Patent ID: 12234843

DETAILED DESCRIPTION OF THE INVENTION

The intended purpose of the following detailed description and the phraseology and terminology employed therein is to describe what is shown in the drawings, which include the depiction of and/or relate to one or more nonlimiting embodiments of the invention, and to describe certain but not all aspects of what is depicted in the drawings, including the embodiment(s) depicted in the drawings. The following detailed description also identifies certain but not all alternatives of the embodiment(s) depicted in the drawings. Therefore, the appended claims, and not the detailed description, are intended to particularly point out subject matter regarded to be aspects of the invention, including certain but not necessarily all of the aspects and alternatives described in the detailed description.

The technology, systems, and methods explained hereinafter are generally applicable, though not exclusively, to mobile utility machines including but not limited to systems and equipment capable of being mounted to or used in combination with various mobile service, municipal, utility, and military vehicles.

According to nonlimiting aspects of the invention, certain advantages can be accomplished by utilizing a purpose-built pulse width modulated proportional solenoid valve having an inlet and an outlet to control a compressor inlet valve of a compressor within a compressor system. Though described herein as an air compressor system, the following is also applicable to systems adapted to compress other gases. The compressor may be an oil-injected rotary screw compressor having a compressor inlet housing containing the compressor inlet valve (for example, a poppet valve as represented in the drawings) for throughput control. A pressure differential pulls the inlet valve open when the compressor is engaged, which as used herein means rotors of the compressor are spinning. The inlet valve can be forced closed using controlled system pressure against the backside of the inlet valve, against the direction of incoming air flow into the inlet valve, to prevent atmospheric air from entering the compressor. An inlet of the pulse width modulated proportional solenoid valve receives a dry full system pressure signal, and the outlet is fluidically connected to an inlet control port on the compressor inlet housing. The inlet control port is fluidically connected to a cavity fluidically connected to the backside of the inlet valve through a closable passage. The inlet control port is also fluidically connected to a bleed orifice that exhausts to atmosphere. A pressure sensor senses service air pressure of compressed air discharged by the air compressor system to one or more downstream use loads intended by an operator, and sends or otherwise provides a pressure signal indicative of the magnitude of the sensed service air pressure to a controller. The controller compares the sensed service air pressure against an electronically set pressure target and generates a control signal proportionally responsive to the pressure signal for the pulse width modulated proportional solenoid valve to respond to. The proportional solenoid valve has multiple partially open positions—up to a theoretically infinite number—between a fully open position and a fully closed position of the proportional solenoid valve. The proportional solenoid valve opens and closes in proportion to the control signal to modulate the compressor inlet valve to maintain constant pressure to match the electronic set point. For example, if the pressure sensor senses a service air pressure that is less than the pressure target, the proportional valve fully or partially closes to cause the compressor inlet valve to open. If the pressure sensor reading is nearing target pressure, at target pressure, or over target pressure, the proportional solenoid valve will fully or partially open to fully or partially close the compressor inlet valve. The result is a usable service air pressure output that is consistent with a desired electronic pressure set point. Key benefits of utilizing an electronic pressure set point include precise maintenance of the set point and resulting efficiency improvements by not overshooting a target pressure to maintain an acceptable system pressure.

Referring now to the drawings,FIG.1shows a schematic view of an air compressor system2with a detailed section of a compressor inlet housing6and a compressor inlet valve3, which as noted above is represented in the drawings as a poppet valve. The air compressor system2includes an air compressor15, a drive22to drive the air compressor15, the inlet housing6that houses the compressor inlet valve3coupled to a compressor stator4via a poppet guide35, a pressure sensor31configured to sense the pressure of service air produced by the compressor15and supplied to a compressed air delivery system (not shown) through a service air outlet11, a logic controller16that receives a voltage signal that directly corresponds with sensed air pressure information from the pressure sensor31and generates control signals responsive to the received sensed air pressure information, and a pulse width modulated proportional solenoid valve23that receives the control signals from the controller16and controls flow of air from an internal system pressure section46to an inlet control port9of the inlet housing6. The proportional solenoid valve23adjusts to any of multiple positions from fully closed to fully open in response to the control signal, and thus indirectly proportional to the service air pressure sensed by the pressure sensor31. The inlet housing6includes a fixed bleed orifice8exhausting from a control pressure section13of the inlet housing6. A service air ball valve18separates the air compressor system2depicted inFIG.1from the service air outlet11, and therefore from the compressed air delivery system and use load, such as an air powered tool or machine, located farther downstream. The air compressor15may include compressor rotors (not shown) and/or other air compression mechanisms disposed inside the compressor stator4. The system2represented inFIG.1is particularly well suited for applications in which the air compressor15is an oil injected rotary screw compressor; though other types of air compressors may be used. The internal system pressure section46may be a portion of an air-oil separation system26, usually included in the air compressor15is an oil injected rotary screw compressor. The controller16is preferably an electronic digital controller, for example, including a digital processor including, memory, and programming instructions for controlling the digital processor.

