TOP FOIL PLATE FOR HYDRODYNAMIC FLUID FILM THRUST BEARINGS

RONDELLE PROFILEE SUPERIEURE POUR PALIERS DE BUTEE A FILM DE FLUIDE HYDRODYNAMIQUE

English Abstract

The top foil (12) of a hydrodynamic fluid film thrust bearing (10) is formed
from a single flat annular disk with radial depressions
(30) extending from the outer diameter to the inner diameter of the disk that
protrude toward the foil plate (16) and define between adjacent
depressions a working surface (39) that is configured to complement the foil
bumpers (14) attached to the foil plate. The bump foils of
the upper foil plate and the bump foils of the lower foil plates can be either
in axial alignment or can be displaced relative to each other.
When the two sets of bump foils are displaced, the leading edge (31) of the
upper bump foils is disposed upstream (relative to the direction
of the air stream entering the bump foils) of the leading edge (33) of the
lower bump foils.

French Abstract

Le profilé supérieur (12) d'un palier de butée (10) à film de fluide hydrodynamique est formé à partir d'un seul disque annulaire plat présentant des évidements radiaux (30) qui s'étendent du diamètre extérieur au diamètre intérieur du disque et font saillie vers la rondelle profilée (16) et définissent, entre des évidements adjacents, une surface de travail (39) configurée de façon à compléter les éléments amortisseurs profilés (14) fixés à la rondelle profilée. Les bosses de la rondelle profilée supérieure et celles de la rondelle profilée inférieure peuvent se trouver soit en alignement axial, soit être décalées les unes par rapport aux autres. Lorsque les deux ensembles de bosses sont décalés, le bord d'attaque (31) des bosses supérieures est placé en amont (par rapport à la direction du flux d'air pénétrant dans les bosses) du bord d'attaque (33) des bosses inférieures.

Claims

11
CLAIMS:
1. A hydrodynamic fluid film thrust bearing having
an upper foil plate (16) formed from a single piece
configured into an annularly shaped member having a flat
upper surface, a plurality of upper bump foils (14) having
opposite side edges (31, 35) circumferentially spaced on
said flat surface, means for attaching one of said opposing
side edges (31, 35) of said upper bump foils (14) to said
flat upper surface and permitting the other one of said
opposing side edges to move axially, a top foil means
overlying said upper bump foils (14), a lower annularly-
shaped foil plate (18) having a flat lower surface, a
plurality of lower bump foils (20) having opposing side
edges (33, 37) identical in number to said upper bump foils
(14) and being circumferentially spaced on said flat lower
surface, and means for attaching one of each of said
opposing wide edges (33, 37) of said lower bump foils (20)
to said flat lower surface and allowing the other of said
opposing side edges (33, 37) to move axially, characterized
in that said upper bump foils (14) and said lower bump
foils (20) are substantially offset relative to each other
in circumferential direction and that said top foil means
comprises a single top foil (12) configured into a flat
washer-shaped member having circumferentially spaced
radially extending depressions (30) projecting toward said
upper foil plate (16) and extending from the inner diameter
of said washer member to the outer diameter of said washer
member, said single top foil (12) having an upper surface
and a lower surface, and having flat surface portions
between adjacent depressions on said lower surface, said
flat surface portions being configured to overlie and
complement each of the upper bump foils (14), whereby the
upper surface of said single top foil (12) may be coated
with a dry low friction lubricant in a single application.
2. A hydrodynamic fluid film thrust bearing
according to claim 1 or 2, characterized in that the

12
opposing side edges (31, 35; 33, 37) of said upper bump
foils (14) and said lower bump foils (20) include a leading
edge and a trailing edge relative to the flow of fluid
entering said thrust bearing, said leading edge (31) of
said upper bump foils (14) being attached to said flat
upper surface of said upper foil plate (16) and said
trailing edge (35) being free to move axially.
3. A hydrodynamic fluid film thrust bearing
according to claim 1 or 2, characterized in that the
opposing side edges (31, 35; 33, 37) of said upper bump
foils (14) and said lower bump foils (20) include a leading
edge and a trailing edge relative to the flow of fluid
entering said thrust bearing, said trailing edge (37) of
said lower bump foils (20) being attached to said flat
lower surface of said lower foil plate (18) and said
leading edge (33) being free to move axially.

