US1823310A - Elastic fluid turbine - Google Patents

Description

Sept. 15, 1931. R. c. ALLEN 1,823,310

ELASTIC FLUID TURBINE Filed May 23. 1929 s Sheets-Sheet 1 INVENTOR.

ATTORNEYS.

Sept. 15, 1931 R. c. ALLEN ELASTIC FLUID TURBINE Filed May 23. 1929 6 Sheets-Sheet 2 INVENTOR R-C. ALLEN.

FIG. 3.

ATTORNEY Sept. 15, 1931. R. c. ALLEN ELASTIC FLUID TURBINE Filed May 23, 1929 6 Sheets-Sheet 4 JNVENTOR. R C.ALLENu A TTORNEYS.

Sept. 15, 1931.

R. c. ALLEN ELASTIC FLUID TURBINE Filed May 23, 1929 6 Sheets-Sheet 5 I N VEN TOR.

A TTORNEYS.

' 6 Sheets-Sheet 6 fly-z; V fi R. c. ALLEN ELASTIC FLUID TURBINE Filed may 23. 19,29

Sept. 15, 1931,

Patented Sept. 15, 1931 umrsn STATES PATENT OFFICE j ROBERT C. ALLEN, OF SWARTHMOBE, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ing normally.

' ELECTRIC 85 IEANUFAGTURIIQ'G CSMPANY, A COREORATION OF PENNSYLVANIA ELASTIC FLUID TURBINE Application filed May 23,

My invention relates to elastic fluid turbines, more particularly to that type employing packingelements normally defining fine clearances, butwhich may be disposed to -it is desirable to increase the clearances in order to avoid rubbing or injury to the packing elements. On the other hand, when operating under full load conditions, it'is desirable that the clearances shall be reduced to a minimum in order to avoid the leakage of steam. Accordingly, therefore, it is a more particular object ofmy invention to provide a turbine of this character with means for shifting the rotor axially in: order that the packing elements may define large clearances under reduced load or starting and stopping conditions and small clearances when operat- While I mayprovide manual means for shifting the turbine rotor axially for the purposes stated,-I prefer. to do this automatically to removethe responsibility from the operator. Accordingly, therefore, it is a :more particular objectof my invention to provide for shifting of the turbine rotor for the purposes stated by means responsive to the load conditions. 1

These and other objects are effected by my invention, as will be apparent from the following description and claims taken in connection with the accompanylng drawings,

forming a part of this application, in which:

or the operating mechanism in section;

, bearing;

Fig. 3 is a sectional view showing the thrust Fig.14 is a detail view, shown partly in 1929. Serial No. 365,483.

section, of motion-limiting means for the rotor;

Fig. 5 is a longitudinal sectional view of a turbine, similarto Fig. 1, but showing an other form of automatic mechanism for controlling axial shifting of the rotor;

Fig. 6 is a detail view of a portion of the automatic operating mechanism employed in Fig. 5;

Fig. 7 shows a turbine in side elevation with automatic mechanism controlling shifting of the rotor in response to operation of the speed changer;

Fig. 8 is a fragmentary view of a turbine showing the automatic mechanism responsive to inlet steam pressure;

Fig. 9 is a view similar to Fig. 7 but showing the automatic mechanism responsive to pressure existing in the exhaust chamber;

Fig. 10 is a view similar to Fig. 7 and showing the automatic mechanism responsive to load conditions of the generator driven by the turbine;

Fig. 11 is a detail view of one type of turbine blade; I

I Fig. 12 is a detail view of an turbine blade;

Fig. 13 is a detail view of packing of the end-tightened type which may be used in connection with dummy pistons, diaphragms, or with glands; and,

Figs. 14, 15 and 16 are detail views of packing of the radial type which may be disposed to provide large clearances.

Referring now to the drawings more in detail, in Fig. 1, I show a turbine including a. housing or cylinder construction 10 and a rotor 11, the rotor being supported in proper relation with respect to the housingconstrucend-tighlened tion by'suitablebearings 12. Glands 13 are arranged between the ends of the casing and the-rotor or spindle 11. shown, steam or elastic fluid enters the chamber 14 from any suitable valve mechanism (not shown), the steam undergoes pressure-velocityconversion in the nozzles 15, and the high velocity steam has velocity energy abstracted therefrom preferably in the velocity compounded stage, at 16. Thereafter, the steam preferably undergoes fractional expansion in the blading shown at 17, 18 and 19, and steam leaving the last row of such blading enters the exhaust chamber from which it passes to a con- -denser (not shown). While I have referred to turbine blading or stages at 16, 17, 18 and 19, it is tobe 'understood that, so far as my invention is concerned, any form orarrangement of blading may be used so long as the principles of my invention may be advantageously utilized.

