Note: Descriptions are shown in the official language in which they were submitted.
67Z
This invention relates to vertical dynamoelectric
machines ancl in particular to an improved air cooling
arrangement for the lubricant of large thrust bearings
employed by such machines.
Vertical disposed dynamoelectric machines have
their rotating shaft suspended from one or more
thrust bearings. The thrust bearing performs the
dual function of supporting the weight of the rotor
which may be in excess of 1,000 pounds and of
counteracting any vertical thrust due to dynamic
loading on the shaft in either an upward or downward
direction. The thrust bearing is generally a
relatively robust and massive structure that generates
large quantities of heat at its bearing surfaces.
Hence such a large thrust bearing demands an adequate
supply of cooled liquid lubricant to prevent the
bearing surfaces from overheating causing unsafe
operation.
Various types of heat exchanger apparatus are
employed by the dynamoelectric machines to maintain
the temperature of liquid lubricants surrounding
the thrust bearing within a desired operable range of
temperatures. Basically, two groups of heat exchanger
apparatus are employed. They are lubricant-to-air
heat exchangers and lubricant-to-water heat exchangers.
Usually, when relatively little heat is generated on
the bearing surfaces, lubricant-to-air heat exchangers
~ '
q~
~667~:
are used. However, in large dynamoelectric machines
having large thrust bearings significantly more heat
is generated and lubricant-to-water heat exchangers
are typically employed. The water heat exchangers
commonly comprise a coil mounted directly in the
lubricant well. Cooling water is pumped through the
coil to cool the lubricant.
The superior efficiency of water type heat
exchanger systems for vertical dynamoelectric machines
has dictated their use in high-heat generating machines
despite the fact that such systems are inconvenient,
costly to manufacture and costly to maintain. One
disadvantage of the water type heat exchanger systems
lies in their susceptibility to freezing when used in
machines that are exposed to low temperature climates.
The possibility of the water heat exchanger system
freezing is a major concern to customers. Another
disadvantage i5 one of water leaking from the cooling
coil into the lubricant resevoir. The probability
of water leakage is quite high because continuous
machine vibration tends to loosen joints in the
cooling coil.
A lubricant cooling apparatus for use in a
vertically disposed dynamoelectric machine that
attempts to provide sufficient cooling for the
lubricant while not having a proclivity for the
disadvantages associated with the water heat exchanger
systems is disclosed in U.S. Patent 3,870,907 issued
March ll, 1975 to Orville W. Hoffman. The lubricant
cooling apparatus disclosed in this patent includes
a plurality of articulated U-shaped ducts vertically
mounted in the liquid lubricant. The ducts pass
through apertures in the floor of the lubricant
resevoir and are mounted to the floor by means of
a gasket and a bolt mechanism. Each duct is provided
with an elongated partition that defines two
. .
~.
67Z
longitudinally extending legs. The outermost leg of
each duct is in airflow communication with the exterior
of the machine. The innermost leg of each duct is in
airflow communication with the interior of the machine.
S Fan blades associated with the rotor of the machine
are operable to draw air through both legs of the
ducts so as to cool the lubricant and thrust bearings.
The ducts extend up into the lubricant from the floor
of the lubricant reservoir. The patent discloses
that in order to optimize the cooling efficiency of
the lubricant cooling apparatus, the convoluted airflow
path extends through the depth of the lubricant twice.
However, air movement along the convoluted path may be
restricted because of its reversal in direction
when moving from the outermost leg to the innermost
leg. The legs, which are narrow, may also be
susceptible to a buildup of dust particles Dn their
surfaces which reduces heat transfer along these
surfaces. Also the cooling efficiency is restricted
to that surface area of the U-shaped ducts coming into
heat exchanging relation with the lubricant. One dis-
advantage with the cooling apparatus of this patent is
that should one of the gaskets from the U-shaped ducts
deteriorate or the bolting mechanism loosen then
lubricant would leak into the electrical part of the
dynamoelectric machine.
It is therefore an object of this invention to
provide a lubricant cooling apparatus which cools
a quantity of liquid lubricant surrounding a thrust
bearing for a vertically disposed dynamoelectric
machine wherein the cooling apparatus provides
airflow passageways that pass once through the depth
of the lubricant.
It is an additional object of this invention to
provide a lubricant cooling apparatus which cools a
quantity of lubricant surrounding a thrust bearing for
1~6~7~;
a vertically disposed dynamoelectric machine wherein
the cooling apparatus does not restrict its surfaces
in heat exchanging relation with the lubricant
just to those surfaces of airflow passageways that
pass once through the depth of the lubricant.
It is a further object of this invention to provide
a lubricant cooling apparatus that does not require a
gasket and bolt mechanism on the floor of the resevoir.
These objects of the invention may be provided
by an improved lubricant cooling apparatus for a
vertical dynamoelectric machine having a primary
airflow passageway and a plurality of spaced apart
secondary airflow passageways. The primary airflow
passageway has a wall portion that includes the side
and top walls of the reservoir wherein a portion of
the reservoir walls is in heat exchanging relation
with the lubricant. The secondary airflow passageways
pass through top and bottom walls of the reservoir.
