US3320345A

US3320345A - Method for the production of cored patterns

Info

Publication number: US3320345A
Application number: US432686A
Authority: US
Inventors: Nick G Lirones
Original assignee: Howmet Corp
Current assignee: Howmet Turbine Components Corp
Priority date: 1965-02-15
Filing date: 1965-02-15
Publication date: 1967-05-16
Anticipated expiration: 1984-05-16

Description

May 16, 1967 N. G. LlRONES I 3,320,345

METHOD FOR THE PRODUCTION OF BORED PATTERNS FIG. 2

/ fi ag I azz' s- May 16, 1967 N. G. LIRONES METHOD FOR THE PRODUCTION OF CORED PATTERNS 2 Sheets-Sheet 2 Original Filed Jan. 27, 1961 INVAENTOR. 722.026 G [1 rones United States Patent 3,320,345 METHOD FOR THE PRODUCTION OF CORED PATTERNS Nici: G. Lirones, North Muskegon, Mich., assignor, by

mesne assignments, to Howmet Corporation, a corporation of Delaware Continuation of application Ser. No. 85,322, Jan. 27, 1961.

This application Feb. 15, 1965, Ser. No. 432,686 Claims. (Cl. 264-255) This invention relates to an apparatus and method for the production of cored patterns and, more particularly, it relates to the preparation of cored patterns having extremely small cores positioned Within the patterns.

This application is a continuation of my copending application Ser. No. 85,322, filed Jan. 27, 1961, and entitled: Apparatus and Method for the Production of Cored Patterns.

The present invention finds particular application in the production of turbine blades and like components provided in engines developing high speed and power. In order for such engines to realize maximum efiiciency, it is required that the turbine vanes and like parts be capable of withstanding high temperatures. In addition to providing new alloys and novel designs of such parts for withstanding such high temperatures while still maintaining adequate strength, it has been proposed that passages be provided in such components through which a coolant, such as air, may be circulated during engine operation. The provision of such passages has been proven extremely difficult and costly in that machining has been impractical because of the length and small dimension of the passages coupled with the character of the metal and also because straight passages were seldom permissible, due to the design of the blades. Conventional casting processes have been found to be inadequate to handle the delicate cores required.

The portions of the blades through which the cooling passages are to formed are extremely thin, and it is therefore necessary that the cores must be positioned with extreme precision. Since the passages are necessarily extremely small, the cores are very delicate and it has been diflicult to maintain the position of the cores during pattern making.

It is an additional object of this invention to provide a method for the positioning of extremely small cores within thin patterns with extreme precision.

It is an additional object of this invention to provide a method which permits the achieving of the foregoing object when the cores are composed of glass or ceramic materials and are to be positioned within exeremely thin wax patterns.

These and other objects of this invention will appear hereinafter and for purposes of illustration, but not of limitation, specific embodiments of this invention are shown in the accompanying drawings, in which FIGURE 1 is a sectional view of two of the mold sections employed in the process of this invention shown in spaced-apart fashion;

FIGURE 2 is a sectional view of the mold sections of FIGURE 1 shown filled with pattern material;

FIGURE 3 is a sectional view of the mold sections of FIGURE 1 shown in spaced-apart fashion after formation of the pattern;

FIGURE 4 is a top plan view of the lower mold section shown in FIGURE 3, with the core elements inserted therein;

FIGURE 5 is a sectional view of the pattermmaking apparatus of this invention, including the second upper mold section associated with the lower mold section of the previous figures; and

FIGURE 6 is a perspective view of the completed pattern with core elements therein in accordance with this invention.

The present invention may be broadly described as a procedure wherein a first die having a cavity corresponding to one portion of a pattern is associated with a second die and this pattern portion formed. The first pattern portion formed will be provided with grooves for the insertion of the desired core elements in their desired positions. A third die member is then provided having a cavity corresponding to the remaining portion of the pattern and the pattern material is injected, thus providing a completed pattern.

This invention will be more readily understood when considering the accompanying drawings wherein FIG- URES 1-3 illustrate first and

second die halves

10 and 12 adapted for carrying out the initial steps of the inventive shown provided with a molding contour 14 corresponding to the under surface 16 of the completed pattern element 18 (FIGURE 6). The second die half 12 has a molding contour 20 corresponding to a surface which approximately bisects the core positions desired in the ultimate pattern element. The surface may be defined as that surface formed by an infinite number of lines drawn from an edge of the element 18 approximately through the center of the core positions therein to an opposite edge. The surface, and accordingly the molding contour 20, of the die half 12 will thus depend on the desired core positions in the pattern element.

