US2998959A

US2998959A - Bladed rotor of axial-flow fluid machine with means to retain blades in position on rotor

Info

Publication number: US2998959A
Application number: US608458A
Authority: US
Inventors: Haworth Lionel; Petrie James Alexander; Moss Frederick
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1955-09-29
Filing date: 1956-09-07
Publication date: 1961-09-05
Anticipated expiration: 1978-09-05
Also published as: GB802476A; FR1158244A

Description

Sept. 5, 1961 L. HAWO H ET AL 2,998,959

BLADED ROTOR OF AXIAL- w FLUID MACHINE WITH MEANS T0 RETAIN BLADES IN POSITION ON ROTOR Filed Sept. 7, 1956 a Sheets-Sheet 1 Sept. 5, 1961 L. HAWORTH ET AL 2,998,959

BLADED ROTOR OF AXIAL-F FLUID MA ME! WITH MEANS TO RETAIN BLADES POSITION ROTOR Filed Sept. 7, 1956 3 Sheets-Sheet 2 Sept. 5, 1961 L. HAWORTH ETAL 2,998,959

BLADED ROTOR 0F AXIAL-FLOW FLUID MACHINE WITH ME BLADES IN POSITION ON ROTOR 5 Sheets-Sheet 5 6ANS TO RETAIN Filed Sept. 7, 195

United States Patent 2,998,959 BLADED ROTOR 0F AXIAL-FLOW FLUID MA- CHINE WITH MEANS TO RETAIN BLADES IN POSITION 0N ROTOR Lionel Haworth and James Alexander Petrie, Littleover, and Frederick Moss, Derby, England, assignors to Rolls-Royce Limited, Derby, England, a British com- Filed Sept. 7, 1956, Ser. No. 608,458 Claims priority, application Great Britain Sept. 29, 1955 7 Claims. (Cl. 25377) This invention relates to rotors of axial-flow fluid machines, such, for instance, as axial-flow compressors and turbines, especially those of gas-turbine engines.

Such a rotor often comprises a disc carrying a ring of rotor blades at its periphery, the blades having shouldered root attachment portions which engage in correspondi-ngly'shaped generally-axial slots in the rim of the disc to retain the blades radially in position. Such a rotor will be referred to as a rotor of the type described.

This invention has for an object to provide a simple construction of means to prevent inadvertent disengagement of the blades from the disc of a rotor of the type described.

According to this invention, in a rotor of the type described, the disc is provided on an axially-facing surface of its rim with annular radially-inwardly-facing channel means coaxially with the rotor, the blade root attachment portions have radially-inwardly-facing channels which together form a substantially continuous annular channel coaxial with the rotor and of greater radius than the annular channel means on the rim, and there is provided means to retain the blades in position on the rim comprising an annular plate adapted to be resiliently contractable in diameter by provision of a gap at one side, said annular plate overlying axially-facing surfaces of the rim and attachment portions and engaging in the uncontracted condition by an edge in the channels in the attachment portions and by an annular flange thereon radially inwards of said edge in the annular channel means on the rim, thereby to be positioned relative to the disc and blade root attachment portions and to retain the blade root attachment portions against displacement in their slots.

Preferably, there is also provided means to prevent undesired disengagement of the annular plate from the channels in the rim and in the blades. In one preferred construction, this means comprises circumferentiallyspaced radially-inwardly-extending lugs on the annular plate and correspondingly-spaced axial projections on the rim providing radial abutments for the lugs to prevent contraction of the annular plate, and a block extending circumferentially between a pair of the lugs and their associated projections and secured to the annular plate thereby to prevent circumferential displacement of the annular plate; the block is conveniently positioned between lugs on the annular plate at each side of the gap therein and is secured to the annular plate by a locking pin passing through bores in the block and adjacent lugs. In another preferred construction, the means comprises circumferentially-spaced axial projections on the disc and conespondingly-spaced radially-inwardly-projecting lugs on the plate which are cut back opposite the projections to leave recesses which are occupied by filler pieces, the latter having tabs which are bent up on each side of the lugs to retain them in the recesses, and diametrically opposite the gap in the plate a lug on the plate engaging between a pair of circumferentially-spaced projections on the disc.

