US815281A - Steam-turbine. - Google Patents

Description

'H'. F.,PULLAGAILl STEAM TURBINB, APPLICATION FILED AUI'GJVB, 1904.

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u www PATENTEp MAR..13, 1906.'

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.UNITED STATES fOFFIOEt- ASSIGNOR To 'ALLIS-CHALMERS oOMrANY, or JERSEY,l A CORPORATION OF NEW JERSEY;

JERSEY CITY, `NEW STEAM-TURBINE,

Tod/ZL whom) it mrtyconcer:

' -Turbinesfof which the following is' a specifir Be it known that I, HUGH FRANCIS FUL- LAGAR, a subject of the King of Great Britain and Ireland, residing at Newcastle upon- Tyne, in the county of N orthumberland,Eng land,- have inyented Improvements in Steamcation.

VIn order'to avoid the use of 'a large outer' balance-'piston vinsteam-tu'rbines of the kind commonly 'used for driving dynamos v'and other machines and having arotary stepped spindle or drumy (hereinafter called a drum and balance-pistons the end thruston lthe several steps ofjfthe drum, I have'describedin the specification of --byme ont cation :a construction of turbine wherein the lication for Letters Patent-'filed another .ap

`e same day asthe present appliend thrust `due to the pressure of steamon" the largest step carried thereby is counterbalancedby 'asepai rate balance-piston that has an effective an,

nular area equal or approximately-equal to that of the large balance-piston usually employed for the same purpose and which eX tends into a steam space or chamber (herein- 4after called for distinctiona "piston-cham-l ber') thatA is preferably arranged at the exhaustend of the turbine, the separate balance-pistonbeing made of muchsmaller di ameterthan theone for which it is substisets of rotary blades of different diameters` tute'd, usually smaller than the large end of the drum, and subjected tothe pressure of steam supplied to from thev 'steam-space between the last two and leakage of steam'from thehpistonfchamberto the exhaust-'chamber-being retarded as Vfar as possible by 'a packing device of ordi- I nary kind comprising interacting circumfer-A V .l ential tween t e periphery of the balance-piston and rooves and projections located be-` 4th'e'wall y'of the 'piston-chamber- .1-

l ters land a -Nowthe present invention relates to stearri-y turbines that are, designed for marine use and.l which usually have designed to counteract of the drum and the blades4 sired proportion 'of the drum dueto steam-pressure. The provision 'made smaller than has hitherto the said piston-chamber tion, and

a' parallel or cylindrical drum and' 'sets' of 'blades ofdifferent 'diamesingle balance-piston (hereinafter called for distinction'the mainpistonw that l is located at the forward endy of the drum and .Steam leakin `-i'susuallyma les1rrialler than would i be nec,- 'rounding eac essary for correct balan vsothatthere maybe an end thrust onthe drum caused by the steam-pressure and unbalanced -thereby in order tov counterbal'ance.

Patented March. 13,11906. ,Application rie-a lAugust 18.1904. serial No. 221,255.

ce of steam-pressures,

the en d thrust `on'the 'drunr in the opposite i direction. d ue tothe action of the propeller vdriven by the turbine; and the invention hasl provide forthe balancing of for its object't-o such turbines by means; ofv balance-pistons.-

smaller indiameter than'those heretofore .em'

ployed, the use of large balance-pistons being objectionable for the reasons aforesaid specification.

Started 65 For this .purpose in a steam-turbineof the kind lastreferred to the rotary drum vis pro#4 vided according to this invention with a sepa- I rate balance or auxiliary piston arranged adjacent to a portion thereof of reduced diamej ter, soas to forman annular'surface' of the.

required area upon which steam from the in# 'let end of the turbine is caused to act in such a way as to counterbalance directly any ldfiof this 'auxiliary piston,-which itself` is `small in diameter, enables the main pistont'o" be been the case. lThe auxiliary balance-piston may be arranged end thruston the onv the rear or theforward end lof the drum.

