EP1610917B1 - Holding furnace and metering device for metal baths - Google Patents

Abstract

The invention relates to a holding furnace comprising a metering device for molten metal, especially for precisely metering molten light metal during die casting, wherefore the holding furnace is provided with a dosing chamber encompassing a controlled discharge valve.

Description

The invention relates to a holding furnace with metering device for molten metal, in particular for metering of molten metal during die casting.

The DE-OS 2022989 describes an automatic dosing device for liquid metals with which metal melts should be precisely metered. The automatic dosing unit is part of a holding furnace, which is fed with molten metal via a loading flap. The discharge of the melt to be metered takes place through a delivery tube, which is provided with two measuring electrodes. If melt is to be metered, the furnace is pressurized with compressed air and the melt rises in the delivery tube until it reaches the measuring electrodes and thus delivers a pulse to a controller. The discharge pipe discharges the set amount of molten metal. Thereafter, the oven is vented over a timer and the flow of molten metal abruptly prevented. However, the accuracy is insufficient for today's conditions and the formation of slags is disadvantageous.

Another device is known for casting molten metal according to the DE-A-19821650 comprising a metering container, which is connected via a closable opening with the melting space of a holding furnace in flow communication. The dosing is emptied by pressurized gas via a riser, wherein the opening is arranged in the bottom of the dosing and can be closed from the inside by means of a valve body to a valve rod. The opening is hemispherical or conical. Valve rod and valve body are arranged inside the metering container. The level in the dosing tank is determined by means of a level sensor in the dosing tank.

At the beginning of a dosing process, the melt flows independently up to the predefined working level via the open bottom valve into the dosing tank. After reaching the target level, the opening of the bottom valve by lowering and turning the valve body locked. By means of a defined gas overpressure, the melt leaves the dosing tank through the riser. Reflux in the riser is possible when refilling the dosing tank. As a result, unwanted oxides can be deposited in the riser.

A similar solution shows the DK 199800409 , wherein the holding furnace is arranged vertically adjustable. The height adjustment takes place by means of a scissor lifter.

The DE-A-10034946 discloses a piston pump whose valve unit is used in combination as an inlet and outlet valve. Such a valve is trapped geometrically and therefore can not be dismantled without expensive cleaning of the piston pump.

A holding furnace, especially for light metal melts is in the JP-A-2001239357 disclosed. Associated with this is a separate metering chamber with a closable opening, which opens into a riser pipe to the point of use. The outlet is closable by means of a valve rod, wherein the closure elements must cooperate in the metering chamber.

The invention is based on the object to provide a holding furnace with a metering device for molten metal, in which, while avoiding the disadvantages of the prior art, a precise metering of molten metals, in particular aluminum melt is possible. The solution of the issue is based on the features of claim 1.

Characteristic is a controlled outlet valve of a pneumatically operated metering chamber in conjunction with contact electrodes or alternative level sensors for molten metal. The metering chamber is rotatably and tiltably mounted with the delivery pipe in the holding furnace. This outlet valve not only prevents the backflow of melt from the riser, but also increases the dosing accuracy, since no inconstant flow obstacles interfere with the pneumatic metering. The melt level in the riser can be kept high, close to the outlet. Oxides can only slightly contaminate the riser and the outlet valve.

Further advantageous embodiments are disclosed in the subclaims. A rotatable and tiltable Dosierkammerhalterung allows the fixed to the metering chamber connected delivery pipe a much better adaptation to the geometric conditions of the casting chamber to be filled, eg a die casting machine. In addition, a decoupling of the dosing unit can be achieved by the casting chamber exposed to strong vibrations via a small tilting movement.

A docking has a positioning aid in the form of a ceramic bushing, in particular of a fiber-reinforced ceramic material. This ceramic bushing fits into an opening of the casting chamber, so that an accurate dosing from below is possible. For this purpose, the docking is still stored in a dome of the conveyor tube, which still contains a sealing element. This arrangement allows both an angle compensation and the compensation of an axial offset up to ± 2 mm. The opening is designed as a socket, which is accommodated in a bush made of gray cast iron.

The conveyor pipe is provided with a heater and a foamed insulation.

