US2423151A

US2423151A - Temperature control mold for casting

Info

Publication number: US2423151A
Application number: US455862A
Authority: US
Inventors: Raymond J Miller
Original assignee: Miller Engineering Corp
Current assignee: Miller Engineering Corp
Priority date: 1942-08-24
Filing date: 1942-08-24
Publication date: 1947-07-01
Anticipated expiration: 1964-07-01

Description

M l, 1947. R. J. MILLER ,4

TEMPERATURE CONTROL MOLD FOR CASTING Filed Aug, 24, 1942 3 sheets sheet l /56 r x $333 m, 1 w

" n u 111 H J? ii I] July 1, 1947. I J, MILLER R 423,51

I TEMPERATURE CONTROL MOLD FOR CASTING Filed Aug. 24, 1942 5 Sh aets-Shmat 2 IN VEN TOR. Ear/ ravo ZN/44m BY %z-//Am July 1, 1947.

5 Sheets-Sheet 3 21 WT 5'6 32 J I [4 .uvmvron w Aggy/vow ZN/use #TTOE/VEY Patented July 1, 1947 TEMPERATURE CONTROL MOLD FOR CASTING Raymond'J. Miller, Detroit, Mich., asslgnor, by

direct and mesne assignments, to Miller Engineering Corporation, Detroit, Mich, a corporation of Michigan 1 Application August 24, 1942, Serial No. 455,862

This invention relates to the art of casting and more particularly to the control of heat transfer in castings to eliminate or materially reduce shrinkage strains caused by portions of the casting cooling and solidifying while other portions remain molten. f

When molten alloy or metal is' poured into a mold to form a casting, it begins to cool, and when its temperature drops to a substantially predetermined point it solidifies. solidification of moltenalloy or metal is accompanied by shrinkage due to reduction of space between the molecules upon passing from a liquid to a solid state.

The length of time required for solidification depends on the rate of heat transfer from the molten alloy or metal. In castings having varying contours the length of time required for solidification depends on the ratio of the external mold surface area to the volume of the castin under consideration,'and depends on the rate of heat transfer from the mold element.

In castings having varying contours the lighter 8 Claims. (Cl. 22-113) or thinner sections have greater surface area in contact with the mold forming substance per unit of volume than do the heavier or thicker sections. The thinner sections are therefore subjected .to more rapid cooling than are the heavier sections, and will solidify while the heavier sections are still molten.

In castings where light or thin sections are intermediate heavier sections and the feeder, the thin sections, being cooled more rapidly, will solidify while the heavier sections remain molten. Under these conditions the thin sections jell or solidify providing a point of anchorage for the molten alloy or metal and effectively cut off the heavier sections from the shrinkage compensating supply of metal at the feeder. The feeders also frequently jell or solidify before the heavier sections and effectively cut off the supply of shrinkage compensating molten alloy or metal from the heavier molten sections.

When the heavier sections solidify and shrinkage occurs therein, shrinkage strains of considerable magnitude are set up in the casting because the supply of molten metal is effectively cut oifby solidification Of thinner sections inter-, mediate the heavy sections and the feeder, or by solidification of the feeder.

It is desirable in order to prevent shrinkage stains that the feeder remain open to supply molten alloy or metal to keep the mold completely filled until the entire casting has completely solidified. In order to obtain this desir- 2 able result it is necessary that the casting be cooled progressively from the points more remote from the feeder toward the point of feed whereby a continuous supply of molten metal will be available to compensate for shrinkage, thereby effectively maintaining the mold completely filled and preventing the introduction of shrinkage strains caused by one portion of the casting attempting to draw metal from surrounding solidified portions thereof.