The die half 12 is provided with obtrusions 21 which are dimensioned to form grooves 23 in the pattern portion 30 formed by the die

halves

10 and 12. The obtrusions 21 and the grooves 23 formed thereby will correspond to approximately one-half the core dimensions to be employed.

The third die half 22 (FIGURE 5) has a molding contour 24 corresponding to the upper surface 26 of the element 18.

Core elements 28 are adapted to be fitted within the recesses 23 formed in a pattern portion 30 by the obtrusions 21. The core elements 28 are preferably formed of hollow glass or ceramic elements whereby they may be removed from the vane ultimately formed therefrom, for example, by the passage of hydrofluoric acid through the hollow spaces in the cores.

It will be noted in FIGURE 4 that the die half 10 has extensions 29 formed therein which provide a resting point for the core elements 28. As can be seen, these extensions 29 correspond directly with the recesses 23.

The operation of this invention may be best understood when considering the following preferred embodiment. In the manufacture of wax patterns for the production of turbine vanes, such as the patterns shown in FIGURE 6, the die

halves

12 and 10 are placed in operative position. Wax is then injected, and there results a pattern portion 30 with the recesses 23 therein. The parting compound which is conventionally employed in pattern making will then be removed from the surface 32 of the pattern portion 30, for example, by swabbing this surface with trichloroethylene. The hollow glass cores 28 may then be inserted in the recesses 23, the die half 22 brought into operative engagement as shown in FIGURE 5, the wax injected for the formation of the completed pattern.

In many instances it has been found unnecessary to provide the recesses 23 throughout the entire length of the pattern portion 30. It has been found desirable to provide intermediate areas where wax injected into the die halves and 22 will entirely surround the elements 28. For example, the die half 12 would be provided with a projection beyond the above-defined contour 20, thus extending beyond the surface corresponding thereto. Therefore, when the

die halves

10 and 12 are mated, the recesses 23 will be interrupted by the cavity formed in the pattern portion 30 by the said projection. The cores 28, which are placed in the recesses, will bridge the cavity, and Wax injected when the

die halves

10 and 22 are mated will completely surround the cores 28.

This above-described construction is advantageously employed where the cores are not straight and it would be improvident to provide corresponding obtrusions 21 in the die half 12. Furthermore, the construction is desirable since it assures the accurate locking of the core elements in the desired positions when wax from the first injection completely surrounds the elements 28. It is, of course, required that the bridging eifect by the formation of the intermediate cavities should not be such that the core elements fracture when wax is injected under pressure.

The principles of this invention are adapted for use in all similar types of pattern manufacture where problems similar to the above may arise. The pattern and core materials and the particular pattern elements set forth in the specific examples, described above, are not to be considered limiting but exemplary only.

It will be apparent from FIGURE 6 that the ends of the cores 28 extend beyond the injected pattern portion so as to be available to become embedded in the ceramic walls of the shell mold that are built up about the pattern as in the shell molding process described in the Operhall Patent No. 2,961,751 or in convention shell molding or investment casting processes. Thus the cores will be supported at their ends to be retained in place within the mold cavity of the shell mold after the injected portion of the pattern has been removed.

It will be understood that the first pattern portion that is formed with the grooves for receipt of core members may constitute an intermediate portion of the pattern having grooves on opposite sides for positioning the described cores and wherein the first die members constitute die parts to define the completed pattern whereby pattern material can be injected therein to complete the pattern with the core members embodied in position of use.

It will be understood that various modifications may be made in the aboveaiescribed process and apparatus for the production of core elements which provide the characteristics of this invention without departing from the spirit of this invention, particularly as defined in the following claims.

I claim:

1. In a method for the production of metal castings having elongate passages of small dimension extending internally therethrough by the build-up of a mold having walls about a pattern formed of disposable material and disposing of the pattern to leave a corresponding mold cavity within the walls of the mold, the process of producing the pattern having cores extending therethrough in the areas corresponding to the passages comprising providing first and second die parts defining a portion of the mold pattern in a cavity therebetween with at least one of said die parts having at least one obtrusion in the face thereof corresponding to the extent that said pattern portion will be occupied by said cores and in which the obtrusions extend to an edge of said pattern, and continue across the adjacent edges of the one die part to conform with corresponding recesses in another die part, closing said die parts, introducing the pattern material into the cavity to form said pattern portion with impressions being formed in the surfaces of said pattern portion due to the presence of said obtrusions, opening said die parts, providing core members having a length greater than the length of said impressions, placing said core members in the impressions formed by said obtrusions whereby the ends of said core members extend beyond the opposite ends of the impressions and beyond said adjacent adges of the die part, providing other die parts defining a cavity therebetwcen corresponding to the completed pattern, mating said die parts with the formed pattern portion in the desired position within the cavity, introducing pattern material into the cavity to complete the pattern with the cores embedded therein and with the ends of the cores extending beyond the completed pattern.

