Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
ELASTOMERIC EXHAUST REED VALVE FOR COMBUSTION DRIVEN
FASTENER HAND TOOL
[0001] (intentionally left blank)
[0002] (intentionally left blank)
[0003] This application claims priority to U.S. 62/196,196, filed July 23,
2015 entitled
"ELASTOMERIC EXHAUST REED VALVE FOR COMBUSTION DRIVEN
FASTENER HAND TOOL.
[0004] (intentionally left blank)
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0005] This invention relates to combustion driven fastener hand tools.
Particularly,
this invention relates to exhaust reed valves for combustion driven fastener
hand tools.
2. Description of the Related Art
[0006] Powered fastener driving tools, e.g. nail guns, have existed for
decades.
Perhaps not coincidentally, the first commercial nail gun was introduced in
1950 after
World War II wherein the technology for rapidly firing projectiles was greatly
advanced.
The first nail guns were pneumatic, driven by compressed air. Although
pneumatic
1
Date Recue/Date Received 2023-03-01
power is still the most prevalent, over time fastener driving tools have been
developed
using other means of power, such as electric motors, solonoids, combustibles,
e.g gas or
explosive powder, have also been developed. Some development of technology
related
to powered fastener drivers, and particularly combustion driven fastener tools
has
occurred. However, there is still much need for further development.
100071 Combustion driven fastener hand tools employing combustibles, e.g. gas
or
powder, to force a piston driver against a fastener introduce a unique set of
parameters
which must be properly balanced in order to achieve a working device. Sizing
of the
combustion chamber and valving are critical, in addition to the fuel delivery
and mixing
components. Moreover, greater optimization of a given design to improve power
and
efficiency can be greatly affected through precise understanding of the
combustion
process. For example, it has been determined that using a combustion chamber
divided
into portions having a control plate therebetween can greatly improve the
efficiency and
power of a combustion driven fastener device. Improvements have also been
developed
concerning the exhaust systems of such combustion driven fastener hand tools.
[0008] U.S Patent No. 8,925,517 discloses a gas-powered tool motor includes a
combustion chamber with an intake valve at one end, an exhaust valve at
another end,
and a control plate or control valve between two portions of the combustion
chamber. A
piston or other positive displacement device is in communication with the
combustion
chamber. The intake and exhaust valves have closure members that are movable
along a
common axis in tandem between collective open positions for recharging the
combustion
chamber with the fuel and air mixture and collective closed positions for
detonating the
fuel and air mixture in the combustion chamber and displacing the positive
displacement
device. The control plate or control valve supports limited air flows from a
first portion
of the combustion chamber to a second portion of the combustion chamber even
in the
closed position of the control valve for supporting two-stage combustion.
2
Date Recue/Date Received 2023-03-01
CA 02992292 2018-01-11
WO 2017/015595 PCT/US2016/043653
[0009] U. S Patent No. 7,201,301, issued April 10, 2007, by Moeller etal.,
discloses a
combustion-powered fastener-driving tool includes a combustion-powered power
source
including a cylinder defining a path for a reciprocating piston and an
attached driver
blade, the piston reciprocating between a pre-firing position achieved prior
to combustion
and a bottom out position. Upon combustion in the power source, the cylinder
includes
at least one exhaust valve configured for releasing combustion gases from the
cylinder.
The at least one exhaust valve is dimensioned so that sufficient gas is
released to reduce
post-combustion pressure in the cylinder to approximately one atmosphere in
the time
available for the piston to travel past the at least one exhaust valve and
return to the at
least one exhaust valve.
[0010] U.S Patent No. 6,997,145, issued February 14, 2006, by Adams, discloses
a
recycling system for linear motors includes a dual piston within a cylinder
housing that is
moved from an upper position to a lower position by combustion pressure such
that a first
portion of the piston pumps compressed air from a first air chamber within a
first bore of
the cylinder housing and a second portion of the piston pumps compressed air
from a
second air chamber within a second larger bore of the cylinder housing. An
exhaust
valve is opened by the compressed air for venting the combustion chamber to
atmosphere. The dual piston moves within the cylinder housing from the lower
position
to the upper position assisted by the compressed air such that a portion of
the volume of
the combustion chamber is converted into a portion of the volume of the second
air
chamber. A control valve is opened in response to movement of the dual piston
through
the upper position for allowing airflow from the second air chamber into the
combustion
chamber.
