Note: Descriptions are shown in the official language in which they were submitted.
CA 02476741 2004-08-05
COMPACT ROTARY COMPRESSOR
BACKGROUND OF THE INVENTION
1. Field of the Invention.
[0001] The present invention relates to a rotary compressor having a compact
design
wherein the compression chamber is defined by the rotor of the motor driving
the
compressor.
2. Description of the Related Art,
[0002] Rotary compressors typically include a housing in which a motor and a
compression
mechanism are mounted being operably connected by a drive shaft. Rotary type
compression
mechanisms typically include a roller disposed about an eccentric portion of a
shaft. The
roller is located in a cylinder block that defines a cylindrical compression
space. At least one
vane extends between the roller and the outer wall of the comprf;ssion chamber
to divide the
compression chamber into a plurality of compression pockets. The roller is
eccentrically
located within the compression chamber and, as the shaft rotates, the
compression pockets
become progressively smaller thereby compressing a refrigerant or other fluid
disposed
therein. Oftentimes, the vane is biased into contact with either the wall of
the compression
chamber or the roller by a spring. Other configurations of rotary compressors
are also
known.
SUMMARY OF THE INVENTION
[0003] The present invention provides a compact rotary compressor in which the
rotor of
the motor includes a single integral part that also defines an internal
compression chamber
and includes an integrally formed vane extending radially inwardly into the
compression
chamber.
[0004] The present invention comprises, in one form thereof, a rotary
compressor for
compressing a fluid that includes a motor having a stator and a rotor. The
rotor includes ar
integrally formed part defining an internal compression chamber and an
integrally formed
vane extending radially inwardly within the compression chamber. A roller is
rotatably
mounted and eccentrically disposed within the compression chamber. The vane is
engaged
CA 02476741 2004-08-05
with the roller wherein rotation of the rotor rotates the roller and thereby
compresses the fluid
within the compression chamber.
[0005] The integrally formed rotor part may also include a radially outer
surface having a
plurality of permanent magnets mounted thereon. Further, the roller may define
a recess
having a bushing mounted therein, wherein the bushing defines a radially
extending slot with
the vane being slidably disposed within the slot. The roller may be mounted on
a stationary
shaft wherein the shaft defines an internal passageway in fluid communication
with the
compression chamber.
[0006] The compressor may also include first and second end plates disposed at
opposite
axial ends of the compression chamber. At least one of the end plates may
define a fluid
passageway providing fluid communication between the internal passageway of
the shaft and
the compression chamber. The shaft extends through one of the end plates. In
some
embodiments, the shaft may extend through only one of the end plates and with
the other end
plate being rotatably mounted on a stationary support structure. The stator
circumscribes the
rotor, the compression chamber disposed therein and the first and second end
plates.
[0007] One of the end plates disposed at an end of the compression chamber may
define a
discharge fluid line having a discharge valve cavity in fluid communication
with the
compression chamber and a discharge valve member disposed within the discharge
valve
cavity and controlling fluid flow from the compression chamber through the
discharge valve
cavity. The end plate may also further define a noise attenuation chamber in
fluid
communication with the discharge fluid line.
[0008] The present invention comprises, in another form thereof, a rotary
compressor for
compressing a fluid that includes a housing and a motor mounted in the
housing. The motor
has a stator and a rotor with the stator circumscribing the rotor. The rotor
defines a rotational
axis and includes an integrally formed part defining an internal compression
chamber and an
integrally formed vane extending radially inwardly within said compression
chamber.
Opposite axial ends of the rotor define first and second rotor faces
respectively. A first end
plate is secured to the first rotor face and a second end plate is secured to
the second rotor
face. A stationary shaft is mounted in the housing and extends through at
least one of the end
plates and is at least partially disposed within the compression chamber. A
roller is rotatably
mounted on the shaft eccentric wherein the roller is rotatable about an axis
spaced from the
rotational axis of the rotor. The vane is engaged with the roller wherein
rotation of the rotor
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rotates the roller on the shaft and thereby compresses the fluid within the
compression
chamber.
