US2209882A

US2209882A - Pressure-casting apparatus

Info

Publication number: US2209882A
Application number: US243710A
Authority: US
Inventors: Charles D Galloway
Original assignee: Individual
Current assignee: Individual
Priority date: 1938-12-03
Filing date: 1938-12-03
Publication date: 1940-07-30
Anticipated expiration: 1957-07-30

Description

July 30, 1940. c. D. GALLowAY 2,209,882

PRESSURE-CASTING APPARATUS Filed Dec. s. 1958 WEA/mf?- F e. 40 m4/af 43 afsbga// way Patented July 30, 1940 UNITED jsTATes PATENT "oFFlcl-J Claims.

In pressure-casting apparatus in which a vacuum is applied to the mold cavity just prior to forcing the molten metal'into the cavity by super-atmospheric pressure, it is important that the mold cavity shall be' hermetically sealed against the entrance of air when the vacuum is applied; and where the mold is in two or more parts which are brought together to close the mold cavity prior to the casting operation, it has been found necessary to provide a gasket between the two confronting parts of the mold'to effect an air-tight seal. Gaskets made of asbestos fabric or similar material resistant to heat in the form of a cord lying in confronting grooves in the opposite faces of themold .have

been found unsatisfactory as they quickly becomev deformed and fail to make an air-tight seal. To overcome this difficulty, applicant provides confronting grooves in the opposite faces of the two parts of 'the mold to form a channel surrounding the mold'cavity at the parting line, into which channel molten metal is forced and solidified. For the initial' tests, this channel had a circular or similar cross-section but the shrinkage of the metal on cooling developed `suilicient space between the surfaces of the gasket and the walls of the channel to permit leakage of air into the mold cavity when vacuum was applied. 'Ihe improvement was then devised whereby advantage is taken of the shrinkage of the metal on cooling tok increase the pressure between the surfaces of the gasket and the walls of the channel to perfect the seal. In general, this improvement consists in providing a channel whose cross-section has the form of two areas connected by a comparatively narrow neck; or, in other y words, the periphery of the cross-section has one or more re-entrant angles or equivalent're-en trant portions whether angular or more or less cuved. Preferably one of the two areas as well as the neck should be comparatively small so that the corresponding portion of themetal in the gasket will solidify first and willthen be drawn, by the subsequent shrinkage of the larger area, into close contact with the surface4 of the channel in the mold where the seal is to be effected. l

In the accompanying drawing:

Fig. 1 is a diagram,'with parts in cross-section, showing the general. arrangement of the mold and the reservoir containing the molten metal from which the mold is illled.

Fig. 2 is a sectional view taken through the two-part mold. Y

Figs. 3, 4, 5 and 6 are cross-sections, on an,

enlarged scale, through alternative designs of the channel and gasket therein, the'latter being exaggerated to illustrate the principle involved.

Fig. 7 is a cross-section, on an enlarged scale, showing the channel and gasket formed on one 5 side only of the parting-line of the mold.'

In Figs. 1 and 2, I represents one-half of the mold, the other half (not shown in Fig. l) being substantially identical except that the ducts for admitting the molten metal and for applying 10 the vacuum need not be duplicated in the second half. 2 is a reservoir of molten metal in which the

vessels

3 and 4 are submerged, the vessel 3 being designed to supply molten metal to the mold cavity; and the vessel 4, which is identical l5 with the vessel 3 being designed to supply molten metal to the gasket channel surrounding the mold cavity. The design of the vessel 3 only will therefore be described .Aty the bottom of the vessel is a ball check valve 5 designed to permit 20 the molten metal to enter the vessel from the reservoir 2 but to prevent it from being forced back. -The vessel is hermetically sealed except for the dip stand pipe 6- and the air supply pipe 1. 'I'he dip stand pipe 6 extends to a i aint nearl 25 the bottom of the vessel 3 and is connected at its upper end tothe mold cavity through the duct or sprue 8. The vertical length of dip stand pipe 6 is such that, when atmospheric pressure is applied to the surface of the .metal in the vessel 30 3 and vacuum is applied to the mold cavity, the differential pressure will not be suilicient to force the molten metalinto the mold butwill raise it only to some intermediate point as A in the stand pipe E. 35 The vessel 4 sconnected by va similar stand pipe 6a to the channel! which surrounds the mold cavity and into which the molten metal is A forced to provide an air-tight' gasket just prior to forcing the molten metal into the mold. Ihe mold is provided with a vacuum chamber Il connectedto the mold cavity by vent ducts II, these vent ducts being of suchrestricted section that, while they-will permit the air to escape from the mold cavity when vacuum is applied, they will 45 not permit the molten metal to pass into the vacuum chamber. Ihe

vessels

3 and 4 are connected by pipes 1 and 1a, respectively, to a valve I2 by means of which connection may be made either to a source of compressed air via the pipe 5o I3 or to the atmosphere via the outlet I4.

p In operation, the mold is closed, the vacuum chamber I0 being connected to the source of vacuum with the valve I2 turned to connect the.` pipes I and 'Ia to the atmosphere. This will K5 air to the pipe 'la which rca-entrant angles cause the metal in pipe B to rise to the level A. The valve I2 is then turned to admit compressed will force molten metal into the gasket channel 8 where it will be prompt- 1y congealed to form an air-tight seal around the mold cavity. The valve I2 is then turned to admit compressed air to the pipe l which will force the molten metal through stand pi 6 into the mold cavity which has already exhausted of air through the vents Il and the vacuum chamber i0. 'I'he valve I2 is then turned to shut of! the supply of compressed air and connect the pipes 1 and the mold is opened for 'removing the casting and the gasket, permitting the molten metal in the pipes G and 6a to drop to the level of the molten metal in the reservoir 2, thus 'restoring the original conditions. l

- In Fig. 3 a design of channel and gasket is shown. comprising in cross-section two similar areas 30 and 3i connected by the narrow neckv 3,2, the shrinkage on cooling producing close contact at thepoints I3.

