US2660413A

US2660413A - Locking arrangement for blading of axial-flow turbines and compressors

Info

Publication number: US2660413A
Application number: US208282A
Authority: US
Inventors: Haworth Lionel; Petrie James Alexander
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1950-02-03
Filing date: 1951-01-29
Publication date: 1953-11-24
Anticipated expiration: 1970-11-24
Also published as: CH289174A; FR1037572A; BE501031A; GB677021A

Description

Nov. 24, 1953 L. HAWORTH ETAL 2,660,413

. LOCKING ARRANGEMENT FOR BLADING OF AXIAL-FLOW TURBINES AND COMPRESSORS File d Jan. 29, 1951 3 Sheets-Sheet 3 52 a 4 1 an I I a MVEhra/(S 51 50 &

LIONEL HAWORTH JAMES A- PETRI Patented Nov. 24, 1953 LOCKING ARRANGEMENT FOR BLADING OF AXIAL-FLOW TURBINES AND COM- PRES SORS Lionel Haworth and James Alexander Petrie, Littieover, England, assignors to Rolls-Royce Limited, Derby, England, a British company Application January 29, 1951, Serial No. 208,282

Claims priority, application Great Britain February 3, 1950 Claims. 1

This invention provides an improved locking arrangement for blading of axial-flow turbines and compressors. It is concerned with turbine or compressor rotor assemblies of the kind (hereinafter referred to as the kind described) in which the blades are retained in position on the periphery of a rotor disc by means of co-operating features on the blades and disc, which features extend circumferentially of the peripheral portion of the disc and permit the blades to be engaged in the disc by sliding in a generally axial sense with respect to the rotor disc axis.

Assemblies of the kind described include those in which the blades are provided with root attachments of the fir-tree or bulb-root type; in certain cases with root attachments of these types, the mean centre lines of the co-operating formations in the periphery of the disc may, although extending in the generally axial sense, be skewed relative to the axis of the disc, so that the assembly of the blades is effected along these skewed lines.

It will be appreciated that in turbine and compressor rotor assemblies of the kind indicated it is necessary to make provision to restrain the blades against sliding in the disc after assembly, and hitherto it has been common practice to provide a tang formation on the apex portion of the root attachment of the blade, i. e. that end of the root attachment remote from the blade profile, which tang formation is bent over when the blade is mounted in the disc and provides an axial abutment restraining the blade from leaving the disc by sliding in the generally axial sense. In another known arrangement, it has been the practice after assembly to peen the root of the blade and the disc in the region of the root fixing. Both these known arrangements sufier from the disadvantage that on dismantling of the turbine or compressor rotor assembly by removing the blades from the rotor disc, the root attachments of the blades are necessarily damaged, and generally in the case of high performance engines the blading at least cannot be used again.

It is an object of the present invention to provide a simple arrangement for the locking blades in position in turbine or compressor assemblies of the kind described, which permits assembly and dismantling of the blades without their be ing damaged, so enabling them to be re-used after dismantling.

According to the present invention there is provided a turbine or compressor assembly wherein the rotor disc and a blade element carried thereon are provided with adjacent axial projections each having a recess formed therein, which recesses are positioned to come opposite one another when the blade element is properly in position in the disc, and wherein there is provided a locking member which is engaged in both recesses to be placed in shear by restraining disengaging movement of the blade element from the disc.

In one preferred arrangement, the axial projection on a blade element is radially outside the projection on the disc, the recess in the projection on the blade element faces inwardly, the recess in the projection on the disc faces outwardly and the recesses together form a circumierentially-extending tunnel to receive the locking memben, Conveniently the locking member has a substantially rectangular section and each recess has a substantially triangular section, the recesses together forming a tunnel of substantially rectangular section to receive the locking member. Moreover in the preferred arrangement, the projection on the disc is an axial flange and the flange has formed therein an outwardly facing continuous groove to afford a recess to co-operate with the inwardly facing recesses on the projections of a plurality of blade elements.

The locking member for such an arrangement may comprise a thick central portion which is partly received in the recess in the projection of the associated blade element and is partly received in the recess in the projection on the disc, and end portions of reduced thickness permitting them to be bent over to retain the locking member in the recesses after assembly.

The projections on the blade elements may also be formed to afford abutments to limit slid- 1ing of the blade elements in the assembly direcion.

An embodiment of the invention will now be described as applied in a gas-turbine, the descrip tion referring to the accompanying drawings in which:

Figure l is an axial section through the gas turbine,

Figure 2 is a substantially enlarged view of the root attachment portions of blades forming part of the gas turbine rotor,

Figure 3 is a View (to the same scale as Figure 2 and partly in axial section) of the root attachment portion of a blade,

Figure 4 is a greatly enlarged section through means including a locking member for retaining a blade against detachment from the rotor,

Figures 5 and 6 illustrate a convenient method of manufacturing one form of the locking member.