[0011] U.S Patent No. 7,591,236, issued September 22, 2009, by Moeller et al.,
discloses a combustion nailer configured for reducing intake of contaminated
air during
operation, includes a combustion engine having a cylinder with a piston
reciprocating
between a prefiring position and a fully extended position, and at least one
air port in the
cylinder below the fully extended position. The at least one air port is
provided with a
3
CA 02992292 2018-01-11
WO 2017/015595 PCT/US2016/043653
venting check valve configured so that the discharge volume from the cylinder
out the at
least one air port is greater than the inflow.
[0012] U.S Patent No. 8,016,046, issued September 13, 2011, by Zhao etal.,
discloses
a combustion tool includes a cylinder having a lower end provided with a
resilient
bumper, a piston dimensioned for reciprocation within the cylinder to impact
the bumper
at an end of the cylinder and having a driver blade depending therefrom for
impacting
fasteners. At least one back pressure release opening is disposed in the
cylinder to be in
alignment with the piston and to be closed by the piston when the piston
impacts the
bumper.
[0013] Conventional exhaust valves for combustion driven fastener tools may
employ
one or more reed (or petal) valves of steel (e.g. spring steel). Such reed
type exhaust
valves also may also be employ with newer combustion driven fastener tools
having a
combustion chamber divided in two portions. These reed valves require
relatively
precise design and manufacturing to ensure reliable operation and a long
service life. In
addition, such valves are very sensitive and can be ruined by being
inadvertently bent or
deformed to even a small degree. Due to the stiffness of the material, such
reed valves
must employ very secure fastening, e.g. a stiffener plate held tightly over
one end of the
valve plate by screws. Stresses within the valve plate must never exceed the
elastic limit
of the material so that it does not permanently deform. In addition, steel is
relatively
expensive and if such valves become damaged, they must typically be replaced.
[0014] In view of the foregoing, there is a need in the art for improved
exhaust valve
apparatuses for combustion driven fastener hand tools. There is a need for
such
apparatuses to be simple to design and occupy small spaces. There is also a
need for
such apparatuses and methods that operate reliably and efficiently over many
uses and at
a reduced cost. These and other needs are met by the present invention as
detailed
hereafter.
4
CA 02992292 2018-01-11
WO 2017/015595 PCT/US2016/043653
SUMMARY OF THE INVENTION
[0015] An exhaust valve comprising an elastomeric flap portion (e.g. of
silicone)
covering one or more exhaust ports in a normally closed position for a
combustion driven
fastener hand tool is disclosed. The elastomeric flap portion is much shorter
than a
comparable steel reed valve, allowing it to be disposed in small spaces. A
single flat
piece of elastomeric material can be configured held fixed to a housing
surface along a
line between one or more pairs of ports such that a flap portion of the
material extends to
each side of the line and covers one of the pairs of ports. The flat piece can
be
conveniently held in position against the housing surface by a rib or standoff
on the
interior surface of an exterior housing. The elastomeric material provides an
excellent
seal over the ports in the closed position and is inexpensive and resistant to
the heat of
exhaust gases.
[0016] A typical embodiment of the invention comprises an exhaust valve for a
combustion driven fastener tool, including a housing forming a combustion
chamber
having one or more exhaust ports from the combustion chamber to an exterior of
the
housing and an elastomeric piece held fixed to an area adjacent to the one or
more
exhaust ports such that at least one flap portion of the flat elastomeric
piece extends over
the one or more exhaust ports. The elastomeric piece can be flat and/or
comprising a
rectangular shape or a circular shape. Alternately, the elastomeric piece can
have a
shaped surface to match a surface of the area adjacent to the one or more
exhaust ports.
For example, the shaped surface can be cylindrical, wherein the surface of the
area
adjacent to the one or more exhaust ports is cylidrical. The elastomeric piece
can
comprise silicone, synthetic rubber, fluoropolymer, fluorosilicone,
fluoroelastomer, or
perfluoroelastomer.
[0017] In further embodiments, the elastomeric piece can be held fixed by a
standoff on
an exterior housing, the exterior housing covering at least a portion of the
housing. In
addition, pins on the standoff can fit into holes in the elastomeric piece.
