US1308103A - parkhurst - Google Patents

Description

F. A. PARKHURST. MOLD AND METHOD 0F CASTING.

APPLICATION FILED APR. 2. 1919.

Patented July 1, .1919.

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A r roms/FY F. A. PARKHURST. MOLD AND M'ETHOD 0F CASTING.

APPLICATION FILED APR. 2v. 1919.

Patented July 1, 1919.

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APPLICATION FILED APR-.2.1919.

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FREDERIC A. PARKHURST, OIl CLEVELAND, OHIO, .ASSICfNOR TO THE ALUMINUM CASTINGS COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO.

MOLD AND METHOD OF CASTING.

Specication of Letters Patent.

Patented July 1, 1919.

Application filed April 2, 1919. Serial No. 286,970.

T o all whom, t may concern.'

Be it known that I, FREDERIC A. PARK- Hrnzsrr, a citizen vof the United States, residing at Cleveland, in the county of Cuyahoga and Stateof Ohio,` have invented certain new and useful Improvements in Molds and- Methods of Casting, of which the following is a specification, reference being had therein to the accompanying drawings.

This invention relates more especially to an improved form of mold gate and to an improved method of introducing molten metal into the mold cavity. While the invention, with respect to some of its features at least, is of general application, it has been developed in connection with molds for casting aluminum alloy internal combustion engine pistons and is especially applicable to the casting of cup-shaped and hollow cylindrical articles from metals or metallic alloys having relatively high crystallization shrinkages, such as characterize the aluminum alloys.

One of the avoid the formation of blow holes in the casting due to the occlusion of air or other gases. n

Another object of the invention is to avoid porosity and cracks in the casting due to crystallization shrinkage.

A further object' of the invention is to reduce to a minimum the bulk of the gate metalof the casting.

Other objects more or less incidental to those above stated will be apparent from the following description in which I set forth a preferred form of mold and method of casting in accordance with my invention.

In the drawings,

Figure 1 is a top plan view, partially in sect-ion', of a mold having my improvedform of gate.

Fig.' 2 is an enlarged fragmentary vertical section on the line 2-2, Fig. 1.

Fig. 3 is an enlarged vertical section on-v objects of the invention is to Figs. 8, 9 and 10 are fragmentary sections on the lines 8 8, 9-9 and 10-10, respectively, Fig. 3.

The construction illustrated in the drawings shows my structural improvements embodied in a permanent mold designed for thecasting of aluminum alloy internal combustion engine pistons of relatively large Referring in detail to the construction illustrated, the mold as shown comprises a plurality of parts adapted when assembled-to form a mold cavity, A, for the piston casting proper. The mold body includes'a base member 1 and two complementary chambered side members 2 and 3 vwhich are movable on the base toward and from each other and thus provide for theremoval ofthe castings in the operation of the mold.V These three main sections of the mold body are preferably formed from cast iron.

The base 1 is formed with a cent-ral depression having a cylindrical side wall l and a conical bottom wall 1b. Each of the side ' members 2 and 3 comprises an inner side wall 4, end Walls 5 and 6, and top andl formed by a plate 9 bolted to the casting,

thus closing the interior chamber 10 of the member. Handles 11, 11 are secured to the plates 9, 9 ,so that the side members of the mold can conveniently be moved to and from operative position on the base.

The inner side walls 4 of the complementary members of the mold body mutually engage withy each other when said members are moved together as shown in Fig. 1. The Wall 4 is formed between its ends with a semi-cylindrical portion 4a, and the lower parts of this semi-cylindrical wall 4 together with ,the cylindrical side wall 1a in the base,- form the upper side wall of the casting cavity proper, the bottom of said cavity being formed by the conical bottom Wall 1""`of the depression in the base mem ber. 4Said. conical wall is formed-With a central depression 1c vwhich provides for a work spot on the head of the -piston casting. The bottom wall of this central depression is formed by a plug 1d which is grooved on its periphery to provide vents for air and other gases.

To secure alinelnent of the mold members 2 and 3, in relation to each other, the base is formed with a cylindrical shoulder 12,

. in the side members-2, 3.

