US3832092A

US3832092A - Device for locking turbomachinery blades

Info

Publication number: US3832092A
Application number: US00407946A
Authority: US
Inventors: G Manharth
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1973-10-19
Filing date: 1973-10-19
Publication date: 1974-08-27
Anticipated expiration: 1991-08-27

Abstract

A blade-locking device, for locking radially projecting blades on a rotor, includes a spacer having a passage therethrough. The passage is accessible by means of an axial separation occurring at one side of the spacer; and the spacer is resiliently deformable to permit spreading of the separation from its undeformed position and returning the separation to its undeformed shape. A locking pin, having enlarged oblong integral ends at opposite extremities thereof, is formed and dimensioned so as to reside within the passage in a friction fit with each of the aforementioned ends projecting beyond the respective spacer extremity. The pin is disposed within the passage by deforming the spacer to enlarge the separation beyond the width necessary to receive the thickness of the pin and placing the pin therein. The pin is rotatable within the passage to a first position wherein one of the ends may pass freely with the spacer through a gap left between a blade tang and rotor slot to be interlocked. In a second position, the ends serve to engage and retain, respectively, the rotor and the blade tang.

Description

United States Patent [191 Manharth in] 3,832,092 1451 Aug. 27, 1974 DEVICE FOR LOCKING TURBOMACHINERY BLADES Gary B. Manharth, Milford, Ohio [73] Assignee: General Electric Company,

Cincinnati, Ohio [22] Filed: Oct. 19, 1973 [21] Appl. No.: 407,946

[75] Inventor:

Primary Examiner-Everette A. Powell, Jr.

Attorney, Agent, or FirmDerek P. Lawrence; Lee H.

Sachs ABSTRACT A blade-locking device, for locking radially projecting blades on a rotor, includes a spacer having a passage therethrough. The passage is accessible by means of an axial separation occurring at one side of the spacer; and the spacer is resiliently deformable to permit spreading of the separation from its undeformed position and returning the separation to its undeformed shape. A locking pin, having enlarged oblong integral ends at opposite extremities thereof, is formed and dimensioned so as to reside within the passage in a fric tion fit with each of the aforementioned ends projecting beyond the respective spacer extremity. The pin is disposed within the passage by deforming the spacer to enlarge the separation beyond the width necessary to receive the thickness of the pin and placing the pin therein. The pin is rotatable within the passage to a first position wherein one of the ends may pass freely with the spacer through a gap left between a blade tang and rotor slot to be interlocked. In a second position, the ends serve to engage and retain, respectively, the rotor and the blade tang.

l3 Claim, 8 Drawing Figures DEVICE FOR LOCKING TURBOMACHINERY BLADES BACKGROUND OF THE INVENTION The present invention relates to turbomachinery rotors and more particularly to means for locking rotor blades within rotor slots.

In the manufacture of bladed turbomachinery rotors, it is common practice to mount the blades on the rotor through the use of dovetail tangs formed at the base of the blades which tangs are received by corresponding slots formed across the periphery of the rotor. It has been a commonly accepted practice, also, and particularly in gas turbine engines for the propulsion of aircraft, to lock the blades within the rotor slots by the use of bent metal strips. These are slipped through the rotor slot and their ends are bent so that they overlie both the tang and adjacent portions of the side of the rotor. This is a simple arrangement which enables individual blades to be replaced, if desired. It has the disadvantage, however, that relative movement between the blade and the rotor in the axial direction will be absorbed by deformation of a portion of the retainer. While such a retainer can be designed to function satisfactorily if an attempt is made to reuse it, reliability problems can arise.

As a related problem, certain blades having large radial dimensions have been improved by means of the addition of shroud structures either at midspan or in the tip area. In order to properly position a plurality of such blades so that the shroud segments associated with the individual blades successfully interlock to form a shroud, means must be provided for defining the radial position of the blade tangs. The bent metal tab retainers of the prior art are not particularly well suited for such a use. Shrouded rotors require that the blade be shifted radially inwardly before it can be individually removed from the slot. Such action is inhibited by these retainers.

