US2918255A - Elastic fluid utilizing apparatus - Google Patents

Description

Dec. 22, 1959 R. E. MCGINNIS Filed March 15, 1957 AT TO RN EY United States ate-at fihce 2,918,255 Patented Dec. 22, 1959 ELASTIC FLUID UTILIZING APPARATUS Ralph E. McGinnis, Folsom, Pa., assignor to WestinghouseElectric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 15, 1957, Serial No. 646,427

7 Claims. (Cl. 253-77)- This invention relates to bladed apparatus and more particularly to a structure for locking a-last blade ofa row of blades to a supporting structure, and has for an object the provision of improved structure of the aforesaid kind having increased strength. 7

Some of the last blade locking devices utilized heretofore have required a subtanstial axial width for the required strength to safely secure the last bladeto the support. This has meant that, in multiple blade row structures, the space between adjacent blade grooves has had tobe increased beyond that which would otherwise be required or, in the alternative, reducing the portion of the support between the entering slot and the adjacent blade groove to a degree which would increase thepossibility of cracks occurring in the support. When the spacing between adjacent blade rows is increased,- the overall length of the supporting structure is increasedra substantial factor in the cost of the apparatus in which the sup porting structure is to be installed.

As is well known, the end walls of the entering slot are stronger than the side *walls'and may, therefore, safely withstand a greater load. It is preferable, therefore, that the securing means engage the end walls and not the sidewalls of the entering slot.

.One embodiment of the pre'sentinvention provides the support with a row of .blades secured in a circumferential groove. The blade groove is' provided with an entering slot which is wider than the blade groove and through which the blades are inserted. The last blade is secured within the entering slot, as hereinafter described.

The entering slot is defined by-parallelside walls and parallel end walls, each of the latter being. provided with a semi-circular groove having a plurality of serrations. The last blade is provided with a substantiallyrectangular rootportion having parallel side walls and parallel'end walls,-each of the latter having a semi-circular groove provided with serrations similar tothe serrations in the endwalls of the entering slot. Whenthe rootof thelast blade is fully inserted in the entering slot,.the semi-circular grooves provided in the root are aligned with the semi-circular grooves provided in the sidewalls, thus forming a circular openingat each end of the last blade root. Within each of the circular openings is placed a pair of cooperating semi-cylinders provided with serrations adapted to mate with the serrations in the openings. During assembly of the last blade locking device, two semi-cylinders are positionedin the semi-circular grooves of the slot end walls with the flat surfaces of the semicylinders in the planes ofthe slot end walls. The two remaining semi-cylinders are positioned in the grooves df'the last blade end walls with their flat surfaces parallel to those of their cooperating semi-cylinders and the blade is then inserted in the slot. Thereafter, each pair of cooperating semi-cylinders are rotated as a unitninety jdeg reesgthereby locking the blade. The semi-cylinders are disposed within the circular grooves so that the serrations of each semi-cylinder engage and mesh with the 2 serrations of two of the semi-circular grooves. In manner, the'last blade is retained in proper position.

The foregoing and other objects are effected by the invention as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of this application, in which:

Fig. 1 is a perspective view of a portion of a bladed rotor formed in accordance with the invention and illustrating a part of the entering slot;

Fig. 2 is a fragmentary plan view of the last blade and the two adjacent blades;

Fig. 3 is a sectional view taken along the line III -III of Fig. 2, looking in the direction indicated by the arrows;

Fig. 4 is a perspective view illustrating the last blade partially inserted in the entering slot; and

Fig. 5 is an exploded view of a portion of the locking device, with one of the locking members rotated ninety degrees from the position occupied when being assembled in the entering slot.