Figures 7, 8 and 9 are a side elevation, an end elevation and a plan view respectively to an enlarged scale of a locking member as produced by the method illustrated in Figures and 6 and prior to use, and

Figure 10 is a perspective view of a locking member such as is illustrated in Figures 7, 8 and 9, as it would appear if removed from the rotor without being damaged.

Referring now to Figure 1, there is illustrated a form of gas-turbine comprising a pair of rotor discs Illa, Hib which carry at their peripheries rotor blades I2. The turbine also comprises stationary structure including a casing 3, a first nozzle guide vane assembly I i, a second nozzle guide vane assembly i5, and inner stationary structure 18, ll. These parts may be of any convenient construction.

The rotor blades 42 are illustrated as being of the kind having each in one piece therewith an outer shroud 12a and at its radially inner end a combined inner shroud and root attachment portion I21), the details of which will be seen from Figures 2 to 4 to which reference will now be made.

Each portion [22) comprises an inner shroud forming part 28 of the root and connected by a stem 21 to a root attachment part 22, illustrated as a root attachment of the fir tree type.

The root attachments 22 are engaged in correspondingly shaped channels 23 broached in the periphery of the rotor disc iii, and in this particular embodiment, the fir-tree root attachments 22 and their channels 23 are skewed with respect to the axis of the turbine rotor Iii.

As is usual the blades I2 are mounted on the disc periphery by sliding the fir-tree root attachment 22 into the co-operating channel 23.

The blades I2 are retained against disengagement from the disc :9 in a radial direction by the co-operating shoulders of the fir-tree formations.

This invention provides means to retain the blades against detachment from their channels by sliding of the root attachments 22 in the channels.

This means comprises in this embodiment a projection M on each blade formed on the upstream-facing surface of the root attachment part 22 at its apex. The projection 2c is hooked to afford a radially-inwardly-extending portion having an axially-directed abutment surface 25 which bears against the axially-directed surface of the disc i0 adjacent the bottom of the channel 23. This abutment surface 25 limits the extent to which a blade can slide relatively to its channel 23 in one direction, in this case from the high-pressure to the low pressure side of the disc [0.

The projection 23 is also undercut, Figure 4, to afford a recess 26 of roughly triangular section extending circumferentially across the projection 24 and facing inwardly towards the rotor axis.

The disc ii) is provided with an axially-extending flange 21 lying slightly radially inwards of the bottoms of the channels 23 and of the projections 24, and this flange 21 has machined in it a continuous, radially-outwardly-facing groove 28 of substantially triangular section.

The groove 28 lies opposite the recesses 25 in the projections 24 when the surfaces 25 abut the disc l0, and the groove 28 and recesses 26 oooperate to aiford a series of substantially rectangular tunnels, one for each blade.

Each tunnel receives a rectangular wire looking member 30 which acts to restrain movement of the blade in a direction to detach the blade l2 from the disc it, that is in this case in a direction from the low pressure side of the disc towards the high pressure side.

The locking members 30 are conveniently formed with tabs 3|, 32 of reduced strength at each end, which tabs are bent upwardly as shown in Figures 2, 3 and 10, one on each side of the projection 24 to retain the locking member in position in the tunnel. Conveniently, one tab 3! is bent up before the locking member 39 is placed in position, which is effected by placing the locking member in groove 28 between two projections as indicated in chain lines in Figure 2 and then sliding it into position in the tunnel, thereafter bending up the tab 32.

The locking member of this embodiment is illustrated by itself in Figures 7 to 19.

The wire locking members 38 are preferably manufactured from continuous strip or wire material by a milling operation involving reducing the thickness of the strip or wire to form the tabs 3|, 32 and simultaneously parting the strip or wire. Such a milling operation is illustrated in Figures 5 and 6 in which 34 indicates the milling cutter, 35 indicates the continuous strip or wire of rectangular section, and the parted locking members are indicated by the same references as are employed in the remainder of the description. As will be seen the cutter M has a profile afiording two side cutting faces 34a to mill a channel in the strip or wire 35 and a central cutting face 34?) to part the strip or wire at the centre of the channel. The axis of the cutter 34 may be skewed relative to the strip or wire 34 so that, when the root attachment 22 is skewed relative to the turbine, the thicker central part of the locking member will be of parallelogram form to conform to the shape of the recess 26 in the projection 24, and the tabs 3!, 32 will when bent up lie flush against the circumferentially directed faces of the projection 28.

By arranging the locking member 39 on the high pressure side of the disc If], the locking member will not be required to support heavy shear loads in operation since the loads on the blade tend to move it from the high pressure side of the disc towards the low pressure side.

One important advantage of this invention is that blades can be assembled and dismantled without damaging the blade of the disc, since in order to remove a blade, it is only necessary to remove the locking member and then draw the blade free from the disc. Thus the blades can, if desired, be replaced in the disc after inspection.

