US3788790A

US3788790A - Machine for casting under pressure

Info

Publication number: US3788790A
Application number: US00227882A
Authority: US
Inventors: A Balevsky; I Nikolov; D Nenov; E Momchilov
Original assignee: NIITM PRI BAN
Current assignee: NIITM PRI BAN
Priority date: 1971-02-20
Filing date: 1972-02-22
Publication date: 1974-01-29
Anticipated expiration: 1991-01-29
Also published as: SU438160A3; FR2125399B1; FR2125399A1; GB1377444A; DE2207786A1; IT961278B

Abstract

An apparatus for casting under pressure wherein the mold parts are connected to relatively telescoping chamber walls, at least one of which can be actuated by a fluid-responsive device, e.g. a hydraulic cylinder, to ensure tight closure of the mold.

Description

United States Patent [191 Balevsky et al.

[ Jan. 29, 1974 MACHINE FOR CASTING UNDER PRESSURE Inventors: Anguel Tonchev Balevsky; Ivan Dimov Nikolov; Dragan lliev Nenov; Emil Nikolov Momchilov, all of Sofia, Bulgaria Assignee: Niitm Pri Ban, Sofia, Bulgaria Filed: Feb. 22, 1972 Appl. No.: 227,882

Foreign Application Priority Data Feb. 20, 1971 Bulgaria 16865 US. Cl 425/242, 164/1 19, 164/285 Int. Cl B22d 27/14 Field of Search.... 425/242; 164/119, 133, 155, 164/285, 337; 264/93 [56] References Cited UNITED STATES PATENTS 3,196,501 7/1965 Balevsky et a1 164/1 19 3,532,154 10/1970 Balevsky et al..... 164/133 X 3,650,313 3/1972 Balevsky et a1 164/1 19 X Primary Examiner-R. Spencer Annear Attorney, Agent, or Firm-Karl F. Ross; Herbert Dubno [5 7 ABSTRACT An apparatus for casting under pressure wherein the mold parts are connected to relatively telescoping chamber walls, at least one of which can be actuated by a fluid-responsive device, e.g. a hydraulic cylinder, to ensure tight closure of the mold.

3 Claims, 1 Drawing Figure 1 MACHINE FOR CASTING UNDER PRESSURE CROSS REFERENCE TO US. PATENTS Casting utilizing fluid pressure differentials is disclosed in the commonly assigned US. Pat. Nos. 3,532,154 and 3,693,698.

FIELD OF THE INVENTION The present invention relates to an apparatus for casting under pressure and, more particularly, to a system for casting high-volatility metals and other materials, e.g. synthetic resins, and substances which decompose at low pressures and at melting temperatures in a mold under counterpressure.

BACKGROUND OF THE INVENTION The principle of casting a flowable material, e.g. a molten metal, under a counterpressure has been proposed heretofore in order to reduce the tendency of the flowable substance to volatiliz'e or decompose. In such cases, the molten substance is forced into a mold which is vented to a space at superatmospheric pressure. In such systems it has been particularly difficult to maintain the mold in a closed condition.

In known machines of this type, the mold is located in a chamber which should be easily opened and closed for extracting the castings and which must be closed by a force exceeding that generated by the counterpressure against which the metal or other substance is cast in the mold. Usually this increased force cannot be produced by the low-power actuating elements used for opening and closing the chamber and a special locking device may be required for the two parts of the mold.

This device must provide a sealing of the mold halves together at their parting surfaces and be capable of absorbing the force generated by a large number of movable mechanically and thermally stressed members. Moreover, strict coordination is requiredbetween the action of the locking device and the remaining parts of the machine to avoid the buildup of pressure within the machine before the locking process is completed and to unlock the machine before the pressure'has been fully relieved. The reliability and safety of the operation of the machine depends on such coordination. In order to provide such coordination, the complexity of the mechanism has been increased and casting machines have been provided heretofore with automatic elements which inherently increase operations auxiliary to the casting step and increase the duration of each casting cycle to the detriment of productivity of the apparatus.

OBJECTS OF THE INVENTION It is a general object of the invention to avoid the aforedescribed drawbacks and disadvantages of priorart machines and apparatus for casting with gas counterpressure, and to provide a considerable simplification of the design with a concomitant acceleration of the process, increased reliability, and enhanced safety.

It is another object of the invention to provide means for automatically locking a chamber and mold of a casting apparatus for the purposes described so that mechanical locking devices and similar mechanisms for synchronizing their operation are rendered superfluous.

Still another object of the invention is to provide an improved apparatus for the counterpressure casting of SUMMARY OF THE INVENTION These objects and others which will become apparent hereinafter are attained, in accordance with the present invention, in a counterpressure casting system in which the compressed gas against the pressure of which the molten substance is forced into the mold, is used in whole or in part for locking the chamber and the mold parts together.

According to an important feature of the invention, the objects set forth above are attained by using a chamber receiving the mold which consists of two generally cylindrical enclosures telescopically movable with respect to-one another, one of the enclosures being rigidly connected to the body of the machine while the other may be raised and lowered by an actuating mechanism, preferably together with the other mold half in order simultaneously to permit the closure of the chamber and the mold.

The movable enclosure has a diameter smaller than the diameter of the outer enclosure in which it moves in such manner that the compressed gas delivered to the closed chamber produces of itself the necessary closing force in accordance with the difference between the diameters of the two enclosures. In other words the movable enclosure constitutes a differential piston which is displaced and retained, in part, by the gas pressure within the chamber.

