Field of the Invention
[0001] This invention relates to refrigeration systems and more particularly to vapor compression
refrigeration systems wherein system refrigerant flow is variably controlled in response
to sensed conditions.
Background Art
[0002] Refrigeration systems for household refrigerators and freezers have heretofore been
designed for low cost and high reliability, both of which require design simplicity
together with a minimum number of parts. Typical refrigerators or freezers employ
a vapor compression system having an electric motor driven hermetic compressor connected
in a circuit with a condenser, evaporator, an optional accumulator, and a refrigerant
flow restriction between the condenser and the evaporator.
[0003] The flow restriction is almost universally a capillary tube sized for optimal system
efficiency under a nominal set of operating conditions. Such capillary tubes were
designed for a constantly running refrigeration system operating at a single ambient
temperature and constant load condition. Capillary tubes used as the sole restriction
offered the advantages of low cost and high reliability. They performed satisfactorily
under operating conditions other than those for which they were designed, albeit at
reduced efficiency.
[0004] A system operating under these idealized design conditions utilized the condenser
to liquify high pressure gaseous refrigerant from the compressor and delivered it,
as a saturated or slightly subcooled liquid, to the capillary tube. The liquified
refrigerant flowing through the capillary tube experienced a substantial pressure
reduction on its way to the evaporator. Refrigerant was vaporized in the evaporator
as it absorbed heat from a system load. The refrigerant then flowed to the compressor
inlet as a low pressure gas.
[0005] When such a system operated under other than the optimum conditions it was far less
efficient. For example, an extreme condition existed when the system "load" was light.
In this case the heat in the refrigerated compartment was inadequate to evaporate
the refrigerant in the evaporator so the evaporator tends to flood with liquid refrigerant.
[0006] This materially reduced the mass of refrigerant available in the system and consequently
a mixture of hot gas and liquified refrigerant from the condenser tended to flow through
the capillary tube into the evaporator. The gaseous refrigerant circulating in the
system without condensing entered the evaporator and gave up heat to the liquified
refrigerant there. The result was an undue burden on the compressor and significant
system operating inefficiency.
[0007] When the load on the refrigerator or freezer was great and ambient atmospheric air
temperature was high the system also operated inefficiently. In this condition the
condenser could not reject sufficiently great amounts of heat to liquify all the refrigerant
passing through it. Both liquified and gaseous refrigerant circulated in the system
in these circumstances resulting in the operating problems noted above.
[0008] Although elimination, or at least reduction, of gaseous refrigerant flow into the
evaporator was desirable to maximize efficiency, any significant restriction of hot
gas flow at extremely high ambient temperatures was undesirable. Restricting such
flow, for example by blocking communication from the condenser to the evaporator,
was potentially damaging to the compressor.
[0009] In practice, the conditions under which household refrigerators or freezers operate
vary widely from optimum design conditions. To accommodate varying conditions these
appliances were constructed so that the compressor cycled on and off under control
of a thermostat in the refrigerated compartment. When the thermostat was satisfied
the compressor stopped. Refrigerant in the condenser continued to flow through the
capillary to the evaporator until the system pressure equalized. This usually occurred
after all the liquified refrigerant passed from the condenser into the evaporator.
[0010] When the thermostat restarted the compressor, gaseous refrigerant had to be compressed
and recondensed for delivery to the evaporator before chilling could recur.
[0011] The rate at which the system pressure equalized and the rate at which chilling commenced
again depended upon the degree of flow restriction created by the capillary. Capillary
tubes sizes could be "loose" or "tight." i.e. less or more restrictive, respectively.
[0012] In a typical household freezer the capillary tube was sized "loose" to allow the
evaporator to flood quickly during compressor start up. The "loose" capillary also
allowed fast equalization of system pressure during the off cycle.
[0013] Fast evaporator flooding allowed the system to quickly reach a high running efficiency
and reduced the compressor run time. Once the evaporator was flooded, however, this
type of system tended to allow gas to enter the capillary tube and pass directly into
the evaporator. As noted, circulation of hot gas in the system was inefficient and
otherwise undesirable.
[0014] Furthermore, when the compressor turned off, the capillary tube continued to pass
hot gas and liquid into the evaporator. This added more heat to the evaporator and
further decreased overall system efficiency.
[0015] A principal advantage of a "loose" capillary design has been that fast pressure equalization
enabled use of a low cost, low torque compressor motor for restarting the compressor
after a short "off" cycle.
[0016] In typical household refrigerators "tight," or more restrictive, capillary tubes
were used. Tight capillary systems tend to be slightly more efficient than "loose"
systems during steady state run conditions. However when these systems were cycled
on and off the "tight" capillary designs did not perform so well. The evaporators
flooded so slowly during start up that any advantages in running efficiencies were
lost over the entire cycle. Furthermore, pressure equalization took so long that low
torque compressor motors experienced difficulty starting the compressor after a short
off cycle. Such compressors were difficult to start against high back pressure.
[0017] In large refrigeration systems these problems were addressed by using a controlled
expansion valve in place of the capillary tube. For example, Owens U.S. Patent No.
3,367,130 discloses an expansion valve which opens and closes in response to the amount
of subcooling of the refrigerant leaving the condenser by responding to a sensor attached
to the external surface of the tube at that point. Valves of this type are too large
and much too expensive to be substituted for a capillary tube in small household refrigeration
systems.
[0018] Other proposals have involved using valves for blocking flow through the capillary
tubes whenever the compressor turns off. These valves have been solenoid operated
or have responded to changes in refrigerant pressure created by the compressor turning
on and off. For example, see U.S. patent 4,267,702 issued May 19, 1981 to Houk. These
kinds of valves did not modulate the refrigerant flows.
[0019] Still other proposals have suggested refrigerant flow modulating valves operated
in response to liquified refrigerant temperature at the condenser outlet. These suggestions
did not propose valve constructions capable of adequately controlling the flow of
liquid refrigerant; did not provide easily manufactured structures; did not remedy
problems caused by the circulation of hot gaseous refrigerant in the systems; and
some did not block the refrigerant flow when the compressor was off.
