US2799066A

US2799066A - Method of and apparatus for die casting under vacuum

Info

Publication number: US2799066A
Application number: US403565A
Authority: US
Inventors: Alfred P Federman; David M Morgenstern
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-01-12
Filing date: 1954-01-12
Publication date: 1957-07-16
Anticipated expiration: 1974-07-16
Also published as: BE544613A

Description

A. P. FEDERMAN ETAL July 16, 1957 METHOD OF AND APPARATUS FOR DIE CASTING UNDER VACUUM 4 Sheeis-Sheet 1 Filed Jan. 12, 1954 V INVENTORS 445950 RFEDERMAN y Q4V/0M MO/FGE/YSTE/F/Y ArraRA/EY July 16, 1957 A. P. FEDERMAN ETAL 2,799,066

METHOD OF AND APPARATUS FOR DIE CASTING UNDER VACUUM i E 1M 1] f 2 H},-

7 E INVENTORS 1/2 709 772 ALFRED R/Z'DfiRMA/V AV susrsm 7 3Y0 IO/V/VORG ArmR/ve'y A. P. FEDERMAN ETAL 2,799,066

July 16, 1957 METHOD OF AND APPARATUS FOR DIE CASTING UNDER VACUUM 4 Sheets-Sheet 3 Filed Jan. 12, 1954 I INVENTORS 14L F950 PF'eaEemzv BYQAV/D M Mme-mum Arr-way July 16, 1957 A. P. FEDERMAN ETAL 2,799,056

METHOD OF AND APPARATUS FOR DIE CASTING UNDER VACUUM Filed Jan. 12, 1954 4 Sheets-Sheet 4 R5 4ZFREO RfZ-QERMAN BYDA V/DMMMMENSTERN ArraRA/EY United States Patent METHOD OF AND APPARATUS FOR DIE CASTING UNDER VACUUNI Alfred P. Federman, Cleveland, and David M. Morgenstern, Euclid, Ohio; said Federman, assignor to said Morgenstern Application January 12, 1954, Serial No. 403,565

12 Claims. (Cl. 22-73) This invention is concerned with the trend in the art of die casting which has to do with the evacuation of the die cavity prior to each casting operation for the obvious purpose of producing smooth surface castings that are substantially non-porous and of increased density throughout. This method is commonly referred to as vacuum die casting.

Although the desirability of such a method has long been recognized, means for carrying it out in an economical and commercial way have heretofore been lackmg.

The measure of success in the production of high quality castings by this method depends upon the degree of vacuum that can be created and maintained in the die cavity until supplanted by the molten material; and the practicability of the method from the standpoint of manufacture or mass production, depends largely upon the speed at which the die cavity and communicating spaces can be evacuated to the required extent.

Thorough evacuation hastens the filling of the die cavity since resistance to the action of the charging means is thus lessened.

A further factor entering into production speed is the t me it takes to chill the casting and thus solidify it sufficiently to permit of its ejection from the die. Because of the denser quality of castings made under vacuum, the walls may be made much thinner, wherefore the chilling period is noticeably reduced.

The fundamental object of our invention is to provide an improved method of and apparatus for producing die castings under adequate vacuum to insure a very high quality of product, and at a speed that will meet the requirements of economical mass production.

- Another object of our invention is to provide equipment that can readily be incorporated in a die casting machine otherwise substantially conventional in design and that will render the machine capable of carrying out our improved method efiiciently and economically.

Another object is to provide equipment of the above character wherein certain parts, such as gaskets and packing, that have to be replaced at rather frequent intervals because of wear and deterioration, are relatively inexpensive and are conveniently replaceable without undue delay thereby to expedite and cheapen maintenance and avoid prolonged periods of suspension of operations for reconditioning purposes.

A further object of the invention is to provide a system of controls by which the performance of a complete cycle of operation of the apparatus is rendered automatic.

As is well known in the art, it is necessary to change one set of die members for another each time a machine is set up for producing a different kind or size of article, and die members having liquid cooling facilities, as many have, may differ from one another in the number and location of inlet and outlet connections for the coolant.

The equipment of our invention includes a two-part Patented July 16, 1957 ice hood or enclosure that surrounds the die members, the parts whereof separate substantially on the parting line between said members; and still further objects are, first, to incorporate in the hood or enclosure coupling means, desirably in the form of a manifold fitted with valves for controlling the individual ports thereof, by which the coolant passages of a die member may be communicatively connected to outside supply and drainage conduits, and, secondly, to provide the hood or enclosure with one or more hand holes affording convenient access to the enclosed parts and connections, together with means for normally closing and sealing the same.

The foregoing objects, with othersthat will appear as this description proceeds, are attained in the embodiment of the invention illustrated in the accompanying drawings wherein Fig. 1 is a fragmentary sectional side elevation of a die casting apparatus incorporating our improvements, showing the die members slightly separated and the hood sealed and evacuated, as indicated by the condition of the gasket;

Fig. 2 is a section substantially on the line 22 of Fig. 1, with certain parts beyond the plane of section omitted;

Figs. 3, 4 and 5 are enlarged sectional details of the hood in the region of the sealing gasket, the respective views showing the condition of the gasket when the die members are slightly separated and before the hood is evacuated; after evacuation of the hood, as in Figs. 1 and 10, and when the die members are in contact with each other;

Figs. 6 and 7 are sectional details, at right angles to each other, of a coolant manifold that is incorporated in the hood; Fig. 7 being taken on the line 77 of Fig. 6;

Fig. 8 is a fragmentary sectional side elevation of the apparatus as it appears between cycles of operation;

Fig. 9 is a similar view, showing the die members in contact with each other and with molten material displaced from the charging cylinder into the die cavity, and

Fig. 10 is a diagrammatic representation of the apparatus and the system of controls by which a cycle of operation is rendered automatic, the parts being shown, as in Fig. l, in the positions they occupy at the time of evacuation of the hood and the spaces communieating therewith.

