US 2952442 A
Description (OCR text may contain errors)
Sept. 13, 1960 E. P. WARNKEN ROTATING" SHROUD 5 Shets-Sheet 2 Filed May 28, 1957 IN VEN TOR. ELMER I? WARN KEN BY Sept. 13, 1960 filed May 28, 1957 E. P. WARN KEN ROTATING SHROUD 3 Sheets-Sheet 3 INVENTOR.
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United States Patent ROTATING SHROUD Elmer P. Warnken, Cincinnati, Ohio, assignor, by mesne assignments, to Studebaker-Packard Corporation, South Bend, Ind., a corporation of Michigan Filed May 28, 1957, 581'. No. 662,229 1 Claim. (11. 253-77 This invention relates to shrouds for securing and rigidifying the outer ends of a row of blades in a rotor for an aircraft engine, or the like.
Rotor blades have a tendency to gain or lose tip angle when of substantial size, especially length, and when rotating at high speeds; therefore, it is an object of this invention to provide a shroud that will so secure and rigidity the tips of the blades that the proper tip angle is maintained in operation.
A further object of this invention is to provide a shroud which controls the tip amplitude during flight conditions to reduce the tendency toward blade deflection and to minimize vibration of the rotor blades.
A further object of this invention is to provide a rotor shroud which ties together the blades in a row to allow every blade in the row to accept its share of mechanical loads which develop during rotating stall of the blades, i.e., when only a portion of the blades are in aero-dynamic stall. I A further object of this invention is to provide a rotor shroud whichmaintains a minimum tip clearance between rotating portions of the compressor and the casing thereof, and thereby minimizes recirculation of air around the tips of the blades.
\A further object of this invention is to provide a light- .Weight segmental shroud that can be readily assembled with rotor blades.
A further object of this invention is to provide a shroud which is mounted .on but not attached to the rotor blades and in which bushings in the shroud are provided with radial slots into which tips of the rotor blades fit so that the shroud can expand or contract with respect to the blades without causing buckling of the blades or shroud.
A further object of this invention is to provide a shroud which is held together by a continuous winding which accepts the load imposed by rapid rotation.
A further object of this invention is to provide a segmental shroud having outwardly projecting channel-shaped segments mounted on the tips of the blades, the segments forming an air-seal with the casing of the rotor, the segments being held together by a resin-impregnated winding of substantially continuous glass fibre rovings, or the like, wound between the flanges of the channel-shaped segments and bound by the resin.
The above and other objects and features of the invention will in part be apparent and will in part be obvious to those of ordinary skill in the art to which this invention pertains from the following detailed description, and the drawings, in which:
Figure 1 is a fragmentary view in transverse section of a portion of the air compressor section of a jet aircraft engine provided with rotor blade shrouds constructed in accordance with an embodiment of this invention;
Fig. 2 is a fragmentary view of a portion of the rotor blades and rotor shroud of one row of rotor blades;
Fig. 3 is a view in section taken on a line III-III in Fig. 2;
2,952,442 Patented Sept. 13, 1960 Fig. 4 is a fragmentary exploded view of the rotor shroud and one blade of the rotor;
Fig. 5 is a view in side elevation of a blade tip bushs;
Fig. 6 is a view in elevation showing the interior of a fragmentary portion of a shroud of a rotor constructed in accordance with another embodiment of this invention;
Fig. 7 is a view in section of the shroud illustrated in Fig. 6 and of a portion of a device for making the shroud, the section being taken on the line VII-VII in Fig. 6; and
Fig. 8 is a view in section of the shroud taken along the line VIII-VIII in Fig. 6, a portion of one blade being shown in association therewith.
In Figure l a portion of the compressor section 10 of a jet aircraft engine is illustrated. The compressor section includes an outer casing 12 in which stator blades 13 are mounted. Within the casing is a rotor 14 provided with rows of rotor blades 16.
As indicated in Fig. 2, a plurality of blades 16 comprises a row. The outer ends of the blades 16 of each row are secured to a rotating shroud 17. As shown in Fig. 4, the shroud 17 includes a plurality of blade-receiving channel-shaped segments 18 forming a ring or shell and a plurality of hoop-receiving channel-shaped segments 19 forming a second ring or shell. The segments 18 and 19 are formed of resin-impregnated fibre glass cloth molded to channel shape, as shown. The angle subtended by each segment may be of any desired size,
but preferably is degrees or less, but may be any size up to 360 degrees. Preferably, the blade receiving segments 18 are short segments, each of which receives the end of one blade, and the hoop-receiving segments 19 are approximately 60 degree segments. The segments 19 are slightly narrower than the segments 18, as indicated in Fig. 3 and are received between flanges 21 and 22 of the blade-receiving segments.
The rows of segments are separated by a cellular member or honeycomb 23 of perforated, light-Weight, rigid material, such as resin-impregnated fibre glass or perforated aluminum of light weight but sufficiently rigid to maintain the segment rings separated when the rotor rotates at high speed. Preferably, the honeycomb is formed of aluminum which has cut away portions or perforations to give it light weight, of the order of approximately eight pounds per cubic foot.