[0020] Owners of household freezers (and of some refrigerators) sometimes station the appliances
out-of-doors or in unheated spaces. Where the appliance utilizes a refrigerant flow
modulating valve which blocks pressure equalization flows when the compressor is off,
problems can be encountered when the temperature ambient of the appliance is low.
At low ambient temperatures, i.e. below 50F and particularly well below freezing,
the condenser temperatures can be so low that when the compressor starts operating
it fails to create a sufficient pressure rise to open the valve. When ambient temperatures
are low enough, the compressor can pump all the gaseous refrigerant from the evaporator
into the condenser without increasing the condenser pressure enough to open the valve.
[0021] Failure of the appliance and loss of its contents becomes a distinct possibility
in these circumstances. The flow controlling valve remains closed and therefore the
thermostat can not be satisfied. The compressor thus operates unceasingly. In these
appliances compressor lubricant is typically circulated with the system refrigerant.
A likelihood of eventual compressor failure thus exists because of lack of lubrication.
Compressor failure occurs unobtrusively and when the ambient temperature rises above
freezing the contents of the appliance will eventually spoil.
[0022] The present invention provides a new and improved, highly efficient household refrigerator
or freezer wherein a refrigerant flow controlling valve is provided which modulates
the flow of liquified refrigerant through an expansion device in response to sensed
condenser outlet refrigerant temperature and pressure conditions in a highly accurate
fashion, blocks refrigerant flow from the condenser when the compressor is off and
yet assures system refrigerant flow at extremely high ambient temperatures to protect
the system.
Disclosure of the Invention
[0024] A flow control valve constructed according to preferred embodiments of the invention
is associated with a vapor compression refrigeration system comprising a cyclically
operated compressor, a condenser, and an evaporator between the condenser and the
evaporator. The refrigerant flow controlling valve is disposed between the condenser
and the evaporator and comprises a housing defining a refrigerant flow chamber for
receiving liquified refrigerant from the condenser outlet, valve seat structure defining
a refrigerant flow port for communicating refrigerant from the condenser to the expansion
device, and a refrigerant flow controlling valve assembly coacting with the valve
seat structure to control the refrigerant flow from the refrigerant flow chamber to
the expansion device. The new flow control valve is so constructed and arranged that
it accurately controls system refrigerant flow in response to subcooling, blocks refrigerant
flow from the condenser when the compressor is cycled off and enables circulation
of hot gaseous refrigerant under extreme high temperature ambient conditions.
[0025] The flow controlling valve assembly comprises a valving member movable into and away
from engagement with the valve seat structure and an expansible chamber pressure actuator
for moving the valving member. The actuator has an operating fluid chamber containing
a predetermined mass of vaporizable operating fluid in pressure and heat transfer
relationship with refrigerant from the condenser outlet. The actuator biases the valving
member toward its closed position to prevent refrigerant flow through the port when
the compressor is cycled off and has a movable operating chamber wall structure for
operating the valving member to vary the flow through the expansion device in response
to the condenser outlet refrigerant temperature when the compressor is operating.
The actuator operating fluid completely vaporizes at a predetermined relatively high
condenser outlet refrigerant temperature (indicative of high ambient temperature)
and the valve port is maintained open at condenser outlet refrigerant temperatures
above the predetermined temperature.
[0026] The valve is constructed and arranged to enable its calibration by controlled distortion
after it has been fabricated. This assures reliable and accurate operation. A valve
seat supporting member forms a refrigerant flow chamber wall with a valve seat projecting
from it. The seat supporting member is yieldable and is yielded to shift the valve
seat location within the refrigerant flow chamber to a calibrated position.
[0027] In a preferred construction the actuator comprises a thin, flexible stiffly resilient
metal diaphragm defining a wall of the actuator chamber. The actuator is disposed
in the refrigerant flow chamber so that the diaphragm position is controlled by the
refrigerant flow chamber temperature and pressure. The valving member is attached
to the diaphragm and defines a generally flat, pliant valving face having an area
substantially larger than that of the flow port.
[0028] The preferred housing comprises first and second cup-like housing members hermetically
joined to form the chamber between them, each housing member having a cavity surrounded
by a peripheral flange and a conduit extending from the cavity. The housing members
are fixed with respect to each other at the flanges with the cavities confronting
so the conduits form refrigerant flow chamber inlet and outlets.
[0029] In a preferred embodiment the valving member is biased to an open position spaced
from engagement with the valve seat structure to communicate the condenser outlet
with the evaporator when sensed condenser outlet refrigerant temperature is less than
the predetermined level and the compressor is off.
Brief Description of the Drawings
[0030]
Figure 1 is a schematic representation of a refrigeration system embodying a refrigerant
flow control valve constructed according to the present invention;
Figure 2 is a cross sectional view of a preferred refrigerant flow controlling valve
constructed according to the present invention;
Figure 3 is an enlarged cross sectional view of part of the flow controlling valve
of Figure 2;
Figure 4 is a graphic representation of vapor pressure versus temperature curves of
system refrigerant and flow controlling valve operating fluid; and,
Figure 5 is a cross sectional fragmentary view of a modified refrigerant flow controlling
valve constructed according to the present invention.
Best Mode for Practicing the Invention
[0031] A vapor compression refrigeration system 10 of the sort used in a household refrigerator
or freezer is schematically illustrated in Figure 1. The system 10 is a hermetic circuit
containing a refrigerant, preferably R12. The system 10 comprises a compressor 12,
a condenser 14, an evaporator 16, an expansion device 18 between the condenser and
the evaporator, and a refrigerant flow controlling valve 20 between the condenser
and the expansion device 18. The compressor circulates the refrigerant through the
system 10 so that heat is transferred from a frozen food compartment 22 to the atmosphere
ambient the system as the refrigerant successively evaporates and condenses in the
evaporator and condenser. A thermostat (not illustrated) in the compartment 22 cyclically
operates the compressor so that the compartment temperature is maintained within desired
limits.
[0032] The compressor 12 compresses gaseous refrigerant flowing from the evaporator and
delivers it, at an elevated temperature, to the condenser. The condenser transfers
heat from the refrigerant flowing through it to atmospheric air so that the refrigerant
condenses in the condenser. Liquified refrigerant flows from the condenser through
the expansion device 18 after which it enters the evaporator, having undergone a substantial
pressure reduction.
