U.S. patent number RE40,399 [Application Number 10/387,037] was granted by the patent office on 2008-06-24 for low charge protection vent.
This patent grant is currently assigned to Scroll Technologies. Invention is credited to Thomas R. Barito, Jason J. Hugenroth.
United States Patent |
RE40,399 |
Hugenroth , et al. |
June 24, 2008 |
**Please see images for:
( Certificate of Correction ) ** |
Low charge protection vent
Abstract
A vent is included into a scroll compressor for protecting a
refrigerant system in the event of loss of charge. The vent
selectively taps an entrapped compression chamber to a housing
chamber which surrounds the motor. In the event of a low charge,
the gas in the compression chamber will be at a high temperature,
and will heat the motor when the vent opens. The vented heated gas
will then actuate a temperature protection device on the motor,
causing the motor to stop rotation. In further embodiments, the
compression chamber which supplies the tapped fluid is the
discharge port.
Inventors: |
Hugenroth; Jason J. (Baton
Rouge, LA), Barito; Thomas R. (Arkadelphia, AR) |
Assignee: |
Scroll Technologies
(Arkadelphia, AR)
|
Family
ID: |
23039798 |
Appl.
No.: |
10/387,037 |
Filed: |
March 12, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
09272439 |
Mar 19, 1999 |
06210120 |
Apr 3, 2001 |
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Current U.S.
Class: |
417/32; 417/26;
417/310 |
Current CPC
Class: |
F04C
28/06 (20130101); F04C 28/28 (20130101); F04C
18/0215 (20130101) |
Current International
Class: |
F04B
49/10 (20060101) |
Field of
Search: |
;417/310,32,25,26,222.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Rodriguez; William H.
Attorney, Agent or Firm: Carlson, Gaskey & Olds
Claims
What is claimed is:
1. A compressor comprising: a motor for driving a compressor
element; a protection device for said motor, said rotation device
being actuated if when a predetermined temperature is exceeded at
said motor; a housing for enclosing said motor, said housing
defining a housing chamber housing said motor; a compression
chamber for compressing a refrigerant, and said refrigerant passing
through said housing chamber to said compression chamber, such that
said refrigerant cools said motor; and a vent for selectively
communicating a fluid directly from an intermediate pressure
portion of said compression chamber to said housing chamber,
.[.if.]. .Iadd.when .Iaddend.conditions in a chamber intermediate a
suction chamber and a discharge port occur because of a loss of
charge in a system associated with said compressor, said vent
allowing gas at an elevated temperature to move into said housing
chamber and contact said motor, and actuate said protection
device.
2. A compressor as recited in claim 1, wherein said compressor is a
scroll compressor.
3. A compressor as recited in claim 2, wherein said vent is placed
in a non-orbiting scroll of said scroll compressor.
4. As recited in claim 1, wherein said vent communicates with a
discharge port.
5. A scroll compressor as recited in claim 4, wherein a valve is
moveable dependent on the pressure difference between a suction tap
and a tap to a compression chamber prior to discharge to
selectively communicate said discharge pressure tap to said housing
chamber.
6. A scroll compressor comprising: a housing defining a housing
chamber; an electric motor received in said housing chamber, said
electric motor being provided with a protection device which is
actuated when said motor reaches a predetermined temperature to
stop rotation of said motor; a supply of suction fluid
communicating with said housing chamber such that said suction
fluid cools said motor; a first scroll member having a base and a
generally spiral wrap extending from said base and a second scroll
member having a base and a generally spiral wrap extending from
said base, said wraps of said first and second scroll members
interfitting to define compression chambers; said motor driving
said first scroll member to orbit relative to said second scroll
member; and a vent for selectively venting gas directly from an
intermediate pressure portion of said compression chambers to said
housing chamber, .[.in the event that.]. .Iadd.when
.Iaddend.conditions in a chamber intermediate a suction chamber and
a discharge port occur because of a loss of charge in a system
associated with said compressor.
