PORTABLE PNEUMATIC TOOL POWERED BY AN ONBOARD COMPRESSOR
BACKGROUND OF THE INVENTION
This application claims priority to U.S. provisional patent application no.
60/286,998 filed April 30, 2001, and to U.S. provisional patent application no.
60/356,755 filed February 15, 2002.
1. FIELD OF THE INVENTION
The field of this invention is portable pneumatic tools.
2. DESCRIPTION OF RELATED ART
Portable pneumatic tools such as pneumatic fastening tools, metal
piercing tools and crimping 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 portable models.
Shop air compressors are large, heavy compressors which 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.
In contrast, portable air compressors do have the ability to be transported
from one work site to another. Still, they remain relatively heavy or bulky and
awkward to transport— requiring time and manpower to move around the
worksite. As with shop models, portable air compressors require a hose to bring
the compressed air from the compressor to the tool. Because of the need for a
compressed air hose, the portable pneumatic tool remains tethered to the
portable air compressor. When the portable air compressor cannot be easily
moved around the worksite, the portability of the portable 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, these
electric powered models then require access to an external electrical power
source which is an additional limitation to the portable compressor's portability.
With either class of external air compressor— shop or portable models —
the required purchase of the external air compressor to accompany the portable
pneumatic tool is an additional expense which can be difficult to bear for some
consumers, especially if the external air compressor will serve no other purpose
than to power the portable pneumatic tool.
Also, with either class of external air compressor, a hose is required to
deliver the compressed air from the external air compressor to the tool. The
hose can get in the way of using the tool, can be time consuming to connect and
disconnect, adds additional weight that must be carried from one work site to
another, and can even be a safety hazard. The hose and required fittings are also
an additional expense to the user and will eventually require maintenance or
replacement.
Thus, as can be easily seen, the dependence of portable pneumatic tools
upon external air compressors limits the portability of these tools, imposes
additional costs and reduces their utility.
The utility of a hand -held pneumatic fastening tool, one type of portable
pneumatic tool, is particularly affected by its dependence upon an external 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 external air compressor connected to the tool at a mimmum
complicates moving the hand -held pneumatic fastening tool around the work
site. Also, the hose protruding from the tool can get in the way of the work to be
done, and can restrict the use of the tool in confined spaces or difficult to reach
places. Setup time can also be a problem. Especially when only a few fasteners
are to be driven, the time required to setup and connect the external air
compressor to the hand -held pneumatic fastening tool is proportionately high to
the actual working time of the tool. In some cases, it may take longer to 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.
All of the above-mentioned problems could be overcome if the portable
pneumatic tool's dependence upon an external air compressor was eliminated.
In the field of hand -held fastening tools, cordless, combustion-based fastening
tools have been proposed and produced. One well known type of combustion-
based fastening tool uses an internal combustion chamber in lieu of an external
air compressor. A combustible gas and air mix in a combustion chamber in
these tools. A spark plug ignites this combustible mixture to create pressure
that works on a piston to drive the fastener.
While eliminating the dependence upon an external air compressor, these
combustion-based fastening tools exhibit other problems. For example, these
combustion-based tools require the recurring purchase of proprietary fuel cells
available from the tool's manufacturer. One tool's fuel cells typically cannot be
used in the tools of another manufacturer. Maintenance can also be a problem.
Some of these combustion-based tools require disassembly after every 30,000 or
so shots to clean the residue of the combustion. Further, the design and
construction of these combustion-based fastening tools differs substantially from
other hand-held pneumatic fastening tools resulting in a substantial lack of part
interchangeability. Finally, these combustion-based fastening tools cannot be
both a cordless fastening tool and a hand -held pneumatic fastening tool relying
upon an external air compressor. The ability to be selectively powered by
combustion or external compressed air would increase the adaptability of the
tool.
U.S. Patent Nos. 3,150,488 to Haley, 4,215,808 to Sollberger et l, and
5,720,423 to Kondo etal each propose a hand -held fastening tool which does not
rely upon an external air compressor and is not combustion-based.
The Haley patent discloses a fastening tool with a pump. The pump
pumps a non-compressible fluid which forces a drive piston rearward in a
cylinder. The retraction of the drive piston in turn compresses air in an
accumulator. Pulling a trigger switch on the fastening tool activates the pump.
At some time after the pump has been running and the air has been compressed
in the accumulator, the drive piston reaches the limit of its rearward movement.