[0033] The system geometry is such that the liquified refrigerant collects at the discharge
end of the condenser before entering the expansion device. The expansion device 18
is preferably formed by a long, small bore capillary tube. The capillary tube design
is "loose" in that the tube bore is sufficiently large to pass flows of the liquid
refrigerant sufficient to relatively quickly flood the evaporator with liquid refrigerant
when the compressor starts up.
[0034] Even though the capillary design is "loose," a quantity of the liquified refrigerant,
substantially at the compressor discharge pressure, tends to be maintained in the
downstream condenser end when the compressor is operating. The condenser continues
to transfer heat from this liquified refrigerant so its temperature drops below the
condensation temperature corresponding to the condenser pressure. This refrigerant
condition is known as "subcooling." The extent of the subcooling depends upon various
system operating conditions.
[0035] The refrigerant flow controlling valve 20 varies the refrigerant flow rate from the
condenser to the evaporator according to refrigeration system operating parameters
to assure efficient operation. The flow controlling valve 20 coacts with the expansion
device 18 so that the rate of refrigerant flow into the evaporator varies between
zero and the maximum flow permitted by the expansion device acting alone. This coaction
enables the refrigeration system to quickly flood the evaporator when the compressor
initially operates at the beginning of an "on" cycle (the expansion device being of
"loose" design), yet virtually precludes the flow of any substantial amounts of gaseous
refrigerant into the evaporator under normal operating conditions.
[0036] The preferred valve 20, illustrated in figures 2 and 3, is particularly adapted for
use in a household freezer. The valve 20 comprises a valve housing 24 defining a refrigerant
flow chamber 26 in communication with the refrigerant condenser, a valve seat structure
30 forming a port 32 leading to the expansion device 18, and a refrigerant flow controlling
valve assembly 34 coacting with the valve seat structure to control the flow of refrigerant
from the refrigerant flow chamber. The valve 20 is constructed primarily of stamped
sheet metal parts and is thus of simple, relatively inexpensive construction.
[0037] The valve housing 24 communicates the condenser 14 to the expansion device 18 and
comprises first and second housing members 36, 38 forming the refrigerant flow chamber
26 and refrigerant flow conduits 40, 42, respectively, for directing the refrigerant
into and away from the refrigerant flow chamber. The housing members 36, 38 are formed
by respective concave confronting cup-like portions 44, 46, having confronting peripheral
flanges 50, 52 hermetically secured together about the chamber 26. The conduits 40,
42 are illustrated as comprising refrigerant flow tubes projecting, respectively,
to sealed, bonded (preferably brazed) joints (not shown) with the condenser 14 and
the expansion device 18. The conduits are also joined to their respective housing
members by sealed, bonded joints such as brazed connections.
[0038] The housing 24 is oriented with the conduit 40 extending upwardly to the condenser
and the conduit 42 extending vertically downwardly to the device 18 (see figure 3).
The chamber 26 is preferably below the lowest condenser elevation so liquified refrigerant
from the condenser flows to the chamber and gaseous refrigerant remains above the
liquid refrigerant level. Under most operating conditions the chamber 26 is flooded
with the liquified refrigerant.
[0039] The flow control valve seat structure 30 forms part of the refrigerant flow chamber
and in the valve illustrated in Figure 3 comprises a seat support member 60 disposed
in the chamber 26 and a valve seat 62 surrounding the refrigerant flow port 32. The
illustrated seat support member 60 is formed by a plate having an outer marginal flange
66 hermetically joined between the confronting housing member flanges 50, 52 and a
central support section 68 for the seat 62. The central section 68 defines a frustoconical
wall 70 adjoining the flange 66, a generally planar annular wall 72 between the wall
70 and the seat 62, and a series of radially extending stiffening ribs 73 embossed
in the wall 70. The rib embossments project from the plane of the wall 72 in the direction
away from the valving member and in the illustrated valve 20, three ribs are provided
extending 120 degrees apart about the port axis.
[0040] The valve seat 62 projects from the central section 68 and is illustrated in figures
2 and 3 as formed by a central, drawn and pierced projection forming the port 32.
The seat region immediately surrounding the port 32 is defined by an annular rim 74
having a sharply radiused projecting edge for contacting the valving structure 34.
The rim 74 is quite narrow and the port 32 has a small area. The rim and port areas
are slight to make negligible any differential pressure force changes acting on the
valving structure when the flow controlling valve 20 is closed or nearly closed. The
small rim area also reduces possible effects of localized transient pressure forces
caused by high velocity refrigerant flows between the rim and the valving member when
the valve is nearly closed.
[0041] The flow controlling valve assembly 34 governs refrigerant flow through the port
32 in relation to sensed refrigeration system conditions. The valve assembly 34 comprises
a valve supporting structure 80 fixed with respect to the housing, an actuator 82,
and a valving member 84 connected to the actuator for movement into and away from
engagement with the valve seat structure for controlling the flow of refrigerant from
the refrigerant flow chamber 26.
[0042] The valve supporting structure 80 is fixed in the chamber 26 for rigidly positioning
and locating the actuator 82 and the valving member 84 with respect to the valve seat
structure 30. The valve supporting structure 80 illustrated in figures 2 and 3 comprises
a rigid stamped sheet metal plate having an outer peripheral flange section 90, an
annular body section 92, and a central, actuator support flange section 94. The flange
section 90 is circular and conformed to the size and shape of the housing flanges.
The section 90 is sandwiched between the housing flange 50 and the seat structure
marginal flange 66 and is hermetically joined to the housing flanges 50, 52 and the
marginal flange 66 by a continuous circumferential weld joint 95.
[0043] The body section 92 extends through the chamber 26 between the flange section 90
and the support flange 94. In the illustrated embodiment the body section forms an
annular corrugation in the valve support structure. A series of refrigerant flow openings
96 is formed about the body section to permit unrestricted refrigerant flow through
the chamber. The corrugated shape of the body section assures that the body section
remains structurally strong and stiff regardless of the presence of the openings 96.
