Note: Descriptions are shown in the official language in which they were submitted.
1_ 2Q8076~
APPARATUS FOR RECOVERIN~ REFRIGERANT
TECHNICAL FIELD:
5 ~l. The present invention pertains to the art of
refrigeration systems.
BACKGROUN~ OF THE INVENTION:
In view of global concern regarding the
environmental consequences attending the release o~
chlorofluorocarbon refrigerants into the atmosphere,
there is now world-wide agreement regarding regulation
of the production and use of chlorofluorocarbons. As a
result of this regulation the cost of
chlorofluorocarbon refrigerants is expected to rise
dramatically.
~ - 2 - 208~7~
Accordingly, there has arisen an interest in
recovering refrigerant fluids. Commonly assigned U.S. Patent
No. 4,766,733 describes such an apparatus for recovering
chlorofluorocarbon refrigerants.
The need to provide field service for refrigeration
equipment requires that refrigerant recovery devices be
readily portable, e.g. so that a service person may transport
the recovery device from his vehicle to a rooftop air
conditioning unit without undue time and effort.
Known portable CFC recovery units include a
conventional refrigerant compressor for transferring
refrigerant from an apparatus, e.g. a refrigeration unit, to a
receiver, e.g. a pressure vessel. The use of a conventional
refrigerant compressor in a portable CFC recovery unit has
several drawbacks.
The ease of portability of a particular portable CFC
recovery unit depends, to a large extent, upon the weight of
the unit. A conventional 1/2 HP refrigerant compressor weighs
about 40 pounds and accounts for a significant portion of the
overall weight, i.e. between about 70 lb and about 100 lb, of
a typical recovery unit.
The difficulties associated with using conventional
refrigerant compressors in a portable CFC recovery unit are
acknowledged by the industry, see e.g. "The Perfect HCFC
Z5 Recovery Machine" by J. Wheeler, Contractinq Business.
October 1990, page 7, and "'Don't Wait To Buy Recyclers' MFRS
Tell HVAC Contractors" by Peter Powell, The Air Conditioning,
Heating and Refrigeration News, October 7, 1991.
-3- 2 ~ 8 ~ ~ ~ O
Furthermore, conventional refrigerant compressors
are designed to operate on a closed loop wherein
lubricant is carried in the refrigerant and is
continuously cycled through the system. In an open
loop refrigerant recovery system lubricant is not
returned to the compressor potentially resulting in
insufficient lubrication and premature wear of the
compressor. This problem is aggravated by the need to
pull a vacuum on the unit from which the refrigerant is
being recovered. Furthermore, the lubricant in the
refrigerant being recovered may include contaminants,
e.g. hydrochloric acid and/or hydrofluoric acid, which
may damage the compressor.
SUMMARY OF THE INVENTION:
A lightweight, i.e. about 30 lb, apparatus for
recovering a compressible refrigeration fluid from a
refrigeration system and delivering the recovered fluid
to a refrigerant receiver is described herein.
The recovery apparatus includes a lightweight, i.e.
about lO lb, refrigerant compressor for transferring
refrigerant. The compressor includes a tubular
cylinder wall, a cylinder head enclosing one end of the
cylinder wall and defining an intake port and an outlet
port, and valve means for controlling flow through the
intake and outlet ports. A piston is slidably received
within the cylinder wall and provided with self
lubricating bidirectional annular seal means for
sealing between the piston and cylinder wall. The
compressor further includes means for reciprocally
moving the piston within the cylinder wall to provide
an intake stroke and an outlet stroke. The self
lubricating feature of the compressor of the present
invention avoids the problems of oil loss, oil
contamination and associated compressor damage as well
2Q8~7GD
as eliminating the need for an oil separator. The
bidirectional seal feature allows the compressor of the
present invention to provide a vacuum intake stroke and
thereby completely empty a system of used refrigerant.
In a preferred embodiment, the cylinder wall
comprises hardened steel and the inner diametral
surface of the cylinder wall is honed to a finish
between about 2 microns and about 16 microns.
In a preferred embodiment, the piston comprises
aluminum or an aluminum alloy.