The blading 17 18 and 19 may be of the reaction type, in which case it is necessary to employ a dummy piston or pistons indicated at 22 and 23 for counterb'a'lancing the differences in pressure existing between the admission and exhaust ends of the reaction blading. In accordance with my invention, I prefer to have dummy'pistons' of such size and arrangement as to counterbalance substantially all "of the end thrust created by the differences in steam pressure existing between V the. itdIIllSSlOIl and exhaust ends of the reaction turbine blading. 7

With the form of turbine shown in "Fig. 1,

the glands 13, the dummy pistons 22 anc 23,

V 26, to cooperate with the interior inclined small clearance to avoid tip leakage.

rotor with this type of blading is shiftable to define small and large clearances.

surface of. the housingor casing construction 10. With the blade 25 in full line position, minimum-clearance is defined between itstip 26 and the interior inclined surface 27 of the casing. constructionlO; and, if the rotor is shifted to the dotted line position, larger clearance is-defined. r

VVit-h the end-tightened formof blading. showninFig. 12, the movingblades 28 carried by the rotor 11 areprovided with sharpedged shrouds 29 which cooperate laterally withan-ysuitable structure, for example, the root portion structure 30 of the fixed blades '31, the shrouds 29 and the root'portion'3O constituting end-tightened packing to define The v Fig. 13 shows end-tightened packing suitable for the glands and dummies and capable, depending upon longitudinal adjustment of the rotor,-of defining large and small clearances.

. radial packing. elements, wherein, upon longitudinal'movementof the rotor to the dotted line position shown in Figs. 14 and 15, the

packing elements are disposedout of registry,

'therebyprovid-ing largesafeclearances.

Figs.f14, 15 and16 showthree forms of ings 47.

At times, particularly when stopping and starting up, due to expansion and contraction effects, to warping, or possibly to a cer tain amount of mechanical unbalance, there is likelihood of. the packing elements rubbing or being injured if the clearances are too small. 7 On the other hand, when operating under normal full load conditions, the clearances should be reduced as much as practicable to minimize leakage. In Fig. 1, I show apparatus for shifting the rotor axially so that-the packing elements may define large and small clearances when required. When shutting down the turbine or when starting, the operator should adjust the turbine rotor so that the packing elements, define'minimum clear-ances; and, after reaching full power conditions, the rotor should be shifted axially in order toreduce the clearances. i

In Fig. '1, I show a thrust 'bearing'31 connected so as to move'axially with the rotor. Upon reference to Fig.3, it will be noted that the thrust bearingconsists of a housing 32 ar' ranged to enclose thrust bearing segments 33 cooperating with opposed sides of the thrust collar 34 carried by the rotor shaft 11. The thrust bearing is movable axially with respect to the'housingstructure 35, any suitable guide bearing means, as indicated at 36, be-

ing provided. The'thrust bearing is alsoguided by the housing construction 35 due to projections 37 engaging in recesses'38 provided by the housing construction ;however, the'recesses 38 and the projections 37 perform other functions, namely, they prevent the thrust bearing from turning with respect to the housing structure 35 and the projections '37 coperate with either abutment surface for the purposeof limiting the axial movementof the turbine rotor.

If the thrust bearing housingis moved "axially, the turbine rotor will be similarly moved. Accordingly, means is-provided for shiftlng thei thrust bearing and the turbine rotorso that the packing elements carried 'by the rotor may occupy eit'her a position dennm-g nnnimum clearances or a posltlon defining maximum clearances. To this end, the

external thread 40 arrangedto engage the lnternal thread 41 of a worm gearring 42,

"thrust bearing housing is provided with an the latter ring being arranged in a recess 43 provided in the housing construction 35 and being prevented from axial movement by lateral abutments 44 constituting'walls of the annular recess The gear ring 42 meshes with a worm 45 carried by the shaft 46, the

latter being carried by bearings 47 secured in place with respect to the housing construction 35, which is extended laterally in order to provide'a chamber 48 for the worm and to provide material for supporting the bear- The shaft 46 extends outwardly from the I I hand wheel 49, the latter operatingthrough the worm gear 42 and the threads 40 and 41 to secure shifting of the thrust bearing and therefore of the rotor.

