US2658718A - Manufacture and attachment of turbine and like blading - Google Patents

Description

Nov. 10, 1953 D. N. WALKER MANUFACTURE AND ATTACHMENT OF TURBINE AND LIKE BLADING Filed Dec. 12, 1945 $15? Mme/ iar Patented Nov. 10, 1953 i UNITED STATES PATENT OFFICE MANUFACTURE AND ATTACHMENT OF TURBINE AND LIKE BLADING Daniel Norman Walker, Manorcroft, Ashby Parva, near Rugby, England, assignor to Power Jets (Research & Development) Limited, London, England Application December 12, 1945, Serial No. 634,592

Claims priority, application Great Britain December 22, 1944 6 Claims. (01. 253-3915) 1 v 2 This invention relates to the manufacture of ripherally spaced axially disposed sheet metal blades for that kind of gas turbine having an Wall portions each of which is a generally radial axial flow bladed rotor assembly Whose blades are continuation of the blade wall base and has a made separately therefrom and re retained deformation in the peripheral direction produced thereon by fixing their roots at anchorages pro- 5 by pressing, stamping, or a like sheet metal workvided on the rotor, and to the manner of attaohing operation by which it is adapted to make ment of the blades in machines of that type. The blade-retaining engagement with a correspondinvention relates in particular to the use of holing formation afforded in a ganerally radial and low tubular blades of sheet metal, which exaxially disposed slotted anchorage formed in said pression is used herein and in the appended claims rotor, the blade roots so formed being held in to mean metal of such thin section as to be sussecure relationship with their anchorages by ceptible of local shaping by pressing, stamping, spacing means within said slots acting to prevent or like operations, Whether formed from flat sheet displacement of the blade-retaining formations or tube or otherwise. of said wall portions in the peripheral direction Hollow sheet metal blades, whether manufacwith the corresponding formation of its anchortured from tube or fabricated from flat sheet, age. have many attractive attributes, but the problem The root construction and anchorage proposed of their anchorage is a difficult one, particularly enables root loads to be properly balanced and in their application to gas turbine rotors in airprovides adequate stability; further to improve craft power plants where the need for light Weight stability, the two spaced walls may be suppleand cheapness of manufacture has to be reconmented by one or more further walls to form a oiled with severe operating conditions, in which threeor a four sided box construction. Morethe blading is exposed to elevated temperatures over, the blade rootmay have at least one wall and subjected to high centrifugal stress and mayoutside and axially spaced from the flank of the be to intermittent loads which in some cases may bladed element to form a radially extending air excite damaging vibrations. One object of the duct which is arranged to communicate with a invention, accordingly, is to provide a blade and passage through the blade to allow a flow of coolmounting therefor in which there is adequate dis ing air therethrough.

tribution of the loads imposed on the root and It will be appreciated that the expressions undesirably stressed formations are avoided. As axial direction andperipheral direction are well as fulfilling this requirement and affording used herein primarily to mean directions parallel a convenient and adequately strong means of atrespectively with the axis of rotation and the tachment between blades and a rotor wheel or plane of rotation of the turbine rotor. It is to disc the invention may be so applied as to afford be observed, however, that in general the anthe possibility of internal cooling by the passage chorages and formations emp oy in the arious of air or other fluid radially along the interior embodiments of the invention need not be strictly of the blades. Primarily however the invention in the axial or the peripheral direction, as the is concerned with providing a construction of case may be, but may be inclined thereto; the blade, and manner of attachment thereof to a expressions referred to, when used in relation to turbine rotor, which will be economical in manuthe direction of anchorages or formations, are facture and will reduce expensive or highly pretherefore to be read as including the inclined arcise operations to a large extent, to which end a gement.