For vmarine purposes two coaxially arranged turbines 'are sometimes combined, 1

one of the turbines (hereinafter called for distinction the ."mainr turbine) being designed .for going ahead and the other (hereinafter called for distinction the reversing-turbine being designed for i going vbine-drum is. provided with a 'main and packing device, such asl describe each turbine has its own'inlet. for steam, so that upon admitting steam to the inlet .astern. f Each tur- 1 lston and .of the main turbine'this turbine 'will rotate the corresponding. propeller ina direction for-going aheadthedrum of the reversing-turbine ber ir'fg simultaneously rotated in theS/me-dio' direction. past the packing device sur- -main piston is usually `led to of the main upon cutting off the supply "of steam y 'to the main turbine and admitting it tothe vreversingturbine the latter, as

the exhaust through the corresponding turbine-drum.

In combined turbines for the purposes mentioned according to this invention the mainpiston at the rear end of the reversingturbine has substituted for it an'auxiliary balance-piston which is preferably of thesame diameter and kthe rear' end of which has an annular surface upon which-steam supplied through Aa separate pipe acts in such a manner as to tend to pressthe auxiliary balance-piston and turbine-drums in a. forward direction when thel main turbine is in use, and thereby partly couuterbalance the steampressure on the drum and rotary blades of that turbine, steam leaking past the packing device of such auxiliar balance-piston being suitably led,` preferab y as hereinafter de scribed, tothe exhaust. Steam'leaking past the packing device .of the mainbalancepis ton of the main-turbine drum may flow-to the exhaust through the drum, asbefore.

the use of an auxiliary balance-piston in the manner hereinbefore described the 25 1 smaller than would otherwise be necessary mainbalance piston can be made much which, as will be readily understood, is a 'matter of considerable practical importance.V

The carrying outof the invention 4is illustrated in the accompanying drawings, of

' which Figures 1 to 4, inclusive, represent,

partly lin longitudinal section and partly in elevation, sufhcient for the purpose of four examples of. turbines constructed Aaccording to this invention.

vIn each of the examples illustrated in Figs.

land 2 ,the rotary turbine drum or spindle comprises a hollow outer cylindrical portion a, a central .portion a', formed by a shaft, and

intermediate annular end portions or carriers a2, these "parts being rigidly connected .to-

gether. so-as to form a hollow drum, herein- Aafterisornetimes .called the drum a, that is supported b the smallerior reduced end porv Vpropeller fixed upon a shaft secured to the rear end of the turbine-shaft a.

' In the example shown in Fig.` 1 the drum a is provided'at its rear endwith' an auxiliary 'balance-piston g, arranged in a chamber g',

' that extendsaround the reduced portion a3 of tion b2 ofthe casing b.A

the drum a and is formed in theadjacent por- The rear end of the chamber gis in communication, through the piston g, holes g2 in the'intermediate portions a2 of the drum, the interior of the-outer portion a, of the drum, and anannular slit ga bevtween the forward intermediate portion az and the piston c, with the steam-inlet j ofthe turbine, so that livesteamwill enter the chamber g', where itl will press upon the rear end of the ton g and t e drum a forward in o position to the force of the steam acting on the front an= nulareiid'portion h of the drum, that extends piston g and tend to move the pis-l outward be ond the'p'eriphery ofthe main piston c, an on the rotar blades a*, the escape of steani from the orward end of the piston g* to the 'exhaust-chamber 7c of the drum a being retarded by a acking device l,

such as hereinbefore referre to arranged be e tween the' piston g and-the surrounding portion b3 of the casing t. m is a passage for` conveyin to the exhaust-'chamber 7c steam that has eaked into the chamber c past the packing device n of the piston c.

, In the .example shown in Fig. 2 the auxiliarybalance-` iston gis arranged on'the reduced forwar portion a4 of the turbine-drum and in front of the main piston c. .Between the pistons c and g there is an intervenl ingstationary'wall or division c, that surrounds the reduced portion aJl of the drum and is provided with a packing device" g or a' gland arranged between it anda longitudinal extension g* of the auxiliary balance-piston g. For-supplying steam from the inlet y' to act on the rear end of the piston g the inlet y' j has a branch passage s, leading to the s Y' ace betweenthe rear end of the piston'g an the wallo, andl between the forward end of the chamber g of the piston g and the exhaustchamber k there is a passage t for leading IOO away the steam that escapes peripherally of the piston g past the packing device l. Steam leaking past the packing device n of th'e' main piston c is led back through that piston and the turbinedrum a to the exhaustchamber k.

