Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
21~6117
D E S C R I P T I O N
Title
IN-LINE INCREMENTALLY ADJUSTABLE
ELECTRONIC EXPANSION VALVE
This patent application relates to a co-pending and
co-owned patent application filed concurrently herewith
entitled "In-Line Incrementally Manually Adjustable Rotary
Expansion Valve" and naming "Michael R. Harstad" as inventor.
Technical Field
This invention partains to expansion valves for use
in refrigeration systems. More particularly, this invention
relates to an in-line electrically actuated refrigeration
system expansion valve that provides for incrementally
adjustable refrigerant flow control between the high and the
low pressure sides of a refrigeration system.
Background Of The Invention
Conventional refrigeration and air conditioning
systems typically utilize a series of recirculating fluid loops
to cool a space by transferring the heat from the space through
the fluid loops and ultimately to a heat sink such as water or
ambient outside air. A commercial air conditioning system, for
instance, typically includes a water chiller having an
evaporator at its low pressure side, a condenser at its high
pressure side, a compressor to boost the pressure of
refrigerant as its flows from the evaporator to the condenser
and an expansion valve to meter refrigerant from the high
pressure condenser to the low pressure evaporator.
2156117
In a first fluid loop, water passes through the
chiller evaporator, where it is cooled in a heat exchange
relationship with relatively cooler system refrigerant, before
being directed to a location where it absorbs heat and is
S returned to the evaporator. In "flooded design" evaporators,
the water in the chilled water loop flows through the tubes of
the evaporator and liquid refrigerant surrounds the outside of
the tubes. The cooler liquid refrigerant surrounding the tubes
absorbs heat energy from the relatively warmer water, thereby
chilling the water.
During the removal of heat energy from the warm
water, the liquid refrigerant vaporizes. The vaporized
refrigerant is pumped out of the evaporator by the compressor
which compresses the refrigerant, raising its pressure and
temperature. The high temperature refrigerant then flows to
the system condenser where its heat is rejected, most
typically, to water in a second fluid loop or directly to
ambient air.
As the refrigerant is cooled in the condenser it
changes state from a hot gas to a warm, relatively high
pressure liquid which is metered through a pressure reducing
expansion valve, to the evaporator. The expansion valve
maintains the pressure differential between the high and low
pressure sides of the refrigeration system.
The pressure of the refrigerant is controllably
reduced as it passes through the expansion valve to ensure that
the refrigerant will effeciently vaporize and absorb heat from
the relatively warm water flowing through the evaporator. The
cycle is completed, and ready to be repeated, when the liquid
refrigerant flows, at reduced pressure, through the expansion
valve to the evaporator.
~ 2156117
The amount of liquid refrigerant introduced into
the evaporator should be that amount which can nwet" the
surface area of the tubes of the evaporator without having more
or less liquid refrigerant in the evaporator than is needed for
a particular cooling load. Accordingly, the expansion valve
should be adjustable, on command, to control the amount of
liquid refrigerant introduced into the evaporator. The
expansion valve can also be used to shut off the flow of
refrigerant through the chiller such as for purposes of
isolating chiller components for maintenance.
Electric, rotary actuated, incremental valves
suitable for use as expansion valves in refrigeration systems
are typically comprised of two types. In both types, the valve
is operated by a stepping motor which provides incremental
rotary motion which is then translated to incremental linear
motion to actuate a valve element.
In the first type of valve, the valve element is
linearly driven against the valve seat to sealingly cover an
aperture to prevent fluid flow therethrough. Alternatively,
the valve element is driven linearly away from the seat to open
the valve by incrementally opening the aperture to flow. The
distance of the valve element from the valve seat is
determinative of the flow area available through the valve, up
to a ~1 which is restricted only by the size of the
aperture itself.
This type of rotary actuated, linearly driven
expansion valve may stick due both to the friction between
valve parts and the viscosity of cont~rin~nts collected upon
the valve body. Overcoming this tendency to stick can require
the use of oversized, more costly motors.
- 21~6117
The ability to carefully control the system is
decreased because the actuator may fail to overcome the
sticking of the valve element, for one or more actuating pulses
or steps of the motor, causing the valve element to be
improperly positioned. The valve controller, having sent a
specified number of pulses intended to actuate the valve to a
desired opening, will in fact have actuated the valve to a
smaller degree than calculated or desired. The system then
indicates the need for further movement of the valve element
and the controller begins to "hunt" for the appropriate valve
setting.