This causes the separation of the drive piston from an accumulator piston, which
in turn allows the compressed air to act on the drive piston. The compressed air
drives the drive piston forward to drive the fastener.
The Sollberger et l. and Kondo et l. patents each disclose similar
proposed fastening tools. In each of these proposed fastening tools, an electric
motor drives a piston rearward in a cylinder through an arrangement of gears
and linkages. Pulling the trigger on these tools causes the electric motor to be
energized to move the piston rearward in the cylinder. As the piston moves
rearward, the air behind the piston which is trapped in the cylinder is
compressed. At a certain point, the piston is freed from the driving force of the
motor and is rapidly propelled forward in the cylinder by the force of the
compressed air trapped behind. As the piston is propelled forward, it strikes
and drives the fastener.
In these three patents, each of the proposed designs does eliminate the
hand-held fastening tool's dependence upon an external air compressor.
However, each of the proposed designs would result in one or more new
drawbacks. First, pulling the trigger on each of these fastening tools would not
immediately result in the firing of the tool and the driving of the fastener.
Rather, pulling the trigger would merely activate the motor or pump which
begins the process of compressing the air. Then, after the air has been
compressed, a release mechanism would automatically fire the tool and drive
the fastener. The lag time between the pulling of the trigger and the firing the
tool could be a safety concern. This lag time would also reduce the operating
speed of the tool and would make operation of the tool less intuitive for the
user.
Second, in these proposed fastening tools the maximum air pressure
needed to perform an amount of work on the drive piston sufficient to drive the
fastener is much greater than with standard pneumatic fastening tools. The work
that the compressed air performs on the drive piston in order to drive the
fastener is a result of the compressed air exerting a force on the drive piston as it
travels downward in its cylinder. The pressure of the compressed air in a
standard pneumatic fastening tool will remain high throughout the drive
piston's travel because the compressed air is provided by an external air
compressor, which is almost a constant-pressure supply source. In contrast, the
pressure of the compressed air in the proposed fastening tools will linearly
decrease to zero as the drive piston returns to its start position. Because of the
lack of air pressure at the end of the drive piston's travel, there must be a
relatively high air pressure at the beginning in order to sufficiently drive the
fastener flush with the workpiece.
The necessity for high air pressure in these proposed astening tools is a
disadvantage because compressing the air to such a high pressure is energy
inefficient. This can make a difference in the weight of these proposed tools if
they are to be powered by batteries. A related effect is that the high pressure
could generate a significant amount of heat that must be dissipated. In addition
to the reduction in efficiency and increase in heat, holding the high pressure
compressed air behind the piston for the relatively long period of time before
these proposed fastening tools finally fire will require relatively expensive and
possible maintenance-intensive seals around the drive piston.
This need for such high air pressure might be obviated if the air in the
cylinder were pre -compressed so that air pressure would be maintained even
when the piston is in its start position. While the air in some of the proposed
fastening tools in the above patents could be pre -compressed, this would
require an additional mechanism onboard the tool to maintain this pressure as
the pre-compressed air would inevitably leak out and need recharging.
Third, each of these proposed tools relies upon new and untested
mechanisms for compressing the air. These new mechanisms are not present in
any present-day hand -held pneumatic fastening tools which rely upon external
air compressors. The parts for these new mechanisms, especially initially, will
be costly to engineer, design, and produce. Likely, these new mechanisms
would not immediately be as reliable as the mature technology embodied in
present-day hand -held pneumatic fastening tools.
Thus, while the proposed fastening tools disclosed in the above-
described patents would not be reliant upon an external air compressor and
would not possess the drawbacks of external air compressors, these proposed
tools would suffer other important, and potentially more serious, drawbacks.
SUMMARY OF THE INVENTION
In one embodiment of the invention, a hand -held fastening tool for
driving a fastener into a workpiece comprises a body, a chamber formed in the
body, a drive piston received in the chamber for reciprocal movement therein,
the drive piston reciprocating in the chamber to drive the f stener into the
workpiece, an electrical power source, a compressor and an electric motor each
mounted to the body, the electric motor powered by the electrical power source
and the compressor powered by the electric motor, a compressed air reservoir in
communication with the compressor, the compressed air reservoir storing the
compressed air that is compressed in the compressor, and a trigger valve
assembly operable to release stored compressed air from the compressed air
reservoir into the chamber to drive the drive piston thereby driving the fastener.
