US3471057A

US3471057A - Apparatus for ladling liquid metal

Info

Publication number: US3471057A
Application number: US686928A
Authority: US
Inventors: Peder Ragnvald Solheim
Original assignee: NORSK HYDRO ELEKTRISH KVAELSTO
Current assignee: NORSK HYDRO ELEKTRISH KVAELSTO; NORSK HYDRO ELEKTRISH KVAELSTOF AS
Priority date: 1966-11-30
Filing date: 1967-11-30
Publication date: 1969-10-07
Anticipated expiration: 1986-10-07
Also published as: GB1188663A; BE707368A; DE1583678A1; DK119841B; FR1548754A; CH465782A; LU54929A1; NL6716229A; NO123618B; SE350205B

Description

Oct. 7, 1969 P. R. SOLHEIM APPARATUS FOR LADLING LIQUID METAL 3 Sheets-Sheet 1 Filed Nov. 30, 1967 In; 4 Fm; 7 4 1 1 I u 2 i 5 8 l. 3 2 9 .1 Q G Cl u v. V/

INVENTOR P w B ATTORNEYS Oct. 7, 1969 P. R. sou-lam 3,471,057

APPARATUS FOR LADLING LIQUID METAL 3 Sheets-Sheet 3 Filed Nov. 30, 1967 INVENTOR PE DER mamvmo- SOME/N BY ATTORNEYS United States Patent Int. 01. B67d 5/54, 5/50 US. Cl. 222-61 2 Claims ABSTRACT OF THE DISCLOSURE Apparatus for ladling of liquid metal having a reservoir of liquid metal with a discharge chamber submerged therein having a gas inlet and an outlet for metal. A source of gas under pressure is connected with the gas inlet and a first conduit rises with is upper end into the discharge chamber to a level above said outlet. The lower end extends down into the reservoir to a depth at which the static pressure is above a predetermined maximum gas pressure to be applied in the discharge chamber during operation. A discharge spout is provided with a second conduit connecting the outlet with such spout. A valve connects in one position the discharge chamber with the source of gas under pressure and in a second position connects the discharge chamber with a lower pressure. Activating means for the valve are provided with means connecting the activating means with the gas in the discharge chamber. The activating means moves the valve from the first-mentioned position to the second position when the gas pressure in the discharge chamber reaches the predetermined maximum gas pressure. Means for returning the valve to the first-mentioned position are provided. The second conduit is a U-shaped tube and that part of the U-shaped tube at which the level of the metal in the tube will be positioned at the end of a ladling has a reduced cross sectional area.

The invention relates to liquid metal ladling, and more particularly to a process and an apparatus for discharging or ladling controlled quantities of liquid light metal, such as magnesium and aluminum and alloys based on one of these metals, from a reservoir such as, for example, a melting furnace.

The ladling of controlled quantities of liquid metal to metal casting machines is an operation of increasing importance in the field of metal casting, which in a considerable measure is due to the development of metal casting machines adapted for mass production. Perhaps especially in connection with the die casting of light metals, a need is felt for an improved accuracy in the ladling of a predetermined volume, in the sense that a more narrow range of deviation is required in the repetitive ladling of the predetermined volume.

A number of different ladling devices for liquid metal are known, see for instance a survey given in Gie'sserei 49 (1962) 8, p. 180-189, among which are devices comprising a valve-less discharge chamber, which chamber during operation dips into the reservoir of liquid metal to be ladled. The invention relates to a device of this type.

Such devices comprise a discharge chamber or crucible intended to dip into the liquid metal reservoir, the discharge chamber being provided with means for introducing pressure gas to expel liquid metal out from the discharge chamber, an inlet passage to permit liquid metal to flow from the reservoir into the discharge chamber, the inlet passage terminating at its upper end above the bottom of said chamber and extending into said reservoir of metal to a depth at which the pressure is equal to or higher than the maximum gas pressure to be applied in the discharge 3,471,057 Patented Oct. 7, 1969 chamber during operation, and a discharge tube which inside the discharge chamber terminates at a lower level than said inlet passage.

According to a known mode of operating a ladling apparatus of the above-mentioned type, the quantity of metal discharged is controlled by first applying a relatively low gas pressure to bring the level of molten in the discharge chamber to a discharge starting level, whereupon molten metal is discharged by applying a predetermined higher gas pressure during a predetermined time interval.

One of the objects of the present invention is to provide a liquid metal ladling apparatus enabling a very high accuracy to be conveniently achieved in the repetitive ladling of a predetermined volume of liquid metal to moulds or other casting devices, such as a die casting machine.

The above and other objects and features of the invention will be more readily apparent from the following description when read in connection with the accompanying drawings, in which:

FIG. 1 is a diagrammatic side view, partially in section, of a container holding a liquid metal reservoir, with ladling apparatus embodying the invention;

FIG. 2 is a view similar to that of FIG. 1 but showing a further embodiment;

FIG. 3 is a view similar to that of FIG. 1 showing an embodiment of the apparatus assembled with an instrumentation suitable for use in automatic operation.

