Note: Descriptions are shown in the official language in which they were submitted.
FASTENER DRIVING APPARATUS
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present disclosure is a continuation-in-part of pending United
States Non-
provisional Patent Application, Serial No. 14/877,742, filed on October 7,
2015 and also claims
priority on the United States Provisional Patent Applications numbered
62/060,690 filed on October 7,
2014, and 62/195,850 filed July 23, 2015.
FIELD OF THE DISCLOSURE
[0002] The present disclosure relates to fastener driving apparatuses, and,
more
particularly, to such fastener or staple driving mechanisms that require
operation as a hand tool.
BACKGROUND
[0003] Electromechanical fastener driving apparatuses (also referred to
herein as a "driver,"
"gun" or "device") known in the art often weigh generally less than 15 pounds
and may be configured
for an entirely portable operation. Contractors and homeowners commonly use
power-assisted devices
and means of driving fasteners into wood. These power-assisted means of
driving fasteners can be
either in the form of finishing fastener systems used in baseboards or crown
molding in house and
household projects, or in the form of common fastener systems that are used to
make walls or hang
sheathing onto same. These systems can be portable (i.e., not connected or
tethered to an air
compressor or wall outlet) or non-portable.
[0004] The most common fastener driving apparatus uses a source of
compressed air to
actuate a guide assembly to push a fastener into a substrate. For applications
in which portability is not
required, this is a very functional system and allows rapid delivery of
fasteners for quick assembly. A
disadvantage is that it does however require that the user purchase an air
compressor and associated
air-lines in order to use this system. A further
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disadvantage is the inconvenience of the device being tethered (through an air
hose) to an air
compressor.
[0005]
To solve this problem, several types of portable fastener drivers operate off
of
fuel cells. Typically, these guns have a guide assembly in which a fuel is
introduced along
with oxygen from the air. The subsequent mixture is ignited with the resulting
expansion of
gases pushing the guide assembly and thus driving the fastener into the
workpieces. This
design is complicated and is far more expensive then a standard pneumatic
fastener gun.
Both electricity and fuel are required as the spark source derives its energy
typically from
batteries. The chambering of an explosive mixture of fuel, the use of
consumable fuel
cartridges, the loud report and the release of combustion products are all
disadvantages of this
solution.
Systems such as these are already in existence and are sold commercially to
contractors under the PaslodeTM name.
[0006]
Another commercially available solution is a fastener gun that uses electrical
energy to drive a stapler or wire brad. Such units typically use a solenoid to
drive the
fastener (such as those commercially available under the ArrowTM name or those
which use a
ratcheting spring system such as the RyobiTM electric stapler). These units
are limited to
short fasteners (typically 1" or less), are subject to high reactionary forces
on the user and are
limited in their repetition rate. The high reactionary force is a consequence
of the
comparatively long time it takes to drive the fastener into the substrate.
Additionally,
because of the use of mechanical springs or solenoids, the ability to drive
longer fasteners or
larger fasteners is severely restricted, thus relegating these devices to a
limited range of
applications. A further disadvantage of the solenoid driven units is they
often must be
plugged into the wall in order to have enough voltage to create the force
needed to drive even
short fasteners.
[0007] A final commercially available solution is to use a flywheel
mechanism and
clutch the flywheel to an anvil that drives the fastener. Examples of such
tools can be found
under the DewaltTM name. This tool is capable of driving the fasteners very
quickly and in
the longer sizes. The primary drawback to such a tool is the large weight and
size as
compared to the pneumatic counterpart. Additionally, the drive mechanism is
very
complicated, which gives a high retail cost in comparison to the pneumatic
fastener gun.
[0008]
Clearly based on the above efforts, a need exists to provide portable solution
to driving fasteners which is unencumbered by fuel cells or air hoses.
Additionally, the
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solution ought to provide a low reactionary feel, be able to drive full size
fasteners and be
simple, cost effective and robust in operation.
[0009]
The prior art teaches several additional ways of driving a fastener or staple.
