US3248759A - Apparatus for delivery of predetermined amounts of molten metals to a die casting machine - Google Patents

Description

F. L. BURKETT May 3, 1966 3,248,759 F MOLTEN APPARATUS FOR DELIVERY OF PREDETERMINED AMOUNTS O METALS TO A DIE CASTING MACHINE Filed March 28, 1965 2 Sheets-Sheet l INVENTOR. F ranc/s L. Burke/2 HTTOQNEYS y 3, 1966 L. BURKETT 3,248,759

APPARATUS FOR D V 0F PREDETERMINED AMOUNTS 0F, MOLTEN MET S TO A DIE CASTING MACHINE Filed March 28, 1965 2 Sheets-Sheet 2 I I [A 54 46 I 40 46 I ?;0

INVENTOR. Franc/Is L. fiur/ns WJMA HTTOR/VEYS United States Patent Office APPARATUS FOR DELIVERY OF PREDETER. MINED AMOUNTS F MOLTEN METALS TO A DIE CASTING MACHINE Francis L. Burkett, Breckenridge, Mich., assignor to The Dow Chemical Company, Midland, Micl1., a corporation of Delaware Filed Mar. 28, 1963, Ser. No. 268,632 1 Claim. (Cl. 22-79) This invention relates to the handling of molten metal and particularly concerns an apparatus for the delivery of successive predetermined amounts of a molten metal to a utilization device.

A great number of apparatuses have been disclosed concerning the delivery of measured amounts of molten metal to a die casting machine. In general, each of these devices comprise one or more separate but connected components, such as, for example, a valve assembly and a rotory pump, one of the so-connected components in turn being attached to a heated delivery pipe. In addition, these devices are relatively complex, having usually a number of moving parts, many of which require close tolerance dimensions for proper operation.

Because of these factors, malfunctions and breakdowns arefrequent, thus requiring a high level of maintenance and experienced operating personnel. Also, a complex apparatus consisting of several separate assembles but connected to one another by various conduits is understandably more difiicult to install and to remove from the supply pot of molten metal in which it is partially or wholly submerged should the apparatus need repair or replacement.

An object of the present invention, therefore, is to provide a simple and economical apparatus for the delivery of a succession of predetermined substantially equal amounts of molten metal to, for example, the shot well of a die casting machine.

Another object of the present invention is to provide an apparatus for the delivery of a succession of substantially equal amounts of molten metal, having a compact integrated pump-valve unit which is readily removable from the molten metal supply pot in which said unit is submerged.

A related object is to provide such a unit having a minimum of parts each of which are readily replaceable.

A further object is to provide an apparatus for the delivery of molten metal which will require little main- 7 tenance. I

Yet another object is to provide an apparatus for the delivery of molten metal which during operation will not cause turbulence in the pot containing the supply of the molten in which the apparatus is partially submerged.

These and other. objects and advantages will become apparent from the following detailed description when read in conjunction with the accompanying drawings which depict one embodiment of the invention wherein:

FIGURE 1 is a side elevational view, partly in section, of an apparatus in accordance with the present invention.

FIGURE 2- is an enlarged view in side elevation, partly cutaway andlargely in section, of the integrated pumpvalve unit of the apparatus of FIG. 1 taken along the line 2--2 of FIG. 3.

FIGURE 3 is a view of the integrated pump-valve delivery unit of the apparatus of the present invention taken along the line 3-3 of FIG. 2.

FIGURE 4 is a cross-sectional view of the control rod and valve stem of the integrated pump-valve unit of the apparatus of the present invention taken along the line 44 of FIG. 2.

Eatented May 3, 1966 FIGURE 5 is a detailed side elevational view showing a modification of the connection of the lip of the pot with the apparatus of the invention from that shown in FIG. 1.

The apparatus of the present invention is used in conjunction with a melting or supply pot containing the molten metal intended to be handled, the apparatus being partially submerged therein. The pot is equipped with a suitable means to maintain the metal therein in a molten state by the application of heat, and is either open -or closed at'the top as desired.