Movement of the rotor in either direction is limited'by suitable abutment means. Referring to Figs. 2, 3 and 4, the projections 37, already referred to, cooperate with abutment surfaces provided in the recesses 38 toplimit axial movement of the thrust hearing and of the rotor, the projections 37 preferably being provided with spacing means so that the clearance existing with respect to theend walls of the recesses 38 may be suitably varied to secure an accurate range of movement. To this'end,'each side of each projection 37 is provided with abutment blocks 51 spaced from the projection 37 by shims 52, the blocks and shims being secured to the projections in any-suitable manner, as by the screws 53. After suitably adjusting the abutment blocks with respect to the abutment surfaces 50, the rotor may be shifted so that its packing elements define either minimum or maximum clearances merely by operating the hand wheel 49 until the abutment meansprevents further operation, at which time the rotor will be either in the position for minimum clearances or in the position for maximum clearances. When shutting down the turbine or when starting up, the operator will'adjust the turbine rotor for maximum clearances so as to avoid the possibility of injury to the packing elements,

-ment means, whereupon the packing elements will be in a position defining minimum clearances.

The thrust bearing housing is preferably ,moved automatically in accordance with "some load condition of theturbine, by suitable mechanism such as shown in Fig. 1. TlllS mechanism 1s controlled in accordance with the admission of steam to the turbine.

A pinion 49 is securedt'o the end of the shaft 46 and meshes with a rack 114, the latter being connected to a piston 115 operating in a cylinder 116. The mechanism is arranged so that when the rack 114 is moved to the right, the thrust bearing housing moves the rotor to provide maximum packing clearances, and when the rack ismoved to the left minimum packing clearances are provided. I

Fluid pressure is supplied to the cylinder 116 for actuating the piston 115 and is controlled by a suitable pilot valve 117. When the pilot valve is moved to the right of the position shown on the drawings, fluid pressure is applied to the piston 115 to move the rack 114 toward the left, and when the pilot valve is moved to the left of the position shown, fluid pressure moves the piston 115 and the rack 114to the right. The pilot valve 117 has a stem 120, which is biased to the right by a spring 118 acting on a collar 119 on the stem.

-At 121-isshown a lever connected to a stationary fulcrum 122. One end of the lever is connected to the governing mechanism 57 and the other end, at 123, is adapted to bear against the collar 119 to move the valve 117. The lever 121 is so arranged with respect to the governing mechanism that the valve 117 is moved to the right of the position shown when the governing mechanism admits steam for carrying load, and to the left when the admission is reduced to substantially no load condition.

At 124 is shown a throttle valve which is also adapted to cut oif the supply of motive fluid to the turbine. A cam member 125 is attached to the throttle valve, and is designed, upon closing movement of the throttle valve, to rotate a lever 126 in counterclockwise direction. The other end of the lever 126 is adapted to contact the free end of the rod 120 and to move the pilot valve 117 to the left.

The operation of this mechanism WlllbQ readily apparent. When the admission of motive fluid is such as to carry no load, the pilot valve 117 is moved to the left by the lever 121 and the rack 114 is moved to the right, whereupon the thrust bearing housing moves the rotor to provide maximum clearances. When, however, the governing mechanism provides increased fluid admission for carrying load, the free end 123 of the lever 121 moves to the right and the spring 118 acting on the collar 119 moves the pilot valve 117 to the right. The rack 114 is there- :upon moved to the left and the thrust bearing housing moves the rotor to the position of minlmum packing clearances.

During such movements of the governing mechanism, the throttle valve is normally fully open. "However, should the throttle valve be closed, the lever 126 is rotated counter-clockwise to move thepilot valve 117 to the left, thereby operating the mechanism to provide maximum clearances.

In Fig. 5, I show another form of means for shifting the rotor axially in an automatic manner due to the direct mechanical connection with the main governor valve indicated at 55, this valve having associated therewith binerotor to the large clearance position.

with a pinion 59 carried by :a shaft 60, the

shaft-.60 being connected by bevel gears '61 and 62 to a shaft 63 coupled at 64 to .the operating shaft- 46. NVith. this arrangement, upon a decrease in load to noload or light load, the operating-. :piston 10f he operating cylinder'will be correspondingly moved and the extension connected thereto will operate the train ofmechanism for shifting the tn? t is to he understood that any suitable mechanism may be employed .to achieve this result and that the .system ofpgearing and shafts illustrated is merely' one example of mechanisin which maybe employed for this purpose. Inshuttmg down a turbine, the load is first :removed. The governor valve then operates *to restrict the admission of steam to prevent the turbine from running away. Thenext operation is o close thethrottle valve and this results in themachine slowing down;

"-ofaccomplishing this purpose. -thethrottle valve is provided "with astem 65 having a rack 66 thereon which meshes with aacpinion 67 carried by ashaft 68 connectedby :the "bevel gears .69 to the bevel gear 70, the :latter gear being arranged to transmitcmdtion to the connected shafts'63 and 46.

