US 3459254 A
Description (OCR text may contain errors)
Aug. 5, 1969 R. J. DEARTH PRESSURE POURING CONTROL ARRANGEMENT Filed Dec. 27, 1966 22E, roam l United States Patent O 3,459,254 PRESSURE POURING CONTROL ARRANGEMENT Raymond J. Dearth, Roselle, Ill., assignor to Amsted Industries Incorporated, Chicago, Ill., a corporation of New Jersey Filed Dec. 27, 1966, Ser. No. 604,910 Int. Cl. B22d 27/14, 17/06 U.S. Cl. 164-119 5 Claims ABSTRACT OF THE DISCLOSURE This invention relates to pressure casting, and more particularly to methods and apparatus for maintaining a substantially constant pressure in a pressure pouring operation.
Pressure casting primarily involves the application of superatmospheric pressure to a sealed tank to force molten metal from a container disposed within the tank through a pouring tube and into the casting cavity of a mold. Various systems have been proposed to accurately control the pressure applied to molten metal in a pressure pouring operation, in order to insure a constant and uniform rate of ilow of metal into the mold. One such system may be found in Patent No. 2,990,592 to Hursen, incorporated herein by reference, which describes an apparatus for providing a constant rate of increase in pressure applied to the molten metal. The present invention may be used in conjunction with, and as an additional improvement to, such systems, to the extent that it provides a means for maintaining a substantially constant pressure on the molten metal after the casting cavity has been lled.
For example, in the production of hollow castings, the molten metal is forced into the mold by a certain amount of pneumatic fluid pressure and is allowed to remain in the mold for a certain period of time. During this period, the portion of the molten metal in contact with the mold v rst begins to freeze, leaving an inner liquid portion. The
,has been filled. A pressure increase in the tank, caused by factors which include temperature gradients between the external source of pneumatic pressure and the pressure in the tank, would cause the metal to be forced out of the mold. Loss of pressure in the tank, caused by factors including leaks in the system, would allow the molten metal to empty from the casting cavity of the mold before the required period of time had elapsed.
Accordingly, an object of this invention is to provide methods and apparatus for maintaining a constant pressure against the molten metal after the mold has been iilled.
Another object of this invention is to provide a constant pressure system in a pressure pouring operation which will compensate for pressure fluctuations caused by temperature gradients, leaks, and other factors.
A further object of this invention is to provide such methods and apparatus in a pressure pouring operation 3,459,254 Patented Aug. 5, 1969 ice which Will maintain any pressure necessary to retain the molten metal in the mold.
The above and other objects, which will become apparent to those skilled in the art will appear in the following speciication and in connection with the accompanying drawing wherein:
FIGURE l is a schematic illustration of the invention herein described with accompanying pressure pouring apparatus shown schematically in vertical cross section.
FIGURE 2 is a schematic cross sectional view of the bracketed portion of FIGURE l.
Describing the invention in detail and referring to FIG- URE 1, a substantially sealed tank 10 is connected to a main pneumatic liuid pressure line 12, adapted to deliver pressurized pneumatic fluid such as compressed air to the tank. The tank houses a ladle 14 which has previously been iilled with molten metal 16 such as steel to be used in a casting operation.
The top of the tank 10 is preferably closed by a removable cover 18 seated on a resilient seal ring 20 and secured to the tank by releasable clamps or other suitable means (not shown) to afford a substantially sealed enclosure. Cover 18 has an opening 22 adapted to receive a pouring tube 24 which extends through the cover into a lower portion of the ladle 14. A mold 26 is provided above the cover 18 of the tank 10 and is mounted on the upper extremity of pouring tube 24. Molten metal 16 may be forced upwardly through pouring tube 24 into mold 26 by the application of superatmospheric pressure on the molten metal in ladle 14.
The mold 26 comprises cope and drag sections 28 and 30, respectively, which define therebetween a coreless casting cavity 32. The cope section 28 contains a riser opening 34 between the atmosphere and casting cavity 32. The drag section 30 is sealed on the upper surface of a flange 36 formed on the upper end of pouring tube 24. A gate 38 in the drag section 30 extends downwardly from cavity 32 and is substantially aligned to communicate with the bore 40 of pouring tube 24.
A source of pressurized pneumatic iiuid, indicated at 42 is connected to main line 12 for raising the molten metal 16 upwardly through the pouring tube 24. Preferably, such source comprises a system which provides Variable pressures, such as that system described in the aforementioned Patent No. 2,990,592. The supply of fluid pressure from source 42 is controlled by main intake shut-olf valve 44 on line 12. An exhaust valve 48 is provided on a branch 50 that bypasses line 12 between main shut-oli' valve 44 and tank 10. Preferably, valves 44 and 48 are pneumatically operated by a common source (not shown).
A pressure relief valve 52 is provided on bypass branch 50 between exhaust valve 48 and tank 10. A shut-off valve 54, preferably activated by a solenoid, is provided on bypass branch 50 between pressure relief valve 52 and tank 10. Pressure relief valve 52 is adapted to relieve any tank pressure which is in excess of the pressure between said valve and the branch shut-off valve 54, as will be hereinafter explained.
A second branch 56 is provided that bypasses main shut-off valve 44 and the rst bypass branch 50 hereinbefore described. A regulator valve 58 is located on bypass branch 56 and a shut-off valve 60, preferably operated by a solenoid, is located on said branch between said regulator valve and the tank 10.