The die casting machine, generally, is of conventional design and construction. It includes the usual stationary die plate 1 and movable die plate 2, the latter being slidable along rods 4 that are connected at their forward ends in the customary manner to the stationary die plate 1.

An enclosure or hood, designated generally by the reference numeral 5, constitutes an important part of our equipment and it comprises a stationary section 6 and a movable section 7. Each of the sections includes top, bottom and side walls, and extending about the open side of the section 6 is an inwardly extending flange 9, to the outer surface of the inner edge portion of which is secured the corresponding portion of a gasket 10. As best appears from Fig. 2, the gasket 10, as well as the cross sectional shape of the hood, is rectangular. This gasket is desirably made of a very durable, flexible plastic material that will withstand, for a considerable length of time, the high temperatures to which the gasket is subjected without its effectiveness becoming impaired. A material especially suited to the purpose is one known to the trade as Neoprene. When relaxed, as under normal conditions, the gasket is extended or, in other words, assumes a dished shape, as illustrated in Figs. 3 and 8. A flange surrounds and extends outwardly from the open side of the hood section 7, and its smooth forward face provides a seat for the gasket 10. The hood sections 6 and '7 include base plates 14 and 2-.5, respectively, and the ends of the sections adjacent said plates are provided with respective flanges 16- and 17 that are secured, by screws 18, to said base plates. The joints between the hood sections and base plates are shown as sealed by gaskets 20. The hood sections are fastened to the die plates 1 and 2 by clamp 22.

Located within the hood, and secured to the base plates 14 and by a suitable number of screws 23 are a stationary die member 24 and a movable die member 25. Ordinarily, in the absence of our equipment, these die members would be attached directly to the die plates 1 and 2. The adjacent faces of the opposed die members are contoured to define between them die cavities 26 that communicate, through runners 27, with a sprue 28. By mechanism later to be described, the die plate 2 is moved toward and from the die plate 1, and in order to insure proper registration of the die members as they approach each other, locating pins or dowels 30, that are carried by the movable die member 25, enter hushed recesses 31 in the stationary die member 24.

The ejecting mechanism by which castings are dislodged from the movable die member, includes a head 35 that is located to the rear of the body portion of said member and to which are secured ejecting pins 36. These pins extend through bores in the movable die member and when the dies are in condition to receive a charge of molten material, the forward ends of said pins are substantially flush with the exposed surface of the movable die member. The retraction of the ejecting pins to bring about this condition is effected by push rods 37 that are fastened to the head 35 and are guided through bores of the movable die member. As the movable die member closely approaches the stationary die member 24, the forward ends of the push rods 37 engage the latter die member thereby to arrest forward movement of the head and consequently of the ejecting pins 36, while the die member 25 completes its forward travel.

When the die plate 2, with the parts carried thereby, is being retracted to the position shown in Fig. 8, actuators or plungers 40, that are slidably supported by said die plate 2, engage the usual stationary abutment 41, thereby to arrest further rearward movement of the head 35 and the ejecting pins 36, along with the push rods 37. It is this action that causes the casting to be dislodged from the movable die member.

A feature of our invention that distinguishes the present apparatus from the conventional machine, is the sealing and lubricating means for the actuators or plungers 4i). These plungers are guided in bushings 43 that fit tightly within holes in the die plate 2. Intermediate the ends of the bore of each bushing 43 is a relatively wide circumferential channel within which a ring 44 of belt or other absorbent material is confined, the same being saturated with a lubricating oil. Within circumferential grooves beyond the ends of the ring 44 are confined O-r'ings 46 that seal the bushing against leakage about the plunger and serve as wipers to confine the oil to the region between said O-rings. An annular groove in the inner end of each bushing 43 contains an O-ring or other suitable packing means 47 for preventing leakage inwardly across the end of the bushing and about the corresponding plunger and through the hole in the base plate 15 through which the inner end of the plunger projects.

Located forwardly of the stationary die plate 1 is a pot or crucible 5i), common to die casting machines employed for handling zinc, lead, or tin alloys, or other materials having similar characteristics. Suitable heating means, such as a gas burner (not shown) is situated in heat exchange relation to the crucible for keeping the contents thereof in molten condition. Supported in the usual way within the crucible 50 is acharging chamber or cylinder 52 that communicates, through a port 53, with the crucible 50, and, through a so-called gooseneck 54 and nozzle 55, with the sprue 28 of the stationary die member 24, the die plate 1 and the base plate 14 being apertured for the accommodation of the nozzle. A charging piston 58 is reciprocable in the cylinder 52 and the rod 59 thereof has connection, through the usual coupling 60, with the rod 61 of a piston 62 that operates in a cylinder 63. This latter cylinder is a part of a pressure fluid system, desirably hydraulic hereinafter to be described, and by means of which various parts of the apparatus are operated.

The feeding means for the molten material, as so far described, will be recognized as conventional in character, and to adapt it to our purpose, a valve 65 is employed for closing the port 53 through which the crucible 50 and the charging cylinder 52 communicate. This valve is carried by the lower end of a lever 66 that is pivotally connected at its upper end to the rod 68 of a piston 69 that operates in a cylinder 70. The lever 66 is fulcrumed intermediate its ends in a bracket 72 that is shown as extending laterally from the charging cylinder 52. The cylinder is also included inthe pressure fluid system referred to above.