In another embodiment of the invention, a method of driving a fastener
into a workpiece with a hand -held fastening tool comprises the steps of drawing
air from the atmosphere and compressing the air in an onboard compressor
mounted to the hand -held fastening tool, the compressor powered by an
electrical power source, filling a compressed air reservoir with the compressed
air compressed in the onboard compressor, and actuating a valve assembly to
release compressed air from the compressed air reservoir into a chamber having
a drive piston reciprocally movable therein causing the drive piston to move in a
chamber formed in the hand -held fastening tool thereby driving a first fastener.
In another embodiment of the invention, a method for performing a task
with a hand -held pneumatic tool comprises the steps of using an electric motor
mounted to the hand -held pneumatic tool to power a compressor mounted to
the hand -held pneumatic tool, the compressor having a compressor piston,
compressing atmospheric air with the compressor piston, storing the
compressed air, actuating a trigger on the hand -held pneumatic tool so that a
drive piston positioned in a chamber formed in the hand -held pneumatic tool is
driven downward in the chamber by the compressed air, and driving a working
mechanism for perf orrning the task with the downward motion of the drive
piston.
In another embodiment of the invention, a hand -held pneumatic tool
comprises a body, a chamber formed in the body, a drive piston received in the
chamber for reciprocal movement therein, a working mechanism for perf orrning
the work of the han -held pneumatic tool, the drive piston reciprocating in the
chamber to drive the working mechanism, an electrical power source, a
compressor and an electric motor each mounted to the body, the electric motor
powered by the electrical power source and the compressor powered by the
electric motor, a compressed air reservoir in communication with the
compressor, the compressed air reservoir storing compressed air that is
compressed in the compressor, and a trigger valve assembly operable to release
stored compressed air from the compressed air reservoir into the chamber to
drive the drive piston thereby driving the working mechanism.
In another embodiment of the invention, a portable pneumatic tool
system comprises a hand -held pneumatic tool having a body, a chamber formed
in the body, a drive piston reciprocating in the chamber under the force of
compressed air in the chamber, the reciprocating movement of the drive piston
powering a working mechanism for perf orrning a task, and a port in
communication with the chamber for bringing compressed air into the chamber.
The portable pneumatic tool system also comprises a portable compressor
assembly adapted to be borne by a user and having an electric motor operatively
connected to and powering a compressor, an electrical power source powering
the electric motor, and a port in communication with the compressor for
delivering compressed air from the compressor, the portable compressor
assembly further having means permitting the portable compressor assembly to
be borne by a user. The portable pneumatic tool system also comprises a
compressed air hose connected at one end thereof to the port of the hand -held
pneumatic tool and at a second end thereof to the portable compressor
assembly.
In another embodiment of the invention, a method of using a portable
pneumatic tool system, the system comprises a hand -held pneumatic tool
having a drive piston reciprocating in a chamber under the force of compressed
air in the chamber, the reciprocating movement of the drive piston powering a
working mechanism for performing a task, and a port in communication with the
chamber for bringing compressed air into the chamber. The system further
comprises a portable compressor assembly adapted to be borne by a user and
having an electric motor operatively connected to and powering a compressor,
an electrical power source powering the electric motor, and a port in
communication with the compressor for delivering compressed air from the
compressor. The method of using the system comprises the steps of grasping
the hand -held pneumatic tool with the user's hand, attaching the portable
compressor assembly to some part of the user's body other than the hand or arm
so that the portable compressor assembly is borne by the user, connecting a
compressed air hose between the port of the compressor assembly and the port
of the hand -held pneumatic tool, compressing atmospheric air in the compressor
of the compressor assembly, and introducing the compressed air compressed in
the compressor into the chamber of the hand-held pneumatic tool to drive the
drive piston thereby driving the working mechanism and perf orrning the task.
In another embodiment of the invention, a portable compressor assembly
for providing compressed air to a hand -held pneumatic tool comprises a body, a
compressor located at least partially inside the body, an electric motor
operatively connected to and powering the compressor, at least one battery
detachably mounted to the body, the battery providing electrical power to the
electric motor, a port in communication with the compressor, the port
connectable to a compressed air line for delivering compressed air to the hand¬
held pneumatic tool, and a control system. The control system comprises
pressure sensing means for sensing the pressure of the compressed air available
to the port, and control means for controlling the electric motor according to a
comparison between the pressure sensed by the pressure sensing means and a
predetermined pressure setting, the predetermined pressure setting being
selectable by the user during use of the portable compressor unit.