[0009] An advantage of the present invention is that it provides a compact
rotary
compressor having relatively high reliability with reduced vibrations and
noise.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The above mentioned and other features and objects of this invention,
and the
manner of attaining them, will become more apparent and the invention itself
will be better
understood by reference to the following description of an embodiment of the
invention taken
in conjunction with the accompanying drawings, wherein:
Figure 1 is a sectional view of a compact rotary compressor in accordance with
the
present invention.
Figure 2 is an enlarged fragmentary view of the indicated portion of Figure 1:
Figure 3 is a sectional view of the compression mechanism of the compressor of
Figure 1 showing a first position.
Figure 4 is a sectional view of the compression mechanism of the compressor of
Figure 1 showing a second position.
Figure 5 is a top plan view of the inner plate of the compressor.
Figure 6 is a sectional view of the inner plate of Figure S taken along line 6-
6.
[0011] Corresponding reference characters indicate corresponding parts
throughout the
several views. Although the exemplification set out herein illustrates an
embodiment of the
invention, in one form, the embodiment disclosed below is not intended to be
exhaustive or to
be construed as limiting the scope of the invention to the precise form
disclosed.
DESCRIPTION OF THE PRESENT INVENTION
[0012] Referring now to the drawings and particularly to Figure l, there is
shown a
compact rotary compressor 10. Compressor 10 has hermetically sealed housing 12
including
base 14 and body portion 16 which are hermetically sealed by welding, brazing,
or the like at
location 18. The size of base 14 is greater than the diameter of cylindrical
body portion 16 to
provide flange 20 having apertures 22 therein for mounting compressor 10.
Compressor 10 is
illustrated as being in a substantially horizontal orientation however,
compressors in
accordance with the present invention may also be vertically orientated.
[0013] Compressor l0,includes electric motor 24 having stator 26. and rotor 28
which
defines a portion of compression mechanism 30 provided for compressing
refrigerant from a
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low pressure to a higher pressure for use in a refrigeration system, for
example. Stator 26,
having coil assembly 32, is rigidly mounted and circumscribes rotor 28.
Extending through
rotor 28 is stationary shaft 34 which is fixedly mounted at end 36 in aperture
38 centrally
formed in body portion 16 of housing 12 by welding, brazing, or the like
(Figures 1 arid 2).
In the illustrated embodiment, weld 40 secures shaft 34 to housing 12.
[0014) Refernng to Figures 3 and 4, a plurality of pockets 41 are formed in
the outer radial
surface of rotor 28 in which permanent magnets 42 are mounted by any suitable
method
including the use of adhesives, for example. Rotor 28 is circumscribed by
lamination stack
44 of stator 26 (Figure 1) and, during operation of compressor 10, stator 26
generates a
rotating electromagnetic field to rotationally drive rotor 28 having permanent
magnets 42
mounted thereon. Rotor 28 also defines an internal compression chamber 52. In
the
illustrated embodiment, rotor 28 is integrally formed from a solid metal
material such as
steel, powder metal, ductile iron, or the like in the general shape of an
annular ring. The rotor
may be manufactured using any suitable method including electric discharge
machining
(EDM). By using a solid integral part to form rotor 28, no lining is required
for internal
compression chamber 52 and the rotor may also include an intel,~ral vane 54
that extends
radially inwardly within compression chamber 52 to engage roller 50 as
discussed in greater
detail below.
[0015) Stationary shaft 34 is formed from any suitable metal material
including steel,
powder metal, ductile iron, or the like by any conventional method including
machining, for
example. Referring to Figure l, an eccentric portion 48 is integrally formed
on shaft 34 and
is located within compression chamber 52 defined by rotor 28. Roller 50 forms
a part of
compression mechanism 30 and is rotatably mounted on eccentric 48. Referring
to Figures 3
and 4, vane 54 is integrally formed with rotor 28 and extends radially
inwardly from the inner
radial surface of rotor 28 that defines compression chamber 52. Vane 54
engages roller 50
and, together with roller 50 divides compression chamber 52 into variable-
volume, crescent
shaped compression pockets 56.
