Patent Publication Number: US-2009218173-A1

Title: Aerial Work Platform with Compact Air Compressor

Description:
BACKGROUND 
     The invention relates generally to temporary lift platforms and, more particularly, aerial work platforms (AWPs). 
     Aerial work platforms (AWPs) generally lift an operator to a desired location at a worksite. Often, the operator requires services, such as pressurized air and electricity. These services enable the use of air-driven tools and electrical tools. In many cases, the operator receives these services from stand-alone units on the ground, i.e., separate from the AWP. For example, the stand-alone units may include a stand-alone electrical generator and a stand-alone air compressor. Unfortunately, the operator must independently setup, move, and generally control both the AWP and the stand-alone units, thereby reducing efficiency at the worksite. The stand-alone units also increase costs due to the need for their own power sources (e.g., engine), control systems, enclosures, wheels, and so forth. Furthermore, the stand-alone air compressor generally includes a reciprocating type (e.g., piston and cylinder) air compressor, which requires a tank to hold the compressed air. Unfortunately, the reciprocating type air compressor requires considerable space to accommodate the tank. Without the tank, the reciprocating type air compressor does not provide a generally constant air pressure to the operator due to the reciprocating mechanism, e.g., piston in cylinder. Unfortunately, many air-driven tools require a generally constant air pressure. 
     BRIEF DESCRIPTION 
     An aerial work platform, in one embodiment, includes a platform, including a hydraulic lift, and a base unit. The base unit includes a combustion engine and a hydraulic pump driven by the combustion engine. The hydraulic pump may be configured to drive the hydraulic lift. The base unit may also include a rotary screw type compressor, belt-driven by the combustion engine. 
    
    
     
       DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIG. 1  is a diagrammatical side view illustrating an aerial work platform in accordance with certain embodiments of the present invention; 
         FIGS. 2-7  are diagrammatical side views illustrating a base unit and several components of the aerial work platform as illustrated in  FIG. 1  in accordance with certain embodiments of the present invention; and 
         FIG. 8  is a flowchart illustrating a process for controlling and operating the aerial work platform as illustrated in  FIGS. 1-6  in accordance with certain embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Turning now the drawings,  FIG. 1  illustrates an aerial work platform (AWP)  10  including a rotary air compressor  12 . Aerial work platform  10  also includes wheeled chassis  13  (e.g., chassis having four wheels) and aerial work platform base unit  14 . As will be discussed in further detail below, aerial work platform  10  may provide various services or resources, such as compressed air and electric power, to an elevated worker. Various devices within AWP base unit  14 , such as rotary air compressor  12 , may provide these resources. 
     In the illustrated embodiment of  FIG. 1 , the rotary air compressor  12  may include a rotary screw compressor or other suitable compressor configured to supply a continuous flow of compressed air without the need for an intermediate storage tank. The rotary screw compressor  12  may include a type of gas compressor that has a rotary-type positive displacement mechanism. The rotary screw compressor  12  may include one or more screws, which rotate within an enclosure to gradually shrink a series of passages defined by threads of the screws and the surrounding enclosure. For example, the rotary screw compressor  12  may include a plurality of counter-rotating screws, which intermesh with one another to progressively reduce air volumes between the intermeshed threads. Air is drawn in through an inlet port in the enclosure, the gas is captured in a cavity, the gas is compressed as the cavity reduces in volume, and the gas is finally discharged through another port in the enclosure. 
     The rotary screw compressor  12  provides many benefits in cost, performance, and efficiency as compared with a reciprocating compressor (e.g., piston-in-cylinder compressor). For example, the rotary screw compressor  12  outputs a generally constant pressure of compressed gas (e.g., air) directly to the desired application without an intermediate storage tank. In contrast, a reciprocating compressor generally requires an intermediate storage tank due to the reciprocating nature of compressing the air, e.g., fluctuations in the pressure. Without a storage tank, the typical reciprocating compressor would provide compressed gas with a generally fluctuating pressure, which is not suitable for many applications. Accordingly, the rotary screw compressor  12  may provide a direct supply of compressed air on demand to a desired application, e.g., the elevated platform. In other words, in contrast to a reciprocating compressor, the rotary screw compressor  12  provides compressed air at the desired pressure immediately (e.g., in real time) to an operator located on the elevated platform, rather than compressing an intermediate storage tank until a desired pressure is reached and then subsequently supplying the air to the operator. Thus, the rotary screw compressor  12  may run only when an operator demands compressed gas (e.g., air), such that the compressor  12  is normally off when compressed gas is not needed by the operator. In contrast, the reciprocating compressor typically operates intermittently (e.g., often when an operator is not demanding air pressure) to maintain a minimum level of air pressure in the storage tank. Furthermore, the time delay associated with reciprocating compressors and their associated tanks can reduce the efficiency at the worksite. In addition, the rotary screw compressor  12  can save space due to the exclusion of an intermediate storage tank. 