These undesirable conditions in castings can be eliminated or reduced to apoint that their effect is unobjectionable if the cooling of the entire casting can be controlled to cool substantially uniformly or progressively towards the feeder. To obtain uniform cooling in castings having variable contours it is necessary to dissipate the heat more rapidly from the larger or thicker sections and to retard the heat transfer from the thin or sively expanded to surround the entire casting and maintained throughout the entire casting until solidification occurs substantially progressively or uniformly over the entire casting. This envelope or skin formed on the outside of the molten alloy or metal contacts the surface of the mold cavity and is maintained during cooling of the molten alloy or metal. The resulting casting has a fine textured smooth surface free from roughness due to a breaking of the surface skin or envelope. By effectively maintaining the feeder open until the entire casting solidifies, a more solid casting having higher physical properties less susceptible to warpage results.

In the so-called Capaco process of casting,

plaster is used as the mold body. During the formation of the plaster mold an excess of moisture is present and the plaster mold is subjected to a drying process whereby virtually all of the moisture is driven off from'the mold. The resulting mold is relatively porous and has a very smooth glass-like internal surface. Molten alloy or metal is poured directly into-these plaster molds and due to the porosity of the molds, gases formed during the pouring, cooling and solidifying processes and entrained air may readily escape through the body of the mold forming substance.

The ingredients from which the plaster molds are formed are such as to provide adequate strength to support the molten alloy or metal, but these molds do not pwsess sufllcient strength to resist the heavier loads to which they are subjected during shrinkage of the castings upon solidification. These plaster molds thus support the metal from the time it is poured until substantially predetermined shrinkage occurs as a result of the solidification of the molten metal or alloy.

The rate of heat dissipation from a mold, particularly a mold formed of low heat conducting material such as plaster, varies almost in direct proportion to-the external surface area of the mold per unit volume of the casting to be formed. By increasing the ratio ofthe external surface area to the volume of the mold cavity over the thicker or heavier sections of the casting, the rate of heat dissipation may be accelerated. Likewise by reducing the ratio of the external surface area to volume of the mold cavity by increasing the thickness of the mold section, the rate of heat dissipation from the thinner portions of the casting may be retarded.

No means has heretofore been provided to vary the rate of heat transfer from castings formed in molds formed of low heat conducting material such as plaster molds. The use of the plaster molding process has therefore been limited to objects wherein shrinkage strains caused by uneven cooling of the castings would not be uhduly objectionable. In order that this process may be used more widely it is necessary that some means be provided to compensate variation in thickness of the sections of a casting to provide progressive cooling towards the point of feed, or to provide more uniform cooling.

An object of this invention therefore resides in the development of a method whereby the heat transfer from castings formed in non-permanent molds of the so-called break-down or knock-out type may be effectively controlled to provide substantially uniform or progressive cooling over the entire casting.

Another object of the invention resides in the provision of an improved method for controlling the rate of heat transfer from a casting by accelerating the rate of heat transfer over the thicker or heavier sections and'retarding the rate of heat transfer over the thinner or smaller sections. I

A further object is to provide a relatively porous mold formed of low heat conducting ma.- terial having varying external surface area per volume of the casting to be formed to transfer heat substantially uniformly progressively from sections of varying thickness and volume of a casting.

Another object is to provide a plaster mold having substantially equal cooling surface area per volume of casting throughout the entire body of the casting to provide substantially uniform or progressive cooling thereof.

Yet a still further object of the invention resides in the provision of a plaster mold having heat radiating fins on the portions of the mold surrounding the thicker or heavier sections of the casting to increase the cooling surface and accelerate the dissipation of heat from the thicker sections of the casting.

Another object resides in the provision of a mold having substantially constant cooling surface area per unit of volume of the casting to be of cooling of the casting can be rendered uniform by the use of directed air currents over the mold to cool sections of varying-contour of the casting uniformly or progressively towards the feeder whereby solidification results substantially simultaneously or progressively towards the feeder over the entire casting.

A further object resides in the provision of a simple and improved method of producing .a forming member for making a non-permanent mold having a substantially constant ratio of external surface area per unit of volume of the casting to be formed.