With reference to Fig. 10, there is a further cylinder 75 that forms a part of said system and is a constituent of the power means for reciprocating the movable die plate 2 and the parts carried thereby. Working within the cylinder 75 is a piston 76, the rod 77 of which has operative connection, through links 78, with toggle joints 80. Each toggle joint is pivotally connected at one of its ends to the movable die plate 2 and at its opposite end to a stationary part 33 of the die casting machine.

In Fig. 10 is also shown a so-called vacuum tank or enclosure 85. Communication between this tank and the hood 5 is had through

pipes

36 and 87 of relatively large capacity, shown as joined through two branches of a T 88. The other branch of said T has connection with a valve 90 that is biased, as by a spring 91, to open posi tion, thereby to place the interior of the hood 5 in communication with the atmosphere. The valve 90 is closed by means of a solenoid 92. The pipe 86 is communicatively connected, through a T 94 and a pipe 95, with a suction pump 96, shown as driven by an electric motor 97.

Valves

98 and 99 are located in the pipe 86 on opposite sides of the T 94. These valves are biased to open position and are adapted to be closed by means of pres sure fluid under the control of the

respective solenoids

100 and 101. When said solenoids are deenergized, the pressure fluidhas access to said valves and holds them closed, as will hereinafter more fully appear.

By means of the suction pump 96, a vacuum of relatively high degree, say approximately 29 inches, is maintained in the tank 85. The interior of the hood 5 may immediately be placed in communication with the tank or enclosure 85, as well as with the suction pump 96, by opening the

valves

98 and 99. As will later appear, when approximate equillibrium is attained between the hood and tank, the valve 98 will be closed and communication with the hood will be confined to the suction pump 96. This continues through the casting operation, after which the valve 99 will be closed and the valves 98 and 90 opened, resulting in the reestablishment of communication between the pump and tank, and the opening of the space enclosed by the hood 5 to the atmosphere. These several steps are included in a cycle of operation later to be described.

Before describing the operating and control system by which a cycle of operation is automatically carried out, we may explain that it is common to provide passages, such as those designated 103, in either or both of the die members, through which Water or other suitable liquid coolant may be circulated. Also, for the production of different sizes and styles of castings, different die members have to be used, Some die members, because of the shape and character of'the die cavities, haveto be provided with circulating passages for the coolant that may have'a plurality of inlet and outlet connections. To pro vide for these different possible conditions we include in the hood a manifold designated 105, sectional details of which constitute Figs. 6 and 7 of the drawings. The manifold is shown as an elongated body that has

bores

107 and 108 extending inwardly from its opposite ends, one constituting an outlet passage and the other an inlet passage for the coolant.

Ports

109 and 110 lead downwardly from said bores and open through the bottom of the body, adjacent which said ports are enlarged and threaded for the reception of the threaded ends of elbow fittings 112. The

ports

109 and 110 are controlled by valves 113, the stems of which are threaded through the top of the body in alignment with said ports. Each

bore

107 and 108 has a hose connection at its outer end, that of the bore 107 being shown at 115 in Fig. 6. The manifold is shown as applied to the hood section 7 immediately to the rear of the flange 12, and one or more of the elbow fittings 112 of the manifold are adapted to be connected with similar fittings of the underlying die member through loops of tubing designated 116 that are attached by unions to the fittings of the manifold and die member. Access to the interior of the hood, for making the foregoing connections and for other purposes, is had through one or more hand holes, such as that designated 118, the same being shown as located in the top wall of the section 7. The hand hole is closed by a plate 119, sealed to the underlying wall about the hand hole by a gasket 120.

As previously mentioned, the

cylinders

63, 70 and 75 are included in a pressure fluid system, desirably hydraulic. In the case of a hydraulic system, there is the usual tank from which the liquid is drawn and to which it is returned. A pump, usually operated by an electric motor, withdraws the liquid from the tank and delivers it at the required pressure to the cylinders, under the control of suitable valves. Since hydraulic systems of this sort are so well known it is regarded unnecessary to show the tank and pump and the part of the system involving them.

The omission of these parts simplifies considerably the diagram of Fig. 10. This view does include, however, hydraulic valves, preferably of the spool type, for controlling the admission of the liquid to the various cylinders, and the escape of the liquid therefrom. Associated with the

respective cylinders

63 and 70 are valves 125 and 126, while two valves, 127 and 128, are associated with the cylinder 75 for a reason that will presently appear.

It may be explained at this point that relatively large spool valves are used in conjunction with the cylinders 63 and 75, because these valves are required to handle liquid in considerable volume, this being indicated by the fact that, in practice, the conduits or pipes used therewith are in excess of one inch. On the other hand, a relatively small spool valve is used with the cylinder 70, the pipes or conduits leading to and from the same being, in practice, about one-half inch. In the diagrammatic view of Fig. 10, however, relative sizes or proportions are ignored in favor of clarity of illustration. Because of the size of the

valves

125, 127 and 128 an appreciable amount of power is required to shift the spools thereof. For this purpose we employ a pressure fluid system, preferably pneumatic. Such system involves, besides a motor driven air pump or compressor (not shown), pilot valves designated 130, 131 and 132, associated, respectively, with the larger

hydraulic valves

125, 127 and 128. Since hydraulic valve 126 is considerably smaller than the others it requires less power to shift its spool. Consequently the spool of this valve can readily be moved in one direction by a spring, and in the opposite direction by a solenoid. The solenoid for operating the hydraulic valve 126, and those used to actuate the

pilot valves

130, 131 and 132, will be designated by reference characters in 6 the course of the following description. Also, the electric circuits, timers, and other devices involved in the operating and control system will be introduced as this description proceeds.