In a preferred embodiment, the means for
reciprocally moving comprises an electric motor, a
crankarm operatively associated with the electric motor
and a connecting rod operatively associated with the
crankarm and with the piston. The crankarm is mounted
on an input shaft and the crankarm and motor are
operatively associated by reduction means for coupling
the motor and the shaft.
In a particularly preferred embodiment the motor
comprises an open frame universal Class A electric
motor having an operating speed range of about 8,000
rpm to about 25,000 rpm, the reduction gear means
provides a reduction between about 4:l and about 6:l
and the shaft and crankarm operate in the range of
about 2,000 rpm to about 4,000 rpm. Compared to the
motor a conventional compressor, the motor of the
compressor of the present invention is very
lightweight, but runs at a relatively high speed. The
reduction means of the compressor of the present
invention allow use of the lightweight high speed motor
by reducing the speed of the input shaft so that the
piston and cylinder assembly of the compressor of the
present invention operates in a range within which self
lubricating piston seals may be employed.
208076~
In a particularly preferred embodiment, the piston
is laterally displaced, toward the compression side,
relative to the crankarm such that an extension of the
centerline of the piston is laterally displaced from
the center of rotation of the crankarm. The lateral
displacement of the piston relative to the center of
rotation of the crankarm dramatically reduces piston
seal wear and thereby prolongs the service life of the
corresponding embodiment of the compressor of the
present invention.
Each of the embodiments of the bidirectional seal
of the compressor of the present invention allow
operation at relatively high speed, i.e. between about
2,000 rpm and 4,000 rpm, at elevated pressure, i.e.
about 400 psig, while exposed to a variety of
refrigerants and associated contaminants.
In a preferred embodiment, the piston defines a
first annular groove and a pair of peripheral annular
grooves. The peripheral grooves are spaced apart from
and disposed on opposite sides for the first annular
groove. An annular seal is disposed in the first
annular groove and elastomeric means are disposed in
the first groove between the piston and the annular
seal for urging the annular seal toward the cylinder
wall. Guide rings are disposed in each of the
respective peripheral grooves for maintaining the
piston in a parallel orientation relative to the
cylinder wall.
In a particularly preferred embodiment, the annular
seal comprises a carbon filled PTFE matrix composite
material, the guide rings comprise a graphite filled
PTFE matrix composite material and the elastomeric
means comprises a ring of chlorosulfonated elastomer, a
polychloroprene elastomer, a perfluorinated elastomer
or an EPDM elastomer.
` ~ - 6 - 2080760
In an alternative preferred embodiment, the piston
de~ines a pair of annular grooves and the seal means includes
a first unidirectional annual seal, disposed in one of said
grooves, for sealing between the piston and cylinder wall to
provide a vacuum intake stroke and a second unidirectional
seal, disposed in the other of said annular grooves, for
sealing between the piston and cylinder to provide a high
pressure outlet stroke.
According to a further broad aspect of the present
invention there is provided an apparatus for compressing a gas
phase refrigerant. The apparatus comprises a tubular cylinder
wall extending from a first end to a second end. - A cylinder
head encloses the second end of the cylinder wall and defines
an intake port and an outlet port. Valve means is provided
for controlling flow through the intake port and the outlet
port. A piston is slidably received with the cylinder wall
for reciprocating movement. The piston is rotationally
symmetrical about a centerline and axially aligned with the
cylinder wall substantially throughout reciprocation thereof.
A first annular groove circumscribes the piston. Self-
lubricating bidirectional annular seal means is disposed in
the first annular groove for sealing between the piston and
the cylinder wall. Means is provided for reciprocally moving
the piston axially within the tubular cylinder wall to provide
an intake stroke and an outlet stroke. This means includes an
electric motor, a crankarm having a center of rotation and
operatively associated with the electric motor. The piston is
laterally displaced toward the compression side relative to
the center of rotation of the crankarm such that an extension
of the centerline of the piston is laterally displaced from
the center of rotation of the crankarm.