When either of the turbines shown in' Figs. i

1 and 2 is in operation, the forces' tending to move the drum a rearwardly in its casing b are the end thrust, due to the action of the steam on the blades, and the pressure of the steam on an annularportion hof the drum of a radial width equal to the difference between the radii of the outer portion a, of the drumand` of the main balance-piston c,while the forces which tend to move the drum a in the other direction and whichshould balance the former forces are the forward thrust, due to the actionof the propeller upon the water, and the pressure of thesteam on the rear end of the auxiliary balance-piston g.

Fi s. .3 and 4 show two examples of combine lturbines constructed according to this invention. In each case a 0, a2 is a bladed drum constructed as hereinbefore described for going ahead, and u is a bladed'drum fixed to and coaxial with the drum a and adapted for going astern. balance-pistons c and g, respectively, each The drums a .and u have' thep'iston g'bepiston c and the drum L aremade hollow, asv

lbefore, so that'the Steam that leaks past'the piston icv can escape` therethrough tothe ex# -ha'ust-chamber' c,l which is common to the two turbine drums. 'case is provided With'a The casing b in, each passage z, for conduct? ing live .steam intothe'chamber g, formed by 4and its rotary bladesthe piston g and the adjacent portion b2 ofthe T5 casing b, and'wherein the steam will tendk to press the auxiliary piston g and the two turbine-drums' in a forward direction 4when the main turbine isi in' use, sc .as to; counteract partly the rearwardend 4thrust of the steam on the" forward end portion h. o f: the drum a Inlthe example shown nlFi'g. 3- the revers- -ingdrum"fw is at the rear of the main drum a, and the auxiliary' balance-piston' g is arjby the shaft a." vThe when the drum a is'to be used the'l steam-inlet. 7 can byme'ansI- of the 35' ranged at the rear of the drum u anden the reducedV end portion a3 of the drum formed the rear 'end of the chamber g of the piston g toa three-way valve 1, which'is in communication through a passage 2 with the steaminlety' of the'main turbine and through a passage 3 'with' theeXhaust-chamb'er k, so that communication with the passage e, and when the drum u is to beu-sed the passage can b .means ofthe valve 1 be placed in communlcation .with 'the exhaust-chamber k through passage 3 and-also into communication 'with'` A4o steam-inlet through .passage '2. Thismay be accomplished by rotating .the'valve 14 one'v hundred eighty degrees; The steam i"s of mitted 'to 'inlet ofthe reversing-Mumia..

Under these. conditions both ends of the drumu are 4 in communication with the eX- hau'st, and the-drum a cannot by any possibility operate to compress viluid into its inlet 'y, and thusretard the operation of thefre-v versingdrum in' developingv powerrfor runmng astern.' 'i i I Inthe modified example, Figli 4 the reversing-turbine dru'm-- u and its fauXilf f iary balance- -s '5 iston v q are "arranged in frontof `the 'main' tur ythem and v the pistone la portionfg* ofthe drum ofsma1ler diameter'and around. that' portion a' -stationary' wall or divisione, pro- I vvided with a packingA device j.'

`inletj ofthe main 'turbine leads to the foriv ward end of the drum a, `and the steam-inlet' reversing-turbineleads to therear j fend of the drum u. The chamber g, lformed between the rear end' ofthe piston g, the cas-' aref the ing b', and the wall o,1 1s connected bythe pas- 'Y place it in communication b sage2 with the steam-inlety 'of the main tur?. bine: or by means of the; passage 3 with the v7 In each of the examples shown' in Flgs. 3

y' is the steama: is the steam- 'The balancevice Z between f the annular passage z vleads from valve 1 b e :placed in ine-drum a and have between against which it presses, pastthe packingl of the' f nular space 7 passing thence into-the exhaust'- The steamsage?4 with a three-way'valve 1, adaptedto I means of-a'paeexhaust-chamber 4 .of ,the reversingfturbin'e.-

and 4in vorder. to leaked past the vpac iliary 5 balance-piston andV chamber g.' from reve'nt steam that has acting upon the blades of the. reversing-drum' 'w and retarding the motion of the main turbine the outer periph- 'fery of the piston g-i's'formed at a part thereof near tothe steam-inlet of thejdrum u with an annular groove 7., which is always inv come Vmunication w1th a `p1pe 8,' provided With'a valve 9, by means of which the annular chamber-formed by the groove 7 and the lsurroundin'gpart of the casing vb can be placed into communication' with the exhaust-chamber 7c,

Fig. 3, or 4,*Fig. 4,When` the main-turbine is 'I to be used. The portion of the packin'degroove 7 an' rear end of-.the drum'u is sufficient in vaxial vlength to prevent'steam that has reached the groove 7 'from passing forwardrto the drum lu .when the valve `9 1sA open.' When the re-V versing-turbine is to beused, the valve 9 is tardin'g theescape' of steam.

