Hydrodynamic fluid film journal bearing

The top foil (12) of the hydrodynamic fluid film journal bearing (10) carries opposing tabs (23,25) at the side edges adjacent the free end (17) thereof and extends radially outward to fit adjacent to the side edges (19,21) of the intermediate foil 14 and the ends of the key 18 when rolled into a cylinder and inserted into the bore of sleeve (24) to prevent skewing of the top foil. In another embodiment skewing is prevented by incorporating opposing tabs (37,39,50,52) at the free ends (31,54) of the top foil (12a) and intermediate foil (14a) that project through predetermined sized slots (40,42) formed in the side edges (44,46) at the fixed end of intermediate slot (14a). The tabs overlie the side edges of the intermediate foil (14b) and bump foil (15) when rolled into a cylinder and prevent skewing and enhancing journal bearing performance.

TECHNICAL FIELD 
This invention relates to journal bearings and particularly to anti-skewing 
means for a hydrodynamic fluid film air bearing. 
BACKGROUND ART 
As is well known in the bearing technology, the hydrodynamic air bearing 
consists of a top foil, an intermediate foil and bump foil that are 
reversed rolled into a cylindrical shape that, in turn, is mounted within 
a sleeve for radially supporting a rotating shaft. An example of apparatus 
utilizing this type of bearing is the air cycle machines utilized for 
cooling aircraft manufactured by the Hamilton Standard division of United 
Technologies Corporation, the assignee of this patent application. In 
these designs, one end of each foil is secured while the opposite end is 
free. Upon reaching a predetermined speed, the air in the sleeve is forced 
between foils that form wedges or air pockets which serve as a cushion for 
supporting the shaft without the need of liquid lubrication. It has been 
found that on occasion, the free end of the foils would move axially and 
become skewed either during operation of the rotating machinery or when 
the journal air bearing is being installed. The effect of the skewing is 
that the bearing tightens which increases shaft torque and under certain 
circumstances could prevent proper air film formation resulting in 
malfunction of the bearing. This invention serves to obviate this problem 
by providing means for preventing the foils from skewing. In one 
embodiment this invention contemplates incorporating end tabs at the end 
of the free end of the top foil that fit into the keyway and in another 
embodiment tabs at the side edges assure that the top foil in the first 
embodiment and all the foils in the second embodiment remain in the 
cylindrical shape. 
SUMMARY OF THE INVENTION 
An object of this invention is to provide and improved hydrodynamic fluid 
film journal bearing. 
A feature of this invention is to provide side tabs to the free end of the 
top foil of the journal bearing to hold it in a cylindrical shape. In 
another embodiment the tabs are mounted at opposite sides of the end of 
the free end of the top foil that extend so as to overlap the side edges 
of the intermediate foil and bump foil to also hold all the foils in the 
cylindrical shape. 
The foregoing and other features of the present invention will become more 
apparent from the following description and accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
One embodiment of this invention one of the preferred embodiments can best 
be understood by referring to FIGS. 1-3 which show the hydrodynamic fluid 
film journal bearing generally illustrated by reference numeral 10 
comprising top foil 12, intermediate foil 14 and bump foil 15. The top 
foil 12 and intermediate foil 14 which are made from sheet metal stock 
with a given spring rate are attached end to end by any suitable bonding 
means such as welding, brazing or the like at the weldment juncture 16 
which is in alignment with the key 18. Key 18 which lies transverse to the 
longitudinal axis of the foils extends in a radial direction when the 
foils are wrapped into a cylinder about the axis of rotation A as shown as 
reference numeral 20 in the phantom view. As will be described in further 
detail hereinbelow, the key 18 fits into a transverse slot or keyway 22 
formed in the wall 23 on the inner diameter of sleeve 24. The bump foil 15 
which is formed from a corrugated thin sheet metal material having a given 
spring rate is wrapped around the top foil 12 and the intermediate foil 14 
when in the coiled position to form a cylinder adapted to fit into the 
bore of sleeve 24 adjacent to wall 23. As will be appreciated from the 
foregoing, the top foil, intermediate foil 14 and bump foil 15 are 
configured in the same rectangular shape and are wrapped around in a 
reverse roll to form a cylinder such that when inserted into sleeve 24 the 
outer foil 12 surrounds the shaft (not shown), the bump foil 15 is 
adjacent to wall 23, and the key 18 extends into the keyway 22 of the 
sleeve 24. The inner face 28 of top foil 12 which lies adjacent to the 
rotating shaft (not shown) is preferably coated with a dry lubricant so 
that when the shaft is accelerating to its operating speed during start up 
or decelerating as the shaft is coasting to stop, and when the pressure of 
the air in the wedge of the foils is not sufficient to support rotation, 
the dry lubricant will serve as an anti-friction means for maintaining 
wear and operability of the bearing. When in the operating condition and 
the shaft has reached a predetermined speed the pressure of the air that 
is forced into the wedges formed between the over lying surfaces of the 
top foil 12, intermediate foil 14 and bump foil 15 serves to support the 
shaft and the spring rates of the foils is selected to obtain the proper 
compliance of the bearing. 