In addition to the inlet control port9and control pressure section13, the compressor inlet housing6defines a supply air inlet10located on a frontside of the compressor inlet valve3and a compressor inlet pressure section12located on a backside of the compressor inlet valve3. The compressor inlet valve3opens and closes an air inlet flow channel12A within the compressor inlet pressure section12that extends between the supply air inlet10and a compressor air inlet49that connects the compressor inlet pressure section12to the compressor15The control pressure section13includes a control pressure channel17that fluidically connects the inlet control port9to an interior chamber19of a supporting cylinder, which serves as the poppet guide35that slidably receives a stem44of the compressor inlet valve3thereon. The compressor inlet valve3further comprises a poppet45on the stem44, and the poppet45is biased by a poppet return spring37to seat against a valve seat20. Because the stem44axially slides along the poppet guide (supporting cylinder)35, the poppet45disengages and engages the valve seat20to, respectively, open and close the air inlet flow channel12A.

The compressor inlet housing6and compressor stator4may take any arrangement(s) sufficient to accommodate the linear movement of the compressor inlet valve3, which travels in a preestablished linear path along the poppet guide35or as fixed to other styles of piston valve members. The poppet guide35may have the form of a cylinder as shown inFIG.1, forming the interior chamber19that is surrounded and covered by the stem44located on the backside of the compressor inlet valve3. The compressor inlet housing6and all fundamental features and components, such as the compressor inlet valve3, may be integrated with an inlet section of the compressor stator4or combined as a standalone assembly to be mounted to the compressor stator4. The integrated fixed bleed orifice8is disposed in the control pressure section13of the inlet housing6and is configured to exhaust to atmosphere. The bleed orifice8may be plumbed remotely. Though represented as being fixed, the bleed orifice8may be adjustable in some manner, such as with a set screw or needle valve.

The compressor inlet valve3provides throughput management for the air compressor system2. As noted previously, the compressor inlet valve3in this nonlimiting example is a poppet valve, whose stem44slides on the poppet guide35in a predetermined linear path along the axis of the poppet guide35. The poppet guide35is described above as having the form of a cylinder but may have another form suitable for guiding travel of the poppet45and providing a pathway for control air pressure to the backside of the poppet45. However, other types and styles of valves may be implemented. When the compressor15is in a normal, unpowered, state, the poppet45is pressed closed against the valve seat20, such as a sealing O-ring, by means of the poppet return spring37. The poppet return spring37presses against the backside of the poppet45and the interior of a base of the poppet guide35. Other arrangements of the compressor inlet valve3are also possible.

The air compressor15is driven by the drive22, which may be any type of power source suitable for providing the mechanical energy needed to drive the air compressor15in a manner sufficient to generate a desired flow of compressed air. Activation of the air compressor system2is dependent on the type of the drive22and the attendant drive design. Some applicable types of drives that can be used as driving sources include combustion engines (e.g., petroleum gas engines, diesel engines, natural gas engines, and propane engines), electric motors (e.g., AC motors and DC motors), and hydraulic motors. Depending on the drive type and input, the compressor15is activated in some capacity by a drive linkage, which may include, as nonlimiting examples, a clutch, a directly coupled drive, or a belt or chain driven by a motor or engine via pullies, gears, or sprockets.