CA 02992292 2018-01-11
WO 2017/015595 PCT/US2016/043653
[0018] In some embodiments, the elastomeric piece can be held by a linear
shape
(which can be the standoff or a separate fastening element). The linear shape
can
comprise a tapered edge contacting the elastomeric piece. In some cases, the
linear shape
can symmetrically bisect the elastomeric piece. In addition, the linear shape
can run
parallel to a piston of the combustion chamber.
[0019] In some embodiments, the one or more exhaust ports can comprise a
plurality of
exhaust ports and the elastomeric piece is held fixed to the area adjacent to
the plurality
of exhaust ports along a linear shape such that the at least one flap portion
comprises
symmetric flap portions formed to each side of the linear shape, each flap
portion
covering at least one of the plurality of exhaust ports. The plurality of
exhaust ports can
be arranged in pairs such that each pair of the exhaust ports is disposed
equidistant from
the linear shape. Here also, the linear shape can run parallel to a piston of
the
combustion chamber.
[0020] Similarly, a method embodiment of the invention can comprise a method
of
operating an exhaust valve for a combustion driven fastener tool, including
providing a
housing foiming a combustion chamber having one or more exhaust ports from the
combustion chamber to an exterior of the housing and holding an elastomeric
piece fixed
to an area adjacent to the one or more exhaust ports such that at least one
flap portion of
the elastomeric piece extends over the one or more exhaust ports. This method
embodiment of the invention can be further modified consistent with the any
other
embodiment of the invention described herein.
[0021] Another embodiment of the invention can comprise an exhaust valve for a
combustion driven fastener tool, including a combustion chamber means for
capturing
and harnessing combustion gases within a housing, one or more exhaust port
means for
expelling the combustion gases from the combustion chamber to an exterior of
the
housing, and an elastomeric piece held fixed to an area adjacent to the one or
more
exhaust port means such that at least one flap portion of the elastomeric
piece extends
over the one or more exhaust port means. The one or more exhaust port means
can
6
comprise a plurality of exhaust ports and the elastomeric piece can be held
fixed to
the area adjacent to the plurality of exhaust ports along a linear shape such
that the at
least one flap portion comprises symmetric flap portions formed to each side
of the
linear shape, each flap portion covering at least one of the plurality of
exhaust ports.
This apparatus embodiment of the invention can be further modified consistent
with
the any other embodiment of the invention described herein.
[0021a] According to an aspect of the invention is an exhaust valve
for a
combustion driven fastener tool, comprising:
a housing forming a combustion chamber having one or more exhaust ports
from the combustion chamber through a wall of the housing to an ambient
environment at an exterior of the housing and not into any secondary
combustion
chamber; and
an elastomeric piece held fixed against the housing to a flat area adjacent to
the one or more exhaust ports such that at least one flap portion of the
elastomeric
piece extends over the one or more exhaust ports,
wherein the elastomeric piece is flat and held fixed by a linear shaped
element
and the linear shaped element holds the elastomeric piece fixed such that the
exhaust
valve opens on two opposite symmetric sides of the linear shaped element and
the
elastomeric piece does not move from the housing along the linear shaped
element
and a surface of the linear shaped element in contact with the elastomeric
piece runs
parallel to a piston travel of the combustion chamber.
[0021b] According to an aspect of the invention is a method of
operating an
exhaust valve for a combustion driven fastener tool, comprising:
providing a housing foiming a combustion chamber having one or more
exhaust ports through a wall of the housing from the combustion chamber to an
ambient environment at an exterior of the housing and not into any secondary
combustion chamber; and
holding an elastomeric piece fixed against the housing to a flat area adjacent
to
the one or more exhaust ports such that at least one flap portion of the
elastomeric
piece extends over the one or more exhaust ports,
wherein the elastomeric piece is flat and held fixed by a linear shaped
element
and the linear shaped element holds the elastomeric piece fixed such that the
exhaust
valve opens on two opposite symmetric sides of the linear shaped element and
the
7
Date Recue/Date Received 2023-03-01
elastomeric piece does not move from the housing along the linear shaped
element and a surface of the linear shaped element in contact with the
elastomeric
piece runs parallel to a piston travel of the combustion chamber.