In a second type of rotary expansion valve, the
valve element is a member which is linearly driven normal to a
flow aperture and the direction of flow of refrigerant through
- 15 the valve. In this type of valve, the amount of flow is
determined by the extent of the area of the aperture which is
uncovered by the valve element.
In addition to the potential "hunting" problems
described above, this second type of rotary actuated expansion
valve is typically comprised of many relatively small parts
which must be ~chined to close tolerances to prevent fluid
leakage therethrough and to improve operating characteristics.
Such close tolerance machining is often expensive and time
consuming, as is the assembly of valves con~ining such parts.
Furthermore, this type of rotary actuated expansion
valve often includes a relatively large number of elastomeric
seals to prevent leakage past the valve element and oftentimes,
one or more springs having a relatively large traverse
distance, all of which are susceptible to wear and breakage.
These items tend to substantially decrease the reliability of
the valve.
2156117
. ,~
It is an object of the present invention to provide
a rotary actuated expansion of relatively rugged design and
simple construction that avoids the problems inherent in
stepper motor driven expansion valves having a linearly driven
valve element.
It is a further object of the present invention to
provide a rotary actuated expansion valve which is highly
reliable yet relatively low in snl~f~scturing and maintenance
requirements and costs.
It is yet another object of the invention to
provide such a valve which is capable of being mass produced.
It is yet another object of the invention to
provide such a valve which is a low friction device.
It is yet another object of the present invention
to provide such a valve as will appropriately respond to a
controller input to permit smooth, pulse-free fluid flow
through the valve.
It is yet another object of the invention to
provide such a valve which is suitable specifically for such
applications as an expansion valve in an air conditioning or
other type of refrigeration system, particularly where such
system includes a flooded evaporator.
These and other objects of the present invention
will be apparent from the attached drawings and description of
the preferred embodiment which follows.
6 ~ 9~
Summary of the Invention
In accordance with one aspect of the present invention there is provided a
refrigerant expansion valve comprising: a motor, said motor being a bi-directional motor
having a drive shaft; a housing said housing defining at least one aperture; a rotating
member having a peripheral edge exposed to refrigerant flow through said valve, said
rotating member disposed in a plane generally perpendicular to the direction of flow
through said valve and defining at least one aperture, the degree to which said aperture of
said rotating member is in registry with said aperture of said housing being determinative
of the amount of refrigerant flow through said valve; and an actuator, said actuator being
operably coupled to said rotatable shaft member of said motor and to said rotating
member, the rotation of said motor shaft causing linear motion of said actuator in said
valve and said linear motion of said actuator causing rotary motion in rotating member.
In accordance with another aspect of the present invention there is provided
a refrigerant expansion valve comprising: a motor, said motor being a bi-directional
motor having a rotatable drive shaft; a housing, said housing defining a plurality of
apertures in said valve; a plate mounted for rotary motion within said valve, said plate
defining a plurality of apelLures; and an actuator, said actuator disposed in said valve for
linear movement in a plane generally coincident with the plane of said plate and being
operably coupled to both said rotatable drive shaft of said motor and to said plate,
rotation of said motor drive shaft causing said actuator to move linearly within said valve
in a plane generally coincident with the plane of said plate, said linear movement of said
drive shaft causing rotary motion of said plate, the degree of registry of said apertures in
said plate with respect to said apertures in said valve being determinative of the amount
of refrigerant flow through said valve; and means for isolating said drive shaft of said
motor from refrigerant flowing through said valve.
In accordance with yet another aspect of the present invention there is
provided a refrigeration system comprising: a compressor; a condenser connected for
flow from said compressor; an evaporator connected for flow to said compressor; and
refrigerant metering means, disposed in flow comlllullication with said condenser and said
evaporator, said metering means including a motor, a rotating member defining a
"
~ 7~
6a
plurality of apertures, a fixed member defining a plurality of apertures and an actuator
operably coupling said motor and said rotating member, said actuator first tr~n.~l~tin~
5 rotary motion of said motor to linear motion and then translating said linear motion to
rotary motion of said plate, the degree to which said apertures in said rotating member
are in registry with said apertures in said fixed member being d~telmillative of the
amount of refrigerant flow through said valve, said refrigerant metering means including
means for limiting the movement of said actuator such that the actuator is prevented from
10 rotating said rotating member to an extent which puts said apertures of said rotating
member in full registry with said apertures of said fixed member thereby limi~ing the
amount of refrigerant flow through said metering means to an amount which is less than
the amount which would occur if said apertures of said fixed and rotating members were
in full registry.
