A gas lubricated thrust bearing is described which employs relatively rigid inwardly cantilevered spokes carrying a relatively resilient annular member or annulus. This annulus acts as a beam on which are mounted bearing pads. The resilience of the beam mount causes the pads to accept the load and, with proper design, responds to a rotating thrust-transmitting collar by creating a gas film between the pads and the thrust collar. The bearing may be arranged for load equalization thereby avoiding the necessity of gimbal mounts or the like for the bearing. It may also be arranged to respond to rotation in one or both directions

Anderson, W. J.

English

NASA Technical Reports Server

United States Patent [191 
Anderson 
[ 1 1  1 3,971,602 
[451 July 27, 1976 
is41 THRUST BEARING 
[75] Inventor: William J. Anderson, North 
Olmsted, Ohio 
[73] Assignee: The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[22] Filed: June 25, 1975 
1211 Appl. No.: 590,182 
[52] U.S. CI ................................. 308/160; 308/163; 
308/ 170 
Int. C1 .* .......................................... F16C 17/06 
Field of Search ........... 308/139, 160, 162, 163, 
308/168, 170, 134.1, 122 
[51] 
[58] 
[561 References Cited 
UNITED STATES PATENTS 
1,664,878 4/1928 Flintermann ........................ 308/1 60 
1,767,238 6/1930 Howarth ............................. 308/160 
r- 
2. 
3,378,319 4/1968 Cutting et al ....................... 308/160 
3,677,612 7/1972 Barnett et al ....................... 308/168 
Primary Examiner-M. H. Wood, Jr. 
Assistant Examiner-Gene A. Church 
Attorney, Agent, or Firm-N. T. Musial; G. E. Shook; 
John R. Manning 
[571 ABSTRACT 
A gas-lubricated thrust bearing employs relatively 
rigid inwardly cantilevered spokes carrying a relatively 
resilient annular member or annulus. This annulus acts 
as a beam on which are mounted bearing pads. The 
resilience of the beam mount causes the pads to ac- 
cept the load and, with proper design, responds to a 
rotating thrust-transmitting collar by creating a gas 
film between the pads and the thrust collar. The bear- 
ing may be arranged for load equalization thereby 
avoiding the necessity of gimbal mounts or the like for 
the bearing. It may also be arranged to respond to ro- 
tation in one or both directions. 
7 Claims, 10 Drawing Figures 
b8 
i 
-7 
'16 2* 
https://ntrs.nasa.gov/search.jsp?R=19760022500 2020-03-20T02:22:19+00:00Z
U.S. Patent July 27, 1976 Sheet 1 of 2 3,97 1,602 
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2. 
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'16 2* 
ROTOR 
ROTATION' 
FlG.2 
U.S. Patent July 27,1976 Sheet 2 o f 2  3,971,402 
FIG.3 
20 
FIG.40 
18b 22 18b 1 5 .  22 
FIG.4 ' L 5 .  
I FIG.5 
FIG.6 
FIG. 7a 
FlG.7b 
3,97 1,602 
1 
THRUST BEARING 
The invention described herein was made by an em- 
ployee of the United States Government and may be 
manufactured and used by or for the Government for 
governmental purposes without the payment of any 
royalties thereon or therefor. 
BACKGROUND OF THE INVENTION 
Thrust bearings employing pads against which a ro- 
tating thrust ring acts are known. Such bearings with 
rigid geometry members or pads forming a load cany- 
ing film with rigid mountings are known. These bear- 
ings are sensitive to contaminating particles carried by 
the gas. A second type employs rigid geometry mem- 
bers or pads to form a load carrying film with compliant 
mountings. To date these use elastomeric materials in a 
compliant mounting. Such materials are severely tem- 
perature limited, and do not have adequate stiffness for 
machines with close tolerance impellers in which axial 
movement of the rotor must be limited. They are not as 
sensitive to contaminating particles as the first type. A 
third type use foil arrangements. These can be started 
and stopped without external pressurization and are 
still less sensitive to contaminating particles. Neverthe- 
less, these have limited stiffness. Attempts to increase 
stiffness have until now led to problems with starting 
torque and power loss. 
OBJECTS OF THE INVENTION 
It is an object of the invention to provide an im- 
proved gas trust bearing. 
It is another object of the invention to provide a gas 
thrust beaiing of the type using bearing pads which are 
less sensitive to contaminating particles than prior pad 
bearing gas thrust bearings. 
