Title:
MOBILE PNEUMATIC COMPRESSOR
Kind Code:
A1


Abstract:
A mobile pneumatic compressor includes an electric motor and a compressor mounted within a compressor housing. A battery mounted to the compressor powers the motor. A frame may surround the compressor housing, and a carrier, including storage compartments, may be mounted to the frame. The frame may comprise a sealed member allowing the frame to be used as a tank for providing a compressed gas reserve. The compressor includes a support mechanism, such as a belt or shoulder strap, allowing the compressor to be borne by a user.



Inventors:
Steinfels, Craig R. (Jackson, TN, US)
Lee, Dustin M. (Eldorado, OH, US)
Application Number:
11/627478
Publication Date:
07/31/2008
Filing Date:
01/26/2007
Primary Class:
International Classes:
F04B53/00
View Patent Images:
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Primary Examiner:
JACOBS, TODD D
Attorney, Agent or Firm:
Harness Dickey (Stanley B&D) (Troy, MI, US)
Claims:
1. A mobile pneumatic compressor comprising: a compressor; an electric motor operatively connected with the compressor for driving the compressor; a compressor housing at least partially enclosing the compressor and electric motor; a battery selectively powering the electric motor; a port in fluid communication with the compressor; a compressed air line removably connected to the port; a carrier attached to the compressor, the carrier comprising a storage compartment; and a support mechanism connecting the compressor with a user's body.

2. The pneumatic compressor of claim 1 wherein the compressor further comprises a frame at least partially surrounding the compressor housing.

3. The pneumatic compressor of claim 2 wherein the carrier is mounted to the frame.

4. The pneumatic compressor of claim 1 wherein the carrier comprises multiple storage compartments.

5. The pneumatic compressor of claim 1 wherein the storage compartment comprises a first wall, the first wall being formed from a non-rigid material.

6. The pneumatic compressor of claim 5 wherein the non-rigid material comprises a material selected from the group consisting of leather, canvas, and nylon fabric.

7. The pneumatic compressor of claim 1 wherein the support mechanism comprises a shoulder strap.

8. The pneumatic compressor of claim 1 wherein the support mechanism comprises a belt securable around the user's waist.

9. The pneumatic compressor of claim 1 wherein the battery comprises a rechargeable battery removably mounted to the compressor housing.

10. The pneumatic compressor of claim 9 wherein the rechargeable battery is adapted to be used alternatively in conjunction with the compressor and with other electric power tools.

11. The pneumatic compressor of claim 9 wherein the compressor comprises a latch that secures the battery to the compressor housing and allows the battery to be released from the compressor housing without the use of additional tools.

12. A mobile pneumatic compressor comprising: a compressor; an electric motor operatively connected with the compressor for driving the compressor; and a compressor housing at least partially enclosing the compressor and electric motor; a battery selectively powering the electric motor; a port in fluid communication with the compressor; a compressed air line removably connected to the port for connecting the compressor with a pneumatic tool; a frame at least partially surrounding the compressor housing; wherein the frame comprises a reservoir portion providing a compressed gas reserve.

13. The pneumatic compressor of claim 12 further comprising a support mechanism connecting the compressor with a user's body.

14. The pneumatic compressor of claim 12 wherein the frame comprises a tubular member.

15. The pneumatic compressor of claim 14 wherein the tubular member is sealed to form the reservoir portion.

16. A mobile pneumatic compressor comprising: a compressor; an electric motor operatively connected with the compressor for driving the compressor; a compressor housing at least partially enclosing the compressor and electric motor; a battery selectively powering the electric motor; a port in fluid communication with the compressor; a compressed air line removably connected to the port for connecting the compressor with a pneumatic tool; a frame at least partially surrounding the compressor housing; and a support mechanism connecting the compressor with a user's body.

17. The pneumatic compressor of claim 16 wherein the frame comprises a reservoir portion providing a compressed gas reserve.

18. The pneumatic compressor of claim 16 wherein the support mechanism comprises a shoulder strap.

19. The pneumatic compressor of claim 16 wherein the support mechanism comprises a belt securable around the user's waist.

20. The pneumatic compressor of claim 16 further comprising a carrier attached to the compressor, the carrier comprising a storage compartment.

21. The pneumatic compressor of claim 16 wherein the frame further comprises a handle for lifting the compressor.

Description:

FIELD OF THE INVENTION

Embodiments of the present invention relate to pneumatic compressors. More particularly, embodiments of the present invention relate to mobile pneumatic compressors that are capable of being borne by a user.

BACKGROUND OF THE INVENTION

Portable pneumatic tools such as pneumatic tools each require a source of compressed air. Currently, almost all portable pneumatic tools rely upon external air compressors to deliver compressed air via a flexible compressed air hose. External air compressors are typically either shop models or so-called portable models.

Shop air compressors are large, heavy compressors that are often fixed in place and not designed to be frequently moved from one work site to another. An immovable shop air compressor and compressed air hose of finite length limit the ability to take the portable pneumatic tool to where the work is to be performed. The portable pneumatic tool is, in effect, tethered to the fixed shop air compressor and its portability is thereby reduced.

Known portable air compressors do have the ability to be transported from one work site to another. Still, many remain relatively immobile, being heavy or bulky and awkward to transport—requiring time and manpower to move between worksites. Once known portable air compressors are moved to the worksite, their relative lack of mobility means that they face many of the same limitations of shop air compressors, requiring long hoses to bring the compressed air from the compressor to the tool. Additionally, some areas of a worksite, such as upper floors, roofs, scaffolding, etc. may be inaccessible to portable compressors because of their weight, size and lack of real portability. When the portable air compressor cannot be easily moved around the worksite, the portability of the pneumatic tool tethered to the compressor is in turn limited.

The lightest and most portable of the portable air compressors are powered by an electric motor. However, many electric powered models then require access to an external electrical power source, which is an additional limitation to the portable compressor's portability. An example of such a prior art portable air compressor is described in U.S. Pat. No. 6,551,066 for a High Pressure Portable Air Compressor, the entire disclosure of which is incorporated herein by reference.

The utility of a hand-held pneumatic fastening tool, one type of portable pneumatic tool, is particularly affected by its dependence upon relatively immobile air compressor. Hand-held pneumatic fastening tools are designed to be quickly carried by hand to where a fastener is to be driven into a workpiece. As explained above, an immobile external air compressor connected to the tool complicates moving the hand-held pneumatic fastening tool around the work site. Setup time can also be a problem, especially when only a few fasteners are to be driven. The time required to move, setup and connect an immobile air compressor to the hand-held pneumatic fastening tool is proportionately high compared to the actual working time of the tool. In some cases, it may take longer to move and setup the external air compressor than to drive the fastener by hand. In such cases, a user will naturally resort to manually driving the fastener with a hammer.

Relatively light-weight, portable inflators are known in the art. For example, U.S. Pat. No. 6,095,762 discloses a battery powered inflator. Such inflators do not have control systems or air reservoirs suitable for use in powering pneumatic tools.