The present invention is a stepper motor driven variable flow rate
expansion valve for a refrigeration system. The valve has a housing which facilitates its
mounting in-line in refrigerant piping and defines a flow passage ther~ rough. Arestrictor is integrally formed within the valve housing to control fluid flow.
First flow apertures are defined in the restrictor and a closure device, the
purpose of which is to vary the degree of opening of the flow apertures in the restrictor in
operation, is rotatably coupled to the restrictor. Second flow apertures are defined in the
closure device which are capable of being rotatably positioned between an open
position in full registry with the restrictor flow apertures and a closed position where the
restrictor flow apertures are closed to flow.
Preferably, the closure member rotates in a plane generally transverse to
the flow of refrigerant thel~lluough and is spaced away from the restrictor so that a
leakage path is at all times m~int~in~d, even if the apertures of the closure device and
restrictor are out of registry. This permits pressure equalization across the valve and in
the refrigeration system in which it is employed subsequent to the shutdown of the
refrigeration system.
A drive mechanism is operably coupled to the closure device such that
linear motion of the drive mechanism produces rotational motion of the closure device so
' ~
. ~
6b ~ ~ ~5 6 ~ ~ ~
as to position the closure device and its flow apertures between the fully open and fully
closed positions. A stepping motor is conn~cted to the drive mechanism and provides a
rotational motive force which causes the linear movement drive mech~ni~m.
~J
_ 2156117
In-line installation of the valve in refrigerant
piping reduces the internal valve friction which results from
the impingement of liquid refrigerant on its components and the
need, as in some expansion valves, to change refrigerant flow
direction within the valve housing. The in-line characteristic
and unique features of the expansion valve hereof overcome the
problems of valve binding and unresponsiveness of previous
stepper motor driven expansion valves without the employment of
costly, oversized drive motors.
The present invention is of relatively
uncomplicated but unique design, both as to its reduced number
of parts and the relative lack of a requirement for critical
tolerances as between the various parts. The design provides
for ease and red~ee~ cost of snllfArture as well as low
maintenAnre in service. Low maintenAn~e requirements are
especially desirable since repair of an expansion valve
requires that the refrigeration system be taken out of service
thereby possibly interrupting the air conditioning of a
commercial building or the provision of chilled water for a
fActuring process.
Brief Descri~tion Of The Drawin~s
Figure 1 is a generally schematic representation of
a chiller-based refrigeration system.
Figure 2 is an elevational view of the expansion
valve of the present invention from the input side of the
valve, with the stepper motor and valve drive system depicted
in phantom.
Figure 3 is a sectional view taken along line 3-3
of Figure 2.
Figure 4 is a side elevational view of the valve,
with the refrigerant line connected to the valve and the valve
metering portion depicted in phantom.
''- 2156117
Figure 5 is a sectional view taken along line 5-5
of Figure 4 with a portion of the rotating metering disc broken
away to expose a portion of the fixed metering disc.
Figure 6 is a partial sectional view of the
expansion valve showing the fluid metering portion of the valve
in the fully opened position.
Figure 7 is similar to Figure 6, but with the fluid
metering portion of the valve in the fully closed position.
Figure 8 is a partial sectional view of the
metering portion of an expansion valve of the present invention
depicting an alternate embodiment of the metering disc
apertures.
Figure 9 is similar to Figure 8, but with the
metering portion of the valve in the fully opened position.
Figure 10 is similar to Figure 8, but with the
valve metering portion in the fully closed position.
Figure 11 is a still further embodiment of the
present invention in which features applicable to the earlier
embodiments are illustrated.
Figure 12 illustrates the disposition of a spacer between the
closure member and restrictor portions of the present invention.
Descri~tion Of The Preferred Embodiment
Referring first to Figure 1, an air conditioning
system is shown generally at 20 and consists of three major
components; chiller 22, chilled water loop 24, and heat
rejection loop 26. Chiller 22 cools the chilled water that
ultimately cools the air conditioned space or process serviced
by the chilled water loop 24. The chilled water loop 24
conveys chilled water from chiller 22 to the coil 29 in a
21~117
space, room, process or zone that is to be temperature
conditioned. Heat rejection loop 26 cools the heated chiller
refrigerant by conveying a portion of the refrigerant's heat to
a heat sink such as ambient air or water.