In general, the apparatus comprises, (a) an integrated pump-valve unit comprising a valve assembly portion and centrifugal pump portion, (b) one or more support members which provide a means to suspend said unit in a supply of molten metal, (c) powering means such as, for example, an air motor for said pump portion ((1) motion means, such as, for example, a reciprocating device for actuating said valve assembly portion and, (e) a delivery pipe to which the unit is attached at the valve assembly.

The pump portion of the above-integrated unit comprises in general, (a) a rotatable impeller as the core element surrounded by a'pump casing which in addition houses the valve assembly, said casing having both an inlet and outlet means to receive and dispense molten metal when the unit is in operation.

The valve assembly portion of the integrated unit, housed by the pump casing, comprises in general, a stationary but replaceable circular valve seat, and a movable conical or round headed valve member capable of engaging the valve seat to form therewith a substantially tight seal, the movable member being connected to the above motion means for actuating said movable valve member in conjunction with the operation of the pump and with the receptacle of a utilization device for receiving the delivered molten metal such as, for example, to the shot Well of a die casting machine.

Referring now to FIGS. 1 and 2, one embodiment of the apparatus of the present invention is shown therein, the integral pump-valve unit 10 of the apparatus being suspended in a supply pot 12 containing molten metal 14 by vertical supports 16 which are attached to horizontal cross members 18, the cross members being in turn attached to the lip 20 of the pot 12 by bolting. Alternatively, said cross members may also be attached to the lip of the pot by freely removable locators 19 as shown in FIG. 5. As depicted the pump portion of the submersible integrated unit 10 comprises an impeller 22 attached to the lower end of a vertical drive shaft 24 which extends upward through the said casing, described below, and out of the pot 12, said shaft having a longitudinal axis corresponding to that of the pump casing, and is attached at its upper end to a powering means, such as, for example, an air motor 26, which is detachably mounted on the aforementioned cross members 18. In addition, surrounding said impeller 22 is a two-piece pump casing comprising a top portion 28 and a bottom portion 30 held together by threaded bolts 32 from the upper side 34 of the unit 10 which are received by tapped threaded bores 36 in the bottom portion 30 of the assembled casing to allow the two said portions to be drawn together and sealed tightly at their mating edges 38. Other conventional fastening means, however, may also be used to hold the said pump casing portions together. A bushing 40 designed to preferentially wear with respect to the drive shaft provides a seal between said drive shaft 24 and the top portion 28 of the pump casing through which said shaft extends.

Attached to the underside 42 of the assembled casing is an extended inlet, having a continuous Wall 60 to form an inlet part or opening 44, for receiving molten metal,

located such that the vertical (longitudinal) axis of the circular shaped inlet opening 44 of the inlet extension ultimately formed by said wall 60, as hereinafter described, corresponds to that of the impeller drive shaft 24. This specified correspondence of the axis of the inlet opening 44 and shaft with that of the valve stem 52, described below, provides a liquid metal inlet 44 designed to avoid turbulence outside the pump casing which could cause undesirable entrainment of sediment from the pot bottom.

In addition, the above described pump casing houses the aforementioned valve assembly which comprises a circular valve seat 46, having a beveled edge 48, said seat being located in the hereinafter described hemielliptical shaped part of the top portion 28 of the pump casing and resting on shoulders provided therein, being held therein by a close tolerance friction fit, and a movable valve member consisting of a valve head 50 and a detachable stem 52, the head being adapted to mate with and engage the valve seat 46 to form therewith a tight seal without a sticking or wedging effect. The stem 52 of the movable valve member, as shown in FIGS. 2 and 4, is attached to an essentially vertically actuating control rod 54 by a spacer block 56, for example, by welding, such that when the control rod is actuated the valve head 50 and stem 52 move accordingly.