[0044] The actuator support flange 94 is a short, stiff annulus which surrounds a central
actuator receiving opening 98. The flange 94 stiffly supports the actuator 82 generally
along the center-line of the chamber 26.
[0045] The actuator 82 is constructed and arranged to shift the valving member 84 between
fully opened and fully closed positions and to control the valving member position
to modulate flow depending on sensed refrigerant temperature and pressure conditions.
The preferred actuator 82 is an expansible chamber pressure actuator having a hermetic
expansible operating chamber 100 filled with an operating fluid. The operating fluid
is in both its liquid and vapor phases under normal operating conditions so the internal
chamber pressure varies with temperature according to the pressure-temperature characteristics
of the fill fluid saturated vapor. The fill fluid of the figures 2 and 3 actuator
is preferably R 500.
[0046] The preferred actuator comprises a stiffly resilient metal diaphragm 102 forming
a movable wall of the operating chamber 100 and carrying the valving member. The position
of the diaphragm 102 relative to the valve seat structure is determined by the refrigerant
pressure in the chamber 26, the pressure of the fill fluid in the operating chamber
100 and the internal diaphragm spring force.
[0047] In the illustrated and preferred embodiment of the invention the actuator 82 is formed
by a stiffly resilient single convolution metal bellows comprised of the diaphragm
102, a second diaphragm 104, a fill tube 106, a supporting eyelet 108, and an extension
member 110. The diaphragms 102, 104 are stamped from a thin (e.g. 0.006 inch thick)
leaf of sinless steel spring material and are initially identical dished discs.
[0048] The "top" (or uppermost, as viewed in the drawing, figure 3), diaphragm 104 is constructed
to be anchored to the supporting structure 80 by the eyelet 108 which is formed by
a malleable metal straight cylindrical sleeve-like body having an annular end flange
111. The eyelet end flange 111 is welded to the centerline of the disc about the opening
and the diaphragm is pierced to form a central opening 112 along its centerline.
[0049] The "bottom" diaphragm 102 carries the valving member 84 on the extension member
110. The extension member illustrated by figures 2 and 3 comprises a flat cylindrical
cup-like body stamped from sheet metal. The body has a flat circular base 115, a cylindric
wall 116, and projecting fingers 117 disposed about the projecting edge of the wall.
The base 115 is welded securely to the diaphragm 102 with the wall 116 and fingers
117 projecting towards the valve seat.
[0050] The diaphragm discs are aligned in confronting relationship and bonded together about
their peripheries by a continuous hermetic weld to provide the operating chamber 100
between them. The partially completed bellows is assembled to the supporting structure
80 with the eyelet 108 extending through the receiving opening 98. The eyelet is upset
to form an outwardly extending corrugation 120 which clamps the eyelet firmly to the
flange 94. The cylindrical end of the eyelet is swaged at the same time to reduce
its diameter to approximate that of the fill tube 106.
[0051] The fill tube 106, initially open at both ends, is inserted in the eyelet end and
hermetically brazed to the eyelet. The valving member 84 is inserted into the extension
cup 110 and the fingers 117 are crimped into engagement with the valving member to
secure it in place. The cup wall 116 extends just beyond the valving member toward
the valve seat.
[0052] The preferred valving member 84 is a flat cylindrical disc defining a generally flat
valving face confronting the valve seat. The valving face has an area which is quite
large compared to the area of the port 32. The preferred and illustrated valving member
84 is composed of a tough, somewhat resilient plastic material, preferably polytetrafluoroethylene
(e.g. Teflon) or equivalent, which is resiliently deflected when moved into positive
sealing engagement with the valve seat without being cut or abraded by the rim 74.
The valving member should be at least some what resilient to assure that the valving
member 84 returns substantially to its undeflected condition when the valve is open.
The rim of the extension cup wall 116 engages the seat structure wall 72 after the
valve fully closes to limit compression of the valving member if the actuator exerts
excessive force after closing the valve.
[0053] It should be noted that the ribs 73 form radially extending channels in the otherwise
planar seat structure wall 72. These channels communicate refrigerant at flow chamber
pressure to most of the valving member face even when the valve 20 is tightly closed.
The small valving member face area occupied by the valve port 32 is insufficient to
create a material differential pressure force on the valving member.
[0054] The Teflon or equivalent plastic material is preferred because it does not react
with compressor lubricating oil circulating in the system with the refrigerant. Other
materials, such as synthetic rubbers or other elastomers, can be used for the valving
member so long as they are compatible with the system refrigerant and the compressor
lubricant.
[0055] The bellows is then charged with the fill fluid in such a way that the flow controlling
valve is opened at both the high and low ambient temperature operating extremes of
the freezer (regardless of the operating condition of the compressor); the flow controlling
valve closes when the compressor cycles off during normal operation; and the valve
modulates the refrigerant flow in response to predetermined subcooling conditions.
[0056] A predetermined quantity of fill fluid is introduced to the bellows via the fill
tube 106. Charging is carried out under strictly controlled pressure and temperature
conditions so that under normal flow controlling valve operating conditions the bellows
operates "above" (i.e. at greater than) its free height. That is, the bellows is extended
against its own inherent spring force. In this charging condition, when the differential
fluid pressure across the bellows diaphragms is zero the bellows force is relaxed
and the bellows "retracts" to its free height. The flow controlling valve is opened
in this condition. When the bellows has been charged with the proper amount of fluid
the projecting fill tube end is crimped and sealed closed.
[0057] The fill fluid in the flow controlling valve of figures 2 and 3 (R 500) is selected
so that its saturated vapor pressure-temperature characteristic curve has, through
the normal operating temperature range, a steeper slope than that of the system refrigerant
(in this case R12). See figure 4 where the fill fluid saturated vapor pressure-temperature
curve 132 is depicted with the refrigerant saturated vapor pressure-temperature curve
134. When the spring force of the bellows is taken into account, the effective fill
fluid pressure-temperature characteristic curve is as illustrated by the line 135
of figure 4.
[0058] When the refrigerant and the fill fluid are both at temperatures ranging below about
50F the effective fill fluid vapor pressure (curve 135) ranges from about the same
as to substantially less than the saturated refrigerant vapor pressure (curve 134).
