US3184811A - Metering and delivery apparatus for molten metal and method of use - Google Patents

Description

y 25, 1955 V F c. BENNETT E'I'AL 3,184,811

METERING AND DELIVERY APPARATUS FOR MOLTEN METAL AND METHOD OF USE Filed Feb. 14, 1962 f INVENTORS. 9 Foal er CI knnefi Frank E. Robbins Ray E. War-nook BY QMW asp/r United States Patent 3,184,811 METERING AND DELIVERY APPARATUS 1 0R MOLTEN METAL AND METHQD 9F USE Foster C. Bennett, Frank E. Robbins, and Ray E. Warnoclr,

Midland, Mich, assignors to The Dow Chemieai Company, Midland, Mich, a corporation of Delaware Filed Feb. 14-, 1962, Ser. No. 173,272 4 Claims. (Cl. 22-70) This invention relates to the handling of molten metal and more particularly is concerned with a new and novel apparatus for delivering controlled and accurately measured amounts of molten metal to a die casting machine and to a method of use therefor.

It is a principal object of the present invention to provide a simple reliable unit for metering and transferring predetermined quantities of molten metal.

It is another object of the present invention to provide an apparatus for moving readily oxidizable molten light metals whereby undesirable burning and solid oxide formation during movement of the metal substantially is avoided.

It is a further object of the present invention to provide an apparatus for repeatedly supplying accurately measured amounts of molten metal to the shot well of a die casting machine.

It is another object of the present invention to provide a metering pump assembly wherein the outlet delivery tube is substantially filled with molten metal at all times.

It is an additional object of the present invention to provide a molten metal metering unit having simple controls which unit is submersible in the molten metal to be moved and which is readily adaptable for use in a covered metal holding pot.

Another object of the present invention is to provide a low cost metal metering unit of compact size which requires a minimum of maintenance and has a high output.

These and other objects and advantages will become apparent from the detailed description presented hereinafter when read in conjunction with the accompanying drawings.

In general, the present new and novel metal delivery apparatus comprises in combination a centrifugal pump communicating with a valve assembly wherein the valve position is controlled to deliver measured amounts of molten metal under pressure to a delivery outlet tube. In a preferred utility, the metal is transferred from the delivery outlet tube into the shot well of a die casting machine.

The figures show several embodiments of the pumpvalve metal transferring assembly of the present invention.

FIGURE 1 is a schematic view, partly in section, of one embodiment of a centrifugal pump and double valve metal metering delivery assembly of the instant invention.

FIGURE 2 is a schematic sectional view of another embodiment of a centrifugal pump and valve metal metering and delivery assembly of the instant invention.

The molten metal metering pump and valve assembly shown in FIGURE 1 comprises in combination a centrifugal pump 11 connected by conduits 12 and 13 to a double valve assembly 14. An outlet metal delivery tube 15 is connected to the valve 14 near one end of the valve body 16. This tube 15 serves, for example, to transfer the measured amount of molten metal to the shot well 17 of a die casting machine (not shown). The valve assembly 14 conveniently is supported within a "ice covered pot of molten metal 18 by means of supports 19a-19b and the pump 11 is held in position by support 20. The valve assembly 14 is activated through a yoke and rod assembly 21 attached to valve stem 22 and connected to and driven by an air pressurized reciprocating piston-cylinder device 23. The actual shifting of the valves 24 and 25 from one position to the other by this drive mechanism 23 is controlled by an interval timer (not shown) which activates the reciprocating drive 23.

A double valve assembly particularly suitable for use in the instant apparatus is that described in copending application, Serial No. 173,273, filed February 14, 1962.

In the embodiment depicted in FIGURE 1, the conduit 12 provides communication between the valve body 16 and pump chamber 26. This conduit 12 has one end attached to the valve body 16 so as to provide access into the valve body 16 between valve seat 27 and valve seat 28 and has its other end aflixed and opening into the pump chamber. One end of the second conduit 13 is attached to the valve body 16 near the end of the valve body 16 opposite that containing outlet delivery tube 15 and joins the valve body 16 to metal inlet tube 29 of pump 11.

If desired, the double valve assembly can be fabricated utilizing separate independent valves and valve seats instead of the illustrated single stern in-line double valve arrangement. However, dissociating the valves into separate units would increase the amount of activating mechanism needed as well as require increasingly complex control systems. In any event, the valves must be arranged so that they both cannot be closed at the same time.

The pump to be employed is any of a variety of conventional centrifugal pumps which can be operated in the presence of the molten metal being moved.