SUMMARY OF THE INVENTION 
A gas-lubricated thrust bearing assembly of the in- 
vention employs inwardly cantilevered, relatively rigid 
beams or spokes carrying a relatively resilient heat 
resistant annular member. On the resilient member are 
mounted rigid thrust bearing pads. The pads are lo- 
cated on the annulus circumferentially between the 
spokes, so that under load the pads yield due to the 
resilience of the annulus. Hence, the annulus acts as a 
resilient beam bearing each pad between a pair of 
spokes. Under selected mounting arrangement, the 
pads may equalize the load among themselves, avoiding 
the necessity for gimbals or the like for load equaliza- 
tion. As will appear hereinafter, the bearing may be 
designed for bidirectional rotation of the bearing rotor. 
Other objects and advantages of the invention will be 
apparent from a reading of the specification in connec- 
tion with the accompanying drawings. 
DESCRIPTION OF THE DRAWINGS 
FIG. 1 is a longitudinal sectional view through a bear- 
FIG. l a  is a partial sectional view useful in describing 
FIG. 2 is a cross-sectional view along the lines 2-2 
FIG. 3 is a partial cross-sectional view along the lines 
FIG. 4 is a partial sectional view of an embodiment of 
the invention designed for self-equalization of the 
thrust load against a plurality of pads. 
ing embodying the invention. 
the operation of the embodiment of FIG. 1. 
of FIG. 1. 
3-3 of FIG. 2. 
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40 
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2 
FIG. 4a is a partial sectional view useful in describing 
FIG. 5 is a partial cross-sectional view along the lines 
FIG. 6 is a partial longitudinal cross-sectional view of 
an embodiment of the invention arranged for bidirec- 
tional thrust loading. 
FIG. 7 is a schematic, partial cross-sectional view of 
still another embodiment of the invention, illustrating 
in FIG. 7a the result of rotation in one direction and in 
FIG. 7b the result of rotation in the reverse direction. 
DETAILED DESCRIPTION 
With reference to FIG. 1, a shaft 10 rotatable about 
an axis 8 in the direction indicated by arrow 9, carries 
a thrust collar 12. The longitudinal thrust of the rotat- 
ing shaft 10 is to be received and borne by the thrust 
bearing 14. The bearing 14 comprises in annular form 
a ring 16 which may be gimbal mounted or, as illus- 
trated by the usual convention, fastened directly to the 
machine frame. The ring 16 carries six inwardly can- 
tilievered members or spokes 18 spaced circumferen- 
tially angularly equally. On the spokes 18 is mounted a 
resilient metallic heat resistant annulus 20 (rather than 
elastomeric) which serves between adjacent pairs of 
spokes as a beam. The annulus 20 is resilient relative to 
the spokes 18 which are stiffer than the annulus 20. On 
the annulus 20 are mounted six rigid, sectoral shaped 
pads 22 spaced equally circumferentially between the 
spokes 18 as viewed in FIG. 2, but the spacing b from 
spoke center-line to adjacent pad circumferentially in 
the direction of shaft rotation (counter-clockwise) is 
greater than the distance from the same pad to the 
succeeding spoke center-line in the same direction. In 
other words, the leading edge of pad 22 is more remote 
(distance b) from its adjacent beam 18 than the lagging 
edge of pad 22 (distance a ) from its adjacent beam 18. 
The number of cantilevered beams and pads are exem- 
plary only and may be selected depending upon the 
bearing size, load requirements and other design fac- 
tors. 
Referring to FIG. 3, it will be apparent that adjacent 
spokes 18 serve as supports between which the resilient 
annulus 20 serves as a beam to carry each pad 22. The 
axial stiffness of the resilient beam or annulus 20 is a 
function of the beam dimensions between each set of 
spokes 18. The angular stiffness considering the load 
pad 22 to be infinitely stiff in bending relative to the 
resilient beam 20 is a function of the ratio of b, the 
distance of the leading edge of the pad 22 from the 
center of its adjacent spoke 18, to a, the distance of the 
lagging edge of the pad 22 from the center of its adja- 
cent spoke. It also will be a function of the thickness of 
the resilient annulus 20, of the difference R2 - R1, the 
radial dimension of the spoke 18 and the distance cen- 
ter to center of adjacent spokes 18. The resilient beam 
20 may be designed to produce during operation near 
optimum pad inclination in the circumferential direc- 
tion, Le., the maximum gas film thickness, for any value 
of unit pad loading and velocity of rotation. 
For a uniform thickness resilient beam or annulus 20 
the leading and trailing edges of each load pad should 
be in radial directions. This would make the resilient 
beam support less stiff at R2 than at R1 resulting in a 
divergent film in the direction of increasing radius, and 
reduced load capacity. The thickness t of the resilient 
beam can be made thicker at R2 than at R1 or the 
leading and trailing edges of each pad can be directed 
the operation of the embodiment of FIG. 4. 
5-5 of FIG. 4. 
