US3184812A - Metering and delivery apparatus for molten metal and method of use - Google Patents

Description

y 25, 1955 F. c. BENNETT ETAL 3,184,812

-- METERING AND DELIVERY APPARATUS FOR MOLTEN v METAL AND METHOD OF USE Filed Feb. 14, 1962 2 Sheets-Sheet 1 f0 Vacuum and pressure a/ve 2 source Con/ro/ 7 INVENTORS. Pas/er C. flannel) Frank 6. Robbins Ray 5. War/700k 1 v To ac/iva/mg 1 M means c. #6277 y 25, 1965 F. c. BENNETT EI'AL 3,184,812

METERING AND DELIVERY APPARATUS FOR MOLTEN METAL AND METHOD OF USE Filed Feb. 14, 1962 2 Sheets-Sheet 2 I I! INVENTORS.

/ F'aa/er C. Bennef/ 25 r Frank E. Robb/n6 Ray 6. War/700k United States Patent 3,184,812 METERING AND DELIVERY AFPARATUS FUR MOIJTEN METAL AND METHQD GE USE Foster C. Bennett, Frank E. Robbins, and Ray 1E. Warnoclr,

Midland, Mich assignors to The Dow Chemicai (1on1- pany, Midland, Mich, a corporation of Eelaware Filed Feb. 14, I962, Ser. No. 173,273 3 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 amounts of molten metal to a die casting machine and a method of use therefor.

It is a principal object of the present invention to provide a simple, reliable unit to meter and deliver predetermined volumes of a molten metal.

It is another object of the present invention to provide a metering pump 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 a pump and valve assembly for moving and delivering controlled volumes of molten magnesium, aluminum or their alloys employing simple mechanical means instead of the devices conventionally used for moving such metals.

It is an additional object of the present invention to provide an inexpensive metering pump unit for moving molten metals which simply and readily can be dismantled for cleaning or checking.

It is another object of the present invention to provide an apparatus and method for transferring molten metal wherein time delays between the start of pump activation and actual metal delivery are reduced to a minimum.

It is also an object of the present invention to provide a molten metal metering apparatus which is submersible in a pot of molten magnesium die casting alloy and which reliably transfers reproducible charges of the alloy from the pot 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 line is substantially filled with molten metal at all times.

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

The present invention comprises in combination a pump connected to a double valve assembly which units operate in a cooperative manner to transfer predetermined amounts of a molten metal particularly from a holding pot into the shot well of a die casting machine.

In general, the pump and double, valve assembly are connected through a tube, hollow passageway or other hollow member extending from between the valves of the valve assembly to the pump and establishing communication between these units. The valve assembly itself is positioned so that one of the valves contacts directly the molten metal to be moved and the other valve communicates with an outlet delivery tube for the molten metal.

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

' In the drawings:

FIGURE 1 is a sectional elevation showing one embodiment of a molten metal metering pump and a valve assembly of the instant invention positioned in a pot of molten metal.

FIGURE 2 is a schematic'sectionalview of the piston pump and double valve of the metering pump and valve assembly shown in FIGURE 1.

FIGURE 3 is a detailed sectional elevation of the piston pump of FIGURE 1.

FIGURE 4 is an elevation of the cylinder of the piston pump of FIGURE 1.

FIGURE 5 is a detailed sectional elevation of the double valve assembly shown in FIGURE 1.

FIGURE 6 is a fragmentary elevation of the valve depicted in FIGURE 5 showing a section embodiment of the valve and valve seat.

FIGURE 7 is a schematic sectional view showing a second embodiment of a metal supply means in combination with the double valve assembly of the present in vention.

The molten metal metering pump and valve assembly shown in FIGURE 1 comprises in combination a piston pump 10 connected by a conduit 11 to a double valve assembly 12. The double valve assembly 12 has an outlet tube 13 for transporting molten metal, as for example to the shot well 14 of a die casting machine (not shown).

