US2919479A

US2919479A - Shell mold

Info

Publication number: US2919479A
Application number: US655770A
Authority: US
Inventors: Hubert A Menningen
Original assignee: Allis Chalmers Corp
Current assignee: Allis Chalmers Corp
Priority date: 1957-04-29
Filing date: 1957-04-29
Publication date: 1960-01-05
Anticipated expiration: 1977-01-05

Description

1960 H. A. MENNINGEN 2,919,479

SHELL MOLD Filed April 29, 1957 2 Sheets-Sheet l 1960 H. A. MENNINGEN 2,919,479

SHELL Morin Filed April 29, 1957 2 Sheets-Sheet 2 SHELL MOLD Hubert A. Menningen, West Allis, Wis, assignor to Allis- Chalmers Manufacturing (Iornpany, Milwaukee, Wis.

Application April 29, 1957, Serial No. 655,770

1 Claim. (Cl. 22-131) This invention relates generally to shell molds. More specifically this invention relates to shell molds made up of a plurality of mold elements positioned side by side'which cooperate to define one'or more mold cavities.

In prior art foundry practices the mold cavity is usually formed by clamping together complementary mold sections in face to face contact. In green sand castings, because of the limitation of forming the mold cavities from a pattern embedded in sand, the mold is usually restricted to two complementary facing parts called the cope and the drag. In other words, if the pattern had an irregularly shaped outer surface it was very diflicult and often impossible to part the cope and drag without pulling part of the sand out of the mold. In some cases of green sand casting thepattern provides for the use of a core element between the cope and the drag to form a depression in the casting. However this method of casting is cumbersome and there are a great many restrictions on the configuration of the castings which can be obtained by this method.

' Permanent mold castings such as die castings also have certain limitations on configurations of items which can be cast by this method because the casting die is indestructible. In permanent mold castings it is difiicult to cast an item having depressions on the outer surface formed by projections on the die that are not aligned with the parting surface or the parting motion of the die.

Shell molding combines some of the advantages and eliminates some of the disadvantages of both green sand and permanent mold casting methods. Therefore castings which cannot be produced by either green sand or permanent mold casting methods can often be produced by shell molding methods. Shell molds are made by heating a sand thermo-setting resin mixture in contact with a pattern at a teinperatureand for a time sufficient to cure the resin and thereby bind the sand particles togetherinto a relatively rigid shell type mold. These molds reproduce very accurately and minimize and in some cases eliminate the need for subsequent machining of the cast article. When molten metal is poured into the shell mold theheat from the metal affects the mold in such a way that the resin loses its bonding quality. Therefore, when the casting had set and the mold has lost its bonding qualities the sand forming the shell mold may be brushed away from the solidified casting. Because shell molds are produced from a pattern in much the same way that die cast articles are made, there are certain limitations on the configurations that can be produced from shell molds. However, since the shell mold will lose its bonding qualities due to the heat given off by the molten metal, shell molds can be produced by combining individual mold elements into a single mold that cannot be made by either green sand molds or permanent molds.

. .This invention contemplates a shell mold made up of a" plurality of individual mold elements. Each element is produced from its own particular die and then assembled with other mold elements to form a single shell mold which will define either a single mold cavity or a plurality of separate mold cavities. The intermediate mold elements are designed to make impressions from either side and in effect act as a cope and a drag at the same time.

Stack molding with shell molds is old in the art as shown by U.S. Patent 2,691,196, Robert T. Banister. However this invention contemplates a mold comprising Unite Sttes tent O "ice a plurality of mold elements in which both sides of the intermediate mold elements form an impression on the cast article.- In effect, each of the intermediate mold elements acts as a cope and a drag thereby reducing the number of mold elements required to produce a given number of castings. Such a mold would be much more economical and smaller than known prior art shell molds.

