US3283372A

US3283372A - Vacuum die casting apparatus

Info

Publication number: US3283372A
Application number: US348060A
Authority: US
Inventors: John H Moorman; Jr Warren Y Dickert
Original assignee: Aluminum Company of America
Current assignee: Alcoa Corp
Priority date: 1964-02-28
Filing date: 1964-02-28
Publication date: 1966-11-08
Anticipated expiration: 1983-11-08

Description

INOV- 1966 J. H. MOORMAN ETAL 3,283,372

VACUUM DIE CASTING APPARATUS 2 Sheets-Sheet 1 Filed Feb. 28, 1964 JNVENTORS John H. Moorman y Warren M Dicker/1J7.

ATTORNEY Nov. 8, 1966 J. H. MOORMAN ETAL 3,

VACUUM DIE CASTING APPARATUS 2 Sheets-Sheet 2 Filed Feb. 28, 1964 INVENTORS Jbhn H. Noormafl 1; BY Warren H. DicKerZlJE ATTORNEY United States Patent This invention relates in general to casting equipment and its operation, and is more specifically concerned with die casting machines or apparatus for producing cast products from molten metal or equivalent readily flowable and castable materials, such as the commercially available plastics.

It is conventional practice to provide casting equipment incorporating a shot-receiving or cold chamber in advance of the die cavity from which flowable material therein to be cast is plunger-charged into the mold or die cavity of the equipment.

It is also common practice to apply vacuum of appreciably high intensity on the die cavity of such conventional die casting apparatus to draw a charge of flowable material into the cold or shot chamber remote to the application of vacuum thereon for subsequent plungercharging thereof into the die cavity or matrix of such equipment.

Such acknowledged and conventional equipment has given rise to many operating difficulties foremost among which have been the inability to provide tight seals between the cavitied mold sections forming the die matrix, which incidentally must be vented; the intensity or level of: vacuum required to draw a charge or shot of the flow able material from its supply reservoir into the cold chamber against the leakage of atmospheric pressure in direct communication from the vented die cavity to the cold chamber; and because of the further fact that each change in die structure can necessitate modification or complete substitution for the vacuum connection thereto.

The present invention is hereinafter described in terms of its adaptation to a conventional die casting machine having a cold or shot chamber which would normally be manually charged with flowable material to be cast and thereafter manipulated in conventional manner to advance a plunger axially through the cold chamber to charge the die cavity with the flowable material from the cold or shot chamber. In contrast to such conventional equipment, the invention is concerned with providing, in integrated unitary assembly, an accurate molten metal, or equivalent, metering system and automatic controls therefor which permit employing low intensity or level of vacuum for delivering predetermined charges or shots of castable materials to the cold chambers of casting equipment and to thereby substantially reduce or even eliminate the aforesaid dilficulties and inefficiencies associated with existing conventional casting apparatus.

It is therefore one of the objects of the invention to provide accurately regulated vacuum induced delivery mechanism for charging molten or liquid flowable material into the cold chamber of a die casting machine under conditions and location substantially isolated from the effects of atmospheric leakage into the cold chamber through vented or otherwise poorly sealed mold sections constituting the die cavity of the equipment.

Another object of the invention is to provide an integrated electrically energized and sequentially timed circuit for controlling the cycle of operation of a cold chamber die casting machine which removes the human error and premature freezing of the materials being cast normally associated with the operation of conventional cold chamber die casting equipment.

3,283,372 Patented Nov. 8, 1966 A still further object of the invention is to provide cold chamber die casting equipment, and automatic controls therefor, which lend themselves to a wide range of adjustment and regulation without regard to changes in volume in the die cavity thereof.

Other additional objects and advantages will be appreciated by those skilled in the art to which the invention appertains on consideration of the following description and appended drawings, in which:

FIG. 1 represents a side elevational View of an integrated die casting machine falling within and illustrative of the scope of the invention;

FIG. 2 represents a diagrammatic wiring diagram of electrical circuitry employed in cyclic control of automatic operation of the installation illustrated in FIG. 1;

FIG. 3 represents a fragmentary top plan view to enlarged scale and more detail of a portion of the injection cylinder or cold chamber of the mechanism of FIG. 1;

FIG. 4 represents a front elevational view of the illustration in FIG. 3;

FIG. 5 represents an end elevational view of the illustration of FIG. 4; and

FIG. 6 represents a fragmentary sectional elevation taken on the plane 6--6 of FIG. 3.