7. A scroll compressor as recited in claim 6, wherein said vent is
mounted in said base of said second scroll member.
8. A scroll compressor as recited in claim 7, wherein a tap from
said at least one compression chamber selectively passes to said
housing chamber, said tap being selectively closed by a valve, said
valve being held at a position allowing flow from said tap to said
housing chamber, and said valve moving to a position blocking flow
from said tap to said housing chamber if a pressure differential
between the pressure in said compression chamber and said housing
chamber exceeds a predetermined differential.
9. A scroll compressor as recited in claim 8, wherein a spring
biases said valve toward a stop surface and to said position
allowing flow from said tap to said housing chamber, and the
pressure in said compression chamber selectively overcoming said
spring force to move said valve to a position blocking flow from
said tap to said housing chamber.
10. A scroll compressor as recited in claim 8, wherein a magnetic
force holds said valve at a position allowing flow from said tap to
said housing chamber, and the pressure in said compression chamber
selectively overcoming said magnetic force and moving said valve to
a position blocking flow from said tap to said housing chamber.
11. A scroll compressor as recited in claim 8, wherein a
temperature sensitive element is associated with said valve, and
holds said valve at a position blocking flow from said tap to said
housing chamber until a predetermined temperature is exceeded at
said element, said element being of a bi-metal composition which
snaps to a second position once a predetermined temperature has
been exceeded, said valve being capable of moving to said position
allowing flow when said bi-metal element has moved to said second
position.
12. A scroll compressor as recited in claim 8, wherein a
temperature sensitive element is associated with said valve and
holds said valve at a position blocking flow from said tap to said
housing chamber until a predetermined temperature is exceeded at
said element.
13. A scroll compressor as recited in claim 8, wherein said valve
includes a spool valve and a closure valve, said pressure in said
compression chamber communicating to a chamber acting on said
closure valve and causing said closure valve to be biased toward
said spool valve, an opposed side of said spool valve being
communicated to said housing chamber pressure, and said closure
valve being spring-biased to allow flow from said compression
chamber to said opposed side of said spool valve, said compression
chamber force biasing said closure valve to a first position
blocking such flow unless the difference in pressure between said
compression chamber and said housing chamber is less than a
predetermined difference.
14. A scroll compressor as recited in claim 13, wherein said spool
valve selectively closes a tap to discharge pressure when held in
said first position, but allows flow from both said compression
chamber and a discharge pressure tap when moved away from said
first position.
15. A scroll compressor as recited in claim 13, wherein said spool
valve selectively closes a tap to discharge pressure when held in
said first position but allows flow from said discharge pressure
tap when moved away from said first position.
16. A scroll compressor as recited in claim 6, wherein said
compression chamber is a discharge port.
17. A scroll compressor as recited in claim 16, wherein a valve is
moveable dependent on the pressure difference between a suction tap
and a tap to a compression chamber prior to discharge to
selectively communicate said discharge pressure tap to said housing
chamber.
18. A scroll compressor comprising: a housing defining a housing
chamber; an electric motor received in said housing chamber, said
electric motor being provided with a protection device which is
actuated when said motor reaches a predetermined temperature to
stop rotation of said motor; a supply of suction fluid, said
suction fluid communicating with said housing chamber such that
said suction fluid cools said motor; a first scroll member having a
base and a generally spiral wrap extending from said base and a
second scroll member having a base and a generally spiral wrap
extending from said base, said wraps of said first and second
scroll members interfitting to define compression chambers; said
motor driving said first scroll member to orbit relative to said
second scroll member; and a vent mounted in said base of said
second scroll member, said vent including a valve biased towards a
position selectively venting gas directly from an intermediate
pressure portion of at least one of said compression chambers to
said housing chamber, and said valve being moved to a position
blocking venting of gas .[.if.]. .Iadd.when .Iaddend.conditions in
a chamber intermediate a suction chamber and a discharge port
corresponds to the compressor operating properly.