. the present application it will su and two membery 14 The mold is 'provided with a main lcore 14 which is preferably made of steel and is of the five part form shown in Figs. 13 to 41S) of my U. S. Letters Patent No. 1,296,597, and is of the same general character as the core shown in the U. S. Letters Patent to Joseph H. Bamberg No. 1,296,588.k For a detailed description reference may be had to said Letters Patent. For the ipurpose of ce to state that the core comprises a central part 14a pairs of members 14", 14c and 14d, 14e which when assembled are adapted to be supported at their upper ends in the mold body lso as to depend within the cavity formed therein and form the inner walls `of the casting cavity proper. The main core parts are supported in the mold body` .by engagement with a pair ofv liners 15, 15 which are suitably secured to the mold members 2, 3, as by screws 15a. The lower ends of the liners serve to form wall of the mold cavity. With the main core parts supported in the liners 15 as shown in Fig. 2, the mold cavity takes substantially a cu shape corresponding to the trunk or skirted piston whichit is desired to cast. To insure proper angular positioning of the core 14 in the mold body,l the central. of the core is provided-with a key16 which projects from the core and is received between wear plates 17 secured in slotsin the mold members 2, 3- and their liners 15, 15. Each of the core parts. is provided with a suitable handle 14f to facilitate assembling` of tbe core in the mold and its removal therefrom. I

The core-members 14b and 14c are shaped to form a recess14lr to provide for a wrist pin boss on the casting while the members 14d and 14e are shaped toform a recess 14 for a similar purpose.. vThe core 14 is provided with vent passages as follows; The middle part 14 of the core is formed on its opposite fiat faces with longitudinal passages 14k, 14k, each of which extends from the `upper end of the core partV to a transverse passage 14m near the lower end of the core part. Then these flatfaces ofthe core partare formed at their lower ends with a series of vent grooves 14 extending from the bottom surface of the core upward to the transverse passage 14m,'and an adequate vent upward through the core the annular top is thus provided for air and' gases collecting on the bottom surface of the core. Each of the liners 15 is formed with vent groovesl 15, 15C, 15d and 15 on its bottom, inner, outer and top sides, respectively.

18, 18 are removablel core pins slid-ably mounted in the mold members 2, 3 with their inner ends projecting into the boss recesses 14g, 14h. To facilitate their removal, said pins have their ends slightly tapered where they engage the mold body and project intothe mold cavity- In the operation of the mold the various parts are secured in operative position by lock devices 19, 19, each of which comprises a pin 19@l mounted on one of the side members of the mold and a coperating pivoted hook 19b on the other side member. When the side members 2, 3 are brought together in proper position on the base 1, the hooks 19b are forced down over' the pins 19 so that the parts of the mold body are firmly secured together. y

l turn now to a descriptiontof the gate of the mold to which my present invention more particularly relates. The gate, which is formed by alining recesses in the adjacent walls 4, 4 of the mold members 2 and 3 and in the base 1, in its entirety comprises a feeder and a supply conduit. The feeder is 95 in the form of an upright cavity 20 adjacent one side of the casting cavity and extending fromlthe bottom of the casting cavity upward to and above the upper end of said cavity, the upper part of the feeder 100 comprisinga riser extension 20a. The feeder communicates with the casting cavity through a short passage 21, said passage extending, preferably, continuously from the bottom to the top of the casting cavity 105 and being relatively narrow in vcomparison with the greater width of the feeder cavity. The adjacent faces of the mold members 2 and 3 are formed with vent grooves 22 extending from the to of the riser chamber 110 20a to the upper sur ace of the mold.

The supply conduit of the gate 'comprises an inletsection 23 which is formed with downwardly converging walls, a lower discharge section 24 which extends fromthe 115 lower end of the inlet section`23 downwardly and laterally into the bottom of the casting cavity of the mold, and an upper discharge section 25 which extends laterally from the upper end of the discharoe sec- 120 tion 24 into the upper part of the fcoder 20. The discharge sectlon 24, 'as well as the inlet section 23, preferably has its walls converging downwardly somewhat. At the lower end of the discharge Section 24, it corn- 1-25 municates with the bottom of the feeder 20, as well as with the casting cavity.

The gate parts are all formed in the side members 2, 3 of the mold, except that the lower ends of the feeder 20 and the ds- 130 recalca p charge section 24 are formed by a recess 2G in the base 1.

lit is usually desirable to provide for heating the body of the metal to maintain it at a suitable temperature and li have shown burnv ers 27, 27 mounted on brackets 28, 28, said burners being arranged so that their flames are directed through openings 9*l in the plates-9, to heatthe inner walls of the mold members 2 and 3, and especially the parts of the'walls 4, in which the gate is formed, this arrangement insuring that the metal in the gatev shall remainmolten longer than' that in the mold proper.

Preferably the surfaces of the mold, iiicluding core parts, which constitute the walls of the'mfdcavity are suitably coat# ed ortreated in weil known manner to reduce as much as possible agitation ofthe Ato tightly lock the mold members 2 and 3 together and firmly clamp' the main core in All) position. troduced.

