US2856653A - Method and apparatus for making hollow shell foundry sand articles - Google Patents

Description

R. H. SUTTER PPARA Oct. 21, 1958 2,856,653 METHOD AND A TUSFOR MAKING HOLLOW Y SHELL FOUNDRY SAND ARTICLES Filed July 22. 1955 7 Sheets-Sheet 1 Get. 21, 1958,

R. H. SUTTER 2,856,653 METHOD AND APPARATUS FOR MAKING HOLLOW SHELL FOUNDRY SAND ARTICLES I Filed July 22. 1955 '7 Sheets-Sheet 3 2 N INVENTOR. SJAAVMO/VO 1,1. :arrae.

Oct. 21, 1958 R H SUTTER 2,856,653

METHOD AND APARATus FOR MAKING HOLLOW SHELL FOUNDRY SAND ARTICLES Filed July 22. 1955 7 Sheets-Sheet 4 61454 l/Vi h \NL V I as 86 a:

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METHOD AND APPARATUS FOR MAKING HOLLOW I SHELL FOUNDRY SAND ARTICLES Filed July 22.' 1955 7 Sheets-Sheet 5 45g] Que INVENTOR. RflYMO/V0 A4 @0772? :5 ik mfffi Oct. 21, 1958 R. H. SUTTER 2,856,653

METHOD AND APPARATUS FOR MAKING HOLLOW SHELL FOUNDRY SAND ARTICLES '7 Sheets-Sheet 6 Filed July 22. 1955 ins x35? INVENTOR.

RH YMCA/0 Oct. 21, 1958 'R. H. SUTTER 2,856,653

METHOD'AND APPARATUS FOR MAKING HOLLOW V SHELL FOUNDRY SAND ARTICLES Filed July 22. 1955 7 Sheets-Sheet 7 ATTOAPAQTVJ:

United States Patent AND APPAR-ATUQFOR MAKING HOL LOW SHELL FOUNDRYSANDARTICLES This invention relates to a production method and apparatus for makinghollow shellnfoundry sand articles and more particularly shell cores and shell 'molds for ultimate use in making metal castings.

The preferred method is primarily characterized by the steps of blowing a foundry sand mix having a thermosetting binder upwardly through a vertically disposed passage into a split box cavity defined by separable having suitable sand blocking air vents until said cavity-is Completely filled with said sand mix under airpressure, shutting off the air pressure supply to permit the air pressure in the cavity to dissipate gradually. through the air vents, removing the surplus sand mix from the cavity after the binder initially has been set through heat supplied from the metal cavity surfaces to adepth sufiicient for desired shell thickness by exhausting'the sand mix below the blow passage while lightly vibrating the box with sufof gravity, moving the box section to a position where the parting line is substantially horizontal, maintaining the sand shell in the heated box box subframe, a reciprocally mounted sand blow chamber, and a fixed sand hopper. rocked through a 90 the cured tions. Top and bottom gas manifolds and radiant gas burners adjustable both as to position and intensity of flame provide accurately controlled heating of the box cavity, each box half beingindependently controlled through a thermo-couple located at its most critical cavity surface. The sand blow chamber is refilled from the fixed sand hopper duringeach-cycle; and automatic timing and power controls are included to provide a completely automatic machine cycle, removalof the said sand core or mold and startingof the next cycle being the only manual operations performed. I

The advantages of shellcoresand shell molds over the more conventional solid type include a saving of two-thirds or more in the quantity of sand used, finer surface, closer tolerances, reduced" cure time permitted by the thin Walls and' easier collapsibility after casting, the latter feature being particularly important in the case of cores. The present method and apparatus are believed to include many important novel features, as reflected in the following. objects:

One important object is the provision of an 'efiicient, fast, accurately controllable built-in heatingisystern for the box sections.

Another object is tomaintain said boxsections heated 2 to a high curing temperature continuously throughout the entire production cycle.

Another object is to provide'rapid complete curing within the machine in order to eliminate the expense and in a -separate curing oven operation, the necessity of multiple pattern boxes and the damage incident to removal of fragileuncured'or partially cured sand cores or molds.

Another object is to provide automatic accurate time controls to effect utmost efliciency in the production of high quality shell cores and shellmolds.

Another object is to cornbinecomplete forming and final curing in a single machine cycle, minimum-wall thickness, and maximum curing temperature in order to provide a minimum time for eachproduction cycle.

