Patent Description:
Compressors increase the pressure of a compressible fluid (e.g., air, gas, etc.) by reducing the volume of the fluid. Often, compressors are staged so that the fluid is compressed several times in different stages, to further increase the discharge pressure of the fluid. As the pressure of the fluid increases, the temperature of the fluid also increases.

In some compressors, the compressed fluid may be cooled in between stages. Compressors are divided into positive displacement compressors and dynamic compressors.

Examples of known valve assemblies for fluid compressor systems are disclosed in <CIT>, <CIT>, <CIT> and <CIT>.

According to a first aspect of the present invention, there is provided a pneumatic inlet/blowdown valve assembly for a fluid compressor system. The assembly comprises an inlet valve wherein a working fluid enters the fluid compressor system, the inlet valve regulating a flow of the working fluid into a first air-end of the fluid compressor system; a blowdown valve couplable to a discharge of a second air-end of the fluid compressor system, the blowdown valve configured to release a pressure within the fluid compressor system; and a piston-cylinder actuator in communication with the inlet valve and the blowdown valve. The piston-cylinder actuator includes: a first piston housed within a first cylinder; and a second piston housed within a second cylinder. The first piston and the second piston are axially connected by a piston shaft. The first cylinder defines a first chamber at a first side of the first piston and a second chamber at a second side of the first piston. The second cylinder defines a third chamber at a first side of the second piston and a fourth chamber at a second side of the second piston. The piston-cylinder further includes a compression spring disposed within the fourth chamber. The first piston and the second piston are configured to be actuated between an idle state wherein the inlet valve is closed to stop the flow of the working fluid into the fluid compressor system and the blowdown valve is open to depressurize the fluid compressor system, and an actuated state wherein the inlet valve is open to allow the flow of the working fluid into the first air-end and the blowdown valve is closed to allow a pressure buildup in the fluid compressor system.

The pneumatic inlet/blowdown valve assembly may further include a blowdown valve piston cap disposed within the blowdown valve, the blowdown valve piston cap coupled to the piston shaft and configured to open and close the blowdown valve.

Optionally, the assembly includes a first solenoid valve connectable between the inlet valve and the first air-end, the first solenoid valve in communication with the fourth chamber.

The first solenoid valve may supply a first stage vacuum pressure to the fourth chamber of the piston-cylinder actuator, the first stage vacuum pressure compressing the compression spring and actuating the first piston and the second piston from the idle state to the actuated state.

Optionally, the assembly includes a second solenoid valve connectable to an interstage pressure tap between the first air-end and the second air-end, the second solenoid valve in communication with the first chamber and the third chamber.

The second solenoid valve may supply an interstage pressure to the first chamber and the third chamber of the piston-cylinder actuator when energized, the interstage pressure maintaining the first piston and the second piston at the actuated state while the fluid compressor system is loading.

Optionally, the assembly includes a quick exhaust valve connected between the second solenoid valve and the first chamber and third chamber, wherein when the second solenoid valve is de-energized, the quick exhaust valve is configured to vent the pressure buildup in the first chamber and the third chamber, and the compression spring pushes the first piston and the second piston to the idle state.

Optionally, the piston shaft of the assembly is mechanically coupled to a slider crank mechanism that moves the inlet valve between an open position and a closed position.

According to a second aspect of the present invention, there is provided a fluid compressor system for compressing a working fluid. The system comprises a first air-end operable to receive and compress the working fluid; a second air-end operable to receive the working fluid from the first air-end and further compress the working fluid; and a pneumatic inlet/blowdown valve assembly according to the first aspect of the present invention.

Optionally, the fluid compressor system may be an oil-free rotary (OFR) compressor.

Although the subject matter has been described in language specific to structural features and/or process operations, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above.