The movable valve member when inside the housing provided by both the assembled pump casing and the continuous wall 60 of the extended inlet is held away from said casing and wall and positioned, in conjunction with the control rod 54 and the aforementioned motion means, for example, an air operated reciprocating piston device 74, for proper engagement with the valve seat 46, by two (or more) spacer elements 58. These spacer elements 58 are attached to the curved part of the wall 60 of the hemielliptical portion, hereinafter described, of the inlet extension and located between said wall and the valve stem 52, the longitudinal axis of said spacer elements, if extended, passing through and intersecting at an acute angle at the longitudinal axis of said stem 52 whereby the movable valve member slides on said elements and is held in proper alignment with said spacer elements 58 and the control rod 54 attached to the aforementioned motion means.

In general, the shape of assembled pump casing and inlet extension need only be of a configuration sufficient to enclose the pump impeller 22 and valve assembly and to provide an adequate inlet opening or part 44, as will be more fully described below, to receive molten metal.

A convenient shape to accomplish the above is shown in FIGS. 2 and 3. Specifically as illustrated in FIG. 2 the shape of the pump casing, commencing at the upper or top side 34 thereof, generally is of a hemispherical shape on one side of its minor axis and of a hemielliptical shape on the other side thereof. Looking at the whole on various successively lower planes (FIG. 2) the side wall of the hemispherically shaped portion continues uniformly downward ending and the underside or bottom 42 of the assembled casing, whereas, the side wall of the hemielliptical portion continues downward toward the vertical (longitudinal) axis of the assembled pump casing and ending also at the underside 42 of the assembled thereof.

The shape of the extending inlet commencing at the underside 42 of the assembled pump casing and normally stepped in from the edge thereof is also a hemielliptical and hemispherical shape, the wall of the hemiclearance between the inlet side wall 60 and the valve stem 52, which extends therewith, to permit an adequate supply of molten metal to enter said extended inlet.

The hemielliptical shaped portion of both the pump casing and extended inlet side wall 60 serves not only, in conjunction with the hemispherical portion, to partially house the impeller 22, but also serves to house the aforementioned valve seat 46, valve head 50, and stem 52 thereof, said seat, head, and stem being aligned on a common longitudinal axis which is inclined at an acute angle with respect to the longitudinal axis of the pump casing. It should be noted here that the inclined longitudinal axis of the seat, head, and stem crosses the longitudinal axis of said pump casing at or near the inlet opening 44 and that the valve stem 52 extends out of said inlet opening with sufficient length to allow coupling, through a spacer 56, to the control rod 54, and with sufficient clearance with the inlet side wall 60 to allow operation of the valve assembly and influx of molten metal.

To the above described integrated pump and valve unit is connected a delivery pipe 62 equipped with a heating means, for example, electric coils 64, to maintain said molten metal in the pipe in that state. The lower end of the pipe 62 is attached to the upper side 34 of the integrated unit 10 and surrounds an outlet bore 66 leading from the valve seat 46 located in the hemielliptical shaped portion of the pump casing. The discharge end 68 of said pipe 62 is constructed and positioned such to direct the flow of molten metal, when the apparatus is operated, to the intended molten metal utilization device, such as, for example, the aforementioned die casting machine 76 and shot well 78 thereof.

It is to be noted that both the delivery pipe 62 and the aforementioned control rod 54 are to be positioned such that they do not obstruct with one another. Preferably, the delivery pipe 62 is equipped with a slip joint 70 located near the integrated pump-unit 10 so that should it become necessary to withdraw the integrated unit 10 entirely from the supply pot either for replacement or repairs, the pipe is easily disconnected therefrom leaving only a short portion of said pipe attached to the unit 10.

In general, the design of said slip joint 70 connection, as is most clearly illustrated in FIG. 2, comprises two circular rings, each attached to the adjoining delivery pipe Wall and each having a conical mating surface capable of engaging the other, said surfaces each having a low angle of engagement, for example, from 5 to 6 degrees, to cause a slight seizing action when mated. The rings are constructed of materials possessing higher strength than that of their adjoining delivery pipe walls so that said rings will retain their shape even at the elevated temperatures normally employed or required in operation of the apparatus in the molten metal intended to be handled. By so-constructing the rings any deformation due to elevated temperature will occur in the adjoining wall rather than in said rings thereby making it possible to keep a tight fit at the slip joint regardless of how many times said slip joint is disconnected and connected. A suitable material from which to construct said rings is the high temperature steel commonly referred to as Stellite, which is defined hereinafter.

