Document
United States Patent [191 [ill Patent Number: 4,934,138
Boyd [45] Date of Patent: Jun. 1 9 , 1990
[54] HIGH TEMPERATURE TURBINE ENGINE 4,152,096 5/1979 Murakami et al. ............... 415/214.1
4,176,519 12/1979 Kronogard ......................... 60/39.32
STRUCrURE
4,247,256 1/1981 Maghon .......................... 416/244 A
[75] Inventor:
Gary L. Boyd, Tempe, Ariz. 4,537,560 8/1985 Emeterro ........................ 416/198 A
4,682,934 7/1987 Knorowski ..................... 416/244 A
A l l i e d - S i g n a l Inc., Morris Township, [73] Assignee: 4,832,574 5/1989 Woodwetl et al. 416/244 A .............
Morris Countv. N.J.
FOREIGN PATENT DOCUMENTS [21] Appl. No.: 280,761 735504 4/1943 Fed. Rep. of Germany .
[22] Filed: k. 6 , 1988
2714209 10/1977 Fed. Rep. of Germany ... 416/241 B
57-168004 10/1982 Japan ............................... 416/241 B
[51] Int. C l . 5 ................................................ M)2C 3/00
578533 7/1946 United Kingdom ............ 416/241 B
[52] U . S . Cl. .............................. 6 0 / 3 9 . 7 5 ; 416/244 A;
2034440 6/1980 United Kingdom ............ 416/241 B
416/241 B [58] Field of Search ................. 60/39.75, 39.32, 39.02; OTHER PUBLICATIONS 416/204 A, 244 A, 244 R, 198 A, 241 B; Ceramic Design Methodology and the AGTlOl Tech.
4W214.1; 403/370 Paper 3/1985 by Gary L. Boyd et al.
~561 References C i t e d Automotive G a s Turbine Ceramic Component Testing Tech. Paper by Carruthers et al.
U.S. PATENT DOCUMENTS Primary Examiner-Louis J. Casaregola
1,551,402 8/1925 Junggrew ....................... 416/198 A
Assistant Examiner-Timothy S . Thorpe 1,721,060 7/1929 Swartz .
Attorney, Agent, or Firm-Terry L. Miller; James W.
2,297,508 9/1942 Schutte ........................... 416/244 R
2,660,399 11/1953 Robinson et al. ............... 416/198 R McFarland; Robert A. Walsh
3,304,052 2/1967 Warner et al. .................. 416/244 R
WI ABSTRACT
3,335,580 8/1967 Simpson, Jr. .
3,356,339 12/1967 Thomas et al. ................. 416/244 R
A high temperature turbine engine includes a hybrid 3,604,819 9/1971 Kraheetal. .
ceramic/metallic rotor member having ceramic/metal
3,680,979 8/1972 Hansen ............................ 416/198 R
joint structure.. The disclosed joint is able to endure 3,872,691 3/1975 Hildebrandt .
higher temperatures than previously possible, and aids
3,941,506 3/1976 Robb et al. ..................... 416/244 A
in controlling heat transfer in the rotor member.
3,943,703 3/1976 Kronogard ......................... 60/39.32
3,976,399 8/1976 Schmoch ........................ 416/198 A
4,011,737 3/1977 Kruger . 11 Claims, 2 Drawing Sheets
US. Patent J U ~ . 19,1990 Sheet 1 of 2 4934,138
U.S. Patent J W ~ . 19,1990 Sheet 2 of 2 4,934,138
4.934.138
1 2
hybrid ceramic/metallic rotor structure for a turbine HIGH TEMPERATURE TURBINE ENGINE engine.
s m u m
More particularly, it is an object for this invention to provide a structure uniting a ceramic turbine rotor por- The United States Government has rights in the pres- 5 tion with a metallic shaft portion for torque transmitting ent invention pursuant to Contract No. DEN3-167 is- corotation with retention of axial and radial selected sued and funded by the Department of Energy (DOE), relationships, and allowance of differential thermal and and administered by the National Aeronautics and centrifugal relative movements between the portions.
Space Administration (NASA).