19. A scroll compressor comprising: a housing defining a housing
chamber; a first scroll member having a base and a generally spiral
wrap extending from said base and a second scroll member having a
base and a generally spiral wrap extending from said base, said
wraps of said first and second scroll members interfitting to
define compression chambers; and a vent mounted in said base of
said second scroll member, said vent including a valve biased
towards a position selectively venting gas directly from an
intermediate pressure portion of at least one of said compression
chambers to said housing chamber, and said valve being moved to a
position blocking venting of gas .[.if.]. .Iadd.when
.Iaddend.conditions in a chamber intermediate a suction chamber and
a discharge port corresponds to the compressor operating
properly.
20. A scroll compressor as recited in claim 19, wherein said vented
gas actuates a motor protection device of an electric motor which
drives said first scroll member.
21. A scroll compressor as recited in claim 19, wherein said valve
has a first face which is exposed to suction pressure and a second
face exposed to a pressure within said at least one compression
chamber, a bias member biasing said valve to a position allowing
venting, and against a pressure from said at least one said
compression chamber.
.Iadd.22. A compressor comprising: a motor driving compressor
elements; a protection device for said motor, said protection
device being actuated when a predetermined temperature is exceeded
at said motor; a housing for enclosing said motor, said housing
defining a housing chamber around said motor; a compression chamber
for compressing a refrigerant, and said refrigerant passing through
said housing chamber to said compression chamber such that said
refrigerant cools said motor; and a vent for selectively
communicating a discharge pressure refrigerant which has been
compressed in said compression chamber to said housing chamber when
conditions in an intermediate pressure chamber at a pressure
intermediate a suction pressure and a discharge pressure occur
because of a loss of charge in a system associated with said
compressor, said vent allowing said discharge pressure refrigerant
to move into said housing chamber and contact said motor, and
actuate said protection device, and said vent including a valve
which has one surface exposed to an intermediate pressure in said
intermediate pressure chamber, and an opposed surface exposed to
the suction pressure, with a spring biasing said valve in a
direction against said intermediate pressure, said valve being
biased by said spring towards a position which communicates said
discharge pressure refrigerant to said housing chamber, with said
intermediate pressure forcing said valve against a force from said
spring to a position blocking flow of said discharge pressure
refrigerant to said housing chamber..Iaddend.
.Iadd.23. A compressor as set forth in claim 22, wherein a tap to
said discharge pressure refrigerant extends into a valve chamber
from a position outward of an outer peripheral surface of said
valve..Iaddend.
.Iadd.24. A compressor as set forth in claim 23, wherein said
discharge pressure refrigerant does not bias said valve, with said
valve being biased by said suction pressure, said intermediate
pressure and said spring..Iaddend.
.Iadd.25. A compressor as set forth in claim 22, wherein said
discharge pressure refrigerant is tapped from a discharge port on
said compressor elements..Iaddend.
.Iadd.26. A compressor as set forth in claim 22, wherein said
compressor elements include a scroll compressor..Iaddend.
.Iadd.27. A compressor comprising: a motor for driving a scroll
compressor; a protection device for said motor, said protection
device being actuated when a predetermined temperature is exceeded
at said motor; a housing for enclosing said motor, said housing
defining a housing chamber around said motor; a compression chamber
for compressing a refrigerant, and said refrigerant passing through
said housing chamber to said compression chamber such that said
refrigerant cools said motor; and a vent for selectively
communicating a discharge pressure refrigerant which has been
compressed in said compression chamber to said housing chamber when
conditions in an intermediate pressure chamber at a pressure
intermediate a suction pressure and a discharge pressure occur
because of a loss of charge in a system associated with said
compressor, said vent allowing said discharge pressure refrigerant
to move into said housing chamber and contact said motor, and
actuate said protection device, and said vent including a valve
which has one surface exposed to an intermediate pressure in said
intermediate pressure chamber, and an opposed surface exposed to
the suction pressure, with a spring biasing said valve in a
direction against said intermediate pressure, said valve being
biased by said spring towards a position which communicates said
discharge pressure refrigerant to said housing chamber, with the
pressure in said intermediate pressure chamber forcing said valve
against a force from said spring to a position blocking flow of
said discharge pressure refrigerant to said housing chamber, a tap
to said discharge pressure refrigerant extending into a valve
chamber for said valve from a position outward of an outer
peripheral surface of said valve..Iaddend.