The first technique is based on a multiple impact design. In this design, a
motor or other
power source is connected to an impact anvil through either a lost motion
coupling or other
device. This allows the power source to make multiple impacts on the fastener
to drive it into
the workpiece. The disadvantages in this design include increased operator
fatigue since the
actuation technique is a series of blows rather than a single drive motion.
A further
disadvantage is that this technique requires the use of an energy absorbing
mechanism once
the fastener is seated. This is needed to prevent the anvil from causing
excessive damage to
the substrate as it seats the fastener. Additionally, the multiple impact
designs are not very
efficient because of the constant motion reversal and the limited operator
production speed.
[0010] A
second design that is taught in US Patent Nos. 3,589,588, 5,503,319, and
3,172,121 includes the use of potential energy storage mechanisms (in the form
of a
mechanical spring). In these designs, the spring is cocked (or activated)
through an electric
motor. Once the spring is sufficiently compressed, the energy is released from
the spring into
the anvil (or fastener driving piece), thus pushing the fastener into the
substrate. Several
drawbacks exist to this design. These include the need for a complex system of
compressing
and controlling the spring, and in order to store sufficient energy, the
spring must be very
heavy and bulky. Additionally, the spring suffers from fatigue, which gives
the tool a very
short life. Finally, metal springs must move a significant amount of mass in
order to
decompress, and the result is that these low-speed fastener drivers result in
a high reactionary
force on the user.
[0011]
To improve upon this design, an air spring has been used to replace the
mechanical spring, US Patent No. 4,215,808 teaches of compressing air
within a guide
assembly and then releasing the compressed air by use of a gear drive. This
patent
overcomes some of the problems associated with the mechanical spring driven
fasteners
described above, but is subject to other limitations. One particular
troublesome issue with
this design is the safety hazard in the event that the anvil jams on the
downward stroke. If the
fastener jams or buckles within the feeder and the operator tries to clear the
jam, he is subject
to the full force of the anvil, since the anvil is predisposed to the down
position in all of these
types of devices. A further disadvantage presented is that the fastener must
be fed once the
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anvil clears the fastener on the backward stroke. The amount of time to feed
the fastener is
limited and can result in jams and poor operation, especially with longer
fasteners. A further
disadvantage to the air spring results from the need to have the ratcheting
mechanism as part
of the anvil drive. This mechanism adds weight and causes significant problems
in
controlling the fastener drive since the weight must be stopped at the end of
the stroke. This
added mass slows the fastener drive stroke and increases the reactionary force
on the
operator. Additionally, because significant kinetic energy is contained within
the air spring
and piston assembly the unit suffers from poor efficiency. This design is
further subject to a
complicated drive system for coupling and uncoupling the air spring and
ratchet from the
drive train which increases the production cost and reduces the system
reliability.
[0012]
US Patent No. 5,720,423 again teaches of an air spring that is compressed and
then released to drive the fastener. The drive or compression mechanism used
in this device
is limited in stroke and thus is limited in the amount of energy which can be
stored into the
air stream. In order to provide sufficient energy in the air stream to achieve
good
performance, this patent teaches use of a gas supply which preloads the guide
assembly at a
pressure higher than atmospheric pressure. Furthermore, the compression
mechanism is
bulky and complicated. In addition, the timing of the motor is complicated by
the small
amount of time between the release of the piston and anvil assembly from the
drive
mechanism and its subsequent re-engagement. Additionally, US Patent No,
5,720,423
teaches that the anvil begins in the retracted position, which further
complicates and increases
the size of the drive mechanism. Furthermore, because of the method of
activation, these
types of mechanisms as described in US Patent Nos. 5,720,423 and 4,215,808
must compress
the air to full energy and then release off the tip of the gear while under
full load. This
method of compression and release causes severe mechanism wear. As will be
discussed
below, the present disclosure overcomes these and other limitations in the
prior art use of air
springs.