Fluid compressors systems increase the pressure of a working fluid such as air or gas, and are widely used in a variety of industries such as in construction, manufacturing, agriculture, energy production, etc. Positive displacement compressor systems such as, but not limited to, rotary screw compressors, confine a successive volume of the working fluid within a closed space that is mechanically reduced, compressing the working fluid and increasing the working fluid's pressure and temperature. Types of rotary screw compressors include contact-cooled rotary (CCR) compressors, also called oil-injected rotary screw compressors, and oil-free rotary (OFR) compressors.

In fluid compressor systems, capacity control is employed to regulate the capacity of the compressed working fluid, where the capacity of the fluid compressor system is the quantity of working fluid at which the fluid compressor system will operate at a specific discharge pressure. In rotary screw compressors, different capacity control schemes are used, including start/stop, load/unload, modulation, variable displacement, and variable speed. Load/unload (having a load operation and an unload operation) and modulation capacity control schemes are controlled through an inlet valve operating in synchrony with a blowdown valve.

The use of pneumatic valves has benefits when compared to other types of valves such as hydraulic valves and diaphragm valves. For example, pneumatic valves may be less prone to leaking, are compact in size, and are easier to service as pneumatic lines can be vented directly to the atmosphere, whereas oil lines in hydraulic valves must be drained to a sump prior to any service operation. CCR compressors include a separation tank which stores compressed air that can be used as a source for actuation of pneumatic valves, including the inlet valve. A minimum pressure check valve (MPCV) maintains a minimum system pressure inside the separator tank. Using this minimum system pressure aids the pneumatic actuation of the inlet valve during a cold start or even when the system changes from an unload state to a load state. Thus, most inlet valves in CCR compressors are pneumatically operated.

OFR compressor systems do not typically have a separation tank with minimum pressure check valve. Hence typically an OFR compressor systems do not have a minimum system pressure when starting from a cold start to actuate a pneumatic inlet valve. In OFR compressor systems, a second stage outlet is connected to the blowdown valve or unloader valve for the unloading operation or to start the OFR compressor systems with a minimum back pressure. The inlet valve and blowdown valve operations are synchronized in such a way that inlet valve will be in a closed condition (Normally Closed) and the blowdown valve will be in an open condition (Normally Open). OFR compressor systems may not develop a pressure buildup unless the blowdown valve is closed. Since both the inlet valve and blowdown valve operations are synchronized, finding a source of energy for closing the blowdown valve is necessary to provide a completely pneumatic inlet valve for an OFR compressor system.

Accordingly, the present disclosure is directed to a fluid compressor system having a pneumatic inlet/blowdown valve assembly that utilizes a combination of pneumatic pressure and vacuum available in the fluid compressor system for the actuation of the inlet valve and the blowdown valve. The inlet valve is integrated with the blowdown valve, where their respective actuation is synchronized with the other.

Referring generally to <FIG>, a fluid compressor system <NUM> is shown. The fluid compressor system <NUM> includes a first air-end <NUM>, a second air-end <NUM>, and a pneumatic inlet/blowdown valve assembly <NUM>. The fluid compressor system <NUM> may include a motor <NUM> driving the first air-end <NUM> and the second air-end <NUM>. The first airend <NUM> receives a compressible working fluid (e.g., air, gas, etc.) and compresses the working fluid in a first stage compression process. This compression also increases the temperature of the working fluid.

In example embodiments, the fluid compressor system <NUM> includes a fluid filter <NUM> disposed upstream from the pneumatic inlet/blowdown valve assembly <NUM> and the first air-end <NUM>. The fluid filter <NUM> may filter particles from the working fluid and prevents particulate matter from entering the fluid compressor system <NUM>.

In example embodiments, the fluid compressor system <NUM> includes an intercooler <NUM> to cool down the working fluid delivered by the first air-end <NUM> and an interstage moisture separator <NUM> to separate moisture from the working fluid prior to entering the second air-end <NUM>. An interstage blowdown solenoid valve <NUM> may be coupled between the interstage moisture separator <NUM> and the second air-end <NUM> to vent an interstage pressure. In example embodiments (not shown), the fluid compressor system <NUM> may include an interstage venturi, also called a first stage venturi, coupled downstream from the first air-end <NUM> and upstream from the second air-end <NUM> to reduce pulsations within the compressed working fluid delivered by the first air-end <NUM>.