Referring to Fig. 10, the positive and negative sides of the circuit that supplies current to the system are designated, respectively, and 136. In the former is the main switch 137, the closing of which conditions the apparatus for operation by completing a circuit designated 140. This latter circuit includes the solenoid 100, hereinbefore described as controlling the operation of the valve 98. It is clear from the illustration that the valve 98 is biased to open position and is closed when pressure fluid, such as compressed air, is admitted to the actuating part of the valve under the control of a pilot valve of the spool type designated 141. This pilot valve is biased to closed position by a spring 142 and is shifted to open position'by the solenoid 100. Inasmuch as this solenoid is presently energized by the closing of the main switch 137, the valve 98 opens to establish communication between the tank 85 and pump 96. Also included in the circuit is a circuit closer 145 that is biased toward closed position and is opened in the course of a cycle of operation of the apparatus, as will presently appear.

146 designates a switch, preferably of the push button type, that, upon actuation, initiates a cycle of operation of the apparatus. This switch is, therefore, termed the starting switch. Associated with it is a holding circuit designated 147 that includes a switch 148 that is biased to open position and is closed by a solenoid 149 when energized. As will clearly appear from the diagrammatic representation of this device, when the starting switch is closed current will be delivered to the solenoid 149, whereupon switch 148 will be rendered effective to close the holding circuit, so that the starting switch may now be released. A circuit designated 150 will thus be closed which includes a solenoid 151 that operates the pilot valve 131, said circuit including a circuit closer 152 that is biased toward closed position.

Upon energization of the solenoid 151, the pilot valve 131 is moved in a direction to deliver compressed air to the left hand end of the hydraulic valve 127 and shift the spool of the latter to a position that will result in de livery of pressure fluid to the hydraulic valve 128. At the beginning of this present phase of the operation the valve 128 is in a condition to permit the pressure fluid to pass on to the cylinder 75 and move the piston 76 therein to approximately the position shown in Fig. 10 which disposes the movable die member 25 in closely spaced relation to the stationary die member 24. At that moment a so-called die cracking limit switch 155 is closed by a cam 156 that is shown as connected, through a rod 157, to the piston 76. This establishes a circuit designated 160 that includes a solenoid 161.. This solenoid, now being energized, shifts the spool of the pilot valve 132 to a position that results in the delivery of compressed air to the right hand end of the hydraulic valve 128, shifting the latter valve to the position shown which results in cutting 011? the supply of pressure fluid to the left hand end of the cylinder 75. It will be observed from Fig. 10 that the liquid from the right hand end of the cylinder 75, in advance of the piston 76, is permitted to pass through the valve 127 and on to the tank or reservoir of the system. The present electric circuit 160 includes, also, a circuit closer 162 that is biased to closed position.

It Will be seen from the foregoing that, upon closing of the die cracking limit switch 155, the piston 76 is relieved of the impelling influence of the pressure fluid. However, through momentum of the moving parts, the piston will coast for a slight distance and move the cam 156 far enough to close what may be termed a die cracked limit switch, designated 163. This switch closes a circuit 164 which separates into three

branch circuits

165, 166 and 167, the branch 166 including a circuit 7 closer 170 that is biased to closed position and beyond which said circuit 166 divides into sub-branch circuits 171 and 172.

The branch circuit 165 includes an electric timer 174 of conventional type which has operative connection with the previously mentioned circuit closer 162 that is in the circuit 160. The timer, upon being energized, after an interval of time for which it is set, functions to open said circuit closer 162. However, during this interval of time, several things occur. it will be observed that the presently closed sub-branch circuit 171 contains the solenoid 92. Accordingly this solenoid is energized to close valve 90. It should be remembered that, with the dies in cracked relation, the sections 6 and 7 of the hood are close enough together to seal the joint between said sections (see Figs. 3 and 4). It will further be observed that the sub-branch circuit 172 includes a solenoid 175 which, when energized, conditions the hydraulic valve 126 to direct pressure fluid into the left hand end of the cylinder 76 and permit return of fluid from the opposite end of the cylinder to the tank of the hydraulic system. The resultant movement of the piston 69 causes the valve to close the inlet port of the charging cylinder 52 so that, when the hood and die cavity are as will presently appear, evacuated, there will be no tendency for atmospheric pressure to displace molten material from the crucible 50 through said port and communicating spaces to the space between the dies.

The branch circuit 167 includes a circuit closer 176 and a switch 177, the latter being operatively associated with the piston 69, and being biased to open position. The switch is closed by a thrust element 178 that is carried by the piston when the latter approaches the right hand end of its stroke (as the parts are viewed in Fig. 10). Beyond the switch 177, so to speak, the branch circuit 167 divides into

sub-branch circuits

180 and 181. The former sub-branch circuit includes an electric timer 182 that has operative connection, as indicated in the diagram, with the circuit closer in the circuit 140. This timer, when energized, will, after a brief interval of time for which the instrument is set, open the circuit 140, thereby to deenergize the solenoid 16d and allow the spring 142 to shift the pilot valve Ml to a position that will effect the closing of the valve 98. In the meantime, the solenoid 1M, which is in the sub-branch circuit 161, will be energized and thereby condition a pilot valve 184 to cause valve 99, wherewith it is associated, to open. At the present time, therefore, the space enclosed by the hood 5 is in communication solely with the suction pump 96.

