US2781962A - Blade fastening means - Google Patents

Description

Feb. 19, 1957 s. WILDER,-JR

BLADE FASTENING-MEANS Filed July 26, 1951 a z i J v w 2 attorneys nitd States BLADE FASTENING MEANS Stuart Wilder, J12, Indianapolis, Ind., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application July 26, 1951, Serial No. 238,756

3 Claims. (Cl. 230-134) This invention relates to blading of a type suitable for use in elastic fluid machines such as axial-flow compressors and the like, and, more particularly, to improved fastening means for securing blades in apparatus of this character.

The invention has for its objectives the provision of a simple and inexpensive fastening means which provides an efiicient positive lock tor securing a footed blade against movement in its mounting slot and which may be readily unlocked to permit blade removal and reinsertion.

The advantages attending the use of liooted blades have long been recognized and have resulted in their widespread application. However, as this type of blade can not depend for its retention on the frictional engagenient between the foot of the blade and the walls of the mating slot wherein it is mounted, there is presented, particularly in the case of blade carrying members used in gas turbine engines, the problem of preventing the blade from rattling and backing out of its slot due to the relatively high tangential and axial forces exerted on the blade. Various means for overcoming this problem have been proposed, but, as far as is known, none alfords the simplicity of construction and installation, the eflicacy of retention and the versatility of application of the present invention.

As applied to a rooted blade with an enlarged foot having a slide fit in a mating slot contained in a blade cam-yi-ng member, the invention features the use of a resilient fastening member having ext-ended outwardlydiverging terminal portions, the fastening member being detachably mounted in a groove extending transversely about the blade root so as to be positively locked thereon. A relieved or notched area intermediate the ends of the mating slot forms a transverse recess having abutting shoulders in the outer portion, preferably, of both of the side walls of the slot. The terminal portions of the fastening member are constrained to permit the blade and fastening member to be slidably inserted as a unit into the slot, the terminal portions being released when aligned with the recess in which they are received so as to bear against the abutting shoulders thereof, thereby positively locking the fastening member and, hence, the blade against movement in the slot.

The nature of the invention together with other objects, features, and advantages thereof will be apparent from the following detailed description and accompanying drawings in which:

Fig. l is a fragmentary axial view of a rooted blade fastened in a blade carrying member in accordance with the present invention, certain parts being in section;

Fig. 2 is a transverse sectional view of the structure of Fig. 1 taken substantially along the plane 22 thereof;

Fig. 3 is a sectional view of the structure of Fig. 1 taken along the plane 3-3 thereof; and

Fig. 4 illustrates a form of blade fastening member in accordance with the invention.

Referring to the drawings, the blade carrying member illustrated in the fragmentary axial sectional view of Fig. 1 may be, for example, a rotor wheel or a portion of a casing or stator of an axial flow compressor or turbine, the general construction of which is well known to those skilled in the art so as not to require description herein. The member 10 carries a ring of blades 12 spaced about the periphery of the rim 14 in respective ones of a plurality of undercut or dovetail blade mounting slots 16, only one of the blades and slots being shown in the drawings.

For purpose of illustration, the invention is shown ap-. plied to a blade 12 having a curved root 18. The root 18 extends substantially the length of the chord of the blade and has integrally formed on opposite sides thereof a pair of arcuate ribs 20, 21 (Fig. 2) which form an enlarged or bulbular blade foot 24 that is adapted to be slidably inserted in the mating slot 16, also of curved form as shown in Fig. 1. The shape of the slot 16 corresponds generally to that out the cross-section of the blade root as shown in Fig. 2 and viewed in plan l rom the surface of the rotor resembles a dumb-bell as shown in Fig. 3.

Because the blade root and slot are figures of revolution, the blade may be installed in the slot by rotating the blade about an axis 0 normal to the plane of Fig. 1 when the leading edge 26 of the blade foot 24 is inserted in the trailing edge 28 of the slot 16. The trailing edge 30 of the blade fiornrs an effective stop and engages the peripheral surface of the rotor rim 14 when the insertion is complete as shown in Figs. 1 and 3.