The discharge end 68 of the delivery pipe 62 is preferably equipped with a hinged upwardly swinging hood or shroud 69 in which is maintained an atmosphere of non-oxidizing gas, such as, for example, sulphur dioxide, or argon, in order to prevent burning of the material and formation of an oxide skin on the pipe walls. Said shroud cover 69 at the discharge end of the pipe is constructed so as to freely swing clear of said pipe, as shown by the dotted lines in FIG. 1, of the end of the discharge pipe to permit cleaning when required and insertion of rods into the delivery pipe, if necessary, to unplug it.

Conventional air or electric motors may be employed as powering means for operating the impeller 22. For convenience and ease in removing said powering means from the balance of the apparatus, the armature thereof can be, for example, quick-detachably coupled to the drive shaft 24.

The motion means for actuating the control rod 54 and valve head 50 may be any conventional or other means whereby said rod and head may be sufficiently moved to open and close the valve assembly to either allow or restrict the flow of molten metal therethrough. Such means may be, for example, a reciprocating air pressure operated device 74 to essentially vertically move the control rod 54, head 50, and stem 52 up or down longitudinally with respect to the longitudinal axis of the valve. seat 46. Regardless of the actuating means employed a quick disconnecting means (not shown) between it and the control rod 54 is also preferably used for convenience in removal of the device 74 for repair or replacement, or for removal of the control rod 54 from said device 74 for similar purposes.

Preferably the motion means is coordinated either by air, electric, or other timing means 86, with, for example, the operation of the die casting machine 76, such that a programmed time sequence is established whereby a rapid succession of predetermined amounts of molten metal can be dispersed to the shot well 78 of a die casting machine 76 or to some other molten metal utilization device.

In operating the embodiment of the apparatus of the present invention depicted in FIGS. 1 and 2 with a molten metal utilization device such as, for example, a die casting machine, the integral pump-valve unit with the delivery pipe 62 attached is submerged, after preheating, into the pot 12 containing the molten metal 14 to be handled such that the entire integrated unit is below the level thereof but such that the inlet opening 44 is located so that the supply of molten metal is taken essentially from the center of the pot rather than, for example, from the bottom. By so locatingthe inlet, inclusion or entrainment in the cast article of settled residues is essentially avoided. The impeller 22 is then continuously operated, at a rate of rotation so as to avoid excessive surging or splashing when the valve assembly is opened, and the valve head 50 disengaged from the valve seat 46 (to the position shown by dotted lines) to allow molten metal to flow into the hot delivery pipe 62 at least in an amount enough to fill said pipe to the discharge level 80. When the desired level in the delivery pipe is obtained the valve head 50 and seat 46 are engaged to stop the flow of metal and maintain a proper head thereof in the delivery pipe. The die casting machine 76 and shot well 78 thereof being ready to receive the initial shot of metal, the valve is again disengaged from the seat and molten metal allowed to enter the delivery tube in an amount previously determined by proper timing and actuation of the valve control rod 54. The rate of rotation of the impeller 22 is adjusted so as to avoid too great a rate of molten metal flow resulting in splashing when discharged into the shot well 78. When said amount has entered the delivery pipe and has displaced a like amount from the pipe into the shot well of the die casting machine, the piston 82 of said shot well, by means not shown, is then rapidly actuated to force the dispensed amount of molten metal into the mold cavity of the die casting machine 76. After solidification of the dispersed amount of molten metal, the mold is opened and the cast piece ejected, followed by closing the mold, and operating the valve head again to dispense still another shot into the shot well to produceanother cast article. The sequence is repeated in rapid succession by coordinating the whole operation to produce the desired number of cast pieces.