According to a still further broad aspect of the
present invention there is provided an apparatus for
compressing a gas phase refrigerant. The apparatus comprises
a tubular cylinder wall extending from a first end to a second
end. A cylinder head encloses the second end of the cylinder
and defines an intake port and an outlet port. Valve means is
. ~
- 6a -
2~07~
provided for controlling flow through the intake port and the
outlet port. A piston is slidably received with the cylinder
wall for reciprocating movement. The piston is rotationally
symmetrical about a centerline and axially aligned with the
cylinder wall substantially throughout reciprocation thereof.
First and second annular grooves circumscribe the piston. A
self-lubricating unidirectional annular seal is disposed in
the first annular groove for sealing between the piston and
the cylinder wall to provide a vacuum intake stroke. A self-
lubricating unidirectional annular seal is disposed in thesecond annular groove for sealing between the piston and the
cylinder wall to provide a high pressure outlet stroke. Means
is also provided for reciprocally moving the piston axially
within the tubular cylinder wall to provide an intake stroke
and an outlet stroke. This means includes an electric motor
and a crankarm having a center of rotation which is
operatively associated with the electric motor. The piston is
laterally displaced towards the compression side relative to
the center of rotation of the crankarm such that extension of
the centerline of the piston is laterally displaced from the
center of rotation of the crankarm.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 shows a schematic diagram of the apparatus
of the present invention.
FIGURE 2 shows a schematic top view of the
compressor of the present invention.
FIGURE 3 shows a cross sectional view of a portion
of the compressor of the present invention.
FIGURE 4 shows a schematic drawing of a portion of an
embodiment of a compressor according to the present invention.
FIGURE 5 shows a schematic drawing of a portion of
an alternative embodiment of a compressor according to the
present invention.
FIGURE 6 shows a cross sectional view of a portion
of an embodiment of the compressor of the present invention.
' ~ ,
~ - 6b - 20807~0
FIGURE 7 shows a cross sectional view of a portion
of a second embodiment of the compressor of the present
invention.
FIGURE 8 shows a cross sectional view of a portion
of a third embodiment of the compressor of the present
invention.
FIGURE 9 shows a schematic diagram of an alternative
embodiment of the compressor of the present invention.
. ~
769
DETAILED DESC~IPTION OF THE INVENTION:
The apparatus of the present invention allows
recovery of a compressible refrigeration fluid from a
refrigeration system 2 and delivery of the recovered
fluid to a refrigerant receiver 6. The refrigeration
system includes a port 4, the receiver includes first
port 8 and second port 10.
The apparatus of the present invention includes a
discriminator chamber 12. The discriminator chamber 12
includes an inlet port 14, a liquid inlet port 15, a
liquid outlet port 16, and a gas outlet port 18.
Conduit 20 provides a fluid flow connection between
refrigeration system port 4 and inlet port 14 of the
discriminator chamber 12. A valve 22 allows control of
flow through conduit 20 and a filter dryer 24 allows
removal of moisture and particulate contaminants from
the refrigerant removed from the refrigeration system
2. A conduit 26 is provided for directing liquid phase
refrigeration fluid from port 16 of discriminator
chamber 12 to port 8 of receiver 6. Conduit 26 is
provided with a solenoid valve 28 for controlling flow
through conduit 26 and an actuator 30 opening and
closing solenoid valve 28.
The apparatus of the present invention includes a
compressor 32, a condensor 34 and a back pressure
regulator 36 for condensing gas phase refrigerant fluid
and providing a low pressure stream of substantially
liquid phase fluid to conduit 26. Conduit 38 allows
gas phase refrigerant fluid to flow from port 18 of
discriminator chamber 12 to compressor 32. Conduit 38
is provided with a solenoid valve 40 for controlling
flow through conduit 38. An actuator 42 is provided
for opening and closing valve 40. Conduit 44
establishes a fluid flow connection between compressor
32 and condensor 34. Fan 46 provides a flow of air for
2081176~
removing heat from between the condenser 34 and the
back pressure regulator 36. Conduit 50 establishes a
fluid flow connection between back pressure regulator
36 and conduit 26.
