US3165294A - Rotor assembly - Google Patents

Description

Jan. 12, 1965 B. J. ANDERSON 3,165,294

ROTOR ASSEMBLY Filed Dec. 28, 1962 United States Patent I This invention'relates to rotor assemblies for fluid flow machines such as compressors and, more particularly,

to a locking arrangement for holding the blading of such machines in assembled position.

There are two main types of conventional rotor assemblies. The first type of conventional rotor structure isthe built-up or disc. type comprised of a plurality of 1 elements axially bolted or otherwise secured together to'form an integral structure. In this type of rotor assembly, it is generally not possible to remove individual blades without disassembling the entire rotor since the blades are generally held in axially extending dovetail slots in the periphery of the disc. The second type of conventional rotor assembly is the drum type rotor assembly such as shown by United States Patent No. 2,931,625 to Lechthaler et al., issued April 5, 1960, and assigned to the assignee of this application. In the drum type rotor assembly the blades are generally vheld in circumferentially extending dovetail slots and may 'be" inserted or removed without disassembling the entire rotor. In addition to permitting easy insertion and removal of rotorblades, the drum type rotor assembly is relatively] lightweight. in combination with adequate strength makes the drum type rotor assembly particularly suited for use in gas turbine engines'used for aircraft propulsion. The present.

proved rotor assembly in which, none: of the blades or blade roots are of special design or shape.

A still further object of this invention to to provide a rotor assembly 'in which theblades of a given stage are consecutively positioned, the entire row of blades then being locked into position without additional move-v ment of the blades being required.

An additional object is to provide an improved rotor assembly not requiring the use of complicated or unusual locking devices or tools.

Yet another object of this invention to to provide a rotor assembly which is simple and inexpensive 'to assemble, disassemble, service and manufacture, but yet is rugged and durable and requires a minimum of maintenance. 1 I 1 I Briefly stated, in accordance with the illustrated embodiment of the invention, a rotor drum is' provided with circumferentially continuous walls defining 'a dovetail slot in the periphery thereof. A loading recess is provided in the radially "inward surface of the slot. A plurality of identically shaped dovetail rotor blade roots are consecutively inserted intozthe dovetail slotatthe.

loading recess and then moved circumferentially into abutting relationshipwithin the slot, the dovetail shapes of the slot and theblade roots preventing radial movement of the blade roots relative to the rotor drum. The

The light weight construction the loading recess.

which:

arsenal Patented Jan. 12, 1965 ice last blade root inserted is positioned radially outward of A locking means engages the last blade root to hold it in the dovetail slot and to prevent circumferential movement of the blade roots within the slot.

While the invention is distinctly claimed and particularly pointed out in the claims appended hereto, the invention, both as to organization and content, will be better understood and appreciated, along with other objects and features hereof, from the following detailed description taken in conjunction with the drawing, in

FIGURE his a partial cross sectional view of a drum type rotor assembly constructed in accordance with this invention;

FIGURE 2 is a perspective view of a portion of the rotor assembly of FIGURE 1 showing one of the dovetail slots and its associated loading recess;

"FIGURE 3 is a view in cross section ofthe dovetail slot of FIGURE 2 illustrating in addition one of the rotor blades in its loading position and the locking means in its unlocked position;

FIGURE 4 is a view similar to FIGURE 3 showing the locking blade positioned in the dovetail slot and the locking means in its locked position;

- FIGURE 5 is a perspective view of the rotor blade shown in FIGURE 3; and

FIGURE 6 is a perspective view similar to FIGURE 5 showing the locking blade of FIGURE 4 in detail.

Referring first to FIGURE 1, a generally cylindrical blade holding member or rotor drum 10 is partially illustrated, the drum 10 having inwardly extending radial flanges 11 and 12 at its ends. The flanges 11 and 12 are secured by suitable fastening means, such as a plurality of circumferentially spaced bolt connections 13, to flanges 14 and 15, respectively. To increase the rigidity of the rotor drum construction, the flanges 14 and 15 are connected by a plurality'of circumferentially spaced axial tie bolts 16. The flanges 14 and 15 are connected to shaft portions (not shown) to form a complete rotor' assembly, the shaft portions being suitably mounted in bearings (not shown) to support and permit rotation of the rotor assembly; As this description proceeds, it will become obvious to those skilled in the art that the structure described above may be changed or modified'substantially without departing from the true spirit and scope of the invention, which will now be described.