In general terms, improved mechanisms illustrative of the invention comprise modified conventional or newly constructed cold chamber, plunger-injection die casting or equivalent machines in which accurately timed and controlled low level vacuum raised molten metal, or similar flowable and castable materials, is delivered in predetermined metered quantities or shots to the cold chamber of such equipment in timed relationship to subsequent transfer and charging of the so-delivered shot or shots into a die cavity indirect communication with the cold chamber, operation of the aforesaid delivery and casting cycle being automatically controlled and executed by a single manually operated switch device.

Referring to the appended illustrations for a more detailed description of a successful commercial installation of the invention, 10 represents the stationary half or section of a mold detachably and rigidly secured to the fixed platen 12.0f a conventional cold chamber die casting machine. A second cooperating section or half 14 of the mold is detachably supported and carried by the rectilinearly translatable platen 16 of the machine, whereby the

mold halves

10 and 14 can be brought into abutting closed and separated open condition. At least one of the

mold sections

10 and 14 is cavitied, as at 18, to provide a die matrix or cavity in accordance with the exterior configuration and weight or volume of the article to be cast.

The translatable platen 16 supports a conventional fluid-operated ejector cylinder 20 the piston of which carries an ejector plate 22 provided with one or more ejector pins 24 extending forwardly therefrom through aligned apertures in the mold section 14, the purpose of which ejector mechanism is to forcibly free a finished casting from adherence within or contact with the translatable mold section 14 on completion of a casting operation.

The cold chamber or injection cylinder 26 of the machine is fixedly secured in respect to the stationary platen 12, communicates at its inner end with the mold cavity or matrix 18, and is open at its outer opposite end to receive an injection plunger or piston 28 slidably supported therewithin. The injection cylinder 26 is preferably horizontally disposed and a double acting fluid-operated cylinder 30. in axial alignment therewith, through the medium of its enclosed piston 32 and rigdly carried connecting rod 34, is employed to reciprocate the injection plunger 28 over the axial length of the cold chamber 26.

The cold chamber die casting machine thus far described is more or less conventional in its design and structure and machines of this general type are in regular commercial use with an opening or charging gate in the upper surface of the injection cylinder 26, in advance of the plunger 28, serving as the entrance for a molten or flowable liquid charge of material to be cast into the injection cylinder 26 prior to advancing the injection plunger 28 to fill the die 18 therewith.

The present invention departs from the above-described conventional die casting equipment by providing a new and novel vacuum metering system in integrated combination and assembly therewith.

The incorporated metering mechanism or system com- 7 prises a generally box-shaped housing or hopper 36 in registered assembly over the normally provided entrance or charging aperture in the upwardly directed surface or wall of the cold chamber or injection cylinder 26. In conversion of existing conventional cold chamber die casting machines, as hereinabove described, the hopper 36 isconfigurated on its underside surface to accurately match and conform to the exposed surface of the injection cylinder 26 immediately surrounding the opening therethrough and a gasket 38 of preferably elevated temperature resisting material is employed between the aforesaid matching surfaces before drawing the hopper into tight sealing unitary assembly on the exposed surface of the cold chamber or injection cylinder by means of a clamp bar 40 engaging the underside exposed surface of the injection cylinder 26 and secured by eye bolts 42 fixedly suspended from the hopper 36 and extending through the bar 40, where they receive strain washers and nuts 44 adjustable to exert the required seal-tight assembly clamping force.

