US 3719432 A
Description (OCR text may contain errors)
March 6, 1973 v s 5 ET AL 3,719,432
ARTICULATED SLEEVE FOR TURBINE BUCKET LASHING Filed April 25, 1971 M K Y CM E .laN N S R O M mwMF T NS M WRDM NOR m I H mm T VP- 8 United States Patent O 3,719,432 ARTICULATED SLEEVE FOR TURBINE BUCKET LASHING Victor S. Musick, Scotia, and Bernard E. Fontaine, Burnt Hills, N.Y., assignors to General Electric Company Filed Apr. 23, 1971, Ser. No. 136,884 Int. Cl. F01d 5/22 US. Cl. 416196 5 Claims ABSTRACT OF THE DISCLOSURE A blade lashing device for a turbine wheel having closely adjacent blades formed with a lug on each blade face. A sleeve is interposed between lugs on opposing blade faces to connect turbines blades. The sleeve is formed with clearances so that it will form an articulated joint between interconnected turbine blades.
BACKGROUND OF THE INVENTION This invention generally pertains to the design of turbomachinery such as steam turbines, was turbines, axial and centrifugal flow compressors and propellers. In particular, this invention relates to bucket or blade lashings in a turbo-machine.
Turbo-machinery may be generally divided into two types. One type of turbo-machine is motivated by a flowing fiuid which passes through a blade path, causing the turbine blades to rotate and which also rotates the turbine shaft. In the other type of turbo-machinery, the shaft rotates, causing the blades to rotate which causes movement of fluid through the turbo-machine. In either type of machine, motive forces are transferred from the shaft to the fluid and vice versa through the turbine blades.
Turbine blades are sometimes long, thin members which are greatly influenced by various forces acting within the turbo-machine environment. These forces, cause stresses in the turbine blades and may be characterized as thermal stresses, centrifugal stresses, bending stresses and torsional stresses. Physical factors which may cause these stresses may be the high speed rotation of a turbine shaft to which the blades are attached, and also the reaction forces upon the blades as high speed fluid contacts the blades, or as the blades are required to motivate a fluid to high speed. These stresses, acting together or in part, may cause severe blade vibration, blade bending, misalignment, or even failure. The end result of these difiiculties is a loss of efficiency, turbine breakdown and even damage to associated turbine parts.
One known method of decreasing turbine blade vibration is to lash all the blades of a turbine wheel together by means of a single hoop or wire. This is sometimes ineffective because the blades tend to vibrate radially and transversely with respect to one another, causing distortion or fracture of the hoop. Another method of decreasing turbine blade vibration is to lash each turbine blade to its adjacent turbine blades by means of a rigid connector. This type of lashing often fails because of high stress concentrations at the point of connection with the turbine blade.
The two aforesaid lashings are also unsatisfactory because even if they should remain intact, there are high torsional stresses introduced into the blade connectors because of blade twisting and untwisting. Also, the use of a lashing wire requires a hole in the blade which may be in a high stress region.
In other prior art designs, it has been known to provide non-rigid connections between blades, but they prevented bucket twisting and untwisting. Consequently, in a transverse plane, these non-rigid connections may have 3,719,432 Patented Mar. 6, 1973 OBJECTS OF THE INVENTION Accordingly, it is an object of this invention to provide an improved turbine blade lashing device which under ordinary operating conditions will be free of transverse loadings.
It is another object of this invention to provide a turbine blade lashing device which will freely allow normal twisting and untwisting of turbine blades.
It is another object of this invention to provide a turbine blade lashing device which will prevent extreme and extraordinary differential blade movement.
It is another object of this invention to provide a blade lashing device which requires a minimal cross-sectional area for interconnecting turbine blades and is relatively simple in construction.
Other objects, advantages and features of the present invention will become apparent from the following description of the preferred embodiment thereof when read in connection with the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING FIG. 4 is a cross section view of the sleeve and lug interconnected.
SUMMARY OF THE INVENTION According to the present invention, a turbine blade lashing is provided for a turbine wheel having a plurality of radially extending blades. A lug is formed on each blade face and opposing lugs are hingedly interconnected by a sleeve. This sleeve is provided with clearances and relief cuts to allow limited untwisting of blades without causing transverse loads to be applied to the sleeve and lugs.
DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, a turbine wheel, shown generally at 11, is formed with a plurality of radially extending blades 13 attached by means of dovetail connection 15 to a turbo machine rotor 17. The manner in which the blades are attached to the rotor is merely illustrative and any known method of attachment may be used in this invention.