Still further, it is an object for this invention to pro- 1 0 vide a turbine engine wherein a ceramic turbine rotor TECHNICAL FIELD portion and an axially adjacent metallic compressor The present invention is in the field of high tempera- rotor portion are coaxially united for torque transmit- ture turbine engine structure. Particularly, the present ting corotation to define a substantial portion of a tur- invention is directed to structure of a high temperature bine engine rotor member.
turbine engine composed of both metallic and ceramic Accordingly, the present invention provides a hybrid components.
ceramic/metallic structure comprising: a first ceramic portion defining a respective first axially extending bore BACKGROUND O F THE INVENTION opening outwardly thereon, said first portion further A long-recognized need in the turbine engine art has defining on said fvst bore an annular step disposed away been to attain higher operating temperatures in order to 2o from said bore opening, a second portion axially adja- achieve both a greater thermodynamic efficiency and cent said first ceramic portion, a metallic annular collet an increased power output per unit of engine weight.
member received into said first bore and including a Ideally, a turbine engine should operate with stoichio- circumferentially arrayed plurality of axially elongate metric combustion in order to extract the greatest possi- radially resilient finger portions, said plurality of finger ble energy value from the fuel consumed. However, the 25 portions proximate the distal end thereof defining a temperatures resulting from stoichiometric and even radially outwardly extending shoulder engaging said near-stoichiometric combustion are beyond the endur- step, tensile means engaging said collet member and ance capabilities of metallic turbine engine components.
extending axially toward said second portion for apply- Consequently, as the turbine engine art has progressed, 3o ing an axially directed tensile force to the collet member an ever greater emphasis has been placed upon both which force is reacted through the second portion to enhanced cooling techniques and the development of secure the latter and said first portion axially together.
temperature and oxidation resistant metals for use in An advantage of the present invention is that it pro- components of the engine which are exposed to the vides a hybrid ceramic/metallic turbine engine rotor highest temperatures. That is, cooling techniques and 35 member wherein the beneficial characteristics of each high temperature metals have been developed for each material are employed to best advantage.
of combustion chambers, turbine stator nozzles, and Another advantage of the present invention resides in turbine blades. This quest has led to the development of the positive axial and concentric mutual torque trans- elaborate cooling schemes for all of these components mitting interrelationship established between the ce- as well as to classes of nickel-based “super alloy” metals 40 ramic and metallic portions of the inventive rotor mem- which may be cast using directionally solidified or sin- ber.
gle crystal techniques. All in all, the quest for higher Further to the above, because of the strong coaxially operating temperatures in a turbine engine fabricated of concentric relationship of the ceramic and metallic metallic components has led to a still increasing com- rotor member portions, a radially outwardly directed plexity and expense in the making of the engine.
45 axially extending cylindrical surface part of the ceramic An alternative approach to the attainment of higher portion may be employed to define a journal bearing operating temperatures in a turbine engine has been surface. That is, the rotor member may be journaled in recognized. This approach involves the use of high- a turbine engine by an external surface part of the ce- strength ceramic components in the engine. Ceramic ramic portion so that only one additional bearing is components are better able than metals to withstand the 50 required to satisfactorily support the rotor member.
high temperature oxidizing environment of a turbine This one additional bearing may be located in a compar- engine. However, the term “high strength” in connec- atively cooler portion of the turbine engine.
tion with ceramic structures must be viewed in context.
Additional objects and advantages of the present While many ceramic materials exhibit superior high invention will appear from a reading of the following temperature strength and oxidation resistance, ceramics 5 5 detailed description of a single preferred embodiment of have historically been difficult to employ in turbine the invention taken in conjunction with the appended engines because of a comparatively low tensile fracture drawing figures.
strength and a low defect tolerance. Consequently, a long-recognized need has been for the development of BRIEF DESCRIPTION OF THE DRAWINGS hybrid ceramic/metallic structures which utilize the FIG. 1 provides a fragmentary longitudinal view, characteristics of each material to best advantage in 60 partly in cross section of a hybrid ceramichnetallic order to allow combustion in a turbine engine to take turbine engine embodying the invention; place closer to or at the stoichiometric level.
FIG. 2 depicts an enlarged fragmentary cross sec- SUMMARY OF THE INVENTION tional view of a portion of the engine presented by FIG.