In another embodiment of the invention, a portable pneumatic tool
system comprises a hand -held pneumatic tool having a body, a chamber formed
in the body, a drive piston reciprocating in the chamber under the force of
compressed air in the chamber, the reciprocating movement of the drive piston
powering a working mechanism for perf orrning a task, and a port in
communication with the chamber for bringing compressed air into the chamber.
The portable pneumatic tool system also comprises a portable compressor
assembly having an electric motor operatively connected to and powering a
compressor, a detachably mounted battery powering the electric motor, and a
port in communication with the compressor for delivering compressed air from
the compressor. The portable pneumatic tool system also comprises a
compressed air hose connected at one end thereof to the port of the hand -held
pneumatic tool and at a second end thereof to the portable compressor
assembly.
In another embodiment of the invention, a battery-powered, hand -held
pneumatic fastening tool comprises a metal fastening tool body, a plastic cover
mounted on the fastening tool body, and a battery detachably mounted on the
plastic cover for providing electrical power to the hand -held pneumatic
fastening tool.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a left-side view of a cordless brad nailer according to one
embodiment of the invention.
FIG. 2 is a right-side side view of the cordless brad nailer of FIG. 1.
FIG. 3 is a left-side view of the cordless brad nailer of FIG. 1 with the
compressor housing removed.
FIG.4 is a right-side view of the cordless brad nailer of FIG. 1 with the
compressor housing removed.
FIGS. 5A-5D are left-side, top, rear and isometric views, respectively, of
the compressor assembly of the cordless brad nailer of FIG. 1.
FIG. 6 is a partial right-side view of the cordless brad nailer of FIG. 1.
FIG. 7 is a sectional view of the cordless brad nailer taken from cutting
plane 7-7 in FIG. 6
FIG. 8 is a partial exploded assembly view of the cordless brad nailer of
FIG. 1.
FIGS. 9 and 10 are schematic illustrations of a cordless brad nailer
according to another embodiment of the invention where the compressor
assembly is selectively detachable.
FIG. 11 is a schematic illustration of a cordless brad nailer according to
another embodiment of the invention where the compressor assembly is borne
by the user.
FIGS. 12-16 are charts demonstrating, in several different operating
conditions, the operation of a control system which can be used with the
invention.
FIGS. 17-19 are flow charts illustrating the logical steps of the control
system demonstrated in FIGS. 12-16.
DETAILED DESCRIPTION OF THE INVENTION
The illustrated embodiment of the invention is a hand -held, cordless
pneumatic brad nailer. It should be understood that while this specification
describes the invention through reference to this specific illustrated
embodiment, the invention is not limited to a cordless pneumatic brad nailer.
Those skilled in the art will comprehend that the invention is equally and in a
similar manner applicable to other portable pneumatic tools. Besides brad
nailers, the invention is applicable to other hand -held pneumatic fastening tools
such as finish nailers, framing nailers, pin nailers, staplers, riveters, etc. Thus,
where reference is made to a brad, other fasteners such as nails, pins, staples,
rivets, etc. may be substituted. In addition to hand -held pneumatic fastening
tools, the invention is also applicable to a wider range of portable pneumatic
tools such as metal piercing tools, crimping tools and impact wrenches. In
general, the invention is applicable to any portable pneumatic tool requiring
relatively infrequent bursts of low volume, high pressure compressed air. The
invention is applicable to corded as well as cordless tools. 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.
While the invention is described through reference to this detailed
embodiment, not all of the details described herein are important for practicing
the invention. The scope of the invention should be ascertained from and shall
be measured by reference to the appended claims.
With reference to FIGS. 1 and 2, the brad nailer comprises a body 10 with
a head portion 11 and a handle portion 12. The body 10 can be made from
aluminum or magnesium alloys, plastic, etc., to rninimize the overall weight of
the brad nailer, these alloys already being commonly used in this art for this
purpose. The body 10 can be a unitary component, or can be constructed from
several separate components. A chamber (not shown) is formed within the head
portion 11 and holds a drive piston (not shown). The drive piston drives a
driver blade (not shown) adapted to strike and drive a brad. The brad is fed to
the driver blade by a magazine assembly 20. In its retracted position, the drive
piston is located in one end of the hollow chamber in the head portion 11. When
compressed air fills the chamber behind the drive piston, the piston rapidly
moves forward in the chamber under the force of the compressed air causing the
driver blade to strike the brad and drive it into the workpiece. Preferably the
brad is driven with a single blow from the driver blade, but the brad nailer may
also be a multi-blow tool in which the brad is completely driven after multiple
blows from the driver blade. A valve system (not shown) controls the
introduction of compressed air into the chamber. The valve system includes a
trigger 30 which extends from the body 10 and is pulled by a user to actuate the
valve system. Many different valve systems for actuating pneumatic tools are
known in the art, and any such appropriate valve system may be used.