use is made of a preferably unthickened continu- Other and more detailed features of the invenation of the sheet metal blade to form the blade tion will app a fr m h following d iptio root, and of forms of anchorage designed to acwith reference to the accompanying drawings,

commodate such a root without excessive manuwhich illustrate by way of example a number of facturing cost. Another advantage of the invenconstructional forms of the invention and in tion is in some instances to afford means whereby which:

one or more blades may be removed and replaced F u e 1 is a fragmentary Sectional S e vawith comparative ease and without disturbing tion of a turbine rotor blade mounting dythe remaind r, ing a simple form of blade root and anchorage in Broadly speaking the invention resides in prowhich the root has axially extending walls coviding an axial flow turbine rotor assembly havoperating with axially extending slots; ing hollow tubular sheet metal blades mounted Figure 2 is a section on line 2--2 of Figure 1;

thereon whose root construction comprises pe- Figure .3 is a perspective view illustrating a blade root of three-sided box-like construction; Figure 4 is a fragmentary section in the axial plane ofa rotorhavingapplied' thereto a blade as illustratedwin "Figure 3;

Figures 5 and 6 are perspective views illustrating methods of making a blade root of four sided;

box-like construction; a a V Figure 7 is a peripheral section;thro ugh the blade roots assembled as in Figure '6.

Referring now in morehdetaileto athe exam-s walls Gadapt'edto-lie in the slits 2. Each Wall *is deformed in i the peripheral direction about an axis extending in the axial direction Icy-a pressing or like operation to'provide corrugations or=ribs;as at I complementary with respect tothe grooves -formed-by the two halves of each bore 3. Adjacent 'bla'de roots are entered over successive teeth lyea'chrootwith its walls 6 in --adjacent*slits 2- and their respective ribs 1 en-- gaging the grooves ailorded by thebores 3at one side of the corresponding slits Locking means in the form of cylindrical or very slightly tapered *pins Bare then inserted ordriven into the practically circular-bores formed by the adjacent ribs lof the adjacent blade walls 6. Adjacent blades are thus locked both to the wheel and in respect of each othenthednserted pins 8 effectively resistingradial-load tending to 'pull the blades off, and the'multiplicity of the anchorage pointsso'provided eiiecting a distribution'of the loadover the-root wall. -Such distribution may be; and in practice preferably is further improved byincreasing the number of grooves.

It will'be noted that this construction lends'itself to cheapness' of manufacture intha'tthe formation of the "slits 2 and holes 3-involve simple cutting and drilling operationsonly; whilst -the'security of "the mounting is such that unthickened continuations of the'blade wall may be used-to form the root; thus avoiding the complications involved -in-providing-such a thickening. As illustratedin the figures, the pins may be made hollow, both with the- -object- -of allowing ooolant air or the V equivalent topass through'them and to permit 1 such slight distortionduring their insertion as *may be desirable to:accommod-ate elasticity or "manufacturing:error-ofthe blade roots. The 'remaining blades are of course entered and se- -cured in'the-same-way all around the wheel. In 1 the example illustrated; axial disturbance oftthe 1 blades is prevented by riveting overthe ends of the pins.

The modified construction illustrated in Figures 3 and 4 follows the same general principles as that illustrated in Figures 1 and 2, but the root has a third wall s so as to form a rectangu- -lar u shape inperipheral cross section, the wall 9 in addition to forming a tie which renders the whole structure more rigid, preventing-displacement of the blade in one axial direction. Since t m use," theaxial thrust tending to displace t e a 4 blade is unidirectional, the wall 9 will be sufilcient in itself to resist such displacement if rpositionedi atthe appropriate. side :of the rotor ll as aniadditional sategua'rmhowever, "since the grooves I must stop short of the wall 9 and thus ithe pins 8 cannot pass completely through the rotor for riveting, partial fourth walls l may be--provided;= by-tabs or extensions on at least "one-of the walls which are turned over after .positioningtheblade and inserting thepins 8, "and. if desired-are welded or otherwise secured ..-:in-;-.place against the rotor. In this construction 7 also (see particularly Figure 4) the third wall 9 is arranged to be spaced away from the flank of the rotor, as by the indentations H, so as to form a ductileading: from a radially inner locality into tna-interior of the blade for the passage of coolcylindr'ical grooves running axially. The blades have hollow-sheet metal bodies '5 made, for example, by processing lengths "of tubeyradially inward extensions of whichiorm spaced parallel ing air..v Asin the previously described embodimentjthe number of grooves may be more than .two.