2. The method as claimed in claim 1 which includes the steps of applying a parting compound to the surfaces of the first and second die parts, and applying solvent to the exposed surfaces of the formed pattern portion to remove the parting compound before positioning said pattern portion within the other die parts to form the completed pattern.

3. The method as claimed in claim 1 in which the cores are of a ceramic material and in which the pattern is formed of a heat disposable material.

4. The method as claimed in claim 1 in which the other die parts are formed with grooves aligned with the impressions in the pattern portion disposed therebetween for receipt of the ends of the core members which extend beyond the pattern portion.

5. The method as claimed in claim 1 in which the first and second die parts have obtrusions in each of their surfaces whereby impressions to receive the cores are formed in both of the opposite surfaces of the pattern portion.

References Cited by the Examiner UNITED STATES PATENTS 665,989 1/1901 Bechtold 264157 771,594 10/1904 Wilhelmi 264279 1,625,449 4/1927 Bohn et al. 264275 1,827,549 10/1931 Villain 264275 2,887,744 5/1959 Halliday 22158 2,921,352 1/1960 Pfeifie 22-158 3,120,573 2/ 1964 Ging-rande et 'al 264277 3,136,833 6/1964 Wikkerink 264277 ROBERT F. WHITE, Primary Examiner.

F. MARLOW, L. S. SQUIRES, R. B. MOFFITT,

Assistant Examiners.

Claims

1. IN A METHOD FOR THE PRODUCTION OF METAL CASTINGS HAVING ELONGATE PASSAGES OF SAMLL DIMENSION EXTENDING INTERNALLY THERETHROUGH BY THE BUILD-UP OF A MOLD HAVING WALLS ABOUT A PATTERN FORMED OF DISPOSABLE MATERIAL AND DISPOSING OF THE PATTERN TO LEAVE A CORRESPONDING MOLD CAVITY WITHIN THE WALLS OF THE MOLD, THE PROCESS OF PRODUCING THE PATTERN HAVING CORES EXTENDING THERETHROUGH IN THE AREAS CORRESPONDING TO THE PASSAGES COMPRISING PROVIDING FIRST AND SECOND DIE PARTS DEFINING A PORTION OF THE MOLD PATTERN IN A CAVITY THEREBETWEEN WITH AT LEAST ONE OF SAID DIE PARTS HAVING AT LEAST ONE OBTRUSION IN THE FACE THEREOF CORRESPONDING TO THE EXTENT THAT SAID PATTERN PORTION WILL BE OCCUPIED BY SAID CORES AND IN WHICH THE OBTRUSIONS EXTEND TO AN EDGE OF SAID PATTERN, AND CONTINUE ACROSS THE ADJACENT EDGES OF THE ONE DIE PART TO CONFORM WITH CORRESPONDING RECESSES IN ANOTHER DIE PART, CLOSING SAID DIE PARTS, INTRODUCING THE PATTERN MATERIAL INTO THE CAVITY TO FORM SAID PATTERN PORTION WITH IMPRESSIONS BEING FORMED IN THE SURFACES OF SAID PATTERN PORTION DUE TO THE PRESENCE OF SAID OBTRUSIONS, OPENING SAID DIE PARTS, PROVIDING CORE MEMBERS HAVING A LENGTH GREATER THAN THE LENGTH OF SAID IMPRESSIONS, PLACING SAID CORE MEMBERS IN THE IMPRESSIONS FORMED BY SAID OBTRUSIONS WHEREBY THE ENDS OF SAID CORE MEMBERS EXTEND BEYOND THE OPPOSITE ENDS OF THE IMPRESSIONS AND BEYOND SAID ADJACENT EDGES OF THE DIE PART, PROVIDING OTHER DIE PARTS DEFINING A CAVITY THEREBETWEEN CORRESPONDING TO THE COMPLETED PATTERN, MATING SAID DIE PARTS WITH THE FORMED PATTERN PORTION IN THE DESIRED POSITION WITHIN THE CAVITY, INTRODUCING PATTERN MATERIAL INTO THE CAVITY TO COMPLATE THE PATTERN WITH THE CORES EMBEDDED THEREIN AND WITH THE ENDS OF THE CORES EXTENDING BEYOND THE COMPLETED PATTERN.