US2611161A

US2611161A - Pattern fixture for making molds for turbines

Info

Publication number: US2611161A
Application number: US81868A
Authority: US
Inventors: Carl H Paul; Bernard F Vogelaar
Original assignee: Caterpillar Tractor Co
Current assignee: Caterpillar Inc
Priority date: 1949-03-17
Filing date: 1949-03-17
Publication date: 1952-09-23
Anticipated expiration: 1969-09-23

Description

p 23, 1952 c. H. PAUL ETAL PATTERN FIXTURE FOR MAKING MOLDS FOR TURBINES 3 Sheets-Sheet L Filed March 17, 1949 IN VEN TORS.

ATTORN Sept. 23, 1952 c. H. PAUL ETAL 2,611,161

PATTERN FIXTURE FOR MAKING MOLDS FOR TURBINES Filed March 17, 1949 3 Sheets-Sheet 2 3/ |\lllllmlllllnlllilllllllllllllflmw INVE ORS ATTORN Sept. 23, 1952 c. H. PAUL EI'AL 2,611,161

PATTERN FIXTURE FOR MAKING MOLDS FOR TURBINES 3 Sheets-Sheet 5 Filed March 17, 1949 Patented Sept. 23, 1952 PATTERN FIXTURE FOR MAKING MOLDS FOB TURBINES Carl Paul, Peoria Heights, and Bernard F.. Vogelaar, East Peoria, Ill.,'assignors to Caterpillar Tractor 00., Peoria, 111., acorporation of California Application March 17, 1949, Serial No. 81,868

2 Claims. 1

This invention relates to a casting and fixtures for making complex molds or mold cores such as are required in the casting of certain forms with irregular or oddly positioned parts.

In a nozzle ring of the type commonly employed in -a gas turbine or the like for directing the expaneling gases toward a turbine wheel, it is desirable-to employ blades havinga twisted form to obtain high efficiency. This twisted blade form is essentially the same as would be achieved by twisting the outer-most end of the blade relative to its inner edge. In the past it has not been possible to cast a nozzle ring having twisted blades in a single integral piece due to the difliculty of forming a suitable mold and particularly to the difliculty of extracting the twisted blade patterns from the core portion of the mold. As a result, it has been conventional practice to fabricate the blades and retainer rings separately and then join them together as by welding or other methods.

It is, therefore, an object of the present invention to provide means to enable the casting of a nozzle ring having twisted blades as a single integral unit. It is a further object of this invention to provide a fixture for use in making molds or cores that will enable th extraction of pattern parts of unusual shape and arrangement.

Further objects and advantages of this invention will be made apparent in the following specification wherein reference is made to the accompanying drawings.

In the drawings:

Fig. 1 is an isometric view of a nozzle ring typifying a casting that is made possible by the present invention;

Fig. 2 is a fragmentary sectional view illustrating the shape of the nozzle blades;

Fig. 3 is a fragmentary sectional view of a cover plate forming a part of the molding fixture;

Fig. 4 is a fragmentary sectional view of a base plate forming a part of the molding fixture;

Fig. 5 is an isometric view of one of the blade patterns;

Fig. 6 is an isometric view of the same blade pattern inverted;

Fig. 7 is a plan view of the assembled pattern fixture with the cover plate removed and two of of concentric annular members I0 and H and a plurality of spaced blades l2 interposed between: and cast integrally therewith. The blades l2 are:

provided for the purpose of directing the expand ing gases toward a turbine wheel (not shown) in a conventional manner. To increase the efiiciency of the nozzle ring, it is conventional practice to employ blades having a twisted form. As is best illustrated in Fig. 2, the shape of each of the blades is essentially the same as would be achieved by twisting the outer leadin edge of.

the blade about the trailing edge while holding the inneredge adjacent the annular member ll fixed. In the past the problem of removing apattern of a blade having such a shape from a sand mold has prevented the manufacture of a nozzle ring having twisted blades by casting in a single integral part. It is the purpose of this invention to provide a combination of pattern equipment which permits the formation of a sand core such as is illustrated at l3 in Fig. 8 having voids l4 therein corresponding exactly to the configuration of the nozzle ring blades l2. The core I3 is then placed in a suitable mold illustrated at l 5 in Fig. 9 which is provided with voids. l6 and I1 corresponding to annular members I0 and II respectively. The nozzle ring is then cast in a conventional manner by filling th voids with molten material.