As already stated, the invention may also be applied to other portable
pneumatic tools. In general, portable pneumatic tools have a drive piston which
drives a working mechanism adapted to perform a task. Throughout this
specification and in the appended claims, reference will be made to a working
mechanism to generically refer to any mechanism powered by a drive piston in
these tools.
The compressed air for powering the brad nailer can be provided by an
onboard compressor assembly 100. In this embodiment, the compressor
assembly 100 is mounted to the body 10 and contained within a compressor
cover 110. FIGS. 3 and 4 show the brad nailer with the compressor cover 110
removed to better view the compressor assembly 100. FIGS. 5A-5D are several
views of the major components of the compressor assembly 100 removed from
the brad nailer. FIG. 7 is a cross-sectional view of the flow path of compressed
air in the compressor assembly 100 taken from cutting plane 7-7 shown in FIG. 6.
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 onboard a hand -held pneumatic tool.
"Onboard" means that the compressor assembly is mounted on and carried by
the tool. In other words, in its ordinary course of use, the tool and its onboard
compressor are moved by hand together, as a unit, from one operation to the
next. "Mounted" shall be broadly construed to mean both permanent and
detachable attachment of one part to another, as well as the attachment of two
parts which have been jointly ormed 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. The term
mounted shall also include both the direct mounting of one part to another, or
the indirect mounting of two parts via other parts. By way of example, the
onboard compressor can be mounted to a tool by screws, bolts, clamps, latches,
hook-and-loop type fasteners, elastic straps, or any other permanent or
detachable fastening system.
The particular compressor assembly 100 in the illustrated embodiment
will now be described with reference to FIGS. 5A-5D. The compressor assembly
100 comprises two principal components: an electric motor 120, and a
compressor 130 which 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. 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 necessary 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. The compressor 130 comprises an integral crank and counterweight
131, a connecting rod 132 and a compressor piston 133 (FIG. 7) enclosed inside of
a compressor cylinder 134. The compressor cylinder is closed by a compressor
cylinder head 135.
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 flow path of the compressed air is shown by the dashed lines and
arrows in FIG. 7. 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 flexible tube 139
attached to the nipple 138, and finally through another nipple 204 and into a
compressed air reservoir 210.
A compressed air reservoir 210 stores the compressed air from the
compressor 130 until it is used to power the drive piston to drive a brad. Many
pneumatic fasteners already have a passageway formed in the handle leading
from a compressed air hose coupler to the valve assembly, and the compressed
air reservoir 210 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 210 may be provided by a small external tank
mounted to the body 10. In the illustrated embodiment, the compressed air
reservoir 210 is formed in a hollow portion of the handle portion 12, and is
completely separate from the compressor 130 and the chamber formed in the
head portion 11 of the body 10. A cap 200 is mounted to the handle portion 12
via screws 203 to enclose the compressed air reservoir 210. The cap 200 is sealed
to the handle portion 12 by a conventional seal 201.
The onboard compressor assembly 100 is mounted to the body 10 via
bracket 220. Bracket 220 is mounted to the cap 200 with screws 221. Mounting
points 122 (FIG. 5A) are formed on the compressor assembly 100 to permit
screws to attach the compressor assembly to the bracket 220. It may be desirable
to isolate vibrations of the working compressor assembly 100 from the body 10.
Excessive vibration of the body 10 could make the tool difficult to use, or at least
could make holding the handle portion 12 uncomfortable. 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 which 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. Flexible tube 139 also
helps isolate vibrations from the compressor assembly 100. In the illustrated
embodiment, the electric motor 120 lies close enough to the body 10 when
mounted thereon that excessive vibration could create knocking between the
electric motor and the body. To avoid this problem, isolation mounts 224 may
be installed around the electric motor 120 and attached to the body 10 to prevent
any such contact.