10021c] According to an aspect of the invention is an exhaust valve for a
combustion driven fastener tool, comprising:
a combustion chamber means for capturing and harnessing combustion gases
within a housing;
one or more exhaust port means through a wall of the housing for expelling
the combustion gases from the combustion chamber means to an ambient
environment at an exterior of the housing and not into any secondary
combustion
chamber; and
an elastomeric piece held fixed against the housing to a flat area adjacent to
the one or more exhaust port means such that at least one flap portion of the
elastomeric piece extends over the one or more exhaust port means;
wherein the elastomeric piece is flat and held fixed by a linear shaped
element
and the linear shaped element holds the elastomeric piece fixed such that the
exhaust
valve opens on two opposite symmetric sides of the linear shaped element and
the
elastomeric piece does not move from the housing along the linear shaped
element
and a surface of the linear shaped element in contact with the elastomeric
piece runs
parallel to a piston travel of the combustion chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Referring now to the drawings in which like reference numbers represent
corresponding parts throughout:
[0023] FIGS. 1A-1C show cutwaway views of the combustion operation of an
exemplary combustion driven fastener hand tool for use with an embodiment of
the
invention;
[0024] FIG. 2 shows exploded views of an exemplary exhaust valve assembly
embodiment of an exemplary combustion driven fastener hand tool;
[0025] FIGS. 3A and 3B show installation of an exemplary exhaust valve onto
the
exterior housing of an exemplary combustion driven fastener hand tool;
[0026] FIG. 3C shows a cross section view of an exemplary exhaust valve
installed
onto the exterior housing of an exemplary combustion driven fastener hand
tool;
7a
Date Recue/Date Received 2023-03-01
[0027] FIG. 4A shows a cross section view of an exemplary exhaust valve
installed
in the final assembly an exemplary combustion driven fastener hand tool;
[0028] FIGS. 4B and 4C show closeup cross section views of detail C indicated
in
FIG. 4A of an exemplary exhaust valve operating; and
[0029] FIGS. 5A-5N show some alternate elastomeric plate and exhaust port
configurations.
7h
Date Recue/Date Received 2023-03-01
CA 02992292 2018-01-11
WO 2017/015595 PCT/US2016/043653
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
1. Overview
[0030] As previously mentioned, embodiments of the invention comprise an
exhaust
valve for use in a combustion driven fastener hand tool. The exhaust valve is
configured
as a reed valve comprising an elastomeric flap (e.g. of silicone) covering one
or more
exhaust ports in a normally closed position. The elastomeric flap is much
shorter than a
comparable reed valve of less flexible material (such as steel), allowing it
to be disposed
in small spaces. A single flat piece of elastomeric material can be configured
held fixed
to a housing surface along a line between one or more pairs of ports such that
a flap of
the material extends to each side of the line and covers one of the pairs of
ports. The flat
piece can be conveniently held in position against the housing surface by a
rib on the
interior surface of an outer housing. The elastomeric material provides an
excellent seal
over the ports in the closed position and is resistant to the heat of exhaust
gases and
inexpensive.
[0031] There are numerous advantages over conventional stiff material (e.g.
steel) reed
valves derived from employing an elastomeric exhaust valve according to an
embodiment
of the present invention. The elastomeric material is very inexpensive
compared with
stiff materials. In addition, there is little or no chance the elastomeric
reed valve will
become permanently deformed. Design and construction of an elastomeric reed
valve is
also simple to accomplish compared with stiff material reed valves due to the
fact that
deformation is not a problem. The very low stiffness of the elastomeric
material also
enables a suitable reed valve to occupy a much smaller physical envelope than
a steel
reed valve for the same application. Finally, the elastomeric reed valve
requires
relatively little fastening force against the housing surface compared with
that required
by a stiff material reed valve. Accordingly, there is no need for stiffener
plates, screws
and threaded holes as needed with stiff material reed valves.
8
100321 It should also be noted that although example embodiments of the
invention are
shown herein applied to a combustion driven fastener hand tool which operates
using a
combustion chamber divided in portions separated by a control valve or plate
and
charged with a gas and air mixture, e.g. as described in U.S Patent No.
8,925,517
embodiments of the invention are not limited to this type of combustion
chamber or fuel.