.Iadd.28. A compressor comprising: a motor for driving compressor
elements; a protection device for said motor, said protection
device being actuated when a predetermined temperature is exceeded
at said motor; a housing for enclosing said motor, said housing
defining a housing chamber around said motor; a compression chamber
for compressing a refrigerant, and said refrigerant passing through
said housing chamber to said compression chamber such that said
refrigerant cools said motor; and a vent for selectively
communicating a tapped refrigerant which has been compressed in
said compression chamber to said housing chamber when conditions in
an intermediate pressure chamber at a pressure intermediate a
suction pressure and a discharge pressure occur because of a loss
of charge in a system associated with said compressor, said vent
allowing said tapped refrigerant to move into said housing chamber
and contact said motor, and actuate said protection device, and
said vent including a valve which has one surface exposed to an
intermediate pressure in said intermediate pressure chamber, and an
opposed surface exposed to the suction pressure, with a spring
biasing said valve in a direction against said intermediate
pressure, said valve being biased by said spring towards a position
which communicates said tapped refrigerant to said housing chamber,
with said intermediate pressure forcing said valve against a force
from said spring to a position blocking flow of said tapped
refrigerant to said housing chamber..Iaddend.
.Iadd.29. A compressor as set forth in claim 28, wherein said
tapped refrigerant is at a discharge pressure..Iaddend.
.Iadd.30. A compressor as set forth in claim 28, wherein said
compressor is a scroll compressor..Iaddend.
.Iadd.31. A compressor comprising: a motor for driving compressor
elements; a protection device for said motor, said protection
device being actuated when a predetermined temperature is exceeded
at said motor; a housing for enclosing said motor, said housing
defining a housing chamber around said motor; a compression chamber
for compressing a refrigerant, and said refrigerant passing through
said housing chamber to said compression chamber such that said
refrigerant cools said motor; and a vent for selectively
communicating a discharge pressure refrigerant which has been
compressed in said compression chamber to said housing chamber when
conditions in an intermediate pressure chamber at a pressure
intermediate a suction pressure and a discharge pressure occur
because of a loss of charge in a system associated with said
compressor, said vent allowing said discharge pressure refrigerant
at an elevated temperature to move into said housing chamber and
contact said motor, and actuate said protection device, and said
vent including a valve which has one surface exposed to an
intermediate pressure in said intermediate pressure chamber, and an
opposed surface exposed to the suction pressure, said discharge
pressure refrigerant communicating through a chamber which contains
said valve from a position radially outward of an outer peripheral
surface of said valve, with said intermediate pressure forcing said
valve to a position blocking flow of said discharge pressure
refrigerant to said housing chamber..Iaddend.
Description
BACKGROUND OF THE INVENTION
This invention relates to a scroll compressor with a vent to
protect a refrigerant system during a low charge situation.
Compressors are utilized to compress a refrigerant in a air
conditioning, refrigeration or heat pump systems, in a refrigerant
cycle, the refrigerant leaving the compressor typically passes to a
condenser, and from the condenser to an expansion device. From the
expansion device the refrigerant is passed to a evaporator, and
then to the compressor. During this cycle through the system, a
working fluid is cooled, as known.
At times, a refrigerant system may lose charge, or refrigerant
mass, such as by leakage. When this happens, the liquid which
typically passes through the expansion device could be a gas. When
gas approaches the expansion device, the flow may be choked at the
expansion device. This could result in significant reduction in the
mass flow rate through the system.