The rotor drum 10 is provided with a plurality of axial spaced circumferentially extending slots 20, one of the slots-20 being shown in greater detail by FIGURES 24.

. As shown by FIGURES 24, the slot '28, which may be of the dovetail slot 20, the recess 23 having its deepest point adjacent slot side wall 21 so that the recess 23 essentially forms a radially inward continuation of the side wall 21. A radially extending threaded or tapped hole 25 is provided adjacent the loading recess 23, a threaded member of plug 26 being received therein. As shown by FIGURE 4, the head 28 of the threaded plug 26 is provided with a recess 29 for receiving a tool such as, for example, an Allen wrench for screwing the threaded plug 26 into and out of the tapped hole 25 between the extreme positions shown by FIGURES 3 and 4.

Returning briefly to FIGURE 1, it will be seen that a circumferential row of blades 32 is supported from each of the dovetail slots 20. The manner in which these blades 32 are positioned, supported, and locked inposi- A loadtion will now be described in detail. One of the blades 32 is illustrated by FIGURE 5, the blade having a root. j

portion 33 of dovetail configuration. side walls 3 1,- and 35 inclined so as to form leading and trailing toe portions 36 and 3'7, respectively. .The dovetail configurations of the slot 29 and the root 33 are the.

same with the. root 33 being sufiiciently smaller in size than the slot 29 to be slidably received therein, the fit between the root 33 and the slot 24) being as snug as practicable.

Referring now to FEGURE 3, the threaded plug 26 isscrewed into the tapped hole 25 to the position shown and then a first one of the blades 32 and its associated The root 33 has root 33 is tipped intothe position shown by solid lines, a

the leading'toe 36 of the root 33 extending into the recess 23. With the leading toe 36extending into the recess 23, the trailing toe 37 can be moved radially into the slot 29. The blade 32 and its associatedroot 33 may then be tipped into the position shown by dotted lines and moved circumferentially in the dovetail slot 2tl to a desired position. With the root 33 and the slot 2tl having the same dovetail configuration and a snug fit, the blade 32 is restrained against radial movement with respect to the'drumlt). Other blade roots may be posi tioned in a similar fashion. At this point it will not only be obvious that the circumferentialextentof therecess 23 must be sufficient to receive the roots 33, but also be; obvious that the circumferential extent should be no greater than required in order to restrain the maximum number of blades against radial movement. Therefore,

it can be stated that the circumferential extentof. the recess 23 is sufficient to receiveonly one of the root portions 33.

The entire circumferentially extending dovetail slot can be filled with blade roots 33 in the manner described: above, the roots 33 being inserted into the slot 20 at the loading recess 23 and then being moved circumferentially into abutting relationship. The last blade root inserted, however, fills the space in thedovetail slot 2tl radially outward of the loading recess23 and is not moved cir-' curnfer entially within, the slot'2tl. This last blade is not heldagainst radial movement relative to therotor drum 10 solely by the dovetail configuration of the slot 20 since the circumferential extent of the recess 23 is neces sarily greater than that of the last blade root in order to permit insertion of the blade roots 33 into the dovetail slot 20. Locking means must be provided for holding;

the last blade or locking blade in the slot 20. To effectively lock the, last blade against radial movement relative to therotor drum 10, a slightly modified structure is used for the last or locking blade 32A as illustrated by FIG- URES 4 and 6. Referring first to FIGURE 6,;blade32A is identical to blades 32 and has a root 33A identical in dovetail shape to roots 33. The onlyidilference between;

the roots 33 and 'the root 33A is that an access passage 4% is provided through the root 33A. Passage 40 is provided with a counterbore 41 as bestshown'by FIG- URE 4.

The root 33A of the locking blade 32A is inserted into the dovetail slot 2! in the same manner as roots 33 and then is positioned in the dovetail slot 20 as shown by FIG-,

URE 4,the access passage 4t) being radially aligned with thethreaded plug 26 which comprises the locking means.