' The valve 9 may in each case be connected the' closed in orderl that the entire 'lengthof thev packing device between theisteam-inletl a; and the chamber'gf may beemployed for 12ewith the'valve 1, so'as to be automatically."v

opened andfclosed on the corresponding operation" of the latter valve.

. S team leaking past the packing device n of :Il i

v themain piston c may 11n each case a nd,'. as-

3 and 4, 4conveniently be led to` the exhaust-chamber kthrou'glithe'saidfmain reg shownin Figs.

piston and the drum c.

The operatlon-'i .the case; of theturbinesf.

shown Figs. 3 and 4 is as follows: Vlhenv the-propeller ie' isk being driven or" going ahead, steam is admitted at j, acts upon the blades of the drum bythe drama "1.10: @,andpasses'f' steam 'also' admittedl at y' and the drum' a. passes through the pipe 2,1the cock .1,

resses'- against .thei- ,for-Wardiend portionrh' oipthedrum a,1 7a` steamescaping past the `packing n "goingtof the exhaust-chamber 7c 'throughthepistonc Steam'from' the'inlet y'. also.;l

andthe'.

passagez to therear-end Vof the 'pistonfgfany-steam. escaping.' piston g 'intqthe an?. d

pipe-8 and the cock 9, and so .avoiding a ct ing' upontheb1adesof the drum/w;V In theltur-" bine shown in Fig., 4 steamkis packing lof partition o. The forces tend# i .ing to-movle the drums a and in'theircasing b'aras stated in reference to the drum afoff Figs. 1- and 2. Y

When, the propeller e is being driven bythe drum u for going astern, steam isvadmittedat w, acts upon the blades of the drum u, and

asses thence into the exhaust-chamber 7c, I ig. 3, or 4, Fig. 4, while the escape of ysteam from the rear end of the drumu ton g into the passage 2, and thence through. the pipe 3 (which is in this case in communi cation with the passage z through the cock 1).y 'i J into the chamber le, Fi@` 3, or 4, Fig. 4, is refv tarded by the packing device Z, the cock 9 being then closed. The forces tending to -Inov the drums a and u forwardly in their casing b are the end thrust, due -to the action of the 4steam. on the blades of the drum u, and the pressure of steam on 'an annular portion 7L of the drum u of a radial width equal to the difference between the'radii of the drum u and the piston g, while the force that tends to.

move the drum a in the other direction is the 1 rearward thrust due to the action peller upon the water.

What I claim'is* of the pro- 1. A steam-turbine comprising abladed drum, a piston fast to said drum and located at the inlet end thereof and less indiameter than said end, means for peripherally of said` piston retarding the escape of steam between said piston and Athe turbine-casing in a direction away from said drum and for causing said steam to exert upon said druina resultant end thrust in thedirection opposite to the aforesaid direction, a second piston, and` means for peripherally of said second piston retarding thee'scape oi steam' between said second piston and said casing and for causing the last-mentioned steam to produce on said second piston an end thrust in the directionl opposite to that of the-rstonentioned end thrust. f

2. A vsteam-turbine 'comprising a bladed drum, a piston fast to said drum and located at the inlet end of'said drum and in Contact with and less in diameter than said end, means for peripherally of said piston retarding the escape of steam between said piston and the turbine-casing in a direction away from said drum and'for causing said steam to exert upon said drum a resultant en d thrust in the direction opposite to the aforesaid direction,` a second piston, and means for peripherallyof said second piston retarding the escape of steam.

vbetween said second piston and said'casing and for causing the last-'mentioned steam to produce on' said second piston an end thrust in the direction opposite mentioned end thrust.

