US2912222A - Turbomachine blading and method of manufacture thereof - Google Patents

Description

1959 G. B. WILKES, JR 2,912,222

TURBOMACHINE BLADING AND METHOD OF MANUFACTURE THEREOF Filed Aug. 2, 1952 Inventor: Gordon B.\/-/i|kes.Jr,

His Attorney.

United States Patent TURBOMACHINE BLADING AND METHOD OF MANUFACTURE THEREOF Gordon B. Wilkes, Jr., Lynnfield, Mass., assignor to General Electric Company, a corporation of New York Application August 2, 1952, Serial No. 302,393

7 Claims. (Cl. 253-77) This invention relates generally to gas operated turbine power plants and specifically to turbomachine blading and the production thereof for such power plants used for aircraft jet propulsion.

In the present method of constructing a jet engine, the axial flow compressor may require more than 2000 individually forged blades, half being rotating and the other half stationary. Because of the physical properties and dimensional accuracy called for in the finished blades, precision forging techniques are essential, making the blading expensive and necessitating a large amount of forging capacity. Each individual blade is forged with an enlarged end and machined to form dovetail grooves (or other securing means for use with wedge pins or keys). The blades are then slid into respective slots in a blade ring, covering one half of one stage, and in turn, the blade ring is slid into a T-slot in a blade carrier, e.g. the compressor casing. Increased production rates forced by the present international situation make it mandatory that the number of forged parts per engine be reduced. Also, economy in material to be removed in any machining process following the forging, as well as in manpower required for such machining, is desirable.

Accordingly, it is an object of the present invention to provide a new and improved blading element for use in gas turbines.

Another object of the invention is to provide a new and improved method of manufacture of aircraft gas turbine blading.

Still another object of the invention is to provide an improved method for the construction and arrangement of the blading used in turbomachines.

A further object of the invention is to provide an improved method for making blading Without requiring machining of excess material from the blade portion to attain the final finished blading structure.

For a consideration of what I believe to be novel and my invention, attention is directed to the following description and the claims appended thereto in connection with the accompanying drawing, in which:

Fig. 1 is a fragmentary isometric view illustrating the manner in which the novel blading is inserted in its carrier;

Fig. 2 is an exploded view prior to the assembly of the blade portion with the base; and

Figs. 3 and 4 are partly sectional views of an assembled blading element taken along line 3-3 of Fig. 1.

In accordance with the illustrated embodiments of my invention, preshaped body and base sections are assembled into blading structures having conventional final form.

Referring to the drawing, there is disclosed a blading carrier or ring at 10, with a T-slot at a. My novel blading is indicated generally at 11, comprised of the shaped air foil body section 12, which can be used as a bucket, blade or diaphragm element, and a sheet metal base including a skirt 13 and web 14, formed separately and punched to receive preselected parts of the air foil 2,912,222 Patented Nov. 10, 1959 are doubled over to increase the flange thicknesses to conform to the blade ring or carrier T-slot dimensions, thus permitting the use of light stock for minimum weight, and to provide convenient spaces for subsequent welding. Where these dimensions are small, no doubling over of the edgeswould be required, Fig. 4. Once the base is formed completely, the air foil section is slipped through the punched holes 13b and 14b in the skirt and web, respectively, and fastened to the web and flange 13a by weld 15, the air foil section 12 having a tongue 12a which projects through opening 14b. The weld 15 may be extended up to the bent over flanges of the skirt, as shown at 15a on the left side of Fig. 3, thus securely welding all three elements of the blading together. To improve the fatigue strength of the assembly, bending stress at the weld is minimized by silver brazing the blade to. the skirt as at 16. This completely fills any gap between these parts left by necessary manufacturing tolerances. Alternatively, as shown in Fig. 4, it is possible to silver brazethe skirt and web pieces of the base as at 17,

Welding only the tongue 12a to the web 14 and in. this manner forestall grinding of the bottom of the base to remove any weld material projecting beyond the bottom .may be either the compressor casing or rotor, the principle of application being unchanged withthe use of either.