In accordance with the invention, the blade is prevented frcm backing out of its slot and from rattling therein by means of a fastening member which is posi;

tively locked to the blade and in the mating slot 16. The fastening member consists of a spring clip or wire snap ring 32 resembling a hairpin with flared or outwardly diverging terminal portions 34, 35 as illustrated in Fig. 4 and is detachably mounted in a grooved recess 38 intermediate the leading and trailing edges of the blade extending transversely around root portion 18 thereof as illustrated in Figs. 2 and 3, whereby the snap ring is positively locked in the grooved recess of the blade. The snap ring conforms generally to the shape of the cross section of the blade foot 24 and is preferably constructed of a resilient spring wire which may have a circular or other cross section.

In order to lock the fastening member and, therefore, the blade in the blade slot, notches 40 and 41 are provided in the surface of the rotor rim 14 as illustrated in Figs. 2 and 3 extending on both sides and intermediate the ends of the slot 16. The faces of the notches form bearing surfaces for the terminal portions 34, 35 of the snap ring. The terminal portions of the snap ring are constrained or bent inwardly towards the surfaces of the blade until the terminal portions 34 and 35 are flush with thesides of the blade, as shown by the broken lines X, X of Fig. 2 to permit the blade and snap ring mounted thereon to be inserted in the blade slot by a circular movernent as described above, the terminal portions being released or relieved from constraint so as to snap-back into substantially their original form and to be received in the transverse notches 4d, 41 when the blade is installed in position, thereby forming a positive lock for the snap ring and the blade. The elongated ends of the snap ring, which extend beyond the upper portion of the slot as shown by the broken lines Y, Y of Fig. 2 are then cut off near the surface of the slot. To release or unlock the blade, the terminal portions of the snap ring are gripped together on opposite sides of the blade and freed of the locking notches 4t), 41, whereby the blade and snap ring may be rotatably slid out of the slot.

It is thus seen that the invention affords a simple, efficient and positive lock for securing a footed blade 3- against movement in its mounting slot. In accordance with the invention, each blade may be individually removed or inserted without interference with other structures, disassembly of other parts or damage to the parts.

Although the invention has been described in connection with a footed blade having a curved root, the invention is not limited to such a blade but may 'be readily applied to various forms of blade roots in various types of blade carrying members, thus indicating the versatility of the invention, a feature not readily afforded by other forms of known blade fastening means.

I claim:

1. In combination, a footed blade, a blade carrying member containing a mating undercut slot having a relieved area in the sidewalls thereof intermediate its ends, said blade foot having a groove formed in the surface thereof and extending thereabout transverse to the longitudinal axis of the foot, and a releasable spring clip mounted in the groove in said blade foot, the foot of said blade being received in said mating slot in said blade carrying member with said spring clip mounted thereon, said clip having diverging terminal portions that project above the peripheral surface of said blade carrying memher and are received in the relieved area in the blade carrying member locking the blade and the blade carrying member together, the terminal portions of said clip being readily accessible and being movable into the groove in said blade foot to unlock the foot of the blade from the blade carrying member and allow separation of one from the other.

2. In combination, a footed blade having a curved foot, a rotor wheel containing a curved undercut mating slot having a transverse notch in the sidewalls of the slot intermediate its ends, said blade foot having a groove formed in the surface thereof and extending thereabout transverse to the longitudinal axis of the foot, and a snapring mounted in said transverse groove on said blade foot, said blade foot being received in said mating slot with said snap-ring mounted thereon, said snap-ring having diverging terminal portions which project above the peripheral surface of said blade carrying member and are received in said transverse notch in the sidewalls of the blade carrying member locking the foot of the blade and the blade carrying member together, the said termi' nal portions of the snap-ring being readily accessible and being movable into the groove in the blade foot to unlock the foot of the blade from the blade carrying member and allow separation of one from the other.

3. In combination, a supporting member formed with an undercut slot having a transverse notch in the sidewalls of the slot, 21 supported member including a foot formed with a groove in the surface thereof transverse to the longitudinal axis of the blade foot, and a clip mounted in said groove, said supported member being re ceived in the mating slot in said supporting member with said clip mounted on the foot thereof, said clip having terminal portions that project above the peripheral surface of said supporting member and are received in said notch in said supporting member locking the members together, the said terminal portions of the clip being readily accessible and being movable into the groove in the foot of the supported member to unlock the members and allow separation thereof.

References Cited in the file of this patent UNITED STATES PATENTS 539,015 Fontneau May 7, 1895 1,890,581 Kohler Dec. 13, 1932 2,434,935 Kroon Jan. 27, 1948 2,445,154 Reed July 13, 1948 FOREIGN PATENTS 976,790 France Nov. 1, 1950

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