Each blade face 19 is formed with a boss 21 and a lug 22 as is shown best in FIGS. 2 and 3. The boss and the lug may be fabricated by any known method and preferably are located at a point from one-half to two-thirds radially outward on the turbine blade. A sleeve 23 is movably mounted between opposing lugs, thereby interconnecting turbine blades. The lugs are generally machined from a portion of the boss which is forged or otherwise attached to the blade face. There is a radius 24 formed on the lug to help promote articulation of the sleeve as will later be described.
As is shown in FIG. 4, the lug and the sleeve member are somewhat similar in cross section. Preferably, the
cross sections of the sleeve and the lug are streamlined to provide a more elficient fluid flow path. A non-circular cross section prevents rotation of the sleeve about the lug which may occur under certain fluid flow conditions causing premature wear of the device.
The sleeve is fabricated with two side cuts 25, one cut at each end of the sleeve member, one cut being diagonally opposite and parallel to the other cut when viewed from a plan view as shown in FIGS. 2 and 3. The cuts each extend from either side of the sleeve to a point approximately midway between the sides of the sleeve. These cuts in the sleeve permit the blades to twist and unt-wist for a limited amount without developing transverse loads on the lugs and sleeve which ordinarily can be very significant.
As viewed in FIG. 4, the lug and the interior circumference of the sleeve have clearances 27 and 29 provided therebetween. The clearance 27 acting in concert with the radius on the lug allows articulation in the transverse direction as blades twist and nntwist. The clearance 29 is more pronounced when the machine is up to speed since this throws by the sleeve radially outwardly and this permits articulation in the radial direction between adjacent blades. Finally, clearances 31 between each end of the sleeve and the boss on the blade face further allow for blade articulation.
While the drawings sequentially show the blades in a twisted position at standstill, this being the preferred construction, allowing the blades to untwist when the machine is up to speed, it is also possible that the blades could be aligned in an untwisted mode at standstill so that they would twist at speed.
The device operates as follows. As a turbo machine rotates to speed, the blades attached to the rotor will have a tendency to either tiwst or untwist, depending upon the fabrication of the blades to the rotor. As is shown in a sequential viewing of FIGS. 2 and 3, the cuts on the sleeve, the clearances between the sleeve and the boss on each blade face, the radius on the lug and the associated interior clearances all allow the blades to move relative to one another a permissible amount without transversely loading the lugs and sleeve. In effect, this invention allows an articulating relation to exist within the blade lashing rather than introducing transverse stresses into the lashing.
Since the sleeve is supported on the lugs, there is a frictional damping eifect between adjacent blades which reduces vibratory stresses while the machine is running.
While there is shown what is considered at present to be the preferred embodiment of. the invention, it is of course understood that various other modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.
What is claimed is:
1. A blade lashing device for a turbo machine including a plurality of radially extending rotor blades mounted circumferentially about the turbine rotor, each rotor blade mounted adjacent another rotor blade to provide closely adjacent opposing blade faces; each opposing blade face formed with a boss having a lug extending therefrom; said blade lashing device including:
a sleeve interposed between each pair of opposing blade faces and mounted on each pair of opposing lugs;
a cut formed at each end of the sleeve, one cut diagonally opposite the other cut; and,
a clearance provided in the radial direction, with respect to the rotor axis, between each boss and the sleeve ends.
2. The blade lashing device as described in claim 1, wherein each cut extends form either side of the sleeve approximately midway between the sides of the sleeve.
3. The blade lashing device as described in claim 1, wherein each lug is formed with a radius.
4. The blade lashing device as described in claim 1 wherein there are clearances formed between the lug and the interior circumference of the sleeve.
5. The blade lashing device as described in claim 1 wherein the lug and the sleeve are non-circular in cross section.
References Cited UNITED STATES PATENTS 1,749,449 3/1930 Stevenson 416-196 3,180,616 4/ 1965 Miller 416-196 3,314,652 4/ 1967 Geberth et al 416-196 3,327,995 6/1967 Blackhurst et al 416-196 FOREIGN PATENTS 1,092,988 11/ 1954 France 416-196 890,884 9/1953 Germany 416-196 22,740 1913 Great Britain 416-196 623,525 5/1949 Great Britain 416-196 843,287 8/1960 Great Britain 416-196 EVERETIE A. POWELL, Jn., Primary Examiner