The shell mold of this invention is particularly advantageous for multiple groove sheaves because the flash left by the mold of this invention is on the periphery of the annular projection defining the grooves of the sheave and not on the driving surfaces of the annular projection. In prior art casting methods in which only two mold elements were used, the parting line of the mold usually ran longitudinally along the multiple groove sheave and therefore a flash mark was left on the driving surfaces of the annular projection. Flash is very detrimental to belt life and usually has to be removed before putting the sheave into operation. Furthermore, when using only two piece molds aseparate pattern is required for each sheave having a different diameter or a different number of grooves. In the shell mold of this invention any number of intermediate elements can be positioned between the end mold elements to produce a mold for a sheave having any desired number of grooves. A master die and variety of inserts can be used to increase the number of molds that can be produced from each master die to further decrease the cost of the molds.

Therefore it is the object of this invention to provide a new and improved shell mold made up of a plurality of individual mold elements.

Another object of this invention is to provide a new and improved shell mold which is capable of producing cast articles having external configurations which are difficult or impossible to produce by other casting proc- Another object of this invention is to provide a new and improved shell mold made up of a plurality of stacked mold elements of which the intermediate elements perform as both a cope and a drag.

Another object of this invention is to provide a new and improved shell mold for stacked castings that is smaller and more economical than known prior art shell molds.

Another object of this invention is to provide a new and improved shell mold for multiple groove V-belt sheaves.

Another object of this invention is to provide a new and improved shell mold for a plurality of independent sheave disks.

Objects and advantages other than those set forth above will be apparent from the following description when read in connection with the accompanying drawings in which:

Fig. 1 is a cross section view of a mold of this invention for a multiple groove V-belt sheave;

Fig. 2 is a top view of one of the intermediate mold elements of the mold shown in Fig. 1;

Fig. 3 is a cross section view of another embodiment of the shell mold of this invention for a single groove V- belt sheave;

Fig. 4 is a cross section view of the shell mold of this invention in which the mold elements define a plurality of separate mold cavities; and

Fig. 5 is a top view of one of the intermediate mold elements of the mold shown in Fig. 4.

Referring now in particular to Figs. 1 and 2, a shell mold 10 for a multiple groove V-belt sheave is made up of a pair of end mold elements 11, 12 and a plurality of 1 tapered surfaces 19, 20, respectively, which define apere.

tures 21, 22 for receiving the core 15. The intermediate mold elements 13 are preferably annular and placed in juxtaposition between the end elements 11, 12. The core 15 is positioned in the aperture 25 formed by the aligned

mold elements

11, 12, 13 and abuts the surfaces 19, 20 in the end elements 11, 12. The inner surfaces of the

mold elements

11, 12 and 13 cooperate to define the external surface of the mold cavity. The core 15 which is not essential in ali molds defines the internal surface of the mold cavity,

In the shell mold 110 the radially inner surface 26 of each intermediate mold element 13 is formed to define an annular groove in a V-belt sheave. The number of grooves n the sheave can be varied by changing the number of intermediate elements 13 in the mold. Each side 27, 27a of the radially inner surface 26 of element 13 is designed to form an impression on the castin The inner surfaces 23, 29 of end elements 11, 12 form the end surfaces of the mold cavity. The core 15 is positioned within the aperture formed by the intermediate element 13 and abuts the end elements 11, 12 at 19, 20 and defines the inner surface of the mold cavity which in this case is the bore of the sheave. The core 15 is hollow and acts as a sprue having conduits 31 for directing molten metal from the core into the mold cavity.

The end mold elements 11, and intermediate mold elements 13 are mounted in juxtaposition and are aligned by means of tapered locating studs 33 in complementary tapered receiving holes 34. The receiving holes 34 are arcuately spaced around one side of each element 13 and end element 12. The locating studs are arcuately spaced on one side of end element 11 and on the side of the intermediate elements 13 opposite to the side defining the receiving holes. The studs 33 are aligned with holes 34 of an adjacent element and are shorter than the depth of the holes to assure contact between the adjacent sides of the elements. Multiple groove V-belt sheaves made from shell molds according to this invention have been tested and it was found that the total run out on the grooves of the sheave was less than five thousandths of an inch.

In Fig. 3 the second embodiment of this invention is illustrated in a shell mold 461 for a single groove V belt sheave. The shell mold 44? has a pair of end elements 41, 42 and a single intermediate element 43. The inner surfaces of elements 41, 42, 43 like the inner surfaces of

elements

11, 12 and 13 of the first embodiment cooperate to define the external surface of the mold cavity. Both sides of the radially inner surface 46 of the intermediate element 43 are formed to make an impression on the casting so as to define an annular belt engaging groove in the casting. Although only one intermediate element 43 is shown it is apparent to those skilled in the art that a plurality of intermediate elements may be used.