The pump 10 and valve assembly 12 are supported independently within a pot of molten metal 15 by means of supports 16 and 17 respectively. The pump it! and valve assembly 12 each are operated through separate yokes 18 and 19 connecting these to air-driven reciprocating pistoncylinder activating devices 20 and 21. These activating devices readily are operated in a controlled, integrated time cycle through synchronized conventional interval timing devices (not shown).

The piston pump 10 has a hollow, cylindrical outer shell 22 having one open end 23 and one closed end 24. Con duit ii is attached to a port 25 in the side wall of cylinder 22 near the closed end 24 and provides a direct connection into the interior of the hollow shell 22. Alternatively, port 25 can be located in the closed end 24 of cylinder 22. Two slotted openings 26, one each on opposite sides of the cylinder 22, extend upward some distance from the open end 23 of the cylinder 22. Supports 16 also are welded to the outside of cylinder 22 and extend upward therefrom.

The piston 27 slides freely within hollow cylinder 22. A piston pin 28, having threads 29, passess along a diameter through piston 27 near its bottom 30. One spacer bushing 31 is positioned on pin 28 on each side of the outside wall 32 of the piston 27 and adjacent this wall. The bushings 31 are of such a diameter that they freely slide within slots 26 in the cylinder 22 and ordinarily are somewhat thicker than the cylinder wall. A second set of spacer bushings 33 is placed onto pin 28 one each adjacent bushings 31. Upright side arms 34 of yoke 18 are fitted, one each over bushings 33 by means of perforations 35 near one end. These arms 34 are held in place by nuts 36 mating with threads 29 of the pin 28. A yoke rod 37 having threads 38 on both ends passes through openings 39 in side arms 34 near the end opposite that attached to the piston 28.

Locking nuts 4% secure these arms 34 in a predetermined position whereby they maintain the piston outer wall 32 parallel to the inner wall 41 of pump cylinder 22. A rod 42 welded to the yoke rod 37 midway between the side arms 34 extends upward and is connected to the reciprocating air driven piston-cylinder apparatus (not shown) which in turn is connected to a timer. Alternatively, for example, the pump piston can be connected to the reciprocating drive by means of a U-bolt having one arm rigidly connected to the drive and the other arm connected by a flexible coupling to the inner face of the piston head. Other means for joining the piston and drive as known to one skilled in the art also can be enough to avoid seizureof these parts as metal viscosity changes with temperature fluctuations but also must be I small enough to avoid excessive blow-by of molten metal. Ordinarily this clearance will range from about 0.02 inch to about 0.10 inch on the diameter. In actual operation with magnesiumbase die casting alloys, a clearance of about 0.035 inch has been found to be very satisfactory with a 6 inch diameter piston. I

The length of the piston stroke is not critical and can be varied within the limit of the eflective cylinder volume to provide a molten metal shot of a predetermined quantity, the quantity being varied for casting parts of different sizes.

- The valve assembly 12 consists of a hollow cylindrical valve body 43 and a double in line valve 44; The valve body 43 has a valve seat 45 at one end and a second valve seat 46 near the other end. On one side of valve body 43. a port 47'is provided to which is connected conduit 11. seat 46 is a port 48 into which is fitted outlet tube 13.

The location of port 47 is not critical except that it be between the valve seats 45 and 46. Conveniently, this port 47 will be located in such a position that when the pump 10 and valve assembly 12 are connected by.

conduit 11 the entire unit can be submerged in the pot of molten metal 15. This assures uniform temperature control of the pump-valve system without having to resort to external heating means.

