US2503630A - Method of making impeller bucket dies - Google Patents

Description

April 1950 s. H. NORTON 2,503,630

METHOD OF MAKING IMPELLER BUCKET DIES Filed Oct. 29, 1945 s Sheets-Sheet 1 ZZZZ'EZZZUP Snmue/ H. Norfon Z7 ww ET April 1950 s. H. NORTON 2,503,630

METHOD OF MAKING IMPELLER BUCKET DIES Filed 0ct.-29, 1945 5 Sheets-Sheet 2 5. H. NORTON METHOD OF MAKING IMPELLER BUCKET DIES April 11, 1950 5 Sheets-Sheet 5 Filed Oct. 29, 1945 Patented Apr. 11, 1950 UNITED STATES PATENT OFFICE Samuel H. Norton, Cleveland, Ohio, assignor to Thompson Products, Inc., Cleveland, Ohio, a

corporation of Ohio.

Application October 29, 1945, Serial No. 625,354

3 Claims. 1

This invention deals with the production of impeller buckets for turbine and compressor wheels of steam turbines or gas turbine engines such as turbo-jet engines and jet-propulsion engmes.

Specifically, the invention relates to the forging of impeller buckets having twisted scooptype blades wherein the metal of the blade must be efficiently balanced anddistributed to withstand excessive stresses at highly elevated temperatures.

Heretofore, impeller buckets for gas turbine engines have been made by expensive precision casting, or mill cutting operations since the complicated shapes required for efficient operation of the compressor and impeller wheels in such engines could not be, produced by forging operations with the known forging technique unless large amounts of metal were lost as fiash scrap. In addition, such impeller bucketsmust be composed of heat and corrosion-resistant alloys which are substantially non-forgeable.

According to this invention, impeller buckets are efficiently produced by forging operations on corrosion and heat-resistant alloys without appreciable loss of metal.

In carrying out the: present invention, permanently deformable patterns, composed of wax, lead or the like, are made to, the exact configuration and size of the desired finished impeller bucket. Such patterns can readily be made by pouring molten wax or lead into the die cavity of coining or finishing dies for producing the fin,- ished; impeller bucket. These patterns, being exact. replicas of the finished impeller bucket, will have the exact distribution of material throughout their blade sections that is desired in the finished product to be capable of resisting the pattern and the twisted final shape of thebucket blade. This bent shape for the second pattern is such that it can be readily formed from a blank shaped like the first pattern, and can then be coined to the desired finished shape. Forging dies are made from the bent patterns. A headed metal rod is then blanked out to form a first blank in the forging dies formed from the 2 first pattern. This first blankis then forged in the dies formed from the second pattern to produce a second blank. The second blank is then coined in finishing or coining dies to the desired finished impeller bucket configuration.

Alternately, according to this invention, a pattern of permanently deformable material; formed to the exact size and configuration of the finished impeller bucket could be bent to the above-dc,- scribed intermediate shape preceding the coining operation, the second forging dies could be made from this pattern, a second pattern. could be made in the second forging dies, the second pattern could be bent to the shape of the first blank, and the first forging dies could be. made from this second pattern.

It is, then, an object of this invention to produce, by forging operations, impeller bucketsv that have heretofore only been made. by precision casting, or complicated milling operations, or expensive forging procedure.

Another object of this invention isto forge impeller buckets without appreciable loss of metal.

A. still. further object of this invention is to provide a method of working di'fficultly forgeable metals into impeller bucket configuration havin complicated twisted blade, shape with the metal so. distributed. throughout. the blade: as. to provide, maximum strength.

A further object of this invention is to provide impeller buckets for gas turbine engines by forging operations, without excessiveloss of metal.

A still further object of the invention is taprovide a. method of forging dies to. produce com plicated blade configurations. without excessively flashing metal.

Other and. further objects of, the invention will be apparent to those skilled in the art from the following detailed description of the annexed sheets of drawings which, by Way of a preferred example, only, illustrate one embodiment of. the invention.

On the drawings:

Figure 1 is an elevational view of a: headed metal rod suitable as a starting piece for forming impeller buckets according to this; invention.

Figure 2Iis an isometric view of the first blank formed from, the headed rod oi Figure 1 according to this invention.

Figure 3 is an end elevational view ofthelblade configuration of the. blank of Figure 1- Figure 4 is an isometric view of the second blank formed from the blank of Figure 2 according to this invention.