- When the blade root attachment portions are of the kind providing between them passages through which a fluid could travel axially of the rotor, the annular plate may also be employed to seal off the ends of the passages by lying fiat against the end surfaces of the root attachment portions and the adjacent surface of the rim.

Two rotor constructions incorporating the invention will now be described, the description referring to the accompanying drawings in which:

FIGURE 1 is an axial section through one construction of rotor,

FIGURE 2 is an enlarged view in the direction of arrow 2 in FIGURE 1,

FIGURE 3 is a view to a larger scale of pant of FIG- URE 2,

FIGURE 4 is a section on the line IV--IV of FIG- URE 3,

FIGURES 5 and 6 are axial views of two portions of the second construction of rotor, the portion shown in FIG- URE 6 being located 180 from the portion shown in FIGURE 5, and

FIGURE 7 is a section on the line VII-VII of FIG- URE 5 but drawn to a larger scale.

Referring to FIGURES 1 to 4, the rotor comprises a rotor disc 10 having rim portion 11 whereon a ring of blades 12 are mounted.

Each blade 12 has a root attachment portion comprising a platform 13 adjacent the operative part of the blade, 9. shouldered part 14, commonly known as a fir-tree root, to engage a correspondingly-shaped generally-axial slot 15 in the disc rim 11, and a stern portion 16 which is circumferentially narrower than the platform 13 and the shouldered part 14 so that axial passages 17 are left be: tween the stem portions 16. The part 14 of the root attachment portion has radially outwardly facing shoulders 14a and the slot 15 has cooperating radially inwardly facing shoulders 15a, these shoulders interengaging in abutment radially against one another to retain the blade radially in position.

The blades are provided with parts 18 in the form of tangs which abut the upstream axially-facing surface of the rim 11 of the disc to prevent disengagement.

of the blades in one sense (to the right as seen in FIG- URE 1).

In order to retain the blades 12 against disengagement Each platform 13 is formed along one edge with an:

axial extension 19 which is undercut with a radiallyduwardly-facing groove 20. The grooves 20 together afford a substantially continuous groove coaxial with the rotor.

The rim 11 is formed on its axially-facing surface 1-1b on the same side of the rim as the grooves 20 and at a radius less than that of the slots 15, with a continuous radially-inwardly-projecting flange 24 which forms with the rim 11 a radially-inwardly-facing channel 21, and radially inwards from the channel 21 the disc 10 is provided with a series of circumferentially spaced axial pro,- jections 22 of which two of said projections are closely adjacent projections 23. The parts of the rim 11 which separate the blade slots 15 are provided, on the same side of the rim as the groove 20, axial projections 11a having in this instance an axial depth of .005" to .010".

A flat annular plate 25 is mounted on the rotor'to co-operate with the grooves 20, channel 21 and

projections

22, 23. The plate 25 is split radially to provide a gap 26 bounded or defined by a pair of spaced radial1y-' extending edges 26b, and is resilient so that it can be contracted in diameter, and to facilitate this operation the lugs 32 can be gripped by an appropriate tool.

The outer edge or the first edge of the plate 25 is blade platforms 13. v

The radially-inner part 29 of the plate 25 is axiallythickened and is formed with a radially-outwardly-dirested flange 30 which is of such diameter that, when the plate is uncontracted, the flange 30 occupies the channel 21.

The plate is also provided with radially-

inwardlyprojecting lugs

31, 32 corresponding in position and num her to the

projections

22, 23, and the lugs and projections when radially aligned co-operate in abutment to prevent contraction of the plate 25. It is therefore apparent that the

projections

22, 23 on the disc and the

lugs

31, 32 on the plate 25 constitute radial abutment means to prevent undesirable contraction and disengagement of the plate from the disc.

To assemble the plate to the disc, the plate is contracted to reduce the diameters of the bead 28 and flange 30 sufliciently to pass axially inside the extensions 19 and also the flange 24

bounding channels

20 and 21 respectively, and the plate is offered up to the disc with the gap 26, which is closed by the contraction, in the position indicated at Ben in FIGURE 2 and thus'with the

lugs

31, 32 in the positions shown at 31a, 32a and offset from the

projections

22, 23. The plate is now released from contraction so permitting the bead 28 to enter the groove formed by grooves 20 and the flange 30 to enter channel 21. The projections 11a on the rim 11 serve to spring the beaded edge 23 into good sealing contact with the axial Wall 2011 of. the groove 20 on each blade. The plate 25 is now rotated to the full line position with the

lugs

31, 32 and

projections

22, 23 radially aligned.