While the condition just described prevails, the time interval, for which the electric timer 174 is set, comes to an end and the timer functions to open the circuit 160. This circuit, as will be recalled, includes the die cracking limit switch and the solenoid 161. Therefore, said solenoid will be deenergized, whereupon the spring loaded spool of the pilot valve 132 will shift to the right and cause similar movement of the corresponding element of the hydraulic valve 125, resulting in delivery of pressure fluid again to the left hand or rear end of the cylinder '75. As a consequence, the piston 76 will be moved to the limit of its forward stroke, and the movable die member 25 will be brought into contact with the stationary die member 24, thereby to close the die cavity. It should be kept in mind, however, that the parts are shown in Fig. 10 in the positions they occupy when the die members are cracked and the hood is evacuated, and not in the positions last referred to, when the die members are together and the die cavity closed, as illustrated in Fig. 9.

Situated in the path of the cam 156 is a so-called die closed limit switch 165. This switch is biased to open position, and is closed by said cam When the piston 76 reaches the right hand end of its stroke, as above explained. The switch 185 is in a circuit 186 that divides into four

branches

188, 189, 190 and 191. The first of these branches, 188, includes a circuit closer 193 and a solenoid 195, associated with the previously mentioned pilot valve 136. Said pilot valve is biased to a position wherein it directs compressed air to the lower end of the hydraulic valve 125, thereby to position the spool of the latter valve so as to direct pressure fluid to the bottom of the cylinder 63 and lift the piston 62 therein, thereby effecting retraction of the charging piston 58. However, when the solenoid 195 is energized, these conditions will be reversed and the pressure fluid will be directed to the top of the cylinder 63 thereby to depress the piston 62 and project the charging piston 58 toward the bottom of the charging cylinder 52, resulting in molten material being displaced through the gooseneck 54, nozzle 55 into the space between the die members.

The branch circuit 189 includes an electromagnetic means or solenoid 196, that is operatively associated with the circuit closer 176. Accordingly, energization of this solenoid results in opening the circuit 167 and its branches 16b and 181. The branch circuit 190 includes an electric timer E97, that is operatively connected to the two previously mentioned

circuit closers

170 and 193 and functions, after a relatively brief interval of time for which the instrument is set, to open the circuit 166, with its branches 171 and 172, and the circuit 188. In the branch circuit 191 is an electric timer 198 that has operative connection with the circuit closer 152 in the circuit 150. Accordingly, a given interval of time after this final. circuit 191 is energized, the circuit 150, through which a cycle of operation is initiated, and all other circuits controlled by the starting switch 146, will be opened thereby to conclude the cycle.

With the character and performance of the control system in mind, the operation of the apparatus may be reviewed briefly as follows: The apparatus is placed in operative condition by closing the main switch 137. This establishes communication between the suction pump 96 and the tank 85, it being assumed that the motor 97 is energized at all times the die casting apparatus is in operation. A cycle is started by momentarily depressing the button 146. The circuit closed by the starting switch is locked in by the action of solenoid 149 and switch 148, as previously explained. Henceforth, the cycle progresses automatically. The movable die member is advanced toward the stationary die member 24 and is stopped with the die members slightly spaced apart or in cracked position. The sections of the hood 5 are brought into a similar relationship and the gasket 10 seals the joint between them. The valve 65 is closed to shut olf communication between the crucible and charging cylinder and the valve 99 opened. The opening of the latter valve subjects the interior of the hood to the relatively high vacuum that prevails in the enclosure or tank 85. This results in an almost instantaneous evacuation of the hood including, of course, the die cavity, which is, at this time, in free communication with the interior of the hood, and immediately thereafter the valve 98 will close because of the opening of the circuit closer 145 by the timer 182. This action is timed to occur at about the moment of equillibrium between the hood and tank, and the hood is now subjected solely to the evacuating action of the pump 96. While this condition prevails, the movable die member 25 is brought into contact with the stationary die member 24 to close the die cavity 26, and pressure fluid is delivered to the top of the cylinder 63, thereby, through the piston 62 and its operative connections with the charging piston 53, to depress the latter to force molten material from the cylinder 52 through the intercommunicating passages into the die cavity. A chilling period of required duration now prevails under the control of the timer 198, and just prior to the termination of such period the valve 99 closes and the valve 98 reopens. With the hood 5 now out off from the suction apparatus, the valve 90 is caused to open and admit air at atmospheric pressure to the hood. The

electric timer 198 then functions to open all circuits excepting circuit 140. One result of this is to cause the hydraulic valves 127 and 128 to direct pressure fluid to the forward end of the cylinder 75 so as to retract the piston 76 and allow the fluid from the opposite end of the cylinder to return to the tank. As the piston 76 moves rearwardly it will cause retraction of the die member 25, the opening of the hood 5, and the actuation of the ejecting mechanism to dislodge the casting. The parts are thus illustrated in Fig. 8, which view shows the condition of the apparatus between cycles, with the charging piston 58 retracted and the valve 65 open.

While we have disclosed herein a highly satisfactory embodiment of our invention, the same is to be regarded as illustrative rather than as limiting, since changes and modifications obviously may be made without departing from the spirit of the invention. Therefore it will be understood that the invention is not limited to the structural details and circuit arrangements shown and described further than is required by the terms of the appended claims.

Our invention further comprehends an improvement over and beyond the conventional method of die casting wherein molten material is deposited in a charging chamber that is normally open to the influence of atmospheric pressure and that is in constant communication with a die cavity defined by and between two relatively movable die members.

The improvement that constitutes our invention in its more comprehensive aspect, and as it relates to the process, consists in moving the die members initially into closely spaced relation to each other, and approximately simultaneously therewith enveloping the die members in a substantially airtight enclosure and shutting off the charging chamber from the influence of atmospheric pressure; establishing communication between the aforesaid enclosure and a second enclosure of considerably greater volume than the first enclosure and in which second enclosure is maintained a vacuum of relatively high degree, as for example 25 to 27 inches of mercury. When communication is established between the enclosures, as aforesaid, a vacuum is immediately drawn in the first mentioned enclosure of from 15 to 25 inches of mercury.