SUMMARY OF THE INVENTION

An embodiment of a mobile pneumatic compressor comprises: a compressor, an electric motor operatively connected with the compressor for driving the compressor, a compressor housing at least partially enclosing the compressor and electric motor, a battery selectively powering the electric motor, a port in fluid communication with the compressor, a compressed air line removably connected to the port for connecting the compressor with a pneumatic tool, a carrier attached to the compressor and comprising a storage compartment, and a support mechanism passively connecting the compressor with a user's body.

In further embodiments, the carrier may have one or more storage compartments formed from a non-rigid material such as leather, canvas, or nylon fabric. Additionally, a shoulder strap or belt may be used by the user to bear the compressor assembly, and the rechargeable battery may be a standardized battery that can be used in conjunction with the compressor assembly and with other electric power tools.

In another embodiment, a pneumatic compressor assembly for use with a portable, battery powered air compressor comprises: a compressor, an electric motor operatively connected with the compressor for driving the compressor, and a compressor housing at least partially enclosing the compressor and electric motor, a battery selectively powering the electric motor, a port in fluid communication with the compressor, a compressed air line removably connected to the port for connecting the compressor with a pneumatic tool, and a frame at least partially surrounding the compressor housing, wherein the frame comprises a sealed portion providing a compressed gas reserve.

In further embodiments, the pneumatic compressor may comprise a support mechanism passively connecting the compressor with a user's body. Additionally, the frame may be formed from a tubular member, and the tubular member may be sealed to form the gas reserve.

In another embodiment, a mobile pneumatic compressor comprises: a compressor, an electric motor operatively connected with the compressor for driving the compressor, a compressor housing at least partially enclosing the compressor and electric motor, a battery selectively powering the electric motor, a port in fluid communication with the compressor, a compressed air line removably connected to the port for connecting the compressor with a pneumatic tool, a frame at least partially surrounding the compressor housing, and a support mechanism passively connecting the compressor with a user's body.

In further embodiments, the frame may comprise a reservoir portion providing a compressed gas reserve, and the support mechanism may comprise a shoulder strap or a belt. Additionally, the pneumatic compressor may comprise a carrier attached to the compressor, and the frame may comprise a handle for lifting the compressor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a mobile compressor borne by the user.

FIG. 2 shows an embodiment of a compressor assembly adapted to be borne by the user where the compressor assembly includes protective elements.

FIG. 3 shows an embodiment of a compressor assembly adapted to be borne by the user where the compressor assembly includes a frame.

FIG. 4 shows the embodiment of FIG. 3 with a carrier attached to the frame.

FIG. 5 shows an embodiment of a compressor assembly attached to a tool belt.

FIG. 6 shows an embodiment of a compressor assembly including a frame and attached to a belt and shoulder strap.

FIG. 7 shows a rear view of an embodiment of a compressor assembly mounted within a rigid housing.

FIG. 8 is a side view of the embodiment of FIG. 25.

FIG. 9 shows an embodiment of a compressor assembly mounted at least partially within a backpack.

FIGS. 10A-10D are left-side, top, rear and isometric views, respectively, of the compressor assembly of the mobile compressor.

FIG. 11 is a sectional view of the compressor assembly showing the air flow path.

FIG. 12 is a longitudinal cross-sectional view of a permanent magnet DC motor.

FIG. 13 is a partial exploded assembly view of the compressor assembly.

FIG. 14 is a schematic illustration of a compressor according to an embodiment where the compressor is capable of utilizing either AC power or DC power.

FIGS. 15-19 are charts demonstrating, in several different operating conditions, the operation of a control system which can be used with the invention.

FIGS. 20-22 are flow charts illustrating the logical steps of the control system demonstrated in FIGS. 15-19.

FIG. 23-25 are schematic illustrations of a further embodiment utilizing a solenoid valve to open or close an air reserve tank.

DETAILED DESCRIPTION OF THE INVENTION

The following description is intended to convey a thorough understanding of the embodiments by providing a number of specific embodiments and details involving a wheel storage rack. It is understood, however, that the invention is not limited to these specific embodiments and details, which are exemplary only. It is further understood that one possessing ordinary skill in the art, in light of known devices, systems and methods, would appreciate the use of the invention for its intended purposes and benefits in any number of alternative embodiments.

Through the description, reference is made to specific examples of pneumatic tools, for example a pneumatic brad nailer. However, the invention is not limited to a specific pneumatic tool or type of tool and is applicable to any portable pneumatic tool for which the compressor is capable of supplying sufficient volume and pressure of compressed air. As the energy density of batteries increases with technology advancements in the future, this invention will become more practical to apply to more and more portable pneumatic tools.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention. As used throughout this disclosure, the singular forms “a,” “an,”and “the” include plural reference unless the context clearly dictates otherwise. Thus, for example, a reference to “a battery” is a reference to one or more batteries and equivalents thereof known to those skilled in the art. Additionally, terms such as “mounted,” “attached” and “connected” shall be broadly construed to mean both permanent and detachable attachment of one part to another, as well as two parts which have been jointly formed as a unitary component. The term mounted shall also include the attachment of one part to another where some degree of relative movement between the two parts is still permitted and shall also include both the direct mounting of one part to another, or the indirect mounting of two parts via other parts.

Commonly assigned U.S. Published Patent Application No. 2002/0158102 discloses a mobile compressor directly attached to a pneumatic tool or attached to a user's body, and copending U.S. patent application Ser. No. 11/415,268 discloses an AC/DC powered pneumatic compressor. U.S. Published Patent Application No. 2002/0158102 and U.S. patent application Ser. No. 11/415,268 are hereby incorporated by reference.

FIG. 1 illustrates a mobile compressor 10 that can be mounted “onboard the user.” The mobile compressor 10 has a compressor assembly that includes a compressor and an electric motor, as well as a battery 300 mounted to the compressor 10 for powering the electric motor. The compressor assembly 100 is used with any standard hand-held pneumatic fastening tool or other portable pneumatic tool 36 with a coupler 38 for connecting to a compressed air supply hose 61. The mobile compressor 10 would also include a coupler 16 for attaching the supply hose 61 leading to the pneumatic tool 36. A reservoir for storing the compressed air could be provided by the air supply hose 61 or a small external tank.

The mobile compressor 10 would be sufficiently small in size and light in weight to be borne by the user such as, for example, on the user's belt. The mobile compressor 10 could also be borne by the user in other fashions. What is meant by “borne by the user” is that the mobile compressor 10 is releasably attached to the user's body or clothing in some manner so that it can be passively carried around with the user. The mobile compressor 10 could have various support mechanisms permitting the compressor to be borne by the user which include a belt, belt loop, shoulder straps, hooks, clips, hook-and-loop type fasteners, or any other mechanism for releasably attaching the compressor 10 to the user's body or clothing.

FIGS. 2-9 illustrate various embodiments of a mobile compressor 10 adapted to be borne by the user. Each of the embodiments shown comprises a compressor housing 110 enclosing a compressor and an electric motor. Additionally, the compressor 10 may include a tank 94 for supplying a reservoir of compressed air to the pneumatic tool. The tank 94 may be mounted within the interior of the compressor housing 110 or may be externally connected with the compressor housing. Alternatively, the tank 94 may be integrally formed with the compressor housing 110.

