US1751758A - Method of making turbine blades - Google Patents

Description

March 25, 1930. J. L. RAY

METHOD OF MAKING TURBINE BLADES Filed Aug. 1, 1928 [Ill-Illlll-I'llli I 'ILI llliullllllfl.

INVENTOR J-L.Ray a am ATTORNEY Patented Mar. 25, 1930 UNITED STATES PATENT oFFms JAMES L. BAY, OF SWARTHMORE, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELEC TRIO & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA METHOD OF MAKING TURBINE BLADES Application filed August 1, 1928. .Serial No. 296,853(

My invention relates to elastic fluid turbines, and more particularl to the blading thereof, and it has for an o ject to improve the efiiciency of apparatus of this character.

Hollow turbine blades possess advantages which make their use highly desirable, especially where blades of the larger sizes are used, such, for example, as for the low-pressure blading. The hollow construction reduces the weight and, consequently, the centrifugal forces and the stresses resulting therefrom and, at the same time, a hollow blade is well adapted to withstand the various bending stresses. It will also be clear thatthese advantages are possessed in the greatest measure by a hollow blade having a decreasing cross-sectional area from the base, or root portion to the tip thereof. As

- the stresses increase from the tip toward the root, it is ossible to ive a blade a variable section an thus, to ecrease the total centrifugal force acting on a blade and hence, to rovide for a lighter rotor construction.

vhile the advantages of a hollow. blade are generally appreciated, there are difiiculties in the. way of manufacture thereof, particularl in the making of forged or. rolled bla es, for it'will be clear that, due to the peculiar shape of a blade, it would be practically possible to form a hole of this shape after the blade had been forged or rolled, much less to form a tapered hole.

It is a more particular object of this invention, therefore, to provide a turbine blade of a hollow construction, and having a variable cross-sectional area, which may. also be readily manufactured by forging, rolling or-other manufacturing operations.

This and other objects are effected by my invention, as will be apparent from the fol-' lowing description and claims taken in connection with the accompanying drawings,

forming a part of this application, in which 1 is an elevation of a blank from which a blade may be rolled or forged;

Fig. 2 is a plan view of the blank shown in Flg. 1;

Fig. 3 is an elevation of the blank shown in Fig. 1 after the forging or rolling operation has been complete ment in some Fig, 4 is aplan of Fig. 3; and,

Figs. 5 and 6 are elevational views of a partially formed blank and of a completed blade respectively, showing a modified form of my invention.

According to my invention, a blank from.

which the blade is made is prepared .so that the blade-forming portion is substantially cylindrical and a round, tapered hole is then reamed lengthwise through the blade from the tip toward the base thereof so as to provide an increasing cross-sectional area from the tip to the base of the blade. A filling.

. piece is then inserted into this hole and is. se-

cured therein against accidental displacea proved manner and the blade is then either Forged, or rolled into its final form, after which the filling piece is removed. In this way, the blade is formed by simple operationsv and, at the same time the filling piece assures that the surfaces of the blade will be definite and well-formed and that the hollow construction will also have the proper shape to give maximum efiicicncy.

Referring to the drawing, I show a blank indicated generally atlO, from which a blade may be formed. This blank comprises a root forming portion 11 and ablade forming portion 12, the latter being, preferably, substantially cylindrical as. shown by Figs. 1 and 2 and, while the root forming portion 11 may be of any desired shape it also is, preferably, cylindrical as shown by these views.

In order to provide for the hollow con- I i struction of the blade, I form a hole which extends from the tip through the blade form ing portion 12 towards the base, or the root forming portion 11, and, in order to facilitate the manufacture, this hole is, preferably,

round and is reamed out to provide the .ta-

without deforming the blade.

In order to facilitate the removal of the tapered pin 14 after the blade forming operations have been completed, the blade may be quenched in some suitable medium, such as oil. The quenching will serve to cool the blade portion 12 and the resultant shrinkage thereof will compress the pin, which latter, being practically out of contact with the cooling medium, will remain in a hot, semi-plastic condition while the shrinkage of the blade 12 occurs. The shrinkage of the blade will, therefore, compress the pin so that when it finally cools it will be smaller and will tend to shrink away from the hole and hence, may be easily removed. While this method of removing the filling piece 14 greatly facilitates its removal, it will be obvious that my invention may be practiced by merely pulling out the pin 14 after the blade and pin have cooled sufiiciently to permit this to be done In Fig. 5, I show a modified form of blank 20 in which a hole 23 is reamed out to a curved ta )er instead of a straight taperas shown in ig. 1. The filling piece 24 is also formed with a curved taper to fit the hole 23. The blade 20 may then be completed as shown in' Fig. 6 by following the same procedure as that previously described with reference to the blade 10. It will be obvious that, in the blade 20, the sectional area is proportioned more precisely in accordance with the variation in intensity of the stresses and hence, a more eificient distribution of material and a reduction in weight is efiected without sacrificing any strength.

With either of the blades described, the filling piece (14 or 24) is of any suitable yieldable material, that is, a material which is deformed along with the blade when the latter is forged to the shape of a blade.- It may be a steel or iron plug, or it may be made of copper, lead, or like material which may be melted out after the blade is formed, Instead of using a metal filling piece, I may also pack the hole with fire clay and after the blade is formed the clay may be dug out.

In this way, it is possible to form a blade having the desired proportions with the minimum expenditure of time andilabor", as'no' expensive manufacturing operations are required and, at the same time, it is assured that the blade will have the proper cross-sectional area which will vary. from the base to the tip a While I have .showrrmy invention in two forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

lVhat I claim is:

1. The method of forming a blade which comprises forming a hole extending from the tip toward the base of the blade forming por- I tion of a blade blank, filling the hole with a yieldable mass, reducing the blank to the form pf 1a blade, and removing the filling from the 2. The method of forming a blade which comprises forming a hole having a curved taper and extending from the tip toward the base of the blade forming portion of a blade blank, filling the hole with a yieldable mass, reducing the blank to the form of a blade, and removing the filling from the hole.

The method of forming a turbine blade which comprises forminga tapered hole extendin from the tip towards the base of the blade forming portion of a blade blank, fitting a filling piece of yieldable material into the tapered hole, reducing the blade forming portion of the blank to the form of a blade, at the same time deforming-the filling piece similarly to the blade, and removing the filling piece from the tapered hole.

4. The method of forming a turbine blade which comprises forming atapered hole extending from the tip towards the base of a blade blank, fitting a filling piece of yieldable material into said hole, securing the filling piece against accidental displacement, reducing the blank to the form of a blade, at the same time deforming the filling piece similarly to the blade, and removing the filling piece.

from the tip to the base thereof, fitting a filling piece of yieldable material'into said hole, reducingthe blank to the form of a blade, at the same time deforming the filling piece similarly to the blade, and removing thefilling piece.

6. The method of mak ing a turbine blade which comprises forming a hole extending from the tip toward the base of a blade blank,

I fitting a filling piece into the hole, heating the blank and filling piece, reducing the blank to form a blade, causing the blank to cool more rapidly than the filling piece so that the resultant shrinkage of the blank will reduce the size of the filling piece for facilitating the removal of the filling piece.

7. The method of forming a turbine blade which comprises forming a hole extending from the tip toward the base of a blank, fitting a filling piece into the hole, heating the blank and filling piece, reducing the blank toform a blade, quenching the blank in a cooling medium, and removing the filling piece after the latter has cooled.

In testimony w'hereof, 1 have hereunto subscribed my name this 20th day of July, 1928,

JAMES L. RAY.

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