US3448898A

US3448898A - Apparatus and method for metering molten metal

Info

Publication number: US3448898A
Application number: US615300A
Authority: US
Inventors: Foster C Bennett
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1967-02-09
Filing date: 1967-02-09
Publication date: 1969-06-10
Anticipated expiration: 1986-06-10

Description

. June 10, 1969 F. C. BENNETT APPARATUS AND METHOD FOR METERING MOLTEN METAL Filed Feb. 1967 Sheet of2 [my machine I I ll INVENTOR. F06 fer C. Bennefi' arro kzvex June 10, 1969 I F. c. BENNETT APPARATUS AND METHOD FOR METERING MOLTEN METAL Sheet 3 of2 Filed Feb. 9, 1967 70 3/207 we// of die. Casi/n9 machine 1 NVENTOR. Fosfer 6. Benneff United States Patent U.S. Cl. 222152 6 Claims ABSTRACT OF THE DISCLOSURE -Apparatus for metering molten metal comprising a partially submersible vessel having an inlet valve and an outlet valve associated therewith adjacent the bottom of the vessel. A gas line communicates with the upper part of the vessel and is connected to controllable compressed inert gas supply and controllable vacuum means. The efiiuent from the outlet valve is directed via a pipe line to a reservoir such as a shot well of a die casting machine. The inlet valve and the outlet valve are each controllable from above the level of the melt.

The method comprises admitting molten metal into a vessel partially submersed therein and discharging the molten metal from the vessel by gas pressure, via an outlet valve, in controlled amounts or charges and especially in a plurality of charges per filling of the vessel.

BACKGROUND OF THE INVENTION Field of the invention Description of the prior art Gas displacement methods have been used heretofore for the metering of molten metal utilizing apparatus without mechanical valves. In the prior art apparatus, use is made of a molten metal trap in a larger leg of the apparatus. The trap effectively serves as a valve and permits gas displacement of molten metal from a smaller leg of the apparatus. While valve maintenance problems are avoided in the prior art apparatus, the lack of positive control of metal displacement results in insufiicient accuracy of metal charge size for precise die casting work.

OBJECTS OF THE INVENTION It is a principal object of the invention to provide sturdy reliable apparatus for the metering of molten diecastable metal in a positive manner by gas displacement, i.e. by the use of compressed gas.

Another object of the invention is to provide for diecasting operations, metering apparatus in which the delivery pipe normally remains full of molten metal throughout operation of the apparatus and employing of the delivery pipe is not necessary even while exhausting the metering chamber or vessel for refilling.

It is a further object of the invention to provide a method for metering molten die-castable metal in a sufficiently precise manner to accommodate die casting operations while avoiding contamination of the metal being metered.

SUMMARY OF THE INVENTION The device of the invention is a partially submersible vessel equipped with both an inlet valve and an outlet valve adjacent the bottom thereof and a gas line connection adjacent the top thereof. The method comprises admitting or drawing in molten metal to the vessel via an 3,448,898 Patented June 10, 1969 "ice inlet valve in a filling operation, and discharging the molten metal from the vessel via an outlet valve, the outlet valve communicating with a mold or other reception vessel such as the shot well of a die casting machine in an emptying operation. Ordinarily the molten metal will be discharged from the vessel as a plurality of charges per filling of the vessel.

BRIEF DESCRIPTION OF THE APPARATUS AND METHOD The invention will be more clearly understood with reference to the drawings in which:

FIG. 1 is a view in vertical section of the apparatus of the invention disposed in a holding pot containing molten metal; and