[0013] A
third means for driving a fastener that is taught includes the use of
flywheels
as energy storage means. The flywheels are used to a hammering anvil that
impacts the
fastener. This design is described in detail in US Patent Nos. 4,042,036,
5,511,715, and
5,320,270. One major drawback to this design is the problem of coupling the
flywheel to the
driving anvil. This prior art teaches the use of a friction clutching
mechanism that is both
complicated, heavy and subject to wear. Further limiting this approach is the
difficulty in
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controlling the energy in the fastener system. The mechanism requires enough
energy to
drive the fastener, but retains significant energy in the flywheel after the
drive is complete.
This further increases the design complexity and size of such prior art
devices.
[0014] A
fourth means for driving a fastener is taught in the present inventors' US
Patent No. 8,079,504, which uses a compression on demand system with a
magnetic detent.
This system overcomes many of the advantages of the previous systems but still
has its own
set of disadvantages which include the need to retain a very high pressure for
a short period
of time. This pressure and subsequent force necessitate the use of high
strength components
and more expensive batteries and motors.
[0015] A fifth means is taught in pending US Patent Application Serial No.
13/922,465, which uses a vacuum to drive a fastener drive assembly. This
clearly has its own
advantages over the previous systems but has its own set of disadvantages,
including the need
to retain a seal against air pressure. This sealing requirement necessitates
the use of more
accurate cylinders and pistons, thus contributing to the manufacturing cost.
[0016] All of the currently available devices suffer from one or more the
following
disadvantages:
= Complex, expensive and unreliable designs. Fuel powered mechanisms such
as
PaslodeTM achieve portability but require consumable fuels and are expensive.
Rotating flywheel designs such as DewaltTM have complicated coupling or
clutching
mechanisms based on frictional means. This adds to their expense.
= Poor ergonomics. The fuel powered mechanisms have loud combustion reports
and
combustion fumes. The multiple impact devices are fatiguing and are noisy.
= Non-portability. Traditional fastener guns are tethered to a fixed
compressor and thus
must maintain a separate supply line.
= High reaction force and short life. Mechanical spring driven mechanisms have
high
tool reaction forces because of their long fastener drive times. Additionally,
the
springs are not rated for these types of duty cycles leading to premature
failure.
Furthermore, consumers are unhappy with their inability seat longer fasteners
or work
with denser wood species.
= Safety issues. The prior art "air spring" and heavy spring driven designs
suffer from
safety issues for longer fasteners since the predisposition of the anvil is
towards the
substrate. During jam clearing, this can cause the anvil to strike the
operators hand.
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= The return mechanisms in most of these devices involve taking some of the
drive
energy. Either there is a bungee or spring return of the driving anvil
assembly or
there is a vacuum or air pressure spring formed during the movement of the
anvil. All
of these mechanisms take energy away from the drive stroke and decrease
efficiency.
[0017] In light of these various disadvantages, there exists the need for a
fastener
driving apparatus that overcomes these various disadvantages of the prior art,
while still
retaining the benefits of the prior art.
SUMMARY OF THE INVENTION
[0018]
In accordance with the present invention, a fastener driving apparatus is
described which derives its power from an electrical source, preferably
rechargeable batteries,
and uses a motor to actuate a spring (such as a gas spring, for example).
After sufficient
movement of a piston in the gas spring, the piston of the gas spring commences
movement,
accelerating an anvil and/or anvil assembly. The anvil assembly preferably has
a mass that is
greater than the weight of the piston, the contact of the piston with the
anvil causes the anvil
to move. In an embodiment, the piston comes to rest on a bumper but the anvil
assembly
continues to move toward and into contact with a fastener such that the anvil
drives the
fastener. The effective mass differential between the piston and the anvil
facilitates sufficient
energy being transferred to the anvil for driving a fastener. A return spring
or other return
mechanism is incorporated to return the anvil, after the anvil drives the
fastener, to a position
where the anvil and/or anvil assembly may again be operatively contacted by
the piston for
another drive by the anvil.