Each secondary passageway includes a vertical
disposed elongated hollow member mounted in sealed
relation to the top and bottom walls. Each hollow
member passes once through the reservoir and has a
wall portion thereof in heat exchanging relation with
the lubricant. Each secondary passageway is in
airflow communication at one end thereof with the
primary passageway and at the other end thereof with
an airflow means in the housing of the machine. The
airflow means is operable with an air inlet means in
the housing to draw air into the housing along the
primary passageway over the side and top walls and
down through the reservoir within the secondary
passageways. This movement of air through the
passageways removes heat from the lubricant. One
significant feature of the lubricant cooling apparatus
may be the increased surface area provided by the
primary passageway that comes into the heat exchanging
. _ .
.~:, ' '
~1667Z
-- 5 --
relation with the lubricant. Another significant
feature may be the passage of air only once through
the vertical elongated members of the secondary
passageways. This latter feature permits airflow
through the secondary passageways which results in
either an increased lubricant cooling efficiency or
an exhaust means that can be utilized as cooling
air for the dynamoelectric machine.
In accordance with one aspect of the invention
there is provided a lubricant cooling apparatus for a
vertical dynamoelectric machine having a hollow housing,
a thrust bearing mounted in fixed relation with the
housing to support in rotatable relation therewith
a drive shaft in the housing and wall means having top,
bottom and side walls defining an annular reservoir
that retains a quantity of liquid lubricant in
lubricating and heat absorbing relation with the
thrust bearing. The lubricant cooling apparatus
comprises a plurality of spaced apart airflow
passageways passing through the top and bottom walls
of the wall means, each of the passageways including a
vertically disposed elongated hollow member mounted in
sealed relation to the top and bottom walls. The
hollow member passes once through the reservoir and
has a wall portion thereof in heat exchanging relation
with the lubricant. Each of the passageways is in
airflow communication at one end thereof with an air
inlet means in the housing and at the other end
thereof with an airflow means in the housing. The
airflow means draws air into the housing through the
air inlet means and down through the reservoir within
the passageways whereby movement of air therethrough
removes heat from the lubricant.
For a better understanding of the nature and
objects of the invention reference may be had by way of
example, to the accompanying diagrammatic drawings in
~,
i67Z
-- 6 --
Figure 1 is a sectional view showing one embodiment
for the lubricant cooling apparatus of the invention.
Figure 2 is a plan view showing another embodiment
for the lubricant cooling apparatus of the invention.
Figure 3 is a sectional view taken along section
line 3-3 of Figure 2.
Referring now to Figure 1, a preferred embodiment
of the invention is now described. The upper portion
of vertically disposed dynamoelectric machine 10
comprises hollow metal housing 12. A drive shaft
14 is rotatably mounted in housing 12 by a thrust
bearing generally shown at 16. Drive shaft 16 supports
a rotor 18 rigidly mounted thereon. A conventional
stator 20 and stator winding 22 are rigidly mounted
by sui~able means to stator frame 13. An air gap is provided
between rotor 18 and stator 20 to enable the rotor to
spin freely within stator frame 13 and housing 12.
Additionally, similar bearings may be used, some
of which are in inverted relation to that shown in
Figure 1. Such inversion of course will oppose any
upward thrust due to dynamic forces acting on the
lower end of shaft 14. As these additional bearings
may be similar to bearing 16 they have been omitted
to clarify the drawing.
Thrust bearing 16 is shown in figure 1 as a
"roller" type bearing. It should be understood that
the invention has application with other types of
thrust bearings such as, for example, a "plate"
type bearing. No further description of thrust
bearing 16 will be provided because the invention is
concerned, for the most part, with the heat produced
by the thrust bearing and not the structure of the
thrust bearing.
A quantity of liquid lubricant such as oil
lubricant is retained within annular reservoir 30 in
:
7~Z
-- 7 --
lubricant and heat absorbing relation with thrust
bearing 16. The reservoir 30 comprises a top wall or
cover 32, a bottom wall 34 and an annular side wall
36. A flanged sleeve 38 is provided to retain
lubricant in bearing well 40. During machine operation
the thrust bearing 16 acts like a pump drawing
lubricant from well 40 and pumping the lubricant back
into reservoir-30. Lubricant may move into the
bearing well 40 from reservoir 30 through openings 42
in the bottom portion of the cylindrical wall 44.
Cylindrical wall 44 surrounds thrust bearing 16
and secures thrust bearing 16 in fixed relation with
housing 12. The passage of liquid coolant between
bearing surfaces of bearing 16 lubricates and cools
these surfaces. It is important that the ambient
temperature of the lubricant in the bearing well 40
prior to coming into contact with the bearing surfaces
be maintained at an acceptable temperature. Acceptable
temperatures are those that maintain the running
temperature of the thrust bearing within a suitable
safe range of temperature values. Should the ambient
temperature of the lubricant rise above an
acceptible temperature then rather than have
unsafe machine operation, thermocouples (not shown)
positioned in cylindrical wall 44 will sense a higher
temperature and bring a halt to machine operation.