In FIG. 1 of the drawing, 1 is a container or reservoir holding the molten metal to be ladled. This container 1 can be of any suitable design and very often will be a holding furnace or the like (though heating means are not shown in the drawing). A discharge chamber or crucible 2 has an inlet conduit 3 allowing molten metal to flow into the chamber 2 from the container 1. A discharge conduit 23 has an inlet arm 5 projecting upwardly into the lower portion of the chamber 2, and a discharge arm 4 that opens into a discharge chute 6 serving to conduct the discharged metal to the point of use. Below the chamber 2 the arm 5 has a part 5a having a reduced cross sectional area. 4a designates a similar part of the arm 4 at or near the level of the molten metal in the container 1. A conduit 7 is connected to the discharge chamber 2 communicating with a source of pressure gas, and a branch conduit 8 provides communication between the discharge chamber 2 and a pressure controller 9.

The apparatus shown in FIG. 2 is similar to that of FIG. 1 except that the discharge tube consists of two

separate parts

24 and 25, which correspond to the

arms

4 and 5 of the U-shaped tube 23 in FIG. 1 and which can together function like a U-shaped tube, one arm 24 being placed inside the other arm 25. Therefore, this construction can be considered as a U-shaped tube, since for the purposes of the invention it has the function of a U- shaped tube. This particular construction of the discharge tube presents constructional advantages and facilitates draining and cleaning operations.

The process and apparatus of the invention Will now be further explained describing ladling operations with reference to the embodiment illustrated in FIG. 3. In this example the discharge chamber 2 is submerged in the molten metal reservoir, and the level of the molten metal as well as the gas pressure, conveniently atmospheric, are the same outside and inside of the discharge chamber 2.

At the arrival of a mould at the remote end of the discharge chute 6, the following sequence of events will take place (details of the mode of operation of the instrumentation shown in FIG. 3 will be explained below).

Pressure gas is supplied to the chamber 2 via conduit 7 and the metal level in the chamber 2 is depressed. The metal displaced flows to the reservoir in the container 1 reaches the upper edge of the conduit 3, the level of the' molten metal in the discharge tube 33 will still be the same as that of the reservoir in the container 1. As pressure gas continues to flow into the chamber 2 the level of the molten metal therein is continuously further depressed, and the metal in the discharge tube 33 will now rise rapidly and molten metal will be discharged into the chute 6 to flow to the mould. When the level of the metal in the chamber 2 is level with the upper edge of the tube arm 35 the main portion of the discharge volume has been expelled. In accordance with a preferred embodiment of the invention, the level of the molten metal in chamber 2 is depressed down into the tube arm 35, for instance to a level indicated by a-a in the drawing. This level will correspond to a certain gas pressure in the chamber 2 and in the pressure controller 9. By means of an instrumentation as illustrated in FIG. 3, and which forms no part of this invention, the gas flow is reversed so that gas is released from the discharge chamber 2, causing the metal level in tube arm 34 to immediately drop below discharge level.

As the gas pressure in the chamber 2 drops toward the initial low pressure (in this example atmospheric pressure), the chamber 2 will be refilled with molten metal from the reservoir in container 1 via conduit 3. A discharge cycle has now been completed, and the next cycle is initiated, conveniently, as known, by the next mould as it arrives to replace the preceding mould.

Adjustment of a particular discharge starting level below the overflow level at the upper edge of conduit 3 for example by means of a predetermined low gas pres sure as used conventionally-requires that much extra control equipment, and, besides, a certain time interval is necessary for such adjustment. In the mode of operation described above, wherein the discharge starting level is automatically self-established as a result of overflow into conduit 3, each discharge cycle can be made very short, resulting in greater discharge capacity per hour.

The inlet conduit 3 extends to a depth in the reservoir of container 1 at which the hydrostatic pressure is sufficicntly high to prevent gas from blowing past at any time during discharge operations. An inlet conduit 3 without sectional restriction can then be used, which permits rapid refilling of the chamber 2.

The cycle discharge volume will chiefly depend on the dimensions of chamber 2 and the vertical distance from the upper edge of inlet conduit 3 to the upper edge of tube arm 35 (or tube arm 5, FIG. 1 or tube 25, FIG. 2). However, using the apparatus of the invention the desired discharge volume can be varied or adjusted within certain limits by adjusting the discharge terminating level a-a in tube arm 35, which is effected by correspondingly adjusting the pressure at which pressure controller 9 will actuate pressure release in chamber 2.

