US2925997A - Rotors for axial-flow fluid machines with pivoted blades and blade pivot retaining means - Google Patents

Description

Feb. 23, 1960 R. HART ET AL 2,925,997'

ROTORS FOR AXIAL-FLOW FLU MACHINES WITH PIVOTED RETAININ NS BLADES AND BLADE PI G MEA Filed Sept. 12, 1955 2 Sheets-Sheet l WMZ@ 2,925,997 1TH PIvoTED R. HART ET AL AXIAL-FI ID MACHINES W S AND VOT RETAINING ANS 2 Sheets-Sheet 2 .OW FLU BLADE PI Feb. 23, 1960 Ro'roRs F BL Filed sept. 12. 1955 United States atent AO Ro'roRs FOR AXIAL-ELow FLUID MACHINES WITH PIvoTED BLADES AND BLADE PIVOT RErAlNING MEANS Raym'ond Hart, Ockbrook, and Peter Rex Hodgkinson, Y Littleover, England, assignors to Rolls-Royce Limited,

Derby, England, a British company Application September 12, 1955, Serial No. 533,782

Claims priority, application Great Britain October 1, 1954 l 8 Claims. (Cl. 253-77) This invention relates to bladed rotors for axial-flow iluid machines and is concerned with bladed rotors of the kind in which blade elements are secured to the periphery of a disc bymeans of pivot pins which engage aligned holes in flanges onl the disc periphery and lugs forming part of the blade roots. Such a bladed rotor will be referred to hereinafter as a bladed rotor of the kind specified.

According to the present invention, a bladed rotor of the kind specified comprises means for retaining the pivot pins against disengagement from the holes in the flanges and in the lugs, which means comprises radially-extending plates mounted on and having interlocking engagement with the periphery of the disc and adapted to engage the ends of the pivot pins to prevent their disengagement from. the holes.

According to one preferred arrangement, the pivot pins are provided with reduced-diameter portions terminating in ilange-like heads and the plates are of arcuate form and are provided with a number of circumferentiallyspaced circumferentially-extending keyhole type slots disposed to co-operate with the heads of a number of the pivot pins to prevent their disengagement. In assembly, either the plates are positioned by engaging the slots over the flange-like heads of the pivot pins or the pins are inserted after the positioning of the plates by passing their heads through the keyhole slots; thereafter, in either case, the plates are displaced circumferentially to enable the smaller-dimensioned ends of the keyhole slots to engage with thereduced-diameter portions between the flangelike heads and the main portions of the pivot pins, and

the plates are also provided with parts which, during the circumferential movement of the plates into their pivot pin retaining positions, interlock with the disc periphery to retain the plates axially in position. Means is also provided to retain the plates circumferentially in position.

In another preferred arrangement, the pivot pins are provided with enlarged heads to prevent disengagement of the pivot pins from the disc periphery in one direction and the retaining plates are provided to bear against the heads of the pivot pins to prevent their disengagement in the opposite direction. In this construction also it is preferred that the retaining plates are provided with features which interlock with the disc periphery by a circumferential displacement to retain the plates axially in position and that means is also provided to hold the plates against circumferential `displacement after assembly.

In yet another arrangement, the pivot pins are plain cylindrical pins and retaining plates are provided on each side of the disc periphery to prevent disengagement of the pivot pins. In' this construction also it is preferredthat the plates be adapted to interlock with features on the disc periphery by a circumferential movement to retain then; axially against the disc periphery and that means be also provided to retain the retaining plates against circumferential displacement after assembly.

Some preferred embodiments of this invention will now be described with reference to the accompanying diagrammatic drawings, in which:

Figure 1 is an axial view of part of a rotor disc carrying a number of pivoted blades at its periphery,

Figure 2 is a section on the line 2-2 of Figure l,

Figure 3 is a view corresponding to Figure 1 of a second embodiment, Y

Figure 4 is a section on the line 4 4 of Figure 3, and

Figure 5 is a view corresponding to Figures 2 and 4 of yet another embodiment.

Referring to Figures 1 and 2, the rotor comprises a disc 10 provided with an axially-thickened periphery formed with a circumferential channel 11 so as to provide a pair of radially-extending axially-spaced flanges 1'2, 13. The rotor also comprises a row of blade elements each of which comprises an aerofoil portion 14, a platform portion 15 and a lug 16 extending from the side of the platform remote from the aerofoil portion 14.

When the blades are assembled to the disc 10 the lugs 16 extend into the channel 11 between the flanges 12 and 13 to which the blades are pivotally connected each by means ofa pivot pin 17 extending through aligned holes 12a, 13a and 16a in the flanges 12 and 13 and inthe correspond-ing lug 16. l

` It is desirable to prevent disengagement of the pivot pins 117 from the flanges 12 and 13 and lugs 16 and in this construction of the present invention the following retaining means is provided.

l Each pivot pin 17 is provided at one end with a reduced diameter portion 17a having at its outer end a flanged head 17b so that there is thereby formed near the end of each pivot pin a circumferential channel 17d.

