Apparatus for the manufacture of muffles for the production of dental prosthetic parts

An apparatus for manufacturing muffles for producing dental prosthetic parts comprises a collar divided at least once in the peripheral direction to form a receiving space for an investment material in which at least one pattern for a dental prosthetic part is arranged before the filling with the investment material. At least one pattern holder simultaneously serves as a spacer for an injection plunger passage and a base part closes an open side of the collar. Holding means encompasses the collar to hold the collar together, with the collar being conical with respect to the longitudinal axis thereof at least in one section for simpler manufacture and better handling. The holding means includes at least one ring, in particular a rigid ring, which has a conical inner surface with which it is pushed onto the conical section in the collar.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of German Utility Model No. DE 20 2005 003 014.7, filed on Feb. 24, 2005, the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an apparatus for the manufacture of muffles for the production of dental prosthetic parts.

BACKGROUND OF THE INVENTION

An apparatus of the prior art is known, for example, from the German patent DE 600 592. In this apparatus, the holding means for the holding together of the collar is formed by a screw connection with a singly divided collar. With a two-fold divided collar, that is, a collar comprising two peripheral parts, the holding means of this known apparatus is formed by circlips or a type of bayonet fastening.

SUMMARY OF THE INVENTION

It is an underlying object of the present invention to simplify an apparatus of the prior art in manufacture and in handling.

This object is satisfied in that the collar is formed conically in at least one section with respect to the longitudinal axis of the collar and in that the holding means include at least one ring, in particular a rigid ring, which has a conical inner surface with which it can be pushed onto the conical section of the collar.

The use of a rigid ring as a holding means has the advantage that an opening of the collar on the hardening of the investment material is practically precluded. The conical design of the collar and of the inner surface of the ring permits a simple fixing and releasing of the ring. This is also simple in manufacture.

Conical sections, which are arranged symmetrically to the transverse central plane, as well as two rings with a conical inner surface are preferably arranged at both sides of the transverse central plane of the collar. A uniform counter-force can be exerted onto the collar by this design.

Particularly good results can be achieved when the collar has respective sections conically converging toward its end at the base side and toward its other end. It is particularly advantageous for the collar to converge conically overall toward its two ends. It is particular favorable in manufacture when the collar, starting from a central region, has a continuous conical convergence up to its two ends.

The conical surfaces are preferably made smooth. A release of the rings from the collar is thereby simplified. By selecting an angle of inclination of smaller than 8° to the longitudinal axis of the collar, an unintentional release of the rings due to the expansion force of the investment compound can be prevented by frictional retaining despite smooth surfaces.

In particular plastic has proved advantageous as the material for the collar. Transparent plastic can also be used for the collar. This has the advantage that the position of the dental prosthesis patterns can also be inspected with a closed collar before and during the filling with the investment compound. The rings preferably consist of metal, in particular of aluminum.

For the better release of the rings, the holding means preferably have a rough or structured surfaced on their outer side. The rings can, for example, be provided with a corrugation.

In accordance with a further embodiment of the invention, which is also claimed per se, the collar consists of more than two parts which each form a peripheral section of the collar. When more than two parts are used, it is easier to check whether a positioned pattern is correctly positioned in the apparatus. It can hereby above all be more easily ensured that no pattern gets too close to the collar. For this purpose, a collar part is connected to the base part and a pattern with a holder is arranged in the designated position. It can be determined by moving the collar part around the base part and by a visual inspection whether the pattern gets too close to the collar. When only two parts are used, in contrast, a check is made more difficult since the pattern is already covered at the side by a collar part.

The use of three collar parts has proved to be advantageous. On the one hand, this is favorable in manufacture and, on the other hand, it is sufficient to permit a visual inspection. In addition, the simple assembly of the collar is thereby possible and the force distribution is optimized, in particular when all the collar parts have the same size. It is in addition particularly advantageous for manufacture for all collar parts to be made completely the same as one another.

In accordance with a further embodiment of the invention, which is also likewise claimed independently, the apparatus is part of a system which has different collars for different muffle sizes as well as common parts which can be combined selectively with the different collars. A common base part can, for example, be provided which is combined with different collar parts depending on which size the receiving space for the investment compound should have. In this manner, the size of the receiving space can be adapted to the size and/or number of the dental prosthesis patterns and the customary investment compounds amounts of 100 g, 200 g and 300 g can be used selectively.

It is particularly advantageous for all parts, except for the collars, to be made as common parts. In particular a cover part and the holding means can also be made as common parts in addition to the base part. Only different collar parts thereby have to be kept in stock to realize receiving spaces of different size.

In accordance with yet another embodiment of the invention, which is also likewise claimed independently, the collar has, in the direction of its longitudinal axis, a first section with a first internal diameter and a second section with a second internal diameter as well as a step therebetween, with the first internal diameter being larger than the second internal diameter. The volume of the receiving space can be kept small due to this stepped embodiment of the collar since a lower volume is required in the region of the pattern holders. The first section therefore preferably extends over the region in which the dental prosthetic patterns are located and the second section extends over the region in which the pattern holders are located.