With the foregoing conditions prevailing, the die members are moved into engagement with each other so as to close the die cavity. The molten material is then impelled from the charging chamber into the die cavity at a piston pressure that depends largely upon the size of the machine involved. It may run from 100 pounds in a relatively small machine to 2500 pounds in a large machine. Next, the molten material in the die cavity is chilled sufliciently to solidify it, and communication between the two enclosures is shut oif, and the first mentioned enclosureis subjected to substantially atmospheric pressure. Said first mentioned enclosure is then opened to afford access to the die members and, at substantially the same time, the die members are moved apart for the removal of the casting. At any time after substantially atmospheric pressure prevails in the first mentioned en'- closure, the charging chamber is again subjected to the influence of atmospheric pressure.

Incidentally, our invention is adapted to the handling of any of the well knownmetals and metal alloys of the class commonly employed in the art of die casting, or other materials known to have the melting, solidifying, and other characteristics of such metals and metal alloys; and, as is well known, the metals and alloys of the class referred to may vary considerably as to melting point. An example of a metal alloy of the aforesaid class is one composed of 95 plus percent of zinc, 3 /2 plus percent of aluminum, with traces of magnesium and copper in sufficient amount to make up 100 percent. This alloy has a melting point of anywhere between 760 F. and 800 F.

It will be understood that all of the herein recited factors relative to materials, melting points, and negative pressures, are familiar or obvious to those skilled in the art, and are to be taken as illustrative and as not affecting the claimed invention.

Having thus described our invention, what we claim is:

1. Equipment incorporated in a die casting machine of the type including die members that are relatively movable toward and from each other and by and between which a die cavity is defined, a crucible for molten material, a charging chamber in communication with the crucible and so related thereto that molten material flows by gravity from the crucible into said chamber, communicative connections between the charging chamber and the die cavity, displacement means for forcing molten material from the charging chamber into the die cavity, ejecting mechanism operatively associated with one of the die members, and actuating means for the ejecting mechanism; said equipment comprising a valve for shutting off communication between the crucible and the charging chamber, a two-part enclosure enveloping the die members, the parts whereof are relatively movable with the die members and are separable in the region of the parting line between said members, the enclosure being otherwise substantially airtight, sealing means for closing the joint between the two parts of the enclosure involving a normally extended flexible gasket carried by one part and a gasket engaging seat carried by the other part of the enclosure, a second enclosure having a volume many times that of the first mentioned enclosure in communication with the latter, a first valve means controlling communication between the enclosures, a second valve means for opening the first mentioned enclosure to the atmosphere, suction apparatus for creating and maintaining a vacuum of relatively high degree in the second enclosure, power means for relatively moving the die members, initially, into closely spaced relation to each other and thereafter into contact and for imparting like movement to the parts of the first mentioned enclosure with the flexible gasket contacting said seat at the conclusion of the initial movement and thereafter, the first mentioned enclosure being constructed to permit said actuating means for the ejecting mechanism to extend from the interior to the exterior of said first mentioned enclosure and to move independently thereof, and packing means between said actuating means and the surrounding part of the first mentioned enclosure.

'2. The combination and arrangement of parts defined by claim 1, and, in conjunction therewith, control means operatively connected to said displacement means and to said valve and valve means, and to said power means for effecting the actuation of the power means to relatively move the die members and the enclosure parts, respectively initially into closely spaced relation to each other, with the flexible gasket in contact with said seat; the closing of said valve; the opening of the first valve means to evacuate the enclosure and cause the gasket to be urged against the seat by atmospheric pressure; the further actuation of the power means to move the die members into contact with each other and close the die cavity; the operation of the displacement means; the closing of the first valve means and the opening of the second valve means; the actuation of the power means to move the die members and enclosure parts, respectively, away from each other and cause the ejecting mechanism through its actuating means to dislodge the casting from the die cavity, and the opening of the aforesaid valve.

3. Equipment incorporated in a die casting machine of the type including two die members that are relatively movable toward and from each other and by and between which a die cavity is defined, power means for so moving said die members, a crucible for molten material, a charging chamber in communication with the crucible and so related thereto that molten material flows by gravity from the crucible into said chamber, communicative between the charging chamber and the die cavity, displacement means for forcing molten material from the charging chamber into the die cavity, and ejecting mechanism operatively associated with one of the die members; said equipment comprising a first valve for shutting off communication between the crucible and the charging chamber, a two-part enclosure enveloping the die members, the parts whereof are relatively movable with the die members and are separable in the region of the parting line between said members, the enclosure otherwise being substantially airtight, sealing means for closing the joint between the two parts of the enclosure involving a normally extended flexible gasket carried by one part and a gasket engaging seat carried by the other part of the enclosure, a tank having a volume many times that of said enclosure, a conduit of relatively large capacity through which the tank communicates with the enclosure, the conduit having an opening leading to the atmosphere, a second valve controlling said opening, a suction pump in communication with said conduit between said opening and the tank, a third valve, the same being included in the conduit between the aforesaid opening and the suction pump, a fourth valve, the same being located in the conduit between the suction pump and tank, and control means operatively connected to said displacement means, to the aforesaid valves, and to said power means, for effecting the closing of the first valve; the actuation of the power means to relatively move the die members and the enclosure parts, respectively, initially into closely spaced relation to each other, with the flexible gasket in contact with said seat; the opening of the third and fourth valves to establish communication between the enclosure and the tank and suction pump; the closing of the fourth valve; the further actuation of the power means to move the die members into contact with each other and close the die cavity; the operation of the displacement means, the closing of the third valve and the opening of the second and fourth valves; the actuation of the power means to move the die members and enclosure parts, respectively, away from each other and cause the ejecting mechanism to dislodge the casting, and the opening of the first mentioned valve.