The compressor 32 may comprise a conventional
refrigerant compressor or a compressor of the present
invention. Referring to FIGURES 2 and 3, a compressor
32' of the present invention includes a
piston/cylinder/cylinder head assembly 101 having a a
tubular cylinder wall 102. The tubular cylinder wall
102 may comprise, e.g. steel or stainless steel.
Preferably, the cylinder wall 102 comprises hardened
steel. Most preferably, the cylinder wall 102
comprises A2 steel, hardened to Rockwell C60-65.
Preferably, the inner diametral surface of the cylinder
wall 102 is honed to a very smooth finish, e.g. a 2 to
16 micron finish, to reduce wear on the piston seals
(discussed further below) and reduce leakage. The
cylinder head 104 encloses one end of the tubular
cylinder wall 102. The cylinder head 104 is provided
with an intake port 106 and an outlet port 108 as well
as an intake valve and outlet valve (not shown) for
controlling flow through intake port 106 and outlet
port 108. A piston 110 is slidably received within the
tubular cylinder wall 102. Preferably, the compressor,
housing, piston 110 and head 104 are each made from
aluminum or a light-weight metal alloy.
An annular seal 112 circumscribes the piston.
Annular seal 112 is a bidirectional self lubricating
annular seal for sealing between the piston 110 and
tubular cylinder wall 102 so that the apparatus of the
present invention provides a high pressure outlet
stroke and a vacuum intake stroke. A piston ring 113
is provided to maintain piston 110 axially aligned
within the tubular wall 102. A piston rod 114 is
~D~O
g
provided for reciprocally moving the piston within the
tubular cylinder wall 102. The piston rod 114 is
rotatably mounted on wrist pin 116. Wrist pin 116 is
secured to the end of crankarm 118. Shaft 120 is
provide for rotating crankarm 118. Gears 122 and 124
couple shaft 120 with the output shaft 126 of motor 128.
Preferably, motor 128 is an open frame Universal
Class A electric motor having an operating speed
between about 8,000 and about 25,000 rpm. The gears
122 and 124 are selected to provide shaft 120 with an
operating range of about 2,000 to 4,000 rpm, i.e.
provide a reduction of from about 4:1 to about 6:1
relative to the operating range of the motor 128.
Significantly, operation of the piston and cylinder
of the compressor of the present invention at speeds of
2,000 to 4,000 rpm places unusually high demands on the
self-lubricating bidirectional seals of the compressor
of the present invention, due to the elevated
temperatures, e.g. 300 F to 500 F, generated by
friction between the piston seals and the cylinder wall
and to the potential for accelerated wear of the seal
materials and associated reduction in service life of
the seals. The piston seal embodiments described below
each provide a long service life, e.g. at least 500
hours of operation, in the high speed, high pressure,
high temperature, chemically hostile environment of the
compressor of the present invention.
FIGURE 4 shows a schematic diagram of a first
piston and cylinder arrangement 144 wherein the
cylinder 146 is oriented so that an extension of the
centerline 145 of the cylinder 146 and piston 150
passes through the center of rotation 149 of the
crankarm 148. The circle swept out by rotation of the
crankarm 148 is shown by the dashed line in FI~URE 4.
Piston 150 is slidably received within the cylinder 146
2080~60
--10--
and is connected to crankarm 148 by wrist pin 152,
connecting rod 154 and crank pin 156. The piston and
cylinder arrangement 144 is shown in the middle of the
compression stroke. As the crankarm 148 is further
rotated in the direction indicated, the compression
stroke, i.e. upward displacement of piston 150,
continues until the end of the crankarm 148 reaches the
top center position and crank arm 148 is aligned with
the centerline of the piston 146. The force acting on
the piston 146 during the compression stroke may be
separated into two components, i.e. the upwardly
directed compressive force Fl and the side force F2,
directed perpendicularly to the compressive force.
In embodiments of the present invention in which
the piston and cylinder arrangement corresponds to that
shown in FIGURE 4, it has been found that the wear
pattern of the seals (described below) of the piston
110 of the present invention corresponds to the
direction of the side force F2, i.e. the seals wear
more quickly on the side of the piston subjected to the
side force F2.
