US3598503A

US3598503A - Blade lock

Info

Publication number: US3598503A
Application number: US859423A
Authority: US
Inventors: Gerard Muller
Original assignee: United Aircraft Corp
Current assignee: Raytheon Technologies Corp
Priority date: 1969-09-19
Filing date: 1969-09-19
Publication date: 1971-08-10
Anticipated expiration: 1988-08-10

Abstract

A turbomachine having a rotor assembly construction wherein a deformable blade lock is inserted in the clearance between the blade root and a slot in the periphery of a disc, the blade lock moving under the influence of centrifugal force in such a manner so as to prevent axial movement of the blade root in the disc slot.

Description

United States Patent Inventor Gerard Muller Morristown, NJ. Appl. No. 859,423 Filed Sept. 19, 1969 Patented Aug. 10, 1971 Assignee United Aircraft Corporation East Hartford, Conn.

BLADE LOCK 2 Claims, 3 Drawing Figs.

U.S. Cl Int. Cl t Field of Search 416/221 Fold 5/32 416/220,

[56] References Cited UNITED STATES PATENTS 2,641,443 6/1953 Comery et a1. 416/221 2,786,648 3/1957 Ledwith 416/221 2,828,942 4/1958 McCullough et a1. 416/221 Primary Examiner-Everette A Powell, Jr. Allamey.Charles A. Warren ABSTRACT: A turbomachine having a rotor assembly construction wherein a deformable blade lock is inserted in the clearance between the blade root and a slot in the periphery of a disc, the blade lock moving under the influence of centrifugal force in such a manner so as to prevent axial movement of the blade root in the disc slot.

BLADE LOCK BACKGROUND OF THE INVENTION This invention relates to blade lockfor a rotor assembly for use in a turbomachine.

It is obvious that in a turbomachine some arrangement must be provided to hold or lock the, blades in place inthe rotor assembly. One of the most commonmethods of retaining blades in a compressor or turbine that. is employed byprior art constructions is the use of keysor .tablocks which lie beneath-the root of the blades at the bottom of the blade locks and are fixed to the disc and blade. However, when the supporting disc has a number of axially extending recesses in its periphery, to receive the roots of the blades which zproject radially outward from the disc, it becomes necessary to prevent axial movement of the blade relative to. the disc because of .the axial thrust exerted on the blade.duringoperationof thecompressor or turbine. One of the inherentand basic disadvantages of the prior art key-or tab'lock constructions is that-these constructions are weak in the axial direction'with the result that the blades may walk out of the disc slots. Typical prior art con structions which have this inherent disadvantageare shown-in U.S. Pat. No. 2,828,942 and U.S. Pat. No. 3,383,095.

SUMMARY OFZTHE INVENTION It is a primary object of this invention toprovidea rotor assembly with a blade lock construction.whichprevents movement of the blade root in the disc inthe axial directiomparticularly during rotation ofthe rotor assembly.

The present invention relates to a deformable tab lock -posi-- tioned in the radial clearance between the base of the'blade root and the slots in the outer periphery of the rotor disc. The tab lock comprises flat strip member which extends-axially in the slot in the rotor disc. ndincludestab or flange means on either end of the flap strip. The downstream tab projects radially outward, while the upstream tab projectsradially inward, the downstream tab lockingagainst the blade root while the upstream tab locks against thedisc.

The flat strip member extending axially in the disc slot includes a contact means. This.contact means which is within the clearance between the disc periphery and the blade root comprises an outwardly extending resilient offset or hump which contacts the base surface of the bladeroot. The point of contact between the tab lock or contact means and the blade root is of significance in that it is offset or asymmetrical with respect to the blade axis and the central plane of the disc. The importance of this contact point being symmetricalv is that as the discrotor gains speed, both the tab rotate about the contact point. More specifically, the downstream tab will, as a result the centrifugal force, rotate counterclockwiseabout the contact point in an outward direction; whereas, theupstream flange will rotate clockwiseabout the contact point. Since the contact point is asymmetricahthe offset being in the upstream direction. the downstream or outwardly extendingflangm-will rotateor deform a greater amount around the contact point than the inwardly extending upstream.flange-Therefore, as a result of this deformation caused by centrifugal force, and as a result of the movement of these flanges, the blade root is locked more securely within-the slot of the rotor disc, thereby preventing axial movement of the root as the rotor disc speeds up.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an axial sectional view through a disc showing the blade lock.

FIG. 2 is a sectional view along line 2-2 of FIG. I;

FIG. 3 is an axial scctionalyiew througha disc showing the blade lock in its deformed position.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention is 'shownin conjunction with acompressor disc for use in a multistage axial 'flow compressor construction, but it will be apparent that'theinvention is equally applicable to the fastening of blades in the discs of axial flow turbines or other similar apparatus. In the arrangement shown, the compressor disc 2 which may have axially projecting flanges 4 thereon for spacing'disc 2 from adjacent similar discs for other stages'of the compressor has a plurality of axially extending slots 6' in its periphery to receive the similarly formed root 8 of the blade 10. The particular shape of the blade root or of the similarly shaped'disc-6 is not critical. For the purpose of the present invention a slot is shown havinga relatively broad base opening :12, the' base surface 14 of which is substantially flat, a narrow neck l6'and broad outer end portion 18. The narrow neck 16 constitutes an outer peripheral portion of the slot radially outwardof the base opening. The blade root is similar in'shapehaving a broad base portion 20,-the

base surface 22 of which is substantially flat and is preferably of such a dimension as to leave when the blade root is assembled in the slot, a clearance space of substantially uniform depth between the surface 2 of the root and the surface 14 of the slot for the insertion of the blade lock 24.