[0019] By using a gas spring and with a stroke differential between the
piston and the
anvil, the present fastener driving assembly is able to generate sufficient
energy to drive a
fastener with only a small increase in pressure in the chamber or other
environment in which
the piston is disposed. This unexpectedly increased the efficiency of the unit
since heat of
compression of a gas is a significant source of energy inefficiency. (This
aspect also reduced
the size of the apparatus as the stroke of the piston is significantly less
than the stroke of the
anvil and anvil assembly. During the inventive process, it was also discovered
that the mass
differential greatly impacts the efficiency of the device. Ideally, the moving
mass within the
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gas spring (primarily the piston) is less than the moving (or eventually
thrown) mass of the
anvil and anvil assembly.
Another unexpected result was the high efficiency of the
apparatus as compared to the inventor's vacuum-actuated fastener driver patent
(United
States Patent 8,079,504) as seal friction loss is a major source of efficiency
reduction. By
limiting the stroke of the gas spring in relation to the stroke of the anvil
and anvil assembly,
the length over which the seal frictional loss occurs was significantly
reduced. This was a
major unexpected benefit of the present disclosure, dramatically increasing
the efficiency
over the prior art. For instance, test results show conversion efficiencies
(potential energy to
kinetic energy in the drive anvil) of over 80%, which is far better than the
65% obtained by
the apparatus of the '504 patent.
[0020]
The fastener driving cycle of the apparatus disclosed herein may start with an
electrical signal, after which a circuit connects a motor to the electrical
power source. The
motor is coupled to the gas spring through a drive mechanism. In an
operational cycle of the
drive mechanism, the mechanism alternatively (1) actuates the piston of the
gas spring and
(2) decouples from the piston. For example, during a portion of its cycle, the
drive
mechanism may move the piston to increase potential energy stored within the
gas spring. In
the next step of the cycle, the mechanism decouples from the piston to allow
the accumulated
potential energy within the gas spring to act on and actuate the piston. The
piston thereupon
moves and causes the anvil assembly to move and drive a fastener. A spring or
other return
.. mechanism is operatively coupled to the anvil and anvil assembly to return
the anvil to an
initial position. In an embodiment, at least one bumper is disposed within the
gas spring or
outside the gas spring to reduce the wear on the piston. In an embodiment
another bumper is
used to reduce the wear on the anvil assembly that otherwise may occur in
operation of the
fastener driving apparatus.
[0021] In an embodiment, the mass of the anvil and anvil assembly is at
least equal to
the moving mass of the gas spring, and more preferably, at least 1.2 times the
moving mass of
the gas spring.
[0022]
In an embodiment, the stroke or movement of the piston is less than one half
the total movement of the anvil and anvil assembly. Further preferred is that
the movement
of the piston results in a volume decrease within the gas spring of less than
20% of the initial
volume (which thus reduces losses from heat of compression.)
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[0023]
In an embodiment, a sensor and a control circuit are provided for determining
at least one position of the anvil, anvil assembly, and/or drive mechanism to
enable the
proper timing for stopping the operational cycle of the apparatus. Further,
this information
can be used to detect a jam condition for proper recovery.
[0024] In an embodiment, the piston launches the anvil and/or anvil
assembly prior to
or within less than 20% of the total fastener stroke. This results in an
improved safety profile
in the event of a jam, as the anvil and anvil assembly will have dissipated
its kinetic energy,
thus allowing the user to fix the jam without having potential energy
remaining in the anvil
and anvil assembly.
[0025] Accordingly, and in addition to the objects and advantages of the
portable
electric fastener gun as described above, several objects and advantages of
the present
invention are:
= To provide a simple design for driving fasteners that has a significantly
lower
production cost than currently available nail guns and that is portable and
does not
require an air compressor.
= To provide a fastener driving device that mimics the pneumatic fastener
performance
without a tethered air compressor.
= To provide an electrical driven high power fastening device that has very
little wear.
= To provide an electric motor driven fastener driving device in which
energy is not
stored behind the fastener driving anvil, thus greatly enhancing tool safety.
= To provide a more energy efficient mechanism for driving nails than is
presently
achievable with a compressed air design.