     The rotary screw compressor  12  also has fewer moving parts than a typical reciprocating compressor, thereby reducing complexity and maintenance costs. Further, the rotary screw compressor  12  may operate to compress any type of gas, in addition to air, as is presently contemplated. The rotary screw air compressor  12  may be configured to operate at high speeds and, therefore, may use less gearing and space to couple the rotary screw compressor  12  to an engine. For example, in one embodiment, the rotary screw compressor  12  may operate at a speed near an engine speed, such as 4000 RPM. Thus, the screw compressor driving mechanism, e.g., a combustion engine, may include similar drive ratios and may not use a significantly larger driving mechanism to step down the engine speed in order to accommodate the air compressor  12 . 
     As illustrated in  FIG. 1 , the integration of the rotary screw compressor  12  within the AWP  10  also provides many benefits in cost, performance, and efficiency. For example, the rotary screw compressor  12  and the AWP  10  may share a variety of components to reduce costs and complexity of the overall system, while also improving the ease of use, controllability, serviceability, and mobility of the components. For example, the compressor  12  and the AWP  10  may share a common enclosure (e.g., base unit  14 ), power source (e.g., engine), control system (e.g., control board, software, user interface, etc.), cooling system (e.g., water or air cooling), transportation system (e.g., wheels, transmission, etc.), and so forth. By further example, a single engine may power a hydraulic pump, an electrical generator, the compressor  12 , and a drive system (e.g., transmission, wheels, etc.) of the AWP  10 . The integration of the compressor  12  and the AWP  10  also enables joint movement around a worksite. 
     Turning now to details of the AWP  10 , various embodiments of the AWP  10  may include an articulated lift, telescopic lift, a scissor lift, or another suitable lift mechanism. In the illustrated embodiment, the AWP  10  may be described as a telescopic lift. Telescopic lifts may be hydraulically powered, and are the closest in appearance to a crane. They may consist of a number of jointed sections, which can be controlled to extend the lift in a number of different directions, which can often include ‘up and over’ applications. This type of AWP is widely used for maintenance and construction of all types, including extensive use in the power and telecommunications industries to service overhead lines, and in arboriculture to provide an independent work platform on difficult or dangerous trees. 
     Some telescopic lifts are limited to only the distance accessible by the length of each boom arm. However, by the use of telescoping sections, the range can be vastly increased. Telescopic lifts may include a wide supportive base unit  14  and/or extending legs/struts to provide support and stability for a load on the telescoping sections. These legs may be manual or hydraulic depending on the size and complexity of the AWP  10 . 
     Another embodiment of the AWP  10  may be described as a scissor lift. A scissor lift is a type of platform which can usually only move in the vertical plane. The mechanism used to achieve this may include linked, folding supports in a crisscross (e.g., X-shaped) pattern. The upward motion is achieved by the application of pressure to the outside of the lowest set of supports, elongating the crossing pattern, and propelling the work platform vertically. The platform may also have an extending bridge to enable closer access to the work area, because of the inherent limits of vertical only movement. The contraction of the scissor action may be hydraulic, pneumatic, and/or mechanical (e.g., via a leadscrew or rack and pinion system). Depending on the power system employed on the lift, it may not use any power to enter descent mode, but rather a simple release of hydraulic or pneumatic pressure. This is a main reason that these methods of powering the lifts may be preferred, as it allows a fail safe option of returning the platform to the ground by release of a manual valve. 