As best shown-in FIGS. 1 and 3, the blade lock is in a form of a thin flat strip 29 which is several times wider than its thickness and which'extends in an axial direction within the slot between the base surface 14 of the slot and the base surface 22 of the blade root. The strip is thinner than the radial depth'of the slot to permit movement of portions of the strip radially in the slot as will be described. In a direction transversely of the strip the latter is parallel to the base surfaces of the blade root and slot, and these surfaces are preferably at right angles to the plane ofthe disc. The strip is long enough to provide material projecting beyond the ends of the slot to form first tab-30and second tab 32. As illustrated tab 30 is the downstream tab and is bent outwardly'with respect to the axis of the disc to overlie the end of the blade root. Meanwhile tab 32 is the upstream tab and this tabis bent inwardly with respect to the axis of the' disc to overlie the side surface of the disc.-

The flat strip member 29 also includes a contact means34 which extendsbetween the flat stripmember 29 and the base surface 22 of the blade root. Contact means 34 includes a resilient curved offset or hump formed to project outwardly'in the flat strip member 29. The contact means 34 contacts the base surface 22 at a point 36 which is offset axially from the central plane 38 of the disc in an upstream direction. More specifically, the contact point 38 is asymmetrical with respect to the central plane of the disc 38and the axis of the blade.

As hereinbefore noted, flat strip member 29 includes first tab 30 andsecond tab 32-. As the-rotor disc attains speed, both tabs, that is, tab 30 and tab 32, will, through centrifugal force and deformation, rotate about contact point 36. Morespecifi cally, tabv30 will-rotateabout contact point 36 'a greater amount than tab 32 because of the asymmetrical or offset position of contact point 36 thetab 30 being spaced farther fromthe'pivot pointthan the tab 32. Therefore. as a result of this rotation or deformation ofthe tab lock, tab lock 30 moves outwardly while tab lock 32 moves inwardly, the combined deformation of the tabs 30' and 32 locking the'blade root withinthe slot in a more secure fashion so as to prevent any axial-movementtherein. FIG. 3 clearly illustrates the locking technique of the construction hereinbefore described with the blade lock in the position it assumes-during operation of the rotor at design speed.

Iclaim:

1. A rotor assembly for a turbomachine comprising a disc having root receiving slots extending transversely of the disc at its periphery, and blades having roots corresponding substantially in shape to and engaging in said slots, the base of each blade root being spaced radially from'the base of the slot to define clearance therebetween, wherein the improvement comprises;

a deformable blade lock comprising a substantially flat resilient strip positioned in said clearance, the flat strip including a hump therein extending between the blade root and disc periphery, the hump being in contact with the blade root at a point offset with respect to the central plane of the disc, and an integral tabs at each end of the flat strip one of said tabs extending radially outward and engaging with the end of the blade root and the other tab extending radially inwardly to overlie the side of the disc thereby to lock the blade root against axial movement in the disc, the contact between the blade root and the hump being offset from the central plane in an upstream direction.

2. A rotor construction for a gas turbine engine comprising a disc having root receiving slots extending transversely of the disc at its periphery, and blades having roots corresponding substantially in shape to and engaging in said slots, the base of the blade roots being spaced radially from the slot to define thinner than and positioned in said clearance, the flat strip having an' offset therein extending outwardly between the blade root and disc periphery, the Offset being in contact with the blade root at a point spaced upstream with respect to the central plane of the disc said strip having a first tab at the upstream end thereof to overlie the side surface of the disc and a second tab at the downstream end thereof to overlie the end of the blade root each tab being connected to the flat strip and being movable in response to centrifugal force, the movement of the downstream tab being greater than the movement of the upstream tab by reason of the greater distance from the contact point between the offset and the blade root about which the strip pivots under centrifugal force.

Claims

1. A rotor assembly for a turbomachine comprising a disc having root receiving slots extending transversely of the disc at its periphery, and blades having roots corresponding substantially in shape to and engaging in said slots, the base of each blade root being spaced radially from the base of the slot to define clearance therebetween, wherein the improvement comprises; a deformable blade lock comprising a substantially flat resilient strip positioned in said clearance, the flat strip including a hump therein extending between the blade root and disc periphery, the hump being in contact with the blade root at a point offset with respect to the central plane of the disc, and an integral tabs at each end of the flat strip one of said tabs extending radially outward and engaging with the end of the blade root and the other tab extending radially inwardly to overlie the side of the disc thereby to lock the blade root against axial movement in the disc, the contact between the blade root and the hump being offset from the central plane in an upstream direction.

2. A rotor construction for a gas turbine engine comprising a disc having root receiving slots extending transversely of the disc at its periphery, and blades having roots corresponding substantially in shape to and engaging in said slots, the base of the blade roots being spaced radially from the slot to define clearance between the blade root and disc periphery, wherein the improvement comprises; a deformable blade lock comprising a substantially flap strip thinner than and positioned in said clearance, the flat strip having an offset therein extending outwardly between the blade root and disc periphery, the offset being in contact with the blade root at a point spaced upstream with respect to the central plane of the disc said strip having a first tab at the upstream end thereof to overlie the side surface of the disc and a second tab at the downstream end thereof to overlie the end of the blade root each tab being connected to the flat strip and being movable in response to centrifugal force, the movement of the downstream tab being greater than the movement of the upstream tab by reason of the greater distance from the contact point between the offset and the blade root about which the strip pivots under centrifugal force.