In alternative embodiments, the compressor assembly 100 may be
mounted to the body 10 in a detachable fashion. FIGS. 9 and 10 schematically
illustrate an alternative embodiment of the invention where a compressor
assembly 100a is completely detachable from a body 10a of a brad nailer. The
compressor assembly 100a could be arranged with grooves which mate with
corresponding flanges 13a formed on the body 10a. Such an arrangement of
grooves and flanges would help stabilize the compressor assembly 100a on the
body 10a. A latch 14a could be employed to selectively hold the compressor
assembly 100a on the body 10a. A hose 101a could extend from the compressor
assembly 100a and attach to a standard coupler 15a on the body 10a to bring the
compressed air to the brad nailer. The advantage of this alternative embodiment
would be the ability to remove the compressor assembly 100a and use the brad
nailer with an external air compressor attached through an air hose to the
coupler 15a. Because there may be instances when the user prefers to use an
external air compressor, the flexibility of the brad nailer to be powered by an
external air compressor or an onboard compressor assembly 110a would be
appreciated. When the brad nailer is being used with an external air compressor
for an extended period of time, the ability to remove the compressor assembly
100a from the brad nailer will also be greatly appreciated by some users so that
the overall weight of the brad nailer can be minimized.
FIG. 11 illustrates another alternative embodiment of the invention where
a compressor assembly 100b would be a separate component from the brad
nailer. In this embodiment, instead of being mounted onboard the tool, the
compressor assembly 100b would be mounted "onboard the user." The
compressor assembly 100b could include both a compressor and electric motor,
as well as a battery 300b releasably mounted to the compressor assembly for
powering the electric motor. The compressor assembly 100b could have more
than one battery detachable mounted thereto. Alternatively, the compressor
assembly 100b could be powered by an electric power cord and an external
electrical power source.
The compressor assembly 100b could be used with any standard hand¬
held pneumatic fastening tool or other portable pneumatic tool with a coupler
for connecting to a compressed air supply hose. The compressor assembly 100b
would also include a coupler for attaching a supply hose leading to the
pneumatic fastener. A reservoir for storing the compressed air could be
provided by the air supply hose or a small external tank.
The compressor assembly 100b 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 compressor assembly 100b could also be borne by the user in other fashions.
What is meant by "borne by the user" is that the compressor assembly 100b is
releasably attached to the user's body or clothing in some manner so that it can
be passively carried around with the user. "Borne by the user" does not include
simply carrying the compressor assembly 110b by hand. The compressor
assembly 100b could have means permitting the compressor assembly 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 assembly 100b to the user's body or clothing.
The embodiment in FIG. 11 would provide the same portability of the
onboard compressor assembly shown in the embodiment of FIGS. 1-8 because no
external air compressor is needed. An additional advantage of this embodiment
would be that the weight of the compressor assembly 100b may be easier to bear
around the user's waist, for example, that at the end of the user's arm as is the
case with a compressor assembly onboard the tool. In the illustration in FIG. 11,
the user is perched on a ladder and lifting the brad nailer high above his body to
install crown molding. In such situations a compressor assembly borne around
the waist may be preferred to a compressor assembly mounted on the brad
nailer itself. Another advantage of this embodiment is that larger or multiple
batteries, having a greater capacity for power storage, may be used because the
capacity of the body to carry the additional weight may be greater than the
capacity of the user's arms to carry the additional weight.
Returning to the embodiment in FIGS. 1-8 with the compressor assembly
100 mounted onboard the brad nailer, the electric motor 120 may be powered by
an onboard battery 300. The battery 300 can be detachably mounted to the
compressor cover 110 in any convenient manner. Mounting the battery 300 to
the compressor cover 110 also establishes the electrical connection of the battery
300 with the compressor assembly 100. It may also be feasible to mount the
battery 300 to some part of the body 10 rather than to the compressor cover 110.
For example, battery 300 might be mounted to the top of the head portion 11 of
the body 10. Traditionally, pneumatic fastening tools are designed so that the
greatest weight of the tool is located in the head portion 11 generally in-line with
the force that will be exerted on the fastener. The weight in this location helps
prevent movement of the fastening tool when the fastener is struck. Placement
of the battery 300 on top of the head portion 11 would advance this objective.
The onboard battery 300 is not the only possible electrical power source
for powering the onboard compressor assembly 100, however. In another
embodiment, the electrical power source may be an electric power cord which
delivers electrical power from an external electrical power source. In yet another
embodiment, a battery borne by the user may electrically connect to the brad
nailer to power the onboard compressor assembly 100. As can be seen, there are
many possible combinations for powering the compressor assemblies shown in
FIGS. 1-11.