In view of the deficiencies of the conventional tur- 65 1 with parts thereof omitted for clarity of illustration; bine engine art, and of the materials of construction and and FIG. 3 provides an exploded perspective view of a structural techniques available for making such engines, it is a primary object for this invention to provide a turbine rotor assembly portion of the turbine engine,
4,934,138
Viewing now FIGS. 2 and 3 in conjunction, it will be with parts thereof omitted or broken away for clarity of illustration. seen that the hybrid ceramic/metallic rotor member 20 includes not only the metallic compressor rotor portion BEST MODE FOR CARRYING OUT THE 22, the ceramic turbine rotor portion 4 4 , and metallic INVENTION 5 power output shaft portion 60(not visible in FIGS. 2 FIG. 1 depicts a hybrid ceramic metallic turbine and 3), but also a torque transmitting and concentricity retaining coupling structure generally referenced with engine 10. The engine 10 includes a housing 12 which the numeral 62, and an axial retention coupling struc- 14, an outlet 16, and a tortuous flow path defines an inlet ture generally referenced with the numeral 6 4 . The 18 communicating the inlet 14 with the outlet 16 for 1 0 coupling structures 62 and 64 are cooperative to unite conveying a flow of fluid therebetween. A hybrid cera- the portions 22,44 and 60 to define the rotor member mic/metallic rotor member generally referenced with 20.
the numeral 20 is journaled in the housing 12 and coop- Both the metallic compressor rotor portion 22 and erates therewith to bound the flow path 18. It will be the ceramic turbine rotor portion 44 include an individ- seen that the rotor member 20 includes a compressor 15 u a l hub part, respectively referenced with the numerals rotor portion 22, rotation of which inducts ambient air 66 and 6 8 . Similarly, each of the rotor portions 22 and via inlet 14, as indicated by arrow 24, and delivers this 44 include a plurality of circumferentially arrayed inte- air pressurized to a flow path section 1 8 as indicated by gral blade parts, respectively referenced with the nu- arrow 26.
merals 70 and 72, which extend both axially and radially The flow path section 18‘ leads axially through a 20 outwardly on the hub parts 66,68. The turbine rotor segment of somewhat less than 180’ of a rotary annular portion 44 includes an integral elongate axially extend- regenerator member 28 which is received in the housing ing stepped cylindrical boss part 74 extending from the 12. Downstream of the regenerator 28, the flow path 18 hub 44 toward the compressor rotor portion 22. Carried leads through an axially extending combustion structure upon a reduced diameter end part 76 of the cylindrical generally referenced with the numeral 30. The combus- 25 part 74 is a metallic collar member 78. The collar mem- tor structure 30 is fabricated of ceramic material and ber 78 on one side defines a plurality of radially and includes a ceramic outer liner 32 which is supported at axially extending circumferentially arrayed curvic cou- one end by a generally cone-shaped outer transition pling teeth 80 which mesh with a similar array of curvic member 3 4 . A ceramic inner combustion liner 36 is teeth 82 defined by the hub part 66 of rotor portion 22.
coaxially disposed within the outer liner 32, and is sup- 30 Because of the intermeshing of the teeth 80,82, the hub ported at one end on a ceramic transition duct member part 66 and collar member 78 are coupled in torque 3 8 . The flow path 18 leads axially toward the one end of transmitting relation, and are also retained concentri- the combustion liner 36, as indicated by arrow 18”.
cally to one another while allowing for differential Within the transition duct member 38, a ceramic turbine thermal and centrifugal expansions of these compo- back shroud member 40 and a ceramic turbine stator 35 nents.
member 42 cooperatively define the flow path 18, and In order to unite with the cylindrical part 74 of the lead the latter radially inwardly to a ceramic turbine rotor portion 44, the collar member 78 includes an axi- rotor portion 44 of the rotor member 20.
ally extending band portion 84 circumscribing the re- Downstream of the turbine rotor portion 44, the flow duced diameter end part 76 of rotor portion 44. The path 18 extends axially and radially outwardly between 40 band portion 84 and reduced diameter part 76 define an a pair of spaced apart cooperative ceramic exhaust duct interference fit therebetween so that collar 78 is perma- members, respectively referenced with the numerals 44. Preferably, the nently united with rotor portion 46,48. A plurality of hybrid ceramic/metallic fastener interference fit between band portion 84 and part 76 of members 50 (one of which is visible in FIG. 1 ) coopera- the rotor member 44 is established by separately rela- tively engage the one exhaust duct member 46 and the 45 tively heating the collar 78 while relatively cooling the housing 12. A ceramic spacer member 52 received over rotor part 76. While this temperature difference be- the fastener members 50 spaces apart the duct members tween the collar 78 and part 76 of rotor 44 exists, the 46,48.