FIG. 2 is a view in vertical section of another embodiment of the present apparatus having the inlet and outlet valves disposed inside the vessel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring more particularly to FIG. 1 the present apparatus is seen to consist of a vessel indicated generally by the numeral 10 partially submersed in molten metal 35 held in a holding pot 12. The holding pot 12 may also be the well of a reverboratory furnace. The vessel 10 is supported by its flanged top 11. Adjacent the bottom wall 13 of the vessel are mounted an inlet valve 14 and an outlet valve 15. Each valve is connected to the vessel 10 by a respective short pipe nipple or inlet 16 and 17. The

valves

14 and 15 are controllable from above the level of the melt and ordinarily from above the level of the vessel 10. As shown, the valves are controlled by double acting air cylinders 18 and 19' which are each mounted on a support plate 20. The support plate 20 is disposed across the top of the holding pot 12. However, it is essential for the proper filling of the vessel 10 that there is communication between the surface of the melt in holding pot 12 and the surrounding atmosphere. Therefore, the cover plate 20 must not be a gas tight cover. Any valve that is controllable from above the melt may be used providing it is suitable for service while submersed in the molten die-castable metal being metered. A suitable type of valve is shown in the partially broken away view of the outlet valve '15. Outlet valve -15 is provided with a valve body 21 having an inner frustoconical surface and a reciprocable rod 22 terminating in a hemispherical lower end 23 which is capable of being sealingly seated against the frustoconical surface. The upper end of the reciprocable rod 22 is connected to the piston (not shown) of the double acting air cylinder 19. The inlet valve 14 is of similar construction. If desired, the vessel 10 is provided with a clean out plate 24 disposed in the flanged top 11 of the vessel.

A gas line or conduit 25 extends through the side wall of the vessel 10' adjacent the cover flange 11 and provides communication from the upper part of the vessel to controllable compressed inert gas supply means and controllable vacuum means (neither of these being shown).

In carrying out the method of the invention with the vessel 10 partially submersed at a predetermined level in molten metal 35 and with the outlet valve 15 closed, the inlet valve 14 is opened and molten metal 35 is admitted through an inlet such as pipe nipple 26, opening into valve 14. The molten metal flows into the vessel 10' and rises to a predetermined level as urged by the head of metal surrounding the vessel. If desired or necessary, filling of the vessel is completed by at least partly evacuating the interior of the vessel. Filling of the vessel 10 is completed in a known manner and in a timed sequence when the flow characteristics of the molten metal through the inlet valve are known. Filling of the vessel need not be too precise if the capacity of the vessel substantially exceeds the quantity discharged after each filling. The vessel is emptied of a precisely measured quantity or quantities, i.e., charges, upon closing inlet valve 14 and opening outlet valve 15. Metal flowing through outlet valve -15 is discharged via pipe line 27 to a desired point, such as the shot well of a die casting machine (not shown), upon applying inert gas pressure to the upper part of the vessel 10 via gas line 25. Quantities discharged are precisely controllable on a time basis in the same manner as in the filling of the vessel 10 upon maintaining well controlled, constant level inert gas pressure on the vessel. By closing the discharge valve 15 after appropriate time lapses, a plurality of charges are discharged from the vessel after a single filling. Typically from 10 to 50 charges are discharged from the vessel after each filling. After substantially emptying the vessel 10 is it refilled and discharged again in a similar manner.

The quantities discharged are accurately controlled using the present apparatus and method and both surface L contamination and settled impurities are avoided by admitting molten metal to the metering apparatus from a level which is neither at the top nor at the bottom of the melt.

In another embodiment of the apparatus of the invention, as shown in FIG. 2, the inlet valve 14 and the outlet valve 15 are each disposed inside the vessel 10. In order to exercise compressed gas control it is necessary to provide

packing glands

28 and 29 for the

reciprocable rods

22 and 30 which are used respectively to control the

valves

15 and 14. Since there is a tendency for the lower part of the vessel 10 which is submersed in the molten metal to expand more than the top of the vessel, it is highly desirable to provide means for maintaining easy alignment between the

air cylinders

18 and 19 and the

respective valves

14 and 15. This is accomplished by providing

openings

31 and 32 through the cover flange 11 which are substantially larger than the

rods

22 and 30 so that the rods may reciprocate freely. Gas tight enclosure is maintained by inserting

flexible sleeves

33 and 34 in the

openings

31 and 32 respectively. The sleeves are welded or otherwise sealingly attached to the cover flange 11. The upper end of each sleeve respectively connects to and supports one of the

glands

28 and 29 through which the

rods

22 and 30 extend. The

glands

28 and 29 are readily connected to

sleeves

33 and 34 as by threadable connection. Although the valves in the apparatus of FIG. 2 are differently located, the apparatus is used in the same manner as the apparatus of FIG. 1.