As illustrated in Figs. 3 to 7, the pattern equipment comprises an annular base plate l8, a cover plate IS, an inner sleeve 20, and a plurality of arcuate blocks 2|, each of which carries a blade pattern 22 extending therefrom. Each of the blocks is provided with top and

bottom faces

23 and 24, respectively, and oblique side faces 25 and 26. The top face 23 is provided with a locating rib 27 adapted to be received in one of a plurality of equally spaced slots 28 provided on the cover I 9. The base plate I8 is provided with a plurality of spaced inclined guide members 29, each of which is adapted for reception by a guide recess 30 provided in the bottom face of each of the blocks 2|. The blocks are adapted to be assembled on the base plate forming an annulus as illustrated in Fig. 7 with the blade patterns 22 projecting inwardly and abutting the inner sleeve 20. positions relative to each other, corresponding exactly to that of the nozzle blades 12 in the finished nozzle ring illustrated in Fig. 1.

After the blade patterns are assembled, core sand is packed about them to form the sand core illustrated at I3 in Fig. 8. Ordinarily the formation of such a core or mold is considered impossible because of the fact that the irregularly In this position, the blade patterns occupy shaped blade patterns cannot be withdrawn without disturbing the sand mold. Such withdrawal or extraction of the blade patterns is made possible by the construction shown through the location and shape of the guide members 29, recesses 30 and configuration of the blocks 2 I The inclination of 'theguide members 29 and recesses 30 causes lifting of one edge of the block 2| as it is withdrawn in a slightly off radial direction,

as illustrated in Fig. 7. This in eifect twists the block through a path corresponding to the twist of the blade pattern. The inclination of the abutting faces of the blocks is designed to provide clearance for this twisting motion as they are withdrawn. The voids M are therefore preferably formed by sliding each of the blocks 2| outwardly away from the sleeve 20. The twisting motion of the blocks'and blade patterns is such that, during removal, any point at any: cross section of the blade pattern will pass through corresponding points at any other cross sections thuspermitting their removal withoutv disturbing. the. surrounding core.

We claim:

1. A pattern fixture for producing a mold of a pluralityof radiallyarranged blade like members of twisted formation which comprises, a base member, a plurality of. blocksarrangecl to be supportedasan annulus on saidbase and each supporting an inwardly projecting blade pattern, and" separate wedge-shaped guide means arranged between thebase and each block to compel-theblocks upon being withdrawn in a generally radial direction-from the annulus to fol- 4 low a path which twists in conformity with the twist of the blade.

2. A pattern fixture for forming a mold of radially arranged twisted blades which comprises, a base, a plurality of blocks adapted to be supported as an annulus onrsaid base and each supporting an inwardly projecting blade pattern, an annular wall adjacent the inner ends of said blade patterns, a cover adapted to overlie the blocks and said wall, each of said blocks having a recess in its base surface adjacent one of its edges, and a wedge on the base projecting into said recess to guide withdrawal of the block in a slightly off radialdirection and raise said adjacent edge progressively during withdrawal to cause the blade pattern to follow the twisted path defined by its own configuration.

CARL H. PAUL. BERNARD F. VOGELAAR.

REFERENCES. CITED The-following references. are of record in the file of this patent:

UNITED. STATES PATENTS Number Name Date 873,684 Rice Dec. 10, 1907 914,474. Barnes Mar. 9,1909

1,226,604 Sherwoodet al. May 15, 1917 1,378,524 Clark May 17,1921 1,537,176 Losel May 12, 1925 1,641,665 Devaud Sept. 6, 1927 2,301,140. Pfeifier Nov. 3, 1942 2,510,735 Bodger June 6," 1950