EP0183242A1 - Device for melting material and introducing it - Google Patents

Abstract

Equipment (1) for melting material and introducing it into a casting mould (6), in which, during the melting operation, a heating device is lowered onto the casting mould, onto which is directly placed a melting container (6) which, already having been placed on the casting mould, has been introduced beforehand together with the casting mould into a device for introducing and withdrawing (7) the said casting mould. The removal and introduction of the container with the casting mould, the two preferably being of integral construction, are largely uncritical compared to the introduction of an otherwise customary melting crucibles into the heating zone. In addition, because of the connection of the container and the casting mould there is, on the one hand, no longer the risk that molten material will run out into the equipment and, on the other hand, the cracking of the customary melting crucibles, which may otherwise easily occur, is avoided in the container according to the invention. Furthermore, a melting container of this kind no longer has to be cleaned but, like the casting mould, is intended to be used only once. <IMAGE>

Description

The innovation relates to a device for melting material and for filling the molten material into a mold according to the preamble of claim 1. In particular, the present innovation relates to such a device for use in a dental laboratory for processing stainless steel or gold and other dental alloys.

Known devices of the above type provide melting containers made of fireclay as containers for the material to be melted, which are introduced into the device for melting and filling by a drawer in the upper part of the device, in which there is a heating or fusion spiral the device is pulled out and the crucible is arranged so that it is surrounded by the heating coil. Another drawer, which is located in the lower part of the device, is used to arrange a casting mold or muffle made of investment material used in dental technology below the crucible. Furthermore, a sealing device is provided, which expediently e.g. consists of two pressure chambers through which the two drawers are sealed airtight with the housing of the device. Furthermore, a gas supply valve and a valve for evacuating this sealed space are provided, via which this space is evacuated for the melting process and a pressure is applied to fill the molten material into the mold. For the control of gas supply and evacuation, e.g.

a temperature controller is provided in connection with a delay relay for switching the valves. The heating voltage, which is switched off with the aid of the temperature controller, is fed to the heating coil via an HF voltage supply.

To prepare the melting and filling process with the device described above, the crucible with the material to be melted and the casting mold are introduced into the device via the two drawers, which is then sealed and evacuated via the corresponding valve. The material is then melted in the crucible and after switching off the heating voltage, the pressure in the previously evacuated space is increased so that the molten material is filled or injected from the crucible into the mold located in the lower part of the device. For this purpose, the crucible, which consists of two parts lying against each other in the vertical direction, is opened downwards. After the filling process has been completed, the mold and the crucible can be removed again via the two drawers. The mold is destroyed to remove the solidified material and the crucible is cleaned for a further melting process.

However, the device described has a number of disadvantages. For example, the cleaning process of the crucible is very time-consuming, since small amounts of the molten material always adhere to the contact surfaces of the two crucible components and must be removed to close the crucible. On the other hand, cracks quickly develop in the contact surfaces, on which an oxide layer also easily forms, so that the crucible, which is relatively expensive, looks for more single use is no longer usable and must be replaced. There is also the risk that the melting pot of fireclay will shatter during the melting process and the molten material will be distributed throughout the device, so that it may become unusable or at least have to be cleaned in a complex manner.

Another disadvantage is that the distance between the crucible and the mold is relatively large, so that an optimal filling of the mold with the molten material is not guaranteed.

It is also disadvantageous that two drawers are used for entering and removing the crucible and the mold, which are also difficult to insert into the device and are an obstacle to the fact that the entire device could advantageously be downsized.

The object of the present innovation is to provide an improved device of the type mentioned at the outset, which no longer uses expensive and sensitive crucibles, allows simple and convenient operation and has a compact construction.

This object is solved by the characterizing part of claim 1.

The device according to the innovation for melting a material and for pouring the molten material into a casting mold uses containers which are either placed on the casting mold or worked directly out of it in one piece. In this way, between the container in which the Ma material is melted, and the mold no longer unnecessarily large distance. Furthermore, there is no longer any danger with such a container that it breaks apart and the melt material runs out into the device, and such a container has the great advantage that it no longer has to be cleaned, but, like the mold, is only intended for single use . In addition, removal and insertion of this container together with the casting mold are much less critical than the introduction of the crucible into the heating area and the removal of the crucible from this area of the device.

Advantageous further developments of the innovation are specified in the subclaims.

The devices according to the invention for lowering the heating coil onto the casting mold and for sealing the device, each consisting of a pressure chamber, can be carried out in a simple manner and require little space. Containers and molds can be introduced into and removed from the device via a single device, which in the device according to the invention consists of an easy-to-use, pivotable chamber, so that a second drawer is unnecessary and therefore the sealing of the device can be done better and easier.

Instead of the expensive and sensitive melting pot made of fireclay (ceramic), the much cheaper containers can be used according to the innovation of investment material used in dental technology, from which the common molds are also made.

