A gas-lubricated bearing is described, employing at least one pad mounted on a rectangular cantilever beam to produce a lubricating wedge between the face of the pad and a moving surface. The load-carrying and stiffness characteristics of the pad are related to the dimensions and modulus of elasticity of the beam. The bearing is applicable to a wide variety of types of hydrodynamic bearings

Etsion, I.

English

NASA Technical Reports Server

Etsion 
[54] CANTILEVER MOUNTED RESILIENT PAD 
GAS BEARING 
[76] Inventors: 
[21] Appl. No.: 
[22] Filed: 
James C. Fletcher, Administrator of 
the National Aeronautics and Space 
Administration, with respect to an 
invention of Izhak Etsion, Haifa, 
Israel 
792,069 
Apr. 28,1977 
[51] Int. Cl.2 .............................................. F16C 17/00 
[52] U.S. c1. ....................................... 308/5 R 308/9; 
308/ 12 1; 308/ 160; 308/ 163; 308/172; 
308/DIG. 1 
[58] Field of Search .................... 308/9, 5 R, 3 R, 26, 
308/160, 163, 164, 134.1, 168, 170, 172, 139, 
135, 121, DIG. 1; 267/160 
References Cited 
U.S. PATENT DOCUMENTS 
1561 
3,384,425 5/1968 Brown ................................. 308/5 R 
3,677,612 7/1972 Barnett et al. ....................... 308/5 R 
3,971,602 7/1976 Anderson ............................. 308/160 
3,998,499 12/1976 Chiarotto ............................. 308/3 R 
4,005,914 2/1977 Newman ................... 308DIG. 1 X 
Primary Examiner-Trygve M. Blix 
Assistant Examiner-Douglas C. Butler 
Attorney, Agent, or Firm-N. T. Musial; J. R. Manning; 
G. E. Shook 
1571 ABSTRACT 
A gas-lubricated bearing employing at least one pad 
mounted on a rectangular cantilever beam to produce a 
lubricating wedge between the face of the pad and a 
moving surface. The load-carrying and stiffness charac- 
teristics of the pad are related to the dimensions and 
modulus of elasticity of the beam. The bearing is appli- 
cable to a wide variety of types of hydrodynamic bear- 
ings. 
4 Claims, 10 Drawing Figures 
https://ntrs.nasa.gov/search.jsp?R=19790002247 2020-03-20T18:00:56+00:00Z
U.S. Patent July 11,1978 Sheet 1 of3 
I 
PR/OR ART 
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FIG.? 
P@/OR ART 
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4,099,799 
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U.S. Patent 
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July 11, 1978 Sheet 2 of 3 4,099,799 
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FIG.9 
FIG.10 
4,099,799 
CANTILEVER MOUNTED RESILIENT PAD GAS 
BEARING 
ORIGIN O F  THE INVENTION 
The invention described herein was made in the per- 
formance of work under a NASA contract and is sub- 
ject to the provisions of Section 305 of the National 
Aeronautics and Space Act of 1958, Public Law 85-568 
(72 Statue 435; 42 USC 2457). 
BACKGROUND O F  THE INVENTION 
1. Field of the Invention 
The present invention relates generally to bearings 
for rotating machinery, and more particularly to such 
bearings having resilient elements to develop a load- 
supporting gas film and provide controlled bearing 
characteristics. 
2. Description of the Prior Art 
Modem gas bearing applications require tolerance to 
dirt ingestion and high-temperature operating capabil- 
ity. The first requirement was met by the development 
of foil bearings and compliant surface or compliant 
mounted bearings. Foil bearings are less successful as 
thrust bearings than as journal bearings. Compliant-type 
bearings using elastomeric materials are temperature 
limited. A new type of bearing has recently been devel- 
oped which combines compliance with high-tempera- 
ture operating capability. This is a resilient pad gas 
thrust bearing that does not contain any elastomers in 
the bearing assembly and is disclosed in commonly 
assigned U.S. Pat. No. 3,971,602, which issued to Wil- 
liam J. Anderson on July 27, 1976. This bearing still 
suffers from certain disadvantages among which are a 
range of appplication limited to annular rotating thrust 
bearings, and bearing characteristics such as load capac- 
ity and stiffness which are difficult to control. 
BRIEF SUMMARY OF THE INVENTION 
It is therefore one object of the present invention to 
provide an improved gas bearing. 
It is another object of the present invention to pro- 
vide an improved resilient pad gas bearing whose range 
of application is not limited to annular rotating thrust 
bearings. 
It is a further object of the present invention to pro- 
vide an improved resilient pad gas bearing having easily 
controllable bearing characteristics. 
The objects of the present invention are achieved by 
a gas bearing including first and second elements mov- 
able relative to one another and positioned to form a 
spachg therebetween, and resilient bearing means dis- 
posed with the spacing for deflecting in response to a 
pre-sure distribution established by the relative move- 
ment of the first and second elements. The resilient 
bearing means includes a resilient cantilever beam rig- 
idly mounted at one end to the first element, and a pad 
rigidly mounted along a line parallel to its trailing edge 
to the other end of the cantilever beam for receiving the 
load pressure of the bearing. 
The foregoing as well as other objects, features and 