= As "indicated in Figurefi the l'ast described "construction-=may be 'Iurther modified and ren- -dered'even more rig'id by the provision of airoot having a fourth-completewall i2. In'thisicase 'both-thewall nane the wall 9 arev formed by downward extensions 'ofuthe blade body 5 'separatefromthe wall's 6 to allow the grooves 17in the latter to extend 'fr'omedge to edge, the Walls '9 "and-1'2 having at itlieiredges corresponding r'ecesses' l 3 which iregistervwith the ends of the "grooves; One :or bOthL'Of liheWaHS 9, [2 may be ieftiirrthefidtted po'sitionzshovm until the blade has been applied to .ithemotor, and then turned down, being then held in place'by inserting locking-pins-8: asabeforeiaandsriveting over the heads, and if desired; by welding 'to the edges of the walls' 6.. An airapassage is'again provided for example by a pressed rib 'l ta as shown, or by indentations:suchiasare shown in Figures '3 and 4. As'an alternativeX'see'Figure 6) to the construc- --tion illustrated. inFigure- :5, the sides 6 and 9 :maybeoffinteg-ral U shape asin Figure 3, with ;the.fourth -wal-l l2 formed by a grooved or corrugatedextension"ofoneaof' thewalls 6 which is 'bentinto position about a radialline after insertring the locking pins-:8; :the rotor having pe- -.riphera=llyv-extending re'cesses- 7a to receive the corrugations :of the *wall 12. When a corrugated :sheetis bent about a line transve'rse tothe cor- -=.ruga=tionsr it will: be -found that the corrugations flatten outs at and adjacent to the bend; the vertex tending to become a A straight line. The

right-handside of Figure 6 shows an extension 1 2 of awall .6; with; theicorrugations 1- extending into-it, before bending. When. the extension 12 is :bent toilieqagainstithe face ofthe rotor and so:form acfourth: wall tot-he bladeroot the corrugationswbecome turneddromthe "axial into the :peripheral direction and are 1 received by the -re cesses lai-nzthe rotor. Theflattening out of the -corrug-ations hat and'adjacentto-the=vertex of -the angle between the extension 12 and-the Wall 6 involves the enclosure of ithe end .of'the locking-pinfi. Thefinishediformation is that of the middle blade'inthe perspectiveview of Figure 6,

and the same aformation 1 iswshown in peripheral --sectiontin:the ri'ghtehand zside ofiFigure '7, the

section being. taken conrthe -center' line ofthe corrugations. The end wall 9 in this case also ;maybe formed to provide an air duct, as by the methods of Figures 4 or 5 V If it-be-desired 'to improve the distribution of loads in the anchoragejt'he rimofthe wheel may 1 be indentedbetween-the' anchorages, as at It in 5 1 6 ;"S aSiOfiifO'I'd appreciable resilience and therefore to enable radially spaced ribs and grooves the better to share the main loads, whilst incidentally aiTording the possibility of substantial frictional gripping between the fiat surfaces of the slots and walls. The indentation may also be used to afiord an inlet for cooling air by carrying it lower than the skirt of the blade as seen in Figure 1.

It is of course not necessary in any of the constructions illustrated in Figures '1 to 7 that the slots in the rotor rim should be strictly axial since they may lie at an inclination, the walls of the blades where necessary being correspondingly distorted from a rectangular arrangement to that of a parallelogram.

It would be apparent from a consideration of the foregoing that various combinations of the devices mentioned can be utilised and are Within the scope of the invention.

It will be appreciated that the various constructions of root mountings described in the foregoing, by virtue of the distribution of the load over substantially the whole of the root area, and its balancing through the generally parallel symmetrically disposed root walls, ofier favourable conditions for sustaining severe stresses.

