US2004661A

US2004661A - Piston sand core

Info

Publication number: US2004661A
Application number: US443081A
Authority: US
Inventors: Jardine Frank
Original assignee: Aluminum Company of America
Current assignee: Howmet Aerospace Inc
Priority date: 1930-04-10
Filing date: 1930-04-10
Publication date: 1935-06-11
Anticipated expiration: 1952-06-11

Description

F. JARDINE PISTON SAND CORE Filed April 10, 1930 2 Sheets-s 1 & wk

F. JARDINE June 11, 1935.

no F/cA/w Milka/me Q YM attorney Patented June 11, 1935 Parana" mm 2,004,661 PISTON SAND CORE I Frank Jardine, Cleveland,

- Aluminum Company of America,

Ohio, assignor to Pittsburgh,

Pa., a corporation of Pennsylvania Application April 10, 1930, Serial No. 443,081

4 Claims.

This invention relates to the art of casting pistons and is primarily concerned with the provision of certain novel mold and core apparatus for casting pistons which preferably are of an 5 aluminum base alloy.

It is now well recognized in this art that when molten alloy comes into contact with the metal of permanent 'molds the accompanying chilling effects provide a highly improved product as compared with casting in a'sand mold. The chilling causes a finer grain structure and also improved properties of toughness, hardness and tensile strength. While it is well known practice today to utilize permanent molds as noted, the use of permanent core parts is not so widespread. This is because of the fact that pistons of certain design have an internal structure of such intricacy that it is impossible to define the same with a permanent core.

In view of the foregoing, this invention contemplates the provision of a core assembly, which comprises, for the major part, a permanent core construction, together with non-permanent core parts which are designed to core out inaccessible recesses in the piston. The invention also comprehends an arrangement wherein the non-permanent core parts are supported and carried by the permanent core construction.

More in detail, the invention has in view the provision of a core assembly including sand cores which are carried by metal supporting members embedded therein. The latter are detachably anchored in the permanent core construction and are so designed as not to prevent the removal of the latter from the piston after casting.

These and other more detailed objects and advantages will become apparent as the description of the invention proceeds. For a full and more complete understanding thereof, reference may be had to the following description and accompanying drawings, wherein:

Figure l is a vertical section, somewhat fragmentary, through molding apparatus designed in accordance with this invention.

Figure 2 is a section taken on the line 2-2 of Figure 3.

Figure 3 is a horizontal section taken about on the plane indicated by the line 33 of Figure 2.

Figure 4 is a detached elevational showing of iii one of the sand core parts,

Figure 5 is a bottom plan view of the core part shown in Figure 4.

Figure 6 is a horizontal section taken on line 6-6 of Figure 2, omitting the metal of the piston;

' bosses.

Figure 7 is a showing similar to Figure 6 taken on line 1-1 of Figure 2;

Figure 8 is a showing similar to Figure 6 taken on line 8-8 of Figure 2; and

Figure 9 is a perspective view of the permanent 5 and sand cores as assembled within the mold.

Referring now to the drawings, a permanent mold of any conventional type is represented by the reference character A. This mold serves to define the outer contour of the piston, which is cast therein. In the present instance the piston B is shown as including certain internal construction comprising wrist pin bosses l and hangers 2 connecting the bosses with top 3 of the piston. Obviously, the wrist pin bosses, together 15 with the hangers 2, wall 4, and top I, define recesses which'are inaccessible to a permanent core as the latter could not be withdrawn therefrom after casting. These recesses are referred to as R. g The remainder of the internal structure of the piston is susceptible to formation by a permanent core which is shown at C. The latter may be of a sectional construction to facilitate removal after casting or as shown in Figure 3, of a single piece, but its design is not material to this inventon other than that it be formed with vertically extending recesses 5.

In the casting of the piston, recesses R are formed by properly shaped non-permanent cores 6 of sand. Partially embedded in'the latter, with portions projecting therefrom, are wire inserts I. The latter are bent over at 8 to provide a firm support for the core. The downwardly projecting portions of the inserts 1 are fitted in the 35 recesses 5 and are preferably deformed at 9 to provide for a good frictional engagement with the permanent core 0. In the embodiment illustrated each sand core part 6 is shown as provided with two of the inserts 1, each of which is located in a recess 5 adjacent to one of the wrist pin Obviously, the number of inserts employed can be varied with the size and shape of thepiston cast.