The second air-end <NUM> receives the working fluid delivered by the interstage moisture separator <NUM> and further compresses it. In example embodiments, the fluid compressor system <NUM> also includes a discharge venturi <NUM>, also called a second stage venturi, to reduce pulsations in the compressed fluid discharged from second stage compression process occurring in the second air-end <NUM>. After passing through the discharge venturi <NUM>, the working fluid may flow through a discharge check valve <NUM>, an after cooler <NUM>, and a second stage moisture separator <NUM>, prior to exiting the fluid compressor system <NUM> for delivery.

In the example embodiment shown in <FIG>, the pneumatic inlet/blowdown assembly <NUM> includes an inlet valve <NUM>, a blowdown valve <NUM>, a pistoncylinder actuator <NUM>, a first solenoid valve <NUM>, and a second solenoid valve <NUM>. The inlet valve <NUM> receives the working fluid entering the fluid compressor system <NUM> and regulates flow of the working fluid before it enters the first air-end <NUM>. In example embodiments, the inlet valve <NUM> includes a butterfly plate <NUM>. The butterfly plate <NUM> rotates between an open position and a closed position to respectively allow or block working fluid through the inlet valve <NUM>.

A blowdown valve inlet <NUM> of the blowdown valve <NUM> is coupled to the discharge venturi <NUM> at the discharge of the second air-end <NUM>. The blowdown valve <NUM> is configured to release the buildup pressure within the fluid compressor system <NUM> through a blowdown valve outlet <NUM> when the fluid compressor system <NUM> is in the unloading operation and the blowdown valve <NUM> is open. In example embodiments, the blowdown valve outlet <NUM> is coupled to a blowdown muffler <NUM> to reduce noise and/or a blowdown diffuser (not shown) to distribute the exhausting hot compressed working fluid.

The piston-cylinder actuator <NUM>, as shown in <FIG> and <FIG>, is mechanically coupled to the inlet valve <NUM> and the blowdown valve <NUM>. The piston-cylinder actuator <NUM> includes a first piston <NUM> housed within a first cylinder chamber <NUM>, and a second piston <NUM> housed within a second cylinder chamber <NUM>. The first cylinder chamber <NUM> has a first cylinder chamber end 133A and a second cylinder chamber end 133B. Likewise, the second cylinder chamber <NUM> has a first cylinder chamber end 135A and a second cylinder chamber end 135B. In example embodiments, the first piston <NUM> and the second piston <NUM> are axially connected by a piston shaft <NUM> having an axis 122A. The piston shaft <NUM> slides within the piston-cylinder actuator <NUM> in a linear motion along the axis 122A, supported by guide bearings <NUM>.

The first cylinder chamber <NUM> defines a first chamber C1 between a first side of the first piston 132A and the first cylinder chamber end 133A and a second chamber C2 between a second side of the first piston 132B and the second cylinder chamber end 133B. The second cylinder chamber <NUM> defines a third chamber C3 between a first side of the second piston 134A and the first cylinder chamber end 135A. The second cylinder chamber <NUM> defines a fourth chamber C4 between a second side of the second piston 134B and the second cylinder chamber end 135B.

The first piston <NUM> and the second piston <NUM> include at least one piston seal <NUM> disposed around an outer circumference of each respective piston. The at least one piston seal <NUM> prevents the escape of air from the first cylinder chamber <NUM>, between the first chamber C1 and the second chamber C2, and the second cylinder chamber <NUM>, between the third chamber C3 and the fourth chamber C4. In the example embodiment shown in <FIG> and <FIG>, the piston seals <NUM> are V-ring seals. In other example embodiments, the piston seals <NUM> may be U-rings, O-rings, flat seals, lip seals, guide rings, among others. The ring seals may be composed from Polytetrafluoroethylene (PTFE), nitrile, neoprene, ethylene propylene diene monomer (EPDM) rubber, a fluorocarbon rubber, or a combination thereof.