Instead, embodiments of the invention may be employed with any known
combustion
chamber that requires an exhaust valve of the combustion chamber where the
valve is
required to allow flow of combusting gases out of the combustion chamber and
resist
flow in the opposite direction. Thus, devices using a an exhaust valve for a
combustion
chamber in any other known application can be used with embodiments of the
invention
as will be understood by those skilled in the art.
2. Exemplary Combustion Driven Fastener Hand Tool
100331 FIGS. 1A-1C show cutwaway views of the combustion operation of an
exemplary combustion driven fastener hand tool 100 for use with an embodiment
of the
invention. FIG. IA identifies the cross section for FIGS. 1B and 1C. FIG. 1B
shows the
combustion chamber 102 with the piston 104 and driver 106 in position after
the
combustion chamber 102 is charged with a mixture of air and fuel and just
prior to
combustion. The piston 104 is near the top of the combustion chamber 102 with
the
space above filled with the air and fuel mixture and the space below exposed
to ambient
air.
100341 FIG. 1C shows the combustion chamber 102 after combustion where the
piston
104 has been driven downward forcing the fastener (not shown) below the driver
106 into
a work piece. Upon combustion within the chamber, combustion gases drive the
piston
104 and driver 106 forward (to force the fastener into a work piece). As the
piston nears
the end of travel it passes exhaust ports 200 in the cylinder wall of the
housing 208.
Exhaust gases under combustion pressure within the combustion chamber 102 are
directed through these ports in the housing 208 to the exhaust valves which
allow the
9
Date Recue/Date Received 2023-03-01
CA 02992292 2018-01-11
WO 2017/015595 PCT/US2016/043653
high pressure combusting gases to escape to the ambient environment and then
close. In
FIG. 1C the piston 104 has passed the exhaust ports 200 and allowed the
combustion
gases within the chamber 102 to force open the flaps of the flat elastomeric
piece 202 and
exit the chamber 102 leaving a partial vacuum (negative pressure) within the
chamber
102. As shown, the flaps are already drawn back to a closed position.
[0035] Exhaust valves are an essential component for a combustion driven
fastener
tool. The exhaust valves are employed to allow the combustion gases to be
ejected after
driving the fastener and then close. The high velocity of the exhaust gases
causes
negative pressure trapped in the combustion chamber 102 after the exhaust
valves close
to force the piston 104 to return to the start position as shown in FIG.1B, As
described
hereafter, standoffs can be integrated directly into the exterior housing 204
to fix the flat
elastomeric piece 202 against the housing 208 surface without requiring
fasteners.
3. Elastomeric Reed Valve for Exhaust Ports
[0036] FIG. 2 shows exploded views of an exemplary exhaust reed valve assembly
embodiment for an exemplary combustion driven fastener hand tool 100. The
housing
208 of the combustion chamber has one or more exhaust ports 200 which function
to
allow combustion gases to exit the housing 208 near the end of the piston
stroke as
described in the previous section. The exhaust reed valve assembly comprises a
piece
202 of elastomeric material which is affixed against the housing 208 over the
exhaust
ports 200. Because the elastomeric material is relatively light and flexible
the force
required to affix the piece 202 against the housing 208 is far less than would
be necessary
with a reed valve of steel. Accordingly, in one example a standoff 300 (see
FIGS. 3A &
3B) on the interior surface of the exterior housing 204 is capable of
providing adequate
force to affix the piece 202 against the housing 208 when exterior housing 204
is
assembled over the housing 208. Small holes 206 can be molded (or punched)
into the
piece 202 to be disposed on small pins 302 on the interior surface of the
outer housing
204 prior to final assembly in order to hold the piece 202 in proper position.
CA 02992292 2018-01-11
WO 2017/015595 PCT/US2016/043653
100371 FIGS. 3A and 3B show installation of an exemplary exhaust valve onto
the
exterior housing of an exemplary combustion driven fastener hand tool. The
interior
surface of the exterior housing 204 is shown with a standoff 300 molded
thereon as part
of the exterior housing 204. The small holes 206 of the piece 202 of
elastomeric material
are placed onto the small pins 302 of the exterior housing 204. In this
example, the pins
302 are disposed on the standoff 300. The exterior housing 204 is designed
such that
when it is assembled onto the primary housing 208 the standoff 300 is disposed
between
the exhaust ports 200. Thus, the elastomeric material piece 202 is sandwiched
between
the standoff 300 and the housing 208, i.e. affixed against the housing 208.