• FIG. 1 einen senkrechten Schnitt durch die Vorrichtung gemäß der Neuerung;
• FIG. 2 ein erstes Ausführungsbeisplel der neuerungsgemäßen Gußform, die einen Behälter zur Materialaufnahme enthält; und
• FIG. 3 ein zweites Ausführungsbeispiel des neuerungsgemäßen Behälters mit einer im Handel erhältlichen Gußform.

The innovation is explained in more detail below with the aid of the drawings. Show it:

• FIG. 1 shows a vertical section through the device according to the innovation;
• FIG. 2 shows a first exemplary embodiment of the casting mold according to the invention, which contains a container for holding material; and
• FIG. 3 shows a second exemplary embodiment of the container according to the invention with a commercially available casting mold.

The in FIG. 1 shown device 1 has three chambers 3, 4 and 8, which are each connected via valves P ₂ , P ₄ and P ₁ to a gas supply and valves V ₃ and V ₆ for evacuating the chambers 4 and 8, these valves via appropriate lines are connected to the chambers. Between the chamber 8, which is located in the lower region of the device, and the chamber 4 in the upper region of the device, there is a hatched chamber 7, which can be swiveled out of the device by rotation about an axis 12, and above it a heating or fusion spiral 5, which is located between the underside of the chamber 3 and a spiral support arrangement 11 attached to it. In the pivotable chamber 7 there is either a casting mold 6 with a container part 6a (FIG. 2) worked out from it or a casting mold with a container 6b (FIG. 3) placed thereon, the casting mold and container being made of the same material that is usually used for casting molds investment used in dental technology. Furthermore, the pivotable chamber 7 is connected via a pressure valve P ₅ and a valve A ₃ to the above gas supply or to an argon gas supply.

The chamber 4 is closed on its upper side with a sight glass 2, over which a photocell 1 is attached, and has one side above it an upper limit switch 9 and a lower limit switch 10 below the sight glass.

The base surface of the chamber 3, on the underside of which the spiral support arrangement 11 is fastened, and the top surface of the chamber 8 are designed as pistons which can be moved upwards and downwards, the top surface of the chamber 8 displacing the chamber 7 above.

• Zunächst wird die schwenkbare Kammer 7 durch Drehung um die Achse 12 aus der Vorrichtung 1 herausgeschwenkt und die Gußform 6 mit dem Behälterteil 6a oder dem aufgesetzten Behälter 6b wird mit dem zu schmelzenden Material wie Stahl oder Gold an einer markierten Position in der Kammer 7 angeordnet. Ist die Kammer 7 wieder in die Vorrichtung 1 eingeschwenkt, so wird die Kammer 8 über das Ventil P₁ mit einem Druck P_max beaufschlagt, so daß die Kammer 7 luftdicht an die Vorrichtung 1 angedrückt wird. Über das Ventil P₂ wird daraufhin die Kammer 3 mit einem Druck P_red beaufschlagt, der geringer ist als P_max, so daß die Spiralen-Trageanordnung 11 mit der Heizspirale 5 auf die Gußform 6 abgesenkt wird. Erreicht die Heizspirale 5 ein minimales Niveau auf der Gußform 6, so wird durch den unteren Begrenzungsschalter 10 die weitere Gaszufuhr über das Ventil P₂ abgeschaltet. Daraufhin wird die Kammer 4 über das Ventil V₃ evakuiert, so daß die Vorrichtung 1 im Schmelz- oder Fusionsbereich evakuiert ist. Weiterhin wird über das Ventil A₃ eine geringe Menge Argongas in die Kammer 7 eingespeist und daraufhin die HF-Spannung eingeschaltet, so daß die Heizspirale 5 über eine nicht dargestellte Versorgungsleitung mit Heizstrom versorgt wird und der Schmelzvorgang beginnt. Mit einem nicht dargestellten Temperaturregler mit der Photozelle 13 wird bei Erreichen eine Solltemperatur die Stromzufuhr abgeschaltet und das Ventil P₄ über ein nicht dargestelltes Verzögerungsrelais geöffnet, so daß die Kammer 4 über die Gaszufuhr mit einem Gasstrom versorgt wird, der das geschmolzene Material in die Gußform drückt. Nach Ablauf der Verzögerungszeit des Relais wird die Gaszufuhr abgeschaltet, d.h. die Ventile P₄ und P₁ geschlossen und über das Ventil V₃ die Kammer 8 evakuiert, so daß die Kammer 7 mit Hilfe der Kammer 8 wieder abgesenkt wird und so die Kammer 7 zum Ausschwenken freigegeben wird.