The compressor cover 110 can be a unitary or multipart, plastic or metal
component which is shaped to fit around the compressor assembly 100 and is
attached to the compressor assembly 100 or the body 10, or both. Preferably, the
compressor cover 110 is attached only to the body 10 so that the compressor
assembly 100 will be free to vibrate somewhat underneath the compressor cover
110. In the illustrated embodiment, the compressor cover 110 comprises two
clam shell halves 110a, 110b each made from injection molded plastic. Plastic
helps minimize the weight of the cordless brad nailer as well as insulate the heat
of the compressor assembly 100 from the user's hands.
The compressor cover 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 cover 110 can also enhance the clean
aesthetic appearance of the brad nailer. Air vents 111, 112 (FIGS. 1 and 2) may be
formed in the compressor cover 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 prevent air from circulating 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.
One feature of this invention is that many of the components of the
cordless brad nailer are the same as traditional components for a pneumatic
fastening tool. For example, the drive piston and valve system of the cordless
brad nailer may be the same as those used in a standard pneumatic brad nailer.
Using these standard parts is advantageous because these parts have already
been field-tested and proven, ensuring their reliability. Also, a ready supply of
spare parts is available to consumers should they break because these parts are
already in wide spread commercial use. The cost of the cordless brad nailer is
also minimized because tooling for making these parts already exists. The same
ability to use standard pneumatic tool parts will apply equally when the
invention is applied to other hand -held pneumatic fastening tools, or other
portable pneumatic tools, because the fundamental process in these tools for
using the energy of compressed air to perform the work will remain unchanged
by the addition of an onboard compressor assembly.
While the purpose of this invention is to overcome a hand-held
pneumatic tool's dependence upon an external air compressor, external air
compressors remain advantageous in many situations. Therefore, another
feature of the invention is the ability to be selectively powered by either an
onboard compressor assembly or an external air compressor. In order to
accommodate an external air compressor, a port 250 (FIG. 8) can be included to
allow a compressed air hose to connect to the compressed air reservoir 210 and
deliver compressed air from an external air compressor. The port 250 includes a
coupler 251 of a standard design for quickly connecting and disconnecting to a
compressed air hose. In order to prevent the compressed air from escaping from
the compressed air reservoir 210 when a compressed air hose is not connected to
the coupler 251, a valve 252 is incorporated into the port 250. When the valve
252 is open, the coupler 251 communicates with the compressed air reservoir
210. When the valve 252 is closed, no compressed air can pass from the
compressed air reservoir 210 through the coupler 251. The valve 252 in the
illustrated embodiment is manually actuated by turning the coupler 251 by hand
from the closed position shown in FIG. 1 to the open position shown in FIG. 3.
A pressure relief valve 230 (FIG. 8) may be connected to the compressed
air reservoir 210 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 (FIGS. 2 and 8) 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 (FIG. 6). 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 210 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 brad nailer cannot be
fired after the battery 300 has been removed. For similar reasons, a switch 243
(FIG. 2) for turning the nailer on and off can be arranged so that when the switch
243 is moved to the off position, it pushes against the lever 260 near an interface
264 (FIG. 6), pivoting the lever 260 about point 262 and actuating the pressure
relief valve 230 to release the compressed air when the nailer has been turned
off.
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 the illustrated embodiment
of the invention— a cordless brad nailer. It should be understood that the
described control systems may also be applied to any of the embodiments of the
invention, as desirable, 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 210 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 brad
nailer, or they could be set at the factory when the brad nailer 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 210 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 the brad
nailer is powered by an onboard battery.
This control system also makes using the tool 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. 8) which monitors the
pressure in the compressed air reservoir 210. The pressure transducer 241 is
mounted to the cap 200 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 (shown diagramatically in FIG. 8)
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 (FIG. 2) 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 242 (FIG. 2) may be mounted on the exterior
of compressor cover 110 to indicate various operating states or faults of the brad
nailer. 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. 12 illustrates the operation of control circuitry 240 in a normal
operating condition by showing the fluctuation of the pressure in the
compressed air reservoir 210. The brad nailer is turned on in stage 1 by
actuation of the switch 243. When the pressure in the compressed air reservoir
210 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 Pmaχ. 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 30 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 30 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.