The segments of the blade-receiving ring are provided with slots 26 in which bushings 27 are received. Each of the bushings 27, as shown in Fig. 3, is provided with a relatively deep slot 28 in which the tip of one of the blades 16 is received. In addition, each bushing is provided with an annular slot or groove 29 in which the edges of the segment are received. As shown, the outer face 31 of the bushing conforms in shape to and engages the outer segment 19. The bushings may be formed of a hard, stiff, durable plastic material, such as nylon or Teflon. The honeycomb is also provided. with a slot 32 of sufiicient size to receive the bushing. The honeycomb thereby aids in holding the bushing in place.
The blade-receiving slot of each bushing extends substantially radially of the shroud segments, and the tips of the blades are slidably received in the slots of the bushings.
The segments are cemented together and to the honeycomb material. As shown in Fig. 3, the edges 33 and 34 of the flanges of the segment rings 18 and 19 are substantially aligned. As shown in Fig. 1, the shroud is received in a slot 35 in the inner face of the casing, and the edges of the flanges of the segment rings are very closely spaced from the base of the slot 35 to form an air-seal between the rotating elements and the casing.
The contour of the inner races of the segments 18 is shown as a substantially smooth curve, but the contour may be varied, particularly at the area adjacent the slots 26 as required to give a proper aerodynamic shape.
The segments of the shroud are reinforced and held together by a retaining winding 36 of elongated fibres of resin impregnated glass, or the like. Winding 36 comprises many turns on the segments in the space between the flanges of the channels. Preferably, as shown in Fig. 3, the thickness of the winding is less than the depth of the flanges 37 of the hoop-receiving segments so that a short air gap G between the winding 36 and the casing 12 will be formed, as shown in Fig. l. The winding may be made with fibre glass rovings impregnated with a suitable resin such as an epoxy resin or a phenolformaldehyde resin. The rovings are wound numerous times around the segment rings to provide a substantially continuous winding or hoop of great strength which holds the segments firmly in assembled relation.
If desired, all portions of the shroud may be formed of metal, and'the winding may be formed of stainless steel wire, or the like. When steel wire is used for the winding, adjacent convolutions may be locked together by an appropriate solder, such as silver solder, or the like. The solder may be applied to the Wire before it is wound, and, then, after the rotor has been wound, the rotor may be heated to cause fusion of the solder to tightly grip the wire and hold it in place.
When the rotor is in operation, the shroud may ex- \pand slightly because of centrifugal force, and, as it expands, the bushings can slide outwardly of the blade tips without causing distortion of the blades or of the shroud.
In Figs. 6-8 inclusive is shown a shroud 41 constructed in accordance with another embodiment of this invention. The shroud 41 includes a central strip or annular shell 42 which may be formed of strong, durable, resilient material such as one of the plastic materials, such as nylon and Teflon. Surrounding the strip 42 is a-ring or retaining band 43 made up of a filamentary winding which may be formed of elongated, resin-impregnated, glass fibres or other suitable filamentary material. The Winding ring 43 is formed on a mandrel 44 (Fig. 7) which may be generally cylindrical and has an annular shoulder 46. A ring 47 slides on one end of the mandrel and co-operates with the shoulder 46 to form an annular slot in which the winding is formed.
The central strip 42 may be formed flat. Aplurality of equally spaced sockets 48 are formed in the central strip. The central strip is wound around the mandrel 44, the central strip being just long enough to form a complete ring. Then the resin-impregnated filamentary material is wound in the slot surrounding the strip 42. The assembly may be heated to set the resin to hold the filamentary material in place. Then the ring 47 and the assembly are slid off the mandrel 44 and the resin may be cured in the usual manner to form the completed shroud 41. The shroud 41 is mounted on blades 49, only one of which is shown, in the manner indicated in Fig. *8. Each blade 49 is provided with a tang .51 at-the outer end thereof. The tang '51 fits in and is .slidably received in one of the sockets 48.
The shroud illustrated in Figs. 6-8 inclusive operates in the same manner as described earlier. As shown, the edges of sockets extend substantially radially, so that, as the shroud expands slightly during operation, the shroud can move out or in along tangs 51, while the shroud holdsthe blades in proper position.
It will be apparent to those skilled in the art to which this invention pertains, that the illustrated embodiments may be modified or changed without departing from the spirit and scope of the appended claims.
Therefore, what I claim as new and desire'to secure by Letters Patent is: l
A rotor which comp-rises a plurality of radially extending rotor blades, an annular shell surrounding the rotor blades, there being a plurality of sockets in said annular shell extending radially of and loosely receiving in radially overlapping relation the tips of the rotor blades, the tips of the rotor blades being slidable lengthwise of the sockets, whereby the annular shell may expand and contract independently of the rotor blades, the sockets terminating short of the outer face of said annular shell, whereby relative sliding movement of the shell and the rotor blades is limited, and a substantiallycontinuous winding of filamentary material outboard of and overlying the sockets and embracing theannular shell to form a retaining band surrounding the annular shell.
References (Zited in the file of this patent UNITED STATES PATENTS 764,450 Geisenhoner July 5, 19.04 1,547,836 Steenstrup July 28, 1925 2,681,788 Wosika June 22, 1954 FOREIGN PATENTS 13,881 Great Britain 1905 228,250 Germany Nov. 5, 1910 267,405 Great Britain Mar. 17, 1927