Valve comprising a dual piston assembly and method of forming a valve

A valve for a refrigeration system and a method of forming a valve includes a dual piston assembly having an inner piston (44) and an outer piston (42) that are moveable relative to each other to control pressure equalization flow through the valve, and an adjustable control stem (66) engageable with the outer piston that enables a low fluid equalization flow when in a first position and a variably higher fluid equalization flow when in a variable second position. The inner piston has a plurality of bleed orifices (46, 48) that are openable by movement of the outer piston relative to the inner piston.

FIELD OF INVENTION

The present invention relates to refrigeration valves, and more particularly, to refrigeration valves used on compressor suction lines during a defrost cycle.

BACKGROUND

Refrigeration systems typically include a refrigerant which flows through a compressor which increases the pressure of the refrigerant, a condenser which condenses the refrigerant from a vapor form to a liquid form, an expansion valve for dropping the pressure, and an evaporator which absorbs heat and causes the refrigerant to vaporize. The compressor is configured to create a suction force that draws the refrigerant from the evaporator. During normal operation, the evaporator coils require defrosting. During the defrost cycle, the compressor suction being applied to the evaporator must be temporarily stopped.

Conventionally, valves have been used to stop the suction by arranging the valve to be normally open to flow without a pressure drop across the valve required to keep the valve open. The valves are then closed by controlling an external energy source such as the hot gas used for defrosting the evaporator coils. However, after the defrost cycle has been completed, conventional valves may be disadvantageous in failing to prevent the main suction from being re-applied to the evaporator too quickly. A quick re-application of suction in the system may consequently cause damage to system components.

Prior attempts to prevent the overly quick reassertion of suction have included providing valves that use replaceable orifices that enable the rate of pressure equalization across the valve to be adjusted. The replaceable orifices may be changed by opening the valve and modifying features inside the body of the valve. However, modifying the valve requires isolating the valve and opening the refrigerant flow path which is inefficient and may cause damage to system components.

SUMMARY OF INVENTION

The present invention is directed towards valves used in a refrigeration system, and more particularly to a valve that is arranged between an evaporator and a compressor of a refrigeration system. The valve is used to stop suction from the evaporator to the compressor during a defrost cycle of the evaporator and resume the suction after the defrost cycle is completed. The valve advantageously enables changing of a pressure equalization bleed rate of the valve, which allows the valve to resume full flow suction when a predetermined pressure differential across the valve is reached. Accordingly, the valve prevents opening the valve too quickly which otherwise may cause damage to the system components.

A dual piston assembly having an inner piston and an outer piston is arranged in the valve, and a control stem is arranged to limit movement of the outer piston. The inner piston and the outer piston are moveable for opening and closing the valve. The inner piston and the outer piston are also moveable relative to each other such that bleed orifices formed on the inner piston may be opened by movement of the outer piston away from the inner piston when the valve first moves toward an open position to enable flow across the valve.

At least one bleed orifice is formed on the inner piston. A plurality of bleed orifices may be formed on the inner piston. The control stem is positioned to either enable a low equalization flow across the valve during which a minimum pressure-equalization flow path is opened, or a pressure-equalization flow path of progressively increasing area until a maximum flow path is opened. A person operating the valve can quickly and easily adjust the rate of pressure-equalizing flow through the valve by changing the position of the control stem without modifying any additional components of the refrigeration system. Being able to externally adjust the rate of pressure-equalizing flow through the valve effectively enables optimization of the defrost cycle for the evaporator, resulting in less wear on the system components and improved overall system efficiency.

Additionally, the valve is advantageous in that the piston assembly and the control stem are arranged in a module assembly that is insertable into a valve body of the valve. The module assembly includes the valve seat, and the valve body includes the inlet and outlet of the valve. By arranging the piston assembly and the control stem in the module assembly, the components may be used with different valve bodies. For example, the module assembly may be removed from a first valve body and reused with another valve body. Thus, the valve body may be secured or welded into the refrigeration system and remain free of wear components.

Still another advantage of the valve is that an external visual indicator of the position of the control stem is provided. The control stem may include a plurality of grooves that are positioned relative to a stop ring on the control stem. Additionally, a set-point collar may be used to identify a set position of the control stem. The person operating the valve may thus easily see the position of the control stem and adjust the position for either a low equalization flow across the valve or a higher equalization flow, depending on the requirements of the application for the valve.