The double valve 44 consists of a valve stem 49 having threaded end sections tl-51' of reduced cross-sectional diameter. A valve head '52 having a center through passage 53 of a diameter to be readily accommodated by threaded end 5%) of stem 49 is placed onto thisstem 49" until its base 54 abuts shoulder 55 of stem 49. The valve head 52 is held in place by nut 56. I

n Threaded end 51'of valve stem 49 is inserted through valve seat45 and upwards through valve seat 46. Valve head 57 is positioned onto the threaded stern section 51 so that its base 58 abuts with shoulder 5 of stem 49. Valve head57 is .held in place by nut dtl. The length of the valve stem 49. between shoulders 55 and 59 is such that when one valve is closed there is ready metal flow.

through the second valve. In the depicted embodiment, the valve heads 52 and 57 are shown to be frustums and are bolted to the valve stem. However, these can be of diverse shapes, e.g. the valve head can be round-bottomed .61, and can be welded, press fitted or otherwise fastened to the valve stem 49.

The valve body 43 is capped with top 62 to form a single unit. The cap 62 is welded to the valve body 43 in the instant. embodiment. Alternatively it can be attached by other means as is known to one skilled in theart such as mating threads, bolts and nuts, clamps, press fitting and the like means to provide a relatively pressure tightcase.

On the valve body 43 and above valve,

The threaded valve stem end is screwed into nut 63 'atfixed to the bottom cross rod 64 of yoke 19. This yoke 19 is attached by means of a rod 65 welded to the upper yoke cross rod '66 to a reciprocating air driven piston-cylinder device (not shown) operating on a predetermined time cycle. I r a The angle of taper of the valve heads 52 and 57and seat curvature of valve seats 45 and% shouldbe great enough toavoid wedging of these members upon impact. Preferably thisangle, as measured from the longi udinal axis of the valve stem to the tapered surface at a minimum is about 15. For those valves wherein the valve head angular relationship holds true.

increase the amount of activating mechanisms needed as well as require increasingly complex control systems. In any event, thevalves must be arranged so that they both cannot be closed at the same time.

Preferably the valve is activated by positive mechanical means rather. than by gravity orspring motion; This is desirable for two reasons; (1) in operation the time cycle relationship between the pump piston movement and valve operationsmust be closely controlled and (2) ordinary spring-activated check valves. do notgive positive shutoff with molten metals which oxidize as readily as magnesium and aluminum. Conveniently, as indicated hereinbefore, both the valve assembly and pump can be activated by an automatic timer thereby assuring precise control of the apparatus and. automatic deliveryof reproducibly constant predetermined amounts of metal to the shot well. Ordinarily the pump and valveassembly are connected and positioned in a melt pot so thatthe open end of the pump faces the bottom of the pot and thevalvesare.

vertical. Positioning the unit in this manner aids to .prevent seizure of the moving parts during operation. Also, the metal isdrawn into the unit from Well below the surface of the molten the downward strokeof the piston pump thereby keeping turbulence on the melt surface at.

bly is not critical or limiting butprefer-ably is such that.

the top of the valve-is at about the same-height as the pump cylinder top thereby facilitating -maint aining the.

assembly below the metal surface in a shallow pot. ,Also,

preferably the. assembly should be raised otf the bottom:

of the melting pot far enough to avoid setting up (1) turbulence in any sludge which may be present along the bottom and (2) hammering of the potby thepiston or valve yoke.

As shown, the pump piston and valve stem are activated byan air driven piston-cylinder device through a yoke and rod arrangement. It is apparent that thevalve and pump piston can be, operated by a wide variety of devices producing reasonably linear reciprocatingmotion. The depicted air driven device is onepreferred means since it is simple, easily and accurately controlled and safe to operate. Conveniently, the pump and valve assembly are operated through an interval timerwherein activation of the units is carried out automatically and inaccordance with a precise cont-rolled integrated schedule or program. Likewise, valves differing in construction and design from those described herein can be used asis apparent to one skilled in the art. V

I The size, of metal increment or shot delivered can be controlled v-eryaccuratelywith the instant embodiment of pump and valve assembly. Major changes, in metal 7 plish'ed by adjusting the length of stroke, of thepiston.

justing piston speed. i V H lThe materials of construction tobe employed for. the

The length of the valve body 43'rnust be sufficient to i accommodate both the'upward movement of the double in-linevalve 44 withinthe capped valve body 43 and port 4% above valve seat 46. r a

