US3181212A

US3181212A - Die casting machine

Info

Publication number: US3181212A
Application number: US198915A
Authority: US
Inventors: Madwed Albert
Original assignee: Automatic Casting Corp
Current assignee: Automatic Casting Corp
Priority date: 1962-05-31
Filing date: 1962-05-31
Publication date: 1965-05-04
Anticipated expiration: 1982-05-04

Description

y 1965 A. MADWED 3,181,212 DIE CASTING MACHINE Filed May 51, 1962 2 Sheets-Sheet 1 IN VEN TOR.

BY 147 at Mqdwei 'TORNEY3 y 4, 1965 A. MADWED 3,181,212

DIE CASTING MACHINE Filed May 51, 1962 2 Sheets-Sheet 2 .a/ J2 125E !g! 20 x5 INVENLFOR. #03871 Mad wed United States Patent 3,181,212 DIE @ASTING MACE-ENE Albert Madwed, Bridgeport, (Iona, assignor, hy mesne assignments, to Automatic Casting Corporation, Bridgeport, Conn., a corporation of Connecticut Filed May 31, 1962, Ser. No. 1%,?15 4 Claims. (til. 22-

The present invention relates to die casting machines and more particularly to improvements in die casting machines whereby the problems arising from the injection of excessive amounts of air into the die cavity are overcome while the necessity of using expensive and troublesome vacuum equipment is avoided.

. Conventional die casting machines comprises a pair of dies, one of which is movable and the other of which is mounted in stationary position on the machine and is provided with an opening through which the molten casting metal is injected. The molten metal is supplied by a pot on the machine and is injected into the die cavity, formed when the movable and stationary dies are brought together, by means of a plunger or piston which forces the molten metal through a gooseneck-type passage and through a nozzle at the end thereof into the die cavity. Metal is supplied to the gooseneck-type passage from a heated pot by a fill port which is closed off by the plunger when the plunger starts down. After the plunger forces metal through the goosenecl: and nozzle and into the die cavity, the plunger starts to return to its full up position and pulls a vacuum between the metal that remains in the gooseneck and the metal that remains in the filled die cavity. As soon as the fill port in the goosenecl; chamber is opened, the atmospheric pressure above the molten metal in the pot forces metal back into the gooseneck to fill the gooseneck and nozzle up to the metal which has previously remained in the die cavity. After the plunger returns to its full up position, the dies remain closed for a preset time to allow the casting to cool. After the preset time the dies open and the casting is pulled away from the nozzle. At this time in the cycle the molten metal in the nozzle gooseneck system tends to fiow back into the pot gooseneck system to reach a hydrostatic level. When the dies are fully opened the casting is ejected by means of knockout pins and a new cycle is begun.

It has been recognized for some time that although such automatic die casting machines are quick and efficient and have met with widespread commercial success, they do present an important problem because of the relatively large amount of air which is present in the gooseneck section and which gives rise to imperfect castings unless it is removed. The air is present in the gooseneck section since it is sucked therein through the nozzle when the dies are separated and the molten metal in the gooseneck section flows back to said hydrostatic level.

To overcome this problem, some commercially available die casting machines are provided with a vacuum device associated with the die cavity whereby the air which is forced into the die cavity during the injection of the molten metal is withdrawn through the vacuum device.

Although such vacuum devices have met with widespread commercial success, they do give rise to many problems also. Their most common disadvantage is the frequency of breakdown resulting from either a failure of the vacuum pump or a clogging due to metal particles which are sucked into the pump from the die cavity along with the air. Each time the vacuum pump stops because of failure or clogging, the entire die casting machine must be shut down until the pump is repaired.

Another important problem encountered with the use of vacuum devices associated with the die cavity is due to the slight surface imperfections present on the face of nearly all dies. These imperfections anow air to be "ice sucked into the die cavity from the atmosphere and thereby allow at least a portion of the air removed by the vacuum pump to reenter the die cavity and give rise to imperfections in the castings.

It is therefore an object of this invention to provide an automatic die casting machine which substantially reduces the amount of air which is injected into the die cavity and which produces castings of excellent quality Without the necessity of using a vacuum device to remove air from the die cavity.

It is an advantage of this invention that expensive and troublesome vacuum devices or the like are not required and that the efliciency of the machine is increased in that the necessity of shutting down the machine due to failure of vacuum equipment is avoided.

These and other objects and advantages of this invention will be apparent to those skilled in the art in the light of the following description and the accompanying drawing in which:

FIGURE 1 is a side view of a segment of an automatic die casting machine according to the invention.