Another object is to maintaina completely sand filled cavity under substantial air pressure during the initial setting of the shell to assure a complete filling of any fine details in the pattern, an accurate smooth surface and close tolerance in dimension.

Another object is to provide for a gradual dissipation of air pressure through suitable air vent to avoid shell a uniform shell thickness;

Another object is-to provide a heating system which incorporates a gas manifold in combination with the stripper plate on either side of the pattern box with multiple threaded outlets for it radiant type gas burners eachof which is adjustable forfintensity. of heat in order to provide 'for uniform temperature control.

Another object is 'to-adapt the machine for use with a variety of difierent pattern boxes by providing the burner plates with numerous alternate threaded location holes for the individual'burfl'ers'and plugging all but those being used.

Another object is to provide a substantially unlimited ariety of heating patterns through: the combined adeach side of the patternbox;

Another object is toemploy uniform propercuring'of all areas of the shell core or mold at a relatively higl1curing of 45010 500 degrees Fahrenheit.

- Another object is to pivotally mount the pattern" box subframe for rocking througli a arc in order to ac commodate normal requirements" 1' a horizontal position Another'object in order to furtherassure uniformity is to charge the blow chamber with duction cycle by shuttle movement of the blow' chamber to afixed sand supply hopper.

Another object is to assure adequatespace'fdr' the "sur-' plus sand to empty back into' "the "blow" chamber after a shell has been formed by inclu'ding provision for chargingthe blow chamber toa limitedheigh't.

Another objectis to achieve'opening of and ejection from the pattern boxthrough -use of a single air cylinder adapted to controlboxopening and stripper pin actuationi Fig. 2 is an end elevation taken in the direction of the arrow 2 of Fig. 1;

Fig. 3 is an end elevation taken along the line 3-3 of Fig. 1;

Fig. 4 is an enlarged fragmentary sectional view of one of the gas burner manifolds shown in Fig. 2;

Fig. 5 is a fragmentary sectional side elevation of the valve arrangement for one side of the sand chamber taken along the line 55 of Fig. 3;

Fig. 6 is a schematic control diagram showing the inter-relationship of the various limit switches, solenoid air valves, pressure cylinders and diaphragms employed in securing automatic machine cycles;

Fig. 7 is a schematic control diagram for producing automatic control of the gas heating system, and

Fig. 8-8A is a schematic electrical control diagram for producing a complete automatic cycle of the entire machine including an alternate heating control. With reference to Fig. 1 it will be seen that thepreferred embodiment consists generally of a stationary machine bed A, a pattern box assembly B, a reciprocable sand blow chamber C, and a stationary sand hopper D. The main subframe 10 of the pattern box assembly B is pivotally mounted on the axis 11 of a pair of stationary trunnions 12 mounted on the transverse member bed 13 of the machine. A pair of air cylinders 14 pivotally anchored to the bed of the machine at 15 each having a piston rod 16 pivotally connected at 17 to arms 18 projecting upwardly from the subframe 10 serve to rock the entire assembly B about the pivotal axis 11 from an upright position as shown in Fig. 1 through 90 to a sand filling position later described in detail.

An air cylinder 19 mounted horizontally on the bed of the machine having a piston rod 20 connected to a bracket 21 moves the sand blow chamber C on wheels 23 along stationary tracks 22 to a forward position shown with an extension 24 of the piston rod in registration with an adjustable stop 25, which forward position corresponds to a filling position for the pattern box later described, and upon retraction of the piston rod 20 to a recharging position under the chute 26 of the sand hopper D.

During the filling cycle sand is blown upwardly from vertical sand chambers 27 through an adapter 28 in a pivoted adapter plate 29 and through a blow hole 30 in the pattern box brought into registration with the adapter 28 and vertical chamber 27 by 90 rocking movement of the assembly B. With reference to Fig. 5 air pressure can be shut off from each of the vertical chambers 27 by actuation of valve 28a while air pressure can be exhausted from the chamber 27 by actuation of valve 29a.

Referring to Figs. 1 and 2 a split pattern box F is heated by upper and lower gas burner assemblies G made integral with the stripper plates. Four corner posts I-I actuated by cylinder assembly I serve to open the pattern box and strip the completed cores 0r molds therefrom and on the return stroke to move the pattern box sections to closed position and hold the same against blow pressure introduced therein.