Each embodiment further comprises a battery 300 for powering the electric motor. The battery may be of any suitable type or configuration of battery or battery pack as would be apparent to one of skill in the art. For example, the battery 300 may be fixedly or releasably mounted to the compressor housing 110 and may be mounted internally or on an external surface. The battery 300 may comprise one or more batteries and may be disposable or rechargeable. Additionally, the battery may be adapted to be used interchangeably with other power tools. Examples of battery units that could be used in conjunction with various embodiments of the compressor assembly and pneumatic tool as described herein are shown in commonly assigned U.S. Pat. No. 5,144,217, which teaches a plug-in type battery pack, and U.S. Pat. No. 6,057,608, which teaches a rail-type or slide-on battery pack. Each of these patents is hereby incorporated by reference.

Referring to the embodiment shown in FIG. 2, the mobile compressor 10 comprises a compressor housing 110 enclosing a compressor 130 and an electric motor 120. The compressor 10 also includes an external tank 94 mounted to the compressor housing 110. The compressor housing may include end caps 26 that connect the tank 94 with the compressor housing 110 and serve to mount gauges 14, dial 28 and coupling 16. The embodiment further comprises a support mechanism, such as a shoulder strap 96, and may include a handle 98 to aid in carrying and maneuvering the mobile compressor 10. A battery 300 is releasably mounted to an end cap 26.

An embodiment of the compressor assembly shown in FIG. 2 may comprise protective elements to reduce the likelihood that the compressor will be damaged in during use or in the event that the unit is dropped or impacted. For example, protective elements may include roll bars 12 that extend from the exterior surface of the compressor housing 110, end caps 26 or tank 94 to protect gauges 14, dial 28, coupling 16, battery 300 or other vulnerable components. Protective elements may also comprise extensions or tabs 18 that extend outwardly from the exterior surface of the compressor housing 110. The tabs 18 may be integrally formed with the compressor housing 110, end caps 26 or tank 94, or may be mounted to the exterior of one or more of these components. The tabs 18 and roll bars 12 may be formed of metal, plastic, rubber, foam, or any other material or combination of materials suitable to cushion or protect the compressor assembly 100 and its components.

Further, as illustrated in FIG. 2, the mobile compressor 10 may have a housing 110 and tank 94 designed and arranged so that the compressor 10 is generally symmetrical 100 side-to-side and top-to-bottom, with the compressor assembly adapted to correctly function in any orientation. Such a configuration may increase the flexibility of the compressor when using, handling and stowing the compressor 10 because the user need not pay particular attention to the angle or orientation of the compressor.

A further embodiment of a compressor assembly is shown in FIGS. 3 and 4. In this embodiment, the mobile compressor 10 includes a frame 20 at least partially surrounding a compressor housing 110. The compressor housing encloses a compressor 130 and an electric motor 120 and may also enclose a tank 94. Alternatively, all or a portion of the frame may be formed from one or more hollow tubes 21, and the tubes 21 may be sealed to serve as a compressed air tank. The frame may be formed of a single primary tube bent to wrap around the compressor housing as shown in FIG. 3-4. Alternatively, the frame may be formed from multiple tubes joined together at joints. These joints may be formed by welding or otherwise bonding multiple tubes or may be formed by attaching the tubes with separately formed joint fixtures that allow fluid communication between the different tubes. The frame comprises a handle 22, and a shoulder strap 96 is attached to the frame. The frame 20 may also include feet 24 to stabilize the mobile compressor 10 when the compressor is placed on a surface. The gauges 14, dial 28 and coupling 16 are positioned so that the frame 20 provides protection from impact.

The embodiment of the compressor assembly shown in FIG. 4 further comprises a carrier 30 attached to the fame 20. The carrier includes various pockets or compartments 32 for storing and carrying tools, fasteners or hardware. The carrier 30 may be formed of fabric or a similar flexible material such as leather, canvas, or nylon fabric, as is commonly used in soft-sided tool cases or tool belts. Alternatively, the carrier 30 may be formed of more rigid material such as plastic or metal, as with a hard-sided toolbox. One or more carriers with varying configurations may be attached to different portions of the frame 20. Alternatively, the carrier may be attached to a compressor housing 110 without the use of a frame. For example, a carrier 30 could be attached the compressor housing 110 shown in FIG. 2. In such an embodiment, the carrier may be connected directly with the compressor housing 110, tank 94 or end caps 26, or the carrier 30 may be attached to the roll bars 12.

FIG. 5 shows an embodiment of the mobile compressor 10 in which the compressor 10 is attached to a tool belt 34. The compressor 10 includes a releasably mounted battery 300. The compressor 10 further includes a tank 94 that may also act as a handle for maneuvering the compressor assembly. One or more carriers 30 attach to the tool belt 34 and include various pocket, compartments, hooks, etc. as appropriate to carry other tools and hardware as the user may find convenient. A shoulder harness 42 may attach to the compressor 10 and/or tool belt 34 and extend over the user's shoulder.

FIG. 6 illustrates an embodiment in which the compressor assembly 100, including the compressor housing 110 and battery 300, mounts to a frame 44. The frame 44 connects the compressor assembly 100 with a belt 34 and with one or more shoulder straps 46. The frame 44 is formed at least in part from tubular sections 45 that may be sealed to serve as a compressed air tank for the compressor assembly. The belt 34 may support the weight of the compressor assembly 100 and frame 44 and may also support various carriers 30 for holding other tools and hardware. These carriers 30 may include a holster 48 for securing the power tool 36 when not in use. A support member 50 extends between frame tubes 45 to support the compressor assembly against the user's back. This support member 50 may be formed of flexible, breathable mesh or any other appropriate material.

In an embodiment of the mobile compressor 10 illustrated in FIGS. 7-8, the compressor housing 110 comprises a rigid housing 52 enclosing the components of the compressor assembly 100. The housing 52 includes a forward shell 54, a rearward shell 56 and a lower shell 58. Each shell is formed of a sufficiently strong and durable material such as plastic, rubber, metal, composite or other material or combination of materials known to one of skill in the art. Support surfaces 60 are formed on the forward shell 54 to support the housing 52 against a user's back and may comprise padding, mesh, or other components to improve the comfort of the housing against the user's back. Shoulder straps 46 attach adjacent the top of the forward shell 54 and extend over the user's shoulders and attach to the forward shell 54 or lower shell 58 adjacent the bottom end of the forward shell 54. Additionally, a belt may be attached to the lower 58 shell or forward 54 shell to help support the housing 52. The lower shell 58 may include protective projections 62 that protect the assembly from impact and stabilize the assembly when it is placed on a surface. These projections 62 may be integrally formed or otherwise attached to the lower shell 58 and may be formed of plastic rubber or other appropriate material.

The rearward shell 56 is pivotally attached to the lower shell 58 to form a clamshell cover for the components of the compressor assembly. Vents 64 are formed in the rearward shell 56 to allow air to enter the compressor. Alternatively, these vents 64 may be formed in other shells of the housing 52. The gauges 14, dial 28 and coupling 16 are positioned on a top surface 66 of the forward shell 54. A handle 68 extends above the top surface 666 and protects the gauges 14, dial 28 and coupling 16 from impact in addition to providing a handle for maneuvering the housing 52. The handle 68 may be fixedly or pivotally mounted and may cooperate with a latching mechanism to selectively hold the rearward shell 56 closed. Alternatively, the gauges 14, dial 28 and coupling 16 may be positioned elsewhere on the housing 52 as convenient and may be protected by roll bars 12 or other projections as shown in FIG. 2.