In example embodiments, a compression spring <NUM> is disposed within the fourth chamber C4, where the compression spring <NUM> is in contact with the second side 134B of the second piston <NUM> and second cylinder chamber end 135B of the second cylinder chamber <NUM>. The compression spring <NUM> biases the second piston <NUM> in a first direction away from the second cylinder chamber end 135B of the second cylinder chamber <NUM>, and towards the first cylinder chamber end 135A of the second cylinder chamber <NUM>.

In embodiments, the piston-cylinder actuator <NUM> includes spring supports 127A and 127B. Spring support 127A is defined on the second side of the second piston 134B. Spring support 127B is defined on the second end 135B of the second cylinder chamber <NUM>. Spring guides 127A and 127B guide spring <NUM>, keeping it in a position concentric with the piston shaft <NUM>, and attached to the second cylinder chamber <NUM> and the second piston <NUM>.

The pneumatic inlet/blowdown valve assembly <NUM> includes a slider crank <NUM> disposed within a slider crank chamber <NUM>. The piston-cylinder actuator <NUM> defines the slider crank chamber <NUM> between the first cylinder chamber <NUM> and the second cylinder chamber <NUM>. The slider crank <NUM> is coupled on one end to the butterfly plate <NUM> of the inlet valve <NUM> and on a second end to the piston shaft <NUM>. The slider crank <NUM> opens and closes the butterfly plate <NUM> of the inlet valve <NUM> depending on the position of the piston shaft <NUM>. As the piston shaft <NUM> moves from the idle state to the actuated state, the butterfly plate <NUM> is rotated within the inlet valve <NUM>, between a closed position, to an open position, respectively. The pneumatic inlet/blowdown valve assembly <NUM> also includes a blowdown valve piston cap <NUM> disposed within the blowdown valve <NUM> and coupled to the piston shaft <NUM>. The blowdown valve piston cap <NUM> is configured to open and close the blowdown valve <NUM> through the blowdown valve inlet <NUM>. As the piston shaft <NUM> moves from the idle state to the actuated state, the blowdown piston cap <NUM> is actuated within the blowdown valve <NUM>, between an open position, to a closed position, respectively.

During operation of the inlet/blowdown valve assembly <NUM>, the first piston <NUM> and the second piston <NUM> are configured to be actuated between an idle state and an actuated state. In the idle state, shown in <FIG>, the inlet valve <NUM> is closed to stop the flow of the working fluid into the first air-end <NUM> and the blowdown valve inlet <NUM> of the blowdown valve <NUM> is open to depressurize the fluid compressor system <NUM> through the blowdown valve outlet <NUM>. In the actuated state, shown in <FIG>, the inlet valve <NUM> is open to allow the flow of the working fluid into the first air-end <NUM> and the blowdown valve inlet <NUM> is closed to allow a pressure buildup in the fluid compressor system <NUM>.

In example embodiments, the fluid compressor system <NUM> is operated between an unload state and a load state by controlling electrical signals to energize and actuate the first solenoid valve <NUM> and the second solenoid valve <NUM> (not shown). The fluid compressor system <NUM> may remain in the unload state (or idle state) when the first solenoid valve <NUM> and the second solenoid valve <NUM> are in a de-energized state. In embodiments, both the first solenoid valve <NUM> and the second solenoid valve <NUM> are energized together to change the state of the fluid compressor system <NUM> to the load state. In other embodiments, the first solenoid valve <NUM> and the second solenoid valve <NUM> are energized asynchronously.

