FILM TENSIONING ELEMENT, METHOD FOR THE APPLICATION OF A FILM TENSIONING ELEMENT IN COMBINATION WITH THE SCAN HEAD OF A SCANNER, AS WELL AS METHOD FOR PRODUCING A FILM TENSIONING ELEMENT

Abstract

A film tensioning element is provided for dental applications with a film extending between tensioning rings. The film has a modulus of elasticity of less than 2 KN/mm.sup.2. The film is made of a tough plastic with a modulus of elasticity of more than 1 KN/mm.sup.2, in particular of PP, or optionally of PA. The film tensioning element is manufactured together with the tensioning rings.

Claims

1. A film tensioning element for dental applications comprising a film which extends between tensioning rings, the film having a modulus of elasticity of less than 2 KN/mm.sup.2, wherein the film is fabricated of a plastic, wherein the film tensioning element is produced together with the tensioning rings.

2. The film tensioning element according to claim 1, wherein the plastic is a tough plastic having a modulus of elasticity of more than 1 KN/mm.sup.2.

3. The film tensioning element according to claim 1, wherein the plastic comprises a polyolefin, a linear polyester or a mixture thereof.

4. The film tensioning element according to claim 3, wherein the polyolefin comprises polypropylene, polyamide or a mixture thereof and wherein the linear polyester comprises polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or a mixture thereof.

5. The film tensioning element according to claim 1, wherein the tensioning rings are fabricated of the same plastic as the film and wherein the tensioning rings are integral with the film.

6. The film tensioning element according to claim 1, wherein the film has a coefficient of static friction μ.sub.H<0.4 and a coefficient of gliding friction μ.sub.G≤0.35.

7. The film tensioning element according to claim 6, wherein the coefficient of static friction μ.sub.H of the film and the coefficient of gliding friction μ.sub.G of the film differ by less than 0.05.

8. The film tensioning element according to claim 1, wherein the film tensioning element is designed as a tensioning dam or as a coffer dam and is intended for use in the mouth of a patient.

9. The film tensioning element according to claim 1, wherein the film tensioning element is produced by a mold labelling or mold coating method.

10. The film tensioning element according to claim 1, wherein the film tensioning element is free of a coating and/or hydrophobic.

11. The film tensioning element according to claim 1, wherein the film is formed as a liquid-tight fabric or has a fabric structure, and wherein the fabric comprises PA or a polyolefin.

12. A film tensioning element and a scan head of a scanner combination comprising a scan head comprising a housing made of thermoplastic or thermoset, a film tensioning element comprising a film which is held stretched between tensioning rings, wherein the film is fabricated of a tough plastic which, at a contact pressure between the film and the scan head of between 1 and 10 N, has a coefficient of sliding friction μ.sub.G of less than 1.5 or less than 1, with respect to the scan head.

13. A film tensioning element in combination with a scan head of a scanner comprising a scan head and a film tensioning element, wherein the film tensioning element is designed as a tensioning dam or as a coffer dam.

14. A method of using a film tensioning element in combination with a scan head of a scanner, comprising guiding the scan head along the film tensioning element, wherein the scan head is guided along the film tensioning element with the application of a contact pressure, and wherein the film tensioning element is used as a support for a uniform movement of the scan head.

15. The method according to claims 14, wherein the contact pressure is at a level between 0 N and 10 N.

16. A method for producing a film tensioning element having two tensioning rings and a film comprising providing a mold comprising a patrix and a matrix, wherein the mold is in open position, introducing a film and bringing the film in contact with the patrix or the matrix by application of negative pressure or positive pressure, wherein the mold is then closed and tensioning rings are injected via injection-molding nozzles in the mold at points at which they are in contact with the film.

17. The method according to claim 16, wherein the patrix is placed under negative pressure and suctions in the film, and wherein the tensioning rings are injected onto the film, one of the tensioning rings at the foot of the patrix and the other one of the tensioning rings at the head of the patrix.

18. The method according to claim 16, wherein the film extends over the head of the patrix during injection molding and, after demolding, is cut out at the tensioning ring adjacent thereto, forming a film tensioning element in the form of a conical section or optionally a hollow cylindrical element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Further advantages, details and features result from the following description of an exemplary embodiment of the invention with reference to the drawing, in which:

[0045] FIG. 1 shows a schematic section through a mold for producing a film tensioning element according to the invention in one embodiment, in the open state;

[0046] FIG. 2 shows the illustration according to FIG. 1, but with the mold partially closed;

[0047] FIG. 3 shows the mold according to FIGS. 1 and 2 in the closed state, ready for injection of the rings;

[0048] FIG. 4 shows the mold according to FIGS. 1 to 3 in the opened state, after removal of the matrix; and

[0049] FIG. 5 shows a film tensioning element produced according to the invention, before and after punching out the end face.