A number of retaining plates 18 are `provided to interlock with features provided on the disc periphery.

diameter portions 17a and between the axially-facing sur-y faces 17y and 17z of the main portions 17x of the pivotA pins and the heads 17b of the pivot pins' which surfaces 517y and 17z -detine the side walls of the channels 17d surrounding the reduced diameter portions 17a.

If desired, the slot nearest one end of the retaining plate 18 may be a parallel-sided slot 19a which extends to one circumferential edge of the plate. i

The retaining plates 18 are retained axially against the llange '13 on the disc periphery by arranging that their outer edges 18a engage in an inwardly-facing circumferential groove 20x cut in an axially-projecting flange 20 at the'outer edge of the flange 13 and by forming the radially-inner edges of the plates 18 with lugs or edge portions 18b extending into engagement in circumferentially extending radially-outwardly-facing grooves 20y cut in circurnferentially-spaced axial projections 21 pro vided at the inner radius lof the flange 13. j

The retaining plates 18 are limited as totheir circurnferential movement in one sense by tongues 22 which project -radially inwards adjacent the lugs 18b and bear against the ends of the axial projections 21.

In assembly, the retaining plates 18 are placed in position, with the larger ends of the keyhole slots 19 aligned with the holes 13a in the flange 13, before attachment of the blades and then the blades are positioned and the pivot pins are inserted, their heads being passed through the larger ends of the keyhole slots 19. 'Ilhen the plates 18 are displaced circumferentiallyv to bring the smaller ends of the keyhole slots into engagement with the reduced-diameter portions 17a behind the flange-like heads 17b. Finally a locking piece 23 is fitted which prevents circumferential displacement of the locking plates in the opposite direction. The locking piece 23 is in the form of a plate having a radially-disposed open-ended keyhole slot 24 to engage one pivot pin. After the plates 18 have been circumferentially displaced as described above the locking plate 23 is positioned between the ends of a pair of the plates 18 and engages by its outer edge in the inwardly-facing circumferential groove 20x in the axially projecting flange 20 and by its inner edge in a circumferentially-extending, radially outwardly-facing groove a formed in a projection 25 corresponding to the outwardly facing grooves 20y in the projections 21. The locking plate 23 is also provided with a pair of lugs 26 which extend one on each side of the projection 2S and wl ich during positioning of the plate 23 extend axially outwardly from the plate 23 to allow limited radial freedom of the plate 23 between the bottoms of the grooves Ztx and 25a in the flange 20 and projection 25, and which when the plate 23 is in position are bent inwards towards the disc periphery to overlie a circumferential shoulder 27 to retain the outer edge of plate 23 in its groove 20x by preventing radially inward displacement ofthe plate 23. The groove 25a in the projection 25 is of such radial depth that with the lugs 26 bent axially outwards of the plate 23, the plate 23 can be displaced radially inwards to an amount sufficient to disengage its outer edge from the groove 20x in the axial flange 20.

It will be seen that in this construction the retaining plates 18, by engaging between the flange-like head 17b of the pivot pins and the main portions 17x thereof, prevent axial displacement of the pivot pins 17.

Referring now to Figures 3 and 4, there`is shown an arrangement in which the pivot pins 17 are provided with ange-like heads 17C of a larger diameter than the main portions 17x of the pivot pins whereby disengagement of the pivot pins 17 is prevented in one direction (to the right as viewed in Figure 4). The movement of the pins in this direction is limited by projections 20a on the disc 10.

The pivot pins 17 are retained against disengagement in the opposite direction by abutment of the axially-facing surfaces 17e of the heads 17e with retaining plates 28 which, as in the arrangement of Figures l and 2, co-operate by their outer edges 18a in an inwardly-facing groove 20x in an axial ange 20 at the outer edge of the ange 13. Also as before, the plates 28 are provided at their radially inner edges with radially-inwardly-projecting lugs or edge portions 28a to engage, by a circumferential movement of the plates, outwardly-facing grooves 20y in axial projections 21. In this construction the plates 28 are fitted after attachment of the blades 14 and are retained circumferentially by providing the last plate 28 to be inserted with radially-inwardly-projecting tongues 28b which abut circumferentially against abutments formed by the circumferentially-facing ends 21a of a pair of the projections 21, the one to prevent circumferential displacement in one direction and the other to prevent a circumferential displacement in the opposite direction. The tongues 28h during assembly project axially outwards from the plate 28, and, after circumferential displacement of all of the plates 28 simultaneously to engage the lugs 28a in the grooves 20y of projections 21, the tongues 28b are bent down axially to the position shown.