If desired, the double valve assembly can be fabricated stead of the depicted single stem arrangement: However, dissociating thevalves into separate-units would i utilizing separate independent valves and valve seats in- In the direct airedriven yoke arrangement as shown, this is done by adjusting the stroke of the piston in" the air cylinder. Delicate changes in volume are made byadjusting the. timing of the valve operation and/ or by adpump and valve'assembly are those that'h a ve the-requisite;

strength; stability of temperature and erosion and-corrosion resistance to stand up inthepresence. of'thelmolten metal being moved] With magnesium, i.e. magnesium. and magnesium based alloys containing. at least about pe-rcent by weight magnesium, chromejsteels suchas 430 stainless for example, are satisfactor-y for all surfaces-com. 'tacting moltenmctal. Molten'aluminum,;i.e..;alurninum and aluminum based alloys containing at least about 70 percent by Weight aluminum, readily can be moved by the instant apparatus fabricatedfrom steel having a refractory coating on those surfaces contacting molten metal as conventionally is practiced in the aluminum art. For moving aluminum, the .apparatus bearing surfaces are coated with or constructed from titanium diboride, zirconium diboride or other construction material inert to molten aluminum.

Either the valve head surface or valve seat surface of the valve members or both can be given a Stellite coating, e.g. Stellite No.1, to provide these with a high resistance to deformation upon impact.

The method for operating this embodiment of the apparatus is as follows. The unit is positioned in a pot of molten metal so that at least the open end of the valve assembly is below the melt surface. At the start of a given cycle, the bottom valve is opened and the top valve is closed, the piston being at the top of a stroke as shown schematically in FIGURE 2. The integrated timer-drive mechanism is activated to move the pump piston downward thereby drawing molten metal through the open valve and up through the connecting conduit until the pump cylinder is substantially filled with a predetermined quantity of metal as the piston reaches the bottom of its stroke. As metal is required in the shot well of a die casting machine the piston begins its upstroke thereby exerting pressure on the metal in the pump cylinder. The lower valve of the valve assembly is kept open by the timer until positive displacement of the piston occurs thereby assuring the maintenance of a head of metal in the outlet tube which may beabove the molten metal surface. As the initial upward displacement of the pump piston begins, the in-line valve is shifted, thereby closing the bottom valve, i.e. metal inlet port, and opening the upper valve, i.e. metal outlet port. The valve shiftis made as rapidly as possible, i.e. within one second or less while the pump piston moves at a comparatively slow rate, for example 2' inches/second. The .upward stroke of the piston forces metal through the open top valve and outlet tube into the shot well of the die chamber. When the required quantity of metal has been transferred and While the pump piston is still on its upward stroke, the top valve is closed thereby reopening the lower valve or inlet port. This controlled early shift of the valve positions maintains a metal head in the outlet port. If the upper valve were left open until the piston actually stopped at the top of its stroke, molten metal would escape from the annulus between the pump piston and cylinder. As the piston reaches the top of its stroke, it is propelled downward and the metal metering and transferring cycle repeated. Each cycle may be started manually when a die casting machine is cleared and ready for another shot, or it may be started automatically with suitable safeguards to prevent premature, late or double metal discharges.

In operating the apparatus herein described, the metal outlet delivery tube remains substantially full of molten metal at all times. When the valves are positioned so that valve head 57 is open with respect to valve seat 46, positive pressure is exerted by the pump on the metal in the delivery tube. By closing this valve prior to the time, the pump action is reversed following the transfer of a predetermined amount of metal into the shot well, the delivery tube remains substantially full of metal during the pump downstroke, i.e. intake portion of the cycle.

The utility of the instant metering and delivery unit was demonstrated in transferring molten ASTM designated AZ91B magnesium alloy (nominal composition 9 7 percent aluminum, 0.7 percent zinc, 0.15 percent manganese, balance magnesium) from a holding pot to the shot well of a die casting machine.