FIG. 9 illustrates an alternative embodiment of the mobile compressor 10. In the embodiment shown, the compressor assembly 100 components are mounted in a backpack 70 that is supported on a user's back by a belt 34 and shoulder straps 46. The compressor and electric motor are mounted together in an enclosed compartment 72 or separately in multiple enclosed compartments. Vents 74 allow air to enter the compartment to supply the compressor. The tank 608 may be positioned in a partially enclosed pocket 76 on the exterior of the backpack or may be mounted within the enclosed compartment 72 together with the compressor and electric motor or in a separate enclosed compartment. The coupling 16 may be positioned at a top end of the tank 94 or may be positioned elsewhere on the backpack 70.

The backpack 70 may include a rigid internal frame with legs that extend into a portion 78 of the belt 34 providing a stable base to support the backpack 70 in an upright position when the backpack is placed on a surface. The backpack 70 may comprise a flexible material such as leather, canvas, or nylon fabric as would be known to one of skill in the art. Alternatively, portion of the backpack, such as the compressor compartment 72, may be formed of or reinforced with rigid or semi-rigid material like plastic, metal or other appropriate materials. Carriers 30 may be attached to the belt 34 for holding other tools and hardware as convenient for the user.

FIGS. 10A-10D are several views of the major operative components of the compressor assembly 100 removed from any frame or housing. FIG. 11 is a cross-sectional view of the flow path of compressed air in the compressor assembly 100.

The scope of the invention is not intended to be limited to any particular design for the compressor assembly. Indeed, the compressor assembly can be of any appropriate design capable of being.

The particular compressor assembly 100 in the illustrated embodiment will now be described with reference to FIGS. 10A-10D. The compressor assembly 100 comprises two principal components: an electric motor 120, and a compressor 130 that is powered by the electric motor 120. The electric motor 120 can be chosen from any of the many types of electric motors known in the art and suitable for this purpose. In the illustrated embodiment, the electric motor 120 is a DC motor. In particular, the electric motor 120 has a no-load speed of about 14,000 rpm and a stall torque of about 8 in-lbs. Other types of motors may also be used.

FIG. 12 illustrates an exemplary permanent magnet motor for use in a compressor assembly in accordance with embodiments of the invention. Permanent magnet DC motor 315 includes an end cap 312, a brush system 343, a wound armature 333, a permanent magnet stator 337 and a motor can 314. The end cap 312 typically provides a rear bearing support such as boot 354. A fan baffle 316 is coupled to motor can 314 and end cap 312. A gear case 318 is coupled to the fan baffle 316 and may also function as a mounting plate and front bearing support for connecting the motor 315 with a compressor.

Permanent magnet stator 337 includes permanent magnets 335. Permanent magnets 335 may each be a semi-cylindrical magnet member adhered to an inner surface of motor can 314 on opposite sides thereof. It should be understood that permanent magnet stator 337 could include more than two permanent magnets 335, such as four, six, eight, etc.

Armature 333 has an armature shaft 336 around which are positioned laminations 338 in which windings 340 are wound, and a tubular insulative member or sleeve 342 surrounding armature shaft 336. A commutator 332 is affixed on one end of armature shaft 336. Brush system 343 includes brushes 334 at least partially enclosed in brush boxes 344, which are electrically coupled to a power source, such as to an output of a rectifier. Shunts 346 electrically connect brushes 334 to their respective brush boxes 344. Springs 348 resiliently bias the brushes 334 against the commutator 332. Opposed ends of armature shaft 336 are received in front and rear bearings 350 and 352. A fan 330 is affixed to one end of armature shaft 336.

Referring again to FIGS. 10A-10D, a fan (not shown) is integral with the electric motor 120 for cooling. The electric motor 120 is operatively connected to the compressor 130 via a reduction gear set 121. Reduction gear set 121 reduces the required torque needed to drive the compressor 130 so that the size and weight of electric motor 120 can be minimized. Reduction gear set 121 achieves a reduction of about 4.7. Other arrangements, such as belts and pulleys, could be used. With some arrangements, a flywheel may be desirable to ensure smooth operation. Reduction gear set 121 transfers power from electric motor 120 to the compressor 130 with minimal loss of power and generates little noise and vibration.

The compressor 130 of the illustrated embodiment is a positive displacement, piston type compressor. In particular, the compressor 130 has a bore of about 1.2 inches and a stroke of about 0.8 inches resulting in a displacement of about 0.9 cubic inches. Other types of compressors may also be used, including rotary displacement compressors and gear type compressors, as desired. Additionally, the compressor may be of the permanently lubricated, oil free, or oil lubricated type. The compressor 130 comprises an integral crank and counterweight 131, a connecting rod 132 and a compressor piston 133 (FIG. 11) enclosed inside of a compressor cylinder 134. The compressor cylinder is closed by a compressor cylinder head 135.

Referring to FIG. 11, compressor 130 operates on a two-stroke cycle. During the intake stroke, suction created by the compressor piston 133 opens a reed-type intake valve 136 (normally biased to its closed position) mounted on the compressor cylinder head 135, permitting air to enter the compressor cylinder 134. During the compression stroke pressure created by the compressor piston 133 opens a spring-biased, check-type exhaust valve 137 (normally biased to its closed position), permitting the compressed air to escape the compressor cylinder 134.

The dashed lines and arrows in FIG. 12 show the flow path of the compressed air. After passing through the exhaust valve 137, the compressed air flows through a passage formed in the compressor cylinder head 135 to a nipple 138. From there, the compressed air passes through a tube 139 attached to the nipple 138, and finally through another nipple 204 and into a compressed air reservoir.

A compressed air reservoir stores the compressed air from the compressor 130 until it is used to power the pneumatic tool. Many pneumatic tools, such as pneumatic fasteners, already have a passageway formed in the handle leading from a compressed air hose coupler to the valve assembly, and a compressed air reservoir may be adequately provided by such an existing passageway, or by such an existing passageway in combination with a compressed air hose. Or, the compressed air reservoir may be provided by a small external tank 94 mounted to the compressor assembly 100 or by a portion of a frame 20 surrounding the compressor assembly as discussed above.

As illustrated in FIG. 13, the compressor assembly 100 is mounted to the cover or housing 110. Mounting points 122 (FIG. 10A) are formed on the compressor assembly 100 to permit screws to attach the compressor assembly to a bracket 220. It may be desirable to isolate vibrations of the working compressor assembly 100 from the housing 110. Excessive vibration of the housing 110 could make the compressor difficult or uncomfortable to use, especially for long periods. To isolate vibrations from the compressor assembly 100, the compressor assembly can be mounted using vibration-damping means. The vibration damping means can be any material, mechanism or effect that prevents or at least reduces the transfer of at least some vibrations from one body mounted to another. In the illustrated embodiment, the vibration damping means are flexible blocks 223 interposed between the mounting points 122 and the bracket 220. Using a flexible tube for tube 139 also helps isolate vibrations from the compressor assembly 100. In the illustrated embodiment, the electric motor 120 lies close enough to the housing 110 when mounted thereon that excessive vibration could create knocking between the electric motor and the housing. To avoid this problem, isolation mounts 224 may be installed around the electric motor 120 and attached to the housing 110 to prevent any such contact.