     The AWP  10  may be designed for mobile use at a worksite, between sites, or both. Thus, the AWP  10  may include wheels, a motor, a transmission, a hitch, or a combination thereof. In some instances, the AWP  10  may exclude a motive drive, such that it relies on external force for movement. In such an embodiment, the external force may be applied by an operator (e.g., manual force), a vehicle, or another piece of equipment capable of pushing or pulling the AWP  10 . Thus, one embodiment of the AWP  10  includes wheels without any drive coupled to the wheels, wherein the AWP  10  includes a vehicle hitch, a tow connector (e.g., loop), manual push and/or pull handles, or a combination thereof. In some embodiments, the AWP  10  may be designed as a small lightweight unit, which can be transported in a truck bed and/or can be moved through a standard doorway. 
     In other embodiments, the AWP  10  may be self propelled via a suitable drive coupled to wheels, tracks, or the like. These AWP  10  units are able to drive (on wheels or tracks) around a site without need for any external force. In some instances, these AWP  10  units are able to move while a job is in progress, e.g., while an operator is positioned on a platform raised to a desired altitude by the AWP  10 . However, such movement may not be possible with AWP  10  units having secure outriggers (e.g., extending legs or struts). In self-propelled AWP  10  units, the drive may include an electric motor, a spark ignition internal combustion engine, a compression ignition (e.g., diesel) engine, a hybrid power unit, and so forth. Furthermore, the AWP  10  may include a suitable transmission coupling the motor to the wheels. The transmission may include an automatic transmission or a manual transmission having a clutch. 
     Referring now to the AWP  10  shown in  FIG. 1 , the AWP  10  includes a hood  16  that opens and closes (e.g., via a hinge) to provide access to internal components (e.g., rotary compressor  12 ) within the base unit  14 . Located on top of the base unit  14  is a bracket  18 , which is coupled to one or more lift cylinders  20 . Lift cylinder  20  is configured to move a boom  24  up and down via rotation about a pivot joint  26 , e.g., a pin or axial joint. The lift cylinder  20  may include one or more hydraulic cylinders, one or more pneumatic cylinders, a screw-driven mechanism, or any combination thereof. As illustrated, the lift cylinder  20  provides leverage offset from the joint  26 , thereby enabling rotational movement of the boom  24  between a generally horizontal and a generally upright or raised orientation relative to the ground. 
     Further, an actuator  28  may be located inside the boom  24  in order to extend or retract the boom unit. Again, like the lift cylinder  20 , the actuator  28  may include a hydraulic cylinder, a pneumatic cylinder, a screw-driven mechanism, or a combination thereof. The illustrated boom  24  includes a base  30  coupled to a fly section  32 , wherein the fly section  32  is extendable and retractable (e.g., telescopic) relative to the base  30 . Thus, the actuator  28  can provide a force to extend the fly section  32 , thereby increasing the length of the boom  24 . The actuator  28  also may provide a controlled retraction of the fly section  32  relative to the base  30 , e.g., by releasing pressure of hydraulic fluid, air, or the like. 
     The boom  24  is coupled via a pivot joint  34  (e.g., a pin or axial joint) to a platform  36 . The platform  36  is configured to support one or more operators and some amount of equipment, which depends on the load capability of the AWP  10 . A cylinder  38  (e.g., hydraulic or pneumatic) may be coupled to the boom  24  and a pivot assembly  40  in order to position the platform  36 . Devices within the shell base unit  14  may be connected to platform  36  via electrical cables, hydraulic conduits, pneumatic conduits, control cables, and other linkages, as indicated by cables  42 . The cables  42  may provide control and access to the resources of the AWP  10  to the elevated worker. Control panel  44  provides control and access to services provided by base unit  14 . In certain embodiments, control panel  44  may include various gauges, displays, switches, keypads, service connections, and general controls, as indicated by reference numerals  46  and  48 . For example, the control panel  44  may include one or more compressed air outputs, hydraulic outputs, electrical outputs, and so forth. The control panel  44  also may include one or more gauges and/or displays indicating air pressure, hydraulic pressure, electrical output voltage, electrical output current, engine speed, engine temperature, platform altitude, and other parameters. The control panel  44  also may include controls to stop, start, or vary parameters of the engine, the compressor  12 , the electrical generator. The control panel  44  also may include steering and drive controls in order to move and maneuver the base unit  14  while the worker is positioned in the platform  36 . 