Still a further object of the invention is to provide a contour forming member for a temperature control mold having a substance applied to its mold contacting surface to facilitate removal of the mold from the forming member.

Yet another objectresides in the provision of a mold having a plurality of sections of variable rate of.heat transferability to render cooling of castings uniform.

Other objects and advantages of this invention will be apparent from the following detailed description considered in connection with the accompanying drawings, submitted for purposes of illustration only, and not intended to define the scope of the invention, reference being had for that purpose to the subjoined claims.

In the drawings wherein similar reference characters refer to similar parts throughout the several views:

Fig. l is a sectional view of a typical article to be formed.

Fig. 2 is a sectional view of a pattern for forming the article of Fig. 1 having atemperature control mold former superimposed thereon.

' Fig. 3 is a sectional view of the temperature control forming mold for making a plaster mold having variable external contour to vary the rate I of heat transferability over spaced sections of the mold.

Fig. 4 is a bottom plan view of the former illustrated in Fig. 3.

Fig. 5 is a sectional view of a temperature control plaster mold having a casting therein.

Fig. 6 is a fragmentary sectional view illustrating a modified form of the invention.

Fig. 7 is a fragmentary bottom plan view of a portion of Fig. 5 illustrating a supporting flange.

Fig. 8 is a sectional view illustrating a still further modified form of the invention.

.Fig. 9 is a sectional view of a clamping ring for maintaining mold sections together.

Fig. 10 is a sectional view taken substantially on the line l0l0 of Fig. 9 looking in the direction of the arrows.

Fig. 11 is a sectional view taken substantially on the line I |ll of Fig. 10, looking in the direction of the arrows.

Fig. 12 is a sectional view of a device for attaching a mold former to a matched plate pattern.

Fig. 13 is a, fragmentary plan view of Fig. 12.

Fig. 14 is a sectional view of a device to facilitate removal of a temperature control member from a forming member.

Fig. 15 is a fragmentary plan view of the device of Fig. 14.

Referring now to the drawings, Fig. 1 is illustrative of any article H! which may be formed by a casting operation. The article I 0 may, for ex-. ample, be a flywheel having a relatively thick rim I2 and axially extending flanges l4 concentrically.

formed over the entire casting whereby the rate mounted on a hub member I6. The hub and rim are interconnected by a plurality of radially extending spokes ll'of relatively small cross sectional area in proportion to the cross sectional area of the rim I2. The ratio of the volume to the surface area of the rim l2 and flanges I4 is much greater than the ratio of the volume to the surface area of the spokes l8.

Inthe casting of an article l such as the fly wheel, the feeder would preferably be positioned at one side of the .rim l2 to supply molten alloy or metal through the rim l2 and spokes 18 to the hub l6. If no means are provided for controlling the rate of heat transfer from the castin the spokes l8 having'large surface area in proportion to their volume,will cool more rapidly than the rim l2 and hub member l6 wherein the ratio of surface area to volume is much less.

considerable magnitude result. The resulting casting is not homogeneous or solid and does not possess the desired degree of strength. The cast ing i susceptible of warping and in any ensuing machining operations or use whereby strains would be relieved, further warping would result.

Fig. illustrates a non-permanent temperature control mold 26 of the break-down or knockout type having upper and lower sections 22 and i 24. The mold 20 is preferably formed of a P rous moldable substance of a substance such as plaster capable of becoming porous after being formed. The rate of heat dissipation of such low heat conducting materials is almost directl proportional and 26 over the larger cross sections of the article In such as around the rim l2'and flanges 14 and over the hub l6 respectively, to "permit rapid transfer of heat from these portions of the casting. The walls 26 and 28 should, of course, P ssess sufilcient strength to adequately support the alloy or metal 36 poured into the mold 20 to form the i article In.

Suitable cooling fins 32 and 34'may beformed on the walls 26 and 28 respectively to increase the ratio of the surface area'or cooling surface to .the volume of the moldcavity to accelerate the transfer of heat from the heavier sections of the casting. The

fins

32 and 34 also increase the strength of the mold 20 to resist the weight of the alloy or metal 30.

