US3012308A - Method of making blade structures - Google Patents

Description

Dec. 12, 1961 w. A. ZECH ETAL 3,012,308

METHOD OF MAKING BLADE STRUCTURES Filed Aug. 12, 1957 2 Sheets-Sheet 1 FIG. 1.

26 a 5 Q g /0 FIG 3 2a 3a ,0 mmvroxs. WILLIAM A. ZECH LEROY M. KROUSE ATTORNEY Dec. 12, 1961 Filed Aug. 12, 1957 FIG. 6.

W. A. ZECH EI'AL METHOD OF MAKING BLADE STRUCTURES 2 Sheets-Sheet 2 F l G. 7.

INVHVTORS.

WILLIAM A. ZECH LEROY M. KROUSE XMM ATTORNEY ted States Patent 3,012,308 METHOD OF MAKING BLADE STRUCTURES William A. Zech, Kenmore, and Le Roy M. Krouse,

Buffalo, N.Y., assignors to Joy Manufacturing (Zompany, Pittsburgh, Pin, a corporation of Pennsylvania Filed Aug. 12, 1957, Ser. No. 677,439 8 Claims. (1. 29--156.8)

Our invention relates to the construction of blades, such as turbine and compressor blades, and more particularly to the consruction of blades having an air foil section with a base at one end thereof for securing the blade to a supporting structure.

Heretofore it has been known to form blades such as turbine blades to have a twisted air foil cross section and to secure root elements at each of its sides at one of its ends whereby the entire structure may be suitably supported in a well-known manner. As can readily be appreciated, due to the twisted air foil section it is difficult to obtain an intimate fit between the engaging surfaces of the air foil section and the root elements. Heretofore one procedure which has been employed to solve this problem has been to grind or machine engaging surfaces on the individual root elements. Another procedure which also has been employed has been to use individually sintered root elements. As can be appreciated the use of such prior procedures has added materially to the cost of the complete blade structure due to the inherent expense of such procedures.

With such multiple piece blade structures it has been common practice to bond the various elements together in various suitable manners such as by brazing. While such a bonded joint is generally satisfactory it is not believed to be completely satisfactory under operating conditions which would tend to weaken the strength of the bonded joint.

An object of our invention is to provide a new and improved method of forming a blade comprising twisting a blade element and a pair of root elements to the same degree so that intimate engagement between mating surfaces thereon is obtained.

A more specific object of our invention is to provide a new and improved method of forming a blade by forming a blade element and a pair of root elements having surfaces thereon conjugate with opposite side surfaces of the blade element and then twisting all the elements so that such conjugate surfaces remain conjugate to permit assembly together in intimate engagement.

These and other objects of our invention will become more apparent when taken in conjunction with the following detailed description of a preferred embodiment thereof and the following drawings in which:

FIGURE 1 is an end elevational view of a pair of rollers for forming an elongated strip therebetween,

FIGURE 2 is a perspective view of the end of one root strip formed in accordance with the principles of our invention,

FIGURE 3 is a perspective view of the end of another root strip formed in accordance with the principles of our invention,

FIGURE 4 is a perspective view of a blade strip having spaced clamping means in engagement therewith for twisting the blade strip,

FIGURE 5 is a perspective view of a twisted blade strip,

FIGURE 6 is a perspective view of an assembled blade of our invention having portions thereof broken away, and;

FIGURE 7 is a perspective view of an assembled blade of our invention having the root elements thereof formed to provide a joint for engaging supporting means.

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Referring to FIGURES 6 and 7 it will be noted that a blade constructed in accordance with the principles of our invention comprises an elongated blade element 2 having a suitable air foil cross section which is twisted slightly on its longitudinal axis to provide the desired air flow characteristics. The blade element 2 may be formed in any suitable manner and is desirably formed by means of passing an elongated st ip 5 of suitable material through a number of mating pairs of rollers, the last pair of which (FIG. 1) has an opening between mating rollers 4 and 6 which defines the desired cross sectional area of the blade element. If desired, the blade strip 5 may be passed between straightening rolls (not shown) after the final forming rollers 4 and 6 to eliminate any undesirable curling or twisting of the blade strip. Inasmuch as such roll forming and straightening is well known in the art, further illustration and description thereof is not believed necessary. As is customary for blade elements of this type the opposite side surfaces 8 and 10 are of different curvatures to obtain the desired air flow characteristics.