     As generally illustrated in  FIG. 1 , certain embodiments of the base unit  14  exclude a driver cab, a driver seat, a driver steering wheel, and the like. Thus, embodiments of the AWP  10  are distinctly and contrastingly different from a vehicle having a chassis with an integral driver cab and lift mechanism. In the illustrated embodiment of  FIG. 1 , the control panel  44  on the platform  36  may provide controls to enable the operator to generally drive the AWP  10  around the worksite, between worksites, and so forth. However, in some embodiments, the AWP  10  may include some controls on the base unit  14  as well. 
       FIG. 2  illustrates a diagram of the AWP base unit  14  and internal components in accordance with certain embodiments of the present technique. As illustrated in  FIG. 2 , the base unit  14  includes a power pack or service package having the rotary screw compressor  12 , a combustion engine  50 , and a hydraulic pump  52 . In the diagram, the devices are coupled by drive mechanism  56 . Drive mechanism  56  may include shafts, pulleys, belts, gears, clutches, or any combination thereof. Gears or belts/pulleys may be used in some embodiments to step up the output of the engine to drive the rotary compressor at a sufficient rate (RPM). For instance, a rotary compressor may need to operate at a minimum 4000 RPM and the engine may operate at a maximum of 2800-3000 RPM. Therefore, a drive system must step up the output of the engine to operate the compressor. However, as illustrated in  FIG. 2 , the drive mechanism  56  consists essentially of a direct drive (e.g., direct drive shaft) between the engine  50  and both the rotary compressor  12  and the hydraulic pump  52 . In this embodiment, the drive mechanism  56  generally excludes clutches, pulleys, and the like. The direct drive (e.g., drive shaft) may be desirable to minimize lost power during transfer and to reduce maintenance by having fewer moving parts. In some embodiments, the AWP base unit  14  may include a power pack or service package, which may consist essentially of the rotary screw air compressor  12 , the engine  50 , and the hydraulic pump  52 . In other words, the power pack does not include a compressor tank, a reciprocating air compressor, and an electrical generator. The inclusion of the rotary screw air compressor  12  in the AWP  10  generally eliminates the need for a connection to a stand-alone air compressor. 
       FIG. 3  illustrates a diagram of the AWP base unit  14  and internal components in accordance with certain embodiments of the present technique. As illustrated in  FIG. 3 , the base unit  14  includes a power pack or service package having the rotary screw air compressor  12 , the engine  50 , the hydraulic pump  52 , and an electrical generator  58 . Also included in AWP base unit  14  is a belt drive system  60 , which may be used to couple engine  50  to the other components. The illustrated belt drive system  60  includes three pulleys and a single belt disposed about these three pulleys. In other embodiments, the system  60  may employ multiple belts, a chain coupled to sprockets on the components, gears, or another suitable arrangement. As previously mentioned, the rotary screw air compressor  12  may not require a compressor pulley (or chain sprocket) to step up the engine speed of the engine  50  to accommodate the rotary screw air compressor  12 . In other embodiments, the pulley may be used to step down the engine speed. The engine  50  may be a spark ignition (i.e., gasoline), a compressor ignition engine (i.e., diesel), or similar engine outputting up to 100 horsepower. 
     The generator  58  may be coupled to the engine  50  as illustrated in  FIG. 3  or with an additional clutch or selective engagement mechanism. In operation, the generator  58  converts the power output (e.g., mechanical energy) of the engine  50  to electrical power. Generally, the generator  58  includes an assembly configured to convert a rotating magnetic field into an electrical current (e.g., AC generator). The generator  58  includes a rotor (rotating portion of the generator) and a stator (the stationary portion of the generator). For example, the rotor of the generator  58  may include a rotating drive shaft disposed in a single stator configured to create an electrical current (e.g., a welding current) from the rotation of the magnetic field. In certain embodiments, the generator  58  may include a four-pole rotor and three-phase weld output configured to provide beneficial welding characteristics. Further, the generator  58  may include a plurality of independent winding sections in the rotors and/or stators, such that the generator  58  is configured to output multiple electrical outputs having different characteristics. For example, the generator  58  may include a first section configured to drive a welding current to a welding gun (e.g., a MIG welding gun) and a second section configured to drive a current for other AC outputs (e.g., auxiliary devices). In certain embodiments, the generator  58  may include power conditioning circuitry, and may be configured to provide both AC and DC output. 