A preferred embodiment of the piston and cylinder
arrangement 158 of the compressor of the present
invention is shown in FIGURE 5. In piston and cylinder
arrangement 158 the centerline 159 of the cylinder 160
and piston 164 is laterally displaced from the center
of rotation 161 of the crankarm 162. Preferably, the
centerline of the cylinder 160 is displaced from the
center of rotation 161 of crankarm 162 by a distance
equal to about one half of the diameter (D) of circle
swept out by rotation of the crankarm 162. Piston 164
is slidably received in cylinder 160 and connected to
crankarm 162 by wrist pin 166, connecting rod 168 and
crank pin 170.
208076~
--11--
The piston and cylinder arrangement 158 is shown in
the middle of the compression stroke. Further rotation
of crankarm 162 continues the compression stroke until
crank pin 170 reaches the top center position on
crankarm 162 in a manner similar to that discussed
above in regard to FIGURE 4. Unlike the embodiment
shown in FIGURE 4, the top center position on the crank
arm 162 is not aligned with the centerline of cylinder
160 and wrist pin 170 crosses the centerline of
cylinder 160 as it sweeps from the piston shown in
FIGURE 5 to the top center position on crankarm 162.
The forces acting on piston 164 may be separated
into two components; i.e. upwardly directed compressive
force F3 and side force F4, directed perpendicularly to
compressive force F3. The inventors have calculated
that, other factors being equal, the preferred
embodiment of FIGURE 5 provides several advantages over
the embodiment shown in FIGURE 4, i.e.:
- while compressive force F3 is slightly
reduced, i.e. F3 is about 3% less than Fl, the side
force F4 is dramatically reduced, i.e. F4 is about
50% less than F2;
- the reduced magnitude of side force F4 results
in a corresponding reduction of the side force on
piston seals and should effectively avoid the
pattern of premature side force related wear
observed with regard to the seal on piston 164;
- the reduced magnitude of side force F4 results
in reduced loads on wrist pins 166 and 170, thereby
prolonging bearing life;
- the re~uired power input to crankshaft 162
during the compression stroke is reduced by about
8%; and
- the reduced magnitude of side force F4 results
in a dramatic reduction, i.e. about 400% of
friction between the piston and cylinder.
~ 2û8~76Q
-12-
The combination of the above advantageous results
should dramatically prolong the service life of the
compressor shown in FIGURE 5.
FIGURE 6 shows one embodiment of the self
lubricating bidirectional annular seal of the
compressor 32 of present invention. Piston 110 defines
an annular groove 130 which circumscribes the piston.
Annular seal 112 is disposed within groove 130.
Preferably, the annular seal 112 comprises a graphite
or carbon filled fluoropolymer, e.g.
polytetrafluoroethylene. A chemical resistant
elastomeric ring 132 urges piston ring 112 towards
cylinder wall 102 to provide a bidirectional seal.
Preferably, the elastomeric ring 132 comprises a
chlorosulfonated polyethylene elastomer, a
polychloroprene elastomer, a perfluorinated elastomer
or an ethylene propylene diene (EPDM) elastomer.
A schematic cross sectional view of a portion of a
alternative embodiment 172 of the self lubricating
bidirectional annular seal of the compressor 32 of the
present invention is shown in FIGURE 7. The embodiment
172 includes a cylinder wall 174 and a piston 176.
Piston 176 defines three spaced apart annular grooves
178, 180, 182. Annular seal 184 is disposed in the
central groove 180 and urged toward cylinder wall 174
by elastomeric ring 186 disposed in grooves 180 between
annular seal 184 and piston 176. Guide rings 188, 190
for maintaining piston 176 in axial alignment with
cylinder wall 174 are disposed in peripheral grooves
178, 182, respectively.