3,97 1,602 
3 4 
so that deflections at R l  will be equal to or greater than of gimbals or the like in mounting the bearing assembly 
those at R2. A slightly convergent film in the direction may be avoided. 
of increasing radius would then result. This is desirable FIG. 6 illustrates a configuration for supporting the 
for greater load capacity. thrust load in either axial direction. There are two sets 
In FIG. 3. the resilient beam 20 is illustrated as rigidlv 5 of pad resilient beam assemblies 14, each mounted to a 
mounted to a flat surface on each radial spoke 118. I;! 
this design, the load will tend not to be self-equalized 
among the different pads 22. The reason is that the 
constraint of the mounting to the spokes 18 constrains 
the annulus 20 at that point to have a zero slope rela- 
tive to the axis, Le., to remain at each spoke in a plane 
substantially normal to the axis. FIGS. 4 and 5 illustrate 
a somewhat different embodiment, in other respects 
similar to that of FIG. 1, except for the attachment of 
the spokes 18 to the annulus 20. In the embodiment of 
FIGS. 4 and 5, the loads among the various pads 22 will 
tend to be self-equalized. The spokes 18a, correspond- 
ing to the spokes 18 of FIG. 1, are shaped to provide 
the effect of a fulcrum edge at their iunctions with the 
set of radial spokes 18. The two sets of spokes 18 are 
joined to a ring 24 which may be gimbal mounted or, as 
indicated, rigidly mounted to the machine frame. The 
collar 12 naturally must be designed to act in either 
axial direction. 
In FIG. 7 is illustrated a configuration for supporting 
the thrust load to accept a rotor rotation in either direc- 
tion. FIG. 7a illustrates rotation of the thrust collar 12 
in one (arbitrarily termed a primary) direction indi- 
cated by an arrow. In FIG. 7b, the reverse direction of 
rotation is indicated by an oppositely directed arrow. 
On the annulus 20 are fastened stops 20a and 20b. 
Each Dair of stom 20a and 206 are located adjacent the 
- space between a pair of pads 22 and each stop equally 
annulus 20. 2o distant from the adjacent pad. Secondary spokes 18c 
Moreover, thickening members Or bars 18b may be 
2o Opposite the spokes 
are arranged in opposition to the spokes 18, whereby 
when the rotor rotates in one direction, the stops 2Oa provided on the side Of 
l8 to enhance the attachment, and the fdcrum 
junction. The arrangement is such that there is little 
constraint on the annulus 20 to remain at the junction 25 leading edge of the pad is 
in a plane to the axis 8' In Other words, the 
beam 2o at the 'pokes 18a is free to pivot 
slightly along the idealized edge of each spoke. 
The operation of and the distinction between the 
embodiment of FIGS. 1 through 3 and that of FIGS. 4 30 
and 5 will be apparent from the drawings of FIGS. la  
and 4u. In these drawings, the representations bear 
bered in the drawings. 
reach the secondary spokes 1& to halt the thrust bear- 
ing and at the Same time locate the pads 22 so that the 
remote from its nearest 
spoke 18 than the lagging edge from its spoke 18. AC- 
cordingly, if the stops are spaced correctly, the pads 22 
will assume an angular disposition to provide the de- 
sired spacing and gas bearing. 
The action of the bearing when the rotor is stopped 
and reversed is such that the initial pad position is not 
the ratio b to a corresponding to the ratio described in 
FIG. 1 is opposite what it should be. The frictional 
reference numerals corresponding to the as num- correct and no load capacity can be developed because 
In the embodiment of FIG. 1 as illustrated in FIG. la, 35 
as the collar 12 approaches speed in the rotation direc- the Pad 
tion 9, the ambient gas, which may be air, is entrapped On the 2o to rotate the 2ob 
between the collar 12 and the pads 22. As the air is being 
drawn between the pad 22 and the collar 12, the resil- positioned so that the ratio is Optimum 
torque to the pad by the rotor 
'Ontact the 'pokes 18'* the two Of 
ient annulus is shaped somewhat as shown (but much 40 for the load in either the primary or reverse directions. 
exaggerated ), constrained at the connection to the The proper functioning of the bidirectional rotation 
spokes 18 to be in a plane normal to the axis of rota- depends on frictional restraint between the resilient 
tion. beams and the radial spokes being less than that be- 
the embodiment of FIG. 4 as illustrated in FIG. k, tween the rotor and pad when reverse rotation begins. 
the constraint is positional only. The annulus may have 45 This is necessary So that the rotor can force the Pad and 
a slope relative to a plane normal to the axis. In both beam in its contacts with spokes 18 
embodiments nevertheless the pad assumes a non-zero and until the reverse Stops 20b contact the spokes. 