DETAILED DESCRIPTION

[0050] FIG. 1 shows a mold 10 for producing a film tensioning element 12 according to the invention. Basically, the mold 10 consists of a patrix 14 and a matrix 16, which can be moved towards each other in a known manner to close the mold.

[0051] A film web 18 is wound on a supply roll 20 and is passed as a film 22 between patrix 14 and matrix 16.

[0052] The film has a modulus of elasticity of less than 2 KN/mm.sup.2. It is made of a tough plastic with a modulus of elasticity of more than 1 KN/mm.sup.2. It can be made of polypropylene, polyamide or polyolefin and have a thickness suitable for the film tensioning element. This can be, for example, between 0.08 mm and 0.4 mm.

[0053] When the mold 10 is closed, the film 22 extends between the patrix 14 and the matrix 16 such that they are separated from the film 22. The patrix 14 has a substantially truncated cone shape, with a truncated cone 24 and an end face 26. In the illustrated exemplary embodiment, the end face 26 is convexly convex.

[0054] Outside the path of the film web 18, the matrix 16 and the patrix 14 abut each other. Thus, the mold 10 is closed. A gap is provided between the patrix 14 and the matrix 16 at the point where the film web 18 passes. The gap is adapted to the thickness of the film web and has, for example, a thickness of 0.1 mm.

[0055] In this respect, the film web 18 fills the mold 10 when the mold 10 is closed.

[0056] In addition, however, two annular spaces 28 and 30 are formed in the matrix 16. When the mold 10 is closed, the annular space 28 extends at the base of the truncated cone 24 of the patrix 14, i.e. at the end of the matrix 16 on the patrix side.

[0057] When the mold 10 is closed, the annular space 30 extends at the transition of the truncated cone 24 to the end face 26, in this respect at the transition of the wall 32 of the matrix 16 to its base face 34.

[0058] Both annular spaces 28 and 30 have a substantially circular cross-section of about one millimeter and extend in the course of the film web 18.

[0059] The annular space 28 is for forming the lip ring of the film tensioning element 12, and the annular space 30 is for forming the vestibular ring of the tensioning element 12.

[0060] Two injection molding channels 36 and 38 extend towards the annular space 28. Instead, it is also possible to implement only one of the injection molding channels 36 and 38, because the annular space 28 is also then filled with injection molding material. It is also possible to use the injection molding channel 36 as such aid, and to let the air displaced by the injection molding escape via the channel 38.

[0061] In contrast, the annular space 30 is provided for forming the vestibular ring of the film tensioning element 12. Channels 40 and 42 extend towards the annular space 30. Again, it is possible to use only one of the channels 40 and 42 for injection molding, and to use the other for the escape of the displaced air.

[0062] From the comparison of FIGS. 1 and 2, it can be seen that in an intermediate position between the open mold 10 according to FIG. 1 and the closed mold 10 according to FIG. 3, the film web 18 extends over the patrix 14 into the matrix 16. A cavity 50 remains between the patrix 14 and the matrix 16, in which the film web 18 runs loosely and unguided.

[0063] Suction channels 52, 54 and 56 are formed in the patrix 14, terminating at the end face 26, which are connected to a vacuum source 60. When the vacuum is turned on, the end face 26 sucks the film web 18 to lie against it. Therefore, when the mold 10 is closed, the film web 18 settles into the gap between the patrix 14 and the matrix 16 without wrinkles and smoothly. In addition to this, it is intended to keep the film web 18 under a certain, but low tension. This tension can be adjusted to the requirements within a wide range. It can be between 0.1 Newton and 10 Newton.

[0064] FIG. 3 shows the mold 10 in the closed state. Here, as in the other figures, the same reference signs correspond to the same or similar parts. The annular spaces 28 and 30 extend along the path of the film web 18, so that when the annular spaces 28 and 30 are injection molded, the injection molding material is injected directly onto the film 22.

[0065] The injection molding material may be the same material as the material of the film. The film tensioning element is produced by the injection molding together with the tensioning rings in one go.

[0066] After injection molding has taken place in the position shown in FIG. 3, the mold 10 is cooled down to such an extent that the injection molding material has solidified. For this purpose, cooling channels (not shown) can be formed in the mold 10, which enable cooling to take place within a few seconds.

[0067] This is followed by demolding. This is shown in FIG. 4. The matrix 16 has already been removed and the finished film tensioning element 12 is exposed. Due to the truncated cone shape of the patrix 14, the film tensioning element 12 can be easily removed. This is preferably done by machine.

[0068] FIG. 5 above shows the film tensioning element 12 with the vestibular ring 62 and the lip ring 64. The film still exists on its face 66 but is no longer needed in use.

[0069] Furthermore, an excess of film 68 adjacent to the lip ring 64 is left over from the injection molding process.

[0070] These two surpluses are punched out and discarded.

[0071] This results in the shape of the film tensioning element 12 according to the invention, as shown in the lower part of FIG. 5.

[0072] The entire process of manufacturing the film tensioning element according to the invention can easily be carried out mechanically and automatically.