11f :theautomatic mechanisms just referred 'to'are both incorporated in a single installahowever, if the steam is shut off, thegovernor valve opens due to .the reduction in speed It is, therefore, desirable to have mechanism operable to shift the rotor or spindle to large clearance positionwhen thethrottle valve is closed. this purpose may assume variousforms and,

Mechanism for the achievement of 'by way of example, in Fig.5., I show one Way In this'view,

. .tion, it will be necessary to render the automatic mechanism associated with the governor valve ineffective when the throt le valve .is closed. To this end,I-show the bevel gears :62gand 7O arrangedyto be connected to the shaft 63 by means of an intermediate clutch ;member 71. When the clutch member 71 connects thegear 62to the shaft'63, theapparatus is then inlposition :to be; operated in respouse. to the governor valve; :and, when the clutch member 71 connectsthe-gears70 to the I shaft 63, the apparatusv is position'toibe operated by. the throttle valve. 'A-spring 72 :israssociated with the clutch'memb'er 7 1.and

spring.

means. ranged to be operated by the speed changer outer end of shaft 46. pose ofgettingthe requisite adjustment may be provided by locating the pivot 90 relatively near to the :yoke 86, and, a suitable it'serves' to connectthe bevel 'gearz62 to the shaft 63.

7 During closure of the throttle valve, mechanism is brought into play to disengage the clutch 71 against the force'of the spring 72 and to engageit with the bevel gear 70, thereby connecting the latter gear to the shaft 63; and-further closing movement of the throttle valve will result in theflautomaiic mechanism being operated to shift the turbine rotor to the position of large clearance.

Referring to the clutch shifting mechanism which comes into play at a suitable time during the closing of movement of the throttle valve, I show, by way of example, the stem 65 having an inclined surface 73 (Fig. 6) which is arranged to engagethe follower'74 carried by the crankshaft 7 5, the latter having :a crank 76 connected by a suitable linkage at 77, 78 and 79 to the other-end of the lever 80 which serves as .a shifting lever to shift the clutch 71. As the throttle valve extension -65 ncves down, the inclined surface 73 serves to tiltthe'follower 74 and the linkage is operated toengagethe clutch 71 with the gear 70. 'VVhen the throttle valve is opened, ust as soon asthe inclined surface 78 passes above the follower 74, the spring 7 2, preferably connected to the lever 80, then operates-to engage the clutch member 71 with the gear 62 to shif-tthelinkage and moves the follower back-tea position to be again operated upon by the inclined surface 73.

It is impossible to increase the load on a .largeturbine without increasing the tension on the synchronizing or speed changing Therefore, within reasonable lim- 1ts,a given position ofload 1S always identified with approximately a corresponding position of the speed changer adjusting In Fig. 7, I showinechanism armechanism for shifting the rotor either to the small clearance position or to the large clearance position. Wh1le mechanlsm suit able for this purpose mayassume various forms, I show, by way of example, a speed changer moto-r82 arranged to operate a gear 83'hav1ng internal threads engaging with.

the threaded member 84, the upper end of which is connected to the speed changer spring 85. This mechanism may be utilized V7130 shift the-rotor; and, for this purpose, I show the lower end of the member '84 provided with a yoke 86 for engagement with the the lever 87, the inner endof the lever being connected to a rack 88 meshing with a pinion 89 connected to said operating Suitable movement for the purdegree of lost motion 'mayexist between the yoke 86 at the outer end of the lever.-87 by the provision of adjusting screws-91'.

It will, therefore,'be apparent that, when the speed changer is adjusted, for a reduction in load, the turbine rotor will beshifted in the large clearance direction. With an increase in load shifting will take place in the other direction. p v p It is impossible tocarry a load on a turbine without first building up steam pressure in the nozzle chamber or inlet passage. Therefore, in Fig. 8, I show apparatus arranged to secure shifting ofthe tur inc rotor in a small clearance direction when steam pressurebuilds up in the admission chamber or passage to a suitable extent. 7 In this view, I show the steamfchamber-93 connected by a pipe 94 with a pressure-responsive device 95, which serves to operate the pilot valve 96 of an operating cylinder 97, the operating piston Fof the latter being connected to a rack 98 engaging a pinion 99 on said operating shaft 6. Therefore, w1th an lncrease 1n steam pressure in the admission chamber or nozzle passage of the turbine to a suitableextent, the apparatus will be operated to shlft the .turbine rotor in a small clearance direction.