Figure 5 is an end elevational view of the blade configuration of the blank of Figure 4.

Figure 6 is an isometric view of the finished impeller bucket formed according to this inven tion.

Figure 7 is an end elevational view of the blade of the impeller bucket of Figure 6.

Figure 8 is a longitudinal cross-sectional view of the impeller bucket of Figure 6.

Figures 9, 10 and 11 are transverse cross-sectional views of the impeller blade taken respectively along lines IX-IX, X-X, and XI--XI of Figure 8.

Figure 12 is a top plan view of the bucket of Figures 6 to 11.

Figure 13 is an end elevational View of the head end of the bucket of Figures 6 to 12.

Figure 14. is an elevational view offinishing or coining dies used for forming the finished impeller buckets of Figures 6 to 13 from the blank of Figures 4 and 5 and illustrating the manner in which these dies are used to form a pattern of permanently deformable material.

As shown on the drawings:

In Figure 1 the reference numeral 10 designates generally a headed metal rod having a large cylindrical head portion I l and a smaller diameter longer cylindrical shank portion I2. This headed rod provides a convenient starting piece for making the impeller bucket is of this invention shown in Figures 6 to 13. The headed rod 10 is easily formed by upsetting rod material to form the head thereon. The rod material is preferably composed of heat and corrosion-resistant metal such as Stellite and the like.

The impeller bucket of Figures 6 to 13 has a very complicated shape including a wedge block head portion l4 and a twisted scoop-type blade portion 15. The head portion I4 is shaped for simple machining to provide a locking attachor upstandingback wall Ma with diverging fiat top and bottom walls Mb. The side edges of the head have a complicated configuration for locking dovetail engagement with a hub. Thus the head has side wall portions Me at right angles to the back wall Ma. These wall portions l lc are relatively flat but only extend for a short distance to merge into inwardly converging side walls Md. Beveled surfaces Me connect the top and bottom walls l4b with the side walls 140 and 14d but upwardly tapering surfaces l4 are provided between the beveled surfaces Me and the side walls I40 and Md to provide locking keyways in the top half of the head.

The front face My of the head is substantially vertical but converges inwardly from the top to the bottom thereof along the side edges I471. thereof. g

' The forged shape of the head is such that it can be easily machined to provide suitable means for fastening the impeller to a hub.

As shown in Figure '12 the longitudinal center line of the blade portion 15 is offset from the longitudinal center line of the head portion I4. The blade l5, as explained above, is of twisted scoop-like configuration and has a curved nonarcuate inner face l5a converging toward a curved non-arcuate outer face l5b from the face My of the head. The converging relationship of the inner face l5a relative to the outer face l5b provides blade walls of gradually decreasing thickness from the head to the free edge of the blade. As shown in the transverse cross-sectional views 9 to 11, the gradually diminishing thickness of the blade Wall is so distributed as to provide an efficient stress-resisting member without utilization of excessive amounts of metal. A lightweight blade of exceptional strength is produced. The curvatures of the inner and outer faces 15a and i512 are dissimilar so that the blade face l5a will have the desired'twisted scoop-like configuration for efiicient operation, while the back face |5b of the blade varies from this configuration to provide the right amount of metal at the right places along the length of the blade for insuring blade strength. A recess I is provided in the face I51) at the tip end of the blade to further decrease the weight of the blade and to permit the blade tip to have close-running clearance relationship with stationary jet-directing vanes used in gas turbine engines.

The blade l5 has oppositely inclined longitudinal edges I511 and We respectively with the edge i511 extending upwardly from the top of the head face My to a level L1 above the head. The edge We tapers downwardly from the face My to a level L2 that is about level with the bottom edge of the back face Ma of the head. The edges 55a andlSe are on the same level at their inner ends adjacent the face My but, as shown in Figure 7, the levels L1 and L2 of the outer edge of the blade are spaced apart by a distance identified at A. The scoop face l5a thus has a spiral configuration.