Referring to the drawing in detail, and in particular to Fig. 1, there is illustrated a portion of a steam turbine rotor 12 provided with a suitable annular undercut groove 14, generally of an inverted T shape, within which is placed a row of blades 16. Each of the blades 16 has a platform portion 18, a vane portion 19 and a rootportion 20 complementary to and retained within the groove 14 Referring to Figs. 2 through 4, there is illustrated in detail the portion of the blade groove 14 which is widened into a transverse groove or entering slot 21 by which the blades 16 are inserted into the groove 14, as is Well known in the art. Within the entering slot 21, there is placed a last blade 22 having a root portion 24, hereinafter described in detail, which differs from that of the other blades in the blade row.

The entering slot 21 is provided with a pair of parallel spaced side walls 26 and a pair of opposed parallel end walls 27. The end walls 27 have approximately the same configuration and the subsequent description will, in the interest of clarity and brevity, be confined to one of the end walls 27, it being understood that the other end wall 27 is similarly constructed.

The end wall 27 is formed with a semi-circular groove 31 having serrations 33 providing shoulders. The diameter of the semi-circular groove 31 is smaller than the distance between the walls 26 so that vertical marginal portions 36 are formed at right angles to the walls 25.

The last blade 22 includes a platform portion 18, a vane portionw, and root 24. The latter is substantially rectangular, as distinguished from all of the other blade roots 20 and comprises parallel side Walls 41 and parallel end walls 44. The size and shape of the lastblade root'24 issubstantially the same as that of the entering slot 21 so that it may be closely housed in the latter; Tne root 24 is substantially symmetrical about its. longitudinal axis and, in the interest of clarity and brevity, the subsequent description will be. confined to one of its end walls 44, it being understood that the other end wail 4-4 is similarly constructed.

The end wall 44 is provided with asemi-circular groove .7 having serrations or projections 50 providing shoul' ders that are similar to the serrations33bf the slot end wall; The diameter of the semi-circular groove47is the same as the diameter of the semi-circular groove 31 with the result that the end Wall 44 has marginal portions 53, substantially the same as marginal wall portions 36 of the slot end wall.

When the last blade root is disposed withirilthel ent'efi ing slot 21 the semi-circular groove 47 is in axial alignment with the semi-circular groove 31, the two grooves thus forming a circular ,or common opening 56, as best illustrated in Figs. 2 and 3. In addition, the serrations 33 and 50 of-the opening 56 are aligned to form uniform circumferential projections which extend radially inwardly.

As best illustrated by Figs. 2 and 3, the last blade platform 18 overhangs the semi-circular groove 47 as at marginal portion 59.

A locking cylinder is located within the circular opening 56 and is split into two members or semi-cylinders 64 and 65. The semi-cylinder 64 is providedwith a head or fiat surface 71 having a suitable socket '72. The

semi-cylinder 65 is shorter than the semi-cylinder 64, as best illustrated by Figs. 3 and 5, and fits under the head 71.

The semi-cylinders 64 and 65 are provided with serrations or projections 74 on the portions of the cylindrical surfaces of the semi-cylinders below the head 71, the serrations 74- providing shoulders meshing with the serrations 33 and 50 of the circular opening 56. The semi-cylinders 64 and 65 are also provided with abutting fiat faces 75. All of the hereinbefore-mentioned shoulder-providing serrations are preferably formed with well rounded edges and fillets in order to reduce stress concentrations, as is well known.

When all of the blades 16 have been properly positioned in the groove 14, the last blade 22 is secured as follows:

The semi-cylinder 64 is placed within the groove 47 of the last blade root so that the serrations mesh and the flat surface 75 is in the same plane with the marginal wall portions 53. The other semi-cylinder 65 is placed within the groove 31, so that the serrations mesh and the surface 75 is in the same plane with the marginal wall portions 36.