During the pouring operation, valves 44 and 54 are opened and valve 60 is closed. Pressure from source 42 is transmitted through line 12 to tank 10, and the molten metal 16 is thus raised upwardly through the pouring tube 24 to ill the casting cavity 32 of the mold 26. The amount of pressure required to fill a particular mold will, of course, vary according tothe size of the casting cavity.
Normally, continuous increments in pressure applied will continue until the operator sees molten metal in the riser opening 34. At this time, no pressure is released from relief valve 52, since the pressure on both sides of said valve is substantially the same.
After the casting cavity 32 has been filled to the desired level, intake shut-off valve 44 is closed, branch shut-off valve 54 is closed, and branch shut-off valve 60 is opened. The same pressure required to fill the mold 26 with molten metal is trapped between branch shut-off valve 54 and pressure relief valve 52. At the same time, bypass branch 56 acts to supply sufficient pneumatic fluid pressure through regulator valve 58 to maintain the tank pressure at or over the desired level.
Bypass branch 50 now serves as a pressure relief branch. As shown in FIGURE 2, relief valve 52 may comprise an enclosure with a port 55 open to the atmosphere on the tank side of the valve. A exible diaphragm S1 is sealed within the enclosure. A sealing disk 53 is attached on the tank side of a diaphragm 51 and is engageable with the end 57 of the branch communicating with the tank 10. The valve is designed to close when the pressure on the tank side (P1) is the same or less than the pressure (P2) between closed valve 54 and the other side of diaphragm 51. It will be recalled that the pressure (P2) is the same as that pressure required to ll the casting cavity of the mold with molten metal. If the pressure (P1) from the tank becomes greater than the required pressure (P2), the diaphragm 51 will liex and allow the excess pneumatic fiuid pressure to bleed off through port 55 into the atmosphere.
The pressure admitted through regulator valve S8 is adjusted to be somewhat over the pressure (P2) required to fill the casting cavity 32 of the mold 26. This will compensate for any leaks in the tank. Any excess pressure through regulator valve 58 and other excess pressure caused by temperature gradients will be bled off by relief valve 52, thereby achieving a substantially constant pressure in the tank.
After the pressure in the tank has been maintained for the required period of time, exhaust valve 48 is opened, allowing any molten metal in the casting cavity 32 to return to the ladle 14.
It may thus be seen that the present invention provides a method and apparatus for maintaining a constant pressure while accommodating uctuations of pressure in the tank due to temperature gradients, leaks and the like. The present invention also has the advantage of maintaining any pressure required to retain the molten metal in the mold.
Having thus described the invention, what is claimed is:
1. In conjunction with a pressure pouring operation wherein the casting cavity of a mold has been filled by the application of superatrnospheric pressure against the molten metal to force the metal generally upwardly into the cavity, the process of maintaining a substantially constant molten metal level in the mold which comprises pressurizing the molten metal with pneumatic fiuid at a pressure above that pressure required to fill the cavity and relieving that pressure from the molten metal which is in excess of the pressure required to fill the cavity.
2. The process according to claim 1 wherein relieving the pressure which is in excess of the pressure required to fill the mold comprises the steps of trapping that pressure required to fill the cavity during the pouring operation and thereafter maintaining a constant molten metal level 4 in the cavity by relieving that pressure from the molten metal in excess of said trapped pressure. A
3. In conjunction with pressure pouring apparatus wherein molten metal within a pressure tank is forced generally upwardly to a mold through a pouring tube by the pressurization of the molten metal with superatmospheric pneumatic pressure fluid, an arrangement for maintaining a constant molten metal level in the mold which comprises a source of pressurized pneumatic fluid, means to deliver said fluid to said tank, said means including relief valve means for releasing excess pressure in the tank over that pressure required to fill the mold and a pressure supply branch for supplying additional pressure to said tank to compensate for pressure losses therein.
4. In conjunction with a pressure pouring operation wherein the casting cavity of a mold is filled by the application of superatmospheric pneumatic uid pressure against the molten metal within a pressure tank to force the metal generally upwardly into the cavity, the process of maintaining a substantially constant molten metal level in the mold which comprises the steps of providing an amount of superatmospheric pressure necessary to fill the mold to the desired level through an external main line to the tank, trapping said amount in said main line between a main shut-off valve in said line and the tank and trapping said amount in a branch shut-off valve and a relief valve on a bypass branch between said main line shutoff valve and said tank, and thereafter maintaining a constant molten metal level in the mold by providing additional pressure over said amount through a second branch on said main line bypassing said main line valve and relieving any pressure in excess of said amount through said relief valve.
5. In conjunction with pressure pouring apparatus wherein molten metal in a pressure tank s forced generally upwardly to a mold through a pouring tube by the pressurization of the molten metal with superatmospheric pneumatic pressure fiuid, an arrangement for maintaining a substantially constant molten metal level in the mold which comprises a source of pneumatic pressure fluid, a main supply line connecting said source to said tank, shutoff valve means on said main line, a first bypass branch, the ends of said branch connected to said main line between said main line valve and said tank, said first bypass branch including a first branch shut-off valve means and a pressure relief valve means, said pressure relief valve including means for relieving pressure in said first branch in excess of the pressure between said first branch shutoff valve means and said pressure relief valve means, and a second bypass branch connected to said main line around said main line shut-olf valve means, said second bypass branch including a second branch shut-off valve means and pressure regulator means.
References Cited UNITED STATES PATENTS 3,201,837 8/1965 Sylvester 164-306 X 3,302,253 2/1967 Moriyama 164-154 3,384,150 5/1968 Newsome 164-281 X J. SPENCER OVERHOLSER, Primary Examiner J. S. BROWN, Assistant Examiner U.S. C1. X.R. 164-306