FIG. 2 is a side view of a segment of the machine illustrated by FIG. 1 and showing the dies in contact and the molten metal being injected into the die cavity.

As illustrated by the drawings, the present die casting machines comprise a furnace 1 having a heating chamber 2 and an opening 3 providing access for a gas flame or other heat supplying means. Into the heating chamber is mounted a vat 4 for maintaining the casting metal 5 in molten condition. The vat is preferably separated into two receptacles, A and B, by means of partition 6, as illustrated, and the level of the molten metal in receptacle A is maintained constant by means of ladle 7 which is pivotally mounted on shaft 8 and which is also slidably secured by pin 9 in slot 14 mounted on shaft 11 adjustably secured to the movable die block frame 12 by means of nuts 13. Any excess molten metal added to receptacle A by the ladle spills back over the partition into receptacle 13.

Within receptacle A of the heating vat 4 is mounted metal injection mechanism 14 having plunger receiving cylinder 15, gooseneck section 16 and provided at the upper end with a nozzle 17 communicating with the sprue opening 18 of die 19 which is mounted in fixed position on the frame 20 of the machine. Plunger 21 is slidably mounted within the plunger receiving cylinder 15 and extends upward into lap cylinder section 22 mounted on the top frame of the machine. The plunger is reciprocated in the cylinder section by means of oil pressure alternatively exerted and exhausted through supply lines 24 and 24a which are connected to a suitable distributing valve (not shown).

When the plunger is actuated downwardly or on forward stroke by exerting oil pressure in line 24 and exhausting through line 24a, it displaces the molten metal from the plunger receiving cylinder 15 of the injection mechanism 14 forcing it through gooseneck section 16 and out the nozzle 17 into the die cavity as illustrated by PEG. 2. This step occurs only when the dies are in engagement.

The movable die 27 is mounted on die block 12 which has attached thereto plunger 28 which may be reciprocally mounted in the same manner as plunger 21. The movable die 27 is moved towards and locked against stationary die 19, for instance, by means of oil pressure energizing plunger 28 and the die block. The die block and movable die are kept in perfect alignment with the stationary die by means of rods 31 on which the die block is slidably mounted by means of sleeves 32.

Associated with the movable die 27 is ejector bearing plate 33 having attached thereto knockout pins 34 and ejector rods 35. When the movable die is in engagement with the fixed die, the ejector plate is in the position shown in FIG. 2 and the knockout pins are retracted so as to be flush with the surface of the movable die. When the casting operation is completed and the movable die is retracted, as shown in FIG. 1, the ejector rods make contact with an ejector block, not shown, compressing springs 36 and forcing the knockout pins against the solidified casting and ejecting the casting from the core 37 on the movable die.

Also shown in FIG. 1 is auxiliary molten metal supply vat 40 which is suitably heated and which may be used to supply additional molten alloy metal periodically as needed to receptacle B of main vat 4 by means of power- Operated ladle 41 which is pivotally mounted on stationary arm 42 and on piston-operated arm 43.

The operation of the casting machines of this invention is similar to that of conventional die casting machines up to a point. For instance, each casting cycle begins when the dies are separated or in open position and the injection plunger is in the up position as illustrated by FIG. 1.

Thus, when the dies are in engagement, as illustrated by FIG. 2, the plunger makes its forward stroke and forces molten metal from the ejection mechanism into the die cavity through nozzle 17. After the preset time the plunger begins its reverse stroke as the exhaust line 24a is converted to a power supply line and supply line 24 is converted to an exhaust line. During the reverse stroke, the injection plunger pulls a vacuum in the upper gooseneck section in the area of the nozzle 17 but when the plunger is retracted past the opening or fill port 14a in the plunger receiving section 15, the molten metal in the supply vat 4 is sucked in through the fill port and completely fills the gooseneck and nozzle to destroy the vacuum. After a preset time for cooling the metal in the die cavity to form the casting, the movable die 27 is withdrawn by actuating plunger 28 and the molten metal in the upper gooseneck and nozzle areas flows back down into the gooseneck until it reaches a hydrostatic level with the rest of the molten metal in the supply vat.

The solidified casting is withdrawn from the sprue opening 18 of die 19 and is atfixed to core 37 until it is ejected by knockout pins 34. The contact position of the movable die block is shown as 12a and the contact position of the movable die is shown as 27a in FIG. 1.