We claim:

1. An axial-flow turbine or compressor assembly comprising a rotor disc with a plurality of slots extending across the disc periphery from one face of the disc to the other face of the disc; a plurality of blade elements, each blade element having a root attachment portion engaged in a corresponding one of said slots; radially-outwardly-facing shoulders on the circumferential faces of said root attachment portions; radiallyinwardly-facing shoulders on the circumferential walls of said slots in co-operating abutment with said outwardly-facing shoulders to retain said root attachment portions against radially outward displacement from the slots: and means to restrain disengagement of the root attachment portions of the blade elements from the slots in the disc by sliding lengthwise of the slots, which means comprises axial projections on said root attachment portions, said axial projections being formed with recesses having axially-facing abutment walls, an axial extension on said disc which axial extension has a co-operating recess with axially-facing abutment walls, the recesses in said axial projections being positioned in the projections to be aligned with the co-operating recess in said axial extension when said root attachment portions are properly positioned in said slots, and a plurality of locking members, said axial projections on the blade elements being radially outside said axial extension on the disc, the recesses in said axial projections facing radially inwardly, and having said co-operating recess in said axial extension facing radially outwardly and co-operating with the recesses in said axial projections to form circumferentially-extending tunnels each to receive one of said locking members, whereby each locking member is loaded in shear through the axially-facing abutment walls by forces tending to cause lengthwise sliding of the associated root attachment portion in the corresponding slot in either direction.

2. A turbine or compressor assembly as claimed in claim 1, wherein the locking members have a substantially rectangular section and each recess has a substantially triangular section, the recesses together forming a tunnel of substantially rectangular section to receive the locking memher.

3. A turbine or compressor assembly as claimed in claim 2, wherein the axial extension on the disc is an axial flange and the flange has formed therein an outwardly-facing continuous groove to afford said co-operating recess.

4. An axial-flow turbine or compressor assembly comprising a rotor disc with a plurality of slots extending across the disc periphery from one face of the disc to the other face of the disc; a plurality of blade elements, each blade element having a root attachment portion engaged in a corresponding one of said slots; radiallyoutWardly-facing shoulders on the circumferential faces of said root attachment portions; radially-inwardly-facing shoulders on the circumferential walls of said slots in co-operating abutment with said outwardly-facing shoulders to retain said root attachment portions against radially outward displacement from the slots; and means to restrain disengagement of the root attachment portions of the blade elements from the slots in the disc by sliding lengthwise of the slots, which means comprises axial projections on said root attachment portions, said axial projections being formed with recesses having axially-facing abutment walls, an axial extension on said disc which axial extension has a cooperating recess with axially-facing abutment walls, the recesses in said axial projections being positioned in the projections to be aligned withthe cooperating recess in said axial extension when said root attachment portions are properly positioned in said slots, and a plurality of locking members, each locking member comprising a thick central portion which is partly received in the recess in the axial projection of the associated blade element and is partly received in said co-operating recess in the axial extension on the disc, and end portions of reduced thickness permitting them to be bent over to retain the locking member in the recess after assembly, whereby each locking member is loaded in shear through the axially-facing abutment walls by forces tending to cause lengthwise sliding of the associated root attachment portion in the corresponding slot in either direction.

5. An axial-flow turbine or compressor assembly comprising a rotor disc with a plurality of slots extending across the disc periphery from one face of the disc to the other face of the disc; a plurality of blade elements, each blade element having a root attachment portion engaged in a corresponding one of said slots; radially-outwardly-facing shoulders on the circumferential faces of said root attachment portions; radiallyinwardly-facing shoulders on the circumferential walls of said slots in co-operating abutment with said outwardly-facing shoulders to retain said root attachment portions against radially outward displacement from the slots; and means to restrain disengagement of the root attachment portions of the blade elements from the slots in the disc by sliding lengthwise of the slots, which means comprises axial projections on said root attachment portions, said axial projections being formed with recesses having axially-facing abutment walls, an axial extension on said disc, which axial extension has a co-operating recess with axially-facing abutment walls, the recesses in said axial projections being positioned in the projections to be aligned with the co-operating recess in said axial extension when said root attachment portions are properly positioned in said slots, and a plurality of locking members, each said locking member projecting into both said co-operating recess and an aligned recess in one of said axial projections thereby to be loaded in shear through the axially-facing abutment walls by forces tending to cause lengthwise sliding of the associated root attachment portion in the corresponding slot in either direction, each said axial projection also comprising an abutment cooperating with the face of the disc radially inwards of the slots to limit sliding of the associated root attachment portion in the associated slot in the direction of said abutment.

LIONEL HAWORTI-I. JAMES ALEXANDER PE'I'RIE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,072,457 Herr Sept. 9, 1913 1,890,581 Kohler Dec. 13, 1932 FOREIGN PATENTS Number Country Date 537,121 Great Britain 1941 606,151 Great Britain 1948 612,097 Great Britain 1948 618,011 Great Britain 1949