From the above general description of the main components of the machine the general cycle of the machine may be understood. Thus after completed sand cores or molds have been removed from the pattern box F, the cylinder assembly I will close the same, cylinders 14 will be actuated to rock the pattern box assembly B through 90 to blow position over the vertical chamber 27 of the reciprocable sand chamber C. Blow pressure introduced into chambers 27 will fill the box cavity with the sand mix under pressure such cavity being vented by suitable sand blocking screen ports (not shown) heated cavity walls of the pattern box causing a thermosetting binder in the sand mix to set up a shell adjacent to the cavity surface of a thickness depending on the length of time the cavity is maintained filled with sand. After an appropriate shell forming time air pressure to the pattern box cavity is shut off through actuation of valves 28, the pressure being permitted to dissipate gradually through the screened vents whereupon the valves 29 are opened to fully exhaust residual air pressure from the sand chambers 27, the surplus sand within the box cavity being induced to fall back into the chambers 27 by gravity and light vibration of the mold effected by a vibrator 30a attached to the end of the adapter plate 29.

When cylinders 14 have been actuated to return the pattern box assembly B to its upright position as shown, in which position curing of the sand cores or molds is completed under continuous heating of burner assembly G, sand chamber C is moved by piston 20 to a recharging position under the hopper chute 26 and thereupon returned to forward position as shown for the next cycle.

Proceeding now to a more detailed description of the various components for operation and the steps carried out in the machine, the pattern box assembly B will be considered first. Members rigidly associated with subframe 10 of this assembly include in addition to the arms 18 providing pivotal connection for the piston rod 16 a transverse bolster plate 31 serving to mount cylinder 32, a tubular guide 33 adapted to receive the lower end 34 of each of the corner posts H and a rectangular transverse frame 35 having a clearance passage 36 for each of the corner posts, the frame 35 serving to mount the lower half 37 of the split pattern box F, cars 38 at either end being engaged by hold-down clamps 39 secured to the frame 35 and a key 40 being provided to accurately locate the box transversely relative to the frame 35. The front side 41 of the frame 35 is removably connected to the ends 42 of the frame 35 by pins 43 in order to facilitate assembly and disassembly of the pattern box.

A rectangular plate 44 having a clearance passage 45 for each of the corner posts serves to mount the lower combination stripper plate and gas burner assembly G through hold-down clamps 46. Plate 44 normally rests on the ends 47 of a pair of bell crank arms 48 controlled by shaft 49 and actuating arm 50 normally pinned at 51 relative to the subframe 10. A gas manifold 52 communicates directly with a plurality of radiant cup type gas burners 53 which direct intensive heat directly onto the back of the lower box section 37. Stripper pins, of which 54 is typical, carried by the stripper plate 55 project upwardly into the lower pattern box section 37 to a position adjacent the cavity surface 56.

An upper rectangular frame 57 secured in fixed relation to the four corner posts H serves to mount the upper pattern box section 58 through hold-down clamps 59 and key 60 in a manner similar to the lower frame 35. An upper plate 61 similar to plate 44 having clearance passages 62 for corner posts H serves to mount the upper burner and stripper plates 63 through clamps 64 a plurality of burners 65 being provided to heat the back of the upper pattern box 58 and stripper pins such as typical pin 66 being provided to project through to the upper cavity surface 67.

The lowermost position of the plate 61 is established at either end by a pair of gauge rods 68, best shown in Fig. l, which engage frame 35 at their lower ends, the upper ends being rigidly attached to the plate 61. Clearance passages 69 are provided for the gauge rods in the upper plate 57 while spacer sleeves 70, slightly shorter than the normal spacing between the frame 57 and plate 61, limit the upward movement of the frame 57 relative to the plate 61. Compression springs 71 between a top plate 72 and the plate 61 normally urge the plate 6.1 downwardly.

Actuating plate 73 is rigidly connected to each of the corner posts H and centrally to a piston rod 74 which is actuated by a large central air cylinder 75 whereby all four of the corner posts may be simultaneously raised or lowered through the operation of such air cylinder.

. b All of the operations in opening the pattern boxand stripping the sand cores or molds from both upper and lower box sections are accomplished'by a singleupward stroke of the piston 74 which through raising the corner posts produces the following sequence of operations:

(a) Initial upward movement of the corner posts raises the upper frame 57 and upper half of the pattern box 58 secured thereto While the upper plate 61 and upper stripper pins 66 remain stationary thereby stripping the sand core or mold from the upper pattern box section.