The temperatures at which the various parts are maintained will depend largely upon the nature of the metal or alloy to be cast. Assuming that-the burners 27 have Finally 'the core pins -18are in been operated-'to heat the' mold parts to thev desired temperature, the mold is new ready to receive the molten metal. Said metal is brought. to the mold in any suitable manner,

as by a ladle, and is poured into the inlet 2 3 ofthe gate. The markedconvergence of the walls of the inlet section 23 from its upper to its lower ends strongly-checks the velocity of the entering metal 'so that `it emerges from the lower end of the inlet section 23 with. a reduced velocity and 'encounters the gently curving wall of thedownwardly and y laterally extending ,discharge section 24 smoothly and without agitationi 4 lln the said discharge section 24 a further check on the velocity of the metal isprovided vboth by the lateral inclination ofthe passage and bythe gradual contraction of its walls from its upper toward. its lower end, so i that a smooth and 'steady flow ofmetal is secured ,and the metal first enteringthe casting cavity emerges from the discharge section 24 and enters the casting cavity with'little if any agitation or splashing, so as to avoid the mixing of airor gases into the metalwith resultant formation bf blow hglesfin the hnished casting.. v

lmolten metal continues to flow into the mold andits upper surface, in the casting cavity, comes into contact with the lower end of thepcore 14, the airy above the metal elther finds its way radially `-outward and into the annular part of the cavity in which it is free to rise and escape through vent grooves 15h, 15, 15d and 159,' formed in the liners 15, or, entering the vent grooves 14, linds its way upward through the core to the eterior of the mold. lt may be observed in this connection that the venting of the air or gases overlying the relatively quiescent mass of rising metal is readily effected in the manner last described, but if there is splashing or agitation of the metal inthe mold, air or gas is occluded in it and ll have found it practically impossible to separate such air or gas, no matter how adequate the provision for venting may be, so that a serous porosity of the casting results. This is especially true of the metal first entering the mold because it seems especially difficult to sepa-rate occluded air or gas bubbles from the body `of the metal which rises upward intocontact with the lower end of the main core. lt, is also particularly true in the case of castings having heavy/.cross sections, it being always more difficult in such cases, ,apparently to eliminate air orgases that become occluded in the metal. llt will thus be seen that the practical 4importance of avoiding splashing of the metal in the vmold cavity is very great.

As the molten metal rises in the annular section of the mold cavity, it simultaneously risesin the feeder 20, and if, at any stage of the pouring, the level of. the metal rises more slowly in the mold cavity than in the feeder, the metal in the feederwill How smoothly through the passage 21 into the `mold cavity andind its way in both directions around the main core to the diametri? cally opposite side of the cavity. ts the passage21 extends continuously from the'botn tom to the top of the mold cavity this smooth and unagitated flow of metal from the feeder into the mold cavity can occur at any level until the cavity is entirely filled It is obvious that after the first entering metal has lilled the bottom parts ofthe cast` ing cavity. and the feeder, the molten metal subsequently entering beneath the surfacelll) of the bath in the cavities is bound to do so without any splashing and resultant occlusion of air or gases. i

ln the process of filling the casting cavity, when the level of the molten metal therein rises te the level ofthe second discharge passage 25, the enteringmetal tends to pass from the lower'end ot the inlet section 23 into the discharge` section 25, and through it directly into the upper part of the feeder 20 and thence through the short passage 21 into the upper part of the casting cavity until the latter is hlled. Il`l'iereupon, by

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' in the short passage 21between reason ofthe hydraulicl head of the metal in the inlet section .of the gate, the flow continues through the discharge'section 25 until the riser chamber 20a is nearly or entirely lled with the molten metal.

The metal which enters the upper part ofy the riser throughthe discharge section 25Y does so at a very 'moderate velocity, this be-` ing insured not only by the checkingof. the flow in the inlet. section of the gate, but also by the angular arrangement of the discharge section 25 in relation to the inlet section- 23.