Chiller 22 has four main components; evaporator 28,
compressor 30, condenser 32, and expansion valve 34.
Evaporator 28 conveys cool, liquid refrigerant into heat
exchange contact with water which is to be chilled. As the
refrigerant absorbs ~eat from the water in the evaporator the
refrigerant vaporizes. Compressor 30 draws the refrigerant
vapor from evaporator 28 and compresses it thereby raising both
the temperature and the pressure of the refrigerant.
The hot, gaseous refrigerant is then pumped by
compressor 30 to condenser 32 where it is cooled and condenses
to a warm liquid. The liquid refrigerant, which is still at
relatively high pressure, then flows to expansion valve 34.
Still referring to Figure 1, expansion valve 34
causes a drop in pressure in the refrigerant as it passes
through it. A portion of the refrigerant flashes to vapor but
the bulk of the refrigerant passes through the valve in the
liquid state.
In chilled water loop 24, relatively warm water
returning from coil 29 associated with the space or process
which is to be temperature conditioned passes through
evaporator 28 and is cooled by the chiller system refrigerant.
Heat rejection loop 26 in building air conditioning systems is
often a rooftop system which includes a cooling tower. Water
that has been heated by the hot refrigerant in condenser 32 is
drawn from the condenser and is pumped through heat rejection
loop 26.
2156117
Fans 33 draw ambient air over a heat exchanger coil
(not shown) in the cooling tower thereby cooling the water in a
heat exchange process with the ambient air. The cooled water
is recirculated to condenser 32 in a continuous refrigerant
cooling process.
Referring additionally now to Figures 2-7,
expansion valve 34 is disposed in the pipe 36 which connects
condenser 32 to evaporator 28. Refrigerant flow direction in
pipe 36 i5 as indicated by the arrow F depicted in Figures 1
and 4. Valve 34 acts as a boundary between the high and low
pressure sides of chiller 22 and performs the function of
delivering liquid refrigerant to evaporator 28 in precisely
metered quantities. Expansion valve 34 includes valve casing
38 and three main functional components, motor 40, linear
actuator 42, and fluid metering section 44.
Valve casing 38 is a structural member, typically
cast as a single unit, and has a motor support flange 46 which
is connected by webbing 50 to a valve housing 52. Valve
housing 52 has an internal bore 54 that houses linear actuator
42. The axis of bore 54 is oriented on an extension of the
central axis of motor 40 and is preferably defined in the upper
portion of the valve housing.
Valve housing 52 also includes mounting bores 56
that are located so as to align with similar bores in pipe
flanges 58 of pipe 36 to permit the in-line installation of the
valve in the refrigerant piping. Pipe flanges 58 are typically
secured to valve housing 52 by bolts 60 making the valve easily
removeable for maintenance if necessary.
- 2156117
The inner circumference 62 of valve housing 52
defines an inlet recess 64 and an outlet recess 66. Inlet
recess 64 and outlet recess 66 are in flow communication
through the housing and define a fluid passageway through valve
casing 38. Preferably, inlet recess 64 is of greater diameter
than outlet recess 66 so that a lip 67 is formed at the
juncture of inlet and outlet recesses.
Motor case 70 is affixed by bolts 72 to motor
flange 46 of valve casing 38. As is best illustrated in Figure
5, vent channel 71 extends between the interior of the motor
case 70 and the interior of valve casing 38 and a debris filter
73 is disposed within the channel.
Motor 40 is a bi-directional, incremental motor,
also known as a stepping or stepper motor, and provides rotary
motion in equal increments in response to the application of an
external control or power signal. Stepping motors such as
motor 40 are well-known and a detailed discussion regarding
motor 40 is not provided herein.
Drive shaft 74 of motor 40 projects through central
bore 76 in motor flange 46 and is aligned with the axis of bore
54. Motor bearing 78, which may be a roller or sleeve bearing,
is disposed in bore 76 and rotatably supports drive shaft 74.
The end portion 80 of drive shaft 74 is threadably engaged with
linear actuator 42 and power is provided to motor 40 via
electrical leads 82.