The otherwise open top of the hopper 36 is also sealed I closed by a cover plate 46 and interposed gasket 48. a The cover plate 46 is secured in unitary assembly on the upper edge surface of the hopper 36 by means of four corner hook-shaped members 50 engaging the outer exlevel established by predeterminedsetting of the regulator posed surfaces of the plate 46 at their upper hooked ends and having their lower ends pivotally pin or bolt-connected in pairs to end bifurcated cross bars 52 below and transverse to the longitudinal axis of the injection cylinder or cold chamber 26. A centrally disposed adjustable bolt member 54, threaded through each of the cross bars 52 and provided on its normally unhcaded end with a cylindrically concaved pedestal washer 56, provides attainment of seal-tight clamping pressure between the comer hookshaped members 50,'cover plate 46, interposed gasket 48, andupper edge surface of the housing or hopper 36.

The cover plate 46 is drilled or otherwise, provided with an aperture to receive and secure therewithin a vacuum pipe or conduit 60 in direct communication with the interior of the hopper 36 and cold chamber 26 in direct communication therewith. A second aperture is also provided through the cover pate 46 to receive an angularly compound directed pipe or delivery conduit 62 which extends some distance below the underside of cover plate 46 in which flat plane the aforesaid vacuum line or conduit 60 had been terminated. The angularly directed conduit 62 is preferably connected through a union to one end of an inverted U curvilinearly bent length of conduit 64 extending downwardly below the exposed surface level of castable flowable material within a reservoir 66 of such material. In the case of molten metal, as distinguished from other flowable liquid materials responding'to die casting practice, such as many of the commercial plastics, the reservoir 66 would preferably be a crucible or similar molten metal holding device.

Any one of several commercially available vacuum sources has been successful in providing the required induced vacuum in the line or conduit 60. A typical vacuum source has been illustrated in FIG. 1 and comprises a vacuum pump 68 in direct circuit connection through a valve 70 and vacuum regulator 72 which responds under atmospheric pressure, controllably reduced by a pressure reducing valve 74, to a desired vacuum vacuum level developed andestablished by this system, as by leaks into the vented die cavity 18 and cold chamber temperature variations, are sensed and automatically corrected by providing the bypass conduits or

lines

78 and 80 which supply negative pressures to open or close a diaphragm incorporated within the vacuum valve 70 to return the vacuum level to equilibrium and the vacuum differential in the main vacuum line -82 to zero. The surge vessel 84 may be, and preferably is, included in the vacuum system, as well as a three-way spring-return 501$.

noid operated vacuum controlling valve 86 to be hereinafter described in more detail, and clean-out trap 88. A four-way spring-return solenoid operated valve 90 is also provided, and will be explained more fully hereinafter, for fluid-pressure actuation and control of the previously identified injection plunger actuating cylinder 30. 1

Automatic operation of the improved die casting mechanism of the invention is provided. through the integrated incorporation therewith of electrically energized and responsive accurately timed electric units and circuitry. On specific reference to FIGS. 1 and 2, it will be observed that the stationary frame and movable platen 16 of the die casting machine support a microswitch92 and cam contact 94, respectively, across the powersupply lines L and L In similar fashion, a microswitch 96 :is rigidly mounted on the forward or connecting rod end of the stationary cylinder 30, with'its cooperating contact 98 carried by the translatory connecting rod 34. The closed position of the

microswitches

92 and 96, as illustrated in FIG. 1, insures safe closed charge-receiving condition of the mold sections 10 and 14and retracted position of the injection plunger 28 in readiness for the performance of a metering and cavity charging casting cycle.

Closing of the manually operated switch 100 across supply lines Is -L causes simultaneous energization-of high precision adjustable electronic timer 102, as well as energizing the three-way spring-return solenoid vacuum controlling valve 86, to connect the vacuum line 60 with the above-explained and described vacuum source to thereby initiate evacuation of the cold chamber or-injection cylinder 26 and die cavity 18 in direct communication therewith. The thus initiated and induced vacuum also reacts through the upper open end of the delivery conduit 62 and its contiguous portion 64 with the result that atmospheric pressure on the exposed surface of the flowable material in the reservoir 66 forces the, same upwardly through the contiguous delivery conduit,64r62 into the cold chamber 26.6 The selected size or uniform therefore be delivered to the cold chamber 26 to accom-- modate any particularly selected capacity of die cavity 18.