The first solenoid valve <NUM> of the pneumatic inlet/blowdown valve assembly <NUM> is connected between the butterfly plate <NUM> and the first air-end <NUM> and is connected to the fourth chamber C4 via a first connecting tube <NUM> as shown in <FIG>. At the start of the loading operation, the pneumatic inlet/blowdown valve assembly <NUM> is in the idle state, with the butterfly plate <NUM> of the inlet valve <NUM> closed. As the motor <NUM> is energized and reaches a maximum speed, a first stage vacuum pressure is built below the butterfly plate <NUM> and upstream of the first air-end <NUM>. The first solenoid valve <NUM> is energized, allowing the first stage vacuum pressure to flow into the fourth chamber C4 of the piston cylinder actuator <NUM>.

As the first stage vacuum is supplied to the fourth chamber C4, the compression spring <NUM> is compressed, pulling the second piston <NUM> towards the second cylinder chamber end 135B of the second cylinder chamber <NUM>. Thus, the piston shaft <NUM> moves the blowdown valve piston cap <NUM>, the first piston <NUM>, the second piston <NUM>, and the slider crank <NUM> into the actuated position. The blowdown valve piston cap <NUM> closes the blowdown valve inlet <NUM>, allowing the pressure within the fluid compressor system <NUM> to increase. The slider crank <NUM> simultaneously rotates the butterfly plate <NUM>, opening the inlet valve <NUM> to allow the working fluid to flow into the first air-end <NUM>, thereby compressing the working fluid and supplying an interstage pressure.

As the butterfly plate <NUM> completely opens, the first stage vacuum is supplied at a reduced amount into the fourth chamber C4. The actuated state of the piston-cylinder actuator <NUM> is maintained through the interstage pressure that the first air-end <NUM> supplies. In example embodiments, an interstage pressure tap 'B' is provided between the interstage moisture separator <NUM> and the second air-end <NUM>. In other embodiments, the pressure tap 'B' is provided between the first air-end <NUM> and the second air-end <NUM>. The interstage pressure is supplied to the first chamber C1 and the third chamber C3 via an inline check valve <NUM> mounted to an inlet port of the second solenoid valve <NUM> and further through the quick exhaust valve <NUM>, passing through channel <NUM>. The pressure buildup in the first chamber C1 and the third chamber C3 aid the first piston <NUM> and the second piston <NUM> to maintain the actuated position of the second cylinder chamber end 133B of the first cylinder chamber <NUM> and the second cylinder chamber end 135B of the second cylinder chamber <NUM>, respectively. The second piston <NUM> holds the compression spring <NUM> in a compressed position while the fluid compressor system <NUM> is loading, as shown in the example embodiment of <FIG>.

In example embodiments, an inline check valve <NUM> is coupled between the interstage pressure tap 'B' and the second solenoid valve <NUM> to restrict interstage vacuum action on the first chamber C1 and the third chamber C3 during startup of the fluid compressor system <NUM> or when the fluid compressor system <NUM> changes from the unloading operation to the loading operation.

In example embodiments, the pneumatic inlet/blowdown valve assembly <NUM> further includes a quick exhaust valve <NUM> connected between the second solenoid valve <NUM> and the first chamber C1 and third chamber C3 via a second connecting tube <NUM>. When the fluid compressor system <NUM> is set to the unloading operation, the second solenoid valve <NUM> is de-energized and the quick exhaust valve <NUM> rapidly vents the pressure buildup in the first chamber C1 and the third chamber C3, allowing the compression spring <NUM> to push second piston <NUM> along with the piston shaft <NUM> back to the idle state shown in <FIG>, where the inlet valve <NUM> is closed and the blowdown valve <NUM> is open to vent the pressure buildup of the fluid compressor system <NUM> through a second stage blowdown piping 'A'.