The mold '20 may be formed with relatively thick walls 36 over the spokes 18 to retard the flow of heat from the alloy or metal of which the spokes are formed. The external surface area of the mold forming walls 36 is low to retard the flow of heat from the alloy or metal of which the spokes l8 are formed.

to the ratio of the external surface area to the internal volume of the cavity of the mold.

' In order to effect uniform cooling of sections of varying contour of the article to be cast in the mold 20,.the ratio of the external surface area of the mold to the volume of the cavity within the mold should be substantially constant.

Controlled cooling is thus effected whereby all parts of the casting cool substantially uniformly and the feeder is maintained open until the heavier or thicker sections of the casting have solidified. Since a constant supply of molten metal is available from the feeder, shrinkage of the metal will merely draw more molten metal from the feeder and shrinkage strains will be effectively avoided.

The mold 20 may be formed of upper and

lower sections

22 and 24. In making temperature control molds 20 for more complicated castings additional sections may be employed. These additional sections may be vertically spaced or may be triangular, rectangular or of any other desired shape adapted to interlock to form the desired temperature control mold contour.

The cooling effect of the external surface area of a low heat conducting plaster mold by radia- 1 tion is substantially in direct proportion to the volume of the metal of the casting at the point under consideration. The .cooling effect of the mass of the body portion of a low heat conducting plaster mold byconduction i substantially in inverse proportion to the volume of the metal of the casting at the point under consideration.

The temperature control mold 20 may, for example, be formed with relatively thin walls 26 The thickened walls 36 and the thin walls 26 and 28 with their heat radiating and

rigidifying fins

32 and 34 are proportional relative to each other in accordance with variations in cross sec-' tional areas of various portions of the article to be cast to produce substantially uniform cooling of the casting.

The size of the mold 20 is dependent on the size of the article ID to be cast, the amount of heat to be dissipated from the alloy or metalof which the article I0 is formed, the rate of heat conductivity of the substance of which the temperature control mold 20 is formed, the rate of heat transfer from th surface of the mold 20 to the atmosphere and other factors.

The lower section 24 of the temperature control mold 20 may be provided with suitable members to support the mold 20 when the mold is being dried and when the alloy or metal 30 is poured thereinto to form the casting. The supporting members may take the form of downwardly extending feet or

concentric flanges

38 and 40 positioned to underlie the heavier portions of the article in to be formed such as the'rim l2 and hub 16 respectively of the flywheel.

The upper and

lower sections

22 and 24 of the mold 20 may be provided with cooperating feeder and

riser forming members

42 and 44 respectively.

The feeder and riser forming member 42 is formed with a riser feeder chamber 46 to supply molten alloy or metal through a controlled'feeder gate 48. to compensate for shrinkage of the casting. The feeder gate 48 is surrounded by a. suitable mass 50 of the substance from whichthe mold 26 is formed to prevent solidification of alloy or metal in the riser 46 until the remainder of the casting has solidified.

The temperature control mold 20 may be proportioned in such a manner that solidification of the alloy or metal 30 forming the casting will start at a point remote from the feeding chamber 46 and move progressively towards the riser. This may be accomplished by progressively decreasing the ratio of the external surface area of the mold to the volume of the alloy or metal of which the feeding. chamber 46 towards the chamber. For

' example, the fins 32 may progressively increase in length or the ratio of their surface area to their volume may progressively increase outwardly fromthe feeding riser 46 as illustrated in Fig. 5

between a male pattern of the article In to be cast and a contour forming member superimposed on the pattern and having a female'impression of the desired outside contour of the mold 20.

Referring now to Figs. 2 to- 4, it will be observed that a male production'pattem 52 of the upper portion of the article to be cast is suitably attached to a. flask 54. A contour forming member 56 is superimposed on the flask and is located circumferentially with reference to the pattern 52 by means of suitable dowel pins 58, and vertically by the contact of the former 56 with the parting face of the pattern.