When the air compressor15is activated (e.g., the rotors of a rotary screw compressor are spinning), the poppet45in the inlet housing6is pulled off its valve seat20by compressor intake vacuum caused by the volumetric flow generated by the rotors spinning, and the mass flow of air (or another gas) entering through the supply air inlet10. The supply air inlet10may be open to atmosphere to provide a supply of air at atmospheric pressure or may be connected to another supply of air or other gases. Typically, the air compressor15will have an intake filter (not shown) either mounted directly to some arrangement of the inlet housing6or remotely mounted with a vacuum-rated hose or tube connected to the inlet housing6. Air drawn into the compressor inlet housing6by the air compressor15enters through the supply air inlet10, flows through the open compressor inlet valve3and through the air inlet flow channel12A, and then enters the air compressor15where the air is compressed and pressurized. If the air compressor15is an oil-injected rotary screw air compressor, the air may be mixed with oil injected from an oil supply line27from an oil sump40of the air-oil separation system26. A resulting pressurized wet discharge stream33from the air compressor15is a mixture of compressed air and oil. The wet discharge stream33enters the air-oil separation system26, which is schematically represented inFIG.1as a generalized air and oil receiver tank and separation system that typically includes a pressure vessel and surrounding system that is configured to separate the air and oil in the wet discharge stream33received from the air compressor15. In this example, the air-oil separation system26can be considered as having three simplified sections: a wet air section43for receiving the compressed air and oil mixture of the wet discharge stream33, the internal system pressure section46for delivering dry system air to the service air outlet11, and the oil sump40for collecting system oil separated out from the wet discharge stream33by any suitable oil separation method, as nonlimiting examples, changes in velocity, changes in direction, gravity, and/or coalescing filter elements. Dry system air from the internal system pressure section46can be used for both service air delivered to the service air outlet11and for pneumatic control of the compressor inlet valve3.

The service air delivered to the service air outlet11is a dry compressed air that may be used to operate downstream use loads, as nonlimiting examples, pneumatic equipment such as impact wrenches, die grinders, angle grinders, air files, reciprocating saws, needle scalers, air sanders, and the like. A minimum pressure valve (MPV)29is depicted as separating the service air outlet11from the air compressor system2. A first function of the minimum pressure valve29is to prevent flow of pressurized air to the service air outlet11until a preselected minimum system pressure is met. This function ensures that ample system pressure is maintained for compressor oil circulation and other pneumatic control functions while the compressor15is operating. Another function of the minimum pressure valve29is to act as a check valve to prevent back flow of service air from a downstream use load into the compressor system2.

A method for maintaining system air pressure in the internal system pressure section46during operation of the compressor15is with pneumatic control over the compressor inlet valve3, which ultimately manages system throughput. In order to do this, the internal system pressure section46is operatively coupled with the inlet control port9of the inlet housing6so that system pressure from the internal system pressure section46can be used to control the operation of the compressor inlet valve3. In the arrangement shown inFIG.1, this control is accomplished with the pulse width modulated proportional solenoid valve23configured to control the position of the compressor inlet valve3during operation of the air compressor15. The proportional solenoid valve23is a normally open valve, shown here in its normally open position. The proportional solenoid valve23is schematically represented inFIG.1as including a valve member, such as a shuttle, piston, or flap, that can shift between a plurality of valve positions, including a fully open position, a full closed position, and one or more partial open positions (up to an infinite number) between the fully open and fully closed positions. The proportional solenoid valve23is also represented as including a solenoid that controls the position of the valve member at any of its valve positions. The solenoid of the proportional solenoid valve23is controlled by electronic control signals generated by the controller16so as to selectively position the valve member in any selected one of the possible valve positions. This compressor control scenario requires valve energization to load the compressor system2. When the proportional solenoid valve23is fully energized closed, system pressure in the internal system pressure section46will deadhead against the inlet of the proportional solenoid valve23, resulting in the proportional solenoid valve23being completely closed and thereby preventing movement of pressurized air from the internal system pressure section46to the inlet control port9. This allows the compressor inlet valve3to open as a result of the poppet45being pulled off its valve seat20by compressor intake vacuum created by the spinning compressor rotors, and remain open to allow atmospheric air to enter the air compressor15. This control method using a normally open proportional solenoid valve basic logic energizes the valve23to load the compressor15.