The reduction of refrigerant flow causes the compressor to draw the
suction side pressure to abnormally low levels. Abnormally low
suction pressure levels can cause the compressor to see undesirably
high pressure ratios. The combined effect of the high pressure
ratios and the low mass flow rate will cause the compressor to run
at abnormally high temperatures, which could damage the
compressor.
Motors in the compressor are typically provided with a protection
device which will shut the compressor motor down in the event of an
unusually high temperature. However, by the time the motor senses
this unusually high temperature through low charge as described
above, damage could already have occurred in the compressor.
One type of compressor is a Scroll compressor. Scroll compressors
are becoming widely utilized in refrigerant compression
applications. A scroll compressor consists of a first scroll member
having a base and a generally spiral wrap extending from the base.
This first scroll member has its wrap interfitting with the wrap of
the second scroll member to define compression chambers. The first
scroll member is driven to orbit relative to the second scroll
member, and entrapped fluid in the chambers is compressed to
compress an entrapped fluid.
SUMMARY OF THE INVENTION
In the disclosed embodiment of this invention, a compressor is
provided with a vent that passes a heated entrapped fluid from a
compression chamber to the suction chamber in the event of
conditions which evidence a low charge. The compressor is of the
hermetically sealed type wherein the suction fluid is passed over
the motor to cool the motor. The motor is exposed to the entrapped
fluid. The hot entrapped fluid will not cool the motor, but instead
heats the motor. This will trip the protection device for the
motor, and allow the motor to stop the system, until the low charge
situation can be corrected.
In disclosed embodiments of this invention, the vents are
incorporated into a Scroll compressor. The vents are preferably
placed in the base of the non-driven scroll member. In one
embodiment, the vent includes a valve housing at the tap to the
compression chamber, and having a valve for selectively closing the
tap. The valve is normally spring-biased to a position at which
flow is allowed to pass from the compression chamber to the suction
chamber. Thus, the valve tends to allow the entrapped fluid to
enter the suction chamber, and contact the motor.
The valve is exposed to the entrapped fluid on a side of the valve
opposite to the spring bias. The spring bias side of the valve is
exposed to suction pressure. In the low charge situation described
above, the pressure differential between the suction pressure and
pressure at the entrapped fluid is relatively small. This
relatively small difference in pressure is not enough to overcome
the force of the spring. Thus, the spring will bias the valve to
the open position and the heated fluid is allowed to pass from the
compression chamber to the suction chamber.
On the other hand, during normal operation, the pressure at the
entrapped fluid is significantly higher than the pressure in the
suction chamber. Thus, the fluid in the compression chamber is able
to overcome the spring force and move the valve to a closed
position.
In a second embodiment, a magnetic force holds the valve at its
open position allowing flow from the compression chamber to the
suction chamber. If compressor operation is proper, and there is a
significant pressure differential between suction and the
compression chamber, the valve is driven away from its open
position by the pressure in the compression chamber and moves to
the closed position.
In another embodiment, the spring-biased embodiment is provided
with a bi-metal disc which snaps between two positions due to the
temperature. If the compressor is included in a heat pump, there
are times when the pressure change between suction and the
compression chamber might be relatively small. In particular, when
the compressor is in a heat pump mode with a low ambient
temperature, the suction pressure may become very low, as described
above. This could occur at temperatures on the order of -20.degree.
F. In these situations it would not be desirable for the motor to
stop.
The compressor running in the heat pump situation described above
remains relatively cool. The bi-metal disc has a non-heated
position which holds the valve at its closed position whenever a
very low temperature is experienced. Thus, during the heat pump
operation described above the bi-metal disc holds the valve closed,
and there is no venting. On the other hand, at almost all normal
operating temperatures, the bi-metal disc will not prevent the
valve from moving. Thus, during the loss of charge situation
described above, the compressor quickly heats. The bi-metal disc
will be at its normal position allowing valve movement. The spring
force then causes the valve to move to its open position. In this
way, the bi-metal disc allows the system to be incorporated into a
compressor utilized in a heat pump.