Description

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Description
Technical Field
This invention relates to hydrodynamic fluid film
thrust bearings and particularly to the construction~of the
S top foil plate.
Background Art
This invention constitutes an improvement over
US-A-4,462,700 granted to G. L. Agrawal on July 31, 1984
entitled "Hydrodynamic Fluid Film Thrust Bearing" (on which
the two-part form of independent claim 1 is based).
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As is well known in this technology,
the thrust bearing consists of a plurality of the
top foil plate segments and a plurality of
segmented bump foils configured in wedge shape or
_ pads. The top foil .plate segme~its fit over the
segmented bump foils and each of the RAgments are
attached to the upper face of a foil plate.
Hence, the number of top foil plate segments is
identical to the number of the bump foil
segments. The leading edge of the segments, i.e.
the top foil plates and the bump foils, are
individually welded to the foil plate and are
uniformly spaced around the circumference of the
foil plate. The trailing edge is unattached and
left free to move axially. The foil plate is an
annularly shaped disk or washer like member and
the inner diameter fits over the rotating shaft
of the rotating machinery. The thrust bearing is
sandwiched between the thrust runner and the
thrust plate.
In this heretofore known thrust bearing
design, each of the segments are welded to the
foil plate and hence in a design that utilizes 7
pads of the bump foils and 7 pads of the top foil
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there are 14 leading edges that are welded to the
foil plate. This number of welds inherently
produces an undesirable warpage to the thrust
bearing which adversely affects the load carrying
capacity of the bearing. Additionally, it is
customary to coat the top surface of each of the
top foil pads with a dry film lubricated coating
to reduce friction during the rotating machine
start-up and coastdown, inasmuch as this surface
comes into contact with the thrust runner since
the rotational speed is not sufficient to
maintain an air film. Since each top foil pad is
coated it has been found that the thickness and
texture of the coating on each of the pads tends
to vary and is not uniform.
G.je have found that wean improve these types
of hydrodynamic foil bearings by fabricating the
tog foil into a single piece that is relatively
flat disk shaped similarly to the foil plate and
is stamped into wedge shaped arcuate segments by
a radial depression to define the top foils. The
disk fits over the bump foils that are welded to
the foil plate and the top foils stamped into the
disk overlie the bump foils . The flat disk, which
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is a one piece configuration, e~minates the
welding requirement and the entire top surface is coated,
thus eliminating the necessity of~coating individual pads.
This results in a more uniform thickness and texture of the
dry lubricant coating.
- Reference ~s made to ER-A-2,458,707 wherein an
hydrodynamic fluid .film thrust bearing is disclosed in .
which a plurality of bump foils are attached to a base
member and a single flexible annular foil plate overlies
the bump foils. The annular foil plate has a plurality of
radially extending depressions aligned with the spaces
between the bump foils to permit formation of the
hydrodynamic at low speed. '
Summary of the Invention
An object of this invention a.s to provide an
improved hydrodynamic fluid film thrust bearing which
avoids the above recited disadvantages.
To achieve this, there 3.s provided in accordance
with the invention a hydrodynamic fluid film thrust bearing
having an upper foil plate formed from a single piece
configured into an annularly shaped member having a flat
upper surface, a plurality of upper bump foils having
opposite side edges circumferentially spaced on said flat
surface, means for attaching one of said opposing side
edges of said upper bump foils to said flat upper surface
and permitting the other one of said opposing side edges to
move axially, a top foil means overlying said upper bump
foils, a lower annularly-shaped foil plate having a flat
lower surface, a plurality of lower bump foils having
opposing side edges identical in number to said upper bump
foils and being circumferentially spaced on said flat lower
surface, and means for attaching one of each of said
opposing side edges of said lower bump foils to said flat
lower surface and allowing the other of said opposing side
edges to move axially, characterized in that said upper
bump foils and said lower bump foils are substantially
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offset relative to each other in circumferential direction
and that said top foil means comprises a single top foil
configured into a flat washer-shaped member having
circumferentially spaced radially extending depressions
projecting toward said upper foil plate and extending from
the inner diameter of said washer member to the outer
diameter of said Washer member, said single top foil having
an upper surface and a lower surface, and having flat
surface portions between adjacent depressions on said lower
surface, said flat surface portions being configured to
overlie and complement each of the upper bump foils,
whereby the upper surface of said single top foil may be
coated with a dry low friction lubricant in a single
application.
By providing a top foil that is formed from a
single sheet metal stock configured in a washer-like shaped
disc having the foil pads complementing the bump foils
stamped therein the necessity of welding individual pads to
the top foil plate is eliminated thereby providing a single
surface to be coated with a dry lubricant and minimizing or
