US1187452A - Steam-turbine. - Google Patents

Description

C: L. shARCH.

` STEAM T URBINE.

APPLICATION FILED AUG-I3. 1913. RENEWED SEPT.20 |915.

V ment in Steam-Turbines, of lwhich the fol- CHARLES EDWIN SEARCH, OF MILWAUKEE, WISCONSIN, ASSIGNOR TO ALLIS-CHALMERS MANUFACTURING COMPANY, OF. MILWAUKEE, WISCONSIN, A CORPORATION OF DELAWARE.

STEAM-TURBINE.

Specification of Letters Patent.

Patented June 13, 191e.

Application filed August 13, 1913, Serial No. 784,780. Renewed September 20, 1915. Serial No. 52,114.

To all whom t may concern:

Be it known 'that I, CHARLES EDWIN SEARCH, a citizen of the United States, residing at Milwaukee, in the county of Milwaukee and State of Wisconsin, have invented a certain new and useful Improvelowing is a specification.

This invention relates to steam turbines and more particularly to the means for securing the shroud strip to the blade and with especial reference to the finished condition of the shroud strip.

The object of the invention is to secure a shroud strip to the ends of a plurality of turbine blades in a secure manner with facility of fastening same and yet preserving certain advantages of the completed structure as will be pointed out hereinafter.

Heretofore it has been usual to secure the shroud strip to a plurality of turbine blades by riveting over integral tenons formed on the ends of the blades, punching corresponding holes in the shroud strip through which the tenons are first passed and which they closely fit, before the riveting over is done. This was a convenient means of fastening and possessed certain advantages that it is unnecessary here to point out. The defects of this mode of fastening were that the shroud strip was not so securely held as to prevent certain vibrations which the present invention absolutely prohibits. Ano-ther disadvantage was that in some cases it happened that when some of the turbine blades were a few thou- `sandthsof an inch shorter' than they should have been, there was no support of the shroud strip portion immediately adjacent the end of the short blade, during the riveting of the tenon on that blade. The consequence was that either the shroud strip was distorted in order to bring that portion into contact with the end of the short blade, or the tenon was riveted over at a point so that a space was left between the shroud vstrip portion and the shoulder yof the short blade, or both of these defects were present at the same time.

Another objection to the riveting-over of tenons integral with the blades was that the rivet heads served as a series of paddles during the rotation throughl the expansive fluid under pressure. It has even been alleged by certain experts that the liquid of condensation was present during thel rotation, immediately adjacent the shroud strip,

strips having teeth bent over to conform to the section of the blades have been proposed to be located adjacent the ends of the blades,l but in either case these devices reduce the effective length of the blades, and also place an obstruction in the path of the elastic fluid.

In the case of the wire, the baiing effect to prevent the fluid from passing around the ends of the blades is also not possible therewith, which, as is well known, must be prevented in the Parsons type of turbine. The blades in that case must run close to the spindle or cylinder. .These wires and strips have in some instances been proposed to be brazed or soldered into place to the end blades of a segment, but always adjacent the ends of the blades where it is objectionable as noted. It has also been proposed to weld thin supporting strips to or near the ends of blades and then solder heavy stiffening rings to the strips, but these constructions are indicated as for producing unitary vane structures for ready application to or removal from a turbine. These would therefore be for foundation strip purposes and would not produce a single thin strip for shroud baffling purposes.

In the present invention, an absolute fastening means is'provided for a single shroud strip, the shroud strip may for baffling purposes run close to the spindle or cylinder as the case may be, and thus prevent leakage, and a smooth construction of shroud strip is had preventing all paddle brake action to the rotation.

Referring to the drawing- Figure 1 is a plan view of a segment of blades partly broken away. Fig. 2 is an elevation of same partly broken away and in section. Fig. 3 is a transverse section of the same. Figs.- 4 andv 5 are transverse sections of modifications.

Referring to the drawings, blades l is shown in union with e follada-- tionvstrip 2, and this may be any well known means of fastening the roots of the blade to the strip for insertion later into the spindle or cylinder 3, for instance, by calking-in the strip 2 into a groove in thev spindle or cylinder.

At the outerend of the plurality of blades 1 is located a shroud strip4 conveniently shown of channel section, and this stripv is secured by means of soldering or brazing, to the extreme ends of the blades 1 against which itfabuts. It may be welded in place, but this would objectionably distort the parts due to the extreme heat required.