In a further embodiment, a spool valve is provided with a closure
valve. The spool valve sees suction pressure on one side and the
entrapped pressure on another side. A spring tends to bias the
closure valve to an open position allowing the entrapped pressure
to move into the suction chamber. Discharge pressure is also
provided at one small surface on the valve. If the pressure
differential between suction and the compression chamber become
small, the spring opens the closure valve, and allows flow from the
compression chamber, and further from the discharge chamber into
the suction chamber.
In further embodiments, the valve moves to open a tap between
discharge and suction when the pressure difference between suction
and the compression chamber is small. Again, a small pressure
difference between suction and intermediate is indicative of loss
of charge. Thus, the heated gas from the discharge chamber is
communicated into the suction chamber, which in turn contacts the
motor.
With regard to any of the above embodiments, a heated entrapped gas
is passed into a chamber which communicates with the motor. This
heats the motor, causing the motor's heat protection circuit to
trip and stop motor operation.
While the disclosed embodiments all show the vent in the base of
the orbiting scroll, it should be understood that the vent could be
located in other locations within the compressor housing. As
examples, the vent could be located within the orbiting scroll, or
the crank case. Further the vent could be located in a location
other than the base of the scroll members.
These and other features of the present invention can be best
understood from the following specification and drawings, the
following of which is a brief description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a schematic view of a refrigerant system.
FIG. 1B is a cross-sectional view through a compressor incorporated
into the FIG. 1A system.
FIG. 2A shows a first vent embodiment.
FIG. 2B shows the first vent embodiment in its closed position.
FIG. 3 shows a second embodiment vent system.
FIG. 4 shows a third embodiment vent system.
FIG. 5 shows a fourth embodiment vent system.
FIG. 6 shows a fifth embodiment vent system.
FIG. 7 shows a sixth embodiment vent system.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A refrigerant system 15 is schematically illustrated in FIG. 1A. A
compressor 20 supplies a compressed refrigerant to a condenser C.
From the condenser C refrigerant flows to an expansion device EX.
From the expansion device the refrigerant flows to an evaporator
EV. From the evaporator EV the refrigerant returns to the
compressor 20.
As described above, in a loss of charge situation, the liquid which
typically leaves the condenser C could still be gaseous. The gas
creates a choked flow condition at the expansion device EX, thus
limiting mass flow. This could then lead to a problem at the
compressor.
FIG. 1B is a schematic view of the compressor 20. In this
embodiment, the compressor is a scroll compressor, however, the
invention may have application to other type compressors. A scroll
compressor includes a non-orbiting scroll 22 and an orbiting scroll
24. A chamber 26 is defined between the wraps of the non-orbiting
scroll 22 and the orbiting scroll 24. Chamber 26 is selected to be
at a location where the refrigerant would be at least partially
compressed. A discharge chamber 27 is formed above the non-orbiting
scroll 22. A suction chamber 28 surrounds the scrolls 22, 24, and
communicates with a suction chamber 32 adjacent a motor 30. Gas
passing into a suction inlet 33 is allowed to flow over the motor,
cooling the motor. In the event the motor reaches a predetermined
temperature, a protection device 34 senses an undesirably high
temperature and stops the motor.
As mentioned above, if a low charge situation occurs, there could
be undesirably high pressure ratios and undesirable heat
encountered in the compression chambers, such as chamber 26. A vent
36 is provided to vent the heated fluid from the chamber 26 into
the suction chambers 28, 32. The heated fluid communicates with the
motor 30, and the protection device 34 will stop motor operation.
This allows the system to be shut down in a low charge situation
without damage to the compressor.
FIG. 2A shows a first embodiment 38 of the vent 36. A tap 40 to the
chamber 26 extends through the non-orbiting scroll 22. A groove 42
is formed into a face 43. A valve housing 44 is placed within an
opening 46 in the non-orbiting scroll 22. An opening or passage 48
extends through the valve housing 44 and communicates to the
suction chamber 28.
