US3720481A

US3720481A - Means for forming and securing turbine compressor blades

Info

Publication number: US3720481A
Application number: US00138241A
Authority: US
Inventors: S Motta
Original assignee: Avco Corp
Current assignee: Avco Corp
Priority date: 1971-04-28
Filing date: 1971-04-28
Publication date: 1973-03-13
Anticipated expiration: 1990-03-13

Abstract

THE INVENTION IS A FORMING DIE FOR USE IN FABRICATING COMPRESSOR BLADES FROM SYNTHETIC FIBERS. SUCH FIBERS ARE SPACED A DETERMINED DISTANCE APART AND FORMED INTO A WEB WHICH IS HELD IN FIXED POSITION APPROXIMATING THE SHAPE OF THE FINISHED BLADE AND THEN IMPREGNATED WITH A BONDING AGENT TO PRODUCE AN INTEGRAL BLADE WITH REINFORCED BLADE PORTIONS AND ROOT PORTIONS. THE INVENTION INCLUDES MEANS FOR MOUNTING BLADES TO A ROTOR BY SECURING A SPLIT BUSHING WITH OPPOSITELY DISPOSED CONICAL BORES IN THE BORE OF THE BLADE ROOT, INSERTING AND SECURING THE BLADE ROOT IN A KEYHOLE SLOT IN THE ROTOR AND BY FORCING THE CONICAL WEDGES TOGETHER IN SAID BUSHING.

D R A W I N G

Description

S. MOTTA March 13, 1973 MEANS FOR FORMING AND SECURING TURBINE COMPRESSOR BLADES Filed April 28, 1971 2 Sheets-Sheet l Him.

INVENTOR. SALVATORE MQTTA l'luv n. P

AT RNEYS.

March 13, 1973 s MOTTA 3,720,481

MEANS FOR FORMING AND SECURING TURBINE COMPRESSOR BLADES Filed April 28, 1971 2 Sheets-Sheet Z I N VEN TOR. SALVATORE MOTTA ATToxEYs.

United States Patent 3,720,481 MEANS FOR FORMING AND SECURING TURBINE COMPRESSOR BLADES Salvatore Motta, Commack, N.Y., assignor to Avco Corporation, Strattord, Conn. Filed Apr. 28, 1971, Ser. No. 138,241 Int. Cl. F0111 5/32 US. Cl. 416-220 3 Claims ABSTRACT OF THE DISCLOSURE The invention is a forming die for use in fabricating compressor blades from synthetic fibers. Such fibers are spaced a predetermined distance apart and formed into a web which is held in fixed position approximating the shape of the finished blade and then impregnated with a bonding agent to produce an integral blade with reinforced blade portions and root portions. The invention includes means for mounting blades to a rotor by securing a split bushing with oppositely disposed conical bores in the bore of the blade root, inserting and securing the blade root in a keyhole slot in the rotor and by forcing the conical wedges together in said bushing.

BACKGROUND The design and fabrication of compressor blades particularly for gas turbine engines creates many problems in insuring that the blades are sufiiciently strong to withstand the enormous centrifugal forces created by rotating them at high speed, particularly in the root portions thereof. While special metal alloys have been developed which are generally satisfactory in this environment, there is a distinct need for still tougher and more reliable blades and blade mounts. Whatever material such blades are made of, there is a continuing need for positive means by which such blades, which must be independently fabricated, can be rigidly effectively secured to a rotor and yet be capable of easy removal therefrom.

THE INVENTION AND ITS OBJECTS The invention seeks to resolve the problems heretofore experienced in fabricating compressor blades, and in effectively securing them to a rotor in easily removable fashion.

Objects of the invention include the provision of a forming die which will permit synthetic fiber filaments to be held in alignment in web form for impregnation with a bonding agent, with the filaments being aligned in the direction of the highest stresses when these occur in different planes during turbine operation.

Another object is to provide an anchoring device for such blades which will bring out the full strength of the filaments and which will at the same time be free from notches and sharp corners which deleteriously affect the performance of the blades in use.

An additional object is to provide a mounting for such blades in a rotor by which the blades are very firmly secured against displacement by centrifugal forces .and yet are easily removable for repair or replacement.

These and other objects of the invention will more clearly appear when reference is had to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view partly in section of a forming die assembly by which a synthetic fiber web is supported for integration with a bonding agent into a unitary compressor blade.

