 C. to 300 C., cooling to a room temperature of <70 C., tempering at 250 C. to 350 C., cooling to a room temperature of <70 C.

15. The method of manufacturing a collet chuck according to claim 13, characterized in that a nitrogen-containing melt of the steel has a nitrogen atmosphere applied to it under pressure in such a manner that the nitrogen remains in the melt and/or the melt of the steel has a nitrogen atmosphere applied to it under pressure in such a manner that the nitrogen diffuses into the steel, so that the steel, after solidification, has an at least substantially homogeneous nitrogen content; and/or in that the nitrogen-containing steel, during a heat treatment after or during solidification, has a nitrogen atmosphere applied to it under pressure in such a manner that the nitrogen remains in the steel and/or the steel has a nitrogen atmosphere applied to it under pressure in such a manner that the nitrogen diffuses into the steel, so that the steel, after its heat treatment, has an at least substantially homogeneous nitrogen content.

Description

[0042] The invention will be described in the following with reference to exemplary embodiments and the figures, in which:

[0043] FIG. 1 shows an exemplary embodiment of a clamping device comprising a collet chuck according to the present invention;

[0044] FIG. 2 is an exploded view of the clamping device of FIG. 1;

[0045] FIG. 3 shows a collet chuck such as it can be used in a clamping device of FIGS. 1 and 2, wherein the entire collet chuck comprises the inventive nitrogen content; and

[0046] FIG. 4 shows an exemplary embodiment similar to the one of FIG. 3, however, the collet chuck having a surface layer of the collet chuck comprising the inventive nitrogen content.

[0047] FIGS. 1 and 2 show an exemplary embodiment of a clamping device comprising a collet chuck 14, positioned within a housing 12. The collet chuck 14 comprises a sleeve-like, in particular hollow cylindrical section 14a which is fixed within the housing 12 so that the collet chuck 14 is held at least in the axial direction of axis A of the tool shank to be clamped in a fixed manner in the housing 12.

[0048] In the direction of a pushbutton 30 positioned on an axial end of the housing 12 opposite the section 14a, at least two clamping levers 16, 18 are arranged in succession to section 14a, which are elastically deformable and displaceable by means of an expanding element 24 in the radial direction against an elastic return force of the material of which the collet chuck 14 is formed.

[0049] The clamping levers 16, 18 have clamping surfaces 16a, 18a on their surfaces facing radially inwardly, preferably extending in an equidistant manner to axis A and which exert a clamping force on the tool shank in the clamped state of the tool shank of the dental tool, wherein in this state the clamping levers 16, 18 are elastically and radially outwardly deformed by a predetermined amount, so that the collet chuck 14 has a mechanical bending stress applied to it.

[0050] The clamping diameter of the collet chuck 14 is designated as D in FIG. 1.

[0051] To be able to insert the tool shank in and to withdraw it from the collet chuck 14, an expanding element 24 is positioned adjacent to the collet chuck 14 to be displaced in the axial direction in the housing 12, which, when it is axially displaced, penetrates the collet chuck 14 while radially outwardly pressing the clamping levers 16, 18 and thus pressing the clamping surfaces 16a, 18a apart in the radial direction, so that the tool shank is released from being clamped in the collet chuck 14. The displacement of the expansion element 24 is achieved by means of a pressure piece 28 comprising the pushbutton 30 protruding from the housing 12. For example, the expansion elements 24 are integrally formed with the pressure piece 28.

[0052] In the illustrated exemplary embodiment, but not necessarily, a supporting ring 26 which extends within a through hole 34 of the pressure piece 28 is inserted in a through hole 20 of the housing 12. This supporting ring 26 has a radially inner guiding surface 26a for the tool shank, which cooperates with a guiding surface 14b on the sleeve-like section 14a of the collet chuck 14 to guide the tool shank in the direction of the axis A.

[0053] The pressure piece 28, together with the expansion elements 24, forms an actuator 36 for the collet chuck 14.

[0054] The collet chuck 14 thus undergoes repeated elastic deformation when the clamping levers 16, 18 are expanded. Moreover, in each inserted state of a dental tool, due to the fact that the tool shank, for its clamping, prevents complete springing back of the clamping levers 16, 18 radially to the inside, a clamping force remains in the collet chuck 14. If a disinfection substance and/or sterilization substance, which is, in particular, a chlorine-containing substance, is applied to the collet chuck 14 in this state, there is a risk of stress corrosion cracking. For this reason, according to the present invention, the collet chuck 14, at least in the area of its surface, i.e. within a surface layer, is of a steel material having a nitrogen content of at least 0.1 wt %. This will be explained in an exemplary manner with reference to FIGS. 3 and 4:

[0055] In the exemplary embodiment of FIG. 3, the entire collet chuck 14 is made of a steel having a nitrogen content of at least 0.1 wt %. This is only schematically shown as nitrogen particles 4.

[0056] The radially inner surface 6 of the collet chuck 14 thus also has a corresponding nitrogen content, as well as the radially outer surface 8.

[0057] In the embodiment of FIG. 4, however, the collet chuck 14 has a surface layer 2 on all surfaces which can come into contact with the disinfection substance and/or the sterilization substance. According to an embodiment, it may also be sufficient to provide only those surfaces with a corresponding surface layer 2 that have a tensile stress applied to them, thus the radially inner surface 6.

[0058] For this reason, in the exemplary embodiment according to FIG. 4, the nitrogen particles 4 are provided in the surface layer 2, rather than in the steel core 10. While not shown in the figure, a transition layer with a reduced number of nitrogen particles 4 may form between the surface layer 2 and the steel core 10.

LIST OF REFERENCE NUMERALS

[0059] 2 surface layer [0060] 4 nitrogen particle [0061] 6 radially inner surface [0062] 8 radially outer surface [0063] 10 steel core [0064] 12 housing [0065] 14 collet chuck [0066] 14a section [0067] 14b guiding surface [0068] 16 clamping lever [0069] 16a clamping surface [0070] 18 clamping lever [0071] 18a clamping surface [0072] 20 through hole [0073] 24 expansion element [0074] 26 supporting ring [0075] 26a guiding surface [0076] 28 pressure piece [0077] 30 pushbutton [0078] 34 through hole [0079] 36 actuator [0080] A axis of the tool shank to be clamped [0081] D clamping diameter