Three-way valve for a refrigeration system

A three-way valve for a refrigeration system having a body portion which includes an intermediate member and first and second end bells. The body portion includes an inlet adapted for connection to a refrigerant compressor, first and second major outlets respectively adapted for connection to a condenser and an evaporator, and a minor outlet adapted for selective connection to the low side of the compressor. The body portion defines a cavity within which a removable cartridge is disposed which contains all movable parts of the valve, as well as all parts subject to wear. The cartridge is freely removable for maintenance purposes after removal of a predetermined one of the end bells. An equalizing check valve is carried by the cartridge which limits back pressure build up via the first major outlet when the valve is positioned to connect the inlet to the second major outlet.

TECHNICAL FIELD 
The invention relates in general to refrigeration valves, and more 
specifically to a three-way valve suitable for alternately directing 
refrigerant from the discharge side of a refrigerant compressor to a 
condenser or an evaporator. 
BACKGROUND ART 
It is common in transport refrigeration systems used to condition the cargo 
space of trucks and trailers to utilize a three-way valve to direct hot 
refrigerant gas from a refrigerant compressor to a condenser during a 
cooling mode, and to an evaporator during defrost and/or a heating mode. 
U.S. Pat. No. 4,912,933, which is assigned to the same assignee as the 
present application, describes such a transport refrigeration system in 
detail. 
A prior art three-way valve of which we are aware is relatively costly to 
manufacture because of a pressure equalizing check valve which is 
assembled into the housing of the three-way valve. The portion of the 
three-way valve housing which receives a check valve requires costly angle 
drilling to form a cavity for the check valve. This prior art three-way 
valve art is also relatively costly to maintain, as a solder joint must be 
unsoldered and two gasketed joints must be opened in order to remove a 
stationary valve seat structure fixed to the inside of the housing. The 
stationary valve seat structure blocks the removal of a movable portion of 
this prior art three-way valve. The movable valve portion carries valve 
seals which contact the stationary valve seats. Re-soldering the joint in 
the field after maintenance of the three-way valve often results in 
refrigerant leaks. 
SUMMARY OF THE INVENTION 
Briefly, the present invention is three-way valve for a refrigeration 
system having a condenser, an evaporator, and a refrigerant compressor 
which includes discharge and suction sides. The three-way valve comprises 
a body portion including an intermediate body member having first and 
second axial ends, and first and second end bell members removably fixed 
to the first and second axial ends, respectively, via first and second 
gasket members. The intermediate body member and first and second end bell 
members cooperatively define an axially extending elongated cavity. The 
body portion of the three-way valve further includes an inlet adapted for 
connection to the discharge side of the refrigerant compressor, first and 
second major outlets adapted for connection to the condenser and 
evaporator, respectively, which are alternately selectable by the 
three-way valve, and a minor outlet adapted for selective connection to 
the suction side of the refrigerant compressor. According to the 
invention, a cylindrical cartridge is removably disposed within the 
elongated cavity of the body portion. The cartridge carries co-operable 
stationary and movable portions of the three-way valve, including first 
and second spaced stationary valve seats and first and second spaced valve 
seals which respectively contact the first and second valve seats to 
provide first and second operative positions. The first and second 
operative positions respectively connect the inlet of the valve body 
portion to the first and second major outlets. Since the movable portion 
of the valve is not required to co-operate with the valve body portion to 
effect the valve sealing functions, the cartridge is readily axially 
removable from the valve body portion for maintenance purposes. This is 
accomplished without interference between the cartridge and valve body 
portion, by removal of a predetermined one of the end bell members. Thus, 
no solder joints need be broken and re-soldered in order to maintain the 
three-way valve. The removable cartridge contains all of the stationary 
and movable parts of the valve which are subject to wear, and thus the 
three-way valve may be quickly serviced by replacing the existing 
cartridge with a new or rebuilt one. 
A pressure limiting or equalizing check valve is co-axially carried by the 
cartridge, with the check valve being disposed to limit back pressure 
build up in the cartridge via the first major outlet when the inlet of the 
body portion is operatively connected to the second major outlet. This 
arrangement eliminates the need for angle drilling of the body portion of 
the three-way valve, ie., the valve housing. A shaft which carries an 
operating piston of the three-way valve also carries the check valve, with 
all drilling of the shaft required for the check valve function being 
co-axial with, and transverse to, the longitudinal axis of the shaft.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring now to FIG. 1, there is shown a perspective view of a three-way 
valve 10 constructed according to the teachings of the invention. 
Three-way valve 10 includes a body portion or housing 12 having first and 
second axial ends 14 and 16, and a longitudinal axis 18. Housing 1 2 
includes a tubular, cylindrical intermediate body member 20 having first 
and second axial ends 22 and 24, respectively. Housing 12 further includes 
first and second end bell members 26 and 28, respectively, each having 
first and second axial ends. The first end 14 of housing 12 is the same as 
the first axial end of end bell 26, and end bell 26 includes a second 
axial end 30. The second end 16 of housing 12 is the same as the second 
axial end of end bell 28, and end bell 28 includes a first axial end 32. 