When the timer 102 times out, or its energized time interval expires, the electric circuit including the VEICUIIIII.

controlling solenoid valve 86 is de-energized causing spring-return shifting of the same to open the vacuum line 60 to atmosphere through the exhaust port 104. Such de-energization simultaneously closes the normally open contacts (FIG. 2) in the electric circuit of a second high precision adjustable electronic timer 106, herein termed the injection plunger delay timer, to energize the same for a predetermined and definitely established time interval suflicient to permit reverse directional drainage of flowable material therewithin, by syphon action, on termination of the aforesaid vacuum metering and delivery cycle established by the time interval set by the timer 102. This additional time interval imposed by timer 106 insures against possible freezing, congealing or dripping of flowable material from an undrained delivery conduit 62-64 into the cold chamber 26 in detrimental interference to subsequent reciprocation of the injection plunger 28 or subsequent vacuum delivery against frozen or congealed material within the conduit 6264.

Time out or de-energization of the delayed time interval performed by timer 106 serves to close the normally open contacts (FIG. 2) in the electric circuit of fourway spring-return solenoid valve 90 controlling fluid pressure delivery and exhaust to injection plunger actuating cylinder 30. It will thus be understood and appreciated that pressure can only be applied to the major power stroke face of piston 32 to advance injection plunger 28 axially through the cold chamber 26 to charge the previously delivered accurately metered shot of flowable material therewithin into the die cavity 18 following complete drainage of the contiguous delivery conduit 62-64.

It will be observed and understood from the above description of the structure and operation of the integrated mechanism, selected primarily for purposes of illustrating the invention, that accurately metered quantities of castable flowable material, including molten metals, are supplied from a reservoir of the same and delivered to the cold chamber of otherwise conventional die casting equipment in safely locked condition of the mold sections and retracted and inoperative position of the injection plunger within the cold chamber thereof. It will also be observed, and in particular from FIGS. 3-6, that the discharge end of the delivery conduit 62-64 is sufiiciently isolated from adjacent areas of the interior walls of the cold chamber 26 to reduce premature chilling and any resulting congelation of the flowable material within the aforesaid delivery conduit or adjacent areas of the cold chamber 26. The compound angular direction of portion 62 of the delivery conduit entering the cold chamber 26 also directs the material discharged therefrom substantially tangentially to the closest interior wall area of cold chamber 26 to thereby reduce to a minimum any turbulence that would otherwise result.

In addition, the isolated location of the vacuum inducing conduit 60 adjacent and slightly in advance of the retracted injecting plunger 28, remote to the conventionally vented mold cavity 18, minimizes and substantially eliminates the effect of atmospheric pressure entering the system through the mold vents and any loose or otherwise faulty sealing surfaces between the mold sections and 14. In fact, practical demonstrations of the mechanism herein described in commercial production has revealed that selection of vacuum conduit 60 in the form of a 1% inch inside diameter steel pipe, or tubing, and employing an inside uniform diameter of /8 inch for the delivery conduit 62-64, permitted using a vacuum level within the range 3 to 12 inches of mercury, as compared to a vacuum level above to inches of mercury when the vacuum had been induced by direct connection to the cavitied mold of substantially the same capacity die casting machine, in accordance with many prior art practices. The conventional higher vacuum level die casting machines have been observed to produce considerable turbulence within the cold chambers thereof, as demonstrated by internal voids in finished castings so produced. The higher level prior art vacuum charging systems have also produced greater pressure differentials between the cold chamber, die cavity and outside atmospheric pressure to make such systems more sensitive to pressure variations therewithin caused by leakage.

Two structural features illustrated in FIGS. 1 and 3 through 5, and not heretofore discussed, have been found desirable although not absolutely essential to the success of the apparatus and practice of the invention. One of these two features concerns the relatively small bore bypass conduit line 108 (FIG. 1), which connects into the vacuum drawing source to provide an induced relatively low vacuum around the tip of the injecting plunger 28 to counterbalance atmospheric leakage into the cold chamber 26 resulting from peripheral wear of the plunger 28. A close tolerance piston or plunger within the cold chamber obviates the need of conduit 108. The second feature is concerned with the aperture 110 (FIGS. 1, 3, 4 and 5) through the wall of the cold chamber 26 adjacent the injecting'plunger 28 in its withdrawn or retracted position. This latter aperture permits introduction of lubricant for plunger 28, when required, and would be normally sealed off.