The onboard battery 300 is not the only possible electrical power source for powering the compressor assembly 100, however. In another embodiment, the electrical power source may be an electric power cord that delivers electrical power from an external electrical power source. For example, referring to the schematic representation in FIG. 14, an embodiment of the present invention comprises a compressor assembly 100 capable of deriving electrical power from either a DC power source, such as a battery, or an external AC power source.

Embodiments of the compressor assembly comprise a power conditioning circuit 360, a battery 300, an electric motor 120, and a compressor 130. The operator may selectively choose to use either AC power or DC battery power, or a control system may automatically choose the power source based on factors such as: which power sources are currently connected, the state of charge in the battery, the power demands of the compressor, or other relevant factors. A preferred embodiment would accommodate an AC power source of about 90 VAC to about 260 VAC and about 48 Hz to about 63 Hz, or alternatively, a DC battery power source of about 7.0 VDC to about 43 VDC.

When the compressor assembly is electrically connected with an AC power source 302, such as a typical wall socket via an electrical cord, an AC voltage feeds into the power conditioning circuit 360. The power conditioning circuit 360 converts the AC power input to a DC voltage output at a level required by the electric motor 120. The power conditioning circuit output is preferably in the range from about 6.0 VDC to about 43 VDC and may be fixed or adjustable. An embodiment of the power conditioning circuit 360 may comprise a regulated switching power supply. Alternatively, any other appropriate power conditioning circuit may be used as would be apparent to one of skill in the art. Embodiments of the compressor assembly may include a mechanical interlock 362 that disconnects the output of the power conditioning circuit when a battery is connected. Further embodiments may comprise a relay to disconnect the battery output when the compressor assembly is connected with an AC power source.

The DC voltage input would preferably be a single voltage input and may comprise a nickel cadmium, lithium ion, nickel metal hydride, or other appropriate battery 300. Alternatively, the power conditioning circuit 360 may comprise a regulator circuit, implementing a multi-voltage adaptor. The multi-voltage adaptor allows a variety of batteries to power the compressor assembly. Embodiments of the compressor assembly including a multi-voltage adapter may be capable of utilizing a plurality of batteries, either singly or in combination. The batteries may have the same voltage or different voltages. The variation in voltage output may cause the total amount of work power to vary, but would not effect the shot by shot performance of a pneumatic nail gun or other tool connected with the compressor assembly. Further embodiments of the compressor assembly may incorporate a battery charger that would recharge the battery when the unit is connected to AC power.

Referring again to FIG. 14, the electric motor 120 powers the compressor 130. The compressed-air output of the compressor 130 passes through a check valve 137 and into an air reservoir or air tank 94. The air tank 94 preferably has a capacity between about 0.1 gallons to about 16.0 gallons, but could be any capacity to fit the application requirements. The tank 94 has an inlet fluidly connected to the check valve 137 and at least one outlet. An over-pressure safety valve 364 is located on a tank output to limit the tank pressure at a safe level. An output of the tank 94 is also fluidly connected to a pressure switch 366. The pressure switch 366 controls the on/off functionality of the electric motor 120 based on the tank pressure. The pressure switch 366 preferably turns the motor 120 on when the tank pressure drops to a certain preset level, and turns the motor 120 off when the tank pressure rises to a certain preset level. The output of the reservoir 94 feeds a regulator valve 368, which controls the air pressure sent to power the pneumatic tool 36. In further embodiments, a pressure gauge 14 is provided on the tank 94 or regulator 368 for monitoring the tank pressure and controlling the output pressure to the tool 36.

FIGS. 23-25 diagrammatically illustrate a further embodiment of a mobile compressor 10 capable of deriving power from either a DC power source or an external AC power source. Embodiments of the compressor assembly 100 comprise a switch assembly 400, a battery 300, an AC power input 410, an electric motor 120, and a compressor 130. The switch assembly 400 comprises means to selectively choose either AC power 410 or DC battery power 300. Alternatively, a control system may automatically choose the power source. The switch assembly 400 comprises a power conditioning circuit that converts the AC power input 410 to a DC voltage output at a level required by the electric motor 120. The compressor assembly 100 further comprises an air reserve or storage tank 94 and a solenoid valve 402 fluidly connected with a tank inlet between the compressor 130 and the tank 94. Embodiments of the compressor assembly also comprise a tool connection port 16, a pressure gauge 14, and a pressure switch 404 fluidly connected with compressor 130 between the compressor and solenoid valve 402.

As illustrated in FIG. 24, when the compressor assembly 100 operates in an AC mode, electric motor 120 draws power from the AC power source 410 and solenoid 402 is open allowing compressor 130 to fluidly connect with tank 94. Compressor 130 can pressurize tank 94 and provide a reserve of compressed air for use with a pneumatic tool 36. Alternatively, as illustrated in FIG. 25, when the compressor assembly 100 operates in a DC mode, electric motor 120 draws power from battery 300, solenoid 402 is closed, and compressor 130 provides compressed air directly to tool port 16 without use of tank 94. Pressure switch 404 may control the on/off functionality of the electric motor 120 based on the pressure available at tool port 16. The pressure switch 404 turns the motor 120 on when the pressure drops to a certain preset level, and turns motor 120 off when the pressure rises to a certain preset level. Pressure gauge 14 shows the pressure available at tool port 16. Additionally, tank 94 may comprise an additional pressure switch (not shown) for controlling motor 120 in response to tank 94 pressure when in AC Mode. Tank 94 may also include a relief valve 230 and a further pressure gage (not shown) showing tank pressure.

In the manner described, embodiments of the compressor assembly may provide advantages of both a DC battery powered compressor and an AC powered compressor. The DC mode illustrated in FIG. 25 provides a compressor assembly that is portable and convenient. Because solenoid 402 is closed in the DC mode, the compressor assembly can be used without requiring the extra time or depletion of the battery charge that would be required to fill the tank. However, when the compressor is attached to an AC power source, power consumption is not a significant concern. As shown in FIG. 24, solenoid 402 is open, and the compressor maintains the advantages of an air reserve tank for use in longer or more intensive jobs.

Referring to FIG. 13, the compressor housing 110 can be a unitary or multipart, plastic or metal component that is shaped to fit around the compressor assembly 100. In an illustrated embodiment, the compressor housing 110 comprises two clamshell halves 110a, 110b each made from injection molded plastic. Plastic helps minimize the weight of the mobile compressor 10 as well as insulate the heat of the compressor assembly 100 from the user's hands.