[0016) Referring to Figures 3 and 4, in order to allow for the relative
sliding movement
between vane 54 which extends radially inwardly from cylinder block portion 46
of rotor 2
and roller 50, roller 50 is provided with cylindrical aperture 58 extending
longitudinally
through roller 50 adjacent the outer periphery thereof and defining an opening
in the outer
radial surface of roller 50. Guide bushing 60 is mounted in aperture 58 and
has a
longitudinally extending slot 62 formed therein to slidably receive vane 54
such that as rotor
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28 rotates, vane 54 reciprocatingly slides within slot 62 as roller 50 rotates
on eccentric
portion 48 and moves toward and away from the compression chamber wall
adjacent vane
54. Bushing 60 may also rotate within aperture 58 to allow for change in
angular position of
vane 54 with respect to aperture 58 as rotor 24 and roller 50 are rotated.
Similarly, aperture
58 has a radially outer opening that is sufficiently larget,to allow for this
relative angular
movement of vane 54 during operation of the compressor. In the illustrated
embodiment,
bushing 60 is a two piece bushing, however, alternative embodiments may employ
a single
piece bushing wherein an interconnecting web of material extends between the
two halves of
the bushing through a portion of space 130 and is sufficiently thin to avoid
interfering with
the reciprocation of vane 54 within slot 62.
[0017] Guide bushing 60 is made from a material with suitable antifriction
properties. In
the illustrated embodiment, bushing 60 is formed using Vespel SP-21, a
material
commercially available from E.I. du Pont de Nemours and Company, and which
facililtates
the reduction of frictional losses caused by sliding movement of vane 54 in
slot 62 and
relative oscillating movement of bushing 60 within aperture 58 of roller 50.
The use of a
guide bushing 60 from a material with good antifriction properties facilitates
the reduction of
wear of the surfaces of roller 50, vane 54, and guide bushing 60 that are in
moving contact to
thereby improve the longevity and reliability of the compressor.
[0018] As discussed above, vane 54 is integrally formed with the cylinder
block portion 46
of rotor 28 and the use of bushing 60 together with such an integrally funned
vane, eliminates
the need for a vane spring to press the vane against the roller. The use of
bushing 60 to
slidably receive vane 54 instead of a spring biased vane, may also reduce the
frictional
resistance to created by the vane during operation of the compressor. The
relatively minimal
frictional losses caused by vane 54 facilitates the minimization of power
losses due to
friction. The use of an integral vane that is slidably received within bushing
60 also
facilitates the reduction of refrigerant vapor leakage across the burner
formed by vane 54
between a relatively high pressure compression pocket to a relatively low
pressure
compression pocket during operation of the compressor. The reduced frictional
losses and
refrigerant leakage facilitate the efficient and reliable operation of the
compressor. The use
of an integral vane 54 also facilitates the reduction of parts needed to
manufacture
compressor 10 thereby simplifying and facilitating the cost efficient
manufacture of
compressor 10.
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[0019] Referring to Figures 1, 5, and 6, compression mechanism 30 also
includes inner
plate 64 is located in adjacent contact with upper axial end surface 66 of
rotor 28 to partially
define and seal compression chamber 52. As shown in Figures 5 and 6, a
plurality of fluid
passages are formed in inner plate 64 to define a portion of the discharge
line which is further
described below. Inner plate 64 is provided with central aperture 68 through
which shaft 34
extends. Positioned in adjacent contact with the opposite surface of inner
plate 64 is outer
plate 70 also having a central aperture 72 through which shaft 34 extends.
Together plates 64
and 70 define a first end plate assembly. Although the illustrated embodiment
employs two
plates, i.e., plates 64, 70 to define the first end plate, the first end plate
is not limited to a two
piece construction. Second end plate 74 is positioned in adjacent contact with
the lower axial
end surface 76 of rotor 28 and partially defines and seals compression chamber
52.
Cylindrical protrusion 78 extends outwardly from the lower surface of plate 74
and is
received in upstanding member 80. Second end plate is rotatably mounted on the
stationary
support defined by member 80 via bearing 88. A thrust bearing 89 is also
located between
member 80 and second plate 74. The first end plate, i.e., inner plate 64 and
outer plate 70,
rotor 28 and second plate 74 are secured together to define compression
chamber 52. In the
illustrated embodiment, a plurality of bolts extend through apertures in outer
plate 70, inner
plate 64, rotor 28, and second end plate 74 to secure these components to one
another.
