US1495478A - Mold - Google Patents

Description

' May 27 1924. 1,495,478

w. A. GIBSON MOLD Filed Oct. 16 1919 4\ l III 2 Sheets-Sheet 1 w wz z Patented May 27, 1924.

UNITED STATES PATENT orl-lcs.

WILLIAM A. GIBSON, OF CLEVELAND, OHIO, ASSIGNOR, BY MESNE ASIGNMENTS, "1'0 ALUMINUM; MANUFACTURES, INCORPORATED, OF CLEVELAND, .0510, A COEPOBA TION OF iIELAWARE.

MOLD.

Application filed October 16, 1919. Serial No. 881,020.

To all whom it may concern:

Be it known that I, WILLIAM A..GIBSON, a citizen of the United States, residing at Cleveland, in the county of Cuyahoga and State of Ohio, have invented certain new and" useful Improvements in Molds, of which the following is a specification, reference being had therein to the accompanying drawings.

The invention relates to the making of castings and especially castings having their constituent material distributed irregularly so as to provide a number of heavy sections separated by relatively thin sections. My improvements have been developed inconnection With skirted pistons with internal wrist pin bosses made of aluminum alloys and said improvements are especially applicable to such castings and to the casting of other cup-shaped or chambered articles.

One object of the present invention .is to overcome the difiiculties incident to crystallization shrinkage which have characterized the use of prior semi-permanent and some permanent molds for the casting of skirted pistons or other cup-shaped, tubular or chambered articles having an irregular distribution of their constituent material.

A further object of the invention is to provide a mold for making skirted pistons which will be cheap to make, economical to maintain and easy to operate.

Another object of the invention is to produce a piston casting of which the gate metal can be removed neatly and with a minimum amount of: machine work.

Another object of the invention is to produce a mold with a frangible refractory core for casting pistons, or other cup shaped articles, which can be operated easily and rap-v idly to produce accurately formed castings.

In carrying out my invention in connection with the casting of aluminum alloy pistons for internal combustion engines, I'

provide a mold having a plurality of ingate passages which lead into those parts of the mold cavity forming the wrist pin bosses and other internal projections constituting the heavier or thicker parts of the casting; and I also provide for maintaining the gate metal molten until all of the metal in the casting proper has solidified. I attain both of these ends and secure a mold whichcan be produced and operated at relatively low cost and which is easy to handle and operate, by providing a moldbody of suitable metal, such as cast iron, to form the extenor head and side walls of the piston castmg and a frangible core of refractory material, such as sand, to form the interior walls of the pistoncasting, the ingate passages of the mold bein 'formed in the core and arranged to lead directly into the inner ends of the boss cavities of the mold as well as into the cavities forming any other heavy internal projections of the casting.

By the use of a mold of this character, it Wlll be seen that, notwithstanding the chilling action of the metal mold body on the outer sides of the piston casting, the low conductivity of the core material surrounding the ingate passages, the relatively low specific heat of said material and the fact that the core is itself surrounded by the hot metal of the casting proper, alltend to keep the metal in said passages in a molten condition and the heavy. sections of the casting, which tend to solidify after the lighter parts of the casting, are maintained indirect communication with the supply of molten metal in the gate passages, so that provision is made for a progressive solidification of the metal, first in the light sections of the casting, then in the heavy sections of the easting and finally in the gate passages, and crystallization shrinkage, which is especially high in the case of the light weight metals shrinkage are prevented.

Furthermore, by leading the ingate pas- I sages into the inner ends of the boss cavities of the mold, I am enabled to neatly and easily separate the gate metal from the casting proper by the otherwise necessary operation of boring out the bosses of the piston. In order that my improved process and mold may be clearly understood, reference is had in the following description to the accompanying drawings which illustrate different forms of semi-permanent molds especially designed for the casting of aluminum alloy pistons for internal combustion engines.

In the drawings, -Fig. 1 is a plan view of a mold embodying my improvements;

Fig. 2 is a section on the line 2-2, Fig. 1; Fig. 3 is an axial section of a piston casting made in the mold shown in Figs. 1 and 2, the casting having the gate or sprue metal attached;

Fig.4 is a detail view of one of the pafts of-the mold;

Fig. 5 is a plan view of another form of mold embodying some of my improvements; Fig. 6 is a section on the line 6-6, Fig. 5. Fig. 7 is a section through a casting made in the mold shown in Figs. 5 and 6.