Conveniently the pump inlet 29 can be curved upward as shown in FIGURE 1. With this modification, during pump operation, molten metal is drawn from the central portion of the melt rather than from the bottom of the pot directly beneath the pump and the probability of including undesirable sludge from the pot bottom in the measured charge thereby substantially is eliminated.

The method of operating this embodiment of metal metering apparatus is as follows. Molten metal is drawn from the pot of metal 18 by the pump 11 through the pump inlet 29 and delivered under pressure to the valve body 16 through conduit 12, the valve assembly 14 being positioned so that the valve 24 adjacent this condit 12 is closed. The valve positions then are shifted and metal pumped for a controlled time interval under a pressure head developed by the centrifugal pump 11 through the metal delivery tube 15 and into the shot well 17 of the die casting machine. As the predetermined amount of metal is metered into the shot well 17, the valves shift closing valve 24 and opening valve 25 whereby molten metal is directed through conduit 13 back to the pump inlet 29;.

This double valve arrangement has the advantage that the centrifugal pump can be operated continuously and the unit employs only one set of timers and controls.

In the embodiment of the metal metering apparatus shown in FIGURE 2, a centrifugal pump 11 having a metal inlet tube 29 is attached through conduit 31 to a single valve unit 32.

This valve unit 32 comprises a valve body 33 having an integral valve seat 34. The conduit 31 is afiixed to the areas: 1

valve body 33 on one side of valve seat 34 and a metal delivery tube is attached to the valve body 33 on the other side of this valve seat 34. A valve head 35, mating with valve seat 34, is mounted on a valve stem 36, which in turn is attached to a rod and yoke assembly 21 attached to a reciprocating air driven position-cylinder device 23. As with the hereinbefore described double valve assembly, the instant single valve 32 is shifted alternatively from open to closed positions in a controlledmanner by an interval timer (not shown) which activates the reciprocating drive 23.

The valve head 35 very suitably can be either a frustrum, round-bottomed or of other diverse shape with a mating valve seat and satisfactorily is fabricated in ac.-

cordance with the description of the corresponding valve members set forth in the hereinbefore identified copend ing application, Serial No. 1733.7 3.

In operation of this second embodiment of metal metering apparatus, molten metal is drawn from pot 18 by centrifugal pump 11 through inlet 29 and is transferred through conduit 31 under pressure to the valve assembly 32. The valve then is opened for a controlled time interval thereby feeding a predetermined amount of metal through conduit 15 into the shot well 17 of a die casting machine (not shown). The valve is closed, the casting removed from the die and the cycle repeated. On short cycle work, i.e. for preparing small size castings, the pump can be kept running continuously. However for large castings, when the valve is closed preferably the pump will be stopped in order to keep turbulence in the pot, from metal movement in and out of the pump inlet, at

'a minimum. The alternate starting and stopping of the pump readily is carried out on an automatic basis and in a controlled relationship to the valve movement.

The pump drive 39 in the assembly preferably is a variable speed unit. This gives control of the pump delivery rate and permits the maintenance of proper metal velocity into the shot well.

For both embodiments, the valve assembly preferably is activated by positive mechanical means rather than by gravity or spring motion.

This is desirable for two reasons; (1) in operation the time cycle relationship for metal delivery as determined by the opening and closing of the valve must be closely controlled and (2) ordinary springactivated check valves do not give positive shut-off with molten metals that oxidize as readily as magnesium and aluminum, for example.

Conveniently, as indicated hereinbefore the valve assembly and, if desired, the centrifugal pump can be activated by an automatic timer, e.g. an interval timer, thereby assuring precise control of the apparatus and auto- "matic transfer of reproducibly constant predetermined amounts of metal to the shot well.

As shown, the valve assembly is activated by an air driven piston-cylinder device through .a yoke androd.

arrangement. It is apparent that the valve position can be shifted by any of a wide'va'riety of devices producing reasonably linear reciprocating motion. The depicted air driven device is one preferred means since it is simple,

1 easily and accurately controlled and is'safe to operate; Likewise, valves differing in design from those described herein can be employed as is apparent to one skilled in the art.

' The positioning of the pump-valve assembly in a molten pot of metal is not critical as long as the pump inlet is percent by weight magnesium, chrome steelssuch as 430 the metal in-the tube.

t stainless for example, are satisfactory for all surfaces exposed to the molten metal, Molten aluminum, i.e. aluminumand aluminum based alloys containing at least about percent by weight aluminum, readily can be moved by the instant apparatus fabricated from steel having a refractory coating 'on those surfaces contacting molten metal as conventionally is practiced in the aluminum art. For moving aluminum, bearing surfaces are coated with titanium diboride, zirconium diboride or other construction material resistant to attack by the melt.