The intermediate body member 20 and first and second end bell members 26 
and 28 are coupled via gasket members 34 and 36, screws 38 associated with 
the first end bell 26, and screws 39 associated with the second end bell 
28. Gasket member 34 is disposed between the second axial end 30 of the 
first end bell member 26 and the first axial end 22 of the intermediate 
body member 20. Gasket member 36 is disposed between the second axial end 
24 of the intermediate body member and the first axial end 32 of end bell 
member 28. 
Housing 12 has an inlet opening 40, best shown in FIG. 3, disposed in the 
second end bell member 28, such as through a side wall thereof adjacent to 
the first axial end 32. Opening 40 includes a tubular member 42 soldered 
in the opening. Tubular member 42 is adapted for connection to the 
discharge or high pressure side D of a refrigerant compressor 43 of an 
associated transport refrigeration system 45 shown in FIGS. 3 and 4. 
Housing 12 further includes first and second major outlet openings 44 and 
46 and a minor outlet opening 48, all shown in FIGS. 3 and 4. The first 
major outlet opening 44 is provided through the side wall of the 
intermediate body member 20. A tubular member 50 is soldered into opening 
44. Tubular member 50 is adapted for connection to a condenser 51 of the 
associated refrigeration system 45. 
The second major opening 46 is provided in the second end bell member 28, 
through a side wall thereof, and closer to the second axial end 16 than 
inlet opening 40. A tubular member 52 is soldered in opening 52, with 
tubular member 52 being adapted for connection to an evaporator 53 of the 
associated refrigeration system 45. 
The minor outlet opening 48, as shown in FIGS. 3 and 4, is disposed 
co-axially through the first axial end 14 of the first end bell member 26. 
Opening 48 is adapted for controllable connection to the suction or low 
pressure side S of refrigerant compressor 43, such as via a normally 
closed electrical solenoid valve 55 which is controlled by refrigerant 
control 57. 
The intermediate body portion 20 and first and second end bell members 26 
and 28 cooperatively define an axially extending, elongated cavity 54. 
FIG. 2 is a partially exploded perspective view of the three-way valve 10 
shown in FIG. 1 illustrating the internal components of three-way valve 10 
which are disposed within the cooperatively defined elongated cavity 54. 
The internal components include a removable cylindrical cartridge 56, 
first biasing means 58, such as a plurality of Belleville springs, and 
second biasing means 60, such as a helical compression spring. The first 
biasing means 58 biases a stationary portion of cartridge 56, and the 
second biasing means 60 biases a movable portion of cartridge 56, as will 
be hereinafter explained. The non-exploded portion of housing 12 indicates 
that this portion of the housing may remain intact while assembling and/or 
replacing cartridge 56. Thus, only the first end bell member 26 need be 
removed to service the three-way valve 10. 
FIGS. 3 and 4 are cross-sectional views of three-way valve 10 taken between 
and in the direction of arrows III--III in FIG. 1. FIGS. 3 and 4 
illustrate the "cooling" and "heating" positions of three-way valve 10. 
Cartridge 56 includes stationary and movable portions 62 and 64, 
respectively. The stationary portion 62 includes a thin-walled tubular 
metallic shell member 66 having first and second axial ends 68 and 70, and 
an opening 72 which extends between its ends defined by an inner surface 
73. Opening 72 and inner surface 73 thus create an axial bore within which 
the movable portion 64 of the cartridge 56 is disposed. 
The stationary portion 62 includes first and second annular members 74 and 
76, respectively. The first annular member 74 is fixed intermediate the 
axial ends 68 and 70 of shell member 66, such as by roll-formed grooves 
and bands 78 and 80. The second annular member 76 is fixed adjacent to the 
second axial end 70, such as by a roll-formed groove and band 82. The 
first annular member 74 has a plurality of circumferentially spaced 
openings 84 aligned with similarly dimensioned and spaced openings 86 in 
shell 66. The first annular member 74 also has a tapered or funnel-shaped 
surface 88 which functions as a valve seat. The second annular member 76 
has a similarly tapered or funnel-shaped surface 90 which also functions 
as a valve seat. 
Shell 66 also has a plurality of circumferentially spaced openings 92, best 
shown in FIG. 2, the centers of which lie in a plane disposed through the 
longitudinal axis 94 of the tubular intake member 42, transverse to the 
longitudinal axis 18 of housing 12. A screen 96, parts of which are shown 
in FIGS. 3 and 4, is wrapped about shell 66 to cover openings 92, to trap 
any debris in the refrigerant being discharged by the refrigerant 
compressor 43 into three-way valve 10 via the tubular intake member 42. 