In order to insure that the blades are correctly spaced and angled about their axes, the blades are shown in'Figs. 3 and 4 as having integral tenons lformed thereon by .cutting away the two sides of each blade end, leaving the tenon preferably with two parallel sides-and with two curved sides, the latter lying in the blade surfaces. The

"shroud strip is correspondingly punched `the channel sides.

with holes of the same cross section as that of the tenons and these latter extend into and fill these holes in the shroud strip, leaving the ends of the tenons in Fig. 3 flush with the surfaceof, the shroud strip between In Fig. 4 the tenon is headed over as usual. In Fig. 5 the tenon is omitted and the yspacing and angling of blades aresecured by other means. Both the devices of Figs. 4 and 5 are less preferable, that of Fig. 4 because of the paddle action of the tenon heads, and that of Fig. 5 because of the necessity of some external means of spacing and angling of the blades. The

lmodification of Fig. 4 may be considered an improvement of the existing prior art of I riveting over of tenons and may be further improved by removing the tenon heads alto ether.

T e ends of the blades 1, as thus coacting with the shroud strip 4, are then soldered to the strip, preferably by having the'segment of blades inverted so as to bring the shroud strip 4 at the bottom. This will more con? veniently serve to insure, that the liquid solder flow between the ends of the blades and the strip. It will as ay matter of fact, build upslightly along the margin of the blade end where it touches the strip so as to. form a fillet `5, as indicated in Figs. 2 and 3' For small blades which are close together,'such ,as those at the high pressure end of the turbine, it has been found more convenient'to perform the soldering operation having the segment of blades in such a position as to bring the shroud strip 4 at the top. In such case the solder will flow through the interstice between the tenon and the hole i'n the shroud strip.- It is entirely unnecessary to have any connection' between the tenon and the shroud strip, as it has been found by actual test that the soldered connection between the end of the blade and the shroud strip is stronger than any tension stress to which the blade may be subjected, even to an actual fracture by tension of the blade itself. 'It has been found shroud strip is made in the form of a ringA shrunk vor screwed on, has not been'heretofore considered because that has been superseded by the riveted-over tenon type' heretofore discussed. Such a strip is notoriously L objectionable because the screws become loose, are too large for commercial application to small blades, or the strip itself Vbecomes detached, and generally and especially the strip cannot be prevented from becomin loose on account of the vibration to which the parts are subjected in use.

It should be understood that it is not desired to be limited to the exact details of con struction shown and described, for obvious modifications will occur to a person skilled in the art.

Itis claimed and desired to secure by Letters Patent,-

1. The combination of a: plurality -of blades and a single thin shroud strip abutting the ends of said blades at least at end surfaces adjacent both edges of said blades and soldered thereto.

2. The combination of a plurality of blades and a single thin shroud strip coacting with the extreme ends of said blades at least at -end surfaces adjacent both edges of said blades and soldered thereto.

3. The combination of a plurality `of blades and a single thin shroud strip having means for spacing said blades and for determining their proper angle, said strip being soldered to the extreme ends ofsaid blades, at least at end surfaces adjacent both edges of said blades.

4. The combination of a plurality of- 'blades and a single thin shroud strip having means for spacing' said blades, said strip being soldered to the extreme ends of said blades, at'least at end surfaces adjacent both edges of said blades.

5. The combination 'of' a plurality of blades and a single thin shroud strip having spacing and angle-determining means for said blades, said strip being soldered to the ends of said blades and presenting a smooth surface of revolution throughout.

6. The combination of a plurality of blades and a single thin shroud strip hav- 130 throughout.

ing spacing means ffor said blades, said blades and presenting a smooth surface ot revolution throughout, y

7 The combination of a plurality of blades and a single thin shroud strip having spacing and angle-determining means for said blades, said strip being soldered to the ends of said vblades at least at end sur-v facesl adjacent both edges of said blades and presenting a smooth surface of revolution being soldered to the en ds'of said blades at leasty at end surfaces adjacent both edges of said blades and presenting a vsmooth surface of vrevolution throughout.

9. The combination of a plurality of blades and a single thin shroud strip abutting the ends of'said blades and soldered thereto, no portion of the original shape of said blades projecting beyond the outer surface of said shroud strip.

10. The combination of a plurality of blades and a single thin Vshroud strip coacting with the extreme endsof said blades and soldered thereto, no portion of the original -shape of said blades projecting beyond the outer surface of said shroud strip.

11. rllhe combination of a plurality of blades and a single thin shroud strip having means for spacing said blades and for de-A termining their proper angle, said strip being soldered to the extreme ends of said blades, no portion of the original shape of said blades projecting beyond the outer sur face of said shroud strip.

12. The combination of a plurality of blades and a single thin shroud strip having means for spacing said blades, said strip being soldered to the extreme ends of said blades, no portion of the original shape of said blades projecting beyond theouter surface of said shroud strip. e f

13. The combination of a plurality ,of blades and a single thin imperforate shroud strip abutting the ends ofsaid blades and soldered thereto. n

14. The combination of a plurality of blades and a single thin imperforate shroud strip coacting with the extreme ends. of said blades and soldered thereto.

' In testimony whereof, the signature ofl the inventor is aflixed hereto in the presence of two Witnesses.

CHARLES EDWIN SEARCH.

l Witnesses:

Gr'. F. DE WEIN, W. H. LIEBER.

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