The above-described complicated shape of the bucket i3 cannot be made with ordinary forging technique because it is impossible, according to known forging practices, to distribute the metal under the action of forging dies, for producing the twisted spiral blade configuration without creation of excessive amounts of flash metal that are wasted. Known forging practices do not permit the displacement of metal from the center of mass thereof to the two widely different levels L1 and L2, without flashing excessive amounts of metal beyond the longitudinal edge [5e of the blade. Thus, due to the extreme slope of the blade end between levels L1 and L2 ordinary forging technique would result in the top die shoving most of the metal downwardly to leave little or no metal at L1 and a heavy flash at L2. While it is possible to move the metal of a startin piece to form the head M of the blade by known forging practices, it has not heretofore been possible to so movethe metal of a starting piece to form the blade portion.

In accordance with this invention coining or finishing forging dies t5 and il shown in Figure 14, are made to produce the finished bucket of Figures 6 to 13. These dies have a parting line 88 which makes it possible to readily remove the complicated shape of the bucket from the dies. The dies are formed according to known die-making practices. The dies are then held in closed upstanding position and a pouring funnel I9 is seated on the dies to direct molten permanently deformable material into the die cavity for forming a pattern exactly conforming with the bucket 13. Molten lead or wax are suitable materials for forming the pattern. The hardened or set pattern is then removed from the dies and the blade ort n o th p t rn is be t r nt isted to move the longitudinaledges d and l5e of the. blade to substantially the same level and thereby produce a relatively flat scoop configuration forthe blade. This configuration is shown in Figures 2 and 3 which represents a forged blank made from dies produced by the bent pattern. The bent pattern is used to produce first breakdown dies which will forge the piece In of Figure 1 to the blank 21} of Figures 2 and 3. As

Figures 2 and s, the blank hasjsubstan ially he same he d 2! as e d M of the. finishe buc et H w r e ade 22 of the blan 2.0 as subst n i lly parallel longitw dinal edges 22a and 22?) with the level of the. edge 2Zqqnly slightly above the level of the edge 22b. The difference in levels is represented by the distance C in Figure 3. It will also be noted from Figure 3 that the distance Z between the longitudinal center of the blade 22 and the edge 22a of the blade is materially greater than the distance X between the longitudinal center and the edge l5d of the finished blade.

The thickness of the blade portion 22 of the blade 20 varies along the length of the blade to increase in, thickness toward the head 2! in the same manner as described in connection with the finished blade I5.

The blank 20 can readily be formed from the starting piece or headed rod is shown in Figure 1 by forging in dies produced from the bent pattern described above. This forging operation, while it materially changes the shape of the. starting piece, does not require material uneven move ment of metal from its center of mass because the blade edges of the blank are at substantially the same level and metal Will move evenly outward in both directions. duced.

In further accordance with this invention, a second pattern is either made from the dies shown in Figure 14 as described hereinabove, or is made from the dies which produce the blank 20. This pattern, like the above described pattern, composed of permanently deformable material such as wax or lead and it has the blade portion thereof bent to the configuration shown in Figures 4 and 5 which represent a second blank made from the blank of Figures 2 and 3. The pattern of either the finished bucket !3 or the blank 20 is bent so that the longitudinal edges of the blade will be intermediate the substantially equal level parallel edges 22a and 22b of the blank 20 and the widely divergent edges lild and l5e of the finished bucket I3. A second break-down set of dies is made from this bent pattern and produces a blank 23 having a head 24 substantially the same as the head M of the finished bucket l3 and a blade 25 with longitudinal edges 25a and 2252) moved from the substantially parallel position in the blank 20 to different levels so that the edge 25a slopes upwardly from the head 24 a slight amount, while the edge 25b slopes downwardly from the head 24 for a slight amount. As shown in Figure 5 the edges 25a and 25b at their free ends are at levels separated by the distance B which is greater than the distance C illustrated in Figure 3 but still less than the distance A illustrated in, Figure 7. In addition, the edge 25a is displaced from the longitudinal center of the blade 25a 2. distance Y which is less than the distance Z of Figure 3 but greater than the distance X of Figure 7.

The blank 23 is readily formed from the blank 20 by forging in the dies produced from the Flash scrap is not proawe-e8 above-described pattern since no appreciable unevenmovement of the metal is necessary to yield the initial twist of the blade 22 of the blank 2!] for producing the blade form 25 of the blank 23.

The finished bucket I3 is then readily coined or finished from the blank 23 in the dies shown in Figure 14, and this finishing or coining operation only results in a further twisting of the blade to change its configuration from that of the blade 25 of the blank 23 to-the configuration of the blade l5 of the finished bucket 13.