The essence of the present invention resides in the discovery that the amount of air which is sucked into the upper gooseneck and nozzle areas of the injection mechanism may be closely controlled, nearly to the point of elimination, by controlling the level of the molten metal in the supply vat. Since the molten metal remaining in the upper gooseneck section flows back to reach a hydrostatic level with the metal in the supply vat when the dies are opened, the amount of molten metal which flows back and is thus displaced by air may be reduced to a minimum by maintaining the molten metal in the supply vat at a constant high level as illustrated by FIG. 1.

The preferred method for effecting this result is accomplished through the use of a supply vat 4 separated into two receptacles A and B by means of divider or partition 6, together with an automatic ladling device which is adjustably attached to the movable die block 12 by means of nuts 13 and which functions to keep the molten metal in receptacle A at a constant and high level.

As shown in FIG. 2, when the dies are in contact during the casting operation, the ladle 7 which is pivotally mounted on shaft 8 is caused to dip below the surface of the molten metal in receptacle B. When the dies are separated, shaft 11 is pulled back and ladle 7 is pivoted on shaft 8 so as to be raised out of receptacle B and tilted into receptacle A. In this way a predetermined amount of molten metal may be withdrawn from receptacle B and spilled over into receptacle A to replace the amount of metal used up in the casting operation. The amount of transferred metal may be controlled by the size of the ladle or by adjusting the length of the shaft 11 by means of nuts 13, but in all cases it is preferred that a slight excess be transferred in that the excess is free to spill back over the partition 6. Thus a constant level in receptacle A is insured, the height of the partition determining the level of the molten metal in receptacle A and the upper gooseneck and nozzle sections of the injection mechanism.

It is of course preferred to eliminate as much air as possible from the present system in order to produce castings which are heavier, less porous, stronger and free of surface imperfections. This is accomplished by maintaining the level of the molten metal in upper gooseneck and nozzle sections as high as practical, for instance as shown in FIG. 1. Thus, the height of the partition 6 is carefully selected to correspond with the height in the gooseneck and nozzle area at which it is desired to maintain the level of the molten metal.

The small amount of air remaining in the nozzle as shown in FIG. 1 is insignificant and represents a tiny portion of that amount of air generally present in the injection system of conventional die casting machines. Likewise even with casting machines equipped with expensive and troublesome vacuum devices, it is impossible to eliminate all of the air from the system since the speed of the casting cycle permits the application of only a partial vacuum. Thus some of the air present in the system is not removed because the vacuum must be discontinued before the injection of the molten metal begins.

In a conventional die casting machine, such as a Cleveland No. 50 used for producing relatively small casings of up to about 1 pound in weight, the volume of air in the die cavity section and the gooseneck injection section can be denoted by symbols DV and GV respectively. Assuming DV as equal to v, then GV will equal approximately 4v and the total volume in the die cavity section and the gooseneck section is DV+GV=v+4v=5v. In a conventional eighty percent vacuum system the pressure of the volume DV-t-GV or 5v drops from 15 p.s.i. to 3 p.s.i. During the injection process, when the metal is about to enter the die cavity section, all the air in the gooseneck section is forced into the die cavity section and volume DV+GV or 5v at 3 p.s.i. is forced into volume DV or v and the pressure is increased to 15 p.s.i. because the 3 p.s.i. air is compressed from a volume 5v to IV or 5 times. Therefore the metal entering the die section is entering against air at the pressure of 15 p.s.i.

However, in the die casting machines according to the present invention, the metal in the gooseneck section fills volume GV with metal and the only air in the gooseneck and die cavity sections is the volume DV or v at atmospheric pressure, that is 15 p.s.i. Therefore the metal injected into the die section is entering against air at the pressure 15 p.s.i. and volume v. Hence for the given geometry of the die casting machine for this example, that is DV=v and GV==4v, this invention will give the same casting results but in a less expensive and more trouble-free manner than conventional die casting machines having a vacuum system pulling an vacuum. It is assumed in the above example that the conditions are adiabatic.

It should be understood that the present invention is not limited to each of the features specifically discussed and illustrated, and alternative embodiments where desired will be obvious to those skilled in the art in the light of the foregoing description. The essential feature of the invention involves the provision of a die casting machine with a suitable ladling and supply vat system whereby the level of the molten metal in the injection mechanism is maintained constantly high, thereby substantially decreasing the amount of air in the system.

Variations and modifications may be made within the scope of the claims and portions of the improvements may be used without others.