For a tight transition to the holding furnace between the conveyor pipe and holding furnace a ceramic sealing ring is arranged, which is still surrounded by a steel ring, which ensures a rapid removal of heat energy at the transition. The durability is increased and the handling is simplified.

Fig. 1:

einen Warmhalteofen in einer Schnittdarstellung

Fig. 2:

eine Dosiervorrichtung für Metallschmelze mit Detailvarianten (Fig. 2a, 2b)

Fig. 3:

eine Dreh- und Kippvorrichtung in einer Draufsicht und

Fig. 4:

eine Dreh- und Kippvorrichtung in einer Seitenansicht

Fig. 5:

eine Detailansicht zum Förderrohr.

The invention will be described below in an embodiment with reference to a drawing. In the drawing show the

Fig. 1:

a holding furnace in a sectional view

Fig. 2:

a metering device for molten metal with detail variants ( Fig. 2a, 2b )

3:

a turning and tilting device in a plan view and

4:

a turning and tilting device in a side view

Fig. 5:

a detailed view of the delivery pipe.

A holding furnace 1 for example, aluminum melt consists in a conventional manner from a force-absorbing steel tub 2 with a heat-resistant insulation 3. The heating is done by a not explicitly shown ceiling, immersion or floor heating. The holding furnace 1 is filled to a minimum level 4 with aluminum melt.

The feeding of the molten metal via a pipe 5, which closes a filling opening of the steel tub 2 tight and the lower end is constantly below the level 4, whereby the oxide formation and the gas entry in Filling is greatly reduced. A funnel 7 is placed on the tube 5 and the molten metal passes from the funnel 6 via a filter 7 into the tube 5.

In a further opening of the steel tub 2, a metering chamber 8 is arranged, in which there is a metering device for each pouring amount of molten metal to be metered. The metering device contains an outlet valve with a valve rod 11 and a valve seat 12. The valve seat 12 establishes the connection to a riser 20. The valve rod 11 is held at the upper end in a gas-tight and heat-resistant bellows 18 and guided and driven by pneumatic cylinder 17. In parallel with this valve drive unit may be an analog gas-tight drive unit for the active actuation of two scanning electrodes 16 and 16'befinden. When starting the dosing process, molten metal is sucked pneumatically via a bottom valve (passive inlet valve 13) and / or an overflow 14 into the dosing chamber 8. When responding (melt surface 15) of the scanning electrodes 16 and 16 ', this suction is stopped abruptly. The scanning electrodes 16 and 16 'fast back. They are less affected by the molten metal and a disturbing thread formation can be largely prevented. An overflow 14 or an active or passive bottom valve 13 prevent or limit the reflux of molten metal from the metering chamber 8 in the holding furnace 1. After opening the outlet valve 11,12 molten metal can be pneumatically conveyed via the riser 20 to the casting machine. After reaching the metered amount, the valve rod 11 closes the valve seat 12 and thereby terminates the metering exactly. A possible reflux of molten metal from the riser 20 into the metering chamber 8 is reliably prevented.

The melt level (melt surface 15) can be easily overflowed, which can increase the dosing accuracy.

The electrodes 16, 16 'have to "hit" when returning to the pneumatic cylinder 17 to solve adhering metal.

The riser 20 is connectable via a conveyor pipe 21 with an outlet beak 22 and a docking 23 with the casting chamber 24.

Only because of the described procedure, the outlet valve and the delivery pipe 21 is minimally affected by oxides / slags, which ensures a reliable melt transfer.

The docking 23 has an angle-independent and laterally displaceable positioning aid in the form of a cap 44. In the unheated area between the docking and the outlet (opening 43) in the casting chamber 24, a ceramic bushing 41 is used as insulation, which allows accurate metering from below by avoiding solidification. Within the docking 23, a sealing element 45 is installed between the delivery pipe 21 and the cap 44. This arrangement allows both an angle compensation and the compensation of an axial offset up to ± 2 mm. The opening 43 of the casting chamber 24 is designed as an exchangeable bushing 42 (welding bushing). It is manufactured in gray cast iron, which allows inexpensive replacement parts with good resistance to melting.

The delivery pipe 21 is provided with a heater 52 and a foamed insulation 51.