[0038] A linear shape for the standoff, i.e. a standoff holding the
elastomeric piece
making a line contact against the elastomeric piece adjacent to a flap
portion, is desirable
because it defines a line along which a flap portion of the elastomeric
material will bend
upon opening of the valve. However, those skilled in the art will appreciate
that the
standoff can be configured in a number of different ways, not limited to the
linear shape
of the present example. For example, the standoff can be alternately
configured as a
number of points that contact the surface of the flat elastomeric piece. It is
also possible
to employ multiple standoffs. For example, two or more linear standoffs formed
along a
common line (or along different lines that are not colinear) can be used to
secure flap
portions in different directions from the same flat elastomeric piece.
[0039] A flap portion of a larger elastomeric piece need only be secured along
a line
along which the flap portion will bend to open over the exhaust port that the
flap portion
covers. Accordingly, the elastomeric piece can be designed to include many
separate
flap portions in different directions such as a petal valve. (With an
elastomeric piece
shaped like a petal valve, a plurality of linear shapes would be used, each
across a root of
the separate "petals," i.e. flap portions, which extend in different radial
directions.) In
this case, however, use of the elastomeric material affords a much smaller
configuration
that provides an excellent seal and is inexpensive to produce.
11
CA 02992292 2018-01-11
WO 2017/015595 PCT/US2016/043653
[0040] It is also important to note that the linear shape, holding the
elastomeric piece
making the line along which a flap portion of the elastomeric material will
bend, need not
be constructed as a standoff 300 on an exterior housing 204. Those skilled in
the art will
appreciate any suitable technique for applying the linear shape to hold the
the elastomeric
piece making a line contact against the elastomeric piece adjacent to a flap
portion can be
used. For example, the linear shape can be formed by a reinforcing strap or
brace
secured over the elastomeric piece, e.g. by screws or other fasteners.
Alternately, the
linear shape can be formed by an adhesive, e.g epoxy or tape. As described
hereafter, the
elastomeric piece can also be formed to have features which can be used to
provide the
linear shape for holding it properly.
[0041] FIG. 3C shows a cross section view of an exemplary exhaust valve
installed
onto the exterior housing of an exemplary combustion driven fastener hand
tool. A cross
section view (section A-A) of the elastomeric material piece 202 sandwiched
between the
standoff 300 of the exterior housing 204 and the primary housing 208 is shown.
In this
example, two valve flaps are formed from a single flat elastomeric piece, with
each valve
flap extending transverse to the combustion cylinder to cover different sets
of exhaust
ports on either side. The use of an elastomer enables a very compact valve
design. Due
to the very low stiffness of the elastomer a very short cantilever length is
required
(measured between the point fixed by the standoff and the exhaust port (e.g.
center of the
port).
[0042] The elastomeric reed valve offers many advantages over a conventional
steel
reed valve. This very simple construction replaces a conventional reed valve
which
would require a significantly longer thin steel plate (due to the material
stiffness) which
must be very securely fastened at on end using screws threaded into the
primary housing
along with a reinforcement over the thin steel. In addition, the conventional
reed valve
requires careful control of its deflection by the exhaust gases so it does not
deform. The
conventional reed valve requires a more complex design (e.g. to control
deflection) more
12
CA 02992292 2018-01-11
WO 2017/015595 PCT/US2016/043653
expensive materials (e.g. steel sheet, screws, reinforcement) as well as more
time
consuming assembly (e.g. forming threaded holes and installing screws).
[0043] As described above, the elastomeric piece 202 is typically flat. A flat
piece is
convenient to manufacture and functions well as the flat flap portions
covering the
exhaust port(s) readily function as valve(s). However, it is important to note
that, even if
it is desirable, it is not essential that the entire elastomeric piece 202 is
flat. For example,
the elastomeric piece 202 can be made having a thickened area along an area
for the
linear shape for holding it, e.g. a rib section or other feature. This feature
of the
elastomeric shape can be used to hold it properly, i.e. holding the
elastomeric piece
making a line along which a flap portion of the elastomeric material will
bend, over the
exhaust ports.