My invention is both simple and economical to manufacture and can be maintained readily when repairs are required. It will be seen that the objects of my invention may be realized by the provision of shaped air foil sections mounted in stamped sheet metal bases having the same cross sectional areas as the T-slots' in the blade carrier or ring, the air foil sections, comprising the body of the blading, being rolled on contoured rolls in long lengths to dimensions closer than those obtainable by forging, and then cut to the desired lengths at assembly. Rolling of the blading stock permits the use of special blade materials and provides smoother surfaces which may be more resistant to extreme operating conditions. In the case of rotor blading or highly stressed stator blading, a taper is applied along the length of the blade, as by roll forging of short lengths. It is not intended to limit the shaping of the air foil sections to the process of the rolling since extruding or forging can produce sections for use with the prefabricated sheet metal base.

In practice, the shaped blade is inserted into the sheet metal base, so that tongue 12a extends beyond the bottom surface of the web. The joint between the blade and skirt is coated with a silver brazing flux to maintain a clean surface for subsequent brazing and the silver brazing alloy is placed in position. The blade tongue is melted down by the inert arc process, and when the weld is extended to the bent over flanges, a small amount of filler material is added to complete the connection to the skirt. Metal arc welding is feasible and can be used if desired. Actual brazing is done during the heat treatment of the assembly.

Having described the method of operation of my invention together with apparatus which I now consider to represent the best embodiment thereof, I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination in a turbomachine, a blading structure defining a plurality of passageways and comprising an assemblage of blading members, each of said members comprising a blade portion shaped into a concavo-convex section and a base portion comprising sheet metal web and skirt elements, said skirt having flanges, said flanges interlocking with and supporting the edges of the web element to form the said base portion, said elements having openings therein, each of said blading members having an integral tongue projecting from one end, said tongue inserted through said openings for fastening to said Web and skirt elements.

2. The method of making turbomachine blading which comprises shaping an air foil section into a blade having a concavo-convex cross section and a projection on one of the curved edges thereof, perforating sheet metal skirt and web elements for the reception of parts of said blade and projection, attaching said elements to each other to fashion a base section therefrom by bending flanges of a skirt element over the edges of a web element, inserting said air foil section through perforations in said elements, and fastening together said air foil section and sheet metal elements, said fastening together comprising the steps of welding said projection to said web element and brazing said shaped air foil section to said skirt element.

3. In the method as set forth in claim 2, said fastening together comprising welding said projection to said web element and to the bent over flanges on the skirt element and brazing said shaped air foil section to said skirt element.

4. In the method as set forth in claim 2, said fastening together including the step of brazing said skirt and web elements along the bent over flanges and edges thereof.

5. A blading member for use in a turbomachine comprising: a concave-convex blade portion having an integral tongue projecting from one end; and a base portion individual to the blading member and secured to the blade portion, the base portion including a skirt element secured to a Web element, the skirt element having a first opening receiving the end of the blade portion carrying the tongue, and the web element having a second opening in substantial radial alignment with the first opening and receiving the tongue.

6. A blading member for use in a turbomachine comprising: a concavo-convex blade portion having an integrad tongue projecting from one end; and a base portion individual to the blading member and secured to the blade portion, the base portion including a sheet metal skirt element and a sheet metal Web element, the skirt element having flanges interlocking with and supporting the web element to form the base portion, the skirt element having a first opening receiving the end of the blade portion carrying the tongue, and the web element having a second opening in substantial radial alignment with the first opening and receiving the tongue.

7. in combination, a blading carrier having an undercut groove and a plurality of blading members, each of the blading members comprising: a substantially radially extending concave-convex blade portion having an integral tongue projecting from one end; and a base portion individual to the blading member and secured to the blade portion, the base portion including a skirt element and a web element, the skirt element having flanges interfit in the undercut groove and a first opening receiving the end of the blade portion carrying the tongue, and the Web element having edge portions interlocking in and supported by the flanges and a second opening in substantial radial alignment with the first opening and receiving the tongue.

References Cited in the tile of this patent UNITED STATES PATENTS 784,670 Fullagar Mar. 14, 1905 2,063,706 Soderberg Dec. 8, 1936 2,220,918 Smith Nov. 12, 1940 2,620,624 Wislicenus Dec. 9, 1952 2,640,319 Wislicenus June 2, 1953 2,640,679 Wheatley June 2, 1953 2,656,146 Sollinger Oct. 20, 1953 2,658,719 Iohanson Nov. 10, 1953 2,771,622 Thorp Nov. 27, 1956 2,772,069 Hockert Nov. 27, 1956 FOREIGN PATENTS 199,180 Great Britain June 21, 1923

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