4. Equipment for incorporation in a conventional die casting machine, such machine being characterized by die members that are relatively movable toward and from each other and by and between which a die cavity is defined, said cavity being substantially closed and conditioned to receive a charge of molten material when said members are in engagement with each other, and power mechanism for effecting relative movement between the die members; said equipment including "a separable enclosure enveloping the die members and made up of two parts that are movable with and are sealed with respect to the respective die members, each part including a peripheral wall section, the wall sections of the two parts meeting in substantially the plane of separation between the die members, normally extended sealing mean for closing the joint between the meeting ends of said wall sections when said sections are relatively near each other and before the sections finally meet, means evacuating said enclosure when initially sealed by said sealing means, and means modifying the operation of said power mechanism to momentarily restrain relative movement between the die members upon initial evacuation of said enclosure whereby the space between the die members including the die cavity is subjected to the same degree of evacuation as the enclosure, and during which evacuation said power mechanism functions to relatively move the die members together to close the die cavity in preparation to receive a charge of molten material.

5. Equipment for incorporation in a conventional die casting machine, such machine being characterized by die plates that are relatively movable toward and from each other and die members detachably connected to and movable with said plates and by and between which members a die cavity is defined, said cavity being substantially closed and conditioned to receive a charge of molten material when said members are in engagement with each other, and power mechanism for effecting relative movement between the die plates and accordingly between the die members; said equipment comprising a separable enclosure enveloping the die members and made up of two parts that are carried by and are sealed to the respective die plates, each part including a peripheral wall section, the wall sections of the two parts meeting in substan tially the plane of separation between the die members, normally extended sealing means for closing the joint between the meeting ends of said wall sections when said sections are relatively near each other and before the sections finally meet, means evacuating said enclosure when initially sealed by said sealing means, and means modifying the operation of said power mechanism to momentarily restrain relative movement between the die members upon initial evacuation of said enclosure, whereby the space between the die members including the die cavity is subjected to the same degree of evacuation as the enclosure, and during which evacuation said power mechanism functions to relatively move the die members together to close the die cavity in preparation to receive a charge of molten material.

6. Equipment for incorporation in a conventional die casting machine, such machine being characterized by die plates that are relatively movable toward and from each other and die members detachably connected to and movable with said plates and by and between which members a die cavity is defined, said cavity being substantially closed and conditioned to receive a charge of molten material when said members are in engagement with each other, power mechanism for effecting relative movement between the die plates and accordingly between the die members, a charging chamber in communication with the die cavity, and charging means for forcing molten material from the charging chamber into the die cavity; said equipment comprising a separable enclosure enveloping the die members and made up of two parts that are movable with and are sealed with respect to the respective die members, each part including a peripheral wall section, the Wall sections of the two parts meeting in substantially the plane of separation between the die members, a second enclosure of relatively large volume in communication with the first mentioned enclosure, a first valve means controlling communication between the enclosures, suction apparatus for creating and maintaining a vacuum of relatively high degree in the second enclosure, normally extended sealing means for closing the joint between the meeting ends of said wall sections when said ends are spaced apart but are relatively near each other, a second valve means for admitting air to the first mentioned enclosure, the aforesaid power mechanism acting to effect relative movement of the die plates, and a control system by which the aforesaid first valve means and the power mechanism are operatively connected and their actions coordinated so as to cause said mechanism to effect an initial relative movement of the die plates such as will locate the die members in slightly spaced relation to each other and dispose the wall sections of the first mentioned enclosure with their meeting ends in closely spaced relation to each other with said sealing means effective to close the joint between said wall sections; cause said first valve means to open and thereby establish communication between the enclosures so as to quickly evacuate the first mentioned enclosure; cause the power mechanism to move the die members, through the intervention of the die plates, into contact with each other to close the die cavity in preparation for a casting operation; cause said charging means to force molten material from the charging chamber into the die cavity; cause the aforesaid first valve means to close; cause said second valve means to open and admit air to the first mentioned enclosure, and cause said mechanism to effect reverse relative movement of the die plates and consequently of the die members and also of the peripheral wall sections of the first mentioned enclosure.

7. Equipment for incorporation in a conventional die casting machine, such machine being characterized by die plates that are relatively movable toward and from each other and die members detachably connected to and movable with said plates and by and between which members a die cavity is defined, said cavity being substantially closed and conditioned to receive a charge of molten material when said members are in engagement with each other, power mechanism for effecting relative movement between the die plates and accordingly between the die members, a crucible for molten material open to the atmosphere, a charging chamber in communication with the crucible and so related thereto that the molten material flows by gravity from the crucible into said chamber, communicative connections between said charging chamber and the die cavity, and displacement means for forcing molten material from the charging chamber into the die cavity; said equipment comprising a valve for shutting off communication between the crucible and the charging chamber, a separable enclosure enveloping the die members and made up of two parts that are carried by and are sealed to the respective die plates, each part including a peripheral wall section, the wall sections of the two parts meeting in substantially the plane of separation between the die members, a second enclosure of relatively large volume in communication with the first mentioned enclosure, a first valve means controlling communication between the enclosures, suction apparatus for creating and maintaining a vacuum of relatively high degree in the second enclosure, normally extended sealing means for closing the joint between the meeting ends of said wall sections when said ends are spaced relatively near but apart from each other, a second valve means for admitting air to the first mentioned enclosure, the aforesaid power mechanism acting to elfect relative movement of the die plates, and a control system by which said valve, the aforesaid first and second valve means and the power mechanism are operatively connected and their actions coordinated so as to sequentially cause said mechanism to effect an initial relative movement of the die plates such as will locate the die members in slightly spaced relation to each other and dispose said wall sections in closely spaced relation to each other with said sealing means effective to close the joint between said sections; cause the aforesaid valve to close; cause said first valve means to open; cause the power mechanism to move the die members, through the intervention of the die plates, into contact with each other; cause said displacement means to force molten material from the charging chamber into the die cavity; cause the aforesaid first valve means to close; cause said second valve means to open; cause said mechanism to effect reverse relative movement of the die plates, die members, and the peripheral wall sections of the first mentioned enclosure, and open the aforesaid valve to reestablish communication between the crucible and the charging chamber.