With the'root 33A positioned in the slot 20, a suitable tool is inserted through the passage 46) into the cavity 29 in the threaded plug 26 to screw the plug 26 outwardly into the locking position shown by FIGURE: 4. The counterbored portion 41 of the passage 40 issufiiciently large to receive the head 28 of the plug 26, the remainder screwing the plug 26 into the tapped 21 and 22 of the dovetail slot 20 are continuous withno interruptions therein.- This means that each of-the blade roots, including root 33A; of the locking blade 32A, is

restrained against radial movementwith respect to the rotor drum 10 across the entire wall surfaces34 and 35, or 34A and 35A, of the root. As a result, the relatively shallow dovetail slot 20 may beutilized since there is no weak area in which a deeper slot must be utilized to gain sufiicient strength. The means, in,turn,'that therelatively thin walled rotor drum 10 can be used to provide a lighter Weight. structure than heretofore possible. Also, the

root 33A difiers from roots 33 only in that an access passage 40 is provided therein. Since a dovetail of special or unusual form is thus notrequired for the locking blade 32A, a more economical and 'uniform rotorassembly results. In addition, there is no requirement that the entire row of bladesbe movedbircumfereritiali as a unit at any time. 7 A assembly anddisassembly,

' It will be understood that the invention isnot limited to the specific details of 'construction'and arrangement ofthe embodiment illustrated and described herein since changes and modificationswill be obvious: to those skilled in the art For example, the dovetailslots-Ztl may be provided in the periphery of a disc type rotor assembly instead of in the rotor drum 10 of a drum type assembly. Also,'it may, bedesirable on occasion to eliminate the access passage/i0 in the root 33Aiand operatethe locking means from within the interior of the rotor drum 10. It

is therefore intended to cover in the appended'claims all such changes and modifications which mayoccurto those skilledvin the art without departing from the true spirit and scope of the invention. What is claimed as new and desired to Patent of the United Statesis: a a Y 1. A bladed rotor assembly for anraxial fluid flow secure by Letters v machine comprisingagenerally cylindrical blade holding member, said blade holding member-having circumferent ally continuous Walls defining at least one circumferentially extending;dovetail shaped slot in the periphery thereof, a plurality of blades all having identically shapeddovetail roots slidably received in said slot, said blade roots circumferentially filling said slot with adjacent roots .in abutting relationship, the dovetail shapes of said slot and said blade roots being such that the roots are restrained against radial movement With respect to said blade holding member, a loading recess in the radially inward surface of the slot, a selected one :of said blade roots positioned in said slot'radially outward of said loading recess,,an d locking means engaging the radially inward portion'of said selected .blade root'to'. maintain said selected blade root in said slot and to prevent circumferentialmovement of said plurality 'oflblade'roots in said slot. I

' .2. A bladed rotor assembly as defined in claim 1 in which.thewcircumferential extent of said loading recess is sufiicient to receive only one of said blade roots. 7

of the passage 40 being smaller in diameter than the head 28. With the head-28 of the plug 26 received in the.

counterbored portion 41 of the passage40, the blade 32A is held against radial movement relative to the rotor drum 10. It will be obvious that the threaded plug 26v also 3. A bladed rotor assembly for, an axial fluidflow 'machine comprising a generally cylindricalbladeholding member, said blade holding member having circumferentially continuous walls defining at. least one circumferentially extending dovetail'shaped slot in the'periphery thereof, a plurality of blades all-having identically shaped This obviously. 'greatlyincreases ease of I dovetail roots slidably received in said slot, said blade 1 ried by said blade holding member, a selected one of said blade roots positioned in said slot radially outward of said loading recess, said locking means being movable radially outwardly to engage said selected blade root so as to maintain said selected blade root in said slot and to prevent circumferential movement of said plurality of blade roots in said slot and movable radially inwardly so as to'permit insertion and removal of said blade roots into and from said slot.

4. A bladed rotor assembly for an axial fluid flow machine comprising a generally cylindrical blade holding member, said blade holding member having circumferentially continuous walls defining at least one circumferentially extending dovetail shaped slot in the periphery thereof, a plurality of blades all having identically shaped dovetailed roots slidably received in said slot, said blade roots circumferentially filling said slot with adjacent roots in abutting relationship, the dovetail shapes of said slot and said blade roots being such that the roots are restrained against radial movement with respect to said blade holding member, a loading recess in the radially inward surface of said slot, the circumferential extent of said loading recess being sufiicient to receive only one of said blade roots, and radially movable locking means comprising a threaded member rotatably received in a radially extending threaded hole in the radially inward surface of said slot, a selected one of said blade roots positioned in said slot radially outward of both said loading recess and said threaded member, said threaded member being movable radially outwardly to engage said selected blade root so as to maintain said selected blade root in said slot and to prevent circumferential movement of said plurality of blade roots in said slot and movable radially inwardly so as to permit insertion and removal 'of said blade roots into and from said slot.