Referring first to the form of construction shown in Figs. 1, 2, 3 and 4, the mold body comprises a base 1 and side members 2 and 3 made of cast iron or other suitable. metal. The base forms the outer bottom wall of the mold cavity and the two side members are formed wlth aligning semi-cylindrical walls 2 and 3'? which together constitute the cylindrical outer wall of said cavlty. The base 1 is provided with a central C11- cular elevation 1 which fits into corresponding recesses formed in the bottoms of side members 2 and 3, the engagement of the said recesses with the elevation of the base serving to align the three parts of the mold. The base 1 has a central depression 1 to form a work spot on the head of the piston casting. The side members of the mold are secured in assembled position on the base byohooks 4, 4: pivoted on side memher 2 so as to swing into engagement with pins 5, 5 on side member 3. When the hooks are forced down over the pins the side members of the mold are drawn tightly together.

The inner walls of the mold cavity are formed by a frangible core 6 of sand or any other suitable and preferably non-conducting material. The core 6 has opposite recesses 6 6 to form the wrist pin bosses of the piston casting and recesses 6", 6 to form strengthening ribs between said bosses and the walls of the piston.

The ingate of the mold is formed in the core 6 and comprises an upright inlet passage 7 terminating at its lower end with a cup-like depression 7", and short lateral passages 7, 7 which lead from the inlet passage 7 above the cup 7 into the inner ends of the boss recesses 6*, 6.

The core 6 is provided at its upper end with an outwardly extending flange 6 which rests in and fits corresponding recesses 2 and 3 in the side members of the mold body. The core is also preferably provided with a laterally extending lug 6 which fits the corresponding recesses in the faces of the side members 2 and 3 and serves to locate the core in suitable angular position in the mold.

ll prefer to form the flange 6 of the core with a metal ring 6 which is shaped to fit the recesses 2 and 3 in the side members of the mold body. The ring 6 is preferably formed with several internal In S or projections o which interlock with the ody accent/o shrinkage of the metal in the of the core. When such a metal ring is em loyed the lug 6 is formed on it. It wil be understood that the ring 6 is made a part of the core when the latter is molded before baking in t-hb well known manner. It will also be understood that the core can be strengthened in the well known manner by the use of inserts of wire or the like and suitable wire inserts can be provided at the top of the core to facilitate lowering it into the body of the mold.

In the side members 2 and 3 of the mold are movably mounted core pins 8 and 9, the inner ends of whichextend into the boss recesses 6 of the core and serve the double purpose of coring out the piston bosses and chilling the metal thereof. The core pins are slightly tapered at their inner ends to facilitate their removal. The side members 2 and 3 are provided with pillars 2 and 3 which are apertured to receive the core pins 8 and 9 and provide for them additional support.

The side'members of the mold are provided with suitable handles 10, 10 by means of whichsaid members can be moved toward and from each other on the base 1.

In the use of the mold above described the side members 2 and 3 are moved together on the base 1 and locked by the hooks 4c. The core 6 is then lowered into position and the core pins 8 and 9 inserted. Then the molten metal, such as a suitable aluminum alloy, is poured into the inlet passage 7 of the gate. For a common piston alloy having the composition of 10% copper and remainder aluminum, the pouring temperature should be from 1275 F. to 1350 F. The first entering metal falls into the cuplike depression 7 which minimizes splashing, and as soon as the said depression 7" is filled the metal flows through the ingate passages 7 into the boss recesses of the core and thence to the bottom of the mold cavity, said cavity being gradually filled as the pouring continues. When the metal of the casting has solidified, as indicated by the gate passage 7 the core pins 8 and 9 are withdrawn, and then the locking hooks 4 are disengaged, the side members of the mold separated and the casting removed. When the core material has been knocked out from the casting the latter appears as shown in Fig. 3.

It will be seen that the piston casting comprises a head a, side walls 6, pin bosses c, a, strengthening ribs d and gate metal or sprue e. The sprue can be removed from the casting proper by the operation of boring out the pin bosses 0, c, as indicated by dotted lines in Fig. 3, the sprue being thus separated by an otherwise necessary machining operation.

In Figs. 5 and 6 T have shown my improvements embodied in a so called pot mold,

its

The core 22 is of the same general character as that provided for the mold first described. It is provided with a flange 22* which fits a corresponding annular recess 21 in the top of the mold body. The core has oppositely disposed recesses 22", 22 to form wrist pm bosses on the casting, a bottom recess 22 to form a boss or pillar on the inner head wall of the piston casting, and a series of radiall extending recesses 22 to form strengthenmg ribs between the" said pin bosses, pillar and walls of the piston casting.

