US1769455A

US1769455A - Core for undercut cup-shaped articles

Info

Publication number: US1769455A
Application number: US388903A
Authority: US
Inventors: Pickering Theodore
Original assignee: DOEHLER DIE CASTING CO
Current assignee: DOEHLER DIE CASTING CO; DOEHLER DIE-CASTING Co
Priority date: 1929-08-28
Filing date: 1929-08-28
Publication date: 1930-07-01
Anticipated expiration: 1947-07-01

Description

Jilly 1, 193 0 PICKERING 1,769,455

CORE FOR UNDERCUT CUP SHAPED ARTICLES Filed Aug. 128; 1929 INVENTOR 7/1'606/0/"6 Pi'af e/vkry BY 7 v ATTO'RNEY Patented July 1, 1930 UNITED STATES 00., A CORPORATION OF NEW"O RK I CORE FOR UNDERC UT CUP-SHAPED ARTICLES Application filed August 28, 1929. "SeriaiNo. 388,903.

My invention has particular reference to the problemsarising in the casting of cupshape articles in permanent molds where the article has an internal undercut.

Sand or other disintegrable cores have been used for the purpose, and in some instances permanent collapsible cores have been used. A permanent core is obviously more desirable for several reasons, among which are economy and a resultant smoother surface to the casting formed by the core. However, the production of collapsible cores requires an accuracy of machining and truing of parts which render such cores rela tively expensive; and moreover the labor of drawing and again assembling such cores is considerable as compared with solid cores.

In particular is this true of cup-shape articles where the internal walls are cylindrical and have overhanging portions. For cxaimple,-pistons forinternal combustion engines present an especial problem by reason of the complex internal shape due to the presence of the wrist-pin bosses.

In-accordance with my invention I take care of the undercuts formed by the bosses by the use of disintegrable core sections and I use a solid permanent core section for all the rest of the casting, the sections being united with sufiicient permanency to withstand the casting pressure, and yet being easily separable after the casting operation. The permanent part constitutes the entire core of the skirt of the piston outside of the transverse plane containing the diameters of the wrist-pin bosses, and the central portion of the remainder. manent part of the core which extends beyond the wrist-pin bosses, constitutes a reduced axial extension transverse to the wristpin bosses. This extension, the sides of which converge, extends to the end of the core or the inner surface of the head of the piston. On either side of the extension of the permanent core and secured thereto there are disintegrable sand portions having a shape complementary to the undercut portion of the article. Thus, when the casting is completed, the permanent portion of That portion of the perthe core may be withdrawn" sand portions may be loosened and removed. Y

' 'rnnonoan PICKIERING, or BATAVIA, NEW YORK, .ASS'IGNOR' nononiinnn-prn-oasr ne I shall now-describe one embodiment of my invention in connection with the accompanying drawings in which: 1

Fig. lis a perspective of acoreembodying my invention;

Fig. 2 is a section of an internal combus-- tion engine piston withia coreplaced therein; and Y Fig. 3 is a transverse line 3"?3 of Figure 2.

section, taken on the .The core illustrated in the drawings;-

whichis the type used in casting pistons for internal combustion engines, is adapted to be used with a permanent mold such, for example, as are used in die casting and which are well known to those skilled'in the art. Essentially, the core consists of three parts, namely, a central permanent part 1 and two disintegrable parts 2.

The permanent part 1' of the core is adapted to fill theinterior ofthe piston outside .the transverse plane containing the diameters of the wrist-pin bosses 3 of, the piston. The outer surface of the; part l'is, therefore, complementary to-the desired contour of the inner surface of the piston outside the transverseplane containing the center lines of the wrist-pin bosses 3. :An

axial extension '4, transverse to the bosses 3 and having converging sldes, extendsfrom' the lower end of the permanent part land is integral therewith. The flange 4 extends along the inside of the piston to the head thereof; along that portion of thepiston which does not-contain undercut recesses. The converging sides of the flange 4 are pro 1 vided with undercut or dove-tail. tongues, 5

which are received in complementary grooves inthe arts 2 to unite the three parts of the core.

his construction is-not, however, essential, as theconv'erging sides of I the flange 4 may be smooth and the parts 2 v glued or otherwise secured thereto..

.The parts 2 may be constructed from plaster of Paris or sand with whicha binding agent has been mixed. The parts2 extend from the center of the. wrist-pin bosses 3, to the head of the piston as shown. Be-

low the recesses in the parts 2 which are provided for forming the wrist-pin bosses, there are provided projections 6 which are adapted to form the undercut recesses of the piston. These recesses, below the 'bosses, are necessary to properly proportion the metal in ,the piston 3A diainetrical groove is provided in the lower edge of the completed core and extends up the sides of the parts? to the lower surface otthe wristsection, the contiguous faces of the sections having dove-tail interlocking relation.

In witness whereof, I hereunto subscribe V my signature.

THEODORE PIOKERING.

pin bosses 3. The grooveis adapted to form;

a reinforcing flange 7 across the head of the piston. It is to be notedthat the parts 2 are be used for making them.- 2

The complete core is placed in the permanent mold and held in'place by the wristidentical and therefore a single pattern may pin cores. The molten metal is then forced in "around the'core. After the metal has cooled sufficiently the permanent part 1 of the core may be removed. The piston or other article is then subjected to a heat treatment which, incidentally, destroys the binding' material in the sand molds and after which they may be jarred loose from the I casting.

It will be evident'to those skilled in the art that I have devised a simplified core for undercut cup-shape articles which considerably reduces the time required for making up such cores. i

Itis obvious that various changes may be made by those skilled in the art in the illustrated embodiment oi my invention above particularly described within the principle and scope of my invention as expressed in internal undercutcomprising a permanent section-forming the entire core outside the undercut portion of the article and having a reduced axial extension forming the central part of the core at the undercut portion of t e article and two disintegrable core sections having ashape com lemental to the undercut portion of the article and detach ably secured to the axial extension on said A first section.

3. A core for cup-shape articles having an internal undercut comprising a permanent section forming the entire core above the undercut a longitu lnal extension forming the central part of the remainder of the core, and two' disintegrable sections for forming the undercut recesses in the article detachably secured to the extension on said permanent I (portion of the article and having