[0044] In addition, it is important to note that the surface of the
elastomeric piece
which contacts the area adjacent to the one or more exhaust valve also need
not be flat.
The elastomeric piece can have a surface shaped to match the area adjacent to
the one or
more exhaust ports. This is a significant advantage over conventional steel
reed valves
which can only be employed against flat surfaces. Because the elastomeric
material can
be readily molded to any shape, an elastomeric piece can be readily
implemented having
any shaped surface desired to match the surface around the exhaust ports that
it contact.
In one notable example, the shaped surface shaped of the elastomeric piece can
be
cylindrical in order to match a cylindrical surface of the area adjacent to
the one or more
exhaust ports that can be used. A cylindrical surface for a combustion chamber
housing
is a natural option for machined parts. Employing a matched surface
elastomeric piece
eliminates the need to separately cut a flat area around the exhaust ports. Of
course, any
other surface shapes are also possible based on the particular application and
area around
the exhaust ports.
[0045] FIG. 4A shows a cross section view of an exemplary exhaust valve
installed in
the final assembly an exemplary combustion driven fastener hand tool. FIGS. 4B
and 4C
show closeup cross section views of detail C indicated in FIG. 4A of an
exemplary
13
CA 02992292 2018-01-11
WO 2017/015595 PCT/US2016/043653
exhaust valve operating. It should be noted that the shape of the standoff 300
where it
contacts the flat elastomeric piece 202 has a tapered edge (or is rounded).
FIG. 4B shows
the exhaust valve prior to combustion. The flat elastomeric piece 202 is held
against the
housing 208 by the standoff 300 of the exterior housing 204 closing the
exhaust ports
200. FIG. 4C shows the valve during combustion after the piston has traveled
to a point
past the the exhaust ports 200. The exhaust gases are now able to pass through
the ports
200 and force open the flap portions of the the flat elastomeric piece 202 (as
indicated by
the arrows).
[0046] The flap portions deform (bend) from the point that the standoff 300
holds the
elastomeric piece 202 against the housing 208. The velocity of the exhaust
gases out of
the ports 200 yields a negative pressure (i.e., a pressure lower than ambient
pressure)
within the combustion chamber. The pressure differential between the negative
pressure
in the combustion chamber and the ambient pressure causes the exhaust valves
to
immediately close (appearing as shown in FIG, 4B) forming a seal between the
elastomeric piece 202 and the surface of the housing 208 surrounding the
exhaust ports.
The seal here is important as it maintains the negative pressure within the
combustion
chamber which additionally causes the piston to be automtically drawn back up
to the
start position ready for the next firing. The elastomeric material is ideal
for forming such
a seal again the smooth (typically, but not necessarily, metal) surface of the
housing 208.
[0047] In addition to the foregoing, symmetry can be usefully employed in the
application of an elasomeric reed valve. In some cases, the linear shape used
to hold the
elastomeric piece can symmetrically bisects the elastomeric piece. See e.g.
FIGS. 4B and
4C. In the example, a simple standoff holds down the elastomeric piece such
that the
valve opens simultaneously on two opposite symmetric sides. This ensures that
the
forces of the escaping exhaust gases will bend the two equal flap portions in
opposing
directions simultaneously and equally thereby prevent the elastomeric piece
from moving
out of position.
14
CA 02992292 2018-01-11
WO 2017/015595 PCT/US2016/043653
[0048] In order to ensure that application of the exhaust gases are applied to
matching
pairs of exhaust ports in order to achieve the balance described above, i.e.
simultaneously
and equally, it is desireable, but not requried, to apply the linear shape
that holds the
elastomeric piece so that it runs parallel to the piston of the combustion
chamber. As
shown in the primary example embodiment, symmetric flap portions are formed to
each
side of the linear shape. See e.g. FIGS. 2, 4B and 4C. Each flap portion
covers at least
one of matching pairs of exhaust ports. The pairs of exhaust ports are
symmetrically
disposed equidistant from the linear shape of the standoff which runs between
them.
Alignment of the linear shape parallel to the piston facilitates the balanced
application of
exhaust gases to the elastomeric piece because the exhaust gases are directed
through
pairs of exhaust ports as the piston passes each pair in sequence. See FIGS.