I claim:

1. An axial fiow gas turbine rotor assembly comprising a rotor wheel having around its periphery a plurality of axially extending slits each opening out, below the periphery, into an axially extending blade anchorage hole, a plurality of hollow tubular sheet-metal blades disposed around the periphery of said wheel, two peripherally spaced and separately anchored root portions on each said blade, one being a generally radially inward continuation of one of the axially extending sheet metal walls of the blade fitting in one of said slits and passing therethrough into a blade anchorage hole wherein it is bulged out to fit the hole, the other of said root portions being a similar continuation of the opposite wall of the blade likewise disposed in another one of the said slits and holes, in combination with a blade-retaining peg extending through each said anchorage hole and engaging said bulged blade-root portion.

2. A turbine rotor as set forth in claim 1 wherein the said pegs are tubular rivets each passing through one of said blade anchorage holes and secured to the sheet metal forming one of said blade root portions.

3. A turbine rotor as set forth in claim 1 wherein said Wheel has a rim made up of axially extending radial teeth alternating with undulations, each said slit being formed in one of said teeth.

4. A turbine rotor as set forth in claim 1 wherein each said blade has at least a third root portion which is a wall also continuing radially inward from the blade and joining the other two root portions, said third wall lying beside the flank of said rotor wheel and having a spacing member engaging said flank and separating said third wall from said fiank to leave open a passage into the interior of said hollow blade.

5. An axial flow gas turbine rotor assembly comprising a rotor wheel having around its periphery a plurality of axially extending slits each opening out, below the periphery, into an axially extending blade anchorage hole, a plurality of hollow tubular sheet-metal blades disposed around the periphery of said wheel, two peripherally spaced root portions on each said blade, anchored separately from each other, one being a generally radially inward continuation of one of the axially extending sheet metal Walls of the .blade abutting against a like root port-ion of one neighbouring blade, the other of said root portions being a similar continuation of the opposite wall of the blade abutting similarly against the other neighbouring blade root, each pair of said abutting blade root portions fitting in a separate one of said slits and passing therethrough into a blade anchorage hole, wherein they are bulged apart to fit said hole, in combination with a blade-retaining peg extending through each said anchorage hole and fitting between said bulged-apart blade-root portions.

6. An axial flow gas turbine rotor assembly comprising a rotor wheel pierced in the axial direction by a plurality of keyhole slots extending inwards from its periphery, a plurality of hollow tubular sheet-metal blades disposed around the periphery of said wheel, two peripherally spaced root portions on each said blade, anchored separately from each other, one being a generally radially inward continuation of one of the axially extending sheet metal walls of the blade abutting against a like root portion of one neighbouring blade, the other of said root portions being a similar continuation of the opposite wall of the blade abutting similarly against the other neighbouring blade root, each pair of said abutting blade-root portions fitting in a separate one of said keyhole slots, the walls being spread apart to conform to the shape of the cylindrical part of the keyhole slot and leave a central opening, in combination with a bladeretaining peg extending through each said central openings in said keyhole slots.

DANIEL NORMAN WALKER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 754,984 Fagerstrom Mar. 22, 1904 849,992 Frikart et al Apr. 9, 1907 927,515 Ehrhart July 13, 1909 1,014,350 Wales et a1 Jan. 9, 1912 1,387,304 Parsons et a1 Aug. 9, 1921 1,534,415 Schmidt Apr. 21, 1925 1,601,402 Lorenzen Sept. 28, 1926 1,603,966 Lorenzen Oct. 19, 1926 1,967,962 Metten July 24, 1934 2,220,420 Meyer Nov. 5, 1940 2,236,426 Faber Mar. 25, 1941 2,440,069 Bloomberg Apr. 20, 1948 FOREIGN PATENTS Number Country Date 6,640 Great Britain of 1907 15,893 Great Britain of 1908 64,805 Sweden Mar. 20, 1928 550,328 Germany May 11, 1932

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