For a tight transition to the holding furnace 1, a ceramic sealing ring 53 is disposed between the conveyor pipe 21 and holding furnace 1, which is still surrounded by a steel ring 54, which ensures a rapid removal of heat energy at the transition. As a result, the escaping molten metal selectively solidifies in the event of a leak, which ensures good durability of the connection and simplifies handling.

For optimum adaptability of the melt transfer at the location and location of the casting chamber 24 metering device including conveying tube 21 is rotatably and tiltably inserted into the holding furnace 1. As a turning and tilting device is a rotary arm 30 in which a tilting ring 31 is used with built-dosing 8. The Förderrohrabstützung 32 is rigidly connected to this tilting ring 31. Forces acting on the conveyor tube 21 are translated as quickly as possible into a movement of the turning and tilting device, which reduces the load on the delivery tube 21 and thereby increases the durability.

The holding furnace 1 may be arranged on a lifting device in the form of a scissors jack. Since the operating cylinder for the scissor lifter can be arranged laterally on the outside of the steel tub 2, the minimum overall height of the scissors lifter can be kept low.

reference numeral

1

Holding furnace

2

steel tub

3

isolation

4

filling level

5

pipe

6

funnel

7

filter

8th

metering

11

valve rod

12

valve seat

13

passive inlet valve

14

overflow

15

melt surface

16

electrode

16 '

electrode

17

pneumatic cylinder

18

bellow

20

riser

21

delivery pipe

22

departure lip

23

docking

24

casting chamber

30

rotating arm

31

tilting ring

32

Conveying pipe support

41

ceramic sleeve

42

Rifle

43

opening

44

dome

45

sealing element

51

isolation

52

heater

Claims (14)

1. A holding furnace (1) for molten metal, in particular for light molten metal, with a metering chamber (8) consisting of a sealable outlet opening that empties into an ascending pipe (20), via which the molten metal can be metered to the application site, wherein the outlet opening can be actively sealed by means of a valve rod (11, 12), characterized in that the metering chamber (8) is mounted with conveyor pipe (21) in the holding furnace (1) so that it can rotate and tilt.
2. The holding furnace according to claim 1, characterized in that this valve rod (11) is powered in a gastight and heatproof manner via an expansion bellows (18).
3. The holding furnace according to one of claims 1 and 2, characterized in that scanning electrodes (16, 16') can be actively retracted when filling the metering chamber (8) after their melt surface (15) has been scanned.
4. The holding furnace according to claim 2 or 3, characterized in that the retraction motion of the scanning electrode (16, 16') is powered in a gastight and heatproof manner via the expansion bellows (15).
5. The holding furnace according to one of claims 1 to 4, characterized in that the molten metal is incorporated into the metering chamber (8) via an overflow (14) in the metering chamber (8).
6. The holding furnace according to one of claims 1 to 5, characterized in that the melt surface (15) can be scanned before the overflow (14) is reached.
7. The holding furnace according to one of claims 1 to 6, characterized in that the molten metal is incorporated into the metering chamber (8) via an actively actuated or passive inlet valve (13).
8. The holding furnace according to one of claims 1 to 7, characterized in that a concentric arrangement of turning arm (30) and tilting ring (31) yields a maximal insulation of the metering chamber (8) filled with molten metal.
9. The holding furnace according to one of claims 1 to 8, characterized in that the molten metal can be transferred from the metering chamber (8) via the ascending pipe (20) into a casting groove, a pipe system, a casting chamber (24) or a casting mold through exposure to pressure, e.g., an inert gas.
10. The holding furnace according to one of claims 1 to 9, characterized in that the pressure progression in the metering chamber (8) can be acquired by means of a sensor array.
11. The holding furnace according to one of claims 1 to 10, characterized in that the metering process is regulated via a programming controller.
12. The holding furnace according to at least one of claims 1 to 11, characterized in that the conveyor pipe (21) has a docking port (23) provided with a positioning aid.
13. The holding furnace according to claim 12, characterized in that the positioning aid is designed as a spherical cap (44).
14. The holding furnace according to claim 1 to 13, characterized in that the melt transition after the docking port (23) is insulated via a ceramic bushing (41) placed inside a replaceable wear bushing (42) in the casting chamber (24).

Images