This condition results in the bellows retracting toward its free height so the valve
20 opens.
[0059] When the fill fluid and refrigerant are at relatively normal operating temperature
levels, e.g. above 50F, the effective fill fluid pressure is markedly higher than
the saturated refrigerant vapor pressure. The bellows extends above its free height
and the valve closes if the compressor is not operating. If the compressor operates
under these conditions the valve opens and may or may not modulate the refrigerant
flow depending on sensed conditions.
[0060] At an ambient temperature around 110F the fill fluid completely evaporates. As the
ambient temperature increases from that level the fill fluid vapor is superheated.
The superheated vapor pressure-temperature characteristic curve approximates that
of a so-called "perfect" gas (i.e. the slope of the pressure-temperature curve is
much less than that of the refrigerant vapor pressure-temperature curve). This is
illustrated in Figure 4 at line segment 136. As a consequence, the saturated refrigerant
pressure at elevated temperatures rises above the actuator operating chamber pressure
and the bellows retracts to fully open the valve 20. The ambient temperature at which
the fill fluid evaporates is determined by the quantity of fill fluid introduced into
the actuator.
[0061] The actuator assembly and the valve seat structure are assembled with their flange
peripheries aligned and then placed between the housing cups. The assembled elements
are fixtured with all the outer flange peripheries aligned and the fill tube 106 extending
part way through its associated conduit. The assembly is completed by welding the
flanges 50, 52, 66 and, 90 to form the hermetic joint 95 about the flange junctures.
[0062] Calibration is accomplished by establishing predetermined conditions within the flow
controlling valve and distorting the structure of the valve 20 to shift the relative
positions of the port 32 and the valving member 84. An example of one calibration
technique is to establish a given flow of air through the valve 20 at a predetermined
pressure and temperature by yielding the valve seat supporting structure a controlled
amount.
[0063] In one series of flow controlling valves it has been found that operationally satisfactory
valves are so constructed and arranged that when such a valve is at a temperature
of 70°F (21°C) and supplied with air or Nitrogen at that temperature and 78 psig,
a flow rate of 0. 15 scfm is established through the valve. To calibrate an uncalibrated
valve, the valve is maintained at 70°F and supplied with 70°F Nitrogen or air until
a flow rate of 0.15scfm is observed. The gas pressure at this flow rate is less than
78 psig.
[0064] A calibration ram 140 (schematically illustrated in figure 3) inserted in the conduit
42 is forced against the seat support structure while the flanges 50, 52, 66 and 90
are securely held in place. The "bumping" force applied to the seat yields the support
section 68 so that the rim 74 is moved toward the valving member 84. This increases
the gas pressure required to achieve a 0.15 scfm flow rate. The process is repeated
as necessary until the 78 psig - 0.15 scfm calibration condition has been established.
[0065] In the preferred valve 20, the supporting section 68 is yielded in a generally circular
path extending about the radially outer ends of the embossed ribs 73. The ribs are
quite stiff and thus dictate where the yielding deflection takes place and thus aid
in assuring reliable calibration.
[0066] Other calibration techniques can be employed. for example, the valve seat structure
can be deformed by introducing high pressure air or Nitrogen into the chamber section
between the valve seat structure and the housing cup 46. Such a gas, at about 650
psi, is effective to deform the seat plate for calibration purposes. The port 34 has
a sufficiently small area that the deforming gas pressure is easily maintained in
the housing without subjecting the actuator 82 to excessive external pressure.
[0067] When the calibration is completed the outlet conduit 42 is swaged to reduce the diameter
of its outlet and the completed valve 20 is ready for assembly into a freezer unit
refrigeration system. In the preferred construction the valve 20 is brazed into the
refrigeration system and oriented so refrigerant flow through the valve occurs generally
vertically downwardly from the condenser through the valve 20 toward the expansion
device 18. This valve orientation tends to reduce the possibility of reduced pressure
refrigerant remaining in the vicinity of the seat supporting structure after passing
through the port 32 and evaporating there. Such evaporation could cause conductive
heat transfer from the actuator fill fluid through the extension member 110 and the
valving member 84, to the evaporating refrigerant via the valve seat structure.
[0068] The fill fluid vapor pressure depends on the temperature of the coolest actuator
location because that temperature governs condensation of the fill fluid. Conductive
heat transfer away from the actuator might thus cause inappropriate actuator response
because the actuator would respond to the evaporating refrigerant temperature downstream
from the valve port 32 rather than the refrigerant temperature in the flow chamber
26.
[0069] After the valve 20 is installed in the freezer the refrigeration system is charged
with refrigerant and the system is operated. During normal operation, at relatively
high ambient temperatures, the flow controlling valve 20 tends to be open when the
compressor is running. In this operating condition the valving member 84 is positioned
according to the lowest flow chamber refrigerant temperature detected by the actuator
82. If the refrigeration system is heavily loaded (for example when a large quantity
of room temperature meat has just been placed in the freezer) the flow chamber refrigerant
temperature is relatively high, signifying that the undesirable passage of hot gas
through the expansion device might be imminent. The operating chamber pressure increases
as the refrigerant temperature increases so the valving member moves toward the port
32 and restricts the refrigerant flow from the flow chamber 26. This action tends
to minimize the possibility of hot gas flowing through the expansion device into the
evaporator.
[0070] As the system load is reduced (for example when the freezer contents reach the thermostat
set point temperature) the quantity of liquified refrigerant at the condenser discharge
end is increased and refrigerant in the flow chamber is subcooled. Accordingly the
flow chamber refrigerant temperature is reduced resulting in the valving member retracting
from the valve port so the refrigerant flows in a less restricted way from the chamber.