Small variations in the discharge volume will systematically result from variations in the level of the molten metal in container 1 under the conditions assumed in the example above, i.e. using as discharge starting level the overflow level as determined by the upper edge of inlet conduit 3. However, these variations in the discharge volume can be made quite insignificant by (1) maintaining a fairly constant molten metal level in the container 1, and (2) using a discharge tube of moderate cross section or, if desired, merely reducing the cross section of that portion of 4a of tube arm 4 (FIG. 1), which is level with the molten metal in the container 1, the reduced cross section being provided over a vertical length sufficient to cover said variations in the metal level in container 1. These systematic variations in the discharge volume will vary proportionally with said cross section under the conditions assumed in the above example.

Variations in the discharge volume will also result from variations in the predetermined gas pressure at 4 which discharge is terminated. These variations as well can be made quite insignificant, by

(1) using accurate pressure control equipment to actuate discharge termination, and

(2). providing a discharge tube having a reduced cross section in that portion 5a of tube arm (FIG. 1) where the metal meniscus will be at the moment of discharge termination.

The cross section of the discharge tube above and below the above-mentioned portions will not affect the ladling volume accuracy, and practically it will be advantageous to provide a discharge tube having a considerable cross section above and below the above-mentioned portions in order to reduce pressure drop in the discharge tube, which is particularly desirable when short cycles are required.

The process and apparatus of this invention has proven to be capable of very accurate and rapid and otherwise satisfactory ladling.

The discharge tube should not extend unnecessarily far above the molten metal level in container 1, since (unless special precautions are taken) this would result in undesirable breathing, that is sucking in and blowing out of the gas present in the chute 6. This gas may advantageously consist of or contain an inert gas.

It will readily be understood that the inlet conduit and the discharge conduit need not have the form of a tube in a narrow sense of the word, but can be passages or conduits of any suitable shape.

Finally, the instrumentation shown in FIG. 3 will now be explained. The above-mentioned pressure controller 9, which can be of any suitable type, has been shown as comprising a U-shaped tube, which contains mercury. This tube communicates with the discharge chamber 2 via a conduit 8. A pressure tank 10 contains pressure gas, which, if desired, can be an inert gas such as argon; 11 is a high pressure gas container, and 12 is a pressure reducing valve providing a constant pressure in the tank 10; 13 is a pipe and 14 is a throttle valve. The discharge rate can be controlled by means of this valve. 15 is a 3-way solenoid valve provided with a spring return 15a, solenoid 15b and ports 0, d and e; 16 and 17 are pipes and 18 is a throttle valve; 19 is a source of electric current and 20 is a starting switch; 21 is a master relay which when engaged will connect the circuit with solenoid 15b across a set of contacts b. A set of contacts a serve as holding contacts for the relay solenoid 21. 22 is an auxiliary relay, which will break the circuit to the relay 21 when the current is supplied thereto via connection point 9a of the pressure controller 9, via the mercury to the adjustable electrode 9b.

A discharge cycle is started by engaging the switch 20 for a moment (preferably by means of an automatic impulse). Master relay 21 will then receive electric current and engage contacts a and b. Now solenoid 15b will receive current to close port e, while ports 0 and d are interconnected to permit gas to flow from tank 10 to the discharge chamber 2. The ladling now proceeds as already described above. At a certain gas pressure in conduit 8 which corresponds to the desired level of the molten metal in tube arm 35, contact is established between the mercury and the electrode 9b, and relay 22 will break the holding current to master relay 21 causing the latter to disconnect, whereby the current to solenoid 15b is broken so that the discharge valve 15 returns to normal position due to the spring 15a. Thereby the gas supply from tank 10 is stopped and the chamber 2 is evacuated via ports d and e, either directly to the atmosphere or, as shown in FIG. 3, to the chute 6, the latter being preferable when the gas employed is a more or less pure inert gas, which can thus be utilized further as a protective gas for the metal in the exit portion of the tube arm 34 and adjacent parts.

I claim:

1. Apparatus for ladling of liquid metal comprising a reservoir of liquid metal, a discharge chamber submerged in said reservoir having a gas inlet and an outlet for metal, a source of gas under pressure, means connecting said source with said gas inlet, a first conduit rising with its upper end into said discharge chamber to a level above said outlet and with its lower end extending down into said reservoir of liquid metal to a depth at which the static pressure is aljpve a predetermined maximum gas pressure to be applied in said discharge chamber during operation, a discharge spout, a second conduit connecting said outlet with said spout, a valve connecting in one position said discharge chamber with said source of gas under pressure in a second position connecting said discharge chamber with a lower pressure, activating means for said valve, means responsive to the pressure of the gas in said discharge chamber controlling said activating means, said activating means moving said valve from the first-mentioned position to said second position when the gas pressure in said discharge chamber reaches said predetermined maximum gas pressure, and means for returning said valve to the first-mentioned position.

2. Apparatus as claimed in claim 1 wherein said second conduit is a U.-shaped tube and wherein that part of said U-shaped tube at which the level of the metal in the tube will be positioned at the end of a ladling has a reduced cross sectional area.

References Cited UNITED STATES PATENTS ROBERT B, REEVES, Primary Examiner H. S. LANE, Assistant Examiner US. Cl. X.R. 280-515