(b) After the clearance at the ends of the spacer cylinders 70 between the frame 57 and plate 61 is taken up bythe upward movement of the frame 57 which clearanceis just sufficient to insure complete stripping, e. g. in-the order of inch and which stripping action is positively assured by the compression springs 71 holding pla te 61 down with the gauge rod-68 continuing to limit the foremost position of the plate 61 continued upward movement of the frame 57 produces simultaneous upward movement of the plate 61 thereby causing both the upper box section and upper stripper pins to progressively increase opening clearance between the box sections.

(c) When the corner posts H have completed approximately one-half of their upward travel, the actuating plate 73 engages the plate 44 raising the lower stripper pins stripping the sand core or mold from the lowerhalf of the box and continuing to raise the same until full box opening is effected whereupon the sand core or mold is in a position most convenient for manual removal from the machine.

A reversal of air pressure in the cylinder 75 produces a reverse sequence in such operations finally closing the box sections together under air pressure designed to withstand the separating forces of blow pressure on theprojected area of the boxcavity.

Closing the box sections which constitutes the first operation of the automatic cycle is followed by rocking the box assembly B over into fill position through actuation of the air cylinders 14. Initial rocking movement permits the adapter plate 29 pivotally mounted on the axis 11 to move downwardly covering the opening at the top of the blow chambers 27, suchadapter plate havingbeen previously raised through inter-engagement of--contact blocks 76, 77 mounted respectively on the lower. end of the subframe and a projection 78 of the adapter plate 29 upon the prior raising of assembly B? to its upright position in order to provide clearance for reciprocating travel of the blow chamberC without interference or wear in the resilient sealing ring 79. Upon completion of the 90 rocking movement of the assembly B the blow passage 30 in the split box will come into registration with the resilient sealing plug 80 at *the top of the adapter 28 thereby providing a fully sealed passage from the blow chambers 27 into the box cavity. Sand is blown into the box cavity by introducing air pressure into the blow chambers 27 as best shown in Fig. 5. This may be accomplished by exhaustingair pressure from the area 81 below the annular valve plug 82 interposed between upper and lower resilient diaphragms 83, 84 thereby permitting air pressure from reservoir 85, to which it is piped by flexible hose (not shown) to move the diaphragm 83'and valve plug 82 downwardly permitting air to enter at the lower ends 86 of the blow chambers 27 valve closure 87-remaining closed to prevent escape of air. Thus the screened air vents (not shown) in the box cavity provide the only exhaust for air pressure which carries the sand from blow chamber 27 upwardly.

When air pressure is restored to the area 81, valve plug 82 is raised to force diaphragm 83 into sealing engagement with the lower edge of the passage 86, valve plug 82 being provided with differential areas to permit such action when the same air pressure prevails in the area 81 and chamber 85. It will be understood that if the diaphragm 83 seals passage 86 while valve 29 remains closed, air pressure within the blow chamber 27 and box cavity will gradually dissipate through the screened vents in such cavity whereafter when valve 29a is opened further exhausting air from blow chamber 27 through the screened opening88 while the box is lightly vibrated, surplus uncured sand will backout of the opening 3ti'under the influence of gravity without any sudden rush of air such as would otherwise accompany the exhausting of air pressure through valve 29 before it had been gradually dissipated. Since any suchsudden rush of air would have a tendency to tear away portions of the partially cured shell, the procedure of permitting an initial gradual dissipation 'of air pressure is much preferred if not essential to uniform quality'in the shell walls. Valve 2% is held in closed position by air pressure admitted to the outside half of diaphragm chambers 89. i

In order to assure adequate space for complete ex-' haustion of the surplus sand from the boxcavity when 27, a baffle 90 is employed and the blow chamber 27 is filled through passage 91 only by limiting the travel of the chamber C under the hopper chute 26 thereby preventing complete filling of the chamber 92 on the other side of the bafiie 90, resulting inadequate volumefor completely emptying surplus sand out of the box cavity notwithstanding any tendency of such sand to pileup in a bill. In order to further assure proper filling and exhausting of the box cavity, .dual chan1bers27a and 27b together with dual valve systems 93 as shown by Fig. 3 are preferred.

