US 2221672 A
Description (OCR text may contain errors)
Nov; 12, 1940.
J. H. DORAN Inventor: John H. Dor'an,
"Milli-ll His Attorney- Patented Nov. 12, 1940 The present invention relates "to elasticfiuid turbines, particularly to-bucketwheels and arrangements for securing the buckets against movementon the rim of the wheel.
- In elastic fluid turbines designed for high admission pressures of operating fiui'd,'fthere 'is a tendency for each bucket, particularly in the high pressure stages, to be"'s1ightlydispliicd' from its normal radial positionyasitpasses' each 10 nozzle'to aposition slightlyin'clined the radial plane. This repeated rockingmovement of the buckets on the rim may result in the 'breakingof the bucket cover or of the tenons. The degree of V inclination of the buckets depends, "among other factors, upon the closeness of the" fit between the cooperating dovetails of the'bucket bases and;
the wheel rim. Due to the narrowness offthe" bucket bases, the movement of the' buckets is v j buckets against, tilting or'rocking intl'ieradial plane on the wheel riinQby fasteningltdgether the bas esof adjacentjbuckets ina suitable'fn'ianv accompanied by a relative slidingmotionjbetween 20 the faces of the adjacent bucketbases. 3533 se curing a number of the bucket bases together, the
sliding motion between adjacentfbuckets is'pre eluded and hence also the rockingof'the indi-' vidual buckets relative to the rim. Special p're- 2 5 cautionary measures must be taken in securing the adjacent bucket-bases togetheif in'orderthat the juncture may withstand the severe stresses imposed.
It is an object of the present invention to provide an improved arrangement and method for @ening the buckets by uniting the edges of the bases of adjacent buckets together in such a manner that the buckets willbe held substantially immovable with respect to the rim" and capable of withstanding severe operating conditions.
For a consideration of what I believe to be novel and my invention, attention is directed to the following description-and the claims appended thereto taken in connection with the accompanying drawing. 1
In the drawing, Fig. 1 is a side elevation of a portion of a bucket wheel embodying myinvention; Fig. 2 is a radial-sectional view thereof taken along the line 2-2; Fig. 3 is a cross-sectional view through the basesof the assembly shown in Fig. 1 taken along the line 3--3; Fig. 4
is a radial-sectional view of a portion of a bucket wheel illustrating a second modification of the invention; and Fig. 5 is a fragmentary cross-sectional view taken through the bases of a plurality of adjoining buckets as that shown in Fig. 4 along the line 55.
Referring to the drawing, It indicates the web of the wheel or rotor and H the grooved rim .thereof whichon opposite sides isprovided with annular shoulders'deiining a dovetail portion'lZ" I for retaining the buckets l3 thereon, The bucket. bases'l'4 are provided witha grooved slot defining an inverted dovetail for cooperatively fittingover" the rim dovetail l2 substa'ntiall'y as shownflThe 5 buckets are assembled on therim in'the'usuall,
man'ner, 'one or more filling slot's (not shown) 11 e, ing provided in the rim as iswell understood. The bucket cover or shroud band ,I 5 may be suit}.
theriveted tenons |6.. H
The bucket fastening means describedl forms' v what. is commonly termed'jthe inverted dovetail type of fastening andjin'itself is well-known in ably secured onto the bucket ends as by, K 1 1 15" 9f 10 the rt It m y betaken as'typical of a suitable': 1 type of fastening means in connection with which my inventionmaybe carried'out. I v, According tomy invention I secure the turbine I ner such as y wielding"; The adjacentedges'of j the bases are preferably preliminarily beveled 1 over substantiallythe @ntire length of the bases in; v forderjto providea deep jfusion of metalbetween gs adjacent bases qf' considera ble length capable of withstanding the severe shearing stresses...' To
prevent undue internar'stressin f of bucket.
fused. The weld shrinks when cooling, causing 40' heavy stresses in the weld. if not relieved. The groove I1 allows the necessaryrelief by opening slightly andpermitting bending of the projections l8 that are welded together." Thus, a strong weld is'formed leaving a minimum of internal 45 stresses in either the weld metal or the 'base blocks.
As shown in Fig. 3, the bottom of thewelds terminate at the cracks ls'defining the surfaces of the abutting bases. To preclude these cracks from initiating fissures in the metal of the. welds during the operation of the machine, I prefer to weld the bucket bases together'in the manner according to the second modification ofv this inven-- tion illustrated in Figs. l and 5. Accordingto bevel groove 2| and the passage formed by the grooves 20 is fused so that there will not be a crack at the bottom of the weld. The danger of weld failure due to fissures developing from the cracks I9 is thus effectively negatived and a juncture of great strength is provided.
It is understood, of course, that all of the buckets on the wheel rim may be welded together, or they may be welded together in groups, two or more adjacent buckets comprising each group.
Having described the principle of operation of my invention together with the apparatus which I now consider to represent the best embodiment thereof, I" desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.
What I claim as new and desire to secure by Letters Patent of the United States is:
1. In an elastic fluid turbine having a rotor with buckets having bases dovetailed thereon,
said bucket bases being provided on the opposite outerside walls with expansion grooves extending lengthwise of the bases' and substantially parallel with the edges thereof, the adjoining edges of adjacent bucket bases being welded together along the length of said bases.
am an elastic fluid turbinehaving a rotor buckets having bases removably attached thereto, the faces of adjacent bucket bases abutting tightly against each other, the outer adjoining edges only of said bucket bases being welded together along substantially the full length thereof, means for substantially precluding the development of fissures through said welded portions including grooves in said bucket bases extending parallel to and adjacent said welded portions.
4. In an elastic fluid turbine, a rotorwith buckets having bases removably secured thereto, the faces of adjacent bucket bases abutting tightly against each other, the outer adjoining edges only of said bucket bases being welded together along substantially the full length thereof, means for substantially precluding the development of fissures through said welded portions including a passage formed by grooves provided in said base faces communicating with the inner extremity of said welded portions throughout the full length thereof. g d
5. An axial flow elastic fluid turbine bucket having a blade anda basesecured to the lower" along'the entirelength of the base for receiving welding material, the faces of the base bein formed with grooves parallelwith and in close proximity to the corner portions.
6. An elastic fluid bucket wheel comprising a disk having a, rim, 2. row of buckets'each h'aving a bladeand a base secured to the lower end of the blade and forming a dovetail connected to the rim, adjacent bases abutting each other and each base having four corner portions cut away along theentire length of the base to form together with adjacent bases grooves, welding 0 1 material filling the' grooves along thev entire length of the bases, each of the four faces of each base being formed with grooves parallel with and in close proximity to the. cut-away corner portions whereby the bases of the buckets are integrally united and excessive stresses inthe welded corner portions are prevented.