The proportional solenoid valve23can be partially opened in a theoretically infinite number of positions between the fully open position and the fully closed position in response to the control signal received from the controller16. As the proportional solenoid valve23is partially opened, some flow of system pressure air from the internal system pressure section46is allowed to pass through the proportional solenoid valve23to the inlet control port9and subsequently into the control pressure section13. System pressure air passing through the proportional solenoid valve23passes through an internal flow orifice30of the proportional solenoid valve23, which causes a pressure drop on the outlet side of the proportional solenoid valve23. The control pressure section13fluidly connects the inlet control port9with the backside of the poppet45via the interior chamber19of the poppet guide35. A passageway through the base of the poppet guide35couples the control pressure channel17with the interior chamber19of the poppet guide35. The poppet45closes the opposite end of the interior chamber19, such that control pressure from the control pressure section13is fluidly connected with the backside of the poppet45. The reduced pressure from the outlet of the proportional solenoid valve23permeates the control pressure section13of the compressor inlet housing6and is simultaneously vented to atmosphere through the bleed orifice8while some back pressure remains to press against the backside of the poppet45and thereby partially or fully close the compressor inlet valve3, depending on the volume of air allowed through the proportional solenoid valve23. The more air allowed to pass through the proportional solenoid valve23, the higher the pressure against the backside of the poppet45, and thus the more closed the compressor inlet valve3is maintained.

The forces acting on the poppet45during the operation of the compressor15are atmospheric pressure on the frontside of the poppet45from the supply air inlet10, pressure or vacuum within the air inlet flow channel12A, and the spring force of the poppet return spring37against the backside of the poppet45. The control pressure from the proportional control valve23can be controlled so as to balance the net sum of these three forces to hold the poppet45in some middle position between fully open and fully closed, thereby creating a reduced flow scenario. In addition, the control pressure from the proportional control valve23can be controlled so as to overcome the net sum of these forces to seal the poppet45against the valve seat20, thereby completely closing the compressor inlet valve3. The percentage that the proportional inlet valve23is open or closed is an indirect response to the service air pressure sensed by the pressure sensor31.

The pressure sensor31senses actual service air pressure, such as immediately downstream of the minimum pressure valve29. The pressure sensor31generates a sensed pressure signal that has a value directly correlated with the magnitude of the sensed service air pressure. The pressure sensor31may be any type of pressure sensor that is capable of generating a sensed pressure signal that is indicative of the service air pressure for use at the controller16.

As noted above, the controller16generates electronic control signals for controlling the position of the proportional solenoid valve23in response to the sensed pressure signal from the pressure sensor31. In one configuration, the controller16stores a target pressure setpoint. The target pressure setpoint can be selected and/or edited by a system operator through any suitable data entry mechanism, such as a keypad and/or graphic user interface, and stored, for example, in a digital memory.

In one arrangement, the pressure sensor31measures the actual service air pressure in the line between the minimum pressure valve29and service air ball valve18and outputs a voltage signal which directly correlates with the sensed service air pressure. The voltage signal is received by the controller16, which generates a control signal, such as an output current, to the proportional solenoid valve23in response to any difference between the target pressure value and the sensed service air pressure. Preferably, the control signal varies proportionally to the magnitude of the difference between the target pressure value and the sensed service air pressure. For example, in the case of the normally open proportional solenoid valve23, if the sensed service air pressure is below the target pressure set point, the proportional valve23will fully or partially close to allow the compressor inlet valve3to fully or partially open, depending on how close the sensed service air pressure is to the target pressure set point. In one arrangement, the controller16has programmatically adjustable variable ramp up and ramp down logic functions depending on the measured difference between the sensed service air pressure measured by the pressure sensor31and the preselected target pressure set point. A benefit of the control method described using a proportional solenoid valve23is that it is not dependent on knowing or maintaining an exact or actual position of the poppet45. Rather, the control method is responsive to the actual service air pressure being supplied to the end user. In this way, the variable control of the position of the valve member of the proportional solenoid valve23causes the compressor inlet valve3to open or close in proportion to the service air pressure downstream from the minimum pressure valve29.