A female impression 62 having all of the desired contour of the upper section'22 of the temperature control mold 26 is thus formed between the member 56 and the pattern 52. A female impression of the lower section 24 of the temperature control mold 20 may be formed in a similar manner between a pattern of the lower portion of the casting and a contour forming member having all of. the desired contour of the lower section 24 of the mold 26.

After the pattern and contour forming members have .been assembled, any suitable mold forming substance 64 such, for example, as plaster may be introduced through a feeder 66 to fill the female impression 62' between the contour forming member 56 and the pattern 52. A plurality of vents 68 in the contour forming member 56 may be provided to ensure complete filling of the female impression 62.

The substance 64 of which the temperature control member 20 is formed may be any suitable mold forming substance such as' plaster. The composition of the plaster is preferably such as to form a relatively porous mold structure whereby gases formed during the casting operation and entrained air may readily escape through the body of the mold. This relatively porous plaster mold structure may be achieved by initially mixing the plaster forming ingredients with somewhat of an excess of moisture and thereafter drying the mold to drive off virtually all of the moisture.

The mold substance 64 is preferably such as to adequately support the casting when poured but does not possess sufiicient strength to resist the forces to which it is subjected when the casting shrinks upon solidification. Shrinkage of the casting may therefore crack or break up the mold and thus avoid the introduction of shrinkage strains within the casting.

The upper section 22 of the mold 211 may be interlocked with the lower mold section 24 by means of circumferentially extending interlocking flanges I0, and the

sections

22 and 24 may be held together by means of suitable clamps engaging the flanges 10. If desired, a weight 12 may be placed on any suitable substantially flat surface such as the portion H of the upper mold section 22 to hold the mold 20 assembled to prevent the pressure of the molten alloy or metal 30 from separating it.

As illustrated in Figs. 9 to 11, the upper and

lower sections

22 and 24 of the mold 20 may be provided with radially extended flanges I6 and 18 respectively having tabs 86 bonded into the body of the substance 64 of the temperature control mold 20. The flanges I6 and 18 have radially extended slots 82 to receive clamping bolts 84 to v securely lock theupper and lower sections 22 and -24 of the mold 26 together; Suitable dowel pins 66 positioned 'in tabs 68 bonded intothe upper and lower sections 22 and may bepro'videdto accurately align the "sections of the mold.

' In the casting of an article in inthe temperature control mold 20, molten alloy or metal 30'" is introduced through the opening 80 in the feeder 42 positioned at one side or in the middle of the mold. The molten alloy or metal 36 flows through thecontrolled gate 48 into the space'within the mold 20 and, completely fills the space within the mold 20. Gases formed upon contact of the molten alloy or metal 36 with the internal surface of the mold 20 and entrained air in the mold are readily dissipated through the mold forming substance 64 of the mold 26. Sprues are therefore unnecessary and a reaction is set up between the inner surface of the mold and the liquid alloy or metal whereby a very smooth

surface results fins

32 and 34 coupled with the sections 26 and 28 of relatively thin section permit rapid dissipation of heat from the heavier sections of the cast ing, andthe walls 36 of heavier section in the mold body 20 tend to retain the heat in the thinner sections of the casting, such, for example, as the spokes IS. The entire casting cools progressively towards the feeder. The controlled supply gate 48 and the riser chamber 46 provide an ample supply of molten metal to compensate for contraction of metal upon solidification. The thinner spoke forming sections remain molten during cooling of the heavier sections and all parts of the casting solidify progressively towards the supply of molten shrinkage compensating alloy or metal.

If desired, air may be circulated-over the mold sections to assist in the dissipation of heat from the mold. The cooling air may be controlled as I to direction to subject only a portion of the mold 29 to the cooling action, to give more accurate and positive control over the cooling of the casting.- The temperature of the air directed over the mold 26 may also be controlled to produce the desired cooling of various portions of the casting to insure uniform solidification of the casting.