In example embodiments, the piston-cylinder actuator includes a vacuum setting screw <NUM> to manually adjust an unload vacuum for different package combinations of the fluid compressor system <NUM>. The linear adjustments set through the vacuum setting screw <NUM> pushes the piston shaft <NUM> forward in steps, moving the slider crank <NUM> which is coupled on the one end to the butterfly plate <NUM>. The setting of the vacuum setting screw may adjust the angular position of the butterfly plate <NUM> in steps to maintain optimum clearance between the butterfly plate <NUM> and a housing of the inlet valve <NUM> housing.

In example embodiments, the interstage pressure supplied to the first chamber C1 and the third chamber C3 via the second solenoid valve <NUM> to keep the blowdown valve <NUM> closed and the compression spring <NUM> compressed. In such embodiments, a larger piston-cylinder area may be used to balance the frictional forces on the first piston <NUM> and the second piston <NUM> to remain in the actuated state. Depending on the interstage pressure available, additional pistons (not shown) employing similar cylinder chamber arrangements may be disposed in the piston-cylinder actuator <NUM>. In example embodiments, the size of the compression spring <NUM> is selected based on the size of the second cylinder chamber <NUM>, so as the second piston <NUM> retracts sufficiently (e.g., completely) during the unload operation.

In other example embodiments (not shown), the pneumatic inlet/blowdown valve assembly <NUM> includes a vacuum-assisted spring return mechanism. In such embodiments, the second solenoid valve <NUM> includes a relief line that is connected back to the first stage vacuum pressure for quickly returning the pneumatic inlet/blowdown valve assembly to its idle state, wherein the compression spring <NUM> biases the blowdown valve piston cap <NUM> to open the blowdown valve <NUM>.

In example embodiments, the fluid compressor system <NUM> is an oil-free rotary (OFR) screw compressor. In other example embodiments (not shown), the fluid compressor system may be a contact-cooled rotary CCR screw compressor, a rotary vane compressor, a reciprocating compressor, a centrifugal compressor or an axial compressor. In other example embodiments, the pneumatic inlet-blowdown valve assembly <NUM> maybe incorporated or retrofitted with other equipment having a compression application, including but not limited to, heating, ventilation, and air conditioning (HVAC) systems, refrigeration systems, gas turbine systems, and so forth.

Claim 1:
A pneumatic inlet/blowdown valve assembly (<NUM>) for a fluid compressor system (<NUM>), comprising:
an inlet valve (<NUM>) wherein a working fluid enters the fluid compressor system (<NUM>), the inlet valve regulating a flow of the working fluid into a first air-end (<NUM>) of the fluid compressor system,
a blowdown valve (<NUM>) couplable to a discharge of a second air-end (<NUM>) of the fluid compressor system (<NUM>), the blowdown valve configured to release a pressure within the fluid compressor system,
and a piston-cylinder actuator (<NUM>) in communication with the inlet valve (<NUM>) and the blowdown valve (<NUM>), the piston-cylinder actuator including:
a first piston (<NUM>) housed within a first cylinder (<NUM>),
a second piston (<NUM>) housed within a second cylinder (<NUM>), the first piston (<NUM>) and the second piston axially connected by a piston shaft (<NUM>), the first cylinder (<NUM>) defining a first chamber (C1) at a first side (132A) of the first piston and a second chamber (C2) at a second side (132B) of the first piston and the second cylinder defining a third chamber (C3) at a first side (134A) of the second piston and a fourth chamber (C4) at a second side (134B) of the second piston,
a compression spring (<NUM>) disposed within the fourth chamber (C4),
and the first piston (<NUM>) and the second piston (<NUM>) configured to be actuated between an idle state wherein the inlet valve (<NUM>) is closed to stop the flow of the working fluid into the fluid compressor system (<NUM>) and the blowdown valve (<NUM>) is open to depressurize the fluid compressor system, and an actuated state wherein the inlet valve is open to allow the flow of the working fluid into the first air-end (<NUM>) and the blowdown valve is closed to allow a pressure buildup in the fluid compressor system.