In the arrangement ofFIG.1, the normally open proportional solenoid valve23is also responsible for both unloading the compressor system2and blowing down the compressor system2. When unloading the compressor system2, the compressor inlet valve3is held closed via control pressure from the proportional solenoid valve23while the air compressor15is still engaged, for example, the rotors are still spinning, which prevents atmospheric air from entering the compressor system2. During unloading, system pressure will begin to drop at a rate determined by the amount of control back pressure provided via the proportional solenoid valve23and the size of the bleed orifice8to atmosphere. An unloaded state is achieved when the service air discharge pressure target is met and is not dropping, which signifies that there is no operator demand for compressor output. The reduction of system pressure within the air compressor system2effectively reduces the load that the compressor rotors are working against, which reduces the load required from the drive22to drive the air compressor15.

System blowdown occurs when the air compressor15is disengaged, for example, either when the drive22is stopped or when the compressor15is decoupled via a clutch or some other capacity of drive coupling. System blowdown is complete when all excess pressure within the air compressor system2upstream of the minimum pressure valve29is vented to atmosphere. For example, all system pressure may be vented through the fixed bleed orifice8in the control pressure section13of the compressor inlet housing6. During a blowdown cycle, the poppet45is held closed against the valve seat20by the control pressure that is also venting through the control pressure section13and the bleed orifice8to atmosphere. This prevents any system oil present in the compressor stator4from flooding or overflowing the compressor air inlet49and passing through the compressor inlet valve3, which could otherwise be caused by backflow of pressurized air in the air compressor15during pressure normalizing with system pressure when the compressor rotors are stopped.

Preferably, reengagement of the compressor system2is inhibited or prevented during compressor system blowdown, for example, by a control routine implemented by the controller16or other switching mechanism, until a low-pressure threshold is met. This may prevent mechanical shock, and in some cases failure, which could otherwise be induced by engaging the compressor15with an existing pressure load present within the air compressor system2.

Turning now to the arrangement shown inFIG.2, another air compressor system2is shown that includes components of the air compressor system2ofFIG.1, with the difference being the use of a normally closed proportional solenoid valve50for compressor pneumatic inlet control between the internal system pressure section46and the inlet control port9(instead of the normally open proportional solenoid valve23ofFIG.1) and a separate blowdown valve52. Reference characters for similarly functioning components are carried over fromFIG.1toFIG.2, and reference is made to the previous description of these components without repeating such description here. Different and additional components have been given unique reference characters.

As before, the proportional solenoid valve50pneumatically controls the position of the compressor inlet valve3during compressor operation. However, in this arrangement the normally closed proportional solenoid valve50must be energized to unload the compressor system2. In the non-energized normally closed state of the proportional solenoid valve50, and during compressor operation, system pressure from the internal system pressure section46deadheads against the inlet of the proportional solenoid valve50, and the poppet45translates under the influence of compressor intake vacuum to its open position and remains open to allow atmospheric air to enter the air compressor15from the supply air inlet10. When the proportional solenoid valve50is fully or partially energized, the solenoid valve50fully or partially opens in proportion to the extent it is energized. This allows system pressure from the internal system pressure section46to pass through the solenoid valve50and into the inlet control port9and the control pressure section13to provide control pressure for the compressor inlet valve3, thereby partially or fully closing the poppet45against the valve seat20in the opposite direction of incoming atmospheric air from the supply air inlet10.

Similarly, as with the normally open proportional solenoid valve23ofFIG.1, the percentage, i.e., proportion between fully open and fully closed, that the proportional solenoid valve50is opened is in response to the pressure sensed by the pressure sensor31. The pressure sensor31senses actual service air pressure directly downstream of the minimum pressure valve29and outputs a voltage or other sensor signal proportional to the sensed service air pressure the controller16. The controller16sends a control signal, such as an electrical current, to the proportional solenoid valve50in response to, and preferably proportional to, any difference between the target pressure setpoint and the actual service air pressure sensed downstream of the minimum pressure valve29, as described previously. In some arrangements of eitherFIG.1orFIG.2, the actual service air pressure may be sensed upstream of the service air ball valve18. In other arrangements, the actual service air pressure may be sensed in the service air outlet11downstream of the service air ball valve18.