After forming the blade strip 5 it is then twisted slightly about a longitudinal axis to provide the degree of twist in the blade strip 5 which is desired in a blade element 2. Such twisting may be performed in any suitable welllcnown manner such as by clamping the opposite ends of the blade strip 5 between longitudinally spaced pairs of die blocks 12 and 14 which are received within any suitable apparatus, not shown, and then rotating the spaced pairs of die blocks 12 and 14 in opposite directions. As shown, the die blocks 12 and 14 are provided with arcuate contact surfaces, respectively, which firmly engage the opposite sides '8 and 10, of the blade strip 5, respectively, to insure a good holding action of the blade strip 5 during the twisting process. After the blade strip 5 has been so twisted FIG. 5) it is then laterally cut in any suitable manner along suitable lines such as those indicated by dotted lines 16 which are spaced longitudinally of the blade strip 5 to form individual blade elements 2 therebetween. A number of blade elements 2 may be cut from a single strip 5 depending on the length of the blade strip 5 initially employed. With this method the small end portion 18 of the blade strip which is engaged between die blocks 12 and 14 may be cut off to eliminate any imperfections which may occur on the surfaces of the blade element during the twisting process by engagement with the clamping means.

In the same manner as heretofore described, elongated root strips 20 and 22 (see FIGS. 2 and 3 respectively) of individual root elements may also be formed. As shown, the strip 20 is provided with a laterally extending concave surface 24 between a pair of flat end lands 26 which surface 24is the conjugate of the surface 8 of the blade strip 5 in its untwisted state. Thereafter the elongated strip 20 is twisted, which may be accomplished in the same manner as the blade strip 5 heretofore described, so that the concave surface 24 has the same. degree of twist as the blade strip 5 and remains the conjugate of the surface 8 in its twisted state. The other strip 22 is formed in the same manner as the blade strip 5 and the root strip 20 heretofore described. It will be noted, however, that the root strip 22 is provided with a'laterally extending convex surface 28 between flat end lands 30 which is the conjugate of the surface 10 of the blade strip 5 in its untwisted state. Again after forming the root strip 22 it is twisted so that the surface 28' remains the conjugate of the surface 10 of the blade strip 5 in its twisted state. After such forming and twisting individual oot elements 32 and 34 of suitable length are cut from the twisted root strips 20 and 22, respectively, in any suitable manner.

Once the blade and root elements above described have 'been formed the root elements 32 and 34 are disposed on opposite sides of the blade element 2 with the twisted surfaces 8, 24 and 16, 28 in intimate engagement with each other. As shown the root elements 32 and 34 are secured to one end of the blade element 2 to form a base for securing the entire blade structure to a suitable support as is well known in the art. The lower end of the blade element 2 and the root elements 32 and 34 preferably lie in the same plane (FIG. 7). When root elements 32 and 34' and blade element 2 are so located they are supported in such relationship in any suitable man ner so as to permit all the elements to be bonded or autogenously connected together in any suitable manner such as by brazing. As shown the end lands 26, 30 of the root elements32 and 34 also engage each other and are also bonded together during the bonding process.

It is to be realized that the outer surfaces of the root elements 32 and 34 are also twisted to the same degree as the surfaces 24 and 28 heretofore described. In order for the blade element 2 to be secured to a suitable support, it is usually necessary that the base be provided with a standard shape such as a dovetail (FIG. 7). The fact that the outer surfaces of the root elements 32 and 34 are twisted does not affect the machining process so that if desired the resultant formed outer surfaces of the root elements 32 and 34 may be of any suitable configuration with relation to each other. 1

Although a bonding of the various elements together is generally satisfactory, I have also provided an additional joining means between the root elements 32 and 34 and the blade element 2. As shown in FIG. 6, aligned openings 42, 44and 46 are provided in the root element 34, blade element 2, and the root element 32, respectively, through which a connecting pin 40 (FIG. 7) extends.

Although the aligned openings may be formed'at various stages during the assembly they are preferably formed er relationship 'prior' to their being bonded together.

When so formed a close fitting pin 49 may be inserted through the alined openings 42, 44 and 46 to hold the elements in proper position during the bonding process and also to bond the pin 4%] into engagement with each element. The ends of the pin are thereafter machined at the same time the root elements 32 and 34 are machined whereby the ends of the pin 49 are a part of the outer contour of the base of the finished blade. It is to be realized if desired the pin 40 may be inserted in the above positions after the bonding process and suitably secured by means of a cold working process such as squeeze riveting. Also, although not stated previously it will be realized that each of the root elements, the blade element and the connecting pin are formed from a suitable metal so that the above described operations may be performed on a commercial basis.

From the above description it will be noted that We have provided a novel blade of simplified construction" .root elements and the blade elements is not solely depended upon for holding the elements together. It will also be appreciated that by proper design a pin may be provided which is itself of sufiicient strength to resist 7, any separation of the blade elements which may occur in normal service.

, Having described a preferred structure and methodof forming such a blade structure in accordance with the patent statutes, it is to be realized that modifications thereof may be made without departing from the broad spirit 4 of our invention. 7 Accordingly, it is respectfully requested that our invention be interpreted as broadly as possible and limited only by the prior art.