Another major drawback of the conventional and prior art blade locking devices, whether of the bent metal tab type or other types, is that they generally require access from both sides of the blade slot for insertion and removal. In some cases, engine design requirements'make it impractical or inconvenient to provide such access during routine maintenance or the like where it is desired to remove one or more blades.

Certain advances in the art in this area have led to the introduction of blade-locking devices which do provide a positive lock for the blades without relying on bendin g of any of the component parts of the locking device, and which do permit blade insertion and removal where access is available only to one side of the rotor. Unfortunately, such locking devices have had the disadvantage that they are comprised of multiple separate components which must be separately manipulated during each removal and insertion. The result is that the insertion and removal process is relatively cumbersome and involves potential faulty parts assembly or placement.

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a simplified blade-locking device of the general character described which reliably retains blades in a predetermined axial position with respect to a rotor and which permits easy disassembly and assembly with few separate parts and minimum manipulation.

In order to accomplish this, as well as further objectives which will become apparent hereinafter, the present invention provides a blade-locking device for locking radially projecting blades on a rotor, each blade having a dovetail tang at its radially inward end and'the rotor having dovetail slots extending across its periphery from one axial side of the rotor to the other, each blade being received in one of the slots with a radial space between the tang and the bottom of the slot. The locking device includes a spacer having a' height approximating the radial dimension of the radial space, a locking pin having a length greater than the length of the spacer and also having first and second enlarged ends which project beyond the spacer. The two ends of the pin have generally oblong configurations and are oriented to project in opposite directions from the centerline of the pin. One of the ends has a width no greater than the radial dimension of the aforementioned radial space and a height greater than that radial dimension, so that it will pass through the radial space in one orientation but not in a second orientation. The spacer has a passage for receiving the pin and permitting it to rotate so that the pin can be positioned with its ends arranged to pass, with the spacer, through the radial space. Alternatively, the pin can be rotated into a position wherein the ends lock the tang in the slot by means of engaging both the blade tang and rotor assembly.

DESCRIPTION OF THE DRAWINGS The present invention will become more clearly understood by reference to the following description taken in conjunction with the appended drawings wherein:

FIG. I is a radial cross section view of a fan blade and rotor combination to which the present invention has been applied;

FIG. 2 is an axial view of a rotor stage incorporating blade and locking means according to the present invention;

FIG. 3 is a view along line 3-3 of FIG. 2 disclosing the integral shroud structure of the blades;

FIG. 4 is an exploded view of the spacer and locking pin structure of the present invention;

FIG. 5 depicts the spacer and locking pin in cooperation and in one relative orientation thereof;

FIG. 6 is a section view through the spacer and locking pin combination along line 66 of FIG. 5;

FIG. 7 is an enlarged section view of the area of cooperation between the locking device of the present invention and the blade and rotor combination; and

FIG. 8 is a section view along line 8-8 of FIG. 7.

DETAILED DESCRIPTION Referring now to the drawings, the present invention is depicted in one fonn thereof individually as well as applied to its normal environment. In FIG. 1, a rotor blade 10 having a large radial dimension is depicted in combination with a rotor disc 12. The blade is typical of blades of this fashion in its incorporation of an airfoil 14, a platform 16, and radially extending tang 18. In addition, this blade incorporates a segmented midspan shroud 20 which is adapted to cooperate with similar shroud segments of adjacent blades to support the blades against undesired movement. (Such shrouds are utilized to strengthen blades whose radial length and structural shape make them relatively flimsy).