advantages of the present invention will become more 
apparent from the following detailed description taken 
in conjunction with the appended drawings. 
BRIEF DESCRIPTION OF THE DRAWINGS 
FIG. 1 is a partial sectional view through the gas 
thrust bearing of the prior art in a static position. 
5 
10 
15 
20 
25 
30 
35 
40 
45 
50 
55  
60 
65 
2 
FIG. 2 is a cross-sectional view of the gas thrust 
bearing of the prior art. 
FIG. 3 is a longitudinal sectional view through the 
gas thrust bearing of the prior art. 
FIG. 4 is a partial sectional view through the gas 
thrust bearing of the prior art in an exaggerated dy- 
namic position. 
FIG. 5 is a partial sectional view useful in describing 
the operation of a bearing embodying the invention, in 
a static position. 
FIG. 6 is a partial sectional view useful in describing 
the operation of a bearing embodying the invention 
shown in exaggerated dynamic position. 
FIG. 7 is a plan view of one particular arrangement in 
accordance with the invention as embodied in a slider- 
type of bearing. 
FIG. 8 is a top plan view of one particular arrange- 
ment in accordance with the invention as embodied in a 
thrust-type bearing. 
FIG. 9 is a perspective view of one particular ar- 
rangement in accordance with the invention as embod- 
ied in a journal-type of bearing. 
FIG. 10 is a sectional view of the arrangement shown 
in FIG. 9 taken along the line 10-10 and looking in the 
direction of the arrows. 
DESCRIPTION OF THE PREFERRED 
EMBODIMENTS 
Referring to FIG. 1 of the drawings, there are illus- 
trated diagrammtically a stationary element 11 and a 
corresponding movable element 13 of a bearing 15. 
These two elements are common to all bearings 
whether they be of the slider, thrust, journal or other 
type of bearing and the invention herein is applicable to 
all the various types of bearings. As examples, for bear- 
ings of the thrust type, the stationary element 11 is a 
supporting mount while the movable element 13 is a 
circular runner. For bearings of the journal type, the 
stationary element 11 is a supporting bushing while the 
movable element 13 is a rotatable shaft. 
The objective of a gas bearing is to provide support 
of an element while allowing relative motion between 
the element and a fixed element and to prevent the 
elements from contacting each other or at least from 
coming into contact in such a fashion that there is fail- 
ure of the system, i.e. relative motion becomes exceed- 
ingly difficult or impossible. As is the case in all gas 
bearings, there is a spacing between the movable and 
stationary elements where a sufficient pressure must 
exist if the two elements are to remain separated, and 
that pressure is created by a gas located between the 
two elements. 
In the prior art bearing of the above-mentioned pa- 
tent, which is a bearing of the thrust type, a resilient 
bearing element, or beam 17, is placed in the spacing. A 
beam, as used in the specification, is defined as a rela- 
tively thin flexible bearing element or strip whose thick- 
ness relative to its other dimensions is such that it may 
be locally deflected by the gas film created between the 
stationary and movable elements of the bearing. As 
viewed in FIGS. 2 and 3, the bearing beam 17 takes the 
form of an annular metallic heat resistant (rather than 
elastomeric) member supported by a plurality of in- 
wardly cantilevered, relatively rigid spokes 19, spaced 
circumferentially angularly equally. On the beam are 
mounted an equal plurality of rigid, sector-shaped pads 
21 spaced equally circumferentially between the spokes 
19, so that under load the pads yield due to the resil- 
4.099.799 
3 
ience of the beam. FIG. P shows a portion of the bearing 
of the above-mentioned patent having a pad 21 carried 
by the resilient beam 17 between a pair of spokes 19. 
The axial stiffness of the resilient beam 17 is a function 
of the beam dimensions between each set of spokes. 
Referring to FIG. 4, in the prior art bearing as the 
runner 13 approaches speed in the rotation direction 23, 
the ambient gas, which may be air, is entrapped be- 
tween the runner 13 and the pads 21. As the air is 
trapped between the pads 21 and the runner 13 the 
resilient beam is shaped somewhat as shown (but much 
exaggerated) and the pad 21 assumes a non-zero angle 
relative to a plane normal to the axis. The entrapped air 
creates the gas bearing, the pad assuming at its leading 
edge (the edge approached first by a part on the shaft 
24) a spacing hi from the runner, and at its trailing edge 
(the edge approached circumferentially later by the 
same point on the shaft 24 as it continues to rotate) a 
spacing h,. Under the conditions illustrated, the load 
capacity of the pad is maximized whenever the pad tilt 
results in a uniformly minimum gas film thickness along 
its trailing edge. 
FIG. 5 illustrates the principle of operation of the 
bearing of this invention. The symbols used in FIG. 1 
are used to designate identical corresponding parts of 
the illustration. In this figure, the annular beam 17 of the 
prior art bearing of the above-mentioned patent is re- 
placed by a rigidly mounted retangular cantilever beam 
25, and the sector-shaped pad 21 is attached thereto 