Preferably, the annular seal 184 and guide rings
188, 190 comprise a graphite or carbon filled
fluoropolymer matrix composite material. Most
preferably, annular seal 184 comprises a carbon filled
polytetrafluoroethylene matrix material known as
208076~
-13-
TURCITE 109. Suitable seals may be obtained
commercially, e.g. from W.S. Shamban Company of Fort
Wayne, Indiana. Most Preferably, the guide rings 188,
190 comprises a graphite filled polytetrafluoroethylene
matrix material known as TURCITE 51. Suitable
wear rings may be obtained commercially, e.g. from W.S.
Shamban Company.
The TURCITE 109 material exhibits a tensile
strength of 3000 psi and an elongation at break of 200%
(each determined according to ASTM D 1457-81A), a
specific gravity of 2.10 and a shore D hardness of 60 -
65. The TURCITE 51 material exhibits a tensile
strength of 1800 psi and an elongation at break of 100%
(each determined according to ASTM D 1457-81A), a
specific gravity of 2.06 and a shore D hardness of 63.
Preferably, elastomeric ring 186 comprises a CFC
resistant, oil resistant and contaminant, e.g. HF or
HCL, resistant, elastomer having good temperature
resistance, i.e. is stable at temperatures in the rang
of 300 F to 400 F. Suitable materials include
perfluorinated elastomers, chlorosulfonated
polyethylene elastomers, a polychloroprene elastomers
and ethylene propylene diene elastomers. Most
preferably, the elastomeric ring 186 comprises an
elastomer known as TUREL~ EGA. Suitable elastomeric
rings may be obtained commercially, e.g. from W.S.
Shamban. It should be noted that the choice of
elastomer potentially limits the applicability of the
compressor, since a single choice of elastomer cannot
offer optimal resistance to all CFCS.
A schematic cross sectional view of another
alternative embodiment of the self lubricating
bidirectional annular seal of compressor 32 that offers
broad based applicability is shown in FIGURE 8 in which
piston body 110' and piston cap 111 sealingly connected
~ - 20807~0
-14-
to piston body 110' are slidably received within
tubular cylinder wall 102 and in which two annular
grooves 134, 139 circumscribe piston body 110'. A
pair of chemically resistant unidirectional seals 136
and 140 are disposed in the grooves 134, 139,
respectively. In the preferred embodiment shown, the
seals 136, 140 are "U-cup" type seals, each defining an
annular groove therein. Helical springs 138, 141
disposed within the respective annular grooves of seals
136, 140, urge the seals 136, 140 radially outwardly
toward the tubular cylinder wall 102. A pair of guide
rings 142, 143, for maintaining the piston body 110' in
axial alignment with the cylinder wall 102, surround
piston 110'.
Preferably, seals 136, 140 each comprise a
fluoropolymer. More preferably, each of the
unidirectional seals 136, 140 comprise a glass filled
fluoropolymer matrix composite material. Most
preferably, U-cup seals 136, 140 comprise a material
known as TURCITE 404. The TURCITE~ 404
material is a glass and molybdenum filled
polytetrafluoroethylene having a tensile strength of
about 3500 psi (ASTM D638), an elongation at break of
about 230% (ASTM D638), a shore D hardness of about 55
(ASTM D2240) and a specific gravity of 2.18 (ASTM
D792).
Preferably, springs 138, 141 each comprises
stainless steel. Most preferably, the springs 138, 141
each comprise 302 stainless steel.
Suitable U-cup seal and spring assemblies are
commercially available, e.g. from American Variseal of
Broomfield, Colorado.
Preferably, guide rings 142, 143 comprise a
graphite filled polytetrafluoroethylene matrix
material. Most preferably, guide rings 142, 143
comprise the TURCITE 51 material described above.