A stop surface 50 provides a valve seat 51. A spring 52 biases a
valve 54 downwardly toward end wall 43. In the position illustrated
in FIG. 2A, gas can flow from chamber 26 through passage 40, groove
42, around the outer periphery 56 of the valve 54, and through
passage 48 into suction chamber 28.
FIG. 2B shows the same valve 54 having been biased to a position 58
where it abuts valve seat 51. In this position, gas cannot flow
past the valve 54, and does not flow from the chamber 26 into the
chamber 28. During normal operation of the compressor, the pressure
in chamber 26 is sufficient to overcome the spring force from
spring 52, and valve 54 remains at the position 58. However, during
the low charge situations described above, the pressure in the
chamber 26 will not be significantly higher than the pressure in
chamber 28. Thus, the valve will not be driven against the force of
the spring 52. Instead, the spring 52 will maintain the valve 54 in
the open position such as shown in FIG. 2A. In this position, the
gas from the chamber 26 will communicate with the motor 30, and the
motor protection device 34 stops motor operation.
FIG. 3 shows another embodiment 60 wherein the valve housing 62 is
formed of a non-magnetic material. However, a ferromagnetic surface
66 is spaced from a valve set 68 of the housing 62. An opening 64
extends through housing 62 to the chamber 28. Valve 70 is formed of
a magnetic material. Valve 70 is held in contact with the surface
66 due to the magnetic attraction. If the pressure difference
between the chamber 26 and the suction chamber 28 is low, the valve
70 remains in the illustrated position and gas flows around the
valve 70 through the groove 42. Motor operation is then stopped.
However, during normal operation, the magnetic force is overcome by
the pressure differential between the chambers 26 and 28 and valve
70 moves to a position abutting valve seat 68. Gas does not flow to
the chamber 28 from the chamber 26.
FIG. 4 shows another embodiment 74. Embodiment 74 is very similar
to the embodiment shown in FIG. 2A, however, a bi-metal disc 76 is
included. Bi-metal disc 76 is shown in its cold or relaxed position
at which it is bowed. In this position, it holds valve 54 at the
closed position 58. Bi-metal disc 76 is of the type of material
which snaps to a second position, shown in phantom at 78, if it
exceeds a predetermined temperature. Thus, should the compressor
reach a predetermined temperature, the bi-metal disc 76 snaps to
the position 78. In this position, spring 52 forces valve 54
downwardly. Thus, the heat pump situation as described above will
not cause a "false" reading of a low charge situation that will
inadvertently and undesirably stop compressor operation. It should
be understood that the temperature for disc 76 to move to position
78 is low. Thus, during normal operation, the disc 76 is at
position 78.
FIG. 5 shows another embodiment 80. A tap or opening 82 to suction
28 is positioned above a valve spool chamber 84. A seal 86 on a
valve spool 88 defines two chambers. A first chamber 90
communicates with the suction chamber 28 through the opening 82. A
tap 92 extends through the valve spool 88 and communicates with a
rear surface of a closure valve member 94. Closure valve member 94
is spring-biased by spring 96 toward a chamber 97. Chamber 97
communicates with opening 40 to chamber 26. Thus, chamber 97 is
generally at the entrapped pressure in chamber 26. A tap 98 to
discharge from outlet 100 is normally closed by a valve portion
102. During normal operation of the compressor, the pressure in
chamber 97 is sufficiently high such that it overcomes the force of
the spring 96 and maintains the closure valve 94 closed, closing
passages 92 and 98. Thus, the gas in the chamber 90 is suction
pressure gas. The pressure in chamber 97 is sufficiently high to
maintain the spool valve 88 in the position such that portion 102
maintains tap 98 closed.
However, if the pressure in the chamber 26 becomes low, spring 96
moves the closure piston 94 to the left from the illustrated
position. Pressure in the entrapped chamber 26 communicates through
passage 92 to chamber 90. The fluid can then pass into the suction
chamber 28. Also, the pressure from tap 98, combined with the force
from the chamber 90, causes the spool valve 88 to move to the left
from the illustrated position. Gas from the discharge chamber may
then pass through port 98, into port 82, and to the suction chamber
28. Again, this heated gas communicates with the motor, and causes
the motor protection device to shut down.