Inasmuch as the integral pump-valve unit of the apparatus of the present invention has comparatively few moving close tolerance parts, necessary maintenance will be 6 very low. With respect to the valve head 50, it is preferably designed and constructed so as to preferentially wear rather than the beveled edge 48 of the valve seat 46. This is done because the head can be more easily removed as compared to the seat by simply disconnecting the valve control rod 54 from the motion means and lowering said rod with the movable valve member attached until the head of said member is removed completely from its housing. The worn valve head is then replaced and inserted by reverse procedure back into its housing. If, however, the complete integral pump-valve unit must be withdrawn from the pot, this is accomplished by merely disconnecting the powering means and the motion means from the cross members 18, removing the delivery pipe 62 from the unit by disengaging the slip joint 70, and withdrawing the entire integrated unit out of the pot. Substantially all of the molten metal in the pump will automatically drain out through the inlet opening 44 at the bottom of the pump. Any repairs can then be effected, and the so-repaired unit preheated, resubmerged, and reconnected for operation, or, if a whole new unit is needed, it too can easily be resubmerged and connected for operation. Time consuming changeovers and repair procedures are thereby eliminated and the operation continued without a costly shut down of the whole operation. To facilitate rapid removal of the integral unit from the pot for repairs or replacement, rapid disconnecting means such as described above should be provided between the drive shaft 24 and powering means and between the motion means and control rod 54.

For ease in accomplishing temperature determinations in the integral pump-valve unit of the present invention,

' one of the vertical support members 16 may be built with a hollow core so that the wire of a thermocouple 84, for example, or other sensory leads may be inserted therein and connected to the said integral unit 10 to record certain data.

The materials of construction to be employed in the integral pump-valve unit, control rod, delivery pipe, and vertical supports are those which will be durable in the presence of the molten metal intended to be handled and which are resistant to erosion and corrosion. When employing molten magnesium for instance, mild steel or preferably the high temperature chrome steels such as, for example, 430 stainless are satisfactory for all surfaces which are to be exposed to the molten magnesium. With respect to the valve head 50 and valve seat 46, or any other member of the apparatus which is to be subjected to precision contact and wear at elevated temperatures; the mating surfaces of either or both can be provided with a Stellite coating for resistance to deformation and abrasion upon impact when engaging said valve and seat, or, in

the case of said other members, can be constructed com-. pletely of Stellite.

With respect to the impeller shaft 24 and valve stem 54 which are subjected to considerable stress at elevated temperature; these parts may also be constructed of tool steel of the conventional 18.4.1 composition (about 18 percent tungsten, about 4 percent chromium, and about 1 percent vanadium, the balance being essentially iron) which provides good strength characteristics at the required operating conditions.

It should be understood that various changes and modification can be made in the apparatus of the present invention without departing from the substance and scope thereof, and it is further understood that the present invention is not limited to the embodiment thereof as shown in the appended drawings.

I claim: An apparatus for the delivery of molten metal to a v utilization device which comprises (1) a submersible incasing, said casing having an inlet and outlet means therein, said inlet means having a longitudinal axis aligned with that of the pump casing, comprising a walled extension attached to the bottom of said pump casing and stepped in from the side walls thereof, said extension having a hemispherical shape on one side of its minor transverse axis and a hemielliptical shape on the other side thereof, the wall of the hemielliptical portion extending downwardly such that the major transverse axis of said inlet means continually reduces itself on the hemielliptical portion thereof until equal to the minor transverse axis to form, with the downwardly extending vertical wall of the hemispherical portion, a circular shaped inlet port such that the axis of the movable valve member of the valve assembly, which is disposed Within the pump casing, is at an acute angle with respect to the longitudinal axis of said pump casing and crosses said longitudinal axis of said casing at the inlet part, said valve assembly portion (b) disposed within the pump casing, including a valve seat, a movable valve member, and a control rod,

References Cited by the Examiner UNITED STATES PATENTS 2,625,720 1/1953 ROSS 2270 X 2,745,153 5/1956 Burkett 2279 3,074,128 1/1963 Brokel 2270 X 3,184,811

5/1965 Bennett et al. 2270 FOREIGN PATENTS 808,444 2/ 1959 Great Britain.

J. SPENCER OVERHOLSER, Primary Examiner.

said valve member being attached to said control rod; (2) 20 R. S. ANNEAR, Examiner.

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