Linear actuator 42 is preferably a polished metal
rod that is closely slideably engaged within bore 54. Actuator
42 is sufficiently shorter in length than the depth of bore 54
to permit it to freely slide back and forth over a substantial
range within bore 54.
2155117
12
Threaded axial bore 84 within linear actuator 42
cooperatively engages the threads of the end portion 80 of
drive shaft 74. The depth of threaded bore 84 is greater than
the length of the threaded portion 80 of the drive shaft to
facilitate the full extent of the linear traverse of actuator
42 in bore 54.
A curvilinear slot 90 is milled into linear
actuator 42. Referring to Figure 4, it will be seen that slot
90 extends through approximately half the width of the linear
actuator and that a bore 92 opens into slot 90 at a right angle
to the axis of actuator 42. Drive pin 94 is press fit into
bore 92 and is of a length approximately equal to the diameter
of linear actuator 42. Pin 94 projects into slot 90 at right
angles to the axis of the linear actuator.
The fluid metering section 44 of expansion valve 34
has two main portions, a fixed disc portion 100 and a rotating
disc 102. Preferably, fixed disc portion 100 is formed in the
same operation in which the re in~er of housing 52 is formed
and is an integral part of the housing. Fixed disc 100 has at
least one flow aperture 104 that restricts fluid flow
therethrough.
In the embodiment shown in Figures 2-7, there are
four flow apertures 104 formed at 90 degree intervals around
fixed disc portion 100. The shape of flow apertures 104 is
defined by two spaced apart radii subtended by two arcs of
varying radial distance from the center of fixed disc portion
100. Fixed disc 100 additionally has a central bore 106 which
provides a mounting aperture for rotating disc 102.
'~ -
21~6117
13
Rotating disc 102 is preferably circular in shape
and has a projecting peripheral edge 110 that extends beyond
the circumference of disc 102. Peripheral edge 110 has an
outwardly opening U-shaped slot 112 that engages drive pin 94.
The circumference of rotating disc 102 is slightly
less than the circumference of inlet recess 64 formed so that
disc 102 is free to rotate within the inlet recess.
Preferably, the circumference of disc 102 is somewhat greater
than the circumference of outlet recess 66 so that the radially
exterior portion of rotating disc 102 is in sliding engagement
with lip 67. Rotating disc 102 has a central bore 114 that
provides for the rotational mounting of disc 102 to fixed disc
portion 100.
A thrust bearing 120, having a central bore
therethrough. is mounted in central bore 106 of fixed disc 100.
Bore 114 of rotating disc 102 is positioned in registry with
the bore of bearing 120 and the combination of bolt 122,
passing through bore 114, bearing 120 and lock nut 124
rotatably secures disc 102 to fixed disc portion 100.
Rotating disc 102 defines at least one flow
aperture 128. Apertures 128 are preferably of the same size,
shape and radial distance from the central axis of rotating
disc 102 as flow apertures 104 are in relation to fixed disc
portion 100. Accordingly, at a predetermined point of
rotation, apertures 128 of disc 102 are brought into full
coincidental registry with apertures 104 of fixed disc portion
100 .
Linear actuator 42 has limited translational
authority within bore 54 with which to rotate disc 102.
Accordingly, the relationship of apertures 104 of fixed disc
100, apertures 128 of rotating disc 102, and peripheral flange
' ,~,, -
2156117
14
110 of rotating disc 102 must be such that at one extreme of
the traverse of linear actuator 42, apertures 128 and apertures
104 are in full registry while at the second extreme of of
traverse, apertures 128 are entirely out of registry with
apertures 104. Apertures 104 are thus fully closed at the
second extreme and fluid flow through expansion valve 34 is
prevented. The fully opened position previously described is
depicted in Figure 6 and the fully closed position in Figure 7.
An alternative embodiment of an expansion valve of
the present invention is depicted in Figures 8, 9 and 10. This
embodiment differs from the previously described embodiment
only in that apertures 104' and apertures 128' comprise a
plurality of circular apertures. Other embodiments using
different shaped, sized and oriented apertures are
contemplated. Varying the nature of the apertures provides an
opportunity to vary the overall range and/or rate of cumulative
opening or closing of the flow apertures and can be used to
change the relationship between the rate or extent of rotation
of the rotating disc 102' and the flow area presented across
the operating range of the valve.
Figure 8 depicts flow apertures 104' in a partially
opened position while Figure 9 depicts apertures 128' in full
registry with apertures 104' in the fully open position.