Unloading the air compressor system2with the normally closed proportional solenoid valve50is generally similar but opposite to the process used with the normally open proportional solenoid valve23. To unload the air compressor system2, the normally closed proportional solenoid valve50is fully or partially energized to overcome the net forces on the poppet45and thereby close the compressor inlet valve3. With the compressor inlet valve3closed, the air compressor system2is unloaded as previously described.

The proportional solenoid valve50is not capable of blowing down the compressor system2in all scenarios, specifically the intentional or unintentional shutdown of the compressor system2or parent machine because the proportional solenoid valve50defaults to the closed position in its normal state. Therefore, the aforementioned separate blowdown valve52is provided to facilitate blowdown. In this example, the blowdown valve52is a type of pneumatic piloted unloader valve. The blowdown valve52is coupled between the internal system pressure section46and the inlet control port9in parallel with the normally closed proportional solenoid valve50. The blowdown valve52receives a pilot signal54from the compressor inlet pressure section12. During operation of the air compressor system2, the compressor inlet pressure section12is under a vacuum. A combination of this vacuum and the system pressure to the inlet of the blowdown valve52from the internal system pressure section46holds an internal valve member (shuttle) within the blowdown valve52in a closed position such that the inlet of the blowdown valve52is not open to the outlet of the blowdown valve52. However, when the air compressor15is deactivated, for example, shut down or disengaged, such that the compressor rotors are no longer spinning, the pressure in the compressor inlet pressure section12begins to normalize with system pressure in the internal system pressure section46. This positive pressure provides the pilot signal54to the blowdown valve52, which moves the shuttle to fluidly connect the inlet with the outlet to open the blowdown valve52. This will effectively blow down the air compressor system2independent of the normally closed proportional valve50. System pressure is allowed through the blowdown valve52and becomes control pressure in the control pressure section13of the compressor inlet housing6. This control pressure holds the poppet45closed while the system depressurizes through the bleed orifice8in the control pressure section13, generally as described previously.

In either scenario ofFIG.1andFIG.2, an air storage vessel55, such as an air tank, may be provided that is operatively fluidly connected between the minimum pressure valve29and the service air ball valve18. Air storage in the air storage vessel55may reduce sudden pressure drops due to changes in operator demand. However, the air storage vessel55may be omitted, for example, if the application does not require a higher rate of volumetric flow than the air compressor system2is capable of at the required application pressure.

Some benefits of air compressor systems encompassing principles disclosed herein may include the ability to enable multiple pressure settings and use only a single valve. For example, a user may set a target pressure at the controller16and hold the target pressure depending on output demand. The pressure sensor31provides the input for the controller16. This arrangement may provide for smoother operation under variable load conditions to previously known mobile air compressor systems, and may have fewer wear parts than previously known mobile air compressor systems.

A compressor inlet valve3and controller16arrangement according to the principles disclosed herein may also be capable of providing benefits for over the road equipment by allowing a tighter tolerance of pressure to be held without an air tank, and/or allowing the modulation of flow/pressure to reduce overall horsepower draw of a mobile utility machine, such as an automobile, truck, etc. This may be particularly helpful for a multifunction machine carried on a mobile platform and with new battery powered systems.

An air compressor system2according to the principles disclosed herein may provide additional benefits when incorporated as part of a mobile utility machine, such as an air compressor, with or without a welding machine or other machines, carried on a utility vehicle, such as a truck, and/or adapted to be mobile and used in a temporary field setting without being permanently installed at the location of use. In such a use, the air compressor is typically driven by a single drive motor (serving as the drive22). The drive motor may be either the primary drive engine for the utility vehicle, or the drive motor may be a utility power engine or motor separate from the primary drive engine of the utility vehicle.