[0071] When the food compartment thermostat is satisfied the compressor is cycled "off"
and the flow controlling valve 20 closes promptly so that the refrigerant in the condenser
remains there at high pressure during the time the compressor is not operating (freezer
compartment cooling is not called for). When the compressor cycles "off" the pressure
in the condenser drops precipitately toward the saturated vapor pressure of the refrigerant
in the condenser. The forces acting on the actuator diaphragm promptly come into balance
with the actuator stabilizing in its extended position so the flow controlling valve
20 is closed. The forces acting on the diaphragm are the fill fluid vapor pressure
force; the bellows spring force; and, the refrigerant vapor pressure force. The spring
and the refrigerant pressure forces oppose the fill fluid pressure force and balance
the fill fluid pressure force when the bellows is positioned "above" its operating
height with the valve closed. This feature of the valve 20 also provides for failsafe
operation in that if the actuator operating fluid chamber should leak or be holed
for any reason, the fluid pressures acting on the bellows would be balanced and the
valve would open due to the diaphragm spring force.
[0072] The valve 20 opens automatically when the compressor restarts. The thermostat calls
for compartment,cooling by turning the compressor "on" and the condenser pressure
rises to the compressor discharge level. This creates additional pressure force acting
on the actuator bellows in opposition to the fill fluid pressure force. Assuming normal
operating conditions, the bellows retracts and the valve 20 opens.
[0073] Household freezers are sometimes located in unheated spaces (such as garages), or
even out-of-doors (for example on open porches), where the atmospheric temperature
ambient the freezer may be quite low. In such environments freezers are quite lightly
loaded but even so, compressors cycle periodically because compartment temperature
set points are below the ambient air temperature and compartment heat gains occur.
At low ambient temperatures the system temperature is so low that operation of the
compressor may not produce an appreciable condenser pressure rise.
[0074] Accordingly, when the compressor cycles "on," the condenser pressure may not be relied
on to increase sufficiently to open the flow controlling valve 20. If the valve 20
remains closed the food compartment thermostat can not be satisfied and the compressor
continues operating. All the system refrigerant may be delivered into the condenser.
Since the compressor lubricating oil is circulated in the system by the refrigerant
the compressor can be damaged from insufficient lubrication.
[0075] The preferred flow controlling valve is biased to its open condition when the ambient
temperature is low. The preferred valve 20 thus enables continued system refrigerant
flow at low ambient temperatures regardless of the compressor operating condition.
This operational feature protects the compressor without materially reducing the refrigeration
system operating efficiency because the system is extremely efficient at low ambient
temperatures anyway.
[0076] As noted previously the flow controlling valve 20 illustrated by Figures 2 and 3
employs an actuator bellows filled with a fluid (R 500) whose saturated vapor pressure-temperature
curve is sloped more steeply than the saturated vapor pressure-temperature curve of
the system refrigerant (R12). Comparing the curves 134 and 135 of Figure 4 reveals
that at low ambient temperatures the system refrigerant vapor pressure force and the
diaphragm spring force exceed the actuator operating fluid pressure force. Thus the
actuator is biased to open the valve 20.
[0077] The valving member 84 is moved only a short distance between its full flow and fully
closed positions. When the valving member is between these limiting flow positions
the refrigerant flow through the port is modulated so that the refrigerant pressure
drop between the condenser and the evaporator varies in accordance with the degree
of refrigerant subcooling. The preferred single convolution bellows is quite stiff
and has a relatively linear spring characteristic through the range of valving member
positions between closed and full flow. That is, the actuator spring force opposing
extension of the bellows remains substantially constant over the operating range of
bellows positions. The flow controlling valve is thus quite sensitive in its response
to detected refrigerant pressure and temperature conditions indicative of the degree
of its subcooling.
[0078] With some slight modifications the valve 20 can be employed in household refrigerators
or refrigerator/freezer combinations. Refrigerators and refrigerator/freezers are
not designed for use in cold surroundings and therefore do not necessarily require
the flow controlling valve to remain open at low ambient temperatures when the compressor
is off. Accordingly when so used the valve 20 contains a fill fluid which is the same
as the system refrigerant, i.e. R12. The saturated vapor-liquid fill fluid and the
bellows coact such that the bellows diaphragm spring force closes the valve 20 when
the compressor is off (i.e. the saturated vapor pressure forces within and outside
the bellows chamber are balanced). In some refrigerator systems it may also be desirable
to form the valving member from a synthetic rubber material rather than "Teflon" so
long as the system refrigerant and lubricant do not react to the rubber selected.
[0079] Figure 5 illustrates part of an alternative refrigerant flow controlling valve construction
wherein the valving member blocks refrigerant flow from the condenser when condenser
outlet refrigerant temperature is above a predetermined level and the compressor is
off, yet is biased to an open position to communicate the condenser outlet with the
evaporator when sensed condenser outlet refrigerant temperature is less than the predetermined
level and the compressor is off. The Figure 5 valve is constructed primarily from
parts which are the same as those described above in reference to Figures 1-3 with
corresponding parts indicated by like, primed reference characters.
[0080] The valve 20' of Figure 5 differs from the valve 20 in that when the flow chamber
temperature is below the predetermined temperature (e.g. 50F or below) and the compressor
is off, the valving member 84' is biased to its open position by a thermally responsive
biasing member 150. In addition, the actuator fill fluid is the same as that used
as the system refrigerant.
[0081] In the illustrated embodiment the biasing member 150 comprises a bimetal element
which changes its configuration in response to sensed temperatures below the predetermined
level and in so doing engages the valving member 84' to prevent it from closing the
port 32'. The illustrated bimetal member is in the form of a two layer disc seated
on the seat structure wall 72' with its outer periphery 152 tack welded to the wall
72'. The disc layer confronting the wall 72' has a smaller coefficient of thermal
expansion and contraction than that of the layer confronting the valving member 84'.
A circular eye 154 is formed at the center of the disc through which the valve seat
156 projects. The valve seat 156 differs from the seat 62 in that the seat 156 projects
slightly further from the wall 72' than would the seat 62 in order to accommodate
the thickness of the bimetal disc.
[0082] In the Figure 5 embodiment the actuator 82' is constructed like the actuator 82 except
the actuator fill fluid is the same as the system refrigerant (in this case R12).
The actuator 82' is filled so that when the internal and external actuator pressures
are the same, the actuator diaphragm spring force urges the valving member 84' into
engagement with the seat 156 to close the port 32'. This tyically occurs when the
compressor is off; but when ambient temperatures are very low the same condition can
persist after the compressor has begun to run. This can result in damage to the system
as is noted previously.