     With reference to the features shown in  FIG. 3 , several embodiments are presently contemplated with somewhat limited features of the power pack or service package noted above. In a first contemplated embodiment, the AWP base unit  14  may include a power pack or service package, which may consist essentially of the rotary compressor  12 , the engine  50 , the hydraulic pump  52 , and the generator  58 . In a second contemplated embodiment, the AWP base unit  14  may include a power pack or service package, which may consist essentially of the rotary compressor  12 , the engine  50 , the hydraulic pump  52 , the generator  58 , and the belt drive system  60 . In a third contemplated embodiment, the AWP base unit  14  may include a power pack or service package, which may consist essentially of the rotary compressor  12 , the engine  50 , and the generator  58 . In a fourth contemplated embodiment, the AWP base unit  14  may include a power pack or service package, which may consist essentially of the rotary compressor  12 , the engine  50 , the generator  58 , and the belt drive system  60 . In the third and fourth contemplated embodiments, the rotary compressor  12  may drive the articulated lift or boom  24  and also various pneumatic tools used by the operator in the platform  36 . In these four contemplated embodiments, the AWP base unit  14  may be described as excluding a reciprocating compressor and an air storage tank. Furthermore, other embodiments are contemplated with or without any of the components shown in  FIG. 3 . 
       FIG. 4  illustrates a diagram of the AWP base unit  14  and internal components in accordance with certain embodiments of the present technique. In the present embodiment, the AWP base unit  14  may include a power pack or service package, which may consist essentially of the rotary compressor  12 , the engine  50 , the hydraulic pump  52 , and the generator  58 . In the illustrated arrangement, the engine  50  drives the generator  58  by belt drive system  60 . The rotary compressor  12  is then coupled to drive mechanism  57 , which is driven by generator  58 . Drive mechanism  57  may include shafts, pulleys, belts, gears, clutches, or any combination thereof. Engine  50  also drives the hydraulic pump  52  via drive mechanism  56 . The arrangement show in  FIG. 4  may be referred to as a piggy back configuration. Specifically in the embodiment the devices are driven by the engine  50  in series, meaning the engine  50  drives the generator  58 , which in turn drives the rotary compressor  12 . In another embodiment, the series arrangement may have the engine  50  drive the rotary compressor  12 , which in turn drives the generator  58 . In the series arrangement, both the generator and rotary compressor are both mechanically driven by the engine, yet only one device is directly coupled to the engine. The series configuration is an alternative to the parallel arrangement, shown in  FIG. 3 , where the rotary compressor  12  and generator  58  are both driven by the engine  50 . 
       FIG. 5  illustrates a diagram of the AWP base unit  14  and internal components in accordance with certain embodiments of the present technique. As illustrated in  FIG. 5 , the base unit  14  includes a power pack or service package having the rotary screw air compressor  12 , the engine  50 , the hydraulic pump  52 , the generator  58 , the belt drive system  60 , a gear box  62 , and a clutch  64 . In the present embodiment, the gear box  62  and/or clutch  64  may be used to engage, change speeds, and/or change the direction of rotary screw air compressor  12 . Any one of the devices of AWP base unit  14  may be similarly clutched to allow for separate control of the components. Such control may be useful for controlling the power draw on the engine, particularly when no load is drawn from the particular component. For example, in one embodiment, a single clutch may be employed to simultaneously engage and disengage both the compressor  12  and the generator  58 . In another embodiment, a first clutch (e.g., clutch  64 ) may be used for the compressor  12 , and a separate independent clutch may be used for the generator  58 . 
     In the present embodiment, the belt drive system  60  is used to couple the engine  50  to the rotary screw air compressor  12  and the generator  58 . The generator  58  may be used to provide AC and/or DC power for various applications, such as electrical tools, a welding gun (e.g., MIG welding gun), a cutting torch (e.g., plasma cutting torch), electrical lighting, and so forth. In some embodiments of the AWP  10 , the boom  24  may include an electrically powered lift system, rather than using hydraulics or pneumatics to lift the boom  24 . In such an embodiment, the generator  58  may be used to power the lift system of the boom  24 . Further, in the illustrated embodiment, the hydraulic pump  52  is directly coupled to the engine  50  via the drive mechanism  56 . The hydraulic pump  52  may be used to drive a hydraulic lift system of the boom  24 , a hydraulically driven stabilizer (e.g., struts or legs on the base unit  14 ), hydraulic tools, and so forth. 