The contour forming member 56 for making the temperature control mold 20 may also be formed by a reproduction process from a master male pattern of the external contour of the section of the mold 20 to be reproduced in the mannerset out in my co-pending application Serial No. 421,115, filed December 1, 1941, now Patent 2,348,086, issued October '7, 1943.

Where the contour forming member 56 has a plurality of symmetrical or identical segments orsections, a male pattern of onlyone of the alike segments or sections need be made. A female impression of this male pattern segment or section may be formed by a reproduction method in plaster, one of the so-called Cerro alloys, consisting for example of 42% tin and 58% bismuth or any suitable substance possessing the characteristics of accurately conforming to the contour of the pattern member and solidifying. Thenecessary number of male impressions required to form a complete male pattern for the contour forming member 56 may then be formed by the reproductive method from the single female impression.

These male segments. may be formed of any suitable substance such, for example, asplaster or one of the so-called Cerro alloys possessing the characteristics of flowing and solidifying under substantially constant volume conditions. The male segments thus formed may be assembled and any desired number of female impressions of the type illustrated in Figs. 3 and 4 made to confine the temperature control mold forming substance 64 or plaster to form the desired configuration. The inside of the'temperature control mold 20 must accurately reproduce the contour of the pattern 52 to form the casting. The

outer contour of the mold 20 serves no purpose other than to radiate heat and therefore need not be formed so accurately.

The contour forming member 56 may if desired be formed by spraying any suitable substance onto a framework spaced'from the pattern. If desired, the forming member 56 may have per.

erted between the mold and the member 56 to effect its release.

7 Holding means ma'y be provided to insure sep-' aration of the temperature control mold from the pattern member as the contour forming member 56 is raised. One desirable form of such holding means comprises vents 92- having back draft to lock the temperature control mold to the member 56.

The vents 92 in the contour forming member 56 may be provided with removable inserts 64. The inserts 94 extend through apertures having angularly .related

walls

96 and 98 extending through the member 56. The inserts 94 have angularly related walls I00 and I02 adapted to align with the

walls

96 and 98 of the member 56 'to maintain the inserts 94 in a predetermined angular relation with reference to the contour forming member 56. Angularly related convergtions of the solid block cut away to reduce its weight particularly where relatively large forming members are employed, to facilitate handling of the forming member.

If the contour forming member 56 and the in termediate members used in the formation of the contour forming member are made of substances not possessing the characteristic of maintaining substantially constant volume upon solidification,

suitable allowance should be made to compensate for shrinkage or expansion in the various operations suggested.

Any suitable means may be provided to remove.

the temperature control mold 20 from the female impression 62 between the pattern '52 and the contour forming member 56. Where the substance 64 of which the mold 20 is formed is plaster, the contour forming member 56 remains in place on the pattern until the plaster. has attained a predetermined set sufficient that the mold 20 will be self supporting.

The contour forming member 56 may be elevated from the pattern 52 by any suitable means such as suction cups engaging its u per surface or by means of hooks embedded in the substance of which the member 56 is formed. The mold 20 having greater surface area in contact with the contour forming member 56 than with the pattern 52 will be lifted from the pattern when the member 56 is elevated. I

The contour forming member 56 with the temperature control mold in place therein may be placed on any suitable supporting surface and subjected to a slight vibration to release the mold therefrom. If desired, pressure may be exerted on the temperature control mold through the vent openings 68 to assist in releasing the mold. It will be apparent that slight air pressure may be exerted through the vent holes 68 to effect the release of the temperature control mold. Where the mold is'formed of plaster and is to be subjected to a drying operation after removal from the contour forming member, the moisture in the mold at the time of removal from the member 56 will prevent the dissipation of the air pressure through the mold whereupon a force can be exing walls I04 and I06 formed in the'inserts 94 provide a back draft vent to lock the temperature control mold to the contour forming member '56.