FIG. 2 is a plan view of the device of FIG. 1.

3,720,481 Patented Mar. 13, 1973 "ice DETAILED DESCRIPTION Referring to FIGS. 1 and 2, a synthetic filamentary material such as boron, which has been wound into a continuous web 10, with the filaments held a predetermined distance apart by coating with a bonding agent, is cut at 11 and placed in a fixture 12. The fixture is provided with a mandrel 13 journalled in bearing blocks 14 and a clamping device 15, which is tightened by a bolt 16 and adjusted by spring pressed means 17. The midpoint of the web is disposed around a split bushing 26 of special configuration which, in turn, is slipped over the mandrel 13, and the ends are clamped by

means

15 and 16. The web is placed in suitable tension and the clamp 15 twisted on its axis 18 to effect the desired pitch of the blade to be produced.

Die

blocks

19 and 20, having inner surfaces 21, machined to produce the desired fairing, are then brought together and secured by conventional means so that the twisted web is held securely in place and its contour defined by the die faces.

The assembly is then treated with a bonding agent as by immersing in a crucible of molten aluminum and permitting the aluminum to infiltrate in the spaces between the blocks. It is then removed and cooled and the blade thus formed taken from the fixture 12, the mandrel 13 removed and the blade properly trimmed.

The result is an integral blade with filament reinforcements aligned in the direction of highest strength not only in the blade portion, but in the root, since the re inforcing filaments extend circumferentially therearound and with the specially designed split bushing secured therein.

Referring to FIGS. 3, 4 and 5, a blade 20 is illustrated as comprising a blade portion 21 and a root portion 22. The root portion has a circular bore 23 in its base of a dimension determined by the diameter of the mandrel 13.

It is important to note that the split bushing 26 is split at 26a (FIG. '5), and has oppositely tapered axial openings 27 and28. The root portion 22, with the split bushing firmly embedded therein, is now inserted axially into a key hole slot 24 in the rotor 25 and assumes the position shown in FIG. 5.

Conical wedges

29 and 30, having a central bore, are then inserted in an opposite axial direction in the bushing 26 so that the exterior surfaces of the wedges meet the internal surfaces of the

bores

27 and 28. One of the wedges is threaded as at 31, while the other is smooth and is of slightly larger diameter than the bolt 3-2 which extends therethrough and is screwed into the threads of wedge 30.

It will be observed that provision has now been made for a solid connection of maximum strength between the rotor and the blade, not only by reason of the split bushing configuration, but also because the filaments act as reinforcing ribs which lie circumferentially of the blade root and circumscribe the bushing. Bolt 32 is simply torqued to expand the bushing. The expansion need be only .001" or .00 but is still effective to produce an exceedingly strong connection, which connection is adapted to be adjusted during turbine shut-down or to be removed or replaced where inspection and repairs become necessary.

Having thus described my invention, I claim:

1. A compressor blade assembly comprising a blade integrally formed of a web of synthetic filaments disposed along the lines of maximum blade stress and infiltrated with a bonding agent, said blade having faired portions and root portions, a rotor, a keyhole slot in said rotor, said root portion being disposed in said slot and having a cylindrical bore lengthwise thereof, a cylindrical split bushing secured in said bore, said bushing having axially located, 1

oppositely disposed cone-shaped openings therein, Wedges disposed in said cone-shaped openings, and means extending through one wedge and adjustably connected to the other to draw said wedges toward each other to securely fix said root in said slot.

2. The assembly according to claim 1 in which the synthetic filaments are composed of boron.

3. The assembly of claim 2 in which the bonding agent is aluminum.

References Cited UNITED STATES PATENTS 2,656,146 10/ 1953 Sollinger 416-220 X 2,859,936 11/1958 Warnken 416-230 X 2,868,439 1/1959 Hampshire et a1. 416-230 X 2,995,777 8/1961 Warnken 1836 3,057,767 10/1962 Kaplan 4l6230 UX 3,098,723 7/1963 Micks 416-241 X 3,600,103 8/1971 "Gray et a1 4l6--230 X 3,616,508 11/1971 Wallett 416230 X FOREIGN PATENTS 426,763 11/1947 Italy 4162l9 5 EVERETTE A. POWELL, JR., Primary Examiner U.S. Cl. X.R. 4l6230, 207