DESCRIPTION OF THE DRAWING SPECIFIC DESCRIPTION In the drawing, there is shown a horizontal and movable plate 1 forming an upper support and mounted upon a plurality of posts 10 angularly spaced about the axis A of the machine. Attached rigidly to the upper plate is a hydraulic cylinder 2 whose piston rod 2a is connected to an upper mold half 6 cooperating with a lower mold half 11 mounted upon another stationary plate 12 carried bya cylindrical outer wall 13 forming an enclosure or a mass 14 of thermally insulating material. A chamber 15 within this mass is provided with a pedestal 16 on which is supported a molten metal ladle or crucible 17 containing a bath 18 of the molten material to be cast.

A syphon tube 19, also referred to as a riser, penetrates into the bath toward the base thereof and opens into the lower mold half 11. v

The mold chamber is defined by a fixed enclosure mounted upon the plate 1 and depending therefrom, while being of generally cylindrical configuration with an inwardly extending frustoconical lip 3a. The latter supports a rubber sealing ring 4 upon which an outwardly turned lip 5a of the lower movable enclosure 5 may come to rest. The latter is vertically shiftable in enclosure 3 and thus is telescopically movable relative thereto. An inwardly extending flange 5b of the movable enclosure 5 is bolted at SC to an outwardly extending flange 6a to the mold which is provided with vertically movable ejector pins 6b adapted to engage stops la depending from the plate 1 in a fully elevated position of the mold half 6. The flanges 6a and 5b define a mold compartment 7 which is at a pressure different from the pressure in the chamber thereabove as will be apparent hereinafter and is also different from the pressure in chamber 9 above the bath 18. The movable enclosure 5, moreover, has an inwardly extending sealing lip 5d adapted to rest upon a rubber sealing ring 8 which, in turn, is seated against a frustocone 21a of the upwardly extending stationary apron 21 rising from plate 12. The portion of the movable enclosure 5 exposed to gas pressure in chamber 20 has a diameter D which is in excess of the diameter D of the portion of the movable enclosure in chamber 7. Pressure may be supplied by a compressor represented generally at 22 to chamber 20 via a valve 23, to chamber 7 via a valve 24 and to chamber 9 via a valve 25.

In operation, the pistonrod 2a may be elevated to raise the mold half 6 and enclosure 5. until ejectors 6b release the previous workpiece, the lowered end of enclosure 5 being lifted from the apron 21 to allow removal of this cast body. When the mold is then closed by reverse operation of the cylinder, chamber 7 and chamber 9 may be pressurized with gas at a differential such that the molten material from bath 18 is driven upwardly through the tube 19 into the mold. Because of the differential piston effect, the pressure in chamber 7 which exceeds ambient pressure acts to retain the mold in its locked position without any additional means. This pressure may be increased by allowing the pressure in chamber 20 'to equal that in chamber 7 or applying a higher pressure in chamber 20. After the mold has been filled, the cycle is repeated and the pressure relieved, e.g. through an venting valve 26.

We claim:

1. An apparatus for casting under counter pressure comprising a mold having at least one movable mold' ends and exposed to the pressures in said chambers to constitute a differential piston retaining said mold chamber closed upon differential pressurization of said chambers, said movable mold member being connected to said movable enclosure and displaceable therewith.

2. The apparatus defined in claim 1, further comprising a stationary horizontal support disposed above said mold, said actuating mechanism being mounted on said support and including a hydraulic cylinder and piston arrangement connected to said movable mold member, said stationary enclosure being fixed to and depending from said support, said movable enclosure being telescopically received in said stationary enclosure, said mold comprising a lower stationary mold half fixed with respect to said support, and an upper movable mold half connected to said movable enclosure, said means for supplying said substance to said mold including a riser tube depending from said stationary mold half and a vessel containing a bath of said substance beneath said mold, said riser tube extending into said bath in said vessel, said means for pressurizing said chambers including a source of compressed gas, a chamber receiving said vessel and connected to said source and valve means between said source, said mold chamber and said chamber receiving said vessel.

3. The apparatus defined in claim 2, further comprising a rubber sealing ring between said enclosures.

23 -2 3;" Y UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. Q ZQQ IQQ Dated a! u u-m 121 Inventor(s) Angucl 'IOBChOY BALEVSKY Qt l1 7 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading, line [733 read the Anig nee's name INSTIM-PO mamzm: I TBCHIIOWIA m MBTALITB,

" Sofia, Bulgaria Signed vand sealed this 3rd day of September 1974.

( SEAL1 Attes-tz McCOY M. GIBSON; JR. C. MARSI IALL DANN Attesting Officer Commissioner of Patents

Claims

1. An apparatus for casting under counter pressure comprising a mold having at least one movable mold part; means communicating with said mold for supplying a molten substance thereto; means forming a mold chamber communicating with said mold and a further chamber adapted to sustain a gas pressure above said substance; means for differentially pressurizing said chambers to drive said substance into said mold; and an actuating mechanism for opening and closing said mold and connected to said movable mold member, said mold chamber comprising two telescopically movable enclosures including a stationary enclosure and a movable enclosure, said movable enclosure having effective piston surfaces of different diameters at its opposite ends and exposed to the pressures in said chambers to constitute a differential piston retaining said mold chamber closed upon differential pressurization of said chambers, said movable mold member being connected to said movable enclosure and displaceable therewith.