It will .be fully understood and appreciated that the apparatus selected for purposes of describing the invention is exemplary only, and not limiting, of the scope of the invention hereinafter defined in the appended claims,

We claim:

1. In a die casting apparatus including an atmospherically vented cavitied die, a horizontally disposed cylindrical cold chamber in open communication therewith, a power-operated injecting plunger reciprocal within said cold chamber to charge flowable liquid casting material delivered thereto directly into said cavitied die, and a charging aperture through an upper wall surface of the cold chamber adjacent and in advance of the injecting plunge-r in its retracted position within the cold chamber remote to said cavitied die, the improvement comprising:

(a) a housing carried by said cold chamber providing an upwardly and outwardly directed sealed chamber in open communication through said changing aperture with the cold chamber and vented cavitied die,

(b) an imperforate wall open ended flowable liquid casting material delivery conduit extending axially coextensively downwardly through and from above a upper wall of said housing and having its open discharge end terminating therewithin isolated from interior walls of the cold chamber and in substantially axially tangential disposition in respect to an interior wall of said cold chamber closely adjacent said charging aperture,

(c) said conduit being curvilinear-1y downwardly axially contiguously directed to locate its opposite open end below an atmospherically exposed surface of a source of flowable casting material located below the cold chamber,

(d) means for inducing a low level vacuum within said cold chamber in advance of the injecting plunger in its retracted position remote to said calvitied die,

(e) electrically energizable operating circuitry incorporating a pair of electrically responsively timed valves sequentially controlling initiation and duration of the induced vacuum and activation of a source of power initiating the injection stroke of the injecting plunger within the cold chamber in consecutively time-delayed sequence,

( f) energization of one of said valves being timed to expire and cut-off the induced vacuum and a metered quantity of flowable liquid casting material responding to the induced vacuum delivered to said cold chamber through said flowable liquid casting material delivery conduit, and

(g) energization of the other of said valves for initiating the injection stroke of said injecting plunger being set to initiate the injecting plunger changing stroke in selective timed delay following expiration of the induced vacuum controlling valve,

whereby flowable liquid casting material within the delivery conduit is directionally oppositely drained into the cold chamber and source of flowable liquid casting material from opposite open ends of the delivery conduit before initiatio of the charging stroke of the injecting plunger.

-2. A die casting apparatus in accordance with claim 1 in which the means for inducing low level vacuum is comm-unicatively connected throughthe upper wall of said housing and is terminated in a .plane above the plane of the open discharge end of the flowable liquid casting material delivery conduit within said housing.

3. A die casting apparatus in accordance with claim 1 in which the means for inducing low level vacuum is cornm-unicatively connected through the upper wall of said housing above the plane of the open discharge end of the flowable liquid casting material delivery conduit within said housing and in advance thereof towards the cavitied die.

4. A die casting apparatus in accordance with claim j 1 in which the electrically energizable operating circuitry incorporates a protective microswitch permitting energization of the electrically energizable operating circuitry only when the cavitied die is conditioned to receive a change of flowable liquid casting material from the ,cold chamber.

5. A die casting apparatus in accordance with claim '1 in which the electrically energizable operating circuitry incorporates a protective microswitch permitting enerigization of the electrically energizable operating circuitry only when the injecting plunger is in fully retracted position within the cold chamber remote to said cavitied die.

References Cited by the Examiner,

UNITED STATES PATENTS J. SPENCER OVERHOLSER, Primary Examiner.