To prevent rotation of the plate 25, a block 34 is provided to extend axially and radially between the lugs 32 and projections 23, and the block 34 is secured to the plate 25 by having a flange, similar to flange 30, which engages in the channel 21 in the disc and by means of a wire pin 35 which passes through holes in the lugs 32 and the block 34', and has its ends bent over to prevent its detachment.

It will be noticed that for the purpose of maintaining the sealing of the passages 17 between the stems 16, the gap 26 in the plate 25 is arranged to extend along the end surface of one of the stems 16.

Referring now to FIGURES 5 to 7, in which the same reference numerals are employed as'in FIGURES 1 to 4, to denote corresponding parts, there is illustrated a construction in which the plate 25 can be presented to the disc in the angular position it is to occupy. Inlthis construction, the plate is provided adjacent the gap 26 with a pair of lugs 132 which are perforated at 132a to receive the contracting tool, and also around its inner edge with a series of circumferentially-spaced radially-inweirdly-extending lugs 131 the spacing of which is the same as that of the projections 22 on the disc. The lugs 131 are cut back axially to form recesses 131a in FIGURE 7 above the projections 22 to permit the lugs 131 on the plate to be passed over the projections when the plate is contracted in diameter for assembly. Also at a position diametrically opposite the gap 26, the plate 25 is provided a further radial lug 133 and the disc has at this position a pair of circumferentially-spaced projections 123 spaced by the width of the lug 133. The lug 133 and projections 123 prevent-rotation of the plate in operation, and facilitate positioning of the plate in assembly.

To assemble the plate to thedisc, the plate 25 is contracted in diameter and is presented axially to the disc in the appropriate angular position to engage the lug 133 between the projections 123 and with the lugs 131 angularly in line with the projections'22. The plate is now allowed to expand so that its outer edge 28, which is preferably beaded as in the construction of FIGURES 1 to 4, engages in the grooves in the extensions 19 of the platforms 13, its flange 30 being sprung into good sealing engagement with the walls of the channel 21 by the annular land 111a. In order to prevent accidental removal of the plate by contraction, filler pieces-134 are 4 inserted in the recesses between the projections 22 and the cut-back parts 131a of the lugs 131, and thin tabs 134a on the filler pieces are bent up to lie on each side of the lugs 131 to retain the filler pieces in position.

It will be appreciated that the combined locking and sealing plate of these constructions is simple in form and readily assembled and removed.

We claim:

1. A rotor of an axial-flow fluid machine, the rotor comprising a disc having a rim with axially-facing surfaces, a plurality of blades, each blade having a root attachment portion provided with radially-facing shoulders, a plurality of slots extending in said rim between i said axially-facing surfaces, each slot having radially facing shoulders complementary to the shoulders on the root attachment portions, said shouldered root attachment portions of said blades being engaged in said slots with radially-facing shoulders of the blades and slots interengaging to retain the blades radially in position, said rim having adjacent one of said axially-facing surfaces an annular radially-inwardly-facing channel coaxial with the 1 rotor, said shouldered root attachment portions having adjacent said one of the axially-facing surfaces radiallyinwardly-facing grooves which having a circumferential extent together to forma substantially continuous annular groove coaxial with the rotor and of greater radius than said annular radially-inwardly-facing channel, means to retain the blades in position on the rim comprising an annular plate of resilient material overlying said one of the axially-facing surfaces of the rim and the root attachment portions of the blades, said plate having a first edge engaging the grooves in the root attachment portions and also having thereon at a substantially smaller radius than said edge an annular flange engaging the annular radially-inwardly-facing channel on the rim, thereby to be positioned relative to the disc and root attachment portions and to retain the root attachment portions against axial displacement in their slots, said plate being split radially at a single' angular position to form a pair of spaced radially-extending edges of the plate between which is a gap permitting contraction in diameter of the plate by closing the gap for engaging and disengaging the said first edge in the grooves and the flange in the channel, and radial abutment means provided between said annular plate and the rim and operative to prevent undesirable contraction and disengagement of the annular plate.