Referring now to FIGS. 1 and 2, the rotor 12 includes a plurality of dovetail slots 22 which are adapted to receive the tangs 18 of the blades in a retaining relationship. The rotor slots 22 are spaced circumferentially about the rotor and extend across its periphery from one axial side thereof to the other. In addition, the slots 22 are of such depth that, upon receiving the tang 18 of each blade 10, there is defined between each tang and the bottom of each slot a space 24 having apredetermined radial dimension 26. This space serves the function of permitting individual blades to be dropped radially inwardly with respect to the rotor prior to removal in order to disengage the shroud segments from contact with one another. (FIG. 3 depicts a top view of adjoining blades disclosing the cooperation of mating segments 20 of the midspan shroud. In order to withdraw a blade axially from cooperation with the rotor, it is first necessary to remove the associated segment 20 from its interlocking relationship with similar segments). The rotor 12 further includes a conical support 28 by which it is linked to a shaft to provide rotation thereto. In addition, the rotor includes a flange 30 to which is bolted a hollow nose cone structure 32 by means of another flange 34 carried by the nose cone.

Rotors of the variety thus described generally rotate with extremely high velocities. As a result, in absence of effective means for maintaining axial blade position, the reaction of the airfoils to foreign object impingement, blade tip rub, or the'air passing therethrough would tend to drive the blades out of the slots 22. If such were to occur, extensive damage could be done to the associated engine and its surroundings. As a result, it has become necessary to devise effective and reliable means for maintaining the blades in their relationship with the rotor. The present invention accomplishes this by means of utilizing the space 24 and placing therein a spacer and locking pin combination to positively interconnect the blade tang 18 with the rotor 12 in a releasable fashion and further to permit easy withdrawal thereof even though access might be limited to a single side of the rotor. Furthermore, the present invention offers a uniquely simplified combination for accomplishing these ends.

Referring to FIGS. 4 and 5, a locking device, according to the present invention, is depicted in its disassembled and assembled states. In addition, the locking pin is shown rotated in first and second significant orientations with respectto the spacer. Generally, the locking device comprises a spacer 40 and a locking pin 42. The spacer 40 is. dimensioned so as to have a height or thickness approximating the radial dimension 26 of the radial space 24. In addition, the spacer has a horizontal dimension or width approximating the width of the space 24. In the present embodiment, the spacer is generally U-shaped in cross section with a passage 44 extending for its entire length in the axial direction. The passage is open-ended at the ends 46 and 48 of the spacer and is further accessible by means of an axial separation 50 in the spacer which extends substantially the entire length of the passage.

In the present. embodiment, the spacer includes first and second

lateral segments

52 and 54, each segment formed to a predetermined length. The segments may be formed of a resilient plastic material or of some other easily fabricated material. In addition, the spacer includes a resiliently deformable spring member 56 which receives and retains the lateral segments in opposed space relationship. The segments are maintained a predetermined distance from one another forming a gap, the gap defining the aforementioned passage 44. In addition, the gap partially defines the separation 50.

The spring member 56 is generally U-shaped and retains the

lateral segments

52 and 54 one to each side of the U." The open end of the spring member further defines the separation 50. In the present embodiment, each of the

lateral segments

52 and 54 includes a lobe or enlarged section near each of its ends and a reduced section near its center. The spring member 56 surrounds and is secured to the reduced portion of the segments. It is to be noted that in this configuration, the flexibility of the spring member 56 permits a spreading of the separation 50 in order to increase the accessibility of the passage 44.

The locking pin 42 has a length greater than the length of the spacer and further has first and second integral enlarged ends 60 and 62. Each of these ends has a generally oblong configuration and each is positioned in an eccentric fashion with respect to the pins so that a majority of its bulk protrudes'to a single side of the pin. The end 62 is dimensioned so that its width 64 is no greater than the radial dimension 26 of the radial space 24. Hence, in one orientation of the pin, the end 62 is of such size that it will pass through the space 24. The end 62 furthermore has a height 66 (which is measured in a direction generally perpendicular to the width 64), which is greater than the radial dimension of space 24. As a result, with the pin oriented in a second position, the end 66 will not pass through the space 24.