For this operation, a pump of the same design as described hereinbefroe was fabricated from 430 stainless steel. This pump had a 6 inch piston (outside diameter) and a clearance of about 0.035 inch between the piston and inner cylinder wall. It was connected to a double valve member by means of a short length of 1% inch inside diameter pipe. The valve assembly also was made from 430 stainless steel and the valve heads were given a Stellite No. 1 coating. The pump yoke was adjusted so that the piston delivered a 6 inch stroke and the valve stroke was adjusted to be about 2 inches.

This length of valve stroke provided an annular opening between the valve seat and valve stem about 1.5 times the cross-sectional area of the connecting pipe. A delivery pipe of somewhat larger area than the connecting conduit was atlixed to the valve for delivery of the metered amount of metal to the die casting machine shot well. The rod and yoke assemblies on both the pump and double valve each were actuated by an independent air-driven reciprocating piston-cylinder apparatus each controlled by a separate electrically operated interval timing mechanism. The pump and valve assembly both were submerged in the pot of molten all-0y. The pump was positioned so that the open end of the cylinder faced the bottom of the pot and the valves were vertical in the pot as shown in FIGURE 1. During continuous operation for a period of two Weeks, this unit reliably transferred reproducbile six pound quantities of the all-0y from the pot to the die casting machine shot'well. No seizing of the pump or valve members was encountered during operation. Also, the operation proceeded smoothly with substantially n-o turbulence noted in the molten metal in the pot.

Alternatively, if desired the piston pump metal delivery means can be replaced by a chamber immersed in the pot of molten alloy and connected to the double valve assemblyas shown in FIGURE 7. In this embodiment, the chamber 67 is a pump in that it is alternately evacuated and pressurized thereby alternately drawing metal through the intake valve of the valve assembly and pushing it through the upper valve of valve assembly 12 and outlet tube 13 and into the shot well of the diecasting machine. In operating this alternative embodiment the valve assembly 12 is positioned so that the bottom valve member is open and the upper valve is closed. The chamber 67 then is evacuated through pressure tube 68, valve 69 being open. This action urges metal through the open valve member of valve assembly 12 and into the chamber 67. The metal level rises in the chamber until it reaches contact 70 whereupon a signal is transmitted to the valve control 71. This signal activates the control 71 and closes valve 69. Conveniently, the contact 76 and valve control 71 are electronically operated although any of a number of pneumatically operated sensing and flow control devices as known to one skilled in the art can be employed. The valve assembly 12 simultaneously is shifted to open the upper valve member and close the lower of the two in-line valves. Valve 69 is reopened and a pressurized inert gas, e.g. argon, is forced through the valve 6% and pressure tube 68 thereby exerting a force on the molten metal in chamber 67 which in turn forces metal contained in the valve body 43 through the open member of the valve assembly 12 and outlet tube 13 and into the shot Well of the die casting machine. When the shot well is filled, the valve assembly 12 is shifted to reverse the position of the in-line valves. The valve 69 is closed and flow of pressurized gas to the chamber 67 stopped. The apparatus now is imposition for another cycle of operation.

As with the piston pump-valve assembly described hereinbefore, the chamber pump-valve assembly embodiment of the instant molten metal metering and delivery apparatus conveniently is operated automatically on an integrated time cycle.

The chamber 67 is fabricated from materials having the requisite strength, stability of temperature and erosion and corrosion resistance to stand up infthe presence of the molten metal and under the superatrnospheric and subatmospheric pressures employed during operation ofthe assembly.

Similarly designed metering and delivery apparatus having bearing surfaces coated with titanium diboride, or other construction materials inert to moltenaluminum can be used with aluminum and aluminum alloys.

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 the appended claims.