along the line 27 parallel to the pad trailing edge and at 
a distance D from that edge. This line serves as a pivot 
about which the pad is tilted as the runner 13 ap- 
proaches speed in the rotation direction 23. It can be 
shown that the radial Divot line which will maximize 
4 
25’ secured to a fixed beam support 28’. Each pad 28’ 
has a sector shape and is used to support an axial or 
thrust load on a shaft 24’. Each sector shaped pad 21’ is 
attached to the cantilever beam 25’ along a line parallel 
5 to the pad trailing edge. This line is at the end opposite 
the support 28’ and serves as a pivot about which the 
pad 21’ is tilted as pointed out above in connection with 
FIG. 5. A load acting on each pad 21‘ at the center of 
pressure causes the deflection of the cantilever beam 25‘ 
10 as shown in FIG. 6. For a mathematical analysis and a 
discussion of the results achieved by the bearing of FIG. 
8 and tabular results for various parameters, reference 
may be made to NASA Technical Note TN-D-88229 
entitled “Analysis and Design of a Cantilever-Mounted 
FIGS. 9 and 10 illustrate the inventive concept as it is 
arranged in a journal-type bearing. In these figures, a 
journal-type bearing is shown comprising a stationary 
element such as a bushing 28 and a rotatable element 
2o such as a shaft 29. Affixed to the interior of the bushing 
28 in the FIG. 9 embodiment are a number of resilient 
cantilever beams 25” and pads 2B”. These may be seen 
more clearly in FIG. 10 which is a sectional view taken 
along the line 10-10 of FIG. 9. 
Obviously, numerous additional modifications and 
variations of the present invention are possible in light 
of the above teachings. It is therefore to be understood 
that within the scope of the appended claims, the inven- 
3o tion may be practiced otherwise than as specifically 
described herein. 
What is claimed as new and desired to be secured by 
letters patent of the United States is: 
1. A gas bearing comprising; 
l5 Resilient-Pad Gas-Lubricated Thrust Bearing”. 
25 
the load capacity of the‘ bearing is its trailing edge. This 35 
is also true for any pivot line parallel to the trailing 
edge. Referring to FIG. 6 as the runner 13 approaches 
speed in the rotation direction 23, the ambient gas is 
trapped between the pad 21 and the runner 13, and the 
rectangular cantilever beam is shaped somewhat (but 40 
much exaggerated). The center of load pressure of the 
pad 21 is indicated by the arrow P. The pad assumes a 
non-zero angle relative to a plane normal to the axis, 
and the entrapped gas creates the gas bearing. 
of the pad’s tilt about the line 27 and the deflection of 
the cantilever beam. These are functions of the beam’s 
thickness t, width b, and length from the pivot line 27 to 
a fixed beam support 28 which is part of the stationary 
element as well as the distance II between the point 50 
where the load is applied and the pivot line. 
FIG. 7 shows a plan view of the inventive concept as 
it is arranged in a slider-type gas bearing which is the 
simplest configuration embodying the present inven- 
tion. A rectangular pad 21 is rigidly mounted along the 55 
pivot line 27 on a cantilever resilient beam 25. This 
beam 25 is rigidly secured to a fixed beam support 28 at 
the edge opposite the pivot line 27. Because of this 
mounting a load acting on the pad 21 deflects the beam 
25 and assures a converging film thickness in the direc- 60 
tion of motion of the runner 13 as shown in FIG. 6.  This 
converging clearance maintains the hydrodynamic lu- 
bricating film to support the load in linear motion. 
FIG. E) shows a plan view of the inventive concept as 
it is arranged in a thrust-type gas bearing wherein each 65 
first and second elements movable relative to one 
another and positioned to form a spacing therebe- 
tween; and 
resilient bearing means disposed within the spacing 
for deflecting in response to a pressure distribution 
established by the movement Of the first 
and second elements, the resilient bearing means 
including 
a resilient cantilever beam extending in the direc- 
tion of said relative movement being rigidly 
mounted at one end to the first element; and 
a pad rigidly mounted along a line parallel to its 
trailing edge to the other end of the cantilever 
beam and having a substantially smooth surface 
facing said second element for receiving the load 
pressure of the bearing, said line being in a plane 
substantially perpendicular to the direction of 
said relative movement. 
2. The gas bearing recited in claim 1 wherein: the 
3. The gas bearing recited in claim 1 wherein: the 
the first element comprises a stationary element; and 
the second element comprises an element rotatable 
4. The gas bearing being recited in claim 1 wherein: 
the first element comprises a bushing having an open- 
the second element comprises a rotatable shaft re- 
The bearing’s characteristics depend on the amount 45 
bearing is of the slider type. 
bearing is of the thrust type; 
relative to the stationary element. 
the bearing is of the journal type; 
ing; and 
ceived within the bushing. 
of the pads 21’ is mounted on a resilient cantilever beam * * e * *  


Cantilever mounted resilient pad gas bearing

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