According to an aspect of the invention, a valve includes a valve body, a dual piston assembly having an inner piston and an outer piston that are moveable relative to each other to control pressure equalization flow through the valve body, and an adjustable control stem engageable with the outer piston that enables a low fluid equalization flow across the valve when in a first position and a progressively increasing fluid equalization flow across the valve when adjusted to a variable second position. The inner piston has a first set of bleed orifices and a second set of bleed orifices that are openable by movement of the outer piston relative to the inner piston. The first set of bleed orifices are open during the low fluid equalization flow, and the first set of bleed orifices and a variable portion of the second set of bleed orifices are open during the high fluid equalization flow.

According to another aspect of the invention, a method of forming a valve includes arranging a dual piston assembly having an inner piston and an outer piston that are moveable relative to each other to control pressure equalization flow through the valve body, arranging an adjustable control stem that is engageable with the outer piston and enables a low fluid equalization flow across the valve when in a first position and a high fluid equalization flow across the valve when in a second position, and forming a plurality of bleed orifices on the inner piston that are openable by movement of the outer piston relative to the inner piston.

Other systems, devices, methods, features, and advantages of the present invention will be or become apparent to one having ordinary skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims.

DETAILED DESCRIPTION

Aspects of the present invention relate to valves used in refrigeration systems, and particularly to a valve that is used to prevent refrigerant flow during a defrosting cycle of an evaporator in a refrigeration system. Referring first toFIG. 1, a schematic drawing of an exemplary refrigeration system10is shown. The refrigeration system10includes a compressor12, a condenser14, an expansion valve16and an evaporator18that are arranged along a refrigerant fluid conduit loop20. During normal operation, fluid flows continuously along the refrigerant fluid conduit loop20. The compressor12is configured to create a suction force that draws the refrigerant from the evaporator18along a suction line22during normal flow of the refrigerant through the refrigerant fluid conduit20.

At predetermined periods during normal operation of the refrigeration system10, the evaporator coils will undergo a defrosting cycle which can be performed using hot gas from the compressor12. During the defrost cycle, the suction force along the suction line22is temporarily stopped using a valve28arranged along the suction line22between the compressor12and the evaporator18. The valve28may be a suction stop valve. The valve28is also arranged to receive hot gas from the compressor12for operation of the valve28.FIGS. 2-8show different positions of the valve28during normal operation, the defrost cycle, and resuming normal operation after the defrost cycle has completed.

Referring first toFIGS. 2-3,FIG. 2shows a full flow open position of the valve28andFIG. 3shows a closed position of the valve28. The valve28includes a valve body30having an inlet32and an outlet34that is in fluid communication with the inlet32through the valve body30. The valve body30further includes a valve seat36that is arranged between the inlet32and the outlet34and openable and closeable for enabling fluid flow and preventing fluid flow through the valve28. The valve28includes a bonnet38that is arranged for connection to the valve body30. The bonnet38additionally receives all remaining components of the valve28forming a module assembly39, as indicated inFIG. 3, that is securely connected to the valve body30when assembled, and also removable from the valve body30. Thus, the valve body30, which may be secured or welded into the refrigeration system10, is advantageously free of wear components. The bonnet38is arranged on an open end of the valve body30, and a valve cartridge40is secured to the bonnet38of the module assembly39using any suitable connection mechanism, such as a threaded connection.

The valve cartridge40houses and guides a piston assembly42,44having an outer piston42and an inner piston44that are arranged in the module assembly39. The outer piston42has an outer diameter that surrounds an outer diameter of the inner piston44such that the outer piston42may be in the form of a sleeve arranged over the inner piston44. The inner piston44and the outer piston42are arranged concentrically along a longitudinal axis and are axially moveable relative to each other.

The inner piston44has a plurality of bleed orifices46,48formed on the external surface of the inner piston44that enable fluid flowing through the suction valve28to pass therethrough. A first set of bleed orifices46is arranged at a lower portion of the inner piston44, and a second set of bleed orifices48is arranged at an axially upper portion of the inner piston44such that the first set of bleed orifices46and the second set of bleed orifices48are axially spaced relative to each other. Any suitable number of bleed orifices46,48may be provided. The second set of bleed orifices48are larger than the first set of bleed orifices46. In an exemplary embodiment, the first set of bleed orifices46may be circular in shape and the second set of bleed orifices48may be elongated in the axial direction.