We claim:

1. A metering and pumping apparatus for transferring predetermined quantities of a molten metal which comprises in combinationa piston pump, double valve assembly, a conduit connecting said pump and said valve assembly, an outlet tube attached to said valve assembly and positive action driving means for said pump and valve assembly, said piston pump having a port, said double valve assembly having two valve heads mounted one above the other in line on a single valve stem and cooperating with separate valve seats mounted in a single valve body, one end of said valve body being open ended and the other end being capped, one end of said conduit being attached to said port. in said pump and the other to a port in the side wall of said valve body between the two valves, saidoutlet tube being attached to said valve body near its capped end and between the cap and the valve adjacent said cap, and said positive action driving I means activating said pump and valve assembly coopera- 2. A metering and pumping apparatus for transferring activated by positive mechanical activating means, a conduit connecting said pump and said valve assembly, an

outlet metal delivery tube attached to said valve assembly, said piston pump havingahollow, cylindrical outer shell having one open and one closed end and a piston freely slidable within the cylinder, a port inthe side wall' of said cylinder near the closed end of said cylinder, saiddouble valve assembly having two valve heads mounted on a single valve stem, a hollow val'vebodyhaving integral therein valve seats mating with said valve heads, one end of said valve body being open and-the other end of said valve body being capped, one end of said conduit being attached to a port in the side Wall of said' valve assembly between the two valves, and the other end beingattached tothe port in said=side wall of said cylinder of said pump, an outlet metal delivery tube attached to a second port in said valve body, said second port being between the cap of said valve body and the valve adjacent this cap, and, said positive mechanical activating means driving saidpump and valve assembly cooperatively in a predetermined time cycle.

3. The apparatus as defined in claim 2 wherein the piston of the pump and the valve stem of valve assembly are attached independently throughseparate yoke and rod assemblies --to reciprocating piston cylinder' drive mechanisms, said drive mechanisms being activated each through an integrated automatic'timeiz.

References fiited by: the Examiner- UNITED STATES PAT ENTS 334,483;v 1/86- Stevens 103-1 53 1,383,241 6/21 Roser 1031-153 FOREIGN PATENTS 585,947 10/59 Canada.

MICHAEL v. BRINDISI, Primary Examiner.

WILLIAM J. STEPHENSON, Examiner.

2/50- Smith'.... 103- 153

Claims (1)

1. A METERING AND PUMPING APPARATUS FOR TRANSFERRING PREDETERMINED QUANTITIES OF A MOLTEN METAL WHICH COMPRISES IN COMBINATION A PISTON PUMP, DOUBLE VALVE ASSEMBLY, A CONDUIT CONNECTING SAID PUMP AND SAID VALVE ASSEMBLY, AN OUTLET TUBE ATTACHED TO SAID VALVE ASSEMBLY AND POSITIVE ACTION DRIVING MEANS FOR SAID PUMP AND VALVE ASSEMBLY, SAID PISTON PUMP HAVING A PORT, SAID DOUBLE VALVE ASSEMBLY HAVING TWO VALVE HEADS MOUNTED ONE ABOVE THE OTHER IN LINE ON A SINGLE VALVE STEM AND COOPERATING WITH SEPARATE VALVE SEATS MOUNTED IN A SINGLE VALVE BODY, ONE END OF SAID VALVE BODY BEING OPEN ENDED AND THE OTHER END BEING CAPPED, ONE END OF SAID CONDUIT BEING ATTACHED TO SAID PORT IN SAID PUMP AND THE OTHER TO A PORT IN THE SIDE WALL OF SAID VALVE BODY BETWEEN THE TWO HALVES, SAID OUTLET TUBE BEING ATTACHED TO SAID VALVE BODY NEAR ITS CAPPED END AND BETWEEN THE CAP AND THE VALVE ADJACENT SAID CAP, AND SAID POSITIVE ACTION DRIVING MEANS ACTIVATING SAID PUMP AND VALVE ASSEMBLY COOPERATIVELY IN A PREDETERMINED TIME CYCLE THEREBY ASSURING THE DELIVERY OF MEASURED AMOUNTS OF MOLTEN METALS.

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