As in the first form of construction the ingate of the mold is formed in the core and comprises an inlet passage 23 which opens at its lower end into the recess 22 and lateral passages 23*, 23 which lead from the passage 23 into the inner ends of the boss recesses 22, 22". If a piston casting were to be formed without the heavy ribs and the boss or pillar on the inner wall of the piston head, the core recess 22 would, of course, be omitted and the inlet passage 23 of the gate would terminate with a cuplike depression below the passages 23", as in the case of the first form of construction.

In the use of the last described mold, the core is lowered into position in the mold body, no special angular position of the core being necessary because the mold is not provided with core pins for the wrist pin bosses. The molten metal on being poured into the inlet passage of the gate flows directly through sai passage and the core recess 22 into the bottom of the on -shaped mold cavity, the first entering meta being received in the cup-like depression 21 in the bottom of the mold body which thus serves to minimize splashing, as in the case of the cuplike depression in the core of the first form of construction. The incoming molten metal first fills the bottom art of the mold cavity, then rises in the si e section of the cavity up to the level of the gate passages 23 and thereupon flows through said latter passages until the mold cavity is filled.

When the metal of the casting has solidified, as shown by the crystallization shrinkage in the inlet passage of the gate, the casting can be withdrawn from the mold.

The casting as it comes from the mold is shown in Fig. 7 and comprises a piston head A, a side wall B, wrist pin bosses C, C, an internal boss or pillar D on the head,

a plurality of radial stren henin ribs E and the gate metal or sprue In t is form of casting the gate metal is removed from the casting proper b first severin it from the inner ends of t e wrist pin osses by boring1 out the latter, or otherwise by any suitab e cutting'tool, whereupon it can be broken from the boss or pillar D, the lower part of the s rue beinlg preferably weakened at F to faci itate suc reaka e, and thereupon the inner end of the pifi smoothly machined.

Advantages incident to my invention will now be readil understood. It will be seen that by formlng the gate passages in a refractory non-conducting material with low specific heat, preferably the core of the mold, t e metal in said passages is maintained in ar D can be a molten state until after the metal in the mold cavity proper has set under the influence of the chilling action of the mold body. This tends to result also, aside from the character of the material in which the gate passages are formed, from the fact that said gate passages are disposed within the chamer of the casting proper so that the walls of said passages are surrounded b the hot metal of the casting. It will also e apparent that by conducting the entering metal directly into each and all of the heavy sections of the casting, the latter are maintained in direct communication with the supply of molten metal in the gate passage which compensates for crystallization shrinkage in the eavy sections and prevents shrinka e cracks between the heavy sections and t e previously solidified thin sections of the casting.

A ain, it will be seen that my improved mol with its metal body and non-conducting frangible core is especially adapted for the casting of pistons as the-chilling action of the metal body of the mold gives a fine grained, hard structure in the outer parts of the piston walls which well adapts the latter for machining and insures a good bearing surface for engagement with the engine cylinder wall, while the frangible core makes possible practically any desired form of internal projections on the piston.

In connection with the chilling action of the mold body it is to be observed that it is possible to secure too great a chilling action and, as I provide no auxiliary means for heating the mold body, I have found it desirable to make the walls of the mold body no heavier than is necessary to enable it to withstand the wear and stresses encountered in operation. By thus limiting the weight or thickness of the walls of the mold its heat absorbing capacity is limited and it is maintained at a satisfactory working temperature by the heat absorbed from the molten metal.

It isnot necessary to provide the core with chill insertsof any sort because diliiculties incident to or stallization shrinkage are obviated by the inherent design of the mold, and consequently the cores are easily produced and, furthermore, the mold is easy to operate and maintain.

The specific forms of construction which v I have shown and described are presented lltl for purposes of explanation and illustration and it will be understood that the invention is not limited to these particular forms except as defined in the appended claims;

What ll claim is:

1. A mold for making cup shaped castings having a plurality of heavy sections projecting from the main body of the castin and separated by light sections, said mol having some of its casting-engaging walls formed of metal and some of frangiblematerial of low heat conductivity in comparison with metal and having a plurality of ingate passages formed in said low conductivity material and leading into extremities of the mold cavity sections forming the said heavy sections of the casting.

2. A mold for making cup shaped castings having a plurality of heavy sections projecting from the main body of the casting and separated by light sections, said mold comprising a metal body, and a frangible core of low heat conductivity in comparison with metal and formed with a plurality of ingate passages leading into extremities of the mold cavity sections that form the said heavy sections of the casting.