     With reference to the features shown in  FIG. 5 , several embodiments are presently contemplated with somewhat limited features of the power pack or service package noted above. In a first contemplated embodiment, the AWP base unit  14  may include a power pack or service package, which may consist essentially of the rotary compressor  12 , the engine  50 , the hydraulic pump  52 , the generator  58 , the gear box  62 , and the clutch  64 . In a second contemplated embodiment, the AWP base unit  14  may include a power pack or service package, which may consist essentially of the rotary compressor  12 , the engine  50 , the hydraulic pump  52 , the generator  58 , the gear box  62 , the clutch  64 , and the belt drive system  60 . In a third contemplated embodiment, the AWP base unit  14  may include a power pack or service package, which may consist essentially of the rotary compressor  12 , the engine  50 , the hydraulic pump  52 , and the clutch  64 . In a fourth contemplated embodiment, the AWP base unit  14  may include a power pack or service package, which may consist essentially of the rotary compressor  12 , the engine  50 , the hydraulic pump  52 , the generator  58 , and the clutch  64 . In these four contemplated embodiments, the AWP base unit  14  may be described as excluding a reciprocating compressor and an air storage tank. Furthermore, other embodiments are contemplated with or without any of the components shown in  FIG. 5 . 
       FIG. 6  illustrates a diagram of the AWP base unit  14  and internal components in accordance with certain embodiments of the present technique. As illustrated in  FIG. 6 , the base unit  14  includes a power pack or service package having the rotary screw compressor  12 , the engine  50 , and the hydraulic pump  52 . In the illustrated embodiment, the compressor  12  is a single screw rotary compressor. The illustrated rotary compressor  12  also may be described as an integrated rotary compressor, which includes many components of the lubrication system, including an oil filter and oil separator, which are represented by numeral  66 . Oil cooler  68  is coupled to the screw compressor  12  and may be used to cool the lubricant after it is heated by the compressor  12 . In some embodiments, the compressor  12  may circulate lubricant separate from other components in the AWP  10 . However, in other embodiments, such as illustrated in  FIG. 6 , the compressor  12  may share resources (e.g., lubricant) with other components in the AWP  10 . 
     In the illustrated embodiment of  FIG. 6 , the rotary compressor  12  uses hydraulic fluid from the hydraulic pump  52  as lubricant for internal components of the compressor  12 . Thus, as illustrated, the base unit  14  may store hydraulic fluid in a tank  70  for use by both the hydraulic pump  52  and the rotary compressor  12 . In an embodiment, the rotary screw compressor  12  may use hydraulic fluid, supplied by hydraulic tank  70 , as a lubricant for the screws, bearings, seals, and other moving parts. In other embodiments, the hydraulic fluid stored in the tank  70  may be used with other components in the base unit  14 , e.g., an electrical generator (e.g., bearing lubricant), an engine (e.g., motor lubricant), a transmission (e.g., transmission fluid), axle lubricant, joint lubricant, and so forth. 
     Further, a fuel tank  72  is coupled to the engine  50 . The fuel tank  72  may include gasoline fuel, diesel fuel, natural gas, or another fuel source, depending on the type of engine  50 . If the engine is a two-stroke engine  50 , then the base unit  14  may further include a supplemental tank to store two-stroke engine oil, which mixes with the fuel stored in the tank  72 . The base unit  14  also includes hydraulic lines (e.g.,  76 ) to distribute hydraulic fluid to various components. Hydraulic line  76  and pressurized air line  78  may be used to route these services to the elevated platform  36 . 
       FIG. 7  illustrates a diagram of the AWP base unit  14  and internal components in accordance with certain embodiments of the present technique. As illustrated in  FIG. 7 , the base unit  14  includes a power pack or service package having the rotary screw compressor  12 , the engine  50 , and the hydraulic pump  52 . In the illustrated embodiment, the rotary compressor  12  is a twin-screw compressor. The illustrated compressor  12  also may be described as a non-integrated compressor  12 , because certain components are external and/or separate rather than internal as shown in  FIG. 6 . Specifically, in the illustrated embodiment, the compressor  12  is coupled to external lubrication components, such as the lubrication system and filter  66  and oil cooler  68 . In some embodiments, the compressor  12  may circulate lubricant separate from other components in the AWP  10 . However, in other embodiments, such as illustrated in  FIG. 7 , the compressor  12  may share resources (e.g., lubricant) with other components in the AWP  10 . 