On the other hand,'with a drop in pressure, the operating cylinder will move the rotor in, a clearance-increasing direction.

Owing to the large proportions of some turbine casings or housings, appreciable distortion takes place on account of atmospheric pressure on the outside of the casing or housing and unequal heating of low pressure portions thereof. It may be impossible, to heat all parts of the structure uniformly and, therefore, rubbing of the elements thereof'may occur. Hence, in Fig. 9, I provide pressure-responsive means arranged to move the rotor in a clearance-in creasing direction whenever the vacuum drops below a predetermined amount, for example, 23 inches or 24 inches. Should the condenser circulating pump loose its water, the vacuum would drop and the turbine would then operate non-condensing and the apparatus just referred towould be utilized to shift the rotor to a safe position. To this end, I show a pipe 101 connected to the exhaust casing of the turbine and to a pressure-responsive device, 102 associated with the relay at 103', the latter operating a rack 104 which meshes with the pinion 105 connected to the operating shaft 16. With this arrangement of apparatus and assuming that the turbine is operating normally, should there be a drop in vacuum, the relay 103 will be actuated to secure shifting of the rotor to increase the clearance.- On the other hand, when normal conditions again obtainand a normal vacuum exists in the exhaust casing of the turbine, the relay 103 termined rate to shift the rotor to the first Fig. 10, I show" the turbine driving a generator 107, the latter having outlet leads 108. Solenoid means is arranged at 109, such means having means responsive both to current and'to voltage. If the load drops be- 7 low a predetermined amount, the spring 110 will overcome the solenoid 109 and energize the fluid relay 111 to actuate the rack 112 and the pinion 113 carried by said shaft 46 in order to shift the turbine rotor in a clearance-increasing direction. With an increase in load, the energy of the solenoid 109 will overcome the spring 110 and the mechanism will be operated to move the turbine rotor in a clearance-decreasing direction. 8 IVhile I have shown my invention in several forms, it will be obvious to those skilled in the'art that it is not so limited, but is susceptible of various other changes and modifications, without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the-prior art or as are specifically set forth in the appended claims.

hat I claim is 1. In a turbine, the combination of a casing construction; a rotor; elements carried by the rotor and, in a first axial position of the latter, defining minimum clearances Wllihjg respect to the casing construction and ina second axial position defining larger clearances of a magnitude avoiding rubbing when the rotor is distorted in starting and stopping the turbine; and means responsive-- to decrease in turbine load below' a predetermined load to shift the rotor to said second axial position so as to define larger clearances of said elements with respect to the casing construction.

2. In a turbine, the combination of a casing construction; a rotor; elements carried by the rotor and, in a first axial position of the latter, defining minimum clearances with respect to the casing construction and in -3.; f second axial position defining: larger clearances of a magnitude avoiding rubbing when the rotor is distorted in starting and stopping the turbine; means responsive to the admission of steam in excess of a prede-;--;.

position and below a predetermined rate to shiftthe rotor to the second position.

3. In a turbine, the combination of a casing construction; a rotor; elements carried; by the rotor and, in a first axial position of the latter, defining minimum clearances and in a second axial position defining larger clearances with respect to the casing construction; a thrust bearing for the rotor and having a housing movable axially with the rotor and relatively to the casing construction; said housing being provided with an external thread; a gear restrained from axial movement by the casing construction and having internal threads in engagement with the housing-threads; a driving gear carried by the housing construction and meshing "with the first gear; and means responsive to turbine load conditions for operating the driving gear in order to shift the rotor from one position to the other.

4. In a turbine, the combination of a casing. construction; a rotor; elements carried c 1 "thelatter, defining minimum clearances and by the rotor and, in a first axial position of in a second axial position defining larger clearances with respect to. the casing construction; abutments associated with the casing construction and with the rotor for limiting the axial movement of the latter; ad-

justable spacing means: connected to one or .more of the abutments in order to limit the axial movement-of the rotor to one of said positions; and means responsive to load conditions of the turbine for shifting the rotor from one position to the other.