The permanent core and sand cores when positioned in the mold are arranged as shown in Figure 9. The vertical hanger 2 being formed within the void 2' and the strut I 1 formed in the void H. The hanger 2 and the struts I! are joined to 'each other through the medium of the, pin bosses as shown" in Figure 7. As best shown in Figure 7 the sand core 6 curves toward the permanent core C to form the void for strut IT. The surface of the sand core adjacent the mold at this curved tip forms the inner surface 65 v of the piston skirt. The surface of the sand core adjacent the permanent core formsthe outer surface of the strut II. Thus the sand cores 6 form a recess that ism-entrant towards the pin bosses in order to form curved struts. It would be obviously impossible to withdraw the perma nent core from the mold should the permanent core be utilized for forming the upper edge of the curved struts. The lower edge of the curved struts is formed in a groove of the permanent core as shown in Figures 9 and 8. The groove is curved as the sand core in Figure 7 and the two curves are complementary to form the voids H.

In carrying out a casting operation in accordance with this invention the sand cores 6 are first properly built up on the wire inserts 1. The permanent core construction C is then assembled and the sand core parts 6 attached thereto by inserting the members I in the recesses .5. The entire core assembly is then inserted in the mold A and the molten aluminum alloy poured. After freezing of the piston, the permanent core is withdrawn from the interior of the piston and the mold A is removed from about the piston. In removing the permanent core C, the wire inserts 1 will pull out of the recesses 5 as they are still held in the sand cores 6. The sand core parts 6 may now be broken up and punched out in the usual manner. The inserts are removed as the sand core breaks up.

While a preferred specific embodiment of the invention is herein set forth, it is to be understood that I am not to be limited to the exact constructions illustrated and described because various modifications might be made in putting the invention into practice within the purview of the appended claims.

What I claim is:

1. Molding apparatus comprising a, permanent mold having a casting cavity therein shaped to form the outer walls of a piston, a permanent core construction removably positioned within said casting cavity and spaced from .the walls thereof to define the inner surfaces of the piston skirt at the open end thereof, the sides of said core construction being offset inwardly to form the inner surfaces of a pair of piston pin bosses and the inner surfaces of webs extending from said piston pin bosses to the skirt, the offset portion of said core construction being extended to form a portion of the inner surface of the piston head and to form the inner walls of a pair of hangers extending from said piston pin bosses to the head and a pair of sand cores arranged to provide re-entrant recesses between each of the sand cores and the permanent core to form.the outer side surfaces of the hangers and the webs and the adjacent inner surfaces of the piston skirt and head.

2. Molding apparatus comprising a permanent mold having a casting cavity therein shaped to form the outer walls of a piston, a permanent core construction removably positioned within .-said casting cavity and spaced from the walls thereof to define the inner surfaces of the piston skirt at the open end thereof, the sides of said core construction being offset inwardly to form the inner surfaces of a pair of piston pin bosses and the inner surfaces of webs extending from said piston pin bosses to the skirt, the offset portion of said core construction being extended to form a portion of the inner surface of the piston head and to form the inner walls of a pair of hangers extending from said piston pin bosses to the head' and a pair of sand cores arranged to provide re-entrant recesses between each sand core and the permanent core so as to form the outer side surfaces of the hangers and the webs and the adjacent inner surfaces of the piston skirt and head, said sand cores being supported by said permanentcore construction.

3. In apparatus for molding pistons or the like, an outer mold, a permanent core removably extending into the outer mold, additional permanent coring means removably extending thru substantially opposite sides of the outer mold and against the first named core, a pair of nonpermanent cores supported by the first named core, and wire straddling the second-named coring means releasably connecting said non-permanent cores to the first named core.

4. In apparatus for molding pistons or the like, an outer mold, a permanent core removably extending into the outer mold, additional permanent coring means extending through opposite sides of the outer mold and against said first named core, a, pair of non-permanent cores positioned on opposite sides of said first'named core and spaced therefrom and from said outer mold to provide casting cavities, said non-permanent cores being spaced from said additional permanent coring means and substantially straddling the same, and wire retainer members imbedded in said non-permanent cores, said first named core being formed with longitudinally openings receiving and frictionally retaining said retainer members.

FRANK JARDINE.