2. A rotor as claimed in claim 1, wherein said radial abutment means comprises circumferentially-spaced radially-inWardly-extending lugs on the annular plate, which lugs are cut back axially on their radially-inner ends to define recesses with the rim of the disc, correspondinglyspaced axial projections on the rim of the disc at a radius less than said lugs and radially aligned with the recesses, and filler pieces in said recesses extending radially between the cut back ends of said lugs and said axial projections, said filler pieces having tabs at their ends which are bent up on each side of the lugs to retain them in the recesses; and comprising also means holding the annular plate against circumferential displacement comprising a lug on the plate at a position diametrically opposite the gap in the plate and a pair of circumferentially-spaccd projections on the disc, said lug on the plate engaging between said circumferentially-spaced projections.

3. A rotor as claimed in claim 1, wherein each of the blade root attachment portions has a part engaging the rim and limiting movement of the blades relative to the rim in an axial direction towards said one of the axiallyfacing surfaces, and wherein an annular land is formed coaxially with the rotor on said one of the axially-facing surfaces, and engages said annular plate to urge the plate into sealing engagement with the sides of said grooves on the blade root attachment portions.

4. A rotor of an axial-flow fluid machine, the rotor comprising a disc having a rim with axially-facing surfaces, a plurality of blades, each blade having a root aasaees attachment portion provided with radially-facing shoulders, a plurality of slots extending in said rim between said axially-facing surfaces, each slot having radially facing shoulders complementary to the shoulders on the root attachment portions, said shouldered root attachment portions of said blades being engaged in said slots to retain the blades radially in position, said rim having adjacent one of said axially-facing surfaces an annular radially-inWardly-facing channel coaxial with the rotor, said shouldered root attachment portions having adjacent said one of the axially-facing surfaces radially-inwardlyfacing grooves which together form a substantially continuous annular groove coaxial with the rotor and of greater radius than said annular radially-inwardly-facing channel, means to retain the blades in position on the rim comprising an annular plate of resilient material overlying said one of the axially-facing surfaces of the rim and the root attachment portions of the blades, said plate having a first edge engaging the grooves in the root attachment portions and also having thereon at a substantially smaller radius than said edge an annular flange engaging the annular radially-inwardly-facing channel on the rim, there-.

by to be positioned relative to the disc and root attachment portions and to retain the root attachment portions against displacement in their slots, said plate being split radially to form a pair of spaced radially-extending edges of the plate between which is a gap permitting contraction in diameter of the plate by closing the gap for engaging and disengaging the edge in the grooves and the flange in the channel, and disengagement-preventing means comprising circumferentially-spaced radially-inwardly-extending lugs on the annular plate and correspondingly-spaced axial projections on the rim providing radial abutments co-operating with the lugs to prevent undesirable contraction and disengagement of the annular plate.

5. A rotor as claimed in claim 4wherein disengagement-preventing means also comprise a block extending circumferentially between a pair of the lugs and their associated axial projections on the rim and secured to the annular plate thereby to prevent circumferential displacement of the annular plate.

6. A rotor as claimed in claim 5, wherein the said pair of the lugs are provided on the annular plate one at each side of the gap therein and there is provided a locking pin passing through bores in the block and said pair of lugs and securing them together.

7. A rotor as claimed in claim 4, wherein each of the blade root attachment portions has a part engaging the rim and limiting movement of the blades relative to the rim in an axial direction towards said one of the axiallyfacing surfaces, and wherein a substantially continuous annular land is formed coaxially with the rotor on said one of the axially-facing surfaces, and engages said annular plate to urge the plate into sealing engagement with the side walls of said groove on the blade root attachment portions.

References Cited in the file of this patent UNITED STATES PATENTS 2,755,062 Hill July 17, 1956 2,755,063 Wilkinson July 17, 1956 FOREIGN PATENTS 161,997 Australia Mar. 17, 1955 699,582 Great Britain Nov. 11, 1953