     In the illustrated embodiment of  FIG. 7 , the rotary compressor  12  uses hydraulic fluid from the hydraulic pump  52  as lubricant for internal components of the compressor  12 . Thus, as discussed above with reference to the embodiment of  FIG. 6 , the base unit  14  of  FIG. 7  may store hydraulic fluid in the tank  70  for use by both the hydraulic pump  52  and the rotary compressor  12 . In the embodiment, pressurized hydraulic fluid and pressurized air may be supplied to the boom  24  and elevated platform  36  by lines  76  and  78 , respectively. 
     Referring now to  FIGS. 1-7 , several devices may be included in AWP  10 , depending on the services that are desired. As more devices are added to the AWP  10 , the power demanded by the devices may exceed the power (e.g., electrical, mechanical, pneumatic) produced by the engine  50 , the generator  58 , the rotary compressor  12 , or a combination thereof. For example, the engine  50  may be overloaded and unable to operate all of the devices simultaneously. Thus, the power output to each device may be reduced in proportion to the limited power, and the available power may be distributed between all of the devices consuming power from the engine  50 . Unfortunately, certain devices may not function properly when operating from the reduced power level. A solution may include an AWP  10  incorporating a larger and more powerful engine  50  capable of providing increased amounts of power. However, as engine size increases, the weight and cost of the engine  50  may also increase. Thus, an embodiment of the present AWP  10  may include a smaller engine  50  with a reduced power output to increase portability and reduce cost. Accordingly, certain priority control features of the AWP  10  may monitor and control distribution of power to the various devices based on priority levels, available power, and operational conditions. Further, it may be desirable to increase the efficiency of the AWP  10  by reducing the power generated by the engine  50  when the available power exceeds the demand. The following discussion presents a control system and method configured to monitor operations of the AWP  10  and distribute power based on a priority scheme. 
       FIG. 8  depicts a flowchart of a process used to regulate and monitor the resources provided by AWP  10  in accordance with certain embodiments of the present technique. The process includes identifying the characteristics of the engine  50  and the power demanded by the devices of the AWP  10 , followed by a sequence to reduce, or eliminate lower priority loads if the engine is not capable of supplying the full power demanded. Further, the process reduces the engine operating speed if the engine  50  is capable of supplying power in excess relative to the power demanded by the devices. The process may utilize a controller having a microprocessor and memory with instructions stored on the memory. Alternatively, the process may utilize a programmable logic controller (PLC) with instructions stored on the PLC. Other controllers also may be used to carry out instructions associated with the process as discussed below. 
     The process may first determine the available power, as illustrated at block  100 . Determining the available power  100  may include determining the amount of power output by the engine  50 , the generator  58 , the rotary compressor  12 , or a combination thereof, for consumption by various devices. For example, an engine with a 64 Hp rating may be capable of outputting approximately 47.7 kW of power, assuming that the entire 64 Hp is transmitted as an output. The available power may also be determined by other methods, including measuring the actual power output by the engine  50 . For example, the available power may be calibrated at the time of manufacture and stored in memory. In another embodiment, the available power may be monitored by and stored in the controller. For example, the controller may monitor the operating characteristics of the engine  50  and detect a reduction in engine operating speed, or other system parameters, under certain load conditions. Based on the response of the engine  50  to the loads, the system may store this value in the controller as the available power of the engine  50 . This process may prove useful to account for variation in engine performance over the life of the engine  50 . 
     The process may also determine the demand for power, as illustrated at block  102 . Determining the demand for power may include determining the maximum amount of power consumed by the devices. For example, if the system has three of five devices consuming power (i.e., turned on), the power demanded may include the sum of the power desired or required to operate the three devices at maximum power. Similarly, if all five devices are consuming power, power demanded may include the sum of the power to operate the five devices at maximum power. For simplicity, the process may simply determine the sum of the power to operate the five devices, even if all five of the devices are not consuming power. Examples of loads may include the load of the rotary compressor  12 , the generator  58 , and the like. 