The compressor housing 110 protects the user from any exposed moving parts of the compressor assembly 100 and from any parts of the compressor assembly 100 which may become very hot during use such as the compressor cylinder head 135. The compressor housing 110 can also enhance the clean aesthetic appearance of the mobile compressor 10. Air vents 111, 112 may be formed in the compressor housing 110 to allow cooling air to enter therein and cool the compressor assembly 100 and to allow intake air to reach intake valve 136. An air gap is left between the interior of the compressor cover 110 and the compressor assembly 100 to allow cooling air to flow between them. Additionally, ribs formed on the interior of the compressor cover 110 may be provided to create a shroud around the fan (not shown) of the electric motor 120. The shroud will direct the air inside of the compressor cover 110 through the fan, thus creating a flow of cooling air which enters the compressor cover 110 through one set of air vents 111, passes through the fan, and exits the compressor cover 110 through a second set of air vents 112. Because some of the air intake through the air vents 111 will enter the compressor 130, a screen 113 may be placed over the air vents 111 to help prevent debris from entering the compressor 130 or clogging the intake valve 136. Additionally, it may be desirable to include a foam filter between the screen 113 and the intake valve 136 to further help prevent a build-up of sawdust or other material from clogging the intake valve.

A pressure relief valve 230 may be connected to the compressed air reservoir 94 to relieve any excess pressure of the compressed air. In addition to being automatically actuated when the pressure of the compressed air exceeds a certain pressure, the pressure relief valve 230 may be arranged so that it is manually actuated when the battery 300 is detached from the compressor cover 110. A battery release button 310 is depressed to detach the battery 300 from the compressor cover 110 in a known manner. When the battery release button 310 is depressed, it pushes against a first end 261 of a lever 260. Lever 260 pivots about a point 262. When the lever 260 pivots upon activation of the battery release button 310, it pulls on the pressure relief valve 230, to which it is connected at a second end 263, causing the compressed air in the compressed air reservoir 94 to be released. It is thought that release of the compressed air when the battery 300 is removed may be desirable because users may mistakenly believe that the pneumatic tool cannot be activated after the battery 300 has been removed. For similar reasons, a switch 243 for turning the mobile compressor on and off can be arranged so that when the switch 243 is moved to the off position, it pushes against the lever 260, pivoting the lever 260 about point 262 and actuating the pressure relief valve 230 to release the compressed air.

In each of the embodiments described above, the compressor assembly may include a control system which turns the electric motor on and off according to the demand for compressed air. Of course, such a control system is not absolutely necessary because the compressor could be set to run continuously when the tool is in use while the pressure relief valve 230 relieves excessive compressed air if the supply does not match the demand. A control system may be preferable to this simple set-up, however, for several reasons set forth below in the description of possible control systems. In the description of each of the possible control systems, reference will be made to an illustrative embodiment of the invention as used with a cordless brad nailer. It should be understood that the described control systems might also be applied to any embodiment of the invention for use with any appropriate pneumatic tool, in a similar manner.

In one possible simple form, the control system will turn the electric motor 120 on when the pressure in the compressed air reservoir 94 is less then a first predetermined pressure and will turn the electric motor 120 off when the pressure is greater than a second predetermined pressure. The first and second predetermined pressures could be the same, if desired. The first and second predetermined pressures could be selectable by the user during use of the mobile compressor 10, or they could be set at the factory when the mobile compressor is built. In any of these possible combinations of features, the control system could simply comprise a pressure sensitive switch, or switches, which sense the pressure of compressed air in the compressed air reservoir 94 and which control the flow of electric energy to the electric motor 120. This control system will help conserve electrical power by not requiring that the compressor run continuously when the tool is in use. Conservation of electrical power is especially vital when an onboard battery powers the compressor 130.

This control system also makes using the mobile compressor 10 more comfortable. The compressor assembly 100 will create noise and vibration when in use that may bother the user if the noise and vibration are continuous.

In another form illustrated in the accompanying drawings, the control system could comprise a pressure transducer 241 (FIG. 13) that monitors the pressure in the compressed air reservoir 94. The pressure transducer 241 is mounted to a cap 200 of the reservoir 94 and returns an electronic signal indicative of the pressure. The electronic signal from the pressure transducer 241 is received by control circuitry 240. Control circuitry 240 comprises so-called one-time programmable microchips and other known components. Control circuitry 240 receives and processes the electronic signal from the pressure transducer 241. Control circuitry 240 uses the electronic signal to control the flow of electrical power to the electric motor 120. In addition, control circuitry 240 may also include sensors and components for sensing certain parameters relating to the state of the battery 300 or for sensing other inputs, as desired. Control circuitry 240 can be turned on and off through a switch 243 mounted to the compressor cover 110. Control circuitry 240 may also have the ability to control output devices such as LEDs or audible buzzers. For example, a set of LEDs (not shown) may be mounted on the exterior of compressor cover 110 to indicate various operating states or faults of the mobile compressor 10. The control circuitry 240 receives this input or these inputs and controls the electric motor 120 and other output devices according to a programmed logic.

FIG. 15 illustrates the operation of control circuitry 240 in a normal operating condition by showing the fluctuation of the pressure in the compressed air reservoir 94. The mobile compressor is turned on in stage 1 by actuation of the switch 243. When the pressure in the compressed air reservoir 94 measured by the pressure transducer 241 (“the measured pressure”) is below the value of Pmot, the control circuitry 240 responds by turning on the electric motor 120. The value of “1” in the “Compressor” register indicates that the compressor assembly is running. With the compressor assembly running, the measured pressure climbs until it reaches the value of Pmax. When the measured pressure is above Pmax, the control circuitry 240 responds by shutting off the electric motor 120. The value of “0” in the “Compressor” register indicates that the compressor assembly is off in stage 2.

In stage 3, the user pulls the trigger of the brad nailer to fire a brad. The measured pressure decreases as a result of the volume of compressed air lost to drive the brad. Because the measured pressure falls below Pmot in stage 4 the control circuitry 240 turns on the electric motor 120. When the measured pressure returns to the level of Pmax, the control circuitry 240 turns off the electric motor 120 in stage 5. In stage 6, the user pulls the trigger to fire a second brad. As before, the control circuitry 240 detects that the measured pressure has fallen below Pmot and turns on the electric motor 120 in stage 7. This illustrates the logic of the control circuitry 240 in a normal operating condition.

As shown in FIG. 16, with the proper sizing of the compressed air reservoir 94 and appropriate adjustments made to the control circuitry 240, it would be possible to fire a brad twice before the control circuitry turns on the electric motor 120 to recharge the compressed air reservoir 94. This would be advantageous because it would permit the firing of several brads in rapid succession. Other operating conditions are also shown in FIGS. 17-19

The functioning of the green LED indicated in FIG. 15 will now be explained. The green LED is part of the set of LEDs, which may protrude from the compressor cover 110. The green LED is turned off by the control circuitry 240 when the measured pressure is below Psafe. Psafe is predetermined to be the pressure at which accidental actuation of the brad nailer trigger would most likely not cause any injury by firing or partially firing a brad since the pressure is low. Thus, it is thought that no signal need be given to a user when the pressure is below the level of Psafe. The green LED is turned on to flash by the control circuitry 240 when the measured pressure is above the level of Psafe and below the level of Pmin. This is shown by the presence of intermittent shaded bars in the “Green LED” register of FIG. 12. The flashing green LED signals to the user that the tool, if accidentally actuated, may be capable of causing an injury. The flashing green LED also indicates that the pressure in the compressed air reservoir 94 is not sufficient to completely drive the brad if the trigger were pulled at that time. Thus, Pmin is predetermined to be the minimum pressure level at which the nailer is capable of completely driving the brad into the workpiece. When the green LED is flashing, the user is made aware that the nailer can be fired, but that the brad will be left proud of the surface of the workpiece. Once the measured pressure is above Pmin, the green LED is turned on, indicating that the brad nailer is ready to fire a brad at any time. This is indicated by the presence of solid shading in the “Green LED” register.