As best shown in the enlarged view of Fig." 4, the burner plate may be drilled and tapped with a pattern of gas passages 94, all communicatingwith gas manifold 52 such as to permit desired location of the burners 53, all surplus passages being plugged as indicated in 95. Such adjustment in location together with adjustment in individual burner intensity as is provided in commerto give substantlally uniform curing throughout all areas. By locating a thermo-couple 96 at any most critical location in the cavity surface for controlling intensity of gas pressure and by providing independent controls for top and bottom box sectionsymaintenance of continuous substantially uniform box cavity temperature is accomplished.

This is a highly important feature from a number of standpoints. A perfectly cured core has maximum strength for such purposes as ejection from the pattern box, handling and resistance to shock from the molten casting. Accordingly a perfectly cured shell core may be made with minimum wall thickness which in turn provides the advantages of minimum material and minimum cure time. If sections of the core are either overcured or under-cured such areas will be relatively weak and subject to damage with resulting imperfections in the casting. While the chances of non-uniform curing are relatively minor where curing ovens are employed with relatively low curing temperatures and noncritical shorter and more critical as the curing temperature is elevated. Thus at the relatively high curing temperatures of 450 to 500 degrees contemplated in the present case, which are necessary in a machine of this type to take advantage of the relative short cure time which accompanies high curing temperatures and to develop a practical and minimum cycle time, critical limits in the duration of cure time and uniformity of cure temperature are encountered at such elevated curing temperatures. In addition, where large quantities of sand must be heated to the curing temperature as well as to maintain the temperature of the pattern boxes against heat lost to the atmosphere, provision for a high heating capacity must be made. Accordingly a heating system for a full curing machine of this type should include a high heating capacity and accurately adjustable intensity of heat to meet uniform temperature requirements throughout the various surface areas of the pattern cavity as is readily possible with the present system.

Referring now to the schematic control diagram of Fig. 6, pressure from source P passes through a regulating valve to main supply lines 100 which communicate with the various solenoid valves SOL-ASOL-G. To initiate an automatic cycle, a push button (not shown) is manually pressed energizing solenoid SOL-A to admit air pressure to line 101 and exhaust same from line 102 thereby actuating air cylinder I to close the box and limit switch LS1. This energizes solenoid SOL-D provided limit switch LS4 has also been closed by return of the blow chamber C to normal fill position through actuation of air cylinder 10, solenoid valve SOL-D admitting air pressure to line 103, and cylinders 14 to rock box assembly B over to blow position, such movement opening limit switch LS2 and closing limit switch LS3. After limit switch LS3 is closed and pressure has built up to close pressure switch PR1, solenoid SOL--F and timer TRI are energized exhausting pressure from line 104 and opening blow valves 28. After timer TRl times out, solenoid SOL-F is deenergized and a second timer TR2 is energized thereby restoring pressure to line 104 closing valves 28 and permitting dissipation of air pressure from the box cavity during the period established by timer TR2. After timer TRZ times out, solenoid SOL-E and timer TR3 are energized thereby exhausting pressure from line 105 and opening valves 29 to exhaust air and surplus sand from the box cavity for a period established by timer TR3. After timer TR3 times out, solenoid SOL-E is de-energized restoring pressure to line 105 and closing valves 29 and solenoid SOL-C is energized admitting pressure to line 106 to rotate box assembly B to upright position thereby opening limit switch LS3 and closing limit switch LS2.

The closing of limit switch LS2 energizes a cure timer TR4 and also energizes solenoid SOL-G and timer TRS. This admits pressure to line 107 and air cylinder 19 moving the blow chamber to refill position under the hopper D where it remains until timer TRS times out deenergizing solenoid SOLG to admit pressure to line 108 and return blow chamber to its blow position closing limit switch LS4. After cure timer TR4 times out, solenoid SOL-43 is energized to open and strip box completing the automatic cycle. The sand core mold is then manually unloaded and the box prepared with a parting agent and the cycle is repeated.