The preferred embodiment is the apparatus shown in FIG. 1.

The present apparatus and method may be employed with any of the die-castable metals which include for example aluminum, magnesium and zinc and their die-castable alloys. In working with magnesium and zinc, the submersed parts of the apparatus may be constructed of chrome steel. In working with aluminum, the submersed parts of the apparatus are constructed of graphite or other refractory material resistant to attack by molten aluminum.

The compressed gas employed in working with molten zinc and molten aluminum may be nitrogen, dry air or other inert gas. In working with molten magnesium the compressed gas is preferably argon that is substantially free of water vapor. However, in the general practice of the invention, any gas which is inert to the metal being metered, i.e., does not detrimentally react with the metal, can be used.

I claim:

1. In combination with a melting pot containing molten metal to be die-cast, a device for metering molten diecastable metal by positive gas displacement which comprises:

an enclosed vessel that is substantially partially submersed in the molten metal to be die cast, said vessel having a bottom Wall, a top Wall and a side wall;

means for supporting said vessel at a predetermined level in the molten metal;

a gas conduit extending through the side wall of said vessel adjacent the top wall, said conduit communicating with the interior of the vessel and with both controllable compressed inert gas supply means and controllable vacuum means;

an inlet communicating with the interior of the vessel adjacent the bottom wall, said inlet being controlled by an inlet valve, and said inlet valve being operable by a double acting air cylinder mounted above said support means;

outlet means extending through the side wall of the vessel adjacent the bottom wall and upwardly through the molten metal and over the side wall of the melting pot, said outlet means communicating with means for conveying the molten metal efliuent of the vessel to die casting means, the outlet means being controlled by an outlet valve, said outlet valve being operable by a double acting air cylinder mounted above said support means;

each of said inlet valv and said outlet valve being entirely immersed in said molten metal and each said valve comprising a reciprocable rod with a hemispherical lower end and a valve body having an inner frustoconical surface communicating with a valve passage and said rod being sealingly seatable against the frustoconical surface;

and said enclosed vessel and associated valving and outlet means being readily removed from said melting pot and inserted in another similar melting pot.

2. The apparatus as in claim 1 in which the inlet valve and the outlet valve are each disposed inside the vessel.

3. The device as in claim 1 in which the inlet and the outlet valve are each mounted outside the vessel.

4. The method of metering molten die-castable metal by positive gas displacement which comprises:

in a filling operation, admitting molten die-castable metal from a melting pot into an enclosed vessel disposed in said melting pot via an inlet controlled by an inlet valve, said vessel being at least partially submersed in the molten metal, and closing the inlet valve;

and in an emptying operation, opening an outlet valve communicating with means for conveying molten metal out of the melting pot to a die casting machine and controllably admitting compressed inert gas to the vessel to discharge preselected amounts of molten metal from the vessel upwardly through said means for conveying molten metal and thence to the die casting machine, said inlet valve and said outlet valve being each submersed in molten metal throughout said filling and emptying operations.

5. The method as in claim 4 in which suflicient metal is drawn into the vessel in one filling operation to provide for a plurality of shots discharged via the outlet valve to the die casting machine.

6. The method as in claim 5 in which the plurality of shots discharged after one filling of the vessel is at least 10' shots.

References Cited UNITED STATES PATENTS 1,112,496 10/1914 Urban 222-1 2,185,376 1/1940 McParlin 222152 2,745,153 5/1956 Burkett 222152 X 2,937,789 5/1960 Tama 222--1 3,208,637 9/1965 Heick 222-1 FOREIGN PATENTS 1,289,845 2/ 1962 France.

STANLEY H. TOLLBERG, Primary Examiner.

US. Cl. X.R.. 2221, 373