two are united, and thereafter allowed to come to tem- Subsequent to the exhaust duct members 46,48, the perature equilibrium. This type of interference fit is flow path 18 leads to an exhaust chamber generally 50 conventionally referred to as a “shrink fit”.
referenced with the numeral 54. A segment of some- It will be noted that a radially outwardly disposed 180’ of the ceramic regenerator member what less than elongate cylindrical surface 86 of the cylindrical por- 28 is exposed to the exhaust chamber 54. Consequently, tion 74 is radially outwardly circumscribed and con- the flow path 18 leads once again through the regenera- fronted by the bearing 56. That is, the surface 86 defines 28, and to ambient via the outlet 16.
tor member 5 5 for the rotor member 20 ajournal surface by which the In order to complete this description of the engine 10, rotor member is rotatably supported in housing 12.
it must be noted that in the combustor 30 fuel is added Axial location of the rotor member 20 in housing 12 is to the pressurized a i r flowing from compressor rotor 22 controlled by a rolling element bearing (not shown in to support combustion. This combustion results in a the figures) engaging the power output shaft portion 60 flow of high temperature pressurized combustion prod- 60 (viewing FIG. 1) of the rotor member 20. The bearing ucts flowing downstream in the combustor 30, and in 58 also serves as a thrust rolling element bearing to flow path 18 subsequent to the combustor. Also, the transmit axial forces from rotor member 20 to the hous- rotor member 20 is journaled in housing 12 by a journal ing 12.
bearing 56 disposed between the rotor portions 22 and Also defined by the ceramic rotor portion 44 is an 44, and a rolling element bearing (not visible in the 65 axially extending stepped blind bore 88. The bore 88 figures) disposed adjacent a metallic power output shaft includes a hemispherical end wall 90 which is disposed portion 60 (only a portion of which is visible in FIG. 1) generally within the hub 68 of the rotor portion. The of the rotor member 20. bore 88 terminates in an opening 92 within end part 76,
4,934,138
5 6
and defines a step 94 disposed toward the end wall 90 F. (650" C.). Under these conditions, a metallic journal and spaced intermediate the latter end wall and opening surface at 86 would not favorably endure. That is, the 92. Step 94 is defined by the cooperation of a smaller surface 86, were it made of a metallic material, would diameter bore portion % with the remainder of bore 88.
oxidize and degrade, resulting in a detrimental operat- Received into the bore 88 is an elongate metallic 5 ing condition for the journal bearing 56, and shortened annular collet member 98. The collet member 98 in- operating life. On the other hand, the ceramic surface 86 cludes a circumferentially arrayed plurality of elongate of the turbine rotor portion 44 well endures 1200" F.
radially resilient finger portions 100 integral with and (650" C.) operation in an oxidizing atmosphere to pro- extending axially from a ring portion 102 of the collet vide a smooth journal surface and long life for bearing member. Each of the finger portions 100 defines a re- 10 5 6 .
spective radially outwardly extending shoulder 104 and Further to the above, in view of the 1200' F. (650" C.)
a radially inwardly extending step 106. The finger por- operating temperature at surface 86 adjacent the left tions 100 may be considered to collectively define a end of bearing 56, it is easily appreciated that the cou- single radially outwardly extending shoulder 104 and a pling structure 64 must endure temperatures in the single radially inwardly extending step 106. The shoul- 15 range extending to about 1200" F. (650" C.). This high 104 of the fingers 100 each engage the step 94 of ders temperature at the coupling structure 64 rules out the bore 88, while a metallic locking sleeve member 108 is use of all conventional shrink fit, brazed, and adhesively received within the fingers 100 and engages the steps joined ceramic/metal joints. None of these conven- 106 thereof. The ring portion 102 of collet 98 includes a tional ceramic/metal joint structures are capable of thread-defining portion 110 into which a termination 20 enduring the operating environment which the cou- portion 112 of an elongate metallic tie bolt member 114 pling structure 64 endures very well.