The user may select the values of Pmax and Pmot during use of the nailer. The switch 243 may be provided with several positions each corresponding to a different set of values for Pmax and Pmot. The switch 243 may have a “Normal” and a “High” position. The mobile compressor is on when the switch 243 is in the “Normal” or the “High” position. The “High” position sets the values of Pmax and Pmot higher than the “Normal” position. The value of Pmin might also be controlled by the position of switch 243. Also, switch 243 may have more than two on positions for an even greater degree of adjustability. Alternatively, a dial 28 may be used to continuously or incrementally control the pressure settings.

The ability to select the values for Pmax and Pmot allows the user to tailor the operation of the mobile compressor to the work to be done. For example, as the type and size of the brad and the workpiece hardness varies, the minimum amount of driving force needed by the brad nailer to completely drive the brad will also vary. Adjustment of the values for Pmax and Pmot allows the pressure of the compressed air to be held closer to the minimum pressure corresponding to the minimum amount of driving force needed.

The tailoring of the values of Pmax and Pmot has several benefits. Electrical power will be conserved because the pressure of the compressed air used to drive the drive piston will not be dramatically greater than what is needed to drive the brad. Also, the efficiency of the compressor 130 increases as the pressure of the compressed air decreases. Conservation of electrical power is particularly important if the electrical power source is a battery. Also, the running time of the compressor assembly 100 will be minimized. Use of the tool could be uncomfortable if the compressor assembly 100 runs too much.

With reference to FIGS. 20-22, an example of the logic followed by the control circuitry 240 during the normal operating condition is shown. FIGS. 20-22 are flow charts that represent the logical steps followed by the control circuitry 240 in operating the mobile compressor in conjunction with a brad nailer. Only the logical steps relevant to the normal operating condition of the nailer will be described now. The other steps will be described later when explaining the other operating conditions of the nailer.

In step 401 in FIG. 20, the switch 243 is moved to an on position. The position of the switch 243, i.e. whether it is in the “High” or “Normal” position, is detected in step 403. This detection sets the values for Pmax and Pmot. The pressure transducer 241 in step 404 measures the pressure in the compressed air reservoir 94. The LEDs are also turned on or off in step 404 according to the measured pressure. In step 406, the measured pressure is judged against the value of Pmot.

If the measured pressure is less than Pmot then the electric motor 120 is turned on in step 407. The position of switch 243 is detected again in step 408 and the values for Pmax and Pmot are established. Moving to point B in FIG. 21, the pressure is measured again using the pressure transducer 241 and the LEDs are turned on and off according to the measured pressure in step 412. In step 414, the measured pressure is judged against the value of Pmax. If the measured pressure is less than the value of Pmax, the logic returns to step 2 in FIG. 20 and the electric motor 120 remains on to continue charging the compressed air reservoir 94. The logic will normally loop between steps 407 and 414 until the measured pressure is greater than Pmax.

If in step 414 the measured pressure is greater than Pmax, then the electric motor 120 is turned off in step 416. The position of switch 243 is detected again in step 421 and the pressure is measured and the LEDs are turned on and off in step 422. The measured pressure is judged against Pmot in step 423. If the measured pressure is greater than Pmot then the logic returns to step 3 and then to step 416 in FIG. 21. The logic will normally loop between steps 416 and 423 until the measured pressure is less than Pmot. If the measured pressure is less than Pmot in step 423, then the logic returns to step 2 in FIG. 20 where the electric motor is turned on in step 407 and the compressed air reservoir 94 is recharged. As before, the logic will normally loop between steps 407 and 414 until the measured pressure is greater than Pmax.

FIG. 16 illustrates the operation of control circuitry 240 in a high demand condition. This operation is the same as the normal operation illustrated in FIG. 15 with the exception of the green LED. In the high demand condition, the brad nailer is fired several times in rapid succession in stages 3 and 4. This causes the measured pressure to dip below Pmin in stage 5. When this occurs, the control circuitry 240 turns the green LED on to flash, signaling to the user that the brad nailer is not ready to fire until the air pressure can recover. The green LED can be turned on to flash in steps 404, 412 and 422 in the logic illustrated in FIGS. 20 and 21.

FIG. 17 illustrates the operation of the control circuitry 240 in a tool idle condition. A single brad is fired in stage 3 and the measured pressure drops below the value of Pmot. In stage 4, the measured pressure is judged against the value of Pmot in step 423 of FIG. 21. Because the measured pressure is below the value of Pmot, the control circuitry turns on the electric motor 120 according to step 407 in FIG. 20. The air pressure recovers in stage 4 as the compressed air reservoir 94 is recharged. When the measured pressure is judged greater than Pmax in step 414 of FIG. 21, the electric motor 120 is turned off in step 416. In step 417, a Timer 2 is set to run. The control logic then loops between steps 416 and 423. In stage 5, the measured pressure decreases very slowly over time (the time domain axis in FIG. 17 has been distorted for illustrative purposes) due solely to leakage of compressed air from the compressed air reservoir 94. At least some leakage of compressed air from the compressed air reservoir 94 is inevitable. When the measured pressure is judged less than the value of Pmot in step 423, the control circuitry 240 again turns on the electric motor 120 at step 407 in FIG. 20.

It is not desirable that this cycle of slowly discharging the compressed air reservoir 94 due to leakage and then recharging be allowed to continue indefinitely. If this cycle in stage 5 were allowed to continue indefinitely, then the charge of the battery 300 would be eventually exhausted. This tool idle situation is most likely to occur when the user puts away the mobile compressor without turning off the switch 243.

To prevent this undesirable cycle of slow discharging and recharging, the value of Timer 2 is judged in step 418 of FIG. 21. If the value of Timer 2 is greater than about 2 hours (or any desirable value), then the control logic passes to position C in FIG. 22. If the value of Timer 2 is not greater than about two hours, then the time rate of change of the measured pressure is judged in step 419. If the time rate of change of the measured pressure is greater than about 10 psi/sec (or any other appropriate standard), then the Timer 2 is reset to zero in step 420 and continues to run, and the pressure is then measured in step 421. Otherwise, the logic passes directly to step 421 and the Timer 2 continues to run. Thus, if the time rate of change of the measured pressure never rises above about 10 psi/sec which indicates that the brad nailer has not been fired during that time period, then Timer 2 will eventually reach about two hours and the logic will pass to point C after step 418.