- 3. A steam-turbine comprising Ia. bladed yto that of the firstdrum, a piston fast ,to said drum'and located at the inlet end of said drum and less in diam-l eter than said end, means for peri herally of said piston retarding theescape o steam between said piston and the turbine-casing ina direction away from said drum and for caussaidsteam to exert upon said drinn a res tant-ei id thrust in the direction opposite tqlthefafores'aid direction, a second piston, means for peripherally of' said-second piston retarding the escape of steam between said 1 second piston and said casing and for causin thelastementioned steam to produce on sai secondfpiston an end thrust in the direction opposite to that of the first-mentioned end t I'ust,"and means for leading to exhaust steam that will have escaped past the said twofpistons in the directions indicated.

4. Asteam-turbine com rising a bladed "drum, a iston fast to vsaid rum and located.

at the in et end of said drum and less in diameter than said end, meansfor peri herally of .said piston retarding the escape o steam between said piston and the turbine-casing in a direction away from said drum and for causin said steam to exert upon said druma re-- su tant end thrust in the direction o positey steam'to produce on said second piston an end thrust in the direction opposite to that of the iirst-rnentioned end thrust.

5. ,A steam-turbine comprising a bladedy drum, a iston fast to said drum and located at the in et end of said drum and in contact with and less in diameter than said end,

l means for periplierally of said piston retard- #ing the 'escape of steambetween said piston.

vand the turbine-casing'in a direction away from said drum and for causing said steam to exert u on said drum a resultant end thrust inthe irectionop osite to the aforesaid di-v rection, a second rum adaptedl by blading for rotation in the direction opposite' to that for which the first-mentioned drum is bladed,

a second piston fast to said second drum and located at the inlet end thereof, and means for peripherally of said second piston retard- .ing the escape of steam-between said second piston and said casing and for causing the last-mentioned steam to produce on said second piston an end thrust in the direction opposite to that of the first mentioned end thrust. l

6. 'A'steam-turbine com rising a bladed drum, a piston fast to said rum and located at the inlet end of said drum and less in diam-- eter than said end, means for peri herally of saidpiston retarding the esca e o steam between said piston'andthe turv ine-casing iny a vdirection away from said drum and for causlng said steam to exert upon said drum a re IOO IIO

4sultant endthru'st in thedirection 'opposite to the aforesaid direction, a second drum adapt# l ede-by blading for rotationin the direction o posite to tnat for .which the first-mentioned drum is bladed,l asecond piston fast to 5 said second drum andin 'contactwith and 1 0- cated at the inlet end thereof, and means for perlpherally'of said second p iston'ret'ardin A the escape -of steamhetween said second IU ast-mentioned steam. to produceon sai seciston and 'said'c'asing and for causin jthe ond piston an end' thrustin the directionfop'- posite-.to that vof the first mentioned end thrust.- f

.7. A steam-turbine com rising a bladed drum,. a iston fast to said rum and located 'at' the in et end ofsaid drum and less-in'dianieter than said end meansfor peri herally of said piston reta-rding the escape o Asteani between said piston andthe turbine-casing `in as .direction away from said drum and for cau s.l

y s aid stearnto'l exert upon saididrum afresu tant end -thrustinQthe direction (pposite to theaioresaid.d`irection, Va secon adapted by bladi'ngjor rotation in the direc'- tion n tione rum is bladed., a'secondpiston' fast to said second drum andlocated at the inlet'end thereof ,;m'eans for peripherally of said second piston retardingthe escape ofsteam between Jsaidseeo'nd 4piston and 4 said easing andror l tween. saidl piston and; the tur 'au'si'n vthe lastjmentioned steam toprodu'c'e on sai second piston 'an'end' thrust-inthe div r'ctiojn o 'postete that of, thema-mm1 tioned en' thrust,' and meansffor leading to exlial'istl stfeanithat will. have escaped past cated.-4

A 'steam-turbine com rising-a blad'ed drum, a iston fast to said. rumand'located at the et end'o said drum' and-less' indiani! eter than' said end, means for peri herallyvof said piston retarding the `esca e" oi) l lemasng in a direction away from s aid drum and forcaus- .ing said lsteamto 4exert upon said .drum-r an aforesaid. direction, a. second: ruin coaxial with andi-fast to the'rst-.mentioned drum: and 'adapted-.bybl'ading for rotation in the die j y." rection-op osite. to Athat forr which lthe firstmentione drum j is blade d, @t second piston fast to 'said second drumandlocatedat the Y said second drum to'be placed intoA communication either 'With the inlet oftherst-meninlet endthereof, means for enablingthat end ofsaid second piston .which is fartherl from tioned drum orwith an exha'stespace according astheiirst-mentioned or thesecond-.inem tioned drum is tojbe used,-4 and meansfor when said `end of said second piston is y 1n l comf munication With said-nletretarding periph'- f 4erally oflsaid second pistonthefsca er'of 'steam .between said second.`r isto'n` 'an fsaid easing. from sais and of Sai Secondpsten ositelto that for Whichthe first-'meneand for] causing the last-menaenedstar ,to produee on said second piston an' end thrust mentioned end thrust.