20 R. S. ANNEAR, Assistant Examiner.

Claims

1. IN A DIE CASTING APPARATUS INCLUDING AN ATMOSPHERICALLY VENTED CAVITIED DIE, A HORIZONTALLY DISPOSED CYLINDRICAL COLD CHAMBER IN OPEN COMMUNICATION THEREWITH, A POWER-OPERATED INJECTING PLUNGER RECIPROCAL WITHIN SAID COLD CHAMBER TO CHARGE FLOWABLE LIQUID CASTING MATERIAL DELIVERED THERETO DIRECTLY INTO SAID CAVITIED DIE, AND A CHARGING APERTURE THROUGH AN UPPER WALL SURFACE OF THE COLD CHAMBER ADJACENT AND IN ADVANCE OF THE INJECTION PLUNGER IN ITS RETRACTED POSITION WITHIN THE COLD CHAMBER REMOTE TO SAID CAVITIED DIE, THE IMPROVEMENT COMPRISING: (A) A HOUSING CARRIED BY SAID COLD CHAMBER PROVIDING AN UPWARDLY AND OUTWARDLY DIRECTED SEALED CHAMBER IN OPEN COMMUNICATION THROUGH SAID CHARGING APERTURE WITH THE COLD CHAMBER AND VENTED CAVITIED DIE, (B) AN IMPERFORATE WALL OPEN ENDED FLOWABLE LIQUID CASTING MATERIAL DELIVERY CONDUIT EXTENDING AXIALLY COEXTENSIVELY DOWNWARDLY THROUGH AND FROM ABOVE AN UPPER WALL OF SAID HOUSING AND HAVING ITS OPEN DISCHARGE END TERMINATING THEREWITHIN ISOLATED FROM INTERIOR WALLS OF THE COLD CHAMBER AND IN SUBSTANTIALLY AXIALLY TANGENTIAL DISPOSITION IN RESPECT TO AN INTERIOR WALL OF SAID COLD CHAMBER CLOSELY ADJACENT SAID CHARGING APERTURE, (C) SAID CONDUIT BEING CURVILINEARLY DOWNWARDLY AXIALLY CONTIGUOUSLY DIRECTED TO LOCATE ITS OPPOSITE OPEN END BELOW AN ATMOSPHERICALLY EXPOSED SURFACE OF A SOURCE OF FLOWABLE CASTING MATERIAL LOCATED BELOW THE COLD CHAMBER, (D) MEANS FOR INDUCING A LOW LEVEL VACUUM WITHIN SAID COLD CHAMBER IN ADVANCE OF THE INJECTING PLUNGER IN ITS RETRACTED POSITION REMOTE TO SAID CAVITIED DIE, (E) ELECTRICALLY ENERGIZABLE OPERATING CIRCUITRY INCORPORATING A PAIR OF ELECTRICALLY RESPONSIVELY TIMED VALVES SEQUENTIALLY CONTROLLING INITIATION AND DURATION OF THE INDUCED VACUUM AND ACTIVATION OF A SOURCE OF POWER INITIATING THE INJECTION STROKE OF THE INJECTING PLUNGER WITHIN THE COLD CHAMBER IN CONSECUTIVELY TIME-DELAYED SEQUENCE, (F) ENERGIZATION OF ONE OF SAID VALVES BEING TIMED TO EXPIRE AND CUT-OFF THE INDUCED VACUUM AND A METERED QUANTITY OF FLOWABLE LIQUID CASTING MATERIAL RESPONDING TO THE INDUCED VACUUM DELIVERED TO SAID COLD CHAMBER THROUGH SAID FLOWABLE LIQUID CASTING MATERIAL DELIVERY CONDUIT, AND (G) ENERGIZATION OF THE OTHER OF SAID VALVES FOR INITIATING THE INJECTION STROKE OF SAID INJECTION PLUNGER BEING SET TO INITIATE THE INJECTING PLUNGER CHARGING STROKE IN SELECTIVE TIMED DELAY FOLLOWING EXPIRATION OF THE INDUCED VACUUM CONTROLLING VALVE, WHEREBY FLOWABLE LIQUID CASTING MATERIAL WITHIN THE DELIVERY CONDUIT IS DIRECTIONALLY OPPOSITELY DRAINED INTO THE COLD CHAMBER AND SOURCE OF FLOWABLE LIQUID CASTING MATERIAL FROM OPPOSITE OPEN ENDS OF THE DELIVERY CONDUIT BEFORE INITIATION OF THE CHARGING OF THE INJECTING PLUNGER.