Alternative embodiments may employ alternative methods of securing these
components
together such as welding.
[0020] Compression assembly 30 is rotatably mounted on shaft 34 by a plurality
of
bearings 82, 84, and 86 which are press-fit into the apertures defined by
outer plate 70 and
inner plate 64, and the inner diameter of roller 50, respectively. Bearing 88
is press-fit onto
protrusion 78 to rotatably support second end plate 74 by rotatably mounting
protrusion 78 in
upstanding member 80. When the compressor is operating and rotor 28 is
rotated, bearings
82, 84, 86, and 88 rotatably support compression assembly 30 as it is
rotatably driven about
stationary shaft 34. As best seen in Figures l, 3 and 4, bearings 82, 84 and
88 which
rotatably support rotor 24 and the first and second end plates enclosing
compression chamber
52 are centered on rotor axis 24a and bearing 86 rotatably supporting xoller
50 is centered o:.
roller axis 50a defined by eccentric portion 48 of shaft 34. Axes 24a and SOa
are spaced apart
whereby roller 50 will form a line, or area, of contact with the inner radial
surface of rotor 24
that defines compression chamber 52 that progressively travels along the
circumference of
the inner radial surface of rotor 24 as rotor 24 and roller 50 rotate about
their respective axes.
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The relative rotation of rotor 24 and compression chamber 52 and roller 50
with respect to
shaft 34 and axes 24a and SOa defines compression pockets for compressing
refrigerant in a
manner typical for rotary compressors that is well known in the art.
[0021] Bearings 82, 84, 86, 88 and 89 may be formed from a polyamide material
having
relatively low coefficients of static and kinetic friction such as Vespel SP-
21. Another
beneficial characteristic associated with polyamide is that it derr~onstrates
thermal stability
over a relatively broad temperature range. For example, polyamide bushings may
be capable
of withstanding a bearing pressure of approximately 300,000 lb ft/inz and a
contact
temperature of 740°F. For the optimum performance of the bushings and
to avoid
overheating, bushings 82, 84, 86 and 88 advantageously have a length to inside
diameter ratio
of no more than 3:2.
[0022] Compressor 10 as described above utilizes a bushing 60 and bearings 82,
84, 86 and
88 that do not require lubrication. While the above-described embodiment is
equipped with
self lubricating bushings and bearings, alternative embodiments may utilize
alternative
bushings and bearings, e.g., needle or ball-type bearings and a conventional
oil sump and
pump for supplying lubricating oil to the bearings.
[0023] 'Assembly of compressor 10 may advantageously include first assembling
compression assembly 30. Initially, roller 50, having guide bushing 60 press
fit therein is
located in compression space 52 such that vane 54 engages slot 62 and rotor 28
is positioned
in abutting contact with second end plate 74. Bushing 86 is press fit within
cylindrical
aperture 58 of roller 50 and shaft 34 is inserted within bushing 86 to thereby
rotationally
engage roller 50 and shaft 34. Inner plate 64 and outer plate 70, having the
respective
bearings 82 and 84 assembled therev~rith, are then positioned on shaft 34 and
fasteners are
used to secure the compression chamber components together. Also mounted to
shaft 34 is
compression kit 89 (Figures 1 and 2) which is provided to secure the relative
position of
compression mechanism 30 with respect to housing 12 and stator 26. Compression
kit 89
axially biases compression mechanism 30 towards upstanding member 80:
Compression kit
89 is shown in Figure 2 and includes wave spring 90 which applies pressure to
steel washer
92 facing upper surface 94 of bearing 82. Retaining ring 96 is located on the
opposite side of
wave spring 90 and has a radially inner portion 97 that engages annular groove
99 formed in
shaft 34. Suitable wave springs are commercially available from the Smalley
Steel Ring
Company located in Lake Zurich, Illinois. The assembled compression mechanism
30 is then
mounted in housing body portion 16 with end 36 of shaft 34 extending through
aperture 38.
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Shaft 34 is secured to body portion 16 of housing 12 with weld 40. Also
located in housing
body portion 16 is inlet 98 through which suction pressure refrigerant enters
motor cavity
100. Stator 26 is shrink fitted into housing body portion 16 and is
electrically coupled via
wire 102 to terminal assembly 104 also mounted in the housing body portion 16.