That is to say, the very abrupt change of direction which the entering stream of metal must make when passing from-the inlet section to the discharge section 25 so greatly litis important to maintain in the feeder section of the gate a molten mass of metal upon which the metal in all parts of -the mold cavity is free to draw to make up for crystallization shrinkage as the freezing progresses. ln my improved form of gate the molten condition of the metal in the feeder is insured by providing the separate discharge passages 24 and 25, the former entering the lower end of the feeder while the latter enters the upperpart thereof. Thus there is a relatively direct supply of the molten metal into the lower part of the feeder to maintain a molten supply in said lower part of the feeder to compensate for crystallization shrinkage in the lower portion of the casting cavity, and also a direct supply, through passage 25 of molten metal for the upper part ofthe feeder so that an adequate body of molten metal is provided inthe upper part of the feeder and in the riser chamber to compensate for crystallization shrinkage in the upper part of they casting cavity. ln other words, an adequate supply of molten metal is maintained in position t ent-er the casting cavity at any level to compensate for crystallization shrinkage and a progressive setting of the metal inthe mold is insured from points opposite the gate around the main core in both directions, then the casting cavity and the feeder `and finally in the feeder itself. l*

After a short interval to permit the metal to set, the locking devices 19 are eased ed,

, the core parts are withdrawn, the pins18 somewhat in advance ,of the main core parts,

then the locking devices 19 are entirely disengaged and the mold members 2 and 3 separated to permit removal of the casting.

It will be seen that my improved method of introducing the metal into the mold cavity by means of the mold and gate structure set forth, by avoiding occlusion of air or other gases in the molten metal, prevents blow holes in the castings which would otherwise result. It will also be seen that the insuring of a' molten mass -of metal in all parts of the feeder chamber during freezing of the metal inthe adjacent parts of the casting cavity, insures a. complete compensation for crystallization shrinkage in the casting proper, and thereby avoids the scrious )orosity which would otherwise result. Furt ermore, by making the gate discharge passages 24 and 25 separate from the feeder cavity, I am' enabled to form and dispose said passages soas to insure a slow and smooth entrance of the metal into the casting and feeder cavities without expanding the feeder cavity; and therefore, since the cross-sectional dimensions of the passages 24 and 25 can be made much smaller than those of the feeder cavity, l secure the desired result with a minimum bulk of gate metal.

I have shown my invention only in connection with molds for the production of piston castings but it is obviously applicable in the production of castings of other articles and other forms and it will be understood that the foregoing disclosure 1s for purposes of illustration and explanation and not intended to define the scope of the passage, an inlet passage extending downwardly and laterally and opening into the bottom of the casting cavity, and a' second inlet passage extendlng laterally from the iii-st inlet passage into the upper part of the feeder cavity.

2. A mold having a cavity foi` the casting proper and provided with a' gate comprising an upright feeder cavity adjacent the casting cavity and communicating with the latter cavity at various levels between the bottomand top thereof through a short narrow passage, an inlet passage extending downwardly and laterally and opening at its lower end into the bottoms of the casting cavity and feeder cavity, and a' second inlet passage extending laterally from the iirst inlet passage into the upper part of the feeder cavity.

3. A mold having a cavity for the casting llli naoaice at its lower end into the bottom of the casting cavity, and a second inlet passage extending laterally from the first inlet passage into the upper part of the feeder cavlty.

4. A mold having a cavity for the casting proper and provided with a gate comprising an upright feeder cavity adjacent the mold cavity and communicating with the mold cavity at various levels between the bottom and the top thereof through a short narrowy passage, said feeder cavity being formed with a riser chamber extending above the top of the casting cavity, an inlet passage extending downwardly and laterally and opening into the bottom of the casting eavity, and a second inlet passage extending laterally from therst inlet passage into the upper part of the feeder cavity.

5. rllhe method of introducing rnolten aluminum alloys or the like into a mold which consists in delivering the molten metal into the bottoms of the casting cavity and an upright feedercavity arranged at one side of the casting cavity, causing the metal to rise in said casting and feeder cavities from the bottoms thereof as the pouring continues, introducing molten metal into the upper part of the feeder cavity after the casting' and feeder cavities havebeen partially filled from below to complete the ll ing of the same, and causing the rnetal to flow from the feeder cavity at variouslevels into the casting cavity to compensate for crystallization s irinkage.

6. The method of introducing molten aluminum alloys or the lilreinto a mold which consists in delivering the molten metal into the bottoms of the casting cavity and an upright feeder cavity arranged at one side of the casting cavity, causing the metal to rise in said cavities from the'bottoms thereof until they are partially dlled, introducing molten metal into the upper part of the feeder cavity to complete ther filling of the said cavities and to rise upward into a riser extension of the feeder cavity, and causing the moltenrnetal to dow from said feeder cavity at various levels into the casting cavity to compensate for crystallization shrinkage.

ln testimony whereof, lf hereunto adir; my signature.

lERlElDPlERltU A. PARHST.

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