.. , . . .. , .. , . . ., . .. . , , ~ . .. . . . . . . .. .. .. ... . . .
r
-15- 2~0769
An alternative embodiment 32" of the compressor of
the present invention is shown in FIGURE 9. The
compressor 32" includes a motor 128' J a rotatably
mounted output shaft 126 ' ~ a rotatably mounted input
shaft 120' ~ a crankarm 118' ~ a piston rod 114' and a
piston/cylinder/cylinder head assembly 101' and is
analogous to compressor 32 ' shown in FIGURES 2 with the
exception that pulleys 194 ~ 196 and belt 198 have been
substituted for gears 122 ~ 124 as a means for
transmitting power from shaft 126' to shaft 120'. The
belt driven compressor is more cost effective than the
gear driven embodiment and, while requiring maintenance
more frequently than the gear driven embodiment, is
easier and less expensive to repair. The belt driven
embodiment is also quieter and exhibits less vibration
than the gear driven embodiment of FIGURE 2~
Referring again to FIGURE 1, valve 28 is normally
closed and valve 40 is normally open. The
discriminator chamber 12 includes float sensor 52 for
sensing the level of liquid phase refrigerant fluid in
the discriminator chamber 12. Sensor 52 is responsive
to the level of liquid phase refrigerant fluid in the
discrimination chamber 12 and provides a control signal
if the discriminator chamber 12 is full of liquid phase
refrigerant fluid. Actuators 30 and 42 are responsive
to the control signal provided by sensor 52~ In
response to the control signal, actuator 42 closes
valve 40 to prevent liquid from flowing from the
discriminator chamber 12 to the compressor 32 and opens
valve 28 to allow the liquid to drain from the
discriminator chamber 12 through conduit 26 to receiver
6~
A bypass conduit 56 is provided to allow fluid to
flow directly from condenser 34 to inlet port 8 of
receiver 6~ The bypass conduit 56 is provided with a
20807BD
-16-
solenoid valve 58 for controlling flow through conduit
56. An actuator 60 is provided to open and close
solenoid valve 58. Valve 58 is normally closed. A
pressure sensor 62 is responsive to the pressure within
discriminator chamber 12 and provides a control signal
if the pressure in discriminator chamber 12 falls below
a predetermined value. Actuator 60 is responsive to
the control signal from pressure sensor 62 and opens
valve 58 in response to the control signal.
The recovery apparatus of the present invention
includes a safety chamber 64. Safety chamber 64
includes an inlet port 66, a gas outlet port 68 and a
liquid outlet port 70. A conduit 72 is provided for
allowing fluid flow between port 10 of receiver 6 and
inlet port 66 of safety chamber 64. Conduit 72 is
provided with a solenoid valve 74 for controlling flow
through conduit 72. An actuator 76 is provided for
opening and closing solenoid valve 74. Conduit 78
allows fluid to flow from gas exit port 68 of safety
chamber 64 to conduit 38 and on to compressor 32.
Conduit 80 is provided with a solenoid valve 82 for
controlling flow through conduit 80. An actuator 84 is
provided for opening and closing solenoid valve 82.
Inlet tube 86 extends into receiver 6 through port
10 of receiver 6 to an open end 88.
If the level of liquid phase refrigerant within
receiver 6 is below the open end 88 of inlet tube 86,
gas phase refrigerant fluid flows through conduit 72,
safety chamber 64 and conduit 78 to compressor 32.
As the receiver fills with refrigeration fluid, the
liquid level rises until the liquid level reaches the
end 88 of inlet tube 86. Once the liquid level in the
receiver is at the level of the open end 88 of inlet
tube 86, the introduction of additional refrigeration
fluid into receiver 6 will result in liquid phase
. .. ., .. , , .,.~ ., .. . .. . . . . . .. ~ . . ... .. . . . . .
-17- 208~76~
refrigerant being forced through conduit 72 and into
inlet port 66 of safety chamber 64. Sensor 90 within
safety chamber 64 is responsive to liquid level within
safety chamber 64. When liquid phase refrigerant
enters safety chamber 64, sensor 90 provides a control
signal. Actuators 30, 42, and 76 and switch 33 are
responsive to sensor 90 and close valves 28, 40 and 74
and cut power to the compressor 32, respectively, in
response to the control signal from sensor 90.
The apparatus of the present invention has two
modes of operation and may be used to recover
refrigeration fluid from a refrigeration system
(recovery mode) and to charge refrigeration fluid from
receiver to a refrigeration system (charging mode).