[0026]
These together with other aspects of the present disclosure, along with the
various features of novelty that characterize the present disclosure, are
pointed out with
particularity in the claims annexed hereto and form a part of the present
disclosure. For a
better understanding of the present disclosure, its operating advantages, and
the specific
objects attained by its uses, reference should be made to the accompanying
drawings and
detailed description in which there are illustrated and described exemplary
embodiments of
the present disclosure.
DESCRIPTION OF THE DRAWINGS
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[0027]
The advantages and features of the present invention will become better
understood with reference to the following detailed description and claims
taken in
conjunction with the accompanying drawings, wherein like elements are
identified with like
symbols, and in which:
[0028] Figure 1 shows a cutaway view of a fastener driving apparatus, in
accordance
with an exemplary embodiment of the present disclosure;
[0029]
Figure 2 shows a cutaway view of a fastener driving apparatus, in accordance
with an exemplary embodiment of the present disclosure wherein the gas spring
is being
compressed;
[0030] Figure 3 shows a cutaway view of a fastener driving apparatus, in
accordance
with an exemplary embodiment of the present disclosure wherein the gas spring
is releasing
the drive anvil;
[0031]
Figure 4 shows a cutaway view of a fastener driving apparatus, in accordance
with an exemplary embodiment of the present disclosure wherein the anvil
assembly has
-- separated from the gas spring and is driving the fastener;
[0032]
Figure 5 shows a cutaway view of a fastener driving apparatus, in accordance
with an exemplary embodiment of the present disclosure wherein the gas spring
has returned
to a starting position, and.
[0033]
Figure 6 shows a piston flange of a fastener driving apparatus, in accordance
-- with an exemplary embodiment of the present disclosure.
[0034]
Like reference numerals refer to like parts throughout the description of
several views of the drawings.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0035]
The best mode for carrying out the present disclosure is presented in terms of
its preferred embodiment, herein depicted in the accompanying figures. The
preferred
embodiments described herein detail for illustrative purposes are subject to
many variations.
It is understood that various omissions and substitutions of equivalents are
contemplated as
circumstances may suggest or render expedient, but are intended to cover the
application or
implementation without departing from the spirit or scope of the present
disclosure.
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Furthermore, although the following relates substantially to one embodiment of
the design, it
will be understood by those familiar with the art that changes to materials,
part descriptions
and geometries can be made without departing from the spirit of the invention.
It is further
understood that references such as front, back or top dead center, bottom dead
center do not
refer to exact positions but approximate positions as understood in the
context of the
geometry in the attached figures.
[0036]
The terms "a" and "an" herein do not denote a limitation of quantity, but
rather denote the presence of at least one of the referenced items.
[0037]
Referring now to Figures 1-6, the present disclosure provides for a fastener
driving apparatus 100. In an embodiment, the apparatus 100 comprises a power
source 10, a
control circuit 20, a motor 30, a gas spring 40, a drive mechanism 50, an
anvil assembly 60,
and an anvil 62. The apparatus 100 may further comprise an anvil retum
mechanism 64 and
at least one bumper 70. The gas spring 40 includes a piston 42, which piston
42 is at least
partially disposed within a sealed chamber 44, and which piston 42 is
selectively actuated by
the drive mechanism 50. A bumper 72 is preferably disposed within the gas
spring 40 to
absorb a portion of the force of impact of the piston 42. The gas spring 40
further comprises
a nose portion 46 (which nose portion may be a part of or coupled to the
piston) and which
nose portion 46 extends out of the chamber and which makes operative contact
with the anvil
62 and/or anvil assembly 60 during a portion of the operational cycle of the
apparatus 100.
The piston 42 also comprises a flange 48 that is at or near the end of the
piston that is distal to
the anvil and anvil assembly, which flange 48 retains the piston 42 within the
gas spring 40.
The flange extends away from and beyond the circumference of the piston and
may also
impact the bumper 72 to absorb the energy of the gas spring during a portion
of the stroke.