In proceeding with the forging operations, described above, the headed rod ID of Figure 1 is initially broken down in a set of first break-down dies to produce the blank 20. The blank 20 is then deformed in a second set of break-down dies to produce the blank 23. The blank 23 is then coined or finish forged in the coining or finishing dies of Figure 14 to produce the finished bucket I3. In the second and third forging operations, the configuration of the blade 22 of the original blank 29 produced in the first forging operation is changed mainly by twisting to increase the differences'in levels of the edges of the blade from C to B and from B to A as shown in Figures 3, 5 and 7, and to decrease the distance between the longitudinal center line of the blade and the high longitudinal edge of the blade from Z to. Y and from Y to X.

From the above descriptions it should be understood that the invention provides a method 01' making impeller buckets having strong stressresisting twisted scoop blade configurations by forging operations which will not result in wastage of metal. The process includes formation of patterns of permanently deformable material from the finished bucket, twisting the patterns to produce blade configurations that can be forged without requiring appreciable uneven movement of metal, and then producing the desired finished shape by a coining operation on a blank having the same configuration as the desired bucket except for the desired twist in the bucket.

It will, of course, be understood that various details of the method ma be varied through a wide range without departing from the principles of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

I claim as my invention:

1. The method of making dies for the production of impeller buckets having anchoring roots and twisted scoop-type blades by successive forming operations which comprises fabricating a pair of dies to the finished shape of said buckets, closing said dies to form a mold, casting an easily deformable material into the mold formed by said dies to produce a pattern having the configuration of the finished impeller bucket including a root and. a twisted scoop shaped blade portion, bending the blade portion of the thus formed pattern to partially untwist the blade for moving the longitudinal edges thereof closer to the same level, fabricating a second pair of dies to conform to the thus bent pattern, bending a second cast deformable pattern to untwist the blade beyond the partially untwisted configuration of the first pattern, fabricating a second pair of dies to conform to the second bent pattern, and repeating the cycle of casting and bending bucket patterns and fabricating dies therefrom to thereby form a series of dies of changing blade configuration 2. The method of making dies for the production of turbine buckets and the like which com- 7 prises closing a pair of bucket finishing dies to form a die cavity of the exact shape desired for the bucket, casting deformable material in said cavity to produce a first deformable pattern having the configuration of the finished bucket including a twisted blade portion, partially untwisting the blade portion of the first pattern to move the longitudinal edges thereof toward the same level, casting a second deformable pattern in said die cavity, untwisting the blade portion of the second pattern beyond the partially untwisted form of the first pattern to move the longitudinal edges of the blade closer to the same level than the edges of the first pattern, forming first and second dies from the first and second patterns, repeating the cycle of casting and bending patterns to produce a series of patterns having the blade portions gradually untwisted from finished blade contour to a blade portion with no appreciable twist and having the longitudinal edges thereof at substantially the same level, and fabricating a die from each pattern thus formed.

3. The method of making dies for the production of impeller buckets having anchoring roots and twisted scoop-type blades by successive forming operations which comprises fabricating a pair of dies to the finished shape of said buckets, closing said dies to form a mold, casting an easily deformable materia1 into the mold formed by said dies to produce a pattern having the configuration of the finished impeller bucket including a root and a twisted scoop shaped blade portion, bending the blade portion of the thus formed pattern to partially untwist the blade for moving the longitudinal edges thereof closer to the samelevel, fabricating a second pair of dies to conform to the thus bent pattern, closing the second pair of dies to form a second mold, casting an easily deformable material into the second mold to produce a second pattern having the partially untwisted blade portion of the first pattern, untwisting the blade portion of the second pattern to move the longitudinal edges thereof closer to the same level than the edges of the first pattern, fabricating a third pair of dies from the second pattern, and repeating the cycle of casting and untwisting patterns and fabricating dies to produce a series of dies of gradually changing blade configuration.

SAMUEL H. NORTON.

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

UNITED STATES PATENTS Number Name Date 1,771,023 Allen July 22, 1930 1,910,943 Wiberg May 23, 1933 2,056,415 Young Oct. 6, 1936 2,383,706 Burger et al Aug. 28,1945 2,422,325 Wheelon June 17, 1947 FOREIGN PATENTS Number Country Date 215,142 Great Britain May 8, 1924 295,633 Great Britain Jan. 31, 1929 668,523 France Nov. 4, 1929

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