US 2999303 A
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Description (OCR text may contain errors)
Sept. 12, 1961 G. o. ECCLES BLADES FOR GAS TURBINE ENGINES Filed May a, 1959 Ill llllllllll I Iv EQM l llllllllll I I I I l I I l l l l l l l l I I I I I I I llullll-l |llll-\l l-Illlllllll-lw FIG.2.
llllllllllll INVENTOR 605? o-smo Ccc AT TORNEYS Filed May 8, 1959, Ser. No. 811,831 Claims priority, application Great Britain May 21, 1958 3 Claims. (Cl. 29-4563} The invention relates to a method of forming platforms, shrouds and the like on blades for gas turbine engines.
The invention is applicable to blades which have passages for cooling or heating fiuid running axially through them.
It has been found in practice that when a blank is formed with such axial passages or holes running through it and a laterally extended portion subsequently formed at one end of the blank by upsetting or forging to form a tip platform or shroud the holes in the area of the platform or shroud tend to bend that is to be deflected from the axial direction.
According to the invention the method of forming the shroud or tip platform portion includes further shaping of the laterally extended portion in a die'having a cavity in it beyond the end of the blade into which some of the metal of the blank is caused to how, drawing out and straightening the holes in that portion of the laterally extended portion which is to be left to form the tip platform or shroud.
Thus, for example, a blank can be extruded so as to form the normal root and blade portions with axial holes running through the blade portion, and the end of the blade portion remote from the root can then be upset to form an embryo shroud portion which is subsequently shaped by extrusion through a die or by means of a forging die. The extrusion die or the forging die will have a cavity formed in it beyond the end of the blade and so located that material in the neighbourhood of the deflected portions of the holes can flow into the cavity thus relieving the stress and drawing out the holes until a they are substantially straight in that part of the metal which is to form the shroud.
Where there are two series of holes each series being on different sides of the centre line of the blade crosssection the effect of the upsetting will be to cause the series of holes to be bent so as to increase the amount of metal between them in the centre of the upset portion. The cavity in the final extrusion die is so placed that this extra metal is drawn out straightening out the holes at least in that portion of the upset part of the blank which is nearest to the blade proper and which will after ma chining form the tip shroud.
An example of this invention is illustrated in the accompanying drawings in which:
FIGURE 1 is a side elevation of a blank with holes drilled in it;
FIGURE 2 is an end elevation of the same blank;
FIGURE 3 is a side elevation after extrusion; FIGURE 4 is an end elevation corresponding to FIG- URE 3;
FIGURE 5 is a side elevation after the upper end has been upset to form an embryo shroud or platform;
FIGURE 6 is a section on line 6--6 of FIGURE 5;
FIGURE 7 shows a further stage in forming the platfo htates Patent f) lc 2,999,303 Patented Sept. 12, 1961 FIGURE 8 is a side elevation of the blade in the stage shown at FIGURE 7; and
FIGURE 9 is a side elevation of the finished blade.
Initially holes 10 are drilled in a blank 11 (FIGURES 1 and 2). The holes may as shown be drilled completely through the blank or they may be blind holes drilled only through the portion of the blade which is to form the blade and tip shroud, leaving the extension of the holes through the root portion to be drilled after extrusion.
The holes are then filled with a filler material which may be a low carbon steel. The blank 11 is then partially extruded to form a blade portion 12 sufiiciently long to provide a potential shroud portion (FIGURES 3 and 4).
These extrusions take place in a split die and the pressure is from two sides of the blank only, that is to say from the top and bottom sides as viewed in FIGURES 2 and 4 so that the holes are progressively elongated in cross section as shown in those figures.
The potential shroud portion is then electrically upset to produce the shape 13 shown at FIGURE 5 and this results in kinking of the holes as shown at 10a in FIG- URE 6.
The shroud, or platform, 13 is then forged between a split die 15 and a solid die 15a in which is a cavity 16 to receive metal 17 from the portion of the shroud 13 at the ends of the holes 19. The portion of the eX- trusion below the platform 13 is gripped between the parts of the split die 15.
Cavity 16 enables metal to flow and tends to straighten the holes 10 and at the same time to relieve stresses in the metal.
The part 17 can be used in subsequent machining operations for marking datums on and for setting up on machines.
The blade is finally machined to the form in FIGURE 9 in which there is a root portion 14a, blade portion 12a and shroud portion 13a. It will be seen that the shroud portion 13a has only straight holes 10b in it.
The metal filler rods are removed at a stage after the last extrusion and/or forging process.
1. The process of forming a platformed or shrouded blade for an internal combustion turbine engine from a blank having a plurality of longitudinal axially disposed holes extending through the potential platform end thereof and filled with a deformable material comprising extruding said blank to provide a blade portion of relatively thin elongated cross-section, upsetting the said end into a laterally widened platform portion having an undersurface facing away from said end, said platform being of greater thickness than needed for the finished product thereby kinking the tilled holes to substantially follow the outline of the widened portion, further shaping the platform portion by engaging its under surface and forcing the platform in a die having a cavity shaped in plan to receive it and having a longitudinal extension cavity of approximately blade thickness and width thereby to extrude metal from the platform in the extension cavity thus drawing out and straightening the holes in that portion of the upset blade end which is left to form the tip platform or shroud.
2. The process of claim 1 in which the upper portion of the extruded platform and extension are machined away and the hole fillers removed.
3. The process of forming a blade for an internal combastion turbine from a blank containing a plurality of longitudina wally-disposed holes extending through one end thereof and filled with a deformable material, said holes being in two series, each series being on a different side of the center line of the blade cross-section, comprising extruding said blank to form a blade portion of relatively thin elongated cross-section, upsetting the said end into a laterally widened platform portion having an undersurface facing away from said end and thereby kinking the holes of each series oppositely to roughly follow the outlines of widened portion, further shaping the platform by pressure applied to its under surface to force it into a hollow die shaped to thereby thin the platform and having a longitudinal cavity of approximately blade thickness and width in alignment with the blade to receive the 4 extruded metal thus drawing out and straightening the holes in the remaining platform portion whereby they are in substantial alignment with the holes in the blade portion.
References Cited in the file of this patent UNITED STATES PATENTS 2,093,775 Colwell Sept. 21, 1937 2,743,509 Freedman May 1, 1956 2,759,257 Schlegel Aug. 21, 1956 2,891,307 Betteridge June 23, 1959 FOREIGN PATENTS 726,909 Great Britain Mar. 23, 1955