5. A bladed rotor assembly as defined in claim 4 in which said selected blade root has a passage extending therethrough for providing access to said threaded memher.

6. A bladed rotor assembly as defined in claim 5, said passage radially aligned with said threaded member, and the radially inward portion of said passage counterbored, said threaded member extending into said counterbored portion when said threaded member is in its radially outward position.

6 7. A bladed rotor assembly for an axial fluid flow machine comprising a thin walled cylindrical drum, said cylindrical drum having circumferentially continuous walls defining a plurality of shallow axially spaced circumferentially extending dovetail shaped slots in the periphery thereof, a plurality of blades all having identically shaped dovetail roots slidably received in each of said slots, said blade roots circumferentially filling each of said slots with adjacent roots in abutting relationship, the dovetail shapes of said slots and said blade roots being such that the roots are restrained against radial movement with respect to said drum, a loading recess in the radially inward surface of each of said slots, the circumferential extent or" each of said loading recesses being suflicient to receive only one of said blade roots, and radially movable locking means associated with each of said slots comprising a threaded member rotatably received in a radially extending threaded hole in the radially inward surface of each of said slots, a selected one of said blade roots in each of said slots positioned radially outwardly of the respective loading recess and threaded members, said threaded members being movable radially outwardly to engage the associated selected blade root so as to maintain said selected blade root in said slot and to prevent circumferential movement of said plurality of blade roots in said slot and movable radially inwardly so as to permit insertion and removal of said blade roots into and from said slot.

8. A bladed rotor assembly as defined in claim 7 in which each of said selected blade roots has a passage extending therethrough for providing access to the associated threaded member, said passage radially aligned with said threaded member, and the radially inward portion of said passage counterbored, said threaded member extending into said counterbored portion when said threaded member is in its radially outward position.

References Cited by the Examiner UNITED STATES PATENTS 886,515 5/08 Jude 253-7 2,315,631 4/43 Lloyd 25377 2,918,255 12/59 McGinnis 25 37 7 2,931,625 4/60 Lechthaler et al 25 3-77 3,088,708 5/ 63 Feinberg 25377 FOREIGN PATENTS 23,387 1910 Great Britain. 659,592 10/51 Great Britain. 704,882 3/54 Great Britain. 409,564 2/45 Italy.

JOSEPH H. BRANSON, 111., Primary Examiner.

Claims (1)

1. A BLADED ROTOR ASSEMBLY FOR AN AXIAL FLUID FLOW MACHINE COMPRISING A GENERALLY CYLINDRICAL BLADE HOLDING MEMBER, SAID BLADE HOLDING MEMBER HAVING CIRCUMFERERTIALLY CONTINUOUS WALLS DEFINING AT LEAST ONE CIRCUMFERENTIALLY EXTENDING DOVETAIL SHAPED SLOT IN THE PERIPHERY THEREOF, A PLURALITY OF BLADES ALL HAVING IDENTICALLY SHAPED DOVETAIL ROOTS SLIDABLY RECEIVED IN SAID SLOT, SAID BLADE ROOTS CIRCUMFERENTIALLY FILLING SAID SLOT WITH ADJACENT ROOTS IN ABUTTING RELATIONSHIP, THE DOVETAIL SHAPES OF SAID SLOT AND SAID BLADE ROOTS BEING SUCH THAT THE ROOTS ARE RESTRAINED AGAINST RADIAL MOVEMENT WITH RESPECT TO SAID BLADE HOLDING MEMBER, A LOADING RECESS IN THE RADIALLY INWARD SURFACE OF THE SLOT, A SELECTED ONE OF SAID BLADE ROOTS POSITIONED IN SAID SLOT RADIALLY OUTWARD OF SAID LOADING RECESS, AND LOCKING MEANS ENGAGING THE RADIALLY INWARD PORTION OF SAID SELECTED BLADE ROOT TO MAINTAIN SAID SELECTED BLADE ROOT IN SAID SLOT AND TO PREVENT CIRCUMFERENTIAL MOVEMENT OF SAID PLURALITY OF BLADE ROOTS IN SAID SLOT.

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