Referring to Figure 6, an exemplary configuration of the flange is shown,
wherein portions of
said flange are immediately adjacent to the interior surface of the gas
spring, and other
portions of said flange are disposed away from the interior of the gas spring,
The flange 48
further comprises an opening or open area 49 to allow air or gas to flow from
one side of the
piston or piston flange to another side of the piston or piston flange. In an
embodiment, the
area of the opening or open area is least 5% of the area of the cross-
sectional area of the
interior of the gas piston.
[0038]
The drive mechanism 50 may comprise, in an embodiment, a rack gear with
intervals of teeth and no teeth. The drive mechanism 50 preferably comprises a
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mechanism 52 as illustrated in the figures. In another embodiment, the drive
mechanism 50
may comprise an interrupted friction wheel. It will be apparent that the drive
mechanism 50
is configured to permit transition from engagement with the gas spring 40 to
disengagement
from the gas spring 40. The drive mechanism 50 is operatively coupled to the
gas spring 40,
and in an particular embodiment, to the piston 42 such that the drive
mechanism 50 may
alternate in actuating the piston 42 (when the gear teeth or cam is engaged,
for example, and
as shown in Figures 1 and 2) and in refraining from applying a drive force on
the piston (as
shown in Figures 3 and 4). In another embodiment, the drive mechanism 50
preferably acts
directly upon the anvil assembly 60, which anvil assembly 60 is at least
operatively coupled
to and moves the piston 42 to store potential energy (as described elsewhere
herein.)
[0039]
In an embodiment, and as shown in Figure 2, the drive mechanism 50 engages
and actuates the piston 42 (and/or anvil assembly 60) to store potential
energy within the gas
spring 40, which actuation of the piston 42 may be referred to as an
"energized position" of
the piston 42. In an embodiment, the initial pressure (before the drive
mechanism 50 actuates
the piston 42) within the gas spring 40 is at least 40 psia. In another
embodiment, the initial
pressure within the gas spring 40 is at least 200 psi. The configuration and
design of the gas
spring 40 are such that the pressure increase during the piston movement is
less than 30% of
the initial pressure, and in an embodiment, less than 50% of the initial
pressure, which allows
the drive mechanism 50 to operate at a more constant torque, thus improving
the motor
efficiency. As shown in Figure 3, the drive mechanism 50 thereafter disengages
the piston 42
(and/or anvil assembly 60), allowing potential energy to act on the piston 42
and cause the
piston 42 to move and act on the anvil 62 and/or anvil assembly 60 (as will be
described in
further detail below). The drive mechanism 50 is timed and/or configured to
prevent further
engagement with the gas spring 40 (and/or anvil assembly 60) until after the
anvil 62 and/or
anvil assembly 60 has returned to an approximate starting position. As shown
in Figure 5,
the drive mechanism 50 may thereafter again act on the piston 42 (and/or anvil
assembly 60)
to again store potential energy within the gas spring 40 and may thereafter
again temporarily
cease to act on the piston 42 (and/or anvil assembly 60) to allow potential
energy to instead
act on the piston 42. In an embodiment, the stroke of the piston 42 is less
than stroke of the
anvil assembly 60.
[0040]
The anvil 62 and/or anvil assembly 60 is operatively coupled to the gas spring
40, such as to the piston 42 or nose portion such that when the piston 42 is
released under
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pressure from the drive mechanism 50, the force from the piston 42 is imparted
onto the anvil
62, causing the anvil 62 and/or anvil assembly to move in a direction and, as
shown in Figure
4 to release (or be launched) away from the piston 42 and drive a fastener,
for example. It
was discovered in the course of developing the disclosure that the ratio of
the thrown mass to
the moving mass within the gas spring 40 (primarily the piston 42) was
exceedingly
important to the efficiency of the fastener driving apparatus 100. It is
preferred to have
thrown mass (which in this case is the anvil assembly 60) that is greater than
50% of the total
moving mass (anvil assembly mass + gas spring moving mass) and even more
preferable to
have the anvil assembly mass at least 60% of the total moving mass. This
discovery allows
the present disclosure to have increased efficiency in transferring the
potential energy into
driving energy on the fastener. In an embodiment, the mass of the anvil 62 is
at least two
times the mass of the piston 42. In an embodiment, the piston 42 has a mass of
90 grams and
the anvil 62 has a mass of 250 grams. In an embodiment, the piston 42 is
hollowed out to
lighten its mass and further may be constructed of lightweight materials such
as hard
anodized aluminum, plastics or the like. The anvil 62 may be operatively
coupled to a guide,
shaft, or other structure that limits and guides the range of motion of the
anvil 62.