What we claim is:

1. The method of manufacturing blades of the type having blade and root elements comprising, twisting a first elongated strip of material having a cross section corresponding to that of a finished blade element, cutting a blade element from the twisted portion of said strip, twisting a second elongated strip having a surface conjugate with one side of said first strip to obtain the same degree of twist therein as said first strip, cutting from the twisted portion of said second elongated strip a first root element, twisting a third elongated strip having a surface conjugate with the other side of said first strip to obtain the same degree of twist therein'as said first strip, cutting from the twisted portion of said third elongated strip a second root element, and rigidly securing said first and second rootelements in intimate engagement with said side surfaces of said blade element.

2. The method of manufacturing blades of the type having blade and root elements comprising, forming an elongated blade element having arcuate side surfaces, twisting said blade element laterally about a longitudinal axis, forming a first root element having a surface thereon intimately engageable with one of said arcuate side surfaces of said blade element in its untwisted state, twisting said first root element so that said surface thereon intimately engages-said one side surface of said blade element in its twisted state, forming a second root element having a surface thereon intimately engageable with the other of said arcuate side surfaces of said blade element in its untwisted state, twisting said second root element so that said surface thereon intimately engages said other side surface of said blade element in its twisted state, and

rigidly securing said root elements in such'engagement with said twisted blade'element.-.

3. The method of manufacturing blades of the type having blade and root elements comprising, twisting a first elongated strip of material having a cross section corresponding to that of a finished blade element, cutting a blade element from the twisted portion of said strip, twisting a second elongated strip having a surface conjugate with one side of said first strip to obtain the same degree of twist therein as said first strip, cutting said second elongated strip to form a root element, and rigidly securing said element in intimate engagement with said side surface of said blade element.

4. The method of manufacturing blades of the type having blade and root elements comprising, forming an elongated blade element having arcuate side surfaces,

twisting said blade element laterally about alongitudinal axis, forming a root element having a surface thereon intimately engageable with one of said arcuate side surfaces of said blade elements in its untwisted state, twisting said root element sothat said surface thereon intimately engages said one side surface of said blade element in its twisted state, and rigidly securing said root element in such engagement with said twisted blade element.

5. The method of manufacturing blades of the type having blade and root elements comprising, twisting a first elongated strip of material having a cross section corresponding to' that of a finished blade element, cutting "a blade element from the twisted portion of said strip,

6. The method of manufacturing blades of the type having blade and root elements comprising, forming an elongated blade element having arcuate side surfaces, twisting said blade element, forming a first root element having a surface thereon complementary with one of said arcuate side surfaces of said blade element in its untwisted state, twisting said first root element so that said surface thereon intimately engages said one side surface of said blade element in its twisted state, forming a second root element having a surface thereon conjugate with the other of said arcuate side surfaces of said blade element in its untwisted state, twisting said second root element so that said surface thereon intimately engages said other side surface of said blade element in its twisted state, forming aligned openings extending through all of said elements, placing a pin member within said aligned openings to extend therethrough and to be closely received therein, and rigidly securing said root elements in such engagement with said blade element and said pin member within said aligned openings.

7. The method of manufacturing blades of the type having blade and root elements comprising, twisting a first elongated strip of material having a cross section corresponding to that of a finished blade element, cutting a blade element from said twisted strip, twisting a second elongated strip having a surface conjugate with one side of said first strip to obtain the same degree of twist therein as said first sL'ip, cutting said second elongated strip to form a first root element, twisting a third elongated strip having a surface conjugate with the other side of said first strip to obtain the same degree of twist therein as said first strip, cutting said third elongated strip to form a second root element, forming aligned openings extending through all of said elements, placing a pin member within said aligned openings to extend therethrough and to be closely received therein, and rigidly securing said first and second root elements in intimate engagement with said side surfaces of said blade element and said pin member within said aligned openmgs.

8. The method of manufacturing blades of the type having blade and root elements comprising, forming an elongated blade element having arcuate side surfaces, twisting said blade element laterally about a longitudinal axis, forming a root element having a surface thereon intimately engageable with one of said arcuate side surfaces of said blade element in its untwisted state, twisting said root element so that said surface thereon intimately engages said one side surface of said blade element in its twisted state, forming aligned openings extending through all of said elements, placing a pin member within said aligned openings to extend therethrough and to be closely received therein, and rigidly securing said root element in such engagement with said twisted blade element and said pin member with said aligned openings.

References Cited in the file of this patent UNITED STATES PATENTS 1,516,607 Johanson Nov. 25, 1924 2,063,706 Soderberg Dec. 8, 1936 2,394,124 Warren Feb. 5, 1946 2,767,460 Schultz Oct. 23, 1956 FOREIGN PATENTS 238,005 Switzerland Sept. 17, 1945 574,440 Great Britain J an. 4, 1946

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