An air compressor system2according to the principles disclosed herein may provide additional benefits when incorporated as part of a multi-function mobile utility machine, such as a truck or other utility vehicle, that supports and/or has a single engine that provides drive power for multiple utility tools and/or functionalities, such as welding, jumpstarting, air compressors, and/or AC power. For example, an air compressor system2according to the principles disclosed herein may be used in a method of air arc gouging (cutting) that utilizes arc cutting equipment as part of an air compressor-welder system of a mobile utility machine. The method may include providing a manual or automatic logic controller (e.g., such as the controller16), using the logic controller to select an operating mode for the air compressor-welder system, sensing an air pressure generated by the air compressor system2, and controlling an amount that the proportional solenoid valve23or50opens to control flow of supply air into the air compressor15in proportional response to the sensed air pressure. The method may be used to control and/or limit and/or be controlled and/or limited by selected welding maximum limits. By utilizing an air compressor system2according to the principles disclosed herein, it may be possible to reduce the horsepower load required from a single engine on a multi-function mobile utility machine to allow more than one function to occur at a time while using the machine.

In another particular application, an air compressor system2according to the principles disclosed herein may be useful for implementation in a battery-driven air compressor system, in which the air compressor15is driven off battery power (rather than an engine) as the drive22. For example, an air compressor system2according to the principles disclosed herein may be used in a method of reducing battery usage from a portable multifunction air compressor (PMAC) system that is part of a mobile utility machine. The method may include sensing an air pressure generated by the air compressor15and controlling an amount that the proportional solenoid valve23or50opens to control flow of supply air into the air compressor15in proportional response to the sensed air pressure. The method may include using a logic controller (e.g., such as the controller16) to manually or automatically select an operating mode of the PMAC system.

In view of the above description according to general and nonlimiting aspects, it can be seen that the use of a proportional solenoid valve23or50to provide variable control of atmospheric air into, and ultimately out of, a compressor system2is disclosed. The proportional solenoid valve23or50may be used with many different variations and implementations. For example, the proportional solenoid valve23or50may be used in conjunction with software program logic, may be used with compressor systems in multifunction machines for compressor system efficiency and overall system load management, may be used with compressors systems in mobile utility systems, including but not limited to systems mounted to various mobile service, municipal, utility, and military vehicles, may be used with a bleed orifice8sized to pair with compressor systems of capacity up to at least 250 CFM, and/or may be used with compressors in multifunctional machines to manage system load and compressor output.

An air compressor system2according to this disclosure may provide compressor output pressure control and/or capacity control inputs and outputs. For example, an air compressor system2according to this disclosure may include the pressure sensor31to measure service air discharge pressure to provide an input signal to the controller16for output to the proportional solenoid valve23or50. An air compressor system2according to this disclosure may include the pressure sensor31to measure system air pressure as an input to a minimum unload pressure input signal to the controller16for output to the proportional solenoid valve23or50. An air compressor system2according to this disclosure may include the pressure sensor31to measure system air pressure as an input signal to the controller16as an indication of compressor load consumption.

An air compressor system2according to this disclosure may provide a variety of operational capabilities. As nonlimiting examples, the system2may provide pulse width modulation control over an electronic proportional solenoid valve23or50in conjunction with a feedback logarithm, such as proportional integral derivative (PID) control, and/or a method of electronically signaling pneumatic inlet control of a compressor system2that can be directly mounted to or remotely mounted from the compressor system2, and/or a method of maintaining a precise pressure output based on an adjustable electronic control signal, and/or a method of variable capacity control of a compressor system2with a fixed compressor input speed, and/or a method of variably unloading a reciprocating compressor system2, and/or a method for variable unload between stages of a reciprocating compressor system, and/or a method to manipulate the position of reciprocating compressor head unloading valves via a control pressure signal, and/or a method of modulating the compressor inlet and capacity control over a single function mobile compressor system, and/or a method of electronically modulating a specific service air pressure setpoint, for example, when used in conjunction with a controller containing programmed control logic.

As previously noted above, though the foregoing detailed description describes certain aspects of one or more particular embodiments of the invention, alternatives could be adopted by one skilled in the art. For example, the compressor systems2and their components could differ in appearance and construction from the embodiments described herein and shown in the drawings, and functions of certain components of the systems2could be performed by components of different construction but capable of a similar (though not necessarily equivalent) function. As such, and again as was previously noted, it should be understood that the invention is not necessarily limited to any particular embodiment described herein or illustrated in the drawings.