US1748364A - Method of making turbine blades - Google Patents

Description

Feb. 25, 1930. RAY 1,748,364

METHOD OF MAKING TURBINE BLADES Filed Oct. 9, 1928 Fig.4. Fig.5; Fi..6.-

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wnmzssss; INVENTOR I 5 a V5 72 ATTORNEY Patented Feb, 25, 1930 j UNITED STATES PATENT OFFICE JAMES L. BAY, OF SWARTHMORE, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC &-MANUFACTUBING COMPANY, A CORPORATION OF PENNSYLVANIA METHOD OF MAKING TURBINE BLADES Application filed October 9, 1928. Serial No. 311,323.

My invention relates to elastic fluid turbines and more particularl to the blading thereof, and it has for an object, to improve the efiiciency of apparatus of this character. In turbine blades of a tapered, hollow construction, the metal is more efficiently disposed with respect to the neutral axes and the requisite-strength may thus be obtained with minimum weight. Inasmuch'as the centrifugal forces, and the stressesresulting therefrom, are directly proportional to, and vary directly as the weight, it becomes important, particularly with the larger blades, such as the low pressure reaction blades, to reduce the weight as much as possible in order to keep the centrifugal stresses within permis sible limits. By decreasing the weight of the blades, it is possible to use a rotor of relatively light construction and thus, to generally reduce the weight, as well as the cost, of

' a turbine and hence, to improve the construction of apparatusof this character. Vhile these advantages may be gained by using hollow blades, of variable cross-section, proportioned to have the proper strength'at each transverse section, the manufacture of such blades has, therefore, been quite expensive and tedious work. Y

It is a more particular object of this invention therefore, to provide a simple and inexpensive method by whichturbine blades of the tapered, hollow type of construction may be made with a high degree of accuracy.

This and other objects are effected by my lowing description and claims taken in connection with the accompanying drawings,

forming a part of this application, in which: Fig. 1 is an elevation of a blade blank;

Fig. 2 is an end view of Fig. 1;

Fig. 3 is a View of the blank shown in Fig.

blade; and, I Figs. 9, 10, 11 and 12are sections on invention as will be apparent from-the folthe lines IXIX, X'X, XIXI and XIIXII, respectively, of Fig. 8.

In accordance with my improved method, the blade-forming portion of a blade blank, which may be cylindrical, is hollowed out by some simple method, as by boring, and the root-forming portionand the base of the blade are forged to substantially their finished form; while the remainder, or outermost portion of the blade is flattened out to a shape which approximates its finished form but which is somewhat smaller. The blade blank is then placed in a finishing die and the hollow portion is expanded by fluid pressure until the blade properly fills the die. In this way, ablade may be made of a tapered, hollow construction which is properly proportioned at its various transverse sections to have the requisite strength and, at the same time, this procedure is relatively inexpensive and easy to carry out, as,no diflicult machining, or forging operations are required.

In the drawing, the blade blank is indicated generally at 10, in Fig. 1, and this blank may conveniently be cylindrical, as shown. and may consist of a blade-forming portion 11, and a root-forming portion 12 and a suitable extension, or tong hold 13 may project from the root-forming portion 12. In preparing this blank, the blade-forming portion 11 is hollowed out in any approved manner, as by boring as indicated at 14, to provide a hollow blade section. The taper is secured either by turning the outside of the blade-, forming portion to the proper'taper, or by taper boring of this" portion, or by'both of these operations, as shown.

The blade is next forged to the form shown in-Fig. 3, wherein it will be noted (Figs. 4 and 5) that the root-forming portion as well asthe base of the blade is forged to the finished form, while as will be apparent from Figs. 6 and 7, the-thin cylindrical outer portion is closed down and bent to a shape which 95 approximates the shape of the finished blade but which is of smaller cross section than the 60 low cylindrical blade section, tapering blade. The blade is then placed in a finishing die and the partially formed portion is expanded to fillthe die by fluid pressure acting through the passage 17. In this way, the

blade is accurately formed to the proper proportions and of variable cross section, as

shown in Figs. 8 to 12. It will be apparent that by using fluid pressure to expand the unfinished portions of the blade, practically any amount of pressure may be provided and thus, it is possible to expand the blade While cold'and also to properly regulate the expanding force so that the metal may be gradually expanded and thus, to avoid rupture of the expanded portion and 'to' assure that the blade willtake the shape of the die.