The second annular member 76 includes an opening 97 facing the second end 
70 of the stationary portion 62 of cartridge 56 for receiving an indexing 
pin 98 which is fixed to the second end bell member 28. The indexing pin 
98 and complementary opening 97 insure that the openings 84 and 92 in 
stationary member 62 will be properly circumferentially oriented relative 
to the tubular members 42 and 50. 
The movable portion 64 of cartridge 56 includes an elongated shaft 100 
having first and second axial ends 102 and 104, respectively. Shaft 100 
has a first diameter starting at the first end 102, defined by outer 
surface 106. The first diameter extends towards the second end 104 for a 
predetermined dimension, and it ends at an inwardly stepping shoulder 108. 
Shoulder 108 steps inwardly to a second diameter defined by a surface 110. 
Surface 110 extends towards the second end 104 for a predetermined 
dimension, ending at a threaded portion 112. Threaded portion 112 
terminates a predetermined dimension from the second end 104, stepping 
inwardly at a shoulder 114 to a still smaller diameter defined by a 
surface 116. Surface 116 extends to the second end 104. The second end 
bell member 28 has an opening 118 sized to slidably receive the second end 
104 of shaft 100, providing a first support point for the movable portion 
64 of cartridge 56, while also enabling slidable axial movement of the 
movable portion 64. 
Shaft 100 has a circumferential groove 120 in surface 110 which contains an 
0-ring seal 122. Shaft 100 has a transverse opening 124 through the second 
diameter portion defined by surface closer to shoulder 108 than groove 
120. 
Shaft 100 has a stepped opening 125 co-axial with axis 18, which opening 
starts at the first axial end 102 of shaft 100 with a relatively large 
first diameter defined by an inner surface 126 which is tapped for a 
predetermined length. Opening 125 steps inwardly at a shoulder 128 to a 
smaller diameter defined by a smooth surface 130. Surface 130 ends at a 
wall portion 132 which has a small central opening 134 which continues the 
stepped opening 125 into fluid flow communication with the transverse 
opening 124. Wall portion 132 includes a raised lip 136 which surrounds 
the entrance to opening 134. 
A pressure equalizing or limiting check valve 138 is removably fixed in the 
stepped opening 125. Check valve 138 includes a fixed portion 140, which 
includes an axially extending through opening 141, and a movable portion 
142 which is biased against lip 136 via a helical compression spring 144. 
Shaft 100 includes a plurality of members which are telescoped over the 
second end 104 and firmly held in serial alignment by a nut 146 which 
engages the tapped portion 112. The first of such members is a piston 148 
which is disposed against shoulder 108. Piston 148 has first and second 
opposed pressure receptive surfaces 150 and 152 disposed transverse to 
axis 18. Piston 148 has an outer periphery 154 having a circumferential 
groove 156 having sealing means 158 disposed therein, such as the 
illustrated cup seal with expander. Sealing means 158 slidingly engages 
the inner surface 73 of shell 66, providing a second slidable support 
point for the movable portion 64 of cartridge 56. 
The next member telescoped onto shaft 100 is a elongated sleeve member 160 
having first and second axial ends 162 and 164, respectively. End 162 has 
a transverse slot 166 which communicates with a machined relief 168 on the 
inside diameter of sleeve member 160 which surrounds the transverse 
opening 124 in shaft 100. Slot 166, relief 168, and openings 124 and 134 
enable the movable portion 142 of check valve 138 to be responsive to back 
pressure produced by the refrigerant condenser 51 via tubular member 50 
when three-way valve 10 is in the "heating" position shown in FIG. 4, as 
will be hereinafter explained. 
The second end 164 of sleeve 160 is stepped to receive a first elastomeric 
valve seal 170, which cooperates with the stationary valve seat surface 88 
of the first annular member 74, as shown in FIG. 4, when three-way valve 
10 is in the "heating" position. 
A spacer member 172 has a first axial end 174 which holds the first valve 
seal 170 in the desired position, and a second axial end 176. A second 
elastomeric valve seal 178 is disposed against the second axial end 176 of 
spacer member 172 and held in position by an elastomeric washer 180 and 
the nut 146. The second valve seal 178 co-operates with the stationary 
valve seat surface 90 of the second annular member 76 when three-way valve 
10 is in the "cooling" position shown in FIG. 3. 
Reviewing the structure of three-way valve 10 described to this point, it 
will be noted that the housing 12 has no valve parts subject to wear, and 
that the cavity 54 defined by housing 12 is cylindrical with no parts 
which interfere with the axial placement or removal of the cartridge 56. 