When it is desired to remove the temperature control mold fromthe contour forming member 56, the vent inserts 94 are removed from the member 56 by moving them outwardly in the direction of their converging walls I04 and I06.

The back draft portion of thevent on the temperature control mold is positioned to lie inside of the angularly extending wall 98 formed in the member 56. When the inserts 94 are removed the contour forming member '56 may thereforebe readily removed from the temperature control mold by merely elevating it.

Figs. 14 and 15 illustrate a modified form of the contour forming member 56 to facilitate removal of the temperature control mold therefrom. The contour forming member 56 has a cut-out section to provide a portion of the temperature control mold such as the fins 32 with bosses or projections I08 adapted to be engaged by'locking flanges IIO having an angular'ly extended surface II2 to enter the space in which the bosses I08. are formed to provide a back draft section to securely lock the temperature control mold to the contour forming member 56.

The locking flanges H0 are 'slidably mounted on a surface H4 of the member 56 to overlie a portion of the space for forming the bosses I08, and are maintained in a predetermined position by means of a flange II6 carried by a cover plate H6 positioned to overlie the contour forming member 56. 'The contour forming member 56 is provided with a flange |2I positioned to engage a wall I23 in the cover H8 to more accurately control the position of the flange H6 and the locking flange H0. The cover plate II8 may be detachably connected by means of a clamp I25 to a flange I26 carried by the contour forming member 56.

When the contour forming member 56 with the temperature control mold therein is raised from the flask and pattern assembly, the mold is retained in the member 56 by means of the back draft of the angularly extended surface I I2 of the locking flange ll0- engaging within the bosses I08.

When the member 56 is to be removed from the temperature control mold the clamps I28 are released and the cover p1atell8 removed. The locking flanges IIO are then withdrawn laterally to release the bosses I08 whereupon the member 56 may readily be separated from the temperature control member.

When the temperature control mold to be forming member 58 and similar'members used in the formation of the member 58 may be coated with any suitable parting substance, possessing the characteristics of not adhering to the surface of the plaster or other substance employed, to facilitate the removal of the plaster temperature control mold. After removal from the forming mold the temperature control mold 20 may be dried to dispel virtually all moisture whereupon steam causedby evaporation of moisture upon contact with the molten metal will be virtually prevented.

The embodiment of the invention illustrated in Fig. 6 is similar in many respects to that illustrated in Fig. 5. Corresponding parts have therefore beengiven corresponding reference numerals with the addition of 100.

It will be observed that the upper and lower sections I22 and I2! of the mold I20 are formed with walls I10 and I12 respectively of substantially uniform thickness surrounding the casting. The control of cooling of the molten alloy or metal in this embodiment of the invention is eflected by varying the length and thickness of the cooling fins I32 and I34 to subject the thicker or heavier sections of the casting being.

formed to a sufllcient degree of cooling to induce them to reach the solidification point at substantially the same time as the thinner sections of the mold. It will be understood of course that suitably directed air currents may be utilized to assist the fins in a control of the cooling rate.

The embodiment of Fig. 8 is somewhat similar to that of Fig. 5 and corresponding parts have been given corresponding reference numerals with v the addition of 200.

The upper and lower sections 222 and 224 of the temperature control mold 220 are provided with relatively

heavy section

280 and 282 respectively over the thinner portions of the casting such, for example, as the spokes l8 and relatively

thin sections

284 and 286 over the heavier sections of the casting. The cooling effect of the mass of the mold by conduction of heat through the mold forming body is substantially in inverse proportion to the cross section of the mold forming cavity. The increased thickness of the

mold sections

280 and 282 therefore act as an the mold upon lateral movement of the locking flange relative to the shell.