The sets of bleed orifices46,48may be sequentially opened by movement of the outer piston42relative to the inner piston44. When the outer piston42moves away from the inner piston44, the first set of bleed orifices46may be first opened. As the outer piston42moves farther away from the inner piston44, the second set of bleed orifices48may then be opened in addition to the first set of bleed orifices46. Accordingly, when both sets of bleed orifices46,48are open, a greater flow of fluid passes through the piston assembly42,44.

The outer piston42is arranged at an interface surface50of the inner piston44, and a spring52is arranged at a second end or bottom end54of the inner piston44. The spring52extends through an inner chamber56of the inner piston44and is engageable between a bottom portion of the valve cartridge40and the upper inner surface of the inner piston44. The spring52is arranged to normally bias the valve28in an open position to provide a minimal pressure drop during normal operation, as shown inFIG. 2. The spring52exerts a force on the piston assembly42,44. When in the open position shown inFIG. 2, the valve28enables full fluid flow from the evaporator18through the valve28to the compressor12during normal operation of the refrigeration system20, as shown inFIG. 1.

Operation of the valve28may be controlled through a hot gas port58arranged in the bonnet38. The hot gas port58of the valve28is configured to receive pressurized gas from the discharge line26of the compressor12, as shown inFIG. 1. The flow through the hot gas port58is controlled using any suitable actuation mechanism. For example, a solenoid60may be used and the solenoid60may be configured to open and close a corresponding valve62that is in fluid communication between the hot gas port58and a piston chamber64in which the piston assembly42,44is moveable. The piston chamber64is also formed in the module assembly39and is arranged above the outer piston42. The solenoid60may be energized to supply pressurized gas to the valve28and de-energized to cease supply of the pressurized gas.

A control stem66is arranged at an end of the module assembly39and extends through the module assembly39into the piston chamber64. The control stem66is formed as a separate component from the module assembly39and is formed as an elongated body. The control stem66is at least partly housed in and securely connected to the bonnet38at a location above the piston assembly42,44. The control stem66may be threaded to the bonnet38and is sealed using a packing nut assembly68that is radially arranged between the control stem66and the bonnet38. The control stem66has a first end70that is positioned within the piston chamber64for engagement by the outer piston42to prevent travel of the outer piston42past a predetermined position. A second end72of the control stem66that is opposite the first end70extends outwardly from the bonnet38and away from the piston assembly42,44. The control stem66may interface with a stem lift tube74that is part of the outer piston42and is arranged in the piston chamber64. The stem lift tube74enables the outer piston42to be drawn open. Using the stem lift tube74enables the valve28to be manually set to ensure flow across the valve28.

The position of the control stem66relative to the piston assembly42,44is advantageously adjustable such that the control stem66may be externally adjusted to adapt the valve28for different system pressure-equalization flow rates without adjusting the other components in the valve28. The position of the control stem66is fixed when assembled, but the control stem66may be moved axially toward and away from the piston assembly42,44. In an exemplary embodiment, the control stem66may be manually moved by an operator of the valve28. In alternative embodiments, the control stem66may be automatically moved in response to the detection of changing system conditions using suitable position sensors and pressure sensors. The position of the control stem66determines whether only the first set of bleed orifices46formed on the inner piston44is to be opened when the outer piston42moves away from the inner piston44, or both the first set of bleed orifices46and a variable portion of the second set of bleed orifices48are to be opened.

For example, when the valve is allowed to open while under high pressure differential conditions, low equalization flow through the first set of bleed orifices46is opened when the control stem66is arranged at a predetermined first distance relative to the piston assembly42,44, as shown inFIG. 4. If high equalization flow across the valve28is desirable, the control stem66is then adjusted to a second position in which the control stem66is arranged at a distance relative to the piston assembly42,44that is greater than the first distance. The outer piston42then has a greater distance of travel relative to the inner piston44and moves further to open both sets of bleed orifices46,48.

The valve28may also include at least one external visual indicator such that the position of the control stem66is visually displayed to the valve operator. The valve28may also include a set-point collar75, as best shown inFIG. 2A, for fixing the position of the control stem66after adjustment. The external visual indicator may be in the form of grooves76formed on the external surface of the control stem66and a stop ring78that is arranged at the second end72of the stem66that protrudes out of the module assembly39. The stop ring78establishes the maximum inward position that the control stem66can be advanced to within the module assembly39.