eliminating non-uniform thickness and texture of the
coating.
The foregoing and other features of the present
invention will become more apparent from the following
description and accompanying drawings.
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Brief Description of Drawings
Fig. 1 is an exploded view in perspective
illustrating the details of this invention
employed in a hydrodynamic fluid film thrust
bearing; and
Fig.. 2 is a sectional view taken through the
radial plane of the thrust bearing depicted in
Fig. 1 c.=ith the burg foils being offset.
Detailed Description of the Preferred Embodiment
l0 While this invention discloses different
embodiments for practicing this invention, it is
to be understood that as one skilled in this art
will appreciate the invention has application for
ether types of hydrodynamic fluid thrust bearings
particularly where it is desirable to eliminate
the necessity of fabricating the top foil into
separate pads.
The invention is best understood by
referring to Figs. 1-2 which disclose the thrust
bearing generally inaicated by reference numeral
10 comprising a top foil plate 12, bump foils 14,
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foil plate 16, foil plate 18 and bump foils 20.
As seen in Fig. 1 which is an exploded view in
perspective, the nine (9) bump foils 14 consists
of corrugated wedge shaped or truncated sector
shaped pads 22 with the corrugations oriented
radially spaced circumferentially around the flat
outer face 24 of foil plate 16.
The backing spring consisting of the lower
foil plate 18 which also has attached thereto
nine (9) bump foils formed into corrugated wedge
shaped pads 26 with the corrugations oriented
similarly to the orientation of the pads 22.
Wedge shaped pads 26 are circumferentitially
spaced around the under flat surface 28 of foil
plate 18. '
The wedge shaped bump foils 14 and 20 which
are made from a spring metallic material that is
highly resilient provide compliancy to the thrust
bearing which is required for proper air film
formation. They also serve as springs so that a
certain minimum preload may always be maintained
by the thrust bearings when shimmed on opposite
sides of a thrust runner to fix the runner's
axial position within the rotary machine, such as
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an air cycle machine, on which it is being used.
The spring rate of the wedge shaped pads and foil
plates are predicated on the particular
parameters of the application for which they are
", 5 - intended for use. Likewise, as one skilled in
this art will appreciate, the number of bump
_ foils will likewise be predicated on the
particular application. Attachment of the bump
foils to the upper and lower foil plates is by
any suitable means. As is well known, either the
leading edge or trailing edge is welded, brazed
or suitably joined to the foil plate and the
opposite end, i.e. the leading or trailing edge,
is left unattached so as to freely move in the
axial direction. This aspect of the invention is
well known and for further details thereof
reference should be made to US-A-4,462,700.
In accordance with this invention, the top
foil plate 12, is formed from a single flat
~u~rl~' shaped spring metallic material that
is stamped to form radial depressions 30 with the
apex 29 oriented downwardly facing the flat
surface 24 of foil plate 16. The adjacent
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depressions 30 define therebetween a plurality of
wedge or sector shaped elevated portions 32
equalling in number and being substantially
configured to the size and shape of each of the
S bump foils 22 so as to define a working surface
39 to complement and cooperate therewith when in
running operation. As noted in Figs 1-3, the
sector portions overlie the bump foils 14 and
serve the same purpose as the heretofore known
individual top -foils. An example of the
heretofore known top foils are described in
L'S-A-4,462,700.
Since the top foil 12 is fabricated from a
single piece it obviates the heretofore known
problems incidental to coating the heretofore
known individual top foils as described
hereinabove. The upper surface of the top fail
plate is coated with a well known dry film low
friction lubricating material that serves to
reduce friction during the start-up and coast-
down of the rotating portion of the rotary
machine. This is particularly important since
this coating is in contact with the thrust runner
whose rotational speed during start-up and coast-
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down is insufficient to maintain an air film.
As shown in Fig. 3 the leading edges 31 and
33 and the tra5_ling edges 35 and 37 of the bump
foils 14 and 20, respectively are substantially
5_ displaced relative to each other in circumferential
'direction.
- This invention affords a number of
advantages over the heretofore known hydrodyna.-nic
fluid film thrust bearing, including, without
limitations:
1) The fabrication of the top foil is
simplified since it is made from a single piece;
2) The number of parts are reduced and
hence inventory is likewise reduced;
3) The top foil is not welded to the
foil plate which facilitates the assembly and
manufacturing thereof; (Heretofore, the top foils
and bump foils were both welded to the foil
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plate, and.'Lhis compound welding sometimes
resulted in warpage of the thrust bearing, which
reduces load carrying capacity thereof); and
4) Because the top foil coating is
applied in one operation over the entire-surface
of the top foil rather than to.the separate top
foil pieces of the heretofore known thrust
bearings, the thickness of the coating and its
texture is more uniform.
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Representative Drawing