With the proper sizing of the compressed air reservoir 210 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 210. This would be advantageous because
it would permit the firing of several brads in rapid succession.
The functioning of the green LED indicated in FIG. 12 will now be
explained. The green LED is part of the set of LEDs 242 (FIG. 2) 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 trigger 30
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
sae and below the level of Pmm. 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 210 is not sufficient to completely drive the brad if the
trigger 30 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 values of Pmaχ and Pmot may be selected by the user during use of the
nailer. The switch 243 may be provided with several positions each
corresponding to a different set of values for Pmaχ and Pmot. In FIG. 2, a switch
243 is illustrated which has a "Normal" and a "High" position. The brad nailer
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 Pmm 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.
The ability to select the values for Pmax and Pmot allows the user to tailor
the operation of the nailer to the work to be done. As the type and size of brad
and the workpiece hardness varies, the minimum amount of driving force
needed 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 P aχ 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. 17-19, an example of the logic followed by the
control circuitry 240 during the normal operating condition is shown. FIGS. 17-
19 are flow charts which represent the logical steps followed by the control
circuitry 240 in operating the 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. 17, 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 Pmaχ and Pmot. The
pressure in the compressed air reservoir 210 is measured by the pressure
transducer 241 in step 404. The LEDs 242 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 P ot 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 Pmaχ and Pmot are established. Moving to point B in FIG. 18,
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 Pmaχ. If the measured
pressure is less than the value of Pmax, the logic returns to step 2 in FIG. 17 and
the electric motor 120 remains on to continue charging the compressed air
reservoir 210. The logic will normally loop between steps 407 and 414 until the
measured pressure is greater than Pmaχ.
If in step 414 the measured pressure is greater than P ax, 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. 18. 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. 17 where the electric motor is turned on in step 407 and
the compressed air reservoir 210 is recharged. As before, the logic will normally
loop between steps 407 and 414 until the measured pressure is greater than Pmaχ.
FIG. 13 illustrates the operation of control circuitry 240 in a high demand
condition. This operation is the same as the normal operation illustrated in FIG.
12 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. 17
and 18.
FIG. 14 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. 18. 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. 17. The air pressure recovers in stage 4 as the compressed air
reservoir 210 is recharged. When the measured pressure is judged greater than
Pma in step 414 of FIG. 18, 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. 14 has been distorted for illustrative purposes) due solely to
leakage of compressed air from the compressed air reservoir 210. At least some
leakage of compressed air from the compressed air reservoir 210 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. 17.
It is not desirable that this cycle of slowly discharging the compressed air
reservoir 210 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 brad nailer 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. 18. 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. 19. 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. 19 is the beginning of an auto shut-off procedure. The
electric motor 120 is turned off in step 424. The disabled compressor is indicated
by a "D" in the "Compressor" register in stage 6 of FIG. 14. 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. 14, 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 Pmm in step 426 due to
the continuing leakage from the compressed air reservoir 210, 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. 14. 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. 14. The logic of control circuitry
240 will remain at step 429 in an auto shut-off state until the switch 423 is turned
to the off position. The continuing slow flashing of the red LED will alert the
user that the nailer is in an auto shut-off condition.
FIG. 15 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. 15, a first brad is fired and as a result the air pressure drops in the
compressed air reservoir 210. 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 210, the logic of control
circuitry 240 is looping between steps 407 and 414 in FIGS. 17 and 18. In stage 6
several more brads are fired and the air pressure drops below the level of Pmm.
The control circuitry 240 responds by ixirning the green LED on to flash in step
412 in FIG. 18.
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. 17 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
brad nailer 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. 19.
Point D in FIG. 19 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. 15. In step 431
the air pressure in the compressed air reservoir 210 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 Pmm, 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
1 safe.
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. 16 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 250 has been accidentally left open by the user and now 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. 17 to
recharge the compressed air reservoir 210. The measured pressure does not
substantially build, however, because the compressed air is escaping through
the open valve 252. 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
210. Eventually, in step 413 the Timer 1 will be judged to be greater than about
three minutes (or any other appropriate Umit), 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. 19.
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 210. The disabled state of the
compressor is shown by a "D" in the "Compressor" register in stage 2 of FIG. 16.
In step 437 the air pressure in the compressed air reservoir 210 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. 16. 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 greater 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 brad nailer is turned off. The continuing
flashing of the red LED signals to the user that the nailer is in an auto shut-off
procedure because the valve 252 has been left open.