Figure 10 depicts the apertures 104' in phantom behind rotating
disc 102' in the fully closed position. The other elements of
the valve 34' depicted in Figures 8-10 are identical to the
elements described in conjunction with the description of the
first embodiment.
2156117
In operation, expansion valve 34 is installed in
pipe 36 which conveys liquid refrigerant from condenser 32 to
evaporator 28. The amount of refrigerant required by
evaporator 28 is determined by the cooling load air
conditioning system 20 is experiencing at any given time.
Responsive to that cooling load, a control system (not shown)
provides cl- ~n~C to motor 40. The greater the cooling load,
the greater the amount of refrigerant flow through expansion
valve 34 that is needed.
Motor 40 is bi-directional, thereby providing for
both opening and closing of expansion valve 34. An input
command from the control system causes the motor 40 and its
drive shaft 74 to rotate in a fixed increment of angular
displacement. This rotation causes threaded portion 80 of
drive shaft 74 to rotate incrementally within axialy bore 84 of
linear actuator 42. Since linear actuator 42 is constrained
from rotating, the incremental rotation of drive shaft 74
causes linear actuator 42 to move axially in bore 54 which
causes disc 102 to rotate to a more opened or closed position,
as the case may be. In sequence then, the incremental
rotational motion of motor 40 produces linear motion of linear
actuator 42 which in turn causes the rotational motion of disc
102.
Frictional forces caused by the impact of high
pressure refrigerant fluid on rotating disc 102 are borne by
thrust bearing 120 and by the periphery of rotating disc 102
which is in sliding engagement with lip 67. It is to be noted
that expansion valve 34 does not employ discrete seal elements
2156117
16
between rotating disc 102 and fixed disc lO0. Accordingly,
when expansion valve 34 is in the closed position, there is the
potential for a small but tolerable amount of leakage through
expansion valve 34.
It is also to be noted that figures 8, 9, and 10
depict apertures 104' and 128' as circular openings, with each
aperture 104' being paired with a corresponding aperture 128'.
The circular apertures of the embodiment depicted in these
figures are in contrast to the apertures 104 and 128 of the
previously depicted embodiment.
Apertures 104 and 128, as described with respect to
Figures 2-7, are defined by two sides that are radii and two
sides that are arcs of the respective discs 100 and 102.
Accordingly, as apertures 128 are rotated into or out of
registry with apertures 104, each incremental rotational step
of the drive motor produces a generally linear increase or
decrease in the size of the overall flow opening presented by
the two discs.
The linear change in opening size is in contrast to
the result obtained when using the circular openings of
apertures 104' and 128' of Figures 8-10 where, since two
circular apertured are being brought into and out of registry,
the incremental angular rotation of disc 102' produces
relatively little change in the overall flow area through the
valve when apertures 128' are nearly fully in or out of
registry with apertures 104'. This circumstance occurs at the
extreme ends of the stroke of linear actuator 42.
At the midpoint of the rotational motion of
apertures 128' with respect to apertures 104', the greatest
rate of change of the cumulative aperture opening of the valve
is achieved. Accordingly, the change of the effective flow
17 21~6117
area achieved per motor step and per the incremental angular
change of position of rotating disc 102' is magnified, as is
valve responsiveness, in the most critical portion of the
valve's operating range.
As depicted in Figures 8, 9, and 10, there are a
relatively large number of apertures 104' and 128'
symmetrically disposed around discs 100' and 102'. An effect
of this arrangement, like that of the Figures 2-7 embodiment,
is to evenly distribute the thrust loads imposed on the
structure of rotating disc 102'. Accordingly, no bending
moments are produced on bolt 122 which would tend to cause
binding of disc 102' and inhibit its free rotation.
Referring now to the embodiment of Figure 11,
modifications/features also applicable to the earlier discussed
embodiments are illustrated which may, in certain instances, be
advantageous. In the embodiment of Figure 11, valve 34''
includes a stop member 200 by which the extent of travel of
linear actuator 42'' in bore 54'' is limited. In that regard,
stop member 200 is threadably inserted into a cooperating
threaded co-axial extension 202 of bore 54''. A seal, such as
0-ring 204 may be employed to provide a fluid tight seal
between stop member 200 and valve casing 38''.