angle relative to a plane normal to the axis. The en- In FIG. 7 is illustrated simple sliding joints between the 
trapped air creates the air bearing, the pad assuming at resilient annulus 20 and the spokes 18 and 1&. Small 
its leading edge (the edge approached first by a point 50 diameter rollers could be incorporated into the spokes 
on the shaft 10) a spacing h, from the collar, and at its to bear against the resilient beam Or annulus 20 to 
lagging edge (the edge approached circumferentially reduce friction in the circumferential direction. The 
later by the Same point on the shaft 10 as it continues bidirectional rotation configuration of FIG. 7 may eas- 
to rotate) a spacing hl. ily be combined with the bidirectional thrust load con- 
For a mathematical analysis and a discussion of the 55 figuration of FIG. 6 to produce a thrust bearing which 
results achieved by the bearings of FIGS. 1 and 4 and may carry the thrust load in both axial directions for 
tabular values for various parameters, reference may rotor rotation in either direction. 
be made to NASA Technical Note TN D-7724, entitled The theory relating to the resilient pad gas thrust 
Analysis of an All-Metallic Resilient-Pad Gas- bearing described herein is more fully developed in a 
Lubricated Thrust Bearing. 60 NASA Technical Note identified as NASA TN D-7724 
The embodiment of FIG. 4, because of the lesser entitled Analysis of an All-Metallic Resilient-Pad Gas- 
constraint at the attachments of the annulus 20 to the Lubricated Thrust Bearing by William J. Anderson, 
beams 18, tends to equalize the bearing forces ab- Lewis Research Center, Cleveland, Ohio 441 35. 
sorbed by the pads 22. Hence an arrangement such as 
that of FIG. 4 or other arrangement in which the at- 65 
tachments of the annulus 20 to the spokes 18 does not 
constrain the annulus to remain parallel to a plane 
normal to the axis 8 is preferred. Consequently, the use 
What is claimed is: 
1. A thrust bearing assembly arranged to cooperate 
with a rotor which rotates in at least one angular direc- 
tion, comprising, 
a mount in annular form, 
3,97 1,602 
5 
spokes cantilevered radially inward from said annular 
form, the cantilevered spokes being arranged at 
equal angular intervals about the axis of said mount 
and the coincident axes of said rotor, 
a heat resistant annulus resilient relative to and sup- 
ported by said cantilevered spokes against axial 
thrust, thereby forming flexible beams between 
adjacent pairs of said cantilevered spokes, and 
thrust pads supported on said resilient beams to re- 
ceive the thrust of said bearing, said pads being also 
spaced at like equal intervals angularly between 
said spoke, the leading edge of each pad being 
farther circumferentially from its adjacent spoke 
than the lagging edge of said pad circumferentially 
from its adjacent spoke. 
2. The bearing assembly as claimed in claim 1 in 
which said pads are relatively rigid. 
3. The bearing assembly as claimed in claim 1, said 
heat resistant annulus being metallic. 
4. The bearing assembly as claimed in claim 3, each 
of the said spokes supporting said annulus against a flat 
spoke surface, said spokes being attached to the annu- 
lus to constrain the annulus along the lines of attach- 
ment to remain in a plane normal to the annulus axis. 
5. The bearing assembly as claimed in claim 3, each 
of the said spokes supporting said annulus against a 
spoke by an attachment functioning as a fulcrum along 
the line of attachment of spoke and annulus. 
6. The bearing assembly as claimed in claim 3, fur- 
ther comprising a frame, an annulus rotatable about its 
5 
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15 
20 
25 
30 
35 
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axis relative to said frame, and cooperating stops, some 
on said annulus and at least one fixed with respect to 
the frame, whereby the rotation of said annulus is lim- 
ited in both directions of rotation. 
7. A thrust bearing comprising 
a bidirectional shaft, 
a thrust collar having axially bidirectional thrust sur- 
faces carried by said collar, and 
a pair of bearing assemblies, a different one for each 
of said thrust surfaces, each bearing assembly com- 
prising 
a mount in annular form and relatively rigid spokes 
cantilevered radially inward from said annular 
form, the cantilevered spokes being arranged at 
equal angular intervals about the axis of said mount 
and the coincident axis of said shaft, 
a metallic annulus resilient relative to said spokes 
against axial thrust, thereby forming flexible beams 
between said cantilevered spokes, and 
rigid thrust pads supported on said beams to receive 
the thrust of said bearing, said pads being also 
spaced at like equal intervals angularly between 
said spokes, the leading edge of each pad being 
farther circumferentially from its adjacent spoke 
than the lagging edges of said pad circumferentially 
from its adjacent spoke, 
said bearing assemblies being faced oppositely to 
receive opposite thrusts from said collar. * * * * *  
45 
50 
55 
60 
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