The last blade is first aligned with the entering slot so that the fiat surface 75 on the semi-cylinder 64 is parallel to the flat surface on the semi-cylinder 65, and then lowered to the bottom of the entering slot. The semi-cylinder 64 is subsequently rotated by a suitable tool inserted within the socket 72, forcing the corresponding semi-cylinder 65 to rotate. Preferably, the semi-cylinders are rotated 90. Thus, the serrations 74 of semi-cylinders 64 and 65 within the circular opening 56 engage one-half of each of the serrations 33 and 50 of the semi-circular grooves 31 and 47. In this manner, the last blade is secured against radial movement relative to the axis of rotation of the rotor. In order to secure the semi-cylinders in blade-blocking position, each head 71 is peened, as at 77, into engagement with the upper portion of the root 24 (Fig. 2).

The foregoing construction provides a last blade locking means in which the load imposed upon the rotor, due to the centrifugal force upon the last blade during operation, is assumed by the portion of the rotor best capable of safely withstanding the load, that is, at the end walls 27 of the entering slot. It will be noted that, in the present construction, there are no serrations along the walls 26 nor along the edge portions 36. In view of the foregoing, the walls 26 assume none of the centrifugal load and the vertical marginal edge portions 36 assume only that part of the centrifugal load carried by the portion of the serrations 33 adjacent the edge portions 36. In addition, the present construction results in an entering slot of minimum width. Hence, the distance between the groove 14 and an adjecent groove (not illustrated) may be smaller than that utilized heretofore with other last blade locking structure.

The foregoing construction provides a last-blade locking structure in which two serrated members are provided at each side of the last-blade root. These serrated members engage the rotor at a location where the loads may be safely assumed by the rotor.

While the invention has been shown in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof.

What is claimed is:

1. In a bladed machine, a rotor having an undercut groove, a plurality of blades received in said groove, said groove being provided with an entering slot for the insertion of said blades into the groove, a last blade disposed in said entering slot, said last blade including a root having a platform, and a locking device comprising at least two members each of which engages said last blade root and said rotor, said members having mutually abutting faces, said platform having a portion overhanging a portion of each of said members.

2. In a bladed machine, a rotor having a groove, a plurality of blades mounted in said groove, means for securing said blades to said rotor, said groove being provided With an entering slot for the insertion of said blades in said groove, said blades including a last blade disposed in said entering slot, said last blade including a root, said root and rotor having a common opening, said means including a locking device Within said opening, said locking device comprising members each having a projection, and a projection on said root and rotor extending into said opening, said members having abutting faces, said members being movable from one position in which they are slidable relative to each other along said abutting faces for generally radial movement of said last blade relative to said rotor to another position in which each of said members engages said root and said rotor projection.

3. In bladed apparatus, a rotor having an undercut groove, a row of blades carried in said groove, said groove having a portion defining a transverse opening for the insertion of said blades into said groove, said blades including a last blade disposed in said transverse opening, said last blade including a root portion having walls, one of said walls having a groove provided with a shoulder, said transverse opening being partially defined by end walls, one of said end walls having a groove provided with a shoulder, said last blade root being positioned within said transverse opening so that said first mentioned groove and said second mentioned groove jointly define an opening on one side of said last blade root, and locking members disposed within said opening, said members each having a shoulder mating with said shoulders of said first and second mentioned grooves, said locking members having abutting faces, said members being movable from one position in which they are slidable relative to each other along said abutting faces for generally radial movement of said last blade relative to said rotor to another position in which the shoulders of each of said members engages the shoulders of said root and said rotor.

4. In bladed apparatus, a rotor having blades mounted thereon, said rotor having a groove and a transverse opening for the insertion of said blades in said groove, means for securing said blades to said rotor, said blades including a last blade disposed in said transverse opening, said last blade including a root portion having walls provided with grooves having projections, said root having a platform, said transverse opening being partially defined by walls provided with grooves having projections, said last blade root being positioned within said transverse opening so that the first mentioned grooves and the second mentioned grooves jointly form openings, said means including locking members having projections and disposed within said openings, said members being disposed within said openings so that the projections on each member engage the projections of one of the first mentioned grooves and of one of the second mentioned grooves, and said platform overhanging a portion of said members.