In the assembly of three-way valve 10, the intermediate body member 20 and 
the second end bell member 28 are joined at a joint sealed via gasket 
member 36, and held in assembled relation with screws 39. The cartridge 56 
is then inserted into cavity 54 such that the second axial end 104 of 
shaft 100 enters opening 118 in the second end bell member 28. The 
stationary portion 62 of cartridge 54 is then rotated until indexing pin 
98 enters opening 97 in the second annular member 76. Belleville springs 
58 and helical spring 60 are positioned inside the first end bell member 
26, gasket 34 is positioned between the first end bell member 26 and the 
intermediate body member 20, and screws 38 are positioned and actuated to 
firmly secure the first end bell member 26 to the intermediate body member 
20. The Belleville springs 58 bias the stationary portion 62 of cartridge 
56 against the second end bell member 28, and the helical spring 60 
contacts surface 150 of piston 148 to provide a force which biases the 
movable portion 64 towards the second end bell member 28. 
The relatively high discharge pressure of the refrigerant compressor is 
communicated to the first pressure receptive side 150 of piston 148 via an 
opening 182 in the side wall of tubular member 42, a longitudinally 
extending opening 184 through the outer wall of intermediate body member 
20, and an opening or groove 186 in the first end bell member 26. The 
outside diameter of shell 66 and the surrounding inside diameter of the 
first end bell member 26 are selected to provide a small spacing 188 
between them, sufficient to continue the pressure path from the aligned 
openings 182, 184 and 186 to the first pressure receptive surface 150 of 
piston 148. 
When refrigerant conduit 190 joining opening 48 to the suction side S of 
the refrigerant compressor 43 is closed by the de-energized position of 
solenoid valve 55, as shown in FIG. 3, the bias of spring 60 plus the 
compressor discharge pressure on surface 150 of piston 148 provides a 
force which exceeds the force created by the compressor discharge pressure 
on surface 152 of piston 148. This results in a differential force which 
moves the movable portion 64 of cartridge 56 to the cooling position of 
three-way valve 10 shown in FIG. 3. In the cooling position of three-way 
valve 10 the second elastomeric valve seal 178 is firmly seated against 
the tapered surface 90 to close the refrigerant path to the tubular member 
52, and thus to the evaporator 53, while opening the refrigerant path to 
the tubular member 50 and condenser 51. Thus, refrigerant entering 
three-way valve 10 via tubular member 42 enters cartridge 56 via opening 
92 and it flows out of three-way valve 10 to the refrigerant condenser 51 
via tubular member 50. 
When refrigerant control 57 senses that a heating cycle should be initiated 
in order to hold a selected set point temperature in a served spaced, and 
also when control 57 determines that the evaporator 53 requires 
defrosting, control 57 energizes solenoid valve 55 to actuate it to its 
open position and vent the refrigerant providing the pressure on side 150 
of piston 148 to the low side S of compressor 43. The force provided by 
compressor discharge pressure on side 152 now exceeds the force provided 
by the bias of spring 60 and the low suction pressure, providing a 
resulting force which moves the movable portion 64 of cartridge 56 to the 
heating position shown in FIG. 4. In the heating position, elastomeric 
valve seal 170 firmly seats against tapered valve seat surface 88. This 
position of three-way valve 10 closes the refrigerant path to the 
condenser 51 and opens it to the evaporator 53. 
With certain refrigerants during certain operating conditions the pressure 
in condenser 51 may rise during a heating cycle and add additional 
pressure to the second side 152 of piston 148. Then, when control 57 
closes solenoid valve 55 to switch three-way valve 10 back to the cooling 
position shown in FIG. 3, the force acting upon surface 150 provided by 
the combination of the bias provided by spring 60 and the condenser 
discharge pressure may not exceed the force provided by the combination of 
the compressor discharge pressure plus the back pressure from the 
condenser 51. Thus, three-way valve 10 will not shift back to the cooling 
position shown in FIG. 3. The pressure limiting check valve 138 prevents 
this condition from occurring. The back pressure from condenser 51 is 
applied to the movable portion 142 of check valve 138, and if it exceeds 
the bias of spring 144 the movable portion 142 is lifted from the seating 
lip 136, venting the back pressure to the low side S of compressor 43 via 
the control opening 141 in fixed portion 140 of check valve 138. 
When three-way valve 10 requires servicing in the field, it is only 
necessary to remove screws 38, the first end bell member 26, springs 58 
and 60 and gasket 34. No solder joints are broken. A cartridge removal 
tool is then threadably engaged with tapped opening 126 in the first axial 
end 102 of shaft 100, and the cartridge 56 is withdrawn from cavity 54. A 
new or rebuilt cartridge is then inserted into cavity 54, as hereinbefore 
described relative to the assembly of three-way valve 10. All of the valve 
parts subject to wear are thus removed when the used cartridge 56 is 
removed, and the three-way valve 10 is easily reassembled using a new 
gasket 34 and a new or rebuilt cartridge 56.