Either the valve head surface, valve seat or both can be given a Stellite coating, e.g. Stellite No. l, to provide these with a high. resistance to deformation upon impact.

The utility of the instant metering and delivery unit was demonstrated in an operation whereby reproducibly controlled amounts of molten ASTM designated AZ9-lB magnesium alloy (nominal composition 9 percent aluminum, 0.7 percent zinc, 0.15 percent manganese, balance magnesium) were transferred from a holding pot to the shot well of a die casting machine. For this. operation, a centrifugal pump having working parts of 430 stainless steel in combination with a double in-line valve assembly also of 430 stainless steel and having a Stellite No. 1 coating on the valve heads and seats was submerged in a holding pot of the molten alloy as shown in FIGURE 1. The pump had a U-shaped inlet tube the opening of which was about half-way up the melt in the pot. The valve assembly was positioned so that the valves were vertical. The pump was run continuously andthe valve assembly activated on a controlled time 'cycle by means of an interval timer following the procedure described hereinbefore. In cyclic operation, accurately measured amounts of the magnesium alloy were delivered to the diecasting machine shot well.

In operating the apparatus described hereinbefore, the metal delivery tube remains substantially full of molten metal at all times. Whenever valve 35 in the one depicted embodiment or valve 24 in the other embodimentis open as the pump operates there is positive. pressure exerted on Following delivery of a predetermined amount of metal to the shot well, the valve is closed, preferably prior to shutting off the pump for those runs where the pump'is stopped between runs, thereby holding the metal in the tube during the non-pumpingportion of a cycle. Actually, in operation using intermittent pumping ordinarily positive pressure isexerted on the molten metal by the pump before the valve is opened and this pressure is maintained until after the valveis closed.

Also, each. cycle may be started manually when a die casting machine is cleared and ready for another metal shot or it may be started automatically with suitable safeguards to prevent premature, late or double metal discharge. 7

Various modifications can'be made in'the present invention without departing from the spirit or scope thereof for it is understood that we limit ourselves only as defined in theappended claims.

We claim: I

1. A metering and pumping apparatusfor-transferring predetermined quantities of a molten metal which comprises in combination a centrifugal pump, a double in-line valve assembly, a first and second conduit joining said pump and said valve assembly, an outlet tube attached to said valve assembly, and an activating means for opening duit attached to the valvebody between the-double valves :ofsaid valve assembly and establishingcommunication between said pump and said valve assembly, said second conduit connected to the inlet tube of said pump andto thevalve body near theend of said valve bodylopposite that containing said outlet tubeuiand on the side of the valve seat opposite that adjacentthe connection of said first conduit and said valvebodythereby establishing communication between said pump inlet and said valve assembly.

2. The metering and pumping apparatus as defined in claim 1 wherein the apparatus is fabricated from a chrome steel.

3. The metering and pumping apparatus as defined in claim 1 wherein the outlet tube discharges into the shot well of a die casting machine.

4. The metering and pumping apparatus as defined in claim 1 wherein the outlet tube is connected to the shot well of a die casting machine.

References Cited by the Examiner UNITED STATES PATENTS 4/49 Pippin 22-79 5/56 Burkett 22-79 FOREIGN PATENTS 585,947 10/59 Canada.

Claims (1)

1. A METERING AND PUMPING APPARATUS FOR TRANSFERRING PREDETERMINED QUANTITIES OF A MOLTEN METAL WHICH COMPRISES IN COMBINATION A CENTRIFUGAL PUMP, A DOUBLE IN-LINE VALVE ASSEMBLY, A FIRST AND SECOND CONDUIT JOINING SAID PUMP AND SAID VALVE ASSEMBLY, AN OUTLET TUBE ATTACHED TO SAID VALVE ASSEMBLY, AND AN ACTIVATING MEANS FOR OPENING AND CLOSING SAID VALVE ASSEMBLY IN A PREDETERMINED CONTROLLED TIME CYCLE, ONE END OF SAID FIRST CONDUIT ATTACHED TO THE PUMP CHAMBER AND THE OTHER END OF SAID FIRST CONDUIT ATTACHED TO THE VALVE BODY BETWEEN THE DOUBLE VALVES OF SAID VALVE ASSEMBLY AND ESTABLISHING COMMUNICATION BETWEEN SAID PUMP AND SAID VALVE ASSEMBLY, SAID SECOND CONDUIT CONNECTED TO THE INLET TUBE OF SAID PUMP AND TO THE VALVE BODY NEAR THE END OF SAID VALVE BODY OPPOSITE THAT CONTAINING SAID OUTLET TUBE AND ON THE SIDE OF THE

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