Referring now to Figure 5, there is shown yet another arrangement and in this arrangement the pivot pins are plain cylindrical pivot pins. The pivot pins 17 in this case are retained by abutment of their axially-facing end surfaces 17f with retaining plates 38, similar to those described with reference to Figures 3 and 4, on each side of the disc periphery, which retaining plates engage by their outer edges 38b in grooves 20y in axialprojections 20 at the outer ends of the flanges 12 Vand 13 and engage through lugs 38a in outwardly-facing grooves 20y in axial projections 21 from the inner ends of the anges 12 and 13.

The retaining plates are conveniently formed from resilient exible sheet metal to facilitate their assembly.

We claim:

l. A bladed rotor for an axial-flow uid machine having a disc formed with anges at its periphery and blade elements having lugs overlapping the flanges by means of which they are mounted on the disc, the flanges and lugs being formed with aligned holes, and pivot pins engaging with said holes, comprising means' for retaining the pivot pins against disengagement, which means comprises a plurality of part-annular plates mounted on the disc to -form together a substantially complete annulus around the disc, said plates engaging at least one axially-facing surface of the pivot pins to prevent axial disengagement of the pins from said holes in one sense at least, the disc having at a first radial distance from its axis a radially-inwardly-facing circumferential groove and having at a lesser radial distance from its axis a plurality of circumferentially-spaced axially-directed projections, each of which projections is provided with a radially-outwardly-facing groove, and each of said plates having a radially outer edge engaging said radially-inwardly facing groove and each of said plates having also circumferentially spaced edge portions spaced radially inwards from said outer edge and engaging the groove in one at least of said axially-directed projections, said inner edge portions of the plates being engaged with the outwardly facing grooves of the projections by circumferential movement of said plates, and means cooperating with the locking plates and disc locking the plates against circumferential movement.

2. A bladed rotor as claimed in claim l wherein the pivot pins are formed with reduced-diameter portions terminating in anged heads, and wherein the plates are of arcuate form and are provided with a number of circnmferentially-spaced circumferentially-extending keyhole-shape slots, the slots each having a reduced portion of less width than the dimension of the heads of the pivot pins, the reduced portions of the slots receiving the reduced-diameter portions of the pivot pins on circumferential movement of the plates, thereby to prevent the disengagement of the pins from the holes.

3. A bladed rotor as claimed in claim 2 wherein the means locking the plates circumferentially in position comprises a locking plate fitting between the ends of a pair of the arcuate plates and mounted on the disc, said locking plate being formed with a radially-extending slot having a reduced portion of less width than the dimension of the heads of the pivot pins, the reduced portion of the slot engaging the reduced-diameter portion of one of the pivot pins, and comprising interengaging parts on said locking plate and on the disc retaining the locking plate against axial and radial displacement relative to the disc.

4. A bladed rotor as claimed in claim 3 wherein said disc is also formed with an axially-projecting shoulder, the locking plate has a radially-outer edge which engages in said inwardly-facing -groove and a radially-inner edge which engages in said outwardly-facing groove, the locking plate has a radial dimension between said edges less than that between the bottoms of the groovesand wherein said locking plate is provided with lugs which are bent inwardly to radially overlie said shoulder to prevent radial displacement of the locking plate and disengagement from said grooves.

5. A bladed rotor as claimed in claim l wherein thc pivot pins are formed with enlarged heads abutting against one of said disc flanges thereby to prevent axial disengagement of the pivot pins from said holes in one direction, and wherein the plates engage the heads of the pivot pins to prevent the axial disengagement of the pins from said holes in the opposite direction.

6. A bladedrotor as claimed in `claim 5 wherein `the means locking the plates against circumferential movement comprises lugs on one at least of the plates engaging oppositely-facing circumferential abutments on the disc afforded by adjacent circumferentially-facing ends of a pair of said projections.

7. A bladed rotor as claimed in claim 1, wherein the pivot pins are plain cylindrical pins, and wherein a plurality of said plates are provided on each side of the disc periphery to engage the ends of the pins to prevent their disengagement.

8. A bladed rotor as claimed in claim 7 wherein the means to retain the plates against circumferential movement comprises a pair of oppositely-facing circumferential abutments on the disc and lugs on one at least of the plates engaging said oppositely-facing circumferential 'abutments on the disc aiorded by adjacent circumferentially-facing ends of a pair of said projections.v

References Cited in the le of this patent UNITED STATES PATENTS @2,537,739 Chilton Jan. 9, `1951 FOREIGN PATENTS 667,979 Great Britain Mar. 12, 1952 679,714 Great Britain Sept. 24, 1952 960,069 France Oct. 17, 1949

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