The other oblong enlarged end 60 of the pin 42 likewise has a height 68 which is greater than the radial dimension of the space 24. This height 68 is directed in a sense or direction opposite that of height 66 of the end 62. In other words, the height of end 60 is generally parallel to the height of end 62 but extends in the generally opposite direction with respect to the centerline of the pin. In its assembled position, the locking-device of the present invention is depicted in FIG. 5 wherein the locking pin 42 and spacer 40 are assembled with the pin retained within passage 44 to which it is accessible by means of separation 50. When retained in the passage 44, the pin 42 is rotatable therein to change the angle of orientation of the first and second ends with respect to the spacer. To inhibit undesirable angular rotation, the spacer and pin may engage one another frictionally in order to retard the rotation of the pin within the passage- To facilitate the positioning of the pin within the passage of the spacer, the spacer includes the resiliently deformable spring 56 which permits spreading of the separation 50 for easy entry of the pin while also enabling the spacer to return elastically to its undeformed position. Additionally, the frictional engagement be tween the pin and spacer are enhanced by means of this spring. In order to achieve a reliable retention of the pin within the spacer, the separation 50, in its undeformed position, has a width smaller than the thickness of at least a portion of the pin 42. In the present configuration, the pin is generally cylindrical in the cross section and the passage is generally circular.

When the pin is positioned within the spacer and its

ends

62 and 60 extend beyond the spacer, it is desirable to prevent relative axial motion between the pin and the spacer. In order to accomplish this, the present embodiment includes radius changes in the pin which result in the formation of

shoulders

70 and 72. These shoulders mate with abutting shoulders 74 and 76 defined within the passage 44 by similar radius changes and combine to form securing means for preventing undesired axial relative motion.

Referring to FIGS. 7 and 8, assembly of the rotor and blade combination will be described, assuming that the rotor has already been positioned in the engine framework and that a number of blades have already been positioned thereon. Each additional blade is applied as follows.

An individual blade 10 is brought into proximity with the rotor 12 and is attached thereto by sliding the dovetail tang 18 into a mating slot 22. The new blade is then lifted radially outwardly until its dovetail tang is brought up tight against mating portions of the associated slot. At the same time, the shroud segment 20 of the new blade is interlocked with the shroud segments of adjacent blades. In order to maintain the blade in its radial and axial positions, the blade-locking device of the present invention is applied.

First, the locking pin 42 is snapped into frictional engagement within the passage 44 of the spacer 40 by way of expandingthe separation 50 to the point where the pin will fit therethrough and into the passage. Then, the spring 56, which has been tensed to accomplish this spreading, is released and recloses the separation 50 engaging the pin. It is to be noted that this is a simple manipulation which can be quickly and easily accomplished and could be performed with one hand by the assembler.

Having thus been assembled, the locking pin is rotated into the position shown in FIG. 5 wherein the width 64 of end 62 is aligned with the thickness of the spacer so as to pass freely through the space 24 as indicated above. This action is accomplished by the assembler by means of sliding the spacer and pin combination through the space to the desired axial position thereof. At this point, the blade 10 is held in the desired radial position by means of the presence of the spacer 40. In order to accomplish axial retention of the blade, the pin 42 is rotated from its present position (that is, with the height of the end 62 generally perpendicular to the radial dimension 26 of the space 24) to a second position wherein the height 66 of the end 62 is generally parallel to the radial dimension of the space 24. In this second position, the position illustrated in FIGS. 7 and 8, the end 62 engages and hooks upon an abutting portion 80 of the rotor 12. (While the end 62 is depicted as being generally hook-shaped, any generally oblong configuration will suffice where a first dimension thereof is such that the end may pass through the space 24 while a second dimension thereof is such that the end will be prevented from passing therethrough).