.5; In' a turbine, the combination of a casing construction; a rotor; elements carrled p by the rotor and, 1n a first axial position or the latter, defining minimum clearances and i in a second axial position defining larger clearances with respect to the casing con struction; abutments provided on the casing construct1on and spaced axlally; a pro ection arranged between the abutments and connected to move with: the rotor; said projectioncontacting with one abutment when the'rotor occupies the first position and with the other abutmentwhen it occupies the second. position; and means: responsive to tur- "bine lo-ad'conditions for shifting the rotor.

6. In combination in a turbine, stator structure, a rotor carried by the stator structure and capableof axial movement relative- 1y; thereto, a plurality of ring packing elementscarried by the stator and by the rotor and defining. relatively large clearance when the rotor 1s 1n one axial position and relaan operating condition of the turbine for *rotating said shaft either 1n one direction or the other to cause the rotor axially. v 7. In combination 'in a turbine, stator structure, a rotor carried by the stator structure and." capable oflaxial. movement relato be moved tively thereto, a plurality of ring packing elements carried by the'stator and by the rotor and defining relativelylarge clearance when the rotor is'in one axial'position and relatively small clearance when the rotor is in'another axial position, a double-acting thrust bearing carried by the rotor and including a housing, a guide formed in the stator structure and limiting movement of the housing to axial movement, cooperating if abutment means carried by said stator structure and by said housing for limiting axial movement of the housing and the rotor, said abutment means being adjustable in order tovary the extent of axial clearance, peripheral threads on the housing, a ring having internal threads engaging the peripheral threads and having peripheral worm teeth,

a guide formed in the stator structure and restricting movement of the rlng to angular movement, a shaft carried by the stator structure and having a worm meshing with said worm teeth, and means responsive to operating condition. of the turbine for turning said shaft either in one direction or theother as operating conditions require.

8. The combination with an elastic fluid turbine having'a stator anda rotor, of cooperating packing elements carried by the stator and the rotor, said packing elementsbeing of a type providing close packing clearances 1n one axial position of the rotor and. in another axialpo'sition thereof, providing large safe clearances to avoid rubbing when the rotor is distorted in starting and stopping the turbine, and means responsive to a predetermined minimum load condition of the turbine for moving the rotor to the axial position thereof providing the large safe clearances.

9. The combination with an elastic fluid turbine having a stator and a rotor, of co operating packing elements carried by the stator and the rotor, said packing elements being of a type providing close packing clearances in one axial position of the rotor and, in another axial position thereof, providing. large safe clearances to avoid rubbing when the rotor is distorted in starting and stopping the turbine, and means respon- I sive to a load condition of theturbine and operative when the load is above a predetermined load to move the rotorto the position of close clearances and operative when the load'is below a predetermined load to movethe rotor to the position of large safe clearances.

10. The combination with an elastic fluid turbine having a stator and a rotor, of cooperating radially-extending packing elements carried by the stator and the rotor, said packing elements, in one axial position of the rotor registering and providing close radial clearances and, in a second axial position of the rotor, being out of registry to provide clearances between the stator and the rotor which avoid rubbing when the rotor is distorted in starting and stopping the turbine, and means responsive to a load condition of the turbine and operative whenever the load is less than a predetermined load to maintain the rotor in said second axial position.

11. The combination with an elastic fluid turbine having a stator and a rotor, of cooperating radially-extending packing elements carried by the stator and the rotor,

7 said packing elements, in one axial position of the rotor registering and providing close radial clearances and, in a second axial position of the rotor, being out of registry to provide clearances between the stator and the rotor which avoid rubbing when the rotor is distorted in starting and stopping the turbine, and means responsive to a load condition of the turbine and operative to maintain the rotor in said second axial position while the load on the turbine is less than a predetermined load and to maintain the rotor in said first axial position while the load is greater than a predetermined load.

12. The combination with an elastic fluid turbine having a stator and a rotor, of cooperating packing elements carried by the stator and the rotor, said packing elements being of a type providing close packing clearances in one axial position of the rotor and, in another axial position thereof, provldlng large safe clearances to avoid rubbing when the rotor isdistorted in starting and stopping the turbine, and means responsive to a pressure within the turbine which varies with the load carried by the turbine and operative when the pressure corresponds to a load above a predetermined load to move the rotor to the position of close clearances and operative when the pressure corresponds to a load below a predetermined load to move the rotor to the position of large safe clearances. V

In testimony whereof, I have hereunto subscribed my name this 16th day of May,

ROBERT C. ALLEN.

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