[0083] The biasing member 150 prevents the valving member from closing on the seat 156 at
low ambient temperatures by buckling into a generally frusto-conical shape with its
inner periphery 158 lifting away from the wall 72' and engaging the valving member
84' to block its motion toward the seat. This condition is illustrated by broken lines
in Figure 5. The valving member is thus prevented from closing at low temperature
when the compressor is off. When temperatures are above the predetermined temperature
the bimetal member hugs the wall and does not interfere with operation of the valve
20'.
[0084] While different preferred embodiments of the invention have been illustrated and
described in detail the invention is not to be considered limited to the precise constructions
disclosed. Various adaptations, modifications and uses of the invention may occur
to those skilled in the art to which the invention relates. The intention is to cover
all such adaptations, modifications and uses which fall within the scope or spirit
of the appended claims.
1. A flow control valve for a vapor compression refrigeration system comprising a cyclically
operated compressor, a condenser, and an evaporator, said flow control valve disposed
between the condenser and the evaporator and comprising a housing defining a refrigerant
flow chamber for receiving liquified refrigerant from the condenser outlet, valve
seat structure defining a refrigerant flow port for communicating refrigerant from
the condenser to the evaporator, and a refrigerant flow controlling valve assembly
co-acting with the valve seat structure to control the refrigerant flow from the refrigerant
flow chamber, said flow control valve assembly controlling system refrigerant flow
in response to sensed refrigerant subcooling, minimizing refrigerant flow from the
condenser when the compressor is cycled off and enabling circulation of hot gaseous
refrigerant under extreme high temperature ambient conditions.
2. In a vapor compression refrigeration system comprising a cyclically operated compressor,
a condenser, and an evaporator; a refrigerant flow controlling valve between the condenser
and the evaporator comprising:
a. a housing defining a refrigerant flow chamber for receiving refrigerant from the
condenser outlet;
b. valve seat structure defining a refrigerant flow port for communicating refrigerant
from the condenser to the expansion device; and,
c. a refrigerant valving assembly co-acting with said valve seat structure to control
the flow of refrigerant through said port, said valving assembly comprising a valving
member movable toward and away from engagement with said valve seat structure for
controlling the flow of refrigerant through said port, and an expansible chamber pressure
actuator for moving said valving member;
d. said actuator defining an operating fluid chamber containing a predetermined mass
of vaporizable operating fluid in pressure and heat transfer relationship with refrigerant
from the condenser outlet, said actuator biasing said valving member toward its closed
position when the compressor is cycled off, said actuator comprising movable operating
chamber wall structure for operating the valving member to vary the flow through the
expansion device in response to the temperature of condenser outlet refrigerant when
the compressor is operating, said operating fluid completely vaporizing at a predetermined
relatively high condenser outlet refrigerant temperature to maintain the valve port
open at condenser outlet refrigerant temperatures above said predetermined temperature.
3. A vapor compression refrigeration system having a cyclically operated compressor,
a condenser, an evaporator, and a refrigerant flow controlling valve for controlling
flow between the condenser and the evaporator; the flow controlling valve comprising:
a. a valving member movable to and from a valve seat structure for controlling refrigerant
flow in response to detected condenser outlet refrigerant temperature;
b. the valving member engaging the seat structure to block refrigerant flow from the
condenser when the condenser outlet refrigerant temperature is above a predetermined
level and the compressor is off;
c. the valving member biased to an open position spaced from engagement with the valve
seat structure to communicate the condenser outlet with the evaporator when sensed
condenser outlet refrigerant temperature is less than the predetermined level and
the compressor is off.
4. The appliance claimed in claim 3, further including an expansible chamber actuator
connected to said valving member for moving said valving member, said actuator biasing
said valving member to said open position at temperatures below said predetermined
temperature.
5. The appliance claimed in claim 3, wherein said actuator contains a fill fluid in a
liquid and saturated vapor state when temperatures are at or below the predetermined
temperature, said fill fluid having a saturated vapor pressure-temperature response
curve which is steeper than that of the system refrigerant, said actuator further
including a stiffly resilient diaphragm connected to said valving member, said diaphragm
resiliently opposing the pressure force of said fill fluid at temperatures below said
predetermined temperature and resiliently urging said valving member to the open position.
6. The appliance claimed in claim 3, wherein at least part of said actuator is disposed
in said refrigerant flow chamber in heat transfer relationship with refrigerant in
said flow chamber, said actuator containing a fill fluid in a liquid and saturated
vapor state when temperatures are at or below the predetermined temperature, said
fill fluid having a saturated vapor pressure-temperature response curve which is steeper
than that of the system refrigerant, said fill fluid in heat transfer relationship
with said refrigerant in said flow chamber.
7. In a vapor compression refrigeration system comprising a cyclically operated compressor,
a condenser, and an evaporator; a refrigerant flow controlling valve between the condenser
and the evaporator for controllably varying the refrigerant pressure drop between
the condenser and the evaporator, said refrigerant flow controlling valve comprising:
a. a valve housing defining a refrigerant flow chamber receiving liquified refrigerant
from the condenser;
b. valve seat structure comprising a projecting valve seat defining a refrigerant
flow port for communicating refrigerant from said flow chamber to the expansion device;
and,
c. a refrigerant flow controlling valve assembly co-acting with said valve seat structure
to control the flow of refrigerant from said refrigerant chamber, said flow controlling
valve assembly comprising:
i. a valve supporting structure within and fixed with respect to said housing;
ii. an actuator comprising at least a thin, flexible stiffly resilient metal diaphragm
defining a wall of a hermetic expansible actuator chamber containing a vaporizable
fluid, said fluid comprising liquid and vapor fractions when the fluid temperature
is less than a predetermined temperature, said fluid in heat transfer relationship
with refrigerant in said flow chamber so that the actuator chamber pressure is controlled
by the refrigerant temperature in said flow chamber; and,
iii. a valving member connected to said diaphragm for movement into and away from
engagement with said valve seat structure for controlling the flow of refrigerant
from said refrigerant chamber, said valving member defining a generally flat, pliant
valving face having an area substantially larger than said refrigerant flow port,
said valving face coating with said valve seat to control the refrigerant flow from
said flow chamber.