The pin 42 having thus been rotated into this second position, wherein end 62 is in registry with the rotor 12, the pin cannot be removed axially in the direction in which it was applied. Furthermore, the end 60 has its height 68 so arranged that, as described above, it extends in a direction generally opposite that of the end 62. Due to this characteristic, the rotation of the pin 42 into the position last described will result in bringing end 60 into registry with a portion of the blade tang 18. This is also shown in FIG. 7. At this point, the blade has been assembled to the rotor and is now retained effectively in both the radial and axial positions.

Subsequently, the nose cone 32 is brought into position and bolted through flange 34 thereof to flange 30 of the rotor 12. It is noted in FIG. 8 that the bolts 82 are spaced circumferentially about the rotor, and that a plurality of apertures 84 also spaced around the flange 34 permit the protrusion of a portion of end 60 therethrough. Due to the fact that the protruding portion lies eccentrically to a single side of the centerline of the pin 42, and due to the selected dimensions of the aperture 84, undesired rotation of the pin 42 within the spacer is further hampered.

In order to ensure proper orientation of the spacer with respect to the space 24 upon assembly, to maintain the angle of orientation of the spacer with respect to the space during engine operation, and to seal the space 24 against the undesired leakage of air therethrough, the present invention further provides rib means for sealing as well as defining and maintaining the angle of orientation of the spacer when the spacer is disposed within the space. This means includes, in the present embodiment, a pair of

upstanding ribs

88 and 90 which are positioned near one end of the spacer 40, and more particularly the end which is to remain on the side of the rotor accessible by the assembler. As can be seen in FIG. 2, the shape of the blade tang 18 combines with the shape of the slot 22 to define a pair of

detents

90 and 92 which have roughly the same outline in the cross section as do the

ribs

88 and 90. The detents serve to accept the ribs and retain them in a sealing relationship in a predetermined position. Furthermore, the detents extend only a limited distance into the axial direction with respect to the rotor and therefore prevent the reversed insertion of the pin and spacer combination. The sealing capability of the ribs is important in order to eliminate efficiency losses associated with leakage of air through space 24.

Thus, as has been described in one embodiment, the present invention provides a strong and effective bladelocking device for retaining rotor blades in a predetermined radial and axial position with respect to an associated rotor. It can be appreciated that, due to the extremely simplified two-piece spacer and pin combination, assembly is radically enhanced when compared to prior art devices requiring the cumbersome bending of metal pieces or assembly of multiple component locking devices. Furthermore, it can be appreciated that ease of assembly and disassembly is greatly improved by pennitting the entire assembly process to occur from access to a single axial side of the rotor. Additionally, the integral character of the

ends

60 and 62 with pin 42 make for a very strong and reliable retaining mechanism not dependent upon threaded connections or the like.

Having thus described the present invention in one embodiment, it is clear that numerous substantial variations thereof may be made without departing from the scope of the present invention. For example, the structural interrelationships between the locking pin 42 and spacer 40 are dictated more by the configuration of the space 24 between the base of the tang 18 and slot 22 than by the inventive dictates of this invention. Any

variation which functions in substantially a similar fashion and provides the improved characteristics of this invention would fall hereunder without necessarily even resembling the embodiment depicted. Other variations might change the shape of the enlarged ends 60 and 62 which have been depicted as generally hookshaped but can be varied to any eccentric and oblong configuration. Similarly, while it is desirable that the pin 42 be generally cylindrical in cross section, it may become desirable to make this cross section noncircular and the mating passage 44 cross section noncircular for the purpose of increasing the difficulty of rotation of the pin within the passage. Other variations hereof will occur to those skilled in the art. I

What is claimed as new and desired to be secured by letters Patent of the United States is:

1. A blade-locking device for locking radially projecting blades on a rotor, each blade having a dovetail tang at its radially inward end and the rotor having dovetail slots extending across its periphery from one axial side of the rotor to the other, each blade being received in a slot with a radial space between the tang and the bottom of the slot, said device comprising:

a spacer having a height approximating the radial dimension of said radial space;

a locking pin having a length greater than the length of the spacer and also having first and second enlarged integral ends, said first and second ends having generally oblong configurations, said first end having a width no greater than the radial dimension of said radial space and a height greater than said radial dimension, and said second end having a height greater than said radial dimension; and

said spacer having a passage along its length for receiving said pin, said passage being accessible to said pin by means of a separation in said spacer extending substantially the entire length of said passage, and said pin being rotatable within said passage to change the angular orientation therewith of said first and second ends.