In Fig. 4 is shown the cross-section, to an enlarged scale. of alpreferred design of channel and gasket. The cross-section of the channel comprises a comparatively paratively small area 2l connected by a comparatively narrow^neck 22. The gasket. after solidifying, is represented in cross-section by the areas 20a and Zia connected byA the neck 22a. The shrinkage of the metal of the gasket, on cooling, has drawn the surfaces of the gasket .and the channel into close contact at the points 23. The parting-line between the two-halves of the 'mold is indicated at P.

In Fig. 5 is shown a slight modiiication of the design shown in Fig. 4 consisting in the `additional 55. producing additional points of contact pressure 56 due torshrinkage.

In Fig. 6 the cross-section of the gasket channel is shown. as comprising the comparativelyv large ar'ea 60 with two relatively small areas El, one on either side. connected to the area 60 by u the narrow neck B2.

In Fig. 7 the gasket channel is formed by a single groove on one side only of the parting-line P of the mold. and comprises in cross-section the comparatively large area l0 and the comparativelvl small area Il connected by the narrow neck 42. -The contact pressure resulting from shrinkage is produced at the points to eiect the seal.

The expression` "re-entrant angies. used in the claims is intended to include such re-entrant por'- thecross-section of thedefined by curved lines (as tions of the periphery of gasket channel as are in Fig. 6), as well as lines and sharp angles.

I do not intend to be limited save ofthe prior art and of the attached claims require. i i

I claim: 1. In a two-part mold adapted for use in a pressure-casting machine having provision for applying vacuum to the mold cavity prior to filling the mold, 'a groove in at least one of the confronting faces of the mold surrounding the mold cavity and providing, when the mold is closed, a closed channel having a cross-section with at least one' peripheral 4re-entrant angle and adapted forcasting a metal gasket in which shrinkage of the congealed metal increases the those' dened by straight as the scope sealing pressure between the surfaces of the gasket and the channel.

1a to the atmosphere, and A large Aarea 20 and a comperipheral re-entrant angle on each side of the parting-line and adapted for casting a metal gasket. in which shrinkage of the congealed metal increases the sealing pressure between the surfaces of the gasket and the channel.

3. In a two-part mold adapted forI use in a pressure-casting machine having provision for applying a vacuum to the mold cavityprior to filling the mold, confronting grooves in the confronting faces of the mold surrounding the mold cavity and providing, when the mold is closed, a closed channel having a cross-'section comprising two areas connected by a comparatively narrow neck, the parting-line. passing through both areas and the neck and adapted for casting a metal gasket in which shrinkage of the congealed metal increases the sealing pressure between the surfaces of the gasket and the channel.

4. In a two-part mold adapted for use in a pressure-casting machine having provision for tween the surfaces of the gasket and the channel.

5. A multi-part mold for die casting having a mold cavity therein, a sprue for admitting molten metal to said mold cavity, means for applying vacuum to said mold cavity, said mold also having therein a second cavity, normally empty, surrounding said mold cavity and adapted to receive molten metal to form agasket surrounding said mold cavity and sealing the parting line thereof during the casting operation, and said mold also having a second sprue therein for admittlng molten metal tosaid second cavity.

. 6. A multi-part mold for die casting having a mold cavity therein, a sprue forming an inlet for molten metal to said mold cavity, means for applying vacuum to said mold cavity, said mold .having asecond cavity therein surrounding said mold cavity and adapted to receive molten metal therein to form a gasket surrounding said mold cavity during casting, said second cavity having in cross-section two relatively large areas con- .,-nected by a portion of relatively small area.

7. A process of die casting comprising, casting a\gasket of metal surrounding and spaced from the cavity of a multi-part mold to seal to the parting-line of'said mold, applying a vacuum to the mold cavity of said mold to exhaust said mold cavity, and filling said mold cavity with molten metal to form a casting.

' 8. In the art of die casting, the improvement which consists in', supplying molten metal to a cavity in a multi-part mold surrounding the mold cavity therein and causing said metal to congeal to form a gasket sealing-the parting-line of said mold cavity, evacuating gases from the mold cavity by the application of vacuum while said cavity is connected to a reservoir of molten metal subjected to atmospheric pressure and while said cavity is located at a height above said metal greater than that to which the metal will be raised by the pressure differential between the atmosphere and the vacuum, and then introducing the metal into the mold cavity by additional pressure/applied to the reservoir.

9. In the art of die casting, the improvement which consists in, introducing molten metal into a cavity in a multi-part mold, said cavity surrounding and being spaced from the mold cavity of `said mold and causing said metal to congeal and thereby form a gasket sealing the partingline of` said mold cavity, evacuating gases from the mold cavity by the application of vacuum -while said cavity is connected to a reservoir of molten metal subjectech to atmospheric pres-fl sure and while said :cavity is located at a height 3 above said metal greater than that to which the metal will be raised by the pressure diierential between the atmosphere and the vacuum, then introducing the metal into'the mold cavity by additional pressure applied tothe reservoir, and then restoring atmospheric pressure to said reservoir andto the mold cavity to return to the reservoir` the surplus metal.

10. A process of sealing multi-part molds having a mold cavity therein for use in die casting into a cavity in said mold 'surrounding the mold cavity therein, and causing said metal to congeal and to press against surfaces of said cavity and to thereby seal the parting-line of said mold cavity as by a gasket.

CHARLES D. GALLOWAY.

-by vacuum which comprises, filling molten metal