9. `A steam-'turbine comprising a fdi'um, aisto'n fast 'to said drum and located at the 'in et .endoi' said drum and in Contact with and.- less in diameter than said end,' means forperipherally -of said piston retarding'the escape of steam between' said piston' lathe direction q positeto am Opf the first-- and the vt1 1rbi1`ieca'sing inafdir'ection awa-y from said .drum vand for causing said s teain to -exert' npon `sa`id drum an `end thrust inthe direction opposite to the aforesaid direction; `laseconddruin coaxial With and fa'stvto the' t first-mentioned drum and, adapted` by blad-y C -iiig'for rotationin the direction opposite to that for'whichtlie first-mentioned `driiinfis'V l` b lade'd, a second 'piston fast toy said second drum -and.'located atthe 'inlet end-thereof; means for enabling that. end of said V'second lpistonwhich .is 'farther' from' said second j drum .to be placed into comnninication either with'the inletof the first-mentioned I drum or witlian exhaust-space .accordingas the firstementioned o'r the second-mentioned tionwith said inlet retarding peripherally of said second` piston thee's'c-ape of steam b efroin s'aidend'of said second .pistonan'd-for causing thei'last-nientioned steam to produce `o`n` said second pistonan end thrust 'in the ing saidfsteani to exert upon said drum an :end thrust in' the direction op foslt-ctothe `aforesaid direction, aj second ru1n'coax1al.

1-0.- A steamturbine comprising -a blade-'d l .drinn isv to be used, and means lfor Whensaidf' 4end 'of said second piston-Is. 1n' communica 9.5.; tween said ksecond.piston and ysaid casing.A

icio` -Withan'd fast to the 51st-mentioned drum and adapted by blading 'for rotation in the directionropposite to that ,for which the firstmentined .drum is bladed, a second/piston fast to said second drum and in contact with` and located .at the inletend thereof, means for 'enabling that end of said second piston Which isI -farther from 'said second druni tof be ylaced/into `connnunication either with the lnlet -ofthe' firstfmentioneddrum or withy an 'tioned or the seeond-mentioneddrum is to be usedfand lIn'eifins forwhen said end of said-sec#` ,ond piston is in communicationwith-saidinletretarding peripherallyof said lsecond piston thefescapel of steam between' saidsecond piston and said .casing from said end 'of sx' tc l ,sec` ond pistn and forl causin the last-mentioned st'ein 'to produce .on'sald secondhpiston an i ni cation .either Withlthe inlet of the first-menend thrust in the direction opposite to that'of l tioneddrum or with said exhaust-space acthe first-mentioned end thrust.

11. A steam-turbine,comprising a bladed drum, a piston fast to said drum and located at the inlet end of said drum and less in diameter than said end, means for peripherally of said piston retardinv the escape of steam betweensaid piston and the turbine-casing in a direction away from said drum and for causing said steam to exert upon said drum an end thrust in the direction opposite to the aforesaiddirection, a second drum coaxial ,With and fast to the firstmentioned drum and adapted by blading for rotation in the di-v ,'15 rection opposite to that for which the firstmentioned drum isbladed, a second piston fast to said second drum and located at the inlet endthereof, means for enabling that end of said second piston which is farther from said second drum tobe placed into commui tioned drum or with an exhaust-sp`ace accord,-

ing as the first-mentioned or the second-mentioned drum is to be used, packing means for when'said end of said second piston is in communication with said inlet retarding peripherally of'said second piston the escape of steam between said. second piston and said casing from said eng of said. second piston, means for causing to produce on Said secondpiston an end thrust in the direction opposite to that of the first-mentioned end thrust, a passage leading .from an annular space at the end of said pack- 'in means nearer to said second drum to-an eX aust-space, a valve'adapted to control thev l flow of steam through said passage, and packing means located etween said passage and the other end of saidsecond piston and adapted when said Valve is open to prevent steam that has leaked past the first-mentioned packing means from passing to said second drum. 1 2. A steam-turbine comprising a bladed,