[0041]
Referring further to Figure 4, a sensor 90 is provided for determining at
least
one position of the anvil, anvil assembly, and/or drive mechanism to enable
the proper timing
for stopping the operational cycle of the apparatus. Further, this information
can be used to
detect a jam condition for proper recovery.
[0042]
At least one bumper 70 may be disposed on the apparatus 100 for absorbing a
portion of the force of impact of the piston 42 within the gas spring 40 or of
the anvil 62
and/or anvil assembly 60, to reduce wear and tear on the components of the
apparatus 100.
The at least one bumper 70 may be of an elastic material, and may be disposed
on the
apparatus 100 at any position where it is capable of absorbing a portion of
the force of impact
by the piston 42 or the anvil 62.
[0043]
The anvil 62 further comprises a return mechanism 64 to enable to the anvil 62
to return to a position where it can be again contacted or acted on by the gas
spring 40. In an
embodiment, the return mechanism 64 is a return spring that is disposed on or
in the guide or
shaft that constrains the anvil 62, which return spring would be disposed
nearer the end or
portion of the anvil 62 that is distal to the gas spring 40. After the gas
spring 50 causes the
anvil 62 to move, and after or in connection with the anvil 62 impacting and
driving a
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fastener, the return mechanism 70 imparts a force on the anvil 62 to cause the
anvil 62 to
return to a position where it may again be operatively acted upon by the gas
spring 40. In the
embodiment where the return mechanism 70 is a return spring, the return spring
may be
disposed with respect to the anvil 62 such that motion of the anvil 62 toward
a fastener to be
driven also causes the spring to compress, and after the anvil 62 has reached
the end of its
drive stroke, the compressed return spring decompresses to actuate the anvil
62 to the anvil's
earlier or original position.
[0044]
In another embodiment, the fastener driving apparatus 100 disclosed herein
comprises a spring in place of the gas spring and piston. In this embodiment,
the spring may
comprise a mechanical spring, a gas spring, an elastomer spring or an
elastomer, for example.
The apparatus further comprises a drive mechanism, an anvil assembly, an
anvil, an anvil
return mechanism, and at least one bumper. Similar to the embodiment described
above, the
drive mechanism may comprise, in an embodiment, a rack gear with intervals of
teeth and no
teeth. The drive mechanism preferably comprises a cam-driven mechanism as
illustrated in
the figures. It will be apparent that the drive mechanism is configured to
permit transition
from engagement with the spring to disengagement from the spring. The drive
mechanism is
operatively coupled to the spring such that the drive mechanism may alternate
in actuating
the spring (when the gear teeth or cam is engaged, for example) and in
refraining from
applying a drive force on the such that other forces are able to act on and
actuate the spring.
In another embodiment, the drive mechanism preferably acts directly upon the
anvil
assembly, which anvil assembly is at least operatively coupled to the spring
and moves the
spring to store potential energy (as described elsewhere herein.)
[0045]
In an embodiment, the drive mechanism engages and actuates the spring
(and/or anvil assembly) to store potential energy within the spring, which
actuation of the
spring may be referred to as an "energized position" of the spring. The drive
mechanism
thereafter disengages the spring (and/or anvil assembly), allowing potential
energy to act on
the spring and cause the spring to move and act on the anvil and/or anvil
assembly (as will be
described in further detail below). The drive mechanism is timed and/or
configured to
prevent further engagement with the spring (and/or anvil assembly) until after
the anvil
and/or anvil assembly has returned to an approximate starting position. The
drive mechanism
may thereafter again act on the spring (and/or anvil assembly) to again store
potential energy
within the spring and may thereafter again temporarily cease to act on the
spring (and/or anvil
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assembly) to allow potential energy to instead act on the spring. In an
embodiment, the
stroke of the spring is less than stroke of the anvil assembly.
