US 2755528 A
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y 24, 1956 c. BUCKEN 2,755,528
APPARATUS AND METHOD FOR THE CASTING 0F SHA PARTS PED ARTICLES OR MACHINE Filed Jan. 24, 1951 "VI/E N TOR Cum BUCKEN BY 'w fiTTORNEYS APPARATUS AND METHOD FOR THE CASTING F SHAPED ARTICLES 0R MACHINE PARTS Curt Biicken, Heilbronn (Neckar), Germany, assignor to Karl Schmidt Gesellschaft mit beschraenkter Haftung, Neckarsulm, Wurttemberg, Germany, a corporation of Germany Application January 24, 1951, Serial No. 207,519
Claims priority, application Germany January 27, 1950 12 Claims. (Cl. 22-17 0) This invention relates to a method for the casting of shaped articles or machine parts.
It is an object of the invention to improve the known methods of casting in permanent moulds with or without pressure, for instance of permanent-mold casting and press-casting in such a way that it is possible without difiiculties to use also subdivided cores with undercuts.
For the purpose of this specification, the generic term press-casting will be used to include both the pressure die-casting or die-casting method, in which molten material is cast under pressure and the permanent-mold casting method, in which the metal is cast in molds or dies without pressure.
As is well known it was not possible so far in presscasting processes to use subdivided cores having undercuts. The casting processes in which the molten or plastic metal is cast under pressure generally have the disadvantage-no matter whether a permanent-mold casting process or a press-casting method is in question or a method in which the melt together with the mold is under an elevated pressure in relation to the atmosphere or exposed to a partial vacuum (vacuum die-casting) that on flowing-in of the molten or plastic metal between the parts of the core and after the solidification thereof it is very difiicult and sometimes even impossible to remove the core parts. Therefore, hitherto it was impossible to use the permanent-mold casting method and oftentimes also the press-casting method with a high metal pressure in the runner e. g. in the manufacture of pistons for internal combustion engines or for machine parts of a complicated construction for the casting of which as a rule largely undercut cores are required.
In order to remove this difliculty in the production of castings according to the permanent-mold casting or press-casting method, according to the present invention the cores are encased. The wall thickness of such a core case or core sleeve may be relatively small, i. e. it need not exceed a few tenths of a millimeter. In order to produce the case or sleeve, as a rule an easily deformable, e. g. non-ferrous metal is used. However, in some instances it is also possible to use a soft sheet material for making the sleeve. In this case it is advisable to use a non-cutting shaping method, by shaping the soft sheet steel in the die under action of the pressure exerted by a rubber press or stamp in such a way that it assumes the shape of the sleeve.
In the permanent-mold casting method a core sleeve produced in this manner is inserted in the die before closing the outer mold. Then the cores are inserted in the core sleeve which is open at its top, in the usual manner. Where the press-cast process is used, the cores together with the core sleeve are introduced into the press-casting machine in a combined condition before the outer moulds are mechanically closed.
Moreover, where the press-cast method is used, it is advantageous to operate with alternating cores in order tes Patent Patented uly 24, 1956 2 to utilize fully the advantages of this method as regards its high operating speed.
Depending on the type of the casting it may be advisable either to leave the thin core case in the casting or to remove it therefrom; 'of course, in the latter case it has to be destroyed.
The invention will be better understood by reference to the following detailed description in connection with the accompanying drawings, illustrating by way of example some details of the novel casting method and die according to the present invention and in which:
Fig. 1 is a section showing three cores to be used for casting the blank or slug of a piston for internal combustion engines,
Fig. 2 is a sectional view of a case therefor,
Fig. 3 is a sectional view showing the core parts encased in this case,
Fig. 4 is a sectional view showing the core parts with their case inserted in the mold or die,
Fig. 5 is a sectional view showing the core case left in the mold on completion of the casting process, and
Fig. 6 is a sectional view showing a method of producing a core case in accordance with the present invention.
Referring now to the drawings in greater detail, and first to Fig. 1, it will be seen that three cores or core elements 1, 2, 2' are shown which are to be used for casting the blank or slug of a piston for internal combustion engines by a permanent-mold casting or presscasting method. The cores 2 and 2' are formed with undercuts 3, 3'. The cores are put into a case or cover 4 of the type shown in Fig. 2. The cover 4 is advantageously in the form of a sleeve consisting of nonferrous metal or of soft sheet steel. The wall thickness is only a few tenths of a millimeter. In Fig. 3 the cores 1, 2, and 2' are shown inserted in the case or cover 4. The cores together with the sleeve 4 are then inserted in a permanent mold 5 in the manner as indicated in Fig. 4, leaving between the sleeve and the permanent mold an interspace which is filled up by the molten or semiplastic metal and on solidification thereof forms the blank 6. On completion of the casting operation the cores 1, 2, 2 are removed from the sleeve so that on opening of the permanent mold the casting 6 together with the sleeve 4 can be removed from the latter, as indicated in Fig. 5. In order to remove the core sleeve 4 from the casting this sleeve must be destroyed.
The core sleeve 4 is advantageously made by noncutting shaping in the manner as shown in Fig. 6. For carrying out this method there is required a die 7 having a cavity 8 whose shape is identical with that to be given to the thin walled metal sheet 9. The latter is shaped by means of a rubber press or stamp 10 by application of pressure in such a way that it engages the inner wall of the cavity 8, thereby assuming the shape of the core sleeve 4. A sheet obtained in this manner has the advantage that its surface is not damaged during the shaping.
While the invention has been described in detail with respect to a now preferred example and embodiment of the invention it will be understood by those skilled in the art after understanding the invention that various changes and modifications may be made without departing from the spirit and scope of the invention and it is intended, therefore, to cover all such changes and modifications in the appended claims.
What I claim is:
l. A method of casting in permanent molds bodies having recesses whose surfaces are provided with undercuts, which comprises forming a thin metallic ease having the external shape of the walls of the recess, and
having a closed end and an open end, inserting into said case through the open end successively a plurality of solid core parts which fill the part of the case corresponding to the recess, at least one of said parts which is first introduced projecting into an undercut-forming portion of the case, inserting the case in a die in which the closed end is spaced from the inner wall of the die, casting metal into the die, and thereafter removing the core parts successively unbroken from the case.
2. A method as claimed in claim :1, in which said body is a piston.
3. A method as claimed in claim 1, in which said body is a piston for an internal combustion engine.
4. A method as claimed in claim 1, in which said case is removed from the casting.
5. A method as claimed in claim 1, in which the case is left in the casting.
6. A method as claimed in claim 1, in which the case is of thin non-ferrous sheet metal material.
7. A method as claimed in claim 1, in which the case is of thin soft sheet steel material.
8. A method as claimed in claim 1, in which the case is formed of metal sheet material having a thickness of not more than about one millimeter.
9. A core for casting bodies having recesses whose surfaces are provided with undercuts comprising a thin metallic case having the external shape of the walls of the recess, and having a closed and an open end, and
References Cited in the file of this patent UNITED STATES PATENTS 114,905 Barron May 16, 1871 1,281,258 Alexander Oct. 15, 1918 1,393,195 Bradley Oct. 11, 1921 1,449,085 Brand Mar. 20, 1923 1,586,603 Brown June 1, 1926- 1,894,983 Eppensteiner Jan. 24, 1933 2,236,306 Bratring Mar. 25, 1941 2,448,294 Blanchard Aug. 31, 1948 2,527,537 Fahlman et a1. Oct. 31, 1950 FOREIGN PATENTS Great Britain Apr. 16, 1922