Referring to Fig. 8-8A illustrating schematically the electrical controls for automatic cycling of the machine, manual depression of the Cycle Start button closes control relay CR1, provided limit switch LS4 is closed by return of the blow chamber from the refill position, thereby closing the box and limit switch LS1 which energizes control relay CR1 and solenoid SOLA limit switch LS1 energizes control relay CR2 and moving the box to blow position. This closes limit switch LS3 and when pressure has built up in the closing cylinders to energize pressure switch PS1, control relay CR3 is energized actuating solenoid SOL-F to open the blow valve and start timer switch TRl. When the blow time expires, timer TR1 opens the circuit to control relay CR3 permitting spring return solenoid SOL-F to stop the blow cycle and simultaneously energizes the timer TRZ to start olenoid SOL-D for the set time cycle upon expiration of which timer TR2 closes the circuit to control relay CR4 actuating timer TR3 and exhaust solenoid SOL-E to start the exhaust cycle. Upon completion of the exhaust cycle timer TR3 closes the circuit to control relay CR5 energizing solenoid SOL-C to start movement of the box to an upright position and simultaneously actuates timer TR4 to start the cure time cycle. When the box has reached an upright position closing limit switch LS2, control relay CR6 is energized actuating the refill solenoid SOL-G to effect movement of the blow chamber to the refill position and simultaneously energizes timer TRS which establishes the refill time after which timer TRS opens the circuit to control relay CR6 permitting spring return solenoid SOL-G to return the blow chamber to its blow position. When the cure time has expired, timer TR4 closes a circuit to control relay CR7 to actuate solenoid SOLB which effects an opening of the box thereby completing the automatic cycle.

During such entire cycle automatic temperature controls maintain the boxes at proper curing temperature through controls also schematically shown. When the gas is turned on by manual switch, control relay CR8 is energized actuating main gas and air solenoids which provide for a sufficient fiow for low heat. When either top or bottom box temperature falls below a predetermined minimum, independent thermo-couple temperature controls for the upper box half and lower box half are closed independently energizing control relay CR9 and control relay CR10 which in turn independently actuate an upper manifold solenoid and lower manifold solenoid to open auxiliary air valves for high heat. The flow for low heat is preferably adjusted just below that required to maintain the box at proper curing temperature with minimum heat loss from drag out incurred with the smallest shell cores to be handled by the machine, while high heat flow is adjusted just above that required to maintain box curing temperature for the largest cores or molds with corresponding highest heat loss from drag out. Such arrangement reduces to a minimum the frequency of switch between high and low heat and tends to produce the most uniform temperature obtainable with the high-low type of heat control.

Alternate electrical controls for the gas system shown in Fig. 7 incorporate safety switches responsive to expira tion of either top or bottom pilot flames as well as safety switches responsive to decrease of flow to either the upper or lower manifolds below normal operating conditions, thereby shutting off all flow completely whenever gas or air flow is below that required for normal operation. In other respects it will be understod that the operation of the alternate high-low control is similar to that previously described.

In actual operations employing box temperatures of 450 to 500 degrees Fahrenheit, complete cycles in the order of 50 to cycles per hour, depending on the size and thickness of shell, have been found entirely feasible, a typical cycle involving approximately 2 seconds to close the mold, 3 /2 to 4 seconds to rock over the box assembly to fill position, a blow cycle of from 6 to 8 seconds, a pressure dissipating cycle 4 to 5 seconds, a surplus sand emptying cycle of 4 to 5 seconds, a return of the box assembly in 9 seconds with the balance of time being used to complete curing. The refilling of the blow chamber involves approximately 7 seconds.

It will be understood that rocking the box between blowing and curing positions facilitates filling and emptying surplus sand along a vertical line parallel with the part-' ing line, which is usually necessary or desirable, while permitting stripping in a vertical line normal to the parting line which is likewise most convenient; in addition it minimizes the time in which the heated box is near the blow chamber which minimizes any possibility of setting up sand in the blow chamber during the curing operation.

As above described, a preferred method and apparatus embodiment of my invention have been provided which meet the various objects set forth in a commercially practical and economic manner. While such preferred method and apparatus embodiment have been described in considerable detail, it will be understood that numerous modifications may be resorted to without departing from the scope of my invention as defined in the following claims.

What is claimed is:

1. An automatic production machine for making hollow shell foundry sand articles characterized by separable metal box sections cooperably defining an article cavity, power means for transferring said box sections from one station to another station, heating means in juxtaposition to said box sections and carried thereby for continuously maintaining the metal walls of said cavity at a suitable sand binder curing temperature, means at said one station alignable with said cavity in communication therewith for blowing sand into said cavity, means for removing the surplus sand from said cavity to said alignable means after initial setting of a surface shell, means for maintaining said shell in said cavity for a predetermined accurate time, and means at said another station for ejecting the completely cured shell from said cavity.