8. Equipment for incorporation in a conventional die casting machine, such machine being characterized by die plates that are relatively movable toward and from each other and die members detachably connected to and movable with said plates and by and between which members a die cavity is defined, said cavity being substantially closed and conditioned to reecive a charge of molten material when said members are in engagement with each other, power mechanism for effecting relative movement between the die plates, a crucible for molten material open to the atmosphere, a charging chamber in communication with the crucible and so related thereto that the molten material flows by gravity from the crucible into said chamber, communicative connections between said charging chamber and the die cavity, and displacement means for forcing molten material from the charging chamber into the die cavity, said equipment comprising a valve for shutting olf communication between the crucible and the charging chamber, actuating means for said valve, a separable enclosure enveloping the die members and made up of two parts that are carried by and are sealed to the respective die plates, each part including a peripheral wall section, the wall sections of the two parts meeting in substantially the plane of separation between the die members, normally extended sealing means for closing the joint between the meeting ends of said wall sections when said sections are relatively near each other and before the sections finally meet, means evacuating said enclosure when initially sealed by said sealing means, and a control system by which said valve actuating means, the evacuating means, and the power mechanism are operatively connected and their actions coordinated so as to sequentially cause said mechanism to effect an initial relative movement of the die plates such as will locate the die members in slightly spaced relation to each other and disposed said wall sections in correspondingly spaced relationship, and with said sealing means effective to close the joint between said sections; cause said valve to close and the evacuating means to function; cause the power mechanism to move the die members, through the intervention of the die plates, into contact with each other; cause said displacement means to force molten material from the charging chamber into the die cavity; cause the aforesaid valve to open, and cause said mechanism to effect reverse relative movement of the die plates and members and the peripheral wall sections of the enclosure.

9. In the method of die casting wherein molten material is delivered to a die cavity defined by and between two relatively movable die members, the improvement which consists in relatively moving the die members initially into closely spaced relation to each other and simultaneously enveloping the die members in a substantially airtight enclosure; evacuating said enclosure while the die members are in said spaced relation to each other; moving the die members into engagement with each other to closethe die cavity while the enclosure is in evacuated condition; delivering molten material to the die cavity; chilling said material to solidify it; subjecting the enclosure to substantially atmospheric pressure and thereafter opening the enclosure in order to gain access to the die members and at the same time moving the die members apart for the removal of the casting.

10.- In the method of die casting wherein molten material is deposited in a charging chamber that is normally open to the influence of atmospheric pressure and is constantly in communication with a die cavity defined by and between two relatively movable die members, the improvement which consists in relatively moving the die members initially into closely spaced relation to each other and simultaneously enveloping the die members in a substantially airtight enclosure and shutting off the charging chamber from the influence of atmospheric pressure; evacuating the enclosure while the die members are in said spaced relation to each other; moving the die members into engagement with each other to close the die cavity while said enclosure is in evacuated condition; forcing the molten material from the charging chamber into the die cavity; chilling the material to solidify it; subjecting the enclosure to substantially atmospheric pressure; opening the enclosure in order to gain access to the die members and at the same time moving the die members apart for the removal of the casting, and opening the charging chamber to the influence of atmospheric pressure.

11. In the method of die casting wherein molten material is deposited in a charging chamber that is normally open to the influence of atmospheric pressure and that is constantly in communication with a die cavity defined by and between two relatively movable die members, the improvement which consists in moving the die members initially into closely spaced relation to each other and simultaneously enveloping the die members in a substantially airtight enclosure and shutting off the charging chamber from the influence of atmospheric pressure; establishing free communication between said enclosure and a second enclosure of considerably greater volume than the first enclosure and in which second enclosure is maintained a vacuum of relatively high degree that is quickly communicated to the first mentioned enclosure; while said enclosures are in communication with each other, moving the die members into engagement with each other to close the die cavity; forcing the molten material from the charging chamber into the die cavity; chilling said material to solidify it; closing off communication between the two enclosures and subjecting the first mentioned enclosure to substantially atmospheric pressure; opening said first mentioned enclosure in order to afford access to the die members; substantially at the same time moving the die members apart for the removal of the casting, and opening the charging chamber to the influence of atmospheric pressure.

12. In the method of die casting wherein molten material is delivered to a die cavity defined by and between two relatively movable die members, with which members are associated, respectively, in substantially fixed relation thereto, two parts of an enclosure that encompass the die members; the improvement which consists in relatively moving the die members and parts of the enclosure initially into closely spaced relation and sealing the joint between the parts of the enclosure thereby to envelop the die members in a substantially airtight enclosure; evacuating said enclosure while the die members are in said spaced relation; moving the die members into engagement with each other to close the die cavity while the enclosure is in evacuated condition; delivering molten material to the die cavity; chilling said material to solidify it; efiecting substantially atmospheric pressure in the enclosure, and moving the parts of the enclosure and the die members apart for the removal of the casting.

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