drum', a piston fast to said drum and located at the in let end-of said drum and less in diameterthan saidl end, means for peripher-` I f ally of said piston retarding the escape `of f lt'th'e aforesaid direction, a second'drum coaitial with andfast tothe first-mentioned drum and adapted by blading for rotation in the direction opposite to that for which the first-mentioned drum is bladed, a second iston -fast to' said second drum and locate at 'the lnlet end thereof, passagesleading from theend'of said second piston opposite to said ,second drum, from the in'let end of the firstmentioned drum, and from an exhaust-space, a three-way valve to which said passageslead i and which is adapted to enable said end of said second piston to be placed into commu- 'nicatio'n either with the inlet of the first-.m en-l t e last-mentioned steam cording as the first-mentioned or the'secondmentioned drum is to be used, and means for l when said end of said second piston Vis in communication with-said inlet retarding pe' ripherally of said second piston the escape of Vsteam between said second piston and said casing from said end` of said second piston` duce on said second piston an end thrust in mentioned end thrust.

13. A steam-turbine comprising' a bladed drum, a piston fast to said drum and located at the' inlet end thereof and lessin diameter than said end, means for retarding 'peripher-- ally of said piston the escape of steam between saidpiston and the turbine-casing in'a ing said steamfto exert upon said drum an en d thrust in -the direction op oslte'to the aforesaid direction, a second jacent tov the exhaustv end of the aforesaid drum and adapted by blading for rotation 1n first-mentione rum is bladed, a second iston fast to said second drum and 'locate at the inlet end thereof, means for enabling that end 'of said second piston which is farther munication either with the inlet ofthe rstmentioned drumA or with an exhaust-space according as the first-mentioned orthe'second-mentioned drum is to be use'd, and means for when said end of said second piston is in ripherally of said second piston the escape of steam between said second-piston and said casing from said end of said second piston and causing the last-mentioned steam to pro. duce on saidsecond piston an end thrust in the direction opposite to that of the firstmentioned end thrust.

14:. A steam-turbine comprising a bladed at the inlet end thereof andlessin diameter than said end, means for retard'ing periphertween said piston and the turbine-casing in a direction away from said drum and for caus-v ing said steam to exert upon said drum an endY thrust in the direction opposite to the aforesaid direction, said piston and drum being adapted to allow steam that has escaped past said means to pass through them into the exhaust-space of said drum, a second drum .coaxial With, fast to, and ha its eX- haust end adjacent tothe exhaust e [d of the aforesaid drum and adapted by blading for rotation in the direction opposite to thatfor v-which the first-mentioned rum is bladed, a second piston fast to saidI second drum and .located at the inlet end thereof, means for enablingthat end ,of said second piston which and causing the last-mentioned steam to prol m` coaxial with, fast to, and havingits exhaust end addrum, a piston fast to said drum and located ally of said piston the escape of steam ,be--

the direction opposite to that of the'iirstdirection away from said drum and for causthe direction (piosite to that for which the from said second drum to be placed into coms,

IOO

communication with said inlet retarding perio f-aitl-ie1" ii'oinisaids'econd' drinn to be placed into communication v either with .the inlet' of' 'second-mentioned drum is to' beused, said` second pistonfand second drum. being'closed `to the passa-ge thfough them of 'steam\t-ha;t2

has escaped past the second piston to the end thereofffaitherrom said second drum,k and means for-when said end ofl said-second piston 1s in communication with said inlet `re'.

, 'terding peripherally of-said second'` piston the escape yof stlemfbetween said second piston- -f and said casingA fromsaid end of said' second CHARLES piston and cs nslngv the 1astment1onedsteamto produce lonffsfiid second pist-onv suifnd' {thrust-1n thedirect-ionfopposite to that of the first-mentioned 'end thrust.

. 1.5,'A reversible turbine com' cation With'tlie exhaust.. i

l* Signed at ,Newcastle-- u'ponfTne, in .the i county' of'NorthuinbeI-lend; this 21st dey ofl 215

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