[0046]
Similar to the gas spring embodiment described previously, the anvil and/or
anvil assembly is operatively coupled to the spring, such that when the spring
is released
from the drive mechanism the force from the spring is imparted onto the anvil
and/or anvil
assembly, causing the anvil and/or anvil assembly to move in a direction and
to release (or be
launched) away from the spring and drive a fastener, for example. It is
preferred to have
thrown mass (which in this case is the anvil assembly) that is greater than
50% of the total
moving mass (anvil assembly mass + spring moving mass) and even more
preferable to have
the anvil assembly mass at least 60% of the total moving mass. In an
embodiment, the mass
of the anvil is at least two times the mass of the spring. In an embodiment,
the spring has a
mass of 90 grams and the anvil has a mass of 250 grams. The anvil may be
operatively
coupled to a guide, shaft, or other structure that limits and guides the range
of motion of the
anvil.
[0047] At least one bumper may be disposed on the apparatus for absorbing a
portion
of the force of impact of the spring, to reduce wear and tear on the
components of the
apparatus. The at least one bumper may be of an elastic material, and may be
disposed on the
apparatus at any position where it is capable of absorbing a portion of the
force of impact by
the spring.
[0048] The anvil further comprises a return mechanism to enable to the
anvil to return
to a position where it can be again contacted or acted on by the spring. In an
embodiment,
the return mechanism is a return spring that is disposed on or in the guide or
shaft that
constrains the anvil, which return spring would be disposed nearer the end or
portion of the
anvil that is distal to the spring that causes the anvil to drive a fastener.
After the spring
causes the anvil to move to drive a fastener, and after or in connection with
the anvil
impacting and driving a fastener, the return mechanism imparts a force on the
anvil to cause
the anvil to return to a position where it may again be operatively acted upon
by the spring.
In the embodiment where the return mechanism is a return spring, the return
spring may be
disposed with respect to the anvil such that motion of the anvil toward a
fastener to be driven
also causes the return spring to compress, and after the anvil has reached the
end of its drive
stroke, the compressed return spring decompresses to actuate the anvil to the
anvil's earlier or
original position.
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[0049]
The present disclosure offers the following advantages: the gas spring,
mechanical spring and elastomer are capable of generating a relatively high
amount of force
in a small amount of space such that the size of the apparatus may be smaller
than other
fastener drivers. Further, because of the relatively small increase from the
initial pressure in
the gas spring to the maximum pressure, the motor of the apparatus is not
significantly
overworked or over torqued, thus leading to a longer useful life of the
apparatus.
Furthermore, it was unexpectedly discovered that this invention has an
improved safety
profile. For example, if a nail becomes jammed, the potential energy of the
air spring does
not act directly on the fastener and thus while the user removes the fastener,
there is reduced
potential for injury. It was a further unexpected discovery of the present
disclosure that the
apparatus has an improved recoil force as opposed to conventional and or the
inventor's prior
fastener inventions. This was a totally unexpected discovery as the
anvil/anvil assembly is a
free traveling mass and as such during the course of the driving of the
fastener does not put a
reactionary force on the operator. In contrast and in prior art tools, air
pressure on the piston
and anvil assembly acts during the entire drive and at the end of the stroke
can result in
significant recoil to the operator.
[0050]
The foregoing descriptions of specific embodiments of the present disclosure
have been presented for purposes of illustration and description. They are not
intended to be
exhaustive or to limit the present disclosure to the precise forms disclosed,
and obviously
many modifications and variations are possible in light of the above teaching.
The exemplary
embodiment was chosen and described in order to best explain the principles of
the present
disclosure and its practical application, to thereby enable others skilled in
the art to best
utilize the disclosure and various embodiments with various modifications as
are suited to the
particular use contemplated.