5. In an elastic fluid turbine, a rotor including wall structure defining an annular groove, an annular row of blades mounted in said groove, means for securing said blades to said rotor, additional wall structure defining a widened portion of said groove providing an entrance opening for said blades, said blades including a last blade having a root portion disposed within the widened portion of said groove, said last blade root having side walls provided with first semi-circular grooves, said widened portion of said groove being partially defined by end walls provided with second semi-circular grooves, said first and second mentioned semi-circular grooves having serrations, said first and second mentioned semi-circular grooves forming a pair of circular grooves, said means including one pair of semi-cylinders disposed in each of said circular grooves, said semi-cylinders having serrations meshing with the serrations of said semicircular grooves, said semi-cylinders having abutting faces, said semi-cylinders being movable from one position in which the serrations of one of said semi-cylinders engage only the serration of one of said semi-circular grooves and are slidable relative to each other along said abutting faces for generally radial movement of said last blade relative to said rotor to another position in which each of said semi-cylinders engages said root and said rotor serrations.

6. In an elastic fluid turbine, a rotor including wall structure defining an annular groove, an annular row of blades mounted in said groove, means for securing said blades to said rotor, additional wall structure defining a widened portion of said groove providing an entrance opening for said blades, said blades including a last blade having a root portion disposed within the widened portion of said groove, said last blade root having side walls provided with first semi-circular grooves, said widened portion of said groove being partially defined by end walls provided with second semi-circular grooves, said first and second mentioned semi-circular grooves having serrations, said first and second mentioned semicircular grooves forming a pair of circular grooves, said means including one pair of mating semi-cylinders disposed in each of said circular grooves, said semi-cylinders having serrations meshing with the serrations of said semi-circular grooves, each pair of said semi-cylinders having flat abutting faces, and each pair of said semicylinders being rotatable from one position in which the serrations of one of said semi-cylinders engage only the serrations of one of said semi-circular grooves and one semi-cylinder is slidable relative to the mating semicylinder along said abutting faces for movement of said last blade into and out of said widened portion of said groove to another position in which each semi-cylinder of each pair engages partly with the serrations of one semi-circular groove in said side wall and partly with the serrations of one semi-circular groove in said end wall.

7. In an elastic fluid turbine, a rotor including wall structure defining an annular undercut groove, an annular row of blades mounted in said groove, additional wall structure defining a widened portion of said groove providing an entrance opening for said blades, said blades including a last blade having a root portion disposed within the widened groove portion, said last blade root having side walls provided with first semi-circular grooves, said widened groove portion being partially defined by end walls provided with second semi-circular grooves, said first and second mentioned semi-circular grooves having serrations, said first and second mentioned semi-circular grooves jointly forming a pair of circular grooves, and one pair of mating semi-cylinders disposed in each of said circular grooves, said semi-cylinders having serrations meshing with the serrations of said semi-circular grooves, each pair of said semi-cylinders having fiat abutting faces, and each pair of said semi-cylinders being rotatable from one position in which the serrations of one of said semicylinders engage only the serrations of one of said semicircular grooves and one semicylinder is slidable relative to the mating semi-cylinder along said abutting faces for movement of said last blade into and out of said widened groove to another position in which each semi-cylinder of each pair engages partly with the serrations of one semi-circular groove in said side wall and partly with the serrations of one semi-circular groove in said end wall, said last blade having a platform having two marginal portions, each of said marginal portions overhanging a portion of each pair of semi-cylinders.

References Cited in the file of this patent UNITED STATES PATENTS 1,687,891 Ray Oct. 16, 1928 2,315,631 Lloyd Apr. 6, 1943 FOREIGN PATENTS 704,882 Great Britain Mar. 3, 1954 718,014 Germany Feb. 28, 1942 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 2,918,255 December 22, 1959 Ralph E. McGinnis Column 3, line 52, for "blade-blocking" read bladelocking line 70, for "adjecent" read adjacent Signed and sealed this 21st day of June 1960,

(SEAL) Attest:

KARL Ho AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents

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