The operation and operation of the device described above can be seen from the following description:

• First, the pivotable chamber 7 is pivoted out of the device 1 by rotation about the axis 12 and the mold 6 with the container part 6a or the attached container 6b is arranged with the material to be melted, such as steel or gold, at a marked position in the chamber 7. If the chamber 7 is pivoted back into the device 1, the chamber 8 is pressurized with a pressure P _max via the valve P ₁ , so that the chamber 7 is pressed onto the device 1 in an airtight manner. Via the valve P ₂ , the chamber 3 is then subjected to a pressure P _red , which is less than P _max , so that the spiral support arrangement 11 with the heating spiral 5 is lowered onto the casting mold 6. If the heating coil 5 reaches a minimum level on the mold 6, the further gas supply via the valve P _{2 is} switched off by the lower limit switch 10. The chamber 4 is then evacuated via the valve V ₃ , so that the device 1 is evacuated in the melting or fusion area. Furthermore, a small amount of argon gas is introduced into chamber 7 via valve A ₃ fed and then the RF voltage turned on, so that the heating coil 5 is supplied with heating current via a supply line, not shown, and the melting process begins. With a temperature controller, not shown, with the photocell 13, the power supply is switched off when a target temperature is reached and the valve P _{4 is opened} via a delay relay, not shown, so that the chamber 4 is supplied with a gas stream via the gas supply, which streams the molten material into the mold presses. After the delay time of the relay, the gas supply is switched off, ie the valves P ₄ and P _{1 are} closed and the chamber 8 is evacuated via the valve V ₃ , so that the chamber 7 is lowered again with the aid of the chamber 8 and thus the chamber 7 Swinging out is released.

During a gas supply through the valve P _s after the valve P _{4 has been closed} , the base area of the chamber 3 and thus the time spiral rises again to a maximum level determined by the upper limit switch 9 due to the overpressure thus caused, so that the chamber 7 can be pivoted out of the device 1 to remove the mold 6.

The low argon pressure that is supplied from the melting process through valve A ₃ prevents, compared to the vacuum in the melting area, that molten material already drips into the mold during the melting process.

Both air and, for example, argon gas can be used for the gas supply to the valves P ₁ , P ₂₉ P ₄ and P ₅ .

The device described above therefore has the advantage of not including an additional one To operate the crucible, which is expensive, fragile, and difficult to clean, and instead uses a container for melting the material, which is made of the same inexpensive material as the mold and is either machined out of the mold 6 as a container part 6a (FIG. 2) or as an additional container 6b (FIG. 3) is placed on an already commercially available casting mold, which consists of silicone, so that in both versions 6a and 6b the molten material gets directly into the casting mold. Container part 6a and container 6b are cylindrical bodies with a diameter which is smaller than the internal heating coil diameter and have an upwardly open, conical opening, in the lower cone tip of which a flow opening for the molten material is provided.

The chamber 3 for lowering the heating coil requires no additional space in the entire device 1 and the device for sealing the device 1, consisting of the chamber 8 and the gas supply with the valve P ₁ , is very easy to carry out, so that the entire device in a more compact design than the conventional, commercially available devices of this type can be produced.

Furthermore, the swivel-out chamber of the present innovation ensures simple and safe operation of the device, since swiveling out a chamber is easier to handle than pushing two drawers and direct access to the heating coil space is no longer necessary.

Claims (7)

1. A device for melting material and for pouring the molten material into a mold with a heating device for heating the material to be melted in the container, the container being in the process of melting in an evacuated space of the device which was previously airtight with a sealing device is closed, with means for evacuating this space and with means for supplying a gas into this space for filling the molten material from the container into the mold, the evacuation and supply of the gas being controlled by a control device, and with means for inputting and for removing the mold and the container with the material in or out of the device, characterized in that the container (6a; 6b) is placed directly on the mold (6) and that the device for inserting and removing (7) the mold with the container placed on it. 2. Device according to claim 1, characterized in that the container (6a) and the mold (6) are made in one piece. 3. Device according to claim 1, characterized in that the device for input and removal (7) consists of a pivotable chamber (7) which is rotatably mounted about a vertical lateral axis (12) of the device (1). 4. The device according to claim 1, characterized in that a movement device (3, P ₂ ) is provided for merging the heating device and the mold with the container, which has a chamber (3) with a movable base and a valve (P ₂ ) Has gas supply, a spiral support arrangement (11) being fastened to the outside of the base surface, to which the heating device is fastened in the form of a heating spiral (5). 5. Device according to claims 1 and 4, characterized in that the sealing device (8, P ₁ , V ₆ ) a further chamber (8) in the lower region of the device (1) and valves (P ₁ , V ₆ ) for gas supply (P ₁ ) and for evacuating (V ₆ ) the chamber (8), the device for inserting and removing (7) the mold (6) and the container (6a; 6b) over a movable cover surface of the chamber (8 ) and is pressed against the housing of the device (1) when the gas is supplied via the valve (P ₁ ). 6. The device according to claim 1, characterized in that the container (6a; 6b) is a cylindrical body with a conical, upwardly opening and provided in the cone tip with a flow opening. 7. The device according to claim 1, characterized in that the container (6a; 6b) and the mold (6) consist of investment material used in dental technology, poured into a silicone mold.

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