is threadably received. The termination portion 112 Finally, it will be noted that the turbine rotor portion traps the locking sleeve member 108 within the fingers 44 defines a rather limited conductive heat transfer path 100, and thereby positively prevents their disengage- extending from the hub part 68 rightwardly toward the ment from step 94. At its end opposite the termination 25 coupling structures 62 and 6 4 . That is, the turbine rotor portion 112, the tie bolt member 114 carries a nut (not portion 44 defines only an annular conductive heat on a threaded part 1 1 4 ' thereof and 86 and the visible in the figures) transfer path radially between the surface which bears upon the power output shaft portion 60 of bore 88 within which heat is conducted axially right- the rotor member 2 0 . Consequently, the collet member wardly, viewing FIG. 2 . Because of the relatively lim- 98 and tie bolt 114 are stressed in tension, while the 3 0 ited size of this heat transfer path and the distance of remainder of the rotor member 20 rightwardly of the coupling structure 62 from the hub part 68, the operat- collet member 98 is loaded in compression. ing temperatures experienced at the collar 78 are low In view of the above, it is easily seen that the coupling enough to allow the shrink fit ceramic/metallic joint structure 62 is preserved in torque transmitting relative thereat to serve satisfactorily.
position by the axial retention effect provided by the 35 While the present invention has been depicted and coupling structure 64. It should be noted that compres- described by reference to a single preferred embodi- sor rotor portion 22 and power output shaft portion 60 ment of the invention, such reference does not imply also define a curvic coupling therebetween so that any limitation upon the invention, and no such limita- torque from turbine 44 may be delivered externally of tion is to be inferred. The invention is intended to be the engine 10 via the shaft portion 60. 40 limited only by the spirit and scope of the appended It will be understood that during manufacture of the claims which provide additional definition of the inven- rotor member 20, the metallic collet member 98 is in- tion.
What is claimed is: serted from outside through the opening 92 and into bore portion % such that the finger portions 100 resil- 1 . A high temperature turbine engine comprising a iently deflect radially inwardly. This deflection of the 45 housing and a hybrid ceramic/metallic rotor member finger portions 100 allows the shoulders 104 to pass cooperatively defining an inlet, an outlet, and a flow through bore portion % and into the remainder of the path communicating a flow stream of elastic fluid there- bore 88 beyond step 9 4 . Thereafter, the metallic locking between, in response to rotation of said rotor member a a i r via said inlet sleeve 108 is inserted into the collet member 98 so that compressor section inducting ambient the fingers 100 cannot deflect radially inwardly to pass 50 and delivering this a i r pressurized to a combustor sec- the shoulders 104 outwardly of the step 94. With the tion, means delivering a supply of fuel to said pressur- sleeve member 108 received into the collet member 98, ized a i r in said combustor section to support combustion the end termination portion 112 of the tie bolt 114 is producing a flow downstream in said flow path of high temperature pressurized combustion products, a turbine threadably engaged at 110 with the collet member 98.
55 section expanding said flow of combustion products to Thus, the sleeve member 108 is trapped within the col- extract mechanical power therefrom rotating said rotor let member 98, and the latter is trapped within the bore 88. Of course, reversal of the assembly procedure al- member, said rotor member including a ceramic turbine lows the rotor member 20 to be disassembled into its portion having a ceramic hub part and a plurality of component parts, should such be desired. aeroreactive blades extending radially outwardly Also, it will be recalled that during operation of the 60 thereon, an integral ceramic boss part extending axially turbine engine 10, the turbine rotor portion 44 is ex- from said hub part, said boss part defining an axially posed to a flow of high temperature pressurized com- extending first central bore opening on an end thereof bustion products. This flow of combustion products has and having an outer smaller diameter bore portion co- operating with the remainder thereof to define a step a temperature in the range of 2000' F. (1090" C.) to 2500' F. (1370" C.), or more, and may be expected to be 65 disposed away from said opening, an axially next-adja- cent metallic rotor member portion confronting said of an oxidizing nature. Consequently, the temperature experienced at the end of the journal bearing surface 86 boss part and defining an axially extending second bore closest axially to the turbine hub 68 will be about 1200" aligning with said first bore, said turbine rotor portion
4,934,138
7 8
and said axially next-adjacent portion including cooper- coupling said first portion and said second portion for torque transmission therebetween and for retention ating means for torque transmission and material coaxial radial alignment thereof dependent upon retention of a of radially coaxial corotational relation dependent upon retention of a selected axial relationship selected axial relationship thereof, a metallic annular 5 therebetween: collet member received axially into said first bore, said collet member including an annular ring portion and a providing on said first portion bore an outer smaller diameter bore portion cooperating with the re- circumferentially arrayed plurality of axially extending mainder of said bore to define a step disposed away radially resilient finger portions extending from said from said bore opening: ring portion to terminate at respective distal ends, said providing a metallic axially elongate collet member 10 plurality of finger portions cooperatively defining a including an annular ring portion having an outer radially outwardly extending shoulder proximate said diameter slidably receivable axially into said distal ends and engaging said step to retain said collet smaller diameter bore portion, and a circurnferen- member in said first bore, an elongate tie bolt member tially arrayed plurality of elongate radially resilient threadably engaging said ring portion and being re- finger portions extending axially from said ring 15 ceived in said second bore to apply an axially directed portion to terminate in respective distal ends tensile force to said collet member which tensile force is thereof: reacted through said axially next-adjacent portion to defining collectively on said plurality of finger por- retain the latter in said selected axial relationship with tions and proximate said distal finger ends thereof a said first ceramic turbine portion.