The set-point collar75may be formed as a separate component and arranged around the second end72of the control stem66. The set-point collar75may be arranged to extend radially outwardly from the control stem66. The set-point collar75may be in the form of a suitable fastener, such as a collar with a set screw that is tightened after the axial position of the control stem66is set. When secured, the set-point collar75is fastened against the control stem66. Using the set-point collar75is advantageous for fixing the position of the control stem66after axially moving the control stem66into the suitable position for the proper equalization flow. The set-point collar75acts as an external position originating mechanism on the control stem66, such that the set-point collar75allows for adjusting the control stem66, for example, to manually ensure the valve open position, and returning the control stem66to the established control stem position.

The operation of the valve28will now be described with respect to the different positions of the valve28shown inFIGS. 2-8. The normally open position is shown inFIG. 2. When in the normally open position, the spring52pushes on the piston assembly42,44. The spring52extends through the inner chamber56of the inner piston44and against the upper inner surface of the inner piston44to bias the inner piston44away from the cartridge base36and against the outer piston42. Accordingly, full fluid flow occurs through the valve28from the inlet32to the outlet34for fluid flow from the evaporator18to the compressor12(as shown inFIG. 1). When the valve28is in the normally open position, the outer piston42is engageable against the control stem66. The refrigerant pressure drop across the valve28is minimized and refrigerant continuously flows through the refrigerant conduit loop20. Forming the valve28to be a normally open valve is advantageous in that little or no energy is required to maintain the valve28in the open position.

When the defrost cycle for the evaporator18is actuated, the normal fluid flow through the valve28is stopped and the valve28will move from the normally open position ofFIG. 2to the closed position ofFIG. 3. The fluid flow is stopped by energizing the solenoid60which opens the valve62to enable hot gas from the compressor12to flow from the hot gas port58to the piston chamber64to the top side of the outer piston42. In an exemplary embodiment, the pressurized gas may provide a pressure of around 150 pounds per square inch (PSI). The pressurized gas generates a force on the outer piston42to overcome the force of the spring52. The outer piston42is forced away from the control stem66and acts against the interface surface50of the inner piston44to force the inner piston44to compress the spring52. When the inner piston44reaches the stop at the valve seat36, the valve28is in the closed position such that fluid does not flow through the valve28and the suction line22(as shown inFIG. 1). The defrost cycle for the evaporator18may then be performed using the hot gas from the compressor12.

When the defrost cycle for the evaporator18is completed, suction in the suction line22is resumed by opening the stop valve28, such that the stop valve28will move from the closed position shown inFIG. 3to the initial opening position shown inFIG. 4. The valve28is advantageous in that the valve28is prevented from quickly opening to enable full flow through the valve28due to the initial high pressure difference across the valve28. Opening the valve28too quickly to resume the suction flow between the evaporator18and the compressor12may cause damage and wear to the system components, such as the evaporator18.

Opening the stop valve28is actuated by de-energizing the solenoid60to stop the flow of pressurized gas through the hot gas port58. If the pressure difference across the valve28is greater than a predetermined value, such as 15 psi, the inner piston44will remain in the closed position. The outer piston42will move away from the inner piston44to engage against the first end70of the control stem66. When the inner piston44remains in the closed position and the outer piston42moves away from the inner piston44, the first set of bleed orifices46formed in the side of the inner piston44is exposed to flow. The second set of bleed orifices48remains closed to flow. Thus, fluid flowing through the valve28initially passes only through the first set of bleed orifices46of the inner piston44. Accordingly, a low equalization flow of fluid80is generated across the valve28when the valve28is in the initial opening position shown inFIG. 4.

The valve28will remain in the initial opening position ofFIG. 4until the pressure differential across the valve28decreases to the predetermined value. When the pressure differential reaches the predetermined value, the valve28will then move from the initial opening position shown inFIG. 4to the full flow open position shown inFIG. 5. When the pressure differential has decreased, the closing force exerted on the inner piston44due to pressure will decrease such that the force of the spring52will bias the inner piston44toward the outer piston42such that the interface surface50of the inner piston44will engage against the outer piston42which is engaged against the control stem66. Accordingly, the control stem66prevents any further movement of the piston assembly and a full flow of fluid82occurs across the valve28.