Point C in FIG. 22 is the beginning of an auto shut-off procedure. The electric motor 120 is turned off in step 424. A “D” in the “Compressor” register indicates the disabled compressor in stage 6 of FIG. 17. The pressure is measured in step 425 and the green LED is turned on and the red LED is turned on to flash slowly. In stage 6 of FIG. 17, the slowly flashing status of the red LED is indicated by intermittent shaded regions in the “Red LED” register. The measured pressure is judged in step 426. If the measured pressure is judged greater than Pmin, then the logic returns to step 4 and then to step 425. The logic will loop between steps 425 and 426 until the measured pressure falls below the value of Pmin.

When the measured pressure is judged less than Pmin in step 426 due to the continuing leakage from the compressed air reservoir 94, in step 427 the air pressure is measured again and the green LED is turned on to flash and the red LED is turned on to flash slowly. The flashing green and red LEDs are shown in stage 7 of FIG. 17. In step 428, the measured pressure is judged against Psafe. If the measured pressure is judged greater than Psafe, then the logic returns to step 5 and then to step 427. The logic will loop between steps 427 and 428 until the measured pressure falls below the value of Psafe.

When the measured pressure is judged less than Psafe in step 428, the green LED is turned off and the red LED is turned on to flash slowly in step 429. The flashing red LED is shown in stage 8 of FIG. 17. The logic of control circuitry 240 will remain at step 429 in an auto shut-off state until the switch 243 is turned to the off position. The continuing slow flashing of the red LED will alert the user that the mobile compressor is in an auto shut-off condition.

FIG. 18 illustrates the operation of the control circuitry 240 in a low battery capacity condition. Obviously, this low battery capacity condition is only applicable when a battery 300 is used as the electrical power source. If a power cord and an external power outlet are used as the only electrical power source, then the features described below will not be necessary. In stage 3 in FIG. 18, a first brad is fired and as a result the air pressure drops in the compressed air reservoir 94. In stage 4, the control circuitry 240 turns on the electric motor 120 to recharge the compressed air reservoir as the user continues to fire brads. In stage 5, the slope of the pressure curve between firing the brads indicates that the pressure is recovering more slowly because the capacity of battery 300 has been substantially exhausted. In stage 5, while the compressor assembly 100 is recharging the compressed air reservoir 94, the logic of control circuitry 240 is looping between steps 407 and 414 in FIGS. 20 and 21. In stage 6 several more brads are fired and the air pressure drops below the level of Pmin. The control circuitry 240 responds by turning the green LED on to flash in step 412 in FIG. 21.

Another brad is fired in stage 6 and finally the electric motor 120 stalls. The control circuitry 240 detects the stall in step 410 or 411 by detecting the voltage and current from the battery. If the battery voltage is less than a predetermined limit or if the battery current is greater than a predetermined limit, then the logic proceeds to step 1 and step 430 in FIG. 20 where the electric motor 120 is turned off. If the control circuitry 240 did not turn off the electric motor 120 there is a substantial risk that the electric motor 120 could be burned out during the stall. A depleted battery can also be detected in step 405 after the mobile compressor is turned on by checking the battery voltage. After the electric motor 120 is turned off in step 430, the logic passes to point D in FIG. 22.

Point D in FIG. 22 is the beginning of an auto shut-off procedure, which is entered when the battery 300 is exhausted. The disabled state of the compressor is shown by a “D” in the “Compressor” register in stage 7 of FIG. 18. In step 431 the air pressure in the compressed air reservoir 94 is measured by the pressure transducer 241 and the green and red LEDs are turned on. In step 432 the measured pressure is judged against the value of Pmin. If the measured pressure is greater than the value of Pmin, then the logic passes to step 6 and then to step 431. The logic loops between steps 431 and 432 until the measured pressure falls below Pmin.

If in step 432 the measured pressure is less than the value of Pmin, then in step 433 the pressure is again measured and the green LED is turned on to flash and the red LED is turned on. In step 434 the measured pressure is judged against the value of Psafe. If the measured pressure is greater than the value of Psafe, then the logic passes to step 7 and then to step 433 again. The logic loops between steps 433 and 434 until the measured pressure falls below the value of Psafe.

If the measured pressure is less than the value of Psafe in step 434, then in step 435 the green LED is turned off and the red LED is turned on. The logic remains at step 435 until the brad nailer is turned off. The red LED signals to the user that the nailer is in an auto shut-off procedure because the battery is exhausted.

FIG. 19 illustrates the operation of the control circuitry 240 in an open quick-connect valve condition. This condition will occur when the valve 252 of port 16 has been accidentally left open by the user because the port 16 is connected to an open ended hose or tool, and the user is trying to use the onboard compressor assembly 100 for compressed air. In stage 1, the switch 243 is turned on and because the measured pressure is below Pmot, the control circuitry 240 turns on the electric motor 120 in step 407 of FIG. 20 to recharge the compressed air reservoir 94. The measured pressure does not substantially build, however, because the compressed air is escaping through the open port 16. After the electric motor 120 is turned on in step 407 and the position of the switch 243 is detected in step 408, a Timer 1 is set to run in step 409 (both Timer 1 and Timer 2 were reset to zero in step 402 when the switch 243 is first turned on). The control logic loops between steps 407 and 414 as the compressor assembly 100 is attempting to recharge the compressed air storage 94. Eventually, in step 413 the Timer 1 will be judged to be greater than about three minutes (or any other appropriate limit), at which point the electric motor 120 will be turned off in step 436. However, if instead the measured pressure reaches the value of Pmax before Timer 1 surpasses about three minutes, then Timer 1 is reset to zero in step 415. After step 436, the logic passes to point E in FIG. 22.

Point E begins an auto shut-off procedure, which the control circuitry 240 enters when the valve 252 is left open, and the onboard compressor assembly 100 tries to recharge the compressed air reservoir 94. The disabled state of the compressor is shown by a “D” in the “Compressor” register in stage 2 of FIG. 19. In step 437 the air pressure in the compressed air reservoir 94 is measured by the pressure transducer 241 and the green LED is turned on and the red LED is turned on to flash. The flashing red LED is indicated by intermittent shaded bars in the “Red LED” register in FIG. 19. In step 438 the measured pressure is judged against the value of Pmin. If the measured pressure is greater than the value of Pmin, then the logic passes to step 8 and then again to step 437. The logic loops between steps 437 and 438 until the measured pressure falls below Pmin.

If in step 438 the measured pressure is less than the value of Pmin, then in step 439 the pressure is again measured and the green LED and red LED are each turned on to flash. In step 440 the measured pressure is judged against the value of Psafe. If the measured pressure is less than the value of Psafe, then the logic passes to step 9 and then to step 439 again. The logic loops between steps 439 and 440 until the measured pressure falls below the value of Psafe.

If the measured pressure is less than the value of Psafe in step 440, then in step 441 the green LED is turned off and the red LED is turned on to flash. The logic remains at step 441 until the mobile compressor is turned off. The continuing flashing of the red LED signals to the user that the mobile compressor is in an auto shut-off procedure because the valve 252 has been left open.

The invention may be practiced in ways other than those particularly described in the foregoing description and examples. Numerous modifications and variations of the invention are possible in light of the above teachings and, therefore, are within the scope of the appended claims. The invention has been described with specific reference to particularly preferred embodiments and examples. Those skilled in the art recognize that various modifications may be made to the invention without departing from the spirit and scope thereof.