Adjacent elements are placed in juxtaposition and aligned by means of complementary tapered surfaces on adjacent elements. The outer portion 49 of one side of the intermediate element 43 is tapered in one direction and the corresponding portion 50 on the other side of element 43 is tapered in the same direction and at substantially the same angle. The end element 41 has a surface 52 tapered complementary to the surface 49 of element 43 and end element 42 has a surface 53 tapered complementary to the surface 50 of element 43. The tapered surfaces on adjacent elements are concentric and form mating surfaces for each other so as to align adjacent disks. In the mold 40 the end upper mold element 41 defines an aperture 54 which acts as a sprue for receiving the molten metal. A core 55 is positioned within the mold cavity and defines the bore of the sheave although a core is not required for all molds for sheaves.

A third embodiment of this invention is illustrated in Figs. 4 and in a shell mold 60 for casting a plurality of disks for an adjustable sheave. The shell mold 60 comprises a pair of end elements 61 and 62 and a plurality of intermediate mold elements 63 which are stacked to form a plurality of independent mold cavities 65. Each intermediate element 63 is designed to make an impression on the casting with both sides 67, 68 and in efiect function as both a cope and a drag. Side 67 forms the back of the disk and side 68 forms the front or driving surface of the disk. Side 68 also defines cavities 71 for axially extending lugs and has extensions 72 which define apertures intermediate the lugs of the sheave disks. Adjacent mold elements combine to form separate mold cavities 65. The mold elements are preferably annular and the'inner portions combine to form a riser 70. Adjacent elements define therebetween gates 73 extending between a mold cavity and the riser for receiving molten metal. A sprue 74 extends longitudinally through the mold elements and communicates with the riser 70 through a conduit 75 in end element 62. The sprue 74 can either be a separate element or formed by the mold elements.

The

stacked elements

61, 62, 63 may be aligned in any suitable way but preferably as illustrated the upper sides of end element 62 and intermediate element 63 are provided with a steplike structure near its outer periphcry. The lower sides of end element 61 and intermediate elements 63 are provided with a step structure complementary to the step structure 79 for receiving and aligning the element stacked immediately beneath.

it is desirable to fill the mold cavity or cavities from the bottom of the mold. Therefore the molten metal is poured into the sprue 74 so that the metal runs to the bottom of the mold, through conduit 75 and then flows upward in the riser 70 and into the mold cavities 65.

In operation the separate mold elements are aligned in juxtaposition and if necessary clamped together. The core if one is used is then placed in position. The molten metal is then poured into the mold and allowed to flow into the mold cavities. While the metal is cooling the heat from the metal causes the shell mold to lose its bonding quality and fall apart. When the casting has set and cooled the core may be brushed away from the solidified casting.

Although but three embodiments have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made herein without departing from the spirit of the invention and the scope of the appended claim.

What is claimed is:

A shell mold comprising two end mold elements, a plurality of annular intermediate mold elements, the radially inward surface of each of said intermediate elements being formed to define an annular belt engaging groove in the casting, means for aligning said elements in juxtaposition, said means comprising a series of armately spaced tapered receiving holes on one side of said elements and a series of complementary tapered locating studs on the opposite sides of said elements, and a core positioned within the apertures of said aligned intermediate elernents and in abutting relation with said end elements, said elements and said core combining to form a mold for a multiple groove V-belt sheave, and means for conducting molten metal into said mold cavity.

References Cited in the file of this patent UNITED STATES PATENTS 303,773 Wiesling Aug. 19, 1884 1,556,429 Davis Oct. 6, 1925 2,147,880 Campbell Feb. 21, 1939 2,691,196 Banister Oct. 12, 1954 2,789,331 Dietert Apr. 23, 1957 2,791,811 Schmid May 14, 1957 2,807,845 Sawyer Oct. 1, 1957 FOREIGN PATENTS 164,434 Australia 1955