I claim:

1. In a die casting machine comprising a vat containing a supply of molten casting metal and a metal injection mechanism having a plunger and an injection cyllinder which is adapted to be partially immersed in said molten metal in said vat, said injection cylinder comprising a gooseneck section which extends above the level of said molten metal and opens into a die cavity, and a plunger receiving section having an intermediate opening adapted to be positioned below the level of said molten metal for allowing said molten metal from said vat to enter the injection cylinder and be forced by said plunger through said gooseneck section into the die cavity, said die cavity being formed by a sectional die, one of said sections being mounted in fixed position relative to and opening into said gooseneck section while the other of said sections is movable into engagement with said fixed die to form said cavity, the improvement which comprises using as the vat one which is provided with a wall, the height of which is selected so as to approach the height at which the gooseneck section opens into the die cavity; and automatic means responsive to the movement of said movable die section for supplying additional molten metal to said vat each time the dies are moved out of engagement in suflicient quantity to cause a surplus of molten metal to overflow said wall whereby molten metal added to said vat is maintained at a substantially constant and high level equal to the height of said wall,

6 said automatic means comprising a pivotal ladle for dipping molten metal from a supply thereof and depositing it in said vat.

2. A die casting machine as defined in claim 1, in which the vat is divided into two receptacles by said Wall, one being a supply receptacle into which the molten metal overflowing said wall is received and from which the molten metal is dipped by said ladle.

3. A die casting machine as defined in claim 1, in which there are mechanical means connecting the pivotal ladle to said movable die section for operation of the ladle thereby as the movable die section moves toward and from the fixed die section.

4. A die casting machine as defined in claim 3, in which the mechanical means connecting the ladle and the movable die section causes the ladle to operate to deposit molten metal in the vat each time the movable die section moves out of engagement with the fixed die section.

References Cited by the Examiner UNITED STATES PATENTS 2,660,769 12/53 Bennett 2270 2,684,510 7/54 Muller 2270 XR 3,056,178 10/62 Jagielski 22-70 3,077,015 2/63 Rearwin 2'2-81 MICHAEL V. BRINDISI, Primary Examiner.

Claims

1. IN A DIE CASTING MACHINE COMPRISING A VAT CONTAINING A SUPPLY OF MOLTEN CASTING METAL AND A METAL INJECTION MECHANISM HAVING A PLUNGER AND AN INJECTION CYLLINDER WHICH IS ADAPTED TO BE PARTIALLY IMMERSED IN SAID MOLTEN METAL TO SAID VAT, SAID INJECTION CYLINDER COMPRISING A GOOSENECK SECTION WHICH EXTENDS ABOVE THE LEVEL OF SAID MOLTEN METAL AND OPENS INTO A DIE CAVITY, AND A PLUNGER RECEIVING SECTION HAVING AN INTERMEDIATE OPENING ADAPTED TO BE POSITIONED BELOW THE LEVEL OF SAID MOLTEN METAL FOR ALLOWING SAID MOLTEN METAL FROM SAID VAT TO ENTER THE INJECTION CYLINDER AND BE FORCED BY SAID PLUNGER THROUGH SAID GOOSENECK SECTION INTO THE DIE CAVITY, SAID DIE CAVITY BEING FORMED BY A SECTIONAL DIE, ONE OF SAID SECTIONS BEING MOUNTED IN FIXED POSITION RELATIVE TO AND OPENING INTO SAID GOOSENECK SECTION WHILE THE OTHER OF SAID SECTIONS IS MOVABLE INTO ENGAGEMENT WITH SAID FIXED DIE TO FORM SAID CAVITY, THE IMPROVEMENT WHICH COMPRISES USING AS THE VAT ONE WHICH IS PROVIDED WITH A WALL, THE HEIGHT OF WHICH IS SELECTED SO AS TO APPROACH THE HEIGHT AT WHICH THE GOOSENECK SECTION OPENS INTO THE DIE CAVITY; AND AUTOMATIC MEANS RESPONSIVE TO THE MOVEMENT OF SAID MOVABLE DIE SECTION FOR SUPPLYING ADDITIONAL MOLTEN METAL TO SAID VAT EACH TIME THE DIES ARE MOVED OUT OF ENGAGEMENT IN SUFFICIENT QUANTITY TO CAUSE A SURPLUS OF MOLTEN METAL TO OVERFLOW SAID WALL WHEREBY MOLTEN METAL ADDED TO SAID VAT IS MAINTAINED AT A SUBSTANTIALLY CONSTANT AND HIGH LEVEL EQUAL TO THE HEIGHT OF SAID WALL, SAID AUTOMATIC MEANS COMPRISING A PIVOTAL LADLE FOR DIPPING MOLTEN METAL FROM A SUPPLY THEREOF AND DEPOSITING IT IN SAID VAT.