2. The device of claim 1 wherein said spacer includes resiliently deformable material facilitating spreading of said separation for easy entry of said pin, and permitting elastic return of said separation to its undeformed position.

3. The device of claim 2 wherein said separation, in its undeformed position, has a width smaller than the thickness of a portion of said pin.

4. The device of claim 3 wherein said spacer is generally U-shaped in the cross section, and said pin is generally cylindrical.

5. The device of claim 1 wherein, when said pin is disposed within said passage and said spacer is disposed within said spacer, said pin is adapted to be rotated from a first position wherein said height of said first end is generally perpendicular to said radial dimension of said space, to a second position wherein said height of said first end is generally parallel to said radial dimension of said space.

6. The device of claim 5 wherein said first end engages said rotor in said second position.

7. The device of claim 6 wherein said second end has its height generally parallel to the height of said first end, but extending in the generally opposite direction so that, when said pin is in said second position, said second end engages said tang.

8. The device of claim 1 wherein said first and second ends of said pin extend axially beyond said spacer when said pin is disposed within said passage; and said device further comprises securing means for preventing axial relative movement between said pin and said passage.

9. The device of claim 8 wherein said pin and said passage mate in a friction fit to prevent undesired relative angular movement; and wherein said securing means comprises first and second abutting shoulders associated respectively with said pin and said passage.

10. The device of claim 1 wherein said spacer includes positioning means for defining and maintaining angular orientation of said spacer when disposed within said radial space, and seal means for preventing undesired leakage through said radial space.

11. The device of claim 10 wherein said positioning and seal means includes an upstanding rib carried by said spacer, said rib adapted to engage a detent formed between said tang and said slot.

12. The device of claim 1 wherein said spacer comprises:

first and second lateral segments, each segment formed to a predetermined length; and

a resiliently deformable spring member for receiving and retaining said lateral segments in opposed, spaced relationship separated from one another by a predetermined gap. said gap defining said passage and partially defining said separation.

13. The device of claim 12 wherein said spring member is generally U-shaped and retains said lateral segments one to each side of the U, and wherein the open end of said spring member further defines said separation.

Claims

1. A blade-locking device for locking radially projecting blades on a rotor, each blade having a dovetail tang at its radially inward end and the rotor having dovetail slots extending across its periphery from one axial side of the rotor to the other, each blade being received in a slot with a radial space between the tang and the bottom of the slot, said device comprising: a spacer having a height approximating the radial dimension of said radial space; a locking pin having a length greater than the length of the spacer and also having first and second enlarged integral ends, said first and second ends having generally oblong configurations, said first end having a width no greater than the radial dimension of said radial space and a height greater than said radial dimension, and said second end having a height greater than said radial dimension; and saiD spacer having a passage along its length for receiving said pin, said passage being accessible to said pin by means of a separation in said spacer extending substantially the entire length of said passage, and said pin being rotatable within said passage to change the angular orientation therewith of said first and second ends.

12. The device of claim 1 wherein said spacer comprises: first and second lateral segments, each segment formed to a predetermined length; and a resiliently deformable spring member for receiving and retaining said lateral segments in opposed, spaced relationship separated from one another by a predetermined gap, said gap defining said passage and partially defining said separation.

13. The device of claim 12 wherein said spring member is generally U-shaped and retains said lateral segments one to each side of the ''''U,'''' and wherein the open end of said spring member further defines said separation.