The rate of flow through the valve28when in the initial opening position shown inFIG. 4may be increased by adjusting the position of the control stem66to the position shown inFIG. 6. The control stem66may be arranged farther outwardly relative to the piston assembly42,44such that the outer piston42travels farther away from the inner piston44to engage against the control stem66when the valve28moves to the initial opening position. As shown inFIG. 6, by enabling the outer piston42to move to a position that is farther away from the inner piston44relative to the initial opening position shown inFIG. 4, both of the first set of bleed orifices46and a variable portion of the second set of bleed orifices48formed on the inner piston44are opened such that fluid flow through the valve28passes through both sets of bleed orifices46,48to enable a progressively higher equalization flow of fluid84through the valve28as compared with the low equalization flow of fluid ofFIG. 4.

When the pressure difference across the valve28reaches the predetermined value, such as 15 psi, the valve28will move to the full flow open position shown inFIG. 7, which is similar to the full flow open position shown inFIG. 5. The closing force acting against the inner piston44due to pressure will decrease enabling the force of the spring52to bias the inner piston44away from the closed position and against the outer piston42which is engaged against the control stem66. Accordingly, the full flow of fluid82will occur through the valve28. Using the control stem66is advantageous in that the rate of flow through the inner piston44may be varied between the small flow rate, as shown inFIG. 4, and the higher flow rate, as shown inFIG. 6, by adjusting the position of the control stem66without adjusting additional components of the valve28. The operation of the valve28may thus be quickly and easily tuned externally by the valve operator for optimization of the defrost cycle in the refrigeration circuit.

A valve includes a dual piston assembly having an inner piston and an outer piston that are moveable relative to each other to control flow through the valve, and an adjustable control stem engageable with the outer piston that enables an adjustable reduced flow rate when the valve is opened under high pressure differentials. The inner piston has a first set of bleed orifices and a second set of bleed orifices that are openable by movement of the outer piston relative to the inner piston. The first set of bleed orifices are open during the low fluid equalization flow, and the first set of bleed orifices and a variable portion of the second set of bleed orifices are open during the higher fluid equalization flow.

The second set of bleed orifices may be larger than the first set of bleed orifices.

The valve may include a piston chamber and a pressurized gas port in fluid communication with the piston chamber.

The valve may include a solenoid that actuates the pressurized gas port.

The valve may include a biasing device that engages the inner piston to bias the valve in a position open to flow.

The valve may include a removable module assembly, wherein the dual piston assembly and the adjustable control stem may be arranged in the module assembly and removable relative to a valve body of the valve.

The valve may include a valve cartridge that houses the inner piston and the outer piston, and is connected to the module assembly.

The valve may include a biasing device that is engageable between the valve cartridge and the inner piston.

The control stem may be threaded to a bonnet of the module assembly, and the valve cartridge may be threaded to the bonnet.

The valve may include a packing nut assembly that seals the control stem relative to the bonnet.

The valve may include at least one visual indicator formed on the control stem that corresponds to a position of the control stem. The visual indicator may be externally visible outside of the valve.

The at least one visual indicator may include at least one of a plurality of grooves formed on the control stem and a stop ring that surrounds an end of the control stem.

The valve may include an adjustable member that is configured to establish at least one predetermined position for the control stem.

The control stem may interface with a stem lift tube arranged adjacent to the outer piston that draws the outer piston open.

A method of forming a valve includes arranging a dual piston assembly having an inner piston and an outer piston that are moveable relative to each other to control pressure equalization flow through the valve during periods of high pressure differential, arranging an adjustable control stem to be engageable with the outer piston and enable a low fluid equalization flow across the valve when in a first position and a higher fluid equalization flow across the valve when in a second position, and forming a plurality of bleed orifices on the inner piston that are openable by movement of the outer piston relative to the inner piston.

Forming the plurality of bleed orifices may include forming a first set of bleed orifices and a second set of bleed orifices. The first set of bleed orifices may be opened during the low fluid equalization flow, and the first set of bleed orifices and a variable portion of the second set of bleed orifices may be opened during the high fluid equalization flow.

The method may include arranging the adjustable control stem at a first distance relative to the dual piston assembly to enable the low fluid equalization flow, and arranging the adjustable control stem at a second distance relative to the dual piston assembly that is variably greater than the first distance to enable the variably higher fluid equalization flow.

The method may include arranging the dual piston assembly and the control stem in a module assembly and removably attaching the module assembly to a valve body of the valve.

The method may include providing an external visual indicator on the control stem that is externally verifiable to determine whether the control stem is in the first position or in a second position.

The method may include providing an external position originating mechanism on the control stem, adjusting the control stem, and returning the control stem to a predetermined control stem position using the external position originating mechanism after the control stem is adjusted.