In order to ensure that the ambient temperature
of the lubricant does not rise above acceptable values
a lubricant cooling apparatus is provided that includes
a primary airflow passageway 50 and a plurality of
spaced apart secondary airflow passageways 52.
Primary passageway 50 is defined between
deflector or housing 12 and top and side walls 32
and 36 of reservoir 30. Air passes into the primary
passageway 50 through air inlet 54 in housing 12.
The plurality of secondary passageway 52 are shown
1il1667Z
passing through top wall 32 and bottom wall 34. The
secondary passageways 52 are in airflow communication
with primary passageway 50 at their respective upper
ends and with an airflow means at their respective
lower ends. In this embodiment the airflow means
includes a fan 56 which draws air along airflow path
62 and out exhaust 58. It should be understood that
in some machines such as, for example, high speed
machines fan 56 and exhaust 58 may be eliminated.
In these machines the airflow means includes rotor
18 which draws air along airflow path 62 and over
itself before exhausting the air in a lower part of
machine 10. The secondary passageways 52 each
comprise a vertically disposed elongated hollow
tubular member or cylinder 60 that is mounted in
sealed relation with top wall 32 and bottom wall 34.
The hollow tubular member may be sealed to top wall 32
by means of a gasket 61. The sealed relation of the
hollow tubular member 60 with the bottom wall is
provided by welding member 60 to bottom wall 34.
The hollow tubular members 60 may be constructed from a
suitable material such as, for example, steel. The
hollow members 60 are spaced apart from one another
permitting liquid lubricant to flow around their
respective lower wall portions. The lower wall
portion of each hollow member 60 and a lower portion
of annular side wall 36 which is common to both
reservoir 30 and primary passageway 50 provide a
large surface area in heat exchanging relation with
the lubricant retained in reservoir 30. Movement of air
along airflow path 62 removes heat from the lubricant
through these wall portions thereby keeping the
ambient temperature of the lubricant within a range of
acceptable values. As shown in Figure 1, each of
hollow tubular members 60 passes once through the
reservoir.
1~1667~:
It should be understood that the wall portions in
heat exchanging relation ~eed not be restricted to
those wall portions coming into direct contact
with the lubricant in resevoir 30. The thickness
of annular side wall 36 and the walls of each hollow
member 60 may be chosen so that heat may conduct up
through wall 36 and the walls of members 60. In
this manner wall portions extending a predetermined
length above the oil level may also be in heat
exchanging relation. The predetermined length
being dependent upon the thickness of the walls.
Lastly, depending on the type of bearing employed,
the sidewall 36 and top wall 32 may be sprayed with
the libricant as it leaves the bearing. In this
particular instance, wall portions covered by sprayed
oil would also be in heat exchanging relation with
air moving along airflow path 62.
The embodiment shown in Figure 1 has a
particular application for high speed rotation. In
such an application fan 56 and exhaust 58 may be
eliminated and the air moving along airflow path 62
also passes over rotor 18. This may provide as much
as half of the cooling required by the rotor 18~
Referring now to figure 2 lubricant resevoir
100 is shown having its top wall removed. Resevoir
100 is shown having a plurality of hollow members
102 spaced between cylindrical wall 104 and annular
sidewall 106. In this embodiment hollow members 10
are rectangular box-like in shape. The rectangular
box-like hollow members in this embodiment provide
a larger surface area than the cylindrical members
of figure 1. The largersurface area improves the heat
exchanging relationship. A plurality of pipes 108
are shown interspaced between some of the hollow
members 102. Pipes 108 pass through cylindrical wall
104 and extend almost to annular side wall 106
..
~.667'~
- 10 --
(see figure 3). Pipes 108 are supported by
cylindrical wall 104 by screwing into threaded apertures
in wall 104. Pipes 108 are submersed in the lubricant
and prevent the lubricant from recirculating back into
the lubricant return slots (not shown) in the
cylindrical wall 104 and bottom wall 110. Pipes
108 communicate lubricant to sidewall 106. This
forces the lubricant to flow from the annular side
well 106 back into the centrally disposed bearing
wall within cylinder wall 104. Pipes 108 may find
particular application in machines employing "plate"
type thrust bearings.
The operation of the lubricant cooling apparatus
of this invention is believed to be apparent from
the foregoing description. However to briefly
summarize the operation reference may be had to
Figure 1. The rotation of shaft 14 and fan 56 draws
cooling air in through inlet 54, along airflow path
62 and out exhaust 58. The liquid lubricant is
retained in reservoir 30 in intimate contact with
the thrust bearing 16 and wall portions of the
cooling apparatus. The airflow along path 62 is
effective to remove enough heat from the lubricant to
maintain the running temperature of the bearing within
a suitable safe range of acceptable temperature values.
It will be appreciated that other embodiments
for the invention may be apparent to a man skilled
in the art in light of the foregoing description.
Accordingly, the invention should be limited to
that which is claimed in the accompanying claims.