     In another embodiment, determining the demand power  102  may include the system  10  considering the actual demand for power. For example, each of the devices may be monitored to determine the power being consumed by each respective device during operation. Monitoring may include receiving and processing signals indicative of the device speed or other data indicative of the power consumed, such as the power output by each of the devices. A comparison of the sum of the power consumed by each of the devices may be made to determine the demand power  102 . Embodiments may also include providing an additional factor to maintain an available power that is greater than the demand power. For example, an additional amount of power may be added to the sum of the power consumed by the devices to ensure that the power available is capable of supporting fluctuations in the power demanded by the devices. 
     Based on the available power and the demand power, the controller may then determine if the power available is equal to or greater than the demand power  104 . In an embodiment, this may include comparing the available power from block  100  to the demand power from block  102 . For example, after making the determinations in block  100  and block  102 , the controller may subtract the demand power from the available power to determine if a power surplus or power shortage exists. Similarly, an embodiment may combine the steps of block  100 ,  102  and  104  into a single step that includes monitoring various parameters to detect that the power available is equal to or greater than the demand power. Other embodiments may include monitoring oil temperature, coolant temperature, device power output, and the like. 
     If the controller determines that the power available is not equal to or greater than the demand power, then the controller may drop or reduce the lowest priority load, as depicted by block  106 . In an embodiment, this may include prioritizing each load and reducing the power distributed to each load accordingly. For example, an embodiment may include categorizing the overload based on the amount of power demanded in excess of the power available. Such an embodiment may include three categories, including low overload, medium overload, and a high overload. If the overload is low, the system may reduce power to the lowest priority device or devices. If the overload is medium, the system may remove power from the lowest and/or medium priority device or devices. If the overload is high, the system may drop power to all of the devices, except for those considered the highest priority loads. 
     Returning now to block  104 , if the controller determines that the power available is equal to or greater than the demand power, the controller may continue to regulate the performance of the engine  50  and the devices. In an embodiment, the process may confirm whether all loads are receiving full power, as depicted at block  108 . Such a determination may be made by the controller to determine whether the controller may continue with the same power regulatory scheme in place or whether previously eliminated/reduced power to devices may be allowed to operate at full power consumption. 
     Where available power exceeds demanded power and all loads (e.g., devices) are receiving full power, it may be indicative of a power surplus. Accordingly, the controller may consider whether the operating speed of the engine  50  may be reduced. For example, if the controller determines that the available power exceeds the demand power by a sufficient amount the controller may command to reduce engine speed, as depicted at block  112 . If the available power does not exceed the demand power by a sufficient amount the priority control may not command a reduction in engine speed  50  as depicted by the return to the beginning of the method of  FIG. 8 . 
     Returning now to block  108 , if all loads are not receiving full power, the process on the controller may consider bringing increasing power to loads that were previously reduced to a limited power level. As depicted at block  114 , the controller may first consider whether power is available to service loads not receiving full power. For example, the controller may compare the power surplus to the additional power suitable to remove a power limitation from a device. If it is determined that the controller may not service an additional load, then the process may return to block  110  to consider whether the engine speed may be reduced. However, if the controller determines that the power surplus is sufficient to service a currently limited load, the controller may increase the power supplied to the load. For example, as depicted at block  116 , the controller may consider the current engine operating speed, and determine whether the system needs an engine speed increase, as depicted at block  116 , to support the additional load. If no engine speed increase is needed, the controller may increase power to the highest priority load not receiving full power, as depicted at block  120 . However, if the controller determines that an engine speed increase is needed, the controller may command an increase in engine speed, as depicted at block  118 , before increasing power to the highest priority load not receiving full power, as depicted at block  120 . 
     Moreover, the engine speed may be reduced or turned off during non-use to reduce noise and fuel consumption when not servicing a load. For example, if there is no draw on the generator  58  after a time, the engine speed may decrease from an idle speed to a low idle speed, or operation of the engine  50  may be temporally interrupted, reducing the engine speed to off. Upon detection of a draw on the engine at a time, the engine speed may ramp up to an operating speed using any of the control techniques discussed above. 
     While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.