2. A machine as set forth in claim 1 wherein the heating system comprises a plurality of gas burners adapted to heat the exterior box surfaces.

3. A machine as set forth in claim 1 including a combi nation gas manifold and stripper plate, and a plurality of gas burners communicating with said manifold.

4. A machine as set forth in claim 1 wherein a plurality of gas burners individually adjustable as to intensity communicate with a manifold, and wherein means are provided for adjustment in location of the individual burners.

5. An automatic production machine for making hollow shell foundry sand articles comprising separable metal box sections defining an article cavity, a sand blow passage communicating with said cavity, sand blocking air vents communicating with said cavity, means adjacent each box section for heating said cavity, a sand blow chamber vertically alignable with said cavity and provided with means for blowing a foundry sand mix including a thermosetting binder upwardly through said blow passage to substantially fill said cavity with said sand mix, means for exhausting the surplus sand mix from the sand shell initially set by contact with the heated cavity surface by gravity flow back into said blow chamber, hopper means alignable with said blow chamber for refilling said blow chamber with sand, and bafile means to prevent complete refilling of sand in said blow chamber in order to avoid interference with gravity flow of surplus sand from said cavity.

6. An automatic production machine for making hollow shell foundry sand articles characterized by a machine bed including fixed trunnions, a fixed track and a fixed sand hopper mounted thereabove, a separable pattern box assembly pivotally mounted on said trunnions for arcuate movement between an upright unloading position and a recumbent blowing position for filling said pattern box tions defining an interior mold cavity in vertical registry with a sand chamber containing a sand mix, the cavity communicating with the sand mix body, blowing sand mix from said chamber into said cavity, initially curing the sand mix in the cavity, transferring the moldbox to a curing and stripping position, heating the moldbox to further cure the sand mix in the cavity to form a finished sand article, elevating the cope portion of the moldbox from the drag portion thereof, retaining the sand article on the drag portion, and elevating the finished sand article from the drag portion to a position intermediate the cope and the drag.

8. A machine as set forth in claim 1 including a common gas manifold and a plurality of gas burners communicating therewith, and including means for varying the manifold pressure and thermo-couple control means located near the cavity surface adapted to control variation of said pressure.

9. A machine for making foundry sand articles characterized by separable metal box sections defining an article cavity, means for transferring the cooperating box sections from one station to another station, means at the one station for filling said article cavity with a sand mix having a thermosetting binder, heating means for curing said binder within said cavity, means at said another station for ejecting said article from said cavity, said last means including a single actuating cylinder and means actuated thereby for sequentially opening and stripping said article from said cavity, each of said metal box sections being provided with a stripper pin plate relatively movable thereto, and means actuated by said single cylinder providing three stages of relative movement be tween said box sections and stripper plates including a first stage where one of said box sections alone moves relative to said other three elements thereby stripping the article from said box section, a second stage wherein said box section and its associated stripper plate move conjointly together, and a third stage wherein said other stripper plate moves relative to said other box section stripping the article therefrom.

10. A machine as set forth in claim 6 wherein said means for producing successive opening and stripping action include four corner posts commonly actuated by said single cylinder.

References fitted in the file of this patent UNITED STATES PATENTS 1,203,619 Hewitt Nov. 7, 1916 1,550,661 Anderson Aug. 25, 1925 1,695,001 Wood Dec. 11, 1928 1,696,670 Byerlein Dec. 25, 1928 1,950,632 Romph Mar. 13, 1934 1,952,201 Flamrnang et al. Mar. 27, 1934 2,607,967 Springer Aug. 26, 1952 2,724,158 Davis et al. Nov. 22, 1955 2,724,878 Valyi Nov. 29, 1955 2,769,216 Dick et al. Nov. 6, 1956 2,790,217 Tyler Apr. 30, 1957 2,792,600 Polzguter et a1. May 21, 1957 FOREIGN PATENTS 732,747 Great Britain June 29, 1955 1,075,939 France Apr. 14, 1954 1,101,401 France Apr. 25, 1955 OTHER REFERENCES The Foundry, October 1950, pp. 162, 164 and 168. Article by Less.

The Iron Age, April 19, 1951, pages 81-85. Article by Czygan.

Fortune, July 1952, pp. -108, 140, 143 and 144.

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