3. A mold for making cup shaped castings having a plurality of heavy sections projecting from the main body of the casting and separated by light sections, said mold having some of its casting engaging Walls formed of metal and some of frangible material of low heat conductivity in comparison with metal, and having a lurality of ingate passages formed in said ow conductivity material and leading into extremities of the mold cavity sections forming the said heavy sections of the casting, the said ingate passages constituting the only openings into the mold cavity.

4. Ac mold for making cup shaped castings having a plurality of heavy sections, projecting from the main body of the casting and separated by light sections, said mold comprising a metal body, and a frangible core of low heat conductivity in comparison with metal and formed with a plurality of ingate passages leading into extremities of the mold cavity sections that form the said heavy sections of the casting, the said ingate passages constituting the only openings into the mold cavity.

5. A mold for making cup-shaped castings with internal projections comprising a body forming the exterior walls of the mold cavity, and a core forming the interior aneaeve walls of said cavity, the core being formed with recesses to produce the internal projections on the casting and with a plurality of ingate passages which lead into said recesses.

6. A mold for casting skirted pistons with internal wrist pin bosses comprising a mold body forming the exterior side and bottom walls of the cup-shaped mold cavity, and a core having recesses in its sides for the piston bosses and forming the interior walls of said cavity, the mold having an ingate comprising an inlet passage extending downwardly through the core and terminating in a cup-like depression that receives the first entering metal and minimizes splashing and a plurality of passages extending laterally from theinlet passage into the said core recesses.

7. A mold for casting skirted pistons with internal wrist pin bosses comprising a metal body part forming the exterior side and 'terior walls of said cavity and formed with recesses for the piston bosses and with ingate passages comprising a downwardly extending inlet passage and passages extending laterally therefrom into the inner ends of the boss recesses.

8. A mold for casting skirted pistons with internal Wrist pin bosses comprising a metal body part forming the exterior side and bottom walls of the cup-shaped mold cavity, and a frangible core constituting the interior walls of said cavity and formed with recesses for the piston bosses and with ingate passages comprising an inlet passage extending downwardly into the bottom of the mold cavity and passages extending laterally from the inlet passage into the inner ends of the boss recesses. v

9. A mold for casting skirtedpistons with internal wrist pin bosses comprising a metal body part forming the exterior side and bottom walls of the cup-shaped mold cavity, and a frangible core constituting the interior walls of said cavity and formed with recesses for the piston bosses and with ingate passages comprising a downwardly extending inlet passage and passages extending laterally therefrom into the inner ends of the boss recesses and core pins movably mounted in the side walls of the mold body and extending part way through the boss recesses in the core. 7

10. A mold for making cup-shaped castings comprising a hollow mold body, an annular member adapted to be'positioned on the said mold body, lateral projections on the said annular member, and a frangible core formed in the said annular member in engagement with and in part supported by, certain of the said projections, certain of the lateral projections of the said annular Oil lltlfl means member cooperating with the said mold body in a manner to position positively the said core in the mold body.

11. In a mold for making cup shaped castings, a mold body having recesses formed in its top face, an annular member having outwardly and inwardly extending projections and adapted to seat in the said recesses, and a core formed in the said annular member in engagement with the said inwardly extending projections whereby the core is positioned in the mold and prevented from movement relative to the annular member.

12. A mold for making cup shaped castings comprisin a hollow mold body the inner walls of w ich form the outer walls of the mold cavity, a recess formed in the mold body near one end of the mold cavity, a frangible core, the outer walls of which form the inner walls of the mold cavity, having a laterally extending flange formed at one end of the core and adapted to seat in the said recess and to support the said core in the mold body.

13. A mold for making cup shaped castings comprising a hollow mold body consisting of a base member and two side sections seated thereon, the upper surface of the said base member and the adjacent curved side wall surfaces of the said side sections together forming the outer end and side walls of a mold cavity, a recess in the upper surfaces of the side sections adjacent the mold cavity, and a frangible core having a flange near one end adapted to seat in the said recess and to support the core in the mold cavity.

14:. A mold for making cup shaped castings comprising a hollow mold body, the inner walls of which form the outer walls of the mold cavity, a recess in the mold body near one end of the mold cavity, an annular member adapted to seat in the said recess and a frangible core attached to the said annular member and positioned thereby in the mold cavity.

15. The process of making a skirted iston with wrist pin bosses which comprises casting the piston in a mold having a frangible core by introducing the molten metal into the mold cavity throu h ingate passages formed in the core an extending radially of the piston into the inner ends of the piston boss cavities of the mold, removing the casting from the mold and separat ing the gate metal from the casting proper by boring out the bosses.

In testimony whereof,l hereunto aifix my signature.

WILLIAM A. ernson.

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