In the recovery mode compressor 32 and condensor
fan 46 are turned on. Compressor 32 lowers the
pressure in receiver 6 as well as compressing the
influent stream 38 of gas phase fluid. Fluid
evaporates from the receiver 6 is directed through
conduit 72, inlet 66, chamber 64, outlet 68, conduit 78
and is combined with influent gas stream 38.
Evaporation of refrigerant fluid from receiver 6 lowers
the temperature of the liquid phase fluid remaining in
receiver 6. The apparatus maintains a pressure
differential to drive fluid from refrigeration unit 2
to receiver 6 until substantially all refrigerant has
been removed from the refrigeration unit.
In the charging mode, the compressor 32 is turned
on, fan 46 is turned off, back pressure regulator 36 is
closed and valve 58 is open. Fluid is evaporated from
the receiver and compressed in the compressor 32 to
form a high pressure elevated temperature stream of
refrigerant fluid. The high pressure elevated
temperature stream of refrigerant is introduced to the
receiver 6 through conduit 26 to increase the pressure
20~76O
-18-
within receiver 6 and force fluid from receiver 6
through a conduit (not shown) to the refrigeration
system 2 being charged.
The discrimination chamber of the present invention
allows liquid phase refrigerant to bypass the
compressor, condensor and back pressure regulator as it
passes from the refrigeration unit to the refrigerant
receiver and thereby allow refrigerant to be removed
for the refrigeration unit in significantly less time
than possible with the apparatus described in U.S.
Patent No. 4,766,733.
Conventional refrigerant receivers are provided
with a safety valve in order to preclude the generation
of internal pressures within a refrigerant receiver
that exceed the pressure rating of the container. The
safety valve opens at a predetermined maximum pressure
that is below the maximum pressure rating of the
receiver. In order to avoid generating internal
pressures with a receiver that would trigger the safety
valve, the amount of refrigerant introduced to a
receiver must be controlled. Conventional, refrigerant
containers are filled by weight. In the contest o
recovering refrigerant from refrigeration units in the
field, a weighting apparatus constitutes a cumbersome
additional piece of equipment to transport. The safety
chamber of the present invention allows control of the
amount of refrigerant introduced to the receiver
without requiring any equipment in addition to the
apparatus of the present invention.
The features of the compressor of the present
invention offer several benefits which are particularly
advantageous in the context of refrigerant recovery.
Conventional refrigeration compressors are
typically heavy, e.g. typically about 40 lb, cumbersome
devices which include a thick cast iron cylinder
2~8~7S~
--19--
wall. The compressor of the present invention is
lightweight, i.e. about 10 lb, and easily portable,
thereby making a lightweight, i.e. on the order of 30
lb, and easily portable refrigerant recovery unit
feasible.
Typically the materials of construction of
conventional refrigerant compressors are not resistant
to impurities, e.g. acids, present in used refrigerant
fluids. The compressor of the present invention is
adapted for transferring contaminated refrigerants.
Conventional refrigeration compressors operate in
closed loop refrigeration systems in which a
lubricating oil migrates through the loop and
continuously lubricates the compressor. The recovery
of used refrigerant is inherently an open loop
process. Each time the used refrigerant passes from
the refrigeration system through the compressor into a
receivçr lubricating oil would be washed out of the
compressor. The refrigerant compressor of the present
invention is self lubricating, i.e. oilless, thereby
eliminating the need for an oil separator and the
additional weight associated therewith and avoiding
problems of oil loss, oil contamination and associated
damage to the compressor.
Conventional refrigerant compressors include
unidirectional seals and are unable to provide a vacuum
intake stroke. The seals on the piston of the
refrigerant compressor of the present invention are
bidirectional and the refrigerant compressor of the
present invention can thereof be used to pull the inlet
pressure below atmospheric pressure, and allow a
refrigerant system to be completely emptied of used
refrigerant.
, . . . . . ....
I ~ r
2Q8d76~
-20-
While preferred embodiments have been shown and
described, various modifications and substitutions may
be made thereto without departing from the spirit and
scope of the invention. Accordingly, it is to be
5 understood that the present invention has been
described by way of illustrations and not limitations.