- 2. A non-permanent mold comprising cope and drag sections formed of low heat conducting material for forming a casting having sections of varying cross-sectional area wherein the walls of the mold vary in thickness substantially in inverse proportion to variations in cross-sectional area of the casting to permit rapid dissipation of heatfrom heavy sections of the casting and to retard the dissipation of heat from light sections of the casting, and an outwardly extending metallic flange embeddedin each of the cope and drag sections of the mold whereby the cope and drag molds may be accurately aligned and clamped together.

3. The method of forming a non-permanent mold formed of low heat conducting material comprising superimposing on a pattern a mold contour former having sections of varying contour separated from the pattern by a space substantially in inverse proportion to the volume of sections of varying contour of the casting to be formed, the mold contour former having spaced vent passages communicating with atmosphere at the top of the space between the pattern and the former, filling said space with a low heat conducting mold forming substance in a semi-plastic condition, separating the mold contour former and mold from the pattern, introducing a fluid through said vent passages to separate the mold from the contour former, and thereafter drying the mold.

insulator to retard the flow of heat from the thinner sections of the casting formed in the mold, whereas the relatively

thin sections

284 and 286 permit rapid dissipation of the heat from the thicker or heavier sections of the casting formed in the mold. Directed air currents may also be utilized to assist in rendering the cooling progressive to achieve the desired results.

I claim:

1. A mold forming member for a temperature control mold comprising a contour forming member, a shell having a female impression for shaping the external surface of the mold, a cover plate for the shell, a removable locking flange having a surface so located as to cooperate with the shell and cover plate in providing back draft on the temperature control mold to lock the mold 4. A non-permanent mold having cope and drag sections formed of low heat conducting material, each of said sections being contoured substantially in inverse proportion to variations of cross-sectional area of the casting to be formed to influence the rate of heat dissipation from a casting formed in the mold, metallic flanges carried by each of said mold sections, and locating inserts in said flanges.

5. The method of forming a plaster temperature control mold comprising superimposing on a male pattern of an article to be cast a contour forming member having walls spaced from the pattern to provide therebetween a female impression of the temperature control mold having vent passages communicating with the atmosphere, introducing plaster into said female impression to form a. mold, separating the contour forming member and plaster mold from the pattern, introducing a fluid through the vent passages to the space between the contour forming member and the mold to release the mold from the member, and thereafter drying the plaster mold.

6. The method of forming a non-permanent temperature control mold comprising superimposing on a male pattern of an article to be cast a vented contour forming member having walls spaced from the pattern to provide therebetween a female impression of the temperature control mold, introducing a moldable substance into said female impression to form a mold, separating the contou forming member and mold from the pattem, and thereafter introducing a fluid through the vent forming portions of the contour forming member to separate the contour forming member from the mold.

'1. In a mold forming device, a mol contour forming member having a female impression to shape the external surface of the mold and including venting openings defined by spaced angularly related walls embodying back draft, and

to the contour forming member and to release mold locking inserts adapted to be removably I positioned in the venting openings and having external surfaces/adapted to align with the walls of the venting openings embodying back draft and having angularly related internal walls embodying back draft to lock the mold to th contour forming member in such a manne that when the mold locking inserts are removed from the mold contouring member the mold contouring member may be separated from the mold.

8. In a device for forming a non-permanent mold, a mold contour forming member adapted to be superimposed on a pattern and having a female impression for shaping the external surface of the mold to provide a substantially predetermined ratio between the external area of the mold and r the volume of the casting cavity throughout to control the rate of solidification of molten alloy or metal in the casting cavity, means to clamp the mold to the mold contour forming member to in- 20 sure separation of the mold from the pattern comprising spaced members movable between clamping and releasing positions to provide a back draft condition between spaced portions of the mold and the mold contour forming member and to eliminate said back draft condition to permit separation of the mold from the contour forming 1 member.

RAYMOND .1. REFERENCES CITED The following references are of record in the tile of this patent:

UNITED STATES PATENTS OTHER REFERENCES Metal Castings by Campbell, published by John Wiley 8: Sons 1936. Pages 32 and 33.