1B and 1C.
[0049] The material of the elastomeric piece can be any suitable elastomeric
material
that can survive the temperatures and combustion gases. For example, suitable
silicone,
synthetic rubber, fluoropolymer (e.g. viton), fluorosilicone, fluoroelastomer,
perfluoroelastomer and other suitable polymers can be employed. The particular
elastomer chosen for a given application will depend upon the requirements for
temperature resistance, durability, stiffness, etc. as will be understood by
those skilled in
the art. The elastomeric material must be able to withstand a high heat flame,
but also
have sufficient flexibility to open quickly and sufficient stiffness to
quickly return to its
original shape. Designs having a short cantilever length make use of the
reduced
stiffness of the elastomeric material (compared with steel reed valves). In
addition, the
hardness of the material will relate to the flexibility and stiffness and
therefore affect how
quickly the valve will open and close.
[0050] Although not required, a suitable elastomeric material can have a
durometer
value in the range of 50 to 60. A lower durometer will yield quicker and
easier
movement of the flap portions. However, too low a durometer may cause the flap
portions to have difficulty closing. A higher duromteter is better in this
regard, because
the flap portions will retain their default shape more providing a tendency to
snap back
CA 02992292 2018-01-11
WO 2017/015595 PCT/US2016/043653
and close more quickly. There is a balance between these factors. In addition,
the
durometer value should be selected considering the physical size of the valve
application.
Those skilled in the art can determine an optimum durometer value to use,
along with
other properties of the elastomeric material, for a given application without
undue
experimentation.
[0051] In one example embodiment, the elastomeric piece 202 can be
approximately
13mm wide by 22mm tall at lmm thick. However, the particular length and width
in a
given application will depend on the port sizes and placement which in turn
will depend
on the combustion chamber size. In general, a short flap portion is used, i.e.
significantly
shorter than any comparable reed valve made of metal would be. Typically, a
thin piece
is desirable because it tends to flex better and return quickly. However, a
piece that is
too thin is not good as it will not be as durable and may have difficulty
retaining its
flatness. The particular dimensions for a given application can be readily
determined by
one skilled in the art without undue experimentation.
[0052] FIGS. 5A-5N show some alternate elastomeric plate and exhaust port
configurations. In the figures, the orientation of the exhaust ports is such
that the top of
each respective figure is the positioned toward the top of the combustion
chamber. The
relative position of the associated exhaust ports is shown as dotted circles
in each
example. (It should be noted that exhaust ports having other than circular
shapes can also
be employed.) In addition, the linear shape for holding each of the different
configations
is also identified by a dashed straight line across to small holes (which can
be pinnned as
described previously). The configurations of FIGS. 5A, 5G and 5L afford the
symmetry
and balanced exhaust gases as previously described, having a linear shape
holdown
parallel to the piston and symmetricaly bisecting the elastomeric piece. The
configurations of FIGS. 5D, 5H, and 51 employ a linear shape holdown
symmetrically
bisecting the elastomeric piece but the linear shape runs transverse to the
piston direction.
Accordingly, the exhaust gases will strike the upper ports before the lower
ports as the
16
CA 02992292 2018-01-11
WO 2017/015595 PCT/US2016/043653
piston passes. Provided the elastomeric piece is suitably retained, such
"unbalanced"
alternate configurations can also be used.
100531 Those skilled in the art will appreciate that embodiments of the
invention
encompass any number exhaust ports which may be arranged in any pattern and
having
an elastomeric piece covering those ports held fixed to the housing in an area
adjacent to
the ports. In addition, the elastomerice piece is not limited to having either
a rectangular
or circular shape, but can be configured having any desired shape.
Furthermore, the flat
elastomeric piece may be fixed along a line or at one or more points. It is
only necessary
that exhaust gases being driven out of the ports can force the flat piece open
momentarily
to allow the gases to escape.
[0054] This concludes the description including the preferred embodiments of
the
present invention. The foregoing description including the preferred
embodiment of the
invention has been presented for the purposes of illustration and description.
It is not
intended to be exhaustive or to limit the invention to the precise forms
disclosed. Many
modifications and variations are possible within the scope of the foregoing
teachings.
Additional variations of the present invention may be devised without
departing from the
inventive concept as set forth in the following claims.
17