In addition, the FIG. 5 embodiment could be arranged and designed
such that when the valve 88 moves to the left, it sandwiches the
valve 94 against the left wall of the chamber 97. In this way, the
tap 92 is not open. Thus, the compression chamber 26 may remain
isolated from the discharge chamber 98. In such an application,
only pressure from the discharge tap 98 would be communicated to
the suction tap 82. Again, the differences between these two
functional embodiments of FIG. 5 would be well with the skill of a
worker in the art given the above description. The valve movement
and relative cross-sectional areas of the valves 88 and 94 would be
easily modified to achieve these alternative functions.
FIG. 6 shows another embodiment wherein the discharge tap 110
communicates with the discharge port 112. A tap 114 communicates
the chamber 110 to a valve chamber 115. Valve chamber 115 also
communicates with a tap 116 to a compression chamber. A bottom area
118 below a valve 120 is isolated from the tap 114. A tap 122 to
suction extends through a stop 124. Stop 124 provides a stop
surface for a spring 126. A seal 128 in the outer periphery of the
valve 120 seals between chambers 115 and 118. When the difference
between the pressure in compression chamber 116 and the suction
pressure through tap 122 is small, and is thus indicative of loss
of charge. The spring 126 moves the valve 120 downwardly. With this
downward movement, the tap 114 is allowed to communicate to the tap
122 and the heated gas is communicated into the suction
chamber.
Alternately, when there is a proper charge, the pressure at tap 116
is sufficiently greater than the pressure at tap 122 to cause the
piston 120 to move upwardly and close any communication between the
tap 114 and the tap 122.
FIG. 7 shows another embodiment when the discharge port 132
communicates to tap 134 to the area surrounding a valve piston 140.
Seals 142 and 144 define a chamber around the outer periphery of
the valve 140 in the illustrated position. A tap 136 to a
compression chamber communicates with an area 138 beneath the
piston 140. A tap 146 to suction extends into a chamber 147 beneath
a valve stop 148. A stop 148 provides a bias surface for the spring
150. As with the previous embodiment, when a loss of charge
situation occurs, the pressure difference between taps 146 and 136
is small. Thus, the spring 150 can move the valve 140 downwardly
from the illustrated position. The tap 134 can then communicate
with the tap 146. During normal operation, the pressure in tap 136
exceeds the pressure at tap 146 and the valve 140 is thus driven
upwardly preventing flow between taps 134 and 146.
The embodiment shown in FIGS. 6 and 7, and the second alternative
embodiment of FIG. 5 all relate to systems wherein the discharge
pressure tap is what is communicated back into the suction chamber.
For purposes of the claims of this application, the term
"compression chamber" and "tapping from a compression chamber" can
be interpreted to either be met by the discharge port, or one of
the compression chambers prior to discharge.
In general, specific embodiments have been illustrated for allowing
a venting of an entrapped gas to the suction chamber in the event
that conditions indicate the compressor may be running at a low
charge condition. While the embodiments all show the venting device
in the non-orbiting scroll, it is possible the vent could be
positioned elsewhere. The vent could be in the orbiting scroll, the
crankcase, or other locations. Further, it may be valuable to
include such a vent in a compressor type other than a scroll
compressor. Again, this invention extends beyond the specific
embodiments.
In addition, although in the preferred embodiment the heated gas
from the compression chamber does shut down the motor, the venting
itself will also serve to relieve detrimental affects of the low
charge situation. Thus, in some applications, the venting could be
utilized without exposing the motor to the heated gas from the
compression chamber, or without the motor protection feature.
A worker of ordinary skill in this art would recognize that many
modifications come within the scope of this invention. For that
reason, the following claims should be studied to determine the
true scope and content of this invention.
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