On the one hand, investment material can hereby be saved and, on the other hand, a faster heat penetration of the investment compound, of the ceramic material and of the spacer for the injection plunger, that is, of the pattern holder, results. Furthermore, time can be saved in the exposure of the dental prosthesis part.

In accordance with yet another embodiment of the invention, which is also likewise claimed independently, the base part is made as a pedestal onto which a plurality of pattern carriers, in particular comprising material which can be burned out, melted out or removed in another manner, for example chemically, can be mounted, and radial ray markings are provided on the upper side of the pedestal for the positioning of the pattern carriers. The positioning of the pattern carriers is simplified thereby such that the available space can be utilized ideally. More dental prosthetic parts can thereby be produced in one workstep. The positioning is particularly simplified when, in accordance with a further embodiment of the invention, markings are additionally provided which extend transversely to the ray markings and which in particular form a cobweb-like marking.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The apparatus shown includes a collar1with three segments2which are each made the same as one another and which can be combined to form a collar forming a receiving space3. The apparatus furthermore includes a pedestal4which can be set into the lower opening5of the collar1and terminates it. A cover part7with a filling funnel8is inserted into the upper opening6of the collar1.

As can in particular be recognized inFIG. 2, the segments2, and thus the collar1, converge, starting from a central region9, in a continuous manner up to their two ends10,11. A holding ring14whose internal diameter d1converges conically accordingly can in each case be mounted on the two conical sections12and13of the collar1formed thereby. The conical areas12,13are made in specular symmetry to the transverse central plane I of the collar1. Accordingly, the two holding rings14are made the same as one another, but are mounted onto the collar1with opposite orientation.

The surfaces of the conical sections12and13of the collar1and of the inner periphery15of the holding rings14are each smooth. The rings14can therefore easily be rotated with respect to the collar1. To further facilitate the rotation, the holding rings14are additionally provided in a part of their outer periphery16with a structuring17in the form of a notch or corrugation.

The conical surfaces12,13of the collar1and the conical inner periphery15of the holding rings14each have an angle of inclination smaller than 8° to the longitudinal axis11of the collar1. It is thereby ensured that, when a radially outwardly directed force is applied to the segments2of the collar1, the holding rings14do not slide off the collar1, but counteract an opening of the collar by friction retention. The holding rings14can, however, be released easily by rotation about the longitudinal axis11of the collar1and a subsequent pulling off upwardly or downwardly. This is simplified by the smooth surfaces. The holding rings14are in particular rigid and made of aluminum. The segments2of the collar1consist of plastic.

As can in turn best be recognized inFIG. 2, the segments2, and thus the collar1, each have a first section18awith a first internal diameter d2and a second section18bwith an internal diameter d3which is smaller in comparison with the former in each case in the direction of the longitudinal axis II of the collar1. A step19is provided between the first section18aand the second section18band connects both sections to one another. The volume of the receiving space3is thereby larger in the upper region of the collar than in the lower region. The dental prosthesis patterns are located in the upper region, while the pattern carriers are located in the lower region and simultaneously serve as spacers for the injection plunger passages.

It can in particular be recognized inFIG. 3that a marking21is present on the upper side20of the pedestal4in the form of a cobweb which includes, in addition to radial ray markings22, markings23extending transversely thereto. The radial ray markings22are arranged uniformly around the center M of the pedestal4and the transverse markings23have approximately the same radial spacing from one another. The points of intersection P of the cobweb marking21represent preferred positions for the pattern carriers which can be positioned on the pedestal4.

One or more pattern carriers with patterns are placed onto the pedestal4to manufacture a muffle with the apparatus in accordance with the invention. Then a check can be made, by putting on a segment2of the collar1, whether the patterns come too close to the inner side24of the collar1. For this purpose, the one segment2can be moved around the pedestal4to check the total periphery. A visual inspection can be carried out easily due to the size of the segment amounting only to a third of the total periphery.

If no problems can be recognized in this process, the two other segments2of the collar1are added and the collar1is completed. Then the two holding rings14are pushed onto the collar1from above and from below. The cover7with the filling funnel8is subsequently inserted. The investment compound can now be filled through the funnel8into the receiving space3of the muffle form in accordance with the invention and hardened. The holding rings14prevent an opening of the collar1by an expansion of the investment compound during hardening.

After the hardening of the investment compound, the rings14are removed from the collar1by rotation. The segments2, the pedestal4and the cover7are then removed. The invested patterns and the pattern holders can subsequently be burned out or melted out. The muffle25of investment material remains behind with the passages for the injection plunger and the hollow spaces for the reception of the dental prosthesis material in the form of the finished dental prosthesis. The dental prosthesis can then be produced in a known manner with this muffle and is then removed from the muffle by sandblasting, for example.

In addition to the segments2of the collar1shown, further segments can be provided which each likewise form a collar, with the receiving spaces3being different from one another, in particular having a different size. The segments2are made such that they can be combined with the same pedestal4, the same cover7and the same retaining rings14. A system thereby results for the manufacture of muffles of different sizes, and possibly shapes, which is cost-favorable in manufacture and storage. The handling is also thereby simplified.