Compression mechanism 30 is positioned within housing body portion 16 such
that rotor 28
is aligned with stator 26. The assembled compression mechanism and housing
body portion
is then mounted to housing base 14 with bearing 88 mounted on protrusion 78
being received
in upstanding portion 80. Housing body portion 16 is then welded to housing
base 14 at seam
18. By positioning compression chamber 52 within rotor 24 and circumscribing
rotor 24,
compression chamber 52 and end plates 64, 70 and 74 with stator 26 the overall
assembled
axial extending length of compressor 10 is relatively limited and thereby
provides a compact
overall design that facilitates. the flexible positioning of the compressor.
[0024] The compact arrangement provided by the present invention allows the
axial length
of the compressor to be reduced to approximately the same axial length of the
stator 26.
[0025] During compressor operation, electrical current supplied to stator 26
via terminal
assembly 104 creates a magnetic flux which in turn causes rotation of rotor
28. The rotation
of rotor 28 drives the rotation of roller 50 about drive shaft 34 through vane
54 which is
integrally formed with rotor 28 and engaged with roller 50. Referring to
Figures 3 and 4, as
rotor 28 and roller ~0 rotate, vane 54 slides within slot 62 in bushing 60 and
the crescent
shaped compression pockets 56 defined within compression chamber 52 become
progressively smaller as they approach discharge port 140. After passing
discharge port 140,
compression pockets 56 enlarge and refrigerant is drawn into the compression
pockets 56
through a suction port (not shown).
[0026] The refrigerant flows through a pathway best seen in Figures l, 5, and
6. The
pathway is partially defined by a plurality of passages located in inner plate
64 and provides
for the intake and discharge of refrigerant fluid by compression mechanism 30.
Relatively
low pressure refrigerant vapor, i.e., suction pressure refrigerant, is
introduced into the motor
cavity 100 through inlet 98. Thus, compressor 10 is a low side compressor in
which motor
cavity 100 is filled with suction pressure refrigerant. The suction pressure
refrigerant is at a
lower temperature than the compressed refrigerant and facilitates the cooling
of the motor.
The present invention is not limited to low side compressors, however, and
alternative
embodiments may employ a variety of configurations including high side
compressor designs
wherein the motor cavity is filled with discharge pressure refrigerant.
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[0027] In the illustrated embodiment, the refrigerant passes through a suction
port (not
shown) in inner plate 64 and is introduced into a relatively large compression
pocket 56
defined within compression chamber 52. The suction port is located in inner
plate 64 such
that discharge valve 106 and the suction poxt are in communication with
separate
compression pockets 56 throughout an entire 360 degree rotation of rotor 28
and roller 50
about shaft 34. After refrigerant is drawn into a compression pocket 56,
rotation of rotor 28
and roller 50 about shaft 34 causes the progressive reduction in size of the
compression
pocket and the compression of the refrigerant vapor disposed therein, when the
compression
pocket is in fluid communication with discharge valve assembly 106 and the
pressure within
the compression pocket is sufficient to open the discharge valve assembly 106,
compressed
refrigerant is discharged from compression chamber 52 through discharge port
140 and the
discharge valve assembly 106 disposed within discharge valve cavity 12 formed
in plate 64
as best seen with reference to Figures 1, 5 and 6.
[0028] The discharge valve assembly includes a valve seat body 142 defining
discharge
port 140 in fluid communication with compression chamber 52 and a spherical
valve member
144 biased into engagement with a valve seat defined by body 142 by spring 146
to thereby
seal the discharge port. A retaining ring 148 secures spring 146 within valve
seat body 142.