While I prefer to make this blade by apply--' ing fluid pressure through' e root portion to the interior of the blade, 't will be obvious that the passage 17 as well as the weld 16 may be omitted, if desired, and that fluid pressure may then be applied from the open end, or tip of-the blade. While I have. shown my invention in but one form, it will be obvious to those skilled. in the artthat it is not so limited, but is susceptible of various changes and modifications wvithout departing from the spirit thereof, and- I desire, therefore, that only. such limitations shall be placed thereupon as are imposed by the prior artor as are specifically set forth in the appended claims. What I claim is:

1. The-method, of making a turbine blade which comprises boring the blade-forming portion of a blade blank from the tip toward the base thereof to provide a hollow ?blade section, forging the root to substantially its finished form and closing downthe hollow blade section to a shape which approximates '50 the shape of the finished blade but whichiis' of smaller'c'ross section than the finished blade, holding the blank in'a die and using fluid pressu-reto ex and the blade section to cause the latter to 11 the die.

2. The method of; makin a turbine blade which comprises forming t e blade portion of a blade blank into a substantially cylindrical shape, boring the blade portion from the tip toward the base thereof to provide a 1:311-

e blade section, forgin the root of the blade to substantially finisher? form and closing down the cylindrical blade section to a shape which approximates the'shape of the finished blade 35 but which is of smaller cross section than the finished blade, holdin the blank in a finishing die and applying uid pressure to the interior of the blade section to.expand the latter' until it properly fills the die.

3. The method of making a turbine blade which comprises boring the blade portion of a blade blank from the tip toward the base thereof to provide a hollow blade section, forging the root and the base of the blade to substantially finished form, closing down and bending the remainder of the hollow blade section to a s'hapewhich approximates the shape of the finished blade but which is of smaller cross section than the finished blade, working down the\inlet and outlet edge portions until they are relatively thin, holding the blank in a finishing die and applying fluid pressure to the interior of the blade section to expand the latter until it-properly n fills the die.

4. The method of making a turbine blade which comprises boring the blade portion of v a blade blank from the tip toward the base thereof to provide a hollow blade section, tapering the outside of the hollow blade section, forging the root and the base of the blade section to substantially finished form, closing down andbending the remainder of the blade section to a shape whichapproximates the shape of the H ished blade but which is of smaller cross se tion than the finished blade, holding the blade in a finishing die and apblade section until the latter is sufiiciently expanded to properly fill the die.

5. The method of making a turbine blade which comprises boring the blade portion of ablade blank from the ti toward the base thereof to provide a hol ow blade section,

tapering the inside of the hollow; blade section, forging the root and the base of the blade section to substantiall finished form, closing down and bending t is remainder of the blade section to a shape which approxi- 'niates the shape of the finished blade but which is.0f smaller cross section than the finished blade, holdin the blade in a finishing die and applying flui pressure to the interior of the blade section until the latter is sufiicientlv expanded to properly fill the die.

6. The method of making a turbine blade which comprises boring the blade portion of a blade blank from the tip toward thebase plying fluid pressure to the interior of the e thereof to provide a hollow blade section, ta-

peringthe outside and inside of the hollow blade section, forging the root and the base of the blade section to a shape which approximates the shape of the finished blade but which is ofsmaller cross section than the finished blade, holdin the blade in a finishing die and applying fluid pressure to the interior of the blade section until the latter is sufii clently expanded to properly fill'the die.

7. The method of making a turbine blade which comprises boring the blade portion of 4 a blade blank from the tip toward the base thereofto provide a hollow blade section,

tapering the hollow blade section from the base toward the tip thereof, forging the root and the base of the blade'to substantially finished forin, closing down and bending the remainder of thehollow blade-section to a shape, which, approximates the shape of the finished blade but which is of smaller cross sect-ion than the finished blade, working down the inlet and outlet edge portions until they are relatively thin, holding the blank in a finishing die and applying fluid pressure to' which comprises boringthe blade portion of a blade blank from the tip towardthe base i the sha the interior of the blade section to expand the latter until it properly'fills the die.

v 8. The method of making a turbine blade thereof to provide a hollow'blade section, forging the root to substantially finished form, closing down and bending the hollow blade sectionto a shape which a iproximates of the finished blade ut which is of sma ler cross section than the finished blade, sealing shut the hollow interior of the blade at the tip thereof, forming a pa:-

sage through the root to the interior of the hollowblade section, holding the blade in a finishing die and applying fiuid pressure through said passage to the interior of the hollow blade secti n until the latter properly fills thedie. 5

9. The method of making a turbine blade whioh comprises boring the blade portion of a blade blankfrom the tip toward thebase thereof to provide a hollow blade section, tapering the hollow blade section from the ,base toward the tip, forging the root'and the scribed 192s.

base of the blade substantially finished form, closing down and bending the remainder of the hollow blade section to a shape which appro'xiinates the shape of the finished blade but which is of .sma

r cross section than the finished blade, sealing shut the hollow interior of the blade at the tip thereof, forming a passage through the root to the hollow interior of the blade section, holding-the blade in a die'and applying fluid pressure through said passage to the interior of the hollow blade section until the latter is sufficiently expanded to properly fillthe'die. v

. In testimony whereof, I have hereunto submy name this 2nd day of October,

JAMES L. RAY.

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