In accordance with this invention, the width of the free end 17 is made 
wider than the other portion of top foil 12 to extend beyond the side 
edges 11 and 13. This extended portion is bent radially outwardly adjacent 
to the stress relief slots 21 and 23 to define tabs 25 and 27. As seen in 
FIG. 3 which is taken along lines 3--3 of FIG. 2 when the top foil and 
intermediate foil are wrapped as depicted by the arrows B and C, (FIG. 1) 
respectively to form a cylinder the tabs 25 and 27 extend into keyway 22 
and overlie a portion of the opposing side edges 15 and 17 of the 
intermediate foil 14 and opposing ends of key 18. This obviously prevents 
the top foil 12, intermediate foil 14 and bump foil 15 from moving axially 
and deforming the cylindrical shape and becoming skewed. 
While this embodiment does not show all the details of the final 
configuration of the hydrodynamic fluid film journal bearing, it is 
disclosed herein to detail the inventive portion of this type of journal 
bearing and the details of the final design configuration, as one skilled 
in this art will appreciate, will depend upon the particular application 
for the intended use. Obviously, other methods of forming the tabs at the 
end of the top foil may be employed without departing from the scope of 
this invention. 
Referring next to FIGS. 4-7 which depict another embodiment of this 
invention disclosing the hydrodynamic fluid film journal bearing that has 
been fully designed for a particular application and includes elements 
common to the hydrodynamic fluid film journal bearing depicted in FIGS. 
1-3, namely, the top foil 12a, the intermediate foil 14a and bump foil 15, 
modified to include another anti-skewing means. In this description, all 
like elements in all the Figs. are depicted with the same reference 
numerals. 
In accordance with this invention and referring particularly to FIG. 4, the 
free end 31 of the top foil 12a is slit at 32 and 34 a short distance 
inwardly from the side edges 36 and 38 and are bent radially outward (into 
the paper as shown in this FIG. 4) to form tabs 37 and 39 that ultimately 
fit into keyway 22. It should be understood that for purposes of this 
description this embodiment is intended for use with the sleeve 24 
depicted in FIG. 2. Because the intermediate foil 14 wraps around the top 
foil 12a, slots 40 and 42 adjacent to key 16 are cut a short distance 
inwardly into the side edges 44 and 46 of intermediate foil 14a to allow 
the tabs 37 and 39 to project into keyway 22. Tabs 50 and 52 formed at 
opposite ends of the free end 54 of intermediate foil 14a are slit and 
bent similar to tabs 37 and 39 to project outwardly as shown in FIG. 4. 
When reversed rolled, tabs 50 and 52 extend radially outwardly to bear 
against one end 31 of bump foil 15 and tabs 37 and 39 bear against the 
opposite end of bump foil 15. 
As best seen in FIGS. 6 and 7 the foils are reversed rolled to form a 
cylinder that fits into sleeve 24 and the key 18 similar to that shown in 
FIG. 3 fits into keyway 22. Obviously, since tabs 37 and 39 fit into the 
diametrically opposite slots 40 and 42 and the width of the tabs and depth 
of the slots are equally dimensioned, top foil 12a is constrained axially. 
This prevents the top foil from skewing such that the cylinder cannot be 
deformed. Like the embodiment disclosed in FIGS. 1-3, this embodiment 
prevents skewing so that there is no deficit in the performance of these 
journal bearings and as a matter of fact the performance are at the 
optimum. This prevents the foils from sliding axially to distort the 
cylinder and skew the free ends which would increase bearing shaft torque, 
tighten the bearings and prevent an optimum air film form being developed, 
all of which would at the very least hinder performance, or cause a 
malfunction of the bearing. 
For illustration of affixing the key to the top foil in both embodiments 
and for the sake of simplicity and convenience FIG. 5 is used for 
explanation purposes. As noted, the fixed end 58 of top foil 12 overlies 
the key 16 and is bonded thereto in a known suitable manner as described 
above and the fixed end 60 is bent inwardly to form a shoulder to 
complement and bear against the side edge of key 16 so as to be likewise 
bonded thereto by suitable means. 
Although this invention has been shown and described with respect to 
detailed embodiments thereof, it will be appreciated and understood by 
those skilled in the art that various changes in form and detail thereof 
may be made without departing from the spirit and scope of the claimed 
invention.