8. The flow control valve claimed in claim 7, wherein said valve seat structure further
comprises a valve seat supporting member having a yieldable support portion forming
an internal wall in said flow chamber, said support portion yielded to shift its position
in the chamber and station said valve seat with respect to said valve supporting structure
at a calibrated location.
9. The flow control valve claimed in claim 7, wherein said valve housing is formed by
confronting cup members having aligned cavities forming said flow chamber with each
cavity surrounded by peripheral flanges which are hermetically joined.
10. The flow control valve claimed in claim 9, wherein said valve seat structure comprises
a seat support member having an outer marginal flange aligned with said peripheral
cup member flanges and hermetically attached thereto.
11. The flow control valve claimed in claim 10, further comprising valve supporting structure
fixed with respect to said housing and comprising a flange section aligned with and
hermetically connected to said cup member flanges and said seat structure flange.
12. The flow control valve claimed in claim 7, wherein said valving member is comprised
of a flexible material which flexes when engaging said valve seat when said valving
member closes said port.
13. The flow control valve claimed in claim 12, wherein said valving member material is
resiliently deformable by contact with said valve seat.
14. The flow control valve claimed in claim 7, wherein said actuator comprises a single
convolution bellows comprised of said first and a second stiffly resilient diaphragm,
said diaphragms hermetically joined at their outer peripheries to form said actuator
chamber, said first diaphragm carrying said valving member and shifting said valving
member through a stroke which is extremely small compared to the diameter of the diaphragm.
15. The flow control valve claimed in claim 7, further comprising compression limiting
structure reacting between said actuator and said valve seat structure for limiting
compression of said valving member.
16. The flow control valve claimed in claim 7, wherein said actuator chamber is filled
with a predetermined quantity of vaporizable fluid, said fluid completely vaporizing
at said predetermined temperature and altering the pressure-temperature response of
said actuator at flow chamber temperatures above said predetermined temperature.
17. In a vapor compression refrigeration system comprising a cyclically operated compressor,
a condenser and an evaporator; a refrigerant flow controlling valve between the condenser
and the evaporator for controllably varying the refrigerant pressure drop between
the condenser and the evaporator, said refrigerant flow controlling valve comprising:
a. a housing defining a refrigerant flow chamber for receiving liquified refrigerant
from the condenser outlet, said housing comprising:
i. first and second cup-like housing members hermetically joined to form said chamber
between them;
ii. each housing member having a cavity surrounded by a peripheral flange and a conduit
extending from the cavity;
iii. said housing members fixed with respect to each other at the flanges with the
cavities confronting so the conduits form refrigerant flow chamber inlet and outlet
conduits;
b. valve seat structure defining a refrigerant flow port for communicating refrigerant
from the condenser to the evaporator, said valve seat structure comprising:
i. a valve seat supporting member forming an internal wall extending across said flow
chamber to separate said inlet and outlet conduits;
ii. a valve seat projecting from said wall and defining said flow port for enabling
refrigerant flow from said inlet conduit to said outlet conduit;
iii. said seat supporting member comprising a yieldable wall portion which is yielded
to shift the valve seat within the refrigerant flow chamber to a calibrated position;
c. a refrigerant flow controlling valve assembly co-acting with said valve seat structure
to control the flow of refrigerant from said refrigerant chamber, said flow controlling
valve assembly comprising a flow controlling valving member, valving member supporting
structure fixed with respect to said housing, and a valving member actuator for moving
said valving member into and out of engagement with said valve seat;
d. said actuator comprising:
i. at least a thin, flexible stiffly resilient metal diaphragm defining a wall of
a hermetic, expansible actuator chamber containing a vaporizable fluid, said fluid
comprising liquid and vapor fractions when the fluid temperature is less than a predetermined
temperature;
ii. said actuator disposed in said refrigerant flow chamber and supported by said
valving member supporting structure with said diaphragm in fluid pressure and heat
transfer relationship with with refrigerant in said flow chamber so that the fluid
pressure in said actuator chamber is controlled by the refrigerant temperature in
said flow chamber and the diaphragm position is effected by the pressure of refrigerant
in said flow chamber; and,
e. said valving member comprising:
i. connected to said diaphragm for movement into and away from engagement with said
valve seat structure for controlling the flow of refrigerant from said refrigerant
chamber, said valving member defining a generally flat, pliant valving face having
an area substantially larger than said refrigerant flow port, said valving face co-acting
with said valve seat to control the refrigerant flow from said flow chamber.
18. In a vapor compression refrigeration system comprising a cyclically operated compressor,
a condenser, and an evaporator; a refrigerant flow controlling valve between the condenser
and the evaporator for controllably varying the refrigerant pressure drop between
the condenser and the evaporator, said refrigerant flow controlling valve comprising:
a. a valve housing defining a refrigerant flow chamber receiving liquified refrigerant
from the condenser;
b. valve seat structure defining a refrigerant flow port for communicating refrigerant
from said flow chamber to the expansion device; and,
c. a refrigerant flow controlling valve assembly co-acting with said valve seat structure
to control the flow of refrigerant from said refrigerant chamber, said flow controlling
valve assembly comprising:
i. a valve supporting structure within and fixed with respect to said housing;
ii. an actuator comprising at least a thin, flexible stiffly resilient metal diaphragm
defining a wall of a hermetic expansible actuator chamber containing a vaporizable
fluid, said fluid comprising liquid and vapor fractions when the fluid temperature
is less than a predetermined temperature, said fluid in heat transfer relationship
with refrigerant in said flow chamber so that the actuator chamber pressure is controlled
by the refrigerant temperature in said flow chamber; and,
iii. a valving member connected to said diaphragm for movement into and away from
engagement with said valve seat structure for controlling the flow of refrigerant
from said refrigerant chamber through said flow port;
d. said valve seat structure further comprising a valve seat supporting member having
a yieldable support portion forming an internal wall in said flow chamber, said support
portion yielded to shift its position in the chamber and station said valve seat with
respect to said valve supporting structure at a calibrated location.