Stop member 200 has a stop portion 206 of a
predetermined length which projects into bore 54''. Actuator
42'' will come to bear against the end of linear actuator 42''
as it travels axially within bore 54'' away from motor 40''.
By varying the overall length of member 200, the
~i extent to which rotating disc 102'' is permitted to
bring the apertures of the fixed and rotating disc into
registry and, therefore, the ~i flow rate permitted
'~ -
21S6117
18
through the valve, can be limited in view of the size/capacity
of the system in which valve 34'' is employed. As a result,
the same single standard valve can be used in a wide variety of
applications and chiller sizes, all through the selection and
use of a very inexpensive and readily accessible bolt-like
part.
Also with respect to Figure 11, the employment of a
bellows member 208, disposed in bore 76'' in valve casing 38''
is illustrated. Bellows 208 is sealingly penetrated by linear
actuator 42'' and is attached thereto for expansion or
contraction in accordance with the direction of movement of the
actuator. The interior of bellows 208 is therefore isolated
from the r~ ~in~Pr of the interior of bore 76''.
By the use of bellows member 208, the need for a
motor case 70, which is in communication through a vent channel
with the interior of the valve member of the previous
embodiments, is dispensed with. Since motor case 70 would
typically be a relatively very heavy and expensive cast piece,
the use of bellows 208 as an isolation boundary may be
advantageous from both a weight and cost standpoint. Also, by
the use of bellows 208, direct access to motor 40'', without
the need to remove a housing which is in communication with the
interior of valve 34'' through a vent passage, is made
available.
Figure 11 also illustrates the use of a
threaded insert 210 in the end of linear actuator 42'' which
engages drive shaft 74'' of motor 40''. By the use of a
threaded, press fit insert, the need to threadably ~rhin~ a
bore into the end of linear actuator 42'' is dispensed with
which, in some circumstances, may provide a cost benefit with
19 2156117
respect to the production of valve 34'' Also, the insert may
permit the valve to be more tolerant with respect to the
alignment of the linear actuator and motor drive shaft thereby
reducing the likelihood that linear actuator 42'' will stick or
bind as it traverses bore 54''.
~inally and as is indicated above, in the earlier '~ ts the
downstream face of the rotating disc portion of the valve is in sliding
engagement with the upstream face of the fixed disc portion. In those
~o~im~nts, the force on the upstream face of the rotating disc portion
caused by the tran~verse impact of high pre~-~ure fluid refrigerant flow
F impinging on it are borne by a thrust bearing.
Referring now to both Figures 11 and 12, a spacer 212 is disposed
between rotating disc portion 102~, which is mounted for rotation on
pin 214, and fixed disc portion 100~ of valve 34''. A~ a result,
rotating disc portion 102'~, in this embodiment, is slightly disengaged
from and is not in slideable contact with the fixed disc portion due to
the creation of gap 216. Therefore, even when apertures 104'' and 128''
of the fixed and rotating disc portions are entirely out of registry, a
leakage path is maintained around the periphery of rotating disc portion
0 102'' and through its apertures into intervening gap 216 and thence,
through apertureq 104'' of fixed disc portion 100''. This permits the
higher, upstream pressure in a refrigeration system in which valve 34''
is employed to equalize across the valve when the refrigeration system
shuts down.
~y spacing rotating disc portion 102'' away from fixed disc
p~rtion 100'', the existence of a leakage path through valve 34'' by
which system pre-~sure~ can equalize when the aperture~ of the fixed and
rotating disc portions of the valve are out of registry is assured but
in a manner which doe not appreciably affect the operation or accuracy
~0 of the valve with respect to its refrigerant flow modulating function.
When apertures 104'' and 12a'' are in registry to any degree, the flow
of refrigerant through valve 34'' will be through the apertures with
2156117
,~
little, if any, refrigerant flow occurring past and/or around the
periphery of rotating disc member 102''. The use of a spacer 212 which
biases rotating disc portion 102'' away from fixed disc portion 100'',
such as a Belville spring or wavy washer, will facilitate the rotation
of rotating disc portion 56 as against the transverse impact of
refrigerant flow F on its upstream face.
While the present invention has been described in
terms of preferred and alternative embodiments, it will be
appreciated that other modifications and versions of the valve
of the present invention will be apparent to those skilled in
the art given the te~chingc herein. Accordingly, the scope of
the present invention should not be limited other than in
accordance with the language of the claims which follow.