20 radially outwardly extending annular shoulder 2. The invention of claim 1 wherein said axially ex- having an outer diameter greater than said smaller tending ceramic boss part further defines a circularly diameter bore portion: cylindrical axially elongate outer surface on said turbine resiliently deflecting said plurality of finger portions rotor portion, said boss part outer surface defining a radially inwardly at said distal ends thereof to re- journal bearing surface for said turbine rotor.
duce said shoulder to a diameter passable through 25 3. The invention of claim 1 wherein said cooperating said smaller diameter bore portion, means includes said axially extending boss part carrying passing s a i d collet member axially into said bore to a metallic collar member &curing tiereto gdjacent-saii engage said shoulder with said step, end thereof, said collar member defining a first circum- applying an axially directed tensile force to said collet ferentially PIur& Of cUrVic teeth, 30 member direct& to withdrawing the latter from said axially next-adjacent metallic portion defining a said bore, and E o n d circmferentially arrayed plurality Of cUrVic reacting said withdrawing force through said rotor coupling teeth meshing with said first plurality.
member second portion to retain the latter and said 4. The invention of claim 3 wherein said collar mem- first portion in said selected axial relationship.
ber includes an axially extending annular band portion 35 9. The method of claim 8 wherein said step of COU- cooperating with the remainder of said collar member piing said first portion and said second portion includes to define an axially extending recess, said axially extend- the steps of: ing boss part of said ceramic turbine rotor portion being providing on said second portion a circumferentially received into said recess to define an interference fit arrayed first plurality of axially and radially ex- relationship with said band portion. 40 tending curvic coupling teeth: 5. The invention of claim 1 wherein a sleeve-like providing a metallic collar member: bCking member is received axially into said cO&t mem- permanently securing said collar member to said first ber and is radially engageable by said plurality of finger portion at said boss part: portions to Prevent disengagement of the latter from providing on said collar member a circumferentially said step. 45 arrayed second plurality of curvic coupling teeth, 6. The invention of claim 5 further including said and plurality of finger members collectively defining a radi- meshing said first plurality of teeth with said second ally inwardly extending second step proximate said plurality of teeth.
distal finger ends, said second step being engageable by 1 0 . The method of claim 8 wherein said step of apply- said sleeve-like locking member to prevent axial move- 50 ing an axially directed tensile force to said collet mem- ment thereof in one axial direction.
ber includes the steps of: 7. The invention Of claim 6 wherein said tie bolt mem- defining a thread surface on said ring portion of said ber defines an abutment surface spaced from and con- collet member, fronting said second step, said abutment surface being providing an elongate tie bolt member having an end engageable by back locking sleeve member to prevent 55 termination part threadably engageable with said axial movement thereof in a second direction opposite collet member, said fist direction to thereby trap said sleeve member threadably engaging said collet member with said tie within said collet member.
bolt; and 8. A method of providing a hybrid ceramic/metallic applying a tensile force to said tie bolt member.
rotor member for a high temperature turbine engine, 60 11. The method of claim 8 further including the steps said method comprising the steps of: of: providing a sleeve-like locking member, providing a ceramic rotor member first portion: defining on said ceramic portion an integral axially inserting said locking member into said collet mem- ber, and extending boss part which in part defines an elon- engaging radially said locking member with said plu- gate axially extending bore opening on an end of 65 rality of finger members to prevent disengagement said boss part, of the latter from said step. providing a metallic rotor member second portion
* * * * *
axially next-adjacent to said first portion;