When the fluid pressure within the discharge pocket 56 that is in fluid
communication with
the discharge port 140 exceeds the pressure necessary to overcome the biasing
force of spring
146, the valve will be forced open and refrigerant will be discharged from
compression
chamber 52 through discharge port 140. The discharged refrigerant is then
communicated
through discharge cavity 112 to fluid channel 110. Fluid channel 110 defines a
passageway
to the circular channel forming discharge muffler 108. Discharge muffler 108,
and passages
110 and 120, are defined by recesses in inner plate 64 and the sealing
engagement of outer
plate 70 with inner plate 64 as best seen in Figure 1. Muffler 108 has two
branches 116 and
118 (Figure 5) each leading to channel 120 which is in continuous fluid
communication with
peripheral groove 122 (Figure 1) on shaft 34. Groove 122 is, in turn, in fluid
communication
with one or more radial channels 124 formed in shaft 34. As best seen in
Figure 1, radial
channel 124 communicates discharged refrigerant to passage 126 extending
longitudinally
through shaft 34 toward discharge fitting 128. The compressed refrigerant is
discharged from
compressor 10 through discharge fitting 128 to a system that utilizes
compressed fluid such
as a refrigeration system or heat pump system.
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[0029] The configuration of discharge muffler passage 108 helps to control
noise and
reduces the flow velocity. By providing a greater cross sectional area than
the discharge port
and channel 110, passage 108 reduces the flow velocity of the discharged fluid
which
facilitates the reduction of noise. Additionally, during operation of the
illustrated
compressor, compressed refrigerant vapors are discharged through valve 106 on
a periodic
basis as the individual compression pockets 56 reach the necessary pressure to
open valve
106. The periodic discharge of vapors through valve 106 may create a pressure
wave within
the discharged vapors. By splitting the discharge flow into two separate
channels, i.e.,
branches 116 and 118, which then meet before the compressed fluid enters
radial channel
120, the pressure waves present in the two separate channels meet and, if they
are out of
phase, at least partially destructively interfere with each other, thereby
reducing the amplitude
of the pressure wave and the vibrations and resulting noise that may be
created thereby. By
altering the respective lengths of branches 116 and 118 the wavelength of the
pressure waves
subject to the most destructive interference can also be altered. In the
illustrated
embodiment, channel 120 is located diametrically opposite channel 110 and
branches 116
and 118 have similar lengths, however, in alternative embodiments, it may be
advantageous
to locate channel 120 such that branches 116 and 118 have unequal lengths to
enhance the
destructive interference of pressure waves having a selected wavelength.
Dashed lines in
Figure 5 illustrate an alternative location 120a for a channel providing
communication
between passage 108 and groove 122 that defines branches having unequal
lengths. As
described above, passage 108 acts as a noise attenuation chamber by both
reducing the
velocity of the discharged refrigerant conveyed therethrough and by promoting
the
destructive interference of the pressure waves conveyed by the discharged
refrigerant.
[0030] Referring to Figures 3 and 4, the radial slot 62 in roller 50 has a
small space 130
located between the distal end 132 of vane 54 and the surface of the roller 50
opposite distal
end 132. As vane 54 reciprocates within slot 62, the volume of space 130 is
alternatively
reduced and expanded. If space 130 is well sealed and without an outlet, the
vapor within
space 130 would be compressed as vane 54 moves further into slot 62 and
expanded as vane
54 move radially ouwardly within slot 62 thereby performing work on the gas
located it
space 130 without obtaining any benefit therefrom and degrading the efficiency
of
compressor 10. If space 130 is not well sealed with respect to the compression
pockets 56
located on opposite sides of vane 54, as vane 54 moves radially outwardly
within slot 62,
vapor from the relatively high pressure adjacent compression pocket might be
drawn into
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space 130 and then expelled to the relatively low pressure adjacent
compression pocket as
vane 54 subsequently moves further into slot 62 thereby leading to the
reexpansion of the
vapor, loss of volumetric efficiency and a possible increase in undesirable
noise.
[0031] To inhibit the loss of efficiency and reverse flow as a result of the
interaction of
vane 54 and slot 62, bushing 60 engages opposite sides of vane 54 and a
communication
passage 134 (Figures 1, 5, and 6) is formed in the inner plate 64 to connect
space 130 with
the discharge muffler passage 108. Thus, as vane 54 moves further into slot
62, vapors
within space 130 may be communicated to passage 108 and, as vane 54 moves
radially
outwardly within slot 62, vapor at discharge pressure may be communicated to
space 130
through passage 134.
[0032] While this invention has been described as having an exemplary design,
the present
invention may be further modified within the spirit and scope of this
disclosure. This
application is therefore intended to cover any variations, uses, or
adaptations of the invention
using its general principles.
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